EP0459991A1

EP0459991A1 - Process for coating finish films and endless edges

Info

Publication number: EP0459991A1
Application number: EP90901812A
Authority: EP
Inventors: Karlheinz Dickerhof; Joachim Roll; Wilhelm Moss; Thomas Schwalm
Original assignee: BASF Lacke und Farben AG
Current assignee: BASF Farben und Fasern AG
Priority date: 1989-02-21
Filing date: 1990-01-26
Publication date: 1991-12-11
Also published as: CA2046873A1; CA2046873C; DE3905268A1; BR9007150A; DK0384506T3; DE59006462D1; EP0384506B1; WO1990010111A1; EP0384506A1; ES2060920T3; AU4957490A; AU633046B2; US5223323A; ATE108843T1

Abstract

PCT No. PCT/EP90/00145 Sec. 371 Date Sep. 30, 1991 Sec. 102(e) Date Sep. 30, 1991 PCT Filed Jan. 26, 1990 PCT Pub. No. WO90/10111 PCT Pub. Date Sep. 7, 1990.The present invention relates to a process for coating finish foils and endless edges, wherein an acid-curing aqueous coating composition, on the basis of aminoplast resin/compound containing hydroxyl groups/self-crosslinking acrylate dispersion, is applied and baked in. The coating composition used contains 5 to 20% by weight of one or more fillers of a mean particle size from 0.015 to 10 mu m, a maximum particle size of </=40 mu m and a density of </=2.9 g/cm3. The invention also relates to the coating compositions positions used in the process and to finish foils and endless edges produced by the process, which especially have the advantage of an extremely low formaldehyde emission, particularly as a composite with a low-formaldehyde chipboard.

Description

Process for coating finish foils and endless edges

The present invention relates to a method for coating finish foils and continuous edges, in which an aqueous, acid-curing coating composition is applied and baked. The invention also relates to the aqueous, acid-curing coating compositions used in this process and the finish foils and endless edges coated by this process, both with and without a three-dimensional pore structure. Impregnated papers, which are pressed onto boards for preprocessing in the sense of a primer (primer film) or often also have a decorative effect (decorative film), have long been tried and tested in the furniture and board industry. The shortage and increase in the price of genuine veneers has contributed significantly to the increased use of the latter foils. After pressing, the foils must be repainted on chipboard or hardboard, as otherwise the surface effect will not be sufficient.

In the course of simplifying the production process, an improved type of impregnated paper, the finished film, is becoming more and more popular. These are impregnated plain-colored or printed paper foils which are provided with a lacquer coating by the foil manufacturer.

The finish foils and endless edges thus obtained (for continuous edge coating) are delivered as rolls to the furniture and panel industry, where they are heated and / or pressure is glued to substrates such as chipboard or hardboard. In this way, surfaces are obtained which, as a rule, no longer require any further painting, ie can be further processed “in a press-fitting manner”.

Due to the development of special, water-repellent pore printing inks, finish foils with a three-dimensional pore structure are also available, which represent an excellent imitation of a wood veneer (cf. for example DE-OS 32 47 677; US-PS 3,811,915; DE-OS 30 24 391). The similarity to a natural veneer has increased the demand for such decorative foils and lacquer systems considerably.

The lacquers used to lacquer the finish foils or endless edges in question and the coatings produced from the lacquers must meet high requirements.

Thus, no or only small amounts of organic solvents and / or formaldehyde are to be emitted both in the coating of finish foils or endless edges and in the further processing of the coated foils or edges.

This requirement for low solvent emissions can only be met by aqueous coating systems. For example, from the publication of the international application WO 88/06176 aqueous two-component lacquers for the one-layer coating of finish foils and endless edges are known which are used for coatings with a low formaldehyde emission (<.3.5 mg / hm 2, determined according to DIN 52368). In these systems, in order to achieve the excellent properties of the resulting coating, it is necessary to give the paints a self-crosslinking acrylate dispersion in very high proportions of 40 to 85% by weight, preferably even 60 to 85% by weight, based in each case on the total composition of the binder component.

A further requirement for lacquers suitable for coating the fi nish foils and endless edges is that they can be applied using the coating machines customary in foil production and that after 140 seconds of heat treatment at 140, usually 10 to 20 seconds up to 210 ° C are cured to the extent that they are used in the manufacture of panels or furniture parts

Press conditions (e.g. 5 to 30 seconds at 150 to 180 ° C

2 and 5 to 20 kp / cm; tightened pressing conditions: up to 180

2

Survive unscathed at 170 to 180 ° C and up to 30 kp / cm) without showing block properties and discoloration. The surfaces obtained in this way should have the highest possible scratch resistance. What is also required is the best possible resistance of the coatings to various reagents, e.g. Foodstuffs such as beer, coffee etc. as required by DIN 68 861, group A.

