DE10238463A1 - Stabilized, aqueous silicon dioxide dispersion - Google Patents

Abstract

Aqueous dispersion containing silicon dioxide powder which is stable in a pH range between 2 and 6, which contains a cation-providing compound which is at least partially soluble in this pH range and whose zeta potential has values of less than or equal to zero. It is made by contacting silicon dioxide powder and at least one cation-providing compound in an aqueous medium with agitation. The dispersion can be used for chemical mechanical polishing of metal surfaces.

Description

The invention relates to an aqueous, dispersion containing stable silicon dioxide in the acidic pH range, their manufacture and use. The invention further relates to a powder which is used to prepare the dispersion can.

Silicon dioxide dispersions are generally not stable in the acidic pH range. A possibility to stabilize such dispersions, for example, the Addition of aluminum compounds.

WO 00/20221 describes one in acid Area stable, watery Silicon dioxide dispersion. It is made by in an aqueous Medium silicon dioxide particles brought into contact with aluminum compounds become. The amount of aluminum compound used to make the in the '221 application claimed dispersion can be obtained via the Rise in zet potential can be tracked and is reached where the increase in the zeta potential curve approaches zero or a plateau is reached. The '221 application also claims dispersions in which the zeta potential is only 50% of the maximum achievable value reached. In any case, the zeta potential shows the claimed Dispersions strongly positive values of up to 30 mV. This means, that the originally negative charged silica particles by adding the aluminum compound now completely are cationized. The claimed dispersion has one good stability on, however, since the surface with positively charged aluminum species is occupied, no silicon dioxide dispersion more. This is disadvantageous in applications in which the dispersion brought into contact with anionic substances or dispersions becomes. This can lead to unwanted flocculation or Sedimentation come.

US 2,892,797 on the other hand describes an aqueous silicon dioxide dispersion which is stabilized by treatment with an alkali metalate. Sodium aluminate is particularly preferred. The anion is used for stabilization, for example [Al (OH) ₄ ] ^- . The dispersions are usually stable in a pH range between 5 and 9. The zeta potential, of the powder treated in this way, has a negative zeta potential. A disadvantage of this process can be the subsequent removal of the cation, for example by ion exchange processes. In special applications, such as chemical mechanical polishing, alkali cations are generally undesirable. Another disadvantage is the low stability in more acidic media below pH 5.

The object of the invention is Silicon dioxide dispersion to provide that in the acidic range is stable without losing the properties of the silica powder must be changed by reloading on the particle surface.

• – die Dispersion in einem pH-Bereich zwischen 2 und 6 stabil ist,
• – die Dispersion zusätzlich mindestens eine Verbindung enthält, die in wässeriger Lösung im pH-Bereich zwischen 2 und 6 wenigstens teilweise in Form mehrwertiger Kationen löslich ist und die Kationen in einer silicatischen Umgebung als anionischer Bestandteil der Partikeloberfläche des Silciumdioxidpulvers stabil sind,
• – das Verhältnis der kationenliefernden Verbindung und der Oberfläche des Siliciumdioxides zwischen 0,001 und 0,1 mg kationenliefernde Verbindung/m² Siliciumdioxid-Oberfläche liegt, wobei die kationenliefernde Verbindung als Oxid berechnet ist und
• – das Zetapotential der Dispersion Werte kleiner Null oder gleich Null aufweist.

The invention relates to an aqueous dispersion containing silicon dioxide powder with a silicon dioxide content of 10 to 60% by weight, which is characterized in that

• The dispersion is stable in a pH range between 2 and 6,
• The dispersion additionally contains at least one compound which is at least partially soluble in the form of polyvalent cations in aqueous solution in the pH range between 2 and 6 and the cations are stable in a silicate environment as an anionic component of the particle surface of the silicon dioxide powder,
• - The ratio of the cation-providing compound and the surface of the silicon dioxide is between 0.001 and 0.1 mg of the cation-providing compound / m ^{2 of the} silicon dioxide surface, the cation-providing compound being calculated as the oxide and
• - The zeta potential of the dispersion has values of less than or equal to zero.

