Process for the preparation of high purity si-75

Abstract

This invention discloses a method for preparing high-purity Si-75, comprising: S1, adding sodium sulfide, sulfur, and deionized water in a molar ratio of 1:(1.0~1.1):(5~8) to a reaction vessel, adding a buffer, and reacting at 80~90℃ for 1~2h; S2, adding a phase transfer catalyst and a hydrolysis inhibitor to the system, adding γ-chloropropyltriethoxysilane dropwise, and reacting at 85~95℃ for 3~5h, allowing the mixture to stand and separate into layers after the reaction, to obtain an organic phase; S3, subjecting the organic phase to short-path distillation and then filtering to obtain high-purity Si-75. Compared with existing technologies, this invention uses a phosphorus-free buffer system, which simplifies waste treatment. It uses water as the reaction medium and does not use large amounts of organic solvents, making it suitable for continuous industrial production. By adding hydrolysis inhibitors, hydrolysis can be effectively prevented during the reaction, increasing safety. The short-path distillation method provides high purification efficiency and can quickly remove impurities. The product has a disulfide content of ≥98.5% and a color of 0 (Gardner color number), which is of great significance to the light-colored rubber industry.

Description

Technical Field

[0001] This invention relates to the field of organosilicon compound preparation technology, and in particular to a method for preparing high-purity Si-75. Background Technology

[0002] Bis(propyltriethoxysilane) disulfide, known in the industry as Si-75, is a sulfur-containing silane coupling agent used in rubber and tires. Its core function is to form covalent molecular bridges between inorganic fillers such as silica and the rubber matrix. The siloxane groups in Si-75 can react with the hydroxyl groups on the surface of silica, and the sulfur atoms can participate in the vulcanization crosslinking of rubber. It can significantly improve the tensile and tear strength of rubber, enhance wear resistance and wet skid resistance, while reducing frictional heat generation, reducing tire rolling resistance, increasing fatigue resistance, and improving fuel economy and driving safety.

[0003] Existing synthesis processes for Si-75 mainly include solvent methods and aqueous phase methods. Under these processes, the disulfide content in Si-75 is between 70% and 80%, and there are generally problems such as numerous byproducts, high levels of polysulfide bond impurities (trisulfides, tetrasulfides, etc.), and low product purity. This leads to uneven dispersion, inconsistent vulcanization rates, and uneven crosslinking density during rubber compounding, significantly impacting the mechanical properties and service life of rubber products.

[0004] Meanwhile, existing aqueous phase processes often use phosphorus-containing buffers such as sodium dihydrogen phosphate, trisodium phosphate, and disodium hydrogen phosphate, leading to difficulties in wastewater treatment, eutrophication of water bodies, and environmental pollution. Conventional solvent-based production processes use solvents such as toluene and ethanol, requiring strict dehydration of raw materials, resulting in high solvent recovery costs, high energy consumption, significant safety hazards, low efficiency, and heavy environmental pressure. Due to hydrolysis issues, conventional aqueous phase processes struggle to obtain high-purity products with a disulfide content exceeding 98.5%, failing to meet the high purity, low impurity, and high stability requirements of high-end green tires for silane coupling agents. Although aqueous phase processes are simple and low-cost, Si-75 produced using conventional aqueous phase processes tends to be yellowish, with product colors generally ranging from 1 to 2 (Garnard color number), failing to meet the requirements for light-colored, transparent rubber compounds.

[0005] Therefore, developing a simple, environmentally friendly, low-cost, stable, colorless high-purity Si-75 product with a disulfide content of over 98.5% is of great significance to the tire, high-end shoe sole, and green and light-colored rubber industries. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing high-purity Si-75. This method uses a phosphorus-free buffer, is simple to synthesize, has low equipment requirements, high disulfide content, few impurities, and is colorless or nearly colorless, directly meeting the requirements for use in green tires, high-performance rubber, and light-colored rubber.

