A liquid styrene-butadiene rubber, its preparation method and application

Abstract

This invention discloses a liquid styrene-butadiene rubber (SBR), its preparation method, and its applications. The monomers of the liquid SBR include butadiene, styrene, and sulfonate-containing ester monomers. This invention uses sodium hydroxyethyl sulfonate and acrylic acid as raw materials to prepare the ester-containing monomers, which are then used as the third monomer in the preparation of the liquid SBR. A low-temperature emulsion polymerization method is employed. By improving the feeding method, raw material ratio, and adding emulsifiers, ester monomers, and molecular weight regulators in multiple stages, a liquid SBR with superior temperature resistance, wear resistance, corrosion resistance, and mechanical properties is obtained.

Description

Technical Field

[0001] This invention relates to the field of liquid styrene-butadiene rubber, specifically to a liquid styrene-butadiene rubber, its preparation method, and its application. Background Technology

[0002] Liquid rubber is a viscous oligomer liquid with a relative molecular weight between 500 and 50,000, exhibiting a certain degree of fluidity at room temperature. Its viscosity varies with molecular weight and molecular configuration. There are many types of liquid rubber, such as liquid styrene-butadiene rubber, liquid nitrile rubber, and liquid ethylene propylene rubber. Compared to solid rubber, liquid rubber has advantages such as good fluidity, ease of processing, and low energy consumption, and is widely used in sealing materials, adhesives, tires, and other fields.

[0003] Liquid styrene-butadiene rubber (SBR) is a diene copolymer liquid rubber prepared by free radical or anionic polymerization of butadiene and styrene. Free radical emulsion polymerization is currently the most commonly used preparation method due to its ease of operation, controllable reaction temperature, and fast polymerization rate. Compared to natural rubber, liquid SBR possesses certain adhesive properties, temperature resistance, abrasion resistance, and mechanical properties, and exhibits good compatibility with some general-purpose rubbers, making it widely used in adhesives, fillers, tires, and other fields. However, in some extreme environments, the properties of traditional liquid SBR are insufficient to meet material requirements; therefore, further development of liquid SBR with superior temperature resistance, abrasion resistance, corrosion resistance, and mechanical properties is needed.

[0004] CN103539912A discloses a method for preparing high-performance butadiene-styrene liquid rubber, which involves dissolving terpene resin at 80-110°C and grafting it onto styrene-butadiene latex via emulsion polymerization to obtain a terpene resin-modified liquid styrene-butadiene rubber. However, the essence of this method is styrene-butadiene rubber modification, which does not involve the polymerization process of styrene-butadiene rubber and belongs to the subsequent polymerization modification of liquid styrene-butadiene rubber.

[0005] CN115124663A discloses a modified styrene-butadiene rubber (SBR), comprising a SBR matrix and a modified polymer bonded to at least a portion of the surface of the SBR matrix. The modified polymer includes polymeric segments of a first monomer and a second monomer. The first monomer is selected from acrylamide compounds, (meth)acrylate compounds, polyolefin compounds, and combinations thereof. The second monomer is selected from azo initiators containing olefinic unsaturated groups. The modified SBR of this application has a high grafting rate, and during the preparation of asphalt waterproof membranes, the polymeric segments of the second monomer in the modified SBR can further promote crosslinking reactions between the functional groups on the polymeric segments of the first monomer and other modifiers containing olefinic unsaturated groups, thereby imparting good aging resistance. This technical solution uses SBR as a base, and performs free radical solution polymerization on this basis, utilizing ester-containing monomers and azo initiators for ternary copolymerization. It does not involve the polymerization of SBR itself, but belongs to the subsequent polymerization modification of SBR.

[0006] CN1468877A discloses a method for synthesizing hydroxyl-terminated styrene-butadiene liquid rubber, which involves using butadiene and styrene as monomers and organic peroxides as initiators to prepare a hydroxyl-terminated polybutadiene-styrene liquid rubber through free radical solution polymerization.

[0007] CN111560096A disclosed a method for preparing styrene-butadiene rubber (SBR), which involves emulsion polymerization at a polymerization temperature ≤5℃ under nitrogen protection, using styrene, butadiene, water, emulsifier, electrolyte, reducing agent, environmentally friendly molecular weight regulator, and initiator as raw materials to obtain SBR. However, this method simply replaces the traditional SBR regulator without further improving its performance.

[0008] CN110527020A discloses a method for preparing styrene-butadiene rubber (SBR), comprising the following steps: 1) mixing butadiene, styrene, emulsifier, electrolyte, scavenger, activator, oxidant, regulator, and demineralized water, and then carrying out an emulsion polymerization reaction; after the reaction is completed, the reaction system is degassed and an antioxidant is added to obtain latex, wherein the oxidant is pinane hydroperoxide; 2) adding the latex to water containing flocculant and concentrated sulfuric acid and stirring, and after the latex coagulates, filtering and drying to obtain raw SBR, wherein the concentrated sulfuric acid is a sulfuric acid solution with a mass fraction greater than or equal to 70%; 3) mixing the raw SBR with carbon black and sulfur and vulcanizing to obtain SBR. This preparation method can effectively shorten the polymerization time, reduce the amount of regulator used, and reduce energy consumption; and using this preparation method, different SBR latexes can be prepared, and qualified SBR products can be produced.

[0009] CN108017743A discloses a modified carboxylated styrene-butadiene latex and its preparation method. The preparation method of the modified carboxylated styrene-butadiene latex includes the following steps: (1) in the presence of an initiator, a mixture containing butadiene, styrene, acrylic acid, a retarder, a molecular weight regulator, water, a pH buffer, a chelating agent, and an emulsifier is polymerized sequentially at 55–60°C and 65–75°C; (2) the polymerization product is mixed with an oil phase containing nitrile functional monomers, styrene, and butadiene, and an aqueous phase containing water, an initiator, an emulsifier, and a molecular weight regulator, and the resulting mixture is polymerized sequentially at 75–80°C and 85–90°C. The modified carboxylated styrene-butadiene latex prepared by the method provided in this invention not only has a small particle size but also excellent stability and extremely high bonding strength. This method involves ternary copolymerization of carboxylated styrene-butadiene latex at 55–60℃ and 65–75℃, followed by copolymerization grafting with functional monomers containing nitrile groups. This method has a high number-average molecular weight and is complex. Summary of the Invention

[0010] The purpose of this invention is to provide a liquid styrene-butadiene rubber, its preparation method, and its application.

