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WO2025233647A1 - Battery box comprising a foamed polisocyanurate material - Google Patents

Battery box comprising a foamed polisocyanurate material

Info

Publication number
WO2025233647A1
WO2025233647A1 PCT/IB2024/000222 IB2024000222W WO2025233647A1 WO 2025233647 A1 WO2025233647 A1 WO 2025233647A1 IB 2024000222 W IB2024000222 W IB 2024000222W WO 2025233647 A1 WO2025233647 A1 WO 2025233647A1
Authority
WO
WIPO (PCT)
Prior art keywords
component
battery box
component composition
flame
foam material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/IB2024/000222
Other languages
French (fr)
Inventor
Rifat Tabakovic
Sarah FEZZY
Leslie WOLSCHLEGER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sika Technology AG
Original Assignee
Sika Technology AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sika Technology AG filed Critical Sika Technology AG
Priority to PCT/IB2024/000222 priority Critical patent/WO2025233647A1/en
Publication of WO2025233647A1 publication Critical patent/WO2025233647A1/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
    • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
    • C08G18/7657—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
    • C08G18/7664—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/09—Processes comprising oligomerisation of isocyanates or isothiocyanates involving reaction of a part of the isocyanate or isothiocyanate groups with each other in the reaction mixture
    • C08G18/092—Processes comprising oligomerisation of isocyanates or isothiocyanates involving reaction of a part of the isocyanate or isothiocyanate groups with each other in the reaction mixture oligomerisation to isocyanurate groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/16—Catalysts
    • C08G18/18—Catalysts containing secondary or tertiary amines or salts thereof
    • C08G18/1875—Catalysts containing secondary or tertiary amines or salts thereof containing ammonium salts or mixtures of secondary of tertiary amines and acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4804—Two or more polyethers of different physical or chemical nature
    • C08G18/4812—Mixtures of polyetherdiols with polyetherpolyols having at least three hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4825—Polyethers containing two hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4829—Polyethers containing at least three hydroxy groups
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/218—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by the material
    • H01M50/22—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by the material of the casings or racks
    • H01M50/227—Organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/233—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions
    • H01M50/24—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions adapted for protecting batteries from their environment, e.g. from corrosion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/249—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders specially adapted for aircraft or vehicles, e.g. cars or trains
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2110/00—Foam properties
    • C08G2110/0041—Foam properties having specified density
    • C08G2110/0066—≥ 150kg/m3
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2110/00—Foam properties
    • C08G2110/0083—Foam properties prepared using water as the sole blowing agent
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/32—Phosphorus-containing compounds
    • C08K2003/321—Phosphates
    • C08K2003/322—Ammonium phosphate
    • C08K2003/323—Ammonium polyphosphate
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to a battery box comprising a structural foam material and a method of encapsulating an electric cell within a battery box and a foamable two- component composition.
  • Battery technology in electric vehicles is developing fast, alongside with the significant interest e-mobility has received in the past years.
  • the manufacturing of electric vehicle batteries has seen significant progress in terms of economically viable and efficient production processes.
  • Two of the current trends that are relevant for this field of application are cell-to-body designs of battery packs (also called structural battery packs) and the recently increased adoption of battery cells of cylindrical form.
  • thermal interface material serves two purposes: First, it provides a mechanical fastening system to keep the cells in place and second, it provides mechanical and thermal protection within the whole battery assembly.
  • the mechanical and adhesive performance of such thermal interface materials is of key importance, and it therefore should have the characteristics of a thermally conductive adhesive.
  • This assembly method using battery cells furthermore has a significant amount of free volume within the battery box, located between the individual cells, which is therefore filled with an injectable or pourable material, mostly with a foam-like cellular structure, in order to reduce weight and to provide shock-absorbing properties.
  • Cell-to-pack assembly requires even more mechanical reinforcement than traditional battery box designs.
  • this foam The functions of this foam are to keep the cells in position during their work life, and to thermally insulate cells from each other.
  • the latter is a safety function in case of cell malfunctions: if one cell heats up uncontrollably, as it is a risk connected to current lithium-based battery cells, then the neighboring cells need to be protected from excessive temperatures, or they will experience a thermal degradation and generate additional heat and even ignite, possibly affecting further neighboring cells. This catastrophic event is called thermal runaway.
  • the material used for filling the interstitial volume is typically expanded to a foam.
  • additional foam material is often attached outside the battery box as intermediate layer between the battery box and further boxes or the car body, or within the battery box, i.e. attached to the battery lid, a reinforcing layer for enclosures within the battery box, or to fill hollow ribs within the battery box.
  • Foams used in traditional cell-to-pack design do not have an important mechanical function and are usually soft to semi-rigid, expanded two-component polyurethane (2C-PU) foams.
  • 2C-PU foams and other traditionally used foam materials however commonly do not provide enough mechanical reinforcement required for cell-to- pack assemblies.
  • foams During processing or manufacturing of the battery, such foams must however cure with a limited exotherm in order to avoid damage to the cells, but they should also cure fast enough in order not to decrease the productivity of the battery assembly line.
  • Structural battery packs i.e., battery boxes containing a structural foam
  • the foam material is much more stiff and mechanically strong than in traditional cell-to-pack designs just described.
  • the stiffness of the cells in this approach beneficially helps to increase the mechanical and driving dynamics of the vehicle.
  • the foam material however has still to fulfill the basic functions regarding thermal insulation as described above. Additionally, to provide the structural strength, the material needs to strongly connect all components of a battery pack, such as the cells, and for this purpose needs to have good adhesion to a multitude of materials. Furthermore, the material needs to have high stiffness for the battery pack to contribute to the overall rigidity of the vehicles. High mechanical properties are also important to prevent physical damage to the cells in case of high- speed impacts. It is also important to achieve the desired mechanical properties over the whole temperature range of use, typically from -20°C to 65°C. The glass transition of the material used should be outside of this range and the drop of stiffness with increased temperature needs to be as limited as possible. In case of a thermal event, it is advantageous if the potting material can withstand high temperatures for extended amounts of time with only limited degradation.
  • US2022209343A1 discloses such a 2C-PU material and method of potting an electric cell, whereby high mechanical stability and flame-retardant properties are obtained.
  • the 2C-PU material contains a liquid flame-retardant additive and a blowing agent and in exemplary shown embodiments comprises a curing component based on monomeric and/or polymeric MDI. While the flameretarding properties of the cured material are sufficient for producing battery packs, care has to be taken during production that the exotherm icity of the curing material does not exceed levels that could damage the electric cells during assembly.
  • the mechanical properties, in particular the compression modulus, measured according to ASTM D1621 of 2C-PU foams are often insufficient to be fully suitable as structural foams in battery boxes.
  • a battery box comprising a structural foam material which exhibits excellent mechanical properties, especially regarding compressive strength and reinforcing abilities.
  • a battery box should have improved stability and, especially in preferred embodiments, excellent flameretardant properties, and should be manufactured in an efficient and inexpensive manner.
  • the structural foam material is based on a foamable two-component composition that is highly suitable for the production of structural battery packs using cell-to-body design. This material should after curing be rigid and mechanically strong enough to provide the desired stability of the battery boxes produced therewith.
  • the material should cure with very limited exotherm icity to avoid thermal damage to the battery pack components such as battery cells.
  • the cured foam material should exhibit a glass transition temperature (Tg) outside the thermal range that is relevant for electric vehicle batteries.
  • Tg glass transition temperature
  • the present invention is related to a battery box comprising a structural foam material F, wherein said structural foam material F is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B; wherein
  • the second component B comprises
  • polyisocyanate I is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyols P in the two-component composition is higher than 2.
  • the battery box comprising a structural foam material according to claim 1 surprisingly offers distinct advantages compared to battery boxes of the state of the art produced using cell-to-body design with 2C-PU foams. More specifically, battery boxes according to claim 1 exhibit better mechanical stability and in particular flame resistance than battery boxes comprising polyurethane foams. Additionally, the structural foam material comprised in the battery box according to claim 1 after curing exhibits a Tg outside of the usage range of electric vehicle batteries and shows exceptional thermomechanical stability and shock absorbing properties. Lastly, battery boxes according to claim 1 can be manufactured in a simple and efficient manner.
  • the structural foam may be used as encapsulating foam to fasten, reinforce, and stabilize the electric cells within the battery box, but it may also be used as insulation, sealant, gap filler, or foamed adhesive within, on, or outside the battery box, or as protective foam layer between individual battery boxes within a battery box assembly.
  • the structural foam with high close cell content offers outstanding thermal insulation, highest level of thermal stability (highest thermal decomposition temperature of the all isocyanatebased chemical structures), and structural reinforcement even on high temperature (i.e. , it maintains its storage modulus over broad range of temperature), shock and noise absorption and superior flame-retardancy in particular in preferred embodiments.
  • the present invention is related to a method of encapsulating an electric cell within a battery box according to this invention, by using a liquid, foamable two-component composition, which is the subject-matter of independent claim 21 .
  • the present invention is related to a foamable two-component composition that is optimized for use in battery boxes according to the present invention, which is the subject-matter of independent claim 23.
  • Such a foamable two-component composition cures into a rigid, structurally reinforcing foam with flame-retardant properties, which is the subject-matter of independent claim 30 and which constitutes a fourth aspect of the present invention.
  • a first aspect of the present invention is directed to a battery box comprising a structural foam material F, wherein said structural foam material F is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B; wherein
  • the second component B comprises
  • polyisocyanate I is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyols P in the two-component composition is higher than 2.
  • polymer firstly encompasses a collective of macromolecules that are chemically uniform but differ in the degree of polymerization, molar mass, and chain length, said collective having been produced by a “poly” reaction (polymerization, polyaddition, polycondensation).
  • the term secondly also encompasses derivatives of such a collective of macromolecules from “poly” reactions, i.e. , compounds that have been obtained by reactions, for example additions or substitutions, of functional groups on defined macromolecules and that may be chemically uniform or chemically nonuniform.
  • prepolymers too, i.e., reactive oligomeric initial adducts, the functional groups of which are involved in the formation of macromolecules.
  • polyurethane polymer encompasses all polymers produced according to the so-called diisocyanate polyaddition process. This also includes polymers that are virtually or completely free of urethane groups. Examples of polyurethane polymers are polyether polyurethanes, polyester polyurethanes, polyether polyureas, polyureas, polyester polyureas, polyisocyanurates, and polycarbodiimides.
  • molecular weight is understood to mean the molar mass (in grams per mole) of a molecule or a molecule residue.
  • Average molecular weight refers to the number average M n of a polydisperse mixture of oligomeric or polymeric molecules or molecule residues, which is typically determined by gelpermeation chromatography (GPC) against polystyrene as standard.
  • room temperature refers to a temperature of 23°C.
  • Percent by weight values abbreviated to % by weight, refer to the proportions by mass of a constituent in a composition based on the overall composition, unless otherwise stated.
  • mass and weight are used synonymously in the present document.
  • a “primary hydroxyl group” refers to an OH group attached to a carbon atom having two hydrogens.
  • the “pot life” refers to the time within which, after mixing the two components, the polyurethane composition can be processed before the viscosity resulting from the progression of the crosslinking reaction has become too high for further processing.
  • stress in the present document refers to the strength of the cured composition, with strength meaning in particular the compression strength and compression modulus, particularly measured according to ASTM D1621 .
  • a composition is referred to as “storage-stable” or “storable” when it can be stored at room temperature in a suitable container over a prolonged period, typically over at least 3 months up to 12 months or more, without this storage resulting in any change in its application or use properties to an extent relevant to its use.
  • the “open time” or “processing time” refers to the period of time in which the composition can be worked or reworked after the curing process has commenced. “Room temperature” refers to a temperature of 23°C.
  • a “battery box” within the meaning of this invention is understood as an initially at least partially hollow body that comprises at least one electric cell (in most cases a series of connected electric cells) and a housing or battery case at least partially surrounding said electric cell by walls.
  • the walls are normally made of metal or alloys, in particular aluminum, or of plastics or any other suitable rigid material.
  • the term battery box can also be understood as “battery pack” or even “battery module”, if satisfying the aforementioned definition.
  • battery boxes have several walls that define the hollow body and preferably a removable lid to fully close the battery box.
  • encapsulating in connection with the method of encapsulating an electric cell within a battery box according to this invention means that the result of said method is that at least one electric cell is at least partially surrounded by the cured foam material after having performed said method.
  • the electric cells are firmly surrounded by the foam material at least to such an extent that they are held in place and the cells are fully restricted in their movement by the foam material.
  • the battery box according to the invention includes at least one electric cell and a battery case or housing, as well as a structural foam material F.
  • the at least one electric cell may be positioned within the battery case and encapsulated in the structural foam material F.
  • the electric cell may be any suitable shape but generally is cylindrical.
  • the battery case may be any suitable shape for retaining the at least one electric cell, and which generally has a bottom, a top (which may be a removable lid), and several walls defined therebetween, connecting the bottom and the top.
  • the bottom of the battery case defines an inner surface and an outer surface; each wall of the battery case defines an inner surface and an outer surface.
  • the battery case defines an enclosed space having an internal volume.
  • the structural foam material F is positioned within the battery case and occupies a portion of the internal volume of the battery case.
  • the structural foam material F is positioned in contact with the at least one electric cell and especially at least partially surrounding the at least one electric cell.
  • structural foam material F is positioned between the walls of the battery case and the lid (or cover), and/or between ribs or sub-cavities within the battery case.
  • the structural foam material F is positioned outside the battery case.
  • the structural foam material F may be in contact with the bottom, the top, or any wall of the battery case.
  • the structural foam material F may be positioned between the outer surface of the bottom of the battery case and a cooling plate.
  • the structural foam material F may be positioned between the outer surface of the battery case and surface of another object, for example the outer surface of another battery case or the inner surface of an automobile chassis or a container wherein the battery box is installed.
  • a plurality of electric cells may be used to form a battery within the battery box.
  • multiple electric cells may be combined to form a single battery that has a higher voltage or amperage than a single electric cell.
  • the wires for connecting the electric cells may be combined in electric communication such that the electric current from the electric cells is combined, for example to form a battery having a combined current or voltage.
  • the battery box may be used to power any of a number of applications, such as a household appliance, outdoor electrical equipment, or a vehicle such as a car or a boat or aircraft, preferably an electric vehicle.
  • the electric cells should preferably be positioned with a suitable distance between adjacent electric cells such that a suitable thickness of structural foam material F is located positioned between adjacent electric cells to provide sufficient shock dampening to prevent damage to the electric cells and preferably to inhibit a fire hazard in cases where an electric cell ignites.
  • the size of the space or gap between adjacent electric cells and/or inner walls of the battery case can be selected based on a number of variables, including but not limited to, the size and/or weight of each electric cell, the operating temperature of each electric cell, the dimensions of each electric cell, and the intended use of the battery box.
  • the size of the space between adjacent electric cells may be from greater than 0 mm to 20 mm, preferably from 0.25 mm to 10 mm, in particular from 0.50 mm to 5 mm, especially from 0.75 mm to 2 mm, although battery modules having additional configurations are further contemplated.
  • the structural foam material F may be formed outside the battery case including openings having a suitable shape and size to later hold the electric cells firmly in place when they are inserted.
  • the structural foam material F may be added after first arranging the electric cells into the desired final position, for example, held together with wire or within the battery case.
