JP2021075819A - Composition for paper - Google Patents

Abstract

To provide a composition for paper with high viscosity, and to provide recycled paper with high strength and without defects.SOLUTION: A composition for paper of the present invention is the composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article, and the water-absorbent resin is reduced in molecular weight. In the composition for paper of the present invention, it is preferable that 50% or more of the ash content is sodium. Recycled paper of the present invention is recycled paper containing pulp recovered from absorbent articles and a water-absorbent resin, and the water-absorbent resin is reduced in molecular weight.SELECTED DRAWING: Figure 2

Description

The present invention relates to a composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article, and a method for producing the same.

Conventionally, techniques for recycling used absorbent articles have been known. For example, Patent Document 1 discloses a method for recycling used disposable diapers, which can make the super absorbent polymer contained in the disposable diapers into fine particles without using chemicals when recycling the used disposable diapers. The recycling method is to break the used paper diaper, decompose it into pulp components and non-pulp components, wash the mixture of the decomposed pulp components and non-pulp components such as vinyl with water, and then remove from the mixture. The pulp component is separated and recovered, and the highly water-absorbent polymer that is mixed with the pulp component from which the non-pulp component has been removed and is water-absorbent and expanded is finely divided into fine particles of 10 μm or less without breaking the fibers of the pulp component by a crusher. It broke into a shape to form a suspension containing a finely divided highly water-absorbent polymer, a pulp component, and water, and the suspension was dehydrated to remove the highly water-absorbent polymer from the pulp component together with water. It recovers pulp components.

Further, in Patent Document 2, used sanitary products are used by applying a physical force to the used sanitary products in an aqueous solution containing polyvalent metal ions or an acidic aqueous solution having a pH of 2.5 or less. The process of decomposing finished sanitary goods into pulp fibers and other materials, the process of separating pulp fibers from the mixture of pulp fibers and other materials produced in the decomposition process, and the process of separating the separated pulp fibers with a pH of 2.5 or less. A method including a step of treating with an ozone-containing aqueous solution is described.

Further, Patent Document 3 describes a method for recovering pulp fibers from used sanitary products containing pulp fibers and a highly water-absorbent polymer to produce recycled pulp that can be reused for sanitary products, and the method is used. The ozone treatment step includes an ozone treatment step of immersing the recycled sanitary ware or pulp fiber in an ozone-containing aqueous solution to decompose the highly water-absorbent polymer in the used sanitary ware or attached to the pulp fiber, and prior to the ozone treatment step. A method characterized by treating used sanitary goods or pulp fibers with a cationic antibacterial agent at the same time or after an ozone treatment step is described.

Further, Patent Document 4 describes a step of decomposing a superabsorbent polymer with ozone water to reduce the molecular weight and solubilizing it, and a step of dissolving the superabsorbent polymer in ozone water and discharging the superabsorbent polymer together with ozone water. Including. The method for recovering the pulp fiber of the present invention includes a step of decomposing the superabsorbent polymer with ozone water to reduce the molecular weight and solubilizing the superabsorbent polymer, and the superabsorbent polymer dissolves in ozone water and discharges the superabsorbent polymer together with ozone water. A method for treating a superabsorbent polymer including a step of recovering the pulp fiber which is a residue of sanitary goods is described.

Further, Patent Document 5 describes a method for decomposing a water-absorbent polymer using an acid or an alkali, or an acid or an alkali and an oxide.

Japanese Unexamined Patent Publication No. 2010-59586 Japanese Unexamined Patent Publication No. 2016-881 JP-A-2017-128840 Japanese Unexamined Patent Publication No. 2017-100133 Japanese Unexamined Patent Publication No. 9-249711

In Patent Document 1, a highly water-absorbent polymer that has expanded by absorbing water is broken into fine particles of 10 μm or less without breaking the fibers of the pulp component by a crusher, and the fine water-absorbent polymer and the pulp component are obtained. A suspension containing water is formed, and the suspension is dehydrated to remove the highly water-absorbent polymer from the pulp component together with water to recover the pulp component. In Patent Documents 2 to 4, the highly water-absorbent polymer adhering to the pulp fibers is removed by immersing the recovered pulp fibers in an ozone-containing aqueous solution. Therefore, the pulp fibers recovered by the methods of Patent Documents 1 to 4 do not contain a highly water-absorbent polymer, and the adhesion between the pulp fibers is low and the viscosity is low.

By the way, the pulp recovered from the absorbent article can be used for producing paper such as recycled paper. Conventionally, in the case of producing paper, a paper strength enhancer is added in order to enhance the adhesiveness between the pulps contained in the produced paper and to increase the strength of the paper. As described above, the pulp fibers recovered by the methods of Patent Documents 1 to 4 have low adhesion between the pulp fibers and low viscosity. Therefore, in order to produce recycled paper using the pulp fibers, conventional methods have been used. As such, it is necessary to add a paper strength enhancer.

Further, Patent Documents 1 and 5 do not particularly describe the production of recycled paper using pulp recovered from a used absorbent article.
The present inventor has found that a highly strong recycled paper can be obtained from a composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article, and has reached the present invention.

An object of the present invention is to provide a composition for paper that can eliminate the above-mentioned drawbacks of the prior art.

The present invention provides a composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article, wherein the water-absorbent resin has a low molecular weight. It has been achieved.
The present invention is a composition for paper containing pulp recovered from an absorbent article and a water-absorbent resin, and the water-absorbent resin has a mesh size of 500 μm in a wet state in which 200 times the mass ratio of water is added. The above object is achieved by providing a composition for paper that passes through a sieve.

The present invention has achieved the above object by providing recycled paper containing pulp and water-absorbent resin recovered from an absorbent article, wherein the water-absorbent resin has a low molecular weight. is there.

The present invention has achieved the above object by providing an absorbent article containing one or more selected from the group consisting of the above-mentioned composition for paper and the above-mentioned recycled paper.

The present invention is a method for producing a composition for paper containing pulp recovered from an absorbent article and a water-absorbent resin, wherein the absorbent article is after a freezing step of freezing water in the absorbent article and the freezing step. A crushing step of crushing the absorbent article by giving an impact to the pulp, a separation step of separating the absorbent material containing the pulp and the water-absorbent resin and a sheet piece derived from the absorbent article after the crushing step, and The above-mentioned object is achieved by providing a method for producing a composition for paper, which comprises a step of lowering the molecular weight of the water-absorbent resin contained in the absorbent material after the separation step. is there.

The present invention is a method for reducing the molecular weight of a water-absorbent resin, which comprises a water-containing step of impregnating the water-absorbent resin with water, a resin freezing step of freezing the water-absorbent resin after the water-containing step, and the freezing step. Later, the above object was achieved by providing a method for reducing the molecular weight of the water-absorbent resin, which comprises a resin crushing step of crushing the water-absorbent resin.

The present invention is an apparatus for reducing the molecular weight of a water-absorbent resin, in which a water-containing portion containing water in the water-absorbent resin, a resin freezing portion for freezing the water-absorbent resin, and the water-absorbent resin are pulverized. The above object has been achieved by providing a low molecular weight processing apparatus for a water-absorbent resin provided with a resin crushing portion.

According to the paper composition of the present invention and the method for producing the same, it is possible to provide a highly viscous paper composition.
Further, according to the recycled paper of the present invention, it is possible to provide a recycled paper having high strength and no defects.
Further, according to the method for reducing the molecular weight of the water-absorbent resin of the present invention, the water-absorbent resin can be efficiently reduced in molecular weight.

FIG. 1 is a perspective view showing an example of an absorbent article used in the method for producing a paper composition of the present invention. 2 (a) to 2 (e) are conceptual diagrams showing an embodiment of the method for producing a paper composition of the present invention.

The paper composition and recycled paper of the present invention include pulp recovered from the absorbent article and a water-absorbent resin recovered from the absorbent article. The water-absorbent resin in the present invention is recovered from an absorbent article and has a low molecular weight. That is, the molecular weight is reduced as compared with the molecular weight in the state contained in the absorbent article.

The composition for paper of the present invention is a powder mixture used as a raw material for paper, and is in a dry state or in a liquid state mixed with a liquid such as water. The liquid also includes a slurry. The recycled paper of the present invention is a paper containing pulp recovered from an absorbent article and a water-absorbent resin recovered from the absorbent article.

The paper composition of the present invention can be produced, for example, as follows. First, the absorbent article is frozen and then crushed to obtain a crushed product of the absorbent article. Next, the absorbent material containing the pulp and the water-absorbent resin is separated from the crushed material. Then, by reducing the molecular weight of the water-absorbent resin contained in the separated absorbent material, a composition for paper containing pulp and the low-molecular-weight water-absorbent resin is produced.

By containing the water-absorbent resin having a low molecular weight, the composition for paper of the present invention has a higher viscosity in the slurry state than in the case of containing the water-absorbent resin not having a low molecular weight.
Whether or not it is a low molecular weight water-absorbent resin is determined by comparing the molecular weight of the water-absorbent resin with the molecular weight of the water-absorbent resin to be determined, if an absorbent article or the water-absorbent resin contained therein is available. When the molecular weight of the water-absorbent resin to be determined is smaller, it can be determined that the water-absorbent resin to be determined has a low molecular weight. The molecular weight of the water-absorbent resin can be measured by, for example, the diffusivity of liquid chromatography or gel permeation chromatography, Rayleigh scattering of light, settling time, viscosity, and the relative mass of molecules with a mass spectrometer. However, since the water-absorbent resin has a crosslinked structure and an infinite network structure, it may be difficult to measure the molecular weight. Therefore, instead of comparing the molecular weights, the particle size, viscosity, sedimentation rate or water absorption rate are compared, and when the particle size, sedimentation rate or water absorption rate of the water-absorbent resin to be determined is smaller, or the determination target When the viscosity of the water-absorbent resin is higher, it can be determined that the water-absorbent resin to be determined has a low molecular weight.

Regardless of whether the absorbent article or the water-absorbent resin contained therein is available, the water-absorbent resin contained in the absorbent article, the composition for paper or recycled paper is a low-molecular-weight water-absorbent resin. Whether or not there is present may be determined by the following methods (1) to (6). Examples of the method for determining whether or not the water-absorbent resin is contained in the paper composition or the recycled paper include an NMR method (nuclear magnetic resonance) and an electron spin resonance method (ESR) FT-IR. Method (Fourier transform infrared spectroscopy), X-ray analysis, Raman spectroscopy, visible / ultraviolet spectroscopy (UV-VIS), visible light spectroscopy, ultraviolet-visible near-infrared spectroscopy (UV-VIS-NIR) , Millimeter-wave imaging, Terrahertz imaging, Catharnomic spectroscopy (CL), Fluorescence spectroscopy, Method using resin coloring reagent, Thermal weight / mass analysis (TG-MS), Thermal decomposition gas chromatograph mass analysis (Py-GC / MS), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), and the like.

(1) Judgment by particle size When the particle size of the water-absorbent resin to be judged is significantly smaller than the particle size of the general water-absorbent resin used for absorbent articles, the molecular weight was reduced. Determined to be a water-absorbent resin.
Specifically, when the water-absorbent resin passes through a sieve having a mesh size of 500 μm in a wet state in which 200 times the mass ratio of water is added, it is determined that the water-absorbent resin has a low molecular weight. Alternatively, when the water-absorbent resin has a particle size of 1 μm or less in a dry state, it is determined that the water-absorbent resin has a low molecular weight.

(2) Judgment by viscosity Low molecular weight when the viscosity of the water-absorbent resin to be judged after water absorption is significantly higher than the viscosity of the general water-absorbent resin used for absorbent articles after water absorption. Judged as a modified water-absorbent resin.
Specifically, when the water-absorbent resin has a viscosity of 150,000 mPa · s or more in a wet state in which 20,000 times the mass ratio of water is added, it is determined that the water-absorbent resin has a low molecular weight. The method for measuring the viscosity will be described later in Examples.

(3) Judgment based on the sedimentation rate of the water-absorbent resin The sedimentation rate of the water-absorbent resin to be judged after water absorption is significantly higher than the sedimentation rate of the general water-absorbent resin used for absorbent articles after water absorption. If it is slow, it is judged to be a low molecular weight water-absorbent resin.
Specifically, when the settling time of the water-absorbent resin measured by the following method for measuring the settling time is 1 minute or more, preferably 10 minutes or more, and more preferably 1 hour or more, the water-absorbent resin is low. It is determined that it is molecularized.
[Measurement method of sedimentation time]
The absorbent resin is made to absorb 20 times the amount of pure water in terms of mass ratio to which the red dye is added, and the absorbent resin is colored. Then, the water-absorbing and colored water-absorbent resin is _{added to a 20-fold amount of pure water or a 0.05% CaCl 2} aqueous solution and stirred. The water depth of pure water or 0.05% CaCl ₂ aqueous solution is 5 cm. The time from the end of stirring to the precipitation of the colored water-absorbent resin is defined as the precipitation time. Whether or not the water-absorbent resin has precipitated is visually determined.

(4) Judgment by water absorption ratio When the water absorption ratio of the water-absorbent resin to be judged is smaller than the water absorption ratio of the general water-absorbent resin used for the absorbent article, the water absorption is reduced. Judged as resin.
Specifically, when the water absorption ratio of the water-absorbent resin measured by the following method for measuring the water absorption ratio is 10 times or less, preferably 5 times or less, it is determined that the water-absorbent resin has a low molecular weight. ..
[Measurement method of water absorption magnification]
Put 1 g of water-absorbent resin in a cylinder of Φ30 mm and measure the bulkiness in the dry state. Add 20 times the amount of pure water by mass ratio, and measure the bulkiness in the wet state after 20 minutes. The water absorption ratio is defined as (bulkyness in a wet state) / (bulkyness in a dry state).

(5) Judgment by Settling Rate of Paper Composition or Recycled Paper Compared to the settling rate of general paper compositions or recycled paper used in absorbent articles when crushed in water, the water-absorbent resin When the settling speed of the paper composition or recycled paper to be judged contained at the time of crushing in water is significantly slow, the water-absorbent resin contained in the paper composition or recycled paper to be judged is low. Judged as a molecularized water-absorbent resin.
Specifically, the settling time of the paper composition or recycled paper measured by the following method for measuring the settling time of the paper composition or recycled paper is 1 minute or more, preferably 10 minutes or more, more preferably 1 hour. In the above cases, it is determined that the water-absorbent resin contained in the paper composition or the recycled paper has a low molecular weight.
[Method for measuring sedimentation time of paper composition or recycled paper]
The composition for paper or recycled paper is made to absorb 20 times the amount of pure water in terms of mass ratio to which the red dye is added to color the composition for paper or the recycled paper. Then, the water-absorbing and colored paper composition or recycled paper is put into 20 times the amount of pure water or 0.05% CaCl ₂ aqueous solution, and the mixture is stirred until it loosens. The water depth of pure water or 0.05% CaCl ₂ aqueous solution is 5 cm. The time from the end of stirring until the colored paper composition or recycled paper settles is defined as the settling time of the paper composition or recycled paper. Whether or not the paper composition or recycled paper has settled is visually determined.

The paper composition of the present invention will be described by taking the paper composition 10, which is a preferred embodiment of the paper composition of the present invention, as an example.
As described above, the paper composition 10 contains the pulp and the water-absorbent resin recovered from the absorbent article. Absorbable articles are mainly used to absorb and retain body fluids excreted from the body such as urine, menstrual blood, and vaginal discharge. The absorbent article may be unused or used. The used absorbent article means an absorbent article after absorbing excrement such as urine excreted by the wearer, and the absorbent article contains water, particularly in the absorber. Examples of excrement include feces and the like in addition to body fluids excreted from the body. Absorbent articles include, but are not limited to, for example, disposable diapers, sanitary napkins, incontinence pads, panty liners, etc., and broadly include articles used for absorbing liquid discharged from the human body. To do. The absorbent article typically comprises a liquid-permeable front sheet, a liquid-impermeable or water-repellent back sheet, and a liquid-retaining absorber interspersed between the two sheets. The absorbent article may further include various members according to its specific use. Such members are known to those of skill in the art. In the present invention, the absorbent article used for recovering the pulp and the water-absorbent resin may be a single absorbent article, but is preferably a plurality of absorbent articles. An absorbent article 1 which is an example of an absorbent article is shown in FIG.

The absorbent article 1 is a used absorbent article. As the absorbent article 1, for example, a used absorbent article discarded by a nursing care facility, a childcare facility, or a household can be used. The absorbent article 1 includes an absorber 4 having an absorbent material, a front surface sheet 2, and a back surface sheet 3. The absorber 4 is interposed between the front surface sheet 2 and the back surface sheet 3, and the peripheral portions of the front surface sheet 2 and the back surface sheet 3 are bonded to each other by an adhesive or the like. Examples of the adhesive include hot melt type adhesives and the like. The absorbent article 1 is a so-called deployable disposable diaper, which has a crotch part A at the center in the longitudinal direction thereof, and is a back part of both parts extending in front of and behind the crotch part A. The fastening tape 5 is provided on both side edges of the side portion B, and the fastening tape 5 is provided on the non-skin facing surface (the surface facing the wearer's skin side when worn) of the ventral side portion C, which is the other portion. A landing zone 6 is provided to stop the landing.
In the present invention, the absorbent article may be a so-called pants-type diaper. Pants-type diapers typically have a crotch in the center of the longitudinal direction, with both sides of the dorsal side, which is one of the two parts extending in front of and behind the crotch. A pair of side seals, a waist opening through which the wearer's torso passes, and a pair of legs through which the wearer's lower limbs pass, with the other part, both sides of the ventral side, joined together. An opening is formed.
Further, in the present invention, the absorbent article may be a so-called napkin, pad, or panty liner. A napkin typically has a crotch portion in the central portion in the longitudinal direction thereof, and a dorsal portion extending in front of and behind the crotch portion and a ventral portion which is the other portion are formed.

Examples of the front surface sheet 2, the back surface sheet 3, the absorber 4, and other constituent materials include those used in conventional absorbent articles. As the front surface sheet 2 and the back surface sheet 3, a non-woven fabric, a sheet material, or the like made of a synthetic resin such as a thermoplastic resin is used. Examples of the thermoplastic resin include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66, and one of these can be used alone or in combination of two or more. .. As the absorber 4, an absorbent material wrapped in tissue paper or the like can be used.

The absorbent material forming the absorber 4 contains pulp and a water-absorbent resin. Examples of the pulp and the water-absorbent resin include various pulps and water-absorbent resins conventionally used for absorbent articles, and are not particularly limited.
As the pulp, for example, the origin classification is wood pulp such as coniferous (N material) pulp and broadleaf tree (L material) pulp; cotton pulp, linter pulp, walla pulp, kenaf pulp, yoshi pulp, bagas pulp, bamboo pulp, quail pulp, fruit. Non-wood pulp such as pulp; used paper pulp, as a classification of manufacturing method, mechanical pulp such as crushed wood pulp, refiner ground pulp, thermomechanical pulp, chemithermomechanical pulp; chemical pulp such as kraft pulp, sulfate pulp, alkaline pulp, etc. Can be mentioned.

The water-absorbent resin is preferably one that can absorb and retain a liquid 20 times or more its own weight and can be gelled. For example, a polymer or copolymer of starch, crosslinked carboxylmethylated cellulose, acrylic acid or an alkali metal acrylate metal salt. Etc., polyacrylic acid and salts thereof, and polyacrylate graft polymers. The shape of the water-absorbent polymer before it is reduced in molecular weight can be spherical, lumpy, grape-like, powdery, film-like or fibrous.

Further, the absorbent material may contain synthetic fibers and the like in addition to pulp and water-absorbent resin. The synthetic fiber may or may not be hydrophilized. Examples of the material of the synthetic fiber include polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET); polyamides such as nylon 6 and nylon 66; polyacrylic acid and polymethacrylic acid alkyl esters. Examples thereof include polyvinyl chloride and polyvinylidene chloride, and one of these can be used alone or in combination of two or more.

In the deployable absorbent article 1 shown in FIG. 1, fastening tapes 5 are provided on both side edges of the dorsal side B. The fastening tape 5 is fixed to the side flap portions 11 existing on both sides of the dorsal side portion B in the width direction. The side flap portion 11 is a portion extending outward in the diaper width direction from both side edges of the absorber 4, and is composed of a laminated body of a sheet for forming a three-dimensional gather 7 and a back surface sheet 3.

The crushed product obtained by crushing the absorbent article 1 may contain a sheet piece 8 derived from the absorbent article 1. Examples of the sheet piece 8 derived from the absorbent article 1 include a sheet piece 8 derived from the front surface sheet 2 or the back surface sheet 3. The sheet piece 8 may be a sheet piece formed by crushing the front surface sheet 2 or the back surface sheet 3, or may be the front surface sheet 2 or the back surface sheet 3 itself that maintains the original shape.

The paper composition 10 is a composition containing pulp and a water-absorbent resin, and can be used as a raw material for paper or recycled pulp, for example. The paper composition 10 may be in the form of a slurry or in a dry state. In the paper composition 10, it is preferable that the water-absorbent resin is attached to the pulp.

The paper composition 10 has a high viscosity because the water-absorbent resin contained in the paper composition has a low molecular weight. Therefore, since the paper composition 10 has high adhesiveness between the pulps contained in the paper composition 10, the paper strength enhancer can be added to the paper composition 10 without adding the paper strength enhancer, or the paper strength enhancer can be used. Even if the amount added is reduced, high-strength recycled paper can be produced.
Further, the paper composition 10 has no graininess because the water-absorbent resin contained in the paper composition has a low molecular weight.

Further, in the paper composition of the present invention, the water-absorbent resin contained in the paper composition passes through a sieve having an opening of 1000 μm in a wet state in which 200 times the mass ratio of water is added. You may. As a result, the paper composition of the present invention has a high viscosity. Therefore, in the paper composition of the present invention, since the pulps contained in the paper composition have high adhesiveness to each other, the paper strength enhancer is not added to the paper composition or the paper strength enhancer. Even if the amount of the added amount is reduced, it is possible to produce recycled paper having high strength.
Further, the composition for paper of the present invention has no graininess.

The preferred composition of the paper composition 10 will be further described.
The water-absorbent resin contained in the paper composition 10 passes through a sieve having an opening of 1000 μm in a wet state in which 200 times the mass ratio of water is added from the viewpoint of increasing the viscosity of the paper composition 10. It is more preferable that it passes through a sieve having a mesh size of 700 μm, and it is more preferable that it passes through a sieve having a mesh size of 500 μm.

The ash content refers to the amount of inorganic or non-combustible residue left after the organic matter is ashed. In order to enable the paper composition 10 to be used as a sanitary material, "Regarding the approval criteria for manufacturing and selling sanitary treatment products" (Notice of Director of Pharmaceutical and Food Safety Bureau, Ministry of Health, Labor and Welfare, No. 0325, No. 0325, dated March 25, 2015) From the viewpoint of conforming to the standards for sanitary materials such as absorbent paper, the ash content is preferably 0.65% by mass or less, and the ash content is more preferably 0.6% by mass or less. It is more preferable that the content of the above is 0.5% by mass or less. The paper composition 10 preferably has a smaller ash content, and the lower limit is not particularly limited, but may be, for example, 0.001% by mass or more.

From the viewpoint of increasing the strength of the paper, the paper composition 10 preferably contains a large amount of sodium polyacrylate derived from a water-absorbent resin, and preferably has a sodium content of 15% or more in the ash content. The content of sodium in the ash is more preferably 16% or more, and the content of sodium in the ash is more preferably 17% or more. Further, from the viewpoint of reducing the alkalinization of the paper, the composition 10 for paper preferably has a sodium content in ash of 100% or less, and a sodium content in ash of 75% or less. It is preferable that the content of sodium in the ash is 50% or less.

The ash content can be measured, for example, as follows.
<Measurement method of ash content>
Examples of the ash content include a method of measuring according to JIS Z 7302-4 and a method of measuring according to "5. Ash content test method" of "2. General test method" of the material standard for physiological treatment products. That is, a sample was taken from the composition for paper and / or recycled paper, the mass of the sample to be put into the sample was precisely weighed, put into a crucible, incinerated until no charcoal was left by high heat, allowed to cool, and then incinerated. The mass of the residue is precisely measured, and the value obtained by multiplying the mass of the incinerated residue by the mass of the charged sample by 100 is defined as the ash content (mass%).

The sodium content in the ash can be measured, for example, as follows.
<Measurement method of sodium content in ash>
The sodium content in the ash can be measured by using a paper composition, recycled paper, or other object to be measured as ash in advance, or the ash obtained when measuring the ash content as a sample. it can. The sodium content can be measured by analyzing the composition of the sample. Composition analysis includes, for example, titration analysis, ion chromatograph analysis, fluorescent X-ray analysis (EDX), spark emission spectroscopic analysis, absorptiometry, inductively coupled plasma emission spectroscopic analysis, frame atomic absorption spectrometry, electroheated atomic absorption spectrometry, Inductively coupled plasma mass analysis and the like can be mentioned.

Next, the recycled paper of the present invention will be described.
The recycled paper of the present invention contains pulp and a water-absorbent resin recovered from an absorbent article, and the water-absorbent resin has a low molecular weight. The recycled paper of the present invention can be produced, for example, by using the above-mentioned paper composition 10 as a papermaking raw material. The recycled paper of the present invention is, for example, sanitary paper such as water-absorbent paper used for applications such as tissue paper, toilet paper, paper diapers, and sanitary products, wrapping paper such as kraft paper and cardboard paper, copy paper, and inkjet. Information paper such as paper, non-carbon paper, photosensitive paper, heat-sensitive paper, mixed paper such as tracing paper, synthetic paper, insulating paper, release paper, newspaper roll paper, non-coated printing paper, coated printing paper, fine coating It may be printing paper, special printing paper, or the like.

The recycled paper of the present invention has high strength because the recycled paper contains a water-absorbent resin having a low molecular weight.
When the water-absorbent resin is not reduced in molecular weight, the water-absorbent resin may be in a granular form in which water is retained inside. When the recycled paper contains grains made of a water-absorbent resin that has not been reduced in molecular weight as described above, the recycled paper has a grainy feel. Further, when the recycled paper contains grains made of a water-absorbent resin that has not been reduced in molecular weight as described above, the moisture in the grains of the water-absorbent resin evaporates, and the inside of the grains of the water-absorbent resin becomes The cavities may cause holes in the recycled paper.
The recycled paper of the present invention has no graininess because the water-absorbent resin contained in the recycled paper has a low molecular weight. Further, the recycled paper of the present invention is free from the above-mentioned defects such as holes.

The recycled paper of the present invention can be used as a sanitary material, so that it can be used as a sanitary material. From the viewpoint of conforming to the standards for sanitary materials such as absorbent paper, the ash content is preferably 0.65% by mass or less, more preferably 0.6% by mass or less, and the ash content is 0.5% by mass. The following is more preferable. Further, the smaller the ash content is, the more preferable it is, and the lower limit is not particularly limited, but for example, it can be 0.001% by mass or more.

From the viewpoint of increasing the strength of the paper, the recycled paper of the present invention preferably contains a large amount of sodium polyacrylate derived from a water-absorbent resin, preferably 15% or more of ash content is sodium, and 16% of ash content. It is more preferable that the above is sodium, and it is further preferable that 17% or more of the ash content is sodium. Further, in the paper composition 10, from the viewpoint of reducing the alkalinization of the paper and suppressing ink bleeding, for example, 100% or less of the ash content is preferably sodium, and 75% or less of the ash content is sodium. More preferably, sodium is 50% or less of the ash content.

The paper composition 10 and the recycled paper using the paper composition 10 can be suitably used for an absorbent article. Since such an absorbent article has strong strength and has a recycled paper having no holes, it can be used without being torn or broken. Further, in such an absorbent article, the water-absorbent resin can be easily fixed by the low-molecular-weight absorbent resin contained in the recycled paper, and the absorption performance can be improved. Further, since such an absorbent article uses recycled paper having no graininess, it is possible to make it comfortable on the skin and gentle on the baby's skin.

Next, a method for producing a paper composition of the present invention will be described with reference to the drawings based on a preferred embodiment thereof. FIG. 2 shows an outline of the method for producing the above-mentioned paper composition 10 as a first embodiment of the method for producing a paper composition of the present invention.
The method for producing the paper composition 10 of the first embodiment shown in FIG. 2 includes a freezing step, a crushing step, a separation step, and a molecular weight reduction step in this order. The low molecular weight step of the method for producing the composition 10 for paper of the first embodiment is a preferred embodiment of the low molecular weight method of the water-absorbent resin of the present invention. In the method for producing the paper composition 10 of the first embodiment, an aggregate of a plurality of absorbent articles 1 is used as the absorbent article (see FIG. 2A). As described above, the absorbent article used in the method for producing the paper composition 10 of the first embodiment has a form such as a deployable type or a pants type, a state of being used or unused, and a size. It may be an aggregate of a plurality of absorbent articles having different sizes. That is, the production method of the first embodiment can be applied to a single variety of absorbent articles, but a mixture of absorbent articles collected from a nursing care facility or the like or by a large-scale collection from a home. It can also be applied to things.

In the freezing step, the water content in the absorbent article 1 is frozen (see FIG. 2B). The freezing step is performed in order to facilitate crushing of the absorbent article 1, particularly the absorber 4, in the subsequent crushing step. By freezing the water content in the absorbent article 1 in the freezing step, the impact strength of the water-containing portion in the absorbent article 1, particularly the absorber 4, can be reduced as compared with that before freezing. When an impact is applied in the crushing step, the portion containing water in the absorbent article 1, particularly the absorber 4, can be easily crushed. Since the absorbent article 1 has been used, the absorbent body 4 contains more water than the front surface sheet 2 and the back surface sheet 3. Therefore, when the water content in the absorbent article 1 is frozen, the impact strength of the front surface sheet 2 and the back surface sheet 3 does not decrease so much, but the impact strength of the absorber 4 greatly decreases. In the absorbent article 1 that has undergone the freezing step, the absorber 4 has a lower impact strength than the front surface sheet 2 and the back surface sheet 3, and is more easily crushed.

The freezing step can be performed by placing the absorbent article 1 under low temperature conditions. The low temperature condition means a condition in which the water content in the absorbent article 1 can be frozen. For example, it is 0 ° C. or lower at 1 atm. Since the body fluid excreted from the body such as urine absorbed by the absorbent article 1 contains salt, the freezing step is preferably −5 ° C. from the viewpoint of surely freezing the water in the absorbent article 1. Hereinafter, it is more preferably performed at −10 ° C. or lower, further preferably −20 ° C. or lower.

Even when the absorbent article 1 does not contain water, depending on the type of adhesive that joins the front surface sheet 2 and the back surface sheet 3, the adhesive strength of the adhesive can be increased by cooling in the freezing step. May decrease. Examples of such an adhesive include a hot melt adhesive used by heating and melting. Hot melt adhesives usually contain a base polymer, tackifier and plasticizer. Specific examples of the base polymer include acrylic, silicone, rubber, and olefin polymers. As the acrylic polymer, for example, a (co) polymer (ethylene vinyl acetate common weight) of a vinyl monomer whose main component is 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, cyanoacrylate, vinyl acetate, methyl methacrylate or the like. An example is one consisting of (coalescence, etc.). Examples of the silicone-based polymer include a polydimethylsiloxane polymer polymer. Examples of the rubber-based polymer include natural rubber, polyisoprene, styrene-butadiene copolymer (SBR), styrene-isoprene-styrene block copolymer (SIS), and styrene-butadiene-styrene block copolymer (SBS). ), Styrene-ethylene-butadiene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS) can be exemplified. Since the adhesive strength of the adhesive is reduced, the front surface sheet 2 and the back surface sheet 3 are likely to be dissociated when an impact is applied in the crushing process, and the joint portions of both sheets 2 and 3 are peeled off, so that both sheets 2 are separated. , 3 is likely to be in a state where the absorber 4 can be taken out.

In the crushing step, the absorbent article 1 is impacted to crush the absorbent article 1 (see FIG. 2C). The crushing step is performed to crush the absorbent article 1 to obtain a crushed mixture containing the constituent materials of the absorbent article 1 and its small pieces. The crushed mixture contains a sheet piece 8 derived from the front surface sheet 2 or the back surface sheet 3, a mass 9 of an absorbent material derived from the absorber 4, and the like. In the first embodiment, the mass 9 of the absorbent material derived from the absorber 4 contains excrement.

The crushing step can be performed using, for example, a so-called crusher, a crusher, or the like. Examples of the crusher and the crusher include a compression type crusher, a striking type crusher, a grinding type crusher, a shear type crusher, and a device in which these are combined. The compression type crusher is a device that crushes an object by compressing it, and examples thereof include a jaw crusher, a gyretry crusher, a cone crusher, and a roll crusher. Striking type crusher, caused to collide with the object a hammer or _impact撃板like, a device for crushing by a blow to the object, for example, impact crusher, hammer crusher, chain crusher, hammer mill, stamp mill, Examples include a pin mill. A grinding type crusher is a device that crushes an object by grinding it. For example, a ball mill, a rod mill, a roller mill, a ring mill, a self-made crusher, a jet mill, a rotary mill, a vibration mill, a planetary mill, and an attritor. , Bead mill and the like. The shear type crusher is a device that crushes an object by shearing, and examples thereof include a cutter mill, a uniaxial crusher, and a biaxial crusher.

In the absorbent article 1 that has undergone the freezing step, the absorber 4 is particularly liable to crack, so that in the crushing step, the absorber 4 is crushed into smaller pieces than the front surface sheet 2 and the back surface sheet 3. To. Therefore, the mass 9 of the absorbent material produced by crushing the absorber 4 is smaller than the sheet piece 8 produced by crushing the front surface sheet 2 or the back surface sheet 3.
The sheet piece 8 derived from the front surface sheet 2 or the back surface sheet 3 obtained after the crushing step has a size such that the opening cannot pass through a 2 mm sieve, which is the standard length of pulp contained in the absorber. Is preferable, and in order to improve the separation rate in the subsequent separation step, the opening is more preferably a size that cannot pass through a sieve of 5 mm, further preferably a size that cannot pass through a sieve of 10 mm, and further. It is even more preferable that the size is such that it cannot pass through a 20 mm sieve.
The lump 9 of the absorbent material obtained after the crushing step preferably has a size capable of passing through a sieve having a mesh size of 2 mm, more preferably a size capable of passing through a sieve having a mesh size of 5 mm, and 10 mm. It is more preferably a size that can pass through a sieve of 20 mm, and even more preferably a size that can pass through a sieve of 20 mm.

In the method for producing the paper composition 10 of the first embodiment, it is preferable that the absorbent material can be taken out from between the front surface sheet 2 and the back surface sheet 3 in the crushing step. Usually, in the absorbent article 1, the absorber 4 is interposed between the front surface sheet 2 and the back surface sheet 3 whose peripheral edges are joined to each other. Therefore, even if the absorbent article 1 is impacted and the absorber 4 is finely crushed, the front surface sheet 2 and the back surface sheet 3 are not broken, and the bonding between the front surface sheet 2 and the back surface sheet 3 is maintained. If so, the space between the front surface sheet 2 and the back surface sheet 3 remains sealed, and the absorbent material cannot be taken out from between the two sheets 2 and 3, and in the subsequent separation step, both sheets 2 and 2 are not taken out. 3 and the absorbent material cannot be separated. Therefore, in the crushing step, the absorbent material is released from between the front surface sheet 2 and the back surface sheet 3 by breaking the front surface sheet 2 or the back surface sheet 3 or breaking the joint between the front surface sheet 2 and the back surface sheet 3. It is preferable to make it in a state where it can be taken out.

In the separation step, the sheet piece 8 derived from the absorbent article 1 and the absorbent material containing pulp and water-absorbent resin are separated from the crushed mixture obtained in the crushing step (see FIG. 2D). .. The sheet piece 8 derived from the absorbent article 1 is, for example, a sheet piece 8 derived from the front surface sheet 2 or the back surface sheet 3. The separation step is performed so that the sheet piece 8 derived from the absorbent article 1 and the absorbent material can be recovered separately. In the first embodiment, since the sheet piece 8 and the lump 9 of the absorbent material are different in size, a method of separating the sheet piece 8 and the lump 9 of the absorbent material according to the size can be used as a method of separating the two. In the first embodiment, the crushed mixture is sieved to separate the sheet piece 8 from the absorbent material. The size of the mesh opening of the sieve can be appropriately selected according to the size of the sheet piece 8 contained in the crushed mixture and the mass 9 of the absorbent material.

In the method for producing the paper composition 10 of the first embodiment, the sheet piece 8 derived from the absorbent article 1 and the absorbent material separated in the separation step are recovered. Here, collecting means, for example, storing the separated sheet piece 8 and the absorbent material in a container at the separated places or moving them to different places. As a method for recovering the sheet piece 8 and a method for recovering the absorbent material, various known methods can be used. For example, the sheet piece 8 and the absorbent material may be contained in a container, respectively. Further, for example, in the separation step, a belt conveyor or the like is arranged under the sieve, the sheet piece 8 is separated on the sieve, and the absorbent material is separated on the belt conveyor, and then the belt conveyor is driven. The absorbent material or the like collected on the belt conveyor may be moved to another place.

In the molecular weight reduction step, the water-absorbent resin contained in the recovered absorbent material 9 is reduced in molecular weight. The molecular weight reduction step may be performed on the absorbent material 9, or may be performed on the separated water-absorbent resin after separating the pulp and the water-absorbent resin contained in the absorbent material 9. .. When the pulp contained in the absorbent material 9 and the water-absorbent resin are separated and then the molecular weight-reducing step is performed on the separated water-absorbent resin, the molecular weight-reduced water-absorbing resin is reduced after the molecular weight-reducing step. The composition 10 for paper can be produced by mixing the resin and the separated pulp.
The method for reducing the molecular weight of the water-absorbent resin is not particularly limited, and may be a chemical method or a physical method. As a chemical method, a method using hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid or the like as a method using an acid, and a method using sodium hydroxide, potassium hydroxide, ammonia, calcium hydroxide or the like as a method using an alkali. As a method using an oxidizing agent or a radical, a method using various percarbonates, various perborates, peracetic acid, hydrogen peroxide, hypochlorite, chlorite, ascorbic acid, ozone, etc. can be mentioned. Be done.

In the method for producing the paper composition 10 of the first embodiment, the water-absorbent resin is reduced in molecular weight by a physical method in the molecular weight reduction step. More specifically, the low molecular weight step according to the first embodiment includes a water content step, a resin freezing step, and a resin crushing step in this order.

In the water-containing step, the water-absorbent resin is impregnated with water. In the water-containing step, in order to facilitate freezing of the water-absorbent resin in the subsequent resin freezing step, and in the subsequent resin crushing step, the molecular chain is extended due to the swelling of the water-absorbent resin, resulting in low molecular weight. Do this to make it easier. The method of impregnating the water-absorbent resin with water is not particularly limited, and examples thereof include a method of immersing in water or an aqueous solution, spraying, and absorbing urine, menstrual blood, stool, drip, and the like.

In the resin freezing step, the water-absorbent resin is frozen. The resin freezing step is performed in order to facilitate crushing of the water-absorbent resin in the subsequent resin crushing step. The resin freezing can be performed by placing the absorbent material 9 or the water-absorbent resin separated from the absorbent material 9 under low temperature conditions. The low temperature condition means a condition in which the water content in the water-absorbent resin can be frozen. For example, it is 0 ° C. or lower at 1 atm. From the viewpoint of reliably freezing the water content in the water-absorbent resin, the freezing step is preferably carried out at −5 ° C. or lower, more preferably −10 ° C. or lower, still more preferably −20 ° C. or lower. The method of freezing the water-absorbent resin is not particularly limited, and examples thereof include a method of immersing the water-absorbent resin in a liquid refrigerant, a method of contacting the water-absorbent resin with a solid refrigerant, a method of blowing cold air, and a method of combining these. Examples of the method of immersing in a liquid refrigerant include a method of immersing in a liquid refrigerant (for example, salt solution, alcohol, etc.), liquefied gas (liquid nitrogen, liquid carbon dioxide, etc.) and freezing. Examples of the method of contacting with the solid refrigerant include a method of cooling the metal plate from the inside or the outside with a cooling substance and freezing the metal plate with the metal plate. Examples of the method of blowing cold air include a method of blowing cooled air to freeze it, a method of blowing liquefied gas boiled at an ultra-low temperature to freeze it, and the like.

In the resin crushing step, the water-absorbent resin is crushed. The resin crushing step is performed to reduce the molecular weight of the water-absorbent resin. The resin crushing step can be performed using the same crusher or crusher as the crushing step described above. Further, the resin crushing step can be performed by using a crusher, a crusher or the like similar to the crushing step described above.

According to the method for producing the paper composition 10 of the first embodiment, the paper composition 10 can be obtained as described above.
In the method for producing the paper composition 10 of the first embodiment, the impact strength of the absorber 4 is significantly lower than the impact strength of the sheet piece 8 derived from the absorbent article 1 by performing the freezing step. Therefore, in the crushing step, when the absorbent article 1 is impacted, the absorber 4 is crushed into smaller pieces as compared with the sheet piece 8 derived from the absorbent article 1. Since the size of the lump of the absorbent material derived from the absorber 4 and the sheet piece 8 derived from the absorbent article 1 obtained after the crushing step are significantly different from each other, the sheet piece 8 derived from the absorbent article 1 and the sheet piece 8 derived from the absorbent article 1 are different from each other. The absorbent material can be separated by a simple method such as sieving.
Further, in the method for producing the paper composition 10 of the first embodiment, the water in the absorber 4 is frozen, so that when the absorbent article 1 is crushed in the crushing step, the absorbent material 9 is absorbed. It is difficult to adhere to the sheet piece 8 derived from the sex article 1. This makes it possible to prevent the sheet piece 8 derived from the absorbent article 1 and the absorbent material 9 from becoming difficult to separate in the separation step.
As described above, according to the method for producing the paper composition 10 of the first embodiment, the absorbent material 9 can be efficiently recovered from the absorbent article 1, and the efficiently recovered absorbent material 9 can be recovered. Since the molecular weight reduction step can be performed, the paper composition 10 can be efficiently produced.
Further, in the method for producing the paper composition 10 of the first embodiment, since the water-absorbent resin is reduced in molecular weight in the molecular weight reduction step, the paper composition 10 having a high viscosity can be produced.

According to the production method of the first embodiment, the composition 10 for paper having a desired viscosity can also be produced. In order to produce the composition 10 for paper having a desired viscosity, for example, the degree of molecular weight reduction of the water-absorbent resin may be adjusted in the molecular weight reduction step. More specifically, the conditions for performing the low molecular weight step such as the resin water content in the water content step, the temperature in the resin freezing step, the processing time in the resin crushing step, and the crushing strength in the resin crushing step may be adjusted.

Further, by adjusting the amount of the water-absorbent resin contained in the paper composition 10, the viscosity of the paper composition 10 can be set to a desired viscosity. In order to adjust the amount of the water-absorbent resin contained in the paper composition 10, for example, after separating the pulp and the water-absorbent resin contained in the absorbent material 9 recovered in the separation step, the separated water-absorbing resin is used. The amount of the water-absorbent resin is adjusted when the composition 10 for paper is produced by performing a molecular weight reduction step on the sex resin and mixing the water-absorbent resin after the molecular weight reduction step with the separated pulp. do it. Further, by setting the ratio of the water-absorbent resin to the pulp in the paper composition 10 to a desired ratio, the viscosity of the paper composition 10 can be set to a desired viscosity.

Since the low molecular weight step according to the first embodiment includes a water content step, a resin freezing step, and a resin crushing step in this order, the water-absorbent resin can be efficiently low molecular weight.
Further, in the low molecular weight reduction step according to the first embodiment, since the water absorbent resin is reduced in molecular weight by a physical method, it is not necessary to perform a step of inactivating the water absorbent resin, and the number of treatment steps is reduced. In addition, since it is not necessary to use an inactivating agent containing a large amount of inorganic substances and chlorides, the ash content and chlorine content can be reduced.

Further, in the method for producing the composition 10 for paper of the first embodiment, it is preferable to have a rough crushing step before the freezing step. The coarse crushing step is a step of crushing the absorbent article 1 coarser than the crushing step. The coarse crushing step is performed in order to increase the surface area of the absorber 4 by roughly crushing the absorbent article 1 and to make the absorber 4 easier to freeze. The coarse crushing step preferably has a shorter treatment time, a smaller impact on the absorbent article 1, or both than the crushing step. Similar to the crushing step, the coarse crushing step can crush the absorbent article 1 by giving an impact to the absorbent article 1. The type of impact may be the same or different between the coarse crushing step and the crushing step.

In the rough crushing step, it is preferable that the absorbent material and excrement can be taken out from between the front surface sheet 2 and the back surface sheet 3.
The sheet piece derived from the front surface sheet 2 or the back surface sheet 3 obtained after the rough crushing step preferably has a size that cannot pass through a sieve having a mesh opening of 5 mm, and has a size that cannot pass through a sieve having a mesh opening of 10 mm. It is preferable that the mesh size is such that the mesh size cannot pass through a sieve having a mesh size of 20 mm.
The mass of the absorbent material obtained after the coarse crushing step preferably has a size capable of passing through a sieve having a mesh size of 5 mm, and preferably has a size capable of passing through a sieve having a mesh size of 10 mm. Is more preferably large enough to pass through a 20 mm sieve.

By performing the coarse crushing step before the freezing step, the surface area of the absorber 4 can be increased, and the water content in the absorber 4 can be easily frozen in the freezing step. Further, by roughly crushing the absorbent article 1 in advance by the coarse crushing step, the time required for the crushing step can be shortened.

Further, in the method for producing the paper composition 10 of the first embodiment, the water content in the absorbent article 1 can be maintained in a frozen state in one or both of the steps after the freezing step, that is, the crushing step and the separating step. It is preferable to carry out at temperature. As a result, in the step after the freezing step, the absorbent material adheres to the front surface sheet 2, the back surface sheet 3, etc. via moisture, and in the separation step, the sheet piece derived from the front surface sheet 2 or the back surface sheet 3 and the absorbent material become Can be prevented from becoming difficult to separate. It is more preferable that both the crushing step and the separating step are performed at a temperature at which the water content in the absorbent article 1 can be maintained in a frozen state. The temperature at which the water content in the absorbent article 1 can be maintained in a frozen state is preferably 0 ° C. or lower, more preferably -5 ° C. or lower, still more preferably -10 ° C. or lower, and more preferably at 1 atm. More preferably, it is −20 ° C. or lower.

Further, in the method for producing the paper composition 10 of the first embodiment, it is preferable that the separation step is performed while applying vibration to the crushed mixture obtained by the crushing step. Specifically, it is preferable to separate the sheet piece derived from the front surface sheet 2 or the back surface sheet 3 and the absorbent material while applying vibration. As a result, even if the crushed mixture is agglomerated, the crushed mixture can be separated while being loosened, so that the sheet piece and the absorbent material can be accurately separated. In addition, by applying vibration, a mass of absorbent material whose moisture is frozen and easily crushed can be crushed into smaller pieces. Therefore, the difference in size between the sheet piece and the lump of the absorbent material can be made larger, so that the sheet piece and the absorbent material can be separated more easily.

Further, in the method for producing the paper composition 10 of the first embodiment, it is preferable that the step after the resin freezing step, that is, the resin crushing step is performed at a temperature at which the water-absorbent resin can be maintained in a frozen state. As a result, the resin crushing step can be performed while maintaining the water-absorbent resin in a state where it can be easily crushed. The temperature at which the water-absorbent resin can be maintained in a frozen state is preferably 0 ° C. or lower, more preferably -5 ° C. or lower, still more preferably -10 ° C. or lower, still more preferably −1 atm. It is 20 ° C. or lower.

Next, a second embodiment of the method for producing a paper composition of the present invention will be described. The second embodiment will be described only with respect to the differences from the first embodiment. The point that the second embodiment is not particularly described is the same as that of the first embodiment, and the description of the first embodiment is appropriately applied.

The method for producing the composition 10 for paper according to the second embodiment includes a coarse crushing step, a freezing step, a separation step, and a molecular weight reduction step in this order. The coarse crushing step, the freezing step, the separation step and the molecular weight reduction step can be carried out in the same manner as the coarse crushing step, the freezing step, the separation step and the molecular weight reduction step in the first embodiment.

In the method for producing the paper composition 10 of the second embodiment, first, a rough crushing step is performed to roughly crush the absorbent article 1. Next, a freezing step is performed to freeze the water content in the absorbent article 1. After that, a separation step is performed to separate and recover the front sheet or the sheet piece derived from the back sheet and the absorbent material. In the second embodiment, unlike the first embodiment, the crushing step is not performed after the freezing step.

In the method for producing the composition 10 for paper of the second embodiment, the surface area of the absorber 4 is increased by the coarse crushing step, and the water content in the absorber 4 is easily frozen. Further, the freezing step freezes the water content in the absorber 4, making it difficult for the absorbent material to adhere to the front surface sheet 2 and the back surface sheet 3. Therefore, also in the separation and recovery method of the second embodiment, as in the first embodiment, a simple method such as sieving the sheet pieces derived from the front surface sheet 2 and the back surface sheet 3 and the absorbent material is performed. Can be separated and recovered.

In the method for producing the paper composition 10 of the second embodiment, it is preferable to separate the sheet piece and the absorbent material while applying vibration in the separation step. As a result, the absorbent body 4 whose impact strength has decreased due to freezing of water can be crushed into finer small pieces, so that the size of the sheet piece and the mass of the absorbent material derived from the absorbent body 4 Can be made larger, and the sheet piece and the absorbent material can be more easily separated and recovered.

Next, an embodiment of an apparatus for producing a composition for paper, which is suitably used in the method for producing the composition 10 for paper according to the first embodiment of the present invention, will be described. The paper composition manufacturing apparatus of the present embodiment is a manufacturing apparatus capable of producing the above-mentioned paper composition 10. The apparatus for producing the paper composition 10 of the present embodiment includes a freezing portion, a crushing portion, a separating portion, and a molecular weight reducing portion in this order from the upstream to the downstream of the apparatus. The low molecular weight portion of the apparatus for producing the paper composition 10 of the present embodiment is a preferred embodiment of the low molecular weight apparatus for the water-absorbent resin of the present invention. Further, it is preferable that the apparatus for producing the paper composition 10 of the present embodiment has a coarsely crushed portion that roughly crushes the absorbent article 1 upstream of the frozen portion. Further, in the manufacturing apparatus of the present embodiment, each part may be independent, or may be connected by a transport part made of a belt conveyor or the like and may be continuous.

The freezing portion is configured to be able to freeze the water content in the absorbent article 1. Specifically, it is preferable that the freezing unit is provided with a freezing device capable of performing the above-mentioned freezing step. Examples of the freezing device include a device for immersing in a liquid refrigerant, a device for contacting with a solid refrigerant, a device for blowing cold air, and a device in which these are combined. Examples of the device for immersing in a liquid refrigerant include a brine refrigerator that is immersed in a liquid refrigerant (salt solution, alcohol, etc.), a liquefied gas (liquid nitrogen, liquid carbon dioxide, etc.) and frozen. Examples of the device that comes into contact with the solid refrigerant include a contact refrigerator that cools a metal plate from the inside or the outside with a cooling substance and freezes the metal plate by sandwiching the metal plate with the metal plate. Examples of the device for blowing cold air include an air blast refrigerator that freezes with cooled air, and a liquefied gas refrigerator that sprays and freezes liquefied gas boiled at an ultra-low temperature.

The crushing portion is configured so that the absorbent article 1 can be impacted to crush the absorbent article 1. Specifically, it is preferable that the crushing portion is provided with a crushing device capable of performing the above-mentioned crushing step. As the crushing device, for example, a so-called crusher, a crusher, or the like can be used. Examples of the crusher and the crusher include a compression type crusher, a striking type crusher, a grinding type crusher, a shear type crusher, and a device in which these are combined. The compression type crusher is a device that crushes an object by compressing it, and examples thereof include a jaw crusher, a gyretry crusher, a cone crusher, and a roll crusher. A striking crusher is a device that collides a hammer, an impact plate, or the like with an object and crushes the object by impacting the object. For example, an impact crusher, a hammer crusher, a chain crusher, a hammer mill, a stamp mill, or a pin mill. And so on. A grinding type crusher is a device that crushes an object by grinding it. For example, a ball mill, a rod mill, a roller mill, a ring mill, a self-made crusher, a jet mill, a rotary mill, a vibration mill, a planetary mill, and an attritor. , Bead mill and the like. The shear type crusher is a device that crushes an object by shearing, and examples thereof include a cutter mill, a uniaxial crusher, and a biaxial crusher.

The separating portion is configured so that the sheet piece 8 derived from the absorbent article 1 and the absorbent material 9 can be separated. Specifically, it is preferable that the separation unit is provided with a separation device capable of performing the above-mentioned separation step. Examples of the separation device include a device using a screen or a filter, a device using an air flow, a device using gravity, a device using vibration, a device using a roller, and a device combining these. .. A device using a screen or a filter is a device that separates the screen or the filter according to the size of the eyes, and examples thereof include a sieve, a filter, and a screen. A device that uses airflow is a device that separates fluids such as air and liquid according to specific gravity and shape. For example, mesh separators, swirl sieving devices, cage separators, screw press collectors, air separators, screw press separators, dust collectors, etc. Examples include a jet separator. A device that uses gravity is a device that separates by using the falling speed and sedimentation according to the specific gravity and shape. For example, water specific gravity separation, heavy liquid separation, liquid nitrogen specific gravity separation, liquefied carbon dioxide specific gravity separation, air drop separation, etc. Can be mentioned. The device using vibration is a device that promotes separation by vibration, and examples thereof include a vibration sieve, a gyro shifter, a circular vibration sieve, a eurus screen, and a ballistic separator. The device using the roller is a device that separates by the difference in the gap due to the difference in the size of the roller, and examples thereof include a particle size sorter. Examples of the combined separation device include a vario separator that combines filter separation, airflow separation, and vibration separation.

Further, it is preferable that either one or both of the crushed portion and the separated portion have a cooling means. As the cooling means, one that can maintain the temperature of the crushed portion or the separated portion at a temperature at which the water content in the absorbent article 1 can be maintained in a frozen state can be used. Such cooling means include, for example, a method of crushing or separating while immersed in a liquid refrigerant, a method of crushing or separating while in contact with a solid refrigerant, a method of crushing or separating while blowing cold air, and a method of separating. Examples thereof include devices capable of performing a method in which these are combined. The method of crushing or separating the crushed part while immersed in the liquid refrigerant is to immerse the crushed part in a liquid refrigerant such as brine (salt solution, alcohol, etc.) or liquefied gas (liquid nitrogen, liquid carbon dioxide, etc.) to maintain the frozen state. Alternatively, a method of separation and the like can be mentioned. Examples of the method of contacting with the solid refrigerant include a method of cooling the metal plate of the crusher or the separator from the inside or the outside with a cooling substance, and maintaining the frozen state by separating the crushed portion or the metal plate with the metal plate. The method of blowing cold air is to blow cooled air to the crusher or separator, or to supply the cooled air to the crusher or separator to keep it frozen, or to crush the liquefied gas boiled at an ultra-low temperature. Alternatively, a method of spraying on a separator or supplying a liquefied gas boiled at an ultra-low temperature to a crusher or a separator to maintain a frozen state can be mentioned.

The low molecular weight portion is configured so that the water-absorbent resin contained in the recovered absorbent material 9 can be low in molecular weight. Specifically, it is preferable that the low molecular weight reduction unit is provided with a low molecular weight reduction device capable of performing the above-mentioned low molecular weight reduction step. Examples of the low molecular weight device include a device provided with a resin freezing section and a resin crushing section when physically performed, and an device provided with a reaction tank which is a reaction section when chemically performed. ..

Further, it is preferable that the low molecular weight portion is provided with a water-containing portion, a resin frozen portion, and a resin crushed portion in this order from upstream to downstream of the manufacturing apparatus for the paper composition 10 of the present embodiment.
The water-containing portion is configured so that the water-absorbent resin can contain water. Specifically, it is preferable that the water-containing portion is provided with a water-containing device capable of performing the above-mentioned water-containing step. Examples of the water-containing device include a immersion bath, a spray device, a shower, a water curtain, and the like.

The resin freezing portion is configured so that the water-absorbent resin can be frozen. Specifically, it is preferable that the resin freezing unit is provided with a resin freezing device capable of performing the resin freezing step described above. Examples of the resin freezing device include the above-mentioned freezing device.

The resin crushing portion is configured so that the water-absorbent resin can be crushed. Specifically, it is preferable that the resin crushing unit is provided with a resin crushing device capable of performing the resin crushing step described above. Examples of the resin crushing device include the above-mentioned crushing device.

Further, the resin pulverization preferably has a cooling means. As the cooling means, one that can maintain the temperature of the resin crushed portion at a temperature at which the water-absorbent resin can be maintained in a frozen state can be used. Examples of such a cooling means include cooling means that can be used as the cooling means included in the crushed portion or the separated portion described above.

Although the present invention has been described above based on the preferred embodiment thereof, the present invention is not limited to the above embodiment.
For example, in the production method of the first embodiment, a sieve was used in the separation step, but instead, an air flow was applied to the crushed mixture of the absorbent article 1 to separate a small mass of the absorbent material. The sheet piece 8 derived from the absorbent article 1 and the absorbent material 9 may be separated by moving to the place of.

Further, when the absorbent article 1 contains excrement as in the method for producing the paper composition 10 of the first and second embodiments, in the separation step, the sheet piece 8 derived from the absorbent article 1 is used. , It is preferable to separate the absorbent material 9 and the excrement. This makes it possible to separate and collect the sheet piece containing no excrement and the absorbent material and excrement. When the sheet piece and the absorbent material and excrement are separated, the sheet piece may be separated into a mixture of the absorbent material and excrement, or the sheet piece, the absorbent material and excrement may be separated. May be separated into.

The present invention further discloses the following additional notes.
<1>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
A composition for paper in which the water-absorbent resin has a low molecular weight.
<2>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin is a composition for paper that passes through a sieve having a mesh size of 500 μm in a wet state in which 200 times the mass ratio of water is added.
<3>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin preferably passes through a sieve having an opening of 1000 μm in a wet state to which 200 times the amount of water is added by mass ratio, and more preferably passes through a sieve having an opening of 700 μm. A composition for paper, preferably one that passes through a sieve having a mesh size of 500 μm.
<4>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin is a composition for paper having a particle size of 1 μm or less in a dry state.

<5>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin is a composition for paper having a viscosity of 150,000 mPa · s or more in a wet state in which 20,000 times the mass ratio of water is added.
<6>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin is a composition for paper, which has a settling time of 1 minute or more, preferably 10 minutes or more, and more preferably 1 hour or more.
<7>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin is a composition for paper having a water-absorbing ratio smaller than that of a general water-absorbing resin used for an absorbent article.

<8>
The composition for paper according to any one of <1> to <7>, wherein 15% or more of the ash content is sodium.
<9>
It is preferable that 15% or more of the ash content is sodium, 16% or more of the ash content is sodium, more preferably 17% or more of the ash content is sodium, and 100% or less of the ash content is sodium. The above <1> to <7>, wherein 75% or less of the ash content is more preferably sodium, and 50% or less of the ash content is more preferably sodium. Composition for paper.
<10>
The composition for paper according to any one of <1> to <9>, wherein the ash content is 0.65% by mass or less.
<11>
The ash content is preferably 0.65% by mass or less, the ash content is more preferably 0.6% by mass or less, and the ash content is further preferably 0.5% by mass or less. Further, the smaller the ash content, the more preferable, and the lower limit is not particularly limited, but for example, for paper according to any one of the above <1> to the above <9>, which can be 0.001% by mass or more. Composition.

<12>
Recycled paper containing pulp and water-absorbent resin recovered from absorbent articles.
The water-absorbent resin is a recycled paper having a low molecular weight.
<13>
Recycled paper containing pulp and water-absorbent resin recovered from absorbent articles.
The water-absorbent resin is a recycled paper that passes through a sieve having an opening of 1000 μm in a wet state in which 200 times the amount of water is added by mass ratio.
<14>
A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin preferably passes through a sieve having an opening of 1000 μm in a wet state to which 200 times the amount of water is added by mass ratio, and more preferably passes through a sieve having an opening of 700 μm. Recycled paper, preferably one that passes through a sieve having a mesh size of 500 μm.

<15>
Recycled paper containing pulp and water-absorbent resin recovered from absorbent articles.
The water-absorbent resin is recycled paper having a particle size of 1 μm or less in a dry state.
<16>
Recycled paper containing pulp and water-absorbent resin recovered from absorbent articles.
The water-absorbent resin is a recycled paper having a viscosity of 150,000 mPa · s or more in a wet state in which 20,000 times the mass ratio of water is added.
<17>
Recycled paper containing pulp and water-absorbent resin recovered from absorbent articles.
The water-absorbent resin is recycled paper having a settling time of 1 minute or longer, preferably 10 minutes or longer, and more preferably 1 hour or longer.
<18>
Recycled paper containing pulp and water-absorbent resin recovered from absorbent articles.
The water-absorbent resin is a recycled paper having a water-absorbing ratio smaller than that of a general water-absorbing resin used for an absorbent article.

<19>
The recycled paper according to any one of <12> to <18>, wherein 15% or more of the ash content is sodium.
<20>
It is preferable that 15% or more of the ash content is sodium, 16% or more of the ash content is sodium, more preferably 17% or more of the ash content is sodium, and 100% or less of the ash content is sodium. The above <12> to <18>, wherein 75% or less of the ash content is more preferably sodium, and 50% or less of the ash content is more preferably sodium. Recycled paper.
<21>
The recycled paper according to any one of <12> to <20>, wherein the ash content is 0.65% by mass or less.

<22>
The ash content is preferably 0.65% by mass or less, the ash content is more preferably 0.6% by mass or less, and the ash content is further preferably 0.5% by mass or less. Further, the smaller the ash content, the more preferable, and the lower limit is not particularly limited, but for example, for paper according to any one of <12> to <20>, which can be 0.001% by mass or more. Composition.
<23>
1 selected from the group consisting of the paper composition according to any one of <1> to <11> and the recycled paper according to any one of <12> to <22>. Absorbent article containing seeds or two or more.

<24>
A method for producing a composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
A freezing step of freezing the moisture in the absorbent article,
After the freezing step, a crushing step of giving an impact to the absorbent article to crush the absorbent article,
After the crushing step, a separation step of separating the absorbent material containing the pulp and the water-absorbent resin from the sheet piece derived from the absorbent article, and
A method for producing a composition for paper, comprising a low molecular weight step of lowering the molecular weight of the water-absorbent resin contained in the absorbent material after the separation step.

<25>
The method for producing a paper composition according to <24>, which comprises a coarse crushing step of coarsely crushing the absorbent article prior to the freezing step.
<26>
The method for producing a paper composition according to <24> or <25>, wherein the crushing step is performed at a temperature at which the water content in the absorbent article can be maintained in a frozen state.
<27>
The method for producing a paper composition according to any one of <24> to <26>, wherein the separation step is performed at a temperature at which the water content in the absorbent article can be maintained in a frozen state.
<28>
The temperature at which the water content in the absorbent article can be maintained in a frozen state is preferably 0 ° C. or lower, more preferably −5 ° C. or lower, still more preferably −10 ° C. or lower at 1 atm. The method for producing a paper composition according to <26> or <27>, wherein the temperature is more preferably −20 ° C. or lower.
<28>
The method according to any one of <24> to <28>, wherein in the separation step, the sheet piece derived from the front surface sheet or the back surface sheet and the absorbent material are separated while being subjected to vibration. A method for producing a composition for paper.

<29>
The molecular weight reduction step is
A water-containing step of impregnating the water-absorbent resin with water,
A resin freezing step of freezing the water-absorbent resin and
The method for producing a composition for paper according to any one of <24> to <28>, which comprises a resin crushing step of crushing the water-absorbent resin.
<30>
The method for producing a paper composition according to <29>, wherein the resin crushing step is performed at a temperature at which the water content of the absorbent resin can be maintained in a frozen state.
<31>
The temperature at which the water content of the absorbent resin can be maintained in a frozen state is preferably 0 ° C. or lower, more preferably −5 ° C. or lower, still more preferably −10 ° C. or lower, and more preferably at 1 atm. The method for producing a paper composition according to <30>, wherein the temperature is more preferably −20 ° C. or lower.
<32>
The method for producing a paper composition according to any one of <29> to <31>, wherein the freezing step is performed by placing the absorbent resin under low temperature conditions.
<32>
The paper freezing step according to any one of <29> to <32>, wherein the resin freezing step is preferably performed at −5 ° C. or lower, more preferably −10 ° C. or lower, still more preferably −20 ° C. or lower. Method for producing the composition.

<33>
It is a method to reduce the molecular weight of the water-absorbent resin.
A water-containing step of impregnating the water-absorbent resin with water,
After the water-containing step, a resin freezing step of freezing the water-absorbent resin and a resin freezing step.
A method for reducing the molecular weight of a water-absorbent resin, comprising a resin crushing step of crushing the water-absorbent resin after the freezing step.

<34>
The method for reducing the molecular weight of a water-absorbent resin according to <33>, wherein the resin crushing step is performed at a temperature at which the water content of the absorbent resin can be maintained in a frozen state.
<35>
The temperature at which the water content of the absorbent resin can be maintained in a frozen state is preferably 0 ° C. or lower, more preferably −5 ° C. or lower, still more preferably −10 ° C. or lower, and more preferably at 1 atm. The method for reducing the molecular weight of the water-absorbent resin according to <34>, which is more preferably −20 ° C. or lower.
<36>
The method for reducing the molecular weight of a water-absorbent resin according to any one of <33> to <35>, wherein the resin freezing step is performed by placing the absorbent resin under low temperature conditions.
<37>
The water absorption according to any one of <33> to <36>, wherein the resin freezing step is preferably performed at −5 ° C. or lower, more preferably −10 ° C. or lower, and even more preferably −20 ° C. or lower. Method for reducing the molecular weight of resin.
<38>
A device that reduces the molecular weight of water-absorbent resin.
A water-containing part that moistens the water-absorbent resin, and
A resin freezing part that freezes the water-absorbent resin,
A low molecular weight treatment apparatus for a water-absorbent resin, comprising a resin crushing unit for crushing the water-absorbent resin.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

<Test 1>
Test 1 was conducted to evaluate whether or not the water-absorbent resin can be reduced in molecular weight by crushing the water-impregnated resin after freezing.
[Manufacturing of resin-containing liquid]
(Example 1)
(1) First, 200 g of ion-exchanged water was absorbed by 1 g of the water-absorbent resin. As the water-absorbent resin, a sodium polyacrylate polymer (manufactured by Sundia Co., Ltd., IM997) was used.
(2) Next, the water-absorbent resin was placed in liquid nitrogen and frozen.
(3) Then, the water-absorbent resin is taken out from the liquid nitrogen and put into a crusher (manufactured by Osaka Chemical Co., Ltd., Wonder Crusher, model: WC-3, Navis product number: 1-3380-01), and the rotation speed memory 3 is used. Grinded for 1 minute.
(4) The frozen pulverized product obtained in (3) was melted at room temperature to obtain a resin-containing liquid.
The resin-containing liquid thus obtained was used as the resin-containing liquid of Example 1. The resin-containing liquid of Example 1 was in the form of a slurry.

(Comparative Example 1)
A resin-containing liquid of Comparative Example 1 was obtained in the same manner as in Example 1 except that the step (2) was not performed in Example 1.
(Comparative Example 2)
_{200 g of a 5% CaCl 2} aqueous solution was absorbed by 1 g of the same water-absorbent resin as that used in Example 1. The resin-containing liquid thus obtained was used as the resin-containing liquid of Comparative Example 2.
(Comparative Example 3)
200 g of ion-exchanged water was designated as Comparative Example 3.
(Comparative Example 4)
200 g of ion-exchanged water was absorbed by 1 g of the same water-absorbent resin as the water-absorbent resin used in Example 1. The resin-containing liquid thus obtained was used as the resin-containing liquid of Comparative Example 4.

Table 1 shows the results of measuring the sedimentation time in water, the sedimentation time in a 0.05% CaCl ₂ aqueous solution, and the water absorption ratio by the above-mentioned measuring methods for Example 1 and Comparative Examples 1, 2 and 4. In addition, the results of (1) measuring the proportion of the water-absorbent resin with reduced molecular weight by the following method, and (2) the results of measuring the viscosity of Examples 1 and Comparative Examples 1 to 4 by the following methods are shown. Shown in 1. Since the ion-exchanged water of Comparative Example 3 does not contain a water-absorbent resin, (1) the ratio of the low-molecular-weight water-absorbent resin was set to 0.

(1) Method for measuring the ratio of low-molecular-weight water-absorbent resin 20 g of the resin-containing liquids of Example 1 and Comparative Examples 1, 2 and 4 was taken out, 1980 g of ion-exchanged water was added, and the mixture was stirred and diluted 100-fold. A mesh having a mesh size of 500 μm was prepared in advance, and the mass was measured. Then, the diluted resin-containing liquids of Example 1 and Comparative Examples 1, 2 and 4 were filtered through the mesh. Then, after drying, the total mass of the mesh and the water-absorbent resin remaining on the mesh was measured. The value calculated by subtracting the mass of the mesh itself from the total mass measured was taken as the mass of the water-absorbent resin remaining on the mesh. Values calculated by subtracting the mass of the water-absorbent resin remaining on the mesh from the mass (0.1 g) of the water-absorbent resin contained in the resin-containing liquids of Example 1 and Comparative Examples 1, 2 and 4 before dilution, respectively. , Divided by the mass (0.1 g) of the water-absorbent resin contained in the resin-containing liquids of Example 1 and Comparative Examples 1, 2 and 4 before dilution. The value obtained by multiplying the value calculated in this manner by 100 was used as the ratio of the low molecular weight water-absorbent resin in Example 1 and Comparative Examples 1, 2 and 4, respectively. The ratio of the water-absorbent resin having a low molecular weight is the ratio of the water-absorbent resin that has passed through the mesh.

(2) Viscosity Measurement Method The viscosity of the resin-containing liquids of Example 1 and Comparative Examples 1 to 4 was measured using a B-type viscometer (model number TVB-10M manufactured by Toki Sangyo Co., Ltd.). In Example 1 and Comparative Examples 1 and 4, the measurement conditions: rotor No. 23 (M4), 30 rpm, 60 seconds, in Comparative Examples 2 and 3, the measurement conditions: rotor No. It was measured at 19 (M1), 30 rpm, and 60 seconds.

〔Test results〕
In Example 1, when the precipitation time was measured using either pure water or a 0.05% CaCl ₂ aqueous solution, no precipitation occurred after 3600 seconds had passed from the end of stirring. “3600 or more” in Table 1 indicates that no precipitation has occurred after 3600 seconds have passed from the end of stirring.
As shown in Table 1, in Example 1 _{, the sedimentation time in pure water and 0.05% CaCl 2} aqueous solution is 1 minute or more, and the water absorption ratio is 10 times or less. Therefore, it can be seen that Example 1 has a low molecular weight.
On the other hand, in Comparative Example 1 _{, the sedimentation time in pure water and 0.05% CaCl 2} aqueous solution is 1 minute or more, but the water absorption ratio is more than 10 times. Further, in Comparative Example 2, the water absorption ratio is 10 times or less, but _{the sedimentation time in pure water and 0.05% CaCl 2} aqueous solution is less than 1 minute. Further, in Comparative Example 3, the sedimentation time in pure water and 0.05% CaCl ₂ aqueous solution is less than 1 minute, and the water absorption ratio is more than 10 times. Therefore, it can be seen that Comparative Examples 1, 2 and 4 are not reduced in molecular weight.

Further, as shown in Table 1, the proportion of the low molecular weight water-absorbent resin was 60% in Example 1, whereas in Comparative Examples 1, 2 and 4, the low molecular weight water-absorbent resin was used. The ratio was 0%. As described above, in Example 1, the proportion of the water-absorbent resin having a low molecular weight is higher than that in Comparative Examples 1, 2 and 4, and therefore, the efficiency of the water-absorbent resin according to the method of the present invention. It can be seen that the water-absorbent resin can be reduced in molecular weight.
Further, as shown in Table 1, the viscosity of Example 1 is higher than that of Comparative Examples 1 to 4. As described above, in Example 1, the water-absorbent resin has a low molecular weight and the molecular chains of the resin are easily entangled. Therefore, according to the method for reducing the molecular weight of the water-absorbent resin of the present invention, the water-absorbent resin can be efficiently produced. It can be seen that the molecular weight can be reduced. Further, it can be seen that according to the method for reducing the molecular weight of the water-absorbent resin of the present invention, it is possible to increase the adhesive strength of paper and to produce a water-absorbent resin having high viscosity.

<Test 2>
Test 2 was conducted to evaluate the quality of recycled paper produced using a paper composition containing a low molecular weight water-absorbent resin.
[Manufacturing of recycled paper]
(Example 2)
0.25 g of the resin-containing liquid of Example 1 was dissolved in 475 g of a 0.5% pulp turbid liquid, and the paper was extracted and dried to produce the recycled paper of Example 2.

(Comparative Example 5)
In Example 2, the recycled paper of Comparative Example 5 was produced in the same manner as in Example 2 except that the resin-containing liquid of Comparative Example 1 was used instead of the resin-containing liquid of Example 1.
(Comparative Example 6)
In Example 2, the recycled paper of Comparative Example 6 was produced in the same manner as in Example 2 except that the resin-containing liquid of Comparative Example 2 was used instead of the resin-containing liquid of Example 1.
(Comparative Example 7)
In Example 2, the recycled paper of Comparative Example 7 was produced in the same manner as in Example 2 except that the ion-exchanged water of Comparative Example 3 was used instead of the resin-containing liquid of Example 1.

Table 2 shows the results of measuring the thickness, texture, number of holes, drying strength, wet strength, feel, thickness, ash content, and sodium content in ash of the recycled papers of Examples 2 and Comparative Examples 5 to 7. Shown in.

[Thickness measurement method]
A measurement sample piece having a length of 200 mm and a width of 100 mm was cut out from the recycled papers of Example 2 and Comparative Examples 5 to 7. For each of the measurement sample pieces, ^{the thickness under load of 25 kg / m 2 was} measured at any five points using a laser displacement meter (manufactured by OMRON Corporation, model number: ZS-LDC), and the measured values were measured. The average value was taken as the thickness of the recycled paper of Example 2 and Comparative Examples 5 to 7.

[Metsuke measurement method]
A measurement sample piece having a length of 200 mm and a width of 100 mm was cut out from the recycled papers of Example 2 and Comparative Examples 5 to 7. The mass of the sample piece for measurement was measured, and the value divided by the area was used as the basis weight of the recycled paper of Example 2 and Comparative Examples 5 to 7, respectively.

[Measuring method of the number of holes]
A measurement sample piece having a length of 200 mm and a width of 100 mm was cut out from the recycled papers of Example 2 and Comparative Examples 5 to 7. For each of the measurement sample pieces, a sample piece was placed on a black mount, and a fluorescent lamp was applied from above in the vertical direction, and an image was taken from above in the vertical direction using a digital camera (PowerShot S120, manufactured by Canon Inc.). .. The captured image was opened with image processing software (Adobe Photoshop CSS version 12.0, manufactured by Adobe), binarized, and then the number of particles was measured with the same software. By laying the black mount underneath, the color of the pores becomes black, and the binarization makes the pores stand out, making it easier to measure the number of particles. The smaller the number of holes, the more preferable.

[Measuring method of drying strength]
From the recycled papers of Example 2 and Comparative Examples 5 to 7, measurement sample pieces having a length of 120 mm and a width of 25 mm were cut out in the MD direction. The strength of the measurement sample piece was measured using a tensile tester (manufactured by Orientec Co., Ltd., "Tencilon" RTC-1150A). The distance between the chucks was 100 mm, and the tensile speed was 300 mm / min. The maximum strength until the sample broke was measured 5 times, and the average was taken as the drying strength. The higher the drying strength, the more preferable.

[Measuring method of wet strength]
The strength was measured in the same manner as in the above-mentioned [Measuring method of dry strength] except that the central portion of the sample piece for measurement was traced in the CD direction with a brush soaked in water and then the strength was measured. By setting the amount of water adhering to the sample to 5 to 15 mg, an appropriate wet state similar to the case where the entire sample is immersed is obtained. Even if water is partially attached, it will naturally become an appropriate wet state due to the diffusion of the liquid due to the capillary phenomenon, so even if the amount of liquid is partially large, if it adheres across the measurement direction of the sample. No effect was seen on the measurement results. The value measured in this way was taken as the wet strength. The higher the wet strength, the more preferable.

[Evaluation method of feel]
A measurement sample piece having a length of 200 mm and a width of 100 mm was cut out from the recycled papers of Example 2 and Comparative Examples 5 to 7. The surface of each of the measurement sample pieces was traced with a finger at any five points to evaluate the graininess caused by the water-absorbent resin. Feeling grainy means feeling a slight pain when compressed strongly with a finger. The evaluation was a two-stage functional value of having a grainy feeling and having no grainy feeling. It is preferable that there is no graininess.
No graininess: Trace the different places 5 times and feel no graininess at all.
Grainy: Trace the different places 5 times and feel the grain more than once.

[Measurement method of ash content]
Approximately 5 mg is cut out from the recycled paper of Example 2 and Comparative Examples 5 to 7, weighed with a balance, placed in a φ5 open pan (aluminum), and heated using STA7200RV (trade name) manufactured by Hitachi High-Tech Science Co., Ltd. Measurement was performed up to 500 ° C. at a speed of 10 ° C./min. Then, the ash remaining in the pan was vapor-deposited with gold, and then the elemental (EDS) analysis of the particles was performed using an energy dispersive X-ray analyzer (EDX) attached to a scanning electron microscope (SEM). In the operation of EDX, the X-ray extraction angle was 30 °, the X-ray folding time was 30 minutes, and a Si (Li) semiconductor detector was used for X-ray detection. The elements are carbon: C, oxygen: O, sodium: Na, magnesium: Mg, aluminum: AL, silicon: Si, gold: Au, calcium: Ca, counting the amount of X-rays peculiar to eight atoms, 8 The ratio of each element was measured with the total amount of one X-ray as 100. Such an operation was repeated 5 times, the average element ratio was calculated, and the ash content was calculated by the following formula.
(Ash content) = (1- (mass loss rate up to 500 ° C)) x (100- (carbon of ash: C ratio)-(gold of ash: Au ratio)) / 100

[Measurement method of sodium content in ash]
Approximately 5 mg is cut out from the recycled paper of Example 2 and Comparative Examples 5 to 7, weighed with a balance, placed in a φ5 open pan (aluminum), and heated using STA7200RV (trade name) manufactured by Hitachi High-Tech Science Co., Ltd. Measurement was performed up to 500 ° C. at a speed of 10 ° C./min. Then, the ash remaining in the pan was vapor-deposited with gold, and then the elemental (EDS) analysis of the particles was performed using an energy dispersive X-ray analyzer (EDX) attached to a scanning electron microscope (SEM). In the operation of EDX, the X-ray extraction angle was 30 °, the X-ray folding time was 30 minutes, and a Si (Li) semiconductor detector was used for X-ray detection. The elements are carbon: C, oxygen: O, sodium: Na, magnesium: Mg, aluminum: AL, silicon: Si, gold: Au, calcium: Ca, counting the amount of X-rays peculiar to eight atoms, 8 The ratio of each element was measured with the total amount of one X-ray as 100. Such an operation was repeated 5 times, the average element ratio was calculated, and the sodium content in the ash was calculated by the following formula.
(Sodium content in ash) = (Sodium in ash: Na ratio) / (100- (Carbon in ash: C ratio)-(Gold in ash: Au ratio))

〔Test results〕
As shown in Table 2, compared to Comparative Example 7 which does not contain the water-absorbent resin, Examples 2 and Comparative Examples 5 and 6 containing the water-absorbent resin have higher drying strength and wet strength. Therefore, it can be seen that the strength of recycled paper is increased by containing a water-absorbent resin. Further, compared to Comparative Example 7, Examples 2 and Comparative Examples 5 and 6 are thicker. Therefore, it can be seen that the recycled paper becomes bulky by containing the water-absorbent resin.
Comparing Example 2 with Comparative Examples 5 and 6, the recycled paper of Comparative Examples 5 and 6 has many holes, whereas the recycled paper of Example 2 does not have holes.
As is clear from the above description, it can be seen that the recycled paper of the present invention has high drying strength, wet strength and bulk, and does not have holes.

1 Absorbent article 2 Front sheet 3 Back sheet 4 Absorbent 8 Sheet piece derived from absorbent article 9 Mass of absorbent material

Claims (12)

A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
A composition for paper in which the water-absorbent resin has a low molecular weight. A composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
The water-absorbent resin is a composition for paper that passes through a sieve having an opening of 1000 μm in a wet state in which 200 times the amount of water is added by mass ratio. The composition for paper according to claim 1 or 2, wherein the content of sodium in the ash is 15% or more. The composition for paper according to any one of claims 1 to 3, wherein the content of ash is 0.65% by mass or less. Recycled paper containing pulp and water-absorbent resin recovered from absorbent articles.
The water-absorbent resin is a recycled paper having a low molecular weight. The recycled paper according to claim 5, wherein 15% or more of the ash content is sodium. The recycled paper according to claim 6, wherein the ash content is 0.65% by mass or less. Absorption containing one or more selected from the group consisting of the paper composition according to any one of claims 1 to 4 and the recycled paper according to any one of claims 5 to 7. Sex goods. A method for producing a composition for paper containing pulp and a water-absorbent resin recovered from an absorbent article.
A freezing step of freezing the moisture in the absorbent article,
After the freezing step, a crushing step of giving an impact to the absorbent article to crush the absorbent article,
After the crushing step, a separation step of separating the absorbent material containing the pulp and the water-absorbent resin from the sheet piece derived from the absorbent article, and
A method for producing a composition for paper, comprising a low molecular weight step of lowering the molecular weight of the water-absorbent resin contained in the absorbent material after the separation step. The molecular weight reduction step is
A water-containing step of impregnating the water-absorbent resin with water,
A resin freezing step of freezing the water-absorbent resin and
The method for producing a paper composition according to claim 9, further comprising a resin crushing step of crushing the water-absorbent resin. It is a method to reduce the molecular weight of the water-absorbent resin.
A water-containing step of impregnating the water-absorbent resin with water,
After the water-containing step, a resin freezing step of freezing the water-absorbent resin and a resin freezing step.
A method for reducing the molecular weight of a water-absorbent resin, comprising a resin crushing step of crushing the water-absorbent resin after the freezing step. A device that reduces the molecular weight of water-absorbent resin.
A water-containing part that moistens the water-absorbent resin, and
A resin freezing part that freezes the water-absorbent resin,
A low molecular weight treatment apparatus for a water-absorbent resin, comprising a resin crushing unit for crushing the water-absorbent resin.

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