DE3942565C2 - - Google Patents

Description

The present invention relates to a method for coating of metallic objects in the tape coating process, in which either a primer A on the metal strip with a dry film thickness of at least 5 μm and a topcoat B having a dry film thickness of at least 10 microns or a single-coat C with a Dry film thickness of at least 10 microns applied and the primer A and the topcoat B or the one-coat coating C each at an object temperature from 200 to 260 ° C and at a baking time of 25 to 70 s be cured, wherein the primer A and / or the Topcoat B or one coat C

• a) 20 to 40 wt .-% of a mixture of
  • a₁) 70 to 95 wt .-% of polyester preferably aromatic dicarboxylic acids or their anhydrides and preferably (cyclo) aliphatic diols
  • a₂) 5 to 30 wt .-% of a triazine resin or
  • a₃) 5 to 30 wt .-% of a blocked polyisocyanate, wherein the sum of the weight fractions of the components a₁ to a₃ each 100 wt .-% is.
• b) 10 to 40 wt .-% of pigments and / or fillers and / or suitable Auxiliaries and additives
• c) 0.1 to 2 wt .-% of a catalyst
• d) 20 to 65 wt .-% of organic solvents and
• e) an additive for producing a structured surface

contains, wherein the sum of the weight proportions of the components a to e each 100 wt .-% is.

The present invention also relates to the in this process used coating agent.

It is known for coating metal strips liquid, thermosetting Use coating compositions consisting of a solution of a hydroxyl groups containing binder, for. A polyester, and a blocked polyisocyanate or a hexamethoxymethylmelamine resin in an organic Solvent exist. The hardened by the coil coating process Coatings have relatively good light and weather resistance and satisfactory mechanical ductility properties. adversely however, it is the very smooth surface typical of this process respectively;  This is particularly disadvantageous when the coating agent used for coating metal strips which are subsequently used during the construction phases Metal sheets or device parts are combined, which in Spraying processes have been painted. By the spray process usually becomes a slightly restless, wavy surface texture generated. The surfaces of equipment parts, which are coated by powder spraying, also have a more or less pronounced surface structure on.

For design-related combinations of sheets, the have been coated with conventional methods the band-coated surfaces fall the fault of the structured Surface particularly in the band-coated sheets on.

A structured surface is usually less sensitive against dirt and shine spots, compared to small ones Scratches, etc., so that in many cases, for. For household appliances, structured surface structures are preferred.

From EP-A 2 15 223 is a method for coating in Banding process known in which a scar-like surface structure is produced by the primer or the topcoat 0.5 to 7 wt .-%, based on the dry weight of the resin, one in the solvent or dispersant suspended or emulsified organic substance, their particle or droplet sizes between 3 and 60 microns lying, which melts at the processing temperature and their Surface tension is different from that of the resin, be added. Preferably used as an additive a wax such. B. modified or unmodified Polyethylene waxes, polypropylene waxes and polyamide waxes. The coatings obtained by this process are due to porous, d. H. not closed surface in relation to the Chemical resistance, anti-corrosion properties and the interim liability still in need of improvement.  

In addition, the coating agents have an insufficient Storage stability.

From EP-A-2 88 964 a method for coating in Banding process known in which a scar-like surface structure produced by the primer 0.01 to 0.05 wt .-% of a polyethylene wax with a Softening point between 100 and 120 ° C, preferably 100 to 110 ° C and a particle size distribution from 5 to 35 microns, preferably 5 to 25 microns, optionally in combination with 0.01 to 5 wt .-% of a Tallölalkydharzadditives and optionally in combination with a leveling agent.

The present invention was therefore based on the object a method for coating metallic objects be provided in the tape coating process, in which at the usual layer thicknesses of 25 to 45 microns closed spritzstrukturähnliche surfaces are achieved and in the the resulting films in particular excellent anti-corrosion properties and good chemical resistance, For example, compared with methyl ethyl ketone, alcohols and Detergents, own. The coatings should have good ductility and both a good substrate and in the case of the two-coat finish also a good To have interim liability. It should also by longer Storage (≳5 months) of the coating used in the process closed after processing according to the invention Achieved surfaces with a scar-like structure be, the structure is not due to storage or only slightly impaired. In addition, the coating compositions used in this process should as simple and easy to handle his.  

This object is surprisingly achieved by a method for coating metallic objects in the tape coating process solved, in which on the metal band either one Primer A with a dry film thickness of at least 5 microns and a topcoat B with a dry film thickness of at least 10 microns or a single-coat C applied with a dry film thickness of at least 10 microns and the primer A and the topcoat B or the single-coat C in each case at an object temperature from 200 to 260 ° C and at a baking time of 25 to 70 s be cured, wherein the primer A and / or the Topcoat B or one coat C

• a) 20 to 40 wt .-% of a mixture of
  • a₁) 70 to 95 wt .-% of polyester preferably aromatic dicarboxylic acids or their anhydrides and preferably (cyclo) aliphatic diols
  • a₂) 5 to 30 wt .-% of a triazine resin or
  • a₃) 5 to 30 wt .-% of a blocked polyisocyanate, wherein the sum of the weight fractions of the components a₁ to a₃ each 100 wt .-%,
• b) 10 to 40 wt .-% of pigments and / or fillers and / or suitable auxiliaries and additives
• c) 0.1 to 2 wt .-% of a catalyst
• d) 20 to 65 wt .-% of organic solvents and  
• e) an additive for producing a structured surface

contains, where the sum of the weight proportions of the components a to e is in each case 100% by weight, characterized in that as component e is used a dispersion prepared has been by

