Abstract: A method for producing a polyacrylic acid (salt)-based water absorbent resin, sequentially including the steps of: storing or producing acrylic acid; mixing acrylic acid containing a polymerization inhibitor with water, a crosslinking agent, and optionally, a basic composition, and/or neutralizing them, to prepare an aqueous monomer solution; polymerizing the aqueous monomer solution; drying an obtained water-containing gel-like crosslinked polymer; and optionally carrying out surface crosslinking, wherein the acrylic acid containing the polymerization inhibitor has a water content of not higher than 1,000 ppm (by mass; the same applies hereinafter), and/or the aqueous monomer solution has a formic acid content of 1 to 700 ppm, relative to the monomer.

Abstract: An object of the present invention is to provide a particle-shaped water absorbing agent having a remarkably improved surface color and excellent water-absorbing properties (better water absorption capacity, and lower water soluble content and residual monomer content) at the same time. In order to attain the object, a particle-shaped water absorbing agent according to the present invention is a particle-shaped water absorbing agent whose main component is a polyacrylic acid and/or a salt thereof, the particle-shaped water absorbing agent having a surface color of Hunter b value in a range of ?5 to 10, and having a cross-linking absorption property index (CPI) in a range of 1 to 100, the CPI defined by the following two equations: GEX=(GVs+17)/Ln (water soluble content);??Equation 1: CPI=(GEX/residual monomer content)×100??Equation 3: where GVs is gel volume in saline, Ln (water soluble content) is a logarithm natural of water soluble content.

Abstract: A crystallization device and a crystallization process are provided for obtaining (meth)acrylic acid with higher purity without causing leakage of a crude solution by preventing complete clogging in a crystallization tube from occurring. The device for crystallizing (meth)acrylic acid includes a crude (meth)acrylic acid solution supply part, a crystallization tube, a heat medium supply tube, a heat medium discharge tube, a storage part of a crude (meth)acrylic acid solution passed through the crystallization tube, a tube for circulating and supplying the crude (meth)acrylic acid solution to the supply part from the storage part, and a pump for circulating and supplying the crude (meth)acrylic acid solution to the supply part from the storage part, and also includes a pressure meter in the circulate-supply tube.

Abstract: PROBLEM An object of the present invention is to provide a crystallization unit capable of producing a purified acrylic acid having high purity efficiently. SOLUTION The present invention provides a crystallization unit to separate an acrylic acid-containing solution into a mother liquid and a purified acrylic acid, wherein the crystallization unit comprises a crystallizer having an exit to take out the mother liquid and the purified acrylic acid alternately; a supply line to supply the acrylic acid-containing solution to the crystallizer; and a recovery line to recover the mother liquid and the purified acrylic acid alternately from the crystallizer which is connected to the exit, and wherein the recovery line is equipped with an opening and closing unit consisting of a ball valve or a gate valve.

Abstract: PROBLEM There is provided a melting method of (meth)acrylic acid crystal which is capable of providing a higher quality of (meth)acrylic acid without carrying out an additional purification treatment to (meth)acrylic acid obtained by a crystallization operation accompanied by melting of (meth)acrylic acid. In addition, there is provided a simple method for adjusting a content of polymerization inhibitor in a product (meth)acrylic acid. SOLUTION In the crystallization method melting (meth)acrylic acid crystal while wetting with the crystalline molten liquid, a polymerization inhibitor is added to a molten liquid melted after initiation of melting, and all of crystal is melted while circulating and feeding the molten liquid containing said polymerization inhibitor to the crystal.

Abstract: A process for producing (meth)acrylic acid of the present invention comprises the steps in the following order: a crystallization step of supplying a cooling medium cooled by a heat source device to a crystallizer to obtain a (meth)acrylic acid crystal from a crude (meth)acrylic acid solution; an adjustment step of returning the cooling medium discharged from the crystallizer to the crystallizer without cooling; a sweating step of supplying a heating medium to the crystallizer to partially melt the (meth)acrylic acid crystal, thereby obtaining a melted liquid, and discharging the melted liquid from the crystallizer; and a melting step of supplying the heating medium to the crystallizer to melt the (meth)acrylic acid crystal, thereby obtaining purified (meth)acrylic acid. According to the present invention, purified (meth)acrylic acid with high purity can be obtained.

