Isocyanate component

When this is carried out in suitable solvents at temperatures in the range 75-120°C, soluble products will be obtained. Polymeric MDI is usually used as the isocyanate component and this results in a stiff chain molecule. One such product is reported to have a of 200-220°C. 

The acrylic polyol component is then mixed with the water contaminated isocyanate component and allowed to cure via the standard polyol isocyanate reaction ... 

At this juncture. It was decided to make a radical formulation change. First, because of the Incompatibility of the Freon 11 with the polyol, the Freon 11 would be removed from the polyol and placed In the Isocyanate component. Second, since 1/1 component ratios are necessary to accommodate the mixing machine, different Isocyanate and polyol components were formulated to establish appropriate viscosities. The final formulation Is shown below. 

Finally, a third formulation was devised which excluded the use of Freon 11 In the polyol component. Freon 11 was placed In the Isocyanate component and both Isocyanate and polyol components were changed to meet viscosity considerations. Subsequent aging studies showed the Isocyanate to age similarly to the previously aged (Formulation 2) Isocyanate. The polyol showed virtually no Increase In acid number at any aging temperature over 13 months. Thus, at ambient temperature we would expect a 6-8 year system lifetime on the Isocyanate before a 10% change In analytical properties would dictate a material change-out. The polyol appears to have a greater lifetime, but would probably be replaced at the same time. 

An oxonium intermediate may be involved here, in a manner directly analogous to the reaction wherein carbon dioxide takes the place of the isocyanate component (Eq. 71). 

The synthesis of PU can be carried out by the reaction described in Eq. (2.24). If the functionality of the hydroxy-containing compounds or the isocyanate is increased beyond 2, branched and possibly crosslinked polymers are produced. Because the nature of the polyol (polyether, polyester, polybutadiene, etc.) and isocyanate components can vary widely, PU are among the most versatile polymers, producing a wide variety of materials such as elastomers, foams, coatings, adhesives, or fibers. 

In RIM, all necessary reactive ingredients are contained in two liquid components an isocyanate component and a resin component. The choice of isocyanate, as well as variations within isocyanate families, exerts a profound effect on the processing and final properties of the plastic. The chemical structures of two of the major diisocyanate types,... 

Polyol and Isocyanate components may be reacted to afford Isocyanate-terminated oligomers which can then be subjected to the general reaction Illustrated in equation 1 above. Together with other synthetic modifications, this permits the preparation of a wide variety of oligomers. One may vary, for example ... 

FRU-M the prescribed amount of chopped glass strand (13 mm in length) was mixed with the prescribed amount of isocyanate-component and thoroughly dispersed before the addition of the polyol component. Then the following operations were carried out according to the procedure of FRU-L without strand mat. 

Two of the three binder systems used by the foundry industry are two-component, room-temperature curing adhesives. All systems use polymeric MDI as the isocyanate component. All of the cross-linkable components are polyols. The first polyol introduced into the industry was an alkyd oil resin consisting of linseed oil, pentaerythritol and isophthalic acid. The system... 

A second type of urethane adhesive is currently being introduced to the U.S. construction industry. The adhesive was originally developed in Japan. The system is two component. The isocyanate component is a modified polymeric MDI. The cross-linkable component contains water with water-soluble or water-emulsifiable resins. The adhesive produces strong, water-resistant bonds and has shown promise as a possible lower cost substitute for resorcinol formaldehyde resins in the adhesion of laminated beams. The product is now being used in Japan to bond wood and various other porous substrates at the rate of about 10 million pounds per year. The first U.S. application of the product has been the bonding of wood doors. The opportunities for products of this type should be excellent in view of the ever-increasing governmental pressures on solvents. 

In order to simplify the procedure of using too many components, a masterbatch , that is a mixture of the components that do not react with each other, (e.g., oligo-polyol, water, chain extender, catalysts, etc.), is made before foaming. Then it is possible to use only two components one is the polyolic component (called component A or formulated polyol, containing a mixture of all raw materials except for the isocyanate, in the proportions needed) and the second component is the isocyanate (called component B or isocyanate component). The polyurethane that results is a consequence of the very efficient contact between the isocyanate component and the polyolic component. Usually, in rigid PU foams only two components are used. In flexible foams, the polyolic component is divided into two components, especially in order to avoid the contact of some hydrolysable component with water, (e.g., stannous octoate). The gravimetric ratio between the components is verified before the foaming process and if necessary, it is corrected. 

Raw Materials for Urethane Coatings Isocyanate Components Di- and Polyhydroxy Components Chain Extenders and Cross-linkers Catalysts... 

If the functionality of the hydroxyl or isocyanate component is increased to three or more, branched or cross-linked polymers are formed. 

Isocyanate Components. Aromatic Di- and Polyisocyanates. The most important monomeric aromatic diisocyanates used for coatings are tolylene diisocyanate (TDI) and 4,4 -methylene bis(phenyl isocyanates) (MDI). Tolylene diisocyanate, a colorless liquid (bp 120 °C at 10 mmHg), is generally used in 80/20 blends of the 2,4-and 2,6-lsomers. Pure 2,4-TDI isomer has also been employed for coatings. 

The isocyanate moiety is highly reactive towards poly(ol)s. This reaction is utilized in the preparation of poly(urethane)s (PU)s. With catalysts such as amines, the reaction occurs rapidly at room temperature. Consequently, urethane polymers are mostly prepared from two components, one containing the isocyanate component, and the other containing the polyol component. The components are nuxed prior to curing. 

Uses Isocyanate component in polyurethane paints, elastomers, fibers, foams, leather tanning, textile finishing, dental and bone cements... 

No hydroxy or acid group containing solvents should be used since they react with the isocyanate component, thus excluding alcohols or glycolethers. Other solvents should have a very low water and acid content. 

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