FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A process for the production of yarn
APPLICANTS
Reliance Industries Limited, 3rd Floor, Maker Chamber IV, 222, Nariman Point, Mumbai - 400 021, Maharashtra, India, an Indian company
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a process for the production of yarn and to an apparatus for producing the same.
BACKGROUND OF THE INVENTION
Yarn is generally produced by a continuous process of melt extruding the polymer through spinnerets, cooling the filaments, using a spin finish application for lubricating the filaments and gathering them into a yarn, drawing the yarn and finally winding the yarn onto bobbins to package the yarn. Variations in the processing steps and conditions influence the physical properties of the yarn which in turn determines its applications.
Industrial yarns of low shrinkage are usually prepared by the above process by including a step of heat-relaxing the yarn before winding the yarn. By adjustment of the relaxation conditions, it has been possible to adjust the properties of the resulting yarn to a limited extent only. By increasing the degree of overfeed during the relaxation, it has been possible to produce yarn of lower shrinkage, but this has been accompanied by a significant and undesired decrease in tenacity of the yarn. A decrease in shrinkage without a significant decrease in tenacity has long been desirable.
Industrial yarns used as reinforcement in articles like safety seat belts, tires, roofing materials or fan belts must have high tenacities of around 7.5grams per denier (gpd) at least. Generally, to produce yarns of such high tenacities, the winding speed of the winder which winds the yarn onto bobbins are kept low ie about 700metres per minute (mpm). However, the low winding

speed in turn lowers the production efficiency for such yarn. Increasing the winding speeds to about 3000mpm will yield textile grade yarn having tenacities in the range of 2 to 4gpd, which are unsuitable for reinforcement purposes.
SUMMARY OF THE INVENTION
According to an embodiment of the invention there is provided a process for the production of yarn comprising:
a. drawing a spun yarn through a drawing system comprising a plurality of godet
pairs, each succeeding pair being maintained at a successively higher temperature
than the preceding pair and, each godet within a pair rotating at the same speed
with the exception of the last pair of godets, and each godet pair rotating at a
relatively higher speed than the pair preceding it with the exception of the last pair
of godets; and
b. winding the drawn yarn on a winder positioned downstream of the drawing
system at a speed of 3 to 20% higher than the speed of the penultimate godet of
the last godet pair;
wherein, the last godet pair is configured in such a manner that the penultimate godet of the last godet pair rotates at a speed which is 2 to 8% lower than the speed of the last godet of the last godet pair and the speed of rotation of the penultimate godet is lower than the speed of the preceding godet pair of the system to cause an overfeed of yarn to the penultimate godet.

According to another embodiment of the invention there is provided an apparatus for producing yarn comprising a drawing system and a winder positioned downstream of the drawing system, the drawing system comprising a plurality of godet pairs, each succeeding pair being maintained at a successively higher temperature than the preceding pair and, each godet within a pair rotating at the same speed with the exception of the last pair of godets, and each godet pair rotating at a relatively higher speed than the pair preceding it with the exception of the last pair of godets, wherein the last godet pair is configured in such a manner that the penultimate godet of the last godet pair rotates at a speed which is 2 to 8% lower than the speed of the last godet of the last godet pair and the speed of rotation of the penultimate godet is lower than the speed of the preceding godet pair of the system to cause an overfeed of yarn to the penultimate godet, and the winder winding the drawn yarn at a speed of 3 to 20% higher than the speed of the penultimate godet of the last godet pair.
It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying graphical representations are included to substantiate the invention and are incorporated into and constitute a part of this specification.
BRIEF DESCRIPTION OF THE DRAWING
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figure. The figure together with a detailed description below, are incorporated in and form part of

the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:
FIG. 1 is a schematic illustration of the apparatus for producing yarn according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
For simplicity and illustrative purposes, the present invention is described by referring mainly to exemplary embodiments thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one of ordinary skill in the art that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and apparatuses have not been described in detail so as not to unnecessarily obscure the present invention.
In the context of the invention, the term "differential speed" as used in the specification in reference to the last pair of godets is the difference between the speed of the penultimate godet and that of the last godet of drawing system. The penultimate godet is that godet encountered by the advancing yarn immediately before it encounters the last godet.
Also, the term "draw ratio" as used in the specification means the ratio of the peripheral speed of two consecutive godet pairs wherein each godet of a given pair is rotating at the same speed.

