Preparation method of water-based polyurethane microfiber base cloth

Abstract

The present application relates to a kind of preparation methods of water-based polyurethane microfiber base cloth, using water-based polyurethane slurry impregnation island fiber nonwoven fabric, water-based polyurethane is obtained after solidification, fibrillation and obtains water-based polyurethane microfiber base cloth, water-based polyurethane slurry mainly consists of water-based polyurethane slurry and water-absorbing resin particles, the water absorption and water retention of water-absorbing resin particles can be adjusted;During solidification, first gelation is carried out in electrolyte solution, then microwave heating is carried out to complete solidification;Before impregnation, the water absorption of water-absorbing resin particles is controlled to be weak, so that the viscosity of water-based polyurethane slurry is 200-800 mPa·s;During gelation, the water absorption of water-absorbing resin particles is controlled to be enhanced, so that water-based polyurethane and water-absorbing resin particles are all converted into gel state;When fibrillation, the water absorption and water retention of water-absorbing resin particles are controlled to be weakened, so that the volume shrinkage of water-absorbing resin particles is obtained.The preparation method of the present application is simple, and the softness and stability of the prepared water-based polyurethane microfiber base cloth are excellent.

Description

Technical Field

[0001] This invention belongs to the field of water-based microfiber leather manufacturing, and specifically relates to a method for preparing water-based polyurethane microfiber base fabric. Background Technology

[0002] Microfiber synthetic leather, as the latest generation of synthetic leather products, is a composite material made of microfiber and polyurethane. It is one of the ideal alternatives to genuine leather, with features such as structural simulation, resilience, breathability, and softness. It is widely used in many fields such as sofas, clothing, shoes, automobiles, and bags, and is the main direction of synthetic leather technology development.

[0003] Currently, microfiber synthetic leather can be divided into water-based microfiber leather and solvent-based microfiber leather according to the different polyurethane slurries used for impregnation. Most domestic microfiber synthetic leather is solvent-based. This is because, compared to water-based microfiber leather, solvent-based microfiber leather has the advantage of a large number of microporous structures in its polyurethane components, resulting in a fuller, softer feel and a strong leather-like texture. The disadvantage is that it uses a large amount of DMF solvent in its preparation process, causing some environmental pollution, and the recycling of DMF requires a significant amount of energy. Water-based polyurethane, using water as the dispersion medium, does not pollute the environment, and water is inexpensive and safe to use, making its application in synthetic leather a development trend and industry consensus. However, the application of water-based polyurethane in synthetic leather is mainly concentrated in surface coating. When used to replace solvent-based polyurethane in the impregnation of microfiber synthetic leather base fabric, it is impossible to obtain water-based microfiber leather with a porous structure using wet processes, and it cannot meet the requirements of microfiber synthetic leather in terms of feel and elasticity. This greatly limits the application of water-based microfiber leather. Microfiber synthetic leather base fabrics made by impregnating with waterborne polyurethane and then directly drying produce leather that is stiff, shriveled, and lacks a bubbly feel, falling far short of the required elasticity and fullness. Therefore, how to prepare microfiber synthetic leather with a microporous structure similar to solvent-based polyurethane using waterborne resins has become a key factor restricting the development of the waterborne microfiber leather industry.

[0004] To address the aforementioned issues, patent CN110184825A provides an environmentally friendly micro-nano foamed waterborne polyurethane microfiber synthetic leather and its manufacturing method. This patent uses a micro-nano bubble generator to prepare a waterborne polyurethane slurry containing micro-nano bubbles. The prepared micro-nano foamed waterborne polyurethane microfiber synthetic leather has excellent air permeability and water vapor permeability. However, it is necessary to control the foaming time, foaming times, and stabilizer content. Furthermore, the final micro-nano foamed waterborne polyurethane microfiber synthetic leather exhibits inconsistent softness between batches. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing waterborne polyurethane microfiber base fabric.

[0006] A method for preparing waterborne polyurethane microfiber base fabric involves impregnating island fiber nonwoven fabric with a waterborne polyurethane slurry, curing the waterborne polyurethane, and opening the fibers to obtain the waterborne polyurethane microfiber base fabric. The waterborne polyurethane slurry mainly consists of waterborne polyurethane slurry and water-absorbing resin particles, and the water absorption and water retention properties of the water-absorbing resin particles are adjustable.

[0007] During the curing process, gelation is first carried out in an electrolyte solution, followed by complete curing by microwave heating;

[0008] Before impregnation, the water absorption of the water-absorbing resin particles is controlled to be weak, so that the viscosity of the water-containing polyurethane slurry is 200-800 mPa·s.

[0009] During the gelation process, the water absorption of the superabsorbent polymer particles is enhanced, so that both the waterborne polyurethane and the superabsorbent polymer particles are transformed into a gel state.

