WERKWIJZE VOOR DE BEREIDING VAN ZONDER VERGELING HARDBARE MELAMINE-FORMALDEHYDEHARSEN.

摘要

Melamine and formaldehyde are reacted in a molar ratio of from 1:1 to 1:3.5 at 70-120 DEG C. Aqueous formaldehyde containing no basic substances and at most 0.03% by weight of acid is used. The condensation is continued until a sample cooled to 20 DEG C is stable for a number of hours and produces cloudiness on dilution with 1.5 times the volume of water. The resins cured without yellowing exhibit no discolouration even after heating at 250 DEG C for 1 hour. Spray drying gives powder resins which are water-soluble and can be employed for the preparation of compression-moulding compositions and laminates.