A melted polymer like polyethylene terephthalate can be extruded by conventional means through a multi-capillary spinneret to form a plurality of advancing filaments. The filaments may be multilobal or circular in cross section. The filaments are then cooled in a quench zone, a spin finish is then applied and gathered into yarn. The present invention provides a process for the production of high tenacity and low shrinkage yarn by a continuous process. In an embodiment of the invention, the yarn is drawn in a drawing system comprising a plurality of godet pairs, preferably at least three pairs of godets. In another embodiment of the invention, the yarn is drawn by five pairs of godets. The first pair of godets encountered by the advancing yarn is preferably cold godets and is maintained at a temperature in the range of 25 to 30°C. The following pair of godets is maintained at a temperature in the range of 90 to 100°C, preferably 95°C and at a peripheral speed in the range of 45o to 700 mpm. The next pair is maintained at a temperature in the range of 110 to 120°C, preferably 118°C and at a peripheral speed in the range of 1700 to 2200 mpm. The fourth pair of genets encountered by the advancing yarn are maintained at a temperature of 240 to 250°C, preferably 245°C and at a peripheral speed in the range of 2500 to 2800 mpm. In each of the above four godet pairs, the yarn enters and leaves from the same godet of each of the respective pairs and both godets in a single pair are maintained at the same temperature. Also, each godet within a pair rotates at the same speed as its partner in the pair and each godet pair rotates at a relatively higher speed than the pair preceding it. The last pair of godets are configured in such a manner that the penultimate godet of the last pair of godets rotates at a speed which is about lOOmpm to 350mpm lower than the speed of the last godet of the last pair such that the speed of rotation of the penultimate godet is even lower than the speed of the preceding godet pair of the system to cause an overfeed of upto 24% to the penultimate godet. The peripheral speed of the last godet is 2 to 8% higher than that

of the penultimate godet. Also, the advancing yarn is fed to the penultimate godet of the last pair of godets and leaves the drawing system from the last godet of the said pair. The drawn yarn is then wound on a winder positioned downstream of the drawing system, at a speed of 2500 to 3000mpm. The winder winds the drawn yarn at a speed of 3 to 20% higher than the speed of the penultimate godet of the last godet pair.
Preferably, the drawing system comprises at least three pairs of godets, and still more preferably, five pairs of godets. Preferably the first pair are cold godets. The draw ratio between the second pair of godets and the third pair of godets is preferably 3.5 and the draw ratio between the third pair of godets and the fourth pair of godets is preferably 1.46.
According to an embodiment of the invention, the yarn produced by the process above is polyester yarn.
The following is a detailed description of the invention with reference to the accompanying drawing, in which Fig 1 is a schematically illustrated apparatus for preparing the high strength and low shrinkage yarn by the embodiments of the present invention.
A yarn labelled R is drawn in an apparatus illustrated schematically in Fig 1. The yarn R is led in arrow direction 18 from a bobbin which is not shown to cold godets 1 and 2 respectively which are at a temperature of 25 to 30°C. The yarn from cold godet 2 moves back to godet 1 and then to hot godets 3 to 8 successively by entering and leaving each successive godet pair at the same point in that pair. The yarn exiting from godet 7 is then overfed to godet 9 as godet 9 has a

peripheral speed lower than the peripheral speed of godet 7 and also lower than the peripheral speed of godet 10. The yarn then exits the drawing system from godet 10 and moves to winder 12 where the yarn is wound at a speed of 2500 to 2800mpm.
In order that those skilled in the art will be better able to practice the present disclosure, the following example is given by way of illustration and not by way of limitation.
Example 1
Polyester yarn was prepared using the apparatus described in Fig 1. The first pair of godets were
maintained at a temperature of 25 to 30°C, the second pair of godets were maintained at 95°C, the third pair of godets were maintained at 118°C, and the third and fourth pair of godets were maintained at 245°C. The variations in the process conditions for preparing the yarn are detailed in Table 1. The parameters of hot air shrinkage of the yarn and tenacity of the yarn and overall increase in productivity are illustrated in Table 2.

