A low-water-consumption alkali-reduced microfiber washing method

Abstract

The invention discloses a low-water-consumption alkali-reduction microfiber washing method, which relates to the technical field of sea-island fiber alkali-reduction treatment methods. The invention comprises the following steps: reducing the sea-island fiber to be treated in a NaOH reducing liquid, squeezing out the reducing liquid, and drying the fiber in an oven; putting the fiber into hot water to wash the remaining COPET and the NaOH introduced during the reduction; using an extrusion roller to extrude the washing liquid carried out from the microfiber synthetic leather, controlling the liquid carrying rate of the microfiber synthetic leather during the process, and reducing the amount of NaOH carried; washing the microfiber synthetic leather at room temperature after squeezing out the residual liquid while the leather is still hot, utilizing the temperature difference between residual heat after hot water washing and the washing liquid at room temperature to accelerate the release of NaOH from the surface of the microfiber synthetic leather, and extruding and drying the microfiber synthetic leather after the room-temperature washing to complete the alkali reduction. The invention cleverly utilizes the accelerated transfer effect of concentration difference and temperature difference, saves water for alkali reduction, and also reduces the discharge and treatment of wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of sea-island fiber alkali reduction treatment methods, in particular to a low-water-consumption alkali reduction microfiber washing method. Background Art

[0002] Microfiber, or ultrafine fiber, refers to fibers with a single filament fineness of less than 1Dtex. The fineness of microfiber is much lower than that of conventional fibers. In the field of synthetic leather, microfiber can mimic the collagen fibers of natural leather in a three-dimensional structure. This results in microfiber synthetic leather having a rich, elastic feel similar to leather. Microfiber synthetic leather also has excellent moisture permeability and has great market potential.

[0003] Island-in-the-sea fibers are a key raw material for producing microfibers. They contain both sea and island components. When the sea component is removed, the remaining island components are microfibers. The process of removing the sea component from island-in-the-sea fibers is called weight reduction. Currently, there are three common weight reduction methods: toluene weight reduction, alkali weight reduction, and hot water weight reduction. Toluene weight reduction requires the use of large amounts of the toxic solvent toluene, while the spinning and non-woven processes that support hot water weight reduction are currently immature. Alkaline weight reduction, on the other hand, is a relatively well-established microfiber production process. This process is solvent-free, making it a green and environmentally friendly method for producing microfibers.

[0004] The general process of alkali reduction is to immerse the microfiber in a high-temperature alkali solution at about 100°C. The microfiber will absorb the alkaline components in the alkali solution, and the pH of the microfiber non-woven fabric can reach 14 when the reduction process is completed. At present, the process of alkali reduction of microfiber is divided into intermittent alkali reduction process and flat-width continuous alkali reduction process. Among them, the intermittent alkali reduction process can be adapted to the reduction of various styles of alkali-reduced microfibers, and the reduction effect is more sufficient, so it is relatively more widely used. However, the intermittent alkali reduction process consumes a lot of water. It takes about 60 tons of water to produce 1 ton of microfiber, of which 50% of the water is generated in the washing step after the reduction.

[0005] Due to the high specific surface area of ultrafine fibers, a large amount of clean water is used to wash ultrafine fiber non-woven fabrics. The current solution to reduce water consumption is to use acidic substances for neutralization. By using neutralization, the water consumption of 1 ton of ultrafine fibers can be reduced to 30 tons. For example, the announcement number is CN111691105B, and the name is an invention patent for an alkali reduction production process for continuous production of ultrafine fibers. It discloses a technical solution of acid neutralization after alkali reduction washing, in which the acid can be tartaric acid, oxalic acid, malic acid, citric acid, benzoic acid, salicylic acid, caffeic acid, etc.; but on the one hand, the acidic environment will corrode the equipment, and on the other hand, the acidic substances will react with some fillers commonly used in ultrafine fibers, such as light calcium carbonate, which may destroy the filler properties. Therefore, there is an urgent need for a low-water-consumption alkali reduction ultrafine fiber washing method to solve this problem. Summary of the Invention

[0006] The object of the present invention is to provide a low-water-consumption alkali-weighted microfiber washing method to solve the problem of large water consumption in the intermittent alkali-weighted washing process.

