EP0881955B1 - Process for the multi-layered coating of substrates with electrophoretic coating material and powder coating material - Google Patents

Abstract

The present invention relates to a process for the multilayer coating of substrates with electrodeposition and powder coating materials, in which electrodeposition is used to apply at least one coat (2) of electrodeposition coating material to the substrate (1), after deposition the substrate (1) is, if desired, wholly or partially air-dried, a coat of powder coating material (3) is then applied, and finally electrodeposition coating material and powder coating material are jointly baked.

Description

The present invention relates to a method for multilayer Coating of substrates with a primer layer Electrocoat and a top coat of powder paint.

Coating mainly electrically conductive substrates Electro dip coating has been a common process for many years. The Electrodeposition paint is an (aqueous) dispersion in one Bath. The substrate to be coated is one of two electrodes switched and immersed in this bath. Then it comes to electrophoretic deposition of the electrocoat on the Substrate. After reaching a sufficiently thick layer of lacquer the coating process ended and the paint layer dried and in usually branded.

Resins that can be electrodeposited on the cathode are e.g. in the U.S. Patent 3,617,458. It is cross-linkable Coating masses that are deposited on the cathode. This Coating compositions are derived from an unsaturated polymer, the Contains amine groups and carboxyl groups, and an epoxidized Material off.

In US Pat. No. 3,663,389, cationic-electrical deposits are made Compositions described, the mixtures of certain Amine-aldehyde condensates and a variety of cationic are resinous materials, one of these materials being through Reaction of an organic polyepoxide with a secondary amine and solubilization can be made with acid.

Aqueous dispersions are known from US Pat. No. 3,640,926 let the cathode deposit electrically and from an epoxy resin ester, Water and tertiary amino acids exist. The epoxy is that Reaction product of. a glycidyl polyether and a basic unsaturated oleic acid. The amine salt is the reaction product of one aliphatic carboxylic acid and a tertiary amine.

Epoxy and polyurethane based binders for the use of Binder dispersions and pigment pastes are also in numerous configurations known. For example, be on the DE-27 01 002, EP-A-261 385, EP-A-004 090 and DE-PS 36 30 667.

Methods are known from EP 0 646 420 A1, EP 0 525 867 A1 and US Pat. No. 3,998,716 known in which an electrocoat is overlaid with powder coating becomes. However, none or all of this prior art Drying of the electrocoat before the powder coating application, so that the loss of substance when baking the electrocoat layer less by degassing solvents and volatile fission products than 20%.

The coating of fabrics with powder coatings is also common Method. Here, the powdery dry paint is evenly applied the substrate to be coated is then applied by Heating the substrate melted and baked the paint. The Special advantages of powder coatings include that they are solvent-free get along and that the losses occurring with conventional paints through Overspray can be avoided, since non-stick powder coating is almost can be completely recycled. The application of the powder coating the substrate is preferably made by electrostatic adhesion by applying high voltage or by friction charging is produced.

The combination of the coating is also state of the art known with electrocoat and with powder coating. For example According to DE-PS 4313762, a powder coating layer is first sintered on and then applied an electrocoat. From the JP 63274800 is also known to apply an electrocoat and at Dry at 110 ° C, apply a powder coating and finally both Burn layers together. Through this two or Multi-layer painting can optimize the product properties become. Priming with electrocoat may also be required are used for substrates that are made of material technology or geometrical Reasons for powder coating are difficult to access. A typical one The application of this multi-layer coating is the coating of Heating radiators. The procedure is such that after the Coating of the substrate with the electro-dip lacquer only in this lacquer burned in a dryer. Temperatures of typically reached above 100 ° C, and the electrocoat sets. After this baking process, the primed substrate becomes again cooled, to then be provided with the powder coating layer become. For the curing of the applied powder coating is then a second burn-in process required. The disadvantage of this The procedure is that the substrate during the Coating process must be dried twice and heated. This is very energy-intensive and there are considerable investments and Operating cost.

a) auf ein Substrat (1) vorzugsweise aus Metall, insbesondere Eisen oder Zink mindestens eine Schicht (2) aus Flüssiglack, vorzugsweise aus Elektrotauchlack aufgebracht wird,

b) das Substrat (1) nach dem Tauchen ganz oder teilweise getrocknet wird,

c) mindestens eine Schicht Pulverlack (3) aufgebracht wird und

d) Elektrotauchlack und Pulverlack gemeinsam eingebrannt werden,wobei das Trocknen bei Temperaturen von ≤ 100 °C, vorzugsweise ≤ 40 °C erfolgt, und dadurch der Gehalt an Lösemitteln derart gesenkt wird, daß der Substanzverlust beim Einbrennen der Elektrotauchlackschicht durch Ausgasen von Lösemitteln und flüchtigen Spaltprodukten weniger als 20 %, vorzugsweise 13 %, beträgt.

