WO2021073044A1

WO2021073044A1 - Environment-friendly synthesis method for dibenzothiazole disulfide as rubber vulcanization accelerator

Info

Publication number: WO2021073044A1
Application number: PCT/CN2020/081063
Authority: WO
Inventors: 骆广生; 田佳鑫; 王凯
Original assignee: 清华大学
Priority date: 2019-10-14
Filing date: 2020-03-25
Publication date: 2021-04-22
Also published as: CN110590703B; CN110590703A

Abstract

The present invention discloses an environment-friendly synthesis method for dibenzothiazole disulfide as rubber vulcanization accelerator, belonging to the technical field of chemical engineering. The method specifically is: completely dissolving 2-mercaptobenzothiazole in the sodium carbonate aqueous solution, then dropwise adding hydrogen peroxide, introducing carbon dioxide to adjust the pH of the system, and carrying out oxidation to generate dibenzothiazole disulfide and sodium bicarbonate. The sodium carbonate solution formed by heating the obtained sodium bicarbonate solution can be used for dissolving the raw material 2-mercaptobenzothiazole so as to realize circulation of the raw materials. The purity of the product prepared by the method in the present invention can reach 99% or more, compared with the traditional mixed acid oxidation method, a large amount of salt-containing wastewater is reduced, and the process is environmentally friendly.

Description

Green synthesis method of rubber vulcanization accelerator dibenzothiazole disulfide

Technical field

The invention belongs to the technical field of chemistry and chemical engineering, and particularly relates to a green synthesis method of a rubber vulcanization accelerator dibenzothiazole disulfide.

Background technique

Dibenzothiazole disulfide is a general-purpose rubber vulcanization accelerator. The vulcanization curve is flat during the vulcanization process, and the vulcanization critical temperature is relatively high. The benzothiazolyl group contained in the structure belongs to the accelerator group, and the disulfide bond belongs to the anti-scorch group, which has good aging resistance. It is usually used in combination with other accelerators to further improve the activity. Because of its bitter taste, it is mainly used to manufacture rubber products for non-food applications such as tires and rubber shoes. Dibenzothiazole disulfide is mostly prepared from 2-mercaptobenzothiazole by oxidation with different kinds of oxidants.

The most traditional method in industry is the sodium nitrite method. As shown in formula 1, sulfuric acid is added dropwise to the slurry of 2-mercaptobenzothiazole and sodium nitrite, air is blown in in the presence of nitric oxide, and oxidation reaction occurs at 60°C. The problem with this method is that the reaction produces a large amount of salty wastewater, which is difficult to treat; it produces nitrogen oxide tail gas, which seriously pollutes the air; in addition, sodium nitrite is a strong carcinogen and endangers human health.

US Patent 4,482,720 (A) reported that 2-mercaptobenzothiazole was first dissolved in NaOH solution to generate 2-mercaptobenzothiazole sodium salt solution, and then a large amount of air diluted chlorine gas was passed into the solution to perform oxidation reaction. The product is shown in formula 2. This method is easy to produce by-products, and excessive chlorine gas participates in the reaction to generate peroxides such as sulfonates and sulfoxides.

Patent CS 393386(A1) discloses a method of direct oxidation by solvent method, using isopropanol aqueous solution as a solvent to directly dissolve 2-mercaptobenzothiazole, and then using hydrogen peroxide as an oxidizing agent, slowly dripping for reaction to obtain the product, such as As shown in Equation 3. The solvent cost of this method is relatively high, and there is a greater potential safety hazard.

The previous method has many problems such as poisonous and harmful reaction process, low product yield and purity, and high environmental protection treatment cost. Therefore, it is necessary to invent a clean, green, and recyclable mother liquor synthesis process for the product dibenzothiazole disulfide.

Summary of the invention

The purpose of the present invention is to provide a green synthesis method of dibenzothiazole disulfide as a rubber vulcanization accelerator. The specific technical scheme is as follows:

A green synthesis method of rubber vulcanization accelerator dibenzothiazole disulfide includes the following steps:

(1) Add 2-mercaptobenzothiazole to the sodium carbonate aqueous solution and heat to completely dissolve to obtain a solution A containing sodium 2-mercaptobenzothiazole;

(2) Add hydrogen peroxide dropwise to the solution A obtained in step (1), and adjust the pH of the solution to 5-10 to perform an oxidation reaction. After the reaction, a sodium bicarbonate solution B containing dibenzothiazole disulfide solid is obtained;

(3) Filtering the solution B obtained in step (2), washing and drying the obtained solid to obtain dibenzothiazole disulfide;

Or a green synthesis method of dibenzothiazole disulfide, a rubber vulcanization accelerator of the present invention, includes the following steps:

(3) The solution B obtained in step (2) is filtered, and the obtained solid is washed and dried to obtain dibenzothiazole disulfide.

