DE10304953A1 - Water-spreading, scratch-resistant and self-cleaning plastic body and method for its production - Google Patents

Abstract

The present invention relates to water-spreading, scratch-resistant and self-cleaning plastic bodies, which are obtainable by applying to a plastic substrate DOLLAR A a) a siloxane coating (a) and cures, DOLLAR A b) the polar portion of the surface energy of the cured siloxane coating increased to a value of at least 10 mN / m and DOLLAR A c) applying a photocatalytic active TiO¶2¶ particles-containing coating (b) and cures and DOLLAR A d) a water-spreading, inorganic coating (c) applies and cures.

Description

The present invention relates water-spreading, scratch-resistant and self-cleaning plastic body and Process for their preparation.

Self-cleaning bodies become superhydrophilic by irradiation with UV light in the presence of water and are capable of degrading organic soil to carbon dioxide and water. This ability of the surface is generally achieved by the photocatalytic effect of titanium dioxide, which can be fixed on solid supports and firmly bonded to the substrate, for example, by baking at high temperatures. An example are silicate glasses for self-cleaning windows like those in EP 850 203 B1 by Rhodia Chemie.

Plastic substrates such as e.g. acrylic or polycarbonate, which in large Scope used as glazing material or for transparent noise barriers be, should be aesthetic establish as transparent as possible and be clean to passengers in a train or motorists a clear view of the surrounding Landscape allow. They are mainly on bridges but also used for loosening monotonous concrete noise barriers and should be against the fatigue the motorist contribute.

By car exhaust, tire abrasion, dust and organic dirt, transparent noise barriers quickly become unsightly and unaesthetic. Therefore, numerous attempts have been made, transparent Equip plastics with self-cleaning coatings. there it was the photocatalytic activity of titanium dioxide for decomposition at the substrate surface Adhesive dirt accessible on the other hand, the organic substrate itself of destruction by protecting the titanium dioxide.

Plastic bodies provided with self-cleaning siloxane coatings are also known. Usually, such substrates have a double layer of siloxane with different composition, wherein only the outer layer contains a photocatalytically active additive, for example TiO ₂ in anatase or brookite modification.

For example, the document describes EP-A-1 022 318 coated plastic plates having a photocatalytically active layer. In the examples, however, only plates or films are found which have a total of 1.2 micron thin coating. Such thin coatings, however, show only a very low scratch resistance.

The problem with these plastic bodies of the The prior art is therefore their low scratch resistance or their low weather resistance. By environmental influences Therefore, the coating is eroded over time, so they her ability for self-cleaning lose.

Furthermore, such plastic bodies are only hydrophilic by irradiation with sunlight. Accordingly show these coatings at night or in very cloudy no or only very low hydrophilic properties, leaving dirt contained rainwater can lead to the known impurities, from the residues of the Raindrops are formed.

It should be noted that impurities lead to a shielding of the self-cleaning coating, so that over time can take the dirt, since the UV light does not penetrate to the TiO ₂ particles.

In addition to the self-cleaning coatings, which become hydrophilic upon irradiation, water-spreading coatings with a permanent hydrophilicity are also known. For example, describe the documents EP-A-0 193 269 and EP-A-0 149 182 Plastic body, which are provided with a SiO ₂ -containing coating.

A disadvantage of these coatings is, however, that such plastic body no self-cleaning Have effect. Thus, contamination of these plastic body via a longer Period can not be avoided if exhaust or similar Components contained in the air, from which the water reflected.

In view of the herein stated and discussed prior art, it was therefore an object of the present Invention scratch-resistant plastic body specify that have self-cleaning properties and permanent are hydrophilic.

Another object of the invention was that the Plastic body a high durability, especially a high resistance against UV irradiation or weathering.

Furthermore, the invention was the Task based, scratch-resistant, self-cleaning plastic body for disposal to provide, which can be produced particularly easily.

So should for the production of the plastic body in particular Substrates can be used that by extrusion, injection molding and by casting.

In addition, it was therefore task the present invention to provide plastic body, which is produced inexpensively can be.

In addition, it was therefore task the present invention water-spreading and self-cleaning Plastic body to disposal whose coatings have a particularly high adhesion have the plastic substrates. This property should be through Moisture is not affected become. Furthermore, the plastic body should have a particularly high scratch resistance respectively.

Another task of the present Invention was scratch-resistant, self-cleaning and water-spreading Plastic body indicating excellent mechanical properties. This Property is in particular for Applications important in which the plastic body has a high stability against To have impact effect.

In addition, the plastic body should be special have good optical properties.

Another objective of the present The invention was to provide plastic bodies that were simple Way in size and shape can be adapted to the requirements.

These tasks are solved as well others, while not literal but from the relationships discussed here such as Of course derive from or inevitably result from the in Claim 1 described plastic body. Appropriate modifications the plastic body according to the invention in the back to claim 1 dependent claims put under protection.

With regard to methods of preparation Claim 25 provides a solution the underlying task.

• a) eine Siloxan-Beschichtung (a) aufbringt und aushärtet,
• b) den polaren Anteil der Oberflächenenergie der ausgehärteten Siloxanbeschichtung auf einen Wert von mindestens 10 mN/m erhöht und
• c) eine photokatalytisch aktive TiO₂-Partikel enthaltende Beschichtung (b) aufbringt und aushärtet und
• d) eine wasserspreitende, anorganische Beschichtung (c) aufbringt und aushärtet,

gelingt es selbstreinigende Kunststoffkörper zur Verfügung zu stellen, die selbstreinigende Eigenschaften aufweisen und permanent hydrophil sind.By being on a plastic substrate

• a) applying and curing a siloxane coating (a),
• b) increases the polar fraction of the surface energy of the cured siloxane coating to a value of at least 10 mN / m and
• c) applying a photocatalytically active TiO ₂ particles containing coating (b) and cures and
• d) applying a water-spreading, inorganic coating (c) and curing,

It is possible to provide self-cleaning plastic bodies which have self-cleaning properties and are permanently hydrophilic.

