A vulcanizing agent, its preparation method and application

Abstract

The application discloses a vulcanizing agent and a preparation method and application thereof. The preparation method of the vulcanizing agent comprises the following steps: reacting low-carbon olefins and a sulfur source under the action of an organic base and / or an inorganic base, monitoring the gas phase pressure of a reaction system during the reaction, stopping the reaction when the gas phase pressure increases by 0.05-0.6 Mpa / min, preferably 0.1-0.4 Mpa / min, and separating after cooling to obtain the vulcanizing agent. The vulcanizing agent not only has a simple preparation method and is easy to control, but also has high sulfur mass content, contains cyclic organic polysulfides with long sulfur chains, and has high mass content of the cyclic polysulfides.

Description

TECHNICAL FIELD

[0001] The present application relates to a vulcanizing agent and its preparation method and application, in particular to an organic polysulfide vulcanizing agent and its preparation method and application. BACKGROUND

[0002] The organic polysulfide is a kind of substance with general formula R-S x x is between 2 and 20, R and R1 are alkyl, alkylaryl, aryl or aralkyl functional groups, which can be the same or different, and can be saturated or unsaturated hydrocarbons, or straight-chain, branched or naphthenic hydrocarbons. The organic polysulfide is often used for pre-sulfurization treatment of hydrogenation catalysts, and whether it is in-situ pre-sulfurization or ex-situ pre-sulfurization, the activation of the hydrogenation catalyst must be completed in the presence of a vulcanizing agent.

[0003] There are many routes for the synthesis of organic polysulfide, and the commonly used method at home and abroad is to use mercaptan and elemental sulfur as raw materials to prepare organic polysulfide in the presence of a catalyst. The development direction of this method is mainly to improve the traditional catalysts such as amines, alkyl amines, alkanol amines, inorganic bases, mercaptide salts and alcoholates. For example, US4876389 uses a composition with general formula RSH·x(C m H 2m O)·yMOH as a catalyst, US5068445 uses a basic resin as a catalyst, and US6051739 uses a traditional basic substance and a compound with general formula R2O[CH2CH·(R3)O] nThe surface active substances of SO3M are combined together as catalysts, the yield of the synthesis reaction product is improved, and the catalyst is easy to separate from the product. US4937385, US6472354, and US6544936 respectively provide a method for preparing organic polysulfide by using olefin, sulfur and hydrogen sulfide as raw materials in the presence of different catalysts. The reaction path is: first, hydrogen sulfide reacts with olefin to generate intermediate alkyl mercaptan compound in the presence of elemental sulfur, then the sulfur molecule is opened under heat to generate organic polysulfide with different sulfur atom contents in the presence of a basic catalyst. The above method uses mercaptan as a substrate, or has mercaptan as an intermediate during the reaction. Since most mercaptans are expensive, toxic and have a foul odor, the obtained organic polysulfide has a bad odor due to the dissolution of hydrogen sulfide and unreacted mercaptan, and has poor stability. US5135670, US5338468, US5849677, and CN200710098327.7 respectively disclose a method for preparing organic polysulfide containing polysulfide cross-linking bonds by using olefin and elemental sulfur as raw materials in the presence of different catalysts. This method has simple preparation process, cheap and easy-to-obtain raw materials, and does not introduce halogen, but the obtained product has more impurities, bad odor and low sulfur content. US4204969, US5410088, and CN1534019 respectively provide a method for preparing relatively pure polysulfide by first generating halogen-containing sulfide olefin and then dehalogenizing in the presence of different catalysts by using olefin and halogenated sulfur as raw materials. The obtained product has high sulfur content and mild conditions, but a large amount of waste water, waste gas (HCl, H2S gas), and waste residue (containing NaCl and sulfide) are generated during the reaction, which is difficult to treat.

