Multi-layer composite coating material, leather composite material and preparation method and application of multi-layer composite coating material and leather composite material

Abstract

The invention provides a multilayer composite coating material, a leather composite material and a preparation method and application thereof, and belongs to the technical field of leather coating materials. According to the technical scheme provided by the invention, the comprehensive performance of the leather composite material can be remarkably improved. The prepared product shows excellent yellowing resistance, and can effectively resist color degradation caused by environmental factors such as ultraviolet rays, damp heat and the like; meanwhile, the paint has good waterproofness and outstanding anti-fouling and easy-to-clean performance, and is easy to clean even if being contaminated by common stains. The material is smooth and skin-friendly in hand feeling, and overcomes the stiffness of a traditional coating while keeping the flexible texture of leather. The bonding between the coating and the leather base material is extremely firm, the layering risk is avoided, and the product is endowed with excellent bending resistance and wear resistance. The performance is improved, so that the obtained material can fully meet the requirements of high-performance leather products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of leather coating materials, in particular to a multi-layer composite coating material, a leather composite material and a preparation method and application thereof. BACKGROUND

[0002] In the field of leather processing and finishing, applying a functional coating to the surface of leather is a key process for improving product added value, appearance and durability. Through finishing, small defects on the surface of leather can be covered, and uniform color, gloss and specific properties such as water resistance, wear resistance, easy cleaning, etc. can be given. At present, the commercialized leather coating material system is mainly based on two types of synthetic polymers, polyurethane (PU) and polyvinyl chloride (PVC).

[0003] Polyurethane coating is widely used in medium and high-grade leather products due to its good flexibility and high film strength. It can provide a full and elastic feel. However, the chemical bonds in its molecular chain are prone to degradation when exposed to ultraviolet light and a humid and hot environment for a long time, resulting in yellowing, powdering or physical property degradation of the coating, and weather resistance becomes its shortcoming. In addition, many high-performance PU coatings rely on organic solvents (such as DMF, toluene) in the production and application process, which brings problems of volatile organic compound (VOC) emission and potential residue, which is contrary to the increasingly stringent environmental protection requirements.

[0004] Polyvinyl chloride coating is characterized by lower cost and excellent water resistance. However, PVC itself is relatively hard, and a large amount of plasticizer needs to be added to obtain flexibility suitable for leather. These plasticizers will migrate and volatilize over time, causing the coating to gradually harden, become brittle or have a sticky surface, which not only affects the touch and appearance, but also poses environmental risks. At the same time, the breathability of PVC coating is generally poor, which affects the comfort of leather products.

[0005] Although the above problems can be alleviated to some extent through formula modification, it is often difficult to achieve an ideal balance in long-term weather resistance, ecological environmental protection, comfortable touch, and durable and firm adhesion between the coating and the porous fiber surface of the leather, etc. In particular, when a composite coating structure with multiple functions needs to be built, how to ensure the stability of the interface between the layers and avoid peeling, while meeting the requirements of high performance and environmental protection, is the main challenge faced by current leather coating technology. Therefore, it is of great significance to develop a new generation of leather coating materials with better comprehensive performance and environmental friendliness and supporting application technology. SUMMARY

[0006] The purpose of this invention is to provide a multilayer composite coating material, a leather composite material, its preparation method and application, which solves the technical problems that exist in existing polymer coating materials when applied to leather substrates, such as insufficient aging resistance, poor environmental friendliness, stiff coating affecting the feel of the substrate, and poor adhesion reliability between functional layers or between the coating and the substrate.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a multilayer organosilicon coating material, comprising the following steps: T1. A surface layer slurry is coated onto release paper and subjected to a first curing treatment to form a surface layer. The surface layer slurry contains MQ vinyl silicone resin, terminal vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, and inhibitor. T2. Apply an intermediate layer slurry to the surface layer and perform a second curing process to form an intermediate layer. The intermediate layer slurry contains MQ vinyl silicone resin, terminal vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, inhibitor, and colorant. T3. Apply a base layer slurry to the intermediate layer. The base layer slurry contains vinyl-terminated silicone oil, hydrogen-containing silicone oil, reinforcing filler, platinum catalyst, inhibitor, colorant, and adhesion promoter.

[0008] Preferably, the bottom layer slurry is applied by a doctor blade with a thickness of 350~450μm, the middle layer slurry is applied by a doctor blade with a thickness of 80~120μm, and the top layer slurry is applied by a doctor blade with a thickness of 40~60μm. The temperature of the first curing treatment and the second curing treatment are each independently 120~140℃, and the time is each independently 3~7 minutes; The inhibitor includes methylbutynol; the adhesion promoter includes a silane coupling agent; and the reinforcing filler includes silica.

[0009] Preferably, the preparation of the top layer slurry, the intermediate layer slurry, and the bottom layer slurry all include the step of stirring at different speeds before and after adding the platinum catalyst; The preparation of the bottom slurry includes the steps of performing a first kneading treatment on a portion of the end vinyl silicone oil and the silica, and then adding the remaining end vinyl silicone oil for a second kneading treatment.

[0010] Preferably, the surface layer slurry comprises, by weight: 40-50 parts of MQ vinyl silicone resin, 50-60 parts of vinyl-terminated silicone oil, 4-6 parts of hydrogen-containing silicone oil, 0.4-0.6 parts of platinum catalyst, and 0.05-0.15 parts of inhibitor; The intermediate layer slurry comprises, by weight: 33-37 parts of MQ vinyl silicone resin, 58-62 parts of vinyl-terminated silicone oil, 7-9 parts of hydrogen-containing silicone oil, 0.4-0.6 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, and 5-9 parts of colorant. The underlying slurry comprises, by weight: 55-65 parts of vinyl-terminated silicone oil, 9-11 parts of hydrogen-containing silicone oil, 18-22 parts of reinforcing filler, 0.4-0.6 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, 5-9 parts of colorant, and 0.05-0.15 parts of adhesion promoter.

