WO1999035325A1

WO1999035325A1 - A process for textile warp sizing using enzymatically modified starches

Info

Publication number: WO1999035325A1
Application number: PCT/DK1998/000564
Authority: WO
Inventors: Hanne Vang Hendriksen; Sven Pedersen; Henrik Bisgård-Frantzen
Original assignee: Novo Nordisk A/S
Priority date: 1997-12-30
Filing date: 1998-12-18
Publication date: 1999-07-15
Also published as: AU1663799A

Abstract

The present invention relates to the sizing of textile fibres. More specifically, the present invention relates to a process for textile warp sizing using enzymatically modified starches.

Description

A process for textile warp sizing using enzymatically modified starches

Background and Description of the invention

The present invention relates to the sizing of textile fibres. The purpose of sizing textile fibres is to increase their strength and protect the fibres, and in this way decrease the risk of damaging the textile fibres when they are subjected to mechanical treatment, such as weaving or knitting. If the yarn is abraded or broken during weaving the efficiency of the process is decreased. Sizing is thus, desirable for maintaining high processing speeds. Furthermore, sizing can prevent that fibers are loosened from the thread (fuzz formation) , which might subsequently lead to a nonuniform fabric if the fuzz is interwoven in the textile product.

In the sizing process a sizing agent is applied around the textile fibre protecting and reinforcing the yarn. For yarns of low quality the sizing agent must penetrate the fiber as well as making a film on the outside for maximum reinfocement . For yarns of high quality a film on the surface is sufficient.

Prior art sizing suspensions were often natural polymers and their derivatives, such as starch or modified starches. Those starches are not effective when used for sizing synthetic and blend fibres, one reason being their high viscosity and tendency to gel (Vigo, T.L., 11, Textile Science and Technology). With the advent of synthetic and blend fibres several synthetic polymers have also been employed as sizing agents, e.g. poly- vinyl alcohol.

The physical and chemical properties of the sizing suspension are highly important. The viscosity of the sizing suspension along with the fabric of the particular textile fibre in question determines how good the properties of the sized fibre will be. The sizing agent to be used must have appropriate hardness properties, good adhesion, tensile strength, abrasion resistance, flexibility, penetrativeness and film forming abilities. Furthermore, the sizing agent must subsequently be easily removed from the woven textile product. In order to be able to penetrate the fibroues surface of the yarn the sizing agent must have a relatively low viscosity. Depending upon the quality of the yarn it must be possible to vary and control the viscosity to ensure the penetrativeness of the sizing agent. For practical handling the sizing suspension must remain stable for numerous hours, often at elevated temperatures and contain from as little as 3% to over 20% solids.

One approach of lowering the viscosity of the starch suspension is to depolymerise the starch molecules. Conventional depolym- erisation methods for starch are oxidation or enzymatic conversion with α-amylase. A problem with the conventional depolym- erisation is that the starch, though becoming less viscous, becomes less film forming and looses binding strength, ultimately resulting in retrogradation. This is mainly a result of the presence of amylose molecules. Thus conventional enzymatically converted starches have limited application options.

Accordingly, it is an object of the present invention to provide sizing suspensions for textile fibres having improved properties, especially reduced viscosity and increased stability, film forming ability and binding strength, and being easily removed after treatment of the textile fibres, such as mechanical treatment.

It is of importance when sizing various synthetic fibres, and especially when sizing fibres of blends of different synthetic fibres or blends of synthetic fibres and natural fibres, that it is possible to adjust the starch suspension to a predefined solubility and viscosity in order to treat the fibres in an op- timal manner. Accordingly, it is a further object of the present invention to provide a sizing starch suspension which has been enzymatically modified to meet predefined requirements for solubility, stability and viscosity, hereby facilitating the practical han- dling of the sizing suspension and the sizing process.

Summary of the invention

The present invention relates to a process for sizing of tex- tile comprising the steps of a) treating a suspension of gelatinized starch with an enzyme selected from the group consisting of cyclodextrin glycosyl transferases, glycosyl trans- ferases and branching enzymes so as to reduce the viscosity of the suspension, and b) applying the treated starch suspension to the textile fibres.

