CA2228326C - Metal deposits on mesoscopic organopolysiloxane particles - Google Patents

Abstract

Organopolysiloxane particles consist of a single molecule, are crosslinked, and contain metal atoms in the zero valent oxidation state, the metal atoms in each case being in intermetallic interaction with at least one further metal atom in the zero valent oxidation state, have an average diameter of 5 to 200 nm and are soluble to the extent of at least 0.1% by weight in at least one organic solvent chosen from the group consisting of methylene chloride, pentane, acetone, toluene and ethanol, at least 80% of the particles having a diameter which deviates from the average diameter by not more than 30%.

Description

METAL DEPOSITS ON MESOSCOPIC
ORGANOPOLYSILOXANE PARTICLES

Technological Field The invention relates to monodisperse, soluble organopolysiloxane particles which consist of a single molecule and comprise metal atoms in the zero valent oxidation state with intermetallic interaction, their preparation and their use. The organopolysiloxane particles have an average diameter of 5 to 200 nm and are therefore in the mesoscopic size range.

Description of the Related Art The deposition of metals or metal alloys on substrate surfaces, usually silicic acids or active charcoal, is known. W. Zou et al., Materials Letters, 24 (:1995), 35-39 describes the preparation of macrogels which have an intercollated metal salt by a sol-gel process starting from metal salt solutions and tetra-ethoxysilane. Platinum-, palladium- or iridium-contain-ing silica gels are obtained by subsequent reductive c~lcining of the ground gels. The metal-coated sub-strates prepared in this way are chiefly used as hetero-geneous catalysts, for example for hydrogenation of carbon-carbon double bonds or in the detoxification of waste gas. However, these catalyst systems have all the disadvantages of a heterogeneous catalyst, such as relatively low activity because of the low catalytically active surface area and low selectivity. Furthermore, the metal particle size, which is important for the catalytic processes, is established rather randomly. The CA 02228326 l998-0l-29 location of the metal particles also depends on the process procedure during gelling, and the metal content accessible for catalytic reactions is therefore diffi-cult to adjust.

An improvement is provided by the known preparation of defined metal colloids, which are stable in solution, by in situ reduction and stabilization, for e~.ample in a microemulsion or inverse microemulsion, or by electrochemical reduction of metal salts in the presence of surfactants having a stabilizing action. It is known from Antonietti et al., Nachr. Chem. Lab. 44, 1'396, 6, page 579 that the stabilization of these colloidal particles by means of a surfactant ceases under more severe conditions, such as elevated tempera-ture, increased salt content and aggressive reaction media. Colloidal aggregates of lower reactivity and selectivity are formed under these conditions.

Another method of stabilization of metal colloids, produced in situ by reduction in the presence o:E amphiphilic block copolymers, such as polysty-rene/polyacrylic acid copolymers, is described in Antonietti et al., Nachr. Chem. Lab. 44, 1996, 6, page 5'79. The advantage of these systems is a substantially lower sensitivity to changes in temperature, to the chemical environment, and to salt effects. Furthermore, the metal colloids stabilized in this way are redisper-sible in organic solvents after drying out. However, this variant also has some disadvantages. Thus, the synthesis of the amphiphilic block copolymers is associ-ated with a high synthesis cost, and furthermore, the colloid particle size cannot be controlled easily because of the influence of the reduction conditions, CA 02228326 l998-0l-29 such as temperature, solvent, reducing agent and metal salt precursor. Finally, active metal centers inside the metal colloids are inaccessible. Another disadvan-tage is that an external reducing agent, such as hydra-zine or sodium borohydride, must always be added forreduction of the metal salt. The reducing agent also considerably influences the resulting metal colloid size and distribution via nucleation processes, and is thus another uncertainty factor in controlled adjustment of the colloid particle size. These colloidal metal systems described to date are also limited only to the organic phase .

No controlled layer build-up of metal nano-st:ructures is possible by the methods described above, and only random metal alloys can be prepared, if at all.

An object of the subject invention is to provide organopolysiloxane particles which are soluble in organic solvents, which have metal deposits, and which have a monodisperse particle size distribution within a size range of from 5 to 200 nm.

Sllmm~ry Of The Invention The invention relates to crosslinked organo-polysiloxane particles which consist of a single mole-cule, and contain metal atoms in the zero valent oxida-tion state, these atoms in each case being in inter-metallic interaction with at least one further metal atom in the zero valent oxidation state, the particles hLving an average diameter of 5 to 200 nm and being s~luble to the extent of at least 0.1~ by weight in at least one organic solvent chosen from the group consist-CA 02228326 l998-0l-29 WP.S 0163 PCA -4-irg of methylene chloride, pentane, acetone, toluene and ethanol, at least 80~ of the particles having a diameter which deviates from the average diameter by not more than 30~.

Detailed Description of the Invention The organopolysiloxane particles typically have mean molar masses of at least 104 g/mol, in particu-lcLr 5 x 105 g/mol, and preferably not more than lolO
g/'mol, in particular 109 g/mol. The average diameters of the metal-containing organopolysiloxane particles are preferably between 10 and 200 nm. Preferably, 80~ of the particles have a diameter which deviates from the average diameter by not more than 20~, in particular not more than 10~. The metal-containing organopolysiloxanes are preferably spherical particles.

The metal-containing organopolysiloxane particles are soluble in solvents and can therefore be ernployed, for example, as homogeneous catalysts, in which, however, the catalytically active metal is irnmobilized in the form of colloids, clusters, or layers Oll the organopolysiloxane particle surface, thus also o:-fering the advantages of a heterogeneous catalyst. The solubility in a solvent is preferably at least 0.01~ by weight, in particular at least 0.1~ by weight. The solvents in which the metal-containing organopoly-siloxane particles dissolve depend, on the one hand on t]-Le build-up of the organopolysiloxane particles, and on t]-Le other hand, on the nature and density of the metal covering on the particle surface. There is at least one suitable solvent for all metal-containing organopoly-siloxane particles. Examples of such solvents are CA 02228326 l998-0l-29 WP.S 0163 PCA -5-alcohols such as methanol, ethanol, n-propanol and iso-propanol; ethers such as dioxane, tetrahydrofuran, diethyl ether and diethylene glycol dimethyl ether;
chlorinated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane and trichloroethylene; saturated hydrocarbons such as pentane, n-hexane, cyclohexane, hexane isomer mixtures, heptane, octane, petroleum distillate or petroleum ether; aliphatically unsaturated hydrocarbons, in particular alkenes, such as pentene, hexene or octene, dienes, such as hexadiene or cyclooctadiene; alkynes such as butyne; aromatic hydrocarbons such as benzene, toluene or xylenes; ketones such as acetone, methyl et:hyl ketone, methyl isobutyl ketone or cyclohexanone;
nitrogen-containing organic solvents, such as nitroben-zene, nitromethane or dimethylformamide; sulfur-contain-ing organic solvents such as carbon disulfide; and oligomeric and polymeric siloxanes with optional func-t~onal groups such as vinyl groups, for example ~
v nyl-terminated dimethylpolysiloxanes; mixtures of these solvents, as well as monomers such as methyl methacrylate or styrene, and liquid polymers. The metal-coated particles are also redispersible in water to the extent of at least 0.1~ by weight.

The atomic properties of an individual metal alom in the zero valent oxidation state in the organo-polysiloxane particles are annulled; metal units are present, but still no metallic solid. The properties of the metal units lie between the properties of an indi-vidual atom and those of a metallic solid. The conduc-tion bands of the individual atoms approach each other.
The energy interval from the base level to the conduc-tion band decreases. Preferably, at least 3, in particu-CA 02228326 l998-0l-29 lar at least 5 metal atoms of the zero valent oxidation state are in intermetallic interaction with one another.

