| 摘要 |
1,243,603. Thermoplastic polymer beads. DOW CHEMICAL CO. 11 Dec., 1969 [12 Dec., 1968], No. 60590/69. Heading C3P. Free-flowing fused beads of a normally solid, water-insoluble, thermoplastic, organic polymer are prepared by (1) suspending a powder of the polymer in an aqueous medium containing 0.05 to 20 weight per cent, based on the polymer, of a solid suspending agent insoluble in and non- reactive with the polymer and medium to provide a stirrable slurry; (2) heating the suspension to a temperature at least equal to the melting point of the polymer while agitating the suspension; and (3) cooling the suspension while continuing the agitation until the molten polymer solidifies to form beads of greater size than the powder particles. Specified polymers are of ethylene, propylene, butene-1, hexene-1, vinyl chloride, vinyl acetate, styrene, alkyl styrenes, ethyl acrylate, methyl methacrylate, n-butyl acrylate and acrylonitrile, and ethylene/ butene, ethylene/ethyl acrylate, styrene/butyl acrylate, ethyl acrylate/methyl methacrylate andα-methyl styrene/2-ethylhexyl acrylate copolymers. Specified suspending agents are kaolin, barium sulphate, zinc oxide, talc, aluminium hydroxide, calcium phosphate, calcium oxalate, titanium dioxide, substantially insoluble neutral phosphates, hydrated magnesium silicates, colloidal clays, methyl cellulose and synthetic polymers. The medium may also contain surface active agents, e.g. organic sulphates and sulphonates, polyoxyethylene ethers of fatty alcohols and alkyl phenols, disodium N - tallow - # - iminodipropionate and octadecylammonium chloride. Examples describe the preparation of beads of (1) polyethylene and (2-7) ethylene/butene-1 copolymers in aqueous media containing disodium N-tallow- # iminodipropionate and zinc oxide, titanium dioxide or tricalcium phosphate. |
