Mitsubishi Gas Chemical Company, Inc.

Akira Amemiya

Akitoshi Sugio

Toshikazu Umemura

Mutsuhiko Takeda

Yoshio Yoshikawa

Tomotaka Furusawa

Katsumasa Tanaka

Toshio Komatsu

Yoshiaki Inoue

Megumu Yuyama

Tadashi Kunii

Masaharu Kimura

Kiyokazu Kawaguchi

Yoshihiro Ono

Tetsuya Abe

Takanari Nawata

Michio Ohba

Masanori Furukawa

Isamu Masumoto

Takeo Suzumori

Hidenori Kimpara

Yoshiharu Ohtsuki

Yoshiharu Otuki

Sadao Otsuka

Sigeru Kimoto

Noriyasu Nakao

Kazuyoshi Taka

In a process for producing a stabilized oxymethylene copolymer by heat-melting, at a temperature ranging between the melting point of the copolymer and a temperature 100.degree. C. higher than the melting point in a degassing apparatus in the presence of a heat stabilizer, a crude oxymethylene copolymer of trioxane with a cyclic acetal or cyclic ether, to decompose and eliminate the instable portions of the copolymer, the improvement which comprises using as the degassing apparatus in heat stabilizing the crude oxymethylene copolymer a combination of (A) an extruder and (B) a surface renewing-type mixer, and carrying out the operation by first feeding a crude oxymethylene copolymer to said extruder (A) to heat-melt and decompose 30-90% by weight of the instable portions of the crude copolymer, removing the decomposed gas via a vent provided in said extruder, and thereafter introducing the molten resin continuously to said surface renewing-type mixer (B) where substantially all of the remaining instable portions of the oxymethylene copolymer are heat-decomposed until the content of the instable portions falls below about 2 wt. %, thereby heat stabilizing the copolymer; said extruder (A) having a single or a plurality of shafts, said surface renewing-type mixer functioning to mix and knead the resin thereby constantly renewing the surface of the resin to volatize the volatiles contained therein.

Process for heat stabilizing oxymethylene copolymers

A process for producing a polyacetal homopolymer or copolymer which comprises continuously feeding a liquid starting mixture containing molten trioxane and a catalyst and optionally a comonomer through a feed opening of a reactor, said reactor being a continuously stirring-type mixer having two stirring shafts having a plurality of plate-like paddles fixed thereto the cross-section of each of said paddles taken perpendicularly of the axial direction of the stirring shaft having a shape of a convex lens, an ellipse or a quasipolygon inscribing a phantom circle at each vertex, one of said paddles facing another paddle fixed to the other stirring shaft and said one paddle being positioned such that it rotates while the edges thereof keep a slight clearance from the inner surface of the barrel and the other paddle; polymerizing the starting mixture while moving it toward the discharge opening by the rotation of the paddles, the improvement wherein the profiles of the paddles are changed, or the arrangement of the paddles is changed continuously or stepwise, so that the transportability of the reaction mixture becomes progressively smaller from the feed opening toward the discharge opening of the reactor.

Process for continuously polymerizing trioxane

A stabilized oxymethylene copolymer composition comprising an oxymethylene copolymer, and incorporated therein,

Stabilized oxymethylene copolymer composition

In a process for producing an oxymethylene homopolymer or copolymer having improved stability which comprises polymerizing trioxane or a mixture of trioxane and a cyclic ether and/or a cyclic acetal in bulk in the presence of a catalyst which is at least one compound selected from the group consisting of boron trifluoride, boron trifluoride hydrate and coordination compounds of boron trifluoride with organic compounds containing an oxygen or sulfur atom, the improvement which comprises performing the bulk polymerization without destroying the bulk polymerization system, or which comprises adding a tertiary phosphine compound to the polymerization system to deactivate the catalyst, before the polymerization system formed by the bulk polymerization is destroyed.

Process for continuous production of oxymethylene polymer or copolymer

In a process for producing a stabilized oxymethylene copolymer which comprises heat-melting an oxymethylene copolymer having unstable, unblocked terminals obtained by the copolymerization of trioxane with a cyclic acetal and/or a cyclic ether to heat decompose it in the presence of available heat stabilizers; the improvement which comprises heating said oxymethylene copolymer having unblocked terminals in a mixer at a temperature between the melting point of said oxymethylene copolymer and a point 100.degree. C. higher than said melting point under a pressure of 0.1 mmHg to a atmospheric pressure for a mean residence time of 5 to 60 minutes, said mixer comprising a casing, a jacket for heating medium fitted over its external wall, and at least two stirring shafts equipped with a plurality of scraping blades disposed in said casing, said stirring shafts being capable of rotating in the same or different directions, and in the meantime, rotating said stirring shafts of said mixer to heat decompose said oxymethylene copolymer while renewing the surface of the molten oxymethylene copolymer.

Process for stabilizing oxymethylene copolymers

An oxygen absorbent comprising (a) metal halide-coated metal powder having at least one metal halide coated on the surface of at least one metal powder, the amount of metal halide coated being in the range of from about 0.001 part to about 10 parts by weight per 100 parts by weight of the metal powder, and the water content of the metal halide-coated metal powder being less than 1% by weight on the basis of total weight of the metal halide-coated metal powder an (b) a water-containing material and a process for producing the same are disclosed.

Oxygen absorbent

A process for polymerizing trioxane made from an aqueous solution of methanol-containing formaldehyde by a conventional method or copolymerizing the trioxane with another monomer, characterized by

Process for polymerizing trioxane

An oxygen absorbent comprising a metal powder and a metal halide coated thereon is disclosed.

An oxygen absorbent comprising at least one alkaline earth metal sulfite, at least one ferrous compound and free water is disclosed.

An oxygen absorbent comprising a dithionite and at least one compound having water of crystallization or water of hydration is disclosed.

A process for treating a waste liquor from a hydrosulfite process by an activated sludge process is improved by aerating the waste in the presence of a metal ion before the activated sludge process.

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Tokyo, Japan

Akira Amemiya