DE4019318C2 - - Google Patents

Description

The present invention relates to a method for Coating of metallic objects in the tape coating process, at which on the metal band either a primer A having a dry film thickness of at least 5 microns and a topcoat B with a Dry film thickness of at least 10 μm or one Single-coat C with a dry film thickness of at least 10 microns is applied and the Primer A and the topcoat B or the one-coat coating C each at an object temperature of 200 up to 260 ° C and with a burn-in time of 25 to 70 s be cured, 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 polyesters of 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 adjuvants 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, where the sum of the parts by weight of the components a to e are each 100% by weight.

The present invention is also the Use of coated by this method metallic objects for the manufacture of household appliances and the use of siloxane compounds in Varnishes for the tape coating process as an additive for production a structured surface.

It is known for coating metal bands to use liquid thermosetting coating compositions, from a solution of a hydroxyl-containing Binder, z. B. a polyester and a blocked polyisocyanate or a hexamethoxymethylmelamine resin consist in an organic solvent. The coatings cured by the coil coating process have relatively good light and weather resistance and satisfactory mechanical ductility properties.  

The disadvantage, however, is that they are responsible for this process typical, very smooth surface. This is particularly disadvantageous when the coating agent for coating metal strips should be used subsequently during the Construction phases with metal sheets or device parts which are combined by spraying have been painted. By the spray process is usually a slightly rough, wavy surface generated. The surfaces of parts of equipment used in the Powder spray processes are also coated a more or less pronounced surface structure on.

For design-related combinations of metal sheets, which has been coated by conventional methods are, with the band coated surfaces that falls Lack of textured surface in the band-coated Especially open up.

A structured surface is usually less sensitive against dirt and shine spots, against small scratches, etc., so that in many Cases, z. B. in household appliances, structured Surface structures are preferred.

From EP-A 2 15 223 is a method for coating Known in strip coating, in which a This creates a scar-like surface structure is that the primer or the topcoat 0.5 to 7 wt .-%, based on the dry weight of Resin, one in the solvent or dispersant suspended or emulsified organic interfering substance, their particle or droplet sizes between  3 and 60 microns, which are at the processing temperature melts and their surface tension is different from different from that of the resin. Preferably used as an additive Wax, such as B. modified or unmodified polyethylene waxes, Polypropylene waxes and polyamide waxes. The structure is the more pronounced, depending higher the proportion of interfering substance in the coating agent is. The coatings obtained by this process are due to the porous, d. H. not closed, Surface in terms of chemical resistance, the corrosion protection properties and the intermediate adhesion still in need of improvement.

From EP-A 2 88 964 is a method for coating Known in strip coating, in which a This creates a scar-like surface structure is that 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 μm, preferably 5 to 25 μm, if necessary in combination with 0.01 to 5% by weight of a tall oil alkyd resin additive and possibly in combination with a Contains flow agent.

Finally, it is known coating compositions siloxane resins add as an additive. These siloxane resins are usually depending on the viscosity and thus ever by average molecular weight and depending the functional groups contained on the silicon atom as leveling, anti-flooding, dispersing auxiliary, Defoaming, adhesion promoting or hammer impacting agents used. So are the low molecular weight Siloxane resins with a number average  Molecular weight of 1000 to 4000 and a viscosity from 5 to 50 mPa · s at 25 ° C as a leveling and anti-flooding agent used. To achieve textured surfaces (hammered effect) become In contrast, high molecular weight siloxane resins with a number average molecular weight <100,000 used.

The present invention was therefore based on the object a method for coating metallic Objects in the band coating process available to provide, in which at the usual layer thicknesses closed from 20 to 45 μm spritzstrukturähnliche surfaces are achieved and in which the resulting films are particularly excellent Anti-corrosion properties and good chemical resistance, for example, towards methyl ethyl ketone, Alcohols and detergents. The coatings should have good ductility and both a good substrate and in the case the two-coat finish also a good To have interim liability. In addition, the in coating agent used in this process be as simple and easy to handle.

This object is surprisingly achieved by a method for coating metallic objects dissolved in the tape coating process, in which on 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 μm is applied and the primer A and the topcoat B and the single-coat C in each case  an object temperature of 200 to 260 ° C and at a Stoving time of 25 to 70 s to be cured 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 polyesters of 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% by weight 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 100% by weight, respectively characterized in that a primer A and / or a topcoat B or a single-coat finish C is applied, which as component e either a siloxane compound having at least one opposite  the functional groups of component a reactive group and with a number average Molecular weight of 300 to 10,000, preferably 500 to 2500, or a siloxane compound without one opposite the functional groups of component a reactive Group and having a number average molecular weight from 700 to 50,000, preferably from 1,000 to 4,000 and / or a viscosity at 25 ° C of 3 to 5000 mPa · s, preferably 5 to 100 mPa · s, contains.

