Catalysis of the epoxy-carboxyl reaction / Werner J. Blank in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 74, N° 926 (03/2002)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 74, N° 926 (03/2002) . - p. 33-41 Titre : Catalysis of the epoxy-carboxyl reaction Type de document : texte imprimé Auteurs : Werner J. Blank, Auteur ; Marie E. Picci, Auteur Année de publication : 2002 Article en page(s) : p. 33-41 Note générale : Bibliogr. Langues : Américain (ame) Tags : 'Etude  expérimentale'  'Mécanisme  réaction'  'Activité  catalytique'  comparative'  'Catalyse  basique'  'Réaction  'Durcissement  matière  plastique'  'Acrylate  copolymère'  'Méthacrylate  'Résine  époxyde' Index. décimale : 667.9 Revêtements et enduits Résumé : We have investigated the reactions of glycidyl ether, glycidyl ester, and other oxirane functional resins with carboxyl or anhydride functional compounds and polymers in the presence of a wide range of amine, phosphonium, and metal catalysts. We confirmed that both amine and phosphonium compounds can catalyze the reaction of epoxy groups with carboxyl and anhydride groups. There are certain deficiencies with these catalysts, such as a tendency to yellow and a reduction in stability at ambient or elevated temperatures. We also observed that many of the known amine catalysts contribute to poorer humidity resistance and exterior durability. Several metal salts were found to be effective catalysts, but they also contributed to a reduction in chemical resistance or they led to paint instability. We have discovered a group of metal chelates that overcome these problems and provide stable formulations in a single package that do not yellow during cure and that give improved resistance properties. The new catalysts have been evaluated in high-solids epoxy/carboxyl coatings, automotive clearcoats, and powder coatings. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5670 [article]

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A selective catalyst for two-component waterborne polyurethane coatings / Z. Alex He in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 74, N° 930 (07/2002)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 74, N° 930 (07/2002) . - p. 31-36 Titre : A selective catalyst for two-component waterborne polyurethane coatings Type de document : texte imprimé Auteurs : Z. Alex He, Auteur ; Werner J. Blank, Auteur ; Marie E. Picci, Auteur Année de publication : 2002 Article en page(s) : p. 31-36 Note générale : Bibliogr. Langues : Américain (ame) Tags : Etude  expérimentale  Zirconium  Complexe  Catalyseur  Adjuvant  Formulation  Peinture  eau  Uréthanne  polymère  deux  constituants  Matériau  revêtement Index. décimale : 667.9 Revêtements et enduits Résumé : The potential for formulating low VOC, high performance, two-component waterborne isocyanate crosslinked coatings has generated a great deal of interest. The difficulties in formulating these coatings, however, are significant. A major problem associated with such systems is the isocyanate-water side reaction, which can lead to gassing/foaming, loss of isocyanate functionality, low gloss, and a reduced pot life. To compensate for this side reaction, these formulations usually contain a large excess of isocyanate. One novel approach to control the water side reaction is the use of catalysts which selectively catalyze the isocyanate-polyol reaction and not the isocyanate-water reaction. The selectivity of a variety of metal catalysts to catalyze the preferred reaction was measured using an FTIR method. A zirconium complex has shown unusually high selectivity for the isocyanate-polyol reaction in comparison to the standard dibutyltin dilaurate catalyst. This zirconium complex catalyst has been evaluated in several waterborne polyurethane formulations and has demonstrated less gassing/foaming, longer pot life, and higher gloss than dibutyltin dilaurate at equal cure time. The mechanism of catalysis and formulating techniques of this novel zirconium catalyst will be discussed. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5644 [article]

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