Title of Invention	"A METHOD OF REACTIVE DYEING OF JUTE FABRIC BY TWO-STEP-TWO-BATH OPERATION"
Abstract	In conventional process of reactive dyeing where exhaustion and fixation of dyes takes place in the same bath (two-step one-bath method), reuse of dye is not possible. In the fixation step, alkali is used for fixation of exhausted dye on to the fabric . But in presence of alkali, a large portion of the dye left out in the liquor gets hydrolysed rendering them useless. So, there is a loss of costly reactive dye and simultaneously, drainage of dye liquor containing a large amount of hydrolysed dye leads to water pollution. In this invention, exhaustion and fixation step of reactive dyeing has been separated i.e. after the exhaustion of dyes on to the fabric, the fabric is taken out and fixation of dye to the fabric in presence of alkali takes place in a separate bath (two-step two-bath method). On the other hand, saved exhaustion bath is reused for dyeing of another fabric sample following conventional process. The sample is termed separate original where fixation of dye takes place in a separate bath and the sample is termed separate reuse which is produced by using the saved dye bath. Four different class of reactive dyes, namely, cold brand, hot brand, vinyl sulphone and HE-brand reactive dyes has been used in this study. By this simple process, costly reactive dyes are utilised to the maximum extent as dye hydrolysis do not take place due to separation of fixation bath and effluent problem is minimised by utilising the exhausted saved dye bath. The process of reuse is found to be beneficial only on higher depth of

Title of Invention

"A METHOD OF REACTIVE DYEING OF JUTE FABRIC BY TWO-STEP-TWO-BATH OPERATION"

Abstract

In conventional process of reactive dyeing where exhaustion and fixation of dyes takes place in the same bath (two-step one-bath method), reuse of dye is not possible. In the fixation step, alkali is used for fixation of exhausted dye on to the fabric . But in presence of alkali, a large portion of the dye left out in the liquor gets hydrolysed rendering them useless. So, there is a loss of costly reactive dye and simultaneously, drainage of dye liquor containing a large amount of hydrolysed dye leads to water pollution. In this invention, exhaustion and fixation step of reactive dyeing has been separated i.e. after the exhaustion of dyes on to the fabric, the fabric is taken out and fixation of dye to the fabric in presence of alkali takes place in a separate bath (two-step two-bath method). On the other hand, saved exhaustion bath is reused for dyeing of another fabric sample following conventional process. The sample is termed separate original where fixation of dye takes place in a separate bath and the sample is termed separate reuse which is produced by using the saved dye bath. Four different class of reactive dyes, namely, cold brand, hot brand, vinyl sulphone and HE-brand reactive dyes has been used in this study. By this simple process, costly reactive dyes are utilised to the maximum extent as dye hydrolysis do not take place due to separation of fixation bath and effluent problem is minimised by utilising the exhausted saved dye bath. The process of reuse is found to be beneficial only on higher depth of

