Process for the production of multilayered coatings

Details Process for the production of multilayered coatings Process for the production of multilayered coatings

1998-08-21

2000-07-25

Dudash, Diana

Stock material or miscellaneous articles

Composite

Of addition polymer from unsaturated monomers

427140, 4274071, 427409, 427410, 4284231, 4284242, 428483, 428515, 428523, B32B 2720, B32B 2730, B05D 136, B05D 302, B05D 716

Patent

active

060934972

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process for producing multilayer coatings on a substrate surface, in which an aqueous polymer dispersion is applied to a substrate surface coated with an aqueous basecoat composition (i), composition obtained in step (A), and topcoat composition,
The prior art has disclosed processes of coating motor vehicle bodies, especially car bodies, where the substrate is generally coated first of all with an electrodeposition coating material and/or anti-stonechip intermediate primer, a primer surfacer layer or a first basecoat, which may be pigmented, and then a basecoat layer is applied using a coating material comprising at least one pigment, and this basecoat layer is coated over, if desired, with a transparent coating material. The resulting single- or multilayer coating system is subsequently baked. Substrates are coated with two basecoats in particular when high-hiding films are to be obtained at low film thicknesses of about 20 to 30 .mu.m.
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, in which the use of a specific aqueous basecoat composition at low film thicknesses gives rise to high-hiding coatings, and where it is desirable that said basecoat composition be suitable both for solid-color finishes and for metallic or mica effect finishes. The basecoat composition used should, furthermore, be compatible with customary clearcoats, such as aqueous or solventborne clearcoats or transparent powder coatings, and these clear coating materials should be able to be applied to the basecoat without there being, in comparison to conventional coating systems, any deterioration in the appearance of the coating system.
The present invention therefore provides a process for producing a multilayer coating on a substrate surface, in which an aqueous polymer dispersion is applied to a substrate surface coated with an aqueous basecoat composition (i), composition obtained in step (A), and topcoat composition. dispersion 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 (ii) containing as film-forming agent an aqueous polymer dispersion, transparent topcoat composition, and dispersion 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. The basecoat can be covered with any desired transparent coating materials, for example aqueous or solventborne coating materials or else powder coatings. Coatings which include the basecoat used in accordance with the invention can be repaired without problems in cases of damage.
The aqueous polymer dispersion employed in accordance with the invention in the basecoat composition (ii) comprises (x) an acrylate polymer and (y) a thickener containing an acrylate copolymer.
The acrylate polymer of component (x) employed in accordance with the invention can as C.sub.1 -C.sub.8 -alkyl (meth)acrylate monomer units comprise the linear and branched-chain derivatives, with preference being given to methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl and isopropyl (meth)acrylate, n-butyl and isobutyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. Further monomers which may be present are (meth)acrylamide monomers and derivatives thereof.
Examples of vinyl-aromatic monomers which can be employed are styrene, .alpha.-alkylstyrene and vinyltolu

REFERENCES:
patent: 5157069 (1992-10-01), Campbell

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