Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/52—Two layers
  • B05D7/53—Base coat plus clear coat type
  • B05D7/534—Base coat plus clear coat type the first layer being let to dry at least partially before applying the second layer

Definitions

• the invention relates to a method for producing two-layer automotive top coats from a basecoat layer and a clear lacquer top layer.
• Two-layer automotive top coats are produced by wet-on-wet application of a transparent top coat on a pre-dried coloring and / or effect base coat.
• Either non-aqueous or aqueous basecoats are used in the respective painting systems of the individual vehicle manufacturers to create the color and / or effect basecoat layer.
• the non-aqueous basecoats contain organic solvents in the order of, for example, from 55 to 80% by weight, while the aqueous basecoats contain only, for example, 10 to 25% by weight of organic solvents.
• the trend is therefore towards the substitution of basecoats based on organic solvents with aqueous basecoats.
• older painting systems, in which non-aqueous basecoats are processed are replaced by new painting systems designed for the processing of waterborne basecoats.
• flash-off conditions for basecoat films in painting systems for the application of basecoats based on organic solvents are different from those in painting systems that are specially designed for the application of waterborne basecoats.
• flash-off conditions prevail, which are characterized by short flash-off times of, for example, 30 to 180 seconds at air temperatures of, for example, 20 to 30 ° C.
• Water-based paints require longer flash-off times at higher air temperatures in order to complete the flash-off process with the Complete the result of producing a pre-dried basecoat film.
• the flash-off times are, for example, 5 to 10 minutes and the air temperatures prevailing during the flash-off are, for example, 40 to 80 ° C. higher.
• coating layers applied from aqueous basecoats are first air-dried for 1 to 2 minutes at 20 to 40 ° C. and then 3 to 5 minutes with warm air at 40 to 80 ° C. for sufficient predrying suitable for the subsequent wet-on-wet application of a clear lacquer coating agent .
• the short flash-off times in painting systems designed for the application of basecoats based on organic solvents result from the short length of the flash-off area and the belt speed specified by the production target of the body coating process.
• the object of the invention is to provide a process for producing two-coat automotive top coats by wet-on-wet application of an aqueous basecoat and a clearcoat while granting only short flash-off times of, for example, 30 to 180 seconds for the basecoat.
• the method is intended to enable aqueous basecoats to be processed in automated automotive painting systems which are designed for processing non-aqueous basecoats and which allow only short flash-off times for the basecoat layers.
• the object is achieved by adhering to the following conditions when formulating aqueous basecoat coating compositions and adhering to the following process conditions during the flashing off of the coating layers applied from these aqueous basecoat coating compositions.
• the invention therefore relates to a method for producing a two-layer color and / or effect topcoat Motor vehicle bodies in an automatic automotive paint shop, whereby a transparent top coat layer of a clear lacquer coating agent is applied to a basecoat layer which has been applied and vented from an aqueous coloring and / or effect agent and the two coating layers are baked together, which is characterized in that an aqueous base lacquer coating agent is used , which contains organic solvents corresponding to a high solid value of 40 to 70%, and wherein the basecoat layer after its application and before application of the transparent topcoat layer for 30 to 180 seconds with circulating air at 25 to 45 ° C with an air throughput of 0.10 up to 0.70 m / s, based on the surface provided with the aqueous basecoat, is vented.
• an aqueous base lacquer coating agent which contains organic solvents corresponding to a high solid value of 40 to 70%
• aqueous basecoat coating compositions are used.
• they each contain one or more conventional binders, organic solvents and pigments and, if appropriate, fillers, crosslinking agents and / or additives customary in paint.
• the aqueous basecoat coating compositions used in the process according to the invention have, for example, weight solids contents of 15 to 50% by weight, for effect waterborne basecoats it is, for example, preferably 15 to 30% by weight, for monochrome waterborne basecoats it is preferably higher, for example 20 to 45% by weight. %.
• the weight solids of the aqueous basecoat coating compositions is formed from the sum of the solids contributions of the binders, pigments, fillers, crosslinking agents and non-volatile additives customary in lacquers.
• the weight ratio of pigment to binder in the aqueous basecoat coating composition is, for example, between 0.05: 1 to 3: 1, for effect waterborne basecoats it is preferably 0.1: 1 to 0.6: 1, for single-color waterborne basecoats it is preferably higher, for example at 0.1: 1 to 2.5: 1, each based on the solid weight.
• the sum of the proportions by weight of coloring pigments, effect pigments and fillers is related to the sum of the proportions by weight of binder, paste resin and crosslinker solids in the finished waterborne basecoat.
