Vulcanizable Compositions Comprising Hydrogenated Nitrile-Diene-Carboxylic Ester Copolymer and Silica

Abstract

The present invention relates to vulcanizable compositions comprising hydrogenated nitrile-diene-carboxylic ester copolymer and silica, to the production thereof and to vulcanizate, and to the use thereof in gaskets and belts.

Claims

1. A vulcanizable composition comprising: i) hydrogenated nitrile-diene-carboxylic ester copolymer containing: (a) 0.1% to 38% by weight, of at least one ,-ethylenically unsaturated nitrile unit, which is selected from acrylonitrile, methacrylonitrile, ethacrylonitrile or mixtures thereof, (b) 15% to 89.9% by weight, by weight of at least one conjugated diene unit, which is selected from 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene(piperylene) or mixtures thereof, and (c) 10% to 65% by weight, by weight of at least one ,-ethylenically unsaturated carboxylic ester unit, where at least 10% by weight, of the ,-ethylenically unsaturated carboxylic ester units (c) based on the total amount of all monomer units of 100% by weight is a PEG acrylate (d) of the general formula (I) ##STR00006## where R is hydrogen or branched or unbranched C.sub.1-C.sub.20-alkyl, n is 1 to 12 and R.sup.1 is hydrogen or CH.sub.3, ii) 10 to 250 parts by weight, of at least one silica, based on 100 parts by weight of hydrogenated nitrile-diene-carboxylic ester copolymer (i) and iii) at least one crosslinking agent.

2. The vulcanizable composition according to claim 1, comprising: i) hydrogenated nitrile-diene-carboxylic ester copolymer containing (a) 10% to 33% by weight of at least one ,-ethylenically unsaturated nitrile unit, which is selected from acrylonitrile, methacrylonitrile, ethacrylonitrile or mixtures thereof, (b) 21% to 79% by weight of at least one conjugated diene unit, which is selected from 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene (piperylene), or mixtures thereof and (c) 11% to 60% by weight of at least one ,-ethylenically unsaturated carboxylic ester unit, where at least 15% by weight of the ,-ethylenically unsaturated carboxylic ester units (c) based on the total amount of all monomer units of 100% by weight are a PEG acrylate (d) of the general formula (I) ##STR00007## where R is hydrogen or branched or unbranched C.sub.1-C.sub.20-alkyl, n is 1 to 12 and R.sup.1 is hydrogen or CH.sub.3, ii) 10 to 250 parts by weight, of at least one silica, based on 100 parts by weight of hydrogenated nitrile-diene-carboxylic ester copolymer (i) and iii) at least one crosslinking agent.

3. The vulcanizable composition according to claim 1, comprising: i) hydrogenated nitrile-diene-carboxylic ester copolymer containing: (a) 8% to 25% by weight of at least one ,-ethylenically unsaturated nitrile unit, which selected from acrylonitrile, methacrylonitrile, ethacrylonitrile or mixtures thereof, (b) 25% to 65% by weight of at least one conjugated diene unit, which is selected from 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene piperylene or mixtures thereof, and (c) 25% to 55% by weight of at least one ,-ethylenically unsaturated carboxylic ester unit, where at least 20% by weight of the ,-ethylenically unsaturated carboxylic ester units (c) based on the total amount of all monomer units of 100% by weight are a PEG acrylate (d) of the general formula (I) ##STR00008## where R is hydrogen or branched or unbranched C.sub.1-C.sub.20-alkyl, n is 1 to 12, and R.sup.1 is hydrogen or CH.sub.3, ii) 10 to 250 parts by weight, parts by weight of at least one silica, based on 100 parts by weight of hydrogenated nitrile-diene-carboxylic ester copolymer (i) and iii) at least one crosslinking agent.

4. The vulcanizable composition according to claim 1, wherein the conjugated diene units (b) have been hydrogenated to an extent of 50% to 100%.

5. (canceled)

6. The vulcanizable composition according to claim 1, wherein the conjugated diene unit (b) is 1,3-butadiene.

7. The vulcanizable composition according to claim 1, wherein the PEG acrylate units (d) are methoxy, ethoxy, butoxy or ethylhexoxy polyethylene glycol (meth)acrylate having 2 to 12 repeat ethylene glycol units.

