METHOD FOR TWO-COLOR MOLDING OF RIM POLYURETHANE

摘要

PROBLEM TO BE SOLVED: To decrease cost and wear of installation tools by making color difference caused by cutting burrs and thinning the surface part in the neighborhood site of a gate inconspicuous and saving amt. of use of a pigment as a whole. SOLUTION: A method for two-color molding of an RIM polyurethane comprises a process wherein a cavity with a mold parting face is vacuumized, an initial process wherein a polyurethane material for the surface part in which the pigment concn. is decreased to 30-90% of the reference concn. is fed into the cavity under a vacuum condition and the surface part of a molded article is RIM-molded, an intermediate process wherein a polyurethane material for the inner part in which the pigment concn. is decreased to 30-80% of the reference concn. is fed into the cavity under a vacuum condition and the most part of the inner part of the molded article is RIM-molded and a final process wherein a polyurethane material for the neighborhood part of the gate in which the pigment concn. is made to the reference concn. is fed into the cavity under a vacuum condition and the neighborhood part of th gate of the inner part of the molded article is RIM-molded.