The present invention also relates to the use coated by this method metallic Articles for the manufacture of household appliances. The subject of the present invention is furthermore the use of the above-mentioned siloxane compound in paints for the tape coating process as an additive to Creation of a structured surface.

It is surprising and unpredictable that always (i.e., also in single-layer processing) closed injection-structure-like Surfaces are achieved, where These resulting coatings are also excellent Corrosion protection properties and good chemical resistance distinguished. Usually namely low molecular weight siloxane resins with number average Molecular weights below 10,000 just as a leveling agent to avoid structured surfaces used while structured surfaces (Hammering effect) by the addition of high molecular weight nonfunctionalized siloxanes with molecular weights <100,000 are generated.

Furthermore, it is surprising that these structured Surfaces are obtained when the low molecular weight Siloxane resins only in amounts of less than 0.15% by weight, based on the total weight of the  Coating agent used. Using however, higher amounts of siloxane resin are ever according to selected binder and type of primer may not get textured surfaces.

When using wax as a structure-producing Additive is the surface structure namely so around more pronounced, the higher the wax content used in the coating agent is (see, for example, EP-A 2 15 223).

Another advantage of the method according to the invention is that the resulting coatings a good Deformability and a good substrate as well as in the case the two-coat coating also a good intermediate liability respectively.

The following are the individual components in the method according to the invention explained in more detail.

The in the coating compositions of the invention Method used polyester resins a₁ are known. They will follow the usual procedures (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 valency Alcohols, optionally together with monohydric alcohols, and in particular aromatic dicarboxylic acids.  

Of course, it is also possible to use aliphatic ones or cycloaliphatic carboxylic acids and polycarboxylic acids be 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 2 to 8 carbon atoms, such as. For example, ethylene glycol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3- propanediol, glycerin, trimethylolethane and trimethylolpropane.

Examples of suitable carboxylic acids or their derivatives are (cyclo) aliphatic dicarboxylic acids, such as z. B. adipic acid, azelaic acid, tetrahydrophthalic acid, Hexahydrophthalic acid, endomethylenetetrahydrophthalic acid and aromatic carboxylic acids, such as. B. Phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid and pyromellitic acid. Well suited (cyclo) aliphatic or aromatic di- or tricarboxylic acids with 4 to 10 carbon atoms, e.g. B. Adipic acid, azelaic acid and / or isophthalic acid. The in the primer, in the topcoat and in the single-coat paint used polyesters have been preferred  Acid numbers from 1 to 15 mg KOH / g, preferably hydroxyl numbers from 5 to 30 mg KOH / g and preferably number average Molecular weights from 5,000 to 20,000, more preferably 6000 to 10,000 and preferably Dispersities <8.

Suitable crosslinking agents for the polyester resins are, for example, triazine resins (a₂). suitable For example, resins are reaction products of aldehydes, such as As formaldehyde, with melamine or benzoguanamine. Preferably, these compounds are partially or completely etherified with alcohols containing 1 to 6 carbon atoms included, 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. Prefers are polyisocyanates as oligomeric polyisocyanates used. Examples of oligomeric polyisocyanates are those with an isocyanurate structure, so z. As the polyisocyanurate polyisocyanates of hexamethylene diisocyanate and isophorone diisocyanate. Examples for other suitable oligomeric polyisocyanates are those with 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 used in the process according to the invention Coating agents contain 0.1 to 2.0 wt .-%, based on the total weight of the coating agent, conventional catalysts, such as. B. conventional acid catalysts or common organotin and organozinc Catalysts. Examples include: dibutyltin dilaurate, para-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic, Phosphoric acid and phosphoric acid derivatives and zinc octoate. Furthermore, the coating compositions 20 to 65% by weight, based on the total weight of the coating agent, one or more organic Solvents, such as. B. aromatic hydrocarbons, Esters, ethers, ketones, alcohols or others organic compounds. Preferred solvents are aromatic hydrocarbons, esters and glycol ethers.

