阅读说明：本技术 一种具有高吸湿透气性的聚氨酯合成革及其制备方法 (Polyurethane synthetic leather with high moisture absorption and air permeability and preparation method thereof ) 是由 胡玉婷 于 2021-08-23 设计创作，主要内容包括：本发明涉及合成革技术领域,公开了一种具有高吸湿透气性的聚氨酯合成革及其制备方法。所述聚氨酯合成革包括无纺布基布和聚氨酯涂层,所述聚氨酯涂层包括以下重量份的原料：水性聚氨酯乳液80-100份,表面活性剂2-6份,吸湿透气颗粒5-10份,水溶性纤维素类增稠剂0.1-2份,异氰酸酯类交联剂0.1-2份,水性着色剂0-8份；所述吸湿透气颗粒包括硅藻土以及包覆在硅藻土外的多孔亲水聚合物包覆层。本发明所采用的吸湿透气颗粒中,在硅藻土表面包覆有多孔亲水聚合物包覆层,能够防止硅藻土的加入导致合成革表面出现毛刺感,且不会对硅藻土的吸湿透气性造成较大影响。(The invention relates to the technical field of synthetic leather, and discloses polyurethane synthetic leather with high moisture absorption and air permeability and a preparation method thereof. The polyurethane synthetic leather comprises non-woven fabric base cloth and a polyurethane coating, wherein the polyurethane coating comprises the following raw materials in parts by weight: 80-100 parts of water-based polyurethane emulsion, 2-6 parts of surfactant, 5-10 parts of moisture-absorbing and breathable particles, 0.1-2 parts of water-soluble cellulose thickening agent, 0.1-2 parts of isocyanate crosslinking agent and 0-8 parts of water-based colorant; the moisture-absorbing and breathable particles comprise diatomite and a porous hydrophilic polymer coating layer coated outside the diatomite. In the moisture-absorbing and breathable particles adopted by the invention, the porous hydrophilic polymer coating layer is coated on the surface of the diatomite, so that the phenomenon that the surface of the synthetic leather is burred due to the addition of the diatomite can be prevented, and the moisture absorption and the breathability of the diatomite are not greatly influenced.)

1. The polyurethane synthetic leather with high moisture absorption and air permeability comprises non-woven fabric base cloth and a polyurethane coating, and is characterized in that the polyurethane coating comprises the following raw materials in parts by weight: 80-100 parts of water-based polyurethane emulsion, 2-6 parts of surfactant, 5-10 parts of moisture-absorbing and breathable particles, 0.1-2 parts of water-soluble cellulose thickening agent, 0.1-2 parts of isocyanate crosslinking agent and 0-8 parts of water-based colorant; the moisture-absorbing and breathable particles comprise diatomite and a porous hydrophilic polymer coating layer coated outside the diatomite.

2. The polyurethane leather of claim 1, wherein the moisture-absorbing and breathable particles comprise diatomaceous earth with a particle size of 300-400 mesh and a porous hydrophilic polymer coating layer with a thickness of 10-20 μm.

3. The polyurethane synthetic leather of claim 2, wherein the moisture-absorbing breathable particles are prepared by a method comprising the steps of:

(A) and (3) diatomite surface treatment: mixing 3-aminopropyltrimethoxysilane and water according to the mass ratio of 1:60-70 to prepare a coupling agent solution; adding diatomite into the coupling agent solution, fully dispersing, and stirring and reacting for 1-2h at the temperature of 30-50 ℃; after the reaction is finished, filtering, and then soaking in birch tar for 1-3h to obtain modified diatomite;

(B) coating with hydrophilic polymer: dissolving water-soluble acrylic resin and water-soluble epoxy resin in water to prepare a coating agent solution; adding the modified diatomite into the coating agent solution, stirring for 2-3h after fully dispersing, and filtering to obtain hydrophilic polymer coated diatomite;

(C) hole making and curing: placing the hydrophilic polymer coated diatomite at 60-70 ℃ under 0.01-0.03MPa for 30-40min, heating to 160-170 ℃ and curing for 2-3h to obtain the moisture-absorbing and breathable particles.

4. The polyurethane synthetic leather according to claim 3, wherein in the step (A), the mass ratio of the diatomite to the coupling agent solution is 1: 50-60.

5. The polyurethane synthetic leather of claim 3, wherein in the step (B), the mass ratio of the water-soluble acrylic resin, the water-soluble epoxy resin and the water in the coating agent solution is 4-5:1: 50-60.

