C - Chemistry – Metallurgy – 09 – D
Patent
C - Chemistry, Metallurgy
09
D
400/6408, 117/47
C09D 5/00 (2006.01) C08F 2/22 (2006.01) C08F 265/04 (2006.01) C08F 291/00 (2006.01) C09D 7/12 (2006.01) C09D 151/00 (2006.01)
Patent
CA 1298013
ABSTRACT An aqueous dispersion of water-insoluble core-shell particles is prepared by emulsion polymerization for use as an opacifying agent in coatings. The particles have inter- ior cores which are swollen with nonaqueous solvent. The polymeric exterior shells have a glass transition tempera- ture greater than about 50°C in the presence of the non- aqueous solvent. The partition coefficient for the non- aqueous solvent between the interior core polymer phase and the exterior shell polymer phase is at least about 1.25. The interior core preferably has a low average molecular weight while the average molecular weight of the exterior shell is high. The interior core is preferably polymerized from ethylenically unsaturated monomers having low polarity and the core is swollen with a nonpolar solvent, such as an aliphatic hydrocarbon. The exterior shell is preferably polymerized from ethylenically unsaturated monomers having moderate to high polarity. Coatings compositions formulated using the core-shell particles show increased opacity, as single light scattering microvoids are formed in individual particles when the solvent evaporates and the core collapses inside the rigid exterior shell. Opacity develops even when aqueous coatings containing the particles are dried under high humidity conditions.
550038
Kowalski Alexander
Scott Joseph David
Vogel Martin
Gowling Lafleur Henderson Llp
Rohm And Haas Company
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