In the following present context the term "starch suspension" means a suspension of gelatinized starch which has been enzymatically modified as in step a) of the above-mentioned proc- ess, and which comprising starch suitable for sizing textile fibres.

By the starch suspension according to the invention it is possible to fulfil the objects of the present invention.

Another aspect of the present invention is the use of a starch suspension as defined above for sizing of textile fibres.

Detailed description

Textile fibres

The starch suspension as described above is used as a sizing suspension. The starch suspension may be used for sizing any kind of textile fibres, such as the textile fibres selected from the groups of natural fibres or synthetic fibres or blends thereof. The natural fibres may be selected from cotton, wool, viscose, silk, and flax. The synthetic fibres may be selected from polyester, polyamide, and acrylic fibres. The textile fibers may be dyed or un-dyed.

Enzymatically modified starch

The starting starch material may be selected from the groups of native starch, such as corn starch, potato starch, wheat starch, waxy starch, high amylose-containing starch, tapioca starch or rice starch.

In another aspect the starting starch material is selected from the groups of modified starches (native starch derivatives) such as physically or enzymatically modified, or chemically modified such as starch esters, starch ethers, acid-modified starch, oxidized starch or cross-linked starch. Combined with the chemical modification a physical or enzymatic modification may also be carried out.

When the starting starch material is a starch ether it is preferably hydroxyethylated starch or cationic starch.

The most common and widespread starch ester for commercial use is starch acetate. The most industrially represented ether starch group is hydroxyalkyl starches, such as hydroxypropy- lated starch, hydroxyethylated starch, carboxymethyl starch and cationic starch.

The starting starch material is enzymatically modified "or con- verted by an enzyme selected from the groups of cyclodextrin glycosyl transferases (EC 2.4.1.19; CGT enzymes), glycosyl transferases and branching enzymes (EC 2.4.1.18).

In yet another aspect the starting material may be a oxidized starch or a dialdehyde starch or an acetylated starch. The above enzymes attack and modify the starch molecules whereby the viscosity of the suspension is reduced without decreasing to the same extent the high molecular character and polymeric nature of the starch. The present inventors have found that by the enzymatical modification of the starch according to this invention the starch suspension is given optimal functionalities for textile sizing, such as a low and stable viscosity, good solubility and good film forming ability, binding strength and abrasion resistance.

The starch suspension according to the present invention has a reduced viscosity compared to conventionally modified starch, preferably ranging from 100 mPa.s to 250 mPa.s, such as 120 mPa.s to 220 mPa.s.

The viscosity is very important for a good result of the sizing. Depending on the quality of the fibres to be sized the sizing suspension should form a film around the fibres protecting the fibre from tearing during mechanical treatment, however sometimes it is desired that the starch suspension also penetrate into the fibre to increase the strength of the fibre, the latter is especially the case, when the fibres are of low quality.

When applied to textile fibres, the starch suspension has an improved film-forming ability compared to conventionally enzymatically modified starches. The improved film-forming ability secures that the starch suspension is applied to the textile fibres in a homogenous layer.

Furthermore, the starch suspension according to the invention has an increased abrasion resistance compared to conventionally enzymatically modified starches. The increase in abrasion resistance decreases the risk of damage occuring to the textile fibres during mechanical treatment. Also of importance is that the starch suspension has an increased tensile strength compared to conventionally enzymatically modified starches. This improved property allows the mechanical treatment of the textile fibres to proceed in a more effective fashion whilst reducing the risk of damaging the fibres, especially of breaking the fibres.

The starting starch material must be gelatinised before the enzymatical modification of the starch may commence.

In one aspect of the present invention the starch is gelatinised by adding a liquid solution agent, such as water, before mixing with the enzyme in question.

In another aspect of the present invention starch starting material in a form of a suspension, wet cake or dry product is premixed with enzymes before adding the liquid suspension agent, e.g. water. Additionally, the starch starting material may be preferential a 20-40 % starch suspension.

