Organic silicon leather with Janus structure and preparation method thereof

Abstract

The invention provides organic silicon leather with a Janus structure and a preparation method of the organic silicon leather. The preparation method comprises the following steps: S1, mixing diphenylmethane diisocyanate, polytetrahydrofuran ether glycol and dibutyltin for a first reaction, then adding 4-DOPO-(((3-hydroxypropyl) imino) methyl) phenol into a reaction system for a second reaction, and finally adding 3-perfluorohexyl-2-hydroxypropyl acrylate for terminating, so as to obtain a prepolymer; the polyurethane macromolecules containing fluorine and double bonds at the end are obtained; and S2, coating the surface of base cloth with the polyurethane macromolecule containing fluorine and double bonds at the end to form a bottom coating, then coating the surface of the bottom coating with hydrogen-containing silicone oil, vinyl silicone oil and a platinum catalyst, and carrying out hydrosilylation reaction through thermal induction treatment to form the organic silicon leather. According to the method, the hydrosilylation reaction is triggered through thermal induction, and the PU-PSi composite coating with the Janus structure is formed in situ. According to the method, no organic solvent is needed, the process is environment-friendly, and the obtained organic silicon leather has high bonding strength and excellent wear resistance, flame retardance and hydrophobicity.

Description

Technical Field

[0001] This invention relates to the field of silicone leather technology, specifically to a silicone leather with a Janus structure and its preparation method. Background Technology

[0002] Microfiber synthetic leather (microfiber leather for short) is a new type of surface material made from high-density nonwoven fabric of microfiber produced by needle punching or hydroentangling processes, which is then impregnated or laminated with polymer coating materials. It possesses a microstructure and texture similar to natural leather, exhibiting excellent performance and has been widely used in automotive interiors, aerospace, medical devices, sports equipment, high-speed rail seats, marine engineering, and other fields. Currently, the mainstream microfiber leather products on the market are mainly microfiber polyurethane (PU) leather. Its leather layer typically uses solvent-based polyurethane resin, which is adhered to the surface of the microfiber base fabric through a wet molding process of impregnation, curing, washing, and drying. This type of product has advantages such as good adhesion, high peel strength, soft texture, good breathability, and ease of care. However, its production process requires the use of large amounts of organic solvents, resulting in serious pollution emissions, long process flows, and high energy consumption—common problems in the industry—which contradict the current requirements of green manufacturing and sustainable development.

[0003] Organosilicon materials (-Si-O-) have attracted attention due to their low surface tension, hydrophobicity and abrasion resistance, good low-temperature flexibility, and flame and refractory properties. Using them as coating materials for microfiber leather can significantly impart excellent weather resistance, abrasion resistance, hydrophobicity and stain resistance, and flame retardancy to the finished product. Furthermore, the molding process of organosilicon coatings typically has low energy consumption and minimal environmental pollution, making it considered one of the important directions for the future upgrading and development of microfiber leather products. However, the adhesion between organosilicon materials and the base fabric is relatively weak, and their curing or reaction molding rate is usually slow. These issues have long constrained their large-scale application in microfiber leather preparation.

[0004] To overcome the aforementioned shortcomings, current efforts are being made to improve the performance of silicone leather through multi-layered structural designs or formulation optimization. For example, Chinese patent CN202410358463.9 describes a silicone leather for mobile phone cases, whose structure, from the inside out, includes a base fabric layer, an adhesive layer, a silicone polymer functional layer, and a smooth, tactile surface layer. This design enhances the feel by adding a hydrogel surface layer to the silicone rubber layer, and adds specific silicone oil, silica, and antistatic agents to the functional layer to enhance scratch and abrasion resistance. The adhesive layer further improves antistatic properties while ensuring strong adhesion. Another example is Chinese patent CN202311751054.7, which describes a soft, high-peel-strength, and breathable silicone leather and its preparation method, including a base layer, an intermediate coating, and a surface coating, aiming to achieve a balance between softness, high peel strength, and good breathability.

