Emulsion polymerization polymeric dispersions

Disponil. [Henkel/Functional Prods. Henkel KOaA Fulcra SA] Emulsifier for emulsion polymerization dispersant for paints surfactant for shampoos. 

PolywettB. [Uniroyal] Polyfiinctional oligomer salts emulsifier for emulsion polymerization dispersant for miner-... 

Chem. Descrip. Dioctyl sodium sulfosuccinate CAS 577-11-7 EINECS/ELINCS 209-4064 Uses Wetting agent and emulsifier for emulsion polymerization dispersant for coatings... 

Uses Penetrant, wetting agent for textiles emulsion breaker emulsifier for agric., emulsion polymerization dispersant, wetting agent, penetrant for paints, pigments, inks Features Antihard water chars. 

Chem. Descrip. Styrene maleic anhydride amic acid resin Uses Surfactant in emulsion polymerization dispersant for metallic pigments overprint varnishes inks... 

High oil solubility with limited water solubility, for emulsion polymerization. Dispersant for pigments, polymers in hydrocarbon and other organic solvents. 

There are many different methods for the syntheses of latexes (19a, b) all of which are based on free-radical polymerization. The various preparation can be broadly divided into the following methods, i.e. emulsion polymerization, dispersion polymerization and suspension polymerization. A more detailed treatment can be found in ref. 19a (p. 12). 

Suspension and emulsion polymerization are two classical polymerization techniques to produce spherical polymeric particles. Larger particles (usually larger than 50 tim) with an appreciable size distribution are produced by suspension polymerization. Submicron polymeric particles (usually smaller than 0.1 im) with extremely uniform in size are obtained by conventional emulsion polymerization processes. Recent techniques, such as swollen emulsion polymerization, dispersion polymerization, etc. give micron-size (usually between 1-50 im) monosize polymeric particles (23). 

Chem. Analysis 0.02% max. ash 0.8% max. moisture Uses Emulsifier, stabilizer for vinyl acetate, acrylate emulsion polymerization for syn. latex for paint, paper coatings, textiles emulsifier for emulsion polymerization dispersant for pigment and wax polishes Properties APHA 80 max. wh. solid readily sol. in water, alcohol, glycol ethers, simple esters and most aromatic solvents insol in aliphatic solvents and mineral oils. sp. gr. 1.070-1.090 cloud pt. (1% aq.) 69-74 C HLB 17.0 pH (1% aq.) 5.5-... 

Uses Emulsifier for emulsion polymerization dispersant detergent antlstat Features Achieves low surfactant Irritation Properties Liq. sol. In water ( 1%) 100% act. 

Uses Surfactant in emulsion polymerization dispersant for metallic pigments ... 

According to the solubility of the core-forming monomer in the reaction media, two different methods—emulsion polymerization and dispersion polymerization— have been exploited to obtain self-assembled nanoparticles by PISA [37, 38]. The dispersion polymerization can be carried out either in water or in organic solvents. The emulsion polymerization starts from a monomer-in-water emulsion, where a water-soluble polymer precursor is chain-extended by polymerizing a water-immiscible monomer, resulting in self-assembled block copolymers. In contrast to the emulsion polymerization, dispersion polymerization is conceptually much simpler and the initial reaction solution is homogeneous. 

In mass polymerization bulk monomer is converted to polymers. In solution polymerization the reaction is completed in the presence of a solvent. In suspension, dispersed mass, pearl or granular polymerization the monomer, containing dissolved initiator, is polymerized while dispersed in the form of fine droplets in a second non-reactive liquid (usually water). In emulsion polymerization an aqueous emulsion of the monomer in the presence of a water-soluble initiator Is converted to a polymer latex (colloidal dispersion of polymer in water). 

The surfactant is initially distributed through three different locations dissolved as individual molecules or ions in the aqueous phase, at the surface of the monomer drops, and as micelles. The latter category holds most of the surfactant. Likewise, the monomer is located in three places. Some monomer is present as individual molecules dissolved in the water. Some monomer diffuses into the oily interior of the micelle, where its concentration is much greater than in the aqueous phase. This process is called solubilization. The third site of monomer is in the dispersed droplets themselves. Most of the monomer is located in the latter, since these drops are much larger, although far less abundant, than the micelles. Figure 6.10 is a schematic illustration of this state of affairs during emulsion polymerization. 

