Organic silicon synthetic leather surface layer and preparation method thereof

Abstract

The invention relates to the field of organic silicon synthetic leather, and discloses an organic silicon synthetic leather surface layer and a preparation method thereof.The surface layer comprises a base layer, a bonding layer, a middle layer and a leather surface layer, and the leather surface layer is formed by curing leather surface layer glue containing base glue, a special hand feeling agent and other raw materials. The base rubber is compounded with two vinyl-terminated polydimethylsiloxane with different viscosities, the hand feeling agent is prepared from alpha-olefin and Si-H-containing organopolysiloxane through hydrosilylation, and meanwhile, the invention discloses specific preparation processes of all the components and the surface layer. The problems that existing organic silicon synthetic leather is insufficient in wear resistance, poor in smooth hand feeling and the like are effectively solved, the defects that cost is high, auxiliaries are prone to migration and the like are overcome, the prepared product has excellent wear resistance, smoothness, folding resistance and stain resistance, the use requirements of the high-end field are met, and high-end green development of the industry is promoted.

Description

Technical Field

[0001] This application relates to the field of silicone synthetic leather, specifically to a silicone synthetic leather surface layer and its preparation method. Background Technology

[0002] As global manufacturing accelerates its transformation towards high-end and green technologies, cutting-edge fields such as automotive interiors, smart wearable devices, medical protective equipment, and precision instruments are placing increasingly stringent performance requirements on leather materials regarding weather resistance, abrasion resistance, tactile comfort, and biocompatibility. Traditional PU leather and PVC leather require the extensive use of organic solvents and plasticizers during production, resulting in not only a high environmental burden but also numerous insurmountable performance defects. For example, PVC leather releases highly asphyxiating hydrogen chloride gas when burned, while PU leather suffers from poor stain resistance, weak salt spray resistance, yellowing, and heavy metal residues. Furthermore, both types of materials exhibit biocompatibility issues due to solvent residues and plasticizer migration. Poor performance and a tendency to trigger allergic reactions in susceptible individuals make it unsuitable for high-end applications. Silicone leather, with its unique -Si-O-Si- main chain structure and methyl helical arrangement, possesses excellent weather resistance, hydrophobicity, high and low temperature resistance, and biocompatibility, making it a preferred alternative to traditional synthetic leather. However, existing silicone synthetic leather still suffers from core technological shortcomings such as insufficient abrasion resistance and a lack of smooth feel. Under high-frequency mechanical stress from repeated friction in car seats and frequent disinfection of medical equipment, the leather surface is prone to scratches and cracks, significantly reducing its service life. At the same time, the high coefficient of friction results in a rough and astringent feel, making it difficult to achieve the silky smooth feel required for high-end products.

[0003] To improve the abrasion resistance and slip properties of silicone synthetic leather, those skilled in the art have conducted numerous technological research and developments and improvements. However, existing technical solutions all have significant application limitations. While using vinyl fluorosilicone oil to enhance abrasion resistance and slip properties can optimize material surface properties, vinyl fluorosilicone oil is far more expensive than ordinary silicone oil, and its processing requirements are stringent, necessitating precise control of vulcanization temperature and catalyst ratio. This can easily lead to uneven crosslinking and performance degradation, limiting its widespread application in the civilian market. The silicone-polyurethane hybrid prepolymer solution, due to the prepolymer and... The high compatibility of silicone leather matrix means that the slip components lack the motivation to migrate to the surface, making it impossible to directly impart a smooth feel to the leather surface. An additional hand-feel layer coating process is required, which makes the production process cumbersome. The solution of adding PE wax powder, silicone wax and other additives has problems such as wax powder migration, surface oil film precipitation, and poor durability of the surface slip layer, which affect the appearance of the leather surface and long-term use stability. The technology of increasing the cross-linking density of vinyl silicone resin to enhance abrasion resistance can only improve the hardness of the leather surface, and the effect on improving the silky smooth feel is very limited, resulting in insufficient overall practicality.

[0004] In summary, existing silicone synthetic leather surface layer technologies cannot simultaneously solve the core problems of insufficient abrasion resistance and poor smoothness. They also generally suffer from drawbacks such as high cost, complex processes, easy migration and precipitation of additives, and poor durability of the smooth layer. These shortcomings make it difficult to meet the stringent requirements of high-end fields such as automotive interiors, smart wearables, medical protective equipment, and precision instruments for silicone leather. Therefore, developing a silicone synthetic leather surface layer that does not require expensive fluorosilicone oil, has a simple production process, and can achieve a synergistic improvement in self-lubrication and high abrasion resistance has become a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of existing silicone synthetic leather, such as insufficient wear resistance and poor smoothness.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: An organosilicon synthetic leather surface layer is provided, comprising a base layer, an adhesive layer, an intermediate layer, and a leather surface layer. The leather surface layer is obtained by curing a leather surface layer adhesive, the intermediate layer is obtained by curing an intermediate layer adhesive, and the adhesive layer is obtained by curing an adhesive layer adhesive. The raw materials for preparing the leather surface layer adhesive include: a base adhesive, vinyl-containing polydimethylsiloxane, vinyl-containing silicone resin, a leveling agent, a hand feel agent, an inhibitor, a matting agent, a crosslinking agent, a catalyst, and a colorant.

[0007] As a preferred embodiment, the raw materials for preparing the tactile agent include Si-H-containing organopolysiloxanes and α-olefins.

[0008] As a preferred embodiment, the preparation method of the hand feel agent is as follows: the α-olefin, the first solvent and the first catalyst are heated and activated in a reaction vessel for a period of time to obtain a mixed solution, the Si-H-containing organopolysiloxane is added to the mixed solution, the temperature is raised and kept at a certain temperature for a period of time, and after the reaction is completed, the first solvent and low-boiling substances are removed to obtain the hand feel agent.

[0009] As a preferred embodiment, the molar ratio of the α-olefin to the silane in the Si-H-containing organopolysiloxane is (0.3-0.8):1.

[0010] As a preferred embodiment, the raw materials for preparing the base adhesive include: vinyl-terminated polydimethylsiloxane, fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil, and water.

[0011] As a preferred embodiment, the vinyl-terminated polydimethylsiloxane comprises a first ethylene-terminated polydimethylsiloxane and a second ethylene-terminated polydimethylsiloxane, wherein the viscosity of the first ethylene-terminated polydimethylsiloxane is 500~5000 mPa·s and the viscosity of the second ethylene-terminated polydimethylsiloxane is 10000~20000 mPa·s.

[0012] As a preferred embodiment, the mass ratio of the first ethylene-terminated polydimethylsiloxane to the second ethylene-terminated polydimethylsiloxane is (2~4):1.

[0013] As a preferred embodiment, the preparation method of the base adhesive is as follows: a portion of the first vinyl-terminated polydimethylsiloxane and the second vinyl-terminated polydimethylsiloxane are added to a kneader, and the fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil and water are added in multiple batches. The mixture is stirred evenly and heated to react. After removing low-boiling substances, the mixture is cooled and the remaining first vinyl-terminated polydimethylsiloxane is added. The mixture is stirred and reacted continuously to obtain the base adhesive.