[0011] This invention uses sodium hydroxyethyl sulfonate and acrylic acid as raw materials to prepare ester-containing monomers, which are then used as a third monomer in the preparation of liquid styrene-butadiene rubber. By using a low-temperature emulsion polymerization method and improving the feeding method, raw material ratio, and adding emulsifiers, ester monomers, and molecular weight regulators in multiple stages, a liquid styrene-butadiene rubber with better temperature resistance, wear resistance, corrosion resistance, and mechanical properties is prepared.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] The present invention provides a liquid styrene-butadiene rubber, wherein the polymer monomers of the liquid styrene-butadiene rubber include butadiene, styrene and sulfonate-containing ester monomers;

[0014] The structural formula of the sulfonic acid-containing ester monomer is:

[0015] The liquid styrene-butadiene rubber according to the present invention, preferably, based on a total weight of 100 parts of butadiene, styrene and sulfonate-containing ester monomers, has the following weight parts: 50-75 parts of butadiene, 20-30 parts of styrene, and 5-24 parts of sulfonate-containing ester monomers.

[0016] The liquid styrene-butadiene rubber according to the present invention is preferably prepared by emulsion copolymerization of butadiene, styrene and sulfonate-containing ester monomers.

[0017] The liquid styrene-butadiene rubber contains 3wt% to 18wt% of sulfonate ester monomers.

[0018] The liquid styrene-butadiene rubber according to the present invention preferably has a Mooney viscosity of 40-60 Pa·s at 25°C and a molecular weight Mn range of 3000-5000.

[0019] Another aspect of the present invention provides a method for preparing liquid styrene-butadiene rubber, wherein the preparation method includes the following steps:

[0020] Based on a total weight of 100 parts of butadiene, styrene, and sulfonate-containing ester monomers, add 160–220 parts of deionized water, 4–8 parts of emulsifier, 0.1–0.3 parts of reducing agent, 0.1–0.4 parts of dispersant, 0.4–0.8 parts of electrolyte, 3–6 parts of molecular weight regulator, 20–30 parts of styrene, 3–20 parts of sulfonate-containing ester monomers, and 0.01–0.1 parts of oxygen scavenger to the reaction vessel. After the addition is complete, add 50–75 parts of butadiene under a protective atmosphere and stir for pre-emulsification. Then add 0.1–0.2 parts of initiator to carry out the polymerization reaction.

[0021] When the three monomers, butadiene, styrene, and sulfonate-containing ester monomer, reach a certain monomer conversion rate, emulsifier, initiator, molecular weight regulator, and sulfonate-containing ester monomer are added respectively. When the monomer conversion rate reaches 82-87%, 0.05-0.2 parts of terminator are added to terminate the reaction. Then, degassing, coagulation, washing, and drying are carried out to obtain the liquid styrene-butadiene rubber.

[0022] According to the preparation method of the present invention, preferably, the step of adding emulsifier, initiator, molecular weight regulator and sulfonate-containing ester monomer respectively when the three monomers, butadiene, styrene and sulfonate-containing ester monomer, reach a certain monomer conversion rate specifically includes:

[0023] When the monomer conversion rate reaches 25%–30%, add 1–2 parts of sulfonate-containing monomer; when the monomer conversion rate reaches 50%–55%, add 0.4–0.8 parts of emulsifier, 0.002–0.004 parts of initiator, and 0.5–0.8 parts of molecular weight regulator; when the monomer conversion rate reaches 65%–70%, add 1–2 parts of sulfonate-containing monomer.

[0024] According to the preparation method of the present invention, preferably, the emulsifier is an anionic-anionic compound surfactant or anionic-nonionic compound surfactant; wherein, the anionic-anionic compound surfactant is a compound of rosin soap and fatty alkyl sulfonate, with a compound mass ratio of (4-5):1; the anionic-nonionic compound surfactant is a compound of rosin soap and polyoxyethylene ether, with a compound mass ratio of (3-4):1.

[0025] According to the preparation method of the present invention, preferably, the amount of the emulsifier is 5 to 6 parts.

[0026] According to the preparation method of the present invention, preferably, the reducing agent is selected from, but not limited to, at least one of sodium formaldehyde sulfoxylate, ferrous sulfate, cuprous sulfate, sodium iron EDTA, sodium copper EDTA, etc.

[0027] According to the preparation method of the present invention, preferably, the amount of the reducing agent is 0.2 to 0.3 parts.

[0028] According to the preparation method of the present invention, preferably, the dispersant is sodium naphthalene sulfonate formaldehyde condensate, selected from, but not limited to, at least one of β-naphthalene sulfonate formaldehyde condensate, methylnaphthalene sulfonate formaldehyde condensate, benzylnaphthalene sulfonate formaldehyde condensate, etc.; more preferably, it is β-naphthalene sulfonate formaldehyde condensate.

[0029] According to the preparation method of the present invention, preferably, the amount of the dispersant is 0.2 to 0.3 parts.

[0030] According to the preparation method of the present invention, preferably, the electrolyte is potassium phosphate or potassium chloride.

[0031] According to the preparation method of the present invention, preferably, the amount of electrolyte used is 0.5 to 0.6 parts.

[0032] According to the preparation method of the present invention, preferably, the molecular weight regulator is selected from, but not limited to, at least one of dodecyl mercaptan, tert-dodecyl mercaptan, and 2,4-diphenyl-4-methyl-1-pentene; more preferably, the molecular weight regulator is tert-dodecyl mercaptan or 2,4-diphenyl-4-methyl-1-pentene.

[0033] According to the preparation method of the present invention, preferably, the amount of the molecular weight regulator is 4 to 5 parts.

[0034] According to the preparation method of the present invention, preferably, the oxygen scavenger is selected from, but not limited to, at least one of sodium dithionite, dimethyl ketoxime, isoascorbic acid, etc., and more preferably sodium dithionite.

[0035] According to the preparation method of the present invention, preferably, the amount of the oxygen scavenger is 0.04 to 0.08 parts.

[0036] According to the preparation method of the present invention, preferably, the initiator is an organic hydrogen peroxide, including but not limited to cumene hydrogen peroxide, dicumene hydrogen peroxide, isopropyl tert-butyl hydrogen peroxide, etc., and more preferably dicumene hydrogen peroxide.

[0037] According to the preparation method of the present invention, preferably, the amount of the initiator is 0.12 to 0.18 parts.

[0038] According to the preparation method of the present invention, preferably, the temperature of the polymerization reaction is 5-25°C, more preferably 10-15°C.

[0039] According to the preparation method of the present invention, preferably, the terminating agent is selected from, but not limited to, at least one of hydroxylamine sulfate, diethylhydroxylamine, isopropylhydroxylamine, etc., and more preferably isopropylhydroxylamine or diethylhydroxylamine.

