Method for encapsulating water-insoluble particles
AssigneeThe Harshaw Chemical Company
InventorClifford C. Hayman
Life of this patent
Estimating the term…
Abstract
An improved method for encapsulating water-insoluble particles, particularly pigments, with dense, amorphous aluminum phosphate or fluorophosphate is disclosed. The capsules are formed in situ in an aqueous dispersion of the substrate by complexing aluminum and/or magnesium ion with phosphoric or fluorophosphoric acid, preferably in the presence of either boric acid or fluoride or complex fluoro ions. The encapsulation method comprises continuously adding separate solutions of the reactants into the dispersion over a 0.5 to 5.0 hour period, at 70.degree. to 100.degree. C., whereby a complex phosphate or fluorophosphate is deposited around the particles in the form of continuous, adherent microcapsules. The chemical, thermal and light stability of the substrate is thereby improved.
Claims10
The method for encapsulating a solid particulate substrate comprising continuously adding to an aqueous dispersion of a water-insoluble particulate substrate at 70.degree. to 100.degree. C. separate aqueous solutions of:
- (a) metal ions selected from the group consisting of aluminum and magnesium, said ions being added as lower alkyl carboxylates and/or halogen-substituted lower alkyl carboxylates,
- (b) phosphate anions added as acids selected from the group consisting of orthophosphoric acid, monofluorophosphoric acid and difluorophosphoric acid, at least some of the phosphate present in the form of a hydroxy aluminum phosphate boric acid complex, and, optionally,
- (c) anions selected from the group consisting of boric acid, fluoride, fluoborate and hexafluorophosphate anions, the molar proportions of (a), (b) and (c) being in the range of 0.8:1.0:0.0 to 1.4:1.0:10.0, and other anions and cations in or added to said dispersion being such as not to react with said substrate and not to interfere with the formulation of insoluble metal phosphate complexes of (a) and (b).
Dependencies are inferred from the claim text.