DESC:FIELD
The present disclosure relates to a process of dyeing.
BACKGROUND
Dyeing of synthetic polymer filaments is an important process in the textile industry. Dyeing can be carried out to obtain colored polymer filaments or to improve their appearance.
On several occasions, polymer filaments demonstrate slight coloration or tinge. Typically, the polymer filaments manufactured from the recycled polymers are associated with a tinge which lowers its aesthetic appeal and commercial value. The aesthetic appeal of such polymer filaments can be improved by dyeing.
Dyeing of the polymer filaments is typically performed as a downstream process after the manufacture of the polymer filaments. A typical dyeing process involves the following steps. The polymer filaments are immersed in a dyeing bath containing a dyeing composition at room temperature. The temperature of the dyeing composition is raised at a rate of 1.5 ?C per minute up to 130 ?C and simultaneously the pressure of the dyeing bath is raised to 2.5 to 3 bars. The dyeing bath containing the polymer filaments is maintained at this temperature and pressure for 30 minutes followed by lowering the temperature of the dyeing composition at a rate of 3 to 5 ?C per minute until the temperature reaches 70 ?C. The pressure is simultaneously reduced to the atmospheric pressure. The dyeing bath is drained; and the dyed polymer filaments are washed and dried.
This conventional dyeing process is time consuming and requires high amount of energy. Apart from this, the conventional dyeing process generates effluent which needs treatment. The effluent treatment process is costly and also needs additional resources.
There is, therefore, a need for developing a process for dyeing polymer filaments that overcomes the above mentioned drawbacks while providing the desired appearance to the polymer filaments.
DEFINITIONS
As used in the present disclosure, the following words and phrases are generally intended to have the meanings as set forth below, except to the extent that the context in which they are used to indicate otherwise.
The expressions L*, a*, b* and whiteness index indicate values defined by the CIE color scale.
The expression “L*” in CIELAB color scale defines lightness. The L* scale varies from 0 meaning black or total absorption to 100 meaning white.
The expression “a*” in CIELAB color scale defines the red/green value. A color measurement movement in the +a direction depicts a shift toward red while movement in the –a direction depicts a shift towards green color.
The expression “b*” in CIELAB color scale defines the yellow/blue value. A color measurement movement in the +b direction represents a shift toward yellow color, while movement in the –b direction depicts a shift toward blue color.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for dyeing polymer filaments.
Another object of the present disclosure is to provide a fast process for dyeing polymer filaments.
Still another object of the present disclosure is to provide an economic process for dyeing polymer filaments.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
In accordance with one aspect of the present disclosure there is provided a process for dyeing a plurality of polymer filaments at drawing stage.
The process of the present disclosure involves dyeing a plurality of polymer filaments while it is being drawn. Dyeing is carried out using at least one method selected from the group consisting of spraying the dyeing composition with high pressure and contacting the dyeing composition. The plurality of polymer filaments are drawn and dyed at a speed in the range from 150 m/min to 250 m/min.
The dyeing operation takes place upstream during the manufacture of polymer filaments. The process of the present disclosure is fast, cost effective and environment friendly.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The present disclosure will now be described with the help of the accompanying drawings in which:
Figure 1 illustrates a dyeing unit comprising a plurality of spray nozzles (V-jet flat spray nozzles) for the application of the dyeing composition according to the process of the present disclosure; and
Figure 2 illustrates spray pattern for the application of the dyeing composition according to the process of the present disclosure.
DETAILED DESCRIPTION
Dyeing process is used for obtaining colored polymer filaments as well as to camouflage the tint or slight coloration that reduces the aesthetic appeal and commercial value of the polymer filaments.
The conventional dyeing processes are accompanied with problems such as high cost, long processing time and generation of effluent. Further, the conventional dyeing process is carried out as a separate unit process which adds to the cost of manufacturing of the polymer filaments.
The present disclosure provides a process for the preparation of dyed polymer filaments while obviating one or more of the problems associated with the conventional dyeing process mentioned herein above.
In the process of the present disclosure, the dyeing of the polymer filaments is carried out at the drawing stage during the manufacturing of the polymer filaments, thereby maintaining high speed and high productivity during manufacturing. Thus, in the process of the present disclosure, the dyeing process is carried out upstream during the manufacture of the polymer filaments.
In contrast, during the conventional process, dyeing is carried out as a separate step after manufacturing of the polymer filaments that leads to decrease in the speed and productivity of manufacturing of the polymer filaments. Further, in a conventional process, the dyeing unit is a distinct unit, which adds to the overall cost.
