Patent Application
20170356128
The present invention relates to a method for pretreatment of cellulose containing textiles by applying an aqueous solution having a pH between about 1 and 7 and comprising at least one agent for durably changing the surface morphology of the cellulose.
Enzymatic processes have been widely used in the treatment of textile substrates. In recent years, cellulose-cleaving enzymes (cellulases) have gained great importance in the textile-chemical treatment of materials containing cellulose fibers. The technically most frequently used “total crude” cellulases are a mixture of microbiologically produced endo-, exocellulases and cellobiohydrolases. The main task of the cellulases is to hydrolytically degrade cellulose by selective cleavage of the β-1,4-glycosidic bond, so that soluble debris is removed from the polymers and taken up by the treatment solution, where further hydrolysis to glucose takes place. Usually, this is done to change the hand of materials, remove lint, and improve undesired tendency to pilling of materials. A special field of application is during washing of indigo-dyed denim textiles, where enzymatic treatment is used in place of or in addition to a bleaching treatment. Here, enzymes allow the so-called wash-down, which leads to the used look of jeans after the washing process of finished textiles.
Furthermore, treating cellulose-containing fibers with an alkaline solution is known in the state of the art, since the rate of degradation of cellulose by cellulases is higher after pretreatment of the cellulosic fibers in alkaline media than in the neutral pH range. Finally, it is known from U.S. Pat. No. 3,736,097A to add a swelling agent (e.g. strong acids or melts of relatively neutral salts) to reyon fibers to permit a closer, more intimate and more frequent contacting relationship between the individual fibers. If this is done before cellulase treatment it would reduce enzymatic degradation in the area that takes up the swelling agent since an open structure of cellulose is needed to enable cellulase activity (EP200583A1).
In all processes, the textiles are exposed to cellulase treatments in large scale washing machines, which treatments weaken the textile through hydrolytic attack and thus support, in combination with the washing mechanics, wear of any dyes present, which leads to the development of a wash-down. Cellulase treatments always lead to a loss of mechanical resistance of the textile, which leads to reduced strength and lower abrasion resistance of treated products compared to non-treated products. This reduction of the use-value is an undesired result of cellulase treatment.
Water as a reaction medium is supporting and increasing the enzymatic action due to little per se swelling ability and thus higher number of accessible sites for enzyme action (e.g., hydrolysis as described in U.S. Pat. No. 5,656,490). However, the positive effect in this case is based on pure swelling of the cellulosic backbone material and is not of durable nature (especially after drying, which eventually leads to hornification of the cellulose material and a dramatic decrease of accessible sites for further enzymatic action).
One solution of the problem is mentioned in EP2000583A1, where before the actual treatment of the cellulosic materials with cellulases, a targeted local activation of the fiber materials is conducted with preparations that contain concentrated alkaline-reactive substances. This may lead to better degradation performance of the cellulose-cleaving enzymes in the treated areas without, for example, any disadvantageous effects on the yarn areas responsible for strength that are located in the interior of the material.
However, the working method proposed in EP2000583A1 has several disadvantages resulting from the use of concentrated alkaline preparations:
Thus, it is an object of the present invention to provide a pretreatment method for a textile, wherein the textile shows only imperceptible loss of mechanical strength, and which overcomes the disadvantages mentioned with regard to EP2000583A1.
The object is solved by the subject matter of the present invention.
The present invention relates therefore to a pretreatment method characterized in that, before treatment with a cellulase-containing solution, an aqueous solution having a pH between 1 and 7 and comprising at least one agent modifying the structure of the cellulose, preferably a neutral salt, wherein the agent is applied to only some selected areas of the respective textile.
The present invention is not limited to be applied only as pre-processing before enzymatic treatment; the durable physicochemical surface activation of cellulosic fibers by neutral salts as herein described may also be applied e.g., before a dying process of cellulosic textiles in order to achieve higher dye absorption or can generally be used for higher uptake of any desired chemical at treated areas on a textile or fabric compared to respective non-treated regions.
