CA2393289A1 - Achromatic lacquers, a method for producing same and the use thereof - Google Patents

Abstract

The invention relates to an achromatic lacquer containing at least one binding agent, at least one root pigment and at least one silicone.

Description

ACHROMATIC hACQUERS, A METHOD FOR PRODUCING
SALE AND THE USE THEREOF
The present invention relates to novel achromatic paints, especially jet black paints. The present invention further relates to a novel process for preparing achromatic paints, especially jet black paints. The present invention relates not least to the use of the novel achromatic paints in automotive OEM
finishing and automotive refinish, in industrial coating, including container coating and coil coating, and in furniture coating.
Achromatic paints differ from the chromatics in that they lack chroma and hue; they exhibit only lightness.
The achromatic colors include black and white and also the gray shades which lie between them or can be mixed from them (cf. Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998 "achromatic point", page 590). In the context of the present invention, however, achromatic colors are understood to embrace black and gray shades.
To produce jet black shades is a declared objective in the paint industry. However, this causes great difficulties particularly in the case of aqueous paints. In general, an improvement in pigment wetting is achieved by adding wetting agents and dispersants.
This raises the color strength, giving cleaner, deeper shades. In the case of carbon black pigments, however, which form the bases of achromatic paints, especially jet black paints, this technique does not provide the desired success.
The German patent DE-C-197 56 465 discloses jet black conventional and aqueous paints which comprise carbon black pigments. The carbon black pigments contain, based on their overall weight, from 0.1 to 30~ by weight of silicon, calculated as silicon dioxide. These carbon black pigments are obtained by adding suitable silicon-containing compounds to the base carbon black material. An alternative possibility which exists is to supply the silicon-containing compounds to the feed stream of the respective carbon black process, shortly before or directly in the carbon black formation zone.
Suitable silicon-containing compounds are organosilicon compounds such as organosilanes, organochlorosilanes, siloxanes and silazanes. Particularly suitable are silicon tetrachloride, siloxanes, and silazanes.
Preference is given to methyl or ethyl silicate, siloxanes, and silazanes for the preparation of the silicon-containing carbon blacks.
A disadvantage of this known technique is that the carbon black pigments are modified as part of the carbon black process, so that the properties. of the respective carbon black pigments are decided as such by the comparatively complex production process and not by means of a simple, targeted modification of customary and known commercial carbon black pigments as part of the paint production process. The targeted preparation of carbon black pigments possessing special suitability for a given end application is therefore very complex.
A further factor is that, at the higher temperatures employed in the production of carbon black, the organosilicon compounds are altered in a way which is difficult to predict, thereby making the targeted production of modified carbon black pigments even more difficult.
It is an object of the present invention to provide novel achromatic paints, especially jet black paints, which can be prepared in a simple yet targeted way and whose carbon black pigments can be modified not as part of the carbon black process but rather as part of the paint production process, in a simple way, to give an ' CA 02393289 2002-06-03 improvement in the jetness without detriment to the other essential performance properties of the respective paints.
Found accordingly have been the novel achromatic paints which comprise at least one binder, at least one carbon black pigment, and at least one silicone.
In the text below, the novel achromatic paints are referred to as "paints of the invention".
Also found has been the novel process for preparing the paints of the invention, in which at least one binder, at least one carbon black pigment, and at least one silicone are mixed with one another, and which is referred to below as "process of~the invention".
A further subject matter of the invention will emerge from the following description.
In the light of the prior art it was surprising and unforeseeable for the skilled worker that the object on which the present invention is based could be achieved by means of the process of the invention and the paints of the invention. Put another way, it was surprising that, by means of the usually accomplished measure of adding an additive, it was possible to provide an alternative, attractive in terms both of performance and of economics, to the complex production process of silicon-containing carbon black pigments. A very particular surprise was that the addition of the silicones does not lead to the well-known, unwanted side effects of silicone additives such as foaming, problems of wetting and adhesion on overcoating (cf.
the textbook "Lackadditive" [Additives for coatings] by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998, page 139) and/or to paint defects such as craters (on this point, cf. Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, ' CA 02393289 2002-06-03 "silicone additives", page 524).
The inventively essential constituent of the paints of the invention is at least one silicone. Silicones are also referred to by those in the art, as will be known, as silicone oils, polysiloxanes, polyorganosiloxanes or organosiloxanes. They are synthetic polymeric compounds in which the silicon atoms are linked in the form of chains and/or networks via oxygen atoms and the remaining valences of the silicon are satisfied by hydrocarbon radicals, preferably methyl, phenyl, ethyl and/or propyl groups, especially methyl groups.
Depending on chain length, degree of branching, and substituents, the silicones may be oils with a viscosity ranging from low to high, or may be solid.
Furthermore, they may have been modified with polyethers. For further details, refer to Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "silicone additives", page 524, "silicone copolymers", page 525, and "silicones", page 525.
In accordance with the invention, linear liquid silicones and silicone oils are used which contain from 10 to 100, preferably. from 11 to 80, more preferably from 12 to 70, with particular preference from 13 to 60, with very particular preference from 14 to 55, and in particular from 15 to 50 Si-0 units. It is preferred to use silicone copolymers that have been modified with polyethers, especially polyethylene oxide-co-propylene oxide). Particularly preferred silicones are head-to-head modified, with the polyether chains being linked to the siloxane chains by way of allyl groups. Very particularly preferred silicones contain polyether chains composed of from 10 to 90 mol o, preferably from 15 to 85 mol%, of ethylene oxide units and from 90 to 10 molo, preferably from 85 to 15 mol%, of propylene oxide units. The polyether chains preferably have a number-average molecular weight Mn of from 500 to 3000, z more preferably from 600 to 2500, with particular preference from 800 to 2200, and in particular from 900 to 2000. The silicones overall preferably have a number-average molecular weight Mn of from 2000 to 10,000, more preferably from 2100 to 9500, with particular preference from 2200 to 9000, with very particular preference from 2300 to 8500, and in particular from 2400 to 8000.
Especially suitable silicones contain, for example, chains having 18 Si-O units and 2 head-to-head-linked polyether chains with a number-average molecular weight Mn of 1250, containing 80 molo of ethylene oxide units and 20 mold of propylene oxide units, or chains having 48 Si-O units and 2 head-to-head-linked polyether chains with a number-average molecular weight Mn of 1860, containing 50 mol°s of ethylene oxide units and 50 mold of propylene oxide units.
