Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-01-11
2004-11-23
Harlan, Robert D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S273000, C525S397000, C526S204000, C526S292300, C524S452000, C524S500000, C524S543000, C524S555000, C524S558000, C524S549000, C524S557000, C524S515000, C524S502000
Reexamination Certificate
active
06822044
ABSTRACT:
The present invention relates to a novel clearcoat material, in particular an aqueous clearcoat material.
The present invention further relates to a process for preparing the novel clearcoat material. The present invention additionally relates to the use of the novel clearcoat material to produce clearcoats and multicoat color and/or effect finishes, especially for motor vehicles. The present invention relates, furthermore, to novel clearcoats and multicoat systems and to the primed or unprimed substrates coated therewith, especially motor vehicle bodies.
Clearcoat materials for producing clearcoats are customary and known. They comprise one-component (1K), two component (2K) or multicomponent (3K, 4K) clearcoats, powder clearcoats, powder slurry clearcoats, and UV-curable clearcoats.
One-component (1K), two-component (2K) or multicomponent (3K, 4K) clearcoats are known from patents DE-A-42 04-518, U.S. Pat. No. 5,474,811, U.S. Pat. No. 5,356,669, U.S. Pat. No. 5,605,965, WO 94/10211, WO 94/10212, WO 94/10213, EP-A-0 594 068, EP-A-0 594 071, EP-A-0 594 142, EP-A-0 604 992, WO 94/22969, EP-A-0 596 460, and WO 92/22615.
One-component (1K) clearcoat materials comprise, as is known, hydroxyl-containing binders and crosslinking agents such as blocked polyisocyanates, tris(alkoxy-carbonylamino)triazines and/or amino resins. In another variant, they comprise as binders polymers containing pendant carbamate and/or allophanate groups, and carbamate- and/or allophanate-modified amino resins as crosslinking agents (cf. U.S. Pat. No. 5,474,811, U.S. Pat. No. 5,356,669, U.S. Pat. No. 5,605,965, WO 94/10211, WO 94/10212, WO 94/10213, EP-A-0 594 068, EP-A-0 594 071, and EP-A-0 594 142).
Two-component (2K) or multicomponent (3K, 4K) clearcoats comprise as essential constituents, as is known, hydroxyl-containing binders and polyisocyanates as crosslinking agents, which are stored separately prior to their use.
Powder clearcoats are known, for example, from German Patent DE-A-42 22 194 or from the product information sheet from BASF Lacke +Farben AG, “Pulverlacke” [Powder coatings], 1990.
Powder clearcoats comprise as essential constituents, as is known, binders containing epoxide groups, and polycarboxylic acids as crosslinking agents.
Powder slurry clearcoats are known, for example, from U.S. Pat. No. 4,268,542 and German Patent Applications DE-A-195 18 392.4 and DE-A-196 13 547 and are described in German Patent Application DE-A-198 14 471.7, unpublished at the priority date of the present specification.
Powder slurry clearcoats comprise, as is known, powder clearcoats in dispersion in an aqueous medium.
UV-curable clearcoats are disclosed, for example, in patents EP-A-O-540 884, EP-A-0 568 967, and U.S. Pat. No. 4,675,234.
Predominantly, these clearcoat materials comprise acrylate copolymers as their binders.
The known clearcoat materials may be used in accordance with the wet-on-wet technique, which is employed with preference in automotive OEM finishing; i.e., 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 the clearcoat film, after which the two films are jointly cured.
Clearcoat materials, especially aqueous clearcoat materials, 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 clearcoat materials, especially aqueous clearcoat materials, since by this means it is possible to influence the profile of performance properties of the clearcoat 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 clearcoat materials, especially aqueous clearcoat materials, which are used to produce clearcoats and multicoat color and/or effect coating systems.
It is an object of the present invention to provide new clearcoat materials, especially aqueous clearcoat materials, which are outstandingly suitable for producing clearcoats, especially as part of multicoat color and/or effect coating systems, and as an advantageous alternative to the conventional clearcoat materials. A further object of the present invention is to propose new processes for preparing the clearcoat 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 clearcoat materials, in particular through the use of chemically structured polymers obtainable by means of controlled free-radical polymerization. The new clearcoats and new multicoat color and/or effect coating systems which result with the aid of these new clearcoat materials shoul
BASF Coatings AG
Harlan Robert D.
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