Paint latex

Latex paints (330) are commonly used in painting houses and buildings in exterior and interior applications as architectural decorations. Latex paints consist of three major components binders, pigments, and water. 

Water is present as a consequence of the emulsion polymerisation process used in preparing the latex, and provides liquidity and spreadability so that it may be distributed evenly. Water-based paints are much less harmful to the environment than solvent-based paints, and this is what drives the trend towards the use of water-based paints. The performance of oil-based paints is generally better because the solvent acts as a plasticiser (197), and aids in the film formahon process. The performance of the water-based paints can approach that of the solvent-based paints through careful formulation of the latex. Paints are usually formulated to contain 60 to 70 volume percent water. 

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Miscellaneous, New, and Developmental Antimicrobial Agents. Table 11 shows some of the antimicrobials that do not neady fit into the principal families. Acrolein (qv) is a unique chemical used for secondary oil recovery (43). Biobor has become the antimicrobial addition of choice for aviation fuels (44). Cbloropbtbalonil (tetrachloroisophthalnitrile [1897-45-6]) is a significant agricultural fungicide, in addition to being one of the most important latex paint film preservatives (producer, ISK). 

Vinyl acetate is another monomer used in latex manufacture for architectural coatings. When copolymerized with butyl acrylate, it provides a good balance of cost and performance. The interior flat latex paint market in North America is almost completely dominated by vinyl acetate—acryHc copolymers. Vinyl acetate copolymers are typicaHy more hydrophilic than aH-acryHc polymers and do not have the same ultraviolet light resistance as acryHcs as a result. 

Styrene—acrylic copolymers provide latices with good water resistance and gloss potential in both interior and exterior latex paints. However, they are typically regarded as having limited exterior durabiUty compared to all-acryhc latex emulsions that are designed for exterior use. 

For the most part, additives control the appHcation or theological properties of a paint. These additives include materials for latex paints such as hydroxyethylceUulose, hydrophobicaHy modified alkah-soluble emulsions, and hydrophobicaHy modified ethylene oxide urethanes. Solvent-based alkyd paints typically use castor oil derivatives and attapulgite and bentonite clays. The volume soHds of a paint is an equally important physical property affecting the apphcation and theological properties. Without adequate volume soHds, the desired appHcation and theological properties may be impossible to achieve, no matter how much or many additives are incorporated into the paint. 

The rate of stripping or the stripabiUty on cataly2ed urethane and epoxy resin finishes can be increased by adding formic acid, acetic acid, and phenol. Sodium hydroxide, potassium hydroxide, and trisodium phosphate [10101-89-0] may be added to the formula to increase the stripabiUty on enamel and latex paints. Other activators include oleic acid [112-80-17, trichloroacetic acid [76-85-9], ammonia, triethanolamine [102-71-6], and monoethyl amine. Methylene chloride-type removers are unique in their abiUty to accept cosolvents and activators that allow the solution to be neutral, alkaline, or acidic. This abihty gready expands the number of coatings that can be removed with methylene chloride removers. 

The product of an emulsion polymerization is a latex ie, polymer particles on the order of 0.5—0.15 p.m stabilized by the soap. These form the basis for the popular latex paints. SoHd mbber is recovered by coagulating the latex with ionic salts and acids (see Latex technology). 

Thixotropy and Other Time Effects. In addition to the nonideal behavior described, many fluids exhibit time-dependent effects. Some fluids increase in viscosity (rheopexy) or decrease in viscosity (thixotropy) with time when sheared at a constant shear rate. These effects can occur in fluids with or without yield values. Rheopexy is a rare phenomenon, but thixotropic fluids are common. Examples of thixotropic materials are starch pastes, gelatin, mayoimaise, drilling muds, and latex paints. The thixotropic effect is shown in Figure 5, where the curves are for a specimen exposed first to increasing and then to decreasing shear rates. Because of the decrease in viscosity with time as weU as shear rate, the up-and-down flow curves do not superimpose. Instead, they form a hysteresis loop, often called a thixotropic loop. Because flow curves for thixotropic or rheopectic Hquids depend on the shear history of the sample, different curves for the same material can be obtained, depending on the experimental procedure. 

Styrene—Butadiene Latex. SB latex is used in coatings, carpet backing, paper adhesives, cement additives, and latex paint. 

Butadiene copolymers are mainly prepared to yield mbbers (see Styrene-butadiene rubber). Many commercially significant latex paints are based on styrene—butadiene copolymers (see Coatings Paint). In latex paint the weight ratio S B is usually 60 40 with high conversion. Most of the block copolymers prepared by anionic catalysts, eg, butyUithium, are also elastomers. However, some of these block copolymers are thermoplastic mbbers, which behave like cross-linked mbbers at room temperature but show regular thermoplastic flow at elevated temperatures (45,46). Diblock (styrene—butadiene (SB)) and triblock (styrene—butadiene—styrene (SBS)) copolymers are commercially available. Typically, they are blended with PS to achieve a desirable property, eg, improved clarity/flexibiHty (see Polymerblends) (46). These block copolymers represent a class of new and interesting polymeric materials (47,48). Of particular interest are their morphologies (49—52), solution properties (53,54), and mechanical behavior (55,56). 

Poly(vinyl acetate) latex paints are the first choice for interior use (149). Their abihty to protect and decorate is reinforced by several advantages belonging exclusively to latex paints they do not contain solvents so that physiological harm and fire ha2ards are eliminated they are odorless they are easy to apply with spray gun, roUer-coater, or bmsh and they dry rapidly. The paint can be thinned with water, and bmshes or coaters can be cleaned with soap and tepid water. The paint is usually dry in 20 minutes to two hours, and two coats may be applied the same day. 

Barium metaborate is used as an additive to impart fire-retardant and mil dew-resistant properties to latex paints, plastics, textiles, and paper products (6). Barium metaborate is marketed by Buckman Labs, Inc., Memphis, Tennessee (12). 

The largest volume commercial derivatives of 1-butanol are -butyl acrylate [141-32-2] and methacrylate [97-88-1] (10). These are used principally ia emulsion polymers for latex paints, ia textile appHcations and ia impact modifiers for rigid poly(vinyl chloride). The consumption of / -butanol ia the United States for acrylate and methacrylate esters is expected to rise to 182,000—186,000 t by 1993 (10). 

So-called pure acryUc latexes are employed for maximum durabiUty as required, for example, in high performance exterior latex paints. On the other hand, interior flat wall latex paints do not need the high resistance to exterior exposure and hydrolysis. The most widely used latexes for this appHcation are vinyl acetate copolymer latexes such as vinyl acetate/butyl acrylate (2-propenoic acid butyl ester) [141-32-2] copolymers having just sufficient... 

Viscosity of Systems with Dispersed Phases. A large proportion of coatings are pigmented and, therefore, have dispersed phases. In latex paints, both the pigments and the principal polymer are in dispersed phases. The viscosity of a coating having dispersed phases is a function of the volume concentration of the dispersed phase and can be expressed mathematically by the Mooney equation (96), a convenient form of which is... 

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