EP1572827A1

EP1572827A1 - Formable water-dispersing plastic bodies and method for the production thereof

Info

Publication number: EP1572827A1
Application number: EP03773648A
Authority: EP
Inventors: Thomas Hasskerl; Patrick Becker; Rolf Neeb; Ghirmay Seyoum
Original assignee: Roehm GmbH Darmstadt
Current assignee: Roehm GmbH Darmstadt
Priority date: 2002-12-17
Filing date: 2003-10-18
Publication date: 2005-09-14
Also published as: RU2005122308A; CN1726268A; WO2004055128A1; CN100351340C; AU2003282033A1; DE10259240A1; JP2006509865A; HK1086294A1; US20060063011A1; TW200420718A

Abstract

The invention relates to water-dispersing plastic bodies made of a plastic substrate, at least one water-dispersing, inorganic coating (a) and an adhesive promoting intermediate layer (b) arranged between the plastic substrate and the inorganic coating. Said coating can be obtained in such a manner that the intermediate layer applied is (b) made of a mixture with a compound which has an evaporating number smaller than or equal to 20. The sum of the layer thicknesses of the inorganic coating (a) and the intermediate layer (b) is 07µm at the most.

Description

Formable water-spreading plastic body and process for its production

The present invention relates to thermally formable water-spreading plastic bodies which have a plastic substrate, a water-spreading, inorganic coating and an adhesion-promoting intermediate layer located between the plastic substrate and the inorganic coating.

Water-spreading plastics have the property that water that gets on their surface does not contract there into separate drops, but that the drops spread out and flow into a closed layer when touched. This results in improved light reflection on the surface moistened with water and - in the case of transparent plastics - better light transmission and makes it more difficult for water to drip from the underside of the plastic body.

Numerous attempts have been made to produce anti-fog coatings from crosslinked hydrophilic polymers on water-repellent plastic surfaces.

According to DE-OS 21 61 645, such a coating is produced from a copolymer of alkyl esters, hydroxyalkyl esters and quaternary aminoalkyl esters of acrylic or methacrylic acid and methylol ethers of methacrylamide as crosslinking agents. They first take up water with swelling and gradually change to a water-spreading state. As a result of the swelling, however, the coating becomes soft and sensitive to mechanical damage. Furthermore, water-spreading bodies are known from EP-A-0 149 182. These plastic bodies have an inorganic coating based on SiO ₂ .

A disadvantage of the water-spreading plastic bodies disclosed in EP-A-0 149 182, however, is that such a plastic body loses its water-spreading property completely during thermal forming, the coating on the formed body becoming milky, cloudy and unsightly.

Subsequent reshaping of the plates provided with a water-spreading layer is, however, desirable for many reasons. In particular, the transport costs of planar plates are lower than that of formed bodies due to the better stackability.

It should also be borne in mind that the production of coated panels and their use, for example as a structural part, is carried out by different companies. Accordingly, coated, formable construction parts can be made for much broader customer groups than pre-formed plates specially produced for a customer.

Furthermore, many particularly favorable coating processes cannot be carried out or can only be carried out with difficulty with formed parts, such as, for example, roll or roll processes.

In view of the prior art specified and discussed herein, it was therefore an object of the present invention to provide water-spreading plastic bodies which can be thermally deformed without the water-spreading property being adversely affected thereby or clouding occurring. In addition, it was therefore an object of the present invention to provide water-spreading plastic bodies whose water-spreading coating has a particularly high adhesion to the plastic substrates. This property should not be affected by moisture.

Another object of the invention was that the plastic bodies have a high durability, in particular a high resistance to UV radiation or weathering.

Furthermore, the invention was based on the object of providing water-spreading plastic bodies which can be produced in a particularly simple manner. For example, substrates which can be obtained by extrusion, injection molding and by casting processes should be able to be used for the production of the plastic bodies.

Another object of the present invention was to provide water-spreading plastic bodies that show excellent mechanical properties. This property is particularly important for applications in which the plastic body is said to have high stability against impact.

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

Another object of the present invention was to provide plastic bodies which can be easily adapted in size and shape to the requirements. These tasks are solved as well as others, which are not named literally, but which can be derived as a matter of course from the contexts discussed here, or which inevitably result from them, by the plastic bodies described in claim 1. Expedient modifications of the plastic body according to the invention are protected in the subclaims which refer back to claim 1.

With regard to manufacturing processes, claim 20 provides a solution to the underlying problem.

By applying the adhesion-promoting intermediate layer (b) located between a plastic substrate and a water-spreading, inorganic coating (a) from a solution with a solvent which has an evaporation number less than or equal to 20, the sum of the layer thicknesses of the inorganic Coating (a) and the intermediate layer (b) is at most 700 nm, it is possible to provide water-spreading plastic bodies that can be thermally formed without adversely affecting the water-spreading property or causing clouding.

The measures according to the invention include achieved the following advantages in particular:

• The water-spreading coatings of the invention

Plastic bodies have a particularly high adhesion to the plastic substrates, although this property is not impaired even when exposed to moisture.

• The plastic bodies according to the invention show a high resistance to UV radiation. • The plastic body according to the invention can be manufactured inexpensively.

The plastic bodies of the present invention can be adapted to certain requirements. In particular, the size and shape of the plastic body can be varied within a wide range without the formability being impaired thereby. Furthermore, the present invention also provides plastic bodies with excellent optical properties.

The plastic bodies 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 can 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, poly (meth) acrylates being particularly preferred.

