Isocyanate compounds

Substituted (l//,3 -quinazol>ne-2,4-diones 774, as well as the 3-unsubstituted parent compound 774 (R = H), are available by treatment of 2-[(trichloroacetyl)amino]benzamides 772 with sodium hydroxide in DMSO. The reaction proceeds via intermediate isocyanate compounds 773 which undergo ring closure to the final products <20050PP560>. 

HDI is one of the most commercially important isocyanate compounds currently used in the United States. HDI, toluene diisoeyanate (TDI) and 4,4 -diphenylmethane diisocyanate (MDI) are widely used in... 

Poly(n-alkyl isocyanate) compounds have a rigid helical structure in solution (174). As shown in Scheme 74, a chirally deuterium-labeled isocyanate is polymerized by sodium cyanide to form a product with a very high rotation value (175). The rotation is highly temperature dependent because of the unique chain structure of the product. Interestingly, the reaction of hexyl isocyanate in the presence of 1 mol % of a related chiral analogue leads to a polymer with a high rotation value. The bias of the chain helicity could be induced by living achiral-chiral copolymers. 

A broad spectrum of hydrogen-containing nucleophiles react with both aromatic and aliphatic isocyanates compounds containing OH groups (H20, alcohols, phenols, oximes, acids), SH groups (H2S, mercaptans), NH groups (NH3, amines, hydrazines, amides, ureas, urethanes), enolizable compounds such as malonic and aceto acetic esters, etc. Some reactions are given in Table 2.5. 

Terminal alkenes can be hydrogenated selectively in the presence of PdCI2 [63] or RhCl(PPhj)3 [64] and heteropoly compounds. The catalytic system is also highly active for the production of urethane or isocyanate compounds by the reductive carbonylation of nitrobenzene. It is considered that polyoxometalate coordinating with Pd2+ in the reduced form is the active species, since easily reducible heteropolyanions are more active [63]. 

Organic isocyanates are the major building blocks of urethane structural adhesives. They can be synthesized by a variety of routes, but most of the commercially available isocyanate compounds used in adhesives are made by the reaction of a precursor primary amine or amine salt with phosgene, followed by dehy-drohalogenation. The reaction with phosgene usually is carried out at a relatively low temperature, less than 60°C, and then the temperature is raised to 100-200°C to remove the HC1. 

Nagata, T., Yamashita, H., Kusumoto, M., and Okazaki, K., Stabilizing Method of Isocyanate Compounds and Isocyanate Compositions Stabilized Thereby, U.S. Patent No. 5,302,749, 1994. 

A double-side adhesive tape was prepared using a mixture of a hydroxylterminated poly butadiene, a polyol, and an isocyanate compound containing an oxadiazinetrione ring 241 A compound suitable for sealing spaced glass panels comprises a reaction product of an unsaturated polymer with functional end groups with HTPB, a decane thiol adduct, and tolylene diisocyanate 242). 

When polyurethane was polymerized in the presence of moisture, some expansion is inevitable. In order to investigate the influence of foam on permeability a rapid chloride ion permeability test was conducted in accordance with AASHTO T-277. Three resin systems RPUMRPE-1, RPUMRPE-2, and HRPE were used. The permeability results of 12 slices are shown in Table 8. It can be seen that every specimen is impermeable. After 6 hours, the permeabilities were the same as at the beginning. Although RPUMRPE-2 contains more isocyanate compound and more expansion than RPUMRPE-1, it still had excellent impermeability which means the pores are closed, and the water cannot pass through. 

Mixed carbamoyl chloride-isocyanate compounds can be prepared by reaction of phosgene with a material possessing both a primary and a secondary amine function ... 

In addition to the one-component contact adhesives described above, there are also two-component systems with isocyanate compounds as hardener component as well as solvent-free formulations. 

Certain secondary amine compounds are commonly used for chemical derivation of isocyanates which, like phosgene, form substituted urea compounds amenable to chromatographic determination. One of the most common of these reagents is 1—(2—pyridyl)-piperazine (PYP) PYP reacts on a one-to-one basis with isocyanate compounds yielding a stable urea derivative which can be quantified specifically and sensitively with reversed phase, high performance liquid chromatography (HPLC) and ultraviolet absorbance detection. 

The OPA technique has been applied to isocyanate compounds (160,161), malonic acids (162), metal acetylacetonates (163), and diazonium com-pounds(164). There are also numerous industrial uses of the technique. 

