Preparation method and application of methyl cyclopentadiene dimer mercaptan

Abstract

The invention relates to the technical field of novel chemical materials, in particular to a preparation method and application of methyl cyclopentadiene dimer mercaptan. The preparation method comprises the following steps: stirring a methyl cyclopentadiene dimer and a solvent, adding a bromine source and an initiator, stirring and heating to a reflux state, and after complete reaction, cooling, filtering, evaporating and concentrating, washing and drying in vacuum to obtain a brominated intermediate; stirring the brominated intermediate and a solvent, adding thioacetate, carrying out a heating reaction, stopping the reaction after the reaction is completed, cooling, carrying out evaporation concentration, separating out a precipitate, filtering, washing, and carrying out vacuum drying to obtain a thioacetate intermediate; stirring the thioacetate intermediate and a solvent, dropwise adding concentrated hydrochloric acid, controlling the reaction temperature, stopping the reaction after the reaction is completed, extracting, combining organic phases, evaporating and concentrating, and drying in vacuum to obtain the methyl cyclopentadiene dimer mercaptan. The finished product can be applied to emulsion free radical polymerization. When the product is applied, the odor is reduced, and the application range is expanded.

Description

Technical Field

[0001] This invention relates to the field of new chemical materials technology, and in particular to a method for preparing methylcyclopentadiene dimer thiol and its application. Background Technology

[0002] Free radical polymerization is currently one of the most commonly used polymerization reactions. If the reaction is not controlled during free radical polymerization, it will continue until the monomer is exhausted, resulting in excessively high molecular weight and deteriorating polymer processing properties. Therefore, chain transfer agents are usually added to adjust the degree of polymerization. After the chain transfer agent is introduced, it reacts with free radicals to generate new free radicals, the original polymer loses its activity, and the molecular weight stops increasing. After the free radicals transfer, the newly generated oligomer molecules continue to react, effectively controlling the polymer molecular weight while maintaining a constant polymerization rate. Emulsion free radical polymerization uses water as a medium, reducing the use of organic solvents and effectively controlling the reaction temperature to avoid localized overheating. The polymerized products have high solids content and low viscosity, and can be directly used in coatings, adhesives, and other fields, imparting good film-forming properties, stability, and mechanical properties to the materials. It is widely used in the synthesis of nitrile rubber and styrene-butadiene latex.

[0003] The most widely used chain transfer agents are currently thiols. Hu Yongling et al. (Hu Yongling, Zhang Chunrong, Tian Yong, et al. Synthesis of tert-dodecyl mercaptan [J]. Chemical Industry and Engineering Progress, 2008, (05): 720-723.) reported a method for synthesizing tert-dodecyl mercaptan. Hydrogen sulfide and dodecene were used as reactants, and an acidic ion exchange resin was used as a catalyst to synthesize tert-dodecyl mercaptan in one step. Patent CN118084748B discloses a method for preparing tert-dodecyl mercaptan. Tetrapropylene, hydrogen sulfide, and a mixed catalyst were added to a reaction vessel and mixed to obtain tert-dodecyl mercaptan. Although tert-dodecyl mercaptan is the preferred choice for the preparation of nitrile rubber due to its efficient chain transfer, its strong odor can have a certain impact on the health of on-site workers. To address these issues, those skilled in the art have developed some novel chain transfer agents, such as α-methylstyrene dimer.

[0004] Methylcyclopentadiene is mainly derived from cracked C9, a byproduct of petroleum cracking. It typically exists as a dimer and is primarily used in the production of high-energy rocket fuel and the gasoline antiknock agent methylcyclopentadiene manganese tricarbonyl (MMT). In recent years, with the continuous expansion of ethylene plants in my country and the increasing production capacity of cracked C9, the output of methylcyclopentadiene has also increased. However, due to environmental and health concerns (mainly manganese emissions), the use of MMT has been strictly restricted or banned in many countries (such as the United States and most parts of the European Union), leading to a sharp decline in demand and an urgent need to expand the application areas of methylcyclopentadiene. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the technical defects of the prior art, the present invention provides a method for preparing methylcyclopentadiene dimer thiol and its application.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing methylcyclopentadiene dimer thiol, comprising the following steps:

[0008] Under gas protection, methylcyclopentadiene dimer and solvent were added, stirred, and bromine source and initiator were added. The mixture was stirred and heated to reflux. The reflux was maintained, and the reaction progress was monitored. After the reaction was complete, the mixture was cooled to room temperature, filtered, evaporated and concentrated, washed, and vacuum dried to obtain the brominated intermediate.

