EP2092028A2

EP2092028A2 - Redispersible surfaced-modified particles

Info

Publication number: EP2092028A2
Application number: EP07819839A
Authority: EP
Inventors: Gerhard Jonschker; Matthias Koch; Joerg Pahnke
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2006-12-11
Filing date: 2007-11-16
Publication date: 2009-08-26
Also published as: US20100010137A1; WO2008071286A3; JP2010512434A; WO2008071286A2; DE102006058200A1; US8586659B2

Abstract

The invention relates to surface-modified particles that can be dispersed in organic solvents and to the use thereof for incorporating into polymers, paints and lacquers.

Description

Redispersible surface-modified particles

The present invention relates to surface-modified particles that are dispersible in organic solvents and their use for incorporation into polymers, paints and coatings.

Inorganic particles, in particular nanoparticles, are usually prepared in aqueous dispersion and often have to be converted into organic media. If, for example, the hydrophilic nanoparticles are brought too quickly into a non-polar environment, it occurs

Agglomeration of the particles. It is particularly important to obtain a sufficiently high coverage of the particle surface with a hydrophobic surface modifier so that the hydrophilic particles can be dispersed in a hydrophobic environment stable and agglomerate-free. However, this is associated with technical difficulties, since the particles precipitate with increasing hydrophobization of the hydrophilic solvent and then are no longer available for further occupancy. However, the achievable to failure occupancy is in most cases not sufficient for agglomerate-free redispersing in the desired hydrophobic target solvent. For this reason, the common methods are usually based on a very slow solvent exchange, often on mediating solvents in large quantities. These multi-step processes are slow and expensive.

Alternative methods start from agglomerated nanoparticles and disperse them using high shear forces with the simultaneous addition of surface modifiers.

The abovementioned processes have the disadvantage that they either require a great deal of effort and require a high consumption of solvent, or the processes require high shear forces which do not ensure complete disruption of the agglomerates. There is therefore a need for particles and processes for their preparation which can be prepared in aqueous media and redispersed from these aqueous dispersions into organic media.

The present object is achieved by particles according to the present invention and by processes for their preparation.

Accordingly, a first object of the present invention is the

Providing surface-modified inorganic particles, which are obtainable by a process in which, in a solvent or solvent mixture, inorganic particles and at least one surface modifier are reacted together, and in step b), the reaction mixture obtained by the action of one or more external Factor destabilized to obtain the surface-modified inorganic particles. Process for the preparation of surface-modified particles, wherein in a step a) inorganic particles and at least one surface modifier are reacted in a solvent or solvent mixture and in a step b) the obtained reaction mixture is destabilized by the action of one or more external factors to obtain the surface-modified inorganic particles , are also the subject of the present invention. In a further embodiment of the present invention, the inorganic particles, in particular nanoparticles, can be suspended in a solvent or solvent mixture before application of the surface modifier, but suspensions of, for example, nanoparticles can also be used directly. The solvent or solvent mixture according to step a) comprises water, alcohols, ketones and / or ethers, in particular water, isopropanol, acetone and / or THF.

Essential to the present invention is the controlled destabilization of the reaction mixture in step b) by the action of one or more external factors. Destabilization in the sense of the present invention means on the one hand a destabilization of the particles, which leads to the precipitation of the surface-modified particles and thus makes the particles separable (and redispersible). On the other hand, destabilization also means the phase separation of two or more solvents, the particles remaining suspended in one of the solvents, preferably the organic one.

If appropriate, the particles according to the invention can be separated off and / or dried. The process of separation can be done by any of the skilled man known types. In addition, it is still possible to dry the particles and then to redisperse them in organic solvents.

Only by the process of the invention are nanoparticles obtainable which can be redispersed without major problems and yield losses in any media and solvents so that the measurable turbidity is significantly lower than that of a dispersion of unmodified particles.

Essential to the invention for the surface-modified nanoparticles is their good redispersibility and the transparency of the dispersions obtained therefrom. This transparency can be determined by the turbidity, the dispersion, using a UV / VIS / NIR spectrometer Lambda 900 with

Integration sphere measured 150 mm, quantify. The dispersions are measured in 0.5 cm layer thickness in transmission. The directed - A -

and diffuse components are calculated. The lower the diffuse component of the transmittance, the less turbid and therefore more transparent the sample appears. The visual appearance of the samples is transparent (opalescent).

Preferably, it is a chemical surface modification, that is, the surface modifier is covalently bonded to the surface of the nanoparticle.

Common processes for preparing surface-modified nanoparticles are based on aqueous particle dispersions to which the surface modifier is added. By occupying the surface can lead to a destabilization of the particle dispersion to form a precipitate, especially when for compatibilization with organic media hydrophobic

Surface covering agents are used. As a result of precipitation, the nanoparticle surface is separated from the remaining modifier remaining in the solution and a preferred, largely complete coverage is prevented. This is particularly disadvantageous if the destabilization occurs at a time when only a small part of the nanoparticle surface has been coated with the surface modifier. The particles thus obtained tend to agglomerate, that is they are not completely redispersible.

