Process for preparing HNBR solutions with alternative solvents

A process for preparing a solution of a hydrogenated nitrile-diene copolymer, said process comprising:

• (i) providing a nitrile-diene copolymer;
• (ii) providing a solvent mixture comprising:
• a first solvent comprising one or more members selected from the group consisting of monochlorobenzene, dichloromethane, benzene, dichlorobenzene, toluene, cyclohexane, and ketone-containing solvents of the general formula R3—CO—R4 where R3 and R4 each independently represent a linear or branched or cyclic alkyl having 1 to 20 carbon atoms;
• and a second solvent selected from cyclopentyl methyl ether (CPME);
• (iii) dissolving the nitrile-diene copolymer according to (i) in the solvent mixture according to (ii) to form a solution;
• and
• (iv) subjecting the solution formed in (iii) to hydrogenation to produce the hydrogenated nitrile-diene copolymer;
• wherein the hydrogenation is conducted in the presence of a metathesis catalyst selected from the group consisting of Grubbs I catalyst of the structure (IV), Grubbs II catalyst of the structure (V), Zhan 1B catalyst of the structure (XV), Grela catalyst of the structure (XVI), and Grubbs-Hoveyda II catalyst of the structure (VII):