[0009] Under gas protection, the brominated intermediate and solvent were added, stirred, and thioacetate was added. The temperature was raised and the reaction was monitored. After the reaction was complete, the reaction was stopped, cooled to room temperature, evaporated and concentrated, the precipitate was precipitated, filtered, washed, and vacuum dried to obtain the thioacetate intermediate.

[0010] Under gas protection, thioacetic acid intermediate and solvent were added, stirred, concentrated hydrochloric acid was added dropwise, the reaction temperature was controlled, the reaction progress was monitored, the reaction was stopped after complete reaction, extracted, the organic phases were combined, evaporated and concentrated, and dried under vacuum to obtain methylcyclopentadiene dimer thiol.

[0011] It should be noted that in the above technical solution, the present invention prepares the chain transfer agent methylcyclopentadiene dimer thiol through three steps: methyl radical bromination, nucleophilic substitution of the brominated product (thioacetic acid ester method), and hydrolysis of the nucleophilic substitution product.

[0012] Furthermore, when the methylcyclopentadiene dimer and solvent are added, the solvent includes solvents with a boiling point greater than 70°C. Even further, the solvent includes at least one of C6 and above n-alkanes, C6 and above cycloalkanes, aromatics, and chlorinated hydrocarbons with a boiling point greater than 70°C; C6 and above cycloalkanes include cyclohexane; chlorinated hydrocarbons include dichloroethane; and aromatics include toluene.

[0013] Furthermore, the bromine source includes at least one of elemental bromine, N-bromosuccinimide (NBS), hydrogen bromide (HBr), and carbon tetrabromide (CBr4); the initiator includes at least one of benzoyl peroxide (BPO), di-tert-butyl peroxide (DTBP), hydrogen peroxide (H2O2), and azobisisobutyronitrile (AIBN).

[0014] Furthermore, the molar ratio of the bromine source to the methylcyclopentadiene dimer is 1.0 to 1.5:1.

[0015] Furthermore, the molar ratio of the initiator to the methylcyclopentadiene dimer is 0.05 to 0.15:1.

[0016] Furthermore, when the brominated intermediate and solvent are added, the solvent includes at least one of dichloromethane (DCM), tetrahydrofuran (THF), acetonitrile (ACN), toluene, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, and ethanol.

[0017] Furthermore, thioacetates include at least one of potassium thioacetate (KSAc), sodium thioacetate (NaSAc), and ammonium thioacetate (NH4SAc).

[0018] Furthermore, when the thioacetic acid intermediate and solvent are added, the solvent includes at least one of dichloromethane (DCM), tetrahydrofuran (THF), acetonitrile (ACN), toluene, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, and ethanol.

[0019] Furthermore, the molar ratio of thioacetate to brominated intermediate is 1.5 to 3:1.

[0020] Secondly, the present invention provides the application of methylcyclopentadiene dimer thiol in emulsion free radical polymerization, comprising the following steps:

[0021] Monomer, soft water, emulsifier, activator, initiator, and chain transfer agent are mixed and subjected to polymerization reaction under temperature and vacuum conditions. The polymerization system is kept alkaline. The chain transfer agent is added in one or several batches depending on the monomer being polymerized. The reaction is terminated when the conversion rate reaches the specified conversion rate to obtain latex. The latex is then processed to obtain the finished product.

[0022] The chain transfer agent includes methylcyclopentadiene dimer thiol, which is prepared according to the aforementioned method for preparing methylcyclopentadiene dimer thiol.

[0023] Methods for processing latex include:

[0024] (1) Heat the latex to degas it, remove the monomers that participated in the reaction, add a coagulant to the degassed latex to coagulate, wash with alkali, dry and obtain the finished product; or (2) The latex is agglomerated and concentrated to obtain a high solids content finished product.

