EP0705357B1 - Use of carboxymethylated guargalactomannan as a sizing agent - Google Patents

Abstract

The invention concerns the use of alkali-metal salts of carboxymethylguargalactomannan with a degree of substitution of less than 0.15 as sizing agents, plus a method of sizing natural and/or synthetic yarn using these compounds.

Description

The present invention relates to the use of alkali metal salts of carboxymethylguargalactomannans with degrees of substitution below 0.15 as sizing agents, and to a process for sizing natural and / or synthetic yarns using these compounds.

It is known that sizing agents are used in the weaving process in order to give the warp thread sufficient strength and, on the other hand, to stick protruding fibers to the yarn body or, in the case of filament yarns, to bond the individual filaments to one another. This increases the strength of the warp thread during weaving. Well-known sizing agents are native or modified starches, carboxymethylcelulloses, polyvinyl alcohols and polyacrylates. Usually, the sizing agents have to be removed from the fabric again after the weaving process, since they would otherwise interfere with the subsequent finishing processes. One way of removing the sizing agents is to simply wash them out with water, which presupposes that the sizing agents can be washed out with water. Such water-washable sizing agents are, in particular, carboxymethyl-substituted starches, carboxymethyl celluloses, polyvinyl alcohols and polyacrylates. Except for the carboxymethyl-substituted starches, the other sizing agents show only poor biodegradability. The carboxymethylated starches are readily biodegradable, but leave something to be desired in their sizing effect, which is why they have to be used in large quantities, which in part has the advantage of good biodegradability is compensated again.

The poor biodegradability of the other sizing agents is particularly disadvantageous because sizing agents make up the main part of the wastewater pollution caused by the textile industry. It is assumed that the sizing agents cause up to 80% of the textile wastewater pollution. There has been no shortage of attempts to provide sizing agents with high efficiency and good water washability, which have improved biodegradability.

In Melliand Textile Reports 8/1983, 526-529, for example, different galactomannans, including guar galactomannans, are described as sizing agents. This article mentions the advantages and disadvantages of galactomann size, as well as its good biodegradability. Examples of galactomannic sizing are those of guar galactomannan, tamarind kernel flour and locust bean gum (carubin). Now, however, the present article claims that guar galactomans are not a viable alternative to the sizes used to date due to poor adhesive strength. On the other hand, the carboxymethyl derivatives of guargalactomannans are not mentioned in the article.

It was therefore an object of the present invention to provide biodegradable sizing agents which are water-washable and which, at least in their sizing effect, are comparable or even better than the sizing agents used to date, such as carboxymethyl cellulose.

Surprisingly, it was found that the object can be achieved if alkali metal salts of carboxymethylguargalactomannan with degrees of substitution below 0.15 are used as sizing agents.

Our own investigations have shown that special guar galactomannan derivatives, namely the alkali metal salts of carboxymethylated guar galactomannan, have good tack and good biodegradability if they have a low degree of substitution.

An object of the present invention is therefore the use of alkali salts of carboxymethylguargalactomannans with degrees of substitution below 0.15 as sizing agents for sizing natural and / or synthetic yarns.

For the purposes of the invention, the terms carboxymethylated guar galactomannan and carboxymethyl guar galactomannan are used synonymously.

Guar galactomannan products are made from Guarsaat's endosperm. Native guar products consist of galactomannans with small amounts of protein, fiber and fat as well as very small amounts of alkali and alkaline earth metals, iron and some trace elements. The chemical structure of the galactomannans in guargalactomannan is described as a linear mannose chain, where the mannose units are fused together by (1 → 4) - β - glycosidic bonds, and every second mannose unit carries a galactose unit by substitution of the hydrogen of the primary hydroxyl group. The galactose molecule is connected to the mannan main chain by a (1 → 6) - α - glycosidic bond. The two sugar units have hydroxyl groups in the cis position, in contrast to glucose, the monomer of cellulose and the starch, which all hydroxyl groups have in the trans position. The cis-hydroxyl groups and the elongated rigid structure of the galactomannan are the reason for many unique properties of guargalactomannan and its derivatives. Guargalactomannan can be modified like other polysaccharides. One type of modification is carboxymethylation, which produces anionic guar galactomannan derivatives. The carboxymethylation can be analogous to the American one Patents US-A-2 520 161 and US-A-2 477 544 are carried out by reacting the guar galactomannan with a cold aqueous solution of alkali hydroxides and then treating the alkali derivatives of guar galactomannan with a halogenated fatty acid or its salt. You can also carboxmethylate with other carboxylic acids or their salts such as with glycolic acid or with sodium glycolate. Depending on the amount of reactants used and reaction times and conditions, different degrees of substitution of guar galactomannan are obtained. A maximum degree of substitution of 3 is possible. For the purposes of the invention, preference is given to those alkali metal salts of carboxylmethyl guar which have degrees of substitution from 0.05 to 0.15.

