Patent GB-535263-A (GB)
Title: Manufacture of artificial filaments
IPC: D01D5/08
Filed: 1939-10-02
Abstract: 535,263. Artificial filaments ; resinous condensation &c. products. DU PONT DE NEMOURS & CO., E. I. Oct. 2, 1939, Nos. 27006 and 27007. Convention dates, Sept. 30, 1938 and July 6, 1939. [Classes 2 (ii) and 2 (iii)] Tapered filaments are obtained by extruding a molten filament-forming synthetic polymer and causing at repeated intervals uniform variation in the mass of polymer passing a given point beyond the extruding device, the diameter of the filaments produced being not less than 3.5 mils. The variation in thickness of the filaments along their length may be effected by varying the rate of extrusion or the take-off rate. The filaments may be cut at the thick or thin sections or both to form bristles. The tapered filaments may also be used for fishing leaders, and fishing lines. The speed at which the filaments are withdrawn from the spinneret may be varied by using elliptic gears attached to a pair of pinch rolls, or by using eccentrics, cams, or irregularly shaped rolls. Bristles in which the size decreases from the maximum to the minimum in a length of one and a half inches, or fishing lines in which the interval is fifteen feet may be obtained. The tapered filaments may be subjected to a cold-drawing operation. A molten polyamide may be extruded to form a filament which is passed through a quenching bath to a take-off mechanism which is run with uniformly varying speed so as to obtain a tapered filament. The filament is soaked in water or other mild swelling agent and then elongated to several hundred per cent. of its original length., It is then subjected to a setting treatment with hot water, steam, or other mild swelling agent. Polyamides from diamines and dibasic acids or from amino acids or lactams, and preferably those having an intrinsic viscosity above 0.4 may be used. As shown in Fig. 1, the molten polymer is extruded through spinneret 2 to form a plurality of filaments which combine to form a single bundle of filaments 4. The filaments pass round roll 5 partly submerged in water 12 and they are drawn by pinchrolls 6. These rolls are driven by means of two meshing elliptical gears or cams 7. As shown in Fig. 3, the filaments are cold-drawn by passing them between rollers 16-21. Rollers 16-18 are geared together and rollers 19-21 are geared together and run at a higher speed, e.g. four times the speed of rollers 16-18. Some of the stretching rollers may be covered with rubber and others may have a metal surface. The points between which stretching occurs are preferably very close together when tapered bristles are being stretched in order to avoid breakage. The bristles may be used for making paint brushes. They may be pointed at the tips by holding against a disc of revolving sandpaper and may be vulcanized into a brush handle. When making bristles, the filaments may be cut at the thin portions so as to produce bristles with a thick middle portion and thin ends. In making brushes, these bristles are bent so as to bring the thin ends together. A bar is passed through the loops formed by the bent bristles and secured at either end of the brush. Variation of thickness may also be obtained by reducing the speed of uniformly rotating take-off rolls below a certain minimum at which oscillation of the filaments in the quenching bath begins. This oscillation produces a varying rate of take-off. Polyamides which may be used include decamethylene adipamide, hexamethylene adipamide, hexamethylene sebacamide, 6-amino caproic acid polymer, 11-amino undecanoic acid polymer, mixed polyamides, interpolyamides, polyamides containing ester or other groups, e.g. one obtained from a diamine, a dibasic acid and a glycol, or one from an amino acid and a hydroxy acid. Polymers derived from a glycol and a di-isocyanate or isothiocyanate are included. The filaments may contain plasticizers, pigments, dyes, fillers, resins, or other substances which are incorporated in the polymer composition or by treatment of the formed filaments. The filaments may be dyed with Calico Black or Sudan Brown. The bristles may be modified by grinding, splitting, or otherwise treating the tips so as to improve paint retention and brushing properties. The bristles may be used for pastry, bottle, polishing, or tooth brushes. The filaments may be used in millinery. Bristles may be attached to the ferrule of a brush by setting them in a solution of methyl methacrylate polymer in methyl methacrylate monomer and completing the polymerization. Specification 461,236 is referred to.