(4) The sodium carbonate solution obtained by heating the filtrate from step (3) to release carbon dioxide is used as a lye for recycling in step (1) to dissolve 2-mercaptobenzothiazole, and repeating steps (2) to (3) to prepare two Dibenzothiazole sulfide.

In the above method, the molar ratio of 2-mercaptobenzothiazole to sodium carbonate in the step (1) is 1:1 to 1:10, and the mass fraction of sodium carbonate in the sodium carbonate aqueous solution is 10% to 20%.

In the above method, the heating temperature in the step (1) is 20 to 90°C.

In the above method, the mass fraction of sodium 2-mercaptobenzothiazole in the solution A in the step (1) is 3%-30%.

In the above method, the mass fraction of hydrogen peroxide in hydrogen peroxide in the step (2) is 1%-30%, and the molar ratio of hydrogen peroxide to sodium 2-mercaptobenzothiazole in solution A is 0.4:1 to 0.6:1 .

In the above method, the oxidation reaction temperature in the step (2) is 10-70°C.

In the above method, in the step (2), the pH of the solution is adjusted by carbon dioxide.

In the above method, the sodium carbonate solution obtained after the filtrate releases carbon dioxide in the step (3), for example, is released by heating, and is recycled as a lye for dissolving 2-mercaptobenzothiazole, and can be recycled more than 5 times.

In the above method, the solid obtained by filtration in the step (3) is washed with water and dried at 80-120° C. to obtain dibenzothiazole disulfide.

The beneficial effects of the present invention are:

(1) The present invention uses sodium carbonate as lye to dissolve 2-mercaptobenzothiazole to form sodium salt, and uses CO ₂ assisted hydrogen peroxide oxidation process for reaction. Compared with the existing oxidation technology, the sodium bicarbonate aqueous solution formed after the oxidation reaction of the present invention will be heated to form a sodium carbonate aqueous solution, which can be recycled without producing _{waste salts such as Na 2} SO ₄ , NaCl, etc., and can greatly reduce the amount of salty wastewater. It can reduce the production of salty wastewater by about 0.5 tons per ton of product produced, and reduce the cost of environmental protection treatment;

(2) The present invention uses carbon dioxide as an acidifier to adjust the pH of the reaction system, which is milder than other acid-base regulators, and can reduce the precipitation of insoluble 2-mercaptobenzothiazole during the acidification process, thereby protecting the reaction system from being prone to In the peroxidation reaction, the product yield can reach more than 98%, and the purity can reach more than 99%.

(3) The sodium carbonate-sodium bicarbonate in the solution of the present invention has a certain buffering effect on the pH of the system during the reaction, and the generation of peroxidation by-products is avoided in a weakly alkaline state.

Detailed ways

The present invention provides a green synthesis method of dibenzothiazole disulfide, a rubber vulcanization accelerator. The present invention will be further illustrated below in conjunction with examples.

The green synthesis method of the rubber vulcanization accelerator dibenzothiazole disulfide provided by the present invention has the following reaction formula:

As shown in formula 4, sodium carbonate is used as lye to dissolve 2-mercaptobenzothiazole, 2-mercaptobenzothiazole and sodium carbonate react to form 2-mercaptobenzothiazole sodium and sodium bicarbonate; as shown in formula 5, slowly Add hydrogen peroxide dropwise to the water phase for oxidation reaction, and use carbon dioxide to adjust the pH of the system. Sodium 2-mercaptobenzothiazole is oxidized by hydrogen peroxide to form dibenzothiazole disulfide and sodium bicarbonate; the sodium bicarbonate generated in it is heated to release carbon dioxide The sodium carbonate solution obtained later can be recycled to Formula 4 to dissolve 2-mercaptobenzothiazole and continue to prepare dibenzothiazole disulfide.

Example 1

(1) Take 50g of 15% sodium carbonate aqueous solution, add 5.6g of 2-mercaptobenzothiazole, stir magnetically at a water bath temperature of 70°C to completely dissolve the solid raw materials to obtain a solution A containing sodium 2-mercaptobenzothiazole .

(2) Cool down the solution A obtained in step (1) to 50°C, slowly _{add 37.07g of a 1.37% H 2} O ₂ _{aqueous solution dropwise, and pass CO 2} into the solution at a flow rate of 22.8 mL/min. The reaction proceeds for 40 minutes and then it is cooled. To room temperature, obtain a sodium bicarbonate solution B containing dibenzothiazole disulfide solid;

(3) The solution B obtained in step (2) is suction filtered, and the solid obtained is washed with water and dried to obtain a solid product of dibenzothiazole disulfide with a yield of 96.8% and a purity of 99.4% as determined by the liquid chromatography of the product.

Example 2

(1) Take 50 g of a 20% sodium carbonate aqueous solution, add 5 g of 2-mercaptobenzothiazole, and stir magnetically at a water bath temperature of 80°C to completely dissolve the solid raw materials to obtain a solution A containing sodium 2-mercaptobenzothiazole;

(2) Cool down the solution A obtained in step (1) to 40°C, slowly add 33.89g of 1.5% H ₂ O ₂ _{aqueous solution dropwise, and pass CO 2} into the solution at a flow rate of 17.8 mL/min. The reaction proceeds for 30 minutes and then cools. To room temperature, obtain a sodium bicarbonate solution B containing dibenzothiazole disulfide solid;

(3) The solution B obtained in step (2) is suction filtered, and the solid obtained is washed with water and dried to obtain a solid product of dibenzothiazole disulfide with a yield of 97.8% and a purity of 99.1% as determined by the liquid chromatography of the product.

Example 3

(1) Take the filtrate obtained in step (3) of Example 2 i.e. sodium bicarbonate solution and heat it at 50°C to obtain a sodium carbonate solution. Add 3 g of 2-mercaptobenzothiazole to the obtained sodium carbonate solution. The water bath temperature is at 50°C. Stir to completely dissolve the solid raw materials to obtain a solution A containing sodium 2-mercaptobenzothiazole;

_{(2) Slowly add 22.37g of 1.50% H 2} O ₂ aqueous solution dropwise to the solution A obtained in step (1) _{, and pass CO 2} into the solution at a flow rate of 10.8 mL/min. After the reaction proceeds for 60 minutes, it is cooled to room temperature to obtain Sodium bicarbonate solution B containing solid dibenzothiazole disulfide;

(3) Suction filtration of the solution B obtained in step (2), the obtained solid is washed with water and dried to obtain a solid product of dibenzothiazole disulfide with a yield of 97.2%.

Example 4

(1) Take the filtrate obtained in step (3) of Example 3, the sodium bicarbonate solution, and heat it at 60°C to obtain a sodium carbonate solution. Add 3 g of 2-mercaptobenzothiazole to the obtained sodium carbonate solution. Stir to completely dissolve the solid raw materials to obtain a solution A containing sodium 2-mercaptobenzothiazole;

(2) Slowly add 1.02 g of 30% H ₂ O ₂ aqueous solution dropwise to the solution A obtained in step (1), and cool to room temperature after the reaction proceeds for 30 minutes to obtain a sodium bicarbonate solution B containing dibenzothiazole disulfide solid;

(3) Suction filtration of the solution B obtained in step (2). The solid obtained is washed with water and dried to obtain a solid product of dibenzothiazole disulfide with a yield of over 98% and a purity of over 99% as determined by the liquid chromatography of the product.

Example 5

(1) Take 50g of a 10% sodium carbonate aqueous solution, add 3g of 2-mercaptobenzothiazole, stir magnetically at a water bath temperature of 90℃, connect the reflux condenser to release the CO ₂ escaping from heating, and completely dissolve the solid raw materials. Solution A containing sodium 2-mercaptobenzothiazole;

(2) Cool the solution A obtained in step (1) to 30°C, slowly add 1.53g 20% H ₂ O ₂ _{aqueous solution dropwise, and pour CO 2} into the solution at a flow rate of 16.4 mL/min, and cool down after the reaction proceeds for 40 minutes To room temperature, obtain a sodium bicarbonate solution B containing dibenzothiazole disulfide solid;

(3) The solution B obtained in step (2) is suction filtered, and the obtained solid is washed with water and dried to obtain a solid product of dibenzothiazole disulfide.

Collecting step (3) the mother liquor obtained by suction filtration once, i.e. sodium bicarbonate solution, the sodium carbonate solution obtained after heating to release carbon dioxide is used as a lye cycle to dissolve the raw material 2-mercaptobenzothiazole, repeat the above steps (1)~( 3) The mother liquor can be recycled for more than 5 times, the product yield is more than 98.5%, and the product liquid chromatography purity is more than 99.3%.

Example 6

(1) Take 50g of sodium carbonate aqueous solution with a mass fraction of 15%, add 4g of 2-mercaptobenzothiazole, and stir magnetically at a water bath temperature of 40°C to completely dissolve the solid raw materials to obtain a solution A containing sodium 2-mercaptobenzothiazole;

_{(2) Slowly add 4.06g of 10% H 2} O ₂ aqueous solution dropwise to the solution A obtained in step (1) _{, and pass CO 2} into the solution at a flow rate of 15 mL/min. The reaction proceeds for 40 minutes and the hydrogen peroxide is added dropwise and stopped. CO ₂ , aging for 30 min under constant temperature water bath stirring at 40°C, and cooling to room temperature to obtain a sodium bicarbonate solution B containing dibenzothiazole disulfide solid;

Collecting step (3) the mother liquor obtained by suction filtration once, i.e. sodium bicarbonate solution, the sodium carbonate solution obtained after heating to release carbon dioxide is used as a lye cycle to dissolve the raw material 2-mercaptobenzothiazole, repeat the above steps (1)~( 3) The mother liquor can be recycled more than 5 times, the product yield is more than 97.4%, and the product liquid chromatography purity is more than 99.2%.