The isocyanate compounds F2PNCO and FP(NCO)2 were first obtained by Anderson (3) via fluorination of P(NCO)3 with antimony trifiuoride. Similarly PF2(NCS) was said to be formed from P(NCS)3. More recent work (273), however, has indicated that Anderson s product is identical with the pentavalent phosphorus compound SPF2(NCS) formed by fluorination of SP(NCS)3. 

The sulfamoylated AZT analogue (25) has been prepared as a membrane permeable analogue of AZT triphosphate. The sulfonylating agent (26) was prepared from diethyl hydroxymethyl phosphonate and chlorosulfonyl isocyanate. Compound (25) was a poor inhibitor of HIV reverse transcriptase but exhibited some anticancer activity. 

Silyl tethered amines are used frequently in amide-forming coupling reactions [e.g.. Fig. 16(c)] (169, 170). Isocyanate compounds are also commercially available, and have been used in the immobilization of enzymes within the sol-gel pores (171). These isocyanates can also be used to prepare silylated phen ligands that have been used in our own studies (172). Silylated isocyanates have... 

PU are compounds formed by reacting the polyol component with an isocyanate compound, typically toluene diisocyanate (TDI) methylene diisocyanate (MDI) or hexamethylene diisocyanate. Polyols are relatively non-toxic (i.e., polyether type polyols are found to be safe, because they are low in oral toxicity with almost no irritation effect to the eyes and skin), however, isocyanates are highly toxic and the product can have a significant toxicity if remnants of isocyanate are in it, which manifests itself mainly as a respiratory (as well as a dermal) hazard. Exposure to the vapour of isocyanates directly may cause irritation for the eyes, respiratory tract and skin. Such an irritation may be too severe to produce bronchitis and pulmonary oedema. As health hazards of isocyanates are considered, one immediately remembers one of the worst industrial disasters of the 20th century, that occurred in Bhopal, India, because of the toxic cloud of methyl isocyanate was released accidentally from the Union Carbide pesticide factory in December 1984. An estimated 3,000 people died immediately with a final of some 20,000, most suffocating from the cloud s toxic chemicals, and some 50,000 were injured, most were residents living near the plant. 

PAI resins prepared by this method have poor melt flowability, melt processability, mechanical properties, and heat resistance. AYhen oligomeric isocyanate compounds are used, PAI types with soft segments can be fabricated. These types can be used in pervaporation membranes, in order to tailor the properties. ... 

There are several routes to synthesize Pis. Most commonly. Pis are synthesized from dianhydride compounds and diamine compounds. There are also commercial processes that use dianhydride compounds and isocyanate compounds to get Pis. 

A solution of a proprietary isocyanate compound (1 wt.% in ethyl acetate) was provided by an industrial partner. The mid-IR spectrum was recorded at a resolution of 4 cm for a scan time of 30 s, then the solution (25 ml) was treated with an excess amount of tri- -butylamine (5 ml, 99% pure from Alfa Aesar) and spectra were recorded every 60 s for a total of 80 minutes. The reaction was carried out at room temperature. 

The mid-IR spectrum of an unknown isocyanate compound is shown in Figure 4, in the range 2200-2400 cm. The materials was supplied by an industrial partner. The dashed line represents the spectrum of the starting isocyanate, and the solid line shows the spectrum 80 minutes after adding the tributyl amine. The disappearance of the characteristic isocyanate peak at 2340 cm is clearly shown. 

The inorganic filler allows to adjust the desired acoustical and mechanical properties. The hydrolysis inhibitor comprises at least one member selected from a carbodiimide compound, an isocyanate compound, and an oxazoline compound. 

Isocyanates, both in monomeric and in polymeric forms, are extensively used for manufacturing polyurethane foams, paints, adhesives, and a number of other products. The health hazards posed by the presence of isocyanates at workplaces, chiefly respiratory tract diseases, have become a source of major concern for occupational health officials. Atmospheric pollution by isocyanates has so far been assessed using two different approaches. One, widely employed to date, involves the determination of several specific isocyanates compounds for which threshold values have been established the other has become a priority choice for air monitoring programs in recent years and entails determining the concentration of all isocyanate species present. 

Reactivity is determined by mixing the polyol with an isocyanate compound, catalyst, and the other components of a standard foam recipe, then measuring the time required for maximum foam rise, maximmn exotherm, or some related phenomenon. 

Toluene diisocyanate (TDI) and the various forms of methylene 4,4 -bis(phenylisocyanate) (MDI) are the most common isocyanate compounds in commercial polyurethanes. Aliphatic isocyanates (hexamethylene diisocyanate) are not generally used in foams, but... 

Figure 2 Some commercially important isocyanate compounds.

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