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Currently, significant progress has been made in the production technology of styrene-butadiene rubber (SBR) in terms of polymerization processes, modification techniques, and the development of new products. 1 Improvement in polymerization processes: The American company Goodyear has developed a new process for producing emulsion styrene-butadiene rubber (ESBR), known as FIM (Field Injected Monomer). This process can reduce the amount of soap used by more than 30%, lower the residual amount of soap in the polymer, and enhance the bonding performance of the cords in tire applications. By co-condensing a high-molecular-weight SBR emulsion and a low-molecular-weight SBR emulsion prepared using the FIM process, the resulting ESBR not only exhibits the same properties as solvated styrene-butadiene rubber (SSBR) in terms of rolling resistance and tread wear resistance, but also outperforms SSBR in aspects such as grip. Japanese company JSR uses a two-step polymerization process to produce ESBR with a moderate styrene content. First, 44 parts of butadiene and 51 parts of styrene were subjected to emulsion copolymerization in the presence of an emulsifier and 0.07 parts of tert-dodecylthiol. When the monomer conversion rate reached 63%, 5 parts of butadiene and 0.1 part of tert-dodecylthiol were added, and polymerization was continued until the conversion rate reached 80%. This yielded an ESBR with a styrene content of 45% and a Mooney viscosity of 93.5; the resulting rubber exhibited excellent wear resistance and tensile strength. In the process of synthesizing ESBR using a series of 10 polymerization reactors at the German Buna chemical plant, the first reactor was used as a mixing reactor; the mixture was fed into the various reactors through filters for polymerization. The filters were washed with dilute aqueous solutions of C10H7SO3H/HCHO condensates, butadiene-styrene-maleic anhydride copolymers, or Diels-Alder adducts of maleic acid, and the resulting wash liquids were recycled back into the polymerization system, thereby reducing the amount of residue in the reactors. The biggest drawback of the traditional synthesis method for SSBR is the low coupling efficiency (50%–70%). Using polyfunctional organolithiums as an initiation system and a one-time feeding process, Beijing University of Chemical Technology synthesized tin-coupled SSBR with a coupling degree of up to 100% (referred to as S100) in a single step. The resulting material exhibited good physical and mechanical properties, excellent low rolling resistance, and high wet grip. Phillips Company uses a series of plug-flow reactors equipped with agitators to carry out continuous solution polymerization without the use of a binder, in order to produce conjugated diene-monovinyl aromatic rubber polymers. This process involves the continuous addition of monomers and organolithium initiators, diluents, colloid inhibitors, and randomizing agents into the agitated tank reactors; the solution polymerization products (with a conversion rate of at least 90%) are then continuously transferred to the plug-flow region to complete the polymerization reaction, after which they are treated with coupling agents. The resulting polymer can be used for compression molding and extrusion, especially for tire treads and sidewalls. This system reduces the residence time required to complete the monomer conversion, decreases the fouling caused by colloids in the reactor, and improves the coupling efficiency; the polymers produced possess excellent physical properties. 2 Development of modification technologies: When preparing ESBR masterbatches, the American company Goodyear first causes 20–40 parts of a vinyl compound containing anti-degradation functional groups, namely N-(4-phenylaminophenyl)methacrylamide, to copolymerize with 60–80 parts of butadiene at 40°C, in the presence of 20–30 parts of ionic surfactants and 10–70 parts of the plasticizer tri(butoxyethyl) phosphate, thereby producing a stable masterbatch polymer. It is then blended with ESBR1502 to produce a functionalized ESBR, thereby **improving** the properties of the masterbatch. A notable feature of this process is that, in the preparation of the masterbatch polymer, it not only avoids the use of toxic co-solvents such as dichloromethane (DCM) and **thefuran (THF), but also eliminates the need for an organic solvent recovery step. Using SBR1502 paste as a raw material, the company also produced hydrogenated thermoplastic SBR1502 with a saturation degree of 97% through the emulsion diamine reduction process (LRP). The strength and aging resistance of hydrogenated ESBR are both superior to those of the unhydrogenated version. Yokohama Rubber Company in Japan uses copolymers composed of naphtha C5 fractions and styrene or vinyl toluene as ESBR modifiers. The modified SBR is primarily used in tire production, and it can significantly improve a tire’s grip on wet roads without affecting its rolling resistance. Nippon Bridgestone Corporation modified ESBR using α-bromophenylacetic acid and tert-butoxycloride in toluene solution to produce halogenated ESBR with excellent heat resistance; the vulcanized rubber showed a significant increase in its 100% elongation stress, tensile strength, and elongation rate. The company also modified ESBR using tetrazole compounds (such as 1-phenyl-5-thio-1,2,3,4-tetrazole) in the presence of tert-butoxycloride, which led to a significant increase in the tensile strength of the vulcanized rubber and an improvement in its resistance to wet (dry) sliding. The Japanese company Zeon first modified SSBR using 4,4′-bisdiethylenediaminodiphenylmethane (EAB). At low strain levels, the dynamically shear modulus of the modified material decreased significantly, its resilience increased, rolling friction heat generation was reduced, and its volume resistivity rose. When used in combination with polybutadiene rubber, the blend exhibits excellent overall properties. 