Thermoplastic polyurethanes catalysts

Thermoplastic polyurethane resins were also prepared by the author [2] from 4,4 -methylene diphenylisocyanate with poly(3,3-bis-(2,2,3,3,4,4,4-hepta-fluorobutoxymethyl)-co-3-(2,2,3,3,4,4,4-heptafluorobutoxymethyl)-3-methy-loxetane) using dibutyltin dilaurate as catalyst and used in low surface energy coating applications... 

Polyurethane pre-polymer or thermoplastic polyurethanes are prepared by the reaction of polyester or polyether diols with diisocyanates. The reaction can be conducted in bulk, in a solvent, or in an aqueous solution or dispersion. Unless the reaction is carried out at an elevated temperature a catalyst is required. Organotin compounds are the prime catalyst for this reaction. 

Published information on urethane polymerization detail largely concerns thermoset urethane elastomers systems.4 13 In particular, the work of Macosko et. al. is called to attention. The present paper supplements this literature with information on the full course of linear thermoplastic urethane elastomer formation conducted under random melt polymerization conditions in a slightly modified Brabender PlastiCorder reactor. Viscosity and temperature variations with time were continuously recorded and the effects of several relevant polymerization variables - temperature, composition, catalyst, stabilizer, macroglycol acid number, shortstop - are reported. The paper will also be seen to provide additional insight into the nature and behavior of thermoplastic polyurethane elastomers. 

Evolution of Nonlinear Rheology and Network Formation during Thermoplastic Polyurethane Polymerization Effects of Mixer Design, Mixing Protocol, Catalyst Concentration, and Timescales... 

Figure 2 Compression set (elastic recovery under compressive deformation) at 70 °C for an E-LAO random copolymer, flexible polyvinylchloride (f-PVC), thermoplastic polyurethanes (TPUs), and thermoplastic vulcanizates (TPVs). Reproduced with permission from Wenzel, T. T. Arriola, D. J. Carnahan, E. M. et at. In Metal Catalysts in Olefin Poiymerization. Topics in Organometallic Chemistiy, Guan, I., Ed. Springer-Verlag Berlin, Germany, 2009 Vol. 26. ...

Coating materials may be based on short or medium-oil alkyds (e.g. primers for door and window frames) nitrocellulose or thermoplastic acrylics (e.g. lacquers for paper or furniture finishes) amino resin-alkyd coatings, with or without nitrocellulose inclusions, but with a strong acid catalyst to promote low temperature cure (furniture finishes) two-pack polyurethanes (furniture, flat boards) unsaturated polyester resins in styrene with free-radical cure initiated by peroxides (furniture) or unsaturated acrylic oligomers and monomers cured by u.v. radiation or electron beams (coatings for record sleeves paperback covers, knock-down furniture or flush interior doors). 

The proper balance between viscosity and gas evolution can be controlled by a number of factors such as a suitable type and concentration of catalyst and surfactant, the presence of a nucleating agent (not always necessary) (17,18) and control of reaction temperature (or exotherm). Additional factors that must be considered are the use of a suitable chemical blowing agent, which is especially important for the production of thermoplastic foams, and the formation of oligomers (prepolymers) which exhibit higher viscosities than monomers in the preparation of thermoset foams (e.g. polyurethane foams). 

A versatile aryl phosphite which can be used as a stabilizer in many types of polymers including adhesives, styrenics, engineering thermoplastics, polyesters (to regulate viscosity and improve color stability), polyolefins (as a catalyst adjuvant), polyurethanes (to prevent scorching and improve color stability), coatings, epoxies, auid PVC where regulatory approval in food contact is not required. 

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