WO2008058678A1 - Coating materials comprising reactive ester waxes and mixed-oxide nanoparticles - Google Patents

Abstract

What are claimed are coating materials, more particularly varnishes, which comprise reactive ester waxes and mixed-oxide nanoparticles consisting of 50% to 99.9% by weight of aluminium oxide and 0.1% to 50% by weight of oxides of elements of main group I or II of the Periodic Table of the Elements, these nanoparticles being surface-modified with a silane or siloxane.

Description

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description

Coating compositions containing reactive ester waxes and mixed oxide nanoparticles

Nanoparticles containing coating compositions are known, wherein the nanoparticles are prepared by sol-gel technique by hydrolytic (co) condensation of tetraethoxysilane (TEOS) with other metal alkoxides in the absence of organic and / or inorganic binders. From DE 199 24 644 it is known that the sol-gel synthesis can also be carried out in the medium. Radiation-curing formulations are preferably used. However, all materials produced by sol-gel process are characterized by low solids contents of inorganic and organic substance, by increased amounts of the condensation product (usually alcohols), by the presence of water and by limited storage stability.

Progress is made by the high-temperature-resistant, reactive metal oxide particles produced by hydrolytic condensation of metal alkoxides on the surface of nanoscale inorganic particles in the presence of reactive binders. The temperature resistance of the reacted formulations is achieved by the heterogeneous copolymerization of reactive groups of the medium with similar reactive groups of the binder. The disadvantage here is the incompleteness of the heterogeneous copolymerization, in which not all reactive groups on the surface of the particles enter the copolymerization. Reason are mainly steric hindrance. However, it is known that the unreacted groups lead to undesired secondary reactions, which can cause discoloration, embrittlement or premature degradation. This is especially true for high temperature applications. The process described in DE 198 46 660 also leads to non-storage-stable systems due to the acidic medium in the presence of the condensation product (usually alcohols). Also known are nanoscale surface-modified particles (Degussa Aerosil ^® R 7200), which are obtained by condensation of metal oxides with silanes in the absence of a binder and hence in the absence of strong shear forces, as they act in viscous media at stirring speeds of> 10 m / s. For this reason, these aerosils have larger particles than the raw materials used, their opacity is markedly higher and their effectiveness is lower than that of the particles described in WO 00/22052 and the paints prepared therefrom.

From DE 100 03 118 certain reactive ester waxes are known and their use as an additive in surface coatings, such as paints.

By combining mixed oxide nanoparticles and reactive ester waxes, for example in the form of micronized wax or as emulsion polymer, the properties which are caused by waxes can be combined with the effect of the nanoparticles and even improved.

The invention relates to coating compositions containing reactive ester waxes and mixed oxide nanoparticles consisting of 50 to 99.9 wt .-% alumina and 0.1 to 50 wt .-% oxides of elements of the I. or II. Main group of the Periodic Table, said nanoparticles modified with a silane or siloxane on the surface.

The aluminum oxide in the mixed oxide nanoparticles is preferably present in the rhombohedral α-modification (corundum). The mixed oxides according to the present invention preferably have a particle size of less than 1 μm, preferably less than 0.2 μm and particularly preferably between 0.001 and 0.1 μm.

Particles of this size according to the invention are to be referred to below as

Mixed oxide nanoparticles are called.

The mixed oxide nanoparticles used according to the invention can be prepared by different processes described below.

These process descriptions refer to the production of pure only Aluminum oxide particles, but it goes without saying that in all these process variants in addition to Al-containing starting compounds and those compounds of elements of the I. or II. Main group of the Periodic Table must be present in order to form the mixed oxides. For this purpose, especially the chlorides, but also the oxides, oxide chlorides, carbonates, sulfates or other suitable salts come into question. The amount of such oxide formers is such that the finished nanoparticles contain the aforementioned amounts of oxide MeO.

Quite generally, in the preparation of the nanoparticles according to the invention, larger agglomerates of these mixed oxides are used, which are then deagglomerated to the desired particle size. These agglomerates can be prepared by methods described below.

Such agglomerates can be prepared, for example, by various chemical syntheses. These are usually precipitation reactions (hydroxide precipitation, hydrolysis of organometallic compounds) with subsequent calcination. Crystallization seeds are often added to reduce the transition temperature to the α-alumina. The sols thus obtained are dried and thereby converted into a gel. The further calcining then takes place at temperatures between 350 ° C and 650 ° C. For the conversion to Ot-Al ₂ O ₃ must then be annealed at temperatures around 1000 ⁰ C. The processes are described in detail in DE 199 22 492.

Another way is the aerosol process. The desired molecules are obtained from chemical reactions of a Precursorgases or by rapid cooling of a supersaturated gas. The formation of the particles occurs either through collision or the constant equilibrium evaporation and condensation of molecular clusters. The newly formed particles grow by further collision with product molecules (condensation) and / or particles (coagulation). If the coagulation rate is greater than that of the new growth or growth, agglomerates of spherical primary particles are formed. Flame reactors represent a production variant based on this principle. Nanoparticles are formed here by the decomposition of precursor molecules in the flame at 1500 ^° C.-2500 ^° C. As examples, the oxidations of TiCl ₄ ; SICI ₄ and Si ₂ O (CH ₃ ) ₆ in methane / O ₂ flames leading to TiO ₂ and SiO ₂ particles. When using AICI ₃ so far only the corresponding clay could be produced. Flame reactors are now used industrially for the synthesis of submicroparticles such as carbon black, pigment TiO ₂ , silica and alumina.