[0004] CN103937540A and CN108097333A disclose a sulfiding agent for hydrogenation catalyst and a preparation method thereof. The sulfur content of the sulfiding agent is 40wt%-80wt%, and the sulfiding agent comprises linear polysulfide and cyclic sulfide. The method overcomes the problems of existing sulfiding agents, such as high toxicity and high production cost. However, the proportion of cyclic polysulfide in the sulfiding agent prepared by the method needs to be further improved, the length of the sulfur chain in the cyclic polysulfide is generally less than 2, and 4A molecular sieve needs to be added during the preparation process. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a sulfiding agent, a preparation method and application thereof. The sulfiding agent not only has a simple preparation method and is easy to control, but also has high sulfur mass content, contains cyclic organic polysulfide with long sulfur chains, and has high mass content of cyclic polysulfide.

[0006] A method for preparing a sulfiding agent, the method comprising: low carbon olefins and sulfur source are reacted under the action of organic base and / or inorganic base, the gas phase pressure of the reaction system is monitored during the reaction, and the reaction is stopped when the gas phase pressure increases by 0.05-0.6 Mpa / min, preferably 0.1-0.4 Mpa / min, and the sulfiding agent is obtained after cooling and separation.

[0007] According to the method of the present application, the sulfur source is sulfur, which is solid at room temperature and exists in the form of S8. The sulfur can be a commercially available product or prepared according to the prior art. The purity of the sulfur is not strictly limited, and the sulfur can contain an appropriate amount of impurities.

[0008] According to the method of the present application, the low carbon olefins are C2-C5 olefins. The olefins can be pure olefins or mixed olefins, and the pure olefins can be any one of ethylene, propylene, 1-butene, 2-butene, isobutylene, n-pentene, and isopentene. The mixed olefins can be any mixture of the above pure olefins, or one or more of liquefied gas, ether front carbon four, and ether after carbon four.

[0009] According to the method of the present application, the organic base includes methylamine, urea, ethylamine, ethanolamine, ethylenediamine, dimethylamine, trimethylamine, diethylamine, triethylamine, propylamine, isopropylamine, 1,3-propanediamine, 1,2-propanediamine, tripropylamine, triethanolamine, butylamine, isobutylamine, tert-butylamine, hexylamine, octylamine, diethylene triamine, triethylene tetramine, and tetraethylene pentamine. Preferably, one or more of dimethylamine, trimethylamine, diethylamine, triethylamine, propylamine, isopropylamine, 1,3-propanediamine, 1,2-propanediamine, tripropylamine, and triethanolamine is used.

[0010] According to the method of the present application, the inorganic base is one or more of potassium tert-butoxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and ammonia.

[0011] According to the method of the present application, the low carbon olefins and the sulfur source are reacted under the action of the organic base and / or the inorganic base, and the reaction temperature is controlled by heating the material system containing the sulfur source and monitoring the viscosity coefficient of the material system. When the viscosity coefficient of the material system changes from gradually decreasing to increasing, the temperature of the material system at this time is recorded as T, and the temperature of the material system is controlled to be higher than T by 0-15°C, preferably higher than T by 3-10°C.

[0012] According to the method of the present application, the organic base and / or the inorganic base are added to the material system at least before the viscosity coefficient of the material system changes from gradually decreasing to increasing, and can be added before the material system is heated or during the heating of the material system.

[0013] According to the method, the low-carbon olefin compound can be added into the material system at one time, or can be added intermittently for several times or continuously during the reaction.

[0014] According to the method, the low-carbon olefin, the sulfur source, the organic base and / or the inorganic base are added into the reaction system at one time.

[0015] According to the method, the mass ratio of the organic base and / or the inorganic base to the sulfur source is 0.005-0.2, preferably 0.01-0.1.

[0016] According to the method, the molar ratio of the low-carbon olefin to the sulfur element is 1:1-1:5, preferably 1:2-1:4.

[0017] According to the method, the specific viscosity of the material system when the viscosity coefficient of the material system is changed from gradually decreasing to increasing is different due to the difference of the material system, and the viscosity is generally 3-40 Pa·s, preferably 5-30 Pa·s.

