CA2048929A1

CA2048929A1 - Hydrogenated butadiene/isoprene/(meth)acrylonitrile copolymers

Info

Publication number: CA2048929A1
Application number: CA 2048929
Authority: CA
Inventors: Hartmuth Buding; Joachim Thormer; Christiane Oppenheimer-Stix; Friedrich Leibbrandt
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1990-08-15
Filing date: 1991-08-12
Publication date: 1992-02-16
Also published as: DE4025781A1; JPH04261407A; EP0471250A1

Abstract

HYDROGENATED BUTADIENE/ISOPRENE/(METH)ACRYLONITRILE CO-POLYMERS

Abstract Selectively hydrogenated butadiene/isoprene/(meth)-acrylonitrile copolymers have improved compression set values at low temperature.

Le A 27 581 - US/JP/CA

Description

2~48929 HYDROGENATED_ BUTADIENE/ISOPRENE/(METH)ACRYLONITRILE CO-POLYMERS

This invention relates to selectively hydrogenated butadiene/isoprene/(meth)acrylonitrile copolymers, to a process for their production by catalytic hydrogenation of the butadiene/isoprene/(meth)acrylonitrile copolymers with hydrogen and to the use of the hydrogenated copolymers for the production of vulcanizates. In the context of the invention, "selective hydrogenation" is understood to be the hydrogenation of the olefinic C=C double bonds with the C-N triple bonds remainlng intact. In the present context, "with the C--N triple bonds remaining intact" means that less than 7, preferably less than 5, more preferably less than 3 and, most preferably, less than 1.5% of the nitrile groups originally present in the polymeric starting product are hydrogenated.
It is known that hydrogenated nitrile rubber ("HNBR") obtained by selective hydrogenation of nitrile rubber (butadiene/acrylonitrile copolymer, hereinafter referred to as "NBR") is distinguished by high tensile strength, minimal abrasion, high oil resistance and remar~able stability to oxidative influences. However, the compres-sion set at low temperature is not entirely satisfactory.
It has now surprisingly been found that isoprene-modified NBR gives a hydrogenation product which combines the desirable properties of HNBR with improved compression set at low temperature (for the same degree of hydrogena-tion). The compression set values which it is now possible to achieve at low temperature could hitherto only be achieved by HNBR having a relatively high C=C double bond content, i.e. with losses of stability, for example to oxidative influences and to aggressive media, such as for example hydrogen sulfide and amines.
Accordingly, the present invention relates to a Le A 27 581-US/JP/CA

20~892~1 process for the selective hydrogenation of butadiene/
isoprene/acrylonitrile copolymers containing 3.5 to 22% by weight copolymerized isoprene and 18 to 50~ by weight copolymerized acrylonitrile, the acrylonitrile being completely or partly replaceable by an equimolar quantity of methacrylonitrile, with hydrogen in an organic solvent under a hydrogen pressure of 1 to 350 bar, preferably 5 to 250 bar and, more preferably, 10 to 200 bar and at tem-peratures of 20 to 250C, preferably 80 to 200'C, more preferably 100 to 180C and, most preferably, 120 to 160=C
in the presence of 2 to 3,000, preferably 3 to 1,000, more preferably 4 to 400 and, most preferably, 5 to 300 ppm metal or metal compound as hydrogenation catalyst (ex-pressed as metal and based on copolymer) to a degree of hydrogenation of at least 85%, based on C=C double bonds of the copolymer.
The present invention also relates to selectively hydrogenated butadiene/isoprene/acrylonitrile copolymers having degrees of hydrogenation, based on the C=C double bonds of the copolymer, of at least 85% which have been obtained by hydrogenation of copolymers containing 3.5 to 22% by weight copolymerized i,oprene and 18 to 50% by weight copolymerized acrylonitrile, the acrylonitrile being completely or partly replaceable by an equimolar quantity of methacrylonitrile.
Finally, the present invention relates to the use of the hydrogenated copolymers for the production of vul-canizates.
The hydrogenated copolymers according to the invention have particularly good properties when the correlation de-scribed below between the copolymerized isoprene and co-polymerized acrylonitrile contents in the starting material (before hydrogenation) is fulfilled:

Le A 27 581 2 20~8~29 Content of copolymerized Acrylonitrile Isoprene (% by weight) (% by weight) 18 - 23 max. 22, preferably 9 - 18, more preferably 10 - 17 23 - 29 max. 17, preferably 6 - 15, more preferably 8 - 14 29 - 35 max. 15, preferably 3.5 - 13, more preferably 6 - 12 25 - 41 max. 12, preferably 3.5 - 11, more preferably 5 - 9 41 - 48 max. 18, preferably 3.5 - 16, more preferably 5 - 15 An optimal combination of properties of the hydrogena-ted copolymers in regard to compression set at low tem-perature and resistance to oxidative attack and to aggres-sive medla is obtained in the hydrogenation of copolymers of which the copolymerized isoprene and acrylonitrile contents are limited by the curves A (upper limit) and B
(lower limit) in Fig. 1. (Equimolar ratios apply to methacrylonitrile.) Processes for the hydrogenation of NBR are known and may also be used for the production of the hydrogenation products according to the invention. Rhodium or ruthenium is generally used as the catalyst, although platinum, iridium, palladium, rhenium, cobalt or copper in the form of the metals, but preferably in the form of metal compounds, may also be used, cf. for example US-PS 3,700, 637, DE-PS 2,539,132, EP-PS 134 023, DE-OS 35 41 689, 35 40 918, EP-A 298 386, DE-OS 35 29 252, DE-OS 34 33 392, US-PS
4,464,515 and 4,503,196.
Suitable catalysts and solvents for hydrogenation in homogeneous phase are described in the following.
Preferred rhodium compounds as catalysts correspond to the following formulae Le A 27 581 3 20~8929 Rh Hal P[~

or /

~ ~ 3~ (Il) in which Hal is a halogen from the group consisting of chlorine, bromine and iodine and R is hydrogen, C14 alkyl (for example methyl, isopropyl), Cl4 alkoxy (for example methoxy) or halogen from the group consisting of chlorine, bromine and iodine.
Preferred ruthenium compounds correspond to the following formula RuX2y[(Ll)n (L2)sZ] (III) in which X is hydrogen, halogen, SnCl3, L1 is hydrogen, halogen, (Rs-COO)n and cyclopentadienyl corresponding to the following formula R5 Rl ~ IV) R4~R2 Le A 27 581 4 2 ~ 2 9 in which Rl to Rs independently of one another repre-sent hydrogen, methyl, ethyl or phenyl; adjacent sub-stituents together may also form a hydrocarbon radical such that L1 is an indenyl or fluorenyl system, L2 is a phosphane, bisphosphane or arsane, y is 0, 0.5 or 1, n is 1 or 2, z is an integer of 1 to 4, R6 is an alkyl, cycloalkyl, aryl or aralkyl containing 1 to 20 carbon atoms.
Examples of Ll ligands of the cyclopentadienyl type include cyclopentadienyl, pentamethyl cyclopentadienyl, ethyl tetramethyl cyclopentadienyl, pentaphenyl cyclopen-tadienyl, dimethyl triphenyl cyclopentadienyl, indenyl and fluorenyl. The benzene rings in the Ll ligands of the indenyl and fluorenyl type may be substituted by C16 alkyl radicals, more particularly methyl, ethyl and isopropyl;
Cl4 alkoxy radicals, more particularly methoxy and ethoxy;
aryl radicals, more particularly phenyl; and halogens, more particularly fluorine and chlorine. Preferred Ll ligands of the cyclopentadienyl type are lhe unsubstituted radicals cyclopentadienyl, indenyl and fluorenyl.
In the ligand L1 of the (R6 COO)n type, R6 may be selected, for example, from linear or branched, saturated hydrocarbon radicals containing 1 to 20, preferably 1 to 12 and, more preferably, 1 to 6 carbon atoms, cyclic saturated hydrocarbon radicals containing 5 to 12 and preferably 5 to 7 carbon atoms, aromatic hydrocarbon radicals from the benzene series containing 6 to 18 and preferably 6 to 10 carbon atoms, aryl-substituted alkyl radicals which, in the aliphatic part, consist of a linear or branched C16 hydro-carbon radical and, in the aromatic part, of a radical of the benzene series, preferably phenyl.
The substituents R6 defined above may optionally be substituted by hydroxy, Cl6 alkoxy, Cl6 carbalkoxy, fluor-Le A 27 581 5 2~4~929 ine, chlorine or di-C14-alkylamino, in addition to which the cycloalkyl, aryl and aralkyl radicals may be substituted by C~-6 alkyl. Alkyl, cycloalkyl and aralkyl groups may contain keto groups.
Examples of the substituent R6 are methyl, ethyl, propyl, isopropyl, tert.-butyl, cyclohexyl, phenyl, benzyl and trifluoromethyl. Preferred substituents R~ are methyl, ethyl and tert.-butyl.
Preferred L2 ligands are phosphanes and arsanes corresponding to the following formulae R7 - P - R9 and R7 - As - R9 l3 18 (V) (VI) ln which R7, R8 and R9 independently of one another have the same meaning as R6.
Preferred L2 ligands corresponding to formulae (V) and (VI) are triphenyl phosphane, diethyl phenyl phosphane, tritolyl phosphane, trinaphthyl phosphane, diphenyl methyl phosphane, diphenyl butyl phosphane, tris-(p-carbmethox-yphenyl)-phosphane, tris-(p-cyanophenyl)-phosphane, tri-butyl phosphane, tris-(trimethoxyphenyl)-phosphanes, bis-(trimethylphenyl)-phenyl phosphanes, bis-(trimethoxy-phenyl)-phenyl phosphanes, trimethylphenyl diphenyl phos-phanes, trimethoxyphenyl diphenyl phosphanes, tris-(di-methylphenyl)-phenyl phosphanes, tris-(dimethoxyphenyl)-phosphanes, bis-(dimethylphenyl)-phenylphosphanes, bis-(dimethoxyphenyl)-phenyl phosphanes, dimethylphenyl diphen-yl phosphanes, dimethoxyphenyl diphenyl phosphanes, tri-phenyl arsane, ditolyl phenyl arsane, tris-(4-ethoxypheny-l)-arsane, diphenyl cyclohexyl arsane, dibutyl phenyl arsane and diethyl phenyl arsane. Triaryl phosphanes, more especially triphenyl phosphane, are particularly preferred.

