Method for decolorizing a textile

Abstract

This invention relates to a method for decolorizing textiles. The invention relates to a method for decolorizing textiles, characterized in that the method comprises the following steps: (a) pretreatment by applying a promoting substance comprising a quaternary ammonium salt to at least a portion of the textile; and (c) ozonation by introducing and holding the textile in an ozonating fluid.

Description

Technical Field

[0001] This invention relates to the field of treatment for decolorizing textiles, particularly, but not limited to, garments made of denim or jeans fabrics.

[0002] More specifically, the present invention relates to a method for bleaching or decolorizing colored fabrics to give such fabrics a wear and aging appearance similar to that acquired after years of use.

[0003] In particular, the object of the present invention is a method for decolorizing textiles due to the synergistic effect of quaternary ammonium cations and ozone. Background Technology

[0004] As is well known, various chemical products and treatments are used in industry and at home to age textiles in order to give certain garments greater appeal and aesthetic value.

[0005] The aging effect is caused by the discoloration of the fabric, which, depending on the circumstances, may be spread across the entire surface of the garment or may be limited to a specific area of ​​the garment itself.

[0006] It should be noted that although denim or denim fabrics are mentioned below, i.e. fabrics made of cotton, the method of the present invention can be applied to any textile.

[0007] It should also be noted that, in this article, the term textiles generally refers to fabrics or garments.

[0008] In the patent text, the terms bleaching and decolorization are used interchangeably, referring to treatment methods that typically alter the color of textiles by making them lighter and more white.

[0009] In the textile industry, methods for localized decolorization of denim or similar fabrics used in jeans have been known for a long time; these methods achieve particularly limited decolorization of specific areas of the product.

[0010] Currently, the most common bleaching method uses potassium permanganate solution, which is sprayed by an operator onto specific areas of the fabric to be treated, particularly the knee and thigh areas in the case of trousers. Potassium permanganate is a strong oxidizing agent that reacts with the fabric's color, causing it to whiten and highlighting worn and aged appearances.

[0011] However, this solution has the disadvantage of exposing operators to significant health and safety hazards when inhaling the aerosols formed during the spraying of potassium permanganate onto the fabric.

[0012] Meanwhile, diffusion bleaching treatment of denim or denim textiles is known to be used to achieve a substantially uniform aging effect across the entire surface of the product, i.e., without any noticeably uneven areas.

[0013] In the known solutions of this kind, the textiles to be treated are placed in an industrial washing machine, the washing liquid of which is supplemented with chemical compounds such as potassium permanganate, sodium hypochlorite, hydrogen peroxide, and laccase.

[0014] These solutions for diffusion decolorization of textiles require large amounts of chemical additives to achieve a sufficiently strong decolorization effect. The use of these substances has a high environmental impact, and the wash water must be purified to reduce contaminant levels. Other drawbacks of these methods are the consumption of large amounts of water in the various washing and rinsing stages.

[0015] To overcome the aforementioned problems, a method for bleaching textiles using ozone was developed several years ago. Ozone is generated on-site using specialized machinery and introduced into an airtight washing machine, into which the textiles to be treated are introduced; the treatment can be carried out by drying or in water.

[0016] In the case of denim and tannin fabrics, ozone treatment provides cleaning of the fabric from indigo redeposition and, in some cases, also provides gentle bleaching.

[0017] To enhance the bleaching effect of ozone, the fabric is wetted with water to promote the oxidation of ozone.

[0018] US patent application US20140068871 describes a method for decolorizing denim fabric by wetting it with water and then subjecting it to a second ozone bath. A similar solution is described in Japanese patent application JPH04100987A.

[0019] International patent application WO 2018065388A1 discloses a method for locally decolorizing denim fabric by soaking certain areas of the fabric in a hygroscopic substance, i.e., a substance that absorbs moisture, and then using ozone.

