Antifouling brightener for leather and preparation method thereof

Abstract

The invention provides an antifouling brightener for leather and a preparation method of the antifouling brightener, and belongs to the technical field of leather finishing agents. The structure of the antifouling brightener for leather provided by the invention does not contain fluorine, the antifouling brightener is not limited by fluorine forbidding, reactive groups such as vinyl and methoxyl are introduced into a main chain while high silicon content is introduced into the main chain, so that film-forming silicon crosslinking is more compact, the surface tension is lower, and the antifouling brightener can react with an antifouling auxiliary agent, so that antifouling is more long-acting and efficient; the physical property of a coating system can be obviously improved. The brightener coating is refreshing and skin-friendly in hand feeling, free of stickiness, suitable for coating of genuine leather and artificial leather, capable of remarkably improving daily use experience and cleaning and maintenance convenience of leather products and good in environmental protection property and market application prospect.

Description

Technical Field

[0001] This invention relates to the field of leather finishing agents, and in particular to a stain-resistant and brightening agent for leather and its preparation method. Background Technology

[0002] Leather products, such as sofas, chairs, bags, and clothing, are easily stained with dirt, ink, and other contaminants during use, affecting not only their appearance but also increasing the difficulty of cleaning. To improve this situation, the industry often uses finishing polishes to treat the leather surface. Anti-fouling polishes are a type of functional coating material whose core function is to form a thin film on the leather surface, reducing surface energy and making it difficult for liquid stains to adhere while facilitating the removal of solid stains, thus protecting the leather.

[0003] Currently, leather stain-resistant brighteners on the market mainly rely on two technological approaches: one is a fluoropolymer system, which utilizes the extremely low surface energy of fluorine atoms to achieve excellent stain resistance, but its application is limited due to environmental regulations restricting certain fluorides; the other is a system based on organosilicon-modified resins, which reduces surface energy by introducing siloxane structures. However, these systems often need to be used in conjunction with physically blended stain-resistant auxiliaries, and the lack of a stable chemical bond between the two leads to the auxiliaries being easily lost during repeated wiping or use, resulting in a rapid decline in stain resistance. Furthermore, some organosilicon materials can cause the coating to feel sticky, affecting the feel and quality of the leather.

[0004] Therefore, developing an environmentally friendly, durable, non-abrasive, and cost-effective anti-fouling and brightening agent that does not affect the feel of leather remains a practical problem that needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a stain-resistant and brightening agent for leather and its preparation method, which solves the technical problems of existing leather stain-resistant and brightening agents being limited in use due to the ban on fluorinated materials, having short-lasting stain-resistant effects, failing after repeated wiping, and having a sticky coating feel.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a stain-resistant and brightening agent for leather, comprising the following steps: S1. 6-Heptene-2,4-diol, trimethoxysilane and the first catalyst are mixed and reacted to remove low-boiling substances, and intermediate product 1 is obtained. S2. After dehydrating the hydroxyl-terminated silicone oil and polycarbonate diol, isophorone diisocyanate and a second catalyst are added to react. Then, dimethylolpropionic acid, 6-hepten-2,4-diol, intermediate product 1 and acetone are added to continue the reaction until the isocyanate group content is qualified. Then, triethylamine is added to react. Then, water is added under stirring to emulsify. Finally, an amine chain extender is added to disperse and remove acetone to obtain an organosilicon-modified waterborne polyurethane emulsion. S3. The organosilicon-modified waterborne polyurethane emulsion is mixed and dispersed with the anti-fouling additive to obtain an anti-fouling and brightening agent for leather.

[0007] Preferably, the reaction in step S1 is carried out at 70°C to 90°C for 4 to 6 hours.

[0008] Preferably, the reaction following the addition of the isophorone diisocyanate in step S2 is carried out at 80°C to 95°C; the reaction following the addition of dimethylolpropionic acid, 6-hepten-2,4-diol, intermediate 1 and acetone is carried out at 55°C to 65°C.

[0009] Preferably, the first catalyst in step S1 is a cassiterite catalyst; The amount of the first catalyst is 0.5% to 2% of the mass of the 6-hepten-2,4-diol.

[0010] Preferably, the mass ratio of 6-hepten-2,4-diol to trimethoxysilane in step S1 is 1:0.8 to 1:1.5.