Le A 27 581 6 20~892~ -Other examples of L2 ligands are bisphosphanes corre-sponding to the following formula Rl R12 P - (CH2)1 - P (VII) Rll/ \Rl3 in which 1 is an integer of 1 to 10 and the substituents, R1~, R11, R12 and R13 independently of one another have the same meaning as R6.
Examples of bisphosphanes are 1,2-bis-diphenylphos-phanoethane, 1,2-bis-dianisylphosphanoethane, 1,3-bis-diphenylphosphanopropane, and 1,4-bis-diphenylphosphano-butane. 1,2 -Bis-diphenylphosphanoethane is preferred, 1,3-bis-diphenylphosphanopropaneandl,4-bis-diphenylphosphano-butane being particularly preferred.
The definition of the compounds (III) is also intended to encompass compounds in which L1 and L2 are attached to one another by one or more covalent bonds. Examples of such compounds are compounds corresponding to the following formula Rl5 RuX2y Cp-(C~2)q-P-(cH2~r-p (VIII) Rl4 \Rl6 Cp: cyclopentadienyl in which q and r independently of one another represent an integer of 1 to 6 and the substituents R14 to R16 independently of one another may have the same meaning as R6 .
Examples of ligands in square brackets in formula (VIII)arel,4-diphospha-6-cyclopentadienyl-1,1,4-triphenyl hexane, preferably 1,5-diphospha-7-cyclopentadienyl-1,1,5-Le A 27 581 7 2~929 triphenyl heptane and, in particular, 1,6-diphospha-8-cyclopentadienvl~ triphenyl octane.
The following are particularly preferred ruthenium complex catalysts corresponding to formula (III):