The zeta potential is the one that works externally Potential of the particles and represents a measure of electrostatic interaction between individual particles. It plays a role in stabilization of suspensions and in particular of dispersions with dispersed, ultrafine particles. The zeta potential can be determined, for example are measured by measuring the colloidal vibration current (CVI) Dispersion or by determining the electrophoretic mobility.

Among cation-providing compounds according to Invention are always to be understood as those that are aqueous solution in the pH range between 2 and 6 are at least partially soluble in the form of polyvalent cations and these cations in a silicate environment as anionic Center are stable. These are compounds that Ca, Sr, Ba, Be, Mg, Zn, Mn, Ni, Co, Sn, Pb, Fe, Cr, Al, Sc, Ce, Ti and Zr as a cation exhibit.

Under silicate environment is too understand that the cations of the above metals in the form of Metal-oxygen bonds with the silicon atoms of the silicon dioxide surface. You can also Replace silicon atoms in the silicon dioxide structure.

Taking an anionic ingredient is a component to understand the negative charge on the surface of a Silicon dioxide powder, measured as zeta potential, not changed or shifts to more negative values.

Stable is to be understood as meaning that the particles of the silicon dioxide powder in the dispersion do not agglomerate further and the viscosity of the dispersion changes within a period of at least one week does not change or changes only slightly (viscosity increases by less than 10%).

Preferred cation-providing compounds can amphoteric compounds with Be, Zn, Al, Pb, Fe or Ti as the cation and mixtures of these compounds.

Amphoteric compounds are those which are at a given pH a stronger one Acid as Base and opposite one strengths Base as an acid behavior.

Particularly preferred cation-providing compounds can be aluminum compounds, such as, for example, aluminum chloride, aluminum hydroxychlorides of the general formula Al (OH) _x Cl with x = 2-8, aluminum chlorate, aluminum sulfate, aluminum nitrate, aluminum hydroxynitrates of the general formula Al (OH) _x NO ₃ with x = 2-8, aluminum acetate, alums such as aluminum potassium sulfate or aluminum ammonium sulfate, aluminum formates, aluminum lactate, aluminum oxide, aluminum hydroxide acetate, aluminum isopropylate, aluminum hydroxide, aluminum silicates and mixtures thereof. Aluminum silicate can be, for example, Sipernat 820 A from Degussa AG, which is a finely divided aluminum silicate with approximately 9.5% by weight aluminum as Al ₂ O ₃ and approximately 8% by weight sodium as Na ₂ O, or a sodium aluminum silicate in the form of a zeolite A.

The type of silica powder in the inventive Dispersion is not limited. So can by sol-gel process, through precipitation processes or silicon dioxide powder produced by pyrogenic processes become. It can be a metal oxide powder completely or partially coated with silicon dioxide be, provided that its zeta potential is the same in the pH range between 2 and 6 or less than zero.

Preferably, pyrogenically produced Silicon dioxide powder can be used.

Under pyrogenic according to the invention is education of silicon dioxide by flame hydrolysis of a silicon-containing Compound or of silicon-containing compounds in the gas phase in a flame caused by the reaction of a fuel gas and a to understand oxygen-containing gas, preferably air. Suitable silicon-containing compounds are, for example, silicon tetrachloride, Methyltrichlorosilane, ethyltrichlorosilane, propyltichlorosilane, dimethyldichlorosilane, Alkoxysilanes and their mixtures. Silicon tetrachloride is particularly preferred. Suitable fuel gases are hydrogen, methane, ethane, propane, where Hydrogen is particularly preferred. In flame hydrolysis first highly disperse, non-porous primary particle formed, which grow together into aggregates in the further course of the reaction and these can continue to assemble into agglomerates. The surface of the pyrogenically produced silicon dioxide particles have silanol groups (Si-OH) and siloxane groups (Si-O-Si).

