Alkali-deweighting microfiber washing method with low water consumption

Abstract

The invention discloses an alkali deweighting microfiber washing method with low water consumption, and relates to the technical field of sea-island fiber alkali deweighting treatment methods. The method comprises the following steps: reducing sea-island fibers to be treated in a NaOH decrement solution, extruding the decrement solution, and drying in a drying oven; putting into hot water, and washing residual COPET and NaOH brought in during decrement; a squeezing roller is used for squeezing out washing liquid brought out of the superfine fiber synthetic leather, the liquid carrying rate of the superfine fiber synthetic leather is controlled in the process, and the NaOH carrying amount is reduced; washing the superfine fiber synthetic leather from which the residual liquid is extruded out at normal temperature while the superfine fiber synthetic leather is hot, accelerating the release of NaOH from the surface of the superfine fiber synthetic leather by utilizing the temperature difference between the residual heat generated after hot water washing and the normal-temperature washing liquid, and extruding and drying the superfine fiber synthetic leather washed at normal temperature to complete alkali decrement; according to the invention, the accelerated transmission effect of the concentration difference and the temperature difference is ingeniously utilized, the water for alkali decrement is saved, and meanwhile, the discharge and treatment of wastewater are also reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of alkali weight reduction treatment methods for sea-island fibers, and specifically to an alkali weight reduction and ultrafine fiber washing method with low water consumption. Background Art

[0002] Ultrafine fiber, also known as superfine fiber, refers to a fiber with a single filament fineness less than 1 Dtex. The single filament fineness of ultrafine fiber is far lower than that of conventional ordinary fibers. In the field of synthetic leather, ultrafine fiber can mimic the collagen fibers of natural leather in three-dimensional structure. Therefore, ultrafine fiber synthetic leather has a plump and elastic feel similar to leather, and at the same time, ultrafine fiber synthetic leather has good moisture permeability and has good market potential.

[0003] Sea-island fiber is an important raw material for making ultrafine fibers. Sea-island fiber contains both sea and island components. When the sea component in the sea-island fiber is removed, the remaining island component is the ultrafine fiber. The process of removing the sea component of sea-island fiber is called weight reduction. Currently, there are three common weight reduction methods, namely toluene weight reduction method, alkali weight reduction, and hot water weight reduction method. Toluene weight reduction requires a large amount of toxic solvent toluene. The spinning, non-woven and other processes supporting hot water weight reduction are not yet mature. The ultrafine fiber production process of alkali weight reduction is relatively perfect. The alkali weight reduction process has no solvent pollution and is a green and environmentally friendly ultrafine fiber production method.

[0004] The general process of alkali weight reduction is to immerse the ultrafine fiber in a high-temperature alkali solution at about 100 °C. The ultrafine fiber will adsorb the alkaline components in the alkali solution. At the end of the weight reduction process, the pH of the ultrafine fiber non-woven fabric can reach 14. Currently, the alkali weight reduction process of ultrafine fiber is divided into intermittent alkali weight reduction process and flat continuous alkali weight reduction process. Among them, the intermittent alkali weight reduction process can adapt to the weight reduction of various style alkali weight reduction ultrafine fibers, and the weight reduction effect is more sufficient, so it is applied relatively more. However, the water consumption in the intermittent alkali weight reduction process is relatively large. Producing 1 ton of ultrafine fiber will use about 60 tons of water, and 50% of the water is generated in the water washing step after weight reduction.

