A METHOD FOR THE OBTAINING OF CHAINS OR FRACTIONS WOUND ON BEAMS, STARTING WITH A SERIES OF CONTINUOUS, PARTIALLY-DRAFTED, THERMOPLASTIC YARNS

Abstract: A process for the drafting, interlacing and sizing of a series of continuous, thermoplastic yarns, which consist of filaments that are substantially parallel to each other, for the manufacture of chains or fractions wound on beams.

Description: This invention concerns a process for the preparation of chains or fractions wound on beams, made from continuous, completely-drawn and interlaced thermoplastic yarns, suitable for use on looms for the production of textile products of all types. The known processes for the preparation of continuous, thermoplastic-polymer yarns for textile use involve spinning the filaments from the molten polymer, cooling them, combining them to form the yarn and then drawing the yarn. Drawing orients the molecules of the filaments and thus gives them the required physical and mechanical characteristics for making them suitable for textile use. There are two techniques used in the known processes for obtaining filament interlacing. According to the more pertinent of the aforesaid techniques, the yarn produced during spinning is wound onto spools in an incompletely-drawn state. Complete drawing of the yarn takes place in a subsequent phase by means of a special drawing or drawing-twisting machine, which has several positions, each of which acting on one individual yarn. These machines do not readily permit the obtaining of perfectly constant yarn characteristics, presumably due to the fact that each yarn is treated individually and is therefore subjected to a particular temperature or particular mechanical setting regarding its particular machine position. According to another known process, the yarn is completely drawn right after being spun, by means of rollers having differential rotational speeds and then wound up on the cops. This process requires expensive spinning machines and, on the average, has a lower production capacity than the above mentioned. As is well known, there are many cases where, in order to make the yarns suitable for loom use, where the mechanical stresses imposed in the loom operation could break the individual filaments, the yarns coming off the drawing or drawing-twisting machine are subjected to a sizing operation, which consists of impregnating the filaments with sizing agents, in accordance with the following process. The beams, upon which the previously warped yarns have been wound, are mounted on support creels. The properly-arranged and parallel yarns are passed through a special apparatus which includes an impregnation bath and squeezing rollers. The yarns are then dried by means of hot air, infrared radiation or heated cylinders, after which they are wound onto beams by winding machine. A recent method described in EP-A-91549, shows the possibility of combining the two separate phases, drawing and sizing, into a single phase, thus providing obvious technical and economical advantages. According to the method of the invention a series of continuous thermoplastic yarns having filaments which are substantially parallel to each other and not completely drawn are simultaneously drawn when immersed in a liquid at controlled temperature, and then subjected to an interlacing process on each individual yarn before being sized and then finally wound. The process according to the invention permits the use of a starting yarn for the preparation of the aforesaid chains or fractions for textile use which is not completely drawn, being as obtained from the spinning process in accordance with known techniques. This present invention constitutes an additional technical development over and above that described in EP-A-91549. It consists in the carrying out of the complete drawing separately, in a thermostatic bath, by means of tension rollers, followed immediately thereafter by the treatment of each individual yarn, while still wet, to interlacing process before entering the sizing bath. The process, according to this invention, consists of the following operations: The not less than 24 cops mounted on the feed creel are each wound with yarn coming from the spinning machine. The yarn is not completely drawn. The yarns unwind from the cops at a constant tension and are kept parallel to each other by means of a comb guide. The yarns pass through a feed and support roller system. The rollers have a constant peripheral velocity. Next, the yarns pass into a vat of a liquid, which is kept at a prefixed controlled temperature so that the filaments of the yarn can be drawn. The yarn leaves the vat and passes through a system of traction rollers which have a constant peripheral velocity that is greater than that of the feed rollers. The system of feed and tensioning rollers can also be located in the vat of the liquid at controlled temperature. The traction-roller system can also squeeze out all the excess liquid from the yarn. The desired simultaneous action of drawing and molecular orientation of the individual filaments is obtained, between the feed and traction rollers, by means of the combined action of the differential peripheral velocities, which generates filament tension, and the softening of the polymer, due to the heat of the thermostatic bath. Following the drawing and the squeezing out of the excess liquid, the still-wet yarns pass through the interlacing devices, which are standard devices and which entangle the filaments by means of a jet of fluid at high velocity. These devices are arranged in a bank, are equal in number to that of the yarns and each one acts separately on each individual yarn. Right after the yarn-interlacing phase, the yarns enter the sizing device. After being dried, the yarns are finally wound onto beams or similar devices by a winding machine. Another possibility for feeding the apparatus consists in winding the yarns onto beams, small beams, large reels, on any such similar device, using a winding machine, and then feeding from these, rather than directly from the spools mounted on the creel. In this case, it is possible to unite several fractional beams at the entrance to the feed rollers from the drawing phase. The new method, the object of the present invention, whereby several continuous thermoplastic yarns are arranged parallel to each other, drawn simultaneously and then interlaced before the sizing phase, permits a considerable cost saving, as compared to traditional means. This is because of the complete elimination of the need for a preliminary drawing phase in which each individual yarn is drawn, either before or after the spinning collection, by using a drawing or drawing-twisting machine, according to the known processes mentioned earlier. Compared to the procedure described in EP-A-91549, this