A napped silica gel coating and a method for preparing the same

Abstract

This invention relates to a method for preparing a velvety silicone coating, comprising the following steps: S1, mixing a silicone base component and a functional component, and vacuum stirring to degas, to obtain a silicone foaming slurry; the functional component includes a composite foaming agent, which is composed of azodicarbonamide and sodium bicarbonate; S2, coating the silicone foaming slurry onto the surface of a substrate to form a wet coating, preheating it to a first temperature, and then curing it to a second temperature to obtain the velvety silicone coating; the second temperature is 40-60°C higher than the first temperature, and the second temperature is lower than the decomposition temperature of the azodicarbonamide. This invention uses azodicarbonamide and sodium bicarbonate as a composite foaming agent, combined with a segmented temperature control design, to achieve a differentiated layered structure within a single coating, with a surface layer foamed into a velvety texture and a densely bonded bottom layer, thus balancing the three-dimensional velvety effect of the coating with high adhesion to the substrate.

Description

Technical Field

[0001] This invention relates to the field of silicone coating technology, and in particular to a textured silicone coating and its preparation method. Background Technology

[0002] Suede composite materials, with their soft, skin-friendly feel, excellent anti-slip and damping properties, and decorative appeal, are widely used in textiles, apparel, digital accessories, and artificial leather. Currently, suede molding processes are mainly divided into two categories: physical modification and chemical modification. Physical modification primarily involves brushing and mechanical napping; chemical modification mainly involves electrostatic flocking, adhesive flocking, and coating modification, which are currently the mainstream processing methods for high-end suede products.

[0003] Due to its excellent high and low temperature resistance, aging resistance, environmental friendliness, non-toxicity, and high elasticity, silicone materials are gradually replacing traditional polyurethane and acrylic coatings, becoming the preferred substrate for functional coatings. However, existing textured silicone coating technologies still have significant problems: (1) Integral silicone foam coating technology: after heating, the entire coating foams synchronously to form a fully porous structure, resulting in a flat coating surface without a three-dimensional texture. Moreover, the fully porous structure significantly reduces the adhesion between the coating and the substrate, making it prone to cracking and delamination; (2) Powder-modified textured silicone coating technology: pseudo-textured texture is achieved by filling with powder. It lacks a three-dimensional foam structure, has a stiff feel, and the powder is prone to agglomeration and shedding, resulting in extremely poor abrasion resistance. Long-term use can easily lead to powdering and shedding. Neither of these two solutions can achieve both the three-dimensional texture of the silicone coating and the high adhesion of the underlying layer.

[0004] Therefore, it is necessary to further improve the existing preparation process of textured silicone coatings. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a textured silicone coating and its preparation method.

[0006] The technical solution adopted in this invention is as follows: This invention provides a method for preparing a textured silicone coating, comprising the following steps: S1. Mix the silicone base material component and the functional component, and vacuum stir to degas, to obtain silicone foaming slurry; The functional component includes a composite foaming agent, which is composed of azodicarbonamide and sodium bicarbonate; S2. The silicone foaming slurry is coated onto the surface of the substrate to form a wet coating. It is first heated to a first temperature for preheating, and then heated to a second temperature for curing to obtain the velvety silicone coating. The second temperature is 40-60°C higher than the first temperature, and the second temperature is lower than the decomposition temperature of the azodicarbonamide.

[0007] Preferably, in step S1, the weight ratio of the azodicarbonamide to the sodium bicarbonate is 3:1.

[0008] Preferably, in step S1, the silicone base material component comprises the following raw materials by weight: 60-80 parts of vinyl-modified silicone resin, 10-20 parts of hydroxyl silicone oil, 3-8 parts of hydrophobic fumed silica, 2-5 parts of composite velvet powder, and 0.5-2 parts of dispersant.

[0009] Preferably, the composite velvet powder is composed of nano-polyurethane velvet powder and silicon micro powder in a weight ratio of 2:1. The particle size of the composite velvety powder is 500~800nm.