In addition, it is desirable that the lacquered but not yet pressed foils do not bend or even roll up.

DE-OS 23 16 158 discloses aqueous acid-curing two-component paints based on etherified aminoplast resins and polyester resins, which are also used for coating films for the furniture industry. The two-component paints described there are notable for rapid curing and high hardness, scratch resistance and stackability of the resulting coating, but have the considerable disadvantage of high formaldehyde emission from finish foils and coated with these paints

Endless edges on. In the course of ever stricter legal requirements with regard to the formaldehyde emission from the Finish foils used in the furniture industry, however, there is a very high demand for finish foils with a lower formaldehyde emission.

The present invention was therefore based on the object of providing a method for coating finish foils and endless edges in which the resulting coated foils have the lowest possible formaldehyde emission. The formaldehyde emission of the coated finish film or endless edge should be used individually as well as in combination with a low-formaldehyde chipboard

2 ((EEmmiissssiioonnsskkllaassssee EEll)) eeiinneenn WWeerrtt vvoonn 3.5 mg / h m, determined according to DIN 52 368, do not exceed

For the practical applicability of the process, it is also necessary that the equipment already available from the film manufacturer can be used to carry out the process and that the finished films or endless edges meet the above-mentioned requirements. This means, in particular, that the paints used in the process can be applied with the customary painting machines and harden quickly and that the resulting surfaces have the highest possible scratch resistance and resistance, for example to water, mustard and coffee solution (DIN 68 861).

Surprisingly, this object is achieved by a method for coating finish foils and endless edges, in which

I) an aqueous coating composition is applied, which is used as paint component I

A) 15 to 55% by weight, preferably 30 to 45% by weight, of one or more water-dilutable melamine resins

B) 0 to 30% by weight, preferably 0 to 15% by weight, of one or more water-dilutable urea resins C) 5 to 55 wt .-%, preferably 20 to 40 wt .-% of one or more polyols

D) 0 to 15% by weight, preferably 3 to 10% by weight, of a self-crosslinking aqueous polyacrylate dispersion and

E) 5 to 20 wt .-%, preferably 7 to 15 wt .-%, <one or more fillers with a medium

Contains particle size from 0.015 to 10 .mu.m, a maximum particle size of <_ 40 .mu.m and a density of 2.9 g / cm 3, the sum of the parts by weight of components A) to E) each 100 wt. -% and the coating composition as paint component II contains 0.5 to 30% by weight, based on the weight of the sum of components A to E, of an acidic curing catalyst, with paint components I and II preferably immediately before Application are mixed, and

II) the resulting wet film is baked for a time of 8 to 50 s at a temperature between 90 and 200 ° C.

The present invention also relates to the aqueous coating composition used in the process according to the invention and to the finish foils and endless edges coated by the process according to the invention, which may optionally also have a three-dimensional pore structure.

It is surprising and was not foreseeable that the process according to the invention could provide finish foils with such a low formaldehyde emission. DE-OS 23 16 158 also mentions that fillers can be added to the paints _* However, this document does not contain any indication that the addition of very special fillers to the coating compositions in precisely defined amounts drastically reduces the formaldehyde emission of finish foils or endless edges coated with these lacquers. Rather, DE-OS 23 16 158 was based on the object of providing suitable lacquers for the coating of foils which harden quickly and nevertheless ensure a sufficient service life of the lacquers.

In view of the large number of known fillers in particular, it was surprising that just by adding 5 to 20% by weight of fillers having an average particle size of 0.015 to 10 .mu.m, a maximum particle size of at most 40 .mu.m and a density of a maximum of 2.9 g / cm 3 for the lacquers used to coat the films

Formaldehyde emissions of the coated foils, especially in combination with chipboard, could be drastically reduced. The formaldehyde emission is significantly lower than can be expected from an equal percentage reduction in the melamine or urea-formaldehyde resin. It is known from JP-OS 57/111367 that the formaldehyde emission from plywood and the like is reduced if adhesives based on copolymers with hydroxyl groups, aminoplast resins and fillers are used. But this document also gives no indication of the influence of the fillers used on the formaldehyde emission.