The gelatinisation may be carried out batch-wise or continuously in a steam injection device (jet-cookers) .

The conversion process is dependent on temperature, concentra- tion of enzyme, pH and time, as well as the stability of the enzyme. In particular, the temperature may be in the range from 80-100°C, concentration of enzyme may be 10-200 μg enzyme protein/g, pH between 5-7, and the incubation time may be var- ied from 12-48 hours.

Subsequent to conversion of the starch starting material the enzymes may be inactivated prior to use of the starch suspension. Since the starch conversion is dependent on physical parameters, such as temperature as mentioned above, any suitable change of the conversion conditions (e.g. pH or temperature) may lead to the inactivation of the enzymes. After inactivation the starch suspension may be used immediately or stored for later use.

The sizing suspension may apart from starch further comprise additives, such as antifoam agents, waxes, antistatic agents or lubricants.

Sizing methods

The sizing of textile fibres may be conducted by mechanical methods. Conventional sizing is conducted in a slasher, in which the warp yarns are continuaously passed through a suspension of the sizing agent (sizing bath) . The wetted yarns are subsequently squeezed of excess liquid for instance between two rollers and then dried on heated cylinders. The sizing may also be conducted as high-pressure sizing, foam sizing or hot melting sizing, which all are energy saving compared to conventional methods. Furthermore, they also reduce effluents from the sizing process by reducing the amount of water evaporating from the sized textile fabrics. In high pressure sizing the starch suspension is applied to the textile fibres through the process of high pressure. Foam sizing encompasses starch suspension in the form of foam being applied to the textile fibres with the subsequent collapse of, and penetration of the foam into the fibres. Finally through the means of hot melting sizing the starch suspension is applied to the textile fibres at high temperatures, immediately followed by a cool down.

For optimal sizing conditions the sizing bath is preferably kept at a temperature between 30 and 90°C and contain from 3 to over 20% (w/w) solids of the sizing agent. This will preferably impart weight gains to the sized yarns after drying of 2 to 30% (w/w) .

Mechanical treatment of the fibres The process according to the invention may further comprise mechanical treatment of the sized textile fibres. The mechanical treatment may be weaving or machine knitting.

Desizing

As described in the introduction it is important that the sizing agent can easily be removed from the sized textile fibres. Water may be used for the removal of an aqueous starch suspen- sion from the textile fibres.

However, in a preferred embodiment of the invention the removal of the starch suspension is accomplished by enzymatical or oxi- dative desizing, preferably by enzymatical desizing. Preferred enzymes for desizing may be α-amylase enzymes, which attack the starch molecules at random, depoly erising the starch to a low molecular substance. The depolymerisation is followed by washing the textile fibres.

In another aspect the removal of the starch suspension from the textile fibres is carried out by oxidative desizing. The oxida- tive desizing solution may be selected from the groups of per- oxodisulphates or hydrogen peroxide.

EXAMPLES

Example 1.

Preparation and viscostability of glucanotransferase modified starch.

The glucanotransferase modified starch suspension is produced by incubating a 30% DS potato suspension of starch at 90°C, pH 6.0 adding 50 μg enzyme protein/g DS (glucanotransferase from Thermococcus litoralis) . After 24hs incubation the enzyme is inactivated by adding 1/40 volume 4M NaOH. After 20 in. stand- ing at room temperature pH is readjusted to around 6.0, and the product is analysed by GPC (Gel permeation Chromatography) . The molecular weight is reduced to approximately 500.000. Compared to native starch the modified product shows less gelling at equivalent DS (visual examination of the suspensions/gels) . The viscostability of the modified suspension is determined by measuring the viscosity for instance using a Brookfiled Vis- cometer at 20-30 rpm, 50°C directly upon preparation of the suspension (at 10-20% DS) and after several hours of storage in an oven (50°C) . For comparison native, acetylated, carboxy- methylated or oxidised starch (commercial available) is also used.

Example 2 To illustrate the effect of using enzymatically modified starch as a sizing agent the following experiment is made.

