Addition-curable polymer material

Abstract

The invention relates to an addition-curable polymer material, which is particularly suitable as a sealing material, especially for so-called PEM (proton exchange membrane) fuel cells and for drinking water systems, and which exhibits good long-term sealing performance and good long-term chemical aging resistance. The polymer material according to the invention comprises a base polymer in the form of a polyolefin-based polymer with an average molar mass of approximately 400,000 g / mol or less, wherein the base polymer is modified with side chains having at least one SiH group, and wherein the molality of the SiH groups in the base polymer is approximately 0.2 mol / kg or more.

Description

[0001] The invention relates to an addition-curable polymer material and its use, in particular in addition-cured form, as a sealing material.

[0002] US patent US 4,340,689 A discloses polymer materials based on ethylene-propylene copolymers (EPM) and ethylene-propylene diene rubber (EPDM). These polymers are modified by a grafting reaction with organic functional groups, such as vinylpyrridine and N-vinylpyrrolidone, and optionally silane functional groups. The resulting polymer materials are used as dispersants and additives to improve the viscosity of lubricating oils.

[0003] From DE 10 2005 045 184 A1, an elastomer blend is known which comprises at least two chemically different rubber components and at least one filler. The two rubber components each have at least two functional groups that can be crosslinked via hydrosilylation. Crosslinking is carried out with a crosslinking agent comprising a hydrosiloxane and / or a hydrosiloxane derivative as well as a hydrosilylation catalyst system. The hydrosiloxane or hydrosiloxane derivative comprises at least two SiH groups per molecule.

[0004] German patent DE 10 2005 045 167 A1 describes a rubber compound comprising a rubber component and a filler, wherein the rubber component has at least two functional groups that can be crosslinked via hydrosilylation. Crosslinking is achieved with a crosslinking agent comprising a hydrosiloxane or a hydrosiloxane derivative and a hydrosilylation catalyst system. The hydrosiloxane or hydrosiloxane derivative comprises at least two SiH groups per molecule.

[0005] The object of the present invention is to propose a material that is particularly suitable as a sealing material, especially for so-called PEM (proton exchange membrane) fuel cells and for drinking water systems. Of particular importance for these materials are good long-term sealing performance (verifiable by compression-stress-relaxation test or CSR test) and good long-term chemical aging resistance.

[0006] This problem is solved according to the invention by an addition-curable polymer material comprising a base polymer in the form of a polyolefin-based polymer with an average molar mass of approximately 400,000 g / mol or less, wherein the base polymer is additionally modified with side chains having at least one SiH group, wherein the molality of the SiH groups in the base polymer is approximately 0.2 mol / kg or more.

[0007] Preferably, according to the invention, base polymers are used which have an average molar mass of approximately 200,000 g / mol or less, in particular approximately 100,000 g / mol or less, most preferably approximately 50,000 g / mol or less. In particular, base polymers with an average molecular weight of approximately 20,000 g / mol or more are suitable, for example in the range of approximately 21,000 g / mol to approximately 25,000 g / mol.

[0008] The inventive addition-curable polymer materials preferably have a molality of SiH groups of approximately 0.28 mol / kg or more.

[0009] The materials according to the invention comprise a base polymer in the form of a polyolefin copolymer, in particular an ethylene-propylene copolymer, wherein a low-viscosity ethylene-propylene copolymer is particularly preferred. The low-viscosity ethylene-propylene copolymer preferably has a Brookfield viscosity of approximately 500 Pa·s (500,000 cps) or less at 60 °C.

[0010] In this case, a monomer ratio of ethylene / propylene in the range of approximately 35 / 65 to approximately 75 / 25 is particularly preferred when using an ethylene-propylene copolymer as the base polymer.

[0011] The base polymer often has a diene content of approximately 10 wt.% or less, preferably approximately 2 wt.% or less.

[0012] The SiH-containing side chains of the base polymer are selected in particular from silane, organosilane and / or siloxane groups, with alkylsiloxane groups and especially ethylsiloxane groups being preferred.

[0013] Typically, the side chains are grafted onto the base polymer using vinyl groups, preferably using at least one of the siloxanes of the following formulas (I) and (II): where the remainders R 1 Alkylenes, especially methylene or ethylene, represent and the R groups 2 Each is individually selected from alkyl, preferably methyl and ethyl, aryl, in particular phenyl, acrylic, hydroxy, alkoxy, in particular methoxy, epoxy, amino, mercapto, aryloxy, in particular phenoxy, and halogen, in particular chlorine. The values ​​for n 1The values ​​range from 1 to 10. The siloxane of formula (I) in the form of vinyltetramethyldisiloxane (VTMDS) is particularly preferred. The siloxanes of formulas (I) and (II) can also be used in combination with each other.

[0014] The aforementioned side chains containing SiH groups, which are connected to the base polymer by grafting, can alternatively be polymerized into the base polymer during the formation of the polymer chain, also as part of a copolymerization.

[0015] The invention further relates to a method for crosslinking the previously described addition-crosslinkable polymer materials according to the invention, wherein the polymer material is addition-crosslinked in the presence of a Pt-, Ru-, Rh- or Pd-based catalyst by means of a crosslinking agent in the form of a component with two or more double and / or triple bond functionalities. The double and / or triple bond functionalities of the crosslinking agent are arranged laterally and / or terminally.

[0016] In the process according to the invention, a double or multiple double and / or triple bond functional component in the form of an ethynyl and / or vinyl functional component is preferably used.

[0017] In the process according to the invention, the base polymer of the polymer material and the crosslinking agent are preferably selected from variants which can be crosslinked together using a Karstedt Pt catalyst.