[0007] To achieve the above object, the present invention provides the following technical solution: a low-water-consumption alkali-reduced microfiber washing method, comprising the following steps:

[0008] S1: The COPET / PET sea-island fiber nonwoven fabric to be treated and impregnated is reduced in a NaOH reducing solution, wherein the concentration of the NaOH reducing solution is 2-5%, the reducing temperature is 90-110° C., and the reducing time is 10-40 min. After the reducing is completed, a microfiber synthetic leather is obtained, and the reducing solution brought out of the microfiber synthetic leather is squeezed out with an extrusion roller. The microfiber synthetic leather is then dried in an oven at a temperature of 100-130° C. for 10-15 min.

[0009] S2 puts the dried microfiber synthetic leather after weight reduction into hot water at 90-100°C to wash the remaining COPET and NaOH introduced during weight reduction;

[0010] S3 uses a squeezing roller to squeeze out the washing liquid from the microfiber synthetic leather. During the process, the liquid carrying rate of the microfiber synthetic leather is controlled to reduce the amount of NaOH carried;

[0011] S4 washes the microfiber synthetic leather at room temperature after squeezing out the residual liquid while it is still hot, and uses the temperature difference between the residual heat after hot water washing and the room temperature water washing liquid to accelerate the release of NaOH from the surface of the microfiber synthetic leather. The microfiber synthetic leather after room temperature water washing is squeezed and dried to complete alkali reduction.

[0012] Preferably, in the above step S3, the squeezing roller is extruded with a pressure of 0.8 to 1 MPa, and the liquid carrying rate of the microfiber synthetic leather after extrusion is 100 to 220%.

[0013] Preferably, in step S2, 5 parts by weight of wastewater is generated for each part by weight of COPET / PET type island fiber nonwoven fabric before impregnation, and in step S4, 10 parts by weight of wastewater is generated for each part by weight of COPET / PET type island fiber nonwoven fabric before impregnation.

[0014] In the above preferred embodiments, the hot water washing time in step S2 is 10 minutes; in step S4, the room temperature washing temperature is 20-30°C, and the room temperature washing time is 10 minutes.

[0015] In the above schemes, the components of the impregnation liquid preferably include, by weight, 100 parts of aqueous polyurethane, 100-200 parts of water, 1-3 parts of silicone wetting agent, 0.3-1.2 parts of polysiloxane defoaming agent, 1-6 parts of crosslinking agent, 3-16 parts of light calcium carbonate filler, and 5-10 parts of alkali-swellable thickener.

[0016] In the preferred embodiment, the impregnation liquid components are uniformly stirred by mechanical stirring to obtain an impregnated slurry, and the impregnated slurry is uniformly filled into the sea-island fiber nonwoven fabric and dried to form a sea-island fiber / polyurethane three-dimensional structure.

[0017] Preferably, in step S1, after the reduction is completed, the sea component in the ultrafine fiber synthetic leather accounts for 3-5% by mass.

[0018] Preferably, in step S4, after the microfiber synthetic leather washed with water at room temperature is squeezed, the pH value of the surface tested by the test paper is 7.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The low-water-consumption alkali-reduced microfiber washing method has simple and reasonable process steps, a short alkali-reduction process, and a short total time. After NaOH reduction, the microfiber is dried and washed once in hot water. Due to the rapid movement of polymers at temperature and the greater concentration difference between alkali and water in the dried microfiber, the washing is faster. After the residual liquid is squeezed out, the microfiber is directly put into cold water for normal temperature washing while hot. The temperature difference accelerates the diffusion of the alkali solution into the cold water tank. After the hot and cold washings, the surface of the material can reach a neutral level, avoiding repeated washing and squeezing operations. The present invention cleverly utilizes the accelerated transmission effect of the concentration difference and the temperature difference, saves water for alkali reduction, and also reduces the discharge and treatment of wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the process flow of the alkali-reduced microfiber washing method of the present invention. DETAILED DESCRIPTION

