Oil and alkyd paints

The paints in this chapter all dry by the second mechanism discussed in Chapter 7 and, in particular, by the same form of that mechanism. This is known as oxidative drying and occurs when the film-former becomes cross-linked as a result of a chemical reaction with oxygen in the atmosphere. 

Before proceeding with the chemistry of the oxidative drying process, the reader would be well advised to turn back to p. 42 and reread the section on oils. He should know the general formula of an oil and, in particular, the arrangement of double bonds in conjugated and non-conjugated fatty acids. 

Such are the complexities of the action of oxygen on drying oils that the mechanisms have not been completely unravelled in over three decades of research. The outline that follows is therefore a likely explanation based on the evidence available, but not a completely proven one. 

Drying and further chemical change during the ageing of the film are markedly influenced by ultra-violet light. 

The drying mechanisms must be consistent with the facts. In particular different mechanisms are required for conjugated and non-conjugated oils. 

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Mineral spirits, a type of petroleum distillate popular for use in solvent-based house paints, consist mainly of aUphatic hydrocarbons with a trace of aromatics. This type of solvent finds use in oil- and alkyd-based house paints because of its good solvency with typical house paint binders and its relatively slow evaporation rate which imparts good bmshabiUty, open-time, and leveling. Other properties include lower odor, relatively lower cost, as well as safety and health hazard characteristics comparable to most other organic solvents. 

Titanates react with ester groups ki paint vehicles, eg, linseed oil, tuna oil, and alkyds, and with hydroxy groups, eg, ki caster oil and some alkyds, to prevent wrinkling of paint films (104,447). 

Zirconium tetrafluoride [7783-64-4] is used in some fluoride-based glasses. These glasses are the first chemically and mechanically stable bulk glasses to have continuous high transparency from the near uv to the mid-k (0.3—6 -lm) (117—118). Zirconium oxide and tetrachloride have use as catalysts (119), and zirconium sulfate is used in preparing a nickel catalyst for the hydrogenation of vegetable oil. Zirconium 2-ethyIhexanoate [22464-99-9] is used with cobalt driers to replace lead compounds as driers in oil-based and alkyd paints (see Driers and metallic soaps). 

There are limitations to the appHcabiHty of exterior latex house paints providing a small continuing market for oil or alkyd exterior house paints. Because film formation from latex paints occurs by coalescence, there is a temperature limit, below which the paint should not be appHed. This temperature can be varied by choice of the T of the latex polymer and the amount of coalesciag agent ia the formula. Ia the United States, most latex paints are formulated for appHcation at temperatures above 5—7°C. If painting must be done when the temperature is below 5—7°C, oil or alkyd paint is preferable. 

Latexes find wide use in industrial and consumer applications, particularly in the areas of synthetic rubber and coatings. Latex paints, for example, provide excellent alternatives to older, oil-based (alkyd) paints, which release substantial quantities of organic solvents to the atmosphere as they dry. Because volatile organic compounds (VOCs) are a factor in depleting the ozone layer, many industrial nations are striving to develop products... 

The cementitious substrates include concrete, masonry, sand-cement, and gypsum plasters. All these substrates retain moisture and are alkaline in nature. The surface alkalinity can result in a chemical attack or saponification of certain types of binders used in paints, notably oils and alkyds, resulting in a marked diminution in the paints resistance to washing, abrasion, and weathering. Alkyd paints are, therefore, not used on fresh concrete, masonry, and plaster surfaces. 

Paints, waterproof Paints oil and alkyd vehicle, and water thinned... 

Modified phenolic resins are condensation products of the resol type which contain other starting materials besides phenol and formaldehyde (e.g., acrylic monomers). The phenolic component itself is often modified (alkyl- or arylphenols). Modification with rosin is the most important one. The compatibility of phenolic resins with other binders can be substantially improved by modification. Rosin-modified phenolic resins may be combined with linseed oils and alkyd resins. Examples of use include putties, priming coats, rust protection paints, and colored topcoats. 

The binder may, for instanee be bitumen (eoal tar or asphalt), or linseed oil (natural materials), alkyd, ehlorinated rubber, epoxy, vinyl, polyurethane ete. (synthetie organie materials), or silieate (inorganie). Some paints are hardened by reaetion with oxygen in the air (oil and aUcyd paints), others by evaporation of the... 

Uses Maleic resin for general purpose oil- and alkyd-based paints Properiies Gardner 8 max. color m.p. 95-110 C acid no. 20-25 Worl inGM203 [Woriee-Chemie]... 

The usual thickeners and flow agents can be used. The usual driers and antioxidants are used in urethane oils and alkyds. Catalysts which speed up the curing reaction (and reduce pot-life) are tertiary amines and metal salts, particularly tin salts. The latter should be checked for toxicity before inclusion in paint. 

The polymer is amorphous and soluble. In this polymer, however, the side groups are rigid and they restrict considerably the bending and coiling of the polymer chains. Except at high molecular weights (unsuitable for paints), polystyrene is therefore weak and brittle, and styrene copolymers (sometimes styrene is copolymerized with drying oils and alkyds) are more suitable as paint resins. 

The main outlets for urethane oils and alkyds are in varnishes for floors, boats and general use, and in undercoats and in industrial maintenance finishes (where gloss retention is less important than long-lasting film integrity and resistance to water and chemicals). Urethane oils and alkyds may be blended with ordinary long oil alkyds in glossy decorative paints in order to increase their resistance properties as described above. 

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