[0011] The present invention also provides a multilayer organosilicon coating material, which is prepared by the above-described method for preparing multilayer organosilicon coating materials.

[0012] Preferably, the above-mentioned multilayer silicone coating material can be used in the preparation of composite leather.

[0013] This invention also provides a method for preparing bovine split-layer transdermal film, comprising the following steps: P1. Bovine split blue hide is subjected to water treatment and hide blank treatment in sequence to obtain bovine split substrate; P2. Provide the above-mentioned multilayer silicone coating material, wherein the underlying slurry is not fully cured; P3. The double-layer substrate is bonded to the bottom slurry of the multilayer silicone coating material, and a third curing treatment is performed. After cooling, the release paper is peeled off to obtain the double-layer film.

[0014] Preferably, in step P1, the leather processing includes drying the water-treated bovine split blue leather at 70~90℃ until the moisture content is ≤10%, and using sandpaper with a mesh size of 280~360 to polish the surface and remove dust; In the water treatment in step P1, the pH value of the bovine split blue hide is adjusted to 2.5-3.5 and then retanned. After retanning, the pH value is adjusted to 5.5-6.5, and then an organosilicon fatliquoring agent is used for filling and fatliquoring at 50-60°C. The third curing process is performed at a temperature of 110~130℃ for 8~12 minutes. In step P3, the pressure applied to the bonded double-layer substrate is 0.2~0.4 MPa.

[0015] The present invention also provides a bovine split-layer film, which is prepared by the above-described method for preparing bovine split-layer film.

[0016] The present invention also provides the application of the above-mentioned bovine split film in the preparation of automotive interiors, furniture upholstery, or medical device accessories.

[0017] The technical effects and advantages of this invention are as follows: The technical solution provided by this invention can significantly improve the overall performance of leather composite materials. The prepared products exhibit excellent resistance to yellowing, effectively resisting color degradation caused by environmental factors such as ultraviolet radiation and humidity; they also possess good water resistance and outstanding stain resistance and easy cleaning properties, making them easy to clean even when stained with common dirt. The material has a smooth and skin-friendly feel, overcoming the stiffness of traditional coatings while maintaining the supple texture of leather. In addition, the adhesion between the coating and the leather substrate is extremely strong, avoiding the risk of delamination and giving the product excellent flexural and abrasion resistance. These performance improvements enable the resulting material to fully meet the stringent requirements for durability, cleanliness, and comfort in fields such as automotive interiors, high-end furniture, and medical accessories, and the entire preparation process is more environmentally friendly, providing an effective solution for developing high-performance leather products. Detailed Implementation

[0018] This invention provides a method for preparing a multilayer silicone coating material, aiming to solve the problems of poor environmental performance, insufficient weather resistance, stiff feel, and poor adhesion to the substrate in existing coating materials. This method, through specific slurry formulation design and a layered coating and curing process, produces a high-performance, environmentally friendly coating material.

[0019] The preparation method includes the following core steps: T1. The topcoat slurry is coated onto release paper and subjected to a first curing treatment to form the topcoat. Here, the topcoat slurry is crucial for forming the outermost functional surface of the coating, and it comprises MQ vinyl silicone resin, terminal vinyl silicone oil, hydrogen-containing silicone oil, a platinum catalyst, and an inhibitor. MQ vinyl silicone resin is an organosilicon resin with a three-dimensional network structure, serving as the main framework of the coating and providing excellent heat resistance, mechanical strength, and gloss. Terminal vinyl silicone oil is a polydimethylsiloxane with vinyl groups at both ends; its molecular chains are flexible, acting as a reactive diluent and flexible component, synergistically with the resin to impart good elasticity and elongation to the coating. Hydrogen-containing silicone oil is a polysiloxane with active silane-hydrogen bonds (Si-H) on its side chains or end groups. Under the action of the platinum catalyst, its Si-H bonds can undergo hydrosilylation reactions with the vinyl groups in the terminal vinyl silicone oil and MQ resin, forming a stable three-dimensional cross-linked network. The platinum catalyst is preferably a platinum complex, such as a platinum-vinylsiloxane complex or a platinum-olefin complex, which is the core substance initiating and promoting the hydrosilylation reaction. Inhibitors, such as methylbutyninol and ethynylcyclohexanol, act by reversibly binding with the platinum catalyst to suppress the reaction at room temperature. This prevents premature gelation of the slurry due to localized heating during mixing and coating, thus ensuring the uniformity of the process operating window and coating quality. In some specific embodiments of the present invention, methylbutyninol is preferably used as the inhibitor.

[0020] T2. Apply an intermediate layer slurry to the surface layer and perform a second curing treatment to form an intermediate layer. The intermediate layer slurry contains MQ vinyl silicone resin, terminal vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, inhibitor, and colorant. One of the main functions of the intermediate layer is to achieve product color customization. The colorant is preferably a silicone-specific color paste with good compatibility with the silicone system or a surface-treated organic pigment to avoid coating cracking or color migration caused by incompatibility between ordinary pigments and silicone oil. The addition of colorant gives the coating a rich and stable color performance.

[0021] T3. Apply a base coat slurry to the intermediate layer. The base coat slurry is a crucial layer responsible for strong adhesion to the subsequent substrate (such as leather). It comprises vinyl-terminated silicone oil, hydrogen-containing silicone oil, reinforcing filler, platinum catalyst, inhibitor, colorant, and adhesion promoter. The reinforcing filler enhances the coating's mechanical strength, abrasion resistance, and tear resistance. Typical reinforcing fillers include fumed silica (silica), precipitated silica, carbon black, and silica powder, with fumed silica having a high specific surface area being preferred because it can tightly bind to the silicone rubber molecular chains through physical adsorption and hydrogen bonding, producing a significant reinforcing effect. The adhesion promoter enhances the chemical bonding and physical anchoring between the base coat slurry and the polar substrate (such as leather fibers). It is preferably a silane coupling agent, such as γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, or allyl glycidyl ether. The hydrolyzable group at one end of the silane coupling agent molecule can react with the hydroxyl groups on the surface of leather fibers, while the organic functional groups (such as amino and epoxy groups) at the other end can participate in or promote the cross-linking reaction with the organosilicon coating, thereby forming a strong chemical bridge at the interface and significantly improving the peel strength.