6. The polyurethane synthetic leather of claim 3, wherein in step (B), the mass ratio of the modified diatomite to the coating agent solution is 1: 50-70.

7. The polyurethane synthetic leather of claim 1 wherein the surfactant is sodium lauryl sulfate.

8. The polyurethane synthetic leather of claim 1 wherein the solid content of the aqueous polyurethane emulsion is 20-40 wt%.

9. A method for preparing the polyurethane synthetic leather according to any one of claims 1 to 8, which comprises the following steps:

(1) uniformly mixing all raw materials of the polyurethane coating, and introducing micro bubbles generated by a micro bubble generator into the mixture to obtain foaming aqueous polyurethane slurry;

(2) and (3) dipping the non-woven fabric into the foaming waterborne polyurethane slurry, drying, and then carrying out alkali decrement treatment and post-treatment to obtain the polyurethane synthetic leather with high moisture absorption and air permeability.

10. The preparation method as claimed in claim 9, wherein in the step (2), the impregnation amount is controlled to be 400-700g/m during the impregnation process²。

Technical Field

The invention relates to the technical field of synthetic leather, in particular to polyurethane synthetic leather with high moisture absorption and air permeability and a preparation method thereof.

Background

The synthetic leather is also called as imitation leather or sizing material, is made by processing various foaming or film-covering polyvinyl chloride (PVC) or Polyurethane (PU) with different formulas on a textile fabric base or a non-woven fabric base, can be processed and manufactured according to the requirements of different strength, abrasion resistance, cold resistance, color, luster, pattern and the like, and has the characteristics of various patterns and varieties, good waterproof performance, neat edge and breadth, high utilization rate and lower price than real leather.

Synthetic leather with textile fabric as a base and polyurethane as a coating has been developed for over 80 years, and is widely applied to various aspects of people's lives at present. The traditional polyurethane synthetic leather produced by taking solvent polyurethane as a main raw material has the problems of volatilization of organic solvents and pollution. The Waterborne Polyurethane (WPU) takes water as a medium, has the advantages of no toxicity, no odor, no pollution, difficult combustion and the like, is a good substitute material of the traditional solvent type polyurethane, and is widely applied to the fields of textile fabric coatings, synthetic leather, natural leather finishing, adhesives and the like. A functional coating product which is formed by coating PU (polyurethane) as matrix resin on textile fabrics is called ecological functional synthetic leather, is fourth-generation artificial leather, and is the development direction of the future synthetic leather.

At present, the difference between polyurethane synthetic leather and natural leather in the aspects of moisture absorption and air permeability is obvious, which is a problem to be solved urgently in the field of synthetic leather. Chinese patent document CN201810850749.3 discloses a method for preparing moisture-absorbing, antibacterial and water vapor permeable graphene modified polyurethane synthetic leather, wherein the moisture absorption and air permeability of the synthetic leather can be improved by adding graphene with a porous structure, but simultaneously, the addition of graphene can also cause burr feeling on the surface of the synthetic leather, and seriously affect the hand feeling.

Disclosure of Invention

In order to solve the technical problems, the invention provides polyurethane synthetic leather with high moisture absorption and air permeability and a preparation method thereof. According to the invention, the special moisture-absorbing and breathable particles are added into the polyurethane synthetic leather, so that the synthetic leather has higher dilution and breathability, and simultaneously, the surface of the synthetic leather is prevented from generating burr feeling, and the synthetic leather has better hand feeling.

The specific technical scheme of the invention is as follows:

the polyurethane synthetic leather with high moisture absorption and air permeability comprises non-woven fabric base cloth and a polyurethane coating, wherein the polyurethane coating comprises the following raw materials in parts by weight: 80-100 parts of water-based polyurethane emulsion, 2-6 parts of surfactant, 5-10 parts of moisture-absorbing and breathable particles, 0.1-2 parts of water-soluble cellulose thickening agent, 0.1-2 parts of isocyanate crosslinking agent and 0-8 parts of water-based colorant; the moisture-absorbing and breathable particles comprise diatomite and a porous hydrophilic polymer coating layer coated outside the diatomite.