[0025] Furthermore, the monomer includes at least one of styrene, butadiene, acrylonitrile, and styrene; the emulsifier includes a primary emulsifier and a co-emulsifier, the primary emulsifier including at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, potassium disproportionated rosinate, potassium oleate, and potassium stearate, and the co-emulsifier including at least one of alkylphenol polyoxyethylene ether, secondary alcohol polyoxyethylene ether, and nonylphenol polyoxyethylene ether; the activator includes at least one of triethanolamine, sodium sulfite, sodium formaldehyde sulfoxylate, ethylenediaminetetraacetic acid tetrasodium, and ethylenediaminetetraacetic acid iron sodium; the initiator includes at least one of potassium sulfate, sodium persulfate, and ammonium persulfate; and the coagulant includes at least one of dinitrile diamine formaldehyde condensate, magnesium sulfate, and polyepoxychloropropane dimethylamine.

[0026] Furthermore, the finished products include nitrile rubber and styrene-butadiene latex. Nitrile rubber includes low Mooney nitrile rubber, and styrene-butadiene latex includes high solids styrene-butadiene latex, that is, high solids content styrene-butadiene latex.

[0027] It should be noted that in the above technical solution, when the prepared methylcyclopentadiene dimer thiol is used as a chain transfer agent, the methylcyclopentadiene dimer thiol has a high boiling point and significantly reduced volatility, greatly reducing the odor of the thiol and thus improving the operating environment. The presence of double bonds and thiols in the molecular structure creates a conjugated or hyperconjugated effect, resulting in a chain transfer capacity superior to commonly used tert-dodecyl thiols. Its use in emulsion free radical polymerization can effectively control the molecular weight of the polymerization product. The presence of unreacted double bonds in the methylcyclopentadiene dimer thiol is beneficial for the later-stage vulcanization and crosslinking of rubber. Expanding the application of methylcyclopentadiene dimers is one method to address the overcapacity of methylcyclopentadiene.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention prepares methylcyclopentadiene dimer thiols. The chain transfer agent, methylcyclopentadiene dimer thiols, is prepared through three steps: methyl radical bromination of methylcyclopentadiene, nucleophilic substitution of the brominated product (thioacetic acid ester method), and hydrolysis of the nucleophilic substitution product. This chain transfer agent has shown good results in the free radical polymerization of emulsions such as nitrile rubber and high-solids styrene-butadiene latex.

[0030] When methylcyclopentadiene dimer thiol can be used as a chain transfer agent, specifically: (1) Since methylcyclopentadiene dimer thiol contains both double bonds and thiols, the two form a conjugated or hyperconjugated effect, reducing the probability of recombination or termination, forming a more stable intermediate, efficiently initiating new chain growth, and the double bond synergistic enhancement effect is obvious, improving the chain transfer ability. Therefore, methylcyclopentadiene dimer thiol can effectively control the molecular weight of the polymerization product and prevent the occurrence of destructive free radical chain reactions; (2) It contains unreacted double bonds, which is beneficial to the later vulcanization crosslinking of rubber; (3) The odor is greatly reduced, which is beneficial to improving the operating environment; (4) It provides a new method to solve the technical problem of expanding the application range of methylcyclopentadiene and solving the overcapacity problem. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that all chemical reagents used in this invention are chemically pure.

[0033] Example 1

[0034] The specific steps for preparing methylcyclopentadiene dimer thiols are as follows:

[0035] Step 1: Under inert gas protection, add 1 mol of methylcyclopentadiene dimer and 2 L of cyclohexane to a dry reactor and stir for 0.5 h. Continue by adding 1.2 mol of NBS (N-bromosuccinimide) and 0.1 mol of AIBN, begin vigorous stirring, and slowly heat to 80 °C under reflux. Maintain reflux for 2–8 hours, monitoring the reaction progress using GC-MS until the methylcyclopentadiene dimer has completely reacted. Cool the mixture to room temperature, filter to remove byproducts, and evaporate and concentrate the filtrate to obtain a solid crude product. Wash the crude product three times with cold methanol and dry under vacuum to obtain a white solid, which is 201.69 g of the brominated intermediate.