Polycarbonates are known in the art. Polycarbonates can be considered formally as polyesters from carbonic acid and aliphatic or aromatic dihydroxy compounds. They are easily accessible by reacting diglycols or bisphenols with phosgene or carbonic acid diesters in polycondensation or transesterification reactions. Polycarbonates derived from bisphenols are preferred. 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 (bisphenoi F), 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane (tetrabromobisphenol A) and 2,2-bis (3,5- dimethyl-4-hydroxyphenyl) propane (tetramethylbisphenol A).

Such aromatic polycarbonates are usually produced by interfacial polycondensation or transesterification, details of which are given in Encycl. Polym. Be. Engng. 11, 648-718.

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

The properties of the polymers can be varied widely by the choice of the bisphenols. If different bisphenols are used at the same time, block polymers can also be built up in multi-stage polycondensation.

Cycloolefinic polymers are polymers that can be obtained using cyclic olefins, in particular polycyclic olefins.

Cyclic olefins include, for example, monoeyclic olefins such as cyclopentene, cyclopentadiene, cyclohexene, cycloheptene, cyclooctene and alkyl derivatives of these monoeyclic olefins having 1 to 3 carbon atoms, such as methyl, ethyl or propyl, such as methylcyclohexene or dimethylcyclohexene, and acrylate and / or methacrylate derivatives monoeyclic compounds. In addition, cycloalkanes with olefinic side chains can also be used as cyclic olefins, such as, for example, cyclopentyl methacrylate.

Bridged polycyclic olefin compounds are preferred. These polycyclic olefin compounds can have the double bond both in the ring, these are bridged polycyclic cycloalkenes, and in side chains. These are vinyl derivatives, allyloxycarboxy derivatives and (meth) acryloxy derivatives of polycyclic cycloalkane compounds. These compounds may also have alkyl, aryl or aralkyl substituents.

Exemplary polycyclic compounds are, without being restricted thereby, bicyclo [2.2.1] hept-2-ene (norbornene), bicyclo [2.2.1] hept-2,5-diene (2,5-norbomadiene), ethyl -bicyclo [2.2.1] hept-2-ene (ethyl norbornene), ethylidene bicyclo [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-decen- (3,8-dihydrodicyclopentadiene), tricyclo [4.4.0.1 ^2,5 ] -3-undecene, tetracyclo [4.4.0.1 ² ' ⁵ , 1 ^7,10 ] -3-dodecene, ethylidene tetracyclo [4.4.0.1 ² ' ⁵ .1 ^7,10 ] -3 -dodecen, methyloxycarbonyltetracyclo [4.4.0.1 ^2.5 , 1 ^7.10 ] - 3-dodecen, ethylidene-9-ethyltetracyclo [4.4.0.1 ² ' ⁵ , 1 ⁷ ' ¹⁰ ] -3-dodecen, 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 -heptadecene, bis (allyloxycarboxy) tri cyclo [4.3.0.1 ² ' ⁵ ] decane, bis (methacryloxy) tricyclo [4.3.0.1 ² ' ⁵ ] decane, bis (acryloxy) tricyclo [4.3.0.1 ^2,5 ] decane.

The cycloolefinic polymers are produced using at least one of the cycloolefinic compounds described above, in particular the polycyclic hydrocarbon compounds. In addition, other olefins which can be copolymerized with the aforementioned cycloolefinic monomers can be used in the preparation of the cycloolefinic polymers. These include ethylene, propylene, isoprene, butadiene, methyl pentene, styrene and vinyl toluene.

Most of the aforementioned olefins, especially the cycloolefins and polycycloolefins, can be obtained commercially. In addition, many cyclic and polycyclic olefins are available through Diels-Alder addition reactions.

The cycloolefinic polymers can be prepared in a known manner, as described in Japanese Patents 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 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.

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

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

In addition, it is possible to obtain cycloolefinic polymers by radical polymerization, using light or an initiator as a radical generator. This applies in particular to the acryloyl derivatives of the cycloolefins and / or cycloalkanes. This type of polymerization can take place both in solution and in bulk. Another preferred plastic substrate comprises poly (meth) acrylates. These polymers are generally obtained by free-radical polymerization of mixtures which contain (meth) acrylates. The term (meth) acrylates encompasses methacrylates and acrylates and mixtures of the two.

These monomers are well known. These include, among others

(Meth) acrylates derived from saturated alcohols, 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. B.

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, where the aryl radicals can in each case be unsubstituted or substituted up to four times;

Cycloalkyl (meth) acrylates such as 3-vinylcyclohexyl (meth) acrylate, bornyl (meth) acrylate;

Hydroxylalkyl (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-ThiocyanatobutyI (meth) acrylate,

Ethylsulfonylethyl (meth) acrylate, Thiocyanatomethyl (meth) acrylate,

Methylsulphinylmethyl (meth) acrylic! At,

Bis ((meth) acryloyloxyethyl) sulfide; polyvalent (meth) acrylates, such as

Trimethyloylpropantri (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% by weight, preferably at least 60% by weight 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 out above, the compositions to be polymerized can also have further unsaturated monomers which are copolymerizable with methyl methacrylate and the aforementioned (meth) acrylates.

These include 1-alkenes such as 1-hexene, 1-heptene; 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 with an alkyl substituent in the side chain, such as.

B. α-methylstyrene and α-ethylstyrene, substituted styrenes with a

Alkyl substituents 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 vinylazole hydrogenated vinylazole, vinyloxoleoleole, hydrogenated vinylazole hydrogenated vinylazole and hydrogenated vinylazole;

Vinyl and isoprenyl ether;

Maleic acid derivatives, such as maleic anhydride, methyl maleic anhydride, maleimide, methyl maleimide; and dienes such as divinylbenzene.

