Aqueous suspensions of fine-particulate fillers, method for the manufacture thereof and use thereof for the manufacture of papers containing fillers
An aqueous slurry of finely divided fillers which are at least partly coated with anionic latices, wherein the slurry is obtainable by treating an aqueous slurry of finely divided fillers with an aqueous dispersion comprising at least one anionic latex and at least one degraded starch, preparation of the aqueous slurries and their use as an additive to the paper stock in the production of filler-containing paper, filler-containing cardboard or filler-containing board by draining the paper stock.
1. An aqueous slurry of finely divided fillers which are at least partly coated with anionic latices, wherein the slurry is obtained by a process comprising treating an aqueous slurry of finely divided fillers with an aqueous dispersion comprising at least one anionic latex and at least one degraded starch,
wherein said at least one anionic latex comprises at least one monomer comprising phosphoric acid groups incorporated in the form of polymerized units.
2. The aqueous slurry according to claim 1 , wherein the glass transition temperature of the anionic latex is in the range of −50 to +10° C.
3. The aqueous slurry according to claim 1 , wherein the monomer which comprises phosphoric acid groups is obtained by a process comprising esterifying a monoethylenically unsaturated C 3 -C 8 -carboxylic acid with optionally a monoalkoxylated phosphoric acid of the general Formula (I)
H—[X] n —P(O)(OH) 2 (I)
in which
X is a straight-chain or branched C 2 -C 6 -alkylene oxide unit and
n is an integer from 0 to 20.
4. The aqueous slurry according to claim 3 , wherein monoalkoxylated phosphoric acid of the Formula (I), in which X is a straight-chain or branched C 2 -C 3 -alkylene oxide unit and n is an integer from 5 to 15, is present in the esterification.
5. The aqueous slurry according to claim 3 , wherein mixtures of monoalkoxylated phosphoric acid of the Formula (I) having from 5 to 15 units of propylene oxide are present in the esterification.
6. The aqueous slurry according to claim 3 , wherein the monoethylenically unsaturated C 3 -C 8 -carboxylic acid is acrylic acid, methacrylic acid, dimethylacrylic acid, ethacrylic acid, maleic acid, citraconic acid, methylenemalonic acid, crotonic acid, fumaric acid, mesaconic acid and/or itaconic acid.
7. The aqueous slurry according to claim 6 , wherein the monoethylenically unsaturated C 3 -C 8 -carboxylic acid is acrylic acid or methacrylic acid.
8. The aqueous slurry according to claim 3 , wherein the anionic latices consist of
(1) styrene and/or acrylonitrile or methacrylonitrile,
(2) acrylates and/or methacrylates of C 1 - to C 10 -alcohols and optionally
(3) acrylic acid, methacrylic acid, maleic acid and/or itaconic acid and
(4) (meth)acrylates of optionally monoalkoxylated phosphoric acids of the Formula (I), in which X and n have the abovementioned meaning.
9. The aqueous slurry according to claim 8 , wherein the anionic latices consist of 2-25% by weight of styrene, 2-25% by weight of acrylonitrile, 50-95% by weight of C 1 -C 4 -alkyl acrylates, 0-5% by weight of acrylic acid and 0.1-5% by weight of (meth)acrylates of monoalkoxylated phosphoric acids of the Formula (I), in which X is a propylene oxide unit and n is an integer of from 5 to 15.
10. The aqueous slurry according to claim 1 , wherein the degraded starch has an average molecular weight Mw of from 1000 to 65 000.
11. The aqueous slurry according to claim 10 , wherein the degraded starch is a maltodextrin.
12. The aqueous slurry according to claim 1 , which comprises from 1 to 70% by weight of at least one finely divided filler and from 0.01 to 10% by weight of said at least one anionic latex and said at least one degraded starch, based on the filler.
13. A process for the preparation of an aqueous slurry according to claim 1 , comprising adding an aqueous dispersion comprising from 0.01 to 10% by weight of at least one anionic latex and at least one degraded starch, based on the filler, to an aqueous slurry of at least one finely divided filler, or mixing the aqueous slurry of a finely divided filler into an aqueous dispersion comprising at least one anionic latex and at least one degraded starch, or mixing the finely divided filler in solid form into an aqueous dispersion comprising at least one anionic latex and at least one degraded starch.
14. An additive to the paper stock in the production of filler-containing paper, filler-containing cardboard or filler-containing board by draining the paper stock, comprising the aqueous slurry according to claim 1 .
15. The aqueous slurry according to claim 1 , wherein a ratio of anionic latex to degraded starch is from 30:1 to 1:1.
16. The aqueous slurry according to claim 1 , wherein a ratio of anionic latex to degraded starch is from 10:1 to 1:1.
17. The aqueous slurry according to claim 1 , wherein a ratio of anionic latex to degraded starch is from 5:1 to 1:1.