WO2025214245A1

WO2025214245A1 - Polyurethane fire-retardant coating composition

Info

Publication number: WO2025214245A1
Application number: PCT/CN2025/087094
Authority: WO
Inventors: He Meng ZHAO; Xin Yao LV; Kuan LIU; Xiao Hong Li
Original assignee: BASF China Co Ltd; BASF SE
Current assignee: BASF China Co Ltd; BASF SE
Priority date: 2024-04-11
Filing date: 2025-04-03
Publication date: 2025-10-16
Anticipated expiration: 2026-10-11
Also published as: CN120818297A

Abstract

The present disclosure discloses a polyurethane fire-retardant coating composition, which is obtained by reacting at least the following components: a first component, which comprises at least one polyol, at least one inorganic filler, and at least one diluent; and a second component, which comprises at least one polyisocyanate; based on the total weight of the polyurethane fire-retardant coating composition, the content of the inorganic filler is 20-70wt%; the isocyanate index of the polyurethane fire-retardant coating composition is 150-800. The polyurethane fire-retardant coating composition according to the present disclosure not only delivers good scratch resistance ability but also provides sustained fire resistance, thermal insulation performance, and voltage resistance performance.

Description

Polyurethane fire-retardant coating composition

Technical Field

The present disclosure relates to the field of polyurethane fire-retardant coating compositions. More specifically, the present disclosure relates to a polyurethane fire-retardant coating composition, a composite material, and a battery product at least partially coated with the polyurethane fire-retardant coating composition.

Background Art

For new energy vehicles, as the demand for the energy density of battery products continues to increase, the risk of thermal runaway in battery products is also intensifying. To reduce the risk of thermal runaway in battery products, a conventional solution is to set up a fire-resistant insulation layer in specific areas within the battery products or on the surface of the battery products, commonly using inorganic insulation materials such as mica sheets and metal oxide insulation layers. However, mica sheets and the like will cause problems, such as an increased number of components, and space being taken up.

As a novel type of coating layer with good operability, resin fire-resistant heat barrier coating layers have also been used in the art. However, combustion residue formed when a resin coating layer such as an epoxy resin or polyurethane coating layer experiences high temperature or burns is very fragile and falls off easily. If thermal runaway actually occurs, such a friable structure will easily peel off the substrate under the action of vibration, external knocks and high-temperature flame blasting, so is unable to continuously provide a fire-resistant heat barrier effect. In addition, in the event of thermal runaway, controlling the issue with the voltage resistance (electrical insulation) is also very important, as electrical sparks and arcs can trigger a chain reaction of explosive combustion in adjacent battery cells.

Summary of the Invention

To address the above issues, the present disclosure is intended to provide an improved polyurethane fire-retardant coating composition. The polyurethane coating layer prepared from the polyurethane fire-retardant coating composition disclosed herein has excellent scratch resistance, fire-resistant insulation, and voltage resistance properties. Furthermore, after exposure to high-temperature combustion, the residual layer formed maintains structural integrity and good mechanical stability, thereby continuously providing fire-resistant insulation and voltage resistance performance.

In a first aspect of the present disclosure, a polyurethane fire-retardant coating composition is provided, which is obtained by reacting at least the following components:

a first component, comprising

at least one polyol;

at least one inorganic filler; and

at least one diluent; and

a second component, comprising

at least one polyisocyanate;

characterized in that, based on the total weight of the polyurethane fire-retardant coating composition, the content of the inorganic filler is 20-70 wt%, preferably 23-70 wt%, and more preferably 50-60 wt%; and

the isocyanate index of the polyurethane fire-retardant coating composition is 150-800, preferably 300-500, and more preferably 300-400.

In a second aspect of the present disclosure, a composite material is provided, comprising a substrate and a polyurethane coating layer prepared from the polyurethane fire-retardant coating composition described in the first aspect, the polyurethane fire-retardant coating composition being applied to at least a portion of a surface of the substrate, and the polyurethane coating layer having a thickness of 0.5-1.5 mm, preferably 0.7-1.2 mm.

In a third aspect of the present disclosure, a battery product is provided, the battery product being at least partially coated with the polyurethane fire-retardant coating composition described in the first aspect. In some embodiments, the battery product is a battery shell, a battery unit, a battery module or a battery pack.

Beneficial effects

The polyurethane coating layer prepared from the polyurethane fire-retardant coating composition according to the present disclosure not only delivers excellent scratch resistance but also provides sustained fire-resistant insulation, thereby endowing the composite material of the present disclosure with outstanding performance in fire-resistant insulation and voltage resistance.

Brief Description of the Drawings

To more clearly illustrate the embodiments of the present disclosure, a brief introduction to the drawings required for the description of the embodiments is provided below.

Figure 1 is a photograph of the composite material of the comparative example 2 after undergoing the fire test according to the present disclosure;

Figure 2a is a photograph of the composite material of the comparative example 3 after undergoing the fire test according to the present disclosure; and

Figure 2b is a side-view photograph of the composite material of the comparative example 3 after undergoing the fire test according to the present disclosure.

Detailed Description of Embodiments

The technical solutions in embodiments in the present disclosure are described clearly and completely below. Obviously, the embodiments described are merely some, not all, of the embodiments of the present disclosure. On the basis of the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without exercise of inventive effort fall within the scope of protection of the present disclosure.

As used in the present disclosure, the term “molecular weight” means the number average molecular weight Mn.

