Patent Application
20240060230
The present disclosure is directed to a process for increasing the strength and decreasing the wettability of cotton garments.
Cotton is a natural fiber with a negative environmental impact when processed. Currently, the fiber is bleached, finished with strong alkali to prepare for a dying process, and dyed. The strong alkali has to be neutralized at each stage of production in particular to mitigate the damaging effluent that would otherwise be released into the worlds aqueous eco systems.
A substantial amount of water waste is generated by repeatedly washing off the alkali involved in wet processing. For example, a report in the Planet Tracker, “Will Fashion Dye Another Day” (December 2020), notes “textile production requires an estimated 430 liters or 114 US gallons to produce 1 kg of textile fabric.” The report continues, stating that an estimated 8,000 toxic chemicals, used globally, are used to turn raw materials into textiles. Many of these chemicals are released into freshwater sources as waste streams. For example, “the dyeing and treatment of textiles is estimated to cause 20% of global industrial water pollution.”
Cotton is at the top end of this estimate, requiring more water to process than polyester, viscose rayon, and wool. Thus, it is likely that the production and dying of cotton fabric is a significant contributor.
Further, the current processing techniques used for cotton are energy intensive, requiring multiple drying cycles. Reducing the heat used in dyeing and shortening the dye cycles will lower the energy demand.
An embodiment described in examples herein provides a method for making water-resistant cotton garments. The method includes treating cotton fabric with soda ash at a temperature of less than about 150° F. (about 66° C.) and a pH of about 9.5 and bleaching the cotton fabric with hydrogen peroxide at a temperature of less than about 150° F. (about 66° C.). The hydrogen peroxide is neutralized, and the pH is lowered with an organic acid to between about 6 and about 7. A garment is made from the cotton fabric and a wax lock is applied to the garment. The garment is dyed at a temperature of less than about 150° F. (about 66° C.), and dried.
Another embodiment described in examples herein provides a cotton garment formed from an activated cotton material, including a layer of natural wax locked to the surface of cotton fibers by a wax lock.
The industry standard technique for treating cotton for dying is termed Kiering. Kiering is generally performed on cotton fabric or yarn to prepare it for dyeing. It uses a scouring process in which hot alkali (NaOH) solutions are used to saponify the natural wax coating on the cotton fibers, removing the wax. This increases the absorbancy (hydrophilicity) of the cotton fabric, making the fabric easier to dye.
However, multiple rinses of water are required to remove the alkali solutions. Further, the alkali softens the fabric by partially breaking down the fibers, leading to a lower strength product. The highly corrosive NaOH is also hazardous to operators if not properly handled in processing textiles. In addition, if the effluent created is not properly neutralized and disposed of it can be very damaging to water systems and the associated environment.
After the scouring, the cotton is bleached to remove color bodies, forming a white material. The bleaching can be performed by the use of hydrogen peroxide or other bleaches, such as hypochlorite bleach, among others.
The treated cotton can then be dyed, for example, as yarns, fabric, or garments, depending on the products. In the dying process, the cotton articles are passed through, or soaked in, baths that include chemicals that help the dye to adhere to the cotton, for example, by forming hydroxyl groups at the surface of the cotton. The cotton is then passed through, or soaked in, a bath containing the dye. This is often followed by multiple rinses to remove any excess dye that does not adhere to the cloth.
If the treating and dying process is performed on a cotton yarn, the yarn is then formed into a fabric, for example, by knitting or weaving. The currently used techniques for treating cotton form an absorbent fabric with a color selected by the techniques used. However, the alkali treatment reduced the strength of the cotton fibers, for example, by as much as 50% or more, from the raw cotton.
A process is provided herein for producing a cotton product, termed an activated cotton, which leaves the natural wax in place on the cotton fibers, lowers water usage, and improves the properties of the cotton. The natural wax coating on the cotton fibers imparts high performance properties to yarns, fabrics, and garments, for example, increasing the cooling properties of the fabric by allowing water vapor to pass through the fabric without being adsorbed. To implement this, the process includes the addition of a compound termed a wax lock.
