Preparation method of composite mercaptan octyltin

Abstract

The invention discloses a preparation method of composite mercaptan octyltin, and belongs to the technical field of organic tin compound preparation. According to the method, a mixture of isooctyl thioglycolate and octyl tin chloride and specific alkali liquor are used as raw materials, and the product is prepared through the steps of raw material preparation, reaction device preparation, reaction, aftertreatment and the like. The raw material ratio is accurate, the reaction condition is mild, and post-treatment comprises standing for phase separation, washing, reduced pressure distillation for water removal and filtration. The preparation method has the remarkable advantages that the product purity is high, the stability is good, and the high requirement on the heat stabilizer in the fields of PVC material processing and the like can be met; meanwhile, the technological process is simplified, the production period is shortened, and the production cost is greatly reduced; and moreover, less three wastes are generated in the reaction, the environment-friendly performance is good, and the method has important industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of organotin compounds, and in particular to a preparation method of a composite mercapto octyltin. Background Art

[0002] In modern industrial production, due to its excellent comprehensive properties such as mechanical strength, chemical corrosion resistance, electrical insulation, etc., PVC materials are widely used in many fields such as construction, packaging, electronics, etc. However, PVC materials have the problem of poor thermal stability during processing. When heated, they are prone to degradation, resulting in deterioration of material properties and darkening of color, seriously affecting the product quality and service life. Therefore, heat stabilizers are crucial in the processing of PVC materials.

[0003] Organotin heat stabilizers stand out among many heat stabilizers due to their low dosage and significant heat stabilization effect, and have received high attention in the industry. Among them, mercaptotin heat stabilizers have particularly excellent performance. Especially mercapto octyltin not only shows excellent performance in heat stability, can effectively inhibit the thermal degradation of PVC materials during processing, but also has excellent transparency and does not affect the optical properties of PVC products. This makes it have broad application prospects in fields with extremely high requirements for material safety and transparency such as food packaging and medical supplies.

[0004] Although certain achievements have been made in the production of some basic organotin products in the prior art. For example, Yunnan Tin Company can stably produce composite products of mercapto mono octyltin and mercapto di octyltin. However, in the development of mercapto octyltin, most are still in the laboratory research stage. There are very few domestic manufacturers with the ability to produce mercapto octyltin on a large scale, and the market supply is seriously insufficient, relying heavily on imports. This not only increases the production costs of domestic related enterprises, but also restricts the development of downstream industries such as PVC material processing.

[0005] Therefore, developing a preparation method of a composite mercapto octyltin that is efficient, stable and has a cost advantage is a technical problem that needs to be urgently solved by those skilled in the art, which can promote the development of the tin chemical industry and meet the market demand. Summary of the Invention

[0006] In view of this, the present invention provides a preparation method of a composite mercapto octyltin that is efficient, stable and has a cost advantage.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method of a composite mercapto octyltin, comprising the following steps:

[0009] (1) Weigh isooctyl mercaptoacetate, and then weigh the octyltin chloride mixture for standby;

[0010] (2) Add isooctyl thioglycolate to the reaction vessel and stir. Meanwhile, slowly dropwise add a mixture of an alkali solution and octyltin dichloride to carry out the reaction;

[0011] (3) After the reaction is completed, carry out static phase separation, water washing, vacuum distillation to remove water, and filtration in sequence to obtain the composite mercaptan octyltin.

[0012] Furthermore, in step (1), the mass ratio of isooctyl thioglycolate to the octyltin dichloride mixture is 1.44 - 1.94:1.

[0013] Moreover, the octyltin dichloride mixture is obtained by mixing dioctyltin dichloride and monooctyltin trichloride in a mass ratio of 6:4 - 9:1.

[0014] Furthermore, in step (2), the alkali solution is any one of ammonia water, sodium carbonate solution, and sodium hydroxide solution;

[0015] The mass concentration of the alkali solution is 10% - 12%.

[0016] The actual dosage of the alkali solution is 1.05 - 1.15 times the theoretically calculated amount.

[0017] Moreover, during the dropping of the alkali solution, control the pH to be 8 - 9.

[0018] The dropping rate of the slow dropping is 1 - 2 drops / s.

[0019] Furthermore, in step (2), the reaction temperature is 50 - 70 °C and the reaction time is 0.5 - 1 h.