As used in the present disclosure, the term "functionality" is also known as equivalent functionality or average functionality. Methods of determining the functionality of polyols are known to those skilled in the art; for example, see M. Ionescu, "Chemistry and Technology of Polyols for Polyurethanes" , 2005, Rapra Technology Limited, pages 34 -39.

The density described in the present disclosure can be tested according to ISO 1183 and is expressed in g/cm³.

The viscosity described in the present disclosure can be tested according to ASTM D2196-15 and is expressed in cps.

I. Polyurethane fire-retardant coating composition

a first component, comprising

at least one polyol;

at least one inorganic filler; and

at least one diluent; and

a second component, comprising

at least one polyisocyanate;

The polyurethane fire-retardant coating composition according to the present disclosure has a relatively high content of the inorganic filler and a high isocyanate index. The polyurethane coating layer prepared from the polyurethane fire-retardant coating composition disclosed herein forms a dense residual layer after exposure to high temperatures (such as fire caused by battery thermal runaway) and maintains structural integrity. Therefore, this dense and robust residual layer can continue to provide fire-resistant insulation and voltage resistance performance.

First component

As described above, the first component includes at least one polyol, at least one inorganic filler, and at least one diluent. Each component is described in detail in the following paragraphs.

Polyol

Examples of suitable polyols include, but are not limited to, polyether polyols, grafted polyether polyols, polyester polyols, polyolefin polyols, and mixtures thereof. In some preferred embodiments, the polyol is preferably a polyether polyol. Compared to a polyester polyol, a polyurethane coating layer prepared from a polyether polyol does not age easily in hot and humid environments.

The polyether polyol is an organic compound containing at least ether and OH groups as functional groups. The polyether polyol is prepared using a catalyst, for example, from epoxides (such as propylene oxide and/or ethylene oxide) or from tetrahydrofuran with hydrogen-active initiator compounds (such as aliphatic alcohols, phenols, amines, carboxylic acids, water, and compounds based on natural substances such as sucrose, sorbitol, or mannitol) . These may include basic catalysts or double metal cyanide catalysts, as recorded in PCT/EP2005/010124, EP 90444 or WO 05/090440, for example.

Polyester polyols are prepared, for example, from aliphatic or aromatic dicarboxylic acids with polyols, polythioether polyols, polyester amides, hydroxylated polyacetals, and/or hydroxylated aliphatic polycarbonates, preferably in the presence of an esterification catalyst. Other possible polyols are documented in, for example, “Kunststoffhandbuch, ” Volume 7, “Polyurethane, ” Carl Hanser Verlag, 3rd Edition, 1993, Chapter 3.1.

In some embodiments, the polyol has an average functionality equal to or greater than 2 (i.e., having at least two groups reactive with isocyanates) , for example, 2, 3, or 4. The polyol may be a dihydroxy polyol, trihydroxy polyol, tetrahydroxy polyol, or higher polyol. In some preferred embodiments, the average functionality of the polyol is 2 to 3.

In other embodiments, the number-average molecular weight of the polyol is 1,000-10,000 g/mol, preferably 2,000-6,000 g/mol. For example, the polyol has a number-average molecular weight of 1,000 g/mol, 2,000 g/mol, 3,000 g/mol, 4,000 g/mol, 5,000 g/mol, 6,000 g/mol, 8,000 g/mol, or 10,000 g/mol. In some embodiments, the polyol is a polyether polyol with a number-average molecular weight of 2,000-6,000 g/mol and an average functionality of 2 to 3.

In some embodiments, the polyol has a viscosity, measured at 25℃ according to ASTM D2196-15, of 50-5,000 cps, preferably 50-2,000 cps, and more preferably 100-1, 500 cps.

Examples of suitable commercially available polyols include2095 (from BASF) , 4003/1 (from BASF) , 2090 (from BASF) , 3505/1 (from BASF) , 3905 (from BASF) , 3907 (from BASF) , 3909 (from BASF) , NJ 360S, and NJ 330S (from NingWu) .

Based on the total weight of the first component, the total amount of polyol is 5-40 wt%, preferably 10-35 wt%. For example, in some embodiments, the total amount of polyol is 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

Inorganic filler

By adding an inorganic filler to the polyurethane fire-retardant coating composition, the mechanical strength of the resulting polyurethane coating layer can be improved; additionally, due to the non-combustibility or flame retardancy of the inorganic filler, its incorporation into the polymer can reduce the concentration of the combustible material, delay or prevent combustion, and so on. Furthermore, some inorganic fillers decompose at high temperatures to form non-combustible oxides and water. Since this decomposition reaction is endothermic, and the generated non-combustible oxides and released water can help lower the temperature and isolate the material from oxygen, the objective of fire prevention/extinguishing can be achieved.

Specifically, when the polyurethane fire-retardant coating composition according to the present disclosure is used for coating battery products, the resulting polyurethane coating layer can form a residual layer after experiencing fire. The inorganic filler can effectively control the expansion of the coating layer during the formation of the residual layer, so that the formed residual layer is more uniform and has a certain level of mechanical strength and can maintain structural integrity. This can significantly enhance the fire-resistant insulation and voltage resistance (i.e., electrical insulation) performance of battery products.

The inorganic filler according to the present disclosure is preferably an electrically insulating inorganic filler. Examples of suitable inorganic fillers include, but are not limited to, nitrides, metal oxides, metal hydroxides, ceramics, and/or (mineral) salts. The inorganic filler according to the present disclosure is one or more selected from nitrides, metal oxides, metal hydroxides, ceramics, and/or mineral salts. Among them, (mineral) salt-type inorganic fillers include, for example, metal silicates, borates, and aluminates. Suitable metal silicate salts may for example be sodium silicate, potassium silicate, lithium silicate, calcium silicate and magnesium silicate.