The process of the present disclosure can be used for dyeing textiles such as fiber and yarn.
In an aspect of the present disclosure there is provided a process for dyeing a plurality of polymer filaments. The process comprises the steps presented herein below.
The plurality of polymer filaments is drawn at a predetermined speed through a draw line path. A dyeing unit is disposed in a spaced relation to the draw line path. A dyeing composition is applied to the plurality of polymer filaments being drawn through the draw line path using the dyeing unit to obtain a plurality of dyed wet polymer filaments. The plurality of dyed wet polymer filaments is cured to obtain a plurality of dyed polymer filaments.
The process steps of drawing the polymer filaments, applying the dyeing composition and curing are carried out at high speed. Therefore, the process of the present disclosure saves time and maintains high speed and high productivity during manufacturing. In accordance with the embodiments of the present disclosure, the predetermined speed is in the range from 150 m/min to 250 m/min.
In accordance with the embodiments of the present disclosure, the polymer is selected from the group consisting of polyester and recycled polyester.
In accordance with one embodiment of the present disclosure, the polymer is polyester. In accordance with another embodiment of the present disclosure, the polyester is polyethylene terephthalate. In accordance with yet another embodiment of the present disclosure, the polymer is a recycled polyester polymer.
The dyeing composition may contain substances that are typically employed for dyeing and coloring of the polymer filaments such as dyes, pigments and auxiliaries.
In accordance with the embodiments of the present disclosure, the dyeing composition comprises at least one dye, at least one solvent and auxiliaries.
In accordance with the embodiments of the present disclosure, the dye is at least one selected from a group consisting of water insoluble dyes and water soluble dyes.
In the process of the present disclosure, the concentration of the dye in the dyeing composition depends upon the nature of the dye and the desired coloration of the dyed polymer filaments.
In accordance with one embodiment of the present disclosure, the dye is diaminostilbene disulphonic acid (DDA). DDA is a white colored dye. The concentration of DDA in the dyeing composition ranges from 1 gpl to 20 gpl.
In accordance with the embodiments of the present disclosure, the solvent is at least one selected from a group consisting of water, methanol, diethyl ether, acetonitrile and acetone.
In accordance with one embodiment of the present disclosure, the solvent is water.
In accordance with the embodiments of the present disclosure, the auxiliary is selected from a group consisting of optical brighteners, topical finish chemicals and wetting agents.
Application of the dyeing composition to the plurality of polymer filaments is carried out by at least one method selected from the group consisting of spraying the dyeing composition at high pressure on the plurality of polymer filaments and contacting the dyeing composition with the plurality of polymer filaments.
During the step of application of the dyeing composition to polymer filaments, the dyeing composition first contacts the outer surface followed by penetration of the dyeing composition inside the polymer filament. Penetration of the dyeing composition at a uniform rate is necessary for uniform dyeing which provides even coloration to the polymer filaments thereby enhancing their aesthetic appeal.
In accordance with one embodiment of the present disclosure, the dyeing unit comprises a plurality of spray nozzles disposed operatively above and operatively below the draw line path on which the plurality of polymer filaments travels. The arrangement of the spray nozzles is demonstrated in Figure 1, wherein 4 represents arrangement of the spray nozzles and 2 represents the plurality of polymer filaments.
In an operative configuration, the polymer filaments are drawn and passed through the dyeing unit and the curing unit. The dyeing unit in this case comprises spray nozzles. The polymer filaments are sprayed with the dyeing composition in the dyeing unit while being drawn. Thereafter, the dyed polymer filaments are immediately cured in the curing unit.
In accordance with the embodiments of the present disclosure, the plurality of spray nozzles comprises at least two spray nozzles.

In accordance with one embodiment of the present disclosure, the plurality of spray nozzles comprises 4 spray nozzles.

In accordance with another embodiment of the present disclosure, the plurality of spray nozzles comprises 108 spray nozzles.
In accordance with the embodiments of the present disclosure, the length of the dyeing unit is in the range from 20 to 50 cm.
In accordance with one embodiment of the present disclosure, the length of the dyeing unit is 30 cm.
In accordance with the embodiments of the present disclosure, the length of the curing unit is in the range from 10 to 40 meters.
In accordance with one embodiment of the present disclosure, the length of the curing unit is 25 meters.
