IMPROVEMENTS IN THE CLEANING OF LIQUID SPRAY APPARATUS

1 . A method of cleaning a liquid spray apparatus for a coating liquid after use, the method comprising passing a water-based cleaning liquid through the liquid spray apparatus; wherein the cleaning liquid contains a thickener.

2 . A method as claimed in claim 1 , wherein the dynamic viscosity of the cleaning liquid is up to 50 dPa·s.

3 . A method as claimed in claim 1 , wherein the dynamic viscosity of the cleaning liquid is at least 1 dPa·s.

4 . A method as claimed in claim 1 , wherein the thickener is a non-associative thickener.

5 . A method as claimed in claim 4 , wherein the thickener is selected from a cellulosic thickener, an acrylic thickener, a starch based thickener, a gum, a clay, a modified ethylene vinyl acetate compound and a zirconium, acetate lactate oxo ammonium complex.

6 . A method as claimed in claim 5 , wherein the thickener comprises a cellulose ether.

7 . A method as claimed in claim 6 , wherein the thickener comprises an alkyl hydroxyalkyl cellulose.

8 . A method as claimed in claim 1 , wherein the thickener is present in an amount of at least 0.1% wt/wt.

9 . A method as claimed in claim 1 , wherein the cleaning liquid comprises:

0.001 to 2% wt/wt preservative,

0.01 to 1% wt/wt foam control agent,

thickener in an amount to give the cleaning liquid a dynamic viscosity in the range from 1 to 50 dPa·s, and

at least 90% wt/wt water,

wherein the pH of the cleaning liquid is in the range from 3 to 11.

10 . A method as claimed in claim 1 , wherein the cleaning liquid contains from 90 to 99.5% wt/wt water.

11 . A method as claimed in claim 1 , wherein the coating liquid is a water-based coating liquid which has passed though the apparatus, and wherein a cleaning liquid is used to clean the apparatus in a single pass on termination of the passage of the coating liquid;

wherein when the cleaning liquid is a cleaning liquid as defined in claim 1 , X ml of effluent cleaning liquid has been expelled from the apparatus when the concentration of the coating liquid in the effluent cleaning liquid has reached 0.1% wt/wt;

wherein when the cleaning liquid is a test cleaning liquid which differs from said cleaning liquid only in that the thickener has been replaced in full by water, Y ml of effluent cleaning liquid has been expelled from the apparatus when the concentration of the coating liquid in the effluent cleaning liquid has reached 0.1% wt/wt;

wherein the volume X is at least 8% less than the volume Y.

12 . A method of spray coating a surface, the method comprising:

a first spray coating stage, which is terminated;

a cleaning stage which comprises a cleaning method as claimed in claim 1 ; and

a second spray coating stage, which is commenced after the cleaning stage and without a rinsing stage or any other intermediate stage having been carried out.

13 . A method as claimed in claim 12 , wherein the coating liquid for the first and second spray coating stages is supplied in containers and the cleaning liquid is supplied in a compatible container which can be fitted into the spray apparatus in the place of a container for the coating liquid.

14 . A method as claimed in claim 12 , wherein the liquid spray apparatus cleaned in the method comprises:

a reservoir having a liquid outlet

a spray applicator connected to the reservoir to receive liquid therefrom

means for urging liquid from the reservoir to the spray applicator

a nozzle in the spray applicator for the expulsion of liquid

a primary gas outlet in the spray applicator for atomising expelled liquid

a secondary gas outlet in the spray applicator for impinging upon the expelled and atomised liquid and modifying its spray profile.

15 . A kit of parts for use in carrying out a method as claimed in claim 12 , the kit of parts comprising:

a liquid spray apparatus,

a first container containing a coating liquid,

a second container containing the same or a different coating liquid,

a third container containing a cleaning liquid.