[0022] See Figure 1 A low-water-consumption alkali-reduced microfiber washing method comprises the following steps:

[0023] S1: The COPET / PET sea-island fiber nonwoven fabric to be treated and impregnated is reduced in a NaOH reducing liquid, wherein the concentration of the NaOH reducing liquid is 2-5%, the reducing temperature is 90-110° C., and the reducing time is 10-40 min. After the reducing is completed, a microfiber synthetic leather is obtained, and the reducing liquid brought out of the microfiber synthetic leather is squeezed out by a squeezing roller. The microfiber synthetic leather is then dried in an oven at a temperature of 100-130° C. for 10-15 min. There are no special requirements for squeezing with a squeezing roller, which is only a preparatory work before drying. It is also possible not to squeeze, but the drying time may be prolonged. For reference, the squeezing roller can be squeezed with a pressure of 0.8-1 MPa, or it can be adjusted by itself.

[0024] S2 puts the dried microfiber synthetic leather after weight reduction into hot water at 90-100°C to wash the remaining COPET and NaOH introduced during weight reduction;

[0025] S3 uses an extrusion roller to squeeze out the washing liquid from the microfiber synthetic leather. During the process, the liquid carrying rate of the microfiber synthetic leather is controlled to reduce the amount of NaOH carried. For reference, the extrusion roller is extruded with a pressure of 0.8-1MPa, which can specifically control the liquid carrying rate of the microfiber synthetic leather after extrusion to be 100-220%.

[0026] S4 washes the microfiber synthetic leather at room temperature after squeezing out the residual liquid while it is still hot, and uses the temperature difference between the residual heat after hot water washing and the room temperature water washing liquid to accelerate the release of NaOH from the surface of the microfiber synthetic leather. The microfiber synthetic leather after room temperature water washing is squeezed and dried to complete alkali reduction.

[0027] Using the above method, the hot water washing process produces 5 parts by weight of wastewater per part by weight of the COPET / PET type island fiber nonwoven fabric before impregnation; the normal temperature water washing process produces 10 parts by weight of wastewater per part by weight of the COPET / PET type island fiber nonwoven fabric before impregnation; that is, a total of 15 parts by weight of wastewater / part by weight of the island fiber.

[0028] In a preferred embodiment, the hot water washing time is 10 minutes. This time is only a recommendation and can be adjusted, for example, to 5 to 15 minutes or longer. However, for process efficiency considerations, 10 minutes is sufficient. 5 minutes or shorter may result in insufficient reduction or excessive NaOH residue.

[0029] In a preferred embodiment, the temperature of room temperature water washing can be 20-30°C, and the room temperature water washing time is 10 minutes. Similarly, this time is only a recommended reference and can be adjusted specifically, for example, 5 minutes, 8 minutes, 12 minutes, etc. Using the method of the present invention, the room temperature water washing process can usually quickly make the pH of the surface of the final extruded microfiber synthetic leather reach 7.

[0030] In addition, the solution of the present invention does not require acid washing, has a fast cleaning speed, and will not destroy the properties of the impregnated filler. Further preferably, the impregnation liquid components, by weight, preferably include 100 parts of aqueous polyurethane, 100-200 parts of water, 1-3 parts of silicone wetting agent, 0.3-1.2 parts of polysiloxane defoaming agent, 1-6 parts of crosslinking agent, 3-16 parts of light calcium carbonate filler, and 5-10 parts of alkali-swellable thickener.

[0031] Generally, the components of the impregnation liquid are uniformly stirred mechanically to obtain an impregnated slurry, which is then uniformly filled into the sea-island fiber nonwoven fabric and dried to form a sea-island fiber / polyurethane three-dimensional structure.

