Electrostatic Fluidised Powder Bed Coating Process
AssigneeAkzo Nobel Coatings International B.V.
InventorsJohn Ring, Michele Falcone, Robert Edward Barker, Andrew George Cordiner
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Abstract
The present invention pertains to a process for forming a coating on a substrate using a tribo-charging electrostatic fluidised bed process; characterised in that a powder coating is used which has a particle size distribution such that a) d(v,90)≦42.5 μm, and b) i) the percentage of particles <10 μm in size is ≦12% by volume, and/or ii) [d(s,90)÷d(s,10)]2≦3.5, [d(s,90)−7] d(s,90) being greater than 7 μm and d(s,90) and d(s,10) being measured in microns.
Claims20
A process for forming a coating on a substrate, the process comprising applying a powder coating to a substrate using a tribo-charging electrostatic fluidised bed process wherein the powder coating has a particle size distribution such that
- a) d(v,90)≦42.5 μm, and
- b) i) the percentage of particles <10 μm in size is ≦12% by volume, and/or
- ii)
- [
- d
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- s
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- 90
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- /
- d
-
- (
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- 10
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- 2
- [
- d
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- 90
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- -
- 7
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- ≤
- 3.5
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- d(s,90) being greater than 7 μm and d(s,90) and d(s,10) being measured in microns.
A process to establish for a powder coating material a particle size distribution suitable for application in a tribo-charging electrostatic fluidised bed process, which comprises
- (i) preparing a powder coating material of a known particle size distribution;
- (ii) depositing powder material on a substrate or substrates using said powder coating material in a tribo-charging electrostatic fluidised bed process;
- (iii) removing and collecting at least part of said powder material deposited on the substrate;
- (iv) measuring the particle size distribution of at least part of the collected powder material;
- (v) comparing with the particle size distribution of the powder material used in the fluidised bed in step (ii), and
- (vi) repeating one or more times as necessary the sequence of preparation, deposition, removal, measuring and comparing steps, until there is obtained a powder coating material that when applied to a substrate by the fluidised bed process deposits powder material having a particle size distribution matching that of the powder material used in the fluidised bed.
A process to establish for a powder coating material a particle size distribution suitable for application in a tribo-charging electrostatic fluidised bed process, which comprises:
- 1) providing a powder coating material of known particle size distribution;
- 2) carrying out a trial tribo-charging electrostatic fluidised bed process using the powder coating material of step 1
- 3) establishing a measure for the top-end particle size deposited in the fluidised bed process;
- 4) preparing from the same powder coating material of step 1 a powder with a top-end particle size that is closer to the top-end particle size deposited in step 2;
- 5) carrying out a further tribo-charging electrostatic fluidised bed coating process using the powder so prepared in step 4;
- 6) establishing a measure of the content of fines in the powder deposited;
- 7) preparing from the powder coating material of step 4 a powder with a reduced fines content in comparison with that measured in step 6);
- 8) carrying out a further tribo-charging electrostatic fluidised bed process using the powder so prepared in step 7;
- and
- 9) repeating as necessary the sequence of preparation and deposition steps with adjustment of the top-end particle size and/or fines content until the powder deposited matches the powder used in the fluidised bed.
A powder coating material formed by a fusion-agglomeration process comprising particles having a particle size distribution such that
- a) d(v,90)≦42.5 μm, and
- b) i) the percentage of particles <10 μm in size is ≦12% by volume, with the percentage of particles of below 20 microns being at least 10% by volume, and/or
- ii)
- [
- d
-
- (
- s
- ,
- 90
- )
- /
- d
-
- (
- s
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- 10
- )
- ]
- 2
- [
- d
-
- (
- s
- ,
- 90
- )
- -
- 7
- ]
- ≤
- 3.5
- ,
- d(s,90) being greater than 7 μm and d(s,90) and d(s,10) being measured in microns.
Dependencies are inferred from the claim text.