8. The vulcanizable composition according to claim 1, wherein n is 2 or 3, R is ethyl or butyl and R.sup.1 is hydrogen or methyl.

9. The vulcanizable composition according to claim 1, wherein the hydrogenated nitrile-diene-carboxylic ester copolymers are copolymers containing 8% to 25% by weight of acrylonitrile units, 25% to 65% by weight of 1,3-butadiene units and 25% to 55% by weight of PEG-2 acrylate units or PEG-3 acrylate units.

10. The vulcanizable composition according to claim 1, wherein the silica (ii) is unsilanized silica or is silanized silica.

11. The vulcanizable composition according to claim 1, wherein the crosslinking agent (iii) is a peroxidic, sulfur-containing or aminic crosslinker, preferably is at least one peroxidic crosslinker, more preferably is a peroxidic crosslinker.

12. The vulcanizable composition according to claim 1, comprising: 100 parts by weight of hydrogenated nitrile-diene-carboxylic ester copolymer (i), 10 to 250 parts by weight of at least one silica (ii), preferably at least one silanized silica, 0.1 to 20 parts by weight, of at least one crosslinker (iii).

13. A process of producing vulcanizable compositions which includes the step of mixing a hydrogenated nitrile-diene-carboxylic ester copolymer according to claim 1 with silica and at least one crosslinker.

14. A process of producing vulcanizates, in the form of mouldings, which includes the step of subjecting the vulcanizable composition according to claim 1 to vulcanization at one or more temperatures in the range from 100 C. to 250 C. in a shaping process.

15. A vulcanizate produced from a vulcanizable composition according to claim 1.

16. A vulcanizate according to claim 15, which is a moulding selected from: belts, gaskets, rollers, footwear components, hoses, damping elements, stators and cable sheaths.

17. A method of producing a moulding, the method comprising the step of forming a moulding from a vulcanizable composition according to claim 1.

18. A method of producing a moulding according to claim 17, wherein the moulding is selected from the group consisting of belts, gaskets, rollers, footwear components, hoses, damping elements, stators and cable sheaths, more preferably for production of belts and gaskets.

19. The vulcanizable composition according to claim 11, the crosslinking agent (iii) is a peroxidic, sulfur-containing crosslinker or is an aminic crosslinker-selected from the group of bis(2,4-dichlorbenzyl) peroxide, dibenzoyl peroxide, bis(4-chlorbenzoyl) peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butyl perbenzoate, 2,2-bis(t-butylperoxy)butene, 4,4-di-tert-butylperoxynonyl valerate, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, tert-butyl cumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, di-t-butyl peroxide or 2,5-dimethyl-2,5-di(t-butylperoxy)-hex-3-yne.

Description

EXAMPLES

Test Methods:

[0174] The RDB content (residual double bond content) in % is determined by the following FT-IR measurement: The IR spectra of the hydrogenated nitrile-diene-carboxylic ester copolymer before, during and after the hydrogenation are recorded by means of an AVATAR 360 Thermo Nicolet FT-IR spectrometer IR instrument. To this end a monochlorobenzene solution of the hydrogenated nitrile-diene-carboxylic ester copolymer is applied to an NaCl platelet, dried to a film and analysed. The degree of hydrogenation is determined by FT-IR analysis according to the ASTM D 567095 method.

[0175] The Mooney viscosity values (ML1+4@100 C.) are determined in each case by means of a shearing disc viscometer in accordance with ASTM D1646-07.

[0176] For the tensile testing, 2 mm sheets were produced by vulcanization of the vulcanizable mixture at 180 C. The dumbbell-shaped test specimens were punched out of these plaques and tensile strength and elongation were determined to ASTM D2240-81.

[0177] Hardness was determined with a durometer to ASTM D2240-81.

[0178] The glass transition temperature was obtained by means of a DSC measurement according to ASTM E 1356-03 or according to DIN 53765. For this purpose, between 10 mg and 15 mg of the sample were weighed into an aluminium boat and sealed. The boat was heated twice from 150 C. to 150 C. at a heating rate of 10 K/min in a DSC instrument from TA Instruments. The glass transition temperature was determined from the second heating curve by the standard mean value method.