According to German patent DE-C-37 09 698, carboxymethylated guar galactomannan with degrees of substitution of 0.22 was used as a sizing agent in a mixture of hydroxyalkyl guar galactomannan and hydroxyalkyl casagalactomannan. According to the present application, however, alkali metal salts of carboxymethylated guargalactomannan with low degrees of substitution are to be used, since our own experiments have shown that their adhesive strength is significantly better and that their biodegradability is superior.

Guar galactomannan products have molecular weights ranging from 0.5 to 11 · 10 ⁶ . If a modification such as carboxymethylation takes place, the guar galactomannan products are generally depolymerized at the same time. Since the molecular weight determination of such polymers can cause difficulties in practice, a move has been made to indicate the viscosity associated with this instead of the molecular weight. According to one embodiment of the present invention, alkali metal salts of oxidatively degraded carboxymethylguargalactomannan are used which, as a 4% strength by weight aqueous solution, have a Höppler viscosity at 20 ° C. between 10 and 3000 mPas, preferably between 20 and 500 mPas.

Due to the method of preparation according to the two American patents already cited, the alkali metal salts of carboxymethylguargalactomannans can contain alkali metal halides as impurities. For the purposes of the invention, preference is therefore given to using alkali metal salts of carboxymethylguargalactomannans which have alkali halide impurities of less than 10% by weight, preferably less than 5% by weight. The impurities in alkali halides can be reduced in a manner known per se, for example by washing out with a methanol / water mixture. Another impurity that can occur according to the above production processes are the salts of the glycolic acids, which can also be removed, for example, by washing with a methanol / water mixture.

Of the alkali metal salts of carboxymethylguargalactomannans, the corresponding sodium salt is particularly preferred.

For the purposes of the invention, the alkali metal salts of carboxymethylated guargalactomannan can be used alone or in any mixture with conventional sizing agents, preferably with the starch derivatives, polyvinyl alcohols and polyacrylates. The mixing ratios are selected depending on the desired size properties and are in the amounts customary for the person skilled in the art.

The alkali salts of carboxymethyl guar galactomannan can be used on all weaving machines as well as on all sizing machines such as marksmen, rapier and air jet looms. In the sense of the invention, the yarns can be both staple yarns and continuous yarns. The yarns can be of natural origin, for example made of cotton or regenerated cellulose, and / or synthetic origin such as cellulose acetate, Polyester, polyacrylonitrile and polyamide. Particularly good results are achieved for cotton and regenerated cellulose and their blends with polyester.

The size coating of alkali metal salts of carboxymethylguargalactomannan with degrees of substitution below 0.15, alone or in a mixture with the usual sizes, is in the range from 1 to 25% by weight, based on the dry weight of the yarn. The amount of alkali metal salts of carboxymethylated guar galactomannan is therefore in the range from about 1/3 to half of 100 parts of starch size and in the latter case in the range of the known synthetic sizes.

When using the alkali metal salts of carboxymethylguargalactomannans according to the invention, there is an excellent sizing effect. Furthermore, the alkali salts of carboxymethylguargalactomannans show an excellent biodegradability, which is even better at these low degrees of substitution than with only slightly more highly substituted guargalactomannans. In addition, alkali salts of carboxymethyl guar galactomannan dissolve quickly and free of lumps in the water, show no signs of skin formation, do not foam in the liquor and can be washed out with water.

Another object of the present invention is a method for sizing natural and / or synthetic yarns in a known manner with alkali salts of carboxymethylguargalactomannans, which is characterized in that alkali salts of carboxymethylguargalactomannans are used with degrees of substitution below 0.15. The application of the alkali salt of carboxymethylguargalactomannans takes place, as is customary for sizing agents, as an aqueous solution with product concentrations of 10 to 150 g / l in the usual sizing machines.

Examples A. Tested alkali salts of carboxymethyl guar galactomannan

Ex. Active content in% by weight Water content in% by weight NaCl content in% by weight Degree of substitution pH at 4% by weight Viscosity Höppler 4% by weight at 20 ° C A1 91.5 6.4 0.32 0.13 6.1 77 A2 80.7 3.2 4.33 0.1 6.4 40 See 1 76.8 2.0 8.61 0.33 5.6 21

The viscosity was determined according to Höppler in accordance with DIN 53015. The above sodium salts of carboxymethylguargalactomannan were tested, for example according to US-A-2 477 544 or US-A-2 520 161.

B. Determination of the sizing effect

A scrubbing tester was developed to determine the sizing effect and was developed by the TN0, Delft / NL fiber institute.