• e₁) one or more polyolefin and / or polyamide waxes and / or one or more silicones and / or one or more several acrylate copolymers,
• e₂) one or more fillers and
• e₃) one or more organic solvents

initially heated with stirring, so that the component e₁ at least partially dissolved in the solvent and then slowly cooled to ambient temperature being, being

• 1. the amounts used to prepare the dispersion the components e₁ and e₂ be chosen so that the weight ratio of the component e₁ to the component e₂ is between 8.5: 1.5 and 2.5: 7.5 and
• 2. The dispersion of the coating agents in an amount is added, the content of the component e₁ in the coating agent of 0.5 to 2.5 wt .-% and a content of the component e₂ in the coating agent from 0.5 to 1.5 wt .-%, each based on the Total weight of components a to e, corresponds.

The present invention also relates to the in coating agent used in this process.  

It is surprising and was not foreseeable that after the inventive Method always closed, spritzstrukturähnliche surfaces achieved be, with these resulting coatings also by excellent anti-corrosion properties and good chemical resistance distinguished. Furthermore, the resulting coatings have a good deformability and a substrate and in the case of two-coat painting also a good intermediate liability.

This high level of properties of the resulting coating will even after prolonged storage of the coating achieved. Although it is now known (see, for example, DE-OS 29 42 487), paints suitable for the Bandolackierverfahren are used, surface-treated particles, such as z. B. coated chalk, add. These known surface-treated However, particles lead in contrast to the structure-producing invention Additives to no structured surfaces. This usually used surface-treated particles serve rather as matting agents. Moreover, these known surface-treated differ Particles of the structuring used according to the invention Additives in that the substance, the surface of which selectively modifies becomes (carrier substance, eg chalk), in a very large surplus (<90 wt .-%) compared to the surface-treated substance (coat material) is present.

In the following, now the individual components of the invention in the first Method explained in more detail coating.  

The in the coating compositions of the method according to the invention used polyester resins a₁ are known. you will be according to the usual methods (see, for example, Dr. P. Olding, Ph. D. BA. & G. Hayward C. Chem., MRSC, Resins for Surface Coatings, Volume III, published by SITA Technology, 203 Gardiner House, Broomhill Road, London SW 18 4J Q, England, 1987) composed of aliphatic and / or cycloaliphatic di-, tri- or higher alcohols, optionally together with monohydric alcohols, and in particular aromatic dicarboxylic acids. It can of course but also aliphatic or cycloaliphatic carboxylic acids as well as polycarboxylic acids are used.

Examples of suitable alcohols are ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,4-dimethylolcyclohexane, Glycerol, trimethylolethane, trimethylolpropane, Dimethylolpropionic acid, pentaerythritol, etherification products of diols and polyols, e.g. B.: Di- and tri-ethylene glycol, Polyethylene glycol, neopentyl glycol ester of hydroxypivalic acid. Preference is given to diols or triols having 2 to 8 carbon atoms, such as Ethylene glycol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, glycerol, trimethylolethane and trimethylolpropane.

Examples of suitable carboxylic acids or their derivatives are (cyclo) aliphatic dicarboxylic acids, such as. For example adipic acid, Azelaic acid, tetrahydrophthalic acid, hexahydrophthalic acid, Endomethylenetetrahydrophthalic acid and aromatic carboxylic acids, such as Phthalic acid, isophthalic acid, terephthalic acid, Trimellitic acid and pyromellitic acid. Well suited are (cyclo) aliphatic or aromatic di- or tricarboxylic acids with 4 to 10 carbon atoms, e.g. For example adipic acid, Acelainsäure and / or Isophthalsäure.  

The in the primer, in the topcoat and in the single-coat paint used polyesters preferably have acid numbers from 1 to 15 mg KOH / g, preferably hydroxyl numbers of 5 to 30 mg KOH / g and preferably number average molecular weights from 5000 to 20,000, more preferred 6000 to 10,000 and preferably dispersities <8.

Suitable crosslinking agents for the polyester resins are recordable Triazine resins (a₂). Suitable resins are, for example Reaction products of aldehydes, such as. B. formaldehyde, with melamine or benzoguanamine. These are preferred Compounds partly or completely etherified with alcohols, containing 1 to 6 carbon atoms, such as. Methanol, Ethanol, n-propanol, isopropanol, n-butanol, isobutanol, Amyl alcohol, hexanol or mixtures.

Particularly preferred is hexamethoxymethylmelamine.

Alternatively, the polyester used with hardened blocked polyisocyanates. To be favoured used as polyisocyanates oligomeric polyisocyanates. Examples for oligomeric polyisocyanates are those with a Isocyanurate structure, such. As the polyisocyanurate polyisocyanates of hexamethylene diisocyanate and isophorone diisocyanate. Examples of other suitable oligomeric polyisocyanates are those having a biuret structure, for example the polyisocyanate with biuret structure based on hexamethylene diisocyanate.

As a blocking agent for the polyisocyanates Caprolactams, e.g. B. ε-caprolactam and oximes in question.

Particularly suitable blocking agents are oximes, preferably Butanone oxime.  