In contrast, the invention has set itself the task of developing a method for multi-layer coating of substrates with electrocoat and powder coating, which works with the same product qualities, is more energy-efficient and less expensive. This object is achieved by a method in which

a) at least one layer (2) of liquid lacquer, preferably of electro-dip lacquer, is applied to a substrate (1), preferably made of metal, in particular iron or zinc,

b) the substrate (1) is completely or partially dried after dipping,

c) at least one layer of powder coating (3) is applied and

d) Electrodeposition paint and powder coating are baked together, the drying taking place at temperatures of ≤ 100 ° C., preferably 40 40 ° C., and the solvent content is reduced in such a way that the loss of substance during baking of the electrodeposition coating layer by degassing solvents and volatile Fission products is less than 20%, preferably 13%.

The method according to the invention accordingly dispenses with one separate drying and baking step for the electrocoat, before the powder coating is applied. Instead, both paints branded in a common step. This procedure means a considerable simplification of the coating process. By the Omitting a burn-in process reduces both Investment and operating costs. Only one is needed Baking oven provided and operated. hereby there is also a saving in heating energy. In addition, the total processing time for the coating process is shorter, so that the productivity of the system is increased.

Since the substrate to be coated is preferably coated with a Electrocoating is pre-primed primarily around an electrically conductive substrate. In particular, it can is a metal, preferably iron or zinc.

In step a), the substrate described is treated according to the invention Liquid paint applied. All are state of the art for this known coating methods can be used.

As coating material are all known in the art Liquid paints can be used. In particular, all the usual aqueous ones come Electrodeposition paints into consideration. Electrodeposition paints are one example usable, the epoxy resins, which are preferably amine-modified, and / or blocked aliphatic polyisocyanate, pigment paste and possibly contain further additives.

In a preferred embodiment of the invention The process is the electrocoat after the removal of the Substrate from the bath, preferably by air drying, e.g. with help of a blower pre-dried. It can preferably be in the air dry air, e.g. Compressed air, act.

At the same time as the drying process, the Substrate made, however, a bleeding or baking of the lacquer is to be avoided. Rather, its purpose is primarily at Use of the usual aqueous electrodeposition paints on these remove any remaining water film. Therefore temperatures of ≤ 100 ° C preferred. Temperatures of ≤ 80 ° C, particularly preferably ≤ 60 ° C, most preferably ≤ 40 ° C be respected.

The drying process does not extend over a period of time more than 60 min. The drying time is preferably ≤ 40 min., particularly preferred at ≤ 30 min., most preferred at ≤ 20 min ..

The pre-drying of the electrocoat layer is carried out until their solvent content has decreased in such a way that in the subsequent stoving the substance of the layer around less than 20%, preferably less than 13%. Because with Burning in of an electrocoat layer always occurs Substance loss due to evaporation of residual solvents and through the release of fission products during the crosslinking of the paint arise. By outgassing these substances it can be too Bubbles form, so that the lacquer layer is destroyed as a whole becomes. However, if the predrying is up to the above Maximum limits of the solvent content is carried out, that leads Outgassing the remaining solvents and the fission products to none Deterioration in product quality.

According to the current state of the art, the branding of the Electrocoating layer carried out before applying the powder coating, to avoid the described degassing phenomena. To In the opinion of experts, it was not considered possible to use the powder coating to apply to a non-baked electrocoat without that both layers would be destroyed by the degassing process. This prejudice could with the method of the invention be overcome.

According to the invention, the aforementioned electrocoating paint is used Powder paint applied.

It is essential that the crosslinking temperatures of the powder coating are higher lie than those of the electrocoat. Preferably, the Temperature difference at 5 to 60 ° C, particularly preferably at 10 to 40 ° C, very particularly preferably at 10 to 30 ° C, most preferably at 10 up to 20 ° C.

According to the invention, all known paint formulations are suitable, e.g. those described in EP-509 392, EP-509 393, EP-322 827, EP-517 536, U.S. 5,055,524 and U.S. 4,849,283. In particular, can the powder coating consist of epoxy resins, also epoxidized Novolaks, from crosslinking agents, preferably phenolic or amine hardeners or bicyclic guanidines, catalysts, Fillers and, if necessary, auxiliaries and additives.

The powder coatings used according to the invention preferably contain Epoxy resins, phenolic crosslinking agents, catalysts, auxiliaries as well as auxiliaries and typical powder additives, flow aids.

Suitable solid epoxy resins are all solid epoxy resins with one Epoxy equivalent weight between 400 and 3,000, preferably 600 to 2000. These are mainly epoxy resins based on Bisphenol A and Bisphenol F. Expoxidized are preferred Novolak. These preferably have an epoxy equivalent weight from 500 to 1,000.

