Alkyd resins fatty acid

Organotin compounds such as monobutyltin oxide, the main substance used, accounting for 70% of consumption, dibutyltin oxide, monooctyltin oxide, and dioctyltin oxide are used in certain esterification and transesterification reactions, at concentrations between 0.001% and 0.5% by weight. They are used in the production of substances such as phthalates, polyesters, alkyd resins, fatty acid esters, and adipates and in trans-esterifications. These substances are in turn used as plasticizers, synthetic lubricants, and coatings. Organo-tins are used as catalysts to reduce the formation of unwanted by-products and also provide the required colour properties (ETICA, 2002). 

Derivatives of commercial importance are ->fatty acid esters, - alkyd resins, - fatty acid amides, - fatty acid nitriles, ->fatty amines, fatty alcohols and - soaps. 

Epoxy resin esters are formed from reacting an epoxy resin with fatty acids from drying oils in the same type of equipment used to make alkyds. The fatty acids react with both the epoxide and hydroxyl groups of the epoxy resin to form the epoxy ester, as in Figure 17. 

Tall oil is not really an oil, but it is often used as an oil or combined with an oil and a resin. Tall oil is a combination of fatty acids and rosin. Normally, it is separated into its different ingredients for use. As a component in alkyds, the fatty acids produce vehicles similar to those made with soybean fatty acids. When limed, tall oil yields a low-cost, high-gloss liquid with poor flexibility that tends to yellow very badly on aging. 

Technical uses of r. range from - metal-working fluids to - lubricants (biodegradable chain saw oil) and - factice. The oil and fatty acids are used in alkyd resins. The acid is a starting material for ->dimerization. 

Alkyd resins are produced by reaction of a polybasic acid, such as phthaUc or maleic anhydride, with a polyhydric alcohol, such as glycerol, pentaerythritol, or glycol, in the presence of an oil or fatty acid. The resulting polymeric material can be further modified with other polymers and chemicals such as acryhcs, siUcones, and natural oils. On account of the broad selection of various polybasic acids, polyhydric alcohols, oils and fatty acids, and other modifying ingredients, many different types of alkyd resins can be produced that have a wide range of coating properties (see Alkyd resins). 

The manufacture of alkyd resins (qv), which are obtained by the reactions of polybasic acids or anhydrides, polyhydric alcohols, and fatty oils and acids, consumes about 17% of the phthahc anhydride demand. While materials such as maleic anhydride, isophthahc acid, and fumaric acid can also be used, phthahc anhydride is the most important. The resin provides a binder for coatings that are apphed for either protection or decoration. Ak quahty concerns have put alkyd resins under pressure from water-based coatings which do not emit organic vapors upon drying. 

Alkyd resins are usually referred to by a brief description based on certain classification schemes. Erom the classification the general properties of the resin become immediately apparent. Classification is based on the nature of the fatty acid and oil length. 

Table 4. Fatty Acid Compositions, Wt %, of Fats and Oils Commonly Used in Alkyd Resins...

Alkyds. Alkyd resins (qv) are polyesters formed by the reaction of polybasic acids, unsaturated fatty acids, and polyhydric alcohols (see Alcohols, POLYHYDRic). Modified alkyds are made when epoxy, sUicone, urethane, or vinyl resins take part in this reaction. The resins cross-link by reaction with oxygen in the air, and carboxylate salts of cobalt, chromium, manganese, zinc, or zirconium are included in the formulation to catalyze drying. 

Thermoplastic polyamides are used in coatings to modify alkyd resins (qv) in thixotropic systems (238) and to plasticize nitroceUulose lacquers (239). DETA-taH oil fatty acid-based polyamides are suggested for use as corrosion inhibitors in alkyd paints (240). Printing inks for fiexo-gravure appHcation on certain paper, film and foil webs rely on EDA- and PDA-based polyamides for their specific performance (241). 

These resins are produeed by reacting a polyhydric alcohol, usually glycerol, with a polybasic acid, usually phthalic acid and the fatty acids of various oils such as linseed oil, soya bean oil and tung oil. These oils are triglycerides of the type shown in Figure 25.30. R], R2 and R3 usually contain unsaturated groupings. The alkyd resins would thus have structural units, such as is shown in Figure 25.31. 

Individual alkyds are usually described in terms of the proportion and type of fatty acid and of the alcohol that they contain. Thus a 70% linseed-oil pentaerythritol aikyd would be expected to comprise linseed oil fatty acids, pentaerythritol and phthalic anhydride, with an equivalent of 70% linseed oil calculated on the weight of the non-volatile resin. 

Epoxide resins can be esterified with fatty acids to give media ranging from air-drying to stoving types. The presence of fatty acid reduces the chemical resistance to the same order as that of the alkyds. It is nevertheless sometimes found advantageous to use an epoxy ester for certain specialised purposes. 

The typical alkyd resin (see above) is eomprised of three basic components an aromatic diacid such as phthalic anhydride which together with a polyol such as glycerol, forms the backbone of the resin molecule and along which are distributed the fatty acids derived from vegetable oils. The solubility, film hardness and colour of alkyd resins depend on the nature of the modifying fatty acid which in most cases contributes some colour to the film. 

The esterification reaction is also used to prepare epoxy esters from epoxy resins having an n value of 4 and vegetable oil fatty acids. They may be used in the same way as alkyds where better chemical resistance and adhesion are required. Unlike the alkyds, the epoxy esters contain virtually no acid groups. 

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