Synthesis method of low-sodium-salt-content high-yield anti-sulfuration reducing agent HTS

Abstract

The invention belongs to the technical field of synthesis of rubber additives, and relates to a synthesis method of an anti-vulcanization reducing agent HTS with low sodium salt content and high yield. The preparation method comprises the following steps: heating sodium thiosulfate pentahydrate, 1.6-dichlorohexane, deionized water, methanol and lauryl trimethyl ammonium chloride, and reacting to obtain an HTS crude product; adding deionized water, cooling, dropwise adding dibenzylamine, dropwise adding a sulfuric acid solution, heating, stirring, reacting, carrying out suction filtration and washing, adding deionized water, dropwise adding a sodium hydroxide solution, layering, adding toluene into a water layer for extraction, taking an organic layer, and carrying out vacuum drying to obtain an HTS product and recovered toluene. By optimizing process steps and reaction parameters, determining the optimal synthesis time and controlling the dripping rhythm of dibenzylamine and sulfuric acid, the content of sodium chloride in the product is remarkably reduced, and the core problem that the salt content exceeds the standard in the traditional process is solved. The preparation process is simple and controllable, the product yield and quality fluctuation are small, and the method is suitable for industrial large-scale production and popularization.

Description

Technical Field

[0001] This invention belongs to the field of rubber additive synthesis technology, and relates to a method for synthesizing HTS, a low-sodium salt content, high-yield anti-sulfurization reducing agent. Background Technology

[0002] HTS (Hydrosulfonate thiosulfate) is an important rubber anti-reversion agent, which can solve the problem of "reversion" of natural rubber and other substances under long-term vulcanization. It is one of the key additives in the manufacture of high-performance, long-life tires (such as radial tires and giant engineering tires) and high-end rubber products. HTS alone can improve the heat resistance, aging resistance, sulfur reversion resistance, and dynamic stability of vulcanizates; when used in combination with NR (Normative Reversion) sulfur accelerators, it can improve the fatigue resistance of rubber and increase the adhesion strength of tire cords. Traditional HTS synthesis processes use sodium thiosulfate pentahydrate and 1,6-dichlorohexane as raw materials, synthesized in one step in water or a water-alcohol mixture, producing a large amount of sodium chloride as a byproduct. Both sodium chloride and the target product HTS are readily soluble in water, making separation difficult. Existing separation processes mostly use ethanol for precipitation separation, which suffers from problems such as huge solvent consumption, incomplete separation, and low yield. Furthermore, the filtration and washing effects are heavily dependent on operating conditions, easily causing batch-to-batch instability in purity and sodium salt content. This makes it difficult to meet the stable requirements of industrial production. Summary of the Invention

[0003] This invention proposes a method for synthesizing HTS with low sodium salt content and high yield, which addresses the problems existing in the traditional HTS synthesis process.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution: A method for synthesizing HTS, a low-sodium salt content, high-yield anti-sulfurization reducing agent, comprises the following steps: (1) Sodium thiosulfate pentahydrate, 1,6-dichlorohexane, deionized water, methanol and lauryltrimethylammonium chloride were heated and reacted to obtain crude HTS; (2) Add deionized water to the crude HTS, cool it down and then add dibenzylamine dropwise, followed by sulfuric acid solution to carry out the salting reaction and obtain the salting reaction solution. (3) The salting reaction solution is heated and stirred to react. After the reaction is completed, the temperature is lowered and the solution is filtered. The filter cake obtained by filtration is washed to obtain refined HTS-dibenzylamine salt. (4) Add the purified HTS-dibenzylamine salt to deionized water, then heat up and slowly add sodium hydroxide solution. After the addition is complete, let it stand to separate the layers to obtain a dibenzylamine layer and an aqueous layer. Separate and recover the dibenzylamine layer. (5) Add toluene to the aqueous layer, stir and extract, let stand to separate the layers, take the organic layer and vacuum dry it to obtain HTS product and recovered toluene.