The method is based on the finding that the efficacy of cellulase on a cellulose-containing textile is increased when the textile is pretreated in the area to be treated with an aqueous solution having a pH between 1 and 7 and containing an agent durably changing the cellulose surface morphology. This chemical agent is capable of at least locally penetrating the cellulose structure and thus effecting a change in the physicochemical nature of the cellulosic fibers.
The method is further based on following unexpected findings: the efficacy of cellulase enzymes acting on a cellulose-containing textile is locally increased when the textile is pretreated in a desired area with an aqueous solution having a pH between about 1 and 7 and comprising an agent durably changing its cellulose surface structure properties. Such an agent is capable of at least penetrating the cellulose structure at the surface and thus causing a change of the cellulose structure and morphology. By this, the respective agent leads to a significant change in the physical properties of the cellulosic base, e.g. fiber strength, flexibility, elasticity etc. Regarding the physicochemical state, interactions between the macromolecules and the surface morphology changing agent are more favorable than intermolecular forces between the macromolecules on the one hand and the agent molecules on the other hand. The at least partial penetration of the agent into the polymeric structure is thus energetically favored.
By using durable surface morphology changing agents the diphasic structure (cellulose in widened state and the liquid phase) is maintained. On the other hand, solvents, which are able to dissolve the polymer, lead to a homogeneous monophasic solution of the macromolecular matter as the stable final state.
According to DIN 60 000, textiles comprise textile fibers, textile semi-finished and finished articles, e.g. yarns or fabrics, and textile finished goods such as textile clothing etc. It is substantial for the invention that the textile contains cellulose (e.g. blended fabrics), however, the textile does not have to consist thereof.
Such a method may provide for pretreatment of the textile (e.g. the textile fiber) preferably at one side of the textile, more preferably at only certain areas, with a morphology changing agent in a way that the agent only slightly penetrates the textile or textile fiber. For this purpose it may be envisaged that before treatment with a cellulase-containing solution or dyeing liquor the said aqueous solution, preferably a neutral salt solution, is applied to the surface of the textile fiber or the textile in a way that it essentially remains at the surface of the textile.
This is especially achieved by applying the pretreatment solution, i.e. an aqueous solution with 1<pH<7 comprising an agent that durably changes the surface morphology by physical and minor chemical processes, by spraying and/or slop-padding and/or knife coating and/or printing.
One embodiment of the invention relates to the textile fiber or a sheet textile obtained from a textile fiber, e.g., a fabric, which is provided with patterns that have after enzymatic wash-down different colors (“stone-wash” effect), and may have a more pleasant or different hand. In case of dyeing application, the textiles have higher dye uptake due to the durably changed surface morphology of the cellulose fibers. Thus, not only the uptake of dyestuff is higher at respective treated areas, but also the uptake of other chemicals is comparably higher due to the durable physicochemical surface morphology change of the cellulose fibers. In some embodiments, the textile is a sheet textile, preferably a fabric, wherein individual given patterns may be applied to the textile, especially by printing a given pattern. In a further embodiment, the surface morphology changing agent is applied only on one side or on some selected areas of the sheet textile. Especially in case of functional textiles different treatments of the two sides of the sheet textile could easily be employed with respect to advantageous functional properties (water transport, absorption, smoothness etc.).
The invention is based on the unexpected finding that in selected areas, in which a non-alkaline agent, preferably a neutral salt—which is not a strong acid or a molten salt hydrate—has been applied, also a higher degradation rate during enzymatic treatment can be achieved because the cellulase enzymes do have a higher reaction rate in these areas due to changed morphology of the amorphous region of the respective cellulose, higher accessibility, etc. In case of dyeing processes an unexpectedly high increase of dye load was observed on pretreated areas (e.g., patterns) due to a durable change of the physical and chemical surface properties.
