Fabric sand washing process and sand-washed fabric

Abstract

The invention discloses a fabric sand washing process and a sand-washed fabric, and relates to the technical field of fabric treatment.The fabric sand washing process comprises the following steps that S1, a wet fabric is placed in a biological enzyme treatment tank, a biological enzyme preparation, a penetrating agent and a buffering agent are added, and oscillation treatment is conducted; s2, adding a nano silicon-based grinding material into the biological enzyme treatment tank, and starting ultrasonic waves to carry out wear treatment; s3, rinsing the treated fabric, and filtering the wastewater in the biological enzyme treatment tank. According to the invention, by introducing bio-enzyme pretreatment in combination with a synergistic mechanism of the nano silicon-based abrasive and ultrasonic waves, strong mechanical friction of traditional pumice on the light and thin fabric is avoided, and the risk of damage of the fabric in the treatment process is reduced while the sand washing effect is ensured.

Description

Technical Field

[0001] This invention relates to the field of fabric treatment technology, and in particular to a fabric sand washing process and sand-washed fabric. Background Technology

[0002] Fabrics typically require sand washing to improve their feel, appearance, and abrasion resistance. Traditional sand washing processes often use pumice stones for mechanical friction, achieving a napped, softened, and vintage look through physical abrasion. However, the intense friction between the pumice stones and the fabric can easily damage the fibers, resulting in a high rate of fabric breakage, especially when processing lightweight or high-density fabrics, which can easily lead to problems such as localized holes and reduced tear strength. Summary of the Invention

[0003] The main objective of this invention is to propose a fabric sand washing process and sand-washed fabric, which aims to reduce the risk of damage to lightweight fabrics during the sand washing process.

[0004] To achieve the above objectives, the fabric sand washing process proposed in this invention includes the following steps: S1: Place the wet fabric in a bio-enzyme treatment tank, add bio-enzyme preparation, penetrant and buffer, and perform shaking treatment; S2: Add nano-silicon-based abrasive to the bio-enzyme treatment tank and turn on the ultrasonic wave for wear treatment; S3: Rinse the treated fabric and filter the wastewater in the bio-enzyme treatment tank.

[0005] In one embodiment, the bio-enzyme preparation in step S1 comprises 2%–3% (owf) cellulase and 0.5%–1% (owf) laccase.

[0006] In one embodiment, the wet fabric in step S1 is oscillated at a speed of 30 rpm between 40°C and 50°C for at least 30 minutes.

[0007] In one embodiment, the penetrant is JFC with a concentration of 0.2 g / L.

[0008] In one embodiment, the buffer is an acetate-sodium acetate buffer system, which is used to control the pH value in step S1 between 5.0 and 6.0.

[0009] In one embodiment, the nano-silicon-based abrasive is silica aerogel.

[0010] In one embodiment, the particle size of the nano-silicon-based abrasive is between 50 nm and 100 nm.

[0011] In one embodiment, the concentration of the nano-silicon-based abrasive is 5 g / L.

[0012] In one embodiment, in step S2, the frequency of the ultrasonic treatment is 25 kHz to 40 kHz, and the treatment time is 15 min to 20 min.

[0013] In one embodiment, in step S3, after removing the nano-silicon-based abrasive, an initial cleaning is performed at 35°C to 45°C for a cleaning time of not less than 5 minutes. During the second cleaning, the pH value of the cleaning solution is controlled above 6.0, and 0.5 g / L of softener is added for a third cleaning.

[0014] In one embodiment, in step S3, a ceramic membrane with a pore size of 0.1 μm is used to filter the wastewater in the bio-enzyme treatment tank.

[0015] In one embodiment, step S4 is included before step S1: the fabric is soaked in warm water at 40°C to 50°C for at least 10 minutes, and a wet fabric is obtained after soaking, with a moisture content of 55% to 65%.

[0016] In one embodiment, step S5 is included after step S3: radio frequency drying of the wet fabric, wherein the moisture content of the dried fabric does not exceed 8%; wherein the temperature during the drying process does not exceed 60°C, and the relative humidity of the environment undergoes at least two gradually decreasing stages in sequence, forming a humidity gradient from high to low.

[0017] In one embodiment, the humidity gradient includes three stages, with the relative humidity of the three stages decreasing from high to low as 70% RH, 50% RH, and 30% RH.

[0018] In one embodiment, the radio frequency field strength during the drying process is 15 kV / m.

[0019] The present invention also proposes a sand-washed fabric, which is obtained by the aforementioned fabric sand-washing process.

[0020] In one embodiment, the sand-washed fabric is cotton, linen, or recycled fiber fabric.

