Improving the Wettability of Enzyme-Bleached Cotton Fabric with

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Improving the Wettability of Enzyme Bleached Cotton Fabric with Inclusion of Sodium Surfactin Matthew Farrell, Miranda DeBoskey, and Mary Ankeny ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.5b01486 • Publication Date (Web): 29 Jan 2016 Downloaded from http://pubs.acs.org on January 30, 2016

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ACS Sustainable Chemistry & Engineering

Improving the Wettability of Enzyme Bleached Cotton Fabric with Inclusion of Sodium Surfactin Matthew J. Farrell*, Miranda J. De Boskey, Mary A. Ankeny [email protected] Cotton Incorporated, 6399 Weston Parkway, Cary NC, 27513, USA KEYWORDS Cotton, enzyme bleaching, surfactant, sodium surfactin, water absorbance ABSTRACT The enzymatic bleaching of cotton fabric has presented itself as a sustainable step forward in the field of textile processing. Instead of employing high temperature and alkalinity to promote the oxidative peroxide bleaching of cotton, enzyme bleaching of cotton fabrics allows near neutral pH bleaching at much lower temperatures by the generation of peracids. A notable drawback observed with enzymatic bleaching of cotton fabrics is that albeit white fabrics are obtained, initial and instantaneous wetting is not easily obtained. It has been found that the naturally derived surfactant sodium surfactin can be used with a conventional textile surfactant during enzymatic bleaching to obtain much faster initial and instantaneous wetting. Adding small amounts (0.005-0.1 g/L) of sodium surfactin to an enzymatic bleach process caused a substantial decrease in the amount of time it takes a water drop to completely absorb on cotton fabric. INTRODUCTION All aspects of textile preparation and processing continue to receive pressure to develop and utilize sustainable practices. Proper preparation of cotton fabrics is a key initial progression in producing an acceptable dyed and finished cotton garment. Depending upon the variety and location, the cellulose content of cotton fiber varies from 88-96%. The remaining 4-12% of cotton is composed of constituents including protein, pectin, minerals, wax, and organic acids.1-2 For the preparation of white cotton fabrics, greige cotton fabric is most commonly bleached utilizing hydrogen peroxide at high temperature and alkalinity.3 In general description, the peroxide serves as the oxidative bleaching agent to decolorize the natural colorants found within cotton. The high alkalinity of the bleach bath serves to destroy motes, saponify oils and waxes, remove organic matter, and contributes to peroxide activation for bleaching. Chemical auxiliaries such as surfactants emulsify the oils and waxes both from the knitting oils and those naturally found in the cotton fiber. Lubricants, dispersants, and chelates are also commonly found in bleach bath recipes to prevent fabric damage and help disperse the chemicals and other auxiliaries throughout the bleach bath. Because of the high temperatures employed in conventional peroxide bleaching of cotton, tremendous amounts of energy and time are utilized to heat and maintain the bleaching temperature. Further, copious amounts of water are required to rinse residual alkali from the bleached fabric. The development of bleach activators have allowed the bleaching of cotton fabrics at significantly lower temperature, pH, and time.4 Compared to the high temperature and high pH hydrogen peroxide bleaching, bleach activators when exposed to hydrogen peroxide form powerful peracid bleaching agents.4 A recent review of the factors effecting the performance of two common activated peroxide systems (APS) on the 1 ACS Paragon Plus Environment


