A yellowing resistant platinum catalyst with extended cure time and method of making same

Abstract

The application relates to the technical field of platinum catalysts, and particularly discloses an anti-yellowing platinum catalyst capable of prolonging the curing time and a preparation method thereof. The platinum catalyst comprises a platinum metal compound, an alkenyl-containing siloxane compound, an alkaline metal salt, an organic solvent and a catalyst carrier; wherein the mass ratio of the platinum metal compound, the alkenyl-containing siloxane compound, the alkaline metal salt and the organic solvent is 1:(8-20):(1.2-3):(6-20). The platinum catalyst has the advantages of being capable of prolonging the curing time and having the anti-yellowing performance, and has a wide application scenario.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and in particular to an anti-yellow platinum catalyst with extended curing time and its preparation method. Background Technology

[0002] In the application of platinum catalysts, the development of industries such as industrial production and materials processing has placed higher demands on the performance of platinum catalysts. Existing problems with platinum catalysts limit their application in certain specific scenarios.

[0003] On the one hand, existing platinum catalysts have short curing times and short operating windows when catalyzing at room temperature. In actual production, especially for complex processes or situations requiring precise control of the reaction process, the short curing time makes it difficult for operators to fully complete preliminary operations such as mixing and molding, easily leading to unstable product quality or low production efficiency. For example, in the silicone molding process of some precision molds, because the platinum catalyst cures too quickly, the silicone has already cured before it has completely filled the mold, resulting in incomplete mold forming and an increased product scrap rate.

[0004] On the other hand, existing platinum catalyst-cured adhesives are prone to yellowing after baking. This problem seriously affects product quality in industries with high requirements for product appearance, such as electronic packaging and optical materials. For example, in electronic packaging, yellowing of the adhesive may affect the heat dissipation performance of electronic components, and it also fails to meet the high appearance requirements of electronic products, reducing their market competitiveness.

[0005] In response to the aforementioned technologies, the inventors believe that it is necessary to develop a platinum catalyst that can extend the curing time and has anti-yellowing properties. Summary of the Invention

[0006] To address the technical deficiencies of existing technologies, this application provides an anti-yellow platinum catalyst that extends curing time and its preparation method.

[0007] In a first aspect, this application provides an anti-yellow platinum catalyst that prolongs the curing time, employing the following technical solution: An anti-yellow platinum catalyst for extending curing time includes a platinum metal compound, an alkenyl-containing siloxane compound, an alkaline metal salt, an organic solvent, and a catalyst support; wherein the mass ratio of the platinum metal compound, the alkenyl-containing siloxane compound, the alkaline metal salt, and the organic solvent is 1:(8-20):(1.2-3):(6-20).

[0008] By adopting the above technical solution, the mass ratio can be precisely adapted to the functional synergy logic of each component. The platinum metal compound, as the catalytic active center, forms a stable platinum-alkenyl complex with the alkenyl siloxane compound in the correct ratio. This avoids both insufficient complexation leading to excessively high platinum activity and rapid curing, and excessive complexation causing catalytic deactivation. The ratio of alkaline metal salt to platinum metal compound neutralizes trace acidic impurities in the system, maintaining a stable complexation reaction environment. The amount of organic solvent ensures sufficient dissolution and dispersion of each component, avoiding side reactions induced by excessively high local concentrations. Ultimately, the curing time of the silicone oil compound corresponding to the catalyst can be stabilized within the mass production suitable range of 3.5–4.5 hours, while effectively suppressing yellowing factors. This solves the dual problems of uncontrolled curing rate and easy yellowing at high temperatures in traditional catalysts, balancing process operability and product appearance quality.

[0009] Preferably, the platinum metal compound is one of sodium chloroplatinate hexahydrate, potassium chloroplatinate hexahydrate, and platinum chloride hexahydrate.

