Sumitomo Chemical Company, Limited

Hiroshi Umezaki

Hidekimi Kadokura

Yoshiaki Takeuchi

Hideaki Murakami

Shoji Sugimoto

Hiroshi Takahashi

Yasuyuki Oki

Akira Morii

Tadaaki Yako

Koji Yamamoto

Toshiyuki Mizoe

Yasushi Teshima

Ken Shimada

Takeshi Matumoto

Atsuro Matsui

Kazuo Iida

Yoshihiro Higuchi

The present invention provides a magnetic recording medium comprising, on a non-magnetic substrate, a magnetic layer containing magnetic fine powder and a binder, wherein the magnetic layer contains alumina powder having an average particle size of at most 1 .mu.m and containing at least one oxide of element selected from the group consisting of Ge, P, Sn, Nb, Ta, Mo and W in an amount of 0.1 to 10 parts by weight per 100 parts by weight of alumina. The magnetic recording medium of the present invention has good durability and good abrasion resistance of the magnetic layer, and good magnetic characteristics, good surface smoothness and a good cleaning effect on a magnetic head.

Magnetic recording medium

Silica-alumina fibers having good mechanical strength and heat resistance are produced by mixing a polyaluminoxane which comprises repeating units of the formula: ##STR1## in which X is an alkyl group, an alkoxy group or a hydroxy group, a silicon-containing compound in an amount of not larger than 40% by weight in terms of silica based on the weight of silica-alumina fibers to be produced, and an aliphatic carboxylic acid having 2 to 14 carbon atoms in an alkyl group in an amount of 0.03 to 0.4 mole per one gram atom of aluminum to obtain a spinning liquid, spinning the spinning liquid under a condition that a content of nonvolatile materials in the solution is maintained at least 97% by weight to form precursor fibers, and calcining the precursor fibers.

Method for producing silica-alumina fiber

There is provided a filter element for the removal of particulates from an exhausted gas by collecting the particulates entrained with the gas characterized in that the filter element includes continuous alumina-silica fibers as inorganic fibers each of which contains not less than 98% by weight of alumina and silica and of which folding strength is not less than about 1.5 Kg/mm.sup.2.

Exhaust gas filter element

Translucent polycrystalline alumina made of aluminum oxide containing magnesium oxide in an amount of larger than 0.01% by weight and less than 0.03% by weight, zirconium oxide in an amount of larger than 0.01% by weight and less than 0.06% by weight and calcium oxide in an amount of less than 0.001% by weight, all based on the weight of aluminum oxide, which alumina has good light transmittance and mechanical strength.

Translucent polycrystalline alumina and process for producing the same

Alumina powder having a .theta.-alumina content of at least 70% by weight and an average primary particle size at least 0.1 .mu.m and containing a tungsten compound in an amount of 0.1 to 5% by weight in terms of tungsten oxide based on alumina can be used as an abrasive for a magnetic recording medium having good properties.

.theta.-alumina powder, preparation thereof and magnetic recording medium

A magnetic recording medium comprising a non-magnetic substrate and a magnetic layer which comprises magnetic powder, a binder and alumina powder having an average primary particle size of not larger than 0.3 .mu.m and containing at least one oxide selected from the group consisting of oxides of silicon, magnesium, lanthanum and zirconium in an amount of 0.05 to 5 parts by weight per 100 parts by weight of alumina, which medium has improved durability, abrasion resistance and surface smoothness of a magnetic layer and good cleaning effect on a magnetic head.

A polishing composition for metallic materials, which comprises water, an alumina polishing agent, and a polishing accelerator, wherein the polishing accelerator is at least one selected from the group consisting of chromium(III) nitrate, lanthanum nitrate, ammonium cerium(III) nitrate, and neodymium nitrate. The polishing composition has a high polishing efficiency and provides a good surface smoothness.