[0010] During the gelation process, the water absorption capacity of the superabsorbent resin particles is more than twice that of the superabsorbent resin particles before impregnation.

[0011] During fiber opening, the water absorption and water retention properties of the absorbent resin particles are reduced, causing the volume of the absorbent resin particles to shrink.

[0012] As a preferred technical solution:

[0013] In the above-described method for preparing a waterborne polyurethane microfiber base fabric, the absorbent resin particles are pH-sensitive hydrogels. Controlling the water absorption of the absorbent resin particles to be weak, controlling the water absorption of the absorbent resin particles to be enhanced, and controlling the water absorption and water retention of the absorbent resin particles to be weakened are all achieved by adjusting the pH value of the environment in which the absorbent resin particles are located.

[0014] In the preparation method of the waterborne polyurethane microfiber base fabric described above, the initial average particle size of the water-absorbing resin particles (i.e., the average particle size of the water-absorbing resin particles when they are not absorbing water) is at least 30 μm, preferably 30-50 μm. Since the water absorption of pH-sensitive hydrogels is relatively weak compared to other common water-absorbing resins, it is necessary to control the initial average particle size of the water-absorbing resin particles to be at least 30 μm in order to obtain larger pores in order to achieve a certain degree of softness.

[0015] In the above-described method for preparing a waterborne polyurethane microfiber base fabric, before impregnation, the pH value of the environment in which the absorbent resin particles are located is adjusted to 'a', with 'a' ranging from 12 to 13.3; the water absorption of the pH-sensitive hydrogel in the environment with pH value 'a' is 105%-115%; during gelation, the pH value of the environment in which the absorbent resin particles are located is adjusted to 'b', with 'b' ranging from 2 to 3.3; the water absorption of the pH-sensitive hydrogel in the environment with pH value 'b' is more than twice that in the environment with pH value 'a'.

[0016] The preparation method of the waterborne polyurethane microfiber base fabric described above results in a liquid retention rate of 95-120% for the island fiber nonwoven fabric after impregnation.

[0017] In the above-described method for preparing an aqueous polyurethane microfiber base fabric, the electrolyte solution is a sodium chloride solution with a concentration of ≥5wt%, for example, it can be 5wt%, 8wt%, 10wt%, 12wt%, 16wt%, 19wt%, etc.

[0018] The preparation method of the waterborne polyurethane microfiber base fabric described above involves microwave heating for 20-35 minutes, and any commonly used industrial heating frequency is acceptable, such as 915 MHz or 2450 MHz.

[0019] The method for preparing a waterborne polyurethane microfiber base fabric as described above uses a COPET / PA6 island fiber nonwoven fabric or a COPET / PET island fiber nonwoven fabric.

[0020] As described above, the preparation method of waterborne polyurethane microfiber base fabric involves fiber opening by soaking in a NaOH solution with a concentration of 2-5 wt% at a temperature of 80-95℃ followed by rolling. The marine phase in the island fiber will dissolve in the NaOH solution. Rolling will cause the water-absorbing resin particles to fall off. The rolling pressure is 0.05-0.4 MPa.

[0021] The method for preparing waterborne polyurethane microfiber base fabric as described above results in a softness of 3.2-4.8 and a batch stability of softness of 10.2-23.2%.

[0022] Invention Mechanism:

[0023] The maintenance of pores during the curing of waterborne polyurethane is essentially related to pH-sensitive hydrogels. Before impregnation and curing, the pH of the resin slurry is adjusted to alkaline. At this point, adding a pH-sensitive hydrogel results in weak water absorption; a small amount will not increase the viscosity of the polyurethane emulsion or disrupt its stability. In contrast, adding ordinary absorbent resins will cause them to absorb a large amount of water and swell, leading to gelation and preventing impregnation. After impregnation, the impregnated island-sea fiber nonwoven fabric is immersed in an electrolyte solution, with acid continuously added until the pH stabilizes at 2-3.3. The waterborne polyurethane and absorbent resin then transform into a gel state, forming a microfiber base fabric semi-finished product.

[0024] As is common knowledge, using high-concentration electrolytes disrupts the intermolecular forces between polyurethane particles and water molecules in waterborne polyurethane emulsions, causing the polyurethane emulsion to transform into a gel state. Within the gel, the dispersed phase (waterborne polyurethane) particles interconnect, forming a structure within the entire system, with the continuous phase (water) encapsulated within. On the other hand, as the ambient pH changes from alkaline to acidic, the pH-sensitive hydrogel begins to absorb a large amount of water from the environment and swells, further dehydrating the polyurethane. This causes the system to slowly lose its fluidity and exhibit solid-like mechanical properties. Subsequent microwave heating further dehydrates and cross-links the waterborne polyurethane, causing it to solidify. During the fiber-opening process, the impregnated island-type fiber nonwoven fabric is immersed in an alkaline solution. At this point, the hydrogel's water absorption and retention capacity decreases, releasing a large amount of water into the surrounding aquatic environment and shrinking. However, since the surrounding polyurethane has solidified, the shrinking pH-sensitive hydrogel leaves pores in situ. As the fiber-opening process continues, the shrunken pH-sensitive hydrogel and the island component are washed out by the alkaline solution, leaving behind these pores.

