Process for degrading nitrile rubbers in the presence of catalysts having an increased activity

1. A process for degrading a nitrile rubber comprising subjecting the nitrile rubber to a metathesis reaction in the presence of a catalyst of the general formula (I),

where

M is ruthenium or osmium,

Y is oxygen (O), sulphur (S), an N—R 1 radical or a P—R 1 radical,

X 1 and X 2 are identical or different ligands,

R 1 is an alkyl, cycloalkyl, alkenyl, alkynyl, aryl, alkoxy, alkenyloxy, alkynyloxy, aryloxy, alkoxycarbonyl, alkylamino, alkylthio, arylthio, alkylsulphonyl or alkylsulphinyl radical, each of which may optionally be substituted by one or more alkyl, halogen, alkoxy, aryl or heteroaryl radicals,

R 2 , R 4 , R 5 are identical or different and are each hydrogen, organic or inorganic radicals,

R 3 is —SO 2 N(CH 3 ) 2 ,

R 6 is hydrogen or an alkyl, alkenyl, alkynyl or aryl radical and

L is a ligand.

2. The process according to claim 1 , wherein L in the general formula (I) is a P(R 7 ) 3 radical, where the radicals R 7 are each, independently of one another, C 1 -C 6 -alkyl, C 3 -C 8 -cycloalkyl or aryl or a substituted or unsubstituted imidazolidine radical (“Im”).

3. The process according to claim 2 , wherein the imidazolidine radical (Im) has a structure of the general formula (IIa) or (IIb),

where

R 8 , R 9 , R 10 , R 11 are identical or different and are each hydrogen, straight-chain or branched C 1 -C 30 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 2 -C 20 -alkynyl, C 6 -C 24 -aryl, C 1 -C 20 -carboxylate, C 1 -C 20 -aryloxy, C 2 -C 20 -alkenyloxy, C 2 -C 20 -alkynyloxy, C 6 -C 20 -aryloxy, C 2 -C 20 -alkoxycarbonyl, C 1 -C 20 -alkylthio, C 6 -C 20 -arylthio, C 1 -C 20 -alkylsulphonyl, C 1 -C 20 -alkylsulphonate, C 6 -C 20 -arylsulphonate or C 1 -C 20 -alkylsulphinyl.

4. The process according to claim 3 , wherein R 10 and R 11 in the imidazolidine radical (Im) are identical or different and are each straight-chain or branched C 1 -C 10 -alkyl, C 3 -C 10 -cycloalkyl, C 6 -C 24 -aryl, C 1 -C 10 -alkylsulphonate, or C 6 -C 10 -arylsulphonate.

5. The process according to claim 3 , wherein the imidazolidine radical (Im) has the structure (IIIa), (IIIb), (IIIc), (IIId), (IIIe) or (IIIf),

where Mes is in each case a 2,4,6-trimethylphenyl radical.

6. The process according to claim 1 or 2 , wherein X 1 and X 2 in the general formula (I) are identical or different and are each hydrogen, halogen, pseudohalogen, straight-chain or branched C 1 -C 30 -alkyl, C 6 -C 24 -aryl, C 1 -C 20 -alkoxy, C 6 -C 24 -aryloxy, C 3 -C 20 -alkyldiketonate, C 6 -C 24 -aryldiketonate, C 1 -C 20 -carboxylate, C 1 -C 20 -allylsulphonate, C 6 -C 24 -arylsulphonate, C 1 -C 20 -alkylthiol, C 6 -C 24 -arylthiol, C 1 -C 20 -alkylsulphonyl or C 1 -C 20 -alkylsulphinyl.

7. The process according to claim 6 , wherein X 1 and X 2 in the general formula (I) are identical or different and are each halogen, benzoate, C 1 -C 5 -carboxylate, C 1 -C 5 -alkyl, phenoxy, C 1 -C 5 -alkoxy, C 6 -C 24 -arylthiol, C 6 -C 24 -aryl or C 1 -C 5 -alkylsulphonate.

8. The process according to claim 6 , wherein X 1 and X 2 in the general formula (I) are identical and are each halogen, CF 3 COO, CH 3 COO, CFH 2 COO, (CH 3 ) 3 CO, (CF 3 ) 2 (CH 3 )CO, (CF 3 )(CH 3 ) 2 CO, PhO (phenoxy), MeO (methoxy), EtO (ethoxy), tosylate (p-CH 3 —C 6 H 4 —SO 3 ), mesylate (2,4,6-trimethylphenyl) or CF 3 SO 3 (trifluoromethanesulphonate).

9. The process according to claim 1 or 2 , wherein the radical R 1 in the general formula (I) is a C 1 -C 30 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 2 -C 20 -alkynyl, C 6 -C 24 -aryl, C 1 -C 20 -alkoxy, C 2 -C 20 -alkenyloxy, C 2 -C 20 -alkynyloxy, C 6 -C 24 -aryloxy, C 2 -C 20 -alkoxycarbonyl, C 1 -C 20 -alkylamino, C 1 -C 20 -alkylthio, C 6 -C 24 -arylthio, C 1 -C 20 -alkylsulphonyl or C 1 -C 20 -alkylsulphinyl radical, each of which may optionally be substituted by one or more alkyl, halogen, alkoxy, aryl or heteroaryl radicals.

