Mixing head for reaction injection molding process has high viscosity material recirculating valve which switches to feed mixing chamber and low viscosity component injection is between feed channel and mixing chamber

摘要

A switching valve(1) can set a connection between the feed channel(3) for the very viscous material component and a recirculating channel(4) or can be switched to connect the feed channel and a mixing chamber(6) in which the viscous component is combined with a low viscosity component. The injection point(7) for the lower viscosity component is downstream from the feed point between feed channel and mixing chamber. The high viscosity component feed channel(3), recirculating channel(4) and flow connection(5) the feed channel and recirculating channel have little and preferably no change in cross-section. The flow connecting bore between the feed channel and mixing chamber has the same cross-section as the feed channel. A cleaning piston(1) moves backwards and forwards in the mixing chamber(6) to act as the switching valve. In one position a connection(5) is created between the feed and recirculating channels. In a second position connection(2) is made between the feed channel and mixing chamber. A profiled end of the cleaning piston deflects the high viscosity component from the feed channel into the mixing chamber. Injection openings(7) for the low viscosity component form a ring around the mixing chamber. Each low viscosity component injection point has an injection nozzle and each can be separately controled. The openings and injection nozzles produce high pressure injection into the mixing chamber. An independent claim is included for a reaction injection molding (RIM) process for operating the claimed mixing head where one of the two materials has high viscosity and contains fibers of not less than0.5, preferably not less than1mm and more preferably not less than3mm, in which the high viscosity material flow is recirculated and then connected to the mixing chamber where a further, low viscosity material is injected into the higher viscosity material via nozzles downstream from the viscous material feed point.