Composite particle dispersions
AssigneeImperial Chemical Industries PLC
InventorJulian A. Waters
Life of this patent
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Abstract
A composite particle dispersion is prepared by mixing an aqueous dispersion of polymer particles which will form the particle shell with pre-formed polymer particles which will form the core at a temperature above the glass transition temperature for the shell particles. In order to ensure composite particle formation, certain interfacial energy criteria have to be satisfied for the core particle surface/shell particle surface/liquid interfaces. In order to allow the desired energy relationships to be established, the core particle surfaces include covalently attached ionic groupings which enable a permanent modification of the core particle surface to be made.
Claims13
A process for preparing a stable aqueous dispersion of composite particles, which process comprises mixing an aqueous dispersion of first polymer particles, where the particle surfaces include covalently attached ionic groupings to give the particles colloidal stability prior to the mixing, with an aqueous colloidally stable dispersion of second polymer particles, and wherein the mixing takes place at a temperature above the operative glass transition temperature of the second polymer particles and under a condition where ##EQU4## Where .gamma..sub.1-3 is the interfacial energy of-the first polymer particle surface/aqueous liquid interface
- .gamma..sub.1-2 is the interfacial energy of the first polymer particle surface/second polymer particle interface
- .gamma..sub.2-3 is the interfacial energy of the second particle surface/aqueous liquid interface
- V.sub.p and V.sub.c represent the relative volumes of, respectively, the average second polymer particle and the average first polymer particle, with V.sub.p +V.sub.c =1
- and where the first polymer particles are able to make contact with the surfaces of the second polymer particles so that when contact occurs between first polymer particles and second polymer particles, composite particles are produced as a stable dispersion in the aqueous phase, the composite particles having colloidal stability.
Dependencies are inferred from the claim text.