[0007] To achieve this technical objective, the present invention adopts the following solution: This invention provides a method for preparing high-purity Si-75, comprising the following steps: S1. Add sodium sulfide, sulfur, and deionized water to the reactor in a molar ratio of 1:(1.0~1.1):(5~8), add buffer, and react at 80~90℃ for 1~2 hours. S2. Add a phase transfer catalyst and a hydrolysis inhibitor to the system, add γ-chloropropyltriethoxysilane dropwise, and react at 85~95℃ for 3~5h. After the reaction is completed, allow the mixture to stand and separate into layers to obtain the organic phase. S3 and the organic phase are subjected to short-path distillation and then filtered to obtain high-purity Si-75.

[0008] Preferably, in step S1, the buffer is one or more combinations of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, acetic acid-sodium acetate, ammonia-ammonium chloride, citric acid-sodium citrate, and trimethylolpropane, and the amount used is 1% to 3% of the mass of sodium sulfide.

[0009] Preferably, in step S2, the phase transfer catalyst is one or a combination of two of hexadecyltrimethylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, and tetradecyltrimethylammonium chloride, and the amount used is 0.2% to 1.0% of the mass of γ-chloropropyltriethoxysilane.

[0010] Preferably, in step S2, the hydrolysis inhibitor is one or more of sodium citrate, potassium iodide, citric acid, and glycidyl ether, and the amount used is 1% to 3% of the mass of sodium sulfide.

[0011] Preferably, in step S2, γ-chloropropyltriethoxysilane is added dropwise at a uniform rate, and the dropping time is controlled to be 1~2h. The molar ratio of γ-chloropropyltriethoxysilane to sodium sulfide is 1:(1.8~2.2).

[0012] Preferably, in step S3, the short-path distillation conditions are: vacuum degree 800~1000Pa, temperature 110~130℃.

[0013] Preferably, in step S4, the high-purity Si-75 obtained has a purity ≥98.5%, a color 0 (Garnard color number), and impurities ≤3%. The purity testing standard refers to GB / T30309, the color testing standard refers to GB / T22295, and the impurity testing standard refers to GB / T30309.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a phosphorus-free buffer system, simplifying waste treatment. Using water as the reaction medium and avoiding the use of large amounts of organic solvents, it is suitable for continuous industrial production. The addition of hydrolysis inhibitors effectively prevents hydrolysis during the reaction, increasing safety. The short-path distillation method ensures high purification efficiency and rapid removal of impurities. The product has a disulfide content ≥98.5% and a color of 0 (Gardner color number), which is significant for the light-colored rubber industry. The high-purity product exhibits excellent dispersibility in silica-reinforced rubber and green tire systems, with stable vulcanization and uniform cross-linking, significantly improving the mechanical and performance properties of rubber. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0016] Unless otherwise specified, the experimental methods used in the embodiments and comparative examples of this invention are conventional methods. Unless otherwise specified, the materials and reagents used are commercially available. Example 1

[0017] 1 mol sodium sulfide, 1.05 mol sulfur, 6 mol deionized water, and 1 g sodium carbonate were added to a reaction vessel. The mixture was stirred and heated to 85°C, and reacted at atmospheric pressure for 1.5 h to obtain an aqueous solution of sodium disulfide. 1.5 g tetrabutylammonium bromide and 1.5 g citric acid were added to the system, and 2.05 mol γ-chloropropyltriethoxysilane was added dropwise at a uniform rate over 2 h. The temperature was raised to 90°C and maintained for 4 h. After the reaction, the mixture was allowed to stand and separate into layers. The lower brine layer was separated to obtain the organic phase. The organic phase was sent to a short-path distillation apparatus, and the light components were removed under a vacuum of 800 Pa and a temperature of 120°C. After filtration, a high-purity Si-75 product was obtained.

