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
1999-11-11
2002-06-11
Niland, Patrick D. (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...
C427S372200, C427S385500, C524S502000, C524S507000, C524S522000, C524S523000, C524S533000, C524S558000, C524S560000, C524S589000, C524S590000, C524S591000, C524S839000, C524S840000, C525S123000, C525S127000, C525S131000, C525S455000
Reexamination Certificate
active
06403701
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a mixer system for preparing water-dilutable coating compositions with precisely defined tinting from various base colors, the resultant coating compositions having improved condensation resistance.
PRIOR ART
Conventional methods of repairing damaged areas on a single- or multicoat paint system comprise the careful cleaning and sanding, possibly filling and surfacing of the damaged area. Subsequently the damaged area, after a further pretreatment if appropriate, is sprayed with effect finishes, 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 regions. After initial drying of the coating thus produced, the coating and the adjacent parts are oversprayed with a clearcoat and, after a flash-off period which may or may not be necessary, the clearcoat—together with the previously applied coats—is dried, preferably at temperatures between 50 and 100° C.
The paints used as effect finishes, and/or as solid-color paints applied in the two-coat process, for repairing damaged areas are usually low-solids paints which comprise, in addition to binders, coloring pigments and/or special-effect pigments and a high proportion of organic solvent mixtures.
These paints are either supplied by the paint manufacturer in the desired shade, or the shade is produced prior to application from a mixture system comprising a plurality of base colors. This preparation from a mixer system has the advantage that it is not necessary for every shade to be produced and stored individually, and that as a result production, distribution and stock-keeping costs can be reduced. In both cases it is necessary for the paint supplied to have an adequate shelf life (at least 12 months). For a mixer system, moreover, the accuracy of shade of the base colors is very important.
Whereas in the sector of production-line finishing use is increasingly made of water-thinnable basecoats, conventional, i.e. solvent-containing, basecoats are still employed in the automotive refinishing sector. These low-solids basecoats which have been used to date for refinishing have a distinctly different composition from the water-thinnable basecoats used hitherto for production-line finishing. Thus, for example, the rheology of conventional systems is very largely controlled by the rate of evaporation of the organic solvents (increase in solids between application device 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, therefore, it is not sufficient simply to exchange the binders used for water-thinnable binders. For economic reasons, to improve safety at work (fire protection) and to reduce the pollution to the environment as paint films dry, the refinishing sector has not been excluded from attempts to reduce, as far as possible, the level of organic solvents in the coating compositions. However, the poor shelf life of the known water-thinnable basecoats has so far prevented the putting together of an above-described mixer system from water-thinnable basecoats of this kind.
DE-A 41 10 520 provides a mixer system which permits the preparation of water-thinnable coating compositions with precisely defined tinting from various base colors. In particular, this mixer system permits the preparation of aqueous coating compositions which are suitable for the refinishing, in particular, of damaged areas on car bodies. At the same time it ensures a high accuracy of shade of the base colors, which allows the paint shop to establish the desired shades in a precise and reproducible manner without recourse to complex measures.
In addition, the mixer systems of DE-A 41 10 520 are of very good shelf life (>12 months), and, finally, the aqueous coating compositions prepared using this mixer system lead, both in the case of effect finishes and in the case of solid colors, to coatings having good mechanical properties. Mixer systems in accordance with DE-A 41 10 520 consist of:
A) various base colors A, which contain less than 5% by weight of water, at least one coloring and/or special-effect pigment, organic solvent, at least one water-thinnable or water-dispersible binder and, if desired, auxiliaries and additives, and
B) at least one water-containing, pigment-free component B.
Also embraced by DE-A 41 10 520 is a process for preparing water-thinnable coating compositions with precisely defined tinting, in which various base colors of a mixer system are prepared separately and stored and are not mixed until shortly before the application of the coating composition, characterized in that the mixer system of the invention is employed.
Finally, DE-A 41 10 520 also relates to the use of mixer systems for preparing aqueous coating compositions for refinishing, especially for preparing waterborne paints for the refinishing, in particular, of car bodies.
In recent times, the requirements for water and moisture resistance, especially for condensation resistance, of automotive refinishes have risen.
This has made it necessary to increase further the condensation resistance of the coatings which can be obtained with the mixer system according to DE-A 41 10 520.
SUMMARY OF THE INVENTION
It has surprisingly been found that the condensation resistance of finished coatings produced from the mixer systems of the general type described in DE-A 41 10 520 can be increased considerably if the mixing component B) described therein has added to it, as binder, a polymer which is obtainable by subjecting an ethylenically unsaturated monomer or a mixture of ethylenically unsaturated monomers to free-radical polymerization in the presence of a water-insoluble initiator and in an aqueous dispersion of a polyurethane resin which has a number-average molecular weight of between 1000 and 30,000 daltons and on average from 0.05 to 1.1 polymerizable double bonds, wherein the weight ratio between the polyurethane resin and the ethylenically unsaturated monomer or monomer mixture is between 1:10 and 10:1. Such polymers are described in DE-A 43 39 870.
DETAILED DESCRIPTION
The mixer system of the invention therefore consists of the components:
A) a plurality of base colors A, which contain less than 5% by weight of water, at least one coloring and/or special-effect pigment, organic solvent, at least one water-thinnable or water-dispersible first binder and, if desired, auxiliaries and additives, and
B) at least one water-containing, pigment-free component B, comprising an aqueous dispersion of a polyurethane resin.
Component A of the Mixer System
In the text below, the individual components of the mixer system of the invention will now be elucidated further.
Component A of the mixer system can comprise any customary paint pigment, provided that it does not react with water within a short time (the period between stirring components A and B together and applying the paints) and that it does not dissolve in water. The component A can comprise special-effect pigments and/or colored pigments based on inorganic or organic compounds. To ensure a scope for application which is as universal as possible and to allow the realization of as many colors as possible, it is preferred to put together a mixer system based on a first subgroup of components A comprising only coloring pigments and on a second subgroup of components A comprising only special-effect pigments. To prepare the component A it is possible to employ all special-effect pigments which are commonly employed in the formulation of aqueous coating compositions. Examples of suitable special-effect pigments are commercial aluminum bronzes, the aluminum bronzes chromated in accordance with DE-A 36 36 183, commercial stainless steel bronzes, and other customary metal platelets and metal flake pigments. Nonmetallic special-effect pigments, such as pearluster pigments or interference pigments, for example, are also suitable for preparing
Lettmann Bernhard
Reusmann Gerhard
Wegner Egon
BASF Coatings AG
Niland Patrick D.
LandOfFree
Mixing system for producing water-dilutable coating agents does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mixing system for producing water-dilutable coating agents, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mixing system for producing water-dilutable coating agents will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2983402