Emulsion-polymerized SBR

The emulsion polymerization process is used by 17 production facilities to produce latex mbber products as well as solid cmmb mbber. Latex production follows the same processing steps as emulsion cmmb mbber production up to the finishing process. Between 5 and 10% of emulsion polymerized SBR and nearly 30% of nitrile mbber production (NBR) are sold as latex. Latex mbber is used to manufacture dipped goods, paper coatings, paints, carpet backing, and many other commodities. 

Firestone and Shell started commercial production of cis-polyisoprene by the anionic process in the 1950 s but these plants are no longer in operation now. About the same time, Phillips started the manufacture of polybutadienes by the anionic route and ever since, there has been a steady growth in their use, particularly in the tire-tread as well as tire-carcass formulations. These solution polybutadienes, generally, have low vinyl contents but recently, Phillips has found some interesting applications for medium vinyl polybutadienes as well.14 Polybutadienes with 50-55 percent vinyl contents behave like emulsion polymerized SBR in tire tread formulations and exhibit very similar tread... 

Figure 15. Molecular weight distribution of anionically polymerized styrene-butadiene random copolymer and emulsion polymerized SBR.

ISO 289-3, 1999, Determination of the delta Mooney value for non-pigmented, oil extended, emulsion polymerized SBR. 

The target polymerization temperature will usually be chosen to optimize production rates or product quality. Cold SBR, which is made near S C, is an interesting case in this regard. The cold product is superior as a rubber to hot (60°C emulsion polymerization) SBR, because it contains less low-molecular-weight polymer which cannot be reinforced with carbon black. There is also less branching and more tra/) -l,4 units in the cold SBR. Hot SBR is easier to mill and extrude because of its low-molecular-weight fraction and is used mostly for adhesive applications while cold SBR, which is made mainly for tires, accounts for about 90% of all production of this polymer. 

In addition to the polymer viscosity, polymerization temperature also plays an important role in shaping the processability. Emulsion-polymerized SBR grades produced at low polymerization temperatures have less chain branching than those produced at higher temperatures. At an equivalent viscosity, cold polymerized E-SBR is normally easier to process than hot polymerized E-SBR, and this applies particularly... 

SBR may also be produced by anionic solution polymerization of styrene and butadiene with alky-llithium initiator (e.g., butyllithium) in a hydrocarbon solvent, usually hexane or cyclohexane. In contrast to emulsion SBR, which may have an emulsifier (soap) content of up to 5% and nonrubber materials sometimes in excess of 10%, solution SBR seldom has more than 2% nonrubber materials in its finished form. Solution SBR has a narrower molecular weight distribution, higher molecular weight, and higher cis-1,4-polybutadiene content than emulsion polymerization SBR. 

The authors collected the test data shown in Table 9.10. From these data it can be noted that the number-average molecular weight, or Af , of a commercial emulsion SBR such as IISRP 1500 or 1712 is typically 90,000-175,000. The primary molecular weight of a solution-polymerized polymer produced with an anionic lithium catalyst can, in contrast, be increased toward 250,000 without gelation. In addition, emulsion-polymerized SBR contains only about 92% rubber hydrocarbon as a result of the presence of residues from the production process solution polymers tend to be near 100% hydrocarbon. As a consequence, the authors concluded that the number-average molecular weight... 

CAS 25155-30-0 EINECS/ELINCS 246-680-4 Uses Emulsifier for emulsion polymerization (SBR, vinyl acetate, vinyl chloride, styrene and acrylic latexes), paints/coatings crop protection food pkg. applies. surfactant for washing fruits and vegs. 

Chem. Descrip. Branched sodium dodecylbenzene sulfonate CAS 25155-30-0 EINECS/ELINCS 246-680-4 Uses Emulsifier for emulsion polymerization (SBR, vinyl acetate, vinyl chloride, styrene, and acrylic latexes), paints/coatings emulsifier, dispersant for agric. formulations surfactant for washing fruits and vegetables food pkg. adhesives, paper defoamer in food-contact paper/ paperboard emulsifier in mfg. of food-contact articles Regulatory FDA 21 CFR 175.105,175.300,175.320,176.170,176.180, 176.200,176.210,178.3400 exempt from tolerance under EPA40CFR 180.1001 (c) (e) BGA XIV compliance Properties Flakes pH 6.0-9.5 (10%) surf. tens. 32 dynes/cm ( CMC) anionic 98% act. 

Chem. Descrip. Linear sodium dodecylbenzene sulfonate CAS 68081-81-2 EINECS/ELINCS 246-680-4 Uses Emulsifier for cleaners, industrial sanitation cleaners, caustic and acid cleaners, metal cleaning, emulsion polymerization (SBR, vinyl ac-... 

Copolymerization of a polar monomer with SBR, chiefly in production of emulsion-polymerized SBR, is also being researched. In this approach the copolymer is combined with zinc white and fatty acid salts as compounding agents. This approach is claimed to prevent poor dispersion of the silica and to improve processability, and also to give a substantial improvement in heat emission, tensile strength and wear resistance. 

Emulsion polymerized SBRs are used alone, as well when as blended with butadiene or natural rubber. In addition with other diene rubbers, higher levels of filler (75 phr of carbon black and plasticizer 20 phr, or more than the quantity contained in oil-extended SBR) may be used. 

Emulsion Polymerized SBR The bulk of styrene-butadiene rubber is produced by free radically initiated emulsion polymerization. Before 1950 polymerization was usually carried out at about 50 C using a water-soluble initiator such as potassium persulphate with the average molecular weight being controlled largely by chain transfer agents such as t-dodecyl mercaptan. Conversion of monomer to polymer was taken to about 72% at which point hydroquinone was added as a polymerization stopper. Because of the non-linear nature of the polymer such rubbers were inferior to natural rubber. For reasons which will shortly become... 

Retrospective View of Vinyl-BR Properties In the 1950s, the Phillips Petroleum Company and the Firestone Tire and Rubber Company started commercial production of polybutadienes by organolithium polymerization for use in tyres. These solution BRs, having low vinyl contents (8-10%), were used in blends with emulsion SBR in tyre treads for balancing traction and wear performance properties. In the early 1970s when styrene monomer was in short supply, developments from Phillips Petroleum Company and EniChem (formerly the International Synthetic Rubber Company) showed that vinyl-BRs with 50-55% vinyl content behaved like emulsion polymerized SBR in tyre tread formulations and exhibited very similar tread wear and wet skid resistance. Tread compounds containing 45%-vinyl polybutadiene showed lower heat build-up and better blow-out resistance than E-SBR and blends of E-SBR with cw-BR. EniChem introduced trial quantities of a medium-vinyl butadiene rubber (MVBR) under the name Intolene 50 in 1973. 

Copolymers are prepared either by radical emulsion polymerization (SBR) or by anionic polymerization in cyclohexane solution (SBR statistical and SBS block copolymers). 

Uses Primary or sec. emulsifier for emulsion polymerization, SBR, PVC latex stabilizer food-pkg. adhesives defoamer in food-contact coatings defoamer in food-contact paper coatings food-contact paper/paperboard Regulatory FDA 21CFR 175.105,176.170,176.180,176.200 SARA nonreport-able... 

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