RuC12 (PPh3)3 RuHCl (PPh3)3 RuH2 (PPh3)4 RuH4 (PPh3)3 RuH (CH3C00) (PPh3)3 RuH (C2H5COO) (PPh3)3 RuH [(CH3)3C CO0] (PPh3)3 Ru (CH3 COO) 2 ( PPh3) 2 RuCl (Cp) (PPh3) 2 RuH (Cp) (PPh3) 2 Ru (SnCl3) (Cp) (PPh3) 2 RuCl (~5-CgH7) (PPh3) 2 RllH (~5-CgH7) (PPh3) 2 Ru (SnCl3) (~5-CgH7) (PPh3)2 RuCl (~5-C~3Hg) (PPh3) 2 RuH (~5-C~3Hg) (PPh3) 2 Ru (SnCl3) (~ -C13Hg) (PPh3) 2 RuCl (~5-C9~7) (dppe) in which "Ph" is phenyl, "Cp" is cyclopentadienyl and "dppe" is 1,2-bis-diphenylphosphanoethane.
Catalysts soluble in the organic solvent used for hydrogenation are preferably used. In the context of the invention, catalysts are "soluble" if more than 50% by weight, preferably more than 65% by weight and, more preferably, more than 80% by weight of a quantity of 3.4 g of catalyst dissolve in 2 liters of the particular solvent at 20~C.
Preferred organic solvents, particularly where rhodium compounds are used, include chlorinated aromatic hydro-Le A 27 581 8 2~8929 carbons, such as for example chlorobenzene and dichloroben-zenes. Preferred organic solvents, particularly where ruthenium compounds are used, include C3 ~ ketones and, in particular, mixtures of a) C3-6 ketone and b) monohydric, secondary or tertiary C3 ~ alcohol, the content of b) in the mixture being from 2 to 60% by weight, preferably from 5 to 50% by weight and, more preferably, from 7 to 40% by weight.