The aqueous coating composition used in the process according to the invention and containing the paint components I (binder concentrate or dispersion) and II (hardener component) will now be explained in more detail below.

The melamine resins used in paint component I (component A) are generally known, generally etherified melamine-aldehyde reaction products, before adds melamine-formaldehyde conversion products. Apart from the degree of condensation, which should be as low as possible, the water thinnability of the melamine resins depends on the etherification component, only the lowest members of the alkanol series giving water-soluble condensates. Hexamethoxymethylmelamine resins are of the greatest importance. If solubilizers are used, butanol-etherified melamine resins can also be dispersed in the aqueous phase.

Examples of suitable melamine resins are those in Han¬

BE 370 (manufacturer: BIP Chemicals Ltd., Great Britain), Maprena] ®MF 900, 904 and 910 (manufacturer: Hoechst AG), CibamirfS (Ciba AG, Switzerland), Resimene ~ 714, 745 and 747 (Monsanto) available called water-soluble melamine resins. Hexamethoxymethylmelamine resins such as, for. B. Cymer ^ 300, 301, 303; LuwipajS '066 and Maprenal®MF 900.

The melamine resins are used in an amount of 15 to 55% by weight, preferably 30 to 45% by weight, based in each case on the sum of the parts by weight of components A to E.

The water-thinnable urea resins used as component B in an amount of 0 to 30% by weight, preferably 0 to 15% by weight, based in each case on the sum of the parts by weight of components A to E, are generally known water-dilutable urea-aldeyhd reaction products, preferably water-dilutable urea-formaldehyde reaction products. Examples of suitable resins are those commercially available under the brand names Dynomirr ^ UM 15 (manufacturer: Norsk Spraengstof Industrie, Norway), Resamiπ * ^ VHW 3525 (manufacturer: Hoechst AG) or Plastopal® (manufacturer: BASF AG, Ludwigshafen) available plasticized or not. plasticized urea-formaldehyde reaction products.

Polyol component C suitable for crosslinking the melamine and formaldehyde resins are, for example, di- and higher-functional alcohols and / or polyester polyols and / or polyurethane polyols and / or polyether polyols. Component C is used in an amount of 5 to 55% by weight, preferably 20 to 40% by weight, based in each case on the sum of the parts by weight of components A to E.

Examples of suitable diols and polyols are ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, butanediol, neσpentylglycol, triethylene glycol, hexanediol, cyclohexanedimethanol 1,4, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, trimethylinethanol, trimethylolethanol, trimethylolethanol, trimethylolethanol, trimethylolethanol, trimethylolethanol, trimethylol ethanol Hexantriol, erythritol, arabitol, adonite, xylitol, sorbitol, mannitol and dulcitol, eth- and / or propoxylated derivatives of trimethylolpropane and trishydroxyethyl isocyanurate. Tri-methylolpropane, diethylene glycol, triethylene glycol and butanediol are preferably used.

Examples of suitable polyester polyols are low molecular weight, water-dilutable, linear and / or branched condensation products of adipic acid, malonic acid, phthalic acid, isophthalic acid, trimellitic anhydride, succinic acid, glutaric acid, sebacic acid, hexahydrophthalic acid, cyclohexyldicarboxylic acid 1,4, ticarboxylic acid 1,4, - Martic acid, itaconic acid or citraconic acid with alcohols containing two or more hydroxyl groups. Examples of suitable diols and polyols are the compounds listed above. The polyester polyols are prepared in a known manner by esterification of the components at higher temperatures with removal of the water of reaction formed. An excess of alcoholic component is preferably used in the production of the polyester polyols, so that products are formed which carry hydroxyl end groups. Mixtures of the polyester polyols with triplets are very particularly preferably used as component C.

Also suitable as component C are polyether polyols, such as, for example, copolymers of polyethylene oxide and polypropylene oxide up to a molecular weight of 7000, which must be water-dilutable, water-dilutable polymerization products of tetrahydrofuran and reaction products of polyester polyols with ethylene or propylene oxide and addition products of alkylene oxides on di- and polyamines, provided that these reaction products are water-dilutable.

