Batch polymerization emulsion, butyl

Emulsion Polymerizations, eg. vinyl acetate [VAc]/ABDA, VAc/ethylene [VAE]/ABDA, butyl acrylate [BA]/ABDA, were done under nitrogen using mixed anionic/nonlonic or nonionic surfactant systems with a redox Initiator, eg. t-butyl hydroperoxide plus sodium formaldehyde sulfoxylate. Base monomer addition was batch or batch plus delay comonomer additions were delay. 

Emulsion Polymerization A typical recipe is give in Table I. Emulsion polymerization was carried out at 60°C under a nitrogen atmosphere using a batch process. Theoretical solids content in all the formulations was 25%, and generally the conversions were better than 98%. A polyvinyl acetate homopolymer and two poly (vinyl acetate-butyl acrylate) copolymers having VA/BA composition of 85/15 and 70/30 were prepared according to the above procedure. 

Four polymerization examples are presented here to illustrate both available sensitivity, experimental difficulties, and hopefully some interesting aspects of the polymerization processes. The first two examples are the semi-continuous emulsion polymerization of methyl methacrylate (MMA) and styrene, respectively. The third example is a batch charged copolymerization of butyl acrylate (BA) with MMA. The fourth example is a semi-continuous solution polymerization of an acrylic system. In this last example aliquots were taken manually and analyzed at 29.7°C under static conditions. No further polymerization occurred after the samples were cooled to this temperature. 

Having shown that carboxy terminated polyesters present typical surfactant characteristics after neutralization with amines, it was of interest to examine their application possibilities in emulsion polymerization. Such polymerizations for styrene and for butyl-methacrylate (BMA) have been carried out either by a batch technique or by a semi- continuous procedure. The reaction conditions were the following ... 

The emulsion copolymerization of vinyl acetate and butyl acrylate has received considerable attention. The butyl acrylate confers improved film forming characteristics to the polymer. The disparities in their water solubilities and of their individual polymerization rates may help to explain the variations in reactivity ratios that have been reported [170,171]. The variation in reactivity ratios may also by related to the following observations The reaction method has an effect on the morphology of the polymer particles. In a batch emulsion process, a butyl acrylate—rich core is formed which is surrounded by a vinyl acetate-rich shell, in a process in which the monomers are fed into the reactor in a semicontinuous manner, particles form with a more uniform distribution of the monomers [172]. The kinetics for a batch process indicates that the initially formed polymer is indeed high in butyl acrylate. As this monomer is used up, eventually a copolymer high in vinyl acetate develops. It is this latter polymer which forms the final shell around the particles. 

Besides two-component LIPNs, three-component LIPNs have also been studied through three-stage emulsion polymerization processes (Zhang et al. 1991, 1994 Isao et al. 1992). These authors synthesized poly(n-butyl acrylate) cross-linked with ethylene glycol dimethacrylate as the seed latex. Styrene and divinylbenzene were added at the second stage. The third stage was linear poly(methyl methacrylate). Starved polymerization conditions resulted in more regular-shaped latex particles than batch addition of monomer. 

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... 

Al-Khanbashi et al. [62] published a review of initial applications of Raman spectroscopy to studies of aqueous-phase emulsion polymerization. The polymerization reactions studied those of styrene-butyl acrylate (STY/BA) and methyl methacrylate (MMA) were conducted as laboratory-scale reactions, but the potential of applying Raman spectroscopy to the field of in-line monitoring of batch emulsion polymerization of batch reactions was not lost on the authors. 

Emulsion copolymerizations can be carried out using batch, semi-continuous, or continuous processes. The copolymers made by these processes differ according to the process used, the copoly-meriztion reactivity ratios of the monomers, and the monomer solubilities in the aqueous phase. To show the difference between batch and semi-continuous polymerization, the latex particle size, surface characteristics, latex stability, copolymer properties, and latex film morphology were investigated for the vinyl acetate-butyl acrylate system (37). The water solubilities are 290 mM and llmM for vinyl acetate and butyl acrylate, respectively, and the copoly-merization reactivity ratios of = 0-0.04 and r 2 show... 

Figure 8. Dynamic mechanical spectra (loss modulus) of vinyl acetate (A)-butyl acrylate (B) co polymers prepared by batch ) and semicontinuous (o) emulsion polymerization copolymers with [A]=89%(I), 71%(II), and 49%(III). (Pichot, Llamo, Pham, Ref. 25)...

Cutting GR, Tabner BJ. Radical concentrations and reaction temperature profiles during the (batch) core—shell emulsion polymerization of methyl methacrylate and butyl acrylate, studied by electron spin resonance spectroscopy. Eur Polym J 1997 33 213-217. 

Svoboda et al. [160] investigated the emulsion copolymerization and ter-polymerization of VC with vinyl accetate, butyl acrylate and/or ethyl acrylate. The polymerizations proceeded under batch and continuous conditions and were initiated by peroxodisulfates. Anionic emulsifiers (sodium dodecyl sulfate, sodium dodecylbenzene sulfonate,..) and blends of anionic and non-ionic emulsifiers (mostly polyoxyethylene type) were used. Copolymer latexes prepared with emulsifier blends were much more stable than those with an anionic emulsifier. As expected, the copolymers prepared by continuous polymerization gave copolymers with homogeneous composition. In the batch copolymerizations, the shift in the copolymer composition with conversion was observed and particles with broader size distribution were prepared. For example, the batch VC/ethyl acrylate polymer latexes gave particles with a diameter from 180 nra to 320 nm. 

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