The diatomite has good water absorbability, and the absorbed water can be naturally evaporated, so that the water absorbability of the synthetic leather can be improved, and meanwhile, the synthetic leather has good air permeability due to the high porosity of the diatomite. However, since the diatomite has high hardness and a rough surface, the synthetic leather has improved moisture absorption and air permeability and also has an influence on hand feeling, so that the surface of the synthetic leather has a burr feeling. Aiming at the problem, the diatomite is coated by the hydrophilic polymer, and the hydrophilic polymer layer has higher flexibility compared with the diatomite, so that the hand feeling of the surface of the moisture-absorbing and breathable particles can be improved, and the burr feeling on the surface of the synthetic leather caused by adding the hydrophilic polymer layer is prevented; in addition, the coating layer adopts hydrophilic polymers and has high porosity, so that the moisture absorption and air permeability of the diatomite are not greatly influenced.

Preferably, in the moisture-absorbing and breathable particles, the particle size of the diatomite is 300-400 meshes, and the thickness of the porous hydrophilic polymer coating layer is 10-20 μm.

Preferably, the method for preparing the moisture-absorbing breathable particles comprises the following steps:

(A) and (3) diatomite surface treatment: mixing 3-aminopropyltrimethoxysilane and water according to the mass ratio of 1:60-70 to prepare a coupling agent solution; adding diatomite into the coupling agent solution, fully dispersing, and stirring and reacting for 1-2h at the temperature of 30-50 ℃; after the reaction is finished, filtering, and then soaking in birch tar for 1-3h to obtain modified diatomite;

(B) coating with hydrophilic polymer: dissolving water-soluble acrylic resin and water-soluble epoxy resin in water to prepare a coating agent solution; adding the modified diatomite into the coating agent solution, stirring for 2-3h after fully dispersing, and filtering to obtain hydrophilic polymer coated diatomite;

(C) hole making and curing: placing the hydrophilic polymer coated diatomite at 60-70 ℃ under 0.01-0.03MPa for 30-40min, heating to 160-170 ℃ and curing for 2-3h to obtain the moisture-absorbing and breathable particles.

In the step (A), 3-aminopropyl trimethoxy silane is hydrolyzed to form silicon hydroxyl, and then reacts with the silicon hydroxyl on the surface of the diatomite so as to be grafted on the diatomite; in the step (B), epoxy groups in the epoxy resin react with amino groups (from 3-aminopropyltrimethoxysilane) on the surface of the modified diatomite to be covalently grafted to the surface of the modified diatomite, and the acrylic resin is bonded to the surface of the modified diatomite by crosslinking with the epoxy resin; in the step (C), in the curing process, the epoxy group in the epoxy resin and the carboxyl group in the acrylic resin carry out ring-opening reaction to form chemical crosslinking. Through the mode, the epoxy resin and the acrylic resin can form the coating layer on the surface of the diatomite, and the adopted epoxy resin and the adopted acrylic resin are both water-soluble resins and have high hydrophilicity, so that the influence of polymer coating on the hygroscopicity of the diatomite can be reduced. In addition, the coating layer is covalently bonded on the surface of the diatomite through the epoxy resin in the coating layer, and the epoxy resin and the acrylic resin in the coating layer are covalently crosslinked, so that the coating layer is not easy to wear or peel off from the surface of the diatomite in the use process of the synthetic leather, and better hand feeling can be maintained.

Soaking birch tar oil to make the birch tar oil be adsorbed in diatomite; in the step (C), the polymer coating layer has low crosslinking strength before curing, and low-pressure high-temperature treatment is carried out at the moment to quickly volatilize the birch tar in the diatomite and form larger gaps in the hydrophilic polymer coating layer, so that the polymer coating is prevented from greatly influencing the moisture absorption and air permeability of the diatomite. In addition, birch tar has a leather-like scorched wood smell, which remains in the diatomaceous earth and can impart a polyurethane synthetic leather-like smell to natural leather.

Preferably, in the step (A), the mass ratio of the diatomite to the coupling agent solution is 1: 50-60.

Preferably, in the step (B), the mass ratio of the water-soluble acrylic resin, the water-soluble epoxy resin and the water in the coating agent solution is 4-5:1: 50-60.

Preferably, in the step (B), the mass ratio of the modified diatomite to the coating agent solution is 1: 50-70.

Preferably, the surfactant is sodium lauryl sulfate.

Preferably, the solid content of the aqueous polyurethane emulsion is 20 to 40 wt%.

A preparation method of the polyurethane synthetic leather comprises the following steps:

(1) uniformly mixing all raw materials of the polyurethane coating, and introducing micro bubbles generated by a micro bubble generator into the mixture to obtain foaming aqueous polyurethane slurry;

(2) and (3) dipping the non-woven fabric into the foaming waterborne polyurethane slurry, drying, and then carrying out alkali decrement treatment and post-treatment to obtain the polyurethane synthetic leather with high moisture absorption and air permeability.