• – Die Kunststoffkörper der vorliegenden Erfindung sind gegenüber der Bildung von Kratzern auf der Oberfläche sehr unempfindlich.
• – Die erfindungsgemäßen Kunststoffkörper zeigen eine hohe Beständigkeit gegen UV-Bestrahlung.
• – Des weiteren zeigen Kunststoffkörper bei UV-Bestrahlung eine hohe Selbstreinigung.
• – Darüber hinaus spreiten die Kunststoffkörper ohne UV-Bestrahlung Wasser. Hierdurch kann die Bildung von tropfenförmigen Rückständen verlässlich vermieden werden. Gleichmäßige, geringe Verschmutzungen, die über die Zeit gebildet werden könnten, werden daher bei Einstrahlung von UV-Licht durch die selbstreinigende Wirkung der photokatalytischen Schicht abgebaut. Hierdurch ist die Verschmutzung über einen langen Zeitraum der erfindungsgemäßen Kunststoffkörper vielfach geringer als von Kunststoffkörpern, die lediglich eine selbstreinigende Beschichtung, jedoch keine permanent wirksame wasserspreitende Beschichtung aufweisen. Dies gilt insbesondere in Jahreszeiten mit geringer Sonneneinstrahlung.
• – Darüber hinaus können die Kunststoffkörper der vorliegenden Erfindung besonders kostengünstig hergestellt werden, ohne daß teuere Additive verwendet werden müssen.
• – Des weiteren ermöglicht die vorliegende Erfindung die Erzeugung von selbstreinigenden, wasserspreitenden Beschichtungen auf schon mit Siloxanen beschichteten Kunststoffsubstraten. Dies hat insbesondere den Vorteil, dass aus der Produktion von Kunststoffkörpern, die mit kratzfesten Beschichtungen versehen sind, Platten herausgenommen werden können und später mit weiteren Beschichtungen versehen werden können, die selbstreinigende oder wasserspreitende Eigenschaften aufweist.
• – Die kratzfesten Kunststoffkörper der vorliegenden Erfindung können auf bestimmte Erfordernisse angepasst werden. Insbesondere kann die Größe und die Form des Kunststoffkörpers in weiten Bereichen variiert werden, ohne dass hierdurch die hervorragenden Eigenschaften beeinträchtigt werden. Des weiteren stellt die vorliegende Erfindung auch Kunststoffkörper mit hervorragenden optischen Eigenschaften zur Verfügung.
• – Die kratzfesten Kunststoffkörper der vorliegenden Erfindung weisen gute mechanische Eigenschaften auf.

The measures according to the invention provide, inter alia, the following advantages in particular:

• The plastic bodies of the present invention are very insensitive to the formation of scratches on the surface.
• - The plastic body according to the invention show a high resistance to UV radiation.
• - Furthermore, plastic bodies show high self-cleaning under UV irradiation.
• - In addition, the plastic body spread without UV irradiation water. As a result, the formation of drop-shaped residues can be reliably avoided. Uniform, low soiling, which could be formed over time, are therefore degraded when exposed to UV light by the self-cleaning effect of the photocatalytic layer. As a result, the contamination over a long period of the plastic body according to the invention is often lower than plastic bodies, which have only a self-cleaning coating, but no permanently effective water-spreading coating. This is especially true in seasons with low solar radiation.
• - In addition, the plastic body of the present invention can be made particularly inexpensive, without expensive additives must be used.
• Furthermore, the present invention enables the production of self-cleaning, water-spreading coatings on already coated with siloxanes plastic substrates. This has the particular advantage that plates can be removed from the production of plastic bodies which are provided with scratch-resistant coatings and can later be provided with further coatings which have self-cleaning or water-spreading properties.
• The scratch-resistant plastic bodies of the present invention can be adapted to specific requirements. In particular, the size and shape of the plastic body can be varied within wide limits, without affecting the excellent properties. Furthermore, the present invention also provides plastic bodies having excellent optical properties.
• - The scratch-resistant plastic body of the present invention have good mechanical properties.

The plastic bodies according to the invention are obtainable by coating plastic substrates. Plastic substrates suitable for the purposes of the present invention are known per se. such Substrates include in particular polycarbonates, polystyrenes, polyesters, for example polyethylene terephthalate (PET), which may also be modified with glycol, and polybutylene terephthalate (PBT), cycloolefinic polymers (COC) and / or poly (meth) acrylates. Polycarbonates, cycloolefinic polymers and poly (meth) acrylates are preferred, with poly (meth) acrylates being particularly preferred.

Polycarbonates are in the art known. Polycarbonates can formally as carbonated polyester and aliphatic or aromatic dihydroxy compounds become. They are easily accessible by reacting diglycols or bisphenols with phosgene or Carbonic acid diesters in polycondensation or transesterification reactions.

Polycarbonates are preferred here, which are derived from bisphenols. These bisphenols include in particular 2,2-bis (4-hydroxyphenyl) propane (Bisphenol A), 2,2-bis (4-hydroxyphenyl) -butane (bisphenol B), 1,1-bis (4-hydroxyphenyl) cyclohexane (Bisphenol C), 2,2'-methylenediphenol (Bisphenol F), 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane (tetrabromobisphenol A) and 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane (tetramethyl bisphenol A).

Common Such aromatic polycarbonates are prepared by interfacial polycondensation or transesterification, details in Encycl. Polym. Sci. Engng. 11, 648-718 are shown.

In interfacial polycondensation the bisphenols as aqueous, alkaline solution in inert organic solvents, such as methylene chloride, chlorobenzene or tetrahydrofuran, emulsified and reacted in a step reaction with phosgene. As Catalysts reach amines, with sterically hindered bisphenols also phase transfer catalysts are used. The resulting Polymers are soluble in the organic solvents used.

over the choice of bisphenols can the properties of the polymers are widely varied. At the same time Use of different bisphenols can be in multi-stage polycondensations also block polymers build up.

Cycloolefinic polymers are polymers, using cyclic olefins, in particular polycyclic ones Olefins available are.

Cyclic olefins include, for example monocyclic olefins, such as cyclopentene, cyclopentadiene, cyclohexene, Cycloheps, cyclooctene and alkyl derivatives of these monocyclic Olefins having 1 to 3 carbon atoms, such as methyl, ethyl or propyl, such as methylcyclohexene or dimethylcyclohexene, as well as Acrylate and / or methacrylate derivatives of these monocyclic compounds. About that also can Cycloalkanes with olefinic side chains as cyclic olefins used, such as cyclopentyl methacrylate.

Preference is given to bridged, polycyclic Olefin. These polycyclic olefin compounds may be the Have double bond both in the ring, it is here around bridged polycyclic cycloalkenes, as well as in side chains. This acts these are vinyl derivatives, allyloxycarboxy derivatives and (meth) acryloxy derivatives of polycyclic cycloalkane compounds. These compounds can be the have further alkyl, aryl or aralkyl substituents.