[0014] This application also provides a method for preparing an organosilicon synthetic leather surface layer, comprising the following preparation steps: S1: A portion of a first vinyl-terminated polydimethylsiloxane and a second vinyl-terminated polydimethylsiloxane are added to a kneader, and fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil, and water are added in multiple batches. The mixture is stirred evenly and heated to react. After removing low-boiling substances, the temperature is lowered and the remaining first vinyl-terminated polydimethylsiloxane is added. The mixture is stirred and reacted continuously to obtain a base adhesive; S2: An α-olefin, a first solvent, and a first catalyst are heated and activated in a reaction vessel for a period of time to obtain a mixed solution; an organopolysiloxane containing Si-H is added to the mixed solution, and the temperature is raised. The reaction is kept at a constant temperature for a period of time. After the reaction is completed, the first solvent and low-boiling substances are removed to obtain the hand-feeling agent; S3: The base adhesive, vinyl-containing polydimethylsiloxane, vinyl-containing silicone resin, and leveling agent are heated and stirred in a mixer. Then, inhibitors, matting powder, crosslinking agents, the hand-feeling agent, and color paste are added. After stirring evenly, the second catalyst is added. After degassing, the leather surface layer adhesive is obtained; S4: The leather surface layer adhesive is coated on release paper and baked to cure to obtain the leather surface layer; an intermediate layer adhesive is coated on the surface of the leather surface layer and cured to obtain the intermediate layer; an adhesive layer adhesive is coated on the surface of the intermediate layer, and the base fabric is bonded to the adhesive layer. After baking and curing, the release paper is peeled off to obtain the organosilicon synthetic leather surface layer.

[0015] As another preferred embodiment, the coating thickness of the leather top layer adhesive is 100~250μm, the coating thickness of the intermediate layer adhesive is 200~300μm, and the coating thickness of the bonding layer adhesive is 80~150μm.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: (1) This application uses hexamethyldisilazane and divinyltetramethyldisilazane to synergistically modify silica, which not only achieves uniform dispersion of silica at the nanoscale, but also constructs a three-dimensional cross-linking network between silica and the matrix, thereby improving the overall strength, scratch resistance and wear resistance of the material, and helping to improve the problem of easy wear of silicone leather in high-frequency friction scenarios; (2) This application uses two types of vinyl-terminated polydimethylsiloxane to precisely stabilize the viscosity of the silicone synthetic leather surface layer adhesive at 50,000 to 70,000 mPa.s. The low viscosity component improves the fluidity and spreadability during coating and optimizes the adaptability of the coating process; the high viscosity component enhances the molecular chain entanglement ability and provides basic toughness for the material. (3) By introducing a specific type of vinyl silicone resin and precisely controlling the crosslinking density of the organosilicon matrix, this application has achieved a synergistic improvement in the surface hardness and wear resistance of synthetic leather, breaking through the performance paradox of "hardness improvement inevitably leads to loss of toughness" in traditional technology, and making synthetic leather have high strength, high toughness and excellent wear resistance. (4) This application prepares a hand feel agent by hydrosilylation reaction of α-olefin and Si-H organopolysiloxane, precisely controlling the molar ratio of α-olefin to silane and retaining excess Si-H groups. These groups can participate in the secondary crosslinking reaction of the surface layer after coating, form chemical bonds with the surface layer matrix, and build a three-dimensional network structure, which significantly improves the adhesion and durability of the hand feel agent wax layer, achieves a "silky smooth" soft touch, and does not decay with long-term use; (5) This application uses a coated fumed silica matting agent to give the leather a matte natural texture and eliminate the plastic feel; at the same time, it disperses frictional stress, reduces the probability of wear, optimizes the touch feel, and takes into account both high-end appearance and practicality. Detailed Implementation

[0017] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0018] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0019] This application provides an organosilicon synthetic leather surface layer, including a base layer, an adhesive layer, an intermediate layer, and a leather surface layer. The leather surface layer is obtained by coating a leather surface layer adhesive onto release paper and curing it. The intermediate layer is obtained by curing an intermediate layer adhesive, and the adhesive layer is obtained by curing an adhesive layer adhesive. The raw materials for preparing the leather surface layer adhesive include: a base adhesive, vinyl-containing polydimethylsiloxane, vinyl-containing silicone resin, a leveling agent, a hand feel agent, an inhibitor, a matting agent, a crosslinking agent, a catalyst, and a color paste.

[0020] In some embodiments, the raw materials for preparing the leather surface adhesive, by weight, are: 100 parts base adhesive, 50-100 parts vinyl-containing polydimethylsiloxane, 15-40 parts vinyl-containing silicone resin, 0.5-1 parts leveling agent, 5-20 parts hand feel agent, 0.02-1 parts inhibitor, 5-10 parts matting agent, 6-20 parts crosslinking agent, 0.2-1 parts catalyst, and 2-5 parts color paste.

[0021] The silicone synthetic leather surface layer of this application solves the problems of insufficient wear resistance and poor smoothness of existing materials, while also improving upon the high cost, complex processes, additive migration and precipitation, and poor smoothness durability of existing technologies. This silicone synthetic leather surface layer, by constructing a structurally stable leather surface layer adhesive that bonds firmly to the matrix, meets the stringent requirements of high-end fields such as automotive interiors, smart wearables, medical protective equipment, and precision instruments, without using expensive fluorosilicone oils and with simplified processes, effectively promoting the high-end and green development of the silicone synthetic leather industry.

[0022] In some embodiments, the raw materials for preparing the base adhesive include vinyl-terminated polydimethylsiloxane, fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil, and water.

[0023] In some embodiments, the raw materials for preparing the base adhesive include 20% to 30% by mass of fumed silica, 4% to 10% by mass of hexamethyldisilazane, 0.3% to 1% by mass of divinyltetramethyldisilazane, 0.5% to 5% by mass of hydroxyl silicone oil, 1% to 5% by mass of water, and the balance being vinyl-terminated polydimethylsiloxane.

[0024] In some preferred embodiments, the vinyl-terminated polydimethylsiloxane comprises a first ethylene-terminated polydimethylsiloxane and a second ethylene-terminated polydimethylsiloxane. The first ethylene-terminated polydimethylsiloxane has a viscosity of 500-5000 mPa·s and a vinyl content of 0.18-0.50 wt%, while the second ethylene-terminated polydimethylsiloxane has a viscosity of 10000-20000 mPa·s and a vinyl content of 0.10-0.16 wt%. The mass ratio of the first ethylene-terminated polydimethylsiloxane to the second ethylene-terminated polydimethylsiloxane is (2-4):1, based on the total amount of ethylene-terminated polydimethylsiloxane added.

[0025] This application stabilizes the viscosity of the final silicone synthetic leather topcoat adhesive at 50,000–70,000 mPa·s by compounding two ethylene-terminated polydimethylsiloxanes of different viscosities. This range, verified through extensive process testing, represents the optimal range balancing production operability and product performance. At this viscosity, the topcoat adhesive exhibits good flowability, ensuring uniform spreading during application and preventing defects such as uneven thickness and missed areas. Simultaneously, it possesses excellent defoaming properties, reducing residual air bubbles within the coating and preventing pinholes, bulges, and other imperfections after curing.

[0026] If the proportion of the first ethylene-terminated polydimethylsiloxane is too high, although it can reduce the viscosity of the system, it will disrupt the balance of the molecular chain solidification network structure, leading to concentrated crosslinking points and reduced toughness. This makes the synthetic leather surface layer prone to cracking and breakage when subjected to external impact or repeated bending. Maintaining a reasonable ratio of the first and second ethylene-terminated polydimethylsiloxanes can meet the coating process requirements while ensuring the entanglement ability of the base adhesive molecular chains. This lays the foundation for the subsequent crosslinking reaction to build a high-strength three-dimensional network structure, ultimately achieving a synergistic improvement in the abrasion resistance and flexibility of the synthetic leather surface layer.

[0027] In a preferred embodiment, the first ethylene-terminated polydimethylsiloxane has a viscosity of 1000 mPa·s and a vinyl content of 0.29~0.36 wt%, and the second ethylene-terminated polydimethylsiloxane has a viscosity of 10000 mPa·s and a vinyl content of 0.12~0.16 wt%. The mass ratio of the first ethylene-terminated polydimethylsiloxane to the second ethylene-terminated polydimethylsiloxane is 2:1, based on the total amount of ethylene-terminated polydimethylsiloxane added.

