EP1228152A1

EP1228152A1 - Method for producing a wood coating agent

Info

Publication number: EP1228152A1
Application number: EP00963978A
Authority: EP
Inventors: Stefan Friebel; Rudi Danz
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 1999-09-09
Filing date: 2000-09-07
Publication date: 2002-08-07
Also published as: AU7507300A; WO2001018131A1; DE19942993A1

Abstract

The invention relates to a method for producing a transparent coating agent for coating wood. According to the invention, a binding agent is selected from the group of physically drying acrylate resins or from acrylate resins that are cross-linked by irradiation, and is subsequently doped with at least one highly efficient and light-stable laser dye. Said laser dye, in the amount of 0.1 to 5.0 wt. % with regard to the entire composition, is dissolved in the binding agent molecule in a dispersed manner. The UV portion of the UV light as well as spectral light portions with wavelengths ranging from 280 nm to 500 nm are completely or selectively absorbed and, with a conversion efficiency of >/= 30 %, are converted into longer wave radiation that does not damage the wood substrates nor the binding agent, whereby at least one photoinitiator, auxiliary agents and, optionally, solvents are admixed.

Description

Process for producing a wood coating material

The invention relates to a method for producing a transparent coating agent for the coating of wood with special etter and light-protecting properties. Field of application is the coating of wooden facades, windows, doors, wooden cladding and the like.

If glazing or colorless coatings are used to protect wood, high-energy radiation from the sun spectrum leads to degradation reactions in the paint film. But also the lignin in the underlying wooden surface is destroyed and in combination with moisture leads to the removal of the colorless lacquer film.

US Pat. No. 5,338,613 describes photopolymerizable polyurethane acrylates for weather-resistant coatings. Organic UV absorbers and pigments are added to the paint to stabilize the light. Although the organic UV absorbers absorb the photonic energy, they have the disadvantage that their effectiveness decreases over time and thus pass on the absorbed light energy to the lattice of the polymer binder and in this way leads to a light-induced degradation of the polymer in the long term. Furthermore, paint formulations containing pigments are less suitable for wood coatings, because on the one hand they hide the wood grain and on the other hand they tend to flake off after being used for more than 5 years.

In US 5,840,788 urethane coatings for golf balls are claimed. The brighteners used are not long-term photo-stable. Your radiation conversion efficiency is not sufficient. These coatings are also unsuitable for adequate wood protection. In particular, the previous inventive solutions do not take into account that wood is also broken down by radiation in the blue spectral range. As an alternative, nano-metal oxides are described in the patent 5,817,160, such as Ti0 ₂ , which have the properties of absorbing UV light but being transparent in visible light. This technique of UV protection has the advantage that, unlike organic UV absorbers, the nano-metal oxides are not consumed. The disadvantage here with clear lacquers is the inadequate protection of UV light in the spectral range from 400 to 440 nm, which only provides inadequate protection for the wood.

Another protective measure against damaging UV radiation is UV shielding. The principle of action of this method is the complete shielding of UV radiation by adding UV-absorbing iron oxide pigments. However, these iron oxide pigments have the decisive disadvantage of coloring and covering properties, so that they are not suitable for producing colorless coatings. In contrast to UV absorbers and light stabilizers, coatings containing iron oxide are difficult to crosslink with UV light. As already mentioned, they also tend to peel off the paint film and chalk out the pigment after only a few years.

The invention has for its object to provide a manufacturing method for a largely weather and UV stable wood coating agent.

This object is achieved according to the invention by a method for producing a transparent coating agent for the coating of wood, in which a binder is selected from the group consisting of the physically drying acrylic resins or radiation-curing acrylic resins and then doped with at least one highly efficient and light-stable laser dye, which is in the form of 0.1 - 5.0% by weight, based on the total composition, is dissolved in the binder in a molecularly disperse manner and the UV component of the UV light and spectral light components in the wavelength range between 280 nm and 500 nm are absorbed completely or selectively and with a conversion efficiency of> 30% in converts undulating radiation which does not damage the wood substrates and the binder, at least one photoinitiator, auxiliary substances and optionally solvents being added.

According to the invention, it is expedient if methylbenzoylforma, Irgacure 184, Irgacure 819 or P37 (benzophenone derivative) are used as the photoinitiator, alone or in combination, other photoinitiators also being conceivable. UV-curing polyurethane acrylates can be used as the acrylate resins.

An alternative solution according to the invention based on another binder is a process for producing a transparent coating agent for the coating of wood, in which a binder is selected from the group of medium to long oil alkyd resins based on drying fatty acids and / or drying oils and then with at least a highly efficient and light-stable laser dye is doped, which is dissolved in the form of 0.1 - 5.0% by weight based on the total composition in the binder in a molecularly disperse manner and the UV component of the UV light and spectral light components in the wavelength range between 280 nm and 500 nm completely or selectively absorbed and with a conversion efficiency of>. 30% is converted into longer-wave radiation that does not damage the wood substrates and the binding agent, with additives and possibly solvents being added.

