Liquid styrene-butadiene rubber, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a liquid styrene-butadiene rubber, and a preparation method therefor and the use thereof. Polymerization monomers of the liquid styrene-butadiene rubber comprise butadiene, styrene and a sulphonate-containing monomer of formula (I). In the present invention, the sulphonate-containing monomer is used for preparing the liquid styrene-butadiene rubber, thereby obtaining a liquid styrene-butadiene rubber having better temperature resistance, wear resistance, corrosion resistance and mechanical properties.

Description

Liquid styrene-butadiene rubber and its preparation method and application

[0001] Cross-reference information

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on October 24, 2023, with application number 202311382441.8 and invention name “A liquid styrene-butadiene rubber, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The invention relates to the field of liquid styrene-butadiene rubber, and in particular to liquid styrene-butadiene rubber and a preparation method and application thereof. Background Art

[0004] Liquid rubber is a viscous oligomer liquid with a relative molecular weight between 500 and 50,000 and 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 offers advantages such as good fluidity, ease of processing, and low energy consumption, making it widely used in sealing materials, adhesives, tires, and other fields.

[0005] Liquid styrene butadiene rubber (LSB) 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 convenient operation, easy control of reaction temperature, and fast polymerization rate. Compared to natural rubber, LSBR has certain adhesion, heat resistance, wear resistance, and mechanical properties, as well as good compatibility with some general-purpose rubbers. Therefore, it is widely used in adhesives, fillers, tires and other fields. However, in some more extreme environments, the performance of traditional LSBR can no longer meet the material requirements. Therefore, there is a need to further develop LSBR with better heat resistance, wear resistance, corrosion resistance, and mechanical properties.

[0006] CN103539912A discloses a method for preparing high-performance butadiene-styrene liquid rubber. A terpene resin is dissolved at 80-110°C and grafted onto styrene-butadiene latex through emulsion polymerization to obtain a terpene resin-modified liquid styrene-butadiene rubber. However, the essence of this method is the modification of styrene-butadiene rubber and does not involve the polymerization process of styrene-butadiene rubber. It belongs to the subsequent polymerization modification of liquid styrene-butadiene rubber.

[0007] CN115124663A discloses a modified styrene-butadiene rubber (SBR), comprising a SBR matrix and a modified polymer bound to at least a portion of the surface of the SBR matrix, wherein the modified polymer comprises a polymer segment of a first monomer and a polymer segment of a second monomer; the first monomer is selected from acrylamide compounds, (meth)acrylate compounds, polyolefin compounds, and combinations thereof; and the second monomer is selected from azo initiators containing ethylenically unsaturated groups. The modified SBR of this application has a high grafting rate, and during the preparation of asphalt waterproofing membranes, the polymer segment of the second monomer in the modified SBR can further promote cross-linking reactions between functional groups on the polymer segment of the first monomer and other modifiers containing ethylenically unsaturated groups, thereby imparting good aging resistance. This technical solution uses SBR as a substrate, conducts free radical solution polymerization on this basis, and uses an ester-containing monomer and an azo initiator for ternary copolymerization. It does not involve polymerization of SBR and is a subsequent polymerization modification of SBR.

[0008] CN1468877A discloses a method for synthesizing hydroxy-terminated butadiene-styrene liquid rubber, which involves using butadiene and styrene as monomers and an organic peroxide as an initiator to prepare a hydroxy-terminated polybutadiene-styrene liquid rubber through free radical solution polymerization.

[0009] CN111560096A previously disclosed a method for preparing styrene-butadiene rubber (SBR), which involved an emulsion polymerization process at a polymerization temperature of ≤5°C under nitrogen protection, using styrene, butadiene, water, an emulsifier, an electrolyte, a reducing agent, an environmentally friendly molecular weight regulator, and an initiator as raw materials to produce SBR. However, this method replaced the traditional SBR regulator and did not further improve its performance.

[0010] CN110527020A discloses a method for preparing styrene-butadiene rubber (SBR), comprising the following steps: 1) mixing butadiene, styrene, an emulsifier, an electrolyte, an oxygen scavenger, an activator, an oxidant, a regulator, and desalted water, and then conducting an emulsion polymerization reaction; after the reaction is completed, degassing the reaction system and adding an antioxidant to obtain a latex, wherein the oxidant is pinane hydroperoxide; 2) adding the latex to water containing a flocculant and concentrated sulfuric acid and stirring, and after the latex coagulates, filtering and drying to obtain SBR raw rubber, wherein the concentrated sulfuric acid is a sulfuric acid solution having a mass fraction of greater than or equal to 70%; 3) mixing the SBR raw rubber with carbon black and sulfur and vulcanizing the mixture to obtain SBR. This preparation method can effectively shorten the polymerization time, reduce the amount of regulator used, and lower energy consumption; and can be used to prepare different SBR latexes and qualified SBR products.

[0011] CN108017743A discloses a modified carboxylated styrene-butadiene latex and a preparation method thereof. The preparation method of the modified carboxylated styrene-butadiene latex comprises the following steps: (1) in the presence of an initiator, a mixed system containing butadiene, styrene, acrylic acid, a retarder, a molecular weight regulator, water, a pH buffer, a chelating agent, and an emulsifier is subjected to polymerization reaction at 55-60°C and 65-75°C in sequence; (2) the polymerization product is mixed with an oil phase containing a nitrile functional monomer, styrene, and butadiene, and an aqueous phase containing water, an initiator, an emulsifier, and a molecular weight regulator, and the resulting mixture is subjected to polymerization reaction at 75-80°C and 85-90°C in sequence. The modified carboxylated styrene-butadiene latex prepared by the method provided by the present invention not only has a small particle size, but also has excellent stability and extremely high bonding strength. The method involves ternary copolymerization of carboxylated styrene-butadiene latex at 55-60° C. and 65-75° C., followed by copolymerization and grafting with a functional monomer containing a nitrile group. This method has a large number average molecular weight and is complex.