The used in the process according to the invention Coating agents may also contain from 10 to 40% by weight, based on the total weight of the coating agent, common pigments, fillers and other common ones Contain additives. As pigments come for example Titanium dioxide or inorganic colored pigments, such as chromium, nickel, cobalt and iron oxide pigments as well as metallizing pigments, such as aluminum bronze, in question. As examples of customary auxiliaries and additives are leveling agents, stabilizers, emulsifiers and To call a bonding agent.

As a constituent essential to the invention contain the Coating agent as a structure-forming additive  (Component e) a siloxane compound having at least one, versus the functional groups of the component a reactive group and with a number average Molecular weight of 300 to 10,000, preferably 500 to 2500 or a siloxane compound without one, against the functional groups of the component a reactive group and with a number average Molecular weight of 700 to 50,000, preferably to 1000 to 4000, and / or a viscosity at 25 ° C from 3 to 5000 mPa · s, preferably 5 to 100 mPa · s.

The time required to create a textured surface Amount depends as well as the surface structure in itself of several factors. So is the same amount of siloxane compound used the surface structure the more pronounced (i.e., coarser), the higher the layer thickness of the Coating is. Furthermore, both in the case of One as well as the two-coat paints the surface structure the more pronounced, the lower the Amount of used in the coating materials Leveling agent is. Furthermore, the surface structure nor about the selection of the binders used (Polyester) and crosslinker (triazine resin or blocked isocyanate) controllable. Finally has also the respective underground (in particular its Surface tension) an influence on the achievable Surface structure. Accordingly, the hangs Quantity therefore also depends on whether the coating agent one or two layers was applied.

In the case of a two-layer processing contains the primer and / or the topcoat usually at least 0.005 wt%, preferably 0.005  to 0.15 wt .-% and particularly preferably 0.05 to 0.15 wt .-%, each based on the total weight of the coating agent, the siloxane compound with at least one, opposite to the functional groups the component a reactive group. by virtue of the influence of the underground on the achievable Structure may vary depending on the ground but required be, higher or lower amounts of the siloxane compound use.

The most favorable use amount but can from Expert easily detected by a few routine tests become.

In the case of a single-layered processing contains the monolayer coating usually at least 0.0001 wt%, preferably 0.0005 to 0.15 wt%, especially preferably 0.0005 to 0.001 wt .-%, respectively based on the total weight of the coating agent, the siloxane compound with at least one opposite functional groups of components reactive group.

According to the invention in the coating compositions Siloxane used, which is a lower Have surface tension as the coating agent without the addition of siloxane compounds. Prefers is the surface tension of the siloxane compounds by at least 5 mN / m, preferably by at least 8 mN / m lower than that of the coating composition without additive the siloxane compounds.

The siloxane resins can be organopolysiloxanes with linear, comb-like, branched or reticular structure  be that at least one, preferably at least two, versus the functional groups of the component Have a reactive groups. It can polyester, polyether and polyacrylate modified Siloxane resins are used as well Condensation products of monomeric siloxanes. When Reactive group, these resins, for example at least 1 hydride, hydroxyl, amino, amido, Contain ester or methylol group. For example, as component e siloxane resins suitable for the following general formula:

With

R¹, R²: hydrocarbon radical
X: reactive group
n: 50, preferably 5 to 15

The substituents R¹ and R² may be the same or various aliphatic, cycloaliphatic or aromatic hydrocarbon radicals, for example a methyl, ethyl, propyl, trifluoropropyl or phenyl radical. The substituents R¹ and However, R² can also be used for a polyester, polyether or polyacrylate.  

Suitable functional groups X are all functional groups which can react under the stoving conditions with the binder and / or crosslinker of the coating composition. Examples of these are hydride, hydroxyl, amino, ester and amido groups. Due to the better hydrolytic stability but preferably siloxane resins are used in which X is the group - (CH₂) _m -Y. Y stands for a primary or secondary amino group, a hydroxyl group or an amido group

or

With
R³ = alkyl or acrylic radical and m generally between 1 and 20, preferably between 2 and 5. Specific examples of suitable siloxane compounds are given below:

Preferably, however, siloxane compounds are used in which the hydrolyzable group via an alkyl group - (CH₂) _n -Y are bonded, such as. B.

with n = 1 to 20, preferably 2 to 5.  

Examples of suitable compounds are also the products commercially available under the following names:
EFKA®-polymer LP 8710, EFKA®-polymer LP 7980, EFKA®-35 and EFKA® 30 to 36 from Efka Chemicals BV; Tegomer® H-SI 2210, -A-SI 2120, -E-SI 2130, -C-SI 2140 and -V-SI 2150 from Th. Goldschmidt AG; Dow Corning® 3 Additive, 7 Additive, 11 Additive, 21 Additive, 25 Additive, 54 Additive, 56 Additive, 29 Additive, 51 Additive, 57 Additive, 59 Additive and 64 Additive from Dow Corning Corp. Europe, Brussels.

Particularly preferred as component e is the α, ω- [3-hydroxy] -propylpolydimethylsiloxane of the formula

with n≈10
used. This siloxane compound is commercially available under the name Tegomer® H-SI 2110 from Th. Goldschmidt AG.

Instead of these described and preferred used Siloxane compounds having at least one functional Group per molecule, in the inventive Method used coating agent  as component e an unfunctionalized siloxane compound with a number average molecular weight from 700 to 50,000, preferably 1000 to 4000, and / or a viscosity of 3 to 5000 mPa · s, preferably 5 to 100 mPa · s, at 25 ° C. This non-functionalized Siloxane compounds are usually in an amount of 0.0005 to 0.15 wt .-%, preferably 0.02 to 0.10 wt .-%, based on the total weight of the coating agent used. These compounds are known and commonly used used as a leveling or slip agent. Examples of suitable compounds are those commercially available under the name Tegomer® the company Th. Goldschmidt AG available products.

The preparation of the method according to the invention used coating agent is carried out by Mixing and possibly dispersing the individual components.

For carrying out the method according to the invention the coating compositions described above are the Bandlackierverfahrens applied. The invention Method comprises a one or two-layered Processing, d. H. it can either only Apply a coat or the coating consists of a primer and a topcoat together, all after the band coating process be applied. The coatings are preferably in the form of a One-coat coating applied, wherein the dry film thickness this single-coat 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 from those described above Coating agents exist. Prefers but the coating compositions described as Topcoat used. The dry film thicknesses are in the case of two-coat painting in general at least 5 μm, preferably 6 to 12 μm, for the primer and at least 10 microns, preferably 15-25 μm, for the topcoat.

The tape coating process is known per se (see, for example, Kittel, Lehrbuch der Lacke und Beschichtungen, Volume VII, Processing of lacquers and coating materials, Publisher W. A. Colomb in the Heenemann Verlagsgesellschaft mbH, Berlin and Oberschwandorf, 1979) and therefore needs no further details to be explained. The curing of the coating agent usually takes place at object temperatures from 200 to 260 ° C after one in the coil coating conventional methods, wherein burn-in at the Coil 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 strips of various iron alloys, Black plate, tinplate and aluminum, possibly with a passivation layer based on various chromium, nickel and zinc compounds are provided. Preference is given to 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., continue for the coating of shelves, partitions and other materials with a high Coating thickness.

In the following the invention with reference to embodiments explained in more detail. All information about Parts and percentages are by weight, if not expressly stated otherwise.

1. Preparation of polyesters

For the preparation of the coating agent according to the usual methods (See, for example, Dr. P. Olding, Ph. D. BA Hayward C. Chem., MRSC, Resins for Surface Coatings, Volume III, published by SITA Technology, 203 Gardiner House, Broomhill Road, London SW 184 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), Solids 60% in Solvesso® 150: 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

Solids 55% in Solvesso® 150, 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 Solvesso® 150: Ethyl 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

Solids 40% in Solvesso® 200, acid number <2 mg KOH / g, number average molecular weight (GPC) about 7000-8000 g / mol, OH number 20-25 mg KOH / g, Tg 70 ° C.  

2.1. Preparation of a primer 1

13.96 parts of the 60% solution of the above-described polyester I, 5.88 parts of the 55% solution of the above-described polyester II, 30.56 parts of rutile-type titanium dioxide, 0.26 part of a commercial antioxidant, 0, 18 parts of fumed silica, 9.13 parts of propylene carbonate, 10.45 parts of the 65% solution of the polyester III described above, 11.68 parts of the 40% solution of the above-described polyester IV, 3.25 parts of a hexamethoxymethylmelamine resin (100%). ig), 0.96 parts of Versaticsäureglycidylether blocked p-toluenesulfonic acid (50%) and 0.88 parts of hydrogenated bisphenol A diglycidyl ether (M _w <800 g / mol) are using a sand mill to a Hegmann fineness of approx 10 μm ground. Subsequently, 12.81 parts of propylene carbonate are added while stirring and stirring is continued until a homogeneous dispersion is formed.

