METHOD FOR OBTAINING LIQUID PHENOL-FORMALDEHYDE RESIN AND A FOAM PLASTIC BASED THEREON

摘要

A method for obtaining a liquid phenol-formaldehyde resin provides for, firstly, condensation of phenol and formaldehyde in an acid medium at a molar ratio between phenol and formaldehyde equal to 1.0:3-0.9 respectively, at a pH of 0.1-0.8 and a temperature of 55-85 DEG C. As a result a new-lacquer resin is obtained which is reacted with formaldehyde in the presence of an oxide or hydroxide of an alkaline or alkaline earth metal. The quantity of the formaldehyde added at this stage equals 0.3-1.0 mole for one mole of the initial phenol, pH equals 8.2-8.9 and the temperature of the process equals 55-80 DEG C. The process is carried out until obtaining the final product in which 25 to 50 % of formaldehyde is linked in the form of methylene groups. A method for obtaining a foam plastic on the basis of the phenol-formaldehyde resin obtained according to the above described method consists in foaming and hardening a composition contained of such a resin, of an acid catalyst, of a surface-active substance and of a foaming agent. The foaming and hardening are effected at a temperature of 15-50 DEG C.