The epoxy resins based on bisphenol A and bisphenol F have in generally a functionality of less than 2 that epoxidized Novolac resins have a functionality greater than 2. Particularly preferred are epoxidized in the powder coatings according to the invention Novolac resins with an average functionality in the range from 2.4 to 2.8 and with an epoxy equivalent weight in the range of 600 to 850. In the epoxidized novolac resins are the phenolic Hydroxyl groups etherified with alkyl, acrylic or similar groups. By reacting the phenolic hydroxyl groups with Epichlorohydrides are introduced into the molecule by epoxy groups. Starting from novolaks, the so-called epoxy novolak is formed. The epoxidized novolaks are structurally related to bisphenol A resins. Epoxidized novolac resins can be made by Epoxidation of novolaks, e.g. from 3 to 4 phenol cores, which are connected to each other via methylene bridges. As Novolak resins can also be alkyl-substituted phenols Formaldehyde can be used.

Suitable epoxy resins are, for example, those under the following names commercially available products:

Epikote 1004, 1055, 3003, 3004, 2017 by Shell-Chemie, DER 640, 671, 662, 663U, 664, 667 from Dow and Araldit GT 6063, 6064, 6084, 6097, 7004, 7220, 7225 from Ciba Geigy.

As an epoxy functional binder for powder clearcoats For example, suitable epoxy group-containing polyacrylate resins, which by Copolymerization of at least one ethylenically unsaturated Monomer containing at least one epoxy group in the molecule with at least one other ethylenically unsaturated monomer, the contains no epoxy group in the molecule, can be produced, wherein at least one of the monomers is an ester of acrylic acid or Is methacrylic acid.

Polyacrylate resins containing epoxy groups are known (cf. e.g. EP-A-299 420, DE-B-22 14 650, DE-B-27 49 576, US-A-4, 091,048 and US-A-3, 781, 379).

As examples of the ethylenically unsaturated monomers that are at least contain an epoxy group in the molecule, glycidyl acrylate, Glycidyl methacrylate and allyl glycidyl ether called.

As examples of ethylenically unsaturated monomers that do not Epoxy group contained in the molecule, alkyl esters of acrylic and Methacrylic acid, which contain 1 to 20 carbon atoms in the alkyl radical, in particular methyl acrylate, methyl methacrylate, ethyl acrylate, Ethyl methacrylate, butyl acrylate, butyl methyl acrylate, 2-ethylhexyl acrylate and Called 2-ethylhexyl methacrylate. More examples of ethylenic unsaturated monomers that do not contain epoxy groups in the molecule, are acids, e.g. Acrylic acid and methacrylic acid. Acid amides, such as e.g. Acrylic acid and methacrylic acid amide, vinyl aromatic compounds, such as styrene, methyl styrene and vinyl toluene, nitriles such as acrylonitrile and methacrylonitrile, vinyl and vinylidene halides such as vinyl chloride and Vinylidene fluoride, vinyl esters, e.g. Vinyl acetate and hydroxyl groups Monomers such as Hydroxyethyl acrylate and hydroxyethyl methacrylate.

The epoxy group-containing polyacrylate resin usually has Epoxy equivalent weight of 400 to 2,500, preferably 500 to 1,500, particularly preferably 600 to 1,200, a number average molecular weight (Gel permeation chromatography using a Polystyrene standards determined) from 1,000 to 15,000, preferably from 1,200 to 7,000, particularly preferably from 1,500 to 5,000 and one Glass transition temperature (TG) from 30 to 80, preferably from 40 to 70, particularly preferably from 50 to 70 ° C (measured using the differential scanning calometry (DSC)).

The epoxy group-containing polyacrylate resin is generally good known methods prepared by radical polymerization become.

Are suitable as hardeners for the epoxy group-containing polyacrylate resin for example polyanhydrides of polycarboxylic acids or of Mixtures of polycarboxylic acids, especially polyanhydrides from Dicarboxylic acids or mixtures of dicarboxylic acids.

Such polyanhydrides can be produced by the polycarboxylic acid or water is withdrawn from the mixture of polycarboxylic acids, where implemented two carboxyl groups to form an anhydride group become. Such manufacturing processes are well known and need therefore not to be explained in more detail.

For curing the epoxy resins, the invention contains Powder coating phenolic or amine hardener. Are used can also use bicyclic guanidines.

Any phenolic resin can be used, for example, as long as it has the methylol functionality required for reactivity having. Preferred phenolic resins are under alkaline conditions reaction products of phenol, substituted phenols and Bisphenol A with formaldehyde. Under such conditions, the Methylol group either ortho or para with the aromatic Ring linked. Are particularly preferred according to the present Invention as a phenolic crosslinking agent containing hydroxyl groups Bisphenol-A or Bisphenol-F resins with one Hydroxy equivalent weight in the range of 180 to 600, especially preferably used in the range from 180 to 300. Such phenolic Crosslinking agents are produced by reacting bisphenol-A or bisphenol-F with components containing glycidyl groups, e.g. the Diglycidyl ether of bisphenol-A. Phenolic crosslinking agents of this type are available, for example, under the trade name DEH 81, DEH 82 and DEH 87 from Dow DX 171 from Shell-Chemie and XB 3082 from Ciba Geigy.