[0005] As a preferred embodiment, in step (1), the mass ratio of sodium thiosulfate pentahydrate, 1,6-dichlorohexane, deionized water, methanol, and lauryltrimethylammonium chloride is (60-80):(10-30):(40-60):(30-50):(0.1-1), the reaction temperature is 77-79℃, and the reaction time is 12-14h.

[0006] Preferably, the amount of deionized water added in step (2) is the same as that added in step (1), and the mass ratio of deionized water: dibenzylamine: sulfuric acid solution in step (2) is (40-60): (40-65): (55-70); the mass fraction of the sulfuric acid solution is 18-25%; the dibenzylamine is added for 20-40 min, and the sulfuric acid solution is added for 50-80 min.

[0007] Preferably, in step (3), the temperature of the salting reaction solution is raised and stirred at 60-80℃, the reaction time is 2.5-3.5h, the temperature of cooling and filtration is 35-55℃, and the washing solution is deionized water.

[0008] Preferably, in step (4), after adding deionized water, the temperature is raised to 35-55℃ and the pH of the water layer is 9.4-9.6.

[0009] This invention employs a two-step conversion and separation method to prepare HTS products. Sulfuric acid solution is used to protonate dibenzylamine to form salt, while sodium hydroxide solution is used to regenerate dibenzylamine and release HTS. During the production process, insufficient sulfuric acid will lead to incomplete formation of amine salts, while excessive sulfuric acid will result in waste and increase the burden of post-processing. Insufficient sodium hydroxide will lead to incomplete regeneration of dibenzylamine, while excessive sodium hydroxide may cause local degradation or emulsification of HTS. The dropping time of dibenzylamine and sulfuric acid solution also needs to be strictly controlled. If both are added too quickly, the local concentration will be too high, forming fine precipitates that encapsulate impurities, resulting in a sharp increase in sodium salt content. If the dropping time is too slow, both will lead to an increase in side reactions. Furthermore, this invention controls the pH of the aqueous layer by precisely controlling the amount of sodium hydroxide solution added in step (4), so that dibenzylamine can be fully regenerated and recovered in this step, ensuring its recovery efficiency and purity. In addition, after the crude HTS product is prepared, deionized water needs to be added for dilution. Otherwise, the system viscosity will be high, affecting mass transfer, which will lead to uneven subsequent reactions and a sharp drop in product yield and purity. The HTS product prepared by this invention has a purity of ≥98%, a sodium chloride content of ≤0.03%, and a yield of ≥95.7%; it recovers ≥41.6g of dibenzylamine (recovery rate ≥77.6%) and ≥380mL of toluene (recovery rate ≥95%). The product has stable performance and meets the requirements for use in rubber vulcanization systems.

[0010] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. This invention optimizes process steps and reaction parameters, determines the optimal synthesis time, and controls the dropping rhythm of dibenzylamine and sulfuric acid, significantly reducing the sodium chloride content in the product and solving the core problem of excessive salt content in traditional processes.

[0011] 2. By forming insoluble amine salts through a salting reaction, combined with a washing process, the purity of the product is greatly improved, avoiding the high consumption defects of traditional ethanol separation.

[0012] 3. Precise control of NaOH dropping rate and pH value of HTS aqueous solution (aqueous layer) enables efficient recovery of dibenzylamine; toluene is recycled, reducing production costs and environmental impact.

[0013] 4. The preparation process is simple and controllable, with small fluctuations in product yield and quality, making it suitable for large-scale industrial production and promotion. Detailed Implementation

[0014] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0015] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification. Example 1