Preferred C3-6 ketones are, for example, acetone, butanone, pentanones, cyclopentanone and cyclohexanone and mixtures thereof. Butanone and, in particular, acetone are preferrecl.
Preferred C3-6 alcohols are, for example, 2-propanol, 2-butanol, 2-methyl-2-propanol, 2- and 3-pentanol, 3-methyl-2-butanol, 2-methyl-2-butanol, 2-, 3- and 4-hexanol, 4-methyl-2-pentanol. The pre~erred alcohol is 2-methyl-2-propanol, 2-butanol being more preferred and 2-propanol being particularly preferred.
The preferred hydroyenated butadiene/isoprene/(meth)-acrylonitrile copolymers according to the invention are rubbers having glass transition temperatures below 0C and preferably below -lO C, as measured for example mechanical-ly/dynamically with induced vibrations at 11 Hz (Vibron Viscoelastometer). They generally have Mooney viscosities (DIN 53 523) in the range from 10 to 150, preferably in the range from 20 to 100 and, more preferably, in the range from 30 to 90 ML (1~4) 100C. The degrees of hydrogenation are at least 85%, preferably between 90 and 99.7~ and, more preferably, between 94 and 99.7%. The degree of hydrogena-tion may be determined by NMR and IR spectroscopy.
on completion of hydrogenation, the reaction products may be removed from the solution by standard methods, Le A 27 581 9 2~929 including for example concentration by evaporation (optio-nally under reduced pressure), injection of steam and addition of a precipitant (non-solvent). The reaction products may then be dried to remove residual solvent or water.
The copolymers hydrogenated in accordance with the invention are generally soluble in such solvents as, for example, acetone, butanone, tetrahydrofuran, dichlorometh-ane, trichloromethane and chlorobenzene.
For most applications, the hydrogenated copolymers according to the invention are used in vulcanized form.
Vulcanization may be carried out, for example, by high-energy radiation or by crosslinking with sulfur or sulfur donors, with peroxides and optionally with polyfunctional crosslinking compounds (such as for example triallyl cyanurate, triallyl isocyanurate, bis-maleic imides, divinyl benzene, methacrylates of polyhydric alcohols, etc.), optionally after addition of fillers, stabilizers, etc. Vulcanization with sulfur is preferred, in which case copolymers hydrogenated in accordance with the invention to degrees of hydrogenation of preferably 94 to 97% should preferably be used.
Detailed descriptions of sulfur vulcanization systems can be found in W. Hoffmann, "Vulkanisation und Vulkanisa-tionhilfsmittel", Verlag Berliner Union GmbH, Stuttgart1965 and in Alliger and Sjothun, "Vulcanization of Elas-tomers", Reinhold Pub. Corp., New York, 1964. Suitable sulfur donors are thiuram polysulfides such as, for ex-ample, dipentamethylene thiuram tetrasulfide and hexasul-fide, tetramethyl thiuram disulfidei amine disulfides suchas, for example, dimorpholyl disulfide; sodium polysulfides and thioplastics.
Preferred sulfur vulcanization systems contain a) sulfur or sulfur donors, b) optionally vulcanization accelerators and Le A 27 581 10 c) optionally one or more activators.
a) is generally used in a quantity of 0.2 to 3.0% by weight sulfur (in the case of sulfur donors, expressed as the sulfur released), based on copolymer.
The vulcanization accelerator b) is generally used in quantities of l to 3.5% by weight, based on copolymer.
Preferred vulcanization accelerators b) include thiazole accelerators, such as 2-mercaptobenzothiazole (MBT), dib~nzo-thiaz~ldi~ulfid~(MBTS),benzothiazyl-2-cyclohexyl sulfenamide (CBS), benzothiazyl-2-tert.-butyl sul~enamide (TBBS), N-morpholinothio-2-benzothiazole (MBS), benzothiazyl-2-diisopropyl sulfenamide (DIBS), benzothiazyl-2-tert.-amyl sulfenamide (rABS), benzothiazyl dicyclohexyl sulfenamide (DCBS) and morpholinothiocarbonyl sulfene morpholide (OTOS).
Other preferred vulcanization accelerators b) include diphenyl guanidine (DPG) and di-o-tolyl guanidine (DOTG);
thiurams, such as thiuram mono- and disulfides; and dithiocarbamates and also thiophosphates and derivatives and salts thereof, for example zinc salts.
The most important activators c) are the metal oxides, particularly zinc oxide. In individual cases, magnesium oxide or calcium hydroxide is also used.
Preferred peroxides for peroxide vulcanization include dial~yl peroxides, ketal peroxides, aralkyl peroxides, peroxide esters, peroxide ethers; such as, for example, di-tert.-butyl peroxide, bis-(tert.-butyl peroxyisopropyl)-benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert.-butylperoxy)-hexane, 2,5-dimethyl-2,5-di-(tert.-butyl-peroxy)-hex-3-ene, 1,1-bis-(tert.-butylperoxy)-3,3,5-trimethyl cyclohexane, benzoyl peroxide, tert.-butyl cumyl peroxide and tert.-butyl perbenzoate.
The peroxide is preferably used in a quantity of 4 to 8% by weight, based on copolymer.
Vulcanization may be carried out at temperatures of Le A 27 581 11 20~8929 100 to 200 C and preferably at temperatures of 130 to 180~C, optionally under a pressure of 10 to 200 bar. After vulcanization, the vulcanizates may be post cured by storase at el ev~t~d t~ripera ~ures .
"Vulcanized" in the context of the invention means that less than 10~ by weight and preferably less than 5~ by weight copolymer can be extracted by extractlon For 10 hours in a Soxhlet extractor using tetrahydrofuran followed by chlorobenzene as extractant, the percentages by weight being based on the copolymer used for extraction. The expression "copol~vmer" means copolymer, i.e. it does not include, for example, any extender oil present.
The hydrogenated copolymers according to the invention are particularly suitable for the production of vulcani-zates which have to be capable of withstanding severe dynamic stressing. They may be used as seals, hoses, membranes, drive belts, gaskets, cable sheaths, etc.
The parts and percentages in the following Examples are by weight.
Examples Pre~aration of mixtures The mixtures were prepared from the following in-gredients in a laboratory kneader which had been heated to 50~:
Parts by weight Hydrogenated copolymer 100 Sulfur 0.5 Stearic acid Zinc oxidel~ 2 Magnesium oxide2~ 2 ~R~Vulkanox ocD3' 'R'Vulkanox ZMB-24) 0.4 Le ~ 27 581 12 20~929 Carbon black N 550 45 ~Vulkacit thiuram5~ 2 Vulkacit CZ6) 0.5 -" ~R~Zinkoxyd aktiv, a product of Bayer AG
2) (R)Maglite DE, a produet of Merek & Co. Ine., USA

3) Oetylated diphenylamine, a produet of Bayer AG

4) Zine salt of 2-mercaptobenzimidazole, a product of Bayer AG
0 5) Tetramethyl thiuram disulfide, a product of Bayer AG
6) Benzothiazyl-2-cyclohexyl sulfenamide, a product of Bayer AG
The hydrogenated eopolymer was introduced after the sulfur had been incorporated on laboratory rolls (roll temperature 50C). After 1 minute, all the constituents apart from V u 1 k acit thiuram and V U 1 k acit CZ were added.
After another 3 minutes, the mixture was cooled to ap-proximately 100C. The accelerator system was then incor-porated and ejected after 1.5 minutes.
Vulcanization was earried Otlt in a press over a period of 20 minutes at 160~C. The eompression set was determined on a ~est sp~cimen I aecording to DIN 53 517 which had been stored for 70 hours at -10C.

