Abstract: A solid substance removing device comprising a body provided with a fluid inlet pipe and a fluid outlet pipe and a filtering part disposed between the fluid inlet pipe and the fluid outlet pipe inside said body, the filtering part having (a) a thickness in the range of 5-500 mm, (b) a percentage of voids in the range of 60-99.5 vol. %, and (c) a contact surface area in the range of 100-2000 m2/m3. Owing to the construction described above, it is made possible to facilitate removal of the solid substance and, at the same time, prevent new generation of a polymer during the production of an easily polymerizing substance.

Abstract: A method of producing highly purified acrylic acid in a high yield is provided. A method of producing acrylic acid including the steps of an oxidation step, an absorption step, a distillation step, a crystallization step, and a dimer decomposition step.

Abstract: The present invention provides an apparatus for producing (meth)acrylic acid and a process for producing (meth)acrylic acid with this apparatus wherein the apparatus enables to produce (meth)acrylic acid stably for a long period of time by effectively inhibiting the polymerization of (meth)acrylic acid in its production process (for example, in a reboiler). At least a part of the apparatus is made of a nickel-chromium-iron alloy with a molybdenum content of 3 to 20 mass %, but not including 3 mass %, or with a molybdenum content of 1 to 4 mass % and a copper content of 0.5 to 7 mass %.

Abstract: A method for washing a spent solid catalyst is disclosed which is characterized by washing the solid catalyst used for the reaction of generating an esterified compound in a device packed with the solid catalyst, distilling the cleaning fluid in a distilling part, and circulating the fraction obtained by the distillation to an esterification reactor. According to this invention, the existing apparatus used during the process for the production of an esterified compound can be adopted without any modification, the water by-produced in the reaction for production an esterified compound and an alcohol as the raw material for esterification can be used as the cleaning fluid, and these effective components can be recovered from the cleaning fluid. Thus, the stimulation from the offensive odor and the volatile component which has heretofore posed a problem during the removal of the solid catalyst is eliminated and the safety in terms of heath and in terms of operation is secured.

Abstract: A method for distilling a raw material liquid containing (meth)acrylic acid substantially free from azeotropic solvents, collected with a collection agent from a mixed gas obtained by gas phase catalytic oxidation reactions which includes feeding to a distillation column the raw material liquid which temperature is substantially equal to that of the entrance place in the column.

Abstract: The present invention provides a production process for a hydroxyalkyl (meth)acrylate which process enables to maintain the oxygen concentration of a gas phase portion of a reactor within a specific low concentration range in any stage of before adding raw materials, during the reaction, and after the reaction. The production process comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl (meth)acrylate, wherein an inert gas and/or a mixed gas of oxygen and an inert gas with a beforehand adjusted oxygen concentration of 0.1 to 14 vol % is used to maintain the oxygen concentration of a gas phase portion of a reactor in the range of 0.1 to 14 vol % (1) before adding the alkylene oxide or (2) during the above reaction or (3) between the completion of the above reaction and the charge for the next reaction.

Abstract: The invention provides a hydrophilic resin and an absorbent article, both of which display still less coloring and discoloring when preserved for a long time. The hydrophilic resin is any one of: 1) a hydrophilic resin, obtained by a process including the step of polymerizing a monomer component including a major proportion of either one or both of acrylic acid and its salt which merely have a content of at most 0.20 ppm in total of hydroquinone and benzoquinone; 2) a hydrophilic resin, comprising a major proportion of an acrylic polymer and a minor proportion of either one or both of hydroquinone and benzoquinone, with the hydrophilic resin further comprising a quinhydronation inhibitor of 10˜1,000,000 times the total weight of hydroquinone and benzoquinone; 3) a hydrophilic resin, comprising a major proportion of an acrylic polymer and merely having a coloring degree (YI) of at most 20 after being left under conditions of the open system, 70° C.

Abstract: The present invention provides an apparatus for producing (meth)acrylic acid and a process for producing (meth)acrylic acid with this apparatus wherein the apparatus enables to produce (meth)acrylic acid stably for a long period of time by effectively inhibiting the polymerization of (meth)acrylic acid in its production process (for example, in a reboiler). At least a part of the apparatus is made of a nickel-chromium-iron alloy with a molybdenum content of 3 to 20 mass %, but not including 3 mass %, or with a molybdenum content of 1 to 4 mass % and a copper content of 0.5 to 7 mass %.

Abstract: For a heat exchanger using a heating medium for the purpose of heating a fluid to be handled during a steady state, this invention provides a method for using relevant devices which enables the heat exchanger to be operated safely and infallibly without suffering the raw material or the reaction product to polymerize in the reactor or the pipes during an unsteady state, suffering the reactor or the pipes to sustain a fracture owing to a rise in the internal pressure of the vessel, and suffering the apparatus for production to sustain serious damage. This invention pertains, mainly in a heat exchanger admitting a heating medium and using it for the purpose of heating a fluid to be handled, to a method for using relevant devices during the unsteady state, characterized by introducing a cooling medium in the place of the heating medium mentioned above.

Abstract: In the purification of an easily polymerizable compound such as (meth)acrylic acid by the use of a purification column adapted to withdraw a liquid from the middle portion of the column, a novel liquid withdrawing tray adapted to prevent the compound from polymerization effectively and permit the purification to be stably performed for a long time, a purification column using this tray, and a method for purifications using this purification column are provided. The liquid withdrawing tray for the purification column is composed of a liquid receiving plate and a liquid withdrawing tube for withdrawing the liquid from the liquid receiving plate.