The epoxy resins and the phenolic crosslinking agents are in such a ratio that the number of epoxy groups the number of phenolic OH groups is approximately 1: 1.

The powder coatings according to the invention contain one or more suitable catalysts for epoxy resin curing. suitable Catalysts are phosphonium salts of organic or inorganic Acids, imidazole and imidazole derivatives, quaternary ammonium compounds as well as amines. The catalysts are generally in proportions of 0.001% by weight to about 10% by weight, based on the total weight of the Epoxy resin and the phenolic crosslinking agent used.

Examples of suitable phosphonium salt catalysts are Ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium chloride, Ethyltriphenylphosphonium thiocyanate, ethyltriphenylphosphonium acetate-acetic acid complex, Tetrabutylphosphonium iodide, tetrabutylphosphonium bromide and tetrabutylphosphonium acetate-acetic acid complex. This and other suitable phosphonium Catalysts are e.g. described in U.S. Patent Nos. 3,477,990 and U.S. Patent 3,341,580.

Suitable imidazole catalysts are, for example, 2-styrylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole and 2-butylimidazole. This and further imidazole catalysts are e.g. described in the Belgian Patent No. 756,693.

Some of the commercially available phenolic crosslinking agents already contain Catalysts for epoxy resin crosslinking.

Powder coatings based on polyesters containing carboxyl groups and Low molecular weight crosslinking agents containing epoxy groups are in a large number are known and are described, for example, in EP-A-389 926, EP-A-371 522, EP-A-326 230, EP-B-110 450, EP-A-110 451, EP-B-107 888, US 4,340,698, EP-B-119 164, WO 87/02043 and EP-B-10 805.

A) 35,0 - 92,2 Gew.-% Carboxylgruppen enthaltende Polyester mit einer Säurezahl von 10 - 150 mg KOH/g,

B) 0,8 - 20,1 Gew.-% niedermolekulare, Epoxidgruppen enthaltende Härtungsmittel,

C) 3,7 - 49,3 Gew.-% Epoxidgruppen enthaltende Polyacrylatharze mit einem Epoxidäquivalentgewicht von 350 - 2000 und

D) 0,5 - 13,6 Gew.-% niedermalekulare Di- und/oder Polycarbonsäuren und/oder Di- und/oder Polyanhydride

enthalten, wobei die Summe der Gew.ichtsanteile von A), B), C) und D) jeweils 100 Gew.-% und das Verhältnis de Epoxidgruppen der Pulverlacke zu der Summe der Carboxyl- und Anhydridgruppen der Pulverlacke 0,75 -1,25:1 beträgt.Powder coatings according to DE 43 30 404.4 are particularly suitable, which are characterized in that they are used as film-forming material

A) 35.0-92.2% by weight of carboxyl-containing polyesters with an acid number of 10-150 mg KOH / g,

B) 0.8-20.1% by weight of low molecular weight curing agents containing epoxy groups,

C) 3.7-49.3% by weight epoxy group-containing polyacrylate resins with an epoxy equivalent weight of 350-2000 and

D) 0.5-13.6% by weight of low molecular weight di- and / or polycarboxylic acids and / or di- and / or polyanhydrides

contain, the sum of the parts by weight of A), B), C) and D) in each case 100% by weight and the ratio of the epoxy groups of the powder coatings to the sum of the carboxyl and anhydride groups of the powder coatings 0.75-1, Is 25: 1.

The carboxyl groups used as component A) Polyesters have an acid number in the range of 10-150 mg KOH / g, preferably in the range of 30-100 mg KOH / g. The hydroxyl number of the Polyester resins should be ≤ 30 mg KOH / g. To be favoured Polyester with a carboxy functionality of ≥ 2 is used. The Polyesters are made according to the usual methods (compare e.g. Houben Weyl, Methods of Organic Chemistry, 4th Edition, Volume 14/2, Georg Thieme Verlag, Stuttgart 1961).

As the carboxylic acid component for the production of the polyester aliphatic, cycloaliphatic and aromatic di- and Suitable polycarboxylic acids, e.g. Phthalic acid, terephthalic acid, Isophthalic acid, trimellitic acid, pyromellitic acid, adipic acid, Succinic acid, glutaric acid, pimelic acid, suberic acid, Cyclohexanedicarboxylic acid, acelaic acid, sebacic acid and the like. This Acids can also be in the form of their esterifiable derivatives (e.g. anhydrides) or their transesterifiable derivatives (e.g. Dimethyl ester) can be used.

As an alcohol component for the production of the carboxyl groups Containing polyester A) are the usually used di and / or Suitable polyols, e.g. Ethylene glycol, 1,2-propanediol and 1,3-propanediol, butanediols, diethylene glycol, triethylene glycol, Tetraethylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-dimethylolcyclohexane, Glycerin, trimethylolethane, trimethylolpropane, Pentaerythritol, ditrimethylolpropane, dipentaerythritol, diglycerin and the like

The polyesters thus obtained can be used individually or as a mixture different polyester can be used. The as component A) suitable polyesters generally have a Glass transition temperature above 30 ° C.