[0028] This application incorporates fumed silica and hexamethyldisilazane into the base adhesive. Fumed silica helps improve the overall strength, scratch resistance, and deformation resistance of the base adhesive. Furthermore, hexamethyldisilazane hydrophobically modifies the fumed silica, forming an organosilicon coating layer on its surface. This effectively reduces the aggregation of nanoparticles, ensuring uniform nanoscale dispersion of the fumed silica within the organosilicon matrix. Aggregation of fumed silica leads to stress concentration within the matrix, causing pinholes, bulges, or localized cracking after coating curing. Uniformly dispersed fumed silica ensures even distribution of mechanical properties within the matrix, guaranteeing the overall performance consistency of the synthetic leather surface layer.

[0029] This application also introduces divinyltetramethyldisilazane into the raw materials of the base adhesive. The ethylene functional group in its molecule can participate in the hydrosilylation crosslinking reaction and form covalent bonds with the base adhesive, vinyl-containing silicone resin, crosslinking agent and other matrix components. This makes the fumed silica not simply physically mixed into the matrix, but become part of the three-dimensional crosslinking network, which greatly improves the density and structural stability of the crosslinking network, further enhances the wear resistance and folding strength of the synthetic leather surface layer, and solves the paradox that the wear resistance of traditional silicone leather decreases while its toughness decreases.

[0030] This application also provides a method for preparing a base adhesive: a portion of a first vinyl-terminated polydimethylsiloxane and a second vinyl-terminated polydimethylsiloxane are added to a kneader, and fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil and water are added in multiple batches. The mixture is stirred evenly and heated to react. After removing low-boiling substances, the mixture is cooled and the remaining first vinyl-terminated polydimethylsiloxane is added. The mixture is stirred and reacted continuously to obtain the base adhesive.

[0031] This application also provides a hand feel agent, the raw materials of which include Si-H-containing organopolysiloxanes and α-olefins, which greatly simplifies the raw material system and production ratio process, and achieves synergistic optimization of hand feel improvement and wear resistance.

[0032] This application's feel agent utilizes α-olefins as reacting monomers, grafting long-chain alkyl groups onto the polysiloxane of the product feel agent. Spontaneous migration is achieved by leveraging the polarity difference between the long-chain alkyl groups and the surface matrix. Furthermore, the alkyl chains intertwine on the surface through van der Waals forces, forming a dense physical network structure. This results in an ordered, hydrophobic alkyl layer on the leather surface, achieving an ultra-smooth feel. This molecular structure design not only fundamentally reduces the dynamic coefficient of friction on the leather surface, achieving a technological leap from "physical filling for wear resistance" to "molecular-level hydrophobic smoothness," but also reduces direct wear on the surface material during mechanical friction through chain segment deformation and stress dispersion mechanisms, thus balancing improved feel and enhanced durability.

[0033] In some embodiments, the α-olefin has 16 to 45 carbon atoms, preferably 20 to 30 carbon atoms. α-olefins with ≥16 carbon atoms are selected as reactants during the synthesis of the feel agent. Compared to short-chain alkyl groups, the stronger van der Waals interactions between long-chain alkyl groups can promote the spontaneous migration of feel agent molecules to the leather surface, forming a dense physical network through the intertwining of alkyl chains.

[0034] In some embodiments, the Si-H-containing organopolysiloxane has at least three H atoms directly bonded to Si atoms, with the hydrogen atoms located at the chain ends and / or on the side chains. Preferably, the hydrogen atom content in the Si-H-containing organopolysiloxane is 0.1~1.6 wt%.

[0035] In a preferred embodiment, the Si-H-containing organopolysiloxane can be linear, dendritic, cyclic, or a mixture of various forms, preferably an MQ-type hydrogen-containing silicone resin with the following structural formula: [(CH3)2HSiO 1 / 2 ] a [(CH3)3SiO 1 / 2 ] b [SiO 4 / 2 ] cWhere a, b, and c are the number of chain segments, and the following conditions must be met: a + b + c = 1, 1 ≤ (a + b) / c ≤ 1.5. The preferred viscosity of the Si-H-containing organopolysiloxane is 40–2500 mPa·s, and the active hydrogen atom content is 0.25–0.75 wt%. Within the above molecular structure and parameter range, the silicon-oxygen segments in the synthesized hand-feel agent exhibit excellent compatibility with the surface adhesive matrix, ensuring that the hand-feel agent is uniformly dispersed in the surface adhesive system. This not only guarantees the uniformity and long-term stability of the smooth touch but also significantly improves the overall fineness and uniformity of the leather texture.

[0036] This application also provides a method for preparing a tactile agent, comprising the following steps: S1: The α-olefin, the first solvent, and the first catalyst are heated and activated in a reaction vessel for a period of time to obtain a mixed solution; S2: An organopolysiloxane containing Si-H is added to a mixed solution, heated and kept at that temperature for a period of time. After the reaction is complete, the first solvent and low-boiling substances are removed to obtain the tactile agent of this application.

[0037] Preferably, the molar ratio of α-olefin to silane groups in the Si-H-containing organopolysiloxane is (0.3-0.8):1, ensuring an excess of silane groups in the reaction system.

[0038] This application's hand-feeling agent, through controlling the molar ratio of α-olefins to Si-H-containing organopolysiloxanes in its synthesis, intentionally retains an excess of silane functional groups. The active silane groups that do not participate in the hydrosilylation reaction, when applied to the organosilicon synthetic leather topcoat, undergo a secondary cross-linking reaction with the vinyl silicone oil and vinyl silicone resin in the topcoat, constructing a three-dimensional network structure with covalent bonds between the hand-feeling agent wax layer and the leather surface. This structure completely breaks through the limitations of traditional hand-feeling agents that rely solely on physical adsorption, enhancing the bonding strength between the wax layer and the matrix, and significantly prolonging the durability of the smooth touch.

[0039] Specifically, this application provides a specific synthesis scheme for a tactile agent, and the preparation steps are as follows: S1: Add α-olefin, toluene solvent and platinum catalyst to a dry reaction vessel under an inert gas atmosphere, heat the reaction system to 60~80 ℃, and continue stirring and activating at this temperature for 1 h to obtain a mixed solution; S2: A toluene solution of an organopolysiloxane containing Si-H is slowly added dropwise to the mixed solution at a rate of 1-2 mL / min through a constant pressure dropping funnel. During the addition, the system temperature is maintained at 60-80 °C. After the addition is completed, the system temperature is raised to 80-100 °C and kept at this temperature for 3-5 h to carry out the reaction. After the reaction is complete, the system is transferred to a vacuum distillation apparatus to remove the toluene solvent and the low-boiling substances generated in the reaction under the conditions of vacuum degree ≤ -0.095 MPa and temperature 120~140 ℃. After the solvent is completely removed, the system is allowed to cool naturally to room temperature to obtain the tactile agent of this application.

[0040] In the raw materials for preparing the leather topcoat adhesive, the vinyl-containing polydimethylsiloxane is a polydimethylsiloxane in which at least two vinyl groups are directly linked to Si, with the vinyl groups located at the chain ends and / or on the side chains. Preferably, the vinyl-containing polydimethylsiloxane is a polydimethylsiloxane with at least two vinyl groups at the end, a viscosity of 500–5000 mPa·s, and a vinyl content of 0.18–0.50 wt%. More preferably, the vinyl-containing polydimethylsiloxane can be the same as the first vinyl-terminated polydimethylsiloxane in the base adhesive raw material.