[0021] The technical solution of this invention replaces strong mechanical friction with bio-enzyme pretreatment, combined with the uniform micro-wear of nano-silicon-based abrasives, avoiding the severe impact of traditional pumice on thin fabrics, effectively reducing the risk of fabric holes and tears, and effectively improving the fabric tear strength retention rate; the nano-silicon-based abrasives are evenly distributed under ultrasonic action, and the force is controllable, resulting in a fabric surface with delicate nap, soft hand feel, and natural luster, with a visual texture superior to traditional processes. Furthermore, the sand washing process of this invention does not require the use of large amounts of pumice, reducing solid waste and silicon dust pollution; the bio-enzyme preparation is biodegradable, reducing chemical pollution and minimizing wastewater treatment pressure. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 A flowchart of an embodiment of the fabric sand washing process provided by the present invention; Figure 2 A flowchart of another embodiment of the fabric sand washing process provided by the present invention; Figure 3 A comparison diagram showing the effect of the fabric sand washing process provided by the present invention on the same sample before and after treatment; Figure 4 This is a comparison chart of the test results of the present invention and the traditional sand washing process; Figure 5 This is a comparison chart of the wear depth distribution of the present invention and the traditional sand washing process.

[0024] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0027] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0028] This invention proposes a fabric sand washing process.

[0029] Please see Figure 1 In one embodiment of the present invention, the fabric sand washing process includes the following steps: S1: Place the wet fabric in a bio-enzyme treatment tank, add bio-enzyme preparation, penetrant and buffer, and perform shaking treatment; S2: Add nano-silicon-based abrasive to the bio-enzyme treatment tank and turn on the ultrasonic wave for wear treatment; S3: Rinse the treated fabric and filter the wastewater in the bio-enzyme treatment tank.

[0030] This invention introduces a synergistic mechanism between bio-enzyme pretreatment and nano-scale abrasives to replace or weaken the strong mechanical friction of traditional coarse abrasives. This significantly reduces physical damage to the fabric during the sand-washing process while maintaining the sand-washing effect, thus improving the yield. It is particularly suitable for sand-washing lightweight, high-density, or fragile fabrics. Sand-washed fabrics produced using this process exhibit excellent softness, uniform napping, and superior retention of mechanical properties.

[0031] Specifically, in step S1, a bio-enzyme pretreatment is performed: the moistened fabric is placed into a bio-enzyme treatment tank, and a bio-enzyme preparation is added to the tank to degrade the surface hairs of the fabric. This preparation can be one or more complex enzymes, such as cellulase, protease, or lipase, depending on the fabric material. For example, cellulase is used for cotton, and protease is used for silk. At the same time, a penetrant is added to promote the rapid and uniform penetration of the enzyme solution into the fiber, and a buffer (such as an acetate-sodium acetate buffer system) is added to maintain the pH value of the treatment solution and ensure that the enzyme activity is within the optimal range.

[0032] Under constant temperature conditions (typically 45℃ to 60℃, depending on the enzyme), the fiber is subjected to vibration treatment using sand washing equipment (such as a vibrating water washer or a circulating pump). This allows the enzyme molecules to undergo a gentle biochemical reaction with the fiber surface, selectively hydrolyzing the microfibers or surface impurities, achieving preliminary biopolishing and softening effects. This process avoids mechanical friction, effectively reducing the risk of fiber damage and providing a good foundation for subsequent sand washing.

[0033] In step S2, a combined abrasive and ultrasonic abrasion treatment is performed: After the bio-enzyme treatment, nano-silicon-based abrasives (such as nano-silica or silicate nanoparticles with a particle size between 50 nm and 200 nm) are added to the bio-enzyme treatment tank. These nano-silicon-based abrasives possess high hardness, regular morphology, and good dispersibility, providing uniform micro-friction at low concentrations. Subsequently, the ultrasonic device is activated, utilizing the cavitation effect generated by ultrasound in the liquid to create high-frequency, microscale impact flows and microjets from the nano-abrasives in the solution, performing fine and controllable micro-abrasion treatment on the fiber surface. This process simulates the fuzzing effect of traditional sand washing, but due to the extremely small abrasive particle size and uniform force distribution, localized stress concentration is avoided, thus significantly reducing the risk of fabric damage.

[0034] In this step, the biochemical softening effect of the enzymes and the physical micro-wearing effect of the nano-abrasives create a synergistic effect. Enzyme treatment weakens the fiber surface structure, making it easier for nanoparticles to gently peel off, thus achieving the desired sandblasted appearance and feel with lower energy. Simultaneously, under the synergistic mechanism of enzymes and ultrasound, ultrasonic cavitation expands the fiber micropores, accelerating enzyme penetration, which in turn propels the abrasive impact via microjets. The ultrasonic cavitation effect expands the fiber micropores by 30%–50%, increasing the enzyme molecule diffusion rate by 2.3 times; at the same time, the cavitation microjets propel the abrasive impact at a frequency of 1200 times / second, improving the wear efficiency by 4 times compared to a single process.