[0010] By adopting the above technical solution, this type of platinum metal compound exhibits excellent solubility in organic solvents, can gradually dissociate and release stable platinum ions, providing uniform active centers for complexation reactions, and is free of impurity ions that easily induce oxidative degradation. Its coordination environment can form controllable complexes with alkenyl siloxanes, preventing excessively strong crosslinking reactions. This characteristic ensures catalyst activity stability, keeping the curing time fluctuation between different batches of products less than 10%, while avoiding the risk of yellowing caused by impurity residues. Combined with performance tests, it is shown that the cured adhesive using this type of platinum source catalyst remains transparent even after high-temperature baking.

[0011] Preferably, the alkenyl-containing siloxane compound is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri(β-methoxyethoxy)silane.

[0012] By adopting the above technical solution, the alkenyl groups in the molecular structure of this type of alkenyl siloxane can form strong coordination bonds with platinum ions, which can effectively regulate the catalytic activity of platinum to delay the crosslinking reaction rate. The etheroxy / methoxy groups in the siloxane segments can also improve the compatibility with organic solvents and carrier silicone oils. When used in combination, the coordination abilities of different siloxanes are complementary, which can further fine-tune the curing rate without destroying the stability of the complex. This can extend the curing time to the appropriate range required for mass production, and avoid ligand detachment leading to platinum ion-catalyzed oxidative degradation of silicone oil, achieving a breakthrough in anti-yellowing performance. Compared with traditional siloxane ligands in the comparative example, it can completely solve the problem of yellowing during high-temperature baking.

[0013] Preferably, the alkaline metal salt is sodium bicarbonate.

[0014] By adopting the above technical solution, sodium bicarbonate, as a weakly alkaline salt, can gently neutralize the trace amounts of hydrochloric acid produced by the dissociation of platinum metal compounds during the reaction, avoiding the acceleration of platinum catalytic activity in an acidic environment. Its alkalinity also prevents the hydrolysis of alkenyl siloxanes as a side reaction, and the residual sodium ions after the reaction have no catalytic oxidation effect. Compared to strongly alkaline salts, it does not damage the platinum-alkenyl complex structure; compared to weakly alkaline organic bases, it leaves no volatile impurities, stabilizes the pH value of the reaction system, ensures a complete and controllable complexation reaction, guarantees consistent curing time, and eliminates yellowing of the adhesive caused by alkaline impurities, ensuring a transparent and flawless adhesive after high-temperature baking.

[0015] Preferably, the organic solvent is one or more of ethanol and isopropanol.

[0016] By adopting the above technical solution, this type of organic solvent exhibits good solubility for platinum metal compounds, alkenyl siloxanes, and sodium bicarbonate, enabling the construction of a homogeneous reaction system to promote uniform complexation reactions. Furthermore, its moderate boiling point (78–82°C) allows for efficient removal via vacuum distillation, leaving no residual solvent to react with the silicone oil. This avoids curing rate fluctuations caused by uneven local reactions, thoroughly removes excess solvent to prevent it from affecting the transparency and weather resistance of the compound, and allows for adjustment of the system viscosity according to the material's solubility requirements during compounding, improving operational convenience.

[0017] Preferably, the catalyst support is a divinyl-terminated silicone oil with a viscosity of 0–1000 mPa*s.

[0018] By adopting the above technical solution, the terminal alkenyl groups of the divinyl-terminated silicone oil can form a weak interaction with the catalyst complex, achieving uniform dispersion and stable loading of the catalyst, avoiding the aggregation of platinum active centers. The viscosity range of 0–1000 mPa·s can adapt to the requirements of concentrate dilution and subsequent compound mixing. The low viscosity facilitates dilution operations, while the high viscosity can improve the dispersion persistence of the catalyst in the compound. Ultimately, it can ensure that the platinum content is uniform and stable after dilution (fluctuation ≤5%), avoiding the problem of excessively fast curing caused by excessively high local concentrations. At the same time, the carrier has excellent compatibility with the base silicone oil system, and will not introduce foreign matter that affects the transparency of the compound, providing auxiliary protection for anti-yellowing performance.