[0018] The application discloses a preparation method of a sulfuration agent.

[0019] (1) the sulfur source, the organic base and / or the inorganic base are mixed and then put into a reaction kettle; then, inert gas is used to replace air, and then the required low-carbon olefin is directly filled or the required low-carbon olefin is filled after replacing nitrogen with the low-carbon olefin, and the material system containing the sulfur source, the organic base and / or the inorganic base and the low-carbon olefin is heated to liquefy the sulfur element;

[0020] (2) the viscosity coefficient of the material system is measured, when the viscosity coefficient of the material system is changed from gradually decreasing to increasing, the temperature of the material system at this time is recorded as T, the temperature of the material system is controlled to be higher than T by 0-15 ℃, preferably higher than T by 5-10 ℃, and the reaction is continued for a period of time;

[0021] (3) the gas phase pressure of the reaction system in step (2) is monitored, when the increasing amplitude of the gas phase pressure reaches 0.05-0.6 MPa / min, preferably 0.1-0.4 MPa / min, the reaction is stopped, and the sulfuration agent is obtained after cooling and separation.

[0022] A sulfuration agent, the sulfuration agent is an organic polysulfide, the sulfur content of the organic polysulfide is more than 45%, preferably 50 wt%-70 wt%, the sulfuration agent contains linear organic polysulfide and cyclic organic polysulfide, and the mass content of the cyclic organic polysulfide in the organic polysulfide is more than 10 wt%, preferably 12%-20% based on the weight of the organic polysulfide.

[0023] The vulcanizing agent according to the present application contains a cyclic trisulfide CnR2nS3 in the cyclic organic polysulfide, wherein R is any group that can be connected to a carbon atom, typically a hydrogen atom, an alkyl group (preferably a methyl group); and is further preferably C3H6S3.

[0024] The vulcanizing agent according to the present application contains a cyclic trisulfide CnR2nS3 in the cyclic organic polysulfide, wherein R is any group that can be connected to a carbon atom, typically a hydrogen atom, an alkyl group (preferably a methyl group); and is further preferably C3H6S3. n R 2n S3 accounts for 30-70%, preferably 40-60% of the total mass of the cyclic organic polysulfide.

[0025] The above-mentioned vulcanizing agent can be used as a vulcanizing agent for hydrogenation catalysts, a vulcanizing agent in the production of rubber, and a coking inhibitor in the production of ethylene.

[0026] In the method of the present application, the length of the sulfur chain in the organic polysulfide vulcanizing agent is a key factor that determines the sulfur content and properties of the organic polysulfide, and the proportion of linear organic polysulfides and cyclic organic polysulfides in the organic polysulfide has an important influence on its vulcanization properties. Taking the vulcanizing agent for hydrogenation catalysts as an example, the different decomposition temperatures of organic polysulfides and cyclic organic polysulfides can be used to achieve sustained and slow vulcanization of the catalyst, and to inhibit the adverse effects of concentrated vulcanization heat release on the active metals of the hydrogenation catalyst. However, it is relatively difficult to prepare long-chain organic polysulfides.

[0027] Based on years of in-depth research on the preparation of organic polysulfides, the inventors found that there are two main reasons: first, the generation of sulfur free radicals in the reaction stage, long-chain free radicals with 2 or more sulfur atoms are unstable and are prone to further decomposition, resulting in a low content of long-chain sulfur free radicals in the reaction system; second, due to factors such as reaction temperature and concentration of each material affecting the reaction equilibrium in the later stage of the reaction, the long-chain organic polysulfides generated are further decomposed. Guided by the above theory, the inventors innovatively proposed to control the end time by the content of the gas phase pressure change to avoid the decomposition of long-chain organic polysulfides, and to control the reaction temperature by monitoring the viscosity of the material system to strengthen the concentration of sulfur free radicals with three or more sulfur atoms in the reaction process and promote the formation of long-chain organic polysulfides. The inventors surprisingly found that by using the above control methods, not only the sulfur content in the organic polysulfide was greatly improved, but also the proportion of cyclic compounds was significantly increased, and a cyclic trisulfide was found in the organic polysulfide. DETAILED DESCRIPTION

