EP3717553A1

EP3717553A1 - Pesu particle foams for applications in aviation interiors

Info

Publication number: EP3717553A1
Application number: EP18800669.6A
Authority: EP
Inventors: Christian Trassl; Denis HOLLEYN; Kay Bernhard
Original assignee: Evonik Operations GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2017-11-27
Filing date: 2018-11-19
Publication date: 2020-10-07
Also published as: CN111406091A; WO2019101667A1; KR20200084898A; MA49867A1; AU2018371107A1; MX2020005297A; TW201925295A; US20210095092A1; ZA202003832B; IL274859A; CA3083553A1; JP2021504523A; BR112020010372A2

Abstract

Polyethersulfone (PESU) 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

PESU particle foams for applications in the aviation interior

Field of the invention

Polymer foams based on polyethersulfone (PESU) 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

Blends of PES and PPSU are well known for other technical applications. Thus, EP 1 497 376 describes a corresponding blend for processing in the

Melt molding, injection molding, die casting, extrusion or blow molding. However, it is not known to make a foam from such a composition.

An alternative material for this, which is already being used as plate material in the aviation industry, is poly (oxy-1,4-phenylsulfonyl-1,4-phenyl) (PESU). This is known, for example, under the product name Divinycell F from DIAB, or Radel sold by the company Solvay. In the further processing of these extrusion foam boards, however, uneconomically large amounts of waste material are produced.

Also porous membranes of such blends are described, for example, in EP 0 764 461. Such membranes are made by casting from an aqueous polymer composition.

Many industrially used foams have either disadvantages in use at high temperatures or in total, and especially at these high temperatures, not optimal mechanical properties. On top of that, very few foams are known are not easy to inflame and can therefore be installed, for example, in the interiors of road, rail or air vehicles. For example, PES foams have a poor flame retardancy, while PPSU foams, for example, have a non-optimal tear strength.

Foams made of PPSU or PES are known in principle, although not in mixture with each other. So in L. Sorrentino were: "Polymeric foams from high-performance

Thermoplastics, Advances in Polymer Technology, Vol. 3, pp. 234-243, 2011 (DOI 10.1002 / adv), corresponding studies for the identification of ideal conditions for the foaming of PPSU or PES are determined.

Blends containing either PPSU or PSE are known as it were, though information in the art is rare. Thus, both polymers are especially useful as a minor component, e.g. described in PS foams to affect the properties in these commodity materials. Foams containing PPSU or PES as the main component are only to be found in a few descriptions, such as the following:

In US 4,940,733 is a foam, based on a blend of a polycarbonate and a second polymer, which may be in addition to a variety of other examples also PES or PPSU. Although such a foam has a high temperature resistance, but no particularly good flame retardancy. In addition to the mechanical properties are missing information.

WO 2015/097058 describes foams based on PPSU or PES containing at least 10% by weight of a polyolefin. The phase-separating polyolefin acts primarily as a nucleating agent. In this case, more uniform pores are achieved, but without the flame retardancy or mechanical properties, such as

Positively affect elongation at break. Due to the phase separation is even more likely to assume a poorer elongation at break. In terms of flame retardancy, the addition of a polyolefin component is also expected to cause deterioration.

US Pat. No. 2013/0059933, US 2012/13599528 and EP 2 692 519 describe PS particle foams to which up to 10% by weight of another polymer, such as, for example, polyacrylates, are added. Such foams are all unsuitable in applications with fire protection requirements. In DE 1020111 10216, small amounts of polysulfones or polyethersulfones are also added to such a PS particle foam. Nevertheless, this foam is also predominantly made of PS, which entails corresponding disadvantages for applications in air traffic. task

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

To provide a composition for producing novel foams or composite materials for use in aircraft construction. In doing so, the resulting

Foams a good combination of applicability at high temperatures, good mechanical properties, in particular with respect to the elongation at break and at least sufficient for many applications in the field of vehicle and aircraft construction

