Single bath bio – scouring and bleaching of cellulosic yarn, knitted and woven fabrics.

Introduction

COTTON fabric has several impurities such as fats and waxes, pectinous substances, proteinous matter, ash etc. Presence of fats and waxes in cotton fabric imparts poor water absorbency. In order to remove these materials, scouring of cotton fabric is normally carried out with strong alkali at high temperature and for longer duration. Although, this treatment gives very good results, it has several drawbacks viz. high energy consumption, longer time of treatment, high loss in weight of cellulosic material and high TDS in the effluent. Considerable work has been reported 1 – 11 on the action of pectinases, proteases, lipases, cellulases and their combinations for scouring of cotton fabrics. During the last few years, alkaline pectinase enzyme has been found to be suitable for scouring of cellulosic material for removal of pectinous material from desized cotton fabric and subsequently removal of fats and waxes.

However, bio-scouring with pectinase enzyme being a milder process, natural colouring matter present is not effectively removed and thereby whiteness of bio-scoured fabric is lower than that for alkali scoured fabric. This difference in whiteness during bio-scouring persists even after bleaching by conventional method of bleaching. Alkali scoured and bleached fabrics show higher whiteness than bio-scoured and conventionally bleached fabrics. In order to overcome this drawback, an activator (Biocat) has been developed as a speciality product during enzyme action as well as facilitating bleaching action. Biocat not only facilitates enzyme action, it also activates and stabilizes peroxy radical, which in turn brings about better whitenss than that obtained by the conventional method. Studies have been carried out for one bath bio scouring and activated bleaching of cellulosic yarn, knitted fabric, terry towel and woven fabrics on semi-bulk and bulk scale with the help of this speciality products.

Experimental Fabric – Mill grey cotton fabric with following constructions were used during trials.

1. 30s X 30s – 64 X 68
2. 20s X 20s – 56 X 60
3. 50s X 50s – 132 X 72

Yarn of 30s count and double jersey knitted fabric were used during trials.

Following recipes have been used for one – bath bio – scouring and activated bleaching of cellulosic yarn, terry towel and knitted fabric.

	Yarn	Terry Towel	Knitted fabric
Type	30s count	-	Double jersey
Batch Size	1 kg	425 kg	400 kg
Sorbelon HPJET	0.7 %	0.7 %	0.7 %
Sorbenz BIO	0.4 %	0.4 %	0.5 %
Soda ash	0.15 %	0.15 %	0.15 %
Biocat	1.4 %	1.4 %	2.0 %
Caustic	1 %	1 %	1 %
H2O2	2 %	2 %	3 %
Temperature	Bio – scouring at 60o C, Bleaching at 95o C
Time, min	90	90	90
Machine	Package dyeing	Soft flow	Soft flow

Sequence of addition of products

Wetting agent, Biocat and sodium carbonate were incorporated together in the treatment bath and temperature was raised to 60o C. pH of the solution should be between 8.5 – 9 only. Enzyme (Sorbenz BIO) was added at 60o C and bio – scouring continued at 60o C for 30 min.

SINGLE BATH PROCESS

At the end of 30 min, required amount of caustic soda was added and run for 5 min. After 5 min, hydrogen peroxide was added progressively in 10 min and temperature was raised from 60 to 95o C and continued for 60 min. at this temperature. At the end of bleaching, peroxide killer was added followed by neutralization of caustic and given hot wash.

Recipe and application condition of bio – desizing of woven cotton fabric.

Recipe

Sorbenz HTX – 0.5 % o.w.f.
Sorbe WET – 0.3 % o. w. f.
M:L – 1:3
Temperature – 70o C
Duration – 1 hr
M/c – Jig.

Procedure

Grey fabric was treated with above recipe at Ph 7 – 7.5 and 70o C for 60 min (2 ends). At the end of 60 min fabric was given a hot wash followed by a cold wash.

Recipe and application conditions for bio – scouring and activated bleaching of woven cotton fabric.

Stage 1
Concentration of Sorbenz BIO	:	0.4 %
Sorbe WET (Wetting Agent)	:	0.5 %
Biocat (H2O2 : Biocat ::1:0.7)	:	2.1 %
Sodium Carbonate	:	0.15 %
M/C	:	Jig
Temperature	:	60o C
Time	:	30 min (2 ends)
Stage 2
Concentration of Caustic (flakes)	:	1.0 %
Hydrogen Peroxide	:	3.0 %
Temperature	:	95o C
Time	:	2 hr (4 to 6 ends)

Stage 1 Concentration of Sorbenz BIO : 0.4 % Sorbe WET (Wetting Agent) : 0.5 % Biocat (H2O2 : Biocat ::1:0.7) : 2.1 % Sodium Carbonate : 0.15 % M/C : Jig Temperature : 60o C Time : 30 min (2 ends) Stage 2 Concentration of Caustic (flakes) : 1.0 % Hydrogen Peroxide : 3.0 % Temperature : 95o C Time : 2 hr (4 to 6 ends)

