| 摘要 |
New resin (A) is a condensation product of HCHO, urea, phenol and opt. melamine at mole ratio 1:1.4-0.8 (1.05-0.9) : 0.006-0.04: 0-0.04. Phenol is incorporated as a crosslinking co-condensate of phenol, HCHO and urea prepd. at pH 4-6 (4.7-4.9) and 70-90 deg.C, using 0.1-3.3 moles phenol per mole HCHO and 1-10 moles urea per mole phenol. This co-condensate is added to a pre-condensate of HCHO, urea and opt. melamine, the mixt. condensed under acid conditions and reaction stopped by adding alkali. More urea is added to provide the required mole ratio. |
