Isocyanates definition

Synonyms Benzene-, 1,3-diisocyanatomethyl- Diisocyanatomethylbenzene 1,3-Diisocyanatomethylbenzene Diisocyanatotoluene Isocyanic acid, methyl phenylene ester Isocyanic acid, methyl-m-phenylene ester Methyl-m-phenylene diisocyanate Methylphenylene isocyanate TDI TDI 80-20 Toluene diisocyanate mixed isomers Tolylene diisocyanate Tolylene isocyanate Definition Mixt. of the 2,4-isomer (89.3%) and the 2,6-isomer (10.7%)... 

The reaction of CDI with primary phosphines was expected to lead first to an azolide ImCOPHR, analogous to imidazole-N-carboxamide as the reaction product of primary amines and CDI. In fact, reaction of phenylphosphine with CDI leads directly to imidazole, carbonmonoxide, and tetraphenylcyclotetraphosphine (THF, reflux, 5h). In analogy to the dissociation of imidazole-AT-carboxamide into isocyanates and imidazole, this can be explained by the assumption that the first-formed ImCOPHC6H5 dissociates into an isocyanate analogue, C6H5P=C=0, which is unstable and decomposes into carbon monoxide and phenylphosphene (C6H5P) which tetramerizes. However, the intermediate formation of phenylphosphene has not yet been definitely proved. 

On 1st January 2000 the new regulations re-classifying isocyanates as resin components came into force. According to the new definitions TDI prepolymers with a clear TDI proportion of 1-7% must be rated as poisonous and provided with risk memoranda R23, R40 and R42/43. Clear TDI proportions of 0.1-1% must be rated as harmful... 

Using 9.2 mmoles each of o-cresol and a-naphthyl isocyanate in 3.00 ml of purified ligroin, the effect of catalysts was tested. The sealed tubes were heated in a 65°C bath and after a definite time the solid urethane derivative was isolated, washed, dried, and weighed. The results (see Fig. 1) show that tri-ethylamine is the most effective amine, boron trifluoride etherate being the most effective acid tested at that time [7]. 

Lactic acid is an example. It is conveniently added to the polyol and upon reaction with the isocyanate, it is inserted into the backbone. Upon exposure to fluids in the body, the polymer is cut at the insertion site. The reduction in tensile properties is dramatic. Although the fragments are suspect, the result is by definition degradable. A number of researchers at W.R. Grace prepared biodegradable hydrophilic polyurethanes by a similar technique but the product was never available commercially. 

According to our definition a multicomponent reaction (MCR) comprises reactions with more than two starting materials participating in the reaction and, at the same time, the atoms of these educts contribute the majority of the novel skeleton of the product (Scheme 3.1) [1], For example, adenine may be formed by the addition of five molecules of isocyanic acid, a reaction of possible high prebiotic relevance [2]. 

The production of polyurethane involves the controlled polymerization of an isocyanate, a long-chain-backbone polyol and a shorter-chain extender or cross-linker. The reaction rates can be controlled through the use of specific catalyst compounds, well known in the industry, to provide sufficient time to pour or otherwise transfer the mix and to cure the polymer sufficiently to allow handling of the freshly demolded part. The use of blowing agents allows the formation of a definite cellular core (thus the term microcellular elastomer ) as well as a non-porous skin, producing an integral sandwich-type cross section. 

This multipart question question illustrates material balance calculations used, for example, in formulating polyurethanes. Refer to Section 1.5.4 for some of the reactions of isocyanate groups. This problem is an extension of the concepts mentioned in Section 3.1.5 on end-group determinations. Some useful definitions follow ... 

As may be recalled from our discussion of the law of definite proportion, isomers are molecules that have been built from the same number and type of atoms but arranged in a different order. We cited, as examples, fulminic acid, cyanic acid, and isocyanic acid HONC, HOCN, and HCNO, respectively. We saw that this simple rearrangement of elements made the first explosive, the second a poison, and the third a pacific participant in several, more constructive, organic syntheses. Isomers that differ only by being mirror images of each other are termed chiral isomers (pronounced kiral, with a hard c sound, the way chemist is pronounced kemisf). 

India, resulted in toxicity and death. The toxicological profile of methyl isocyanate was not known, and the chemical was released under uncontrolled conditions. Industrial accidents by definition are not specified conditions of exposure but must be borne in mind as a factor to consider. With increased knowledge of chemicals and the factors that affect these chemicals, the ability to assess and react to adverse conditions is enhanced. 

Adhesives are nonmetaUic substances used to join two surfaces by means of surface adherence (adhesion) and inherent strength (cohesion), DIN 16920. This definition of adhesives does not cover water glass adhesives, adhesive ceramics, or adhesive mortars. The substances used as adhesives are polymers that go through a liquid phase at least once (reactive adhesives) or more than once (hotmelts, thermally activated adhesives). The liquid phase can also be achieved by dissolution in suitable solvents (nonreactive adhesives). In dispersion adhesives, the polymer molecules are dispersed (finely distributed) in a liquid - usually water - whereby the polymer molecules themselves are not dissolved. Fig. 6. These adhesives are also known as water-based or aqueous adhesives. It must be remembered that solvents are contained in these adhesives in addition to the water. Genuine aqueous adhesives contain less than 5% solvents in the liquid phase. The dispersions crnitain, in contrast to the solute adhesive molecules, additional substances, disposal of which requires specific additional measures. Since the dispersions represent stable systems in water, the water-resistance of such adhesives is reduced. Their thermal and water resistance can be increased by additional crosslinking (usually with isocyanates). 

PH3 (2 to 4 atm) reacts with organic isocyanates, XC6H4NCO (X = H, p-Cl, P-NO2 [172] a77-CH3 [173]), in benzene in the presence of triethylamine or tributylamine to give tricarbamoyl-phosphanes, (XC6H4NHC(0))3P. Ethyl, octyl (in the presence of tripropylamine at lOO C and 340 atm), or 1-naphthyl isocyanate react analogously [173]. The reaction of 2,4-tolylene diisocyanate with PH3 is slow, and no definite product could be isolated. Phenyl isothiocyanate failed to react with PH3 under reaction conditions analogous to those for the isocyanates [172]. 

Synonyms Bis (2,4-dihydroxyphenyl) methanone and bis (2-hydroxy-4-methoxyphenyl) methanone Classification Organic benzophenone deriv. Definition Mixture of benzophenone-6 and -2 and other tetra-substituted benzophenone materials Uses UV absorber in NC lacquer, fluorescent paint, inks, and for protecting furniture woods, cosmetics, colored liq. toiletries, cleaning agents, isocyanate systems, and butyrate metal lacquers Manuf./Distrib. Celanese http //www. celanesechemicals. com http //www.chemvip.com EM Ind. 

Castor oil phosphate polymer with 3-isocyanatomethyl-3,5,5-trimethyl cyclohexyl isocyanate Castor oil, polymer with 5-isocyanato-1 -(isocyanatomethyl)-l, 3,3-trimethylcyclohexane, phosphates. See Castor oil phosphate/lPDI copolymer Castor oil, polymerized Synonyms Polymerized castor oil Definition Rubber-like polymer resulting from combination of castor oil with sulfur or diisocyanates... 

Definition Elastomer made by reaction of an isocyanate prepolymer with a short chainextending agent at ambient or high temp. one-and two-pack systems avail. 

Definition Methacrylate based on methacrylated aliphatic isocyanate Empiricai C11H15NO4... 

Many authors divide polymerizations into chain reactions and stepwise reactions. Of course, all reactions proceed in steps, that is, one reaction step follows another. Termolecular reactions are rare but in the organic chemistry sense, the term stepwise reaction signifies that intermediate products can be isolated and subsequently again made to react. This means that, in the absence of impurities, certain reactions can be frozen. In actual fact, anionic addition polymerizations can be frozen at low temperatures and made to run again at higher temperatures. That this procedure is not possible in the presence of water or carbon dioxide is an experimental consideration and not a conceptual difficulty. If we lived in an isocyanate atmosphere, no steps could be isolated in the polyamide synthesis. Thus, such classifications are based on experimental expertise, which can never be the basis of a physical definition. 

An immediate implication of the present results is that selective substitutions confined to a few definited sites, induce modifications of the chemical behaviour of groups located in different parts of the molecules. Moreover, the fact that the groups indirectly affected are the interchain -S-S- bonds, whose structural role is unique in insulin, implies the extension of the effects of localized substitutions to the molecule as a whole. Many attempts have been made in the past to consider the hormonal activity as depending on the integrity of certain key chemical groups, the "active sites". This concept was mainly based on the finding that only some specific substituent like iodine, methoxyl, phenyl-isocyanate lead to inactivation. 

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