Patent GB-1148095-A (GB)
Title: Improvements in and relating to the manufacture of fabrics
Inventor: GRAY THOMAS EDWARD HORACE
IPC: D04H3/16
Filed: 1965-09-22
Abstract: 1,148,095. Reticulated films. DUNLOP CO. Ltd. 22 Sept., 1966 [22 Sept., 1965], No. 40480/65. Heading B5B. [Also in Division D1] A method of manufacturing a net or net-like fabric comprises moving a die along a zig-zag course for a predetermined distance and simultaneously extruding a "plastic material" (as hereinafter defined) from the die on to a stationary support surface, and at the end of the said predetermined distance moving the die or support surface or both relative to one another in a direction perpendicular to the resultant direction of the said zigzag course, moving the die along a second zigzag course for a second predetermined distance in a resultant direction substantially parallel and in reverse to the firstmentioned resultant direction and simultaneously extruding a plastic material from the die on to the stationary support surface, so that part of the plastic material deposited along the first-mentioned zigzag course is contacted by at least part of the plastic material deposited along the second zigzag course. The term "plastic material" is defined as meaning a substantially dry, vulcanizable, natural or synthetic rubber composition capable of extrusion and selftacky in the unvulcanized state; a solution or aqueous dispersion of a natural or synthetic rubber which is solidifiable on removal of the solvent or by coagulation and drying; a synthetic thermoplastic composition capable of melt or compression extrusion and settable by cooling and which is self-tacky prior to being fully set; a thermosettable resin composition capable of extrusion and being self-tacky prior to being fully set; and a wet, spinnable, regenerated cellulose-producing composition or a protein fibre-producing composition settable by coagulation. Examples include natural rubber, polyvinyl chloride, interpolymers of butadiene and styrene, interpolymers of butadiene and acrylonitrile, polybutadiene, synthetic cis-polyisoprene, interpolymers of isobutylene with diolefines, interpolymers of ethylene and propylene with or without a further monomer to confer unsaturation on the interpolymer, polyolefines, e.g. polyethylene and polypropylene, interpolymers of butadiene, styrene and acrylonitrile, a polyurethane-forming composition, liquid polyepoxide resins, and viscose. The plastic material may be employed in the form of a latex or a solution. When natural or synthetic rubber is used, the composition will usually contain vulcanizing ingredients for the rubber and the composition can be at least partially vulcanized by heat subsequent to its deposition in the form of the net or net-like fabric on the support surface. The polyurethaneforming composition can be a fluid pre-polymer composition based on the reaction product of a polymeric diol, e.g. a polyether diol or a polyester diol, and an organic polyisocyanate. A chain-extending agent or a cross-linking agent can be mixed with the composition as desired. Alternatively, the polyurethane-forming composition can be a "one-shot" composition in which a polymeric diol, a polyisocyanate and a cross-linking agent or chain-extending agent, as desired, are mixed together immediately prior to extrusion through the die. In operation of the apparatus shown, a plastic material is fed through feed pipe 2 and is extruded from die nozzle 1 on to the upper surface of belt 14. During extrusion, die nozzle 1 is reciprocated over a predetermined distance by rotation of shaft 4 and at the same time the knee member 6 is moved perpendicularly to the direction of reciprocation of die nozzle 1 from a position near one edge of the belt 14 to a position near the other edge thereof over a predetermined distance by rotation of the shaft 12, thus causing die nozzle 1 to move in a zigzag course resulting in deposition 20 of plastic material along the zigzag course of the belt 14. The rotation of shaft 12 is co-ordinated with the rotation of shaft 16 so that when knee member 6 reaches one extremity of its travel across the belt 14, the finger 17 engages between two teeth 18 of toothed wheel 19 and rotates wheel 19 through a predetermined distance, thus causing belt 14 to move through the predetermined distance perpendicularly to the direction of reciprocation of die nozzle 1. The movements of the belt 14 and the die nozzle 1 across belt 14 are governed mainly by the choice of the wheel and crank mechanism 3, the cam 9 and the toothed wheel 19. The nozzle may have a variety of shapes so as to produce a strand of plastic material having various crosssections, e.g. triangular, rectangular, circular, or any other cross-section or shape that will allow the extruded plastic material to adhere to itself at the points of contact upon the zigzag courses. The support surface is preferably made of material inert to the extruded plastic material and from which the resulting net can be easily released, a suitable material being polyethylene. Each zigzag course of the die may be uniform, i.e. of constant amplitude and wavelength, or non-uniform, i.e. having more than one amplitude and/or wavelength. Adjacent zigzag courses may have the same or different patterns and the plastic material deposited along adjacent zigzag courses may be in contact by abutment or overlap or both. As shown, the plastic material deposited along each course may be displaced laterally from that deposited along an adjacent course by a distance equal to the amplitude of the zigzags, and also by each zigzag course being out of phase with an adjacent course by half a wavelength. If desired, the amplitudes of the zigzag courses and the distances through which the support surface is moved relative to the die in a direction perpendicular to the resultant direction of the zigzag courses at the end of each zigzag course can be such that the plastic material deposited along the course is contacted not only by material deposited along the immediately adjacent courses but also by material deposited along at least one zigzag course further away than the immediately adjacent course. The predetermined distances of the zigzag courses may be the same for all courses, thus forming a net of constant width, or the predetermined distances can vary, thus forming a shaped net or net-like fabric. Extrusion of the plastic material may be continuous during manufacture or it can be discontinued at the end of at least one predetermined distance and restarted when the die and/or support surface have moved in a direction perpendicular to the resultant direction of the last completed zigzag course. Extrusion can be discontinued and restarted at any time during manufacture, thus forming a net or net-like fabric having holes of desired shapes at any desired positions. Adhesion between the extruded stranded plastic material at the points of contact may occur by vulcanization, solidification or coagulation, depending on the nature of the plastic material. An example is given relating to the production of an elastomeric polyurethane net.