According to the present invention, a sufficient degree of occupancy of the surface of the nanoparticles with the surface modifier can only be achieved if the destabilization of the particle dispersion is controlled in a controlled manner, ie a destabilization of the surface-modified nanoparticle-containing suspension is initiated only by targeted action of external factors. Destabilization may preferably be controlled by external factors, such as by changing the pH after surface modification Addition of solvent or by adding solubilizer to the particle dispersion, by temperature change or by salt addition. For example, with solvent addition of different polarity as the external factor, the polarity of the reaction mixture is increased. Due to the above procedures is a premature

Destabilization, which would lead to an insufficient degree of occupancy of the surface of the nanoparticles prevented, and thus allows the occupancy of the surface with the surface modifier to a desired occupancy level. Targeted destabilization thus only takes place after a corresponding change in the external factors, generally at a later time than in the known methods.

In some cases of implementation, the particular challenge is that the surface modifier must first be formed into a reactive species in an upstream reaction. This is the case, in particular, when alkoxysilanes are used, which have a significantly higher reactivity with respect to the particle surface if the alkoxide radical is wholly or partly hydrolyzed. Then, the initial goal is to achieve the most stable possible solution of the reactive form of the surface modifier, which is then rapidly brought to react with the nanoparticle surface and thus destabilize by changing the external factor (s). This can e.g. can be realized by adjusting a pH close to the isoelectric point of the silane in which the hydrolysis of the alkoxy radicals proceeds rapidly but the crosslinking is inhibited. When the pH is later changed as an external factor, the activated silanes then react very rapidly and almost quantitatively with the nanoparticle surface. The nanoparticles precipitated in this way have a significantly better redispersibility than nanoparticles occupied in another reaction procedure.

In a further preferred embodiment, the surface modifier is a polymer which is dissolved together with the dispersion of the particles, In this case, an additional solvent can be used as a solubilizer. Preferably, acetone is used as a solubilizer. The solubilizer is used in proportions of from 1 to 50% by weight, based on the particle dispersion, preferably in proportions of from 5 to 20% by weight. In joint solution with the particles that can

Polymer react with their surface and functionalize it. An external factor is now the stability (solubility) of the polymer and thus the modified particles influenced so that it comes to the failure of the same. The external factor may be a change in the solvent composition, for example, by distilling off one component, or preferably by adding a non-solvent for the polymer which is miscible with the other solvents or a temperature change. Preference is given to using polymers having a plurality, particularly preferably a reactive group, which are able to react with the particle surface. In particular, the individual reactive group may be a terminal silane on the polymer.

The functionalized, precipitated particles can be conveniently separated from the solvent mixture and completely redispersed in a hydrophilic or hydrophobic, preferably in a hydrophobic solvent (butyl acetate, xylene, aliphatic hydrocarbons). The surface coverage is not only a compatibilization with the target matrix (solvent, paint system or polymer melt), it can also effectively prevent the agglomeration of dried particles.

In order to achieve destabilization after occupancy, it is also suitable to add one or more salts, e.g. Sodium chloride. Furthermore, by lowering or increasing the temperature also a

Destabilization can be achieved. It is within the skill of the art to use the appropriate external factor for the targeted control of destabilization.

In a further embodiment of the present invention, the surface modifier is so-called LCST or

UCST polymers. The special polymers mentioned are polymers which have a lower critical solution temperature (LCST) or an upper critical solution temperature (UCST). Depending on the polymer used, a homogeneous mixture is produced by heating or cooling. at

Inversion of the process precipitates the polymer on the particle surface, that is, the external factor in this case is a change in temperature.

Suitable LCST polymers for the present invention are, for example, those described in WO 01/60926 and WO 03/014229. Particularly suitable LCST polymers are polyalkylene oxide derivatives, preferably polyethylene oxide (PEO) derivatives, polypropylene oxide (PPO) derivatives, olefinically modified PPO-PEO block copolymers, acrylate-modified PEO-PPO-PEO triblock copolymers, and polymers or their derivatives from the class of polymethyl vinyl ethers, poly-N-vinylcaprolactams, ethyl (hydroxyethyl) - celluloses, poly (N-isopropylacrylamide) and polysiloxanes. Particularly preferred LCST polymers are siloxane polymers or polyethers modified with olefinic or silanolic groups.

Suitable UCST polymers are in particular polystyrene, polystyrene copolymers and polyethylene oxide copolymers.

Preference is given to using LCST or UCST polymers having solvolysable or functional groups which have strong interactions and / or chemical bonds with the substrate or the application medium, such as the paint matrix, can enter. All functional groups known to those skilled in the art are suitable, in particular silanol, amino, hydroxyl, olefin, hydroxyl, epoxy, acid anhydride and acid groups.

The LCST or UCST polymers preferably have molecular weights in the

Range of 300 to 500000 g / mol, in particular from 500 to 20,000 g / mol.

In addition to the external factors, the high degree of coverage of the surface, and thus the preservation of nanoparticles that are readily redispersible, can also be achieved by using appropriate surface modifiers. Suitable surface modifiers here are amphiphilic silanes, as described below. Here, too, it is obvious to the person skilled in the art, when using amphiphilic silanes, to control the de-stabilization of the particle dispersion by influencing additional external factors, as described above.

Suitable particles are selected from the group comprising hydrophilic and hydrophobic, in particular hydrophilic particles, in particular nanoparticles, based on oxides, hydroxides, sulfides, sulfates, carbonates of silicon, titanium, zinc, aluminum, cerium, cobalt, chromium, nickel, iron , Yttrium and / or zirconium, or with oxides or hydroxides of silicon coated metals, such as Ag ₁ Cu, Fe, Au, Pd, Pt or alloys. The particles based on oxides, hydroxides, sulfides, sulfates, carbonates of titanium, zinc, aluminum, cerium, cobalt, chromium, nickel, iron, yttrium and / or zirconium may optionally be coated with oxides or hydroxides of silicon. The individual oxides can also be present as mixtures. The particles preferably have an average particle size, determined by means of a Malvern ZETASIZER (dynamic light scattering) or transmission electron microscope, of from 3 to 200 nm, in particular from 20 to 80 nm and very particularly preferably from 30 to 50 nm. In specific also preferred embodiments of the present invention The invention is the distribution of the particle sizes narrow, ie the fluctuation range is less than 100% of the average, more preferably at most 50% of the average value (after particle distribution function, determined by dynamic light scattering). Particular preference is given to using nanoparticles based on silicon dioxide.