Full Text	This invention relates to reuse of reactive dyes. Colouration of jute fabric with reactive dye is most popular due to its high wash fastness property and eco-friendly in nature. There are four different classes of reactive dyes depending on their method of application and reactivity of dyes viz., cold brand reactive dye, hot brand reactive dye, vinyl sulphone reactive dye and high exhaustion (HE) brand reactive dyes. The steps involved for the dyeing of jute fabric with reactive dyes are mainly two : a) Exhaustion - The dye molecules are moved from the dye bath to the fibre surface and from fibre surface to the inside of the fibre under specific conditions of salt concentration, temperature & time and b) Fixation - Here the dye molecules, which are diffused inside the fibre, are reacted with the OH-group of cellulose molecules by using alkali following either addition or substitution reaction. Hence it is a two-step one-bath method. During the application of reactive dye on jute, along with dye absorption dye hydrolysis also takes place. The hydrolysed dye is retained on fabric and it is removed by severe washing. This results in wastage of dye. Hydrolysis of the dye by water is more rapid at higher pH values. Even the dyes with lower reactivity, when they are in alkaline environment for an extended period, they gradually hydrolyse. So, reuse of the dye bath is very difficult. Improvement of utilisation of reactive dyes is the most important factor now a days as the dyes are costly. Average exhaustion of reactive dyes using conventional procedure is only 40 -60%. The remaining dye is generally discharged as effluents which creates water pollution. So, optimum utilisation of costly reactive dyes is an important challenge with respect to jute fabric where a large amount of dyes are required for a particular depth of shade. Low utilisation of reactive dyes are mainly due to hydrolysis of the dye and the process of hydrolysis becomes accelerated in alkaline condition. If the process of fixation ie., the treatment with alkali is carried out in a separate bath then the original dye bath can be utilised for the dyeing of second batch of sample, thereby improving the utilisation of reactive dyes. In this invention a two-step two-bath method of reactive dyeing of jute has been developed where by fixation of dye of the original sample is carried out in a separate bath and the original dye bath is reused for dyeing of a second batch of sample. Hence this process utilised costly reactive dyes to its maximum extent and drainage of dye is minimum resulting in low water pollution. Prior art: Many studies have been devoted to improve the substantivity of cellulosic fibre for reactive dyes, thus diminishing or eliminating the amount of electrolyte required and increasing the efficiency of dye fibre interaction. However, none to date has achieved success, since all suffer from one or more disadvantages, such as significantly reduced light fastness, unsatisfactory dye fixation efficiency or poor wet fastness, marked change in hue, limited suitability of the treatments for different kinds of reactive dyes, unpleasant odour released during application etc. Till date research was mainly restricted for improving exhaustion / fixation efficiency of costly reactive dyes but only a few attempts was made to reuse the reactive dyes rather than to try only to improve the exhaustion efficiency. In conventional application method, reactive dye is deactivated after fixation stage leaving dye unsuitable for reuse. Till date no study has been done for maximum utilisation of reactive dyes on jute fibre to make the process economic as well as ecofriendly. Details of invention : Conventional reactive dyeing process involves exhaustion of dye bath for a particular duration at a particular temperature and then fixation of adsorbed dye in the same bath after addition of alkali. The fabric is then washed, soaped, again washed and dried. Dye bath is drained which contains a large ampunt of reactive dye in hydrolysed and deactivated form as well as inactive form. So, reuse of dye bath is an important factor for which two different method have been studied ie., two-step one-bath method (conventional method) and two-step two-bath method (developed method) for reuse of the dye bath. Four different samples have been produced. Ten different reactive dyes belonging to different class of reactive dyes were used in the experiment and they are tabulated in table 1. The process parameters used for different class of dyes are tabulated in table 2. A bleached jute fabric (2vol. Hydrogen peroxide) was used for the dyeing experiment and 8%(owf) dye was used for dyeing as the advantage of reuse of dye bath can be achieved only on higher depth of shade. All the samples produced are conditioned in standard atmosphere and tested. Evaluation of max, K/S value, colour strength(%) was done in computer colour matching system ( Spectrascan 5100 R) using appropriate software. Washing fastness was done in a launrer-O-metre following ISO-3 method and evaluated by computer colour matching system. All the results have been tabulated in table 4-8. Four different dyed samples were produced for any particular dye. They are : Sample A ( Original sample) - Bleached jute fabric has been dyed following conventional method ie., exhaustion and fixation has been done in the same bath ( m:l::l:20). It is to be noted that before adding alkali for fixation, pH of the bath is to be checked. After dyeing, the sample is washed thoroughly in cold water, soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, original sample is made. The spent dye bath has been saved for reuse. Sample B ( Original reuse sample) - The pH of the saved dye bath is adjusted to that of the original value by adding 50% acetic acid. A bleached sample entered in the dyebath for exhaustion without adding any further salt and then fixation of the dye is done by adding alkali in the same bath. The sample is then washed , soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, original