[0018] Furthermore, cross-linking is preferably carried out by means of an anti-Markovnikov addition reaction involving the SiH groups and the double bond and / or triple bond functions of the cross-linking agent.

[0019] In preferred embodiments of the method according to the invention, the double or multiple double and / or triple bond functional component is selected from monomers, oligomers and polymers, in particular in the form of silane, silanol and siloxane derivatives.

[0020] In the process according to the invention, the addition crosslinking of the base polymer of the polymer material is preferably carried out by means of a Pt-catalyzed alkene hydrosilylation.

[0021] Particularly preferred are methods according to the invention in which the crosslinking agent is a crosslinking agent according to one of the following formulas (III) and (IV): where n 2 and n 4each independently exhibit integer values ​​in the range of 4 to 2,000, in particular 1,000 to 2,000, preferably approximately 1,600, and n 3 has an integer value of 0 or more, provided that n 3 < n 2 + n 4 is. R 3 is individually selected from alkyl, aryl, acrylic, hydrogen, hydroxy, alkoxy, epoxy, amino, mercapto, halogen and siloxane groups. R 3' is individually selected from alkyl, alkene, in particular allyl, alkyne, aryl, acrylic, hydrogen, hydroxy, alkoxy, allyloxy, epoxy, amino, mercapto, halogen and siloxane groups. R 4 and R 4' are individually selected from alkyl, especially methyl, alkene, especially vinyl and allyl, alkyne and norbornene, especially vinylnorbornene; where R 5 The group is individually selected from alkyl, aryl, acrylic, hydrogen, hydroxy, alkoxy, epoxy, amino, mercapto, halogen and siloxane groups, and R7 The selection is individually made from alkene, in particular allyl, alkyne and norbornene, in particular vinylnorbornene; and where n 5 integer values ​​from 0 to 100, preferably 6 to 100, and n 6 exhibits integer values ​​from 4 to 2000, preferably 80 to 2000.

[0022] An example of a commercially available crosslinking agent according to formula (III) is the vinylsiloxane HANSA SFA 43303 (manufacturer CHT Germany GmbH).

[0023] Typically, at least one quarter of the R are in formula (IV). 5 -groups alkyl groups. The remaining parts of the R 5 -Groups are selected from aryl, acrylic, hydrogen, hydroxy, alkoxy, epoxy, amino, mercapto, halogen. The R 5 -Groups can also represent alkyl groups in general.

[0024] Other preferred crosslinking agents are the following polysiloxanes of the following formulas (V) and (VI): where the values ​​for x 1, x 2 and for x 3 independently of each other, the values ​​are 1 to 6; a crosslinking agent of formula (V) is available, for example, as article no. MTV-112 from Gelest Inc., Morrisville, PA, USA (CAS: 217174-00-0); where y in formula (VI) has a value of 2 to 6; a crosslinking agent of formula (VI) is available from Gelest, Inc., Morrisville, PA, USA, under article no. DMS-VD11, molecular weight: 700 - 800 g / mol.

[0025] The present invention further relates to a polymer material composition comprising approximately 50 to approximately 95 wt.% of an addition-crosslinked polymer material obtainable according to the previously described process according to the invention, and one or more fillers, wherein the proportion of the fillers in the polymer material is approximately 5 to approximately 50 wt.%, in particular approximately 15 to approximately 30 wt.%.

[0026] In the polymer material composition according to the invention, the degree of crosslinking of the addition-crosslinked polymer material is preferably approximately 50% or more.

[0027] Preferred polymer material compositions according to the invention comprise a filler, in particular in the form of a hydrophobic and / or a hydrophilic mineral filler.

[0028] The filler(s) for the polymer material composition according to the invention are selected in particular from silica-, silicone resin- and titanate-based fillers.

[0029] These fillers act as acid scavengers and serve to increase the mechanical strength. Preferably, the proportion of these additives in the total mass of the polymer material composition (hybrid elastomer material) according to the invention is approximately 5 to approximately 50 wt.%, more preferably approximately 15 to approximately 30 wt.%.

[0030] A particularly preferred filler for the polymer material composition according to the invention is a hydrophobic and / or hydrophilic silica, which, due to its high specific surface area, acts as a reinforcing filler. Silicas listed in Table 1 below are particularly suitable as fillers in this regard. Table 1 Silica BET surface [m²] 2 / G] Carbon content [%] according to ISO3262-20 AEROSIL R 972 90 - 130 0,7 - 1,0 AEROSIL R 974 150 - 190 0,8 - 1,4 AEROSIL R 202 80 - 120 3,5 - 5,0 AEROSIL R 208 80 - 140 4,5 - 6,5 AEROSIL R 805 125 - 175 4,5 - 6,5 AEROSIL R 812 230 - 290 2,0 - 3,0 AEROSIL R 812 S 195 - 245 3,0 - 4,0 AEROSIL R 104 125 - 175 1,0 - 2,0 AEROSIL R 816 170 - 210 0,9 - 1,8 AEROSIL R 711 125 - 175 4,5 - 6,5 AEROSIL R 7200 125 - 175 4,5 - 6,5 AEROSIL R 8200 135 - 185 20, - 4,0 AEROSIL R 9200 150 - 190 0,7 - 1,3 AEROSIL R 504 125 - 175 2,0 - 4,5 AEROSIL R 972 Pharma 90 - 130 - AEROSIL R 976 S 215 - 260 1,8 - 2,1 AEROSIL RY 50 15 - 45 3,0 - 4,5 AEROSIL NY 50 20 - 40 2,5 - 4,0 AEROSIL RY 200 80 - 120 4,0 - 6,5 AEROSIL RY 200 S 65 - 95 3,0 - 5,0 AEROSIL RY 200 L 80 - 120 4,0 - 6,0 AEROSIL RY 300 110 - 140 6,0 - 8,5 AEROSIL RX 50 25 - 45 0,5 - 1,0 AEROSIL NAX 50 30 - 50 0,5 - 1,0 AEROSIL RX 200 115 - 165 1,5 - 3,5 AEROSIL RX 300 180 - 220 2,5 - 5,0 AEROSIL NX 90 G 50 - 80 0,7 - 1,5 AEROSIL REA 200 110 - 150 5,0 - 7,5 AEROSIL REA 90 40 - 70 3,0 - 6,0 AEROSIL NA 50 Y 25 - 45 2,0 - 4,0 AEROSIL NA 200 Y 100 - 150 3,0 - 6,5 AEROSIL NA 50 H 30 - 50 < 2,0 AEROSIL RA 200 HS 120 - 160 < 3,5 AEROSIL 300 V 270 - 330 - AEROSIL 200 175 - 225 -

