Stock material or miscellaneous articles – Composite
Patent
1997-02-18
1998-10-13
Dudash, Diana
Stock material or miscellaneous articles
Composite
427140, 427421, 427470, B05D 104, B05D 136
Patent
active
058209867
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for the production and repair of multicoat special-effect coatings and to coated substrates which can be produced by this method.
Multicoat special-effect coatings which are preparable by containing at least one plateletlike pigment, automotive finishing. If the coating materials containing plateletlike pigments which are employed to produce the basecoat are coating materials containing aluminum flakes, then, for example, the widespread metallic coatings are obtained.
Both during and after the production-line finishing process, instances of damage to the coating occur which must be repaired. In this context, either the basecoat can be repaired prior to coating with a transparent coating material, or the baked, multicoat coating can be repaired, using a coating material containing at least one plateletlike pigment, further coating with a transparent coating material followed by renewed baking being carried out in the latter case. It is of great importance that the repaired sites on the finished coating cannot be recognized by differences in the color and in the brightness.
In order to achieve this, in production-line automotive finishing at least the last spray pass for the production of the basecoat is carried out with the aid of a pneumatic application process.
Pneumatic application processes, however, have the disadvantageous feature that a relatively large proportion of the quantity of coating material sprayed does not reach the substrate, and consequently the air circulated in the spraybooth must be at high speeds so that the relatively large quantities of overspray can be deposited and disposed of.
The technical object of the present invention is to provide a method for the production and repair of multicoat special-effect coatings, in which containing at least one plateletlike pigment, material containing at least one plateletlike pigment, coating material, a coating material containing at least one plateletlike pigment, material, and steps (1), (2), (3), and (4) or of steps (1), (3), (4), (5), (6) and (7), which method does not have the above-described disadvantages of the prior art.
This object is surprisingly achieved by a method which is characterized in that 18% by weight and at a temperature of 23.degree. C. and at a shear rate of 1000 s.sup.-1 after a shear period of 6 s has an apparent viscosity of from 40 to 200, preferably from 60 to 150 mPa s, after a shear period of 300 s at a shear rate of 1000 s.sup.-1 has an apparent viscosity of from 40 to 200, preferably from 60 to 150 mPa s, at a shear rate of 5 s.sup.-1 after a shear period of 10 s has an apparent viscosity of from 100 to 2000, preferably from 200 to 800 mPa s, and after a shear period of 300 s at a shear rate of 5 s.sup.-1 has an apparent viscosity of from 100 to 2000, preferably from 500 to 1500 mPa s, the measurements carried out at the shear rate of 5 sec.sup.-1 having been carried out directly after pre-shearing for 300 s at a shear rate of 1000 s.sup.-1, and the apparent viscosity measured at a shear rate of 5 s.sup.-1 after a shear period of 300 s being from 0 to 1000, preferably from 200 to 600 mPa s higher than the apparent viscosity measured at a shear rate of 5 s.sup.-1 after a shear period of 10 s, elecrostatic spraying, and with the aid of a spray application process in which a spray jet is produced which consists of coating droplets and which is distinguished in that measurement point which lies at the center of the spray jet and 300 mm away from the nozzle have a diameter which is less than 20 .mu.m and at least 5%, preferably from 10 to 30%, of the coating droplets passing this measurement point have a diameter which is greater than 60 .mu.m, measurement point which lies at the center of the spray jet and 300 mm away from the nozzle have a speed which is less than 6 m/s and at most 30%, preferably from 0 to 20%, of the coating droplets passing this measurement point have a speed of more than 10 m/s, and of the spray jet and 300 mm away from the nozzle have a momentum which is equal
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Bischoff Ewald
Herbst Dieter
Libutzki Harry
Streitberger Hans-Joachim
Topfel Heinz
BASF Lacke & Farben AG
Dudash Diana
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