Method of injection molding a thermoset polyurethane article

Details Method of injection molding a thermoset polyurethane article Method of injection molding a thermoset polyurethane article

1975-11-21

1977-07-12

Thurlow, Jeffery R.

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

Shaping against forming surface

260 775AP, 260 775AT, 260 775AA, 260453AR, 264331, 264349, 264DIG77, B29G 300

Patent

active

040354679

ABSTRACT:
In accordance with a preferred embodiment of this invention, a controlled phase change is used to trigger an exothermic polymerization reaction in an injection molding process. The subject method comprises first, dispersing a crystalline urea reactant, 1,3-bis-(3-isocyanatotolyl) urea, in a liquid polyoxyalkylene polyol or mixtures thereof. Since the polyols do not dissolve the urea at room temperature, the dispersion is storage stable over an extended period of time. This is unexpected because the isocyanate and hydroxyl functionalities are normally quite reactive. In the barrel of the injection molding machine, the dispersion is heated to a temperature at which the polyol will begin to dissolve and thereby react with the crystalline urea to initiate a controllable polyurethane-forming reaction. At present, the specific urea disclosed above is preferred because of its ability to (1) form a storage stable dispersion, (2) dissolve in the polyol at a temperature below its decomposition temperature, and (3) react with the polyol at controllable rates once it has dissolved. All three properties are important to this invention and they enable the practitioner to use conventional injection molding equipment.

REFERENCES:
patent: 2757184 (1956-07-01), Pelley
patent: 2757185 (1956-07-01), Barthel
patent: 2818404 (1957-12-01), Hill
patent: 2902474 (1959-09-01), Arnold et al.
patent: 3409461 (1968-11-01), Mehlo et al.
patent: 3427639 (1969-02-01), Strauss
patent: 3458373 (1969-07-01), Knipp et al.
patent: 3917792 (1975-11-01), Conacher, Jr.
patent: 3939222 (1976-02-01), Dieterich

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