The coating compositions used in the process according to the invention contain from 0.1 to 2.0 wt .-%, based on the total weight the coating agent, conventional catalysts, such as As customary acid catalysts or customary organotin and organozinc catalysts. As examples may be mentioned: dibutyltin dilaurate, para-toluene sulphonic acid, Dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, Phosphoric acid and phosphoric acid derivatives and zinc octoate. Furthermore, the coating compositions contain from 20 to 65% by weight, based on the total weight of the coating agent, a or more organic solvents such. B. aromatic Hydrocarbons, esters, ethers, ketones, alcohols or else other organic compounds. Preferred solvents are aromatic hydrocarbons, esters and glycol ethers.

The coating compositions used in the process according to the invention may also be 10 to 40 wt .-%, based on the Total weight of the coating agent, conventional pigments, Fillers and other conventional additives included. When Pigments come, for example, titanium dioxide or inorganic Colored pigments, such as chromium, nickel, cobalt and iron oxide pigments and metallizing pigments, such as aluminum bronze, in Question.

As examples of customary auxiliaries and additives are leveling agents, Stabilizers, emulsifiers and adhesion promoters to call.

It is essential to the invention that in the inventive Method used coating compositions as structuring Additive containing a dispersion using one or more fillers (component e₂) and one or more waxes, silicones or acrylate copolymers (Component e₁) are produced.

Suitable as component e₁ are all substances whose Surface tension is different from the surface tension of Component a resins used differs.  

Appropriately, the surface tension differ of resin and component e₁ expressed as the contact angle when wetted with distilled water, at least 20 °, preferably at least 30 °, more preferably by at least 40 °, for example measured with a Contact angle measuring device (contactangle measuring system) Company Krüss.

In addition, substances are preferably used as component e₁, at the processing temperature of the coating agent (reached surface temperature during firing) in the liquid state.

As component e₁ are preferably used all in itself conventional waxes, but synthetic waxes preferred are. In particular, come modified or unmodified Polyethylene waxes, polypropylene waxes and polyamide waxes in Consideration. The waxes usually have a number average Molecular weight between 300 and 10,000, preferably between 500 and 5000 and preferably melting points between 100 and 180 ° C.

The polyethylene and polypropylene waxes are either homopolymers or copolymers with from 0.5 to 40% by weight of comonomer units, derived from saturated or unsaturated monocarboxylic acids or derive their amides. Examples of such Comonomer units are the residues of acrylic acid, methacrylic acid, Maleic acid, fumaric acid, acrylamide, stearic acid or Stearic acid amide.

Further suitable as component e₁ are various waxy silicones, such as polydimethylsiloxanes, Polydiphenylsiloxanes or modified silicones, z. B. polyester, polyether, acrylate and polyfluoroethylene-modified Silicones with number average molecular weights greater than 100,000.  

As component e₁ are also suitable also different solid acrylate copolymers which, like wax, have a pronounced Temperature dependence of solubility in organic solvents demonstrate.

The fillers used as component e₂ are preferred a BET surface area of <200 m² / g, most preferably a BET surface area of <300 m² / g. The middle Particle size of these fillers should be as small as possible equal to 15 microns, preferably less than or equal to 10 microns. The The average bulk density of these particles should preferably less than or equal to 120 g / l.

Examples of suitable as component e₂ compounds various silicic acids, preferably fumed silica, various silicates, such as. As aluminum, magnesium and Magnesium / aluminum silicates, talc, alumina, calcium carbonate, Magnesium carbonate, barium sulfate, calcium sulfate and Pigments such. As titanium dioxide, each preferably with the above parameters. Of course you can also solid organic compounds such as high molecular weight Polyethylene, polyacrylate, polyamide, polypropylene and polyurea powders are used, the but in itself have no structure-generating effect.

Suitable solvents (component e₃) are all solvents, in which the component e₁ a well-pronounced Temperature dependence of solubility shows, i. H. in which the component e₁ practically insoluble at room temperature is (solubility preferably <0.1 g / l), at boiling temperature of the solvent but is very good to unlimited solubility (preferred solubility <50 g / l, more preferably unlimited Solubility).  

Examples of suitable solvents in the case of polyolefin and polyamide waxes are aliphatic, cycloaliphatic and aromatic hydrocarbons such as As xylene, toluene, commercially available in the fractionation of Light oil obtained from the tar distillation technical benzene with a Density d²⁰₄ of 0.870 and with a boiling point of 165 to 180 ° C, wherein pass at least 90% of the distillate at 180 ° C; various commercial hydrocarbon solvents with one - depending on the type - Boiling point between 160 ° C and 255 ° C and with a density d²⁰₄ - depending on the type - between 0.859 and 0.895; various commercial, At least 98 wt .-% of aromatic-containing solvents with a - ever according to type different - boiling range between 162 and 270 ° C and one Density at 12 ° C - depending on the type - between 0.877 and 0.987 as well as a commercial one aromatic-rich special gasoline with a boiling point between 155 and 175 ° C and a density d²⁰₄ of 0.875, white spirit and propylene carbonate.

The preparation of the dispersion used as a structuring additive takes place in that first the components e₁, e₂ and e₃ heated with stirring be so that the component e₁ in the solvent e₃ at least partially solved. The temperature of the mixture is preferably the same the boiling point of the solvent e₃ under the prevailing conditions. The mixture thus obtained with the suspended fillers e₂ and the dissolved wax or silicone or acrylate copolymer (component e₁) is then allowed to cool slowly, which - due to the sinking Temperature decreasing solubility - the component e₁ separates again.