[0032] In addition, the above-mentioned specific control of the concentration of the NaOH reducing liquid, the reducing temperature, and the reducing time in the alkali reduction is the preferred combination obtained by the present invention after a large number of experiments, which can control the mass ratio of the sea component in the obtained ultrafine fiber synthetic leather at the end of the reduction to be within a range suitable for the next step of hot water washing; for reference, for example, the sea component in the sea island fiber accounts for about 30% of the weight of the sea island fiber. Under the scheme given in the present invention, the mass ratio of the sea component in the ultrafine fiber synthetic leather obtained at the end of the reduction can be controlled to be 3-5%.

[0033] The technical solutions and effects of the present invention are further illustrated below through several embodiments. It should be noted that the following are not all embodiments of the present invention, but are only randomly selected samples from many embodiments. They are representative but should not be understood as absolute limitations on the present invention.

[0034] Since the main purpose of the present invention is to reduce water consumption rather than to improve the reduction rate and other effects, the main design experiment is to prove whether the cleaning after the reduction is sufficient. The pH test results of the material surface after the last cleaning and before the final drying are used as proof. The final extrusion step uses the same extrusion roller operation, 1MPa pressure, uniform speed and the same roller time to ensure that the pH test conditions are as close as possible.

[0035] In the following examples and comparative examples, since the proportion of the impregnation liquid components has almost no effect on the amount of water used for alkali reduction, a fixed proportion is used as an example control variable. Specifically, the raw materials of the impregnation liquid components are calculated by weight as follows: 100 parts of water-based polyurethane using Zhongke Henry AK-01A with a modulus lower than 3MPa, 150 parts of water, 1 part of silicone wetting agent using Dow Chemical 5211, 0.75 parts of polysiloxane defoaming agent using Stahl DF-2459, and 3 parts of crosslinking agent using St. Tal carbodiimide 5580, 12 parts of light calcium carbonate filler using Anhui Xueling 1250 mesh calcium carbonate, and 7 parts of alkali-soluble thickener using BYK-HV80; the sea-island fiber adopts the common commercial ratio, that is, the sea component in the COPET / PET type sea-island fiber non-woven fabric accounts for 30% of the total mass. The non-woven fabric is divided into multiple portions by weight of 50g per portion (about the size of an A4 sheet), and the above impregnation liquid is evenly filled and dried to obtain the samples to be treated. The samples are divided into 5 groups, each with multiple portions.

[0036] Example 1:

[0037] Take the first sample of the first group to be treated, and reduce it in a NaOH reducing liquid. The concentration of the NaOH reducing liquid is 5%, the reducing temperature is 100°C, and the reducing time is 30 min. After the reduction, a microfiber synthetic leather is obtained. The reducing liquid is squeezed out with an extrusion roller, and then the microfiber synthetic leather is dried in an oven at 110°C for 10 min. The microfiber synthetic leather dried after reduction is put into 5 kg of 100°C hot water for 10 min. The washing liquid brought out of the microfiber synthetic leather is squeezed out with an extrusion roller, and the pressure between the rollers is 1 MPa. The liquid carrying rate of the microfiber synthetic leather after extrusion is controlled to be 100-220%; while hot, the microfiber synthetic leather is quickly moved to a 10 kg The samples were washed at room temperature for 10 minutes in 20°C water, and the washing liquid brought out from the microfiber synthetic leather was squeezed out again. The surface pH was tested with pH paper and was 7. The reduction operation of the 2nd to 21st 50g samples to be treated in the first group was repeated according to the same parameters, and they were all washed in the first hot water wash and room temperature water wash in turn. After washing at room temperature, the washing liquid brought out from the microfiber synthetic leather was squeezed out, and the surface pH of the 2nd to 20th samples was measured with pH paper to be 7, and the surface pH of the 21st sample was 8, that is, 20 samples to be treated generated a total of 15kg of wastewater, and each 50g of sea island fiber before impregnation generated 750g of wastewater.

