Patent GB-1013392-A (GB)
Title: Improvements in or relating to extrudable compositions
IPC: C08J9/06
Filed: 1962-11-16
Abstract: the invention comprises a dry, extrudable, substantially free-flowing resin powder composition, comprising, in physical admixture with plasticizing ingredients, a major amount of a blotter-type polyvinyl halide resin having good liquid-absorbing characteristics at room temperature, a minor amount of a small-particle size polyvinyl resin having a particle diameter not in excess of 3 microns, and a chemical blowing agent having a decomposition temperature of at least 280 DEG F., the blowing agent being dispersed throughout the composition in an amount in the range of 0.8 to 1 2% by weight and serving to effect the formation of the composition into an expanded, closed-cell mass, upon heating to a temperature above the decomposition temperature of the blowing agent.  The polyvinyl resins may together comprise 40 to 60% by weight of the total composition, preferably 50%.  The blotter-type polyvinyl halide resin may comprise 60 to 90% by weight of the resin content of the composition, and the small-particle size polyvinyl resin 40-10%, the preferred proportions being 80% and 20% respectively.  The weight ratio of the two resins may be from 3: 2 to 9: 1, preferably 4: 1.  The blotter-type polyvinyl halide resins specified are polyvinyl chlorides, bromides, iodides and fluorides, preferably polyvinyl chloride.  The small particle polyvinyl resins specified are polyvinyl chloride, polyvinyl acetate and polyvinylidene chloride, The chemical blowing agents, usually in amount about 1% by weight of the total composition, specified are dinitrosopenta-methylenetetramine, diazoaminobenzene, a,a1-azo-bis-isobutyronitrile, azodicarbonamide, and benzilmonohydrazone.  The composition may also contain various other materials which act as plasticizers, stabilizers, fillers, lubricants or pigments.  Plasticizers specified are neutral esters of phthalic acid and alcohols having 6 to 9 carbon atoms; neutral phosphoric acid esters; neutral esters of sebacic acid and alcohols having 4 to 6 carbon atoms; neutral phthalyl glycolates of alcohols having 1 to 4 carbon atoms; esters of alkoxy glycols; mixed o- and p-toluene ethyl sulphonamides, epoxidized vegetable oils and alkyd polyester resins. Stabilizers specified are, lead silicate, lead oxide, lead salts of p-(tert.-butyl) phenol, dibasic lead phosphite, sodium and calcium silicates, and organic compounds and complexes of zinc, cadmium and barium.  Lubricants specified are stearic acid or other long-chain aliphatic acids. Fillers specified are barytes, china clay, silica, whiting, calcium carbonate, asbestine, slate dust, serpentine, and talc. Pigment material specified is titanium dioxide. Example (1) refers to a mixture of 20 lbs. of a blotter-type polyvinyl chloride resin and 10 lbs. of small-particle size polyvinyl chloride resin, together with plasticizers, fillers, stabilizers and pigments, and 0.5 lbs. of azodicarbonamide as blowing agent.  After thoroughly mixing, extrusion is carried out at 2600 DEG  F., and the sheeted polyvinyl chloride is heated at 340 DEG  to 375 DEG  F. to effect expansion, and the product had a smooth outer skin and a uniformly small cellular structure.