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

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

[0007] To achieve the above object, the present invention provides the following technical solution: a method for washing microfibers with alkali reduction using low water consumption, comprising the following steps: S1: the impregnated COPET / PET type sea island fiber nonwoven fabric to be treated is reduced in a NaOH reduction liquid, the concentration of the NaOH reduction liquid is 2-5%, the reduction temperature is 90-110°C, the reduction time is 10-40min, and the ultrafine fiber synthetic leather is obtained after the reduction is completed, and the reduction liquid brought out of the ultrafine fiber synthetic leather is squeezed out by an extrusion roller, and then the ultrafine fiber synthetic leather is dried in an oven, the oven temperature is 100-130°C, and the drying time is 10-15min; S2 puts the ultrafine fiber synthetic leather dried after weight reduction into hot water at 90-100°C to wash the remaining COPET and NaOH introduced during 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 ultrafine fiber 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 normal temperature water washing liquid to accelerate the release of NaOH from the surface of the ultrafine fiber synthetic leather. The ultrafine fiber synthetic leather after normal temperature water washing is squeezed and dried to complete alkali reduction. Preferably, in the above step S3, the extrusion roller is extruded with a pressure of 0.8-1 MPa, and the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion is 100-220%.

[0008] Preferably, in step S2, 5 parts by weight of wastewater is generated for each part by weight of COPET / PET type sea 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 sea island fiber nonwoven fabric before impregnation.

[0009] In the preferred embodiment, 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.

[0010] In the above schemes, the impregnation liquid components 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 swelling thickener in parts by weight.

[0011] Preferably, in the above preferred solution, the components of the impregnating solution are uniformly prepared into an impregnating slurry by mechanical stirring. The impregnating slurry is uniformly filled in the sea-island fiber nonwoven fabric and dried to form a three-dimensional structure of sea-island fiber / polyurethane.

[0012] Preferably, in step S1, after the weight reduction is completed, the sea component in the superfine fiber synthetic leather accounts for 3-5% by mass.

[0013] Preferably, in step S4, after the superfine fiber synthetic leather after normal temperature washing is extruded, the surface pH tested by litmus paper is 7.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This method for washing superfine fibers with alkali reduction with low water consumption has simple and reasonable technological steps, a short alkali reduction process, and a short total time. After NaOH reduction and drying, the superfine fibers are washed once in hot water. Since the high temperature makes the molecular movement fast, and the concentration difference between alkali and water in the dried superfine fibers is greater, the washing is more rapid. After squeezing out the remaining liquid, it is directly put into cold water for normal temperature washing while it is still hot. The temperature difference accelerates the diffusion of the alkali solution into the cold water tank. After washing with hot and cold water, the surface of the material can reach a neutral level, avoiding the operation of repeated washing and rolling. The present invention cleverly utilizes the accelerating transfer effect of concentration difference and temperature difference, saves water for alkali reduction, and at the same time reduces the discharge and treatment of wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic process flow diagram of the method for washing superfine fibers with alkali reduction of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Refer to Figure 1 , a method for washing superfine fibers with alkali reduction with low water consumption, comprising the following steps: S1 The impregnated COPET / PET type sea-island fiber nonwoven fabric to be treated is subjected to weight reduction in a NaOH weight reduction solution. The concentration of the NaOH weight reduction solution is 2-5%, the weight reduction temperature is 90-110°C, and the weight reduction time is 10-40 min. After the weight reduction is completed, a superfine fiber synthetic leather is obtained. The weight reduction solution carried out by the superfine fiber synthetic leather is extruded by an extrusion roller, and then the superfine fiber synthetic leather is dried in an oven. The oven temperature is 100-130°C, and the drying time is 10-15 min. When extruding with the extrusion roller, there are no special requirements. It is only a preparatory work before drying. Extrusion is not necessary, but the drying time may be extended. For reference, the extrusion roller can be made to extrude with an attached pressure of 0.8-1 MPa, or adjusted by oneself; S2 The superfine fiber synthetic leather dried after weight reduction is put into hot water at 90-100°C to wash the remaining COPET and NaOH brought in during weight reduction; S3 uses a squeezing roller to extrude the washing liquid carried out from the superfine fiber synthetic leather, and controls the liquid carrying rate of the superfine fiber synthetic leather during the process to reduce the NaOH carrying amount; for reference, the squeezing roller exerts a pressure of 0.8 - 1 MPa, and specifically, the liquid carrying rate of the superfine fiber synthetic leather after extrusion can be controlled at 100 - 220%; S4 Immediately after extrusion, wash the superfine fiber synthetic leather with normal temperature water while it is still hot. Utilize the temperature difference between the residual heat carried after hot water washing and the normal temperature washing liquid to accelerate the release of NaOH from the surface of the superfine fiber synthetic leather. After normal temperature washing, the superfine fiber synthetic leather undergoes extrusion and drying to complete the alkali weight reduction. Using the above method, during the hot water washing process, for every weight part of COPET / PET type sea-island fiber nonwoven fabric before impregnation, 5 weight parts of wastewater are generated; during the normal temperature washing process, for every weight part of COPET / PET type sea-island fiber nonwoven fabric before impregnation, 10 weight parts of wastewater are generated; that is, a total of 15 weight parts of wastewater per weight part of sea-island fiber.