The amount of solvent used in the preparation of the dispersion can be varied within wide ranges and is generally between 95 and 40 wt .-%, based on the total weight the sum of the components e₁ to e₃. In the selection of the manufacture the dispersion used amounts of components e₁ and e₂ is still to be considered that the ratio of the amount of the component e₁ to the amount of the component e₂ an influence on the surface structure the coatings produced using these dispersions.  The structure of the resulting coatings is the same Wax amount or generally at the same amount of the component e₁ so coarser and rougher, the smaller the amount of filler used. Farther is the surface structure of the resulting coating the more pronounced the higher the total amount of the components e₁ and e₂.  

To prepare the dispersions, the components are e₁ and e₂ used in such amounts that the weight ratio the component e₁ to the component e₂ between 8.5: 1.5 and 2.5: 7.5, preferably between 7.0: 3.0 and 4.0: 6.0.

The structuring dispersion in turn becomes the coating agent added in an amount containing a content of Component e₁ in the coating agent from 0.5 to 2.5 wt .-%, preferably from 1.0 to 1.5 wt .-% and a content the component e₂ in the coating agent of 0.5 to 1.5% by weight, preferably from 0.8 to 1.2% by weight, this information being based on the total weight of the coating agent are obtained from components a to e.

The incorporation of the structuring dispersion into the coating compositions can be done by different methods The type of incorporation has an influence on the Surface texture of the resulting coating has. So there is the possibility, first the binders in the solvent or solvent mixture to solve and the other ingredients such as pigments, fillers, additives, etc. in solution or in the case of insoluble constituents with the to disperse usual grinding units in the paint industry. The structuring dispersion is then after dispersing added with stirring.

Another and most preferred way of incorporation is the dispersion together with the insoluble Ingredients using in the paint industry to disperse conventional grinding units in the binder solution and then the remaining ingredients below Add stirring.  

Finally, there is also the opposite of the first Process preferred procedure, the individual components the dispersion, namely the components e₁ and e₂, using the usual in the paint industry milling units to disperse in the solvent, this dispersion to heat with stirring, so that the component e₁ in solution and then the dispersion slowly to room temperature cool. Thereafter, the incorporation of the thus obtained Dispersion as described in Method 1.

In all 3 variants of the incorporation of the structuring Dispersions show that using the appropriate Coating materials produced coatings included Surface structure. However, the dispersion becomes incorporated according to the first described method, d. H. the Incorporation takes place without dispersing step, ie without use conventional grinding units, so tend the resulting Coatings for speckling. Furthermore, the surface structure much rougher and shorter wavelength than during incorporation the dispersion after the second and third Method. The second incorporation method is opposite to the third method has the advantage that they are easier and with less effort is feasible. In addition, the surface texture of coatings where the dispersion after in the second method in the coating agent was incorporated, longer wavelength than coatings the dispersion according to the third method in the coating agent was incorporated.

On the other hand, the usually as a structuring additive used wax dispersions using milling units incorporated into the coating, so show the resulting coatings have a smooth surface, so no structure.  

The surface structure of the resulting coating becomes additionally influenced by other parameters. So is the surface structure is more pronounced (i.e., coarser), depending higher in the case of two-coat paints, the layer thickness the primer and the lower the layer thickness of the topcoat is. For single-coat finishes, the surface texture is the more pronounced (ie coarser), the higher the layer thickness of the coating is. Furthermore, both in the case of one- as well as two-coat paints the Surface structure the more pronounced, the smaller the amount on used in the coating materials leveling agent is. Finally, the surface texture is still over the selection of the used binders (polyesters) and crosslinkers (Triazine resin or blocked isocyanate) controllable.

To carry out the method according to the invention, the above-described coating means by means of the tape coating process applied. The inventive method comprises a one- or two-layer processing, i. H. it Either only one layer can be applied or the Coating is composed of a primer and a topcoat together, all after the band coating process be applied.

The coatings are preferred in the form of a single-coat finish applied, the dry film thickness this monolayer coating at least 10 microns, preferably 15 to 25 microns, is.

In the case of a two-coat finish, both the primer as well as the topcoat of the above-described coating compositions consist. However, the described are preferred Coating used as a topcoat. The Dry film thicknesses are in the case of two-coat painting generally at least 5 microns, preferably 6 to 12 μm, for the primer and at least 10 μm, preferably 15 to 25 microns, for the topcoat.  

The tape coating process is known per se (cf. z. B. Kittel, Lehrbuch der Lacke und Beschichtungen, Volume VII, Processing of paints and coating materials, publisher W.A. Colomb in Heenemann Verlagsgesellschaft mbH, Berlin and Oberschwandorf, 1979) and therefore does not need it here to be explained in more detail. The curing of the coating agent usually takes place at object temperatures of 200 to 260 ° C according to a standard in the coil coating process, wherein baking times in the band coating of 25 to 70 seconds can be selected.

Examples of the means of the method according to the invention coated metallic objects are metal sheets and Metal bands of different iron alloys, black plate, Tinplate and aluminum, possibly with a Passivation layer based on different chromium, Nickel and zinc compounds are provided. To be favoured phosphated and chromated steel sheets used. The inventive method is particularly suitable for the coating of household appliances, such. Eg refrigerators, Freezers, Freezers, Washing machines, Dishwashers, Dryers, microwave ovens, gas and Electric stoves etc., furthermore for the coating of shelves, Partitions and other materials with a high Coating thickness.

In the following the invention with reference to exemplary embodiments explained in more detail. All information about parts and percentages are weights, if not expressly other is determined.  