[0022] Regarding the coating process, to precisely control the thickness and final performance of each coating layer, blade coating is preferred. Specifically, the bottom layer slurry is preferably coated using a blade with a blade gap (i.e., wet film thickness) of 350-450 μm, such as 360 μm, 380 μm, 400 μm, 420 μm, or 440 μm, and more preferably 380-420 μm. The intermediate layer slurry is preferably coated using a blade with a blade gap of 80-120 μm, such as 85 μm, 95 μm, 105 μm, or 115 μm, and more preferably 90-110 μm. The top layer slurry is preferably coated using a blade with a blade gap of 40-60 μm, such as 45 μm, 50 μm, or 55 μm, and more preferably 45-55 μm. Blade coating is a mature coating preparation technology that can obtain a wet film with uniform thickness by precisely controlling the gap between the blade and the substrate (in this case, release paper or an existing coating).

[0023] Regarding the curing process, to ensure the full progress of the hydrosilylation reaction in each layer without affecting the underlying structure, the curing conditions need to be controlled. The temperatures for the first and second curing treatments are each independently 120~140℃, for example 125℃, 130℃, or 135℃, more preferably 125~135℃; the times are each independently 3~7 minutes, for example 4 minutes, 5 minutes, or 6 minutes, more preferably 4~6 minutes. These conditions are sufficient to allow the top and intermediate layers to fully crosslink and cure, forming a stable coating.

[0024] Regarding the slurry preparation process, to ensure thorough dispersion and uniform mixing of all components and prevent catalyst deactivation, the preparation of the top layer slurry, intermediate layer slurry, and bottom layer slurry preferably includes a stirring step at different speeds before and after adding the platinum catalyst. The conventional operation involves first thoroughly mixing all raw materials except the catalyst at a certain speed (e.g., 400-600 rpm), then slowly adding the platinum catalyst, and then appropriately increasing the speed (e.g., 700-900 rpm) for a short period of stirring to ensure uniform catalyst dispersion. Furthermore, for the bottom layer slurry containing reinforcing fillers (e.g., precipitated silica), to prevent filler agglomeration and ensure uniform dispersion in the silicone oil for optimal reinforcing effect, the preparation of the bottom layer slurry preferably includes a first kneading treatment of a portion of the vinyl-terminated silicone oil with the precipitated silica, followed by a second kneading treatment with the remaining vinyl-terminated silicone oil. The kneading treatment is typically carried out in a kneader, where mechanical shearing and extrusion ensure that the high specific surface area of ​​the precipitated silica is thoroughly wetted and dispersed by the silicone oil.

[0025] Regarding the specific formulation composition, in order to obtain a coating with excellent overall performance, the composition of each layer of slurry by weight is preferably within the following range: The surface layer slurry comprises: 40-50 parts of MQ vinyl silicone resin (more preferably 42-48 parts, for example 45 parts), 50-60 parts of vinyl-terminated silicone oil (more preferably 52-58 parts, for example 55 parts), 4-6 parts of hydrogen-containing silicone oil (more preferably 4.5-5.5 parts, for example 5 parts), 0.4-0.6 parts of platinum catalyst (more preferably 0.45-0.55 parts, for example 0.5 parts), and 0.05-0.15 parts of inhibitor (more preferably 0.08-0.12 parts, for example 0.1 parts).

[0026] The intermediate layer slurry comprises: 33-37 parts of MQ vinyl silicone resin (more preferably 34-36 parts, for example 35 parts), 58-62 parts of vinyl-terminated silicone oil (more preferably 59-61 parts, for example 60 parts), 7-9 parts of hydrogen-containing silicone oil (more preferably 7.5-8.5 parts, for example 8 parts), 0.4-0.6 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, and 5-9 parts of colorant (more preferably 6-8 parts, for example 7 parts).

[0027] The underlying slurry comprises: 55-65 parts (more preferably 58-62 parts, e.g., 60 parts) of vinyl-terminated silicone oil, 9-11 parts (more preferably 9.5-10.5 parts, e.g., 10 parts) of hydrogen-containing silicone oil, 18-22 parts (more preferably 19-21 parts, e.g., 20 parts) of reinforcing filler, 0.4-0.6 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, 5-9 parts of colorant, and 0.05-0.15 parts (more preferably 0.08-0.12 parts, e.g., 0.1 parts) of adhesion promoter. The above parts can be understood as weight ratios, and all components are commercially available.

[0028] The present invention also provides a multilayer silicone coating material, which is prepared by any of the above-mentioned preparation methods. The material uses release paper as a temporary carrier and has a multilayer composite structure consisting of a top layer, an intermediate layer and a bottom layer. Each layer is cured and tightly bonded by hydrosilylation reaction. It is itself an independent functional film material with excellent surface properties (such as smoothness, stain resistance and yellowing resistance), mechanical properties and potential adhesive properties.

[0029] The aforementioned multilayer silicone coating material can be used in the preparation of various composite leathers. Specifically, it can be used as a surface modification layer and laminated with various substrates (such as natural leather, artificial leather, synthetic leather, fabrics, etc.) through bonding, calendering, etc., to impart the excellent properties of silicone coating to the substrate, thus enabling its wide application in fields requiring high-performance surfaces.

[0030] This invention also provides a method for preparing a cow split leather with a laminated coating. This method involves combining the aforementioned high-performance multilayer silicone coating material with a specially treated cow split leather substrate to prepare a laminated leather product with excellent overall performance. The method includes the following steps: P1. The cow split leather is subjected to water treatment and hide pretreatment in sequence to obtain the cow split substrate. This is a key pretreatment to ensure the bonding strength and substrate quality of the final product.

