GB820762A - Machine and process for the production of laminates - Google Patents

Abstract

820,762. Laminates; coating webs. MONTECATINI SOC. GENERALE PER. L'INDUSTRIA MINERARIA E CHIMICA. July 12, 1957 [July 18, 1956; June 28, 1957], No. 22117/57. Class 140. Laminates of paper, fabric, glass fibre or other material are produced by superimposing webs of the material impregnated with a curable resin and passing them through a heated curing chamber while maintained pressed against a flexible conveyer belt following a convex arcuate path. In an apparatus for carrying out the method the curing chamber is divided into sections maintainable at different temperatures. The upper part only of a horizontal conveyer belt may be convexly arcuate, the webs being held to it by tension produced by braking the supply rolls or by a second, superposed belt. Alternatively, webs from braked supply rolls may be passed around the lower, and almost completely around the upper, lap of a belt, both laps being convexly arcuate. Alkyd resins, with or without the addition of styrene, or methacrylate resins, may be used, and the webs may be initially coated with lowviscosity resin and allowed to stand in rolls, which are slowly rotated, to complete the impregnation, high-viscosity resin being applied to them on entering the laminating apparatus. Suitable constituents for a low-viscosity resin are propylene glycol, maleic anhydride, phthalic anhydride and styrene monomer, and a catalyst such as benzoyl peroxide; for a high-viscosity resin suitable constituents are maleic anhydride, diethylene glycol and diallyl phthalate. As illustrated in Figs. 6, 7 and 8, which show the left-hand, centre and right-hand parts of the preferred apparatus, a web of thin cover paper, and webs of kraft paper, all of which are preimpregnated, are supplied from rolls 38, 39, 40, 41 and 42, to a pair of intergeared steel pressure rollers 48, one of which is driven from a variable speed motor 66 and the spacing of which is regulable by screw means 58. The rollers 48 are in a plane at right angles to the desired direction of issue of the laminated webs. Highviscosity resin is supplied to each web through a perforated pipe 62 from reservoir 59 by a pump 60, and is held within the webs by upper and lower wider webs of " Cellophane (Registered Trade Mark) supplied from rolls 46, 47, past infra-red lamps 52, 52<SP>1</SP>. The shafts of the rolls 38-42 carry adjustable brakes to tension the webs and the laminate produced. A graduated tape 71 is fed in to one edge of the webs to enable the finished laminate to be measured and cut to length. The laminated, but uncured, web 64 issuing from the rollers 48 is delivered to a flexible stainless steel or other metal conveyer band 74 passing over a drum driven by a chain 78 from the motor 66. The band 74 travels over adjustable cross-bars 77 (Fig. 8 upper part, and Fig. 7 lower part) in a substantially elliptical path through a correspondingly shaped, five zoned, treatment enclosure 90, passing at the extreme end over an idler drum 76 (Fig. 8), the spindle 83 of which is slidable laterally in blocks to tension the band. This adjustment takes place under the influence of a weighted lever 87, movement of which rotates the spindle and a sprocket thereon over which passes an anchored chain 85. The laminate 64 passes with the conveyer band through the treatment zones and emerges beneath the centre part of the apparatus (Fig. 7) being supported beneath the band 74 by spring- pressed rollers 93. The first four zones, in which the laminate is heated to various temperatures, each comprise a fan 138 (Fig. 7) which circulates air through the enclosure 90 and pipes 143 and 137 and over a thermostaticallycontrolled heating element 144. If the laminated web becomes overheated, due to too rapid polymerization, a thermocouple 146 in the enclosure 90 actuates hydraulically operated dampers 148, 149, which interrupt the circulation and open an outlet for hot air and an inlet for cold air respectively. At the same time a second thermocouple 150 actuates a signal on a panel 67 from which the whole apparatus is controlled. The fifth zone is a cooling zone in which a fan 152, Fig. 8, draws in air at the point where the laminate emerges and discharges it through a pipe 153. On its return run the band 74 passes photoelectric cells 81, and mechanical feelers 82, Fig. 6, which respectively operate through hydraulic means on the spindle of the drum 75 to correct small lateral displacements of the band, and to stop the band in the event of larger displacements. On leaving the band 74 the laminate 64 passes over idler rolls 96, 97, Fig. 7, where the upper surface can be inspected and between pairs of adjustable circular edge-trimming knives 98 to a pair of positively driven variable-speed rolls 100 having screw or photo-cell operated lateral adjustments and hand wheel-operated pressureadjustment means whereby the tension of the laminated web throughout the apparatus may be controlled. Beyond the rolls 100 the cover layers of " Cellophane " (Registered Trade Mark) are separated and wound on rolls 118, and the resin on the under side of the laminate (the upper side in the apparatus) is ground off between rolls emery covered 122, 123. The finished laminate is severed by a guillotine 130 and wound up at 135. For initial impregnation each web is unwound from a braked roll such as 2, Fig. 1, passes beneath rolls 6, 7 in a trough 8 containing low-viscosity resin, to squeeze rolls 14, 15, mounted above the trough, and is wound up at 16. Excess resin runs down the web to the trough 8, thus assisting distribution on and impregnation of the web. The trough 8 is mounted on a linkage support 9, 9<SP>1</SP> controlled by a hand wheel 11 whereby the trough may be lowered and removed laterally by means of rollers 12 running on rails 13. The impregnated roll 16 is removed and placed, with others, in a frame having chain and sprocket means for slowly rotating all the rolls simultaneously during completion of the impregnation. The flanges of the rolls 16 have radial grooves 22 via which any excess resin escapes and falls into a trough in the base of the frame.