Process for making a cationic vinyl oligomer composition

1. A process for making an aqueous coating composition comprising a cationic vinyl oligomer comprising the following steps:

I. preparation of a cationic vinyl oligomer by solution or bulk polymerisation of components comprising:

i) 2 to 50 wt % of vinyl monomers bearing amine functional groups selected from the group consisting of non-ionic amine functional groups (a), permanent quaternary ammonium functional groups (b), neutralised amine functional groups (c) and mixtures thereof;

ii) 20 to 98 wt % of C 1 to C 18 alkyl (meth)acrylates;

iii) 0 to 30 wt % of styrene based monomers;

iv) 0 to 15 wt % of vinyl monomers bearing hydroxyl functional groups; and

v) 0 to 15 wt % of vinyl monomers different from those from i), ii), iii) and iv);

where i), ii), iii), iv) and v) add up to 100%; and

II. dispersion of the cationic vinyl oligomer in an aqueous medium and neutralisation of non-ionic amine functional groups.

2. A process according claim 1 comprising an additional step III, the preparation of a cationic vinyl oligomer-polymer by emulsion polymerisation of vinyl monomers in the presence of the dispersed cationic vinyl oligomer prepared in step II; and wherein the weight % of the cationic vinyl oligomer is 1 to 70 wt % based on the weight of the cationic vinyl oligomer-polymer.

3. A process according to claim 2 wherein step III comprises the emulsion polymerisation of components comprising:

i) 0 to 10 wt % of vinyl monomers bearing amine functional groups selected from the group consisting of non-ionic amine functional groups (a), permanent quaternary ammonium functional groups (b), neutralised amine functional groups (c) and mixtures thereof;

ii) 40 to 100 wt % of C 1 to C 18 alkyl (meth)acrylates;

iii) 0 to 30 wt % of styrene based monomers;

iv) 0 to 15 wt % of vinyl monomers bearing hydroxyl functional groups; and

v) 0 to 20 wt % of vinyl monomers different from those from i), ii), iii) and iv);

where i), ii), iii), iv) and v) add up to 100%.

4. A process according to claim 2 wherein the weight % of the cationic vinyl oligomer is 5 to 55 wt % based on the weight of the cationic vinyl oligomer-polymer.

5. A process according to claim 1 wherein the weight average molecular weight of the cationic vinyl oligomer is ≦80,000 g/mol.

6. A process according to claim 1 wherein the cationic vinyl oligomer is prepared by solution polymerisation.

7. A process according to claim 1 wherein the Tg of the cationic vinyl oligomer is in the range of from 30 to 100° C.

8. A process according to claim 2 wherein the Tg of the vinyl polymer is ≧30° C.

9. A process according to claim 2 wherein the cationic vinyl oligomer-polymer comprises less than 30 wt % of styrene based monomers based on the weight of the cationic vinyl oligomer-polymer.

10. A process according to claim 2 wherein the cationic vinyl oligomer-polymer comprises less than 15 wt % of hydroxyl functional monomers based on the weight of the cationic vinyl oligomer-polymer.

11. A process according to claim 1 wherein the aqueous coating composition comprises less than 1 wt % surfactant.

12. A process according to claim 1 wherein the cationic vinyl oligomer comprises in the range of from 0 to 5 wt % of vinyl monomers containing carboxylic acid functional groups.

13. A process according to claim 2 wherein the vinyl polymer comprises in the range of from 0 to 20 wt % of vinyl monomers containing carboxylic acid functional groups.

14. A substrate coated with an aqueous coating composition obtained from the process according to claim 1 .

15. A substrate coated with a primer coating comprising an aqueous coating composition obtained from the process according to claim 1 and at least one top coating.