Isocyanates phenol blocked

Phenolic-blocked isocyanate prepolytner Thixotrope (Thixin R)... 

Phenol-Blocked Isocyanate Prepolymer + Ketimine (PBIP)... 

Fig. 7. Room-temperature curing concept for a phenol-blocked isocyanate-terminated prepolymer.

Phenol blocked isocyanates also have been used to prepare hyperbranched polyurethanes by a step-growth polycondensation mechanism, using DBTDL as a catalyst. 4... 

Water based poly(ester-imide) wire enamels were developed in the 1960s and 1970s. The resins were made water soluble in different ways. Resins with a defined acid number were neutralized with alkanolamines [144-148] or ammonia [149]. In another process the poly(ester-imide) resins were submitted to an ami-nolysis with alkanolamines [150-153] or ammonia [154-156], when the resin network is more or less degraded. Solvents for this poly(ester-imide) is water and usually a small amount of high boiling solvents like N-methylpyrrolidon or diethylene glycol monomethylether. Titanium catalysts stable to hydrolysis, like titanium-ammonium lactate and titanium lactate, were used [157]. To improve thermal and mechanical properties, phenol blocked isocyanates can be added to the water based poly(ester-imide)s. The blocked isocyanates are dispersed by means of an ethoxylated nonylphenol and are added to the water based wire enamel. Improvement of the property level is claimed [158]. 

Polyurethanes (single-component system) Block polyisocyanates and hydroxyl polymers Phenol-blocked isocyanates and hydroxyl groups Unblocking or removal of phenol to form a free isocynate followed by addition of hydroxyl groups to form urethane linkages 8 ... 

Polyurethane has a special place here because it is used to obtain elastomeric properties required in construction and some automotive sealants. Nonyl phenol-blocked and isocyanate (or polyisocyanurate) combination is added to PVC plastisol. These sealants have relatively stable viscosity Most important properties include ... 

Commercially available blocked isocyanates include Hylene MP or 4715 from Du Pont (now withdrawn), which is phenol-blocked MDI (Du Pont International S.A., Geneva, Switzerland) Mondur S, a phenol-blocked TDI adduct, Mondur SH, a cresol-blocked TDI trimer, and Experimental E-320-blocked isocyanate, a ketoxime-blocked tetraisocyanate, all from Mobay (Pittsburgh, Pennsylvania, USA) and Isonate 123P, which is s-caprolactam-blocked PAPI, from the Upjohn Company (Dow Chemical Europe, Horgen, Switzerland). These are shown in Fig. 8.9. Uniroyal also market a product. 

The Ashland Chemical Company markets a commercial chemical class called aminimides which act as isocyanate precursors, eliminating the problem of by-product phenol from the use of phenol-blocked isocyanates (see Fig. 8.10). 

Phenols are used as blocking agents in wire coatings. Phenol blocked isocyanates react with amines at room temperatin-e. They are used as flexibilizing reactive additives in amine cured epoxy coatings (131). 

Conunercially available blocked isocyanates have included Hylene MP from duPont (XXI) " which is phenol-blocked MDI Mon-dur S (XXII), a phenol-blocked TDI adduct Mondur SH (XXIII), a cresol-blocked TDI tiimer and Experimental E-320 blocked isocyanate (XXIV), a ketoxime-blocked tetraisocyanate, all from Mobay and Isonate 123P (XXV)" which is -caprolactam-blocked PAPI from the Upjohn Company. The Ashland Chemical Company has marketed a conuner-cial chemical class called aminimides which act as isocyanate precursors, eliminating the problem of by-product phenol from the use of phenol-blocked isocyanates.Their chemistry relevant to this use, is as follows ... 

Isocyanates form addition products reversibly with compounds which contain moderately reactive hydrogen, such as phenol, oximes, lactams and malonates. Fig. 14 is an example of a typical blocking-unblocking reaction. These addition compounds, called blocked isocyanates, are stable to water. They have been used in place of free isocyanate. The phenol-blocked isocyanates are the most common. In 1957 the DuPont Co. developed an aqueous dip based on blocked isocyanate. This process, called D-417, used phenol-blocked methylene bis(4-phenyl isocyanate) and a water soluble epoxide, the reaction product of glycerine and epichlorohydrin. RFL is used as the topcoat or second step dip ... 

One-part polyurethane adhesives can also correspond to prepolymers with isocyanate functions blocked reversibly (due to reaction with oximes, phenols, etc.). The isocyanate groups are then regenerated, either by heating to a more or less high temperature, or by substitution of the blocking agent by a diol (oligomer, at least partly) (O Fig. 14.18). 

Developments in aliphatic isocyanates include the synthesis of polymeric aliphatic isocyanates and masked or blocked diisocyanates for appflcafions in which volatility or reactivity ate of concern. Polymeric aliphatic isocyanates ate made by copolymerizing methacrylic acid derivatives, such as 2-isocyanatoethyl methacrylate, and styrene [100-42-5] (100). Blocked isocyanates ate prepared via the reaction of the isocyanate with an active hydrogen compound, such as S-caprolactam, phenol [108-95-2] or acetone oxime. 

A large number of hindered phenoHc antioxidants are based on the Michael addition of 2,6-di-/ f2 -butylphenol and methyl acrylate under basic catalysis to yield the hydrocinnamate which is a basic building block used in the production of octadecyl 3-(3,5-di-/ f2 butyl-4-hydroxyphenyl)propionate, [2082-79-3], tetrakis(methylene-3(3,5-di-/ f2 butyl-4-hydroxylphenyl)propionate)methane [6683-19-8], and many others (63,64). These hindered phenolic antioxidants are the most widely used primary stabilizers in the world and are used in polyolefins, synthetic and natural mbber, styrenics, vinyl polymers, and engineering resins. 2,6-Di-/ f2 -butylphenol is converted to a methylene isocyanate which is trimerized to a triazine derivative... 

One-part urethane sealants (Table 3) are more compHcated to formulate on account of an undesirable side reaction between the prepolymer s isocyanate end and water vapor which generates carbon dioxide. If this occurs, the sealant may develop voids or bubbles. One way to avoid this reaction is to block the isocyanate end with phenol and use a diketamine to initiate cure. Once exposed to moisture, the diketamine forms a diamine and a ketone. The diamine reacts with the isocyanate end on the prepolymer, creating a cross-link (10). Other blocking agents, such as ethyl malonate, are also used (11). Catalysts commonly used in urethane formulations are tin carboxylates and bismuth salts. Mercury salt catalysts were popular in early formulations, but have been replaced by tin and bismuth compounds. 

Masked or blocked diisocyanates are used in coatings applications. The blocked diisocyanates are storage-stable, nonvolatile, and easy to use in powder coatings. Blocked isocyanates are produced by reaction of the diisocyanate with blocking agents such as caprolactam, 3,5-dimethylpyrazole, phenols, oximes, acetoacetates, or malonates. 

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