阅读说明：本技术 一种pu复合皮革及其制备方法 (PU composite leather and preparation method thereof ) 是由 胡超群 于 2021-08-12 设计创作，主要内容包括：本发明提供一种PU复合皮革,包括皮革胚料和表面处理层,表面处理层成分包括聚氨酯、架桥剂、增粘剂和平滑剂；皮革胚料包括基布层、接着层和表面层,其胚料的材料组分为聚氨酯、溶解介质、硬化剂、触媒、溶剂、阻燃剂和颜料等；本发明还提供该复合皮革制备方法包括表面层制作,接着层制作,将表面层、接着层和基布层粘接贴合在一起,剥离,熟化处理和表面层处理的步骤。通过该制备方法得到的PU复合皮革,充分发挥原料的分散性、流平性,产品目面无黑点、涂抹不均、手感剂分散均匀、无气泡及磨耗性优良,进而实现产品的平整和高良率。(The invention provides PU composite leather, which comprises a leather blank and a surface treatment layer, wherein the surface treatment layer comprises polyurethane, a bridging agent, a tackifier and a smoothing agent; the leather blank comprises a base cloth layer, an adhesion layer and a surface layer, and the material components of the blank comprise polyurethane, a dissolving medium, a hardening agent, a catalyst, a solvent, a flame retardant, pigment and the like; the invention also provides a preparation method of the composite leather, which comprises the steps of surface layer preparation, adhesion and sticking of the surface layer, the adhesion layer and the base cloth layer, stripping, curing treatment and surface layer treatment. The PU composite leather obtained by the preparation method fully exerts the dispersibility and the leveling property of the raw materials, and the product has no black spots on the mesh surface, uneven smearing, uniform dispersion of the hand feeling agent, no bubbles and excellent abrasion resistance, thereby realizing the flatness and high yield of the product.)

1. The PU composite leather is characterized in that: the leather comprises a leather blank and a surface treatment layer, wherein the surface treatment layer comprises the following material components in percentage by mass: 85.6 to 90.2 percent of polyurethane, 3.7 to 4.5 percent of bridging agent, 0.5 to 1.0 percent of tackifier and 6.2 to 8.3 percent of smoothing agent.

2. The PU composite leather of claim 1, wherein: the leather blank comprises a base cloth layer, an adhesion layer and a surface layer, wherein the surface layer comprises the following material components in percentage by mass: 50.5 to 69.1 percent of polyurethane, 9.9 to 16.5 percent of pigment and 26 to 28 percent of dissolving medium.

3. The PU composite leather of claim 2, wherein: the adhesive layer comprises the following material components in percentage by mass: 25.7 to 27.7 percent of polyurethane, 54.7 to 56.7 percent of hardener, 0.04 to 1.04 percent of accelerant, 3.4 to 5.4 percent of solvent, 10.6 to 12.6 percent of flame retardant and 0.6 to 2.6 percent of pigment.

4. The PU composite leather of claim 2, wherein: the base cloth layer is woven fabric, the thickness of the base cloth layer is 800-1000 mu m, and the mass of the base cloth layer is 220g/m²～390g/m²。

5. The preparation method of the PU composite leather according to any one of claims 1 to 4, comprising the following steps:

s1 surface layer preparation, wherein the surface layer preparation comprises surface layer solution preparation, surface layer solution defoaming treatment, surface layer solution coating processing and surface layer drying and forming to obtain a surface layer;

s2 manufacturing an adhesion layer, wherein the manufacturing of the adhesion layer comprises the steps of preparing an adhesion layer solution, coating the adhesion layer solution, drying and forming the adhesion layer to obtain the adhesion layer;

s3, bonding and adhering the surface layer obtained in the step S1, the bonding layer obtained in the step S2 and the base cloth layer together to form a leather blank;

s4, peeling, namely peeling the leather blank in the step S3 from a release paper mold to obtain the leather blank;

s5, curing, namely curing the leather blank in the step S4 in an oven and cooling to obtain a cured leather blank;

s6 surface layer treatment, namely performing surface layer treatment on the cured leather blank obtained in the step S6 to obtain a surface treatment layer; and the surface layer treatment comprises the steps of preparing surface treatment layer liquid, coating the surface treatment layer liquid, processing and baking to obtain the finished product of the PU composite leather.

