GB802682A - Improvements in or relating to the production of moistureproof sheet wrapping materials - Google Patents

Abstract

802,682. Coating webs. BRITISH CELLOPHANE, Ltd. Feb. 1, 1956 [Feb. 4, 1955], No. 3412/55. Drawings to Specification. Class 140. Apparatus for coating a travelling web comprises a pair of spaced parallel rollers with axes in the same horizontal plane between which rollers, when the apparatus is in use, a pair of sheet materials is passed and coated with a liquid coating composition in the nip formed between the sheet materials, bearings for the rollers slidable in a horizontal plane to permit the rollers to move away from or towards each other, a pair of shoes for each roller placed one at each end of the roller, for riding in contact with the barrel of the roller or with a hub formed on the roller, each of said shoes at adjacent ends of the rollers being held in a fixed relationship to the other, and urging means for pressing each roller into contact with its shoes. The urging means may comprise spring, or fluid pressure means and may be applied to the roller barrels, the hubs or the bearings. The shoes at adjacent ends of the barrel may be placed back to back or may be in a face to face relationship and in the former case adjusting means may be present between the shoes, to expand or contract the gap between the rollers. The hubs may be formed integral with the rollers, e.g. by grinding the hub and the barrel in one operation or they may consist of cylinders of hard metal rigidly attached at each end of the roller. The shoes may be of steel or cast iron, and may be lined with e.g. bronze or white metal, and may be provided with lubricating means. When the end shoes are in back-to-back relationship, further shoes which ride in contact with the curved surface of the rollers may be provided and the centre of the area or line of contact or the resultant centre of the lines of contact thereof is arranged to be diametrically opposite the nip formed by the rollers and in the centre of the axial length of the roller barrel. These further shoes may consist of arcuate shoes which may be of hard material and be smooth and highly polished, e.g. of phosphor bronze or polytetrafluorethylene. They may also be in the form of a backing roller whose axis is parallel to the axes of the barrels, or they may be in the form of a block having four wheels riding in contact with the roller. Guards may be provided over the hubbed part of the rollers, dust being excluded by rubber seals. The rollers may be driven so that the peripheral speed of the barrels equals the speed of forward travel of the film being coated or one roller only may be driven and the other moved by contact with the moving film or both rollers may be driven by the turning movement of the films associated with them. In examples a water-sensitive, organic, non-fibrous film, e.g. of regenerated cellulose, is coated with an aqueous dispersion of a vinylidene chloride/ acrylonitrile copolymer. Specifications 2702/07, [Class 138], and 663,645 are referred to.