GB1031543A - Process for curing polyepoxides and resulting products - Google Patents

Abstract

Polyepoxides are cured by mixing with a polymercaptan which is a reaction product of hydrogen sulphide and a polyglycidyl ether of a polyhydric phenol containing on average more than three glycidyl groups and at least three aromatic groups per molecule. A liquid mercaptan containing not more than 2 mercapto groups per molecule may also be added. The polymercaptan is preferably derived from H2S and a novolac polyglycidyl ether, using 3 to 20 moles of H2S per mole of epoxy resin, at 1-10 atmospheres and preferably 20-100 DEG C., in the presence of an alkaline catalyst, e.g. NaSH, NaOEt, NaOPh, or diethylamine or melamine amounting to 0.001 to 5% by weight of the resin. The liquid mercaptan may be e.g. 1,2- and 1,3-dithioglycerol, 1,4-butanedithiol, 1,5 - pentanedithiol, bis - (2 - mercaptoethyl) sulphide and ether, ethylene glycol monomercaptoacetate, 1 - mercapto - 4 - (mercapto - ethyl or - butyl) cyclohexane, 1,4-dimercapto - hexane, 1 - pentanethiol and 2 - hexanethiol, and may amount to 1-50% by weight of the mercaptan mixture. Many suitable polyepoxides are listed, including polyglycidyl ethers of polyhydric phenols and polyhydroxy aliphatic compounds, poly-(epoxyalky.) esters of polycarboxylic acids and of polymerized unsaturated acids, epoxidized esters of unsaturated acids, epoxidized dienes, di-(epoxyalkyl) ethers, and 3,4-epoxy-6-methylcyclohexylmethyl 3,4 - epoxy - 6 - methylcyclohexane carboxylic acid. The ratio of mercaptan to epoxide groups (in equivalents) is preferably at least 0.8 : 1. Accelerators may be used, and may be phenols, sulphides, mercaptans, organic phosphines, organic arsines, organic antimony compounds, amines, amine salts and quaternary ammonium salts (several are listed). From 0.1 to 4 parts by weight per 100 of polyepoxide may be used. Solvents or diluents may be added to the epoxide or mercaptan for mixing and may be benzene, toluene, cyclohexane, ketones, ethers, esters or chlorinated hydrocarbons. Monoepoxy compounds may be used as diluents, e.g. butyl or phenyl glycidyl ether or glycidyl esters, in amount up to 20 weight per cent of the polyepoxide. Plasticizers, e.g. dibutyl phthalate, extenders, e.g. tars and oils, fillers, pigments, fibrous materials and resins may also be added. Fillers may amount to 10-200 weight per cent related to the resin mixture, and may be sand, crushed quartz or limestone, powdered aluminium or zinc or mica, bentonite, Monetta clay, ground glass or asbestos. Other resins added may be phenol-aldehyde, urea-aldehyde, furfural, polyacetal, carbonate or polyamide resins. In examples, a polyglycidyl ether of a bi-phenol A is mixed with a polymercaptan derived from a novolac resin, with and without butyl glycidyl ether and various liquid mercaptans, and various amine and other accelerators, and solvents, TiO2 and tar, and is cast into sheets and cured.ALSO:Adhesive tapes are prepared by coating a glass fibre textile metal, wood, concrete, paper, asbestos paper, molar flakes, cotton bats, duck muslin and canvas with a composition comprising a polyepoxide and a polymercaptan which is the reaction product of hydrogen sulphide and a polyglycidyl ether for a polyhydric phenol, by dipping or spreading e.g. using a doctor blade. A preferred tape contains also in the resin mixture a phthalocyanine compound and aluminium powder, asbestos, powdered mica, zinc dust, bentonite, ground glass fibres and moretta clay. Other resins which may be included are phenol-aldehyde, urea-aldehyde, furfural resins, polyacetals, carbonate and polyamides.ALSO:Adhesive tapes for metal-metal bonding are prepared by impregnating a cotton, rayon or synthetic fibre textile with a composition comprising a polyepoxide and a polymercaptan which is the reaction product of hydrogen sulphide and a polyglycidyl ether of a polyhydric phenol (see Division C3). The tape is inserted between the metals and the assembly is heated to form the bond.