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Bio-Polishing of Polyester and Polyester/Cotton Fabric STEFANIE G. MCCLOSKEY1

AND JOSEPH

M. JUMP

Novozymes North America, Franklinton, North Carolina 27525, U.S.A. ABSTRACT Enzymatic bio-polishing offers a finish for pill prevention. The present study demonstrates that a cutinase can be used for bio-polishing of polyester fabrics and can be combined with a compatible cellulase to treat polyester and cotton blended fabrics. Two different cutinases were investigated with 100% polyester woven fabric. One cutinase and one cellulase were tested separately and in combination with 50%/50% polyester/cotton blend knit fabric. Following enzymatic treatment, weight loss, high-performance liquid chromatography (HPLC) analysis of the treatment liquor and pilling note were evaluated. An improvement in pilling note for both polyester and polyester blends was demonstrated. Additionally, HPLC analysis of the treatment liquors indicated polyester hydrolysis due to cutinase activity which correlated well with pilling note results

Pilling is a fabric flaw defined as a build-up of pills, or balls of entangled fibers that are anchored to the fabric surface by one or more fibers [6]. According to Hatch in Textile Science, the mechanism of pilling is as follows: (1) mechanical action causes fibers to migrate out of the fabric body to the surface; (2) further action causes the surface fibers to rotate around other protruding fibers forming pills; and (3) additional action may continue to form more pills or to sever fibers anchoring pills. The pilling propensity of the fabric depends on the surface fuzz formation, the rate of fuzz entanglement, and finally the rate of pills breaking off. The rate of the pills breaking off is directly related to the tenacity of the anchor fibers. Pilling of fabric changes the aesthetic properties. The smoothness, color and general hand of the fabric can be compromised. Pilling prevention is an ongoing challenge for manufacturers of cotton, polyester and blended fabrics. Currently there are several technologies for pill prevention. Low-pill (low tenacity) polyester can be manufactured by lowering the degree of polymerization of the homopolymer or by adding a co-monomer like pentaerythritol to the polymerization process. The result is a polyester with lower tenacity; pills still form, but the anchor fibers are easier to break [1, 8, 12]. Another modification is a chemical treatment. A harsh caustic treatment or aminolysis of the polyester fiber will result in a more hydrophilic fiber that may have some pill resistance as the surface fibrils have been removed [5, 6]. An alternative finish for polyester is the application of a 1 To whom correspondence should be addressed: tel: ⫹1 919-4943000; fax: ⫹1 919-494-3422; e-mail: [email protected]

Textile Res. J. 75(6), 480 – 484 (2005) DOI: 10.1177/0040517505053846

bonding agent to the surface thus creating a flexible network on the surface of the fabric [7]. A limiting option is to select a fabric construction that results in lower pilling propensity. Polyester is often added to cotton fabric to improve product economics while increasing tenacity and resiliency. This increase in tenacity can be troublesome with respect to pilling. Cotton fibers have a lower tenacity, and as the pills are formed the anchor fibers can be easily broken with further mechanical action. Once the tenacity of the fabric is increased with added polyester, the pill break-off rate is much lower. Furthermore, 100% polyester fabrics can be notorious for pilling problems and because of the high tenacity of the polymer the anchor fibers rarely break releasing pills [6, 9]. Bio-polishing is a finishing process in which a fabric is treated with an enzyme to impart properties such as anti-pilling, softness and smoothness. This concept was initially developed in Japan where the first experiments were performed on cotton woven fabrics using cellulases. Improved properties were obtained without using traditional chemical treatments [13]. Further work was done on knitted fabrics where fuzz removal was added to the processing benefits [3]. Additional work published by Bazin and Sasserod [4] revealed a reduction in fuzz level which resulted in a dramatic reduction in pilling on both 100% cotton and polyester cotton blends using cellulase. Further studies were performed to illustrate the durability of properties and process variables to impart certain characteristics [7, 10, 11]. Although much work has been published on cellulosic bio-polishing and even some polyester cotton blends where the cellulosic component of the blend has © 2005 Sage Publications

www.sagepublications.com

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been modified, little work has been published on polyester bio-polishing. A patent published by Andersen et al. [2] describes a method to reduce pilling propensity and improve color clarification by enzymatic treatment on polyester fabrics in the presence of detergents. In this study we have evaluated bio-polishing polyester and polyester blends with cotton using enzymatic technology. The enzymes used in this study were two different cutinases for 100% polyester fabric treatment and a blend of cutinase and cellulase for polyester cotton blended fabric treatment. After treatment, fabric samples were evaluated for weight loss, pilling note and highperformance liquid chromatography (HPLC) analysis of the treatment liquors for degradation products of polyester. On both fabrics a significant improvement in pilling prevention was demonstrated.