[0179] Swelling: To determine swelling, dumbbell-shaped test specimens as used for tensile testing were stored in IRM903 according to DIN ISO 1817 at 150 C. for 168 h. Thereafter, the samples were measured and weighed, and the volume swelling and increase in mass were determined. Subsequently, tensile strength and elongation were determined to ASTM D2240-81.

[0180] Compression set was determined according to DIN ISO 815-2.

Measurement of Loss Modulus G

[0181] Loss modulus was determined in an amplitude-dependent measurement using a Alpha RPA 2000 Rubber Process Analyzer at 1 Hz and 60 C. The shear rates were 0.65/s at 10%, 1.29/s at 20%, 1.94/s at 30%, 3.23/s at 50%, and 6.46/s at 100%.

The Following Substances were Used in the Examples:

[0182] The following chemicals were purchased as commercial products from the companies specified in each case or originate from production plants of the companies specified.

[0183] For the polymerization:

TABLE-US-00001 PEG-2-MA butoxy diethylene glycol methacrylate (BDGMA), molecular weight 230.3 g/mol, Evonik Industries AG PEG-3-MA ethoxy triethylene glycol methacrylate, molecular weight 246.3 g/mol, Evonik Industries AG Disponil SDS G sodium lauryl sulfate; BASF Na salt of CAS 61790-51-0 disproportionated resin acid Na.sub.2CO.sub.3 Merck KGaA t-DDM tertiary dodecyl mercaptan; LANXESS Deutschland GmbH Glidox 500 pinane hydroperoxide; Renessenz Premix solution contains 0.986 g of Fe(II)SO.sub.4*7 Fe(II)SO.sub.4 H.sub.2O and 2.0 g of Rongalit C in 400 g of water Rongalit C sodium salt of a sulfinic acid derivative; commercial product from BASF Diethylhydroxylamine Merck KGaA Vulkanox BKF 2,2-methylenebis(4-methyl-6-tert- butyl-phenol); LANXESS Deutschland GmbH

[0184] Substances used in the vulcanizable composition:

TABLE-US-00002 Therban 3407 hydrogenated nitrile-diene rubber (HNBR) with acrylonitrile content 34% by weight; <0.9% RDB and a Mooney viscosity ML(1 + 4@ 100 C.) of 70 Therban LT 1707 hydrogenated nitrile-diene rubber (HNBR) with acrylonitrile content 17% by weight; <0.9% RDB and a Mooney viscosity ML(1 + 4@ 100 C.) of 70 Corax N330 carbon black; Orion Engineered Carbons Coupsil VP 6508 silanized silica (available from Evonik) Vulkasil N silica (precipitated silica) (available from LANXESS Deutschland GmbH) Dynasylan VTEO vinyltriethoxysilane, silanizing agent (available from Evonik) Rhenofit DDA 70% masterbatch based on octylated diphenylamine; Rheinchemie Vulkanox zinc salt of 4- and 5-methyl-2- ZMB2/C5 mercaptobenzothiazole; LANXESS Deutschland GmbH Maglite DE magnesium oxide; CP Hall. Kettlitz-TAIC triallyl isocyanurate, 70% masterbatch; Kettlitz Chemie GmbH & Co KG. Perkadox di(tert-butylperoxyisopropyl)benzene 14-40 B-PD 40% supported on silica; Akzo Nobel Polymer Chemicals BV

I Preparation of the Nitrile-Butadiene-PEG Acrylate Copolymers (PEG-NBR 1 and 2)

[0185] PEG-NBR 1 and 2 as used in the example series which follow were produced according to the base formulation specified in Table 1, with all feedstocks stated in % by weight based on 100% by weight of the monomer mixture. Table 1 also gives the particular polymerization conditions (temperature, conversion and time).

