CN116693468A - Method for synthesizing rubber accelerator CBS by stepwise oxidation of hydrogen peroxide - Google Patents

Abstract

The invention relates to a method for synthesizing a rubber accelerator CBS by stepwise oxidation of hydrogen peroxide; uniformly stirring 2-mercaptobenzothiazole and deionized water in a reactor to obtain a solution, and dropwise adding hydrogen peroxide into the solution to synthesize 2,2' -dithiodibenzothiazole; cooling DM to 30-40 ℃, adding cyclohexylamine and a catalyst, dropwise adding hydrogen peroxide, stopping feeding, stirring and heating after starch-potassium iodide test paper detects the reaction end point, cooling to room temperature, and filtering a water washing product to be neutral; and (5) putting the obtained wet product into an oven, and drying to obtain the rubber accelerator CBS. According to the invention, the raw material M is subjected to self-oxidation under the action of hydrogen peroxide to obtain DM, and a catalyst is added in the next oxidation process to improve the yield, so that the rubber accelerator CBS is directly obtained from the raw material M without intermediate separation, a new hydrogen peroxide step-by-step oxidation one-pot process is established, and the yield can reach more than 90% and the purity is more than 99%.

Description

A kind of hydrogen peroxide step oxidation method of synthesizing rubber accelerator CBS

technical field

The invention relates to a method for synthesizing a rubber accelerator, in particular to a method for synthesizing a rubber accelerator CBS (N-cyclohexyl-2-benzothiazole sulfenamide) by stepwise oxidation with hydrogen peroxide.

Background technique

Rubber accelerator CBS (N-cyclohexyl-2-benzothiazole sulfenamide) because of its primary amine structure, will not produce N-nitrosamines that can cause cancer during the vulcanization process, and the alkalinity of CBS is higher than other types The higher the accelerator, the more significant the effect of reducing the activation energy of the vulcanization process in the vulcanization process.

The CBS synthesis process mainly includes chlorine gas oxidation, sodium hypochlorite oxidation, oxygen catalytic oxidation, hydrogen peroxide oxidation, oxidant-free oxidation, etc. At present, sodium hypochlorite oxidation is mainly used in China.

Chinese patent CN102863402A (January 9, 2013) proposes to use sodium hypochlorite as an oxidant, and to directly synthesize and produce CBS with crude MBT and cyclohexylamine as raw materials. The method has the advantages of simple operation, lower production cost and higher yield, but due to the addition of sodium hypochlorite, the product contains a large amount of sodium chloride in addition to CBS and water, resulting in high salt content in wastewater and difficult treatment, both increasing It increases the cost of waste liquid treatment and is not conducive to environmental protection.

Compared with sodium hypochlorite oxidation, hydrogen peroxide oxidation products are theoretically only CBS and water, which is a green and environmentally friendly process route, in line with the "5R" green chemical concept. However, the selective oxidation of hydrogen peroxide in the later stage of the reaction is poor, resulting in a low yield of the product obtained by the process. The current process reproduces the hydrogen peroxide oxidation method by experiment and the yield is only 62.2%. Part of the organic matter directly enters the water treatment system, resulting in increased wastewater treatment costs, increased production costs, and low economic benefits for income generation. So far, there have been no reports of successful industrial applications in China (China Rubber, 2022, 38(03): 43-47). Based on the advantages and disadvantages of the above two processes, it has been reported that the development of a process related to the mixed oxidation method was carried out, that is, hydrogen peroxide oxidation was used in the early stage of the reaction, and sodium hypochlorite oxidation was used in the later stage.

Chinese patent CN112409291A (February 26, 2021) proposes a synthetic rubber accelerator CBS with accelerator M, cyclohexylamine and water as raw materials, hydrogen peroxide as the main oxidant, and sodium hypochlorite as the secondary oxidant. The gel accelerator CBS prepared by the method has a melting point of 99 DEG C and a yield of CBS of 98.2%. Although the product yield has been improved compared with the hydrogen peroxide oxidation method, the problem of salty wastewater caused by the presence of sodium hypochlorite has not been fundamentally resolved, and there will be a reaction between hydrogen peroxide and sodium hypochlorite, which has certain potential safety hazards.

