Method and apparatus for the injection of additives into plastics material

摘要

This invention provides a method and apparatus for injecting an additive into a stream of homogenized plastics material. The apparatus includes a homogenizing means such as a screw conveyor for the plastics material and at least one injector for injecting an additive, usually a colorant, into the boundary layer only of the homogenized plastics material prior to the latter being subjected to mastication in a gear pump. The additive is injected into the plastics material at such a position in the boundary layer that as the material passes through the gear pump the additive is mixed substantially wholly with the boundary layer of plastics material and for this purpose the injection of additive is at a position such that it passes through the gear pump in the region of the intermeshing gears of the pump.