Neutral surface morphology changing agents may especially be substances selected from the classes of ionic liquids (e.g., 1-N-butyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium chloride, or homologous substances and corresponding acetate salts, but not limited to those), of organic compounds (e.g., N-methyl-morpholine-N-oxide, DMSO, N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF)), of inorganic salts (e.g., Mg(NO3)2, LiNO3, CaCl2, ZnCl2, LiCl, NaSCN, MgCl2), and mixtures such as LiCl/N,N-dimethylacetamide, NH4Cl/1,3-dimethylurea, NaCl/urea. Preferably concentrated solutions of ecologically safe substances such as CaCl2, NaCl/urea, which additionally may lead to ecological advantages and cost benefits besides their intrinsic safety, or any mixtures of above mentioned substances, are employed. Especially advantageous are mixtures that only slightly affect the function of e.g., enzymes, the aforementioned solutions of CaCl2 or NaCl/urea being especially advantageous, also with respect to safe handling during processing and environmental friendliness.
The interaction between fiber and enzymes or dyes or other post-treatment agents (e.g., chemicals) depends on the one hand on the type of cellulosic fiber (e.g., cotton, viscose fibers, lyocell fibers, etc.) as well as the concentration and activity of the post-treatment agents used. Depending on the respective processing step during finishing, the fiber changes with regard to its surface reactivity.
In order to select appropriate conditions for the corresponding textile fiber type to meet the above requirements, it may be favorable if the surface morphology changing agent comprises a thickening agent. Such a thickening agent may be selected from natural polymers (e.g. natural gums, different starches, pectins, agar-agar or gelatin, etc.) or artificial thickening agents (e.g. polyurethanes, modified cellulosics, sulfonates etc.). In order to support the progress of the desired reaction/treatment it may also be favorable if the pretreatment solution comprises a moisturizer, wherein it is especially preferable if the moisturizer comprises glycerol representing a natural and harmless substance with respect to environmental and safety impact. Often, the mentioned treatment conditions are of hygroscopic nature, in which case the addition of a supplemented moisturizer is usually not necessary.
The treatment of cellulosic substrates by solutions of various surface morphology changing agents has been studied extensively because of the possibility to change the reactivity of cellulose. For example alkaline treatment solutions for swelling of cellulosics known in the art may contain alkali ions (Li+, Na+, K+ ions), but also alkaline earth hydroxides and quaternary ammonium hydroxide are known from EP 2000583 A1. The treatment in different solvent systems (e.g., alcoholic solutions of swelling agents) has also been described in the state of the art. Swelling agents with strongly acidic reactivity, such as orthophosphoric acid or polyphosphoric acid, sulfuric acid or nitric acid have also been described specifically as swelling agents in U.S. Pat. No. 3,736,097 A. However, the described solutions according to EP 2000583 A1 and U.S. Pat. No. 3,736,097 A possess extreme pH levels, either extremely high (pH=14 in case of alkaline treatment) or extremely low (pH<1) in case of concentrated mineral acid treatment or concentrated molten salt hydrates. This is a huge problem so-far unsolved for the industry; safe handling is difficult and laborious, since the reagents are extremely corrosive and dangerous for the affected workers, which is especially true when applied by spraying the respective treatment solution onto the fabric or garment. Extremely low pH levels (pH<1) additionally influence the properties of cellulose on the basis of acid hydrolysis resulting in major degradation to glucose monomeric units, eventually leading to full degradation of the fibers. With respect to delicate man-made cellulosic fibers (such as viscose, lyocell, modal, etc.), mercerization is generally quite difficult; however, using the herein described technology, this is made possible. A neutral salt solution for achieving comparable effects by durably changing the surface morphology of the cellulose as described in the present invention with a pH between 1 and 7, more preferably between 2 and 7, is overcoming the so-far unsolved concerns. The change in cellulose surface morphology in case of man-made fibers can be seen after dyeing respective locally treated textiles (lyocell, viscose, modal), in which a higher dyestuff uptake in the activated regions is made possible (see
Notably, the agents used in the separate pre-treatment step permanently change the physical structure of cellulose. Therefore cellulases can work faster. Cellulases are enzymes with high molecular mass (approx. 40 kDa=40.000 g/mol). They need an open (amorphous) structure to penetrate and cleave cellulose. In the instant invention, water is used only as a solvent for the enzyme to help penetrate cellulose and is the prerequisite for cellulases to work in the subsequent step.
