Polyacrylic acid (salt), polyacrylic acid (salt)-based water-absorbing resin, and process for producing same

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 (δ 13 C) of at least −20% when measured by accelerator mass spectrometry.

1 - 26 . (canceled) 
     
     
         27 . A polyacrylic acid (salt) having a carbon stable isotope ratio (δ 13 C) measured by accelerator mass spectrometry method of −20% or higher. 
     
     
         28 . The polyacrylic acid (salt) according to  claim 27 , having a hydrogen isotope ratio δD vs. SMOW) of −15 to −300%. 
     
     
         29 . The polyacrylic acid (salt) according to  claim 27 , wherein the carbon stable isotope ratio (δ 13 C) is −15 to −10%. 
     
     
         30 . The polyacrylic acid (salt) according to  claim 27 , wherein  14 C/C of the polyacrylic acid (salt) is 1.0×10 −14  or more. 
     
     
         31 . A polyacrylic acid (salt)-type water-absorbing resin obtained from the polyacrylic acid (salt) according to  claim 27 , wherein the polyacrylic acid (salt)-type water-absorbing resin have a carbon stable isotope ratio (δ 13 C) measured by accelerator mass spectrometry method of −20% or higher. 
     
     
         32 . The polyacrylic acid (salt)-type water-absorbing resin according to  claim 31 , wherein a propionic acid content contained in the polyacrylic acid (salt)-type water-absorbing resin is 2000 ppm or less. 
     
     
         33 . The polyacrylic acid (salt)-type water-absorbing resin according to  claim 31 , wherein the polyacrylic acid (salt)-type water-absorbing resin satisfies physical properties defined in the following (1) to (6):
 (1) CRC (ERT 441.2-02) is 10 [g/g] or more;   (2) AAP (ERT 442.2-02) is 20 [g/g] or more;   (3) Ext (ERT 470.2-02) is 35 mass % or less;   (4) Residual Monomers (ERT 410.2-02) is 1000 ppm or less;   (5) particles with a particle diameter of 150 pm or larger and smaller than 850 pm measured by PSD (ERT 420.2-02) are in an amount of 90 mass % or more; and   (6) SFC (saline flow conductivity) is 1 [×10 −7 .cm 3 .s.g −1 ] or more.   
     
     
         34 . The polyacrylic acid (salt)-type water-absorbing resin according to  claim 31 , wherein the polyacrylic acid (salt)-type water-absorbing resin is surface-crosslinked with an organic surface-crosslinking agent and, if necessary, coated with a surface treatment agent selected from a polyvalent metal salt, a polyamine polymer, and water-insoluble inorganic particles. 
     
     
         35 . The polyacrylic acid (salt)-type water-absorbing resin according to  claim 31 , wherein the polyacrylic acid (salt)-type water-absorbing resin satisfies one or more of the following content:
 the content of 3-hydroxypropionic acid is 1000 ppm or less;   the content of a polymerization inhibitor is 1 to 160 ppm;   the content of Fe is 0 to 2 ppm; and   the content of mono- or di-hydroxyacetone is 0 to 10 ppm or less.   
     
     
         36 . A sanitary material containing the polyacrylic acid (salt)-type water-absorbing resin according to  claim 31 . 
     
     
         37 . A method for producing a polyacrylic acid (salt)-type water-absorbing resin selected from a water-soluble polyacrylic acid (salt) or a polyacrylic acid (salt)-type water-absorbing resin comprising a polymerization step for a water-soluble unsaturated monomer and a drying step for the obtained water-containing gel-like crosslinked polymer, wherein the polymerization step is for polymerizing acrylic acid with a carbon stable isotope ratio (δ 13 C) of −20% or higher as the water-soluble unsaturated monomer. 
     
     
         38 . The method for producing a polyacrylic acid (salt)-type water-absorbing resin according to  claim 37 , wherein a raw material main component of the acrylic acid is obtained from biomass derived from a C4 plant. 
     
     
         39 . The method for producing a polyacrylic acid (salt)-type water-absorbing resin according to  claim 37 , wherein the carbon stable isotope ratio (δ 13 C) of acrylic acid in the polymerization step is changed depending on one of a production line, production time, and a product lot number. 
     
     
         40 . The method for producing a polyacrylic acid (salt)-type water-absorbing resin according to  claim 37 , wherein the water-soluble unsaturated monomer is obtained by mixing acrylic acid having different carbon stable isotope ratios (δ 13 C). 
     
     
         41 . The method for producing a polyacrylic acid (salt)-type water-absorbing resin according to  claim 37 , wherein the dried material obtained in the drying step is surface-crosslinked with an organic surface-crosslinking agent after the drying step and, if necessary, coated with a surface treatment agent selected from a polyvalent metal salt, a polyamine polymer, and water-insoluble inorganic particles after the drying step. 
     
     
         42 . The method for producing a polyacrylic acid (salt)-type water-absorbing resin according to  claim 37 , wherein the water-soluble unsaturated monomer further satisfies one or more of the following:
 the content of 3-hydroxypropionic acid is 1000 ppm or less;   the content of the polymerization inhibitor is 1 to 160 ppm;   the content of Fe is 0 to 2 ppm; and   the content of mono- or di-hydroxyacetone is 0 to 10 ppm or less.   
     
     
         43 . The method for producing a polyacrylic acid (salt)-type water-absorbing resin according to  claim 37 , wherein a drying temperature at the drying step is 50 to 300° C. (drying is conducted under reduced pressure if the drying temperature is 100° C. or lower) and a drying time at the drying step is 10 to 120 minutes. 
     
     
         44 . The method for producing a polyacrylic acid (salt)-type water-absorbing resin according to  claim 37 , wherein a fine powder recycle step is employed besides the above steps. 
     
     
         45 . A method for identifying a polyacrylic acid (salt) after production, wherein  13 C volume of the polyacrylic acid (salt) after production is quantitatively analyzed by accelerator mass spectrometry. 
     
     
         46 . The method for identifying a polyacrylic acid (salt) according to  claim 45 , wherein other trace components and/or a plurality of physical properties are further measured.