[0036] Under inert gas protection, 1 mol of the brominated intermediate and 1.5 L of DMF were added to the reactor, and the mixture was stirred for 0.5 h. 2.5 mol of potassium thioacetate (KSAc) was added, and the temperature was raised to 40-60 °C. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the brominated product was completely reacted, at which point the reaction was stopped. The mixture was cooled to room temperature, and the solvent was removed by evaporation. The concentrate was poured into ice water, and a white precipitate formed. After filtration, the filter cake was washed three times with cold water and dried under vacuum to obtain 203.52 g of the thioacetate intermediate.

[0037] Under an inert gas atmosphere, 1 mol of thioacetate intermediate and 1 L of ethanol were added to a reactor and stirred for 0.5 h. Concentrated hydrochloric acid was added dropwise to the reactor, and the reaction temperature was controlled to be below 30 °C by cooling. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the thioacetate intermediate was completely reacted, at which point the reaction was stopped. The reaction product was extracted with 1500 mL of ethyl acetate, the organic phases were combined, the solvent was evaporated to remove the solvent, and the product was concentrated and dried under vacuum to obtain 163.12 g of a colorless oily methylcyclopentadiene dimer thiol product. The product was then sealed and stored in a container under an inert atmosphere under refrigeration or freezing.

[0038] Example 2

[0039] The specific steps for preparing methylcyclopentadiene dimer thiols are as follows:

[0040] Step 1: Under inert gas protection, add 1 mol of methylcyclopentadiene dimer and 2 L of toluene to a dry reactor and stir for 0.5 h. Continue by adding 1.2 mol of elemental bromine and 0.1 mol of benzoyl peroxide, begin vigorous stirring, and slowly heat to 110 °C under reflux. Maintain reflux for 2–8 hours, monitoring the reaction progress using gas chromatography-mass spectrometry (GC-MS) until the methylcyclopentadiene dimer has completely reacted. Cool the mixture to room temperature, filter to remove byproducts, and evaporate and concentrate the filtrate to obtain a solid crude product. Wash the crude product three times with cold methanol and dry under vacuum to obtain a white solid, which is 195.37 g of the brominated intermediate.

[0041] Under inert gas protection, 1 mol of the brominated intermediate and 1.5 L of dichloromethane were added to the reactor and stirred for 0.5 h. Then, 2.5 mol of sodium thioacetate was added, and the temperature was raised to 40-60 °C. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the brominated product was completely reacted, at which point the reaction was stopped. The mixture was cooled to room temperature, and the solvent was removed by evaporation. The concentrate was poured into ice water, and a white precipitate formed. After filtration, the filter cake was washed three times with cold water and dried under vacuum to obtain 198.74 g of the thioacetate intermediate.

[0042] Under an inert gas atmosphere, 1 mol of thioacetic acid intermediate and 1 L of acetone were added to a reactor and stirred for 0.5 h. Concentrated hydrochloric acid was added dropwise to the reactor, and the reaction temperature was controlled to be below 30 °C by cooling. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the thioacetic acid intermediate was completely reacted, at which point the reaction was stopped. The reaction product was extracted with 1500 mL of ethyl acetate, the organic phases were combined, the solvent was evaporated to remove the solvent, and the product was concentrated and dried under vacuum to obtain 162.75 g of a colorless, oily methylcyclopentadiene dimer thiol product. The product was then sealed and stored in a container under an inert atmosphere and refrigerated or frozen.

[0043] Example 3

[0044] The specific steps for preparing methylcyclopentadiene dimer thiols are as follows:

[0045] Step 1: Under inert gas protection, add 1 mol of methylcyclopentadiene dimer and 2 L of dichloroethane to a dry reactor and stir for 0.5 h. Continue by adding 0.1 mol of benzoyl peroxide and introducing hydrogen bromide gas. Begin vigorous stirring and slowly heat to 40 °C under reflux, maintaining reflux for 2–8 hours. Monitor the reaction progress using GC-MS until the methylcyclopentadiene dimer has completely reacted. Cool the mixture to room temperature, filter to remove byproducts, and evaporate and concentrate the filtrate to obtain a solid crude product. Wash the crude product three times with cold methanol and dry under vacuum to obtain a white solid, which is 174.52 g of the brominated intermediate.

