Claims:
1. A warp knit denim fabric comprising a plurality of dyed spun yarns at least 45% w/w of fabric knitted as warp yarns, each spun yarn having tenacity at least 18cN/tex and each spun yarn comprises natural fibers at least 60% w/w of the spun yarn, wherein
the dye is selected from oxidative, reactive, vat dye or pigment or combination thereof.

2. The warp knit denim fabric as claimed in claim 1, wherein the spun yarn comprises 100% natural fibers or a blend of natural fibers with regenerated cellulosic fibres, synthetic fibers or combination thereof, said blend having natural fibers at least 60% w/w of the spun yarn.

3. The warp knit denim fabric as claimed in claim 1 or 2, wherein the fabric comprises a plurality of filament yarns, a plurality of elastomeric yarns or combination thereof along with the plurality of the spun yarns.

4. The warp knit denim fabric as claimed in claim 3, wherein the linear density of the filament yarn and elastomeric yarn ranges from about 20 denier to about 150 denier.

5. The warp knit denim fabric as claimed in claim 1 or 2, wherein the fabric comprises 100% spun yarns.

6. The warp knit denim fabric as claimed in one of the claims 1 to 5, wherein the liner density of the spun yarn is from about 10s Ne to 120s Ne and more preferably 20s Ne to 60s Ne.

7. The warp knit denim fabric as claimed in any one of the claims 1-6, wherein the natural fiber includes cotton fibers, wool, linen, hemp, jute etc.

8. A method for manufacturing a warp knit denim fabric as claimed in any one of the claims 1-7, the method comprising the steps of:
producing a spun yarn having tenacity at least 18cN/tex and each spun yarn comprises natural fibers at least 60% w/w of the spun yarn;
dyeing the spun yarn with one of the oxidative, reactive, vat dye or pigment or combination thereof; and
warp knitting the spun yarn at a predetermined speed in a predefined pattern to obtain a warp knit denim fabric having the spun yarns at least 45% w/w of fabric.

9. The method as claimed in claim 8, wherein the predetermined speed ranges from 400 to 700 rpm.

10. The method as claimed in claims 8 or 9, wherein the fabric course per inch ranges from 5 to 30 and preferably 8 to 25.

11. The method as claimed in any one of the claims 8 to 10, wherein the fabric weight ranges from about 150 GSM to about 350 GSM.
, Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)

&

THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

WARP KNIT DENIM FABRIC WITH SPUN YARN AND METHOD FOR MANUFACTURING A WARP KNIT DENIM FABRIC;

ARVIND LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS NARODA ROAD, AHMEDABAD - 380025, GUJARAT, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to a warp knitted denim fabric and a method for preparing a warp knit denim fabric.
BACKGROUND OF THE INVENTION
Denim fabric is commonly defined as a fabric having indigo dyed warp yarn and undyed weft yarn woven in twill structure.
Traditionally, the denim fabric is manufactured with spun cotton yarn in warp and weft, which is known as non-stretch fabric. The traditional denim manufacturing method includes various steps such as spinning, dyeing, sizing, weaving, finishing, garmenting and washing process. Now a days, the denim fabric is manufactured with elastomeric yarn.
Generally, the denim fabric is heavier in weight. In order to make denim lighter and softer, synthetic fibres and/or natural are nowadays blended with cotton fibres. Further, various weave patterns have been experimented to impart more comfort in wearing. But, even after so much of modifications, it is found that the comfort in wearing in the woven denim garments may not match or lack in the comfort level that gets in wearing knitted garments.
In current state of art, there are two types of knitting processes namely warp knit and weft knit. The weft knit is also known as circular knit. The weft knitted fabric is used for manufacturing T-shirt, lingerie, sportswear, leggings, and many more. The weft knitted fabric by this process moves as per body movement. However, the circular knitted fabric has demerit of garment stability after certain usage, the garment expands after certain use and become over-sized or bulgy.
The warp knitted fabric is used for sportswear, technical textile, upholstery etc. The warp knitted fabric has more dimensionally stable structure as compared to weft knitted fabric. The warp knitted fabric has better control (more balanced) at a time of knitting compared to weft knitted fabric because the yarn movement in warp knitting process comprises swinging and shogging motion. Further, there is problem of yarn runoff from holes (torn part of garment) in weft knitted fabric, whereas, such defect doesn’t occur in warp knitted fabric. Therefore, the life of warp knitted garment is more compared to its weft knitted counterpart.
In warp knitting process, the machine is run at higher speed and a single needle is used for more than one yarn that results into development of greater stress and strain on yarn. Therefore, spun yarns comprising natural fibers including cotton is not used as it couldn’t withstand this cyclic load of warp knitting. Hence, synthetic filament yarns are used for manufacturing warp knitted fabric. However, the synthetic filament yarns are not user friendly and causes discomfort during wearing.