6. The method for preparing PU composite leather according to claim 5, wherein: the stirring speed of the prepared surface layer solution in the step S1 is 350-450 rpm, the stirring time is 60-65 min, the viscosity of the surface layer solution is 2000-3000 cps, and the treatment time of the surface layer solution defoaming treatment is 60-65 min.

7. The method for preparing PU composite leather according to claim 6, wherein the PU composite leather is prepared by the method: the speed of the surface layer solution coating processing of the step S1 is 9m/min to 11m/min, and the using amount is 35g/m²～45g/m²(ii) a The surface layer drying and forming temperature is 100-125 ℃, and the time is 2-3 min.

8. The method for preparing PU composite leather according to claim 5, wherein: and S2, drying and forming the adhesive layer at 125-135 ℃ for 2.5-3.5 min, wherein the drying degree of the adhesive layer is 70-80%.

9. The method for preparing PU composite leather according to claim 5, wherein: the speed of bonding in the step S3 is 8-10 m/min, and the bonding pressure is 0.25-0.35 MPa.

10. The method for preparing PU composite leather according to claim 5, wherein: the coating speed of the surface treatment layer liquid in the step S6 is 11 m/min-13 m/min, and the using amount is 50g/m²～60g/m²(ii) a And S6, baking and forming the surface treatment layer at 95-130 ℃ for 2-3 min.

Technical Field

The invention relates to the technical field of preparation of polyurethane composite materials, in particular to PU composite leather and a preparation method of the PU composite leather.

Background

The color and the decoration design of the automotive interior need to fully consider the requirements of humanity, the quality of the interior is mainly reflected in the aspects of the color, the texture, the luster, the material, the appearance decoration and the like of interior parts, a safe, comfortable and pleasant driving space is created for customers, and then a high-quality feeling is created, so that the automobile interior is an important means for winning the customers. In recent years, with the development of social economy and the transformation of market supply and demand relations, consumers have changed consumption ideas of passenger cars, so that the demands on car functions and the demands on quality and culture of cars are added more, the influence of car interiors on the sensory quality of the cars is focused, and the details are paid more attention. Polyurethane (abbreviated as PU) is a short name for Polyurethane, and is widely used in many fields of national economy due to its excellent properties.

At present, some interior manufacturers at home and abroad use polyurethane materials to manufacture composite leather, the product quality greatly fluctuates, and the surface treatment processing is used as the last working procedure of PU synthetic leather processing, so that the product quality is greatly influenced. Mainly reflects the problems that the surface treatment roller coating type processing is limited by the leveling property of raw materials, the mesh surface of a product is black, the coating is uneven, a hand feeling agent is uneven in dispersion, bubbles and the abrasion performance are poor, and the like. Therefore, the invention provides novel PU composite leather and a preparation method of the PU composite leather.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide PU composite leather, which comprises a base cloth layer, an adhesive layer, a surface layer and a surface treatment layer, wherein the surface layer can improve the problems of easy coating bubbles and poor surface quality by improving the components of the surface treatment layer.

In order to achieve the purpose, the invention provides PU composite leather, which comprises a leather blank and a surface treatment layer, wherein the surface treatment layer comprises the following material components in percentage by mass: 85.6 to 90.2 percent of polyurethane, 3.7 to 4.5 percent of bridging agent, 0.5 to 1.0 percent of tackifier and 6.2 to 8.3 percent of smoothing agent;

the leather blank comprises a base cloth layer, an adhesion layer and a surface layer, wherein the surface layer comprises the following material components in percentage by mass: 50.5-69.1% of polyurethane, 9.9-16.5% of pigment and 26-28% of dissolving medium, wherein the dissolving medium is MEK and DMF;

the adhesive layer comprises the following material components in percentage by mass: 25.7 to 27.7 percent of polyurethane, 54.7 to 56.7 percent of hardener, 0.04 to 1.04 percent of accelerant, 3.4 to 5.4 percent of solvent, 10.6 to 12.6 percent of flame retardant and 0.6 to 2.6 percent of pigment;

the base fabric layer is woven fabric, such as fiber, cotton, woven fabric and nonwoven fabricCloth; preferably, the thickness of the base cloth layer is 800 to 1000 μm, and the mass thereof is 220g/m²～390g/m²。

