Stock material or miscellaneous articles – Composite – Of metal
Patent
1995-06-23
1996-06-04
Beck, Shrive
Stock material or miscellaneous articles
Composite
Of metal
428463, 427409, 427515, 427518, 427520, B05D 714
Patent
active
055231640
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP93/03035, filed Oct. 30, 1993.
The present invention relates to a novel method for forming paint films and to coatings obtained by the method. More specifically, the present invention relates to a method for forming topcoat paint films which are particularly excellent in acid resistance and scratch resistance, and have excellent flexibility and adherence when recoated, and to coatings obtained by means of this method for forming paint films.
In recent years, the durability of paint films, and particularly rain stains due to acid rain and scratching due to car-wash brushes or sand particles thrown up during travelling, have been giving problems as far as automobile paint films are concerned.
Prior known measures to solve such problems include the application of clear coats using Y-caprolactone-modified acrylic resins and melamine hardeners (Japanese Unexamined Patent [Kokai] 64-66274), for example, for scratch resistance, and the application of clear coats in which carboxylic acids and epoxy reaction are used with acrylic resins and melamine curing agents, for example, for acid resistance (Japanese Unexamined Patent 4-114069).
However, with the former technique paint films with excellent scratch resistance are obtained, but resistance to acid raid is inadequate; and with the latter technique paint films with excellent acid resistance are obtained, but scratch resistance is inadequate.
Raising the glass transition temperature of the cured clearcoat paint film of the outer surface layer is also known to be an effective method for obtaining a higher degree of acid resistance, but this has the problem that it invites undesirable conditions such as lowering the bending resistance and recoating adhesion of the paint film, as well as lowering scratch resistance.
Therefore, it has been extremely difficult to find a technique giving paint films which have a balance of high levels of acid resistance and scratch resistance and are also excellent in bending resistance and recoating adhesion.
Given this situation, the present inventors have made it their aim to offer a method for forming paint films by the 2-coats/1-bake method in which the paint films are provided with a balance of high levels of both acid resistance and scratch resistance, together with excellent bending resistance and recoating adhesion, and coatings obtained by this method.
As the result of concerted research to achieve the aforementioned aim, the present inventors discovered that the aim can be achieved by combining a clearcoat paint in which the resin component comprises a copolymer of a vinyl monomer mixture containing specified quantities of (meth)acrylic acid cycloalkyl esters, alkyl-etherified melamine resin and blocked polyisocyanate compounds, and a basecoat paint in which the resin component comprises a vinyl type copolymer having hydroxyl groups placed at positions separated from the main chain, alkyl-etherified melamine resin and possibly blocked polyisocyanate compounds and/or cellulose type resin; and they have perfected the present invention based on this insight.
Thus, the present invention offers a method for forming paint films characterised in that, in forming a paint film by coating a basecoat paint including a colouring and after then coating a clearcoat paint over the top curing the said basecoat and clearcoat simultaneously by heating, a paint in which the resin component comprises (a) a copolymer of a vinyl monomer mixture containing at least 20% by weight as cycloalkyl esters of acrylic acid or methacrylic acid 40-90% by weight, (b) an alkyl-etherified melamine resin 5-50% by weight, and (c) blocked polyisocyanate compounds 5-50% by weight, is used as the said clearcoat paint, and a paint in which the resin component comprises (d) a copolymer of a vinyl monomer mixture containing at least 10% by weight as monomers represented by the general formula ##STR2##
(In the formula, X.sup.1 -X.sup.5, which may be the same or different, are each a hydrogen atom or a methyl group; i is 0 or 1 or 2; j i
REFERENCES:
patent: 4879337 (1989-11-01), Shibato et al.
Kawamura Masataka
Sato Atsushi
Sato Shigekazu
Shibato Kishio
BASF Lacke & Farben AG
Beck Shrive
Cameron Erma
Sabourin Anne Gerry
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