Vinyl ester emulsion polymerization

Uses Emulsifier in emulsion polymerization (acrylic esters, styrene and vinyl monomers), ester waxes and fatty acids stabilizer for emulsions, suspensions, and latexes... 

Uses Emulsifier for emulsion polymerization (acrylic esters, styrene and vinyl monomers)... 

Almost all synthetic binders are prepared by an emulsion polymerization process and are suppHed as latexes which consist of 48—52 wt % polymer dispersed in water (101). The largest-volume binder is styrene—butadiene copolymer [9003-55-8] (SBR) latex. Most SBRlatexes are carboxylated, ie, they contain copolymerized acidic monomers. Other latex binders are based on poly(vinyl acetate) [9003-20-7] and on polymers of acrylate esters. Poly(vinyl alcohol) is a water-soluble, synthetic biader which is prepared by the hydrolysis of poly(viayl acetate) (see Latex technology Vinyl polymers). 

Random copolymers of vinyl chloride and other monomers are important commercially. Most of these materials are produced by suspension or emulsion polymerization using free-radical initiators. Important producers for vinyl chloride—vinyUdene chloride copolymers include Borden, Inc. and Dow. These copolymers are used in specialized coatings appHcations because of their enhanced solubiUty and as extender resins in plastisols where rapid fusion is required (72). Another important class of materials are the vinyl chloride—vinyl acetate copolymers. Principal producers include Borden Chemicals Plastics, B. F. Goodrich Chemical, and Union Carbide. The copolymerization of vinyl chloride with vinyl acetate yields a material with improved processabihty compared with vinyl chloride homopolymer. However, the physical and chemical properties of the copolymers are different from those of the homopolymer PVC. Generally, as the vinyl acetate content increases, the resin solubiUty in ketone and ester solvents and its susceptibiUty to chemical attack increase, the resin viscosity and heat distortion temperature decrease, and the tensile strength and flexibiUty increase slightly. 

Some Aspects of Vinyl Ester Emulsion Polymerization... 

Core-shell rubber (CSR) particles are prepared by emulsion polymerization, and typically exhibit two or more alternating rubbery and glassy spherical layers (Lovell 1996 Chapter 8). These core-shell particles are widely used in thermoplastics, especially in acrylic materials (Lovell, 1996), and have also been used to modify thermosets, such as epoxies, cyanates, vinyl ester resins, etc. (Becu et al., 1995). 

The formation of coagulum is observed in all types of emulsion polymers (i) synthetic rubber latexes such as butadiene-styrene, acrylonitrile-butadiene, and butadiene-styrene-vinyl pyridine copolymers as well as polybutadiene, polychloroprene, and polyisoprene (ii) coatings latexes such as styrene-butadiene, acrylate ester, vinyl acetate, vinyl chloride, and ethylene copolymers (iii) plastisol resins such as polyvinyl chloride (iv) specialty latexes such as polyethylene, polytetrafluoroethylene, and other fluorinated polymers (v) inverse latexes of polyacrylamide and other water-soluble polymers prepared by inverse emulsion polymerization. There are no major latex classes produced by emulsion polymerization that are completely free of coagulum formation during or after polymerization. 

Vinyl acetate is polymerized in aqueous emulsion and used widely in surface coating and in adhesives. Copolymerized with vinyl esters of branched carboxylic acids and small quantities of acrylic acid, it gives paint latices of excellent performance characteristics. G. C. Vegter found that a coagulum-free latex of very low residual monomer content can be produced from a mixture of an anionic and a nonionic emulsifier according to a specific operating procedure. The freeze/thaw stability of polymeric latices has been investigated by H. Naidus and R. Hanzes. 

To survey as completely as possible the grafting behavior of EVA copolymers toward various vinyl compounds, our investigations covered the grafting of vinyl acetate, vinylidene chloride, and acrylic and meth-acrylic esters. As polymerization processes, at first we preferred suspension polymerization to exclude the influence of solvents by terminating or transfer reactions during polymerization. Grafting by emulsion polymerization, in which the EVA copolymer was dissolved in the monomer before polymerization, was difficult because coagulate was formed as polymerization proceeded. 

Among the processes used for the formation of polyolefins, the longest-known but least selective one is free radical polymerization. A free radical species X produced e.g. by thermolysis of benzoyl peroxide or by photolysis of azabisisobutyronitrile (AIBN) - can react with the double bond of a vinyl derivative H2C=CHR to form a new radical of the type XCH2-CHR which can then add another H2C=CHR unit repetition of this process leads to polyolefin formation (Figure 2, top). This process works best for vinyl derivatives with unsaturated side groups, which provide resonance stabilization for an adjacent radical centre, e.g. with vinyl and acrylic esters, vinyl cyanides and vinyl chloride and with styrene and 1,3-dienes. It is extensively used in the emulsion polymerization of vinylic and acrylic derivatives and in the light-induced formation of photoresists for the nanofabrication of semiconductor chips and integrated electronic circuits. 