[0005] Although existing technologies have proposed various multi-layered silicone leather solutions that have improved some performance characteristics to a certain extent, they have not fundamentally solved the problem of insufficient bonding strength between the silicone coating and the microfiber base fabric. Furthermore, improving bonding strength may sacrifice the original low-temperature flexibility and hydrophobic properties of the silicone material. In addition, complex multi-layered structures often lead to cumbersome production processes, increased costs, and may affect the uniformity of the finished product's feel and durability. Therefore, developing a microfiber leather preparation technology that can maintain the inherent excellent properties of silicone materials, achieve high-strength and efficient bonding with the base fabric, and offer a simple process with balanced overall performance remains a pressing problem in this field. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides an organosilicon leather with a Janus structure and its preparation method, thus solving the problems mentioned in the background section.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] According to a first aspect of the present invention, a method for preparing silicone leather having a Janus structure is provided, comprising the following steps:

[0011] S1. Diphenylmethane diisocyanate, polytetrahydrofuran ether diol and dibutyltin are mixed for the first reaction. Then, 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol is added to the reaction system for the second reaction. Finally, 3-perfluorohexyl-2-hydroxypropyl acrylate is added for end capping to obtain a polyurethane macromolecule with fluorine-terminated double bonds. The specific reaction process is as follows.

[0012]

[0013] S2. The polyurethane macromolecules containing fluorine and double bonds are coated onto the surface of the base fabric to form a bottom coating. Then, hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst are coated onto the surface of the bottom coating. A hydrosilylation reaction is carried out through thermal induction treatment to form the organosilicon leather.

[0014] This application first prepares a macromolecular polyurethane prepolymer containing fluorine and double bonds as the lower surface coating material, and then uses an organosiloxane as the upper surface coating material. Through thermal induction catalysis, an integrated PU-PSi coating with a Janus structure is prepared by in-situ reaction molding on the surface of the microfiber base fabric. The PU layer firmly bonds the microfiber base fabric, and the PSi layer provides the microfiber leather with excellent wear resistance and flame retardant properties.

[0015] Preferably, in step S1, the mass ratio of diphenylmethane diisocyanate, polytetrahydrofuran ether diol, 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and 3-perfluorohexyl-2-hydroxypropyl acrylate is 50~51:30~40:5~10:5~10.

[0016] Preferably, in step S1, the temperature of the first reaction is 80~90℃ and the time is 1.5~2h;

[0017] The second reaction is carried out at a temperature of 80-90℃ for 2-3 hours.

[0018] The sealing temperature is 80~90℃, and the time is 0.5~1h.

[0019] Preferably, the mass of the dibutyltin accounts for 2 to 6% of the total mass of the diphenylmethane diisocyanate, polytetrahydrofuran ether diol, 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and 3-perfluorohexyl-2-hydroxypropyl acrylate.

[0020] Preferably, in step S2, the mass ratio of the hydrogen-containing silicone oil, vinyl silicone oil, and platinum catalyst is 50~55:40~45:3~5.

[0021] Preferably, the ratio of the total mass of the diphenylmethane diisocyanate, polytetrahydrofuran ether diol, 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and 3-perfluorohexyl-2-hydroxypropyl acrylate to the total mass of the hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst is 2 to 4:1.

[0022] Preferably, in step S2, the temperature of the heat-induced treatment is 120~160℃ and the time is 5~15min.

[0023] Preferably, after the hydrosilylation reaction is completed, a baking treatment is performed, wherein the baking treatment temperature is 140~160℃ and the time is 5~10min.

[0024] In the above preparation process, the coating method can be scraping, roller coating or spraying.

[0025] The platinum catalyst is selected from chloroplatinic acid or cassiterite catalyst.

[0026] According to a second aspect of the present invention, an organosilicon leather with a Janus structure obtained according to the above preparation method is provided, comprising a base fabric and a polyurethane coating and an organosilicon coating sequentially fixed to the surface of the base fabric, wherein the polyurethane coating and the organosilicon coating are covalently connected to form a PU-PSi composite coating with a Janus structure.

