[article]
| Titre : |
Rapid-set, waterborne coatings from polyzwitterionic polymers formulated with a critical solvent combination |
| Type de document : |
texte imprimé |
| Auteurs : |
D. L. Schmidt, Auteur ; G. D. Rose, Auteur ; R. D. Mussell, Auteur |
| Année de publication : |
2003 |
| Article en page(s) : |
p. 59-64 |
| Note générale : |
Bibliogr. |
| Langues : |
Américain (ame) |
| Tags : |
Feuil Peinturage Coacervation Interpolymère Vinylique dérivé polymère Solvant Ion amphotère Polyélectrolyte Liant Formulation Peinture eau |
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
Waterborne coatings that rapidly set and become tack-free can be prepared from polymers containing both pendant anionic (acidic) and cationic functionality. This phenomenon is related to anion-cation interactions that function as ionic cross-links and dramatically enhance the physical properties and water resistance of the coatings. We define this process as “controlled ionic-coacervation,” which is a controlled aggregation of soluble polymer molecules without precipitation to yield clear, rapid-set films. The best coating properties can only be obtained by using a “critical solvent combination.” This coacervation process appears to function only with those polymers containing both anionic and cationic functionality. The critical solvent combination requires water plus at least two other organic solvents: (a) a lower boiling (70° to 134°C) water-soluble organic solvent having at least one hydroxyl group and (b) a higher boiling (135 to about 250°C) organic solvent. Loss of only a small amount of solvent from a recently applied coating formulation causes the coating to rapidly become tack-free. Drying times can be further reduced by immersion in water shortly after the coatings become tack-free. Quaternary ammonium groups furnish the cationic functionality and the anionic functionality is either weak-acid groups, such as carboxylate, or strong-acid groups such as sulfonate. Polyzwitterionic type polymers that have carboxylic acid functionality are cationic (and soluble) at low pH because the weak acid is protonated. Increasing the pH yields anionic carboxylate groups that produce anion-cationic interchain interactions and insolubility. Dissolved carbon dioxide can keep the pH low enough to prevent carboxylate formation. Consequently, controlled evolution of carbon dioxide during the coating process yields rapid-set coatings. |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5582 |
in JOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 75, N° 941 (06/2003) . - p. 59-64
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