2.2 Preparation of a primer 2

13.4 parts of the 60% solution of the above-described polyester I, 5.64 parts of the 55% solution of the above-described polyester II, 29.32 parts of rutile-type titanium dioxide, 0.25 part of a commercial antioxidant, 0, 17 parts of fumed silica, 8.76 parts of propylene carbonate, 10.03 parts of the 65% solution of the above-described polyester III, 11.2 parts of the 40% solution of the above-described polyester IV, 5.05 parts of butanone oxime-blocked trimerized hexamethylene diisocyanate , 75% in Solventnaphtha® 100, 0.08 parts dibutyltin dilaurate and 0.84 parts hydrogenated bisphenol A diglycidyl ether (M _w <800 g / mol) are ground using a sand mill to a Hegmann fineness of about 10 microns , Subsequently, 15.26 parts of propylene carbonate are added with stirring and stirred until a homogeneous dispersion is formed.

Example 1 (comparison)

A topcoat 1 is prepared by adding 13.96 parts of the 60% solution of the above-described polyester I, 5.88 parts of the 55% solution of the above-described polyester II, 30.56 parts of rutile-type titanium dioxide, 0, 26 parts of a commercial antioxidant, 0.18 parts of fumed silica, 9.13 parts of propylene carbonate, 10.45 parts of the 65% solution of the above-described polyester III, 11.68 parts of the 40% solution of the above-described polyester IV, 3rd , 25 parts of a Hexamethoximethylmelaminharzes (100%), 0.96 parts with Versaticsäureglycidylether blocked p-toluenesulfonic acid (50%) and 0.88 parts of hydrogenated bisphenol A diglycidyl ether (M _w <800 g / mol) using a sand mill be ground to a Hegmann fineness of about 10 microns. 12.61 parts of propylene carbonate and 0.2 part of a commercially available hydroxyl-containing siloxane resin (commercial product Tegomer® H-SI 2110 from Th. Goldschmidt AG, an α, ω-hydroxiorganofunctional polydimethylsiloxane of the structure

with n≈10, an OH number of 105 ± 10 mg KOH / g and a viscosity of 50 ± 10 mPa · s at 25 ° C) added and stirred until a homogeneous Dispersion arises. The composition of this Topcoat 1 is shown in Table 1. First, by means of the tape coating process Primer 1 on phosphated sheet steel (Bonder 901) with a dry film thickness of 6 μm applied and 48 s in rotary oven until reaching an object temperature Hardened from 220 ° C. Subsequently, too by means of the band painting process of Topcoat 1 with a dry film thickness of 22 μm applied and 62 s in a rotary dish oven until reaching an object temperature of Cured at 235 ° C. From the coating thus obtained visually becomes the surface texture assessed. The result is shown in Table 2.

Examples 2 to 8

There are analogously to Example 1 2-coat coatings made, which differ from the coating of Example 1 only by a different one Content of the topcoats on hydroxylgruppenhaltigem Differentiate siloxane. The composition the topcoats used is 2 to 8 shown in Table 1. The results of the visual Assessment of the surface structure of the Coatings are summarized in Table 2.  

example 9 (Comparison)

First, a topcoat 9 is prepared by adding 13.4 parts of the 60% solution of the above-described polyester I, 5.64 parts of the 55% solution of the above-described polyester II, 29.32 parts of rutile-type titanium dioxide , 25 parts of a commercial antioxidant, 0.17 parts of fumed silica, 8.76 parts of propylene carbonate, 10.03 parts of the 65% solution of the above-described polyester III, 11.2 parts of the 40% solution of the above-described polyester IV, 5.05 parts of butanone oxime blocked trimerized hexamethylene diisocyanate, 75% in Solventnaphtha® 100, 0.08 parts of dibutyltin dilaurate and 0.84 parts of hydrogenated bisphenol A diglycidyl ether (M _w <800 g / mol) using a sand mill on a Hegmann Milled fineness of about 10 microns. Subsequently, with stirring, 15.06 parts of propylene carbonate and 0.2 parts of a commercially available hydroxyl-containing siloxane resin (commercial product Tegomer® H-SI 2110 from Th. Goldschmidt AG, an α, ω-hydroxiorganofunktionelles polydimethylsiloxane of the structure

with n≈10, an OH number of 105 ± 10 mg KOH / g and a viscosity of 50 ± 10 mPa · s at 25 ° C) added and stirred until a homogeneous  Dispersion arises. The composition of this Topcoat 9 is shown in Table 3.