The relative total content of metal in the zcro valent oxidation state of the organopolysiloxane particles is at least 10 ppm, preferably at least 0.1~
by weight, in particular at least 1~ by weight, and preferably not more than 50~ by weight, more preferably nc,t more than 10~ by weight, and in particular not more than 5~ by weight. The relative metal content can be determined by elemental analysis.

The organopolysiloxane particles can contain any desired metal atoms in the zero valent oxidation state. The metals preferably chosen are those which can be reduced from their compounds by reducing agents such as alcohols, aldehydes, hydrazine, sodium borohydride or hydridosilanes or -siloxanes, or by W irradiation, i.e.
their redox potential in the chemical environment existing in each case is greater than that of the particular reducing agent. For the example of the silicon hydride bond, all metals of which the redox potential in the particular chemical environment is greater than the defined zero in relation to hydride-hydrogen transfer can therefore be deposited starting from their metal salts. This applies, for example, to a]l noble metals, such as platinum, palladium, rhodium, rhenium, gold, silver, iridium and the like, and also to, for example, copper, bismuth and cobalt.

In the crosslinked organopolysiloxane parti-c~es, the metal atoms in the zero valent oxidation state can be in a different accumulation at various points.
One metal and also various metals can be present in one organopolysiloxane particle, it also being possible for various metals to be present at various points in the organopolysiloxane particle.

For example, the metal atoms may be on the organopolysiloxane particle surface, where they may then be present, depending on the covering density, in the form of clusters of metal deposits up to 1 nm diameter;
colloids with structures of more than 1 nm diameter which are clearly detectable as individual particles on the organopolysiloxane; or in a complete metal layer. In spite of a high covering of metal, no metal structures are detectable in these structures under a particle e]ectron microscope. The plasmon resonance can be measured by W.

For example, a layer build-up is possible, and can be structured, for example, as follows:

1) organopolysiloxane core 2) first metal deposit 3) organopolysiloxane layer 4) second metal deposit This layer structure is also optionally possible without a siloxane intermediate layer, it being possible for another metal layer to be present on the second layer.
Further layers can also be built up in this manner. The metal deposits, such as 2. and 4., can be present as a complete metal layer, metal clusters or metal colloids.

Another variant of the layer build-up is a metal layer applied to an organopolysiloxane core and an organopolysiloxane network of defined network mesh size CA 02228326 l998-0l-29 and defined chemical environment built up around this metal layer. Such organopolysiloxane particles can be employed both as a size-selective and as a chemically specific catalyst.

The metal deposits on the organopolysiloxane particle surface which are described above can further-mc,re carry complexing ligands on the metal surface, such a~ molecules of the above solvents or anions or neutral ligands resulting from the preparation process, such as chloride, nitrate and cyclooctadiene.

The organopolysiloxane content of the organo-polysiloxane particles preferably essentially consists of 0.5 to 80~ by weight of units of the general formula [R3SiOl/2] (1), O to 99.0~ by weight of units of the general formula [R2SiO2/2] (2), O to 99.5~ by weight of units of the general formula [RSiO3/2]
ar,d, O to 99.5~ by weight of units of the general formula [siO4/2]
in which R is a hydrogen atom or identical or different monovalent, SiC-bonded, C1 to Cl8 hydrocarbon radi-cals which optionally carry functional groups.

Examples of unsubstituted radicals R are alkyl radicals such as the methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neo-pentyl or tert-pentyl radical, hexyl radi-CCL1S such as the n-hexyl radical, heptyl radicals such as, the n-heptyl radical, octyl radicals such as the n-octyl radical, and iso-octyl radicals such as the 2,2,4-trimethylpentyl radical, nonyl radicals such as the n-nonyl radical, decyl radicals such as the n-decyl radical, dodecyl radicals such as the n-dodecyl radical, and octadecyl radicals such as the n-octadecyl radical;
cycloalkyl radicals such as cyclopentyl, cyclohexyl, 4-ethylcyclohexyl and cycloheptyl radicals, norbornyl radicals and methylcyclohexyl radicals; aryl radicals such as the phenyl, naphthyl, anthryl, and phenanthryl radicals; alkaryl radicals such as o-, m- and p-tolyl radicals, xylyl radicals and ethylphenyl radicals; and aralkyl radicals such as the benzyl radical and the alpha- and ~-phenylethyl radicals.

Examples of hydrocarbon radicals R which carry functional groups are halogenated hydrocarbon radicals, in particular haloalkyl radicals such as the chloro-methyl, 3-chloropropyl, 3-bromopropyl, 3,3,3-tri-fluoropropyl and 3,3,4,4,5,5,5-heptafluoropentyl radi-cal; and haloaryl radicals such as the o-, m- and p-chlorophenyl radicals; hydrocarbon radicals which carry primary, secondary and tertiary amines, for example aminoalkyl radicals such as the 2-aminoethyl, 3-amino-propyl, N-(2-aminoethyl), 3-aminopropyl, N-(2-amino-et:hyl)-3-amino-(2-methyl)propyl and pyrimidinyl radi-cals, and aminoaryl radicals such as the aminophenyl radical; quaternary ammonium radicals; hydrocarbon radicals which carry mercapto groups such as the 2-mercaptoethyl and 3-mercaptopropyl radicals; cyanoalkyl radicals such as the 2-cyanoethyl and 3-cyanopropyl i radical; hydrocarbon radicals which carry acrylic groups, for example acryloxyalkyl radicals such as the 3-acryloxypropyl and 3-methacryloxypropyl radical;
hydrocarbon radicals which carry hydroxyl groups, for example hydroxyalkyl radicals, such as the hydroxypropyl radical; hydrocarbon radicals which carry phosphonic acid, phosphonato, and sulfonato groups; and unsaturated hydrocarbon radicals which are interrupted by the heteroatoms O, N or S, such as the furanyl, pyridyl or thiophenyl radicals.

The radical R is preferably selected from unsubstituted Cl- to C6-alkyl radicals, phenyl radicals or hydrogen, in particular, the methyl radical.

The organopolysiloxane content in the envelop-ir.g siloxane layers of the organopolysiloxane particlescan have a composition the same as or different to that ir, the underlying siloxane core. The siloxane shell preferably has a thickness of 1 to 10 nm, in particular not more than 5 nm, and particularly preferably not more than 2 nm.

In particular, the organopolysiloxane parti-cl.es comprise at least 0.1~ by weight of metal and the organopolysiloxane content of the organopolysiloxane particles consists of 1 to 80~ by weight of units of the general formula (1), 0 to 98~ by weight of units of the general formula (2), 0 to 99~ by weight of units of the general formula (3), an CA 02228326 l998-0l-29 0 to 99~ by weight of units of the general formula (4),with the proviso that the sum of the units of the general formulae (3) and (4) is at least 1~ by weight.

Metal-containing organopolysiloxane particles and organopolysiloxane shells which are built up at least to the extent of 80 mol~ from units of the general fc,rmula (2) have elastomeric properties. These particles or siloxane envelopes built up in this way are swellable ir the above organic solvents, in particular in toluene, tetrahydrofuran, dioxane, petroleum ether, chlorinated hydrocarbons and alkenes. In these swollen particles, metal clusters, colloids and layers lying inside are thus accessible for catalytic reactions, for example. At the same time, a size selectivity for the catalyzed reaction can be established via the adjustment of the mesh width in an enveloping swellable siloxane layer.