The silicones of the type specified are customary and known and are available on the market.
The silicone content of the paints of the invention may vary very widely and is guided on the one hand by the particular carbon black pigment used and on the other hand by the compatibility of the other constituents of the paints of the invention with the silicones. The skilled worker is therefore easily able to determine the amount on the basis of his or her general art knowledge with the assistance, where appropriate, of simple preliminary tests. The amount is preferably from 0.01 to 2.0~, more preferably from 0.02 to 1.50, with particular preference from 0.03 to 1.2%, with very particular preference from 0.03 to 1.0o, and in particular from 0.04 to 0.8% by weight based in each case on the overall amount of the paint of the invention.
The further inventively essential constituent of the paint of the invention is at least one carbon black pigment. Carbon black pigments are also referred to by those in the art as pigment blacks, color blacks or carbon pigments. They are normally prepared by the furnace black, Degussa gas black and lamp black process. In general they have primary particle sizes of from 10 to 200 nm. For further details, refer to Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "industrial carbon blacks", pages 300 and 301, and "pigment blacks", pages 452 and 453. The choice of which carbon black pigment is employed in the paint of the invention is guided primarily by the desired shade or the desired depth of color and by the particular end utility. The skilled worker is therefore easily able to determine the carbon blacks best suitable. in each case, on the basis of his or her general art knowledge with the assistance, where appropriate, of simple preliminary tests. The amount of the carbon black pigments in the paints of the invention may vary widely. It is preferably from 0.5 to 20%, more preferably from 1.0 to 18%, with particular preference from 1.2 to 16%, with very particular preference from 1.3 to 15%, and in particular from 1.4 to 14% by weight, based in each case on the paint of the invention.
A further essential constituent of the paint of the invention has at least one binder. Regarding the definition, refer to Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "binders", pages 73 and 74).
Examples of suitable binders are oligomeric and polymeric, thermally curable, linear and/or branched and/or block, comb and/or random poly(meth)acrylates or acrylic copolymers, especially those described in patent DE-A-197 36 535, polyesters, especially those described in patents DE-A-40 09 858 or DE-A-44 37 535, alkyds, acrylated polyesters, polylactones, polycarbon-'' CA 02393289 2002-06-03 - 7 _ ates, polyethers, epoxy resin-amine ,adducts, (meth)acrylatediols, partially hydrolyzed polyvinyl esters, polyurethanes and acrylated polyurethanes, as described in patents EP-A-0 521 928, EP-A-0 522 420, EP-A-0 522 419, EP-A-0 730 613 or DE-A-44 37 535, or polyureas.
The selection of the binders is guided in particular by whether the paints of the invention are conventional paints, comprising organic solvents, or aqueous paints, or water- and solvent-free liquid paints (100 systems), solid pulverulent paints (powder coatings), or water-dispersed powder coatings (powder slurries).
The selection of the binders is further guided by whether the paints of the invention are physically cured paints. As is known, physical curing takes place by loss of solvent from the applied paint film and/or with coalescence of binder . particles. For further details, refer here to Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "curing", pages 274 and 275).
Additionally, the selection of the binders is guided by whether the paints of the invention are self-crosslinking paints or externally crosslinking paints.
As is known, the term "self-crosslinking" refers to the capacity of a binder to undergo crosslinking reactions with itself. A prerequisite for this is that the binders already contain both kinds of complementary reactive functional groups which are necessary for crosslinking, such as hydroxyl groups and blocked isocyanate groups or N-methylol groups. Externally crosslinking paints, on the other hand, are those in which one kind of the complementary reactive functional groups, say the hydroxyl groups, are present in the binder and the other kind, say the blocked isocyanate groups or the N-methylol groups, are present in a curing or crosslinking agent. For further details of this, refer to Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "curing", pages 274 to 276, particularly page 275, bottom.
Moreover, the selection of the binders is guided by the intended use. The paint of the invention is preferably used in automotive OEM finishing and automotive refinish as a surfacer, solid-color topcoat material or as a basecoat material, especially an aqueous basecoat material, as part of what is known as the wet-on-wet technique (cf., for example, European patent EP-B-0 089 497) for producing multicoat color and/or effect paint systems. In addition it is suitable for industrial coating, including coil coating and container coating, and also for furniture coating.
The skilled worker is therefore easily able to determine the binders which are best suited in each case, taking into account the requirements associated with the form of the paint of the invention and/or with its aggregate state and its particular intended use, on the basis of his or her general art knowledge with the assistance where appropriate of simple preliminary tests. The same applies to the amount of the binders in the paints of the invention, which may vary extremely widely and is preferably from 1.0 to 99.499%, more preferably from 2.0 to 98%, with particular preference from 3.0 to 95%, with very particular preference from 4.0 to 92%, and in particular from 5.0 to 90% by weight based in each case on the paint of the invention.
The paint of the invention may be a one-component (1K) system.
For the purposes of the present invention a one-component (1K) system is a thermosetting coating material in which the binder and the crosslinking agent are present alongside one another, i.e., in one component. A prerequisite for this is that the two constituents crosslink with one another only at relatively high temperatures.
The paint of the invention may also be a two-component (2K) or multicomponent (3K, 4K) system.
For the purposes of the present invention, this means a paint of the invention in which in particular the binder and the crosslinking agent are present separately from one another in at least two components which are not combined until shortly before application. This form is chosen when binder and crosslinking agent react with one another even at room temperature, which is the case, as is known, when using hydroxyl groups on the one hand and isocyanate groups on the other. Paints of the invention of this kind are employed in particular for coating thermally sensitive substrates, especially in automotive refinish.
Besides the inventively essential constituents described above, the paints of the invention may comprise additional pigments in customary and known amounts.
The pigments in question are primarily white pigments, especially when the paint of the invention is a gray paint. Suitable white pigments are described, for example, in Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, 1998, "white pigments", page 629.
The paint. of the invention may further comprise effective amounts of customary and known effect pigments which do not per se induce any chromaticity.
Examples of suitable effect pigments are described, for example, in Rompp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, 1998, page 176, "effect pigments"; or pages 380 and 381 "metal oxide-mica pigments" to "metal pigments".