[0019] Preferably, the viscosity of the divinyl end-capped silicone oil is 350 mPa*s.

[0020] By adopting the above technical solution, a viscosity of 350 mPa·s is the optimal matching value for the carrier silicone oil. This not only ensures the fluidity of the catalyst stock solution during dilution, making it easy to stir evenly, but also forms a stable dispersion system after dilution, preventing catalyst sedimentation. Furthermore, this viscosity has a high degree of matching with the base silicone oil mixture, allowing for rapid dispersion and no agglomeration when added to the adhesive.

[0021] Secondly, this application provides a method for preparing a yellow platinum-resistant catalyst with extended curing time, using the following technical solution: A method for preparing a flavonoid-resistant catalyst with extended curing time includes the following steps: Step 1: Mix the platinum metal compound, the alkenyl-containing siloxane compound, and the organic solvent, and heat to 70-75°C, stirring until homogeneous; Step 2: Add alkaline metal salt and maintain the temperature while stirring for 180–210 minutes; Step 3: Allow to cool naturally to room temperature, then filter; Step 4: After filtration, excess organic solvents and alkenyl-containing siloxane compounds are removed to obtain the platinum catalyst stock solution. Step 5: Dilute the platinum catalyst stock solution with a catalyst support to obtain a platinum catalyst with a platinum content of 5000-10000 ppm.

[0022] By adopting the above technical solution, low-temperature heating at 70-75℃ promotes the smooth progress of the complexation reaction, while avoiding the decomposition of alkenyl siloxanes or the deactivation of platinum complexes caused by high temperatures. A stirring time of 180-210 minutes ensures a sufficient complexation reaction and reduces unreacted platinum ion residue (avoiding excessive activity). Natural cooling and filtration remove trace amounts of insoluble impurities. Subsequent removal of excess components improves catalyst concentration stability. A final platinum content of 5000-10000 ppm is suitable for most silicone oil crosslinking scenarios, balancing curing efficiency and operating window. The overall process allows for precise control of catalyst activity, stabilizing the curing time within the target range. Filtration and purification steps further reduce yellowing inducing factors. The diluted catalyst is uniformly dispersed, suitable for large-scale production, and exhibits excellent batch-to-batch performance consistency.

[0023] Preferably, the step four, which removes excess organic solvents and alkenyl-containing siloxane compounds, is performed by vacuum distillation.

[0024] By employing the above-mentioned technical solution, vacuum distillation can lower the boiling point of organic solvents and unreacted alkenyl siloxanes, efficiently removing impurities at low temperatures. This avoids the high-temperature damage to the platinum-alkenyl complex structure caused by conventional distillation and does not introduce new impurities. This operation can maximize the preservation of the stability of the catalyst's active center, ensure accurate concentration of the stock solution, and prevent excess ligands or solvent residues from affecting the subsequent curing and anti-yellowing properties of the adhesive. Compared with other purification methods, it also has the advantages of simple operation and high efficiency, making it suitable for industrial mass production.

[0025] Preferably, this application also includes the application of the above-mentioned anti-yellow platinum catalyst that prolongs the curing time in the preparation of the adhesive.

[0026] In summary, this application has the following beneficial effects: 1. Controllable curing rate adaptable to mass production requirements, significantly improving process feasibility and product yield. The core principle lies in precisely controlling the mass ratio of platinum metal compound and alkenyl siloxane compound to form a platinum-alkenyl complex with controllable activity. Sodium bicarbonate is used to gently neutralize the acidity of the system to stabilize the complexation environment. Simultaneously, a low-temperature process of 70–75℃ and a stirring time of 180–210 minutes ensure sufficient complexation reaction, avoiding excessive activity due to unreacted platinum ions. Based on this, the catalyst can stabilize the curing time of silicone oil adhesive within a suitable range of 3.5–4.5 hours, providing ample operating window for mass production processes such as coating and potting. This effectively avoids molding defects such as uneven adhesive distribution and residual bubbles caused by excessively rapid curing of traditional catalysts, while ensuring consistent performance across different batches, significantly improving the stability and yield of large-scale production.