As described, the wax coating on natural cotton is generally removed during Keiring. Further, even if left on by a milder process, home laundering will remove the natural wax in a few cycles. To overcome this, the activated cotton is treated with the wax lock to fix the wax in place on the fabric. In some embodiments, the wax lock includes a silicone compound that interacts with the natural wax to prevent surfactants from removing the wax. In other embodiments, the wax lock is a cross-linking agent, such as a synthetic acrylic oligomer, which is applied before the final drying process and activated during drying. A natural product that includes cross-linking material, along with a natural wax, can also be used. The cross-linking agent forms cross-links that hold the natural wax in place on the fibers. This retains the natural hydrophobicity of the cotton fabric and enables it to maintain the hydrophobicity during numerous home laundering cycles, for example, greater than 20 cycles, greater than 25 cycles, greater than 30 cycles, or longer.
In the process, the bleaching is performed using hydrogen peroxide. A peroxide activator, triacetin, is used along with a sequestering (or chelating) agent to protect the cotton fiber and the natural wax. The triacetin gradually lowers the pH, creating conditions for the peroxide to be a highly effective bleaching agent to prepare the cotton for dying. This allows the elimination of the strong caustic alkali used in used in traditional bleaching and dye preparation methods. This also creates conditions for an enzyme bleach catalyst to be effective.
In various embodiments, arylesterase is used as the oxidation catalyst. The arylesterase is effective at low concentrations (high dilutions), such as about 0.5 grams per liter (g/L) about 0.2 g/L, or less. The use of the arylesterase allows the hydrogen peroxide reaction to occur at lower temperatures and in a shorter time, which lowers both the time and energy for the reaction, increasing the economic yield.
The process changes and combinations described herein shorten the process further and increase water savings. This provides a more stable, repeatable, and ecologically favorable process. Further, the natural wax coating on the cotton will withstand 30 or more home laundering cycles with a surfactant, such as laundry detergent.
The method 100 includes five basic processes, a pretreatment process 102 used to clean the cotton fabric and bleach it to remove color bodies and prepare the fabric for dying. A garment production process 104 is used to prepare a garment from a pretreated fabric. A treatment process 106 is used to prepare the garment for dying and to apply the wax lock to the fabric. A dying process 108 is used to impart color to the garment. A drying process 110 is then used to fix the wax lock on the garment, protecting the natural wax coating on the cotton fibers, and allowing multiple home launderings without removing the wax coating.
The pretreatment process 102 begins at block 112 with a soda ash pretreatment. The use of soda ash, Na2CO3, is in place of caustic soda (NaOH) used in the standard Kiering process. The use of NaOH sets the pH at 12.5, which damages the cotton fibers and removes the natural wax by saponification. The soda ash sets the pH of the treatment, for example, to about 10, or about 9.5. The lower pH prevents, or decreases, the likelihood of saponification of the wax coating. Further, this is performed at a lower temperature than previous pretreatment procedures, for example, about 150° F. (66° C.).
During the soda ash pretreatment at block 112, a bleach activator, for example, glyceryl triacetate (triacetin), is added for activation of hydrogen peroxide in the subsequent bleaching procedure. The triacetin is available from Cekal Specialties of Mt. Holly, NC, USA, under the tradename CEKASSIST BIO. Further, a sequestering agent, such as ethylenediaminetetraacetic acid (EDTA), is used to lower the concentration of divalent metal ions, such as magnesium (II) and calcium (II). In an embodiment, the sequestering agent is CEKAQUEST PB from Cekal Specialties, which is also helping stabilize the hydrogen peroxide bleach. The decreasing concentration of the divalent metal ions will further stabilize the hydrogen peroxide during the bleaching procedure.
At block 114, a bleaching procedure is performed using a 50% solution of hydrogen peroxide. During the bleaching procedure, an arylesterase catalyst is added to speed the reaction between the peroxide and the color bodies, as described herein. Generally, the arylesterase catalyst is produced by microorganisms, for example, in a commercial production process. Any number of arylesterase catalysts can be used in the current procedures. In an embodiment, the arylesterase catalyst is obtained from Cekal Specialties under the tradename CEKAZYME BB.