Pyrogenic silica powder also include doped silica powder and pyrogenic ones Silicon-metal mixed oxide powder, provided that its zeta potential in the pH range between 2 and 6 is equal to or less than zero.

The production of doped powder is, for example, in DE-A-196 50 500 described. Typical doping components are aluminum, potassium, sodium or lithium. The proportion of the doping component is generally not greater than 1% by weight

Under pyrogenic mixed oxide powder are to be understood as those in which both precursors of the mixed oxide are common be hydrolyzed in the flame. Typical mixed oxide powders are Silicon-aluminum mixed oxides or silicon-titanium mixed oxides.

According to a particular embodiment, the ratio of the cation-providing compound and the surface area of the silicon dioxide can preferably be between 0.0025 and 0.04, and particularly preferably between 0.005 and 0.02 mg, cation-providing compound / m ² silicon dioxide surface.

The silicon dioxide surface corresponds to the specific surface of the silicon dioxide powder determined in accordance with DIN 66131. The BET surface area can be between 5 and 600 m ² / g, the range between 30 and 400 m ² / g being preferred and the range between 50 and 300 m ² / g being particularly preferred.

The pH of the dispersion according to the invention is between 2 and 6. It can preferably be between 3 and 5.5. With a BET surface area of the silicon dioxide powder of up to 50 m ² / g between 3 and 4, with a BET surface area between 50 and 100 m ² / g between 3.5 and 4.5, with a BET Surface area between 100 and 200 m ² / g between 4 and 5 and with a BET surface area of more than 200 m ² / g between 4.5 and 5.5.

If necessary, the pH value through acids or bases can be set. Preferred acids can be hydrochloric acid, sulfuric acid, nitric acid or Carboxylic acids, such as acetic acid, oxalic acid or citric acid his. Preferred bases can Alkali hydroxides, such as KOH or NaOH, ammonia, ammonium salts or Be amines. If necessary by adding salts buffer systems are formed.

According to a particular embodiment, the viscosity of the dispersion according to the invention, at a shear energy of 1.28 s ^-1 , can be at least 10% lower than the viscosity of a dispersion of the same composition, but without a cation-providing compound. The viscosity can preferably be 25%, particularly preferably it can be 50% lower than in the case of a dispersion of the same composition, but without a cation-providing compound.

According to a particular embodiment, the number of agglomerates with a size of more than 1 μm in the dispersion according to the invention be at least 50% lower than the number in a dispersion of the same composition, but without a cation-providing compound. The number of agglomerates with a size of more than 1 μm can preferably be 75%, particularly preferably it can be 90% lower than in the case of a dispersion of the same composition, but without a cation-providing compound.

The dispersion according to the invention can also contain preservatives. Suitable preservatives can for example
Benzyl alcohol mono (poly) hemiformal,
Tetramethylolacetylene diurea, formamide monomethylol,
Trimethylol urea, N-hydroxymethylformamide, 2-bromo-2-nitropropane-1,3-diol, 1,6-dihydroxy-2,5-dioxahexane,
Chloromethylisothiazolinone, orthopenylphenol, chloroacetamide,
Sodium benzoate, octylisothiazolone, propiconazole,
Iodopropynyl butyl carbamate, methoxycarbonylaminobenzimidazole,
1,3,5-triazine derivatives, methylisothiazolinone,
Benzisothiazolinone and mixtures thereof.

Another object of the invention is a method for producing the dispersion according to the invention, which is characterized in that silicon dioxide powder and at least one cation-providing compound in an amount between 0.001 and 0.1 mg of cation-providing compound / m ² silicon dioxide surface in an aqueous medium with movement be brought into contact.

Get in touch while moving is stirring, for example or to understand dispersing. For dispersion are suitable for Example dissolver, gear wheel, rotor-stator machines, ball mills or agitator ball mills. There are higher energy inputs possible with a planetary mixer / mixer. The effectiveness of this Systems is however machined with a sufficiently high viscosity Mix connected to the needed high shear energies to break up the particles. With High pressure homogenizers can aqueous Dispersions with aggregate sizes in the Dispersion of less than 200 nm can be obtained.

