Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Patent
1994-12-09
1998-11-24
Reddick, Judy M.
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
427409, 524437, 524441, 524507, 524512, 524513, 524549, 524811, B05D 136
Patent
active
058403728
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the production of a multilayer protective and/or decorative coating on a substrate surface, in which binder is applied to the substrate surface, the polyacrylate resin being obtainable by polymerization of (a) a mixture of esters of methacrylic acid and/or esters of acrylic acid, together if required with (b) further monomers different from (a) or mixtures of such monomers, subsequently
The invention also relates to aqueous paints suitable for carrying out the process described above.
The above-described process for the production of multilayer protective and/or decorative coatings is known as the basecoat/clearcoat process and is employed in particular in the production of finishes, in particular metallic finishes, on car bodies (cf. e.g. DE-A-38 41 540, EP-A-287 144, DE-A-36 28 124, EP-A-195 931 and EP-A-256 540).
The extent of the metallic effect in the multilayer coatings produced by the process under discussion depends on how many of the metallic pigment particles present in flake form and contained in the basecoat are present in the baked finish in parallel orientation to the substrate surface. The orientation of the metallic pigment particles can be disturbed in particular after the application of the transparent topcoat and/or during the baking procedure.
The object on which the present invention is based consists in the provision of a process of the type described above with which multilayer coatings can be obtained having an improved metallic effect in comparison to multilayer coatings of the prior art. This object is surprisingly achieved in that, in the pigmented basecoat, a polyacrylate resin is employed which can be obtained by employing as component (a) a mixture of esters of methacrylic acid and/or esters of acrylic acid which contains furfuryl acrylate and/or furfuryl methacrylate.
The polyacrylate resins employed in accordance with the invention can be prepared by polymerization of (a) a mixture of esters of methacrylic acid and/or esters of acrylic acid, together if appropriate with (b) further monomers different from (a) or mixtures of such monomers. It is essential to the invention to employ as component (a) a mixture of esters of methacrylic acid and/or esters of acrylic acid, which contains furfuryl acrylate and/or furfuryl methacrylate, preferably furfuryl methacrylate. It is preferred for component (a) to contain a quantity of furfuryl acrylate and/or furfuryl methacrylate such that the proportion of furfuryl acrylate and/or furfuryl methacrylate, based on the total weight of (a)+(b)=100% by weight, is 0.25 to 10% by weight, preferably 1.0 to 9.0% by weight and particularly preferably 2.0 to 7.0% by weight. The polymerization of components (a) and (b) can be carried out in an organic solvent or in a mixture of organic solvents. The solution of the polyacrylate resin obtained in this way can then be converted to an aqueous dispersion by adding water. The polyacrylate resins employed in accordance with the invention can also be prepared by polymerization of components (a) and (b) in an aqueous emulsion. Both the polymerization in organic solvents and the polymerization in aqueous emulsion are in general carried out by free-radical methods. The above-described polymerization processes are so well known that they require no further description here.
In order to obtain water-dilutable polyacrylate resins, components (a) and/or (b) must comprise monomers containing hydrophilic groups, for example carboxyl groups, sulfonic acid groups or hydrophilic polyether chains, for example --(CH.sub.2 --CH.sub.2 --O).sub.n H, --(--CHCH.sub.3 --CH.sub.2 --O).sub.n H or --(CH.sub.2 --CH.sub.2 --O).sub.x (CHCH.sub.3 --CH.sub.2 --O).sub.y H, in which n is a number from 4 to 20, x is a number from 1 to 19 and y is a number from 1 to 19. Polyacrylate resins containing carboxyl groups are in general neutralized, at least in part. As neutralizing agents it is preferred to employ tertiary amines. If the polyacrylate resins employed in accordance with the invention conta
REFERENCES:
patent: 4497929 (1985-02-01), Brown et al.
patent: 4663411 (1987-05-01), Reeb et al.
Gast Achim
Lettmann Bernhard
Rink Heinz Peter
BASF Lacke+Farben AG
Reddick Judy M.
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