The bridging agent is a multifunctional carbodiimide polymer, and the tackifier is an alkaline tackifier, such as an acrylic polymer; the smoothing agent is silicon series and silicon polymer thereof.

The hardening agent is a yellowing-resistant hardening agent, the catalyst is a special catalyst formed by amine organic acid salt, the solvent is butanone and polycondensate thereof, and the flame retardant is a phosphorus flame retardant.

In order to achieve the above object, the present invention also provides a preparation method of the PU composite leather, the preparation method comprising the steps of:

s1 surface layer preparation, wherein the surface layer preparation comprises surface layer solution preparation, surface layer solution defoaming treatment, surface layer solution coating processing and surface layer drying and forming to obtain a surface layer;

s2 manufacturing an adhesion layer, wherein the manufacturing of the adhesion layer comprises the steps of preparing an adhesion layer solution, coating the adhesion layer solution, drying and forming the adhesion layer to obtain the adhesion layer;

s3, bonding and adhering the surface layer obtained in the step S1, the bonding layer obtained in the step S2 and the base cloth layer together to form a leather blank;

s4, peeling, namely peeling the leather blank in the step S3 from a release paper mold to obtain the leather blank;

s5, curing, namely curing the leather blank in the step S4 in an oven and cooling to obtain a cured leather blank;

s6 surface layer treatment, namely performing surface layer treatment on the cured leather blank obtained in the step S6 to obtain a surface treatment layer; and the surface layer treatment comprises the steps of preparing surface treatment layer liquid, coating the surface treatment layer liquid, processing and baking to obtain the finished product of the PU composite leather.

Preferably, the production environment temperature of the step S1 to the step S6 is 0 ℃ to 40 ℃, and the production environment humidity is 20% to 80%; preferably, the steps S1 and S2 may be performed simultaneously, or the surface layer of step S1 may be first formed, and the subsequent layer of step S2 may be formed;

further, the stirring speed of the prepared surface layer solution in the step S1 is 350-450 rpm, the stirring time is 60-65 min, and the viscosity of the surface layer solution is 2000-3000 cps.

Preferably, the treatment time of the surface layer solution defoaming treatment in step S1 is 60 to 65 min. The prepared surface layer solution is defoamed by a circulating defoaming machine, so that the defoaming effect is fully ensured, and the surface layer solution is prevented from air entering in the conveying process during circulating use so as to improve the surface layer coating quality.

Preferably, the speed of the surface layer solution coating process in the step S1 is 9-11 m/min, and the amount is 35g/m²～45g/m². And S1, drying and forming the surface layer at 100-125 deg.c for 2-3 min.

Further, the stirring speed of the prepared adhesive layer solution in step S2 is 800rpm to 1000 rpm. The coating speed of the solution of the adhesive layer in the step S2 is 9-11 m/min, and the using amount is 153g/m²～187g/m². And S2, drying and forming the adhesive layer at 125-135 ℃ for 2.5-3.5 min, wherein the drying degree of the adhesive layer is 70-80%.

Furthermore, the bonding speed of the step S3 is 8-10 m/min, and the bonding pressure is 0.25-0.35 MPa.

Further, the curing treatment temperature in the step S5 is 125-135 ℃, and the time is 2-10 min.

And step S6, the stirring speed of the prepared surface treatment layer liquid is 350-450 rpm, the stirring time is 60-65 min, and the viscosity of the surface treatment layer liquid is 1000-2000 cps.

