A method for the production of highly reactive low-viscosity modified phenolic resins

摘要

A process for producing a highly reactive low-viscosity modified phenolic resin comprising the steps of: (1) polycondensating a petroleum heavy oil or pitch, a formaldehyde polymer, and a phenol in the presence of an acid catalyst to prepare a modified phenolic resin; wherein a mixture containing the petroleum heavy oil or pitch and the formaldehyde polymer in a ratio of the number of moles, in terms of formaldehyde, of the formaldehyde polymer to that of the petroleum heavy oil or pitch of 1 to 15 is heated under agitation in the presence of an acid catalyst, wherein the acid catalyst is used in an amount of 0.1 to 30 % by weight, relative to the total weight of the petroleum heavy oil or pitch, the formaldehyde polymer and the phenol, and the phenol is gradually added to the mixture while being heated under agitation until a ratio of the number of moles of the phenol to that of the petroleum heavy oil or pitch of 0.3 to 5 to thereby effect the polycondensation of the petroleum heavy oil or pitch, the formaldehyde polymer and the phenol leading to the preparation of the modified phenolic resin, said heating under agitation is conducted at 50 to 160 DEG C for 0.5 to 10 hours; and (2) reacting the resultant modified phenolic resin with a phenol at temperature higher than 120 DEG C and not more than 200 DEG C for 15 minutes to 2.0 hours in the presence of the acid catalyst to lower the molecular weight of the modified phenoloc resin, wherein the phenol and the acid catalyst are employed, per 100 parts by weight of the modified phenolic resin, in an amount of from 100 to 300 parts and 0.1 to 15 parts by weight, respectively. The highly reactive low-viscosity modified phenolic resin obtained according to this process has high reactivity with epoxy resins and low resin melt viscosity. In addition, this resin can be used for producing a molding material having good moldability and considerably low moisture absorption when combined with an epoxy resin.