Nanohektorites, which are marketed, for example, by Südchemie under the Optigel® brand or by Laporte under the Laponite® brand, are also preferably used. Furthermore, silica sols (SiO ₂ in water) prepared from ion-exchanged water glass are also particularly preferred.

Particularly suitable as surface modifiers are organofunctional silanes, quaternary ammonium compounds,

Phosphonates, phosphonium and sulfonium compounds, copolymers, polymers or mixtures thereof. Preferably, the surface modifiers are selected from the group of organofunctional silanes. Preference is furthermore given to short-chain polymers (molecular weight (M w) below 50000 g / mol, in particular below 10000 g / mol) which have one or more, in particular only one, terminal trialkoxysilane, quaternary ammonium, phosphate, phosphonium and sulfonium group.

In particular, according to the invention, the described requirements for a surface modifier fulfill an adhesion promoter which carries two or more functional groups. One group of the coupling agent chemically reacts with the oxide surface of the nanoparticle. Here come alkoxysilyl groups (e.g., methoxy, ethoxysilanes), halosilanes (e.g., chloro) or acidic groups of phosphoric acid esters.

Phosphonic acids and phosphonic acid esters into consideration. About a more or less long spacer are the groups described with a linked to the second, functional group. These spacers are unreactive alkyl chains, siloxanes, polyethers, thioethers or urethanes or combinations of these groups of the general formula (C ₁ Si) _n H m (N ₁ O ₁ S) _x where n = 1-50, m = 2 -100 and x = 0-50. The functional group is preferably acrylate, methacrylate, vinyl,

Amino, cyano, isocyanate, epoxy, carboxy or hydroxy groups.

Silane-based surface modifiers are described, for example, in DE 40 11 044 C2. Phosphoric acid-based surface modifiers include i.a. as Lubrizol® 2061 and 2063 from LUBRIZOL (Langer & Co.). Suitable silanes are, for example, vinyltrimethoxysilane, aminopropyltriethoxysilane, N-ethylamino-N-propyldimethoxysilane, isocyanatopropyltriethoxysilane, mercaptopropyltrimethoxysilane, vinyltriethoxysilane, vinylethyldichlorosilane, vinylmethyldiacetoxysilane, vinylmethyldichlorosilane,

Vinylmethyldiethoxysilane, vinyltriacetoxysilane, vinyltrichlorosilane, Phenylvinyldiethoxysilan, Phenylallyldichlorsilan, 3- Isocyanatopropoxyltriethoxysilan, methacryloxypropenyltrimethoxysilane, 3- methacryloxypropyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 1, 2-epoxy-4- (ethyltriethoxysilyl) -cyclohexane, 3-acryloxypropyltrimethoxysilane, 2-methacryloxyethyltrimethoxysilane, 2-acryloxyethyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 2-methacryloxyethyltriethoxysilane, 2-acryloxyethyltriethoxysilane, 3-methacryloxypropyltris (methoxyethoxy) silane _; 3-methacryloxypropyltris (butoxyethoxy) silane, 3

Methacryloxypropyltris (propoxy) silane, 3-methacryloxypropyltris (butoxy) silane, 3-acryloxypropyltris (methoxyethoxy) silane, 3-acryloxypropyltris (butoxyethoxy) silane, 3-acryloxypropyltris (propoxy) silane, 3-acryloxypropyltris (butoxy) silane. Particularly preferred is 3-methacryloxypropyltrimethoxysilane. These and other silanes are commercially available, for example, from ABCR GmbH & Co., Karlsruhe, or from Sivento Chemie GmbH, Dusseldorf. Vinylphosphonic acid or vinylphosphonic acid diethyl ester can also be listed here as adhesion promoters.

In addition, suitable surface modifiers include amphiphilic silanes according to the general formula (I) where the radicals R may be identical or different and are hydrolytically removable radicals, Sp is either O or straight-chain or branched alkyl having 1-18 G

Atoms, straight-chain or branched alkenyl having 2-18 C atoms and one or more double bonds, straight-chain or branched

Alkynyl having 2-18 C atoms and one or more triple bonds, saturated, partially or completely unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by alkyl groups having 1-6 C atoms,

A _{hp means} a hydrophilic block,

B _{hb is} a hydrophobic block and wherein at least one reactive functional group is bound to A _hP and / or B _hb .

The amphiphilic silanes have the advantage that they combine several properties. For example, they can impart a surface with hydrophilic properties to particles via the hydrophilic block and, at the same time, impart a surface with hydrophobic properties via the hydrophobic block. This results in a self-organized switchability of the hydrophilicity / hydrophobicity depending on the environment of the particle surface. In addition, the additional reactive functional group may form further bonds, eg to a surrounding medium. The surface of the particles is therefore adapted for the most diverse applications by a single modification and thus becomes compatible for all applications. In addition, the amphiphilic silanes due to the greater chain length increased mobility with respect to the orientation and orientation of the silanes, for example on a surface on. This helps to improve the alignment of the respective areas of the amphiphilic silane interacting with the surrounding medium and thus also improves the compatibility of the coated therewith

Particles with different media.