[0031] The water treatment process is a conventional leather tanning technique aimed at placing leather fibers in a physical and chemical state suitable for subsequent processing. In this invention, to optimize the affinity with the silicone coating, the conventional water treatment process has been adapted. Specifically, this includes adjusting the pH of the cowhide split blue leather to 2.5–3.5 (e.g., 2.8, 3.0, 3.2, more preferably 2.8–3.2) before retanning. This acidic environment facilitates the penetration and binding of tanning agents (such as chrome tanning agents). During retanning, a masking agent (such as sodium formate) can also be added to regulate the tanning agent binding rate and prevent over-tanning of the surface. After retanning, a neutralization process is required to adjust the pH to 5.5–6.5 (e.g., 5.8, 6.0, 6.2, more preferably 5.8–6.2) to provide a suitable weakly acidic to near-neutral environment for subsequent fatliquoring. Finally, the silicone fatliquoring agent is used for filling and fatliquoring at 50-60°C (e.g., 52°C, 55°C, 58°C, more preferably 53-57°C). The macromolecular structure of the silicone fatliquoring agent can not only combine well with leather fibers, giving the leather softness, but its hydrophobic silicone segments can also form an interface with good affinity with the subsequent silicone coating on the fiber surface, which helps to improve adhesion. At the same time, it can also prevent the small molecule silicone oil in the underlying slurry from excessively penetrating into the leather pores and affecting curing.

[0032] The pre-coating treatment is performed after the water treatment to bring the substrate to a suitable physical state for coating and bonding. This includes drying the water-treated split leather at 70-90°C (e.g., 75°C, 80°C, 85°C, more preferably 75-85°C) until the moisture content is ≤10% (preferably ≤8%, more preferably ≤6%). Controlling the moisture content is crucial for subsequent bonding and curing with the wet undercoat slurry; excessive moisture can interfere with the activity of the platinum catalyst, potentially leading to incomplete curing. After drying, the surface is sanded and dusted using sandpaper with a grit of 280-360 grit (e.g., 300 grit, 320 grit, 340 grit, more preferably 300-340 grit). Sanding removes loose fibers, increases surface roughness, and significantly increases the mechanical contact area with the undercoat slurry, improving physical adhesion strength; dusting ensures a clean bonding interface, preventing impurities from affecting the bonding effect.

[0033] P2. Provide the above-mentioned multilayer silicone coating material, wherein the underlying slurry is in an incompletely cured state. Typically, after applying the underlying slurry in step T3, complete high-temperature curing is not performed or only slight surface drying is allowed to maintain a certain degree of fluidity and reactivity so as to adhere to the substrate.

[0034] P3. The cowhide split substrate is bonded to the bottom layer of the multilayer silicone coating material, followed by a third curing treatment. A certain pressure is applied during bonding, preferably 0.2~0.4 MPa (e.g., 0.25 MPa, 0.3 MPa, 0.35 MPa, more preferably 0.25~0.35 MPa), to ensure sufficient contact between the paste and the leather surface and partial penetration into the fiber gaps. The temperature of the third curing treatment is preferably 110~130℃ (e.g., 115℃, 120℃, 125℃, more preferably 115~125℃), and the time is preferably 8~12 minutes (e.g., 9 minutes, 10 minutes, 11 minutes, more preferably 9~11 minutes). This temperature and time are sufficient to completely cure the bottom layer paste and form a strong bond with the leather substrate through the action of silane coupling agents, while avoiding excessive shrinkage and deformation of the cowhide split leather due to excessive temperature. After curing, it needs to be cooled (e.g., naturally cooled or forced cooled to room temperature (20-30℃)) before peeling off the release paper. The cooling step helps release internal stress caused by temperature changes, preventing the coating from cracking or warping due to thermal stress and stabilizing the physical structure of the product. This ultimately yields the New Zealand split-layer film.

[0035] This invention also provides a cow split laminate film, which is prepared by any of the above-mentioned cow split laminate film preparation methods. This product combines the texture of natural cow split with the superior performance of an organosilicon coating, exhibiting excellent abrasion resistance, yellowing resistance, water and stain resistance, a skin-friendly feel, and high peel strength to the substrate.

[0036] This invention also provides the application of the above-mentioned split leather in the preparation of high-end leather products. Specific application scenarios include, but are not limited to: Automotive interiors: such as car seat covers, headrests, armrests, door panel covers, dashboard coverings, steering wheel coverings, etc., utilizing their wear-resistant, weather-resistant, stain-resistant, easy-to-clean, and comfortable feel.

[0037] Furniture upholstery: such as the covering material for high-end sofas, dining chairs, headboards, and living room furniture, leveraging its advantages of being beautiful, durable, skin-friendly, and easy to clean.

[0038] Medical equipment accessories, such as medical mattresses, stretcher pads, wheelchair cushions, and medical bag linings, utilize their environmental friendliness and non-toxicity (low VOC), ease of disinfection and cleaning, resistance to liquid penetration, and potential for antibacterial modification (which can be achieved by adding antibacterial agents to the coating).

[0039] In addition, it can also be applied to aerospace interiors, yacht interiors, high-end electronic product protective cases, fashion bags and special clothing accessories, etc., to meet the market's diversified demand for high-performance and environmentally friendly leather materials.

[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] The properties and sources of some of the materials used in the embodiments are as follows: MQ vinyl silicone resin is characterized by the molar ratio of M units "≡SiO1 / 2" to Q units "SiO2", i.e., M / Q = 0.7:1-0.9:1; the vinyl content is 1.8-3%. The hydrogen content in the end-side hydrogen-containing silicone oil is 0.6-1%, and the viscosity is 50-120 mPa·s; In vinyl-terminated silicone oils, the viscosity is 60,000-90,000 mPa·s; The catalyst is a platinum catalyst, 5000 ppm; The silicone-specific color paste is from the Dawei Silicone-Specific Color Paste Series of Sichuan Dawei Technology Co., Ltd.

