GB1027056A - Thermoset resins and intermediates therefor - Google Patents

Abstract

Glycol formthionals <FORM:1027056/C2/1> where X is O or S, n is an integer and the unit <FORM:1027056/C2/2> has an average molecular weight of 77-107 and a sulphur content of 43-65%, are prepared by saturating formalin with H2S at pH 3-9 below 15 DEG C. A preferred mixture contains largely HOCH2SCH2OCH2OH and HOCH2SCH2SCH2OH in approximately 3 : 1 mole ratio. Water-soluble resins may be obtained by heating together substantially equimolar amounts of urea and glycol-formthional at pH 4-6 below 60 DEG C. until traces of solid appear. These polymers contain units <FORM:1027056/C2/3> apparently fewer than 100, probably fewer than 10 per molecule, on average.ALSO:A thermosetting resin comprises 40-100 weight per cent of a glycol-formthional/urea resin having repeating units <FORM:1027056/C3/1> where X = O or S, n is an integer, and the unit <FORM:1027056/C3/2> has an average molecular weight of 77-107 and a sulphur content of 43-65%, and 0-60% complementally of a natural polyacetal of recurring unit <FORM:1027056/C3/3> and/or an aminoplast resin as filler, and/or an epoxy compound or epoxy resin as stabilizer and/or a polybasic acid anhydride as hardener. The glycol-formthionals are prepared by saturating formalin with H2S at pH 3-9, below 15 DEG C. Water-soluble, A-stage, glycol-formthional/urea resins are obtained by heating substantially equimolar amounts of urea and glycol-formthional at pH 4-6, below 60 DEG C., until traces of solids appear. The pH of the solution may be stabilized by addition of phenolic antioxidants, e.g. 2,6-di-t-butyl-4-methyl-(or -methoxy-) phenol. These polymers apparently contain less than 100, probably less than 10, units as above. Solutions of these resins may be used with or without modifiers to laminate coat or impregnate substrates, and may be thinned with organic solvents, e.g. alcohols, ketones, ethers. They may be mixed with reactive fillers, e.g. starch, cellulose, melamine/formaldehyde, guanidine/formaldehyde, benzoguanidine/formaldehyde, biguanide/formaldehyde, guanylurea/formaldehyde, biuret/formaldehyde or urea/formaldehyde. a -Cellulose is preferred, amounting to up to 55% by weight of the resin/filler mixture, and may be precoated with a melamine/formaldehyde or benzoguanidine/formaldehyde which is cured before the filler and the resin are mixed. Non-reacting fillers also may be added, e.g. carbon black, glass, asbestos, silica, cadmium red, cadmium yellow, TiO2, or phthalocyanine green, and lubricants, e.g. MoS2, polytetrafluorethylene or glycerol monostearate. A water-insoluble B-stage resin still capable of being shaped may be obtained by heating the A-stage resin mixture at pH 3-6, below 60 DEG C., losing volatiles until less than 3 weight per cent of water remains. This resin may then be milled and stabilized by treatment with epoxy compounds or resins, e.g. glycidyl ethers, or low molecular weight condensates thereof with phenols or polyols, which may be applied by spraying, followed by an acetone solution of a volatile organic acid. Hardeners, e.g. maleic, pyromellitic or phthalic anhydride, may similarly be added at this stage. Solid C-stage resins are obtained by heating the B-stage resins at 60-180 DEG C. under pressures up to 15,000 p.s.i. In examples A-stage resins are used to laminate paper and birch veneers. B-stage mixtures are made, using as filler a -cellulose impregnated with a melamine/formaldehyde precondensate, and incorporating minor amounts of glyceryl monostearate and TiO2; these are dried and ground and sprayed with nonylphenol glycidyl ether in hexane, formic acid in acetone, and phthalic anhydride is finally added. Cure is at 140 DEG C. and 3000 p.s.i. A cup and saucer are made from this powder.