[0025] Beneficial effects:

[0026] (1) The present invention provides a method for preparing waterborne polyurethane microfiber base fabric by adjusting the pH value of the environment in which the water-absorbing resin particles are located to regulate the water absorption and water retention of the water-absorbing resin particles, so that the volume of the water-absorbing resin particles shrinks and eventually forms foam cells, providing a new approach.

[0027] (2) The method for preparing waterborne polyurethane microfiber base fabric of the present invention has simple steps and stable foaming effect. The waterborne polyurethane microfiber base fabric prepared by this method has fine pores and uniform resin distribution, and has good hand feel and elasticity. Attached Figure Description

[0028] Figure 1 Here is a SEM image of the waterborne polyurethane microfiber substrate of Example 1;

[0029] Figure 2 SEM image of the waterborne polyurethane microfiber substrate for Comparative Example 1.

[0030] Figure 3 SEM image of the waterborne polyurethane microfiber substrate for Comparative Example 2;

[0031] Figure 4 The image shows a SEM image of the waterborne polyurethane microfiber substrate of Comparative Example 3. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] Terms and definitions:

[0034] pH-sensitive hydrogels: Based on their different responses to the external environment, hydrogels can be classified into pH-sensitive hydrogels, thermosensitive hydrogels, salt-sensitive hydrogels, photosensitizing hydrogels, etc. pH-sensitive hydrogels refer to hydrogels whose swelling volume changes discontinuously with changes in environmental pH. Generally, pH-sensitive hydrogels are formed through a cross-linked macromolecular network structure. The network contains acidic (basic) groups. With changes in the strength of the dissolved medium particles and the pH value, these groups ionize, leading to changes in the dissociation of hydrogen bonds between macromolecular chain segments within the network, ionic interactions, and changes in the ionic solubility inside and outside the polymer, as well as the interaction between the polymer and the solvent. This results in changes in the gel network structure, causing changes in the swelling volume of the polymer chains. Commercially available pH-sensitive water-absorbing and swelling resins can be purchased, or a method for preparing a pH-sensitive water-absorbing and swelling resin is provided in CN112552449A for self-preparation.

[0035] The term "electrolyte solution" refers to an alkali metal salt solution. The purpose of this solution is to use an electrolyte to disrupt the interaction between polyurethane particles and water molecules in an aqueous polyurethane emulsion, thereby causing the polyurethane emulsion to become a gel state. The salt solution may be, for example, one or more of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium phosphate, and potassium phosphate, or a mixture thereof.

[0036] The following are the performance testing methods described in the examples:

[0037] Viscosity of water-based polyurethane slurry: The viscosity of polyurethane slurry was measured using an NDJ-4 rotary viscometer at a test temperature of 25℃.

[0038] Initial average particle size: D50 value of the cumulative volume distribution curve, where 50% by volume of particles have a diameter smaller than this value, determined by laser diffraction using a Malvem Mastersizer 2000 laser particle size analyzer.

[0039] pH value: Measured using a pH meter (Thermo Fisher's Orion Lab Star meter), with an accuracy of 0.1 or less.

[0040] Water absorption test: The weight Mt of the dry hydrogel was measured, and the wet weight Ms of the hydrogel after immersion in the target pH aqueous solution (adjusted uniformly with NaOH aqueous solution) for 1 min (the hydrogel absorbs water very quickly, and is saturated with water after 1 min) was measured. The water absorption rate of the hydrogel was evaluated as Ms / Mt×100%.

[0041] Softness and batch stability of softness: The softness of the base fabric was tested according to standard ISO 17235-2002, with a test ring diameter of 20mm. The testing instrument was a leather softness tester, Shanghai Qingbo Testing Equipment Co., Ltd., model: QB-8326. Five points were taken from the same roll of microfiber base fabric for softness testing: one point each at the beginning, middle, and end; one point between the beginning and middle; and one point between the middle and end. After measuring the softness at the five points, the average value was taken as the softness. Simultaneously, the standard deviation of the softness at the five points was calculated as the batch stability of softness, using the following formula:

[0042]

[0043] In the formula, x i Let i be the softness of the i-th point. The average softness of the five points is n = 5.