Illustrative polycyclic compounds include, but are not limited to, bicyclo [2.2.1] hept-2-ene (norbornene), bicyclo [2.2.1] hept-2,5-diene (2,5-norbornadiene), ethyl -bicyclo [2.2.1] hept-2-ene (ethylnorbornene), ethylidenebicyclo [2.2.1] hept-2-ene (ethylidene-2-norbornene), phenylbicyclo [2.2.1] hept-2-ene, bicyclo [4.3 .0] nona-3,8-diene, tricyclo [4.3.0.1 ^2,5 ] -3-decene, tricyclo [4.3.0.1 ^2,5 ] -3,8-decene- (3,8-dihydro-dicyclopentadiene), tricyclo [4.4.0.1 ^2,5] -3-undecene, tetracyclo dodecene -3-[4.4.0.1 ^2,5, 1 ^7,10], ethylidene-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] -3 dodecene, Methyloxycarbonyltetracyclo [4.4.0.1 ^2,5, 1 ^7,10] -3-dodecene, ethylidene-9-ethyltetracyclo [4.4.0.1 ^2,5, 1 ^7,10] -3-dodecene, pentacyclo [4.7.0.1 ^2,5 , O, O ^3,13 , 1 ^9,12 ] -3-pentadecene, pentacyclo [6.1.1 ^3,6 .0 ^2,7 .0 ^9,13 ] -4-pentadecene, hexacyclo [6.6.1.1 ^3.6 .1 ^10.13 .0 ^2,7 .0 ^9,14 ] -4-heptadecene, dimethylhexacyclo [6.6.1.1 ^3.6 .1 ^10.13 .0 ^2.7 .0 ^9.14 ] -4 -heptadecen, bis (allyloxycarboxy) tricyclo [4.3.0.1 ^2,5 ] decane, bis (m ethacryloxy) tricyclo [4.3.0.1 ^2,5 ] decane, bis (acryloxy) tricyclo [4.3.0.1 ^2,5 ] decane.

The cycloolefinic polymers are using at least one of the previously described cycloolefinic Compounds, in particular polycyclic hydrocarbon compounds produced. About that can out in the preparation of the cycloolefinic polymers further olefins used with the aforementioned cycloolefinic Monomers can be copolymerized. These include u.a. Ethylene, propylene, isoprene, butadiene, methylpentene, styrene and vinyltoluene.

Most of the aforementioned olefins, especially the cycloolefins and polycycloolefins, can be commercial to be obtained. About that In addition, many cyclic and polycyclic olefins are by Diels-Alder addition reactions available.

The preparation of the cycloolefinic polymers can be carried out in a known manner, as described, inter alia, in Japanese Patent Nos. 11818/1972, 43412/1983, 1442/1986 and 19761/1987 and Japanese Patent Laid-Open Nos. 75700/1975, 129434/1980, 127728 / 1983, 168708/1985, 271308/1986, 221118/1988 and 180976/1990 and in the European patent applications EP-A-0 6 610 851 . EP-A-0 6 485 893 . EP-A-0 6 407 870 and EP-A-0 6 688 801 is shown.

The cycloolefinic polymers may be, for example using aluminum compounds, vanadium compounds, Tungsten compounds or boron compounds as a catalyst in one solvent be polymerized.

It is believed that the polymerization depending on the conditions, in particular the catalyst used, under ring opening or under opening the double bond can take place.

In addition, it is possible cycloolefinic To obtain polymers by radical polymerization, wherein light or an initiator is used as a radical generator. this applies especially for the acryloyl derivatives of cycloolefins and / or cycloalkanes. This Type of polymerization can be done both in solution and in substance.

Another preferred plastic substrate includes poly (meth) acrylates. These polymers are generally obtained by radical polymerization of mixtures containing (meth) acrylates contain. The term (meth) acrylates includes methacrylates and Acrylates and mixtures of both.

These monomers are well known. These include, inter alia, (meth) acrylates derived from saturated alcohols, such as, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl ( meth) acrylate, pentyl (meth) acrylate and 2-ethylhexyl (meth) acrylate;
(Meth) acrylates derived from unsaturated alcohols, such as. Oleyl (meth) acrylate, 2-propynyl (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate;
Aryl (meth) acrylates, such as benzyl (meth) acrylate or phenyl (meth) acrylate, wherein the aryl radicals may each be unsubstituted or substituted up to four times;
Cycloalkyl (meth) acrylates such as 3-vinylcyclohexyl (meth) acrylate, bornyl (meth) acrylate;
Hydroxyalkyl (meth) acrylates such as 3-hydroxypropyl (meth) acrylate, 3,4-dihydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate;
Glycol di (meth) acrylates such as 1,4-butanediol di (meth) acrylate, (meth) acrylates of ether alcohols such as tetrahydrofurfuryl (meth) acrylate, vinyloxyethoxyethyl (meth) acrylate;
Amides and nitriles of (meth) acrylic acid, such as N- (3-dimethylaminopropyl) (meth) acrylamide, N- (diethylphosphono) (meth) acrylamide, 1-methacryloylamido-2-methyl-2-propanol;
sulfur-containing methacrylates such as ethylsulfinylethyl (meth) acrylate, 4-thiocyanatobutyl (meth) acrylate, ethylsulfonylethyl (meth) acrylate, thiocyanatomethyl (meth) acrylate, methylsulfinylmethyl (meth) acrylate, bis ((meth) acryloyloxyethyl) sulfide; polyvalent (meth) acrylates such as trimethyloylpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate and pentaerythritol tri (meth) acrylate.

According to a preferred aspect of the present invention, these mixtures contain at least 40 wt .-%, preferably at least 60 wt .-% and particularly preferably at least 80% by weight, based on the weight of the monomers, of methyl methacrylate.

In addition to the (meth) acrylates set forth above can the compositions to be polymerized also include other unsaturated monomers having, with methyl methacrylate and the aforementioned (meth) acrylates are copolymerizable.

These include, inter alia, 1-alkenes, such as hexene-1, heptene-1;
branched alkenes such as vinylcyclohexane, 3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene, 4-methylpentene-1;
acrylonitrile; Vinyl esters, such as vinyl acetate;
Styrene, substituted styrenes having an alkyl substituent in the side chain, such as. Α-methylstyrene and α-ethylstyrene, substituted styrenes having an alkyl substituent on the ring such as vinyltoluene and p-methylstyrene, halogenated styrenes such as monochlorostyrenes, dichlorostyrenes, tribromostyrenes and tetrabromostyrenes;
Heterocyclic vinyl compounds, such as 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinylthiophene, vinylthiolane, vinylthiazoles and hydrogenated vinylthiazoles, vinyloxazoles and hydrogenated vinyloxazoles;
Vinyl and isoprenyl ethers;
Maleic acid derivatives such as maleic anhydride, methylmaleic anhydride, maleimide, methylmaleimide; and dienes, such as divinylbenzene.

In general, these comonomers in an amount of 0 to 60% by weight, preferably 0 to 40% by weight and particularly preferably 0 to 20 wt .-%, based on the weight the monomers used, wherein the compounds individually or as Mixture can be used.

The polymerization is generally started with known free-radical initiators. Among the preferred initiators include the azo initiators well known in the art, such as AIBN and 1,1-azobiscyclohexanecarbonitrile, and peroxy compounds such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tert-butyl per-2-ethylhexanoate, ketone peroxide, methyl isobutyl ketone peroxide, cyclohexa nonperoxide, dibenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyisopropyl carbonate, 2,5-bis (2-ethylhexanoylperoxy) -2,5-dimethylhexane, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxy-3,5 , 5-trimethylhexanoate, dicumyl peroxide,
1,1-bis (tert-butylperoxy) cyclohexane, 1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane, cumyl hydroperoxide, tert-butyl hydroperoxide, bis (4-tert-butylcyclohexyl) peroxydicarbonate, Mixtures of two or more of the aforementioned compounds with one another and mixtures of the abovementioned compounds with unspecified compounds which can also form free radicals.