Small particles can also be formed from drops with the help of centrifugal force, compressed air, sound, ultrasound and other methods. The drops are then converted into powder by direct pyrolysis or by in situ reactions with other gases. As known methods, the spray and freeze drying should be mentioned. In spray pyrolysis, precursor drops are transported through a high temperature field (flame, oven), resulting in rapid evaporation of the volatile component or initiating the decomposition reaction to the desired product. The desired particles are collected in filters. As an example, the production of BaTiO ₃ from an aqueous solution of barium acetate and titanium lactate can be mentioned here.

By grinding can also be attempted to crush corundum and thereby produce crystallites in the nano range. The best grinding results can be achieved with stirred ball mills in a wet grinding. In this case, grinding beads must be used from a material that has a greater hardness than corundum.

Another way to produce corundum at low temperature is the conversion of aluminum chlorohydrate. This is also to seed with added, preferably from Feinstkorund or hematite. To avoid crystal growth, the samples must be kaliziniert to 700 ° C up to 900 ⁰ C at temperatures. The duration of the calcination is at least four hours. Disadvantage of this method is therefore the big one D

Time and the residual amounts of chlorine in the alumina. The method has been described in detail in Ber. DKG 74 (1997) no. 11/12, p. 719-722.

From these agglomerates, the nanoparticles must be released. This is preferably done by grinding or by treatment with ultrasound. According to the invention, this deagglomeration is carried out in the presence of a solvent and a coating agent, preferably a silane or siloxane, which saturates the resulting active and reactive surfaces during the milling process by a chemical reaction or physical attachment and thus prevents reagglomeration. The nano-mixed oxide remains as a small particle. It is also possible to add the coating agent after deagglomeration.

Preferably, in the preparation of the mixed oxides, agglomerates are used which, as described in Ber. DKG 74 (1997) no. 11/12, pp. 719-722, as previously described.

The starting point here is aluminum chlorohydrate, which has the formula A 1 (OH) _x Cl y, where x is a number from 2.5 to 5.5 and y is a number from 3.5 to 0.5 and the sum of x and y is always 6 amounts to. This aluminum chlorohydrate is mixed with crystallization seeds as an aqueous solution, then dried and then subjected to a thermal treatment (calcination).

Preference is given to starting from about 50% aqueous solutions, as they are commercially available. Such a solution is mixed with nuclei which promote the formation of the α-modification of Al ₂ O ₃ . In particular, such nuclei cause a lowering of the temperature for the formation of the α-modification in the subsequent thermal treatment. As germs are preferably in question finely disperse corundum, diaspore or hematite. Particular preference is given to using finely divided α-Al ₂ O ₃ nuclei having an average particle size of less than 0.1 μm. In general, 2 to 3 wt .-% of germs based on the resulting alumina from. This starting solution additionally contains oxide formers in order to produce the oxides MeO in the mixed oxide. For this purpose, especially the chlorides of the elements of the I. and II. Main group of the Periodic Table, in particular the chlorides of the elements Ca and Mg, but also other soluble or dispersible salts such as oxides, oxychlorides, carbonates or sulfates. The amount of oxide generator is such that the finished nanoparticles contain from 0.01 to 50% by weight of the oxide Me. The oxides of the I. and II. Main group may be present as a separate phase in addition to the alumina or with this real mixed oxides such as spinels, etc. form. The term "mixed oxides" in the context of this invention should be understood to include both types.

This suspension of aluminum chlorohydrate, germs and oxide formers is then evaporated to dryness and subjected to a thermal treatment (calcination). This calcination is carried out in suitable devices, for example in push-through, chamber, tube, rotary kiln or microwave ovens or in a fluidized bed reactor. According to a variant of the method according to the invention, it is also possible to inject the aqueous suspension of aluminum chlorohydrate, oxide formers and germs directly into the calcining apparatus without prior removal of the water.

The temperature for the calcination should not exceed 1400 ⁰ C. The lower temperature limit depends on the desired yield of nanocrystalline mixed oxide, the desired residual chlorine content and the content of germs. The formation of the nanoparticles begins at about 500 ⁰ C, but to keep the chlorine content low and the yield of nanoparticles high, but you will work preferably at 700 to 1100 ° C, especially at 1000 to 1100 ° C.

It has surprisingly been found that for calcination generally less than 30 minutes, preferably 0.5 to 10, in particular 0.5 to 5 minutes are sufficient. Already after this short time under the conditions given above for the preferred temperatures, a sufficient yield of nanoparticles can be achieved. But you can also according to the information in Ber. DKG 74 (1997) no. 11/12, p. 722 for 4 hours at 700 ⁰ C or 8 hours at 500 ⁰ C calcine.

