DESC:FIELD OF THE INVENTION
This invention relates to process for continuous dyeing of yarn or fabric comprising thermoplastic material with oxidative dyes.

BACKGROUND OF THE INVENTION
Oxidative dyes impart a hue to a yarn or fabric after oxidation. Examples of oxidative dyes/colorants include and are not limited to vat dyes, sulphur and the like. The oldest vat dye is indigo which is used to color natural fibers like cotton, silk and wool. Indigo is typically applied by the ring dyeing method in rope/sheet form, and is applied in leuco form, followed by an oxidation step which imparts the rich color and hue.
Thermoplastic material have desirable functional properties like crease recovery, moisture management (wick moisture away from body), and abrasion resistance (reduce chafing) and the like. Dyeing of thermoplastic material with oxidative dyes is desirable. However, dyeing methods which work for natural fibers do not work for thermoplastic material as the large oxidative dye molecules cannot penetrate through the molecular structure of the thermoplastic filaments or fibers.
Hence, there is a need for a process of dyeing thermoplastic material including yarns or fabrics with oxidative colors so as to get fibers having the advantageous functional properties of thermoplastic material along with the aesthetic look of oxidative dyes.

SUMMARY OF THE INVENTION
Accordingly, the present invention provides a continuous process for dyeing yarn or fabric having thermoplastic fibers/filaments. The process comprising steps of: dyeing the yarn or fabric having thermoplastic material by passing through a dye trough containing an oxidative dye solution, drying the dyed yarn or fabric having thermoplastic material at 100-130°C for a predetermined period, passing the dried yarn or fabric having thermoplastic material through a fixation unit at 160-220°C for a predetermined period, and washing the yarn or fabric having thermoplastic material for removing unfixed dye to obtain the oxidative dyed yarn or fabric having thermoplastic fibers. According to the present invention, the present process is carried out in the absence of swelling agents.
In an embodiment, the oxidative dyed yarn or fabric having thermoplastic material can be further washed with an oxidizing agent for having a reproducible washed down appearance to garments manufactured from the oxidative dyed yarn or fabric having thermoplastic fibers. According to the present invention, the oxidizing agent includes hydrogen peroxide, potassium permanganate, perborate, or chorine-based compound.
According to the present invention, the oxidative dye solution comprises an oxidative dye, a dispersing agent, an alkali, a sequestering agent, a reducing agent, a neutralizer and a wetting agent. The oxidative dye includes indigo, vat or a sulphur dye.
According to the present invention, the yarn or fabric includes cellulosic fibers with or without elastomeric filament along with the thermoplastic material and the thermoplastic material includes thermoplastic filament or thermoplastic fibers of acrylic, polyester or polyamide.
According an embodiment of the present invention, the predetermined period of dyeing is 30-60 seconds and the predetermined period of passing the dried yarn or fabric having thermoplastic material through a fixation unit is 60-120 seconds.

DETAILED DESCRIPTION OF THE INVENTION
All materials used herein were commercially purchased as described herein or prepared from commercially purchased materials as described herein.
Where the term “comprising” is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun, e.g. “a” “an” or “the”, this includes a plural of that noun unless something otherwise is specifically stated. Hence, the term “comprising” should not be interpreted as being restricted to the items listed thereafter; it does not exclude other elements or steps, and so the scope of the expression “a device comprising items A and B” should not be limited to devices consisting only of components A and B. This expression signifies that, with respect to the present disclosure, the only relevant components of the device are A and B.
Thermoplastic fibers or filaments typically comprises a polymer that becomes pliable or moldable above a specific temperature (glass transition temperature) and solidifies upon cooling. Non-limiting examples include polyester, acrylic, polyamide, and the like.
Conventional processes for continuous dyeing of cellulosic fibers with oxidative dyes such as indigo or sulfur are operated as pad-steam processes, or pad-dry processes, or alternatively as pad-dry-pad-steam processes. The fiber or fabric obtained from conventional processes is fully through-dyed and then washed to get a washed-down look, but the washed down look may be variable from batch to batch. There is a market/fashion desire for a reproducible washed down look in thermoplastic or cellulosic fiber-derived garments. Accordingly provided herein are processes for continuous dyeing of thermoplastic material or blends comprising thermoplastic material and cellulosic fibers and garment/ fabrics thereof and methods for generating reproducible washed down look to garments made from said yarns or fabrics comprising thermoplastic material.
The method of dyeing disclosed herein is a continuous dyeing process suitable for dyeing yarns or fabrics comprising thermoplastic material. The yarns referred herein include thermoplastic filaments and spun yarns comprising thermoplastic fibers or blend of thermoplastic fibers and cellulosic fibers with or without elastomeric filaments. The fabric referred herein includes woven fabrics having either warp yarns, weft yarns or warp and weft yarns comprising thermoplastic yarns.
The continuous dyeing process for dyeing yarn or fabric comprising thermoplastic material comprises the following steps:
A yarn or woven fabric comprising thermostatic material according to the present invention is passed through a dye trough containing oxidative dye solution without swelling agents. The woven fabric comprising thermostatic material may be subjected to known pre-treatment processes such as de-sizing, scouring, and heat setting prior to dyeing. A single dye trough treatment or multiple dye trough treatments may be used with a single dip or multiple dips. The oxidative dyeing composition includes an oxidative dye, a dispersing agent, an alkali, a sequestering agent, a reducing agent, a neutralizer and a wetting agent in a generally known proportion and does not contain swelling agents. The exemplary proportion is mentioned below:
Ingredients of the dye composition Quantity
Oxidative Dye 5-50 gpl
Dispersing agent 5 gpl
Alkali 2 gpl
Sequestering agent 2 gpl
Reducing agent 5 gpl
Neutralizer 2 gpl
Wetting agent 0.5-1 gpl