[0017] In a preferred embodiment, the hot water washing time is 10 min. This time is only for reference and can be adjusted specifically, for example, 5 - 15 min or longer. However, considering the process efficiency, 10 min is sufficient. 5 minutes or shorter may result in insufficient weight reduction or more NaOH residue; In a preferred embodiment, the temperature of the normal temperature washing can be 20 - 30 °C, and the normal temperature washing time is 10 min. Similarly, this time is only for reference and can be adjusted specifically, for example, 5 minutes, 8 minutes, 12 minutes, etc. Using the method of the present invention, during the normal temperature washing process, the pH of the surface of the finally extruded superfine fiber synthetic leather can usually reach 7 quickly.

[0018] In addition, the solution of the present invention does not require pickling, has a fast cleaning speed, and does not damage the characteristics of the impregnated filler. Further preferably, the components of the impregnating liquid are calculated by weight parts and preferably include 100 parts of waterborne polyurethane, 100 - 200 parts of water, 1 - 3 parts of silicone-based 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.

[0019] Generally, the components of the impregnating liquid can be uniformly mixed by mechanical stirring to obtain the impregnating slurry. The impregnating slurry is uniformly filled in the sea-island fiber nonwoven fabric and dried to form a sea-island fiber / polyurethane three-dimensional structure.

[0020] In addition, the specific control of the concentration, temperature, and time of the NaOH reduction solution in the alkali weight reduction described above is an optimal combination obtained through a large number of experiments in the present invention, which can control the mass ratio of the sea component in the obtained ultrafine fiber synthetic leather within a range suitable for the next hot water washing at the end of the weight reduction; 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 solution provided by the present invention, the mass ratio of the sea component in the ultrafine fiber synthetic leather obtained at the end of the weight reduction can be controlled within 3-5%.

[0021] The technical solutions and effects of the present invention are further illustrated by the following several examples. It should be noted that the following are not all examples of the present invention, but only randomly selected samples from numerous examples, which are representative but should not be construed as an absolute limitation to the present invention.

[0022] Since the main purpose of the present invention is to reduce water consumption rather than improve effects such as the weight reduction rate, the main designed experiment is to prove whether the cleaning after the weight reduction is sufficient. It is proved by the pH test result of the material surface after squeezing out the washing liquid after the last cleaning and before final drying. The same operation of the squeezing roller is adopted in the last squeezing step, with a pressure of 1 MPa, a constant speed, and the same passing time through the roller to ensure that the pH test conditions are as similar as possible.