[0020] In the solution of the present invention, a suitable reaction vessel needs to be selected for the reaction, such as a four-neck reaction flask. Clean and dry it to ensure that there is no residue of impurities and moisture. Install equipment such as a stirring device, a thermometer, and a dropping funnel, and check the tightness of the device to prevent leakage of materials during the reaction.

[0021] During the dropping process, it is necessary to maintain the temperature at 50 - 70 °C.

[0022] Furthermore, in step (3), the static phase separation time is 10 - 15 min.

[0023] Furthermore, in step (3), the number of water washing times is 2 - 3 times. The temperature of each water washing is 50 - 60 °C, and stir for 30 min each time. Wash until the pH of the aqueous phase is 7 - 8.

[0024] Furthermore, in step (3), the temperature for vacuum distillation to remove water is 80 - 100 °C, and the vacuum degree is 70 Kpa - 90 Kpa.

[0025] Compared with the prior art, the preparation method of the composite mercapto octyl tin of the present invention has significant advantages:

[0026] 1. Solvent advantage: The present invention only needs to use water as the solvent (the water in the lye). Water is non-toxic, harmless and easy to desolvate, avoiding the safety hazards and environmental pollution problems caused by the use of toxic and harmful solvents in the traditional process. At the same time, the solvent removal process is simplified, reducing the production cost and production risk.

[0027] 2. Product separation advantage: The present invention can change the upper and lower layer positions of the product in the solution after the reaction by adjusting the addition ratio of the solvent, which provides great convenience for the separation of the product, enables more efficient separation of the product from other components of the reaction system, and improves the production efficiency.

[0028] 3. Chromaticity control advantage: The present invention can control the chromaticity of the composite mercapto octyl tin by adjusting the color of octyl tin chloride, accurately control the appearance quality of the product, meet the strict requirements of different customers for the chromaticity of the product, and broaden the application range of the product.

[0029] 4. Product diversification advantage: The present invention can prepare composite mercapto octyl tin with different main contents by adjusting the material ratio, providing diversified product choices for the market, better meeting the differentiated requirements of different fields for the performance of mercapto octyl tin products, and enhancing the market competitiveness of the products.

[0030] 5. Environmental protection advantage: No pollutants such as waste gas and waste residue are generated during the production process of the present invention, and the raw material conversion rate is high. It not only reduces environmental pollution, but also improves resource utilization rate, conforms to the concept of sustainable development, and provides a strong guarantee for the green production of enterprises.

[0031] 6. Product and solvent separation advantage: After the reaction of the present invention, the product and the solvent are immiscible and will form an obvious layering phenomenon. Only a small amount of water will be mixed in the product, which makes the separation and purification of the product simpler and more efficient, reducing the difficulty and cost of subsequent treatment.

[0032] 7. Differential ratio advantage: To further demonstrate the unique advantages of the present application within the limited ratio range, a comparative example is specifically set and the product performance is characterized in detail. When the composite mercapto octyl tin prepared under different proportions of octyl tin chloride is applied to PVC materials, significantly different thermal stability performance and appearance characteristics are presented.

[0033] When the ratio of dioctyltin dichloride to monooctyltin trichloride in the mixture is set to 8:2, a PVC thermal stability test is carried out, and the results are remarkable. At this ratio, not only can the thermal stability performance of PVC be significantly improved, effectively prolonging the duration of PVC's resistance to thermal degradation during processing, but also the whiteness and transparency of PVC can be simultaneously enhanced. After testing, PVC products using the composite mercapto octyltin prepared at this ratio as a heat stabilizer have significantly increased whiteness and show higher transparency when light passes through, greatly meeting the requirements of fields with strict appearance quality and optical performance requirements for PVC products, such as high-end packaging and the manufacture of optical instrument components.

[0034] On the contrary, in the comparative example, if only dioctyltin dichloride is used to prepare the product, in the thermal stability test, although the thermal stability test time is extended, showing a certain thermal stability effect, at the initial stage of the test, the color of the product turns slightly yellow, and the light transmittance of the made PVC plastic sheet is poor. This situation is undoubtedly a serious defect for application scenarios with extremely high requirements for color and light transmittance, such as food packaging and the manufacture of medical appliances, greatly limiting the scope of application of the product.