[0046] Under inert gas protection, 1 mol of the brominated intermediate and 1.5 L of N,N-dimethylformamide were added to a reactor and stirred for 0.5 h. Then, 2.5 mol of ammonium thioacetate was added, and the temperature was raised to 40-60 °C. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the brominated product was completely reacted, at which point the reaction was stopped. The mixture was cooled to room temperature, and the solvent was removed by evaporation and concentration. The concentrate was poured into ice water, and a white precipitate formed. After filtration, the filter cake was washed three times with cold water and dried under vacuum to obtain 182.15 g of the thioacetate intermediate.

[0047] Under an inert gas atmosphere, 1 mol of thioacetate intermediate and 1 L of ethanol were added to a reactor and stirred for 0.5 h. Concentrated hydrochloric acid was added dropwise to the reactor, and the reaction temperature was controlled to be below 30 °C by cooling. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the thioacetate intermediate was completely reacted, at which point the reaction was stopped. The reaction product was extracted with 1500 mL of ethyl acetate, the organic phases were combined, the solvent was evaporated to remove the solvent, and the product was concentrated and dried under vacuum to obtain 162.94 g of a colorless, oily methylcyclopentadiene dimer thiol product. This product was then sealed and stored in a container under an inert atmosphere and refrigerated or frozen.

[0048] Example 4

[0049] The specific steps for preparing methylcyclopentadiene dimer thiols are as follows:

[0050] Step 1: Under inert gas protection, add 1 mol of methylcyclopentadiene dimer and 2 L of cyclohexane to a dry reactor and stir for 0.5 h. Continue by adding 1 mol of NBS (N-bromosuccinimide) and 0.1 mol of AIBN, begin vigorous stirring, and slowly heat to 80°C under reflux. Maintain reflux for 2–8 hours, monitoring the reaction progress using gas chromatography-mass spectrometry (GC-MS) until the methylcyclopentadiene dimer has completely reacted. Cool the mixture to room temperature, filter to remove byproducts, and evaporate and concentrate the filtrate to obtain a solid crude product. Wash the crude product three times with cold methanol and dry under vacuum to obtain a white solid, which is the brominated intermediate. The weight of the brominated intermediate is approximately 5% less than that in Example 1.

[0051] Under inert gas protection, 1 mol of the brominated intermediate and 1.5 L of DMF were added to the reactor and stirred for 0.5 h. 3 mol of potassium thioacetate (KSAc) was added, and the reaction was heated to 40-60 °C. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the brominated product was completely reacted, at which point the reaction was stopped. The mixture was cooled to room temperature, and the solvent was removed by evaporation and concentration. The concentrate was poured into ice water, and a white precipitate formed. After filtration, the filter cake was washed three times with cold water and dried under vacuum to obtain the thioacetate intermediate. The weight of the thioacetate intermediate was approximately 0.5% greater than that in Example 1.

[0052] Under inert gas protection, 1 mol of thioacetate intermediate and 1 L of ethanol were added to the reactor and stirred for 0.5 h. Concentrated hydrochloric acid was added dropwise to the reactor, and the reaction temperature was controlled to be below 30 °C by cooling. The reaction progress was monitored by gas chromatography-mass spectrometry (GC-MS) until the thioacetate intermediate was completely reacted, at which point the reaction was stopped. The reaction product was extracted with 1500 mL of ethyl acetate, the organic phases were combined, the solvent was evaporated to remove the solvent, and the product was concentrated and dried under vacuum to obtain a colorless, oily methylcyclopentadiene dimer thiol product. This product was then sealed and stored in a container under an inert atmosphere for refrigeration or freezing.