The invention furthermore relates to a process for the preparation of the metal-containing crosslinked organopolysiloxane particles consisting of a single molecule, in which A) the organopolysiloxane component of the organopoly-siloxane particles is prepared as a colloidal suspension of organopolysiloxane particles in a first step by metering silanes of the general formula (5) RaSi(oR1)4a (5) and, when appropriate, organosilicon compounds of the general formula ( 6) Rb(R ~)csi~4-b-c/2 (6), CA 02228326 l998-0l-29 ir, which Rl has the meanings of R, a has the value 0, 1, 2 or 3, b and c in each case independently of one another have the values 0, 1, 2, 3 or 4 and R has the above meanings, into an agitated mixture of emulsifier and water and in a second step, an organosilicon compound of the general formula (7) (R23Si)dYl (7) in which yl if d = 1, is a hydrogen atom, -oR3, -oNR32 or -ooCR3 and if d = 2, is -O- or -S-, R2 and R3 have the meanings of R and d has the value 1 or 2, is added to the colloidal suspension, with the proviso that the organosilicon compounds of the general formula (,') are water-soluble or hydrolyze in water to give a wcLter- soluble compound.

Interparticulate condensation of the organo-polysiloxane particles is prevented by saturating the condensable groups remaining after the first step with organosilicon compounds containing exclusively monofunc-ti.onal triorganosilyl groups.

Preferably, no by-products, such as hydrochlo-ric acid or ammonia, which substantially increase the ionic strength of the aqueous colloidal system are formed during the hydrolysis or condensation reaction of the organosilicon compounds of the general formula (7).
Organosilicon compounds of the general formula (7) which W~.S 0163 PCA -13-are particularly preferably employed are trimethylmeth-oxysilane, trimethylethoxysilane, hexamethyldisiloxane, vinyldimethylmethoxysilane, vinyldimethylethoxysilane, 1,1,3,3-tetramethyldisiloxane and mixtures thereof.

When the second reaction step has ended, the organopolysiloxane particles can be isolated from the cc,lloidal suspensions by known processes, for example by cc,agulation of the lattices by means of addition of sa.lts or by addition of polar solvents.

After isolation of organopolysiloxane parti-cles containing a total of more than 15~ by weight of ur.its of the general formulae (3) and (4), after the second step, an organosilicon compound of the general formulae (8) and/or (9) (R23Si)dy2 (8), R22Si-Y3 \/ (9), (CH2) e in which y2/ if d = 1, is a hydrogen or halogen atom, -oR3, -NR32, -oNR32 or -ooCR3 and if d = 2, is -O-, -N(R3)- or -S-, Y3 is the radical -O-, -N(R3)- or -S-, e is a value from 1 to 30, in particular 2, 3 or 4, and d, R2 and R3 have the above meanings, is added in a third reaction step in an aprotic solvent.

W~.S 0163 PCA -14-Organosilicon compounds of the general formula (8) are preferably employed in the third step.

Organosilicon compounds of the general formula (8) which are particularly preferably employed in this third reaction step are trimethylchlorosilane, dimethyl-chlorosilane, vinyldimethylchlorosilane, hexamethyl-disilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, or mixtures of disilazanes or chlorosilanes.

The amounts of compounds of the general formulae (5) to (9) employed are chosen such that the desired organopolysiloxane particles are obtained. The amounts of compounds of the formulae (5) and (6) em-ployed are incorporated virtually quantitatively in the first reaction step and control the degree of crosslink-ing of the organopolysiloxane particles in aqueoussuspension. The compounds of the general formula (7) or (8) and (9) employed in the second and, if appropriate, in the third reaction step are in each case employed in excess and are thus not incorporated completely into the organopolysiloxane particles. Preferably, 0.2 to 10, in particular 0.5 to 3 parts by weight of compounds of the general formula (7) in the second reaction step, or of the total of the compounds of the general formulae (7), (8) and (9) in the second and third reaction step are employed per part by weight of compounds of the general formulae (5) and (6).

If a third reaction step is carried out, the ratio of the amount of compounds of the general formula ( ,7 ) employed in the second reaction step to the amount of compounds of the general formulae (8) and (9) em-ployed in the third reaction step is preferably 1 : 10 to 2 : 1, in particular 1 : 5 to 1 : 1.

The radical R3 is preferably unsubstituted C1-tc,C6-alkyl radicals or the phenyl radical, with methyl, ethyl and propyl radicals being particularly preferred.

Particularly suitable emulsifiers are alkyl su.lfates, for example those having a chain length of 8-18 carbon atoms, and aryl and alkyl ether-sulfates ha.ving 8-18 carbon atoms in the hydrophobic radical and 1-40 ethylene oxide (EO) or propylene oxide (PO) units;
sulfonates, for example alkylsulfonates having 8-18 carbon atoms, alkylarylsulfonates having 8-18 carbon atoms and esters and half-esters of sulfosuccinic acid with monohydric alcohols or alkylphenols having 4-15 carbon atoms; if appropriate, these alcohols or al.kylphenols ethoxylated with 1-40 EO units;
alkali metal and ammonium salts of carboxylic acids having 8-20 carbon atoms in the alkyl, aryl, al.karyl or aralkyl radical;
phosphoric acid partial esters and alkali metal and ammonium salts thereof, for example alkyl and al.karyl phosphates having 8-20 carbon atoms in the organic radical and alkyl ether- or alkaryl ether-phosphates having 8-20 carbon atoms in the alkyl or alkaryl radical and 1-40 EO units;
alkyl polyglycol ethers having 2-40 EO units and alkyl radicals of 4-20 carbon atoms;
alkylaryl polyglycol ethers having 2-40 EO
units and 8-20 carbon atoms in the alkyl and aryl radicals;
ethylene oxide/propylene oxide (EO/PO) block copolymers having 8-40 EO and PO units;

fatty acid polyglycol esters having 6-24 carbon atoms and 2-40 EO units;
alkyl polyglycosides, naturally occurring sub-st.ances and derivatives thereof, such as lecithin, lanolin, saponins and cellulose; and cellulose alkyl et.hers and carboxyalkylcelluloses, the alkyl groups of which in each case have up to 4 carbon atoms;
linear organo(poly)siloxanes containing polar groups and having alkoxy groups with up to 24 carbon at.oms and/or up to 40 EO and/or PO groups;
salts of primary, secondary and tertiary fatty amines having 8-24 carbon atoms with acetic acid, sulfuric acid, hydrochloric acid and phosphoric acids;
quaternary ammonium salts, such as halides, sulfates, phosphates, acetates or hydroxides, the alkyl groups of which independently of one another have 1-24 carbon atoms; if appropriate, the alkyl or alkaryl or aralkyl groups of the quaternary ammonium compounds can also be partly ethoxylated (1-40 EO units);
alkylpyridinium, alkylimidazolinium and alkyl-oxazolinium salts, the alkyl chain of which has up to 18 C atoms, in the form of their halides, sulfates, phos-phates or acetates.

Aliphatically substituted benzenesulfonic acids and salts thereof and optionally partly ethoxy-lated quaternary ammonium halides and hydroxides are preferred. Dodecylbenzenesulfonic acid and benzyldi-methyl-{2-[2-(p-1,1,3,3--tetramethylbutylphenoxy)ethoxy]-ethyl}ammonium chloride (benzethonium chloride) are particularly preferred.

The amount of emulsifier to be employed is 0.5 to 50~ by weight, preferably 1.0 to 30~ by weight, in each case based on the total amount of organosilicon starting compounds emp:loyed in the first and second reaction step. The organosilicon starting compounds of the general formulae (9) to (11) are preferably added in metered form during the first reaction step. Preferably, all the starting components of the general formulae (9) to (11) are mixed in the desired ratio before the metering during the first reaction step; in order to obtain a homogeneous mixture, if appropriate, 0.1 - 30~
by weight, based on the sum of the starting components of the general formulae (9) to (11), of an alkanol of the formula R70H in which R7 is an alkyl radical having 1 to 5 carbon atoms, is additionally added as a solubi-lizing agent, the alkanols methanol and ethanol being particularly preferred.

