Urethane alkyd coatings

The resulting unsaturated diols (practically monoglycerides of fatty acids, reaction 17.12) react with diisocyanates (for example with toluene diisocyanate) at around 80-90 °C, usually in a solvent such as toluene, xylene or naphtha. Unsaturated PU are obtained, which are crosslinked by a radical mechanism with the transformation of the multiple double bond in a crosslinked network (Figure 17.9). This reaction is used for the fabrication of urethane alkyd coatings. Other polyols may be used instead of glycerol ethylene glycol, neopentylglycol, trimethylolpropane, pentaerythritol and others. 

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... 

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. 

One-Package Urethane Alkyd (Oil-Modified Urethanes) Coatings (ASTM Type 1)... 

Urethane-modified alkyds are similar to simple alkyds except that dibasic acid is replaced with a difunctional isocyanate such as toluene diisocyanate or hexamethylene diisocyanate. The process is also similar to simple alkyds. Coatings made with urethane-modified alkyds dry faster and harder than alkyds, yet retain flexibility. These systems have better water-, chemical- and abrasion-resistance than alkyd resins, and cost is also relatively low (Wicks et al., 1998). These are used in clear finishes for wood floors, cabinets, OEM, maintenance, and architectural coatings. The aliphatic-based systems are excellent for exterior use, or where UV exposure is possible, while aromatic-based systems usually have better abrasion-resistance. Chemo-enzymatic synthesis of urethane-based systems produces better control of stereochemistry and can impart unique properties (Athawale Bhabhe, 1998 Athawale Gaonkar, 1999 Athawale Joshi, 2000, 2004 Bhabhe Athawale, 1998). 

The service life of the coating systems is significantly affected by service conditions. For example, a two-coat alkyd primer with the topcoat exposed to a rural or residential area would last only 3 years. The triple system of moist-cured urethane zinc-rich coat, a high-build acrylic urethane coat, and an acrylic urethane top coat will last 15 years. 

Uses Detoamer, air release agent tor water-based industrial coatings, high-solids coatings, acrylic urethanes, alkyds, epoxies, printing inks, wood lacquers, adhesives, latex detoamer in food-contact paper/pa-perboard food pkg. adhesives... 

Uses Filler, colorant for corrugated inks and envelope inks, polyboard and film inks, acrylic, urethane, primer, and alkyd coatings, paper plics. Properties BIk. resin dens. 10-10.5 Ib/gal pH 8.6-9.4 nonionic 47.5-50% total solids 39.5-41% carbon Jetblack945G [MD-Both Ind.]... 

Chem. Descrip. Manganese-based drier complex Uses Drier for urethane alkyd lacquers such as floor coatings, water-based coatings such as amine-neutralized resins, water-emulsifiable alkyds, and alkyd-actylics Features Cobalt-free... 

Uses Carrier in inks hard resin additive in overprint varnishes reactive polyol in melamine- and urethane-cured coatings for wood and metal intermediate for polyester and alkyd coatings cure accelerator, hardener, gloss aid, chem. resist, aid in coatings Properties Wh. pastilles sol. ( 25% solids) in Arcosolv soivs., butanol, NMP insol. in water, propylene glycol, and ethylene glycol m.w. 2500 (wt. avg.) bulk dens. 5.556 Ib/gal acid no. < 0.1 hyd. no. 255 VOC 0.10%... 

Uses Intermediate in prod, of solvents, urethanes, unsat. poly ters, gel coats, sat. polyester and alkyd coatings, polymeric plasticizers solvent, compatibilizer for adjuvants, fabric softener carriers, nonionic surfactants, pigment dispersions solubilizer, emulsifier in air freshener applies. solvent, solubilizer, compatibilizer, emulsifier, stabilizer, hu-mectant, neutralizer, emollient in personal care food-contact coatings Features Nonvolatile ManufJDistrib. Aldrich Fluka Lyondell Trade Names MPDiol Glycol... 

Polyurethane coatings are based on the reaction of a monoglyceride with a polyol and a diisocyanate to form a urethane oil or urethane alkyd. All the isocyanates react, leaving no toxic groups. These resins are alkali and water resistant and superior to ordinary alkyds as a weather-resistant coating and corrosiOTi-inhibiting surface coating. 

Urethane alkyds Epoxy resins are also chemically combined with drying oils as part of the molecule that further reacts with isocyanates to produce urethane alkyds. Upon application as a liquid coating, the resin-oil combination converts by oxidation to a solid. 

One-package urethane alkyd (oil-modified urethanes) coatings (ASTM type 1), alternatively called uralkyds. Here, curing takes place by oxidation of the double bonds present in the fatty acid portion of the coating system. 

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. 

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