[0012] Summary of the Invention

[0013] The purpose of the present invention is to provide a liquid styrene-butadiene rubber and a preparation method and application thereof.

[0014] The present invention uses sodium isethionate and acrylic acid as raw materials to prepare an ester-containing monomer, which is then used as a third monomer in the preparation of liquid styrene-butadiene rubber. A low-temperature emulsion polymerization method is adopted, and by improving the feeding method and raw material ratio, and multi-stage addition of an emulsifier, an ester monomer, and a molecular weight regulator, a liquid styrene-butadiene rubber with better heat resistance, wear resistance, corrosion resistance, and mechanical properties is prepared.

[0015] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0016] In one aspect, the present invention provides a liquid styrene-butadiene rubber, wherein the polymerization monomers of the liquid styrene-butadiene rubber include butadiene, styrene and a sulfonic acid group-containing ester monomer;

[0017] The structural formula of the sulfonic acid ester monomer is:

[0018] According to the liquid styrene-butadiene rubber of the present invention, preferably, based on 100 parts by total weight of the butadiene, styrene and sulfonic acid group-containing ester monomer, the weight parts of each monomer are: 50-75 parts of butadiene, 20-30 parts of styrene, and 5-24 parts of sulfonic acid group-containing ester monomer.

[0019] According to the liquid styrene-butadiene rubber of the present invention, preferably, the liquid styrene-butadiene rubber is prepared by emulsion copolymerization of butadiene, styrene and sulfonic acid group-containing ester monomers.

[0020] The content of the sulfonic acid ester monomer structure in the liquid styrene-butadiene rubber is 3 wt% to 18 wt%.

[0021] According to the liquid styrene butadiene rubber of the present invention, preferably, the Mooney viscosity of the liquid styrene butadiene rubber at 25° C. is 40 to 60 Pa·s, and the molecular weight Mn ranges from 3000 to 5000.

[0022] Another aspect of the present invention provides a method for preparing liquid styrene-butadiene rubber, wherein the preparation method comprises the following steps:

[0023] Based on 100 parts by total weight of butadiene, styrene, and sulfonic acid group-containing ester monomer, 160-220 parts of desalted water, 4-8 parts of emulsifier, 0.1-0.3 parts of reducing agent, 0.1-0.4 parts of diffusing agent, 0.4-0.8 parts of electrolyte, 3-6 parts of molecular weight regulator, 20-30 parts of styrene, 3-20 parts of sulfonic acid group-containing ester monomer, and 0.01-0.1 parts of scavenger are added to a reaction container. After the addition is completed, 50-75 parts of butadiene are added under a protective gas atmosphere, and the mixture is stirred for pre-emulsification, and then 0.1-0.2 parts of initiator are added to carry out polymerization reaction.

[0024] When the three monomers of butadiene, styrene and sulfonic acid ester monomer reach a certain monomer conversion rate, an emulsifier, an initiator, a molecular weight regulator and the sulfonic acid ester monomer are respectively added; when the monomer conversion rate reaches 82-87%, 0.05-0.2 parts of a terminator are added to terminate the reaction; then degassing, coagulation, washing and drying are carried out to obtain the liquid styrene-butadiene rubber.

[0025] According to the preparation method of the present invention, preferably, when the three monomers of butadiene, styrene and sulfonic acid ester monomer reach a certain monomer conversion rate, the steps of respectively adding an emulsifier, an initiator, a molecular weight regulator and a sulfonic acid ester monomer specifically include:

[0026] When the monomer conversion rate reaches 25% to 30%, add 1 to 2 parts of sulfonic acid ester monomer; when the monomer conversion rate reaches 50% to 55%, add 0.4 to 0.8 parts of emulsifier, 0.002 to 0.004 parts of initiator, and 0.5 to 0.8 parts of molecular weight regulator; when the monomer conversion rate reaches 65% to 70%, add 1 to 2 parts of sulfonic acid ester monomer.

[0027] According to the preparation method of the present invention, preferably, the emulsifier is an anionic-anionic compound surfactant or an anionic-nonionic compound surfactant; wherein the anionic-anionic compound surfactant is a compound of rosin soap and fatty alkyl sulfonate, and the compounding mass ratio is (4-5):1; the anionic-nonionic compound surfactant is a compound of rosin soap and polyoxyethylene ether, and the compounding mass ratio is (3-4):1.

[0028] According to the preparation method of the present invention, preferably, the amount of the emulsifier is 5 to 6 parts.

[0029] 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, EDTA sodium iron salt, EDTA sodium copper salt, etc.

[0030] According to the preparation method of the present invention, preferably, the amount of the reducing agent is 0.2 to 0.3 parts.

[0031] According to the preparation method of the present invention, preferably, the dispersant is sodium naphthalenesulfonate formaldehyde condensate, selected from but not limited to at least one of β-naphthalenesulfonate formaldehyde condensate, methylnaphthalenesulfonate formaldehyde condensate, benzylnaphthalenesulfonic acid formaldehyde condensate, etc.; more preferably, it is sodium β-naphthalenesulfonate formaldehyde condensate.

[0032] According to the preparation method of the present invention, preferably, the amount of the diffusing agent is 0.2 to 0.3 parts.