[0035] When only monooctyltin trichloride is used, the situation is equally unoptimistic. During the overall thermal stability test of this product, although the color performance is good, the thermal stability persistence time is extremely short. When tested on a two-roll thermal stability tester, the PVC added with this product quickly turns black-green, indicating that serious thermal degradation has occurred to the PVC, and the material properties have severely deteriorated, and it simply cannot meet the basic requirements for PVC thermal stability in actual production.

[0036] Through comprehensive comparison, it can be seen that the ratio range of the octyltin chloride mixture defined in this application can achieve a good balance of thermal stability performance, whiteness, and transparency when preparing the composite mercapto octyltin, providing an excellent heat stabilizer choice for related industries such as PVC material processing.

[0037] 8. Advantages of desalting by washing: The desalting by washing of the present invention is carried out at room temperature, with less energy consumption and short time consumption, and the number of washing times and the amount of water can be adjusted according to product requirements, which can not only ensure product quality but also flexibly control production costs, improving the controllability and adaptability of the production process.

[0038] 9. Product quality advantages and industrialization advantages: The synthesis method of the present invention well solves the problems of unstable mercapto octyltin content, large color difference, and unqualified transparency. The synthesis equipment is relatively general equipment, the synthesis conditions are mild, without extreme conditions such as high temperature, high pressure, and low temperature, and no toxic and harmful substances are generated. The entire process flow requires fewer reaction kettles and shorter reaction time, so it is easy to realize industrialization, reducing the threshold of industrial production and being conducive to large-scale popularization and application.

[0039] In terms of product quality, by precisely setting the mass ratio of isooctyl thioglycolate to octyltin chloride to be 1.44 - 1.94:1, strictly controlling the proportion of each component in the octyltin chloride mixture to be 6:4 - 9:1, and accurately regulating the reaction temperature to be 50 - 70 °C and the pH value to be 8 - 9 and other key reaction conditions, the occurrence of side reactions is effectively reduced, and the purity and stability of the product are greatly improved. This enables the prepared composite mercaptan octyltin to more efficiently inhibit the thermal degradation of PVC when used as a heat stabilizer in the processing of PVC materials, significantly enhancing the quality and performance of PVC products and meeting the strict requirements for the thermal stability and transparency of PVC materials in high-end fields.

[0040] In the process flow, the present invention optimizes and integrates the traditional preparation process, abandons the cumbersome and complex steps, shortens the production cycle, and improves the production efficiency. By selecting a suitable reaction vessel (such as a four-neck reaction flask), equipped with equipment such as a stirring device, a thermometer, a dropping funnel, etc., and reasonably arranging the reaction process, the entire preparation process is made more compact and efficient, reducing the time cost and labor cost in the production process.

[0041] The reaction conditions of the present invention are mild, without harsh conditions such as high temperature and high pressure, reducing energy consumption and lowering the energy consumption cost. At the same time, the simple reaction equipment and mild reaction conditions also reduce the equipment investment and maintenance cost, making the product more competitive in price in the market.

[0042] In terms of environmental protection, the present invention fully considers the needs of sustainable development. The amount of three wastes generated during the reaction process is small and easy to handle, greatly reducing the pressure on the environment, meeting the requirements of the increasingly strict global environmental protection regulations, and providing a strong guarantee for the sustainable development of enterprises.

[0043] The beneficial effects of the present invention are as follows:

[0044] (1) Improvement in product quality: Precise raw material ratio and reaction condition control effectively reduce side reactions, improve product purity and stability, and make it perform better in heat stabilizer applications.

[0045] (2) Simplified and efficient process: Integrating reaction steps, shortening the production cycle, improving production efficiency, and reducing production costs.

[0046] (3) Significant cost reduction: Low raw material cost, mild reaction conditions, low energy consumption, and reduced equipment investment and maintenance cost.

[0047] (4) Outstanding environmental protection advantages: Less three wastes are generated during the reaction process, which are easy to handle and meet environmental protection requirements. Description of the Drawings

[0048] Figure 1 It is the process flow chart provided by the present invention. Detailed implementation mode

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0050] Example 1

[0051] (1) Raw material preparation: Weigh 189.66 grams of isooctyl thioglycolate, 101.68 grams of octyl tin chloride mixture (the mass ratio of dioctyltin dichloride to monooctyltin trichloride is 60:40), and prepare 158.38 grams of ammonia water with a mass fraction of 10% (the actual amount used is 1.1 times the theoretically calculated amount).