[0035] The same fabric was sand-washed using both traditional sand-washing and the sand-washing process of this invention. The fabric damage rate, fuzz reduction rate, and energy consumption were then tested according to relevant testing standards. Please refer to [link / reference]. Figure 4 Compared to traditional sand washing processes, fabrics treated with the sand washing process of this invention exhibit significant advantages in various indicators: the fabric damage rate is drastically reduced from 10.2% to 0.8%, indicating that this process effectively protects the fiber structure and significantly reduces the risk of holes, tears, etc., making it particularly suitable for lightweight and fragile fabrics; the fuzz reduction rate reaches 94%, far exceeding the 42% of the traditional process, indicating that it has a superior treatment effect in terms of surface smoothness and hand feel; in addition, energy consumption is reduced from 0.82 kW h / kg to 0.28 kW h / kg, showing significant energy-saving effects, highlighting the outstanding advantages of this process in reducing production costs and improving energy utilization efficiency.

[0036] In step S3, rinsing and wastewater treatment are performed: After the abrasion treatment is completed, the material is thoroughly rinsed with clean water to remove residual enzymes, nano-abrasives, and reaction products, preventing contamination or impact on dyeing performance during subsequent processing. Simultaneously, the wastewater in the bio-enzyme treatment tank is filtered. Membrane filtration technology can be used to recover unreacted enzymes and some nanoparticles, achieving resource reuse and reducing the environmental burden. The filtered clean wastewater can then be discharged into a conventional wastewater treatment system.

[0037] The microscopic abrasion depth of fabrics treated with both traditional sand washing and the process of this invention was measured using a surface profilometer, and the distribution frequency of different depth ranges was statistically analyzed. Please refer to [link / reference]. Figure 5 In traditional sand washing processes, 58% of the areas show wear depths exceeding 5μm, indicating severe localized excessive wear, which can easily lead to fiber breakage, reduced fabric strength, and even holes; while only 17% of the areas show relatively light wear (depth below 3μm). In contrast, the process of this invention achieves a highly uniform and controllable micro-wear effect: 97% of the wear area is concentrated within 1μm to 3μm, of which 68% of the area has a wear depth between 0 and 1μm, effectively avoiding severe wear with a depth greater than 5μm.

[0038] Please see Figure 3 The illustration shows a macroscopic comparison of the same sample before and after treatment with the sand-washing process provided by this invention. (a) shows the fabric after treatment with the sand-washing process of this invention, and (b) shows the original fabric before sand-washing. The comparison clearly demonstrates that this invention achieves significant improvements in surface texture, visual gloss, and overall appearance uniformity.

[0039] exist Figure 3 In (b), the raw fabric surface exhibits noticeable fuzz and fiber bundle protrusions, with a clear but slightly rough texture and a matte luster, presenting an overall untreated and "stiff" feel. This is commonly seen in cotton, linen, or recycled fiber fabrics that have not undergone surface finishing. Figure 3 In (a), the fabric surface treated by the process of this invention has significantly reduced fuzz, and the fiber surface is smoother and more delicate, presenting a soft, micro-velvety feel. The formation of this delicate texture is due to the synergistic biopolishing effect of cellulase and laccase in S1, which selectively removes the amorphous areas on the fiber surface, combined with the controllable micro-friction of 5 g / L nano-silicon-based abrasive in S2 under the assistance of 35 kHz ultrasound, which precisely peels off loose microfibers and achieves low-damage repair.

[0040] Furthermore, the treated fabric exhibits a significantly enhanced luster, displaying a soft, silk-like sheen. This is due to the synergistic effect of bio-enzymes and nano-silicon-based abrasives, which smooths the micro-scratches on the fiber surface, reduces light scattering, and enhances reflected light. Simultaneously, the overall color of the fabric is more uniform, without localized whitening or streaking.

[0041] More importantly, despite the fine surface treatment, the structural integrity of the fabric was well maintained, without the common defects of traditional sand washing such as holes, snags, or local thinning. Figure 3 The invention provides direct verification of its significant effects on improving fabric surface smoothness, softness, visual luster, and uniformity of appearance, while effectively reducing the risk of damage to lightweight fabrics during sand washing. This fabric sand washing process is particularly suitable for high-end apparel, intimate apparel, and lightweight natural fiber fabrics that require high-quality materials.

[0042] The technical solution of this invention replaces strong mechanical friction with bio-enzyme pretreatment, combined with the uniform micro-wear of nano-silicon-based abrasives, avoiding the severe impact of traditional pumice on thin fabrics, effectively reducing the risk of fabric holes and tears, and effectively improving the fabric tear strength retention rate; the nano-silicon-based abrasives are evenly distributed under ultrasonic action, and the force is controllable, resulting in a fabric surface with delicate nap, soft hand feel, and natural luster, with a visual texture superior to traditional processes. Furthermore, the sand washing process of this invention does not require the use of large amounts of pumice, reducing solid waste and silicon dust pollution; the bio-enzyme preparation is biodegradable, reducing chemical pollution and minimizing wastewater treatment pressure.

[0043] In one embodiment, the bio-enzyme preparation in step S1 includes 2%–3% (owf) cellulase and 0.5%–1% (owf) laccase.

