Method and apparatus for reaction injection moulding bicolored polyurethane parts

摘要

Method and apparatus for molding two-color polyurethane parts by RIM, by which two-color parts that have different colors, properties, etc. in the surface and the interior are produced by the RIM molding of polyurethane using inexpensive two-component mixing heads. Another object is to insure that a surface area can be selectively formed in specific desired parts of the molded part. The pressure in the cavity 104 of the mold 101 is reduced. A small amount of surface forming RIM polyurethane material U1 is injected into the evacuated cavity 104 from the surface-forming two-component mixing head 121 through the common gate 108 on the mold 101, whereby the surface area of the molded part is formed by RIM. The material U1 is made of a non-yellowing material and loaded with a coloring component. Subsequently, interior forming RIM polyurethane material U2 is injected into the evacuated cavity 104 from the interior-forming two-component mixing head 122 through the common gate 108, whereby the interior of the molded part is also formed by RIM. The material U2 is made of a yellowing material without the loading of any coloring component.