With these devices, at least two predispersed suspension streams under high pressure via one Nozzle relaxed. Both dispersion beams meet each other exactly and the particles grind themselves. In another embodiment, the predispersion also put under high pressure, but the collision occurs of particles against armored wall areas. The operation can be arbitrary often repeated to get smaller particle sizes.

The process of making the dispersion according to the invention can run like this be that the cation-providing compound, in solid form or as watery Solution, to a watery Dispersion of silicon dioxide is given.

It can also be done that the silicon dioxide powder all at once or in portions aqueous solution the cation-providing compound is given.

It is also possible that Silicon dioxide powder and the cation-providing compound simultaneously, in portions or continuously, in the liquid Dispersion phase is entered.

Under at the same time is also here to understand that the silica powder and the cation source Compound in the form of a physical or chemical mixture can already be pre-mixed.

Such a powder, in which at least one cation-providing compound and silicon dioxide powder is present and the proportion of the cation-providing compound, calculated as oxide, is between 0.001 and 0.1 mg of cation-providing compound / m ² silicon dioxide surface, is a further subject of the invention.

Typical impurities are included on the part of the raw materials and imported by the production Impurities. The proportion of impurities is smaller than 1% by weight, usually at less than 0.1% by weight

Preferably, the cation supplying Compound an aluminum compound and the silica a pyrogenic manufactured silica powder.

The powder according to the invention can be quickly dissolved in aqueous Incorporate media.

It can be done in the simplest case a physical mixture of silicon dioxide powder and at least a cation-providing connection. Conveniently, individual containers are completely used up. This is there is no need for a homogeneous distribution of silicon dioxide and cation-providing To have a connection.

The powder according to the invention can furthermore also be obtained by spraying onto silicon dioxide powder at least one compound which is soluble in the pH range <6 or by chemical reaction in the pH range <6. The solution of the cation-providing compound can be sprayed on continuously or in batches in heated mixers and dryers with spray devices. Suitable devices can be, for example: ploughshare mixer, plate, fluidized bed or fluid bed dryer ner.

The solution of the cation supplier The connection can be sprayed or nebulized with an ultrasonic nozzle. Possibly the mixer can also be heated.

Furthermore, the powder according to the invention by vapor deposition of a cation-providing compound, for example Aluminum chloride, can be obtained in a fluidized bed or mixer.

Another object of the invention is the use of the dispersion according to the invention for chemical mechanical Polishing of metal surfaces, especially for the polishing of copper surfaces, for the production of ink-jet papers, for gel batteries, for clarification / fining Wine and fruit juices, for water-based Dispersion paints to improve the floating behavior of the pigments and fillers and to increase the scratch resistance, improvement of the stability and the "blackness" of carbon black dispersions for ink-jet inks, Stabilization of emulsions and dispersions in the biocide sector, as an amplifier for natural latex and synthetic latices, for the production of latex / rubber Articles such as gloves, condoms, baby pacifiers or foam rubber, in the sol-gel area, to remove surface stickiness (Anti-blocking), to achieve an anti-slip effect (anti-slip) for paper and cardboard, to improve slip resistance, for the production of optical fibers, for the production of quartz glass.

It is surprising that one with a silicon dioxide dispersion brought into contact with a cation-providing compound good stability in the acidic range shows and at the same time the surface of the silicon dioxide particles their negative surface charge maintains or even reinforced.

The mechanism of this stabilization has not yet been resolved. However, it must be different from that described in WO 00/20221. Be here Silicon dioxide particles completely through positively charged aluminum species reloaded and the particles get a positively charged one Shell.

The mechanism must also be different than in US 2,892,797 described. Here, a negative charged metal ion is built into the surface of a silicon dioxide particle. Although the particles modified in this way, like the particles in the dispersion according to the invention, have a negative surface charge, they show little stability in the acidic pH range.