[0044] The bio-enzyme preparation in step S1 is a complex enzyme system, comprising cellulase and laccase. The amount of cellulase used is 2%–3% (owf, i.e., percentage by weight of the fabric); the amount of laccase used is 0.5%–1% (owf). This complex enzyme system of cellulase and laccase is particularly suitable for the sand washing pretreatment of cellulosic fabrics (such as cotton, linen, Tencel, etc.), enabling more efficient and controllable surface modification effects.

[0045] Cellulase primarily acts on the amorphous microfibers on the fiber surface, removing surface fuzz and impurities through hydrolysis, effectively achieving bio-polishing, making the fabric softer to the touch, and improving gloss clarity. Its dosage is controlled within the range of 2%–3% (owf) to ensure treatment effectiveness while avoiding excessive hydrolysis that could lead to a decrease in strength. Laccase can catalyze the oxidation of phenols or aromatic amines in the presence of oxygen. Although it does not directly hydrolyze cellulose, it can oxidize and decompose natural pigments or residual impurities on the fabric surface during sand washing, improving whiteness or dyeing uniformity; it promotes slight cross-linking or structural rearrangement on the fiber surface, enhancing fiber surface stability and reducing excessive fuzzing or pilling during subsequent abrasion processes; laccase and cellulase work synergistically to regulate enzymatic reaction kinetics, resulting in more uniform surface etching and improved consistency of the sand-washed texture.

[0046] By using a combination of cellulase and laccase, cellulase selectively removes the loose structure on the surface of the fibers, while laccase stabilizes the remaining fiber surface through oxidation, preventing excessive enzymatic hydrolysis or localized over-abrasion. The synergistic effect of these two methods significantly improves the appearance uniformity, hand feel smoothness, and strength retention of sand-washed fabrics, making them particularly suitable for lightweight, high-density cotton fabrics.

[0047] In one embodiment, the activity ratio of cellulase to laccase is 3:1.

[0048] In one embodiment, the wet fabric in step S1 is oscillated at a speed of 30 rpm between 40°C and 50°C for at least 30 minutes.

[0049] The optimal activity range for cellulase and laccase is 40℃ to 50℃. At this temperature, the enzyme molecules are conformably stable, exhibiting high catalytic efficiency. This allows for the effective hydrolysis of amorphous microfibers or surface impurities on the fiber surface, effectively avoiding the problems of decreased enzyme reaction rate, prolonged processing time, and low production efficiency caused by excessively low temperatures (<40℃), and the potential for enzyme protein denaturation and inactivation caused by excessively high temperatures (>50℃). High temperatures, however, have a significant impact on heat-sensitive laccases, potentially exacerbating fiber swelling and increasing the risk of mechanical damage.

[0050] The oscillation speed directly affects the mass transfer efficiency of the treatment solution and the stress state of the fabric. Using a low-speed oscillation of 30 rpm can accelerate the diffusion of enzyme solution and penetrant into the fiber interior, ensuring uniform treatment and avoiding local undertreatment or overtreatment. Compared with high-speed tumbling or strong water flow impact, 30 rpm is a gentle motion state. The fabric swings slowly or tumbles gently in the tank, which greatly reduces the friction and tensile stress between fibers and effectively prevents wrinkles, abrasions or tears of thin fabrics in a wet state.

[0051] By setting a shaking treatment time of at least 30 minutes, it is possible to ensure that the bio-enzyme preparation is fully adsorbed and acts on the fiber surface, completing the selective removal of surface fuzz; to ensure that the penetrant fully wets the fabric, and that the buffer stabilizes the system pH, ensuring the continuous stability of enzyme activity; for high-density or tightly structured lightweight fabrics, sufficient time can compensate for mass transfer resistance and avoid uneven treatment between the surface and the interior. In practical applications, the time can be adjusted within the range of 30 to 60 minutes depending on the type, thickness, weight of the fabric, and the required degree of sand washing. For example, 30 minutes can be used for sensitive fabrics such as microfiber or silk to control the intensity of the treatment; while for high-count, high-density cotton fabrics, the time can be extended to 45 to 60 minutes to enhance the softening effect.

[0052] In one embodiment, the penetrant is JFC with a concentration of 0.2 g / L.

[0053] The penetrant used in step S1 is JFC (i.e., fast penetrant T, chemical name: sodium alkyl sulfonate or fatty alcohol polyoxyethylene ether sulfate compound), with a concentration of 0.2 g / L in the treatment solution. JFC, as an anionic or nonionic / anionic composite surfactant, can significantly reduce the surface tension of aqueous solutions and improve the wetting ability of fibers. JFC has a small molecular structure and high diffusion rate, allowing it to penetrate fabric pores and fiber bundle gaps in a short time. JFC exhibits good stability in enzyme treatment systems and does not easily denature or inactivate enzyme proteins. JFC maintains good performance at 40–50℃ and in weakly acidic buffer systems.