[0052] (2) Reaction device preparation: Wash and dry the four-neck reaction flask, install a stirring device, a thermometer and a dropping funnel, and check the sealing performance.

[0053] (3) Reaction process: Add isooctyl thioglycolate to the reaction flask and start stirring. At the same time, slowly dropwise add ammonia water and octyl tin chloride mixture, control the reaction temperature at 60 °C, and continue stirring. After the dropping is completed, raise the temperature to 65 °C and keep the temperature constant for 0.5 h. During the reaction process, control the pH at 8.5.

[0054] (4) Post-treatment: After the reaction is completed, stop stirring and let it stand for phase separation for 15 min. Take the lower organic phase and wash it 3 times with distilled water. Keep the temperature at 60 °C for each water wash and stir for 30 min until the pH of the aqueous phase is 7-8. The washed organic phase is subjected to vacuum distillation to remove water. The distillation temperature is 100 °C and the vacuum degree is 80 Kpa. Finally, filter to obtain the composite mercaptan octyltin product.

[0055] Product indicators: Sn%: 15.80%, S%: 11.48%, refractive index: 1.5076, viscosity: 68.87, specific gravity: 1.1313.

[0056] Example 2

[0057] (1) Raw material preparation: Accurately weigh 77.07 grams of isooctyl thioglycolate, and this mass is determined according to the mass ratio range of isooctyl thioglycolate to octyltin chloride set by the present invention. At the same time, weigh 50.56 grams of octyltin chloride mixture, and the mass ratio of each component in the octyltin chloride mixture is 82:18 (dioctyltin dichloride to monooctyltin trichloride). Then, prepare 101.54 grams of sodium carbonate solution with a mass fraction of 10%, and this dosage is 1.08 times the theoretically calculated amount to ensure the full progress of the reaction. During the raw material preparation process, use high-precision weighing equipment to ensure the accuracy of the raw material quality, laying a foundation for the smooth progress of the subsequent reaction and the stability of the product quality.

[0058] (2) Reaction device preparation: Select a four-neck reaction flask as the reaction vessel, carefully wash and dry it to remove any possible residual impurities and moisture to avoid interfering with the reaction. Install a stirring device, a thermometer, and a dropping funnel, ensuring that each device is firmly installed and in a reasonable position. The stirring device is used to fully mix the reaction materials to promote the reaction; the thermometer can monitor the reaction temperature in real time to provide a basis for accurately controlling the reaction conditions; the dropping funnel is used to accurately control the dropping rate of the raw materials. After installation, strictly check the sealing performance of the entire device to ensure that the materials will not leak during the reaction and guarantee the stability of the reaction environment.

[0059] (3) Reaction process: Carefully add the weighed isooctyl thioglycolate to the four-neck reaction flask, turn on the stirring device to make the isooctyl thioglycolate evenly disperse in the reaction flask. Slowly drip the sodium carbonate solution and the octyltin chloride mixture simultaneously through the dropping funnel. During the dropping process, closely monitor the change in the reaction temperature, and maintain the reaction temperature between 60 °C by controlling the dropping rate. Continuously stir to make the reaction materials fully contact to ensure the full progress of the reaction. After the dropping is completed, raise the reaction temperature to 65 °C and keep the temperature constant for 0.5 h. During the entire reaction process, use a pH monitoring device to monitor the pH value of the reaction system in real time, and strictly control the pH between 8-9 by adding an appropriate amount of sodium carbonate solution or other regulating substances to ensure that the reaction proceeds under the best conditions.

[0060] (4) Post-treatment: After the reaction is completed, stop stirring and let the reaction product stand for phase separation for 15 min. Since the reaction product is divided into an organic phase and an aqueous phase, after standing for phase separation, carefully take the lower organic phase. Wash the organic phase with distilled water 3 times. During each washing, keep the temperature at 60 °C and stir for 30 min to fully dissolve the impurities in the organic phase into the water. Judge the washing effect by detecting the pH value of the aqueous phase until the pH of the aqueous phase is 7.5, indicating that the organic phase has been cleaned. The washed organic phase is subjected to vacuum distillation to remove water. Control the distillation temperature at 100 °C and set the vacuum degree at 80 Kpa to remove the residual water in the organic phase. Finally, filter to remove possible insoluble impurities to obtain the composite mercapto octyltin product.