Furthermore, according to the method of the invention the agents are applied only on some areas of the fabric, e.g., on only one side, enabling selected localized effects of cellulase treatment (or dyestuff or more generally chemical uptake). Simply applying cellulases on the surface of denim would not lead to any visible effect, since cellulases require abrasion as a result of mechanical action to successfully hydrolyze cellulose. This is, for example, achieved by using cellulases in stone-washing but no selection of preferred areas of cellulase reaction is possible with this method.
Thus, the localized effect of cellulase according to the present invention is achieved by localized pretreatment with the solution containing certain agents which durably change the surface morphology of cellulose.
The invented process can be compared to developing a photographic image: When applying the chemical agent (e.g. by printing) an invisible negative is formed on the fabric material. During cellulase wash in the stone-wash process (with mechanical agitation), the picture is developed. With the present invention it is thus possible to provide fabric with image presentation. This is also true in case of dyeing processes for example. Specific patterns can be obtained during dyeing due to higher dyestuff (or more generally speaking: chemical-) uptake in the respective pretreated areas. Furthermore it is also possible to only activate certain areas of textiles fully treated with the aqueous salt solution by very accurate laser treatment using e.g. a CO2 laser. One example of locally laser-activated and subsequently dyed (blue direct dye) textile is shown in
Consequently, the present invention is based on the idea of activating cellulose fibers locally and thus limiting the morphology change of cellulose to treated areas of the textile. Later processing, e.g. by cellulase enzymes during stonewashing of denim or also dyeing, thus results in greater abrasion at the treated areas or higher dyestuff (or chemical) uptake, respectively.
This is achieved by limiting the effect of the activating treatment to treated areas of a material, which may be, for example, the surface of the textile structure, or for example only one surface side of a fabric. According to one embodiment of the invention, the amount of morphology changing agent is applied in a way that only the outermost structure of the cellulose fibers gets activated for the subsequent cellulase action, dyeing treatment or other application.
Application of the surface modifying agent solution may be carried out by means of common methods, e.g., by spraying, slop-padding, printing, knife coating, and minimum application techniques on one or both sides of the fabric. In one embodiment, printing techniques (screen printing, foam printing) are preferred. This technique allows a one-sided durable surface modification of the cellulose fibers as well as the implementation of a patterning effect.
The advantages of the present method over EP 2000583 A1 are especially apparent when looking at the application types, because due to the use of non-caustic conditions the safety-related restrictions are largely suspended. This is specifically true with respect to U.S. Pat. No. 3,736,097 A, when it comes to exactly opposite pH extremes or molten salts.
The surface morphology changing agents may be selected from the classes of ionic liquids, organic matters (N-methylmorpholine-N-oxide (NMMO), DMSO, DMAC, DMF), concentrated inorganic (neutral) salt solutions (Mg(NO3)2, LiNO3, CaCl2, ZnCl2, LiCl, NaSCN, MgCl2), and more complex mixtures, such as LiCl/N,N-dimethylacetamide, NH4Cl/1,3-dimethylurea, NaCl/urea, or from other cellulose modification agents or mixtures thereof.
Advantageous concentrations of application solutions are in the range of 0.02 M to saturated solutions, wherein the concentration is determined by the desired effect, the textile substrate to be treated, and an optional intermediate drying step. In the intermediate drying step, the non-volatile portion of the preparation is concentrated at the surface so that a higher concentration than in the original solution applied is achieved. Heating may thus additionally increase the surface activation effect and physicochemical reactivity of the treated area. Based on the invention, the optimum concentration range for a desired result can also readily be determined by the average skilled person of the art by means of serial experiments.
