Isocyanates with amines

Conversely, the rate of reaction of isocyanates with amines to yield ureas is both rapid and quantitative. Much has been written concerning the reaction... 

In the manufacture of highly resident flexible foams and thermoset RIM elastomers, graft or polymer polyols are used. Graft polyols are dispersions of free-radical-polymerized mixtures of acrylonitrile and styrene partially grafted to a polyol. Polymer polyols are available from BASF, Dow, and Union Carbide. In situ polyaddition reaction of isocyanates with amines in a polyol substrate produces PHD (polyhamstoff dispersion) polyols, which are marketed by Bayer (21). In addition, blending of polyether polyols with diethanolamine, followed by reaction with TDI, also affords a urethane/urea dispersion. The polymer or PHD-type polyols increase the load bearing properties and stiffness of flexible foams. Interreactive dispersion polyols are also used in RIM appHcations where elastomers of high modulus, low thermal coefficient of expansion, and improved paintabiUty are needed. 

The reactions of isocyanates with amines and with water have been reviewed in detail [116], as have the preparations of many polymers... 

Systematic studies of the reaction rates of isocyanates with amines were carried out by Craven (53) and Baker and Bailey (4f). 

Carboxylic acid azides give rise to three different reactions under different conditions. Azide coupling (equation 9) was the earliest method in peptide synthesis and is still one of the most important in fragment condensation and preparation of cyclic peptides due to its almost complete lack of racemization. At elevated temperatures a frequent side reaction is the Curtius rearrangement. Trapping of the intermediate isocyanate with amines (equation 10) gives urea derivatives and with carboxylic acids rearranged amides are obtained (equation 11). ... 

Additionally, reactions of isocyanate with amines provide another cross-linking approach to make nanogels. Cross-linked micelles with pH-responsive features were obtained by the addition of excess amounts of 1,8-diaminooctane to micellar aggregates consisting of poly (poly(ethylene glycol) methyl ether methacrylate)-b/oc -poly(methyl methacrylate-co-poly (3-isopropenyl-a,a-dimethylbenzyl isocyanate)) [PPEGMEMA-b-P(MMA-co-TMI)] (Figure 54.9). 

Polyurethanes are block copolymers containing blocks of low molecular weight polyethers or polyesters linked together by a urethane group. The variety of linkages in polymers results from the further reaction of urethane groups with isocyanates and of isocyanates with amines, water, or carboxylic acids. 

Isocyanate plastic n. A plastic based on polymers made by the polycondensation of organic isocyanates with other compounds. Reaction of isocyanates with hydroxyl-containing compounds produces polyurethanes having the urethane group -NHC (=0)0-. Reaction of isocyanates with amine-containing compounds produces... 

So far, this method was not extended to the post cure processes of PUs. However, if its use is intended, there are difficulties to be expected. The overlapping of the NMR nitrogen resonance signals as isocyanate with amine and urea with biuret mentioned by these authors [337] will be complicated here even more by overlapping with other additional nitrogen signals characteristic to a polyurethane system, like urethane and possible allophanate nitrogens [337-340],... 

An alternative stable interactive organic dispersion in polyol has recently been introduced. This consists of particles of polyurea dispersed in polyol, formed by the in situ polyaddition reaction of isocyanates with amines in a polyol medium, and offers similar advantages to the polymer/polyols. 

Isocyanates will react with all compounds containing hydrogen atoms attached to a nitrogen atom [2]. There are four basic reactions chemists employ to make polyurethanes. The reaction of isocyanates with hydroxyl groups to produce urethane is the primary reaction. The reaction of isocyanates with amines yields urea and the reactions of isocyanates with urea and urethane produce biurets and allophanates, respectively. 

Primary and secondary amines react quickly with isocyanates yielding urea (Section 3.2.3). The inherent high reactivity of isocyanate, particularly aromatic isocyanate, with amine containing materials is a disadvantage of using an amine-cured binder. Accordingly, systems formed using amine-cured binders often react... 

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