Patent GB-580526-A (GB)
Title: Improvements in the curing of polymeric materials
IPC: C08G18/60
Filed: 1942-06-01
Abstract: Organic diisocyanate-modified polyesters or polyester-amides are cured by heating them in the presence of formaldehyde or of a formaldehyde-liberating substance, and also of a material which is substantially neutral but which develops acidity only under curing conditions, i.e. at temperatures of about 100-150 DEG  C. Specified formaldehyde-liberating substances are paraformaldehyde, trioxane, dimethylolurea, trimethylolmelamine, hexamethylolmelamine, diphenylolpropane tetra - alcohol, methylolchloracetamide, methylolstearamide, N-methylol-p-toluenesulphonamide, dimethylolurea dimethyl ether, dimethylolurea dibutyl ether, 1 : 2-glycol methylene ether, N : N1-dimethyloluron dimethyl ether, di-(b -hydroxyethyl) formal, hexamethylene tetramine-zinc chloride complexes, and certain thermo-hardening phenol-formaldehyde condensation products. Preferably 5-15 parts of the formaldehyde-liberation substance are used per 100 parts by weight of the polymer. Specified substances which are substantially neutral, but which develop acidity under curing conditions are butadiene sulphone, 2 : 3-dimethylbutadiene sulphone, butadiene tetrabromide, styrene di-bromide, acetylene tetrabromide, tribromo-hydroquinone, 1 - bromo - 2 - naphthol, 1 : 6 - dibromo - 2 - naphthol, 1 : 4 : 6 - tribromo - 2 - naphthol, 2 : 4 - dibromo - 1 - naphthol, methyl a  : b  - dibromopropionate, b  - chloroethyl a  : b  - dibromoisobutyrate, ethyl-a -bromo-propionate, phenyl trichloroacetate, a  : a  : b -trichloro-propionitrile, trichloroacetamide, trichloroacetyldiethylamide, N-trichloroacetylanilide, N - N1-di - (trichloroacetyl) methylenediamine, N : N1-di-(trichloroacetyl) ethylenediamine, chloranil, and interpolymers of asymmetrical dichloroethylene and vinyl chloride.  These may be used, for instance, in from 0.5 to 4 parts per 100 parts by weight of the polymer.  Specified stabilizers which may be included in the mix are hydroquinone, N : N1-hexamethylene-bisorthohydroxy - benzamide, N - phenyl - a  - naphthylamine, N - phenyl - b  - naphthylamine, and a  : a  - bis - (2 - hydroxy - 3 : 5 - dimethylphenyl) butane.  Specified optional additions are carbon black, clay, asbestos, blanc fixe, whiting, lithopone, mica, natural or synthetic rubbers, vulcanized vegetable oils, dark substitute, while substitute, "Cumar" (Registered Trade Mark) resin, wood rosin, pitch, detackifying agents such as stearic acid, paraffin wax, oleic acid, lauric acid and dibutyl ammonium oleate, and plasticisers such as tricresyl phosphate, dibutyl phthalate, butylphthalyl butyl glycollate and N - alkyl - toluenesulphonamides.  According to examples: (1) a mixture of a diisocyanate-modified polyester-amide, paraformaldehyde, hydroquinone, carbon black, and an interpolymer of asymmetrical dichloroethylene and vinyl chloride, is compounded on a rubber mill and is then cured in a mould under hydraulic pressure at 125 DEG  C. for 30 minutes; (2) a mixture of a diisocyanate-modified polyester-amide, paraformaldehyde, hydroquinone, carbon black and styrene dibromide is cured at 125 DEG  C. for 20 minutes; (3) a mixture of a diisocyanate-modified polyester-amide, paraformaldehyde, hydroquinone, carbon black and 1-bromo-2-naphthol is cured at 125 DEG C. for 10 minutes. Specification 580,524 is referred to.