[0018] The obtained products were tested according to the standards GB / T30309 for purity, GB / T22295 for color, and GB / T30309 for impurities. The test results are as follows: The product has a disulfide content of 99.3%, a color of 0 (Gardner color number), and impurities ≤3%. After one year of storage, the disulfide content is 99.2%. After being placed at 150℃ for 24 hours, the color is 0 (Gardner color number). The main components of the waste liquid are sodium chloride, sodium carbonate, tetrabutylammonium bromide, and citric acid. Example 2

[0019] 1 mol sodium sulfide, 1.03 mol sulfur, 6.5 mol deionized water, and 2.1 g sodium hydroxide were added to a reaction vessel, stirred, and heated to 88 °C. The reaction was carried out at atmospheric pressure for 1.2 h to obtain an aqueous solution of sodium disulfide. 1.8 g hexadecyltrimethylammonium bromide and 1.8 g citric acid were added to the system, and 2.08 mol of γ-chloropropyltriethoxysilane was added dropwise at a uniform rate over 1.5 h. The temperature was raised to 92 °C and maintained for 3.5 h. After the reaction, the mixture was allowed to stand and separate into layers. The lower brine layer was separated to obtain the organic phase. The organic phase was sent to a short-path distillation apparatus, and the light components were removed under a vacuum of 900 Pa and a temperature of 125 °C. After filtration, a high-purity Si-75 product was obtained.

[0020] Test results: Disulfide content 99.5%, color 0 (Gardner color number), impurities ≤3%. After one year of storage, the disulfide content was 99.4%. After 24 hours at 150℃, the color was 0 (Gardner color number). The main components of the waste liquid are: sodium chloride, sodium hydroxide, hexadecyltrimethylammonium bromide, citric acid, etc. Example 3

[0021] 1 mol sodium sulfide, 1.03 mol sulfur, 6.5 mol deionized water, and 2.1 g potassium carbonate were added to a reaction vessel, stirred, and heated to 88 °C. The reaction was carried out at atmospheric pressure for 1.2 h to obtain an aqueous solution of sodium disulfide. 1.8 g benzyltriethylammonium chloride and 1.8 g potassium iodide were added to the system, and 2.08 mol of γ-chloropropyltriethoxysilane was added dropwise at a uniform rate over 1.5 h. The temperature was raised to 92 °C and maintained for 3.5 h. After the reaction, the mixture was allowed to stand and separate into layers. The lower brine layer was separated to obtain the organic phase. The organic phase was sent to a short-path distillation apparatus, and the light components were removed under a vacuum of 900 Pa and a temperature of 125 °C. After filtration, a high-purity Si-75 product was obtained.

[0022] Test results: Disulfide content 99.2%, color 0 (Garland color number), impurities ≤3%. After one year of storage, the disulfide content was 99.1%. After 24 hours at 150℃, the color was 0 (Garland color number). The main components of the waste liquid are: sodium chloride, potassium carbonate, benzyltriethylammonium chloride, potassium iodide, etc. Example 4

[0023] 1 mol sodium sulfide, 1.03 mol sulfur, 6.5 mol deionized water, and 1.8 g acetate-sodium acetate were added to a reaction vessel. The mixture was stirred and heated to 88°C, and reacted at atmospheric pressure for 1.2 h to obtain an aqueous solution of sodium disulfide. 1.8 g tetrabutylammonium bromide and 1.8 g potassium iodide were added to the system, and 2.08 mol of γ-chloropropyltriethoxysilane was added dropwise at a uniform rate over 1.5 h. The temperature was raised to 92°C and maintained for 3.5 h. After the reaction, the mixture was allowed to stand and separate into layers. The lower brine layer was separated to obtain the organic phase. The organic phase was sent to a short-path distillation apparatus, and the light components were removed under a vacuum of 900 Pa and a temperature of 125°C. After filtration, a high-purity Si-75 product was obtained.

[0024] Test results: Disulfide content 99.3%, color 0 (Garland color number), impurities ≤3%. After one year of storage, the disulfide content was 99.3%. After 24 hours at 150℃, the color was 0 (Garland color number). The main components of the waste liquid are: sodium chloride, sodium acetate, tetrabutylammonium bromide, potassium iodide, etc. Example 5

[0025] 1 mol sodium sulfide, 1.04 mol sulfur, 6.6 mol deionized water, and 1.9 g ammonia-ammonium chloride were added to a reaction vessel. The mixture was stirred and heated to 88 °C, and reacted at atmospheric pressure for 1.2 h to obtain an aqueous solution of sodium disulfide. 1.8 g tetrabutylammonium bromide and 1.7 g potassium iodide were added to the system. 2.08 mol of γ-chloropropyltriethoxysilane was added dropwise at a uniform rate over 1.5 h. The temperature was raised to 92 °C and maintained for 3.5 h. After the reaction, the mixture was allowed to stand and separate into layers. The lower brine layer was separated to obtain the organic phase. The organic phase was sent to a short-path distillation apparatus, and the light components were removed under a vacuum of 900 Pa and a temperature of 125 °C. After filtration, a high-purity Si-75 product was obtained.

