Patent GB-992726-A (GB)
Title: Method and apparatus for encapsulating strandular articles
IPC: B29C48/08
Filed: 1962-05-18
Abstract: 992,726. Web coating apparatus. DOW CHEMICAL CO. May 18, 1962 [May 31, 1961], No. 19229/62. Heading D1L. [Also in Division B2] Substantially continuous strandular substrates e.g. mono- and multi-filaments, yarns spun of staple fibres, ribbon, tape, or a substrate consisting of a multiplicity of strands or tapes, or strands and tapes, which may be boned in substantially sideby-side relationship by the thermoplastic coating material, are encapsulated in a thermoplastic material by applying a layer of heat-plastified normally solid thermoplastic material to coacting rolls, and passing the substrate into the zone of the heat plastified material between the coacting rolls in a direction opposite to the direction of rotation of the rolls. The strandular substrate is passed through an opening provided between the rolls of the reverse roll coater, the opening being created by the presence of a circumferential groove in at least one roll of the coating rolls. The encapsulated substrate may be given a subsequent shaping or forming treatment. The strandular substrate 11, 14, may be of natural or synthetic origin such as glass fibres, and may contain or consist of cellulose e.g. rayon, regenerated cellulose, polyamides e.g. polymerized e-caprolactam, copolymerized hexamethylene diamine and adipic acid, polyesters e.g. polyethylene terephthalate, acrylics e.g. polymers containing at least 80% acrylonitrile, polyolefins e.g. polymers of ethylene and propylene, and copolymers of ethylene and propylene. The thermoplastic material 12 may be normally solid and may consist of or contain the interpolymerization product of one or more monoolefinic monomers containing from 2 to 8 carbon atoms per molecule e. g. polymerized ethylene, propylene, butylene, or mixtures thereof, polymers of vinyl chloride, vinylidene chloride, and copolymers thereof with other vinyl monomers, polyamides, polyesters e.g. polyethylene terephthalate, cellulose ethers and esters. The substrate may be given a surface-conditioning treatment prior to encapsulation with, for example, titanates, titanium organics or resinous organic nitrogen polymers such as a polyalkyleneimine e.g. polyethyleneimine. The temperature of the thermoplastic material on the rolls is maintained above its melting point and below its decomposition temperature. As shown, yarns 11 are led through spacer 16 and into the nip between driven rolls 17 rotating in the direction of travel of the yarns. The yarns pass through an orifice like opening formed by coacting regular circumferential grooves between rolls 18 which may be heated and which rotate counter to the direction of travel of the yarns. Molten resin 19 is introduced through ports 20 to encapsulate the yarns to create tape 10 which is smoothed or embossed and possibly cooled by rolls 21, driven in the direction of travel of the tape. The roll coating apparatus may be tilted or the rolls may be moved such that the plane containing the roll axes is other than perpendicular to the plane of the substrate passing therebetween. The resin may be applied under pressure in the form of a melt, powder, flakes, or granules which melt on the heated roll. The side of the orifice opposite to which the substrate enters may be pressurized thus creating a film bubble generator. Apparatus for encapsulating a substantially continuous strandular substrate with a normally solid film-forming thermoplastic material comprises, in combination, a header means 26 for delivering the thermoplastic material in molten form to co-operating channels in a roll housing 27, damming means to control the flow of the molten material in the direction of rotation of the rolls 28, coacting rolls and means for supporting the rolls in the housing, and means for passing the substrate between the rolls in a direction opposite to the direction of the rotation of the rolls. Header 26 is provided with an inlet or primary port 29, through which molten resin is fed under pressure to sleeve 34, via secondary port 31 and branch ports 33, which sleeves terminate adjacent rolls 28 and are provided with a protuberance or dam 38 which extends towards and along the sides of grooves 39 in rolls 28. Rolls for coating and bonding together a series of independent yarns, cords, and wires are shown in Fig. 8. Fig. 9 shows substrate 11 passing between coating rolls 45, the resin 12 being delivered to and supported between rolls 45, 46. The resin may be molten or delivered as a solid which is melted between rolls 45, 46.