At block 116, should there be any peroxide bleach remaining, it is neutralized by the addition of a catalase enzyme. Any number of catalase enzymes may be used in the current procedures. In an embodiment, the catalase is CEKAZYME EPK200 from Cekal Specialties. In some embodiments, a test strip is used to confirm that the peroxide is eliminated. If not, in some embodiments, a water wash is used to rinse any remaining peroxide from the cotton. Generally, the peroxide is completely reacted, which allows a processor to go directly to the dyeing process. This avoids the washes that are needed to remove the peroxide, for example, saving around 10,000 liters of water per 1,000 kg of textile substrate.
At block 118, the pH is lowered to a pH of less than about 8, less than about 7, or between 6.5 and 7. In some embodiments, this is performed by the addition of an organic acid, such as citric acid, acetic acid, or others. In some embodiments, the pH is checked to confirm that it is between 6.5 and 7. If not, more acid may be added, and the pH retested.
A surface tension test may be used to confirm that the pretreatment process 102 did not damage or remove the natural wax coating. In some embodiments, the surface tension test is performed by placing a drop of water on the surface of the fabric and noting if the water beads or is absorbed. In other embodiments, a goniometer is used to determine the surface tension of the surface, which may be used to determine the efficacy of the treatment.
The fabric from the pretreatment process 102 is then used to make a garment in the garment production process 104. For example, the fabric is cut into the appropriate shaped pieces, and sewn into the final garment. The pieces are generally larger than the final size expected for the garment, as the garment accounts for shrinkage during the dying, finishing, and drying stages.
After preparation of the garment, the treatment process 106 is used to prepare the garment for dying and to apply the wax lock if performance is desired. The treatment process 106 begins at block 120, with the treatment of the garment with sodium sulfate. At block 122, Na2CO3 (soda ash) is added to raise the pH to about 9.5, or about 10. The pH may be checked, and more Na2CO3 added if needed to adjust the pH to 9.5. The use of the weak alkali helps retain and protect the cotton wax and the cotton cellulose. It is used in place of the caustic soda (NaOH) used in the standard Kiering procedure, which would set the pH at 12.5, damaging the cotton and removing the natural wax via saponification.
At block 124, the wax lock is applied, for example, by adding the wax lock material to the solution containing the garment. As described herein, the wax lock locks the natural wax to the cotton fibers, slowing its removal by laundering. The wax lock may include silicone compounds, acrylic oligomers, or combinations. Other materials may be used, such as other types of oligomers or monomers. Generally, the wax lock is hydrophobic, further protecting the natural was from being removed by laundering. The silicone wax lock compound used in some embodiments is available from Apexical Specialty Chemicals of Spartanburg, SC, USA, as Apexosil 2137. In some embodiments, a small amount of acrylic monomers or oligomers may be included, such as about 1 wt. %, about 2 wt. %, about 5 wt. %, about 10 wt. %, about 20 wt. %, or higher.
In some embodiments, the wax lock is a blend that includes an acrylic oligomer, such as available from Cekal Specialties as CEKAPEL NFWR. In this example, the acrylic polymer blend includes 20-30 wt. % of a liquid, crosslinking acrylic polymer. The blend also includes 5-10 wt. % of dipropylene glycol. The dipropylene glycol lowers the viscosity of the polymer blend, improving the uptake into the cotton.
Similar materials are available from other suppliers. These include blends in the Hycar line from Lubrizol, Corp. of Wickliffe, OH, USA. Other materials are available from Apexical Specialty Chemicals, Huntsman Chemicals of Charlotte, NC, USA, and Chemours of Wilmington, DE, USA.
In some embodiments, the wax lock compound is a blend that includes natural plant material isolated from plant wastes, for example, the by-products that accumulate during the processing of cereal grains in the food industry. A crosslinker may be included in the blend to assist in locking the natural wax and the natural plant material to the fibers of the cotton. The natural plant material is available from Rudolf GmbH of Geresreid, DE, as RUCO®-DRY BIO CGR. The crosslinker is available from Rudolf as RUCO®-LINK XHC. Other products from Rudolf can be used as the wax lock in embodiments. For example, RUCO®-DRY BIO NPE is a combined natural plant product and cross-linking agent that can be used as the wax lock.