TABLE-US-00003 TABLE 1 Preparation of the nitrile-butadiene-PEG acrylate copolymers (PEG-NBR 1-2) PEG-NBR 1 2 Acrylonitrile 36 18 1,3-Butadiene 49 31 Ethoxy triethylene 15 glycol methacrylate (PEG-3-MA) Butoxy diethylene 51 glycol methacrylate (PEG-2-MA) Disponil SDS G 2.4 2.4 Na salt of the 0.5 0.5 disproportionated resin acid Na.sub.2CO.sub.3 0.12 0.12 pH 7.5 0.5 7.5 0.5 t-DDM 0.57 0.25 Glidox 500 0.02 0.02 Premix solution FeSO.sub.4 0.017 0.02 Diethylhydroxylamine 0.2 0.2 Vulkanox BKF 0.1 0.1 Polymerization 12 0.5 12 0.5 temperature [ C.] Polymerization 74 75 conversion [%] Polymerization 7 6.4 time [h]

[0186] The nitrile-butadiene-PEG acrylate copolymers were prepared batchwise in a 201 autoclave with stirrer system. In each of the autoclave batches, 4.73 kg of the monomer mixture and a total amount of water of 10 kg were used, as was EDTA in an equimolar amount based on the Fe(II). 9 kg of this amount of water were initially charged with the emulsifier in the autoclave and purged with a nitrogen stream. Thereafter, the monomers and the amount of the t-DDM molecular weight regulator specified in Table 1 were added and the reactor was closed. Once the reactor contents had been thermostatted, the polymerizations were initiated by addition of the premix solutions and of pinane hydroperoxide (Glidox500).

[0187] The progress of the polymerization was monitored by gravimetric conversion determinations. Upon attainment of the conversions reported in Table 1 the polymerization was terminated by adding an aqueous solution of diethylhydroxylamine. Unconverted monomers and other volatile constituents were removed by means of steam distillation.

[0188] Prior to the coagulation of each NBR latex, a 45% dispersion of Vulkanox BKF (0.1% by weight of Vulkanox BKF based on NBR rubber) was added to each. This was followed by coagulation with CaCl.sub.2, washing and drying of the crumbs obtained.

[0189] The dried PEG-NBR rubbers were characterized by the Mooney viscosity, the ACN content and the glass transition temperature, and the content of the termonomers was determined by 1H NMR analysis (Table 2).

TABLE-US-00004 TABLE 2 Properties of the nitrile-butadiene- PEG acrylate copolymers (PEG-NBR 1 and 2) PEG-NBR 1 2 ACN content [% by wt.] 31 15.9 BD content [% by wt.] 53.9 25.1 PEG-3-MA [% by wt.] 15.1 PEG-2-MA [% by wt.] 49 Mooney viscosity 28 10 ML(1 + 4@100 C.) Glass transition temperature 26 40 Tg of crude polymer [ C.]

II Preparation of the Hydrogenated Nitrile-Butadiene-PEG Acrylate Copolymers (PEG-HNBR 1 and 2)

Procedure for Hydrogenations

[0190] The hydrogenations which follow were performed using the above-synthesized nitrile-butadiene-PEG acrylate copolymers (PEG-NBR 1 and 2).

[0191] Dry monochlorobenzene (MCB) was sourced from VWR, Wilkinson catalyst from Materia Inc. and triphenylphosphine from VWR, and were used as obtained. The results of the hydrogenation experiments are summarized in Table 2.

[0192] Hydrogenations 1-5 were performed in a 10 I high-pressure reactor under the following conditions: [0193] Solvent: monochlorobenzene [0194] Solids concentration: 12-13% by weight of PEG-NBR terpolymer in MCB (518 g) [0195] Reactor temperature: 137-140 C. [0196] Reaction time: up to 4 hours [0197] Catalyst & loading: Wilkinson catalyst: 0.337 g (0.065 phr); [0198] Co-catalyst: triphenylphosphine: 5.18 g (1.0 phr) [0199] Hydrogen pressure (p H.sub.2): 8.4 MPa [0200] Stirrer speed: 600 rpm

[0201] The PEG-NBR-containing polymer solution is degassed three times with H.sub.2 (23 C., 2 MPa) with vigorous stirring. The temperature of the reactor was raised to 100 C. and the H.sub.2 pressure to 6 MPa. 123.9 g of a chlorobenzene solution consisting of Wilkinson catalyst (0.337 g) and triphenylphosphine (5.18 g) were added and the pressure was raised to 8.4 MPa, while the reactor temperature was adjusted to 137-140 C. Both parameters were kept constant during the reaction. The course of the reaction was monitored by means of measurement of the residual double bond content (RDB) of the nitrile-butadiene-PEG acrylate copolymer by means of IR spectroscopy. The reaction was ended after not more than 4 hours and/or attainment of an RDB content of <1% by releasing the hydrogen pressure.