[0044] Example 1

[0045] A method for preparing a waterborne polyurethane microfiber base fabric, comprising the following steps:

[0046] (1) Preparation of raw materials;

[0047] Waterborne polyurethane slurry: Manufacturer: Zhejiang Huafeng Synthetic Resin Co., Ltd., Brand: JF-PDY-P531H;

[0048] Alkaline solution I: Sodium hydroxide aqueous solution;

[0049] pH-sensitive hydrogel: Poly(AM-co-MAH-B-CD-co-DMAPS), manufactured by Nanjing Genasis, brand name R-NCO-NJ, ground to an average particle size of 36μm before use;

[0050] Island-sea fiber nonwoven fabric: COPET / PET island-sea fiber nonwoven fabric; wherein, the mass ratio of COPET to PET is 30:70;

[0051] Electrolyte solution: 5 wt% sodium chloride aqueous solution;

[0052] Acid solution: 0.05 wt% hydrochloric acid aqueous solution;

[0053] Alkali Solution II: A 5 wt% NaOH aqueous solution;

[0054] (2) Add alkali solution I to the waterborne polyurethane slurry to adjust the pH value of the waterborne polyurethane slurry to a (13.3) and adjust the solid content of the waterborne polyurethane slurry to 40% to obtain an alkaline resin slurry.

[0055] (3) By weight, 100 parts of alkaline resin slurry and 3 parts of pH-sensitive hydrogel are mixed evenly to obtain water-containing polyurethane slurry.

[0056] The viscosity of the prepared water-containing polyurethane slurry was 430 mPa·s;

[0057] (4) Impregnate the island fiber nonwoven fabric in an aqueous polyurethane slurry, and control its liquid carrying rate to 95% to obtain the impregnated island fiber nonwoven fabric.

[0058] (5) The impregnated island fiber nonwoven fabric is immersed in an electrolyte solution, and acid is continuously added to the electrolyte solution until the pH value stabilizes at b (2.7). Then, it is immersed for more than 10 minutes until the waterborne polyurethane and pH-sensitive hydrogel are transformed into a gel state to obtain the microfiber base fabric semi-finished product. Among them, the water absorption of the pH-sensitive hydrogel in the environment with a pH value of a is 107%, and the water absorption of the pH-sensitive hydrogel in the environment with a pH value of b is 2.5 times that in the environment with a pH value of a.

[0059] (6) Microwave heating is applied to the microfiber base fabric semi-finished product to further crosslink and cure the waterborne polyurethane; wherein the microwave heating time is 25 min and the heating frequency is 915 MHz.

[0060] (7) The cross-linked and cured microfiber base fabric semi-finished product is immersed in alkaline solution II at a temperature of 95°C and then rolled to remove the marine phase and pH-sensitive hydrogel in the island fiber, thus obtaining waterborne polyurethane microfiber base fabric; wherein, the rolling pressure is 0.3 MPa.

[0061] The final waterborne polyurethane microfiber base fabric (such as...) Figure 1 The softness (as shown) is 3.2, and the batch stability of softness is 13.6%.

[0062] Comparative Example 1

[0063] A method for preparing a waterborne polyurethane microfiber base fabric is basically the same as in Example 1, except that: in step (1), a pH-sensitive hydrogel is not prepared, and in step (3), the pH-sensitive hydrogel is replaced with an equal mass of alkaline resin slurry (same as in Example 1).

[0064] The final waterborne polyurethane microfiber base fabric (such as...) Figure 2 The softness (as shown) is 2.2, and the batch stability of softness is 18.5%.

[0065] Comparing Comparative Example 1 and Example 1, it can be seen that the waterborne polyurethane microfiber base fabric prepared in Comparative Example 1 has poor softness and stability because pH-sensitive hydrogel was not used. This is because without hydrogel to build the pores, the cured waterborne polyurethane lacks pores, making the base fabric relatively hard.

[0066] Comparative Example 2

[0067] A method for preparing a waterborne polyurethane microfiber base fabric is basically the same as in Example 1, except that hot air heating is used instead of microwave heating in step (6), wherein the temperature of hot air heating is 120°C and the time is 30 min.

[0068] The final waterborne polyurethane microfiber base fabric (such as...) Figure 3 The softness (as shown) is 2.5, and the batch stability of softness is 23.2%.

[0069] Comparing Comparative Example 2 and Example 1, it can be seen that the waterborne polyurethane microfiber base fabric prepared in Comparative Example 2 has poor softness because hot air is used to heat the microfiber base fabric semi-finished product. This is because hot air heating will cause the hydrogel to dehydrate significantly, shrink during solidification, and the pores will also shrink, making it difficult to wash the hydrogel during the fiber opening process, resulting in insufficient softness of the prepared waterborne polyurethane microfiber base fabric.

[0070] Comparative Example 3

[0071] A method for preparing a waterborne polyurethane microfiber base fabric is basically the same as in Example 1, except that: the electrolyte solution is omitted in step (1), step (5) is omitted, and hot air heating is used instead of microwave heating in step (6), wherein the temperature of hot air heating is 120°C and the time is 30 min.

[0072] The final waterborne polyurethane microfiber base fabric (such as...) Figure 4 The softness (as shown) is 2.3, and the batch stability of softness is 25.8%.

