Abstract: A method of enhancing and stabilizing the physical property (for example, liquid permeability) of a water absorbent resin by means of a simple technique without requiring any alteration of the raw materials or high capital investment, is provided. Disclosed is a method for producing a water absorbent resin, which includes a polymerization step of polymerizing an aqueous solution of acrylic acid (salt) to obtain a water-containing gel-like crosslinked polymer; a drying step of drying the water-containing gel-like crosslinked polymer, to obtain a water absorbent resin powder; a classification step of classifying the water absorbent resin powder; and a surface crosslinking step of surface crosslinking the water absorbent resin powder, wherein in the classification step that is carried out before the surface crosslinking step and/or after the surface crosslinking step, a tapping material is installed below the metal sieve mesh used in the classification step, and thereby classification is carried out.

Abstract: A polyacrylic acid (salt), or a polyacrylic acid (salt)-based water-absorbing resin, contains a tracer for detecting various troubles in the water-absorbing resin during the period from the production of the water-absorbing resin to the use and discard thereof by a consumer. The polyacrylic acid (salt)-based water-absorbing resin has a stable carbon isotope ratio, as determined by accelerator mass spectrometry, of less than ?20% and a radioactive carbon content of 1.0×10?14 or mole. The polyacrylic acid (salt)-based water-absorbing resin has: a CRC of 10 [g/g] or mole; an AAP of 20 [g/g] or mole; an Ext of 35 wt. % or less; a content of residual monomers of 1,000 ppm or less; a PSD in which the proportion of particles having a particle diameter of 150 ?m or larger but less than 850 ?m is 90 wt. % or more; and an FSR of 0.15 [g/g/s] or more.

Abstract: Disclosed are a polyacrylate (salt) and a polyacrylate (salt) water-absorbent resin containing a tracer which can be verified back to the manufacturing process of the water-absorbent resin when dealing with various problems with the water-absorbent resin which can occur from the manufacturing process of the water-resistant resin, during the use thereof by a consumer, up until the disposal thereof. The disclosed polyacrylate (salt) and the polyacrylate (salt) water-absorbent resin have a carbon stable isotope ratio (?13C) of at least ?20% when measured by accelerator mass spectrometry.

Abstract: The disclosed process for producing a water-absorbing resin comprising: a polymerization step of polymerizing an aqueous unsaturated monomer; and a drying step of drying a particulated water-containing gel-liked crosslinked polymer, obtained in a finely crushing step during the polymerization or after the polymerization. In the process, the drying step is interrupted with a dryer kept in a heated state and thereafter the drying step is restarted.

Abstract: The disclosed process for producing a water-absorbing resin comprising: a polymerization step of polymerizing an aqueous unsaturated monomer; a drying step of drying a particulated water-containing gel-liked crosslinked polymer, obtained in a finely crushing step during the polymerization or after the polymerization; a pulverizing step after the drying, a classification step after the drying, and a surface treatment step after the classification. In the process is, the surface-treatment step is interrupted with a heating treatment apparatus kept in a heated state and thereafter the surface treatment step is restarted.

Abstract: The disclosed process for continuously producing a water-absorbing resin comprising a plurality of joined continuous steps; a polymerization step of polymerizing an aqueous unsaturated monomer solution, a drying step of drying a particulated water-containing gel-like crosslinked polymer obtained in a finely crushing step during the polymerization or after the polymerization, a pulverizing step after the drying, a classification step after the drying, and a surface treatment step for the water-absorbing resin powder after the classification step. In the process, with some of the above steps kept running, the other steps are interrupted, and subsequently all the steps are restarted.

Abstract: Provided is a process for producing a water-absorbing resin powder which contains a given amount of water added thereto, has a low dust content, and has high material properties. When a water-absorbing resin powder which has undergone surface crosslinking is produced on an industrial scale, various problems concerning production are eliminated and a long-term stable operation is possible without causing a deterioration in the material properties of the resin. Even when the process is continued over a long period, the material properties are stabilized (decrease in standard deviation) or improved (improvement in AAP). The process for producing a water-absorbing resin comprises, in the following order, a first classification step for classifying a water-absorbing resin, a surface crosslinking step after the classification, a water addition step for adding water to the water-absorbing resin powder after or during the surface crosslinking, a second classification step, and a conveying step.

Abstract: A method of producing a particle-shape water-absorbing resin material is realized. With this method, it is possible to prevent deterioration of properties of the particle-shape water-absorbing resin material, and reduces damages onto surfaces thereof. This method is arranged such that (a) water-absorbing resin particles are surface-treated by using a crossing agent so that surfaces of the particles are cross-linked, (b) an additive for giving a function to the particles is added to the particles, (c) and a step of mixing the particles and the additive is carried out in a step of performing particle-size regulating treatment for the particles which includes agglomerated particles.

Abstract: [PROBLEM] It is an object of the present invention to enhance and stabilize properties of a water-absorbing resin, for example, damage resistance or water-absorbing speed, by a simple and convenient method without requiring change of raw materials or expensive facility investment, in a large scale production method for the water-absorbing resin. [MEANS FOR SOLVING THE PROBLEM] It is solved by circulation of the water-absorbing resin in a predetermined amount or more in the pulverization step before the surface cross-linking step. That is, at least a part of the classified polymer is supplied again to the same or different pulverization step, before the surface cross-linking step, wherein circulation pulverization ratio in the pulverization step, represented by the following equation is 1.10 to 1.