[0033] According to the preparation method of the present invention, preferably, the electrolyte is potassium phosphate or potassium chloride.

[0034] According to the preparation method of the present invention, preferably, the amount of the electrolyte used is 0.5 to 0.6 parts.

[0035] 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.

[0036] According to the preparation method of the present invention, preferably, the amount of the molecular weight regulator is 4 to 5 parts.

[0037] 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., more preferably sodium dithionite.

[0038] According to the preparation method of the present invention, preferably, the amount of the deoxidizer is 0.04 to 0.08 parts.

[0039] According to the preparation method of the present invention, preferably, the initiator is an organic hydrogen peroxide, including but not limited to cumene hydroperoxide, diisopropyl hydroperoxide, isopropyl tert-butyl peroxide, etc., more preferably diisopropyl hydroperoxide.

[0040] According to the preparation method of the present invention, preferably, the amount of the initiator is 0.12 to 0.18 parts.

[0041] According to the preparation method of the present invention, preferably, the temperature of the polymerization reaction is 5 to 25°C, more preferably 10 to 15°C.

[0042] According to the preparation method of the present invention, preferably, the terminator is selected from but not limited to at least one of hydroxylamine sulfate, diethylhydroxylamine, isopropylhydroxylamine, etc., more preferably isopropylhydroxylamine or diethylhydroxylamine.

[0043] According to the preparation method of the present invention, preferably, the amount of the terminator is 0.05 to 0.1 parts.

[0044] In the preparation method of the present invention, degassing is preferably performed in a degassing tower, more preferably for 4-5 hours. After degassing, the ester-containing styrene-butadiene latex is obtained. The liquid styrene-butadiene rubber is then obtained after coagulation, washing, and drying. Coagulation, washing, and drying are conventional techniques for preparing liquid styrene-butadiene rubber and are not limited thereto. Examples of "protective gas" include nitrogen and argon.

[0045] The preparation method of the modified high-performance liquid styrene-butadiene rubber of the present invention is simple and clear, and can be industrially produced by ternary copolymerization using existing equipment. On the basis of traditional styrene-butadiene rubber, a sulfonic acid group-containing ester monomer is introduced, which contains both an ester group and a sulfonic acid group. The introduction of the ester structure has the advantages of improving the heat resistance and ozone stability of the liquid styrene-butadiene rubber, and improving the mechanical properties, while the introduction of the sulfonic acid group can change the polarity of the liquid styrene-butadiene rubber, further improving the wear resistance by changing the surface polarity of the styrene-butadiene rubber. At the same time, the present invention utilizes a method of multi-stage addition of an emulsifier, a sulfonic acid group-containing ester monomer, an initiator, and a molecular weight regulator to regulate the molecular weight of the modified high-performance liquid styrene-butadiene rubber and improve the problem of uniform distribution of ester groups in the liquid styrene-butadiene rubber.

[0046] According to the preparation method of the present invention, preferably, the sulfonic acid group-containing ester monomer is prepared by the following reaction formula, and the specific steps include:

[0047] Acrylic acid, sodium isethionate, a dehydrating agent and a catalyst are added to a reaction vessel, and the temperature is raised under a protective gas atmosphere to carry out an esterification reaction. During the reaction, generated water and the dehydrating agent are continuously evaporated. The dehydrating agent is separated and then refluxed into the reaction vessel to continue the reaction. When the amount of separated water no longer increases and reaches the theoretical calculated amount, the reaction is stopped, the reaction system is filtered to obtain a filter cake, and the filter cake is subjected to reduced pressure distillation to obtain the sulfonic acid group-containing ester monomer.

[0048] In the preparation process of the sulfonic acid group-containing ester monomer of the present invention, preferably, the temperature of the esterification reaction is 110-120° C., and the reaction time is 12-15 hours.

[0049] In the preparation process of the sulfonic acid group-containing ester monomer of the present invention, preferably, the molar ratio of sodium isethionate to acrylic acid is 1:(1-1.5), more preferably 1:(1.2-1.3).

[0050] In the preparation process of the sulfonic acid group-containing ester monomer of the present invention, preferably, the dehydrating agent is selected from at least one of toluene, ethylbenzene, and p-toluene; more preferably, toluene or xylene.

[0051] In the preparation process of the sulfonic acid group-containing ester 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 isethionate.

[0052] In the preparation process of the sulfonic acid group-containing 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.

[0053] In the preparation process of the sulfonic acid group-containing ester monomer of the present invention, preferably, the amount of the catalyst used is 0.2 wt% to 0.8 wt% of the total mass of sodium isethionate and acrylic acid, more preferably 0.4 wt% to 0.6 wt%.

[0054] Another aspect of the present invention provides liquid styrene-butadiene rubber obtained by the above preparation method.

[0055] According to the liquid styrene butadiene rubber of the present invention, preferably, the content of the sulfonic acid ester monomer structure in the liquid styrene butadiene rubber is 3wt% to 18wt%; the Mooney viscosity of the liquid styrene butadiene rubber at 25°C is 40 to 60 Pa·s, and the molecular weight Mn ranges from 3000 to 5000.

