Patent Description:
The present disclosure describes a process for fabric bleaching using a novel enzyme blend combined with a specifically designed chemical system, which reduces the use of caustic soda and hydrogen peroxide in the conventional oxidative bleaching process, replacing the manipulation of these chemicals.

The Textile Industry (TI) is one of the biggest industries in the world with a current worth of nearly <NUM> trillion USD. Nevertheless, it is also one of the world's top polluting industries, partaking a heavy environmental impact in terms of resource consumption, effluents contamination and textile elimination.

It has long been known that the TI processes are characterized, not only by the large volume of water required, but also by the high temperatures and the variety of chemicals used. There is a long sequence of wet processing stages requiring inputs of water, chemical and energy, generating waste at each stage.

Water is a finite resource that is quickly becoming scarce and is used at every step of the process both to convey the chemicals used during that step and to wash them out before beginning the next step. The water becomes full of chemical additives and is then expelled as wastewater; which in turn pollutes the environment. The liquid effluents of the TI have usually a high Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD), high conductivity and colouring.

Along with the direct contamination and consumption of water, this industry's processes are usually carried out at high temperatures, also representing a very high energy consumption level. Most energy used in the TI is still obtained from coal and fossil fuels, meaning this energy use is an important source of greenhouse gases emission.

The minimization of the above-mentioned issues means all processing steps need to be optimized in such a way that their environmental impact is reduced and they become more sustainable, resulting in reduced effluents charge and energy and water consumption. There are different variables that can be addressed for the optimization of textile processes, such as process temperature, water requirement and chemical system used. It is mandatory to find alternative processes that work at a lower temperature, require less water or where harsh chemicals can be replaced for eco-friendly and more sustainable and safe products.

Focusing on the particular case of cotton, it remains one of the more prominent textile fibres and it has regained importance due to the heavy environmental impact of synthetic fibres. Among the different steps of cotton pre-treatment (before dyeing) we can have desizing, mercerizing, alkaline scouring and bleaching, some of them requiring severe chemical treatment and the need to perform multiple washing steps between them.

Naturally occurring fibres, such as cotton, still contain colouring materials even after scouring processes and the cause of this colour may be the naturally occurring pigments present in the fibre structure. This colour can come from different contaminations occurring during the processing of natural fibres like for example, oils and greases coming from the processing equipment.

The bleaching process aims to eliminate all coloured contaminants that are on the fibres, as well as the remaining of other contaminants that have resisted to previous pre-treating processes (desizing, scouring, etc.) such as bark remnants of the cotton plant.

Nowadays, the major process used for cotton whitening is the oxidative bleaching with hydrogen peroxide.

Considering a typical oxidative bleaching process by exhaustion, it usually consists in the steps depicted in <FIG>.

The conventional bleaching of cotton gives an article with a white level adequate to the subsequent dyeing steps and free of additional contaminants. Nevertheless, it is important to have in mind that this step is performed at a very high temperature, requiring a considerable amount of time and high energy to reach. It also includes several water baths that represent a big water consumption, with the disposed water becoming contaminated with harsh chemicals, such as NaOH.

This chemical is used in substantial quantities in the bleaching process and it is an important contributor to the pollution load in bleaching effluents. A high concentration of NaOH in water will result in toxic effects for the wildlife. Likewise, highly concentrated solutions of NaOH (which is the case of the solutions used for textile bleaching) are also corrosive and irritating to the skin, eyes and mucous membranes, increasing the risk of harmful accidents among textile workers.

On the perspective of textile workers safety, it is also important noting that fifty-percent-concentration hydrogen peroxide solutions can also represent major safety hazards, such as skin burns; eye injuries; potential for rapid pressurization within tanks, pipes, pumps, and/ or storage vessels, etc. Therefore, being able to replace the handling of this chemical would also be advantageous.

There are other traditional bleaching processes that can be applied, nonetheless they are even more damaging than the oxidative bleaching with hydrogen peroxide. Chlorine is known to be extremely toxic to the environment and to consumers, while sodium hypochlorite is very hazardous to human health due to the etching effect that may cause skin and lungs damage. In its compound form, sodium hypochlorite is also very toxic to aquatic organisms and bacteria.

The TI has been exploring the potential of enzymes for several years. Enzymes are protein catalysts produced by living cells that catalyse specific reactions. The use of enzymes in textile processes has gained increased interest due to the fact that enzymes are non-toxic, biodegradable and environmentally friendly.

Many processes, such as desizing, scouring, anti-pilling, can be accomplished with the help of these products. Nevertheless, an industrially viable enzyme that is capable of directly bleaching cotton fabric has still not been developed. Also, it has not been possible to include enzymes in the conventional bleaching processes as they are usually not stable to the severe pH, temperature and oxidative conditions of these processes.