[0038] Example 2:

[0039] Take the first portion of the sample to be treated in the second group and reduce it in a NaOH reducing liquid. The concentration of the NaOH reducing liquid is 3%, the reducing temperature is 110°C, and the reducing time is 40 min. After the reduction, a microfiber synthetic leather is obtained. The reducing liquid is squeezed out with an extrusion roller, and then the microfiber synthetic leather is dried in an oven at a temperature of 100°C for 15 min. The microfiber synthetic leather dried after reduction is put into 5 kg of 100°C hot water for 10 min. The washing liquid brought out of the microfiber synthetic leather is squeezed out with an extrusion roller, and the pressure between the rollers is 0.9 MPa. The liquid carrying rate of the microfiber synthetic leather after extrusion is controlled to be 100-220%; while hot, the microfiber synthetic leather is quickly moved to a 10 kg The samples were washed at room temperature for 10 minutes in 23°C water, and the washing liquid brought out from the microfiber synthetic leather was squeezed out again. The surface pH was tested with pH paper and was 7. The reduction operation of the 2nd to 21st 50g samples to be treated in the second group was repeated according to the same parameters, and they were all washed in the first hot water wash and room temperature water wash in turn. After washing at room temperature, the washing liquid brought out from the microfiber synthetic leather was squeezed out, and the surface pH of the 2nd to 20th samples was measured with pH paper to be 7, and the surface pH of the 21st sample was 8, that is, 20 samples to be treated generated a total of 15kg of wastewater, and each 50g of sea island fiber before impregnation generated 750g of wastewater.

[0040] Example 3:

[0041] Take the first sample to be treated in the third group and reduce it in a NaOH reducing liquid. The concentration of the NaOH reducing liquid is 5%, the reducing temperature is 110°C, and the reducing time is 20 min. After the reduction, a microfiber synthetic leather is obtained. The reducing liquid is squeezed out with an extrusion roller, and then the microfiber synthetic leather is dried in an oven at a temperature of 130°C for 10 min. The microfiber synthetic leather dried after reduction is put into 5 kg of 90°C hot water for 10 min. The washing liquid brought out of the microfiber synthetic leather is squeezed out with an extrusion roller, and the pressure between the rollers is 1 MPa. The liquid carrying rate of the microfiber synthetic leather after extrusion is controlled to be 100-220%; while hot, the microfiber synthetic leather is quickly moved to a 10 kg The samples were washed at room temperature for 10 minutes in 25°C water, and the washing liquid brought out from the microfiber synthetic leather was squeezed out again. The surface pH was tested with pH paper and was 7. The reduction operation of the 2nd to 21st 50g samples to be treated in the third group was repeated according to the same parameters, and they were all washed in the first hot water wash and the room temperature wash in turn. After washing at room temperature, the washing liquid brought out from the microfiber synthetic leather was squeezed out, and the surface pH of the 2nd to 20th samples was measured with pH paper to be 7, and the surface pH of the 21st sample was 8, that is, 20 samples to be treated generated a total of 15kg of wastewater, and each 50g of sea island fiber before impregnation generated 750g of wastewater.

[0042] Comparative Example 1:

[0043] Reduction: Take the first sample to be treated in the fourth group and reduce it in NaOH reducing solution. The concentration of NaOH reducing solution is 5%, the reducing temperature is 100℃, and the reducing time is 30min.

[0044] Rolling: Use squeezing rollers to squeeze out the water washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after squeezing is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 14.

[0045] Initial washing: transfer the microfiber synthetic leather to a primary washing container filled with 10 kg of 20°C water and wash for 10 minutes;

[0046] Initial rolling: Use squeezing rollers to squeeze out the water washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after extrusion is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 11.

[0047] Rewash: Transfer the microfiber synthetic leather to a secondary washing container filled with 10 kg of 20°C water and wash for 10 minutes;

[0048] Re-rolling: Use the squeezing roller to squeeze out the washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after squeezing is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 8.

