Patent ID: 6153658
Filing Date: 2000-11-28
Classification: C08F,C08J

Abstract:
A process for the preparation of expandable polymer particles containing a polymer of a vinylarene monomer, said polymer comprising from 2.5 to 6% by weight of polymer chains having a molecular weight from 10,000 to 20,000 g/mol as measured in accordance with gel permeation chromatography of vinylarene monomer and from 3 to 12 weight % based on the weight of vinylarene polymer of a blowing agent, which process comprises:1) polymerizing, by suspension polymerization at a temperature from 75 to 100.degree. C., 100 parts by weight of a vinylarene monomer, in the presence of 3 to 10 parts by weight of a radical initiator having a half life of one hour in benzene at 70 to 110.degree. C., until at least 60% of the vinylarene monomer is polymerized;2) cooling the reaction mixture to a temperature from 70 to 75.degree. C.; and3) adding to the resulting polymerization mixture 400 to 4,900 parts by weight additional vinylarene monomer as well as 0.05 to 1 weight % based on the amount of vinylarene monomer added in step 3, of a radical initiator having a half life of 1 hour in benzene at 70 to 110.degree. C. and polymerizing at a temperature from 80 to 140.degree. C. to completion, in which process the blowing agent can be added before, during or after the polymerization process.