Preferably, the coating speed of the surface treatment layer liquid in the step S6 is 11m/min to 13m/min, and the using amount is 50g/m²～60g/m². And S6, baking and forming the surface treatment layer at 95-130 ℃ for 2-3 min.

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

1. the PU polyurethane composite leather comprises a base cloth layer, a bonding layer, a surface layer and a surface treatment layer, and through the improvement of the components of each layer, the PU synthetic leather has the advantages that the strength coating bubbles are not generated, the surface tension can be kept stable, and the wear resistance is good (when the load is 9.8N, the circulation is carried out for 30000 times, and the problems of whitening at the apex angle and folding white flower of the composite leather are avoided).

2. In addition, through a special preparation method, the dispersibility and the leveling property of the raw materials are fully exerted, the problem of uneven coating generated in the prior coating process is solved, and the product has no black spots on the surface, uneven coating, uniform dispersion of a hand feeling agent, no bubbles and excellent abrasive performance; and then realize the level and smooth, perfect of product, improve the yield, satisfy customer's demand. In particular, the treatment time for the surface layer solution defoaming treatment in step S1 is 60 to 65 min. The prepared surface layer solution is defoamed by a circulating defoaming machine, so that the defoaming effect is fully ensured, and the surface layer solution is prevented from air entering in the conveying process during circulating use so as to improve the surface layer coating quality.

3. The PU polyurethane composite leather of the invention improves the strength of the composite leather through the PU polyurethane raw material and the composite leather structure with specific components, the component performance and the preparation process of the product, thereby achieving the purpose of improving the service life of the product and improving the competitiveness of the product.

Drawings

FIG. 1 is a process flow diagram of a preparation method of PU composite leather of the invention;

FIG. 2 is a schematic cross-sectional view of a PU composite leather according to the present invention;

the labels in the figure are: 1-base cloth layer, 2-adhesion layer, 3-surface layer, 4-surface treatment layer and 5-leather blank.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples, so that those skilled in the art can fully understand the technical contents of the present invention. It should be understood that the following examples are intended to further illustrate the present invention and should not be construed as limiting the scope of the present invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art based on the foregoing description are intended to be covered by the present invention. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

The invention provides PU synthetic leather, which comprises a leather blank 5 and a surface treatment layer 4, wherein the leather blank 5 comprises a base cloth layer 1, an adhesion layer 2 and a surface layer 3, the adhesion layer 2 is arranged between the base cloth layer 1 and the surface layer 3, and the surface treatment layer 4 is coated on the surface layer 3; the surface treatment layer 4 comprises polyurethane, a bridging agent, a tackifier and a smoothing agent; the surface treatment layer 4 comprises the following material components in percentage by mass: 85.6 to 90.2 percent of polyurethane, 3.7 to 4.5 percent of bridging agent, 0.5 to 1.0 percent of tackifier and 6.2 to 8.3 percent of smoothing agent; the bridging agent is multifunctional carbodiimide polymer, and the tackifier is alkaline tackifier, such as acrylic polymer; the smoothing agent is silicon series and silicon polymer thereof.

The surface layer 3 comprises polyurethane, pigment and a dissolving medium; the surface layer 3 comprises the following material components in percentage by mass: 50.5-69.1% of polyurethane, 9.9-16.5% of pigment and 26-28% of dissolving medium, wherein the dissolving medium is MEK and DMF.

The adhesion layer 2 comprises polyurethane, a hardener, a catalyst, a solvent, a flame retardant and a pigment; the material components of the adhesion layer 2 comprise the following components in percentage by mass: 25.7 to 27.7 percent of polyurethane, 54.7 to 56.7 percent of hardener, 0.04 to 1.04 percent of accelerant, 3.4 to 5.4 percent of solvent, 10.6 to 12.6 percent of flame retardant and 0.6 to 2.6 percent of pigment; the hardening agent is yellowing resistant, the catalyst is special catalyst formed by amine organic acid salt, the solvent is butanone and polycondensate thereof, and the flame retardant is phosphorus flame retardant.