[0020] Of all the solutions mentioned above, using water to enhance the oxidizing effect of ozone has yielded unsatisfactory results. In particular, the bleaching effect is weak or moderate, and it is not possible to selectively bleach fabrics to achieve strong color contrasts, which are currently in high demand in the fashion industry.

[0021] The aforementioned US application US20140068871 also describes a method for locally decolorizing fabrics by treating them in an ozone bath after spraying water only on certain areas of the fabric. However, this solution also suffers from the same drawbacks as the other known solutions mentioned above: the decolorization achievable by using only water as an ozone promoter is not significant enough. Furthermore, this method does not meet the needs of the modern textile industry, which treats dozens or hundreds of garments simultaneously in an ozone generator, but these garments must be manually pre-treated by spraying water on limited areas of the fabric before this stage; only a small number of garments can be pre-treated at a time, resulting in many garments being completely dry by the end of this stage before ozone treatment, rendering the subsequent ozone treatment useless.

[0022] Other treatment methods, which are more expensive and complex than previous methods, have been developed for the localized decolorization of textiles using ozone, such as the treatment method described in EP0554648A1, in which differential bleaching is achieved by additional pretreatment, such as applying a substance that blocks the decolorizing effect of ozone to a portion of the fabric or dyeing the fabric with dyes that have different sensitivities to ozone.

[0023] None of the above-mentioned methods for bleaching textiles with ozone achieved aging effects comparable to those achievable with conventional treatments, which use potentially harmful or polluting chemicals. In the case of selective bleaching, none of the above methods achieved a significant color contrast between bleached and unbleached areas. Summary of the Invention

[0024] Therefore, the object of the present invention is to provide a method for bleaching colored textiles, particularly denim or nylon fabrics, by ozone treatment, which is effective and rapid and does not involve high water consumption.

[0025] Another important objective of this invention is to reduce the ozonation treatment time of textiles while providing a significant and effective bleaching effect.

[0026] Another object of the present invention is to provide a method for local decolorization of textiles that is safe for the health of the operator.

[0027] A key objective of this invention is to locally decolorize textiles by creating a strong color contrast between the treated area and the unbleached area.

[0028] Those skilled in the art will understand from reading this document that these and other objectives are achieved by a textile decolorization method involving an initial pretreatment step, wherein the fabric is wetted with a promoting substance comprising a quaternary ammonium salt, and then the pretreated textile is placed in an ozonating fluid.

[0029] Surprisingly, it has been observed that quaternary ammonium salts enhance the oxidizing effect of ozone, resulting in a significantly more pronounced bleaching effect when textiles pretreated with this accelerator are subjected to ozonation treatment compared to those treated with ozone alone.

[0030] Preferably, the quaternary ammonium salt constituting such an accelerator is cetrimonium chloride, also known as cetrimide, or cetrimide or CTAC.

[0031] Alternatively, the quaternary ammonium salt used is benzalkonium chloride, also known as alkyl dimethyl benzyl ammonium chloride.

[0032] Conveniently, these quaternary ammonium salts are mixed with other auxiliary components, such as surfactants (wetting agents, defoamers, degassing agents, etc.), buffers for pH changes, and any other substances that promote product application.

[0033] A mixture of cetrimonium chloride and benzalkonium chloride and / or other quaternary ammonium salts can also be used.

[0034] The accelerator used in this method can be conveniently applied with a brush or soaked gloves without the risk of producing unwanted halos and / or stains on the finished product, unlike potassium permanganate, which can only be applied as fine particles due to its high reactivity. The ability to apply the product even without spraying it onto fabrics significantly reduces the risk of operator inhalation.

[0035] In a first form of the decolorization method of the present invention, which is particularly suitable for obtaining diffuse and substantially uniform bleaching, textiles are placed in a bath comprising a quaternary ammonium salt-based facilitator, and then dried at least partially, and subsequently placed in an ozone treatment machine.

