ISSN:
1435-1536
Schlagwort(e):
Key words Alkali swelling
;
Acrylic polymer dispersion
;
Ionic crosslinking
;
Ion exchange
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
Notizen:
Abstract The alkalization of carboxylated acrylic polymer latexes by sodium hydroxide gives rise to swelling of the particles. For a poly(n-butyl acrylate) latex copolymerized with 15 wt % methacrylic acid (MAA) and 7 wt % acrylonitrile the particle volume increases by a factor of 30. The alkali-swelling does not depend on the type of monovalent cation used in the base (LiOH, NaOH, KOH, NH4OH). In contrast, when bivalent cation bases such as Ca(OH)2 are employed no latex swelling is observed during neutralization because of ionic crosslinking of the copolymer chains. Crosslinking also takes place when the bivalent cations (Ca2+, Zn2+, Mg2+) are added as chlorides to dispersions with latexes previously swollen by sodium hydroxide. In these experiments the original size of the latexes is reached again at a molar ratio MAA: bivalent metal ion of 2:1, i.e. at charge compensation of the carboxyl groups. The shrinking behavior is almost independent of the type of bivalent metal ion used. On the other hand, it is more pronounced when trivalent cations such as Fe3+ are added. In general, the experiments demonstrate that the alkali swelling of acrylic latexes is dominated by electrostatic forces.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/s003960050394
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