1. Preparation of polyesters

For the preparation of the coating compositions are according to the usual Methods (see, for example, P. Olding, Ph.D. BA, & G. Hayward C. Chem. MRSC, Resins for Surface Coatings, Volume III, published by SITA Technology, 203 Gardiner House, Broomhill Road, London SW 148 JQ, England 1987) made the following polyesters:

Polyester I Parts by weight terephthalic acid 30 isophthalic 26 adipic acid 6 trimellitic 2 ethylene glycol 5 Hexanediol- (1,6) 11 2,2-dimethyl-propanediol (1.3) 20

Acid number 10 mg KOH / g, number average molecular weight 5500 g / mol (GPC),
Solid 60% in a mixture of a commercial, 99 wt .-% aromatics-containing solvent having a boiling point of 186-206 ° C and a density at 12 ° C of 0.895 g / ml and butyl glycol 4: 1.

Polyester II Parts by weight isophthalic 40 terephthalic acid 20 2,2-dimethyl-propanediol (1.3) 15 Hexanediol- (1,6) 25

Solid 55% in a commercial, containing 99 wt .-% aromatics Solvents with a boiling point of 186-206 ° C and a density at 12 ° C of 0.895 g / ml, number average molecular weight 5000 (GPC), Tg 20 ° C, OH number 17-22 mg KOH / g, acid number <3 mg KOH / g.

Polyester III Parts by weight isophthalic 12 phthalic anhydride 45 adipic acid 5.5 ethylene glycol 8.8 Hexanediol- (1,6) 8.5 2,2-dimethyl-propanediol (1.3) 20.2

Acid number <5 mg KOH / g, viscosity at 23 ° C 4000 mPa · s, solids 65% in a mixture of a commercial, 99 wt .-% aromatics containing solvent having a boiling point of 186-206 ° C. and a density at 12 ° C of 0.895 and ethylene glycol acetate 8: 2, OH number <20 mg KOH / g.

Polyester IV Parts by weight terephthalic acid 43 isophthalic 22 ethylene glycol 13 2,2-dimethyl-propanediol (1.3) 22

Solid 40% in a commercial 98 wt .-% containing aromatics Solvents with a boiling point of 221-270 ° C and a density at 12 ° C of 0.987 g / ml, acid number <2 mg KOH / g, number average molecular weight (GPC) approx. 7000-8000 g / mol, OH number 20-25 mg KOH / g, Tg 70 ° C.

2.1 Preparation of Dispersions 1 to 5

86.84 parts of propylene carbonate, 7.24 parts of a commercial, very pure silica with amorphous structure (BET surface area 200 ± 25 m² / g; average size of primary particles 12 nm; bulk weight about 120 g / l; Tamping volume according to DIN 53 194 about 1000 ml / 100 g; loss on drying 1 hour at 105 ° C <1.5%; Loss of ignition for 1 h at 1000 ° C <1%; SiO₂ content, based on the 1 h at 105 ° C dried substance <99.8%) and 5.92 parts of a commercial grade  Ethylene bis-stearamide wax (melting point 140-145 ° C; specific gravity at 20 ° C = 0.97; average particle size 8 μm) are stirred heated to boiling temperature (about 240 ° C) and below Reflux kept at this temperature until an almost clear dispersion arises. After that it gets slow allowed to cool to room temperature with gentle stirring and thus the dispersion 1 is obtained.

Analogously, further dispersions 2 to 5 were prepared, which differs from the dispersion 1 only by a different Share of the above-described commercial Distinguish between silica and wax. The composition Dispersions 1 to 5 are in Table 1 specified.  

Table 1

Composition of dispersions 1 to 7

2.2 Preparation of dispersions 6 and 7

There were 2 further dispersions analogous to the dispersion 6 and 7 made, differing from the dispersion 2 only by the commercial silica used differ.  

Thus, to prepare dispersion 6, commercial, very pure silica with amorphous structure, a BET surface area of 380 ± 30 m² / g, one average size of primary particles of 7 nm, one Bulk density of about 60 g / l, a ramming volume after DIN 53 194 of 1700 ml / 100 g, a loss on drying (1 hour at 105 ° C) of <1.5%, a loss on ignition (1 hour at 1000 ° C) of <1% and a SiO₂ content, based on the 1 h at 105 ° C dried substance, used by <99.8%. The composition this dispersion 6 is given in Table 1. For the preparation of the dispersion 7 was commercial, very pure silica with amorphous structure, one BET surface area of 120 ± 30 m² / g, a medium Size of the primary particles of 16 nm, a bulk density of about 60 g / l, a tamping volume according to DIN 53 194 of about 2000 ml / 100 g, a loss of drying (1 hour at 105 ° C) of <0.5%, a loss on ignition (1 hour at 1000 ° C) of <2% and a SiO content to the 1 h at 105 ° C dried substance, used by <98.3%. The composition of this dispersion 7 is given in Table 1.

3. Preparation of a Topcoat 1

13.4 parts of the 60% solution of the above Polyester I, 7.2 parts of the 55% solution of the above Polyester II, 32.5 parts of titanium dioxide from Rutile type, 0.5 parts of a commercial antioxidant, 0.2 parts of fumed silica, 5.2 parts of propylene carbonate and 5.2 parts of ethyl glycol acetate are added an agitator mill on a Hegmann fineness of milled about 10 microns.  

