Abstract: The present invention provides a method for manufacturing a water-absorbing resin which (i) is made of acrylic acid that is suitable for mass production of water-absorbing resin and (ii) has an excellent water-absorbing property. In the method, a polyacrylic acid (salt)-based water-absorbing resin is manufactured by sequentially carrying out predetermined monomer preparing step, polymerization step, drying step, and surface crosslinking step. An acetic acid concentration in acrylic acid or the like supplied in the monomer preparing step is in a range of 300 ppm to 10000 ppm on the acrylic acid basis, and an acetic acid concentration lowering rate defined by a predetermined formula is 35% or higher.

Abstract: A process for producing (meth)acrylic acid comprising the step of repeating a crystallization operation “n” times to produce purified (meth)acrylic acid from crude (meth)acrylic acid, wherein: the each crystallization operation comprises a crystallizing step and a melting step; a polymerization inhibitor is not added to a (meth)acrylic acid melt obtained in the melting step of the first to n?1th crystallization operation(s) and a (meth)acrylic acid solution subjected to the crystallizing step of the second to nth crystallization operation(s); and a concentration of a polymerization inhibitor in a (meth)acrylic acid solution subjected to the crystallizing step of the first crystallization operation is adjusted so that a concentration of the polymerization inhibitor in a (meth)acrylic acid solution subjected to the crystallizing step of the nth crystallization operation is 2 ppm by mass or higher.

Abstract: The present invention provides a method for manufacturing a water-absorbing resin which (i) is made of acrylic acid that is suitable for mass production of water-absorbing resin and (ii) has an excellent water-absorbing property. In the method, a polyacrylic acid (salt)-based water-absorbing resin is manufactured by sequentially carrying out predetermined monomer preparing step, polymerization step, drying step, and surface crosslinking step. An acetic acid concentration in acrylic acid or the like supplied in the monomer preparing step is in a range of 300 ppm to 10000 ppm on the acrylic acid basis, and an acetic acid concentration lowering rate defined by a predetermined formula is 35% or higher.

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: 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 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 process for producing (meth)acrylic acid comprising the step of repeating a crystallization operation “n” times to produce purified (meth)acrylic acid from crude (meth)acrylic acid, wherein: the each crystallization operation comprises a crystallizing step and a melting step; a polymerization inhibitor is not added to a (meth)acrylic acid melt obtained in the melting step of the first to n?1th crystallization operation(s) and a (meth)acrylic acid solution subjected to the crystallizing step of the second to nth crystallization operation(s); and a concentration of a polymerization inhibitor in a (meth)acrylic acid solution subjected to the crystallizing step of the first crystallization operation is adjusted so that a concentration of the polymerization inhibitor in a (meth)acrylic acid solution subjected to the crystallizing step of the nth crystallization operation is 2 ppm by mass or higher.

Abstract: The objective of the present invention is to provide a process for producing highly pure (meth) acrylic acid stably and efficiently with crystallization. The process for production of (meth)acrylic acid according to the present invention is characterized in comprising the steps of cooling a crude (meth)acrylic acid solution in a crystallization apparatus until the temperature of a cooling medium discharged from the crystallization apparatus is stabilized in the range of higher than the solidification point of the crude (meth)acrylic acid solution in the crystallization apparatus and not more than the solidification point plus 5° C.; then bringing the crude (meth)acrylic acid solution in the crystallization apparatus to a supercooled condition by setting the temperature of a cooling medium supplied to the crystallization apparatus at the temperature of not more than the solidification point of the crude (meth)acrylic acid solution minus 1° C.

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: 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 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: The objective of the present invention is to provide a process for producing highly pure (meth) acrylic acid stably and efficiently with crystallization. The process for production of (meth)acrylic acid according to the present invention is characterized in comprising the steps of cooling a crude (meth)acrylic acid solution in a crystallization apparatus until the temperature of a cooling medium discharged from the crystallization apparatus is stabilized in the range of higher than the solidification point of the crude (meth)acrylic acid solution in the crystallization apparatus and not more than the solidification point plus 5° C.; then bringing the crude (meth)acrylic acid solution in the crystallization apparatus to a supercooled condition by setting the temperature of a cooling medium supplied to the crystallization apparatus at the temperature of not more than the solidification point of the crude (meth)acrylic acid solution minus 1° C.

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 methods of efficiently purifying and producing acrylic acid by removing solid acrylic acid polymers dissolving and existing in crude acrylic acid supplied to purifying process. The purifying method of the present invention comprises: filtrating the crude acrylic acid to obtain a filtrate at temperature from 15 to 70° C. and at liquid linear velocity of 5 m/s or less, wherein the crude acrylic acid contains an acrylic acid of 50% by mass or more; and purifying the acrylic acid from the filtrate. The producing method of the present invention comprises carrying out the purifying method.

Abstract: The objective of the present invention is to provide method for acrylic acid in which a generation of polymerized substance is prevented while acrylic acid is stored in a storage tank. A method of the present invention for producing acrylic acid, comprising storing acrylic acid in a storage tank, wherein a process liquid containing 50 mass % or more of acrylic acid is subjected to at least one filtering operation at 15 to 70° C. when the process liquid is supplied to the storage tank.

Abstract: The objective of the present invention is to provide methods of efficiently purifying and producing acrylic acid by removing solid acrylic acid polymers dissolving and existing in crude acrylic acid supplied to purifying process. The purifying method of the present invention comprises: filtrating the crude acrylic acid to obtain a filtrate at temperature from 15 to 70° C. and at liquid linear velocity of 5 m/s or less, wherein the crude acrylic acid contains an acrylic acid of 50% by mass or more; and purifying the acrylic acid from the filtrate. The producing method of the present invention comprises carrying out the purifying method.

Abstract: The objective of the present invention is to provide method for acrylic acid in which a generation of polymerized substance is prevented while acrylic acid is stored in a storage tank. A method of the present invention for producing acrylic acid, comprising storing acrylic acid in a storage tank, wherein a process liquid containing 50 mass % or more of acrylic acid is subjected to at least one filtering operation at 15 to 70° C. when the process liquid is supplied to the storage tank.