In an advantageous embodiment moisturizers such as glycerol are added to the solution before application in order to prevent complete drying and solidification or hornification/fiber agglomeration and chemically non-reactive material, which is especially true when applying an additional heating step.
Textile structures containing cellulose may, for example, be woven fabrics, knitted fabrics, fleeces, sheets etc., wherein the form of the material to be treated is not limited. Cellulosic substrates may preferably be made of cotton, bast fibers, viscose, modal fibers, lyocell fibers or mixtures thereof with other cellulosic fibers or other fiber materials, especially synthetic materials. In a preferred type, dyed textiles of cotton or other cellulose fibers or mixtures thereof with synthetic fibers (e.g. Lycra, polyester fibers, polyurethane fibers, polyamide) are treated, wherein in an especially preferred embodiment, indigo-dyed denim fabrics of cellulose fibers are treated. Non-colored fabrics may also be used and treated according to the inventive description before the actual dyeing, in which case a higher dyestuff uptake can be achieved through the durable change of surface morphology of the underlying cellulosic substrate. In an especially preferred embodiment the cellulose material is just treated locally at certain areas of one fabric side, yielding special effects and patterns on the textile surface after dyeing.
Appropriate enzymatic cellulase treatment methods or dyeing procedures can be selected from the methods proposed in the state of the art or are well-known to a person skilled in the art.
The application of said aqueous solution containing a durable surface modification agent for cellulosics for example leads to an accelerated hydrolysis of the respective cellulose fibers during enzymatic cellulase treatment. If the treatment is effected at the surface, it is mainly the surface that is hydrolytically attacked by cellulases and the strength and mechanical resistance of the material in the core of the textile structure is less affected. In an especially preferred treatment method denim fabric ring-dyed with indigo is activated, which has the advantage that the indigo dye is rapidly detached from the fabric surface. Thus, the time of washing processes of denim may be advantageously reduced, and when the activation follows predetermined patterns, special patterning effects and designs can be implemented and achieved. In another type of application a textile is treated with said aqueous solution before treatment with further chemicals resulting in higher chemical uptake of the cellulosic material due to the change of physicochemical properties of the cellulose fibers. This can inter alia be used for specialized textiles, garments, cellulosic goods in hygiene, medical care or household, in which a higher loading of chemicals with certain properties is desired.
The use of neutral activation conditions, which is highly advantageous over EP 2000583 A1 and U.S. Pat. No. 3,736,097 A and—even when present in e.g. an enzyme treatment bath later on—in many cases does not have disadvantageous impacts on the function of the enzymes, reduces the time required for washing out the respective chemicals (e.g. neutral salts) before an actual enzyme treatment, which saves process time, costs and water/waste water.
Suitably, it may be further envisioned that after application of the respective treatment solution and before enzymatic treatment with cellulases, a drying step is conducted, especially by heating the textile.
The preferred embodiment envisions that the textile (before enzymatic post-treatment) has already been dyed on at least some areas, preferably indigo-dyed, wherein with particular preference the textile comprises textile fibers woven into a fabric, preferably a denim fabric, or the preparation is applied to ready-made finished textiles before washing treatment.
Further details of the invention are described with reference to the following examples.
The Examples which follow are set forth to aid in the understanding of the invention but are not intended to, and should not be construed to limit the scope of the invention in any way.
Test Procedure with the Denim Example
Specimens (denim, 10×15 cm, approx. 7.5 g, 500 g/m2) are treated with the test solution. Application is effected at the surface, in this case by dabbing with a sponge. One pattern is treated with the soft side of the sponge (A), another one with the rough side of the sponge (B). The exposure time to the chemicals is 30 minutes.
Then, the specimen may be pressed through the squeezer of a Foulard (e.g. 5 bar), causing the chemicals to penetrate far into the interior of the fabric.