The paint of the invention, especially the externally crosslinking paint of the invention, may further comprise crosslinking agents in customary and known, effective amounts.
Examples of suitable crosslinking agents are amino resins, compounds or resins containing anhydride groups, compounds or resins containing epoxide groups, tris(alkoxycarbonylamino)triazines, compounds or resins containing carbonate groups, blocked and/or nonblocked polyisocyanates, beta-hydroxyalkylamides, and compounds containing on average at least two groups capable of transesterification, examples being reaction products of malonic diesters and polyisocyanates or of esters and partial esters of polyhydric alcohols of malonic acid with monoisocyanates, such as described in European patent EP-A-0 596 460.
Crosslinking agents of this kind are obtainable commercially.
Not least, the paint of the invention may comprise customary and known paint additives in effective amounts.
Examples of suitable paint additives are organic and inorganic fillers which do not per se induce' any chromaticity, transparent pigments, thermally curable reactive diluents, low-boiling and/or high-boiling organic solvents ("long solvents"), UV absorbers, light stabilizers, free-radical scavengers, thermal labile free-radical initiators, crosslinking catalysts, devolatilizers, slip additives, polymerization inhibitors, defoamers, emulsifiers, wetting agents, adhesion promoters, leveling agents, film-forming auxiliaries, rheology control additives or flame retardants. Further examples of suitable paint additives are described in the textbook "Lackadditive"
[Additives for coatings] by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998.
The preparation of the paint of the invention has no special features but instead takes place in a customary and known way by mixing of the above-described constituents in suitable mixing equipment such as stirred tanks, dissolvers, stirrer mills or extruders by the techniques suitable for preparing the respective paints of the invention. Particular advantages result if the carbon black pigments for use in accordance with the invention are incorporated by way of pigment pastes. These pastes may already contain the silicones for use in accordance with the invention, or a portion thereof.
The paint of the invention, especially the aqueous basecoat material of the invention, is used for producing the paint systems of the invention, especially multicoat paint systems, on primed. or unprimed substrates.
Suitable substrates include all surfaces intended for painting; that is, for example, metals, plastics, wood, ceramic, stone, textile, fiber composites, leather, glass, glass fibers, glass wool and rock wool, mineral-and resin-bound building materials, such as plaster-board and cement slabs or roofing shingles, and composites of these materials. Accordingly, the paint system of the invention is also suitable for applications outside of automobile finishing. In this case it is suitable in particular for the painting of furniture, for do-it-yourself painting, and for industrial painting, including coil coating and container coating. In the context of do-it-yourself painting and industrial coating it is suitable for coating and refinishing virtually all parts for private or industrial use such as radiators, domestic appliances, small metal parts such as nuts and bolts, hubcaps, wheel rims or packaging.

