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
2002-01-11
2004-05-18
Reddick, Judy M. (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...
C524S431000, C524S543000, C524S548000, C524S551000, C524S553000, C524S555000, C524S556000, C524S558000, C524S560000, C524S561000, C524S563000, C524S564000, C524S565000, C524S567000, C524S570000, C524S577000
Reexamination Certificate
active
06737468
ABSTRACT:
The present invention relates to a novel basecoat material, in particular an aqueous basecoat material. The present invention further relates to a process for preparing the novel basecoat material. The present invention additionally relates to the use of the novel basecoat material to produce color and/or effect basecoats and multicoat color and/or effect coating systems, especially for motor vehicles. The present invention relates, furthermore, to novel basecoats and multicoat systems and to the primed or unprimed substrates coated therewith, especially motor vehicle bodies.
Basecoat materials, especially aqueous basecoat materials, comprising acrylate copolymers as binders are known from the patent DE-A-39 42 804. The acrylate copolymers are prepared by two-stage emulsion polymerization. The basecoat materials possess a high level of storage stability. The basecoats produced with them have a good metallic effect, good adhesion to the surfacer coat and to the clearcoat, good gloss, and good resistance under the constant condensation conditions of DIN 50017.
The patents WO 99/15597 or DE-A-197 41 554 likewise disclose aqueous basecoat materials which comprise at least one acrylate copolymer based on from 30 to 60% by weight of C
1
-C
8
alkyl (meth)acrylate monomers, from 30 to 60% by weight of vinylaromatic monomers and from 0.5 to 10% by weight of (meth)acrylic acid, at least one nonassociative thickener, which contains at least one acrylate copolymer based on C
1
-C
6
alkyl (meth)acrylate and (meth)acrylic acid, and at least one further poly(meth)acrylate resin which contains at least one reactive group for isocyanates. The aqueous basecoat films do not form cracks during the drying process and are highly compatible with powder clearcoat materials or powder slurry clearcoat materials.
The known basecoat materials may be used in accordance with the wet-on-wet technique, which is employed with preference in automotive OEM finishing; i.e., the basecoat materials are applied to a primed or unprimed substrate to give a basecoat film which, however, is not cured but instead is only initially dried and overcoated with a clearcoat film, after which the two films are jointly cured.
Basecoat materials, especially aqueous basecoat materials, thus have numerous advantages which render them attractive for industrial utilization.
The acrylate copolymers themselves may be prepared by well-known polymerization techniques in bulk, solution or emulsion. Polymerization techniques for preparing acrylate copolymers, especially polyacrylate resins, are general knowledge and are widely described (cf., e.g., Houben-Weyl, Methoden der organischen Chemie, 4th Edition, Volume 14/1, pages 24 to 255 (1961)).
Further examples of suitable copolymerization techniques for preparing acrylate copolymers are described in patents DE-A-197 09 465, DE-C-197 09 476, DE-A-28 48 906, DE-A-195 24 182, EP-A-0 554 783, EP-B-0 650 979, WO 95/27742, DE-A-38 41 540, and WO 82/02387.
Suitable reactors for the copolymerization processes are the customary and known stirred vessels, cascades of stirred vessels, tube reactors, loop reactors, and Taylor reactors, as described for example in patents DE-B-1 071 241 and EP-A-0 498 583 or in the article by K. Kataoka in Chemical Engineering Science, Volume 50, No. 9, 1995, 1409 to 1416.
The free-radical polymerization used to prepare the acrylate copolymers, however, is often very exothermic and difficult to control. The implications of this fact for the reaction regime are that it is necessary to avoid high monomer concentrations and/or the batch mode, where the entirety of the monomers is introduced as an initial charge in an aqueous medium, emulsified and subsequently polymerized to completion. Even the tailoring of defined molecular weights, molecular weight distributions, and other properties frequently causes difficulties. The tailoring of a certain profile of properties in the acrylate copolymers, however, is of great importance for their use as binders in basecoat materials, especially aqueous basecoat materials, since by this means it is possible to influence the profile of performance properties of the basecoat materials in a direct way.
There has therefore been no lack of attempts to control the free-radical copolymerization of olefinically unsaturated monomers.
For instance, International Patent Application WO 98/01478 describes a process in which the copolymerization is conducted in the presence of a free-radical initiator and of a thiocarbonylthio compound as chain transfer agent.
International Patent Application WO 92/13903 describes a process for preparing copolymers having a low molecular weight by means of free-radical chain polymerization in the presence of a group transfer agent containing a carbon-sulfur double bond. These compounds act not only as chain transfer agents but also as growth regulators, so that only low molecular weight copolymers result.
International Patent Application WO 96/15157 discloses a process for preparing copolymers having a comparatively narrow molecular weight distribution, in which a monomer is reacted with a vinyl-terminated macromonomer in the presence of a free-radical initiator.
Furthermore, International Patent Application WO 98/37104 discloses the preparation of acrylate copolymers having defined molecular weights by means of free-radical polymerization in the presence of a chain transfer agent containing a C—C double bond and containing radicals which activate this double bond in terms of the free-radical addition reaction of monomers.
Despite the significant process in this area, there is still a lack of a universally applicable process of controlled free-radical polymerization which in a simple manner provides chemically structured polymers, especially acrylate copolymers, and by means of which it is possible to tailor the profile of properties of the polymers in respect of their use in basecoat materials, especially aqueous basecoat materials, which are used to produce color and/or effect basecoats and multicoat color and/or effect coating systems.
It is an object of the present invention to provide new basecoat materials, especially aqueous basecoat materials, which are outstandingly suitable for producing color and/or effect basecoats and multicoat color and/or effect coating systems and as an advantageous alternative to the conventional basecoat materials. A further object of the present invention is to propose new processes for preparing the basecoat materials, permitting their profile of properties to be varied in a simple way and to be adapted precisely to the profiles of properties of the other coats of the multicoat systems. The aim is to realize these objects in a simple manner by tailoring the profile of properties of the basecoat materials, in particular through the use of chemically structured polymers obtainable by means of controlled free-radical polymerization. The new multicoat color and/or effect coating systems which result with the aid of these new basecoat materials should possess at least the good profile of properties of the known multicoat systems, and in fact should preferably exceed them. In particular, they are intended to possess outstanding optical quality, intercoat adhesion and condensation resistance and to exhibit no cracking (mud cracking), flow defects or surface structures. Moreover, these chemically structured polymers ought to be suitable for use as grinding resins, making it possible advantageously to prepare pigment pastes which can be incorporated particularly well by mixing, for the surfacers, basecoat materials and clearcoat materials used to produce the new multicoat color and/or effect coating systems.
Accordingly, we have found the novel use of a copolymer (A) in a basecoat material, especially an aqueous basecoat material, which is used to produce color and/or effect basecoats and multicoat color and/or effect coating systems, where the copolymer (A) is preparable by free-radical polymerization of
a) at least one olefinically unsaturated monomer and
b) at least one olefinical
BASF Coatings AG
Reddick Judy M.
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