Coating processes – Applying superposed diverse coating or coating a coated base – Cellulosic coating
Patent
1991-12-31
1993-10-26
Beck, Shrive
Coating processes
Applying superposed diverse coating or coating a coated base
Cellulosic coating
524 38, 524114, 4274071, 427409, 427417, B05D 136, C08L 114
Patent
active
052564533
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for the production of a multi-layer paint coating on the surface of a substrate, in which and a cellulose ester is applied to the surface of the substrate then
The invention also relates to a base paint for the production of the base coat of a multi-layer paint coating.
The process for production of a multi-layer paint coating on the surface of a substrate has already been known for a long time and is also described, for example, in U.S. Pat. No. 4,477,536.
It is a declared aim of the manufacturers of paint to reduce as far as at all possible the content of organic solvents, particularly in the base paints for the production of multi-layer paint coatings. The associated increase in the proportion of nonvolatile constituents results in an increase in the viscosity. When the viscosity under application conditions exceeds a certain limit, paint coatings having considerable disadvantages (blushing, poor metallic effect and poor appearance . . . ) are obtained On the other hand, the addition of substances which, by virtue of their relatively low molecular weight, only cause a relatively low increase in the viscosity results, as a rule, in inferior paint coatings, because the transparent finish incipiently dissolves the base paint (the base paint and the finish are applied by the wet-on-wet process).
The object on which the present invention is based consists, accordingly, in providing base paints which have as high a content as possible of nonvolatile constituents, without the occurrence of the above-mentioned problems.
SUMMARY OF THE INVENTION
This object is achieved, surprisingly, by the use of base paints which contain 5 to 20, preferably 7 to 15, percent by weight of crosslinked polymer microparticles, 2 to 15, preferably 4 to 13, percent by weight of a cellulose ester or of a mixture of at least two types of cellulose ester having different molecular weight distributions, and 5 to 20, preferably 7 to 15, percent by weight of an epoxidized fatty acid ester or of a mixture of epoxidized fatty acid esters, in which the weight percentages relate to the total content of nonvolatile constituents, excluding pigments and inorganic fillers, and the cellulose ester or the mixture of cellulose esters is so selected that a solution of 15 parts by weight of the cellulose ester or of a mixture of at least two cellulose esters in 85 parts by weight of a mixture of acetone and ethanol (ratio by weight of acetone to ethanol=9:1) at 23.degree. C. has a viscosity of 200 to 600, preferably 300 to 500, mPa.s
It is known to employ epoxidized fatty acid esters in base paints free from polymer microparticles, particularly for improving the absorption of spray dust. The addition of epoxidized fatty acid esters to base paints free from polymer microparticles results, even when relatively small amounts are added, in the incipient dissolution problems described above, which are more or less visible depending on the color shade of the base paint.
It is surprising that it is possible, by means of a combination of crosslinked polymer microparticles with a cellulose ester or a mixture of cellulose esters in which the cellulose ester component exhibits a certain viscosity behavior, and an epoxidized fatty acid ester, to obtain base paints which, in spite of an increased content of nonvolatile constituents, are very reliable in application and afford two-layer paint coatings which exhibit no disadvantages due to incipient dissolution processes and, in addition, are also distinguished by an improved clear coat hold out and an improved resistance to chemicals. A further advantage of the base paints according to the invention lies in the fact that the cover over unevenness in the underlying layer of filler particularly well, which results in good clear coat hold out.
DETAILED DESCRIPTION OF THE INVENTION
In addition to the cellulose ester, the epoxidized fatty acid ester and the polymer microparticles, the base paints employed in accordance with the invention also contain a
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Dobbelstein, deceased Arnold
Heithorn Monika
Mahr Gerold
Wieditz Stefan
BASF Lacke & Farben Aktiengesellschaft
Beck Shrive
Dudash Diana L.
Marshall Paul L.
Werner Frank C.
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