As component D, the paint component I used in the process according to the invention contains 0 to 15% by weight, preferably 3 to 10% by weight, based in each case on the sum of the parts by weight of components A to E, of an aqueous solution self-crosslinking polyacrylate dispersion. The polyacrylate resins contain, as self-crosslinking groups, acid amide derivative groups which correspond to the general structural formula —C0-N (R ¹ ) -CH (R ² ) -OR ³ , where

R 1 ■ H atom or a -CH (R2) -OR3 grouping,

R 2 "H atom or a -COOR4 group,

3 R - H atom or a 'containing 1 to 10 C atoms'

Hydrocarbon residue, preferably methyl, ethyl,

(Iso) propyl or (iso) butyl radical, 4 R »alkyl radical having 1 to 5 carbon atoms. The -CO-N (R1) -CH (R2) -0R3 groups can be introduced into the polyacrylate molecules both via a polymerized monomer and via a polymer-analogous reaction. The -CO-N (R) -CH (R) -0R - are preferred

Groups in which R 1 and R2 are hydrogen atoms and R3 is a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms, preferably methyl, ethyl, (iso) propyl or (iso) butyl.

In addition to the acid amide derivative groups described above, the self-crosslinkable polyacrylate resins can also contain carboxyl groups. With the help of a few less orienting experiments, the person skilled in the art can determine which carboxyl group content he has to choose for his particular problem.

In addition to the acid amide derivative and carboxyl groups, the polyacrylate resin can also contain other functional groups, e.g. Hydroxyl groups or free amide groups.

The aqueous acrylate dispersions which can be used can be prepared by copolymerization of (meth) acrylic acid esters, preferably methyl, ethyl, propyl or butyl (meth) acrylates, the corresponding (meth) acrylic acid amide derivatives and, if appropriate, an appropriate amount of carboxyl groups by copolymerization monomers containing a polymerizable double bond, for example Fumaric or maleic acid, preferably (meth) acrylic acid with the possible use of smaller amounts of other monomers, e.g. Vinyl acetate, hydroxyalkyl (meth) acrylates, styrene, (meth -) - acrylic acid amides, etc., can be produced.

Dispersions with the following characteristics are preferred:

Solids: 40 to 60% by weight, preferably 40 to 50% by weight, based on the total weight of the aqueous polyacrylate dispersion.

Average particle diameter: 0.1 to 0.5 .mu.m, preferably 0.1 to 0.3 .mu.m.

Minimum film-forming temperature (MFT): 0 to 70 ° C, preferably between 20 and 60 ° C.

Viscosity: 200 to 5,000 mPas, preferably 200 to 1,000 mPas and

pH: 2 to 10, preferably greater than 7.

As an essential component of the invention, the paint component I contains one or more fillers with a maximum particle size of 40 μm, preferably p.20 μm, an average particle size of 0.015 to 10 μm, preferably 0.015 to 8 μm and a density of < , 2.9 g / cm 3, preferably 2.8 g / cm 3. When selecting the filler, the hardener component (approx. .5% by weight hardening catalyst) is used, in particular when using larger amounts the total weight of the coating composition) to ensure that there are no adverse interactions of the filler with the curing catalyst (eg gas evolution). Platelet-like fillers are preferably used because they achieve the best results in reducing formaldehyde emissions.

Examples of suitable fillers are different types of talc, mica and kaolin of the above-mentioned particle sizes and densities and other aluminum- and / or magnesium-containing silicates of the above-mentioned particle sizes and densities. Examples of these are the talc types “Micro Talum IT Extra” (manufacturer: Norwegian) and “Talcum Steamic” which are commercially available under the following brand names 00S "(manufacturer: Luzenac), aluminum silicates" China-Clay Suprime "(manufacturer ECCI)," ASP 600 "and Satintone 1 (manufacturer: Engelhard) and mica types" Mikal 00180 "(manufacturer: Arlati ) and English Mica Mica M "(manufacturer: MICA).

The specified selection of suitable fillers results from the required properties of the coating compositions used according to the invention. If, for example, the average particle size of the fillers used is too small, this results in an excessive thixotropy of the paints for the practical application of the paints. If the average particle size is too large, on the other hand, the surface quality of the resulting coating no longer meets the high requirements of the film manufacturers. Their density also has a decisive influence on the suitability of the fillers.

These fillers mentioned above are used in an amount of 5 to 20% by weight, preferably 7 to 15% by weight, based in each case on the sum of the parts by weight of components A to E. However, if glossy surfaces are to be achieved, the amount of component E used is only 5 to 10% by weight, based on the sum of the parts by weight of components A to E.