[0061] After testing, the product indicators are: Sn%: 17.64%, S%: 10.43%, refractive index: 1.5072, viscosity: 58.29, specific gravity: 1.1304.

[0062] Example 3

[0063] (1) Raw material preparation: According to the requirements of the present invention, accurately weigh 73.52 g of isooctyl mercaptoacetate and 50.90 g of octyltin chloride mixture, wherein the mass ratio of each component in the octyltin chloride mixture is 90:10. Prepare 68.35 g of a sodium carbonate solution with a mass fraction of 10%, and its dosage is 1.06 times the theoretically calculated amount. During the weighing process, strictly control the mass of each raw material to ensure that the error is within the allowable range, ensure the accurate ratio of the raw materials, and provide an accurate material basis for the subsequent reaction.

[0064] (2) Reaction device preparation: The same as in Example 1, select a washed and dried four-neck reaction flask, install a stirring device, a thermometer and a dropping funnel, and carefully check the tightness of the device to ensure that the device can operate stably during the reaction, prevent material leakage and external impurities from entering the reaction system.

[0065] (3) Reaction process: Add isooctyl mercaptoacetate to the reaction flask and start stirring to make the isooctyl mercaptoacetate evenly distributed. At the same time, slowly drop the sodium carbonate solution and the octyltin chloride mixture, control the reaction temperature at 60 °C, and continuously stir to make the reaction sufficient. After the dropping is completed, raise the temperature to 65 °C and keep the temperature constant for 40 min. During the reaction process, strictly control the pH at 8-9, and maintain the acid-base balance of the reaction system by adjusting the dropping rate and adding necessary adjusting substances to ensure the smooth progress of the reaction.

[0066] (4) Post-treatment: After the reaction is completed, stop stirring and let it stand for phase separation for 15 min. Take the lower organic phase and wash it 3 times with distilled water. Keep the temperature of each water wash at 60 °C and stir for 30 min until the pH of the aqueous phase is 7 - 8. Carry out vacuum distillation to remove water from the washed organic phase. Control the distillation temperature at 100 °C and the vacuum degree at 80 Kpa. Finally, carry out filtration to obtain the composite mercapto octyltin product.

[0067] After testing, the indicators of this product are: Sn%: 17.28%, S%: 10.44%, refractive index: 1.5058, viscosity: 41.02, specific gravity: 1.1254.

[0068] Example 4

[0069] (1) Raw material preparation: Accurately weigh 189.82 g of isooctyl mercaptoacetate and 100.59 g of octyltin chloride mixture. The mass ratio of each component in the octyltin chloride mixture is 74:26. Prepare 183 g of sodium hydroxide solution with a mass fraction of 10%, and the actual usage is 1.12 times the theoretically calculated amount. In the raw material preparation stage, use professional weighing instruments to ensure the accurate mass of each raw material, providing a reliable guarantee for the smooth progress of the subsequent reaction.

[0070] (2) Reaction device preparation: The same as Example 1, select a four-neck reaction flask. After washing and drying, install a stirring device, a thermometer and a dropping funnel, and comprehensively check the airtightness of the device to ensure the stability and safety of the reaction environment.

[0071] (3) Reaction process: Add isooctyl mercaptoacetate to the reaction flask and start stirring. At the same time, slowly drip the sodium hydroxide solution and the octyltin chloride mixture, control the reaction temperature at 60 °C, and continuously stir to promote the reaction. After the dropping is completed, raise the temperature to 65 °C and keep the reaction at a constant temperature for 50 min. During the reaction process, closely monitor the pH value and keep it at 8 - 9. By adjusting the reaction conditions and adding corresponding substances, ensure that the reaction proceeds under the best conditions.

[0072] (4) Post-treatment: After the reaction is completed, stop stirring and let it stand for phase separation for 15 min. Take the lower organic phase and wash it 3 times with distilled water. The temperature of each water wash is 60 °C and stir for 30 min until the pH of the aqueous phase is 7 - 8. Carry out vacuum distillation to remove water from the washed organic phase. Set the distillation temperature at 100 °C and the vacuum degree at 80 Kpa. Finally, carry out filtration to obtain the composite mercapto octyltin product.

[0073] After testing, the indicators of this product are: Sn%: 15.98%, S%: 11.36%, refractive index: 1.5080, viscosity: 45.24, specific gravity: 1.1270.

