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Bioscouringof Cotton: Commerical

pplicationsof lkalineStable

ectinase

ByRobert B.Waddell, Dexter Chemical Corp., Charlotte, N.C.

l1

e textile industry continues to

look for new, innovative

methods for improving quality

and production, and also to ad-

dress environmental issues. It is cer-

tain that enzymes will play an impor-

tant role in meeting these objectives.

In recent years, enzymes have become

increasingly useful in the processing of

natural fabrics. Amylases have long

been used as desizing agents for wo-

ven fabrics, and more recently cellu-

lases, lipases, laccases, catalases, and

proteases have found their place in the

production of quality textile fabrics.

The most recent addition to this list is

an alkaline stable pectinase.

Alkaline stable pectinase has proven

to be highly effective for pre-scouring

cotton fabric prior to dyeing. The term

bioscouring has been used to de-

scribe this process. Production results

have shown bioscouring to be an effec-

tive way to improve fabric quality and

at the same time offer a milder, sub-

strate specific scour.

In this paper wewill examine the

objectives of scouring, and the com-

mercial applications of the bioscouring

process.

SCOURINGOBJECTIVES

Cotton fibers consist of approximately

92-96 cellulose and 4-8 impurities

that impede aqueous chemical process-

ing (Fig.I). The primary non-cellulosic

impurities are comprised of waxes,

pectins, proteins, andminerals.1These

components create a hydrophobic

barrier that protects the fiber during

the growth and development stage and

also serves as a lubricant during fiber

AATCC REVIEW

28

ricoThe results from such scours vary

depending on application time, bath

temperature, and chemical concentra-

tions. This type of process covers a

very broad spectrum. It is a non-spe-

cific scour that not only removes the

impurities but can also modify the

cellulosic part of the fiber as well. It

also leaves high levels of alkali in the

fabric that must to be neutralized be-

fore proceeding to the dye bath.

Bioscouring

Bioscouring is a process by which an

alkaline stable pectinase is used to

selectively remove pectin and waxes

from the cotton fiber. By breaking the

pectin interface, which lies between

the waxes and the cellulose fiber, the

waxes are exposed and can be emulsi-

fied when the bath temperature is

brought above their melting point.3

Subsequent rinsing helps to remove

these impurities from the bath. Unlike

alkaline scouring,

this process is sub-

strate specific, and

does not alter the

cellulose compo-

nent. The

bioscouring process

does not swell or

remove the seed

coat fragments

called motes. This

can be beneficial

when scouring for

the natural look.

Because of the mot

and color retention

in cotton fabrics

scoured with this

processing. Most of the waxes should

be removed during the scouring pro-

cess to facilitate fiber wettability and

to ensure level dyeing. These waxes

are found in the outer layers of the

fiber called the primary wall and cu-

ticle(Fig.2 2

SCOURING METHODS

Alkaline Scouring

Traditional scouring of cotton fabrics

has been carried out by the combined

use of alkali, surfactants, and chelating

agents. The alkali, usually caustic

soda, is used to swellmotes and to

saponify oils and waxes. Surfactants

are used to expedite fabric wet out,

emulsify oils and waxes, and to keep

the emulsified material dispersed in

the scour bath and during rinsing.

Chelates are used to formwater-

soluble complexeswith metals, which

facilitates their removal from the fab-

II Cellulose 94.0

. Pectin 1.2

0 Waxes 1.3

0 Protein 0.6

.Ash 1.2

.Other 1.7

Fig. 1. Typical mature cot1on fiber composition. 1

Primary Wall

Cuticle

Secondary Wall

Fig. 2. Cot1on fiber.2

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process, pastel or light shades need to

be bleached prior to dyeing, but me-

dium to dark shades can be dyed di-

rectly after the bioscour.

APPLICATIONS

In mid 1998, scientists and technicians

from Novozymes NA and Dexter

Chemical began working together to

develop a viable process using an

alkaline stable pectinase. Like all en-

zymes, pectinase activity and effi-

ciency is determined by three vari-

ables: time, temperature, and pH. In

designing a product and process that

could be adapted to existing textile

processing equipment, each of these

variables had to be taken into consider-

ation. Processing cost also had to be

carefully monitored to ensure market-

ability.

