Preparation method and application of pre-prime coat material for leather finishing of automotive trim

Abstract

The invention belongs to the technical field of leather chemical industry, and discloses a preparation method and application of a pre-prime coat material for finishing automotive interior leather. The coating comprises the following components in percentage by weight: 8%-15% of resin, 28%-36% of an adhesion promoter, 18%-26% of transparent microspheres, 8%-15% of an auxiliary agent, 0.5%-1.5% of a flatting agent, 0.1%-0.3% of a preservative and the balance of water. The pre-prime coating material can significantly reduce the coating frequency, is especially suitable for colored and light-colored leather, does not affect the hand feeling of the leather, and maintains the original superior characteristics of the leather. Through the material, the saturation and covering power of the whole color can be effectively improved through pre-prime coating, and the number of times of coating is at least reduced to 4-6 from the original number of times of coating of 6-8.

Description

Technical Field

[0001] This invention belongs to the field of leather chemical technology, and specifically relates to a method for preparing and applying a pre-primer material for finishing automotive interior leather. More specifically, it relates to a method for preparing and applying a pre-primer material for high-coverage finishing of automotive interior leather. Background Technology

[0002] In the leather processing industry, finishing highly saturated colors (such as red, yellow, and blue) and light-colored leather has always been a technical challenge. These leather products need to have vibrant colors, uniform color distribution, and good covering power, while also maintaining the natural softness and texture of the leather.

[0003] The existing main solutions are to use organic pigment paste for finishing or to pre-coat with hollow microspheres, but these two methods have the following drawbacks and problems.

[0004] While organic pigment pastes offer vibrant colors, their hiding power is weak, requiring multiple coats to achieve the desired coverage. This not only increases production costs but also extends the production cycle and reduces efficiency. This problem is particularly pronounced in the production of high-saturation colored and light-colored leathers. Hollow microsphere pre-coating materials, due to the strong light scattering effect of the microspheres, are prone to causing whitening on the coating surface. This whitening not only affects the appearance quality of the leather but also requires additional coatings for concealing, further increasing the number of coatings and production costs. Multiple coatings can create an excessively thick coating film on the leather surface, causing the leather to lose its natural softness and appear plasticky. This not only reduces the perceived quality of the product but also negatively impacts the user experience. Furthermore, existing multi-coating processes are complex, energy-intensive, and significantly increase production costs. Multiple coatings also increase the difficulty of quality control, making it difficult to guarantee product consistency and stability. Existing pre-base coating materials have limited pigment carrying capacity and cannot provide sufficient color saturation in the pre-base coating stage. This requires the addition of a large amount of pigment paste in subsequent base and intermediate coatings, which further increases the thickness of the coating and affects the feel of the leather.

[0005] Chinese patent CN201510145678.X discloses a high-octane leather finishing pigment paste and its preparation method. This technology uses organic pigments as the main coloring component, combined with acrylic resin and polyurethane resin as film-forming substances. While organic pigments can provide vibrant colors, their opacity is poor, requiring multiple layers to achieve the desired coverage. Typically, 4-6 layers or even more are needed, which not only increases production costs but also causes the leather to harden and lose its natural leather texture.

[0006] Chinese patent CN201810456789.2 discloses a leather pre-coating material based on hollow microspheres, which uses hollow polymer microspheres as the main masking component. These microspheres can form tiny cavities in the coating, improving the masking performance through light scattering. However, this technology has certain drawbacks: First, the hollow microspheres scatter light too strongly, resulting in a noticeable whitening effect on the coating surface; second, these microspheres have limited pigment carrying capacity, failing to effectively carry enough pigment to provide a uniform color distribution; finally, the use of hollow microspheres affects the density of the coating, reducing its mechanical properties.

[0007] The standard production process for existing high-saturation colored leather typically includes the following steps: sealing the base → pre-priming (1-2 coats) → base coat (1-2 coats) → embossing → intermediate coat (1-2 coats) → top coat (1-2 coats). This multi-layered coating process, which requires a large amount of organic pigment paste to enhance the overall saturation, is not only inefficient and costly, but also struggles to completely resolve issues such as uneven color, "showing through" the base coat, and whitening. Product quality is significantly compromised due to uneven color.