The ethers, hydrocarbons, ketones and organo-polysiloxanes described above, in particular tetrahydro-furan, cyclohexane, methylcyclohexane or toluene, are preferably used as the aprotic organic solvent in the third step. The reaction both in the first (emulsion polycondensation/addition polymerization) and in the second reaction step is preferably carried out at 5 -95~C, more preferably at 10 - 85~C, and in particular preferably at 10 - 40~C. The pH is in each case 1 - 12, preferably 1 - 4, or 7 -- 11, depending on the acid/base stability of the radicals R, Rl, R2 and R3 of the starting compounds (5) to (9).

In the preparation of the colloidal suspen-sions during the first reaction step, it is advanta-geous, for the stability of the emulsion, to subsequent-ly stir the mixture for a further 1 to 24 hours after the end of metering of the organosilicon starting compounds of the general formulae (5) and (6). The alkanol liberated during the hydrolysis can be removed by distillation, if appropriate under reduced pressure, but this is not preferred. The solids content of the colloidal suspension prepared after the first step should preferably be not more than 25~ by weight, since otherwise a high increase in the viscosity makes the further reaction more difficult. In the reaction of the colloidal suspension with an organosilicon compound of the general formula (7) in the second reaction step, it is also advantageous to subsequently stir the mixture for a further 1 - 48 hours after the end of the addition of compounds of the general formula (7), to achieve a reaction which is as complete as possible.

The reaction with organosilicon compounds of the general formulae (8) and (9) in the third reaction step is preferably carried out at 5 - 95 C, more prefer-ably at 10 - 85~C, and in particular at 10 - 40~C. To achieve a reaction which is as complete as possible, it is in turn advantageous to subsequently stir the mixture for a further 1 to 24 hours after the end of the addi-tion of the compounds of the general formulae (8) and (9) .

All the customary working-up processes known from polymer synthesis, such as precipitation and subse-quent separating off of the polymer, or evaporation of solvents and unreacted starting materials, can be used for working up and isolating the metal-free organopoly-siloxane particles. Precipitation of the organopoly-siloxane particles with short-chain alcohols is pre-ferred for this procedure, and methanol is a particular-- CA 02228326 l998-0l-29 ly preferred precipitating agent here, with subsequent filtration at room temperature.

The organopolysiloxane particles obtained in the form of a powder are dried, preferably under a high vacuum under a pressure of <0.0001 MPa at 20 C to 100~C, in particular under a high vacuum at 20~C to 50~C.
The metal-free organopolysiloxane particles prepared and isolated in process stage A) can also be redispersed.

In the process for the preparation of the metal-containing crosslinked organopolysiloxane parti-cles consisting of a single molecule, the metal content of the organopolysiloxane particles can be deposited in process stage B) on the metal-free organopolysiloxane particles, prepared, for example, by process stage A, by reduction of a metal compound with a reducing agent by, for example, the following processes:

B1) the metal content can be deposited in organic solvents. For this method, the metal-free organopolysiloxane particles are dissolved in a suitable solvent. Examples of suitable solvents are the solvents which are suitable for the metal-containing organopoly-siloxane particles.

Bla) the metal content is deposited on metal-free organopolysiloxane particles which carry hydrido functions (SiH groups). The preferred concentrations of hydrido-functional organopolysiloxanes are at least 1~
by weight and not more than 50~ by weight, preferably not more than 30~ by weight, and in particular not more than 20~ by weight, based on the total weight of the solution.

Metal compounds which can be used, and suit-able mixtures of metal compounds of various metals are all those which can be reduced to the metal by a silicon hydride bond in the corresponding chemical environment, i.e. have a positive redox potential with respect to hydride-hydrogen transfer, such as noble metal compounds or mixtures thereof, for example platinum compounds such as hexachloroplatinic acid, palladium compounds such as palladium dichloride, ruthenium compounds such as ruthenium trichloride, iridium compounds, rhenium compounds, for example in the form of their trichlorides, gold compounds such as tetrachloroauric acid, silver compounds such as silver perchlorate, copper compounds such as copper sulfate, copper chlo-ride, and copper nitrate, and cobalt compounds such as cobalt nitrate and coba:lt chloride.

Metal-free organopolysiloxane particles which carry hydrido functions (SiH groups) are dissolved in a suitable solvent. Examples of suitable solvents are the solvents which are suitable for the metal-containing organopolysiloxane particles.

The metal compounds should be soluble in a solvent which is miscible with the solvent used for the hydrido-functionalized organopolysiloxanes. Suitable solvent classes for the metal compounds and suitable examples of these are the solvents mentioned above for the metal-containing organopolysiloxane particles.

~ CA 02228326 1998-01-29 The dissolved reaction partners are then mixed. Mixtures of metal compounds of various metals can optionally be added simultaneously or successively, for example for the preparation of separate various metal colloids on the same metal-free organopolysiloxane particles, it being necessary only to ensure that the total molar amount of metal compounds added does not exceed the molar amount of silicon hydride groups present having a reducing action. Suitable molar ratios of reductive silicon hydride groups to the metal com-pound or metal compound mixture or to the total metal compounds employed are in the range of the molar ratios from 1 : 1 to 100,000 : 1, in particular from 10 : 1 to 1000 : 1, and particularly preferably from 10 : 1 to 100 : 1.

Mixing can take place during the reaction, but the reaction can also be allowed to proceed without mixing. The reactions are preferably carried out in a temperature range from -80~C to 150~C, in particular in a temperature range from 0~C to 100~C, and particularly preferably in a temperature range from 25~C to 80~C.
The reaction times are 1 second to 10 days, preferably 1 minute to 2 hours, and particularly preferably 30 minutes to 1 hour.

After the reduction of the metal, which can be detectable, for example, by the change in color of the solutions, the remaining residual hydrido groups can optionally be saturated by means of a suitable reaction, such as hydrosilylation or alcoholysis. The amount of reactant employed for the after-reaction, in general, depends here on the mathematical molar excess of silicon hydride bonds which should remain on the organopoly-siloxane particle after the complete redox reaction. A
1.5- to 2-fold molar excess is preferred here, and a 2-to 5-fold molar excess is particularly preferred.

Suitable substances are all compounds or mixtures of compounds which can react with the hydrogen of the silicon hydride hond, if appropriate under metal catalysis, and increase the storage stability with respect to interparticulate condensation of the parti-cles. Examples of such substances are molecules which carry terminal C=C double bonds, such as alkenes, for example 1-octene. These form stable Si-C linkages via hydrosilylation, as do the alkynes, such as butyne.
There may furthermore also be mentioned here macromono-mers terminated by vinyl on one or both sides, such as ~ vinyl-terminatedpolyalkylsiloxanes,allyl-terminat-ed polystyrenes and allyl-terminated polyethers; and longer-chain, cyclic or aromatic alcohols, such as pentanol, hexanol, cyclohexanol and benzyl alcohol.
These react to give Si--O-C compounds, which are rela-tively insensitive to hydrolysis because of thesterically bulky radical of the alcohol and thus sub-stantially increase the storage stability.

The alkenes are preferred here, and 1-octene is particularly preferred. The after-reaction is prefer-ably carried out at the same reaction temperature as themetal reduction. The after-reaction is particularly preferably carried out at 50~C to 100~C. The reaction times are preferably 30 minutes to 2 hours, more prefer-ably one hour to 90 minutes.