[0026] Test results: Disulfide content 99.6%, color 0 (Garland color number), impurities ≤3%. After one year of storage, the disulfide content was 99.5%. After 24 hours at 150℃, the color was 0 (Garland color number). The main components of the waste liquid are: sodium chloride, ammonium chloride, tetrabutylammonium bromide, potassium iodide, etc. Example 6

[0027] 1 mol sodium sulfide, 1.04 mol sulfur, 6.6 mol deionized water, and 1.95 g citric acid-sodium citrate were added to a reaction vessel, stirred, and heated to 88 °C. The reaction was carried out at atmospheric pressure for 1.2 h to obtain an aqueous solution of sodium disulfide. 1.8 g tetrabutylammonium chloride and 1.7 g potassium iodide were added to the system, and 2.08 mol γ-chloropropyltriethoxysilane was added dropwise at a uniform rate over 1.5 h. The temperature was raised to 92 °C and maintained for 3.5 h. After the reaction, the mixture was allowed to stand and separate into layers. The lower brine layer was separated to obtain the organic phase. The organic phase was sent to a short-path distillation apparatus, and the light components were removed under a vacuum of 900 Pa and a temperature of 125 °C. After filtration, a high-purity Si-75 product was obtained.

[0028] Test results: Disulfide content 99.4%, color 0 (Garland color number), impurities ≤3%. After one year of storage, the disulfide content was 99.3%. After 24 hours at 150℃, the color was 0 (Garland color number). The main components of the waste liquid are: sodium chloride, sodium citrate, tetrabutylammonium chloride, potassium iodide, etc. Comparative Example 1 (The difference from Example 5 is that the buffer is different)

[0029] 1 mol sodium sulfide, 1.04 mol sulfur, 6.6 mol deionized water, and 0.9 g sodium dihydrogen phosphate / 1 g disodium hydrogen phosphate were added to a reaction vessel. The mixture was stirred and heated to 88 °C, and reacted at atmospheric pressure for 1.2 h to obtain an aqueous solution of sodium disulfide. 1.8 g tetrabutylammonium bromide and 1.7 g potassium iodide were added to the system, and 2.08 mol of γ-chloropropyltriethoxysilane was added dropwise at a uniform rate over 1.5 h. The temperature was raised to 92 °C and maintained for 3.5 h. After the reaction, the mixture was allowed to stand and separate into layers. The lower brine layer was separated to obtain the organic phase. The organic phase was sent to a short-path distillation apparatus, and the light components were removed under a vacuum of 900 Pa and a temperature of 125 °C. After filtration, the Si-75 product was obtained.

[0030] Test results: Disulfide content 99.1%, impurities ≤3%, color 0 (Gardner color number). The main components of the waste liquid are: sodium chloride, phosphate, tetrabutylammonium bromide, potassium iodide, etc. Although the disulfide content is 99%, the waste liquid contains phosphate, making treatment difficult. Comparative Example 2 (Preparation of Si-75 using conventional anhydrous ethanol solvent method)

[0031] 5 mol of anhydrous ethanol was added to a reaction vessel, and nitrogen gas was introduced for protection. Then, 1 mol of anhydrous sodium sulfide and 1.05 mol of elemental sulfur were added, and the mixture was heated to 65-70°C and refluxed for 1 hour to obtain a sodium disulfide ethanol suspension. Subsequently, 1 g of tetrabutylammonium bromide phase transfer catalyst was added, and 2.05 mol of γ-chloropropyltriethoxysilane was added dropwise over a time of 1 hour at a temperature of 60-70°C. After the addition was complete, the mixture was heated to 75-80°C and refluxed for 4 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain crude Si-75. The crude Si-75 was first filtered under reduced pressure to remove the sodium chloride solid generated in the reaction, and then transferred to a distillation vessel. The temperature was raised to 80°C to distill off the ethanol solvent, and then the temperature was further raised to 120°C to distill off other low-boiling byproducts. Finally, the mixture was cooled and filtered to obtain the Si-75 product.