The base cloth layer 1 is a woven fabric such as fiber, cotton, woven fabric and non-woven fabric; the thickness of the base cloth layer is 800-1000 μm, and the mass is 220g/m²～390g/m²。

The invention also provides a preparation method for preparing the synthetic leather, which comprises the following steps:

s1 surface layer preparation, wherein the surface layer 3 preparation comprises surface layer solution preparation, surface layer solution defoaming treatment, surface layer solution coating processing and surface layer drying and forming to obtain a surface layer 3; the stirring speed of the prepared surface layer solution is 350-450 rpm, the stirring time is 60-65 min, and the viscosity of the surface layer solution is 2000-3000 cps.

The treatment time of the surface layer solution defoaming treatment in the step S1 is 60 min-65 min. The prepared surface layer solution is defoamed by a circulating defoaming machine, so that the defoaming effect is fully ensured, and the surface layer solution is prevented from air entering in the conveying process during circulating use so as to improve the surface layer coating quality. The speed of the surface layer solution coating processing is 9 m/min-11 m/min, and the using amount is 35g/m²～45g/m². The surface layer is dried and formed at the temperature of 100-125 ℃ for 2-3 min.

S2 manufacturing an adhesion layer, wherein the manufacturing of the adhesion layer 2 comprises preparing an adhesion layer solution, coating the adhesion layer solution, and drying and forming the adhesion layer to obtain the adhesion layer 2; the stirring speed of the prepared solution of the adhesive layer is 350rpm to 450 rpm. The speed of the coating processing of the solution of the adhesive layer is 9m/min to 11m/min, and the using amount is 153g/m²～187g/m². The drying and forming temperature of the subsequent layer is 125-135 ℃, the time is 2.5-3.5 min, and the drying degree of the subsequent layer is 70-80%;

s3, bonding and adhering the surface layer 3 obtained in the step S1, the adhesive layer 2 obtained in the step S2 and the base cloth layer 1 together to form a leather blank 5; the bonding speed is 8m/min to 10m/min, and the bonding pressure is 0.2MPa to 0.3 MPa;

s4, peeling, namely peeling the leather blank 5 in the step S3 from the release paper mold to obtain the leather blank 5;

s5, curing, namely curing the leather blank 5 obtained in the step S4 in an oven and cooling to obtain a cured leather blank; the curing treatment temperature is 125-135 ℃, and the curing treatment time is 2-10 min;

s6, surface layer treatment, namely, performing surface layer treatment on the cured leather blank obtained in the step S6 to obtain a surface treatment layer 4; the surface treatment comprises preparing a surface treatment layer solution,And coating, processing and baking the surface treatment layer liquid to obtain the finished product of the composite leather. The stirring speed of the prepared surface treatment layer liquid is 350-450 rpm, the stirring time is 60-65 min, and the viscosity of the surface treatment layer liquid is 700-1000 cps; the coating speed of the surface treatment layer liquid is 13-15 m/min, and the using amount is 50g/m²～60g/m²The baking forming temperature of the surface treatment layer is 95-130 ℃, and the time is 2-3 min.

S1-S6, the production environment temperature is 0-40 ℃, and the production environment humidity is 20-80%; step S1 and step S2 may be performed simultaneously, or step S1 may be performed first for the surface layer 3, and step S2 may be performed after step S2.

Example 1:

the preparation method of the PU synthetic leather provided in this embodiment: preparing a release paper mold and a base cloth layer; the production environment temperature is 0-40 ℃, and the production environment humidity is 20-80%.

S1 surface layer preparation, according to the surface layer 3 material components, selecting the mass percentage of 57.4% polyurethane, 13.9% inorganic pigment iron oxide and carbon black, the rest is dissolving medium MEK and DMF to prepare surface layer solution; the stirring speed of the prepared surface layer solution is 350-450 rpm, the stirring time is 60-65 min, and the viscosity of the obtained surface layer solution is 2000-3000 cps; fully defoaming the surface layer solution for 60-65 min; the speed of the surface layer solution coating process is 9m/min, and the usage amount is 35g/m²～45g/m²(ii) a Drying and forming the surface layer at 100-125 deg.c for 3 min.