[0027] 2. Excellent anti-yellowing properties expand the high-end application scenarios of the adhesive. The principle stems from the formation of a strong and stable complex between the selected vinyl silane ligand and platinum ions, effectively preventing ligand detachment that could lead to the oxidative degradation of silicone oil molecular chains catalyzed by platinum ions. Simultaneously, sodium bicarbonate inhibits side reactions induced by acidic environments, and the vacuum distillation process thoroughly removes excess solvent and unreacted ligands, eliminating yellowing factors caused by residual impurities. Thanks to this, the cured adhesive remains transparent even after baking at 130℃, completely overcoming the shortcomings of traditional catalysts that easily yellow at high temperatures. This meets the stringent requirements for appearance and weather resistance in applications such as optical device packaging and high-end electronic component sealing, significantly broadening the application areas and market value of the adhesive. Attached Figure Description

[0028] Figure 1 From left to right, these are the adhesives prepared using the catalysts from Examples 1 to 5;

[0029] Figure 2 From left to right, these are the rubber compounds prepared using catalysts from comparative examples 1 to 3. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the embodiments.

[0031] The raw materials used in the specific embodiments of this invention are all conventional commercially available products.

[0032] Example 1 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 10g of chloroplatinic acid hexahydrate, 60g of isopropanol, and 80g of vinyltrimethoxysilane in sequence. Turn on the water bath and slowly raise the temperature of the materials to 70°C. Simultaneously, start the stirrer and stir continuously for 30 minutes to ensure that the isopropanol, chloroplatinic acid, and vinyltrimethoxysilane are thoroughly mixed.

[0033] Step 2: After stirring continuously for 30 minutes, slowly add 12g of sodium bicarbonate. Maintain the temperature at 70℃ and continue stirring for 210 minutes to allow the reaction to proceed completely.

[0034] Step 3: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0035] Step 4: Place the filtered material in a vacuum distillation apparatus to remove excess isopropanol and vinyltrimethoxysilane by vacuum distillation, and obtain the platinum catalyst stock solution.

[0036] Step 5: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst stock solution obtained in the previous step until the platinum content reaches 10,000 ppm to prepare the required catalyst.

[0037] Example 2 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 12g of chloroplatinic acid hexahydrate, 96g of isopropanol, and 120g of vinyltriethoxysilane in sequence. Turn on the water bath and slowly raise the temperature of the materials to 70°C. Simultaneously, start the stirrer and stir continuously for 30 minutes to ensure that the isopropanol, chloroplatinic acid, and vinyltriethoxysilane are thoroughly mixed.

[0038] Step 2: After stirring continuously for 30 minutes, slowly add 16g of sodium bicarbonate. Maintain the temperature at 75℃ and continue stirring for 180 minutes to allow the reaction to proceed completely.

[0039] Step 3: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0040] Step 4: Place the filtered material in a vacuum distillation apparatus to remove excess isopropanol and vinyltriethoxysilane by vacuum distillation, thereby obtaining the platinum catalyst stock solution.

[0041] Step 5: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst stock solution obtained in the previous step until the platinum content reaches 10,000 ppm to prepare the required catalyst.

[0042] Example 3 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 15g of chloroplatinic acid hexahydrate, 150g of isopropanol, and 150g of vinyltris(β-methoxyethoxy)silane sequentially. Turn on the water bath and slowly raise the temperature of the materials to 70°C. Simultaneously, start the stirrer and stir continuously for 30 minutes to ensure thorough mixing of the isopropanol with the chloroplatinic acid and vinyltris(β-methoxyethoxy)silane.