Have 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 the provision of a novel composition for the production of temperature-resistant, flame-retardant show m materials for use in lightweight construction, especially in the aerospace industry, shipbuilding, automotive or rail vehicle. This composition according to the invention for the production of foams is characterized in that it is a PESU particle foam having a glass transition temperature between 180 and 215 ° C. as foamed PESU and in which the mean cell diameter of the particle foam is less than 1000 μm, preferably less than 500 miti, more preferably less than 250 gm. A cell is understood to be the region in a particle foam which is defined by foaming a single particle. This is particularly surprising since the actual glass transition temperature of the PESU is 225 ° C.

Given glass transition temperatures are inventively - unless otherwise stated - measured by DSC (Differential Scanning Calometry). The expert 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, it is again cooled to a temperature which is at least 20 ° C below the lowest to be determined glass transition or melting temperature, the cooling rate should be a maximum of 20 ° C / min, preferably a maximum of 10 ° C / 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 the production of the PESU preferably consists of 80 to 99.5% by weight of PESU. 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 at least minimal miscibility with the blend of PES and PPSU. In principle, all known pigments can be used as pigments. Of course, especially with larger amounts, 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 PES, PPSU or blends of these two and can accordingly be applied to the

Preparation of a foam are transferred from the composition of the invention.

The fibers are usually known fiber materials, the one

Polymer composition can be added. In a particularly suitable design In the present invention, the fibers are PES, PPSU or blend fibers, the latter being PSE and PPSU.

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 second polymer component for adjusting the physical properties. The additional polymers may be, for example, polyamides, polyolefins, in particular PP, PEEK, polyesters, in particular PET, other sulfur-based polymers, such as, for example, PSU, polyetherimides or polymethacrylimide.

The choice of blowing agent is relatively free and determined for the skilled person in particular by the chosen foaming method and the foaming temperature. Suitable for example

Alcohol, 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 NaHCO 3, citric acid or their derivatives, azodicarbonamide (ADC) or compounds thereof,

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

Preferably, the PESU particle foam according to 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 PESU particle foam, it is apparent to those skilled in the art to obtain the inventive

Glass transition temperature and cell size easy to adhere to these mechanical properties. Surprisingly, it has also been found that the particle foam of the invention under the aerospace industry, especially for use in the interior of a

Aircraft's important fire safety regulations or fire characteristics according 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 PESU particle foam 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 would not receive approval. The foams according to the invention preferably have a degree of foaming which constitutes a reduction of the density in relation to the pure blend 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 . In addition to the PESU particle foam and process for its preparation are part of the present invention.

Basically, there are two preferred approaches for making the PESU particulate foams. In a first process variant, a composition consisting of 80 to 99.5% by weight of PESU, 0.5 to 10% by weight of blowing agent and 0 to 10% by weight of additives by means of an extruder

Perforated plate processed into a foamed granules. The temperatures between feed zone and screw tip are in a range between 180 and 380 ° C. In most cases, there is 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 300 and 350 ° C and the melt temperature when exiting through the perforated plate between 200 and 360 ° C. As a rule, the loading with the propellant takes place in the extruder. The granules then foam on leaving the perforated plate. The granules thus foamed are then preferably further foamed to form a particle foam.

In a variant of this embodiment, the composition may be passed into an underwater granulator upon exiting the extruder. 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.

In a second process variant for producing a PESU particle foam, a composition consisting of 90 to 100% by weight of PESU and 0 to 10% by weight of additives is also initially processed into granules by means of an extruder with perforated plate, but not loaded with a blowing agent. Here, too, the temperatures, which are again not necessarily uniform, between the feed zone and the screw tip are in the range between 180 and 380.degree. Likewise, the temperature of the perforated plate between 300 and 350 ° C and the melt temperature at the exit through the perforated plate between 200 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.

