Method for producing a superabsorbent recycled polymer and superabsorbent recycled polymer

Abstract

The present disclosure aims to provide a method for manufacturing a superabsorbent recycled polymer that can suppress the adhesion of particles to each other, efficiently dry each particle, and have excellent whiteness. A method for manufacturing a superabsorbent recycled polymer regenerated from a used superabsorbent polymer, characterized by including: a dehydration step in which the used superabsorbent polymer is dehydrated to form a dehydrated superabsorbent polymer; a particle group attachment step in which a particle group of a superabsorbent polymer is attached to the dehydrated superabsorbent polymer to form a superabsorbent polymer to which the particle group is attached, and the particle group is caused to absorb moisture held by the dehydrated superabsorbent polymer; and a drying step in which the superabsorbent polymer to which the particle group is attached is dried to form the superabsorbent recycled polymer.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing a superabsorbent polymer regenerated from a used superabsorbent polymer, and a superabsorbent polymer regenerated from a used superabsorbent polymer. Background Technology

[0002] The study investigated the regeneration and reuse of used superabsorbent polymers.

[0003] For example, Patent Document 1 discloses the following method for regenerating absorbent resin.

[0004] A method for regenerating absorbent resin, characterized in that it is a method for regenerating absorbent resin that has absorbed the absorbed liquid from a used body fluid absorbent article and performing a washing and dehydration treatment, wherein the washing and / or dehydration treatment includes an operation in an environment in which the absorbed liquid absorbed by the absorbent resin is discharged.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-326161 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Although the method described in Patent Document 1 cleans and / or dehydrates the absorbent resin that has absorbed the absorbent liquid, it does not dehydrate all the absorbent liquid from the absorbent resin. Therefore, the regenerated absorbent resin tends to exhibit the color of the absorbent liquid.

[0010] Furthermore, in the method described in Patent Document 1, the absorbent resins are fixed together during the drying process in order to obtain the recycled absorbent resin, so as described in the embodiments of Reference 1, a crushing process and a grading process are required.

[0011] Therefore, the object of this disclosure is to provide a method for manufacturing a highly absorbent recycled polymer that can inhibit particle adhesion to each other, allow each particle to dry efficiently, and produce a highly absorbent recycled polymer with excellent whiteness.

[0012] Solution for solving the problem

[0013] The present discloses a method for manufacturing a superabsorbent polymer regenerated from a used superabsorbent polymer, characterized in that the method comprises: a dehydration step in which the used superabsorbent polymer is dehydrated to form a dehydrated superabsorbent polymer; a particle attachment step in which particles of the superabsorbent polymer are attached to the dehydrated superabsorbent polymer to form a particle-attached superabsorbent polymer, and the particles absorb the moisture held by the dehydrated superabsorbent polymer; and a drying step in which the particle-attached superabsorbent polymer is dried to form the superabsorbent recycled polymer.

[0014] The effects of the invention

[0015] The method for manufacturing the superabsorbent recycled polymer disclosed herein can produce a superabsorbent recycled polymer that can inhibit particle adhesion to each other, allow each particle to dry efficiently, and has excellent whiteness. Detailed Implementation

[0016] Specifically, this disclosure relates to the following technical solutions.

[0017] [Technical Solution 1]

[0018] A method for manufacturing a superabsorbent polymer recycled from a used superabsorbent polymer, characterized in that the method comprises:

[0019] A dehydration step, in which the used superabsorbent polymer is dehydrated to form a dehydrated superabsorbent polymer;

[0020] The particle cluster attachment step involves attaching a cluster of superabsorbent polymer (SAP) particles to the dehydrated SAP to form an SAP with attached particle clusters, and then allowing the particle clusters to absorb the moisture held by the dehydrated SAP.

[0021] A drying step, in which the superabsorbent polymer with attached particle clusters is dried to form the superabsorbent recycled polymer.

[0022] The above manufacturing method includes a predetermined dehydration step, a particle cluster attachment step, and a drying step. In the particle cluster attachment step, the superabsorbent polymer (SAP) particles attach to the dehydrated SAP and absorb the moisture held by the dehydrated SAP. Furthermore, the surface area of ​​the SAP particles increases due to their attachment to the dehydrated SAP. Therefore, the above manufacturing method can suppress particle adhesion during the drying step and efficiently dry each particle, thus efficiently forming a superabsorbent recycled polymer.

[0023] It should be noted that in this specification, the inhibition of particle adhesion to each other is sometimes referred to as "adhesion inhibition," and the efficient drying of each particle is referred to as "efficiency drying."

[0024] Furthermore, because the aforementioned highly absorbent recycled polymer has particles attached to its surface, light is easily diffused and reflected, resulting in excellent whiteness that gives users a sense of cleanliness and reassurance.

[0025] [Technical Solution 2]

[0026] According to the method described in technical solution 1, the superabsorbent recycled polymer has a whiteness (W) of more than 80 and a yellowness (YI) of less than 20.

[0027] Superabsorbent polymers (SAPs) recycled from used SAPs are often colored in the same color as the liquids they absorbed during use. For example, when used SAPs absorb excrement, they are often colored in a tea-like hue.

[0028] Furthermore, under such circumstances, most of the superabsorbent polymers formed from used superabsorbent polymers retain their tea-colored hue.

[0029] In the above manufacturing method, the superabsorbent recycled polymer has a predetermined whiteness W and a predetermined yellowness YI, thus exhibiting excellent whiteness and enabling users to feel a sense of cleanliness.

[0030] [Technical Solution 3]

[0031] According to the method described in technical solution 1 or 2, in the dehydration step, the used superabsorbent polymer is contacted with salt, acid or alkali to form the dehydrated superabsorbent polymer.

[0032] In the above manufacturing method, during the dehydration step, a dehydrated superabsorbent polymer is formed by contact with salt, acid, or alkali. Therefore, the dehydrated superabsorbent polymer tends to have a high solids content, and during the particle attachment step, the superabsorbent polymer particles easily attach to the dehydrated superabsorbent polymer. Furthermore, the drying step exhibits excellent fixation inhibition and efficient drying performance.

[0033] [Technical Solution 4]

[0034] According to the method described in technical solution 3, in the dehydration step, the used superabsorbent polymer is brought into contact with the salt to form the dehydrated superabsorbent polymer.