Compared to the wooden substrate, the coating according to the invention also provides high light protection in the blue spectral range and is light-stable. The coating systems according to the invention can be crosslinked using the economical technology of radiation curing (for example by means of UV radiation). In addition, the coatings are transparent so that the wood grain can take full effect and is not covered by pigments. The production technology of the layers is economically efficient and easy to implement. Here is the layer thickness of the paint to be coordinated with the concentration of the respective laser dye.

The at least one laser dye is to be matched to the intended use and is selected from special rhodamines, pyrro ethenes, exalites, furan or lumogens. Of the rhodamines, rhodamine 560, rhodamine 575, rhodamine 590 and rhodamine 610 are particularly suitable. Particularly suitable pyrromethenes are pyrromethene 546, pyrromethene 556, pyrroethene 567, pyrromethene 580, pyrromethene 597 and 1,4-di [2- (5-phenyloxazolyl)] benzene. Of the Exalites, Exalit 428, Exalit 400E, Exalit 404, Exalit 411, Exalit 417, LD466, LD473 and LD489 have proven to be particularly suitable. Preferred Lumogens are Lumogen F240, Lumogen F Red 300, Lumogen F Violet 570 and Lumogen F Yellow 083.

Since not all laser dyes absorb the desired wavelength range, one or more laser dyes can be used in combination with an organic UV absorber.

Flow additives, wetting additives or the like can be considered as auxiliary substances. Fillers can also be added to reduce the price of the coating agent.

If the coating system has a high viscosity, the addition of a solvent, e.g. Acetone, required.

Embodiment 1

0.04 g Lumogen F Violett 570 are dissolved in 4 g hexanediol diacrylate and 1 g Ebecryl 112 and then mixed with 5 g IRR 245. 0.3 g Tinuvin 400, 0.05 g BYK 333, 0.04 g BYK 088 and 0.3 g P37 (benzophenone derivative - photoinitiator) are added to this mixture. After application to the wood, the lacquer film is cross-linked with UV radiation (mercury (Hg) or gallium (Ga) -doped Hg lamp). The crosslinking can take place under a normal atmosphere or better under an inert gas (eg nitrogen). Embodiment 2

0.05 Lumogen F Violett 570 is dissolved in 4 g of hexanediol diacrylate and 1 g of Ebecryl 111 and then mixed with 2 g of Ebecryl 284 and 3 g of IRR 245. 0.2 g Tinuvin 400, 0.04 g BYK 333, 0.04 g BYK 088 and 0.3 g P37 (benzophenone derivative - photoinitiator) are added to this mixture. After application to the wood, the lacquer film is cross-linked with UV radiation (Hg or Ga-doped Hg lamp). The crosslinking can take place under a normal atmosphere or better under an inert gas (e.g. nitrogen).

Embodiment 3

0.1 g of Lumogen F Violett 570 is dissolved in 3 g of hexanediol diacrylate, 1 g of Ebecryl 112 and 1 g of acetone and then mixed with 2 g of Ebecryl 284 and 4 g of IRR 245. 0.04 g BYK 333, 0.04 g BYK 088 and 0.3 g P37 (benzophenone derivative - photoinitiator) are added to this mixture. After application to the wood, the lacquer film is cross-linked with UV radiation (Hg or Ga-doped Hg lamp). The crosslinking can take place under a normal atmosphere or better under an inert gas (e.g. nitrogen).

Embodiment 4

300 mg of the Lumogen F 240 laser dye and / or the Pyrromethen 546 laser dye are dissolved in 100 ml of dimethylformamide in an ultrasonic bath and the residue is filtered off. 10 g of the filtrate is mixed with 10 g of Ebecryl 284, 4 g of HDDA, 1 ml of acetone and 0.3 g of the photoinitiator benzoin ethyl ether. The lacquer produced is applied to a wooden substrate and cured with UV radiation in the wavelength range from 340 to 380 nm with subsequent temperature treatment at 100 ° C. The result is light-stable layers that have an absorption> 95% in the wavelength range below 450 nm and thus offer sufficient light protection for wood. Embodiment 5

The laser dyes Lumogen F Red 300 and / or F Violet 570 are dissolved in xylene (300 mg each in 20 ml xylene). 1.33 g of the laser dye solution are then added to the mixture of 2.0 g Ebecryl and 0.90 g HDDA with the addition of the photoinitiator methylbenzoyl format (3%). The laser dye lacquer formulation is cured on wooden substrates with UV radiation.

Embodiment 6

8 g of Primal E 3083 (acrylic resin) are dispersed with 0.3 g of butyl glycol, 0.25 g of Mobilcer M, 0.01 g of ammonia and 0.5 g of water. A solution of 0.05 g Lumogen F Violett 570, 0.2 g Tinuvin 400, 0.04 g BYK 333, 0.05 g BYK 022 in 5 ml acetone is added to this emulsion. After application to the wood, the resin cross-links to form a weather-resistant lacquer film.