[0027] Preferably, the base fabric is a microfiber nonwoven fabric with a fiber diameter of 0.1~5mm and an areal density of 100~500g / m³. 2 ;

[0028] The thickness of both the polyurethane coating and the silicone coating is 10~100μm.

[0029] More preferably, the polyurethane coating accounts for 50-70% of the total thickness of the PU-PSi composite coating, and the silicone coating accounts for 30-50% of the total thickness of the PU-PSi composite coating. Beneficial effects

[0030] This invention provides an organosilicon leather with a Janus structure and its preparation method. It has the following beneficial effects:

[0031] (1) The present solution provides a method for preparing silicone leather with Janus structure. First, polyurethane macromolecules containing fluorine and double bonds are prepared. They have a double bond surface enrichment effect, which can realize the molecular-level covalent bond connection between the originally incompatible silicone component and polyurethane component at the interface, thereby realizing a double-sided coating. The polyurethane layer is bonded to the microfiber base fabric, and the silicone layer provides functionality as a cotton layer.

[0032] (2) The present solution provides an organosilicon leather with a Janus structure, which solves the problem that organosilicon leather in traditional technology requires a multi-layer structure, realizes an integrated coating structure, simplifies the production process and improves the bonding strength. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the organosilicon leather with a Janus structure prepared in Example 1 of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

[0035] The peel strength of the PU-PSi composite coating prepared in this invention was tested in accordance with GB / T 2716-2018 "Preparation of Chemical Test Samples for Leather";

[0036] The abrasion resistance of the PU-PSi composite coating was tested according to GB / T 21196-2007 "Textiles - Martindale Method for Determination of Abrasion Resistance of Fabrics".

[0037] Flame retardancy was tested for PU-PSi composite coating in accordance with GB / T 5455-2014 "Determination of vertical damage length, smoldering and afterflame time of burning performance of textiles".

[0038] Hydrophobicity was tested for the PU-PSi composite coating according to GB / T 30447-2013 "Test Method for Contact Angle of Nanofilms".

[0039] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0040] Example 1

[0041] Step 1: Add 50 parts of diphenylmethane diisocyanate, 35 parts of polytetrahydrofurandiol and 2 parts of dibutyltin to a three-necked flask containing a stirrer and a reflux condenser. Purge with nitrogen and heat in an oil bath at 80°C for 1.5 h. Then add 8 parts of 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and react for 2 h. Finally, add 5 parts of 3-perfluorohexyl-2-hydroxypropyl acrylate and react for 0.5 h. Then cool to 30°C to obtain a polyurethane macromolecule with fluorinated double bonds at the ends.

[0042] Step 2: Mix 50 parts of hydrogen-containing silicone oil, 45 parts of vinyl silicone oil and 5 parts of chloroplatinic acid evenly to obtain a composite material. The ratio of the mass of the polyurethane macromolecular prepolymer containing fluorine and double bonds at the control end to the total mass of hydrogen-containing silicone oil, vinyl silicone oil and chloroplatinic acid is 3:1.

[0043] Step 3: First, apply polyurethane macromolecules containing fluorine-terminated double bonds to the fiber with a diameter of 0.5 μm and an areal density of 200 g / m² using a blade coating method. 2 On the surface of the microfiber base fabric, a coating thickness of 50 μm was applied, and leveling was performed for 30 min to enrich double bonds. Then, the combined material from step 2 was coated with a 30 μm thick layer. Next, a thermal induction treatment was performed at 140℃ for 10 min to initiate a hydrosilylation reaction. Finally, post-treatment was performed by baking at 150℃ for 8 min, forming a Janus-structured PU-PSi integrated coating with a 60% PU layer and a 40% PSi layer. Figure 1 As shown.

