Emulsion polymerization, vinyl chloride

Sodium tridecyl sulfate surfactant, emulsion polymerization vinyl chloride emulsions Calimulse ALS... 

Peggion, Testa and Talamini proposed a mechanism identical to that of Priest for the formation of particles in vinyl chloride emulsion polymerization (14). This was based on an extensive study of the kinetics of polymerization as a function of concentrations of various emulsifiers above and below the CMC. 

Growth of Polymer Particles in Vinyl Chloride Emulsion Polymerization... 

Figure 11 gives, in addition, the initiator dependence at constant particle number as the slope of log TTvs. log a. Thus, it is suggested at the extremes of high and low particle numbers (or a ) that initiator dependence increases from zero in the Case II range to 1/2 where tt < 1/2 and where TT > 1/2. The zero order initiator dependency is well known for Case II polymerizations and the 1/2 order initiator dependency at IT > 1/2 has been reported by numerous authors. An initiator dependence of 1/2 has been observed by Ugelstad (8) for vinyl chloride emulsions where n 1/2. 

Friis and Hamielec (1975) have used GPC to study the MWD development in vinyl acetate and vinyl chloride emulsion polymerizations. For these monomers, the main chain-stopping mechanism is thought to ha transfer, and so the compartmentalize nature of the system is relatively unimportant. These workers found that the MWDs produced at early times, where branching reactions are unimportant, have a P value dose to 2, as expected for transfer-dominated reactions. 

Recently, Ugelstad et al. l969i proposed a semiempirtcal rate coefficient for radical desorption in vinyl chloride emulsion polymerization. On the other hand, Nomura et al. (1971, 1976) have derived a rate coefficient for radical desorption theoretically with both stochastic and deterministic approaches and have successfully applied it to vinyl acetate emulsion polymerization. They also pointed out that radical desorption from the particles and micelles played an important role in micellar particle formation, Fiiis et al. 1973 also derived the rate coefficient for radical desorption in a different way. Lift et al. (1981) discussed in more detail the chemical reactions incorporated in the physical process of radical desorption in the emulsion polymerization of vinyl acetate. 

Equation (29) is an empirical equation presented by Ugelstad and Merk (1970) and may be useful in styrene emulsion polymerization because tbe value of w is about 10 or less than that under normal reaction conditions in this system. On the other hand, Eqs, (30) and (33) are applicable to vinyl acetate and vinyl chloride emulsion polymerizations (Ugelstad et al.. 1969 Harada et al., 1971 Friis and Nyhagen, 1973). Equation (34) explains very well tbc rate of aqueous dispersion polymerization of vinyl acetate in tha absence of emulsifier (Nomura et a ., 1978). 

Ugelstad er al. (1969) first suggested experimentally that in vinyl chloride emulsion polymerization fcf may be expressed in the following form... 

In Fig. 4, theoretical values of n calculated by Eq. (30) are plotted against the value of C = pJkfNj, Experimental values of n obtained at the conversion point hr vinyl acetate and vinyl chloride emulsion polymerizations where monomer droplets disappear in the water phase (20 4( ... 

The value of a increases from 0,6 to 1.0 with increasing radical desorption. For vinyl acetate and vinyl chloride emulsion polymerization, the calculated values of order with respect to Sc and p axe 1 and 0, respectively. These are in good agreement with experimental results (Ugelstad et ah, 1969 Nomura et ., 1976). For other monomers and details see the recent paper by Hansen and Ugelstad (1979). 

In Stage 111, the reduction in >p and increase in d lead to a reduction in desorption coefficient with an increase in polymer-phase viscosity. For vinyl chloride emulsion polymerization the separate monomer phase disappears at about 70% conversion (AT,. = 0.7). Therefore, as soon as iVp reaches a constant value, the only parameter that changes for AT < is I. In fact, it is mainly the increase in that causes the acceleration in rate. For X > the situation is more complex, with both lc,p and falling as polymer concentration increases. For vinyl acetate, the separate monomer phase already disappears at 20% conversion. For X > X, is almost constant however [Mp], fe,p, and all decrease with conversion. These effects will he discussed in more detail later. 

For the calculation of molecular weights in CSTR emulsion reactors, a vsefnl classification comes to mind. This includes those monomer systems whose molecular weight and branching development depends on particle size and those that do not. Styrene falls into the former class and vinyl chloride and vinyl acetate into the latter class. Thus, in vinyl chloride emulsion polymerization where LCB is neglected, the instantaneous molecular weight distribution is given by... 

