Binder-emulsion preparation

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). 

Sulfur-asphalt binders can be prepared by various mechanical means. One conventional method is to combine liquid sulfur and asphalt at 285°-300°F in a Gifford Wood colloid mill. A rotor stator gap setting of 0.02 in. at 7000 rpm for 8 min will prepare satisfactory emulsions. This emulsion is immediately mixed with preheated aggregate. The laboratory binder was prepared by TTI (Texas Transportation Institute) scientists in cooperation with SNPA (Societe Nationale des Petroles d Aquitaine) scientists and is believed to be comparable with the binders prepared by the turbine in the field trials. The need for dispersing sulfur in the asphalt is discussed by Garrigues (9) and by Kennepohl et al., Deme, and McBee et al. elsewhere in this volume. 

Multilayered half cells (YSZ/NiO-YSZ/Ce02/steel) were prepared by water-based tape casting technology. For the anode, a ratio of 1 1 was used for NiO and YSZ and the half-cell was produced with pure and doped NiO. Vynil- and acrylic-base emulsions were used as binders to prepare the slurries for the steel and ceramic layer, respectively. 

Acrylates are primarily used to prepare emulsion and solution polymers. The emulsion polymerization process provides high yields of polymers in a form suitable for a variety of appHcations. Acrylate polymer emulsions were first used as coatings for leather in the eady 1930s and have found wide utiHty as coatings, finishes, and binders for leather, textiles, and paper. Acrylate emulsions are used in the preparation of both interior and exterior paints, door poHshes, and adhesives. Solution polymers of acrylates, frequentiy with minor concentrations of other monomers, are employed in the preparation of industrial coatings. Polymers of acryHc acid can be used as superabsorbents in disposable diapers, as well as in formulation of superior, reduced-phosphate-level detergents. 

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. 

Larch arabinogalactan is approved in 21 CFR 172.610 as a food additive for use as an emulsifier, stabilizer, binder or bodying agent for essential oils and noimutritive sweeteners, flavor bases, nonstandardized dressings, and pudding mixes. It has also been used in the preparation of cosmetic and pharmaceutical dispersions and as an emulsifier in oil—water emulsions (69). Industrially, the main use has been in Hthography as a gum arabic substitute. 

Vinylidene Chloride Copolymer Latex. Vinyhdene chloride polymers are often made in emulsion, but usuaUy are isolated, dried, and used as conventional resins. Stable latices have been prepared and can be used direcdy for coatings (171—176). The principal apphcations for these materials are as barrier coatings on paper products and, more recently, on plastic films. The heat-seal characteristics of VDC copolymer coatings are equaUy valuable in many apphcations. They are also used as binders for paints and nonwoven fabrics (177). The use of special VDC copolymer latices for barrier laminating adhesives is growing, and the use of vinyhdene chloride copolymers in flame-resistant carpet backing is weU known (178—181). VDC latices can also be used to coat poly(ethylene terephthalate) (PET) bottles to retain carbon dioxide (182). 

A modified latex composition contains a phosphorus surface group. Such a latex is formed by emulsion polymerization of unsaturated synthetic monomers in the presence of a phosponate or a phosphate which is intimately bound to the surface of the latex. Thus, a modified latex containing 46% solids was prepared by emulsion polymerization of butadiene, styrene, acrylic acid-styrene seed latex, and a phosphonate comonomer in H20 in the presence of phosphated alkylphenol ethoxylate at 90°C. The modified latex is useful as a coating for substrates and as a binder in aqueous systems containing inorganic fillers employed in paper coatings, carpet backings, and wallboards [119]. 

It was apparent that the dense adsorption layer of HPC which was formed on the silica particles at the LCST plays a part in the preparation of new composite polymer latices, i.e. polystyrene latices with silica particles in the core. Figures 10 and 11 show the electron micrographs of the final silica-polystyrene composite which resulted from seeded emulsion polymerization using as seed bare silica particles, and HPC-coated silica particles,respectively. As may be seen from Fig.10, when the bare particles of silica were used in the seeded emulsion polymerization, there was no tendency for encapsulation of silica particles, and indeed new polymer particles were formed in the aqueous phase. On the other hand, encapsulation of the seed particles proceeded preferentially when the HPC-coated silica particles were used as the seed and fairly monodisperse composite latices including silica particles were generated. This indicated that the dense adsorption layer of HPC formed at the LCST plays a role as a binder between the silica surface and the styrene molecules. 