Abstract: [PROBLEM] It is an object of the present invention to enhance and stabilize properties of a water-absorbing resin, for example, damage resistance or water-absorbing speed, by a simple and convenient method without requiring change of raw materials or expensive facility investment, in a large scale production method for the water-absorbing resin. [MEANS FOR SOLVING THE PROBLEM] It is solved by circulation of the water-absorbing resin in a predetermined amount or more in the pulverization step before the surface cross-linking step. That is, at least a part of the classified polymer is supplied again to the same or different pulverization step, before the surface cross-linking step, wherein circulation pulverization ratio in the pulverization step, represented by the following equation is larger than 1.

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: Disclosed is a method for producing a water absorbent resin, by which a surface-crosslinked water absorbent resin having excellent physical properties can be efficiently obtained at low cost, while assuring high productivity. When the production scale is increased to a continuous production on a huge scale (for example, 1 t/hr or more), the physical properties are improved and stabilized (for example, standard deviation of the physical properties is reduced) by a surface-crosslinking treatment, and the absorption against pressure (AAP) and liquid permeability (SFC) are further improved.

Abstract: [PROBLEM] It is an object of the present invention to efficiently obtain efficiently a water-absorbent resin having excellent property. [SOLUTION] A production method for a water-absorbent resin, comprising: a polymerization step for obtaining hydrogel by subjecting a monomer aqueous solution to a polymerization reaction; and a drying step for drying the hydrogel; wherein drying in the drying step is performed using a continuous through-flow belt-type drying machine; pore opening rate of the through-flow belt in the continuous through-flow belt-type drying machine is 20 to 50%; solid content of the hydrogel supplied to the drying step is 35% by weight or more; and area occupancy rate of the hydrogel is 85 to 100% relative to the through-flow belt.

Abstract: Disclosed is a method for producing a water absorbent resin, by which a surface-crosslinked water absorbent resin having excellent physical properties can be efficiently obtained at low cost, while assuring high productivity. When the production scale is increased to a continuous production on a huge scale (for example, 1 t/hr or more), the physical properties are improved and stabilized (for example, standard deviation of the physical properties is reduced) by a surface-crosslinking treatment, and the absorption against pressure (AAP) and liquid permeability (SFC) are further improved.

Abstract: Disclosed is a method for producing a water absorbent resin, by which a surface-crosslinked water absorbent resin having excellent physical properties can be efficiently obtained at low cost, while assuring high productivity. When the production scale is increased to a continuous production at 1 t/hr or more, the physical properties are improved and stabilized (for example, standard deviation of the physical properties is reduced) by a surface-crosslinking treatment, and the absorption against pressure (AAP) and liquid permeability (SFC) are further improved.

Abstract: A process for producing a water absorbent resin is provided with which it is possible to efficiently and inexpensively obtain a surface-crosslinked water-absorbing resin having excellent material properties, while ensuring high productivity. In continuous production scaled up to a large scale (in particular, 1 t/hr or more), the physical properties are improved and stabilized (for example, a reduction in standard deviation of the physical properties) by a surface crosslinking treatment to further improve absorption against pressure (AAP) and saline flow conductivity (SFC).

Abstract: [PROBLEM] It is an object of the present invention to efficiently obtain efficiently a water-absorbent resin having excellent property. [SOLUTION] A production method for a water-absorbent resin, comprising: a polymerization step for obtaining hydrogel by subjecting a monomer aqueous solution to a polymerization reaction; and a drying step for drying the hydrogel; wherein drying in the drying step is performed using a continuous through-flow belt-type drying machine; solid content of the hydrogel supplied to the drying step is 35% by weight or more, and thickness variation rate (1) represented by the following EXPRESSION 1 of the hydrogel loaded onto through-flow belt in the continuous through-flow belt, is 1.05 to 5: [MATH. 1] Thickness variation rate (1)=(Maximum thickness of hydrogel in a width direction of the through-flow belt)/(Average thickness of hydrogel in a width direction of the through-flow belt).

Abstract: An object of the present invention is to provide a water absorbing agent having a low amount of residual monomer, small variance of the amount of residual monomer among ranges of particle size distribution and favorable absorption properties, and being sanitary; an absorbing article; and a method for the production of a water absorbing agent. The water absorbing agent of the present invention has the amount of residual monomer of not higher than 500 ppm, and a residual monomer index of not greater than 0.30.

Abstract: In obtaining a water-absorbing resin with high property in high productivity, produced a production method for a water-absorbing resin in high property and stably. Provided is a production method for a water-absorbing resin, comprising: a step for polymerizing an acrylic acid aqueous solution; a step for drying the resultant water-containing gel; a step for pulverizing and classifying the dried substance; and a step for surface cross-linking after classification, wherein a hopper having an inclination angle of a cone part of equal to or larger than 45 degree, and a drawing rate of 30 to 80% is used.

Abstract: Provided is a production method for the particulate water-absorbing agent, which can contribute to property enhancement, and further improvement of productivity or the like, as well. One example of the production method for the particulate water-absorbing agent relevant to the present invention includes the polymerization step for obtaining a polymer gel; the drying step for drying the polymer gel to obtain a dried substance; the pulverization step for pulverizing the dried substance or the polymer gel to obtain the particulate water-absorbing resin; the classification step for sieving the particulate water-absorbing resin; the granule sizing step for granule sizing the particulate water-absorbing agent obtained from the particulate water-absorbing resin; and the transporting step for transporting the products produced in each of the steps to other steps.