ESBR

Despite being referred to as a commodity, ESBR is a high performance product. It is manufactured to a high quality level because of its principal apphcation in safety critical products. In other application areas, such as conveyor belts, the products are expected to perform well for many years under demanding conditions. In order to achieve the required performance and to work with easy and consistent manufacturing processes, very tight specifications are applied by rubber goods manufacturers. 

The production of ESBR is highly capital intensive, hence the industry in Europe only employs about 1200 people however, a further 300000 are involved in the manufacture of tyres and industrial rubber goods. 

2 Applied processes and techniques in the production of emulsion styrene butadiene rubber 

---

COLORANTS FORFOOD,DRUGS,COSTffiTICS AND TffiDICALDEVICES] (Vol 6) ESBR See Emulsion styrene-butadiene rubber. 

Unlike SSBR, the microstmcture of which can be modified to change the polymer s T, the T of ESBR can only be changed by a change in ratio of the monomers. Glass-transition temperature is that temperature where a polymer experiences the onset of segmental motion (7). 

For ESBR polymerized at 50°C, knowing the percentage of bound styrene in the copolymer allows estimation of the T by the following, where S is the weight fraction of the styrene (% bound styrene) (8). 

The glass-tiansition tempeiatuiesfoi solution-polymeiized SBR as well as ESBR aie loutinely determined by nuclear magnetic resonance (nmr), differential thermal analysis (dta), or differential scanning calorimetry (dsc). 

The monomers, butadiene (qv) and styrene (qv), are the most important ingredients in the manufacture of SBR polymers. For ESBR, the largest single material is water for solution SBR, the solvent. 

The quahty of the water used in emulsion polymerization has long been known to affect the manufacture of ESBR. Water hardness and other ionic content can direcdy affect the chemical and mechanical stabiUty of the polymer emulsion (latex). Poor latex stabiUty results in the formation of coagulum in the polymerization stage as well as other parts of the latex handling system. 

In converting ESBR latex to the dry mbber form, coagulating chemicals, such as sodium chloride and sulfuric acid, are used to break the latex emulsion. This solution eventually ends up as plant effluent. The polymer cmmb must also be washed with water to remove excess acid and salts, which can affect the cure properties and ash content of the polymer. The requirements for large amounts of good-quaUty fresh water and the handling of the resultant effluent are of utmost importance in the manufacture of ESBR and directly impact on the plant operating costs. 

Eatty acid soap was first used for ESBR. Its scarcity prompted the investigation of rosin acids from gum and wood as substitutes (1). The discovery of the disproportionation of rosin allowed rosin acid soaps to overcome the polymerization inhibition of untreated rosin acids. Rosin acid soaps gave the added benefit of tack to the finished polymer. In the 1990s, both fatty acid and rosin acid soaps, mainly derived from tall oil, are used in ESBR. 

ESBR and SSBR are made from two different addition polymerisation techniques one radical and one ionic. ESBR polymerisation is based on free radicals that attack the unsaturation of the monomers, causing addition of monomer units to the end of the polymer chain, whereas the basis for SSBR is by use of ionic initiators (qv). 

Eree-radical initiation of emulsion copolymers produces a random polymerisation in which the trans/cis ratio caimot be controlled. The nature of ESBR free-radical polymerisation results in the polymer being heterogeneous, with a broad molecular weight distribution and random copolymer composition. The microstmcture is not amenable to manipulation, although the temperature of the polymerisation affects the ratio of trans to cis somewhat. 

Black masterbatch can be made with or without oil-extended SBR. Commercially there are available, worldwide, 11 numbered ESBR cold black masterbatches and 15 ESBR cold oil-black masterbatches (27). These types range in black type and content as well as oil type and amount. Of course, not every listed product is available from every supplier. 

There is an industry trend to supply SBR certifiably free of volatile nitrosamines or nitrosatable compounds. This has generally been accomplished by replacing shortstop systems based on carbamates and hydroxyl amines with products that are not based on secondary amines or are secondary amines of high molecular weight, such as dibenzyldithiocarbamate. A more recendy issued patent for ESBR shortstop is based on isopropyUiydroxylamine, a primary amine that does not form nitrosamine (46). 

FIGURE 33.3 Dispersive component of surface energy and dispersion quality in ESBR as a function of heat treatment of N234. 

Einsteinium, as an actinide metal, has several compounds similar to other transuranic elements that are formed with some of the nonmetals, as follows einsteinium dioxide (EsO ), einsteinium trioxide (Es O ), einsteinium trichloride (EsCy, einsteinium dibromide (EsBr ), and einsteinium triiodide (EsI ). 

In the late 1920s Bayer Company began studies of the emulsion polymerization process of polybutadiene for producing synthetic rubber. Incorporation of styrene as a comonomer produced a supenor polymer compared to polybutadiene. The product, Buna S, was the precursor of the single largest-volume polymer produced in the 1990s, emulsion styrcne-buladieiie rubber (ESBR). 

In the 1960s, anionic polymerized solutron SBR (SSBR) began to challenge emulsion SBR in the automotive tire market. Organolithium compounds allow control of the butadiene microstructure, not possible with ESBR. Because this type of chain polymerization takes place without a termination step, an easy synthesis of block polymers is available, whereby glassy (polystyrene) and rubbery (polybutadicnc) segments can be combined in the same molecule. These thermoplastic elastomers (TPE) have found use ill nontire applications. 

Snap. A critical ingredient for emulsion polymerization is the soap, which performs a number of key roles, including production of oil (monomer) m water emulsion, provision of the loci for polymerization (micelle), stabilization of the latex particle, and imputation of characteristics to the finished polymer. Both fatty acid and rosin acid soaps, mamly derived from tall oil, are used in ESBR,... 

---