Essential for the amphiphilic silanes according to the invention is the structure of the individual subunits, as shown in formula (I).

The amphiphilic silanes contain a head group (R) ₃ Si, where the radicals R may be the same or different and represent hydrolytically removable radicals. Preferably, the radicals R are the same.

Suitable hydrolytically removable radicals are, for example

Alkoxy groups having 1 to 10 carbon atoms, preferably having 1 to 6 carbon atoms, halogens, hydrogen, acyloxy groups having 2 to 10 carbon atoms and in particular having 2 to 6 carbon atoms or NRVGruppen, wherein the radicals R ^' same or different may be selected from hydrogen or alkyl having 1 to 10 carbon atoms, in particular having 1 to 6 carbon atoms. Suitable alkoxy groups are, for example, methoxy, ethoxy, propoxy or butoxy groups. Suitable halogens are in particular Br and Cl. Examples of acyloxy groups are acetoxy or propoxy groups. Oximes are also suitable as hydrolytically removable radicals. The oximes may hereby be substituted by hydrogen or any organic radicals. The radicals R are preferably alkoxy groups and in particular methoxy or ethoxy groups.

Covalently bonded to the above-mentioned head group is a spacer Sp, which acts as a link between the Si head group and the hydrophilic block A _hP and performs a bridging function in the context of the present invention. The group S _P is either -O- or straight-chain or branched alkyl having 1-18 C atoms, straight-chain or branched alkenyl having 2-18 C atoms and one or more double bonds, straight-chain or branched alkynyl having 2-18 C atoms and one or more triple bonds, saturated, partial or fully unsaturated cycloalkyl having 3-7 C atoms, which with

Alkyl groups with 1-6 C atoms may be substituted.

The Ci-Ci ₈ alkyl group of Sp is, for example, a methyl, ethyl, isopropyl, propyl, butyl, sec-butyl or tert-butyl, and also pentyl, 1, 2 or 3-methylbutyl, 1, 1, 1, 2, or 2,2-dimethylpropyl, 1 -

Ethylpropyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl or tetradecyl. Optionally it may be perfluorinated, for example as difluoromethyl, tetrafluoroethyl, hexafluoropropyl or octafluorobutyl.

A straight-chain or branched alkenyl having 2 to 18 carbon atoms, where a plurality of double bonds may also be present, is, for example, vinyl, allyl, 2- or 3-butenyl, isobutenyl, sec-butenyl, furthermore 4-pentenyl, iso-pentenyl, Hexenyl, heptenyl, octenyl, -C ₉ Hi ₆ , -CioHi ₈ to -Ci ₈ H ₃ 4, preferably allyl, 2- or 3-butenyl, isobutenyl, sec-butenyl, furthermore preferred is 4-pentenyl, iso-pentenyl or hexenyl.

A straight-chain or branched alkynyl having 2 to 18 C atoms, wherein a plurality of triple bonds may also be present, is, for example, ethynyl, 1- or 2-propynyl, 2- or 3-butynyl, furthermore

Pentynyl, 3-pentynyl, hexynyl, heptynyl, octynyl, -CgHi ₄ , -C ₁₀ H _{1 6} to -C 1 ₈ H ₃₂ , preferably ethynyl, 1- or 2-propynyl, 2- or 3-butynyl, 4-pentynyl, 3 - Pentynyl or hexynyl.

Unsubstituted saturated or partially or fully unsaturated cycloalkyl groups having 3-7 C atoms may include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclopenta-1,3- dienyl, cyclohexenyl, cyclohexa-1,3-dienyl, cyclohexa-1, 4-dienyl, phenyl, cycloheptenyl, cyclohepta-1,3-dienyl, cyclohepta-1,4-dienyl or cycloheptane. 1, 5-dienyl be substituted with d- to C ₆ - alkyl groups.

The spacer group Sp is followed by the hydrophilic block A _hp . This may be selected from nonionic, cationic, anionic or zwitterionic hydrophilic polymers, oligomers or groups. In the simplest embodiment, the hydrophilic block is ammonium, sulfonium, phosphonium groups, alkyl chains having carboxyl, sulfate and phosphate side groups, which may also be present as a corresponding salt, partially esterified anhydrides with free acid or Salt group, OH-substituted alkyl or cycloalkyl chains (eg, sugars) having at least one OH group, NH- and SH-substituted alkyl or cycloalkyl chains or mono-, di- tri- or oligo-ethylene glycol groups. The length of the corresponding alkyl chains can be 1 to 20 C atoms, preferably 1 to 6 C atoms.

The nonionic, cationic, anionic or zwitterionic hydrophilic polymers, oligomers or groups can be prepared from corresponding monomers by polymerization in accordance with methods generally known to the person skilled in the art. Suitable hydrophilic monomers contain at least one dispersing functional group which consists of the group consisting of

(i) functional groups which can be converted by neutralizing agents into anions, and anionic groups, and / or (ii) functional groups which are neutralized by neutralizing agents and / or

Quaternizing agents can be converted into cations, and cationic groups, and / or

(ιϊϊ) nonionic hydrophilic groups. Preferably, the functional groups (i) from the group consisting of carboxylic acid, sulfonic acid and phosphonic acid groups, acidic sulfuric acid and phosphoric acid ester groups and carboxylate, sulfonate, phosphonate, sulfate ester and phosphate ester groups, the functional groups (ii) from the A group consisting of primary, secondary and tertiary amino groups, primary, secondary, tertiary and quaternary ammonium groups, quaternary phosphonium groups and tertiary sulfonium groups, and the functional groups (iii) selected from the group consisting of omega-hydroxy and omega-alkoxy-poly ( alkylene oxide) -1-yl groups.