Experimental FABRIC Both 100% Dacron type 54 woven fabric and a 50%/ 50% polyester cotton single knit were obtained from TestFabrics Inc. The 100% polyester fabric was scoured, rinsed and dried as a preparation for enzymatic treatment. The blended fabric was used as received. Fabric swatches were cut to 14 cm ⫻ 14 cm. All swatches were conditioned overnight at a constant temperature and humidity [70 ⫾ 2°F, 65 ⫾ 2% relative humidity (RH)]. The weight was then measured and recorded.

The cutinase activity was measured according to Novozymes analytical method 2001-07992-01. In this assay, glycerol tributyrate was incubated with the cutinase composition in 0.1 mM glycine buffer (pH 7) at 30°C over time. The lipase unit (LU) is the amount of enzyme which releases 1 ␮mol of titratable butyric acid per minute. The incubation is held for a minimum of 2 minutes and the resulting activity is calculated and expressed in LU/g. BIO-POLISHING Bio-polishing was carried out in a Launder-O-Meter (LOM) LP2 from Atlas Electric Devices Company. Twenty steel balls, buffer and enzyme were added to 500 mL steel beakers. The 50 mM sodium bicarbonate buffer was adjusted to pH 8 and used for all experiments. The liquor ratio was 20:1 and the enzymes were dosed as U/ml (LU or ECU per liquor volume). Two swatches with a total weight of 7.0 ⫾ 0.1 g were used in each beaker and each treatment was run in duplicate. The beakers were loaded into a LOM preheated to 70°C and incubated at 42 rpm for a specified time. Following enzyme treatment, the residual enzyme activity on the swatches was inactivated at 80°C in 2 g/L soda ash solution for 10 minutes. After inactivation, the swatches were rinsed and centrifuged in a conventional home washer and tumble dried for 60 minutes. All swatches were conditioned overnight at a constant temperature and humidity (70 ⫾ 2°F, 65 ⫾ 2% RH).

Evaluations

ENZYMES Two experimental cutinases and one commercial cellulase preparation each produced by Novozymes were investigated in this study (see Table I). The cellulase activity was measured according to Novozymes analytical method 302.02/01. In this assay, carboxymethylcellulose (CMC) was incubated with the cellulase composition in 0.1 M phosphate buffer (pH 7.5) at 40°C for 30 minutes. The reduction in viscosity was determined by a vibration viscometer and the result was compared to a purified standard reference cellulase and expressed in endocellulase units (ECU) as ECU/g. A standard cellulase was purified and used to generate a standard curve for comparison.

WEIGHT LOSS Weight loss is indicative of fabric hydrolysis resulting in the release of water-soluble low molecular weight degradation products (i.e. terephthalic acid salts for polyester and glucose and cellobiose for cotton). Final swatch weight was measured and recorded after conditioning to determine weight loss. A mean weight loss was calculated by averaging the weight loss data for all swatches in one treatment type. PILLING Pilling was measured according to ASTM D4970 (Pilling Resistance and Other Related Surface Changes

TABLE 1. Enzymes and their application characteristics. Enzyme

Composition

Organism

pH

Temperature

Cutinase A Cutinase B Cellulase

Mono-component Mono-component Family 45 EG V Mono-component

Humicola insolens Humicola insolens Humicola insolens

8–10 7–9 6–8.5

50–70°C 65–80°C 50–70°C

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of Textile Fabrics-Martindale Pressure Tester Method). A swatch from each beaker was tested and evaluated after 125, 500 and 2000 revolutions on a Nu-Martindale Abrasion and Pilling Tester from James H. Heal & Co. Ltd. A pilling note was obtained by one expert observer visually comparing the sample to a standard on a scale from 1 to 5, where 5 is no pilling and 1 is severely pilled. A mean pilling note was calculated by averaging all swatches treated under the same conditions. HPLC

