GB1598448A - Textured yarn - Google Patents

Description

(54) TEXTURED YARN (71) We, COURTAULDS LIMITED, a British Company, of 18, Hanover Square, London W1A 2BB, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the production of textured continuous multi-filament yarn.

The most widely used method of texturising continuous multi-filament yarns is false twist crimping. In this process the yarn is false twisted by means of false twist spindle, friction discs or a friction bush and is heated and then cooled while in the false twisted configuration to set the distortion in the yarn. The resulting yarn (which is frequently given a subsequent heat relaxation treatment) has increased bulk and covering power because of its crimp. However, it lacks the soft handle of spun staple yarn.

The false twist crimping process can be carried out during drawing of the yarn, such a process being known as draw-texturising. In one variation of this process undrawn or partially orientated thermoplastic yarn is draw texturised using a draw ratio which is lower than that required to produce a fully drawn yarn. The product of this process is a draw-texturised yarn having an extension at break of from 30 to 70 per cent. The component filaments of the yarn produced have a random variation in their count and in their crimp frequency both along the filaments and from filament to filament. The random variation in the crimp frequency means that the filaments of the yarn are more separated and fabrics formed from the yarn have improved softness and handle.

The present invention treats this drawtexturised yarn having an extension at break of from 30 to 70 per cent to convert it to a loopy yarn in which individual filaments stand out from the yarn at spaced-apart points as loops, frequently crunodal loops which cannot readily be pulled out of the yarn. The loops give the yarn a soft handle more closely approaching that of a spun staple yarn. The loops contribute to the handle in fabrics formed from the yarn similarly to protruding fibre ends in a spun staple yarn.

According to the invention a process for producing a loopy yarn comprises passing a draw-texturised continuous multi-filament yarn having an extension at break of from 30 to 70per cent through a tension zone wherein it is subjected to a tension sufficient partially to remove the crimp therefrom and a relaxation zone wherein the tension is relaxed, at least part of the relaxation zone comprising a yarn passageway wherein a jet of fluid impinges on the yarn at an angle of from 30 to 1500 to its direction of travel.

The process of the invention can conveniently be combined with the drawtexturising step on a conventional drawtexturising machine, particularly a double heater machine. The yarn is simultaneously drawn and false twisted as it passes through the first heater and the false twist spindle or discs, the draw ratio being lower than that required to produce a fully drawn yarn. The second heater of the machine can then form the tension zone referred to above.

In this zone the yarn is stretched partially to remove the crimp. As explained above, the component filaments of the underdrawn draw-texturised yarn have a random variation both in their count and in their crimp frequency both along the filaments and from filament to filament. The degree of tension applied in the tension zone is adapted to make use of this variation in the filaments. It must be sufficient that over a short portion of yarn some of the filaments are pulled substantially straight but some retain their crimp. The preferred degree of tension generally corresponds to an underfeed in the tension zone of from 2 to 12per cent.

The yarn is preferably heated in the tension zone, for example to a temperature above 100"C but below the degradation temperature of the yarn. The heater in the tension zone (the second heater on a double heater draw-texturising machine) can, for example, be at a temperature in the range of from 1500 to 200"C. The heating step is not necessary for the production of a textured yarn, but heating is preferred to produce a yarn which is subsequently thermally stable.

Alternatively, yarn which has been drawtexturised as described above and which has an extension at break of from 30 to 70 per cent can be collected on a package, optlonally after a heat relaxation treatment in the second heater of a double heater texturising machine, and then treated by the process of the present invention in a separate step.

After leaving the tension zone, that is after leaving a tensioning roll or other tensioning device at the end of that zone, the yarn passes into a relaxation zone where the tension is relaxed. The yarn is preferably overfed by from 5 to 25 per cent through this relaxation zone. Higher and lower overfeeds will produce a loopy yarn, but the lower overfeeds give an insufficiently conspicuous texture to the yarn and the higher overfeeds give loops which are too large and which tend to be unstable and easily pulled out.

