Curing of liquid polyepoxide resins

Liquid polyepoxide resins prepared from dihydric phenols and more epichlorhydrin and having at least two epoxide groups per molecule and more epoxide groups than hydroxyl groups and free from functional groups other than hydroxyl are cured by addition of FriedelCrafts catalysts preferably in the presence of diluents neutral to the catalyst and polyepoxide, e.g. dibutyl phthalate, chlorinated polyphenols. There also may be present as diluents compounds which are polymerized by the catalyst, e.g. phenyl glycidylether, allyl glycidylether, epichlorhydrin, turpentine, styrene oxide. Suitable catalysts are boron trifluoride complexes with ether, water, acetic acid and butanol; stannic chloride, antimony pentachloride. The catalyst and resin may be applied from jets of a spray gun on to the surfaces to be united, e.g. glass cloth or laminates. In examples: (1) "Technical TPG" was hardened by addition of antimony pentachloride in butyl acetate; (3) the resin as in (1) mixed with a 10 per cent solution of boron fluoride etherate in methyl ethyl ketone and aluminium powder was poured into a mould and hardened in 3 minutes without shrinking; (5) "Technical DPG" containing 25 per cent epichlorhydrin was sprayed from one jet of a twin jet gun and a 10 per cent solution of boron fluoride/butanol in butanol was sprayed from the secondary jet to give a 4 per cent concentration of catalyst. The sprayed panels were coated with thick films of high gloss which hardened in 8 minutes.