Waterborne paints production

Emulsions are dispersions of one fluid into another. Both oil-in-water and water-in-oil emulsions are encountered. Foams are similar to emulsions, but the dispersed phase is a gas. Emulsions are everywhere some examples of products that are based on emulsions are salad dressings, mayonnaise, egg yolk, milk, margarine, cream, ice cream, waterborne paints and bitumen. Emulsions are generally not stable, so they need to be stabilized against coalescence. One can use surfactants for that, or polymers, such as proteins and polysaccharides, or particles. 

Most household maintenance products contain mixtures of lipophiles and hydrophiles that can produce unanticipated toxic effects. Irritant-induced asthma is an example of such an effect. Solvent-based and waterborne paints contain solvents that are nonsensitizing irritants that are individually not known to induce asthma. Despite this, exposures to both types of paints have been shown to cause the asthma-like condition reactive airways dysfunction syndrome (RADS).I13 14 RADS is discussed in detail in Chapterl8. 

Neutralizing agents are used in waterborne paints to neutralize binders and stabilize the product. Ammonia and various alkylated aminoalcohols are used, depending on the type of binder and method of application. On hardening, the amines mainly evaporate along with the water. 

Corrosion inhibitors are used to prevent the formation of corrosion products when waterborne paints are applied to metallic substrates (flash rust). They include oxidiz-... 

Thus, numerous low-emission paints have been developed, including high-solids paints, waterborne paints, aqueous dispersions for industrial use, powder coatings, and radiation-curing coatings. At the forefront in adopting these environmentally friendly products is heavy industry, in particular the automobile and household appliance industries. Medium-sized and smaller businesses will profit from this experience, adapting it for their own needs. 

Corrosion-resistant and wear-resistant materials (e.g., stainless steel and in special cases suitable plastics) have to be used for the equipment required to produce and apply waterborne paints. This applies to production vessels, storage and transportation vessels, to the feed system used for application (e.g., closed circuit tanks, pipelines, and pumps) all of which must be able to withstand chemical mechanical stress. The use of corrosion-resistant materials for the spraying equipment is also advantageous. 

For waterborne paint systems (especially emulsions used for decorative purposes) defoamers based on mineral oils are often used. In addition to the mineral oil as carrier, these products contain finely dispersed hydrophobic particles (e.g., silica, metal stearates, polyureas) as defoaming components. A small amount of silicone is sometimes included to intensify the defoaming action. For high-quality waterborne coatings in industrial applications, defoamers are used that contain hydrophobic silicone oils as the principal defoaming component instead of mineral oils. They have a better defoaming effect, but are more expensive. In most cases silicone defoamers do not cause the gloss reduction that is often observed with mineral oil products. 

The stirrers are mainly of the flat-blade, disk, propeller, or turbine type [7.16]-[7.19]. Rotor-stator systems are also used as continuous mixers (Fig. 7.5). These machines are employed particularly if an emulsion or an emulsion-like product has to be produced (e.g., waterborne paints) [7.20]-[7.22]. 

Dip coating is one of the simplest and oldest coating methods. In addition to dipping in solvent- or waterborne paints, electrodeposition has become important for large-scale series production (Table 8.5). 

Uses Defoamer for architectural and waterborne general coatings grind defoamer during production and applic. of waterborne paints Features Effective against microfoam DM-3880-C [Hi-Mar Spec. fhornley]... 

Recommended for products waterborne paints architectural / decorative, automotive, plastic, wood ... 

The procedures specified by the US EPA for testing paint products for compliance with VOC limits are described in Federal Reference Method 24, which employs several ASTM test standards. VOC values for waterborne or solventborne coatings are calculated by the following formula ... 

Emulsion polymerization has become an important process for the production of a large number of industrial polymers in the form of polymer colloids or latexes. They are the base of adhesives, paints and especially of waterborne coatings. An interest has been developed in recent years in emulsion polymerization systems in which the classical low molecular weight surfactaints are replaced by polymeric surfactants, either hydrophilic-hydrophobic block and graft copolymers (1-4) or functionalized oligomers (5). 

Polyester resins possess premium performance properties such as exterior durability, gloss, flexibility hardness, color stability, and versatility of cure. Polyesters are used in product finishes for household appliances, food and beverage containers, aircraft and equipment, automotive primers and bake coats, metal furniture, and fixtures. For example, water-soluble saturated polyesters are used in industrial baking paints, and in combination with melamine resin. Polyesters can be formulated in high solids and waterborne formulations to meet the requirements for the low VOC coatings being mandated by the EPA. 

Figovsky, O., Karchevsky, V., and Beilin, D. High-Performance Waterborne Protective Coatings Based on Curable Water Dispersion of Chlorine-Sulphonated Polyethylene, Proceedings of the International Paint Auxiliary Products Industry Congress Exhibition BOYA/PAINT 2008, Istanbul, Turkey, 2008,115-125. 

Car paints are cured with heat in special oven lines. Electrodeposition coatings (used as anticorrosive primers) contain only small amounts of volatile organic compounds (VOC), whereas intermediate and topcoats release considerable amounts of VOCs. Intermediate coats based on waterborne resins have been developed to decrease VOC emission and are already being used in some automotive plants. Basecoats, as part of base-clear topcoat systems, contain very high amounts of volatile organic solvents. Waterborne basecoats were developed more recently to lower this source of solvent emission. Some car manufacturers are operating pilot lines with the aim of introducing waterborne basecoats into their production processes. Many car producers in the United States and Europe have already switched their topcoat lines over to waterborne basecoats [11.3]. 

In other industrial application sectors there is an increasing tendency to employ low-solvent paints. In furniture production, for example, waterborne, UV-curing paints are superceding high-solvent nitrocellulose lacquers. 

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