Whilst in the relaxation zone the yarn goes through a passageway wherein a jet of fluid impinges on the yarn. This combination of yarn passageway and inlet for fluid impinging on the yarn has been proposed as an interlacing jet for uniting the filaments of a yarn. When a flat yarn is fed to such a jet, it generally forms condensed coherent portions at intervals along the length of the yarn. We have found surprisingly that when an under-drawn draw-texturised yarn is stretched and then fed to the interlacing jet while relaxed, as in the process of the present invention, the filaments of the yarn are intermittently formed into loops projecting from the yarn rather than forming alternating condensed coherent portions and false twist crimped sections as might be expected.

The yarn entering the relaxation zone comprises at any point along its length filaments pulled straight and filaments retaining some crimp. We have found that in some ways the yarn behaves similarly to a composite yarn formed from a core yarn and one or more surrounding yarns which are overfed more than the core yarn. Such a composite yarn has previously been suggested for producing textured yarns having loops, slubs or knots. The process of the present invention gains some of the advantages of a composite yarn, such as increased stability of the textured yarn, while using a single yarn without variation of overfeed. It also has the advantage that the filaments of the yarn retain some of their crimp to add to the textured appearance and handle given by the loops.

The interlacing jet in its simplest form can consist of a yarn passageway having a fluid inlet directed perpendicularly at the centre of the passageway. The yarn passageway can be a tube, for example having a diameter of from 1.5 to 6 mm or a slot of similar width.

The air inlet can for example have a diameter of from 0.6 to 3 mm. Alternatively, the interlacing jet can have two fluid inlets directed at the yarn at angles of from 45" to 60 and from 135 to 1200, respectively, to its direction of travel. The fluid which impinges on the yarn is preferably air. The fluid pressure is preferably from 3.5 to 10.5 kg/cm2 (gauge). When a high over feed is used, the fluid pressure may need to be above the minimum to produce stable loops in the yarn.

Example of yarns which can be treated by the process according to the invention are polyester yarns, for example polyethylene terephthalate, polyamide yarns, for example nylon 6 and nylon 66 and polyolefin yarns, for example polypropylene. The yarns can be of generally circular cross-section or for example multi-lobal yarns, such as trilobal, pentalobal or octalobal, can be used. The multi-lobal yarns generally have somewhat higher interfilament adhesion so that stable loopy yarns may be produced at slightly lower fluid pressure.

We have found that the yarn should preferably be moist as it is treated with the jet of fluid. An attractive loopy yarn can be formed more readily using higher running speeds and lower fluid pressures if the yarn is moist. The yarn is preferably treated with a wettmg agent, tor example water or a detergent solution in the relaxation zone and before the yarn passageway. For example the desired amount of water is applied to the yarn if it brushes across a wicking device. Alternatively, water can be applied to the yarn as a fine spray, or by a lick roller.

Alternatively, moisture laden air or steam can be used as the jet of fluid which impinges on the yarn.

The invention will now be described, by way of example. with reference to the drawing accompanying the Provisional specification, the single Figure of which is a diagrammatic view of one station of a double heater draw-texturising machine adapted to carry out the process according to the present invention.

An undrawn or partly drawn yarn 1 is withdrawn from a package 2 by feed rolls 3.

The yarn is then simultaneously drawn and false twisted between the feed rolls 3 and draw rolls 4. The yarn passes successively through the first heater 5 and a false twist spindle 6 before reaching the draw rolls 4.

The draw ratio between draw rolls 4 and feed rolls 3 is arranged to be such that the yarn coming from draw rolls 4 has an extension at break of from 30 to 70 per cent.

This under-drawn draw-texturised yarn is then passed through a tension zone defined by the draw rolls 4 and tensioning rolls 8. In this zone the yarn is passed through a second heater 7 and is stretched between the draw rolls 4 and the tensioning rolls 8.

The stretched yarn is then passed through a relaxation zone defined by the tensioning rolls 8 and take-off rolls 14. In this zone the yarn is passed across a moistening device comprising a water reservoir 9 and a wick 10. Thence it goes through a yarn passage way 11 having two air inlets 12 and 13, each arranged to direct a jet of air at the yarn.