[0053] Example 5

[0054] The methylcyclopentadiene dimer thiol prepared in Example 1 was used in the preparation of nitrile rubber. The specific steps are as follows:

[0055] The polymerization reactor was evacuated and then purged with nitrogen to achieve a vacuum of 0 MPa, maintaining an inert environment. 250 parts soft water, 70 parts butadiene, 30 parts acrylonitrile, 4 parts composite emulsifier (specifically, 3.5 parts sodium dodecyl sulfate and 0.5 parts nonylphenol polyoxyethylene ether), 0.15 parts triethanolamine activator, and 0.15 parts methylcyclopentadiene dimer mercaptan chain transfer agent were added to the reactor. The pH of the polymerization system was adjusted to 8, the temperature was adjusted to 6°C, and 0.25 parts potassium persulfate initiator was added. When the reaction conversion rate reached 30-40%, 0.15 parts methylcyclopentadiene dimer mercaptan chain transfer agent was added a second time. When the reaction conversion rate reached 45-55%, 0.15 parts methylcyclopentadiene dimer mercaptan chain transfer agent was added a third time. Online viscosity and conversion rate tests were used to control the Mooney viscosity of the rubber to below 20. When the reaction conversion rate reaches 70-80%, 0.1 parts of the terminator diethylhydroxylamine are added. After the reaction is terminated, the material is discharged. Unreacted butadiene and acrylonitrile are recovered by heating and degassing. After degassing, the temperature is adjusted to 55℃ and the pH value to 3. A coagulant, dinitrile diamine formaldehyde condensate, is added, and the coagulated rubber compound is subjected to alkali washing. After alkali washing, the rubber compound is dried sequentially using a conventional extruder, a two-stage vacuum dehydrator, and a drying oven to obtain a low Mooney nitrile rubber. This nitrile rubber has a Mooney viscosity of 18, a tensile strength of 18.6 MPa, and a volatile matter content of 0.42%.

[0056] Example 6

[0057] The methylcyclopentadiene dimer thiol prepared in Example 1 was used in the preparation of styrene-butadiene latex, and the specific steps are as follows:

[0058] The polymerization reactor was evacuated and then purged with nitrogen to achieve a vacuum of 0 MPa, maintaining an inert environment. 100 parts soft water, 90 parts styrene, 0.5 parts sodium dodecyl sulfate (emulsifier), 0.1 parts sodium sulfite (activator), 0.5 parts potassium persulfate (initiator), and 0.15 parts methylcyclopentadiene dimer mercaptan (chain transfer agent) were added to the reactor. The temperature was controlled at 15℃ and the negative pressure at -50 kPa to -55 kPa. 10 parts butadiene were added dropwise to the polymerization reactor, and the reaction time was 12 hours. After the reaction, the resulting latex product was sent to a blending tank. After passing inspection, it was sent to the subsequent homogenization and agglomeration process. The homogenizer pressure was 60 MPa. The agglomerated latex was then sent to a degassing tank for vacuum evaporation and concentration. The initial concentration temperature was 65℃ ± 3℃, and when the viscosity significantly increased, the temperature was controlled at 55℃ ± 3℃. The solid content of the latex was determined based on the liquid level in the degassing tank. Concentration was stopped when the solid content reached 60% or more, yielding a high-solids styrene-butadiene latex. The tested styrene-butadiene latex had a solid content of 65.74% and a particle diameter of 535 nm.

[0059] Comparative Example 1

[0060] The commonly used chain transfer agent tert-dodecyl mercaptan is applied to the preparation of nitrile rubber. The specific steps are as follows:

[0061] The polymerization reactor was evacuated and then purged with nitrogen to achieve a vacuum of 0 MPa, maintaining an inert environment. 250 parts soft water, 70 parts butadiene, 30 parts acrylonitrile, 4 parts composite emulsifier (specifically, 3.5 parts sodium dodecyl sulfate and 0.5 parts nonylphenol polyoxyethylene ether), 0.15 parts triethanolamine activator, and 0.2 parts tert-dodecyl mercaptan chain transfer agent were added to the reactor. The pH of the polymerization system was adjusted to 8, the temperature was adjusted to 6°C, and 0.25 parts potassium persulfate initiator was added. When the reaction conversion rate reached 30-40%, 0.2 parts tert-dodecyl mercaptan chain transfer agent was added a second time. When the reaction conversion rate reached 45-55%, 0.2 parts tert-dodecyl mercaptan chain transfer agent was added a third time. Online viscosity and conversion rate tests were used to control the Mooney viscosity of the rubber below 20. When the reaction conversion rate reached 70-80%, 0.1 parts diethylhydroxylamine terminating agent was added. After the reaction was terminated, the material was discharged. Unreacted butadiene and acrylonitrile were recovered through heating and degassing. After degassing, the temperature was adjusted to 55°C and the pH to 3, and a coagulant, dinitrile diamine formaldehyde condensate, was added. The resulting rubber compound was then subjected to alkali washing. After alkali washing, the rubber compound was dried sequentially using a conventional extruder, a two-stage vacuum dehydrator, and a drying oven to obtain a low Mooney nitrile rubber. This nitrile rubber has a Mooney viscosity of 18, a tensile strength of 18.8 MPa, and a volatile matter content of 0.41%.