Ebecryl 111, Ebecryl 112, Ebecryl 284, IRR 245 and P37 are trademarks of UCB Chemicals.

BYK 333, BYK 088 are trademarks of BYK Chemie GmbH. Tinuvin 400 is a trademark of Ciba Specialty Chemicals. Lumogen is a trademark of BASF AG for fluorescent pigments based on aldazine derivatives. Primal is a trademark of Röhm and Haas. Mobilcer is a trademark of Mobil Corp.

Furan is a trademark of Lambda Physik GmbH for benzofurans, especially bis (benzo [b] furan-2-yl) biphenyls, especially benzofuran 2, 2 '- [1, 1' -biphenyl] -4, 4 '-diyl-bis - tetrasulfonic acid (tetrasodium salt), sold under the Lambdachrome ' ¹ ' No. 4260.

The following chemical names can be given for the above products:

Rhodamine 560 o- (6-amino-3-imino-3H-xanthene-9-yl) -benzoic acid Rhodamine 575

Benzoic acid, 2- [6- (ethylamino) -3- (ethylimino) -2, 7-dimethyl-3H-xanthen-9-yl], perchlorate

Rhodamine 590

Benzoic acid, 2- [6- (ethylamino) -3- (ethylimino) -2, 7-dimethyl-3H-xanthene-9-yl] ethyl ester, monohydrochloride

Rhodamine 610

2- [6- (diethylamino) -3- (diethylimino) -3H-xanthene-9-yl] benzoic acid

Pyrromethenes 546

1,3,5,7,8-pentamethylpyrromethene difluoroborate complex

Pyrromethenes 556

Disodium-1, 3,5,7, 8-pentamethylpyrromethene-2, 6-disulfonate-difluoroborate complex

Pyrromethenes 567

1,3,5,7,8-pentamethyl-2, 6-diethylpyrromethene-difluoroborate complex

Pyrromethenes 580

1,3,5,7,8-pentamethyl-2, 6-di-n-butylpyrromethene-difluoroborate complex

Pyrromethenes 597

1,3,5,7,8-pentamethyl-2,6-di-t-butylpyrromethene-difluoroborate complex

Irgacure 184 1-hydroxy-cyclohexyl phenyl ketone

Irgacure 819 bis-acylphosphine oxide

BYK 333 polymethylalkylsiloxane

BYK 088 Mixture of a foam-destroying mineral oil and polysiloxane

Ebecryl 111 aliphatic monoacrylate

Ebecryl 112 aliphatic monoacrylate Ebecryl 284 difunctional aliphatic polyurethane acrylate (molecular weight 1200 g / mol) IRR 245 difunctional aliphatic polyurethane acrylate (molecular weight 6100 g / mol) P37 oligo eres benzophenone

Tinuvin 400

2- [2-Hydroxy-4- (2-hydroxy-3-dodecyloxypropyloxy) phenyl] -4, 6- bis (2,4-dimethylphenyl) 1,3,5-triazine

LD 466 7-diethylaminocoumarin

Claims

Claims:

1. A process for producing a transparent coating for the coating of wood, in which a binder is selected from the group of physically drying acrylate resins or radiation-curing acrylate resins and then doped with at least one highly efficient and light-stable laser dye, which is in the form of 0.1-5 , 0% by weight based on the total composition in which binder is molecularly dispersed and completely or selectively absorbs the UV component of the UV light and spectral light components in the wavelength range between 280 nm and 500 nm and with a conversion efficiency of _> Converts 30% into longer-wave radiation that does not damage the wood substrates and the binding agent, whereby at least one

Photoinitiator, auxiliaries and optionally solvents are added.

2. The method according to claim 1, characterized in that as photoinitiator methylbenzoyl format, Irgacure 184, Irgacure

819 or P37 (benzophenone derivative) is used alone or in combination.

3. The method according to claim 1 or 2, characterized in that UV-crosslinking polyurethane acrylates are used as acrylate resins.

4. A process for producing a transparent coating for the coating of wood, in which a binder is selected from the group of medium to long-oil alkyd resins based on drying fatty acids and / or drying oils and then doped with at least one highly efficient and light-stable laser dye, which in the form of 0.1 - 5.0 wt .-% based on the total composition in the Binder is molecularly dispersed and completely or selectively absorbed the UV component of the UV light and spectral light components in the wavelength range between 280 nm and 500 nm and with a conversion efficiency of> _. 30% is converted into longer-wave radiation that does not damage the wood substrates and the binding agent, with additives and optionally solvents being added.

5. The method according to any one of the preceding claims, characterized in that the at least one laser dye is matched to the application and made of special rhodamines,

Pyrromethenes, exalites, furans or lumogens is selected.

6. The method according to any one of the preceding claims, characterized in that the at least one laser dye is used in combination with an organic UV absorber.

7. The method according to any one of the preceding claims, characterized by the addition of fillers.