[0010] Preferably, in step S1, the functional components comprise the following raw materials by weight: 50-70 parts of hydrogen-containing silicone oil, 8-15 parts of composite foaming agent, 0.3-0.8 parts of platinum catalyst, 1-3 parts of silane coupling agent, and 0.5-1.5 parts of curing regulator.

[0011] Preferably, in step S1, the weight ratio of the silicone base component to the functional component is 1:0.8~1.2.

[0012] Preferably, in step S2, the first temperature is 80~100℃, and the preheating time of the first temperature is 3~5min.

[0013] Preferably, in step S2, the second temperature is 130~150℃, and the curing time at the second temperature is 8~12min.

[0014] Preferably, in step S2, a single-sided heating method is used, and only the exposed surface of the wet coating is heated.

[0015] In another aspect, the present invention provides a textured silicone coating prepared by the preparation method described in any of the above technical solutions.

[0016] The beneficial effects of this invention are: (1) The present invention uses azodicarbonamide and sodium bicarbonate as composite foaming agents, combined with segmented temperature control design, to achieve a differentiated layered structure in a single coating layer with foamed velvet surface and dense bonding bottom layer, thereby taking into account both the three-dimensional velvet effect of the coating and the high adhesion of the substrate. During the coating process, the composite foaming agent migrates and accumulates in the wet coating surface. In the low-temperature preheating stage, the surface layer is directly heated, and sodium bicarbonate slowly decomposes to produce gas. Azodicarbonamide provides a large number of heterogeneous nucleation sites in the form of solid particles, reducing the energy barrier for bubble nucleation and refining the initial pores. The bottom layer has a lower temperature due to the lower concentration of the composite foaming agent and the heat insulation effect of the substrate, so no foaming reaction occurs, and it remains dense. In the high-temperature curing stage, the sodium bicarbonate in the surface layer continues to decompose and replenish gas, and the initial microbubbles gradually grow. Azodicarbonamide plays a role in inhibiting bubble merging and stabilizing the pores, ultimately forming a uniform and dense three-dimensional microporous structure, giving the coating surface a three-dimensional velvety feel. The bottom layer has a lower concentration of the composite foaming agent, and no effective bubble nuclei are formed in the preheating stage. The rapid cross-linking and curing cause the viscosity of the system to rise sharply, resulting in a foam-suppressing effect. It only cross-links and cures, with basically no foaming, and finally forms a dense adhesive layer.

[0017] (2) The velvety silicone coating prepared by the method of the present invention can form a uniform and three-dimensional fine velvety structure on the surface, which is soft and skin-friendly. At the same time, the bottom layer can form a firm interface bond with the substrate. The coating adhesion is stable and reaches level 0 in 100 grids. The velvety feel does not decrease after 500 cycles of rubbing and there is no powder or hair shedding.

[0018] (3) The process parameters of the present invention have a wide window and high stability, and can be adapted to various coating methods such as screen printing, coating, and spraying. The process is simple and does not require complicated post-processing, and can achieve automated, large-scale, and low-cost mass production. Attached Figure Description

[0019] Figure 1 The image shows the microstructure of the cross-section of the textured silicone coating obtained in Example 1. Figure 2 This is an image showing the appearance of the velvet silicone coating obtained in Example 1 applied to the surface of a fabric. Detailed Implementation

[0020] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0021] This invention provides a method for preparing a textured silicone coating, comprising the following steps: S1. Mix the silicone base material component and the functional component, and vacuum stir to degas, to obtain silicone foaming slurry; The functional components include a composite foaming agent, which is composed of azodicarbonamide and sodium bicarbonate. S2. Apply silicone foaming slurry to the surface of the substrate to form a wet coating. First, heat it to the first temperature for preheating, and then heat it to the second temperature for curing to obtain a velvety silicone coating. The second temperature is 40-60°C higher than the first temperature, and the second temperature is lower than the decomposition temperature of azodicarbonamide.

