Process for the preparation of low molecular weight hydrogenated nitrile rubber

1. A process for the preparation of a, optionally hydrogenated, nitrile rubber comprising the steps of

a) reacting a nitrile rubber in the absence of any co-olefin and in the presence of at least one compound selected from the group consisting of compounds of the general formulas I, II, III or IV,

wherein:

M is Os or Ru,

R and R 1 are, independently, hydrogen or a hydrocarbon selected from the group consisting of C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 1 -C 20 alkyl, aryl, C 1 -C 20 carboxylate, C 1 -C 20 alkoxy, C 2 -C 20 alkenyloxy, C 2 -C 20 alkynyloxy, aryloxy, C 2 -C 20 alkoxycarbonyl, C 1 -C 20 alkylthio, C 1 -C 20 alkylsulfonyl and C 1 -C 20 alkylsulfinyl,

X and X 1 are independently any anionic ligand,

L and L 1 are, independently any neutral ligand, optionally, L and L 1 can be linked to one another to from a bidentate neutral ligand;

wherein:

M 1 is Os or Ru;

R 2 and R 3 are, independently, hydrogen or a hydrocarbon selected from the group consisting of C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 1 -C 20 alkyl, aryl, C 1 -C 20 carboxylate, C 1 -C 20 alkoxy, C 2 -C 20 alkenyloxy, C 2 -C 20 alkynyloxy, aryloxy, C 2 -C 20 alkoxycarbonyl, C 1 -C 20 alkylthio, C 1 -C 20 alkylsulfonyl and C 1 -C 20 alkylsulfinyl,

X 2 is a anionic ligand, and

L 2 is a neutral mono- or polycyclic π-bonded ligand,

L 3 is a ligand selected from the group consisting of phosphines, sulfonated phosphines, fluorinated phosphines, functionalized phosphines bearing up to three aminoalkyl-, ammoniumalkyl-, alkoxyalkyl-, alkoxylcarbonylalkyl-, hydrocycarbonylalkyl-, hydroxyalkyl- or ketoalkyl-groups, phosphites, phosphinites, phosphonites, phosphinamines, arsines, stibenes, ethers, amines, amides, imines, sulfoxides, thioethers and pyridines,

Y − is a non-coordinating anion,

n is an integer in the range of from 0 to 5,

wherein

M 2 is Mo or W,

R 4 , R 5 are, independently, hydrogen or a hydrocarbon selected from the group consisting of C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 1 -C 20 alkyl, aryl, C 1 -C 20 carboxylate, C 1 -C 20 alkoxy, C 2 -C 20 alkenyloxy, C 2 -C 20 alkynyloxy, aryloxy, C 2 -C 20 alkoxycarbonyl, C 1 -C 20 alkylthio, C 1 -C 20 alkylsulfonyl and C 1 -C 20 alkylsulfinyl;

R 6 and R 7 are independently selected from any unsubstituted or halo-substituted alkyl, aryl, aralkyl groups or silicon-containing analogs thereof,

wherein

M is Os or Ru,

R and R 1 are independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, and substituted or unsubstituted alkyl

X and X 1 are independently any anionic ligand, and

L an L 1 are independently any neutral ligand;

and optionally

b) hydrogenating the product of step a).

2. A process according to claim 1 wherein the hydrogenation is performed under homogeneous catalytic conditions.

3. A process according to claim 2 wherein the homogeneous catalytic reduction is carried out in situ without first isolating the product of step a).

4. A process according to claim 1 wherein no further hydrogenation catalyst is added before or during step b).

5. A process according to claim 1 , wherein the metathesis catalyst is a compound of Formula I wherein L and L 1 are independently selected from the group consisting of trialkylphosphines, imidazolidinylidenes or imidazolidines.

6. A process according to claim 5 wherein either L or L 1 is a trialkylphosphine and the remaining ligand is a imidazolidinylidenes, X and X 1 are chloride ions and M is ruthenium.

7. A process according to claim 6 wherein the ratio of compound to nitrile rubber is in the range of from 0.005 to 5.

8. A process according to claim 7 , wherein the process is carried out in an inert solvent selected from the group consisting of monochlorobenzene, dichloromethane, benzene, toluene, tetrahydrofuran and cyclohexane.

9. A process according to claim 1 , wherein the hydrogenation is carried out using a catalyst of formula:

(R 8 m B) I RhX 3 n

wherein each R 8 is independently selected from the group consisting of a C 1 -C 8 -alkyl group, a C 4 -C 8 -cycloalkyl group, a C 6 -C 15 -aryl group and a C 7 -C 15 -aralkyl group;

B is selected from the group consisting of phosphorus, arsenic, sulfur, and a sulphoxide group (S=0);

X 3 is selected from the group consisting of hydrogen and an anion; and

I is 2, 3 or 4, m is 2 or 3 and n is 1, 2 or 3.

10. A process according to claim 9 wherein the hydrogenation catalyst is (PPh 3 ) 3 RhCl.

11. An, optionally hydrogenated, nitrile rubber having a molecular weight (M w ) in the range of from 20,000 to 250,000, a Mooney viscosity (ML 1+4 @ 100 deg. C.) of in the range of from 1 to 50, and a MWD (or polydispersity index) of less than 2.5.

12. A polymer composite comprising at least one, optionally hydrogenated, nitrile rubber polymer having a Mooney viscosity (ML 1+4 @ 100° C.) in the range of from 50-30, at least one filler and optionally at least one cross-linking agent.

13. A polymer composite according to claim 11 wherein the raw polymer Mooney viscosity (ML 1+4 @ 100° C.) is below 50.

14. A polymer composite according to claim 12 wherein the polymer composite further comprises a peroxide system.

15. A process for preparing a polymer composite according to claim 12 comprising reacting at least one, optionally hydrogenated, nitrile rubber polymer having a Mooney viscosity (ML 1+4 @ 100° C.) in the range of from 50-30, at least one filler and optionally at least one cross-linking agent.

16. A process for the manufacture of a shaped article comprising the step of injection molding a polymer composite comprising at least one, optionally hydrogenated, nitrile rubber polymer having a Mooney viscosity (ML 1+4 @ 100° C.) in the range of from 50-30, at least one filler and at least one cross-linking agent.

17. A process according to claim 16 , wherein the shaped article is seal, hose, bearing pad, stator, well head seal, valve plate, cable sheathing, wheel, roller, in place gaskets or pipe seal.