[0202] The hydrogenated PEG-HNBR thus formed was isolated from the solution by means of steam coagulation. For this purpose, the chlorobenzene solution was diluted to a polymer content of 7% by weight and metered continuously into a stirred, water-filled glass reactor preheated to 100 C. At the same time, 0.5 bar steam was introduced into the coagulation water. The polymer crumbs thus precipitated were roughly dewatered and then dried to constant weight at 55 C. under reduced pressure.

TABLE-US-00005 TABLE 3 Properties of the hydrogenated nitrile- butadiene-PEG acrylate copolymers (PEG-HNBR 1 and 2) PEG-HNBR 1 2 PEG-NBR 1 2 ROB % <0.5 <0.5 Mooney viscosity 129 61 ML(1 + 4@100 C.) Glasbergangstemperatur 30 50 Tg Rohpolymer [ C.]

III Production of Vulcanizates of the Hydrogenated Nitrile-Diene-Carboxylic Ester Copolymers:

Production of the Vulcanizable Compositions:

[0203] All the compositions were produced on a mixing roll mill. The diameter of the rollers was 80 mm, the length 200 mm. The rollers were preheated to 40 C., the speed of the front roller was 16.5 rpm and that of the rear roller was 20 rpm, thereby achieving a friction of 1:1.2.

[0204] The rubber was initially charged and mixed for one (1) minute until a smooth milled sheet had formed. Subsequently, first the carbon black, then the additives and finally the crosslinking chemicals were incorporated. The total mixing time was 5 to 8 minutes.

TABLE-US-00006 TABLE 4a Composition and properties of the vulcanizates (inventive examples are identified by an asterisk *). V1 V2 I1* V3 I2* V4 Vulcanizate HNBR copolymer parts parts parts parts parts parts PEG-HNBR 1 100 100 100 HNBR (Therban 3407) 100 100 100 Other components phr phr phr phr phr phr Corax N330 30 30 Coupsil VP 6508 25 25 Vulkasil N 25 25 Dynasilan VTEO 0.5 0.5 Rhenofit DDA 70 1.4 1.4 1.4 1.4 1.4 1.4 Vulkanox ZMB2/C5 0.4 0.4 0.4 0.4 0.4 0.4 Maglite DE 2 2 2 2 2 2 Kettlitz-TAIC 1.5 1.5 1.5 1.5 1.5 1.5 Perkadox 14-40 B-PD 7 7 7 7 7 7 Vulcanizate properties Glass transition temp. 33 26 33 26 32 26 (Tg) [ C.] Hardness [ShA] 58 62 55 64 56 63 M10 [MPa] 0.5 0.5 0.4 0.6 0.4 0.6 M25 [MPa] 0.8 0.9 0.7 1 0.8 1 M50 [MPa] 1.2 1.3 1.1 1.5 1.1 1.4 M100 [MPa] 2.4 2.5 1.9 2.7 1.9 2.5 Elongation at break [%] 285 307 240 239 290 241 Tensile strength [MPa] 22 25 10 14 15 13

[0205] Vulcanizates comprising conventional HNBR Therban 3407 and silanized silica (V3, Coupsil) or comprising silica and silanizing agent (V4, Vulkasil N and Dynasilan VTEO), as compared with vulcanizates comprising conventional HNBR Therban 3407 and carbon black (V2, Corax N330), have an increase in tensile strength by 11 to 12 MPa.

[0206] By comparison, in the case of vulcanizate based on the hydrogenated nitrile-diene-carboxylic ester copolymers, the tensile strength in the case of use of silica and silane is reduced to a significantly lesser degree (namely by only 7 MPa) than in the case of use of the already silanized silica (Coupsil VP 6508). This gives rise to a synergistic effect of the hydrogenated nitrile-diene-carboxylic ester copolymer and of the in situ silanization of the silica with silanizing agent.