The relative speed of rolls 8 and 14 is such that the yarn is overfed in the relaxation zone and is allowed to relax while being sub jected to the jets of air from the inlets 12 and 13.

The take-off rolls 14 feed the yarn to a take-up package 15.

The apparatus shown in the drawing can be modified by the omission of rolls 14. In this case the overfeed in the relaxation zone is determined by the speed of the tensioning rolls 8 and the take-up package 15. The yarn preferably passes through a guide eye soon after the exit from the yarn passageway 11 so that movement of the yarn caused by the take-up mechanism is not transmitted to the yarn in passageway 11.

The invention is illustrated by the following Example: EXAMPLE The yarn used in this Example was a 167 decitex 64 filament semi-matt polyethyleneterephthalate yarn spun at a speed of 1200 m/min. This was treated in an apparatus as shown in the drawing. The draw ratio between the feed rolls 3 and the draw rolls 4 was 2.72. The temperature of the first heater 5 was 1900C. The false twist spindle 6 was rotated at a speed sufficient to impart a false twist of 1630 turns per metre.

The degree of underfeed in the tension zone between the draw rolls 4 and the tension rolls 8 was 6 per cent. The temperature of the second heater 7 was 185"C.

The degree of overfeed between the tension rolls 8 and the take-off rolls 14 was 12 per cent, the take-up speed being 154 metres per minute. The air pressure used at the air inlets 12 and 13 was 5.6 kg/cm2 (gauge).

The yarn produced had a multiplicity of small loops and whorls, the average diameter of the loops being about equal to the average apparent diameter of the yarn where not looped. Many of the loops were crunodal, that is one or more filaments "looped the loop". The yarn filaments also retained some of their crimp, with the crimp in each filament varying along its length in random fashion.

The loops in the yarn were not pulled out under normal processing tensions. The yarn was knitted into a plain knit fabric and had a much softer handle than a conventional false twist crimped yarn and an appreciably softer handle than an under-drawn drawtexturised yarn not subjected to the process of the present invention. The yarn also had increased covering power.

WHAT WE CLAIM IS: 1. A process for producing a loopy yarn comprising passing a draw-texturised continuous multi-filament yarn having an extension at break of from 30 to 70 per cent through a tension zone wherein it is subjected to a tension sufficient partially to remove the crimp therefrom and a relaxation zone wherein the tension is relaxed, at least part of the relaxation zone comprising a yarn passageway wherein a jet of fluid impinges on the yarn at an angle of from 30 to 1500 to its direction of travel.

2. A process according to claim 1, in which the yarn is underfed through the ten sion zone by from 2 to 12 per cent.

3. A process according to claim 1 or claim 2, in which the yarn is heated to a temperature above 100 C in the tension zone.

4. A process according to any of claims 1 to 3, in which the yarn is overfed through the relaxation zone by from 5 to 25 per cent.

5. A process according to any of claims 1 to 4, in which the yarn is moist as it is treated with the jet of fluid.

6. A process according to claim 5, in which the yarn is moistened by treating it with a wetting agent in the relaxation zone before the yarn passageway.

7. A process according to any of claims 1 to 4, in which moisture laden air or stream is used as the jet of fluid which impinges on the yarn.

8. A process according to any of claims 1 to 7, in which the fluid pressure of the jet is from 3.5 to 10.5 kg/cm2 (gauge).

9. A process according to any ot claims 1 to 8, in which the jet of fluid impinges on the yarn substantially perpendicularly to its direction of travel.

10. A process according to any of claims 1 to 8, in which two jets of fluid impinge on the yarn from two fluid inlets directed at the yarn at angles of from 45" to 60 and from 135 to 1200, respectively, to its direction of travel.