[0008] Therefore, there is an urgent need in this field to develop a new pre-coating material and application process that enables leather to achieve excellent coverage with fewer coatings while maintaining the leather's soft feel and natural texture. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides a method for preparing a pre-priming material for automotive interior leather finishing and its application. This pre-priming material can significantly reduce the number of coating layers, is particularly suitable for colored and light-colored leathers, and does not affect the feel of the leather, maintaining its original superior properties. Using this material, the pre-priming effectively improves the overall color saturation and hiding power, reducing the number of coating layers by at least two, from the original 6-8 layers to 4-6 layers.

[0010] The above-mentioned objective of this invention is achieved through the following technical solution: A pre-primer material for automotive interior leather finishing, comprising, by weight percentage: 8-15% resin, 28-36% adhesion promoter, 18-26% transparent microspheres, 8-15% additives, 0.5%-1.5% leveling agent, 0.1%-0.3% preservative, and the balance being water.

[0011] The additive is a silicone-modified polyurethane compound. A preferred additive is BYK-349, which improves surface smoothness; the waterborne polyurethane is a commercially available product. By compounding silicone and polyurethane additives, a significant synergistic effect can be achieved in the coating system. Silicone segments tend to migrate to the coating surface, giving the leather an excellent smooth feel; while the modified polyurethane molecules, due to their good compatibility and structural similarity, act as a dispersion medium in the resin system, effectively stabilizing the distribution of silicone and preventing excessive migration or aggregation. The synergistic effect of both achieves a balance between feel and compatibility, and creates a uniform and stable state on the coating surface, simultaneously improving leveling and the durability of the feel.

[0012] The transparent microspheres are micron-sized polymer microspheres, preferably acrylic or polyurethane microspheres, with a refractive index between 1.45 and 1.55.

[0013] The leveling agent is a water-based silicone leveling agent. TEGO Glide 410 is preferred.

[0014] The preservative is a compound preservative. KLARIX 840B is preferred.

[0015] The adhesion promoter is any one of aliphatic polyurethane, epoxy-modified polyurethane, or silane coupling agent-modified polyurethane, preferably aliphatic polyurethane.

[0016] The resin is any one of flexible acrylic resin, flexible polyurethane resin, and styrene-acrylic acid copolymer, preferably flexible acrylic resin.

[0017] This invention also provides a method for preparing the above-mentioned pre-primer material for automotive interior leather finishing, wherein the components are mixed sequentially and uniformly dispersed to obtain the pre-primer material; specifically including the following steps: 1. Pre-dispersion stage: Add half of the water in the formula to the dispersion vessel, turn on the stirrer and heat to 30-40℃; slowly add the preservative at a speed of 300-500 rpm and stir for 5 minutes to make the preservative evenly dispersed in the water. 2. Resin and adhesion promoter mixing stage: Maintain temperature and speed, slowly add resin and adhesion promoter; the key to this stage is to form a uniform and stable state; after the addition is complete, increase the speed to 800-1000 rpm and continue stirring for 15-20 minutes until there are no visible particles or agglomerates, and the whole thing presents a single continuous and uniform state. III. Fine Dispersion Stage of Microspheres: The transparent microspheres are pre-mixed in the remaining water (the water remaining after removing the water from step one). The mixture is then slowly added to the dispersion vessel at a speed of 600-800 rpm. The feeding speed must be controlled in this step to prevent the microspheres from breaking due to high speed. After the feeding is complete, continue stirring and dispersing for 20-30 minutes until the microspheres are uniformly dispersed in the system and there are no visible agglomerated particles. IV. Mixing stage of additives and leveling agent: Reduce the speed to 400-600 rpm, add the additives and leveling agent in sequence; stir for 10-15 minutes after adding the materials to ensure that all additives are fully mixed; V. Settling Stage: Under an environment of 20-30℃, continuously stir at a low speed of 50-100 rpm for at least 24 hours to allow the components to fully interact and achieve stable performance, finally obtaining the pre-primer material.

[0018] This invention also seeks protection for the application of the pre-base coating material prepared by the above preparation method in leather finishing processes.

[0019] Specifically, it is mainly used in the finishing process of automotive interior leather, which includes full-grain leather, corrected grain leather, Nappa leather, and embossed leather.