In accordance with one embodiment of the present disclosure, the spray nozzles are V-jet flat application nozzle. The application pattern of V-jet flat application nozzle is shown in Figure 2, wherein 6 represents a spray nozzle (V-jet flat application nozzles) and 8 represents the band of dyeing composition obtained from 6 after spraying the dyeing composition.
The dyeing composition is applied using the spray nozzles operating at a predetermined pressure such that the dyeing composition penetrates inside the polymer filaments.
In accordance with the embodiments of the present disclosure, the plurality of spray nozzles operate at a pressure in the range from 1 bar to 5 bars.

In accordance with the embodiments of the present disclosure, the plurality of spray nozzles discharge the dyeing composition at a rate in the range of 15 to 400 L/min.

In accordance with the embodiments of the present disclosure, each of the plurality of spray nozzles generates a band of dye having a width in the range of 150 mm to 250 mm.
In accordance with one embodiment of the present disclosure, the band width is 180 mm.
In accordance with another embodiment of the present disclosure, the dyeing unit comprises a dyeing bath containing the dyeing composition. The dyeing composition is applied to the plurality of polymer filaments by contacting the plurality of polymer filaments with the dyeing composition followed by squeezing over rubber-covered rollers so that the dyeing composition penetrates inside the polymer filaments.
In the spraying method of the present disclosure, the penetration of the dyeing composition inside the polymer filaments is achieved using high pressure. In the contacting method of the present disclosure, the penetration of the dyeing composition is achieved by squeezing each polymer filament over rubber-covered rollers. These procedures ensure that a defined quantity of the dyeing composition is uniformly penetrated and distributed within and across the polymer filaments.
In accordance with the embodiments of the present disclosure, during the step of application of a dyeing composition, the plurality of polymer filaments picks up solvent in the range from 20 and 50 weight %.
In accordance with the embodiments of the present disclosure, the curing is carried out at a temperature in the range from 160 ?C to 180 ?C.
The process of curing is carried out in a pre-determined manner depending on the nature of the polymer filaments and the dyeing composition.
During the process of curing, the solvent is removed and the dye undergoes fixing and curing on the polymer filaments.
The dyed polymer filaments obtained by the process of the present disclosure show desirable physical properties with respect to their coloration. Thus, the process of dyeing has improved aesthetic appeal of the plurality of polymer filaments.
In accordance with the embodiments of the present disclosure, the dyed polymer filaments are crimped after dyeing.
Depending on the desired use, the polymer filaments can be cut into the desired staple length and packaged as per the use after dyeing.
The dyed polymer filaments obtained by the process of the present disclosure demonstrate improved coloration as the thermal history of the dyes is lesser as compared to the conventional dyeing processes.
In an exemplary embodiment of the present disclosure, dyeing of the plurality of polyester filaments was carried out at the drawing stage using a dyeing composition containing diaminostilbene disulphonic acid in water at a concentration in the range from 1 gpl to 20 gpl. It was observed that the whiteness index of the dyed polymer filaments improved by a value in the range from 1.5 units to 13.1 units as compared to the control. This indicates that the dyed plurality of polymer filaments has more whiteness as compared to the control. The b* value of the dyed plurality of polymer filaments decreased by 0.3 to 4.1 units as compared to the control indicating that the dyed plurality of polymer filaments has lesser yellowness as compared to the control. The a* value increased in all the experiments. The increase in a* value was in the range from 0.1 to 1.5. Whereas, the L* value of dyed polymer filaments did not show significant change.
The present disclosure carries out dyeing during the manufacture of the polymer filaments thereby saving energy and time. Furthermore, the generation of effluents which is typically associated with the afore-stated processes, is avoided in the process of the present disclosure.
The present disclosure is further described in light of the following examples which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure.
EXAMPLES:
Example 1: Dyeing polymer filaments with Pad-dry-cure method
Recycled polyester filaments of 6 denier were drawn at a speed of 230 m/min. The tow of drawn polymer filaments were passed through a 30 cm long dyeing unit containing diaminostilbene disulphonic acid (DDA) in water at the concentration mentioned in Table-1. The wet dyed polymer filaments were squeezed between rubber-covered rollers. The wet dyed polymer filaments were passed to the curing unit which was 25 m in length and maintained at 175 ?C to obtain dyed polymer filaments.
The dyed polymer filament were analyzed for L*, a*, b*, whiteness index and strength. The results are shown herein below in Table-1.