[0042] Example 1 I. Slurry Preparation 1. The surface coating slurry is formulated with the following components: 40-50 parts MQ vinyl silicone resin, 50-60 parts vinyl-terminated silicone oil, 5 parts hydrogen-containing silicone oil, 0.1 parts methylbutyninol, and 0.5 parts platinum catalyst. By catalyzing the addition reaction of hydrogen-containing compounds with vinyl groups with a platinum catalyst, a three-dimensional cross-linked network is formed, resulting in excellent wear resistance.

[0043] 2. The intermediate layer slurry is formulated with the following components: 35 parts MQ vinyl silicone resin, 60 parts vinyl-terminated silicone oil, 8 parts hydrogen-containing silicone oil, 0.1 parts methylbutyninol, and 0.5 parts platinum catalyst. 3. The bottom layer slurry is formulated with the following components: 60 parts vinyl-terminated silicone oil, 10 parts hydrogen-containing silicone oil, 0.1 parts silane coupling agent (γ-aminopropyltriethoxysilane), 20 parts silica, 0.1 parts methylbutyninol, and 0.5 parts platinum catalyst. II. Leather Making Process Step 1: Water Treatment The blue leather undergoes a 35℃ rehydration process, during which ammonium sulfate, formic acid, and oxalic acid are used to gradually adjust the pH to around 3 to provide an acidic environment for subsequent retanning. Sodium formate is added during retanning to act as a masking agent, slowing down the bonding speed of chrome tanning agents and preventing over-tanning of the surface. Then, a neutralization process is used to adjust the pH to 6 using baking soda and sodium formate to provide suitable conditions for fatliquoring. The amount of sodium formate should not be too small, otherwise the pH will rise too quickly and cause excessive neutralization of the surface. Finally, an organosilicon fatliquoring agent is used for filling and fatliquoring, with the water temperature raised to 55℃ to ensure the emulsification and penetration of the fatliquoring agent, avoiding floating oil and localized over-oiling.

[0044] Step 2: Skin processing After undergoing a complete water treatment process, the split leather of the cowhide is hung to dry at 80℃ for 1 hour until the moisture content is ≤8%. Then, it is sanded and dusted using 320-grit sandpaper. Hanging to dry until the moisture content is ≤8% is to avoid high moisture content, which would affect the curing and adhesion of the silicone base coating. Sanding with 320-grit sandpaper increases the surface roughness, improves the adhesion between the base and the split leather, and reduces the length of loose fibers on the surface to avoid false bonding.

[0045] Step 3: Slurry preparation Top layer: 50 parts of MQ vinyl silicone resin, 50 parts of vinyl-terminated silicone oil, 5 parts of end-side hydrogen-containing silicone oil, and 0.1 parts of methylbutyninol were sequentially added to a high-speed dispersing mixer. The mixing speed was set to 500 rpm, and the mixing time was 30 min. Then, 0.5 parts of platinum catalyst were slowly added, the speed was adjusted to 800 rpm, and the mixing was continued for 15 min to obtain a uniform silicone rubber composition. Gradient speed mixing ensures that the raw materials are fully dispersed and mixed evenly, avoiding incomplete crosslinking caused by uneven local concentration. At the same time, gentle stirring can prevent catalyst deactivation.

[0046] Intermediate layer: 35 parts of MQ vinyl silicone resin, 60 parts of vinyl-terminated silicone oil, 7 parts of organosilicon-specific color paste, 8 parts of end-side hydrogen-containing silicone oil, and 0.1 parts of methylbutyninol were sequentially added to a high-speed dispersing mixer. The mixing speed was set to 500 rpm, and the mixing time was 30 min. Then, 0.5 parts of platinum catalyst were slowly added, the speed was adjusted to 800 rpm, and the mixing was continued for 15 min to obtain a uniform silicone rubber composition. Gradient speed mixing ensures that the raw materials are fully dispersed and mixed evenly, avoiding incomplete crosslinking caused by uneven local concentration. At the same time, gentle stirring can prevent catalyst deactivation.

[0047] Bottom layer: Add 40 parts of end-vinyl silicone oil and 20 parts of silica to a kneader, set the speed to 25 rpm, and knead for 1 hour. Then slowly add another 20 parts of end-vinyl silicone oil, set the speed to 30 rpm, and knead for 1.5 hours. Remove the mixture, and add it in sequence with 10 parts of end-side hydrogen-containing silicone oil, 7 parts of organosilicon-specific color paste, 0.1 parts of silane coupling agent, and 0.1 parts of methylbutyninol to a high-speed disperser, set the stirring speed to 100 rpm, and the stirring time to 1 hour. Then slowly add 0.5 parts of platinum catalyst, adjust the speed to 300 rpm, and stir for 30 minutes to obtain a uniform silicone rubber composition. The step-by-step slow addition of end-vinyl silicone oil ensures uniform kneading with silica and avoids agglomeration.

[0048] Step 4: Apply silicone topcoat slurry The silicone topcoat slurry was applied to the release paper using a 50μm doctor blade. After coating, the paper was placed in an oven at 130℃ for 5 minutes to ensure that the hydrosilylation reaction was fully carried out and a stable cross-linked structure was formed.

[0049] Step 5: Apply silicone intermediate layer slurry The silicone intermediate layer slurry was coated onto the release paper using a 100μm doctor blade. After coating, the paper was placed in an oven at 130℃ for 5 minutes to ensure that the hydrosilylation reaction was fully carried out and a stable cross-linked structure was formed.

[0050] Step 6: Apply silicone primer and adhere to the second-layer substrate. Apply the base coat to the top coat using a 400μm doctor blade. Immediately press the Newton second layer substrate lightly (approximately 0.3MPa) onto the base coat, then place it in an oven at 120℃ for 10 minutes. After removing from the oven and allowing it to cool to room temperature, peel off the release paper. A 260-300μm thickness is used to ensure penetration into the Newton second layer substrate, achieving good adhesion and preventing detachment. 120℃ for 10 minutes is the optimal curing process to ensure the hydrosilylation reaction proceeds while preventing shrinkage of the Newton second layer due to excessive temperature. Peeling after cooling to room temperature prevents internal stress caused by sudden temperature changes in the coating, preventing cracking or warping and stabilizing the physical structure of the coating.