[0032] Test results: Disulfide content 74.4%, color 2.5 (Gardner color number), impurities ≤3%. Products prepared by conventional anhydrous ethanol solvent method do not reach a disulfide content of over 98.5%, and the color (Gardner color number) cannot reach 0, thus failing to meet the requirements for light-colored transparent rubber materials.

[0033] Furthermore, this comparative example uses ethanol as a single solvent, which has poor solubility for inorganic sulfur salts, results in a large filtration volume, and significant product entrainment in the filter cake, thus lowering the yield. The system is also highly alkaline, making it prone to silane alcoholysis and hydrolysis side reactions during distillation and rectification. Incomplete solvent removal leads to the formation of gel-like impurities during rectification, which are difficult to clean, and the externally distilled ethanol contains impurities and cannot be directly reused. This method results in lower yields and purity, darker color, and higher costs, making it unsuitable for large-scale production.

[0034] As can be seen from the above examples and comparative examples, the present invention uses a phosphorus-free buffer system, which simplifies the treatment of waste, uses water as the reaction medium, and does not use a large amount of organic solvents, making it suitable for continuous industrial production. The present invention uses a short-path distillation method, which has high purification efficiency, can quickly remove impurities, and produces a product with a disulfide content of ≥98.5% and a color of 0 (Garnard color number), which is of great significance to the light-colored rubber industry.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should all be considered to be within the protection scope of the present invention.

Claims

1. A method for preparing high-purity Si-75, characterized in that, Includes the following steps, S1. Add sodium sulfide, sulfur, and deionized water to the reactor in a molar ratio of 1:(1.0~1.1):(5~8), add buffer, and react at 80~90℃ for 1~2 hours. S2. Add a phase transfer catalyst and a hydrolysis inhibitor to the system, add γ-chloropropyltriethoxysilane dropwise, and react at 85~95℃ for 3~5h. After the reaction is completed, allow the mixture to stand and separate into layers to obtain the organic phase. S3 and the organic phase are subjected to short-path distillation and then filtered to obtain high-purity Si-75.

2. The method for preparing high-purity Si-75 according to claim 1, characterized in that, In step S1, the buffer is one or more combinations of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, acetic acid-sodium acetate, ammonia-ammonium chloride, citric acid-sodium citrate, and trimethylolpropane, and the amount used is 1% to 3% of the mass of sodium sulfide.

3. The method for preparing high-purity Si-75 according to claim 1, characterized in that, In step S2, the phase transfer catalyst is one or a combination of two of hexadecyltrimethylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, and tetradecyltrimethylammonium chloride, and the amount used is 0.2% to 1.0% of the mass of γ-chloropropyltriethoxysilane.

4. The method for preparing high-purity Si-75 according to claim 1, characterized in that, In step S2, the hydrolysis inhibitor is one or more of sodium citrate, potassium iodide, citric acid, and glycidyl ether, and the amount used is 1% to 3% of the mass of sodium sulfide.

5. The method for preparing high-purity Si-75 according to claim 1, characterized in that, In step S2, γ-chloropropyltriethoxysilane is added dropwise at a uniform rate, and the dropping time is controlled to be 1~2h. The molar ratio of γ-chloropropyltriethoxysilane to sodium sulfide is 1:(1.8~2.2).

6. The method for preparing high-purity Si-75 according to claim 1, characterized in that, In step S3, the short-path distillation conditions are: vacuum degree 800~1000Pa, temperature 110~130℃.

7. The method for preparing high-purity Si-75 according to claim 1, characterized in that, In step S4, the high-purity Si-75 obtained has a purity ≥ 98.5% and a color 0 (Gardner color number).