[0031] The BET values ​​given in Table 1 represent the specific surface area. The carbon content of the fillers indicates the degree of hydrophobization of the otherwise hydrophilic silica particles. The AEROSIL products listed in Table 1 are available from Evonik Industries AG.

[0032] In general, solid particles are suitable as additives for improving the gas permeation resistance of a hybrid elastomer material according to the invention used as a sealing material.

[0033] Finally, the present invention relates to the use of the previously described polymer material composition according to the invention as a sealing material in PEM (proton exchange membrane) fuel cells or in seals for drinking water systems.

[0034] Preferably, the polymer material composition according to the invention, particularly when used as a sealing material, contains additives, in particular hydrophobic and / or hydrophilic fillers, selected from silica-, silicone resin- and titanate-based fillers.

[0035] The invention will be explained in more detail below using the examples and figures.

[0036] They show in detail: Fig. 1 Crosslinking isotherm of a material according to the invention; Fig. 2 Shoulder bar as test specimen for tensile tests; Fig. 3 Cold retraction behavior of a material according to the invention; Fig.4 Gough-Joule effect in a material according to the invention; Fig. 5. Storage resistance of conventional and addition-crosslinked polymer materials according to the invention in various aqueous media; Fig. 6. Sealing force behavior of a material according to the invention during a CSR test in aerobic hot air; and Fig. 7. Sealing force behavior of a material according to the invention during a CSR test in aqueous media. EXAMPLES

[0037] The following examples describe the production of the addition-curable polymer materials according to the invention, as well as a method for their crosslinking. Further examples examine and explain the material properties of the materials according to the invention in detail.

[0038] The base polymer used here, which is equipped with SiH-containing side chains by means of grafting, is a polyolefin-based copolymer in the form of a low-molecular-weight ethylene-propylene rubber (EPM copolymer), known as trilene. ® CP-80 is available on the market (manufacturer: LION Elastomers). This EPM copolymer has an ethylene / propylene monomer ratio of approximately 41 / 59. Its molecular weight is approximately 23,000 g / mol. The Brookfield viscosity is 500,000 cps (500 Pa·s) at 60 °C.

[0039] For the grafting of the SiH-containing side chains, a siloxane of formula (I) in the form of vinyltetramethyldisiloxane (VTMDS; CAS: 55967-52-7) is used.

[0040] A peroxide in the form of 2,5-bis(tert-butyl-peroxy)-2,5-dimethylhexane (DTBPH; CAS: 78-63-7) is used as a grafting catalyst.

[0041] The molality of the SiH groups of the grafted base polymer can be determined by nuclear magnetic resonance (NMR) spectroscopy. Example 1:

[0042] In a closed reaction vessel with a reflux condenser, 80 g of the EPM copolymer (trilene) are added. ® The EPM copolymer (CP-80) is placed in a container and heated under an argon atmosphere with stirring to a reaction temperature of approximately 180 °C. Once the reaction temperature is reached, 11 phr of VTMDS and 0.25 phr of DTBPH are added dropwise to the EPM copolymer simultaneously over a period of 3 minutes. The siloxane and catalyst can also be added successively or as a pre-prepared mixture of the two components.

[0043] After a reaction time of 60 minutes at a constant reaction temperature, the grafted EPM copolymer is removed from the reaction vessel and placed in a vacuum drying oven at approximately 80 °C and a reduced pressure of approximately 50 mbar for approximately 24 hours. This removes any unreacted peroxide and VTMDS components from the polymer mass during the grafting reaction.

[0044] The addition-curable EPM polymer material obtained according to the invention is still in the form of a liquid polymer (Brookfield viscosity approx. 500,000 cps (500 Pas) at 60 °C).

[0045] The addition-curable polymer material obtained according to this example has a molality of the SiH groups of approximately 0.28 mol / kg. Example 2:

[0046] In this example, the grafting reaction described in Example 1 is carried out continuously as an alternative.

[0047] For this purpose, the EPM copolymer (trilene) is used.® The EPM copolymer (CP-80) is pre-tempered to approximately 130 °C for about 12 hours. This also reduces any residual moisture. The copolymer is then fed to the inlet zone of a twin-screw extruder (screw diameter: 18 mm; length / diameter ratio (L / D): 48) via a melt pump. The inlet zone is heated to 140 °C and purged with argon.

[0048] In the twin-screw extruder, a temperature profile is set along six equally long zones, with the temperatures in zones 1 to 6 being specified as follows: 120-140-170-200-220-220 °C.

[0049] The speed of the twin-screw extruder is set to 80 revolutions per minute, ensuring a sufficiently long residence time of approximately 150 seconds for the EPM copolymer. The twin-screw extruder conveys the EPM copolymer at a rate of approximately 1,300 g / h.

