GB587515A - Improvements in or relating to cellulose ester coating compositions - Google Patents

Abstract

A coating composition comprises cellulose aceto-butyrate and an organic di-isocyanate modified polyester or polyester-amide of the kind described in Specification 553,733, i.e. a high molecular weight polymer obtained by heating an organic di-isocyanate with a low molecular weight linear polymer produced from ingredients comprising a di-basic carboxylic acid or an ester-forming derivative of such an acid, at least one complementary bifunctional esterifiable compound having two alcoholic groups or one alcoholic and one amino group, and optionally one or more additional bifunctional compounds of the group comprising diamines, amino-acids, hydroxy acids, and ester or amide forming derivatives of these. The composition may be used for coating cables particularly electric cables comprising conducting wires with insulating layers of rubber and sleeves of braided cotton, silk, or asbestos. The composition gives coatings of good flexibility, toughness, water-proofness, oil-resistance, freedom from tackiness, and heat-resistance. Coatings which are not thermoplastic at temperatures in the region of 150 DEG C. are obtained. Plasticizers may be present, e.g. dibutyl phthalate, dimethyl glycol phthalate, trichlorethyl phosphate, triphenyl or tricresyl phosphate. The composition may contain an anti-oxidant, e.g. hydroquinone, phenyl-b -naphthylamine, or benzidine. The modified polyesters or polyester-amides are soluble in some mixtures of aromatic hydrocarbons with alcohol but they may be rendered insoluble by the action of formaldehyde. Paraformaldehyde may be included in one portion of the composition and ammonium chloride or oxalate or other acid-liberating substance in another portion, the two portions being blended just before the composition is used. In an example, an organic di-isocyanate modified polyesteramide is dissolved in a mixture of benzol and alcohol, and hydroquinone is added. Paraformaldehyde is added to one portion of the solution and ammonium chloride is added to another portion. Each portion is then mixed with a separate solution of cellulose acetobutyrate containing tricresyl phosphate, benzol, alcohol, and acetone. The two solutions are then mixed together and a cotton braided cable is coated several times with the lacquer so formed. After drying, the coating is allowed to age by hanging the cable at room temperature for several days. In another example methyl ethyl ketone is used as the solvent. Specifications 580,524 and 581,134 also are referred to.