Examples of suitable commercially available polyesters are those under following brand names commercially available products: Crylcoat 314, 340, 344, 2680, 316, 2625, 320, 342 and 2532 from UCB, Drug bos, Belgium; Grilesta 7205, 7215, 72-06, 72-08, 72-13, 72-14, 73-72, 73-93 and 7401 from Ems-Chemie; Neocrest P670, P671, P672, P678, P662 from ICI and Uralac P2400, P2450, P5980, PS 998, P 3561 Uralac P3400 and Uralac P5000 from DSM.

The acidic polyester component A) also includes unsaturated, Polyester resins containing carboxyl groups in question. These will obtained by polycondensation, for example of maleic acid, Fumaric acid or other aliphatic or cycloaliphatic Dicarboxylic acids with an ethylenically unsaturated double bond, optionally together with saturated polycarboxylic acids, as Polycarboxylic. The unsaturated groups can also by the alcohol component, e.g. by Trimethylolpropane monoallyl ether, into which polyester is introduced.

The powder coatings according to the invention contain 0.8 - as component B) 20.1% by weight of low molecular weight epoxy groups Curing agent. An example of a particularly suitable one is a low molecular weight curing agent containing epoxy groups Triglycidyl isocyanurate (TGIC). TGIC is commercially available at, for example the name Araldit PT 810 (manufacturer: Ciba Geigy). Other suitable low molecular weight epoxy groups Hardening agents are 1,2,4-triglycidyltriazolin-3,5-dione, diglycidyl phthalate and the diglycidyl ester of hexahydrophthalic acid.

Polyacrylate Resins Containing Epoxy Groups (Component C) are understood to be polymers which are obtained by copolymerization of at least one ethylenically unsaturated monomer, the at least contains an epoxy group in the molecule, with at least one other ethylenically unsaturated monomer that does not contain an epoxy group, can be produced, at least one of the monomers being an ester of Acrylic acid or methacrylic acid.

Polyacrylate resins containing epoxy groups are known (cf. e.g. EP-A-299 420, DE-B-22 14 650, US-A-4,091,048 and US-A-3,781,379).

As examples of ethylenically unsaturated monomers, the at least one Epoxy group in the molecule, glycidyl acrylate, Glycidyl methacrylate and allyl glycidyl ether called.

As examples of ethylenically unsaturated monomers that do not Epoxy group contained in the molecule, alkyl esters of acrylic and Methacrylic acid, which contain 1 to 20 carbon atoms in the alkyl radical, in particular methyl acrylate, methyl methacrylate, ethyl acrylate, Ethyl methacrylate, n-butyl acrylate, iso-butyl acrylate, t-butyl acrylate and the corresponding methacrylates, 2-ethylhexyl acrylate and 2-ethylhexyl methacrylate called. More examples of ethylenic unsaturated monomers that do not contain epoxy groups in the molecule, are acids, e.g. Acrylic acid and methacrylic acid, acid amides, such as e.g. Acrylic acid and methacrylic acid amide, vinyl aromatic Compounds such as styrene, methyl styrene and vinyl toluene, nitriles such as Acrylonitrile and methacrylonitrile, vinyl and vinylidene halides, such as Vinyl chloride and vinylidene fluoride, vinyl esters such as e.g. Vinyl acetate and Vinyl propionate, and monomers containing hydroxyl groups, e.g. Hydroxyethyl acrylate and hydroxyethyl methacrylate.

The polyacrylate resin (component C) containing epoxy groups has an epoxy equivalent weight of 350 to 2000. The polyacrylate resins containing epoxy groups usually have a number average molecular weight (determined by gel permeation chromatography using a polystyrene standard) from 1000 to 15000 and a glass transition temperature (T _G ) from 30 to 80 (measured using differential scanning calorimetry (DSC)).

The acrylic resin containing epoxy groups is generally good known methods prepared by radical polymerization become. Such epoxy groups are commercially available Polyacrylate resins, for example, are available under the name Almatex PD 7610 and Almatex PD 7690 (manufacturer: Mitsui Toatsu).

The powder coatings according to the invention contain as binders as Component D) 0.5-13.6% by weight of low molecular weight di- and / or Polycarboxylic acids and / or di- and / or polyanhydrides. Prefers are as component D) saturated, aliphatic and / or cycloaliphatic dicarboxylic acids used, e.g. glutaric, Adipic acid, pimelic acid, suberic acid, acelaic acid, Cyclohexanedicarboxylic acid, sebacic acid, malonic acid, dodecanedioic acid and succinic acid. In addition, as component D) too aromatic di- and polycarboxylic acids are suitable, e.g. phthalic acid, Terephthalic acid, isophthalic acid, trimellitic acid and pyromellitic acid, of course also in the form of their anhydrides, insofar as they exist. Dodecanedioic acid (= 1,10-decanedicarboxylic acid) is particularly preferred as component D) used.