TABLE-US-00007 TABLE 4b Composition and properties of the vulcanizates (inventive examples are identified by an asterisk *). Vulcanizate V5 V6 I3* V7 HNBR copolymer parts parts parts parts PEG-HNBR 2 100 100 HNBR (Therban LT 1707) 100 100 Other components phr phr phr phr Corax N330 30 30 Coupsil VP 6508 25 25 Rhenofit DDA 70 1.4 1.4 1.4 1.4 Vulkanox ZMB2/C5 0.4 0.4 0.4 0.4 Maglite DE 2 2 2 2 Kettlitz-TAIC 1.5 1.5 1.5 1.5 Perkadox 14-40 B-PD 7 7 7 7 Vulcanizate properties Glass transition 47 41 47 41 temp. (Tg) [ C.] Hardness [ShA] 48 53 51 55 M10 [MPa] 0.3 0.3 0.3 0.4 M25 [MPa] 0.5 0.6 0.5 0.7 M50 [MPa] 0.8 1 0.9 1 M100 [MPa] 1.8 1.8 2 1.7 Elongation at break [%] 231 287 197 287 Tensile strength [MPa] 9.6 17 6.7 11.9

[0207] The inventive mixture 13*, in the case of use of silanized silane, by comparison with the carbon black-containing comparative vulcanizate V5, has a reduction in tensile strength of only 2.9 MPa. By contrast, the exchange of carbon black in the comparative vulcanizate V6 for silanized silica in the comparative vulcanizate V7 leads to a reduction of 5.1 MPa.

TABLE-US-00008 TABLE 5 Vulcanizate properties after storage at 150 C. for 14 days Vulcanizate V1 V2 I1* V3 I2* V4 Hardness [ShA] 71 69 64 70 66 70 Change in hardness [ShA] 13 7 9 6 10 7 M10 [MPa] 0.8 0.8 0.6 0.7 0.6 0.8 M25 [MPa] 1.5 1.4 1 1.3 1.1 1.4 M50 [MPa] 2.6 2.1 1.6 2 1.7 2.4 M100 [MPa] 6.3 4.8 3 4.2 3.2 6.1 Elongation at break [%] 205 261 212 215 260 139 Tensile strength [MPa] 21.1 23.7 11.8 16.3 18.2 11.4 Change in elongation at 28 19 12 10 10 42 break [%] Change in tensile strength 2.3 12 16.8 19 22.1 13.6 [%]

[0208] In the case of conventional hydrogenated nitrile-diene copolymer Therban 3407, the ageing of the vulcanizate at 150 C. for 2 weeks leads to an increase in hardness and hence a deterioration of 7 points from 62 to 69 (V2). The addition of silanized silica (V3) or silica and silanizing agent (V4) results in virtually no change since there is a rise in hardness by 6 or 7 points here too.

[0209] By contrast, the addition of silanized silica (I1*) and silica and silanizing agent (I2*) leads to a smaller increase in hardness of 9 and 10 points compared to the increase in the hardness of a vulcanizate (V1) containing PEG-HNBR according to the invention but not containing any silanized silica or silica and silanizing agent.

[0210] The use of silica thus brings about a reduced increase in hardness in the course of ageing of vulcanizates based on PEG-HNBR.

TABLE-US-00009 TABLE 6 Compression set after ageing at 20 C. for 24 hours Vulcanizate V1 V2 I1* V3 I2* V4 V5 V6 I3* V7 Compression set [%] 41 90 36 88 40 94 30 30 23 28

[0211] The inventive vulcanizates I1 and I2 have a similar or even lower and hence better compression set than the comparative vulcanizates V2, V3 and V4 based on conventional hydrogenated nitrile-diene copolymer Therban 3407.

[0212] The inventive mixture I3* has an improved compression set at 20 C. compared to the comparative vulcanizate V5; the reduction in CS is optimized in the case of use of PEG HNBR with silica compared to the use of Therban LT 1707 with silica.