  • the electric cells may be held in place in spatial relationship with one another using a mold or a scaffolding.
  • the electric cells may be held in place and positioned within a mold or other encasing surrounding the electric cells.
  • the electric cells may be arranged in a desired final position in spatial relationship to one another and placed within the battery case, for example resting on the inside surface of the bottom of the battery case.
  • the structural foam material F may be formed by mixing a liquid, foamable two-component composition as described further below and transferring it into an enclosed space defined by a wall of a battery box case, said case containing at least one electric cell, the cell being at least partially surrounded by the mixed liquid, foamable two-component composition and allowing the mixed liquid, foamable two-component composition to react, thereby forming a cured rigid polyisocyanurate foam, which constitutes the structural foam material F.
  • the mixed liquid, foamable two-component composition can flow through the gap between adjacent electric cells and settle at a level height around the electric cells and in the gap or spaces defined between the electric cells.
  • the mixed liquid, foamable two-component composition may be poured, sprayed, or injected into the battery case having the electric cells arranged within.
  • the mixed liquid, foamable two-component composition preferably has sufficient flowability before curing to permit the mixed liquid, foamable two-component composition to flow through the spaces defined by the gap between the adjacent electric cells and/or between an electric cell and the battery case.
  • the liquid encapsulating composition preferably has sufficient flowability to settle at a substantially level height before curing to form a cured rigid polyisocyanurate foam, which constitutes the structural foam material F.
  • the battery box according to the invention comprises a structural foam material F.
  • the structural foam material F is a foamed, at least partially polyisocyanurate- crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B; wherein
  • the first component A comprises - at least one polyol P
  • the second component B comprises
  • polyisocyanate I is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyols P in the two-component composition is higher than 2, preferably higher than 2.5, in particular higher than 3, more preferably higher than 3.5.
  • a preferred upper limit for the molar ratio of all NCO groups of polyisocyanate I in the two-component composition to all hydroxyl groups of polyols P in the two- component composition is 6, in particular 5.
  • At least one of the components A and B furthermore contains at least one flame-retardant additive. This is discussed in more detail further below.
  • said structural flame-retardant foam material F exhibits a V1 level flame resistance as measured by the UL 94 Test for Flammability of Plastics.
  • said structural flameretardant foam material F exhibits a VO or a V2 level flame resistance as measured by the UL 94 Test for Flammability of Plastics.
  • said structural flame-retardant foam material F exhibits a compression modulus, measured according to ASTM D1621 , of at least 150 MPa, especially at least 200 MPa, preferably at least 250 MPa, most preferably at least 300 MPa.
  • said structural flame-retardant foam material F exhibits a foam density, measured according to ASTM D1622, of between 0.1 and 0.6 g/cm 3 , preferably between 0.3 and 0.45 g/cm 3 .
  • said structural flame-retardant foam material F is a rigid, reinforcing structural encapsulating compound surrounding individual battery cells within the battery pack.
  • the structural flame-retardant foam material F is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B.
  • the first and second components of the composition are intrinsically storagestable and are stored in separate containers until they are mixed with one another shortly before or during application.
  • the first component A of the two-component composition according to the invention comprises at least one polyol P and water.
  • One of the components A or B, preferably the first component A, of the two-component composition also comprises at least one isocyanate trimerization catalyst.
  • one of the components A or B, preferably the first component A, the first component A of the two-component composition also comprises at least one flame retardant additive.
  • the first component A of the two- component composition additionally comprises at least one of an urethanization catalyst, a blowing catalyst, a foam stabilizer, a surfactant, a colorant, an antioxidant, a nucleating agent, a filler, a plasticizer, and/or other additives used in polyisocyanurate foam formulations.
  • polyols P having an average molecular weight M n in the range from 200 to 20'000 g/mol, preferably 250 to 10'000 g/mol, especially 300 to 5'000 g/mol. If more than one type of polyol is used as polyol P, then the average molecular weight M n of polyol P refers to the average molecular weight M n of all polyols comprised in polyol P.
  • polyols P having an average OH functionality in the range from 2 to 6, more preferably from 2.5 to 5. If more than one type of polyol is used as polyol P, then the average OH functionality of polyol P refers to the average OH functionality of all polyols comprised in polyol P.
  • polyols P having an average molecular weight M n in the range from 250 to 10'000 g/mol, in particular 300 to 5'000 g/mol and an average OH functionality in the range from 2 to 6, in particular 2.5 to 5.
  • Suitable polyols P as a constituent of the first component A are especially the following commercially available polyols or mixtures thereof:
  • polyether polyols especially polyoxyalkylenediols and/or polyoxyalkylenetriols, especially polymerization products of ethylene oxide, 1 ,2-propylene oxide, 1 ,2- or 2,3-butylene oxide, oxetane, tetrahydrofuran or mixtures thereof, where these are polymerized with the aid of a starter molecule having two or more active hydrogen atoms, especially a starter molecule such as water, ammonia or a compound having multiple OH or NH groups, for example ethane-1 ,2-diol, propane-1 ,2- or -1 ,3-diol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols or tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, o
  • polytrimethylene glycols which are linear, unbranched C3 or C4 polyether diols.
  • Such polytrimethylene glycols can be produced from the polymerization of propanediol, in particular from biobased propanediol.
  • Such polytrimethylene glycols are commercially available under the trade name Velvetol® from WeylChem Allessa GmbH.
  • polytetrahydrofuran diols usually produced from tetrahydrofuran by acid catalysis at 30 to 40 °C.
  • polytetrahydrofuran is polytetramethylene ether glycol (PTMEG).
  • PTMEG polytetramethylene ether glycol
  • the polytetrahydrofuran diols are produced in a manner known to the skilled person and are commercially available, for example under the trade names Terathane® PTMEG from Tri-iso or PolyTHF® from BASF.
  • Preferred polyether polyols are polyoxypropylenediols, polyoxypropylenetriols or ethylene oxide-terminated (EO-endcapped) polyoxypropylenediols or -triols.
  • the latter are mixed polyoxyethylene/polyoxypropylene polyols (block copolymers) which are especially obtained by further alkoxylating polyoxypropylene diols or triols with ethylene oxide on conclusion of the polypropoxylation reaction, and ultimately mainly have primary hydroxyl groups as a result.
  • Preferred polyether polyols have a degree of unsaturation of less than 0.02 meq/g, especially less than 0.01 meq/g.
  • Polyester polyols also called oligoesterols, prepared by known processes, especially the polycondensation of hydroxycarboxylic acids or lactones or the polycondensation of aliphatic and/or aromatic polycarboxylic acids with di- or polyhydric alcohols.
  • polyester diols from the reaction of dihydric alcohols such as, in particular, ethane-1 ,2-diol, diethylene glycol, propane-1 ,2-diol, dipropylene glycol, butane-1 ,4-diol, pentane-1 ,5-diol, 3- methylpentane-1 ,5-diol, hexane-1 ,6-diol, neopentyl glycol, or trihydric alcohols such as glycerol, 1 ,1 ,1 -trimethylolpropane or mixtures of the aforementioned alcohols, with organic dicarboxylic acids or the anhydrides or esters thereof, such as, in particular, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthal
  • polyester polyols are polyester diols.
  • Polycarbonate polyols as obtainable by reaction, for example, of the abovementioned alcohols - used to form the polyester polyols - with dialkyl carbonates, diaryl carbonates or phosgene.
  • Block copolymers bearing at least two hydroxyl groups and having at least two different blocks having polyether, polyester and/or polycarbonate structure of the type described above, especially polyether polyester polyols.
  • Polyhydroxy-functional fats and oils also called fatty acid polyols, especially natural fats and oils optionally modified with ketone resins, especially castor oil or reaction products of castor oil with ketone resins; or polyols obtained by chemical modification of natural fats and oils - called oleochemical polyols - for example the polyols obtained by epoxidation of unsaturated oils and subsequent ring opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils; or polyols obtained from natural fats and oils by degradation processes, such as alcoholysis or ozonolysis, and subsequent chemical linkage, for example by transesterification or dimerization, of the degradation products or derivatives thereof thus obtained.
  • fatty acid polyols especially natural fats and oils optionally modified with ketone resins, especially castor oil or reaction products of castor oil with ketone resins
  • polyols obtained by chemical modification of natural fats and oils called ole
  • Suitable degradation products of natural fats and oils are in particular fatty acids and fatty alcohols and also fatty acid esters, in particular the methyl esters (FAME), which can be derivatized to hydroxy fatty acid esters, for example by hydroformylation and hydrogenation.
  • FAME methyl esters
  • Polyhydrocarbon polyols also called oligohydrocarbonols, such as, for example, polyhydroxy-functional polyolefins, polyisobutylenes, polyisoprenes; polyhydroxy-functional ethylene/propylene, ethylene/butylene or ethylene/propylene/diene copolymers, as produced, for example, by Kraton Polymers; polyhydroxy-functional polymers of dienes, especially of 1 ,3- butadiene, which can especially also be prepared from anionic polymerization; polyhydroxy-functional copolymers of dienes, such as 1 ,3-butadiene, or diene mixtures and vinyl monomers, such as styrene, acrylonitrile, vinyl chloride, vinyl acetate, vinyl alcohol, isobutylene and isoprene, for example polyhydroxyfunctional acrylonitrile/butadiene copolymers, as can be prepared, for example, from epoxides or aminoalcohols and carboxyl-term
  • Particularly suitable polyols P are polyester polyols and polyether polyols, in particular polyoxyethylene polyols, polyoxypropylene polyols, and polyoxypropylene polyoxyethylene polyols, preferably polyoxyethylene diols, polyoxypropylene diols, polyoxyethylene triols, polyoxypropylene triols, polyoxypropylene polyoxyethylene diols, and polyoxypropylene polyoxyethylene triols.
  • polyol P consists of a mixture of diols and higher functional polyols, in particular polyether diols and polyols, preferably selected from the polyether diols and polyols just described above.
  • said polyol P comprises or consists of polyether polyols having an average OH-functionality of between 2 and 6.
  • said polyol P furthermore comprises polyester polyols, poly(meth)acrylate polyols, and/or polycarbonate polyols.
  • the first component A of the two-component composition preferably comprises between 50 wt.-% and 99 wt.-%, in particular between 75 wt.-% and 95 wt.-%, most preferably between 85 wt.-% and 90 wt.-%, based on component A, of polyol P
  • the first component A of the two-component composition according to the invention furthermore comprises water.
  • Water is added as foaming agent, as it reacts with isocyanate groups to form CO 2 , which effects a foaming of the composition.
  • the first component A of the two-component composition preferably comprises between 0.01 wt.-% and 2.0 wt.-%, in particular between 0.02 wt.-% and 1 .0 wt.-%, most preferably between 0.05 wt.-% and 0.5 wt.-%, based on component A, of water.
  • One of the components A or B, preferably the first component A, of the two- component composition also comprises at least one isocyanate trimerization catalyst.
  • Any compound that catalyzes the isocyanate trimerization reaction can be used as trimerization catalyst without particular restriction, such as for example tertiary amines, triazines, phosphines, and metal salt trimerization catalysts.
  • trimerization catalysts include aromatic compounds such as tris(dimethylaminomethyl)phenol, 2,4-bis(dimethylaminomethyl)phenol and 2,4,6-tris(dialkylaminoalkyl)hexahydro-S-triazine.
  • suitable metal salt trimerization catalysts are alkali metal salts of organic carboxylic acids. Preferred alkali metals are potassium and sodium. And preferred carboxylic acids are acetic acid and 2-ethylhexanoic acid.
  • Preferred metal salt trimerization catalysts are, for example, potassium acetate (commercially available as Polycat® 46 from Air Products and Catalyst LB from Huntsman) and potassium-2-ethylhexanoate (commercially available as Dabco® K15 from Air Products).
  • Suitable as trimerization catalyst furthermore trialkylphosphine compounds with alkyl groups having 1 to 8 carbon atoms, in particular tributylphosphine and trioctylphosphine.
  • Two or more different trimerization catalysts can be used in the two-component composition of the present invention.
  • the first component A of the two-component composition preferably comprises between 0.1 wt.-% and 5 wt.-%, in particular between 0.2 wt.-% and 2.5 wt.-%, most preferably between 0.3 wt.-% and 1 wt.-%, based on component A, of at least one trimerization catalyst.
  • One of the components A or B, preferably the first component A, of the two- component composition preferably also comprises at least one urethanization catalyst and/or at least one blowing catalyst, preferably both.
  • urethanization catalyst is a catalyst that catalyzes, preferably with high selectivity, the reaction between alcoholic hydroxyl groups and isocyanate groups, thus catalyzing the formation of a urethane group.
  • Urethanization is a reaction that occurs when component A containing polyol P is mixed with component B containing aromatic polyisocyante I. Such a reaction will proceed also spontaneously and uncatalyzed, albeit to a lesser extent, as aromatic isocyanates are reactive enough.
  • a urethanization catalyst is present in the composition such that this process is more controllable.
  • structural foam material F While to ultimate properties of structural foam material F are based on the trimerization reaction of isocyanate groups (catalyzed by the trimerization catalyst described above), also a partial urethane crosslinking takes place which improves the properties of the foam.
  • a urethanization catalyst is also denoted as “gelling catalyst”.
  • a “foaming catalyst” is a catalyst that catalyzes, preferably with high selectivity, the reaction between water and isocyanate groups, thus catalyzing the isocyanate hydrolysis and formation of gaseous carbon dioxide and an amine, the latter being able to react with a further isocyanate group under formation of a urea bond.
  • This reaction in particular the carbon dioxide formation occurring, is what enables foaming of the composition.
  • Such a reaction will proceed also spontaneously and uncatalyzed, albeit to a lesser extent, as aromatic isocyanates are reactive enough.
  • a blowing catalyst is present in the composition such that this foaming process is more controllable and occurs with a higher gas yield before full curing.
  • a compound may act as urethanization catalyst and foaming catalyst at the same time, but of course reduced selectivity for each respective reaction.
  • Suitable as urethanization catalyst and/or foaming catalysts are all known catalysts that accelerate the reaction of the isocyanate groups with hydroxyl groups of polyol P and/or water, especially compounds of tin, iron, bismuth, zinc, manganese, chromium, cobalt, copper, nickel, molybdenum, lead, cadmium, mercury, antimony, vanadium, titanium, aluminum, potassium or rare earth metals, especially organotin(IV) compounds such as dibutyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dibutyltin dichloride, dibutyltin diacetylacetonate or dioctyltin dilaurate, bismuth(lll) complexes, zinc(ll) acetate, zinc(ll) 2- ethylhexanoate, zinc(ll) laurate, zinc(ll) acetylacetonate, cobalt(ll
  • said blowing catalyst is an amine-based catalyst, preferably selected from the list 1 ,4-diazabicyclo[2.2.2]octane (DABCO), 1 ,8-diazabicyclo[5.4.0]undec- 7-ene (DBU), 1 ,5-diazabicyclo[4.3.0]non-5-ene (DBN), 2,2'-dimorpholinodiethyl ether (DMDEE), and other catalytically active compounds containing tertiary amino groups. Most preferred is ,4-diazabicyclo[2.2.2]octane (DABCO).
  • said urethanization catalyst is a metalorganic catalyst, preferably selected from organotin(IV) compounds such as dibutyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dibutyltin dichloride, dibutyltin diacetylacetonate or dioctyltin dilaurate, bismuth(lll) complexes, or zinc(ll) complexes.
