Low-molecular-weight epoxy-bisphenol resins
Polimery 1997, No 11-12, 685
The original two-step procedure used to prepare title resins involved (z) adding bisphenol A to epichlorohydrin over chlorocholine chloride and Ca(OH)2 as catalysts (9.85:1:0.001:0.074 by moles) at 55—65°C until phenol's OH was converted in >90% and (zz) dehydrochlorinating of by-products and P-chlorohydrin by (a) driving off the excess of epichlorohydrin at 115—135°C/20 mm Hg, dissolving the intermediates in MEK and dehydrochlorinating (50—55°C) with aq. 20% NaOH, or (b) with aq. 40% NaOH in the unconverte depichlorohydrin solution without or (c) with some z-PrOH added. The epoxide equivalents and viscosities (25°C) of the resins, 176—185 g/mol and 6 900—11 400 mPa s, respectively, were suggestive of low contents of higher oligomers and a-glycol groups. The variant c consumption of epichlorohydrin was 0.56 kg/kg resin.