[0020] The specific method for applying the pre-base coating material provided by the present invention to leather finishing includes the following steps: S1. Raw leather, selected from raw leather that has been tanned and retanned; S2. Sealing base coat: Apply the sealing paste to the leather flesh side using a through-feed roller coater, with a coating amount of 40–50 g / m². 2 The sealant composition is: 700-800 parts water and 200-300 parts water-based acrylic resin emulsion. The curing temperature is 100-120℃, and the roller coating speed is 9-15 m / min.

[0021] S3. Pre-base coating: The prepared pre-base coating material and pigment paste are mixed at a weight ratio of 85-90:10-15 to form a slurry, which is then applied to the leather grain surface 1-2 times using a through-feed roller coater. The first coating amount is 60–70 g / m². 2 A second coat is optional; if a second coat is applied, the coating amount should be 40–50 g / m². 2 Curing temperature 120-130℃, roller coating speed 10-15m / min.

[0022] S4. Primer coating: Apply the primer slurry to the pre-primer coating surface using a reverse roller coater, with a coating weight of 90–110 g / m². 2The composition of the primer coating is as follows: 600-700 parts of a composite resin emulsion, 100-150 parts of aliphatic polyurethane, 60-70 parts of matting release agent, 120-130 parts of pigment paste, and 20-30 parts of carbodiamine crosslinking agent. The curing temperature is 110-130℃, and the roller coating speed is 6-8 m / min.

[0023] S5. Embossing: Using a pass-through embossing machine, select the appropriate embossing roller according to different needs to emboss the desired texture.

[0024] S6. Intermediate Coating: Apply the intermediate coating slurry over the primer coating using a spray gun or high-grade roller coater. The intermediate coating slurry consists of: 40-80 parts water, 10-20 parts high-abrasion-resistant feel agent, 150-200 parts polyurethane resin, 180-240 parts matting resin A, 200-250 parts matting resin B, 80-120 parts gloss-enhancing resin, 100-120 parts pigment paste, and 55-65 parts isocyanate crosslinking agent. Curing temperature: 110-130℃; spraying speed: 9-11 m / min; coating amount: 30-40 g / m². 2 .

[0025] S7. Top Coating: Apply the top coating slurry over the intermediate coating using a spray gun. The top coating slurry consists of: 120-160 parts water, 30-40 parts water-based silicone emulsion feel agent, 40-60 parts high abrasion-resistant feel agent, 200-260 parts matting resin A, 200-260 parts matting resin B, 80-160 parts aliphatic polyurethane gloss-enhancing resin, 20-40 parts pigment paste, and 65-75 parts isocyanate crosslinking agent. Curing temperature: 110-130℃; spraying speed: 9-11 m / min; coating amount: 25-35 g / m². 2 The finished leather is obtained.

[0026] In step S3, the pigment paste is a Stahl PP series pigment paste.

[0027] The hollow structure of the microspheres, along with the flexible acrylic resin and aliphatic polyurethane adhesion promoter, forms a tight functional synergistic network within the system. The excellent film-forming properties and flexibility of the flexible acrylic resin not only encapsulate and fix the microspheres, ensuring their uniform dispersion and providing a durable and stable light-scattering function, but also effectively prevent localized whitening caused by uneven scattering interfaces while maintaining opacity and a soft gloss. Simultaneously, the flexible segments of the resin and the elastic deformation capacity of the microspheres work together to further enhance the overall soft feel and compressive resilience of the coating. In this composite structure, the aliphatic polyurethane adhesion promoter plays a crucial role. One end of its molecule penetrates deeply into the surface of the leather fibers, while the other end firmly bonds to the acrylic resin-microsphere composite, thus forming a strong adhesive layer between the leather blank and the coating. This adhesive layer significantly improves the wet and dry adhesion of the coating to the leather blank, effectively preventing coating peeling due to mechanical deformation or environmental aging. Through the synergistic effect of the microspheres, acrylic resin, and polyurethane adhesion promoter, simultaneous optimization and composite enhancement of optical properties, soft feel, and adhesion strength are achieved.

[0028] By combining the pre-primer material and the specific application method of this invention in a synergistic manner, the number of coating layers is effectively reduced and the uniformity of coverage is improved. Furthermore, this pre-primer material can be produced using conventional roller coating equipment, eliminating the need for specialized equipment and saving on procurement costs.

