INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY #233


1.  Headline:  The breakdown of the size of polymers can be
    carried out using oxidizing agents such as ammonium
    persulphate and hydrogen peroxide at high pH and high
    temperature. Using the enzyme amylase less aggressive
    chemicals are required and less fibre damage is obtained.

2.  Background:  See below.

3.  Cleaner Production Principle:  material substitution,
    chemicals are substituted by enzymes.

4.  Description of Cleaner Production Application:

    Process and Waste Information

    Introduction

    During the weaving process the warp (chain) threads are
    exposed to considerable mechanical strain. In order to
    prevent breaking, they are usually reinforced by coating
    (sizing) with a gelatinous substance (size).

    In the weaving of cotton blend fabrics, the size material
    most often contains starch in native or modified form,
    sometimes in combination with other polymers such as
    polyvinyl alcohol (PVA), polyacrylic acid (PAA) or
    carboxymethyl cellulose (CMC). A small amount of fats or
    oils may be added to the size also, with the aim of
    lubricating the warp coat surface.

    As a consequence of the sizing, the warp threads of the
    fabric are not able to absorb water  or finishing agents
    to a sufficient degree. This means that first the size
    must be removed (desizing) before finishing. Some types
    may be removed in a simple scouring process (water soluble
    sizes). But in most cases chemical breakdown of the size
    polymer in a separate desizing treatment is necessary in
    order to obtain the desired quality of the final fabric
    [2].


TABLE 1: Biodegradability of size raw materials


                       BOD(5) g/g    COD(tot.) g/g
               BOD/CODx100%

starch, natural                             0.65    1.18
                                        55
starch, oxidized                   0.60    0.99    61
PVA                                   0.01    1.79
                              0.55


The conventional process

The breakdown of the size polymer is carried out using oxidi
zing agents such as ammonium persulphate or hydrogen peroxide
at high pH and temperature.


oxidizing agents --->  desizing   --->  size,
                                                  d
                              esizing agents,
                                                  wet
                              polluted cotton.

The treatment reduces the tensile strength of the fabric and
results in poor removal of some PVA-containing sizes.

The quantity of size is about 15 % of the yarn weight [4].

TABLE 2: In- and output desizing

Input desizing per kilo cotton    Output per kilo cotton

25-50 g H2O2          70 g size
5-150 g NaOH          tensides
10-15 g tensides       oxidizing agents
54  litres water           54 litres polluted water
                  wet  polluted cotton

The COD value can be from 3500 mg O2 /l to 23000 mg O2 /l [1].

Enzymatic desizing

Complete removal of starch-containing size without fibre damage
is best obtained by using enzymatic desizing agents. Formerly
amylase derived from mould, pancreas or malt where used in
desizing. Today liquid bacterial amylase preparations dominate.

The desizing process can be divided into three stages:

Impregnation: Enzyme solution is absorbed by the fabric.
Incubation: The size is broken down by the enzyme.
After-wash: The breakdown products from the size are removed
from the fabric.

Impregnation
-   Thorough wetting of fabric with enzyme solution.
    Temperature 70C or higher. Liquid pick up of 1 litre per
    kg fabric.
-   Sufficient enzyme stability (temp, pH, calcium ion level).
-   Gelatinization of the size (starch) to the highest
    possible extent.

Incubation.
-   Long incubation time allows a low enzyme concentration.

After-wash.
-   The desizing process is not finished until the size
    breakdown products have been removed from the fabric. This
    is best obtained by a subsequent detergent wash (with
    NaOH) at the highest possible temperature.

There are four procedures for desizing:
                                Jigger or winch
                                pad-roll (or pitt)
                                J-box (continuous)
                                Pad-stream (continuous)
TABLE 3: Process conditions

         jigger/winch  pad roll j-box        pad-steam
              aquazym  aquazym  aquazym  aquazym

impregnation:

dosage, (g/100 l)     50-250                     100-300
30-200                      75-350
temp, C   65      70      80      80
water hardness
ppm Ca/dH >60/8        >60/8        >6/1    >6/1
pH        6.0-7.0      6.0-7.0      6.5-7.5      5.5-7.5

wetting agent
g/100 l       50      50      50      50
incubation:
incubation time         --   2-4 h        10-20 min.    15-
120 sec
temp,øC   15-20         --     85      100

after-wash:
temp, øC  90-95        90-95        95-100       95-100
NaOH kg/ 100 l         0.5-1 0.5-1        1-3     1-3

There are three enzymes Aquazym 120l, Aquazym Ultra 250l and
Termamyl 60l. In this table only data on the aquazym and the
aquazym-ultra are presented.

Scale of operation
Not available.

Stage of development
The process is fully implemented. In the Netherlands a big
finishing company KTV is using the enzyme for more than 20
years.

Level of commercialization
The enzyme is commercial available at Novo Nordisk.

Material/Energy Balances and Substitutions
Less oxidizing agent must be used and there is less oxidizing
agent waste.

5.  Economics

Investment Costs
Not available

Operational and Maintenance Costs
Not available

Payback Time
Not available


6.  Advantages

-   Avoidance of chemical fibre damage
-   Superior biodegradability of effluent
-   Less handling of aggressive chemicals

7.  Constraints

The use of the enzyme depends on the kind of size. If there are
chemicals used in the size to which the enzyme is not resistant
then it is impossible to use the enzyme.

8.  Contacts and Citations

Type of Source Material
Articles, interviews.

Citation

1.  SPIN document, textielveredeling, march 1993.
2.  Novo Nordisk enzymes for the textile industry, desizing,
    dec.1991
3.  Dorthe Marcher et al.,paper presented at the seminar on
    Sizing, Italy, march 1993.
4.  A. Klingenberg, Textielchemicalien, Stichting Natuur en
    Milieu, Utrecht, 1986.

Level of detail of the Source Material
A bit more detail is available.

Industry/Program Contact and Address
Not available. No permission is asked to or given by the
contact.

Abstractor Name and Address
Annelies den Braber
TME, Institute for Applied Environmental Economics
Grote  Marktstraat 24
2511 BJ The Hague
Netherlands
tel: +3170-3464422
fax: +3170-3623469

9.  Keywords: ISIC  I2242, wastewater, desizing, textile
    finishing, enzyme, amylase, Novo Nordisk, biotechnology,
    the Netherlands, textile, material substitution, polymers,
    cotton, BOD, COD.

10. Reviewer's Comments:  This case study was submitted to
    UNEP IE by the Institute for Applied Environmental
    Economics (TME) of the Netherlands on the part of the UNEP
    IE working group on Biotechnology.  The case study was
    edited for the ICPIC diskette in August 1995.  It has not
    undergone a formal technical review.