These compounds are common in from 0.01 to 3% by weight, preferably from 0.05 to 1% by weight, based on the weight of the monomers used.

The aforementioned polymers can be used individually or used as a mixture. In this case, various polycarbonates, Poly (meth) acrylates or cycloolefinic polymers are used, for example, in molecular weight or in the monomer composition differ.

The plastic substrates according to the invention can, for example be prepared from molding compositions of the aforementioned polymers. Here are generally thermoplastic molding processes used, such as extrusion or injection molding.

The weight average molecular weight M _w of the present invention as a molding material for the preparation of the plastic substrates to be used in homo- and / or copolymers can vary within wide ranges, the molecular weight usually being matched to the intended use and the processing of the molding composition. In general, however, it is in the range between 20,000 and 1,000,000 g / mol, preferably 50,000 to 500,000 g / mol, and more preferably 80,000 to 300,000 g / mol, without this being intended to limit this. This size can be determined, for example, by gel permeation chromatography.

Furthermore, the plastic substrates be produced by casting chamber method. Here are, for example put suitable (meth) acrylic mixtures in a mold and polymerized. Such (meth) acrylic mixtures generally have the above set forth (meth) acrylates, in particular methyl methacrylate. Furthermore, you can the (meth) acrylic mixtures the copolymers set forth above, and, in particular for adjusting the viscosity, Polymers, in particular poly (meth) acrylates.

The weight average molecular weight M _{w of} the polymers prepared by cast-chamber processes is generally higher than the molecular weight of polymers used in molding compositions. This results in a number of known advantages. In general, the weight-average molecular weight of polymers prepared by cast-chamber processes is in the range of 500,000 to 10,000,000 g / mol, without limitation.

Preferred plastic substrates produced by the casting chamber method can be obtained commercially from Cyro Inc. USA under the trade name ^® Acrylite.

In addition, the for the preparation of the plastic substrates to be used molding compositions and the acrylic resins usual Contain additives of all kinds. These include antistatics, Antioxidants, mold release agents, flame retardants, lubricants, dyes, Flow improvers, fillers, Light stabilizers and organic phosphorus compounds, such as phosphites, Phosphorinanes, phospholanes or phosphonates, pigments, weathering agents and plasticizer. The amount of additives is, however, to the purpose limited.

Particularly preferred molding compositions containing poly (meth) acrylates are commercially available under the trade name Acrylite ^® by the company. Cyro Inc. USA. Preferred molding compositions consisting of cycloolefinic polymers can be obtained under the trade name Topas ^® from Ticona and ^® Zeonex from Nippon Zeon. Polycarbonate molding compositions are available, for example, under the trade name ^® Makrolon from Bayer or ^® Lexan from General Electric.

Particularly preferably, the plastic substrate comprises at least 80 wt .-%, in particular at least 90 wt .-%, based on the total weight of the substrate, poly (meth) acrylates, polycarbonates and / or cycloolefinic polymers. Particularly preferred the plastic substrates of polymethyl methacrylate, wherein the polymethyl methacrylate conventional additives may contain.

According to a preferred embodiment, plastic substrates may have an impact strength according to ISO 179/1 of at least 10 kJ / m ² , preferably at least 15 kJ / m ² .

The shape and size of the plastic substrate are not essential for the present invention. In general, plate- or tabular Substrates used which have a thickness in the range of 1 mm to 200 mm, in particular 5 to 30 mm.

Before the plastic substrates with a coating, they can by suitable methods be activated to improve adhesion. For this purpose, for example the plastic substrate with a chemical and / or physical Be treated method, wherein the respective method of the plastic substrate dependent is.

The plastic bodies of the present invention are first provided with a siloxane coating, which protects the plastic substrate against the photocatalytic degradation by the photocatalytically active TiO ₂ -containing coating (b) protects.

Scratch-resistant siloxane coatings which can be used to produce the coating (a) are known per se and are used to furnish polymeric glazing materials. They are characterized by their inorganic character by good resistance to UV radiation and weathering. The preparation of such paints, for example, in EP-A-0 073911 described. Common among other paints, in addition to the siloxane condensation products water and / or alcohol as a solvent.

These siloxane varnishes can be obtained, inter alia, by condensation or hydrolysis of organic silicon compounds of the general formula (I) R ¹ _n SiX _4-n (I), wherein R ^{1 represents} a group having 1 to 20 carbon atoms, X represents an alkoxy group having 1 to 20 carbon atoms or a halogen, and n represents an integer of 0 to 3, wherein different groups X or R ^{1 may} each be the same or different.

The term "having 1 to 20 carbon Group "marks Residues of organic compounds having 1 to 20 carbon atoms. He comprises Alkyl, cycloalkyl, aromatic groups, alkenyl groups and alkynyl groups with 1 to 20 carbon atoms, as well as heteroalipatic and heteroaromatic Groups besides carbon and Hydrogen atoms, in particular oxygen, nitrogen, sulfur and phosphorus atoms respectively. It can the groups mentioned are branched or unbranched, with the Substituted R ' or may be unsubstituted. The substituents include in particular Halogens, 1 to 20 carbon groups, nitro, sulfonic acid alkoxy, cycloalkoxy, Alkanoyl, alkoxycarbonyl, sulfonic acid ester, sulfinic acid, sulfinic acid ester, Thiol, cyanide, epoxy, (meth) acryloyl, amino and hydroxy groups. In the context of the present invention, the term "halogen" denotes a fluorine, chlorine, Bromine or iodine atom.

The preferred alkyl groups include Methyl, ethyl, propyl, isopropyl, 1-butyl, 2-butyl, 2-methylpropyl, tert-butyl, pentyl, 2-methylbutyl, 1,1-dimethylpropyl, hexyl, Heptyl, octyl, 1,1,3,3-tetramethylbutyl, Nonyl, 1-decyl, 2-decyl, undecyl, dodecyl, pentadecyl and the eicosyl group.

To the preferred cycloalkyl groups belong cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the cyclooctyl group, optionally with branched or unbranched alkyl groups are substituted.

To the preferred alkenyl groups belong the vinyl, allyl, 2-methyl-2-propene, 2-butenyl, 2-pentenyl, 2-decenyl and the 2-eicosenyl group.

To the preferred alkynyl groups belong the ethynyl, propargyl, 2-methyl-2- propyne, 2-butynyl, 2-pentynyl and the 2-decynyl group.

To the preferred alkanoyl groups belong the formyl, acetyl, propionyl, 2-methylpropionyl, butyryl, Valeroyl, pivaloyl, hexanoyl, decanoyl and the dodecanoyl group.

To the preferred alkoxycarbonyl groups belong the methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, tert-butoxycarbonyl, hexyloxycarbonyl, 2-methylhexyloxycarbonyl, Decyloxycarbonyl or dodecyloxycarbonyl group.

