MOULDING OF FILLED SYNTHETIC PLASTICS MOULDING COMPOSITIONS

摘要

This specification discloses a method of producing moulded synthetic plastics artefacts by a continuous moulding or extrusion sequence. There is disclosed a method of injection moulding amino-formaldehyde thermosetting material to produce a cured artefact having filler homogeneously dispersed therein without requiring the preliminary step of compounding a moulding powder having the filler already homogeneously dispersed therein which comprises the steps of: (a) providing a dry thermosetting amino-formaldehyde material which is partly condensed but essentially solid at room temperatures; (b) introducing said dry material and filler in at best a rough, non-homogeneous blend directly into the barrel of an injection moulding machine in the absence of solubilizing quantities of solvent, said machine having a heated barrel and a rotary screw movable in said barrels; (c) by means of said screw simultaneously feeding the blend along the barrel, further condensing the material, plasticized material to provide a homogeneous blend; (d) injecting homogeneous blend from said barrel into a heated mould; and (e) curing the artefact in the mould. The thermosetting component may consist essentially of a reaction product between formaldehyde and a precursor selected from the group consisting of ureas and amino-s-triazines.