Isocyanuric derivs

Burdett (6) found that lEM can be trimerized to form the tris-substituted isocyanurate derivative ... 

Of the two reactions, isocyanurate formation is the most widely utilized. Diisocyanates can be converted via this reaction into trifunctional isocyanurate derivatives and subsequently used to introduce branching and crosslinking into a polyurethane.These crosslinks have greater thermal stability than either allophonate or biuret linkages, and hence they are more useful in elevated temperature applications. 

H12MDI is less volatile than HDI and is sometimes used as afree diisocyanate in coatings to be applied by roll coating, but not by spray coating. It is a mixture of stereoisomers since both isocyanate groups are secondary, reactivity is lower than HDI or IPDI. Combined allophanate-isocyanurate derivatives are available with low free monomer content. Reference 7 covers the chemistry and uses of H12MDI. 

Commercial IPDI is a mixture of Z-(cis) and E-(trans) isomers in a 75 25 ratio. The isomers are difficult to separate. Isocyanurate derivatives of IPDI and prepolymers with TMP are widely used. 

Another approach using carbamate-functional reactants is to react a polyisocyanate such as IPDI isocyanurate or HDI isocyanurate with hydroxypropyl carbamate (50). These carbamates are used in automotive clear coats with an MF resin that has been partially reacted with butyl carbamate to reduce its fimc-tionality. The remaining methoxymethyl groups of the melamine resin react with the carbamate groups of the isocyanurate-derived carbamate to give cross-linked films with outstanding environmental etch and mar resistance. The use of a combination of a carbamate-functional acrylic resin, a polycarbamate derived from a polyisocyanate, and an MF resin has also been patented (51). 

Forsyth M., MacFarlane D.R., Meakin P.,.Smith M.E Bastow T.J. (1995) An nmr investigation of ionic structure and mobility in plasticized solid polymer electrolytes, Electrochimica Acta, International symposium on polymer electrolytes, vol.40, n°13-14, pp. 2343-2347, (October 1995), ISSN 0013-4686 Fort Y., Gottardi C. Caubere P. (1993). New selective syntheses of (meth)acrylic monomers Isocyanates, carbamates, ureas and isocyanurates derivatives. Tetrahedron. Letters, vol.34, n°24, pp.3857-3860, (June 1993), ISSN 0040-4039 Fredlake C.P., Crosthwaite J.M., Hert D.G., Aki S.N.V.K. Brennecke J.F.J. (2004). 

Alkoxy isocyanates are not known in their monomeric form because they undergo rapid cyclotrimerization to give the corresponding isocyanurate derivatives. ... 

Characterization was also performed with MALDI-TOF mass spectrometry with Ag" -labeling as described in section 2.3. Individual solutions of (1)3 (CNC)6 or t2)3 (CNC)6 comprising the isocyanurate derivative CNC (Figure 3) have given the expected intense signals in the MALDI-TOF mass spectra at m/z = 4348.1 and 4618 respectively, for the monovalent Ag" complexes. As expected, the MALDI-TOF mass spectrum of the mixture shows two additional signals for the heteromeric assemblies (l)2(2)i (CNC)6 and (1)i(2)2 (CNC)6 at m/z = 4437.9 and 4527.7, respectively, in agreement with the calculated values. 

Figure 11. Molecular structures for melamine derivative 10 and bis-isocyanurate derivative 19 and MALDl-TOF mass spectrum of the 1 2 mixture of 19 and 10 after labeling with Ag (matrix 2,5-dihydroxybenzoic acid)...

The formation of isocyanurates in the presence of polyols occurs via intermediate aHophanate formation, ie, the urethane group acts as a cocatalyst in the trimerization reaction. By combining cyclotrimerization with polyurethane formation, processibiUty is improved, and the friabiUty of the derived... 

Sta.bilizers. Cyanuric acid is used to stabilize available chlorine derived from chlorine gas, hypochlorites or chloroisocyanurates against decomposition by sunlight. Cyanuric acid and its chlorinated derivatives form a complex ionic and hydrolytic equilibrium system consisting of ten isocyanurate species. The 12 isocyanurate equilibrium constants have been determined by potentiometric and spectrophotometric techniques (30). Other measurements of two of the equilibrium constants important in swimming-pool water report significantly different and/or less precise results than the above study (41—43). A critical review of these measurements is given in Reference 44. 

Organic Derivatives. Although numerous mono-, di-, and trisubstituted organic derivatives of cyanuric and isocyanuric acids appear in the hterature, many are not accessible via cyanuric acid. Cyanuric chloride 2,4,6-trichloro-j -triazine [108-77-0], is generally employed as the intermediate to most cyanurates. Trisubstituted isocyanurates can also be produced by trimerization of either aUphatic or aromatic isocyanates with appropriate catalysts (46) (see Isocyanates, organic). Alkylation of CA generally produces trisubstituted isocyanurates even when a deUberate attempt is made to produce mono- or disubstituted derivatives. There are exceptions, as in the production of mono-2-aminoethyl isocyanurate [18503-66-7] in nearly quantitative yield by reaction of CA and azitidine in DMF (47). 

