Styrene semicontinuous

Figure 3. Conversion representation for styrene semicontinuous emulsion polymerization (( ) zero conversion axis)...

Maleate Surfmers were found to outperform methacrylic and crotonic compounds in the copolymerization of styrene, butyl acrylate and acrylic acid in seeded and nonseeded semicontinuous processes [17]. The maleate Surfmer achieved high conversion without homopolymerization in the aqueous phase which can result in emulsion instability. The methacrylate Surfmer was too reactive as opposed to the crotonate which was not sufficiently reactive. The reported dependence of the maleate Surfmer conversion on the particle diameter is consistent with a reaction at the particle surface. 

With this in mind, the anionic polymerization of styrene (PS), styrene-butadiene (SB), or SI is typically carried out by feeding distilled and dried monomer and solvent and purified n-butyl-lithium to a CSTR operating in semicontinuous mode. The reaction mix is heated to the reaction temperature and the second monomer is fed at a programmed feed rate that allows the desired copolymer microstructure to be built, whether a block SB or SI, or tapered or random copolymers. Solution SBR is commonly... 

The composition and quantity of styrene-maleic anhydride (SMA) copolymer resins were varied in emulsion copolymerisation of methyl methacrylate and n-butyl acrylate conducted by both batch and semicontinuous processes. The resulting particle sizes and levels of coagulum were measured to determine the optimum conditions for incorporation of the SMA resins into the resulting latexes. A semicontinuous process, in which no buffer was included and the SMA was added in a second stage comonomer emulsion, was found to produce coagulum-free latexes. 13 refs. 

The diffusion and reaction of amino-telechelic polybutadiene in poly(styrene-n-butyl acrylate/ TMI)(PSBT) was studied. Amonodisperse seed latex was prepared by semicontinuous emulsion polymerisation. Two core-shell latices were also prepared semicontinuously, using the seed latex as the core and poly(styrene-n-butyl acrylate) as the shell. These monodisperse latices were mixed with equivalent amounts of the amino-telechelic polybutadiene artificial latex before casting into films. Consumption of the TMI (dimethyl meta-isopropenyl benzyl isocyanate) in these films was monitored by FTIR as a function of time and the amino/TMI ratio. 6 refs. 

The semicontinuous surfactant-free synthesis of a core/shell styrene/acrolein latex and its analysis for surface aldehyde functions are described. A calorimetric assay based on reaction with dinitrophenylhydrazine is compared with reduction by tritiated sodium borohydride and integration of aldehyde peaks in the proton NMR spectrum of the dissolved polymer. X-ray photoelectron spectroscopy confirmed the surface location of the aldehyde functions and the analytical reaction products. The three assay procedures were in reasonable agreement, suggesting all the aldehyde functions were accessible to aqueous reagents. Relevance to protein carriers is indicated. 21 refs. CANADA... 

Shaffer et al [365] have continued to modify staining techniques for TEM of latex particles. Recent work on structured latex particles prepared by seeded emulsion polymerization focused on the effects of changes in polymerization variables, such as batch versus semicontinuous, core-shell ratio, shell thickness and shell composition. In this system the core was poly(n-butyl acrylate) and the shell was poly(benzyl methacrylate-styrene). A few drops of the latex was combined with a few drops of a 2% uranyl acetate solution which serves as a negative stain. A drop of that mixture was deposited on a stainless steel formvar-coated grid. After drying it was stained in ruthenium tetroxide vapor to differentiate the rubbery core, which is not... 

Emulsion polymerization is mostly carried out in stirred tank reactors operated semicontinuously. The reason for using semicontinuous operation is that under similar reaction conditions, the polymerization rate is higher than in bulk (see Section ), which makes the thermal control of the reactor difficult even with the relatively low overall viscosity of the reaction medium. Therefore, heat generation rate is controlled by feeding the monomers slowly. In addition, the semicontinuous operation allows better control of polymer characteristics. Continuous stirred tank reactors are used for the production of some high-tonnage emulsion polymers such as styrene-butadiene rubber. 

Aerdts AM, Theelen S JC, Smith TMC, German AL. Grafting of styrene and methyl-methacrylate concurrently onto polybutadiene in semicontinuous emulsion processes and determination of copolymer microstructure. Polymer 1994 35 1648-1653. 

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