[0050] The siloxane component VTMDS and the peroxide DTBPH are fed into the polymer mass of the EPM copolymer (base polymer) in Zone 1 via peristaltic pumps. The feed rate of VTMDS is set to approximately 85 g / h (0.5 mol / h), while the peroxide is added at approximately 5 g / h.

[0051] The extrudate is stored in a vacuum drying oven at approximately 80 °C and a pressure of approximately 50 mbar for approximately 24 hours. This process removes unreacted peroxide and VTMDS.

[0052] The addition-curable EPM polymer material according to the invention is also present here as a liquid polymer (Brookfield viscosity approx. 500,000 cps (500 Pa·s) at 60 °C). The addition-curable polymer material according to the invention obtained in this example has a molality of the SiH groups of approx. 0.21 mol / kg.

[0053] In the following examples, the addition-curable polymer material obtained in Example 1 is processed according to the invention into an addition-curable polymer material composition, and the resulting composition is then processed into an addition-cured sealing material. This sealing material according to the invention is subsequently tested for various relevant properties. Comparable test results are expected for the addition-curable polymer material according to the invention in Example 2. Example 3:

[0054] In this example, a compound is produced based on the addition-curable polymer material obtained in Example 1, which contains, in addition to the addition-curable polymer material, a filler, a crosslinking agent and a Pt catalyst.

[0055] Table 2 below lists the individual components of the compound, along with their respective quantities used in the formulation. Table 2 Compound components Shares in [g] Addition-curable EPM copolymer from Example 1 11,12 Silica AEROSIL 200 1,5 Crosslinking agent Vinylsiloxane Hansa SFA 43303 6,0 Pt catalyst Karstedt CAT 512 0.12 (10 drops) Total weight 18,74

[0056] In a first step, the components of the formulation in Table 2, with the exception of the Pt catalyst, are mixed in a centrifugal mixer for approximately 2.5 minutes at 3,000 rpm. Since the components heat up during this process, the mixture is then cooled to room temperature.

[0057] In a subsequent mixing process, the Pt catalyst is added to the mixture in the centrifugal mixer and mixed at room temperature, preferably below room temperature, at approximately 500 rpm.

[0058] After the mixture is removed from the centrifugal mixer, it is metered into a test plate mold. The crosslinking reaction of the mixture is initiated by increasing the temperature of the mixture in the test plate mold to approximately 180 °C. For the production of test plates with dimensions of 150 mm width, 150 mm length, and 2 mm thickness, the material is held at this temperature for approximately 10 minutes to form the finished test plates. For the production of test plates with dimensions of 100 mm width, 100 mm length, and 6 mm thickness, the material is held at a temperature of approximately 180 °C in the test plate mold for approximately 15 minutes.

[0059] The test pieces used in the individual tests are punched out from these test plates.

[0060] The resulting addition-crosslinked polymer material of the test plates has a Shore A hardness of 25.

[0061] The silica content of AEROSIL 200 (manufacturer Evonik Industries AG) can be varied in a range from approximately 0.5 g to approximately 5 g, so that Shore A hardnesses of 30 can also be achieved in the final product.

[0062] The proportion of the crosslinking agent, a vinylsiloxane of formula (III) with a vinyl content of 0.06 mol / kg and a viscosity of 30,000 mPas, available as Hansa SFA 43303 from CHT Germany GmbH, can be varied in the formulation from approximately 3.0 g to approximately 6.0 g, whereby the degree of crosslinking varies depending on the proportion of crosslinking agent.

[0063] The proportion of Pt catalyst can also be varied to influence the degree of crosslinking, particularly in the range of 0.06 g (5 drops) to 0.24 g (20 drops). The Pt catalyst Karstedt CAT 512 is available from Evonik Industries AG.

[0064] The vulcameter test (DIN 53529-3:1983-06) of the reaction mixture or compound according to Table 2 using a vulcameter of type MDR (rotorless) from Göttfert Werkstoff-Prüfmaschinen GmbH, starting with the initially uncrosslinked mixture at 170 °C, yielded the measured values ​​summarized in Table 3.

[0065] The values ​​t10, t50, and t90 correspond to the respective time periods required to achieve a degree of crosslinking of 10%, 50%, and 90%, respectively. vmax corresponds to the maximum reaction rate. tvmax corresponds to the time until the maximum reaction rate is reached. A curve of the crosslinking isotherm at 170 °C (according to DIN 53529, parts 1 to 3) is shown in Fig. 1 shown. Table 3 Crosslinking characteristics at 170 °C Minimum torque [Nm] 0,068 Maximum torque [Nm] 0,259 Δ Max-Min [Nm] 0,191 t10 [min] 0,28 t50 [min] 0,74 t90 [min] 3,32 tvmax [min] 0,32 vmax [Nm / min] 0,29 Example 4

[0066] The addition-cured material obtained in Example 3 was subjected to various further tests, which are described in more detail below. The test results can be found in Tables 4 to 6. Table 4 Properties of the unaged and untempered material of Example 3; Shore hardness test (DIN 53505; DIN ISO 7619-1); tensile test at 23 °C (DIN 53504 S2 test specimen; elongation rate 200 mm / min) Shore A hardness [Shore A] 25 Micro-Shore A hardness [Micro-Shore A] 22 density [g / cm 3 ] 0,940 Voltage module M25% [MPa] 0,30 Voltage module M50% [MPa] 0,50 Voltage module M100% [MPa] 1,00 Tear resistance [MPa] 1,20 Elongation at break [%] 139