[0023] In the following examples and comparative examples, since the component ratio of the impregnating solution hardly affects the water consumption for alkali weight reduction, a fixed ratio is used as an example to control variables. Specifically, the raw materials of the impregnating solution components are counted by weight: 100 parts of waterborne polyurethane using Zhongke Henry AK-01A with a modulus lower than 3 MPa, 150 parts of water, 1 part of silicone-based wetting agent using Dow Chemical 5211, 0.75 part of polysiloxane defoamer using Stahl DF-2459, 3 parts of crosslinking agent using Stahl carbodiimide 5580, 12 parts of light calcium carbonate filler using Anhui Xueling 1250-mesh calcium carbonate, 7 parts of alkali-swellable thickener using BYK-HV80; the sea-island fiber adopts a common commercially available ratio, that is, the sea component in the COPET / PET type sea-island fiber nonwoven fabric accounts for 30% of the total mass, and is divided into multiple parts by 50 g per weight portion (about the size of an A4 sheet), and are uniformly filled with the above impregnating solution and dried respectively to obtain samples to be processed, which are divided into 5 groups, with multiple parts in each group.

[0024] Example 1: Take the first sample to be processed in the first group and carry out weight reduction in the NaOH weight reduction solution. The concentration of the NaOH weight reduction solution is 5%, the weight reduction temperature is 100 °C, and the weight reduction time is 30 min. After the weight reduction, an ultrafine fiber synthetic leather is obtained. Extrude the carried-out weight reduction solution with an extrusion roller, and then dry the ultrafine fiber synthetic leather in an oven at a temperature of 110 °C for 10 min; put the dried ultrafine fiber synthetic leather after weight reduction into 5 kg of hot water at 100 °C and wash it for 10 min; use an extrusion roller to extrude the water washing solution carried out by the ultrafine fiber synthetic leather, with the pressure between the rollers being 1 MPa, and control the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion to be 100-220%; quickly transfer the ultrafine fiber synthetic leather to 10 kg of water at 20 °C and wash it at normal temperature for 10 min while it is hot, and extrude the water washing solution carried out by the ultrafine fiber synthetic leather again. Test the surface pH with a pH test paper to be 7; repeat the weight reduction operation of the 2nd to 21st 50-g samples to be processed in the first group according to the same parameters, and continue to wash them in the water for the first hot water wash and normal temperature water wash in sequence. After the normal temperature water wash, extrude the water washing solution carried out by the ultrafine fiber synthetic leather. The surface pH of the 2nd to 20th samples measured with a pH test paper is 7, and the surface pH of the 21st sample is 8. That is, a total of 15 kg of wastewater is generated by 20 samples to be processed, and 750 g of wastewater is generated by every 50 g of sea-island fiber before impregnation.

[0025] Example 2: Take the first sample to be processed in the second group and carry out weight reduction in the NaOH weight reduction solution. The concentration of the NaOH weight reduction solution is 3%, the weight reduction temperature is 110 °C, and the weight reduction time is 40 min. After the weight reduction, an ultrafine fiber synthetic leather is obtained. Extrude the carried-out weight reduction solution with an extrusion roller, and then dry the ultrafine fiber synthetic leather in an oven at a temperature of 100 °C for 15 min; put the dried ultrafine fiber synthetic leather after weight reduction into 5 kg of hot water at 100 °C and wash it for 10 min; use an extrusion roller to extrude the water washing solution carried out by the ultrafine fiber synthetic leather, with the pressure between the rollers being 0.9 MPa, and control the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion to be 100-220%; quickly transfer the ultrafine fiber synthetic leather to 10 kg of water at 23 °C and wash it at normal temperature for 10 min while it is hot, and extrude the water washing solution carried out by the ultrafine fiber synthetic leather again. Test the surface pH with a pH test paper to be 7; repeat the weight reduction operation of the 2nd to 21st 50-g samples to be processed in the second group according to the same parameters, and continue to wash them in the water for the first hot water wash and normal temperature water wash in sequence. After the normal temperature water wash, extrude the water washing solution carried out by the ultrafine fiber synthetic leather. The surface pH of the 2nd to 20th samples measured with a pH test paper is 7, and the surface pH of the 21st sample is 8. That is, a total of 15 kg of wastewater is generated by 20 samples to be processed, and 750 g of wastewater is generated by every 50 g of sea-island fiber before impregnation.

[0026] Example 3: Take the first sample to be processed in the third group and carry out weight reduction in the NaOH weight reduction solution. The concentration of the NaOH weight reduction solution is 5%, the weight reduction temperature is 110°C, and the weight reduction time is 20 min. After the weight reduction, an ultrafine fiber synthetic leather is obtained. Extrude the weight reduction solution carried out by using an extrusion roller, and then dry the ultrafine fiber synthetic leather in an oven at a temperature of 130°C for 10 min; put the dried ultrafine fiber synthetic leather after weight reduction into 5 kg of hot water at 90°C and wash it for 10 min; use an extrusion roller to extrude the washing solution carried out by the ultrafine fiber synthetic leather, with the pressure between the rollers being 1 MPa, and control the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%; quickly transfer the ultrafine fiber synthetic leather to 10 kg of water at 25°C and wash it at normal temperature for 10 min while it is hot. Extrude the washing solution carried out by the ultrafine fiber synthetic leather again, and test the surface pH with a pH test paper to be 7; repeat the weight reduction operation for the 2nd to 21st 50-g samples to be processed in the third group according to the same parameters, and continue to wash them in turn in the water used for the first hot water wash and normal temperature wash. After the normal temperature wash, extrude the washing solution carried out by the ultrafine fiber synthetic leather, and use a pH test paper to measure that the surface pH of the 2nd to 20th samples is 7, and the surface pH of the 21st sample is 8. That is, a total of 15 kg of wastewater is generated from 20 samples to be processed, and 750 g of wastewater is generated per 50 g of sea-island fiber before impregnation.

[0027] Comparative Example 1: Weight reduction: Take the first sample to be processed in the fourth group and carry out weight reduction in the NaOH weight reduction solution. The concentration of the NaOH weight reduction solution is 5%, the weight reduction temperature is 100°C, and the weight reduction time is 30 min; Rolling: Use an extrusion roller to extrude the washing solution carried out by the ultrafine fiber synthetic leather, with the pressure between the rollers being 1 MPa, control the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%, and test the surface pH with a pH test paper to be 14 after rolling; Primary washing: Transfer the ultrafine fiber synthetic leather to a primary washing container filled with 10 kg of water at 20°C and wash it for 10 min; Primary rolling: Use an extrusion roller to extrude the washing solution carried out by the ultrafine fiber synthetic leather, with the pressure between the rollers being 1 MPa, control the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%, and test the surface pH with a pH test paper to be 11 after rolling; Secondary washing: Transfer the ultrafine fiber synthetic leather to a secondary washing container filled with 10 kg of water at 20°C and wash it for 10 min; Secondary rolling: Use an extrusion roller to extrude the washing solution carried out by the ultrafine fiber synthetic leather, with the pressure between the rollers being 1 MPa, control the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%, and test the surface pH with a pH test paper to be 8 after rolling; Final washing: Transfer the ultrafine fiber synthetic leather to a tertiary washing container filled with 10 kg of water at 20°C and wash it for 10 min; Final rolling: Use a squeezing roller to extrude the washing liquid carried out from the ultrafine fiber synthetic leather. The pressure between the rollers is 1 MPa. Control the liquid retention rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%. After rolling, use a pH test paper to measure the surface pH to be 7; Continue to use the above steps and the washing water for one to three times to process the 2nd to 11th samples to be processed in the 4th group in sequence. Among them, for the 2nd to 5th samples to be processed, the pH measured after primary rolling can be maintained at 11, and the pH measured after final rolling is 7. For the 6th to 8th samples to be processed, the pH measured after primary rolling is between 12 and 13, the pH measured after secondary rolling is between 9 and 10, and the pH measured after final rolling can reach 7. For the 9th and 10th samples to be processed, the pH measured after primary rolling is 13, the pH measured after secondary rolling is between 10 and 11, and the pH measured after final rolling can reach 7. For the 11th sample to be processed, the pH measured after primary rolling is between 13 and 14, the pH measured after secondary rolling is 11, and the pH measured after final rolling is 8. That is, after processing 10 batches, the three pools of water must be replaced, a total of 30 kg of wastewater is generated, corresponding to 3 kg of wastewater generated for every 50 g of sea-island fiber before impregnation.

