Eka Nobel Ab

Eka Ab

Bernt Larsson

Sven G Jaras

Bo V Larsson

Mats G Nystrom

Bozena Tokarz

Elisabet Johansson

Gunilla Nobelius

Hans-Olof Thoresson

Kjell R Andersson

Wolgang Herrmann

Silica particles which are substantially spherical, have a particle size of 1 to 100 .mu.m, a very narrow pore size distribution and a low alkali metal content. The particles can be prepared by sol-gel technique using emulsification technique for drop formation. The process comprises a sol growth step in a basic environment based on ammonium or amines and a post-treatment in such an environment. The silica particles are particularly suitable for use in chromatography as they have very good particle and porosity properties and high purity.

Method for preparation of silica particles

In the production of paper or pulp sheets from a paper stock, a binder is added which comprises cationic and anionic components to improve the paper characteristics and the stock characteristics, such that increased retention and a more readily dewatered stock are obtained. The anionic component consists of colloidal anionic particles having at least one surface layer of aluminum silicate or aluminum-modified silicic acid, such that the surface groups of the particles contain silicium and aluminum atoms in a ratio of from 9.5:0.5 to 7.5:2.5. The cationic component consists of cationic carbohydrate having a degree of substitution of 0.01-1.0.

Papermaking process

The invention relates to a composition for forming a heat-insulating ceramic coating on a metal, said composition comprising, in % by weight:

Ceramic coating on metal

A soil-repellent coating composition comprising silica, polyvinyl alcohol and a wetting agent in an aqueous carrier medium. The composition is characterized in that it, in addition to the aqueous carrier medium, contains 0.5-30% by weight of silica and 0.01-6% by weight of polyvinyl alcohol, and 0.05-2.5% by weight of a wetting agent, based on the total weight of the composition. The ready-made coating composition comprises 0.05-5% by weight of silica, 0.05-0.5% by weight of polyvinyl alcohol and 0.05-0.5% by weight of the wetting agent. The silica is present in the form of an alkali stabilized, preferably ammonium stabilized silica sol with an average particle size of 4-30 nm. The polyvinyl alcohol preferably has a hydrolysis degree of 85-100% and an average molecular weight of 15,000-100,000. The weight ratio of silica to polyvinyl alcohol is above 3:1 and preferably from 5:1 to 40:1. The wetting agent preferably is nonionic. The aqueous carrier medium of the composition may comprise a water-miscible, low-boiling solvent such as ethanol in an amount of up to 20% by weight.

Soil-repellent coating composition

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Hisings Backa, Sweden

Bernt Larsson