10. The process according to claim 1 or 2 , wherein the radical R 6 is hydrogen, a C 1 -C 30 -alkyl radical, a C 2 -C 20 -alkenyl radical, a C 2 -C 20 -alkynyl radical or a C 6 -C 24 -aryl radical.

11. The process according to claim 1 , wherein a catalyst of the general formula (IV)

where

M, L, X 1 , X 2 , R 1 , R 2 , R 3 , R 4 and R 5 have the meanings given for the general formula (I), is used.

12. The process according to claim 11 , wherein, in the general formula (IV),

M is ruthenium,

X 1 and X 2 are both chlorine,

R 1 is an isopropyl radical,

R 2 , R 4 , R 5 are all hydrogen,

R 3 is —SO 2 N(CH 3 ) 2 , and

L is a substituted or unsubstituted imidazolidine radical of the formula (IIa) or (IIb),

where

R 8 , R 9 , R 10 , R 11 are identical or different and are each hydrogen, straight-chain or branched C 1 -C 30 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 2 -C 20 -alkynyl, C 6 -C 24 -aryl, C 1 -C 20 -carboxylate, C 1 -C 20 -alkoxy, C 2 -C 20 -alkenyloxy, C 2 -C 20 -alkynyloxy, C 6 -C 24 -aryloxy, C 2 -C 20 -alkoxycarbonyl, C 1 -C 20 -alkylthio, C 6 -C 24 -arylthio, C 1 -C 20 -alkylsulphonyl, C 1 -C 20 -alkylsulphonate, C 6 -C 24 -arylsulphonate or C 1 -C 20 -alkylsulphinyl.

13. The process according to claim 1 , wherein a catalyst of the formula (IXX),

where Mes is a 2,4,6-trimethylphenyl radical, is used.

14. The process according to claim 1 , wherein a catalyst of the general formula (XVI),

where D 1 , D 2 , D 3 and D 4 each have a structure of the general formula (XVII) which is bound via the methylene group to the silicon of the formula (XVI),

where

M, L, X 1 , X 2 , R 1 , R 2 , R 3 , R 5 and R 6 have the meanings given for the general formula (I), is used.

15. The process according to claim 1 , wherein the amount of catalyst used is from 5 to 1000 ppm of noble metal based on the nitrile rubber used.

16. The process according to claim 1 , wherein the metathesis is carried out without a coolefin or in the presence of a coolefin.

17. The process according to claim 1 , wherein copolymers or terpolymers which comprise repeating units of at least one conjugated diene, at least one α,β-unsaturated nitrile and, one or more further copolymerizable monomers are used as nitrile rubbers.

18. The process according to claim 1 , wherein the nitrile rubbers used have a Mooney viscosity (ML 1+4 at 100° C.) in the range from 30 to 70.

19. The process according to claim 1 wherein the degraded nitrile rubber is subsequently subjected to a hydrogenation.

20. The process according to claim 3 , wherein R 10 and R 11 in the imidazolidine radical (Im) are identical or different and are each straight-chain or branched C 1 -C 10 -alkyl selected from the group consisting of i-propyl or neopentyl.

21. The process according to claim 3 , wherein R 10 and R 11 in the imidazolidine radical (Im) are identical or different and are each straight-chain or branched C 3 -C 10 -cycloalkyl selected from adamantyl.

22. The process according to claim 3 , wherein R 10 and R 11 in the imidazolidine radical (Im) are identical or different and are each straight-chain or branched C 6 -C 24 -aryl selected from phenyl.

23. The process according to claim 3 , wherein R 10 and R 11 in the imidazolidine radical (Im) are identical or different and are each straight-chain or branched C 1 -C 10 -alkylsulphonate selected from methanesulphonate.

24. The process according to claim 3 , wherein R 10 and R 11 in the imidazolidine radical (Im) are identical or different and are each straight-chain or branched C 6 -C 10 -arylsulphonate selected from p-toluenesulphonate.

25. The process according to claim 6 , wherein X 1 and X 2 in the general formula (I) are identical or different and are each halogen selected from the group consisting of fluorine, chlorine or bromine.

26. The process according to claim 1 or 2 , wherein the radicals R 2 , R 4 and R 5 in the general formula (I) are identical or different and are halogen selected from the group containing chlorine or bromine.

27. The process according to claim 15 , wherein the amount of catalyst used is from 5 to 500 ppm based on the nitrile rubber used.

28. The process according to claim 27 , wherein the amount of catalyst used is in the range from 5 to 250 ppm based on the nitrile rubber used.

29. The process according to claim 1 , wherein the metathesis is carried out without a coolefin or in the presence of a coolefin which is a straight-chain or branched C 2 -C 16 -olefin.

30. The process according to claim 29 , wherein the straight-chain or branched C 2 -C 16 -olefin, selected from the group consisting of ethylene, propylene, isobutene, styrene, 1-hexene or 1-octene.

31. The process according to claim 18 , wherein the nitrile rubbers used have a Mooney viscosity (ML 1+4 at 100° C.) in the range from 30 to 50.

32. The process according to claim 19 wherein the degraded nitrile rubber is subsequently subjected to a hydrogenation in situ.