Abstract: The present invention provides a method for stabilizing waste oil which is taken of each chemical apparatus of the manufacturing line of (meth)acryl acid and/or ester thereof, and treating the waste oil such as draining it out of the production apparatus, for example, a distillation tower from its bottom, sending and transporting it by a pump through a pipeline, and storing it in a storage tank in a simple manner while keeping the waste oil in a stable state. The waste oil can be stabilized by coexisting with solvent. The solvent used in the present invention is typically at least one selected from the group consisting of water, alcohol, ether, carboxylic acid, ketone, aromatic hydrocarbons, and aliphatic hydrocarbons.

Abstract: In the purification of an easily polymerizable compound such as (meth)acrylic acid by the use of a purification column adapted to withdraw a liquid from the middle portion of the column, a novel liquid withdrawing tray adapted to prevent the compound from polymerization effectively and permit the purification to be stably performed for a long time, a purification column using this tray, and a method for purifications using this purification column are provided. The liquid withdrawing tray for the purification column is composed of a liquid receiving plate and a liquid withdrawing tube for withdrawing the liquid from the liquid receiving plate.

Abstract: In the reaction of catalytic gas phase oxidation induced by the supply of at least a raw material to be oxidized and a molecular oxygen-containing gas to a reactor for catalytic gas phase oxidation, a method for starting up the reactor for catalytic gas phase oxidation is disclosed which is characterized by causing the raw material and the molecular oxygen-containing gas to pass a range in which the concentration of the raw material is less than the lower explosion limit of the raw material and the concentration of oxygen is not less than the limiting oxygen concentration, but excluding the concentration of the raw material of 0 vol. %. The method enables the reactor to be started up economically and safely by avoiding the explosion range induced by the composition of a raw material and a molecular oxygen-containing gas supplied to the reactor and decreasing the amount of a diluting gas to be supplied.

Abstract: A method for stopping a purifying column handling an easily polymerizing compound-containing solution is disclosed, which method is characterized by lowering the inner oxygen concentration of the column below the limit of oxygen concentration by supplying an inert gas to the column while the concentration of the gas of easily polymerizing compound is in the range of 100% to the lower limit of the flammable range in volume % of the purifying column or by further supplying a reflux liquid thereby cooling the interior of the column at a rate in the range of 0.01-10° C./min. This invention enjoys exceptionally high economic value in respect that it is capable of preventing the easily polymerizing compound from the occurrence of polymerization in the purifying column, precluding the interior of the purifying column from being clogged by adhesion of a polymer, and moreover avoiding the possibility of explosion.

Abstract: The present invention provides a process for producing a (meth)acrylic ester which enables to obtain a (meth)acrylic ester in an excellent reaction yield. The process for producing a (meth)acrylic ester uses an alcohol and an acid as raw materials and an ion-exchange resin as a catalyst, and the process is characterized by comprising a dehydration step and an esterification step, wherein the esterification reaction step follows the dehydration step in which water impregnated in the ion-exchange resin is removed by using as a dehydrating solvent at least one member selected from the group consisting of the alcohol, the acid, and the resulting ester.

Abstract: In a process for the purification of (meth)acrylic acid and/or its ester using a distillation unit containing a distillation column, a multitubular reboiler and a pipe connecting these elements, an oxygen containing gas is supplied from a least one point in regions between the distillation column and an inlet of the multitubular reboiler and/or in regions between the inlet and an inlet side tube sheet of the multitubular reboiler. This process can effectively prevent the formation of polymerization products and can stably purify (meth)acrylic acid and/or its ester over a long time.

Abstract: A method for starting up a distilling column destined to handle an easily polymerizing compound-containing solution characterized by supplying at the start of the operation of the distilling column a polymerization inhibitor to the bottom liquid of the distilling column having a temperature of not higher than 80° C. Further, by supplying a reflux liquid through the top of the distilling column or the middle stage of the column prior to the start of the temperature elevation of the distilling column, thereby preventing the polymerization of the easily polymerizing compound more effectively.

Abstract: A solid substance removing device comprising a body provided with a fluid inlet pipe and a fluid outlet pipe and a filtering part disposed between the fluid inlet pipe and the fluid outlet pipe inside said body, the filtering part having (a) a thickness in the range of 5-500 mm, (b) a percentage of voids in the range of 60-99.5 vol. %, and (c) a contact surface area in the range of 100-2000 m2/m3. Owing to the construction described above, it is made possible to facilitate removal of the solid substance and, at the same time, prevent new generation of a polymer during the production of an easily polymerizing substance.

Abstract: A method is disclosed for preventing the polymerization of (meth)acrylic acid and esters thereof, which method is characterized by using an N-nitrosophenyl hydroxyl amine or a salt thereof, an N-oxyl compound, an N-hydroxy-2,2,6,6-tetramethylpiperidine compound, and a 2,2,6,6-tetramethylpiperidine compound in combination in a purifying column. The N-nitrosophenylhydroxylamine or the salt thereof is partly decomposed in the purifying column and is allowed to ascend the interior of the column and effectively inhibit the polymerization of (meth)acrylic acid. Since the method does not need to use any metal compound, it permits the disposal of the waste liquid to be effected easily. Further, the combined use of the relevant components ensures effective prevention of the polymerization in the gas and the liquid phase.

Abstract: This invention resides in providing a method for the prevention of possible polymerization of the easily polymerizable substance during the purification thereof by a column provided with (a) at least one tray directly fixed to a support ring with a bolt and a nut and/or (b) at least one tray fixed to a support ring with a vertical clamp or a distillation column provided in the lower part thereof with a splash collision plate.