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

The polymerization is generally started with known radical initiators. The preferred initiators include, among others, the azo initiators well known in the art, such as AIBN and 1, 1-azobiscyclohexane carbonitrile, and also peroxy compounds, such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tert-butyl per-2-ethylhexanoate, ketone peroxide, methyl isobutyl ketone peroxide, and cyclohexyl peroxide , tert-butyl peroxybenzoate, tert-butyl peroxyisopropyl carbonate, 2,5-bis (2-ethylhexanoyl-peroxy) -2,5-dimethylhexane, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-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 abovementioned compounds with one another and mixtures of the abovementioned compounds with compounds not mentioned which can likewise form free radicals. These compounds are often used in an amount of 0.01 to 3% by weight, preferably 0.05 to 1% by weight, based on the weight of the monomers.

The aforementioned polymers can be used individually or as a mixture. Various polycarbonates, poly (meth) acrylates or cycloolefinic polymers can also be used here, which differ, for example, in molecular weight or in the monomer composition.

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

The weight average molecular weight M _{w of} the homopolymers and / or copolymers to be used according to the invention as a molding composition for the production of the plastic substrates can vary within wide limits, the molecular weight usually being matched to the intended use and processing mode 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 particularly preferably 80,000 to 300,000 g / mol, without any intention that this should impose a restriction. This size can be determined, for example, by means of gel permeation chromatography.

Furthermore, the plastic substrates can be produced by casting chamber processes. For example, suitable (meth) acrylic mixtures are given in a mold and polymerized. Such (meth) acrylic mixtures generally have the (meth) acrylates set out above, in particular methyl methacrylate. Furthermore, the (meth) acrylic mixtures can contain the copolymers set out above and, in particular for adjusting the viscosity, polymers, in particular poly (meth) acrylates. The weight average molecular weight M _{w of} the polymers produced by casting 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 which are produced by casting chamber processes is in the range from 500,000 to 10,000,000 g / mol, without any intention that this should impose any restriction.

Preferred plastic substrates which have been produced by the casting chamber process can be obtained commercially from Röhm GmbH & Co. KG under the trade name © Plexiglas GS.

In addition, the molding compositions to be used for the production of the plastic substrates and the acrylic resins may contain all kinds of conventional additives. These include, among others, antistatic agents, antioxidants, mold release agents, flame retardants, lubricants, dyes, flow improvers, fillers, light stabilizers and organic phosphorus compounds such as phosphoric acid esters, phosphoric acid diesters and phosphoric acid monoesters, phosphites, phosphorinanes, phospholanes or phosphonates, pigments, weathering protection agents and plasticizers. However, the amount of additives is limited to the application.

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

The plastic substrate particularly preferably comprises at least 80% by weight, in particular at least 90% by weight, based on the total weight of the Substrates, poly (meth) acrylates, polycarbonates and / or cycloolefinic polymers. The plastic substrates particularly preferably consist of polymethyl methacrylate, it being possible for the polymethyl methacrylate to contain customary additives.

In accordance with a preferred embodiment, plastic substrates can have a sluice-iron viscosity of at least 10 kJ / m ² , preferably at least 15 U / m ² .

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

Before the plastic substrates are provided with a coating, these can be activated by suitable methods in order to improve the adhesion. For this purpose, for example, the plastic substrate can be treated with a chemical and / or physical method, the respective method being dependent on the plastic substrate.

The plastic bodies of the present invention are first provided with an adhesion-promoting intermediate layer (b) located between the plastic substrate and the inorganic coating.

The essential property of the adhesion-promoting layer is that it has a greater adhesive strength both to the plastic surface and to the water-spreading layer than the latter to the plastic surface. While there are numerous organic polymer materials that adhere well to a water-repellent plastic surface, sufficient adhesion to the water-spreading layer of certain j

Characteristics. These properties are based on polymers which have polar groups and are located in the adhesion-promoting layer, the polymers showing low solubility and low swellability in water. In general, the solubility of the polymers of the intermediate layer is less than 1 g / l.

This polarity can generally be achieved by polar groups, which can be part of the main chain and / or of side chains.

The polymer can thus be obtained by polyaddition or polycondensation reactions. These include, for example, polyethers, polyesters, polycarbonates, polyurethanes, epoxy resins and polyamides.

Another group of compounds suitable as a polymer are polyvinyl compounds. These include, for example, polyolefins, such as polypropylene, polyethylene; Polyaryl compounds such as polystyrene; Poly (meth) acrylates and polyvinyl acetates. Vinyl compounds suitable for the preparation of these polymers have been set out above.

In order for these polymers to have the adhesion promoting effect set out above, these polymers can comprise polar groups. These groups can be incorporated into the polymer, for example, by choosing suitable copolymers. Furthermore, these groups can also be grafted onto a polymer by graft copolymerization.

Particularly polar groups are hydroxyl, carboxyl, sulfonyl, carboxamide, nitrile and silanol groups. They are preferably part of a macromolecular compound which simultaneously contains non-polar groups, such as alkyl, alkylene, aryl or arylene groups. The ratio of polar to non-polar groups of the polymers must be chosen so that adhesion is achieved both to the water-repellent, ie non-polar, plastic surface and to the water-spreading, ie hydrophilic layer. The polarity must not be so great that the material of the adhesive layer itself would be water-soluble or water-swellable. The swelling when saturated with water at 20 ° is not more than 10% by volume and preferably not more than 2% by volume. However, the polarity of the polymers should also not be so low that the material would be soluble in completely non-polar solvents such as gasoline. Most suitable materials are soluble in limited polar organic solvents such as chlorinated hydrocarbons, esters, ketones, alcohols or ethers or their mixtures with aromatics.

