Particulate-containing foamed plastic

Claim 1

In a reaction injection molding (RIM) process, the method of incorporating particulate reinforcing material into a mix of two or more primary liquid resin components capable of reacting to produce a particulate-reinforced plastic mix moldable to form a plastic article, wherein said method comprises the steps of: providing a mixing head of the RIM type having a mixing chamber with first and second sets of port means opening into said chamber, and control means in said chamber for opening and closing said port means; providing respectively separate sources of said primary reactive components and pumping these separately to respectively different port means of said first set in said mixing head; providing a separate source of an auxiliary liquid component, mixing said particulate material into said auxiliary component and pumping the particulate-containing mixture to port means of said second set in said mixing head; operating said control means to open the port means of said second set while also opening the port means of said first set to allow all of said liquid components to enter said mixing chamber together; regulating the pumping means for said primary and auxiliary components so that the pressure of said primary components at said first set of port means substantially exceeds the pressure of said particulate-containing auxiliary component at said second set of port means during a pour cycle.