In the case of electrically conductive substrates it is possible to use primers produced conventionally from electrocoat materials. Both anodic and cathodic electrocoat materials are suitable for this purpose, but especially cathodics.
The paints of the invention may also be used to coat primed or unprimed plastics such as, for example, ABS, AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, PA, PE, HDPE, LDPE, LLDPE, UHMWPE, PET, PMMA, PP, PS, SB, PUR, PVC, RF, SAN, PBT, PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM, and UP (abbreviated codes in accordance with DIN 7728P1). The plastics to be painted may of course also be polymer blends, modified plastics or fiber-reinforced plastics. It is also possible to employ the plastics commonly used in vehicle construction, especially motor vehicle construction.
Nonfunctionalized and/or apolar substrate surfaces may be subjected prior to coating in a known manner to a pretreatment, such as with a plasma or by flaming, or may be provided with a hydroprimer.
The paint of the invention may be applied by any customary application method, such as spraying, knife coating, brushing, flow coating, dipping, impregnating, trickling or rolling, for example . The substrate to be coated may itself be at rest, with the application equipment or unit being moved. Alternatively, the substrate to be coated, in particular a coil, may be moved, with the application unit being at rest relative to the substrate or being moved appropriately.
Preference is given to employing spray application methods, such as compressed air spraying, airless spraying, high-speed rotation, electrostatic spray application (ESTA), alone or in conjunction with hot spray applications such as hot air spraying, for example. The applications may be conducted at temperatures of max. 70 to 80°C, so that suitable application viscosities are achieved without the brief exposure to thermal loading being accompanied by any changing or damage to the aqueous basecoat material or its overspray, which may be intended for reprocessing.
Hot spraying, for instance, may be configured in such a way that the paint is heated only very briefly in the spray nozzle or shortly before the spray nozzle.
The spray booth used for the application may be operated, for example, with a circulation system, which may be temperature-controllable, and which is operated with a suitable absorption medium for the overspray, an example being the paint of the invention itself.
The paints of the invention are generally applied in a wet film thickness such that curing thereof results in coats having the thicknesses which are advantageous and necessary f.or their functions. In the case of the surfacer coat this thickness is from 10 to 150 um, preferably from 10 to 120 um, with particular preference from 10 to 100 pm, and in particular from 10 to 90 um, in the case of the basecoat it is from 5.0 to 50 um, preferably from 5.5 to 40 pm, with particular preference from 6 to 30 um, and in particular from 10 to 25 ~zm, and in the case of the solid-color topcoat it is from 5.0 to 100 um, preferably from 5.5. to 80 pm, with particular preference from 6 to 70 ~zm, and in particular from 10 to 60 um.
The applied paint films of the invention, especially the surfacer films, basecoat films, and solid-color topcoat films, are cured thermally.
In the case of the wet-on-wet technique, the basecoat films of the invention, especially aqueous basecoat films, are not cured thermally but instead are predried and then overcoated with customary and known clearcoat materials. After that, the basecoat films of the v invention and the clearcoat films are thermally cured together, using the methods described below. This results in the multicoat paint systems of the invention.
Curing may take place after a certain rest time. This may have a duration of from 30 s to 2 h, preferably from 1 min to 1 h, and in particular from 1 min to 45 min. The rest time serves, for example, for the leveling and devolatilization of the paint films or for the evaporation of volatile constituents such as solvents. The rest time may be shortened and/or assisted by the application of elevated temperatures up to 90°C and/or by a reduced atmospheric humidity < 10 g water/kg air, in particular < 5 g/kg air, provided this does not entail any damage to or change in the paint films, such as premature complete crosslinking.
Thermal curing has no special features in terms of its method but instead takes place in accordance with the customary and known methods such as heating in a forced air oven or irradiation with IR lamps. Thermal curing here may also take place in stages. Thermal curing takes place advantageously at a temperature of from 50 to 100°C, with particular preference from 60 to 100°C, and in particular from 80 to 100°C for a time of from 1 min up to 2 h, with particular preference 2 min up to 1 h, and in particular 3 min to 45 min. Where substrates are used which can withstand high thermal loads, thermal crosslinking may also be conducted at temperatures above 100°C. In general it is advisable in this case not to exceed temperatures of 180°C, preferably 160°C, and especially 155°C.
