GB578699A - Improved process and apparatus for producing composite sheet material - Google Patents

Abstract

578,699. Compound sheet materials. INDIAN JUTE MILLS ASSOCIATION, and ANGELO BROS., Ltd. Jan. 12, 1944, No. 649. Convention date, Feb. 17, 1943. [Class 140] Compound sheet material suitable for boards, panels, or tea-chests is made by uniting in a continuous manner webs of woven fabric, using shellac or modified shellac, applied without solvent, as adhesive. The fabric layers are drawn under tension through apparatus in which they are preheated to melt or keep molten the shellac, and then subjected to hot compounding pressure followed by cold compounding pressure. A woven fabric F, Fig. 1, with a coating C of shellac on one side is passed around a guide roller 22, a heated positively driven roller 2, and is united by the shellac so melted to another fabric F' which may or may not be coated but is preheated by a heated roller 5, in the nip formed between the heated roller 2 and the unheated pressure roller 1. The united layers are further compressed between roller 1 and a further unheated pressure roller 10, and are drawn out of the apparatus under a tension roller 14 by rollers 15, 16 with roughened or rubber-covered surfaces. Two fabrics may be fed together around the preheating roller 2, to produce a three ply fabric. One or both preheating rollers 2 and 5 may be supplemented by one or more further preheating rollers. An endless metal band, which may also be heated. may travel around two or more of such further rollers or around the preheating roller 2 or 5 and one or more further rollers. Alternatively, the preheating rollers 2 and 5 may be preceded by a hot plate over which the fabric passes. In the form shown in Fig. 5 two fabrics F, F' each with a coating C, C' of shellac, are led around heating rollers 2 and 5, united in the nip between these rollers, the compound fabric is subjected to cold compression between rolls 1 and 10 and is drawn under tension through the apparatus by tension and draw rolls similar to 14, 15, 16 of Fig. 1. An intermediate layer F', Fig. 5, of uncoated woven fabric or of other sheet material may be modified or supplemented by other heating devices in the same way as the rollers 2 and 5 of Fig. 1. The fabrics may be of open or close, plain or twill weave, of jute, cotton, or flax. An intermediate or external layer of paper or cardboard, which may be waxed or metal-surfaced, metal foil, metal mesh, or thin wood veneer may be added. Natural shellac, shellac ester, or shellac modified by a heat-treatment, if desired, in the presence of lime, aluminium chloride, or hexamethylene tetramine, may be used. Pigments, plasticizers such as castor oil or triphenyl phosphate, waterproofing, insecticide or fungicide materials may be added. The shellac may be applied molten to one or more of the fabric layers and allowed to solidify before passing around the roller 2 or 5 where it is re-melted. Alternatively powdered shellac may be applied to the fabric as it passes around a roller 2 or 5 or over a travelling band or hot plate, or molten shellac may be poured or sprayed on the fabric as it passes over the preheating roller 2 or 5 or other preheating device, or directly into the first compression nip.