Examples of analytical methods

The zeta potential is determined with one device of the type DT-1200 from Dispersion Technology Inc., according to CVI process.

The viscosity of the dispersions was determined using a rotary rheometer from Physica Model MCR 300 and a measuring cup CC 27, measurements being made at shear rates between 0.01 and 500 s ⁻¹ and 23 ° C. The viscosity is given at a shear rate of 1.28 s ^-1 . This shear rate is in a range in which shear thinning effects have clear effects.

The particle / agglomerate sizes were with the devices LB 500 and LA 300, both from Horiba, or a Zetasizer device 3000 HSa from Malvern.

dispersion

As dispersing devices for example a Dispermat AE-3M dissolver from VMA-GETZMANN with a dissolver disc diameter of 80 mm or a rotor / stator dispersing unit Ultra-Turrax T 50 from IKA-WERKE with the dispersing tools S50N-G45G used. When using rotor-stator devices, the batch container is opened Cooled at room temperature.

The dispersion can also be carried out using a high energy mill carried out become. For approaches with 50 kg of silicon dioxide powder each in a 60 1 stainless steel batch container Part of the demineralized water submitted. With the help of a dispersing and suction mixer the company Ystrahl type Conti-TDS 3 is the corresponding amount of Aerosil powder sucked in and roughly predispersed. During the powder entry by adding sodium hydroxide solution and aluminum chloride solution pH of 3.5 + - 0.3 held.

After the powder has been added, the dispersion with the Conti TDS 3 (stator slot width of 4 mm) with closed Suction nozzle and maximum speed completed. By adding more Sodium hydroxide solution was adjusted to a pH of 3.5 before the rotor / stator dispersion, after 15 minutes of dispersion not changed Has. By adding the remaining amount of water, a SiO2 concentration of 20 wt .-% set. This predispersion is carried out with a high energy mill, type Ultimaizer System, company Sugino Machine Ltd., model HJP-25050, at a Pressure of 250 MPa and a diamond nozzle diameter of 0.3 mm and two milling passes ground.

chemicals

The aerosil types 50, 90, 200 and 300 from Degussa AG were used as silica powder. AlCl ₃ in the form of the hexahydrate was used as the water-soluble aluminum compound. In order to make it easier A 1% by weight solution, based on Al ₂ O ₃ , was used for metering and homogenization. A 1N NaOH solution or a 1N HCl solution was used for pH corrections.

To the dispersions regarding their viscosity to be able to compare if necessary, by adding further 1N NaOH a uniform pH adjusted to 3.5.

dispersions

The different batch sizes and the properties of the dispersions obtained are Table 1 and 2 can be seen.

Example 1a (comparative example)

100 g of Aerosil 50 (approx. BET surface area 50 m ² / g) were incorporated in portions into 385 g of demineralized water using a dissolver at a setting of approx. 1800 rpm. This resulted in a pH of 3.5. The remaining 15 g of demineralized water were then added to achieve a 20 percent dispersion and then dispersed for 15 minutes at 2000 rpm and 15 minutes using an Ultra Turrax at approximately 5000 rpm.

Examples lb-g

100 g of Aerosil 50 were removed using a Dissolver at a setting of approx. 1800 rpm in 385 g demineralized water and 1.25 g of a 1 weight percent aqueous aluminum chloride solution (based on alumina) incorporated in portions. This resulted a pH of 3.4. It was dissolved by adding 0.7 g of 1N NaOH pH 3.5 adjusted. Now the missing 13.1g of water became Achieve a 20 weight percent dispersion and subsequently 15 minutes at 2000 rpm and 15 minutes with an Ultra Turrax dispersed at approx. 5000 rpm.

Examples lc-g were made analogously 1b performed.

Example 2a (comparative example)

100 g of Aerosil 90 were removed using a Dissolvers in portions at a setting of approx. 1800 rpm in 370 g demineralized water incorporated and redispersed at 2000 rpm for 15 minutes. Then will the pH was adjusted to 3.5 with 1N HCl and for 15 minutes with a Ultra Turrax dispersed at approx. 5000 rpm. Subsequent remaining Adding water to obtain a 20 weight percent dispersion and readjusting the pH to 3.5.

