Thermoplastic resin composition

A thermoplastic resin composition comprised of a homogeneous resin dispersion which comprises (A) a thermoplastic resin component having a solubility parameter of at least 9.5 cal.sup.1/2 cm.sup.-3/2 and being at least one thermoplastic resin selected from the group consisting of polyester, polyamide, polyesteramide, polyurethane, polyvinyl chloride, polycarbonate, polyacetal, polyvinylidene chloride, polyacrylonitrile, polymethacrylonitrile, polymethyl acrylate, polyvinyl alcohol, cellulose and their derivatives, (B) a modifier component having a solubility parameter of not greater than 8.5 cal.sup.1/2 cm.sup.-3/2 and being at least one polymer selected from the group consisting of homopolymers or copolymers of polytetrafluoroethylene, polyvinyldiene chloride, polychlorotrifluoroethylene, fluororubber, polyalkylsiloxane, polyphenylsiloxane, butyl rubber, polyisobutylene, polyethylene, ethylene/propylene rubber and polypropylene, and (C) a dispersibility improver, wherein said dispersibility improver is comprised of a silicon-containing polyacetal copolymer having (i) a siloxane segment derived from between 0.01 to 30 wt. % of a terminal-reactive silicone oil of the following general formula I:

• ##STR7## wherein R.sub.1 represents an alkyl or phenyl group, R.sub.2 represents a divalent organic group, X represents a group selected from the group consisting of --NH.sub.2, --OH, ##STR8## --R.sub.4 OH, --R.sub.5 COOH, --R.sub.6 COOR.sub.7, --R.sub.8 and --OR.sub.9, where R.sub.3 represents a divalent organic group, R.sub.4 to R.sub.6 each represent an alkylene group having 1 to 10 carbon atoms, R.sub.7 to R.sub.9 each represent an alkyl group having 1 to 10 carbon atoms and n represents a number between 5 to 10, and
• (ii) between 99.99 to 70 wt. % of polyacetal segment covalently bonded to said siloxane segment wherein the degree of polymerization of the siloxane segment is between 5 to 1,000, and the degree of polymerization of the polyacetal segment is between 5 to 2,000 and wherein the weight ratio of thermoplastic resin component to the modifier component is 99.9 to 85/0.1 to 15, and the amount of the dispersibility improver is between 0.01 to 5 parts by weight per 100 parts by weight in total of the thermoplastic resin component and the modifier component.