Abstract: The objective of the present invention is to provide a process for production of (meth)acrylic acid with improved production efficiency by efficiently shifting from heating procedure to cooling procedure for a crystallizer. A process for production of (meth)acrylic acid according to the present invention is characterized in comprising the steps of crystallizing (meth)acrylic acid from a crude (meth)acrylic acid solution by using a batch type crystallizer, and melting the obtained (meth)acrylic acid crystal to obtain a (meth)acrylic acid melted liquid; wherein preliminary cooling of the crystallizer for the next crystallization step is started during transferring the (meth)acrylic acid melted liquid from the crystallizer.

Abstract: A particle concentration measuring device includes: a measurement region formation part which has a wall (10) of substantially ring-form and through an inner opening of which gas relatively flows orthogonally; a light curtain forming unit (12A, 12B) forming a planar light curtain (FL) in the inner opening: a particle detecting unit (15) receiving scattered light from particles passing through the light curtain (FL) to detect the particles; and a calculating unit (22) calculating particle concentration based on the total number of the particles detected by the particle detecting unit (15) in a volume of an airflow passing through the light curtain (FL) in a unit time.

Abstract: [Problem] There is provided, in a process for producing acrylic acid having a catalytic gas-phase oxidation reaction step, a condensation step, a collection step, a distillation step, a crystallization step, an acrylic acid recovering step or the like, a production method for acrylic acid, in which contamination of acrylic acid with protoanemonin without providing any additional purification treatment to the resultant purified acrylic acid can be reduced.

Abstract: The present invention provides a method for effectively preventing the precipitation related to manganese acetate in the pipe for sending a polymerization inhibitor and the like, and the polymerization of (meth)acrylic acid. A first method of the present invention for producing (meth)acrylic acid, characterized in comprising steps of: producing a (meth)acrylic acid-containing gas by catalytic vapor phase oxidation reaction; and obtaining a (meth)acrylic acid-containing fluid by providing the (meth)acrylic acid-containing gas into a condensation column or an absorption column; wherein manganese acetate is used as a polymerization inhibitor; manganese acetate is dissolved into a (meth)acrylic acid aqueous solution containing not more than 10% by mass of (meth)acrylic acid, and the like, to obtain a manganese acetate aqueous solution; and the manganese acetate aqueous solution is provided into the condensation column or the absorption column.

Abstract: A method for producing a polyacrylic acid (salt)-based water absorbent resin, sequentially including the steps of: storing or producing acrylic acid; mixing acrylic acid containing a polymerization inhibitor with water, a crosslinking agent, and optionally, a basic composition, and/or neutralizing them, to prepare an aqueous monomer solution; polymerizing the aqueous monomer solution; drying an obtained water-containing gel-like crosslinked polymer; and optionally carrying out surface crosslinking, wherein the acrylic acid containing the polymerization inhibitor has a water content of not higher than 1,000 ppm (by mass; the same applies hereinafter), and/or the aqueous monomer solution has a formic acid content of 1 to 700 ppm, relative to the monomer.

Abstract: PROBLEM An object of the present invention is to provide a crystallization unit capable of producing a purified acrylic acid having high purity efficiently. SOLUTION The present invention provides a crystallization unit to separate an acrylic acid-containing solution into a mother liquid and a purified acrylic acid, wherein the crystallization unit comprises a crystallizer having an exit to take out the mother liquid and the purified acrylic acid alternately; a supply line to supply the acrylic acid-containing solution to the crystallizer; and a recovery line to recover the mother liquid and the purified acrylic acid alternately from the crystallizer which is connected to the exit, and wherein the recovery line is equipped with an opening and closing unit consisting of a ball valve or a gate valve.

Abstract: The objective of the present invention is to provide a crystallization device and a crystallization process for obtaining (meth)acrylic acid with higher purity without causing leakage of a crude solution by preventing complete clogging in a crystallization tube from occurring.

