A water-reducing high-moisture-permeable microfiber synthetic leather and its preparation method

Abstract

The invention discloses a water-reducible high-permeability ultrafine fiber synthetic leather and a preparation method thereof. The preparation method comprises: rinsing a PET / PVA island-island fiber nonwoven fabric with deionized water and then immersing it in a polyvinyl alcohol solution, followed by drying; impregnating the PET / PVA island-island fiber nonwoven fabric with an anionic aqueous polyurethane having a solid content of 50%, and then drying to obtain a (PET / PVA) / WPU composite material; placing the (PET / PVA) / WPU composite material in hot water for decompression for 30 to 40 minutes, and then washing it three times after completion; immersing the opened (PET / PVA) / WPU composite material in a chitosan solution with a mass concentration of 3% and a sodium alginate solution with a mass concentration of 3%, and drying, and repeating the cycle ten times to achieve layer-by-layer self-assembly between the anionic aqueous polyurethane, the cationic chitosan, and the anionic sodium alginate. The water vapor permeability of the ultrafine fiber synthetic leather substrate prepared by the invention reaches 1376.77 g / m 2 24 hours and greatly improved safety, the preparation process does not generate pollution, low cost and low energy consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic leather, and particularly relates to a water-reducing high-moisture-permeable ultrafine fiber synthetic leather and a preparation method thereof. Background Art

[0002] Natural leather has been used for thousands of years, long beloved by consumers for its rich feel, excellent elasticity, strength, and excellent breathability and moisture permeability. However, the processing of raw hides is an extremely energy-intensive process, with complex production processes and the use of large quantities of chemical solvents, resulting in significant pollution. Furthermore, with the development and progress of society, people's awareness of environmental protection and animal protection has gradually increased, leading to the emergence of synthetic leather. The feel and performance of synthetic leather are benchmarked against natural leather, aiming to approach or even surpass it. Microfiber synthetic leather, also known as microfiber leather, is the latest generation of synthetic leather and is currently considered the best alternative to natural leather, with broad development prospects.

[0003] Microfiber synthetic leather is usually made from sea-island fiber nonwovens and polyurethane elastomers. Sea-island fiber nonwovens are divided into fixed-island and irregular-island types. The raw materials for fixed-island microfibers are generally polyamide (PA) / water-soluble polyester (COPET). The microfiber synthetic leather base fabric made of polyester (PET) / water-soluble polyester (COPET) fixed-island microfibers has a higher density and a tighter fiber arrangement, and is generally used for suede leather. The raw materials for irregular-island microfibers are generally polyamide (PA) / polyethylene (PE) or polyamide (PA) / low-density polyethylene (LDPE). The microfiber synthetic leather base fabric has a lower density and is light and thin, and is mainly used in the manufacture of smooth leather.

[0004] Weight reduction is the most important step in the preparation process of microfiber synthetic leather. The weight reduction method can be divided into alkali weight reduction and toluene weight reduction according to whether it is fixed island fiber. The alkali weight reduction method is a dissolution method suitable for fixed island type composite microfibers. Use high concentration NaOH with a certain concentration and a certain temperature to dissolve COPET to obtain a single dispersed phase fiber component. For indeterminate island type sea island fibers, hot toluene is needed to reduce the weight, dissolve the continuous phase PE fiber, and obtain a single dispersed phase fiber. Both weight reduction methods are polluting and are not the best weight reduction solutions.

[0005] Natural leather has good water vapor permeability, usually between 800 and 1500 g / m 2 24 hours, while the water vapor permeability of microfiber suede is generally between 200 and 1000g / m 2Compared with natural leather, the water and air permeability of microfiber synthetic leather still has room for improvement within 24 hours. Secondly, the reduction process in the preparation of microfiber synthetic leather is too polluting, which is contrary to the development goal of green production. Therefore, it is particularly important to develop green and environmentally friendly reduction methods. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a water-reducing high-permeability microfiber synthetic leather and a preparation method thereof. The water vapor permeability of the prepared microfiber synthetic leather substrate reaches 1376.77 g / m 2 24 hours and greatly improved safety, the preparation process does not generate pollution, low cost and low energy consumption.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a water-reducing high-moisture-permeable microfiber synthetic leather comprises the following steps:

[0009] Step 1: immersing the PET / PVA island-in-sea fiber nonwoven fabric in a polyvinyl alcohol solution having a mass concentration of 4% to 10% for 30 to 40 minutes after rinsing with deionized water, and then drying;