[0029] The advantages of this invention compared to the prior art are: The pre-priming material for automotive interior leather finishing provided by this invention achieves excellent opacity. The microsphere particle size distribution effectively fills tiny defects and pores on the leather surface without obscuring the leather's natural texture. Using this pre-priming material, only 1-2 pre-priming coats, totaling 4-5 coats, are needed to achieve the opacity effect that traditional processes require 7-8 coats, significantly reducing the number of coats. The pre-priming material and its specific applications for automotive interior leather finishing provided by this invention avoid whitening caused by excessive light scattering. It has excellent pigment carrying capacity, capable of holding up to 15% pigment content, ensuring color saturation and uniformity. Spectrophotometer testing shows that leather products coated with this pre-priming material exhibit excellent color difference. The ∆E is significantly better than that of traditional processes, reducing color fluctuations. The pre-primer material provided by this invention, with its optimized component ratio, achieves a perfect balance of opacity, adhesion, and feel. Furthermore, through the synergistic effect of additives and soft acrylic resin, the coating maintains excellent softness. Comparative verification shows that the softness of the feel is improved by more than 0.3 compared to the traditional BLC process.

[0030] The pre-primer material for automotive interior leather finishing provided by this invention, when applied to leather finishing, directly reduces production costs by decreasing the number of coating layers. Finishing costs can be reduced by more than 20%, while production efficiency increases by more than 30%. Simultaneously, due to process simplification, product quality consistency and stability are improved. The water-based system of this invention's pre-primer material reduces the use of organic solvents, and the reduced number of coating layers also effectively lowers energy consumption, aligning with the trend of green manufacturing. This pre-primer material is suitable not only for high-saturation colored leather but also for light-colored leather, and it also exhibits good compatibility with inorganic pigment systems. Excellent finishing effects can be achieved on various types of leather materials (including full-grain leather, corrected-grain leather, split leather, etc.). Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Figure 1 This is a process flow diagram for the application of the pre-primer material of the present invention.

[0032] Figure 2 This is a flowchart of the existing conventional coating process.

[0033] Figure 3 The interior leather photograph was prepared for Example 1.

[0034] Figure 4 A photograph of the interior leather was prepared for comparative example 3.

[0035] Figure 5 The image shows the interior leather after the process of the present invention has been applied in Application Example 1.

[0036] Figure 6 The image shows a photograph of leather that has not been processed by the process of the present invention in Application Example 1. Detailed Implementation

[0037] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used are all commercially available. All chemicals used are purchased from GSC Group, and pigment pastes are purchased from Sthal Group.

[0038] Example 1 The pre-primer material is prepared according to the following proportions by weight percentage: Transparent acrylic microspheres (refractive index 1.50): 22%; Flexible acrylic resin: 12%; Aliphatic polyurethane adhesion promoter: 32%; Organosilicon-modified polyurethane feel additive: 10%; Leveling agent: 2%; Preservative: 1%; Deionized water: 21%; The components are mixed in sequence and dispersed evenly to obtain a pre-coating material.

[0039] When using pre-priming materials for finishing applications on raw leather, specific finishing methods include: Select automotive interior leather and apply it using the following process: S1. Raw leather: Selected full-grain raw leather for automotive interiors, tanned and retanned using existing technology, with a thickness controlled at 1.2-1.3mm. After softening by tumbling, vibrating, and dust removal processes, ensure that the leather fibers are stretched and flat, and free of fiber contamination.

[0040] S2. Sealing base: Apply the sealing paste to the leather flesh side using a through-feed roller coater, with a coating amount of 45g / m². 2 The sealant composition is: 700 parts water and 300 parts water-based acrylic resin emulsion. The curing temperature is 100℃, and the roller coating speed is 12m / min.

[0041] S3. Pre-base coating: The prepared pre-base coating material and pigment paste are mixed at a weight ratio of 85:15 to form a slurry, which is then applied to the grain surface of the leather using a through-type roller coater. The first coating amount is 65 g / m². 2 The second coating amount is 45 g / m². 2 Curing temperature 120℃, roller coating speed 10m / min.

[0042] The pigment paste is from the Starr PP series.

[0043] S4. Primer coating: Apply the primer slurry to the pre-primer coating surface using a reverse roller coater, with a coating weight of 100 g / m². 2 The composition of the primer coating is as follows: 700 parts of a composite resin emulsion, 100 parts of aliphatic polyurethane, 60 parts of matting release agent, 120 parts of pigment paste, and 20 parts of carbodiamine crosslinking agent. The curing temperature is 120℃, and the roller coating speed is 8m / min.

[0044] S5. Embossing, using a through-type embossing machine, embossing pressure 100 Bar, embossing roller temperature 90℃, embossing roller speed 6M / min.

[0045] S6. Intermediate Coating: Apply the intermediate coating slurry over the primer coating using a spray gun or high-grade roller coater. The intermediate coating slurry consists of: 80 parts water, 10 parts high-abrasion-resistant feel agent, 200 parts polyurethane resin, 220 parts matting resin A, 210 parts matting resin B, 100 parts gloss-enhancing resin, 120 parts pigment paste, and 60 parts isocyanate crosslinking agent. Curing temperature: 120℃; spraying speed: 9 m / min; coating weight: 40 g / m². 2 .

[0046] S7. Top Coating: Apply the top coating slurry over the intermediate coating using a spray gun. The top coating slurry consists of: 155 parts water, 40 parts water-based silicone emulsion feel agent, 60 parts high abrasion-resistant feel agent, 240 parts matting resin A, 240 parts matting resin B, 160 parts aliphatic polyurethane gloss-enhancing resin, 30 parts pigment paste, and 75 parts isocyanate crosslinking agent. Curing temperature: 120℃; spraying speed: 9 m / min; coating weight: 28 g / m². 2 The finished automotive interior leather is obtained.

[0047] Example 2 The pre-primer material is prepared according to the following proportions by weight percentage: Transparent acrylic microspheres (refractive index 1.50): 26%; Flexible acrylic resin: 8%; Aliphatic polyurethane adhesion promoter: 35%; Organosilicon-modified polyurethane feel additive: 8%; Leveling agent: 2%; Preservative: 1%; Deionized water: 20%; Other preparation methods are the same as in Example 1.

[0048] Comparative Example 1 (without microspheres): The pre-coating material does not contain transparent microspheres; its proportions are replaced by equal amounts of adhesion promoter and resin in the original ratio to prepare a conventional sealing paste. Other aspects are the same as in Example 1.

[0049] Comparative Example 2 (without adhesion promoter): The pre-primer material does not contain adhesion promoters; its proportions are replaced by an equal amount of flexible acrylic resin. Everything else is the same as in Example 1.

[0050] Comparative Example 3 (Conventional Pre-primer Material): Step S3 does not use the pre-primer material of this invention; instead, it directly uses a commercially available general-purpose leather pre-primer material (mainly composed of acrylic resin and fillers). The finished product is shown below. Figure 4 The overall feel is very heavy. The lighting is also poor.

[0051] Comparative Example 4 (Conventional Pre-primer Material): Use a commercially available general-purpose leather pre-coating material (mainly composed of acrylic resin and fillers).

[0052] Steps S1 and S2 are the same as in Example 1. S3. Pre-base coating: A commercially available general-purpose leather pre-base coating material (mainly composed of acrylic resin and fillers) is mixed with pigment paste at a weight ratio of 85:15 to form a slurry, which is then applied to the grain surface of the leather using a through-type roller coater. The first coating amount is 65 g / m². 2 The second coating amount is 45 g / m². 2 Curing temperature 120℃, roller coating speed 10m / min.

[0053] The pigment paste is from the Starr PP series.

[0054] S4. Primer Coating: Apply the primer slurry to the pre-primer coating surface using a reverse roller coater. The primer slurry consists of: 700 parts of a composite resin emulsion, 100 parts of aliphatic polyurethane, 60 parts of matting release agent, 120 parts of pigment paste, and 20 parts of carbodiamine crosslinking agent. Curing temperature: 120℃; Roller speed: 8 m / min; First coat weight: 80 g / m². 2 The second time was 60g / m 2 S5. Embossing, using a through-type embossing machine, embossing pressure 100 Bar, embossing roller temperature 90℃, embossing roller speed 6M / min.

[0055] S6. Intermediate Coating: Apply the intermediate coating slurry over the primer coating using a spray gun or high-grade roller coater. The intermediate coating slurry consists of: 80 parts water, 10 parts high-abrasion-resistant feel agent, 200 parts polyurethane resin, 220 parts matting resin A, 210 parts matting resin B, 100 parts gloss-enhancing resin, 120 parts pigment paste, and 60 parts isocyanate crosslinking agent. Curing temperature: 120℃; spraying speed: 9 m / min; initial coating amount: 35 g / m². 2 The second time was 30g / m 2 .

[0056] S7. Top Coating: Apply the top coating slurry over the intermediate coating using a spray gun. The top coating slurry consists of: 155 parts water, 40 parts water-based silicone emulsion feel agent, 60 parts high abrasion-resistant feel agent, 240 parts matting resin A, 240 parts matting resin B, 160 parts aliphatic polyurethane gloss-enhancing resin, 30 parts pigment paste, and 75 parts isocyanate crosslinking agent. The curing temperature is 120℃, the spraying speed is 9 m / min, and the initial coating amount is 25 g / m². 2 The second time was 20g / m 2 The finished automotive interior leather is obtained.

[0057] Application Example 1 This invention also specifically applies to corrected grain leather where the raw leather and coating color differ significantly. In Example 1, the full-grain raw leather is replaced with corrected grain leather, which has a significantly different color from the coating; otherwise, the process remains the same as in Example 1. Before-and-after comparison photos are shown below. Figure 5 and Figure 6 As shown, the pre-coating material provided by this invention can significantly cover leather with large color differences.

[0058] The performance of the leathers obtained in the examples and comparative examples was tested, and the results are shown in Table 1.

[0059] Table 1. Performance Test Results The leathers prepared in Examples 1 and 2 exhibit significantly superior performance compared to the comparative example in terms of adhesion, feel, and color uniformity. The transparent microspheres, soft acrylic resin, and aliphatic polyurethane adhesion promoter in the pre-coating material of this invention produce a significant synergistic effect. The microspheres provide elastic support and light scattering, the soft resin forms a flexible and continuous film, and the adhesion promoter ensures a strong bond between the coating and the raw leather, collectively creating a coating with a full feel and excellent coverage. The leather prepared in Example 1 demonstrates a better overall performance balance. Compared to Example 2, it has a softer and fuller feel, better color uniformity, and only slightly lower coating adhesion, but it is still superior to currently available commercial samples. This indicates that there is an optimal ratio range for microspheres, adhesion promoter, and acrylic resin (20-24% microspheres, 30-34% adhesion promoter, 10%-13% acrylic resin). Within this range, the overall performance is better. The leather prepared in Comparative Example 1 shows a significant decrease in various physical properties, poorer coverage uniformity, and a stiffer feel. The leather prepared in Comparative Example 2 showed a significant decrease in adhesion, and other properties also declined. The leather prepared in Comparative Example 3 (conventional pre-priming) exhibited no outstanding properties or obvious advantages, and failed to meet the requirements for coverage and excellent hand feel. The leather prepared in Comparative Example 4 (conventional pre-priming) required multiple coats. While it showed excellent coverage uniformity, excessive coating resulted in an overly thick coating, degrading the texture and making it resemble plastic.

[0060] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A pre-primer material for automotive interior leather finishing, characterized in that, By weight percentage, it comprises the following components: 8-15% resin, 28-36% adhesion promoter, 18-26% transparent microspheres, 8-15% additives, 0.5%-1.5% leveling agent, 0.1%-0.3% preservative, and the balance being water.

2. The pre-priming material for automotive interior leather finishing as described in claim 1, characterized in that, The additive is an organosilicon-modified polyurethane compound.

3. The pre-primer material for automotive interior leather finishing as described in claim 1, characterized in that, The transparent microspheres are micron-sized polymer microspheres, specifically acrylic or polyurethane microspheres, with a refractive index between 1.45 and 1.

55.

4. The pre-primer material for automotive interior leather finishing as described in claim 1, characterized in that, The leveling agent is a water-based silicone leveling agent.

5. A pre-primer material for automotive interior leather finishing as described in claim 1, characterized in that, The adhesion promoter is any one of aliphatic polyurethane, epoxy-modified polyurethane, or silane coupling agent-modified polyurethane.

6. A pre-primer material for automotive interior leather finishing as described in claim 1, characterized in that, The resin is any one of flexible acrylic resin, flexible polyurethane resin, or styrene-acrylic acid copolymer.