Unless neutralized, the primary and secondary amino groups may also serve as isocyanate-reactive functional groups.

Examples of suitable hydrophilic monomers having functional groups (i) are acrylic acid, methacrylic acid, beta-carboxyethyl acrylate, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid; olefinically unsaturated sulfonic or phosphonic acids or their partial esters; or maleic mono (meth) acryloyloxyethyl ester,

Succinic acid mono (meth) acryloyloxyethyl ester or Phthalsäuremo- no (meth) acryloyloxyethylester, in particular acrylic acid and

Methacrylic acid.

Examples of suitable hydrophilic monomers having functional groups (II) are 2-aminoethyl acrylate and methacrylate or allylamine.

Examples of suitable hydrophilic monomers with functional groups (iii) are omega-hydroxy or omega-methoxy-polyethylene oxide-1-yl, omega-methoxy-polypropylene oxide-1-yl, or omega-methoxy-poly (ethylene oxide-co-poly) polypropylene oxide) -1-yl acrylate or methacrylate, as well as hydroxy-subsitituted ethylene, acrylates or methacrylates, such as, for example, hydroxyethyl methacrylate. Examples of suitable monomers for the formation of zwitterionic hydrophilic polymers are those in which a betaine structure occurs in the side chain. Preferably, the side group is selected from - (CH ₂₎ _m - (N ⁺ (CH ₃₎ ₂₎ - (CH ₂₎ n-SO ₃ -, - (CH ₂₎ m- (N ⁺ (CH3) 2) - ( CH ₂ ) n-PO ₃ ² -, - (CH ₂ ) _m - (N ⁺ (CH ₃ ) ₂ ) - (CH ₂ ) _n -

0-PO ₃ ^{2 "} or (CH ₂ ) _m - (P ⁺ (CH ₃ ) ₂ ) - (CH ₂ ) n -SO ₃ ^" , where m is an integer in the range of 1 to 30, preferably from the range 1 to 6, particularly preferably 2, and n is an integer from the range of 1 to 30, preferably from the range 1 to 8, particularly preferably 3.

It may be particularly preferred if at least one structural unit of the hydrophilic block has a phosphonium or sulfonium radical.

In general, corresponding structures can be produced according to the following scheme:

T% H ^F. rsflux

The desired amounts of lauryl methacrylate (LMA) and

Dimethylaminoethylmethacrylat (DMAEMA) by known methods, preferably copolymerized in toluene radically by addition of AIBN. Subsequently, a betaine structure by reaction of the amine with 1, 3

Propansultone obtained by known methods. In another variant of the invention, it is preferred if a copolymer consisting essentially of lauryl methacrylate (LMA) and hydroxyethyl methacrylate (HEMA) is used, which can be prepared in a known manner by free radical polymerization with AIBN in toluene.

In selecting the hydrophilic monomers, it is to be noted that it is preferable to combine the hydrophilic monomers having functional groups (i) and the hydrophilic monomers having functional groups (ii) so as not to form insoluble salts or complexes. On the other hand, the hydrophilic monomers having functional groups (i) or functional groups (ii) can be arbitrarily combined with the hydrophilic monomers having functional groups (iii).

Of the hydrophilic monomers described above, the monomers having the functional groups (i) are particularly preferably used.

Preferably, the neutralizing agents for the anionic functional groups (i) are selected from the group consisting of ammonia, trimethylamine, triethylamine, tributylamine, dimethylaniline, diethylaniline, triphenylamine, dimethylethanolamine, diethylethanolamine, methyldiethanolamine, 2-aminomethylpropanol, dimethylisopropylamine, dimethylisopropanolamine, triethanolamine , Diethylenetriamine and triethylenetetramine, and the neutralizing agents for the cation-convertible functional groups (ii) selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, lactic acid, dimethylolpropionic acid and citric acid.

Most preferably, the hydrophilic block is selected from mono- and triethylene glycol structural units. Attached to the hydrophilic block Ah _P is the hydrophobic block B _h t _> - The block Bh _b is based on hydrophobic groups or, like the hydrophilic block, on the polymerization of suitable hydrophobic monomers.

Examples of suitable hydrophobic groups are straight-chain or branched alkyl having 1-18 C atoms, straight-chain or branched alkenyl having 2-18 C atoms and one or more double bonds, straight-chain or branched alkynyl having 2-18 C atoms and one or more triple bonds , saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by alkyl groups having 1-6 C atoms. Examples of such groups are already mentioned in advance. In addition, aryl, polyaryl, aryl-C 1 -C 6 -alkyl or esters having more than 2 C atoms are suitable. In addition, the groups mentioned may also be substituted, in particular with halogens, with perfluorinated groups being particularly suitable.

Aryl-C ₁ -C ₆ -alkyl is, for example, benzyl, phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl or phenylhexyl, where both the phenyl ring and the alkylene chain, as described above, may be partially or completely substituted by F, particularly preferably benzyl or phenylpropyl.

