阅读说明：本技术 一种具有微孔通道的超纤贴面革面层膜的制备方法 (Preparation method of microfiber leather facing layer film with microporous channel ) 是由 张昊 钱晓明 于 2020-07-23 设计创作，主要内容包括：本发明公开了一种具有微孔通道的超纤贴面革面层膜的制备方法,包括以下步骤：将DMSO<Sub>2</Sub>结晶体和WPU搅拌均匀,得到均相的铸膜液；将铸膜液脱泡；脱泡完成后,将铸膜液刮制成平板状铸膜液；将平板状铸膜液放入过饱和盐溶液凝固浴中,再将初生膜完全干燥,得到固化膜；将固化膜清洗至DMSO<Sub>2</Sub>结晶体和过饱和盐溶液中的溶质完全洗出,得到具有微孔通道的超纤贴面革面层膜。本方法通过引发DMSO<Sub>2</Sub>的自结晶效应与铸膜液体系的单扩散效应并将二者协同以构建超纤贴面革面层膜的微孔通道,简单有效,在不影响超纤贴面革产品的耐磨性和抗污染性能等品质的前提下大幅改善了超纤贴面革面层膜的透气透湿性能。(The invention discloses a preparation method of a microfiber leather facing layer film with a micropore channel, which comprises the following steps: adding DMSO 2 Uniformly stirring the crystal and the WPU to obtain a homogeneous casting solution; defoaming the casting solution; after defoaming, scraping the membrane casting solution into a flat-plate-shaped membrane casting solution; putting the flat-plate casting solution into a supersaturated salt solution coagulation bath, and completely drying the primary membrane to obtain a cured membrane; cleaning the cured film to DMSO 2 And completely washing out solute in the crystals and the supersaturated salt solution to obtain the microfiber leather surface layer film with the micropore channels. The method is carried out by inducing DMSO 2 The self-crystallization effect and the single diffusion effect of the membrane casting solution system are cooperated to construct the microporous channel of the microfiber-coated leather surface layer membrane, so that the method is simple and effective, and the air permeability and moisture permeability of the microfiber-coated leather surface layer membrane are greatly improved on the premise of not influencing the wear resistance, pollution resistance and other qualities of a microfiber-coated leather product.)

1. A preparation method of a microfiber leather facing layer film with micropore channels is characterized by comprising the following steps:

(1) adding DMSO₂Uniformly stirring the crystal and the WPU to obtain a homogeneous casting solution;

(2) defoaming the casting solution; after defoaming, scraping the membrane casting solution into a flat-plate-shaped membrane casting solution;

(3) putting the flat-plate casting solution into a supersaturated salt solution coagulation bath, and completely drying the primary membrane to obtain a cured membrane;

(4) cleaning the cured film to DMSO₂And completely washing out solute in the crystals and the supersaturated salt solution to obtain the microfiber leather surface layer film with the micropore channels.

2. The method for preparing a microfiber leather facing layer film with microporous channels according to claim 1, wherein the step (1) specifically comprises: adding DMSO₂And stirring the crystal and the WPU for 15-20min at the temperature of 10-60 ℃ until the mixture is uniformly stirred to obtain a homogeneous casting solution.

3. The method for preparing a microfiber laminated leather top layer film having microporous channels according to claim 1, wherein in step (1), DMSO is added₂The mass of the crystals is at most 50% of the total mass of the casting solution.

4. The method of preparing a microfiber laminated leather top layer film according to claim 3, wherein DMSO is a DMSO₂The mass of the crystals accounts for at most 20% of the total mass of the casting solution.

5. The method of preparing a microfiber laminated leather top layer film according to claim 4, wherein DMSO is a DMSO₂The mass of the crystals accounts for at most 15% of the total mass of the casting solution.

6. The method of preparing a microfiber laminated leather top layer film according to claim 5, wherein DMSO is a DMSO₂The mass of the crystal accounts for 10-15% of the total mass of the casting solution.

7. The method for preparing a microfiber leather facing layer film with microporous channels according to claim 1, wherein the step (2) is specifically: placing the casting solution into a vacuum oven to defoam for at least 3 hours; and after defoaming, pouring the casting solution on a glass plate, and scraping the casting solution into a flat-plate casting solution by using a film scraping rod.

8. The method for preparing a microfiber leather facing layer film with microporous channels according to claim 1, wherein the step (3) is specifically: and putting the flat-plate casting solution into a supersaturated salt solution coagulating bath at the temperature of 4-80 ℃ for at least 0.5h, and then putting the flat-plate casting solution into an oven at the temperature of 10-90 ℃ for drying and curing for at least 1h until the nascent membrane is completely dried, thereby obtaining the cured membrane.

9. The method for preparing a microfiber leather facing layer film having a microporous channel according to claim 8, wherein the drying temperature of the oven is 60 ℃ to 80 ℃; the supersaturated salt solution is sodium chloride solution, potassium chloride solution, anhydrous sodium sulfate solution or anhydrous potassium sulfate solution.

