Traditional low viscosity epoxy resin production has 2 methods. One is a one-step process catalyzed by NaOH. It undergoes three stages: the formation of sodium phenolate, the formation of a glycidyl ether from HCl, (3) the formation of diglycidyl ether from HCl, and the second step of ion-catalyzed two-step process. Two stages: the condensation of bisphenol A with epichlorohydrin (ECH) to form the chlorohydrin ether and the chlorohydrin ether to form the diglycidyl ether. Either method of forming a glycidyl ether and diglycidyl ether can continue to work with bisphenol A, ECH to form high molecular weight polyglycidyl ether. Therefore, on the one hand, diglycidyl ether should not be formed as much as possible in the etherification, and on the other hand, bisphenol A should be completely reacted during etherification to avoid the chain growth reaction. The suitable range of ECH/bisphenol A molar ratio for synthesizing low molecular weight epoxy resin is between 8 and 13. If the molar ratio is too low, the viscosity of the product increases, but the molar ratio exceeds 15 does not improve the performance, but it is easy to delaminate when washed.
To this end, Chen Zhiyi and others with 0.5molBPA, 5molECH, 1.25molNaOH and the amount of trimethylbenzyl ammonium chloride (BTMACC), water reaction, the first BPA and ECH condensation etherification and then closed loop reaction, the viscosity of 6Pa. s (25 °C), epoxy equivalent weight 185.2g/eq, total chlorine content 0.14% of low molecular weight epoxy resin for electrical purposes. Based on theoretical calculations, 1 mol of bisphenol A (BPA) is reacted with 2 mol of epichlorohydrin (ECH) and 2 mol of sodium hydroxide to produce 1 mol of bisphenol A diglycidyl ether (DGEBA).
Fang Hailong and other two-step process route, the first condensation of phenol, ethylamine, formaldehyde phenolic amine-based resin, and then reacted with epichlorohydrin phenolic epoxy resin. As the final product molecular structure contains amine methyl groups and glycidylamine groups, the resin viscosity is reduced, and the product curing performance is improved. It can be seen from the experimental results that the product has a viscosity of 8 to 10 Pa.s (20°C), an epoxy value of 0.55% to 0.57%, and a glass transition temperature of the cured product of 250°C or more.