The paint systems of the invention, especially the multicoat paint systems of the invention, have an outstanding profile of properties which is very well balanced in terms of mechanics, optics, corrosion resistance, and adhesion. In particular, the multicoat paint systems of the invention exhibit an outstanding D.O.I. (distinctiveness of the reflected image) and an outstanding surface smoothness.
Examples and comparative experiments Preparation Example 1 The preparation of a grinding resin dispersion based on polyurethane In a reaction vessel equipped with a stirrer, a reflux condenser, and 2 feed vessels, 63.5 parts by weight of isophorone diisocyanate were added to a mixture of 77.6 parts by weight of a polyesterdiol having a number-average molecular weight of 630 based on adipic acid, hexanediol, and neopentyl glycol, 9.3 parts by weight of neopentyl glycol, 3.0 parts by weight of trimethylolpropane monoallyl ether, 0.1 part by weight of dibutyltin dilaurate, and 110.2 parts by weight of methyl isobutyl ketone. The resultant reaction mixture was then heated at 105°C. At an isocyanate content of 1.8% by weight, 15.1 parts by weight of trimethylol-propane were added to the reaction mixture and the reaction was continued until free isocyanate groups were no longer detectable.
To the resultant polyurethane solution there was added at 105°C over the course of three hours a mixture of 69.6 parts by weight of n-butyl acrylate, 69.6 parts by weight of methyl methacrylate, 16.6 parts by weight of hydroxypropyl methacrylate, and 13.0 parts by weight of acrylic acid. At the same time, 5.1 parts by weight of tert-butyl perethylhexanoate, dissolved in 42.8 parts by weight of methyl isobutyl ketone, were metered in over the course of 3.5 hours. After a further 2.5 hours at 105°C, the reaction mixture was cooled to 90°C. Then 10.6 parts by weight of dimethylethanolamine and 483.2 parts by weight of deionized water were added. Removal of the methyl isobutyl. ketone in vacuo gave a stable polyurethane dispersion having a solids content of 43%
by weight and a pH of 7.9.
Preparation Example 2 Preparation of a binder dispersion A 4 1 steel reactor suitable for free-radical copolymerization, with metering attachments and reflux condenser, was charged with 583 parts by weight of propanol and this initial charge was heated to 95°C.
Over the course of 5 minutes, a mixture of 2.2 parts by weight of Trigonox~ 421 (free-radical polymerization initiator from Akzo) and 13 parts by weight of propanol was added. At the same time, a mixture of 83.2 parts by weight of acrylic acid, 240 parts by weight of styrene, and 290 parts by weight of butyl acrylate was metered in at a uniform rate over the course of 2 hours and also 3.5% of a mixture of 181 parts by weight of Trigonox~ and 181 parts by weight of propanol was metered in over the course of 30 minutes. Subsequently, the resultant reaction mixture was heated at 95°C for a further 20 minutes.
After this time, a mixture of 86.2 parts by weight of styrene and 115 parts by weight of n-butyl acrylate was metered in at a uniform rate over the course of 2 hours, and, beginning at the same time, 6.2% of the mixture of 181 parts by weight of Trigonox~ and 181 parts by weight of propanol was metered in over the course of one hour. After the end of the two feed streams, the reaction mixture was postpolymerized for one hour.
Subsequently, after this time, a mixture of 180 parts by weight of methyl methacrylate, 315 parts by weight of styrene, and 495 parts by weight of n-butyl acrylate was metered in at a uniform rate over the course of 4 hours, and, beginning at the same time, 48.1$ of the mixture of 181 parts by weight of Trigonox~ and 181 parts by weight of propanol was metered in over the course of 4 hours.
Finally, 42.2% of the mixture of 181 parts by weight of Trigonox~ and 181 parts by weight of propanol were metered in over the course of 2 hours.
After the end of the feed streams, the temperature of the reaction mixture was held at 95°C for 1.5 hours more.
The resultant solution had a solids content of 70.6 by 1S weight (2 g initial mass + 2 g xylene; 1 hour at 130°C) and an acid number of 41.8 mg KOH/g. The solution was adjusted to a solids content of 37~ by weight using 75.6 parts by weight of 25$ aqueous ammonia and isopropanol. The viscosity of the dilute solution was 4.4 dPas. The copolymer had a number-average molecular weight Mn of 15.981 and a mass average molecular weight Mw of 53.316 (determined by gel permeation chromatography with polystyrene as internal standard).
Example 1 and comparative experiment Cl The preparation of a jet black inventive paint (Example 1) and of a noninventive paint (comparative experiment C1) For Example 1, 30 parts by weight of the binder dispersion of preparation Example 2 were introduced as an initial charge. Added to this with stirring were 4.4 parts by weight of propanol, 0.4 part by weight of a commercial wetting agent based on a phosphoric monoester (Pigmentverteiler LR 8807 from BASF AG), and 0.4 part by weight of a technical-grade ammonia solution, with stirring.