[0011] Preferably, the dehydration in step S2 is carried out under negative pressure conditions; The mass ratio of the hydroxyl-terminated silicone oil to the polycarbonate diol is 3:1 to 7:1. The amount of isophorone diisocyanate used is 40% to 60% of the total mass of the hydroxyl-terminated silicone oil and the polycarbonate diol; The second catalyst is T12.

[0012] Preferably, the antifouling additive in step S3 is an antifouling and noise-absorbing additive.

[0013] Preferably, the amount of the antifouling additive is 1% to 20% of the mass of the silicone-modified waterborne polyurethane emulsion.

[0014] This invention provides a stain-resistant and brightening agent for leather, which is prepared by the above-described method.

[0015] The present invention also provides a leather article having a coating formed by the above-mentioned anti-fouling and brightening agent for leather on its surface.

[0016] The technical effects and advantages of this invention are as follows: The leather anti-fouling and brightening agent provided by this invention is fluorine-free, thus avoiding usage restrictions due to the ban on fluorine. Unlike conventional silicone-modified polyurethane resins, which have low silicone content and lack reactivity, limiting their anti-fouling effect to blending with anti-fouling additives, this invention introduces high silicone content into the main chain, along with reactive groups such as vinyl and methoxy groups. This results in denser cross-linking of the film-forming silicone, lower surface tension, and the ability to react with anti-fouling additives, leading to longer-lasting and more efficient anti-fouling performance and significantly improving the physical properties of the coating system. The brightening agent coating of this invention has a refreshing and skin-friendly feel, without stickiness, and is suitable for coating genuine leather and artificial leather. It significantly improves the daily user experience and ease of cleaning and maintenance of leather products, demonstrating good environmental friendliness and promising market application prospects. Detailed Implementation

[0017] This invention provides a method for preparing a stain-resistant and brightening agent for leather. The method involves molecular design and stepwise synthesis to construct a reactive organosilicon-modified polyurethane system, which is then compounded with functional additives to obtain a high-performance product. The method includes the following three key steps: Step S1: This step aims to synthesize a key reactive intermediate (intermediate product 1). Specifically, a certain amount of 6-hepten-2,4-diol, trimethoxysilane, and a suitable amount of a first catalyst are mixed in a reaction vessel. 6-Hepten-2,4-diol is a straight-chain aliphatic diol containing both hydroxyl and carbon-carbon double bonds, capable of participating in various reactions such as condensation and addition. Trimethoxysilane is a common organosilane coupling agent, containing both highly reactive silane-hydrogen bonds (Si-H) and hydrolyzable methoxy groups. The mixed reaction is carried out under heating conditions, promoting the addition reaction between the silane-hydrogen bonds and the double bonds, while the methoxy groups may also partially participate in the reaction or be retained. After the reaction, the product is purified by removing low-boiling substances (usually using conventional methods in the art such as vacuum distillation or vacuum extraction) to obtain intermediate product 1. This intermediate introduces structural units from organosilanes and retained or unsaturated / reactive groups into the molecule, providing reaction sites for subsequent steps.

[0018] Step S2: This step aims to prepare a silicone-modified waterborne polyurethane base emulsion. First, a hydroxyl-terminated silicone oil and a polycarbonate diol are blended and dehydrated. The hydroxyl-terminated silicone oil is a polydimethylsiloxane with hydroxyl groups at both ends, a core material for introducing long-chain silicone and reducing the surface energy of the system. The polycarbonate diol (such as UH200) is a polymer diol with carbonate bonds as its chain segment, which imparts good toughness, hydrolysis resistance, and weather resistance to polyurethane. Dehydration is performed to eliminate the interference of moisture on the subsequent isocyanate reaction, usually by heating under negative pressure (i.e., vacuum). After successful dehydration, isophorone diisocyanate and a second catalyst are added to the system. IPDI is an alicyclic diisocyanate with characteristics of resistance to yellowing and balanced performance. The second catalyst is used to accelerate the addition polymerization reaction between the isocyanate and hydroxyl groups. This stage of the reaction forms a polyurethane prepolymer. Subsequently, dimethylolpropionic acid, additional 6-hepten-2,4-diol, intermediate product 1 obtained in step S1, and acetone (as a solvent for adjusting viscosity) are added to the system. DMPA, a carboxyl-containing diol, is introduced as a hydrophilic chain extender, giving the polymer chains ionizable carboxyl groups. This stage of the reaction continues until the isocyanate group content of the system is found to be acceptable by conventional methods in the art (such as di-n-butylamine titration), i.e., reaching the theoretical value or a predetermined low content level, indicating that the main chain extension reaction is essentially complete. Next, triethylamine is added to neutralize the carboxyl groups on the polymer chains, forming an ammonium carboxylate salt, which imparts water dispersibility to the polymer. After neutralization, water is added to the system under high-speed stirring to emulsify, forming an oil-in-water emulsion. Finally, an amine chain extender (such as a polyamine compound) is added, which can react with the residual isocyanate groups in the emulsion to further extend the chain or produce mild crosslinking, improving the emulsion stability and coating performance. After the reaction is complete, taking advantage of the volatile nature of acetone, a stable organosilicon-modified waterborne polyurethane emulsion with a certain solid content is obtained by removing acetone (usually by vacuum distillation).

