EP3673009A1

EP3673009A1 - Pei particle foams for applications in aviation interiors

Info

Publication number: EP3673009A1
Application number: EP18753207.2A
Authority: EP
Inventors: Christian Trassl; Denis HOLLEYN; Kay Bernhard
Original assignee: Evonik Operations GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2017-08-24
Filing date: 2018-08-20
Publication date: 2020-07-01
Also published as: RU2020111351A; AU2018321107A1; US11814499B2; TW201920405A; WO2019038213A1; KR20200044073A; CA3073778A1; JP7315534B2; AU2018321107C1; TWI851541B; AU2018321107B2; KR102628067B1; RU2020111351A3; JP2020531648A; US20230105032A1; SG11202001473WA; US20200207939A1; MX2020001993A; IL272841A; BR112020003712A2

Abstract

Polyetherimide (PEI)-based polymer foams comply with the statutory requirements on interiors in aviation demanded by the aviation industry. The requirements concerning fire behaviour, resistance to media and mechanical strength in particular represent significant challenges. Suitable polymer foams are produced as semi-finished products in the prior art. Post-processing into shaped parts is uneconomic in terms of time and the use of material, because of the large volumes of cutting waste, for instance. The invention solves this problem in that the material that is, in principle, suitable can be processed into particle-foam shaped parts. Said shaped parts can be produced without post-processing in short cycle times and hence economically. Furthermore, new options arise for function integration, such as the direct foam moulding of inserts, etc., and in respect of design freedom.

Description

PEI particle foams for applications in the aviation interior

Field of the invention

Polymeric foams based on polyetherimides (PEI) fulfill the aviation requirements of the aviation industry. Especially the requirements of the fire behavior, the media resistance and the mechanics make a big difference here

Challenge dar. According to the prior art suitable polymer foams are produced as semi-finished products. Post-processing to moldings is uneconomical in terms of time and material utilization, such as e.g. due to large amounts of cut waste. The invention solves this problem by the fact that the material suitable in principle can be processed into particle foam moldings. These moldings can be produced without reworking in short cycle times and thus economically. Furthermore, this opens up new possibilities of functional integration, such as by direct foaming of inserts, etc., and in terms of creative freedom.

State of the art

Suitable foams for installation in the aviation industry are well known. However, for the most part only foams of pure PMI (polymethacrylimide), PPSU (polyphenylene sulfones) or PES (polyethsulfones) are described. Also found in the literature but unsuitable from a toxicological point of view is also PI (polyarylimide). All these

Materials have hitherto been used exclusively as block or plate materials.

Other materials are less detailed than plate material for installation in the

Aerospace industry described. Thus, for example, poly (oxy-1, 4-phenylsulfonyl-1, 4-phenyl) (PESU) is such a material. This is sold, for example, under the product name Divinycell F by DIAB. In the further processing of these extrusion foam boards, however, uneconomically large amounts of waste material are produced. An economical method of avoiding cut-off in the manufacture of three-dimensional foam moldings is the use of bead foams rather than block foams. All of the prior art particulate foams have either disadvantages in use at high temperatures, or overall, and especially at these high temperatures, inadequate mechanical properties. In addition, very few foams are known that are not easy to inflame and Therefore, for example, in the interiors of road, rail or aircraft can be installed. For example, particle foams based on polypropylene (EPP), polystyrene (EPS), thermoplastic polyurethane elastomer (E-TPU) or PMI (ROHACELL Triple F) have inadequate flame retardancy, while all of them are inherently suitable

flame retarded polymers, e.g. PES, PEI or PPSU according to the current state of the art can only be processed into block foams.

task

Object of the present invention, it was in view of the prior art

Composition for producing novel foams or composite materials, which are, for example, a foam core with thermoplastic or crosslinked

Cover layers may be available for use in aircraft construction. The resulting foams should have a good combination of applicability at high temperatures, good mechanical properties, in particular with respect to a sufficient elongation at break and for many applications in the field of vehicle and aircraft at least sufficient flame retardancy.

In particular, the foam should have a high resistance to various liquid, acidic, basic or hydrophobic liquids and to emulsions. Furthermore, from the composition to be developed by a variety of methods and with a wide range of three-dimensional shapes of the foam should be feasible and in the production of the final component as little or no waste as possible.

