Urethane alkyd resins

Urethanes (alkyd resin plus diisocyanate) bind sand to form a temporary mold in many foundry operations. 

The mechanism of curing urethane alkyd resins is based on the oxidation with molecular oxygen of the allylic position (reaction 17.13). 

Figure 17.9 Radical crosslinking of urethane alkyd resins...

Urethane acrylates Urethane adhesives Urethane alkyds Urethane-based resins... 

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. 

Uses. Neopentyl glycol is used extensively as a chemical intermediate in the manufacture of polyester resins (see Alkyd resins), polyurethane polyols (see Urethane polymers), synthetic lubricants, polymeric plasticizers (qv), and other polymers. It imparts a combination of desirable properties to properly formulated esterification products, including low color, good weathering and chemical resistance, and improved thermal and hydrolytic stabiUty. 

Trimethylolpropane (TMP), the reduced crossed aldol condensation product of //-butyraldehyde and formaldehyde, competes in many of the same markets as glycerol (qv) and pentaerythritol. The largest market for TMP is as a precursor in unsaturated polyester resins, short-oil alkyds, and urethanes for surface coatings (see 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. 

Urethane alkyds and urethane oils are oil and alkyd resin-modified polyurethanes dissolved in a volatile solvent. Upon application and solvent evaporation, the coating is crosslinked and cured via oxidation by atmospheric oxygen. 

Unsaturated polyester resins (UPRs) Uralkyd resins, 202 Urea-methylol reaction, 410 Urethane alkyds, 241 Urethane coatings, 202 Urethane elastomers, implanted, 207 Urethane foams, tests for, 244 Urethane gels, 205 Urethane-grade ATPEs, 223 Urethane-grade polyol types, 212 Urethane-grade raw materials, 246 Urethane hydrogel, preparation of, 250-251... 

Chemoenzymatic synthesis of alkyds (oil-based polyester resins) was demonstrated. PPL-catalyzed transesterification of triglycerides with an excess of 1,4-cyclohexanedimethanol mainly produced 2-monoglycerides, followed by thermal polymerization with phthalic anhydride to give the alkyd resins with molecular weight of several thousands. The reaction of the enzymatically obtained alcoholysis product with toluene diisocyanate produced the alkyd-urethane. 

Glycerol is used for drugs, personal care (including toothpaste), skin, and hair care products (42%), food and beverages (18%), tobacco (13%), polyether polyols for urethanes (11%), and alkyd resins (6%). 

Although blending with other coating resins provides a variety of ways to improve the performance of alkyds, or of the other resins, chemically combining the desired modifier into the alkyd structure eliminates compatibility problems and gives a more uniform product. Several such chemical modifications of the alkyd resins have gained commercial importance. They include vinylated alkyds, silicone alkyds, urethane alkyds, phenolic alkyds, and polyamide alkyds. 

Inhibitive Primers. The traditional primers are red lead and linseed oil, alkyd resins and zinc potassium chromate, proprietary epoxy, alkyd, urethane and latex systems with modified phosphate, borate and molybdate pigments. Chromate-based pigments, although in use in aircraft coatings, automotive primers and coil coating primers, are subject to environmental concern on the toxicity of hexavalent chromium which is likely to result in their replacement by innocuous products. 

A varnish is a solvent-thinned combination of a drying oil and a hard resin. Also, a varnish is the clear film obtained using a varnish as a coating vehicle. By extension, vehicles used for clear films are called varnishes although the vehicle may be a true varnish, an alkyd resin solution, a urethane-modified oil, or even a lacquer. 

Other uses for alkyds are in general industrial coatings such as machinery and metal furniture. Alkyd resin-chlorinated rubber based coatings are used in traffic paints, but use is declining because of VOC concerns. Some alkyds are still used in refinish paints for automobiles. Uralkyds are used as a vehicle for urethane varnishes for the do-it-yourself market. 

Use Alkyd resins, rosin esters, urethane coatings and foams, surfactants, lubricating oil additives. 

Use Organic synthesis, lacquers, product of hydrotropic salts, alkyd resins, polyamides, polyester adhesives, low-temperature plasticizers, urethane elastomers. 

Use Conditioning agent, manufacture of varnishes, alkyd resins, synthetic drying oils, urethane foams and coatings, silicone lubricant oils, lactone plasticizers, textile finishes, surfactants, epoxidation products. 

Hercules PE. [Hercules] Pentaeryth-ritols used in prod, of alkyd resins, rosin esters, oil-modified urethane resins, drying oils, synthetic lubricants, plasticizers, intumescent paints, plastics, stabilizers for plastics, explosives. 

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