[0041] In some embodiments, the vinyl silicone resin is an MQ type or MTQ type methyl vinyl silicone resin with the structural formula: [(CH3)2(CH2=CH)SiO 1 / 2 ] a [(CH3)3SiO 1 / 2 ] b [(CH2=CH)SiO 3 / 2 )] c [SiO 4 / 2 ] d Where a, b, c, and d are the number of chain segments, and the following conditions must be met: a + b + c + d = 1, 0.5 ≤ (a + b) / (c + d) ≤ 1.5, and the vinyl content is 1.5–7 wt%. The vinyl-containing silicone resin can be a powder solid or a liquid. When the vinyl-containing silicone resin is a powder solid, it is first dissolved in a second solvent.

[0042] The leather topcoat of this application incorporates a specific type of vinyl-containing silicone resin. Its molecular structure is rich in vinyl functional groups, allowing it to participate simultaneously with linear vinyl silicone oil, base adhesive, and other components in the hydrosilylation crosslinking reaction of the crosslinking agent, constructing a dense and uniform three-dimensional crosslinked network. This three-dimensional crosslinked network significantly enhances the surface hardness of the silicone synthetic leather surface layer through high-density crosslinking, providing structural support for improved wear resistance. Furthermore, the flexible segments of the linear vinyl silicone oil and base adhesive can form an "elastic buffer zone" within the crosslinked network, ensuring that while surface hardness is improved, material embrittlement is avoided, maintaining excellent deformation resistance. When the surface layer of the silicone synthetic leather of this application is subjected to external friction, the three-dimensional crosslinked network can quickly disperse stress, effectively preventing surface damage caused by localized stress concentration, thus structurally solving the problem of easy cracking in high-hardness materials.

[0043] The leveling agent, polyether-epoxy co-modified silicone oil, is synthesized by attaching polyether and epoxy alkane to the chain segments of polymethylsiloxane macromolecules. Its molecular structure is as follows: (CH3)3SiO[(CH3)2SiO] a [(R1)(CH3)SiO] b [(R2)(CH3)SiO] c Si(CH3)3, where a, b, and c are the number of repeating units, R1 is allyl glycidyl ether, and R2 is a polyoxyethylene / polyoxypropylene repeating unit. Its viscosity is 300~1000 mPa·s, and its epoxy group content is 1.3~1.9 wt%.

[0044] Leveling agents facilitate the formation of oriented molecular layers, dynamically regulate surface tension, balance local tension differences, and enhance the wetting ability of the leather topcoat adhesive on release paper or substrate. This not only helps achieve a high-gloss or controllable matte visual effect but also works synergistically with matting agents to optimize the surface microstructure, further improving the appearance quality and tactile consistency of the coating.

[0045] In some embodiments, the matting agent is fumed silica with a surface coated with polydimethylsilane rubber and a particle size between 5 and 15 μm. The matting agent facilitates the formation of an irregular micro-textured structure on the leather surface, dispersing stress during external friction and scratching. It synergistically enhances material strength with the silicone matrix, reducing the probability of wear and scratches under high-frequency mechanical stress, and extending product lifespan. Simultaneously, the optimized microstructure of the matting agent makes the leather surface feel smoother and more delicate, improving touch comfort. Some types can also cover surface imperfections, enhance stain resistance, and expand product application scenarios.

[0046] In some embodiments, the crosslinking agent is a polydimethylsiloxane having at least three hydrogen atoms directly bonded to Si, wherein the hydrogen atoms are located at the chain ends and / or side chains, and the hydrogen atom content is 0.1 to 1.6 wt%. The crosslinking agent can be linear, dendritic, cyclic, or a mixture thereof.

[0047] In some embodiments, the inhibitor is methylbutynol, etynylcyclohexanol, alkynyl-containing maleic acid or its derivatives, alkynyl-containing fumaric acid or its derivatives, polyvinyl polysiloxane, pyridine, unsaturated amides, organophosphorus compounds, or phosphites. Ethynylcyclohexanol is preferred.

[0048] In some embodiments, the catalyst is a platinum catalyst, wherein the Pt content in the platinum catalyst is 3000~7000 ppm. Specifically, it is an isopropanol solution of chloroplatinic acid, a tetrahydrofuran solution of chloroplatinic acid, a chloroplatinic acid-divinyltetramethyldisiloxane complex, or a chloroplatinic acid-1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane complex. The preferred catalyst is a chloroplatinic acid-divinyltetramethyldisiloxane complex.

[0049] In some embodiments, the color paste is a commercially available silicone rubber-specific color paste, prepared by uniformly dispersing the pigment using silicone oil or silicone rubber as a carrier.

[0050] This application provides a method for preparing a leather surface adhesive: a base adhesive, a vinyl-containing polydimethylsiloxane, a vinyl-containing silicone resin, and a leveling agent are heated and stirred in a mixer, and then an inhibitor, a matting agent, a crosslinking agent, a hand feel agent, and a color paste are added. After stirring evenly, a second catalyst is added, and after degassing, a leather surface adhesive is obtained.

[0051] In some embodiments, the raw materials for preparing the interlayer adhesive include: a two-component polysiloxane resin and a color paste. Preferably, the raw materials for preparing the interlayer adhesive, by weight, include 100 parts of a two-component polysiloxane resin and 2-5 parts of a color paste.

[0052] In some embodiments, the raw materials for preparing the adhesive layer include: a two-component polysiloxane resin, an adhesion promoter, and a colorant. Preferably, the raw materials for preparing the adhesive layer, by weight, include 100 parts of two-component polysiloxane resin, 0.5 to 4 parts of adhesion promoter, and 2 to 5 parts of colorant.

[0053] In some embodiments, the adhesion promoter is at least one of vinyltriethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, or a hydrolysate thereof.

[0054] This application also provides a method for preparing a silicone synthetic leather surface layer, comprising the following preparation steps: S1: Add a portion of the first vinyl-terminated polydimethylsiloxane and the second vinyl-terminated polydimethylsiloxane to a kneader, add fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil and water in multiple batches, mix evenly and heat to react, remove low-boiling substances, cool down and add the remaining first vinyl-terminated polydimethylsiloxane, stir and continue to react to obtain the base adhesive; S2: α-olefin, first solvent and first catalyst are heated and activated in a reaction vessel for a period of time to obtain a mixed solution; Si-H-containing organopolysiloxane is added to the mixed solution, heated and kept at the temperature for a period of time, and after the reaction is completed, the first solvent and low-boiling substances are removed to obtain the tactile agent; S3: The base adhesive, vinyl polydimethylsiloxane, vinyl silicone resin, and leveling agent are heated and stirred in a mixer. Then, inhibitors, matting agents, crosslinking agents, hand feel agents, and color pastes are added. After stirring evenly, the second catalyst is added, and after degassing, the leather surface layer adhesive is obtained. S4: Apply the leather surface layer adhesive to the release paper, bake and cure to obtain the leather surface layer; apply the intermediate layer adhesive to the surface of the leather surface layer, cure to obtain the intermediate layer; apply the adhesive layer adhesive to the surface of the intermediate layer, and attach the base fabric to the adhesive layer. After baking and curing, peel off the release paper to obtain the silicone synthetic leather surface layer of this application.

[0055] In some embodiments, the coating thickness of the leather top layer adhesive is 100~250 μm, the coating thickness of the intermediate layer adhesive is 200~300 μm, and the thickness of the adhesive layer is 80~150 μm.