Due to the shortcomings of the above methods, there is an urgent need for a method for preparing rubber accelerator CBS that is easy to operate, mild in process conditions, and low in cost.

Contents of the invention

In order to overcome the shortcoming and deficiency of above-mentioned technique, the object of the present invention is to provide a kind of preparation method of hydrogen peroxide step oxidation synthetic rubber accelerator CBS. First, the raw material M is oxidized by itself under the action of hydrogen peroxide to obtain the intermediate product accelerator DM (2,2'-dithiodibenzothiazole, hereinafter referred to as DM); and then continue to react with cyclohexylamine under the action of hydrogen peroxide to form The target product CBS, acid green 1 and other catalysts added at this time can greatly improve the selective oxidation of hydrogen peroxide, so that it can obtain a higher product yield on the basis of clean production. Moreover, the process in this paper is a "one-pot method" in actual operation, without intermediate separation, and is suitable for industrial production.

The object of the invention is achieved through the following technical solutions:

Step 1: Stir 2-mercaptobenzothiazole and deionized water in a reactor evenly to obtain a solution, then add hydrogen peroxide dropwise to the solution to synthesize 2,2'-dithiodibenzothiazole;

Step 2: Cool DM to 30-40°C, add cyclohexylamine and catalyst and add hydrogen peroxide dropwise, stop feeding, stirring and heating after the end point of the reaction is detected by starch-potassium iodide test paper, cool to room temperature, and filter and wash the product to medium properties; put the obtained wet product into an oven and dry to obtain the rubber accelerator CBS.

The weight ratio of the 2-mercaptobenzothiazole to deionized water is 2-4:1.

The reaction temperature of the solution during the synthesis of 2,2'-dithiodibenzothiazole is 40-60°C.

The weight ratio between the 2-mercaptobenzothiazole and the hydrogen peroxide is 2-4:1, and the mass fraction of the hydrogen peroxide is 5-30%.

The catalyst is acid green 1,2-mercaptobenzothiazole and the weight ratio of the catalyst is 92-138:1.

The molar ratio of cyclohexylamine to M is 2-3:1.

Technical scheme of the present invention can be represented by following equation:

The raw material M undergoes self-oxidation under the action of hydrogen peroxide to obtain CBS at last, which is an existing pure hydrogen peroxide oxidation technology, but the oxidation selectivity of pure hydrogen peroxide is poor and the yield is low. The present invention divides the reaction into two steps, and mainly improves the second oxidation process. First, the raw material M is oxidized by itself under the action of hydrogen peroxide to obtain DM. The key point is to add a catalyst in the next oxidation process to increase the yield. process, but starting directly from the relatively simple and easy-to-obtain raw material M, without the separation of intermediates, the rubber accelerator CBS is directly obtained, and a new "one-pot method" process for hydrogen peroxide oxidation is established, and the yield can reach more than 90%. The purity is above 99%.

Beneficial effects of the present invention:

1) The raw material M is first oxidized by itself under the action of hydrogen peroxide to obtain the intermediate product DM, which significantly reduces the production cost

2) The use of hydrogen peroxide as a single oxidizing agent avoids the use of sodium hypochlorite and the generation of saline waste water, and obtains a higher product yield on the basis of clean production. The yield exceeds 90%, and the purity can reach more than 99%.

3) It has the advantages of mild process conditions, simple operation, clean and efficient, and meets the requirements of green chemistry.

4) It has good social and economic benefits and is suitable for industrial application.

Detailed ways

The present invention will be described in further detail below in conjunction with specific examples, but the implementation and protection of the present invention are not limited thereto. The reagents or instruments used were not indicated by the manufacturer, and they were regarded as conventional products that can be purchased from the market.

