Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Reexamination Certificate
2002-12-16
2004-03-16
Cameron, Erma (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
C427S359000, C427S385500, C427S407100, C427S409000
Reexamination Certificate
active
06706333
ABSTRACT:
The present invention relates to novel aqueous color and/or effect coating materials. The present invention also relates to the use of the novel coating materials to produce novel deformable color and/or effect laminates. The present invention further relates to a novel process for producing deformable color and/or effect laminates. Moreover, the present invention relates to the use of the novel deformable laminates to produce novel shaped color and/or effect parts.
Aqueous color and/or effect coating materials have been known for a long time. They are used in particular as solid-color topcoats or basecoats, especially aqueous basecoats, to produce multicoat color and/or effect coating systems. Solid-color topcoats or basecoats of this kind are described in detail, for example, in the patent applications EP 0 089 497 A1, EP 0 256 540 A1, EP 0 260 447 A1, EP 0 297 576 A1, WO 96/12747, EP 0 523 610 A1, EP 0 228 003 A1, EP 0 397 806 A1, EP 0 574 417 A1, EP 0 531 510 A1, EP 0 581 211 A1, EP 0 708 788 A1, EP 0 593 454 A1, DE-A-43 28 092 A1, EP 0 299 148 A1, EP 0 394 737 A1, EP 0 590 484 A1, EP 0 234 362 A1, EP 0 234 361 A1, EP 0 543 817 A1, WO 95/14721, EP 0 521 928 A1, EP 0 522 420 A1, EP 0 522 419 A1, EP 0 649 865 A1, EP 0 536 712 A1, EP 0 596 460 A1, EP 0 596 461 A1, EP 0 584 818 A1, EP 0 669 356 A1, EP 0 634 431 A1, EP 0 678 536 A1, EP 0 354 261 A1, EP 0 424 705 A1, WO 97/49745, WO 97/49747, EP 0 401 565 A1, EP 0 496 205 A1, EP 0 358 979 A1, EP 469 389 A1, DE 24 46 442 A1, DE 34 09 080 A1, DE 195 47 944 A1, DE 197 41 554.7 A1 and EP 0 817 684, column 5, lines 31 to 45. These are polyurethane-based coating materials.
These solid-color topcoats and basecoats give color and/or effect topcoats and basecoats having outstanding optical properties. The basecoats in particular are notable for outstanding dichroic effects and/or metallic effects.
A disadvantage of the known solid-color topcoats and basecoats is that they still always include comparatively large amounts of organic solvents. This is necessary in order to disperse the color and/or effect pigments effectively in the solid-color topcoats and basecoats, and to bring about effective leveling of the coating materials. Moreover, the known solid-color topcoats and basecoats are difficult to deform, making them unsuitable for the production of deformable color and/or effect laminates.
On the other hand, color coating materials are known which provide coatings that are deformable to a high-extent. These materials are used in particular for coating coils, as part of the coil coating process.
Coil coating is the term used for a special form of roller coating (Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, N.Y., 1998, page 617, “Roller coating”) and also, occasionally, the spray and flow coating of metal strips with liquid coating materials. It comprises a continuous process, i.e., all operations such as cleaning, pretreatment, painting and curing, etc., are conducted in one operation in one installation. Schematically, the steps involved in coil coating are as follows: following the cleaning and degreasing of the strip, there is a multistage chemical pretreatment with subsequent passivation, rinsing, and drying. After cooling, the liquid coating material is applied to one or two sides using two or three rolls, usually by the reverse roller coating technique. After a very short evaporation time, the applied coat is cured at temperatures from 180 to 260° C. for from 10 to 60 s. For the production of a multicoat system, application and curing are repeated. The speeds of coil coating lines are up to 250 m/min (Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, N.Y., 1998, page 55, “Coil coating”).
The liquid coating materials used to date for coil coating, however, lead to considerable emissions of organic solvents, which economically and environmentally is no longer acceptable.
Attempts have therefore been made to replace the conventional coil coating materials by solvent-free powder coating materials. In relation to the liquid coating materials it is a disadvantage, however, that the necessary powder coating thicknesses are very high. They are in fact between 40 and 50 &mgr;m. If the powder coating materials are applied more thinly, the coating is no longer pore-free. This leads to optical defects and sites for corrosive attack.
German Patent Application DE 196 32 426 A1 discloses a coil coating process using a very fine powder coating material with very narrow particle size distribution, which permits the production of pore-free coatings with a dry film thickness of less than 10 &mgr;m. A disadvantage is that the preparation of the very fine powder coating material is comparatively difficult.
Generally, coil coating with powder coating materials has the disadvantage of the need to use special application installations such as electrostatic powder spraying units in the case of slow-moving coils or so-called powder cloud chambers in the case of fast-moving coils.
German Patent Applications DE 199 08 013.5, DE 199 20 141.2, DE 199 08 018.6 and DE 100 01 442.9, unpublished at the priority date of the present specification, propose using aqueous pigmented and unpigmented powder slurries for coil coating. How this is to be done in detail, however, is not described.
Overall, the known coating materials, which are very suitable for the coil coating process, give color coatings whose optical properties fail to match those of the known color and/or effect basecoats and topcoats.
Also known are color coating materials that are outstandingly suitable for producing self-supporting dry-paint films and paint sheets, or for coating films. Here again, the optical properties are not entirely satisfactory.
Consequently, the known coating materials, which give highly deformable coatings and/or dry-paint films, have also as yet been unable to establish themselves in such demanding applications as that of OEM automotive finishing, especially the finishing of top-class automobiles.
On the other hand, increasing numbers of auto makers wish to reduce their manufacturing effort by—rather than they themselves painting the automobile bodies—buying in prefabricated, painted bodywork parts from suppliers and assembling them into bodies, or laminating prefabricated dry-paint films onto the bodywork parts or bodies.
The suppliers in turn, which carry out the coil coating processes or produce the dry-paint films, desire on environmental grounds, in order to reduce the organic emissions, to make use as far as possible of coating materials which contain no organic solvents.
Owing to their known high profile of properties, coating materials and coatings based on acrylate copolymers could offer an alternative to the known water-based coating materials, on the one hand, and to the coating materials commonly used for the coil coating process. Coating materials based on acrylate copolymers are described, for example, in the patents EP 0 447 428 B1, EP 0 593 454 B1, EP 0 052 776 B1 and DE 42 04 518 A1.
Acrylate copolymers may be prepared by widely and well-known polymerization techniques in bulk, solution, or emulsion. Polymerization processes for preparing acrylate copolymers, especially polyacrylate resins, are common knowledge and have been described many times (cf., e.g., Houben-Weyl, Methoden der organischen Chemie, 4th edition, volume 14/1, pages 24 to 255 (1961)).
Further examples of suitable copolymerization processes for preparing acrylate copolymers are described in the patents DE 197 09 465 A1, DE 197 09 476 C1, DE 28 48 906 A1, DE 195 24 182 A1, EP 0 554 783 A1, EP 0 650 979 B1, WO 95/27742A, DE 38 41 540 A1 and WO 82/02387 A.
However, free-radical addition polymerization employed to prepare acrylate copolymers is frequently very exothermic and difficult to control. What this means for the reaction regime is that high concentrations of monomers and/or the so-called batch procedure, where the total amount of the monomers is introduced as initial charge in an aqueous medium, emulsified and subsequently polymerized to complet
Bremser Wolfgang
Hintze-Brüning Horst
Lassmann Walter
BASF Coatings AG
Cameron Erma
LandOfFree
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