First, by means of the tape coating process Primer 2 on phosphated sheet steel (Bonder 901) with a dry film thickness of 6 μm applied and 48 s in rotary oven until reaching an object temperature Hardened from 220 ° C. Subsequently, too by means of the band painting process of Topcoat 9 with a dry film thickness of 22 μm applied and 62 s in a rotary dish oven until reaching an object temperature of Cured at 235 ° C. From the coating thus obtained visually becomes the surface texture assessed. The result is shown in Table 4.

Examples 10 to 16

There are analogously to Example 9 2-coat coatings made, which differ from the coating of Example 9 only by a different one Content of the topcoats on hydroxylgruppenhaltigem Differentiate siloxane. The composition the topcoats used 10 to 16 is shown in Table 3. The results the visual assessment of the surface structure of the coatings are in Table 4 summarized.  

Table 1

Composition of the topcoats of Examples 1 to 8

Table 2

Surface structure of the coatings of Examples 1 to 8

Table 3

Composition of the topcoats of Examples 9 to 16

Table 4

Surface structure of the coatings 9 to 16

example 17 (Comparison)

A coating agent 17 is prepared by adding 33.32 parts of the 60% solution of the above-described polyester I, 33.50 parts of rutile-type titanium dioxide, 0.5 part of a commercial antioxidant, 0.2 part of fumed silica, 11, 0 parts of the 40% solution of the polyester IV described above, 4.3 parts of a Hexamethoximethylmelaminharzes (100%), 0.8 parts with Versaticsäureglycidylether blocked p-toluenesulfonic acid and 1.0 parts of hydrogenated bisphenol A diglycidyl ether (M _w < 800 g / mol) using a sand mill to a Hegmann fineness of about 10 microns are ground. 5.4 parts of Solvesso® 150, 9.48 parts of butyl acetate and 0.5 part of the commercially available siloxane resin described in Example 1 (commercial product Tegomer® H-SI 2110 from Th. Goldschmidt AG) are then added with stirring and stirred until until a homogeneous dispersion is formed. The composition of this coating agent 17 is shown in Table 5.

The coating agent 17 thus obtained is monolayered by means of the tape coating method Phosphated steel sheet (Bonder 901) in one Dry film thickness of 24 ± 10 microns applied and 48 s in the turntable oven until reaching hardened an object temperature of 220 ° C. The examination of the resulting coating is carried out according to the corresponding ECCA regulations (ECCA is the abbreviation for European Coil Coating Association). Within the measurement accuracy were the same results as for Example 22 was obtained.  

The assessment of the surface structure of the resulting Coating was done visually as well by profile measurements with the Perthometer S6P the Company Feintest GmbH. The test results are in Tables 7 and 8 shown.

Examples 18 to 24

There are analogous to Example 17 monolayer made, differing from Example 17 only by a different content of the coating agent on hydroxyl-containing siloxane differ. The composition of the used Coating agent is in Table 5 shown. The results of the visual assessment the surface structure of the coating are shown in Table 7 and the results of the Perthometer Measurements are summarized in Table 8. The examination of the technical properties of the coatings Examples 18 to 24 after the in Table 6 according to the ECCA regulations resulted within the measurement accuracy respectively the same values. To avoid repetition Therefore, only the measured values of the Example 22 is included in Table 6.

example 25

It is initially analogous to the preparation of the coating composition 22 a coating agent 25th made of the coating agent 22nd only differs in that instead of the siloxane resin Now butyl acetate is used.  

It will now be first by means of the tape coating process the coating agent 25 on phosphated Steel sheet (Bonder 901) with a Dry film thickness of 10 microns applied and 48 s in the turntable oven until reaching a Object temperature of 220 ° C cured. Subsequently is also using the Bandlackierverfahrens the coating agent 22 with applied to a dry film thickness of 23 microns and 62 s in the turntable oven until reaching an object temperature of Cured at 235 ° C. The examination of the resulting Coating takes place according to the corresponding ECCA Rules. The results are in table 6 shown. The assessment of the surface structure was done visually. The result is also shown in Table 6.

example 26

It is analogous to Example 22 phosphated steel sheet (Bonder 901) with the coating agent 22nd with a dry film thickness of 23 μm coated. Unlike example 22 becomes but now on the resulting coating the Coating agent 25 with a dry film thickness of 10 microns by means of the tape coating process applied and 62 s in the turntable oven until reaching an object temperature cured from 235 ° C. The results of Check the coating according to the appropriate ECCA regulations as well as the result of the visual Assessment of the surface structure are summarized in Table 6.  

