| 摘要 |
<p>This invention pertains to the manufacture of foams from phenolic resins and to the foams so produced. Such foams are made by mixing a blowing agent with the resin in a soft or fluid state, adding a hardening catalyst which produces an exothermic reaction of sufficient intensity to vaporize the blowing agent and form the foam, and hardening the foam. In such processes a strong acid is usually employed to generate the exothermic reaction but its action is accompanied by undesirable side effects, e.g. during the use of the foams as insulators for a metal object the residual acid in the resin may produce corrosion. To reduce that objection the resin has been processed to remove or neutralize the acid, or both, the attempt being to eliminate the large part of the acid and neutralize the residue. Such processing is difficult and imperfect. According to the invention Resorcinol is included in the composition of the phenolic resin which is to be foamed by acid catalysts. The presence of the Resorcinol is productive of several advantages including improvement of electrical properties, color stability and reduction of corrosive tendencies.</p> |