reuse sample is made. Sample C ( Separate original sample) - Bleached jute fabric is entered in the dye bath ( m:l::l:20) for exhaustion of dye for a particular duration and temperature. Then dye bath is saved for reuse and the sample is taken out for fixation in a separate bath (m:l :: 1:5) containing alkali and salt. The sample is then washed in cold water, soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, separate original sample is made. Sample D (Separate reuse sample) - Bleached jute fabric is entered in the saved dye bath and dyed for a specific temperature and duration after further addition of dye (2%, owf) and salt ( ½ the amount added in the original bath). After the exhaustion step, alkali is added for fixation and run for a particular period at a particular temperature. The sample is then washed in cold water, soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, separate reuse sample is made. Evaluation of two-step two-bath process with conventional process : In conventional process ie, two-step one-bath process, dyes are generally not reused and the dye bath containing active dye as well as hydrolysed dyes are drained out. If reused from original bath is tried, the colour yield is very poor in all class of dyes (table-4,5 & 7) except vinyl sulphone reactive dyes (table-6) and washing fastness property is very poor. It is also found that the colour yield in case of original reuse sample varies from dye to dye depending on the resistance to hydrolysis of dye in alkaline dye bath. We used 9 reactive dyes comprising of 4 different classes for quality assessment of the new method. Whiteness, yellowness and brightness indices of raw and bleached jute fabrics at 10° angle of observation are given in table- 3 . It is observed that the whiteness index of raw jute fabric bleached with 2 vol. hydrogen peroxide is satisfactory enough for conventional / two-step two-bath process of reactive dyeing. Conventional two-step one- bath method is modified to two-step two-bath method. The original sample after exhaustion step is transferred to the fixation bath where low liquor ratio is used. The separate original sample thus produced are having K/S value equal to or even better than the conventionally produced original sample which are evident from table-4-7. Now the saved dye bath is reused for dyeing to produce separate reused sample. It is seen from the tables that the colour yield is about 50-80 % of the conventionally produced samples in case of cold brand, hot brand and vinyl sulphone reactive dye. In case of HE brand reactive dye, colour yield in case of separate reuse sample is about 25-50 % of the original sample depending on the dye. So, benefit of the process is more utilisation of the costly reactive dye equivalent to the colour yield percent achieved in case of separate reuse sample which is other wise drained out adding pollution to water. Washing fastness property of both the separate samples ie, separate original and separate reuse are good and equivalent to the original sample produced by conventional process. Compensation of separate reuse bath has been done with 2%(owf) dye and salt (equivalent to half the original amount of added salt). The colour yield produced by the separate reuse sample has been tabulated in table-8. It is seen from the table that the colour yield improved appreciably in separate reuse samples after compensation and become equal to that of the original sample produced by conventional process in case of cold brand , hot brand and HE reactive dyes. In case of vinyl sulphone dyes, the colour yield produced after compensation is even higher than that produced in the conventionally dyed samples. So, it is proved that by adding a small amount of the dye , the colour yield in case of separate reuse sample can be compensated to that of the original sample but the amount of compensation varies from dye to dye and which is around 2% (owf) if the original sample is produced using 8% (owf) dye. Table 1 : Reactive dyes used in the experiment (Table Removed) Table 2 : Process parameters used for dyeing of different class of dyes (Table Removed) SC = Sodium Carbonate, SH = Sodium Hydroxide. Table 3 : Whiteness, yellowness and brightness indices of grey and bleached jute fabric (Table Removed) Table 4 : Reuse of cold brand reactive dyes using two-step one-bath process and two-step two-bath process. (Table Removed) A- Original Sample ; B- Original reuse sample ; C- Separate original sample and D- Separate reuse sample Table 5 : Reuse of hot brand reactive dyes using two-step one-bath process and two-step two-bath process. (Table Removed) A-Original Sample ; B-Original reuse sample ; C-Separate original sample and D- Separate reuse sample Table 6 : Reuse of Vinyl sulphone reactive dyes (cold method) using two-step one-bath process and two-step two-bath process. (Table Removed) Table 7 Original Sample ; B- Original reuse sample ; C- Separate original sample and D- Separate reuse sample Table 7 : Reuse of HE brand reactive dyes using two-step one-bath process and two-step two-bath process. (Table Removed) A- Original Sample ; B- Original reuse sample ; C- Separate original sample and D- Separate reuse sample Table 8 : Effect of compensation of dye and salt in the separate reuse bath on colour yield of dyed sample. (Table Removed) Col. Str - Colour Strength WF - Wash Fastness We claim that: (i) Reuse of costly reactive dye is possible by following two-step two-bath method of dyeing. This process is eco-friendly as the effluent contains minimum amount of dye. Moreover, as the fixation of separate original sample is carried out at low liquor ratio, it requires less alkali for fixation. So, the process is economic as well. (ii) Compensation of separate reuse bath with small amount of dye and salt produced separate reuse sample which is equivalent to separate original sample with respect to colour yield and wash fastness property. (iii) The process is simple which requires only a separate dye fixation bath.

