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
2001-06-22
2003-11-18
Wu, David W. (Department: 1713)
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...
C524S560000, C524S563000, C524S562000, C524S564000, C524S590000, C525S185000, C525S186000, C525S190000, C525S326300
Reexamination Certificate
active
06649688
ABSTRACT:
The present invention relates to a coating composition consisting of at least three components (3K system) comprising a component (I) comprising at least one hydroxyl-containing oligomeric or polymeric resin dispersed or dissolved in one or more organic, optionally water dilutable solvents, as binder (A), a component (II) comprising at least one polyisocyanate dispersed or dissolved in one or more organic, optionally water dilutable solvents, as crosslinking agent (F), and a component (III) which comprises water. The present invention additionally relates to a process for preparing these coating compositions and also to the use of the coating compositions in automotive OEM finishing, refinish, and for the coating of plastics, and also as topcoat materials or primer-surfacers.
Coating compositions or 3K systems of the abovementioned type where binders (A) contain acid groups as well as the hydroxyl groups are known from the German patents DE-A-195 42 626 and DE-A-44 21 823. These known coating compositions already have comparatively few surface problems, such as popping marks or structuring, and as regards gloss, relaxation, spraying reliability, fullness, weathering stability, and other important technological properties they possess a good profile of properties. It is recommended therein that use be made of (meth)acrylic oxaalkyl esters or oxacycloalkyl esters such as ethyl triglycol (meth)acrylate and methoxyoligoglycol (meth)acrylate having a molecular weight Mn of preferably 550, or other ethoxylated and/or propoxylated, hydroxyl-free (meth)acrylic acid derivatives, for the preparation of the polyacrylate resins used as binders (A). However, these polyacrylate resins (A) are used in 3K systems which give high gloss coatings.
The increasingly more stringent requirements of the market are making it necessary to improve these known coating compositions still further in terms of their homogeneity, stability, handling, and popping limits. Moreover, the solvent content is to be lowered further than has been possible to date. Furthermore, even on forced drying, the known 3K systems should give coatings which have no surface defects. They should have an even higher gasoline resistance and an even lower gray haze than the known 3K systems.
Furthermore, it is desirable or necessary in some cases to use matt coatings rather than highly glossy coatings. However, the 3K systems known to date have always been optimized with respect to the high gloss of the coatings produced using them.
It is an object of the present invention to provide a new 3K system which is easy to prepare, homogeneous, stable, easy to handle, low in solvent, resistant to popping, reliable in its spraying properties, and stable on forced drying and which gives matt coatings which do not have surface defects or gray haze but which instead are stable to weathering and resistant to gasoline.
The invention accordingly provides the novel coating composition consisting of at least three components, comprising
(I) a component comprising at least one hydroxyl-containing oligomeric or polymeric resin dispersed or dissolved in one or more organic, optionally water dilutable solvents, as binder (A),
(II) a component comprising at least one polyisocyanate dispersed or dissolved in one or more organic, optionally water dilutable solvents, as crosslinking agent (F), and
(III) a component which comprises water,
wherein component (I) or components (I) and (II) comprise or comprises at least one hydroxyl-containing polyacrylate resin (A) containing polyether sidegroups and/or endgroups of the general formula I
Y—(—O—R—)
n
— (I)
in which the index and variables have the following meanings:
n=3 to 100;
R=C
2
to C
6
alkanediyl and C
3
to C
8
cycloalkanediyl;
Y=hydrogen atom or C
1
to C
4
alkyl; as binder (A).
In the text below, the polyacrylate resins (A) for use in accordance with the invention containing polyether sidegroups and/or endgroups are referred to for the sake of brevity as “constituents important to the invention”.
In the text below the novel coating composition consisting of at least three components is referred to for the sake of brevity as the “coating composition of the invention”.
The present invention further provides a process for preparing the coating compositions of the invention, and also provides for their use in refinish, for the coating of plastics, and also as topcoat materials or primer-surfacers.
In the light of the prior art it was unforeseeable that the solution of the problem, with all of its advantages, might be achieved by means of the polyacrylate resins (A) containing polyether sidegroups and/or endgroups. This was all the more surprising in view of the fact that the prior art polyacrylate resins containing hydroxyl and acid groups, which are close relations chemically, are used in 3K systems which give high gloss coatings.
The coating compositions of the invention are notable, surprisingly, for a profile of properties which is improved over the prior art in relation in particular to the homogeneity, fullness, lower popping tendency, spraying reliability, leveling, and insensitivity to forced drying, and also in respect of the weathering stability and very good adhesion of the resultant coatings of the invention.
It is surprising, furthermore, that the coating compositions of the invention comprising said at least three components may be prepared simply by mixing without the need for complicated mixing and/or dispersing apparatus as described, for example, in the German patent DE-A-195 10 651. The coating compositions of the invention are therefore especially suitable for the field of automotive refinish, since they can be prepared by the painter by simple mixing of the components directly prior to their application and can be cured at low temperatures.
A further advantage is that the coating compositions of the invention prepared from said at least three components contain only a small fraction of volatile organic solvents, despite the fact that the coating compositions are prepared using crosslinkers and binders dispersed and/or dissolved in organic media.
Moreover, the coating compositions of the invention ensure a high level of variability, since it is possible to use not only the crosslinking agents, pigments and additives that are recommended for aqueous coating compositions but also those used in conventional systems.
Finally, a feature of the inventive components of the coating compositions of the invention is a very good storage stability, which corresponds to that of conventional coating compositions.
The constituent of the coating compositions of the invention that is important to the invention is present in component (I) or in components (I) and (III), but especially in component (I). It inventively comprises at least one polyacrylate resin (A) containing polyether sidegroups and/or endgroups. In component (I) or components (I) and (III) for use in accordance with the invention, it is present in an amount, based on the components, of from 20 to 90, preferably from 30 to 80, with particular preference from 40 to 75, and in particular from 45 to 70% by weight.
As the constituent important to the invention, suitable compounds include preferably all oligomeric or polymeric acrylate copolymers having a number average molecular weight Mn of between 1 000 and 50 000 daltons and an OH number of from 40 to 300 mg KOH/g. If the mixing of components (I), (II) and (III) is to take place by manual stirring, it is of advantage for the coating composition of the invention if the constituents of the invention are selected such that their 50% strength solution in ethoxyethyl propionate at 23° C. has a viscosity of ≦10 dpas. Where mechanical mixing is to take place, it is possible to use constituents of the invention that are of high viscosity, whose 50% strength solution in ethoxyethyl propionate at 23° C. has a viscosity of ≦100 dpas. The upper limit on the viscosity is imposed merely by the performance of the mixing units.
The constituent important to the inv
Löcken Wilma
Mayer Bernd
Nienhaus Egbert
Rink Heinz-Peter
BASF Coatings AG
Sastri Satya
Wu David W.
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