[0010] Step 2: impregnating the PET / PVA island-in-sea fiber nonwoven fabric treated in step 1 with an anionic aqueous polyurethane having a solid content of 50% for 3 to 5 minutes, and then drying to obtain a (PET / PVA) / WPU composite material;

[0011] Step 3: Place the (PET / PVA) / WPU composite material obtained in step 2 in hot water at 80-100°C for 30-40 minutes, and then wash it with water 3-5 times;

[0012] Step 4: The (PET / PVA) / WPU composite material opened in step 3 is immersed in a chitosan solution with a mass concentration of 1% to 3% and a sodium alginate solution with a mass concentration of 3% to 5% in turn, and dried after each immersion for 3 minutes. The cycle is repeated ten times to achieve layer-by-layer self-assembly between anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate to obtain a water-reducible, highly moisture-permeable microfiber synthetic leather.

[0013] This invention also has the following technical features:

[0014] Preferably, the drying in step 1 is performed at 80° C. for 10 to 15 minutes.

[0015] Preferably, the drying in step 2 is performed at 80° C. for 30 to 60 minutes.

[0016] Preferably, the drying in step 4 is performed at 80° C. for 20 to 30 minutes.

[0017] Preferably, the average molecular weight of the polyvinyl alcohol in step 1 is 20,000.

[0018] The present invention also protects a water-reducing high moisture permeability ultrafine fiber synthetic leather prepared by the method described above.

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

[0020] The present invention occupies the pores of the PET / PVA island-in-the-sea fiber nonwoven fabric by impregnation with PVA solution, indirectly controlling the impregnation amount and uniformity of WPU, so that the WPU filler is evenly distributed in the gaps between the fibers; dissolving the PVA by water reduction, and controlling the fiber pores and size by the impregnation amount of PVA, thereby physically improving the water vapor permeability of the substrate; further, chitosan and sodium alginate are sequentially impregnated, and through the anionic and cation binding between the anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate and electrostatic adsorption, layer-by-layer self-assembly is achieved, thereby improving the water vapor permeability of the substrate to 1376.77 g / m 2 24 hours;

[0021] The whole process of water reduction of the present invention does not use any solvents, does not generate pollution, and has low reduction cost, low energy consumption, and simple equipment requirements. It is currently the most advanced and environmentally friendly reduction technology.

[0022] The ultrafine fiber synthetic leather prepared by the present invention does not require softening treatment, has a good fiber opening effect, and does not introduce any particulate matter content, salt ion content, organic matter, or non-volatile components during the process, thereby greatly improving the safety of the ultrafine fiber synthetic leather. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope image (400 μm) of the PET / PVA island-in-the-sea fiber nonwoven fabric after impregnation with PVA in Example 1;

[0024] Figure 2 This is a scanning electron microscope image (100 μm) of the PET / PVA island-in-the-sea fiber nonwoven fabric after impregnation with PVA in Example 1;

[0025] Figure 3 This is an electron microscope image of the (PET / PVA) / WPU composite material in Example 1 after hot water reduction and before washing;

[0026] Figure 4 This is an electron microscope image of the (PET / PVA) / WPU composite material in Example 1 after being washed with hot water after weight reduction;

[0027] Figure 5 This is a scanning electron microscope image (200 μm) of the (PET / PVA) / WPU composite material in Example 1 after layer-by-layer deposition of chitosan-sodium alginate;

[0028] Figure 6 This is a scanning electron microscope image (100 μm) of the (PET / PVA) / WPU composite material in Example 1 after layer-by-layer deposition of chitosan-sodium alginate. DETAILED DESCRIPTION

[0029] The specific contents of the present invention are further explained in detail below with reference to the embodiments.

[0030] Example 1

[0031] This embodiment provides a method for preparing a water-reducing, highly moisture-permeable microfiber synthetic leather, comprising the following steps:

[0032] Step 1: PET / PVA fixed island fiber nonwoven fabric is selected as the substrate, and polyvinyl alcohol (PVA) with an average molecular weight of 20,000 is dissolved in hot water at 90°C to prepare a PVA solution with a concentration of 4%; the PET / PVA island fiber nonwoven fabric washed with deionized water is immersed in the PVA solution for 40 minutes, and then dried at 80°C for 10 minutes to shape the nonwoven fabric, and the amount of PVA impregnation is controlled to fill some of the pores between the fibers, fixing the fiber position and pore size;

