Process for ink jet printing

1. An ink-jet printing process comprising the steps (a) and (b) in any order or simultaneously:

(a) applying an ink by means of an ink jet printer to a localised region of a substrate to form an image on the substrate; and

(b) applying a fixing composition comprising a liquid medium and a polymeric biguanide comprising a repeat unit of Formula (1) or a salt thereof by means of an ink jet printer to a localised region of the substrate:

wherein:

X and Y are the same or different and represent divalent organic linking groups; and characterised in that the localised regions referred to in steps (a) and (b) are substantially coextensive and wherein the fixing composition in step (b) is free from binders.

2. A process according to claim 1 wherein X and Y are independently each C 4-8 -alkylene.

3. A process according to claim 1 wherein X and Y are both hexylene.

4. A process according to claim 1 wherein the polymeric biguanide comprises one or more poly(hexamethylene biguanide) polymer chains in which the individual polymer chains, excluding the terminating groups, are of Formula (2) and salts thereof:

wherein:

n is from 2 to 40.

5. A process according to claim 1 which is free from steps in which the dye is removed from the substrate after printing.

6. A process according to claim 1 wherein the ink-jet printer is of the ‘five pen’ type in which yellow, magenta, cyan and black are applied by four pens and the fixing composition is applied by a fifth pen.

7. A process according to claim 1 wherein in a drop of ink applied in step (a) either before, after or simultaneously with the fixing composition applied in step (b) lies within the boundaries of the spread drop of the fixing composition.

8. A process according to claim 1 wherein the fixing composition in step (b) comprises:

(a) from 0.1 to 10 parts of a polymeric biguanide;

(b) from 10 to 60 parts of a water-soluble organic solvent; and

(c) from 35 to 85 parts water;

wherein all parts are by weight and the total number of parts (a)+(b)+(c)=100.

9. A process according to claim 1 wherein the fixing composition in step (b) is free from materials having a boiling point above 200° C. at atmospheric pressure other than the biguanide.

10. A substrate printed with an image by means of a process according to claim 1 .

11. A fixing composition comprising an aqueous medium and a polymeric biguanide as described in claim 1 , characterised in that the composition is free from binder, has been filtered through a filter having a mean pore size below 10 μm and contains less than 500 ppm total of divalent and trivalent metal ions.

12. A set of liquids suitable for use in an ink-jet printer comprising:

(a) a first liquid which is an ink comprising a colorant and a liquid medium; and

(b) a second liquid which is a fixing composition comprising:

(i) 0.01 to 50 parts of a polymeric biguanide comprising a repeat limit of Formula (1) or a salt thereof

wherein:

 X and Y are the same or different and represent divalent organic linking groups; and

(ii) 50 to 99.8 parts of a liquid;

wherein all parts are by weight and the total number of parts (i)+(ii)=100; and characterised in that the second liquid is free from binders.

13. An ink-jet printer cartridge comprising a plurality of chambers and a set of liquids, wherein the liquids are contained in individual chambers of the ink-jet printer cartridge and the set of liquids is according to claim 12 .

14. An ink-jet printer cartridge comprising a plurality of chambers and a fixing composition, wherein the fixing composition is contained in the chamber of the ink-jet printer cartridge and the fixing composition comprises a liquid medium and a polymeric biguanide comprising a repeat unit of Formula (1) or a salt thereof;

wherein:

X and Y are the same or different and represent divalent organic linking groups; and the fixing composition is free from binders.

15. An ink-jet printing process according to claim 1 wherein the ink is not applied to a significantly larger area than the fixing composition and the fixing composition is not applied to a significantly larger area than the ink.

16. An ink-jet printing process according to claim 1 wherein the localised regions referred to in steps (a) and (b) are coextensive to the extent of at least 80% of the total area printed with the ink and fixing composition.

17. An ink-jet printing process according to claim 1 which is such that the fixing composition is applied only to the region where the ink forms an image.