[0073] Comparing Comparative Example 3 with Example 1, it can be seen that the waterborne polyurethane microfiber base fabric prepared in Comparative Example 3 has poor softness and stability because it was directly cured without gelation. This is because the pH-sensitive hydrogel could not be fixed in place during curing, but instead precipitated to the surface as the polyurethane chains were adjusted. After alkali washing, the internal pores could not be obtained.

[0074] Comparative Example 4

[0075] A method for preparing a waterborne polyurethane microfiber base fabric is basically the same as in Example 1, except that the pH-sensitive hydrogel in step (1) is ground to an average particle size of 20 μm before use.

[0076] The final waterborne polyurethane microfiber base fabric has a softness of 2.9 and a batch stability of softness of 17.2%.

[0077] Comparing Comparative Example 4 and Example 1, it can be seen that the waterborne polyurethane microfiber base fabric prepared in Comparative Example 4 has poor softness because the initial average particle size of the pH-sensitive hydrogel used in Comparative Example 4 is too small. This is because the initial average particle size of the pH-sensitive hydrogel determines the size of the pores formed subsequently, resulting in insufficient softness of the prepared waterborne polyurethane microfiber base fabric.

[0078] Comparative Example 5

[0079] A method for preparing a waterborne polyurethane microfiber base fabric is basically the same as in Example 1, except that the pH value in step (5) is stabilized at b (6); so that the water absorption of the pH-sensitive hydrogel in an environment with a pH value of b is 1.4 times that in an environment with a pH value of a.

[0080] The final waterborne polyurethane microfiber base fabric has a softness of 2.7 and a batch stability of softness of 14.1%.

[0081] Comparing Comparative Example 5 and Example 1, it can be seen that the waterborne polyurethane microfiber base fabric prepared in Comparative Example 5 has poor softness due to the excessively high pH value b. This is because the difference between pH values ​​a and b before soaking is too small, resulting in a small difference in water absorption of the hydrogel at different pH values. Consequently, the hydrogel does not shrink sufficiently and is difficult to clean during the fiber opening process, thus leading to insufficient softness of the prepared waterborne polyurethane microfiber base fabric.

[0082] Comparative Example 6

[0083] A method for preparing a waterborne polyurethane microfiber base fabric is basically the same as in Example 1, except that: in step (1), waterborne polyurethane slurry, alkali solution I and pH-sensitive hydrogel are not prepared, and steps (2) to (3) are not performed. In step (4), the waterborne polyurethane slurry used is replaced with an equal mass of micro-nano foamed waterborne polyurethane (prepared using the method of Example 1 in patent CN110184825A).

[0084] The final waterborne polyurethane microfiber base fabric has a softness of 3.8 and a batch stability of softness of 98.1%.

[0085] Comparing Comparative Example 6 with Example 1, it can be seen that the micro-nano foamed waterborne polyurethane prepared by existing technology in Comparative Example 6 results in poor softness and stability of the prepared waterborne polyurethane microfiber substrate.

[0086] Comparative Example 7

[0087] A method for preparing a waterborne polyurethane microfiber base fabric is basically the same as in Example 1, except that: in step (1), a polyacrylic acid cellulose hydrogel is prepared, but a pH-sensitive hydrogel is not prepared, and in step (3), the pH-sensitive hydrogel is replaced with an equal mass of polyacrylic acid cellulose hydrogel.

[0088] The viscosity of the water-based polyurethane slurry is too high, making subsequent operations impossible.

[0089] Comparing Comparative Example 1 and Example 1, it can be seen that because the polyacrylic acid cellulose hydrogel was used in Comparative Example 1 instead of the pH-sensitive hydrogel, the viscosity of the water-containing polyurethane slurry was too high, and it gradually became gel-like and could not be used.

[0090] Example 2

[0091] A method for preparing a waterborne polyurethane microfiber base fabric, comprising the following steps:

[0092] (1) Preparation of raw materials;

[0093] Waterborne polyurethane slurry: Manufacturer: Zhejiang Huafeng Synthetic Resin Co., Ltd., Brand: JF-PDY-P521H;

[0094] Alkaline solution I: Sodium hydroxide aqueous solution;

[0095] pH-sensitive hydrogel: pH-sensitive hemicellulose hydrogel, manufactured by Ruixi Biotechnology, brand name R-PHXW-NJ, ground to an average particle size of 35μm before use;

[0096] Island-sea fiber nonwoven fabric: COPET / PA6 island-sea fiber nonwoven fabric; wherein, the mass ratio of COPET to PA6 is 35:65;

[0097] Electrolyte solution: 5 wt% sodium chloride aqueous solution;

[0098] Acid solution: 0.05 wt% hydrochloric acid aqueous solution;

[0099] Alkaline solution II: A 3 wt% NaOH aqueous solution;

[0100] (2) Add alkaline solution I to the waterborne polyurethane slurry to adjust the pH value of the waterborne polyurethane slurry to a (12.5) and at the same time adjust the solid content of the waterborne polyurethane slurry to 40% to obtain alkaline resin slurry.

