2-Ethylhexyl acrylate, emulsion polymerization

ASA structural latexes have been synthesized in a two stage seeded emulsion polymerization. In the first stage, partially crosslinked poly(n-butyl acrylate) and poly( -butyl acrylate-sfaf-2-ethylhexyl acrylate) rubber cores are synthesized. In the second stage, a hard styrene acrylonitrile copolymer (SAN) shell is grafted onto the rubber seeds (16). 

The use of core-shell impact modifiers for sPS is also patented in EP 318793 [15] (see Table 19.1). These impact modifiers are usually prepared using the emulsion polymerization process, although other methods such as the microsuspension polymerization process are possible. The core usually consists of polymers prepared from an acrylate, especially butyl or 2-ethylhexyl acrylate or butadiene. These rubber particles are then grafted with vinyl monomers, where... 

Stable aqueous emulsions of poly(2-ethylhexyl acrylate) (PEHA) were also produced by RESAS from CO2 (68). In this case, a polymer suspension in CO2 was expanded instead of a dissolved solute. A C02-philic surfactant, Monasil PCA (PDMS-g-pyrrolidonecarboxylic acid), was utilized in dispersion polymerization to form a stable polymer suspension at 65°C and 345 bar. A hydrophilic surfactant, (e.g., SAM 185, Pluronic L61, or Pluronic L62), that is soluble in CO2 and CO2/2-EHA monomer mixtures as well as water was added to CO2 to stabilize the suspension after it had been rapidly expanded through a capillary into aqueous solution. The resulting aqueous emulsion with up to 15.6 wt % polymer content was stable for weeks with an average particle size of 2 to 3 pm. Another approach is to introduce the hydrophilic surfactant in the aqueous phase in addition to the surfactant in the CO2 phase. This approach is more general, since many hydrophilic surfactants are not soluble in CO2. During expansion of the suspension into an aqueous solution, the hydrophilic surfactant—for example, triblock Pluronic copolymers—dilfuses to the particle surface to provide stabilization. The resulting aqueous latexes were stable for 100 days for a polymer content reaching 12.7 wt %. 

A number of copolymers are known where vinyl acetate is the major component. In coatings, vinyl acetate is often used in copolymers with alkyl acrylates (line 2-ethylhexyl acrylate) or with esters of maleic or fumaric acids. Such copolymers typically contain 50-20% by weight of the comonomer and are usually formed by emulsion polymerization in batch processes. They are used extensively as vehicles for emulsion paints. 

In an autoclave are placed 140 gm of a 25% aqueous solution of sodium lauryl sulfate, 4200 ml of distilled water, and a solution of 46.5 gm of ammonium persulfate in 500 ml of water. The mixture is warmed to 80°C while, over a period of 1 hr, a monomer emulsion obtained by dispersing 3500 gm of 2-ethylhexyl acrylate and 70 gm of a 25% aqueous solution of sodium lauryl sulfate in 1-liter of distilled water is added. By the end of the addition period, the polymerization is substantially complete. The latex has a solid content of 37%, a surface tension of 56 dynes/cm, a pH of 2.0, and an average particle size between 0.03 and 0,06 jum. 

Using FT-MIR spectrometers equipped with ATR probes, Chatzi et al. [171], Kammona et al. [172], Hua and Dube [173], and Roberge and Dubd [174] obtained similar results for 2-ethylhexyl acrylate/styrene and VA/butyl acrylate/ MMA emulsion homo- and copolymerizations. Particularly, Hua and Dube [173] present a review about the use of FT-IR-ATR spectroscopy for kinetic studies in polymerization systems. In all cases, MLR or PLS calibration models were used for interpretation of spectral data. 

References cited provide details of polymerization of the monomers indicated. Heterogeneous polymerizations (emulsion, miniemulsion) are indicated by the monomer being in italics. Monomer/RAF agent combinations that are relatively ineffective are indicated by the monomer being in parentheses. DMAM, A/,W-dimethylacrylamide EHA, 2-ethylhexyl acrylate HPMAM, /V-(2-hydroxypropyl) methacrylamide MAM, methacrylamide NIPAM, W-isopropyl acrylamide tBA, ferf-butyl acrylate VBz, vinyl benzoate. 

A limitation of external plasticizers of this kind is that they may eventually be lost by evaporation or by migration into the substrate, leaving an imperfect and brittle film. This limitation may be overcome by the use of copolymers and these are now widely used in surface coatings and other applications. Comonomers which may be employed for this purpose include butyl acrylate, 2-ethylhexyl acrylate, diethyl fumarate, diethyl maleate and vinyl esters of fatty acids (e.g. a branched Cio fatty acid). Typically, the copolymers contain 15-20% by weight of such comonomers. These copolymers are readily prepared by the emulsion polymerization techniques described previously for the homopolymer. 

Up to now, poly(methyl methacrylate) and methyl methacrylate copolymers e.g. with styrene, butyl acrylate and dodecyl methacrylate) have been the most widely used acrylic polymers for nanocomposite preparation by emulsion and suspension polymerization. Less research has been based on other acrylic polymers, such as polyacrylonitrile, poly(butyl acrylate), " poly(butyl methacrylate), poly(2-ethylhexyl acrylate), poly(2-hydroxyethyl methacrylate), polyacrylamide, poly(lauryl acrylate)," poly(butyl acrylate-co-styrene)," " poly(acrylonitrile-co-styrene), poly(acrylonitrile-co-meth-acrylate)," poly(ethyl acrylate-co-2-ethylhexyl acrylate)" and poly(2-ethylhexyl acrylate-co-acrylic acid)," and sometimes small amounts of hydophilic acrylic monomers, such as hydroxyethyl methacrylate, methacrylic acid and acrylic acid, have been used as comonomers. " Therefore, it may be stated that, so far, the preparation of acrylic-clay nanocomposites has been based mainly on high glass transition temperature polymers, although nanocomposite materials with lower glass transition temperatures with improved or novel properties, which exhibit a balance of previous antagonistic properties, can also be achieved and are very desirable. Regarding nanocomposites of low glass transition temperature polymers, such as poly(butyl acrylate), poly(ethyl acrylate) and poly(2-ethylhexyl acrylate), which have been utilized as the main components of acrylic pressure-sensitive adhesives, little information is available. 

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