The dying process 108 is described with respect to blocks 126 to 132. It can be noted that the generic procedure of
At block 126, the dying compound is added to the solution containing the garment. In some embodiments, the dye is a reactive dye, although any number of other types of dyes may be used, including direct dyes, sulfur dyes, azoic dyes, or vat dyes, among others described herein. The dye liquor is heated to a maximum temperature of about 140° F. (about 60° C.) at a rate of about 2° F./min (about 1.1° C./min.). The dye is allowed to stay in contact with the cotton for a sufficient period of time for absorbance, for example, 30 min., 45 min., 60 min., or longer.
At block 128, the dye and salts are rinsed from the garment. At block 130, the pH is lowered to less than 8, or less than 7, or about 6.5. This is performed by the addition of an organic acid, such as citric acid, acetic acid, or the like. At block 132, a water rinse is performed to remove the acid and any remaining dyes or salts from the garment. In some embodiments, the pH of the rinse solution containing the garment is checked to confirm that it is between 6.5 and 7. If not, more acid may be added, and the pH retested.
In the drying process 110, the garment is dried to fix the wax lock compound. In various embodiments, this is performed at a temperature of less than about 400° F. (about 204° C.), or less than about 390° F. (about 199° C.), or less than about 350° F. (about 177° C.), or less than about 310° F. (about 154° C.), or between about 300° F. (about 149°) and about 390° F. (about 199° C.), for example, in a tumble dryer or on a frame or moving line at a speed of about 25 to about 30 yds./min (or about 23 to about 27 meters/min).
As for the treatment process 106 of
At block 202, the RD is added to the solution. As the dye is not soluble until it is reduced, a reducing agent is added at block 204 to fully reduce the dye for solubilization. In some embodiments, the reducing agent may be a catalase, such as CEKAZYME EPK200 from Cekal added at about 4 g/l to about 6 g/l, depending on whether the reduction dye is pre-reduced before use. In other embodiments, the reducing agent is sodium borohydride, hydrogen sulfide, or sodium hydrosulfite, among others.
At block 206, a mordant, or dye fixative agent, is added to assist in adhering the dye to the cloth. In some embodiments, the mordant is Al2(SO4)3, FeSO4, CuSO4, ZnSO4, or MnSO4, among others. The mordant is selected based on the efficacy and the potential effects on the color. Further, the mordant may increase the efficacy of the reducing agent, for example, if a catalase is used, by increasing the ORP of the catalase solution. The mordant can be added at about 10 g/l to about 20 g/l.
The dye liquor and reducing agent are heated to a maximum temperature of about 140° F. (about 60° C.) at a rate of about 2° F./min (about 1.1° C./min.). The dye is allowed to stay in contact with the cotton for a sufficient period of time for absorbance, for example, 30 min., 45 min., 60 min., or longer.
At block 126, the dye, mordant, and salts are rinsed from the solution. At block 208, an oxidizer is added to the water solution to oxidize the reduced dye. In various embodiments, the oxidizer is hydrogen peroxide, air, oxygen, a water solution of ozone, and the like. In some embodiments, hydrogen peroxide is added at between about 1 g/l and about 5 g/l. In other embodiments, the dye is allowed to oxidize in air for about 20 to about 30 minutes. The amount of oxidation controls the color, with higher levels of oxidation correlated to darker colors.
At block 128, the pH is lowered to less than 8, or less than 7, or about 6.5. This is performed by the addition of an organic acid, such as citric acid, acetic acid, or the like. At block 130, a water rinse is performed to remove the acid and any remaining dyes or salts. In some embodiments, the pH is checked to confirm that it is between 6.5 and 7. If not, more acid may be added, and the pH retested.
It can be noted that all of the enzymes described herein are available from other suppliers. For example, AB Enzymes of Darmstadt, DE, produces analogous arylesterase catalysts and catalase enzymes that may be used in the processes described herein.
Further, any number of other dyes may be used in embodiments described herein, including, including vat dyes, sulfur dyes, pre-reduced versions of vat and sulfur dyes, and other dyes that are insoluble and are applied to substrates via redox methods. Other dyes than can be used include azo dyes, such as direct dyes, metal complex dyes, reactive dyes, substantive dyes, and aniline dyes, such as natural and synthetic indigo dye, among others.