In order to set the appropriate processing viscosity correctly, both the paint components I and II can also contain liquid diluents. Suitable liquid diluents consist of at least 50% by weight, preferably 95 to 100% by weight, based on the sum of the parts by weight of all liquid diluents, of water. In addition, organic solvents such as e.g. monohydric or polyhydric alcohols, ethers, esters and ketones, e.g. N-methylpyrrolidone, butanol, isopropanol, ethanol,

Ethyl and butyl glycol and their acetates, butyl diglycol, ethylene glycol dibutyl ether, ethylene glycol diethyl ether, di- contain ethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, acetone, isophorone, propylene glycol or mixtures thereof.

The amount of diluent used is generally for paint component I 0 to 20% by weight, based on the total weight of all components of paint component I. Paint component II usually contains 30 to 80% by weight, based on the total weight of paint component II, thinner.

As the hardener component (lacquer component II), the aqueous two-component lacquer used in the process according to the invention contains a water-dilutable acid, its aqueous solution or an acid blocked with amines or amino alcohols or its aqueous solution. Suitable water-dilutable acids are phosphoric acid, maleic acid, hydrochloric acid, para-toluenesulfonic acid and its derivatives, naphthalenesulfonic acid and its derivatives, and the corresponding reaction products of these acids with amines or amino alcohols, such as, for example, an aqueous solution of the ammonium salt of p-toluene. sulfonic acid used. Solutions of para-toluenesulfonic acid in acid-stable acrylate dispersions are also particularly suitable. Crosslinkable, non-ionic acrylate dispersions with a solids content of 50% and a minimum film-forming temperature of 28 to 32 ° C. are preferably used. In the formulation of the coating compositions according to the invention as a one-component system, the sulfonic acids are used in blocked form, for example as the ammonium salt.

Para-toluenesulfonic acid, hydrochloric acid and phosphoric acid are preferably used, with para-toluenesulfonic acid and the solutions of p-toluenesulfonic acid in acid-stable acrylic dispersions being particularly preferred. The use of solutions of para-toluenesulfonic acid in acid-stable acrylic Lat dispersion as a hardener component has the advantage that the surface properties, in particular the surface covering, is improved. In order to achieve the most uniform possible distribution of this curing catalyst in the coating compositions, the acids or their derivatives are preferably used as a solution in water or a water-dilutable solvent. The paint components I and II are mixed in such a ratio before application that for 100 parts by weight of the paint component I consisting of components A to E (ie without diluent), 0.5 to 30 parts by weight of the pure hardener component II, ie paint component II without diluents. The pot life (time during which the mixture can be processed) of the mixture obtained depends, for example, on the type and concentration of the hardener component and the processing temperature. According to the requirements of the film manufacturers, the pot lives of the mixtures are over 24 hours. The paint components I and II, on the other hand, are stable for longer than 2 months separately.

The aqueous coating compositions used according to the invention may also contain conventional auxiliaries and additives in the usual amounts, for example 0 to 10% by weight, preferably 0 to 3% by weight, matting agent ( Silicic acid derivatives ...), 0 to 2% by weight, preferably 0.5 to 1.0% by weight, waxes (polyethylene and polypropylene waxes, for example), 0 to 2.0% by weight, preferably 0.5 to 1.0% by weight, emulsifier (ethoxylated alkylphenols, ethoxylated fatty acids), 0 to 2.0% by weight, preferably 0.5 to 1.0% by weight, defoamer and 0 to 10 wt .-%, preferably 0 to 3 wt .-% of other additives such as plasticizers (ethoxylated glycerol ...), thixotropic agents (polyacrylates, polyurethanes, cellulose derivatives ...), leveling and wetting agents (sodium salts of poly - Acrylates ...) and film-forming aids (phosphoric acid esters, glycols). The percentages by weight relate in each case on the overall composition of paint component I, that is to say including any diluent present.

Lacquer components I and II are produced in a customary manner by mixing the components. Sometimes it is advisable to first dissolve a component in a solvent if it is not in liquid form and to mix this solution with the other components.

The aqueous coating composition described above can also be pigmented, in which case the paint component I contains 0 to 40% by weight, preferably 0 to 30% by weight, in each case based on the total weight of the paint component I, pigment. The optimum pigment content in each case depends on the desired opacity and the pigment used and can be found by the person skilled in the art with the aid of routine tests that are simple to carry out. To incorporate the pigments, on the one hand, the various pigments can be ground together with the binder, or the paint component I is used as a paint for an aqueous pigment paste.

All inorganic and organic pigments can be used as pigments, which are both water-wettable and not sublimable at the temperatures used and which do not change in color under the process and pH conditions.