According to the present invnetion, the oxidative dye is selected from indigo, vat and sulphur dye. The dispersing agent is Setamol WS. The Sequestering agent is Dekol FBSN. The reducing agent is selected from Thiourea Dioxide, Hydroxy Acetone, Sodium borohydride, Sodium Hydrosulphite. Preferable neutralizer are Organic Acids and Acetic acid and the wetting agent includes Nonionic, Anionic, Lenetol HPED.
According to the present invention the dyed yarn or fabric is then dried at about 100-130 °C for a predetermined period. Advantageously, the predetermined period is for 30-60 sec.
After the drying process, the dyed yarn or fabric is immediately passed through a fixation unit where dye molecules are fixed on to the fabric at about 160-220 °C for a predetermined period and then forwarded to washing process. According to the present invention, the predetermined period is around 60 to 120 sec.
In the washing process, the dyed yarn or fabric is washed by passing through one or more washing troughs to remove any unfixed dye in order to obtain the oxidative dyed yarn or fabric having thermoplastic material.
According to the present invention, the oxidative dyed yarn, or fabric having thermoplastic material may be further washed with an oxidizing and soaping agent in water using either a hot wash or a cold wash, to obtain the oxidative dyed yarn or fabric with a reproducible washed-down effect. The oxidative agents used for washing includes hydrogen peroxide, potassium permanganate, perborate, or chorine based compound.
The yarns or fabric comprising thermoplastic material oxidative dyed according to the present invention includes thermoplastic filaments, thermoplastic fibers or their blends with cellulosic, non-cellulosic fibers with or without elastomeric material or filaments. The thermoplastic material includes filaments or fibers of acrylic, polyester and polyamide.
The process of the present invention is a continuous process and allows to dye yarns and fabrics of thermoplastic material continuously without the use of swelling agents. The process is cost effective also. Garments manufactured from the said dyed yarns or fabric has a reproducible washed -down appearance.
The following example further illustrate the present invention and is not to be construed as limiting the scope thereof.

Example 1
All materials used herein were commercially purchased as described herein or prepared from commercially purchased materials as described herein. A fabric comprising polyester filament/yarns as a thermoplastic material was dyed as described and claimed by a continuous process wherein drying temperature and time was 120°C and 60 sec. The temperature and time in the fixation unit was 200°C. The dye composition in grams per liter used is as mentioned below:
Indigo Dye as an oxidative dye: 30 gpl; Setamol WS as Dispersing agent: 5 gpl; Alkali:2 gpl; Dekol FBSN as Sequestering agent: 2 gpl; Hydroxy Acetone as a reducing agent: 5 gpl; Acetic acid as Neutralizer: 2 gpl, Lenetol HPED as a Wetting agent 0.8 gpl. The fabrics dyed was then converted into the garments and tested for washed down appearance.
It was observed that the garments had a washed-down appearance even after 10 washes.
The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
,CLAIMS:

1. A process for continuous dyeing yarn or fabric having thermoplastic material, the process comprising steps of:
dyeing a yarn or fabric having thermoplastic material by passing through a dye trough containing an oxidative dye solution without swelling agent;
drying the dyed yarn or fabric having thermoplastic material at 100-130 °C for a predetermined period;
passing the dried yarn or fabric having thermoplastic material through a fixation unit at 160-220 °C for a predetermined period; and
washing the yarn or fabric having thermoplastic material for removing unfixed dye to obtain an oxidative dyed yarn or fabric having thermoplastic material.
2. The process as claimed in claim 1, wherein the oxidative dyed yarn or fabric having thermoplastic material can be further washed with an oxidizing agent for having a reproducible washed-down appearance to garments manufactured from the oxidative dyed yarn or fabric having thermoplastic fibers.
3. The process as claimed in claim 2, wherein the oxidizing agent is either hydrogen peroxide, potassium permanganate, perborate or chorine-based compound
4. The process as claimed in claim 1 or 2, wherein the oxidative dye solution comprises an oxidative dye, a dispersing agent, an alkali, a sequestering agent, a reducing agent, a neutralizer and a wetting agent.
5. The process as claimed in one of the preceding claims 4, wherein the oxidative dye includes indigo, vat or a sulphur dye.
6. The process as claimed in any one of the preceding claims 1-5, wherein the yarn or fabric includes cellulosic fibers with or without elastomeric filament along with the thermoplastic material.
7. The process as claimed in claim 1 or 6, wherein the thermoplastic material includes fibers/filaments of acrylic, polyester and polyamide.
8. The process as claimed in one of the preceding claims 1-7, wherein the predetermined period of dyeing is 30-60 seconds.
9. The process as claimed in one of the preceding claims 1-8, wherein the predetermined period of passing the dried yarn or fabric having thermoplastic material through the fixation unit is 60-120 seconds.
10. A garment manufactured from the oxidative dyed fabric or yarns dyed with the process as claimed in any one of the preceding claims 1-9.