Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-08-29
2002-09-10
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S502000, C524S522000, C524S523000, C524S533000, C524S558000
Reexamination Certificate
active
06448326
ABSTRACT:
The present invention relates to a mixer system for the preparation of water-thinnable coating compositions with accurately defined colors, produced from various base colorants.
In addition, the present invention relates to a process for the preparation of these coating compositions with accurately defined colors, in which various base colorants are stored separately and are added to the coating composition and mixed to the desired color only a short time prior to application.
Furthermore, the present invention also relates to the use of the mixer system for the preparation of waterborne paints for coating automobile bodies and/or plastic components and for the preparation of aqueous coating compositions for refinishing.
Traditional methods for repairing damaged areas of a one-coat or multicoat finish comprise careful cleaning and rubbing, possibly puttying and filling of the damaged area. Subsequently the damaged area, after a further treatment if appropriate, is sprayed with special effect paints, such as metallic basecoats, or with solid-color paints in such a way that the paint hides the damaged area and runs into the adjacent zones. After the coating produced in this way has dried, the coating and the adjacent parts are sprayed with a clearcoat and after a flash-off period which may or may not be necessary, the clearcoat is dried together with the previously applied coats preferably at temperatures between 50 and 100° C. The paints used as special effect paints and/or as solid-color paints applied in a two-coat process for repairing damaged areas are usually low-solid paints which contain, besides binders, colored and other special effect pigments and a high proportion of organic solvent mixtures.
These paints are either supplied by the paint manufacturer in the desired color or the color is produced prior to application by a mixer system consisting of a plurality of base colorants. This preparation by a mixer system has the advantage that it is not necessary for every color to be produced individually and stored and that in this way production, distribution and storage costs can be reduced. In both cases it is necessary for the supplied paints to have an adequate shelf life (at least 12 months). Furthermore, for a mixer system the color accuracy of the base colorants is very important.
While water-thinnable basecoats have been increasingly used in the production line finishing sector, conventional, i.e. solvent-borne, basecoats are still used in the automotive refinishing sector. These low-solid basecoats used hitherto for refinishing have a composition distinctly different from that of the water-thinnable basecoats used so far in production line finishing. Thus, for example, the rheology of conventional systems is largely controlled by the rate of evaporation of the organic solvents (increase of solids between the application equipment and the object to be painted), while the rheology of aqueous systems is controlled by external thickeners or by appropriate modifications to the binder. For the transition from conventional to water-thinnable systems a straightforward replacement of the binders used by water-thinnable binders is thus insufficient.
Likewise the use in the refinishing sector of the water-thinnable systems employed in the production line finishing sector is at present impossible because of the different demands made on the systems in the two sectors. That is to say, the water-thinnable metallic basecoats used in production line finishing (automotive factory finishing) do not have a shelf life that is adequate for the refinishing sector, since these water-thinnable paints suffer problems of stability linked to gas evolution (hydrogen formation by the reaction of water with the aluminum bronze) and/or of special effect stability. Both problems impair permanently the color or brightness of the resultant coatings. For this reason these systems have not found use in refinishing.
However, not only water-thinnable paints containing special effect pigments have problems associated with shelf life. Colored pigments, too, can be attacked by prolonged action of water, for example in an alkaline medium. In order that the choice of commercially available pigments is not unduly constrained, a need also exists for the formulation of storage-stable base colorants using these colored pigments.
For reasons of economy and in an effort to improve work safety (fire protection) and reduce environmental stress due to the drying of paint films, the refinishing sector has also endeavored to reduce as much as possible the organic solvents content in coating compositions. However, the poor shelf life of the known water-thinnable basecoats has hitherto prevented the creation of a mixer system as described above from such water-thinnable basecoats.
A process for the production of a multicoat coating in which first an aqueous coating composition, preferably containing metallic pigments, is applied to a filled substrate and dried prior to applying a conventional waterborne basecoat followed by a clearcoat, is known from EP-A-320,552. Application of the aqueous coating composition prior to the basecoat/clearcoat coating is said to enhance the metallic effect, especially brightness.
This process described in EP-A-320,552 is suitable mainly for the production of a factory finish, but the description also refers to the possibility of using this process in the refinishing sector.
The aqueous compositions employed in the process of EP-A-320,552 are produced by the incorporation of an aluminum pigment paste into aqueous mixer paints. The aluminum paste used here is a paste-like mix of aluminum bronze in organic solvents and an emulsifier. However, this aluminum paste separates out after only a few hours and thus forms a deposit. This in turn normally causes color variations. This separated-out paste can only be stirred up to a limited extent using suitable stirring equipment. Furthermore, finishers usually do not have such stirring equipment at their disposal. Aluminum pastes of this type are therefore unsuitable for the creation of mixer systems for refinishing.
The aqueous coating compositions obtained after incorporation of the aluminum paste into the aqueous mixer paints also have an inadequate shelf life, which does not meet the requirements of the finishers.
Furthermore, aqueous coating compositions for the preparation of a multicoat coating in the production line finishing sector are known from EP-A-195,931 and EP-A-297,576. The preparation of the aqueous coatings is effected by incorporating a pigment paste into the aqueous binder dispersion. The pigment paste is produced by grinding of the appropriate pigments with as low amounts of a grinding resin as possible with or without organic solvents and with or without water. However, the creation of a mixer system for the refinishing sector and the measures necessary for this purpose, such as separate storage of the individual components, are not described in EP-A-195,931 and EP-A-297,576. The pigmented aqueous coatings themselves are unsuitable for the refinishing sector on account of an inadequate shelf life.
Aqueous coating compositions for the production of a multicoat coating in the production line finishing sector are also known from EP-B-38,127. The preparation of the aqueous coating compositions is again carried out by incorporating a pigment paste in the aqueous binder dispersion. The pigment paste is prepared by grinding of the pigments with a melamine resin and organic solvents. However, the creation of a mixer system for the refinishing sector and the measures necessary for this purpose are again not described. These pigmented aqueous coating compositions of EP-B-38,127 are again unsuitable for the refinishing sector on account of an inadequate shelf life.
Water-thinnable coating compositions with an improved shelf life, especially those containing metallic pigments, are described in EP-A-368,499. The satisfactory shelf life is achieved by first preparing an anhydrous binder solution from 25 to 95% by weight of a polyether polyo
Mayer Bernd
Piontek Susanne
BASF Coatings AG
Cain Edward J.
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