[0044] Example 2

[0045] Step 1: Add 51 parts of diphenylmethane diisocyanate, 30 parts of polytetrahydrofurandiol and 5 parts of dibutyltin to a three-necked flask containing a stirrer and a reflux condenser. Purge with nitrogen and heat in an oil bath at 80°C for 1.5 h. Then add 10 parts of 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and react for 2 h. Finally, add 5 parts of 3-perfluorohexyl-2-hydroxypropyl acrylate and react for 0.5 h. Then cool to 30°C to obtain a polyurethane macromolecule with fluorinated double bonds at the ends.

[0046] Step 2: Mix 55 parts of hydrogen-containing silicone oil, 40 parts of vinyl silicone oil and 5 parts of castor oil evenly to obtain a composite material. The ratio of the mass of the polyurethane macromolecular prepolymer containing fluorine and double bonds at the control end to the total mass of hydrogen-containing silicone oil, vinyl silicone oil and chloroplatinic acid is 2:1.

[0047] Step 3: First, apply polyurethane macromolecules containing fluorine-terminated double bonds to the fiber with a diameter of 1 μm and an areal density of 300 g / m² using a blade coating method. 2 The surface of the microfiber base fabric is coated with a thickness of 30 μm. After leveling for 30 min to enrich the double bonds, the combined material from step 2 is coated with a thickness of 20 μm. Then, it is thermally induced at 140 °C for 8 min to carry out the hydrosilylation reaction. Finally, it is baked at 140 °C for 8 min for post-treatment to form a Janus structure PU-PSi integrated coating with a PU layer accounting for 60% and a PSi layer accounting for 40%.

[0048] Example 3

[0049] Step 1: Add 51 parts of diphenylmethane diisocyanate, 30 parts of polytetrahydrofurandiol and 4 parts of dibutyltin to a three-necked flask containing a stirrer and a reflux condenser. Purge with nitrogen and stir and heat in an oil bath at 80°C for 1.5 h. Then add 10 parts of 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and react for 2 h. Finally, add 5 parts of 3-perfluorohexyl-2-hydroxypropyl acrylate and react for 0.5 h. Then cool to 30°C to obtain a polyurethane macromolecule with fluorinated double bonds at the ends.

[0050] Step 2: Mix 53 parts of hydrogen-containing silicone oil, 42 parts of vinyl silicone oil and 5 parts of castor oil evenly to obtain a composite material. The ratio of the mass of the polyurethane macromolecular prepolymer containing fluorine and double bonds at the control end to the total mass of hydrogen-containing silicone oil, vinyl silicone oil and chloroplatinic acid is 4:1.

[0051] Step 3: First, apply polyurethane macromolecules containing fluorine-terminated double bonds to the fiber with a diameter of 0.1 μm and an areal density of 500 g / m² using a blade coating method. 2The surface of the microfiber base fabric is coated with a 10μm thick layer. After leveling for 30 minutes to enrich the double bonds, the combined material from step 2 is coated with a 10μm thick layer. Then, it is thermally induced at 160℃ for 5 minutes to carry out the hydrosilylation reaction. Finally, it is baked at 160℃ for 5 minutes for post-treatment to form a Janus structure PU-PSi integrated coating with 50% PU layer and 50% PSi layer.

[0052] Example 4

[0053] Step 1: Add 51 parts of diphenylmethane diisocyanate, 30 parts of polytetrahydrofurandiol and 4 parts of dibutyltin to a three-necked flask containing a stirrer and a reflux condenser. Purge with nitrogen and stir and heat in an oil bath at 80°C for 1.5 h. Then add 10 parts of 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and react for 2 h. Finally, add 5 parts of 3-perfluorohexyl-2-hydroxypropyl acrylate and react for 0.5 h. Then cool to 30°C to obtain a polyurethane macromolecule with fluorinated double bonds at the ends.

[0054] Step 2: Mix 50 parts of hydrogen-containing silicone oil, 45 parts of vinyl silicone oil and 5 parts of chloroplatinic acid evenly to obtain a composite material. The ratio of the mass of the polyurethane macromolecular prepolymer containing fluorine and double bonds at the control end to the total mass of hydrogen-containing silicone oil, vinyl silicone oil and chloroplatinic acid is 2.5:1.

