FABRIC

TECHNICAL FIELD OF THE INVENTION

The present invention relates to method of manufacturing laser friendly denim fabrics.

BACKGROUND OF THE INVENTION

Denim is popular apparel for many generations. Over a period of time, Denim has undergone various changes such as non-stretch to stretch, comfort stretch, high stretch, skinny denim, performance denim, ripped denim etc. Nowadays, main focus of denim garment industry is on improving aesthetic, visual appearance and hand feel of the denim garments. The denim garments include jeans, jacket, shirt, dresses etc. During manufacturing, the denim garment undergoes different washing processes. The washing processes are categorised in two categories, i.e., a dry washing process and a wet washing process. The dry processes include micro sanding, brushing, fraying, and making whiskers and chevrons on denim garments. The wet processes include different washes like rinse, enzyme, stone and bleach. It is well known in denim industry to remove dye from predefined area to achieve desired aesthetic look of garment. For example, dye is removed from predefined area to create whiskers or chevrons on a denim fabric. Typically, the aforementioned processes, such as making whiskers and chevrons on denim garments, are carried out manually using water and suitable chemicals. However, these processes consume huge amount of water and require a lot of time for execution. Additionally, manual intervention may be required at each stage of the processes. Further, being a manual process, reproducibility of the same pattern on each denim garment may not be possible, which hampers uniformity of the design on the denim garments.

Nowadays, the textile industries, including denim garment finishing industries, are trying to reduce water consumption. It is now well known in the garment industry that denim garments can be subjected to laser treatments for removing dye from predefined area to achieve desired aesthetic look of garment instead of using water and chemicals. Due to the laser treatment, desired results can be obtained in short time span and reproducibility of the same pattern can be achieved. The laser finishing process is a highly controlled system, wherein laser intensity and pixel density along with laser exposure time are controlled. However, there is no control on temperature generated due to the laser rays. The intensity of laser rays is mainly based on fiber contents of the fabric to be treated and also on desired aesthetic look. Thus, the portion of the fabric may get melt due to exposure to the laser rays. Typically, when synthetic fibers of the fabric are exposed to laser rays, the exposed area of the synthetic fibers melts or burn and also gets stiffen causing defect in fabric/garment. Further, the fabric does not show a good whisker or chevron effect thereon when exposed to laser rays.

Therefore, there is felt a need of a process of manufacturing a laser friendly fabric which can be safely exposed to laser rays.

SUMMARY OF THE INVENTION

The present invention envisages a method of manufacturing a laser friendly denim fabric. The method comprises following steps. Initially, a yarn is made in a ring spinning machine to have a twist multiplier ranging from 4.5 to 6. Further, the yarn is passed through a dye solution at a speed ranging from 22 meter/minute to 35 meter/minute to obtain a dyed yarn. A fabric is woven using weft yams and a plurality of the dyed yarns as a warp yams on a weaving machine.

The present invention further envisages a yarn dyed with a dye. The dye is penetrated from 16% to 20% of a cross-sectional area of the yarn. A fabric is woven using the yams as warp yams kept on a surface of the fabric exposed to laser rays.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING

Figure 1 shows a cross sectional view of a surface dyed yam.

DETAILED DESCRIPTION OF THE INVENTION Although specific terms are used in the following description for sake of clarity, these terms are intended to refer only to particular structure of the invention, and are not intended to define or limit the scope of the invention.

References in the specification to“an embodiment” mean that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

The present invention envisages a method of manufacturing a laser friendly denim fabric. The method is elaborated in subsequent paragraphs.

Accordingly, the first step of the laser-friendly fabric manufacturing process includes manufacturing of yam, preferably a warp yarn. The yarn may be made from natural fibers and man-made fibers including cotton and cotton-synthetic fibres blends and the like. The yarn morphology is changed by changing various process parameters and spinning technique.

In an embodiment, the yams are spun by ring spinning machine. According to the present invention, yam twist flows from surface to the core of the yarn. The method includes the step of making a yarn in a ring spinning machine to have a twist multiplier ranging from 4.5 to 6. More specifically, the yam multiplier is increased as compared to yarn twist multiplier in conventional yam manufacturing processes. The increase in the yam twist multiplier results in compact structure of the yam. Thus, during dyeing, the dye particles cannot get penetrated deep into the yam. The yam is spun from two rovings in a ring spinning machine. Increase in the yam twist multiplier typically results into harsh yarns in case yam is made from single roving, thereby resulting in providing harsh feel to the fabric. To avoid this, the yarn is spun using two rovings. Such yarn gives smooth and soft feel to the fabric. The method further includes the step of dyeing the yarn. In an embodiment, the yarn is dyed with indigo dye or sulphur dye or combination thereof in such a way that the dye does not penetrate inside the core of the yam. According to an embodiment of the present invention, changes may be carried out in the condition of dyeing. In one embodiment, dyeing of yarn with a dye is carried out in alkaline medium. In another embodiment, the pH during dyeing is maintained more towards neutral to ensure surface dyeing. More specifically, the pH value of the alkaline medium is kept between 11 to 11.5.