Example 1

Step 1: Add 100mL of water to a 500mL four-necked bottle, add M (0.165mol, 27.5g) under stirring, and slowly add 20% hydrogen peroxide (6.88g) with a mass fraction of 20% at 40°C, the weight ratio between M and hydrogen peroxide 4:1, drop completely;

Step 2: Cool down to 35°C and add cyclohexylamine (0.495mol, 48.9g), the molar ratio between cyclohexylamine and M is 3:1, add the catalyst Acid Green 1 (0.2g) and slowly add dropwise the mass fraction of 20 % hydrogen peroxide, the weight ratio of M to the catalyst is 138:1, after the starch-potassium iodide test paper detects the end point of the reaction, stop feeding, stirring and heating, cool to room temperature, filter and wash the product until neutral, put the obtained wet product into Dry in an oven to obtain 41.03 g of rubber accelerator CBS with a yield of 91.7% and a purity of 99.2%.

Example 2

Step 1: Add 100mL of water to a 500mL four-necked bottle, add M (0.165mol, 27.5g) under stirring, and slowly add 5% hydrogen peroxide (6.88g) with a mass fraction of 5% at 40°C, the weight ratio between M and hydrogen peroxide 4:1, drop completely;

Step 2: Cool down to 35°C and add cyclohexylamine (0.33mol, 32.6g), the molar ratio between cyclohexylamine and M is 2:1, add the catalyst Acid Green 1 (0.3g) and slowly add dropwise the mass fraction of 5 % hydrogen peroxide, the weight ratio of M to the catalyst is 92:1, after the starch-potassium iodide test paper detects the end point of the reaction, stop feeding, stirring and heating, cool to room temperature, filter and wash the product until neutral, put the obtained wet product into Dry in an oven to obtain 40.81 g of rubber accelerator CBS with a yield of 91.2% and a purity of 99.1%.

Example 3

Step 1: Add 100mL of water to a 500mL four-necked bottle, add M (0.165mol, 27.5g) under stirring, and slowly add 20% hydrogen peroxide (13.75g) with a mass fraction of 20% at 50°C, the weight ratio between M and hydrogen peroxide 2:1, drop completely;

Step 2: Cool down to 35°C and add cyclohexylamine (0.404mol, 39.9g), the molar ratio between cyclohexylamine and M is 2.45:1, add the catalyst Acid Green 1 (0.25g) and slowly dropwise add a mass fraction of 20 % hydrogen peroxide, the weight ratio of M to the catalyst is 110:1, after the starch-potassium iodide test paper detects the end point of the reaction, stop feeding, stirring and heating, cool to room temperature, filter and wash the product until neutral, put the obtained wet product into Dry in an oven to obtain 41.30 g of rubber accelerator CBS with a yield of 92.3% and a purity of 99.2%.

Example 4

Step 1: Add 100mL of water to a 500mL four-neck bottle, add M (0.165mol, 27.5g) under stirring, and slowly add 30% hydrogen peroxide (9.32g) with a mass fraction of 30% at 60°C, the weight ratio between M and hydrogen peroxide It is 2.95:1, the drop is complete;

Step 2: Cool down to 35°C and add cyclohexylamine (0.33mol, 32.6g), the molar ratio between cyclohexylamine and M is 2:1, add catalyst Acid Green 1 (0.225g) and slowly add dropwise a mass fraction of 30 % hydrogen peroxide, the weight ratio of M to the catalyst is 122:1, after the starch-potassium iodide test paper detects the end point of the reaction, stop feeding, stirring and heating, cool to room temperature, filter and wash the product until neutral, put the obtained wet product into Dry in an oven to obtain 41.26 g of rubber accelerator CBS with a yield of 92.2% and a purity of 99.1%.