Abstract: The objective of the present invention is to provide a process for production of (meth)acrylic acid with improved production efficiency by efficiently shifting from heating procedure to cooling procedure for a crystallizer. A process for production of (meth)acrylic acid according to the present invention is characterized in comprising the steps of crystallizing (meth)acrylic acid from a crude (meth)acrylic acid solution by using a batch type crystallizer, and melting the obtained (meth)acrylic acid crystal to obtain a (meth)acrylic acid melted liquid; wherein preliminary cooling of the crystallizer for the next crystallization step is started during transferring the (meth)acrylic acid melted liquid from the crystallizer.

Abstract: PROBLEM There is provided a melting method of (meth)acrylic acid crystal which is capable of providing a higher quality of (meth)acrylic acid without carrying out an additional purification treatment to (meth)acrylic acid obtained by a crystallization operation accompanied by melting of (meth)acrylic acid. In addition, there is provided a simple method for adjusting a content of polymerization inhibitor in a product (meth)acrylic acid. SOLUTION In the crystallization method melting (meth)acrylic acid crystal while wetting with the crystalline molten liquid, a polymerization inhibitor is added to a molten liquid melted after initiation of melting, and all of crystal is melted while circulating and feeding the molten liquid containing said polymerization inhibitor to the crystal.

Abstract: A process for producing (meth)acrylic acid of the present invention comprises the steps in the following order: a crystallization step of supplying a cooling medium cooled by a heat source device to a crystallizer to obtain a (meth)acrylic acid crystal from a crude (meth)acrylic acid solution; an adjustment step of returning the cooling medium discharged from the crystallizer to the crystallizer without cooling; a sweating step of supplying a heating medium to the crystallizer to partially melt the (meth)acrylic acid crystal, thereby obtaining a melted liquid, and discharging the melted liquid from the crystallizer; and a melting step of supplying the heating medium to the crystallizer to melt the (meth)acrylic acid crystal, thereby obtaining purified (meth)acrylic acid. According to the present invention, purified (meth)acrylic acid with high purity can be obtained.

Abstract: A particle concentration measuring device includes: a measurement region formation part which has a wall (10) of substantially ring-form and through an inner opening of which gas relatively flows orthogonally; a light curtain forming unit (12A, 12B) forming a planar light curtain (FL) in the inner opening: a particle detecting unit (15) receiving scattered light from particles passing through the light curtain (FL) to detect the particles; and a calculating unit (22) calculating particle concentration based on the total number of the particles detected by the particle detecting unit (15) in a volume of an airflow passing through the light curtain (FL) in a unit time.

Abstract: The objective of the present invention is to provide a method for inhibiting polymerization of (meth)acrylic acid and the like. By the method, the generation of deposit in a pipe, which is exclusively used for providing a solution of a dialkyldithiocarbamic acid copper salt to a distillation column and the like, is prevented, and the problems such as the clogging of the pipe and polymerization in the distillation column are solved. The method according to the present invention for inhibiting polymerization of (meth)acrylic acid and/or an ester thereof is characterized in comprising a step of inhibiting polymerization of (meth)acrylic acid and/or the ester thereof by using a solution of a dialkyldithiocarbamic acid copper salt dissolved in an organic solvent, wherein a content amount of copper sulfate in the solution of the dialkyldithiocarbamic acid copper salt is 100 ppm or less by mass.

Abstract: [Problem] There is provided, in a process for producing acrylic acid having a catalytic gas-phase oxidation reaction step, a condensation step, a collection step, a distillation step, a crystallization step, an acrylic acid recovering step or the like, a production method for acrylic acid, in which contamination of acrylic acid with protoanemonin without providing any additional purification treatment to the resultant purified acrylic acid can be reduced.

Abstract: A communication terminal, in case that transmission/reception of a frame is carried out between a management terminal and another communication terminal, reads out its frame content, and on the basis of a content of the frame which was readout, sets up power off time for turning off power of the communication terminal, and turns off power of the communication terminal, during a period of the power off time. By this means, depending on a content of a frame which is transmitted/received between another communication terminal and the management terminal, power off time of the communication terminal is calculated, and therefore, it is possible to turn off power of the communication terminal during such a period that transmission/reception is not carried out to/from the management terminal, and it is possible to suppress power consumption of the communication terminal.