[0028] Comparative example 2: Weight reduction: Take the 1st sample to be processed in the 5th group and carry out weight reduction in the NaOH weight reduction solution. The concentration of the NaOH weight reduction solution is 5%, the weight reduction temperature is 100 °C, and the weight reduction time is 30 min; Rolling: Use a squeezing roller to extrude the washing liquid carried out from the ultrafine fiber synthetic leather. The pressure between the rollers is 1 MPa. Control the liquid retention rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%. After rolling, use a pH test paper to measure the surface pH to be 14; Washing: Transfer the ultrafine fiber synthetic leather to a primary washing container filled with 20 kg of water at 20 °C and wash for 10 min; Primary rolling: Use a squeezing roller to extrude the washing liquid carried out from the ultrafine fiber synthetic leather. The pressure between the rollers is 1 MPa. Control the liquid retention rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%. After rolling, use a pH test paper to measure the surface pH to be 10; Weak acid washing: Transfer the ultrafine fiber synthetic leather to 10 kg of a citric acid solution with a concentration of 5% and carry out weak acid washing for 10 min; Secondary rolling: Use a squeezing roller to extrude the washing liquid carried out from the ultrafine fiber synthetic leather. The pressure between the rollers is 1 MPa. Control the liquid retention rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%. After rolling, use a pH test paper to measure the surface pH to be 8; Washing: Transfer the ultrafine fiber synthetic leather to a secondary washing container filled with 10 kg of water at 20 °C and wash for 10 min; Final rolling: Use a squeezing roller to extrude the washing liquid carried out from the ultrafine fiber synthetic leather. The pressure between the rollers is 1 MPa. Control the liquid retention rate of the ultrafine fiber synthetic leather after extrusion to be 100 - 220%. After rolling, use a pH test paper to measure the surface pH to be 7; Continue to adopt the above steps, wash water twice and weak acid, and process the 2nd to 21st samples to be processed in the 5th group in sequence. Among them, for the 2nd to 12th samples to be processed, the pH measured after rough rolling can be maintained at 10, and the pH measured after final rolling is 7. For the 13th to 17th samples to be processed, the pH measured after rough rolling is 11, the pH measured after intermediate rolling is 9, and the pH measured after final rolling is 7. For the 18th to 20th samples to be processed, the pH measured after rough rolling is 12, the pH measured after intermediate rolling is between 10 and 11, and the pH measured after final rolling can reach 7. For the 21st sample to be processed, the pH measured after rough rolling is 13, the pH measured after intermediate rolling is 11, and the pH measured after final rolling is 8. After processing 20 batches, the water and citric acid must be replaced. Except for citric acid, a total of 30 kg of wastewater is generated, corresponding to 1.5 kg of wastewater generated per 50 g of sea-island fiber before impregnation.

[0029] In Examples 1 to 3 of the present invention, when washing until the pH of the material surface reaches 7, the water consumption is 15 times the mass of the sea-island fiber. Comparative Examples 1 and 2 are two existing common intermittent alkali weight reduction washing methods. In Comparative Example 1, during the repeated washing and rolling operation, the pH value of each water wash is likely to become higher and more wastewater is generated. In Comparative Example 2, the improved weak acid washing can accelerate the water wash progress, but still 30 times the mass of the sea-island fiber of wastewater needs to be generated. In addition, compared with Comparative Examples 1 and 2, the present invention significantly has the advantage of a relatively shorter process flow.