In some specific embodiments, the inorganic filler is one or more selected from mica, talc, clay, calcium magnesium carbonate, calcium carbonate, calcium sulfate, calcium silicate, barium sulfate, silicon dioxide, aluminum hydroxide, magnesium hydroxide, silicon oxide, aluminum oxide, calcium oxide, titanium dioxide, magnesium oxide, zinc oxide, aluminum nitride, boron nitride, silicon nitride, hollow glass (microspheres) , ceramic microspheres, vermiculite, diatomaceous earth, wollastonite, glass fibers, ceramic fibers, basalt fibers, and/or silicates. It should be understood that the inorganic filler according to the present disclosure is at least one of the aforementioned inorganic fillers or any combination thereof.

Furthermore, the inorganic filler may be spherical, elliptical, flake-like, or fibrous in shape. The average particle size (D50) of the inorganic filler may be 200 -3000 mesh, preferably 300 -2000 mesh.

In some embodiments, the inorganic filler has a length-to-diameter ratio of 10-1000, for example, a fibrous (also referred to as “needle-like” or “elongated” ) inorganic filler or flake-like inorganic filler. Inorganic fillers within the above length-to-diameter ratio range (including fibrous and flake-like inorganic fillers) can effectively control the expansion of the polyurethane coating during the formation of the residual layer, so that the formed residual layer is more uniform, has a certain level of mechanical strength, and can maintain structural integrity.

Fibrous inorganic fillers with a length-to-diameter ratio of 10-1000 may be selected from glass fibers, ceramic fibers (e.g., oxide (alumina/silica) ceramic fibers) , basalt fibers, glass flakes, mica, and/or wollastonite, which can be used alone or in combination. The wollastonite may also be a chain-like calcium silicate mineral containing a small amount of iron, aluminium, magnesium, manganese, titanium and/or potassium.

In some embodiments, an inorganic filler with a lower melting point can also be added, such as a glass powder/glass fiber, borate (zinc borate) , metal oxide (zinc oxide, boron oxide) , or a combination thereof. These inorganic fillers have a melting point below 950℃, allowing them to act as fluxing agents. Therefore, such inorganic fillers are also referred to as “fluxing agents. ” With the addition of a fluxing agent, the inorganic filler can melt at lower temperatures and combine with other inorganic fillers to form a denser, continuous (ceramic-like) structure, thereby enhancing the strength of the residual layer after burning. The amount of the fluxing agent in the inorganic filler ranges from 0-70 wt%, preferably at least 20 wt%.

In some embodiments, the inorganic filler includes fillers with a melting point below 950℃and a length-to-diameter ratio of 10-1000, such as ground glass fibers, borates (zinc borate) , metal oxides (zinc oxide, boron oxide) , or combinations thereof.

Based on the total weight of the polyurethane fire-retardant coating composition, the total amount of the inorganic filler is 20-70 wt%, for example, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, or 70 wt%; preferably 23-70 wt%, and more preferably 50-60 wt%.

Diluent

The diluent is selected from a reactive diluent and/or a non-reactive diluent. By adding a diluent, the viscosity of the first component and the polyurethane fire-retardant coating composition can be reduced effectively.

A reactive diluent can be selected from styrene, C1-C10 alkyl acrylates, and/or C1-C10 alkyl methacrylates; preferably: hydroxyethylmethacrylate, hydroxypropylmethacrylate (HPMA) , hydroxybutylmethacrylate, hydroxypentylmethacrylate, hydroxyhexylmeth acrylate, hydroxyethylacrylate, hydroxypropylacrylate, hydroxybutylacrylate or combinations thereof.

In some preferred embodiments, a non-reactive diluent may also be added, which can be selected from esters, ethers, or ketone compounds; its molecular weight is less than or equal to 300 g/mol, and its viscosity is 20-400 cps. Among them, ester compounds are more preferred, e.g., trimethyl phosphate and triethyl phosphate (TEP) .

Based on the total weight of the first component, the content of the diluent is 1-45 wt%, preferably 2-25 wt%, and more preferably 5-25 wt%.

In some embodiments, the first component according to the present disclosure includes:

5-40 wt%, preferably 10-35 wt%of at least one polyol;

20-70 wt%, preferably 23-70 wt%of at least one inorganic filler; and

1-45 wt%, preferably 2-25 wt%of at least one diluent.

In addition to the above components, optionally, the first component also includes at least one flame retardant, at least one chain extender and/or crosslinking agent, at least one catalyst, at least one polymerization inhibitor, and/or at least one defoamer.

Flame retardant

According to the present disclosure, suitable solid flame retardants may include those described in US2011/0006579 or those described in US89058601A, such as halogen-containing and/or phosphorus-containing compounds, antimony oxides, boron-containing compounds, hydrated aluminum oxide, or ammonium polyphosphate.

In some embodiments, the flame retardant does not comprise an electrically conductive flame retardant such as carbon black or graphite. In some embodiments, the flame retardant includes melamine, ammonium polyphosphate, and aluminum hydroxide, etc.

In some embodiments, based on the total weight of the polyurethane fire-retardant coating composition, the content of the flame retardant is at least 5 wt%, preferably at least 10 wt%.