• the aqueous basecoat coating compositions used in the process according to the invention have a high solid value of 40 to 70%.
• the high solid value of the aqueous basecoat coating compositions is calculated using the formula
• Solvent content and solids content must therefore be coordinated so that a high solid value of 40 to 70% results according to the above formula.
• the waterborne basecoats used in the process according to the invention contain customary ionically or non-ionically stabilized binder systems. These are preferably anionically and / or non-ionically stabilized. Anionic stabilization is preferably achieved by at least partially neutralized carboxyl groups in the binder, while non-ionic stabilization is preferably achieved by lateral or terminal polyethylene oxide units in the binder.
• the water-based paints can be physically drying in nature or can be crosslinked to form covalent bonds.
• the water-based lacquers which crosslink with the formation of covalent bonds can be self- or externally crosslinking systems. In the latter case, it can be a one- or multi-component waterborne basecoat.
• the waterborne basecoats used in the process according to the invention contain one or more customary film-forming binders. If the binders are not self-crosslinking or self-drying, they can optionally also contain crosslinking agents. Both the binder component and the crosslinker component which may be present are not subject to any restrictions. For example, conventional polyester, polyurethane and / or poly (meth) acrylate resins can be used as film-forming binders. The selection of the crosslinking agents that may be present is not critical; it is based in a manner familiar to the person skilled in the art on the functionality of the binders. The waterborne basecoats used in the process according to the invention contain color and / or effect pigments and, if appropriate, fillers.
• coloring inorganic or organic pigments and fillers are titanium dioxide, micronized titanium dioxide, iron oxide pigments, carbon black, silicon dioxide, barium sulfate, micronized mica, talc, kaolin, chalk, phyllosilicates, azo pigments, phthalocyanine pigments, quinacridone pigments, pyrrolopyrrole pigments, pyrrolopyrrole pigments.
• effect pigments are metal pigments, for example made of aluminum, copper or other metals; Interference pigments such as, for example, metal oxide-coated metal pigments, for example titanium dioxide-coated aluminum, coated mica such as, for example, titanium dioxide-coated mica, graphite effect pigments, platelet-shaped iron oxide, platelet-shaped copper phthalocyanine pigments.
• metal pigments for example made of aluminum, copper or other metals
• Interference pigments such as, for example, metal oxide-coated metal pigments, for example titanium dioxide-coated aluminum, coated mica such as, for example, titanium dioxide-coated mica, graphite effect pigments, platelet-shaped iron oxide, platelet-shaped copper phthalocyanine pigments.
• Effect pigments are generally presented in the form of a commercially available aqueous or non-aqueous paste, optionally mixed with preferably water-dilutable organic solvents and additives and then mixed with an aqueous binder under scissors. Powdery effect pigments can first be processed into a paste using preferably water-dilutable organic solvents and additives.
• Color pigments and / or fillers can be rubbed, for example, in part of the aqueous binder.
• the rubbing can preferably also take place in a special water-thinnable paste resin. Grinding can be carried out in conventional units known to those skilled in the art. Then complete with the remaining portion of the aqueous binder or the aqueous paste resin for finished pigment pigment grinding.
• the waterborne basecoats used in the process according to the invention can contain further paint additives in conventional paint quantities, for example between 0.1 and 5% by weight, based on their solids content.
• further additives are neutralizing agents, anti-foaming agents, wetting agents, adhesion-promoting substances, catalysts, leveling agents, anti-cratering agents, light stabilizers and thickeners such as for example synthetic polymers with ionic and / or associative groups such as polyvinyl alcohol, poly (meth) acrylamide, poly (meth) acrylic acid, polyvinyl pyrrolidone, hydrophobically modified ethoxylated polyurethanes or polyacrylates, crosslinked or uncrosslinked polymer microparticles.
• the waterborne basecoats used in the process according to the invention contain organic solvents, the proportion of which is such that the waterborne basecoats have high solid values of 40 to 70%, for example the waterborne basecoats contain 20 to 30% by weight of organic solvents.
• the composition of the organic solvents in the waterborne basecoats preferably consists of 30 to 60% by weight of low-boiling, for example preferably below 120 ° C., water-miscible or without a miscibility gap, for example a water solubility at 20 ° C. of more than 70 g per liter of water-containing organic solvents.
• Such organic solvents are preferably selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, isobutanol, methoxypropanol, methyl ethyl ketone, acetone or mixtures thereof; n- and isopropanol are particularly preferred.
