PRODUCTION OF EXPANDABLE SYNTHETIC THERMOPLASTIC RESIN

PURPOSE:To coat the surfaces of expandable thermoplastic resin particles firmly with a treating agent effectively in a short time without causing any trouble in the peeling of the powder, by mixing said resin particles with a surface treating agent powder with stirring at a high speed by using a high-energy mixer, while keeping them at a temp. not higher than a foaming temp. CONSTITUTION:Expandable thermoplastic resin particles (A) having a particle size of 0.2-2.5mm, obtd. by incorporating a blowing agent (a) such as propane, butane, dichloromethane, etc. in thermoplastic resin particles (b) such as PS resin, PE resin, polymethacrylate resin, etc. under pressure and a surface treating agent (B) such as a molding cycle accelerator (e.g., a carboxylic acid amide) in a specified ratio are introduced into a high-energy mixer such as a Henschel mixer. They are mixed with stirring at a high speed for 10-30sec, while keeping the temp. of the mixer at a temp. not higher than the temp. at which the component A is expanded (e.g., at 60 deg.C or lower).