Table 1: Results of the Pad-dry-cure method
Sr Concentration of dye in the dyeing composition L* a* b* DE* whiteness index (wie) Relative strength*
1 0 (Control group) 90.366 0.669 -5.571 104.3 100
2 2.0 gpl DDA 89.81 1.911 -8.192 2.954 111.68 128.88
3 3.0 gpl DDA 90.447 1.783 -8.066 2.734 112.14 121.84
4 4.0 gpl DDA 88.211 1.983 -8.07 3.552 109.17 170.63
5 5.0 gpl DDA 90.28 2.081 -6.488 1.686 107.89 150.26
6 7.0 gpl DDA 90.148 2.161 -8.4 3.206 112.79 161.27
7 8.0 gpl DDA 89.554 1.93 -8.531 3.319 112.48 145.36
8 9.0 gpl DDA 89.61 1.852 -8.741 3.468 113.4 152.01
9 10.0 gpl DDA 90.665 1.934 -9.654 4.285 117.46 143.69
DDA = diaminostilbene disulphonic acid
*Strength of the dyed polymer filament is indicated with a mean value of 100. A value of strength less than 100 value indicates weaker dyed polymer filaments, whereas, a value above 100 indicates stronger dyed polymer filaments.
Entry-1 shows result of a control experiment, wherein the polymer filaments were treated with water. Entries 2-9 show results of the experiments wherein the polymer filaments were dyed with the dyeing compositions of the present disclosure containing varying amount of DDA in water.
The whiteness index of the dyed polymer filaments showed an improvement in the range from 3.6 units to 13.1 units with concurrent decrease in the b* value in the range from 0.9 to 4.1 units as compared to the control.
The a* value of the dyed polymer filaments increased in all the experiments. The increase in a* value was in the range from 0.71 to 1.5 units as compared to the control. Whereas, the L* value of dyed polymer filaments did not show a significant change.
The dyed polymer filaments showed more strength as compared to the control experiment.
Example 2:
Polyester filaments (~271360) of 6 denier were drawn at a speed of 230 m/min. The tow of polymer filaments were passed through a 30 cm (2.67 m) long dyeing unit containing diaminostilbene disulphonic acid (DDA) in water at the concentration mentioned in Tables 2, 3, 4 and 5. The dyeing composition was sprayed with V-jet flat application spray nozzles spraying the dyeing composition at a pressure of 1.0 bar. Each spray nozzle generated a band 180 mm wide.
The wet dyed polymer filaments were passed to the curing unit which was 25 m in length and maintained at 170 ?C to obtain dyed polymer filaments.
Table-2 shows results of experiments carried out using the dyeing composition containing diaminostilbene disulphonic acid in water at a concentration ranging from 8 gpl to 15 gpl. The dyeing composition was sprayed with the help of 4 V-jet flat application spray nozzles spraying the dyeing composition at the rate of 16 L/min at a pressure of 1.0 bar.
Table 2:
Parameter
Control Tow Tow-A Tow-B Tow-C
White portion White portion White portion
L* 82.53 82.51 83.10 83.05
a* 1.87 2.16 2.08 2.13
b* -0.33 -1.16 -1.08 -1.16
Whiteness index (Wie) 69.67 73.20 74.17 74.49
The whiteness index of the dyed polymer filaments showed improvement in the range from 3.53 units to 4.82 units with concurrent decrease in the b* value in the range from 0.75 to 0.83 units as compared to the control.
The a* value of the dyed polymer filaments increased in the range from 0.21 to 0.29 units as compared to the control. Whereas, the L* value of dyed polymer filaments did not show a significant change.
Table-3 shows results of experiments carried out using the dyeing composition containing diaminostilbene disulphonic acid in water at a concentration of 20 gpl. The dyeing composition was sprayed with the help of 4 V-jet flat application spray nozzles spraying the dyeing composition at the rate of 16 L/min at a pressure of 1.0 bar.
Table 3:
Parameter Normal Tow Tow-A Tow-B Tow-C
White portion White portion White portion
L 82.53 82.95 83.10 83.00
a* 1.87 2.08 2.24 2.32
b* -0.33 -1.12 -1.26 -1.37
Whiteness index (Wie) 69.67 74.09 75.02 75.37
The whiteness index of the dyed polymer filaments showed improvement in the range from 4.42 units to 5.70 units with concurrent decrease in the b* value in the range from 0.79 to 1.04 units as compared to the control.
The a* value of the dyed polymer filaments increased in the range from 0.21 to 0.45 units as compared to the control. Whereas, the L* value of dyed polymer filaments did not show a significant change.