[0101] (3) Mix 100 parts of alkaline resin slurry and 1 part of pH-sensitive hydrogel evenly by weight to obtain water-containing polyurethane slurry.

[0102] The viscosity of the prepared water-containing polyurethane slurry is 300 mPa·s;

[0103] (4) Impregnate the island fiber nonwoven fabric in an aqueous polyurethane slurry, and control its liquid carrying rate to 95% to obtain the impregnated island fiber nonwoven fabric.

[0104] (5) The impregnated island fiber nonwoven fabric is immersed in an electrolyte solution, and acid is continuously added to the electrolyte solution until the pH value stabilizes at b (2.8). Then, it is immersed for more than 10 minutes until the waterborne polyurethane and pH-sensitive hydrogel are transformed into a gel state to obtain the microfiber base fabric semi-finished product. Among them, the water absorption of the pH-sensitive hydrogel in the environment with a pH value of a is 108%, and the water absorption of the pH-sensitive hydrogel in the environment with a pH value of b is 3.2 times that in the environment with a pH value of a.

[0105] (6) Microwave heating is applied to the microfiber base fabric semi-finished product to further crosslink and cure the waterborne polyurethane; wherein the microwave heating time is 35 min and the heating frequency is 915 MHz.

[0106] (7) The cross-linked and cured microfiber base fabric semi-finished product is soaked in alkaline solution II at a temperature of 85°C and then rolled to remove the marine phase and pH-sensitive hydrogel in the island fiber, thus obtaining waterborne polyurethane microfiber base fabric; wherein, the rolling pressure is 0.05MPa.

[0107] The final waterborne polyurethane microfiber base fabric has a softness of 4.5 and a batch stability of 20% in terms of softness.

[0108] Example 3

[0109] A method for preparing a waterborne polyurethane microfiber base fabric, comprising the following steps:

[0110] (1) Preparation of raw materials;

[0111] Waterborne polyurethane slurry: Manufacturer: Zhejiang Huafeng Synthetic Resin Co., Ltd., Brand: JF-PDY-515Y;

[0112] Alkaline solution I: Potassium hydroxide aqueous solution;

[0113] pH-sensitive hydrogel: polycarboxymethyl chitosan hydrogel, manufactured by Ruixi Biotechnology, brand name R-JSJT-NJ, ground to an average particle size of 38μm before use;

[0114] Island-sea fiber nonwoven fabric: COPET / PA6 island-sea fiber nonwoven fabric; wherein, the mass ratio of COPET to PA6 is 40:60;

[0115] Electrolyte solution: 5 wt% sodium chloride aqueous solution;

[0116] Acid solution: 0.05 wt% hydrochloric acid aqueous solution;

[0117] Alkaline solution II: A 4 wt% NaOH aqueous solution;

[0118] (2) Add alkaline solution I to the waterborne polyurethane slurry to adjust the pH value of the waterborne polyurethane slurry to a (12.5) and at the same time adjust the solid content of the waterborne polyurethane slurry to 35% to obtain alkaline resin slurry.

[0119] (3) Mix 100 parts of alkaline resin slurry and 1 part of pH-sensitive hydrogel evenly by weight to obtain water-containing polyurethane slurry.

[0120] The viscosity of the prepared water-containing polyurethane slurry was 290 mPa·s;

[0121] (4) Impregnate the island fiber nonwoven fabric in an aqueous polyurethane slurry, and control its liquid carrying rate to 100% to obtain the impregnated island fiber nonwoven fabric.

[0122] (5) The impregnated island fiber nonwoven fabric is immersed in an electrolyte solution, and acid is continuously added to the electrolyte solution until the pH value stabilizes at b(2). Then, it is immersed for more than 10 minutes until the waterborne polyurethane and pH-sensitive hydrogel are transformed into a gel state to obtain the microfiber base fabric semi-finished product. Among them, the water absorption of the pH-sensitive hydrogel in the environment with a pH value of a is 110%, and the water absorption of the pH-sensitive hydrogel in the environment with a pH value of b is 2.5 times that in the environment with a pH value of a.

[0123] (6) Microwave heating is applied to the microfiber base fabric semi-finished product to further crosslink and cure the waterborne polyurethane; wherein the microwave heating time is 25 min and the heating frequency is 2450 MHz.

[0124] (7) The cross-linked and cured microfiber base fabric semi-finished product is immersed in alkaline solution II at a temperature of 85°C and then rolled to remove the marine phase and pH-sensitive hydrogel in the island fiber, thus obtaining waterborne polyurethane microfiber base fabric; wherein, the rolling pressure is 0.1 MPa.

