Method of molding rigid foamed polyurethane articles
First Claim
1. The method of making rigid articles of polyurethane foam in which a mixture of a polyol and isocyanate and a blowing agent is supplied to and foamed within a mold which includes separable parts defining a mold cavity therebetween when closed which comprises:
- injecting the polyol and isocyanate and blowing agent in admixed form to the mold cavity, and applying suction to the cavity via a restricted slit-like gap extending about the periphery of the cavity at the juncture of the mold parts not later than immediately following the injection of the aforementioned mixture into the cavity to cause extremely rapid foaming of the said admixture with expansion and flow thereof to fill the cavity without significant flashing through said gap, admixing said polyol and isocyanate not sooner than immediately prior to the injection thereof to the mold cavity and immediately adjacent the point of entry of the mixture into the cavity, said method furthermore including admixing a liquid blowing agent with at least one of said polyol and isocyanate not later than time of admixing the polyol with the isocyanate.
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Abstract
A method and apparatus for molding plastic materials, particularly foamed plastic materials, in which the materials are introduced into a mold cavity together with a foaming agent with the mold cavity being evacuated not later than immediately after the molding material is supplied thereto. The reduced pressure in the mold cavity causes the material to foam extremely quickly so as completely to fill the cavity while, at the same time, the mold is held closed by the pressure differential between the inside and outside thereof.
72 Citations
6 Claims
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1. The method of making rigid articles of polyurethane foam in which a mixture of a polyol and isocyanate and a blowing agent is supplied to and foamed within a mold which includes separable parts defining a mold cavity therebetween when closed which comprises:
- injecting the polyol and isocyanate and blowing agent in admixed form to the mold cavity, and applying suction to the cavity via a restricted slit-like gap extending about the periphery of the cavity at the juncture of the mold parts not later than immediately following the injection of the aforementioned mixture into the cavity to cause extremely rapid foaming of the said admixture with expansion and flow thereof to fill the cavity without significant flashing through said gap, admixing said polyol and isocyanate not sooner than immediately prior to the injection thereof to the mold cavity and immediately adjacent the point of entry of the mixture into the cavity, said method furthermore including admixing a liquid blowing agent with at least one of said polyol and isocyanate not later than time of admixing the polyol with the isocyanate.
- View Dependent Claims (2, 3, 4, 5, 6)
Specification