DESC:TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of dyeing fabric with indigo dyes in open form.

BACKGROUND OF THE INVENTION
A fabric dyeing generally includes two processes i.e. package dyeing and sheet and/or rope dyeing. As known in the art, the package dyeing process is time consuming as well as involves cumbersome steps. The package dyeing process also involves excessive use of chemicals and water. The fabric or yarn may be dyed by various classes of dyes such as reactive dyes, oxidative dyes, vat dyes, direct class and the like.
Indigo dye is used in denim industries for many decades. Indigo belongs to the class of vat dye. It has color fading and wash down characteristics that fades the color with each wash. In case of dyeing the knitted fabric with Indigo color, the yarn used for fabric making has to be dyed. To get the indigo dyed yarn, special set up is required because indigo dyeing is not feasible in package form. Accordingly, the sheet or rope dyeing process is used. Further, the dyed yarn needs to be converted into the package form. This process consumes lots of time.
Another way of getting dyed fabric is by fabric dyeing process. Indigo dyeing is not feasible in case of fabric dyeing process because indigo dye is a vat dye that has fading property that may result into uneven dyeing on fabric. The fabric is coated with a wax type material during finishing processes. In this case when the fabric is subjected to dyeing, the dye may not penetrate in the fabric as it is hard to penetrate through the wax coat. If the fabric in tube form is subjected to Indigo dye, the fabric may get dyed in uneven form. Further, Indigo dye may not penetrate into the fabric in tube form. t
Furthermore, the dyeing of Indigo/vat dye involves oxidation and reduction process. The dyeing takes place on yarn form followed by fabric manufacturing process. Generally, the knitted fabric is on tube form, so it has to be cut for the further process.
Accordingly, there is need of a method suitable for dyeing of fabric with indigo dye.

SUMMARY OF THE INVENTION
The present invention relates to a method of dyeing fabric. The method comprises the following steps. In a first step, the fabric is pre-treated with water and wetting agent to clean the fabric and to increase fabric absorbency. In the next step, the treated fabric is dried partially at a temperature of 100-150°C. In an embodiment, the fabric is not completely dried and contains moisture when dyed. In the next step, the fabric is dyed using the dyeing composition. In the next step, the dyed fabric is washed and treated with color fixing agent. In the next step, the dyed fabric is dried at temperature of 100-150°C. In the last step, the dried fabric undergoes final finishing process.
The cut open fabric is pre-treated before the dyeing process. The pre-treatment includes dipping the fabric into water followed by treating with 5-10 GPL of wetting agent, 2 -5 GPL of Sequestering agent and 2-4 GPL of caustic soda for the 10 to 30 min, followed by washing and drying process. The fabric is partially dried that means the fabric has at least 30% moisture. The dyeing of the fabric on the thermoset machine
The dyeing composition includes Indigo dye of about 10 GPL, about 10-15 GPL of reducing agent, about 2-5 GPL of sequestering agent, about 2-5 GPL of wetting agent, about 0.5-2 GPL of dispersing agent, about 5-8 GPL of caustic and water. The fabric is made up from natural fibre, man-made fibre or combination thereof. The fabric is knitted or woven fabric. The fabric includes the fabric in open form.