Then, with stirring, 9.5 parts of the 65% solution of the above-described polyester III, 12.5 parts of the 40% solution of the above-described polyester IV, 1.0 part of hydrogenated bisphenol A diglycidyl ether (M _w <800 g / mol ), 1.0 part of polyisobutyl acrylate (80% in a commercial 99 wt .-% aromatics-containing solvent having a boiling point of 186-206 ° C and a density at 12 ° C of 0.895), 2.7 parts of a commercially available adhesive resin solution ( 40% in xylene) 5.9 parts of butanone oxime blocked trimerized hexamethylene diisocyanate (75% in a commercial, obtained in the fractionation of light oil from the tar distillation, technical grade benzene with a boiling point of 165-180 ° C and a density d²⁰₄ of 0.870 , wherein at least 90% of the amount of distillate at 180 ° C), 0.1 parts of dibutyltin dilaurate and 3.1 parts of methyldiglycol added and stirred until a homogeneous dispersion.

Example 1

11.4 parts of the 60% solution of the above-described polyester I, 6.3 parts of the 55% solution of the above-described polyester II, 27.4 parts of rutile type titanium dioxide, 0.2 part of fumed silica and 8.1 parts of butyl acetate are milled to a Hegmann fineness of about 10 μ using an agitator mill. Then 8.2 parts of the 65% solution of the above-described polyester III, 10.9 parts of the 40% solution of the above-described polyester IV, 5.0 parts of butanone oxime-blocked trimerized hexamethylene diisocyanate (75% in a commercial, obtained in the fractionation of light oil from the tar distillation, technical benzene having a boiling point of 165-180 ° C and a density d²⁰₄ of 0.870, wherein at least 90% of the distillate at 180 ° C pass), 0.1 parts of dibutyltin dilaurate, 1.02 Parts bisphenol A diglycidyl ether (M _w <800 g / mol), 20.7 parts of the above-described dispersion 1, 0.3 parts of a commercial leveling agent based on a polyacrylate resin and 0.4 parts of a commercial light stabilizer added and stirred until, until a homogeneous dispersion is formed.

The composition of the coating composition thus obtained 1 is summarized in Table 2.

The coating composition 1 thus obtained is monolayered by means of the tape coating process on phosphated Steel sheet (Bonder 901) in a dry film thickness of 20 ± 10 microns applied and 48 s in the turntable oven cured to reach an object temperature of 220 ° C. The examination of the resulting coating is carried out in accordance with the relevant ECCA regulations (ECCA is the abbreviation for European Coil Coating Association). The results are shown in Table 3. to Testing of storage stability became the coating agent 1 before application 5 months at room temperature stored. The coatings thus obtained showed no Loss of quality.

example 2

The coating composition 1 described in Example 1 is phosphated by means of the tape coating process Steel sheet (Bonder 901) in a dry film thickness of 20 ± 10 microns applied and 48 s in the turntable oven until reaching an object temperature of Hardened 220 ° C. Subsequently, also by means of the tape coating method of the above-described topcoat 1 in a dry film thickness of 15 ± 5 microns applied and 62 s in a rotary oven until reaching cured at an object temperature of 235 ° C. The exam the resulting 2-layer coating takes place according to the corresponding ECCA regulations. The results are shown in Table 3.  

Examples 3 to 4

There are analogously to Example 1, the coating composition. 2 and 3, which differ from the coating agent 1 only by the composition and amount of used Dispersions 2 and 3 differ. The composition this coating agent 2 and 3 is shown in Table 2.

The coating compositions 2 and 3 are analogous to Example 1 single layer by means of the tape coating process applied to phosphated steel sheet (Bonder 901) and cured. Of the coatings thus obtained The structure of the surface is assessed visually. The Results are shown in Table 5.

Examples 5 to 7

Using dispersions 2, 6 and 7, the only by the particular silica used distinguish, the coating agent 4 to 6 manufactured. The incorporation of the dispersions was carried out in contrast to the coating compositions 1 to 3 such that the dispersion together with the polyester I, the polyester II, titanium dioxide, fumed silica and Butyl acetate with the aid of an agitator mill (Vollrath Laboratory sand mill VSME with 3000 revolutions / min and glass beads with a diameter of 2-3 mm as grinding media) ground to a Hegmann fineness of about 10 microns become. Subsequently, the remaining ingredients the coating agent added with stirring and stirred until a homogeneous dispersion arises.

The composition of these coating compositions 4 to 6 is shown in Table 2.  

The resulting coating compositions 4 to 6 are analogous to Example 1 in one layer by means of the tape coating process applied to phosphated steel sheet (Bonder 901) and cured. Of the coatings thus obtained how the structure of the surface is assessed visually. The results are shown in Table 5.

The comparison of Examples 5 to 7 shows that the Type of silica used influence the structure obtained has. The in the examples 5 to 7 different coating agents used namely only by that in the dispersions used silica, and in particular the in the BET surface area and thus the particle size of the silicon dioxide used. The for the Practical application of the coated metal sheets best structure is obtained in Example 6.

Furthermore, the comparison of Examples 3 and 5 shows that in addition to the composition of the structuring dispersion also the way of incorporation of the dispersion in the Coating agents have an influence on the surface structure of the coatings obtained.

