GB404279A - Improvements in or relating to plastic materials - Google Patents

Abstract

Varnishes, lacquers, or enamels are manufactured by dissolving in organic solvents the products obtained by reacting a polyvinyl ester in solution with an acetal in the presence of a substantially anhydrous alcohol and an acid catalyst. In an example, polyvinyl acetate of molecular weight 13,000 (by Standinger's method) is heated with acetal, methanol and a solution of hydrogen chloride in methanol, the thin solution obtained is diluted with a mixture of toluene and glycol monoethyl ether acetate, and dibutyl phthalate is added, producing a lacquer suitable for spraying.ALSO:Plastic materials are manufactured by reacting a polyvinyl ester in solution with an acetal in the presence of a substantially anhydrous alcohol and an acid catalyst, e.g. hydrogen chloride. The viscosity and solubility of the product can be varied by varying the degree of polymerization of the initial polyvinyl ester, less viscous products suitable for coating and impregnating compositions, in which the resin is dissolved in organic solvents, being obtained from the polyvinyl esters of the lower degree of polymerization. If the quantity of acetal used is less than that theoretically required for complete replacement of the ester group of the polyvinyl ester, the products obtained even from low polymerized esters form jellies or much more viscous solutions than those obtained with theoretical quantities of the acetals. The extent to which the softening point of the products is raised above that of the parent polyvinyl esters depends on the nature and amount of the acid catalyst (the elevation increasing with increase in the amount of catalyst), the duration of heating, the nature of the polyvinyl ester employed (the elevation being less in the case of the lower polymers) and the amount and nature of the acetal used. The reaction may be carried out by heating at normal or increased pressure and the products may be isolated from the reaction mixture by removing the volatile constituents by evaporation under normal or reduced pressure or by precipitating the resin with water. The products may be bleached, e.g. by means of sodium hydrosulphite. They may be dissolved in organic solvents to produce varnishes, lacquers or enamels, and may also be used as substitutes for shellac, e.g. in the manufacture of gramophone record discs or cylinders, and also for the manufacture of moulded objects, e.g. by the injection moulding process, if desired with the addition of plasticizing agents, e.g. dibutyl phthalate. They may also be mixed, if desired with the aid of volatile solvents, with other resins (synthetic or natural), e.g. aldehyde resins or gum copal, with cellulose esters or ethers, e.g. nitrocellulose, cellulose acetate, ethyl or benzyl cellulose, with softening agents or oils, with filling materials, e.g. silica, barium sulphate, wood meal or cork dust, or with colouring matters, e.g. carbon black or coal tar dyes, or with mixtures of these substances. In examples: (1) and (2) polyvinyl acetate of a molecular weight of approximately 30,000 (by Standinger's method), obtained by polymerizing vinyl acetate by means of benzoyl peroxide, is heated with absolute alcohol, acetal and a saturated solution of hydrogen chloride in absolute alcohol; (3) the acetal is replaced by methylal, yielding a solution which sets to a jelly on standing; (4) methane sulphonic acid is used as catalyst in the process of (1); (5) p-toluenesulphonic acid is used as catalyst; (6) camphorsulphonic acid (Reychler's acid) is used as catalyst; (7) polyvinyl acetate of molecular weight 13,000 is heated with acetal, methanol and a solution of hydrogen chloride in methanol yielding a thin solution which is diluted with a mixture of toluene and glycol monoethyl ether acetate, and dibutyl phthalate is added, producing a lacquer suitable for spraying; (8) as in (7) but using less acetate, producing a solution which sets to a jelly on standing.ALSO:Plastic materials manufactured by reacting a polyvinyl ester in solution with an acetal in the presence of a substantially anhydrous alcohol and an acid catalyst may be mixed with plasticizing agents, e.g. dibutyl phthalate, and also, if desired with the aid of volatile solvents, with other resins (synthetic or natural), e.g. aldehyde resins or gum copal, with cellulose esters or ethers, e.g. nitrocellulose, cellulose acetate, ethyl or benzyl cellulose, with softening agents or oils, with filling materials, e.g. silica, barium sulphate, wood meal or cork dust, or with colouring matters, e.g. carbon black or coal tar dyes, or with mixtures of these substances.