Patent GB-848080-A (GB)
Title: Improvements in the manufacture of voluminous yarns
Inventor: GROOMBRIDGE DENIS WILLIAM
IPC: D01D5/04
Filed: 1956-05-09
Abstract: Voluminous yarns are made by a dry spinning method which comprises extruding a solution of a filament forming substance in a volatile solvent into an evaporative atmosphere through two sets of orifices of differing dimensions contained in a single spinning jet, bringing the two sets of filaments formed respectively by the two sets of orifices together to form a single yarn after they have become substantially completely set, drawing the said yarn away, and winding it up, the dimensions of the orifices in one of the sets being so correlated with the rate at which the solution is supplied to the spinning jet and with the rate at which the yarn is drawn away that the linear rate of extrusion of the solution through them is at the most equal to the rate at which the yarn is drawn away so that substantially uncrinkled support filaments are formed thereby, and the dimensions of the orifices of the other set being so correlated with the same factors that the linear rate of extrusion of the solution through them is above that at which the solution immediately after extrusion, and the filaments which it forms, will tend to travel through the cell under the influence of various forces acting on them at any point up to and including that at which they come together with the support filaments to form a single yarn, so that crinkled filaments are formed thereby.  Preferably the support filaments and crinkled filaments are brought together while still in the spinning cell.  Apparatus for carrying out the process above comprises, a spinning jet in which the orifices are of two types, those of the one type being at least twice as long as those of the other and also of cross sectional area such that they offer a higher resistance to the passage of a viscous liquid.  The lengths of the individual orifices can be varied by countersinking them to various depths, or by countersinking some and leaving others untouched. Preferably the two types of orifices are grouped separately, e.g. in two concentric circles differing in diameter by at least 5 mm. Preferably too, the support filaments are extruded from the longer set of orifices, which may in addition have a larger cross sectional area than the crinkled filament orifices.  The yarn is drawn away at a rate equal to or higher than the rate at which the solution is extruded to form uncrinkled support filaments.  The filament forming material from which the voluminous yarns are made may be a cellulose ester of a lower fatty acid of up to 4 carbon atoms, e.g. acetone-soluble cellulose acetate, or triacetate, or polymers and copolymers of acrylonitrile, vinyl chloride and other vinyl compounds.  With reference to dry spinning of acetone-soluble cellulose acetate, the spinning solution may be heated, e.g. to 50 DEG -80 DEG  C. before extrusion and may contain a pigment or dyestuff.  Preferably the rate of travel of the support filaments when the crinkled filaments first make contact with them should be less than 0,8 times the rate of extrusion of the crinkled filaments. The spinning jet used may have sets of orifices of other than circular cross section, e.g. semi-circular, slot-like or crescent-shaped.