[0022] This invention achieves gradient foaming through the synergistic design of the wide-temperature activation characteristics of the composite foaming agent and the segmented temperature control process. The second temperature of the curing stage is controlled to be lower than the decomposition temperature of azodicarbonamide (generally ≥190℃). Therefore, azodicarbonamide does not participate in gas generation throughout the process, and sodium bicarbonate dominates the foaming process. During the process of coating the slurry onto the substrate surface, the composite foaming agent will migrate and accumulate to the surface layer due to rheological shear and interfacial migration. With the segmented temperature difference design of 40~60℃, the layered structure is formed: (1) In the low-temperature preheating stage: the surface layer of the wet coating is directly heated and the accumulated sodium bicarbonate slowly decomposes to generate gas. At the same time, azodicarbonamide provides a large number of heterogeneous nucleation sites in the form of solid particles, which significantly reduces the nucleation energy barrier of bubbles, disperses the gas into a large number of tiny bubbles, and refines the pore size. The bottom layer remains in a dense and unfoamed state due to the low content of the composite foaming agent and the low temperature due to the heat insulation effect of the substrate. (2) During the high-temperature curing stage: Sodium bicarbonate on the surface continuously and rapidly decomposes and replenishes gas, and the initial microbubbles continue to grow and solidify. At the same time, azodicarbonamide is interspersed between the microbubbles, inhibiting the merging of adjacent bubbles and stabilizing the size and uniformity of the pores. Although the bottom layer heats up with the overall system, it cannot form effective pores due to the low content of the composite foaming agent, the lack of initial bubble nuclei during the preheating stage, the rapid cross-linking and curing of the silicone matrix, and the foam-suppressing effect of the rapid rise in system temperature. Ultimately, a differentiated structure is achieved in the same coating: the surface layer is foamed into a velvety texture, while the bottom layer is densely bonded, solving the problem of the difficulty in achieving both the velvety texture of the silicone coating and the adhesion to the substrate.

[0023] In a preferred embodiment, in step S1, the weight ratio of azodicarbonamide to sodium bicarbonate is 3:1. The present invention selects azodicarbonamide and sodium bicarbonate in the above ratio as composite foaming agents, which is beneficial for forming a uniform and dense three-dimensional microporous structure on the coating surface, giving the coating a soft, delicate, and velvety feel.

[0024] In a preferred embodiment, in step S1, the silicone base material component comprises the following raw materials by weight: 60-80 parts of vinyl-modified silicone resin, 10-20 parts of hydroxyl silicone oil, 3-8 parts of hydrophobic fumed silica, 2-5 parts of composite velvet powder, and 0.5-2 parts of dispersant. In the silicone base material component of this invention, vinyl-modified organosilicon resin serves as the film-forming host and crosslinking framework, providing the basic mechanical properties of the coating. The vinyl groups on its molecular chain provide active sites for subsequent hydrosilylation crosslinking. The vinyl content in the vinyl-modified organosilicon resin can be 0.8~1.5wt%, and the viscosity can be 8000~15000mPa·s. Hydroxyl silicone oil can adjust the slurry flowability, improve the uniformity of foamed micropores, and refine the fluff structure. The viscosity of the hydroxyl silicone oil can be 500~1000mPa·s. Hydrophobic fumed silica has both rheological and reinforcing effects. Composite velvet powder can fill the foamed micropores on the coating surface, assisting in constructing a three-dimensional velvet texture and improving wear resistance. The dispersant can be an organosilicon dispersant, such as an organosilicon-modified polyether dispersant. In addition, 5~6 parts by weight of inert organosilicon diluent, such as low-viscosity methyl silicone oil, can be added to the silicone base material component according to the requirements of different coating methods to adjust the slurry viscosity and solid content, improve coating leveling and operational adaptability. This invention does not impose particular limitations on the preparation of the silicone base material component. For example, it includes the following steps: vinyl-modified silicone resin and hydroxyl silicone oil are stirred at 300-500 rpm for 10-15 minutes at room temperature; then hydrophobic fumed silica, composite velvety powder, and dispersant are added, and the mixture is stirred at 800-1000 rpm for 25-35 minutes under a vacuum of -0.08 to -0.1 MPa at 40-50°C; finally, the mixture is filtered through a 200-mesh filter to remove impurities and cooled to room temperature. Using the above method, a uniformly dispersed, finely textured silicone base material component without agglomerated particles can be obtained.