[0016] In a 2000 mL four-necked flask, add 68 g of sodium thiosulfate pentahydrate (CAS No.: 10102-17-7), 20 g of 1,6-dichlorohexane (CAS No.: 2163-00-0), 50 g of deionized water, 39.6 g of methanol, and 0.4 g of lauryltrimethylammonium chloride (CAS No.: 112-00-5). Heat the mixture in a water bath to 78 °C and then maintain the temperature for 13 hours. Add 50 mL of deionized water and then lower the water bath temperature to 65 °C. Add 53.6 g of dibenzylamine (CAS: 103-49-1) dropwise at a uniform rate over 30 min. After the addition is complete, add 62.5 g of 20% sulfuric acid solution dropwise over 60 min. Then raise the water bath temperature to 70 °C and stir the mixture at 100 r / min for 3 hours. After the reaction was completed, the temperature was lowered to 40℃ and the mixture was filtered. The filter cake was washed three times with 500mL of distilled water, dried for 2 minutes, and then 350mL of distilled water was added. The mixture was stirred manually with a glass rod for 2 minutes until it was evenly mixed. The mixture was then placed in a water bath and the temperature was raised to 40℃. 32g of 30% NaOH solution was added dropwise at 100rpm for 15 minutes. After stirring for another 5 minutes, the dibenzylamine was recovered by separation. 400mL of toluene was added for extraction. After separation, the organic phase was dried in a vacuum drying oven at 0.1MPa and 55℃ for 5 hours until constant weight was obtained, yielding 47.9g of HTS product.

[0017] The HTS product yield was 96.3%, the HTS purity was 98.8%, the sodium chloride content was 0.04%, the dibenzylamine recovery rate was 77.6%, and the toluene recovery rate was 95.0%. Example 2

[0018] Unless otherwise specified in this embodiment and the following embodiments, the process is the same as in Example 1. In a 5000mL four-necked flask, 130g of sodium thiosulfate pentahydrate, 44g of 1,6-dichlorohexane, 102g of deionized water, 81g of methanol, and 0.82g of lauryltrimethylammonium chloride were added. The mixture was heated in a water bath to 81°C and then kept at that temperature for 10 hours. 100mL of deionized water was added, and the water bath temperature was lowered to 72°C. 109g of dibenzylamine was added dropwise at a uniform rate over 25 minutes. After the addition was complete, 126g of a 20% sulfuric acid solution was added dropwise over 50 minutes. The water bath temperature was then raised to 73°C, and the mixture was stirred at 100r / min for 3 hours. After the reaction was completed, the temperature was lowered to 40℃ and the mixture was filtered. The filter cake was washed three times with 800mL of distilled water, dried for 2 minutes, and then 700mL of distilled water was added. The mixture was stirred manually with a glass rod for 2 minutes until it was evenly mixed. The mixture was then placed in a water bath and the temperature was raised to 38℃. 65g of 27% NaOH solution was added dropwise at 100rpm for 12 minutes. After stirring for 5 minutes, 86g of dibenzylamine was recovered by separation. 750mL of toluene was added for extraction. After separation, the organic phase was dried in a vacuum drying oven at 0.1MPa and 55℃ for 5 hours until constant weight was obtained, yielding 96.6g of HTS product.

[0019] The HTS product yield was 97.1%, the HTS purity was 98.9%, the sodium chloride content was 0.05%, the dibenzylamine recovery rate was 78.3%, and the toluene recovery rate was 95.2%. Example 3

[0020] 5m 3 In a stirred synthesis vessel, 135 kg of sodium thiosulfate pentahydrate, 44 g of 1,6-dichlorohexane, 110 kg of distilled water, 83 kg of methanol, and 857 g of lauryltrimethylammonium chloride were added, and the mixture was heated to 81 °C and reacted for 10 h. Then, 100 mL of distilled water was added, and the temperature was lowered to 70 °C. 113 kg of dibenzylamine was added dropwise over 30 min, followed by 135 kg of 20% sulfuric acid over 60 min. The temperature was raised to 69 °C, and the mixture was stirred at 98 r / min for 2.5 h. The mixture was then cooled to 37 °C and filtered. The filter cake was treated with 0.730 mL of [unspecified material]. 3 Wash three times with distilled water, drain, and then add 0.5 mg of distilled water. 3 Distilled water was heated to 38℃, and 61 kg of 29% NaOH solution was added dropwise over 18 minutes. After stirring for 5 minutes, 85.6 kg of dibenzylamine was recovered by separation. 0.77 mg / L of NaOH solution was added. 3 Extracted with toluene, the organic phase was separated and dried under vacuum at 55°C to constant weight, yielding 96.3 kg of HTS product.

