Evonik Degussa Gmbh

Degussa Aktiengesellschaft

Evonik Operations Gmbh

Sascha Reitz

Wolfgang Lortz

Gabriele Perlet

Werner Will

Christoph Batz-Sohn

Uwe Diener

Helmut Mangold

Stable, pourable silicon dioxide dispersion, in which the average, number-related aggregate diameter of the silicon dioxide particles in dispersion is less than 200 nm, and which comprises at least 35 wt. % of a silicon dioxide powder, 3 to 35 wt. % of at least one polyol, 20 to 60 wt. % of water, 0 to 10 wt. % of an additive and a substance having an alkaline action in an amount such that a pH of 10&#x3c;pH&#x3c;12 is established. It can be prepared by a procedure in which silicon dioxide powder is introduced into water and a polyol in a rotor/stator machine, the pH being less than 5, and the mixture is dispersed until the current uptake of the rotor/stator machine is largely constant, and a substance having an alkaline action is subsequently added in an amount such that a pH of the dispersion of 10&#x3c;pH&#x3c;12 results, the substance having an alkaline reaction being added so rapidly that no gel formation takes place. It can be used as a component of a flame-retardant filling of hollow spaces between building components, in particular for insulating glass arrangements.

Silicon dioxide dispersion comprising polyol

Provided is a process for preparing surface-modified silicon dioxide particles with a mean particle diameter of at most 100 nm, involving (A) high-pressure grinding of a predispersion having (i) surface-modified silicon dioxide particles which are at least partly aggregated, are bonded to the surface-modifying component via Si&#x2014;O&#x2014;Si bonds, and still have reactive groups on their surface; (ii) an organosilicon compound which has a silicon-carbon bond and a functional group which can react with the reactive groups to form a covalent Si&#x2014;O&#x2014;Si bond; and (iii) a solvent, to form a dispersion; and (B) removing the liquid phase of the dispersion. Also provided are redispersible, surface-modified silicon dioxide particles obtained by this process, and their use in toner powders, silicone rubber, adhesives, and scratch-resistance surface coatings.

Process for preparing redispersible surface-modified silicon dioxide particles

Aqueous dispersion which comprises hydrophobized silicon dioxide particles and in each case one or more dispersing additives, a basic composition, and which is free of color pigments, inactive fillers and binders, in which the hydrophobized silicon dioxide particles have a methanol wettability of 30 to 60 and are present in the dispersion with a proportion of 0.1 to 50% by weight,&#x2014;the proportion of water is 30 to 90% by weight based on the dispersion,&#x2014;the dispersing additive is at least one phosphate ester of an ethoxylated alcohol having 8 to 18 carbon atoms, the proportion of which is 3 to 25% by weight based on the proportion of the hydrophobized silicon dioxide particles,&#x2014;the basic composition comprises or consists of one or more amines of the general formula RNH, RNH and RN, where R is an alkyl group or a hydroxyl-substituted alkyl group having in each case 2 to 10 carbon atoms, and is present with a proportion of 5 to 30% by weight based on the proportion of hydrophobized silicon dioxide particles,&#x2014;the dispersion further comprises one or more polyols having 2 to 15 carbon atoms, the proportion of which is 1 to 10% by weight based on the proportion of hydrophobized silicon dioxide particles,&#x2014;the pH of the dispersion being 9 to 11.

Dispersion comprising hydrophobized silicon dioxide particles

A dispersion containing aluminum oxide of pyrogenic origin and water, where the aluminum oxide is present in the form of aggregated primary particles with a BET surface area of 20 to 200 m/g and has a mean, volume-based aggregate diameter in the dispersion of less than 100 nm, and is surface-modified with (i) organophosphonic acids, or salts thereof, and (ii) at least one hydroxycarboxylic acids or salts thereof.

Aluminium oxide-containing dispersion

An aqueous dispersion that can be used in the coating of glass, ceramics and metal surfaces is prepared by placing, in water, an aggregated titanium dioxide powder having a specific surface area of from 20 to 150 m/g in such an amount that the desired dispersion contains at least 20 wt. % titanium dioxide, and at least one amino alcohol having from 1 to 6 carbon atoms, and at least one carboxylic acid selected from dibasic carboxylic acids and/or hydroxycarboxylic acids having from 2 to 6 carbon atoms. A pre-dispersion is produced by introducing energy in an amount of less than 200 kJ/m. Then a dispersion is produced in which the aggregated titanium dioxide powder has a mean, volume-related aggregate diameter of less than 150 nm by grinding the pre-dispersion with a high-energy mill at a pressure of at least 500 bar.

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Hanau, Germany

Sascha Reitz