[0051] Example 2 Step 1: Water Treatment The blue leather undergoes a 35℃ rehydration process, during which ammonium sulfate, formic acid, and oxalic acid are used to gradually adjust the pH to around 3 to provide an acidic environment for subsequent retanning. Sodium formate is added during retanning to act as a masking agent, slowing down the bonding speed of chrome tanning agents and preventing over-tanning of the surface. Then, a neutralization process is used to adjust the pH to 6 using baking soda and sodium formate to provide suitable conditions for fatliquoring. The amount of sodium formate should not be too small, otherwise the pH will rise too quickly and cause excessive neutralization of the surface. Finally, an organosilicon fatliquoring agent is used for filling and fatliquoring, with the water temperature raised to 55℃ to ensure the emulsification and penetration of the fatliquoring agent, avoiding floating oil and localized over-oiling.

[0052] Step 2: Skin processing After undergoing a complete water treatment process, the split leather of the cowhide is hung to dry at 80℃ for 1 hour until the moisture content is ≤8%. Then, it is sanded and dusted using 320-grit sandpaper. Hanging to dry until the moisture content is ≤8% is to avoid high moisture content, which would affect the curing and adhesion of the silicone base coating. Sanding with 320-grit sandpaper increases the surface roughness, improves the adhesion between the base and the split leather, and reduces the length of loose fibers on the surface to avoid false bonding.

[0053] Step 3: Slurry preparation Top layer: 40 parts of MQ vinyl silicone resin, 60 parts of vinyl-terminated silicone oil, 5 parts of end-side hydrogen-containing silicone oil, and 0.1 parts of methylbutyninol were sequentially added to a high-speed dispersing mixer. The mixing speed was set to 500 rpm, and the mixing time was 30 min. Then, 0.5 parts of platinum catalyst were slowly added, the speed was adjusted to 800 rpm, and the mixing was continued for 15 min to obtain a uniform silicone rubber composition. Gradient speed mixing ensures that the raw materials are fully dispersed and mixed evenly, avoiding incomplete crosslinking caused by uneven local concentration. At the same time, gentle stirring can prevent catalyst deactivation.

[0054] Intermediate layer: 35 parts of MQ vinyl silicone resin, 60 parts of vinyl-terminated silicone oil, 7 parts of organosilicon-specific color paste, 8 parts of end-side hydrogen-containing silicone oil, and 0.1 parts of methylbutyninol were sequentially added to a high-speed dispersing mixer. The mixing speed was set to 500 rpm, and the mixing time was 30 min. Then, 0.5 parts of platinum catalyst were slowly added, the speed was adjusted to 800 rpm, and the mixing was continued for 15 min to obtain a uniform silicone rubber composition. Gradient speed mixing ensures that the raw materials are fully dispersed and mixed evenly, avoiding incomplete crosslinking caused by uneven local concentration. At the same time, gentle stirring can prevent catalyst deactivation.

[0055] Bottom layer: 40 parts of end-vinyl silicone oil and 20 parts of silica were added to a kneader at 25 rpm for 1 hour. Then, another 20 parts of end-vinyl silicone oil were slowly added at 30 rpm for 1.5 hours. The mixture was then removed and added sequentially to a high-speed disperser along with 10 parts of end-side hydrogen-containing silicone oil, 7 parts of organosilicon-specific color paste, 0.1 parts of silane coupling agent (same as in Example 1), and 0.1 parts of methylbutyninol. The mixing speed was set to 100 rpm for 1 hour. Subsequently, 0.5 parts of platinum catalyst were slowly added at 300 rpm for 30 minutes to obtain a uniform silicone rubber composite. By adding the end-vinyl silicone oil in stages and slowly, uniform kneading with silica was ensured, preventing agglomeration.

[0056] Step 4: Apply silicone topcoat slurry The silicone topcoat slurry was applied to the release paper using a 50μm doctor blade. After coating, the paper was placed in an oven at 130℃ for 5 minutes to ensure that the hydrosilylation reaction was fully carried out and a stable cross-linked structure was formed.

[0057] Step 5: Apply silicone intermediate layer slurry The silicone intermediate layer slurry was coated onto the release paper using a 100μm doctor blade. After coating, the paper was placed in an oven at 130℃ for 5 minutes to ensure that the hydrosilylation reaction was fully carried out and a stable cross-linked structure was formed.

[0058] Step 6: Apply silicone primer and adhere to the second-layer substrate. Apply the base coat to the top coat using a 400μm doctor blade. Immediately press the Newton second layer substrate lightly (approximately 0.3MPa) onto the base coat, then place it in an oven at 120℃ for 10 minutes. After removing from the oven and allowing it to cool to room temperature, peel off the release paper. A 260-300μm thickness is used to ensure penetration into the Newton second layer substrate, achieving good adhesion and preventing detachment. 120℃ for 10 minutes is the optimal curing process to ensure the hydrosilylation reaction proceeds while preventing shrinkage of the Newton second layer due to excessive temperature. Peeling after cooling to room temperature prevents internal stress caused by sudden temperature changes in the coating, preventing cracking or warping and stabilizing the physical structure of the coating.

[0059] Example 3 Step 1: Water Treatment The blue leather undergoes a 35℃ rehydration process, during which ammonium sulfate, formic acid, and oxalic acid are used to gradually adjust the pH to around 3 to provide an acidic environment for subsequent retanning. Sodium formate is added during retanning to act as a masking agent, slowing down the bonding speed of chrome tanning agents and preventing over-tanning of the surface. Then, a neutralization process is used to adjust the pH to 6 using baking soda and sodium formate to provide suitable conditions for fatliquoring. The amount of sodium formate should not be too small, otherwise the pH will rise too quickly and cause excessive neutralization of the surface. Finally, an organosilicon fatliquoring agent is used for filling and fatliquoring, with the water temperature raised to 55℃ to ensure the emulsification and penetration of the fatliquoring agent, avoiding floating oil and localized over-oiling.