[0062] Comparative Example 2

[0063] The commonly used chain transfer agent tert-dodecyl mercaptan is applied in the preparation of styrene-butadiene latex. The specific steps are as follows:

[0064] The polymerization reactor was evacuated and then purged with nitrogen to achieve a vacuum of 0 MPa, maintaining an inert environment. 100 parts soft water, 90 parts styrene, 0.5 parts sodium dodecyl sulfate (emulsifier), 0.1 parts sodium sulfite (activator), 0.5 parts potassium persulfate (initiator), and 0.25 parts tert-dodecyl mercaptan (chain transfer agent) were added to the reactor. The temperature was controlled at 15℃, and the negative pressure at -50 kPa to -55 kPa. 10 parts butadiene were added dropwise to the polymerization reactor, and the reaction time was 12 hours. After the reaction, the resulting latex product was sent to a blending tank. After passing inspection, it was sent to the subsequent homogenization and agglomeration process, where the homogenizer pressure was 60 MPa. The agglomerated latex was then sent to a degassing tank for vacuum evaporation and concentration. The initial concentration temperature was 65℃ ± 3℃, and when the viscosity significantly increased, the temperature was controlled at 55℃ ± 3℃. The solid content of the latex was determined based on the liquid level in the degassing tank. Concentration was stopped when the solid content reached 60% or more, yielding a high-solids styrene-butadiene latex. The tested solid content of the styrene-butadiene latex was 62.37%, and the particle diameter was 521 nm.

[0065] Analysis: The results of Examples 5-6 and Comparative Examples 1-2 show that the chain transfer agent methylcyclopentadiene dimer thiol provided by this invention has a stronger chain transfer ability than the commonly used tert-dodecyl thiol, and requires a smaller amount to be added under the same conditions. When applied to emulsion free radical polymerization of nitrile rubber and styrene-butadiene latex, the performance indicators of the final products are comparable, or even better. Furthermore, in actual operation, operators found that the finished products of Comparative Examples 1-2 had a stronger foul odor compared to Examples 5-6.

[0066] The methylcyclopentadiene dimer thiol prepared by this invention can effectively control the increase in molecular weight during the polymerization process and reduce the malodorous odor. At the same time, it also broadens the application range of methylcyclopentadiene and has good application prospects.

[0067] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing methylcyclopentadiene dimer thiol, characterized in that, Includes the following steps: Under gas protection, methylcyclopentadiene dimer and solvent were added, stirred, and bromine source and initiator were added. The mixture was stirred and heated to reflux. The reflux was maintained, and the reaction progress was monitored. After the reaction was complete, the mixture was cooled to room temperature, filtered, evaporated and concentrated, washed, and vacuum dried to obtain the brominated intermediate. Under gas protection, the brominated intermediate and solvent were added, stirred, and thioacetate was added. The temperature was raised and the reaction was monitored. After the reaction was complete, the reaction was stopped, cooled to room temperature, evaporated and concentrated, the precipitate was precipitated, filtered, washed, and vacuum dried to obtain the thioacetate intermediate. Under gas protection, thioacetic acid intermediate and solvent were added, stirred, concentrated hydrochloric acid was added dropwise, the reaction temperature was controlled, the reaction progress was monitored, the reaction was stopped after complete reaction, extracted, the organic phases were combined, evaporated and concentrated, and dried under vacuum to obtain methylcyclopentadiene dimer thiol.