[0056] Preferably, in the raw materials for preparing the leather surface adhesive, the ratio of the total molar number of active hydrogen to the total molar number of vinyl groups is (1.5~3.5):1, wherein the total molar number of active hydrogen refers to the sum of the molar number of hydrogen atoms directly bonded to silicon atoms in the crosslinking agent and the hand-feeling agent, and the total molar number of vinyl groups refers to the sum of the molar number of vinyl groups in the vinyl-containing silicone resin, the base adhesive, and the vinyl-containing polydimethylsiloxane.

[0057] This application provides a specific method for preparing the surface layer of silicone synthetic leather, following the steps below: S1: Add 70% of the first vinyl-terminated polydimethylsiloxane and the second vinyl-terminated polydimethylsiloxane to a kneader, and add fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil and water in 3 to 5 portions. After mixing evenly, heat to 120 to 180 ℃ and remove low-boiling substances under vacuum degree ≤ -0.09 MPa for 2 to 3 hours. After cooling to 80 to 100 ℃, add the remaining 30% of the first vinyl-terminated polydimethylsiloxane and stir at high speed for 1 hour to obtain the base adhesive. S2: Add α-olefin, toluene solvent, and Karstedt platinum catalyst to a dry reaction vessel under an inert gas atmosphere. The amount of catalyst added is 20 ppm of the total mass of the raw materials based on platinum. Heat the reaction system to 60-80 °C and continuously stir and activate it at this temperature for 1 h to obtain a mixed solution. Slowly add a toluene solution of Si-H organopolysiloxane to the mixed solution dropwise at a rate of 1-2 mL / min through a constant pressure dropping funnel, maintaining the system temperature at 60-80 °C during the dropwise addition. After the dropwise addition is completed, heat the system to 80-100 °C and keep it at this temperature for 3-5 h to carry out the reaction. After the reaction is completed, transfer the system to a vacuum distillation apparatus to remove the toluene solvent and the low-boiling substances generated in the reaction under a vacuum degree ≤-0.095 MPa and a temperature of 120-140 °C. After the solvent is completely removed, let the system cool naturally to room temperature to obtain the tactile agent. S3: The base adhesive, vinyl-containing polydimethylsiloxane, vinyl-containing silicone resin, and leveling agent are sequentially added to a planetary mixer and stirred at 30-50 rpm for 30 min at 50-60 ℃. Then, the inhibitor, matting agent, crosslinking agent, hand feel agent, and color paste are added and stirred for 60 min. After stirring, the second catalyst is added and stirred at 60-80 rpm. The mixture is then degassed for 5-10 min under a vacuum of ≤-0.095 MPa to obtain the leather surface layer adhesive. S4: Coat the leather surface layer with adhesive onto the release paper, with a coating thickness of 100~250 μm, and bake at 130~150 ℃ for 2~5 min to cure, forming the leather surface layer; coat the surface of the leather surface layer with an intermediate layer adhesive, with a coating thickness of 200~300 μm, and bake at 130~150 ℃ for 2~5 min to cure, forming the intermediate layer; coat the surface of the intermediate layer with an adhesive layer adhesive, with an adhesive layer thickness of 80~150 μm, then bond the base fabric and adhesive layer together, bake at 130~150 ℃ for 5~10 min, and peel off the release paper to obtain the silicone synthetic leather surface layer of this application.

[0058] Example 1 An organosilicon synthetic leather surface layer is prepared according to the following method: S1: According to the weight percentage of raw materials, the raw materials for preparing the base adhesive include: 42.93 wt% first vinyl-terminated polydimethylsiloxane, 21.47 wt% second vinyl-terminated polydimethylsiloxane, 25 wt% fumed silica, 6 wt% hexamethyldisilazane, 0.6 wt% divinyltetramethyldisilazane, 2 wt% hydroxyl silicone oil and 2 wt% water; wherein the mass ratio of first vinyl-terminated polydimethylsiloxane to second vinyl-terminated polydimethylsiloxane is approximately 2:1.

[0059] Approximately 70% of the first vinyl-terminated polydimethylsiloxane and all of the second vinyl-terminated polydimethylsiloxane were placed in a kneader. Fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil and water were added in 3 to 5 portions. After mixing evenly, the mixture was heated to 120 to 180 °C and the low-boiling substances were removed under a vacuum of ≤-0.09 MPa for 2 to 3 hours. After cooling to 80 to 100 °C, the remaining 30% of the first vinyl-terminated polydimethylsiloxane was added. The mixture was stirred at high speed for 1 hour to obtain the base adhesive. S2: Add 152.88 g of α-olefin with C24~C28 carbon atoms, 20 g of toluene solvent, and Karstedt platinum catalyst to a dry and sealed reaction vessel filled with inert gas. The amount of catalyst added is 20 ppm of the total mass of the raw materials based on platinum. Heat the reaction system to 60~80 ℃ and stir continuously at this temperature for 1 h to obtain a homogeneous and stable mixed solution. 100 g of Si-H-containing organopolysiloxane was dissolved in toluene to prepare a MQ-type hydrogen-containing silicone resin toluene solution with a solid content of 50 wt%. The solution was slowly added dropwise to the mixed solution through a constant pressure dropping funnel at a rate of 1-2 mL / min. During the addition, the system temperature was maintained at 60-80 °C. After the addition was completed, the system temperature was raised to 80-100 °C and the reaction was maintained at this temperature for 4 h. After the reaction was completed, the system was transferred to a vacuum distillation apparatus to remove the toluene solvent and the low-boiling substances generated in the reaction under a vacuum degree ≤-0.095 MPa and a temperature of 120-140 °C. After the solvent was completely removed, the system was allowed to cool naturally to room temperature to obtain the tactile agent. S3: The raw materials for preparing the leather topcoat are as follows (by weight): 100 parts base adhesive, 75 parts vinyl-containing polydimethylsiloxane, 25 parts vinyl-containing silicone resin, 1 part leveling agent, 0.05 parts inhibitor, 8 parts matting agent, 13 parts crosslinking agent, 10 parts hand feel agent, 0.8 parts catalyst, and 5 parts color paste.

[0060] The base adhesive, vinyl-containing polydimethylsiloxane, vinyl-containing silicone resin, and leveling agent are sequentially added to a planetary mixer and stirred at 30-50 rpm for 30 min at 50-60 ℃. Then, inhibitors, matting agents, crosslinking agents, hand feel agents, and color pastes are added and stirred for 60 min. After stirring, a second catalyst is added and stirred at 60-80 rpm. The mixture is then degassed for 5-10 min under a vacuum of ≤-0.095 MPa to obtain the leather surface layer adhesive. S4: Apply the leather surface layer adhesive to the release paper with a coating thickness of 100-250 μm, and bake at 130-150 ℃ for 2-5 min to cure, forming the leather surface layer; apply the intermediate layer adhesive to the surface of the leather surface layer, the intermediate layer adhesive consisting of 100 parts by weight of two-component polysiloxane resin and 5 parts by weight of color paste, with a coating thickness of 200-300 μm, and bake at 130-150 ℃ for 2-5 min to cure, forming the intermediate layer; apply the adhesive layer adhesive to the surface of the intermediate layer, the adhesive layer adhesive consisting of 100 parts by weight of two-component polysiloxane resin, 2 parts by weight of adhesion promoter and 5 parts by weight of color paste, with a thickness of 80-150 μm; then bond the base fabric to the adhesive layer, bake at 130-150 ℃ for 5-10 min, and peel off the release paper to obtain the silicone synthetic leather surface layer of this application; The sources of the raw materials are as follows: the first vinyl-terminated polydimethylsiloxane is product HS-1000 from Hoshine Silicon Oil Co., Ltd., with a viscosity of 1000 mPa·s; the second vinyl-terminated polydimethylsiloxane is product HS-10000 from Hoshine Silicon Oil Co., Ltd., with a viscosity of 10000 mPa·s; the fumed silica is product HS-300 from Hoshine Silicon Oil Co., Ltd.; hexamethyldisilazane and divinyltetramethyldisilazane were purchased from Xinyaqiang Silicon Chemical Co., Ltd.; and the hydroxyl silicone oil is product PMX-0930 from Dow Chemical. The Si-H-containing organopolysiloxane was purchased from Shandong Dayi Chemical Co., Ltd., model DY-HMQ103 methyl hydrogen-containing MQ type silicone resin, with a hydrogen content of 0.65-0.75 wt%; the α-olefin was purchased from Daopu Chemical, model C24-C28; the vinyl-containing polydimethylsiloxane was Hesheng Silicone Oil Co., Ltd., model HS-1000; the vinyl-containing silicone resin was purchased from Jiangxi Xinjiayi New Material Co., Ltd., model XJY-8206A methyl vinyl MQ type silicone resin, with a vinyl content of 1.8-2.2 wt%. The crosslinking agent is H-075t-120 hydrogen-containing silicone oil from Jiangxi Haiduo Organosilicon Materials Co., Ltd.; the matting agent is ACEMATT TT3300 matting powder from Degussa; the leveling agent is DY-ETE302G-2 polyether epoxy co-modified silicone oil from Shandong Dayi Chemical Co., Ltd.; the inhibitor is YZJ-1 from Guangzhou Siyou New Materials Technology Co., Ltd.; the catalyst is PT-5000 from Guangzhou Siyou New Materials Technology Co., Ltd.; the two-component polysiloxane resin is SILASTIC™ LCF 8400 Binder silicone fabric coating resin from Dow Chemical; and the adhesion promoter is G-040 from Guangzhou Xingguang Organosilicon Technology Co., Ltd.