The required balance of affinities for the two adjacent layers is generally achieved if the material of the adhesion-promoting layer contains 0.4 to 100 milliequivalents of polar groups per 100 g of the polymer material.

The polar groups differ in their polarizing effectiveness. This takes the order of nitrile, hydroxyl, prim. Carboxamide, carboxyl, sulfonyl, silanol too. The stronger the polarizing effect, the lower the required content in the polymer material. While from the weakly polar groups 4 to 100 m equivalent polar groups are used per 100 g of polymer material, 0.4 to 20 m equivalent / 100 g of the strongly polar groups are sufficient. If the content of polar groups is chosen too low, the water-spreading ones will not be sufficiently liable Layer reached. On the other hand, if the polar group content is too high, the water swellability increases too much, which in turn reduces the adhesion.

The polarity of the polymers obtained by polycondensation or polyaddition and comprising hydroxyl groups can be increased, inter alia, by reaction with silanes which have at least two hydrolyzable groups per silicon atom have such as halogen atom, alkoxy groups and / or aryloxy groups.

These compounds include tetraalkoxysilanes, for example tetramethoxysilane, tetraethoxysilane; Trialkoxysilanes, for example methyl-trimethoxysilane, methyl-triethoxysilane, ethyl-trimethoxysilane, n-propyl-trimethoxysilane, n-propyl-triethoxysilane, i-propyl-triethoxysilane; Dialkoxysilanes, for example dimethyldimethoxysilane, dimethyl-diethoxysilane, diethyl-dimethoxysilane, diethyl-diethoxysilane, di-n-propyl-dimethoxysilane, di-n-propyldiethoxysilane, di-i-propyl-dimethoxysilane, di-i-propylane diet.

According to the polymers which can be obtained by polycondensation or polyaddition, the polymers which can be obtained by radical polymerization of vinyl compounds can also be modified.

To modify these polyvinyl compounds, it is possible in particular to use silanes which comprise vinyl groups which cannot be hydrolyzed. The particularly suitable vinyl silane compounds include CH ₂ = CH-Si (OCH ₃ ) ₃ , CH ₂ = CH-Si (OC ₂ H ₅ ) ₃ , CH ₂ = CH-SiCl ₃ , CH ₂ = CH-Si ( CH ₃ ) (OCH ₃ ) ₂ , CH ₂ = CH-CO ₂ -C ₃ H ₇ -Si (OCH ₃ ) ₃ , CH ₂ = CH-CO ₂ -C ₃ H ₇ -Si (OCH ₃ ) ₃ , CH ₂ = C (CH ₃ ) -Cθ2-C ₃ H ₇ -Si (OCH ₃ ) ₃ , CH ₂ = C (CH3) -C0 ₂ -C ₃ H ₇ -Si (OC2H5) 3 and CH ₂ = C (CH3 ) -Cθ2-C ₃ H ₇ -SiCl3.

In addition, preference is given to polymers which have groups which lead to crosslinking during and / or after the formation of the intermediate layer (b). Silanes with 3 hydrolyzable groups and a vinyl group are particularly suitable for this purpose, examples of these silanes having been set out above. The polar polymers can be present individually or as a mixture in the adhesion-promoting intermediate layer (b).

The intermediate layer (b) can furthermore contain customary additives and additives. These include, in particular, flow control agents, which also include surfactants.

It is essential that this intermediate layer is obtained by application from a solution which has a solvent with an evaporation number less than or equal to 20, preferably less than or equal to 15. The evaporation number (VD) is the ratio of the evaporation time measured for the liquid to be tested and the evaporation time for diethyl ether (C- ₂ H ₅ OC- ₂ H ₅ ) as the reference liquid, the measuring conditions being described in DIN 53 170.

Such compounds are generally known and commercially available. Carboxylic acid esters are preferably used, ethyl acetate, propyl acetate and butyl acetate being particularly preferred.

According to a particular aspect of the present invention, the intermediate layer (b) is applied from a solution which comprises at least 70% by weight, preferably at least 90% by weight, of one or more solvents with an evaporation number less than or equal to 20.

According to a particular aspect of the present invention, when the plastic substrate comes into contact with the compounds with an evaporation number less than or equal to 20, the substrate softens. This softening effect of the compound with an evaporation number less than or equal to 20 can be determined by an increase in the haze value according to the Taber test (DIN 52347) after 10 revolutions. The test according to DIN 52347 is carried out with a contact force of 5.4 N, the friction wheels "CS10F" from Teledyne Taber being used. The haze value will according to section 5.3.1. Experimental arrangement A determined. For this purpose, the plastic substrate is immersed in an appropriate solvent for 60 minutes. Preferred compounds with an evaporation number less than or equal to 20 show a delta haze of at least 4%, preferably at least 6% and particularly preferably 6.8% in the subsequent Taber test after 10 revolutions of the friction wheel. The preferred substrate is in particular PMMA.