Examples 8 to 10

The individual constituents of Dispersion 1 (Example 8) or 2 (Example 9) or 3 (Example 10), namely Propylene carbonate, commercially available, very pure silica with amorphous structure (BET surface area) 200 ± 25 m² / g; mean size of the primary particles 12 nm; Bulk density approx. 120 g / l; tamped volume according to DIN 53 194 about 1000 ml / 100 g; loss on drying 1 hour at 105 ° C <1.5%, loss on ignition 1 h at 1000 ° C <1%; SiO content, based on the 1 h at 105 ° C dried substance <99.8%) and  commercial ethylene-bis-stearamide wax (Melting point 140-145 ° C, specific gravity at 20 ° C = 0.97; average particle size 8 μm) initially 20 minutes by means of those described in Example 5 Ground laboratory sand mill and then stirring heated to boiling temperature (about 160 ° C) and reflux kept at this temperature until one almost clear dispersion arises. After that it gets slow allowed to cool to room temperature with gentle stirring.

The respective dispersion thus obtained was instead of Dispersion 1 or 2 or 3 analogously to Example 1 in the Coating agent 1 (Example 8) or 2 (Example 9) or 3 (Example 10) incorporated.

The coating composition thus obtained is analogous to Example 1 single layer by means of the tape coating process applied to phosphated steel sheet (Bonder 901) and cured. From the coating thus obtained is visually assess the structure of the surface. The results are shown in Table 5.

These results of the structural investigations show that with decreasing proportion of silica at constant Wax content of the dispersions which are intrinsically fine, uniform and always closed structure coarser and gets rough. When using a pure wax dispersion (i.e., without silica addition) gives a coarse Structure with holes to the sheet, so that such coatings for the practical use only conditionally can be used (Comparative Example 1).  

Comparative Examples 1 and 2

There are analogous to Example 3, the coating agent. 7 and 8 produced from the coating agent 2 of Example 3 differ in that the used Dispersion no silica and thus only Wax and solvent (dispersion 4, Comparative Example 1) or no wax and thus only silica and solvent (dispersion 5, comparative example 2) contains. The composition of these coating agents 7 and 8 is shown in Table 4.

These coating agents 7 and 8 are analogous to Example 3 in one layer by means of the tape coating process on phosphatized steel sheet (Bonder 901) applied and cured. Of the coatings thus obtained the surface structure is assessed. The results are listed in Table 6.

Comparative Examples 3 and 4

There are analogous to Example 5, the coating agent. 9 and 10 produced by the coating agent 4 of Example 5 differ in that the used Dispersion no silica (Comparative Example 3) or no wax (Comparative Example 4). The composition of these coating agents 9 and 10 is given in Table 4. These coating agents 9 and 10 are analogously to Example 5 monolayer by of the tape coating process on phosphatized steel sheet (Bonder 901) applied and cured. Of the so obtained Coatings is assessed the surface structure. The results are shown in Table 6.  

Comparative Examples 5 and 6

It is analogous to Example 3 (for Comparative Example 5) or Example 5 (for Comparative Example 6) the coating agent 11 and 12 made of the coating agent 2 or 4 differ only by that instead of the dispersion 2 only 0.9 parts of the example 1 described silica can be used. The application and curing takes place analogously to Example 3 or Example 5. The results of the assessment the surface structure are listed in Table 6.

Comparative Example 7

A coating agent 13 is produced thereby that the individual components of the dispersion 2, namely Propylene carbonate, wax and silica, together with the polyester I, the polyester II, titanium dioxide, pyrogenic Silica and butyl acetate with the aid of an agitator mill (Full wire laboratory sand mill VSME with 3000 revolutions / min and glass beads with a diameter from 2-3 mm as a grinding media) to a Hegmann fineness be ground of about 10 microns. Subsequently, the remaining constituents of the coating agent below Stir and stir until a homogeneous Dispersion arises.

The composition of the coating agent 13 is in Table 4 is shown.

The coating agent 13 is analogous to Example 1 single-layered by phosphatizing on the phosphatized Steel sheet (Bonder 901) applied and hardened. From the obtained coating becomes the structure visually assessed the surface. The results are shown in Table 6.  

example 11

57.7 parts of the 55% solution of the above Polyester II, 21.01 parts rutile-type titanium dioxide and 17.15 parts of dispersion 2 described above using a stirrer mill to a Hegmann fineness ground of about 10 microns. Then be 3.8 parts with stirring of a hexamethoxymethyl-melamine resin (100%) and 0.34 parts of p-toluenesulfonic acid (blocked) added and stirred until a homogeneous dispersion is formed.

The coating composition 14 thus obtained is analogous to Hardened Example 1 and 2.

The results of the structural investigations show a uniform structure, as Table 5 shows.

Comparative Examples 8-12

Coating compositions are prepared analogously to Example 5, which differs from the coating agent 4 only distinguish that as additive not the dispersion 2 was used, but various commercially available surface-treated particles. In detail were used:  

All coating materials resulted in coatings without Structure.  

Table 2

Composition of the coating compositions 1 to 6

Table 3

Test results of the coatings of Examples 1 and 2

Table 4

Composition of the coating compositions 7 to 13

Table 5

Results of the structural investigations of the coatings of Examples 1 to 11

Table 6

Results of the structural investigations of the coatings of Comparative Examples V1-V12

Summary of the test results

The comparison of Examples 8, 9 and 10 shows that with decreasing proportion of silica at constant wax content in the case of dispersions which are in themselves fine, uniform and always closed structure becomes coarser and rougher. at Use of a pure wax dispersion (ie without Silicon addition) results in a rough structure with holes to the plate, so that such coatings for the practical use are only conditionally usable (Comparative Example 1). Be pure Silica dispersions used (Comparative Examples 2 and 4), regardless of the type of incorporation, no Structure preserved.