The most common polymer of a vinyl ester is poly(vinyl acetate), CAS 9003-20-7, with the formula [-CH2CH(OC(0)CH3)-]n. Other vinyl esters also are known, such as poly(vinyl butyrate), poly(vinyl benzoate) CAS 24991-32-0, and poly(vinyltrifluoroacetate), CAS 25748-85-0. Poly(vinyl acetate) is typically obtained from the monomer with radical initiators, either by emulsion or suspension polymerization. The polymer Is used in water-based emulsion paints, adhesives [22], gum base for chewing gum, etc. Also, poly(vinyl acetate) is used as a precursor for the preparation of other polymers such as poly(vinyl alcohol) or poly(vinyl acetals). Thermal decomposition of poly(vinyl acetate) starts at a relatively low temperature, around 200° C, some of the reports regarding its thermal decomposition being given in Table 6.5.8 [13]. The same table includes references for poly(vinyl butyrate) and poly(vinyl cinnamate), CAS 9050-06-0. 

Emulsion Copolymerizations. Due to the good copolymerizability of VEC with vinyl ester monomers, it seemed likely that VEC could be incorporated into a vinyl acetate/butyl acrylate latex. First, it was important to determine if VEC is prone to hydrolysis in the acidic medium used for vinyl acetate emulsion polymerization. As a check, a single experiment was carried out using an acetic acid-sodium acetate buffer at pH=4 and heating for 4 hours at 80°C. In this experiment, 6.1% of the VEC was hydrolyzed to the 3-butene-1,2-diol. Since VEC is only soluble in water up to 3.3 %, it is expected that most of the VEC will be in the oil phase during the emulsion polymerization and that only a small amount will be hydrolyzed. 

Polymer Colloids Emulsion polymerization produces monodisperse polymer spheres 50 to 500 nm in diameter by the scheme shown in Figure 11.9. Water-immiscible vinyl monomers such as styrene, acrylic esters, and methacrylic... 

Phosphate ester surfactants include GAFAC RE-90 (Rhfine-Poulenc cmc = 0.05%) and Emphos CS-136 (nonyl ph ol ethoxy(6) phosphate esto cmc = 0.022% Vfitco) which are used in the emulsion polymerization of acrylics, vinyl acrylics and vinyl acetate. 

Bernard et al. [105] used the same strategy to decorate polyVAc latex particles with a dithiocarbonate end-functionalized dextran (dextran-RAFT), well-suited for the CRP of non-activated vinyl esters such as VAc. Dextran-RAFT was obtained by Cu(I)-catalyzed Huisgen [3+2] dipolar cycloaddition [106] between an alkyne end-functionalized dextran and an azido-containing dithiocarbonate. The low functionalization yield (30%) was apparently not an impediment for the syntheses of stable poly VAc latex particles (diameters from 80 to 150 nm) via batch emulsion polymerization. The involvement of the dithiocarbonate end-group was corroborated by the retardation effect observed when the dextran-RAFT concentration was increased. In addition, a drastic effect on particle size was observed as compared to emulsion polymerization experiments performed with native or alkyne-functionalized dextran (particle diameter above 500 nm). 

Chem. Descrip. Sodium lauryl sulfate CAS 151-21-3 EINECS/ELINCS 205-788-1 Uses Surfactant, detergent for use in shampoos, bubble baths, liq. hand dish detergents, and mild industrial cleaners surfactant in emulsion polymerization, esp. for styrene, butadiene, vinyl chloride, vinylidene chloride, and acrylic ester monomers food pkg. adhesives, paper, cellophane, rubber articles, textiles defoamer in food-contact paper/paper-board emulsifier in mfg. of food-contact articles resinous/polymeric food-contact coatings Features High foam... 

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. 

Polyvinyl acetate (PVAc) is the largest volume polymer produced from a vinyl ester (1). In 1990, over 2.5 billion pounds of vinyl acetate monomer were produced in the United States alone (2). The bulk of this monomer was used for making PVAc and PVAc copolymers, which are widely used in water-based paints, adhesives, coatings, and binders for nonwoven paper products. PVAc is also the precursor to polyvinyl alcohol (PVA) and polyvinyl butyral, which cannot be made by direct polymerization. Methods of PVAc polymerization vary depending on the end use. Solution polymerizations of vinyl acetate in methanol are generally employed in processes in which PVAc is used as an intermediate in the production of PVA. PVAc latexes are generally made by emulsion polymerization, and PVAc in bead form is often synthesized by suspension polymerization (3,4). 

Emulsion polymerization requires free-radical polymerizable monomers which form the structure of the polymer. The major monomers used in emulsion polymerization include butadiene, styrene, acrylonitrile, acrylate ester and methacrylate ester monomers, vinyl acetate, acrylic acid and methacrylic acid, and vinyl chloride. All these monomers have a different stmcture and, chemical and physical properties which can be considerable influence on the course of emulsion polymerization. The first classification of emulsion polymerization process is done with respect to the nature of monomers studied up to that time. This classification is based on data for the different solubilities of monomers in water and for the different initial rates of polymerization caused by the monomer solubilities in water. According to this classification, monomers are divided into three groups. The first group includes monomers which have good solubility in water such as acrylonitrile (solubility in water 8%). The second group includes monomers having 1-3 % solubility in water (methyl methacrylate and other acrylates). The third group includes monomers practically insoluble in water (butadiene, isoprene, styrene, vinyl chloride, etc.) [12]. 

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