Nippon Shokubai Kagaku Kogyo Co., Ltd.

Nippon Shokubai Co., Ltd.

Masao Baba

Masatoshi Ueoka

Yuichi Kita

Kentaro Sakamoto

Kazuhiko Sakamoto

Yoji Akazawa

Atsushi Okubo

Hiroshi Yoshida

Takahisa Sato

Takahiro Takeda

Yohji Akazawa

Syoichi Matsumoto

Yoshikuni Mori

Hidefumi Haramaki

Akio Fukui

Koichi Nakagawa

Saburo Nakahara

Sumio Nakashima

Yoichi Nakagawa

Michito Okane

Yosuke Ogata

Hiroaki Tanaka

Tomoaki Tobo

Disclosed herein is a method for inhibiting polymerizable (meth)acrylic acid and esters thereof from polymerizing during their production, transportation and storage by using as the inhibitor N-oxyl compound and more than one compound selected from the group consisting of manganese salt compound, copper salt compound, 2,2,6,6,-tetramethylpiperidine compound and nitroso compound. The N-oxyl compound is one or more kinds selected from 2,2,6,6,-tetramethylpiperidinooxyl, 4-hydroxy-2,2,6,6,-tetramethylpiperidinooxyl and 4,4',4'-tris-(2,2,6,6,-tetramethylpiperidinooxyl)phosphite. The combined use of the inhibitors provides superior inhibiting effect to use alone.

Method for inhibiting polymerization of (meth) acrylic acid and esters

This invention is directed to a polymerization inhibitor and a polymerization inhibiting method which enables the continuous operation of a device for producing vinyl compounds over a long period of time and virtually eliminates corrosion. Further, the polymerization inhibitors according to the present invention are superior in polymerization inhibition when transferring and storing the vinyl compound products and in other cases. The polymerization inhibitor according to the present invention contains manganese dithiocarbamate or a thiuram compound as an effective component. The polymerization inhibiting method of this invention comprises individual or joint use of said inhibitors, or joint use of a copper salt, another manganese salt, or quinones in addition to said inhibitors. Further, the method may comprise jointly using copper dithiocarbamates in a manganese salt as polymerization inhibitors, or jointly using quinones in addition to the salts.

Polymerization inhibitor and inhibiting method for vinyl compound

Disclosed herein is a method for inhibiting polymerizable (meth)acrylic acid and esters thereof from polymerizing during their production and storage by using as the inhibitor N-oxyl compound, phenol compound, and phenothiazine compound in combination with one another. The combined use of the three inhibitors provides superior inhibiting effect to use alone alone or in pairs.

A process for producing acrylic acid is described, which process comprising providing a mixed gas of acrylic acid and by-products produced by catalytic gas phase oxidation of propylene and/or acrolein, contacting the mixed gas with water to obtain an aqueous solution, and adding an azeotrope solvent to the aqueous solution for distillation to obtain a mixture of the by-products, water and the azeotrope solvent from a tower top and acrylic acid from a tower bottom. Highly pure acrylic acid is obtained by using, as the azeotrope solvent, a mixed solvent of solvent A selected from diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl-tert-butyl ketone, n-propyl acetate and mixtures thereof and solvent B selected from toluene, heptane, methyl cyclohexane and mixtures thereof.

Process for purification of acrylic acid

Spherical fine particles of colored resin are provided. The fine particles are of a spherical shape and are superior in heat resistance, solvent resistance, and chemical resistance, and sufficiently satisfactory in durability and coloring, and industrially advantageous. The spherical fine particles of colored resin are made by incorporating an amino resin cured matter and an inorganic pigment into one body, and a ratio of the inorganic pigment against a total amount of the amino resin cured matter and inorganic pigment is in a range of from about 1 to 30% by weight.

Method for producing spherical fine particles of colored resin

In the production of methacrylic acid by the vapor phase catalytic oxidation of isobutylene, t-butanol, methacrolein isobutyl aldehyde or isobutyric acid, or mixture thereof, the reaction product gas is condensed by contact with an aqueous phase containing methacrylic acid and acetic acid thereby forming an aqueous solution of methacrylic acid and a gas phase containing methacrolein and methacrylic acid. The aqueous solution of methacrylic acid is extracted with a saturated hydrocarbon solvent containing from 6-9 carbon atoms. The methacrylic acid is extracted into the solvent phase and an aqueous phase containing acetic acid is also formed. Methacrolein is recovered from the gas containing methacrolein and methacrylic acid by contacting the gas with an aqueous phase containing methacrylic acid and acetic acid. An aqueous phase containing methacrylic acid, acetic acid and methacrolein is formed in the methacrolein recovery step. This aqueous phase is contacted with a molecular oxygen containing gas to desorb methacrolein into a gas containing methacrylic acid and methacrolein and also forming an aqueous phase containing methacrylic acid and acetic acid. This aqueous phase is recycled to either or both of the methacrylic acid condensation step and the methacrolein recovery step. Methacrylic acid is recovered from the gas containing methacrylic acid and methacrolein produced in the methacrolein desorption step by mixing this gas with an aqueous phase containing acetic acid recovered from the methacrylic acid extraction step (C). This results in a gas-containing methacrolein which is recycled to the vapor phase reaction.

