Vanillin as low-temperature isocyanate-blocking agent and its use in one-component aqueous coatings / Philipp Knospe in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 20, N° 2 (03/2023)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 20, N° 2 (03/2023) . - p. 501-520 Titre : Vanillin as low-temperature isocyanate-blocking agent and its use in one-component aqueous coatings Type de document : texte imprimé Auteurs : Philipp Knospe, Auteur ; René Reichmann, Auteur ; Jochen S. Gutmann, Auteur ; Michael Dornbusch, Auteur Année de publication : 2023 Article en page(s) : p. 501-520 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Agents de blocages Analyse thermomécanique dynamique Déblocage Dispersions et suspensions Durée de vie (Ingénierie) Formulation (Génie chimique) Liants en phase aqueuse Polyisocyanates Revêtements en phase aqueuse Trimères En chimie, un trimère est un objet moléculaire ou une structure composée de l'association de 3 éléments de base semblables entre eux. C'est un composé chimique issu de la réaction entre trois molécules identiques (appelées monomères). La réaction chimique qui produit des trimères est appelée trimérisation. Vanilline Index. décimale : 667.9 Revêtements et enduits Résumé : Mainly because of the high sensitivity of the isocyanate group to atmospheric moisture, it is blocked with a blocking agent for many applications and thus kept as inert as possible at room temperature (Zhang et al. in Langmuir ACS J Surf Colloids 37:12705, 2021, Meier-Westhues in Polyurethane: Lacke, Kleb-und Dichtstoffe, Vincentz Network, Hannover, p 36, 2007). When exposed to temperature, the protective group unblocks, and the isocyanate group reacts with the reactant that was previously present together with the blocked isocyanate (Meier-Westhues in Polyurethane: Lacke, Kleb- und Dichtstoffe, Vincentz Network, Hannover, p 36, 2007, Goldschmidt and Streitberger in BASF handbook on basics of coating technology, Vincentz Network, Hannover, pp 96–99, 2007). Many of the substances which are used today as blocking agents have toxicological concerns or unblock at high temperatures, which limits their application areas (Guillem Parra et al. in Blocked isocyanate polyurethane compositions using a new blocking agent, method of manufacture and uses thereof: European patent application, 2019, https://data.epo.org/publication-server/document?iDocId=6506253&iFormat=0). In this work, vanillin is presented as an effective deblocking agent at low temperatures and is compared with similar structures. The process of deblocking from an hexamethylene diisocyanate trimer (HDI-trimer) is followed by means of IR-spectroscopic measurements at different temperatures and thermogravimetric analysis. Temperature-dependent oscillation measurements using a rheometer are suitable for measuring onset temperatures and for qualitatively tracking the unblocking process. The combination of the results is used to draw conclusions about the existing deblocking mechanism. The comparatively low deblocking temperature of vanillin enables the formulation of an HDI-trimer modified with sulfonate groups and blocked with vanillin, which is dispersed in the aqueous phase and then reacted with OH-functional binders. Deblocking and subsequent reaction with the binder are followed by means of IR spectroscopy, and the mechanical properties of the coating films are examined. Vanillin is therefore suitable as a toxicologically harmless blocking agent for isocyanates and enables the production of crosslinkers for one-component water-based coatings (Arya et al. Adv Tradit Med (ADTM) 21:1, 2021). Note de contenu : - Raw materials - Analytical methods - Synthesis of the compounds : 4-(Hydroxymethyl)benzaldehyde - Vanillin-Na-4-HBS-trimer - Application testing - Table 1 : Mean values of deblocking temperatures from selected blocking agents - Table 2 : Formulations for the reaction between vanillin-Na-4-HBS-trimer and different water-based binders - Table 3 : Coating properties of reaction of vanillin-Na-4-HBS-trimer with different water-based binders DOI : https://doi.org/10.1007/s11998-022-00696-w En ligne : https://link.springer.com/content/pdf/10.1007/s11998-022-00696-w.pdf?pdf=button% [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39294 [article]

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