Blb) The meta:L content is deposited on metal-free organopolysiloxane particles with added reducing agent. In contrast to stage Bla), in this process a low molecular weight reducing agent which is not bonded to the organopolysiloxane particle is employed. The advan-tage over stage Bla) is that a wider redox range becomes accessible, and metal c~mpounds which are redox-stable with respect to the silicon hydride bond can also additionally be reduced Furthermore, this stage is not limited to the hydrido-functionalized metal-free organo-polysiloxane particles as carriers, and finally the build-up of metal layer structures on a carrier particle is possible by this pro~ess, since the amount of reduc-ing agent available is not correlated to the amount of hydrido-functionalized metal-free organopolysiloxane particles.

Suitable reducing agents are all substances which have a reducing action and dissolve in adequate amounts - preferably, at least 1~ by weight - in the solvents suitable for the organopolysiloxanes. Examples of suitable reducing agents are hydrazines such as hydrazine and hydroxylhydrazine; metal borohydrides such as sodium or potassium borohydride; aldehydes such as acetaldehyde; reducing sugars such as fructose and glucose; alcohols such as ethanol; polyglycol;
dihydroxybenzenes such as resorcinol and hydroquinone;
alkali metal and alkaline earth metal hydrides such as sodium hydride; aluminum hydrides such as lithium aluminum hydride; and organic acids having a reducing action, or salts thereof, such as citric acid and sodium citrate.

Metal compounds which can be used, and suit-able mixtures of metal compounds of various metals, are all those which are reduced to the metal by the reducing agent in the corresponding chemical environment, i.e.
have a redox potential which is positive with respect to the ~educing agent. Suitable examples are the metal compounds listed for stage la) or mixtures thereof, and further metal compounds having an even more positive redox potential.

The metal compounds should be dissolved in a solvent which is miscib:le with the solvent used for the organopolysiloxane particles and the reducing agent. If appropriate, the solvent can also simultaneously be the reducing agent, such as alcohols or aldehydes. Suitable solvents for the metal compounds are described above for the organopolysiloxane particles.

The dissolved reaction partners are then mixed. Mixtures of meta:L compounds of various metals can optionally also be added simultaneously or successively, for example for the preparation of separate various metal colloids on the same metal-free organopolysiloxane particle, it being necessary to ensure only that the total amount of metal compounds added does not exceed the amount of reducinq agent present. Suitable molar ratios of reducing agent to metal compound or metal compound mixture or to the total metal compounds em-ployed are in the range of the molar ratios from 1:1 to 100:1, preferably from 2:1 to 10:1, and in particular from 1.5:1 to 2:1.

Mixing can take place during the reaction, but the reaction can also be allowed to proceed without mixing. The reactions are preferably carried out in a temperature range from -80~C to 150-C, preferably in a temperature range from 0~C to 100~C, and in particular ~ CA 02228326 1998-01-29 in a temperature range from 25 C to 80 C. A redox reaction can furthermore be stimulated by irradiation, for example by W light:. For example, colloids of gold and silver can be deposited in this manner. The reac-tion times are preferably 1 second to 10 days, morepreferably 1 minute to two hours, and in particular 30 minutes to one hour.

B2.) The metal content can be deposited in aqueous dispersion. The dispersed metal-free organopoly-siloxane particles prepared in process stage A) arereacted with suitable metal compounds and, if appropri-ate, with additional reducing agent. Metal-containing organopolysiloxane part:icles built up in different ways can be prepared by different process steps.
B2a.) The aqueous metal-free organopoly-siloxane particle dispersions in which R is preferably a methyl or, in particular, hydrogen radical are em-ployed. The solids content of the dispersions preferably varies here from 0.1~ by weight to 25~ by weight, more preferably from 4% by weight to 16~ by weight, and in particular from 8~ by weight to 12~ by weight.

All substances which have an effective reduc-ing action and which dissolve to the extent of at least 1~ by weight in a solvent mentioned below which is miscible with the organopolysiloxane dispersion are suitable as the reducing agent. Examples of these substances having a reducing action are hydrazine hydroxide, alcohols, hydroquinone, aldehydes, sugars and organic acids, such as citric acid.

Metal compounds which can be used are men-tioned above under step Bla). The metal compounds are CA 02228326 l998-0l-29 soluble to the extent of at least 0.01~ by weight in a solvent used for the organopolysiloxane dispersion and the reducing agent. Suitable solvents for the metal compounds are water or solvents of unlimited miscibility with water, such as short-chain alcohols, such as methanol, ethanol or isopropanol, ketones, such as acetone, ethers such as dioxane or tetrahydrofuran, dimethylformamide and dimethyl sulfoxide.

The dissolved reaction partners are then mixed. The amounts of metal compounds and ratio to the amount of reducing agent are preferably chosen as mentioned above under step Bla). Mixing can take place during the reaction, but the reaction can also be allowed to proceed without mixing. The reactions are preferably carried out in a temperature range from 0~C
to 100~C, more preferably in a temperature range from 10~C to 90~C, and in particular in a temperature range from 25~C to 70~C. A redox reaction can furthermore be stimulated by irradiat:ion, for example by W light. For example, colloids of gold and silver can be deposited in this manner. The reaction times are 1 second to 10 days, preferably 1 minute to two hours, and in particu-lar 30 minutes to one hour.

If alkoxy and hydroxyl groups which are still capable of condensatic,n are present on the organopoly-siloxane particle afte:r the end of the deposition of the metal, these are preferably saturated with an organo-silicon compound of the above general formula (7).

In step B2b), an organopolysiloxane layer can again be prepared on the metal-containing organopoly-siloxane particle prepared according to step B2a) by condensing onto it trialkoxysilanes or mixtures of di-ard trialkoxysilanes. Redispersible, multilayered, metal-containing organopolysiloxane particles can be prepared.

If mixtures of di- and trialkoxysilanes are employed, an elastomer layer can be prepared. Silanes of the above general formula (5) in which a has the value 2 or 3 are preferably employed.

The same or another metal can in turn be deposited on the organopolysiloxane layer, and thereaf-ter again an organopolysiloxane layer. The layers can be applied several times on one another. The last step in this process is the final blocking step for alkoxy and hydroxyl groups which are still capable of condensation on the organopolysiloxane particle using, preferably, an organosilicon compound of the above general formula (7).

The organopolysiloxane dispersions, reducing agents, metal compounds, solvents and ratio of reducing agent: metal compound are described above for process B2a).

In stage C, o:rganopolysiloxane particles which already contain a metal can be provided with a metal coating with the aid of further metal compounds.

The organopolysiloxanes which are prepared according to stage B and contain metal on the particle surface, or aqueous dispersions thereof, can be reacted with metal compounds in an organic or aqueous phase. The noble metal which has already been deposited catalyzes CA 02228326 l998-0l-29 the reduction of the less noble metal on the substrate surface here.

The metal compound here must be soluble in a suitable solvent. For the aqueous dispersions, these are the solvents listed in process step B2b), and for the metal-containing particles soluble in an organic phase, these are the solvents listed in process step Bla) and Blb).

All metal compounds which have a positive redox potential with respect to the reducing agent in the particular chemical environment are suitable.
Suitable reducing agent:s are those mentioned in process step Bla) and Blb). Thus, for example, using reducing agents, layers of nickel, copper or silver or mixtures thereof can be deposited on a particle coated with only a low palladium content.

The metal-containing organopolysiloxane particles prepared in stage B and C can be worked up, isolated and dried in the same way as the metal-free organopolysiloxane particles in stage A.