[0035] In the above manufacturing method, during the dehydration step, the used superabsorbent polymer is contacted with a predetermined salt, and the used superabsorbent polymer is dehydrated by utilizing the osmotic pressure difference. Therefore, the above manufacturing method can form a dehydrated superabsorbent polymer with a high solids content. Furthermore, there is a tendency for the solids content of the dehydrated superabsorbent polymer to increase. As a result, during the particle attachment step, it is easy for superabsorbent polymer particles to attach to the dehydrated superabsorbent polymer, and the adhesion inhibition and efficient drying performance of the drying step are easily excellent.

[0036] [Technical Solution 5]

[0037] According to the method described in technical solution 3, the used superabsorbent polymer contains acid groups, and in the dehydration step, the used superabsorbent polymer is immersed in an aqueous solution containing the alkali to form the dehydrated superabsorbent polymer, wherein the alkali is an alkali metal hydroxide.

[0038] In the above manufacturing method, during the dehydration step, an aqueous solution containing an alkali metal hydroxide is used to dehydrate the used superabsorbent polymer. Consequently, a portion of the acid groups and their salts (especially calcium salts) present in the used superabsorbent polymer form alkali metal salts. Therefore, the superabsorbent recycled polymer, particularly the portion derived from the used superabsorbent polymer, exhibits excellent water absorption. Furthermore, there is a tendency for the solids content of the dehydrated superabsorbent polymer to increase. As a result, during the particle attachment step, it is easy for superabsorbent polymer particles to attach to the dehydrated superabsorbent polymer, and the fixation inhibition and efficient drying performance of the drying step are readily excellent.

[0039] [Technical Solution 6]

[0040] According to the method described in technical solution 3, the used superabsorbent polymer contains acid groups, and in the dehydration step, the acid has an acid dissociation constant (pK) greater than that of the acid groups. aSmall acid dissociation constant (pK) in water a Acids in water.

[0041] In the above manufacturing method, during the dehydration step, an aqueous solution containing a predetermined acid is used to form the dehydrated superabsorbent polymer. Therefore, the acid groups of the used superabsorbent polymer tend to change from their salt form to have free acid groups, resulting in a higher solids content in the dehydrated superabsorbent polymer. Consequently, during the particle attachment step, it is easier for superabsorbent polymer particles to attach to the dehydrated superabsorbent polymer, and the fixation inhibition and efficient drying performance of the drying step are easily improved.

[0042] [Technical Solution 7]

[0043] According to any one of technical solutions 1 to 6, in the dehydration step, the dehydrated superabsorbent polymer has a solids content of 10% by mass or more.

[0044] In the above manufacturing method, the superabsorbent polymer after dehydration has a predetermined solids content in the dehydration step. Therefore, in the particle cluster attachment step, it is easy for the superabsorbent polymer particles to attach to the dehydrated superabsorbent polymer, and the fixation inhibition and efficient drying performance in the drying step are easily excellent.

[0045] [Technical Solution 8]

[0046] According to any one of technical solutions 1 to 7, in the particle cluster attachment step, the superabsorbent polymer with attached particle clusters has a solids content of more than 30% by mass.

[0047] In the above manufacturing method, in the particle cluster attachment step, the superabsorbent polymer with attached particle clusters has a predetermined solids ratio, thus the drying step exhibits excellent fixation inhibition and efficient drying performance.

[0048] [Technical Solution 9]

[0049] According to any one of technical solutions 1 to 8, in the particle group attachment step, the particle group of the superabsorbent polymer has a solid content of 90% by mass or more.

[0050] In the above manufacturing method, in the particle cluster attachment step, the superabsorbent polymer particles have a predetermined solids ratio. Therefore, in the particle cluster attachment step, the superabsorbent polymer particles easily attach to the dehydrated superabsorbent polymer, and the fixation inhibition and efficient drying of the drying step are excellent.

[0051] [Technical Solution 10]

[0052] According to any one of technical solutions 1 to 9, in the particle cluster attachment step, the particle cluster of the superabsorbent polymer comprises more than 60% by mass of particles having a particle size of more than 45 μm and less than 300 μm.

[0053] In the above manufacturing method, during the particle cluster attachment step, the superabsorbent polymer particle cluster contains a predetermined amount of particles with a predetermined particle size. Therefore, during the particle cluster attachment step, the superabsorbent polymer particle cluster easily adheres to the dehydrated superabsorbent polymer, and the drying step exhibits excellent fixation inhibition and efficient drying performance. Furthermore, the superabsorbent recycled polymer has a particle cluster containing a predetermined amount of particles with a predetermined particle size on its surface, thus facilitating diffuse light reflection and resulting in excellent whiteness.

[0054] [Technical Solution 11]

[0055] According to any one of technical solutions 1 to 10, in the drying step, the superabsorbent polymer with attached particle clusters is dried at a drying temperature of 80°C to 150°C for 60 minutes to 180 minutes.

[0056] In the above manufacturing method, during the drying step, the superabsorbent polymer with attached particle clusters is dried under predetermined conditions, thereby suppressing coloring, discoloration, etc., of the superabsorbent recycled polymer.

[0057] [Technical Solution 12]

[0058] According to any one of technical solutions 1 to 11, the used superabsorbent polymer is contained in used sanitary products containing pulp fibers.

[0059] The dehydration step includes the following sub-steps:

[0060] A primary dehydration sub-step, in which the mixture containing the used superabsorbent polymer and the pulp fibers is dehydrated once to form a post-dehydrated superabsorbent polymer having a solids content of 2.0% to 9.0% by mass, and the post-dehydrated superabsorbent polymer is separated from the pulp fibers; and

[0061] The process includes a two-stage dehydration sub-step in which the superabsorbent polymer after the first dehydration is dehydrated in such a way that it forms a superabsorbent polymer after the second dehydration with a solid content of 10.0% to 40.0% by mass.

[0062] In the above manufacturing method, the dehydration step includes a first dehydration sub-step and a second dehydration sub-step. In the first dehydration sub-step, the superabsorbent polymer after the first dehydration is formed into a superabsorbent polymer with a predetermined solids ratio. Therefore, the mixture of the superabsorbent polymer after the first dehydration and pulp fibers can be easily separated from the constituent materials of the hygiene products. Furthermore, in the separated mixture, the superabsorbent polymer after the first dehydration is separated from the pulp fibers, and the superabsorbent polymer after the first dehydration is easily removed.

[0063] Next, in the two-stage dehydration sub-step, a second-stage dehydrated superabsorbent polymer (dehydrated superabsorbent polymer) with a predetermined solids content is formed from the superabsorbent polymer after the first stage of dehydration. Therefore, the moisture retained by the superabsorbent polymer after the first stage of dehydration can be removed, the superabsorbent polymer is cleaned, and in the particle attachment step, the superabsorbent polymer particles easily attach to the dehydrated superabsorbent polymer. Furthermore, the fixation inhibition and efficient drying performance of the drying step are easily excellent.

[0064] [Technical Solution 13]

[0065] A superabsorbent polymer regenerated from a used superabsorbent polymer, characterized in that,

[0066] The superabsorbent polymer (SAP) recycling polymer comprises a group of SAP particles recovered from the used SAP and SAP particles attached to the surface of the SAP.

[0067] The superabsorbent recycled polymer has a whiteness (W) of over 80 and a yellowness (YI) of less than 20.

[0068] The aforementioned superabsorbent recycled polymer has a group of superabsorbent polymer particles attached to its surface, and has a predetermined whiteness W and a yellowness YI of less than 20. Therefore, the superabsorbent recycled polymer has excellent whiteness, which can give users a sense of cleanliness and reassurance.

[0069] [Technical Solution 14]

[0070] According to the highly absorbent recycled polymer of technical solution 13, the highly absorbent recycled polymer has a water absorption ratio of more than 30 times (g / g).

[0071] The aforementioned highly absorbent recycled polymer has a predetermined water absorption ratio and excellent absorbency.

[0072] [Technical Solution 15]

[0073] According to technical solution 13 or 14, the above-mentioned highly absorbent recycled polymer has a water retention ratio of more than 20 times (g / g).

[0074] The aforementioned highly absorbent recycled polymer has a predetermined water retention ratio and excellent water retention properties.

[0075] The following describes in detail the method for manufacturing a superabsorbent polymer regenerated from a used superabsorbent polymer (hereinafter, sometimes referred to as "method for manufacturing a superabsorbent polymer") and the superabsorbent polymer regenerated from a used superabsorbent polymer (hereinafter, sometimes referred to as "superabsorbent polymer").

[0076] The method for manufacturing the superabsorbent recyclable polymer disclosed herein includes the following steps.

[0077] • The above-mentioned superabsorbent polymer is dehydrated to form a dehydrated superabsorbent polymer (hereinafter, sometimes referred to as the "dehydration step");

[0078] • The particle group of the superabsorbent polymer is attached to the superabsorbent polymer after dehydration to form a superabsorbent polymer with attached particle group, and the particle group absorbs the moisture held by the superabsorbent polymer after dehydration (hereinafter, sometimes referred to as the "particle group attachment step").

[0079] • The drying step (hereinafter sometimes referred to as the "drying step") involves drying the superabsorbent polymer with attached particle clusters to form the superabsorbent recycled polymer.

[0080] <Dehydration Steps>

[0081] In the above dehydration step, the used superabsorbent polymer is dehydrated to form a dehydrated superabsorbent polymer.

[0082] In this disclosure, there are no particular limitations on the use of superabsorbent polymers as long as they have absorbed liquids; for example, superabsorbent polymers contained in used sanitary products can be listed. Examples of such sanitary products include disposable diapers, absorbent pads, disposable shorts, sanitary napkins, panty liners, bed pads, and pet pads.

[0083] It should be noted that the aforementioned used hygiene products include hygiene products used by the user and which have absorbed the user's excrement, hygiene products used by the user but which have not absorbed the user's excrement, and unused and discarded hygiene products (e.g., hygiene products in which a superabsorbent polymer has absorbed the treatment liquid used for recycling the hygiene products).

[0084] As components of the aforementioned superabsorbent polymers, examples include those known in the technical field of hygiene products, such as starch-based, cellulose-based, and synthetic polymer-based superabsorbent polymers. Examples of starch-based or cellulose-based superabsorbent polymers include starch-acrylate (salt) graft copolymers, starch-acrylonitrile copolymers (saponified), and crosslinked sodium carboxymethyl cellulose. Examples of synthetic polymer-based superabsorbent polymers include polyacrylate-based, polysulfonate-based, maleic anhydride-based, polyacrylamide-based, polyvinyl alcohol-based, polyethylene oxide-based, polyaspartate-based, polyglutamate-based, polyalgate-based, starch-based, and cellulose-based superabsorbent polymers (SAP).

[0085] The aforementioned superabsorbent polymers can be classified into polymers with acid groups (e.g., carboxyl or sulfonyl groups) and polymers without such acid groups.

[0086] Methods known in the art for dehydrating used superabsorbent polymers include, for example, salts, acids, alkalis, hydrophilic organic solvents, temperature changes, and desiccant.

[0087] In the dehydration step, dehydration can be carried out in such a way that the dehydrated superabsorbent polymer has a predetermined solids content. Examples of the predetermined solids content include preferably 10.0% by mass or more, more preferably 20.0% by mass or more, and even more preferably 30.0% by mass or more. Furthermore, the predetermined solids content is preferably 50.0% by mass or less, and more preferably 40.0% by mass or less. Therefore, in the particle cluster adhesion step, it is easy for the superabsorbent polymer particles to adhere to the dehydrated superabsorbent polymer, and the adhesion inhibition and efficient drying performance in the drying step are readily excellent.

[0088] In this specification, the solids content is determined as described below.

[0089] (1) Determine the mass of the sample to be tested (particle clusters of superabsorbent polymers, superabsorbent polymers with attached particle clusters, superabsorbent recycled polymers, etc.) before drying: m1 (g).

[0090] (2) Dry the sample to be tested at 50℃ for 180 minutes and measure its mass after drying: m2 (g).

[0091] (3) Calculate the solids percentage (mass%) using the following formula:

[0092] Solid content (mass%) = 100 × m2 / m1.

[0093] In the above-described dehydration step, dehydration can be achieved by immersing the used superabsorbent polymer in the salt itself or in an aqueous solution (e.g., a saturated aqueous solution) containing the salt. Examples of salts include salts of bases and acids. Examples of bases include hydroxides of alkali metals (e.g., lithium, sodium, potassium) and hydroxides of alkaline earth metals (e.g., beryllium, magnesium, calcium, strontium, barium).

[0094] Examples of hydroxides of the aforementioned alkali metals include lithium hydroxide, sodium hydroxide, and potassium hydroxide, as well as any combination thereof. Examples of hydroxides of the aforementioned alkaline earth metals include beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, as well as any combination thereof.

[0095] When the aforementioned superabsorbent polymer has an acidic group (e.g., a carboxyl group or a sulfonyl group), the base is preferably an alkali metal hydroxide. This is from the viewpoint that it does not easily hinder the water absorption of the superabsorbent recycled polymer.

[0096] There are no particular limitations on the acids mentioned above; for example, inorganic acids and organic acids can be listed.

[0097] Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, bromic acid, and iodic acid. Examples of organic acids include those having an acid group, such as a carboxyl group or a sulfonyl group. It should be noted that organic acids having a sulfonyl group are called sulfonic acids, and organic acids having a carboxyl group but not a sulfonyl group are called carboxylic acids. From the viewpoint of protecting equipment, organic acids having a carboxyl group are preferred, and carboxylic acids are particularly preferred.

[0098] When the aforementioned organic acid has a carboxyl group, the organic acid can have one or more carboxyl groups per molecule, and preferably more than one carboxyl group. This is because, by doing so, the organic acid becomes more readily able to form chelates with divalent or higher metals contained in excrement, such as calcium, thus reducing the water absorption of highly absorbent recycled polymers and easily lowering the ash content of recycled pulp fibers manufactured from used hygiene products.

[0099] Examples of the aforementioned organic acids include citric acid, tartaric acid, malic acid, succinic acid, oxalic acid (the above are carboxylic acids with multiple carboxyl groups), gluconic acid (C6), valeric acid (C5), butyric acid (C4), propionic acid (C3), glycolic acid (C2), acetic acid (C2) such as glacial acetic acid, formic acid (C1), lactic acid (the above are carboxylic acids with one carboxyl group), methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid (the above are sulfonic acids), etc.

[0100] In the case where the aforementioned superabsorbent polymer has acid groups (e.g., carboxyl or sulfonyl groups), the acid may also be an acid with a dissociation constant (pK) greater than that of the acid groups in the superabsorbent polymer.a The acid dissociation constant (pK) in water is large. a Acids (in water). As a result, the acid groups of superabsorbent polymers readily form salts (e.g., alkali metal salts), and consequently, the water absorption and water retention ratios of the superabsorbent recycled polymers described later become excellent.

[0101] When the acid has multiple acid groups, for example, when the acid is a dicarboxylic acid or a tricarboxylic acid, the acid dissociation constant (pK) of the acid is preferred. a The smallest acid dissociation constant (pK) in water a The acid dissociation constant (pK) of the acid groups in the superabsorbent polymer is greater than that in water. a (in water), and when the superabsorbent polymer has multiple acid groups, the acid dissociation constant (pK) of the above-mentioned acid is preferred. a The smallest acid dissociation constant (pK) in water a (in water) greater than the largest acid dissociation constant (pK) among various acid groups of superabsorbent polymers. a (in water). This is based on the view that the acid groups of highly absorbent polymers readily form salts (such as alkali metal salts).

[0102] In this specification, the acid dissociation constant (pK) is... a (In water) the values ​​recorded in the Electrochemical Handbook edited by the Electrochemical Association can be used.

[0103] According to the electrochemistry handbook, the acid dissociation constants (pK) of major compounds are... a (In water, at 25℃) as described below.

[0104] [Organic acids]

[0105] Tartaric acid: 2.99 (pK) a1 ), 4.44 (pK) a2 )

[0106] • Malic acid: 3.24 (pK) a1 ), 4.71 (pK) a2 )

[0107] Citric acid: 2.87 (pK) a1 ), 4.35 (pK) a2 ), 5.69 (pK) a3 )

[0108] [Inorganic acids]

[0109] Sulfuric acid: 1.99 (pK) a2 )

[0110] Acid dissociation constants (pK) of acids not listed in the Electrochemistry Handbook aThe acid dissociation constant (pK) in water can be determined by measurement. a Equipment used in water, for example, the T3 compound physical property evaluation and analysis system manufactured by Sirius Corporation.

[0111] Regarding carbonic acid as the aforementioned acid, it is preferred because it is not easily retained in aqueous solutions or can be easily removed by heating or the like.

[0112] In addition, acids other than carbonic acid, such as superabsorbent polymers in a wet state and superabsorbent polymers in a dry state, can impart antibacterial properties to superabsorbent polymers in a wet state and superabsorbent polymers in a dry state when the superabsorbent polymers are in an acidic pH condition.

[0113] Examples of the aforementioned salts include lithium carbonate, sodium carbonate, potassium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, lithium chloride, sodium chloride, and potassium chloride.

[0114] The salt is preferably used either as salt itself or in an aqueous solution, preferably as salt itself. Furthermore, the aqueous solution is preferably a saturated aqueous solution. Therefore, the dehydrated superabsorbent polymer readily achieves the predetermined solids content.

[0115] When the aforementioned superabsorbent polymer contains acid groups (e.g., carboxyl or sulfonyl groups), dehydration can be achieved by immersing the used superabsorbent polymer in an aqueous solution containing acid during the dehydration step. The acid is preferably an acid with a dissociation constant (pK) greater than that of the acid groups in the superabsorbent polymer. a Small acid dissociation constant (pK) in water a The acid (hereinafter, sometimes referred to as "pre-defined strong acid") in water. This is from the point of view of the efficiency of dehydration of the superabsorbent polymer used.

[0116] When the acid has multiple acid groups, for example, when the acid is a dicarboxylic acid or a tricarboxylic acid, the acid dissociation constant (pK) of the acid is preferred. a The largest acid dissociation constant (pK) in water a The acid dissociation constant (pK) of the acid groups in the superabsorbent polymer is smaller than that in water. a (in water), and when the superabsorbent polymer has multiple acid groups, the acid dissociation constant (pK) of the above-mentioned acid is preferred. a The largest acid dissociation constant (pK) in water a The acid dissociation constant (pK) of the superabsorbent polymer (in water) is smaller than that of the smallest acid group among various acid groups. a (in water). This is from the perspective of the efficiency of dehydration of highly absorbent polymers.

[0117] As the aforementioned strong acids, examples of acids described in the salt section include sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid.

[0118] The aforementioned aqueous solution containing acid preferably has a predetermined pH, which is preferably 4.5 or less, more preferably 4.0 or less, even more preferably 3.5 or less, and even more preferably 3.0 or less. Therefore, the dehydrated superabsorbent polymer readily possesses the aforementioned predetermined solids content.

[0119] Furthermore, the predetermined pH is preferably 0.5 or higher, and more preferably 1.0 or higher. If the predetermined pH is too low, the acid groups of the superabsorbent polymer are prone to change from a salt (e.g., sodium salt) state to a free acid state, and sometimes the water absorption of the superabsorbent recycled polymer decreases.

[0120] It should be noted that in this instruction manual, pH refers to the value at 25°C. Furthermore, pH can be measured, for example, using the twin pH meter AS-711 manufactured by Horiba Corporation.

[0121] In the dehydration step, for example, the used superabsorbent polymer is placed in an aqueous solution containing acid, and stirred for about 5 to 60 minutes, depending on the temperature, thereby dehydrating the superabsorbent polymer and forming a dehydrated superabsorbent polymer.

[0122] During the dehydration step, the acid groups of superabsorbent polymers with acid groups tend to change from a salt (e.g., sodium salt) state to a free acid state, thus the superabsorbent polymer tends to have reduced water absorption.

[0123] If a superabsorbent polymer that has absorbed water is placed in an aqueous solution containing acid, the negatively charged hydrophilic groups (e.g., -COO) will... - ) Positively charged hydrogen ions (H + Neutralization (e.g., -COOH) weakens the ionic repulsion of the hydrophilic groups, reduces water absorption, and dehydrates the superabsorbent polymer.

[0124] There are no particular restrictions on the temperature of the acid-containing aqueous solution in the dehydration step; for example, it can be room temperature (25°C) or a temperature higher than room temperature.

[0125] Specifically, the temperature of the acid-containing aqueous solution in the dehydration step is preferably higher than room temperature, more preferably 60°C to 100°C, further preferably 70°C to 95°C, and even more preferably 80°C to 90°C. Therefore, the acid in the acid-containing aqueous solution can easily kill bacteria originating from excrement and the like.

[0126] When the superabsorbent polymer has acid groups (e.g., carboxyl or sulfonyl groups), in the dehydration step, it is possible to dehydrate it by immersing the used superabsorbent polymer in an aqueous solution containing an alkali.

[0127] Examples of the aforementioned bases include hydroxides of alkali metals (e.g., lithium, sodium, potassium) and alkaline earth metals (e.g., beryllium, magnesium, potassium), as described in the "salt" section, with hydroxides of alkali metals (e.g., lithium, sodium, potassium) being preferred. Thus, the acid groups of the superabsorbent polymer, particularly the portion derived from the used superabsorbent polymer, form salts, and the water absorption of the portion derived from the used superabsorbent polymer, and consequently the superabsorbent polymer itself, readily becomes excellent.

[0128] The aforementioned aqueous solution containing alkali preferably has a predetermined pH, which is preferably 8.0 or higher, more preferably 9.0 or higher, and even more preferably 10.0 or higher. Furthermore, the predetermined pH is preferably 14.0 or lower, and more preferably 13.0 or lower. Therefore, the dehydrated superabsorbent polymer readily possesses the aforementioned predetermined solids content.

[0129] It should be noted that the method for pH measurement is as described above.

[0130] As the aforementioned hydrophilic organic solvent, it is preferable to have miscibility with water, such as alcohol solvents (e.g., methanol, ethanol, propanol and its isomers, butanol and its isomers), ketone solvents (e.g., acetone, methyl ethyl ketone), nitrile solvents (e.g., acetonitrile), etc.

[0131] When the used superabsorbent polymer is present in the form of a mixture with pulp fibers, such as when the used superabsorbent polymer is contained in used sanitary products, the above dehydration step can include the following sub-steps.

[0132] • A first dehydration sub-step, in which the mixture containing the above-mentioned used superabsorbent polymer and the above-mentioned pulp fiber is dehydrated once in such a way that the above-mentioned used superabsorbent polymer is formed into a first-dehydrated superabsorbent polymer with a predetermined solids ratio, and the predetermined first-dehydrated superabsorbent polymer is separated from the pulp fiber.

[0133] • A second dehydration sub-step in which the superabsorbent polymer after the first dehydration is dehydrated in such a way that it forms a superabsorbent polymer after the second dehydration with a predetermined solids ratio.

[0134] Therefore, in the first dehydration step, the pulp fibers are easily separated from the superabsorbent polymer after the first dehydration, and the superabsorbent polymer after the first dehydration is easily separated from the pulp fibers. In addition, in the subsequent particle attachment step, the superabsorbent polymer particles easily attach to the superabsorbent polymer after dehydration, and the fixation inhibition and efficient drying performance of the drying step are excellent.

[0135] The predetermined solids content of the superabsorbent polymer after one dehydration is preferably 2.0% to 9.0% by mass, more preferably 3.0% to 9.0% by mass, and even more preferably 3.0% to 9.0% by mass. The predetermined solids content of the superabsorbent polymer after two dehydrations is preferably 10.0% to 40.0% by mass, more preferably 11.0% to 35.0% by mass, and even more preferably 12.0% to 30.0% by mass.

[0136] The solids content of the superabsorbent polymer after one dehydration and the solids content of the superabsorbent polymer after two dehydrations (the superabsorbent polymer after dehydration) can be adjusted by adjusting the salt, acid, alkali, hydrophilic organic solvent, temperature change, type of absorbent, and immersion time.

[0137] <Particle Cluster Adhesion Steps>

[0138] In the particle cluster attachment step, the particles of the superabsorbent polymer are attached to the dehydrated superabsorbent polymer to form a superabsorbent polymer with attached particles, and the particles absorb the moisture held by the dehydrated superabsorbent polymer.

[0139] The composition of the particle group of the above-mentioned superabsorbent polymer is not particularly limited. It can have the same composition as the above-mentioned superabsorbent polymer (used superabsorbent polymer), and can have the same or different composition as the above-mentioned superabsorbent polymer (used superabsorbent polymer).

[0140] The specific composition of the particle group of the aforementioned superabsorbent polymer is as described in the "Dehydration Step" section, and therefore will not be described here.

[0141] The aforementioned superabsorbent polymer particle group is preferably not used. This is from the viewpoint of the whiteness of the superabsorbent recycled polymer.

[0142] In addition, the particle group of the aforementioned superabsorbent polymer can be the micro powder generated during the manufacture of superabsorbent polymer or the micro powder recovered during the manufacture of hygiene products.

[0143] Examples of micropowder produced during the manufacture of the aforementioned superabsorbent polymers include micropowder produced during the crushing of bulk polymers, micropowder produced during the granulation of emulsion polymers, solution polymers, and reverse suspension polymers.

[0144] As for the fine powder recovered during the manufacture of the aforementioned hygiene products, examples include fine powder recovered using a dust collector.

[0145] The superabsorbent polymer (SAP) particle clusters preferably have a solids content of 90.0% by mass or more, and more preferably 95.0% by mass or more. Therefore, in the particle cluster attachment step, the SAP particle clusters adhere to the dehydrated SAP, readily absorbing its moisture, and exhibiting excellent fixation inhibition and efficient drying in the drying step. It should be noted that the upper limit for the solids content of the SAP particle clusters is 100.0% by mass.

[0146] The method for determining the solids content is as described above.

[0147] The aforementioned superabsorbent polymer particle cluster preferably has a particle size smaller than that of the dehydrated superabsorbent polymer, more preferably 300 μm or less, even more preferably 200 μm or less, and even more preferably 150 μm or less. Furthermore, the aforementioned superabsorbent polymer particle cluster preferably has a particle size greater than 1 μm, more preferably greater than 30 μm, even more preferably greater than 45 μm, and even more preferably greater than 50 μm.

[0148] It should be noted that the particle size of the dehydrated superabsorbent polymer mentioned above refers to the particle size after the dehydrated superabsorbent polymer is dried at 50°C for 180 minutes.

[0149] Furthermore, the aforementioned superabsorbent polymer particle group contains particles with a particle size within the aforementioned upper and lower limits at a mass ratio preferably of 60% or more by mass, more preferably 70% or more by mass, further preferably 80% or more by mass, and even more preferably 90% or more by mass. Additionally, the aforementioned superabsorbent polymer particle group can contain particles with a particle size within the aforementioned upper and lower limits at a mass ratio of 100% or less by mass.

[0150] Therefore, the aforementioned superabsorbent polymer particle clusters exhibit excellent operability. Furthermore, in the particle cluster attachment step, the superabsorbent polymer particles readily adhere to the dehydrated superabsorbent polymer, and the fixation inhibition and efficient drying performance in the drying step are also excellent. Additionally, the aforementioned superabsorbent recycled polymer exhibits good diffuse light reflection and excellent whiteness.

[0151] In this specification, the mass ratio of the particle group of the superabsorbent polymer and the particles of the superabsorbent recycled polymer with a predetermined particle size can be determined according to ISO 17190-3 using a sieve with the nominal mesh size specified in JIS Z 8801-1, as follows.

[0152] (1) Prepare a sieve with a nominal mesh size (hereinafter referred to as "lower limit sieve") having a lower limit value of the particle size of the sample to be measured and a sieve with a nominal mesh size (hereinafter referred to as "upper limit sieve") having an upper limit value of the particle size of the sample to be measured.

[0153] For example, when determining the amount of particles with a diameter of 45 μm to 300 μm in a sample, a lower limit sieve with a nominal mesh size of 45 μm and an upper limit sieve with a nominal mesh size of 300 μm are prepared.

[0154] (2) Precisely determine the mass of the sample to be measured: m3 (g), for example 100g.

[0155] (3) Place the sample to be measured on the upper limit sieve of the device equipped with the lower limit sieve below the upper limit sieve, sieve for 10 minutes, and measure the mass of the residue that passes through the upper limit sieve and remains on the lower limit sieve: m4 (g).

[0156] (5) Calculate the mass ratio of particles with a predetermined particle size using the following formula: R (mass%):

[0157] R (mass%) = 100 × m4 / m3.

[0158] In the particle attachment step, the superabsorbent polymer particles are preferably mixed at a ratio of 50 to 150 parts by weight, more preferably 60 to 120 parts by weight, and even more preferably 70 to 100 parts by weight, relative to 100 parts by weight of the dehydrated superabsorbent polymer. This results in superior adhesion inhibition and efficient drying in the subsequent drying step. Furthermore, the whiteness of the aforementioned superabsorbent recycled polymer is also tends to be excellent.

[0159] The aforementioned superabsorbent polymer with attached particle clusters preferably has a solids content of 30.0% by mass or more, more preferably 35.0% by mass or more, and even more preferably 40.0% by mass or more. Furthermore, the aforementioned superabsorbent polymer with attached particle clusters preferably has a solids content of 90.0% by mass or less. Therefore, the subsequent drying step exhibits excellent adhesion inhibition and efficient drying performance.

[0160] <Drying Steps>

[0161] In the drying step, the superabsorbent polymer with attached particle clusters is dried to form a superabsorbent recycled polymer.

[0162] In the drying step, the superabsorbent polymer with attached particle clusters is dried at a drying temperature of, for example, 80°C to 150°C, preferably 100°C to 120°C. This allows for the easy formation of a superabsorbent recycled polymer with suppressed coloring and excellent water absorption in a short drying time. It should be noted that if the drying temperature is increased, the acid groups in the superabsorbent recycled polymer undergo dehydration condensation, reducing its water absorption and sometimes resulting in a tea-colored hue.

[0163] In the drying step, the superabsorbent polymer with attached particle clusters can be dried for a period of time, for example, 30 to 300 minutes, preferably 60 to 180 minutes. If the drying time is short, the solids content of the resulting superabsorbent recycled polymer may be low, depending on the drying temperature. If the drying time is long, the acid groups of the superabsorbent recycled polymer may undergo dehydration condensation, reducing its water absorption.

[0164] The above drying steps can also be carried out under reduced pressure, for example, above 0.1 kPa and below 100 kPa.

[0165] The aforementioned superabsorbent recyclable polymer preferably has a particle size of more than 250 μm, more preferably more than 300 μm, and even more preferably more than 350 μm. Furthermore, the aforementioned superabsorbent polymer with attached particle clusters preferably has a particle size of 800 μm or less, more preferably 750 μm or less, and even more preferably 700 μm or less.

[0166] Furthermore, the aforementioned superabsorbent recycled polymer contains particles with particle sizes within the aforementioned upper and lower limits at a mass ratio preferably of 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and even more preferably 90% by mass or more. Additionally, the aforementioned superabsorbent recycled polymer can contain particles with particle sizes within the aforementioned upper and lower limits at a mass ratio of 100% by mass or less. Therefore, the aforementioned superabsorbent recycled polymer can be easily reused in various applications using superabsorbent polymers, such as hygiene products.

[0167] The aforementioned superabsorbent recycled polymer preferably has a solids content of 90.0% by mass or more, and more preferably 95.0% by mass or more. Furthermore, the aforementioned superabsorbent recycled polymer preferably has a solids content of 100.0% by mass or less. Therefore, the superabsorbent recycled polymer is less prone to solidification and readily exhibits excellent water absorption.

[0168] It should be noted that the method for determining the solids content is as described above.

[0169] The superabsorbent recycled polymer has a whiteness (W) of preferably 80 or higher, more preferably 82 or higher, and even more preferably 84 or higher. Therefore, the superabsorbent recycled polymer has excellent whiteness, which allows the user to feel a sense of cleanliness.

[0170] In addition, the superabsorbent recycled polymer has a yellowness (YI) of preferably 20 or less, more preferably 19 or less, and even more preferably 18 or less. As a result, the superabsorbent recycled polymer has excellent whiteness, which can give users a sense of cleanliness.

[0171] In this specification, whiteness (W) and yellowness (YI) are measured as follows.

[0172] (1) In a constant temperature and humidity room with a temperature of 20±5℃ and a humidity of 65±5%RH, prepare a cross-illumination photometer Z-300A manufactured by Nippon Denshoku Kogyo Co., Ltd.

[0173] (2) Spread 4.5g of highly absorbent recycled polymer evenly over the glass window (40mm in diameter) of the colorimeter's sample stage.

[0174] (3) Place a black plate (size: 80mm×80mm, mass: 280g) attached to the colorimeter on the superabsorbent recycled polymer and apply a load to the superabsorbent recycled polymer.

[0175] (4) Select mode: reflection, transmission. A colorimeter with a window diameter of 30 mm was used to measure the whiteness (W) and yellowness (YI) of the superabsorbent recycled polymer.

[0176] The aforementioned superabsorbent recycled polymer preferably has an absorbency ratio of 30 times (g / g) or more, more preferably 40 times (g / g) or more, and 45 times (g / g) or more. The aforementioned superabsorbent recycled polymer preferably has an absorbency ratio of 80 times (g / g) or less, and more preferably 70 times (g / g) or less. This is from the viewpoint of the superabsorbent recycled polymer's absorbency and shape retention.

[0177] In this instruction manual, the water absorption ratio is determined as follows.

[0178] (1) Prepare a bag (200mm×200mm) made of nylon mesh (250 mesh nylon mesh manufactured by NBC Meshtec Co., Ltd.) and determine its mass: N0 (g).

[0179] (2) Place about 5g of the sample in a nylon mesh bag and determine the mass including the nylon mesh bag: A0 (g).

[0180] (3) Put 1L of physiological saline into a beaker and soak the nylon mesh bag containing the sample in it. Let it stand for 3 minutes.

[0181] (4) Lift the nylon mesh bag and let it stand on the water control net for 3 minutes to drain the water.

[0182] (5) Determine the mass of the nylon mesh bag containing the sample after water removal: A (g).

[0183] (6) Prepare another set of nylon mesh bags cut to the same size, without putting in the sample, and perform (3) and (4) in the same way. Measure the mass of the nylon mesh bags after water control: N (g).

[0184] (7) Calculate the water absorption ratio (times) using the following formula:

[0185] Water absorption rate (times) = (AN-(A0-N0)) / (A0-N0).

[0186] (8) Perform the measurement 10 times and average the 10 measurements.

[0187] The aforementioned superabsorbent recycled polymer preferably has a water retention ratio of 20 times (g / g) or more, more preferably 25 times (g / g) or more, and 30 times (g / g) or more. The aforementioned superabsorbent recycled polymer preferably has a water retention ratio of 50 times (g / g) or less, and more preferably 45 times (g / g) or less. This is from the viewpoint of the water retention and shape retention properties of the superabsorbent recycled polymer.

[0188] In this instruction manual, the water retention ratio is determined as follows.

[0189] (1) For the sample after the above water absorption ratio was determined, the mass B (g) after dehydration at 150g for 90 seconds was determined using a centrifuge (domestic centrifuge manufactured by China Centrifuge Co., Ltd., model H130, speed 850rpm = 150G).

[0190] Water retention ratio=(BN-(A0-N0)) / (A0-N0)

[0191] The measurement was performed 10 times, and the 10 measurements were averaged.

[0192] The superabsorbent recycled polymer manufactured by the manufacturing method of this disclosure can be used without limitation in fields that use superabsorbent polymers, such as the field of hygiene products.

[0193] There are no particular restrictions on the aforementioned hygiene products; for example, disposable diapers, disposable shorts, sanitary napkins, panty liners, absorbent pads, bed pads, and pet pads can be listed.

[0194] Example

[0195] The following examples illustrate this disclosure, but this disclosure is not limited to these examples.

[0196] [Example 1]

[0197] <Dehydration Steps>

[0198] The mixture of superabsorbent polymer No. 1 (polyacrylate-based SAP) and pulp fiber was extracted from the absorbent core of a used disposable diaper. In this mixture, the superabsorbent polymer No. 1 and pulp fiber were integrated, making them difficult to separate. Furthermore, both the superabsorbent polymer No. 1 and pulp fiber were colored a tea-toned shade.

[0199] The above mixture was immersed in a dilute sulfuric acid aqueous solution at pH 2.0 for 10 minutes to dehydrate the superabsorbent polymer, forming a superabsorbent polymer after primary dehydration. The superabsorbent polymer No. 1 after primary dehydration and the pulp fibers were easily separated. Next, the superabsorbent polymer No. 1 after primary dehydration and the pulp fibers were separated.

[0200] The superabsorbent polymer No.1 after one dehydration was recovered, and its solids content was determined according to the method described in this specification, with a result of 15% by mass.

[0201] The superabsorbent polymer No. 1 after the first dehydration was kept in a container filled with sodium sulfate particles for 30 minutes. Sodium sulfate that had absorbed liquid adhered to the surface of the superabsorbent polymer No. 1 after the first dehydration. The sodium sulfate adhering to the surface of the superabsorbent polymer No. 1 after the first dehydration was removed using a sieve, resulting in superabsorbent polymer No. 1 after the second dehydration. The superabsorbent polymer No. 1 after the second dehydration was recovered, and its solids content was determined according to the method described in this specification, resulting in 20% by mass.

[0202] The superabsorbent polymer No.1, after two dehydrations, is colored in a light tea color.

[0203] <Particle Cluster Adhesion Steps>

[0204] 100g of the twice-dehydrated superabsorbent polymer No.1 was added to superabsorbent polymer particle group No.1 (polyacrylate-based SAP, particle size: 100% by mass > 50μm and < 150μm, solids content: 98% by mass) to form superabsorbent polymer No.1 with attached particle group. The solids content of superabsorbent polymer No.1 with attached particle group was 30% by mass.

[0205] <Drying Steps>

[0206] The superabsorbent polymer No. 1 with attached particle clusters was dried at 100°C for 60 minutes to obtain superabsorbent recycled polymer No. 1. The particles of superabsorbent recycled polymer No. 1 were not adhered to each other.

[0207] The whiteness (W), yellowness (YI), water absorption ratio, and water retention ratio of the superabsorbent recycled polymer No.1 are shown in Table 1.

[0208] [Comparative Example 1]

[0209] The superabsorbent polymer particles No. 1 were not attached to the superabsorbent polymer No. 1 after two dehydrations. Otherwise, superabsorbent recycled polymer blocks were obtained in the same manner as in Example 1. The superabsorbent recycled polymer blocks were formed by the particles adhering to each other during drying. The superabsorbent recycled polymer blocks were pulverized using a known pulverizer to obtain superabsorbent recycled polymer No. 2 with the same particle size as superabsorbent recycled polymer No. 1.

[0210] The whiteness (W), yellowness (YI), water absorption ratio, and water retention ratio of the superabsorbent recycled polymer No.2 are shown in Table 1.

[0211] [Table 1]

[0212] Superabsorbent recycled polymer No. No.1 No.2 Whiteness (W) 81 75 Yellowness (YI) 19 24 Water absorption ratio (times (g / g)) 47 38 Water retention ratio (times (g / g)) 28 20

Claims

1. A method of producing a superabsorbent recycled polymer from a used superabsorbent polymer, characterized by, The method includes: a dehydration step in which the used superabsorbent polymer is dehydrated to form a dehydrated superabsorbent polymer; a particle group attaching step in which a particle group of a superabsorbent polymer is attached to the dehydrated superabsorbent polymer to form a superabsorbent recycled polymer to which the particle group is attached, and the particle group absorbs moisture held by the dehydrated superabsorbent polymer; and a drying step in which the superabsorbent recycled polymer to which the particle group is attached is dried. In the dehydration step, the dehydrated superabsorbent polymer has a solid content of 10% by mass or more, In the particle group attaching step, the superabsorbent recycled polymer to which the particle group is attached has a solid content of 30% by mass or more.

2. The method according to claim 1, wherein The superabsorbent recycled polymer has a white degree (W) of 80 or more and a yellow index (YI) of 20 or less.

3. The method according to claim 1 or 2, wherein In the dehydration step, the dehydrated superabsorbent polymer is formed by bringing the used superabsorbent polymer into contact with a salt, an acid, or a base.

4. The method according to claim 3, wherein In the dehydration step, the dehydrated superabsorbent polymer is formed by bringing the used superabsorbent polymer into contact with the salt.

5. The method according to claim 3, wherein The used superabsorbent polymer contains an acid group, and in the dehydration step, the dehydrated superabsorbent polymer is formed by immersing the used superabsorbent polymer in an aqueous solution containing the base, the base being a hydroxide of an alkali metal.

6. The method according to claim 3, wherein The used superabsorbent polymer contains acid groups, and in the dehydration step, the acid has an acid dissociation constant (pK) greater than that of the acid groups. a The small acid dissociation constant (pK) in water a Acids in water.

7. The method according to claim 1 or 2, wherein In the particle group attaching step, the particle group of the superabsorbent polymer has a solid content of 90% by mass or more.

8. The method according to claim 1 or 2, wherein In the particle group attaching step, the particle group of the superabsorbent polymer contains 60% by mass or more of particles having a particle size of more than 45 μm and 300 μm or less.

9. The method according to claim 1 or 2, wherein In the drying step, the superabsorbent recycled polymer to which the particle group is attached is dried at a drying temperature of 80°C to 150°C for 60 minutes to 180 minutes.

10. The method according to claim 1 or 2, wherein The used superabsorbent polymer is included in a used sanitary product containing pulp fibers, The dehydration step includes the following substeps: 1st dehydration substep in which the mixture containing the used superabsorbent polymer and the pulp fiber is once dehydrated in a manner that the used superabsorbent polymer forms a once-dehydrated superabsorbent polymer having a solid content of 2.0 to 9.0 mass%, and the once-dehydrated superabsorbent polymer is separated from the pulp fiber; and 2nd dehydration substep in which the once-dehydrated superabsorbent polymer is dehydrated in a manner that it forms a twice-dehydrated superabsorbent polymer having a solid content of 10.0 to 40.0 mass%.

11. A superabsorbent recycled polymer derived from a used superabsorbent polymer having absorbed excrement, characterized in that, the superabsorbent recycled polymer is produced by the method according to claim 1, the superabsorbent recycled polymer has a particle group of superabsorbent polymers derived from the used superabsorbent polymer and having absorbed the excrement, and superabsorbent polymers bound to the surface of the superabsorbent polymers, the superabsorbent recycled polymer has a white color degree (W) of 80 or more and a yellow color degree (YI) of 20 or less.

12. The superabsorbent recycled polymer according to claim 11, wherein, the superabsorbent recycled polymer has a water absorption capacity of 30 times (g / g) or more.

13. The superabsorbent recycled polymer according to claim 11 or 12, wherein, the superabsorbent recycled polymer has a water retention capacity of 20 times (g / g) or more.