Improvements in urea-formaldehyde moulding compositions

摘要

Thermosettable moulding compositions comprise: (1) at least 75% of a mixture containing from 60 to 85% of a urea-formaldehyde resin and from 15 to 40% of total filler consisting essentially of a -cellulose; (2) up to 15% based on the total composition of a compatible, solid and stable chlorine-containing hydrocarbon derivative having a chlorine content of from 45 to 70%; and (3) from 0,5 to 10% based on the total composition of antimony trioxide. The percentages are on a weight basis. The chlorine containing hydrocarbon derivative is preferably a solid polymer or copolymer of a chloro-ethylene and may contain a low proportion of a comonomer such as vinyl acetate. The minimum proportion of the chlorine compound is calculated by the equation where P=weight per cent of chlorine compound and A=weight per cent of antimony trioxide in the solid composition. Chlorine compounds exemplified are polyvinyl chloride, polyvinylidene chloride, a vinyl chloride-vinyl acetate copolymer derived from more than 80% vinyl chloride, a vinyl chloride-vinylidene chloride copolymer and octachloronaphthalene. The chlorine compound may be stabilized by the addition of heat-stabilizers such as calcium carbonate, calcium stearate, tin stearate, zinc stearate, zinc resinate and inorganic salts of copper, zinc and manganese. Accelerators such as oxalic, benzoic, phthalic and hydrobromocinnamic acids, trimethyl phosphate, benzoyl peroxide and ethylene bis-benzene sulphonate; stabilizers such as hexamethylene tetramine and ammonium carbonate; plasticizers such as glycerine and its mono-ethers butyl urea and toluene sulphonamide; lubricants or mould release agents such as stearic and oleic acids and their zinc salts; and pigments such as titanium dioxide and Hansa yellow may also be added to the compositions. Examples are given in which the properties of various compositions according to the invention are compared with comparable compositions lacking either the chlorine compound or the antimony trioxide or both. The preparation of the urea-formaldehyde resin used is by reacting 2 p.b.w. of urea with 3 p.b.w. of formalin (50%) for 3-5 hours, at a pH of 7-9 and at 25 DEG C.