Sequence of addition of components

Wetting agent, Biocat and sodium carbonate were added together and temperature raised to 60o C. pH of the solution should be between 8.5 and 9 only. Enzyme (Sorbenz BIO) was added at pH 8.5 – 9 and at temperature 60o C. Bio – Scouring was continued at 60o C for 30 min (2 ends). At the end of 30 min, required amount of caustic was added and run for 5 min. After 5 min hydrogen peroxide was added in two installments at temperature 60o C and fabric run for 2 ends and temperature was raised from 60 to 95o C and treatment continued for 2 hr (4 to 6 ends). At the end of bleaching, peroxide killer was added followed by neutralization of caustic soda and then given a hot was and cold wash.

Whiteness index and color measurement
Whiteness index was measured on Premier Colorscan.
Absorbency
Absorbency was measured by AATCC 79 – 1992.
Sinking time
Sinking time was measured in sec of 0.5 gm yarn in 200 ml distilled water.

Results and discussions

Yarn, knitted and terry towel fabrics are normally treated at high concentration of caustic soda, wetting agent, stabilizers followed by peroxide treatment for 1 hr at 95o C to remove pectinous material and fats and waxes. This treatment improves absorbency of cellulosic material. Although, this treatment gives very good results, it has several drawbacks, while combined bio-scouring and activated bleaching overcomes drawbacks associated with alkali treatment. One of the most important drawbacks of conventional alkali scouring is higher weight loss observed in case of yarn, terry towel and knitted fabric. Yarn or fabric shows lower weight loss during bio-scouring treatment, as compared with that during conventional scouring and bleaching. Bio-scoured and bleached fabric show soft feel and bio-scoured bleached bath has low TDS. Bulk trial results of bio-souring and activated bleaching result in better absorbency and whiteness as compared with alkali scouring and bleaching (Table 1)

Results obtained indicated that combined bio-scouring and bleaching are superior to those for conventional method.

Desizing and combined bio-scouring and bleaching of cotton fabric

Cotton fabric was desized with Sorbenz HTX. Desized fabric was bio-scoured and bleached by one – bath two – stage method. Results of these studies indicate that bio-scouring and bleaching fabric show good absorbency and comparable whiteness as compared with that of alkali scouring followed by bleaching (Table 2).

Decomposition of hydrogen peroxide was studied in solution by conventional recipe in presence of a stabilizer, at pH 11.0 and activated bleaching in presence of Biocat and peroxide at pH 10.5. Results of the decomposition show that in case of activated bleaching gradual and higher decomposition of peroxide is observed as compared with that under conventional bleaching in presence of a stabilizer (Fig. 1). Thus inferior whiteness during bleaching of bio-scoured fabric by conventional method of bleaching can taken care of by adopting activated bleaching as mentioned above.

Bio- scouring and activated bleaching has following advantages as compared with alkali scouring followed by conventional method of bleaching.

· Weight loss of cellulosic materials is less in case of yarn, knitted fabrics and terry towels. · Degradation of cellulosic materials is less, especially for full whites where high peroxide concentrations are used. · TDS of bath after bio-scouring and bleaching was found to be lower as compared with that in case of alkali scoured followed by the conventional bleaching process. Generally, bio-scouring show 2.5 times to 8 time low TDS in the bath for yarn, knitted and cotton fabric as compared with alkali scouring and bleaching. · Softer feel of bio-scoured and bleached fabric.

Conclusions

Bio-scouring and activated bleaching of cellulosic material reduces load on effluent as compared with conventional method. Bio-scoured and bleached yarn/fabric have better quality and less degradation than the alkali scoured and bleached fabrics.

References

1. K. Sawada et. al., J. Soc. Dyers and Colorist. 114 (12), 355 (1998)
2. U. Robner, Melliand Textilber., 74, 144 (1993), E – 63
3. G. Piller et. al., Book of Abstracts on Symposium on Biotechnology in Textile Industry, Portugal, 3 –7 May, 15 (2000)
4. M. Lawson, ibid, 15 (2000)
5. C. Szakacs et. al., ibid, 16 (2000)
6. M. Calafell et. al. ibid, 17 (2000)
7. I. Hardin et.al. ibid, 16 (2000)
8. Y. Li et. al. Text. Chem. And Colorist, 29 (8), 71, (1997)
9. Y. Li et. al., AATCC, Book of Papers, 444 (1997)
10. N. Lange et. al., Book of Abstracts on Symposium on Bio-technology in Textile Industry, Portugal, 3 – 7, May, 16 (2000)
11. N. Lange et. al., 18th IFATCC Congress, Copenhagen, B – 10 September, 4 (1999).