To the preferred alkoxy groups belong the methoxy, ethoxy, propoxy, butoxy, tert-butoxy, hexyloxy, 2-methylhexyloxy, decyloxy or Dodecyloxy group.

To the preferred cycloalkoxy groups belong Cycloalkoxygruppen whose hydrocarbon radical is one of the above mentioned preferred cycloalkyl groups.

Preferred heteroaliphatic groups include the aforementioned preferred cycloalkyl groups in which at least one carbon moiety is replaced by O, S or a group NR ⁸ and R ^{8 is} hydrogen, an alkyl containing from 1 to 6 carbon atoms, having from 1 to 6 carbon atoms Alkoxy or an aryl group.

According to the invention, aromatic groups are radicals of mononuclear or polynuclear aromatic compounds having preferably 6 to 14, in particular 6 to 12, carbon atoms. Heteroaromatic groups denote aryl radicals in which at least one CH group has been replaced by N and / or at least two adjacent CH groups have been replaced by S, NH or O. Preferred aromatic or heteroaromatic groups according to the invention are derived from benzene, naphthalene, biphenyl, diphenyl ether, diphenylmethane, diphenyldimethylmethane, bisphenone, diphenylsulfone, thiophene, furan, pyrrole, thiazole, oxazole, imidazole, isothiazole, isoxazole, pyrazole, 1,3,4-oxadiazole , 2,5-diphenyl-1,3,4-oxadiazole, 1,3,4-thiadiazole, 1,3,4-triazole, 2,5-diphenyl-1,3,4-triazole, 1,2,5 -Triphenyl-1,3,4-triazole, 1,2,4-oxadiazole, 1,2,4-thiadiazole, 1,2,4-triazole, 1,2,3-triazole, 1,2,3,4 Tetrazole, benzo [b] thiophene, benzo [b] furan, indole, benzo [c] thiophene, benzo [c] furan, isoindole, benzoxazole, benzothiazole, benzimidazole, benzisoxazole, benzisothiazole, benzopyrazole, benzothiadiazole, benzotriazole, dibenzofuran, dibenzothiophene , Carbazole, pyridine, pyrazine, pyrimidine, pyridazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,4,5-triazine, quinoline, isoquinoline, quinoxaline, quinazoline, cinnoline, 1.8 Naphthyridine, 1,5-naphthyridine, 1,6-naphthyridine, 1,7-naphthyridine, phthalazine, pyridopyrimidine, purine, pteridine or 4H-quinolizine, diphenyl ether, anthracene and phenanthrene.

worin q für eine Zahl von 1 bis 6 steht, oder die Formel (IV)

worin R² Methyl oder Wasserstoff und r eine Zahl von 1 bis 6 bedeutet, darstellen.Preferred radicals R ¹ can be represented by the formulas (II), - (CH ₂ ) _m NH - [(CH ₂ ) _n -NH] _p H (II), wherein m and n are a number from 1 to 6, and p is zero or one, or the formula (III)

wherein q is a number from 1 to 6, or the formula (IV)

wherein R ^{2 is} methyl or hydrogen and r is a number from 1 to 6 represent.

Most preferably, the radical R ^{1 represents} a methyl or ethyl group.

Regarding the definition of the group X in formula (I) with respect to the alkoxy group having 1 to 20 carbon atoms and the halogen Reference is made to the aforementioned definition, wherein the alkyl radical the alkoxy group preferably also by the previously set forth Formulas (II), (III) or (IV) can be represented. Prefers the group X is a methoxy or ethoxy radical or a bromine or chlorine atom represents.

These compounds can be individually or used as a mixture to prepare siloxane coatings.

Depending on the number of halogens or oxygen attached to the silicon alkoxy groups form chains or branched siloxanes by hydrolysis or condensation of the silane compounds of the formula (I). Preferably, at least 60 wt .-%, in particular at least 80% by weight of the silane compounds used at least three alkoxy groups or halogen atoms, by weight the condensable silanes.

Tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane and tetra-n-butoxysilane; Trialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltripropoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 2-hydroxypropyltrimethoxysilane, 2-hydroxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3 Isocian atopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane , 3- (meth) acryloxypropyltriethoxysilane, 3-ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane;
Dialkoxysilanes include dimethyldimethoxysilane, dimethyl-diethoxysilane, diethyl-dimethoxysilane, diethyl-diethoxysilane, di-n-propyl-dimethoxysilane, di-n-propyldiethoxysilane, di-i-propyl-dimethoxysilane, di-i-propyl-diethoxysilane, di-n-propyl butyl-dimethoxysilane, di-n-butyldiethoxysilane, di-n-pentyl-dimethoxysilane, di-n-pentyl-diethoxysilane, di-n-hexyl-dimethoxysilane, di-n-hexyl-diethoxysilane, di-n-peptyl-dimethoxysilane, Di-n-peptyl-diethoxysilane, di-n-octyl-dimethoxysilane, di-n-octyl-diethoxysilane, di-n-cyclohexyl-dimethoxysilane, di-n-cyclohexyl-diethoxysilane, diphenyl-dimethoxysilane and diphenyl-diethoxysilane.

Particularly preferred are methyltrimethoxysilane, Methyltriethoxysilane, ethyltrimethoxysilane and ethyltriethoxysilane. According to one particular aspect of the present invention is the proportion of these particularly preferred alkyltrialkoxysilanes at least 80 Wt .-%, in particular at least 90 wt .-%, based on the weight the silane compounds used.

According to another aspect of the present invention, it is also possible to use siloxane coatings which contain colloidally dissolved SiO ₂ particles. Such solutions can be obtained by the sol-gel method, wherein in particular tetraalkoxysilanes and / or tetrahalosilanes are condensed.

Conventionally, water-containing coating compositions are prepared from the abovementioned silane compounds by hydrolyzing organosilicon compounds with an amount of water sufficient for the hydrolysis, ie> 0.5 mole of water per mole of the groups intended for hydrolysis, for example alkoxy groups. preferably under acid catalysis. As acids, for example, inorganic acids, such as hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, etc., or organic acids, such as carboxylic acids, organic sulfonic acids, etc., or acidic ion exchangers may be added, the pH of the hydrolysis reaction usually being between 2 and 4.5 , preferably at 3.

In general, after the shows Combining the reactants, a temperature rise. In certain make For example, it may be necessary to apply heat from the outside to start the reaction by heating of the batch at 40 - 50 ° C. In general Care is taken that the Reaction temperature 55 ° C does not exceed. The reaction time is usually relatively short, it is usually below one hour, for example at 45 min.

The silane compounds can be condensed to polymers which generally have a weight average molecular weight M _w in the range of 100 to 20,000, preferably 200 to 10,000 and more preferably 500 to 1500 g / mole. This molecular weight can be determined, for example, by NMR spectroscopy.