7. A method for preparing a pre-primer material for automotive interior leather finishing as described in any one of claims 1-6, characterized in that, The components are mixed sequentially and dispersed evenly to obtain the pre-primer material; specifically, the following steps are included:

1. Pre-dispersion stage: Add half of the water in the formula to the dispersion vessel, turn on the stirrer and heat to 30-40℃; slowly add the preservative at a speed of 300-500 rpm and stir for 5 minutes to make the preservative evenly dispersed in the water.

2. Mixing stage of resin and adhesion promoter: While maintaining the temperature and speed, slowly add the resin and adhesion promoter; increase the speed to 800-1000 rpm and continue stirring for 15-20 minutes until a homogeneous state is achieved. III. Fine dispersion stage of microspheres: The transparent microspheres are pre-mixed in the remaining water (the water remaining after removing the water from step one), and then slowly added to the dispersion vessel at a speed of 600-800 rpm; continue stirring and dispersing for 20-30 minutes until the microspheres are uniformly dispersed in the system and there are no visible agglomerated particles. IV. Mixing stage of additives and leveling agent: Reduce the speed to 400-600 rpm, add the additives and leveling agent in sequence; stir for 10-15 minutes after adding the materials to ensure that all additives are fully mixed; V. Standing stage: Under an environment of 20-30℃, the mixture is continuously stirred at a low speed of 50-100 rpm for at least 24 hours to finally obtain the pre-primer material.

8. The application of the pre-priming material for automotive interior leather finishing as described in claim 1 in the leather finishing process.

9. The application as described in claim 8, characterized in that, Specifically, it is mainly used in the finishing process of automotive interior leather, which includes full-grain leather, corrected grain leather, Nappa leather, and embossed leather.

10. The application as described in claim 9, characterized in that, The specific method for applying pre-priming materials in leather finishing includes the following steps: S1. Raw leather, selected from raw leather that has been tanned and retanned; S2. Sealing base coat: Apply the sealing paste to the leather flesh side using a through-feed roller coater, with a coating amount of 40–50 g / m². 2 The composition of the sealing paste is: 700-800 parts water, 200-300 parts water-based acrylic resin emulsion; curing temperature 100-120℃, roller coating speed 9-15m / min; S3. Pre-base coating: The prepared pre-base coating material and pigment paste are mixed at a weight ratio of 85-90:10-15 to form a slurry, which is then applied to the leather grain surface 1-2 times using a through-type roller coater; the first coating amount is 60-70 g / m². 2 If a second coat is applied, the coating amount should be 40–50 g / m². 2 The curing temperature is 120-130℃, and the roller coating speed is 10-15m / min. S4. Primer coating: Apply the primer slurry to the pre-primer coating surface using a reverse roller coater, with a coating weight of 90–110 g / m². 2 The composition of the primer coating is as follows: 600-700 parts of composite resin emulsion, 100-150 parts of aliphatic polyurethane, 60-70 parts of matting release agent, 120-130 parts of pigment paste, and 20-30 parts of carbodiamine crosslinking agent; the curing temperature is 110-130℃, and the roller coating speed is 6-8m / min. S5. Embossing: Use a through-feed embossing machine to create the desired texture; S6. Intermediate Coating: Apply the intermediate coating slurry over the primer coating using a spray gun or high-grade roller coater. The intermediate coating slurry consists of: 40-80 parts water, 10-20 parts high abrasion-resistant hand feel agent, 150-200 parts polyurethane resin, 180-240 parts matting resin A, 200-250 parts matting resin B, 80-120 parts gloss-enhancing resin, 100-120 parts pigment paste, and 55-65 parts isocyanate crosslinking agent. The curing temperature is 110-130℃, the spraying speed is 9-11 m / min, and the coating amount is 30-40 g / m². 2 ; S7. Top Coating: Apply the top coating slurry over the intermediate coating using a spray gun. The top coating slurry consists of: 120-160 parts water, 30-40 parts water-based silicone emulsion hand feel agent, 40-60 parts high abrasion-resistant hand feel agent, 200-260 parts matting resin A, 200-260 parts matting resin B, 80-160 parts aliphatic polyurethane gloss-enhancing resin, 20-40 parts pigment paste, and 65-75 parts isocyanate crosslinking agent. The curing temperature is 110-130℃, the spraying speed is 9-11 m / min, and the coating amount is 25-35 g / m². 2 ; to obtain finished leather.

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