Examples of suitable pigments are titanium dioxide of the rutile type, yellow, red and black iron oxides, carbon black and phthalocyanines. Titanium dioxide is preferably used as the pigment.

To carry out the process according to the invention, paint components I and II are mixed, specifically in the case of preferred two-component paints only shortly before application. If, on the other hand, the formulation can be borrowed as a one-component lacquer by appropriate selection of the hardener component, mixing can also take place earlier. The finish foils and endless edges are then coated with this mixture using machines specially developed for this purpose. Anilox rollers or are used as paint application or metering devices

Wire squeegees available. The amount of paint applied is

2 Licher between 5 to 50 g / m with a wet film layer thickness of 10 to 80 .mu.m. Drying ducts with heated air, so-called convectors or IR emitters or combinations of both or hot rollers (calenders) are usually used for drying the lacquer. After drying, the paper web is wound up as a roll and delivered to the furniture industry in this form.

As soon as the mixture of the lacquer component (I) and the hardener component (II) has been applied and brought to a temperature of 140 to 210 ° C., it generally hardens within 10 to 55 seconds within 10 to 20 seconds, without the formation of bubbles, to such an extent that the lacquer surfaces thus created survive the further process steps - in particular the increasingly stringent pressing conditions used - without showing block properties or discoloration.

The foils and endless edges produced by the process according to the invention have the particular advantage that they have a very low formaldehyde emission of less

Show 2 as 3.5 mg / hm. In combination with chipboard, especially those of emission class El, they show an extremely low formaldehyde emission of

2 <.3.5 mg / hm (emission determined according to DIN 52368).

Furthermore, the film surfaces obtained by the process according to the invention are notable for good scratching strength from. They also show good resistance to coffee solutions (DIN 68861) and good to satisfactory swelling behavior. Finally, the coating compositions used in the process have short drying times, so that the films are cured to the extent already after heat treatment at 140 ° C. to 210 ° C. for a time of less than 60 s, generally 10 to 20 s, that they can withstand the pressing conditions used in the manufacture of the panels or furniture parts (for example 5 to 30 s at 150 to 180 ° C. and 5 to 20 kp / cm ² ) without blocking properties and discoloration.

The aqueous coating compositions in question are also suitable for painting wooden substrates, such as Hardboard, particle board and wood-based materials, suitable. In many cases it can be advantageous to pre-coat with a primer. If particularly absorbent substrates are to be coated, either a separate one is used

Primers, e.g. on a dispersion basis, submitted or painted twice with the same paint material.

The present invention will now be explained in more detail with reference to exemplary embodiments. Unless expressly stated otherwise, all information on parts and percentages is by weight.

example 1

First, a paint component 1-1 is produced as follows:

40 parts of a 100% hexamethoxymethylmelamine resin with a viscosity of 3000 mPas (measured at 21 ° C), 1 part of methoxypropanol and 35 parts of a branched polyester polyol with an OH number of 750 mgKOH / g and an acid number of <1 mgKOH / g are mixed with 1 part of a micronized polypropylene wax (melting point 140 ° C.), 1 part of a non-ionic emulsifier (acrylic-polyglycol ether, density 3 1.12 g / cm) and 11 parts of a platelet-shaped

Aluminum silicate (average particle size 0.015 .mu.m, maximum particle size 15 .um., Density = 2.6 g / cm) mixed with stirring.

4 parts of water and 7 parts of an aqueous, self-crosslinking anionic acrylate dispersion containing amide groups (average particle size 0.25 .mu.m, viscosity at 23 ° C. 200 mPas, solids content 50%) are then added to the resulting mixture with stirring.

100 parts of the paint component 1-1 thus prepared are mixed with stirring with 5 parts of a 40% aqueous p-toluenesulfonic acid solution (paint component II) and the coating composition 1 obtained is mixed with 40 parts of water to a viscosity of 20 s (measured in a DIN 4 flow cup at 20 ° C). The content of this coating composition 1 in hexamethoxymethylmelamine resin is 27.6% by weight, based on the overall formulation.

This coating composition 1 is applied to a white impregnate (weight of impregnate 2 80 g / m) (wet film thickness 30 .mu.m) by means of a wire knife and then dried at 160 ° C. in the nozzle channel for 20 s. The most important properties and test results of the film A thus obtained are summarized in Table 1.