Virtually all of the organo derivatives of CA are produced by reactions characteristic of a cycHc imide, wherein isocyanurate nitrogen (frequendy as the anion) nucleophilically attacks a positively polarized carbon of the second reactant. Cyanuric acid and ethylene oxide react neady quantitatively at 100°C to form tris(2-hydroxyethyl)isocyanurate [839-90-7] (THEIC) (48—52). Substitution of propylene oxide yields the hydroxypropyl analogue (48,49). At elevated temperatures (- 200° C). CA and alkylene oxides react in inert solvent to give A/-hydroxyalkyloxazohdones in approximately 70% yield (53). Alternatively, THEIC can be prepared by reaction of CA and 2-chloroethanol in aqueous caustic (52). THEIC can react further via its hydroxyl fiinctionahty to form esters, ethers, urethanes, phosphites, etc (54). Reaction of CA with epichlorohydrin in alkaline dioxane solution gives... 

Poly (Difluoroamino)-Substituted Cyanuric and Isocyanuric Acid Derivatives. For Cyanuric Acid and Derivatives see Vol 3, C589-R ff. For Difluoroamino Compounds see Vol 5, DI258-L... 

The epoxy resin component is made by a 2-stage process involving reaction of l-chloro-2,3-epoxypropane (epichlorhydrin) with isocyanuric acid to give the l,3,5-tris(2-hydroxy-3-chloropropyl) derivative, which is then treated with sodium hydroxide to eliminate hydrogen chloride to form the title compound. One batch contained more than the normal amount of hydroly sable chlorine, and when excess epichlorhydrin was distilled off, the residual material decomposed with explosive violence. It was later established that the abnormal chlorine content was associated with reduced thermal stability, and criteria for hydrolysable chlorine, epoxy content and pH have been set to prevent distillation of off-spec, material. 

The formation of isocyanurates in the presence of polyols occurs via intermediate allophanate formation, i.e, die urethane group acts as a cocatalyst in the dimerization reaction. By combining cyclotrimeiization with polyurethane formation, processibility is improved, and the friability of the derived foams is reduced. Modification of cellular polymers by incorporating amide, imide, oxazolidinone, or carbodiimide groups has been attempted but only the urethane-modified isocyanurate foams are produced in the 1990s. PUIR foams often do not require added fire retardants to meet most regulatory requirements. A typical PUIR foam formulation is shown in Table 2. 

Triglycidyl derivative of aminophenol (7). Tetraglycidyl derivative of methylenedianiline (5) (6). Polynuclear phenol glycidyl ether (4) (4). d Triglycidyl isocyanurate (6) (8). 

There are derivations of this chemistry now available that provide an isocyanurate/sodium bromide blend in tablet form. This niche product is often suitable for cooling systems that suffer from small, but regular, process leaks and other contaminating, oxidizable material in the cooling water (see Section 6.2.7 on bromine chemistry). 

In the presence of two equivalents of 5,5-diethylbarbiturate (DEB) or isocyanuric acid derivatives (CYA), dimelamines la-d form stable double rosette assemblies la-d3 (DEB) 6 in apolar solvents such as chloroform, benzene or toluene even at 10 4 M concentration (Figure 4.2).9,10 They consist of 9 different components held together by 36 hydrogen bonds. X-ray diffraction studies of lb3 (DEB)6 showed that the two rosette layers are tightly stacked on top of each other with an interatomic separation of 3.5 A at the edges and... 

FIGURE 4.3. Molecular structures and schematic representations of tetra- hexa- and octamelamines 2, 3 and 4, respectively, and di(melamine-cyanurate) 5. The molecular structure of DEB and different isocyanuric acid derivatives (CYA) are also shown. 

Modification of poly(carbodiimide) foams with polyols afford hybride foams containing urethane sections. However, the thermal stabilities of the poly (urethane carbodiimide) foams are lower. Using isocyanate trimerization catalysts, such as l,3,5-tris(3-dimethylaminopropyl)hexahydro-s-triazine, in combination with the phospholene oxide catalyst gives poly(isocyanurate carbodiimide) foams with improved high temperature properties. The cellular poly(carbodiimide) foams derived from PMDI incorporate six-membered ring structures in their network polymer structure. ... 

The tautomerism of 1,3,5-triazines has been reviewed previously (B-76MI22000, pp.138,152,168). NMR and IR studies have shown that cyanuric acid exists mainly in the oxo form. Although the cyanurates and isocyanurates are the two major derivatives, there is no doubt that compounds with both types of functional group present in the same molecule are possible (e.g. Scheme 36). Trithiocyanuric acid exists predominantly in the thioamido form. In contrast, melamine exists in the amino form. /S-Oxoalkyl-1,3,5-triazines exist mainly in the enol form, and thus they undergo ene type reactions with dienophiles. 

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