• Examples of other organic solvents which are present in the water-based basecoats used in the process according to the invention and which can preferably make up 40 to 70% by weight of the organic solvent composition in the water-based basecoat are monohydric alcohols with 5 or more carbon atoms, for example hexanol; Ethylene glycol ether or ester, for example ethylene glycol dimethyl ether, diethylene glycol mono- or di-Cl-C6-alkyl ether, butyl glycol, butyl diglycol, ethyl glycol acetate, butyl glycol acetate; Propylene glycol ether or ester, for example propylene glycol dimethyl ether, dipropylene glycol mono- or di-Cl-C6-alkyl ether, ethoxypropanol, propoxypropanol, butoxypropanol, methoxypropyl acetate, ethoxypropyl acetate; Ethylene glycol, propylene glycol, and
• the water-based paints are applied to motor vehicle bodies, which can consist of one type of substrate or of several types of substrates connected to one another in a mixed construction.
• motor vehicle bodies which can consist of one type of substrate or of several types of substrates connected to one another in a mixed construction.
• it is metallic or plastic substrates.
• plastic substrates can be provided with a plastic primer, for example, metallic substrates generally have an electrophoretically applied primer and, if necessary, one or more additional lacquer layers, such as a filler layer.
• the waterborne basecoats are applied by spraying in one or more spray passes in a dry layer thickness of 10 to 50 ⁇ m, for effect waterborne basecoats the dry layer thickness is preferably 10 to 25 ⁇ m, for example, and is preferably higher for plain-colored waterborne basecoats, for example 15 to 40 ⁇ m.
• the water-based lacquer and clear lacquer are applied in the process according to the invention according to the known wet-on-wet principle, i.e. the basecoat layer applied from the aqueous basecoat coating composition is first predried by flashing off before the clearcoat coating is applied.
• the predrying according to the invention by flashing off is important so that the finished two-layer coating meets the requirements for the technological properties such as adhesion and stone chip resistance as well as for the optical properties such as color, effect formation and topcoat level.
• the basecoat layers created from the aqueous basecoat coating compositions are applied after application and before application of the transparent topcoat layer for 30 to 180 seconds with circulating air at 25 to 45 ° C vented with an air flow rate of 0.10 to 0.70 m / s, based on the surface provided with the aqueous basecoat film.
• the applied waterborne basecoat is flashed off in the Basecoat flash-off zone of the automotive OEM painting and lasts 30 to 180 seconds, preferably 60 to 150 seconds. This time period results, for example, from the overall length of the basecoat flash-off zone of the motor vehicle series painting system of, for example, 5 to 15 m and the belt speed prevailing there, for example from 2 to 6 m / min.
• the ventilation takes place under circulating air conditions at air temperatures of 25 to 45 ° C, preferably 30 to 40 ° C.
• the ambient air conditions are selected so that an air throughput of 0.10 to 0.70 m / s, preferably 0.15 to 0.60 m / s, based on the surface coated with aqueous basecoat, is used.
• the air flow rate based on the surface coated with aqueous basecoat is calculated as the quotient of the air volume passed through the vent zone in cubic meters per second and the surface in the vent zone coated and vented with aqueous basecoat, for example in the order of 20 to 150 square meters.
• the air volume passed through the venting zone in the method according to the invention is, for example, 1 to 2 cubic meters per running meter of venting zone and second.
• the surface in the flash-off zone coated with aqueous basecoat and to be ventilated is calculated from the number of coated motor vehicle bodies, for example 1 to 3 car bodies, which are simultaneously located in the basecoat flash-off zone, and the surface of the respective body coated and to be vented with aqueous basecoat in square meters, for example in the On the order of 15 to 35 square meters in the car sector or 20 to 65 square meters in the commercial vehicle sector.
• the expression “surface of an individual body coated with an aqueous basecoat and to be ventilated” means not only the surface of an individual body that is subsequently to be provided with a clear lacquer coating, but also includes portions of the surface that are not to be lacquered, for example in the interior of the body.
• the air is vented under circulating air conditions.
• the circulating air has 5 to 15 g of water per cubic meter.
• a part, for example 5 to 20%, preferably 5 to 10% of the air volume passed through the venting zone per second can also leave the venting zone as exhaust air and supplemented by a corresponding amount of fresh air which are mixed with the circulated air.
• the fresh air preferably contains less than 15 g, particularly preferably 5 to 12 g of water per cubic meter.
• the water content of the admixed fresh air can be adjusted by means of conventional dehumidification methods such as compression of air and / or condensation or absorption of the water from air.
• the circulating air is expediently moved at a flow speed of 4 to 8 m / s, measured on the object.
• This is preferably a turbulent air flow which is directed from top to bottom and from the sides onto the bodywork provided with the base coat layer to be vented.