The amounts of the powder coating components A) to D) are such chosen that the ratio of the epoxy groups from B) and C) to the Sum of the carboxyl and anhydride groups from A) and D) 0.75-1.25: 1 is. This ratio is preferably 0.9-1, 1: 1.

The Puiverlacke contain 50 to 90%, preferably 60 to 80 wt .-% Binder and 10 to 50 wt .-%, preferably 20 to 40 wt .-% fillers.

Glycidyl group-functionalized crystalline fillers are used Silicic acid modifications into consideration. Usually they are in the mentioned range from 10 to 50 wt .-%, based on the Total weight of the powder coating used. In some cases, however filler contents of more than 50% by weight are also possible.

The crystalline silica modifications include quartz, cristobalite, tridymite, keatite, stishovite, melanophlogite, coesite and fibrous silica. The crystalline silica modifications are glycidyl group functionalized, the glycidyl group functionalization being achieved by a surface treatment. These are, for example, silica modifications based on quartz, cristobalite and fused silica, which are produced by treating the crystalline silica modifications with epoxysilanes. The glycidyl group-functionalized silica modifications are available on the market, for example, under the names Silbond ^R 600 EST and Silbond ^R 6000 EST (manufacturer: Quarzwerke GmbH) and are produced by reacting crystalline silica modifications with epoxysilanes.

The powder coatings advantageously contain 10 to 40% by weight, based on on the total weight of the powder coating glycidyl group functionalized crystalline silica modifications.

The powder coatings can also contain other inorganic fillers, for example titanium oxide, barium sulfate and fillers based on silicate, such as e.g. Talc, kaolin, magnesium, aluminum silicates, mica and similar included. In addition, the powder coatings may still Tools and additives included. Examples of these are leveling agents, Trickle aids and degassing agents, such as benzoin.

To support non-destructive outgassing, the Finally, degassing agents are added to powder coating. Preferably the concentrations of this degassing agent are ≤ 2% by weight, particularly preferably 0.1 to 0.8% by weight, very particularly preferably at 0.2 to 0.5% by weight, most preferably at ≤ 0.4% by weight.

in Betracht,wobei R ein Alkanol mit 1 - 6 C-Atomen ist. Hierbei sind R₁ sowie R₂ Benzoyl - oder Phenylgruppen. R₁ sowie R₂ können darüber hinaus gleich oder verschieden sein. D.h. R₁ und R₂ können gleichermaßen Benzoyl - bzw. Phenylgruppen sein. Ebenso kann der eine Rest eine Benzoylgruppe sein, während der andere Rest eine Phenylgruppe ist. Beispiele für bevorzugt einsetzbare Verbindung ist Benzoylphenylmethanol (Benzoin).Compounds of the formula in particular come as degassing agents

into consideration, wherein R is an alkanol with 1-6 C atoms. Here R ₁ and R _{2 are} benzoyl or phenyl groups. R ₁ and R ₂ can also be the same or different. That is, R ₁ and R ₂ can equally be benzoyl or phenyl groups. Likewise, one residue can be a benzoyl group, while the other residue is a phenyl group. Examples of a compound which can preferably be used is benzoylphenylmethanol (benzoin).

The powder coatings are produced by known methods (cf. e.g. Product information from BASF Lacke + Farben AG, "Powder coatings", 1990) by homogenization and dispersion, for example by means of an extruder, screw kneader, etc. After The powder coatings are produced by grinding and, if necessary, by sifting and sieving to the desired grain size distribution set.

The powder coatings described are following the order baked together with the electrocoat. During the The electrocoating and powder coating layers are baked on melting of the powder coating and thus its uniform distribution, and to harden the binders. Preferably that is Branding at temperatures from 150 to 220 ° C, very special preferably carried out at 160 to 200 ° C. The burn-in process lasts 10 to 40 minutes, preferably 15 to 30 minutes.

All common methods are used to apply the powder coating according to the state of the art. A is particularly preferred Apply by electrostatic adhesion, preferably by application a high voltage or by friction charging.

The method according to the invention finds a preferred use the coating of radiators, car bodies and Ruto accessories, machine parts, compressors, shelves, Office furniture and comparable industrial products.

The subject of the invention also includes a multi-layer coating Substrate which is characterized in that it is manufactured by first coating a layer on the substrate in an electrodeposition bath Electrocoating applied and then dried, then a layer of powder paint is applied and finally electrocoat and powder coating are baked together in one step.

The electrocoat layer of the multi-coated The substrate according to the invention preferably has a thickness of 5 to 35 µm, very particularly preferably 10 to 25 µm. The powder coating layer has preferably a thickness of 30 to 200 microns, very particularly preferred 50 to 120 µm.

Figur 1

zeigt den Schichtaufbau des Substrates.