[0056] The method for preparing a sulfonic acid ester functional monomer designed and developed by the present invention is well-suited for industrial synthesis. Unlike the current industrial production method that uses concentrated sulfuric acid as a catalyst, the present invention uses sodium isethionate and acrylic acid as raw materials, an organic sulfonic acid as a catalyst, and a dehydrating agent as a solvent. The esterification reaction is azeotropically removed, thereby improving the efficiency of the esterification reaction. This method allows for the industrial production of sulfonic acid ester monomers with a yield exceeding 90%, achieving self-sufficiency in the raw material of sulfonic acid ester monomers for the preparation of modified high-performance liquid styrene-butadiene rubber. Subsequently, the sulfonic acid ester monomer is ternary copolymerized with butadiene and styrene using an emulsion copolymerization method. A modified high-performance liquid styrene-butadiene rubber is prepared by adding an emulsifier, sulfonic acid ester monomer, molecular weight regulator, and initiator in multiple stages. The modified high-performance liquid styrene-butadiene rubber incorporates the sulfonic acid ester, has a Mooney viscosity range of 40 to 60 Pa·s (25°C), a molecular weight Mn range of 3000 to 5000, and exhibits good fluidity and ease of processing. The introduction of ester groups improves the polymer's heat resistance, while the introduction of sulfonic acid groups enhances its wear resistance. This modified high-performance liquid styrene-butadiene rubber can be used to replace rubber processing oils, toughening agents, and improve tire tread rubber.

[0057] Another aspect of the present invention provides the use of the above liquid styrene-butadiene rubber in tires or epoxy resin toughening agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG1 is the NMR spectrum of the sulfonic acid ester monomer prepared in Example 3.

[0059] FIG2 is a nuclear magnetic resonance spectrum of the modified high-performance liquid styrene-butadiene rubber prepared in Example 3.

[0060] Figure 3 shows the effect of different addition amounts of modified high-performance liquid styrene-butadiene rubber on the wear resistance of epoxy resin cured products. DETAILED DESCRIPTION

[0061] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0062] All numerical specifications herein (e.g., temperatures, times, concentrations, and weights, including ranges for each thereof) are generally approximate and may be modified (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about."

[0063] Example 1

[0064] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, comprising the following specific steps:

[0065] S1: Sodium isethionate (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 at room temperature. Under nitrogen, the temperature was raised to 110°C for 12 hours to allow for the esterification of acrylic acid and sodium isethionate. During the reaction, water and a dehydrating agent 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 to reach the theoretical value, and the reaction was terminated. The feed solution was filtered to obtain a filter cake, which was added to a reactor and subjected to reduced pressure distillation at 50°C and 0.2 MPa to remove the dehydrating agent, toluene. Subsequently, reduced pressure distillation was performed at 72°C and 0.4 MPa to obtain 175.1 g of the sulfonic acid group-containing ester monomer, with a yield of 86.7%.

[0066] S2: In a 10L polymerization kettle, 160 parts of desalted water, 4 parts of emulsifier (rosin soap and fatty alkyl sulfonate in a 4:1 emulsifier), 0.1 part of sodium formaldehyde sulfoxylate, 0.1 part of sodium β-naphthalenesulfonate formaldehyde condensate, 0.4 part of potassium phosphate, 3 parts of tert-dodecyl mercaptan, 20 parts of styrene, 3 parts of sulfonic acid ester monomer and 0.01 part of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 75 parts of butadiene were added, and then 0.1 part of diisopropylbenzene hydroperoxide was added at 5°C to carry out polymerization reaction.

[0067] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester monomer reaches 25%, 1 part of sulfonic acid ester monomer is added; when the monomer conversion rate reaches 50%, 0.4 part of emulsifier, 0.002 part of diisopropylbenzene hydroperoxide, and 0.5 part of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 1 part of sulfonic acid ester monomer is added. When the monomer conversion rate reaches 82%, 0.05 part of hydroxylamine sulfate is added to terminate the reaction and the material is discharged. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0068] Example 2

[0069] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, comprising the following specific steps:

[0070] S1: Sodium isethionate (148 g, 1 mol), acrylic acid (108 g, 1.5 mol), and benzenesulfonic acid (2.048 g, 0.8 wt%) were added to a reaction kettle containing 1536 g of toluene at room temperature. Under nitrogen, the temperature was raised to 120°C and the reaction mixture was reacted for 15 hours to effect esterification of the acrylic acid and sodium isethionate. During the reaction, water and a dehydrating agent were continuously distilled off. The dehydrating agent was separated and refluxed into the reaction kettle to continue the reaction. The amount of water separated was calculated to reach the theoretical value, and the reaction was terminated. The feed solution was filtered to obtain a filter cake, which was added to a reactor and subjected to reduced pressure distillation at 50°C and 0.2 MPa to remove the dehydrating agent, toluene. Subsequently, reduced pressure distillation was performed at 72°C and 0.4 MPa to obtain 178.4 g of the sulfonic acid group-containing ester monomer, with a yield of 88.3%.

[0071] S2: In a 10L polymerization kettle, 220 parts of desalted water, 8 parts of emulsifier (rosin soap and fatty alkyl sulfonate in a ratio of 5:1 emulsifier), 0.3 parts of ferrous sulfate, 0.4 parts of sodium methylnaphthalenesulfonate formaldehyde condensate, 0.8 parts of potassium chloride, 6 parts of dodecyl mercaptan, 21 parts of styrene, 5 parts of sulfonic acid ester monomer and 0.1 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 70 parts of butadiene were added, and then 0.1 parts of cumene hydroperoxide were added at 25°C to carry out polymerization reaction.