[0049] Final washing: transfer the microfiber synthetic leather to a three-wash container filled with 10 kg of 20°C water and wash for 10 minutes;

[0050] Final rolling: Use squeezing rollers to squeeze out the washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after squeezing is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 7.

[0051] Continue to use the above steps and one to three water washings to treat the 2nd to 11th samples to be treated in the 4th group in turn, among which the 2nd to 5th samples to be treated can maintain a pH of 11 after initial rolling and a pH of 7 after final rolling. The pH of the 6th to 8th samples to be treated is between 12 and 13 after initial rolling, and is between 9 and 10 after re-rolling. The pH can reach 7 after final rolling. The pH of the 9th and 10th samples to be treated is 13 after initial rolling, and is between 10 and 11 after re-rolling. The pH can reach 7 after final rolling. The pH of the 11th sample to be treated is between 13 and 14 after initial rolling, and is 11 after re-rolling. The pH is 8 after final rolling. That is, after treating 10 batches, the three pools of water must be replaced, generating a total of 30 kg of wastewater, corresponding to 3 kg of wastewater for every 50 g of sea island fiber before impregnation.

[0052] Comparative Example 2:

[0053] Reduction: Take the first sample to be treated in the fifth group and reduce it in a NaOH reducing solution. The concentration of the NaOH reducing solution is 5%, the reducing temperature is 100℃, and the reducing time is 30min.

[0054] Rolling: Use squeezing rollers to squeeze out the water washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after squeezing is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 14.

[0055] Washing: Transfer the microfiber synthetic leather to a primary washing container filled with 20 kg of 20°C water and wash for 10 minutes;

[0056] Initial rolling: Use squeezing rollers to squeeze out the water washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after extrusion is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 10.

[0057] Weak acid washing: transfer the microfiber synthetic leather to 10 kg of 5% citric acid solution and wash with weak acid for 10 minutes;

[0058] Re-rolling: Use the squeezing roller to squeeze out the washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after squeezing is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 8.

[0059] Washing: Transfer the microfiber synthetic leather to a secondary washing container filled with 10 kg of 20°C water and wash for 10 minutes;

[0060] Final rolling: Use squeezing rollers to squeeze out the washing liquid from the microfiber synthetic leather. The pressure between the rollers is 1MPa. The liquid carrying rate of the microfiber synthetic leather after squeezing is controlled at 100-220%. After rolling, the surface pH is tested with pH test paper to be 7.

[0061] Continue to use the above steps, two water washings and weak acid to treat the 2nd to 21st samples to be treated in group 5 in turn, among which the 2nd to 12th samples to be treated can maintain a pH of 10 after initial rolling and a pH of 7 after final rolling. The pH of the 13th to 17th samples to be treated is 11 after initial rolling, 9 after re-rolling, and 7 after final rolling. The pH of the 18th to 20th samples to be treated is 12 after initial rolling, and the pH is between 10 and 11 after re-rolling. The pH can reach 7 after final rolling. The pH of the 21st sample to be treated is 13 after initial rolling, 11 after re-rolling, and 8 after final rolling. After processing 20 batches, the water and citric acid must be replaced. In addition to citric acid, a total of 30 kg of wastewater is generated, corresponding to 1.5 kg of wastewater for every 50 g of sea island fiber before impregnation.

[0062] In Examples 1 to 3 of the present invention, the material surface pH reaches 7, and the water consumption is 15 times the mass of the sea island fiber. Comparative Examples 1 and 2 are two common existing intermittent alkali reduction washing methods. Among them, the repeated washing and rolling operation of Comparative Example 1 makes the pH value of each washing easily become high, and more wastewater is generated. The improved weak acid washing in Comparative Example 2 can speed up the washing progress, but it still needs to generate wastewater 30 times the mass of the sea island fiber; in addition, compared with Comparative Examples 1 and 2, the present invention has the significant advantage of a relatively short process flow.