Preferably, in the step (2), the impregnation amount is controlled to be 400-700g/m during the impregnation process²。

Compared with the prior art, the invention has the following advantages:

(1) in the moisture-absorbing and breathable particles, the surface of the diatomite is coated with the porous hydrophilic polymer coating layer, so that the condition that the surface of the synthetic leather is burred due to the addition of the diatomite can be prevented, and the moisture absorption and breathability of the diatomite cannot be greatly influenced;

(2) in the moisture-absorbing and breathable particles, the interior of the porous hydrophilic polymer coating layer and the covalent connection between the porous hydrophilic polymer coating layer and the diatomite can prevent the coating layer from being worn or peeled off from the surface of the diatomite in the use process of the synthetic leather, so that the synthetic leather maintains better hand feeling.

Detailed Description

The present invention will be further described with reference to the following examples. The following examples are intended only to illustrate the invention in detail and are not intended to limit the scope of the invention in any way.

Example 1

The polyurethane synthetic leather with high moisture absorption and air permeability comprises non-woven fabric base cloth and a polyurethane coating, wherein the polyurethane coating comprises the following raw materials in parts by weight: 80 parts of water-based polyurethane emulsion, 2 parts of surfactant, 5 parts of moisture-absorbing and breathable particles, 0.1 part of water-soluble cellulose thickening agent and 0.1 part of isocyanate crosslinking agent.

The moisture-absorbing breathable particles comprise diatomite and a porous hydrophilic polymer coating layer which is coated outside the diatomite and has the thickness of 10-20 mu m, and the preparation method comprises the following steps:

(A) and (3) diatomite surface treatment: mixing 3-aminopropyltrimethoxysilane and water according to the mass ratio of 1:70 to prepare a coupling agent solution; adding diatomite with the particle size of 300-400 meshes into the coupling agent solution, wherein the mass ratio of the diatomite to the coupling agent solution is 1:50, and stirring and reacting for 1h at 50 ℃ after fully dispersing; after the reaction is finished, filtering, and then soaking in birch tar for 1h to obtain modified diatomite;

(B) coating with hydrophilic polymer: mixing water-soluble acrylic resin, water-soluble epoxy resin and water in a mass ratio of 4:1:50, and preparing a coating agent solution after fully dissolving; adding modified diatomite into a coating agent solution, wherein the mass ratio of the modified diatomite to the coating agent solution is 1:50, fully dispersing, stirring for 2 hours, and filtering to obtain hydrophilic polymer coated diatomite;

(C) hole making and curing: placing the hydrophilic polymer coated diatomite at 60 ℃ under 0.01MPa for 40min, heating to 170 ℃ and curing for 2h to obtain the moisture-absorbing and breathable particles.

A preparation method of the polyurethane synthetic leather comprises the following steps:

(1) uniformly mixing all raw materials of the polyurethane coating, and introducing micro bubbles generated by a micro bubble generator into the mixture to obtain foaming aqueous polyurethane slurry;

(2) the non-woven fabric is dipped into the foaming aqueous polyurethane slurry, and the dipping amount is controlled to be 700g/m²And after drying, carrying out alkali decrement treatment and surface grinding treatment to obtain the polyurethane synthetic leather with high moisture absorption and air permeability.

Example 2

The polyurethane synthetic leather with high moisture absorption and air permeability comprises non-woven fabric base cloth and a polyurethane coating, wherein the polyurethane coating comprises the following raw materials in parts by weight: 90 parts of water-based polyurethane emulsion, 2 parts of surfactant, 8 parts of moisture-absorbing and air-permeable particles, 1 part of water-soluble cellulose thickening agent, 1 part of isocyanate crosslinking agent and 4 parts of water-based pigment paste.

The moisture-absorbing breathable particles comprise diatomite and a porous hydrophilic polymer coating layer which is coated outside the diatomite and has the thickness of 10-20 mu m, and the preparation method comprises the following steps:

(A) and (3) diatomite surface treatment: mixing 3-aminopropyltrimethoxysilane and water according to the mass ratio of 1:65 to prepare a coupling agent solution; adding diatomite with the particle size of 300-400 meshes into the coupling agent solution, wherein the mass ratio of the diatomite to the coupling agent solution is 1:55, fully dispersing, and stirring and reacting for 1.5h at 40 ℃; after the reaction is finished, filtering, and then soaking in birch tar for 2 hours to obtain modified diatomite;

(B) coating with hydrophilic polymer: mixing water-soluble acrylic resin, water-soluble epoxy resin and water in a mass ratio of 4.5:1:55, and preparing a coating agent solution after fully dissolving; adding modified diatomite into a coating agent solution, wherein the mass ratio of the modified diatomite to the coating agent solution is 1:60, fully dispersing, stirring for 2.5 hours, and filtering to obtain hydrophilic polymer coated diatomite;

(C) hole making and curing: placing the hydrophilic polymer coated diatomite at 0.02MPa and 65 ℃ for 35min, heating to 165 ℃ and curing for 2.5h to obtain the moisture-absorbing breathable particles.