  • organotin(IV) compounds such as dibutyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dibutyltin dichloride, dibutyltin diacetylacetonate or dioctyltin dilaurate, bismuth(lll) complexes, or zinc(ll) complexes.
  • the first component A of the two-component composition preferably comprises between 0.005 wt.-% and 1 wt.-%, in particular between 0.01 wt.-% and 0.5 wt.-%, most preferably between 0.02 wt.-% and 0.1 wt.-%, based on component A, of urethanization catalyst.
  • the first component A of the two- component composition preferably comprises between 0.1 wt.-% and 5 wt.-%, in particular between 0.01 wt.-% and 2.5 wt.-%, most preferably between 0.02 wt.-% and 0.5 wt.-%, based on component A, of blowing catalyst.
  • Foam stabilizer or surfactant Foam stabilizer or surfactant
  • One of the components A or B, preferably the first component A, of the two- component composition preferably also comprises at least one foam stabilizer.
  • a foam stabilizer is a surfactant that is able to stabilize a foam structure before the polymer matrix has fully cured. Such a foam stabilizer may optionally but preferably be used to improve the foam quality of structural foam F. Foam stabilizers may help in the early stages of the foaming process to improve the foam quality and the formed foam cells, when curing of the composition has not yet progressed sufficiently to stabilize the formed foam by the cured polymer matrix alone.
  • a foam stabilizer or surfactant is contained in the two-component composition.
  • Suitable as foam stabilizer are all known foam stabilizers commonly used in polyurethane or polyisocyanurate foams.
  • Preferred foam stabilizers are silicone- based foam stabilizers, for example silicone polymers or silicone-polyether copolymers.
  • suitable and preferred foam stabilizers are those available under the trade name line Tegostab® by Evonik, for example Tegostab® B 8870, Tegostab® B 8491 , Tegostab® B 8444, Tegostab® B 8460, and Tegostab® B 8523, as well as Dabco® DC193 (by Evonik).
  • the first component A of the two-component composition preferably comprises between 0.1 wt.-% and 5 wt.-%, in particular between 0.2 wt.-% and 2.5 wt.-%, most preferably between 0.3 wt.-% and 1 wt.-%, based on component A, of foam stabilizer.
  • Flame-retardant additive preferably comprises between 0.1 wt.-% and 5 wt.-%, in particular between 0.2 wt.-% and 2.5 wt.-%, most preferably between 0.3 wt.-% and 1 wt.-%, based on component A, of foam stabilizer.
  • One of the components A or B, preferably the first component A, of the two- component composition preferably also comprises at least one flame-retardant additive.
  • Flame-retardant additives are used in preferred embodiments with especially high requirements regarding flame-retardant properties. However, even without flameretardant additives the structural foam material F exhibits improved such properties compared to polyurethane foams of the state of the art.
  • addition of such an additive may bring additional benefits, such as easier compounding and application in case of liquid flame-retardant additives and improved mechanical properties in case of solid flame-retardant additives.
  • Suitable as flame-retardant additives are all commonly used flame retardants in the field of polyurethane and polyisocyanurate foam composition formulation.
  • Suitable as flame-retardant are especially aluminum hydroxide or magnesium hydroxide, and also especially organic phosphoric acid esters such as, in particular, triethyl phosphate, tricresyl phosphate, triphenyl phosphate, diphenyl cresyl phosphate, isodecyl diphenyl phosphate, tris(1 ,3-dichloro-2-propyl) phosphate, tris(2-chloroethyl) phosphate, tris(2-ethylhexyl) phosphate, tris(chloroisopropyl) phosphate, tris(chloropropyl) phosphate, isopropylated triphenyl phosphate, mono-, bis- or tris(isopropylphenyl) phosphates of different degrees of isopropylation, resorcinol bis(diphenylphosphate), bisphenol A bis(diphenylphosphate), ammonium polyphosphate
  • the flame-retardant additive may be solid or liquid at room temperature (23°C). It is also possible to use a mixture of two or more different flame-retardant additives, including a mixture or solid and liquid flame-retardant additives.
  • said flame-retardant additive is solid at 23°C.
  • said flame-retardant additive comprises or consists of ammonium polyphosphate. This additive surprisingly improves the compression modulus of the structural foam material F.
  • the amount of said flame-retardant additive within said structural flame-retardant foam material F is between 1 wt.-% and 10 wt.-%, preferably between 2 wt.-% and 7.5 wt.-%, more preferably between
  • the flame-retardant additive is preferably comprised in component A.
  • the amount of said flame-retardant additive within component A is between 2 wt.-% and 20 wt.-%, preferably between
  • the first component A of the two-component composition may comprise further optional additives, which are discussed further below.
  • the second component B of the two-component composition according to the invention comprises at least one polyisocyanate I; wherein polyisocyanate I is an aromatic polyisocyanate.
  • the second component B of the two-component composition according to the invention comprises at least one aromatic polyisocyanate I, in particular an oligomeric or polymeric polyisocyanate I.
  • Olemeric polyisocyanates are meant to be polyisocyanates which have been obtained by reacting at least two monomeric polyisocyanates, especially via a dimerization and/or trimerization reaction of the isocyanate groups. Thereby uretdione, isocyanurate and/or biuret units can be formed for example. However, oligomeric polyisocyanates still have at least two free isocyante groups per molecule. Processes for preparing oligomeric polyisocyanates are known to those skilled in the art.
  • Aromatic polyisocyanates denote polyisocyanates where the isocyanate groups are directly bonded to an aromatic ring. Most common aromatic polyisocyanates are based on diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI), wherein MDI-based polyisocyanates are preferred.
  • MDI diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate
  • TDI toluene-2,4-diisocyanate
  • the proportion of monomeric polyisocyanates, in particular diisocyanates, in the polyisocyanate I is at most 1 wt.%, especially at most 0.5 wt.%, preferably at most 0.3 wt.%, particularly at most 0.2 wt.%, more preferred at most 0.1 wt.%, most preferably less than 0.1 wt.%, based on the weight of component B.
  • the overall content of monomeric polyisocyanates, in particular diisocyanates, in the two-component compositions is below 0.5 wt.-%, preferably below 0.4 wt.-%, more preferably below 0.3 wt.-%, in particular below 0.2 wt.-%, most preferably below 0.1 wt.-%, based on the total two-component composition.
  • the component B may comprise at least one monomeric polyisocyanate, in particular diisocyanate, but in some embodiments it may be desirable to keep the content of monomeric polyisocyanates at low level, for example below 0.1 wt.-%.
  • removal of unwanted excess monomers can be achieved by distillation or extraction, preferably by thin-film distillation under high vacuum or by extraction with suitable solvents that are inert toward isocyanate groups.
  • suitable solvents that are inert toward isocyanate groups.
  • the at least one oligomeric polyisocyanate comprised in polyisocyanate I has an uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure.
  • Particularly preferred are biuret, allophanate, isocyanurate and/or iminooxadiazinedione structures.
  • isocyanurate structures are particularly preferred.
  • the at least one polyisocyanate I consists to an extent of at least 50 mol.%, preferably at least 60 mol.%, more preferably at least 70 mol.%, preferably at least 80 mol.% or 90 mol.%, based on the sum total of all uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and oxadiazinetrione structures present in the polyisocyanate composition, of an isocyanurate structure.
  • the at least one oligomeric or polymeric polyisocyanate I comprises one or more oligomeric polyisocyanates which are based on oligomers of diisocyanates.
  • the at least one oligomeric polyisocyanate I comprises or consists of oligomers of diphenylmethane 4,4'-, 2,4'-, and/or 2,2'- diisocyanate.
  • the polyisocyanate composition comprises a mixture of at least two oligomeric polyisocyanates whereby the at least two oligomeric polyisocyanates differ in their chemical structure and at least one of them is based on aromatic isocyanates, in particular MDI.
  • said oligomeric or polymeric polyisocyanate I comprises both an isocyanurate of hexamethylene 1 ,6-diisocyanate (HDI) and polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI).
  • Suitable oligomers, polymers, and derivatives suitable as oligomeric polyisocyanate I are especially those derived from diphenylmethane 4,4'-, 2,4'-, and/or 2, 2'-diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI). Preferred are those derived from MDI.
  • Particularly suitable commercially available examples of oligomeric polyisocyanates I are in particular TDI oligomers such as Desmodur® IL (from Covestro); and also mixed isocyanurates based on TDI/HDI, for example as Desmodur® HL (from Covestro).
  • MDI forms that are liquid at room temperature are also particularly suitable.
  • modified MDI which are mixtures of MDI with MDI derivatives such as, in particular, MDI carbodiimides or MDI uretonimines or MDI urethanes, known by trade names such as Desmodur® CD, Desmodur® PF, Desmodur® PC (all from Covestro) or Isonate® M 143 (from Dow), and mixtures of MDI and MDI homologs (polymeric MDI or PMDI), available under trade names such as Desmodur® VL, Desmodur® VL50, Desmodur® VL R10, Desmodur® VL R20, Desmodur® VH 20 N, and Desmodur® VKS 20F (all from Covestro), Isonate® M 309, Voranate® M 229 and Voranate® M 580 (all from Dow) or Lupranat® M 10 R (from BASF).
  • modified MDI are mixtures of MDI with MDI derivatives such as, in particular
  • said oligomeric or polymeric polyisocyanate I comprises or consists of polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2, 2'-diisocyanate (PMDI).
  • said oligomeric or polymeric polyisocyanate I comprises or consists of a polyurethane polymer containing isocyanate groups.
  • This isocyanate-functional polymer is preferably prepared beforehand, by combining the at least one monomeric aromatic diisocyanate and the at least one polyol in a molar NCO/OH ratio of at least 1.1 , in particular at least 1 .3, preferably at least 1 .5, more preferably at least 1 .8, in the absence of moisture at a temperature in the range of 20 to 160 °C, preferably 40 to 140 °C, optionally in the presence of a suitable catalyst.
  • This synthesis is well known in the field.
  • Suitable as polyols for this purpose are all polyols described further above as polyol P, and preferred embodiments of these polyols correspond to the preferred embodiments of polyol P.
  • Suitable as monomeric diisocyanates for this purpose are all monomeric diisocyanates, in particular diphenylmethane 4,4'-, 2,4'-, and/or 2, 2'-diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI). Preferred is MDI.
  • a preferred isocyanate-functional polymer comprised in polyisocyanate I has a content of monomeric diisocyanate, in relation to the total polymer, of below 0.5 weight-%, preferably below 0.3 weight-%, more preferably below 0.2 weight-%, most preferably below 0.1 weight-%.
  • Such a low monomer isocyanate-functional polymer allows curable compositions which have a content of monomeric diisocyanates of below 0.1 weight-% and are safe to use without special protective measures and do not require hazard labelling.
  • the reaction is preferably conducted at a molar NCO/OH ratio of at least 3/1 , preferably 3/1 to 10/1 , particularly 3/1 to 8/1 , followed by the removal of most of the remaining monomeric diisocyanate by a distillation process, preferably by thin film distillation or short path distillation under vacuum.
  • Another possibility to obtain an isocyanate-functional polymer with a low content of monomeric diisocyanate is by chemically reducing the content of monomeric diisocyanates, for example by adding small amounts of water, preferably in combination with a surfactant.
  • said polyisocyanate I is selected from polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI) and/or prepolymers based on diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (MDI).
  • PMDI polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate
  • MDI 2,2'-diisocyanate
  • polyisocyanate I is polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI) having an NCO-functionality of between 2.1 and 3.0.
  • PMDI 2,2'-diisocyanate
  • the second component B of the two-component composition preferably comprises between 50 wt.-% and 100 wt.-%, in particular between 75 wt.-% and 95 wt.-%, most preferably between 85 wt.-% and 90 wt.-%, based on component B, of polyisocyanate I.
  • the two-component composition may comprise further substances that are reactive with isocyanates, especially
  • - di- or polyfunctional alcohols especially those having an average molecular weight M n in the range from 250 to 500 g/mol, especially ethoxylated and/or propoxylated bisphenol A, bisphenol F, trimethylolpropane or glycerol,
  • - chain extenders especially diols having a molecular weight M n in the range from 62 to 150 g/mol, especially ethylene glycol, propane-1 ,3-diol, butane-1 ,4-diol or pentane-1 ,5-diol,
  • - latent hardeners such as, in particular, ketimines, aldimines or oxazolidines.
  • the two-component composition may additionally comprise further constituents in either one or both of components A and B, especially the following auxiliaries and admixtures:
  • - fillers especially ground or precipitated calcium carbonates, optionally coated with fatty acids, especially stearates, barytes, quartz flours, quartz sands, dolomites, wollastonites, kaolins, calcined kaolins, sheet silicates, such as mica or talc, zeolites, aluminum hydroxides, magnesium hydroxides, silicas, including finely divided silicas from pyrolysis processes, industrially produced carbon blacks, graphite, metal powders, for example of aluminum, copper, iron, silver or steel, PVC powders or hollow beads;
  • fatty acids especially stearates, barytes, quartz flours, quartz sands, dolomites, wollastonites, kaolins, calcined kaolins, sheet silicates, such as mica or talc, zeolites, aluminum hydroxides, magnesium hydroxides, silicas, including finely divided silicas from pyrolysis processes, industrially produced carbon blacks, graphite
  • - fibers especially glass fibers, carbon fibers, metal fibers, ceramic fibers, polymer fibers, such as polyamide fibers or polyethylene fibers, or natural fibers, such as wool, cellulose, hemp or sisal;
  • nanofillers such as graphene or carbon nanotubes
  • - dyes especially titanium dioxide, chromium oxide, iron oxides or organic pigments;
  • plasticizers especially phthalates, terephthalates, trimellitates, adipates, sebacates, azelates, succinates, citrates, benzoates, diesters of ortho- cyclohexanedicarboxylic acid, acetylated glycerol, monoglycerides, fatty acid methyl or ethyl esters, also called “biodiesel", natural or modified vegetable oils, organic phosphoric or sulfonic esters, sulfonamides, urethanes, high-boiling hydrocarbons, polybutenes, polyisobutylenes, polystyrenes or chloroparaffins;
  • hydrocarbon resins such as hydrocarbon resins, natural or synthetic waxes or bitumen
  • urea compounds especially urea compounds, sheet silicates such as bentonites, derivatives of castor oil, hydrogenated castor oil, polyamides, polyurethanes, fumed silicas or hydrophobically modified polyoxyethylenes;
  • - desiccants especially molecular sieves, calcium oxide, monooxazolidines such as Incozol® 2 (from Incorez) or orthoformic esters;
  • - adhesion promoters especially titanates or organoalkoxysilanes such as aminosilanes, mercaptosilanes, epoxysilanes, vinylsilanes, (meth)acrylosilanes, carbamatosilanes, alkylsilanes, S-(alkylcarbonyl)mercaptosilanes, aldiminosilanes or oligomeric forms of these silanes;
  • thermoplastic polymers for example homo- or copolymers of unsaturated monomers, especially from the group comprising ethylene, propylene, butylene, isobutylene, isoprene, vinyl acetate and alkyl (meth)acrylates, especially polyethylenes (PE), polypropylenes (PP), polyisobutylenes, ethylene-vinyl acetate copolymers (EVA) and atactic poly-a- olefins (APAO);
  • PE polyethylenes
  • PP polypropylenes
  • EVA ethylene-vinyl acetate copolymers
  • APAO atactic poly-a- olefins
  • Such additives may present as constituents of the first component A or of the second component B.