[0055] Step 3: First, apply polyurethane macromolecules containing fluorine-terminated double bonds to the fiber with a diameter of 5 μm and an areal density of 100 g / m² using a blade coating method. 2 The surface of the microfiber base fabric is coated with a thickness of 100 μm. After leveling for 30 min to enrich the double bonds, the combined material from step 2 is coated with a thickness of 50 μm. Then, it is thermally induced at 120 °C for 15 min to carry out the hydrosilylation reaction. Finally, it is baked at 140 °C for 10 min for post-treatment to form a Janus structure PU-PSi integrated coating with a PU layer accounting for 70% and a PSi layer accounting for 30%.

[0056] Comparative Example 1

[0057] Step 1: Add 50 parts of diphenylmethane diisocyanate, 35 parts of polytetrahydrofurandiol and 2 parts of dibutyltin dilaurate to a three-necked flask containing a stirrer and a reflux condenser. Purge with nitrogen and heat in an oil bath at 80°C for 1.5 h. Then add 8 parts of 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and react for 2 h. Finally, add 5 parts of 3-perfluorohexyl-2-hydroxypropyl acrylate and react for 0.5 h. Then cool to 30°C to obtain a polyurethane macromolecule with fluorinated double bonds at the ends.

[0058] Step 2: Mix 50 parts of hydrogen-containing silicone oil, 45 parts of vinyl silicone oil and 5 parts of chloroplatinic acid evenly to obtain a composite material. The ratio of the mass of the polyurethane macromolecular prepolymer containing fluorine and double bonds at the control end to the total mass of hydrogen-containing silicone oil, vinyl silicone oil and chloroplatinic acid is 3:1.

[0059] Step 3: First, apply polyurethane macromolecules containing fluorine-terminated double bonds to the fiber with a diameter of 0.5 μm and an areal density of 200 g / m² using a blade coating method. 2 The surface of the microfiber base fabric is coated with a thickness of 50 μm. After leveling for 30 min to enrich the double bonds, the combined material from step 2 is coated with a thickness of 30 μm. Then, it is thermally induced at 140℃ for 10 min to carry out the hydrosilylation reaction. Finally, it is baked at 150℃ for 8 min for post-treatment to form a Janus structure PU-PSi integrated coating with a PU layer accounting for 60% and a PSi layer accounting for 40%.

[0060] Comparative Example 2

[0061] Step 1: Add 50 parts of diphenylmethane diisocyanate, 35 parts of polytetrahydrofurandiol and 2 parts of dibutyltin to a three-necked flask containing a stirrer and a reflux condenser. Purge with nitrogen and stir and heat in an oil bath at 80°C for 1.5 h. Then add 8 parts of 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and react for 2 h. Finally, add 5 parts of hydroxypropyl acrylate and react for 0.5 h. Then cool to 30°C to obtain polyurethane macromolecules with double bonds at the ends.

[0062] Step 2: Mix 50 parts of hydrogen-containing silicone oil, 45 parts of vinyl silicone oil and 5 parts of chloroplatinic acid evenly to obtain a composite material. The ratio of the mass of the polyurethane macromolecular prepolymer containing double bonds at the control end to the total mass of hydrogen-containing silicone oil, vinyl silicone oil and chloroplatinic acid is 3:1.

[0063] Step 3: First, apply polyurethane macromolecules containing double bonds to fibers with a diameter of 0.5 μm and an areal density of 200 g / m² using a blade coating method. 2 The surface of the microfiber base fabric is coated with a thickness of 50 μm. After leveling for 30 min to enrich the double bonds, the combined material from step 2 is coated with a thickness of 30 μm. Then, it is thermally induced at 140 °C for 10 min to carry out the hydrosilylation reaction. Finally, it is baked at 150 °C for 8 min for post-treatment.