Table 1

Process conditions Control 1 Control 2 Yarnl Yarn 2 Yarn 3
Polyester Intrinsic Viscosity (IV) 0.87 0.83 0.83 0.87 0.83
Draw ratio between godet pair 3-4 and godet pair 5-6 3.5 3.5 3.5 3.5 3.5
Draw ratio between godet pair 5-6 and godet pair 7-8 1.46 1.46 1.46 1.46 1.46
Differential speed of godet 9 and 10 (mpm) 0 0 339 125 300
Overfeed at godet 9 12.42% 12.42% 21.00% 12.42% 12.42%
Winding speed (mpm) 2570 2570 2760 2640 2730
Table 2
Parameters Control 1 Control 2 Yarnl Yarn 2 Yarn 3
Hot air shrinkage (%) 4.4 3.73 3.28 3.8 4.8
Tenacity (in gpd) 7.23 7.23 7.25 7.57 7.73
Increase in productivity (%) - - 7.39 2.72 6.23
It is evident from Table 2 that Yarn 1 shows lower shrinkage and higher tenacity than the Control 1 and Control 2, while Yarn 2 also shows low shrinkage and higher tenacity. On the other hand, Yarn 3 shows the highest tenacity. The table also shows an increase in productivity or throughput by upto 7.39% in the case of Yam 1, 2 and 3 as compared to the Control 1 and Control 2. The higher winding speed in the case of Yarn 1, 2 and 3 vis-a-vis the winding speed of the Control 1 and 2 is due to the higher capacity of the winder operating as per the process of the invention. Thus the process of the invention is more economical for production of yarn on an industrial scale. Also, the yarn did not vibrate or become unstable on the last pair of godets, which indicates that the differential speed of the last godet pair does not create yarn instability.

The present invention discloses a process for the production of yarn and more particularly discloses the optimal differential speed between the last pair of godets to obtain high tenacity and low shrinkage yarn. Also, the present invention requires no major modifications in the conventionally used apparatus for preparing the yarn which makes the invention cost-effective.
What has been described and illustrated herein are preferred embodiments of the invention along with some of their variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention, which is intended to be defined by the following claims—and their equivalents—in which all terms are meant in their broadest reasonable sense unless otherwise indicated.

We claim:
1. A process for the production of yarn comprising:
a. drawing a spun yarn through a drawing system comprising a plurality of godet
pairs, each succeeding pair being maintained at a successively higher temperature
than the preceding pair and, each godet within a pair rotating at the same speed
with the exception of the last pair of godets, and each godet pair rotating at a
relatively higher speed than the pair preceding it with the exception of the last pair
of godets; and
b. winding the drawn yarn on a winder positioned downstream of the drawing
system at a speed of 3 to 20% higher than the speed of the penultimate godet of
the last godet pair;
wherein, the last godet pair is configured in such a manner that the penultimate godet of the last godet pair rotates at a speed which is 2 to 8% lower than the speed of the last godet of the last godet pair and the speed of rotation of the penultimate godet is lower than the speed of the preceding godet pair of the system to cause an overfeed of yarn to the penultimate godet.
2. The process as claimed in claim 1, wherein the speed of rotation of the penultimate godet is lower than the speed of the preceding godet pair of the system to cause an overfeed of upto 24% yarn to the penultimate godet.
3. The process as claimed in claim 1 or 2, wherein the drawing system comprises at least three pairs of godets.

4. The process as claimed in claim 3, wherein the drawing system comprises at least five pairs of godets having a draw ratio of 3.5 between the second pair of godets and the third pair of godets and a draw ratio of 1.46 between the third pair of godets and the fourth pair of godets.
5. The process as claimed in any one of claims 1 to 4, wherein the first pair of godets are cold godets.
6. The process as claimed in any one of claims 1 to 5, wherein the yarn produced in polyester yarn.
7. An apparatus for producing yarn comprising a drawing system and a winder positioned downstream of the drawing system, the drawing system comprising a plurality of godet pairs, each succeeding pair being maintained at a successively higher temperature than the preceding pair and, each godet within a pair rotating at the same speed with the exception of the last pair of godets, and each godet pair rotating at a relatively higher speed than the pair preceding it with the exception of the last pair of godets, wherein the last godet pair is configured in such a manner that the penultimate godet of the last godet pair rotates at a speed which is 2 to 8% lower than the speed of the last godet of the last godet pair and the speed of rotation of the penultimate godet is lower than the speed of the preceding godet pair of the system to cause an overfeed of yarn to the penultimate godet, and the winder winding the drawn yarn at a speed of 3 to 20% higher than the speed of the penultimate godet of the last godet pair.

8. The apparatus as claimed in claim 7, wherein the speed of rotation of the penultimate godet is lower than the speed of the preceding godet pair of the system to cause an overfeed of upto 24% yarn to the penultimate godet.
9. The apparatus as claimed in claim 7 or 8, wherein the drawing system comprises at least three pairs of godets.
10. The apparatus as claimed in any one of claims 7 to 9, wherein the drawing system comprises at least five pairs of godets having a draw ratio of 3.5 between the second pair of godets and the third pair of godets and a draw ratio of 1.46 between the third pair of godets and the fourth pair of godets.
11. The apparatus as claimed in any one of claims 7 to 10, wherein the first pair of godets are cold godets.