[0043] Step 2: After stirring continuously for 30 minutes, slowly add 30g of sodium bicarbonate. Maintain the temperature at 75℃ and continue stirring for 210 minutes to allow the reaction to proceed completely.

[0044] Step 3: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0045] Step 4: Place the filtered material in a vacuum distillation apparatus to remove excess isopropanol and vinyltris(β-methoxyethoxy)silane by vacuum distillation to obtain the platinum catalyst stock solution.

[0046] Step 5: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst stock solution obtained in the previous step until the platinum content reaches 10,000 ppm to prepare the required catalyst.

[0047] Example 4 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 12g of chloroplatinic acid hexahydrate, 120g of isopropanol, 90g of vinyltrimethoxysilane, and 90g of vinyltriethoxysilane in sequence. Turn on the water bath and slowly raise the temperature of the materials to 70°C. Simultaneously, start the stirrer and stir continuously for 30 minutes to ensure that the isopropanol, chloroplatinic acid, and vinylsilane are thoroughly mixed.

[0048] Step 2: After stirring continuously for 30 minutes, slowly add 22g of sodium bicarbonate. Maintain the temperature at 70℃ and continue stirring for 180 minutes to allow the reaction to proceed completely.

[0049] Step 3: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0050] Step 4: Place the filtered material in a vacuum distillation apparatus to remove excess isopropanol and vinylsilane by vacuum distillation, and obtain the platinum catalyst stock solution.

[0051] Step 5: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst stock solution obtained in the previous step until the platinum content reaches 5000 ppm to prepare the required catalyst.

[0052] Example 5 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 20g of chloroplatinic acid hexahydrate, 180g of isopropanol, 120g of vinyltris(β-methoxyethoxy)silane, and 120g of vinyltriethoxysilane in sequence. Turn on the water bath and slowly raise the temperature of the materials to 75°C. Simultaneously, start the stirrer and stir continuously for 30 minutes to ensure that the isopropanol, chloroplatinic acid, and vinylsilane are thoroughly mixed.

[0053] Step 2: After stirring continuously for 30 minutes, slowly add 24g of sodium bicarbonate. Maintain the temperature at 75℃ and continue stirring for 210 minutes to allow the reaction to proceed completely.

[0054] Step 3: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0055] Step 4: Place the filtered material in a vacuum distillation apparatus to remove excess isopropanol and vinylsilane by vacuum distillation, and obtain the platinum catalyst stock solution.

[0056] Step 5: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst stock solution obtained in the previous step until the platinum content reaches 5000 ppm to prepare the required catalyst.

[0057] Comparative Example 1 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 10g of chloroplatinic acid hexahydrate, 55g of isopropanol, and 60g of divinyltetramethyldisiloxane in sequence. Turn on the water bath and slowly raise the temperature of the materials to 70°C. Simultaneously, start the stirrer and stir continuously for 30 minutes to ensure that the isopropanol, chloroplatinic acid, and vinylsilane are thoroughly mixed.

[0058] Step 2: After stirring continuously for 30 minutes, slowly add 12g of sodium bicarbonate. Maintain the temperature at 70℃ and continue stirring for 180 minutes to allow the reaction to proceed completely.

[0059] Step 3: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0060] Step 4: Place the filtered material in a vacuum distillation apparatus to remove excess isopropanol and vinylsilane by vacuum distillation, and obtain the platinum catalyst stock solution.

[0061] Step 5: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst stock solution obtained in the previous step until the platinum content reaches 10,000 ppm to prepare the required catalyst.

[0062] Comparative Example 2 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 10g of chloroplatinic acid hexahydrate, 60g of isopropanol, and 80g of tetramethyltetravinylcyclotetrasiloxane in sequence. Turn on the water bath and slowly raise the temperature of the materials to 80°C. Simultaneously, start the stirrer and stir continuously for 30 minutes to ensure that the isopropanol, chloroplatinic acid, and vinylsiloxane are thoroughly mixed.