During calcination, agglomerates accumulate in the form of nearly spherical nanoparticles. These particles consist of Al ₂ O ₃ and MeO. The content of MeO acts as an inhibitor of crystal growth and keeps the crystallite size small. As a result, the agglomerates, as obtained by the calcination described above, clearly differ from the particles used in the process described in WO 2004/069 400, which are coarser, inherently homogeneous particles and not agglomerates of pre-fabricated nanoparticles.

To obtain nanoparticles, the agglomerates are preferably comminuted by wet grinding in a solvent, for example in an attritor mill, bead mill or stirred mill. Thus, for example, after a two-hour grinding, a suspension of nanoparticles having a d50 value of less than 100 nm is obtained. Another possibility for deagglomeration is sonication.

For modifying the surface of these nanoparticles with

Coating agents, such as e.g. Silanes or siloxanes there are two possibilities. According to the first preferred variant, deagglomeration can be carried out in the presence of the coating agent, for example by adding the coating agent to the mill during milling. A second possibility consists of first destroying the agglomerates of the nanoparticles and then treating the nanoparticles, preferably in the form of a suspension in a solvent, with the coating agent.

Suitable solvents for deagglomeration are both water and conventional solvents, preferably those which are also used in the paint industry, such as alcohols, in particular methanol, ethanol, isopropanol or 1-butanol, ketones, in particular acetone, methyl ethyl ketone or methyl isobutyl ketone , Ethers, in particular tetrahydrofuran or esters, O

in particular ethyl acetate, butyl acetate or methoxypropyl acetate. When deagglomerating in water, an inorganic or organic acid, for example HCl, HNO3, formic acid or acetic acid, should be added to stabilize the resulting nanoparticles in the aqueous suspension. The amount of acid may be 0.1 to 5 wt .-%, based on the mixed oxide. From this aqueous suspension of the acid-modified nanoparticles is then preferably the grain fraction having a particle diameter of less than 20 nm separated by centrifugation. Subsequently, at elevated temperature, for example at about 100 ^° C., the coating agent, preferably a silane or siloxane, is added. The nanoparticles thus treated precipitate, are separated and dried to a powder, for example by freeze-drying.

Suitable coating agents here are preferably silanes or siloxanes or mixtures thereof.

In addition, suitable coating agents are all substances which can bind physically to the surface of the mixed oxides (adsorption) or which can bond to form a chemical bond on the surface of the mixed oxide particles. Since the surface of the mixed oxide particles is hydrophilic and free hydroxy groups are available, suitable coating agents are alcohols, compounds having amino, hydroxyl, carbonyl, carboxyl or mercapto functions, silanes or siloxanes. Examples of such coating compositions are polyvinyl alcohol, mono-, di- and tricarboxylic acids, amino acids, amines, waxes, surfactants, hydroxycarboxylic acids, organosilanes and organosiloxanes.

Suitable silanes or siloxanes are compounds of the formulas

a) R [-Si (R'R ") - O-] n Si (R ¹ R ¹¹ JR" ¹ or cyclo - [-Si (R'R ") - O-] _r Si (R'R") -O-

Wonn y

R, R ¹ , R ", R ¹ " - identical or different from each other, an alkyl radical having 1-18 C atoms or a phenyl radical or an alkylphenyl or a phenylalkyl radical having 6 - 18 C-atoms or a radical of the general formula - ( C _m H _{2 m} -O) p-C q H ₂ q ₊ i or a radical of the general formula C _s H _{2 S} y or a radical of the general formula -XZ _t- i,

n is an integer meaning 1 ≦ n <1000, preferably 1 <n <100, m is an integer 0 <m <12 and p is an integer 0 <p <60 and q is an integer 0 <q <40 and r is an integer 2 <r <10 and s is an integer 0 <s <18 and

Y is a reactive group, for example α, β-ethylenically unsaturated groups, such as (meth) acryloyl, vinyl or allyl groups, amino, amido, ureido, hydroxyl, epoxy, isocyanato, mercapto, sulfonyl, Phosphonyl, trialkoxylsilyl,

Alkyldialkoxysilyl, dialkylmonoalkoxysilyl, anhydride and / or carboxyl groups,

Imido, imino, sulfite, sulfate, sulfonate, phosphine, phosphite, phosphate,

Phosphonate groups and

X is a .functional oligomer with t an integer 2 <t <8 and

Z in turn a rest

R [-Si (R'R ") - O-] _n Si (R ¹ R") - ^ "or cyclo - [- Si (R ¹ FT) -O-Jr Si (R ¹ FT) -O- as defined above.