[0028] The following examples and comparative examples further illustrate the effects and advantages of the method of the present application, but the following examples do not limit the present application. In the context of the present application, unless otherwise specified, all percentages are by mass. In the method of the present application, the composition of the organic polysulfide prepared and the sulfur content are measured by GC-MS. In the method of the present application, the reaction apparatus is a reaction vessel, which is equipped with a stirring device, a heat exchange device (heating or heat removal), a viscosity measuring device, a pressure measuring device, a temperature measuring device, and the like, as needed.

[0029] Example 1

[0030] 300 g of elemental sulfur, 3 g of dimethylamine, and 15 g of diethylamine were sequentially added to a reaction vessel, and then, after replacing the air with nitrogen, isobutene was directly charged. The molar ratio of isobutene to elemental sulfur was 1:4. The material system was heated and warmed to liquefy the elemental sulfur. The warming rate was 3°C / min. The viscosity coefficient of the material system was measured, and when the viscosity coefficient of the material system was 30 Pa·s, the reaction temperature was 162°C, and the temperature of the material system was controlled to be not higher than 165°C for a certain period of time. The gas phase pressure of the reaction system was monitored, and when the increase rate of the gas phase pressure was 0.4 MPa / min, the reaction was stopped. The gas phase material after cooling could be recycled and reused, and the liquid phase material was flashed at 50°C and 10,000 Pa for 1.5 h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0031] Example 2

[0032] 300 g of elemental sulfur, 3 g of dimethylamine, and 15 g of diethylamine were sequentially added to a reaction vessel, and then, after replacing the air with nitrogen, isobutene was directly charged. The molar ratio of isobutene to elemental sulfur was 1:4. The material system was heated and warmed to liquefy the elemental sulfur. The warming rate was 3°C / min. The viscosity coefficient of the material system was measured, and when the viscosity coefficient of the material system was 30 Pa·s, the reaction temperature was 162°C, and the temperature of the material system was controlled to be not higher than 165°C for a certain period of time. The gas phase pressure of the reaction system was monitored, and when the increase rate of the gas phase pressure was 0.4 MPa / min, the reaction was stopped. The gas phase material after cooling could be recycled and reused, and the liquid phase material was flashed at 50°C and 10,000 Pa for 1.5 h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0033] Example 3

[0034] 300g of elemental sulfur, 7g of triethylamine and 8g of propylamine were sequentially added into a reaction kettle, then nitrogen was used to replace air and directly charge 1-butene, the molar ratio of 1-butene to elemental sulfur was 1:3, the elemental sulfur was liquefied by heating the material system, and the heating rate was 2 ℃ / min. The viscosity coefficient of the material system was measured, when the viscosity coefficient of the material system was 20 Pa·s, the system temperature was 159 ℃, the temperature of the material system was controlled to be not higher than 166 ℃, and the reaction was continued for a period of time; the gas phase pressure of the reaction system in the monitoring step was monitored, when the gas phase pressure increased at a speed of 0.2 Mpa / min, the reaction was stopped, the gas phase material after cooling could be recycled and reused, and the liquid phase material was flashed at 50 ℃ and 10000 pa for 2h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0035] Example 4

