Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Reexamination Certificate
2002-02-14
2004-12-28
Berman, Susan (Department: 1711)
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
C427S515000, C522S099000, C522S148000, C526S279000
Reexamination Certificate
active
06835420
ABSTRACT:
The present invention relates to a novel coating material curable thermally and, if desired, with actinic radiation and also to a novel highly scratch-resistant multicoat clearcoat system produced using it. The present invention also relates to the use of the novel highly scratch-resistant multicoat clearcoat system in automotive OEM finishing and automotive refinish, in industrial coating, including coil coating and container coating, in the coating of plastics, and in furniture coating. The present invention further relates to a novel process for producing multicoat clearcoat systems and multicoat color and/or effect paint systems.
Automobile bodies, plastics parts for automobiles or domestic appliances, and industrial components are nowadays protected by a clearcoat. This clearcoat may be used as the sole coating film or may form the topmost coat of a multicoat color and/or effect paint system. Automobile bodies in particular are very extensively provided with a multicoat color and/or effect paint system of this kind.
The requirements imposed on the resistance of coating systems which are exposed to weathering, especially insolation and acid rain, and also, even more frequently, to mechanical stress, especially that produced by wash-brush cleaning installations, are becoming increasingly stringent. This is so most particularly for vehicle finishes, which have to meet these requirements while also satisfying very high optical demands regarding gloss, surface smoothness, and color.
To date this problem has been solved by applying to the substrates a multicoat paint system which, in accordance with the heightened environmental compatibility requirements, is constructed in particular from aqueous coating materials. In the case of metal substrates, this system is produced, conventionally, from an aqueous electrocoat material, a water-based surfacer, a basecoat material, in particular an aqueous basecoat material, and a solventborne clearcoat material. The electrocoat material and the water-based surfacer are each baked following their application, and then form the primer system. The basecoat material, particularly the aqueous basecoat material, is applied to this system and dried. Over this film, which is not yet fully cured, the clearcoat material is applied, after which the two films are cured together (wet-on-wet technique). Where the substrates used comprise plastics, water-based primers are conventionally employed in place of the electrocoat materials.
The wet-on-wet technique for producing multicoat color and/or effect paint systems is described, for example, in the patents U.S. Pat. No. 3,639,147, DE-A-3 333 072, DE-A-38 14 853, GB-A-2 012 191, U.S. Pat. No. 3,953,644, EP-A-0 260 447, DE-A-39 03 804, EP-A-0 320 552, DE-A-36 28 124, U.S. Pat. No. 4,719,132, EP-A-0 297 576, EP-A-0 069 936, EP-A-0 089 497, EP-A-0 195 931, EP-A-0 228 003, EP-A-0 038 127, and DE-A-28 18 100.
The optical or visual appearance and the weathering stability are primarily the responsibility of the two topmost coats of the multicoat paint system. Thus it is the basecoat, especially aqueous basecoat, which gives the multicoat paint system its color and/or optical effects such as metallic effects or interference effects, while the clearcoat provides not only scratch resistance and etch resistance, i.e., resistance to damaging environmental substances, but also the appearance qualities, i.e., the gloss, brilliance, and evenness. In this system, aqueous basecoat material and clearcoat material must be very precisely matched to one another in order to produce a system having the desired advantageous profile of properties.
Aqueous basecoat materials and the corresponding paint systems which substantially meet these requirements are known from the patents EP-A-0 089 497, EP-A-0 256 540, EP-A-0 260 447, EP-A-0 297 576, WO 96/12747, EP-A-0 523 610, EP-A-0 228 003, EP-A-0 397 806, EP-A-0 574 417, EP-A-0 531 510, EP-A-0 581 211, EP-A-0 708 788, EP-A-0 593 454, DE-A-43 28 092, EP-A-0 299 148, EP-A-0 394 737, EP-A-0 590 484, EP-A-0 234 362, EP-A-0 234 361, EP-A-0 543 817, WO 95/14721, EP-A-0 521 928, EP-A-0 522 420, EP-A-0 522 419, EP-A-0 649 865, EP-A-0 536 712, EP-A-0 596 460, EP-A-0 596 461, EP-A-0 584 818, EP-A-0 669 356, EP-A-0 634 431, EP-A-0 678 536, EP-A-0 354 261, EP-A-0 424 705, WO 97/49745, WO 97/49747 or EP-A-0 401 565.
