Phenol blocking

Hyperbranched polyurethanes are constmcted using phenol-blocked trifunctional monomers in combination with 4-methylbenzyl alcohol for end capping (11). Polyurethane interpenetrating polymer networks (IPNs) are mixtures of two cross-linked polymer networks, prepared by latex blending, sequential polymerization, or simultaneous polymerization. IPNs have improved mechanical properties, as weU as thermal stabiHties, compared to the single cross-linked polymers. In pseudo-IPNs, only one of the involved polymers is cross-linked. Numerous polymers are involved in the formation of polyurethane-derived IPNs (12). 

Fig. 6. Curing temperature of phenol-blocked TDI, catalyzed and uncatalyzed.

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.

The ketimine is an acetone-blocked diamine. The synthesis and applications of ketimines will be discussed later. The curing concept for the adhesive is shown in Fig. 7. Phenol-blocked prepolymers would normally unblock at approximately 150°C. However, an aliphatic diamine, generated by the hydrolysis of the ketimine to an aliphatic diamine and ketone as a result of exposure to the moisture in the air, is sufficient to cure the windshield adhesive at room temperature. 

Sulfonated or sulfomethylated lignins are reacted with phenol-blocking reagents, such as ethylene oxide, propylene oxide, or butylene oxide [1571]. 

Morgan RJ, Steller PH. 1994. Acute paraplegia following intrathecal phenol block in the presence of occult epidural malignancy. Anaesthesia 49 142-144. 

Oxidation of mixtures of 2,6-disubstituted phenols leads to linear poly(arylene oxides). Random copolymers are obtained by oxidizing mixtures of phenols. Block copolymers can be obtained only when redistribution of the first polymer by the second monomer is slower than polymerization of the second monomer. Oxidation of a mixture of 2,6-di-methylphenol (DM ) and 2fi-diphenylphenol (DPP) yields a random copolymer. Oxidation of DPP in the presence of preformed blocks of polymer from DMP produces either a random copolymer or a mixture of DMP homopolymer and extensively randomized copolymer. Oxidation of DMP in the presence of polymer from DPP yields the block copolymer. Polymer structure is determined by a combination of differential scanning calorimetry, selective precipitation from methylene chloride, and NMR spectroscopy. 

Yoshida E, Kunugi S (2002) Micelle formation of poly(vinyl phenol)-block-polystyrene by alpha, omega-diamines. J Polym Sci A Polym Chem 40 3063-3067... 

Petrillo CR, Knoploch S. Phenol block of the tibial nerve for spasticity a long-term follow-up study. Int Disabil Stud 1988 10(3) 97-100. 

Yadav SL, Singh U, Dureja GP, Singh KK, Chaturvedi S. Phenol block in the management of spastic cerebral paky. Indian J Pediatr 1994 61(3) 249-55. 

Garland DE, Tilling M, Keenan MA. Percutaneous phenol blocks to motor points of spastic forearm muscles in head-injured adults. Arch Phys Med Rehabil 1984 65(5) 243-5. 

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 ... 

Hirose M, Takahashi S, Ogawa K, Futakuchi M, Shirai T. Phenolics Blocking agents for heterocyclic amine-induced carcinogenesis. Food Chem Toxicol 1999 9-10 985-992. 

Similar to the previous formulation, the rheological properties are regulated with extensive use of fillers. Here, a typical combination of coarse, untreated limestone and special surface-treated calcium carbonate is used. This formulation also differs from the previous one in that it includes blocked polyisocyanurate which can react at elevated temperature after phenol blocking is removed by dissociation at elevated temperature. 

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 ... 

Chem. Descrip. Phenol-blocked polyisocyanate Uses Binder for wire enamels... 

If the para- substituent group R- (above) is an alkyl group of about four or more carbon atoms (e.g. tertiary butyl, (CH3)3 C-), the product is soluble in oils otherwise in alcohols, ether-alcohols or alcohol/aromatic hydrocarbon mixtures. If the resin is made from a phenol blocked in the para-position, with a high formaldehyde level and using an alkaline catalyst, it will react when heated with un-saturatcd materials, such as drying oils or rosin to produce a modified phenolic resin. The mechanism is thought to be of the type ... 

Poly(styrene-b-vinyl phenol) block copolymer... 

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). 

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