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bleaching of cotton fabric showed that the most important variables affecting the performance was the cotton fabric (greige or prescoured), the temperature utilized, and the bleach activator utilized.5 Prescouring before bleaching is not a conventional process; bleaching and scouring are traditionally a one bath process. On the other hand, cationic bleach activators are a newer generation of bleach activators that help alleviate water solubility issues commonly associated with conventional bleach activators and promote the attraction of the bleaching compound to the negatively charged fiber surface.4 These new types of cationic bleach activators have seen industrial interest, but to date, have not been widely adopted. Pre-cationization of cotton fabrics has also been suggested as an alternative bleach activator, utilizing the cationic charge to promote peroxide bleaching.6 However, precationization requires an added treatment step to obtain benefits in the bleaching stage. Ozone has also been considered as an environmentally friendly bleaching agent. Ozone has the second strongest oxidizing power next to fluorine,7 can be carried out at room temperature,8 but generally requires specialized equipment such as an ozone generator.9 Peracetic acids generated in situ from acetic anhydride and acetic acid have also been studied as an environmentally friendly bleaching method.10-11 This method requires catalysts and generally results in a mixture of products, including the desired peracetic acid. Conversely, an alternative sustainable bleaching approach of cotton relies upon enzymatic bleaching. Our experiences with enzymatic bleaches have shown that instantaneous wetting after bleaching is not readily produced with enzymatic bleaches. This limitation can be overcome with inclusion of pectinase to remove pectins and improve wettability of the fabric.12 Instantaneous wetting of a prepared for dye fabric is a common quick check test of the efficacy of the scouring or bleaching process. A cotton fabric that does not readily absorb water is considered not properly prepared, a major hurdle slowing the adoption of enzymatic bleaching of cotton. One bath processes incorporating bleaching agents and pectinase have been demonstrated, but utilization of an alkaline pectinase requires important considerations such as increased processing time and selection of suitable chelators.13 Kaneka Corporation produces a naturally derived surfactant, sodium surfactin (1) (SS), extensively used in cosmetics. Surfactin was first isolated and identified as a natural biosurfactant in 1968 from a culture of bacillus subtilis.14 Chemically SS is a lipopeptide with an extremely low critical micelle concentration of 0.0003%. It should be noted that because of the ester bond found within the peptide ring, at pH>10 SS is prone to hydrolysis, presenting some issues in conventional scouring and bleaching processes that routinely exceed pH 11. However, enzymatic bleaching and scouring typically occurs around a neutral pH of 6-8 and may allow utilization of SS in the preparation of cotton knits.15 The purpose of this work is to examine the use of SS in an enzymatic bleach process without pectinase and observe if there is an improvement in the absorbency of enzyme bleached cotton fabric.

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1

EXPERIMENTAL Materials Greige 100% cotton interlock fabric was obtained from Cotton Incorporated. Sultafon® D, a nonionic scouring agent was obtained from Bozzetto Incorporated. Marlube CMN, a polyacrylamide lubricant, Marsperse 6000, a polyacrylic acid dispersant, and Marquest PB, a hydrogen peroxide bleach bath stabilizer, were all obtained from Marlin Chemical Company. Reagent grade soda ash, 50% sodium hydroxide, 35% hydrogen peroxide, and 56% acetic acid were all obtained from Brenntag USA. DowanolTM PGDA (propylene glycol diacetate) was obtained from Dow Chemical Company. Prima-Green® EcoWhite and Oxy-Gone® T-400 were obtained from Genecor International. Prima-Green® EcoWhite is a bacterial arylesterase enzyme that catalyzes the hydrolysis of PGDA into propylene glycol and the bleaching agent peracetic acid. Similarly, Oxy-Gone® T-400 is a catalase enzyme that catalyzes the decomposition of residual hydrogen peroxide in the bleached fabric. Sodium Surfactin was obtained from Kaneka Corporation. Methods Bleaching 50 gram samples of greige 100% cotton interlock were bleached at a 10:1 liquor ratio in a Mathis laboratory Labomat beaker dyeing machine. For a conventional bleach comparison, Table 1, all chemicals and auxiliaries except for Oxy-Gone® T-400 and acetic acid are added and heated to 205°F and held for 30 minutes. The bath was then drained for one minute before water was added and rinsed at 160°F for five minutes. The bath was allowed to drain again before adding Oxy-Gone® T-400 and water and heating to 140°F for five minutes. The bath was allowed to drain again and water was added and the sample was then rinsed at 120°F for five minutes. The bath was drained again, and the acetic acid was added along with water and the bath was held at 90°F for five minutes. Finally, the sample was rinsed in warm water in a sink and dried in a forced air oven at 200°F. 3 ACS Paragon Plus Environment


For the enzymatic bleaches, Table 2 shows the base recipe used for all experiments. Table 3 shows the surfactant recipe utilized for each experiment along with the base enzymatic bleach recipe. All chemicals and auxiliaries shown in Tables II and III except Oxy-Gone® T-400 are added and heated to 140°F and held for 45 minutes. The bath was then drained for one minute before water was added and the sample was rinsed at 185°F for 10 minutes. The bath was allowed to drain again before adding Oxy-Gone® T-400 and water and heating to 140°F for 15 minutes. The samples were then rinsed in warm water in the sink and dried in a forced air oven at 200°F. Table 1 – Conventional Bleach Recipe Sultafon® D (g/L)