One specimen is immediately rinsed, a second part is dried at 60° C. for 5 min and then rinsed, each one for approx. 5 min under running water. No intermediate drying is conducted before the enzyme treatment.
The wet specimens are individually introduced into approx. 200 mL of treatment solution (liquor ratio 1:25, pH 4.6 Na-acetate buffer, 30 mL/L Primafast 100 (cellulase preparation, Genencor)) and treated therein for 60 min at 55° C. (heating gradient 2°/min) in a laboratory dying apparatus (Labomat). The bath is immediately removed, refilled with soft water, and the solution is alkalized in order to stop the enzyme activity. This treatment is done for 10 min at 75° C. (heating gradient 5°/min) in the laboratory dying apparatus. Then, the specimens are extensively washed in water and dried. The characterization of color changes was done by measuring the color coordinates as CIE-Lab values.
The effectiveness of the treatment of the activated areas was confirmed by comparative specimens: a non-activated comparative specimen was enzyme-treated, and specimens treated with activation solutions were treated without addition of cellulase, in order to detect a possible color change due to the activation chemicals used.
Table 1 compares the results of the untreated and the activated fabrics. The lighter color is easily recognizable through the increased degradation at the surface of the materials. The overall color difference LIE has also been calculated and is shown. LIE values above 10 clearly show the increased loss of color in the pretreated areas (in practice, LIE values below 1 are classified as non-determinable, non-visible differences, a person skilled in the art classifies such differences as undistinguishable color differences).
Further examples clearly demonstrating the positive and significant impact of treating cellulosic materials such as textiles, garments etc. are shown in the following. In this case the dyeing effect and dyestuff uptake is dramatically increased by the durable change of surface morphology of the cellulosic fibers using the herein described method.
Specimens (white, raw fabric made of cotton, 15×15 cm) are treated with a said aqueous test solution at app. pH 5 comprising LiCl (e.g. 0.1% to saturated solution, more preferably 0.1 to 20%, most preferably 1 to 5%), Mg(NO3)2 (e.g. 0.1 to 40%, more preferably 1 to 40%, most preferably 10 to 40%) and optionally a thickening agent or urea (0.1 to 30%) at the middle third of the sample for comparison with respective untreated areas. Application is carried out at the surface, in this case by brushing the respective aqueous neutral salt solutions. Generally it is possible to reduce the LiCl content by increased addition of Mg(NO3)2. The application of said solution on the fibers, yarns, fabrics or garments may also be performed by immersion, padding, spraying, brushing, printing, foaming, sponging.
The textile samples are then dried by at room temperature until dry or heating at 80° C. for 20 min, more preferably at 100° C. for 10 min, most preferably at 130° C. for 2 min for proper activation of the change in morphology of the cellulose surface. Activation in this case means permanent and durable change of the physicochemical properties of the respective treated cellulosic material triggered by sole application of the respective solution, further by additional drying, the application of heat (for example in a tumble dryer, on a stenter machine, stenter dryer, microwave irradiation, IR irradiation) or even laser-treatment (e.g. IR laser). Generally it is possible to adjust time and temperature; the lower the temperature is (e.g. 20 to 150° C.), the longer the activation/drying time is (e.g. 0.5 to 60 min). In case of laser application the activation time is dependent on the laser dwell time, laser power, laser intensity, frequency, mark speed, pixel density etc. and therefore only milliseconds up to seconds, in case of microwave irradiation the irradiation time is dependent on the power (50 to 1000 W) and time (1 to 60 sec).
Then, the textile samples are washed with water in order to remove the applied chemicals. One specimen is immediately subjected to the dyeing process (known to a person skilled in the art) in wet state; another specimen is dried at 100° C. for 10 min and stored before the actual dyeing process.
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| Number | Date | Country | Kind |
|---|---|---|---|
| 09009606.6 | Jul 2009 | EP | regional |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13386013 | Apr 2012 | US |
| Child | 15597296 | US |