[0040] According to the preparation method of the present invention, preferably, the amount of the terminating agent is 0.05 to 0.1 parts.

[0041] In the preparation method of this invention, the degassing is preferably carried out in a degassing tower, more preferably for 4-5 hours, to obtain ester-containing styrene-butadiene latex; then, after coagulation, washing, and drying, the liquid styrene-butadiene rubber is obtained. Coagulation, washing, and drying are all conventional techniques in the preparation of liquid styrene-butadiene rubber, and this invention does not limit these processes. "Protective gas" includes, for example, nitrogen or argon.

[0042] The preparation method of the modified high-performance liquid styrene-butadiene rubber (SBR) in this invention is simple and clear, and can be industrialized using existing equipment for ternary copolymerization. Based on traditional SBR, a sulfonic acid-containing ester monomer is introduced, resulting in a product containing both ester and sulfonic acid groups. The introduction of the ester group structure improves the heat resistance, ozone stability, and mechanical properties of the liquid SBR, while the introduction of the sulfonic acid group alters the polarity of the liquid SBR, further enhancing its wear resistance by changing the surface polarity. Simultaneously, this invention utilizes a multi-stage addition method of emulsifier, sulfonic acid-containing ester monomer, initiator, and molecular weight regulator to control the molecular weight of this modified high-performance liquid SBR and improve the uniform distribution of ester groups within the liquid SBR.

[0043] According to the preparation method of the present invention, preferably, the sulfonate-containing ester monomer is prepared by the following reaction formula, the specific steps of which include:

[0044]

[0045] Acrylic acid, sodium hydroxyethyl sulfonate, a dehydrating agent, and a catalyst are added to a reaction vessel. Under a protective atmosphere, the temperature is raised to carry out an esterification reaction. During the reaction, water and the dehydrating agent generated are continuously distilled off. The dehydrating agent is separated and then returned to the reaction vessel to continue the reaction. The reaction is stopped when the amount of separated water no longer increases and reaches the theoretical calculation amount. The reaction system is filtered to obtain a filter cake, and the filter cake is distilled under reduced pressure to obtain the sulfonic acid-containing ester monomer.

[0046] In the preparation process of the sulfonic acid ester monomer of the present invention, preferably, the esterification reaction temperature is 110-120°C and the reaction time is 12-15 h.

[0047] In the preparation process of the sulfonic acid ester monomer of the present invention, preferably, the molar ratio of sodium hydroxyethyl sulfonate to acrylic acid is 1:(1-1.5), more preferably 1:(1.2-1.3).

[0048] In the preparation process of the sulfonic acid ester monomer of the present invention, preferably, the dehydrating agent is selected from at least one of toluene, ethylbenzene, and p-toluene; more preferably, it is toluene or xylene.

[0049] In the preparation process of the sulfonate-containing monomer of the present invention, preferably, the amount of the dehydrating agent added is 4 to 6 times the total mass of acrylic acid and sodium hydroxyethyl sulfonate.

[0050] In the preparation process of the sulfonic acid ester monomer of the present invention, preferably, the catalyst is an organic sulfonic acid, selected from but not limited to at least one of methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and 2-naphthalenesulfonic acid, more preferably benzenesulfonic acid or p-toluenesulfonic acid.

[0051] In the preparation process of the sulfonate-containing monomer of the present invention, preferably, the amount of catalyst used is 0.2wt% to 0.8wt% of the total mass of sodium hydroxyethyl sulfonate and acrylic acid, more preferably 0.4wt% to 0.6wt%.

[0052] In another aspect, the present invention provides a liquid styrene-butadiene rubber obtained by the above preparation methods.

[0053] According to the present invention, the liquid styrene-butadiene rubber preferably contains 3wt% to 18wt% of sulfonate ester monomer structure; the liquid styrene-butadiene rubber has a Mooney viscosity of 40 to 60 Pa·s at 25°C and a molecular weight Mn range of 3000 to 5000.

[0054] The method for preparing sulfonate-containing functional monomers designed and developed in this invention is well-suited for industrial synthesis. Unlike current industrial production methods that use concentrated sulfuric acid as a catalyst, this invention uses sodium hydroxyethyl sulfonate and acrylic acid as raw materials, organic sulfonic acid as a catalyst, and a dehydrating agent as a solvent. By removing water generated during the esterification reaction through azeotropic extraction, the efficiency of the esterification reaction is improved. This method allows for the industrial-scale preparation of sulfonate-containing monomers with yields exceeding 90%, achieving self-sufficiency of sulfonate-containing monomer raw materials for the preparation of modified high-performance liquid styrene-butadiene rubber. Subsequently, an emulsion copolymerization method is used to ternarily copolymerize the sulfonate-containing monomer with butadiene and styrene. Through a multi-stage process of adding emulsifiers, sulfonate-containing monomers, molecular weight regulators, and initiators, a modified high-performance liquid styrene-butadiene rubber is prepared. This modified high-performance liquid styrene-butadiene rubber incorporates sulfonate-containing esters and has a Mooney viscosity range of 40–60 Pa·s (25℃) and a molecular weight (Mn) range of 3000–5000, exhibiting good flowability and easy processing properties. The introduction of ester groups improves the polymer's heat resistance, while the introduction of sulfonic acid groups enhances its abrasion resistance. This modified high-performance liquid styrene-butadiene rubber can be used as a substitute for rubber processing oils, toughening agents, and for improving tire tread compounds.

[0055] Another aspect of the present invention provides the application of the above-mentioned liquid styrene-butadiene rubber in tires or epoxy resin toughening agents. Attached Figure Description

[0056] Figure 1 The NMR spectrum of the sulfonic acid ester monomer prepared in Example 3 is shown.

[0057] Figure 2 The NMR spectrum of the modified high-performance liquid styrene-butadiene rubber prepared in Example 3 is shown.

[0058] Figure 3 Figure showing the effect of different addition amounts of high-performance liquid styrene-butadiene rubber on the abrasion resistance of epoxy resin cured products. Detailed Implementation

[0059] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0060] All numerical specifications in this invention (e.g., temperature, time, concentration, and weight, including ranges for each) are generally approximate values ​​that may be changed (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about".

[0061] Example 1

[0062] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, including the following specific steps:

[0063] S1: At room temperature, sodium hydroxyethyl sulfonate (148 g, 1 mol), acrylic acid (72 g, 1 mol), and benzenesulfonic acid (0.44 g, 0.2 wt%) were added to a reactor containing 880 g of toluene. Under nitrogen protection, the temperature was raised to 110 °C and reacted for 12 hours to carry out the esterification reaction of acrylic acid and sodium hydroxyethyl sulfonate. During the reaction, water and dehydrating agent generated in the reaction were continuously distilled off. The dehydrating agent was separated and refluxed into the reactor to continue the reaction. The amount of water separated was calculated. After reaching the theoretical value, the reaction was stopped. The feed liquid was filtered to obtain a filter cake, which was added to the reactor. The dehydrating agent toluene was removed by vacuum distillation at 50 °C and 0.2 MPa. Then, the monomer containing sulfonic acid groups was obtained by vacuum distillation at 72 °C and 0.4 MPa, with a yield of 175.1 g (86.7%).