The metal-containing organopolysiloxane particles can be employed, for example, as homogeneous catalysts or reactions catalyzed by metal, such as hydrosilylations and hydrogenations, in optics for selective absorption of, for example, W radiation, in electronics, on the basis of magnetic and conductive properties, for coati.ng, on the basis of the above properties, and for flameproofing.

Examples:

CA 02228326 l998-0l-29 In the following examples, unless stated otherwise in each case, a) all amounts are based on weight b) all pressures are 0.10 MPa (absolute) c) all temperatures are 20~C
d) PEM = Particle electron microscope e) GPC = Gel permeation chromatography f) DBS = dodecylbenzenesulfonic acid Static and dynamic light scattering were measured with a unit which comprises, inter alia, a StabiliteTM 2060-lls Kr laser from Spectra-Physics, a goniometer Sp-86 from ALV and an ALV-3000 Digital Strukturator/Korrelator. The krypton ion laser operated at a wavelength of 647.1 nm.

Sample preparation: the samples (organopoly-siloxane particles in toluene; concentration range as stated in the examples) were filtered three times through MillexTM-FGS filters (0.2 ~m pore size) from Millipore. The measurement temperature in the light scattering experiments was 20~C. The dynamic light scattering measurements were carried out as a function of the angle from 50~ to 130~ in 20~ steps, and the correlation functions were evaluated with the Simplex algorithms. In the static light scattering experiment, the dependence of the angle of the scattered light was measured from 30~ to 140 in 5- steps.

Structural characterization of the organo-polysiloxane particles by means of static and dynamic light scattering was carried out as described in DE-A-195 19 446.

CA 02228326 l998-0l-29 Preparation examples of organosiloxane micro-gel dispersions and redispersible particles therefrom:

a) Preparation of a dispersion comprising hydrido-functional organopolysiloxane microgel particles 1000 g of deionized water and 4 g of dodecyl-benzenesulfonic acid (DBS) are initially introduced into a 2 l three-necked flask at 50 C. 160 g of methyltri-methoxysilane are added dropwise to this solution in the course of 45 minutes and the mixture is subsequently stirred for about 30 minutes. Thereafter, a mixture of 21 g of methyltrimethoxysilane and 19 g of triethoxy-silane is added in the course of 30 minutes. The mixture is subsequently stirred at 50 C for a further 3 hours.
The resulting dispersion is filtered.

The solids content of the dispersion is about 8.5% by weight and the hydrogen content is about 0.01%
by weight, based on the total weight of the dispersion.
Static and dynamic light scattering measurements in water gave an Rh value of 10.5 nm, Rg less than 10 nm and a molar mass of about 2 x 106 g/mol. A monodisperse decay behavior of the autocorrelation function was found with the dynamic light scatt:ering.

b) Preparation of organopolysiloxane microgel parti-cles with a hydrido-functionalized shell 3000 g of deionized water and 12 g of DBS are initially introduced into a 4 l three-necked flask and are heated to 50 C. 60() g of methyltrimethoxysilane are added dropwise to this acidic emulsifier solution in the course of two hours, while stirring. 180 g of trimethyl-methoxysilane are then added to the dispersion and the mixture is stirred at room temperature overnight.

~ CA 02228326 1998-01-29 .

The dispersic~n is then broken with 5000 g of a 20% strength by weight solution of sodium chloride and is filtered and the solid is rinsed first several times with 500 g of water and then several times with 300 g of methanol. The residue is taken up in 1500 g of toluene and the mixture is dried over 200 g of sodium sulfate.
The resulting solution is concentrated to 1000 g. 80 g of dihydridotetramethy]disiloxane and 50 g of the acid catalyst Tonsil OTP. FF' (Sud-Chemie AG) are added to the resulting solution at :room temperature and the mixture is heated to 70~C and stirred at this temperature for 2 hours. The solution is then filtered and the filtrate is evaporated to dryness at 40~C under 1 mbar. 300 g of a white powder are obtained. The hydrogen content of the substance is 0.11% by weight. According to GPC (polysty-rene calibration), the polydispersity of the particles is 1.05. The particle dimensions were determined by static and dynamic light scattering in toluene:
hydrodynamic radius Rh: 11. 2 nm; radius of gyration Rg:
10 nm; molar mass 3.6 x 106 g/mol. The ratio of Rh to Rg shows that the particles are spherical.

c) Preparation of an organopolysiloxane microgel particle with a hydrido-functional core and a swellable shell 500 g of dei,onized water and 4 g of DBS are initially introduced into a 1 l three-necked flask and are heated to 50~C. 14.5 g of triethoxysilane are added dropwise to this acid emulsifier solution in the course of 15 minutes, while stirring. The dispersion is then stirred for a further 45 minutes and a mixture of 43 g of methyltrimethoxysilane and 56 g of dimethyldimethoxy-silane is then added dropwise over a period of 90 minutes. The dispersion is subsequently stirred at 50~C

CA 02228326 l998-0l-29 for a further 2 hours, 30 g of trimethylmethoxysilane are then added and the mixture is subsequently stirred for a further 4 hours.

The dispersion is precipitated with 1000 g of a 20~ strength by weight solution of sodium chloride and filtered and the solid is washed first several times with 100 g of water and then several times with 100 g of methanol. The residue is taken up in 500 g of toluene and the mixture is dried over 100 g of sodium sulfate.
The resultant solution is concentrated to 200 g. 20 g of dihydridotetramethyldisiloxane and 15 g of the acid catalyst Tonsil OPT. FF (Sud-Chemie) are added to this solution at room temperature and the mixture is heated to 70~C and stirred at t:his temperature for 2 hours. The solution is then filtered and the filtrate is evaporated to dryness at 40~C under 1 mbar. 48 g of a white powder are obtained. The hydrogen content of the substance is 0.05~ by weight. According to GPC (polystyrene calibra-tion), the polydispersity of the particles is 1.1. The particle dimensions were determined by static and dynamic light scattering in toluene: hydrodynamic radius Rh: 20.5 nm; radius of gyration Rg: 22 nm; molar mass 6 x lo6 g/mol.

d) Preparation of an organopolysiloxane microgel particle with a hydrido-functional layer with a swell-able shell 500 g of deionized water and 4 g of DBS are initially introduced into a 1 l three-necked flask and are heated to 50~C. 25 g of methyltrimethoxysilane are added dropwise to this acid emulsifier solution in the course of 15 minutes, while stirring. The dispersion is then stirred for a further 30 minutes. Thereafter, 9 g of triethoxysilane are -Ldded dropwise over a period of 30 minutes. The dispersion is subsequently stirred at 50~C for a further 30 minutes, and a mixture of 37.2 g of methyltrimethoxysilane and 48.5 g of dimethyldi-methoxysilane is then added dropwise in the course ofone hour. The dispersion is further stirred at 50~C for two hours. Further working up is carried out as de-scribed in preparation example c). 51 g of a white powder are obtained. The hydrogen content of the sub-stance is 0.03~ by weight. According to GPC (polystyrenecalibration), the polydispersity of the particles is 1.15. The particle dimensions were determined by static and dynamic light scattering in toluene: hydrodynamic radius Rh: 18.5 nm; radius of gyration Rg: 20 nm; molar mass 5.2 x 106 g/mol.

Example 1 (Reaction of metal compounds with highly crosslinked hydrido-functionalized organopolysiloxane particles which can be redispersed in organic solvents, for the preparation of cluster~" colloids and layer structures on the particle surface) 1 g of the hydrido-functionalized organo-siloxane microgel from preparation example b), hydrogen content 0.11~ by weight, is dissolved in 10 g of tolu-ene. Metal salt solutions in methanol or solid metalcompounds as listed in Table 1 are added to the solution at room temperature.