Examples I to 3 The following butadiene/isoprene/aerylonitrile eopoly-mers were dissolved in ehlorobenzene to form 9.3% by weight solutions and hydrogenated at 120C under a hydrogen pressure of 150 bar in the presenee of 167 ppm Rh in the form of RhCl [P(C5H5)3]3, based on copolymer. The hydrogena-ted copolymers remained behind after removal of the sol-vent.

Le A 27 581 13 2048~2~ -Startin~ products for hydro~nation Example Copolymerized Copolymerized isoprene (%) acrylonitrlle (~) 1 ~.1 34.1 2 7.9 33.3 3 12.0 33.5 The hydrogenation results and the compression sets of the hydrogenated copolymers are listed in the following Table.

Le A 27 581 14 ,~
, o\ ~
o o ~ _ ( ) Ul H
O
C.) H
o O 0 0 ~
.C v a) h ~ ~ 3 u~
U~ ~ ~ c~ r I`
o ~ o a~ ~ ~ ~1 O
âJ
O ~
O O ~ O
t) a) u~
~J ~H
O--' ~ h a) ~ 0~o ~ ~D ~
Q, ~ ~ _ o~ ~ co U~
a S~
O OJ
O
O
~ ~m ~ o-- Ll~
O ~: h h H
~,~ O ~ ~--` ~ U~
Q) ~ o\
o~ a~_ a~
a~
o rl ~ o U~ ~ o o o--O~ ~ _~ ~ r~ ,1 ~0\O~ CO 1`
C,~--~ ~ a~
a~ ~
Q h o ~
~R O ~ 3 ta u ~
11~ a) u~ R
~n ~ Q) a) o\
O
U~O P~~1 ~ O
u~ ~ m S: O H O Z ~1 H
If`) u~ h a) ~ ~~ :`
h E~ ~ ~\
~ ~~ ~:
O O~

Claims

1. A process for the selective hydrogenation of butadi-ene/isoprene/acrylonitrile copolymers containing 3.5 to 22%
by weight copolymerized isoprene and 18 to 50% by weight copolymerized acrylonitrile, the acrylonitrile being completely or partly replaceable by an equimolar quantity of methacrylonitrile, with hydrogen in an organic solvent under a hydrogen pressure of 1 to 350 bar and at tempera-tures of 20 to 250°C in the presence of 2 to 3,000 ppm metal or metal compound as hydrogenation catalyst (expres-sed as metal and based on copolymer) to a degree of hydro-genation of at least 85%, based on C=C double bonds of the copolymer.

2. A process as claimed in claim 1, in which hydrogena-tion is carried out under a hydrogen pressure of 5 to 250 bar.

3. A process as claimed in claim 1, in which hydrogena-tion is carried out under a hydrogen pressure of 10 to 200 bar.

4. A process as claimed in claim 1, in which hydroge-nation is carried out at a temperature of 80 to 200°C.

5. A process as claimed in claim 1, in which hydrogena-tion is carried out at a temperature of 100 to 180°C.

6. A process as claimed in claim 1, in which hydrogena-tion is carried out at a temperature of 120 to 160°C.

7. A process as claimed in claim 1, in which hydrogena-tion is carried out in the presence of 3 to 1000 ppm catalyst expressed as metal and based on copolymer.

8. A process as claimed in claim 1, in which hydrogena-tion is carried out in the presence of 4 to 400 ppm cata-lyst expressed as metal and based on copolymer.

9. Selectively hydrogenated butadiene/isoprene/acrylonit-rile copolymers having degrees of hydrogenation, based on the C=C double bonds of the copolymer, of at least 85%
which have been obtained by hydrogenation of copolymers Le A 27 581 16 containing 3.5 to 22% by weight copolymerized isoprene and 18 to 50% by weight copolymerized acrylonitrile, the acrylonitrile being completely or partly replaceable by an equimolar quantity of methacrylonitrile.

10. Copolymers as claimed in claim 9 of which the copoly-merized isoprene and acronitrile contents are limited by curves A and B of Fig. 1 and copolymers in which the copolymerized acrylonitrile is completely or partly repla-ced by equimolar quantities of copolymerized methacrylo-nitrile.

11. The use of the copolymers claimed in claims 9 and 10 for the production of vulcanizates.

Le A 27 581 17