[0064] S2: In a 10L polymerization reactor, add 160 parts of demineralized water, 4 parts of emulsifier (a 4:1 mixture of rosin soap and fatty alkyl sulfonate emulsifier), 0.1 parts of sodium formaldehyde sulfoxylate, 0.1 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 0.4 parts of potassium phosphate, 3 parts of tert-dodecyl mercaptan, 20 parts of styrene, 3 parts of sulfonate-containing ester monomer, and 0.01 parts of sodium dithionite. After the addition is complete, purge with nitrogen three times, add 75 parts of butadiene, and then add 0.1 parts of dicumyl peroxide at 5°C to carry out the polymerization reaction.

[0065] When the monomer conversion rates of butadiene, styrene, and sulfonate-containing ester monomers reach 25%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 50%, add 0.4 parts of emulsifier, 0.002 parts of dicumyl peroxide, and 0.5 parts of tert-dodecyl mercaptan. When the monomer conversion rate reaches 65%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 82%, add 0.05 parts of hydroxylamine sulfate to terminate the reaction and discharge the product. After discharge, degas the product in a degassing tower for 4 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups can be obtained.

[0066] Example 2

[0067] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, including the following specific steps:

[0068] S1: At room temperature, sodium hydroxyethyl sulfonate (148 g, 1 mol), acrylic acid (108 g, 1.5 mol), and benzenesulfonic acid (2.048 g, 0.8 wt%) were added to a reactor containing 1536 g of toluene. Under nitrogen protection, the temperature was raised to 120 °C and reacted for 15 hours to carry out the esterification reaction of acrylic acid and sodium hydroxyethyl sulfonate. During the reaction, water and dehydrating agent generated in the reaction were continuously distilled off. The dehydrating agent was separated and refluxed into the reactor to continue the reaction. The amount of water separated was calculated. After reaching the theoretical value, the reaction was stopped. The feed liquid was filtered to obtain a filter cake, which was added to the reactor. The dehydrating agent toluene was removed by vacuum distillation at 50 °C and 0.2 MPa. Then, the monomer containing sulfonic acid groups was obtained by vacuum distillation at 72 °C and 0.4 MPa, yielding 178.4 g of the monomer, with a yield of 88.3%.

[0069] S2: In a 10L polymerization reactor, add 220 parts of demineralized water, 8 parts of emulsifier (a 5:1 mixture of rosin soap and fatty alkyl sulfonate emulsifier), 0.3 parts of ferrous sulfate, 0.4 parts of sodium methylnaphthalene sulfonate formaldehyde condensate, 0.8 parts of potassium chloride, 6 parts of dodecyl mercaptan, 21 parts of styrene, 5 parts of sulfonate-containing ester monomer, and 0.1 parts of sodium dithionite. After the addition is complete, purge with nitrogen three times, add 70 parts of butadiene, and then add 0.1 parts of cumene hydroperoxide at 25°C to carry out the polymerization reaction.

[0070] When the monomer conversion rates of butadiene, styrene, and sulfonate-containing ester monomers reach 30%, add 2 parts of sulfonate-containing ester monomer. When the monomer conversion rate reaches 55%, add 0.8 parts of emulsifier, 0.004 parts of cumene hydroperoxide, and 0.8 parts of dodecyl mercaptan. When the monomer conversion rate reaches 70%, add 2 parts of sulfonate-containing ester monomer. When the monomer conversion rate reaches 87%, add 0.05 parts of diethylhydroxylamine to terminate the reaction and discharge the product. After discharge, degas the product in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups can be obtained.

[0071] Example 3

[0072] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, including the following specific steps:

[0073] S1: At room temperature, sodium hydroxyethyl sulfonate (148 g, 1 mol), acrylic acid (86.4 g, 1.2 mol), and benzenesulfonic acid (1.172 g, 0.5 wt%) were added to a reactor containing 950 g of toluene. Under nitrogen protection, the temperature was raised to 120 °C and reacted for 15 hours to carry out the esterification reaction of acrylic acid and sodium hydroxyethyl sulfonate. During the reaction, water and dehydrating agent generated in the reaction were continuously distilled off. The dehydrating agent was separated and refluxed into the reactor to continue the reaction. The amount of water separated was calculated. After reaching the theoretical value, the reaction was stopped. The feed liquid was filtered to obtain a filter cake, which was added to the reactor. The dehydrating agent toluene was removed by vacuum distillation at 50 °C and 0.2 MPa. Then, 186.6 g of the sulfonic acid-containing ester monomer was obtained by vacuum distillation at 72 °C and 0.4 MPa, with a yield of 92.4%.

[0074] S2: In a 10L polymerization reactor, add 190 parts of demineralized water, 5 parts of emulsifier (a 4:1 mixture of rosin soap and fatty alkyl sulfonate emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzyl naphthalene sulfonic acid formaldehyde condensate, 0.5 parts of potassium phosphate, 4 parts of 2,4-diphenyl-4-methyl-1-pentene, 26 parts of styrene, 12 parts of sulfonate-containing ester monomer, and 0.05 parts of isoascorbic acid. After the addition is complete, purge with nitrogen three times, add 60 parts of butadiene, and then add 0.15 parts of isopropyl tert-butyl peroxide at 15°C to carry out the polymerization reaction.

[0075] When the monomer conversion rates of butadiene, styrene, and sulfonate-containing ester monomers reach 25%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 50%, add 0.5 parts of emulsifier, 0.003 parts of isopropyl tert-butyl peroxide, and 0.6 parts of 2,4-diphenyl-4-methyl-1-pentene. When the monomer conversion rate reaches 65%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 85%, add 0.05 parts of isopropyl hydroxylamine to terminate the reaction and discharge the product. After discharge, degas the product in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups can be obtained.