A suspension containing approximately 30% DS enzymatically modified starch is prepared according to example 1, and diluted to 10% DS. Additives in the form of waxes, antifoaming agents, antistatic agents and lubricants are additionally added to the starch suspension. Cotton yarns are then sized in a laboratory sizing machine using the above suspension as the sizing agent and at a temperature in the sizing bath of 60-90°C. The yarn is subsequently pressed to remove excess liquid and dried at 100- 140°C.

Absorption

For evaluation of the sized yarn it is conditioned at 20°C, 65% relative air humidity and weighed for determination of the absorption and compared to non-sized yarn. Alternatively, the absorption is determined based upon weighing after desizing of the experimentally sized yarn compared to control yarn, according to:

Absorption(%)= W(after desizing) - (before desizing) *C W(after desizing) *C

C= W(control yarn before desizing) . W: weight

W (control yarn after desizing)

5

Wear test

Sized yarn is tested in a wear test apparatus stretching the yarn until breakage. The yarn wears cyclically along itself and the number of strokes until breakage of each yarn is recorded. lθ This is done using minimum 50 samples and the interval in which 95% of the samples break calculated.

Washing out properties

Since the removal of the sizing agent after weaving is of out- 15 most importance, and this is also tested. A cotton band is sized as described above and then washed out with either

1. Soda (2 g/1) , 100°C,30 min.

2. Enzyme (α-amylase, f .eg. Termamyl commercial available, Novo Nordisk) , 60-80°C, 10 min, pH 6.0-7.0

20 3. Pure water, 100°C, 30 min.

After washing the band is pressed. To the wet band a 0.01 N iodine solution is applied drop wise and the stain compared to a standard colour scale (Tegewa) . Alternatively, a drop of water is placed on the desized textile and the time of absorption de-

25 tected. This comparison is made to show at which conditions the sizing agent is removed.

Weaving efficiency

The weaving efficiency of the sized yarn is finally tested in 30 practice using conventional sizing machines and weaves (the weaving efficiency is calculated as realised weaving time compared to theoretical weaving time) .

35

Claims

claims

1.A process for sizing of textile fibres comprising the steps 5 of

a) treating a suspension of gelatinized starch with an enzyme selected from the group consisting of cyclodextrin glycosyl transferases, glycosyl transferases and branching enzymes so as l╬╕ to reduce the viscosity of the suspension, and

b) applying the treated starch suspension to the textile fibres.

15 2. A process according to claim 1, wherein the textile fibres are selected from the groups of natural fibres or synthetic fibres or blends thereof.

3. A process according to any of the preceding claims, wherein 20 the starch is native starch, or modified starch.

4. A process according to any of the preceding claims, wherein the starch is corn starch or potato starch or wheat starch or waxy starch or tapioca starch or rice starch or high amylose-

25 containing starch.

5. A process according to any of the preceding claims, wherein the starch is a starch ester, or starch ether, or cross-linked starch, or oxidised starch or acid-modified starch.

30

6. A process according to any of the preceding claims, wherein the starch is a starch ether, such as hydroxyethylated starch or cationic starch.

35 7. A process according to claims 1-5, wherein the starch is acetylated starch.

8. A process according to claims 1-5 , wherein the starch is oxidized starch.

9. A process according to any of the preceding claims, wherein 5 the additives are antifoam agents, waxes, antistatic agents or lubricants.

10. A process according to claim 1-9, wherein the sizing of textile fibres is conducted through the mechanical methods of 0 high pressure sizing, or foam sizing, or hot melting sizing.

11. A process according to claim 1-10, wherein the treated starch suspension has a viscosity ranging from 100 mPa.s to 250 mPa.s, such as from 120 mPa.s to 220 mPa.s. 5

12. A process according to claim 1-11, further comprising mechanical treatment of the sized textile fibres.

13. A process according to claim 12 , wherein the mechanical 20 treatment is weaving or knitting.

14. A process according to claim 12 or 13 , f rther comprising removal of the treated starch suspension from fibres.

25 15. A process according to claim 14, wherein the removal is