  • Substances reactive with isocyanate groups are preferably a constituent of the first component A. It may be advisable to subject certain constituents to chemical or physical drying before mixing them into the respective component.
  • Another aspect of the present invention is a foamable two-component composition consisting of a first component A and a second component B; wherein
  • the second component B comprises
  • polyisocyanate I is polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'- diisocyanate (PMDI) having an NCO functionality of between 2.1 and 3.0; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyol P in the two-component composition is higher than 2.
  • a flameretardant additive with an amount of between 1 wt.-% and 7.5 wt.-%, based on the total two-component composition
  • polyisocyanate I is polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'- diisocyanate (PMDI) having an NCO functionality of between 2.1 and 3.0; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyol P in the two-component composition is higher than 2.
  • said polyol P consists of polyether polyols.
  • said flame-retardant additive is solid at 23°C, more preferably comprising or consisting of ammonium polyphosphate.
  • said molar ratio of all NCO groups of polyisocyanate I in the two-component composition to all hydroxyl groups of polyol P in the two-component composition is higher than 2.5.
  • the amount of said flame-retardant additive within said 3 wt.-% and 6 wt.-%, based on the total two-component composition is higher than 2.5.
  • said two-component composition furthermore contains an urethanization catalyst, a blowing catalyst, a foam stabilizer, a surfactant, a colorant, an anti-oxidant, a nucleating agent, a filler, a plasticizer, and/or other additives used in polyisocyanurate foam formulations.
  • the mixing ratio of the first component A and the second component B of the two- component composition depends on the formulation of the individual components and may be tailored to the requirements of the application process.
  • the amounts of polyol A and polyisocyanate I and/or the mixing ratio of components A and B are adjusted such that the molar ratio of all NCO groups in the two- component composition to all OH groups in the two-component composition is higher than 2, in particular higher than 2.5, in particular higher than 3, more preferably higher than 3.5.
  • a preferred upper limit for the molar ratio of all NCO groups of polyisocyanate I in the two-component composition to all hydroxyl groups of polyols P in the two- component composition is 6, in particular 5.
  • the reason for this excess of NCO groups compared to OH groups is the two-step curing mechanism described further below and the formation of an isocyanurate- crosslinked polymer network.
  • the excess of NCO groups allows for the trimerization reaction of NCO groups to proceed after most or all OH groups from the polyol have depleted due to the faster urethane-forming reaction. Furthermore, additional NCO groups are consumed during the foaming reaction.
  • the mixing ratio in parts by weight between the first component A and the second component B is in the range from 1 :0.1 to 1 :1.5, in particular from 1 :0.2 to 1 :1.
  • the mixing ratio in parts per volume between the first component A and the second component B is in the range from 1 :0.2 to 1 : 1 .8, especially 1 :0.3 to 1 : 1 .2.
  • Another aspect the present invention is directed to the use of a two-component composition as described before, including all embodiments and preferences, as structural reinforcement and/or encapsulating material, particularly for the manufacturing of battery boxes, in particular battery boxes for electric vehicles.
  • the two-component composition described before including all preferred embodiments for all possible components A and B, is advantageously used as structural foam material.
  • said two-component composition as described before, including all embodiments and preferences, is used as structural foam material for the manufacturing of battery boxes, in particular battery boxes for electric vehicles.
  • Another aspect of the present invention is a method for producing a battery box, by using a two-component composition as described before, including all embodiments and preferences, as structural foam material.
  • this method is a method of encapsulating an electric cell within a battery box, the method comprising:
  • liquid, foamable two-component composition - mixing a liquid, foamable two-component composition and transferring it into an enclosed space defined by a wall of a battery box case, said case containing at least one electric cell, the cell being at least partially surrounded by the mixed liquid, foamable two-component composition; - allowing the mixed liquid, foamable two-component composition to react, thereby forming a cured rigid polyisocyanurate foam; the liquid, foamable two-component composition before mixing comprising: a first component comprising an isocyanate reactive compound and water; a second component comprising an isocyanate compound; and at least one of the first and second component including at least one isocyanate trimerization catalyst; and at least one of the first and second component including a flame-retardant additive in an amount less than 10% by weight based on the total weight of the liquid two- component composition.
  • the resulting battery box is a battery box as described further above, wherein said cured rigid polyisocyanurate foam corresponds to structural foam material F described throughout this document.
  • Conveying and mixing of the two components A and B may be done with any suitable equipment. Preferred are conveying of the two components by pumps and mixing with a static or dynamic mixer, preferably however using high pressure impingement mixing. The mixed composition may then be applied into or onto the battery box using elevated pressure, for example by pouring or spraying, and allowing it to cure after application.
  • the curing step including the foaming, occurs at room temperature or faster at elevated temperatures, catalyzed by the trimerization catalyst and optionally present urethanization and/or blowing catalysts.
  • the trimerization reaction occurs somewhat slower than the urethanization reaction or the blowing reaction and is supported (accelerated) by heat, which may also stem from the exothermic curing reaction, in particular the urethanization reaction.
  • electric cells embedded in the mixed and partially cured two-component composition may still be moved or replaced, as the partially cured two-component composition has not yet developed the full rigidity and mechanical strength, which is obtained after completion of the trimerization reaction.
  • the trimerization curing reaction may take days or weeks to fully complete, which is however not a problem.
  • the material already has sufficient stability and strength that the battery box can be moved or even incorporated into, e.g., an electric vehicle.
  • the heat generated during charging cycles of the battery which may reach for example 60°C during fast charging cycles, will support and accelerate the trimerization curing and thus the final curing of the material.
  • it is also possible to accelerate trimerization curing by placing the battery box under slight heating conditions for a short time, which however should not exceed approximately 60° to 80°C.
  • Another aspect of the present invention is a rigid, structurally reinforcing foam with flame-retardant properties, obtained from mixing and curing the two-component composition as described further above.
  • said rigid, structurally reinforcing foam with flame-retardant properties corresponds to structural foam material F described throughout this document.
  • the structural foam material F of the present invention offers vastly superior mechanical properties, in particular a higher compression modulus and softening point. Furthermore, the flame-retardant properties are intrinsically better compared to polyurethane foams of the state of the art. This means that structural foam material F according to this invention is a much better structural, thermal and stiffening resistant material when used in battery boxes and can sustain much higher stress forces and much higher temperature exposure than polyurethane foams.
  • Polyurethane foams start to soften and loose structural properties at much lower temperature (normally between 70°C and 90°C), while structural foam material F starts to soften at much higher temperatures, for example 170°C to about 180°C and maintains the structural properties (compression strength and compression modulus) at high temperature exposure. Further advantageous implementations of the invention are evident from the exemplary embodiments.
  • the respective components A and B of the exemplary two-component compositions F1 to F6 were prepared individually by adding the respective ingredients shown in Table 2 to stand mixer equipped with a propeller blade. Subsequently the mixture was mixed for 2 minutes at 1500 rpm.
  • both respective components A and B were mixed in a volume ratio A : B as indicated in Table 2 for each experiment, which corresponds to a weight ratio A : B as indicated in Table 2 for the same experiment.
  • the volume (v/v) and weight (w/w) ratios indicated in Table 2 for each experiment are normalized to 1 part (weight or volume) of component A.
  • 1 weight part of component A was mixed with 0.56 weight parts of component B.
  • 1 volume part of component A was mixed with 0.66 volume parts of component B.
  • Table 2 furthermore shows the resulting NCO index (molar ratio of all NCO groups of polyisocyanate I to all hydroxyl groups of polyols P in mixture) for each respective experiment.
  • NCO index molecular weight of polyethylene glycols
  • Table 2 furthermore shows the resulting NCO index (molar ratio of all NCO groups of polyisocyanate I to all hydroxyl groups of polyols P in mixture) for each respective experiment.
  • experiment F2 3.28 mol NCO groups were present initially after mixing per 1 mol of OH groups from the available polyols.
  • Compression modulus was measured according to ASTM D1621-16 (Compressive Properties of Rigid Cellular Plastics) on fully cured and expanded samples, using a load rate of 0.01 /s.
  • Foam density was measured according to ASTM D 1475-13 on fully cured and expanded samples.
  • Dynamic mechanical analysis (DMA) measurements were conducted with a TA instruments model- Q850
  • the glass transition temperatures (Tg) were determined from the phase angle tan 5 which corresponds to the ratio of the loss modulus to the storage modulus.
  • the samples were heated from 25°C to 200°C at a heating rate of 3°C min -1 .
  • the frequency was kept constant at 1 Hz (amplitude 20 pm).
  • Tg values were determined on samples after curing at room temperature for 24h.
  • UL94 rating (flammability properties) of cured and expanded samples was measured according to LIL94 standard (Test for Flammability of Plastic Materials for Parts in Devices and Appliances) on fully cured and expanded samples having a thickness of 3 mm. Evaluation was done for vertical samples and classification according to V-2, V-1 , and V-0 (best rating) as defined in the test specifications.
  • Table 3 shows that the compositions according to the invention exhibit vastly superior mechanical properties, in particular compression modulus, compared to a 2C-PU foam material (F2).
  • the measured Tg value (for F3) is far outside the working temperature of electric vehicle batteries.
  • the foams according to the invention show high volumetric expansion (low density) and superior flame-retardant properties compared to a 2C-PU foam material (F2).

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Abstract

The present invention describes a battery pack comprising a structural foam material; wherein said structural flame-retardant foam material is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component and a second component; wherein - the first component comprises at least one polyol; and - water; and - the second component comprises at least one polyisocyanate; wherein at least one of the components furthermore contains at least one isocyanate trimerization catalyst; and wherein said polyisocyanate is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of the polyisocyanate in the two- component composition to all hydroxyl groups of the polyol in the two-component composition is higher than 2.

Description

BATTERY BOX COMPRISING A FOAMED POLISOCYAN URATE MATERIAL
Technical field
The invention relates to a battery box comprising a structural foam material and a method of encapsulating an electric cell within a battery box and a foamable two- component composition.
Background art
Battery technology in electric vehicles is developing fast, alongside with the significant interest e-mobility has received in the past years. In this regard, the manufacturing of electric vehicle batteries has seen significant progress in terms of economically viable and efficient production processes. Two of the current trends that are relevant for this field of application are cell-to-body designs of battery packs (also called structural battery packs) and the recently increased adoption of battery cells of cylindrical form.
In order to decrease complexity and weight, the industry has moved from cell- module-pack design to cell-to-pack or cell-to-body design. That is, cells are directly bonded to the battery pack or battery box, hence avoiding the need of intermediate assemblies of battery packs and all the related inefficiencies in term of number of parts, weight, cost, and complexity.
For example, cell-to-pack designs are implemented by bonding battery cells, for example cylindrical battery cells, to a cooling plate or cooling ribbon with a thermal interface material. The thermal interface material serves two purposes: First, it provides a mechanical fastening system to keep the cells in place and second, it provides mechanical and thermal protection within the whole battery assembly. The mechanical and adhesive performance of such thermal interface materials is of key importance, and it therefore should have the characteristics of a thermally conductive adhesive.
This assembly method using battery cells furthermore has a significant amount of free volume within the battery box, located between the individual cells, which is therefore filled with an injectable or pourable material, mostly with a foam-like cellular structure, in order to reduce weight and to provide shock-absorbing properties. Cell-to-pack assembly requires even more mechanical reinforcement than traditional battery box designs.
The functions of this foam are to keep the cells in position during their work life, and to thermally insulate cells from each other. The latter is a safety function in case of cell malfunctions: if one cell heats up uncontrollably, as it is a risk connected to current lithium-based battery cells, then the neighboring cells need to be protected from excessive temperatures, or they will experience a thermal degradation and generate additional heat and even ignite, possibly affecting further neighboring cells. This catastrophic event is called thermal runaway.
In order to reduce the overall vehicle weight, the material used for filling the interstitial volume is typically expanded to a foam. Furthermore, additional foam material is often attached outside the battery box as intermediate layer between the battery box and further boxes or the car body, or within the battery box, i.e. attached to the battery lid, a reinforcing layer for enclosures within the battery box, or to fill hollow ribs within the battery box.
Foams used in traditional cell-to-pack design do not have an important mechanical function and are usually soft to semi-rigid, expanded two-component polyurethane (2C-PU) foams. 2C-PU foams and other traditionally used foam materials however commonly do not provide enough mechanical reinforcement required for cell-to- pack assemblies.
During processing or manufacturing of the battery, such foams must however cure with a limited exotherm in order to avoid damage to the cells, but they should also cure fast enough in order not to decrease the productivity of the battery assembly line.
Structural battery packs, i.e., battery boxes containing a structural foam, are an evolution of this concept. In this approach, the foam material is much more stiff and mechanically strong than in traditional cell-to-pack designs just described. The stiffness of the cells in this approach beneficially helps to increase the mechanical and driving dynamics of the vehicle.
The foam material however has still to fulfill the basic functions regarding thermal insulation as described above. Additionally, to provide the structural strength, the material needs to strongly connect all components of a battery pack, such as the cells, and for this purpose needs to have good adhesion to a multitude of materials. Furthermore, the material needs to have high stiffness for the battery pack to contribute to the overall rigidity of the vehicles. High mechanical properties are also important to prevent physical damage to the cells in case of high- speed impacts. It is also important to achieve the desired mechanical properties over the whole temperature range of use, typically from -20°C to 65°C. The glass transition of the material used should be outside of this range and the drop of stiffness with increased temperature needs to be as limited as possible. In case of a thermal event, it is advantageous if the potting material can withstand high temperatures for extended amounts of time with only limited degradation.
The implementation of such structural battery packs is usually achieved with a 2C- Pll material having a high concentration of reactive groups, which provides the desired mechanical properties due to high degree of cross-linking, but in turns exacerbates the exothermic reaction during its curing and makes temperature control during processing more challenging.
US2022209343A1 , for example, discloses such a 2C-PU material and method of potting an electric cell, whereby high mechanical stability and flame-retardant properties are obtained. The 2C-PU material contains a liquid flame-retardant additive and a blowing agent and in exemplary shown embodiments comprises a curing component based on monomeric and/or polymeric MDI. While the flameretarding properties of the cured material are sufficient for producing battery packs, care has to be taken during production that the exotherm icity of the curing material does not exceed levels that could damage the electric cells during assembly. Furthermore, the mechanical properties, in particular the compression modulus, measured according to ASTM D1621 , of 2C-PU foams are often insufficient to be fully suitable as structural foams in battery boxes.
Thus, there is still a need for new and improved structural foam materials suitable for the production of battery boxes or battery packs that overcome the aforementioned disadvantages and provide novel benefits. Disclosure of the invention
It is an object of the present invention to provide a battery box comprising a structural foam material which exhibits excellent mechanical properties, especially regarding compressive strength and reinforcing abilities. Such a battery box should have improved stability and, especially in preferred embodiments, excellent flameretardant properties, and should be manufactured in an efficient and inexpensive manner. The structural foam material is based on a foamable two-component composition that is highly suitable for the production of structural battery packs using cell-to-body design. This material should after curing be rigid and mechanically strong enough to provide the desired stability of the battery boxes produced therewith. The material should cure with very limited exotherm icity to avoid thermal damage to the battery pack components such as battery cells. Additionally, the cured foam material should exhibit a glass transition temperature (Tg) outside the thermal range that is relevant for electric vehicle batteries. Lastly, the material should in its cured state have high and long-lasting thermomechanical stability.