[0019] Step S3: This step involves compounding the final product. The silicone-modified waterborne polyurethane emulsion obtained in step S2 is mixed and dispersed with the antifouling additive in a suitable mixing device (such as a dispersion tank) until a homogeneous and stable system is formed, thus obtaining the target product—the leather antifouling brightener. The purpose of mixing and dispersion is to ensure that the antifouling additive is uniformly distributed in the emulsion system.

[0020] Regarding the reaction conditions in step S1: The temperature of the reaction described in step S1 is preferably controlled within the range of 70°C to 90°C. More preferably, to balance the reaction rate and control side reactions, the temperature can be controlled between 75°C and 85°C. Even more preferably, a reaction temperature of 80°C is used, at which temperature the catalyst activity is suitable and the reaction is stable. The reaction time is preferably 4 to 6 hours. More preferably, it is 4.5 to 5.5 hours to ensure that the reaction proceeds fully.

[0021] Regarding the two-stage reaction temperatures in step S2: In step S2, the main polymerization reaction after the addition of isophorone diisocyanate is preferably carried out at a temperature controlled between 80°C and 95°C. More preferably, it is between 85°C and 90°C, as this temperature range is conducive to the full reaction of IPDI with the hydroxyl groups of the polyol. Subsequently, the reaction after the addition of chain extenders such as dimethylolpropionic acid and intermediate 1 is preferably carried out at a temperature controlled between 55°C and 65°C. More preferably, it is between 58°C and 62°C, for example, 60°C, as this lower temperature is beneficial for controlling the chain extension reaction rate and avoiding the risk of gelation.

[0022] Regarding the first catalyst and its dosage: The first catalyst mentioned in step S1 is preferably a platinum-based catalyst suitable for hydrosilylation reactions, such as a caster catalyst, which is a commonly used catalyst with high efficiency and selectivity. The dosage of the first catalyst is preferably 0.5% to 2% of the mass of the 6-hepten-2,4-diol. More preferably, it is 0.8% to 1.5%. Even more preferably, it is about 1%, which can control costs and reduce metal residue while ensuring catalytic efficiency.

[0023] Regarding the raw material ratio in step S1: In step S1, the preferred mass ratio of 6-hepten-2,4-diol to trimethoxysilane is 1:0.8 to 1:1.5. More preferably, it is 1:1.0 to 1:1.3. Even more preferably, it is 1:1.2, as this ratio is close to an equimolar reaction, which is beneficial for the synthesis of the target intermediate product.

[0024] For several preferred process parameters in step S2: The dehydration operation is preferably carried out under negative pressure to lower the boiling point of water, improve dehydration efficiency, and prevent the raw materials from oxidizing due to high temperature.

[0025] The mass ratio of the hydroxyl-terminated silicone oil to the polycarbonate diol is preferably 3:1 to 7:1. More preferably, it is 4:1 to 6:1. Even more preferably, it is about 5.3:1, a ratio that effectively balances coating flexibility, surface energy reduction effect, and cost.

[0026] The amount of isophorone diisocyanate used is preferably 40% to 60% of the total mass of the bihydroxyl-terminated silicone oil and polycarbonate diol. More preferably, it is 45% to 55%. Based on calculations of the example proportions, it is further preferred to be about 47.6%.

[0027] The second catalyst is preferably an organotin catalyst, such as dibutyltin dilaurate, which is often simply referred to as T12 in the industry.

[0028] Regarding the antifouling additive and its dosage: The antifouling additive mentioned in step S3 is preferably an antifouling and sound-absorbing additive that reduces surface tension, improves slipperiness, and enhances antifouling effect. It can be a commercially available silicone, fluorosilicone (excluding restricted substances such as PFOA / PFOS), or wax-based additive. The dosage of the antifouling additive is preferably 1% to 20% of the mass of the silicone-modified waterborne polyurethane emulsion. More preferably, it is 3% to 15%. Depending on different performance requirements, specific dosages such as 3%, 7%, or 10% can be further selected.