The t-functional oligomer X is preferably selected from:

Oligoether, oligoester, oligoamide, oligourethane, oligohamine, oligoolefin, oligovinyl halide, oligovinylidenedihalogenide, oligoimine, oligovinyl alcohol, esters, acetal or ethers of oligovinyl alcohol, cooligomers of maleic anhydride, oligomers of (meth) acrylic acid, oligomers of (meth) acrylic acid esters,

Oligomers of (meth) acrylic acid amides, oligomers of (meth) acrylic acid imides, oligomers of (meth) acrylonitrile, particularly preferably oligoethers, oligoesters, oligourethanes. Examples of radicals of oligoethers are compounds of the type - (C _a H _2a -O) _b - C ₃ H ₂₃ - or O- (C _a H _2a -O) _b -C _a H ₂ aO with 2 <a <12 and 1 <b <60, for example a diethylene glycol, triethylene glycol or tetraethylene glycol residue, a dipropylene glycol, tripropylene glycol, tetrapropylene glycol residue, a dibutylene glycol, tributylene glycol or tetrabutylene glycol residue. Examples of residues of Oligoestem are compounds of the type -C _b H _2b - (C (CO) C ₃ H ₂₃ - (CO) O- C _b H _2b -) _c - or -OC _b H _2b - (C (CO ) C ₃ H ₂₃ - (CO) O-

C _b H _2b -) _c -O- with a and b different or equal to 3 <a ≤ 12, 3 <b <12 and 1 <c <30, eg an oligoester of hexanediol and adipic acid.

b) organosilanes of the type (RO) ₃ Si (CH ₂ ) _m -R 'R = alkyl, such as methyl, ethyl, propyl, m = 0.1-20 R ¹ = methyl, phenyl, -C ₄ F ₉ ; OCF ₂ -CHF-CF ₃ , -C ₆ F ₁₃ , -O-CF ₂ -CHF ₂

-NH ₂ , -N ₃ , SCN, -CH = CH ₂ , -NH-CH ₂ -CH ₂ -NH ₂ ,

-N- (CH ₂ -CH ₂ -NH ₂ ) ₂

-OOC (CH ₃ ) C = CH ₂

-OCH ₂ -CH (O) CH ₂ -NH-CO-N-CO- (CH ₂ ) ₅

-NH-COO-CH ₃ , -NH-COO-CH ₂ -CH ₃ , -NH- (CH ₂ ) ₃ Si (OR) ₃

SH

-NR ¹ R ¹¹ R " ¹ (R ¹ = alkyl, phenyl; R" = alkyl, phenyl; R " ¹ = H, alkyl, phenyl, benzyl,

C ₂ H ₄ NR ¹¹¹¹ with R "" = A, alkyl and R = H, alkyl).

Examples of silanes of the type defined above are, for. Hexamethyldisiloxane, octamethyltrisiloxane, other homologous and isomeric compounds of the series Si _n O _n -I (CH 2) ₂ n _{+ 2} , where n is an integer 2 <n <1000, e.g. B. Polydimethylsiloxane 200® fluid (20 cSt). Hexamethylcyclotrisiloxane, octamethylcyclo tetrasiloxane, other homologous and isomeric compounds of the series (Si-O) _r (CH ₃ ) 2r, where r is an integer 3 <r <12, dihydroxytetramethydisiloxane, dihydroxyhexamethyltrisiloxane,

Dihydroxyoctamethyltetrasiloxane, other homologous and isomeric compounds of the series

HO - [(Si-O) _n (CH ₃ ) _2n ] -Si (CH ₃ ) ₂ -OH or HO - [(Si-O) _n (CH ₃ ) _2n HSi-O) _m (C ₆ H ₅ ) _2m ] -Si (CH ₃ ) ₂ -OH, where m is an integer 2 <m <1000, preferably the α, ω-dihydroxypolysiloxanes, z. Polydimethylsiloxane (OH end groups, 90-150 cSt) or polydimethylsiloxane-co-diphenylsiloxane (dihydroxy end groups, 60 cST).

Dihydrohexamethytrisiloxane, Dihydrooctamethyltetrasiloxan other homologous and isomeric compounds of the series H - [(Si-O) _n (CH ₃ ) _2n ] -Si (CH ₃ ) ₂ -H, where n is an integer 2 <n <1000, preferred are the α, ω-dihydropolysiloxanes, e.g. B. polydimethylsiloxane (hydride end groups, M _n = 580).

Di (hydroxypropyl) hexamethyltrisiloxane, dihydroxypropyl) octamethyltetrasiloxane, other homologous and isomeric compounds of the series HO- (CH ₂ ) _u [(Si-O) n (CH ₃ ) ₂ (CH ₂ ) u-OH, the α, ω are preferred -Dicarbinolpolysiloxanes with 3 <u <18, 3 <n <1000 or their polyether-modified successor compounds based on ethylene oxide (EO) and propylene oxide (PO) as homo- or mixed polymer HO- (EO / PO) _v - (CH ₂ ) u [(Si-O) _t (CH ₃ ) 2t] -Si (CH ₃ ) ₂ (CH ₂ ) _u - (EO / PO) _v -OH, preferred are α, ω-di (carbinol polyether) -polysiloxanes with 3 <n <1000, 3 <u <18, 1 <v <50.

Instead of α, ω-OH groups are also the corresponding difunctional compounds with epoxy, isocyanato, vinyl, AIIyI- and di (meth) acryloyl used, for. B. Polydimethylsiloxan with vinyl end groups (850 - 1150 cST) or TEGORAD 2500 from. Tego Chemie Service. There are also the esterification of ethoxylated / propoxylated trisiloxanes and higher siloxanes with acrylic acid copolymers and / or maleic acid copolymers as a modifying compound in question, z. B. BYK Silclean 3700 from Byk Chemie or TEGO® Protect 5001 from Tego Chemie Service GmbH.