ANALYSIS

Liquor samples were taken from each beaker after LOM incubation for HPLC analysis. The samples were filtered and loaded into vials. The samples were then injected on an Agilent 1100 series HPLC and detected with a variable wavelength detector at 254 nm at 25°C. The mobile phase was a combination of solvent A– filtered deionized water plus 0.1% trifluoroacetic acid and solvent B–100% acetonitrile. A gradient was used where solvent B increased from initial concentration of 10% up to 95% at the end of the 19-minute run time. An Adsorbosil C18 column from Alltech was used. The flow rate was 0.8 ml/minute. After each injection the needle was rinsed in dimethylformamide and the column was allowed to equilibrate for 5 minutes at initial conditions. Peak area counts for known degradation products of polyester (terephthalic acid and monohydroxyethylene terephthalate) were averaged for samples treated under the same conditions.

FIGURE 1. The effect of dosage on weight loss for cutinase degradation of 100% polyester fabric. Conditions: 2 hours LOM treatment at 70°C, pH 8.

Results and Discussion BIO-POLISHING

OF

100% POLYESTER

Initial work was performed to study the enzymatic degradation of 100% polyester fabric comparing both cutinases (see Table I). Cutinase B gave higher weight loss than that of cutinase A, whereas cutinase A gave little to no weight loss compared with a blank (Figure 1). A blank is defined as a treatment performed where no enzyme is added. Both cutinases gave improvement on pilling note compared to the blank at 2000 revolutions (Figure 2). The values for 125, 500 and 2000 revolutions were measured with respect to pilling; however, only the data for 2000 revolutions is shown. The trends for all revolutions measured were the same. Although there was little to no weight loss for cutinase A, an improvement in pilling note was observed as compared to the blank. Weight loss was measured for the additional experiments; however, it was not used as an indicator for pilling prevention. Additionally, the HPLC results were measured to detect enzymatic degradation of the polyester polymer

FIGURE 2. The effect of dosage on pilling note at 2000 revolutions for 100% polyester fabric. Conditions: 2 hours LOM treatment at 70°C, pH 8

(Figure 3). Cutinase B showed considerably higher degradation according to HPLC area count of degradation products of polyester. This correlates with higher pilling note and weight loss. However, Figure 3 does illustrate that both enzymes are acting on the polyester as a substrate and the pilling prevention data is an enzymatic hydrolysis effect, decreasing the likelihood of simply an effect of protein adsorption. Cutinase B has a higher specific activity toward polyester fiber than cutinase A. A higher specific activity

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483 TABLE 2. Bio-Polishing of 50%/50% Polyester/cotton blend, LOM treatment, 2 hours, pH 8 at 70°C Enzyme treatments

FIGURE 3. The effect of dosage on HPLC area count of polyester degradation peaks for 100% polyester fabric. Conditions: 2 hours LOM treatment at 70°C, pH 8.

explains why there is an overall higher level of performance of cutinase B as compared with cutinase A with respect to pilling note, weight loss and degradation products via HPLC. BIO-POLISHING

OF

POLYESTER/COTTON BLENDS

Additional trials were made to investigate enzymatic degradation of 50%/50% polyester cotton blend fabric combining cutinase A and a cellulase. Cutinase B was not available for the blended fabric trials. Two dose– response trials were performed. The first dose–response trial was maintaining a 0.75 ECU/ml dose of cellulase and increasing the dosage of cutinase A from 0 to 50 LU/ml. The second dose–response trial was maintaining a 50 LU/ml dose of cutinase A and increasing the dosage of cellulase from 0 to 1 ECU/ml. All data from polyester/cotton blend bio-polishing is shown in Table II. The weight loss measured for each dose–response increased with increased dosage of both enzymes. This result is expected as the dosages selected for these experiments are within the linear part of dose profile. Typical dose–response curves for cellulase hydrolysis of cotton showed an initial linear response which at a certain dose began to level off. After this dose it is no longer beneficial to increase the cellulase dosage. Both cellulase and cutinase A gave an improvement in pilling note as compared to the blank. When both enzymes were combined, the most significant improvement in pilling note was observed at almost all doses evaluated. For this particular fabric, the cellulase alone had a more significant impact on pilling than cutinase A alone.