Example 2b

100 g of Aerosil 90 were alternated in portions using a dissolver at a setting of approx. 1800 rpm incorporated in 370 g demineralized water and at one setting of about 2000 revs / min. Then under dispersion with an Ultra Turrax at approx. 5000 rpm 2.50 g of a 1 percent by weight solution (based on aluminum oxide) of aluminum chloride and 15 Minutes dispersed. Rpm and 15 min with an Ultra Turrax at dispersed approx. 5000 rpm. Subsequently, 26.3 g of demineralized water and 1.24 g of 1N NaOH added to make a 20 weight percent dispersion with a pH of 3.5.

Example 3a (comparative example)

250 g of demineralized water and 20 g of a 1 percent by weight, aqueous Aluminum chloride solution (based on aluminum oxide) submitted. Using a dissolver Aerosil 90 was added in portions. The pH was measured kept at 3.5. After adding approx. 40 g Aerosil 90 powder thickened the dispersion was very strong and no further addition was possible.

Examples 3b, 3c

100 g of Aerosil 90 were incorporated into 250 g of demineralized water using a dissolver, and 10 g of a 1% by weight aqueous aluminum chloride solution (based on aluminum oxide) and 1N NaOH were added in portions, so that the pH was between 3. 3 and 4.2 was. Then, using an Ultra-Turrax at 5000 rpm, a further 100 g of Aerosil 90 and another 10 g of a 1% by weight aluminum chloride solution (based on aluminum oxide) and as much 1N NaOH were added in portions, that the pH was 3.5 at the end of the addition.

In example 3c a pH was set from 4.0.

Example 4 (comparative example)

50 g of Aerosil 90 (were Dissolvers in portions at a setting of approx. 1800 rpm in 350 g demineralized water incorporated and redispersed at 2000 rpm for 15 minutes. Subsequently were dispersed with an Ultra Turrax at about 5000 rpm 100 g of a 1 percent by weight solution (based on aluminum oxide) of aluminum chloride added and dispersed for 15 minutes and the pH of 2 with 30% sodium hydroxide solution at a pH of 3.5 brought.

Examples 5

Example 5a was carried out analogously to 2a. The Examples 5b-d were carried out analogously to 2b. For examples 5e-g was approx. 100 ml of the dispersion of Example 5d dropwise with 30% Sodium hydroxide solution brought to the pH values listed in Table 2, with a magnetic stirrer Homogenized for approx. 5 minutes and the zeta potential measured in each case.

Examples 6

Example 6a was carried out analogously to 2a. The Examples 6b-d were carried out analogously to 2b.

1 shows the zeta potential in mV (•) and the viscosity in mPas (o) of examples 1a-g as a function of mg Al ₂ O ₃ / m ² SiO ₂ surface.

Example 7 - Powder Production

Tabelle 2: Analytische Daten der Dispersionen(1)

500 g of silicon dioxide powder (Aerosil 200, from Degussa) are placed in a 20 1 Lödige mixer. At a speed of 250 rpm, 20 g of a 5 percent by weight (based on Al ₂ O ₃ ) aluminum chloride solution with a spraying rate of approx. 100 ml / h are within 10 - 15 min. applied. The powder has 0.01 mg Al ₂ O ₃ / m ² silicon dioxide surface, a BET surface area of 202 m ² / g and a tamped density of approx. 60 g / l. The water content is approx. 4% and, if desired, can be reduced by heating the wiper or drying it in a drying cabinet, rotary tube or fluid bed. An aqueous dispersion (20% by weight) has a pH of 2.6. Table 1: Aqueous Aerosil dispersions (1)

Table 2: Analytical data of the dispersions (1)

Claims (18)

