GB780479A - Improvements relating to thermoplastic compositions and sheeting made therefrom - Google Patents

Abstract

A composition having a basis of a plasticized thermoplastic film-forming substitution derivative of cellulose contains titanium dioxide, a chromium compound and a poly-cyclic organic nitrogen compound which can be formulated as containing chelate rings in which a co-valently linked atom of a metallic element of valency greater than one is co-ordinated with one or more nitrogen atoms forming part of a system of conjugated double bonds. The chromium compound is preferably a metallic chromate, and the metal of the cyclic compound is preferably one of atomic number 23 to 29, ie.. vanadium, chromium, manganese, iron, cobalt, nickel or copper. The chromium compound may be a chromate of an alkaline earth metal, magnesium or aluminium or of a heavy metal such as zinc, cadmium, lead or manganese, or may be a chromium salt of a fatty acid such as acetic acid or of an organic hydroxy acid such as lactic, tartaric or citric acid. Salts, especially organic acid salts, of other am-photeric metals, e.g. manganese, tungsten, vanadium or aluminium, may also be present. The polycyclic nitrogen compound may be a metallic coordination compound of bis-aceto-acetonyl ethylene diamine or of 2-hydroxybenzene-azo-methine - azo - 21 - hydroxybenzene and similar compounds in which one or both o-phenylene groups are replaced by other o-aromatic bivalent groups, e.g. o-naphthylene groups or nuclearly halogenated, alkylated or aralkylated o-phenylene or o-naphthylene groups. The polycyclic compound may also be a metal complex of an aromatic azo compound having a hydroxy group in both beta-positions relative to an azo group as in 2 - hydroxybenzene - azo - 21 - hydroxybenzene, 2 - hydroxybenzene - azo - 21 - hydroxy - 31 - phenyl - 51 - methyl - 31 - 41 - diazole, 2 - hydroxybenzene - azo - 21,41 - dihydroxybenzene, 2 - hydroxy - 4 - chlor - benzene - azo - 21,41 - dihydroxybenzene and 2-hydroxy - 4 - chlorobenzene - azo - 21 - hydroxy - naphthalene. Metal complexes of substitution products of these azo compounds may also be used, especially those free from acidic groups. Preferred polycyclic compounds are the metal phthalocyanines, tetrazaporphins and octaphenyl tetraza-porphins. The cellulose derivative may be an ester such as the acetate, propionate, butyrate, acetate-propionate or acetate-butyrate or an ether such as ethyl or benzyl cellulose. The plasticizer may be tri-(monochlorethyl) phosphate, dimethyl or diethyl phthalate (both preferably in conjunction with a minor proportion, e.g. 25 per cent, of a stiffening plasticizer such as triphenyl phosphate), dibutyl phthalate or tartrate, triacetin, triethyl or acety triethyl citrate, or methyl- or ethyl-phthalyl ethyl glycolate. The compositions may be suitable for moulding and hot extrusion and particularly for the production of sheet materials by the block process or by casting or extrusion. The simultaneous presence of chromium compounds and polycyclic compounds in the compositions reduces the tendency for the titanium oxide (particularly if in the anatase form) to cause sheeting prepared from the compositions to become crazed on outdoor exposure. In an example, sheets are made by the block process from a composition consisting of 100 parts of cellulose acetate of acetyl value (expressed as acetic acid) 51 to 53 per cent, 40 parts of tri-(monochlorethyl) phosphate, 0.06 part of titanium dioxide (anatase), 0.02 part of chlorinated copper phthalocyanine and 0.08 part of barium chromate. Two such sheets moistened with solvent are assembled with a sheet of wire fabric between them in a heated press to form a single wire-reinforced sheet suitable for use as a substitute for window glass. The Provisional Specification refers also to non-cellulosic thermoplastic compositions based on polyamides such as the nylons, polyesters such as polyethylene terephthalate, and polyurethanes, as well as some polyvinyl and polyvinylidene compounds, e.g. copolymers of vinyl chloride with vinyl acetate and of vinylidene chloride with vinyl chloride and acrylonitrile.