[0063] The above embodiments and comparative examples were designed and carried out after the experimental research had made it clear that the amount of wastewater generated was sufficient. They are only for indicating the wastewater output. In actual production, the amount of water used for each washing may not be exactly the same as the above examples, but the amount of wastewater generated by the single method and per unit weight of the sea island fiber is relatively close. Since it is difficult to conduct experiments with a small amount of water washing, multiple batches of washing can only be carried out until the pH fails to meet the standard as wastewater.

[0064] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims.

[0065] Any matters not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. A low water consumption alkali reduction microfiber washing method, characterized in that: The following steps are involved: S1 reduces the COPET / PET sea island fiber nonwoven fabric to be treated after impregnation in a NaOH reducing liquid, wherein the concentration of the NaOH reducing liquid is 2-5%, the reducing temperature is 90-110°C, and the reducing time is 10-40 minutes. After the reduction is completed, a microfiber synthetic leather is obtained, and the reducing liquid brought out from the microfiber synthetic leather is squeezed out with an extrusion roller, and then the microfiber synthetic leather is dried in an oven at a temperature of 100-130°C and a drying time of 10-15 minutes. S2 reduces the microfiber synthetic leather after drying. The microfiber synthetic leather is put into hot water at 90-100°C to wash the remaining COPET and the NaOH introduced during the weight reduction; S3 uses an extrusion roller to squeeze out the washing liquid from the microfiber synthetic leather, and controls the liquid carrying rate of the microfiber synthetic leather during the process to reduce the amount of NaOH carried; S4 washes the microfiber synthetic leather at room temperature after squeezing out the remaining liquid while it is still hot, and utilizes the temperature difference between the residual heat after hot water washing and the washing liquid at room temperature to accelerate the release of NaOH from the surface of the microfiber synthetic leather. The microfiber synthetic leather after room temperature washing is squeezed and dried to complete the alkali weight reduction.

2. The low water consumption alkali-reduced microfiber washing method according to claim 1, characterized in that: In the step S3, the squeezing roller is extruded with a pressure of 0.8 to 1 MPa, and the liquid carrying rate of the microfiber synthetic leather after extrusion is 100 to 220%.

3. The low water consumption alkali-reduced microfiber washing method according to claim 1, characterized in that: In the step S2, 5 parts by weight of wastewater is generated for each part by weight of the COPET / PET type island fiber nonwoven fabric before impregnation. In the step S4, 10 parts by weight of wastewater is generated for each part by weight of the COPET / PET type island fiber nonwoven fabric before impregnation.

4. The low water consumption alkali-reduced microfiber washing method according to claim 3, characterized in that: In step S2, the hot water washing time is 10 minutes; in step S4, the room temperature water washing temperature is 20-30° C., and the room temperature water washing time is 10 minutes.

5. A low water consumption alkali-reduced microfiber washing method according to any one of claims 1 to 4, characterized in that: The components of the impregnation liquid include, by weight, 100 parts of water-based polyurethane, 100-200 parts of water, 1-3 parts of silicone wetting agent, 0.3-1.2 parts of polysiloxane defoaming agent, 1-6 parts of crosslinking agent, 3-16 parts of light calcium carbonate filler, and 5-10 parts of alkali-swellable thickener.

6. The low water consumption alkali-reduced microfiber washing method according to claim 5, characterized in that: The impregnation liquid components are uniformly stirred by mechanical means to obtain an impregnated impregnation slurry, which is then uniformly filled into the sea-island fiber nonwoven fabric and dried to form a sea-island fiber / polyurethane three-dimensional structure.

7. A low water consumption alkali-reduced microfiber washing method according to any one of claims 1 to 4, characterized in that: In the step S1, after the weight reduction is completed, the sea component in the ultrafine fiber synthetic leather accounts for 3-5% by mass.

8. A low water consumption alkali-reduced microfiber washing method according to any one of claims 1 to 4, characterized in that: In step S4, after the microfiber synthetic leather is washed at room temperature and squeezed, the pH value of the surface of the leather tested by the test paper is 7.

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