Chain extender/crosslinker

In some embodiments, the first component according to the present disclosure further comprises a chain extender and/or a crosslinker. Chain extenders/crosslinkers suitable for the present disclosure have a molecular weight less than 500 g/mol, e.g. less than 400 g/mol, less than 300 g/mol, less than 200 g/mol or less than 100 g/mol.

A chain extender has two functional groups reactive to isocyanate, e.g. OH-, -SH or NH₂ groups. Based on the total weight of the first component, the content of the chain extender is 5 -30 wt%, preferably 10 -25 wt%, more preferably 10 -20 wt%.

Practical examples of chain extenders include monoethylene glycol (MEG) , diethylene glycol (DEG) , 1, 2-propanediol, 1, 3-propanediol (DPG) , 1, 4-butanediol (BDO) , 1, 3-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, tetraethylene glycol, dipropylene glycol, cyclohexanediol and aliphatic or aromatic amine chain extenders, e.g. aliphatic or aromatic diamines such as ethylenediamine, triethylenediamine and/or diethyl toluene diamine (DETDA) . Other possible chain extenders of low molecular weight are for example mentioned in "Polyurethane Handbook" , Carl Hanser Verlag, 2nd edition (1994) , Chapters 3.2 and 3.3.2. In some preferred embodiments, the chain extender is selected from monoethylene glycol (MEG) , 1, 3-propanediol (DPG) and 1, 4-butanediol (BDO) .

The crosslinker has at least three functional groups reactive to isocyanate. Practical examples of crosslinkers include 1, 2, 4-and 1, 3, 5-trihydroxycyclohexane, glycerol (GLY) , trimethylolpropane (TMP) , pentaerythritol, triethanolamine (TEOA) , diethanolamine (DEOA) and hydroxyl-containing polylkylene oxides of low molecular weight based on ethylene oxide and/or 1, 2-propylene oxide and the abovementioned diols and/or triols. Other possible crosslinkers of low molecular weight are for example mentioned in "Polyurethane Handbook" , Carl Hanser Verlag, 2nd edition (1994) , Chapters 3.2 and 3.3.2.

Catalyst

In some embodiments, the first component according to the present disclosure further comprises a catalyst. Catalyst can accelerate the reaction of a polyol with an isocyanate. Practical examples of conventional catalysts used in the preparation of polyurethanes include, for example, amidines such as 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine; tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, N-methylmorpholine, N-ethylmorpholine, N-cyclohexylmorpholine, N, N, N', N'-tetramethylethylenediamine, N, N, N', N'-tetramethylbutylenediamine, N, N, N', N'-tetramethylhexylenediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis (dimethylaminopropyl) urea, dimethylpiperazine, 1, 2-dimethylimidazole and 1-azabicyclo (3, 3, 0) octane, preferably 1, 4-diazabicyclo (2, 2, 2) octane and alkanolamine compounds, such as triethanolamine, triisopropanolamine, N-methyldiethanolamine and N-ethyldiethanolamine and dimethylethanolamine. Similar useful catalysts include organic metal compounds, preferably organotin compounds, e.g. tin (II) salts of organic carboxylic acids, e.g. tin (II) acetate, tin (II) octanoate, tin (II) ethylhexanoate, tin (II) laurate; and dialkyl tin (IV) salts of organic carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate; and bismuth carboxylates, such as bismuth (III) neodecanoate, bismuth 2-ethylhexanoate and bismuth octanoate or mixtures thereof. Organic metal compounds may be used alone, or preferably in combination with strongly basic amines.

In some embodiments, the catalyst is preferably a trimerization catalyst; practical examples include alkali metal carboxylate salts, alkaline earth metal carboxylate salts, quaternary ammonium carboxylate salts, or any combination thereof. Practical examples of suitable alkali metal carboxylate salts include, but are not limited to, potassium neopentanoate, potassium formate, potassium acetate, potassium propanoate, potassium butanoate, potassium pentanoate, potassium hexanoate, potassium neohexanoate, potassium heptanoate, potassium octanoate, potassium neooctanoate, potassium 2-ethylhexanoate, potassium decanoate, potassium butyrate, potassium isobutyrate, potassium nonanoate, potassium stearate, potassium neodecanoate, potassium neoheptanoate, sodium octanoate, lithium stearate, sodium hexanoate, lithium octanoate, etc., or any combination thereof. In another aspect, at least one carboxylate salt is potassium neopentanoate, potassium acetate, potassium octanoate, potassium 2-ethylhexanoate, or any combination thereof.

Defoamer

In some embodiments, the first component according to the present disclosure further comprises a defoamer. The defoamer is a compound which has surface activity and prevents or inhibits foam formation. In the present disclosure, a preferred defoamer is a polysiloxane.

By adding a defoamer, foaming of the polyurethane can be suppressed, and it is thus possible to reduce porous structures in the polyurethane coating layer and increase the density and mechanical strength of the polyurethane coating layer.

Surfactants can also be used as defoamers. Practical examples of suitable surfactants include anionic, cationic or non-ionic surfactants. The surfactant may be a single surfactant, or a mixture of surfactants. In a preferred embodiment, the surfactant is non-ionic.

Foaming agent

As is known in the art, during a reaction between an isocyanate and a polyol, a foaming agent will promote the release of gas, which will form porous structures in the polyurethane coating layer. However, to increase the mechanical strength of the polyurethane coating layer and the composite material mentioned below, these porous structures are undesirable. Therefore, in some embodiments, the polyurethane fire-retardant coating composition according to the present disclosure does not contain a foaming agent. Foaming agents include "physical foaming agents" , "chemical foaming agents" or combinations thereof.