Other non-explicit tasks may be apparent from the description, claims, or examples of this text, without being explicitly set forth at this point.

solution

The objects are achieved by providing a novel composition for the production of temperature-resistant, flame-retardant foam materials for use in the aerospace industry, in particular in aircraft construction. This composition according to the invention for producing foams is characterized in that it is is a particle foam based on polyetherimides (PEI). The particle foam according to the invention has a glass transition temperature between 180 and 215 ° C. as the foamed material, and in which the average cell diameter of the particle foam is less than 2 mm, preferably less than 1 mm, more preferably less than 500 μm and very particularly preferably less than 250 μm.

This is particularly surprising, since the actual glass transition temperature of the PEI 215 to 217 ° C and thus the material can not be processed according to the current state of the art, for example by means of underwater pelletizing, to a particle foam.

According to the invention, the term cell describes a region in a foam which contains no matrix material but is at least partially enclosed by it. Cells are also called pores. Ideally, in a rigid foam these pores or cells are closed, which in turn means that the cell is completely enclosed by the matrix material of the foam. In the case of a softer foam at least partially open cells are present. These can be explained by the arrangement of incomplete walls or in the

Nevertheless, identify the extreme case of webs as single cells. This also determines the size of such open cells. The size of a cell can be easily measured in many cases, for example with the aid of a microscope. Even taking these factors into account, it is easy for a person skilled in the art to observe the maximum cell size in the foam.

A foam particle is understood according to the invention to mean the region in a particle foam which is defined by foaming a single unfoamed or prefoamed particle. The boundary between the individual, interconnected foam particles can be easily recognized with the naked eye or determined under a light microscope. This is particularly applicable when the interfaces between two foam particles are clearly visible. Since this does not necessarily have to be the case, a simplified method is used according to the invention: for this purpose, a theoretical average diameter of a

Foam particles simply from the diameter of the unfoamed particles, the

Total volume of unfoamed particles and the volume of the finished foam part calculated. The skilled worker knows that in the case of particle foams, a regular size distribution of the foam particles can be achieved in such a way that only in the peripheral areas of the foam particles

Foam part slight deviations occur. Furthermore, an advantage of the present invention is that the volume fraction of the gusset between the individual foam particles is so small that it hardly comes into play in the volume measurement of the finished foam part. These foam particles are preferably less than 1 cm in the finished foam, more preferably less than 0.7 cm. Given glass transition temperatures are inventively - unless otherwise stated - measured by DSC (Differential Scanning Calometry). The skilled person knows that the DSC is only sufficiently meaningful if, after a first heating cycle up to a temperature which is at least 25 ° C above the highest glass transition or

Melting temperature, but at least 20 ° C below the lowest decomposition temperature of a material, the material sample is held for at least 2 min at this temperature. Thereafter, the mixture is again cooled to a temperature which is at least 20 ° C below the lowest glass transition or melting temperature to be determined, the cooling rate should be a maximum of 20 ° C / min, preferably a maximum of 10 ° C I min. After a further waiting time of a few minutes, the actual measurement takes place, in which the sample is heated to at least 20 ° C. above the highest melting or glass transition temperature at a heating rate of generally 10 ° C./min or less.

The composition according to the invention for producing the particle foam in a first alternative embodiment of the invention preferably consists of 80 to 99.5% by weight PEI. Furthermore, this composition has 0.5 to 10% by weight, preferably 1 to 9% by weight of a blowing agent. In addition, among other things 0 to 10 wt%, preferably 1 to 5 wt% additives may be included. The additives may in particular be flame retardant additives, plasticizers, pigments, UV stabilizers, nucleating agents, impact modifiers, adhesion promoters, rheology modifiers, chain extenders, fibers and / or nanoparticles.

As flame retardant additives usually phosphorus compounds, in particular phosphates, phosphines or phosphites are used. Suitable UV stabilizers or UV absorbers are generally known to the person skilled in the art. As a rule, one uses HALS compounds, Tiuvine or triazoles. The impact modifiers used are generally polymer particles comprising an elastomer or soft phase. These are often core (shell) shell particles, with an outer shell that is as a maximum weakly crosslinked and as a pure polymer would have an at least minimum miscibility with the PEI. In principle, all known pigments can be used as pigments. Of course, especially for larger quantities, the influence on the foaming process - as with all other additives used in larger amounts of more than 0.1% by weight - should be investigated. This is feasible for the skilled person with relatively little effort.