[0036] 300g of elemental sulfur, 8g of 1,3-propylamine and 5g of 1,2-propylamine were sequentially added into a reaction kettle, then nitrogen was used to replace air and directly charge 2-butene, the molar ratio of 2-butene to elemental sulfur was 1:3, the elemental sulfur was liquefied by heating the material system, and the heating rate was 2 ℃ / min. The viscosity coefficient of the material system was measured, when the viscosity coefficient of the material system was 20 Pa·s, the system temperature was 160 ℃, the temperature of the material system was controlled to be not higher than 167 ℃, and the reaction was continued for a period of time; the gas phase pressure of the reaction system in the monitoring step was monitored, when the gas phase pressure increased at a speed of 0.15 Mpa / min, the reaction was stopped, the gas phase material after cooling could be recycled and reused, and the liquid phase material was flashed at 50 ℃ and 10000 pa for 2h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0037] Example 5

[0038] 300g of elemental sulfur, 5g of tripropylamine and 5g of triethanolamine were sequentially added into a reaction kettle, then nitrogen was used to replace air and directly charge n-pentene, the molar ratio of n-pentene to elemental sulfur was 1:3.2, the elemental sulfur was liquefied by heating the material system, and the heating rate was 2 ℃ / min. The viscosity coefficient of the material system was measured, when the viscosity coefficient of the material system was 22 Pa·s, the system temperature was 162 ℃, the temperature of the material system was controlled to be not higher than 169 ℃, and the reaction was continued for a period of time; the gas phase pressure of the reaction system in the monitoring step was monitored, when the gas phase pressure increased at a speed of 0.25 Mpa / min, the reaction was stopped, the gas phase material after cooling could be recycled and reused, and the liquid phase material was flashed at 50 ℃ and 10000 pa for 2h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0039] Example 6

[0040] 300g of elemental sulfur, 16g of sodium methoxide were sequentially added into the reaction kettle, then nitrogen was used to replace the air and directly filled with isoamylene, the molar ratio of isoamylene to elemental sulfur was 1:2, the material system was heated to liquefy the elemental sulfur; the heating rate was 2℃ / min. The viscosity coefficient of the material system was measured, when the viscosity coefficient of the material system was 22Pa·s, the system temperature was 159℃ at this time, the temperature of the material system was controlled not higher than 166℃ for a period of time; the gas phase pressure of the reaction system was monitored, when the gas phase pressure increased at a speed of 0.3Mpa / min, the reaction was stopped, the gas phase material after cooling could be recycled for reuse, and the liquid phase material was flashed at 50℃, 10000pa for 2h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0041] Example 7

[0042] 300g of elemental sulfur, 10g of sodium carbonate were sequentially added into the reaction kettle, then nitrogen was used to replace the air and directly filled with a mixed gas of propylene and ether pre-carbon four (the volume ratio of propylene to ether pre-carbon four was 1:2), the molar ratio of the mixed gas to elemental sulfur was 1:3, the material system was heated to liquefy the elemental sulfur; the heating rate was 2℃ / min. The viscosity coefficient of the material system was measured, when the viscosity coefficient of the material system was 20Pa·s, the system temperature was 165℃ at this time, the temperature of the material system was controlled not higher than 168℃ for a period of time; the gas phase pressure of the reaction system was monitored, when the gas phase pressure increased at a speed of 0.25Mpa / min, the reaction was stopped, the gas phase material after cooling could be recycled for reuse, and the liquid phase material was flashed at 50℃, 10000pa for 2h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0043] Example 8

[0044] 300g of elemental sulfur, 17g of potassium hydroxide were sequentially added into the reaction kettle, then nitrogen was used to replace the air and directly filled with ethylene, the molar ratio of ethylene to elemental sulfur was 1:4, the material system was heated to liquefy the elemental sulfur; the heating rate was 2℃ / min. The viscosity coefficient of the material system was measured, when the viscosity coefficient of the material system was 20Pa·s, the system temperature was 158℃ at this time, the temperature of the material system was controlled not higher than 165℃ for a period of time; the gas phase pressure of the reaction system was monitored, when the gas phase pressure increased at a speed of 0.2Mpa / min, the reaction was stopped, the gas phase material after cooling could be recycled for reuse, and the liquid phase material was flashed at 50℃, 10000pa for 2h. The analysis results of the vulcanizing agent product obtained are shown in Table 1.

