Improvements in or relating to epoxide resins

The invention comprises an epoxide resin-forming compound of th formula in which the two acid residues R1(CO-)2 are derived from the same dicarboxylic acid, the said acid being capable of forming an internal anhydride, preferably an aryl dicarboxylic acid, and -OR2O- derives from a glycol. The epoxy compound may be made by the steps (a) reacting two molecular proportions with one molecular proportion of a glycol and (b) reacting the dibasic acid thus formed with epichlorhydrin in the presence of an amine catalyst, including a quaternary ammonium salt. Preferably the dicarboxylic anhydride is phthalic anhydride and the glycol is ethylene glycol. Step (a) can be effected by warming the components to 110 DEG C. Step (b) is carried out by heating the sodium salt of the dibasic acid product of (a) with excess of epichlorohydrin to 120 DEG C. in the presence of tetraethyl ammonium bromide or by heating the free dibasic acid product with epichlorhydrin in the presence of an amine catalyst such as tetraethyl ammonium bromide at 80-100 DEG C. and converting the chlorohydrin product to a di-epoxide by treatment with an aqueous alkali in the presence of a solvent. The chlorohydrin product may also be converted to a di-epoxide by heating it with excess epichlorhydrin in the presence of a quaternary ammonium salt. Other glycols such as propylene glycol or neopentyl glycol, and other anhydrides such as tetrahydrophthalic, maleic or hexachloroendomethylene tetrahydrophthalic anhydride may be used.ALSO:An epoxide resin is made by hardening a compound of the formula in which the two residues R1(CO-)2 are derived from the same dicarboxylic acid, which is capable of forming an internal anhydride, and -OR2O- is a glycol residue, by heating with phthalic anhydride at 130-140 DEG C., or by action of acids such as phosphoric or phthalic acid, or amines such as ethylene diamine or tetraethylene pentamine. In an example, a monomer prepared from phthalic anhydride, ethylene glycol and epichlorhydrin is hardened with phthalic anhydride or tetraethylene pentamine.