The term "physical foaming agent" means a foaming agent that does not undergo a chemical reaction with the first component and the second component to provide foaming gas. The physical foaming agent may be a gas or a liquid. Liquid physical foaming agents generally evaporate when heated to form gas, and evaporate from the polyurethane elastomer obtained. Practical examples include liquid carbon dioxide (CO₂) , HCFC, HFO's, pentane and all isomers thereof, acetone, entrained air, other inert gases or combinations thereof.

The term "chemical foaming agent" means a foaming agent which undergoes a chemical reaction with a polyisocyanate component or another component to release gas. Practical examples include formic acid, methyl formate, water and combinations thereof.

Polymerization inhibitor

In some embodiments, the first component according to the present disclosure further comprises a polymerization inhibitor to avoid polymerization reactions of free radicals of (meth) acrylates. Preferred polymerization inhibitors include (2, 2, 6, 6-tetramethylpiperidin-1-yl) oxyhydroxyl (TEMPO) , monomethyl ether of hydroquinone (MEHQ) , dihydroxy benzene, benzoquinone, hindered phenols and hindered phenols based on triazine derivatives.

The first component according to the present disclosure has a viscosity of 100 -5000 cps, e.g. 100 cps, 500 cps, 1000 cps, 2000 cps, 3000 cps, 4000 cps or 5000 cps. In some embodiments, the viscosity of the first component is 100-3000 cps, more preferably 100-1000 cps.

Second component

As stated above, the second component according to the present disclosure comprises at least one polyisocyanate.

Polyisocyanate

The present disclosure does not limit the type of polyisocyanate, which means an organic compound containing two or more active isocyanate groups per molecule, i.e., a functionality of 2 (in which case the polyisocyanate is also known as a diisocyanate) or greater than 2. Practical examples of polyisocyanates may include any aliphatic, alicyclic, araliphatic and aromatic bifunctional or polyfunctional isocyanates known in the art and any required mixtures thereof. The polyisocyanate can be a monomer, prepolymer and/or polymeric isocyanate.

Practical examples of suitable polyisocyanates include, but are not limited to, aromatic isocyanates, aliphatic isocyanates, alicyclic isocyanates and araliphatic isocyanates. Practical examples of suitable polyisocyanates include tri-, tetra-, penta-, hexa-, hepta-and/or octa-methylene diisocyanate, 2-methylpentamethylene-1, 5-diisocyanate, 2-ethylbutylene-1, 4-diisocyanate, pentamethylene-1, 5-diisocyanate, butylene-1, 4-diisocyanate, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI) , 1, 4-and/or 1, 3-bis (isocyanatomethyl) cyclohexane (HXDI) , cyclohexane-1, 4-diisocyanate, 1-methylcyclohexane-2, 4-and/or 2, 6-diisocyanate and/or bicyclohexylmethane-4, 4′-, 2, 4′-and 2, 2′-diisocyanate, diphenylmethane-2, 2′-, 2, 4′-and/or 4, 4′-diisocyanate (MDI) , polymeric MDI, naphthylene-1, 5-diisocyanate (NDI) , toluene-2, 4-and/or 2, 6-diisocyanate (TDI) , 3, 3′-dimethyldiphenyl diisocyanate, 1, 2-diphenylethane diisocyanate and/or phenylene diisocyanate and combinations thereof.

In some preferred embodiments, the polyisocyanate is one that has two isocyanate groups. In some preferred embodiments, the polyisocyanate is an aromatic isocyanate. Methylene diphenyl diisocyanate (MDI) and/or toluene diisocyanate (TDI) are especially preferred for the present disclosure.

Other possible polyisocyanates are for example given in "Kunststoffhandbuch, Band 7, Polyurethane" [Plastics handbook, Vol. 7, Polyurethanes] , Carl Hanser Verlag, 3rd Edition, 1993, Chapters 3.2 and 3.3.2.

An isocyanate prepolymer can be obtained by reacting the abovementioned polyisocyanate in excess with a polyol at a temperature of, for example, 30 -100℃, preferably about 80℃. 4, 4'-MDI together with diazacyclobutanone imine modified MDI, and a commercially available polyol based on a polyester, e.g. a polyester derived from adipic acid, or a polyether, e.g. a polyether derived from ethylene oxide and/or propylene oxide, are preferred for producing a prepolymer used in the present disclosure. 4, 4'-MDI and a polyol derived from ethylene oxide and/or propylene oxide are preferred for producing a prepolymer used in the present disclosure.

Polyols used for preparing isocyanate prepolymers are known to those skilled in the art, and for example are described in "Kunststoffhandbuch [Plastics handbook] , Vol. 7, Polyurethanes" , Carl Hanser Verlag, 3rd Edition, 1993, Chapter 3.1.

Modified polyisocyanates are also generally used, i.e. products obtained by chemical reaction of organic polyisocyanates and having two or more active isocyanate groups per molecule. Worthy of special mention are polyisocyanates containing an ester group, urea group, biuret group, allophanate group, carbodiimide group, isocyanurate group, urea dione group, carbamate group and/or ethyl carbamate group.

Preferred polyisocyanates are liquid at room temperature. In some embodiments, the polyisocyanate has a viscosity of 1 -1000 cps, more preferably 100 -500 cps, measured in accordance with ASTM D2196-15 at 25℃. For example, the polyisocyanate has a viscosity of 100 cps, 200 cps, 300 cps, 400 cps or 500 cps.

