Patent GB-578324-A (GB)
Title: Improvements in or relating to the drawing of tapered artificial filaments
IPC: D01D5/20
Filed: 1944-04-28
Abstract: <PICT:0578324/IV/1> <PICT:0578324/IV/2> Artificial filaments, preferably those prepared from synthetic linear polyamides, having recurring tapered portions uniformly disposed along their length are cold drawn between widely-spaced draw points while heating them to a temperature of between 40 DEG  and 100 DEG  C., the drawing tension being of insufficient magnitude to cause rupture of the filaments, but sufficient to effect drawing of the portions of greatest diameter to at least 80 per cent of the extent to which they are capable of being cold drawn.  Drawing is effected between two pairs of driven rollers, the respective pairs being driven at different peripheral speeds and the rollers of each pair being driven at the same peripheral speed.  Heating of the filaments is effected by passing them through a heated aqueous solution, preferably hot water, or other heated liquids such as aliphatic and aromatic hydrocarbons, or by heated gases or vapours such as air, nitrogen and steam which are inert towards the filaments.  A plurality of filaments having their tapered portions in phase may be simultaneously drawn, in which case a guide is provided to arrange the filaments side by side in ribbon-like configuration.  The draw points are preferably spaced at a distance not less than five times the unit length of the tapered portions of the drawn filaments, and the filaments are preferably drawn at such a rate that it takes at least two seconds for a point on a filament to pass between the draw points, during which time it is in contact with the heating medium for at least one second.  A pigment may be added to the polymer or to the polymer forming reactants or the filaments may be dyed, and the cold drawn filaments may be subsequently conditioned and cut into bristles.  The process is also applicable to tapered films.  The filaments are preferably formed from polyamides prepared from bifunctional polyamide forming reactants, and they may contain groups other than the amide groups, e.g. ester groups.  Mixtures of polyamides and interpolyamides may also be used and the term polyamide is inclusive of such polymers as those derived from glycol and a diisocyanate or a diisothiocyanate. Numerous suitable polyamides are specified, among which the superpolyamide hexamethylene sebacamide or hexamethylene adipamide alone or in admixture with phenol-formaldehyde resin is stated to be suitable for the manufacture of paint brush bristles.  Referring to Fig. 2, the tapered filament 23 coming from a spool or directly from the preceding operation, is cold drawn between pairs of rolls 11, 12 and 13, 14, and heated during its travel therebetween by hot water which is continuously fed to trough 37.  The filament is advanced over rolls 11, 12, passed through trough 37, passed around idler 24, advanced over rolls 13, 14, and finally collected on spool 25 driven through multiplate clutch 33.  The axes of rolls 11, 12 and 13, 14 are out of parallel to permit advancement of the filament thereover, and the peripheral speed of rolls 13, 14 is in excess of that of rolls 11, 12.  When a plurality of filaments are simultaneously subjected to the drawing operation, they are arranged in a ribbon-like configuration by a guide 34 (Fig. 4) placed in advance of rolls 11, 12.  The guide 34 may have a straight or concave contour and may be so placed as to cause the filaments to change their path by an appreciable angle.  Instead of a stationary guide, a concave roller may be substituted and the guide in either form may be grooved.  The filaments may be previously passed through water to reduce the frictional resistance of the guide.  Specifications 461,236 and 535,263 are referred to.