[0067] The test specimen used in the tensile test according to DIN 53504 S2 is in the Fig.Figure 2 shows a schematic representation. The test specimen is a so-called shoulder bar 10 with two so-called heads 12, 14, which are connected to each other via a web 16. The shoulder bar 10 has a total length A of 75 mm, and the heads 12, 14 have a width B of 12.5 ± 1 mm. The web 16 has a length C of 25 mm ± 1 mm and a width D of 4 mm ± 0.1 mm. The thickness of the shoulder bar 10 is 2 mm ± 0.2 mm. The measurement is taken with a so-called extensometer on a section E of the web 16, which has an initial gauge length of 20 mm ± 0.5 mm. Table 5 Compression set test of the initially unaged, untempered material of example 3 (DIN ISO 815; test specimen type B); Compression set in hot air for 24 hours at 125 °C, 25% compression; cold removal at 23 °C [%] 16,5 Table 6: Hot strength assessment using a Dynamic Mechanical Thermal Analysis (DMTA) of the unaged and untempered material of Example 3; a tensile test is performed at the specified different temperatures under isothermal conditions; the measured stress moduli are given in the table; the test specimen is 8 mm wide, 40 mm long, and 2 mm thick. Strength at 25 °C (at 40% elongation) [MPa] 0,357 Heat resistance at 50 °C (at 40% elongation) [MPa] 0,335 Heat resistance at 75 °C (at 40% elongation) [MPa] 0,330 Heat resistance at 100 °C (at 40% elongation) [MPa] 0,320 Heat resistance at 115 °C (at 40% elongation) [MPa] 0,315 Example 5

[0068] Furthermore, a static cold retraction measurement according to ASTM D1329 or ISO 2921 was performed on the addition-cured material from Example 3 using Dynamic Mechanical Analysis (DMA) (the test specimen is 8 mm wide, 40 mm long, and 2 mm thick). The DMA was performed using a DMA Gabo Eplexor 500N instrument (manufacturer: Netzsch Gerätebau GmbH). The change in strain [%] is shown as a measurement curve for the temperature range from -100 °C to +50 °C. Fig. 3 shown.

[0069] A material test specimen, defined as uniaxially stretched by 7.5% in the longitudinal direction at 23 °C, was first frozen and then slowly heated at a rate of 2 K / min, starting at -100 °C. The test specimen was heated from the glass transition zone (hatched area in...) onwards. Fig. 3) It became increasingly mobile and its deformation state gradually shifted towards its original length. The so-called onset point is reached at a temperature of approximately -53 °C, and the so-called endset point at a temperature of approximately -45 °C.

[0070] Finally, the in Fig.The mobility increase shown in Figure 3 of 100% was achieved. From the course of the strain state as a function of temperature, so-called Temperature Retraction (TR) values ​​can be determined, which describe the cold flexibility of the elastomer material in a mechanical context and are related to the calorimetric measurements from the Dynamic Differential Calorimetry analysis.

[0071] TRxx values ​​represent the temperature in °C at which the test specimen is able to change its strain state by xx%. The TR10 value thus indicates the temperature at which the test specimen has changed its strain state by 10%. The TR30 value indicates the temperature at which the test specimen has changed its strain state by 30% (microscopic, internal material mobility). Various TRxx values ​​are summarized in Table 7. Table 7 TRxx value Temperature [°C] TR10 -52,7 TR30 -49,5 TR50 -46,6 TR70 -35,5

[0072] These values ​​show that the addition-cured material obtained in Example 3 exhibits excellent cold flexibility. Example 6

[0073] In this example, the Gough-Joule effect is determined on the addition-cured material of Example 3 according to the invention under tensile stress. The Gough-Joule effect under tensile stress is an indicator of the presence and degree of entropy or rubber elasticity of an elastomer material.

[0074] The test can be performed in both tension and compression modes. The classic Gough-Joule effect is described in the literature, including in G. Heinisch: Lexikon der Kautschuktechnologie, entry: Gough Joule Effekt, Gentner-Verlag 1977, ISBN 3872472232, to which reference is made here.

[0075] For the test, a cylindrical test specimen with a diameter of 12.5 mm and a height of 6 mm is produced (ISO 815 type B).

[0076] To demonstrate a significantly pronounced entropy elasticity as a crucial characteristic of a chemically cross-linked elastomer material, the non-isothermal determination method for the Gough-Joule effect is suitable (see R. Hornig: Thermomechanical description of the entropy-elastic Gough-Joule effect for uniaxial tensile deformations, GAK 05 / 2021, pp. 208-221).

[0077] Under an isothermal loading condition with constant deformation, only stress relaxation takes place in the elastomer material.

[0078] This is not the case with non-isothermal processes if the elastomer material has experienced a significant reduction in entropy during the loading process and also allows for a significant reduction in entropy due to the formulation.

[0079] The Gough-Joule effect will prevail over static stress relaxation if, in the deformation state, e.g. at 23 °C, such a significant reduction in entropy occurs that a subsequent supply of heat energy, i.e. a temperature increase to, for example, +120 °C on the constantly deformed test specimen, leads to a noticeable increase in stress after a certain temperature increase or measurement time.

[0080] Fig.Figure 4 shows the Gough-Joule effect in tensile mode for a test specimen with a rectangular cross-section (test specimen = 8 mm wide, 40 mm long, 2 mm thick), made from the addition-cured material of Example 3, with a Shore A microhardness of 22, at a constant strain deformation of 40% over the entire non-isothermal measurement period. The measurement begins at -10 °C and a stress of 0.5 MPa. The temperature is increased at 2 K / min until a temperature of 120 °C is reached. The aforementioned stress increase is shown in Fig. 4. This effect can be observed from a temperature of approximately 90 °C. The lower extrapolation line in the end region of the measurement curve illustrates the relaxation effect with increasing temperature, while the opposing effect of entropy elasticity (upper extrapolation line) indicates a change in the material.

