Urethane coating components solvents

In more recent years one- and two-component urethane coatings based on polyethers have made a significant penetration of the urethane coatings market. Due to low cost and wide latitude in physical properties ranging from very flexible to hard, tough and solvent-... 

The acetates of most alcohols are also commercially available and have diverse uses. Because of their high solvent power, ethyl, isopropyl, butyl, isobutyl, amyl, and isoamyl acetates are used in ceUulose nitrate and other lacquer-type coatings (see Cellulose, esters). Butyl and hexyl acetates are exceUent solvents for polyurethane coating systems (see Coatings Urethane polymers). Ethyl, isobutyl, amyl, and isoamyl acetates are frequentiy used as components in flavoring (see Flavors and spices), and isopropyl, benzyl, octyl, geranyl, linalyl, and methyl acetates are important additives in perfumes (qv). 

Asphalt has been used as a major component in many coating formulations. These include epoxy-asphalts (much used in refineries) and urethane-asphalts. Of these the urethane-asphalts, some of which are true copolymers, are the most satisfactory substitutes for hot asphalt. They can be used at exposures higher in temperature than can hot asphalt due to their freedom from cold flow, and are reasonably good barriers. Like the asphalt emulsions and solvent putties, however, they can be penetrated, though at a much slower rate, by small molecule acids. Fluid (cold) applied membranes are discussed elsewhere in this volume. 

Chem. Descrip. Acrylic polymer in naptha, toluene Uses Leveling agent, anticratering agent for solvent-based systems, thermoset high-solids coatings, two-component urethanes, food-contact coatings... 

Uses Defoamer mold release applies. intennediate for esters useful as lubricants, defoamers in rubber, phannaceuticals components for urethane resins boiler water additive for food contact defoamer for beet sugar and yeast processing emollient, solvent in cosmetics, phannaceuticals lubricant base for textiles, paper, metalworking food-pkg. adhesives in paper/paperboard in contact with aqTfatty foods plasticizer in food-contact polymers defoamer in food-contact coatings and paper/paperboard... 

These products can be broadly defined as coatings that contain the urethane or urea groups. To a lesser extent, groups such as allophanate or biuret can be present. They are available one or two component systems, able to cure at room or higher temperature. These coatings can be based on linear PU dispersions, or crosslinkable dispersions and they can also be produced by solvent free processes. 

The main rule to follow in 2 component isocyanate systems is to avoid solvents which contain active hydrogen. For instance, alcohols can react with the isocyanate reducing the crosslink density. In severe cases, this can lead to a decrease in resistance and adhesion characteristics resulting in unacceptable coatings. The water content of solvents has to be closely controlled, again to avoid reaction with the isocyanate component. Where applicable, urethane grade solvents should be used, as these are designed to remove contaminants, such as water and alcohols, which could prematurely react with the isocyanate prior to application. 

Urethanes Urethane adhesion promoters are used widely to bond PVC to polyester, nylon, and other fabrics, including sized glass fiber. In multicoat operations, the additive is used only in the first coat. With, polyester fabric, the isocyanate component in urethane formation can be used alone. Solvent or plasticizer solutions of oligomerized toluene diisocyanate (TDl) are available under the trade names Vulcabond (Akzo Nobel), Vanchem HM-50 (Vanderbilt), Thanecure T9 (TSE Industries), and Desmodur (Bayer). For improved resistance of the bond to heat and moisture, products based on bisphenyl diisocyanate (MDl) are also used. These include Vanchem HM-4346 and Rubinate 9480 (Huntsman). These are typically used at 3-7 phr levels in plastisols for coating polyester fabric. The second or subsequent coats should contain titanium dioxide and UV light stabilizer for outdoor service. With translucent products, an aliphatic isocyanate such as Desmodur N-lOO or TMl META (Cytec) should be used. 

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