Figur 2

zeigt die Herstellungsschritte.

The implementation of the method according to the invention and the production of the substrate according to the invention is shown schematically in FIGS. 1 and 2.

Figure 1

shows the layer structure of the substrate.

Figure 2

shows the manufacturing steps.

Figure 1 shows schematically the layer structure of the invention Substrate. The layer is initially on the substrate 1 itself 2 made of electro dipping paint, which is usually 10 times thicker Layer 3 of powder coating is covered.

In the manufacture of the substrate according to the invention, the substrate first coated in an electro-dip bath 4. Then it will Electrodeposition bath removed and in a drying plant 5 Blow dry with air. Then e.g. creating one High voltage in a cabin 6 powder coating finely distributed on the Sprayed surface of the substrate. This powder paint is then in the furnace 7 together with the electrocoat layer at temperatures baked from approx. 150 to 220 ° C.

The method according to the invention is described below using a Example explained in more detail.

1. Preparation of an amine-modified active hydrogen atom epoxy resin

1780 g of Epikote 1001 (epoxy resin from Shell with an epoxy equivalent weight of 500), 280 g Dodecylphenol and 105 g of xylene submitted and under a nitrogen atmosphere melted at 120 ° C. Then, under a light vacuum Traces of water removed by circling. Then 3 g of N, N-dimethylbenzylamine are added to, the reaction mixture is heated to 180 ° C. and maintains this temperature for approx. 3 h until the epoxy equivalent weight (EEW) rose to 1162. Then you cool and give in quick succession 131 g of hexylglycol, 131 g of diethanolamine and 241 g of xylene. This increases the temperature slightly. The reaction mixture is then left on Cool to 90 ° C and add 183 g of butyl glycol and for further dilution 293 g of isobutanol. When the temperature has dropped to 70 ° C, there is 41 g of N, N, -dimethylaminopropylamine are added, this temperature is kept for 3 h and carries out.

The resin has a solids content of 70.2% and a base content of 0.97 milliequivalents / gram.

2. Preparation of a blocked aliphatic polyisocyanate

488 g are placed in a reaction vessel under a nitrogen atmosphere Trimerized hexamethylene diisocyanate via isocyanurate formation (Commercial product from BASF AG with an isocyanate equivalent weight of 193) and 170 g of methyl isobutyl ketone and heated to 50 ° C. Then 312 g of di-n-butylamine are added dropwise so that the Internal temperature is kept at 60 to 70 ° C. At the end of the addition is stirred for 1 h at 75 ° C and then with 30 g of n-butanol diluted and cooled. The reaction product has a solids content of 79.6% (1 h at 130 ° C) and an amine number of less than 5 mg KOH / g.

3. Preparation of an aqueous dispersion that is an active Cationic amine modified containing hydrogen atoms Epoxy resin and a blocked aliphatic polyisocyanate as contains separate component

1120 g of the resin solution prepared according to point 1 are mixed with 420 g of the blocked solution prepared according to point 2 Polyisocyanate mixed at room temperature with stirring. As soon as the Mixture is homogeneous (after about 15 minutes) 2.2 g of a 50th % By weight solution of a commercially available defoaming agent (Surfynol; commercial product of Air Chemicals) in Ethylene glycol monobutyl ether and 18 g of glacial acetic acid are stirred in. After that 678 g of deionized water are added over 4 portions. It is then mixed with a further 1154 g of deionized water in small amounts Portions diluted.

The resulting aqueous dispersion is in a Vacuum distillation freed from low-boiling solvents and then with deionized water to a solids content of 33 Diluted wt%.

4. Production of a rubbing resin according to DE-OS-34 22 457

640 parts of a diglycidyl ether based on bisphenol A and Epichlorohydrin with an epoxy equivalent weight of 485 and 160 Parts of one with an epoxy equivalent weight of 189 parts mixed at 100 ° C. Another vessel contains 452 parts Hexamethylenediamine submitted, heated to 100 ° C and 720 parts of the above hot epoxy resin mixture added within one hour, with slight cooling to increase the temperature at 100 ° C hold. After a further 30 minutes the excess hexamethylene diamine is removed under reduced pressure, at the end a temperature of 205 ° C and a pressure of 30 mbar is reached. Then 57.6 parts of stearic acid, 172.7 Parts of dimer fatty acid and 115 parts of xylene were added. Then inside from 90 min at 175 to 180 ° C the water formed azeotropically distilled off. Then 58 parts of butyl glycol and 322 parts Isobutanol added. The product has a solids content of 70% by weight and a viscosity measured at 75 ° C with a plate and cone viscometer, from 2240 mPas.

5. Production of a pigment paste

586 parts of the rubbing resin prepared according to point 4. are mixed intensively with 990 parts of deionized water and 22 parts of glacial acetic acid. Then 1129 parts of TiO ₂ and 146 parts of an extender based on aluminum silicate are mixed. This mixture is crushed in a grinding unit to a Hegman fineness of less than 12 µm. Deionized water is then added until a solids content of 48 to 52% by weight (1/2 h, 180 ° C.) has been reached.