Surprisingly, it has been found that all these objects can be achieved with the battery box comprising a structural foam material according to independent claim 1.
Specifically, in a first aspect the present invention is related to a battery box comprising a structural foam material F, wherein said structural foam material F is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B; wherein
- the first component A comprises
- at least one polyol P; and
- water; and
- the second component B comprises
- at least one polyisocyanate I; wherein at least one of the components A and B furthermore contains at least one isocyanate trimerization catalyst; and wherein polyisocyanate I is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyols P in the two-component composition is higher than 2.
The battery box comprising a structural foam material according to claim 1 surprisingly offers distinct advantages compared to battery boxes of the state of the art produced using cell-to-body design with 2C-PU foams. More specifically, battery boxes according to claim 1 exhibit better mechanical stability and in particular flame resistance than battery boxes comprising polyurethane foams. Additionally, the structural foam material comprised in the battery box according to claim 1 after curing exhibits a Tg outside of the usage range of electric vehicle batteries and shows exceptional thermomechanical stability and shock absorbing properties. Lastly, battery boxes according to claim 1 can be manufactured in a simple and efficient manner. The structural foam may be used as encapsulating foam to fasten, reinforce, and stabilize the electric cells within the battery box, but it may also be used as insulation, sealant, gap filler, or foamed adhesive within, on, or outside the battery box, or as protective foam layer between individual battery boxes within a battery box assembly. In all these cases the structural foam with high close cell content offers outstanding thermal insulation, highest level of thermal stability (highest thermal decomposition temperature of the all isocyanatebased chemical structures), and structural reinforcement even on high temperature (i.e. , it maintains its storage modulus over broad range of temperature), shock and noise absorption and superior flame-retardancy in particular in preferred embodiments.
Accordingly, in a second aspect the present invention is related to a method of encapsulating an electric cell within a battery box according to this invention, by using a liquid, foamable two-component composition, which is the subject-matter of independent claim 21 . In a third aspect the present invention is related to a foamable two-component composition that is optimized for use in battery boxes according to the present invention, which is the subject-matter of independent claim 23.
Such a foamable two-component composition cures into a rigid, structurally reinforcing foam with flame-retardant properties, which is the subject-matter of independent claim 30 and which constitutes a fourth aspect of the present invention.
Particularly preferred embodiments are outlined throughout the description and the dependent claims.
Ways of carrying out the invention
A first aspect of the present invention is directed to a battery box comprising a structural foam material F, wherein said structural foam material F is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B; wherein
- the first component A comprises
- at least one polyol P; and
- water; and
- the second component B comprises
- at least one polyisocyanate I; wherein at least one of the components A and B furthermore contains at least one isocyanate trimerization catalyst; and wherein polyisocyanate I is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyols P in the two-component composition is higher than 2.
The prefix “poly” in substance names such as “polyol”, “polyisocyanate”, “polyether” or “polyamine” in the present document indicates that the respective substance formally contains more than one of the functional group that occurs in its name per molecule.
In the present document the term “polymer” firstly encompasses a collective of macromolecules that are chemically uniform but differ in the degree of polymerization, molar mass, and chain length, said collective having been produced by a “poly” reaction (polymerization, polyaddition, polycondensation). The term secondly also encompasses derivatives of such a collective of macromolecules from “poly” reactions, i.e. , compounds that have been obtained by reactions, for example additions or substitutions, of functional groups on defined macromolecules and that may be chemically uniform or chemically nonuniform. The term further encompasses so-called prepolymers too, i.e., reactive oligomeric initial adducts, the functional groups of which are involved in the formation of macromolecules.
The term “polyurethane polymer” encompasses all polymers produced according to the so-called diisocyanate polyaddition process. This also includes polymers that are virtually or completely free of urethane groups. Examples of polyurethane polymers are polyether polyurethanes, polyester polyurethanes, polyether polyureas, polyureas, polyester polyureas, polyisocyanurates, and polycarbodiimides.
In the present document, “molecular weight” is understood to mean the molar mass (in grams per mole) of a molecule or a molecule residue. “Average molecular weight” refers to the number average Mn of a polydisperse mixture of oligomeric or polymeric molecules or molecule residues, which is typically determined by gelpermeation chromatography (GPC) against polystyrene as standard.
In the present document, "room temperature" refers to a temperature of 23°C. Percent by weight values, abbreviated to % by weight, refer to the proportions by mass of a constituent in a composition based on the overall composition, unless otherwise stated. The terms “mass” and “weight” are used synonymously in the present document.
A “primary hydroxyl group” refers to an OH group attached to a carbon atom having two hydrogens.
In this document, the “pot life” refers to the time within which, after mixing the two components, the polyurethane composition can be processed before the viscosity resulting from the progression of the crosslinking reaction has become too high for further processing.
The term “strength” in the present document refers to the strength of the cured composition, with strength meaning in particular the compression strength and compression modulus, particularly measured according to ASTM D1621 .
All industry standards and norms mentioned in this document relate to the versions valid at the date of first filing, if not otherwise specified.
A composition is referred to as “storage-stable” or “storable” when it can be stored at room temperature in a suitable container over a prolonged period, typically over at least 3 months up to 12 months or more, without this storage resulting in any change in its application or use properties to an extent relevant to its use.
The “open time” or “processing time” refers to the period of time in which the composition can be worked or reworked after the curing process has commenced. “Room temperature” refers to a temperature of 23°C.
A “battery box” within the meaning of this invention is understood as an initially at least partially hollow body that comprises at least one electric cell (in most cases a series of connected electric cells) and a housing or battery case at least partially surrounding said electric cell by walls. The walls are normally made of metal or alloys, in particular aluminum, or of plastics or any other suitable rigid material. The term battery box can also be understood as “battery pack” or even “battery module”, if satisfying the aforementioned definition. Normally, battery boxes have several walls that define the hollow body and preferably a removable lid to fully close the battery box.
The term “encapsulating” in connection with the method of encapsulating an electric cell within a battery box according to this invention means that the result of said method is that at least one electric cell is at least partially surrounded by the cured foam material after having performed said method. In preferred embodiments, the electric cells are firmly surrounded by the foam material at least to such an extent that they are held in place and the cells are fully restricted in their movement by the foam material.
The battery box according to the invention includes at least one electric cell and a battery case or housing, as well as a structural foam material F. In some embodiments, the at least one electric cell may be positioned within the battery case and encapsulated in the structural foam material F. The electric cell may be any suitable shape but generally is cylindrical. The battery case may be any suitable shape for retaining the at least one electric cell, and which generally has a bottom, a top (which may be a removable lid), and several walls defined therebetween, connecting the bottom and the top. The bottom of the battery case defines an inner surface and an outer surface; each wall of the battery case defines an inner surface and an outer surface. The battery case defines an enclosed space having an internal volume. In some embodiments, the structural foam material F is positioned within the battery case and occupies a portion of the internal volume of the battery case. In particular, the structural foam material F is positioned in contact with the at least one electric cell and especially at least partially surrounding the at least one electric cell. In the same or other embodiments, structural foam material F is positioned between the walls of the battery case and the lid (or cover), and/or between ribs or sub-cavities within the battery case.
In the same or other embodiments, the structural foam material F is positioned outside the battery case. In these embodiments, the structural foam material F may be in contact with the bottom, the top, or any wall of the battery case. For example, the structural foam material F may be positioned between the outer surface of the bottom of the battery case and a cooling plate. In the same or further embodiments, the structural foam material F may be positioned between the outer surface of the battery case and surface of another object, for example the outer surface of another battery case or the inner surface of an automobile chassis or a container wherein the battery box is installed.
A plurality of electric cells may be used to form a battery within the battery box. For example, multiple electric cells may be combined to form a single battery that has a higher voltage or amperage than a single electric cell.
The wires for connecting the electric cells may be combined in electric communication such that the electric current from the electric cells is combined, for example to form a battery having a combined current or voltage. The battery box may be used to power any of a number of applications, such as a household appliance, outdoor electrical equipment, or a vehicle such as a car or a boat or aircraft, preferably an electric vehicle.
In preferred embodiments, the electric cells are positioned in the structural foam material F, and at least partially surrounded or in close contact with the structural foam material F. In instances where the battery box contains multiple electric cells, the structural foam material F can be positioned around each electric cell, and in the gap or spaces defined between individual electric cells. The structural foam material F may be positioned between the electric cell or electric cells and the battery case to provide mechanical support to the electric cell or electric cells.
In embodiments where several electric cells are at least partially surrounded by structural foam material F the electric cells should preferably be positioned with a suitable distance between adjacent electric cells such that a suitable thickness of structural foam material F is located positioned between adjacent electric cells to provide sufficient shock dampening to prevent damage to the electric cells and preferably to inhibit a fire hazard in cases where an electric cell ignites. The size of the space or gap between adjacent electric cells and/or inner walls of the battery case can be selected based on a number of variables, including but not limited to, the size and/or weight of each electric cell, the operating temperature of each electric cell, the dimensions of each electric cell, and the intended use of the battery box. In some examples, the size of the space between adjacent electric cells may be from greater than 0 mm to 20 mm, preferably from 0.25 mm to 10 mm, in particular from 0.50 mm to 5 mm, especially from 0.75 mm to 2 mm, although battery modules having additional configurations are further contemplated.
In some embodiments, the structural foam material F may be formed outside the battery case including openings having a suitable shape and size to later hold the electric cells firmly in place when they are inserted.
In more preferred embodiments, the structural foam material F may be added after first arranging the electric cells into the desired final position, for example, held together with wire or within the battery case. The electric cells may be held in place in spatial relationship with one another using a mold or a scaffolding. The electric cells may be held in place and positioned within a mold or other encasing surrounding the electric cells. In further examples, the electric cells may be arranged in a desired final position in spatial relationship to one another and placed within the battery case, for example resting on the inside surface of the bottom of the battery case. Once the desired arrangement of the electric cells is attained, the structural foam material F may be formed by mixing a liquid, foamable two-component composition as described further below and transferring it into an enclosed space defined by a wall of a battery box case, said case containing at least one electric cell, the cell being at least partially surrounded by the mixed liquid, foamable two-component composition and allowing the mixed liquid, foamable two-component composition to react, thereby forming a cured rigid polyisocyanurate foam, which constitutes the structural foam material F. In some of these embodiments, the mixed liquid, foamable two-component composition can flow through the gap between adjacent electric cells and settle at a level height around the electric cells and in the gap or spaces defined between the electric cells. For example, the mixed liquid, foamable two-component composition may be poured, sprayed, or injected into the battery case having the electric cells arranged within. The mixed liquid, foamable two-component composition preferably has sufficient flowability before curing to permit the mixed liquid, foamable two-component composition to flow through the spaces defined by the gap between the adjacent electric cells and/or between an electric cell and the battery case. The liquid encapsulating composition preferably has sufficient flowability to settle at a substantially level height before curing to form a cured rigid polyisocyanurate foam, which constitutes the structural foam material F.
Structural flame-retardant foam material F
The battery box according to the invention comprises a structural foam material F. The structural foam material F is a foamed, at least partially polyisocyanurate- crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B; wherein
- the first component A comprises - at least one polyol P; and
- water; and
- the second component B comprises
- at least one polyisocyanate I; wherein at least one of the components A and B furthermore contains at least one isocyanate trimerization catalyst; and wherein polyisocyanate I is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyols P in the two-component composition is higher than 2, preferably higher than 2.5, in particular higher than 3, more preferably higher than 3.5.
A preferred upper limit for the molar ratio of all NCO groups of polyisocyanate I in the two-component composition to all hydroxyl groups of polyols P in the two- component composition is 6, in particular 5.
Preferably, at least one of the components A and B furthermore contains at least one flame-retardant additive. This is discussed in more detail further below.
In preferred embodiments of the battery pack according to the invention, said structural flame-retardant foam material F exhibits a V1 level flame resistance as measured by the UL 94 Test for Flammability of Plastics.
However, in the same or other preferred embodiments, said structural flameretardant foam material F exhibits a VO or a V2 level flame resistance as measured by the UL 94 Test for Flammability of Plastics.
All these embodiments can be produced, for example, by adjusting the types and amounts of flame retardants used in a specific formulationin the same or other preferred embodiments of the battery pack according to the invention, said structural flame-retardant foam material F exhibits a compression modulus, measured according to ASTM D1621 , of at least 150 MPa, especially at least 200 MPa, preferably at least 250 MPa, most preferably at least 300 MPa. In the same or other preferred embodiments of the battery pack according to the invention, said structural flame-retardant foam material F exhibits a foam density, measured according to ASTM D1622, of between 0.1 and 0.6 g/cm3, preferably between 0.3 and 0.45 g/cm3.
In the same or other preferred embodiments of the battery pack according to the invention, said structural flame-retardant foam material F is a thermal insulating material located in a cavity within, or partially surrounding an outer surface of, the battery pack.
In the same or other preferred embodiments of the battery pack according to the invention, said structural flame-retardant foam material F is a rigid, reinforcing structural encapsulating compound surrounding individual battery cells within the battery pack.
The structural flame-retardant foam material F is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B. The first and second components of the composition are intrinsically storagestable and are stored in separate containers until they are mixed with one another shortly before or during application.
First component A
The first component A of the two-component composition according to the invention comprises at least one polyol P and water. One of the components A or B, preferably the first component A, of the two-component composition also comprises at least one isocyanate trimerization catalyst.
Preferably, one of the components A or B, preferably the first component A, the first component A of the two-component composition also comprises at least one flame retardant additive.
In the same or other preferred embodiments, the first component A of the two- component composition additionally comprises at least one of an urethanization catalyst, a blowing catalyst, a foam stabilizer, a surfactant, a colorant, an antioxidant, a nucleating agent, a filler, a plasticizer, and/or other additives used in polyisocyanurate foam formulations.
Polyol P
The first component A of the two-component composition according to the invention comprises at least one polyol P preferably having an average OH functionality of at least 2.
Especially suitable polyols P are those that are liquid at room temperature.
Preference is given to polyols P having an average molecular weight Mn in the range from 200 to 20'000 g/mol, preferably 250 to 10'000 g/mol, especially 300 to 5'000 g/mol. If more than one type of polyol is used as polyol P, then the average molecular weight Mn of polyol P refers to the average molecular weight Mn of all polyols comprised in polyol P.
Preference is given to polyols P having an average OH functionality in the range from 2 to 6, more preferably from 2.5 to 5. If more than one type of polyol is used as polyol P, then the average OH functionality of polyol P refers to the average OH functionality of all polyols comprised in polyol P.
Particular preference is given to polyols P having an average molecular weight Mn in the range from 250 to 10'000 g/mol, in particular 300 to 5'000 g/mol and an average OH functionality in the range from 2 to 6, in particular 2.5 to 5.
