GB874072A - Improvements in or relating to the moulding of fibrous material coated and/or impregnated with plaster - Google Patents

Abstract

874,072. Moulding hollow articles &c. NAPRON Ltd. July 17, 1957 [July 17, 1956; Oct. 24, 1956; April 29, 1957(2)] Nos. 22046/56, 32394/56, 13532/57 and 13534/57. Class 87(2). A method of moulding comprises coating a mould with a layer or layers of fibrous material impregnated and/or coated with wet plaster, removing the lining after it has stiffened sufficiently to permit this, drying the removed lining, and impregnating it from one or both sides with a synthetic resin element. Preferably a mould is coated with a release agent such as shellac, paraffin wax, or linseed oil, and is lined with a paper layer which may may be wetted with water, or starch or flour paste, and patterned to simulate wood. To the paper layer is then applied a coating of wet plaster which may be reinforced with a water-soluble urea-formaldehyde resin. After withdrawing the lining from the mould it is impregnated with a synthetic resin cement, e.g. a phenol-formaldehyde or styrenated alkyd resin. Alternatively the mould may be lined with at least one layer of glass fibre impregnated with wet plaster. If a hollow article with a smooth inner surface is required the glass fibre-plaster layer or laminate may be covered with a paper layer. The lined mould may be heated internally by burners, radiators, or hot air. Coffins, sewing machine covers, pram bodies, ducting, transformer casings furniture, and car bodies may be made by the method. Reinforcement, e.g. a wooden rail along an edge of a sewing machine cover, may be embedded between layers of fibrous material during the process. Hollow ware of such shape as to prevent easy removal from the mould may be formed in two parts which are brought together before the final drying and, if desired, before impregnation with the synthetic resin cement, and the seam lapped over with fibrous material such as paper or glass cloth. A laminated hollow body may be moulded by forming two shells of plasterimpregnated fibrous material of slightly differing sizes, and placing the smaller within the larger with an intermediate layer of synthetic resin cement which may contain glass fibres. As further alternatives the mould may be lined with textile fabric, wood veneer, leather cloth or a leather substitute comprising a flexible web coated on one side with polyvinyl chloride. In the example described with reference to Fig. 1, a mould 1 is lined with wood veneer 2 coated internally with a thin layer 3 of an aqueous slow setting plaster containing urea-formaldehyde resin reinforcement. A thick layer 4 of glass fibres mixed with a similar but less slow-setting plaster paste is then applied. When the whole has set sufficiently it is removed, allowed to dry, and then impregnated with styrenated alkyd resin. Manufacture of a coffin as disclosed in Specification 874,073 is described.