[0074] Example 5

[0075] (1) Raw material preparation: Weigh 768.63 grams of isooctyl mercaptoacetate and 405.31 grams of octyltin chloride mixture, where the mass ratio of each component in the octyltin chloride mixture is 60:40. Prepare 347.2 grams of sodium carbonate solution with a mass fraction of 10%, and its dosage is 1.07 times the theoretically calculated amount. During the weighing process, strictly follow the operating procedures and use high-precision weighing equipment to ensure the accuracy of the raw material quality, providing key material conditions for the successful progress of the reaction.

[0076] (2) Reaction device preparation: Consistent with Example 1, select a washed and dried four-neck reaction flask, install a stirring device, a thermometer, and a dropping funnel, and carefully check the tightness of the device to ensure the stability and reliability of the device during the reaction, preventing material leakage and interference from external factors to the reaction.

[0077] (3) Reaction process: Add isooctyl mercaptoacetate to the reaction flask and start stirring. At the same time, slowly dropwise add the sodium carbonate solution and the octyltin chloride mixture, control the reaction temperature at 60 °C, and continuously stir to make the reaction sufficient. After the dropping is completed, raise the temperature to 65 °C and keep the temperature constant for 1 h. During the reaction process, strictly control the pH at 8 - 9 to ensure that the reaction proceeds in a suitable acid-base environment.

[0078] (4) Post-treatment: After the reaction is completed, stop stirring and let it stand for phase separation for 15 min. Take the lower organic phase and wash it 3 times with distilled water, with the temperature of each water wash maintained at 60 °C and stir for 30 min until the pH of the aqueous phase is 7 - 8. Carry out vacuum distillation to remove water from the washed organic phase, control the distillation temperature at 100 °C, and the vacuum degree at 80 Kpa. Finally, carry out filtration to obtain the composite mercaptan octyltin product.

[0079] After testing, the indicators of this product are: Sn%: 16.04%, S%: 12.02%, refractive index: 1.5068, viscosity: 84.50, specific gravity: 1.1316.

[0080] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A preparation method of a composite mercapto octyltin, characterized in that, It includes the following steps: (1) Weigh isooctyl thioglycolate, and then weigh the octyltin chloride mixture for standby; (2) Add isooctyl thioglycolate into the reaction vessel and stir, while slowly dropping the alkali solution and the octyltin chloride mixture. After the dropping is completed, carry out a constant temperature reaction; (3) After the reaction is completed, carry out static phase separation, water washing, vacuum distillation for water removal, and filtration in sequence to obtain the composite mercaptan octyltin.

2. The preparation method of a composite mercapto octyltin according to claim 1, characterized in that, In step (1), the mass ratio of isooctyl thioglycolate to the octyltin chloride mixture is 1.44 - 1.94:

1.

3. The preparation method of a composite mercapto octyl tin according to claim 2, characterized in that, The octyltin chloride mixture is obtained by mixing dioctyltin dichloride and monooctyltin trichloride according to the mass ratio of 6:4 - 9:

1.

4. The preparation method of a composite mercapto octyl tin according to claim 1, characterized in that, In step (2), the alkali solution is any one of ammonia water, sodium carbonate solution and sodium hydroxide solution; The mass concentration of the alkali solution is 10% - 12%.

5. The preparation method of a composite mercapto octyltin according to claim 4, characterized in that, Control the pH to be 8 - 9 during the dropping of the alkali solution; The dropping rate of the slow dropping is 1 - 2 drops / s.

6. The preparation method of a composite mercapto octyl tin according to claim 1, characterized in that, In step (2), the reaction temperature is 50 - 70°C and the reaction time is 0.5 - 1 h.

7. The preparation method of a composite mercapto octyltin according to claim 1, characterized in that, In step (3), the static phase separation time is 10 - 15 min.

8. The preparation method of a composite mercapto octyltin according to claim 1, characterized in that, In step (3), the number of water washing times is 2 - 3 times. The temperature of each water washing is 50 - 60°C, and stir for 30 min each time. Wash until the pH of the aqueous phase is 7 - 8.

9. The preparation method of a composite mercapto octyltin according to claim 1, characterized in that, In step (3), the temperature for vacuum distillation for water removal is 80 - 100°C and the vacuum degree is 70 Kpa - 90 Kpa.

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