Example 2

Analogously to Example 1, a paint component 1-2 is produced by 30 parts of a water-dilutable, elastic urea-formaldehyde resin (acid number <3 mgKOH / g) and 20 parts of a water-dilutable, largely mixed with methanol ethereal melamine-formaldehyde resin (solids 80-85%, viscosity at 23 ° C 1.6-2.4 Pas) with 35 parts of a water-dilutable, partially unsaturated polyester polyol (OH number 420 mg / KOH / g, acid number <5 mgKOH / g,), 6 parts of a kaolin (average particle size of 0.80 .mu.m, maximum particle size 35 .um., Density 2.6 g / cm 3), 2 parts of a

Talc (average particle size of 5 .mu.m, maximum particle size 25 .mu.m, density 2.8 g / cm 3) and 1 part of a nonionic emulsifier (acrylic polyglycol ether, density 3 1.12 g / cm) are mixed with stirring . Then 6 parts of water are added with stirring. 100 parts of the paint component 1-2 thus prepared are mixed with stirring with 5 parts of a 40% aqueous p-toluenesulfone solution and with water to a viscosity of 20 s (measured in a DIN 4 flow cup at 20 ° C.) set.

This coating composition 2 is applied analogously to Example 1 by means of a wire doctor knife onto a white impregnate (weight 2 = 80 g / m) (wet film thickness 30 .mu.m) and then dried for 20 s at 160 ° C. in the nozzle channel. The most important properties and test results of the film B thus obtained are summarized in Table 1.

Example 3

The film A obtained in Example 1 is coated with a particle board (emission class E 2, i.e. measured formaldehyde

2 emission: 5 mg / hm) pressed and the formaldehyde emission of the composite examined. The results are shown in Table 1. Comparative Example 1 (VI)

A paint component 1-3 is produced analogously to Example 1, with the difference that the filler aluminum silicate is replaced by 11 parts of water. 5 parts of 40% strength aqueous p-toluenesulfonic acid are added as paint component II and adjusted to a viscosity of 20 s (DIN-4 flow cup, 20 ° C.) with 20 parts of water. The content of hexamethoxymethyl melamine resin in this coating composition 3 is 32.0% by weight, based on the overall formulation. The application and drying of this coating composition 3 and the testing of the film C obtained are carried out analogously to Example 1. The properties and test results of the film C are summarized in Table 1.

Comparative Example 2 (V2)

In accordance with Comparative Example 1, a paint component 1-4 is also produced analogously to Example 2, with the difference from Example 2 that the fillers talc and kaolin are replaced by 8 parts of water. The film top coat 4 is produced therefrom using 5 parts of 40% p-toluenesulfonic acid solution and applied and dried analogously to Example 2. The properties and test results of the resulting film D are also shown in Table 1.

Comparative Example 3 (V3)

The film C obtained in the comparative example is pressed with a particle board (emission class E 2) analogously to Example 3 and the formaldehyde emission of the composite is examined. The results are shown in Table 1. Comparative Example 4 (V4)

A lacquer component 1-5 is produced analogously to Example 1, with the difference that the filler aluminum silicate is made up of 11 parts barium sulfate (average particle size

3 0.8 .um, density 4.4 g / cm) is replaced. The coating composition 5 is produced from this paint component 1-5 using 5 parts of 40% p-toluenesulfonic acid solution and applied and dried analogously to Example 1. The properties and test results of the resulting film E are shown in Table 1.

Table 1 :

Example 1 2 3 VI V2 V3 V4

Degree of gloss

(60% reflection angle) 20% 12%

Scratch resistance ^a <20 12

Coffee test ^D > 1-2 2-3

Mustard test ^b ) 1 1

Water column ⁰ ) 2 2-3

Formaldehyde emission according to DIN 52368 2.3 3.0 - 3.0 3.8 - 2.7 (mg / hm2) of the film of the composite - - 3.0 - - 11.0 - a) the number of double strokes is also given a wooden spatula under pressure until the surface is damaged. r b) After 16 h exposure to coffee solution (DIN 68 861) or mustard or 100 cm

2 water column / cm surface on the painted surface, the condition of the surface is visually assessed in comparison with the surface not under stress:

0 no visible changes

1 recognizable changes in gloss or color

2 slight changes in gloss or color, the structure of the test surface has not changed

3 strong markings are visible, but the structure of the test area is largely undamaged

4 strong markings visible, the structure of the test area has changed

5 Test area heavily changed or destroyed

The examples illustrate that by adding fillers with an average particle size of 0.015 to 10 .mu.m, a maximum particle size of at most 40 .mu.m and a density of at most 2.9 g / cm 3 to the paints