Suitable plasticizers, rheology modifiers and chain extenders are generally known to the person skilled in the art from the production of films, membranes or molded parts from PEI or blends containing PEI and can accordingly be transferred to the preparation of a foam from the composition according to the invention with little effort. The optionally added fibers are typically known fiber materials that can be added to a polymer composition. In a particularly suitable embodiment of the present invention, the fibers are PEI, PES, PPSU or blend fibers, the latter of a selection of the polymers mentioned.

The nanoparticles, which can be present, for example, as tubes, flakes, rods, spheres or in other known forms, are generally inorganic materials. These can take on different functions in the finished foam. Thus, these particles partially act as nucleating agents during foaming. Furthermore, the particles can influence the mechanical properties as well as the (gas) diffusion properties of the foam. Furthermore, the particles additionally contribute to the low flammability.

In addition to the nanoparticles listed, microparticles or poorly miscible, phase-separating polymers can also be added as nucleating agents. The polymers described are separated from the others in the consideration of the composition

Nucleating agents, as these primarily affect the mechanical properties of the foam, the melt viscosity of the composition and thus the

Take foaming conditions. The additional effect of a phase-segregating polymer as nucleating agent is an additional desired, but in this case not primary, effect of this component. For this reason, these additional polymers are listed above in the overall balance separately from the other additives.

The additives may optionally also contain up to 9% by weight of a further polymer component for adjusting the physical properties. The additional polymers may be, for example, polyamides, polyolefins, in particular PP, polyesters, in particular PET, sulfur-based polymers, such as, for example, PSU, PPSU, PES or poly (meth) acrylimide.

The choice of blowing agent is relatively free and determined for the skilled person in particular by the chosen Schäumungsmethode, the solubility in the polymer and the foaming temperature.

For example, alcohol such as e.g. Isopranol or butanol, ketones, such as acetone or

Methyl ethyl ketone, alkanes, such as iso- or n-butane, pentane, hexane, heptane or octane, alkenes, such as pentene, hexene, heptene or octene, CO2, N2, water, ethers, such as diethyl ether, aldehydes , such as Formaldehyde or propanal, fluorinated (chlorinated) hydrocarbons, chemical blowing agents or mixtures of several of these substances.

The chemical blowing agents are less or non-volatile substances that are chemically decomposed under the foaming conditions and thereby the actual

Form blowing agent. A very simple example of this is tert-butanol, which is under

Foaming conditions isobutene and water forms. Further examples are NaHCCh, citric acid or their derivatives, azodicarbonamide (ADC) or compounds thereof,

Toluenesulfonylhydrazine (TSH), oxybis (benzosulfohydrozide) (OBSH) or 5-phenyltetrazole (5-PT).

Preferably, the particle foam of the invention has a tensile strength according to IS01926 greater than 0.5 MPa, an elongation at break according to IS01926 between 8 and 12%, a shear modulus according to ASTM C273 at room temperature greater than 8 MPa, a shear strength according to ASTM C273 at

Room temperature greater than 0.45 MPa, a pressure module according to ISO 844 at room temperature greater than 13 MPa and a compressive strength to ISO 844 at room temperature greater than 0.4 MPa. When using the method described below for the production of the particle foam, it is for the expert, to obtain the glass transition temperature according to the invention and

Cell size easy to adhere to these mechanical properties. Surprisingly, it was also found that the particle foam according to the invention under the in the

Aircraft industry, in particular for use in the interior of an aircraft important fire safety regulations or fire properties applicable to FAR 25.852 is applicable.

Furthermore, it is very surprising that all the required material properties required for the

Be used in an aircraft interior, are met by a particle foam according to the invention just as well as by a corresponding foam in plate form. For PMI e.g. this relationship is not given because of this polymethacrylimide

Slabstock from a block foam meets the conditions, while a particle foam often has worse mechanical properties than a block foam. As special

Surprising advantage has also shown that such a particle foam in contrast to a block foam has no appreciable to no cell orientation. This results in a particle foam in many cases advantageous isotropic mechanical properties, while a corresponding block foam often anisotropic mechanical

Characteristics such that they differ in a surface and an axis perpendicular to this surface. Depending on the specific application, isotropic mechanical properties can be quite advantageous, especially if pressure loads occur uniformly from different directions.

