Method and use of a binder for providing a metallic coat covering a surface

Abstract

A method for providing a metallic coat covering a surface is disclosed, which comprises: (i) applying an electrically conductive two component binder on said surface; (ii) electrostatic spraying a metal powder on the binder applied in step (i); wherein the metal powder comprises metal particles with an average diameter less than 80 micron.

Claims

1. Method for providing a metallic coat covering a surface, said method comprising: (i) airlessly spraying an electrically conductive two component binder on a surface, wherein the electrically conductive two component binder comprises polyurethane and/or polyurea and between 0.2 and 10% (w/w) quaternary nitrogen compounds; (ii) electrostatic spraying a metal powder on the binder applied in step (i) thereby providing a metallic coat saturated with metal particles; wherein the metal powder comprises metal particles with an average diameter less than 80 micron.

2. The method according to claim 1, wherein the two components of the electrically conductive two component binder are mixed in the nozzle of a spray device.

3. The method according to claim 1, wherein the polymer is dispersed in a vegetable oil chosen from the group consisting of castor oil, soy bean oil, sunflower oil and canola oil.

4. The method according to claim 3, wherein the metal particles have an average diameter smaller than 60 micron.

5. The method according to claim 4, wherein the metal particles have a spherical shape.

6. The method according to claim 5, wherein the metallic coat s less than 200 micron thick.

7. The method according to claim 6, wherein the surface is a circuit board, a roof or a panel.

8. The method according to claim 3, wherein the metal particles have an average diameter between 2 and 55 microns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is further elucidated in the following non-limiting examples of preferred embodiments. In the examples, reference is made to the appended figures wherein:

(2) FIG. 1: shows a schematic view applying copper particles (3) on a binder (2) which is applied to the object (1).

(3) FIG. 2: shows a schematic process for providing a metallic coat according to the present invention.

(4) FIG. 3: schematically shows applying of the copper particles (3) by electrostatic spraying to binder (2) on object (1).

(5) FIG. 4: schematically shows an object coated with a copper coat provided with a method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Example

Comparative Example

(6) A 3 dimensional object is coated with a conventional method.

(7) More specifically, a two component polyurethane binder (ALBODUR 921 of Alberdingk Boley) is applied by airless spraying on the surfaces of the object. Subsequently, a metal powder comprising copper particles with an average diameter of 30 micron were applied to the binder by scattering of the metal powder to the binder. FIG. 1 shows how the copper particles (3) reach the binder (2) on the object (1) by gravity. Thereafter the applied coat is cured by subjecting it to ultra red light and a polishing step was performed.

(8) A metallic coat was obtained. However, the saturation of the matrix was not complete and equal. Specifically, by applying the copper powder, the binder is moved away which resulted in a rough surface, as can be seen in FIG. 1, number 4.

Example 1

(9) A 3 dimensional object is coated with a method according to the present invention.

(10) FIG. 2 is a schematic overview of the method followed in this example. More specifically, FIG. 2 shows transport means (1), wherein the placed 3 dimensional object is placed an is subjected to applying of the binder (2), electrostatic applying of the metal powder (3), drying (4) and finally grating and/or polishing (5).

(11) More specifically, the binder used is a two component polyurethane binder dispersed in castor oil, namely the ALBODUR 921 of Alberdingk Boley. The second component is diphenylmethane-4.4-diisocyanate. This two component polyurethane binder is made electrically conductive by mixing it with commercially available quaternary nitrogen compounds sold under the name of Tego@ADDID 240 from Evonik Industries AG, until a mixture comprising 5% quaternary nitrogen compounds is obtained.

(12) Forthcoming, this mixture is applied to the surface of the 3 dimensional object by airless spraying.

(13) Subsequently, a metal powder comprising copper particles with an average diameter of 30 micron is applied by use of an electrostatic spray gun. FIG. 3 shows a schematic insight in electrostatic spraying the copper particles in the binder. The copper particles 3 reach the binder (2) on object (1).

(14) Thereafter, the coated object is subjected to infrared in order to cure the coat.

(15) Finally, the coat is polished by Bristle Brushes available from 3M.

(16) A perfect smooth coat was obtained as is shown schematically in FIG. 4. FIG. 4 shows a complete and equal saturation of the matrix, i.e. the binder, on horizontal as well as on the leaning surface of the 3 dimensional object.

Example 2

(17) The steps of example 1 were followed on a similar 3 dimensional object. However the binder was a two component binder of polyurea in castor oil, and the second component was diphenylmethane-4.4-diisocyanate. This two component binder is made electrically conductive by mixing it with commercially available quaternary nitrogen compounds sold under the name of Tego@ADDID 240 from Evonik Industries AG, until a mixture comprising 3% quaternary nitrogen compounds is obtained.

(18) The 3 dimensional object exhibited a smooth coat with a complete and equal saturation of the matrix, i.e. the binder, on horizontal as well as on leaning surfaces.