After much consideration it was

determined that batch processed cotton

and poly/cotton knits would be the

most applicable candidate for this new

enzyme process. The three variables;

time, temperature, and pH could be

easily controlled to meet the enzyme s

requirements in jets and other batch

equipment. Applications such as multi-

stage continuous, and pad-batch woven

processing would follow as more expe-

rience with the alkaline stable pecti-

nase was gained and as other enzymes

are developed to work in combination

with the pectinase.

Check pH

8.5-9.5 ~

i

Load Fabric

Add

Chelate

Detergent

Sodium Carbonate Buffer

Lubricant Defoarner Optional)

Fig. 3. Bioscour process profi le.

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Cotton Knit Application

Trials on production scale equipment

started in January 1999at Cross Creek

Apparel in Mt. Airy, N.C. Initial work

was done to compare the bioscour

process to the plant s then current

production process for prescouring

cotton knits. Loads of the same fabric

and color were run on the same equip-

ment and the fabrics compared. Trials

were run on navy and hunter green

colors successfully.The bioscoured

fabrics had very level, on-shade

dyeings with excellent wettability and

extractables. The control process used

was an extensive, high alkaline scour.

This control process had been running

for an extended period with little qual-

ity problems. As a result of the first

trial s success, a follow-up set of pro-

duction trials was scheduled.

The next trials were conducted by

injecting the bioscour process directly

into the plant s production. One jet

1000 Ib) was set aside to run the

bioscour, for a period of one week.

During this period 13lots were suc-

cessfully scoured and dyed. The fiber

reactive colors evaluated on this trial

consisted of royal blue, medium blue,

navy, black, and red. All of the lots,

regardless of the style, weight, or

color, met or exceeded quality expec-

tations.

Following these successful trials,

the bioscour process was adopted and

200F/5 min.

135F/

10 min.

Fill 140F

Add

Dextrol Bioscour

implemented May 1999). Since that

time, no production problems have

occurred as a result of the bioscour

process. Over the last year several

other knit dyehouses have adopted the

process. A typical process profile can

be seen in Fig. 3.

With this procedure the batch

equipment, usually a jet, is filled at

any temperature up to 135F.The fabric

is loaded, either before or after the

first chemical tank add. The bath is

circulated, sampled, and the pH

checked before addition of the second

chemical tank. The temperature is

brought to 135Fand held for 10min-

utes. This is the actual bioscour part of

the procedure. The bath is then heated

to 200F to melt and emulsify waxes,

and held for five minutes. The scour is

followedby at least one 180Frinse

before proceeding to the dyebath.

The latest modifications include

reducing the time used in the rinse

procedure by skipping the drain step

and going directly to an overflow

wash. Other procedure modifications,

such as adding a 120Frinse prior to

the bioscour process, have proven to

be effective in helping remove knitting

oils and reducing foam levels.

Cotton Woven brics

Most traditional cotton woven fabrics

are wet processed by one of three

methods: pad batch, batch, or continu-

180F/5 min.

Overt low rinse at 140F/1 0 min.

----

Proceed to Dyeing Procedure

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ous preparation. Pad batch processing

usually consists of a saturator and a

storage method for extended applica-

tion time or dwell, followedby a

washer. Batch processing can be car-

ried out in a variety of equipment such

as becks, jigs, kiers, and soft-flowjets.

Continuous preparation can be broken

down into two types-rope and open-

width ranges. Both rope and open-

width ranges vary in the number of

consecutive processes or stages, de-

pending on the desired result.

Pad Batch Bioscour

The adaptation of the bioscour proce-

dure to a pad batch process is rela-

tively easy. The fabric is wet out in the

saturator, passed through a nip roller to

get a controlled wet pickup, held at

room temperature for 12-24 hours, and

then washed. Due to an extended

amount of dwell time the temperature

of the saturator can be maintained at

the enzyme optimum of 135For lower.

The pH is set at 8.5-9.5 in the satura-

tor bath by the addition of a buffer.

The saturator also contains a wetter/

emulsifier to facilitate good fabric wet

out and removal of waxes during

washing.A chelate may be added to

the saturator bath or metered into the

first wash box to avoid a buildup of

hard soaps.Wash temperatures of

180For above are required for good

wax emulsification and removal.