Four commercial methods are used to polymerize vinyl chloride. These are emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization. The first two are the only techniques of significance with respect to fluid vinyl systems. 

Commercial grade PVC is produced primarily by free-radical-initiated suspension and emulsion polymerization of vinyl chloride. Suspension polymerization accoimts for over 80% of PVC produced. Solution and bulk polymerization are also employed to some extent. However, there are difficulties with bulk polymerization because PVC is insoluble in its monomer and therefore precipitates. In suspension polymerization, vinyl chloride droplets are suspended in water by means of protective colloids such as poly(viEyl alcohol), gelatin, or methyl cellulose in pressure vessels equipped with agitators and heat... 

POLYSTEP B-LCP surfactant, vinyl chloride emulsion polymerization... 

A Smith-Ewart case 1 behavior in 1) can be observed during emulsion polymerization of monomers with a high chain-transfer rate constant such as vinyl chloride because the monomer radicals have a high tendency to escape from the particles. Especially for vinyl chloride emulsion polsunerization, Ugelstad and Hansen (113) derived the following equation 18 to calculate n, which predicts dependence, h a... 

For the polymerization of ethene with vinyl acetate and vinyl chloride, emulsion polymerization in water is particularly suitable. The polymerizates have gained some importance as adhesives, binding materials for pigments, and coating materials [184,185]. 

A special case of phase separation is met with in the case that the polymer is insoluble in its own monomer as is the case with vinyl chloride. Emulsions of vinyl chloride in water may be formed by the diffusion method described above. A small amount of a compound Y is homogenized in water containing emulsifier. After further dilution with water, vinyl chloride is added and a stable emulsion of vinyl chloride is formed. By the subsequent polymerization,PVC is precipitated inside the droplets. Each droplet maintains its identity but is made up of two phases, one consisting of polymer swollen with monomer and compound Y (this phase may be subdivided into several particles inside the droplet) and an outer phase being composed of monomer and compound Y. The situation is different from the case of aqueous dispersions discussed so far in that the compound Y is present in what may be denoted the continuous phase inside the particles. Thus, in this case Y acts as a compound Y in relation to water and functions as a compound L inside the droplets. The continuous phase inside the droplet will contain only traces of polymer and the situation may therefore be described by the following equation ... 

Poly(vinyl chloride) (PVC) is one of the most widely produced polymeric materials in use today. It is commercially produced by four major processes suspension, bulk, emulsion and solution. An industrially important method of production of PVC is emulsion polymerization. There are a lot of data regarding the kinetics and mechanism of emulsion polymerization of vinyl monomers. However, relatively little work has been done on the kinetics of vinyl chloride emulsion polymerization and much less on the emulsion copolymerization. Concerning the preparation of copolymer latexes of vinyl chloride monomer, there are only patents [1-3]. 

According to Ugelstadt et al. [78] as well as Friis and Hamielec [79], Eqs. (27-29) describe the rate of vinyl chloride emulsion polymerization well up to the pressure drop. Nilsson et al. [80], however, observed (using a highly sensitive calorimeter reactor) that the approximation of the suppressed water-phase termination is not entirely justified especially at higher conversions. 

The formation of primary radicals governs the rate of initiation and particle population. Because radical generation occurs in the aqueous phase, whereas radical termination occurs in the polymer particles, the polymerization rate and molecular weight can be increased at the same time. In vinyl chloride emulsion polymerization, the emulsifier greatly affects the polymerization kinetics and the physicochemical and colloidal properties of the polymer. The average polymer particle size is of the order 0.1-0.3 p,m, which is the size of primary particle nuclei in bulk and suspension polymerizations. The following is a summary of the typical kinetic features of batch vinyl chloride emulsion polymerization [61] ... 

Uses DetergenL penetranL emulsifier, dispersant for bleaching, dyeing operations emulsifier for min. oil, emulsion polymerization (vinyl chloride, vinyl chloride/ acrylic)... 

Aerosol 18 Aerosol TR-70 BIO-SOFT D-40 Disponil SLS 2010 LIpolan PJ-400 Liponox NC-200 Monawet MT-70 POLYSTEP B-3 POLYSTEP B-24 POLYSTEP B-25 Rhodaoal LDS-22 Rhodapon TDS Sodium lauryl sulfate Sodium tridecyl sulfate Sunnol NP-2030 emulsifier, emulsion polymerization vinyl chloride/acrylics Liponox NC-200 Liponox NC-300 emulsifier, emulsion polymerization vinyl monomers Agnique OP-4070... 

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