According to a further preferred embodiment, however, the plastic substrate does not become cloudy when the intermediate layer is applied. Accordingly, the connection with an evaporation number less than or equal to 20 should have the maximum possible contact time, the maximum contact time being given by the time period within which there is no clouding of the plastic substrate due to contact of the connections with an evaporation number less than or equal to 20. The limit of this exposure time can be determined by simple preliminary tests, the time being measured until a visible clouding of the plastic substrate occurs due to the action of the compound with an evaporation number less than or equal to 20. The turbidity caused by the contact compounds with an evaporation number less than or equal to 20 can be determined by an increase in the haze value of 20%, methods for determining the turbidity in DIN 52347, in particular Section 5.3.1. Experimental arrangement A are set out. This exposure time is preferably at least 60 minutes, preferably at least 240 minutes.

The coating mixtures described above can be applied to the plastic substrates using any known method. These include immersion processes, spray processes, doctor blades, flood coatings and roller or roller application. Flooding is particularly preferred.

The flood coating processes are known to the person skilled in the art. Generally, a liquid is poured over the material. The pressure is generally so low that the liquid hitting the substrate is none Droplet generated. Excess coating agent is collected in a tub and, if necessary, applied again using a filter. In general, the application takes place via nozzles, but the pressure is chosen to be relatively low. These nozzles are guided over the plate or along the edge of the plate via mechanical devices, so that the liquid applied with very low pressure creates a flood curtain that evenly coats the substrate. The amount of liquid and the feed with which the jet is guided over the substrate are selected so that the coating is applied evenly. More detailed information on this can be found in Brock / Groteklaes / Mischke "Textbook of coating technology", 2nd edition, 1998, Vincentz Verlag.

The coating compositions used for flooding generally contain a solids content in the range from 0.01 to 5% by weight, preferably in the range from 0.1 to 3% by weight, in order to achieve a low layer thickness.

The coatings applied in this way can generally be in a relatively short time, for example within 1 minute to 1 hour, generally within about 3 minutes to 30 minutes, preferably within about 5 minutes to 20 minutes and at a comparatively low temperature, for example Harden or dry at 70 - 110 ° C, preferably at approx. 80 ° C.

The layer thickness of the intermediate layer is not particularly critical, although the sum of the layer thicknesses of the inorganic coating (a) and the intermediate layer (b) may not exceed 700 nm. For economic reasons, however, this is chosen to be relatively low if possible, the lower limit resulting from the stability of the entire coating (a) and (b). In general, however, the thickness of the adhesion-promoting intermediate layer after curing is in a range from 50 nm to 400 nm, preferably 100 nm to 200 nm, without any intention that this should impose a restriction. The layer thicknesses of the coatings (a) and / or (b) can be determined by recording a transmission electron microscope (TEM), the mean value being generally determined via the integral of the layer surface. After the adhesion-promoting intermediate layer (b) has dried, a water-spreading inorganic coating (a) is applied thereon.

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

In the context of the present invention, the term inorganic means that the carbon content of the inorganic coating is at most 25% by weight, preferably at most 17% by weight and very particularly preferably at most 10% by weight, based on the weight of the inorganic coating (a ). This size can be determined using elementary analysis.

In particular, polysiloxanes, silane co-condensates and silica sols can be applied as the inorganic coating, the carbon content of which is limited to the ranges set out above.

Silane condensates which can be used to produce the coating (a) are known per se and are used for finishing polymeric glazing materials. Due to their inorganic character, they are characterized by good resistance to UV radiation and weather influences.

These silane condensates can be obtained, inter alia, by condensation or hydrolysis of organic silicon compounds of the general formula (I)

R ¹ nSiX ₄ . _n ^(l) 'in which R ^{1 is} a group having 1 to 20 carbon atoms, X is an alkoxy radical with 1 to 20 carbon atoms or a halogen and n is an integer from 0 to 3, preferably 0 or 1, various radicals X or R ¹ can each be the same or different.

The term "a group having 1 to 20 carbon atoms" denotes residues of organic compounds with 1 to 20 carbon atoms. It includes alkyl, cycloalkyl, aromatic groups, alkenyl groups and alkynyl groups with 1 to 20 carbon atoms, as well as heteroalipatic and heteroaromatic groups which, in addition to carbon and hydrogen atoms, have in particular oxygen, nitrogen, sulfur and phosphorus atoms. The groups mentioned can be branched or non-branched, the radical R ^{1 being} substituted or unsubstituted. The substituents include in particular halogens, groups having 1 to 20 carbon atoms, 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 the methyl, ethyl, propyl, isopropyl, 1-butyl, 2-butyl, 2-methylpropyl, tert-butyl, pentyl and 2-methylbutyl groups.

The preferred cycloalkyl groups include the cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the cyclooctyl group, which are optionally substituted with branched or unbranched alkyl groups. The preferred alkoxy groups include the methoxy, ethoxy, propoxy, butoxy, tert-butoxy, hexyloxy, 2-methylhexyloxy, decyloxy or dodecyloxy group.

The preferred cycloalkoxy groups include cycloalkoxy groups whose hydrocarbon radical is one of the preferred cycloalkyl groups mentioned above.

The radical R ¹ very particularly preferably represents a methyl or ethyl group.

With regard to 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. Group X is preferably a methoxy or ethoxy radical or a bromine or chlorine atom.

These compounds can be used individually or as a mixture to produce silane co-condensates.

At least 80% by weight, in particular at least 90% by weight, of the silane compounds used preferably have four alkoxy groups or halogen atoms, based on the weight of the condensable silanes.

Tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane and tetra-n-butoxysilane.

Tetramethoxysilane and tetraethoxysilane are particularly preferred. According to a particular aspect of the present invention, the proportion of these particularly preferred tetraalkoxysilanes is at least 80% by weight, in particular at least 90% by weight, based on the weight of the silane compounds used. According to a further aspect of the present invention, silane condensates can also be used which contain colloidally dissolved SiO ₂ particles. Such solutions can be obtained by the sol-gel process, in particular tetraalkoxysilanes and / or tetrahalosilanes being condensed.