[0036] In a second form of this method, which is particularly suitable for localized decolorization of textiles, the facilitating substance is selectively applied only to specific areas of the textile, such as the thigh and knee areas in the case of jeans. Once the facilitating substance has been applied, the textile is optionally dried to prevent moisture from affecting the next step, and then the textile is introduced into an ozone generator and subjected to ozonation treatment, resulting in more pronounced decolorization in the areas where the facilitating substance has been applied.

[0037] There are various methods for applying accelerators. For example, in the case of local decolorization, the accelerator can be applied by brushing, using a soaked glove, or by local spraying. In the case of diffusion application, the accelerator can be applied by using rags soaked in the same substance or by spraying in an airtight washing machine.

[0038] In both forms of this method, there may be a final step of neutralizing residual ozone, which can be done by applying a reducing product to the bath or more simply by rinsing once or several times and then drying.

[0039] Highly advantageously, the combined effect of ozone applied to textiles and the promoting agent provides a more significant color change than that obtained by ozone decolorization methods known to date.

[0040] Compared to known solutions, the method of the present invention uses an ammonium salt-based accelerator that can react with ozone in the presence of moisture or once the substance is completely dry.

[0041] In known solutions, the decolorization effect of ozone varies significantly depending on the degree of residual moisture and therefore the time elapsed from the pretreatment stage, making it difficult to control because the execution time of each stage of the method needs to be planned very strictly; in these solutions, the accelerators used are actually just water or hygroscopic substances that can absorb moisture.

[0042] Compared to known solutions, the decolorization effect produced by the synergistic effect of ozone and quaternary ammonium salt in the method of this invention is not affected by humidity or the time elapsed between the product pretreatment stage and the ozonation stage. Therefore, the advantages that this solution can achieve are obvious. Detailed Implementation

[0043] In this patent text, the term "ozonation" refers to a process of treating textiles with ozone, which involves placing textiles in an ozone-rich fluid. In the textile industry, the ozonation process is carried out by placing the textiles to be treated in an airtight machine, similar to an industrial washing machine, into which ozone generated by an ozone generator is introduced. The ozonation process can be carried out under dry conditions, i.e., without the use of water, by pumping ozone gas into the machine, or alternatively by immersing the textiles in a water bath containing dissolved ozone.

[0044] The method of the present invention basically includes the following main stages:

[0045] (a) Pretreatment: In this first pretreatment step, the textile is at least partially wetted with a promoting substance comprising a quaternary ammonium salt, preferably cetrimonium chloride and / or benzalkonium chloride;

[0046] (c) Ozonation: In this stage, the pretreated product is placed in a known type of ozone generator and immersed in an atmosphere rich in this gas for a certain period of time.

[0047] The following intermediate stages may be optionally performed after pretreatment stage (a) but before ozonation stage (c):

[0048] (b) Drying: In this stage, the textiles are dried according to known methods to eliminate moisture that may affect the ozone treatment in the next stage.

[0049] Finally, in some forms of this method, an additional step is performed after the ozonation stage (c):

[0050] (d) Neutralization: In this stage, residual ozone is neutralized by applying a known reducing product to the bath or by a series of consecutive rinses of the product followed by further drying.

[0051] During the ozonation stage (c), the oxidizing effect of ozone, combined with the promoting substance consisting of ammonium salts applied in the previous pretreatment stage (a), results in the decolorization of the fabric. In other words, the ammonium salt compounds enhance the bleaching effect of ozone in the area of ​​the fabric to which it is applied.

[0052] The method disclosed in this invention can be used to achieve localized or diffuse bleaching of textiles. In the first case, the area where the accelerator is applied shows a more significant discoloration than the area where the accelerator is not applied. If the pretreatment is applied dispersedly throughout the textile, a substantially uniform bleaching is obtained, but more significant than if ozone is used alone.

[0053] Preferably, the promoting agent used is a cetrimonium chloride solution. Although solutions with lower or higher solute concentrations can be used, the solute concentration by weight is preferably 1% to 30%; excellent results are obtained with a concentration of 3%.

