Highly-reactive modified phenol-formaldehyde resins - by reaction of phenol@ and formaldehyde in presence of calcium hydroxide, followed by addn. of melamine and-or urea and-or di:cyano:di:amide

摘要

Highly reactive modified phenol-formaldehyde (PF) resins (I) are claimed, which harden completely in a short time and are suitable for the continuous prodn. of decorative laminates; (I) are obtd. by reaction of 10 mols. aq. formaldehyde soln. with 3-4 mols. phenol at 310-360 K in the presence of 0.02-0.1 mol. Ca(OH)2. 1-2 mols. polyamine component, consisting of 0.1-1 mol. urea and/or 0.1-0.8 mol. melamine and/or 0.1-0.5 mol. dicyandiamide, is added to the condensate, and the PF resin is opt. adjusted to pH 6.0-7.5 by addn. of acid. The reactivity of (I) can be controlled by varying the amt. of Ca(OH)2 and the reaction time and temp., to give an aq. resin soln. with a consistency suitable for the direct impregnation of sodium kraft paper with 80-120% resin; alternatively, the resin can be diluted with MeOH, acetone, etc.; other properties such as hydrolytic stability are modified by varying the amts. of the N-contg. additives; the impregnated paper is dried at 375-420 K to 5-7% residual moisture, and the resulting prepregs are processed on a continuous laminating press at 420-440 K and 2-5 MPa, together with patterned paper; the prods. have post-forming quality, and have water absorption below 7% (2 hrs. in boiling water) with no blistering. USE/ADVANTAGE - (I) are useful for the prodn. of decorative laminates as surface finishes for wood and plastics in the furniture and interior finish industries. Provides highly reactive PF resins which can be fully cured in a short time without addn. of accelerators; (I) are suitable for continuous prodn. methods and contain the smallest possible amts. of free phenol, formaldehyde or organic solvent