[0025] In a preferred embodiment, the composite velvet powder is composed of nano-polyurethane velvet powder and silica powder in a weight ratio of 2:1; The particle size of the composite velvety powder is 500~800nm.

[0026] This invention uses a composite velvet-feel powder made from nano-polyurethane velvet powder and silica micropowder in the above-mentioned proportions. The nano-polyurethane velvet powder provides a soft, velvety feel, while the silica micropowder, with its excellent rigidity, heat resistance, wear resistance, and compatibility with the silica matrix, improves upon the shortcomings of single nano-polyurethane velvet powder in silica matrix, such as easy agglomeration, collapse, and detachment. The composite velvet-feel powder is a nano-scale lightweight powder with an apparent density lower than that of the silica matrix. It naturally floats in liquid slurry due to buoyancy. After coating and short-term leveling of the slurry, the powder further accumulates on the coating surface. During the low-temperature preheating stage: the composite velvet-like powder, on the one hand, synergistically provides more heterogeneous nucleation sites with azodicarbonamide in the composite foaming agent, assisting in directional foaming of the surface layer; on the other hand, it can reduce the surface thermal conductivity, slow down the heat transfer to the underlying coating, and increase the temperature difference between the surface and the underlying layer, making it more difficult for the underlying layer to reach the decomposition temperature, further suppressing foaming behavior, thus helping to achieve a state of micro-foaming on the surface and no foaming on the underlying layer during the low-temperature preheating stage. During the high-temperature curing stage: the bubbles grown on the surface layer encapsulate the powder, allowing the powder to ultimately fill and fix in the three-dimensional microporous structure of the surface layer, enhancing the fullness and three-dimensionality of the velvet texture; at the same time, the powder is concentrated on the surface layer and will not damage the dense bonding structure of the underlying layer, ensuring the adhesion between the coating and the substrate. For example, the particle size of the composite velvet-like powder can be 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, etc.

[0027] In a preferred embodiment, in step S1, the functional components comprise the following raw materials by weight: 50-70 parts of hydrogen-containing silicone oil, 8-15 parts of composite foaming agent, 0.3-0.8 parts of platinum catalyst, 1-3 parts of silane coupling agent, and 0.5-1.5 parts of curing regulator. In the functional components of this invention, hydrogen-containing silicone oil (with a hydrogen content of 0.3-0.8 wt%) acts as a crosslinking agent and undergoes a hydrosilylation reaction with the matrix resin under the action of a platinum catalyst. The silane coupling agent forms a chemical bond between the substrate and the silicone coating layer, improving coating adhesion and preventing coating peeling and edge lifting. It also improves the dispersibility of powders such as composite velvety powder and hydrophobic fumed silica in the organosilicon matrix, preventing agglomeration and ensuring uniform foaming and consistent velvety texture. For example, aminosilanes such as KH-550 can be used as silane coupling agents. The curing regulator can delay the crosslinking reaction at room temperature, thereby extending the pot life of the slurry and preventing premature curing failure during processing. For example, acetylacetone can be used as a curing regulator. Similarly, 15-32 parts by weight of an inert organosilicon diluent can also be added to the functional components. The present invention does not impose any particular limitation on the preparation of functional components. For example, it includes the following steps: stirring hydrogen-containing silicone oil, silane coupling agent and curing regulator at room temperature at a speed of 200~300 r / min for 5~10 min, then adding composite foaming agent and platinum catalyst, stirring at a speed of 500~600 r / min for 15~20 min under vacuum conditions of -0.07~-0.09 MPa, and storing in a sealed, light-proof container.

[0028] In a preferred embodiment, in step S1, the weight ratio of the silicone base component to the functional component is 1:0.8~1.2. The silicone foaming slurry of the present invention employs a design of separate storage of two components, which are then reconstituted before use to avoid premature crosslinking during storage. The silicone base component is the matrix film-forming component, providing the main body for film formation; the functional component is the crosslinking and foaming control component, used to control the crosslinking rate and gradient foaming effect. For example, the weight ratio of the silicone base component to the functional component can be 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, etc. The preparation of the silicone foaming slurry may include the following steps: mixing the silicone base component and the functional component, and vacuum stirring at 400~500 r / min for 8~12 min at room temperature to remove air bubbles.

[0029] In a preferred embodiment, in step S2, the first temperature is 80~100℃, and the preheating time is 3~5 min. The present invention further selects the first temperature as 80~100℃, which is beneficial for the surface-enriched sodium bicarbonate to gradually decompose and generate gas during the preheating stage, forming initial microbubble nuclei; it also avoids the cross-linking reaction from starting too quickly, preventing the bubbles from being locked by the cross-linking network in the early stages of formation and thus unable to grow sufficiently in the subsequent high-temperature curing stage, ensuring the formation of a uniform and three-dimensional microporous structure on the surface. For example, the preheating conditions can be 80℃×5min, 90℃×4min, 100℃×3min, etc.; in this case, the second temperature can be 120~160℃.

[0030] In a preferred embodiment, in step S2, the second temperature is 130~150℃, and the curing time at the second temperature is 8~12 min. The present invention further selects the second temperature as 130~150℃. This temperature range is conducive to the rapid decomposition and gas generation of the surface sodium bicarbonate, allowing the initial microbubbles formed in the preheating stage to further grow and solidify into a three-dimensional microporous structure. Simultaneously, it facilitates the rapid cross-linking reaction of the underlying silicone matrix, causing a sharp increase in system viscosity and inhibiting foaming. This results in the underlying layer undergoing only dense cross-linking and curing with minimal foaming, thereby forming a layered structure with a foamed, velvety surface and a densely bonded underlying layer. For example, the curing conditions can be 130℃×12 min, 140℃×10 min, 150℃×8 min, etc.; in this case, the first temperature can be 70~110℃.

[0031] In a preferred embodiment, step S2 employs a single-sided heating method, heating only the exposed surface of the wet coating. This invention uses a single-sided directional heating method, where heat is input unidirectionally from the coating surface. This ensures that the surface layer is heated first, followed by the underlying layer, through the heat transfer path. Combined with short-term low-temperature preheating to limit downward heat transfer, substrate insulation to enhance temperature difference, and surface-enriched powder to reduce coating thermal conductivity, this ensures that the surface layer reaches the decomposition and gas-generating temperature of the composite foaming agent during the low-temperature preheating stage, while the underlying layer receives less heat and heats up slowly, remaining stable and non-foaming. This lays the foundation for subsequent layered structure formation. For example, far-infrared heating can be used.

[0032] In another aspect, the present invention provides a textured silicone coating prepared by the preparation method described in any of the above technical solutions.

[0033] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0034] Example 1 A method for preparing a textured silicone coating includes the following steps: Preparation of silicone base material components: 70 parts of vinyl-modified silicone resin and 15 parts of hydroxyl silicone oil were stirred at 400 r / min for 12 min at room temperature; then 5 parts of hydrophobic fumed silica, 3 parts of composite velvet powder (nano polyurethane velvet powder and silica powder in a weight ratio of 2:1, with a particle size of 600 nm), 1 part of silicone-modified polyether dispersant and 6 parts of inert silicone diluent were added. The mixture was stirred at 900 r / min for 30 min at 45℃ and -0.09 MPa vacuum. Finally, the mixture was filtered through a 200-mesh filter to remove impurities and cooled to room temperature for later use.

[0035] Preparation of functional components: 60 parts of hydrogen-containing silicone oil, 2 parts of KH-550 silane coupling agent and 1 part of acetylacetone curing modifier were stirred at 250 r / min for 8 min at room temperature. Then, 12 parts of composite foaming agent (azodicarbonamide and sodium bicarbonate in a weight ratio of 3:1), 0.5 parts of platinum catalyst and 24.5 parts of inert organosilicon diluent were added. The mixture was stirred at 550 r / min for 18 min under a vacuum of -0.08 MPa. It was then sealed and stored in the dark for later use.

[0036] Preparation of velvety silicone coating: The silicone base material component and functional component are mixed at a weight ratio of 1:1 and vacuum stirred at 450 r / min for 10 min at room temperature to degas, resulting in silicone foaming slurry; The silicone foaming slurry is coated on the surface of the substrate to form a wet coating with a thickness of 0.2 mm. The exposed surface of the wet coating is heated by a single-sided far-infrared heating method: first, it is preheated to 90℃ for 4 min, and then heated to 140℃ for 10 min to cure.

[0037] Depend on Figure 1 As can be seen, the textured silicone coating prepared in this embodiment has a distinct layered structure, with a uniform and fine three-dimensional micropore layer on the surface and a dense cross-linked layer at the bottom; from Figure 2 As can be seen, the coating has a uniform, delicate, and three-dimensional velvety texture, without any grainy feel.

[0038] Example 2 A method for preparing a textured silicone coating includes the following steps: Preparation of silicone base material components: 65 parts of vinyl-modified silicone resin and 18 parts of hydroxyl silicone oil were stirred at 400 r / min for 12 min at room temperature; then 6 parts of hydrophobic fumed silica, 4 parts of composite velvet powder (nano polyurethane velvet powder and silica powder in a weight ratio of 2:1, with a particle size of 500 nm), 1.5 parts of silicone-modified polyether dispersant and 5.5 parts of inert silicone diluent were added. The mixture was stirred at 900 r / min for 30 min at 45℃ and -0.09 MPa vacuum. Finally, the mixture was filtered through a 200-mesh filter to remove impurities and cooled to room temperature for later use.

[0039] Preparation of functional components: 55 parts of hydrogen-containing silicone oil, 2.5 parts of KH-550 silane coupling agent and 1.2 parts of acetylacetone curing modifier were stirred at 250 r / min for 8 min at room temperature. Then, 10 parts of composite foaming agent (azodicarbonamide and sodium bicarbonate in a weight ratio of 3:1), 0.6 parts of platinum catalyst and 30.7 parts of inert organosilicon diluent were added. The mixture was stirred at 550 r / min for 18 min under a vacuum of -0.08 MPa. It was then sealed and stored in the dark for later use.

[0040] Preparation of velvety silicone coating: The silicone base material component and functional component are mixed at a weight ratio of 1:0.9 and vacuum stirred at 450 r / min for 10 min at room temperature to degas, so as to obtain silicone foaming slurry; The silicone foaming slurry is coated on the surface of the substrate to form a wet coating with a thickness of 0.15 mm. The exposed surface of the wet coating is heated by a single-sided far-infrared heating method: first, it is preheated to 85℃ for 5 min, and then heated to 135℃ for 11 min to cure.

[0041] Example 3 A method for preparing a textured silicone coating includes the following steps: Preparation of silicone base material components: 75 parts of vinyl-modified silicone resin and 12 parts of hydroxyl silicone oil were stirred at 400 r / min for 12 min at room temperature; then 4 parts of hydrophobic fumed silica, 2.5 parts of composite velvet powder (nano polyurethane velvet powder and silica powder in a weight ratio of 2:1, with a particle size of 800 nm), 0.8 parts of silicone-modified polyether dispersant and 5.7 parts of inert silicone diluent were added. The mixture was stirred at 900 r / min for 30 min at 45℃ and -0.09 MPa vacuum. Finally, the mixture was filtered through a 200-mesh filter to remove impurities and cooled to room temperature for later use.

[0042] Preparation of functional components: 65 parts of hydrogen-containing silicone oil, 1.5 parts of KH-550 silane coupling agent and 0.8 parts of acetylacetone curing modifier were stirred at 250 r / min for 8 min at room temperature. Then, 14 parts of composite foaming agent (azodicarbonamide and sodium bicarbonate in a weight ratio of 3:1), 0.4 parts of platinum catalyst and 18.3 parts of inert organosilicon diluent were added. The mixture was stirred at 550 r / min for 18 min under a vacuum of -0.08 MPa. It was then sealed and stored in the dark for later use.