[0076] Example 4

[0077] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, including the following specific steps:

[0078] S1: At room temperature, sodium hydroxyethyl sulfonate (148 g, 1 mol), acrylic acid (93.6 g, 1.3 mol), and benzenesulfonic acid (0.9664 g, 0.4 wt%) were added to a reactor containing 1208 g of toluene. Under nitrogen protection, the temperature was raised to 115 °C and reacted for 14 hours to carry out the esterification reaction of acrylic acid and sodium hydroxyethyl sulfonate. During the reaction, water and dehydrating agent generated in the reaction were continuously distilled off. The dehydrating agent was separated and refluxed into the reactor to continue the reaction. The amount of water separated was calculated. After reaching the theoretical value, the reaction was stopped. The feed liquid was filtered to obtain a filter cake, which was added to the reactor. The dehydrating agent toluene was removed by vacuum distillation at 50 °C and 0.2 MPa. Then, the monomer containing sulfonic acid group was obtained by vacuum distillation at 72 °C and 0.4 MPa, with a yield of 181.3 g (89.8%).

[0079] S2: In a 10L polymerization reactor, add 200 parts of demineralized water, 6 parts of emulsifier (rosin soap and polyoxyethylene ether compound emulsifier in a 3:1 ratio), 0.1 parts of EDTA sodium copper salt, 0.2 parts of β-naphthalenesulfonate sodium formaldehyde condensate, 0.4 parts of potassium chloride, 5 parts of 2,4-diphenyl-4-methyl-1-pentene, 23 parts of styrene, 15 parts of sulfonate-containing ester monomer, and 0.06 parts of dimethyl ketoxime. After the addition is complete, purge with nitrogen three times, add 60 parts of butadiene, and then add 0.12 parts of dicumyl peroxide at 10°C to carry out the polymerization reaction.

[0080] When the monomer conversion rates of butadiene, styrene, and sulfonate-containing ester monomers reach 25%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 55%, add 0.8 parts of emulsifier, 0.002 parts of dicumyl peroxide, and 0.5 parts of 2,4-diphenyl-4-methyl-1-pentene. When the monomer conversion rate reaches 65%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 83%, add 0.05 parts of hydroxylamine sulfate to terminate the reaction and discharge the product. After discharge, degas the product in a degassing tower for 4 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups can be obtained.

[0081] Example 5

[0082] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, including the following specific steps:

[0083] S1: At room temperature, sodium hydroxyethyl sulfonate (148 g, 1 mol), acrylic acid (86.4 g, 1.2 mol), and benzenesulfonic acid (1.4064 g, 0.6 wt%) were added to a reactor containing 1200 g of toluene. Under nitrogen protection, the temperature was raised to 110 °C and reacted for 13 hours to carry out the esterification reaction of acrylic acid and sodium hydroxyethyl sulfonate. During the reaction, water and dehydrating agent generated in the reaction were continuously distilled off. The dehydrating agent was separated and refluxed into the reactor to continue the reaction. The amount of water separated was calculated. After reaching the theoretical value, the reaction was stopped. The feed liquid was filtered to obtain a filter cake, which was added to the reactor. The dehydrating agent toluene was removed by vacuum distillation at 50 °C and 0.2 MPa. Then, 185.2 g of the sulfonic acid-containing ester monomer was obtained by vacuum distillation at 72 °C and 0.4 MPa, with a yield of 91.7%.

[0084] S2: In a 10L polymerization reactor, add 180 parts of demineralized water, 7 parts of emulsifier (rosin soap and polyoxyethylene ether compound emulsifier in a 4:1 ratio), 0.3 parts of sodium formaldehyde sulfoxylate, 0.3 parts of benzyl naphthalene sulfonic acid formaldehyde condensate, 0.6 parts of potassium phosphate, 4 parts of tert-dodecyl mercaptan, 25 parts of styrene, 8 parts of sulfonate-containing ester monomer, and 0.04 parts of isoascorbic acid. After the addition is complete, purge with nitrogen three times, add 63 parts of butadiene, and then add 0.18 parts of diisopropylbenzene hydrogen peroxide at 10°C to carry out the polymerization reaction.

[0085] When the monomer conversion rates of butadiene, styrene, and sulfonate-containing ester monomers reach 30%, add 2 parts of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 55%, add 0.4 parts of emulsifier, 0.002 parts of dicumyl peroxide, and 0.6 parts of tert-dodecyl mercaptan. When the monomer conversion rate reaches 70%, add 2 parts of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 86%, add 0.15 parts of isopropyl hydroxylamine to terminate the reaction and discharge the product. After discharge, degas the product in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups can be obtained.

[0086] Example 6

[0087] This embodiment provides a method for preparing modified high-performance liquid styrene-butadiene rubber and its application, which is prepared by a method including the following specific steps:

[0088] S1: At room temperature, sodium hydroxyethyl sulfonate (148 g, 1 mol), acrylic acid (108 g, 1.5 mol), and benzenesulfonic acid (0.512 g, 0.2 wt%) were added to a reactor containing 1350 g of toluene. Under nitrogen protection, the temperature was raised to 115 °C and reacted for 12 hours to carry out the esterification reaction of acrylic acid and sodium hydroxyethyl sulfonate. During the reaction, water and dehydrating agent generated in the reaction were continuously distilled off. The dehydrating agent was separated and refluxed into the reactor to continue the reaction. The amount of water separated was calculated. After reaching the theoretical value, the reaction was stopped. The feed liquid was filtered to obtain a filter cake, which was added to the reactor. The dehydrating agent toluene was removed by vacuum distillation at 50 °C and 0.2 MPa. Then, the monomer containing sulfonic acid was obtained by vacuum distillation at 72 °C and 0.4 MPa, with a yield of 172.1 g (85.2%).

[0089] S2: In a 10L polymerization reactor, add 210 parts of demineralized water, 5 parts of emulsifier (a 4:1 mixture of rosin soap and fatty alkyl sulfonate emulsifier), 0.2 parts of ferrous sulfate, 0.3 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 0.5 parts of potassium phosphate, 5 parts of tert-dodecyl mercaptan, 29 parts of styrene, 18 parts of sulfonate-containing ester monomer, and 0.08 parts of dimethyl ketoxime. After the addition is complete, purge with nitrogen three times, add 50 parts of butadiene, and then add 0.16 parts of dicumyl peroxide at 10°C to carry out the polymerization reaction.

[0090] When the monomer conversion rate of butadiene, styrene, and sulfonate-containing ester monomers reaches 25%, 2 parts of sulfonate-containing ester monomer are added. When the monomer conversion rate reaches 50%, 0.5 parts of emulsifier, 0.004 parts of dicumyl peroxide, and 0.5 parts of tert-dodecyl mercaptan are added. When the monomer conversion rate reaches 65%, 1 part of sulfonate-containing ester monomer is added. When the monomer conversion rate reaches 85%, 0.15 parts of diethylhydroxylamine are added to terminate the reaction and discharge the product. After discharge, the product is degassed in a degassing tower for 4 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups can be obtained.