Marsperse 6000 (g/L)

Marlube C-MN (g/L)

Marquest PB (g/L)

50% Sodium Hydroxide (g/L)

35% Hydrogen Peroxide (g/L)

Oxy-Gone® T-400 (g/L)

56% Acetic Acid (g/L)

2

1

1

0.4

4

4

0.04

0.5

40

60

80

100

250

Temperature (degrees F)

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200

150

100

50

0 0

20

120

Time (min)

Figure 1. Conventional Bleach Process

Table 2 - Enzymatic Bleach Bath Base Recipe Marsperse 6000 (g/L)

Marlube C-MN (g/L)

Marquest PB (g/L)

Soda Ash (g/L)

35% Hydrogen Peroxide (g/L)

PGDA (g/L)

Prima-Green® EcoWhite (g/L)

Oxy-Gone® T-400 (g/L)

2

1

0.4

2

8.6

3

0.1

0.08


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Table 3 – Enzymatic Bleach Bath Surfactant Recipes Trial (SD,SS)

Sultafon® D (g/L)

Sodium Surfactin (g/L)

SD1,SS0

1

0

SD0,SS1

0

1

SD1,SS1

1

1

SD1,SS0.005

1

0.005

SD1,SS0.05

1

0.05

SD1,SS0.1

1

0.1

200 180

Temperature (degrees F)

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160 140 120 100 80 60 40 20 0 0

20

40

60

80

100

120

Time (min)

Figure 2. Enzymatic Bleach Process

Evaluation A simple water drop test was used to check for evidence of scouring and bleaching. A drop of water was placed onto the bleached fabrics and the time for the water drop to completely absorb into the fabric was recorded. L*, a*, b*, and CIE whiteness values were determined for the bleached samples utilizing an Xrite Color i7 benchtop spectrophotometer, 10° standard observer, and D65 as the illuminant. The pH of the bleach bath was recorded before and after scouring to ensure the pH did not exceed pH 10. Burst strength of the bleached fabrics were determined using a James Heal Truburst2 burst strength fabric analyzer averaging five tests per sample.



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RESULTS and DISCUSSION Table 4 shows the colorimetric data obtained for the bleached samples. Nearly identical L*, a*, and b* data are found for all bleached samples. As Figure 3 shows, there is small variation in the CIE whiteness values for the enzymatic bleaches. However, the conventional bleach yielded the highest whiteness. It is well known and expected that peracetic acid bleaching generally yields lower whiteness values as compared to conventional bleaching of cotton. TABLE 4 Colorimetric Results

Greige

n/a

Sodium Surfactin (g/L) n/a

SD1,SS0

1

0

95.81

-0.49

3.63

SD0,SS1

0

1

95.54

-0.51

3.63

SD1,SS1

1

1

95.79

-0.51

3.65

SD1,SS0.005

1

0.005

95.67

-0.54

3.91

SD1,SS0.05

1

0.05

95.68

-0.47

3.64

SD1,SS0.1

1

0.1

Conventional

2

0

95.71 95.88

-0.54 -0.41

3.85 2.59

Sultafon® D (g/L)

L*

a*

b*

87.7

1.12

12.23

WI-CIE 90 80 70 60 50 40 30 20 10 0

Figure 3. CIE Whiteness Values


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As seen in Table 5, adding SS to the bleaching bath drastically decreases the initial wetting time. The typical enzymatic bleach shows slow initial wetting times (D1,SS0). Adding even 0.005 g/L of SS decreases the initial wetting time by ½. Addition of 0.1 g/L of SS led to an instantaneous absorption of a water drop as compared to an average of 19.2 seconds without SS. Interestingly and as discussed further below, utilizing SS alone yielded a fabric that did not absorb water at the two minute mark. Also, as seen in Table 5, the pH of the enzyme bleaching bath increased as the amount of SS increased. However, the initial bleach bath did not exceed 10 for any sample, and the final pH of all bleach baths was between 6.5-7. TABLE 5 pH, Water Drop, and Burst Strength Results

Greige

n/a

Sodium Surfactin (g/L) n/a

SD1,SS0

1

0

7.9

6.58

19.2

SD0,SS1

0

1

8.1

6.57

>120

SD1,SS1

1

1

9.64

6.63

Improving the Wettability of Enzyme-Bleached Cotton Fabric with

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