[0072] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester monomer reaches 30%, 2 parts of sulfonic acid ester monomer are added; when the monomer conversion rate reaches 55%, 0.8 parts of emulsifier, 0.004 parts of cumene hydroperoxide, and 0.8 parts of dodecyl mercaptan are added; when the monomer conversion rate reaches 70%, 2 parts of sulfonic acid ester monomer are added. When the monomer conversion rate reaches 87%, 0.05 parts of diethylhydroxylamine are added to terminate the reaction and discharge the material. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0073] Example 3

[0074] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, comprising the following specific steps:

[0075] S1: Sodium isethionate (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 at room temperature. Under nitrogen, the temperature was raised to 120°C and the reaction mixture was stirred for 15 hours to effect esterification of the acrylic acid and sodium isethionate. During the reaction, water and a dehydrating agent 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 to reach the theoretical value, and the reaction was terminated. The feed solution was filtered to obtain a filter cake, which was added to a reactor and subjected to reduced pressure distillation at 50°C and 0.2 MPa to remove the dehydrating agent, toluene. Subsequently, reduced pressure distillation was performed at 72°C and 0.4 MPa to obtain 186.6 g of the sulfonic acid group-containing ester monomer, with a yield of 92.4%.

[0076] S2: In a 10L polymerization kettle, 190 parts of desalted water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate in a 4:1 emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzylnaphthalenesulfonic 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 sulfonic acid ester monomer and 0.05 parts of isoascorbic acid were added. After the addition was completed, nitrogen was replaced three times, 60 parts of butadiene were added, and then 0.15 parts of isopropyl tert-butyl peroxide were added at 15°C to carry out polymerization reaction.

[0077] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester monomer reaches 25%, 1 part of sulfonic acid ester monomer is added; when the monomer conversion rate reaches 50%, 0.5 part of emulsifier, 0.003 part of isopropyl tert-butyl peroxide, and 0.6 part of 2,4-diphenyl-4-methyl-1-pentene are added; when the monomer conversion rate reaches 65%, 1 part of sulfonic acid ester monomer is added. When the monomer conversion rate reaches 85%, 0.05 part of isopropylhydroxylamine is added to terminate the reaction and discharge the material. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0078] Example 4

[0079] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, comprising the following specific steps:

[0080] S1: Sodium isethionate (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 at room temperature. Under nitrogen, the temperature was raised to 115°C for 14 hours to allow for the esterification of acrylic acid and sodium isethionate. During the reaction, water and a dehydrating agent 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 to reach the theoretical value, and the reaction was terminated. The feed solution was filtered to obtain a filter cake, which was added to a reactor and subjected to reduced pressure distillation at 50°C and 0.2 MPa to remove the dehydrating agent, toluene. Subsequently, reduced pressure distillation was performed at 72°C and 0.4 MPa to obtain 181.3 g of the sulfonic acid group-containing ester monomer, with a yield of 89.8%.

[0081] S2: In a 10L polymerization kettle, 200 parts of desalted water, 6 parts of emulsifier (rosin soap and polyoxyethylene ether in a ratio of 3:1 emulsifier), 0.1 part of EDTA copper sodium salt, 0.2 part of sodium β-naphthalenesulfonate formaldehyde condensate, 0.4 part of potassium chloride, 5 parts of 2,4-diphenyl-4-methyl-1-pentene, 23 parts of styrene, 15 parts of sulfonic acid ester monomer and 0.06 part of dimethyl ketoxime were added. After the addition was completed, nitrogen was replaced three times, 60 parts of butadiene were added, and then 0.12 parts of diisopropylbenzene hydroperoxide were added at 10°C to carry out polymerization reaction.

[0082] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester monomer reaches 25%, 1 part of sulfonic acid ester monomer is added; when the monomer conversion rate reaches 55%, 0.8 part of emulsifier, 0.002 part of diisopropylbenzene hydroperoxide, and 0.5 part of 2,4-diphenyl-4-methyl-1-pentene are added; when the monomer conversion rate reaches 65%, 1 part of sulfonic acid ester monomer is added. When the monomer conversion rate reaches 83%, 0.05 part of hydroxylamine sulfate is added to terminate the reaction and discharge the material. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0083] Example 5

[0084] This embodiment prepares a modified high-performance liquid styrene-butadiene rubber, comprising the following specific steps:

[0085] S1: Sodium isethionate (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 at room temperature. Under nitrogen, the temperature was raised to 110°C and the reaction was continued for 13 hours to effect esterification of the acrylic acid and sodium isethionate. During the reaction, water and a dehydrating agent 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 to reach the theoretical value, and the reaction was terminated. The feed solution was filtered to obtain a filter cake, which was added to a reactor and subjected to reduced pressure distillation at 50°C and 0.2 MPa to remove the dehydrating agent, toluene. Subsequently, reduced pressure distillation was performed at 72°C and 0.4 MPa to obtain 185.2 g of the sulfonic acid group-containing ester monomer, with a yield of 91.7%.

[0086] S2: In a 10L polymerization kettle, 180 parts of desalted water, 7 parts of emulsifier (rosin soap and polyoxyethylene ether in a 4:1 emulsifier), 0.3 parts of sodium formaldehyde sulfoxylate, 0.3 parts of benzylnaphthalenesulfonic acid formaldehyde condensate, 0.6 parts of potassium phosphate, 4 parts of tert-dodecyl mercaptan, 25 parts of styrene, 8 parts of sulfonic acid ester monomer and 0.04 parts of isoascorbic acid were added. After the addition was completed, nitrogen was replaced three times, 63 parts of butadiene were added, and then 0.18 parts of diisopropylbenzene hydroperoxide were added at 10°C to carry out polymerization reaction.