[0091] Structural characterization and performance testing:

[0092] To characterize the structural features of the obtained high-performance liquid styrene-butadiene rubber, nuclear magnetic resonance (NMR) measurements were performed on the sulfonate-containing ester monomer and the liquid styrene-butadiene rubber obtained in Example 3. The test results are as follows: Figure 1 and Figure 2 As shown.

[0093] from Figure 1 The 1H NMR spectrum of sulfonic acid ester monomers shows that: 1¹H NMR (400 MHz, CDCl₃), δ 6.48–6.41 (m, CH₂=CH⁻, 1H), 6.22–6.12 (m, CH₂=CH⁻, 1H), 5.83–5.62 (m, CH₂=CH⁻, 1H), 4.59–4.52 (t, CH₂=CH-COO-CH₂⁻, 2H), 2.78–2.71 (m, CH₂=CH-COO-CH₂-CH₂-SO₃Na, 2H). The peaks correspond to the characteristic peaks of sulfonic acid ester monomers, indicating successful preparation of the sulfonic acid ester monomer. Other examples are not listed here. The yields of sulfonic acid ester monomers in Examples 1–6 remained at approximately 85%. Furthermore, unlike laboratory synthesis, this method can be used for industrial-scale production.

[0094] from Figure 2 The 1H NMR spectrum of liquid styrene-butadiene rubber shows that: 1 HNMR (400MHz, CDCl3), the peak at δ4.66(a) is -COO-CH2-CH2-SO3Na next to the ester group, the peak at δ2.74(b) is -CH2-SO3Na next to the sulfonic acid group, the peak at δ2.56(c) is C6H5-CH- next to the benzene ring, and the peak at δ2.26(d) is -CH-COO-CH2-CH2-SO3Na next to the ester group. This proves that the high-performance liquid styrene-butadiene rubber modified by the sulfonic acid ester monomer was successfully prepared.

[0095] To characterize the basic properties of the obtained liquid styrene-butadiene rubber, the liquid styrene-butadiene rubbers containing sulfonic acid groups and ester groups prepared in Examples 1-6 were subjected to corresponding property tests. Specifically, the styrene content was determined according to the refractive index method in GB / T 8658-1998; the content of sulfonic acid group ester monomers was determined by NMR area integration; the molecular weight was determined according to the gel permeation chromatography method in SH / T1759-2007; and the Mooney viscosity was measured using a Mooney viscometer (GT-7082S2) according to GB / T 1232.1-2016. The test results are shown in Table 1.

[0096] Table 1

[0097] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Based on styrene content, wt% 19.3 20.4 24.7 21.2 23.1 28.3 Sulfonate content, wt% 3.4 8.1 12.7 14.6 10.3 17.8 Molecular weight, Mn 4584 3169 3956 3768 4327 3862 Mooney viscosity, Pa·s@25℃ 56.1 44.3 49.8 47.2 54.7 50.2 Glass transition temperature, °C -46 -49 -56 -58 -51 -54

[0098] As can be seen from Table 1, the modified high-performance liquid styrene-butadiene rubbers prepared in Examples 1 to 6 all contain sulfonic acid esters, and have Mooney viscosity ranges from 40 to 60 Pa·s and molecular weight Mn ranges from 3000 to 5000, exhibiting good flowability and easy processing properties.

[0099] To verify the effects of multiple-stage addition of emulsifiers, sulfonate-containing monomers, initiators, and molecular weight regulators on the properties of modified high-performance liquid styrene-butadiene rubber during the preparation process, relevant data were compared with those of comparative examples under different conditions, using Example 3 as a reference. The preparation methods of the comparative examples are as follows:

[0100] Comparative Example 1

[0101] Compared with Example 3, Comparative Example 1 uses a single monomer feeding method without any additional feeding. The specific S2 is as follows:

[0102] In a 10L polymerization reactor, 190 parts of demineralized water, 5 parts of emulsifier (a 4:1 mixture of rosin soap and fatty alkyl sulfonate emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzyl naphthalene sulfonic acid formaldehyde condensate, 0.5 parts of potassium phosphate, 4 parts of 2,4-diphenyl-4-methyl-1-pentene, 26 parts of styrene, 14 parts of sulfonate-containing ester monomer, and 0.05 parts of isoascorbic acid were added. After the addition was completed, the mixture was purged with nitrogen three times. Then, 60 parts of butadiene were added, followed by 0.15 parts of isopropyl tert-butyl peroxide at 15°C to carry out the polymerization reaction.

[0103] When the monomer conversion rate reaches 50%, add 0.5 parts of emulsifier, 0.003 parts of isopropyl tert-butyl peroxide, and 0.6 parts of 2,4-diphenyl-4-methyl-1-pentene. When the monomer conversion rate reaches 85%, add 0.05 parts of isopropyl hydroxylamine to terminate the reaction and discharge the product. After discharge, degas the product in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, liquid styrene-butadiene rubber can be obtained.

[0104] Comparative Example 2

[0105] Compared to Example 3, Comparative Example 2 used a single initiator addition method, while keeping all other conditions unchanged. Specifically, S2 is as follows:

[0106] In a 10L polymerization reactor, 190 parts of demineralized water, 5 parts of emulsifier (a 4:1 mixture of rosin soap and fatty alkyl sulfonate emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzyl naphthalene sulfonic acid formaldehyde condensate, 0.5 parts of potassium phosphate, 4 parts of 2,4-diphenyl-4-methyl-1-pentene, 26 parts of styrene, 12 parts of sulfonate-containing ester monomer, and 0.05 parts of isoascorbic acid were added. After the addition was completed, nitrogen was purged three times. Then, 60 parts of butadiene were added, followed by 0.153 parts of isopropyl tert-butyl peroxide at 15°C to carry out the polymerization reaction.

[0107] When the monomer conversion rates of butadiene, styrene, and sulfonate-containing ester monomers reach 25%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 50%, add 0.5 parts of emulsifier and 0.6 parts of 2,4-diphenyl-4-methyl-1-pentene. When the monomer conversion rate reaches 65%, add 1 part of the sulfonate-containing ester monomer. When the monomer conversion rate reaches 85%, add 0.05 parts of isopropyl hydroxylamine to terminate the reaction and discharge the product. After discharge, degas the product in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups can be obtained.

