α butyrolactone

Example 2

37.6 g of EPICLON® N-770 (phenol novolak epoxy resin, epoxy equivalent 188 manufacture by DIC Corporation) as a compound having at least two epoxy groups per molecule was added to a 300 mL 3-neck flask filled with 75.2 g of γ-butyrolactone (Mitsubishi Chemical Corporation) as a solvent and dissolved under a nitrogen gas atmosphere at 60° C. 20.1 g (0.65 equivalents to 1 equivalent of epoxy) of 3,5-dihydroxybenzoic acid (Fujifilm Wako Pure Chemical Corporation) used as the hydroxybenzoic acid compound and 0.173 g (0.660 mmol) of triphenylphosphine (Tokyo Chemical Industry Co., Ltd.) as a reaction catalyst were added thereto and reacted for 21 hours at 110° C. The reaction solution was returned to room temperature and diluted to 20% by mass of solid components with α-butyrolactone. The solution was filtered and 197.7 g was collected (resin solution c2). The obtained reaction product had a number average molecular weight of 2,400 and a weight average molecular weight of 8,300.

Example 1

150 g of EPICLON® N-695 (cresol novolak epoxy resin, epoxy equivalent 210 manufactured by DIC Corporation) as a compound having at least two epoxy groups per molecule was added to a 300 mL 3-neck flask filled with 300 g of α-butyrolactone (Mitsubishi Chemical Corporation) as a solvent, and dissolved under a nitrogen gas atmosphere at 60° C. 70.4 g (0.65 equivalents to 1 equivalent of epoxy) of 3,5-dihydroxybenzoic acid (Fujifilm Wako Pure Chemical Corporation) used as the hydroxybenzoic acid compound and 0.661 g (2.52 mmol) of triphenylphosphine (Tokyo Chemical Industry Co., Ltd.) as a reaction catalyst were added thereto and reacted for 24 hours at 110° C. The reaction solution was returned to room temperature and diluted to 20% by mass of solid components with α-butyrolactone, the solution was filtered and 804.2 g was collected (resin solution c1). The obtained reaction product had a number average molecular weight of 3,000 and a weight average molecular weight of 8,100.