Suitable polyols P as a constituent of the first component A are especially the following commercially available polyols or mixtures thereof:
- polyether polyols, especially polyoxyalkylenediols and/or polyoxyalkylenetriols, especially polymerization products of ethylene oxide, 1 ,2-propylene oxide, 1 ,2- or 2,3-butylene oxide, oxetane, tetrahydrofuran or mixtures thereof, where these are polymerized with the aid of a starter molecule having two or more active hydrogen atoms, especially a starter molecule such as water, ammonia or a compound having multiple OH or NH groups, for example ethane-1 ,2-diol, propane-1 ,2- or -1 ,3-diol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols or tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, octanediols, nonanediols, decanediols, undecanediols, cyclohexane-1 ,3- or -1 ,4-dimethanol, bisphenol A, hydrogenated bisphenol A, 1 ,1 ,1 -trimethylolethane, 1 ,1 ,1 -trimethylolpropane, glycerol, aniline, ethylenediamine or mixtures of the aforementioned compounds. Likewise suitable are polyether polyols with polymer particles dispersed therein, especially those with styrene/acrylonitrile (SAN) particles or polyurea or polyhydrazodicarbonamide (PHD) particles.
Furthermore suitable are polytrimethylene glycols, which are linear, unbranched C3 or C4 polyether diols. Such polytrimethylene glycols can be produced from the polymerization of propanediol, in particular from biobased propanediol. Such polytrimethylene glycols are commercially available under the trade name Velvetol® from WeylChem Allessa GmbH. Of the Velvetol® types, Velvetol® H250, Velvetol® H500, Velvetol® H1000 and Velvetol® H2000 are particularly preferred, which, depending on the type, have an average molecular weight Mn, measured by gel permeation chromatography (GPC) against polystyrene as a standard, in the range between 250 and 2000 g/mol.
Furthermore suitable are polytetrahydrofuran diols, usually produced from tetrahydrofuran by acid catalysis at 30 to 40 °C. In chemical terms, polytetrahydrofuran is polytetramethylene ether glycol (PTMEG). The polytetrahydrofuran diols are produced in a manner known to the skilled person and are commercially available, for example under the trade names Terathane® PTMEG from Tri-iso or PolyTHF® from BASF.
Preferred polyether polyols are polyoxypropylenediols, polyoxypropylenetriols or ethylene oxide-terminated (EO-endcapped) polyoxypropylenediols or -triols. The latter are mixed polyoxyethylene/polyoxypropylene polyols (block copolymers) which are especially obtained by further alkoxylating polyoxypropylene diols or triols with ethylene oxide on conclusion of the polypropoxylation reaction, and ultimately mainly have primary hydroxyl groups as a result.
Preferred polyether polyols have a degree of unsaturation of less than 0.02 meq/g, especially less than 0.01 meq/g. - Polyester polyols, also called oligoesterols, prepared by known processes, especially the polycondensation of hydroxycarboxylic acids or lactones or the polycondensation of aliphatic and/or aromatic polycarboxylic acids with di- or polyhydric alcohols. Preference is given to polyester diols from the reaction of dihydric alcohols such as, in particular, ethane-1 ,2-diol, diethylene glycol, propane-1 ,2-diol, dipropylene glycol, butane-1 ,4-diol, pentane-1 ,5-diol, 3- methylpentane-1 ,5-diol, hexane-1 ,6-diol, neopentyl glycol, or trihydric alcohols such as glycerol, 1 ,1 ,1 -trimethylolpropane or mixtures of the aforementioned alcohols, with organic dicarboxylic acids or the anhydrides or esters thereof, such as, in particular, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid or hexahydrophthalic acid or mixtures of the aforementioned acids, or polyester polyols formed from lactones such as, in particular, s-caprolactone. Particular preference is given to polyester polyols formed from adipic acid or sebacic acid or dodecanedicarboxylic acid and hexanediol or neopentyl glycol.
Particularly suitable polyester polyols are polyester diols.
- Polycarbonate polyols as obtainable by reaction, for example, of the abovementioned alcohols - used to form the polyester polyols - with dialkyl carbonates, diaryl carbonates or phosgene.
- Block copolymers bearing at least two hydroxyl groups and having at least two different blocks having polyether, polyester and/or polycarbonate structure of the type described above, especially polyether polyester polyols.
- Polyacrylate polyols and polymethacrylate polyols.
- Polyhydroxy-functional fats and oils, also called fatty acid polyols, especially natural fats and oils optionally modified with ketone resins, especially castor oil or reaction products of castor oil with ketone resins; or polyols obtained by chemical modification of natural fats and oils - called oleochemical polyols - for example the polyols obtained by epoxidation of unsaturated oils and subsequent ring opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils; or polyols obtained from natural fats and oils by degradation processes, such as alcoholysis or ozonolysis, and subsequent chemical linkage, for example by transesterification or dimerization, of the degradation products or derivatives thereof thus obtained. Suitable degradation products of natural fats and oils are in particular fatty acids and fatty alcohols and also fatty acid esters, in particular the methyl esters (FAME), which can be derivatized to hydroxy fatty acid esters, for example by hydroformylation and hydrogenation.
- Polyhydrocarbon polyols, also called oligohydrocarbonols, such as, for example, polyhydroxy-functional polyolefins, polyisobutylenes, polyisoprenes; polyhydroxy-functional ethylene/propylene, ethylene/butylene or ethylene/propylene/diene copolymers, as produced, for example, by Kraton Polymers; polyhydroxy-functional polymers of dienes, especially of 1 ,3- butadiene, which can especially also be prepared from anionic polymerization; polyhydroxy-functional copolymers of dienes, such as 1 ,3-butadiene, or diene mixtures and vinyl monomers, such as styrene, acrylonitrile, vinyl chloride, vinyl acetate, vinyl alcohol, isobutylene and isoprene, for example polyhydroxyfunctional acrylonitrile/butadiene copolymers, as can be prepared, for example, from epoxides or aminoalcohols and carboxyl-term inated acrylonitrile/butadiene copolymers (commercially available, for example, under the Hypro® CTBN or CTBNX or ETBN name from Emerald Performance Materials); and hydrogenated polyhydroxy-functional polymers or copolymers of dienes.
Particularly suitable polyols P are polyester polyols and polyether polyols, in particular polyoxyethylene polyols, polyoxypropylene polyols, and polyoxypropylene polyoxyethylene polyols, preferably polyoxyethylene diols, polyoxypropylene diols, polyoxyethylene triols, polyoxypropylene triols, polyoxypropylene polyoxyethylene diols, and polyoxypropylene polyoxyethylene triols.
In one preferred embodiment, polyol P consists of a mixture of diols and higher functional polyols, in particular polyether diols and polyols, preferably selected from the polyether diols and polyols just described above.
In especially preferred embodiments said polyol P comprises or consists of polyether polyols having an average OH-functionality of between 2 and 6. In the same or other preferred embodiments said polyol P furthermore comprises polyester polyols, poly(meth)acrylate polyols, and/or polycarbonate polyols.
The first component A of the two-component composition preferably comprises between 50 wt.-% and 99 wt.-%, in particular between 75 wt.-% and 95 wt.-%, most preferably between 85 wt.-% and 90 wt.-%, based on component A, of polyol P
Water
The first component A of the two-component composition according to the invention furthermore comprises water.
Water is added as foaming agent, as it reacts with isocyanate groups to form CO2, which effects a foaming of the composition.
It might be advantageous to ensure that a sufficiently high isocyanate excess is present, as parts of the isocyanate groups react with the water to form gaseous carbon dioxide, which ultimately effect the foaming of the composition.
The first component A of the two-component composition preferably comprises between 0.01 wt.-% and 2.0 wt.-%, in particular between 0.02 wt.-% and 1 .0 wt.-%, most preferably between 0.05 wt.-% and 0.5 wt.-%, based on component A, of water.
Trimerization catalyst
One of the components A or B, preferably the first component A, of the two- component composition also comprises at least one isocyanate trimerization catalyst. Any compound that catalyzes the isocyanate trimerization reaction can be used as trimerization catalyst without particular restriction, such as for example tertiary amines, triazines, phosphines, and metal salt trimerization catalysts.
Examples of suitable trimerization catalysts include aromatic compounds such as tris(dimethylaminomethyl)phenol, 2,4-bis(dimethylaminomethyl)phenol and 2,4,6-tris(dialkylaminoalkyl)hexahydro-S-triazine. Examples of suitable metal salt trimerization catalysts are alkali metal salts of organic carboxylic acids. Preferred alkali metals are potassium and sodium. And preferred carboxylic acids are acetic acid and 2-ethylhexanoic acid.
Preferred metal salt trimerization catalysts are, for example, potassium acetate (commercially available as Polycat® 46 from Air Products and Catalyst LB from Huntsman) and potassium-2-ethylhexanoate (commercially available as Dabco® K15 from Air Products).
Suitable as trimerization catalyst furthermore trialkylphosphine compounds with alkyl groups having 1 to 8 carbon atoms, in particular tributylphosphine and trioctylphosphine.
Two or more different trimerization catalysts can be used in the two-component composition of the present invention.
The first component A of the two-component composition preferably comprises between 0.1 wt.-% and 5 wt.-%, in particular between 0.2 wt.-% and 2.5 wt.-%, most preferably between 0.3 wt.-% and 1 wt.-%, based on component A, of at least one trimerization catalyst.
Urethanization catalyst and blowing catalyst
One of the components A or B, preferably the first component A, of the two- component composition preferably also comprises at least one urethanization catalyst and/or at least one blowing catalyst, preferably both.
An “urethanization catalyst” is a catalyst that catalyzes, preferably with high selectivity, the reaction between alcoholic hydroxyl groups and isocyanate groups, thus catalyzing the formation of a urethane group. Urethanization is a reaction that occurs when component A containing polyol P is mixed with component B containing aromatic polyisocyante I. Such a reaction will proceed also spontaneously and uncatalyzed, albeit to a lesser extent, as aromatic isocyanates are reactive enough. However, it is preferred that a urethanization catalyst is present in the composition such that this process is more controllable.
While to ultimate properties of structural foam material F are based on the trimerization reaction of isocyanate groups (catalyzed by the trimerization catalyst described above), also a partial urethane crosslinking takes place which improves the properties of the foam. In the field of polyurethane or polyisocyanurate foam technology, a urethanization catalyst is also denoted as “gelling catalyst”.
A “foaming catalyst” is a catalyst that catalyzes, preferably with high selectivity, the reaction between water and isocyanate groups, thus catalyzing the isocyanate hydrolysis and formation of gaseous carbon dioxide and an amine, the latter being able to react with a further isocyanate group under formation of a urea bond. This reaction, in particular the carbon dioxide formation occurring, is what enables foaming of the composition. Such a reaction will proceed also spontaneously and uncatalyzed, albeit to a lesser extent, as aromatic isocyanates are reactive enough. However, it is preferred that a blowing catalyst is present in the composition such that this foaming process is more controllable and occurs with a higher gas yield before full curing.
In some cases, a compound may act as urethanization catalyst and foaming catalyst at the same time, but of course reduced selectivity for each respective reaction.
Suitable as urethanization catalyst and/or foaming catalysts are all known catalysts that accelerate the reaction of the isocyanate groups with hydroxyl groups of polyol P and/or water, especially compounds of tin, iron, bismuth, zinc, manganese, chromium, cobalt, copper, nickel, molybdenum, lead, cadmium, mercury, antimony, vanadium, titanium, aluminum, potassium or rare earth metals, especially organotin(IV) compounds such as dibutyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dibutyltin dichloride, dibutyltin diacetylacetonate or dioctyltin dilaurate, bismuth(lll) complexes, zinc(ll) acetate, zinc(ll) 2- ethylhexanoate, zinc(ll) laurate, zinc(ll) acetylacetonate, cobalt(ll) 2- ethylhexanoate, copper(ll) 2-ethylhexanoate, nickel(ll) naphthenate, aluminum lactate, aluminum oleate, diisopropoxytitanium bis(ethylacetoacetate); compounds containing tertiary amino groups, especially N-ethyldiisopropylamine, N,N,N',N'- tetramethylalkylenediamines, pentamethylalkylenetriamines and higher homologs thereof, bis-(N,N-diethylaminoethyl) adipate, tris(3-dimethylaminopropyl)amine, 1 ,4-diazabicyclo[2.2.2]octane (DABCO), 1 ,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1 ,5-diazabicyclo[4.3.0]non-5-ene (DBN), 2,2'-dimorpholinodiethyl ether (DMDEE), N-alkylmorpholines, N,N'-dimethylpiperazine; aromatic nitrogen compounds such as 4-dimethylaminopyridine, N-methylimidazole, N-vinylimidazole or 1 ,2-dimethylimidazole; organic ammonium compounds such as benzyltrimethylammonium hydroxide or alkoxylated tertiary amines; called “delayed action” catalysts, which are modifications of known metal or amine catalysts; and combinations of the compounds mentioned, especially of metal compounds and tertiary amines.
In preferred embodiments of the two-component composition according to the invention, said blowing catalyst is an amine-based catalyst, preferably selected from the list 1 ,4-diazabicyclo[2.2.2]octane (DABCO), 1 ,8-diazabicyclo[5.4.0]undec- 7-ene (DBU), 1 ,5-diazabicyclo[4.3.0]non-5-ene (DBN), 2,2'-dimorpholinodiethyl ether (DMDEE), and other catalytically active compounds containing tertiary amino groups. Most preferred is ,4-diazabicyclo[2.2.2]octane (DABCO).
In the same or other preferred embodiments of the two-component composition according to the invention, said urethanization catalyst is a metalorganic catalyst, preferably selected from organotin(IV) compounds such as dibutyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dibutyltin dichloride, dibutyltin diacetylacetonate or dioctyltin dilaurate, bismuth(lll) complexes, or zinc(ll) complexes.
The first component A of the two-component composition preferably comprises between 0.005 wt.-% and 1 wt.-%, in particular between 0.01 wt.-% and 0.5 wt.-%, most preferably between 0.02 wt.-% and 0.1 wt.-%, based on component A, of urethanization catalyst. In the same or other preferred embodiments, the first component A of the two- component composition preferably comprises between 0.1 wt.-% and 5 wt.-%, in particular between 0.01 wt.-% and 2.5 wt.-%, most preferably between 0.02 wt.-% and 0.5 wt.-%, based on component A, of blowing catalyst.
Foam stabilizer or surfactant
One of the components A or B, preferably the first component A, of the two- component composition preferably also comprises at least one foam stabilizer.
A foam stabilizer is a surfactant that is able to stabilize a foam structure before the polymer matrix has fully cured. Such a foam stabilizer may optionally but preferably be used to improve the foam quality of structural foam F. Foam stabilizers may help in the early stages of the foaming process to improve the foam quality and the formed foam cells, when curing of the composition has not yet progressed sufficiently to stabilize the formed foam by the cured polymer matrix alone.
Accordingly, it is preferred that a foam stabilizer or surfactant is contained in the two-component composition.
Suitable as foam stabilizer are all known foam stabilizers commonly used in polyurethane or polyisocyanurate foams. Preferred foam stabilizers are silicone- based foam stabilizers, for example silicone polymers or silicone-polyether copolymers.
Examples of suitable and preferred foam stabilizers are those available under the trade name line Tegostab® by Evonik, for example Tegostab® B 8870, Tegostab® B 8491 , Tegostab® B 8444, Tegostab® B 8460, and Tegostab® B 8523, as well as Dabco® DC193 (by Evonik).
The first component A of the two-component composition preferably comprises between 0.1 wt.-% and 5 wt.-%, in particular between 0.2 wt.-% and 2.5 wt.-%, most preferably between 0.3 wt.-% and 1 wt.-%, based on component A, of foam stabilizer. Flame-retardant additive
One of the components A or B, preferably the first component A, of the two- component composition preferably also comprises at least one flame-retardant additive.
