GB643999A - Improvements in or relating to methods of forming particulate-coated articles and the particulate-coated articles resulting from said methods - Google Patents

Abstract

643,999. Coated fabrics. MINNESOTA MINING & MANUFACTURING CO. Feb. 12, 1947, No. 4060. Convention date, Nov. 12, 1943. [Class 140] [Also in Group XXIII] Particulate-coated articles are made by positively holding each of a multiplicity of particles in a predetermined position with respect to each other and to a final bond during their application to the article, until the final bond has set, the final bond being an integral part of the article. The particles may be secured to a temporary support, as by means of a temporary adhesive, and subsequently embedded in the binder in which they are to be permanently held, this position being maintained until the binder has set, after which the temporary support is removed. The temporary support 20 may be withdrawn from a roll 21 and coated with temporary adhesive by a roll 22. It then passes over rollers and forms a horizontal flight F with the adhesive coated surface downwards, passing between electrodes E, where particles 26, fed from a hopper 27 on to a conveyer belt 28, are deposited upon it electrostatically, the excess being deposited in a receptacle 29. The permanent backing 30 is coated with the final binder 33 by a roller 32 and is applied to the particle-coated face of the support 20 at a combining roller 36, an adjustable pinch-roller 37 being provided if desired. The combined web is kept under pressure by rollers or by plates P until the binder has set, when the temporary support and adhesive are stripped off on passing between rollers 41, 42, leaving the particle-coated backing, which is collected separately. Alternatively, the particles may be applied by gravity to a temporary support previously coated with a normally tacky adhesive, and the thus coated surface brought into contact with a bindercoated backing, the webs being formed into a wet roll. After hardening of the binder, the roll is unwound and the temporary support stripped. The temporary support or adhesive may be embossed to present a pattern of varying contours. As temporary adhesives, glue, tanned or plasticized glue, resin, starch, dextrin, syrup, wax, pressure-sensitive rubber adhesives, casein and silicate cements are mentioned. A so-called " backless sandpaper " may be made by applying a combined binder and backing material in a viscous, plastic condition to a particle-coated temporary support; the combined binder and backing may be in the form of a coating on a web which is subsequently stripped off. The particle coating may previously have been given a sand-sizing coat, or a coating of a wetting agent to facilitate immersion in the permanent binder, e.g. furfural, when a phenol-formaldehyde resin binder is used. Articles comprising a particulate coating on a cloth, paper or other cellulosic backing, the binder being such that its curing temperature would destroy or damage the backing, e.g. metal, ceramic materials such as silicate cements, phosphate cements, phenolaldehyde resins, urea aldehyde-alkyd resin combinations, or methyl methacrylate resins, may be made by using a heat-resisting temporary support, such as steel, applying the binder to the particle coating and curing it, and then securing the permanent backing to the binder by a suitable adhesive, such as vinyl acetal resins, ethyl cellulose adhesives, or animal glue, and stripping off the temporary support, or the particles and binder may be deposited in the form of a layer and cured on a temporary heat-resistant carrier, a temporary support caused to adhere to the exposed surface, the layer and temporary support stripped from the backing, the layer then bonded to its permanent backing and the temporary support removed. The particles may be abrasive particles, which may be elongated and given an orientation, or they may be particles or beads of glass, stone, metal, flock, cork, mineral or roofing granules. In addition to sandpaper, floors or ships' decks may be coated according to the invention to provide a non-slip tread.