초록

A process for preparing an aqueous dispersion of composite particles composed of addition polymer and finely divided inorganic solid is described.

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We claim: 1. A process for preparing an aqueous dispersion of particles, said particles comprising at least one addition polymer and at least one finely divided inorganic solid, said process comprising dispersing at least one ethylenically unsaturated monomer in an aqueous medium and polymerizing t

We claim: 1. A process for preparing an aqueous dispersion of particles, said particles comprising at least one addition polymer and at least one finely divided inorganic solid, said process comprising dispersing at least one ethylenically unsaturated monomer in an aqueous medium and polymerizing the monomer by free-radical aqueous emulsion polymerization with at least one free-radical polymerization initiator in the presence of at least one dispersely distributed, finely divided inorganic solid and at least one of each of an anionic, cationic and nonionic dispersant, wherein a) the at least one finely divided inorganic solid is present as a stable aqueous dispersion that when prepared at an original solids concentration of ≧1% by weight, based on the aqueous dispersion of said at least one finely divided inorganic solid, the dispersion contains in dispersed form one hour after preparation more than 90% by weight of the originally dispersed finely divided inorganic solid and the dispersed finely divided inorganic solid particles have a diameter ≦100 nm, and b) the dispersed particles of said at least one inorganic solid exhibit a nonzero electrophoretic mobility in an aqueous standard potassium chloride solution at a pH which corresponds to the pH of the aqueous reaction medium before the addition of the anionic, cationic or nonionic dispersants, said process further comprising c) adding at least one of each of an anionic, cationic and nonionic dispersant to the aqueous dispersion of the finely divided inorganic solid before beginning dispersing said at least one ethylenically unsaturated monomer therein, d) then adding from 0.01 to 30% by weight of the total amount of said at least one monomer to the aqueous dispersion and polymerizing to a conversion of at least 90%, and e) thereafter adding the remainder of said at least one monomer under polymerization conditions at the rate at which it is consumed. 2. The process as claimed in claim 1, wherein from 1 to 1000 parts by weight of said at least one finely divided inorganic solid are present per 100 parts by weight of said at least one ethylenically unsaturated monomer, said process further comprising a) adding from 0.01 to 10 parts by weight of at least one cationic dispersant, from 0.01 to 100 parts by weight of at least one nonionic dispersant, and at least one anionic dispersant in an equivalent ratio of anionic to cationic dispersant of more than 1 when the dispersed solid particles have an electrophoretic mobility having a negative sign, or b) adding from 0.01 to 10 parts by weight of at least one anionic dispersant, from 0.01 to 100 parts by weight of at least one nonionic dispersant, and at least one cationic dispersant in an equivalent ratio of cationic to anionic dispersant of more than 1 when the dispersed solid particles have an electrophoretic mobility having a positive sign. 3. The process as claimed in claim 2, wherein a) in the presence of dispersed solid particles having an electrophoretic mobility having a negative sign, some or all of said at least one anionic dispersant is replaced by the equivalent amount of at least one monomer A containing at least one acid group and/or its corresponding anion, and b) in the presence of dispersed solid particles having an electrophoretic mobility having a positive sign, some or all of said at least one cationic dispersant is replaced by the equivalent amount of at least one monomer B containing at least one amino, amido, ureido or N-heterocyclic group and/or the N-protonated or N-alkylated ammonium derivatives thereof. 4. The process as claimed in claim 1, wherein said at least one nonionic dispersant is added before said at least one cationic and anionic dispersant. 5. The process as claimed in claim 1, wherein said at least one inorganic solid is selected from the group consisting of silicon dioxide, aluminum oxide, hydroxyaluminum oxide, calcium carbonate, magnesium carbonate, calcium orthophosphate, magnesium orthophosphate, iron(II) oxide, iron(III) oxide, iron(II/III) oxide, tin(IV) oxide, cerium(IV) oxide, yttrium(III) oxide, titanium dioxide, hydroxyapatite, zinc oxide, and zinc sulfide. 6. The process as claimed in claim 1, wherein said at least one inorganic solid is a silicon dioxide sol which has an electrophoretic mobility having a negative sign. 7. The process as claimed in claim 1, wherein the total amount of said at least one monomer added to the aqueous dispersion ranges from 0.5 to 20% by weight. 8. The process as claimed in claim 7, wherein the total amount of said at least one monomer ranges from 1 to 10% by weight. 9. The process as claimed in claim 1, wherein the finely dispersed inorganic solid particles have a diameter of >0 nm to ≦90 nm. 10. The process as claimed in claim 9, wherein the finely dispersed inorganic solid particles have a diameter of >0 nm to ≦80 nm. 11. The process as claimed in claim 1, wherein the initial concentration of finely divided inorganic solids is ≦60% by weight. 12. The process as claimed in claim 11, wherein the initial concentration of finely divided inorganic solids is ≦55% by weight. 13. The process as claimed in claim 2, wherein, when the dispersed solid particles have an electrophoretic mobility having a negative sign, the amount of said at least one cationic dispersant added ranges from 0.05 to 5 parts by weight, and the amount of said at least one nonionic dispersant ranges from 0.05 to 50 parts by weight, and when the dispersed solid particles have an electrophoretic mobility having a positive sign, the amount of said at least one anionic dispersant added ranges from 0.05 to 5 parts by weight, and the amount of said at least one nonionic dispersant ranges from 0.05 to 50 parts by weight. 14. The process as claimed in claim 13, wherein, when the dispersed solid particles have an electrophoretic mobility having a negative sign, the amount of said at least one cationic dispersant added ranges from 0.1 to 3 parts by weight, and the amount of said at least one nonionic dispersant ranges from 0.1 to 20 parts by weight, and when the dispersed solid particles have an electrophoretic mobility having a positive sign, the amount of said at least one anionic dispersant added ranges from 0.1 to 3 parts by weight, and the amount of said at least one nonionic dispersant ranges from 0.1 to 20 parts by weight. 15. An aqueous dispersion of composite particles obtained by the process as claimed in claim 1. 16. A composite-particle powder obtained by drying the aqueous dispersion of composite particles, as claimed in claim 15. 17. A method comprising applying a composition comprising the aqueous dispersion of composite particles as claimed in claim 15 on a substrate to form a protective coat or an adhesive.