Water-containing coating compositions are usually prepared from the aforementioned silane compounds by mixing organosilicon compounds with an amount of water sufficient for hydrolysis, i.e. > 0.5 mole of water per mole of the groups intended for hydrolysis, e.g. Alkoxy groups hydrolyzed, preferably with acid catalysis. As acids e.g. 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 are added, the pH of the hydrolysis reaction generally being between 2 and 4.5, preferably at 3 lies.

In general, an increase in temperature is evident after the reactants have been combined. In certain cases, it may be necessary to apply heat from the outside at the start of the reaction, for example by heating the batch to 40-50 ° C. In general, care is taken to ensure that the reaction temperature does not exceed 55 ° C. The reaction time is usually relatively short, it is usually less than one hour, for example 45 minutes.

The silane compounds can be condensed to give polymers which generally have a weight average molecular weight M _w in the range from 100 to 20,000, preferably 200 to 10,000 and particularly preferably 500 to 1500 g / mol. This molar mass can be determined, for example, by NMR spectroscopy. The condensation reaction can be stopped, for example, by cooling to temperatures below 0 ° C. or by increasing the pH with suitable bases, for example organic bases, such as amines, alkali metal or alkaline earth metal hydroxides.

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

The silane condensates which can be used according to the invention can contain 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 octoates or naphthenates. The proportion of the curing catalysts is generally 0.1-2.5% by weight, in particular 0.2-2% by weight, based on the total silane co-condensate, without any intention that this should impose a restriction. Zinc naphthenate, octoate, acetate, sulfate, etc. are particularly mentioned.

Furthermore, oxide layers, in particular semimetal and metal oxides, can also be used as the water-spreading coating (a). Suitable compounds include, in particular, oxides and hydroxides which are derived from silicon, aluminum, titanium, zirconium, zinc and / or chromium.

These oxides can be used individually or as mixtures, for example as mixed oxides. The solubility of these oxides and / or hydroxides in water should be as low as possible, for example the solubility in water at 20 ° should be less than 1000 g / l, preferably less than 200 yg / l.

These oxides can be applied, for example, in the form of colloidal solutions which are obtained by hydrolysis of alkoxy compounds. Such colloidal solutions are known for example from EP-A-0 149 182, EP-A-0 826 663, EP-A-0 850 203 and EP-1 022 318. The particle size of these oxide particles is not critical, but the transparency depends on the particle size. The particles preferably have a size of at most 300 nm, they being in particular in a range from 1 to 200 nm, preferably 1 to 50 nm.

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

Basic colloidal solutions are cheaper than acidic solutions. In addition, basic colloidal solutions of oxide particles are particularly simple and can be stored for a long time.

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

Furthermore, the coating compositions for producing the inorganic coating (a) can contain customary additives and processing aids. These include, in particular, leveling agents, which also include surfactants.

The previously described coating compositions for producing the inorganic coating (a) can be applied to the plastic substrates by any known method, which have been set out above by way of example.

Flooding processes are particularly preferred, although the selection of additives is limited to substances which have essentially no adverse effect on the water-spreading effect. Anionic flow control agents which have a high miscibility with water are preferably used. At 20 ° C. in particular, at least 10 g, preferably at least 50 g and particularly preferably at least 150 g are soluble in 1000 g of water without phase formation, in particular micelle formation.

In the context of the present invention, flow control agents are compounds which reduce the surface energy of water. According to a particular aspect of the present invention, an aqueous mixture comprising 0.1% by weight of leveling agents shows a surface tension at 20 ° C. which is at least 5 mN / m, preferably at least 10 mN / m and particularly preferably at least 15 mN / m below the surface tension of pure water. The surface tension can be determined with the Krüss interface tensiometer K8600 E / E according to Lecompte du Noüy according to DIN 53914.

Anionic leveling agents are known in the art, these leveling agents generally having carboxy, sulfonate and / or sulfate groups. These leveling agents preferably comprise at least one sulfonate group. To be distinguished from this are amphoteric leveling agents which, in addition to an anionic group, also comprise a cationic group.

The anionic leveling agents preferably comprise 2 to 20, particularly preferably 2 to 10, carbon atoms, it being possible for the organic radical to contain both aliphatic and aromatic groups. According to a particular aspect of the present invention, anionic leveling agents are used which comprise an alkyl or a cycloalkyl radical having 2 to 10 carbon atoms. The anionic leveling agents may have further polar groups, for example carboxy, thiocarboxy or imino, carboxylic acid ester, carbonic acid ester, thiocarboxylic acid esters, dithiocarboxylic acid ester, thiocarbonic acid ester, dithiocarbonic acid ester and / or dithiocarbonic acid amide groups.

Leveling agents of the formula (II) are particularly preferably used

wherein X is independently an oxygen or a sulfur atom, Y is a group of the formula OR ² , SR ² or NR ² , wherein R ^{2 is} independently an alkyl group with 1 to 5, preferably 1 to 3 carbon atoms and R ^{3 is} an alkylene group with 1 to 10, preferably 2 to 4 carbon atoms and M is a cation, in particular an alkali metal ion, in particular potassium or sodium, or an ammonium ion.

The addition of anionic leveling agents is limited to an amount that shows essentially no adverse effect on the water-spreading coating. In general, 0.01 to 1% by weight, in particular 0.03 to 0.1% by weight, of one or more anionic leveling agents is added to the coating composition, based on the total weight of the coating composition.