The condensation reaction may, for example by cooling to temperatures below 0 ° C or by increasing the pH with suitable bases, for example alkali or Alkaline earth metal hydroxides, be terminated.

For further processing, a Part of the water-alcohol mixture and the volatile acids from the reaction mixture be separated, for example by distillation.

Subsequently, with suitable organic solvents such as. Alcohols, such as ethanol, methanol, isopropanol, butanol, Ethers, such as diethyl ether, dioxane, ethers and esters of polyols, such as. Ethylene glycol, propylene glycol and ethers and esters of these Compounds, hydrocarbons, e.g. aromatic hydrocarbons, Ketones, such as acetone, methyl ethyl ketone, the solids content to approx. 15-35% by weight, based on the total weight of the mixture. Particularly preferred is as a solvent Ethanol and / or propanol-2.

It has also proven to be beneficial have proven to add such solvents to the coating compositions which usually the intended as a substrate of the coating plastic dissolve. In the case of polymethylmethacrylate (PMMA) as substrate recommends For example, an addition of solvents such as toluene, acetone, Tetrahydrofuran in amounts of 2 to 20 wt .-%, based on the Total weight of funds, make up. The water content is generally on 5 - 20 Wt .-%, preferably to 11 to 15 wt .-%, based on the total weight the means, set.

To improve the shelf life, the pH of the hydrous siloxane coatings can be adjusted to a range of 3 to 6, preferably between 4.5 and 5.5. For this purpose, it is also possible, for example, to add additives, in particular propionamide, which are available in US Pat EP-A-0 073 911 are described.

The siloxane coatings which can be used according to the invention can curing catalysts, for example in the form of zinc compounds and / or other metal compounds, such as cobalt, copper or calcium compounds, in particular their Octoate or naphthenates. The proportion of curing catalysts is usually 0.1 - 2.5 % By weight, especially 0.2-2 Wt .-%, based on the total siloxane without this a restriction should be done. Particular examples include zinc naphthenate, octoate, acetate, sulfate, etc.

The siloxane coatings described above can be obtained commercially under the trade names ^® Acriplex 100 and ^® Acriplex 180 SR from Rohm GmbH & Co. KG.

The siloxane coatings set out above can applied to the plastic substrates by any known method become. These include including dipping, spraying, knife coating, flood coating and roller or roller application.

The siloxane coatings applied in this way can be generally in a relatively short time, for example within 2 to 6 hours, usually within about 3 to 5 hours and at a comparatively low temperature, for example at 70-110 ° C, preferably at about 80 ° C cure to excellent scratch and adhesive coatings.

The layer thickness of the siloxane coating (a) is relatively uncritical. In general, this size is after hardening but in a range of 1 to 50 μm, preferably 1.5 to 30 μm and especially preferably 3 to 15 μm, without this being a limitation should be done. The layer thicknesses of the coatings (a), (b) and / or (c) can be obtained by taking a scanning electron microscope (SEM) be determined.

According to a particular aspect of present invention the polar part of the surface energy after curing the first siloxane layer is preferably at most 8 mN / m, more preferably at the most 6 mN / m.

According to a preferred embodiment of the present invention, the proportion of silicon in the siloxane coating (a) after curing is at least 20% by weight, preferably at least 30% by weight, based on the total weight of the coating, without any limitation should. The proportion of the carbon is preferably at most 36 wt .-%, in particular at most 25 wt .-%, based on the total weight of the coating. These proportions can be determined by elemental analysis according to J. Liebig or by atomic absorption spectroscopy (AAS).

After curing the first siloxane coating becomes the surface activated by the polar portion of the surface energy of the cured siloxane coating is increased to a value of at least 10 mN / m. Especially preferred the polar component of the surface energy will be at least Increased 15 mN / m.

The surface energy is determined by the method Ownes-Wendt-Rabel & Kaelble certainly. For this purpose, measurement series with the standard series according to Busscher carried out, when used as test fluids Water [SFT 72.1 mN / m], formamide [SFT 56.9 mN / m, diiodomethane [SFT 50.0 mN / m] and alpha-bromonaphthalene [SFT 44.4 mN / m]. The measurement is at 20 ° C carried out. The surface tension and the polar and disperse portion of these test liquids are known and are used to calculate the surface energy of the substrate used.

The surface energy can with a Contact angle measuring system G40 from the company Krüss, Hamburg, being the implementation in the user manual of the contact angle measuring system G40, 1993 is. With regard to the calculation methods, see A. W. Neumann, Über die Measuring methodology for the determination of interfacial energy quantities, part I, journal for Phys. Chem., Vol. 41, pp. 339-352 (1964), and A.W. Neumann, About Measuring methodology for the determination of interfacial energy quantities, part II, journal for Phys. Chem., 43, pp. 71-83 (1964).

To activate the Siloxangrundlacks Various physical and chemical processes are suitable. These include including a treatment of the surface with chemical processes, especially with alkalis, corona treatment, flaming, plasma or Atmospheric plasma treatment. Here, chemical processes and corona treatment are preferred.

The activation can be on chemical Paths take place, wherein the coated with the Siloxangrundlack substrate subjected to a treatment with preferably liquid reagents becomes. Here, preference is given to only the uppermost atomic layers of the siloxane coating etched. According to one special aspect, the surface is treated with an alkaline solution, whose pH is at least 10, preferably at least 12.

For example, this can be done with the siloxane varnish coated substrate with an aqueous and / or alcoholic solution be treated by alkali metal hydroxides. Preferred alcohols are methanol, ethanol, propanol and / or butanol. The concentration the alkali metal hydroxides is preferably in the range of 1 to 20, in particular 2 to 10 wt .-%, based on the weight of the etching solution. alkali metals In particular, lithium, sodium, potassium, rubidium and / or cesium. Of these, Sodium and / or potassium are preferred.

The exposure time of the alkaline solution is dependent on the pH value and therefore can be in a wide range. In general, however, suffice a few minutes. Particularly preferably, the contact time of the alkaline solution in the range of 30 seconds to 60 minutes, especially 1 minute to 10 minutes. This surface treatment can be stopped, for example by neutral washing or addition of acids.

The alkaline solutions can be made by any known method be applied to the siloxane coating. These methods were previously stated.

Furthermore, the polar portion of the surface energy can be increased by corona treatment. This method is for example in EP-A-1 180 426 described. The duration of treatment depends on the energy used and is preferably in the range from 1 to 20 seconds, in particular from 2 to 5 seconds. A generator suitable for corona treatment can be obtained, for example, from the company Softal Electronic GmbH, Hamburg, which can be operated in the high-frequency range at 20 to 30 kHz (generator 3005).

After activation of the first siloxane layer, which contains no photocatalytically active portions, a second layer containing TiO ₂ particles is applied.

The lacquer for producing the second layer can essentially correspond to the first siloxane lacquer, but photocatalytically active TiO ₂ particles have to be introduced.

Such a lacquer can be prepared, for example, by mixing a siloxane lacquer described above with a composition containing aqueous and / or alcoholic TiO ₂ particles.