[0125] The final waterborne polyurethane microfiber base fabric has a softness of 4.8 and a batch stability of softness of 10.2%.

[0126] Example 4

[0127] A method for preparing a waterborne polyurethane microfiber base fabric, comprising the following steps:

[0128] (1) Preparation of raw materials;

[0129] Waterborne polyurethane slurry: Manufacturer: Zhejiang Huafeng Synthetic Resin Co., Ltd., Brand: JF-PDY-515Y;

[0130] Alkaline solution I: Potassium hydroxide aqueous solution;

[0131] pH-sensitive hydrogel: polysaccharide-albumin pH-sensitive hydrogel, manufactured by Ruixi Bioshell, brand name R-BSA-PH, ground to an average particle size of 41μm before use;

[0132] Island-sea fiber nonwoven fabric: COPET / PET island-sea fiber nonwoven fabric; wherein, the mass ratio of COPET to PET is 30:70;

[0133] Electrolyte solution: 5 wt% sodium chloride aqueous solution;

[0134] Acid solution: 0.05 wt% hydrochloric acid aqueous solution;

[0135] Alkali Solution II: A 5 wt% NaOH aqueous solution;

[0136] (2) Add alkali solution I to the waterborne polyurethane slurry to adjust the pH value of the waterborne polyurethane slurry to a (13.1) and at the same time adjust the solid content of the waterborne polyurethane slurry to 35% to obtain an alkaline resin slurry.

[0137] (3) Mix 100 parts of alkaline resin slurry and 5 parts of pH-sensitive hydrogel evenly by weight to obtain water-containing polyurethane slurry.

[0138] The viscosity of the prepared water-containing polyurethane slurry was 550 mPa·s;

[0139] (4) Impregnate the island fiber nonwoven fabric in an aqueous polyurethane slurry, and control its liquid carrying rate to 100% to obtain the impregnated island fiber nonwoven fabric.

[0140] (5) The impregnated island fiber nonwoven fabric is immersed in an electrolyte solution, and acid is continuously added to the electrolyte solution until the pH value stabilizes at b (2.8). Then, it is immersed for more than 10 minutes until the waterborne polyurethane and pH-sensitive hydrogel are transformed into a gel state to obtain the microfiber base fabric semi-finished product. Among them, the water absorption of the pH-sensitive hydrogel in the environment with a pH value of a is 115%, and the water absorption of the pH-sensitive hydrogel in the environment with a pH value of b is 2.1 times that in the environment with a pH value of a.

[0141] (6) Microwave heating is applied to the microfiber base fabric semi-finished product to further crosslink and cure the waterborne polyurethane; wherein the microwave heating time is 20 min and the heating frequency is 2450 MHz.

[0142] (7) The cross-linked and cured microfiber base fabric semi-finished product is immersed in alkaline solution II at a temperature of 95°C and then rolled to remove the marine phase and pH-sensitive hydrogel in the island fiber, thus obtaining the waterborne polyurethane microfiber base fabric; wherein, the rolling pressure is 0.4 MPa.

[0143] The final waterborne polyurethane microfiber base fabric has a softness of 3.9 and a batch stability of softness of 17.4%.

[0144] Example 5

[0145] A method for preparing a waterborne polyurethane microfiber base fabric, comprising the following steps:

[0146] (1) Preparation of raw materials;

[0147] Waterborne polyurethane slurry: Manufacturer: Zhejiang Huafeng Synthetic Resin Co., Ltd., Brand: JF-PDY-P521H;

[0148] Alkaline solution I: Sodium hydroxide aqueous solution;

[0149] pH-sensitive hydrogel: Poly(N-isopropylacrylamide-co-itaconic acid) hydrogel, manufactured by Nanjing Genus, brand name JNS-GEL3, ground to an average particle size of 30μm before use;

[0150] Island-sea fiber nonwoven fabric: COPET / PA6 island-sea fiber nonwoven fabric; wherein, the mass ratio of COPET to PA6 is 30:70;

[0151] Electrolyte solution: 5 wt% sodium chloride aqueous solution;

[0152] Acid solution: 0.05 wt% hydrochloric acid aqueous solution;

[0153] Alkaline solution II: A 2 wt% NaOH aqueous solution;

[0154] (2) Add alkaline solution I to the waterborne polyurethane slurry to adjust the pH value of the waterborne polyurethane slurry to a(12) and adjust the solid content of the waterborne polyurethane slurry to 20% to obtain alkaline resin slurry.

[0155] (3) Mix 100 parts of alkaline resin slurry and 2 parts of pH-sensitive hydrogel evenly by weight to obtain water-containing polyurethane slurry.

[0156] The viscosity of the prepared water-containing polyurethane slurry was 360 mPa·s;

[0157] (4) Impregnate the island fiber nonwoven fabric in an aqueous polyurethane slurry and control its liquid carrying rate to 120% to obtain the impregnated island fiber nonwoven fabric.