Instead of α, ω-OH groups are also the corresponding difunctional compounds with -NHR "" with R "" = H or alkyl used, for. For example, the well-known aminosilicone oils from Wacker, Dow Corning, Bayer, Rhodia, etc., which are distributed randomly on the polysiloxane chain (cyclo), are used.

Carry alkylamino groups or (cyclo) alkylimino groups on their polymer chain.

Organosilanes of the type (RO) ₃ Si (CnH ₂ n + i) and (RO) ₃ Si (C _n H _{2n +} I), wherein R is an alkyl, such as. For example, methyl, ethyl, n-propyl, i-propyl, butyl n I to 20.

Organosilanes of the type R'x (RO) ySi (CnH2n + 1) and (RO) 3Si (CnH2n + 1), wherein

R is an alkyl, such as. Methyl, ethyl, n-propyl, i-propyl, butyl,

R ^{1 is} an alkyl, such as. For example, methyl, ethyl, n-propyl, i-propyl, butyl, R ^{1 is} a cycloalkyl n is an integer of 1 - 20 x + y 3 x 1 or 2 y 1 or 2.

Organosilanes of the type (RO) ₃ Si (CH ₂ ) (TrR ¹ , where

R is an alkyl, such as. As methyl, ethyl, propyl, m is a number between 0.1 - 20

R ^{1 is} methyl, phenyl, -C ₄ F ₉ ; OCF ₂ -CHF-CF ₃ , -C ₆ Fi ₃ , -O-CF ₂ -CHF ₂ , -NH ₂ , -N ₃ , -SCN, -CH = CH ₂ , -NH-CH ₂ -CH ₂ -NH ₂ , -N- (CH ₂ -CH ₂ -NH ₂ ) ₂ ,

-OOC (CH ₃ ) C = CH ₂ , -OCH ₂ -CH (O) CH ₂ , -NH-CO-N-CO- (CH ₂ ) ₅ ,

-NH-COO-CH ₃ , -NH-COO-CH ₂ -CH ₃ ,

-NH- (CH ₂ ) ₃ Si (OR) ₃ , -S _x - (CH ₂ ) ₃ ) Si (OR) ₃ , -SH-NR ¹ R ¹¹ R ¹ "(R ¹ = alkyl, phenyl; R "= alkyl, phenyl, R ¹¹¹ = H, alkyl, phenyl, benzyl, C ₂ H ₄ NR ¹¹¹¹ R" ¹ "with R ¹ " ¹ = A, alkyl and R = H, alkyl).

Preferred silanes are the silanes listed below: triethoxysilane, octadecyltimethoxysilane,

3- (trimethoxysilyl) -propylmethacrylate, 3- (trimethoxysilyl) -propylacrylate, 3- (trimethoxysilyl) -methylmethacrylate, 3- (trimethoxysilyl) -methylacrylate, 3- (trimethoxysilyl) -ethylmethacrylate, 3- (trimethoxysilyl) -ethylacrylate, 3- (Trimethoxysilyl) pentyl methacrylates, 3- (trimethoxysilyl) pentyl acrylates, 3- (trimethoxysilyl) hexyl methacrylates, 3- (trimethoxysilyl) hexacrylates, 3- (trimethoxysilyl) butyl methacrylates, 3- (trimethoxysilyl) butyl acrylates, 3- (trimethoxysilyl ) -heptylmethacrylate, 3- (trimethoxysilyl) -heptylacrylate, 3- (trimethoxysilyl) -octylmethacrylate, 3- (trimethoxysilyl) -octylacrylate, Methyltrimethoxysilane, Methyltriethoxysilane, Propyltrimethoxisilane, Propyltriethoxisilane, Isobutyltrimethoxisilane, Isobutyltriethoxysilane, Octyltrimethoxysilane, Octyltriethoxysilane, Hexadecyltrimethoxysilane, Phenyltrimethoxysilane, Phenyltriethoxysilane, Tridecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilanes, tetramethoxysilanes, tetraethoxysilanes, oligomeric tetraethoxysilanes (DYNASIL® 4 0 Degussa), tetra-n-propoxysilane,

3-glycidyloxypropyltrimethoxysilanes, 3-glycidyloxypropyltriethoxysilanes,

3-methacryloxypropyltrimethoxysilanes, vinyltrimethoxysilanes, vinyltriethoxysilanes,

3-Mercaptopropyltrimethoxysilane,

3-aminopropyltriethoxysilanes, 3-aminopropyltrimethoxysilanes, 2-aminoethyl-3-aminopropyltrimethoxysilanes, triaminofunctional propyltrimethoxysilanes (DYNASYLAN® TRIAMINO from Degussa), N- (n-butyl-3-aminopropyltrimethoxysilanes, 3-aminopropylmethyldiethoxysilanes.