Example 3:
Dyeing of non-siliconized 6 denier polyester filaments was carried out using the process of the present disclosure. The experiments were carried out using the procedure described in example 2, herein above.
Table-4 shows results of experiments carried out using a dyeing composition containing diaminostilbene disulphonic acid in water at a concentration of 8 gpl. The dyeing composition was sprayed with the help of 108 V-jet flat application spray nozzles spraying the dyeing composition at the rate of 300 L/min at a pressure of 1.0 bar. Tow samples were manually cut and processed on medium card for colour measurement.
Table 4:
Trial L* a* b* Whiteness index (Wie)
Control Tow 83.02 2.51 -0.81 72.75
Tow A 82.97 2.72 -1.25 74.30
Tow B 83.05 2.66 -1.16 74.45
The whiteness index of the dyed polymer filaments showed improvement in the range from 1.55 units to 1.70 units with concurrent decrease in the b* value in the range from 0.35 to 0.44 units as compared to the control.
The a* value of the dyed polymer filaments increased in the range from 0.15 to 0.21 units as compared to the control. Whereas, the L* value of dyed polymer filaments did not show a significant change.
Table-5 shows results of experiments carried out using the dyeing composition containing diaminostilbene disulphonic acid in water at a concentration of 8 gpl. The dyeing composition was sprayed with the help of 108 V-jet flat application spray nozzles spraying the dyeing composition at the rate of 300 L/min at a pressure of 1.0 bar. Tow samples were manually cut and processed on medium card for colour measurement.
Table 5:
Trial L* a* b* Whiteness index (Wie)
Control Tow 82.68 2.48 -0.83 72.25
Tow-A 82.92 2.74 -1.36 75.20
Tow-B 82.86 2.72 -1.33 74.94
The whiteness index of the dyed polymer filaments showed improvement in the range from 2.69 units to 2.95 units with concurrent decrease in the b* value in the range from 0.5 to 0.53 units as compared to the control.
The a* value of the dyed polymer filaments increased in the range from 0.24 to 0.26 units as compared to the control. Whereas, the L* value of dyed polymer filaments did not show a significant change.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The dyeing process of the present disclosure described herein above has several technical advantages, including but not limited to the realization of:
? a dyeing process that is carried out at high speed,
? a dyeing process that is cost effective, and
? a dyeing process that is environment friendly.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. ,CLAIMS:1. A process for dyeing a plurality of polymer filaments; said process comprising the following steps:
a. drawing the plurality of polymer filaments at a predetermined speed through a draw line path; wherein a dyeing unit is disposed in a spaced relation to said draw line path;
b. applying a dyeing composition to said plurality of polymer filaments being drawn through said draw line path using said dyeing unit to obtain a plurality of dyed wet polymer filaments; and
c. curing said plurality of dyed wet polymer filaments to obtain a plurality of dyed polymer filaments.
2. The process as claimed in claim 1, wherein said predetermined speed is in the range from 150 m/min to 250 m/min.
3. The process as claimed in claim 1, wherein said polymer is selected from the group consisting of polyester and recycled polyester.
4. The process as claimed in claim 1, wherein said dyeing composition comprises at least one dye, at least one solvent and auxiliaries.
5. The process as claimed in claim 1, wherein said dyeing unit comprises a plurality of spray nozzles disposed operatively above and operatively below said draw line path.
6. The process as claimed in claim 5, wherein said dyeing composition is applied using said spray nozzles operating at a predetermined pressure such that the dyeing composition penetrates inside the polymer filaments.
7. The process as claimed in claim 6, wherein said predetermined pressure is in the range from 1 bar to 5 bars; and wherein the plurality of spray nozzles are adopted to discharge dyeing composition at a rate in the range of 15 to 400 L/min.
8. The process as claimed in claim 5 or 6, wherein each of said plurality of spray nozzles generate a band of dye having width in the range of 150 mm to 250 mm.
9. The process as claimed in claim 1, wherein said dyeing unit comprises a dyeing bath containing the dyeing composition; wherein said dyeing composition is applied by contacting the plurality of polymer filaments with the dyeing composition followed by squeezing over rubber-covered rollers so that the dyeing composition penetrates inside the polymer filaments.
10. The process as claimed in claim 1, wherein said curing is carried out at a temperature in the range from 160 ?C to 180?C.
11. The process as claimed in claim 1, wherein said dyed polymer filaments are crimped after dyeing.
12. The process as claimed in claim 1, wherein said dyeing composition comprises diaminostilbene disulphonic acid and water as a solvent.