Basically, the skilled person various methods for the actual foaming of

Polymer compositions are known, in particular with respect to methods for

thermoplastic foams are applicable to the present composition. For example, the composition may 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 in connection to the 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, an adhesion between the materials, e.g. by partially filling open pores on the foam surface with cover material.

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

In a later foaming of the PESU, e.g. after the propellant loading in a

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 process variant in which the loading with T friction medium takes place in the extruder, the PESU can alternatively also be discharged from the extruder into an optionally heated mold, optionally containing cover materials. This is under molding to a

Foamed particle foam or a composite material. Alternatively, the

Composition are discharged at the exit from the extruder in a foam injection device. In this device is then foamed directly under shaping.

Regardless of the variants used, the particle foams or composite materials can be provided with inlets during foaming and / or channels can be incorporated into the particle foam.

The foams of the invention, or the foams produced by the process according to the invention find particular in the construction of space or

Aircraft, especially in their interior use. That can do that

Particle foams produced by the process of the invention or not, as well as the composite materials realized therefrom include. Especially because of the heavy

Flammability foams of the invention can also be installed in the interior of these vehicles.

Furthermore, the HT foams produced according to the invention can be further processed into foam moldings or foam core composite materials. These foam moldings or foam core composite materials may in particular be used in series production, e.g. for bodywork or interior trim in the automotive industry, interior parts in

Rail vehicle or shipbuilding, in the aerospace industry, in mechanical engineering, at the manufacture of sports equipment, in furniture construction or in the construction of wind turbines.

Claims

claims

1. Use of a PESU particle foam in the aviation industry, thereby

characterized in that the foamed PESU has a glass transition temperature between

180 and 215 ° C, and that the mean cell diameter of the particle foam is less than 1000 pm.

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

3. Use of a PESU particle foam according to claim 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 PESU particle foam according to claim 2 or 3, characterized

characterized in that the blowing agents are an alcohol, a ketone, an alkane, an alkene, CO2, N2, water, an ether, an aldehyde, chemical blowing agents or mixtures of several of these substances.

5. Use of a PESU particle foam according to at least 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 PESU particle foam according to any one of claims 1 to

5, characterized in that it is for use in lightweight construction for use in the aerospace industry, shipbuilding, automotive or in the

Rail vehicle construction is.

7. A process for producing a PESU particle foam for use according to any one of claims 1 to 5, characterized in that a

Composition consisting of 80 to 99.5% by weight, PESU 0.5 to 10% by weight

Blowing agent and 0 to 10% by weight of additives is processed by means of an extruder with perforated plate to form a foamed granules, wherein the temperatures between 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 Exit through the perforated plate between 200 and 360 ° C, and that the foamed granules are then further foamed into a particle foam.

8. A process for producing a PESU particle foam for use according to

at least one of claims 1 to 5, characterized in that a

Composition consisting of 90 to 100% by weight, PESU and 0 to 10% by weight

Additives is processed by means of an extruder with perforated plate to a granulate, wherein the temperatures between 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 200 and 360 ° C, that the granules are then loaded in an autoclave so with a blowing agent 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 foamed from above 200 ° C to a particle foam.

9. A method for producing a composite part, characterized in that the particle foam produced by means of a method according to any one of claims 7 or 8 is glued, sewn or welded with cover materials.

10. A method for producing a composite part, characterized in that the particle foam produced by a method according to claim 8 is foamed in the presence of a cover material so that it is connected to this by means of gluing or welding.

11. The method according to claim 7, characterized in that the PESU when leaving the extruder in an optionally heated mold, optionally containing cover materials, is given while forming a particle foam or a

Foamed composite material.

12. The method according to any one of claims 7 to 11, characterized in that are incorporated during the foaming inlets and / or channels in the particle foam.

13. Use of a particle foam produced in accordance with one of claims 7, 8, 11 or 12 in aircraft construction.

14. Use of a product according to any one of claims 9, 10, 11 or 12 produced

Composite material in aircraft construction.