Practical examples of suitable commercially available polyisocyanate compounds include M20S (from BASF) or MIPS (from BASF) .

In addition to the above components, the first component and/or the second component may also include at least one dehydrating agent.

Dehydrating agent

As stated above, water, and water vapour contained in entrained air, will also cause porous structures to arise in the polyurethane coating layer formed. To reduce porous structures in the polyurethane coating layer, in some embodiments, the polyurethane fire-retardant coating composition according to the present disclosure further comprises a dehydrating agent. The dehydrating agent can help to absorb residual water, thereby reducing the formation of porous structures that impair the mechanical properties of the polyurethane coating layer obtained.

Suitable dehydrating agents include zeolites, molecular sieves, active silanes (such as vinyltrialkoxysilanes) , minerals (such as calcium oxide) and mixtures thereof.

In some embodiments, based on the total weight of the polyurethane fire-retardant coating composition, the content of the dehydrating agent is 0.5-10 wt%, preferably 1-8 wt%.

Other components

The polyurethane fire-retardant coating composition may further contain an aid and/or an additive. Any known aids and added substances/materials for preparing polyurethanes can be used here. Suitable practical examples include mould release agents, dyes, pigments, hydrolysis inhibitors, antifungal/antibacterial substances and stabilizers (preferably against hydrolysis, light, heat or discoloration) . Such substances are known and are recorded for example in "Kunststoffhandbuch, Band 7, Polyurethane” , Carl Hanser Verlag, 3rd edition, 1993, Chapters 3.4.4 and 3.4.6 to 3.4.11.

According to the present disclosure, the mixing ratio of the first component to the second component ranges from 0.5: 1 to 5: 1, for example, 0.5: 1, 1: 1, 2: 1, 3: 1, 4: 1, and 5: 1.

The isocyanate index (i.e., NCO index) of the polyurethane fire-retardant coating composition according to the present disclosure ranges from 150 to 800, for example, 150, 200, 300, 400, 500, 600, 700, or 800. In some preferred embodiments, the isocyanate index is 300-500, more preferably 300-400.

In other words, when preparing the polyurethane fire-retardant coating composition according to the present disclosure, the polyisocyanate and an isocyanate-reactive compound react at an isocyanate index of 150-800, preferably 300-500, and more preferably 300-400. The expression "isocyanate-reactive compound" means that the compound contains at least two groups that are reactive to isocyanate (and includes the polyol component mentioned above) . Preferably, the isocyanate-reactive compound contains active hydrogen, e.g. OH-, SH-, NH-and CH-acid groups.

II. Composite material

According to a second aspect of the present disclosure, a composite material is provided, comprising

a substrate; and

a polyurethane coating layer prepared from the polyurethane fire-retardant coating composition as described above (for details see the first section, i.e. I. Polyurethane fire-retardant coating composition) , applied to at least a portion of a surface of the substrate, the polyurethane coating layer having a thickness of 0.5-1.5 mm, preferably 0.7-1.2 mm.

The polyurethane coating layer has strong fire-resistant insulation properties and can slow down the transfer of high temperatures to the surrounding environment, thereby preventing the spread of high temperatures/burning for a certain period of time. As a result of applying a polyurethane coating layer on the substrate, the composite material can serve as a protective barrier to promptly block the spread of high temperatures produced by local thermal runaway to the surroundings.

Specifically, the residual layer formed after the polyurethane coating layer undergoes combustion has good mechanical stability, thereby continuously providing fire-resistant insulation and voltage resistance capability.

In some embodiments, the substrate may be a metal material or a resin material, i.e. the substrate may be made of a metal material, or may be made of a resin material. As a structural member of a battery product, the substrate must have a certain mechanical strength to protect internal battery elements from damage when subjected to external knocks or compression, and/or bear the weight of the internal battery elements. In addition, the substrate also has a waterproofing effect. Exemplary metal materials include aluminium alloys, iron, steel and aluminium, etc. Exemplary resin materials include polyurethanes, polyurea, epoxy resins and unsaturated resins, etc.

In some embodiments , the substrate has a thickness of 0.3 mm to 3.5 mm. In particular, when a base layer is made of a metal material, the thickness thereof is preferably 0.5 mm -2 mm, e.g. 0.5 mm, 0.8 mm, 1 mm, 1.5 mm or 2 mm; when the base layer is made of a resin material, the thickness thereof is preferably 1 mm -3.5 mm, e.g. 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm or 3.5 mm. As stated above, the polyurethane coating layer has excellent fire-resistant and heat barrier performance, and thus allows the substrate to have a smaller thickness, to achieve the goal of making the composite material lightweight.

In some embodiments, the density of the polyurethane coating layer according to the present disclosure is 1.0-2.1 g/cm³, preferably 1.2-1.8 g/cm³.

In some embodiments, the Shore hardness of the polyurethane coating layer according to the present disclosure is 60-80; its tensile strength (measured according to DIN 53504) is 3-8 MPa; its adhesion strength (measured according to ISO 844) is greater than 1 MPa.

The composite material according to the present disclosure may be prepared by the following method:

1) Provide the first component;

2) Provide the second component;

3) Mix and react the first component and the second component in a certain ratio to obtain a liquid reaction mixture of polyurethane (i.e., the polyurethane fire-retardant coating composition described in the first aspect above) ;

4) Apply the liquid reaction mixture of polyurethane obtained in the third step onto the surface of the substrate;

5) Cure to form a polyurethane coating.