• the air flow is expediently carried out uniformly and vertically on the base coat layer to be vented.
• the air is expediently extracted downwards.
• the venting zone can be operated under constant operating conditions or by varying individual or multiple operating parameters.
• the operating parameters can be varied in the form of a continuous or abrupt change over the entire length or one or more parts of the length of the venting zone.
• the venting zone can be divided into one or more, for example 1 to 3, zones which can be separated from one another by locks.
• the variation of the operating parameters during the ventilation is always within the limits specified by the invention for the ventilation process to be considered as a whole.
• the flash-off zone is divided into two zones, the bodies coated with water-based paint firstly in the first zone at low air temperatures, for example from 25 to 30 ° C., and then in the second zone at higher air temperatures, for example from 30 ventilated up to 45 ° C; the air throughput can be selected to be the same or different in both zones, for example, in the first zone lower than in the second, for example the flow velocity of the circulating air measured on the object in the second zone can be above 8 m / s.
• the average air throughput is within the limits specified by the invention.
• the water-based lacquer layers predried by flashing are overpainted with a conventional chemically crosslinking clear lacquer in a dry layer thickness of, for example, 30 to 100 ⁇ m and baked together with the latter at temperatures of, for example, 100 to 150 ° C.
• An advantage of the method according to the invention results from the low air temperatures that prevail during the ventilation of the water-based lacquer layers. It is thus possible for the flashed-off basecoat layers to be overcoated with a clear lacquer without the bodies having cooled down beforehand.
• all known clearcoats or transparent pigmented coating agents are suitable as clearcoats.
• Solvent-containing one-component (1K) or two-component (2K) clearcoats, water-dilutable 1K or 2K clearcoats, powder clearcoats or aqueous powder clearcoat slurries can be used.
• the stoving conditions of the two-layer coating consisting of waterborne basecoat and clearcoat depend on the clearcoat system used.
• the process according to the invention allows the production of two-coat automotive top coats from an aqueous basecoat and clearcoat topcoat using the wet-on-wet process, with only short flash-off times of 30 to 180 seconds for the basecoat.
• the method according to the invention it is possible to process waterborne basecoats in automated motor vehicle series painting systems which are per se designed for the processing of non-aqueous basecoats and which allow only short flash-off times for the basecoat films. A costly conversion of paint systems which are unsuitable for the processing of aqueous basecoats can be avoided.
• the process according to the invention can even be carried out in such a way that both the waterborne basecoats and non-aqueous basecoats are processed within a motor vehicle series painting system. example
• a car body is coated in a painting booth for experimental purposes:
• a KTL-primed and with a filler layer 4.3 m long car body is in a dry layer thickness of 15 microns with a silver-colored water-based paint (composition: solids content 20 wt .-%, dimethylethanolamine 1 wt .-%, butyl glycol 8.5 wt .-%, N-methylpyrrolidone 2% by weight, water 59% by weight, n-propanol 7% by weight, n-butanol 2.5% by weight, high solid value: 50%; pigment / Binder ratio: 0.2: 1) coated.
• the coated area is approximately 20 square meters.
• the mixture is then vented in a 5 m long ventilation zone with circulating air (water content 12 g per cubic meter) of 40 ° C for 90 s.
• the circulating air output is 1.5 cubic meters per second and running meter ventilation zone.
• the paint obtained is cooker-free and also meets the other technological requirements of modern automotive painting.

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• 1999
  • 1999-02-15 DE DE19906247A patent/DE19906247A1/de not_active Withdrawn
• 2000
  • 2000-02-11 JP JP2000599520A patent/JP2002537099A/ja active Pending
  • 2000-02-11 WO PCT/EP2000/001132 patent/WO2000048748A1/de not_active Ceased
  • 2000-02-11 EP EP00907551A patent/EP1112126B1/de not_active Expired - Lifetime
  • 2000-02-11 KR KR1020017010332A patent/KR100603997B1/ko not_active Expired - Fee Related
  • 2000-02-11 BR BRPI0008215-5A patent/BR0008215B1/pt not_active IP Right Cessation
  • 2000-02-11 CN CNB008038066A patent/CN1156341C/zh not_active Expired - Fee Related
  • 2000-02-11 MX MXPA01008258A patent/MXPA01008258A/es active IP Right Grant
  • 2000-02-11 US US09/913,568 patent/US6548119B1/en not_active Expired - Fee Related
  • 2000-02-11 DE DE50000049T patent/DE50000049D1/de not_active Expired - Lifetime
  • 2000-02-11 ES ES00907551T patent/ES2170048T3/es not_active Expired - Lifetime
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