[0081] The measured values ​​in Fig.Figure 4 illustrates that the addition-crosslinked material according to the invention from Example 3 exhibits entropy-elastic behavior and thus has an elastomeric character or can be classified as an elastomeric sealing material. Example 7

[0082] In this example, the chemical resistance of the addition-cured material according to the invention from Example 3 is tested in hot air at various temperatures. The test specimens used are of ISO 815 type B (diameter 12.5 mm ± 0.5 mm, height 6.3 mm ± 0.3 mm).

[0083] The increase in hardness of the addition-cured material according to the invention, as shown in Example 3, due to chemical aging processes remains within limits even over long periods in the temperature range of 80 °C to 125 °C. However, as expected, higher temperatures result in more pronounced effects on the increase in hardness, even with the material according to the invention. Table 8 Hot air resistance / hardness change [Shore A] under aerobic conditions in a convection oven Hardness change [Shore A] Storage time [h] / temperature 80 °C 100 °C 125 °C 120 +1,3 +2,1 +2,3 168 +1,6 +2,6 +2,5 216 +1,8 +2,0 +2,4 288 +2,0 +2,9 +2,6 360 +1,7 +2,9 +2,5 480 +1,7 +1,8 +2,6 624 +1,5 +2,8 +2,5 720 +1,6 +2,2 +2,6 984 +1,8 +1,9 - 1.000 +2,0 +2,0 - 2.000 +1,9 +2,5 -

[0084] However, under the thermal conditions to which seals of proton exchange membrane fuel cell stacks (PEM-FC fuel cell stacks) are exposed, the addition-crosslinked material according to Example 3 meets the requirements.

[0085] Table 9 below shows the weight loss and migration tendency of the addition-crosslinked material according to the invention as shown in Example 3 with increasing storage time in hot air at different temperatures.

[0086] The hardness changes shown in Table 8 correlate with the weight changes documented in Table 9. With increasing heat exposure, low-viscosity components or components with low molecular weight are extracted or evaporated from the material, resulting in an increase in Shore A hardness and a decrease in the weight of the test specimen. Table 9 Weight changes during hot air aging Weight changes [wt.%] Storage time [h] / temperature 80 °C 100 °C 125 °C 120 -0,175 -0,219 -0,359 168 -0,208 -0,288 -0,474 216 -0,197 -0,403 -0,382 288 -0,220 -0,311 -0,428 360 -0,232 -0,345 -0,347 480 -0,220 -0,357 -1,296 624 -0,232 -0,403 -2,071 720 -0,255 -0,414 -2,591 984 -0,255 -0,533 - 1.000 -0,301 -0,665 - 1.148 -0,313 -0,863 - 1.244 -0,324 -1,450 - 1.556 -0,347 -2,486 - 1.724 -0,382 - - 2.000 -0,394 - - Example 8

[0087] In this example, the chemical resistance of the addition-crosslinked material according to Example 3 in various media is documented.

[0088] Table 10 shows the changes in hardness, volume, and weight with increasing immersion time of the addition-cured material according to Example 3 in demineralized water at 90 °C. The test specimens according to Fig.2 (according to DIN 53504 S2: shoulder bar 10 with a total length A of 75 mm, width B of the heads 12.5 ± 1 mm, length C of the web 25 mm ± 1 mm, width D of the web 4 mm ± 0.1 mm, thickness of the shoulder bar 2 mm ± 0.2 mm; initial gauge length E 20 mm ± 0.5 mm) were inserted without stress, with the test specimens being held in contact with the aqueous medium on all sides. Regarding its resistance to the medium in demineralized water, the addition-cured material according to the invention, as shown in Example 3, fulfills the requirements desired for an elastomeric sealing material for PEM-FC fuel cell stacks. Table 10 Chemical resistance in demineralized water at 90 °C Storage time [h] Hardness change [Shore A] Volume change [Vol.-%] Weight change [wt.%] 168 + 4,4 ± 0 + 0,50 408 + 3,8 - 0,20 - 0,50 624 + 4,6 + 0,14 + 0,45 672 + 4,0 - 0,12 + 0,48 912 + 4,4 - 0,18 + 0,60 1080 + 4,1 + 0,04 + 0,98 1248 + 3,8 + 0,35 + 1,60 1440 + 2,9 + 0,49 + 1,58 1608 + 1,6 + 1,19 + 2,04 2265 + 1,2 + 2,19 + 3,60 2424 + 1,1 + 2,62 + 4,09

[0089] In further immersion tests, the chemical resistance of the addition-cured material according to the invention, as shown in Example 3, was investigated in alkylbenzenesulfonic acid and in an FKM ionomer dispersion. For comparison, the results of the immersion tests on a standard LSR (Liquid Silicon Rubber) material, ShinEtsu X34-4269A / B (available from Shin-Etsu Silicones Europe BV), are also shown.

[0090] Fig. Section 5 provides an overview of possible age-related cracking and changes on the test specimen surface after various storage periods in the test medium of 1 wt% alkylbenzenesulfonic acid (ABS) in water and a real medium of 10 wt% perfluorosulfonic acid (PFSA) ionomer dispersion 3M800EW E-21669D (manufacturer 3M / Dyneon) in water (diluted to an acid concentration of 0.091 mol / l), each at a storage temperature of 75 °C.

[0091] The water-based PFSA-containing 3M800EW product used in this example, which is used here to produce the real medium, has the following properties according to the technical data sheet: Equivalence weight [PFSA eq. wt g / mol SO2H] 800 Polymer content [wt.%] 20 Total acid capacity [meq / g] 1,25 Surface tension [mN / m] 73 Viscosity at 25 °C [mPas] 150 - 360

[0092] The real medium, with its acid concentration, simulates the adverse scenario of a high concentration of perfluorosulfonic acid in the process water that forms during the electrochemical process in the fuel cell stack. One cause of this is the progressive aging of the fuel cell membranes during operation. Sulfonic acid groups on the membrane surface ensure proton exchange in the fuel cell, but these groups are subject to a continuous degradation or degradation process, releasing sulfonic acid into the surrounding medium. This sulfonic acid accumulates in the resulting process water, comes into contact with the elastomeric sealing material of the fuel cell stack seal, and behaves as a chemically aggressive substance.