10. The method for preparing a microfiber leather facing layer film with microporous channels according to claim 1, wherein the step (4) is specifically: the solidified film is put into deionized water with the temperature of 20-50 ℃ for cleaning for at least 0.5h to DMSO₂And completely washing out solute in the crystals and the supersaturated salt solution to obtain the microfiber leather surface layer film with the micropore channels.

Technical Field

The invention relates to the technical field of leather facing membrane, in particular to a preparation method of a microfiber facing leather facing membrane with a micropore channel.

Background

Leather has a high demand as a necessity in people's daily life. Because the raw leather resources for producing natural leather are limited, and the production process brings high energy consumption and high pollution, synthetic leather has attracted more and more attention as a new material for replacing natural leather in recent years. The superfine fiber synthetic leather (microfiber leather) has the characteristics of small diameter, large specific surface area, low bending rigidity, extremely soft hand feeling and the like, so that the superfine fiber synthetic leather becomes an ideal choice for replacing natural leather, and has great market potential in the field of high-grade synthetic leather.

The air permeability and moisture permeability of the microfiber leather surface layer film are key factors for evaluating the quality of microfiber leather, and the microfiber leather surface layer film with excellent air permeability and moisture permeability is closer to real leather in both sanitary performance and comfort. In the traditional process, the polymer material for preparing the microfiber leather surface layer film is solvent type Polyurethane (PU), and because a large amount of toxic solvents are used, the production process of the PU surface layer film not only can cause serious pollution to the environment, but also has the risk of solvent residue, and seriously threatens the human health.

In contrast, the Waterborne Polyurethane (WPU) has the characteristics of no toxicity, no harm and no need of using a solvent in the production process due to the fact that water is used as a dispersion medium, has become an ideal substitute for the traditional solvent-based PU in the synthetic leather industry, and has become a research hotspot for modifying leather surface layer films in recent years. The microfiber leather face layer film prepared by using WPU as a raw material comprises a suede leather face layer film and a laminated leather face layer film, wherein the suede leather face layer film can be prepared by a mechanical foaming method, and a micropore channel with a large size can be constructed by the mechanical foaming method, so that the suede leather face layer film is good in air permeability and moisture permeability and comfortable in hand feeling. However, the mechanical foaming method is not suitable for the leather facing film because the wear resistance and the anti-pollution performance are required to be high and the surface micropore size of the leather facing film cannot be too large. At present, the method for preparing the microfiber leather facing layer film by using the WPU is relatively simple, and only the WPU is scraped into a flat sheet film and then the moisture of the film layer is dried. However, WPU forms a dense surface layer film, and the air permeability and the moisture permeability of the WPU cannot meet the requirements of synthetic leather. A polyester type PU coating product is disclosed in the literature, Maxinyuan, Gaoshao, et al, preparation and performance research of solvent-free polyurethane surface resin for synthetic leather [ J ], Chinese leather, 2017,46(3):59-61. As the product forms a compact surface layer film, the air permeability and the moisture permeability of the surface layer film are poor through tests. Therefore, there is a need to find a suitable method for constructing microfiber-coated leather facing film microporous channels to improve the air and moisture permeability of the formed film.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to solve the technical problem of providing a preparation method of a microfiber leather facing layer membrane with a micropore channel.

The technical scheme for solving the technical problem is to provide a preparation method of a microfiber leather facing layer film with a micropore channel, which is characterized by comprising the following steps:

(1) adding DMSO₂Uniformly stirring the crystal and the WPU to obtain a homogeneous casting solution;

(2) defoaming the casting solution; after defoaming, scraping the membrane casting solution into a flat-plate-shaped membrane casting solution;

(3) putting the flat-plate casting solution into a supersaturated salt solution coagulation bath, and completely drying the primary membrane to obtain a cured membrane;

(4) cleaning the cured film to DMSO₂And completely washing out solute in the crystals and the supersaturated salt solution to obtain the microfiber leather surface layer film with the micropore channels.

Compared with the prior art, the invention has the beneficial effects that:

(1) the method is carried out by inducing DMSO₂The self-crystallization effect and the single diffusion effect of the membrane casting solution system are cooperated to construct the microporous channel of the microfiber-coated leather surface layer membrane, so that the method is simple and effective, the air permeability and moisture permeability of the microfiber-coated leather surface layer membrane are greatly improved on the premise of not influencing the wear resistance, pollution resistance and other qualities of a microfiber-coated leather product, and the method has important significance for further improving the microfiber leather quality and breaking through the industrialized bottleneck of microfiber leather.

(2) Because of the characteristics of benefiting human health and efficiently recycling and reusing by recrystallization, DMSO (dimethyl sulfoxide)₂Is particularly suitable for the production process of microfiber leather with strict environmental protection requirements, and is very beneficial to industrial application. At the same time, DMSO₂The recycling of the waste water is also beneficial to controlling the industrial production cost.

(3) At room temperature, DMSO₂Is water-solubleWhite needle-like crystals of (2). Due to DMSO₂The self-crystallization effect of (1) which occurs during saturation precipitation in supersaturated solutions, which results in DMSO₂Can play a role of a pore-foaming agent in a WPU membrane casting solution system.