0.3 part by weight of a commercial emulsifier (Surfynol~ 104 E, 50o in ethylene glycol), 0.05 part by weight of sodium nitrite and 6.45 parts by weight of deionized water were mixed with one another and the resultant mixture was added with stirring to the mixture described above.
The resultant mixture was admixed, with vigorous stirring, with 2.2 parts by weight of amorphous carbon black (Printex U~ from Degussa), 0.7 part by weight of pyrogenic silica (Aerosil~ 200 CV), 12 parts by weight of precipitated barium sulfate (Blanc Fixe~ Micro from Sachtleben) and 4 parts by weight of propanol.
The resultant mixture was ground on a horizontal stirrer mill (grinding media SAZER; 1.6-2.5 mm diameter, Si-Zr beads) at a maximum temperature of 50°C
to a Hegmann fineness of from 13 to 15 um (wedge um) .
The stirrer mill was rinsed first with 10.5 parts by weight of water and then with 10.5 parts by weight of propanol. Subsequently, 18 parts by weight of the binder dispersion of preparation Example 2 and also 0.1 part by weight of the silicone Tego Glide~ 410 (100 0) from Tego Chemie GmbH were added to the mixture.
The pH of the resultant premix of the invention was adjusted to 8.7-9.0 using ammonia. The viscosity of the premix of the invention was adjusted to 40 s in the DIN 4 flow cup using a mixture of propanol and water (1:1) .
74.4 parts by weight of this premix were mixed with 53.9 of dimethyl ether and applied. The resultant paint system was measured by colorimetric.
For comparative experiment C1, Example 1 was repeated but without using any silicone. The resultant paint ,' CA 02393289 2002-06-03 system was likewise measured by colorimetry. The values obtained in this case were defined as the standard.
Table 1 indicates the deviations of the colorimetric results obtained in the case of Example 1 from the standard. A distinct shade shift relative to the standard is evident, i.e., the shade becomes cleaner and f etter .
Table 1: Color distances in the Cielab color space (illuminant: D65) Example dL* da* db* dC* dH* dE*
No.
1 0.2 -0.1 -0.3 0.3 -0.1 0.4 C1 Standard Example 2 and comparative experiment C2 The preparation of a jet black inventive paint and production of an inventive multicoat paint system (Example 2 ) and preparation of a noninventive paint and production of an noninventive multicoat paint system (comparative experiment C2) For Example 2 and comparative experiment C2, first of all a black paste was prepared. This was done by introducing 52 parts by weight of the grinding resin dispersion from preparation Example 1 as an initial charge. To this dispersion there were added, with stirring, 13 parts by weight of a commercial dispersant (Disperbyk~ 184 from Byk Chemie), 10 parts by weight of a carbon black pigment (Monarch~ 1400), 7.0 parts by weight of a loo strength diethanolamine solution, and 18 parts by weight of deionized water. The resultant mixture was predispersed for 30 minutes. It was then ground in a stirrer mill (grinding media: 1.0 mm;
charge: 750) until an energy input of 0.6 kilowatt hour/kg was reached.

