Ube Industries, Inc.

Genji Koga

Tomohiko Yamamoto

Yukio Inaba

Joji Funatsu

Hideki Noguchi

Shuji Tanaka

Katsuo Imatani

Hiroshi Kofuji

Tetsuro Kawashita

Shinichirou Yamamoto

A refined dihydroxyaryl compound, for example, catechol, having a high degree of purity and a very low metal content is produced by evaporating a starting dihydroxyaryl compound in a distillation column, condensing the vapor fraction in a condenser connected to a top outlet of the distillation column, and collecting the condensed fraction from the condenser into a storage tank through a conduit, wherein the condenser and optionally the conduit and/or the storage tank have inside surfaces thereof formed from a metal material containing at least 25% by weight of nickel, and the condensed dihydroxyaryl compound fraction is brought into contact with the specific nickel (25% or more)-containing metal inside surface.

Method of refining dihydroxyaryl compound

Oxamide is produced in a high purity by a process comprising (A) melting a starting material comprising 70 to 100 wt % of an oxalic acid diester of an aliphatic alcohol and 0 to 30 wt % of the same aliphatic alcohol as mentioned above, (B) feed-mixing an ammonia-containing gas to the starting material melt, while stirring, to produce oxamide and the aliphatic alcohol (by-product), (C) continuing the ammonia-feed-mixing procedure while controlling a feed rate of ammonia to an extent such that a content of the aliphatic alcohol in the reaction mixture is maintained at a level of 3 to 45% by weight, to produce a wetted solid reaction product comprising the resultant oxamide and the aliphatic alcohol, and then (D) collecting the oxamide from the reaction product by evaporating away the aliphatic alcohol.

Process for producing oxamide

Oxamide granules are produced by (A) feed-mixing ammonia to a starting material comprising 60 to 100 weight % of a diester of oxalic acid with a C.sub.1-6 aliphatic alcohol, and 0 to 40 weight % of the same aliphatic alcohol as mentioned above, to produce oxamide and the aliphatic alcohol as by-product, while controlling the aliphatic alcohol content to 5 to 40% based on the weight of the reaction mixture to provide the resultant oxamide wetted by the aliphatic alcohol; (B) granulating the wetted product while maintaining the content of the aliphatic alcohol at a level of 5 to 40% based on the weight of the wetted reaction product; (C) heat-evaporating away the aliphatic alcohol from the wetted granules; and optionally (D) re-wetting the resultant dry oxamide granules with water in an amount of 5 to 20% based on the weight of the dry oxamide granules; and (E) re-drying the re-wetted oxamide granules, to provide oxamide granules having an enhanced mechanical strength and form-stability in water.

Process for producing oxamide granules

High purity crystals of a biphenyltetracarboxylic dianhydride produced by dehydration of a biphenyltetracarboxylic acid, which contain almost no biphenyltricarboxylic acid or its anhydride, or a small amount such as an amount of not more than 0.2 wt. %, are of value to produce an aromatic polyamic acid or polyimide having an increased high molecular weight. The high purity crystals of a biphenyltetracarboxylic dianhydride can be prepared from a biphenyltetracarboxylic acid by a dehydration process wherein the biphenyltetracarboxylic acid is heated under carefully controlled conditions.

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Ube, Japan

Genji Koga