Patent ID: 6670405
Filing Date: 2003-12-30
Classification: C08F,C08J

Abstract:
A method for producing a block-shaped or plate-shaped polymethacrylimide foamed material, comprising:copolymerizing a copolymerization mixture comprising methacrylic acid, methacrylonitrile and optionally a copolymerizable monomer in the presence of a radical-forming initiator to obtain a copolymer; post-polymerizing and cyclizing said copolymer to polymethacrylimide; and foaming said polymethacrylimide to obtain a foamed material; wherein said copolymerizing is performed in the presence of a mixture comprising at least four initiators with graduated half lives; wherein each of the initiators has a half live of Â½ hour at a certain temperature and said temperature differs by at least 10Â° C. for each of said initiators.