Table 5

Composition of the coating compositions of Examples 17 to 24

Table 6

Test results of the coatings of Examples 22, 25 and 26

Table 7

Surface structure of the coatings 17 to 24

Table 8

Results of the Perthometer Measurements¹) of the Coatings of Examples 17 to 24

example 27 (Comparison)

A coating agent 27 is prepared by adding 33.32 parts of the 60% solution of the above-described polyester I, 33.50 parts of rutile-type titanium dioxide, 0.5 part of a commercial antioxidant, 0.2 part of fumed silica, 11, 0 parts of the 40% solution of the polyester IV described above, 6.0 parts of butanone oxime-blocked, trimerized hexamethylene diisocyanate, 75% strength in Solventnaphtha® 100, 0.1 part of dibutyltin dilaurate and 1.0 part of hydrogenated bisphenol A diglycidyl ether (M. _w <800 g / mol) using a sand mill to a Hegmann fineness of about 10 microns are ground. 5.4 parts of Solvesso® 150, 8.48 parts of butyl acetate and 0.5 part of the commercial siloxane resin described in Example 1 (commercial product Tegomer® H-SI 2110 from Th. Goldschmidt AG) are then added with stirring and stirred until until a homogeneous dispersion is formed. The composition of this coating agent 27 is shown in Table 9.

The coating agent 27 thus obtained is monolayered by means of the tape coating method Phosphated steel sheet (Bonder 901) in one Dry film thickness of 24 ± 10 microns applied and 48 s in the turntable oven until reaching hardened an object temperature of 220 ° C. The examination of the resulting coating is carried out according to the corresponding ECCA regulations (ECCA is the abbreviation for European Coil Coating Association). Within the measurement accuracy were the same results as for  Example 32 was obtained. The assessment of Surface structure of the resulting coating was done visually. The test results are in Table 11.

Examples 28 to 34

There are analogous to Example 27 single-coat made, which differ from the coating of Example 27 only by a different one Content of the coating agent on hydroxylgruppenhaltigem Differentiate siloxane. The composition the coating agent used is shown in Table 9. The results the visual assessment of the surface structure of the coating are shown in Table 11.

Checking of technical properties the methods given in Table 10 after the ECCA regulations revealed within the scope of measurement accuracy each the same values. To avoid of repetitions, therefore, only the measured values Example 32 is included in the table 10.

example 35

It is initially analogous to the preparation of the coating composition 32 a coating agent 35th made of the coating agent 32nd only differs in that instead of the siloxane resin Now butyl acetate is used.

It will now be first by means of the tape coating process the coating agent 35 on phosphated Steel sheet (Bonder 901) with a Dry film thickness of 10 microns applied and 48 s in the turntable oven until reaching a Object temperature of 220 ° C cured. Subsequently  is also using the Bandlackierverfahrens the coating agent 32 with a dry film thickness of 24 microns applied and 62 s in the turntable oven until reaching cured at an object temperature of 235 ° C. The examination of the resulting coating takes place according to the corresponding ECCA regulations. The results are shown in Table 10. The evaluation of the surface structure was carried out visually. The result is also in Table 10 shown.

example 36

It is analogous to Example 32 phosphated steel sheet (Bonder 901) with the coating agent 32nd with a dry film thickness of 23 μm coated. Unlike example 32 but now on the resulting coating the Coating agent 35 having a dry film thickness of 10 microns by means of the tape coating process applied and 62 s in the turntable oven until reaching an object temperature cured from 235 ° C. The results of Check the coating according to the appropriate ECCA regulations as well as the result the visual assessment of the surface structure are summarized in Table 10.  

Table 9

Composition of the topcoats of Examples 27 to 34

Table 10

Test results of the coatings of Examples 32, 35 and 36

Table 11

Evaluation of the surface structure of the coatings of Examples 27 to 34

example 37 (Comparison)

It is analogous to Example 17, a single-coat prepared from Example 17 by another composition of the solvents used and especially by the siloxane compound used different. And that was as a siloxane compound now a connection without one opposite the functional groups of component a reactive Group used, namely the commercial product Baysilon® paint additive M 51 from Bayer, a Methylpolysiloxane having a viscosity according to DIN 53 015 of 45-55 mPa · s and a surface tension according to DIN 53,914 of about 20 mN / m. The composition of the used Coating agent is shown in Table 12. The results of the visual assessment the surface structure of the coating are in Table 13 is shown.