Examples of suitable hydrophobic olefinically unsaturated monomers for the hydrophobic block B _hP are

(1) substantially acid-group-free esters of olefinically unsaturated acids, such as (meth) acrylic acid, crotonic acid, ethacrylic acid, vinylphosphonic acid or vinylsulfonic acid alkyl or cycloalkyl esters having up to 20 carbon atoms in the alkyl radical, in particular methyl, ethyl, propyl, n-butyl, sec-butyl, tert-butyl, hexyl, ethylhexyl, stearyl and lauryl acrylate, methacrylate, crotonate, methacrylate or vinyl phosphonate or vinyl sulfonate; cycloaliphatic (meth) acrylic acid, crotonic acid, ethacrylic acid, vinylphosphonic acid or vinylsulfonic acid esters, in particular cyclohexyl, isobomyl, dicyclopentadienyl, octahydro-4,7-methano-1H-indenemethanol or tert-butylcyclohexyl (meth ) acrylate, crotonate, ethacrylate, vinyl phosphonate or vinyl sulfonate. These may be minor amounts of higher functional (meth) acrylic acid, crotonic acid or ethacrylic alkyl or cycloalkyl esters such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, pentane-1, 5-diol, hexane-1, 6 -diol, octahydro-4,7-methano-1H-indenedimethanol or cyclohexane-1, 2-, -1, 3- or -1, 4-diol di (meth) acrylate, trimethylolpropane tri (meth) acrylate or pentaerythritol tetra (meth) acrylate and the analogous ethacrylates or crotonates. In the context of the present invention, minor amounts of higher-functional monomers (1) are amounts which do not lead to crosslinking or gelation of the polymers;

(2) monomers which carry at least one hydroxyl group or hydroxymethylamino group per molecule and are substantially free of acid groups, such as

Hydroxyalkyl esters of alpha, beta-olefinically unsaturated carboxylic acids, such as hydroxyalkyl esters of acrylic acid, methacrylic acid and ethacrylic acid, in which the hydroxyalkyl group contains up to 20 carbon atoms, such as 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 3-hydroxybutyl , 4-hydroxybutyl acrylate, methacrylate or ethacrylate; 1,4-bis (hydroxymethyl) cyclohexane, octahydro-4,7-methano-1H-indenedimethanol or methylpropanediol monoacrylate, monomethacrylate, monoethacrylate or monocrotonate; or reaction products of cyclic esters, e.g. epsilon-caprolactone and these hydroxyalkyl esters;

- olefinically unsaturated alcohols such as allyl alcohol Allyl ethers of polyols, such as trimethylolpropane monoallyl ether or pentaerythritol mono-, di- or triallyl ether. The higher functionality monomers are generally used only in minor amounts. In the context of the present invention, minor amounts of higher-functional monomers are amounts which do not lead to crosslinking or gelation of the polymers,

- Reaction products of alpha, beta-olefinic carboxylic acids with

Glycidyl esters of an alpha-branched monocarboxylic acid having 5 to 18 carbon atoms in the molecule. The reaction of the acrylic or methacrylic acid with the glycidyl ester of a carboxylic acid having a tertiary alpha carbon atom may be carried out before, during or after the polymerization reaction. The monomer (2) used is preferably the reaction product of acrylic and / or methacrylic acid with the glycidyl ester of Versatic® acid. This glycidyl ester is commercially available under the name Cardura® E10. In addition, reference is made to Römpp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, .1998, pages 605 and 606;

Formaldehyde adducts of aminoalkyl esters of alpha, beta-olefinically unsaturated carboxylic acids and of alpha, beta-unsaturated carboxylic acid amides, such as N-methylol and N, N-dimethylol aminoethyl acrylate, aminoethyl methacrylate, acrylamide and methacrylamide; such as

Acryloxysilane groups and hydroxyl-containing olefinically unsaturated monomers, preparable by reaction of hydroxy-functional silanes with epichlorohydrin 30 and subsequent reaction of the intermediate with an alpha, beta-olefinically unsaturated

Carboxylic acid, in particular acrylic acid and methacrylic acid, or their hydroxyalkyl esters; (3) vinyl esters of alpha-branched monocarboxylic acids having 5 to 18 carbon atoms in the molecule, such as the vinyl esters of Versatic® acid sold under the trademark VeoVa®;

(4) cyclic and / or acyclic olefins such as ethylene, propylene, but-1-ene, pent-1-ene, hex-1-ene, cyclohexene, cyclopentene, norbornene, butadiene, isoprene, cyclopentadiene and / or dicyclopentadiene;

(5) amides of alpha, beta-olefinically unsaturated carboxylic acids, such as

(Meth) acrylic acid amide, N-methyl, N, N-dimethyl, N-ethyl, N, N-diethyl, N-propyl, NN-dipropyl, N-butyl, N, N-dibutyl and / or N, N-cyclohexylmethyl (meth) acrylamide;

(6) monomers containing epoxide groups, such as the glycidyl esters of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid and / or itaconic acid;

(7) vinyl aromatic hydrocarbons such as styrene, vinyltoluene or alpha-alkylstyrenes, especially alpha-methylstyrene;

(8) nitriles, such as acrylonitrile or methacrylonitrile;

(9) vinyl compounds selected from the group consisting of vinyl halides such as vinyl chloride, vinyl fluoride, vinylidene dichloride,

vinylidene; Vinylamides, such as N-vinylpyrrolidone; Vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether and vinyl cyclohexyl ether; and vinyl esters such as vinyl acetate, vinyl propionate, and vinyl butyrate;

