CA1242846A

CA1242846A - Process for the production of a cross-linked nitrile rubber

Info

Publication number: CA1242846A
Application number: CA000468288A
Authority: CA
Inventors: Joachim Thormer; Zsolt Szentivanyi; Hartmuth Buding
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1983-11-23
Filing date: 1984-11-21
Publication date: 1988-10-04
Also published as: EP0144805A3; DE3342309A1; EP0144805A2; EP0144805B1; JPS60124638A; DE3462402D1

Abstract

ABSTRACT

Process for the production of a cross-linked nitrile rubber"

Nitrile rubbers, from 85 to 96% of the double bonds of which are hydrogenated, may be cross-linked with peroxides to produce products which have outstanding ozone-resistance, if peroxides are used, the half-life of which is longer than 2 minutes in benzene at 170°C.

Description

, "Process for the production of a cross-linked nifrile rubber"
This invention relates to a process for the production of a cross-linked nitrile rubber, from 85 to S 96% of the double bonds of which are hydrogenated.
It is known from DE-OS 29 13 992 to vulcanise part;ally hydrogenated nitrile rubbers using a sulphur vulcanising system. Cross-linking with certain peroxides (Exarnple 4, No. 16) produces only unsatisfactory results.
Appropriate choice of peroxide has been found not only to avoid these poor results, but even to produce better results, partlcularly with regard to ozone-resistance, than when sulphur vulcanisation is used.
Thus, an object of the present invention is to provide a process for the production of cross-linked nitrile rubbers, from 85 to 98%, preferably from 90 to 95%, of the double bonds of which are hydrogenated, using from I to 10%, by weight, preferably from 4 to 7%, by weight, of peroxides, based on the quantity of polymer in the mixture, characterised in that peroxides are used, the half-life of which is longer thun 2 minutes in benzene at 170C and is longer than 8 mintues in LDPE (low-density polyethylene)at the same temperature.
Suitable nitrile rubbers consist of from 10 to 50%, by weight, of acrylonitrile units and from 90 to 50%, by weight, of conjugated diene units, such as butadiene, isoprene or l,3-pentadiene. The partial hydrogenation of nitrile rubbers is known.
The following are examples of suitable peroxides:
bis-t_butylperoxiisopropyl)-benzene; 2,5-dim~thyl-2,5-di (t-butylperoxi)-hexane-a~d ~,~-dîmelhyl-2,5-di(t-butylperoxi)-hexene-(3).
The term "half-life" means that, at a given temper-ature and after one half-life 50% of the quantity of peroxide which was present at the beginning of the half-8~
life has decomposed.
The rubber mixture nay contain other constituentswhich are conventionally used in the peroxlde cross-linking of polymers, such as fillers, plasticisers, anti-agents, processing auxiliaries, pigments, co-activators, such as triallyl isocyanurate, and acid acceptors.
The products which may be obtained according to the present invention have rnany uses: they may be used, for example, for sealings of all types, tubes, in particular hydraulic pipes, toothed belts, cable coverings, profiles, linings, rollers, membranes and rubber/metal parts.
Example Rubber compositions having the compositions given in the following Table are vulcanised at 1~C for 18 minutes.
A nitrile rubber consisting of 39%, by weight, of acrylonitrile and 61%, by weight, of butadiene and having a degree of hydrogenation of 90% is used.
The ozone-resistance of the vulcanisates is determined at various elongations according to DIN 53 509 (23C, 60% rel. air humidity, 250 pphm of ozone in air.) Peroxide cross-linking is found to result in better products with regard to the ozone-resistance thereof, than sulphur cross-linking.

- 3 8~i Table Parts, by weight Rubber 100 100 5tea~ic acid Wax (Lunacera C44) 2 ZnO active 3 5 MgO 7 7 Styrenised diphenylamine 1,1 2 Zinc salt of 2-nercaptobenzimidazole 0,4 3 Carbon black (Corax N 550) 50 50 Processing auxiliary - 2 Sulphur -0,125 Tetramethyl thiuram disulphide - 2 Sulphur donors TrialIylisocyanurate 1,75 Bis-(t-butylperoxiisopropyl-benzene) 7,5 Results (in hours) of 020ne ageing until the first sign of a crack Elongation 10% ~168 168 20% ~168 6 30% ~168 4 60% 24 4

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the production of a cross-linked nitrile rubber, from 85 to 96% of the double bonds of which are hydrogenated, which comprises using as the cross-linking agent from 1 to 10%, by weight, based on the rubber, of a peroxide having a half-life at 170°C of more than 2 minutes in benzene and more than 8 minutes in low density polyethylene at the same temperature.

2. A process as claimed in claim 1 wherein the nitrile rub-ber is from 90 to 95% hydrogenated.

3. A process as claimed in claim 1 wherein from 4 to 7%, by weight, of peroxide is used.

4. A process as claimed in claim 1, 2 or 3 wherein the rubber comprises from 10 to 50%, by weight, of acrylonitrile units and from 90% to 50%, by weight, of conjugated diene units.

5. A process as claimed in claim 1, 2 or 3 wherein the pe-roxide is selected from the following: bis-t-butylperoxiisopropyl)-benzene; 2,5-dimethyl-2,5-di(t-butylperoxi)-hexane and 2,5-dimethyl-2,5-di(t-butylperoxi)-hexene-(3).

6. A process as claimed in claim 1, 2 or 3 wherein the rubber comprises from 10 to 50%, by weight, of acrylonitrile units and from 90% to 50%, by weight, of conjugated diene units and the peroxide is selected from the following: bis-t-butylperoxiisopropyl)-benzene;
2,5-dimethyl-2,5-di(t-butylperoxi)-hexane and 2,5-dimethyl-2,5-di (t-butylperoxi)-hexene-(3).