[0033] Step 2: impregnating the PET / PVA island-in-sea fiber nonwoven fabric treated in step 1 with an anionic aqueous polyurethane having a solid content of 50% for 5 minutes, and then drying at 80° C. for 30 minutes to obtain a (PET / PVA) / WPU composite material;

[0034] Step 3: The (PET / PVA) / WPU composite material obtained in step 2 is placed in 80°C hot water for 30 minutes for dewatering; the water-soluble PVA fiber is automatically dissolved in hot water to reduce the water content of the impregnated base fabric. As time goes by and the water temperature increases, water molecules penetrate into the non-crystalline region of the PVA fiber. At the same time, the water molecules are also affected by the affinity of the hydroxyl groups in the PVA molecules, causing the fiber to expand laterally and shrink longitudinally. When the water temperature continues to increase, the PVA fiber is dissolved into small gel-like fragments. After the impregnation is completed, the base fabric is repeatedly washed three times to completely open the fibers.

[0035] Step 4: dilute acetic acid to a concentration of 1.5%, dissolve chitosan in the acetic acid solution, and stir at high speed with a magnetic stirrer to quickly dissolve it to obtain a chitosan solution with a mass concentration of 3%; add sodium alginate to deionized water in portions, stir at high speed with a magnetic stirrer for 15 minutes, and dissolve it to obtain a sodium alginate solution with a mass concentration of 3%;

[0036] The (PET / PVA) / WPU composite material opened in step three was immersed in chitosan solution and sodium alginate solution in turn for 3 minutes. After each immersion, it was dried at 80°C for 30 minutes. This cycle was repeated ten times to achieve layer-by-layer self-assembly between anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate, thereby obtaining a water-reducible and highly moisture-permeable microfiber synthetic leather.

[0037] Figure 1 This is a scanning electron microscope image (400 μm) of the PET / PVA island-in-the-sea fiber nonwoven fabric after impregnation with PVA in Example 1; Figure 2 The electron microscope scanning image (100 μm) of the PET / PVA island-island fiber nonwoven fabric after impregnation with PVA in Example 1; Figure 1 and Figure 2 It can be seen from the figure that the dried PVA binds the island fibers together and the pores between the island fibers become larger; from the feel analysis, the island fiber nonwoven fabric feels significantly harder after being impregnated with PVA, which has the effect of shaping the nonwoven fabric. Therefore, the amount of PVA impregnation can be controlled to fill part of the pores between the fibers and fix the fiber position and pore size.

[0038] Figure 3 This is an electron microscope image of the (PET / PVA) / WPU composite material in Example 1 after hot water reduction and before washing; Figure 4 This is an electron microscope scanning image of the (PET / PVA) / WPU composite material in Example 1 after hot water weight reduction and washing; from the scanning electron microscope image before washing, it can be seen that after hot water weight reduction, the fiber changes from a sea island fiber to a bundle of ultrafine fibers, but there is still residual PVA on the surface of the non-woven fabric fiber that has not been washed with hot water, and the PVA bonds the PET ultrafine fibers after fiber opening together again, and the weight reduction effect is not good; compared with the base cloth before washing, there is no PVA residue on the surface of the base cloth after washing, the PET ultrafine fibers are loose, the fiber gaps are large, and the weight reduction effect is excellent.

[0039] Figure 5 This is a scanning electron microscope image (200 μm) of the (PET / PVA) / WPU composite material in Example 1 after layer-by-layer deposition of chitosan-sodium alginate; Figure 6 This is a scanning electron microscope image (100 μm) of the (PET / PVA) / WPU composite material after chitosan-sodium alginate layer-by-layer deposition in Example 1. Figure 5 and Figure 6 It can be seen that the anionic and cation-anionic combination between anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate changes the fiber surface from smooth to rough through electrostatic adsorption, which shows that chitosan and sodium alginate are effectively deposited on the surface of PET ultrafine fibers, and chitosan-sodium alginate layer-by-layer self-assembly is achieved on the fiber surface.

