Cationically modified white pigments, their production and use
Cationically modified white pigments (W) in particulate form, essentially consisting of a particulate inorganic white pigment (M) of a particle size in the range of 0,1 to 40 μm and an applied water soluble, cationic, crosslinked polymer (P A ) containing quaternary ammonium groups in salt form, obtainable by reaction of epichlorohydrin or of epichlorohydrin derivatives or precursors with amines, under conditions leading to at least partial crosslinking, optionally in combination with an anionic optical brightener (B) and where the molar ratio of (B) to (P A ) is such that the number of cationic charges of the total polymer (P A ) is higher than the number of anionic charges of the total anionic optical brightener (B), are surprisingly useful as cationic white pigments in various fields of technique, especially in papermaking.
1. A cationically modified white pigment (W) in particulate form, consisting essentially of:
a particulate inorganic white pigment (M) of a particle size in the range of 0,1 to 40 μm;
an applied water soluble, cationic, crosslinked polymer (P A ) containing quaternary ammonium groups in salt form, where (P A ) is a polymer obtained by crosslinking with an at least bifunctional secondary or tertiary amine the chloroterminated reaction product of an oligofunctional aliphatic alcohol with epichlorohydrin and optionally further reacting any non reacted chlorine with a tertiary amine under conditions leading to at least partial crosslinking, in combination with
an anionic optical brightener (B) and where the molar ratio of (B) to (P A ) is such that the number of cationic charges of the total polymer (P A ) is higher than the number of anionic charges of the total anionic optical brightener (B).
2. Cationically modified white pigment (W) according to claim 1 , wherein (B) and (P A ) are employed in the form of a combination thereof, which
either is a mixture of (B) in free acid or alkali metal salt form and (P A ) in which the counter-ions to the cationic quaternary ammonium groups are anions of mineral acids, anions of low molecular carboxylic acids or anions deriving from a quaternizing agent, in which mixture the number of cationic charges of the polymer (P A ) is higher than the number of anionic charges of the anionic optical brightener (B),
or is a polycationic polymer (P AB ) which is a partial (B)-salt of (P A ), wherein a part of the counter-ions to the quaternary cationic groups of (P A ) are anionic groups of anionic optical brightener (B).
3. Cationically modified white pigment (W) according to claim 2 , wherein (P AB ) is a cationic polymer obtained by carrying out the crosslinking for the production of (P A ) in the presence of (B).
4. Cationically modified white pigment (W) according to claim 1 , in dry, pourable, particulate, optionally agglomerated, form, or in the form of an aqueous suspension.
5. Process for the production of a white pigment (W) according to claim 1 wherein (M) is admixed with an aqueous solution of (P A ) in combination with (B), substantially in the absence of other functional papermaking additives and paper fibres.
6. A method for the production of: a white mineral pigment or filler containing substrate or paper comprising the steps of:
providing a substrate;
providing a white mineral pigment or filler (W) as defined in claim 1 ; and
adding white pigment or filler (W) to said substrate.
7. Process for the production of paper containing a white, inorganic filler or pigment, wherein an optically brightened white pigment (W) according to claim 1 is employed as a white filler or pigment.
8. Aqueous composition containing (W) as defined in claim 1 .
9. Aqueous composition according to claim 8 , which is a paper coating paste.
10. A process for the production of coated paper, wherein an aqueous paper coating composition according to claim 9 is applied to a paper sheet and dried.
11. Process according to claim 7 , wherein (W) is used together with a cationic starch (C).
12. A (W)-containing substrate, produced according to claim 7 .
13. A white mineral pigment or filler containing substrate comprising cationically modified white pigment (W) as defined in claim 1 .
14. Paper comprising cationically modified white pigment (W) as defined in claim 1 .
15. Cationically modified white pigment (W) according to claim 1 , wherein the oligofunctional aliphatic alcohol is selected from hydroxy compounds of the following formula
X—(OH) x1 (Ia),
in which X signifies the x1-valent radical of a C 3-6 -alkane or of a corresponding cyclic ether
and x1 signifies a number from 3 to the number of carbon atoms in X,
or a mixture of oligohydroxyalkanes of formula (Ia),
or a mixture of one or more oligohydroxyalkanes of formula (Ia) with a C 2-3 -alkanediol.
16. A cationically modified white pigment (W 2 ′) in particulate form, consisting essentially of:
a particulate inorganic white pigment (M) of a particle size in the range of 0,1 to 40 μm;
an applied water soluble, cationic, crosslinked polymer (P A2 ′) containing quaternary ammonium groups in salt form, obtainable by reaction of a chloroterminated addition product of epichlorohydrin with an oligofunctional aliphatic alcohol selected from hydroxy compounds of the following formula
X—(OH) x1 (Ia),
in which X signifies the x1-valent radical of a C 3-6 -alkane or of a corresponding cyclic ether
and x1 signifies a number from 3 to the number of carbon atoms in X,
or a mixture of oligohydroxyalkanes of formula (Ia),
or a mixture of one or more oligohydroxyalkanes of formula (Ia) with a C 2-3 -alkanediol;
with
an at least bifunctional secondary or tertiary amine, under conditions leading to at least partial crosslinking, and optionally further reacting any non reacted chlorine with a tertiary amine.
17. The cationically modified white pigment (W 2 ′) according to claim 16 , in dry, pourable, particulate, optionally agglomerated, form, or in the form of an aqueous suspension.
18. Process for the production of a white pigment (W 2 ′) according to claim 16 , wherein (M) is admixed with an aqueous solution of (P A2 ′), substantially in the absence of other functional papermaking additives and paper fibres.
19. A method for the production of a white mineral pigment or filler containing substrate comprising the steps of
providing a substrate
providing a white mineral pigment or filler (W 2 ′) as defined in claim 16
applying (W 2 ′) to the substrate.
20. Process for the production of paper containing a white, inorganic filler or pigment, wherein a white pigment (W 2 ′) according to claim 19 is employed as a white filler or pigment.
21. Aqueous composition containing (W 2 ′) as defined in claim 16 .
22. Aqueous composition according to claim 21 , which is a paper coating paste.
23. A process for the production of coated paper, wherein an aqueous paper coating composition according to claim 22 is applied to a paper sheet and dried.
24. Process according to claim 20 , wherein (W 2 ′) is used together with a cationic starch (C).
25. A (W 2 ′)-containing substrate, produced according to claim 20 .