III. Battery product

According to a third aspect of the present disclosure, a battery product is provided, at least partially coated with the polyurethane fire-retardant coating composition as described in the second aspect above. Practical examples of the battery product include a battery shell, a battery unit, a battery module, a battery pack, a battery unit shell, a battery module shell, a battery pack shell, a tray, a thermal management system, a cooling module, a cooling plate, an FPC (such as a busbar) and an electrical connector, etc. Further, in some embodiments, the composite material is used as a housing of the battery product, e.g. a top cover; in some embodiments, the composite material may be simultaneously used as a top cover, a bottom plate and a side plate of the battery product.

In some embodiments, the battery product is a cell unit, comprising a housing and a bare cell located inside the housing, a material of the housing of the cell unit being the composite material as described in the second aspect above.

In some embodiments, the battery product is a battery module, comprising a housing and multiple cell units located inside the housing; practical examples of the housing include a top cover, a bottom plate and a side plate, wherein a material of at least one of the top cover, bottom plate and side plate is the composite material as described in the second aspect above.

In some embodiments, the battery product is a battery pack, comprising a housing and multiple battery modules located inside the housing; practical examples of the housing include a top cover, a bottom plate and a side plate, wherein a material of at least one of the top cover, bottom plate and side plate is the composite material as described in the second aspect above.

It should be understood that only some application scenarios of the polyurethane fire-retardant coating composition according to the present disclosure have been set out above as examples. Those skilled in the art will understand that the polyurethane fire-retardant coating composition according to the present disclosure may also be used in other products that require heat barrier or fire-resistant performance.

Examples

The present disclosure is now described with reference to Examples and Comparative Examples, but these Examples and Comparative Examples are not intended to limit the present disclosure.

I. Materials:

II. Preparation of the Composite Materials, Examples 1-6

The materials listed under the first component in the amounts shown in Table 1 below (in weight %) were mixed and added to a reaction vessel. They were mixed at 1800 rpm for 3-5 minutes until the mixture was uniform to prepare the first component. The materials listed under the second component in the amounts shown in Table 1 below (in weight %) were added to another reaction vessel and mixed at 1800 rpm for 3-5 minutes to prepare the second component. The first and second components were mixed in proportion according to the NCO index shown in Table 1 below to obtain a polyurethane reaction mixture (i.e., the polyurethane fire-retardant coating composition) .

An excess of polyurethane reaction mixture was poured onto the surface of a steel plate (size: 11 × 13 cm, thickness: 0.8 mm) . A scraper (gap = 1.2 mm ± 0.2) was then moved across the steel plate from one end to the other, removing excessive polyurethane reaction mixture and ensuring that the initial coating thickness of Examples 1-6 remained consistent. The steel plate then undergoes curing at 80 degrees Celsius to form a polyurethane coating layer.

III. Comparative Examples 1-3 of Composite Materials

Comparative Example 1 of the composite material uses the same steel plate as in Examples 1-6, except that the steel plate is not coated with the polyurethane coating layer.

The preparation method of Comparative Examples 2-3 of composite materials is the same as the preparation steps of Examples 1-6, except for the formulations of the first and second components.

Table 1

IV. Test Results

Hardness Test

In order to evaluate the scratch resistance of the polyurethane coating layer, the Shore hardness of the polyurethane coating layers in Examples 1-6 was measured according to DIN ISO48-4 (2018) (standard) , and the results are shown in Table 2. The results indicate that the polyurethane coating layer according to the present application has good mechanical hardness, i.e., good scratch resistance.

Table 2: Test Results

Burning test

To test the fire-resistant and heat barrier performance of these composite materials, a burning test is carried out according to GB 38031-2020 (8.2.7.1) , the specific steps comprising:

Adjust the flame temperature to stabilize it at 1000℃;

Draw a cross sign on the front and back of the composite materials of Examples 1-6 and of Comparative Examples 1-3 to identify the burning point, aligning the thermocouple with the burning point;

Align the Bunsen burner nozzle with the burning point on the side of the composite material coated with a polyurethane coating layer, igniting at a vertical distance of 50 mm from the burning point;

Close the fume hood and burn for 10 minutes, using methane from a combustion chamber pipeline as the gas source;

Record the temperature of the composite material backplate (i.e., the side remote from the polyurethane coating) (see Table 2 “Backplate Temperature” ) .

After being burned at 1000℃ for 10 minutes, the polyurethane coating layer will form a carbonized structure layer (i.e., “residual layer” ) on the steel plate surface, which is mainly composed of the inorganic filler. As shown in Table 3 below, the residual layer formed in Examples 1-6 remains undamaged, meaning it is in an intact state, so the residual layer is able to continuously provide fire resistance and thermal insulation and prevent gas diffusion. This is especially advantageous for battery products; in particular, when thermal runaway occurs inside a battery product, the application of the polyurethane coating layer of the present disclosure to a housing of the battery product enables fire-resistant and heat barrier performance to be provided continuously, lowering the risk of further combustion.

In contrast, as shown in Figure 1, the polyurethane coating layer of Comparative Example 2 bulges after burning at 1000℃ for 10 minutes; as shown in Figure 2a, the central position of the polyurethane coating layer in Comparative Example 3 has melted and peeled off, exposing the substrate steel plate. Figure 2b further shows a side view of the edge of the steel plate of Comparative Example 3, indicating that the residual layer has a hollow structure and has separated from the steel plate by 1.9 cm. In other words, the residual layer structure formed after burning of the polyurethane coating layer in Comparative Examples 2-3 has poor stability and cannot provide effective fire resistance and thermal insulation performance.