Such compounds can be obtained in particular from Raschig under the trade names Raschig OPX or Raschig DPS.

In addition to the anionic leveling agent, the coating composition can comprise further leveling agents, in particular nonionic leveling agents. Of these, ethoxylates are particularly preferred, esters and alcohols and phenols in particular Ethoxy groups can be used. These include nonylphenol ethoxylates.

The ethoxylates comprise in particular 1 to 20, in particular 2 to 8, ethoxy groups. The hydrophobic residue of the ethoxylated alcohols and esters preferably comprises 1 to 40, preferably 4 to 22 carbon atoms, it being possible to use both linear and branched alcohol and / or ester residues.

The addition of nonionic leveling aid is limited to an amount that shows essentially no adverse effect on the water-spreading coating. In general, 0.01 to 2% by weight, in particular 0.1 to 1% by weight, of one or more nonionic flow control agents is added to the coating composition, based on the total weight of the coating composition.

If both an anionic and a nonionic leveling aid are added to the coating composition to produce the inorganic coating, the weight ratio of anionic leveling aid to nonionic leveling aid is preferably in the range from 0.01: 1 to 1: 1, particularly preferably 0.05: 1 to 0.3: 1st

The lacquers applied in this way can generally be in a relatively short time, for example within 0.5 minute to 1 hour, generally within about 1 minute to 30 minutes, preferably within 3 minutes to 20 minutes and at a comparatively low temperature, for example Cure at 60 - 110 ° C, preferably at approx. 80 ° C, to create excellent adhesive coatings. The layer thickness of the inorganic coating (a) is relatively uncritical, but the sum of the layer thicknesses of the inorganic coating (a) and the intermediate layer (b) may not exceed 700 nm. In general, however, this size after curing is in a range from 50 nm to 600 nm, preferably 100 nm to 400 nm and particularly preferably 150 nm to 250 nm, without any intention that this should impose a restriction.

The sum of the sum of the layer thicknesses of the inorganic coating (a) and the intermediate layer (b) may not exceed 700 nm, this value preferably being in the range from 100 to 500 nm.

The plastic bodies of the present invention can be thermoformed very well without damaging their water-spreading coating. The shaping is known to the person skilled in the art. The plastic body is heated and shaped using a suitable template. The temperature at which the forming takes place depends on the softening temperature of the substrate from which the plastic body was produced. The other parameters, such as the forming speed and forming force, are also dependent on the plastic, these parameters being known to the person skilled in the art. Of the forming processes, bending forming processes are particularly preferred. Such methods are used in particular for processing cast glass. More detailed information can be found in "Acrylic glass and polycarbonate correct machining and processing" by H.Kaufmann et al. published by the technology transfer ring Handwerk NRW and in VDI guideline 2008 sheet 1 and DIN 8580/9 /.

The plastic bodies of the present invention provided with a water-spreading coating show a high abrasion resistance. The abrasion resistance according to DIN 53778 is preferably greater than or equal to 3,000 cycles, in particular greater than or equal to 5,000 cycles and particularly preferably greater than or equal to 10,000 cycles. According to a particular aspect of the present invention, the plastic body is transparent, the transparency TDÖS / I _O according to DIN 5033 being at least 70%, preferably at least 75%.

The plastic body preferably has a modulus of elasticity according to ISO 527-2 of at least 1000 MPa, in particular at least 1500 MPa, without this being intended to impose a restriction.

The plastic bodies according to the invention are generally very resistant to weathering. The weather resistance according to DIN 53387 (Xenotest) is at least 5000 hours.

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

The plastic bodies of the present invention can be used, for example, in the construction sector, in particular for producing greenhouses or conservatories, or as a noise barrier.

The invention is explained in more detail below by means of examples and comparative examples, without the invention being restricted to these examples. example 1

Preparation of the adhesion-promoting intermediate layer A copolymer of 87.6% methyl methacrylate and 12.4% gamma-methacryloyloxypropyltrimethoxysilane dissolved in butyl acetate, the solids content being 0.7% by weight, and by flooding in a thin layer on PMMA- Plates applied over a length of 3m. The evaporation number of butyl acetate is 11. After draining, the coated plate is dried in an oven at 80 ° C. for 20 minutes.

Production of the water-spreading layer

25 parts by weight of an anionic silica sol (solids content 30%; © Levasil available from Bayer AG) are mixed with 0.1 part by weight (O-ethyl-dithiocarbonic acid (3-sulfopropyl) ester, potassium salt; © Raschig OPX available from Raschig AG) and 0 , 4 parts by weight of an ethoxylated fatty acid alcohol (© Genapol X80) supplemented with deionized water to 100 parts by weight, adjusted to a pH of 9.5 with NaOH and coated by flooding in a thin layer on the plate provided with the adhesion-promoting layer. The flood path length was 3 m (plate length), the feed speed of the flood nozzle was 0.75 m / min.

After flashing off, the plate provided with an adhesion-promoting layer and a water-spreading layer is dried for 20 minutes at 80 ° C. in a forced-air drying cabinet.