[0061] According to the calculation formula:

[0062] In this embodiment, the first vinyl-terminated polydimethylsiloxane with a viscosity of 1000 mPa·s and the second vinyl-terminated polydimethylsiloxane with a viscosity of 10000 mPa·s are mixed at a mass ratio of 2:1, resulting in a viscosity of approximately 2150 mPa·s.

[0063] Example 2 In step S1, the raw material ratio for preparing the base adhesive is adjusted as follows: 34.67 wt% first vinyl-terminated polydimethylsiloxane, 17.33 wt% second vinyl-terminated polydimethylsiloxane, 28 wt% fumed silica, 10 wt% hexamethyldisilazane, 1 wt% divinyltetramethyldisilazane, 5 wt% hydroxyl silicone oil, and 4 wt% water; In step S2, the amount of C24~C28 α-olefin added was adjusted to 203.84 g, that is, the molar ratio of α-olefin to silane groups in Si-H organopolysiloxane in Example 2 was 0.8:1; In step S3, the raw material ratio for preparing the leather surface adhesive is adjusted as follows: 100 parts base adhesive, 100 parts vinyl-containing polydimethylsiloxane, 15 parts vinyl-containing silicone resin, 1 part leveling agent, 0.5 parts inhibitor, 10 parts matting agent, 20 parts crosslinking agent, 15 parts hand feel agent, 1 part catalyst, and 5 parts color paste. The other preparation steps are consistent with those in Example 1.

[0064] Example 3 In step S1, the raw material ratio for preparing the base adhesive is adjusted as follows: 48wt% first vinyl-terminated polydimethylsiloxane, 24wt% second vinyl-terminated polydimethylsiloxane, 20wt% fumed silica, 5wt% hexamethyldisilazane, 0.4wt% divinyltetramethyldisilazane, 1.6wt% hydroxyl silicone oil, and 1wt% water. In step S2, the amount of C24~C28 α-olefin added was adjusted to 76.44 g, that is, in Example 3, the molar ratio of α-olefin to silane groups in Si-H organopolysiloxane was 0.3:1. In step S3, the raw material ratio for preparing the leather surface adhesive is adjusted as follows: 100 parts base adhesive, 50 parts vinyl-containing polydimethylsiloxane, 40 parts vinyl-containing silicone resin, 0.5 parts leveling agent, 0.08 parts inhibitor, 8 parts matting agent, 10 parts crosslinking agent, 8 parts hand feel agent, 0.05 parts catalyst, and 3 parts color paste. The other preparation steps are consistent with those in Example 1.

[0065] Example 4 The amount of C24~C28 α-olefin added was adjusted to 382.2 g, and the other preparation steps were consistent with those in Example 1. That is, the molar ratio of α-olefin to silane groups in the Si-H organopolysiloxane in Example 4 was 1.5:1.

[0066] Example 5 The amount of C24~C28 α-olefin added was adjusted to 50.96 g, and the other preparation steps were consistent with those in Example 1. That is, the molar ratio of α-olefin to silane groups in the Si-H organopolysiloxane in Example 5 was 0.2:1.

[0067] Example 6 The α-olefin was adjusted to a C6~C8 olefin with a molecular weight of 98 and an addition amount of 41.16 g. Other preparation steps were consistent with those in Example 1. In Example 6, the molar ratio of α-olefin to silane groups in the Si-H organopolysiloxane was 0.6:1.

[0068] Example 7 The α-olefin was adjusted to a C16~C20 olefin with a molecular weight of 252 and an addition amount of 105.84 g. Other preparation steps were consistent with those in Example 1. In Example 7, the molar ratio of α-olefin to silane groups in Si-H organopolysiloxane was 0.6:1.

[0069] Example 8 The α-olefin was adjusted to a C30~C45 olefin with a molecular weight of 450 and an addition amount of 189 g. Other preparation steps were consistent with those in Example 1. In Example 8, the molar ratio of α-olefin to silane groups in Si-H organopolysiloxane was 0.6:1.

[0070] Example 9 In step S1, the mass ratio of the first vinyl-terminated polydimethylsiloxane to the second vinyl-terminated polydimethylsiloxane was adjusted to 5:1, while the other preparation steps remained the same as those in Example 1.

[0071] Example 10 In step S1, the mass ratio of the first vinyl-terminated polydimethylsiloxane to the second vinyl-terminated polydimethylsiloxane was adjusted to 1:1, and the other preparation steps remained the same as those in Example 1.

[0072] Example 11 The amount of the hand feel agent added was adjusted to 2 parts by mass, and the other preparation steps were kept the same as those in Example 1.

[0073] Example 12 The amount of the hand feel agent was adjusted to 30 parts by weight, and the other preparation steps were kept the same as those in Example 1.

[0074] Comparative Example 1 In the preparation steps of S2 hand feel agent, the α-olefin is replaced with a single-end vinyl-terminated polydimethylsiloxane with the structural formula CH2=CH-Si(CH3)2-[O-Si(CH3)2]19-CH2-CH2-CH2-CH3, a molecular weight of 1548, and an addition amount of 650.16g. The molar ratio of vinyl groups to silanol groups in the Si-H-containing organopolysiloxane is 0.6:1. Other preparation steps are consistent with the preparation steps in Example 1.

[0075] Comparative Example 2 In step S3, vinyl-containing polydimethylsiloxane with a vinyl content of 2 wt% is used to replace vinyl-containing silicone resin with a vinyl content of 2 wt%, and the other preparation steps are consistent with the preparation steps in Example 1.

[0076] Comparative Example 3 In step S3, no hand-feeling agent is added during the preparation of the leather surface adhesive; the other preparation steps are consistent with those in Example 1.

[0077] Comparative Example 4 In step S1, only the first vinyl-terminated polydimethylsiloxane is used, and the second vinyl-terminated polydimethylsiloxane is not added. The other preparation steps are consistent with the preparation steps in Example 1.