For dyeing the yarn, the yarn is passed through the dye solution at a speed ranging from 22 meter/minute to 35 meter/minute to obtain a dyed yam. Typically, this speed of the yam is 10% more than the speed of passing the yam in conventional dyeing processes. The increase in the speed of passing the yam through the dyeing solution reduces the contact time between the yarn and the dyeing solution. Thus, the dye particles get lesser time to penetrate into the yarn. Typically, the speed of passing the yam is adjusted so as to prevent the dye particles to enter beyond 20% of a cross-sectional area of the yarn. The dye particles enter the yarn from circumference of the yarn and travel towards the core of the yam. Reduction in contact time between the yarn and the dye solution and increased twist multiplier of the yarn makes it difficult for the dye particles to enter deep into the core of the yarn.

Figure 1 shows a cross sectional view of the surface dyed yarn (100). The dye does not penetrate too deep into the core of the yarn. The dyed yarn as shown in the Figure 1 has un-dyed core (120) and surface dyed (110) with indigo dye or sulphur dye or combination thereof.

In an embodiment, the method includes the step of sizing. The yarns are sized with water soluble size recipe which does not hinder the action of laser ray. The water-soluble size of the yarns provides easement during the laser treatment of the fabric. The method includes the step of weaving a fabric with weft yarns and a plurality of the dyed yarns as warp yams on a weaving machine. In an embodiment, weft yarns include yams made of natural fibers or a blend of natural and synthetic fibers, stretch yams, or 100% synthetic filaments or combination thereof. The fabric is woven in denim weaves such as twill, satin/sateen and dobby and the like.

The method includes a sub-step of weaving the warp yarns by keeping them on a surface of the fabric exposed to laser rays. More specifically, the fabric is woven in such a way that warp yams remain on surface of the fabric exposed to laser rays. This helps to remove dye on the surface by using laser ray. Thereafter, the woven fabric undergoes finishing process such as singing, desizing, and a final finishing.

The woven fabric thus manufactured is laser friendly and allows to provide garment with reproducible aesthetic look. The garments made from the woven fabric may be treated with laser. The laser removes dyes from pre-defmed area of the garment and gives desired garment finishing effect. As the dye is not penetrated deep into the yarns of the fabric, the laser treatment does not cause any damage to the fabric when exposed. Typically, if the fabric has polyester content, the polyester may melt when exposed to laser rays for longer duration of time. Presently, invented fabric is laser friendly. The dye is not penetrated deeply into the yams. Thus, even if the fabric has polyester content, the risk of melting polyester in the fabric is reduced.

Laser treatment is typically useful for fabric which is dyed with dyes having a wash down characteristic. Indigo and sulphur dyes are having wash-down effect which means said dyes can be easily removed after each wash. Laser sensitivity rating of the fabric is given based on response of the fabric to laser.

The present invention further discloses a yam and a fabric made of the yams. The yarn is made of natural fibers and man-made fibers including cotton and cotton- synthetic fibres blends. The yam is dyed with Indigo or sulphur dyes or combination thereof, wherein the Indigo or sulphur dye is penetrated from 16% to 20% of a cross-sectional area of the yarn. In an embodiment, the yarn is dyed as per the method described in foregoing paragraphs. As the dye is not penetrated deep into the yarn, it can be easily removed by exposing to laser rays to achieve aesthetic effects such as making whiskers and chevrons on denim fabrics. The fabric is woven using the plurality of aforementioned yarns. During weaving the fabric, the dyed yams are retained as warp yams.

Following table illustrates effect of the method of the present invention on a fabric. Table 1 -

LSF is a well known grading system for determining the effect of the laser treatment on the fabric. It is well known that higher LSF grade depicts better laser treatment effect on the fabric. With reference to Table 1, a fabric, which is not manufactured according to the process steps of the present invention, shows LSF of grade 6 when exposed to laser treatment. On the other hand, a fabric, which is manufactured according to the process steps of the present invention, shows LSF of grade 9, thereby showing a better laser treatment effect.

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.