S2 subsequent layer preparation: according to the material components of the adhesion layer 2, 25.7% of polyurethane, 54.5% of yellowing-resistant hardener polyol polyurethane, 0.8% of medium amine organic acid salt, 4.4% of solvent butanone and 14.6% of phosphorus flame retardant are selected by mass percentage to prepare adhesion layer solution; the stirring speed of the solution of the adhesion layer is 350rpm to 450 rpm; the coating speed of the solution for the adhesive layer was 11m/min, and the amount used was 153g/m²～187g/m²(ii) a The drying and forming temperature of the subsequent layer is 125-135 ℃, the time is 3.5min, and the drying degree of the subsequent layer is 80 percent。

S3, bonding and adhering the surface layer 3 obtained in the step S1, the adhesive layer 2 obtained in the step S2 and the base cloth layer 1 together to form a leather blank 5; the bonding speed is 8m/min to 10m/min, and the bonding pressure is 0.25MPa to 0.35 MPa.

S4, peeling, namely peeling the leather blank 5 in the step S3 from the release paper mold to obtain the leather blank 5;

s5, curing, namely curing the leather blank 5 obtained in the step S4 in an oven and cooling to obtain a cured leather blank; the curing treatment temperature is 125-135 ℃, and the curing treatment time is 2-10 min.

S6 surface layer treatment: according to the material components of the surface treatment layer liquid of the surface treatment layer 4, 87.9 percent of polyurethane, 4.1 percent of bridging agent carbodiimide, 0.75 percent of alkaline tackifier, 7.25 percent of smoothing agent silicon and the balance of dissolving medium water are selected in percentage by mass to prepare the surface treatment layer liquid; the stirring speed of the surface treatment layer liquid is 350rpm to 450rpm, the stirring time is 60min to 65min, and the viscosity of the surface treatment layer liquid is 1500 cps; the coating speed of the surface treatment layer liquid is 13m/min, and the using amount is 50g/m²～60g/m²The baking forming temperature of the surface treatment layer is 95-130 ℃, and the time is 3 min.

The performance of the waterborne polyurethane composite leather prepared by the method is detected, and the result is shown in table 1; as can be seen from the comparative examples in Table 1, the performance of the polyurethane synthetic leather of the invention is greatly improved, wherein under the conditions of different deformation amounts, the PU synthetic leather has no strength coating bubbles, the surface tension can be kept stable, the abrasion resistance (load of 9.8N, circulation of 30000 times) has no damage, no bottom exposure and other abnormalities, and the top corner whitening and the fold whitening are basically not generated.

Example 2:

the present example provides another PU synthetic leather and the preparation method thereof, which is different from example 1 in that:

s1 surface layer, selecting 50.4% polyurethane, 1.7% bridging agent carbodiimide, 8.0% alkaline tackifier and 16.5% inorganic pigment according to the material components of the surface layer 3Preparing a surface layer solution by using iron oxide, carbon black and the balance of MEK and DMF (dimethyl formamide) as dissolving media; the stirring speed of the prepared surface layer solution is 350-450 rpm, the stirring time is 60-65 min, and the viscosity of the obtained surface layer solution is 2000-3000 cps; fully defoaming the surface layer solution for 30-35 min; the speed of the surface layer solution coating process is 10m/min, and the usage amount is 30g/m²～35g/m²(ii) a Drying and forming the surface layer at 100-125 deg.c for 3 min.

S2 subsequent layer preparation: according to the material components of the adhesion layer 2, 26.7% of polyurethane, 55.7% of yellowing-resistant hardener polyol polyurethane, 1.04% of intermediate amine organic acid salt, 4.0% of solvent butanone and 12.2% of phosphorus flame retardant are selected by mass percentage to prepare adhesion layer solution; the stirring speed of the solution of the adhesion layer is 2300rpm to 2500 rpm; the coating speed of the solution for the adhesive layer was 10m/min, and the amount used was 153g/m²～187g/m²(ii) a The drying and forming temperature of the subsequent layer is 125-135 ℃, the time is 2.5min, and the drying degree of the subsequent layer is 75%.