[0043] Preparation of velvety silicone coating: The silicone base material component and functional component are mixed at a weight ratio of 1:1.1 and vacuum stirred at 450 r / min for 10 min at room temperature to degas, resulting in silicone foaming slurry; The silicone foaming slurry is coated on the surface of the substrate to form a wet coating with a thickness of 0.25 mm. The exposed surface of the wet coating is heated by a single-sided far-infrared heating method: first, it is preheated to 95℃ for 3 min, and then heated to 145℃ for 9 min to cure.

[0044] Example 4 The difference between this embodiment and Embodiment 1 is that the heating temperature used to prepare the textured silicone coating is different. The process of "preheating to 90°C for 4 minutes and then curing at 140°C for 10 minutes" is changed to "preheating to 90°C for 4 minutes and then curing at 130°C for 12 minutes". The remaining steps remain unchanged.

[0045] Example 5 The difference between this embodiment and Embodiment 1 is that the heating temperature used to prepare the textured silicone coating is different. The process of "preheating to 90°C for 4 minutes and then curing at 140°C for 10 minutes" is changed to "preheating to 80°C for 5 minutes and then curing at 140°C for 10 minutes". The remaining steps remain unchanged.

[0046] Example 6 The difference between this embodiment and Embodiment 1 is that the heating temperature used to prepare the textured silicone coating is different. The process of "preheating to 90°C for 4 minutes and then curing at 140°C for 10 minutes" is changed to "preheating to 100°C for 3 minutes and then curing at 150°C for 8 minutes". The remaining steps remain unchanged.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that sodium bicarbonate is used in place of azodicarbonamide in an equal amount. The remaining steps remain unchanged.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is that hydrophobic nano-silica is used in an equal amount to replace azodicarbonamide. The remaining steps remain unchanged.

[0049] Comparative Example 3 The difference between this comparative example and Example 1 is that the textured silicone coating is prepared by one-time high-temperature curing. The process of "preheating to 90°C for 4 minutes and then curing to 140°C for 10 minutes" is changed to heating to 140°C for 14 minutes. The remaining steps remain unchanged.

[0050] Comparative Example 4 The difference between this comparative example and Example 1 is that nano-polyurethane fluff powder is used to replace silicon micropowder in an equal amount. The remaining steps remain unchanged.

[0051] The performance of the silicone coatings prepared in Examples 1-6 and Comparative Examples 1-4 was tested, and the results are recorded in Table 1.

[0052] Test method: (1) Evaluation of the velvet appearance effect: Five trained evaluators were selected to visually observe the uniformity of the coating surface and judge whether there is a grainy feel; then, they lightly touched the coating surface with their fingertips to evaluate the fineness and three-dimensionality of the velvet. Evaluation criteria: Excellent: The velvet is uniform and fine, with high three-dimensionality and no grainy feel; Good: The velvet uniformity, fineness and three-dimensionality are relatively good, with slight grainy feel; Medium: The velvet feel is thin, the uniformity and three-dimensionality are average, and there is a rough feel in some areas; Poor: There is no obvious velvet feel and the surface is rough.

[0053] (2) Cross-cut adhesion test: The test shall be conducted in accordance with GB / T 9286-1998 "Cross-cut test for paint and varnish film". Grade determination: Grade 0 (no peeling), Grade 1 (peeling area ≤ 5%), Grade 2 (peeling area 5~15%), Grade 3 (peeling area 15~35%), Grade 4 (peeling area 35~65%), Grade 5 (peeling area > 65%, basically completely peeled off) the worst.

[0054] (3) Friction resistance test: The coating sample to be tested is fixed flat on the test table, the friction head is wrapped with standard wool friction cloth, and a reciprocating friction test is performed after the load is applied (the load is 500g and the friction stroke is 30mm); the machine is stopped after 100, 200, 300 and 500 frictions respectively, and the changes in the appearance and feel of the coating are observed. The number of frictions at which the feel of the coating is significantly reduced or the coating is damaged is recorded.