Example 5

Step 1: Add 100mL of water to a 500mL four-necked bottle, add M (0.165mol, 27.5g) under stirring, and slowly add 30% mass fraction of hydrogen peroxide (13.75g) at 50°C, the weight ratio between M and hydrogen peroxide 2:1, drop completely;

Step 2: Cool down to 35°C and add cyclohexylamine (0.495mol, 48.9g), the molar ratio between cyclohexylamine and M is 3:1, add catalyst Acid Green 1 (0.2g) and slowly dropwise add a mass fraction of 30 % hydrogen peroxide, the weight ratio of M to the catalyst is 138:1, after the starch-potassium iodide test paper detects the end point of the reaction, stop feeding, stirring and heating, cool to room temperature, filter and wash the product until neutral, put the obtained wet product into Dry in an oven to obtain 41.08 g of rubber accelerator CBS with a yield of 91.8% and a purity of 99.3%.

Example 6

Step 1: Add 100mL of water to a 500mL four-necked bottle, add M (0.165mol, 27.5g) under stirring, and slowly add 30% mass fraction of hydrogen peroxide (9.32g) at 50°C, the weight ratio between M and hydrogen peroxide It is 2.95:1, the drop is complete;

Step 2: Cool down to 35°C and add cyclohexylamine (0.404mol, 39.9g), the molar ratio between cyclohexylamine and M is 2.45:1, add the catalyst Acid Green 1 (0.275g) and slowly dropwise add a mass fraction of 30 % hydrogen peroxide, the weight ratio of M to the catalyst is 100:1, after the starch-potassium iodide test paper detects the end point of the reaction, stop feeding, stirring and heating, cool to room temperature, filter and wash the product until neutral, put the obtained wet product into Dry in an oven to obtain 41.66 g of rubber accelerator CBS with a yield of 93.1% and a purity of 99.5%.

The above embodiment is only a preferred implementation mode of the present invention, and is only used to explain the present invention, rather than limit the present invention. Any skilled person who is familiar with this field may use the above technical content to change or remodel the equivalent implementation of the equivalent change. example. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (6)

1. a method for hydrogen peroxide step oxidation synthetic rubber accelerator CBS, is characterized in that, comprises the steps: 1): Stir 2-mercaptobenzothiazole and deionized water in a reactor evenly to obtain a solution, then add hydrogen peroxide dropwise to the solution to synthesize 2,2'-dithiodibenzothiazole; 2): Cool down 2,2'-dithiodibenzothiazole to 30-40°C, add cyclohexylamine and catalyst and add hydrogen peroxide dropwise, stop feeding, stirring and heating after the reaction end point is detected by starch-potassium iodide test paper , cooled to room temperature, suction filtered and washed the product until neutral; put the obtained wet product in an oven, and dry to obtain the rubber accelerator CBS. 2. The method for synthesizing rubber accelerator CBS by hydrogen peroxide stepwise oxidation as claimed in claim 1, characterized in that the weight ratio of 2-mercaptobenzothiazole to deionized water is 2 to 4:1. 3. the method for hydrogen peroxide step oxidation synthetic rubber accelerator CBS as claimed in claim 1, it is characterized in that, the solution reaction temperature when synthesizing 2,2'-dithiodibenzothiazole is at 40～60 ℃. 4. the method for hydrogen peroxide step oxidation synthetic rubber accelerator CBS as claimed in claim 1, is characterized in that, the weight ratio between 2-mercaptobenzothiazole and hydrogen peroxide is 2～4: 1, and the massfraction of hydrogen peroxide is in 5-30%. 5. The method for synthesizing rubber accelerator CBS by hydrogen peroxide stepwise oxidation as claimed in claim 1, characterized in that the catalyst is Acid Green 1; the weight ratio of 2-mercaptobenzothiazole to the catalyst is 92-138:1. 6. The method for synthesizing rubber accelerator CBS by step oxidation with hydrogen peroxide as claimed in claim 1, characterized in that the molar ratio of cyclohexylamine to 2-mercaptobenzothiazole is 2-3:1.