Water assisted devolatilization

Claim 1

In a process for reducing the amount of residual monomer and solvent to less than 500 ppm in: (A) a polymer comprising: (i) from 100 to 30 weight % of one or more monomers selected from the group consisting of C 8-12 vinyl aromatic monomers which are unsubstituted or substituted by a C 1 ∝ alkyl radical; and (ii) from 0 to 70 weight % of one or more monomers selected from the group consisting of C 1-4 alkyl esters of acrylic or methacrylic acid, acrylonitrile and methacrylonitrile; which polymers may be grafted on to from 0 to 40 weigh % of one or more rubbery polymers selected from the group consisting of: (iii) polymers consisting essentially of one or more C 4-6 conjugated diolefin monomers; and (iv) polymers consisting essentially of from 20 to 80 weight of one or more C 8-12 vinyl aromatic monomers and from 80 to 20 weight % of one or more C 4-6 conjugated diolefins; or (B) a blend of said polymer and polyphenylene oxide; which polymer or polymer blend contains less than 1 weight % of residual monomer, dimer, trimer and solvents, which process comprises: (i) heating and maintaining said polymer or polymer blend at a temperature from 200° to 270° C.; (ii) injecting into said polymer or polymer blend an amount of water greater than the amount of residual monomer, dimer, trimer, and solvent but less than 1 weight %, said injection being at temperatures from 200° to 270° C. and pressures from 500 to 1500 psi; (iii) passing said polymer or polymer blend through a flash chamber devolatilizer maintained at a temperature from 200° to 270° C. and a pressure of less than 5 torr to flash off a vapour phase comprising water, monomer, and solvent; (iv) withdrawing said vapour phase from said flash chamber devolatilizer and passing it to a condenser maintained at a reduced pressure greater than 5 torr by ejecting a gas inert to said vapour phase into said vapour phase intermediate said flash chamber and said condenser; and (v) condensing at least the water in said vapour phase.