Amino molding compound for cold manifold injection molding

摘要

A urea-formaldehyde corn is mixed or ground with added paraformaldehyde and urea in addition to a catalyst system and other conventional additives to produce a mixture of fine powder. This mixture is optionally densified and granulated. The addition of urea and paraformaldehyde to the corn causes a low viscosity under cold manifold injection condition, which is particularly suited for cold manifold molding applications. The condensation of resin in the corn is preferably kept low by using high formaldehyde: urea ratios and pH values during drying. The plastic life of the molding compound is improved by employing a catalyst system such as zinc sulfate and hexamethylenetetramine. The molding compound is stable at about 82 DEG -110 DEG C. for over about 5 minutes and can be injected at applied pressures of below about 125 megapascals (18,000 psi) at such manifold temperatures with reasonable cycle times and without setting in the sprue or runners.