A preparation method of the polyurethane synthetic leather comprises the following steps:

(1) uniformly mixing all raw materials of the polyurethane coating, and introducing micro bubbles generated by a micro bubble generator into the mixture to obtain foaming aqueous polyurethane slurry;

(2) the non-woven fabric is dipped into the foaming water-based polyurethane slurry, and the dipping amount is controlled to be 500g/m²And after drying, carrying out alkali decrement treatment and surface grinding treatment to obtain the polyurethane synthetic leather with high moisture absorption and air permeability.

Example 3

The polyurethane synthetic leather with high moisture absorption and air permeability comprises non-woven fabric base cloth and a polyurethane coating, wherein the polyurethane coating comprises the following raw materials in parts by weight: 100 parts of water-based polyurethane emulsion, 6 parts of surfactant, 10 parts of moisture-absorbing and air-permeable particles, 2 parts of water-soluble cellulose thickening agent, 2 parts of isocyanate crosslinking agent and 8 parts of water-based pigment paste.

The superfine fiber is fixed island superfine fiber; the thickening agent is a polyurethane associative thickening agent; the colorant is water-based color paste and/or water-based toner.

The moisture-absorbing breathable particles comprise diatomite and a porous hydrophilic polymer coating layer which is coated outside the diatomite and has the thickness of 10-20 mu m, and the preparation method comprises the following steps:

(A) and (3) diatomite surface treatment: mixing 3-aminopropyltrimethoxysilane and water according to the mass ratio of 1:60 to prepare a coupling agent solution; adding diatomite with the particle size of 300-400 meshes into the coupling agent solution, wherein the mass ratio of the diatomite to the coupling agent solution is 1:60, and stirring and reacting for 2h at 30 ℃ after fully dispersing; after the reaction is finished, filtering, and soaking in birch tar for 3 hours to obtain modified diatomite;

(B) coating with hydrophilic polymer: mixing water-soluble acrylic resin, water-soluble epoxy resin and water in a mass ratio of 5:1:60, and preparing a coating agent solution after fully dissolving; adding modified diatomite into a coating agent solution, wherein the mass ratio of the modified diatomite to the coating agent solution is 1:70, fully dispersing, stirring for 3 hours, and filtering to obtain hydrophilic polymer coated diatomite;

(C) hole making and curing: placing the hydrophilic polymer coated diatomite at 0.03MPa and 70 ℃ for 30min, heating to 160 ℃, and curing for 3h to obtain the moisture-absorbing and breathable particles.

A preparation method of the polyurethane synthetic leather comprises the following steps:

(1) uniformly mixing all raw materials of the polyurethane coating, and introducing micro bubbles generated by a micro bubble generator into the mixture to obtain foaming aqueous polyurethane slurry;

(2) the non-woven fabric is dipped into the foaming water-based polyurethane slurry, and the dipping amount is controlled to be 400g/m²And after drying, carrying out alkali decrement treatment and surface grinding treatment to obtain the polyurethane synthetic leather with high moisture absorption and air permeability.

Comparative example 1

The comparative example differs from example 1 only in that no hygroscopic and breathable particles are added to the polyurethane leather.

Comparative example 2

The comparative example differs from example 1 only in that the moisture-absorbing breathable particles are diatomaceous earth having a particle size of 300-400 mesh.

Comparative example 3

The present comparative example differs from example 1 only in that no impregnation of birch tar is performed in step (a) during the preparation of the hygroscopic air-permeable granules.

Comparative example 4

This comparative example differs from example 1 only in that during the preparation of the hygroscopic, breathable particles, step (C) is replaced by: placing the hydrophilic polymer coated diatomite at 0.07MPa and 165 ℃ for 2.5h to obtain the moisture absorption breathable particles. .