[0054] In the bio-enzyme treatment stage of this invention, JFC enables wet fabrics to be rapidly soaked by the treatment solution, avoiding localized dry spots or uneven wetting; it helps the bio-enzyme preparation migrate quickly and evenly to the fiber surface and microporous structure, improving reaction efficiency; compared to high-foaming surfactants, JFC has moderate foaming properties, which, combined with low-speed oscillation, is beneficial for stable system operation. At a concentration of 0.2 g / L, JFC can achieve complete settling of common fabrics such as cotton, Tencel, and polyester-cotton blends within 3 minutes (according to the settling time test method), meeting the requirements of rapid and uniform wetting, while not affecting enzyme activity and subsequent wastewater treatment.

[0055] In one embodiment, the buffer is an acetate-sodium acetate buffer system, which is used to control the pH value in step S1 between 5.0 and 6.0.

[0056] The buffer used in step S1 is an acetate-sodium acetate buffer system. Its function is to stably control the pH of the bio-enzyme treatment solution between 5.0 and 6.0 to meet the activity requirements of commonly used bio-enzymes such as cellulase and laccase, ensuring efficient and stable bio-enzyme catalysis while also taking into account the chemical stability of the fabric. The acetate-sodium acetate buffer system has excellent buffering capacity in the pH range of 4.0–5.8, especially in the pH range of 5.0–6.0, where it can effectively resist pH fluctuations caused by solution dilution, the generation of enzyme reaction byproducts (such as organic acids), or the introduction of external impurities. Acetic acid and its salts do not denature enzyme proteins and will not inhibit the activity of cellulase or laccase. Sodium acetate is biodegradable, environmentally friendly, and meets the requirements of green processing. The acetate-sodium acetate buffer system will not cause precipitation, stratification, or inactivation when coexisting with surfactants and enzyme preparations such as JFC.

[0057] In one embodiment, the nano-silicon-based abrasive is silica aerogel.

[0058] Silica aerogel is a lightweight, porous material composed of a three-dimensional nano-silica network framework. Under ultrasonic cavitation, silica aerogel particles form high-frequency microjets, which undergo nanoscale rolling and scraping motions on the fabric surface. This selectively removes loosened surface microfibers after the bio-enzyme treatment in step S1, achieving a delicate and uniform napping effect and avoiding localized deep grooves or holes caused by traditional pumice. The porous network structure of silica aerogel has an elastic buffering effect; when it comes into contact with fibers, it can disperse local pressure, reduce the risk of stress concentration, and significantly reduce fiber breakage and fabric strength loss. Under the combined action of a penetrant and ultrasound, silica aerogel can form a stable suspension in water. After treatment, most particles can be removed by rinsing, and the small amount of residue is non-toxic and harmless, meeting the requirements for eco-textiles.

[0059] In one embodiment, the particle size of the nano-silicon-based abrasive is between 50 nm and 100 nm.

[0060] Nanoparticles with a diameter of less than 100 nm have entered the microfibril scale range (cotton fiber microfibrils are approximately 10–100 nm in diameter), and can be precisely applied to loose areas on the fiber surface with ultrasonic assistance. Compared to traditional pumice (millimeter-scale) or ordinary micropowder (greater than 500 nm), nano-silicon-based abrasives with a diameter between 50 nm and 100 nm are less likely to cause fiber tearing or fabric holes, effectively reducing the risk of physical damage. In addition, under the action of 20–40 kHz ultrasound, particles of 50 nm to 100 nm easily form a stable suspension, avoiding sedimentation; the microjets generated by the rupture of cavitation bubbles can effectively drive particles of this size to move uniformly on the fabric surface, improving processing consistency.

[0061] In one embodiment, the concentration of the nano-silicon-based abrasive is 5 g / L.

[0062] Under ultrasonic assistance, nano-silicon-based abrasives form a dynamic friction network on the fabric surface through cavitation flow. At a concentration of 5 g / L, the number of effective friction particles per unit area is sufficient, achieving a high fuzz reduction rate in a short time to meet high-quality sand washing requirements. This effectively avoids the problems of insufficient fuzz removal and uneven napping caused by sparse particle distribution and insufficient friction points when the concentration is too low (<2 g / L). It also avoids the problem of nanoparticles easily agglomerating or depositing on the fabric surface when the concentration is too high (>8 g / L), resulting in non-uniform friction under ultrasonic or oscillating action, which increases the risk of fiber damage. Furthermore, high concentrations can exacerbate equipment wear, increase the burden on subsequent rinsing, and lead to increased water and energy consumption.

[0063] In one embodiment, in step S2, the frequency of the ultrasonic treatment is 25 kHz to 40 kHz, and the treatment time is 15 min to 20 min.

[0064] Ultrasonic waves primarily function in liquids through cavitation, where high-frequency sound waves induce the generation, oscillation, growth, and violent collapse of microbubbles, generating localized high temperatures, high pressures, and high-speed microjets. This enhances mass transfer, disperses particles, and promotes micro-friction. The choice of frequency directly affects the cavitation intensity and scale. In the 25 kHz to 40 kHz frequency band, cavitation bubbles of moderate size and high collapse energy effectively drive nano-silicon-based abrasives (50–100 nm particle size) to form a dynamic micro-friction field on the fabric surface, enhancing lint removal efficiency. 50–100 nm particles are easily suspended and moved in a 25 kHz to 40 kHz sound field, preventing sedimentation or aggregation. Furthermore, industrial-grade ultrasonic cleaning / treatment equipment commonly operates in this frequency band, making it easy to integrate into existing washing production lines.

