Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Reexamination Certificate
2002-03-18
2004-08-17
Tsoy, Elena (Department: 1762)
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
C427S140000, C427S385500, C427S421100
Reexamination Certificate
active
06777033
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for refinishing substrates, in particular vehicle bodies, by means of spot repair.
DESCRIPTION OF RELATED ART
In vehicle refinishing, often only parts of a vehicle body or small damaged areas of a vehicle component need coating. When refinishing, it is vital to coat the vehicle part or damaged area so that there is no differences in color shade, special effect or other visually perceptible features relative to the surrounding old finish.
Various spot repair methods have already been developed in order to obtain very good quality, visually unblemished refinish coatings. WO 95/14540 (U.S. Pat. No. 5,871,809) accordingly describes a refinishing process that is intended to avoid clouding, especially in special effect, water-borne base coats. The water-borne base coat is applied onto the existing coating in two spray passes, preferably without interim flashing-off between the spray passes, in each case until a boundary of the old finish is reached. This operation is repeated until the entire part to be coated has been provided with the base coat.
EP 773 840 (U.S. Pat. No. 5,820,986) describes another process for avoiding color shade differences in refinishing, in which ESTA-applied (electrostatically supported application); special-effect base coats exhibiting specific Theological behaviour are refinished by HVLP (high volume low pressure) application of the special-effect base coat.
WO 95/07148 (U.S. Pat. No. 5,683,745) describes a refinishing process in which, during application of the base coat onto the regions of the old finish adjacent to the damaged area, the spray gun is inclined diagonally towards the damaged area and a normal or only moderately reduced spray gun inlet pressure is used.
It has not, however, hitherto proved possible to completely and satisfactorily solve all problems with regard to visual matching between the refinish and the old finish. For example, quality is still occasionally impaired by edge marks. Especially in the case of light-colored pigmented coatings, edge marks may occur in the transitional zone between the old finish and the repair finish. Clearly visible over spray margins are obtained that are generally perceptible as peripheral zones that are lighter, darker and/or differ in color shade. In some light beige or light yellow color shades, for example, a yellow/red edge mark is observed.
There accordingly still is a requirement for a novel refinishing process by means of spot repairing that overcomes the disadvantages of the prior art.
SUMMARY OF THE INVENTION
The present invention provides a process for refinishing substrates, in particular vehicle bodies or parts thereof, by means of spot repair finish. In this process, even in the case of pigmented coatings of critical color shades, in particular with specific light color shades, very good quality finishes are obtained and visually perceptible differences of any kind are largely avoided, such as differences in color shade, over spray margins and edge marks, between the old finish and the repair finish.
The invention relates to a process for refinishing substrates, in particular vehicle bodies or parts thereof, by means of spot repair, wherein at least one color- and/or special effect-imparting coating layer of a color- and/or special effect-imparting coating composition is applied onto a damaged area of a substrate and wherein the process comprises the following steps:
A) preparing a mixture 1 by mixing the color- and/or special effect-imparting coating composition with a diluent V containing organic solvents in a ratio by volume of color- and/or effect-imparting coating composition:diluent V of 2.0:1 to 1:1.3, preferably of 1.5:1 to 1:1.2, particularly preferably of 1.2:1 to 1:1.1, wherein the diluent V comprises:
a) 35-65 wt. % of at least one (cyclo)aliphatic ketone having 3-8, preferably 5-6, C atoms in the (cyclo)alkyl residue and
b) 65-35 wt. % of at least one glycol ether ester, preferably a glycol ether acetate, having 3-8, preferably 4-6, C atoms in the glycol ether residue, whereby the sum of weight percentages of a) and b) is 100 wt-%,
B) applying the mixture 1 produced in step A) onto the damaged area in a layer thickness such that an opaque coating layer is obtained,
C) preparing a mixture 2 by mixing the color- and/or special effect-imparting coating composition with the diluent V in a ratio by volume of color- and/or effect-imparting coating composition:diluent V of 1:1 to 1:3, preferably of 1:1.5 to 1:2.5,
D) applying the mixture 2 produced in step C) onto the damaged area at reduced spray gun inlet pressure and
E) curing the color- and/or special effect-imparting coating layer applied in this manner.
DETAILED DESCRIPTION OF THE EMBODIMENTS
In the process according to the invention, a precoated damaged area of a substrate is coated with a color- and/or special-effect imparting base coat and a clear coat or alternatively with a color- and/or effect-imparting one-layer topcoat. It has surprisingly been found that the process according to the invention gives rise to refinish coatings having perfect visual quality that exhibit no differences in color shade relative to the surrounding old finish and no edge marks in the transition between the old finish and repair finish.
The process according to the invention is carried out by initially preparing in step A) a mixture 1 of the color- and/or special effect-imparting coating composition and the diluent V. The color- and/or effect-imparting coating composition comprises the pigmented coatings known to the person skilled in the art and conventional for vehicle refinishing, such as, for example, one-component or two-component base coats or one-component or two-component one-layer top coats. The pigmented coatings substantially comprise solvent-based coatings.
Binder systems usable in the color- and/or effect-imparting coating compositions are, for example, those based on water-dilutable or solvent-dilutable polyurethane, acrylated polyurethane, polyacrylate, polyester, acrylated polyester and/or alkyd resins. The binder systems may be physically drying and/or chemically cross-linking by means of addition polymerization, polycondensation and/or polyaddition reactions. Chemically cross-linkable binder systems contain appropriate cross-linkable functional groups. Suitable functional groups are, for example, hydroxyl groups, isocyanate groups, acetoacetyl groups, unsaturated groups, for example (meth)acryloyl groups, epoxy groups and amino groups. Cross-linking agents having appropriate complementarily reactive functional groups may be present for cross-linking purposes. Preferred chemically cross-linkable binder systems are those comprising binders containing hydroxyl groups and polyisocyanate cross-linking agents.
The coating compositions may contain further resins, for example cellulose esters and/or melamine resins.
The above list of binder systems is given merely by way of example. The binders may also be further modified and combined with each other at will. There are no particular restrictions as to the binders that may be used. It is possible to use any binders that are known to the person skilled in the art and, in particular, are conventional in vehicle refinishing for formulating color- and/or effect-imparting coating compositions.
The color- and/or effect-imparting coating compositions contain color-imparting pigments. Color-imparting pigments comprise any organic or inorganic pigments conventional in coatings. Examples of inorganic or organic color-imparting pigments are titanium dioxide, micronized titanium dioxide, iron oxide pigments, carbon black, azo pigments, phthalocyanine pigments, quinacridone or perylene or pyrrolopyrrole pigments. Soluble dyes and/or transparent pigments may optionally also be present.
The coating compositions may also contain special-effect pigments. Examples of special-effect pigments are metal pigments, for example made from aluminium or copper, interference pigments, such as metal oxide-coated metal pigments, for example titanium dioxide
Berschel Guenter
Duda Andrew
Kloeckner Harald
Benjamin Steven C.
E. I. du Pont de Nemours and Company
Tsoy Elena
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