Flame-retardant additives are used in preferred embodiments with especially high requirements regarding flame-retardant properties. However, even without flameretardant additives the structural foam material F exhibits improved such properties compared to polyurethane foams of the state of the art.
Apart from the improved flame-retarding properties, addition of such an additive may bring additional benefits, such as easier compounding and application in case of liquid flame-retardant additives and improved mechanical properties in case of solid flame-retardant additives.
Suitable as flame-retardant additives are all commonly used flame retardants in the field of polyurethane and polyisocyanurate foam composition formulation.
Suitable as flame-retardant are especially aluminum hydroxide or magnesium hydroxide, and also especially organic phosphoric acid esters such as, in particular, triethyl phosphate, tricresyl phosphate, triphenyl phosphate, diphenyl cresyl phosphate, isodecyl diphenyl phosphate, tris(1 ,3-dichloro-2-propyl) phosphate, tris(2-chloroethyl) phosphate, tris(2-ethylhexyl) phosphate, tris(chloroisopropyl) phosphate, tris(chloropropyl) phosphate, isopropylated triphenyl phosphate, mono-, bis- or tris(isopropylphenyl) phosphates of different degrees of isopropylation, resorcinol bis(diphenylphosphate), bisphenol A bis(diphenylphosphate), ammonium polyphosphates, melamine or derivatives thereof, as well as boron compounds or antimony compounds.
The flame-retardant additive may be solid or liquid at room temperature (23°C). It is also possible to use a mixture of two or more different flame-retardant additives, including a mixture or solid and liquid flame-retardant additives.
In preferred embodiments, said flame-retardant additive is solid at 23°C. In especially preferred embodiments, said flame-retardant additive comprises or consists of ammonium polyphosphate. This additive surprisingly improves the compression modulus of the structural foam material F.
In the same or other preferred embodiments, the amount of said flame-retardant additive within said structural flame-retardant foam material F is between 1 wt.-% and 10 wt.-%, preferably between 2 wt.-% and 7.5 wt.-%, more preferably between
3 wt.-% and 6 wt.-%, based on the total structural flame-retardant foam material F. The flame-retardant additive is preferably comprised in component A.
In the same or other preferred embodiments, the amount of said flame-retardant additive within component A is between 2 wt.-% and 20 wt.-%, preferably between
4 wt.-% and 15 wt.-%, more preferably between 6 wt.-% and 12 wt.-%, based on component A of the two-component composition.
The first component A of the two-component composition may comprise further optional additives, which are discussed further below.
Second component B
The second component B of the two-component composition according to the invention comprises at least one polyisocyanate I; wherein polyisocyanate I is an aromatic polyisocyanate.
Polyisocyanate I
The second component B of the two-component composition according to the invention comprises at least one aromatic polyisocyanate I, in particular an oligomeric or polymeric polyisocyanate I.
"Oligomeric polyisocyanates" are meant to be polyisocyanates which have been obtained by reacting at least two monomeric polyisocyanates, especially via a dimerization and/or trimerization reaction of the isocyanate groups. Thereby uretdione, isocyanurate and/or biuret units can be formed for example. However, oligomeric polyisocyanates still have at least two free isocyante groups per molecule. Processes for preparing oligomeric polyisocyanates are known to those skilled in the art.
“Aromatic polyisocyanates” denote polyisocyanates where the isocyanate groups are directly bonded to an aromatic ring. Most common aromatic polyisocyanates are based on diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI), wherein MDI-based polyisocyanates are preferred.
In preferred embodiments, the proportion of monomeric polyisocyanates, in particular diisocyanates, in the polyisocyanate I is at most 1 wt.%, especially at most 0.5 wt.%, preferably at most 0.3 wt.%, particularly at most 0.2 wt.%, more preferred at most 0.1 wt.%, most preferably less than 0.1 wt.%, based on the weight of component B.
In the same or other preferred embodiments, the overall content of monomeric polyisocyanates, in particular diisocyanates, in the two-component compositions is below 0.5 wt.-%, preferably below 0.4 wt.-%, more preferably below 0.3 wt.-%, in particular below 0.2 wt.-%, most preferably below 0.1 wt.-%, based on the total two-component composition.
Thus, the component B may comprise at least one monomeric polyisocyanate, in particular diisocyanate, but in some embodiments it may be desirable to keep the content of monomeric polyisocyanates at low level, for example below 0.1 wt.-%.
In practice, removal of unwanted excess monomers can be achieved by distillation or extraction, preferably by thin-film distillation under high vacuum or by extraction with suitable solvents that are inert toward isocyanate groups. Such processes are known to the person skilled in the art.
Preferably, the at least one oligomeric polyisocyanate comprised in polyisocyanate I has an uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure. Particularly preferred are biuret, allophanate, isocyanurate and/or iminooxadiazinedione structures. Especially preferred are isocyanurate structures. According to a preferred embodiment, the at least one polyisocyanate I consists to an extent of at least 50 mol.%, preferably at least 60 mol.%, more preferably at least 70 mol.%, preferably at least 80 mol.% or 90 mol.%, based on the sum total of all uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and oxadiazinetrione structures present in the polyisocyanate composition, of an isocyanurate structure.
Especially, the at least one oligomeric or polymeric polyisocyanate I comprises one or more oligomeric polyisocyanates which are based on oligomers of diisocyanates.
In a highly preferred implementation, the at least one oligomeric polyisocyanate I comprises or consists of oligomers of diphenylmethane 4,4'-, 2,4'-, and/or 2,2'- diisocyanate.
According to another special implementation, the polyisocyanate composition comprises a mixture of at least two oligomeric polyisocyanates whereby the at least two oligomeric polyisocyanates differ in their chemical structure and at least one of them is based on aromatic isocyanates, in particular MDI. In an especially preferred embodiment thereof, said oligomeric or polymeric polyisocyanate I comprises both an isocyanurate of hexamethylene 1 ,6-diisocyanate (HDI) and polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI).
Preparation processes for the oligomeric polyisocyanates having uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure in the polyisocyanate composition are described, for example, in J. Prakt. Chem. 336 (1994) 185 - 200, in DE 1 670666, DE 1 954 093, DE 2 414413, DE 2 452 532, DE 2 641 380, DE 3 700 209, DE 3 900 053 and DE 3 928 503 or in EP 0 336205, EP 0 339 396 and EP 0 798 299.
Suitable oligomers, polymers, and derivatives suitable as oligomeric polyisocyanate I are especially those derived from diphenylmethane 4,4'-, 2,4'-, and/or 2, 2'-diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI). Preferred are those derived from MDI. Particularly suitable commercially available examples of oligomeric polyisocyanates I are in particular TDI oligomers such as Desmodur® IL (from Covestro); and also mixed isocyanurates based on TDI/HDI, for example as Desmodur® HL (from Covestro). Also particularly suitable are MDI forms that are liquid at room temperature (so-called “modified MDI”), which are mixtures of MDI with MDI derivatives such as, in particular, MDI carbodiimides or MDI uretonimines or MDI urethanes, known by trade names such as Desmodur® CD, Desmodur® PF, Desmodur® PC (all from Covestro) or Isonate® M 143 (from Dow), and mixtures of MDI and MDI homologs (polymeric MDI or PMDI), available under trade names such as Desmodur® VL, Desmodur® VL50, Desmodur® VL R10, Desmodur® VL R20, Desmodur® VH 20 N, and Desmodur® VKS 20F (all from Covestro), Isonate® M 309, Voranate® M 229 and Voranate® M 580 (all from Dow) or Lupranat® M 10 R (from BASF). The abovementioned oligomeric polyisocyanates are in practice typically mixtures of substances having different degrees of oligomerization and/or chemical structures. They preferably have an average NCO functionality of 2.1 to 4.0.
In very preferred embodiments of the two-component composition, said oligomeric or polymeric polyisocyanate I comprises or consists of polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2, 2'-diisocyanate (PMDI).
In the same or other preferred embodiments of the two-component composition, said oligomeric or polymeric polyisocyanate I comprises or consists of a polyurethane polymer containing isocyanate groups.
This isocyanate-functional polymer is preferably prepared beforehand, by combining the at least one monomeric aromatic diisocyanate and the at least one polyol in a molar NCO/OH ratio of at least 1.1 , in particular at least 1 .3, preferably at least 1 .5, more preferably at least 1 .8, in the absence of moisture at a temperature in the range of 20 to 160 °C, preferably 40 to 140 °C, optionally in the presence of a suitable catalyst. This synthesis is well known in the field. Suitable as polyols for this purpose are all polyols described further above as polyol P, and preferred embodiments of these polyols correspond to the preferred embodiments of polyol P.
Suitable as monomeric diisocyanates for this purpose are all monomeric diisocyanates, in particular diphenylmethane 4,4'-, 2,4'-, and/or 2, 2'-diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI). Preferred is MDI.
A preferred isocyanate-functional polymer comprised in polyisocyanate I has a content of monomeric diisocyanate, in relation to the total polymer, of below 0.5 weight-%, preferably below 0.3 weight-%, more preferably below 0.2 weight-%, most preferably below 0.1 weight-%. Such a low monomer isocyanate-functional polymer allows curable compositions which have a content of monomeric diisocyanates of below 0.1 weight-% and are safe to use without special protective measures and do not require hazard labelling.
For such a polymer, the reaction is preferably conducted at a molar NCO/OH ratio of at least 3/1 , preferably 3/1 to 10/1 , particularly 3/1 to 8/1 , followed by the removal of most of the remaining monomeric diisocyanate by a distillation process, preferably by thin film distillation or short path distillation under vacuum.
Another possibility to obtain an isocyanate-functional polymer with a low content of monomeric diisocyanate is by chemically reducing the content of monomeric diisocyanates, for example by adding small amounts of water, preferably in combination with a surfactant.
In especially preferred embodiments said polyisocyanate I is selected from polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI) and/or prepolymers based on diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (MDI).
In the same or other especially preferred embodiments said polyisocyanate I is polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI) having an NCO-functionality of between 2.1 and 3.0.
The second component B of the two-component composition preferably comprises between 50 wt.-% and 100 wt.-%, in particular between 75 wt.-% and 95 wt.-%, most preferably between 85 wt.-% and 90 wt.-%, based on component B, of polyisocyanate I.
Optional additives
As optional constituents of the first component A, the two-component composition may comprise further substances that are reactive with isocyanates, especially
- di- or polyfunctional alcohols, especially those having an average molecular weight Mn in the range from 250 to 500 g/mol, especially ethoxylated and/or propoxylated bisphenol A, bisphenol F, trimethylolpropane or glycerol,
- chain extenders, especially diols having a molecular weight Mn in the range from 62 to 150 g/mol, especially ethylene glycol, propane-1 ,3-diol, butane-1 ,4-diol or pentane-1 ,5-diol,
- small amounts of primary polyamines, especially in order to directly obtain a structurally viscous, firm material that flows away to a lesser degree with the mixing of the two components,
- amino alcohols, or
- latent hardeners such as, in particular, ketimines, aldimines or oxazolidines.
The two-component composition may additionally comprise further constituents in either one or both of components A and B, especially the following auxiliaries and admixtures:
- fillers, especially ground or precipitated calcium carbonates, optionally coated with fatty acids, especially stearates, barytes, quartz flours, quartz sands, dolomites, wollastonites, kaolins, calcined kaolins, sheet silicates, such as mica or talc, zeolites, aluminum hydroxides, magnesium hydroxides, silicas, including finely divided silicas from pyrolysis processes, industrially produced carbon blacks, graphite, metal powders, for example of aluminum, copper, iron, silver or steel, PVC powders or hollow beads;
- fibers, especially glass fibers, carbon fibers, metal fibers, ceramic fibers, polymer fibers, such as polyamide fibers or polyethylene fibers, or natural fibers, such as wool, cellulose, hemp or sisal;
- nanofillers such as graphene or carbon nanotubes;
- dyes; - pigments, especially titanium dioxide, chromium oxide, iron oxides or organic pigments;
- plasticizers, especially phthalates, terephthalates, trimellitates, adipates, sebacates, azelates, succinates, citrates, benzoates, diesters of ortho- cyclohexanedicarboxylic acid, acetylated glycerol, monoglycerides, fatty acid methyl or ethyl esters, also called "biodiesel", natural or modified vegetable oils, organic phosphoric or sulfonic esters, sulfonamides, urethanes, high-boiling hydrocarbons, polybutenes, polyisobutylenes, polystyrenes or chloroparaffins;
- solvents, especially those as customarily used in paints, varnishes or coatings;
- modifiers such as hydrocarbon resins, natural or synthetic waxes or bitumen;
- rheology modifiers, especially urea compounds, sheet silicates such as bentonites, derivatives of castor oil, hydrogenated castor oil, polyamides, polyurethanes, fumed silicas or hydrophobically modified polyoxyethylenes;
- desiccants, especially molecular sieves, calcium oxide, monooxazolidines such as Incozol® 2 (from Incorez) or orthoformic esters;
- adhesion promoters, especially titanates or organoalkoxysilanes such as aminosilanes, mercaptosilanes, epoxysilanes, vinylsilanes, (meth)acrylosilanes, carbamatosilanes, alkylsilanes, S-(alkylcarbonyl)mercaptosilanes, aldiminosilanes or oligomeric forms of these silanes;
- non-reactive thermoplastic polymers, for example homo- or copolymers of unsaturated monomers, especially from the group comprising ethylene, propylene, butylene, isobutylene, isoprene, vinyl acetate and alkyl (meth)acrylates, especially polyethylenes (PE), polypropylenes (PP), polyisobutylenes, ethylene-vinyl acetate copolymers (EVA) and atactic poly-a- olefins (APAO);
- further additives, especially wetting agents, leveling agents, defoamers, deaerators, stabilizers against oxidation, heat, light or UV radiation, or biocides; and other substances customarily used in curable compositions.
Such additives may present as constituents of the first component A or of the second component B. Substances reactive with isocyanate groups are preferably a constituent of the first component A. It may be advisable to subject certain constituents to chemical or physical drying before mixing them into the respective component. Another aspect of the present invention is a foamable two-component composition consisting of a first component A and a second component B; wherein
- the first component A comprises
- at least one polyol P;
- at least one isocyanate trimerization catalyst;
- at least one foam stabilizer; and
- water; and
- the second component B comprises
- at least one polyisocyanate I; wherein at least one of the components A and B furthermore contains a flameretardant additive with an amount of between 1 wt.-% and 7.5 wt.-%, based on the total two-component composition; and wherein polyisocyanate I is polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'- diisocyanate (PMDI) having an NCO functionality of between 2.1 and 3.0; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyol P in the two-component composition is higher than 2.
All preferred embodiments are the same as described and discussed above for structural foam material F. Particular preferred are the following embodiments.
In preferred embodiments of the foamable two-component composition according to the invention, said polyol P consists of polyether polyols.
In the same or other preferred embodiments of the foamable two-component composition according to the invention, said flame-retardant additive is solid at 23°C, more preferably comprising or consisting of ammonium polyphosphate.
In the same or other preferred embodiments of the foamable two-component composition according to the invention, said molar ratio of all NCO groups of polyisocyanate I in the two-component composition to all hydroxyl groups of polyol P in the two-component composition is higher than 2.5. In the same or other preferred embodiments of the foamable two-component composition according to the invention, the amount of said flame-retardant additive within said 3 wt.-% and 6 wt.-%, based on the total two-component composition.
In the same or other preferred embodiments of the foamable two-component composition according to the invention, said two-component composition furthermore contains an urethanization catalyst, a blowing catalyst, a foam stabilizer, a surfactant, a colorant, an anti-oxidant, a nucleating agent, a filler, a plasticizer, and/or other additives used in polyisocyanurate foam formulations.
The mixing ratio of the first component A and the second component B of the two- component composition depends on the formulation of the individual components and may be tailored to the requirements of the application process.
When formulating the two-component composition, it should be ensured that the amounts of polyol A and polyisocyanate I and/or the mixing ratio of components A and B are adjusted such that the molar ratio of all NCO groups in the two- component composition to all OH groups in the two-component composition is higher than 2, in particular higher than 2.5, in particular higher than 3, more preferably higher than 3.5.
A preferred upper limit for the molar ratio of all NCO groups of polyisocyanate I in the two-component composition to all hydroxyl groups of polyols P in the two- component composition is 6, in particular 5.
The reason for this excess of NCO groups compared to OH groups is the two-step curing mechanism described further below and the formation of an isocyanurate- crosslinked polymer network. The excess of NCO groups allows for the trimerization reaction of NCO groups to proceed after most or all OH groups from the polyol have depleted due to the faster urethane-forming reaction. Furthermore, additional NCO groups are consumed during the foaming reaction. In preferred embodiments of the two-component composition, the mixing ratio in parts by weight between the first component A and the second component B is in the range from 1 :0.1 to 1 :1.5, in particular from 1 :0.2 to 1 :1.
In the same or other preferred embodiments of the two-component composition, the mixing ratio in parts per volume between the first component A and the second component B is in the range from 1 :0.2 to 1 : 1 .8, especially 1 :0.3 to 1 : 1 .2.
Another aspect the present invention is directed to the use of a two-component composition as described before, including all embodiments and preferences, as structural reinforcement and/or encapsulating material, particularly for the manufacturing of battery boxes, in particular battery boxes for electric vehicles.
The two-component composition described before, including all preferred embodiments for all possible components A and B, is advantageously used as structural foam material.
In preferred embodiments of this use, said two-component composition as described before, including all embodiments and preferences, is used as structural foam material for the manufacturing of battery boxes, in particular battery boxes for electric vehicles.
Another aspect of the present invention is a method for producing a battery box, by using a two-component composition as described before, including all embodiments and preferences, as structural foam material.
In particular, this method is a method of encapsulating an electric cell within a battery box, the method comprising:
- mixing a liquid, foamable two-component composition and transferring it into an enclosed space defined by a wall of a battery box case, said case containing at least one electric cell, the cell being at least partially surrounded by the mixed liquid, foamable two-component composition; - allowing the mixed liquid, foamable two-component composition to react, thereby forming a cured rigid polyisocyanurate foam; the liquid, foamable two-component composition before mixing comprising: a first component comprising an isocyanate reactive compound and water; a second component comprising an isocyanate compound; and at least one of the first and second component including at least one isocyanate trimerization catalyst; and at least one of the first and second component including a flame-retardant additive in an amount less than 10% by weight based on the total weight of the liquid two- component composition.
In especially preferred embodiments of this method, the resulting battery box is a battery box as described further above, wherein said cured rigid polyisocyanurate foam corresponds to structural foam material F described throughout this document.
Conveying and mixing of the two components A and B may be done with any suitable equipment. Preferred are conveying of the two components by pumps and mixing with a static or dynamic mixer, preferably however using high pressure impingement mixing. The mixed composition may then be applied into or onto the battery box using elevated pressure, for example by pouring or spraying, and allowing it to cure after application.
The curing step, including the foaming, occurs at room temperature or faster at elevated temperatures, catalyzed by the trimerization catalyst and optionally present urethanization and/or blowing catalysts. The trimerization reaction occurs somewhat slower than the urethanization reaction or the blowing reaction and is supported (accelerated) by heat, which may also stem from the exothermic curing reaction, in particular the urethanization reaction.
During or after the curing step, electric cells embedded in the mixed and partially cured two-component composition may still be moved or replaced, as the partially cured two-component composition has not yet developed the full rigidity and mechanical strength, which is obtained after completion of the trimerization reaction.
The trimerization curing reaction may take days or weeks to fully complete, which is however not a problem. After the urethanization reaction the material already has sufficient stability and strength that the battery box can be moved or even incorporated into, e.g., an electric vehicle. The heat generated during charging cycles of the battery, which may reach for example 60°C during fast charging cycles, will support and accelerate the trimerization curing and thus the final curing of the material. However, it is also possible to accelerate trimerization curing by placing the battery box under slight heating conditions for a short time, which however should not exceed approximately 60° to 80°C.
Another aspect of the present invention is a rigid, structurally reinforcing foam with flame-retardant properties, obtained from mixing and curing the two-component composition as described further above.
Preferably, said rigid, structurally reinforcing foam with flame-retardant properties corresponds to structural foam material F described throughout this document.
Compared to the state of the art, in particular polyurethane foams, the structural foam material F of the present invention offers vastly superior mechanical properties, in particular a higher compression modulus and softening point. Furthermore, the flame-retardant properties are intrinsically better compared to polyurethane foams of the state of the art. This means that structural foam material F according to this invention is a much better structural, thermal and stiffening resistant material when used in battery boxes and can sustain much higher stress forces and much higher temperature exposure than polyurethane foams. Polyurethane foams start to soften and loose structural properties at much lower temperature (normally between 70°C and 90°C), while structural foam material F starts to soften at much higher temperatures, for example 170°C to about 180°C and maintains the structural properties (compression strength and compression modulus) at high temperature exposure. Further advantageous implementations of the invention are evident from the exemplary embodiments.
Exemplary embodiments
Materials For the experiments, the substances listed in Table 1 were used.
Table 1 Preparation of samples
The respective components A and B of the exemplary two-component compositions F1 to F6 were prepared individually by adding the respective ingredients shown in Table 2 to stand mixer equipped with a propeller blade. Subsequently the mixture was mixed for 2 minutes at 1500 rpm.
Table 2
*not according to the invention.
For curing and testing of the two-component compositions F1 to F6, both respective components A and B were mixed in a volume ratio A : B as indicated in Table 2 for each experiment, which corresponds to a weight ratio A : B as indicated in Table 2 for the same experiment. The volume (v/v) and weight (w/w) ratios indicated in Table 2 for each experiment are normalized to 1 part (weight or volume) of component A. For example, in experiment F2, 1 weight part of component A was mixed with 0.56 weight parts of component B. In the same experiment F2, 1 volume part of component A was mixed with 0.66 volume parts of component B. Table 2 furthermore shows the resulting NCO index (molar ratio of all NCO groups of polyisocyanate I to all hydroxyl groups of polyols P in mixture) for each respective experiment. For example, in experiment F2, 3.28 mol NCO groups were present initially after mixing per 1 mol of OH groups from the available polyols.
After mixing at room temperature, curing and foaming started spontaneously.
Mechanical and thermal properties
Compression modulus was measured according to ASTM D1621-16 (Compressive Properties of Rigid Cellular Plastics) on fully cured and expanded samples, using a load rate of 0.01 /s.
Foam density was measured according to ASTM D 1475-13 on fully cured and expanded samples.
Dynamic mechanical analysis (DMA) measurements were conducted with a TA instruments model- Q850 The glass transition temperatures (Tg) were determined from the phase angle tan 5 which corresponds to the ratio of the loss modulus to the storage modulus. The samples were heated from 25°C to 200°C at a heating rate of 3°C min-1. The frequency was kept constant at 1 Hz (amplitude 20 pm). Tg values were determined on samples after curing at room temperature for 24h. UL94 rating (flammability properties) of cured and expanded samples was measured according to LIL94 standard (Test for Flammability of Plastic Materials for Parts in Devices and Appliances) on fully cured and expanded samples having a thickness of 3 mm. Evaluation was done for vertical samples and classification according to V-2, V-1 , and V-0 (best rating) as defined in the test specifications.
The results of these measurements are shown in Table 3.
Table 3
“n/m” means that this value was not measured. *not according to the invention.
“Bum” means that the sample burned and did not reach an LIL94 rating.
The data presented in Table 3 shows that the compositions according to the invention exhibit vastly superior mechanical properties, in particular compression modulus, compared to a 2C-PU foam material (F2). The measured Tg value (for F3) is far outside the working temperature of electric vehicle batteries.
Furthermore, the foams according to the invention show high volumetric expansion (low density) and superior flame-retardant properties compared to a 2C-PU foam material (F2).

Claims

Claims
1 . A battery box comprising a structural foam material F, wherein said structural foam material F is a foamed, at least partially polyisocyanurate-crosslinked reaction product of a mixed two-component composition consisting of a first component A and a second component B; wherein
- the first component A comprises
- at least one polyol P; and
- water; and
- the second component B comprises
- at least one polyisocyanate I; wherein at least one of the components A and B furthermore contains at least one isocyanate trimerization catalyst; and wherein polyisocyanate I is an aromatic polyisocyanate; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyols P in the two- component composition is higher than 2.
2. The battery box according to claim 1 , wherein said molar ratio of all NCO groups of polyisocyanate I in the two-component composition to all hydroxyl groups of polyol P in the two-component composition is higher than 2.5.
3. The battery box according to either of claims 1 or 2, wherein at least one of the components A and B furthermore contains at least one flame-retardant additive.
4. The battery box according to claim 3, wherein said structural foam material F exhibits a V1 level flame resistance as measured by the UL 94 Test for Flammability of Plastics.
5. The battery box according to any of claims 1 to 4, wherein said structural foam material F exhibits a compression modulus, measured according to ASTM D1621 , of at least 150 MPa.
6. The battery box according to any of claims 1 to 5, wherein said structural foam material F exhibits a compression modulus, measured according to ASTM D1621 , of at least 250 MPa.
7. The battery box according to any of claims 1 to 6, wherein said structural foam material F exhibits a foam density, measured according to ASTM D1622, of between 0.1 and 0.6 g/cm3, preferably between 0.3 and 0.45 g/cm3
8. The battery box according to any of claims 1 to 7, wherein said structural foam material F is a thermal insulating material located in a cavity within, or partially surrounding an outer surface of, the battery box.
9. The battery box according to any of claims 1 to 8, wherein said structural foam material F is a rigid, reinforcing structural encapsulating compound at least partially surrounding individual battery cells within the battery box.
10. The battery box according to any of claims 1 to 9, wherein said polyol P comprises or consists of polyether polyols having an average OH- functionality of between 2 and 6.
11 . The battery box according to claim 10, wherein said polyol P furthermore comprises polyester polyols, poly(meth)acrylate polyols, and/or polycarbonate polyols.
12. The battery box according to any of claims 1 to 11 , wherein said polyisocyanate I is selected from polymeric diphenylmethane 4,4'-, 2,4'- and/or 2,2'-diisocyanate (PMDI) and/or prepolymers based on diphenylmethane 4,4'-, 2,4'-, and/or 2, 2'-diisocyanate (MDI).
13. The battery box according to claim 11 , wherein said polyisocyanate I is polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI) having an NCO-functionality of between 2.1 and 3.0.
14. The battery box according to any of claims 1 to 13, wherein said two- component composition furthermore contains an urethanization catalyst, a blowing catalyst, a foam stabilizer, a surfactant, a colorant, an anti-oxidant, a nucleating agent, a filler, a plasticizer, and/or other additives used in polyisocyanurate foam formulations.
15. The battery box according to any of claims 3 to 14, wherein said flameretardant additive is solid at 23°C.
16. The battery box according to claim 15, wherein said flame-retardant additive comprises or consists of ammonium polyphosphate.
17. The battery box according to any of claims 3 to 16, wherein the amount of said flame-retardant additive within said structural flame-retardant foam material F is between 1 wt.-% and 10 wt.-%, based on the total structural flame-retardant foam material F.
18. The battery box according to any of claims 3 to 16, wherein the amount of said flame-retardant additive within said structural flame-retardant foam material F is between 2 wt.-% and 7.5 wt.-%, based on the total structural flame-retardant foam material F.
19. The battery box according to any of claims 3 to 16, wherein the amount of said flame-retardant additive within said structural flame-retardant foam material F is between 3 wt.-% and 6 wt.-%, based on the total structural flame-retardant foam material F.
20. The battery box according to any of claims 1 to 19, wherein said battery box is a battery box of an electric vehicle.
21 . A method of encapsulating an electric cell within a battery box, the method comprising:
- mixing a liquid, foamable two-component composition and transferring it into an enclosed space defined by a wall of a battery box case, said case containing at least one electric cell, the cell being at least partially surrounded by the mixed liquid, foamable two-component composition;
- allowing the mixed liquid, foamable two-component composition to react, thereby forming a cured rigid polyisocyanurate foam; the liquid, foamable two-component composition before mixing comprising: a first component comprising an isocyanate reactive compound and water; a second component comprising an isocyanate compound; and at least one of the first and second component including at least one isocyanate trimerization catalyst; and at least one of the first and second component including a flame-retardant additive in an amount less than 10% by weight based on the total weight of the liquid two-component composition.
22. The method according to claim 21 , wherein the resulting battery box is a battery box according to any one of claims 3 to 21 , wherein said cured rigid polyisocyanurate foam corresponds to structural foam material F.
23. A foamable two-component composition consisting of a first component A and a second component B; wherein
- the first component A comprises
- at least one polyol P;
- at least one isocyanate trimerization catalyst;
- at least one foam stabilizer; and
- water; and
- the second component B comprises
- at least one polyisocyanate I; wherein at least one of the components A and B furthermore contains a flame-retardant additive with an amount of between 1 wt.-% and 7.5 wt.-%, based on the total two-component composition; and wherein polyisocyanate I is polymeric diphenylmethane 4,4'-, 2,4'-, and/or 2,2'-diisocyanate (PMDI) having an NCO functionality of between 2.1 and 3.0; and wherein the molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyol P in the two- component composition is higher than 2.
24. The foamable two-component composition according to claim 23, wherein said polyol P consists of polyether polyols.
25. The foamable two-component composition according to any of claims 23 or 24, wherein said flame-retardant additive is solid at 23°C.
26. The foamable two-component composition according to claim 25, wherein said flame-retardant additive comprises or consists of ammonium polyphosphate.
27. The foamable two-component composition according to any of claims 23 to 26, wherein said molar ratio of all NCO groups of polyisocyanate I in the two- component composition to all hydroxyl groups of polyol P in the two- component composition is higher than 2.5.
28. The foamable two-component composition according to any of claims 22 to 26, wherein the amount of said flame-retardant additive within said 3 wt.-% and 6 wt.-%, based on the total two-component composition.
29. The foamable two-component composition according to any of claims 23 to 28, wherein said two-component composition furthermore contains an urethanization catalyst, a blowing catalyst, a foam stabilizer, a surfactant, a colorant, an anti-oxidant, a nucleating agent, a filler, a plasticizer, and/or other additives used in polyisocyanurate foam formulations.
30. A rigid, structurally reinforcing foam with flame-retardant properties, obtained from mixing and curing the two-component composition according to any of claims 23 to 29.
PCT/IB2024/000222 2024-05-08 2024-05-08 Battery box comprising a foamed polisocyanurate material Pending WO2025233647A1 (en)

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J. PRAKT, CHEM, vol. 336, 1994, pages 185 - 200

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