[0087] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester monomer reaches 30%, 2 parts of sulfonic acid ester monomer are added; when the monomer conversion rate reaches 55%, 0.4 parts of emulsifier, 0.002 parts of diisopropylbenzene hydroperoxide, and 0.6 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 70%, 2 parts of sulfonic acid ester monomer are added. When the monomer conversion rate reaches 86%, 0.15 parts of isopropylhydroxylamine are added to terminate the reaction and discharge the material. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0088] Example 6

[0089] This embodiment provides a preparation method and application of a modified high-performance liquid styrene-butadiene rubber, which is prepared by a preparation method comprising the following specific steps:

[0090] S1: Sodium isethionate (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 at room temperature. Under nitrogen, the temperature was raised to 115°C for 12 hours to effect esterification of the acrylic acid and sodium isethionate. During the reaction, water and dehydrating agent were continuously distilled off. The dehydrating agent was separated and refluxed into the reactor to continue the reaction. The amount of separated water was calculated to reach the theoretical value, and the reaction was terminated. The feed solution was filtered to obtain a filter cake, which was added to a reactor and subjected to reduced pressure distillation at 50°C and 0.2 MPa to remove the dehydrating agent, toluene. Subsequently, reduced pressure distillation was performed at 72°C and 0.4 MPa to obtain 172.1 g of the sulfonic acid group-containing ester monomer, with a yield of 85.2%.

[0091] S2: In a 10L polymerization kettle, 210 parts of desalted water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate in a 4:1 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 sulfonic acid ester monomer and 0.08 parts of dimethyl ketoxime were added. After the addition was completed, nitrogen was replaced three times, 50 parts of butadiene were added, and then 0.16 parts of diisopropylbenzene hydroperoxide were added at 10°C to carry out polymerization reaction.

[0092] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester monomer reaches 25%, 2 parts of sulfonic acid ester monomer are added; when the monomer conversion rate reaches 50%, 0.5 parts of emulsifier, 0.004 parts of diisopropylbenzene hydroperoxide, and 0.5 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 1 part of sulfonic acid 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 material. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0093] Structural characterization and performance testing:

[0094] In order to characterize the structural characteristics of the obtained high-performance liquid styrene-butadiene rubber, nuclear magnetic resonance (NMR) measurements were performed on the sulfonic acid ester monomer and the liquid styrene-butadiene rubber obtained in Example 3. The test results are shown in Figures 1 and 2, respectively.

[0095] From Figure 1, we can see that: 1HNMR (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). These peaks correspond to the characteristic peaks of the sulfonic acid group-containing ester monomer, indicating that the sulfonic acid group-containing ester monomer was successfully prepared. The remaining embodiments are not listed here one by one. The yields of the sulfonic acid group-containing ester monomers in Examples 1-6 were all maintained at about 85%. At the same time, unlike laboratory synthesis, this method can be used for industrial synthesis and production amplification.

[0096] From Figure 2, we can see that the following is the NMR spectrum of liquid styrene-butadiene rubber: 1 HNMR (400 MHz, 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 with the sulfonic acid ester monomer was successfully prepared.

[0097] To characterize the basic properties of the resulting liquid styrene-butadiene rubber, the sulfonic acid and ester-containing liquid styrene-butadiene rubber prepared in Examples 1 to 6 were subjected to corresponding property tests. Styrene content was determined using the refractive index method specified in GB / T 8658-1998; sulfonic acid ester monomer content was determined by nuclear magnetic resonance area integration; molecular weight was determined using gel permeation chromatography according to SH / T 1759-2007; and Mooney viscosity was measured using a Mooney viscometer (GT-7082S2) in accordance with GB / T 1232.1-2016. The test results are shown in Table 1.

[0098] Table 1

[0099] 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, have Mooney viscosities ranging from 40 to 60 Pa·s, and have molecular weights Mn ranging from 3000 to 5000, exhibiting good fluidity and easy processing properties.

[0100] In order to verify the effect of multi-stage addition of emulsifier, sulfonic acid ester monomer, initiator, and molecular weight regulator on the performance of modified high-performance liquid styrene-butadiene rubber during the preparation process, the relevant data were compared with the comparative examples under different conditions with reference to Example 3. The preparation method of the comparative example is as follows:

[0101] Comparative Example 1

[0102] Compared with Example 3, Comparative Example 1 adopts a one-time monomer addition method without any additional addition. The specific S2 is as follows:

[0103] In a 10L polymerization kettle, 190 parts of desalted water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate compound ratio 4:1 emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzylnaphthalenesulfonic 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 sulfonic acid ester monomer and 0.05 parts of isoascorbic acid were added. After the addition was completed, nitrogen was replaced three times, 60 parts of butadiene were added, and then 0.15 parts of isopropyl tert-butyl peroxide were added at 15°C to carry out polymerization reaction.

[0104] When the monomer conversion rate 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 isopropylhydroxylamine are added to terminate the reaction and discharge the material. After discharge, the material is degassed in a degassing tower for 5 hours to obtain ester-containing styrene-butadiene latex, and liquid styrene-butadiene rubber can be obtained after coagulation, washing, and drying.

[0105] Comparative Example 2

[0106] Compared with Example 3, Comparative Example 2 adopts the method of adding the initiator once, and the other conditions remain unchanged. The specific S2 is as follows:

[0107] In a 10L polymerization kettle, 190 parts of desalted water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate compound ratio 4:1 emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzylnaphthalenesulfonic 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 sulfonic acid ester monomer and 0.05 parts of isoascorbic acid were added. After the addition was completed, nitrogen was replaced three times, 60 parts of butadiene were added, and then 0.153 parts of isopropyl tert-butyl peroxide were added at 15°C to carry out polymerization reaction.