[0029] This invention also provides a stain-resistant and brightening agent for leather, which is prepared by any one or more preferred methods described above. This product is water-based, environmentally friendly, and storage-stable, making it suitable for modern leather finishing production lines.

[0030] This invention further provides a leather product whose surface is coated with a functional coating formed by the aforementioned leather anti-fouling and brightening agent. The leather product includes, but is not limited to, various products made of genuine leather (such as cowhide, sheepskin, pigskin, etc.) or artificial leather (such as PVC leather, PU synthetic leather, etc.), such as: furniture (sofas, chairs, headboards), automotive interiors (seats, steering wheels, dashboard coverings), clothing and footwear (leather jackets, leather pants, leather shoes, leather boots), bags and handbags (briefcases, handbags, backpacks), and other leather accessories such as gloves and belts. The coating method can be any method commonly used in the art, such as spraying, brushing, roller coating, curtain coating, or impregnation. After coating, drying (at room temperature or with heating) and curing will form a firmly adhering, high-performance anti-fouling and brightening coating. The technical solutions provided by this invention are described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of this invention.

[0031] The main raw materials used in the examples are: 6-hepten-2,4-diol (commercially available), trimethoxysilane (commercially available), caster catalyst (commercially available), isophorone diisocyanate IPDI (commercially available), hydroxyl-terminated silicone oil (commercially available), polycarbonate diol UH200 (commercially available), T12 (commercially available), dimethylolpropionic acid DMPA (commercially available), acetone (commercially available), triethylamine TEA (commercially available), diethylenetriamine DETA (commercially available), deionized water, and antifouling and noise-absorbing additives (self-made, see the preparation method in the examples of Chinese patent CN 119684834 B).

[0032] Example 1 Preparation of intermediate 1: 10 parts of 6-hepten-2,4-diol, 12 parts of trimethoxysilane, and 0.1 parts of caster catalyst were added to the reactor in sequence. The mixture was stirred and heated to 80°C and kept at that temperature for 4-6 hours. After the reaction was completed, the mixture was vacuumed for 1 hour to remove low-boiling substances, thus obtaining intermediate 1.

[0033] 53 parts of dihydroxy silicone oil and 10 parts of UH200 were sequentially added to a four-necked flask equipped with a stirrer and thermometer. After the addition was complete, the mixture was stirred and heated to 110°C, and dehydrated at -0.1 to -0.085 MPa for 1 to 2 hours. After the moisture content was deemed acceptable, the temperature was lowered to 50°C, and 30 parts of IPDI and 0.1 parts of T12 were added. After the addition was complete, the temperature was raised to 90°C and held for 2 hours. Then, the temperature was lowered to 60°C, and 4 parts of DMPA, 4 parts of 6-hepten-2,4-diol, 4 parts of intermediate 1, and 10 parts of acetone were added. After the addition was complete, the temperature was raised to 60°C, and the reaction proceeded until the NCO content was between 1.84 and 1.94. The reaction mixture was deemed acceptable within a certain percentage. The temperature was then lowered to 45℃, and 3 parts of TEA were added and reacted for 30 minutes. After the reaction was complete, the rotation speed was increased to 1300 r / min, and 220 parts of water were added within 2 minutes. After the addition was complete, the mixture was dispersed at high speed for 5 minutes. Then, 1 part of DETA solution was added dropwise, and the mixture was dispersed at high speed for 1 hour. After the dispersion was complete, acetone was removed to obtain the silicone-modified waterborne polyurethane emulsion (Si-WPU). 100 parts of Si-WPU and 3 parts of self-made anti-fouling and sound-absorbing additive were then added sequentially to the dispersion vessel and dispersed at 500 r / min for 1 hour to obtain leather anti-fouling and brightening agent 1.

[0034] Example 2 The preparation method of intermediate 1 is the same as that in Example 1.