[0093] In the addition-crosslinked material according to the invention as shown in Example 3, no microscopically visible surface changes such as pitting or cracks occur even after prolonged contact with such aqueous-acidic, highly aggressive media.

[0094] This is the particular advantage of the organic, polyolefinic elastomer materials according to the invention, which have a significantly better long-term chemical resistance (tested up to 1836 h) in aqueous-diluted sulfonic acid media compared to conventional LSR materials, such as ShinEtsu X34-4269A / B. Example 9

[0095] In this example, the static long-term sealing force behavior (using CSR testing) of the addition-crosslinked materials according to Example 3 is tested.

[0096] In a so-called Compression Stress Relaxation (CSR) test, the long-term course of the static sealing force under constant deformation is determined. In addition to an initial physical stress relaxation (settlement behavior), chemical relaxation follows, caused by chemical aging processes in the elastomer material. These processes are determined by the mechanical deformation height (compression), the temperature and media exposure, as well as the storage time.

[0097] When chemical aging processes in hot air or an aqueous medium cause the elastomer material to completely lose its elastic sealing force, it reaches the so-called leakage or force zero point.

[0098] For testing the static long-term sealing performance, cylindrical test specimens according to DIN ISO 815 type B (diameter 12.5 mm; height 6 mm) are used. CSR testing is carried out according to ISO 3384-2.

[0099] Besides the preferred Wykeham-Farrance method, there is also the Jamak and Shawbury Wallace method. Both methods are known from the literature (R. Hornig: Comparison of various CSR methods regarding the static long-term sealing behaviour of AEM, ACM and HNBR compounds, International Polymer Science and Technology, Vol. 37, No. 11, 2010).

[0100] The plot of the measured values ​​over the time axis can be done as a percentage, where the absolute initial force for a 25% compression (static preload) is given in Newtons.

[0101] The media used below for testing the static long-term sealing performance of the addition-crosslinked material according to the invention as shown in Example 3 are aerobic hot air, demineralized water and the real medium of the aqueous PFSA ionomer dispersion 3M800EW. CSR testing: Hot air aging at 90 °C, 100 °C and 125 °C

[0102] Fig.Figure 6 shows the long-term static sealing force behavior during hot air aging in a convection oven under three different isothermal temperature conditions: 90 °C, 100 °C, and 125 °C. The measured decrease in static sealing force depends on the loading rate until the required static preload is reached, which is necessary for an initial 25% compression or compression deformation.

[0103] Therefore, the highest possible loading rate should be chosen to exclude or completely avoid relaxation processes during this loading process. In the present example, this can be achieved with a loading rate of 2 mm / s.

[0104] The static preload required for the test specimens used to achieve the specified initial 25% compression deformation is 71.3 N.

[0105] In Fig.6. Physical relaxation is noticeable at the beginning of the storage period (during the first approximately 30 minutes), while chemical relaxation due to aging in hot air begins at approximately 100 h (hot air aging at 125 °C), approximately 200 h (hot air aging at 100 °C) or approximately 500 h (hot air aging at 90 °C), depending on the storage temperature.

[0106] The curve's progression in Fig. Figure 6 thus illustrates the worst-case scenario, including the initial part of the physical stress relaxation. Typical operating temperatures in PEM-FC fuel cell stacks are around 80 °C. As shown from Fig. As can be seen in Figure 6, the addition-crosslinked material according to the invention exhibits sufficient thermo-oxidative aging resistance.

[0107] As expected, chemical relaxation begins earlier with increasing temperature. For technical use as an elastomeric sealing material for PEM-FC fuel cell stacks, the addition-cured material according to the invention, as shown in Example 3, possesses sufficient thermo-oxidative aging resistance. CSR testing: Water and relevant acid deposits

[0108] Fig. Figure 7 shows the static long-term sealing performance for aqueous media aging. The media used were demineralized water as medium I and aqueous dilution of perfluorosulfonic acid as medium II with an initial acid group concentration of 0.091 mol / l (base: PFSA ionomer dispersion 3M800EW). The measurements were performed on test specimens with a static preload of 71.3 N, resulting in an initial compression deformation of 25%.

[0109] The sealing force drop also depends on the static preload here, which is why the necessary build-up of the preload is carried out here as well at 2 mm / s.

[0110] The test specimens were immersed in demineralized water (Medium I) at 90 °C. Immersion in the PFSA ionomer dispersion described above (Medium II) was carried out at 75 °C.