Formaldehyde emission from films coated with these lacquers is drastically reduced. As a comparison of the emission values of Example 1 with those of Comparative Example 1 (VI) and of Example 2 with those of Comparative Example 2 (V2) shows, the observed decrease in formaldehyde emission is higher than that of a percentage equal to Ernie ¬ Drying of the melamine-formaldehyde resin or urea-formaldehyde resin in the hardened film is to be expected. For example, the proportion of hexamethoxymethylmelamine resin in the filler-containing coating composition 1 of Example 1 is 27.6% by weight, based on the overall formulation, while the proportion of hexamethoxymethylmelamine resin in the analogously constructed filler-free coating composition 3 of Comparative Example 1 ( VI) is 32.0% by weight, based on the total formulation. With the same amount of coating applied to the varnishes (wet film thickness 30 um see above), it is therefore expected based on the emission values of Comparative Example 1

2 (vi) (3.0 mg / hm) a reduction in the emission to 2.6 mg / hm in Example 1. However, a significantly greater reduction in the formaldehyde emission was measured

2 2.3 mg / hm in Example 1.

A comparison of the emission values of comparative example 4

(V4) and Example 1 impressively confirms the fact that only by using very specific fillers is a reduction in the formaldehyde emission of the coated films that is greater than by an equal percentage reduction in the melamine-formaldehyde resin or urea-formaldehyde resin is to be expected (see above). The influence of the fillers on the formaldehyde emission becomes even clearer in the case of the laminations of the foils with a particle board, as the comparison of the emission values of Example 3 and Comparative Example 3 (V3) shows.

Claims

1. A process for coating finish foils and endless edges, in which

I) an aqueous coating composition is applied, which is used as coating component I

B) 0 to 30% by weight, preferably 0 to 15% by weight, of one or more water-dilutable urea resins

C) 5 to 55% by weight, preferably 20 to 40% by weight, of one or more polyols

E) 5 to 20% by weight, preferably 7 to 15% by weight, of one or more fillers with an average particle size of 0.015 to 10 .mu.m, a maximum particle size of <.40 .um and ner density of ^ 2.9 g / cm 3 e ^" n ^" , the

The sum of the parts by weight of components A to E is 100% by weight and the coating composition as coating component II is 0.5 to 30% by weight, based on the weight of the sum of components A to E, of an acidic one

Contains curing catalyst, the paint G

component I and II, preferably mixed immediately before application, and

II) the resulting wet film is baked at a temperature between 90 and 200 ° C. for a period of 8 to 50 s.

Aqueous coating composition, in particular for coating finish foils and endless edges, which are used as coating component (I)

C) 5 to 55 wt .-%, preferably 20 to 40 wt .-% of one or more polyols

E) 5 to 20% by weight, preferably 7 to 15% by weight, of one or more fillers with an average particle size of 0.015 to 10 .mu.m, a maximum particle size of <. 40 .um and a density of .

2.9 g / cm 3 contains ~ l ^* t, the sum of the

The proportions by weight of components A to E are in each case 100% by weight and the coating composition as coating component II is 0.5 to 30% by weight, based on the weight of the sum of the components

A to E, an acidic curing catalyst ent ent, the paint components I and II e

preferably mixed immediately before application.

3. The method or coating composition according to claim 1 or 2, characterized in that as component E fillers with an average particle size of 0.015 to 8 µm, a maximum particle size of <.20 µm and a density of 2.8 g / cm 3 can be used.

4. The method or coating composition according to any one of claims 1 to 3, characterized in that platelet-shaped fillers are used as component E.

5. The method or coating composition according to any one of claims 1 to 4, characterized in that talc, mica and / or kaolin types are used as component E.

6. The method or coating composition according to any one of claims 1 to 5, characterized in that water-dilutable, etherified with methanol melamine-formaldehyde resins are used as component A.

7. The method or coating composition according to any one of claims 1 to 6, characterized in that the paint component II contains p-toluenesulfonic acid or solutions of para-toluenesulfonic acid in acid-stable acrylate dispersions as the curing catalyst.

8. The method or coating composition according to any one of claims 1 to 7, characterized in that a mixture of a triol and a polyester polyol is used as component C. i

9. The method or coating composition according to any one of claims 1 to 8, characterized in that the coating composition contains customary auxiliaries and additives as well as optionally pigments.

10. finish film or endless edge, characterized in that it has been coated by one of the methods according to claim 1 and 3 to 9.

11. Use of the finish foils or endless edges according to claim 10 for gluing with chipboard or hardboard.