The coating compositions, in particular the silanes or siloxanes, are preferably added in molar ratios of mixed oxide nanoparticles to silane or siloxane of from 1: 1 to 10: 1. The amount of solvent in the deagglomeration is generally 50 to 90 wt .-%, based on the total amount of mixed oxide nanoparticles and solvent. The deagglomeration by grinding and simultaneous modification with the Besen ichtungsmittel preferably takes place at temperatures of 20 to 150 ⁰ C, more preferably at 20 to 90 ⁰ C.

If deagglomeration is carried out by grinding, the suspension is subsequently separated from the grinding beads.

After deagglomeration, the suspension can be heated to complete the reaction for up to 30 hours. Finally, the solvent is distilled off and the remaining residue is dried. It may also be advantageous to leave the modified mixed oxide nanoparticles in the solvent, to convert them into a solvent desired for the application and to use the dispersion for further applications.

It is also possible to use the mixed oxide nanoparticles in the corresponding

Suspend solvents and perform the reaction with the coating agent after deagglomeration in a further step.

The surface-modified mixed oxide nanoparticles prepared in this way are incorporated with the reactive ester waxes in any desired coating compositions.

The amount of such nanoparticles in the coating compositions is usually 1 to 8, preferably 2 wt .-%.

The reactive ester waxes in the context of the present invention are reaction products of a polyol, long-chain aliphatic carboxylic acids and at least one ethylenically unsaturated carboxylic acid, which may be oligomerized by the addition of a dicarboxylic acid. As long-chain aliphatic carboxylic acids, it is possible to use all carboxylic acids having more than 7 carbon atoms, but preferably C ₈ -C ₂₂ -fatty acids and C ₂₂ -C ₅ -O-wax acids, either in pure form or else preferably in the form of mixtures of technical products such as coconut fatty acid, Tallow fatty acid, sunflower acid, montan wax acid, paraffin oxidate or olefin oxidate. to Molgewichtsvergrößerung the mixtures of long-chain carboxylic acids may still be mixed with small amounts of dicarboxylic acids such as adipic acid, dodecanedioic acid, Montanwachsdicarbonsäuren.

As polyols, polyhydric aliphatic alcohols having 2 to 10

Carbon atoms and 2 to 10 OH groups are used, such as glycols, glycerol, trimethylolpropane, glycerol, pentaerythritol, sugar alcohols, sorbitol and their internal ethers such as sorbitans, their oligomers such as diglycerol, dipentaerythritol, their polymers such as polyglycols or polyglycerols or the alkoxylates of said polyols.

As ethylenically unsaturated carboxylic acids, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid, and their anhydrides or esters can be used. The stoichiometry is chosen so that one mole of polyol fatty acid partial ester is reacted with one mole of the unsaturated carboxylic acid.

The reactive ester wax is exemplified on the reaction product of pentaerythritol, a mixture of long-chain aliphatic carboxylic acids based on technical montan wax acid and acrylic acid:

CH ₂ OR _n i

H ₂ C = CH-OC-OH ₂ CC-CH ₂ O-CO-Rm

CH ₂ O-CO-R _m

R _n = H, CO-R _m , R _m = alkyl radical of montan wax acid

The preparation of the reactive ester wax can be carried out by reacting the polyol with the long-chain aliphatic carboxylic acid to a partial ester, this can be further converted by esterification with a dicarboxylic acid to a polyester wax. An ethylenically unsaturated acid is then bound via esterification to this partial ester component, so that a solid reactive product having a melting point between 40 and 90 ^° C. is formed. Such reactive compounds are described in DE 100 03 118 and T b

commercially available eg under the name ^® Licomont ER 165 (Clariant). The amount of reactive ester wax in the coating compositions is generally 2 to 10, preferably 2 to 4 wt .-%.

The coating compositions of the invention, which are preferably paints, especially radiation-curable coatings, also contain conventional and known binders.

For this purpose, in particular highly reactive acrylates with different molecular weight distribution in question. In addition, such paints still contain

Reactive thinner such as DPGDA, TPGDA, HDDA, TMPTA as well as photoinitiators and various additives. In the curing of these paints, a polymerization takes place between the unsaturated groups in the paint binder and in the reactive ester wax.

As lacquer binders for one-component and multi-component polymer systems, the following components known from lacquer technology can be used:

mono- to polyfunctional acrylates, for example butyl acrylate, ethylhexyl acrylate, norbornyl acrylate, butanediol diacrylate, hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, mono- or polyethoxylated trimethylolpropane triacrylate, trimethylolpropane triethoxytriacrylate, pentaerythritol tetraethoxytriacrylate, pentaerythritol tetraethoxy-tetraacrylate, polyether acrylate, polyether acrylate,

Polyurethane acrylates, for example Craynor ^® CN 925, CN 981 of Cray Valley Resins GmbH, Ebecryl ^® EB 1290 from UCB GmbH, Laromer® 8987 from BASF AG, Photomer® 6019 or Photomer ^® 6010 the company. Cognis,

Polyester acrylates, for example Craynor ^® CN 292 from Cray Valley Resins GmbH, Laromer® ^® LR 8800 from BASF AG, Ebecryl ^® EB 800 UCB GmbH, Photomer ^® 5429 F and Photomer ^® 5960 F from. Cognis, Epoxy acrylates, for example Laromer® ^® EA 81 from BASF AG, Ebecryl ^® EB 604 UCB GmbH, Craynor ^® CN104D80 of Cray Valley Resins GmbH, dendritic polyester / ether acrylates of the company. Perstorp Specialty Chemicals AG or the company. Bayer AG.