Comparative example 5

This comparative example differs from example 1 only in that 3-aminopropyltrimethoxysilane was replaced by gamma-methacryloxypropyltrimethoxysilane in step (a) during the preparation of the hygroscopic breathable particles.

Comparative example 6

This comparative example differs from example 1 only in that no curing is carried out in step (C) during the preparation of the hygroscopic breathable particles.

Leather Performance test

The polyurethane synthetic leathers obtained in examples 1 to 3 and comparative examples 1 to 6 were subjected to air permeability, water absorption and a burr feeling test.

And (3) testing air permeability: and (3) detecting the air permeability of the polyurethane synthetic leather according to a QB/T2799 and 2006 leather air permeability determination method.

Water absorption test: the water absorption degree of the polyurethane synthetic leather is detected according to GB/T4689.21-2008 determination of static water absorption of leather physical and mechanical tests.

And (3) burr feeling test: dividing the burr feeling of the polyurethane synthetic leather into 5 grades of superior, good, middle, poor and inferior according to subjective judgment of a leather expert group, respectively marking the grades as 5, 4, 3, 2 and 1, determining standard samples of the grades, then carrying out burr feeling test on the sample by 5 experts and 15 volunteers according to the 5 grades, and taking an average value after scoring in 0-5 minutes; referring to the method in GB/T21196-.

The results of the measurements are shown in the following table:

the following conclusions can be drawn by analyzing the detection results:

(1) the air permeability and water absorption of the synthetic leather of comparative example 1 are significantly lower than those of example 1, which shows that the moisture absorption and air permeability of the polyurethane synthetic leather can be effectively improved after the moisture absorption and air permeability particles of the present invention are added, because the moisture absorption and air permeability particles of the present invention have high hydrophilicity and porosity.

(2) The burr feeling of the synthetic leather of the comparative example 2 is obviously higher than that of the synthetic leather of the example 1, and the air permeability and the water absorbability are not obviously different, which shows that the hand feeling of the synthetic leather can be improved after the hydrophilic polymer layer is coated on the surface of the diatomite, and the moisture absorption and air permeability of the synthetic leather cannot be greatly influenced, because the hydrophilic polymer layer has higher flexibility compared with the diatomite, the hand feeling of the surface of the moisture absorption and air permeability particles can be improved, and the burr feeling of the surface of the synthetic leather caused by adding the hydrophilic polymer layer is prevented; in addition, the coating layer adopts hydrophilic polymers and has high porosity, so that the moisture absorption and air permeability of the diatomite are not greatly influenced.

(3) The reason why the air permeability and water absorption of the synthetic leather of comparative example 3 are significantly lower than those of example 1 indicates that the moisture absorption and air permeability of the polyurethane synthetic leather can be improved by performing low-pressure high-temperature treatment before curing after coating with the hydrophilic polymer in the preparation process of the moisture absorption and air permeability particles is that, during the low-pressure high-temperature treatment, birch tar in the diatomite volatilizes rapidly and a large gap can be formed in the hydrophilic polymer coating layer, thereby preventing the polymer coating from causing large influence on the moisture absorption and air permeability of the diatomite.

(4) The synthetic leather of comparative example 4 has significantly lower air permeability and water absorption than example 1, which shows that if birch tar volatilization and polymer coating layer curing are combined into one step in the preparation process of the moisture-absorbing and air-permeable particles, the moisture absorption and air permeability of the polyurethane synthetic leather are reduced, because: in the curing process, the crosslinking strength of the polymer coating layer is gradually increased, so that the pore-forming effect of birch tar volatilization is reduced, and the porosity of the polymer coating layer is low, so that the moisture absorption and air permeability of the diatomite are greatly influenced.

(5) The reason why the burred feeling after the friction of the synthetic leather of comparative example 5 is significantly higher than that of example 1 is that 3-aminopropyltrimethoxysilane can form covalent bonding with the diatomaceous earth and the epoxy resin in the polymer coating layer, thereby improving the bonding strength of the porous hydrophilic polymer coating layer on the surface of the diatomaceous earth and preventing it from being worn away or falling off from the surface of the diatomaceous earth to expose the diatomaceous earth during the friction.

(6) The reason why the burr feeling after friction of the synthetic leather of comparative example 6 is significantly higher than that of example 1 is that the curing enables covalent crosslinking to be formed between the epoxy resin and the acrylic resin, thereby preventing the polymer coating layer from being abraded to expose the diatomaceous earth when the synthetic leather is subjected to friction.

Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that the embodiments may be modified or changed without departing from the spirit of the present invention within the scope of the appended claims.