DETAIL DESCRIPTION OF INVENTION
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to particular structure of the invention selected for illustration in the drawings and are not intended to define or limit the scope of the invention.
In general aspect, the present invention provides dyeing fabric with indigo dyes in open form. Generally, the knitted fabric is produced in tube form, in accordance with the present invention, the tube is cut and the fabric is made in open form for dyeing.
In accordance with the present invention, a method of dyeing knitted or woven fabric with Indigo dye is disclosed. The fabric is made up from natural fibre, man-made fibre or combination thereof. The cut open fabric is pre-treated before the dyeing process. The pre-treatment is important that helps removing a coat of wax like material from the fabric and for the even dying of the fabric by easy penetration of the indigo dye. The pre-treatment includes dipping the fabric into water followed by treating with 5-10 GPL of wetting agent, 2 -5 GPL of Sequestering agent and 2-4 GPL of caustic soda for the 10 to 30 min, followed by washing and drying process. The fabric is partially dried that means the fabric has at least 30% moisture. The dyeing of the fabric on the thermoset machine. The partially dried fabric is dyed on thermoset machine. After pre-treatment, the fabric is subjected to dyeing process.
The method of dyeing comprises the following steps. In a first step, the fabric is pre-treated with water and wetting agent to clean the fabric and to increase fabric absorbency. The treated fabric is dried partially for about 10-20 Sec at a temperature of 100-150°C. In an embodiment, the fabric is not completely dried, the fabric is dried upto 70% and contains moisture about 30% when dyed. In the next step, the fabric is dyed using the dyeing composition. The dyeing composition includes Indigo dye of about 5 – 20 GPL, about 10-15 GPL of reducing agent such as Sodium hydro sulfide, about 2-5 GPL of sequestering agent for example KLEERIX PER, about 2-5 GPL of wetting agent such as KLEENOX WLF, about 0.5-2 GPL of dispersing agent for example SETAMOL WS, about 5-8 GPL of caustic and water. The dyed fabric is dried at temperature of 100-150°C.
In the next step, the dyed fabric is washed and treated with color fixing agent. In the next step, the dyed fabric is dried. In the last step, the dried fabric undergoes final finishing process. It is to be noted here that the obtained fabric is evenly dyed and cost effective as compared to available fabric in the market. The method of the present invention reduces the consumption of the chemicals (agents used for pre-treatment and dyeing) and water thereby reducing the cost involved in the dyeing process. The comparative data is given below:
@ Hemaxee. Please insert Table for comparative data as discussed.
EXAMPLE:
Indigo dyed knitted fabric
30s Ne cotton yarn
Fabric structure: Fleece
Fabric weight: 280 GSM
Dyeing composition:
GPL Ingredient
10 Indigo dye
2 Wetting agent
2 Sequestering agent
5 Caustic
10 Reducing agent

Example 2:
Indigo dyed knitted fabric
20s Ne Cotton yarn
Fabric structure: Twill
Fabric weight: 320 GSM
Dyeing composition:
GPL Ingredient
15 Indigo dye
2 Wetting agent
2 Sequestering agent
5 Caustic
10 Reducing agent

With the dyeing method of the present invention, the use of water is reduced upto at least 20% and reduction in use of chemical is at least 10% as compare to existing dyeing method.
The embodiments of the invention shown and discussed herein are merely illustrative of modes of application of the present invention. Reference to details in this discussion is not intended to limit the scope of the claims to these details used to illustrate the invention.
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 scope of the present invention.
,CLAIMS:
1. A method of dyeing fabric, the method comprising the steps of:
pre-treating a fabric with water and wetting agent, the pre-treating process comprises the steps of:
dipping the fabric into water,
treating the wet fabric with 5-10 GPL of wetting agent, 2 -5 GPL of sequestering agent and 2-4 GPL of caustic soda for the 10 to 30 min, and
washing the treated fabric;
drying the treated fabric partially at a temperature of 100-150°C by maintaining at least 30% moisture in the fabric;
dyeing the dried fabric using a dyeing composition;
washing the dyed fabric;
treating the washed fabric with a color fixing agent;
drying the dyed fabric at temperature of 100-150°C; and
finishing the dried fabric.

2. The method as claimed in claim 1, wherein the fabric is dyed on the thermoset machine.

3. The method as claimed in claim 1, wherein the dyeing composition includes Indigo dye of about 5 – 20 GPL, reducing agent of about 10-15 GPL, sequestering agent of about 2-5 GPL, wetting agent of about 2-5 GPL, dispersing agent of about 0.5-2 GPL, caustic of about 5-8 GPL and water.

4. The method as claimed in claim 1, wherein the fabric is knitted or woven fabric.

5. The method as claimed in claim 1, wherein the fabric is made up from natural fibre, man-made fibre or combination thereof.

6. The method as claimed in claim 1, wherein the fabric includes the fabric in open form.

7. A dyed fabric obtained from the method as claimed in claims 1-6.