Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Patent
1995-05-22
1999-01-05
Beck, Shrive
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
427482, 427485, 427486, B05D 104, B05D 106
Patent
active
058559647
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the production of a multicoat finish on a substrate surface, in which subsequently
2. Description of the Prior Art
The invention also relates to powder clearcoats which are suitable for this process.
The process described above is known. It is employed in particular for the production of automotive topcoats, in particular for the production of metallic finishes (cf. eg. DE-A-38 14 853, U.S. Pat. No. 3,953,644, EP-A-299 420 (in particular page 5, line 22/23), U.S. Pat. No. 4,402,983, EP-A-45 040 and GB-A-20 12 191).
It is desirable for economic and ecological reasons to employ powder clearcoats in step (3) of the basecoat/clearcoat process described above. When powder clearcoats are used, the clearcoats obtained are in need of improvement, in particular with regard to gloss and leveling.
SUMMARY OF THE INVENTION
The object on which the present invention is based consists in the provision of a process of the type described above with which the finishes which can be obtained are improved with regard to the finishes of the prior art. The finishes should be improved in particular with regard to the gloss and leveling of the stoved clearcoat.
This object is surprisingly achieved in that, in step (3) of the basecoat/clearcoat process described above, a powder clearcoat is employed which has a particle size distribution in which particle size smaller than 10 .mu.m; logarithm of the quotient of the largest and the smallest particle size is less than or equal to 0.25; and size smaller than 100 .mu.m.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 illustrates the particle size distribution of a prior art clearcoat as described in Example 1.
FIG. 2 illustrates a particle size distribution of a clearcoat according to the present invention as described in Example 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In step (1) of the process, it is in principle possible to employ all pigmented basecoats which are suitable for the production of multicoat finishes. Such basecoats are well known to those skilled in the art. Both water-dilutable basecoats and basecoats based on organic solvents can be employed. Suitable basecoats are described in, for example, U.S. Pat. No.3,639,147, DE-A-33 33 072, DE-A-38 14 853, GB-A-2 012 191, U.S. Pat. No. 3,953,644, EP-A-260 447, DE-A-39 03 804, EP-A-320 552, DE-A-36 28 124, U.S. Pat. No. 4,719,132, EP-A-297 576, EP-A-69 936, EP-A-89 497, EP-A-195 931, EP-A-228 003, EP-A-38 127 and DE-A-28 18 100.
In step (2) of the process, the solvents or the water are/is removed in a flash-off phase from the basecoat applied in step (1). The basecoat can also be stoved. However, this is disadvantageous on economic grounds, since in this case two stoving procedures instead of one are required to produce the multicoat finish.
In step (3), the powder clearcoat is preferably applied electrostatically. It is in principle possible to employ all powder clearcoats suitable for the production of multicoat finishes. Such powder clearcoats are well known. Suitable powder clearcoats are described in, for example, DE-A-38 14 853, GB-A-20 12 191, U.S. Pat. No. 3,953,644, DE-A-23 03 650, EP-A-299 420, U.S. Pat. No. 4,402,983 and EP-A-45 040.
It is essential to the invention that the powder clearcoat employed in step (3) has a particle size distribution in which the powder clearcoat particles have a particle size smaller than 10 .mu.m; particularly preferably for at least 60% by weight of the powder clearcoat particles, the common logarithm of the quotient of the largest and the smallest particle size is less than or equal to 0.25, preferably less than or equal to 0.20 and particularly preferably less than or equal to 0.15; and clearcoat particles have a particle size smaller than 100 .mu.m.
It is preferred for the average particle size of the powder clearcoat particles mentioned in b) (in other words, those powder clearcoat particles which fulfill the condition that the common logarithm of the quotient of the largest and smalle
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Derwent, Sealing pipes using cyanoacrylate-diimethacrylate composition, one pg. No date avail.
Rademacher Josef
Reiter Udo
BASF Lacke & Farben AG
Beck Shrive
Parker Fred J.
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