[0078] Comparative Example 5 In step S1, only the second vinyl-terminated polydimethylsiloxane is used, without adding the first vinyl-terminated polydimethylsiloxane, and the other preparation steps are consistent with the preparation steps in Example 1.

[0079] Comparative Example 6 In step S1, the first vinyl-terminated polydimethylsiloxane and the second vinyl-terminated polydimethylsiloxane are replaced with a single vinyl-terminated polydimethylsiloxane with a viscosity of 2000 mPa·s.

[0080] Comparative Example 7 In step S4, the intermediate layer is not prepared, and the thickness of the adhesive layer is increased to 300~400 µm. The other preparation steps are consistent with the preparation steps in Example 1.

[0081] Performance testing The silicone synthetic leathers prepared in the above embodiments and comparative examples were subjected to the following performance tests: 1. Abrasion resistance: The test was conducted according to "QB / T 2726-2005 Determination of Abrasion Resistance of Leather - Physical and Mechanical Tests". Specific test parameters were set as follows: Grinding wheel type: CS-10 standard grinding wheel; Load: 1000g; Friction speed: 70rpm; Friction revolutions: 15000 revolutions (meeting the durability requirements of the automotive interior leather industry). After the test, the wear condition of the sample surface was visually assessed and rated according to the criteria shown in Table 1.

[0082] Table 1. Abrasion Resistance Evaluation Criteria

[0083] 2. Wear Loss: The test was conducted according to "QB / T 2726-2005 Determination of Abrasion Resistance of Leather - Physical and Mechanical Tests". Specific test parameters were set as follows: Grinding wheel type: CS-10 standard grinding wheel; Load: 1000g; Friction speed: 70rpm; Friction revolutions: 15000 revolutions (meeting the durability requirements of the automotive interior leather industry). The percentage of mass loss of the sample before and after friction was measured.

[0084] 3. Folding fastness: Refer to "QB / T 2714-2005 Physical and Mechanical Tests of Leather - Determination of Folding Fastness". Cut standard samples along the width of the leather. Take 6 samples in 1 group. Fold the samples 200,000 times at (23±2)℃. Then observe the changes in the surface and lining of the folded part and observe whether there are cracks.

[0085] 4. Smoothness: Assess by touch, evaluate the overall feel, with 10 people evaluating simultaneously and the average value taken. The grades and corresponding feelings are shown in Table 2 below.

[0086] Table 2 Smoothness Evaluation Criteria

[0087] 5. Smoothness and Durability: The test shall be conducted in accordance with "QB / T 2726-2005 Determination of Physical and Mechanical Tests for Leather – Abrasion Resistance". Specific test parameters are as follows: Grinding wheel type: CS-10 standard grinding wheel; Load: 1000g; Friction speed: 70rpm; Friction revolutions: 15000 revolutions (meeting the durability requirements of the automotive interior leather industry). The percentage change in the dynamic coefficient of friction (COF) before and after friction is measured using a coefficient of friction meter. A smaller percentage change indicates better and longer-lasting smoothness, while a larger percentage indicates poorer smoothness.

[0088] 6. Viscosity: Refer to GB / T 2794-2022 Determination of Viscosity of Adhesives, use a rotational rheometer, test at (23.0±0.5)℃, and record the shear rate for 10s. -1 Viscosity at that time.

[0089] 7. Stain resistance: Refer to "QB / T 5070-2017 Test Method for Stain Resistance of Artificial Leather and Synthetic Leather" to determine its stain resistance to oil-based pens, water-based pens, alcohol, red wine, coffee, olive oil and fine sand mixture.

[0090] The silicone synthetic leather prepared with the above-mentioned surface adhesive was subjected to the above-mentioned performance tests. The test results for abrasion resistance, wear loss, folding fastness, smoothness, smoothness durability, and viscosity are recorded in Table 3 below. The test results for stain resistance are recorded in Table 4 below.

[0091] Table 3 Performance test results of each embodiment and comparative example

[0092]

[0093] Table 4. Stain resistance test results of each embodiment and comparative example.

[0094] The synthetic leather prepared from the silicone synthetic leather surface adhesive of this application is superior to the comparative product in all core performance aspects. In abrasion resistance tests simulating daily use scenarios, it can maintain surface integrity for a longer period of time and resist frictional wear; in terms of touch, it reaches the highest level of dry and smooth standard in the industry, with a delicate and comfortable touch experience; even after repeated friction, its smooth feel can be maintained stably, without easily becoming rough or sticky, and its texture remains outstanding even after long-term use.

[0095] Examples 1-5 mainly focus on adjusting the molar ratio of α-olefins in the feel agent to silane groups in Si-H organopolysiloxanes, with a preferred ratio of (0.3-0.8):1. Excess α-olefins completely consume the silane functional groups, preventing the retention of active sites in the system. Consequently, the feel agent prepared in this way is only physically adsorbed onto the surface of the synthetic leather and cannot participate in the secondary crosslinking reaction of the vinyl components of the surface layer adhesive. It is difficult to form a stable and dense crosslinked network structure on the leather surface. For example, in actual use, the physically adsorbed feel agent in the silicone synthetic leather prepared in Example 4 is easily detached due to friction and changes in environmental temperature and humidity, ultimately affecting the wear resistance and smoothness durability of the silicone synthetic leather.

[0096] In Example 5, the α-olefin content was too low, resulting in a low content of alkyl functional groups in the hand feel agent. This caused an imbalance in the polarity of the molecular chain of the hand feel agent product, and the driving force for the spontaneous migration of molecules to the surface layer of leather was greatly weakened. It was difficult to form a uniform, dense and firm lubricating protective film on the leather surface, which ultimately reduced the wear resistance, hand feel and stain resistance.

[0097] Examples 6-8 primarily adjusted the carbon number of the α-olefin in the hand-feeling agent, with a preferred range of 16-45. Example 6 used C6-C8 α-olefins to synthesize the hand-feeling agent. The limited alkyl chain length in the hand-feeling agent product structure resulted in weak intermolecular van der Waals forces, insufficient motivation for the hand-feeling agent molecules to migrate autonomously to the leather surface, reduced uniform spreading on the leather surface, and difficulty in forming a continuous lubricating protective film. Simultaneously, the shorter alkyl chain segments, due to weakened entanglement and cross-linking ability, made it difficult to construct a dense physical network structure, providing less abrasion-resistant support on the leather surface. This resulted in reduced abrasion resistance, hand feel, and stain resistance of the treated silicone synthetic leather surface. The results combined with those of Examples 7 and 8 indicate that a carbon number of 16-45 for the synthesized hand-feeling agent is more suitable, with a preferred carbon number of 20-30. α-olefins with more than 45 carbon atoms are hard, waxy solids at room temperature due to their large molecular weight. They are not only difficult to synthesize and separate and purify, but also have not yet been commercially applied on a large scale and are not feasible for mass production.

[0098] In Examples 9, 10, 4, and 5, the mass ratio of the first vinyl-terminated polydimethylsiloxane to the second vinyl-terminated polydimethylsiloxane in the base adhesive formulation was adjusted. Excessive low-viscosity vinyl-terminated polydimethylsiloxane interferes with the construction of the molecular chain solidification network, disrupts structural balance, and causes excessive concentration of crosslinking points, significantly reducing material toughness. In practical applications, this structural defect directly leads to insufficient impact and bending resistance of the synthetic leather surface layer. When subjected to external impact or repeated bending, stress tends to accumulate at the concentrated crosslinking points, leading to cracking, breakage, and ultimately reduced flexural strength and abrasion resistance, as seen in Examples 9 and 4.