[0063] Step 2: After stirring continuously for 30 minutes, slowly add 15g of sodium bicarbonate. Maintain the temperature at 80℃ and continue stirring for 180 minutes to allow the reaction to proceed completely.

[0064] Step 3: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0065] Step 4: Place the filtered material in a vacuum distillation apparatus to remove excess isopropanol and vinylsilane by vacuum distillation, and obtain the platinum catalyst stock solution.

[0066] Step 5: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst stock solution obtained in the previous step until the platinum content reaches 5000 ppm to prepare the required catalyst.

[0067] Comparative Example 3 A platinum catalyst is prepared by the following method: Step 1: Prepare a water bath equipped with a stirrer, condenser, and thermometer for the experiment. In a three-necked flask, add 10g of chloroplatinic acid hexahydrate and 300g of divinyltetramethyldisiloxane. Turn on the water bath and slowly raise the temperature of the materials to 120℃, while simultaneously starting the stirrer and stirring continuously for 90 minutes.

[0068] Step 2: After the reaction is complete, allow the material in the flask to cool to room temperature under natural conditions, and then filter it using filter paper.

[0069] Step 3: Take an appropriate amount of divinyl-terminated silicone oil and dilute the catalyst obtained in the previous step to a platinum content of 5000 ppm to prepare the desired catalyst.

[0070] Performance testing I. Sample Preparation Preparation of basic silicone oil mixtures: Accurately weigh 1000 grams of methyl vinyl silicone oil with a viscosity of 20000 and place it in a suitable container.

[0071] Add 100 grams of methyl hydrogen silicone oil with a mass fraction of 0.18% to the container.

[0072] Then add 0.05% of the total amount of 1-ethynylcyclohexanol inhibitor.

[0073] Use appropriate mixing equipment to thoroughly mix the components to obtain a basic silicone oil mixture.

[0074] Preparation of silicone oil test samples: Take several disposable cups and accurately weigh 50 grams of the well-stirred base silicone oil mixture into each cup.

[0075] Add the catalyst prepared in the example or comparative example at a dosage of 30 ppm to the silicone oil mixture in each disposable cup according to the set dosage. After addition, stir again to ensure that the catalyst is fully dispersed in the silicone oil mixture to obtain the test silicone oil sample.

[0076] II. Curing Time Test For each test silicone oil sample, timing begins the instant the catalyst is added and the mixture is stirred thoroughly.

[0077] Observe the state changes of the silicone oil samples. Record the time when the surface of the compound stops flowing completely; this time is the curing time. Each silicone oil sample should be measured three times, and the average value should be taken as the final curing time data to improve the accuracy and reliability of the data.

[0078] III. Anti-yellowing test Carefully place the fully cured adhesive, which has passed the curing time test, into the oven; Set the oven temperature to 130℃ and the baking time to 2 hours; After baking, remove the rubber compound and allow it to cool naturally to room temperature.

[0079] Observe the appearance of the rubber compound with the naked eye, paying particular attention to whether yellowing occurs. Record and describe the appearance characteristics of the rubber compound, such as color and color uniformity. The appearance characteristics are shown in the attached figure. Figure 1 and Figure 2 As shown, Figure 1 From left to right, these are the adhesives prepared using the catalysts from Examples 1 to 5. Figure 2 From left to right, these are the rubber compounds prepared using catalysts from comparative examples 1 to 3.

[0080] The results of the curing time test and the anti-yellowing test are shown in Table 1 below.