The foams according to the invention preferably have a degree of foaming which constitutes a reduction in density compared with the unfoamed material of between 1 and 98%, preferably between 50 and 97%, particularly preferably between 70 and 95%. Preferably, the foam has a density between 20 and 1000 kg / m ³ , preferably 40 and 250 kg / m ^3, particularly preferably between 50 and 150 kg / m ³ .

In addition to the particle foam according to the invention, processes for its production are also part of the present invention. In principle, there are two preferred procedures for producing the PEI particle foams according to the invention. In a first process variant, a composition consisting of 80 to 99.5% by weight of PEI, 0.5 to 10% by weight of blowing agent and 0 to 10% by weight of additives is processed by means of an extruder with perforated plate to a foamed or foamable granules. The temperatures between feed zone and screw tip are preferably in a range between 320 and 400 ° C. Furthermore, there is usually no uniform temperature over this distance, but, for example, a gradient with increasing temperature in the conveying direction of the polymer melt. The temperature of the perforated plate is between 250 and 350 ° C and the melt temperature at the exit through the perforated plate between 230 and 360 ° C. As a rule, the loading with the propellant takes place in the extruder. The granules then foam on exiting the perforated plate when the pressure in the underwater granulation is less than the expansion force of the propellant. The granulate thus foamed is then preferably further processed into a particle foam. In a variant of this embodiment, the composition at the exit from the

Extruders are directed into an underwater granulator. This is designed so with respect to a combination of temperature and pressure that foaming is prevented. This procedure results in a granulate laden with propellant, which can later be foamed by renewed energy supply to the desired density and / or can be further processed under optional shaping to form a particle foam workpiece. The energy input necessary for prefouching can be achieved by means of contact heat, e.g. in a convection oven or

radiation-based by means of IR or microwave radiation.

In a second process variant for producing a PEI particle foam is a

Composition consisting of 90 to 100% by weight of PEI and 0 to 10% by weight of additives by means of an extruder with perforated plate also initially processed into granules, but not loaded with a propellant. Here, too, the temperatures, which are again not necessarily uniform, between intake zone and screw tip lie in a range between 320 and 400 ° C. Likewise, the temperature of the perforated plate between 250 and 350 ° C and the melt temperature at the exit through the perforated plate between 230 and 360 ° C. Here, the granules are then loaded in an autoclave with a propellant so that it contains between 0.5 and 10 wt% propellant. The propellant loaded granules can then be foamed by relaxing and / or by heating to a temperature of about 200 ° C to a particle foam.

With regard to the actual foaming, the skilled person is fundamentally familiar with various methods for foaming polymer compositions which are applicable to the present composition, in particular with regard to methods for thermoplastic foams. For example, the composition can be foamed at a temperature between 150 and 250 ° C and a pressure between 0, 1 and 2 bar. Preferably, the actual foaming takes place, if not following extrusion, at a temperature between 180 and 230 ° C in a normal pressure atmosphere.

In the variant of later loading with a propellant, a composition, still without propellant, in an autoclave at a temperature e.g. between 20 and 120 ° C and a pressure e.g. between 30 and 100 bar applied to the propellant and then foamed by lowering the pressure and raising the temperature to the foaming temperature in the autoclave. Alternatively, the composition imparted with the blowing agent in the

Autoclave cooled and removed after cooling. This composition can then be foamed later by heating to the foaming temperature. This can also be done, for example, with further shaping or in conjunction with other elements such as inserts or cover layers. Particularly preferably, the particle foam produced - regardless of the method used - then glued with a cover materials, sewn or welded.

Welded means that by heating the components, a material bond or an adhesion between the materials, e.g. by partially filling open pores at the

Foam surface with cover material, arises.

The cover material can be wood, metals, decorative films, composite materials, prepregs or other known materials.

In a later foaming of the material used, e.g. after blowing agent loading in an autoclave, the produced particle foam can alternatively in the presence of a

Covering material are foamed so that it is connected to this by means of gluing or welding.

In the variant of the method in which the loading with blowing agent takes place in the extruder, the PEI can alternatively also be added on leaving the extruder in an optionally heated mold, optionally containing cover materials. It is foamed with shaping to form a particle foam or a composite material. Alternatively, upon exiting the extruder, the composition may be passed into a foam spray device. In this device is then foamed directly under shaping.

Regardless of the variants used, the particle foams or composite materials can be seen during the foaming with inserts and / or channels can be installed in the particle foam. The foams according to the invention or the foams produced by the process according to the invention are used in the construction of spacecraft or aircraft, especially in their interior or exterior use. This may include the particle foams produced by the process of the invention or not, as well as the composite materials realized therefrom. In particular, due to the low flammability foams of the invention can be installed in the interior of these vehicles.