[0035] 53 parts of dihydroxy silicone oil and 10 parts of UH200 were sequentially added to a four-necked flask equipped with a stirrer and thermometer. After the addition was complete, the mixture was stirred and heated to 110°C, and dehydrated at -0.1 to -0.085 MPa for 1 to 2 hours. After the moisture content was deemed acceptable, the temperature was lowered to 50°C, and 30 parts of IPDI and 0.1 parts of T12 were added. After the addition was complete, the temperature was raised to 90°C and held for 2 hours. Then, the temperature was lowered to 60°C, and 4 parts of DMPA, 4 parts of 6-hepten-2,4-diol, 4 parts of intermediate 1, and 10 parts of acetone were added. After the addition was complete, the temperature was raised to 60°C, and the reaction proceeded until the NCO content was between 1.84 and 1.94. The reaction was deemed acceptable if the concentration was within a certain range. The temperature was then lowered to 45°C, and 3 parts of TEA were added and reacted for 30 minutes. After the reaction was complete, the rotation speed was increased to 1300 r / min, and 220 parts of water were added within 2 minutes. After the addition was completed, the mixture was dispersed at high speed for 5 minutes, and then 1 part of DETA solution was added dropwise. After the addition was completed, the mixture was dispersed at high speed for 1 hour. After the dispersion was completed, acetone was removed to obtain the organosilicon-modified waterborne polyurethane emulsion (Si-WPU). Then, 100 parts of Si-WPU and 7 parts of self-made anti-fouling and sound-absorbing additive were added to the dispersion vessel in sequence and dispersed at 500 r / min for 1 hour to obtain leather anti-fouling and brightening agent 2.

[0036] Example 3 The preparation method of intermediate 1 is the same as that in Example 1.

[0037] 53 parts of dihydroxy silicone oil and 10 parts of UH200 were sequentially added to a four-necked flask equipped with a stirrer and thermometer. After the addition was complete, the mixture was stirred and heated to 110°C, and dehydrated at -0.1 to -0.085 MPa for 1 to 2 hours. After the moisture content was deemed acceptable, the temperature was lowered to 50°C, and 30 parts of IPDI and 0.1 parts of T12 were added. After the addition was complete, the temperature was raised to 90°C and held for 2 hours. Then, the temperature was lowered to 60°C, and 4 parts of DMPA, 6 parts of 6-hepten-2,4-diol, 6 parts of intermediate 1, and 10 parts of acetone were added. After the addition was complete, the temperature was raised to 60°C, and the reaction proceeded until the NCO content was between 1.84 and 1.94. The reaction was considered acceptable if the temperature was within % of the acceptable range. The temperature was then lowered to 45℃, and 3 parts of TEA were added and reacted for 30 minutes. After the reaction was complete, the rotation speed was increased to 1300 r / min, and 220 parts of water were added within 2 minutes. After the addition was completed, the mixture was dispersed at high speed for 5 minutes, and then 1 part of DETA solution was added dropwise. After the addition was completed, the mixture was dispersed at high speed for 1 hour. After the dispersion was completed, acetone was removed to obtain the silicone-modified waterborne polyurethane emulsion (Si-WPU). Then, 100 parts of Si-WPU and 7 parts of self-made anti-fouling and sound-absorbing additive were added to the dispersion vessel in sequence and dispersed at 500 r / min for 1 hour to obtain leather anti-fouling and brightening agent 3.

[0038] Example 4 The preparation method of intermediate 1 is the same as that in Example 1.

[0039] 53 parts of dihydroxy silicone oil and 10 parts of UH200 were sequentially added to a four-necked flask equipped with a stirrer and thermometer. After the addition was complete, the mixture was stirred and heated to 110°C, and dehydrated at -0.1 to -0.085 MPa for 1 to 2 hours. After the moisture content was deemed acceptable, the temperature was lowered to 50°C, and 30 parts of IPDI and 0.1 parts of T12 were added. After the addition was complete, the temperature was raised to 90°C and held for 2 hours. Then, the temperature was lowered to 60°C, and 4 parts of DMPA, 4 parts of 6-hepten-2,4-diol, 4 parts of intermediate 1, and 10 parts of acetone were added. After the addition was complete, the temperature was raised to 60°C, and the reaction proceeded until the NCO content was between 1.84 and 1.94. The reaction was considered acceptable if the temperature was within % of the acceptable range. The temperature was then lowered to 45°C, and 3 parts of TEA were added and reacted for 30 minutes. After the reaction was complete, the rotation speed was increased to 1300 r / min, and 220 parts of water were added within 2 minutes. After the addition was completed, the mixture was dispersed at high speed for 5 minutes. Then, 1 part of DETA solution was added dropwise, and the mixture was dispersed at high speed for 1 hour. After the dispersion was completed, acetone was removed to obtain the silicone-modified waterborne polyurethane emulsion (Si-WPU). 100 parts of Si-WPU and 10 parts of the self-made anti-fouling and sound-absorbing additive were then added to the dispersion vessel in sequence and dispersed at 500 r / min for 1 hour to obtain leather anti-fouling and brightening agent 4.