Process for recovering methacrolein

A method for inhibiting polymerization of a maleimide, which comprises adding to said maleimide, as a polymerization inhibitor, at least one compound selected from the group consisting of thiodipropionic esters, 4-t-butyl-catechol, 2,4-dimethyl-6-t-butyl phenol, 2,5-di-t-butylhydroquinone, 2-t-butyl-hydroquinone, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-trizaine, 2,2'-thiobis-(4-methyl-6-t-butylphenol), 4,4'-thiobis-(6-butyl-m-cresol), and triethyleneglycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate].

Method for inhibiting polymerization of maleimides

A process for producing a methacrylic ester which comprises catalytically oxidizing isobutylene, tert-butanol, methacrolein or isobutyl aldehyde in a vapor phase; removing light-boiling substances form the resulting reaction product by distillation or stripping; extracting methacrylic acid from the resulting methacrylic acid aqueous solution using a saturated chain aliphatic hydrocarbon having 6 to 9 carbon atoms as a solvent; recovering the solvent from the obtained solvent solution of methacrylic acid; esterifying the resulting methacrylic acid by the reaction of it with a lower aliphatic alcohol or a lower alicyclic alcohol having 1 to 12 carbon atoms using a porous strongly acidic cation exchange resin as a catalyst for esterfication; and then subjecting the thus obtained esterification reaction product to a purification step.

Process for producing methacrylic ester

A method for the production of a maleimide by dehydration and ring-closure of maleinamic acid obtained by the reaction of maleic anhydride with an amine, which method is characterized by effecting ring-closure imidation of said maleinamic acid by heating said maleinamic acid in a water-insoluble or water-immiscible inert organic non-polar solvent in the presence of a catalyst of an amine salt produced from the amine and an acid, a mixture of the amine salt and the acid, or a supported catalyst on a solid carrier the catalyst or the acid.

Method for production of maleimides

A method for the production of maleimides, which comprises subjecting maleinamic acids to ring-closure imidation in an organic solvent capable of forming an azeotrope with water in the presence of an acid catalyst at a temperature in the range of 120.degree. to 250.degree. C. while removing the formed water in the form of an azeotrope with said organic solvent and thereafter purifying the produced maleimides.

A method for the production of maleimides, which comprises subjecting maleinamic acids to ring-closure imidation in an organic solvent capable of forming an azeotrope with water in the presence of an acid catalyst at a temperature in the range of 120.degree. C. to 250.degree. C. while removing the formed water in the form of an azeotrope with said organic solvent and thereafter purifying the produced maleimides.

Method for production of N-phenyl and N-cyclohexyl maleimides

In a process for producing an acrylic or methacrylic ester by esterifying acrylic or methacrylic acid with a lower aliphatic alcohol having 1 to 3 carbon atoms in the presence of an acidic catalyst, the improvement which comprises

Process for producing acrylic or methacrylic esters

In a process for producing acrylic acid which comprises contacting with water an acrylic acid-containing reaction product gas which has been obtained by the catalytic vapor phase oxidation of an olefinic compound of a general formula, CH.sub.2 .dbd.CHX, wherein X represents at least one group selected from the group consisting of CH.sub.3 and CHO, with a molecular oxygen-containing gas thereby collecting the acrylic acid in the form of an aqueous solution, separating the acrylic acid from the aqueous solution, and refining the thus separated acrylic acid, the improvement comprising a step of subjecting the bottom liquor of a rectification tower for acrylic acid to a decomposition evaporation and a step of subjecting the evaporation residue having a composition of 1-25 wt % of acrylic acid, 9-49 wt % of acrylic acid dimer, wherein total amount of the acrylic acid and its dimer is in the range of 10-50 wt %, and correspondingly 90-50 wt % of other matters to an extraction with water to separate the acrylic acid, its dimer and hydroquinone by the extraction.

Growing community of inventors

Himeji, Japan

Masao Baba