| 摘要 |
1489737 Phenolic resins SAINT-GOBAIN INDUSTRIES 7 April 1976 [30 April 1975] 14119/76 Heading C3R A process for the manufacture of phenolic resins intended for the production of foams comprises condensing a mixture of formaldehyde and phenol, generally in a molar ratio of from 1À0 to 1À7, in at least 2 successive stages, the HCHO generally being added in 2 stages, in the presence of an alkaline catalyst, e.g. NaOH, characterized in that after cooling of the reaction mixture at the end of the last stage of condensation, preferably to a temperature of from 30‹ to 35‹ C., a quantity of acid, e.g. HCl, sufficient to lower the pH to from 3 to 4 is added to the reaction mixture and the resinous phase is removed from the aqueous medium. The phenolic resins obtained generally have solids contents of from 70 to 74% wt. and viscosities from 1500 to 2000 cP. at 20‹ C. |
