| 摘要 |
A porous plastic material entrapping a plasticizer is made by mixing an aqueous latex of a thermoplastic polymer with a plasticizer, coagulating the latex, removing the water, and heating the product to fuse it into a porous mass having at least part of the plasticizer trapped in its pores. Specified polymers are polyethylene, polyvinyl chloride, polyvinyl acetate, polyacrylates, polystyrene, polyvinylidene chloride and polyvinylidene fluoride as well as polyamides such as nylon, butyl rubber and copolymers of vinyl chloride and vinyl acetate, styrene with acrylates, butadiene or vinyl pyrrolidone, butadiene with vinyl toluene or acrylonitrile, and vinyl pyrrolidone with ethyl acrylate. The plasticizers disclosed belong to the primary and secondary types, the former being defined as those which solvate the polymer and include phthalates, and adipates of alcohols and phenols, and phosphate esters as well as 2-pyrrolidone, acetyltributyl citrate, and polypropylene glycol. Secondary plasticizers may be aliphatic or aromatic hydrocarbons including mineral oils, castor oil, and oleic acid. Mixtures of the two types may be used, e.g. dioctyl phthalate with castor oil. Dyes, toners and pigments may be included in the mixture and the fusion may be carried out in a heated mould. Specified methods for coagulating the latices of the invention include the addition of an electrolyte, solvent extraction and freezing. |