Evaluations

Dose cellulase (ECU/ml)

Dose cutinase A (LU/ml)

Weight loss %

Pilling at 2000 rev.

HPLC area count at 254 nm

0 0.75 0.75 0.75 0.75 0.75 0 0.25 0.5 0.75 1

0 0 10 20 30 50 50 50 50 50 50

1.0 1.1 1.3 1.4 1.4 1.6 1.3 1.6 1.6 1.6 1.7

1.25 2.5 3 2.3 3 3 1.5 2.8 2.5 3 3

9 8 1888 2713 3058 3503 3699 3616 3524 3530 3559

HPLC results were measured to detect enzymatic degradation of the polyester polymer due to cutinase activity. Not surprisingly, the area count of degradation products of polyester increased as the enzyme dose increased. As the cellulase dose increased, the area count did not change because the dosage of cutinase A was constant.

Conclusions Both the 100% polyester fabric and polyester cotton blended fabrics fuzz and pill when exposed to abrasion. Some cotton fabrics are industrially bio-polished with a cellulase in order to remove surface fibers and prevent pilling. This study demonstrated that 100% polyester fabric can be treated with a cutinase to impart a biopolished finish. Furthermore, a polyester cotton blend fabric can be treated with a cellulase combined with a cutinase to impart a bio-polished finish. The addition of this technology to polyester finishers and the bio-polishing world offers an environmentally friendly and mild alternative to the chemical and mechanical finishes currently being used in industry.

Literature Cited 1. Albrecht, W., Part 1. “Early History, Tomorrow’s Ideas and Profits: Polyester 50 Years of Achievement,” The Textile Institute, Manchester, 1993, pp. 52–55. 2. Andersen, B. K., Borch, K., Masanobu, A., and Damgaard, B. Novo Nordisk A/S. “Method of Treating Polyester Fabrics.” 1999. U.S. Pat. 5,997,584. 3. Asferg, L., and Videbaek, T., Softening and polishing of cotton fabrics by cellulase treatment, Int. Textile Bull. Dyeing/Printing/Finishing, 2, 5– 8 (1990). 4. Bazin, J., and Sasserod, S., Enzymatic Bio-Polishing of Cellulosic Fabric 58e`me Congre`ss de l’Association des

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5. 6. 7.

8.

TEXTILE RESEARCH JOURNAL Chimistes de l’Industrie Textile Science, Mullhouse, France. October 25, 1991. Harrison, P. W., (ed.), Surface Modification of Polyester by Alkaline Treatments, Textile Prog. 20(2), 1–22 (1989). Hatch, K., (ed.) “Textile Science,” West Publishing Company, St. Paul, 1993, pp. 52–53, 218, 420. Liu, J., et al., Selecting Cellulases for Bio-Polishing Based on Enzyme Selectivity and Process Conditions, Textile Chem. Colorist Am. Dyestuff Reporter, 32(5), 30 –36 (2000). Militky, J., Vanicek, J., Krystufek, J., and Hartych, V., “Modified Polyester Fibres, Textile Science and Technology,” Vol. 10, Elsevier Science Publishing Co. Inc., Amsterdam, 1991, pp. 42-45, 64 – 69.

9. Nunn, D. M., (ed.) “The Dyeing of Synthetic-Polymer and Acetate Fibres,” The Dyers Company Publications Trust, West Yorkshire, 1979, p. 133. 10. Pedersen, G., and Sasserod, S., “Durability of Bio-polishing – Cellulase Treatment of Cotton,” Novo Nordisk, April 1992. 11. Pedersen, G., Screws, G., and Cedroni, D., Biopolishing of Cellulosic Fabrics, Can. Textile J. 109, 31–35 (1992). 12. Tomasino, C., “Part 3. Textile Processing, Tomorrow’s Ideas and Profits: Polyester 50 Years of Achievement,” The Textile Institute, Manchester, 1993, pp. 158 –161. 13. Yamagishi, M., Cellulose Treatment of Cotton Fabrics, Kako Gijutsu 23(3), 6 –10, 1988.