[0055] (4) Evaluation of powder and lint shedding: After 500 rubbing tests, observe whether the coating has powder or lint falling off. Judgment criteria: If there is no obvious color change on the rubbing cloth (color difference ΔE≤2) and no visible particulate powder or lint residue is observed, it is judged as no powder or lint shedding; otherwise, it is judged as powder and lint shedding.

[0056] Table 1

[0057] As shown in Table 1, the velvety silicone coatings prepared in the embodiments of the present invention can all form a uniform and delicate three-dimensional microporous structure, while also possessing excellent substrate adhesion and abrasion resistance. Comparative Example 1 uses sodium bicarbonate for foaming, and Comparative Example 2 uses other functional fillers to replace azodicarbonamide, resulting in decreased cell uniformity, insufficient fineness, and a grainy feel. Comparative Example 3 uses one-time high-temperature curing, which prevents differentiated foaming and cross-linking of the coating surface and bottom layer, resulting in the loss of the three-dimensional velvety feel and a significant decrease in adhesion and abrasion resistance due to the destruction of the dense bonding structure caused by the simultaneous foaming of the bottom layer. Comparative Example 4 uses a single nano-polyurethane velvety powder, which lacks the modification effect of silica powder, resulting in decreased powder dispersibility and interfacial bonding force, leading to a poorer velvety feel and a grainy feel, while also adversely affecting adhesion and abrasion resistance.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a textured silicone coating, characterized in that, Includes the following steps: S1. Mix the silicone base material component and the functional component, and vacuum stir to degas, to obtain silicone foaming slurry; The functional component includes a composite foaming agent, which is composed of azodicarbonamide and sodium bicarbonate; S2. The silicone foaming slurry is coated onto the surface of the substrate to form a wet coating. It is first heated to a first temperature for preheating, and then heated to a second temperature for curing to obtain the velvety silicone coating. The second temperature is 40-60°C higher than the first temperature, and the second temperature is lower than the decomposition temperature of the azodicarbonamide.

2. The method for preparing the textured silicone coating as described in claim 1, characterized in that, In step S1, the weight ratio of the azodicarbonamide to the sodium bicarbonate is 3:

1.

3. The method for preparing the textured silicone coating as described in claim 1, characterized in that, In step S1, the silicone base material component comprises the following raw materials by weight: 60-80 parts of vinyl modified silicone resin, 10-20 parts of hydroxyl silicone oil, 3-8 parts of hydrophobic fumed silica, 2-5 parts of composite velvet powder, and 0.5-2 parts of dispersant.

4. The method for preparing the textured silicone coating as described in claim 3, characterized in that, The composite velvet powder is composed of nano polyurethane velvet powder and silicon micro powder in a weight ratio of 2:

1. The particle size of the composite velvety powder is 500~800nm.

5. The method for preparing the textured silicone coating as described in claim 1, characterized in that, In step S1, the functional components comprise the following raw materials by weight: 50-70 parts of hydrogen-containing silicone oil, 8-15 parts of composite foaming agent, 0.3-0.8 parts of platinum catalyst, 1-3 parts of silane coupling agent, and 0.5-1.5 parts of curing regulator.

6. The method for preparing the textured silicone coating as described in claim 1, characterized in that, In step S1, the weight ratio of the silicone base component to the functional component is 1:0.8~1.

2.

7. The method for preparing the textured silicone coating as described in claim 1, characterized in that, In step S2, the first temperature is 80~100℃, and the preheating time for the first temperature is 3~5 minutes.

8. The method for preparing the textured silicone coating as described in claim 1, characterized in that, In step S2, the second temperature is 130~150℃, and the curing time at the second temperature is 8~12min.

9. The method for preparing the textured silicone coating as described in claim 1, characterized in that, In step S2, a single-sided heating method is used, which heats only the exposed surface of the wet coating.

10. A textured silicone coating, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

Images