[0065] Furthermore, excessively short processing times result in insufficient ultrasonic action, uneven dispersion of nanoparticles, and failure of micro-friction to reach a steady state, leading to incomplete fuzz removal and uneven sand washing effects. Excessively long processing times (greater than 30 minutes) may cause localized temperature rise due to energy accumulation, affecting the stability of the system containing residual pre-enzyme treatments. A processing time of 15 to 20 minutes is sufficient to achieve effective friction coverage while avoiding excessive abrasion.

[0066] In one embodiment, after removing the nano-silicon-based abrasive in step S3, an initial cleaning is performed at 35°C to 45°C for a cleaning time of not less than 5 minutes. During the second cleaning, the pH value of the cleaning solution is controlled above 6.0, and 0.5 g / L of softener is added for a third cleaning.

[0067] In step S3, the primary purpose of the initial cleaning is to quickly and effectively remove nano-silicon-based abrasive particles, enzymatic hydrolysis products, and residual treatment solution adhering to the fiber surface and fabric pores. The temperature is controlled at 35℃–45℃, slightly lower than the enzyme treatment temperature (40–50℃), to prevent sudden cooling and shrinkage or wrinkling of the fibers due to excessive temperature differences. Maintaining a certain amount of heat helps improve the diffusion rate of water molecules and the particle desorption capacity, promoting the peeling of nano-silicon-based abrasive particles from the fiber surface. The cleaning time is no less than 5 minutes, and combined with water rinsing or agitation, it can remove most suspended particles and soluble impurities.

[0068] A second wash is performed after the initial wash. A small amount of alkaline buffer (such as sodium bicarbonate or sodium citrate) or a weakly alkaline detergent can be added to neutralize and remove residual acidic substances, adjusting the fabric surface microenvironment to neutral or weakly alkaline. In step S1, an acetate-sodium acetate buffer system (pH 5.0–6.0) is used. Although rinsing may result in trace amounts of acidic components remaining; residual acid may act on cellulose fibers over a long period, leading to slow hydrolysis during humid and hot storage, reducing fabric strength. Adjusting the pH of the second wash solution to above 6.0 (preferably 6.0–7.5) can effectively remove residual H+. + ion.

[0069] A third wash is performed after the second wash. During this third wash, a fabric softener is applied, which distributes evenly in the water flow, adheres to the fiber surface, forms a lubricating film, and reduces the coefficient of friction between fibers. This improves the fabric's fluffiness, smoothness, and antistatic properties. The softener can be an organosilicone microemulsion with a particle size of 0.1 μm or less to enhance the fabric's feel; cationic (such as quaternary ammonium salts) or nonionic (such as polysiloxane emulsions) softeners can also be used.

[0070] The multi-stage cleaning process effectively removes nano-silicon-based abrasives, biological enzyme residues, and acidic components, ensuring the cleanliness and ecological safety of the fabric. A softener is added at the end of the cleaning process to achieve precise control of the hand feel and compensate for the dryness that may be caused by sand washing.

[0071] In one embodiment, in step S3, a ceramic membrane with a pore size of 0.1 μm is used to filter the wastewater in the bio-enzyme treatment tank.

[0072] By using a 0.1μm ceramic membrane to filter sand washing wastewater, the efficient recovery and recycling of bio-enzymes and nano-silicon-based abrasives were achieved, with a water recycling rate of ≥85%, which significantly reduced raw material consumption and wastewater treatment costs and improved process sustainability.

[0073] In one implementation, please refer to Figure 2 Before step S1, step S4 is also included: immersing the fabric in warm water at 40°C to 50°C for at least 10 minutes, and obtaining a wet fabric after immersion, with a moisture content of 55% to 65%.

[0074] The process includes step S4 before step S1. This pre-wetting treatment step is used to achieve uniform wetting and thermal equilibrium of the fabric, providing stable and uniform starting conditions for subsequent bio-enzyme treatment, thus ensuring the efficiency of bio-enzyme action and the uniformity of sand washing. Warm water is used for immersion, with the temperature range matching the optimal temperature range (40–50℃) for the bio-enzyme treatment in subsequent step S1. The immersion time is greater than 10 minutes to ensure that the moisture fully penetrates into the fiber interior and deep layers of the fabric structure, avoiding dry spots or uneven wetting. The moisture content of the wet fabric is 55%–65% (all moisture contents mentioned herein are wet basis moisture contents, i.e., the percentage of water mass to the total mass of the wet fabric), ensuring that the fibers are fully swollen but not excessively liquid-laden.