Particularly suitable are, in particular, coating compositions which contain collodially dissolved SiO ₂ particles. These particles preferably have the same size as the TiO ₂ particles described below. Such dispersions can be prepared by the sol-gel process, in particular tetraalkoxysilanes and / or tetrahalosilanes being condensed.

Such compositions containing TiO ₂ particles include EP-A-0 826 663 . EP-A-0 850 203 and EP-1 022 318 known. Further, such compositions may be obtained commercially, for example, from Showa Denko Kabushiki Kaisha, Japan under the trade name NTB 30A or Toto Ltd., Japan.

The TiO ₂ particles are photocatalytically active. Accordingly, at least some of the TiO ₂ particles are present in the brookite and / or anatase modification. The particle size is not critical, but the trans parency depends on the particle size. Preferably, the particles have a size of at most 300 nm, wherein they are in particular in a range of 1 to 200 nm, preferably 1 to 50 nm.

The second layer containing TiO ₂ particles can be applied and cured by the methods described above.

According to a particular embodiment, the TiO ₂ particles in the second coating are in an amount in the range from 0.01 to 90% by weight, preferably 0.1 to 75% by weight, based on the total weight of the second coating after Hardening, available.

The layer thickness of the coating (b) containing TiO ₂ particles is likewise not critical. In general, this size after curing in the range of 0.05 to 2 microns, preferably 0.1 to 1 micron.

After drying the coating (b) containing TiO ₂ particles, a water-spreading inorganic coating (c) is applied thereto.

The term water-spreading means that a drop of water on the surface a contact angle of at most 20 °, preferably at the most 10 ° forms. This size will at 20 ° C determined with a contact angle measuring system G40 from. Krüss, Hamburg.

In the context of the present invention the term inorganic means that the carbon content of the inorganic coating at most 25 wt .-%, preferably maximum 17 wt .-% and most preferably at most 10 wt .-%, based on the weight of the inorganic coating (c) is. This size can be determined by elemental analysis.

As water-spreading inorganic Coating (c) can in particular polysiloxanes, silane condensates and silica sols applied whose carbon content is equal to that previously stated Restricted areas is.

The silane condensates and polysiloxanes have been presented in general form previously, with these being preferred at least 80 wt .-%, in particular at least 90 wt .-% of the used Silane compounds have four alkoxy groups or halogen atoms, based on the weight of the condensable silanes.

According to a further aspect of the present invention, it is also possible to use silane condensates for producing the water-spreading coating (c) which contain colloidally dissolved SiO ₂ particles. Such solutions can be obtained by the sol-gel method, wherein in particular tetraalkoxysilanes and / or tetrahalosilanes are condensed.

Furthermore, oxide layers, in particular Semi-metal and metal oxides as water-spreading coating (c) be used. In particular, suitable compounds include Oxides and hydroxides composed of silicon, aluminum, titanium, zirconium, Derive zinc and / or chromium.

These oxides can be used singly or as mixtures, for example as mixed oxides, but the proportion of TiO ₂ is limited to amounts which do not reduce the permanent water-spreading action of the outer inorganic coating too much.

The solubility of these oxides and / or Hydroxides in water should be as possible be low, for example, the solubility in water at 20 ° under 1000 ug / l, preferably below 200 μg / l lie.

These oxides can be applied, for example, in the form of colloidal solutions obtained by hydrolysis of alkoxy compounds. Such colloidal solutions are for example EP-A-0 149 182 . EP-A-0 826 663 . EP-A-0 850 203 and EP-1 022 318 known.

The particle size of these oxide particles is uncritical, but the transparency depends on the particle size. The particles preferably have at most a size of 300 nm, in particular in a range of 1 to 200 nm, preferably 1 to 50 nm.

According to a particular aspect of Present invention, the colloidal solution is preferably in a pH greater or equal to 7.5, in particular larger or equal to 8 and more preferably greater than or equal to 9 applied.

Basic colloidal solutions are cheaper than acidic solutions. About that In addition, basic colloidal solutions of oxide particles are particularly easy and over storable for a long time.

The coating compositions described above can be sold commercially under the trade name ^® Ludox (Grace, Worms); ^® Levasil (Bayer, Leverkusen); ^® Klebosol, (Clariant).

Furthermore, the coating compositions for the preparation of the inorganic coating (a) conventional additives and processing aids. These belong to Other especially flow control agents, which also include surfactants.

The inorganic water-spreading Coating (c) can be applied by any known method being examples of this previously stated.

The applied coating agent can be generally in a relatively short time, for example within 0.5 minutes to 1 hour, usually within about 1 hour Minutes to 30 minutes, preferably within 3 minutes to 20 minutes and at a comparatively low temperature, for example at 60-110 ° C, preferably at about 80 ° C to water-spreading coatings (c) cure.

The layer thickness of the inorganic coating (c) is relatively uncritical, but the photocatalytic action of the underlying coating (b) must not be completely lost. In general However, this size is after curing in a range of 0.05 .mu.m to 2 .mu.m, preferably 0.05 .mu.m to 1 .mu.m and more preferably 0.05 .mu.m to 0.5 .mu.m, without this being a restriction.

According to a particular aspect of The present invention is the thickness of the inorganic water-spreading Coating (c) preferably in the range of 30 nm to 600 nm, preferably 50 nm to 400 nm, and more preferably 100 nm to 250 nm.

According to a particular embodiment of the plastic body is the total layer thickness of the coatings (a), (b) and (c) after curing in a range of 2 to 30 μm, in particular from 3 to 15 μm.

The with a photocatalytic Coated plastic body of the present invention show a high abrasion resistance. The rub resistance is preferred greater or equal to DIN 53778 10,000 cycles, in particular larger or equal to 15,000 cycles, and more preferably greater than or equal to 20,000 cycles.

According to a particular aspect of the present invention, the plastic body is transparent, wherein the transparency τ _{D65 / 10} according to DIN 5033 is at least 70%, preferably at least 75%.

Preferably, the plastic body has a Modulus of elasticity according to ISO 527-2 of at least 1000 MPa, in particular at least 1500 MPa without this a restriction should be done.

The plastic bodies according to the invention are generally very stable across from Weathering. So is the weathering resistance according to DIN 53387 (Xenotest) at least 5000 hours.

Even after a long UV irradiation of more than 5000 hours, the yellow index according to DIN 6167 (D65 / 10) is the preferred one Plastic bodies less than or equal to 8, preferably less than or equal to 5 without this a restriction should be done.

The plastic body of the present invention can for example, in the construction sector, in particular for the production of greenhouses or Conservatories, or as a noise barrier serve.

The invention will be understood by the following Examples and comparative examples explained in more detail, without the invention limited to these examples shall be.

example 1

PMMA plates of a dimension of 150 x 350 x 3 mm were provided with a scratch-resistant lacquer (Acriplex 100 SR, Röhm GmbH & Co. KG), wherein the layer thickness of the paint after curing was 7.5 microns.