[0060] Step 2: Skin processing After undergoing a complete water treatment process, the split leather of the cowhide is hung to dry at 80℃ for 1 hour until the moisture content is ≤8%. Then, it is sanded and dusted using 320-grit sandpaper. Hanging to dry until the moisture content is ≤8% is to avoid high moisture content, which would affect the curing and adhesion of the silicone base coating. Sanding with 320-grit sandpaper increases the surface roughness, improves the adhesion between the base and the split leather, and reduces the length of loose fibers on the surface to avoid false bonding.

[0061] Step 3: Slurry preparation Top layer: 50 parts of MQ vinyl silicone resin, 60 parts of vinyl-terminated silicone oil, 5 parts of end-side hydrogen-containing silicone oil, and 0.1 parts of methylbutyninol were sequentially added to a high-speed dispersing mixer. The mixing speed was set to 500 rpm, and the mixing time was 30 min. Then, 0.5 parts of platinum catalyst were slowly added, the speed was adjusted to 800 rpm, and the mixing was continued for 15 min to obtain a uniform silicone rubber composition. Gradient speed mixing ensures that the raw materials are fully dispersed and mixed evenly, avoiding incomplete crosslinking caused by uneven local concentration. At the same time, gentle stirring can prevent catalyst deactivation.

[0062] Intermediate layer: 35 parts of MQ vinyl silicone resin, 60 parts of vinyl-terminated silicone oil, 7 parts of organosilicon-specific color paste, 8 parts of end-side hydrogen-containing silicone oil, and 0.1 parts of methylbutyninol were sequentially added to a high-speed dispersing mixer. The mixing speed was set to 500 rpm, and the mixing time was 30 min. Then, 0.5 parts of platinum catalyst were slowly added, the speed was adjusted to 800 rpm, and the mixing was continued for 15 min to obtain a uniform silicone rubber composition. Gradient speed mixing ensures that the raw materials are fully dispersed and mixed evenly, avoiding incomplete crosslinking caused by uneven local concentration. At the same time, gentle stirring can prevent catalyst deactivation.

[0063] Bottom layer: 40 parts of end-vinyl silicone oil and 20 parts of silica were added to a kneader at 25 rpm for 1 hour. Then, another 20 parts of end-vinyl silicone oil were slowly added at 30 rpm for 1.5 hours. The mixture was then removed and added sequentially to a high-speed disperser along with 10 parts of end-side hydrogen-containing silicone oil, 7 parts of organosilicon-specific color paste, 0.1 parts of silane coupling agent (same as in Example 1), and 0.1 parts of methylbutyninol. The mixing speed was set to 100 rpm for 1 hour. Subsequently, 0.5 parts of platinum catalyst were slowly added at 300 rpm for 30 minutes to obtain a uniform silicone rubber composite. By adding the end-vinyl silicone oil in stages and slowly, uniform kneading with silica was ensured, preventing agglomeration.

[0064] Step 4: Apply silicone topcoat slurry The silicone topcoat slurry was applied to the release paper using a 50μm doctor blade. After coating, the paper was placed in an oven at 130℃ for 5 minutes to ensure that the hydrosilylation reaction was fully carried out and a stable cross-linked structure was formed.

[0065] Step 5: Apply silicone intermediate layer slurry The silicone intermediate layer slurry was coated onto the release paper using a 100μm doctor blade. After coating, the paper was placed in an oven at 130℃ for 5 minutes to ensure that the hydrosilylation reaction was fully carried out and a stable cross-linked structure was formed.

[0066] Step 6: Apply silicone primer and adhere to the second-layer substrate. Apply the base coat to the top coat using a 400μm doctor blade. Immediately press the Newton second layer substrate lightly (approximately 0.3MPa) onto the base coat, then place it in an oven at 120℃ for 10 minutes. After removing from the oven and allowing it to cool to room temperature, peel off the release paper. A 260-300μm thickness is used to ensure penetration into the Newton second layer substrate, achieving good adhesion and preventing detachment. 120℃ for 10 minutes is the optimal curing process to ensure the hydrosilylation reaction proceeds while preventing shrinkage of the Newton second layer due to excessive temperature. Peeling after cooling to room temperature prevents internal stress caused by sudden temperature changes in the coating, preventing cracking or warping and stabilizing the physical structure of the coating.

[0067] Comparative Example 1 An environmentally friendly and wear-resistant second-layer laminated film differs from Implementation Case 1 in that the silicone fatliquoring agent is replaced with a conventional fatliquoring agent.

[0068] An environmentally friendly and wear-resistant cowhide split film leather differs from Implementation Case 1 in that it does not undergo the leather blank treatment of "hanging and drying at 80℃ for 1 hour until the moisture content is ≤8%, and then sanding and dusting with 320-grit sandpaper".

