Patent GB-399811-A (GB)
Title: Improvements in or relating to the production of artificial straws or like materials
IPC: D01D5/00
Filed: 1932-04-07
Abstract: Unitary filaments of flattened cross-section are produced by associating a plurality of individual artificial filaments in the form of a flattened thread and then applying a solvent, restricted solvent, or softening agent to the thread by means of an applying surface adapted to maintain the filaments in the desired form so as to cause the filaments to coalesce, the application of pressure being unnecessary.  The filaments may consist of cellulose acetate or other organic derivative of cellulose; filaments of cellulose formate, propionate, and butyrate, of nitrocellulose, of ethyl and benzyl cellulose, and of condensation products of cellulose and glycols or other polyhydric alcohols are specifically mentioned. By using suitable solvents such as zinc chloride solution or Schweitzer's reagent, viscose or cuprammonium artificial filaments may also be caused to coalesce in this manner.  The filaments united <PICT:0399811/IV/1> may be elementary filaments, or may themselves be unitary filaments of rounded or other cross-section, formed by the coalescence of a number of elementary filaments.  The production of the ribbon may take place continuously with the production of the filaments by the wet or dry methods, and while they are proceeding to a winding or twisting and winding or other collector device, or during a bobbin-to-bobbin or other winding or twisting and winding operation.  Solvents specified for use in conjunction with filaments of cellulose acetate or other organic derivative of cellulose are low boiling solvents such as acetone, ethylene dichloride and ethyl or methyl alcohol, dichlorethylene and ethyl or methyl alcohol, and the like, also medium or high boiling solvents or plastifiers such as diacetin, triacetin, ethyl lactate, diacetone alcohol (alone or mixed with water or alcohol), dibutyl tartrate or tricresyl phosphate, and mixtures thereof. When volatile solvents are employed, means may be used to assist in the evaporation thereof from the product, if desired in conjunction with the recovery of the solvent.  Solvents or softeners not removed by evaporation may be allowed to remain in the products or may be removed by washing.  The application of the solvent may be effected by passing the filaments over wicks, rods, or rollers dipping into or otherwise supplied with the solvent, or by passing the filaments between two such applying surfaces, for example, with the aid of the moistening device described in Specification 366,585.  The amount of solvent applied may be rendered adjustable, so that products retaining the form of the individual filaments, or products in which the filaments have completely coalesced, may be obtained as desired. The finished ribbon may be collected by simple winding on to a bobbin, or by hanking. Stickiness due to residual solvent may be removed by applying a suitable lubricant, for example, by means of a wick.  The formation of the flattened thread prior to application of the solvent may be effected by passing the elementary filaments round curved surfaces of relatively small diameter, or by passing them through a reed adapted to separate them and hold them in any desired form.  After passing them through such a reed, the flattened bundle may be twisted slightly to increase the thickness of the ribbon, for example, by passing the filaments round a rod or bar set at a suitable angle. The adhesion of the filaments may be assisted by maintaining the threads under tension, for example, by means of a gate tension device, which may also serve to bring the filaments initially into association in a flattened form.  The threads formed may then be collected under tension.  Alternatively, tension rollers may be employed to impart tension to the filaments either before or after adhesion, or both.  In the case where tension is applied after adhesion, the necessary are of contact between the filaments and the rollers should be maintained by means of nipping rollers or jockey rollers.  Ornamental effects may be produced in the products by the incorporation of effect materials, or by other methods as described in Specification 368,738.  The ribbons, tapes, or straw-like products may be woven or otherwise formed into fabrics, and may be used in millinery or for electrical insulation purposes.  In the apparatus shown, the filaments 3 drawn from bobbins 4 through guides 5 on the axes of the bobbins, are led through a number of closely spaced pigtail guides 6 mounted on a bar 7, forming a flat ribbon 8.  The filaments are then passed in a zig-zag manner between vertical rods 9 which cause the filaments to form a compact ribbon 10 lying in a vertical plane.  The ribbon 10 passes through the device 11 wherein solvent is applied from the surfaces of wicks 12 which maintain the ribbon in the flattened condition.  The unitary thread 13 so formed is passed through a drying chamber 14 provided with steam pipes 15, air being drawn off by means of a pipe 18 and passing in the opposite direction to the filaments, going finally, if desired, to a solvent recovery plant.  The ribbon 13 then passes to guides 19 and a collapsable reeling device 20 which provides the power drawing the filaments along their path.  The device 11 is an elaboration of that described in Specification 366,585, and comprises a pipe leading from the bottom to a piece of flexible tubing bent into the shape of a U and connected at the other end to a pipe which can be fixed at any desired height to the vessel by means of an adjustable clip.  In this manner the level of the solvent in the vessel can be varied as desired, and thus the amount of solvent applied can be adjusted. Specification 328,312, [Class 2 (ii), Cellulose &c.], also is referred to.