' - 20 -For the preparation of the aqueous basecoat materials, first of all a make-up mixture was prepared.
This was done by introducing 21.4 parts by weight of a solution of a thixotropic agent based on a synthetic phyllosilicate (3°s in deionized water) as an initial charge and subjecting it to pretreatment with a dissolver at maximum stirrer speed for ten minutes.
Thereafter, 39.0 parts by weight of the grinding resin dispersion from preparation Example 1 and, after that, 0.6 part by weight of a commercial defoamer based on a combination of liquid hydrocarbons, hydrophobic silica, synthetic copolymers, and nonionic emulsifiers were added. To the results of the mixture there were added 3.0 parts by weight of butyl diglycol, 1.5 parts by weight of butyl glycol, 5.0 parts by weight of Shellsol~ T, 5.0 parts by weight of N-methylpyrrolidone, and 2.5 parts by weight of ethylhexanol. Then 5.0 parts by weight of a commercial wetting agent solution based on acetylenediol (12.5 in butyl diglycol) and 2.5 parts by weight of polypropylene glycols were added. In order to adjust the pH to 7.8-8.5, an additional 3.0 parts by weight of a 10% strength amine solution were added, after which the desired solids content was set using 11.5 parts by weight of deionized water, so giving the make-up mixture.
61.5 parts by weight of the above-described make-up mixture were introduced as an initial charge. To this initial charge there were added, with stirring, 20.0 parts by weight of the above-described black paste and 0.1 part by weight of a commercial silicone oil (Tego Glide~ 450 from Tego Chemie GmbH, 100%). The resultant mixture was then admixed with 7.3 parts by weight of a commercial melamine resin (Cymel~ 327, 90%) and with 11.1 parts by weight of deionized water, with stirring.
The resultant mixture was stirred at maximum stirrer speed for 30 minutes and adjusted to a pH of 7.8 using ' - 21 -10~ strength dimethylethanolamine solution. The spray viscosity of the aqueous basecoat material was adjusted to 28 s in the DIN 4 flow cup using deionized water.
For the preparation of the noninventive aqueous basecoat material of comparative experiment C2, Example 1 was repeated but without adding any silicone oil.
For producing the inventive and the noninventive multicoat paint system, first of all test panels were produced. This was done by coating steel panels (bodywork panels) that had been coated with a customary and known, cathodically deposited and baked electrocoat, with a commercial surfacer, after which the resultant surfacer film was flashed off at 20°C and a relative humidity of 65~ for 5 minutes and dried in a forced air oven at 80°C for 5 minutes, and then baked at 150°C. After that, the surfacer coat had a dry thickness of from 30 to 35 um.
After the test panels had cooled to 20°C, the inventive aqueous basecoat material of Example 1 and the noninventive aqueous basecoat material of comparative experiment C2 were applied, flashed off at 20°C and a relative humidity of 65~ for 5 minutes, and dried in a forced air oven at 80°C for l0 minutes, so that the dry basecoat films had a dry film thickness of approximately 15 um.
To the basecoat films of Example 2 and of comparative experiment C2 there was applied a commercial two-component clearcoat material, after which the basecoat films and the clearcoat films of Example 2 and of comparative experiment C2 were baked at 130°C for 30 minutes. The resultant multicoat paint systems were measured by colorimetry. The results obtained can be found in Table 2. They show that the multicoat paint system of the invention exhibited a deeper black than ~.