(10) allyl compounds selected from the group consisting of allyl ethers and esters, such as propyl allyl ether, butyl allyl ether, Ethylene glycol diallyl ether, trimethylolpropane triallyl ether or allyl acetate or allyl propionate; As far as the higher-functional monomers are concerned, what has been said above applies mutatis mutandis;

(11) Siloxane or polysiloxane monomers which may be substituted with saturated, unsaturated, straight-chain or branched alkyl groups or other hydrophobic groups already mentioned above. In addition, polysiloxane macromonomers which have a number average molecular weight Mn of from 1,000 to 40,000 and on average from 0.5 to 2.5 ethylenically unsaturated double bonds per molecule, such as

Polysiloxane macromonomers having a number average molecular weight Mn of from 1,000 to 40,000 and an average of from 0.5 to 2.5 ethylenically unsaturated double bonds per molecule; in particular polysiloxane macromonomers which have a number-average molecular weight Mn of 2,000 to 20,000, more preferably 2,500 to 10,000 and in particular 3,000 to 7,000 and an average of 0.5 to 2.5, preferably 0.5 to 1, 5, ethylenically unsaturated double bonds per molecule, as in DE 38 07 571 A 1 on pages 5 to 7, DE 37 06 095 A 1 in columns 3 to 7, EP 0 358 153 B 1 on pages 3 to 6, in US 4,754,014 A 1 in columns 5 to 9, in DE 44 21 823 A1 or in international patent application WO 92/22615 on page 12, line 18, to page 18, line 10; and

(12) carbamate or allophanate group-containing monomers such as acryloyloxy or methacryloyloxyethyl, propyl or butyl carbamate or allophanate; Further examples of suitable monomers containing carbamate groups are described in patents US 3,479,328 A 1, US 3,674,838 A 1, US 4,126,747 A 1, US 4,279,833 A 1 or US 4,340,497 A 1.

The respective hydrophilic and hydrophobic blocks can in principle be combined with one another in any desired manner. Preferably have the amphiphilic silanes have an HLB value in the range of 2-19, preferably in the range of 4-15. The HLB value is defined as

Earth polar proportions

HLB = • 2U

Molar mass and indicates whether the silane behaves rather hydrophilic or hydrophobic, ie which of the two blocks A _hP and B _{hb dominates} the properties of the silane. The HLB value is calculated theoretically and results from the mass fractions of hydrophilic and hydrophobic groups. An HLB value of 0 indicates a lipophilic compound, a chemical compound with an HLB value of 20 has only hydrophilic moieties.

The amphiphilic silanes are further distinguished by the fact that at least one reactive functional group is bound to A _hp and / or B _h b. The reactive functional group is preferably present at the hydrophobic block B _h b, and in particular preferably at the end of the hydrophobic block. In the preferred embodiment, the head group (R 1) 3 Si and the reactive functional group have the greatest possible spacing, which permits a particularly flexible design of the chain lengths of the blocks Ah _P and B _hb , without the possible reactivity of the reactive groups, for example with the surrounding medium. to significantly limit.

The reactive functional group may be selected from silyl groups having hydrolytically removable radicals, OH, carboxy, NH, SH groups, halogens or double bonds containing reactive groups, such as acrylate or vinyl groups. Suitable silyl groups with hydrolytically removable radicals have already been described in advance in the description of the head group (R) 3Si. Preferably, the reactive group is an OH group. The nanoparticles according to the invention are isolated after destabilization. This is done by centrifuging, filtering and optionally by washing with water and / or alcohol.

The surface-modified nanoparticles obtained in this way can be easily dispersed in a new medium. In the simplest case, the nanoparticles are mixed with the dispersant.

The use of the nanoparticles according to the invention in paints, inks, adhesives and plastics, in particular in transparent applications, is likewise an object of the present invention. Thus, by incorporating the particles of the invention, in particular in the case of nanoparticles, the chemical, thermal and mechanical stability of polymers improved or targeted parts of the electromagnetic

Spectrum can be influenced. Particularly noteworthy here is the protection against UV rays.

The incorporation into polymers and lacquers can be carried out by customary methods for the preparation of polymer preparations. For example, the polymer material can be mixed with nanoparticles according to the invention, preferably with the dried particles, preferably in an extruder or kneader, and incorporated into 2K coating systems by mixing the nanoparticles with the polymer starting components of 2K coating systems. Preferred polymers are polycarbonate (PC), polyethylene terephthalate (PETP), polyimide (PI), polystyrene (PS), polymethyl methacrylate (PMMA), polyolefins, preferably polybutadiene and polyisoprene and copolymers containing at least a portion of one of the polymers mentioned, and 2K coating systems.

The following examples merely illustrate the invention without limiting the scope of protection. In particular, those described therein The features, properties and advantages of the defined compound (s) on which the example in question is based are also applicable to other substances and compounds not mentioned in detail but within the scope of the claims, unless otherwise stated elsewhere.

Examples:

Surface modification:

4.16 g of a 30% strength by weight dispersion of SiO ₂ nanoparticles (particle diameter 9 nm) in water are diluted to 5% by weight with isopropanol (26 ml).

Different amounts of hexadecyltrimethoxysilane (HDTMS) as surface modifier are added to this single-phase dispersion (see Table 1.1). After a reaction time of 12 h, the polarity of the reaction mixture is greatly increased by the addition of 15 ml of water as an external factor, whereby the surface-modified particles precipitate. The particles are filtered off and taken up in n-butyl acetate.