[0040] The above-obtained products underwent performance testing: the leather was sprayed or rolled with a stain-resistant brightener, dried, and then its performance, including physical properties and stain resistance, was tested. The results are shown in Table 1 below. Table 1 Performance Test Results performance Example 1 Example 2 Example 3 Example 4 Compatibility good good good good feel Skin feel Skin feel Skin feel Skin feel Resistant to stains on denim (Martindale - denim tested 1000 times) Level 5, uncontaminated Level 5, uncontaminated Level 5, uncontaminated Level 5, uncontaminated Durable ballpoint pen writing It can be erased after 10 writings. It can be erased after 10 writings. It can be erased after 10 writings. It can be erased after 10 writings. Dry-rub resistant (500 times) Level 5 No Wear Level 5 No Wear Level 5 No Wear Level 5 No Wear Resistant to wet rubbing (250 times) Level 5 No Wear Level 5 No Wear Level 5 No Wear Level 5 No Wear As can be seen from the above embodiments, the present invention provides a leather anti-fouling brightener with excellent comprehensive performance and its preparation method. The prepared brightener has good compatibility with leather substrates and forms a skin-friendly coating after application. This coating exhibits good protection against common stains (such as denim stains and ballpoint pen marks), and the stains are easy to wipe away. After multiple dry and wet rubbing tests, the coating itself showed no visible wear, and the anti-fouling performance remained stable, indicating that it has outstanding durability and long-lasting anti-fouling ability.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a stain-resistant and brightening agent for leather, characterized in that, Includes the following steps: S1. 6-Heptene-2,4-diol, trimethoxysilane and the first catalyst are mixed and reacted to remove low-boiling substances, and intermediate product 1 is obtained. S2. After dehydrating the hydroxyl-terminated silicone oil and polycarbonate diol, add isophorone diisocyanate and the second catalyst to react. Then add dimethylolpropionic acid, 6-hepten-2,4-diol, intermediate product 1 and acetone to continue the reaction until the isocyanate group content is qualified. Then add triethylamine to react. Then add water to emulsify under stirring. Finally add amine chain extender to disperse and remove acetone to obtain organosilicon modified waterborne polyurethane emulsion. S3. The organosilicon-modified waterborne polyurethane emulsion is mixed and dispersed with the anti-fouling additive to obtain an anti-fouling and brightening agent for leather.

2. The preparation method according to claim 1, characterized in that, The reaction described in step S1 is carried out at 70°C to 90°C for 4 to 6 hours.

3. The preparation method according to claim 1, characterized in that, The reaction following the addition of the isophorone diisocyanate in step S2 is carried out at 80°C to 95°C; the reaction following the addition of dimethylolpropionic acid, 6-hepten-2,4-diol, intermediate 1 and acetone is carried out at 55°C to 65°C.

4. The preparation method according to claim 1, characterized in that, In step S1, the first catalyst is a cassiterite catalyst; The amount of the first catalyst is 0.5% to 2% of the mass of the 6-hepten-2,4-diol.

5. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of 6-hepten-2,4-diol to trimethoxysilane is 1:0.8 to 1:1.

5.

6. The preparation method according to claim 1, characterized in that, The dehydration described in step S2 is carried out under negative pressure conditions; The mass ratio of the hydroxyl-terminated silicone oil to the polycarbonate diol is 3:1 to 7:

1. The amount of isophorone diisocyanate used is 40% to 60% of the total mass of the hydroxyl-terminated silicone oil and the polycarbonate diol; The second catalyst is T12.

7. The preparation method according to claim 1, characterized in that, The antifouling additive mentioned in step S3 is an antifouling and noise-absorbing additive.

8. The preparation method according to claim 7, characterized in that, The amount of the antifouling additive is 1% to 20% of the mass of the silicone-modified waterborne polyurethane emulsion.

9. A stain-resistant and brightening agent for leather, characterized in that, It is prepared by any one of claims 1 to 8.

10. A leather product, characterized in that, Its surface is coated with a coating formed by the anti-fouling and brightening agent for leather as described in claim 9.