GB581146A - Curing of polymeric materials - Google Patents

Abstract

Organic diisocyanate modified polyesteramides are cured by heating with a dichromate in presence or absence of an acid, an acid anhydride, an acid reacting salt or a substantially neutral material which developes acidity only under curing conditions and/or an acid accepting material. A chromate and an acidic material may be used instead of the dichromate. Fillers specified are carbon black, clay, asbestos, blanc fixe and mica; other plastic materials, for example, synthetic rubbers, vulcanized vegetable oils, dark substitute, white substitute, wood rosin, and pitch; detackifying agents, for example, stearic acid, paraffin wax, oleic acid and lauric acid; plasticisers, for example, tricresyl phosphate, dibutyl phthalate, butylphthalyl butyl glycollate and N-alkyltoluene-sulphonamides; stabilisers or anti-oxidants, for example, hydroquinone, N : N1-hexamethylene-bis-o-hydroxybenzamide, N-phenyl-a-naphthylamine, N-phenyl-naphthylamine and N : N1 - bis - (2 - hydroxy - 3 : 5 - dimethylphenyl) butane. Small quantities of pigments, for example from 1-3 per cent by weight, such as are customarily used in rubber technology, may also be used to impart c colour. Formaldehyde-liberating substances may also be used, for example paraformaldehyde, compounds containing a reactive methylol group or groups such as dimethylolurea, trimethylolmelamine, hexamethylolmelamine, diphenylolpropane tetra-alcohol, methylolchloracetamide, methylolstearamide, and N-methylol-p-toluene-sulphonamide, ethers of compounds containing a reactive methylol group or groups such as dimethylolurea dimethylether, dimethylolurea dibutyl ether, hexamethylolmelamine hexamethyl ether and N : D1-dimethyloluron dimethylether, 1 : 2-glycol methylene ether, di-(b -hydroxyethyl) formal, hexamethylene tetramine-zinc chloride complexes, thermo-hardening phenol-formaldehyde condensation products derived by alkaline condensation from phenols with more than two free positions ortho and para to the phenolic hydroxyl group, for example, phenol, m-cresol, diphenylolpropane, 1 : 3 : 5-xylenol, or mixtures containing at least one such phenol, for example, cresylic acid containing 50 per cent by weight of m-cresol, or the products obtained by condensing such phenol-formaldehyde condensation products with monohydric alcohols boiling above 80 DEG C., for example, n-butanol. The ingredients are milled at below 70 DEG C., the acidic material being added last, curing is effected at 100-150 DEG C. and the mix may be shaped or calendered on to a substrate. In examples, the organic diisocyanate modified polyester-amide obtained as described in example 1 of Specification 580,524, is mixed, milled and heated to 141 DEG C. with the following ingredients: (1) carbon black, stearic acid, ammonium dichromate, dibutyl phthalate, and 1-bromo-2-naphthol; (2) as in (1) with the addition of litharge and zinc stearate; (3) carbon black, stearic acid, potassium chromate, barium and lead chromate pigments, and chloranil. Diphenylolpropane tetra-alcohol is prepared by reacting diphenylol-propane with formaldehyde in presence of alkali. Specifications 580,526 and 581,143 also are referred to.