Process for hydrogenating carboxylated nitrile rubber, the hydrogenated rubber and its uses
View Patent ↗Polymers of a conjugated diene, an unsaturated nitrile and an α,β-unsaturated carboxylic acid are selectively hydrogenated to reduce carbon-carbon double bonds, without also reducing carboxyl groups and nitrile groups, using a rhodium-containing compound as catalyst. The hydrogenated polymers are novel and display excellent adhesive properties at both room temperature and high temperature, excellent hot tear strength, and excellent abrasion resistance.
1. A process for selectively hydrogenating carbon-carbon double bonds of a polymer of a conjugated diene, an unsaturated nitrile and an unsaturated carboxylic acid, which comprises the steps of dissolving the polymer in a solution which consists of an organic solvent and then subjecting the polymer to hydrogenation in the presence of a rhodium-containing compound as catalyst and a co-catalyst ligand, wherein the weight ratio of the rhodium-containing compound to the co-catalyst ligand is from 1:3 to 1:55,
wherein the polymer comprises from about 50 to about 85% conjugated diene, from about 15 to 50% of unsaturated nitrile and from about 0.1 to 10% unsaturated carboxylic acid, and
wherein an insignificant amount of nitrile and carboxylic acids groups are reduced during hydrogenation.
2. A process according to claim 1 , wherein the rhodium-containing compound is a compound of the formula:
(R m B) i RhX n
wherein each R is a C 1 -C 6 -alkyl group, a C 4 -C 8 cycloalkyl group, a C 6 -C 15 -aryl group or a C 7 -C 15 aralkyl group, B is an atom of phosphorus, arsenic or sulfur, or is a sulfonyl group S═O, X is hydrogen or an anion, I is 2, 3 or 4, m is 2 or 3 and n is 1, 2 or 3.
3. A process according to claim 1 , wherein the co-catalyst ligand is of formula:
R m D
where each R is a C 1 -C 6 -alkyl group, m is 2 or 3 and B is an atom of phosphorus, arsenic or sulfur, or is a sulfonyl group S═O.
4. A process according to claim 2 , wherein B is phosphorus.
5. A process according to claim 1 , wherein the rhodium-containing compound is tris-(triphenylphosphine)-rhodium(I)-chloride, tris-(triphenylphosphifle)-rhodium (III)Chloride, tris-(dimethyisulfoxide)-rhodium(III)-Chlorilde, or tetrakis-(triphenylphosphine)-rhodium hydride.
6. A process according to claim 1 , wherein the amount of the rhodium-containing compound is in the range 0.03 to 0.5%, based on the weight of the polymer to be hydrogenated.
7. A process according to claim 4 , wherein the co-catalyst ligand is triphenylphosphifle.
8. A process according to claim 1 , wherein the weight ratio of rhodium-containing compound to co-catalyst ligand is in the range 1:3 to 1:45.
9. A process according to claim 1 , wherein the amount of co-catalyst is in the range 0.1 to 33 parts by weight per hundred parts by weight of polymer.
10. A process according to claim 9 , wherein the amount of co-catalyst is in the range 0.5 to 20 parts by weight per hundred parts by weight of polymer.
11. A process according to claim 10 , wherein the amount of co-catalyst is in the range 1 to less than 5 parts by weight per hundred parts by weight of polymer.
12. A process according to claim 1 , wherein the amount of co-catalyst is greater than 2 parts by weight per hundred parts by weight of polymer.
13. A process according to claim 1 , wherein the polymer that is subjected to selective hydrogenation has a molecular weight greater than about 60,000 (Mw).
14. A process according to claim 2 , wherein the polymer that is subjected to selective hydrogenation has a molecular weight greater than about 100,000 (MW).
15. A process according to claim 1 , which is carried out at a temperature in the range of 60 to 160° C. and a pressure in the range 10 to 250 atmospheres.
16. A process according to claim 1 , wherein the selective hydrogenation is carded out until at least 80% of the carbon-carbon double bonds have been hydrogenated.
17. A process according to claim 16 , wherein the selective hydrogenation is carried out until at least 90% of the carbon-carbon double bonds have been hydrogenated.
18. A process according to claim 17 , wherein the selective hydrogenation is carried out until at least 95% of the carbon-carbon double bonds have been hydrogenated.
19. A process according to claim 18 , wherein the selective hydrogenation is carded out until at least 99% of the carbon-carbon double bonds have been hydrogenated.
20. A process according to claim 1 , wherein the polymer comprises from 85 to 50% by weight of conjugated diene, from 0.1 to 10% by weight of α,β-unsaturated carboxylic acid and from 15 to 50% by weight of acrylonitrile or methacrylonitrile.
21. A process according to claim 1 , wherein the conjugated diene is selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 3-pentadiene and piperylene.
22. A process according to claim 21 , wherein the conjugated diene is 1,3-butadiene.
23. A process according to claim 1 , wherein the nitrile is selected from the group consisting of acrylonitdle, methacrylonitrile and α-chioroacrylonitrile.
24. A process according to claim 23 , wherein the nitrile is acrylonitrile.
25. A process according to claim 1 , wherein α,β-unsaturated acid is selected from the group consisting of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid and itacoflic acid.
26. A process according to claim 1 , wherein the α,β-unsaturated acid is selected from the group consisting of acrylic acid and methacrylic acid.