[0108] Comparative Example 3

[0109] Compared to Example 3, Comparative Example 3 used a one-time addition of sulfonic acid ester monomers, while keeping the other polymerization process conditions unchanged. Specifically, S2 is as follows:

[0110] In a 10L polymerization reactor, 190 parts of demineralized water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate in a 4:1 ratio), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzyl naphthalene sulfonic acid formaldehyde condensate, 0.5 parts of potassium phosphate, 4 parts of 2,4-diphenyl-4-methyl-1-pentene, 26 parts of styrene, 14 parts of sulfonate-containing ester monomer, and 0.05 parts of isoascorbic acid were added. After the addition was completed, nitrogen was purged three times. Then, 60 parts of butadiene were added, followed by 0.15 parts of isopropyl tert-butyl peroxide at 15°C to carry out the polymerization reaction.

[0111] When the monomer conversion rates of butadiene, styrene, and sulfonate-containing ester monomers reach 50%, 0.5 parts of emulsifier, 0.003 parts of isopropyl tert-butyl peroxide, and 0.6 parts of 2,4-diphenyl-4-methyl-1-pentene are added. When the monomer conversion rate reaches 85%, 0.05 parts of isopropyl hydroxylamine are added to terminate the reaction and discharge the product. After discharge, the product is degassed in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the high-performance liquid styrene-butadiene rubber containing sulfonate and ester groups is obtained.

[0112] The properties of the liquid styrene-butadiene rubber prepared in Comparative Examples 1-3 are compared with those in Example 3, as shown in Table 2.

[0113] Table 2

[0114] Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Combined with styrene content, wt% 24.7 21.6 23.2 24.3 Sulfonate content, wt% 12.7 7.4 9.6 8.3 Molecular weight, Mn 3956 5138 3864 4016 Mooney viscosity, Pa·s@25℃ 49.8 61.3 48.6 50.2

[0115] Comparing Example 1 with Example 3, it can be observed that the styrene content and sulfonate ester content are both reduced, while the molecular weight and Mooney viscosity are increased. This is because the single-feeding method accelerates the polymerization of styrene in the early stages of the polymerization reaction, resulting in uneven distribution of styrene on the polymer chain and a decrease in the binding rate of sulfonate ester monomers. Furthermore, the single addition of molecular weight regulators and emulsifiers leads to poor molecular weight control.

[0116] Comparing Comparative Example 2 with Example 3, it can be found that the content of styrene and the content of sulfonic acid esters are reduced accordingly. This is because the initiator is added only once, which results in a faster reaction in the early stage of polymerization and a slower reaction in the later stage. According to the field test, the reaction time required for Comparative Example 2 is much longer than that for Example 3.

[0117] Comparative Example 3 to Example 3 shows that the styrene content did not decrease significantly, but the content of sulfonate esters decreased significantly. This is because the polymerization rate of sulfonate esters is weaker than that of styrene and butadiene. Therefore, the addition of sulfonate esters at one time will cause the sulfonate ester segments to be unevenly distributed in the polymer molecular chain and the binding rate to decrease, thus resulting in a decrease in content.

[0118] To further characterize the application performance of the obtained liquid styrene-butadiene rubber, this invention provides its application as a toughening agent for epoxy resins, including but not limited to toughening agents. The modified high-performance liquid styrene-butadiene rubber prepared in Example 3 was tested for epoxy resin toughening, with ordinary liquid styrene-butadiene rubber (Comparative Example 4) without added sulfonate ester monomers as a control. The addition amount was 5 wt%. The thermal decomposition temperature and erosion wear properties of the cured epoxy resin after toughening were tested, and the test results are shown in Tables 3 and 4, respectively. Figure 3 As shown.

[0119] Comparative Example 4

[0120] Compared to Example 3, Comparative Example 4 did not add a sulfonic acid ester monomer. Specifically, S2 is as follows:

[0121] In a 10L polymerization reactor, 190 parts of demineralized water, 5 parts of emulsifier (a 4:1 mixture of rosin soap and fatty alkyl sulfonate emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzyl naphthalene sulfonic acid formaldehyde condensate, 0.5 parts of potassium phosphate, 4 parts of 2,4-diphenyl-4-methyl-1-pentene, 26 parts of styrene, and 0.05 parts of isoascorbic acid were added. After the addition was complete, the mixture was purged with nitrogen three times. Then, 74 parts of butadiene were added, followed by 0.15 parts of isopropyl tert-butyl peroxide at 15°C to carry out the polymerization reaction.

[0122] When the conversion rate of butadiene and styrene monomers reaches 50%, 0.5 parts of emulsifier, 0.003 parts of isopropyl tert-butyl peroxide, and 0.6 parts of 2,4-diphenyl-4-methyl-1-pentene are added. When the monomer conversion rate reaches 85%, 0.05 parts of isopropyl hydroxylamine are added to terminate the reaction and discharge the product. After discharge, the product is degassed in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex. After coagulation, washing, and drying, the ordinary liquid styrene-butadiene rubber can be obtained.

[0123] Table 3

[0124] Thermal decomposition temperature, Tmax, ℃ Epoxy resin cured products 373 Comparative Example 4: Modified Epoxy Resin Cured Product 365 Example 3: Modified epoxy resin cured product 387

[0125] As shown in Table 3, the thermal decomposition temperature of the pure epoxy resin cured product is 373℃, while that of the modified epoxy resin cured product in Comparative Example 4 is 365℃. This is because the ordinary liquid styrene-butadiene rubber (SBR) and epoxy resin underwent a cross-linking reaction, forming an incompletely cross-linked network structure. Furthermore, since the thermal stability of liquid SBR is relatively weaker than that of epoxy resin, the thermal decomposition temperature of the ordinary liquid SBR-modified epoxy resin cured product is lower. However, the thermal decomposition temperature of the modified epoxy resin cured product in Example 3 is 387℃, higher than the 373℃ of the pure epoxy resin cured product. This is because the introduction of the ester group structure improves the polymer's heat resistance.

[0126] Depend on Figure 3 It can be seen that as the amount of liquid styrene-butadiene rubber (SBR) prepared in Comparative Example 4 and Example 3 increases, the erosion wear rate decreases and the wear resistance gradually increases. However, the epoxy resin modified with the modified high-performance liquid SBR in Example 3 exhibits better wear resistance, which is due to the addition of sulfonic acid groups further enhancing the mechanical properties of the material. It was also found that the wear resistance weakens when the addition amount exceeds a certain threshold. This is because the wear resistance of the cured product is affected not only by the modifier but also by the bonding properties; therefore, exceeding a certain addition amount will weaken the wear resistance of the cured product.

[0127] To further characterize the application performance of the modified high-performance liquid styrene-butadiene rubber obtained in Example 3, the modified high-performance liquid styrene-butadiene rubber prepared in Example 3 was used to replace the rubber processing oil in the preparation of tire rubber compounds, using the mixing formula in Table 4.

