Multicoat refinishing process

Details Multicoat refinishing process Multicoat refinishing process

1994-04-22

1997-05-27

Dudash, Diana

Coating processes

Restoring or repairing

427142, 427409, 427421, B32B 3500, B05D 136

Patent

active

056330375

DESCRIPTION:

BRIEF SUMMARY
The subject matter of the present invention is a multicoat refinishing process in which system by cleaning, sanding and, if necessary, applying a surfacer and/or body filler, adjacent original finish areas, (2), pigments is applied to the coating obtained in this way at such a film thickness that the basecoat hides the area of damage and tapers off in the adjacent region of the original finish coated with the coating material from stage (2), obtained in this way, if necessary to the parts of the coating from stage (2) not coated with a basecoat and, if necessary, to the adjacent original finish, and then appropriate together with the coating obtained in stage (2) is dried at temperatures between room temperature and 140.degree. C., preferably at temperatures below 100.degree. C. and particularly preferably at temperatures below 80.degree. C.
The repair of areas of damage of a paint finish is usually carried out by thorough cleaning of the area of damage, sanding, if necessary applying a surfacer and applying a refinish body filler to the area of damage. The painting of the area of damage then follows. However, in a panel repair of this kind, differences in shade can often be expected. The repair of metallic paints is particularly difficult, since the shade and brightness of the special effect are highly dependent on the method of working. The width of the spray gunnozzle and the spray pressure, inter alia, play a crucial role here. The method of thinning and the spray viscosity likewise influence shade and special effect.
If in a panel repair of this kind shade differences are to be expected and the area is not demarcated by decorative trim or edges, it may be expedient and economical to compensate the shade differences by a blend-in of the adjacent area using the so-called tapering-off technique.
As described in Chapter 7 "Automotive Refinishing" of the Glasurit Handbook "Pigments and Paints", 11th Edition, Curt R. Vincentz Verlag Hanover 1984, in the case of metallic multicoat finishes the repair area and the adjacent parts are resprayed for this purpose with a conventional, i.e. solvent-borne, highly thinned clearcoat after the preparative work described above, such as cleaning, sanding, surfacing, etc. It is important that this clearcoat is also sprayed on to the repair area, i.e. the body filler patches. Customary conventional clearcoats, for example 2-component clearcoats based on hydroxyl-containing acrylate copolymers as binders and isocyanates as crosslinking agents, are used as the clearcoat for this purpose.
After the clearcoat coating produced in this way has been surface-dried at room temperature or a slightly elevated temperature, the area of damage is resprayed with special-effect paints, such as metallic basecoats, in such a way that the paint hides the area of damage and tapers off into the adjacent areas, i.e. from the edge of the area of damage outwards the film thickness gradually diminishes to 0 .mu.m. If desired, the edge zone can in the case of difficult colors be resprayed using lower spray pressure. Low-solid conventional special-effect paints are usually employed for this repair of the area of damage.
After the basecoat coating produced in this way has been surface-dried, the refinish area and the adjacent parts are completely resprayed with the clearcoat described above and are dried together with the coats applied before-hand at temperatures preferably between room temperature and 100.degree. C., after a flash-off time which may or may not be necessary. Since the metallic basecoats used in this process contain an extremely high proportion of up to 90% of organic solvents, the use of aqueous basecoats is desirable for reasons of economy and to improve work safety (fire protection) and reduce environmental pollution. In particular, when the known aqueous basecoats are applied directly, for this purpose, to an aqueous refinish body filler, the areas of damage cannot be repaired satisfactorily, since this gives rise to shade changes and special effect variations in the region of the

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