Secondly, since the residual layer itself is not flammable and has a low thermal conductivity, the residual layer is also capable of weakening heat conduction. As shown in Table 3 below, the backplate temperatures of Examples 1-6 are all below 302℃, indicating that the composite materials according to the present disclosure have good fire resistance and thermal insulation performance. In contrast, the backplate temperature of Comparative Example 1 (without the polyurethane coating layer) reaches 443℃. As mentioned above, the residual layers of Comparative Examples 2-3 bulged and had melted and peeled off, etc., so their backplate temperatures were no longer tested.

Voltage resistance test

To evaluate the voltage resistance of the composite materials, the composite materials of Examples 1-6 and Comparative Example 2 (since the carbonized layer of Comparative Example 3 had melted and peeled off, its voltage resistance performance was not further tested) underwent the above burning test (i.e., 10 minutes at 1000℃) . Afterwards, the composite material was tested at an initial AC voltage (= 500 V) for 60 seconds, then the voltage was increased by 500 V each time and testing was continued for 60 seconds until electrical breakdown occurred.

As shown in Table 3 below, the electrical breakdown AC voltages of the composite materials in Examples 1-6 were 2000 V or higher. In contrast, the composite material of Comparative Example 2 had electrical breakdown at an AC voltage of 500 V. These test results indicate that the polyurethane coating layer according to the present disclosure and the composite materials containing the polyurethane coating layer have excellent voltage resistance performance.

Table 3: Burning and Voltage Resistance Test Results

The basic principles and exemplary embodiments of the present disclosure have been described above. Those skilled in the art should understand that the above description is merely intended to explain the present disclosure, which is not limited by the embodiments above. Without departing from the spirit and scope of the present disclosure, the present disclosure may also have various changes and improvements, all of which fall within the scope of protection of the present disclosure.

Claims

Polyurethane fire-retardant coating composition, obtained by reacting at least the following components:

a first component, comprising

at least one polyol;

at least one inorganic filler; and

at least one diluent; and

a second component, comprising

at least one polyisocyanate;

characterized in that, based on the total weight of the polyurethane fire-retardant coating composition, the content of the inorganic filler is 20-70 wt%, preferably 23-70 wt%, and more preferably 50-60 wt%; and

the isocyanate index of the polyurethane fire-retardant coating composition is 150-800, preferably 300-500, and more preferably 300-400.
Polyurethane fire-retardant coating composition according to Claim 1, characterized in that the polyurethane fire-retardant coating composition further comprises a flame retardant, and the content of the flame retardant is more than 5wt%, preferably more than 10wt%based on the total weight of the polyurethane fire-retardant coating composition.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the average functionality of the polyol is 2 to 3; optionally, the number average molecular weight of the polyol is 1000-10000 g/mol, preferably 2000-6000 g/mol.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the inorganic filler is one or more selected from nitride, metal oxide, metal hydroxide, ceramic, and/or mineral salt.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the inorganic filler is one or more selected from mica, talc, clay, magnesium calcium carbonate, calcium carbonate, calcium sulfate, calcium silicate, barium sulfate, silica, aluminum hydroxide, magnesium hydroxide, alumina, silica, calcium oxide, titanium dioxide, magnesium oxide, zinc oxide, aluminum nitride, boron nitride, silicon nitride, hollow glass, ceramic microspheres, vermiculite, diatomaceous earth, wollastonite, glass fiber, ceramic fiber, basalt fiber, and/or silicate.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the length-to-diameter ratio of the inorganic filler is 10-1000.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the inorganic filler further includes inorganic fillers with a melting point below 950℃.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the amount of the diluent is 1-45 wt%, preferably 5-25 wt%, based on the total weight of the first component.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the diluent is selected from a reactive diluent and/or a non-reactive diluent.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the first component further includes a chain extender, a crosslinking agent, a catalyst, a polymerization inhibitor, and/or a defoamer.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the polyurethane fire-retardant coating composition further comprises a dehydrating agent.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the polyurethane fire-retardant coating composition does not contain a foaming agent.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the viscosity of the first component measured at 25℃ according to ASTM D2196-15 is 100-5000 cps, preferably 100-3000 cps.
Polyurethane fire-retardant coating composition according to Claim 1 or 2, characterized in that the mixing ratio of the first component to the second component is 0.5 : 1 to 5 : 1.
Composite material, comprising

a substrate; and

a polyurethane coating layer, which is prepared from the polyurethane fire-retardant coating composition according to any one of Claims 1-14 and which is applied to at least a portion of a surface of the substrate, the polyurethane coating layer having a thickness of 0.5-1.5 mm, preferably 0.7-1.2 mm.
Composite material according to Claim 15, characterized in that the Shore hardness of the polyurethane coating layer is 60-80.
Composite material according to Claim 15, characterized in that the density of the polyurethane coating layer is 1.2-2.1 g/cm³, preferably 1.2-1.8 g/cm³.
Composite material according to Claim 15, characterized in that the tensile strength of the polyurethane coating layer is 3-8 MPa.
Composite material according to Claim 15, characterized in that the bonding strength of the polyurethane coating layer is greater than 1 MPa.
Battery product, characterized in that the battery product is at least partially coated with the polyurethane fire-retardant coating composition according to any one of Claims 1-14.
Battery product according to Claim 20, characterized in that the battery product is a battery shell, battery unit, battery module, or battery pack.