[0128] Table 4

[0129] Components Formula 1, g Formula 2, g Solution-polymerized styrene-butadiene rubber 60 60 butadiene rubber 40 40 8# Carbon Black 7.5 7.5 sulfur 0.5 0.5 Accelerator TMTD 3.0 3.0 Processing oil 20.0 0.0 Example 3 0.0 20.0 stearic acid 1.0 1.0 Zinc oxide 5.0 5.0

[0130] The properties of the vulcanized rubber obtained according to Table 4 are shown in Table 5.

[0131] Table 5

[0132] project Formula 1 Formula 2 Tensile strength, MPa 14.54 16.32 Tear strength, MPa 43.15 45.76 Shore A hardness 73 74 <![CDATA[DIN wear volume, cm 3 > 0.173 0.064

[0133] As shown in Table 5, after replacing the rubber processing oil with this modified high-performance liquid styrene-butadiene rubber, the tensile strength and tear strength of the tire vulcanizate are improved, and the wear resistance is enhanced. Therefore, this modified high-performance liquid styrene-butadiene rubber can be used to replace the rubber processing oil, thereby improving the physical and mechanical properties of the tread rubber.

[0134] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A liquid styrene-butadiene rubber, wherein, The polymer monomers of the liquid styrene-butadiene rubber include butadiene, styrene, and sulfonate-containing ester monomers; The structural formula of the sulfonic acid-containing ester monomer is: Based on a total weight of 100 parts for butadiene, styrene, and sulfonate-containing ester monomers, the weight parts of each monomer are as follows: 50-75 parts butadiene, 20-30 parts styrene, and 5-24 parts sulfonate-containing ester monomers.

2. The liquid styrene-butadiene rubber according to claim 1, wherein, The liquid styrene-butadiene rubber is prepared by emulsion copolymerization of butadiene, styrene and sulfonate-containing ester monomers.

3. The liquid styrene-butadiene rubber according to claim 1, wherein, The liquid styrene-butadiene rubber contains 3wt% to 18wt% of sulfonic acid ester monomer structures. The liquid styrene-butadiene rubber has a Mooney viscosity of 40–60 Pa·s at 25°C and a molecular weight (Mn) ranging from 3000 to 5000.

4. A method for preparing liquid styrene-butadiene rubber according to any one of claims 1-3, wherein, The preparation method includes the following steps: Based on a total weight of 100 parts of butadiene, styrene, and sulfonate-containing ester monomers, add 160–220 parts of deionized water, 4–8 parts of emulsifier, 0.1–0.3 parts of reducing agent, 0.1–0.4 parts of dispersant, 0.4–0.8 parts of electrolyte, 3–6 parts of molecular weight regulator, 20–30 parts of styrene, 3–20 parts of sulfonate-containing ester monomers, and 0.01–0.1 parts of oxygen scavenger to the reaction vessel. After the addition is complete, add 50–75 parts of butadiene under a protective atmosphere and stir for pre-emulsification. Then add 0.1–0.2 parts of initiator to carry out the polymerization reaction. When the three monomers, butadiene, styrene, and sulfonate-containing ester monomer, reach a certain monomer conversion rate, emulsifier, initiator, molecular weight regulator, and sulfonate-containing ester monomer are added respectively. When the monomer conversion rate reaches 82-87%, 0.05-0.2 parts of terminator are added to terminate the reaction. Then, degassing, coagulation, washing, and drying are carried out to obtain the liquid styrene-butadiene rubber.

5. The preparation method according to claim 4, wherein, The specific steps of adding emulsifier, initiator, molecular weight regulator and sulfonate-containing ester monomer respectively when butadiene, styrene and sulfonate-containing ester monomer reach a certain monomer conversion rate include: When the monomer conversion rate reaches 25%–30%, add 1–2 parts of sulfonate-containing monomer; when the monomer conversion rate reaches 50%–55%, add 0.4–0.8 parts of emulsifier, 0.002–0.004 parts of initiator, and 0.5–0.8 parts of molecular weight regulator; when the monomer conversion rate reaches 65%–70%, add 1–2 parts of sulfonate-containing monomer.

6. The preparation method according to claim 4 or 5, wherein, The emulsifier is an anionic-anionic compound surfactant or anionic-nonionic compound surfactant; wherein the anionic-anionic compound surfactant is a compound of rosin soap and fatty alkyl sulfonate, with a compound mass ratio of (4-5):1; the anionic-nonionic compound surfactant is a compound of rosin soap and polyoxyethylene ether, with a compound mass ratio of (3-4):

1. The reducing agent is selected from at least one of sodium formaldehyde sulfoxylate, ferrous sulfate, cuprous sulfate, sodium iron EDTA, and sodium copper EDTA. The dispersant is selected from at least one of sodium β-naphthalenesulfonate formaldehyde condensate, sodium methylnaphthalenesulfonate formaldehyde condensate, and benzylnaphthalenesulfonate formaldehyde condensate. The electrolyte is potassium phosphate or potassium chloride; The molecular weight regulator is selected from at least one of dodecyl mercaptan, tert-dodecyl mercaptan, and 2,4-diphenyl-4-methyl-1-pentene; The oxygen scavenger is selected from at least one of sodium dithionite, dimethyl ketoxime, and isoascorbic acid; The initiator is selected from at least one of cumene hydroperoxide, dicumene hydroperoxide, and isopropyl tert-butyl hydroperoxide; The terminating agent is selected from at least one of hydroxylamine sulfate, diethylhydroxylamine, and isopropylhydroxylamine.

7. The preparation method according to claim 4, wherein, The sulfonic acid-containing ester monomer is prepared by the following steps: Acrylic acid, sodium hydroxyethyl sulfonate, a dehydrating agent, and a catalyst are added to a reaction vessel. Under a protective atmosphere, the temperature is raised to carry out an esterification reaction. During the reaction, water and the dehydrating agent generated are continuously distilled off. The dehydrating agent is separated and then returned to the reaction vessel to continue the reaction. The reaction is stopped when the amount of separated water no longer increases and reaches the theoretical calculation amount. The reaction system is filtered to obtain a filter cake, and the filter cake is distilled under reduced pressure to obtain the sulfonic acid-containing ester monomer.

8. The preparation method according to claim 7, wherein, The molar ratio of sodium hydroxyethyl sulfonate to acrylic acid is 1:(1 to 1.5).

9. The preparation method according to claim 7, wherein, The dehydrating agent is selected from at least one of toluene, ethylbenzene, and p-toluene; the catalyst is selected from at least one of methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and 2-naphthalenesulfonic acid.

10. The use of the liquid styrene-butadiene rubber according to any one of claims 1-3 in tires or epoxy resin toughening agents.

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