[0108] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester monomer reaches 25%, 1 part of sulfonic acid ester monomer is added; when the monomer conversion rate reaches 50%, 0.5 parts of emulsifier and 0.6 parts of 2,4-diphenyl-4-methyl-1-pentene are added; when the monomer conversion rate reaches 65%, 1 part of sulfonic acid ester monomer is added. When the monomer conversion rate reaches 85%, 0.05 parts of isopropylhydroxylamine are added to terminate the reaction and discharge the material. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0109] Comparative Example 3

[0110] Compared with Example 3, Comparative Example 3 adopts the method of adding the sulfonic acid ester monomer once, and the other polymerization process conditions remain unchanged. The specific S2 is as follows:

[0111] In a 10L polymerization kettle, 190 parts of desalted water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate in a 10L polymerization kettle) were added, 190 parts of desalted water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate in a composite ratio of 4:1 emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzylnaphthalenesulfonic 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 sulfonic acid ester monomer and 0.05 parts of isoascorbic acid were added. After the addition was completed, nitrogen was replaced three times, 60 parts of butadiene were added, and then 0.15 parts of isopropyl tert-butyl peroxide were added at 15°C to carry out polymerization.

[0112] When the monomer conversion rate of butadiene, styrene, and sulfonic acid ester 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 isopropylhydroxylamine are added to terminate the reaction and discharge the material. After discharge, the material 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 sulfonic acid and ester groups is obtained.

[0113] The properties of the liquid styrene-butadiene rubber prepared in Comparative Examples 1 to 3 are compared with those in Example 3 and are shown in Table 2.

[0114] Table 2

[0115] Comparative Example 1 and Example 3 show that both the bound styrene content and the sulfonic acid ester content are reduced, while the molecular weight and Mooney viscosity are increased. This is because the single-addition 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 the sulfonic acid ester monomer. Furthermore, the single addition of the molecular weight regulator and emulsifier results in poor molecular weight control.

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

[0117] Comparative Example 3 Compared with Example 3, it can be found that the content of bound styrene has not decreased significantly, but the content of sulfonic acid ester has decreased significantly. This is because the reactivity ratio of sulfonic acid ester is weaker than that of styrene and butadiene. Therefore, adding sulfonic acid ester at one time will cause the sulfonic acid ester chain segments to be unevenly distributed in the polymer molecular chain and the binding rate to be reduced, thereby resulting in a decrease in content.

[0118] To further characterize the application performance of the resulting liquid styrene-butadiene rubber, the present invention provides an application as an epoxy resin toughening agent, including but not limited to a toughening agent. The modified high-performance liquid styrene-butadiene rubber prepared in Example 3 was tested for epoxy resin toughening. The conventional liquid styrene-butadiene rubber of Comparative Example 4, which did not contain a sulfonic acid ester monomer, was used as a control. The addition amount was 5 wt%. The thermal decomposition temperature of the cured epoxy resin after toughening and the erosion wear performance were tested. The test results are shown in Table 3 and Figure 3, respectively.

[0119] Comparative Example 4

[0120] Compared with Example 3, Comparative Example 4 does not add a sulfonic acid ester monomer. The specific S2 is as follows:

[0121] In a 10L polymerization kettle, 190 parts of desalted water, 5 parts of emulsifier (rosin soap and fatty alkyl sulfonate with a compound ratio of 4:1 emulsifier), 0.2 parts of EDTA sodium iron salt, 0.3 parts of benzylnaphthalenesulfonic 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 completed, nitrogen was replaced three times, 74 parts of butadiene were added, and then 0.15 parts of isopropyl tert-butyl peroxide were added at 15°C to carry out 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 isopropylhydroxylamine are added to terminate the reaction and discharge the material. After discharge, the material 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] As can be seen from the comparative data in Table 3, the thermal decomposition temperature of the pure epoxy resin cured product is 373°C, while the thermal decomposition temperature of the modified epoxy resin cured product of Comparative Example 4 is 365°C. This is because the ordinary liquid styrene-butadiene rubber undergoes a cross-linking reaction with the epoxy resin, forming an incompletely cross-linked network structure. At the same time, since the thermal stability of liquid styrene-butadiene rubber is relatively weaker than that of epoxy resin, the thermal decomposition temperature of the ordinary liquid styrene-butadiene rubber modified epoxy resin cured product is lower. However, the thermal decomposition temperature of the modified epoxy resin cured product of Example 3 is 387°C, higher than the 373°C of the pure epoxy resin cured product. This is because the introduction of the ester structure improves the heat resistance of the polymer.

[0125] As shown in Figure 3, as the amount of liquid styrene-butadiene rubber 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 styrene-butadiene rubber in Example 3 has better wear resistance. This is because the addition of sulfonic acid groups further enhances the mechanical properties of the material. It was also found that the wear resistance decreases when the addition amount exceeds a certain level. This is because the wear resistance of the cured product is affected not only by the modifier but also by the bonding properties. Therefore, when the addition amount exceeds a certain level, the wear resistance of the cured product decreases.

[0126] In order to further characterize the application performance of the obtained modified high-performance liquid styrene-butadiene rubber, the modified high-performance liquid styrene-butadiene rubber prepared in Example 3 was used to replace rubber processing oil in the preparation of tire rubber compounds, using the mixing formula in Table 4.

[0127] Table 4

[0128] The properties of the vulcanized rubber obtained by processing according to Table 4 are shown in Table 5.

[0129] Table 5

[0130] As shown in Table 5, after the modified high-performance liquid styrene butadiene rubber is used to replace the rubber processing oil, the tensile strength and tear strength of the tire vulcanized rubber are improved, and the wear resistance is enhanced. Therefore, the 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.