Examples 38 to 44

There are analogous to Example 37 one-coat made, differing from Example 37 only by a different content of the coating agent on the commercial product Baysilon® paint additive M 51 distinguish the company Bayer. The composition the coating agent used is in Table 12 is shown. The results of the visual Assessment of the surface structure of the coatings are shown in Table 13.  

Table 12

Composition of the coating compositions of Examples 37 to 44

Table 13

Evaluation of the surface structure of the coatings of Examples 37 to 44

Summary of the test results

The comparison of Examples 1 to 16 shows that in Case of a two-layer processing of the coating agent to achieve a pronounced Structure in each case most favorable amount of siloxane compound with reactive groups between 0.05 and 0.15 wt .-%, based on the total weight of the coating agent lies. In the case of a single-layered Processing is to achieve a pronounced structure in each case most favorable amount the siloxane compound with reactive Groups, however, between 0.0005 and 0.001 wt .-%, based on the total weight of the coating agent. This applies to both the melamine and the isocyanate-crosslinked systems.

Claims (12)

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 at 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) 70 to 95 wt .-% 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 component 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

contains, wherein the sum of the weight proportions of the components a to e is in each case 100 wt .-%, characterized in that a primer A and / or a topcoat B or a single-coat C is applied, which as component e either a siloxane compound having at least one , a group reactive toward the functional groups of component a and having a number average molecular weight of from 300 to 10,000 or a siloxane compound without a group reactive toward the functional groups of component a and having a number average molecular weight of from 700 to 50,000 and / or a viscosity 25 ° C from 3 to 5000 mPa · s. 2. The method according to claim 1, characterized that a primer A and / or a topcoat B or a single-coat C is applied, the as component a₁ polyester of aromatic dicarboxylic acids or their anhydrides and (cyclo) aliphatic Contains diols. 3. The method according to claim 1 or 2, characterized that a primer A and / or a topcoat B or a single-coat C applied which as component e is either a siloxane compound with at least one opposite to the functional Groups of component a reactive Group and having a number average molecular weight from 500 to 2500 or a siloxane compound without one opposite the functional groups of the Component a reactive group and with a  number average molecular weight of 1000 to 4000 contains. 4. The method according to claim 1 to 3, characterized that a primer A and a topcoat B be applied, the primer A and / or the topcoat B at least 0.005 wt .-%, preferably 0.005 to 0.15 wt .-% and particularly preferably 0.05 to 0.15 wt .-%, each based on the total weight of the coating agent, the siloxane compound with at least one opposite the functional groups of component a reactive Group contains. 5. The method according to claim 1 to 3, characterized that a single-coat C applied is at least 0.0001 wt .-%, preferably 0.0005 to 0.15 wt%, and more preferably 0.0005 to 0.001 wt .-%, each based on the Total weight of the coating agent, the siloxane compound with at least one opposite the functional groups of component a reactive Group contains. 6. The method according to any one of claims 1 to 5, characterized characterized in that a primer and / or a Topcoat or a single-coat coating applied which, as the component e, is a siloxane compound with at least one, preferably at least two, hydroxyl, amino, hydride, methylol or Contains ester groups. 7. The method according to any one of claims 1 to 6, characterized in that a primer and / or a topcoat or a single-coat is applied, the component e α, ω- [3-hydroxipropyl] - polydimethylsiloxane of the formula with n≈10 contains. 8. The method according to any one of claims 1 to 7, characterized characterized in that a primer and / or a Topcoat or a single-coat coating applied is, as the component a₁ a polyester a number average molecular weight of 2000 to 20,000, an acid number of 1 to 15 mg KOH / g and an OH number of 5 to 30 mg KOH / g. 9. The method according to claim 1 to 3, characterized that a primer A and / or topcoat B or a single-coat C applied which are 0.0005 to 0.15 wt .-%, based on the Total weight of the coating agent, the siloxane compound without one versus the functional one Groups of component a reactive group contain. 10. Use of the method according to any one of Claims 1 to 9 produced metallic objects for the production of household appliances. 11. Use of a siloxane compound with at least one, over the functional groups of the binder and / or curing agent reactive group and having a number average molecular weight of 300 to 10,000, preferably 500 to 2,500, or one Siloxane compound without such functional groups and having a number average molecular weight of 700 to 50,000, preferably 1000 to 4000 and / or  a viscosity at 25 ° C of 3 to 5000 mPa · s in Varnishes for the tape coating process as an additive to Creation of a structured surface.