Binder additives which contain no reactive double bonds include, for example, the following products:

Polyurethane polymers and their precursors in the form of polyisocyanates, polyols, polyurethane prepolymers, as a capped prepolymer and as reacted polyurethanes in the form of a melt or solution. In detail these are:

Polyols in the form of polyethers, for example polyethylene glycol 400, Voranol ^® P 400 and

Voranol ^® CP 3055 of Dow Chemicals, polyesters, such Lupraphen ^® 8107, Lupraphen ^® 8109 the Elastorgan ^® GmbH, Desmophen ^® 670, Desmophen ^® 1300 Bayer AG ₁ Oxyester ^® T 1136 from Degussa AG, alkyd resins, for example WORLÉEKYD ^® C

625 of Worlee Chemie GmbH,

Polycarbonates, such as Desmophen ^® C 200, hydroxyl-containing polyacrylates, for example,

Desmophen ^® A 365 from Bayer AG, polyisocyanates such as Desmodur ^® N 3300, Desmodur ^® VL, Desmodur ^® Z 4470,

Desmodur ^® IL or Desmodur ^® L 75 from Bayer AG, vestanate ^® T 1890 L of

Degussa AG, Rodocoat ^® WT 2102 Rhodia Syntech GmbH,

Polyurethane prepolymers, such as Desmodur ^® E 4280 of Bayer AG, vestanate ^® EP-U 423 from Degussa AG,

PMMA and further poly (meth) alkyl acrylates, for example Plexisol ^® P 550 and Degalan LP 50/01 ^® from Degussa AG,

Polyvinyl butyral and other Polyvinylacrylate such Mowital® ^® B 30 HH Clariant GmbH, 1 o

Polyvinyl acetate and its copolymers, eg Vinnapas® ^® B 100/20 VLE Wacker-Chemie GmbH.

For all polymers, both the aliphatic and the aromatic variants are expressly included. The binder may also be chosen so that it is identical to the silane or siloxane used for functionalizing the nano-mixed oxide.

The binders preferably have a molecular weight of 100 to 800 g / mol. The content of binder in the entire coating composition is preferably 80 to 99, in particular 90 to 99 wt .-%.

The coating compositions of the invention may also contain other additives, such as those customary in paint technology, such as reactive diluents, binder additives, solvents and co-solvents, waxes, matting agents, lubricants, defoamers, deaerators, leveling agents, thixotropic agents, thickeners, inorganic and organic pigments, fillers , Adhesion promoters, corrosion inhibitors, UV stabilizers, HALS compounds, free-radical scavengers, antistatics, wetting agents and / or the catalysts, cocatalysts, initiators, free-radical initiators, photoinitiators, photosensitizers, etc., which are required depending on the type of curing. Other additives include polyethylene glycol, PE, Waxes, PTFE waxes, PP waxes, amide waxes, FT paraffins, montan waxes, grafted waxes, natural waxes, macro- and microcrystalline paraffins, polar polyolefin waxes, sorbitan esters, polyamides, polyolefins, PTFE, wetting agents or silicates in question.

The subject according to the invention is intended to be explained in more detail with reference to the following examples, without restricting the possible variety. Examples

Example 1 :

To a 50% aqueous solution of aluminum chlorohydrate was added so much magnesium chloride that after calcination the ratio of

Alumina to magnesium oxide was 99.5: 0.5%. In addition, the

Solution 2% crystallization seeds added to a suspension of fine corundum.

After the solution was homogenized by stirring, the drying was carried out in a rotary evaporator. The solid Aluminiumchlorohydrat- magnesium chloride mixture was crushed in a mortar, whereby a coarse powder was formed.

The powder was calcined in a rotary kiln at 1050 ⁰ C. The contact time in the hot zone was a maximum of 5 min. A white powder was obtained whose grain distribution corresponded to the feed material. An X-ray structure analysis showed that predominantly α-alumina is present.

The images of the SEM image taken (scanning electron microscope) showed crystallites in the range 10-100 nm, which are present as agglomerates. The residual chlorine content was only a few ppm.

80 g of the mixed oxide thus obtained (MgO-doped corundum) was suspended in 120 g of methanol and deagglomerated in a vertical stirred ball mill from Netzsch (type PE 075). After 2 h, 20 g of 3- (trimethoxysilyl) propyl methacrylate (Dynasilan Memo, Degussa) were added and the suspension was deagglomerated in the stirred ball mill for a further 2 h. Subsequently, the suspension was separated from the beads. The suspension remains stable for weeks without evidence of sedimentation of the coated mixed oxide. The dispersion was converted by solvent exchange into the solvent suitable for the coating compositions.