[0030] The above examples and comparative examples were designed and carried out when the wastewater generation amount was relatively clear through experimental research, only to show the wastewater output. In actual production, the water consumption for each water wash may not be exactly the same as that in the above examples, but the amount of wastewater generated per unit weight of the sea-island fiber by a single method is relatively close. Since it is difficult to conduct experiments for a small amount of water wash, only multiple batches of washing until the pH cannot meet the standard can be used as the determination of wastewater.

[0031] The above is only the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope defined by the claims.

[0032] Where the present invention is not described in detail, it is all well-known technology to those skilled in the art.

Claims

1. A method for washing alkali-deweighted superfine fibers with low water consumption, characterized in that It includes the following steps: S1. Subject the impregnated COPET / PET sea-island fiber nonwoven fabric to be processed to weight reduction in a NaOH weight reduction solution. The concentration of the NaOH weight reduction solution is 2-5%, the weight reduction temperature is 90-110°C, and the weight reduction time is 10-40 min. After the weight reduction, an ultrafine fiber synthetic leather is obtained. Extrude the weight reduction solution carried out by the ultrafine fiber synthetic leather with an extrusion roller, and then dry the ultrafine fiber synthetic leather in an oven. The oven temperature is 100-130°C, and the drying time is 10-15 min; S2. Put the dried ultrafine fiber synthetic leather after weight reduction into hot water at 90-100°C to wash the remaining COPET and the NaOH brought in during weight reduction; S3. Use an extrusion roller to extrude the washing solution carried out by the ultrafine fiber synthetic leather, and control the liquid carrying rate of the ultrafine fiber synthetic leather during the process to reduce the NaOH carrying amount; S4. Immediately wash the ultrafine fiber synthetic leather after extruding the remaining liquid with normal temperature water. Utilize the temperature difference between the remaining heat carried after hot water washing and the temperature of the normal temperature water washing solution to accelerate the release of NaOH from the surface of the ultrafine fiber synthetic leather. The ultrafine fiber synthetic leather after normal temperature water washing is subjected to extrusion and drying to complete the alkali weight reduction.

2. The low-water-consumption alkali weight reduction superfine fiber washing method according to claim 1, characterized in that: In the step S3, the extrusion roller exerts a pressure of 0.8-1 MPa, and the liquid carrying rate of the ultrafine fiber synthetic leather after extrusion is 100-220%.

3. A low-water-consumption alkali weight reduction superfine fiber washing method according to claim 1, characterized in that: In the step S2, for each weight part of the COPET / PET sea-island fiber nonwoven fabric before impregnation, 5 weight parts of wastewater are generated. In the step S4, for each weight part of the COPET / PET sea-island fiber nonwoven fabric before impregnation, 10 weight parts of wastewater are generated.

4. A low-water-consumption alkali weight reduction superfine fiber washing method according to claim 3, characterized in that: In the step S2, the hot water washing time is 10 min; in the step S4, the temperature of the normal temperature water washing is 20-30°C, and the normal temperature water washing time is 10 min.

5. A low-water-consumption alkali weight reduction superfine fiber washing method according to any one of claims 1 to 4, characterized in that: The components of the impregnation solution are calculated by weight parts and include 100 parts of waterborne polyurethane, 100-200 parts of water, 1-3 parts of an organosilicon wetting agent, 0.3-1.2 parts of a polysiloxane defoaming agent, 1-6 parts of a crosslinking agent, 3-16 parts of a light calcium carbonate filler, and 5-10 parts of an alkali-swellable thickener.

6. A method for washing low-water-consumption alkali-deweighted superfine fibers according to claim 5, characterized in that: The components of the impregnation solution are uniformly prepared into an impregnation slurry by mechanical stirring. The impregnation slurry is uniformly filled in the sea-island fiber nonwoven fabric and dried to form a sea-island fiber / polyurethane three-dimensional structure.

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

8. A low-water-consumption alkali weight reduction superfine fiber washing method according to any one of claims 1 to 4, characterized in that: In the step S4, after the ultrafine fiber synthetic leather after normal temperature water washing is extruded, the surface pH is tested with a test paper to be 7.

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