After curing of the paint was the polar fraction of the surface energy 5.5 mN / m. After that, the surface was left for five minutes with a 5% KOH Water / ethanol mixture (1: 3 parts by weight) and then treated neutral washed. The surface energy was used with a contact angle measuring system G40 from. Krüss, Hamburg determined, using as test liquids Water [SFT 72.1 mN / m], formamide [SFT 56.9 mN / m, diiodomethane [SFT 50.0 mN / m] and alpha-bromonaphthalene [SFT 44.4 mN / m] were used. The polar part of the surface energy was 15.3 mN / m.

After activation, a colloidal solution containing TiO ₂ particles and SiO ₂ particles was applied by flood coating (3: 1 mixture of NTB 30A (TiO ₂ ) with NTB 30B (SiO ₂ ) available from Showa-Denko). The course of the paint and the adhesion were good. The resulting coating was cured at 80 ° C for three hours.

Subsequently, an inorganic water-spreading layer was applied with a wire bar. For this purpose, a 12 μm thick layer of an anionic alumina-modified silica sol (solids content 3%; ^® Ludox AM available from DuPont) containing 0.01 parts by weight of an octahoxylated isotridecyl alcohol as nonionic emulsifier was coated.

The still wet with the water-spreading Layer provided plate dried for 5 min at 80 ° C in a convection oven.

The determination of the layer thickness of extremely thin Layers can be made by thin section in the transmission electron microscope, the water-spreading Layer has a thickness of 0.15 microns had.

The scratch resistance of the coating according to the wet scrubbing festival according to DIN 53778 was a wet scrub tester from Gardner, Model M 105 / A performed. A value of 20,000 cycles was determined.

A drop of water on the outer coating was applied, spread to less than 10 °.

Furthermore, the plate was provided with a colored marking ( ^® Edding Marker 400) and irradiated with several UV fluorescent tubes (type Ergoline Turbo Power from. JK, Bad Honnef) for 7 days. As a result, the applied mark faded almost completely.

Comparative Example 1

Example 1 became essentially repeated, but applied no water-spreading coating has been. The coating also showed a high scratch resistance of 20,000 cycles, with the applied mark also completely fading. However, the contact angle with water was about 37 ° after the plate was stored for 24 h in the dark.

Comparative Example 2

It was a PMMA plates with a water-spreading coating according to EP 149 182 provided (Example 3 according to EP 149 182 ). The contact angle with water was less than 10 °. However, the label applied with the marker was clearly visible after irradiation with UV light.

Claims (25)

Water-spreading, scratch-resistant and self-cleaning plastic body, obtainable by applying to a plastic substrate a) a siloxane coating (a) and cures, b) the polar component of the surface energy of the cured siloxane coating to a value of at least 10 mN / m and c ) applying a photocatalytically active TiO ₂ particles containing coating (b) and cures and d) applying a water-spreading, inorganic coating (c) and cures. Plastic body according to claim 1, characterized in that the Plastic substrate cycloolefin copolymers, polyethylene terephthalates, Polycarbonates and / or poly (meth) acrylates. Plastic body according to claim 2, characterized in that the Plastic substrate consists of polymethylmethacrylate. Plastic body according to one or more of the preceding claims, characterized in that the plastic substrate has an impact resistance of at least 10 kJ / m ² according to ISO 179/1. Plastic body according to one or more of the preceding claims, characterized that this Plastic substrate has a thickness in the range of 1 mm to 200 mm. Plastic body according to one or more of the preceding claims, characterized that the Siloxane coating obtainable by condensation of a composition, the at least 80 wt .-% alkyltrialkoxysilanes, based on the content of condensable silanes. Plastic body according to one or more of the preceding claims, characterized that the Siloxane coating comprises condensable polysiloxanes, the have a molecular weight in the range of 500 to 1500 g / mol. Plastic body according to one or more of the preceding claims, characterized that the Proportion of silicon of the siloxane coating (a) at least 30 Wt .-%, based on the total weight of the coating is. Plastic body according to one or more of the preceding claims, characterized that he the polar part of the surface energy the siloxane coating (a) by hardening to a value smaller or equal to 6 mN / m before lowering the polar fraction of surface energy increased to at least 10 mN / m. Plastic body according to one or more of the preceding claims, characterized that he the polar part of the surface energy the siloxane coating (a) after curing by treatment increased with alcoholic potassium hydroxide solution. Plastic body according to one or more of the preceding claims, characterized in that the TiO ₂ particles have a size in the range of 1 nm to 300 nm. Plastic body according to one or more of the preceding claims, characterized gekennzeich net, that the TiO ₂ particles in the second coating (b) in an amount in the range of 0.01 to 90 wt .-%, based on the total weight of the second coating (b) after curing, is present. Plastic body according to one or more of the preceding claims, characterized that the Layer thickness of the siloxane coating (a) after curing in Range of 1.5 to 30 microns lies. Plastic body according to one or more of the preceding claims, characterized that the Layer thickness of the coating (b) after curing in the range of 0.01 to 2 microns is. Plastic body according to one or more of the preceding claims, characterized that the Layer thickness of the coating (c) after curing in the range of 0.01 to 1 μm. Plastic body according to one or more of the preceding claims, characterized that the Layer thickness of the coatings (a), (b) and (c) after curing in Range of 3 to 15 microns. Plastic body according to one or more of the preceding claims, characterized that the carbon content of water-spreading, inorganic Coating (c) at most 17 wt .-%, based on the weight of the coating (c), is. Plastic body according to one or more of the preceding claims, characterized that the water-spreading, inorganic coating (c) by hardening colloidal solutions inorganic and / or organometallic compounds is available. Plastic body according to one or more of the preceding claims, characterized that water on the water-spreading, inorganic coating (c) forms a contact angle of at most 10 °. Plastic body according to one or more of the preceding claims, characterized that the Abrasion resistance of the plastic body according to DIN 53778 at least 15,000 is. Plastic body according to one or more of the preceding claims, characterized that the Plastic body has an E-module according to ISO 527-2 of at least 1500 MPa. Plastic body according to one or more of the preceding claims, characterized that the Plastic body a weathering resistance according to DIN 53 387 of at least 5000 hours. Plastic body according to one or more of the preceding claims, characterized that the Plastic body a transparency according to DIN 5033 of at least 70%. Plastic body according to one or more of the preceding claims, characterized that the Plastic body a yellow index less than or equal to 5 after 5000 hours of UV irradiation having. Process for producing self-cleaning plastic bodies according to one or more of Claims 1 to 24, characterized in that a siloxane coating (a) is applied to a plastic substrate a) and cured, b) the polar fraction of the surface energy of the cured siloxane coating to a value increased by at least 10 mN / m and c) applying a photocatalytically active TiO ₂ particles containing coating (b) and cures and d) applying a water-spreading, inorganic coating (c) and cures.