GB762092A - Process for improving the flow properties of thermosetting resin moulding compositions - Google Patents

Abstract

The flow of heat-hardenable synthetic resin moulding compositions is improved by subjecting the compositions to the vapour of a solvent which swells the resin and which has a normal boiling-point below 100 DEG C. By this means it is possible to advance the cure of the resin to a greater degree before moulding and hence reduce the final curing time, and still obtain satisfactory flow, or to reclaim moulding materials that would otherwise have been too far advanced, or to reduce the resin content of the moulding composition. The treatment is preferably carried out in a vessel which is evacuated and into which the solvent vapour is carried, e.g. by an air stream bubbling through the solvent in an attached vessel, and is continued until the moulding composition has taken up from 0.5 to 3.5 per cent of its weight of solvent or until beads of solvent appear on the surface. After treatment the material may be stored without loss of solvent. In an example an over-hardened wood-flour filled phenolaldehyde moulding composition is spread out in a vacuum container and is subjected to a vacuum of 20-30 mm. mercury absolute. The container is then connected to a vessel containing acetone and a stream of air bubbling through the acetone carries the vapour into the container. After a few seconds beads of acetone form on the moulding material and the acetone is then disconnected and the remaining vacuum of about 200 mm. absolute, broken. The temperature of the acetone was about 8-12 DEG C. higher than the moulding powder. The flow time of the heated powder in a beaker mould was 10.8 seconds compared with 51 seconds for the untreated powder. Specification 747,969, [Group III], is referred to.