invention is different because of the fact that it also provides for the interlacing of the filaments prior to the sizing operation. In this manner, there is the great advantage of being able to considerably increase the velocity of the sizing process and, more important obtained a sized yarn having a great number of interlacing points, thus making the yarn suitable for use on very high speed, modern looms. It has been found, in fact, that it is generally preferable to carry out interlacing on yarns that are still humid, so as to obtain better results from the point of view of the connection effect between the filaments. Compared to the procedure described in FR-A-2.344.657, this invention is characterized by the sizing treatment following the interlacing step. As above mentioned, the process steps sequences of the invention affords the manufacture of yarns having better characteristics of cohesion between the filaments; in particular such cohesion characteristics can be further improved by subjecting the yarns while still wet to the interlacing treatment. Another outstanding advantage provided by this invention consists in the possibility of substituting the more usual types of interlacing devices with known voluminizing devices, such as the known Taslan process, for example, which used a high-velocity fluid jet. These devices obviously provide interlacing and voluminization at the same time. The very great advantage of being able to combine, in one plant, the drawing phase, voluminization phase, sizing phase and preparation of chains or fractions on weaving beams can, therefoce, be obtained. With known procedures, in fact, the drawn yarn is fed into costly voluminizing machines. This invention also provides, furthermore, an outstanding economic advantage by making it possible to obtain a better quality yarn, a better performing yarn in the loom and increased productivity with existing traditional equipment by adding the drawing and interlacing device to the equipment. This modification causes no appreciable change in standard warping systems, which remain substantially just as they are. It has also been found, after having carried out numerous tests, that the fabrics obtained with the yarns treated in accordance with our new procedure have excellent compactness and uniformity characteristics and that loom down-time is substantially reduced, as compared to the down-time normally occurring when using standard yarns. This invention is further illustrated by the following non-limiting examples: Example 1 100 cops of partially-oriented, lucid, polyester yarns (POY), having the following characteristics, are loaded onto a warping feed creel Count: 127 Dtex Number of filaments: 24 Filament cross-section: circular Breaking load: 330 grams Ultimate elongation: 156% Theoretical residual draw: 1.628 (127/78) The yarns are warped under a tension of 10 g, passing them through the blades of a rectilinear comb. The yarns are anchored and dragged with a tension of 10 g by a three-roller system, which roll together at a constant peripheral speed of 148 meters/min. The yarns are then immersed in a vat of demineralized water, which is held at a constant temperature of 80°C. A system of three drawing and squeezing cylinders, which rotate together at a constant peripheral speed of 250 meters/min., acts simultaneously on all the yarns, giving them a draw-to-feed ratio of 1.689. Upon leaving the drawing and squeezing cylinders, the yarns pass through the interlacing jets, which are fed by compressed air under 3 Atm of pressure. The yarns are then immersed in a vat containing a hot-glue bath, consisting of a 10% water solution of Adex-TweR ○ acrylic glue made by the Cesalpinia company, and maintained at a constant temperature of 90°C. The sizing speed is kept slighthly under 240 meters/min., so as to obtain a certain amount of yarn swelling, which favors the absorption of sizing. The yarns are then dried by passing them through hot-air ovens. The yarns then receive thermal fixing by passing into contact with steam-heated cylinders, the temperature of the cylinders ranging from 105°C to 90°C from the first one to the last one. When leaving the fixing cylinders, the yarns are wound on beams measuring 1800 mm in height and in six fractions, each measuring 12000 m in length. The average characteristics of the drawn and glued yarns thus obtained are as follows: Count: 79.1 Dtex Breaking strength: 319 g Ultimate elongation: 34% Shrinkage in boiling water: about 2% Glue remaining on yarn: 8/8.5% During the next phase the 6 glued fractions are wound on a weaving beam, measuring 1550 mm in height, for a total of 6000 yarns. The beam is loaded onto a water loom and wafted with texturized polyester yarn having a count of 56 Dtex and 24 filaments, at a speed of 490 beats/min., with a cloth weave and a density of 30 wefts/cm. The fabric is then dyed in a jet-type cord-dyeing machine. Dispers Blue Color Index 056 dispersed dye is used. The fabric is centrifuged, dried in hot air, passed through a stenter machine and thermo-fixed at 180°C at 25 meters/min. The obtained fabric has a height of 140 cm. Specular inspection on a black table, for revealing fabric defects, reveals high uniformity and compactness of the chained yarns with lucid yarns being totally absent. Example 2 The same procedure is used as in the foregoing example except that 1160 cops of the same yarn are loaded onto the creel and 8 weaving beams, having a height of 44 inches each, are wound with 15000 m of chain lengths each. The 8 weaving beams are then loaded onto a chain-type, rectilinear knitting frame. Dyeing anx fixing operations are then carried out on the obtained knitted fabric, as done in the previous example. Examination by passing the fabric under the specular instrument reveals perfect evenness of weave and dye homogeneity.

Claims: A process for beaming synthetic filament yarn comprising the steps of drawing at least 24 yarns made of partially drawn susbtantially parallel synthetic filaments in a liquid containing vat in parallel relationship to each other, sizing, drying and winding the parallel yarns onto a weaving beam, characterized in that, after the drawing step, the yarns while still wet are subjected separately to an interlacing treatment using a fluid jet and then to the sizing treatment. A process, in accordance with claim 1, where the interlacing treatment is carried out by means of a device which also provides voluminization of the yarn. A process, in accordance with one of the preceding claims, where the synthetic filaments are of the following types: polyesters, polyamides, polyethylenes, polypropylenes and their modifications.

Inventors: BALLARATI, VITO, TAJANA, FRANCO
Applicants: VAL LESINA S.P.A.
Application year: 1984
Main classification: D02H5
IPC codes: D02H5, D06B3, D02J1