Alkyd resin formation

Alkyd Resins. Polyesters bearing pendant ester groups react with such groups on adjacent chains, resulting in alkyd resin formation. These reactions are catalyzed by titanates. Acrylic polymers are cross-linked with glycols or to hydroxyl-containing alkyds (485,486) (see Alkyd resins). 

Kienle and Petke were among the first to study the effect on the ratio and properties of alkyd resin formation of acids other than phthalic acid or anhydride. In all cases where either aliphatic or aromatic acids were used the greatest time involved the first half of the reaction. The acid values near gelation were between the calculated values for the dimer and tetramer. The percent esterification attained at gelation was about the same for the different dibasic acids (approximately the same amount of water evolved). A summary of some other acids in comparison to phthalic anhydride is shown in Table V. 

The most common example of alkyd resin formation is from the polycondensation of glycerin, phthalic anhydride, and fatty acid. The reaction between trifimctional glycerin and difimctional anhydride could gel before the polycondensation was complete, but with the addition of a monocarboxylic fatty acid the formation of a somewhat linear polymer is possible. This polymer is soluble in aliphatic solvents if the eontent of fatty acid is sufficiently high. 

HOaQCHjlfiCOiH, CSH14O4. Important dicarboxylic acid obtained by oxidizing ricino-leic acid (from castor oil) also obtained by oxidation of cyclo-octene or cyclo-octadiene formerly obtained from cork. Used in the formation of alkyd resins and polyamides. Esters are used as plasticizers and heavy duty lubricants and oils. 

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). 

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

More usually, phthalic anhydride is reacted with a polyfunctional material such as glycerol to form a network polyester (a glyptal). This class of polymer, modified with monofunctional additives and known as alkyd resins, is very important in the paint and plastics industry. Consequently most of the theoretical studies have been concerned with the formation of infinite networks ( microgel ) and the distinction between this and the so-called gel-point [75]. 

The resulting silicone-alkyd copolymers are thus formulated into coatings that have the same general and physical properties as alkyd resins and that can be applied in the usual manner. Silicone-alkyd copolymers generally require no special primer types. While there are numerous silicone intermediates that can be and are employed in the formation of organic-silicone copolymers, a few are shown (19) in Figure 1. 

The formation of alkyd resins is a typical example of condensation polymerization. In 1847, Berzelius reported a resinous product formed by the reaction of tartaric acid and glycerol. In 1901, Watson Smith (England) prepared a brittle resinous polymer by... 

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