The yield of dibenzothiazole disulfide prepared by the method of the invention can reach more than 96.8%, and the highest can reach more than 98.5%; the purity can reach more than 99%.

Claims

A green synthesis method for rubber vulcanization accelerator dibenzothiazole disulfide, characterized in that it comprises the following steps:

(1) Add 2-mercaptobenzothiazole to the sodium carbonate aqueous solution and heat to completely dissolve to obtain a solution A containing sodium 2-mercaptobenzothiazole;

(2) Add hydrogen peroxide dropwise to the solution A obtained in step (1), and adjust the pH of the solution to 5-10 to perform an oxidation reaction. After the reaction, a sodium bicarbonate solution B containing dibenzothiazole disulfide solid is obtained;

(3) Filtering the solution B obtained in step (2), washing and drying the obtained solid to obtain dibenzothiazole disulfide;

(4) The sodium carbonate solution obtained by heating the filtrate from step (3) to release carbon dioxide is used as a lye for recycling in step (1) to dissolve 2-mercaptobenzothiazole, and repeating steps (2) to (3) to prepare two Dibenzothiazole sulfide.
The method according to claim 1, wherein the molar ratio of 2-mercaptobenzothiazole to sodium carbonate in the step (1) is 1:1 to 1:10, and the mass fraction of sodium carbonate in the sodium carbonate aqueous solution is 10%-20%.
The method according to claim 1, wherein the heating temperature in the step (1) is 20-90°C.
The method according to claim 1, wherein the mass fraction of sodium 2-mercaptobenzothiazole in the solution A of the step (1) is 3%-30%.
The method according to claim 1, characterized in that the mass fraction of hydrogen peroxide in the hydrogen peroxide in the step (2) is 1%-30%, and the molar ratio of hydrogen peroxide and sodium 2-mercaptobenzothiazole in solution A The ratio is 0.4:1 to 0.6:1.
The method according to claim 1, wherein the oxidation reaction temperature in the step (2) is 10 to 70°C.
The method according to claim 1, wherein in the step (2), the pH of the solution is adjusted by carbon dioxide.
The method according to claim 1, characterized in that the sodium carbonate solution obtained after the filtrate is heated to release carbon dioxide in the step (3) is used as a lye to be recycled for dissolving 2-mercaptobenzothiazole, and can be recycled. Times or more.
The method according to claim 1, characterized in that, the solid obtained by filtration in the step (3) is washed with water and dried at 80-120° C. to obtain dibenzothiazole disulfide.
A green synthesis method for rubber vulcanization accelerator dibenzothiazole disulfide, characterized in that it comprises the following steps:

(1) Add 2-mercaptobenzothiazole to the sodium carbonate aqueous solution and heat to completely dissolve to obtain a solution A containing sodium 2-mercaptobenzothiazole;

(2) Add hydrogen peroxide dropwise to the solution A obtained in step (1), and adjust the pH of the solution to 5-10 to perform an oxidation reaction. After the reaction, a sodium bicarbonate solution B containing dibenzothiazole disulfide solid is obtained;

(3) The solution B obtained in step (2) is filtered, and the obtained solid is washed and dried to obtain dibenzothiazole disulfide.
The method according to claim 10, wherein the molar ratio of 2-mercaptobenzothiazole to sodium carbonate in the step (1) is 1:1 to 1:10, and the mass fraction of sodium carbonate in the sodium carbonate aqueous solution is 10%-20%.
The method according to claim 10, wherein the mass fraction of sodium 2-mercaptobenzothiazole in the solution A in the step (1) is 3%-30%. The heating temperature is 20 to 90°C.
The method according to claim 10, characterized in that the mass fraction of hydrogen peroxide in the hydrogen peroxide in the step (2) is 1%-30%, and the molar ratio of hydrogen peroxide and sodium 2-mercaptobenzothiazole in solution A The ratio is 0.4:1 to 0.6:1.
The method according to claim 10, wherein the oxidation reaction temperature in the step (2) is 10-70°C, and the pH of the solution is adjusted by carbon dioxide.
The method according to claim 10, wherein the sodium carbonate solution obtained after the filtrate releases carbon dioxide in the step (3) is recycled as a lye for dissolving 2-mercaptobenzothiazole.