In particular, the pure PEI particle foams are particularly suitable for being installed in the interior of an aircraft. In addition to jets or small aircraft, aircraft also include helicopters or even spacecraft. Examples of the installation in the interior of such an aircraft are, for example, the fold-out trays on the seat back of a passenger machine, the filling of a seat or a partition, and, for example, in internal doors.

In addition, particle foams based on a blend containing PEI are also suitable for incorporation in the exterior of an aircraft. Outside means not only as a filling in the outer skin of an aircraft, but in particular in an aircraft nose, in the rear area, in the wings, in the outer doors, in the oars or in rotor blades.

Claims

claims

1. Use of a PEI particle foam in aircraft construction, characterized in that the foamed PEI has a glass transition temperature between 180 and 215 ° C, and that the average cell diameter of the particle foam is less than 2 mm.

2. Use of a particle foam according to claim 1, characterized in that it was obtained from a composition consisting of 80 to 99.5% by weight of PEI, 0.5 to 10% by weight of a blowing agent and 0 to 10% by weight of additives.

3. Use of a particle foam according to claim 1 or 2, characterized in that the additives are flame retardant additives, plasticizers, pigments, UV stabilizers, nucleating agents, impact modifiers, adhesion promoters, rheology modifiers, chain extenders, fibers and / or nanoparticles

4. Use of a particle foam according to any one of claims 1 to 3, characterized in that it is the blowing agents to an alcohol, a ketone, an alkane, an alkene, C02, N2, water, an ether, an aldehyde, chemical blowing agents or mixtures of several of these substances.

5. Use of a particle foam according to any one of claims 1 to 4, characterized in that the particle foam has a tensile strength according to IS01926 greater than 0.5 MPa, an elongation at break according to IS01926 between 8 and 12%, a shear modulus according to ASTM C273 at room temperature greater than 8 MPa , a shear strength according to ASTM

C273 at room temperature greater than 0.45 MPa, a pressure module according to ISO 844 at

Room temperature greater than 13 MPa and a compressive strength according to ISO 844 at

Room temperature greater than 0.4 MPa met. 6. Use of a particle foam according to any one of claims 1 to 5, characterized in that the particle foam is installed in the interior of an aircraft.

7. Use of a particle foam according to any one of claims 1 to 6, characterized in that the mean cell diameter of the particle foam smaller

500 μιτι amounts.

8. A process for producing a PEI particle foam for use according to any one of claims 1 to 7, characterized in that a composition consisting of 80 to 99.5 wt%, PEI, 0.5 to 10 wt% propellant and 0 to 10% by weight

Additives by means of an extruder with perforated plate to a foamed granules is processed, wherein the temperatures between the feed zone and screw tip in a range between 180 and 380 ° C, the perforated plate between 250 and 350 ° C and the melt temperature when exiting through the perforated plate between 230 and 360 ° C, and that the foamed granules is then further foamed to a particle foam.

9. A process for producing a PEI particle foam for use according to any one of claims 1 to 7, characterized in that a composition consisting of 90 to 100 wt%, PEI and 0 to 10 wt% additives by means of an extruder with perforated plate to a Granules are processed, wherein the temperatures between the feed zone and screw tip in a range between 180 and 380 ° C, the perforated plate between 300 and 350 ° C and the melt temperature when exiting through the perforated plate between 250 and 360 ° C, that the granules subsequently in an autoclave so loaded with a propellant that it contains between 0.5 and 10 wt% propellant, and that the propellant laden granules then by relaxing and / or by heating to a temperature of about 200 ° C to a particle foam is foamed.

10. A method for producing a composite part, characterized in that the particle foam produced by means of a method according to claim 8 or 9 with

Cover materials glued, sewn or welded.

A method for producing a composite part, characterized in that the particle foam produced by means of a method claim 8 or 9 is foamed in the presence of a cover material in such a way that it is connected thereto by means of gluing or welding.

12. The method according to claim 8, characterized in that the PEI is given at the exit from the extruder in an optionally heated mold, optionally containing cover materials, while being foamed under shaping to a particle foam or a composite material.

13. The method according to any one of claims 8 to 12, characterized in that are incorporated during the foaming inserts and / or channels in the particle foam.