S6 surface layer treatment: according to the material components of the surface treatment layer liquid of the surface treatment layer 4, selecting 90.7 percent of polyurethane, 3.7 percent of bridging agent carbodiimide, 1.5 percent of alkaline tackifier, 8.1 percent of smoothing agent silicon and the balance of dissolving medium water by mass percent to prepare the surface treatment layer liquid; the stirring speed of the surface treatment layer liquid is 350rpm to 450rpm, the stirring time is 30min to 35min, and the viscosity of the surface treatment layer liquid is 600cps to 800 cps; the coating speed of the surface treatment layer liquid is 12m/min, and the using amount is 50g/m²～60g/m²The baking forming temperature of the surface treatment layer is 95-130 ℃, and the time is 3 min.

The PU synthetic leather prepared according to the above method was subjected to the property test, and the results are shown in Table 1.

Example 3:

the present example provides another PU synthetic leather and the preparation method thereof, which is different from example 1 in that:

s1 surface layer, selecting 59.8% polyurethane and 13.2% polyurethane according to the material components of the surface layer 3% of inorganic pigments iron oxide and carbon black, the balance being the dissolution media butanone and dimethylformamide. The stirring speed of the prepared surface layer solution is 350-450 rpm, the stirring time is 60-65 min, and the viscosity of the obtained surface layer solution is 2000-3000 cps; fully defoaming the surface layer solution for 60-65 min; the speed of the surface layer solution coating process is 10m/min, and the usage amount is 35g/m²～40g/m²(ii) a Drying and forming the surface layer at 100-125 deg.c for 3 min.

S2 subsequent layer preparation: according to the material components of the adhesion layer 2, 27.7% of polyurethane, 56.7% of yellowing-resistant hardener polyol polyurethane, 0.65% of medium amine organic acid salt, 5.4% of solvent butanone and 12.6% of phosphorus flame retardant are selected by mass percentage to prepare adhesion layer solution; the stirring speed of the solution of the adhesion layer is 2300rpm to 2500 rpm; the coating speed of the solution for the adhesive layer was 10m/min, and the amount used was 153g/m²～187g/m²(ii) a The drying and forming temperature of the subsequent layer is 90-110 ℃, the time is 2min, and the drying degree of the subsequent layer is 70%.

S6 surface layer treatment: according to the material components of the surface treatment layer liquid of the surface treatment layer 4, 89.7 percent of polyurethane, 2.7 percent of bridging agent carbodiimide, 0.75 percent of alkaline tackifier and 6.1 percent of smoothing agent silicon are selected in percentage by mass, and the balance of dissolving medium is water to prepare the surface treatment layer liquid; the stirring speed of the surface treatment layer liquid is 350-450 rpm, the stirring time is 30-35 min, and the viscosity of the surface treatment layer liquid is 800-1000 cps; the coating speed of the surface treatment layer liquid is 10m/min, and the using amount is 50g/m²～60g/m²The baking forming temperature of the surface treatment layer is 95-130 ℃, and the time is 2.5-3 min.

The PU synthetic leather prepared according to the above method was subjected to the property test, and the results are shown in Table 1.

TABLE 1 Performance test Table for PU synthetic leather

The dispersibility of the raw materials of the surface treatment coating agent can change along with the change of the viscosity of the mixed coating agent, the coating effect on the surface of a product can be greatly different, and the pattern of a coating roller (the dispersibility of the raw materials) has certain influence on the coating effect. Through the above examples, we can see that the performance of the polyurethane synthetic leather of the invention is greatly improved, wherein under the condition of different deformation, the strength coating bubble of the PU synthetic leather can not occur, the surface tension can also be kept stable, and the wear resistance (load of 9.8N, cycle of 30000 times), the top angle whitening and the folding white bloom are also basically solved. Has wide application prospect.

It should be noted that the above-mentioned preferred embodiments are merely illustrative of the technical concepts and features of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.