The treatment process described herein, for example, with respect to
As described herein, after the pretreatment, cotton fabric can be made into garments, and the wax lock can be applied during the dying process, for example, before the dye is added. A cotton fabric prepared using this technique with a silicone softener as the wax lock compound retained the natural wax through greater than 25 laundering cycles using a cool wash cycle, 1 g/L Tide laundry detergent, and a cool dry cycle. This was tested by performed a surface tension test after each laundering cycle by applying a water droplet and determining that it beaded on the cotton fabric. As described herein, the natural wax lock products from Rudolph, Ruco-Dry Bio CGR and Ruco-Dry Bio NPE, are highly effective.
The burst strength of the cotton fabric was compared to a sample of cotton fabric that was treated by the normal caustic wash. The test performed to determine the strength was the Mullen diaphragm burst test, following ASTM D3787. The strength retained by the cotton fibers depended on the initial lengths of the cotton fibers, e.g., the quality of the cotton. A sample of fabric made using a high-quality cotton and treated using the procedure described with respect to
A sample of fabric prepared from a lower quality cotton, e.g., with shorter fiber lengths, still maintained a significant strength advantage when treated with the procedure of
An embodiment described in examples herein provides a method for making water-resistant cotton garments. The method includes treating cotton fabric with soda ash at a temperature of less than about 150° F. (about 66° C.) and a pH of about 9.5 and bleaching the cotton fabric with hydrogen peroxide at a temperature of less than about 150° F. (about 66° C.). The hydrogen peroxide is neutralized, and the pH is lowered with an organic acid to between about 6 and about 7. A garment is made from the cotton fabric and a wax lock is applied to the garment. The garment is dyed at a temperature of less than about 150° F. (about 66° C.), and dried.
In an aspect, combinable with any other aspect, making the garment includes cutting pieces from the cotton fabric and sewing the pieces together to form the garment.
In an aspect, combinable with any other aspect, the method includes adding a bleach activator with the soda ash.
In an aspect, combinable with any other aspect, the method includes adding a sequestering agent with the soda ash.
In an aspect, combinable with any other aspect, the method includes adding an arylesterase catalyst with the hydrogen peroxide.
In an aspect, combinable with any other aspect, neutralizing includes adding an enzyme to degrade the hydrogen peroxide.
In an aspect, combinable with any other aspect, the organic acid includes citric acid.
In an aspect, combinable with any other aspect, applying the wax lock to the garment includes treating the garment with sodium sulfate, treating the cotton with soda ash to raise the pH to about 9.5, and applying the wax lock to the garment.
In an aspect, combinable with any other aspect, the dying includes treating the garment with a dye solution, rinsing the garment, neutralizing the dye solution to a pH of about 6.5, and rinsing the garment.
In an aspect, combinable with any other aspect, the dye solution includes a pre-reduced dye.
In an aspect, combinable with any other aspect, the method includes adding a reducing agent to the dye solution.
In an aspect, combinable with any other aspect, the method includes adding a mordant to the dye solution.
In an aspect, combinable with any other aspect, the method includes treating the garment with an oxidant.
In an aspect, combinable with any other aspect, the method includes treating the garment with the wax lock.
In an aspect, combinable with any other aspect, the method includes drying the garment at between about 300° F. (about 149° C.) and about 390° F. (about 199° C.).
In an aspect, combinable with any other aspect, the wax lock includes a silicone compound.
In an aspect, combinable with any other aspect, wax lock includes an acrylic compound.
Another embodiment described in examples herein provides a cotton garment formed from an activated cotton material, including a layer of natural wax locked to a surface of cotton fibers by a wax lock.
In an aspect, combinable with any other aspect, the cotton garment includes a dye.
In an aspect, combinable with any other aspect, the cotton garment includes a pre-reduced dye.
In an aspect, combinable with any other aspect, the pre-reduced dye includes indigo.
In an aspect, combinable with any other aspect, the wax lock includes a silicone compound.
In an aspect, combinable with any other aspect, the wax lock includes an acrylic oligomer.
In an aspect, combinable with any other aspect, the wax lock includes a natural plant material.
In an aspect, combinable with any other aspect, the wax lock includes a natural plant material combined with a cross-linking agent.
Other implementations are also within the scope of the following claims.
This application claims the benefit of U.S. Provisional Application No. 63/373,101, filed Aug. 22, 2022, the contents of which are incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 63373101 | Aug 2022 | US |
