Alkyd-based polyols

More often the solvent-based coatings are made of alkyds, acrylics, PU or EP polymers. Alkyd-based polyols and unsaturated dibasic acids were the first synthetic polymers used in coating technology. It was successful in chemically combining oil or oil derived fatty acids into a polymer structure, thus enhancing the mechanical properties, drying speed and durability over and above those of the oils themselves and the oleoresins then available [61]. 

Polyols. Several important polyhydric alcohols or polyols are made from formaldehyde. The principal ones include pentaerythritol, made from acetaldehyde and formaldehyde trimethylolpropane, made from -butyraldehyde and formaldehyde and neopentyl glycol, made from isobutyraldehyde and formaldehyde. These polyols find use in the alkyd resin (qv) and synthetic lubricants markets. Pentaerythritol [115-77-5] is also used to produce rosin/tall oil esters and explosives (pentaerythritol tetranitrate). Trimethylolpropane [77-99-6] is also used in urethane coatings, polyurethane foams, and multiftmctional monomers. Neopentyl glycol [126-30-7] finds use in plastics produced from unsaturated polyester resins and in coatings based on saturated polyesters. 

The presence of a multiplicity, of allyl groups in a polymer results in a thermosetting composition. Thus, the various drying oil alkyds, containing side chains derived from dehydrated castor oil and linseed oil, are cross-linked by polymerization of allylic double bonds. Allyl starch and allyl sucrose are extremely interesting materials prepared by treatment of the polyols with allyl chloride in the presence of base. Coatings prepai ed from these compounds are readily cross-linked by the application of heat. 

Uses Polyurethane polyol used in soh/.-based systems modifier for acrylic, polyester, and alkyd resins high-solids coatings, machinery and equip, coatings, appliance coatings, automotive topcoats, paper and wood coatings, aerospace coatings Features Lower VOC... 

Alkyd resins can be prepared from either monoglycerides or fatty acids. The former approach is based on the alcoholysis of the oil by part of a polyol, followed by the esterification of the remaining hydroxy functions using a polyacid. The latter approach is instead based on a one-step process consisting of the direct reaction among the fatty acid, the polyol and a polyacid [14]. 

A substantial number of studies on the characterization of vehicle paints, mainly alkyd and acrylic resins, have been reported. Alkyd resins, which are complex polyesters formed by co-polymerizing phthalic anhydride, polyols, and saturated and rm-saturated fatty acids, can usually be classified with MS techniques on the basis of hydrocarbon chain length and modification components such as melamine. Characterizations of acrylic resins are based on Cl MS analysis of monomers that are reasonably reproducible by pyrolysis techniques. 

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