Accordingly, there is need of a warp knitted denim fabric with spun yarn that gives denim like look, provides comfort of knitted fabric during wearing, which can be dyed with denim class dyes and also exhibit denim sensibility.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides one or more means in one or more embodiments/aspects for solving at least one of the aforementioned problems.
In an aspect, the present invention provides a warp knit denim fabric comprising a plurality of dyed spun yarns at least 45%w/w of fabric knitted as warp yarns, each spun yarn having tenacity at least 18cN/tex and each spun yarn comprises natural fibers at least 60%w/w of the spun yarn. The spun yarns are dyed with oxidative, reactive, vat dye or pigment or combination thereof.
In another aspect, the present invention provides a method for manufacturing a warp knit denim fabric, the method comprising the steps of producing a spun yarn having tenacity at least 18 cN/tex and each spun yarn comprises natural fibers at least 60% w/w of the spun yarn, dyeing the spun yarn with one of the oxidative, reactive, vat dye or pigment or combination thereof and warp knitting the spun yarn at a predetermined speed in a predefined pattern thereby forming a warp knit denim fabric having spun yarns at least 45%w/w of fabric.
According to an embodiment of the present invention, wherein the predetermined speed ranges from 400 to 700 rpm.
According to another embodiment of the present invention, the spun yarn comprises 100% natural fibers or a blend of natural with regenerated cellulosic fibers, synthetic fibers or a combination thereof, said blend having natural fibers at least 60% w/w of the spun yarn.
According to an embodiment of the present invention, the liner density of the spun yarn is from about 10 Ne to about 120 Ne and more preferably 20s Ne to 60s Ne.
According to the present invention, the natural fibers includes cotton fibers, wool, linen, hemp, jute etc. According to an embodiment of the present invention, cotton fibers are preferable for the warp knit denim fabric.
According to the present invention, the regenerated cellulosic fibres includes lyocell, viscose, modal, and cupramonium rayon etc.
DETAILED DESCRIPTION OF THE INVENTION
According to first aspect of the present invention, a warp knit denim fabrics of the present invention is made by warp knitting a plurality of dyed spun yarns at least 45% w/w of the fabric. According to the present invention, each spun yarn has a tenacity at least 18 cN/tex and comprises natural fibers at least 60% by weight. The dye is selected from oxidative dye, reactive dye, vat dye or pigment dye or combination thereof.
According to an embodiment of the present invention, the spun yarn may comprise 100% natural fibers. As per another embodiment of the present invention, the spun yarn may comprise a blend of natural fibres with regenerated cellulosic fibres, synthetic fibers or combination thereof wherein the blend comprises natural fibers at least 60% w/w of the spun yarn. The spun yarn may be a single ply, two ply or three ply.
According to an embodiment of the present invention, the warp knit denim fabrics may comprise a plurality of filament yarns, a plurality of elastomeric yarns or combination thereof along with the plurality of the spun yarns to get good product aesthetic as well as stretch and strength. The fabric may comprise filaments yarns ranging from 5% to 50% of the weight of the warp knit denim fabric. The fabric may comprise elastomeric yarns ranging from 2% to 20%of the weight of the warp knit denim fabric. According to the present invention the preferable density of the filament yarn and elastomeric yarn ranges from about 20 denier to about 150 denier.
According to another embodiment of the present invention, the warp knit denim fabric may comprise 100% spun yarn.
According to an embodiment of the present invention the spun yarn before knitting are dyed with oxidative, reactive, vat dye or pigment for denim or non-denim effect. The warp knit denim fabric may comprise spun yarns dyed with oxidative, reactive, vat dye or pigment or combination of vat dyed spun yarns and reactive dye dyed spun yarn knitted together on a warp knitting machine to provide the warp knit denim fabric and provide the desired denim effect.
In second aspect, the present invention provides a method for manufacturing a warp knit denim fabric. The method comprises steps of producing the spun yarns of desired properties; dyeing the spun yarn with one of the oxidative, reactive, vat dye or pigment or combination thereof and warp knitting the spun yarns along or in combination with elastomeric yarns, filaments yarns or combination thereof at a predetermined speed to produce the warp knit denim fabric.
According to the first step of the present invention, the spun yarn is produced by a compact spinning technology to reduce hairiness and provide more even yarn. The spun yarn produced by the compact spinning technology in such a way that the spun yarn has tenacity at least 18cN/tex. The compact spinning process/technology for making yarn is known, however, the present invention utilizes the compact spinning process/technology to produce the spun yarn of a particular tenacity for working over the knitting machines. Further, according to the present invention, the linear density of the spun yarn is from about 10s Ne to 120s Ne and more preferably 20s Ne to 60s Ne.