[0040] Example 2

[0041] This embodiment provides a method for preparing a water-reducing, highly moisture-permeable microfiber synthetic leather, comprising the following steps:

[0042] Step 1: PET / PVA fixed island fiber nonwoven fabric is selected as the substrate, and polyvinyl alcohol (PVA) with an average molecular weight of 20,000 is dissolved in 90°C hot water to prepare a PVA solution with a concentration of 10%; the PET / PVA island fiber nonwoven fabric washed with deionized water is immersed in the PVA solution for 30 minutes, and then dried at 80°C for 15 minutes to shape the nonwoven fabric. The amount of PVA impregnation is controlled to fill some of the pores between the fibers, fixing the fiber position and pore size;

[0043] Step 2: impregnating the PET / PVA island-in-sea fiber nonwoven fabric treated in step 1 with an anionic aqueous polyurethane having a solid content of 50% for 3 minutes, and then drying at 80° C. for 60 minutes to obtain a (PET / PVA) / WPU composite material;

[0044] Step 3: The (PET / PVA) / WPU composite material obtained in step 2 is placed in 100°C hot water for 40 minutes; the water-soluble PVA fiber can automatically dissolve in hot water to reduce the water content of the impregnated base fabric. As time goes by and the water temperature increases, water molecules penetrate into the non-crystalline region of the PVA fiber. At the same time, the water molecules are also affected by the affinity of the hydroxyl groups in the PVA molecules, causing the fiber to expand laterally and shrink longitudinally. When the water temperature continues to increase, the PVA fiber is dissolved into small gel-like fragments. After the impregnation is completed, it is repeatedly washed with water 5 times to completely open the base fabric.

[0045] Step 4: dilute acetic acid to a concentration of 1.5%, dissolve chitosan in the acetic acid solution, and stir at high speed with a magnetic stirrer to quickly dissolve it to obtain a chitosan solution with a mass concentration of 1%; add sodium alginate to deionized water in portions, stir at high speed with a magnetic stirrer for 15 minutes, and dissolve it to obtain a sodium alginate solution with a mass concentration of 5%;

[0046] The (PET / PVA) / WPU composite material opened in step three was immersed in chitosan solution and sodium alginate solution in turn for 3 minutes, dried at 80°C for 20 minutes after each immersion, and repeated ten times to achieve layer-by-layer self-assembly between anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate to obtain water-reducible high moisture permeability microfiber synthetic leather.

[0047] Example 3

[0048] This embodiment provides a method for preparing a water-reducing, highly moisture-permeable microfiber synthetic leather, comprising the following steps:

[0049] Step 1: PET / PVA fixed island fiber nonwoven fabric is selected as the substrate, and polyvinyl alcohol (PVA) with an average molecular weight of 20,000 is dissolved in 90°C hot water to prepare a PVA solution with a concentration of 6%; the PET / PVA island fiber nonwoven fabric washed with deionized water is immersed in the PVA solution for 35 minutes, and then dried at 80°C for 12 minutes to shape the nonwoven fabric, and the amount of PVA impregnation is controlled to fill some of the pores between the fibers, fixing the fiber position and pore size;

[0050] Step 2: impregnating the PET / PVA island-in-sea fiber nonwoven fabric treated in step 1 with an anionic aqueous polyurethane having a solid content of 50% for 4 minutes, and then drying at 80° C. for 50 minutes to obtain a (PET / PVA) / WPU composite material;

[0051] Step 3: The (PET / PVA) / WPU composite material obtained in step 2 is placed in 90°C hot water for 35 minutes; the water-soluble PVA fiber can automatically dissolve in hot water to reduce the water content of the impregnated base fabric. As time goes by and the water temperature increases, water molecules penetrate into the non-crystalline region of the PVA fiber. At the same time, the water molecules are also affected by the affinity of the hydroxyl groups in the PVA molecules, causing the fiber to expand laterally and shrink longitudinally. When the water temperature continues to increase, the PVA fiber is dissolved into small gel-like fragments. After the impregnation is completed, the base fabric is repeatedly washed with water 4 times to completely open the fiber.

[0052] Step 4: dilute acetic acid to a concentration of 1.5%, dissolve chitosan in the acetic acid solution, and stir at high speed with a magnetic stirrer to quickly dissolve it to obtain a chitosan solution with a mass concentration of 2%; add sodium alginate to deionized water in portions, stir at high speed with a magnetic stirrer for 15 minutes, and dissolve it to obtain a sodium alginate solution with a mass concentration of 4%;

[0053] The (PET / PVA) / WPU composite material opened in step three was immersed in chitosan solution and sodium alginate solution in turn for 3 minutes, dried at 80°C for 25 minutes after each immersion, and repeated ten times to achieve layer-by-layer self-assembly between anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate to obtain water-reducible high moisture permeability microfiber synthetic leather.