The particular mixture is then stirred at room temperature or elevated temperature for a time stated in CA 02228326 l998-0l-29 Table I
Working up is carried out by evaporating off the solvent at 40~C under a high vacuum or by precipitation of the particles in 100 g of cold (-70~C) methanol.

5 ExampleMetal compoundAmount Imgl ReactionReaction time Color temperatureIminutes l~CI
laHexachloro 50mg in 0.5 g 80 30 brown platinic acid meth;mol Ib ditto 100 in 0.5 g 80 30 gray-MeOH brown lc ditto 200 in 0.5 g 80 30 black MeOH
ld ditto ~00 in 0.8 g 80 30 black MeOH
le ditto 100 mg 25 1.500 brown If PdC12 100 in 0.5 g 25 15 black MeOH
Ig ditto 250 in 0.8 g 25 15 black MeOH
IhSilver tosylate100 mg 80 60 yellow li ditto 300 mg 80 60 brown IjTetrachloro-auric50 in 0.5 g80 60 purple acid MeOH
Ik ditto 200 in 0.8 g 80 60 red-violet MeOH
Il Iridium 100 in 0.5 g 80 30 black trichloride MeOH
Im Rhodium 100 in 0.5 g 80 30 black trichloride MeOH
After the working up, all the products are 20 completely soluble again in toluene. Agreement of the actual with the theoretically calculated metal contents is found by elemental analysis.

The existing oxidation state 0 (zero valent) of the metal is detected by NMR, such as, for example, 25 by l95Pt-NMR. In all the samples measured, the chemical shift of -6000 ppm characteristic of Pt~ is found.

CA 02228326 l998-0l-29 The metal deposit and the nature thereof on the particle surface can be detected by electron micro-graphs.
Furthermore, the molecular dimensions are determined by static and dynamic light scattering in solution. The results are listed in Table Ia.

Table Ia Sample Rh [nm] Rg [nm] Distribution la 13.5 12 monodisperse lf 12 11.5 monodisperse lj 11 11 monodisperse Example 2 (Analogous to Example 1, but after deposition of the metal, reaction with l-octene is also carried out.) 2 g of the hydrido-functionalized organo-siloxane microgel from preparation example b are dis-solved in 15 g of toluene, and 0.5 g of a 10~ strength methanolic solution of hexachloroplatinic acid is then added at room temperature, while stirring. The reaction mixture is heated to 8()7C. After 30 minutes, 15 g of 1-octene are added at this temperature. The reaction mixture is heated to the reflux temperature and kept there for 15 minutes. After cooling, the product is precipitated in 150 ml of cold methanol at -70~C, filtered off and rinsed several times with cold metha-nol.

5 g of a gray-white product which is soluble in toluene, tetrahydrofuran and the like are obtained.

CA 02228326 l998-0l-29 Example 3 (Analogously to Example 1, but the metal deposit forms a core or a layer inside the particle.) Example 3.1 Metal-containinq Particle core 2 g of the hydrido-functionalized organopoly-siloxane from preparation example lc: hydrogen content 0.05~ by weight, are dissolved in 15 g of toluene. The metal salt or the metal salt solution is then added at room temperature. The metal compounds and reaction temperatures and times used in each case are summarized in Table II.

Table II

ExampleMetal salt Amount [mgl Reaction Reaction Color Temperature time [minutesl 3.1 aHexachloroplatinic200 in 0.8 g 80~C 120 min- black-acid cyclohexanone utes brown 15 3.1 bTetrachloroauric acid 100 in 0.5 g 60~C 1500 purple methanol 3.1 cSilvertosylate 150 80~C 120 yellow-brown The metal-containing cores can be detected by electron micrographs.

Example 3.2: Metal-containinq layer in the particle 2 g of the hydrido-functionalized organo-polysiloxane from preparation example d are dissolved in 15 g of toluene. The metal salt or the metal salt solution is then added at room temperature. The metal CA 02228326 l998-0l-29 compounds and reaction temperatures and times used in each case are summarized in Table III.

Table III

Example Metal saltAmount lmglReaction Reaction Color temperature time [minutesl 5 3.2 aHexachloro-200 in 0.8 g 80~C 120 minutes yellow-platinic acidcyclohexanone brown 3.2 bTetrachloro-100 in 0.5 g 60~C 1.500 red-violet auric acid methanol 3.2 cSilver tosylate150 80~C 120 yellow Neither colloids, clusters nor metal-contain-ing cores can be detected by electron micrographs. A
thin metal layer must t:herefore be present.

Example 4 Methylpolysiloxane microgel particles as the base + external reducing agent.

The synthesis of the methylpolysiloxane microgel particles is described in DE-A-19519446.

5 g of the methylpolysiloxane microgel parti-cle are dissolved in 50 g of toluene at room tempera-ture. A metal salt solution according to Table IV is added to the solution and the mixture is stirred.
Thereafter, the reducing agent according to Table IV is added. After the reacti.on, the products are precipitated in 500 ml of cold (-~0~C) methanol, filtered off and dried under a high vacuum.

~ CA 02228326 l998-0l-29 Table IV
Example~letal saltAmount ImglReducing Reaction Reaction agent temperature time l~CI Iminutes 4 aHexachloroplatinic 100 in 0 5 g100 mg 25 31) acid hexanone hydrazine 4b ditto 200 in I g ethanol 80 C 180 ethanol 4c ditto 150 in I g 0 5 g 80 C 30 cyclohexanoneacetaldehyde 4d Palladium 100 in 100 mg 25 10 dichloride cyclohexanonehydrazine 4eSilver tosylate 100 100 mg 80 C 15 hydrazine 4fTetrachloroauric 100 ditto 80~C 15 acid 4gCopper acetyl- 100 ditto 100~C 180 acetonate 4hNickel carbonyl 100 ditto 50'C 240 All the samples are soluble in toluene and tetrahydrofuran. With the exception of 4e and 4f, all the products are black. 4e is brown-yellow and 4f is purple.

No loose metal colloids or clusters are visible under the PEM. Only where carrier particles have formed are there also metal clusters and colloids. There are therefore no "free" metal clusters or colloids in the product.

Example 5 (Reduction in aqueous systems with Si-H) 50 g of a 10-2 molar salt solution are added dropwise to 50 g of the acid (pH is 1 to 2) aqueous dispersion of hydrido-functionalized organopolysiloxane microgel particles from preparation example a at room temperature, while stirring vigorously. Stirring is then CA 02228326 l998-0l-29 continued for a time and at a temperature according to Table V.

Table V

Example Metal salt Reaction Reaction temperature I ~CI time [minutes Sa Hexachloroplatinic acid 80 IS
5b Palladium dichloride 25 10 Sc Silver nitrate 80 30 Sd Tetrachloroauric acid 80 30 The resulting dispersions are then brought to 50~C, 5 g of trimethylethoxysilane are added and the mixtures are stirred at this temperature for 2 hours.

These dispersions are broken with 20~ strength by weight sodium chloride solution and rinsed several times with completely desalinated water (500 g in total). The residue is taken up in about 100 g of a mixture of 80 parts of toluene and 20 parts of acetone and the mixture is dried over sodium sulfate. The toluene is then stripped off and the residue is dried under a high vacuum at 40~C for 1 hour.

All the samples are soluble in toluene and tetrahydrofuran.

No loose metal colloids or clusters are visible under the PEM. Only where carrier particles have formed are there also metal clusters and colloids. There are therefore no "free" metal clusters or colloids in the product.

