Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Patent
1998-07-21
2000-10-10
Dudash, Diana
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
427140, 427142, 4274071, 427410, 428414, 428483, B32B 2700, B05D 136
Patent
active
061299898
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for producing multilayer coatings on a substrate surface, in which aqueous polymer dispersion is applied as basecoat to a substrate surface coated with a customary primer surfacer, thus obtained, and substrates which can be produced by this process.
The prior art discloses processes for coating motor-vehicle bodies, especially car bodies, in which the substrate is generally coated first with an electro-deposition coating material and/or anti-stonechip intermediate primer or a primer surfacer coat, and then a basecoat is applied, using a coating material containing at least one pigment, and this basecoat layer is over-coated, if desired, with a transparent coating material. The resulting single-layer or multilayer coating system is then baked.
The basecoats used to produce the basecoat layer are customarily systems based on water and/or solvent. As principal binder they generally include polyurethane dispersions or acrylate dispersions combined with water-miscible crosslinkable polyesters and water-miscible melamine resins, which give rise to a range of problems such as, for example, low storage stability, a tendency toward yellowing, and unstable viscosity. A further factor is that the polyurethane dispersions lead to difficulties in connection with the production of metallic coatings, for example using aluminum bronzes. Repair carried out to these coatings leads to visuallly unacceptable results.
The object of the present invention is to provide a process for producing multilayer coatings and a process for repairing multilayer coatings on a substrate surface, wherein an aqueous basecoat composition is employed which does not have the abovementioned disadvantages and which is suitable as a basecoat both for solid-color coatings and metallic and/or mica effect finishes. Furthermore, this coating composition should be compatible with customary transparent coating materials, for example aqueous or solvent-containing clearcoats or transparent powder coatings, and these transparent coating materials should be able to be applied to the basecoat without any deterioration in the appearance of the coating system.
The present invention accordingly provides a process for producing a multilayer coating on a substrate surface, in which aqueous polymer dispersion is applied as basecoat composition to a substrate surface coated with a customary primer surfacer, thus obtained, and comprising -C.sub.8 -alkyl (meth)acrylate monomers, from 30 to 60% by weight of vinyl-aromatic monomers and from 0.5 to 10% by weight of (meth)acrylic acid, and acrylate copolymer based on (C.sub.1 -C.sub.6)-alkyl (meth)acrylate and (meth)acrylic acid.
The present invention also provides a process for repairing multilayer coatings, in which aqueous coating composition containing aqueous polymer dispersion as film-forming agent, topcoat composition, and comprising -C.sub.8 -alkyl (meth)acrylate monomers, from 30 to 60% by weight of vinyl-aromatic monomers and from 0.5 to 10% by weight of (meth)acrylic acid, and acrylate copolymer based on (C.sub.1 -C.sub.6)-alkyl (meth)acrylate and (meth)acrylic acid.
Surprisingly it has been found that the novel process for producing multilayer coatings is highly suited to the production of multilayer coatings on substrates and for repairing multilayer coatings, especially for car bodies. Any desired transparent coating materials can be applied to the basecoat, examples being aqueous or solvent-containing coating materials or else powder coatings, which is not possible in the processes known from the prior art. Coatings comprising the basecoat used in accordance with the invention can be repaired without problems in cases of damage.
As C.sub.1 -C.sub.8 -alkyl(meth)acrylate monomer units, the acrylate polymer of component (i) employed in accordance with the invention can comprise the linear and branched-chain derivatives, with methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl and isopropyl (meth)acrylate, n-butyl and isobutyl (meth)acrylate and 2-ethylhexyl (meth)acr
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BASF Coatings AG
Dudash Diana
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