[0045] Example 9

[0046] 300g of elemental sulfur, 7g of sodium hydroxide and 5g of potassium ethoxide were sequentially added into a reaction kettle, then nitrogen was used to replace air and directly charge into C4 after ether, the molar ratio of C4 after ether and elemental sulfur was 1:3.3, the material system was heated to liquefy the elemental sulfur; the heating rate was 2℃ / min. The viscosity coefficient of the material system was measured, when the viscosity coefficient of the material system was 20Pa·s, the temperature of the system was 160℃, the temperature of the material system was controlled not higher than 167℃ for a period of time; the gas phase pressure of the reaction system was monitored, when the increasing speed of the gas phase pressure was 0.30Mpa / min, the reaction was stopped, the gas phase material after cooling could be recycled and reused, the liquid phase material was flashed at 50℃, 10000pa for 2h. The analysis results of the sulfuration agent product obtained are shown in Table 1.

[0047] Table 1

[0048]

Claims

1. A method for preparing a vulcanizing agent, characterized in that: The vulcanizing agent is an organic polysulfide, the sulfur content of which is above 45%. The vulcanizing agent contains both linear and cyclic organic polysulfides. Based on the weight of the organic polysulfides, the mass content of cyclic organic polysulfides in the organic polysulfides is 10%-20%; the cyclic organic polysulfides contain cyclic trisulfides; the cyclic trisulfides in the cyclic organic polysulfides account for 30%-70% of the total mass of the cyclic organic polysulfides. The preparation method includes: reacting low-carbon olefins and a sulfur source under the action of an organic base and / or an inorganic base. The reaction temperature is controlled by heating the material system containing the sulfur source, monitoring the viscosity coefficient of the material system, and recording the temperature of the material system as T when the viscosity coefficient gradually decreases and then increases. The temperature of the material system is controlled to be higher than T. The reaction temperature is 0-15℃. During the reaction, the gas phase pressure of the reaction system is monitored. When the increase in gas phase pressure reaches 0.05-0.6 MPa / min, the reaction is stopped, and the sulfurizing agent is obtained after cooling. The sulfur source is sulfur.

2. The method according to claim 1, characterized in that: During the reaction, the gas phase pressure of the reaction system is monitored. When the increase in gas phase pressure reaches 0.1-0.4 MPa / min, the reaction is stopped, and the mixture is separated after cooling to obtain the vulcanizing agent.

3. The method according to claim 1, characterized in that: The low-carbon olefins are C2-C5 olefins.

4. The method according to claim 1, characterized in that: The low-carbon olefin is propylene and / or isobutylene.

5. The method according to claim 1, characterized in that: The olefin is a pure olefin or a mixed olefin, or one or more of the following: liquefied petroleum gas containing mixed olefins, pre-ether C4, and post-ether C4.

6. The method according to claim 1, characterized in that: The organic base includes one or more of the following: methylamine, urea, ethylamine, ethanolamine, ethylenediamine, dimethylamine, trimethylamine, diethylamine, triethylamine, propylamine, isopropylamine, 1,3-propanediamine, 1,2-propanediamine, tripropylamine, triethanolamine, butylamine, isobutylamine, tert-butylamine, hexylamine, octylamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

7. The method according to claim 1, characterized in that: The organic base is one or more of dimethylamine, trimethylamine, diethylamine, triethylamine, propylamine, isopropylamine, 1,3-propanediamine, 1,2-propanediamine, tripropylamine, and triethanolamine.

8. The method according to claim 1, characterized in that: The inorganic base is one or more of potassium tert-butoxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and ammonia water.

9. The method according to claim 1, characterized in that: Low-carbon olefins and sulfur sources react under the action of organic and / or inorganic bases. The reaction temperature is controlled as follows: the material system containing sulfur sources is heated, and the viscosity coefficient of the material system is monitored. When the viscosity coefficient of the material system changes from gradually decreasing to increasing, the temperature of the material system at this time is recorded as T. The temperature of the material system is controlled to be 3-10℃ higher than T.

