Enzyme mixtures and processes for desizing textiles sized with starch

Mixtures of various starch-degrading enzymes (amylases) which comprise at least one high temperature amylase (HTA) and at least one low temperature amylase (LTA) in an activity ratio of HTA to LTA of 10%:90% to 90%:10% develop at least 60% of their maximum activity in the temperature range from 30.degree. to 90.degree. C. Such mixtures can be diluted with water and treated with customary additives. These mixtures are suitable for desizing textiles sized with starch by treatment of the textiles with the mixtures mentioned and subsequent rinsing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to mixtures of various starch-degrading enzymes 
(amylases) which comprise at least one high temperature amylase and at 
least one low temperature amylase. The invention furthermore relates to a 
process for desizing textiles sized with starch, in which these textiles 
are treated with the enzyme mixtures mentioned. 
Before production of woven fabric, textiles are charged with sizes. The 
sizes improve, or render possible for the first time, mechanical 
processing of the yarns in the weaving mill at high machine speeds. In the 
course of weaving, the warp of the woven fabric is exposed to considerably 
higher mechanical stresses than the weft. To avoid yarn breakages, the 
yarn must therefore be sized before the weaving process. Various materials 
can be employed as sizes, such as, for example, gelatin, linseed oil, 
carob bean gum and, increasingly in recent years, also synthetic 
materials, such as polyvinyl alcohols, polyacrylates and water-soluble 
cellulose derivatives, such as carboxymethyl cellulose. Although above all 
the synthetically prepared sizing agents mentioned last have technological 
advantages, even today starch is still one of the most important sizes for 
ecological reasons. In Europe, potato starch is employed above all, while 
overseas large amounts of maize starch and rice starch are used. 
2. Description of the Related Art 
Because of the different mechanical stresses, the sized warp and the sized 
weft of woven fabrics have different properties, which manifest themselves 
adversely, for example, in the bleaching process, during dyeing and in 
further treatment. For this reason, desizing of the woven fabric is 
absolutely essential before any further processing. While readily 
water-soluble sizes can already be removed by hot washing, starch 
withstands this simple process. The starch must be converted into a 
water-soluble form so that it can be washed out. In the relatively early 
years of use of starch, the desired effect of desizing was achieved by 
treatment with dilute sulfuric acid. However, this treatment very severely 
damaged the woven fabric. For this reason, enzymatic desizing, which is 
gentle on the fiber, rapidly found acceptance on the market. 
Various starch-degrading enzymes (amylases) which are active either at 
temperatures of 30.degree. to 70.degree. C. (low temperature amylases) or 
at temperatures of 70.degree. to 110.degree. C. (high temperature 
amylases) are currently available for enzymatic desizing. They can be 
obtained from bacteria, fungi, plants or animals. The low temperature 
amylases are often starch-degrading enzymes which originate from Bacillus 
subtilis or Bacillus amyloliquefaciens. Corresponding enzymes from 
Aspergillus oryzae can also be employed. The high temperature amylases 
often originate from the bacterium Bacillus licheniformis. Either high or 
low temperature amylases must therefore by chosen for the process, 
depending on the temperature at which the desizing is carried out. There 
are as yet no products which comprise starch-degrading enzymes and 
universally have activity in all the customary temperature ranges. 
DE-A 29 09 396 describes a desizing agent and a process for its 
preparation. The auxiliary comprises an intimate mixture of a 
starch-degrading enzyme with a surfactant in water. With the mixture 
described, the otherwise customary addition of a surfactant during 
desizing can be omitted. However, the desizing agent cannot be employed 
successfully over the entire temperature range, but requires a use 
temperature from 90.degree. C. up to boiling point. JP 06/235 163 (1987; 
cited according to C.A. 121 (1994), 282294q) and JP 02/80 673 (1990; cited 
according to C.A. 113 (1990), 61270 m) describe enzymatic desizing with 
amylases at 100.degree. to 115.degree. C. or 50.degree. C. Because of 
their very good heat stability, the amylases described in WO 94/19454 are 
suitable for desizing at high temperatures. DE-A 28 36 516 describes a 
process for cold desizing of textiles with .alpha.-amylases. WO 91/19794 
describes an improved enzymatic desizing with .alpha.-amylases with 
addition of nonionic surfactants. A simultaneous hydrogen peroxide 
bleaching and enzymatic desizing is described by the Applications EP-A 55 
664, EP-A 119 920 and U.S. Pat. No. 4,643,736 (sodium hypochlorite 
bleaching) and DE-A 27 35 816 (H.sub.2 O.sub.2). U.S. Pat. No. 4,371,372 
describes a combined dyeing and enzymatic desizing process at temperatures 
below 30.degree. C. 
It is now everyday practice in textile processing companies for lightweight 
textile goods which can be desized in the cold to be alternated with heavy 
goods, for which cold desizing is inadequate. Furthermore, the order 
situation brings, in irregular sequence, both small order batches, for 
which cold desizing again is preferred, and large order batches, for which 
continuous treatment under high temperature conditions is more economical. 
There is therefore a need for enzymatic desizing agents which can be used 
universally both in the high and in the low temperature technique of 
desizing and are more economical to store. 
It has now been found that this requirement can be met by using the enzyme 
mixtures according to the invention described below. Surprisingly, it has 
additionally be found here that the enzymes of the mixture, which are 
supposedly unsuitable for work in both temperature ranges, in no way cause 
trouble, which would nevertheless have been expected because of their 
inertia in the supposedly "incorrect" temperature range and due to 
possible decomposition or degradation products in this "incorrect" 
temperature range. Rather, it has been found that, in practice, the 
presence of the enzymes suitable for two different temperature ranges has 
an unexpected synergism, which manifests itself in the fact that the 
mixture according to the invention needs to be employed in a smaller 
amount than a comparable special enzyme in order to achieve the desired 
effect. This represents an economic advantage which goes far beyond merely 
holding one instead of two desizing agents in stock. 
SUMMARY OF THE INVENTION 
The invention relates to mixtures of various starch-degrading enzymes 
(amylases) which comprise at least one high temperature amylase (HTA) and 
at least one low temperature amylase (LTA) in an activity ratio of HTA to 
LTA of 10%:90% to 90%:10%. It has more than 60% of its maximum activity in 
the temperature range from 30.degree. to 90.degree. C., and can 
furthermore be diluted with water and treated with customary additives. 
DETAILED DESCRIPTION OF THE INVENTION 
The ratio in which the HTA and LTA are mixed depends on their activity at 
the optimum temperature and pH. This is determined by the method of H. U. 
Bergmeyer (H. U. Bergmeyer, Methods for Enzymatic Analysis, 3rd Edition, 
Volume 2, pages 151-152, Verlag Chemie GmbH, Weinheim). Amylases hair:ng a 
maximum activity in the temperature range from 30.degree. to 70.degree. C. 
are called LTA.; amylases having a maximum activity in the temperature 
range from 70.degree. to 110.degree. C. are called HTA. The maximum 
activity of the individual LTA and HTA on the market are in each case in a 
very much narrower temperature range specific to the individual amylases. 
The mixtures according to the invention comprise activity contents of 10% 
of HTA and 90% of LTA up to 90% of HTA and 10% of LTA. The activity ratios 
are preferably HTA:LTA=20%:80% to 80%:20%, particularly preferably 30%:70% 
to 70%:30%, especially preferably 40%: 60% to 60%:40%. Such mixtures 
develop 60% of their maximum activity in the range from 30.degree. to 
90.degree. C. and accordingly mutually fill the activity gaps between the 
activity maxima of the HTA and the LTA. It is possible to employ smaller 
amounts of HTA/LTA mixture than would be necessary with a conventional 
amylase (cf. Examples). It is furthermore possible to employ less active 
and therefore cheaper amylases for the mixtures according to the 
invention. Even more, it is possible to keep in stock only one enzyme 
mixture according to the invention for a wide temperature range, instead 
of many enzymes, each of which are sufficiently active only in a specific 
and narrow temperature range. 
Like other enzymes, the mixtures according to the invention can be diluted 
with water and treated with the customary additives. 
The mixtures according to the invention furthermore preferably have at 
least 80% of the maximum activity in the temperature range from 45.degree. 
to 75.degree. C. 
The invention furthermore relates to a process for desizing of textiles 
sized with starch by treatment of the textiles with starch-degrading 
enzymes (amylases) and subsequent rinsing, which comprises carrying out 
the treatment at 30.degree. to 98.degree. C. with a mixture of the type 
described above. 
The desizing can be carried out either discontinuously (for example Jigger, 
cold pad-batch) and continuously (for example steamer). 
The mixtures according to the invention can be prepared by simple mixing of 
the commercially available enzymes at room temperature. The mixtures can 
be diluted as desired both with demineralized and with normal tap water. 
The mixtures can furthermore comprise the customary standardizing agents 
and preservatives, for example alcohols, glycols or glycol ethers, such as 
1-methoxy-2-propanol, isopropanol, butyldiglycol, sodium benzoate, calcium 
salts and isothiazolones, for example 
5-chloro-2-methyl-3-(2H)-isothiazolone or 2-methyl-3-(2H)-isothiazolone. 
Possible textiles to be desized according to the invention are, for 
example, those of cotton and cotton blend fabrics; cotton blend fabrics 
are, for example, those of cotton with polyester, polyamide, 
polyacrylonitrile or other cellulosic fibers, such as regenerated 
cellulose. 
