SBR latex

Latex mbber foams are generally prepared in slab or molded forms in the density range 64—128 kg/m (4—8 lbs/fT). Synthetic SBR latexes have replaced natural mbber latexes as the largest volume raw material for latex foam mbber. Other elastomers used in significant quantities are polychloroprene, nitrile mbbers, and synthetic i j -polyisoprene (115). 

Almost all synthetic binders are prepared by an emulsion polymerization process and are suppHed as latexes which consist of 48—52 wt % polymer dispersed in water (101). The largest-volume binder is styrene—butadiene copolymer [9003-55-8] (SBR) latex. Most SBRlatexes are carboxylated, ie, they contain copolymerized acidic monomers. Other latex binders are based on poly(vinyl acetate) [9003-20-7] and on polymers of acrylate esters. Poly(vinyl alcohol) is a water-soluble, synthetic biader which is prepared by the hydrolysis of poly(viayl acetate) (see Latex technology Vinyl polymers). 

Styrene—butadiene latexes generally are quite stable mechanically because of the presence of relatively large amounts of emulsifying and stabilizing agents, and therefore require addition of less stabilizer in compounding. The apphcations of SBR latex are classified in Table 21. This classification indicates the scope of the industry and illustrates the large number of diverse applications in which synthetic latices are employed. The latex types previously found most suitable for particular applications are also listed. 

Types of Latex Compounds. For comparison with dry-mbber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural mbber latex compounds, including one without antioxidant, and data on tensile strength and elongation of sheets made from those, both before and after accelerated aging, are also Hsted. The effects of curing ingredients, accelerator, and antioxidant are also Hsted. Table 24 also includes similar data for an SBR latex compound. A phenoHc antioxidant was used in all cases. 

The latex may consist entirely of natural latex or synthetic SBR latex or maybe a mixture of both. In the Dunlop process, natural mbber foams shrink more than SBR foams duriag washing and dryiag. The load-beariag capacity of the foams at a given density falls significantly as SBR is used ia place of natural mbber. 

Natural mbber latex is also used in adhesives for tape, packaging, envelopes, and in the footwear industry. It is used in the carpet industry as a binder for backing compounds, but this is another area in which synthetic SBR latex has competed effectively. There are a number of relatively small and specialized appHcations for natural mbber latex including mbberized coir or hair and cast products such as toys. Latex sheeting which is used in dental dams and for numerous other purposes can be made by dipping or casting onto a continuous belt. 

SBR latex and solid SBR have similar ingredients, except for the use of thickeners (only for latex). The major ingredients, in addition to the elastomer, for the SBR adhesives are given below. 

Sequestrants. These protect SBR latex from ions through complex formation. EDTA (ethylenediamine tetraacetic acid) is the most common. 

Recently a lot of attention is being given to the field of latex-based nanocomposites. Various organoclays as well as pristine clays have been intercalated in aqueous medium with NR latex, SBR latex, NBR latex, as well as carboxylated nitrile mbber (XNBR) latex [184—187], to achieve a good degree of dispersion. 

In an industrial application dissolution/reprecipitation technology is used to separate and recover nylon from carpet waste [636]. Carpets are generally composed of three primary polymer components, namely polypropylene (backing), SBR latex (binding) and nylon (face fibres), and calcium carbonate filler. The process involves selective dissolution of nylon (typically constituting more than 50wt% of carpet polymer mass) with an 88 wt % liquid formic acid solution and recovery of nylon powder with scCC>2 antisolvent precipitation at high pressure. Papaspyrides and Kartalis [637] used dimethylsulfoxide as a solvent for PA6 and formic acid for PA6.6, and methylethylketone as the nonsolvent for both polymers. 

Styrene-butadiene rubber (SBR) latexes which are compatible with cementitious compounds are copolymers. They show good stability in the presence of multivalent cations such as calcium (Ca++) and aluminum (A1+++) and are unaffected by the addition of relatively large amounts of electrolytes (e.g., CaCl2). Outdoor exposure to... 

The resins used are polymers and copolymers of the esters of acrylic and methacrylic acids. They range in physical properties from soft elastomers to hard plastics, and are used in cementitious compounds in much the same manner as SBR latex. Acrylics are reported to have better UV stability than SBR latex and therefore remain flexible under exterior exposure conditions longer than SBR latex [88]. 

Compound SBR latex backing adhesive PVC" backing Polyurethane backing... 

Recently, Mitra et al. have prepared chemically crosslinked nanosized gels from different rubber lattices [148,149]. When added in small quantity (2-16 phr), these low moduli deformable gels have been found to influence the mechanical properties of virgin elastomers like NR and SBR considerably. For example, sulfur prevulcanized nanosized SBR latex gels were prepared and characterized using various methods [148]. The morphology of gel-filled NR and SBR systems has been studied... 

Nano-powdered styrene/butadiene rubber has been synthesized by the radiation crosslinking of styrene-butadiene rubber (SBR). Tri-methylolpropane triacrylate can be used as crosslinking agent. This monomer improves the radiation crosslinking of the SBR latex. 

Black masterbatch -from SBR latex [STYRENE-BUTADIENE RUBBER] (Vol 22)... 

Considerable quantities or SBR latex are used in the manufacture of foam rubber, adhesives, fabric treating, and paints. The solid content of lattices runs from 50% to 65-70%. 

Styrene butadiene rubber (SBR) latex 25 000 tonnes Continuous isothermal reaction (5°C) in a series of reactors (33ni3 capacity each). 

Although the early literature described the application of a tubular reactor for the production of SBR latexes(1), the standard continuous emulsion polymerization processes for SBR polymerization still consist of continuous stirred tank reactors(CSTR s) and all of the recipe ingredients are normally fed into the first reactor and a latex is removed from the last one, as shown in Figure 1. However, it is doubtful whether this conventional reactor combination and operation method is the most efficient in continuous emulsion polymerization. As is well known, the kinetic behavior of continuous emulsion polymerization differs very much according to the kind of monomers. In this paper, therefore, the discussion about the present subject will be advanced using the... 

The molecular weight, glass transition temperature (T) and size of dispersed polymer particles in the latexes can affect the strength and c loride ion permeability of latex-modified mortar and concrete to a certain extent [87,93] (Tables 6.11 and 6.12). SBR latexes with smaller particle size appear to initially provide lower chloride ion permeability to the mortars, but a difference in the permeability between the smaller and larger particle sizes eventually becomes insignificant as the concrete ages. The initial decrease in the permeability observed with smaller particles is attributed to the fact that smaller particle size coalesce into films faster than the larger particle sizes. 

Styrene-Butadiene Rubber Latices. SBR latex is used mainly when the requirements are fairly modest and low cost is necessary. An example is in fixing vinyl-based floor coverings to wooden or concrete sub-floors—in which products comprising heavily filled styrene-butadiene rubber latices give adequate results. 

These ortho-linked compounds have also shown considerable promise in emulsion and solution SBR and are particularly valuable in carboxyl-ated SBR latex films combining good activity with excellent color—i.e., no pinking. The results of resinification tests on films laid from cafboxyl-ated SBR latex shown in Table VI demonstrate that the polycyclic nature of these compounds contributes significantly to their stabilizing activity, monocyclic compounds of similar structure being markedly poorer in activity. 

---