Method of lithographic printing with a reusable substrate

1. Direct-to-plate method of lithographic printing with a reusable substrate having a hydrophilic surface comprising the steps of:

(a) making a negative-working imaging layer by coating on the hydrophilic surface a solution comprising hydrophobic thermoplastic particles and a hydrophilic binder;

(b) making a printing master having ink-accepting areas by image-wise exposing the imaging layer to heat or light;

(c) applying ink and fountain solution to the printing master;

(d) removing the ink-accepting areas from the printing master by supplying a micro-emulsion comvrising a mixture of a cyclic organic compound containing at least one double bond, an alcohol, water and an emulsifying agent to the imaging layer; and

(e) treating the micro-emulsion according to a method comprising:

( 1 ) heating the micro-emulsion to a temperature of about 50° C. or higher thereby obtaining an aqueous phase and an organic phase, and

( 2 ) separating the aqueous phase from the organic phase.

2. Direct-to-plate method according to claim 1 comprising the additional step (f) wherein the aqueous phase is used for preparing a fresh micro-emulsion or for rinsing the substrate after step (d) or before step (a).

3. Method according to claim 1 , wherein the cyclic organic compound is dipentene.

4. Method according to claim 2 , wherein the alcohol is an aliphatic alcoholether.

5. Method according to claim 4 wherein the aliphatic alcoholether is butoxyethanol.

6. Method according to claim 4 , wherein the cyclic organic compound is dipentene.

7. Method according to claim 6 , wherein the aliphatic alcoholether is butoxethanol.

8. Method according to claim 7 , wherein the emulsifying agent is an anionic compound.

9. Method according to claim 8 , wherein the emulsifying compound comprises an ailcylene-oxide chain.

10. Method according to claim 9 , wherein the micro-emulsion further comprises a compound according to formula I:

11. Direct-to-plate method according to claim 9 comprising the additional step (f), wherein the aqueous phase is used for preparing a fresh micro-emulsion or for rinsing the substrate after step (d) or before step (a).

12. Method according to claim 11 , wherein the reusable substrate is a plate cylinder of a rotary press or a plate or sleeve mounted on a plate cylinder of a rotary press.

13. Method according to claim 6 , wherein the emulsifying agent is an anionic compound.

14. Method according to claim 1 , wherein the emulsifying agent is an anionic compound.

15. Method according to claim 1 , wherein the emulsifying agent comprises an alkylene-oxide chain.

16. Method according to claim 1 , wherein the micro-emulsion further comprises a compound according to formula I:

wherein X is OH, O − or a polymer backbone.

17. Method according to claim 1 wherein the reusable substrate is a plate cylinder of a rotary press or a plate or sleeve mounted on a plate cylinder of a rotary press.

18. Method according to claim 1 wherein the solution or the micro-emulsion is sprayed or jetted onto the substrate.

19. Method for treating a micro-emulsion comprising a mixture of cyclic organic compound containing at least one double bond, an alcohol, water and an emulsifying agent, the method comprising the steps of:

(1) heating the micro-emulsion to a temperature above 50° C. thereby obtaining an aqueous phase and an organic phase and

(2) separating the aqueous phase from the organic phase and wherein the micro-emulsion further comprises a compound according to formula I: