Patent GB-581144-A (GB)
Title: Improvements in the curing of polymeric organic materials
IPC: C08L75/00
Filed: 1943-02-10
Abstract: Organic - diisocyanate - modified polyester - amides are cured in the presence of a non-phenolic formaldehyde-liberating substance and of a curing catalyst, a thermo-hardening phenol-formaldehyde condensation product derived by alkaline condensation from a phenol with more than two free positions ortho and para to the phenolic hydroxyl group or groups being also present.  Suitable non-phenolic formaldehyde-liberating substances are described in Specification 580,524, and may be paraformaldehyde, trioxane, compounds containing a reaction methylol group or groups or ethers of such compounds or hexa-methylene tetramine-zinc chloride complexes.  Suitable curing catalysts are described in Specifications 580,524 and 580,526. They may be organic or inorganic acids or anhydrides, or acid salts or materials which are substantially neutral but develop acidity under curing conditions.  Suitable phenol-formaldehyde condensation products may be derived from phenol, m - cresol, diphenylolpropane, 1,3,5-xylenol, resorcinol or mixtures containing such a phenol, e.g. cresylic acid containing 45-50 per cent by weight of m-cresol. Mono-hydric alcohols boiling above 80 DEG  C., e.g. butanol or cyclohexanol may be present during formation of these condensation products.  Other materials which may be present during curing are non-basic fillers, e.g. carbon black, clay, asbestos, blanc fixe, mica, other plastics, e.g. natural or synthetic rubber, vulcanized vegetable oils, dark substitute, white substitute, a "Cumar" resin, wood rosin or pitch, detackifying agents, namely, stearic acid, paraffin wax, oleic acid or lauric acid, plasticisers, e.g. tricresyl phosphate, dibutyl phthalate, butyl phthalyl butyl glycollate, or N-alkyl sulphonamides, stabilisers or antioxidants, e.g. hydroquinone, N,D1-hexamethylene - bis - o - hydroxybenzamide, N - phenyl - a  - naphthylamine, N - phenyl - b  - naphthylamine, or a a -bis-(2-hydroxy-3,5-dimethylphenyl)-butane.  Non-basic pigments may also be included.  As described in Specification 581,143, acid-accepting materials may also be present to minimise scorching. Examples describe the curing of mixes containing diisocyanate - modified polyester - amide, hydroquinone, carbon black, stearic acid and paraformaldehyde together with (1), (3) (b) and (4) styrene dibromide and an alkaline condensed phenol-formaldehyde resin; (2) 1-bromo-2-naphthol and butylated diphenylolpropaneformalde resin; (3) (a) styrene dibromide and diphenylolpropane - formaldehyde resin; (5) phthalic anhydride and diphenylol propane-formaldehyde resin.  The modified polyesteramide of examples 1-4 is made according to example 7 of Specification 580,524, and that of example 5 according to example 1 of that Specification.  The alkaline condensed phenol-formaldehyde resin used in examples 1 and 3 (b) is made by refluxing for 15 mins., 100 parts of phenol, 124 parts of 37 per cent formaldehyde solution and a little sodium hydroxide.  That of example 4 is similarly prepared, the reaction mass being cooled and neutralized with hydrochloric acid, and the product separated, washed and dried in vacuo.  The butylated resin of example 2 is made by refluxing 536 parts of diphenylolpropane, 720 parts of 37 per cent formaldehyde, 640 parts of butanol, 400 parts of xylene, and 100 parts of 4 per cent caustic soda for 4 hours. Water is then removed azeotropically, organic liquids being returned to the reaction vessel, phthalic anhydride is added and azeotropic distillation continued.  The resin is isolated by vacuum distillate of organic liquids.  The resin of example 3 (a) and 5 is prepared by heating diphenylol propane, formaldehyde and caustic soda under nitrogen, cooling, neutralizing and washing and drying the product.  The proportions of polymers cured according to the invention are compared with those of polymers cured without the presence of the thermo-hardening phenolformaldehyde resin.