| 摘要 |
PROBLEM TO BE SOLVED: To obtain a curing agent used to give a cured epoxy resin being excellent in humidity resistance and adhesion to a metal or an inorganic matter and having low-stress properties by using as an essential component a cocondensate prepared by condensing an ortho-substituted phenol with formaldehyde and condensing the condensate with phenol. SOLUTION: A cocondensate represented by the formula is obtained by condensing 20-80 mol% ortho-substituted phenol such as an ortho-alkyl-substituted phenol such as o-cresol, 2-ethylphenol, or 2-n-butylphenol with formaldehyde and condensing the formed condensate with 80-20 mol% phenol. In the formula, R is a monovalent organic group; a, b, and c satisfy the relationships: a/(a+b+c)=0.2-0.8, and (b+c)/(a+b+c)=0.8-0.2. It is desirable that the cocondensate has a softening point of 60-110 deg.C, a solution viscosity of 20-90μm2/s, and a weight-average molecular weight of 400-3,000. It is used as an essential component of an epoxy resin curing agent and is used in an amount of, desirably, at least 60 wt.% based on the entire curing agent.
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