2. The method for preparing methylcyclopentadiene dimer thiol as described in claim 1, characterized in that, When methylcyclopentadiene dimer and solvent are added, the solvent includes at least one of C6 and above n-alkanes, C6 and above cycloalkanes, aromatics, and chlorinated hydrocarbons with a boiling point greater than 70°C. C6 and above cycloalkanes include cyclohexane, chlorinated hydrocarbons include dichloroethane, and aromatics include toluene.

3. The method for preparing methylcyclopentadiene dimer thiol as described in claim 1, characterized in that, The bromine source includes at least one of elemental bromine, N-bromosuccinimide, hydrogen bromide, and carbon tetrabromide; the initiator includes at least one of benzoyl peroxide, di-tert-butyl peroxide, hydrogen peroxide, and azobisisobutyronitrile.

4. The method for preparing methylcyclopentadiene dimer thiol as described in claim 1, characterized in that, The molar ratio of bromine source to methylcyclopentadiene dimer is 1.0 to 1.5:

1.

5. The method for preparing methylcyclopentadiene dimer thiol as described in claim 1, characterized in that, The molar ratio of the initiator to the methylcyclopentadiene dimer is 0.05 to 0.15:

1.

6. The method for preparing methylcyclopentadiene dimer thiol according to claim 1, characterized in that, When a brominated intermediate and a solvent are added, the solvent includes at least one of dichloromethane, tetrahydrofuran, acetonitrile, toluene, N,N-dimethylformamide, dimethyl sulfoxide, acetone, and ethanol.

7. The method for preparing methylcyclopentadiene dimer thiol according to claim 1, characterized in that, Thioacetates include at least one of potassium thioacetate, sodium thioacetate, and ammonium thioacetate; When the thioacetic acid ester intermediate and solvent are added, the solvent includes at least one of dichloromethane, tetrahydrofuran, acetonitrile, toluene, N,N-dimethylformamide, dimethyl sulfoxide, acetone, and ethanol.

8. The method for preparing methylcyclopentadiene dimer thiol as described in claim 1, characterized in that, The molar ratio of thioacetate to brominated intermediate is 1.5 to 3:

1.

9. The application of methylcyclopentadiene dimer thiol in emulsion free radical polymerization, characterized in that, Includes the following steps: Monomer, soft water, emulsifier, activator, initiator, and chain transfer agent are mixed and subjected to polymerization reaction under temperature and vacuum conditions. The polymerization system is kept alkaline. The chain transfer agent is added in one or several batches depending on the monomer being polymerized. The reaction is terminated when the conversion rate reaches the specified conversion rate to obtain latex. The latex is then processed to obtain the finished product. The chain transfer agent includes methylcyclopentadiene dimer thiol, which is prepared by the method described in any one of claims 1-8. Methods for processing latex include: (1) Heat the latex to degas it, remove the monomers that participated in the reaction, add a coagulant to the degassed latex to coagulate, wash with alkali, dry and obtain the finished product; or (2) The latex is agglomerated and concentrated to obtain a high solids content finished product.

10. The application of the methylcyclopentadiene dimer thiol as described in claim 9 in emulsion free radical polymerization, characterized in that, The monomer includes at least one of styrene, butadiene, acrylonitrile, and styrene; the emulsifier includes a primary emulsifier and a co-emulsifier, the primary emulsifier including at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, potassium disproportionated rosinate, potassium oleate, and potassium stearate, and the co-emulsifier including at least one of alkylphenol polyoxyethylene ether, secondary alcohol polyoxyethylene ether, and nonylphenol polyoxyethylene ether; the activator includes at least one of triethanolamine, sodium sulfite, sodium formaldehyde sulfoxylate, ethylenediaminetetraacetic acid tetrasodium, and ethylenediaminetetraacetic acid ferric sodium; the initiator includes at least one of potassium sulfate, sodium persulfate, and ammonium persulfate; and the coagulant includes at least one of dinitrile diamine formaldehyde condensate, magnesium sulfate, and polyepoxychloropropane dimethylamine.