Drawings

FIG. 1 shows DMSO according to the invention₂Schematic diagram of pore-forming mechanism in film-forming process;

FIG. 2 is an SEM photograph of the top surface, cross-section and bottom surface of example 1 of the present invention;

FIG. 3 is an SEM photograph of the top surface, cross-section and bottom surface of example 2 of the present invention;

FIG. 4 is an SEM photograph of the upper surface, the lower surface and a cross section of example 3 of the present invention;

FIG. 5 is an SEM photograph of the upper surface, cross-section and lower surface of comparative example 1 of the present invention;

FIG. 6 is an SEM photograph of the upper surface, cross-section and lower surface of comparative example 2 of the present invention;

fig. 7 is an SEM image of the upper surface, cross-section and lower surface of comparative example 3 of the present invention.

FIG. 8 shows DMSO in comparative example 3 of the present invention₂Schematic diagram of pore-forming mechanism in film-forming process;

in the figure: 1. DMSO dispersed in casting solution system₂(ii) a 2. DMSO with increased crystal growth₂；

Detailed Description

Specific examples of the present invention are given below. The specific examples are only intended to illustrate the invention in further detail and do not limit the scope of protection of the claims of the present application.

The invention provides a preparation method (method for short) of a microfiber leather facing layer film with a micropore channel, which is characterized by comprising the following steps:

(1) adding DMSO₂Stirring (dimethyl sulfone) crystals and WPU (waterborne polyurethane) at the temperature of 10-60 ℃ for 15-20min until the mixture is uniformly stirred to obtain a homogeneous casting solution;

in step (1), DMSO is₂The mass of the crystals is at most 50% of the total mass of the casting solution, preferablyDMSO₂The mass of the crystals is at most 20% of the total mass of the casting solution, and DMSO is more preferable₂The mass of the crystals is at most 15% of the total mass of the casting solution, and DMSO is more preferable₂The mass of the crystal accounts for 10-15% of the total mass of the casting solution;

in the step 1), the preparation temperature of the casting solution is 10-40 ℃, and room temperature is preferred.

(2) Placing the casting solution into a vacuum oven to defoam for at least 3 hours (preferably 4 hours); after defoaming, pouring the casting solution on a glass plate, and scraping the casting solution into a flat-plate casting solution by using a film scraping rod;

(3) putting the flat-plate casting solution into a supersaturated salt solution coagulating bath for at least 0.5h (preferably 0.5h) to initiate a synergistic effect, and then putting the flat-plate casting solution into an oven for drying and curing for at least 1h (preferably 2h) until the primary membrane is completely dried to obtain a cured membrane;

in step 3), the temperature of the coagulation bath is 4 ℃ to 80 ℃, preferably room temperature. The supersaturated salt solution is a sodium chloride solution, a potassium chloride solution, an anhydrous sodium sulfate solution or an anhydrous potassium sulfate solution and the like.

In step 3), the drying temperature of the oven is 10 ℃ to 90 ℃, preferably 60 ℃ to 80 ℃.

(4) The cured film is washed in deionized water at 20-50 deg.C (preferably 25 deg.C) for at least 0.5h (preferably 0.5h) to DMSO₂And completely washing out solute in the crystals and the supersaturated salt solution to obtain the microfiber leather surface layer film with the micropore channels.

As shown in FIG. 1, is DMSO₂Schematic diagram of pore-forming mechanism in film-forming process. When DMSO is used₂DMSO at lower solids in the casting solution system₂Will diffuse into the supersaturated salt solution coagulation bath along with the single diffusion effect of the casting solution system, at the moment, the DMSO₂The self-crystallization effect is not initiated in enough time, and the size of a film-forming micropore channel is small; when DMSO is used₂When the solid content in the casting solution system is higher, part of DMSO₂Will diffuse into the supersaturated salt solution coagulation bath along with the single diffusion effect of the casting solution system, and part of DMSO₂The diffusion into the coagulation bath of supersaturated salt solution takes longer and this is due to the reduction of moisture in the surrounding environmentPartial DMSO₂Sufficient time and environment are available to initiate the self-crystallization effect, and the growth of the crystals leads to an increase in the size of the film-forming microporous channels.

Priming DMSO₂The method of the self-crystallization effect is to control DMSO₂Solid content in the casting solution system and supersaturated salt solution coagulating bath are introduced to absorb water in the casting solution, so that DMSO (dimethyl sulfoxide)₂Supersaturation is generated in the membrane casting solution system, and then DMSO is initiated₂Causing it to self-crystallize.

The single diffusion effect of the casting solution system is initiated by introducing a supersaturated salt solution coagulating bath, the casting solution system can form a directional dehydration effect, and the water and partial DMSO in the casting solution system₂Can diffuse into the supersaturated salt solution coagulation bath, and the water in the supersaturated salt solution coagulation bath can not diffuse into the WPU membrane casting solution system, thereby further initiating the monodispersion effect.