Tab. 1.1: Experimental Overview of the Functionalized SiO ₂ Nanoparticles: Sample SiO ₂ / Butyl Acetate [% by Weight] Surface Coverage ^* [gr / nm ² ] HDTMS ** [μl]

1 (reference) 10

2 10 0.1 19

3 10 0.3 58

5 10 1.0 194

6 *** 10 0.8 155

7 *** 10 1.0 194 ^* relative to the spec. Surface of the nanoparticles (O _sp = 300 m ^ / g), ** hexadecyltrimethoxysilane * ^* * without isopropanol Isopropanol serves as a solubilizer in the surface modification between the dispersion of SiO ₂ nanoparticles and the HDTMS. Without isopropanol (see Table 2.1), the silane is present in two phases at the beginning of the surface modification and the particles precipitate in the water in the case of advanced silanation. Therefore, no measurement of the diffuse and directed scattering of samples 6 and 7 is possible (see turbidity experiments).

Turbidity experiments: Measuring instrument: UVΛ / IS / NIR spectrometer Lambda 900 with integrating sphere

150 mm

The dispersions are measured in 0.5 cm layer thickness in transmission. The directional and diffuse components are calculated (Table

2.1).

Tab. 2.1: Diffuse and directional scattering at 450 nm (measured in

Butyl acetate).

Samples Surface coverage [gr / nm ² ] Transm. diffuse [%] transm. ger. [%]

Butyl acetate - 0.42 92.86

1 - 43.69 7.89

2 0,1 16,10 51, 74

3 0.3 8.08 68.52

4 0,8 4,12 81, 82

5 1, 0 5,89 80,55

6 ^* 0.8 - -

7 * 1, 0 - -

* no stable dispersion during the measurement

The results of the turbidity measurements document the increasing proportion of the diffuse transmittance and, consequently, the increase of the directed transmission with decreasing surface coverage with the silane. The process of surface modification ensures agglomerate-free nanoparticles that in comparison to the reference experiment (without surface modifier or without isopropanol) are characterized by a low diffuse component of the transmittance. The visual appearance of the samples (0.3 - 1.0 gr / nm ² ) is transparent (opalescent).

Claims

claims

1. Surface-modified inorganic particles, characterized in that they are obtainable by a process in which in a step a) in a solvent or solvent mixture of inorganic particles and at least one

Surface modifiers are reacted together and in a step b) the resulting reaction mixture is destabilized by the action of one or more external factor to obtain the surface-modified inorganic particles.

2. Surface-modified nanoparticles according to claim 1, characterized in that the inorganic particles are suspended before applying the surface modifier in a solvent or solvent mixture.

3. Surface-modified particles according to claim 1 or 2, characterized in that the particles on oxides, hydroxides, sulfides, sulfates, carbonates of silicon, titanium, zinc, aluminum, cerium, cobalt, chromium, nickel, iron, yttrium and / or zirconium or mixtures thereof, or based on metals coated with oxides or hydroxides of silicon, such as Ag, Cu, Fe, Au, Pd, Pt or alloys.

4. Surface-modified particles according to claim 1 or 2, characterized in that the particles based on oxides, hydroxides, sulfides, sulfates, carbonates of titanium, zinc, aluminum, cerium, cobalt, chromium, nickel, iron, yttrium and / or zirconium or Mixtures thereof are coated with oxides or hydroxides of silicon.

5. Surface-modified particles according to one or more of claims 1 to 4, characterized in that the particles have a average particle size, determined by means of dynamic light scattering or transmission electron microscope, from 3 to 200 nm.

6. Surface-modified particles according to one or more of claims 1 to 5, characterized in that the solvent or solvent mixture comprises water, alcohols, ketones and / or ethers.

7. Surface-modified particles according to one or more of claims 1 to 6, characterized in that the external factor is selected from a change in the pH after the surface modification, a solvent addition or a solubilizer addition to the particle dispersion, a temperature change or a salt addition.

8. Surface-modified particles according to one or more of claims 1 to 7, characterized in that the surface modifier is selected from the group of organofunctional silanes, quaternary ammonium compounds, phosphonates, phosphonium and sulfonium compounds,

Copolymers, polymers or mixtures thereof.

9. Surface-modified particles according to one or more of claims 1 to 8, characterized in that the surface modifier is covalently bonded to the surface of the inorganic particles.

10. Surface-modified particles according to one or more of claims 1 to 9, characterized in that the surface modifier is an LCST or UCST polymer.

11. Surface-modified particles according to one or more of claims 1 to 10, characterized in that the particles are separated and / or dried.

12. Surface-modified particles according to one or more of

Claims 1 to 11, characterized in that they are redispersible in organic solvents.

13. Surface-modified particles according to one or more of claims 1 to 12, characterized in that they are transparent dispersible, measured by the turbidity of the dispersion, which is determined by means of a UV / VIS / NIR spectrometer Lambda 900 with integration sphere 150 mm.

14. A process for preparing surface-modified inorganic particles according to claim 1, wherein in a step a) in a solvent or solvent mixture, inorganic particles and at least one surface modifier are reacted together and in step b) the resulting reaction mixture by the action of one or more external factor Obtaining the surface-modified inorganic particles is destabilized.

15. The method according to claim 14, characterized in that the particles are separated and / or dried.

16. Use of surface-modified particles according to one or more of claims 1 to 13 in paints, adhesives and plastics.

17. Use of surface-modified particles according to one or more of claims 1 to 13 for improving the chemical, thermal and mechanical stability of polymers.