Emulsion soap catalyst

Styrene—Butadiene Rubber (SBR). This is the most important synthetic mbber and represents more than half of all synthetic mbber production (Table 3) (see Styrene-butadiene rubber). It is a copolymer of 1,3-butadiene, CH2=CH—CH=CH2, and styrene, CgH5CH=CH2, and is a descendant of the original Buna S first produced in Germany during the 1930s. The polymerization is carried out in an emulsion system where a mixture of the two monomers is mixed with a soap solution containing the necessary catalysts (initiators). The final product is an emulsion of the copolymer, ie, a fluid latex (see Latex technology). 

Emulsion Polymerization. In this method, polymerization is initiated by a water-soluble catalyst, eg, a persulfate or a redox system, within the micelles formed by an emulsifying agent (11). The choice of the emulsifier is important because acrylates are readily hydrolyzed under basic conditions (11). As a consequence, the commonly used salts of fatty acids (soaps) are preferably substituted by salts of long-chain sulfonic acids, since they operate well under neutral and acid conditions (12). After polymerization is complete the excess monomer is steam-stripped, and the polymer is coagulated with a salt solution the cmmbs are washed, dried, and finally baled. 

Commercial chloroprene polymerization is most often carried out in aqueous emulsion using an anionic soap system. This technique provides a relatively concentrated polymerization mass having low viscosity and good transfer of the heat of polymerization. A water-soluble redox catalyst is normally used to provide high reaction rate at relatively low polymerization temperatures. 

In industry, iodine is used for dyes, antiseptics, germicides. X-ray contrast medium, food and feed additives, pharmaceuticals, medical soaps, and photographic film emulsions and as a laboratory catalyst to either speed up or slow down chemical reactions. 

The monomers are piped from the tank farm to the caustic soda scmbbers where the inhibitors are removed. Soap solution, catalysts, and modifiers are added to produce a feed emulsion which is fed to the reactor train. Fewer reactors are normally used than the number required for a cmmb product line. When polymerization is complete, the latex is sent to a holding tank where stabilizers are added. 

Polymers may be made by four different experimental techniques bulk, solution, suspension, and emulsion processes. They are somewhat self-explanatory. In bulk polymerization only the monomers and a small amount of catalyst is present. No separation processes are necessary and the only impurity in the final product is monomer. But heat transfer is a problem as the polymer becomes viscous. In solution polymerization the solvent dissipates the heat better, but it must be removed later and care must be used in choosing the proper solvent so it does not act as a chain transfer agent. In suspension polymerization the monomer and catalyst are suspended as droplets in a continuous phase such as water by continuous agitation. Finally, emulsion polymerization uses an emulsifying agent such as soap, which forms micelles where the polymerization takes place. 

These considerations are important in regard to different systems such as paints, cements, adhesives, photographic products, water purification, sewage disposal, emulsions, chromatography, oil recovery, paper and print industry, microelectronics, soaps and detergents, catalysts, and biological systems (such as cell, virus). In some... 

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. 

In the polymerization of styrene or the copolymerization of isoprene and styrene, a soap such as potassium laurate has been found to be a powerful catalyst. The reaction, starting from an emulsion of monomer drops, ends with polymer particles, and is characterized both by the gradual disappearance of the soap from the aqueous phase during the reaction, and by the fact that the polymer particles, much smaller than in an uncatalyzed reaction, increase in size as the yield of polymer is increased. 

Emulsion Polymerization. As noted with suspension polymerization, emulsion polymerization also involves the dispersion of VCM in an aqueous medium. As distinguished from suspension polymerization, however, the emulsion process involves the use of a surface active agent or soap as the emulsifier and a water-soluble catalyst or initiator instead of the monomer-soluble catalyst used in suspension processes. Although agitation is necessary, it is not as important as in the suspension processes because the emulsion is maintained by use of the soap and protective colloids to insure latex stability. 

Precaution Combustible liq. corrosive to copper, brass, and aluminum Hazardous Decomp. Prods. Thermal decomp, prods. CD, CO NO, Uses Solubilizer for resins in aq. coatings fatty acid soaps as emulsifier for waxes, floor polishes, min. oil emulsions, insecticides mfg. of nonionic emulsions vapor-phase corrosion inhibitor PU foam catalyst ... 

The initiator is in the aqueous phase. Particles are much smaller (about 10 times) than those in suspension polymerization (where the catalyst is monomer-soluble and the kinetics are similar to bulk-type polymerizations). The emulsion polymerization kinetics are governed by Eq. (6-37), which differs considerably from bulk polymerization kinetics. Figure 6-8 shows the relation of polymerization to soap concentration. 

One of the authors (H. M.) had an opportimity to discuss the problem of emulsion polymerisation in the period between 1935 and 1938 with Drs. Fikentscher, H. Hopff, and E. Valko in Ludwigshafen am Rhine. At that time they offered several arguments in favour of polymerisation taking place preponderantly in the aqueous phase. Valko even considered it as highly probable that the monomer, solubilised in the micelles of the soap solution, was most favourably exposed to the action of a water-soluble catalyst and, therefore, might be considered as the principal site of the reaction. At a seminar on high polymers in Kansas City in September 1945, Dr. F. C. Fryling told us that he had, at the same time, independently arrived at very similar conclusions on the basis of his own observations. It appears, therefore, that some of the more recent developments were anticipated to a certain extent in the unpubhshed work between 1930 and 1940. 

Polymerisation in emulsion, in which the monomer is (a) dispersed in monomer droplets stabilized by an adsorbed layer of soap molecules (Fryling and Harrington, 1944, Kolthoff and Dale, 1945, Price and Adams, 1945, Siggia et ah, 1945, Vinograd etal, 1944) (b) solubilised in the soap micelles (Harkins, 1945, McBain, 1942, McBain and Soldate, 1944) which exist in an aqueous soap solution of sufficient concentration and (c) molecularly dissolved in the water. The amount of polymer formed in the droplets, in the micelles, and in solution will depend upon the way in which the monomer and catalyst are distributed in the three existing phases the monomer phase, the soap micelle phase, and the water phase - and possibly also upon the accessibility and reactivity of the monomer in these three phases. In certain aqueous soap emulsions, such as styrene, dichlorostyrene, or isoprene, the amount of molecularly dissolved monomer is small and, therefore, the reaction will occur preponderantly either in the monomer droplets or in the soap micelles. If the polymer formation occurs preponderantly in the micellar phase, one is inclined to speak of a typical emulsion polymerisation. If, however, polymerisation takes place to a considerable extent both in the monomer droplets and the soap micelles, the case is intermediate between suspension and emulsion polymerisation. There also exist emulsion... 

Uses Solubilizer for resins In aq. coatings fatly acid soaps as emulstfler for waxes, floor polishes, min. oil emulsions. Insecticides mfg. of nonlonic emulsions vapor-phase corrosion Inhibitor PU foam catalyst titanate solubilizer neutralizer raw material for synthesis HCI salt In curing of resins In durable-press textiles RegtMory Canada DSL... 

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