Another report came from Canada in 1959 when Bender published research results of utilizing eastern Canadian barks as furnish for wet-process insulation board and hardboard (33). Bark species included in the study were black spruce and balsam fir each contained 25-35% wood. A Sprout-Waldron disk refiner was used to prepare the bark fiber, and boards were made with lh% wax emulsion but contained no added binder. Physical tests indicated the boards met some commercial specifications the author believed that addition of more woody fiber would improve the properties. In addition, a few experimental dry-process particleboards were made with addition of some unnamed binder that was a byproduct material. 

Although polyester film, introduced by Du Pont under the trade name Mylar in the 1960s, has been added to the traditional supports like paper and cellulose acetate, the principle of photographic film preparation has remained unchanged since daguerreotype was developed. The sensitive surface always contains a silver halide crystal emulsion with a gelatin binder. Despite all the efforts to replace them, silver salts remain the basis of these emulsions, and film manufacturers still require gelatin, which they consume at the rate of 20,000 tons a year. The suppliers are few, and they are carefully selected. The world leader in this area is Rousselot, now a subsidiary of Sanofi Elf Aquitaine, with four units in Europe and one in the United States. 

In this special volume on polymer particles, recent trends and developments in the synthesis of nano- to micron-sized polymer particles by radical polymerization of vinyl monomers in environmentally friendly heterogeneous aqueous and supercritical carbon dioxide fluid media are reviewed by prominent worldwide researchers. Polymer particles are prepared extensively as synthetic emulsions and latexes, which are applied as binders in the industrial fields of paint, paper and inks, and films such as adhesives and coating materials. Considerable attention has recently been directed towards aqueous dispersed systems due to the increased awareness of environmental issues. Moreover, such polymer particles have already been applied to more advanced fields such as bio-, information, and electronic technologies. In addition to the obvious commercial importance of these techniques, it is of fundamental scientific interest to completely elucidate the mechanistic details of macromolecule synthesis in the microreactors that the polymer particles in these heterogeneous systems constitute. 

The paint samples were prepared from a high-grade silicone resin emulsion paint [48] with a binder ratio of 10 wt% styrene acrylate to 10 wt% silicone resin emulsion (both 50% solids). The coatings were applied to a mineral substrate and dried at room temperature. Part of each sample was etched for a few minutes in 10% nitric acid so that the organic polymer could be visualized better. 

After the paper making process is complete, latexes that are useful as binders for the application of clays or CaCC>3 to paper for printing paper may be prepared using the dimer of AMS. In a typical formulation, styrene, butadiene, Me methacrylate, and acrylonitrile were emulsion polymerized in the presence of AMS dimer to obtain a copolymer latex.473 Surprisingly, the AMS dimer was used in combination with tert-dodecylmercaptan, so there may have been some residual odor. Unsaturated carboxylic acids, such as acrylic acid, or sulfonic acids, such as 2-ethylsulfonyl acrylate, or unsaturated amides, such as acrylamide, are also useful, providing the polarity necessary in these applications.474... 

Use Pharmacy (emulsions), adhesives, leather dressing, textile printing and sizing, thickener and emulsifier, dyes, food products (ice cream, desserts), toothpastes, coating soap chips and powders, hair-wave preparations, confectionery, printing inks, tablet binder. 

It has been proved that incorporation of carboxylic acid groups in the polymeric chain has a significant effect on colloidal properties of latex, processability, and end-use property. Carboxylated styrene-butadiene latexes (XSBR) are prepared via batch emulsion copolymerization with different amounts of acrylic acid in the absence of emulsifier. They are among the most important polymeric colloids, and can be used as binder in paper coatings, carpet backing, paints, and nonwoven. There are several studies on the preparation and properties of XSBR latexes. 

---