For producing a single-coat or multicoat clearcoat system, use is nowadays made of the customary and known one-component (1K), two-component (2K), multicomponent (3K, 4K) power or powder slurry clearcoat materials or UV-curable clearcoat materials.
One-component (1K), two-component (2K) or multicomponent (3K, 4K) clearcoat materials are described, for example, in the patents U.S. Pat. Nos. 5,474,811, 5,356,669, 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 or WO 92/22615.
Powder clearcoat materials are known, for example, from the German patent DE-A-42 22 194 or the BASF Lacke+Farben AG product information leaflet “Pulverlacke” [powder coating materials], 1990.
Powder slurry coating materials comprise powder coatings in the form of aqueous dispersions. Slurries of this kind are described, for example, in the US patent U.S. Pat. No. 4,268,542 and the German patent applications DE-A-195 18 392.4 and DE-A-196 13 547, and in the German patent application DE-A-198 14 471.7, which was unpublished at the priority date of the present specification.
UV-curable clearcoat materials are disclosed, for example, in the patents EP-A-0 540 884, EP-A-0 568 967 or U.S. Pat. No. 4,675,234.
Each of these clearcoat materials has specific strengths and weaknesses. Accordingly, these clearcoat materials produce multicoat systems which satisfy the optical requirements. However, the scratch-resistant one-component (1K) clearcoats are sometimes not sufficiently stable to weathering, whereas the weathering-stable two-component (2K) or multicomponent (3K, 4K) clearcoats are often not sufficiently scratch-resistant. Some one-component (1K) clearcoats, although scratch-resistant and stable to weathering, exhibit surface defects such as shrinkage (wrinkling) in combination with frequently employed aqueous basecoats.
Powder clearcoats, powder slurry clearcoats, and UV-curable clearcoats, on the other hand, have a not entirely satisfactory intercoat adhesion, without fully solving the problems of scratch resistance or of etch resistance.
EP-A-0 568 967 discloses a process for producing multicoat paint systems, wherein a thermally curable clearcoat film is applied by the wet-on-wet technique to a pigmented basecoat film and then the two films are heat-cured together. Atop the cured clearcoat there is then applied at least one further clearcoat film based on coating materials curable with actinic radiation, which is cured with actinic radiation or thermally and with actinic radiation. This process provides clearcoats with high chemical resistance and optical quality. The scratch resistance, however, is unsatisfactory.
EP-A-0 568 967 further discloses a process wherein a coating material curable with actinic radiation is applied to the pigmented basecoat film and cured. Then a further film of the same coating material is applied and is cured using actinic radiation. Although the result is a highly glossy surface without perceptible texture, this clearcoat yellows. Also, the scratch resistance continues to leave something to be desired.
More recently, materials known as sol-gel clearcoats and based on siloxane-containing coating formulations have been developed which are obtained by hydrolysis and condensation of silane compounds. These materials, which are used as coating compositions on plastics, are described, for example, in the German patents DE-A-43 03 570, DE-A-34 07 087, DE-A-40 11 045, DE-A-40 25 215, DE-A-38 28 098, DE-A-40 20 316 or DE-A-41 22 743.
Sol-gel clearcoats impart very good scratch resistance to substrates made of plastic, such as spectacle lenses or motorcycle helmet visors, for example. T
Baumgart Hubert
Farwick Thomas
Röckrath Ulrike
Silber Stefan
Zumbrink Andrea
BASF Coatings AC
Berman Susan
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