Patent GB-993517-A (GB)
Title: Treatment of sheet material
IPC: D06M17/06
Filed: 1960-05-13
Abstract: A method of applying to substantially dry sheet material, which is disposed in a gaseous medium such as air, a substantially water-insoluble stable synthetic polymeric material in powder or granular form, or natural or synthetic rubber in the form of granules coated with a stable synthetic polymeric material, comprises allowing the powder or granules to fall by gravity upon the sheet material so that the powder or granules adhere to the sheet material as discrete spaced particles, heat and if desired pressure being applied to make the discrete particles adhere to the sheet material, the heat and pressure applied being not so great as to cause the discrete particles to coalesce into a continuous shteet or into large aggregates.  The sheet material may be a fabric or a foamed material which may be flexible, e.g. polythene, polyvinyl chloride, polyvinyl acetate, natural or silicone rubbers, butadiene-methyl methacrylate, rubber-modified phenolic resins, and polyurethane; semi-stiff, e.g. butadiene-styrene, and rubberized polystyrene; or rigid, e.g. styrene polymers or copolymers, phenolic and polyester resins. The synthetic polymeric material may be a thermosetting resin, a normally thermoplastic material which is adapted to be further treated on the fabric to yield a thermosetting material, or a thermoplatsic material which softens between 80  DEG C. and 200  DEG C., e.g. polyethylene. The average distance between the discrete particles may be approximately three times the average diameter of the particles.  The diameter of the discrete particles may vary from 0,005-0,125 inch. The powder or granules may be allowed to fall upon a moving sheet, e.g. from a container therefor which moves or vibrates when the particles or granules are allowed to fall.  The treated sheet may be vibrated or otherwise moved after the powder or granules have been deposited in order to cause the particles to assume their final discrete distribution and may be moved linearly in its own plane whilst the particles are allowed to fall upon it from a source of supply which is moved transversely of the direction of movement of the sheet.  The sheet may be heated before the particles are applied.ALSO:Apparatus for carrying out a method of applying to substantially dry sheet material which is disposed in a gaseous medium such as air a substantially water insoluble stable synthetic polymeric material in powder or granular form, or natural or synthetic rubber in the form of granules coated with a stable synthetic polymeric material, by allowing the powder or p  granules to fall by gravity upon the sheet material so that the powder or granules adhere to the sheet material as discrete spaced particles, heat and if desired pressure being applied to make the discrete particles adhere to the sheet material, the heat and pressure applied being not so great as to cause the discrete particles to coalesce into a continuous sheet or into large aggregates, comprises a conveyer for carrying the sheet to be treated, a hopper disposed above the conveyer to carry powder or granules of the polymeric material, means for heating the polymeric material upon the sheet, and means for dispensing the polymeric material from the hopper on to the sheet as it is conveyed so as to effect together with the heating means a uniform distribution of discrete separate particles adhered upon the sheet, the dispensing means including a slot in the hopper extending transversely of the conveyer and means for opening and closing the slot to adjust the rate of fall therethrough of the powder or granules.  The dispensing means may include a lip extending beyond the slot in the longitudinal direction of the conveyer, and may also include means e.g. an electric vibrator, for vibrating the lip.  The lip may extend horizontally from the slot and may also extend transversely across the full width of the sheet.  The heating means may comprise an oven or an infra-red lamp or a plurality of infra-red lamps adjustable in number and/or position.  The apparatus may comprise means for heating the sheet in advance of the dispensing means.  Apparatus for making laminated sheet material by applying discrete spaced particles upon a first sheet so that they adhere thereto as set out above wherein the polymeric material is a thermoplastic material which softens between 80 DEG C. and 200 DEG C., laying against the first sheet a second sheet so that the discrete particles are between the sheets and uniting the sheets by heat and if desired pressure, the discrete particles having a heat softening point which is lower than the heat softening point or scorching point of either sheet, comprises the apparatus set out above comprising a conveyer for conveying two superposed sheets with thermoplastic discrete particles therebetween and a pair of driven rollers spaced by the conveyer, one of the rollers being heated to a temperature sufficient to soften the particles, the rollers being spaced and arranged to apply pressure to unite the sheets.  Examples of sheet materials and polymeric materials are given.