Polishing composition for metallic material

When an abrasive having an oleophilic surface used in a magnetic recording medium obtained by subjecting an inorganic powder having a Mohs hardness of 5 or above and an average particle size of 2 .mu.m across or below to a dry contact treatment with a dispersing agent having an oleophilic group under grinding conditions giving an impact value of 1G or greater is used in combination with a magnetic powder as a magnetic recording layer of magnetic recording medium, the wear at a magnetic head can be prevented and still characteristics can be improved.

Abrasive, production thereof and use thereof in magnetic recording medium

A method for producing .gamma.-form lithium aluminate powders usable as a material for an electrolyte tile of molten carbonate fuel cells which comprises mixing aluminum alkoxide with one member selected from the group consisting of the lithium salts of inorganic and organic acids, lithium hydroxide and lithium oxide in the presence of a non-aqueous solvent, carrying out reaction with addition of water of 1.5 to 20 moles (including water of crystallization contained in the lithium compound) based on 1 mole of aluminum alkoxide with stirring, and removing the solvent to obtain a solid matter which is then calcined at a temperature in a range of from 650.degree. C. to 1000.degree. C.

Method for producing lithium aluminate powders

A magnetic recording medium comprising a substrate and a magnetic layer formed on the substrate and comprising an inorganic powder having an average primary particle size of 0.35 .mu.m or less, an angle of repose of 40.degree. or more and a Mors hardness of 5 or more as a reinforcing material, and a magnetic powder, is excellent in wear resistance and durability of the magnetic layer and improves wear and injury of a magnetic head.

High purity organometallic compounds can be obtained by the process which comprises subjecting an organometallic compound in a liquid state under stirring to preliminary oxidation or hydrolysis in a proportion of about 0.1 to 50% by weight of the organometallic compound to form solid reaction products, and separating by distillation the unreacted organometallic compound from the solid reaction products to recover the purified organometallic compound; and high purity metallic compounds such as a solid metallic hydroxide or oxide can be obtained by the process which comprises following the process as mentioned above, oxidizing or hydrolyzing completely the recovered purified organometallic compound.

Process for producing high purity metallic compound

When an abrasive having an oleophilic surface used in a magnetic recording medium obtained by subjecting an inorganic powder having a Mohs hardness of 5 or above and an average particle size of 2 .mu.m across or below to a dry contact treatment with a dispersing agent having an oleophilic group under grinding conditions giving an impact value of 1 G or greater is used in combination with a magnetic powder as a magnetic recording layer of magnetic recording medium, the wear at a magnetic head can be prevented and still characteristics can be improved.

Pigmented aluminum oxide powders are provided herein obtained by adding at least 0.5 wt. % of carbon black to aluminum oxide powder, said carbon black having a mean particle size of less than about 100 mn and a specific surface area more than 30 m.sup.2 /g, and mixing the aluminum oxide powder-carbon black composition under an impact value of more than 1 G, preferably by use of a vibration mill. The present invention also provides a method of producing said pigmented aluminum oxide powder.

Pigmented aluminum oxide powder and method of producing the same

Powdery alumina hydrate is produced from an alkylaluminum compound by hydrolysis of the alkylaluminum compound by water through the following steps; converting the alkylaluminum compound to an ether complex compound: partially hydrolyzing the ether complex compound in the presence of an non-reactive solvent at a temperature of not higher than about 150.degree.C with stirring so that no alumina hydrate is precipitated until at least 0.8 moles of water reacts with one mole of the alkylaluminum compound, thereby forming polyaluminoxane; completely hydrolyzing the resulting polyaluminoxane at a concentration of not more than about 3.0 grams-atoms as aluminum per liter of non-reactive solvent at a temperature of about 10.degree. to about 150.degree.C with stirring, so that one mole of the feed alkylaluminum compound may be ultimately hydrolyzed completely with 2 to 10 moles of water, thereby precipitating alumina hydrate; and then separating the resulting alumina hydrate from the non-reactive solvent. The alumina hydrate has a good forming ability and also an ability to provide formed shapes having a good mechanical strength.

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Niihama, Japan

Hiroshi Umezaki