3 Development and Application of New Products (1) Differentiation and Specialization With the rapid development of the rubber processing industry, SBR manufacturers have, in recent years, continuously introduced new products and new grades tailored to various application areas, in response to market demands. In traditional low-temperature ESBR products, the content of bound styrene is typically 23.5%. To meet the various requirements of the tire and other rubber processing industries, a number of product grades with either higher or lower levels of bound styrene have been introduced to the market. Among them, product grades with a bound styrene content of around 40% include SBRl721, SBRl516, SBRl513, JSRl013N, SES-1013, JSR0202, NIPOL9526, NIPOL9529, and others ； E10102 and E10204 with a styrene content of 15%–17%, E10104 and ISP’s 8107 with a styrene content of 4.5%–6.5%, etc ； Furthermore, due to its ease of processing, high bonding properties, and strong raw rubber strength, the use of powder SBR is increasing year by year. For example, the American company ISP can produce 6 grades of powder SBR with varying styrene contents: 1006crumb, 1009crumb, 1012crumb, 1013crumb, 1502crumb, 4503crumb, and 8113crumb. (2) Functionalization and high performance: To meet the increasingly stringent quality requirements of the market for automobile tires, rubber raw materials have their properties improved by adjusting factors such as molecular weight and distribution, degree of branching, content of various monomers, glass transition temperature, and microstructure, thereby evolving toward functionalization and higher performance. During the SSBR polymerization process, the properties of the polymer are improved by methods such as tin coupling modification, silicon modification, and adjusting the vinyl content. By adding the third monomer acrylonitrile (at a concentration of 20%) during the ESBR polymerization process, the resulting functional NSBR polymer exhibits excellent anti-slip properties, making it suitable for use in manufacturing tire treads and sports shoes. (3) Environmental friendliness. In recent years, the development and application of environmentally friendly SBR products at home and abroad have shown the following two characteristics: ① The commonly used terminator, sodium dimethyldithiocarbamate, reacts with nitrites to produce a by-product called N-nitrosodimethylamine, which is released in large quantities during the polymerization and drying processes and is harmful to human health. By using new terminating agents and termination methods, it is not only possible to eliminate nitrosamines from rubber products, but also to reduce the concentration of carcinogens at the workplace to below 1.0 ng/m3. At present, the products of some manufacturing enterprises in Europe are basically free of nitrosamines, and both Qilu and Shenhua companies in China are also capable of producing SBR products without nitrosamines. ②For a long time, the aromatic oils used as fillers in oil-extended styrene-butadiene rubber have been subject to certain restrictions in Europe and the United States due to their content of polycyclic aromatic hydrocarbons. People have been considering how to replace this oil. If paraffin oil or naphthenic oil is used instead, it will lower the glass transition temperature of the filler rubber, resulting in increased elasticity of the vulcanized rubber and thus compromising the tire’s resistance to wet skid. Europe has enacted legislation requiring that, starting from 2010, low-aromatic-content, non-polluting aromatic oils be used in all rubber and its products. Although SBR has undergone decades of development and its production process technology has become standardized, improvements in product quality, process efficiency, and energy conservation are still ongoing. In the future, technology development will focus on developing efficient initiators and new types of additives, optimizing process control, increasing polymerization conversion rates, and improving condensation techniques ； To produce environmentally friendly ESBR free of nitrosamines, polymerization formulations should use environmentally friendly terminators and other additives that do not generate nitrosamines ； Further improve monomer recovery and post-treatment technologies, and accelerate the development of continuous SSBR production technologies to promote the healthy development of the rubber industry.