[0054] Benzalkonium chloride solution or a mixture of the above-mentioned quaternary ammonium salts or other quaternary ammonium salt compounds can be used instead of cetrimonium chloride.

[0055] In some forms of the invention, the promoting substance further comprises at least one auxiliary compound, such as a surfactant or pH buffer or other similar substance, for promoting application to textiles.

[0056] According to a possible form of the invention, aimed at achieving localized decolorization or bleaching only in certain specific areas of a textile, during pretreatment step (a), an operator applies a quaternary ammonium salt compound directly to one or more defined surface areas of the textile, such that these areas, and only these areas, are soaked in the compound. In this case, the operator applies the mixture directly to the fabric using a brush or soaked gloves, or sprays it by a spray gun, or more generally by any other method of selectively wetting one or more defined areas of the product in a desired manner or pattern.

[0057] In a second form of the method, during the pretreatment stage (a), a promoting solution is applied to the textile in a diffusion manner to achieve a non-localized color-changing effect that extends to the entire surface of the textile.

[0058] The diffusion application of the second form of accelerator according to the method of the present invention can be carried out, for example, by placing the textile in a water bath inside a washing machine, dissolving the same accelerator substance in the washing liquid of the washing machine.

[0059] Other alternative solutions can be used, such as atomizing the promoter inside the washing machine drum through nozzles included in the machine itself, into which the product to be treated is placed; in this case, the treatment cycle does not include a water bath.

[0060] Another technique that can be used to achieve diffusion surface decolorization, although with a larger accumulation point, is soaked shredded fabric. These shredded fabrics, pre-cut to a certain size, are soaked in a promoting substance, and then, after light extraction, are spun in a washing machine (waterless bath) with the textiles, releasing trace amounts of the promoting substance through contact with the product surface.

[0061] It should be noted that although textiles are mentioned in the description, the method of the present invention can be similarly applied to multiple textiles that are pretreated (a) simultaneously or separately, and then simultaneously ozonated (c), and optionally, depending on the form of the method, to undergo other treatments such as drying (b) and neutralization (d).

Claims

1. A method for decolorizing textiles, characterized in that, The method includes the following steps: (a) Pretreatment, which is carried out by applying a promoting substance comprising a quaternary ammonium salt to at least a portion of the textile; (c) Ozonation, which is carried out by introducing the textile into and holding it in an ozonating fluid under dry conditions.

2. The method according to claim 1, characterized in that, The method is applied to textiles including denim-type colored cotton.

3. The method according to claim 1, characterized in that, The method includes a drying step (b) of the textile between the pretreatment step (a) and the ozonation step (c).

4. The method according to claim 1, characterized in that, The ozonation step (c) is followed by a neutralization step (d) of residual ozone on the textile, which is carried out by using a reducing compound applied to the bath or by a subsequent rinsing and drying step.

5. The method according to any one of claims 1 to 4, characterized in that, In the pretreatment step (a), the promoting substance is selectively and locally applied to one or more defined areas of the textile.

6. The method according to claim 5, characterized in that, In the pretreatment step (a), the promoter is applied manually by an operator using a brush or soaked gloves, or by atomizing it with a spray gun.

7. The method according to any one of claims 1 to 4, characterized in that, In the pretreatment step (a), the promoting substance is applied to the textile by means of a water bath, by atomization, or by contact with multiple pre-cut soaked shreds of fabric.

8. The method according to any one of claims 1 to 4, characterized in that, The promoting substance is a quaternary ammonium salt solution with a concentration of 1% to 30%.

9. The method according to claim 8, characterized in that, The promoting substance is a 3% quaternary ammonium salt solution.

10. The method according to any one of claims 1 to 4, characterized in that, The quaternary ammonium salt includes cetrimonium chloride.

11. The method according to any one of claims 1 to 4, characterized in that, The quaternary ammonium salt includes benzalkonium chloride.

12. The method according to any one of claims 1 to 4, characterized in that, The promoting substance includes at least one auxiliary compound, which is a surfactant or a pH buffer, for promoting application to the textile.