Owens-corning Fiberglas Corporation

John J McCluskey

Edward L Wilson

Gordon P Armstrong

Richard T Linak

Ronald Z Bell

Low pressure molding compositions comprising a thermosetting resin and a thermoplastic resin are thickened with a combination thickening agent within a specific concentration range to retard rapid initial thickening of the molding compositions.

Thickening agents for low pressure molding compositions

A method and apparatus for producing a sheet molding composite are provided. The sheet molding composite consists of two outer sheets of plastic material between which is sandwiched a moldable material or compound containing fiber-reinforced resin. The resin-containing material is maintained in a deformable, flexible state until it is placed in a mold and subjected to heat, at which time it is cured in the shape of the final molded product. The molding composite is made by depositing a layer of a pre-blended resin-containing material on the upper surface of one of the sheets of plastic material and by then depositing a layer of randomly disposed glass fibers onto this first layer. A second layer of preblended resin-containing material from the same source is also deposited on an upper surface of a second of the plastic sheets. The latter sheet is then turned over and moved into parallel relationship with respect to the first sheet and with the second layer of resin-containing material moved into contact with the reinforcing fibers on the first layer of resin-containing material. The composite is then kneaded to thoroughly mix the fibers and resin-containing material and at least one of the plastic sheets and material therebelow is punctured by needles to remove air through the resulting passages. The resin can then be partially cured and the partially cured composite wound on a reel where it can be stored until molded. To obtain uniformity throughout the composite, the layers of resin-containing material deposited on the sheets must be uniform. Heretofore, this has required very careful blending of the materials for each of the sheets and very careful mixing thereof by kneading, when in the composite. In accordance with the invention, the layers of resin-containing material for the two outer sheets are supplied from the same source so that identical compositions are achieved for those layers. The blending and mixing steps are thus simplified or shortened by this arrangement with uniformity still being assured.

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Granville, OH, United States of America

John J McCluskey