Aqueous dispersion containing silicon dioxide powder with a silicon dioxide content of 10 to 60% by weight, characterized in that - the dispersion is stable in a pH range between 2 and 6, the dispersion additionally contains at least one compound which is in aqueous solution in the pH range between 2 and 6 is at least partially soluble in the form of polyvalent cations and these are stable in a silicate environment as an anionic component of the particle surface of the silicon dioxide powder, - the ratio of the cation-providing compound and the surface of the silicon dioxide between 0.001 and 0.1 mg of cation-providing Compound / m ² silicon dioxide surface, the cation-providing compound is calculated as oxide and - the zeta potential of the dispersion has values less than or equal to zero. aqueous Dispersion according to claim 1, characterized in that the cation-providing Connection an amphoteric connection with Be, Zn, Al, Pb, Fe or Ti as a cation, and mixtures of these compounds. aqueous Dispersion according to claim 2, characterized in that the amphoteric Connection is an aluminum connection. aqueous Dispersion according to the claims 1 to 3, characterized in that the silicon dioxide powder is pyrogenic silica powder. Aqueous dispersion according to claim 4, characterized in that the BET surface area is between 5 and 600 m ² / g. aqueous Dispersion according to the claims 1 to 5, characterized in that their pH is between 3 and 5 lies. aqueous Dispersion according to the claims 1 to 6, characterized in that acids are preferred for pH regulation Hydrochloric acid, Sulfuric acid, Nitric acid, C1-C4-carboxylic acids, or bases, preferably alkali metal hydroxides, ammonia, ammonium salts or Amines are used. Aqueous dispersion according to claims 1 to 7, characterized in that its viscosity at a shear energy of 1.28 s ^{-1 is} at least 10% less than the viscosity of a dispersion of the same composition, but without a cation-providing compound. aqueous Dispersion according to the claims 1 to 8, characterized in that the number of agglomerates with a size of more than 1 μm is at least 50%, lower than with a dispersion of the same composition, however without a cation-providing connection. aqueous Dispersion according to the claims 1 to 9, characterized in that the average secondary particle size of the silicon dioxide powder is less than 200 nm. aqueous Dispersion according to the claims 1 to 10, characterized in that they contain preservatives contains. A process for producing the aqueous dispersion according to claims 1 to 11, characterized in that silicon dioxide powder and at least one cation-providing compound in an amount between 0.001 and 0.1 mg of cation-providing compound / m ² silicon dioxide surface in contact in an aqueous medium with movement become. A process for the preparation of the aqueous dispersion according to claim 12, characterized in that the cation-providing compound, in solid form or as aqueous Solution, to a watery Dispersion of silicon dioxide is given. A process for the preparation of the aqueous dispersion according to claim 12, characterized in that the silica powder at once or in portions to an aqueous solution the cation-providing compound is given. A process for the preparation of the aqueous dispersion according to claim 12, characterized in that silicon dioxide powder and cation-providing Connection simultaneously, in portions or continuously, into the liquid Dispersion phase is entered. Powder consisting of at least one cation-providing compound and silicon dioxide powder, the proportion of the cation-providing compound, calculated as oxide, being between 0.001 and 0.1 mg of cation-providing compound / m ^{2 of} silicon dioxide surface. Powder according to claim 16, characterized in that the cation-providing Compound an aluminum compound and the silica a pyrogenic produced silica powder. Use of the dispersion according to claims 1 to 11 for chemical-mechanical polishing of metal surfaces, in particular for polishing copper surfaces, for producing ink-jet papers, for gel batteries, for clarifying / fining wine and fruit juices, for water-based emulsion paints to improve the Floating behavior of the pigments and fillers and to increase the scratch resistance, improve the stability and the "blackness" of carbon black dispersions for ink-jet inks, stabilize emulsions and dispersions in the biocide area, as an enhancer for natural latex and synthetic latices, in the sol-gel area, to remove surface stickiness (antiblocking), to achieve an anti-slip effect (anti-slip) in paper and cardboard, to improve slip resistance, to manufacture optical fibers, to manufacture quartz glass.