[0054] Example 4

[0055] This embodiment provides a method for preparing a water-reducing, highly moisture-permeable microfiber synthetic leather, comprising the following steps:

[0056] Step 1: PET / PVA fixed island fiber nonwoven fabric is selected as the substrate, and polyvinyl alcohol (PVA) with an average molecular weight of 20,000 is dissolved in hot water at 90°C to prepare a PVA solution with a concentration of 4%; the PET / PVA island fiber nonwoven fabric washed with deionized water is immersed in the PVA solution for 30 minutes, and then dried at 80°C for 10 minutes to shape the nonwoven fabric, and the amount of PVA impregnation is controlled to fill some of the pores between the fibers, fixing the fiber position and pore size;

[0057] Step 2: impregnating the PET / PVA island-in-sea fiber nonwoven fabric treated in step 1 with an anionic aqueous polyurethane having a solid content of 50% for 5 minutes, and then drying at 80° C. for 30 minutes to obtain a (PET / PVA) / WPU composite material;

[0058] Step 3: The (PET / PVA) / WPU composite material obtained in step 2 is placed in 85°C hot water for 30 minutes for dewatering; the water-soluble PVA fiber is automatically dissolved in hot water to reduce the water content of the impregnated base fabric. As time goes by and the water temperature increases, water molecules penetrate into the non-crystalline region of the PVA fiber. At the same time, the water molecules are also affected by the affinity of the hydroxyl groups in the PVA molecules, causing the fiber to expand laterally and shrink longitudinally. When the water temperature continues to increase, the PVA fiber is dissolved into small gel-like fragments. After the impregnation is completed, the base fabric is repeatedly washed three times to completely open the fibers.

[0059] Step 4: dilute acetic acid to a concentration of 1.5%, dissolve chitosan in the acetic acid solution, and stir at high speed with a magnetic stirrer to quickly dissolve it to obtain a chitosan solution with a mass concentration of 3%; add sodium alginate to deionized water in portions, stir at high speed with a magnetic stirrer for 15 minutes, and dissolve it to obtain a sodium alginate solution with a mass concentration of 3%;

[0060] The (PET / PVA) / WPU composite material opened in step three was immersed in chitosan solution and sodium alginate solution in turn for 3 minutes. After each immersion, it was dried at 80°C for 30 minutes. This cycle was repeated ten times to achieve layer-by-layer self-assembly between anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate, thereby obtaining a water-reducible and highly moisture-permeable microfiber synthetic leather.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a water-reducing high-permeability microfiber synthetic leather, characterized in that: The following steps are involved: Step 1: immersing the PET / PVA island-in-sea fiber nonwoven fabric in a polyvinyl alcohol solution having a mass concentration of 4% to 10% for 30 to 40 minutes after rinsing with deionized water, and then drying; Step 2: impregnating the PET / PVA island-in-sea fiber nonwoven fabric treated in step 1 with an anionic aqueous polyurethane having a solid content of 50% for 3 to 5 minutes, and then drying to obtain a (PET / PVA) / WPU composite material; Step 3: Place the (PET / PVA) / WPU composite material obtained in step 2 in hot water at 80-100°C for 30-40 minutes, and then wash it with water 3-5 times; Step 4: The (PET / PVA) / WPU composite material opened in step 3 is immersed in a chitosan solution with a mass concentration of 1% to 3% and a sodium alginate solution with a mass concentration of 3% to 5% in turn, and dried after each immersion for 3 minutes. The cycle is repeated ten times to achieve layer-by-layer self-assembly between anionic waterborne polyurethane-cationic chitosan-anionic sodium alginate to obtain a water-reducible, highly moisture-permeable microfiber synthetic leather.

2. The method for preparing the water-reducing high moisture permeability microfiber synthetic leather according to claim 1, wherein: The drying step is carried out at 80° C. for 10 to 15 minutes.

3. The method for preparing the water-reducing high moisture permeability microfiber synthetic leather according to claim 1, wherein: The drying in step 2 is performed at 80° C. for 30 to 60 minutes.

4. The method for preparing the water-reducing high moisture permeability microfiber synthetic leather according to claim 1, wherein: The drying described in step 4 is drying at 80° C. for 20 to 30 minutes.

5. The method for preparing the water-reducing high moisture permeability microfiber synthetic leather according to claim 1, wherein: The average molecular weight of the polyvinyl alcohol described in step 1 is 20,000.

6. A water-reducible high moisture permeability microfiber synthetic leather prepared by the method according to any one of claims 1 to 5.

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