[0099] Excessive use of high-viscosity vinyl-terminated polydimethylsiloxane significantly reduces the flowability and spreadability of the topcoat adhesive, making it impossible to distribute evenly on the substrate surface during coating. Consequently, the added matting agent struggles to form a uniform and regular micro-texture on the leather surface, a structure crucial for dispersing stress during external friction and scratching. Without this stress dispersion mechanism, stress concentrates in localized areas when the synthetic leather surface is subjected to friction and scratching, accelerating material wear and ultimately resulting in reduced abrasion resistance, as seen in Examples 10 and 5.

[0100] Examples 11-12 and Comparative Example 3 adjusted the content of the hand feel agent in the top coat adhesive. The amount of hand feel agent added to the leather top coat adhesive should be 5-20 parts. If it is too low, the ideal smooth touch cannot be achieved, and if it is too high, the formulation cost will be significantly increased and the overall performance balance of the coating may be affected.

[0101] In Comparative Example 1, a hand feel agent was synthesized by using a single-end vinyl-terminated polydimethylsiloxane and a Si-H-containing organopolysiloxane. The polymerized product does not contain long-chain alkyl groups, which prevents the hand feel agent molecules from migrating to the leather surface and forming a continuous lubricating protective film on the leather surface. As a result, the wear resistance, hand feel, and stain resistance are all inferior.

[0102] Comparative Example 6 aimed to stabilize the viscosity of the final silicone synthetic leather surface layer adhesive at 50,000–70,000 mPa·s. In step S1, the first and second vinyl-terminated polydimethylsiloxanes were replaced with vinyl-terminated polydimethylsiloxanes with a viscosity of 2,000 mPa·s. The single vinyl-terminated polydimethylsiloxane formed a relatively homogeneous cross-linked network, unlike the combination of two viscosities. This lack of a high-density cross-linked microregion that effectively disperses stress resulted in a less pronounced heterogeneous cross-linked topology, inhibiting the heterogeneous reinforcement mechanism and failing to achieve a synergistic improvement in the abrasion resistance and flexibility of the synthetic leather surface layer.

[0103] Comparative Example 7 shows that, in order to simplify the preparation process of silicone synthetic leather, the intermediate layer and the adhesive layer can be combined into one design. After testing, the performance of the silicone synthetic leather prepared by the combination is not significantly different from that of the sample prepared by the layers.

[0104] In summary, the silicone synthetic leather surface layer and preparation method provided in this application specifically address the core problems of insufficient abrasion resistance and poor smoothness in existing silicone synthetic leathers. It also improves upon shortcomings such as high cost, complex processes, easy migration and precipitation of additives, and poor durability of the smooth layer. This application optimizes the properties of the base adhesive by rationally compounding vinyl-terminated polydimethylsiloxanes of different viscosities, designs and synthesizes a dedicated smoothness agent, and precisely controls its preparation ratio to construct a dense and stable cross-linked network. Combined with the scientific design of the multi-layer structure and precise control of the preparation process, this allows the synthetic leather to possess excellent abrasion resistance, smoothness, and good performance durability, while also exhibiting outstanding fold resistance and stain resistance. It can meet the needs of high-end applications and effectively promotes the development of the silicone synthetic leather industry towards high-end and green directions.

[0105] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A silicone synthetic leather surface layer, characterized in that, It includes a base layer, an adhesive layer, an intermediate layer, and a leather top layer. The leather top layer is obtained by curing a leather top layer adhesive, the intermediate layer is obtained by curing an intermediate layer adhesive, and the adhesive layer is obtained by curing an adhesive layer adhesive. The raw materials for preparing the leather top layer adhesive include: base adhesive, vinyl-containing polydimethylsiloxane, vinyl-containing silicone resin, leveling agent, hand feel agent, inhibitor, matting agent, crosslinking agent, catalyst, and color paste.

2. The organosilicon synthetic leather surface layer as described in claim 1, characterized in that, The raw materials for preparing the hand-feeling agent include Si-H-containing organopolysiloxanes and α-olefins.

3. The organosilicon synthetic leather surface layer as described in claim 2, characterized in that, The preparation method of the hand feel agent is as follows: the α-olefin, the first solvent and the first catalyst are heated and activated in a reaction vessel for a period of time to obtain a mixed solution, the Si-H-containing organopolysiloxane is added to the mixed solution, the temperature is raised and kept at a certain temperature for a period of time, and after the reaction is completed, the first solvent and low-boiling substances are removed to obtain the hand feel agent.

4. The organosilicon synthetic leather surface layer as described in claim 2, characterized in that, The molar ratio of the α-olefin to the silane in the Si-H-containing organopolysiloxane is (0.3-0.8):

1.

5. The organosilicon synthetic leather surface layer as described in claim 1, characterized in that, The raw materials for preparing the base adhesive include: vinyl-terminated polydimethylsiloxane, fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil, and water.

6. The organosilicon synthetic leather surface layer as described in claim 5, characterized in that, The vinyl-terminated polydimethylsiloxane comprises a first ethylene-terminated polydimethylsiloxane and a second ethylene-terminated polydimethylsiloxane, wherein the viscosity of the first ethylene-terminated polydimethylsiloxane is 500~5000 mPa·s, and the viscosity of the second ethylene-terminated polydimethylsiloxane is 10000~20000 mPa·s.

7. The organosilicon synthetic leather surface layer as described in claim 6, characterized in that, The mass ratio of the first ethylene-terminated polydimethylsiloxane to the second ethylene-terminated polydimethylsiloxane is (2~4):

1.

8. The organosilicon synthetic leather surface layer as described in claim 6, characterized in that, The preparation method of the base adhesive is as follows: a portion of the first vinyl-terminated polydimethylsiloxane and the second vinyl-terminated polydimethylsiloxane are added to a kneader, and the fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil and water are added in multiple batches. The mixture is stirred evenly and heated to react. After removing low-boiling substances, the mixture is cooled and the remaining first vinyl-terminated polydimethylsiloxane is added. The mixture is stirred and reacted continuously to obtain the base adhesive.

9. A method for preparing an organosilicon synthetic leather surface layer, characterized in that, The preparation steps include the following: S1: Add a portion of the first vinyl-terminated polydimethylsiloxane and the second vinyl-terminated polydimethylsiloxane to a kneader, add fumed silica, hexamethyldisilazane, divinyltetramethyldisilazane, hydroxyl silicone oil and water in multiple batches, mix evenly and heat to react, remove low-boiling substances, cool down and add the remaining first vinyl-terminated polydimethylsiloxane, stir and continue to react to obtain the base adhesive; S2: α-olefin, first solvent and first catalyst are heated and activated in a reaction vessel for a period of time to obtain a mixed solution; Si-H-containing organopolysiloxane is added to the mixed solution, heated and kept at the temperature for a period of time, and after the reaction is completed, the first solvent and low-boiling substances are removed to obtain a tactile agent; S3: The base adhesive, vinyl polydimethylsiloxane, vinyl silicone resin, and leveling agent are heated and stirred in a mixer. Then, inhibitors, matting powder, crosslinking agent, hand feel agent, and color paste are added. After stirring evenly, a second catalyst is added. After degassing, leather surface adhesive is obtained. S4: The leather surface layer adhesive is applied to the release paper and baked to cure to obtain the leather surface layer; the intermediate layer adhesive is applied to the surface of the leather surface layer and cured to obtain the intermediate layer. An adhesive layer is coated on the surface of the intermediate layer, and the base fabric is bonded to the adhesive layer. After baking and curing, the release paper is peeled off to obtain the silicone synthetic leather surface layer.

10. The preparation method according to claim 9, characterized in that, The coating thickness of the leather top layer adhesive is 100~250μm, the coating thickness of the intermediate layer adhesive is 200~300μm, and the coating thickness of the bonding layer adhesive is 80~150μm.

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