[0158] (5) The impregnated island fiber nonwoven fabric is immersed in an electrolyte solution, and acid is continuously added to the electrolyte solution until the pH value stabilizes at b (3.3). Then, it is immersed for more than 10 minutes until the waterborne polyurethane and pH-sensitive hydrogel are transformed into a gel state to obtain the microfiber base fabric semi-finished product. Among them, the water absorption of the pH-sensitive hydrogel in the environment with a pH value of a is 105%, and the water absorption of the pH-sensitive hydrogel in the environment with a pH value of b is 2.4 times that in the environment with a pH value of a.

[0159] (6) Microwave heating is applied to the microfiber base fabric semi-finished product to further crosslink and cure the waterborne polyurethane; wherein the microwave heating time is 35 min and the heating frequency is 915 MHz.

[0160] (7) The cross-linked and cured microfiber base fabric semi-finished product is soaked in alkaline solution II at a temperature of 80°C and then rolled to remove the marine phase and pH-sensitive hydrogel in the island fiber, thus obtaining the waterborne polyurethane microfiber base fabric; wherein, the rolling pressure is 0.2 MPa.

[0161] The final waterborne polyurethane microfiber base fabric has a softness of 4.2 and a batch stability of softness of 23.2%.

Claims

1. A method for preparing a waterborne polyurethane microfiber base fabric, comprising impregnating a sea-island fiber nonwoven fabric with a waterborne polyurethane slurry, followed by curing and fiber opening of the waterborne polyurethane to obtain the waterborne polyurethane microfiber base fabric, characterized in that... The water-based polyurethane slurry is mainly composed of water-based polyurethane slurry and water-absorbing resin particles. The water absorption and water retention properties of the water-absorbing resin particles are adjustable. During the curing process, gelation is first carried out in an electrolyte solution, followed by complete curing by microwave heating; Before impregnation, the water absorption of the water-absorbing resin particles is controlled to be weak, so that the viscosity of the water-containing polyurethane slurry at 25°C is 200-800 mPa·s. During the gelation process, the water absorption of the superabsorbent polymer particles is enhanced, so that both the waterborne polyurethane and the superabsorbent polymer particles are transformed into a gel state. During the gelation process, the water absorption capacity of the superabsorbent resin particles is more than twice that of the superabsorbent resin particles before impregnation. During fiber opening, the water absorption and water retention properties of the water-absorbing resin particles are reduced, causing the volume of the water-absorbing resin particles to shrink. The superabsorbent polymer (SAP) particles are pH-sensitive hydrogels. Controlling the water absorption of SAP particles to be weak, the water absorption of SAP particles to be enhanced, and the water absorption and water retention of SAP particles to be weakened are all achieved by adjusting the pH value of the environment in which the SAP particles are located. The initial average particle size of the superabsorbent resin particles is at least 30 μm.

2. The method for preparing a waterborne polyurethane microfiber base fabric according to claim 1, characterized in that, Before impregnation, the pH value of the environment where the water-absorbing resin particles are located is adjusted to 'a', with the value of 'a' ranging from 12 to 13.

3. The water absorption of the pH-sensitive hydrogel in the environment with a pH value of 'a' is 105%-115%. During the gelation process, the pH value of the environment where the water-absorbing resin particles are located is adjusted to 'b', with the value of 'b' ranging from 2 to 3.

3. The water absorption of the pH-sensitive hydrogel in the environment with a pH value of 'b' is more than twice that in the environment with a pH value of 'a'.

3. The method for preparing a waterborne polyurethane microfiber base fabric according to claim 1, characterized in that, After impregnation, the liquid retention rate of the island fiber nonwoven fabric is 95-120%.

4. The method for preparing a waterborne polyurethane microfiber base fabric according to claim 1, characterized in that, The electrolyte solution is a sodium chloride solution with a concentration of ≥5wt%.

5. The method for preparing a waterborne polyurethane microfiber base fabric according to claim 1, characterized in that, Microwave heating time: 20-35 minutes.

6. The method for preparing a waterborne polyurethane microfiber base fabric according to claim 1, characterized in that, The island-island fiber nonwoven fabric is either COPET / PA6 island-island fiber nonwoven fabric or COPET / PET island-island fiber nonwoven fabric.

7. The method for preparing a waterborne polyurethane microfiber base fabric according to claim 6, characterized in that, The fiber opening process involves soaking the fiber in a NaOH solution with a concentration of 2-5 wt% at a temperature of 80-95℃ followed by rolling, with a rolling pressure of 0.05-0.4 MPa.

8. The method for preparing a waterborne polyurethane microfiber base fabric according to claim 6, characterized in that, The softness of waterborne polyurethane microfiber base fabric is 3.2-4.8, and the batch stability of softness is 10.2-23.2%.

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