If the fabric has been sized with

starch, an amylase should be added to

the saturator mix to, in effect, desize

and scour simultaneously.Care must

be taken in selection of the amylase to

ensure compatibility and effectiveness

at the 8.5-9.5 pH range.

Wovens on Batch Equipment

Processing woven fabrics on batch

equipment is similar to the method

used for knits. This process can be

adapted to all of the batch equipment

including jigs, becks, kiers, or soft-

flowjets. The main difference between

wovens and knits is the need for the

addition of an amylase to remove

starch sizing.

AATCC REVIEW

Continuous Bioscouring of

Wovens

On single stage continuous rope ranges

such as a I-box steamer, it is possible

to get excellent scouring and desizing

without major modifications to tradi-

tional procedures. By adjusting the

saturator pH down to 8.0-8.5 the alka-

line stable pectinase becomes more

stable and is less sensitive to tempera-

ture. Because the fabric being intro-

duced into the I-box does not see full

temperature for 10-15minutes, the

alkaline stable pectinase has time to

work before exceeding its deactivation

temperature. This allows the steam

temperature in the I-box to be held at

an easier to maintain a temperature of

190-200F.In this procedure, a ther-

mally stable amylase should be used to

maximize dwell time efficiency. The

saturator bath should contain wetter,

emulsifier, buffer, amylase, and pecti-

nase. Chelate is then metered into the

first hot wash box. This type of equip-

ment can be used very effectively to

scour fabrics for the natural look or

to scour yarn dyed fabrics that need

improvedwettability, such as towels.

On multiple stage ranges, the

bioscour process can be used in a

variety of ways. On a two-stage range

the alkaline stable pectinase can be

combined with amylase to give the

results of a desize and scour.On three-

stage ranges the bioscour procedure

may be able to replace the traditional

caustic scour. Due to variations in

continuous ranges, the bioscour proce-

dure must be customized to accommo-

date each set of conditions.

CONCLUSION

As experience with the bioscour proce-

dure was gained, many advantages

surfaced. Some were obvious, while

others were a bit more subjective and

case specific. The bioscour process fits

within the traditional prescour time

frame, and the chemical cost is compa-

rable. In some cases, the scour time

has been reduced and the scouring

efficiency has been improved. Due to

more uniform wax removal and better

wettability, bioscoured fabrics have

yielded smoother dyeings. Many of the

streaks and the motley appearance

associated with heavy shades are re-

duced or eliminated. In some cases,

bioscoured fabrics dye heavier than

traditionally prescoured fabrics. This

can translate into dye cost savings and

reduced color in the effluent. Because

of the low alkalinity of the bioscour

procedure, no acid neutralization is

required before dyeing can start. This

can reduce the amount of water used

by a few thousand gallons per load.

Bioscoured fabrics maintain a high

mote count unlike caustic scoured

fabrics. This is an advantage when the

natural look is desired. A high leve

of wettability can be achieved without

affecting the fabric appearance. This

cannot be done with traditional alka-

line scours.

In many dyehouses caustic soda is

manually weighed, carried, and dis-

pensed by operators. The alkaline

stable pectinase described is much

safer to handle than caustic. This pecti

nase, unlike caustic, will not harm

human tissue, which in turn reduces

personal risk to the operator. Also, the

quantity used is only a fraction of the

caustic use level, therefore eliminating

the heavy lifting associated with buck-

ets of caustic.

References

Lange, N. E. K., Book of Papers

AATCC International Conference

Exhibition, Philadelphia, 1998,p463.

2 Hardin, 1.R. and J. Kim,

Book of

Papers

AATCC International Confer-

ence Exhibition, Philadelphia, 1998

p319.

3. Etters, J.N., P. A. Husain, and N. E. K

Lange,

BioPreparation The New Ad

vanced Way of Preparing Fabric

Yarn 1999,pp4,6.

uthor s ddress

Robert B.Waddell,Dexter Chemical

Corp., P.O.Box 7403, Charlotte, N.C.

28241-7403; telephone 704-588-3991;

fax 704-588-4049; e-mail

MrRWaddell@aol.com.

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