Composition and media
View Patent ↗A coating composition comprising pigment, medium and a binder characterised in that (i) the binder comprises a cationic polymer comprising a repeat unit of Formula (1): wherein: X and Y are the same or different and represent divalent organic linking groups; and (ii) the weight ratio of pigment to binder in the composition is at least 2:1. The compositions are useful for preparing ink jet recording materials with good water resistance, print quality and dry time.
1. A coating composition comprising pigment, medium and a binder characterised in that (i) the binder comprises a cationic polymer comprising a repeat unit of Formula (1):
wherein:
X and Y are the same or different and represent divalent organic linking groups;
and (ii) the weight ratio of pigment to binder in the composition is at least 4:1 and the pigment has a BET surface area greater than 25 m 2 /g.
2. A composition according to claim 1 wherein the weight ratio of pigment to binder in the composition is at least 4:1 and has an upper limit of 10:1.
3. A composition according to claim 1 or claim 2 wherein the binder comprises a cationic polymer comprising a repeat unit of Formula (1) and one or more further binders.
4. A composition according to claim 1 or 2 wherein the pigment comprises alumina or surface modified silica or a mixture thereof.
5. A composition according to claim 1 or 2 wherein the medium is a liquid and comprises water or a mixture of water and one or more water-soluble organic solvent(s).
6. A composition according to claim 1 or 2 wherein the cationic polymer is a polymeric biguanide consisting essentially, excluding the terminating groups, of repeat units of Formula (2) and salts thereof:
wherein:
n is from 2to 100.
7. A porous coating composition according to claim 6 which comprises:
(a) 0.5 to 25 parts of a binder comprising 0.5 to 15 parts of a cationic polymer comprising a repeat unit of Formula (2) and 5 to 24.5 parts of a further binder comprising polyvinylalcohol, methylcellulose, polyvinylpyrrolidone, or any combination thereof;
(b) from 7.5 to 50 parts of porous pigment;
(c) 4.0 to 90 parts of a liquid medium comprising from 0 to 10 parts of water-soluble organic solvent and from 40 to 80 parts water;
wherein all parts are by weight, the total number of parts (a)+(b)+(c)=100.
8. A coating composition according to claim 1 or 2 which comprises:
(a) 0.5 to 25 parts of a binder comprising 0.5 to 15 parts of a cationic polymer comprising a repeat unit of Formula (1) and 0 to 24.5 parts of a further binder,
(b) 7.5 to 50 parts of pigment; and
(c) 1 to 90 parts of a liquid medium comprising a mixture of water and organic solvent;
wherein all parts are by weight, the total number of parts (a)+(b)+(c)=100.
9. A recording material obtained from applying a composition as defined in claim 1 or 2 to a substrate.
10. A recording material according to claim 9 wherein the substrate is plain paper, treated paper or a transparent plastic film.
11. An ink-jet printing process that comprises applying an ink to a recording material defined in claim 10 by means of an ink-jet printer.
12. A composition according to claim 1 wherein the weight ratio of pigment to binder in the composition is at least 5:1.
13. A composition according to claim 1 wherein the weight ratio of pigment to binder in the composition is at least 6:1.