Document <CIT> relates to novel compositions for biobleaching coupled with stone washing of indigo dyed denims comprising a blend of glucose oxidase, catalases and cellulases in the ratio of <NUM>:<NUM>:<NUM> along with sugar base, peroxide source and optional adjuvants, wherein the process is carried out at optimized conditions of neutral pH (<NUM> - <NUM>) and a temperature of <NUM>.

Document <CIT> discloses a method for pre-treating a cotton-polyester blended fabric with a biological enzyme. The method comprises the steps of scouring and bleaching, washing and drying and is characterized in that the scouring and bleaching step comprises the sub-step of adding the cotton-polyester blended fabric to a scouring and bleaching solution to be scoured and bleached, wherein the mass ratio of the cotton-polyester blended fabric to the scouring and bleaching solution is (<NUM>:<NUM>)-(<NUM>:<NUM>); the temperature is controlled to be <NUM>-<NUM>; the treatment time is <NUM>-<NUM> minutes; and the scouring and bleaching solution comprises the following components by weight percent: <NUM>-<NUM>% of compound biological enzyme, <NUM>-<NUM>% of hydrogen peroxide, <NUM>-<NUM>% of tetra acetyl ethylene diamine, <NUM>-<NUM>% of sodium cocoamphoacetate, <NUM>-<NUM>% of ferrous sulfate and the balance of water. The method has the advantages of desizing and bleaching in one bath, mild treatment conditions, small damage to the fabric and short treatment time. Further bleaching processes are disclosed in <CIT>, <CIT> and <CIT>.

In order to optimize and minimize the environmental impact of one of the most universal cotton processing steps, the oxidative bleaching, we have come up with an alternative pre-treatment process that accomplishes fabric whitening using less water, less energy and less harsh chemicals.

The process of the present disclosure is a simplified treatment that results in a fabric that retains the characteristics of cotton and shows a better handle and hydrophilicity and a cleaner and smoother surface than the conventionally bleached cotton.

It was developed a bleaching process to spare some resources and increase the quality of the treated fabric, water and energy consumption.

Additionally, the process of the present disclosure decreases the chemical load used, namely it eliminates the use of NaOH and includes more sustainable versions of the auxiliary chemicals used.

The chemical intervenients were as follows:.

An aspect of the present disclosure relates to a process for fabric bleaching comprising the following steps:.

In an embodiment for better results, the process may further comprise the following steps:.

In an embodiment for better results, the process may further comprise the following steps:
adding a catalase solution to the third bath maintaining the first temperature of the bath during the catalase reaction.

In an embodiment for better results, the duration of the enzymatic reaction is at least <NUM> minutes, preferably from <NUM> minutes to <NUM> hour, more preferably <NUM> minutes.

In an embodiment for better results, the second temperature of the first bath is from <NUM>-<NUM>, preferably <NUM>.

In an embodiment for better results, the duration of the peroxidation reaction is at least <NUM> minutes, preferably from <NUM>-<NUM> minutes, more preferably <NUM> minutes.

In an embodiment for better results, the temperature of the second bath is from <NUM>-<NUM>, preferably <NUM>.

In an embodiment for better results, the duration of the washing is at least <NUM> minutes, preferably from <NUM>-<NUM> minutes, more preferably <NUM> minutes.

In an embodiment for better results, the temperature of the third bath is from <NUM>-<NUM>, preferably <NUM>.

In an embodiment for better results, the duration of the washing with the sequestering and dispersing agent is at least <NUM> minutes, preferably from <NUM>-<NUM> minutes.

In an embodiment for better results, the duration of the catalase reaction is at least <NUM> minutes, preferably from <NUM>-<NUM> minutes.

In an embodiment for better results, the blend of enzymes is:.

In an embodiment for better results, the blend of enzymes further comprises oxidoreductase.

In an embodiment for better results, the liquor ratio between fabric: water is from <NUM>:<NUM> -<NUM>:<NUM>; preferably <NUM>:<NUM> -<NUM>:<NUM>.

In an embodiment for better results, the wetting agent concentration is from <NUM>,<NUM> - <NUM> % (wt/wt), preferably <NUM> - <NUM> %(wt/wt).

In an embodiment for better results, the enzyme blend concentration is from <NUM>,<NUM> - <NUM> % (wt/wt), preferably <NUM> - <NUM> %(wt/wt).

In an embodiment for better results, the sequestering and dispersing agent concentration is from <NUM> - <NUM>/l, preferably <NUM> -<NUM>/l.

In an embodiment for better results, the catalase concentration is from <NUM> - <NUM>/l.

In an embodiment for better results, the wetting agent is ethoxylated isotridecanol.

In an embodiment for better results, the bleaching activator is a manganese salt.

In an embodiment for better results, the sequestering and dispersing agent is <NUM>-hydroxy-<NUM>-carboxy-<NUM>,<NUM>-pentanedioic acid.

Another aspect of the present disclosure relates to a bleached fabric obtainable by the process described in the present disclosure wherein the weight loss is inferior to the standard process, being less than <NUM>%.

In an embodiment for better results, the fabric is a natural yarn fabric, preferably a cotton fabric.