[0069] The bovine split-layer film obtained in Examples 1-3 and Comparative Examples 1-2, and similar commercially available products (comparative examples) were tested for abrasion resistance, aging resistance, stain resistance, and flexural strength. The results are shown in Table 1 below: Table 1 Performance Test Results Test item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Company PU coated cow split leather (control) Peeling force / N 21N 21N 21N Bottom layer not cured 12N (delamination) 20N Martindale abrasion, 12KPa >1 million times >1 million times >1 million times - - 50,000 times Taber abrasion, 1kg 4000 times, 4-5 grade 4000 times, 4-5 grade 4000 times, 4-5 grade - - 2000 times, 3 grade Sunlight yellowing resistance, 80°C, 72h 5 grade 5 grade 5 grade - - 3 grade UV yellowing resistance, 30W, 8h 5 grade 5 grade 5 grade - - 3 grade Wet heat yellowing resistance, 70°C, 95%, 3 weeks 5 grade 5 grade 5 grade - - 3 grade Heat yellowing resistance, 120°C, 24h 5 grade 5 grade 5 grade - - 2 grade Hand feeling Smooth and skin-friendly Smooth and skin-friendly Smooth and skin-friendly - - Smooth Ball pen anti-graffiti >30 times >30 times >30 times - - ≤2 times Stain removal Easy to clean Easy to clean Easy to clean - - More difficult to clean Room temperature bending, 25°C >1 million times >1 million times >1 million times - - 50,000 times Low temperature bending, -15°C >1 million times >1 million times >1 million times - - 20,000 times As shown in the table above, the environmentally friendly wear-resistant denier double-layer film prepared in Examples 1-3 of this invention has better wear resistance, aging resistance, flexural resistance, and stain resistance than commercially available similar products (comparative examples). Martindale has a wear resistance of >100,000 cycles, and Taber has a wear resistance of 4,000 cycles, reaching level 4. Compared with Comparative Examples 1-2, Example 1 uses a conventional fatliquoring agent, which leads to the bottom layer slurry not curing. Without skin pretreatment, the adhesion is poor, which easily leads to delamination and peeling.

[0070] As demonstrated by the above embodiments, this invention provides a multilayer silicone coating material with stable processing and significant effects, its preparation method, and a complete preparation technology for a second-layer bovine laminate film based thereon. The prepared coating material exhibits strong bonding and uniform performance across all layers. The final second-layer bovine laminate film product demonstrates significant advantages in peel strength, abrasion resistance, yellowing resistance, anti-graffiti and stain-removing properties, and flexural strength, and has a smooth, skin-friendly feel, comprehensively surpassing traditional commercially available products of the same type. Comparative results further confirm the necessity of key steps in this invention, such as the selection of specific fatliquoring agents and the substrate pretreatment process. This invention successfully prepares a high-performance, environmentally friendly second-layer bovine laminate film.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a multilayer organosilicon coating material, characterized in that, Includes the following steps: T1. A surface layer slurry is coated onto release paper and subjected to a first curing treatment to form a surface layer. The surface layer slurry contains MQ vinyl silicone resin, terminal vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, and inhibitor. T2. Apply an intermediate layer slurry to the surface layer and perform a second curing process to form an intermediate layer. The intermediate layer slurry contains MQ vinyl silicone resin, terminal vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, inhibitor, and colorant. T3. Apply a base layer slurry to the intermediate layer. The base layer slurry contains vinyl-terminated silicone oil, hydrogen-containing silicone oil, reinforcing filler, platinum catalyst, inhibitor, colorant, and adhesion promoter.

2. The preparation method according to claim 1, characterized in that, The bottom layer slurry is coated with a doctor blade with a thickness of 350~450μm, the middle layer slurry is coated with a doctor blade with a thickness of 80~120μm, and the top layer slurry is coated with a doctor blade with a thickness of 40~60μm. The temperature of the first curing treatment and the second curing treatment are each independently 120~140℃, and the time is each independently 3~7 minutes; The inhibitor includes methylbutynol; the adhesion promoter includes a silane coupling agent; and the reinforcing filler includes silica.

3. The preparation method according to claim 1, characterized in that, The preparation of the top layer slurry, intermediate layer slurry and bottom layer slurry all include the step of stirring at different speeds before and after adding the platinum catalyst; The preparation of the bottom slurry includes the steps of performing a first kneading treatment on a portion of the end vinyl silicone oil and the silica, and then adding the remaining end vinyl silicone oil for a second kneading treatment.

4. The preparation method according to claim 1, characterized in that, The surface layer slurry comprises, by weight: 40-50 parts of MQ vinyl silicone resin, 50-60 parts of vinyl-terminated silicone oil, 4-6 parts of hydrogen-containing silicone oil, 0.4-0.6 parts of platinum catalyst, and 0.05-0.15 parts of inhibitor; The intermediate layer slurry comprises, by weight: 33-37 parts of MQ vinyl silicone resin, 58-62 parts of vinyl-terminated silicone oil, 7-9 parts of hydrogen-containing silicone oil, 0.4-0.6 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, and 5-9 parts of colorant. The underlying slurry comprises, by weight: 55-65 parts of vinyl-terminated silicone oil, 9-11 parts of hydrogen-containing silicone oil, 18-22 parts of reinforcing filler, 0.4-0.6 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, 5-9 parts of colorant, and 0.05-0.15 parts of adhesion promoter.

5. A multilayer organosilicon coating material prepared by any one of claims 1 to 4.

6. The application of the multilayer organosilicon coating material according to claim 5 in the preparation of composite leather.

7. A method for preparing a bovine split-layer transdermal patch, characterized in that, Includes the following steps: P1. Bovine split blue hide is subjected to water treatment and hide blank treatment in sequence to obtain bovine split substrate; P2. Provide a multilayer silicone coating material according to claim 5, wherein the underlying slurry is not fully cured; P3. The double-layer substrate is bonded to the bottom slurry of the multilayer silicone coating material, and a third curing treatment is performed. After cooling, the release paper is peeled off to obtain the double-layer film.

8. The preparation method according to claim 7, characterized in that, In step P1, the leather processing includes drying the water-treated bovine split blue leather at 70~90℃ until the moisture content is ≤10%, and then using sandpaper with a mesh size of 280~360 to polish the surface and remove dust. In the water treatment in step P1, the pH value of the bovine split blue hide is adjusted to 2.5-3.5 and then retanned. After retanning, the pH value is adjusted to 5.5-6.5, and then an organosilicon fatliquoring agent is used for filling and fatliquoring at 50-60°C. The third curing process is performed at a temperature of 110~130℃ for 8~12 minutes. In step P3, the pressure applied to the bonded double-layer substrate is 0.2~0.4 MPa.

9. A bovine split-layer film prepared by the preparation method of claim 7 or 8.

10. The use of the bovine split film as described in claim 9 in the preparation of automotive interior trim, furniture upholstery, or medical device accessories.