the noninventive paint system.
Table 2: Black measurement according to Lippok/Lohmer (DIN 55979) Example Black numbers according to DIN 55979:
No. M~

2 293 289

Claims (10)

claims

1. An achromatic paint comprising at least one binder, at least one carbon black pigment, and at least one silicone.

2. The achromatic paint of claim 1, characterized in that it contains, based on its overall amount, from 0.01 to 2.0% by weight of silicone.

3. The achromatic paint of claim 1 or 2, characterized in that at least one low-viscosity or high-viscosity silicone oil is used.

9. The achromatic paint of one of claims 1 to 3, characterized in that it is a jet black paint.

5. The achromatic paint of one of claims 1 to 4, characterized in that it comprises at least one white pigment, at least one effect pigment, at least one crosslinking agent and/or at least one paint additive.

6. A process for preparing an achromatic paint by for mixing at least one binder, at least one carbon black pigment, and at least one further constituent, characterized in that at least one silicone is used as further constituent.

7. The process of claim 6, characterized in that the silicone is used in an amount of from 0.01 to 2%
by weight, based on the resultant paint.

8. The process of claim 6 or 7, characterized in that a low-viscosity or high-viscosity silicone oil is used as silicone.

9. The process of one of claims 6 to 8, characterized in that at least one white pigment, at least one effect pigment, at least one crosslinking agent and/or at least one paint additive is or are mixed in.

10. The use of the achromatic paints of one of claims 1 to 5 or of the achromatic paints prepared by the process of one of claims 6 to 9 in automotive OEM finishing and automotive refinish, in do-it-yourself painting, in industrial coating, including container coating and coil coating, and in furniture coating.