Emulsion polymerization also has the advantages of good heat transfer and low viscosity, which follow from the presence of the aqueous phase. The resulting aqueous dispersion of polymer is called a latex. The polymer can be subsequently separated from the aqueous portion of the latex or the latter can be used directly in eventual appUcations. For example, in coatings applications-such as paints, paper coatings, floor pohshes-soft polymer particles coalesce into a continuous film with the evaporation of water after the latex has been applied to the substrate. 

Emulsion Polymerization. Emulsion polymerization is the most important industrial method for the preparation of acryhc polymers. The principal markets for aqueous dispersion polymers made by emulsion polymerization of acryhc esters are the paint, paper, adhesives, textile, floor pohsh, and leather industries, where they are used principally as coatings or binders. Copolymers of either ethyl acrylate or butyl acrylate with methyl methacrylate are most common. 

M ass Process. In the mass (or bulk) (83) ABS process the polymerization is conducted in a monomer medium rather than in water. This process usually consists of a series of two or more continuous reactors. The mbber used in this process is most commonly a solution-polymerized linear polybutadiene (or copolymer containing sytrene), although some mass processes utilize emulsion-polymerized ABS with a high mbber content for the mbber component (84). If a linear mbber is used, a solution of the mbber in the monomers is prepared for feeding to the reactor system. If emulsion ABS is used as the source of mbber, a dispersion of the ABS in the monomers is usually prepared after the water has been removed from the ABS latex. 

Acrylonitrile and its comonomers can be polymerized by any of the weU-known free-radical methods. Bulk polymerization is the most fundamental of these, but its commercial use is limited by its autocatalytic nature. Aqueous dispersion polymerization is the most common commercial method, whereas solution polymerization is used ia cases where the spinning dope can be prepared directly from the polymerization reaction product. Emulsion polymerization is used primarily for modacryhc compositions where a high level of a water-iasoluble monomer is used or where the monomer mixture is relatively slow reacting. 

Aqueous media, such as emulsion, suspension, and dispersion polymerization, are by far the most widely used in the acryUc fiber industry. Water acts as a convenient heat-transfer and cooling medium and the polymer is easily recovered by filtration or centrifugation. Fiber producers that use aqueous solutions of thiocyanate or zinc chloride as the solvent for the polymer have an additional benefit. In such cases the reaction medium can be converted directiy to dope to save the costs of polymer recovery. Aqueous emulsions are less common. This type of process is used primarily for modacryUc compositions, such as Dynel. Even in such processes the emulsifier is used at very low levels, giving a polymerization medium with characteristics of both a suspension and a tme emulsion. 

The discovery of PTFE (1) in 1938 opened the commercial field of perfluoropolymers. Initial production of PTFE was directed toward the World War II effort, and commercial production was delayed by Du Pont until 1947. Commercial PTFE is manufactured by two different polymerization techniques that result in two different types of chemically identical polymer. Suspension polymerization produces a granular resin, and emulsion polymerization produces the coagulated dispersion that is often referred to as a fine powder or PTFE dispersion. 

Aqueous emulsion polymerization is carried out using a fluorinated emulsifier, a chain-transfer agent to control molecular weight, and dispersion stabilizers such as manganic acid salts and ammonium oxalate (13,14). 

There are two principal PVC resins for producing vinyl foams suspension resin and dispersion resin. The suspension resin is prepared by suspension polymerization with a relatively large particle size in the 30—250 p.m range and the dispersion resin is prepared by emulsion polymerization with a fine particle size in the 0.2—2 p.m range (245). The latter is used in the manufacture of vinyl plastisols which can be fused without the appHcation of pressure. In addition, plastisol blending resins, which are fine particle size suspension resins, can be used as a partial replacement for the dispersion resin in a plastisol system to reduce the resin costs. 

Inversion ofMon cjueous Polymers. Many polymers such as polyurethanes, polyesters, polypropylene, epoxy resins (qv), and siHcones that cannot be made via emulsion polymerization are converted into latices. Such polymers are dissolved in solvent and inverted via emulsification, foUowed by solvent stripping (80). SoHd polymers are milled with long-chain fatty acids and diluted in weak alkaH solutions until dispersion occurs (81). Such latices usually have lower polymer concentrations after the solvent has been removed. For commercial uses the latex soHds are increased by techniques such as creaming. 

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). 

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