Another aspect of the present disclosure also relates to an article comprising the fabric described in the present disclosure.

Among the advantages of the process of the present invention, are the significant savings in terms of resources consumption, namely:.

The following figures provide preferred embodiments for illustrating the invention and should not be seen as limiting the scope of invention.

The process of the present disclosure is an alternative pre-treatment process that accomplishes fabric whitening using less water, less energy and less harsh chemicals. It minimizes environmental impact of one of the most universal cotton processing steps, the oxidative bleaching.

In an embodiment, the present disclosure is used to bleach all <NUM>% cotton articles used as starting material for the Textile Industry.

In an embodiment the conventional process described in <FIG> consists in the following steps:.

In an embodiment, the process of the present disclosure may comprise the following steps:.

In an embodiment, considering an initial water temperature of <NUM>, a machine with a heating and cooling rate of <NUM>/min, a machine that takes <NUM> minutes to fill in and <NUM> minutes to drain the water and the optimized process conditions, the bleaching process is reduced from <NUM> with the conventional procedure to <NUM> with the process of the present disclosure, meaning a reduction of approximately <NUM>% in process time.

In addition to the decrease of environmental impact due to resource savings, which has already been described, the effluents generated by the process of the present disclosure show decreased values for practically all parameters of effluent analysis, namely on BOD and COD, as shown in Tables <NUM> and <NUM>.

The overall difference of colour can be calculated by spectrophotometric reading and it is expressed by the DE value, obtained based on the comparison between samples that went through the conventional bleaching and samples treated by the process of the present disclosure. Standard values for colour tolerance accepted amongst the industry players are usually ≤ <NUM>.

The spectrophotometric analysis of the dyed samples shows DE values between <NUM> and <NUM>, which can be attributed to the slight differences in whiteness level obtained in the samples post-bleaching. This means the colour yield of samples subjected to the process of the present disclosure is not exactly the same but it is close enough to the conventionally bleached samples and, therefore, it is expected to be easy to adjust the dyeing recipes. In some cases, this colour difference will possibly mean the need to use less dyestuff.

In conclusion, in terms of final article characteristics, the process of the present disclosure is a perfectly viable option to replace the conventional bleaching process as the final article is softer, smoother, with cleaner surface, better hydrophilicity and lower weigh loss. Even though there seems to be some variation in the colour yield, dyeing recipes are expected to be easily adjusted. When assessing the variation of colour yield against all the benefits and advantages of the process of the present disclosure, it can be deemed a manageable adaptation.

Moreover, on an environmental perspective, the process of the present disclosure allows meaningful savings in terms of water, energy and time consumption and originates less polluted effluents.

It will be appreciated by those of ordinary skill in the art that unless otherwise indicated herein, the particular sequence of steps described is illustrative only and can be varied without departing from the disclosure. Thus, unless otherwise stated the steps described are so unordered meaning that, when possible, the steps can be performed in any convenient or desirable order.

Furthermore, it is to be understood that the disclosure encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, descriptive terms, etc., from one or more of the claims or from relevant portions of the description is introduced into another claim. For example, any claim that is dependent on another claim can be modified to include one or more limitations found in any other claim that is dependent on the same base claim.

Furthermore, where the claims recite a composition, it is to be understood that methods of using the composition for any of the purposes disclosed herein are included, and methods of making the composition according to any of the methods of making disclosed herein or other methods known in the art are included, unless otherwise indicated or unless it would be evident to one of ordinary skill in the art that a contradiction or inconsistency would arise.

Where ranges are given, endpoints are included. Furthermore, it is to be understood that unless otherwise indicated or otherwise evident from the context and/or the understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value within the stated ranges in different embodiments of the invention, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise. It is also to be understood that unless otherwise indicated or otherwise evident from the context and/or the understanding of one of ordinary skill in the art, values expressed as ranges can assume any subrange within the given range, wherein the endpoints of the subrange are expressed to the same degree of accuracy as the tenth of the unit of the lower limit of the range.

The above described embodiments are combinable.

Claim 1:
A process for fabric bleaching comprising the following steps:
preparing a first water bath with a wetting agent and the fabric;
wherein the first water bath is warmed to a first temperature up to a maximum of <NUM>-<NUM> and the pH of the bath is at a maximum of pH <NUM> - <NUM>;
adding an enzyme blend to the bath, wherein the enzyme blend comprises at least <NUM> of the following enzymes: alpha-amylase, beta-amylase, pectate lyase, cellulase, endoglucanase, lipase;
maintaining the first temperature of the bath during the enzymatic reaction;
adding a peroxide donor and a bleaching activator to the bath;
warming the bath to a second temperature of a minimum of <NUM> for the peroxidation reaction;
wherein the peroxide donor concentration is from <NUM> to <NUM>/l,
wherein the bleaching activator concentration is from <NUM> to <NUM>/l;
wherein the peroxide donor is sodium percarbonate, sodium perborate or a mixture thereof.