The activity of the mixtures according to the invention can be determined, 
for example, with soluble starch as the substrate at various temperatures 
in the above-mentioned range. The data of the following Table 1 were 
compiled with a desizing agent (mixture) according to the invention of an 
LTA from Bacillus amyloliquefaciens and an HTA from Bacillus 
licheniformis. The data obtained with the mixture are compared with those 
of another HTA (Aquazym 250 L, NOVO Nordisk), which is conventional and is 
already employed as an individual enzyme for desizing. It is not identical 
to the HTA contained in the mixture according to the invention. 
The exact ratio in which the enzymes from the range of the HTA and that of 
the LTA are mixed depends on their optimum temperature and pH in an 
individual case; this can be determined by simple preliminary experiments. 
The activities can be determined, for example, by the method of H. U. 
Bergmeyer (loc. cit.). 
To determine these activities, 200 .mu.l of a 0.5% strength by weight 
starch solution (analytically pure; in 50 mmol potassium phosphate buffer 
at pH 7.3) were incubated with 50 .mu.l of enzyme solutions of different 
dilution at 25.degree. C., 60.degree. C., 70.degree. C. and 90.degree. C. 
for 3, 10 and 30 minutes. At the end of the incubation period, 250 .mu.l 
of a color reagent which had the following composition: 
1.0 g of 3,5-dinitro-salicylic acid 
20 ml of 2 mol NaOH 
30 g of K Na tartrate.multidot.4H.sub.2 O 
remainder to 100 ml H.sub.2 O 
were added. The batch was incubated at 100.degree. C. for 5 minutes and 2.5 
ml of distilled water were then added. The extinction was determined at 
546 nm against a nonincubated value. The activity was calculated as 
micromoles of reducing ends formed by enzymatic cleavage (calibrated with 
maltose) per minute. As far as possible, exclusively batches in which the 
increase in reducing ends was linear over the period of time in question 
were used for the calculation. The activities of the mixture described and 
of a conventional commercially available high temperature amylase were 
determined. The results are summarized in Table 1. 
TABLE 1 
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Starch-degrading activities of a mixture according to the invention 
and another conventional HTA (Aquazym 250 L, NOVO Nordisk) 
at different temperatures by comparison (U = units) 
Product Temperature (.degree.C.) 
Activity (U/ml) 
______________________________________ 
HTA 25 992 
Mixture 25 4882 
HTA 60 12174 
Mixture 60 13876 
HTA 70 17524 
Mixture 70 13540 
HTA 90 10480 
Mixture 90 8151 
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The above table compares the activities of the mixture according to the 
invention with those of a conventional HTA at various temperatures. The 
conventional HTA is not the HTA which is a constituent of the mixture. 
Rather, it is an HTA which is available specifically for desizing at 
elevated temperatures. The activities were determined by the method of 
Bergmeyer (loc. cit.). 
Both the mixture and the conventional HTA have about the same activity at 
60.degree. C. At 70.degree. C., the conventional HTA is even more active 
than the mixture, and the same applies at 90.degree. C. 
In an experiment related to use, it has now been found, surprisingly, that 
the mixture according to the invention is considerably more suitable for 
desizing than the conventional HTA. In contrast to the results in Table 1, 
the mixture is thus snore active than the conventional HTA, although the 
desizing was carried out at high temperatures (90.degree. C.). 
Thus, only 40% of the amount necessary when the conventional HTA was 
employed was required of the enzyme mixture according to the invention for 
complete desizing. The mixture thus works far more effectively in practice 
than a conventional HTA (Examples 6 and 7). In practice, this means that 
for successful desizing, less of the mixture than of a conventional HTA 
has to be employed. The higher efficiency of the mixture according to the 
invention furthermore approximately halves the costs for the desizing 
agent.

EXAMPLES 
Example 1 
100% by volume of cotton gabardine with a fabric weight of 270 g/m.sup.2 
and a size deposit of 6%, comprising 90% of starch and 10% of 
polyacrylate, was treated with a mixture comprising 40% by volume of an 
HTA, 10% by volume of an LTA and 50% by volume of water. Desizing was 
carried out by the cold batch process with 1 ml/l of the mixture according 
to the invention with the addition of 2 ml/l of nonionic wetting auxiliary 
(90 parts of fatty alcohol polyglycol ether, 10 parts of water). The 
impregnating temperature was 20.degree. C. and the liquor pick-up 90%. 
After a batching time of 6 hours, the fabric was rinsed in 3 passes, 
1.times.90.degree. C. alkaline, 1.times.90.degree. C. neutral and once at 
30.degree. C. neutral. Evaluation was carried out in accordance with the 
TEGEWA violet scale: rating 7 to 8 (9=completely desized, 1=not desized). 
