Patent GB-732774-A (GB)
Title: Improvements relating to the production of decorated articles from thermosetting synthetic resins
IPC: B29C43/18
Filed: 1951-04-26
Abstract: An absorbent paper wafer to which a design has been applied is subjected to a degreasing operation to remove any oily or fatty matter that may be in or on the wafer; the degreased wafer is then impregnated with synthetic resin solution, dried and applied to the surface of the thermo-setting resin article being moulded, the application being effected before curing of the article is complete; whereupon curing is completed.  The design may be applied by printing, in which case oil in the printing ink is removed by the degreasing, or by photography or a hand process. The wafers may be prepared individually or may be cut out many at a time from a large sheet of a material including a synthetic resin, preferably partly cured, to which one or more pieces of design-bearing paper have been bonded.  Paper strip bearing the design may be passed from a roll successively through a degreasing bath, an oven, a bath of synthetic resin solution, stainless steel rollers to remove excess resin solution and another oven to a take-up roll or to a cutter or punch which cuts off or cuts out individual wafers (Fig. 6, not shown). The article may be moulded by several methods.  In one method moulding powder is pressed hot into the shape of the article, the resin being thereby partly cured (the resin may be phenol-, urea-, thiourea- or melamine-formaldehyde), the mould is opened, the wafer is placed on the article or on the mould, the mould is closed and hot-pressing is complete; in such a method the wafer may cover only a part of the surface of the article (e.g. tea plate) being made (Figs. 1 to 4, not shown) or the whole of the article (Fig. 5, not shown); the wafer may be applied by hand or by the aid of the mechanical guiding means described in Specification 739,802. In another method the degreased design-bearing paper wafer is first applied to a thin sheet of resin-impregnated paper to form a duplex sheet, as described in Specification 739,801, then this sheet is applied to a resin-impregnated paper backing to form a sandwich, the design-bearing paper wafer being in the middle.  The backing may comprise one, two or three sheets of thin paper.  The sandwich may be left flat or moulded to shape.  The surface of the backing is roughened as by sandblasting to improve bonding.  The sandwich is put into a recess in the mould, backing side away from the mould, moulding powder is placed in the mould, and the article formed by hot-pressing.  The wafer is rendered transparent by the curing of the resin therein, and the design is seen therethrough as a reversed image of the design originally printed.  The resin for the design-bearing paper may be melamine-formaldehyde, that for the backing urea-formaldehyde, and that for the article urea- or phenolformaldehyde.  In a modification of this method the backing is placed against the mould and rendered transparent during moulding, the design on the moulded article being then seen through the backing directly, i.e. not reversed.  In a further modification the moulding powder is initially pressed to shape as a coherent tacky mass, then the wafer is put into the mould recess and finally the moulding is completed.  Where the design is to be seen through a paper layer, the paper is preferably free from pigment.  Where a layer of paper is behind the design it may be opaque, to hide the colour of the article itself, and may be coloured.