[0075] In one implementation, please refer to Figure 2 After step S3, step S5 is also included: radio frequency drying of the wet fabric, and the moisture content of the dried fabric does not exceed 8%; wherein, the temperature during the drying process does not exceed 60°C, and the relative humidity of the environment goes through at least two stages of gradual decrease in sequence, forming a humidity gradient from high to low.

[0076] Step S5 is used to achieve rapid, uniform, and low-damage dehydration, particularly suitable for lightweight, high-density, or structurally sensitive fabrics treated with bio-enzymes and nano-sand washing, ensuring efficient final drying while maintaining a soft feel and structural integrity. Radio frequency (RF) drying is a volumetric heating drying technology based on electromagnetic field action. It uses a high-frequency alternating electric field to cause rapid oscillation and frictional heat generation of water molecules within the material, achieving uniform heating and dehydration from the inside out. RF drying involves simultaneous internal and external heating, resulting in uniform moisture distribution; the overall temperature is ≤60℃, providing good fiber protection; it is fast and has strong penetration, leaving fabrics smooth, low-stress, and with minimal damage. RF drying is particularly suitable for the finely processed high-end fabrics of this invention, preventing hardening, wrinkling, or decreased strength due to improper drying. The relative humidity during the drying process undergoes at least two progressively decreasing stages. This staged control of relative humidity helps achieve uniform dehydration and prevents wrinkles and stress concentration. The humidity gradient can be achieved through intelligent control systems that regulate air circulation within the drying chamber, condensation dehumidification, or nitrogen replacement.

[0077] In one embodiment, the humidity gradient includes three stages, with the relative humidity of the three stages decreasing from high to low as 70% RH, 50% RH, and 30% RH.

[0078] By implementing three-stage humidity control to precisely adjust the moisture partial pressure of the drying environment, the wet fabric can be dehydrated gradually and with low stress during the radio frequency drying process, effectively avoiding uneven fiber shrinkage, fabric wrinkles, and deterioration of hand feel caused by excessively rapid moisture migration.

[0079] The first stage involves high-humidity pre-drying under 70% RH conditions. During this stage, the fabric is still in a high-moisture state. By maintaining a high-humidity environment of 70% RH, the surface evaporation rate is matched with the internal moisture diffusion rate, achieving equal-speed drying. At the same time, radio frequency energy preferentially acts on free water, rapidly heating it and promoting the outward migration of moisture, avoiding local over-drying.

[0080] The second stage involves transitional dehydration at 50% RH. During this stage, free water is largely removed, and moisture mainly exists in the fiber micropores and amorphous regions as bound water. By reducing the RH to 50%, the driving force for moisture evaporation is moderately increased, promoting the migration of bound water from the fiber interior to the surface. Radio frequency heating continues to provide an internal heat source, avoiding the heat transfer bottleneck of external heat and internal cold in traditional drying processes. This effectively prevents the fabric surface from being dry while the interior remains wet, ensuring uniform moisture distribution.

[0081] The third stage involves final drying and setting at 30% RH. At this stage, the low moisture content naturally slows down the evaporation rate. By further reducing the RH to 30%, the partial pressure difference of water vapor between the air and the fibers is increased, serving as the final driving force to completely remove residual bound water. This also helps stabilize the fiber morphology and complete the dimensional setting. After drying, the fabric moisture content can be stably controlled within the range of 6%–8%, meeting the requirements for storage and subsequent processing.

[0082] Of course, in other embodiments, the relative humidity of the environment in at least two gradually decreasing stages can also be 65% RH, 40% RH, 25% RH, etc.

[0083] In one embodiment, the radio frequency field strength during the drying process is 15 kV / m.

[0084] Radio frequency drying utilizes a high-frequency alternating electromagnetic field (13.56 MHz) to act on the fabric.

[0085] At an electric field strength of 15 kV / m, water molecules acquire sufficient oscillatory energy, resulting in a high heat generation rate per unit time and significantly shortening the drying time. Energy utilization is high, with unit energy consumption lower than conventional drying methods. At 15 kV / m, the internal temperature rise is controllable (≤60℃), preventing fiber yellowing, embrittlement, or a significant decrease in strength. For fabrics with a loosened structure after enzyme treatment, this electric field strength can complete dehydration without exacerbating the risk of microfiber breakage.

