Chemistry diisocyanates

The properties of polyurethanes can be varied by changing the type or amount of the three basic building blocks of polyurethane chemistry diisocyanate, short-chain diol, and long-chain diol. Polyurethanes are generally classified by the type of polyol used, for example, polyester polyurethane or polyether polyurethane. 

Bisaminimides form diisocyanates. This reaction and its application in polymer chemistry have been reviewed (77). A review of the general subject of... 

The product is useful as a model compound for studies of the chemistry of derivatives of colored diamines. Specifically, the submitters used the compound for the preparation of colored diisocyanates. 

Liquid organic rubbers with reactive functionality can be prepared by several methods. End-functional oligomers are preferred. Chains attached to the network at only one end do not contribute as much strength to the network as those attached at both ends [34], Urethane chemistry is a handy route to such molecules. A hydroxy-terminated oligomer (commonly a polyester or a polyether) can be reacted with excess diisocyanate, and then with a hydroxy methacrylate to form a reactive toughener [35]. The methacrylate ends undergo copolymerization with the rest of the acrylic monomers. The resulting adhesive is especially effective on poIy(vinyl chloride) shown in Scheme 2. 

Preparation of polyfethylene oxide) (PEO) and poly(arylene ether) based hydrophilic-hydrophobic block copolymer is of special interest because PEO has been proven to be particularly reliable and versatile for the surface modification of biomaterials. The first poly(ediylene oxide)-/ /oc/c-polysulfonc (PEO-fc-PSF) copolymers were reported by Aksenov et al.217 They employed diisocyanate chemistry to link hydroxy-terminated sulfone oligomers and polyfethylene... 

The transition metal catalysed addition of HCN to alkenes is potentially a very useful reaction in organic synthesis and it certainly would have been more widely applied in the laboratory if its attraction were not largely offset by the toxicity of HCN. Industrially the difficulties can be minimised to an acceptable level and we are not aware of major accidents. DuPont has commercialised the addition of HCN to butadiene for the production of adiponitrile [ADN, NC(CH2)4CN], a precursor to 1,6-hexanediamine, one of the components of 6,6-nylon and polyurethanes (after reaction with diisocyanates). The details of the hydrocyanation process have not been released, but a substantial amount of related basic chemistry has been published. The development of the ligand parameters % and 0 by Tolman formed part of the basic studies carried out in the Du Pont labs related to the ADN process [1],... 

Guevera, R., and Moslem , A.A. (1983). Hygroexpansive and sorptive behaviour of wood modified with propylene oxide and oligomeric diisocyanate. Journal of Wood Chemistry and Technology, 3(1), 95-114. 

We have already been introduced to polyurethane chemistry in Chapter 10, Section 2, where we used toluene diisocyanate (TDI) reacting with a diol to give a polyurethane. Polyurethanes derived from MDI are more rigid than those from TDI. New applications for these rigid foams are in home insulation and exterior autobody parts. The intermediate MDA is now on the Reasonably Anticipated to Be Human Carcinogens list and the effect of this action on the market for MDI remains to be seen. The TLV-TWA values for MDA and MDI are some of the lowest of the chemicals we have discussed, being 0.1 and 0.005 ppm respectively. 

Chemistry of Polyurethanes. A binder system capable of many permutations results from the reaction of difunctional alcohols with diisocyanates to form polyurethanes (5,14). 

The preparation of imides from reaction of isocyanates with anhydrides dates back to the early days of organic chemistry [96]. With the advent of polyimide chemistry in the early 1960s, this chemistry was soon explored for the synthesis of polyimides. However, in contrast to the preparation of polyimides via thejr poly(amic acid) intermediate, the reaction of aromatic dianhydrides with aromatic diisocyanates is much less understood. The reaction of aromatic dianhydrides with aliphatic or aromatic diisocyanates is believed to form a cyclic seven-membered intermediate which then splits out C02 to form the polyimide [97], see Scheme 27. The addition of water, which has been reported to accelerate the anydride/isocyanate reaction, can result in several transformations of either the anhydride or the isocyanate reagent, see Scheme 28... 

A reconstructed ion chromatogram (GC-MS) containing extractable contaminants isolated from a typical lot of foam is shown in Figure 4. The qualitative composition of the extractable contaminants was provided by GC-MS. Contaminant profiles were identical for each of the two solvent systems employed, methylene chloride (1003 ) and ethyl ether/hexane (5/95). The contaminant chemistry shown here and again in Figure 5 in several instances is consistent with the manufacturing process data shown in the box, most notably the presence of residual toluene diisocyanate (starting materials, see Scheme II) and an aliphatic amine (possible reaction catalyst). 

Urethanes. The basis for urethane chemistry is the reaction of an isocyanate group with a component containing an active hydrogen. The first step in formulating a urethane sealant is to prepare what is commonly called (lie prepolymer, typically by reaction of a hydroxy-terminated polyether with a stoichiometric amount of a diisocyanate. 

Figure 7.7 SAXS profiles for two hydroxyl-terminated oligomers crosslinked by alkoxysilane sol-gel chemistry. First, 1 mole of macrodiol, SS (hydrogenated polybutadiene, HPBD or polycaprolactone, PCL, Mn= 2 kg mol-1), was reacted at 80°C with 2 mole of dicyclohexylmethane diisocyanate, H12 MDI. After complete reaction, the prepolymer was dissolved in tetrahydro-furan and the y-aminosilane, yAPS was added dropwise at room temperature. After 1 h of reaction, the solvent was removed under pressure. The final network was obtained in the absence of a solvent by hydrolysis and condensation of the ethoxysilane groups by the addition of 0.1 mol% TFA, trifluor-oacetic acid. After stirring at room temperature, the mixture was cast into a mold and cured for 24 h at 100°C under pressure, and then postcured at 150°C for 12 h. (Cuney et al., 1997 - Copyright 2001, Reprinted by permission of John Wiley Sons, Inc.)...

The functionalization of SAMs via ruthenium-catalyzed cross metathesis of vinyl-terminated SAMs has been reported by Lee et al.76 to install a variety of acrylic derivatives on SAMs bearing vinyl groups on their outer surface. The major drawback of this approach is the intra-SAM metathesis which causes the formation of a mixture of surface-bound products, limiting the reproducibility of the method. The formation of urethanes by the reaction of diisocyanates77 or isothiocyanates78 with hydroxyl- and amino-terminated SAMs has been reported as well. The reaction of hydroxyl-terminated SAMs with diisocyanates, allowed the preparation of isocyanate SAMs that proved to be reactive towards amines, alcohols, and water, displaying the standard chemistry of the isocyanate groups.77... 

All industrial polyurethane chemistry is based on only a few types of basic isocyanates. The most significant aromatic diisocyanates are TDI and MD. TDI is derived from toluene. This is initially nitrated to dinitrotoluene, then hydrogenated to diamine, and finally phosgenated to diisocyanate. A defined mixture of isomers comprising toluene-2,4-and 2,6-diisocyanate is obtained. Approximately 1.3 million tons/year of TDI are produced world-wide, most of which is used in the production of polyurethane flexible foam materials. 

Furans. The last statement is certainly true of furans derived from sugars (142,143), particularly furfural and furfuryl alcohol, which is readily derived from furfural (144)- Dr. McKillip of QO Chemicals discusses furan resin chemistry and furan polymers in Chapter 29. Dr. Stanford and his colleagues at the University of Manchester Institute of Science and Technology discuss the use of a diisocyanate derived from furfural for polyurethane production in Chapter 30. 

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