Removal of nickel catalyst from polymer solutions by water addition and centrifugation

Abstract

A process is provided comprising the steps of contacting a Group VIII metal hydrogenation catalyst residue containing polymer solution with from about 2 to about 50 parts by weight water based on 100 parts by weight of polymer solution, centrifuging the polymer from metal containing particles with a centrifugal force such that the centrifugal force times the time duration of centrifugation divided by the viscosity of the polymer solution equals or exceeds about 50 G-minutes/cp, and recovering a polymer solution comprising less than 10 ppm by weight, based on the polymer, of the Group VIII metal.

We claim: 
     
       1. A process to remove a Group VIII metal hydrogenation catalyst residue from a hydrogenated conjugated diolefin polymer solution comprising the steps of: a) contacting the polymer solution with from about 2 to about 50 parts by weight of water based on 100 parts by weight of the polymer, said water ha ving a PH of between about 5 and about 9 and containing less than about t 0.3% by weight of solutes based on 100 parts by weight of water;   b) separating the polymer solution from he catalyst residue by centrifugation with a centrifugal force such that the centrifugal force times the time of centrifugation divided by the viscosity of the polymer solution at centrifugation temperature equals or exceeds about 50 G-minutes/cp; and   c) recovering a polymer solution comprising less than 10 ppm by weight, based on the polymer, of the Group VIII metals.   
     
     
       2. The process of claim 1 wherein the hydrogenation catalyst was prepared by combining a Group VIII metal carboxylate or alkoxide with an alkyl or hydride of a metal selected from Groups I-A, II-A and III-B of Medeleev's Periodic Table of Elements. 
     
     
       3. The process of claim 1 wherein the hydrogenation catalyst is prepared by combining a component selected from the group comprising nickel carboxylate, nickel alkoxide, cobalt carboxylate, iron alkoxide, palladium carboxylate and palladium alkoxide with a component selected from the group consisting of lithium alkyl, lithium hydride, magnesium alkyl, magnesium hydride, aluminum alkyl and aluminum hydride. 
     
     
       4. The process of claim 1 wherein the hydrogenation catalyst is prepared by combining nickel (2-ethylhexanoate) and an aluminum alkyl. 
     
     
       5. The process of claim 4 wherein the aluminum alkyl is triethylaluminum. 
     
     
       6. The process of claim 1 wherein the hydrogenation catalyst residue is in the form of a colloidal suspension. 
     
     
       7. The process of claim 1 wherein the polymer solution comprises from about 1 to about 40 percent by weight polymer based on the total polymer solution, in an inert solvent. 
     
     
       8. The process of claim 1 wherein the centrifugal force times the time duration of the centrifugation divided by the viscosity of the polymer solution at centrifugation temperature is equal to or greater than about 100 G-minutes/cp. 
     
     
       9. The process of claim 1 wherein the polymer is a copolymer comprising a monomer comprising conjugated diolefin units and styrene. 
     
     
       10. The process of claim 9 wherein the copolymer is a block copolymer comprising at least one block which comprises monomer units of conjugated diolefins and at least one block which comprises styrene monomer units. 
     
     
       11. The process of claim 7 wherein the polymer is anionically polymerized in the inert solvent prior to hydrogenation of the polymer. 
     
     
       12. The process of claim 1 wherein the temperature of the centrifugation is between 20° and 210° C. 
     
     
       13. The process of claim 1 wherein the temperature of the centrifugation is between 90° and 150° C.