[0081] Table 1 Performance Test Results

[0082] As shown in Table 1, the platinum catalysts prepared in Examples 1-5, at an addition of 30 ppm, resulted in silicone oil curing times that remained stable within a moderate range of 3 hours 40 minutes to 4 hours 30 minutes. This duration provides ample processing window time for multiple steps in the production process, such as coating and pouring, effectively avoiding molding defects such as uneven distribution and residual bubbles caused by excessively rapid curing, thus significantly improving production yield. In contrast, the catalysts in Comparative Examples 1-3 resulted in curing times of only 25 minutes to 1 hour 30 minutes. This excessively rapid curing rate significantly compressed the processing time, making it difficult to precisely control the morphology of the silicone oil in large-scale production and thus lacking practical mass production feasibility. Furthermore, the... The cured adhesives prepared in the examples maintained a completely transparent appearance after being baked at 130°C for 2 hours, without any yellowing or fogging. This indicates that the catalyst of the present invention does not trigger oxidative degradation of the silicone oil system during the catalytic crosslinking reaction, thus preventing yellowing. It can maintain the optical transparency and appearance consistency of the product for a long time, making it suitable for applications with stringent appearance quality requirements, such as optical device packaging. In contrast, the cured adhesives of Comparative Examples 1-3 all showed obvious yellowing after baking under the same conditions. It is speculated that improper ligand selection or reaction conditions deviating from the scope of the present invention led to the catalyst inducing molecular chain breakage or oxidation of the adhesive during subsequent high-temperature use, which seriously affected the product's aesthetics and weather resistance.

[0083] In summary, the platinum catalysts of Examples 1-5 of this invention achieve both controllable curing rate and excellent anti-yellowing performance by selecting vinylsilane ligands with specific structures and precisely controlling the reaction temperature and stirring time. In contrast, the comparative examples could not achieve the above-mentioned core performance due to improper ligands or reaction conditions. This further proves that the technical solution of this invention has significant inventiveness and practicality, and has outstanding advantages over the prior art.

[0084] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A flavonoid-resistant catalyst for extending curing time, characterized in that: It includes platinum metal compounds, alkenyl-containing siloxane compounds, basic metal salts, organic solvents and catalyst supports; wherein the mass ratio of platinum metal compounds, alkenyl-containing siloxane compounds, basic metal salts and organic solvents is 1:(8-20):(1.2-3):(6-20).

2. The anti-yellow platinum catalyst for extending curing time according to claim 1, characterized in that: The platinum metal compound is one of sodium chloroplatinate hexahydrate, potassium chloroplatinate hexahydrate, and platinum chloride hexahydrate.

3. The anti-yellow platinum catalyst for extending curing time according to claim 1, characterized in that: The alkenyl-containing siloxane compound is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri(β-methoxyethoxy)silane.

4. The anti-yellow platinum catalyst for extending curing time according to claim 1, characterized in that: The alkaline metal salt is sodium bicarbonate.

5. The anti-yellow platinum catalyst for extending curing time according to claim 1, characterized in that: The organic solvent is one or more of ethanol and isopropanol.

6. The anti-yellow platinum catalyst for extending curing time according to claim 1, characterized in that: The catalyst support is a divinyl-terminated silicone oil with a viscosity of 0–1000 mPa*s.

7. The anti-yellow platinum catalyst for extending curing time according to claim 6, characterized in that: The viscosity of the divinyl end-capped silicone oil is 350 mPa*s.

8. A method for preparing a flavonoid-resistant catalyst with extended curing time according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Mix the platinum metal compound, the alkenyl-containing siloxane compound, and the organic solvent, and heat to 70-75°C, stirring until homogeneous; Step 2: Add alkaline metal salt and maintain the temperature while stirring for 180–210 minutes; Step 3: Allow to cool naturally to room temperature, then filter; Step 4: After filtration, excess organic solvents and alkenyl-containing siloxane compounds are removed to obtain the platinum catalyst stock solution. Step 5: Dilute the platinum catalyst stock solution with a catalyst support to obtain a platinum catalyst with a platinum content of 5000-10000 ppm.

9. The method for preparing a flavonoid-resistant catalyst with extended curing time according to claim 8, characterized in that: The fourth step, the treatment to remove excess organic solvents and alkenyl-containing siloxane compounds, is vacuum distillation.

10. The application of the anti-yellow platinum catalyst for extending curing time according to any one of claims 1 to 7 in the preparation of adhesives.

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