Example 2:

80 g of the mixed oxide (with MgO doped corundum) from Example 1 was in 120 g

Acetone suspended and in a vertical stirred ball mill Fa. Netzsch (Type PE 075) deagglomerated. After 2 h, 15 g of trimethoxy-octylsilane and 5 g of 3- (trimethoxysilyl) -propyl methacrylate (Dynasilan Memo, Degussa) were added, and the suspension was deagglomerated in the recycle ball mill for a further 2 h. Subsequently, the suspension was separated from the beads. The suspension remains stable for weeks without evidence of sedimentation of the coated mixed oxide. The dispersion was converted by solvent exchange into the solvent suitable for coating compositions.

Example 3: 80 g of the mixed oxide (MgO doped corundum) from example 1 were suspended in 120 g of acetone and deagglomerated in a vertical stirred ball mill from Netzsch (type PE 075). After 2 h, 15 g of trimethoxy-octylsilane and 5 g of 3- (trimethoxysilyl) -propyl methacrylate (Dynasilan Memo, Degussa) were added, and the suspension was deagglomerated in the recycle ball mill for a further 2 h. Subsequently, the suspension was separated from the beads. The suspension remains stable for weeks without evidence of sedimentation of the coated mixed oxide. The dispersion was converted by solvent exchange into the solvent suitable for coating compositions.

applications

The coated mixed oxides from Examples 1 to 3 were tested for scratch resistance, gloss and sliding friction together with a reactive ester wax in paint. The application examples refer to the tests in a 100% UV varnish and show the improved matting, a higher scratch protection and a good slip.

I. 100% UV varnish system

recipe:

Laromer ^® LR 9007 (BASF), 69.5 wt .-%

Laromer ^® LR 8967 (BASF), 23.0 wt .-%

Talc 10 MOOS (LUZENAC) 3.4% by weight Tego Airex 920 ^® (TEGO) 0.7 wt .-% Irgacure ^® 500 (CIBA) 3.4 wt .-%

Laromer ^® LR 9007 modified pentaacrylate Laromer ^® LR 8967 modified polyether acrylate talc 10 MOOS filler Tego ^® Airex 920 silicone free deaerator Irgacure ^® 500 photoinitiator

The mixed oxide nanoparticles of Examples 1 to 3 were in

Dipropylene glycol diacrylate (DPGDA) transferred by solvent exchange and dispersed in the UV varnish by means of dissolver. Previously, a reactive Esterwachs was (Ceridust ^® 5091 from the company. Clariant) dispersed under high shear forces in the binder. Ceridust ^® 5091 is a mixture of the reaction product of pentaerythritol with a mixture of long-chain carboxylic acids based on technical montan wax acid and acrylic acid (reactive Esterwachs) and an amide wax.

shine

The paints were applied to glass plates at a wet film thickness of 30 μm, hardened with UV radiation and, using the micro-gloss from BYK-Gardner, the gloss was determined at an angle of 20 °. As the values in the following table show, the combination of nanoparticles and ester wax achieves a stronger matting compared to the two additives individually.

Gloss (measured at an angle of 20 °)

2% mixed oxide nanoparticles / example 1 + 2% Ceridusf 5091 92

2% mixed oxide nanoparticles / Ex. 2 + 2% Ceridusf 5091 100

2% mixed oxide nanoparticles / example 3 + 2% Ceridus 5091 96

2% mixed oxide nanoparticles / example 1 + 4% Ceridusf 5091 83

2% mixed oxide nanoparticles / example 2 + 4% Ceridusf 5091 80

scratch resistance

The paints were applied to glass plates with a 30 μm wet film thickness and cured. Using scotch-brite sponges (No. 96, 3M company) and various weights were on the abrasion tester (mtv Messtechnik) the scratch resistance determined by the residual gloss measured after scratching at an angle of 20 ° and the gloss reduction (initial gloss minus Gloss after scratching).

Gloss reduction at a weight of 135 g:

Gloss reduction at a coating weight of 493 g:

sliding friction

Of the glass plates coated with a wet film thickness of 30 μm, the sliding friction coefficient was determined by means of a Friction / Peel Tester (Twing-Albert) and a carriage with a leather sole (load 349 g).

Claims

claims:

1. Coating compositions containing reactive ester waxes and mixed oxide nanoparticles consisting of 50 to 99.9 wt .-% alumina and 0.1 to 50 wt .-% oxides of elements of the I. or II. Main group of

Periodic table, wherein these nanoparticles are modified with a silane or siloxane on the surface.

2. Coating compositions according to claim 1, characterized in that it is a lacquer.

3. Coating compositions according to claim 1, characterized in that it is a radiation-curable lacquer.

4. Coating compositions according to claim 1, characterized in that the aluminum oxide in the nanoparticles consists of α-A ^ Os.

5. Coating compositions according to claim 1, characterized in that they contain with silanes or siloxanes modified nanoparticles obtained by deagglomeration of nanoparticle-containing agglomerates by grinding and simultaneous treatment with the silane or siloxane in water or an organic solvent.

6. Coating compositions according to claim 1, characterized in that they contain as reactive ester wax, a reaction product of a polyol, long-chain aliphatic carboxylic acids, optionally a dicarboxylic acid, and an ethylenically unsaturated carboxylic acid.

7. Coating compositions according to claim 1, characterized in that it is a reaction product of pentaerythritol as reactive ester wax,

Montanwachssäure and acrylic acid.