Patent GB-1181768-A (GB)
Title: Process and Apparatus for Drawing and Heat-setting a Warp of Polyester Yarns
IPC: D01F6/62
Filed: 1968-09-19
Abstract: 1,181,768. Polyester filaments. FMC. CORP. 19 Sept., 1968 [1 Nov., 1967], No. 44631/68. Heading B5B. A multiplicity of high tenacity linear polyester yarns are simultaneously prepared by continuously and simultaneously drawing a warp of substantially unoriented polyester yarns at a drawing tension of from 0À4 to 0À6 g.p.d., based on the undrawn denier, at least 5À5 times up to the maximum draw ratio of the yarns, heatsetting the oriented yarns by passing the warp in contact with a series of spaced moving surfaces, each of said surfaces moving at a speed substantially equal to that of the yarn as drawn and being held at from 120‹ to 160‹ C., preventing a change in the length of the yarns drawing heat-setting any greater than 10% of the drawn length, and individually collecting said yarns at from 15À24 to 91À44 m. per min. Preferably the yarns are stretched to between 6 and 7 times their undrawn length, and during heat setting a change in the length of the yarns no greater than 5% of the drawn length is permitted. The substantially unoriented, as-spun yarns used are produced without purposely attempting to draw the yarn during the spinning operation, although some pre-orientation may occur during normal spinning. Thus, as-spun yarns, pre-oriented to a degree wherein they will shrink no more than about 25% when placed in boiling water, are acceptable for the process. Polyethylene terephthalate yarns are preferred, but the method is applicable to other polyester resins, especially other terephthalate resins, e.g. those prepared from terephthalic acid and other dicarboxylic acids, e.g. isophthalic acid, phthalic acid, or bibenzoic acid and glycols containing from 2 to 10 methylene groups. Copolymers of ethylene terephthalate and minor monomer components which improve dyeability, e.g. p,p<SP>1</SP>-sulphonyldibenzoic acid, may be used. Preferably, the warp of substantially unoriented yarns is drawn between a set of driven feed rolls having parallel axes and a set of driven draw rolls having parallel axes, an intermediate heating zone being maintained between said sets of rolls, at least the last of the feed rolls being maintained at a temperature of from 90‹ to 100‹ C., and said heating zone being maintained at from 165‹ to 185‹ C. Desirably, the yarns have a lubricant finish applied prior to heat-setting on a set of spaced internally-heated rolls having a smooth metallic surface so that some slippage can occur between the yarns and the rolls. In apparatus as shown, a multiplicity of as-spun yarn packages 2 from conventional creels, supply yarns 4 which are formed into a warp by passage through comb 5 and thence pass to a set of feed rolls 6, 8, 10, 12. Roll 6 is suitably a rubber-covered idler roll, while roll 8 is a driven hard chrome matt surface roll in contact with roll 6. Rolls 10 and 12 are heatable, non-contacting, driven hard surface rolls. The warp passes from roll 12 over and in contact with platen 14, which is heatable, over a finish applicator roll 16 in pan 18, and passes around the surfaces of a set of contacting, counter-rotating draw rolls 20, 22, 24 and 26. Roll 20 may be hard surfaced, e.g. a chrome matt finish, and may be internally heatable or coolable. Rolls 22 and 26 are rubber-covered and roll 24 has a hard surface. All the draw rolls are positively driven at the same speed and may include means for internal heating or cooling. From the drawing section, the warp passes directly to the heat-setting section which comprises a set of large, internally heated cans or rolls 28 to 36 which have surfaces of polished steel, and are positively driven in counterrotation at the same speed as draw rolls 20 to 26. Alternatively, small idler rolls may be placed between similar large rolls permitting the heatsetting rolls to be rotated in the same direction, or a series of heated moving endless belts may be used. The yarns passing over the rolls of the heat-setting section contact only a portion of each roll before passing to the next roll, so that there is a uniform intermittent heating and cooling of the yarn during heat-setting. The warp 4 is made to conform to the heat-setting surfaces and prevented from changes in length by passage through a comb 37 and a set of tensioning rolls 38, 39, and 40, of which rolls 38 and 40 are rubber-surfaced and roll 39 has a hard surface; and then narrowed through comb 41 and collected as individual ends on beam 42. Beam 42 may be replaced by individual yarncollecting spools or cones. In a modified form of apparatus (not shown) the hot feed rolls or the platen are replaced with one or more heated stationary cylinders. Yarns spun using this process show typically a tenacity of at least 6 g.p.d. and an elongation of from 10 to 18%.