Polyurethanes intermediates

Polymers. The molecular weights of polymers used in high energy electron radiation-curable coating systems are ca 1,000—25,000 and the polymers usually contain acryUc, methacrylic, or fumaric vinyl unsaturation along or attached to the polymer backbone (4,48). Aromatic or aUphatic diisocyanates react with glycols or alcohol-terrninated polyether or polyester to form either isocyanate or hydroxyl functional polyurethane intermediates. The isocyanate functional polyurethane intermediates react with hydroxyl functional polyurethane and with acryUc or methacrylic acids to form reactive p olyurethanes. 

Over the years many blends of polyurethanes with other polymers have been prepared. One recent example is the blending of polyurethane intermediates with methyl methacrylate monomer and some unsaturated polyester resin. With a suitable balance of catalysts and initiators, addition and rearrangement reactions occur simultaneously but independently to give interpenetrating polymer networks. The use of the acrylic monomer lowers cost and viscosity whilst blends with 20% (MMA + polyester) have a superior impact strength. 

Complex vanadium-phosphorus-oxide catalysts are the most successful industrial catalysts for the selective oxidation of /i-butane to maleic anhydride (MA) with uses in tetrahydrofurans (THE) and polyurethane intermediates. A schematic diagram of the reaction is shown in figure 3.21(a). These catalysts have been studied extensively (e.g. Centi et al 1993, Bordes 1987). In the selective catalysation of a-butane to MA, the best active phase in the V-P-0 system is identified as the vanadyl pyrophosphate, (VO)2P207 (hereafter... 

The MW of oligo-polyols, is usually in the range of 400 to 6500 daltons, and it has an important effect on the polyurethane properties. Thus, if the polyol has a low MW, a hard polyurethane will result and if the polyol has a high MW, it creates elastic, flexible polyurethanes. Intermediate MW lead to semirigid or semiflexible structures [2]. 

Curitbane . [Air ProdsyPolyurethanes] liq. catalysts amine curing agent for polyurethane intermediate in mfg. of polyamides, pdyimides, coatings, plastics. 

Carbon monoxide is purified and used as a feedstock for several primary petrochemicals The largest quantity is used for carbonylation of methanol to produce acetic acid. Acetic acid is used in the production of vinyl acetate, acetic anhydride and cellulose acetates. Phosgene, formed by the reaction of carbon monoxide with chlorine, is reacted with amines to form polyurethane intermediates. Phosgene is also reacted with bisphenol A to form polycarbonate resins, used for engineering plastics. 

Organic zinc primer, epoxy or polyurethane intermediate eoat, and aliphatie polyurethane top coat. 

Inorganic zinc silicate polymer, chemically curing epoxy or polyurethane intermediate coat, and aliphatic polyurethane top coat. 

Although two-pack epoxy primers and polyurethane intermediate coats have high solids contents, they still contain significant amounts (20-30 wt%) of organic solvents. In polyurethane topcoats, the VOC is even higher. Anticorrosive, waterborne primers based on aqueous dispersions of two-pack epoxy resins and one-pack acrylic resins have been developed to decrease solvent emission. Waterborne, one-pack acrylic topcoats are also used. All of these waterborne paints contain 2 - 5 % organic cosolvents that are required for film formation. 

As polyurethane intermediates react rapidly and stoichiometrically with each other, a system of nomenclature is widely used to describe the structure of individual block copolymers. Suppose, for example, a typical polyurethane consisted of polycaprolactone,4,4 -diphenylmethane diisocyanate, and 1,4-butane diol, present in the molar ratio 1 3 2, then such a polymer is reported as a 1 3 2 block copolymer and this represents a simple, convenient and rapid method of identifying the basic urethane polymer structure. The ratio of each component in the block copolymer has a dramatic effect on its properties, as shown by the data in Table 2.2. 

The most common epoxy resin is based on the diglycidyl ether of bisphenol A. Epoxy resins are sometimes esterified with fatty acids or modified with polyurethane intermediate chains for elastification. 

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