Example 2 
In comparison with Example 1, desizing was carried out by the hot batch 
process, under otherwise identical conditions. The impregnating 
temperature was 70.degree. C. at a batching time of 2 hours and a liquor 
pick-up of 90%. Rinsing process as Example 1. The fabric was evaluated in 
accordance with the TEGEWA violet scale: rating 8. 
Example 3 
A 100% cotton woven fabric with a fabric weight of 150 g/m.sup.2 and a size 
deposit of 9%, comprising 82% of starch, 13% of polyvinyl alcohol and 5% 
of pilling wax was treated with the mixture from Example 1 according to 
the invention. Desizing was carried out with 2 ml of the mixture according 
to the invention by the hot batch process with the addition of 2 ml/l of 
nonionic wetting agent (90 parts of fatty alcohol polyglycol ether, 10 
parts of water). The goods were impregnated at 60.degree. C. and squeezed 
off to a liquor pick-up of 90%, and were then batched up and, after a 
batching time of 3 hours, further processed analogously to Example 1. The 
evaluation was carried out in accordance with the TEGEWA violet scale: 
rating 9. 
Example 4 
A 100% cotton woven fabric with a fabric weight of 150 g/m.sup.2 and a size 
deposit of 9%, comprising 82% of starch, 13% of polyvinyl alcohol and 5% 
of pilling wax were treated with the mixture from Example 1 according to 
the invention. Desizing was carried out with 2 ml/l of the mixture from 
Example 1 according to the invention by the hot batch process with the 
addition of 3 ml/l of nonionic wetting agent (90 parts of fatty alcohol 
polyglycol ether, 10 parts of water). The impregnating temperature was 
60.degree. C. at a liquor pick-up of 90% and a subsequent batching time of 
12 hours. The material was washed with water at 90.degree. C., 60.degree. 
C. and finally at 30.degree. C. Degree of desizing according to the TEGEWA 
violet scale: rating: 9. 
Example 5 
In a comparison experiment, the desizing mentioned under Example 4 was 
carried out with a customary HTA with the same activity with the addition 
of 3 ml/l of nonionic wetting agent. The degree of desizing was 
significantly lower (according to the TEGEWA violet scale: rating: 5). 
Example 6 
0.8 ml/l of the mixture from Example 1 according to the invention was used 
on a continuously operating pretreatment unit with an impregnating, 
steaming and washing compartment. The fabric was impregnated at 70.degree. 
C., and immediately thereafter steamed in a steamer at 98.degree. C. for 
40 seconds. The fabric was then subjected to hot washing out with the 
addition of 3 g/l of sodium carbonate, and rinsed in the cold. Degree of 
desizing according to the TEGEWA violet scale: rating: 9. 
Example 7 
A comparison experiment to Example 6 with 0.8 ml/l of a customary HTA 
(Aquazym 250 L (Novo Nordisk), which was not a constituent of the mixture 
according to the invention but had a similar activity, gave the following 
surprising result: in order to achieve desizing with the rating 9 
according to the violet scale, 2.5 times the amount (2 ml/l) of the 
customary HTA had to be employed, compared with 0.8 ml/l according to 
Example 6. This resulted in a significant cost advantage when the mixture 
according to the invention was employed. 
TABLE 2 
______________________________________ 
Activity comparison (U = units) 
Degree of 
desizing 
Activity according 
Amount (U)/amount 
to the 
employed Activity (U)/ml 
employed TEGEWA 
Enzyme (ml/l) 70.degree. C. 
90.degree. C. 
70.degree. C. 
90.degree. C. 
scale 
______________________________________ 
Mixture 
0.8 13 540 8 151 
10 832 
6 521 
9 
Customary 
2.0 17 524 10 480 
35 048 
20 960 
9 
HTA 
______________________________________ 
The table illustrates that, in spite of a lower enzyme activity, when 
determined by measurement, the mixture according to the invention gives a 
desizing result during use which is comparable to the customary HTA. 
Example 8 
400 kg of 100% cotton woven fabric with a fabric weight of 150 g/m.sup.2 
and a size deposit of 6.7%, comprising 100% of modified starch, were 
desized on a jigger with 1 ml/l of the mixture from Example 1 according to 
the invention. The liquor ratio was 1:6; after 2 passes at 90.degree. C., 
the fabric was rinsed hot in 3 passes and in the cold in 2 passes. Degree 
of desizing according to the TEGEWA violet scale: rating: 8. 
Example 9 
The comparison experiment to Example 8 was carried out with 1 ml/l of a 
customary high temperature amylase; the fabric thus treated showed a 
degree of desizing with the rating 6 according to the TEGEWA violet scale.