[0131] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A liquid styrene-butadiene rubber, wherein: The polymerization monomers of the liquid styrene-butadiene rubber include butadiene, styrene and sulfonic acid ester monomers; The structural formula of the sulfonic acid ester monomer is:

2. The liquid styrene-butadiene rubber according to claim 1, wherein Based on 100 parts of the total weight of the butadiene, styrene and sulfonic acid group-containing ester monomer, the weight parts of each monomer are: 50-75 parts of butadiene, 20-30 parts of styrene, and 5-24 parts of sulfonic acid group-containing ester monomer.

3. The liquid styrene-butadiene rubber according to claim 1, wherein The liquid styrene-butadiene rubber is prepared by emulsion copolymerization of butadiene, styrene and sulfonic acid ester monomers.

4. The liquid styrene-butadiene rubber according to claim 1, wherein In the liquid styrene-butadiene rubber, the content of the sulfonic acid ester monomer structure is 3wt% to 18wt%.

5. The liquid styrene-butadiene rubber according to claim 1, wherein The Mooney viscosity of the liquid styrene-butadiene rubber is 40-60 Pa·s, and the molecular weight Mn ranges from 3000 to 5000.

6. A method for preparing the liquid styrene-butadiene rubber according to any one of claims 1 to 5, wherein: The preparation method comprises the following steps: Based on 100 parts of the total weight of butadiene, styrene and sulfonic acid ester monomer, 160-220 parts of desalted water, 4-8 parts of emulsifier, 0.1-0.3 parts of reducing agent, 0.1-0.4 parts of diffusing agent, 0.4-0.8 parts of electrolyte, 3-6 parts of molecular weight regulator, 20-30 parts of styrene, 3-20 parts of sulfonic acid ester monomer and 0.01-0.1 parts of deoxidizer are added into a reaction container. After the addition is completed, 50-75 parts of butadiene are added in a protective gas atmosphere, and stirred for pre-emulsification, and then 0.1-0.2 parts of initiator are added for polymerization reaction; When the three monomers of butadiene, styrene and sulfonic acid ester monomer reach a certain monomer conversion rate, emulsifier, initiator, molecular weight regulator and sulfonic acid 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, and then degassing, condensation, washing and drying are carried out to obtain the liquid styrene-butadiene rubber.

7. The preparation method according to claim 6, wherein: When the three monomers of butadiene, styrene and sulfonic acid ester monomer reach a certain monomer conversion rate, the steps of respectively adding an emulsifier, an initiator, a molecular weight regulator and a sulfonic acid ester monomer specifically include: When the monomer conversion rate reaches 25% to 30%, add 1 to 2 parts of sulfonic acid ester monomer; when the monomer conversion rate reaches 50% to 55%, add 0.4 to 0.8 parts of emulsifier, 0.002 to 0.004 parts of initiator, and 0.5 to 0.8 parts of molecular weight regulator; when the monomer conversion rate reaches 65% to 70%, add 1 to 2 parts of sulfonic acid ester monomer.

8. The preparation method according to claim 6 or 7, wherein: The emulsifier is an anionic compound surfactant or an anionic compound surfactant; wherein the anionic compound surfactant is a compound of rosin soap and fatty alkyl sulfonate, and the compounding mass ratio is (4-5):1; the anionic compound surfactant is a compound of rosin soap and polyoxyethylene ether, and the compounding mass ratio is (3-4):

1.

9. The preparation method according to claim 6 or 7, wherein: The reducing agent is selected from at least one of sodium formaldehyde sulfoxylate, ferrous sulfate, cuprous sulfate, EDTA sodium iron salt, and EDTA sodium copper salt.

10. The preparation method according to claim 6 or 7, wherein: The diffusing agent is selected from at least one of sodium β-naphthalenesulfonate formaldehyde condensate, sodium methylnaphthalenesulfonate formaldehyde condensate, and benzylnaphthalenesulfonic acid formaldehyde condensate.

11. The preparation method according to claim 6 or 7, wherein: The electrolyte is potassium phosphate or potassium chloride.

12. The preparation method according to claim 6 or 7, wherein: The molecular weight regulator is at least one selected from dodecyl mercaptan, tert-dodecyl mercaptan, and 2,4-diphenyl-4-methyl-1-pentene.

13. The preparation method according to claim 6 or 7, wherein: The deoxidizer is selected from at least one of sodium dithionite, dimethyl ketoxime and isoascorbic acid.

14. The preparation method according to claim 6 or 7, wherein: The initiator is selected from at least one of cumene hydroperoxide, diisopropyl hydroperoxide and isopropyl tert-butyl peroxide.

15. The preparation method according to claim 6 or 7, wherein: The terminator is selected from at least one of hydroxylamine sulfate, diethylhydroxylamine, and isopropylhydroxylamine.

16. The preparation method according to claim 6, wherein: The sulfonic acid ester monomer is prepared by the following steps: Acrylic acid, sodium isethionate, a dehydrating agent and a catalyst are added to a reaction container, and the temperature is raised under a protective gas atmosphere to carry out an esterification reaction. During the reaction, generated water and the dehydrating agent are continuously evaporated, and the dehydrating agent is separated and refluxed into the reaction container to continue the reaction. When the amount of separated water no longer increases and reaches a theoretical calculated amount, the reaction is stopped, the reaction system is filtered to obtain a filter cake, and the filter cake is subjected to reduced pressure distillation to obtain the sulfonic acid group-containing ester monomer.

17. The preparation method according to claim 16, wherein: The molar ratio of the sodium isethionate to acrylic acid is 1:(1-1.5).

18. The preparation method according to claim 16, 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.

19. Use of the liquid styrene-butadiene rubber according to any one of claims 1 to 5 in tires or epoxy resin toughening agents.

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