TABLE-US-00010 TABLE 7 Vulcanizate properties after ageing in IRM 903 at 150 C. for 168 hours Vulcanizate V1 V2 I1* V3 I2* V4 Change in volume [%] 14 21 14 21 14 18 Hardness [ShA] 53 54 53 59 54 59 Change in hardness [ShA] 5 8 2 5 2 5 M10 [MPa] 0.4 0.4 0.4 0.5 0.4 0.5 M25 [MPa] 0.8 0.8 0.7 1 0.8 1 M50 [MPa] 1.2 1.3 1.2 1.6 1.2 1.5 M100 [MPa] 2.8 3 2.2 3.2 2.2 3.1 Elongation at break [%] 202 233 192 191 218 201 Tensile strength [MPa] 13.3 16.3 8.1 11.3 10.8 12.5 Change in elongation at 29 28 20 20 25 17 break [%] Change in tensile strength 38 39 20 18 28 5 [%]

[0213] The inventive vulcanizates I1 and I2 have an identical change in volume and hence no deterioration.

TABLE-US-00011 Vulcanizate V5 V6 I3* V7 Change in volume [%] 36 51 36 51 Hardness [ShA] 38 39 43 41 Change in 10 13 8 14 hardness [ShA] M10 [MPa] 0.2 0.2 0.3 0.3 M25 [MPa] 0.4 0.5 0.5 0.5 M50 [MPa] 0.7 0.8 1 1 M100 [MPa] 1.9 2.3 2.7 2.3 Elongation at break [%] 165 171 139 163 Tensile strength [MPa] 5.8 7.5 4.8 5.8 Change in elongation 29 40 29 43 at break [%] Change in tensile 39.6 55.9 28.4 51.3 strength [%]

[0214] The inventive vulcanizate I3* has comparable swelling (=change in volume) to V5 and hence no deterioration in properties on exchange of the filler and simultaneous reduction from 30 parts by weight to 25 parts by weight.

TABLE-US-00012 G (10%) G (100%) PEG HNBR 1 CB 242 192 PEG HNBR 2 CB 175 134 Therban 3407 CB 374 294 Therban LT 1707 CB 232 179 PEG HNBR 1 Coupsil 193 164 PEG HNBR 2 Coupsil 164 120 Therban 3407 Coupsil 340 260 Therban LT 1707 Coupsil 207 155

[0215] The inventive vulcanizates I1* and I2* comprising PEG-HNBR and silica/silanized silane have a significantly lower loss factor G than PEG-HNBR filled with carbon black. The change in the loss factor G in the case of Therban 3407 and Therban LT 1707, which do not contain any PEG acrylate, is significantly smaller. Thus, the synergistic effect of silica with the PEG acrylate units results in a lower loss factor and hence less energy is dissipated, and hence lower evolution of heat is expected in the product under dynamic stress.

[0216] As a result of the use of the hydrogenated nitrile-diene-carboxylic ester copolymers (i), the preferably silanized silica (ii) is better attached to the polymer matrix, which reduces filler-filler interactions. This is apparent from the amplitude-dependent measurement of the loss modulus, as shown in FIG. 1. While vulcanizates of the conventional hydrogenated nitrile-diene copolymer Therban 3407 comprising carbon black or silanized silica (Coupsil) have a higher loss modulus G at low amplitudes, vulcanizates of the hydrogenated nitrile-diene-carboxylic ester copolymers comprising silica have a significant reduction in loss modulus compared to carbon black.

[0217] At the same time, at higher amplitudes, as a result of the dissolution of the filler-filler network, an elevated drop in loss modulus is observed for the copolymer. In the case of the vulcanizates comprising hydrogenated nitrile-diene-carboxylic ester copolymer, the change with elevated amplitude is significantly smaller, and particularly small in the case of use of silica/silanizing agent or silanized silica (Coupsil).

[0218] The particular advantage of the invention is that vulcanizates based on the hydrogenated nitrile-diene-carboxylic ester copolymers according to the invention, in combination with silica and preferably silanized silica, have a lower and hence improved compression set than conventional vulcanizates based on HNBR, lower heat buildup and an advantageous combination of low glass transition temperature Tg, measured according to DIN 53765, and lower swelling in IRM 903, measured according to DIN ISO 1817 at 150 C. for 7 days.

[0219] In terms of the combination of these properties, the hydrogenated nitrile-diene-carboxylic ester copolymers according to the invention are superior to hydrogenated nitrile-diene-carboxylic ester copolymers commercially available to date.