The layer thickness of the extremely thin layers can be determined using a thin section in a transmission electron microscope. Depending on the direction of the flood, the thickness of the intermediate layer was in the range from 140 to 220 nm, that of the inorganic coating 170 to 270 nm. The determination of the adhesion of the coating was carried out in accordance with the wet abrasion test according to DIN 53778 with a wet abrasion tester from Gardner, model M 105 / A. A value of 10,000 cycles with a total layer thickness of 310 nm was determined (upper area of the coated plate, seen in the direction of the flood). With a total layer thickness of 490 nm, a value of 17000 cycles was determined (lower area of the plate)

The plastic body was also thermally formed. Thermal forming was carried out by heating the coated plates in a forced-air drying cabinet to 150-170 ° C. The choice of temperature depends on the heat resistance of the substrate. In the case of extruded PMMA, which in comparison to cast PMMA is characterized by plasticizing comonomers, e.g. Acrylates, distinguished and having a lower molecular weight, already suffice a lower temperature. In the case of cast PMMA, which has molecular weights of more than 1 million to several million, often consists of pure MMA homopolymer and is possibly weakly crosslinked, a higher temperature is used. After the plates have softened, they are bent over a semicircular shape with a predetermined radius of curvature and left to cool, with further details on bending forming in "Acrylic glass and polycarbonate correct machining and processing" by H.Kaufmann et al. published by Technologie-Transfer-Ring Handwerk NRW. After forming with a bending radius of 47.5 mm, the plates produced according to Example 1 have no clouding or cracks in the coating and spread water well with low contact angles.

The water spread can only be assessed visually on the curved substrates, since curved samples can no longer be measured in the goniometer. It was assessed qualitatively as good. A wet scrub test cannot be carried out on the curved samples either, since this also requires flat substrates.

Comparative Example 1

Example 1 was essentially repeated, except that the adhesion-promoting intermediate layer composed of a mixture of the copolymer with MOP (1-methoxypropanol-2) was applied by flooding. The evaporation rate of MOP is 22.

The layer thicknesses of the coatings were identical to those of Example 1. The water spread was also good.

The abrasion resistance was also 10,000 to 17,000 cycles, depending on the flow path length of the solution during flooding. Thermal deformation showed severe clouding, although the visually assessed water spread was poor.

Claims

claims

1. Formable, water-spreading plastic body comprising a plastic substrate, at least one water-spreading, inorganic coating (a) and an adhesion-promoting intermediate layer (b) located between the plastic substrate and the inorganic coating, obtainable by making the intermediate layer (b) from a mixture with a solvent which has an evaporation number less than or equal to 20, the sum of the layer thicknesses of the inorganic coating (a) and the intermediate layer (b) being at most 700 nm.

2. Plastic body according to claim 1, characterized in that the solvent has an evaporation number less than or equal to 15.

3. Plastic body according to claim 1 or 2, characterized in that the mixture from which the intermediate layer is applied comprises at least 70% by weight of a solvent which has an evaporation number less than or equal to 20.

4. Plastic body according to one of the preceding claims, characterized in that the compound having an evaporation number less than or equal to 20 has a delta haze of at least 6% after an exposure time of 60 minutes and 10 friction wheel rotations.

5. Plastic body according to one of the preceding claims, characterized in that the solvent is a carboxylic acid ester.

6. Plastic body according to one of the preceding claims, characterized in that the plastic substrate comprises cycloolefin copolymers, polyethylene terephthalates, polycarbonates and / or poly (meth) acrylates.

7. Plastic body according to one of the preceding claims, characterized in that the plastic substrate consists of polymethyl methacrylate.

8. Plastic body according to one of the preceding claims, characterized in that the plastic substrate has an impact strength of at least 10 kJ / m ² according to ISO 179/1.

9. Plastic body according to one of the preceding claims, characterized in that the plastic substrate has a thickness in the range of

1 mm to 200 mm.

10. Plastic body according to one or more of the preceding claims, characterized in that the thickness of the adhesion-promoting intermediate layer (b) is in the range of 50 and 400 nm.

11. Plastic body according to one or more of the preceding claims, characterized in that the adhesion-promoting intermediate layer comprises vinyl polymers modified with polar groups.

12. Plastic body according to one of the preceding claims, characterized in that the carbon content of the inorganic coating (a) is at most 17 wt .-%, based on the weight of the coating (a).

13. Plastic body according to one of the preceding claims, characterized in that the inorganic coating (a) is obtainable by curing colloidal solutions of inorganic and / or organometallic compounds.

14. Plastic body according to one of the preceding claims, characterized in that the inorganic coating (a) is obtainable by condensation of a composition which is at least 80 % By weight of alkyltrialkoxysilanes and / or tetraalkoxysilanes, based on the content of condensable silanes.

15. Plastic body according to one of the preceding claims, characterized in that the layer thickness of the coatings (a) and (b) is in the range from 100 to 500 nm.

16. Plastic body according to one or more of the preceding claims, characterized in that the abrasion resistance of the plastic body according to DIN 53778 is at least 10,000 cycles.

17. Plastic body according to one of the preceding claims, characterized in that the plastic body has a modulus of elasticity according to ISO 527-2 of at least 1500 MPa.

18. Plastic body according to one of the preceding claims, characterized in that the plastic body has a weather resistance according to DIN 53 387 of at least 5000 hours.

19. Plastic body according to one or more of the preceding claims, characterized in that the plastic body has a transparency according to DIN 5033 of at least 70%.

20. A process for the production of water-spreading plastic bodies according to one or more of claims 1 to 19, characterized in that a) an adhesion-promoting coating (b) made from a mixture with a compound which has an evaporation number less than or equal to 20 is applied to a plastic substrate and cures, and then b) a water-spreading, inorganic coating (a) is applied and cured.

21. The method according to claim 20, characterized in that the Coating b) applied by flooding.

22. The method according to claim 20 or 21, characterized in that the coating (a) is applied by flooding.