[0021] The HTS product prepared in this embodiment had a yield of 96.8%, a purity of 98.6%, a sodium chloride content of 0.03%, a dibenzylamine recovery rate of 77.9%, and a toluene recovery rate of 95.3%.

[0022] Comparative Example 1 The difference between this comparative example and Example 1 is that lauryltrimethylammonium chloride was omitted from the raw materials, while the amounts of other substances and the preparation process remained the same as in Example 1. The product yield was 90.5%, the sodium chloride content was 6.2%, the HTS purity was 97.2%, and the dibenzylamine recovery rate was 75.3%.

[0023] Comparative Example 2 The difference between this comparative example and Example 1 is that the methanol in the raw material addition stage and the toluene used in the extraction process were replaced with an equal mass of ethanol. The remaining substances and preparation process were consistent with Example 1. The product yield was 51.6%, the sodium chloride content was 10.1%, and the HTS purity was 93.8%.

[0024] Comparative Example 3 The difference between this comparative example and Example 1 is that dibenzylamine in the raw material dropwise addition process was replaced with an equal mass of dicyclohexylamine. The remaining substances and preparation process were consistent with Example 1. The product yield was 40.3%, the sodium chloride content was 11.9%, and the HTS purity was 92.3%.

[0025] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for synthesizing HTS, a low-sodium salt content, high-yield anti-sulfurization reducing agent, characterized in that, The steps are as follows: (1) Sodium thiosulfate pentahydrate, 1,6-dichlorohexane, deionized water, methanol and lauryltrimethylammonium chloride were heated and reacted to obtain crude HTS; (2) Add deionized water to the crude HTS, cool it down and then add dibenzylamine dropwise, followed by sulfuric acid solution to carry out the salting reaction and obtain the salting reaction solution. (3) The salting reaction solution is heated and stirred to react. After the reaction is completed, the temperature is lowered and the solution is filtered. The filter cake obtained by filtration is washed to obtain refined HTS-dibenzylamine salt. (4) Add the purified HTS-dibenzylamine salt to deionized water, then heat up and slowly add sodium hydroxide solution. After the addition is complete, let it stand to separate the layers to obtain a dibenzylamine layer and an aqueous layer. Separate and recover the dibenzylamine layer. (5) Add toluene to the aqueous layer, stir and extract, let stand to separate the layers, take the organic layer and vacuum dry it to obtain HTS product and recovered toluene.

2. The method for synthesizing the low-sodium-content, high-yield anti-sulfurization reducing agent HTS according to claim 1, characterized in that, In step (1), the mass ratio of sodium thiosulfate pentahydrate, 1,6-dichlorohexane, deionized water, methanol, and lauryltrimethylammonium chloride is (60-80):(10-30):(40-60):(30-50):(0.1-1), the reaction temperature is 77-79℃, and the reaction time is 12-14h.

3. The method for synthesizing the low-sodium-content, high-yield anti-sulfurization reducing agent HTS according to claim 1, characterized in that, In step (2), the amount of deionized water added is the same as that in step (1). The mass ratio of deionized water: dibenzylamine: sulfuric acid solution in step (2) is (40-60): (40-65): (55-70). The mass fraction of the sulfuric acid solution is 18-25%. The dibenzylamine is added for 20-40 min, and the sulfuric acid solution is added for 50-80 min.

4. The method for synthesizing the low-sodium-content, high-yield anti-sulfurization reducing agent HTS according to claim 1, characterized in that, In step (3), the temperature of the salting reaction solution is raised and stirred at 60-80℃, the reaction time is 2.5-3.5h, the temperature of cooling and filtration is 35-55℃, and the washing solution is deionized water.

5. The method for synthesizing the low-sodium-content, high-yield anti-sulfurization reducing agent HTS according to claim 1, characterized in that, In step (4), after adding deionized water, the temperature is raised to 35-55℃, and the pH of the water layer is 9.4-9.6.