Hot emulsion polymerization

AfpoL [Cal Polymers] SBR copolymer, hot emulsion polymerized for adhesives mfg. 

Hot emulsion polymerization uses typical emulsion recipes containing potassium peroxydisulfate (free radical generator) and dodecyl mercaptan (chain transfer agent) in an aqueous soap emulsion at a reaction temperature of 50 C. 

Uses Emulsifier for hot emulsion polymerization of NBR, NR latex stabilization lubricant corrosion inhibitor... 

The original SBR process is carried out at. 50° C and is referred to as hot polymerization. It accounts for only about 5% of aU the mbber produced today. The dominant cold polymerization technology today employs more active initiators to effect polymerization at about 5°C. It accounts for about 85% of the products manufactured. Typical emulsion polymerization processes incorporate about 75% butadiene. The initiators are based on persulfate in conjunction with mercaptans (197), or organic hydroperoxide in conjunction with ferrous ion (198). The rest of SBR is produced by anionic solution polymerization. The density of unvulcanized SBR is 0.933 (199). The T ranges from —59" C to —64 C (199). 

Simplified nitrile mbber polymerization recipes are shown in Table 2 for "cold" and "hot" polymerization. Typically, cold polymerization is carried out at 5°C and hot at 30°C. The original technology for emulsion polymerization was similar to the 30°C recipe, and the redox initiator system that allowed polymerization at lower temperature was developed shortiy after World War II. The latter uses a reducing agent to activate the hydroperoxide initiator and soluble iron to reactivate the system by a reduction—oxidation mechanism as the iron cycles between its ferrous and ferric states. 

RESINS (Acrylonitrile-Butadiene-Styrene). Commonly referred to as ABS resins, these materials are thermoplastic resins which are produced by grafting styrene and acrylonitrile onto a diene-rubber backbone. The usually preferred substrate is polybutadiene because of its low glass-transition temperature (approximately —80°C). Where ABS resin is prepared by suspension or mass polymerization methods, stereospedfic diene rubber made by solution polymerization is the preferred diene. Otherwise, the diene used is a high-gel or cross-linked latex made by a hot emulsion process. 

The 121 sample films were formulated into a replicate series. Those utilizing emulsion polymerized PVC were cast from plastisol onto glass plates and fused in a circulating hot air oven. Those incorporating suspension polymerized PVC were fluxed via a Banbury and two-roll compounding mill and finished on an inverted L 8-inch X 16-inch four-roll calender. Plastisol films were of nominal 8-mil thickness calendered film was 4 mils. 

Butadiene-Styrene Rubber occurs as a synthetic liquid latex or solid rubber produced by the emulsion polymerization of butadiene and styrene, using fatty acid soaps as emulsifiers, and a suitable catalyst, molecular weight regulator (if required), and shortstop. It also occurs as a solid rubber produced by the solution copolymerization of butadiene and styrene in a hexane solution, using butyl lithium as a catalyst. Solvents and volatiles are removed by processing with hot water or by drum drying. 

Identification Identify emulsion-polymerized Butadiene-Styrene Rubber latex and solid by comparing their infrared absorption spectra with the respective four typical spectra as shown in the section on Infrared Spectra. Prepare latex samples by first drying them at 105° for 4 h, then by dissolving them in hot toluene and evaporating on a potassium bromide plate. Prepare solid samples by dissolving them in hot toluene and evaporating on a potassium bromide plate. 

Redox systems are used for polymerizations at lower temperatures. Many of these redox initiator couples were developed for the emulsion copolymerization of butadiene and styrene, since the 5-10"C cold recipe yields a better rubber than the hot SO C emulsion polymerization. 

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. 

Not all solvent adhesives will he replaced with latexes per se. For some applications, hot melt adhesive systems are heing developed. However, just as ethylene-vinyl acetate copolymers produced by emulsion polymerization are a major component of many hot melt systems, suitably designed emulsion polymers to meet specific requirements will probably he present in these systems, too. 

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... 

Sulfobutanedioio acid 1,4-bis(1 -methylpentyl) ester sodium sail. Alphasol MA Aerosol MA Bis(l-methylamyl) sodium sulfosuccinate Butanedioic acid, sulfo-, 1,4-bis(1-methylpentyl) ester, sodium salt Oihexyl sodium sulfosuccinate EINECS 227-847-0 Lankropol KMA Sodium dihexyl sulfosuccinate Sodium 1,4-diisohexyl 2-sulphosucoinate. Emulsifier, wetting agent, especially in solutions of electrolytes used as a solubilizer for soaps, emulsion polymerization aid. Solid soluble in H2O, pine oil, oleic acid, MezCO, kerosene, CCI4, EtOH, CsHe, hot olive oil, glycerol insoluble in liquid petrolatum. Harcros. 

The techniques used in manufacturing PSAs are solution and emulsion polymerization and hot-melt process. In general, acrylic PSAs are produced by solu-... 

It should be noted again that in the procedure attributed to Wilson [123], as in many other suspension polymerization procedures mentioned above and in many procedures for emulsion polymerizations to be described later, reaction temperatures are given which are above the boiling point of the monomer (72.7°C at 760 mm Hg), not to mention, above the boiling point of the vinyl acetate-water azeotrope (66°C) (composition, 92.7% vinyl acetate, 7.3% water, cf. Table I). For reactions carried out in sealed ampoules or closed bottles, this reaction temperature is readily explained. How such reaction temperatures are reached in a reflux apparatus open to the atmosphere is in question. It is hardly likely that the rate of polymerization is so rapid that no free monomer exists when it is added with conventional initiators to hot water. We presume that most of the polymerizations reported to proceed at about 66 C in an aqueous medium are simply run at reflux. At such a temperature, initiation by dibenzoyl peroxide is rather slow. If the suspension polymerization is to be forced at higher temperatures, provisions will have to be made to force the monomer into the... 

Styrene-butadiene rubber is the largest volume synthetic elastomer commercially available. It ean be produced by free-radical emulsion polymerization of styrene and butadiene either at 50 to 60°C (hot emulsion SBR) or at about 5°C (cold emulsion SBR). The two kinds of SBR have sigmfieantly different properties. The hot emulsion SBR process, which was developed st, leads to a more branehed polymer than the cold emulsion process. Cold SBR has a better abrasion resistance and, eonsequently, provides better tread wear and dynamic properties. 

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