[0064] Peel strength, abrasion resistance, flame retardancy and hydrophobicity of the silicone leather with Janus structure prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were tested respectively. The test results are shown in Table 1.

[0065] Table 1

[0066] Test Project Peel strength (N / cm) Wear resistance cycles (times) Smoldering time (s) Contact angle (°) Example 1 122 ＞50000 1.5 125 Example 2 134 ＞50000 1.6 122 Example 3 137 ＞50000 1.5 128 Example 4 178 ＞50000 1.3 125 Comparative Example 1 56 ＜10000 2.5 102 Comparative Example 2 0.7 ＜3000 5.6 95

[0067] The PU-PSi composite coating with Janus structure prepared in the above embodiments has high peel strength. Furthermore, the preparation method does not require organic solvents, is environmentally friendly, and has excellent adhesion strength, wear resistance, flame retardancy, and hydrophobicity, making it suitable for high-value-added applications such as automotive interiors and textiles.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a silicone leather having a Janus structure, characterized by: Includes the following steps: S1. Diphenylmethane diisocyanate, polytetrahydrofuran ether diol and dibutyltin are mixed for the first reaction, then 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol is added to the reaction system for the second reaction, and finally 3-perfluorohexyl-2-hydroxypropyl acrylate is added for end capping to obtain a polyurethane macromolecule with fluorine-terminated double bonds; S2. The polyurethane macromolecules containing fluorine and double bonds at the ends are coated onto the surface of the base fabric to form a bottom coating. Then, hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst are coated onto the surface of the bottom coating. A hydrosilylation reaction is carried out through thermal induction treatment to form the organosilicon leather.

2. The method for preparing silicone leather with Janus structure according to claim 1, characterized in that: In step S1, the mass ratio of diphenylmethane diisocyanate, polytetrahydrofuran ether diol, 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and 3-perfluorohexyl-2-hydroxypropyl acrylate is 50~51:30~40:5~10:5~10.

3. The method of claim 1, wherein the method is characterized by: In step S1, the temperature of the first reaction is 80~90℃, and the time is 1.5~2h; The second reaction is carried out at a temperature of 80-90℃ for 2-3 hours. The sealing temperature is 80~90℃, and the time is 0.5~1h.

4. The method of claim 1, wherein the method is characterized by: The mass of the dibutyltin accounts for 2 to 6% of the total mass of the diphenylmethane diisocyanate, polytetrahydrofuran ether diol, 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and 3-perfluorohexyl-2-hydroxypropyl acrylate.

5. The method of claim 1, wherein the method is characterized by: In step S2, the mass ratio of the hydrogen-containing silicone oil, vinyl silicone oil, and platinum catalyst is 50~55:40~45:3~5.

6. The method of claim 1, wherein the method is characterized by: The ratio of the total mass of the diphenylmethane diisocyanate, polytetrahydrofuran ether diol, 4-DOPO-(((3-hydroxypropyl)imino)methyl)phenol and 3-perfluorohexyl-2-hydroxypropyl acrylate to the total mass of the hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst is 2 to 4:

1.

7. The method of claim 1, wherein the method further comprises: In step S2, the temperature of the heat-induced treatment is 120~160℃ and the time is 5~15min.

8. The method of claim 1, wherein the method is characterized by: After the hydrosilylation reaction is completed, a baking process is performed at a temperature of 140~160℃ for 5~10 minutes.

9. The silicone leather having a Janus structure according to the production method of any one of claims 1 to 8, characterized by, It includes a base fabric and a polyurethane coating and a silicone coating sequentially fixed to the surface of the base fabric, wherein the polyurethane coating and the silicone coating are covalently connected to form a PU-PSi composite coating with a Janus structure.

10. The silicone leather with Janus structure according to claim 9, characterized in that: The base cloth is an ultra-fine fiber non-woven cloth, with a fiber diameter of 0.1-5mm and a surface density of 100-500g / m 2 ; The thickness of both the polyurethane coating and the silicone coating is 10~100μm.

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