[0111] In medium II, the addition-cured material according to Example 3 exhibits high chemical aging resistance. In the aqueous, demineralized medium I, even after 10,000 hours of storage, sealing force losses of only 60% are observed at 90 °C, demonstrating excellent long-term sealing performance of the addition-cured materials according to the invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 4,340,689 A

[0002] DE 10 2005 045 184 A1

[0003] DE 10 2005 045 167 A1

[0004] Cited non-patent literature

[0000] G. Heinisch: Lexicon of Rubber Technology, entry: Gough Joule Effect, Gentner-Verlag 1977, ISBN No. 3872472232

[0074] R. Hornig: Thermomechanical description of the entropy-elastic Gough-Joule effect for uniaxial extensional deformations, GAK 05 / 2021, pp. 208-221

[0076] R. Hornig: Comparison of various CSR methods regarding the static longterm sealing behaviour of AEM, ACM and HNBR compounds, International Polymer Science and Technology, Vol. 37, No. 11, 2010

[0099]

Claims

[1] Addition crosslinkable polymer material comprising a base polymer in the form of a polyolefin-based polymer with an average molar mass of approximately 400,000 g / mol or less, wherein the base polymer is modified with side chains having at least one SiH group, wherein the molality of the SiH groups in the base polymer is approximately 0.2 mol / kg or more. [2] Material according to claim 1, wherein the mean molar mass of the base polymer is approximately 200,000 g / mol or less, in particular approximately 100,000 g / mol or less, most preferably approximately 50,000 g / mol or less. [3] Material according to claim 1 or 2, wherein the molality of the SiH groups in the base polymer is approximately 0.28 mol / kg or more. [4] Material according to any one of claims 1 to 3, wherein the base polymer is a polyolefin copolymer, in particular an ethylene-propylene copolymer, most preferably a low-viscosity ethylene-propylene copolymer. [5] Material according to claim 4, wherein the base polymer is an ethylene-propylene copolymer and has an ethylene / propylene monomer ratio in the range of approximately 35 / 65 to approximately 75 / 25. [6] Material according to claim 4 or 5, wherein the base polymer has a diene content of approximately 10 wt.% or less, preferably approximately 2 wt.% or less. [7] Material according to any one of claims 1 to 6, wherein the side chains having SiH groups are silane, organosilane and / or siloxane groups, in particular alkylsiloxane groups, more preferably ethylsiloxane groups. [8] Material according to any one of claims 1 to 7, wherein the side groups are grafted onto the base polymer, preferably using at least one of the siloxanes of formulas (I) and (II): wherein the residue R 1 Alkylene, in particular methylene or ethylene, is represented, and wherein the R groups 2each individually selected are from alkyl, preferably methyl and ethyl, aryl, in particular phenyl, acrylic, hydroxy, alkoxy, in particular methoxy, epoxy, amino, mercapto, aryloxy, in particular phenoxy, and halogen, in particular chlorine, and wherein n 1 represents an integer value in the range of 1 to 10. [9] Method for crosslinking addition-crosslinkable polymer materials according to any one of claims 1 to 8, wherein the polymer material is addition-crosslinked in the presence of a Pt, Ru, Rh or Pd-based catalyst by means of a crosslinking agent in the form of a double or multiple double and / or triple bond-functional component, wherein the double and / or triple bond functions of the double and / or triple bond-functional component are arranged laterally and / or terminally. [10] Method according to claim 9, wherein the double and / or triple bond functions of the two or more double and / or triple bond functional component comprise an ethynyl and / or vinyl function. [11] Method according to claim 9 or 10, wherein the base polymer of the polymer material and the crosslinking agent can be crosslinked using a Karstedt Pt catalyst. [12] Method according to any one of claims 9 to 11, wherein the two or more double and / or triple bond functional component is selected from monomers, oligomers, polymers, in particular in the form of silanes, silanols and siloxanes. [13] Method according to any one of claims 9 to 12, wherein the addition crosslinking of the base polymer of the polymer material is carried out by means of a Pt-catalyzed alkene hydrosilylation. [14] Method according to any one of claims 9 to 13, wherein the crosslinking agent is a crosslinking agent according to any one of formulas (III) to (VI) wherein n 2 and n 4 each independently exhibit integer values ​​in the range of 4 to 2,000, in particular from 1,000 to 2,000, where n 3 has an integer value of 0 or more, where n 3 < n 2 + n 4 is, where R 3 individually selected from alkyl, aryl, acrylic, hydrogen, hydroxy, alkoxy, epoxy, amino, mercapto, halogen and siloxane groups, where R 3' is individually selected from alkyl, alkene, in particular allyl, alkyne, aryl, acrylic, hydrogen, hydroxy, alkoxy, allyloxy, epoxy, amino, mercapto, halogen and siloxane groups, and wherein R 4 and R 4' each individually selected from alkyl, in particular methyl, alkene, in particular vinyl and allyl, alkyne and norbornene, in particular vinylnorbornene; wherein R5 individually selected from alkyl, aryl, acrylic, hydrogen, hydroxy, alkoxy, epoxy, amino, mercapto, halogen and siloxane groups, where R 6 individually selected from alkyl groups, in particular an ethyl group, and R 7 individually selected from alkene, in particular allyl, alkyne, and norbornene, in particular vinylnorbornene; and wherein in formula (IV) n 5 integer values ​​from 1 to 100, preferably 6 to 100, and n 6 has integer values ​​from 4 to 2,000, preferably 80 to 2,000; where the values ​​for x 1 1 to 6, for x 2 1 to 6 and for x 3 1 to 6; where y has a value from 2 to 6. [15] Polymer material composition comprising - approximately 50 to approximately 95 wt.% of an addition-crosslinked polymer material, obtainable according to a method according to any one of claims 9 to 14; - one or more fillers, wherein the proportion of the fillers in the polymer material is approximately 5 to approximately 50 wt.%, in particular approximately 15 to approximately 30 wt.%. [16] Material composition according to claim 15, wherein the degree of crosslinking of the addition-crosslinked polymer material is approximately 50% or more. [17] Material composition according to claim 15 or 16, wherein the composition comprises a filler, in particular in the form of a hydrophobic and / or a hydrophilic mineral filler. [18] Material composition according to claim 16 or 17, wherein the filler or fillers are selected from silica-, silicone resin- and titanate-based fillers. [19] Use of a material composition according to any one of claims 16 to 18 as a sealing material in PEM (proton exchange membrane) fuel cells or in seals for drinking water systems.

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