Epoxy resins diisocyanate reaction

High molecular weight thermoplastics called phenoxy resins are formed by the hydrolysis of the epoxy resins so that no epoxy groups are present. These transparent resins can be further reacted, forming cross-linked material through reaction of the hydroxyl pendant groups with diisocyanates or cyclic anhydrides. 

Epoxy resins may be produced which contain tertiary carbamates by the use of glycidol as the chain-terminating alcohol in a diisocyanate - diol reaction. For example, a stepwise reaction has been used in which one equivalent of glycidol has been reacted with 1,6-hexamethylene diisocyanate to produce a mixture represented ideally by the reaction ... 

Adhesives which are meant to cure at temperatures of 120 or 171°C require curatives which are latent at room temperature, but react quickly at the cure temperatures. Dicyanodiamide [461-58-5], (TH INI is one such latent curative for epoxy resins. It is insoluble in the epoxy at room temperature but rapidly solubilizes at elevated temperatures. Other latent curatives for 171°C are complexes of imidazoles with transition metals, complexes of Lewis acids (eg, boron trifluoride and amines), and diaminodiphenylsulfone, which is also used as a curing agent in high performance composites. For materials which cure at lower temperatures (120°C), these curing agents can be made more soluble by alkylation of dicyanodiamide. Other materials providing latency at room temperature but rapid cure at 120°C are the blocked isocyanates, such as the reaction products of toluene diisocyanate and amines. At 120°C the blocked isocyanate decomposes to regenerate the isocyanate and liberate an amine which can initiate polymerization of the epoxy resin. Materials such as Monuron can also be used to accelerate the cure of dicyanodiamide so that it takes place at 120°C. 

A similar structure to the one in Figure 6.6 is obtained by using instead of epoxy resins diphenylmethane diisocyanate (MDI pure or crude ). For example by using crude MDI with the functionality of around 2.2-2.5 -NCO groups/mol, by the reaction with terminal groups of high molecular weight polyether triols (5000-6500 daltons), nonreactive NAD... 

Complex mixtures of value as cationic binders for use in cathodic coatings have been derived from the reactions of substituted ureas, nonylphenol and formaldehyde. For example, the diketimine from diethylenetriamine and methyl isobutyl ketone (which served as a protective group in the first stsge of the process) by reaction with tolylene diisocyanate (semi-blocked with 2-ethylhexanol) afforded a urea. Treatment of the reaction mixture, presumably after removal of the ketonic group, with nonylphenol and aqueous formaldehyde gave a product which after solvent dilution was then reacted with bis-phenol A epoxy resin in diglyme solution (ref. 50). Such products can only be visualised as complex mixtures. 

Macro-diisocyanates based on the reaction of an excess of 2,4-toluene diisocyanate with different poly(dimethylsiloxane)diols of different lengths have been prepared by Nikolaev et al. [71]. These macro-diisocyanates were reacted with 2 in stoichiometric proportions and the resulting adduct (22) was cured with a commercial epoxy resin in the presence of what was termed poly(ethylene)-poly(amine) at room temp-cerature, 80, and 100°C. The mechanical and thermal properties of steel-to-steel assemblies joined by these adhesives were better than those obtained using more common binders. 

Diaminodiphenylmethane n (DDM, methyl-enediamine, MD). A silvery, crystalline material obtained by heating formaldehyde aniline with aniline hydrochloride and aniline. It is used as a curing agent for epoxy resins and as an intermediate in making diisocyanates for urethane elastomers and foams by reaction with phosgene. Possible occupational hazards in the use of DDM are toxic hepatitis and liver damage. 

The most common way to convert LP polymers to solid elastomers is to couple the terminal -SH groups. This is done either by oxidation to disulfides using organic or inorganic oxidizing agents or by reaction with epoxy resins, aromatic amines, diisocyanates, aldehydes, etc [16,35] ... 

Two resin types were investigated, including epoxy esters from stepwise reaction of sucrose-partial drying oil ester with cyclic anhydride and diepoxide, and polyurethanes from sucrose-partial drying oil ester and diisocyanate. Details of synthesis of the resins and their evaluation as coatings are discussed below. 

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