Example 6 (Aqueous systems with external reducing agents) The synthesis, of the dispersion comprising aqueous methylpolysiloxane microgel particles is described in DE-A-19519446. A 10-Z molar metal salt solution is added to 50 g of a dispersion comprising methylpolysiloxane microgel particles (solids content about 8~ by weight) at room temperature, while stirring vigorously. The reducing agent is then added as a solution or in bulk, according to Table V. Thereafter, the mixture is subsequently stirred for a time and at a temperature according to Table VI.

Table VI

ExampleMetal salt Reducing agent in Reaction Reaction Igl temperature time in [ocl [minutes 6 aHexachloroplatinic0.2 g hydroxyl 80~C 30 acid amine 6 b Palladium 0.2 g hydroxyl 25 10 dichloride amine 6cSilver nitrate 0.2 g glucose 50 20 6dTetrachloroauricI g 10% strength 80 30 acid aqueous solution of sodium borohydride 6eNickel sulfate diKo 80 60 6fCopper sulfate 0.2 g glucose 80 60 6gIridium trichlorideI g 10% strength 80 60 aqueous solution of sodium borohydride 6hRhodium trichloride diKo 80 60 The resulting dispersions are then worked up further as described in Example 5.

CA 02228326 l998-0l-29 All the samples are soluble in toluene and tetrahydrofuran.

No loose metal colloids or clusters are visible under the PEM. Only where carrier particles have formed are there also metal clusters and colloids. There are therefore no "free" metal clusters or colloids in the product.

ExamPle 7 (Reduction by W irradiation) 50 g of 10-2 molar silver nitrate solution are added to 50 g of methylpolysiloxane microgel dispersion employed in Example 6 at room temperature, while stirring vigorously. The solution is irradiated with a mercury halogen lamp ~1 W) at 25 C for 15 minutes. A
yellow dispersion is obtained.

The dispersion is worked up as described in Example 5. The yellow powder is soluble in toluene and tetrahydrofuran.

No loose metal colloids or clusters are visible under the PEM. Only where carrier particles have formed are there also metal clusters and colloids. There are therefore no "free" metal clusters or colloids in the product.

ExamPle 8 (Building up a layer structure in aqueous dispersions) 20 g of methyltrimethoxysilane are slowly added dropwise to an initial mixture of 500 g of water and 2 g CA 02228326 l998-0l-29 of dodecylbenzenesulfonic acid at 50~C in the course of 10 minutes, while stirring. 10 minutes after the end of the dropwise addition, ', g of triethoxysilane are added.
The mixture is subsequently stirred for a further 10 minutes. 10 g of a 1~ strength hexachloroplatinic acid are then added to the dispersion and the mixture is subsequently stirred for 30 minutes. The solution becomes brown-black. 20 g of methyltrimethoxysilane are then added dropwise in the course of 10 minutes. After a further 10 minutes, 5 g of trimethoxysilane are once again added and the mixture is subsequently stirred for 10 minutes. Thereafter, 10 g of a 1% strength palladium dichloride solution are slowly added to the initial mixture. (The dispersion becomes black). After 10 minutes, 50 g of methyltrimethoxysilane are once again added in the course of one hour.

The dispersion is then worked up as described in Example 5.

The resulting black powder is soluble in organic solvents, such as tetrahydrofuran, toluene and the like.

Use ExampleB:
Example 9 (Hydrogenation) 120 g of a 30~ strength by weight solution of 1-octene in cyclohexane are initially introduced into a200 ml Schlenk tube. ]00 mg (corresponding to 4 mg of platinum or 25 ppm of platinum, based on the 1-octene) of the compound prepared in Example lb are used as a catalyst. The Schlenk tube is then evacuated several times until the solvent boils, in order to degas the -solution. Thereafter, hydrogen gas (overpressure of 2 bar) is forced into the stirred solution at room temperature. An exothermic hydrogenation starts immediately. The internal temperature reaches about 65~C. After 30 minutes, the hydrogenation is at an end.
Only octane can be detected in the GC.

Example 10 (Hydrosilylation) 13.2 g of 1-octene and 13 mg (corresponding to 0.5 mg of platinum, or 18 ppm, based on the total weight of the starting material) of the catalyst prepared in Example lc are initially introduced into a flask. The solution is heated to 120~C and 14.8 g of triethoxysilane are added dropwise. The reaction is exothermic. After about 20 minutes, the reaction has proceeded to conclusion.

Example 11 (Coatings) 1 g of the powder prepared in Example ld is dissolved in 9 g of loluene. A polypropylene film is immersed in this solution for 10 minutes. Thereafter, the film is washed with 3 times 10 ml of acetone and the film is dried at room temperature under normal pressure for two days.

Electron micrographs show a virtually monomolecular layer of metal-containing particles on the substrate surface.

Claims (6)

1. Crosslinked organopolysiloxane particles which consist of a single molecule, containing metal atoms in the zero valent oxidation state, these atoms in each case being in intermetallic interaction with at least one further metal atom in the oxidation state 0, said particles having an average diameter of 5 to 200 nm, and soluble to the extent of at least 0.1% by weight in at least one organic solvent chosen from the group consisting of methylene chloride, pentane, acetone, toluene and ethanol, at least 80% of the particles having a diameter which deviates from the average diameter by not more than 30%, and the relative total content of metal in the zero valent oxidation stage being from about 10 ppm to 50% by weight.

2. The organopolysiloxane particles as claimed in claim 1, in which the mean molar masses of said particles are from about 5 x 5 g/mol to about 10 10 g/mol.

3. The organopolysiloxane particles as claimed in claim 1, in which the organopolysiloxane content essentially consists of 0.5 to 80% by weight of units of the general formula [R3SiO 1/2] (1), 0 to 99.0% by weight of units of the general formula [R2SiO 2/2] (2), 0 to 99.5% by weight of units of the general formula [RSiO 3/2] (3) and, 0 to 99.5% by weight of units of the general formula [SiO 4/2] (4), in which R is a hydrogen atom or identical or different monovalent, SiC-bonded, C1 to C18 hydrocarbon radicals which optionally carry functional groups.

4. A process for the preparation of the metal-containing crosslinked organopolysiloxane particles consisting of a single molecule, as claimed in claim 1, in which A) the organopolysiloxane component of the organopolysiloxane particles is prepared as a colloidal suspension of organopolysiloxane particles in a first step by metering silanes of the general formula (5) R a Si(OR1)4-a (5), and, if appropriate, organosilicon compounds of the general formula (6) R b(R1O)c SiO4-b-c/2 (6), in which R1 has the meanings of R, a has the value 0, 1, 2 or 3, b and c in each case independently of one another have the values 0, 1, 2, 3 or 4 and R has the above meanings, into an agitated mixture of emulsifier and water and in a second step, an organosilicon compound of the general formula (7) (R2 3 Si)d Y1 (7) in which Y1 if d = 1, is a hydrogen atom, -OR3, -ONR3 2 or -OOCR3 and if d = 2, is -O- or -S-, R2 and R3 have the meanings of R and d has the value 1 or 2, is added to the colloidal suspension, with the proviso that the organosilicon compounds of the general formula (7) are water-soluble or hydrolyze in water to give a water-soluble compound and B) the metal content of the organopolysiloxane particles is deposited on the metal-free organopolysiloxane particles, which have been prepared according to process stage A, by reduction of a metal compound with a reducing agent.

5. In a catalytic process employing a zero valent metal catalyst, the improvement comprising employing as said catalyst a homogenous catalyst comprising the particles of claim 1.

6. A process for the flameproofing of a combustible material, said process comprising incorporating into said material, or coating onto said material, the composition comprising the particles of claim 1.