GB776495A - Process for the production of hardenable condensation products - Google Patents

Abstract

Epoxy resins soluble in the usual solvents for such resins, e.g. ketones and glycol monoethers, and suitable for casting or for electrical insulation, are produced by reacting an epihalogenhydrin in alkaline medium with a novolak which has been produced by reacting excess phenol with formaldehyde under acid conditions, separating the aqueous layer and distilling to remove excess phenol and render the resin anhydrous, excess phenol being added during the novolak-epichlorhydrin reaction; alternatively the novolak containing the original excess phenol and without dehydration may be reacted with the epichlorhydrin. The additional phenol added may be phenol, cresol, xylenol, chlorphenol or their glycide ethers may be employed. The optimum formaldehyde/phenol ratio for the production of the novolak is 0.5, but for phenol homologues, e.g. p- or o-cresol the ratio may be somewhat higher. The product may be mixed with fillers or dyestuffs and then hardened by addition of conventional hardening agents, e.g. amines-triethanolamine or piperidine, or polybasic acids or their anhydrides, e.g. phthalic and maleic acids, (1) 440 gs. novolak produced by reacting formaldehyde and phenol in molar ratio 0.5/1 and freeing the product of water and phenol by distillation is mixed with 170 gs. phenol dissolved in 2400 gs. 10 per cent NaOH solution and 556 gs. epichlorhydrin are added, the resulting exothermic reaction being maintained at 80 DEG C. by cooling; the resin is dehydrated by decantation, distillation and purified by solution in acetone and filtering followed by distillation or reduced pressure. In Examples (2)-(5), the novolak obtained in Example (1) is reacted with epichlorhydrin and (2) cresol, (3) xylenol, (4) glycide phenol ether, (7) chlorphenol. In Examples (5) and (6) a cresol-formaldehyde novolak is reacted, (5) with phenol, and (6) with cresol. Example (8), 1410 gs. phenol, 645 gs. 36 per cent formaldehyde and 14 gs. oxalic acid are boiled under reflux; the CH2O content of the aqueous layer is then 0.2-0.3 per cent 600 gs. NaOH dissolved in 6000 gs. water are added, the mixture is heated to 60 DEG C. and 1390 gs. epichlorhydrin added; after decantation, washing and filtration, 1840 gs. resin are obtained.