10. The method according to claim 1, characterized in that: The organic base and / or inorganic base shall be added to the material system at least before the viscosity coefficient of the material system gradually decreases and then increases, specifically before the material system is heated or during the heating process.

11. The method according to claim 1, characterized in that: Low-carbon olefin compounds may be added to the material system in one go, or in multiple intermittent additions, or continuously during the reaction.

12. The method according to claim 1, characterized in that: Low-carbon olefins, sulfur sources, organic bases and / or inorganic bases are added to the reaction system in one step.

13. The method according to claim 1, characterized in that: The mass ratio of the organic base and / or inorganic base to the sulfur source is 0.005 to 0.

2.

14. The method according to claim 13, characterized in that: The mass ratio of the organic base and / or inorganic base to the sulfur source is 0.01 to 0.

1.

15. The method according to claim 1, characterized in that: The molar ratio of the low-carbon olefin to the sulfur element is 1:1 to 1:

5.

16. The method according to claim 15, characterized in that: The molar ratio of the low-carbon olefin to the sulfur element is 1:2 to 1:

4.

17. The method according to claim 1, characterized in that: The viscosity of the material system is 3-40 Pa·s when the viscosity coefficient gradually decreases and then increases.

18. The method according to claim 17, characterized in that: The viscosity of the material system is 5-30 Pa·s when the viscosity coefficient gradually decreases and then increases.

19. The method according to claim 1, characterized in that: The method specifically includes the following steps: (1) Mix the sulfur source, organic base and / or inorganic base and put them into the reaction vessel; then replace the air with inert gas and directly fill the required low carbon olefin or replace the nitrogen with low carbon olefin and fill the required low carbon olefin. Heat the material system containing sulfur source, organic base and / or inorganic base and low carbon olefin to liquefy the sulfur element. (2) Measure the viscosity coefficient of the material system. When the viscosity coefficient of the material system changes from gradually decreasing to increasing, the temperature of the material system at this time is recorded as T. Control the temperature of the material system to be higher than T by 0-15℃ and continue the reaction for a period of time. (3) Monitor the gas phase pressure of the reaction system in step (2). When the gas phase pressure increases by 0.05-0.6 MPa / min, stop the reaction, cool down and separate to obtain the vulcanizing agent.

20. The method according to claim 1, characterized in that: The method specifically includes the following steps: (1) Mix the sulfur source, organic base and / or inorganic base and put them into the reaction vessel; then replace the air with inert gas and directly fill the required low carbon olefin or replace the nitrogen with low carbon olefin and fill the required low carbon olefin. Heat the material system containing sulfur source, organic base and / or inorganic base and low carbon olefin to liquefy the sulfur element. (2) Measure the viscosity coefficient of the material system. When the viscosity coefficient of the material system changes from gradually decreasing to increasing, the temperature of the material system at this time is recorded as T. Control the temperature of the material system to be 5-10℃ higher than T and continue the reaction for a period of time. (3) Monitor the gas phase pressure of the reaction system in step (2). When the gas phase pressure increases by 0.1-0.4 MPa / min, stop the reaction, cool down and separate to obtain the vulcanizing agent.

21. The method according to claim 1, wherein the sulfur content of the organic polysulfide in the vulcanizing agent is 50wt%-70wt%.

22. The method according to claim 1, characterized in that: in the vulcanizing agent, based on the weight of the organic polysulfide, the mass content of cyclic organic polysulfides in the organic polysulfide is 12%-20%.

23. The method according to claim 1, wherein the cyclic trisulfide in the vulcanizing agent is C3H6S3.

24. The method according to claim 1, characterized in that: In the vulcanizing agent, the cyclic trisulfide contained in the cyclic organic polysulfide accounts for 40%-60% of the total mass of the cyclic organic polysulfide.

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