According to the present invention, the spun yarn comprises natural fibers at least 60% w/w of the spun yarn. Accordingto an embodiment of the present invention, the spun yarn comprises 100% natural fibers or a blend of natural fibres with regenerated cellulosic fibres, synthetic fibers or combination thereof wherein the blend may comprise natural fibers at least 60% w/wof the spun yarn.
According to the present invention, the spun yarn can be an elastomeric yarn having tenacity at least 18cN/tex and linear density from about 20 denier to about 150 denier.
According to an embodiment, the first step may include dyeing of the spun yarn with oxidative, reactive, vat dye or pigment. The spun yarn may be dyed with denim dyes using a rope dyeing machine.
According to another embodiment of the present invention, the first step of producing the spun yarn may include a step of forming a warp beam from the dyed spun yarn directly.
In the second step, the warp beam obtained from the first step may be warp knitted at a predetermined speed in a predetermined pattern to obtain the warp knit denim fabric having the spun yarns at least 45% w/w of the warp knit denim fabric. The fabric may include the 100% spun yarns. The fabric thus obtained has a weight that ranges from 150 GSM to 350 GSM as per ASTM D 3776 method. It is understood that the number of ends depends on intended end use of the fabric. The method of the present invention facilitates uniform shade to the fabric because all the ends are from one dye-lot and also dyed at the same time. This is achieved as the present invention omits the beam to a cone winding process and subsequent warping process after dyeing.
In the context of the present invention, it is understood here that the number of bars used in the knitting machine depends on fabric requirement and said number varies as per the requirement. The guide bar (GB) carries yarn as per predefined pattern of fabric. It is understood that the predetermined pattern can be selected as per the requirements and various knit patterns are very well known which can be used in the present invention. The number in pattern chain denotes yarn underlap. The spun yarn can underlap on maximum ten yarns, more preferably, six yarns. It is further understood that single guide bar machine is used for mesh or open fabric structure, however, more than one guide bars are used for dense and complicated structure.
According to an embodiment of the present invention, the speed of warp knitting machine is kept at 400 rpm – 700 rpm for spun yarn.
According to an embodiment of the present invention, the warp knitting step may include knitting of the spun yarn along with filament yarns, elastomeric yarns or combination thereof wherein the spun yarns are at least 45% w/w of the fabric. It is to be noted here that dope dyed filament yarn may also be used. The elastomeric yarn is used to stretch by 5% - 25% during fabric manufacturing process.
According to the present invention, the fabric course per inch ranges from 5 to 30 and preferably 8 to 25.
According to the present invention, the fabric gauze may be maximum 32”.
According to the present invention, the fabric weight ranges from about 150 GSM to about 350 GSM.
According to the present invention, the linear density of the filament yarn and elastomeric yarn ranges from about 20 denier to about 150 denier.
According to another embodiment of the present invention the warp knit denim fabric may be dyed with oxidative, reactive, vat dye or pigment or combination thereof for the desired denim effect. Further, the denim effect may be further enhanced by napping or sanding the denim surface of the fabric.
After knitting, the warp knitted fabric undergoes various known finishing processes depending on the structure of the warp knit denim fabric. In case of elastomeric yarn, fabric finishing may include heat set, scouring, drying and final finishing. In case of without elastomeric yarn, fabric finishing route includes scouring, drying and final finishing. In accordance with an embodiment of the present invention, in the scouring process, impurities are removed. In drying process, fabric is dried at about 160 °C to 180 °C temperature. In final finishing process, fabric parameter is finalized. In this process, the fabric is passed through compactor machine at 170 °C to 200 °C. Temperature may vary based on fabric quality and requirement. In this process, special finishing may be applied to fabric such as performance finish and over dyeing.
According to the present invention, the natural fibers includes cotton fibers, wool, linen, hemp, jute etc. According to an embodiment of the present invention, most natural fibers preferable for the warp knit denim fabric are cotton fibers as cotton fibers are widely accepted and used for making the denim fabric.
The warp knit denim fabric of the present invention has better comfort, high productivity, dyeing compatibility and stable structure.
Examples
Hereinafter, the present invention will be described in more detail based on example. The example is not intended to limit the scope of the present invention. It is believed the invention will be better understood from the following detailed example:
Example1:
The warp knit denim fabric made by the method as claimed in the present invention had a following pattern:
GB 1: 1 in 1 out; 11/10/10/11
GB 2: 1 in 1 out; 11/01/01/11
GB 3: Full; 3/4/1/0
Yarn linear density: 40s Ne (reactive dyed yarn) in GB (1, 2, 3)
Spun yarn tenacity: 18 cN/Tex
Course per inch: 15
Machine Gauge: 28 Gauge
Fabric weight: 200 GSM
Fibre content: 100% Cotton
Machine Speed: 550 rpm
It was found that the garment made from warp knit denim fabric has more comfort than woven fabric.
The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.