11. A process for producing a loopy yarn substantially as herein described with reference to the drawing accompanying the Provisional specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. The stretched yarn is then passed through a relaxation zone defined by the tensioning rolls 8 and take-off rolls 14. In this zone the yarn is passed across a moistening device comprising a water reservoir 9 and a wick 10. Thence it goes through a yarn passage way 11 having two air inlets 12 and 13, each arranged to direct a jet of air at the yarn. The relative speed of rolls 8 and 14 is such that the yarn is overfed in the relaxation zone and is allowed to relax while being sub jected to the jets of air from the inlets 12 and 13. The take-off rolls 14 feed the yarn to a take-up package 15. The apparatus shown in the drawing can be modified by the omission of rolls 14. In this case the overfeed in the relaxation zone is determined by the speed of the tensioning rolls 8 and the take-up package 15. The yarn preferably passes through a guide eye soon after the exit from the yarn passageway 11 so that movement of the yarn caused by the take-up mechanism is not transmitted to the yarn in passageway 11. The invention is illustrated by the following Example: EXAMPLE The yarn used in this Example was a 167 decitex 64 filament semi-matt polyethyleneterephthalate yarn spun at a speed of 1200 m/min. This was treated in an apparatus as shown in the drawing. The draw ratio between the feed rolls 3 and the draw rolls 4 was 2.72. The temperature of the first heater 5 was 1900C. The false twist spindle 6 was rotated at a speed sufficient to impart a false twist of 1630 turns per metre. The degree of underfeed in the tension zone between the draw rolls 4 and the tension rolls 8 was 6 per cent. The temperature of the second heater 7 was 185"C. The degree of overfeed between the tension rolls 8 and the take-off rolls 14 was 12 per cent, the take-up speed being 154 metres per minute. The air pressure used at the air inlets 12 and 13 was 5.6 kg/cm2 (gauge). The yarn produced had a multiplicity of small loops and whorls, the average diameter of the loops being about equal to the average apparent diameter of the yarn where not looped. Many of the loops were crunodal, that is one or more filaments "looped the loop". The yarn filaments also retained some of their crimp, with the crimp in each filament varying along its length in random fashion. The loops in the yarn were not pulled out under normal processing tensions. The yarn was knitted into a plain knit fabric and had a much softer handle than a conventional false twist crimped yarn and an appreciably softer handle than an under-drawn drawtexturised yarn not subjected to the process of the present invention. The yarn also had increased covering power. WHAT WE CLAIM IS:

1. A process for producing a loopy yarn comprising passing a draw-texturised continuous multi-filament yarn having an extension at break of from 30 to 70 per cent through a tension zone wherein it is subjected to a tension sufficient partially to remove the crimp therefrom and a relaxation zone wherein the tension is relaxed, at least part of the relaxation zone comprising a yarn passageway wherein a jet of fluid impinges on the yarn at an angle of from 30 to 1500 to its direction of travel.

2. A process according to claim 1, in which the yarn is underfed through the ten sion zone by from 2 to 12 per cent.

3. A process according to claim 1 or claim 2, in which the yarn is heated to a temperature above 100 C in the tension zone.

4. A process according to any of claims 1 to 3, in which the yarn is overfed through the relaxation zone by from 5 to 25 per cent.

5. A process according to any of claims 1 to 4, in which the yarn is moist as it is treated with the jet of fluid.

6. A process according to claim 5, in which the yarn is moistened by treating it with a wetting agent in the relaxation zone before the yarn passageway.

7. A process according to any of claims 1 to 4, in which moisture laden air or stream is used as the jet of fluid which impinges on the yarn.

8. A process according to any of claims 1 to 7, in which the fluid pressure of the jet is from 3.5 to 10.5 kg/cm2 (gauge).

9. A process according to any ot claims 1 to 8, in which the jet of fluid impinges on the yarn substantially perpendicularly to its direction of travel.

10. A process according to any of claims 1 to 8, in which two jets of fluid impinge on the yarn from two fluid inlets directed at the yarn at angles of from 45" to 60 and from 135 to 1200, respectively, to its direction of travel.

11. A process for producing a loopy yarn substantially as herein described with reference to the drawing accompanying the Provisional specification.

12. A process for producing a loopy

yarn substantially as described in the foregoing Example.

13. A loopy yarn produced by the process claimed in any of claims 1 to 12.