In this abrasion tester, 30 individual threads were clamped in such a way that they are subject to a combined load consisting of thread-thread and thread-metal friction. The deflection pins were mounted on a strip that was moved up and down by a motor. A trailer weight of 50 g ensured for tensile stress. After scrubbing until all threads broke, the number of scrubbing cycles being recorded for each thread break, the test was evaluated from a statistical point of view. The median value, which is characterized in that 50% of all values are above and 50% below this value, was taken as a measure of the size effect.

The warp yarns were sized on a laboratory sizing machine from Sucker, Mönchengladbach, with 40 threads being sized from the creel. Raw white cotton ring yarns with a fineness of Nm 50/1 were routinely used.

The following test conditions existed: Test conditions yarn Nm 50/1, CO ring attitude 30 threads / cm Dipping roller 144 daN Nip roller 0.5 bar (large pressure gauge) Temperature trough approx. 85 ° C Drying temperature approx. 130 ° C speed approx. 30 m / min

Table 1 summarizes the abrasion resistance found at various sizes (according to DIN 54285), expressed as the number of strokes up to the thread break (median value). Table 1: Abrasion resistance table g / l product Size content Number of strokes 30 A1) 3.0 120 50 A1) 5.0 336 90 A1) 9.8 983 30 A2) 3.4 81 50 A2) 5.0 205 80 A2) 8.9 596 30 See 1) 3.4 76 50 See 1) 4.9 142 90 See 1) 9.3 385 120 See 1) 13.4 607 30 See 2) 2.9 95 50 See 2) 4.8 187 90 See 2) 9.6 481

It can be seen from Table 1 that the sodium salt of carboxymethylated guargalactomannan with higher degrees of substitution (see FIG. 1) shows poorer sizing effects at the same or higher sizing contents than those with degrees of substitution below 0.15, since thread breakage occurs after a few strokes. Furthermore, Table 1 shows that the sodium salts of carboxymethylguargalactomannans (A1) and A2)) according to the invention in the Sizing effect is clearly superior to the previously used carboxymethyl cellulose derivative Horsil NV-P (registered trade name of Henkel KGaA (cf. 2)).

C. Biodegradability

A short-term Zahn-Wellens-Test (ZWT) was carried out to determine the biodegradability. Test matrix is hardened distilled water to which an amount of wet sludge corresponding to approx. 1 g / l dry matter was added. Incubation was carried out for 7 days at 19 to 25 ° C. with stirring and constant air supply. Regular DOC determinations were carried out. Table 2 summarizes the results for A1) and cf. 1). Table 2: Biodegradability Test substance Test concentration mg DOC / l % DOC decrease after days based on the 0-hour value 0.25 1 3rd 7 A1) 100 5 23 90 93 See 1) 100 4th 3rd 30th 70

From Table 2 it can be seen that the compounds used according to the invention can be broken down much better than the somewhat more highly substituted guar galactomannan derivatives.

Claims (9)

1. The use of alkali metal salts of carboxymethyl guar galactomannan with degrees of substitution below 0.15 as sizes for sizing natural and/or synthetic yarns.
2. The use claimed in claim 1, characterized in that alkali metal salts of carboxymethyl guar galactomannan with degrees of substitution of 0.05 to 0.15 are used.
3. The use claimed in claim 1 or 2, characterized in that alkali metal salts of oxidatively degraded carboxymethyl guar galactomannan with a Höppler viscosity in the form of a 4% by weight aqueous solution at 20°C in the range from 10 to 3,000 and preferably in the range from 20 to 500 mPa·s are used.
4. The use claimed in any of claims 1 to 3, characterized in that alkali metal salts of carboxymethyl guar galactomannan containing less than 10% by weight and preferably less than 5% by weight of alkali metal halide impurities are used.
5. The use claimed in any of claims 1 to 4, characterized in that the alkali metal salts of carboxymethyl guar galactomannan are used in admixture with conventional sizes, preferably starch derivatives, polyvinyl alcohols and polyacrylates.
6. The use claimed in any of claims 1 to 5, characterized in that the alkali metal salts of carboxymethyl guar galactomannan are applied as sizes in quantities of 1 to 25% by weight, based on the dry weight of the yarn.
7. The use claimed in any of claims 1 to 6, characterized in that the alkali metal salts of carboxymethyl guar galactomannan are used for sizing yarns of cotton, regenerated cellulose and blends thereof with polyester.
8. The use claimed in any of claims 1 to 7, characterized in that the sodium salts of carboxymethyl guar galactomannans are used.
9. A process for sizing natural and/or synthetic yarns in known manner with alkali metal salts of carboxymethyl guar galactomannan, characterized in that alkali metal salts of carboxymethyl guar galactomannan with degrees of substitution below 0.15 are used.