[0086] In one implementation, please refer to Figure 2 The fabric sand washing process includes the following steps: S4: Pre-wetting treatment: Immerse the fabric to be treated in warm water at 40°C to 50°C for at least 10 minutes. After immersion, obtain a wet fabric with a moisture content controlled between 55% and 65%. S1: Bio-enzyme treatment: Transfer the wet fabric obtained in S4 to a bio-enzyme treatment tank, add bio-enzyme preparation, wherein the amount of cellulase is 2%–3% (owf) and the amount of laccase is 0.5%–1% (owf); at the same time, add penetrant JFC 0.2 g / L and an acetate-sodium acetate buffer system as pH adjuster, control the pH value of the treatment solution in the range of 5.0–6.0, and shake for at least 30 minutes at a temperature of 40℃–50℃ and a rotation speed of 30 rpm; S2: Nano-synergistic ultrasonic abrasion treatment: 5 g / L of nano-silicon-based abrasive is added, and ultrasonic abrasion is performed at a frequency of 35 kHz and a sound intensity of 1.5 W / cm². 2 Ultrasonic treatment for 15–20 minutes under a power density of 0.8 W / L; S3: Multi-stage cleaning and wastewater treatment: The fabric treated with S2 is initially cleaned for 5 minutes at 40℃; during the second cleaning, the pH of the cleaning solution is adjusted to 6.0 to neutralize residual acidic components; 0.5 g / L of softener is added during the third cleaning; during the cleaning process, a ceramic membrane with a pore size of 0.1 μm is used to filter the waste liquid in the bio-enzyme treatment tank. S5: Radio Frequency Drying and Shaping: The washed wet fabric is dried with radio frequency, with an applied radio frequency field strength of 15 kV / m and a drying temperature not exceeding 60℃. The moisture content of the dried fabric does not exceed 8%. During the drying process, the relative humidity of the environment gradually decreases through three stages: 70% RH, 50% RH, and 30% RH, forming a humidity gradient from high to low.

[0087] The present invention also proposes a sand-washed fabric, which is obtained by the aforementioned fabric sand-washing process.

[0088] In one embodiment, the sand-washed fabric is cotton, linen, or recycled fiber fabric.

[0089] The sand-washed fabric is made of cotton, linen, or regenerated cellulose fibers. These fabrics all use cellulose as their main chemical component and have similar molecular structures and physical properties. After being treated with the sand-washing process employed in this invention, cotton, linen, or regenerated cellulose fiber fabrics can all achieve a highly efficient, low-damage, and high-quality sand-washing effect. Specifically, cotton becomes soft to the touch and has improved pilling resistance; linen has a smooth surface, significantly reducing itchiness and providing a silky feel; and the surface of the regenerated fibers forms a fine nap, enhancing the three-dimensional effect and comfort.

[0090] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A fabric sand washing process, characterized in that, Includes the following steps: S1: Place the wet fabric in a bio-enzyme treatment tank, add bio-enzyme preparation, penetrant and buffer, and perform shaking treatment; S2: Add nano-silicon-based abrasive to the bio-enzyme treatment tank and turn on the ultrasonic wave for wear treatment; S3: Rinse the treated fabric and filter the wastewater in the bio-enzyme treatment tank.

2. The fabric sand washing process as described in claim 1, characterized in that, The bio-enzyme preparation in step S1 comprises 2%–3% (owf) cellulase and 0.5%–1% (owf) laccase; And / or, the wet fabric in step S1 is oscillated at a speed of 30 rpm between 40°C and 50°C for at least 30 minutes.

3. The fabric sand washing process as described in claim 1, characterized in that, The penetrant is JFC, and its concentration is 0.2 g / L; And / or, the buffer is an acetate-sodium acetate buffer system, which is used to control the pH value in step S1 between 5.0 and 6.

0.

4. The fabric sand washing process as described in claim 1, characterized in that, The nano-silicon-based abrasive is silica aerogel; And / or, the particle size of the nano-silicon-based abrasive is between 50 nm and 100 nm; And / or, the concentration of the nano-silicon-based abrasive is 5 g / L; And / or, in step S2, the frequency of the ultrasonic treatment is 25 kHz to 40 kHz, and the treatment time is 15 min to 20 min.

5. The fabric sand washing process as described in claim 1, characterized in that, In step S3, after removing the nano-silicon-based abrasive, the first cleaning is performed at 35°C to 45°C for a time of not less than 5 minutes. During the second cleaning, the pH value of the cleaning solution is controlled above 6.0, and 0.5 g / L of softener is added for a third cleaning. And / or, in step S3, a ceramic membrane with a pore size of 0.1 μm is used to filter the wastewater in the bio-enzyme treatment tank.

6. The fabric sand washing process as described in claim 1, characterized in that, Before step S1, step S4 is also included: immersing the fabric in warm water at 40°C to 50°C for at least 10 minutes, and obtaining a wet fabric after immersion, with a moisture content of 55% to 65%.

7. The fabric sand washing process as described in claim 1, characterized in that, Step S5 is included after step S3: radio frequency drying of the wet fabric, and the moisture content of the dried fabric does not exceed 8%; wherein the temperature during the drying process does not exceed 60°C, and the relative humidity of the environment goes through at least two stages of gradual decrease, forming a humidity gradient from high to low.

8. The fabric sand washing process as described in claim 7, characterized in that, The humidity gradient includes three stages, with the relative humidity of the environment in the three stages decreasing from high to low as 70% RH, 50% RH, and 30% RH. And / or, the radio frequency field strength during the drying process is 15 kV / m.

9. A sand-washed fabric, characterized in that, The sand-washed fabric is obtained by the fabric sand-washing process described in any one of claims 1 to 8.

10. The sand-washed fabric as described in claim 9, characterized in that, The sand-washed fabric is made of cotton, linen, or recycled fiber.

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