Full Text

This invention relates to reuse of reactive dyes. Colouration of jute fabric with reactive dye is most popular due to its high wash fastness property and eco-friendly in nature. There are four different classes of reactive dyes depending on their method of application and reactivity of dyes viz., cold brand reactive dye, hot brand reactive dye, vinyl sulphone reactive dye and high exhaustion (HE) brand reactive dyes. The steps involved for the dyeing of jute fabric with reactive dyes are mainly two : a) Exhaustion - The dye molecules are moved from the dye bath to the fibre surface and from fibre surface to the inside of the fibre under specific conditions of salt concentration, temperature & time and b) Fixation - Here the dye molecules, which are diffused inside the fibre, are reacted with the OH-group of cellulose molecules by using alkali following either addition or substitution reaction. Hence it is a two-step one-bath method.
During the application of reactive dye on jute, along with dye absorption dye hydrolysis also takes place. The hydrolysed dye is retained on fabric and it is removed by severe washing. This results in wastage of dye. Hydrolysis of the dye by water is more rapid at higher pH values. Even the dyes with lower reactivity, when they are in alkaline environment for an extended period, they gradually hydrolyse. So, reuse of the dye bath is very difficult. Improvement of utilisation of reactive dyes is the most important factor now a days as the dyes are costly.
Average exhaustion of reactive dyes using conventional procedure is only 40 -60%. The remaining dye is generally discharged as effluents which creates water pollution. So, optimum utilisation of costly reactive dyes is an important challenge with respect to jute fabric where a large amount of dyes are required for a particular depth of shade. Low utilisation of reactive dyes are mainly due to hydrolysis of the dye and the process of hydrolysis becomes accelerated in alkaline condition. If the process of fixation ie., the treatment with alkali is carried out in a separate bath then the original dye bath can be utilised for the dyeing of second batch of sample, thereby improving the utilisation of reactive dyes. In this invention a two-step two-bath method of reactive dyeing of jute has been developed where by fixation of dye of the original sample is carried out in a separate bath and the original dye bath is reused for dyeing of a second batch of sample. Hence this process utilised costly reactive dyes to its maximum extent and drainage of dye is minimum resulting in low water pollution.
Prior art:
Many studies have been devoted to improve the substantivity of cellulosic fibre for reactive dyes, thus diminishing or eliminating the amount of electrolyte required and increasing the efficiency of dye fibre interaction. However, none to date has achieved success, since all suffer from one or more disadvantages, such as
significantly reduced light fastness, unsatisfactory dye fixation efficiency or poor wet fastness, marked change in hue, limited suitability of the treatments for different kinds of reactive dyes, unpleasant odour released during application etc. Till date research was mainly restricted for improving exhaustion / fixation efficiency of costly reactive dyes but only a few attempts was made to reuse the reactive dyes rather than to try only to improve the exhaustion efficiency. In conventional application method, reactive dye is deactivated after fixation stage leaving dye unsuitable for reuse. Till date no study has been done for maximum utilisation of reactive dyes on jute fibre to make the process economic as well as ecofriendly.
Details of invention :
Conventional reactive dyeing process involves exhaustion of dye bath for a particular duration at a particular temperature and then fixation of adsorbed dye in the same bath after addition of alkali. The fabric is then washed, soaped, again washed and dried. Dye bath is drained which contains a large ampunt of reactive dye in hydrolysed and deactivated form as well as inactive form. So, reuse of dye bath is an important factor for which two different method have been studied ie., two-step one-bath method (conventional method) and two-step two-bath method
(developed method) for reuse of the dye bath. Four different samples have been produced.
Ten different reactive dyes belonging to different class of reactive dyes were used in the experiment and they are tabulated in table 1. The process parameters used for different class of dyes are tabulated in table 2. A bleached jute fabric (2vol. Hydrogen peroxide) was used for the dyeing experiment and 8%(owf) dye was used for dyeing as the advantage of reuse of dye bath can be achieved only on higher depth of shade. All the samples produced are conditioned in standard atmosphere and tested. Evaluation of max, K/S value, colour strength(%) was done in computer colour matching system ( Spectrascan 5100 R) using appropriate software. Washing fastness was done in a launrer-O-metre following ISO-3 method and evaluated by computer colour matching system. All the results have been tabulated in table 4-8. Four different dyed samples were produced for any particular dye. They are :
Sample A ( Original sample) - Bleached jute fabric has been dyed following conventional method ie., exhaustion and fixation has been done in the same bath ( m:l::l:20). It is to be noted that before adding alkali for fixation, pH of the bath is to be checked. After dyeing, the sample is washed thoroughly in cold water,
soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, original sample is made. The spent dye bath has been saved for reuse.
Sample B ( Original reuse sample) - The pH of the saved dye bath is adjusted to that of the original value by adding 50% acetic acid. A bleached sample entered in the dyebath for exhaustion without adding any further salt and then fixation of the dye is done by adding alkali in the same bath. The sample is then washed , soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, original reuse sample is made.
Sample C ( Separate original sample) - Bleached jute fabric is entered in the dye bath ( m:l::l:20) for exhaustion of dye for a particular duration and temperature. Then dye bath is saved for reuse and the sample is taken out for fixation in a separate bath (m:l :: 1:5) containing alkali and salt. The sample is then washed in cold water, soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, separate original sample is made.
Sample D (Separate reuse sample) - Bleached jute fabric is entered in the saved dye bath and dyed for a specific temperature and duration after further addition of dye (2%, owf) and salt ( ½ the amount added in the original bath). After the
exhaustion step, alkali is added for fixation and run for a particular period at a particular temperature. The sample is then washed in cold water, soaped (2 g/1) at boil for 15 min, again washed and dried in air. So, separate reuse sample is made.
Evaluation of two-step two-bath process with conventional process :
In conventional process ie, two-step one-bath process, dyes are generally not reused and the dye bath containing active dye as well as hydrolysed dyes are drained out. If reused from original bath is tried, the colour yield is very poor in all class of dyes (table-4,5 & 7) except vinyl sulphone reactive dyes (table-6) and washing fastness property is very poor. It is also found that the colour yield in case of original reuse sample varies from dye to dye depending on the resistance to hydrolysis of dye in alkaline dye bath. We used 9 reactive dyes comprising of 4 different classes for quality assessment of the new method.
Whiteness, yellowness and brightness indices of raw and bleached jute fabrics at 10° angle of observation are given in table- 3 . It is observed that the whiteness index of raw jute fabric bleached with 2 vol. hydrogen peroxide is satisfactory enough for conventional / two-step two-bath process of reactive dyeing.
Conventional two-step one- bath method is modified to two-step two-bath method. The original sample after exhaustion step is transferred to the fixation bath where low liquor ratio is used. The separate original sample thus produced are having K/S value equal to or even better than the conventionally produced original sample which are evident from table-4-7. Now the saved dye bath is reused for dyeing to produce separate reused sample. It is seen from the tables that the colour yield is about 50-80 % of the conventionally produced samples in case of cold brand, hot brand and vinyl sulphone reactive dye. In case of HE brand reactive dye, colour yield in case of separate reuse sample is about 25-50 % of the original sample depending on the dye. So, benefit of the process is more utilisation of the costly reactive dye equivalent to the colour yield percent achieved in case of separate reuse sample which is other wise drained out adding pollution to water. Washing fastness property of both the separate samples ie, separate original and separate reuse are good and equivalent to the original sample produced by conventional process.
Compensation of separate reuse bath has been done with 2%(owf) dye and salt (equivalent to half the original amount of added salt). The colour yield produced by the separate reuse sample has been tabulated in table-8. It is seen from the table that the colour yield improved appreciably in separate reuse samples after
compensation and become equal to that of the original sample produced by conventional process in case of cold brand , hot brand and HE reactive dyes. In case of vinyl sulphone dyes, the colour yield produced after compensation is even higher than that produced in the conventionally dyed samples. So, it is proved that by adding a small amount of the dye , the colour yield in case of separate reuse sample can be compensated to that of the original sample but the amount of compensation varies from dye to dye and which is around 2% (owf) if the original sample is produced using 8% (owf) dye.
Table 1 : Reactive dyes used in the experiment