6. Production of a used according to the invention Electrocoating bath

2200 parts by weight of the dispersion prepared according to point 3 are made with 810 parts by weight of those according to item 5 Pigment paste added and with deionized water to 5000 Parts by weight filled up.

7. Production of a powder coating used according to the invention (21 a more) 8. Coating method according to the invention

A flat radiator, height 600mm, length 1000mm with 2 plates, on which 1 convector plate is welded on the inside, is degreased and phosphated, then immersed in an electrocoating bath and used as a cathode connected.

Parameters: voltage between 100 and 400 V, preferably 150 to 300 V
Temperature 24 to 35 ° C, preferably 28 to 32 ° C
Time 120 to 300s, preferably 150 to 240s.

Then the radiator is rinsed and air so far blown off so that no more liquid drips off. Then the Radiator coated with powder from the outside and placed in a drying oven at 150 to 220 ° C, preferably at 160 to 200 ° C for 10 to 40 min, preferably baked for 15 to 30 minutes.

So that the resulting powder coating film does not show any malfunctions, as few fission products and Escape solvent from the KTL. Preferably the Branding losses of KTL at most 15%, preferably at most 13% be.

Powder Example: Production of an epoxy polyester powder coating

Zeile 22

Dann wird der Heizkörper von außen mit Pulverlack elektrostatisch beschichtet Parameter: Pistolenspannung 50 bis 90 Kilovolt, Abstand Pistole/Radiator 15 bis 45 cm.

30 parts of Uralac P 5980 polyester resin (DSM polyester resin with an acid number of 70-85), 24 parts of Epikote 1055 epoxy resin (Shell epoxy resin with an epoxy equivalent weight of 850), 6 parts of an Epikote 3003 FCA leveling agent masterbatch are placed in a premixer -10, 0.2 parts of a polypropylene wax Lancowaehs PP1362, 0.4 parts of diphenoxy-2-propanol (degassing agent), 30 parts of titanium dioxide and 10 parts of calcium carbonate and premixed. This premix is dispersed in the extruder at operating temperatures between 100 and 130 ° C and, after it has been discharged from the extruder nozzle, is cooled as quickly as possible via squeeze rollers. The grinding is done in classifier mills. A classified grain size setting has proven to be particularly favorable.

Line 22

Then the radiator is electrostatically coated with powder coating from the outside. Parameters: gun voltage 50 to 90 kilovolts, gun / radiator distance 15 to 45 cm.

Claims (10)

1. A process for the multilayer coating of substrates with electrodeposition and powder coating materials, in which

   a) to a substrate (1) made preferably of metal, especially iron or zinc, at least one coat (2) of a liquid coating material, preferably an electrodeposition coating material, is applied,

   b) after deposition the substrate (1) is wholly or partially dried,

   c) at least one coat of powder coating material (3) is applied, and

   d) electrodeposition coating material and powder coating material are jointly baked,

   wherein drying takes place at temperatures of ≤100°C, preferably ≤40°C, and wherein the content of solvents is lowered such that the loss of substance when baking the electrodeposition coat, by gaseous expulsion of solvents and volatile elimination products, is less than 20%, preferably 13%.
2. The process as claimed in claim 1, wherein the predrying of the electrodeposition coat takes place by blowing with air and/or at elevated temperatures, preferably up to 40°C.
3. The process as claimed in either of claims 1 and 2, wherein drying lasts ≤60 minutes, preferably ≤30 minutes.
4. The process as claimed in one of claims 1 to 3, wherein the joint baking of electrodeposition coating material and powder coating material takes place at temperatures from 150 to 220°C, preferably from 160 to 200°C.
5. The process as claimed in claim 4, wherein the joint baking takes place for a duration of from 10 to 40 minutes, preferably from 15 to 30 minutes.
6. The process as claimed in one of claims 1 to 5, wherein the application of the powder coating material takes place by electrostatic adhesion, preferably by high voltage or frictional charging.
7. The process as claimed in one of claims 1 to 6, wherein the electrodeposition coating material employed in step a) crosslinks at less than 170°C, preferably from 140°C to 160°C.
8. The process as claimed in one of claims 1 to 7, wherein a powder coating material is employed whose crosslinking temperature lies from 10 to 60°C, preferably from 10 to 40°C above the crosslinking temperature of the electrodeposition coating material.
9. The process as claimed in one of claims 1 to 8, wherein a powder coating material is employed which comprises degassing agent(s) in a concentration of up to 2% by weight, with very particular preference 0.4% by weight.
10. The process as claimed in one of claims 1 to 9, wherein the powder coating material comprises as degassing agents compounds of the formula

    

    in which R is an alkanol having 1 - 6 carbon atoms and R₁ and R₂ are benzoyl- or phenyl groups, and where R₁ and R₂ can be identical or different.

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