The comparison of Examples 3, 5 and 9 shows that the Art the incorporation of the dispersion in the coating agent an influence on the surface structure of the resulting Coating has, and that by milling the dispersion with remaining constituents of the paint, especially the speck formation can be eliminated.

The comparison of Examples 5 to 7 shows that further also the type of silica used, especially the BET surface of the silica, an influence on the Structure has.

Finally, by choosing the binder / crosslinker of the paint the structure of the resulting coatings be influenced (Examples 5 and 11). In all examples 1 to 11, however, by the use of the dispersion as structuring additive in contrast to the incorporation of Wax a distinct and, above all, closed Achieved structure.

Claims (11)

1. A method for coating metallic objects in the tape coating process, wherein applied to the metal strip either a primer A with a dry film thickness of at least 5 microns and a topcoat B with a dry film thickness of at least 10 microns or a single-coat C with a dry film thickness of at least 10 microns and the primer A and the topcoat B or the single-coat C are cured at an object temperature of 200 to 260 ° C and a baking time of 25 to 70 s, wherein the primer A and / or the topcoat B or the single-coat C

• a) 20 to 40 wt .-% of a mixture of
  • a₁) from 70 to 95% by weight of polyester,
  • a₂) 5 to 30 wt .-% of a triazine resin or
  • a₃) 5 to 30 wt .-% of a blocked polyisocyanate, wherein the sum of the weight fractions of the components a₁ to a₃ each 100 wt .-% is.
• b) 10 to 40% by weight of pigments and / or fillers and / or suitable auxiliaries and additives,
• c) 0.1 to 2% by weight of a catalyst,
• d) 20 to 65 wt .-% of organic solvents and
• e) an additive for producing a structured surface

contains, wherein the sum of the weight proportions of the components a to e in each case 100 wt .-%, characterized in that as component e) a dispersion is used, which has been prepared by

• e₁) one or more polyolefin and / or polyamide waxes and / or one or more silicones and / or one or more acrylate copolymers,
• e₂) one or more fillers and
• e₃) one or more organic solvents

are first heated with stirring, so that the component e₁ is at least partially dissolved in the solvent and then slowly cooled to ambient temperature, wherein

• 1. the amounts used to prepare the dispersion of the components e₁ and e₂ be chosen so that the weight ratio of the component e₁ to the component e₂ between 8.5: 1.5 and 2.5: 7.5 and
• 2. the dispersion is added to the coating compositions in an amount which has a content of the component e₁ in the coating agent of 0.5 to 2.5 wt .-% and a content of the component e₂ in the coating agent of 0.5 to 1.5 % By weight, based in each case on the total weight of components a to e.

2. Coating composition containing

• a) 20 to 40 wt .-% of a mixture of
  • a₁) from 70 to 95% by weight of polyester,
  • a₂) 5 to 30 wt .-% of a triazine resin or
  • a₃) 5 to 30 wt .-% of a blocked polyisocyanate, wherein the sum of the weight fractions of the components a₁ to a₃ each 100 wt .-%,
• b) 10 to 40% by weight of pigments and / or fillers and / or suitable auxiliaries and additives,
• c) 0.1 to 2% by weight of a catalyst,
• d) 20 to 65 wt .-% of organic solvents and
• e) an additive for producing a structured surface,

wherein the sum of the proportions by weight of components a to e is in each case 100% by weight, characterized in that component e is a dispersion which has been prepared by

• e₁) one or more polyolefin and / or polyamide waxes and / or one or more silicones and / or one or more acrylate copolymers,
• e₂) one or more fillers and
• e₃) one or more organic solvents are first heated with stirring, so that the component e₁ is at least partially dissolved in the solvent and then slowly cooled to ambient temperature, wherein
  • 1. the amounts used to prepare the dispersion of the components e₁ and e₂ be chosen so that the weight ratio of the component e₁ to the component e₂ between 8.5: 1.5 and 2.5: 7.5 and
  • 2. the dispersion is added to the coating compositions in an amount which has a content of the component e₁ in the coating agent of 0.5 to 2.5 wt .-% and a content of the component e₂ in the coating agent of 0.5 to 1.5 % By weight, based in each case on the total weight of components a to e.

3. Process or coating composition according to claim 1 or 2, characterized characterized in that as component a₁ polyester of aromatic Dicarboxylic acids or their anhydrides and (cyclo) aliphatic Diols are used. 4. A method or coating composition according to any one of claims 1 to 3, characterized in that the used for the preparation of the dispersion Amounts of components e₁ and e₂ be chosen so that the weight ratio of the component e₁ to the component e₂ between 7.0: 3.0 and 4.0: 6.0. 5. A method or coating composition according to any one of claims 1 to 3, characterized in that the dispersion is the coating agents is added in an amount that is a content of the component e₁ from 1.0 to 1.5 wt .-% and the component e₂ from 0.8 to 1.2 wt .-%, in each case based on the total weight of components a to e, equivalent.   6. A method or coating composition according to any one of claims 1 to 5, characterized in that the fillers used as component e₂ have a BET surface area of more than 200 m² / g. 7. A method or coating composition according to any one of claims 1 to 6, characterized in that as a component e₁ polyolefin and / or Polyamide waxes with a melting point between 100 and 180 ° C. be used. 8. A method or coating composition according to any one of claims 1 to 7, characterized in that the polyester used as component a₁ a number average molecular weight of 5,000 to 20,000, a Acid number of 1 to 15 mg KOH / g and an OH number of 5 to 30 mg KOH / g have.