(Table Removed)
Table 2 : Process parameters used for dyeing of different class of dyes

(Table Removed)
SC = Sodium Carbonate, SH = Sodium Hydroxide.
Table 3 : Whiteness, yellowness and brightness indices of grey and bleached jute
fabric

(Table Removed)
Table 4 : Reuse of cold brand reactive dyes using two-step one-bath
process and two-step two-bath process.

(Table Removed)
A- Original Sample ; B- Original reuse sample ; C- Separate original sample and D- Separate reuse sample
Table 5 : Reuse of hot brand reactive dyes using two-step one-bath process and two-step two-bath process.

(Table Removed)
A-Original Sample ; B-Original reuse sample ; C-Separate original sample and D- Separate reuse sample
Table 6 : Reuse of Vinyl sulphone reactive dyes (cold method) using two-step one-bath process and two-step two-bath process.

(Table Removed)
Table 7 Original Sample ; B- Original reuse sample ; C- Separate original sample and D- Separate reuse sample
Table 7 : Reuse of HE brand reactive dyes using two-step one-bath
process and two-step two-bath process.

(Table Removed)
A- Original Sample ; B- Original reuse sample ; C- Separate original sample and D- Separate reuse sample
Table 8 : Effect of compensation of dye and salt in the separate reuse bath on
colour yield of dyed sample.

(Table Removed)
Col. Str - Colour Strength WF - Wash Fastness

We claim that:
(i) Reuse of costly reactive dye is possible by following two-step two-bath method of dyeing. This process is eco-friendly as the effluent contains minimum amount of dye. Moreover, as the fixation of separate original sample is carried out at low liquor ratio, it requires less alkali for fixation. So, the process is economic as well.
(ii) Compensation of separate reuse bath with small amount of dye and salt produced separate reuse sample which is equivalent to separate original sample with respect to colour yield and wash fastness property.
(iii) The process is simple which requires only a separate dye fixation bath.

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Patent Number

272713

Indian Patent Application Number

1593/DEL/2004

PG Journal Number

18/2016

Publication Date

29-Apr-2016

Grant Date

21-Apr-2016

Date of Filing

25-Aug-2004

Name of Patentee

INDIAN COUNCIL OF AGRICULTURAL RESEARCH

Applicant Address

KRISHI BHAWAN, DR. RAJENDRA PRASAD ROAD NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DR. SAMBHU NATH CHATTOPADHYAY	CHEMICAL & BIOCHEMICAL PROCESSING DIVN. NATIONAL INSTITUTE OF RESEARCH ON JUTE AND ALLIED FIBRE TECHNOLOGY, 12, REGENT PARK, KOLKATA-700 040, INDIA.
2	DR. NIMAL CHANDRA PAN	CHEMICAL & BIOCHEMICAL PROCESSING DIVN. NATIONAL INSTITUTE OF RESEARCH ON JUTE AND ALLIED FIBRE TECHNOLOGY, 12, REGENT PARK, KOLKATA-700 040, INDIA.
3	DR. ABHINDRA DAY	CHEMICAL & BIOCHEMICAL PROCESSING DIVN. NATIONAL INSTITUTE OF RESEARCH ON JUTE AND ALLIED FIBRE TECHNOLOGY, 12, REGENT PARK, KOLKATA-700 040, INDIA.

PCT International Classification Number

D06P 1/38

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA