JP2019178461A - Recycled pulp fiber, and manufacturing method of recycled pulp fiber - Google Patents

Abstract

The present invention provides a recycled pulp fiber derived from a used sanitary product, which can be used in applications that come into contact with moisture and has few protein-containing components that can be eluted in water.
SOLUTION: Recycled pulp fibers derived from used sanitary goods, in which the above-mentioned recycled pulp fibers are dispersed at a solid content concentration of 5.0% by mass, the protein is measured by the Modified Lowry method. Recycled pulp fibers containing at a concentration of 60 μg / mL or less.
[Selection] Figure 2

Description

  The present disclosure relates to recycled pulp fibers derived from used sanitary goods, and methods for producing recycled pulp fibers from used sanitary goods, including pulp fibers.

The production of recycled pulp fiber from used sanitary goods is being considered.
For example, Patent Document 1 describes a regenerated fiber obtained by regenerating a sanitary article containing cellulose pulp and having a superabsorbent polymer (SAP) amount of less than 10%.

  Patent Document 2 discloses a sanitary product obtained by pulverizing a dirty sanitary product containing a water-absorbing resin that has absorbed water into a gel and dispersing the crushed sanitary product in water containing a disinfectant. A method for recovering the material from a dirty sanitary article containing a water-absorbing resin that absorbs water and forms a gel, characterized in that a part of the adhered dirt is separated from the pulverized product of the sanitary article. Are listed.

International Publication No. 2014/007105 JP 2009-73198 A

  Since used sanitary products contain body fluids, food residues, bacteria, etc., when recycled pulp fibers collected from used sanitary products are used for contact with moisture, the recycled pulp When the fibers come into contact with moisture, it is preferable that body fluids, food residues, bacteria, and the like are not released into the moisture as much as possible.

  However, the regenerated fiber described in Patent Document 1 collects recycled pulp fiber from hygiene products so as not to include other constituent materials, and reduces the amount of protein-containing components derived from body fluids and the like. is not. In addition, the recovery method described in Patent Document 2 disinfects or sterilizes germs that adhere to sanitary products using a disinfectant, and does not reduce the amount of protein-containing components derived from body fluids or the like.

  Therefore, an object of the present disclosure is to provide a recycled pulp fiber derived from a used sanitary product, which can be used for an application that comes into contact with moisture and has few protein-containing components that can be eluted in water.

  The present disclosure is a recycled pulp fiber derived from a used sanitary article, in which an aqueous dispersion in which the recycled pulp fiber is dispersed at a solid content concentration of 5.0% by mass is used to produce a protein in a modified lowry method. Recycled pulp fibers were found containing at a concentration of 60 μg / mL or less as measured by.

  The recycled pulp fiber derived from the used sanitary article of the present disclosure has a small amount of protein-containing components that can be eluted in water, and can be used for applications that come into contact with moisture.

FIG. 1 is a block diagram showing a system 1 according to the first embodiment. FIG. 2 is a schematic diagram of the ozone treatment device 19. FIG. 3 is a flowchart illustrating an example of a method according to the first embodiment. FIG. 4 is a schematic diagram of an ozone treatment device 19a according to the second embodiment. FIG. 5 is a schematic view of an ozone treatment device 19b according to the third embodiment.

Specifically, the present disclosure relates to the following aspects.
[Aspect 1]
Recycled pulp fiber derived from used sanitary goods,
An aqueous dispersion in which the recycled pulp fiber is dispersed at a solid content concentration of 5.0% by mass contains a protein at a concentration of 60 μg / mL or less as measured by the Modified Lowry method.
The above recycled pulp fiber.

Recycled material, which is a recycled component material collected from used sanitary goods, is a component derived from used sanitary goods, such as bodily fluids (for example, excrement) when it comes into contact with liquids during use. , Secretions), food residues, bacteria, etc. are preferably not eluted in the liquid. In particular, since bacteria have a great influence on the human body, it is preferable that the recycled pulp fiber does not contain bacteria derived from used sanitary goods.
All of these components have common points including proteins (hereinafter, body fluids, food residues, bacteria, etc. may be referred to as “protein-containing components”).

On the other hand, virgin pulp fibers have a high ratio of being used for moisture absorption because of their high water absorption, and recycled pulp fibers can be used for moisture absorption as well as virgin pulp fibers. The value is expected to increase and the pulp fiber recycling market is expected to expand.
The recycled pulp fiber contains a predetermined amount of protein that can be eluted in water, that is, a protein-containing component derived from a used sanitary article contains a very small amount of protein that can be eluted in water. It can be used for applications that come into contact with moisture, for example, moisture absorption applications. The recycled pulp fiber can give a sense of security to the user who uses the recycled pulp fiber.

[Aspect 2]
The recycled pulp fiber according to aspect 1, wherein Bacillus cereus and Bacillus subtilis are not detected by the pour culture method.

Bacillus genus bacteria such as Bacillus cereus and Bacillus subtilis are resident bacteria that are ubiquitous in soil, water, plants, etc., and are highly durable because they form spores. . Spores are highly resistant to heat, disinfectants, etc., and may not be removed by general disinfection techniques, but rarely, bacteremia, endocarditis, respiratory infections, May cause food poisoning, eye infection, etc.
The above recycled pulp fiber is not likely to cause bacteremia, endocarditis, respiratory infections, food poisoning, eye infections, etc., since the Bacillus cereus and Bacillus subtilis are not detected by the pour culture method. The recycled pulp fiber can be used with confidence.

[Aspect 3]
The recycled pulp fiber according to aspect 1 or 2, wherein no Bacillus spp. Are detected by the pour culture method.

  The recycled pulp fiber is not likely to cause bacteremia, endocarditis, respiratory infection, food poisoning, eye infection, etc., because the Bacillus genus bacteria are not detected by the pour culture method. Recycled pulp fiber can be used with confidence.

[Aspect 4]
The recycled pulp fiber according to any one of aspects 1 to 3, wherein no bacteria are detected by the pour culture method.

  Bacteria, specifically, general viable bacteria are not detected in the recycled pulp fiber by the pour culture method. Therefore, the recycled pulp fiber can be used for water absorption applications where animals can come into contact. Moreover, the user can use the said recycled pulp fiber in comfort.

[Aspect 5]
The recycled pulp fiber according to any one of aspects 1 to 4, wherein bacteria are not detected by a plate culture method.

  The recycled pulp fiber is not likely to cause bacteremia, endocarditis, respiratory infections, food poisoning, eye infections, etc., because bacteria, specifically enteric bacteria, are not detected by the plate culture method. The user can use the recycled pulp fiber with peace of mind.

[Aspect 6]
The recycled pulp fiber according to any one of aspects 1 to 5, which has a ΔYI of 0 to 20 with respect to a standard white board.

The pulp fiber contained in the used sanitary goods may absorb excrement (for example, feces, urine, etc.) and may be colored brown or yellow. Therefore, in order to reuse the pulp fiber of used sanitary goods as recycled pulp fiber, it is necessary to bleach the color caused by excrement. In addition, since the user often has a psychological resistance to the recycled pulp fiber derived from used sanitary goods, from the viewpoint of reducing the user's psychological resistance, the recycled pulp fiber, It is preferable to have high whiteness.
Since the recycled pulp fiber has a predetermined ΔYI, that is, has a whiteness equal to or higher than that of virgin pulp, the user hardly feels psychological resistance to the article using the recycled pulp fiber.

[Aspect 7]
The recycled pulp fiber according to any one of aspects 1 to 6, which has a ΔW of 0 to 20 with respect to a standard white board.

  Since the recycled pulp fiber has a predetermined ΔW, that is, has a whiteness equal to or higher than that of virgin pulp, the user hardly feels psychological resistance to the article using the recycled pulp fiber.

[Aspect 8]
A method of producing recycled pulp fibers from used sanitary goods, including pulp fibers,
An aqueous solution containing the pulp fiber is a treatment tank equipped with an ejector, and the ejector includes a driving fluid supply port, a mixed fluid discharge port connected to the treatment tank, and a suction fluid supply port therebetween. A supply step of supplying ozone to the suction fluid supply port while supplying the drive fluid supply port of what is provided;
The mixed solution formed by mixing the aqueous solution and the ozone in the ejector is discharged from the mixed fluid discharge port into the treatment liquid in the treatment tank, and the protein-containing component in the pulp fiber Is a recycled pulp fiber, in which an aqueous dispersion in which the recycled pulp fiber is dispersed at a solid content concentration of 5.0% by mass has a protein concentration of 60 μg / mL or less measured by the Modified Lowry method. Recycled pulp fiber forming step to form what is contained in,
Including the above method.

  The said manufacturing method can manufacture the recycled pulp fiber which contains in a very small quantity what can be eluted in water among the protein containing components derived from used sanitary goods. Moreover, the said method can manufacture the recycled pulp fiber which can be used for the use which contacts with a water | moisture content, for example, a moisture absorption use. Furthermore, the said manufacturing method can manufacture the recycled pulp fiber which can give a user a sense of security.

[Aspect 9]
The used sanitary article further includes a superabsorbent polymer. In the supplying step, the aqueous solution further includes the superabsorbent polymer. In the recycled pulp fiber forming step, the superabsorbent polymer is further decomposed. The method of embodiment 8, wherein

  In the above production method, the superabsorbent polymer is reduced, and recycled pulp fibers containing a very small amount of protein-containing components derived from used sanitary products that can be eluted in water can be produced. .

[Aspect 10]
The method according to aspect 9, comprising an inactivation step of inactivating the superabsorbent polymer using an acidic aqueous solution before the supplying step.

  Since the production method includes a predetermined inactivation step, ozone is hardly deactivated in the supply step and the recycled pulp fiber formation step, and thus the production method reduces the superabsorbent polymer and uses it. Among the protein-containing components derived from the finished sanitary goods, recycled pulp fibers containing a very small amount that can be eluted in water can be produced.

  Recycled pulp fibers derived from the used sanitary products of the present disclosure (hereinafter, “recycled pulp fibers derived from used sanitary products” may be referred to as “recycled pulp fibers”) are described in detail below. To do.

The recycled pulp fiber of the present disclosure includes a protein of 60 μg / mL or less measured by the Modified Lowry method. By doing so, among the protein-containing components derived from used sanitary goods, it contains a very small amount that can be eluted in water, so it is used not only for moisture absorption but also for applications that come into contact with water Can do. In addition, the recycled pulp fiber can give a sense of security to the user who uses the recycled pulp fiber.
In the present specification, “elution” means that the target component moves into the aqueous solution in any form, for example, dissolution, dispersion or the like.

The protein concentration contained in the recycled pulp fiber is measured as follows.
(1) Prepared Modified Lowy Protein Assay Kit (hereinafter sometimes referred to as “ML Kit”) manufactured by Thermo Fisher Scientific.

(2) In a 1 liter beaker, 500 g of an aqueous dispersion having a recycled pulp fiber solid content concentration of 5.0 mass% is prepared.
When the recycled pulp fiber is present in a dry state, the aqueous dispersion is mixed with recycled pulp fiber (25.0 g as a solid content) and deionized water (amount that gives a total amount of 500.0 g). Can be formed. And when the said recycled pulp fiber exists in aqueous solution (For example, in the manufacturing method of recycled pulp fiber, when recycled pulp fiber is collect | recovered as aqueous solution), Comprising: Solid content concentration of recycled pulp fiber is 5.0 mass% When it is above, an aqueous dispersion having a solid content concentration of the cycle pulp fiber of 5.0% by mass can be prepared by adding deionized water to the aqueous solution.

Further, when the recycled pulp fiber is present in an aqueous solution and the solid content concentration of the recycled pulp fiber is less than 5.0% by mass, the solid content concentration of the recycled pulp fiber is 5.0% by mass by filtration. Adjust to.
In the present specification, the solid content (for example, the solid content of recycled pulp fiber) and the solid content concentration (for example, the solid content concentration of recycled pulp fiber in the aqueous dispersion) are obtained by dividing a fraction thereof at 105 ° C. Measured by drying for 16 hours. Note that the sample itself (for example, recycled pulp fiber itself) used for measuring the solid content and the solid content concentration is not used for the measurement of the protein concentration because the thermal history is added.
In addition, the said solid content density | concentration is prescribed | regulated considering that an aqueous dispersion contains impurities other than a recycled pulp fiber.

In this specification, solid content and solid content concentration are based on the residue (m ₁ (g) obtained by drying a sample (for example, recycled pulp fiber, aqueous dispersion): m ₀ (g) under the above-mentioned conditions. And the following formula:
Solid content (mass%), solid content concentration (mass%) = 100 × m ₁ / m ₀
Can be measured.

(3) The aqueous dispersion is stirred for 15 minutes at a rotational speed of 300 rpm using an overhead stirrer.
(4) A micro cooling centrifuge Model 3740 manufactured by Kubota Corporation is prepared. The aqueous dispersion stirred with an overhead stirrer is centrifuged for 5 minutes at 12,000 rpm and 4 ° C., and the supernatant is collected.

(5) The protein concentration contained in the supernatant is measured using ML Kit. The protein concentration is measured according to “Test Tube Procedure” of “INSTRUTIONS” of ML Kit.
If the supernatant contains an interfering substance for measuring protein concentration with the ML Kit, the method described in the ML Kit, eg dialysis, gel filtration, sample dilution, acetone or trichloro The effect of interfering substances can be eliminated by precipitation of proteins using acetic acid.
The absorbance is measured using a UV-2450 type UV-visible spectrophotometer manufactured by Shimadzu Corporation.
The measurement is performed at room temperature, preferably 25 ° C.

The recycled pulp fiber of the present disclosure is preferably free from detection of Bacillus cereus and Bacillus subtilis, more preferably Bacillus spp., And even more preferably bacteria by the pour culture method.
Bacillus genus bacteria such as Bacillus cereus and Bacillus subtilis are resident bacteria that are ubiquitous in soil, water, plants, etc., and are highly durable because they form spores. . Spores are highly resistant to heat, disinfectants, etc., and may not be removed by general disinfection techniques, but rarely, bacteremia, endocarditis, respiratory infections, May cause food poisoning, eye infection, etc.

Examples of bacteria that can be detected by the pour culture method include general live bacteria such as Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, green-concentrated bacteria, non-glucose-fermented bacilli, and Aeromonas bacteria.
Since the bacteria are not detected by the pour culture method, the recycled pulp fiber is less likely to cause bacteremia, endocarditis, respiratory infections, food poisoning, eye infections, etc. The fiber can be used with confidence.

It is preferable that the recycled pulp fiber of the present disclosure does not detect bacteria, specifically enteric bacteria, by a plate culture method. By doing so, the risk of opportunistic infection is reduced, and the recycled pulp fiber can be used with confidence.
Examples of the intestinal bacteria include Escherichia Coli, Klebsiella oxytoca, Citrobacter freundii, and Klebsiella spp. Klebsiella pneumoniae, Enterobacter cloacae, Proteus mirabilis, Enterobacter spp. , Enterobacter aerogenes, Morganella morganii, Providencia rettgeri and the like.

The culture method including the plate culture method and the pour culture method is performed as follows.
(1) In a 1 liter beaker, 500 g of an aqueous dispersion having a recycled pulp fiber solid content concentration of 5.0% by mass is prepared.
When the recycled pulp fiber is present in a dry state, the aqueous dispersion is mixed with recycled pulp fiber (25.0 g as a solid content) and deionized water (amount that gives a total amount of 500.0 g). Can be formed. And when the said recycled pulp fiber exists in aqueous solution (For example, in the manufacturing method of recycled pulp fiber, when recycled pulp fiber is collect | recovered as aqueous solution), Comprising: Solid content concentration of recycled pulp fiber is 5.0 mass% When it is above, an aqueous dispersion having a solid content concentration of the cycle pulp fiber of 5.0% by mass can be prepared by adding deionized water to the aqueous solution.

  Further, when the recycled pulp fiber is present in an aqueous solution and the solid content concentration of the recycled pulp fiber is less than 5.0% by mass, the solid content concentration of the recycled pulp fiber is 5.0% by mass by filtration. Or use the aqueous solution itself as an aqueous dispersion to increase the inoculation amount of the serially diluted sample described below (for example, inoculation when the solid content concentration of recycled pulp fiber is 2.5% by mass) Double the amount).

(2) The aqueous dispersion is stirred for 15 minutes at a rotational speed of 300 rpm using an overhead stirrer.
(3) Put 50 mL of the aqueous dispersion stirred using an overhead stirrer into a sterile bag with a filter (sterilized bag with a filter for homogenizer, manufactured by LMS) and stir for 5 minutes.
(4) The filtered aqueous dispersion filtered through a sterilized bag with a filter is dispensed into a sterilized test tube, diluted 10-fold to 10 ^-9 , and dispensed into a sterilized test tube. Prepare.

(5-1) The number of intestinal bacteria is measured by a plate culture method.
Specifically, 0.1 mL of each serially diluted sample is inoculated on a BTB lactose-added agar medium (Nippon Becton Dickinson, 251251), and the serially diluted sample is applied with a conage bar and cultured at 35 ° C. for 24 hours. .
(5-2) The number of general viable bacteria is measured by the pour culture method.
Specifically, 1 mL of a serially diluted sample and a standard agar medium (manufactured by Nippon Pharmaceutical Co., Ltd., 396-00175 SCD agar medium “Daigo”, 15 to 20 g) for examination of viable bacteria are placed in a petri dish and mixed at 35 ° C. for 48 hours. Incubate.

(6) In each of the number of enteric bacteria and the number of general viable bacteria, the number of colonies that have grown after culture is counted.
In all serially diluted samples that have been serially diluted 10 times to 10 ⁻⁹ , if the number of colonies is zero, it is determined that the target bacteria are “not detected”.
(7) When colonies of intestinal bacteria or general living bacteria are formed after culturing, the type of bacteria can be identified. The identification can be performed by a biochemical property inspection method.

The recycled pulp fiber of the present disclosure preferably has a ΔYI of 0 to 20, more preferably 0 to 15 and even more preferably 0 to 10 with respect to a standard white board. By doing so, it is difficult for the user to feel psychological resistance to the article using the recycled pulp fiber.
The recycled pulp fiber of the present disclosure preferably has a ΔW of 0 to 20, more preferably 0 to 15 and even more preferably 0 to 10 with respect to a standard white board. By doing so, it is difficult for the user to feel psychological resistance to the article using the recycled pulp fiber.

ΔYI and ΔW of the recycled pulp fiber can be measured as follows.
(1) Prepared recycled pulp fiber dried at 120 ° C. for 60 minutes in a constant temperature and humidity chamber of temperature: 20 ± 5 ° C. and humidity: 65 ± 5% RH, and the recycled pulp fiber has a moisture content of 50% by mass. Deionized water is added to form a wet recycled pulp fiber, and the wet recycled pulp fiber is allowed to stand in a sealed container for 24 hours.
In addition, a moisture content (mass%) means the ratio of deionized water with respect to the recycled pulp fiber dried at 120 degreeC for 60 minutes.
(2) A colorimetric color difference meter (ZE2000 type—manufactured by Nippon Denshoku Industries Co., Ltd.) manufactured by Nippon Denshoku Industries Co., Ltd. is prepared in a constant temperature and humidity chamber of temperature: 20 ± 5 ° C. and humidity: 65 ± 5% RH. To do.

(3) 4.5 g of wet recycled pulp fiber is uniformly spread on a glass window (diameter 40 mm) of a sample table of the color difference meter.
(4) A black plate (size: 80 mm × 80 mm, mass: 280 g) attached to the color difference meter is placed on the spread recycled pulp fiber, and a load is applied to the recycled pulp fiber.
(5) The color difference meter is selected as mode: reflection, transmission window diameter: 30 mm, YI value and W value of recycled pulp fiber are measured, and ΔYI which is a color difference (absolute value) from the YI value of a standard white board (= | [YI value of recycled pulp fiber] − [YI value of standard white board] |) and ΔW (= | [W value of recycled pulp fiber] −) which is a color difference (absolute value) between the W value of the standard white board [W value of standard white board] |) is calculated.
(6) Using different recycled pulp fibers, measure a total of 10 times ΔYI and a total of 10 times ΔW, and adopt a total of 10 times of ΔYI and a total of 10 times of average value of ΔW. .

  In the present disclosure, the sanitary article is not particularly limited as long as it absorbs a protein-containing component. For example, a disposable diaper, a urine pad, a sanitary napkin, a sanitary short, a bed sheet, a pet sheet, and a food sheet Etc.

In the present disclosure, as a contact with moisture, a moisture non-absorption application that contacts moisture but does not intend to absorb moisture, and moisture absorption intended to contact and absorb moisture And usage.
Examples of the moisture non-absorbing application include cardboard, paper (printing paper, packaging paper, books, magazines, etc.) and the like.
Examples of the moisture absorbing application include disposable diapers, urine removing pads, sanitary napkins, sanitary shorts, bed sheets, pet sheets, food sheets, wet tissues, and the like.

  The recycled pulp fiber of the present disclosure is not particularly limited as long as the protein contains a predetermined concentration, but can be manufactured according to the following embodiment, for example.

[First Embodiment]
In the first embodiment, used sanitary goods for recycling are collected or obtained from the outside, and the mixture of pulp fibers and superabsorbent polymer is separated from the collected used sanitary goods, and the separated mixture Is used for the production of recycled pulp fibers. At that time, a plurality of used sanitary products are collected and collected in a collection bag (hereinafter also referred to as “collection bag”) so that excrement, bacteria, etc. do not leak outside. Each used sanitary article is rolled or folded with the top sheet facing inward so that odors, excrement, etc. do not diffuse around.

  A system 1 used in a method for producing recycled pulp fiber from a mixture of pulp fiber and superabsorbent polymer separated from used sanitary goods will be described. The system 1 is a system that collects pulp fibers from used sanitary goods and manufactures recycled pulp fibers. FIG. 1 is a block diagram illustrating an example of a system 1 according to the first embodiment. The system 1 includes an ozone treatment device 19, preferably a bag breaking device 11, a crushing device 12, a first separation device 13, a first dust removal device 14, a second dust removal device 15, and a third dust removal device 16. A second separator 17, a third separator 18, and a fourth separator 20.

  The bag breaking device 11 opens a hole in an inactivated aqueous solution in a collection bag in which used sanitary goods are enclosed. The bag breaking device 11 includes, for example, a solution tank, a stirrer, and a crushing blade. The solution tank stores the inactivated aqueous solution. The stirrer is provided in the solution tank and stirs the inactivated aqueous solution to generate a swirling flow. The crushing blade is provided in the lower part of the solution tank, and a hole is made in the collection bag drawn downward by the swirling flow of the inactivated aqueous solution in the solution tank. However, the inactivated aqueous solution is an aqueous solution that inactivates the superabsorbent polymer. Due to the inactivation, the water absorption performance of the superabsorbent polymer is lowered. As a result, the superabsorbent polymer releases water, i.e., dehydrates, to an amount acceptable for water absorption performance.

  The crushing device 12 crushes used sanitary goods in an acidic aqueous solution together with the collection bag. The crushing device 12 includes, for example, a crushing unit and a pump. The crushing unit is connected to the solution tank, and crushes the used sanitary goods (mixed liquid 91) in the collection bag sent together with the acidic aqueous solution from the solution tank in the acidic aqueous solution together with the collection bag. Examples of the crushing unit include a biaxial crusher (example: a biaxial rotary crusher, a biaxial differential crusher, a biaxial shear crusher), and specifically, a Sumi cutter (Sumitomo Heavy Industries). Environment Co., Ltd.). The pump is connected to the downstream side of the crushing part, and the crushed material obtained in the crushing part is drawn out from the crushing part together with the acidic aqueous solution (mixed liquid 92) and sent to the next step. The crushed material includes pulp fibers, superabsorbent polymer, and other materials (collecting bag material, film, nonwoven fabric, elastic body, etc.).

  The first separation device 13 stirs the mixed solution 92 containing the crushed material obtained in the crushing device 12 and the acidic aqueous solution, and removes dirt such as excrement from the crushed material. The water-absorbing polymer and the acidic aqueous solution are separated (mixed solution 93) and sent to the first dust removing device 14. Examples of the first separation device 13 include a washing machine including a washing tub / dehydration tub and a water tub surrounding the washing tub, and specifically, a horizontal washing machine ECO-22B (made by Inamoto Seisakusho Co., Ltd.). A washing tank / dehydration tank (rotating drum) is used as a washing tank / sieving tank (separation tank).

  The first dust removing device 14 is configured to treat the acidic aqueous solution (mixed solution 93) containing the pulp fibers and the superabsorbent polymer sent from the first separating device 13 with a screen having a plurality of openings. It isolate | separates into a water absorbing polymer (mixed liquid 94) and another material (foreign material). The pH of the acidic aqueous solution is preferably maintained within a predetermined range from the viewpoint of inactivating the superabsorbent polymer (including adjusting the size and specific gravity). The predetermined range is a range where the variation in pH is within ± 1.0, and is adjusted by adding an acidic solution or the like as necessary. Examples of the first dust removing device 14 include a screen separator, and specifically, a pack pulper (manufactured by Satomi Manufacturing Co., Ltd.).

  The second dust removing device 15 is configured to treat the acidic aqueous solution (mixed solution 94) containing the pulp fibers and the superabsorbent polymer delivered from the first dust removing device 14 with a screen having a plurality of openings. It isolate | separates into a water absorbing polymer (mixed liquid 95) and another material (foreign material). The pH of the acidic aqueous solution is preferably maintained within a predetermined range as described above. As the 2nd dust removal apparatus 15, a screen separator is mentioned, for example, A lamo screen (made by Aikawa Tekko Co., Ltd.) is mentioned specifically ,.

  The third dust removing device 16 is configured to centrifuge the acidic aqueous solution (mixed solution 95) containing the pulp fiber and the highly water-absorbing polymer sent from the second dust removing device 15 to separate the pulp fiber and the highly water-absorbing polymer ( The mixture is separated into the mixed liquid 96) and other materials (foreign matter having a large specific gravity). The pH of the acidic aqueous solution is preferably maintained within a predetermined range as described above. As the 3rd dust removal apparatus 16, a cyclone separator is mentioned, for example, Specifically, ACT low concentration cleaner (made by Aikawa Tekko Co., Ltd.) is mentioned. An acidic aqueous solution containing pulp fibers and a superabsorbent polymer at a predetermined flow rate so that the pulp fibers and superabsorbent polymer in the acidic aqueous solution having a relatively low specific gravity rise and foreign matters (metal, etc.) having a high specific gravity descend. The mixed liquid 95) is supplied into the inverted conical housing of the third dust removing device 16.

  The second separation device 17 is configured to treat an acidic aqueous solution (mixed solution 96) containing pulp fibers and a superabsorbent polymer sent from the third dust removing device 16 with a screen having a plurality of openings. Liquid 97) and a superabsorbent polymer in an acidic aqueous solution. Examples of the second separation device 17 include a drum screen separator, and specifically, a drum screen dehydrator (manufactured by Toyo Screen Co., Ltd.).

  The third separation device 18 is configured to remove the pulp fiber delivered from the second separation device 17, the superabsorbent polymer and the acidic aqueous solution (mixed solution 97) remaining unseparable by a screen having a plurality of openings. While separating into a solid (mixture 98) containing a water-absorbing polymer and a liquid containing a super-absorbent polymer and an acidic aqueous solution, pressure is applied to the solid to crush the super-absorbent polymer in the solid. Examples of the third separation device 18 include a screw press dehydrator, specifically, a screw press dehydrator (manufactured by Kawaguchi Seiki Co., Ltd.). The third separation device 18 sends the liquid containing the superabsorbent polymer and the acidic aqueous solution from the slit on the side surface of the drum screen, and removes the pulp fiber and the superabsorbent polymer from the gap of the lid whose pressure at the tip of the drum screen is adjusted. The containing solid is delivered while crushing the superabsorbent polymer. Examples of the pressure applied to the lid include 0.01 MPa or more and 1 MPa or less.

  The ozone treatment device 19 treats the pulp fiber (mixture 98) containing the crushed superabsorbent polymer in the solid delivered from the third separation device 18 with ozone. Thereby, the superabsorbent polymer is oxidized and decomposed, dissolved in the treatment liquid, removed from the pulp fiber, and recycled pulp fiber not containing the superabsorbent polymer is sent out together with the treatment liquid (mixed liquid 99). Moreover, the ozone treatment apparatus 19 decomposes the protein-containing component in the recycled pulp fiber (pulp fiber), and removes the protein-containing component that can be eluted into the water from the recycled pulp fiber (pulp fiber).

  FIG. 2 is a schematic diagram of the ozone treatment device 19. The ozone treatment device 19 includes a pretreatment device 19-1 and a treatment device 19-2. The pretreatment device 19-1 removes at least a part of the superabsorbent polymer from the pulp fibers of the mixture 98. Thereby, the viscosity of the pulp fiber containing the superabsorbent polymer of the mixture 98 is lowered. The processing device 19-2 removes at least a part of the superabsorbent polymer in the pretreatment device 19-1, and further removes the superabsorbent polymer from the pulp fibers of the mixture 98 having a reduced viscosity.

  The pretreatment device 19-1 includes a pretreatment tank 101, an ozone diffusion device 102, a pump 122 (pretreatment liquid transfer unit), a pump 121 (pretreatment liquid circulation unit), and an ozone decomposition device 103. Yes.

The pretreatment tank 101 is a tank containing the pretreatment liquid P1. The pretreatment liquid P1 is initially water, for example, and pretreatment ozone Z1 (described later) dissolves as the treatment of the pretreatment device 19-1 proceeds, or the ozone Z1 is dissolved in advance. Also good.
The ozone diffusing device 102 is a device for diffusing the pretreatment ozone Z1 into the pretreatment liquid P1 in the pretreatment tank 101, and includes an ozone diffusing unit 102a and an ozone generating unit 102b. The ozone generator 102b generates pretreatment ozone Z1 that decomposes the superabsorbent polymer so that it can be dissolved in the pretreatment liquid P1.

  The ozone diffusion unit 102a is provided in the pretreatment tank 101, and in the pretreatment liquid P1, the mixture 98 (a superabsorbent polymer is removed from the bottom of the pretreatment tank 101 and present in the pretreatment liquid P1). The pretreatment ozone Z1 is diffused from below the mixture 98. For example, the ozone Z1 is diffused into a large number of fine bubbles. Thereby, the superabsorbent polymer of the mixture 98 is oxidized and decomposed and dissolved in the pretreatment liquid P1. That is, the superabsorbent polymer of the pulp fiber is reduced, and the viscosity of the pulp fiber containing the superabsorbent polymer is lowered.

  The pump 122 (pretreatment liquid transfer unit) connects the delivery port 101c provided at the lower part of the pretreatment tank 101 and the supply port 105a provided at the upper part of the treatment tank 105 (described later) of the processing apparatus 19-2. It is provided in the middle of the piping 135 to be performed. The pump 122 removes at least a part of the pretreatment liquid P1 containing the mixture 98 in which the superabsorbent polymer is reduced in the pretreatment tank 101 from the lower part of the pretreatment tank 101, and the treatment liquid P2 from the upper part of the treatment tank 105. Transfer to

The pump 121 (pretreatment liquid circulation unit) is provided in the middle of a pipe 132 that connects a delivery port 101 b provided in the lower part of the pretreatment tank 101 and a supply port 101 a provided in the upper part of the pretreatment tank 101. . The pump 121 extracts at least a part of the pretreatment liquid P1 containing the mixture 98 from the lower part of the pretreatment tank 101 and supplies it from the upper part of the pretreatment tank 101 into the pretreatment liquid P1. The pump 121 receives an aqueous solution obtained by mixing the mixture 98 and water via the pipes 131 and 132 and supplies the aqueous solution from the supply port 101 a to the pretreatment tank 101 via the pipe 132. The flow of the liquid in the pipes 131 and 132 is controlled by the valve V1 of the pipe 131 and the valve V2 of the pipe 132.
The ozone decomposing apparatus 103 receives the ozone Z1 accumulated in the upper part of the pretreatment tank 101 via the pipe 134, decomposes ozone, renders it harmless, and releases it to the outside.

  The pretreatment liquid P1 in the pretreatment tank 101 is initially only the pretreatment liquid P1, and as the process proceeds, the mixture 98, pretreatment ozone Z1, and the like are mixed with the original pretreatment liquid P1. However, in the first embodiment, they are collectively referred to as a pretreatment liquid P1.

  The processing device 19-2 includes a processing tank 105, an ozone supply device (ozone supply unit) 106, an ejector 107, a pump 123 (an aqueous solution supply unit, a processing liquid circulation unit), a pump 124, and an ozonolysis device 108. Is provided.

  The processing tank 105 is a tank containing the processing liquid P2, and a cylindrical shape is preferable from the viewpoint of allowing a mixed liquid 98L (described later) discharged from the ejector 107 to easily generate a swirling flow in the processing liquid P2. For example, the treatment liquid P2 is initially water, and as the treatment of the treatment device 19-2 progresses, the processing ozone Z2 (described later) melts, and as the treatment of the pretreatment device 19-1 progresses. The pretreatment liquid P1 containing the mixture 98 (superabsorbent polymer and pulp fiber) is contained. Alternatively, ozone Z2 may be dissolved in advance.

The ozone supply device 106 generates ozone Z2 that decomposes the superabsorbent polymer so that it can be dissolved in the treatment liquid P2, and supplies the ozone Z2 to the ejector 107.
The pump 123 (aqueous solution supply unit, treatment liquid circulation unit) supplies an aqueous solution containing a mixture 98 of a superabsorbent polymer and pulp fibers to the ejector 107. The pump 123 is provided in the middle of the pipe 136, and the pipe 136 connects the delivery port 105b at the lower part of the processing tank 105 and the supply port 105c at the lower part of the processing tank 105 and above the delivery port 105b. Yes. The pipe 136 in the vicinity of the supply port 105c is preferably inclined slightly upward from the viewpoint of easily raising the swirl flow formed by the mixed liquid 98L discharged from the ejector 107 in the processing liquid P2.

  The ejector 107 (aspirator) is provided in the middle of the pipe 136 and has a driving fluid supply port DI, a suction fluid supply port AI, and a mixed fluid discharge port CO. The ejector 107 causes the driving fluid to flow from the driving fluid supply port DI to the mixed fluid discharge port CO, makes the constriction part in the middle of the flow path depressurized by the venturi effect, and draws the suction fluid from the suction fluid supply port AI to the constriction part. It is mixed with the driving fluid and discharged from the mixed fluid discharge port CO as a mixed fluid.

  Here, the treatment liquid P2 containing the superabsorbent polymer and pulp fiber (mixture) in the treatment tank 105 is supplied to the driving fluid supply port DI by the pump 123 and flows toward the mixed fluid discharge port CO. Accordingly, ozone Z2 from the ozone supply device 106 is sucked into the ejector 107 from the suction fluid supply port AI. As a result, the treatment liquid P2 containing the superabsorbent polymer and the pulp fiber and the ozone Z2 are mixed and discharged as a mixed liquid 98L from the mixed fluid discharge port CO to the treatment tank 105. While the superabsorbent polymer is oxidatively decomposed and removed by the ozone Z2, the discharged mixed liquid swirls in the processing tank 105 and gradually rises upward while stirring the processing liquid P2.

The pump 124 is provided in the middle of a pipe 139 that connects a delivery port 105d provided in the lower portion of the processing tank 105 and a subsequent device (not shown). The pump 124 extracts at least a part of the processing liquid P2 containing the mixture 98 from which the superabsorbent polymer has been removed in the processing tank 105 from the lower part of the processing tank 105, and transfers it to the subsequent apparatus.
The ozone decomposing apparatus 108 receives the ozone Z2 accumulated in the upper part of the treatment tank 105 through the pipe 138, decomposes the ozone Z2, detoxifies it, and releases it to the outside.

  The processing liquid P2 in the processing tank 105 is initially only the processing liquid P2, and as the processing proceeds, a mixture, ozone, and the like are mixed with the initial processing liquid P2. In the embodiment, they are collectively referred to as processing liquid P2.

  In the ozone treatment device 19, the pretreatment device 19-1 and the treatment device 19-2 are used in combination for the following reason. In terms of processing efficiency, it is better to use only the processing device 19-2 including the ejector 107. However, in the aqueous solution containing the mixture 98 supplied to the ozone treatment device 19, if the concentration of the superabsorbent polymer adhering to the pulp fiber is high, the viscosity of the mixture 98 increases and the ejector 107 may be clogged. . Therefore, in order to deal with this, in the first embodiment, first, the aqueous solution containing the mixture 98 is processed by the pretreatment device 19-1, so that the viscosity of the mixture 98 is reduced to the extent that the ejector 107 is not clogged. That is, it becomes easy to reduce the superabsorbent polymer. Further, the protein-containing component in the recycled pulp fiber (pulp fiber) is decomposed, and the protein-containing component that can be eluted into the water from the recycled pulp fiber (pulp fiber) can be easily removed.

  Next, the fourth separation apparatus 20 separates the treatment liquid (mixed liquid 99) containing the pulp fibers treated by the ozone treatment apparatus 19 into the treatment liquid and the pulp fibers using a screen having a plurality of openings. Thereby, recycled pulp fibers are collected.

  Next, a method for producing recycled pulp fiber from a mixture of pulp fiber and superabsorbent polymer separated from used sanitary goods will be described. FIG. 3 is a flowchart illustrating an example of a method according to the first embodiment. This method includes an ozone treatment step S19, and preferably a perforation step S11, a crushing step S12, a first separation step S13, a first dust removal step S14, a second dust removal step S15, and a third dust removal step. S16, 2nd isolation | separation process S17, 3rd isolation | separation process S18, and 4th isolation | separation process S20 are provided. This will be described below.

  The hole making step S11 is executed by the bag breaking device 11. The collection bag enclosing the used sanitary goods is put into a solution tank in which the inactivated aqueous solution is stored, and a hole is made in the surface in contact with the inactivated aqueous solution in the collection bag. When the collection bag is perforated, the inactivated aqueous solution is sealed around the collection bag so that dirt, bacteria, odors, etc. of used sanitary goods in the collection bag are not released to the outside. When the inactivated aqueous solution enters the collection bag from the hole, the gas in the collection bag escapes to the outside of the collection bag A, the specific gravity of the collection bag becomes heavier than that of the inactivated aqueous solution, and the collection bag becomes more in the inactivated aqueous solution in the solution tank. It sinks deeply. The inactivated aqueous solution inactivates the superabsorbent polymer in the used sanitary goods in the collection bag.

The superabsorbent polymer in the used sanitary goods is inactivated and its water absorption capacity is reduced, so that the superabsorbent polymer is dehydrated and the particle size is reduced. As a result, in each subsequent process, the handling of the pulp fiber containing the superabsorbent polymer is simplified, and the processing efficiency is improved.
Examples of the inactivated aqueous solution include an acidic aqueous solution and an aqueous solution containing a polyvalent metal ion.

  When an acidic aqueous solution (for example, an aqueous solution containing an inorganic acid or an organic acid) is used as the inactivating aqueous solution, the ash content of recycled pulp fiber can be lowered as compared with the case of using an aqueous solution containing a polyvalent metal ion, and It becomes easy to adjust the degree of inactivation (particle size, specific gravity, etc.) of the superabsorbent polymer by pH.

  The pH of the acidic aqueous solution is preferably 1.0 or more and 4.0 or less, and more preferably 1.2 or more and 2.5 or less. If the pH is too high, the water-absorbing ability of the superabsorbent polymer cannot be sufficiently lowered, and the sterilizing ability may be lowered. If the pH is too low, the equipment may be corroded, and a lot of alkaline chemicals are required for the neutralization treatment in the wastewater treatment. In particular, in order to separate the pulp fiber and the superabsorbent polymer from other materials, it is preferable that the size and specific gravity of the pulp fiber are relatively close to the size and specific gravity of the superabsorbent polymer. . Therefore, by setting the pH of the acidic aqueous solution to 1.0 or more and 4.0 or less, the highly water-absorbing polymer can be made smaller by inactivation, and thereby the size, specific gravity, etc. of the pulp fiber and the highly water-absorbing polymer Can be relatively close to each other.

Examples of the organic acid include citric acid, tartaric acid, gluconic acid, glycolic acid, malic acid and the like, and hydroxycarbonate organic acids such as citric acid are particularly preferable. Due to the chelating effect of citric acid, metal ions and the like in excreta can be trapped and removed, and the cleaning effect of citric acid can be expected to provide a high soil removal effect. Examples of the inorganic acid include sulfuric acid, hydrochloric acid, and nitric acid, but sulfuric acid is preferable from the viewpoint of not containing chlorine and cost. The organic acid concentration of the organic acid aqueous solution is not particularly limited, but when the organic acid is citric acid, it is preferably 0.5% by mass or more and 4% by mass or less. The inorganic acid concentration of the inorganic acid aqueous solution is not particularly limited, but when the inorganic acid is sulfuric acid, it is preferably 0.1% by mass or more and 0.5% by mass or less.
In addition, in this specification, pH means pH at the temperature of 20 degreeC.

Examples of the polyvalent metal salt include alkaline earth metal ions and transition metal ions.
Examples of the alkaline earth metal ions include beryllium, magnesium, calcium, strontium and barium ions. The alkaline earth metal ions are preferably calcium chloride, calcium nitrate, calcium hydroxide, calcium oxide, magnesium chloride, magnesium nitrate, and more preferably an aqueous calcium chloride solution.

  The transition metal ion is not particularly limited as long as it is incorporated into the superabsorbent polymer, and examples thereof include ions of iron, cobalt, nickel, copper and the like. The transition metal ion is preferably an inorganic acid salt or an organic acid salt from the viewpoints of cost, availability, and the like. Examples of the inorganic acid salt include iron salts such as iron chloride, iron sulfate, iron phosphate and iron nitrate, cobalt salts such as cobalt chloride, cobalt sulfate, cobalt phosphate and cobalt nitrate, nickel salts such as nickel chloride and nickel sulfate. And copper salts such as copper chloride and copper sulfate. Examples of the organic acid salts include iron lactate, cobalt acetate, cobalt stearate, nickel acetate, and copper acetate.

  The crushing step S12, the first separation step S13, the first dust removal step S14, the second dust removal step S15, the third dust removal step S16, the second separation step S17, and the third separation step S18 are respectively the crushing device 12 and the first separation step S18. The separation device 13, the first dust removal device 14, the second dust removal device 15, the third dust removal device 16, the second separation device 17, and the third separation device 18 are implemented. Since it is already completed, description here is abbreviate | omitted.

  The ozone treatment step S19 is performed by the ozone treatment device 19. The pulp fibers in the solid delivered from the third separator 18 and the crushed superabsorbent polymer (mixture 98) are treated with an aqueous solution containing ozone. Thereby, the superabsorbent polymer is oxidatively decomposed and removed from the pulp fiber. As a result, the superabsorbent polymer adhering to the pulp fiber of the mixture 98 (eg, remaining on the surface of the pulp fiber) is oxidatively decomposed by an aqueous solution (treatment liquid) containing ozone, and has a low molecular weight that is soluble in the aqueous solution. It is removed from the pulp fiber by changing to an organic substance. Moreover, the protein-containing component adhering to the surface or inside of the pulp fiber is decomposed by the ozone treatment, and the protein-containing component that can be eluted into the water is removed from the pulp fiber (recycled pulp fiber).

  The ozone treatment device 19 shown in FIG. 2 performs a pretreatment supply step S19-1a, a pretreatment step S19-1b, and a pretreatment liquid transfer step S19-1c in the pretreatment device 19-1 as the ozone treatment step S19. In the processing device 19-2, a supply process S19-2a and a processing process S19-2b are further performed.

The pretreatment supply step S19-1a supplies the mixture 98 into the pretreatment liquid P1 in the pretreatment tank 101.
In the pretreatment step S19-1b, the ozone Z1 is pretreated from below the mixture toward the mixture 98 existing in the pretreatment liquid P1 away from the bottom of the pretreatment vessel 101 in the pretreatment vessel 101. It dissipates by the ozone dissipating part 102a in the tank 101, and the superabsorbent polymer in the mixture 98 is reduced.
In the pretreatment liquid transfer step S19-1c, at least part of the pretreatment liquid P1 including the mixture 98 in which the superabsorbent polymer is reduced in the pretreatment step S19-1b is extracted from the lower part of the pretreatment tank 101, Transfer from the upper part of the treatment tank 101 to the treatment liquid P2.

Specifically, it is as follows.
In the pretreatment supply step S19-1a, the mixture 98 containing the pulp fibers (the superabsorbent polymer remains) separated in the third separation step S18 is added with water to form an aqueous solution. The aqueous solution is supplied into the pretreatment liquid P1 from the supply port 101a at the upper part of the pretreatment tank 101 by the pump 121 via the pipes 131 and 132 (V1 open, V2 closed).

  Next, in the pretreatment step S19-1b, the pretreatment liquid P1 is an acidic aqueous solution (for suppressing ozone deactivation and inactivating the superabsorbent polymer), and has a specific gravity of about 1. Accordingly, the pulp fibers settle from the upper part to the lower part of the pretreatment liquid P1. On the other hand, ozone Z1 containing ozone generated by the ozone generator 102b is diffused from the ozone diffuser 102a to the pretreatment tank 101 via the pipe 133. The ozone Z1 is continuously dissipated in the state of fine bubbles (eg, microbubbles or nanobubbles) from near the lower part of the pretreatment tank 101 into the pretreatment liquid P1, and rises from the lower part to the upper part of the pretreatment liquid P1. Go.

  Next, in the pretreatment liquid P1, pulp fibers that settle from the upper part to the lower part and ozone Z1 that rises from the lower part to the upper part collide while proceeding in opposition. The ozone Z1 adheres to the surface of the pulp fiber so as to wrap the pulp fiber. At that time, ozone in the ozone Z1 reacts with the superabsorbent polymer in the pulp fiber, oxidatively decomposes the superabsorbent polymer, and dissolves it in the pretreatment liquid P1. Since it is a counterflow, the contact probability of the superabsorbent polymer contained in the pulp fiber and the ozone Z1 can be increased. Thereby, the superabsorbent polymer of a pulp fiber is reduced and the viscosity of the pulp fiber containing a superabsorbent polymer is reduced. Therefore, in the subsequent processing step S19-2b, the ejector 107 can be prevented from being clogged with pulp fibers containing the superabsorbent polymer.

  Next, in the pretreatment liquid transfer step S19-1c, at least a part of the pretreatment liquid P1 including the mixture 98 in which the superabsorbent polymer is reduced in the pretreatment step S19-1b is sent to the lower part of the pretreatment tank 101. 101c is pulled out by a pump 122 through a pipe 135 and supplied from the supply port 105a at the top of the processing tank 105 into the processing liquid P2. In addition, ozone of ozone Z1 containing ozone accumulated in the upper part of the pretreatment tank 101 is decomposed by the ozone decomposing apparatus 103, detoxified, and released to the outside.

  However, the pretreatment supply step S19-1a is a step of extracting at least a part of the pretreatment liquid P1 containing the mixture from the lower part of the pretreatment tank 101 and supplying it from the upper part of the pretreatment tank 101 into the pretreatment liquid P1. You may have. Specifically, at least a part of the pretreatment liquid P1 containing the mixture is drawn by the pump 121 from the delivery port 101b at the lower part of the pretreatment tank 101 via the pipes 131 and 132 (V1 closed, V2 open). It is supplied into the pretreatment liquid P1 from the supply port 101a at the top of the processing tank 101.

Supply process S19-2a supplies ozone Z2 to the suction fluid supply port AI of the ejector 107, supplying the aqueous solution containing the mixture 98 to the drive fluid supply port DI of the ejector 107.
In the processing step S19-2b, the mixed solution 98L in which the aqueous solution and the ozone Z2 are mixed in the ejector 107 is processed in the processing tank 105 from the mixed fluid discharge port CO of the ejector 107 connected to the lower part of the processing tank 105. By discharging into the liquid P2, the superabsorbent polymer in the mixture 98 is reduced.

  Specifically, it is as follows. In the pretreatment liquid transfer step S19-1c, at least a part of the pretreatment liquid P1 including the mixture 98 in which the superabsorbent polymer is reduced is supplied into the treatment liquid P2 of the treatment tank 105, and the mixture 98 is treated with the treatment liquid P2. And contained in the processing liquid P2. The treatment liquid P2 is an acidic aqueous solution (for suppressing deactivation of ozone and inactivating the superabsorbent polymer) and has a specific gravity of about 1.

  In the supply step S19-2a, at least a part of the processing liquid P2 including the mixture 98 is drawn from the lower portion of the processing tank 105 and supplied to the driving fluid supply port DI as an aqueous solution. That is, at least a part of the treatment liquid P2 containing the pretreatment liquid P1 containing the mixture 98 is drawn out from the delivery port 105b at the lower part of the treatment tank 105 by the pump 123 via the pipe 136, and is driven as an aqueous solution of the ejector 107 Supplied to the supply port DI. Next, ozone Z2 containing ozone generated by the ozone supply device 106 is supplied to the suction fluid supply port AI of the ejector 107 via the pipe 137.

  In the subsequent processing step S19-2b, the mixed liquid 98L generated by mixing the processing liquid P2 containing the mixture 98 and the ozone Z2 in the ejector 107 is discharged from the mixed fluid discharge port CO to the processing liquid P2 in the processing tank 105. The At this time, since the treatment liquid P2 containing the mixture 98 and the ozone Z2 are mixed in a very narrow region in the ejector 107, the mixture 98L of the pulp fiber / superabsorbent polymer mixture 98 and the ozone Z2 is very close. Can be formed.

  Further, the mixed liquid 98L is discharged into the processing liquid P2 in the processing tank 105, whereby the processing liquid P2 can be stirred. Since the ozone Z2 is continuously discharged in a fine bubble state (example: microbubble or nanobubble) when discharged to the processing liquid P2, it can diffuse very widely in the processing liquid P2. By these, the contact probability of the superabsorbent polymer contained in the pulp fiber in the treatment tank 105 and the ozone contained in the ozone Z2 can be extremely increased. Thereby, the superabsorbent polymer is removed from the pulp fiber. Thereby, the protein-containing component adhering to the surface or inside of the pulp fiber is decomposed, and the protein-containing component that can be eluted into water from the pulp fiber (recycled pulp fiber) is removed.

  Thereafter, at least a part of the treatment liquid P2 containing the pulp fiber from which the superabsorbent polymer has been removed in the treatment step S19-2b is drawn out from the delivery port 105d at the bottom of the treatment tank 105 by the pump 124, The mixed liquid 99 is transferred to the subsequent apparatus. Note that the ozone Z2 containing ozone accumulated in the upper part of the treatment tank 105 is decomposed and detoxified by the ozone decomposing apparatus 108 and released to the outside.

When supplying ozone Z1 and Z2 containing ozone to the pretreatment liquid P1 and the treatment liquid P2, the ozone concentration in the pretreatment liquid P1 and the treatment liquid P2 is, for example, 1 to 50 ppm by mass. As for the ozone concentration in ozone Z1 and Z2, 40-200 g / m < ³ > is mentioned, for example. As for the density | concentration of the pulp fiber (a super absorbent polymer is included) in ozone Z1 and Z2, 0.1-20 mass% is mentioned, for example. The time for which the pulp fibers are present in the pretreatment tank 101 and the treatment tank 105 is, for example, 2 minutes to 60 minutes. The ozone Z1 and Z2 are preferably supplied into the pretreatment liquid P1 and the treatment liquid P2 as microbubbles or nanobubbles. Microbubbles have a bubble diameter of about 1-1000 μm, and nanobubbles have a bubble diameter of about 100-1000 nm.

  Microbubbles or nanobubbles are fine bubbles, have a large surface area per unit volume, and a slow rising rate in the liquid, so that the probability of bubbles coming into contact with pulp fibers can be increased and the surface of many pulp fibers can be contacted. . As a result, the pulp fibers can be uniformly wrapped with fine bubbles, and the contact area between the pulp fibers and ozone can be further increased. Moreover, due to the buoyancy of the bubbles, the sedimentation rate of the pulp fiber containing the superabsorbent polymer can be reduced, and the contact time between the pulp fiber and ozone can be further increased. Therefore, the superabsorbent polymer contained in the pulp fiber can be more reliably oxidized and decomposed and easily removed from the pulp fiber. Moreover, the protein-containing component adhering to the surface or inside of the pulp fiber is more reliably decomposed, and the protein-containing component that can be eluted into the water from the pulp fiber (recycled pulp fiber) can be easily removed.

  In addition, the deactivation of ozone can be suppressed and the effect of ozone (oxidative decomposition of superabsorbent polymer, removal of protein-containing components, bleaching, deodorization) can be enhanced by using an acidic aqueous solution as the treatment solution. it can. In addition, in addition to being able to inactivate highly water-absorbing polymers, there is continuity between treatments when using an acidic aqueous solution in crushing treatment, dust removal treatment, etc. There is no fear of any inconvenience, and the process can be performed stably and reliably. Moreover, the organic acid of acidic aqueous solution is preferable from a viewpoint of reduction of the influence on an operator, an apparatus, etc. by an acid, and a citric acid is preferable especially from a viewpoint of removal of a metal.

  The fourth separation step S20 is executed by the fourth separation device 20, and the treatment liquid containing pulp fibers treated by the ozone treatment device 19, that is, the mixed solution 99 passes through the screen having a plurality of openings and is mixed. The pulp fiber and the treatment liquid are separated from the liquid 99. As a result, the processing liquid P <b> 2 is separated from the mixed liquid 99 through the screen and sent out from the fourth separator 20. The separated treatment liquid P2, that is, the ozone treatment liquid, may be returned to the ozone treatment apparatus 19 and reused. The cost of the ozone treatment liquid can be reduced. On the other hand, the pulp fibers in the mixed solution 99 cannot pass through the screen and remain in the fourth separation device 20 or are sent out separately.

The concentration of ozone in the aqueous solution is measured as follows.
(1) About 0.15 g of potassium iodide, 5 mL of a 10% by mass citric acid solution, and 85 mL of a sample in which ozone is dissolved are put into a 100 mL graduated cylinder.
(2) After reacting the contents of the graduated cylinder, the reaction product is transferred to a 200 mL Erlenmeyer flask.
(3) A starch solution is added to the Erlenmeyer flask and colored purple.
(4) While stirring the contents of the Erlenmeyer flask, titrate with 0.01 mol / L sodium thiosulfate until the contents of the Erlenmeyer flask become colorless, and read titration: A (mL).
(5) The concentration of ozone (mass ppm) in the aqueous solution is expressed by the following formula:
Concentration of ozone in aqueous solution (mass ppm)
= A (mL) x 0.24 x 0.85 (mL)
Calculated by

  Since the ozone Z2 is continuously discharged in the form of fine bubbles when discharged to the processing liquid P2, it can diffuse extremely widely in the processing liquid P2. Thereby, not only the pulp fibers in the mixed liquid 98L discharged from the ejector 107 but also the pulp fibers in the treatment liquid in the treatment tank 105, the reaction between the superabsorbent polymer and the protein-containing component and the ozone Z2. Can proceed very efficiently. Then, the superabsorbent polymer and the protein-containing component in the mixture 98 can be appropriately oxidized and decomposed and removed by dissolving in the treatment liquid P2, and the unevenness of the pulp fiber treatment can be suppressed. Thereby, the purity of the recycled pulp fiber can be increased, and a recycled pulp fiber that can be easily reused can be produced. Therefore, the superabsorbent polymer can be appropriately removed from the pulp fiber, and the recycled pulp fiber can be efficiently produced.

[Second Embodiment]
In the second embodiment, the ozone treatment step S19a and the ozone treatment device 19a are different from the ozone treatment step S19 and the ozone treatment device 19 in the first embodiment, respectively. Hereinafter, differences will be mainly described.

  FIG. 4 is a schematic diagram of the ozone treatment device 19a. The ozone treatment device 19a includes a pretreatment device 19a-1 and a treatment device 19a-2. The basic configurations of the preprocessing device 19a-1 and the processing device 19a-2 are the same as the preprocessing device 19-1 and the processing device 19-2 of the first embodiment. However, the pipe 135 branches at a halfway branch point Q1, the branched branch pipe 135a merges with the pipe 136 at the junction Q2, and is connected to the drive fluid supply port DI of the ejector 107. It is different. Thereby, the ozone treatment apparatus 19a can select at least one of the treatment tank 105 and the ejector 107 as a supply destination of the pretreatment liquid P1 of the pretreatment tank 101. For example, the ozone treatment device 19a includes a valve V3 positioned downstream of the branch point Q1 in the middle of the pipe 135, a valve V4 positioned in the middle of the branch pipe 135a between the branch point Q1 and the junction point Q2, and a pipe 136. And a valve V5 located on the upstream side of the midway junction Q2. The supply destination of the pretreatment liquid P1, the treatment of the treatment liquid P2, and the like can be selected by opening and closing each of the valve V3, the valve V4, and the valve V5.

  In the ozone treatment step S19a, on the condition that at least one of the pretreatment liquid P1 and the treatment liquid P2 is supplied to the drive fluid supply port DI of the ejector 107, each of the valves V3, V4, V5 is opened and closed, for example The following cases (A) to (D) can be considered. (A) Open, close, and open valves V3, V4, and V5, respectively. (B) The valves V3, V4, and V5 are closed, opened, and closed, respectively. (C) The valves V3, V4, and V5 are closed, opened, and opened, respectively. (D) Open, open, and open valves V3, V4, and V5, respectively.

  In the case of (A) above, in the pretreatment liquid transfer step S19a-1c, the pretreatment liquid P1 (containing the mixture 98 containing the superabsorbent polymer and pulp fibers) in the pretreatment tank 101 is treated via the pipe 135. 105 is supplied to the supply port 105a. On the other hand, in the supply step S19a-2a, the treatment liquid P2 (containing the mixture 98 containing the superabsorbent polymer and pulp fibers) in the treatment tank 105 is supplied to the drive fluid supply port DI of the ejector 107 through the pipe 136. This case is the same as the case of the first embodiment (FIG. 2). Therefore, the same effect as the first embodiment can be obtained.

  In the case of (B) above, in the pretreatment liquid transfer step S19a-1c, the pretreatment liquid P1 in the pretreatment tank 101 is supplied to the drive fluid supply port DI of the ejector 107 through the pipe 135 and the branch pipe 135a. Therefore, pretreatment liquid transfer process S19a-1c = supply process S19a-2a. At this time, the processing liquid P2 in the processing tank 105 is not supplied to the ejector 107. In this case, as compared with the case of the first embodiment (FIG. 2), that is, (A), all the pretreatment liquid P1 in the pretreatment tank 101 is directly supplied to the drive fluid supply port DI of the ejector 107. Therefore, since all the pulp fibers pass through the ejector 107, all the pulp fibers can be brought into contact with the ozone Z2 by the ejector 107, and the processing efficiency of removing the superabsorbent polymer can be improved.

  In the case of (C) above, in the pretreatment liquid transfer step S19a-1c, the pretreatment liquid P1 in the pretreatment tank 101 is supplied to the drive fluid supply port DI of the ejector 107 via the pipe 135 and the branch pipe 135a. Therefore, pretreatment liquid transfer process S19a-1c = supply process S19a-2a. Moreover, in supply process S19a-2a, the process liquid P2 (a super absorbent polymer and pulp fiber are included) of the process tank 105 is supplied to the drive fluid supply port DI of the ejector 107 via the piping 136. FIG. In this case, as compared with the case of (B), the processing liquid P2 in the processing tank 105 is further supplied to the driving fluid supply port DI of the ejector 107. Therefore, at least a part of the pulp fiber that has once passed through the ejector 107 can be further passed through the ejector 107. That is, at least a part of the pulp fiber can be contacted with the ozone Z2 by the ejector 107 a plurality of times, and the treatment efficiency of removing the superabsorbent polymer can be further improved.

  In the case of (D) above, in the pretreatment liquid transfer step S19a-1c, the pretreatment liquid P1 in the pretreatment tank 101 is supplied to the supply port 105a of the treatment tank 105 through the pipe 135. At the same time, in the supply step S19a-2a, the pretreatment liquid P1 in the pretreatment tank 101 is supplied to the drive fluid supply port DI of the ejector 107 through the pipe 135 and the branch pipe 135a. Moreover, in supply process S19a-2a, the process liquid P2 (a super absorbent polymer and pulp fiber are included) of the process tank 105 is supplied to the drive fluid supply port DI of the ejector 107 via the piping 136. FIG. In this case, as compared with the case of the first embodiment (FIG. 2), that is, (A), a part of the pretreatment liquid P1 in the pretreatment tank 101 is directly supplied to the drive fluid supply port DI of the ejector 107. . Therefore, a part of the pulp fiber surely passes through the ejector 107, so that a part of the pulp fiber can be reliably brought into contact with the ozone Z2 by the ejector 107, and the processing efficiency of removing the superabsorbent polymer can be improved.

[Third Embodiment]
In the third embodiment, the ozone treatment step S19b and the ozone treatment device 19b are different from the ozone treatment step S19 and the ozone treatment device 19 in the first embodiment, respectively. Hereinafter, differences will be mainly described.

  FIG. 5 is a schematic diagram of the ozone treatment device 19b. The ozone treatment device 19b is different from the ozone treatment device 19 of the first embodiment in that the pretreatment device and the (main) treatment device are integrated. That is, the pretreatment tank and the treatment tank are the same tank 101R. The pretreatment liquid and the treatment liquid are the same liquid P3. The mixed fluid discharge port CO of the ejector 107 is located in a lower part of the tank 101R than the ozone diffusing unit 102a. The pretreatment step S19-1b is carried out above the tank, and the treatment step S19-2b is carried out below the tank, whereby the ozone treatment device 19b is divided into one pretreatment tank (or treatment tank). The space of the pipe 135 connecting the space and the pretreatment tank and the treatment tank is unnecessary, and the apparatus is space-saving.

  In the third embodiment, the pretreatment step S19-1b and the treatment step S19-2b can be performed in the same tank, and the mixture 98 that has undergone the pretreatment step S19-1b is treated with the treatment step S19-2b. Therefore, since it is not necessary to transfer to another tank, the processing efficiency can be increased.

Hereinafter, although an example is given and this indication is explained, this indication is not limited to these examples.
As a protein measurement means, Modified Fisher Protein Assay Kit (lower limit of quantification: 60 μg / mL) manufactured by Thermo Fisher Scientific for ML method, and Coomassie (Bradford) assay limit of Coomassie method 7 ) And Micro BCA Protein Assay Kit for Micro BCA method (lower limit of quantification: 7 μg / mL).

[Production Example 1 and Production Example 2]
As a crushing device, using a Sumi cutter (manufactured by Sumitomo Heavy Industries Environment Co., Ltd.), a total of 1400 used disposable diapers (about 250 kg) collected from an elderly care facility were crushed, Formed. In addition, about 1 t of 0.16 mass% calcium hydroxide aqueous solution was used as an inactivation aqueous solution.
The crushed material-containing aqueous solution is introduced into a horizontal washing machine ECO-22B (manufactured by Inamoto Seisakusho Co., Ltd.) as a first separator, and pulp fibers and superabsorbent polymer are separated from other constituent materials, and pulp An aqueous solution containing fibers and a superabsorbent polymer was formed. Next, an aqueous solution containing pulp fibers and a superabsorbent polymer was passed through the first dust removing device, the second dust removing device, and the third dust removing device, and then moved to the stirring tank.

A part of the aqueous solution containing the pulp fiber and the superabsorbent polymer in the stirring layer was extracted, and the solid content concentration was adjusted to 5.0% by mass to obtain a first sample.
The first sample was centrifuged using a micro-cooled centrifuge (Model 3740, Kubota Corporation, rotation speed: 12,000 rpm, temperature: 4 ° C., time: 5 minutes). 1 (Production Example 1) was formed.

  In order to add 1 part by weight of citric acid to 1 part by weight of the solid content of the pulp fiber, 2% by weight citric acid aqueous solution is added to the stirring tank, and the contents of the stirring tank are moved to the ozone treatment device. Then, ozone treatment and ejector treatment were performed to decompose the superabsorbent polymer. A part of the contents passed through the ozone treatment apparatus was extracted to form a second sample. The solid content concentration of the second sample was about 2% by mass. The second sample was dehydrated and its solid content concentration was adjusted to about 5% by mass.

In the ozone treatment process using the ozone treatment apparatus, the ozone concentration in the pretreatment process S19-1b was 200 g / m ³ , and the ozone supply amount was 100 g / h. In the treatment step S19-2b, the ozone concentration was 200 g / m ³ and the ozone supply amount was 100 g / h.
Using a micro-cooled centrifuge (Model 3740 manufactured by Kubota Corporation, rotation speed: 12,000 rpm, temperature: 4 ° C., time: 5 minutes), the second sampling sample whose solid content concentration was adjusted to about 5 mass% was used. Centrifuge and remove sample no. 2 (Production Example 2) was formed.

[Production Example 3]
Virgin pulp fiber (manufactured by Weyerhaeuser, NB416) is dispersed in a 2% by mass citric acid aqueous solution to prepare a virgin pulp fiber dispersed aqueous solution having a solid content concentration of 5.0% by mass, and a virgin pulp fiber dispersed aqueous solution is produced. Under the same conditions as in Example 2, ozone treatment and ejector treatment were performed. A part of the treated virgin pulp fiber-dispersed aqueous solution was withdrawn to form a third withdrawn sample. The solid content concentration of the third sample was adjusted to 5.0% by mass.
The third sample was centrifuged using a micro-cooled centrifuge (Model 3740, Kubota Corporation, rotation speed: 12,000 rpm, temperature: 4 ° C., time: 5 minutes). 3 was formed.

[Production Example 4]
Superabsorbent polymer (Sumitomo Seika Co., Ltd., Aqua Keep) is dispersed in a 2% by mass citric acid aqueous solution to prepare a superabsorbent polymer dispersed aqueous solution having a solid content concentration of 5.0% by mass. The aqueous polymer dispersion was subjected to ozone treatment and ejector treatment under the same conditions as in Production Example 2. A part of the superabsorbent polymer-dispersed aqueous solution after the treatment was extracted to form a fourth sample. The fourth sampling sample contained decomposed superabsorbent polymer corresponding to 5% by mass of superabsorbent polymer.
The fourth sample was centrifuged using a micro-cooled centrifuge (Model 3740, Kubota Corporation, rotation speed: 12,000 rpm, temperature: 4 ° C., time: 5 minutes). 4 was formed.

[Production Example 5 and Production Example 6]
Sample No. To each of 3 and 4, bovine serum albumin (BSA) was added so that the concentration of BSA was 100 μg / mL (for ML method) and 20 μg / mL (Coomassie method and Micro BCA method). 5 and 6 were prepared.

[Production Example 7 and Production Example 8]
Sample No. Among the filtrate and the residue obtained by ultrafiltration of No. 2, the filtrate was sample No. It was set to 7.
The residue is washed with an ultrafiltration filter using approximately the same amount of deionized water as the filtrate, and the washing solution is washed with a micro-cooled centrifuge (Model 3740 manufactured by Kubota Corporation, rotation speed: 12). 000 rpm, temperature: 4 ° C., time: 5 minutes). 8 was formed.

[Example 1]
[Create calibration curve]
Calibration curves were prepared according to the methods described in Modified Lowry Protein Assay Kit, Coomassie (Bradford) Protein Assay Kit, and Micro BCA Protein Assay Kit.

[Measurement of protein concentration]
Sample No. The protein concentrations of No. 1 to No. 8 were measured by the ML method, the Coomassie method, and the Micro BCA method. The results are shown in Table 1.
Specifically, in the ML method, by adding 1.0 mL of Lowry reagent to 0.2 mL of sample and incubating at room temperature for 10 minutes, then adding 100 μL of Folin-Ciocalteu reagent and incubating at room temperature for 30 minutes A test solution was prepared. Using the test solution as a control, the absorbance at 750 nm was measured with a quartz microcell having an optical path length of 1 cm using pure water as a control, and the protein concentration was calculated using a calibration curve.

  In the Coomassie method, a test solution was prepared by adding 1.0 mL of Coomassie reagent to 1.0 mL of a sample and incubating at room temperature for 10 minutes. Using the test solution as a control, the absorbance at 595 nm was measured with a quartz microcell having an optical path length of 1 cm using pure water as a control, and the protein concentration was calculated using a calibration curve.

In the Micro BCA method, 1.0 mL of a BCA Working reagent was added to 1.0 mL of a sample, and a test solution was prepared by incubating in a 60 ° C. water bath for 60 minutes. For the test solution, the absorbance at 562 nm was measured with a quartz microcell having an optical path length of 1 cm using pure water as a control, and the protein concentration was calculated using a calibration curve.
In any protein measuring means, the absorbance was measured using a UV-2450 type ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation.

[ML method]
In the ML method, sample no. 3 and no. 4 the protein concentration is below the detection limit and sample no. 5 and no. In 6, the protein concentration was 100 μg / mL, similar to the concentration of added BSA. In addition, in the ML method, sample No. whose protein is below the detection limit. 2, sample no. 7 and sample no. In 8, no protein was detected.
Therefore, it can be seen that the ML method can easily measure the total amount of protein-containing components that can be eluted into water from any recycled material of used sanitary goods at a time.

[Coomassie method]
In the Coomassie method, sample no. 3 the protein concentration is below the detection limit and sample no. In 5, the protein concentration was 22 μg / mL, similar to the concentration of added BSA. However, sample no. 4 the protein concentration was measured to be 30 μg / mL and sample no. 6 was detected at a higher concentration than the added BSA. 4 and sample no. 6 is considered to have a factor that inhibits protein quantification. In the Coomassie method, sample no. While no protein was detected from sample 7, sample no. 8 protein was detected.
From these results, it is considered that in the Coomassie method, the decomposed superabsorbent polymer exhibited a protein-like response (false positive).

  In the Coomassie method, sample no. 2, a protein concentration of 30.0 μg / mL was detected. Also in No. 2, it is considered that the decomposed superabsorbent polymer exhibited a protein-like response (false positive).

[Micro BCA method]
In the Micro BCA method, sample no. 4 the protein is below the detection limit and sample no. 5 and no. In 6, the protein concentration was approximately the same as the concentration of added BSA. However, sample no. 2 and sample no. From 3 the protein was detected. In the Micro BCA method, sample no. While protein was detected from sample 7, sample no. Since no protein is detected from No. 8, it is considered that the water-soluble component (citric acid acting as a chelating agent) inhibits protein detection as an inhibitor that shows false negatives.
From the above, the Micro BCA method suggests that citric acid has an effect on protein quantification.

[Example 2]
About 15 kg of 100 used paper diapers collected from an elderly care facility are put into a sterilized stirring container, and then the concentration of pulp fiber (3 kg) is about 5% by mass in the stirring container. 600 kg of sterilized water was added to the container, and the contents of the container were stirred for 10 minutes. It was set to 9.

Sample No. 9 and sample no. The number of bacteria of 2 was determined by the pour culture and plate culture methods described herein. The results are shown in Table 2. In addition, major bacterial species were identified by biochemical characterization. The results are shown in Table 2.
In Example 2, sample no. 2 means the second sampling sample.
In Table 2, ND means not detected.

When confirmed by the biochemical property inspection method, the sample No. Most of the general viable bacteria contained in No. 9 were Bacillus cereus, and Bacillus subtilis was also included. Sample No. When the number of bacteria contained in 1 (first sampling sample) was measured by the pour culture method, a number of bacteria of 1.39E + 5 was detected. In addition, when identified by biochemical property inspection method, sample No. 1 (first sampling sample) contained Bacillus cereus and Bacillus subtilis.
Sample No. From 2 (second sampling sample), neither Bacillus cereus nor Bacillus subtilis were detected.

[Example 3]
Sample No. 1, sample no. 2 and sample no. ΔW and ΔYI of the (recycled) pulp fiber in No. 3 were measured. The results are shown in Table 3.
In Example 3, sample No. 1 and sample no. 2 means (recycled) pulp fibers obtained by drying the first sampling sample and the second sampling sample under the same conditions as the measurement of the solid content. 3 means the virgin pulp fiber (manufactured by Weyerhaeuser, NB416) itself.

19 Ozone treatment apparatus 19-2a Supply process 19-2b Treatment process 98 Mixture 105 Treatment tank 107 Ejector AI Suction fluid supply port CO Mixed fluid discharge port DI Drive fluid supply port P2 Treatment liquid Z2 Ozone

Claims (10)

Recycled pulp fiber derived from used sanitary goods,
An aqueous dispersion in which the recycled pulp fiber is dispersed at a solid content concentration of 5.0% by mass contains protein at a concentration of 60 μg / mL or less measured by the Modified Lowry method.
The recycled pulp fiber.   The recycled pulp fiber according to claim 1, wherein Bacillus cereus and Bacillus subtilis are not detected by the pour culture method.   The recycled pulp fiber according to claim 1 or 2, wherein Bacillus bacteria are not detected by the pour culture method.   The recycled pulp fiber according to any one of claims 1 to 3, wherein no bacteria are detected by the pour culture method.   The recycled pulp fiber according to any one of claims 1 to 4, wherein bacteria are not detected by a plate culture method.   The recycled pulp fiber according to any one of claims 1 to 5, which has a ΔYI of 0 to 20 with respect to a standard white board.   The recycled pulp fiber according to any one of claims 1 to 6, which has a ΔW of 0 to 20 with respect to a standard white board. A method of producing recycled pulp fibers from used sanitary goods, including pulp fibers,
The aqueous solution containing the pulp fiber is a treatment tank provided with an ejector, and the ejector includes a driving fluid supply port, a mixed fluid discharge port connected to the treatment tank, and a suction fluid supply port therebetween. A supply step of supplying ozone to the suction fluid supply port while supplying to the drive fluid supply port of what is provided;
The mixed solution formed by mixing the aqueous solution and the ozone in the ejector is discharged from the mixed fluid discharge port into the treatment liquid in the treatment tank, and the protein-containing component in the pulp fiber Is a recycled pulp fiber, in which an aqueous dispersion in which the recycled pulp fiber is dispersed at a solid content concentration of 5.0% by mass has a protein concentration of 60 μg / mL or less measured by the Modified Lowry method. Recycled pulp fiber forming step to form what is contained in,
Said method.   The used sanitary article further includes a superabsorbent polymer, and in the supplying step, the aqueous solution further includes the superabsorbent polymer, and in the recycled pulp fiber forming step, the superabsorbent polymer is further decomposed. The method according to claim 8.   The method according to claim 9, comprising an inactivation step of inactivating the superabsorbent polymer with an acidic aqueous solution before the supplying step.

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