CN111278901A

CN111278901A - Method and system for recovering pulp fibers from used absorbent articles

Info

Publication number: CN111278901A
Application number: CN201880069837.8A
Authority: CN
Inventors: 小西孝义; 平冈利夫; 加藤孝; 栗田范朋
Original assignee: Unicharm Corp
Current assignee: Unicharm Corp
Priority date: 2017-11-01
Filing date: 2018-07-26
Publication date: 2020-06-12
Anticipated expiration: 2038-07-26
Also published as: WO2019087489A1; TWI726234B; TW201923195A; AU2018360436B2; JP6762287B2; PH12020550534A1; KR20200079257A; AU2018360436A1; KR102304591B1; JP2019085447A; CN111278901B

Abstract

A method for removing a super absorbent polymer from pulp fibers having a super absorbent polymer remaining therein, which are separated from a used absorbent article, with high processing efficiency. A method of recovering pulp fibers from a used absorbent article comprising pulp fibers and a superabsorbent polymer, wherein the method comprises: a solid-liquid separation step (S18) in which an inactivated aqueous solution containing pulp fibers and a superabsorbent polymer separated from a used absorbent article is separated into a solid containing pulp fibers and a superabsorbent polymer and a liquid containing a superabsorbent polymer and an inactivated aqueous solution, and the superabsorbent polymer is crushed; and an oxidizing agent treatment step (S19) in which pulp fibers and collapsed superabsorbent polymer contained in the separated solids are treated with an aqueous solution containing an oxidizing agent.

Description

Method and system for recovering pulp fibers from used absorbent articles

Technical Field

The present invention relates to a method and system for recovering pulp fibers from used absorbent articles.

Background

A method of recovering pulp fibers from an absorbent article such as a used disposable diaper is known. For example, patent document 1 discloses a method for producing recycled pulp from used sanitary products. The method comprises the following steps: physical force is applied to the used sanitary article in an acidic aqueous solution and the like, and the used sanitary article is decomposed into pulp fibers and other raw materials; separating pulp fibers from a mixture of pulp fibers and other raw materials; and treating the separated pulp fibers with an aqueous ozone-containing solution. By treating the pulp fibers with the ozone-containing aqueous solution, it is possible to oxidize and decompose the super absorbent polymer remaining in the separated pulp fibers, reduce the molecular weight of the super absorbent polymer, solubilize the super absorbent polymer, and remove the super absorbent polymer from the pulp fibers.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-

Disclosure of Invention

Problems to be solved by the invention

In order to make pulp fibers recovered from used absorbent articles more useful, it is important to reduce the concentration of superabsorbent polymer in pulp fibers, so that the efficiency of the treatment of reducing the concentration of superabsorbent polymer is improved. In the method of patent document 1, the pulp fibers are treated with the aqueous solution containing ozone, whereby the super absorbent polymer remaining in the pulp fibers can be oxidatively decomposed and removed from the pulp fibers. Among them, the treatment with the ozone-containing aqueous solution takes a relatively long time, and there is room for improvement from the viewpoint of improving the efficiency of the treatment. A technique capable of removing a super absorbent polymer from pulp fibers having the super absorbent polymer remaining therein separated from a used absorbent article with high treatment efficiency is desired.

The invention aims to provide a method and a system for removing a super absorbent polymer from pulp fiber which is separated from a used absorbent article and has the super absorbent polymer remained, with high treatment efficiency.

Means for solving the problems

The method of recovering pulp fibers from a used absorbent article comprising pulp fibers and a super absorbent polymer of the present invention is as follows. (1) A method of recovering pulp fibers from a used absorbent article comprising pulp fibers and a superabsorbent polymer, wherein the method comprises: a solid-liquid separation step of separating an inactivated aqueous solution containing pulp fibers and a superabsorbent polymer separated from a used absorbent article into a solid containing the pulp fibers and the superabsorbent polymer and a liquid containing the superabsorbent polymer and the inactivated aqueous solution, and crushing the superabsorbent polymer contained in the solid; and an oxidizing agent treatment step of treating the pulp fibers contained in the separated solids and the crushed superabsorbent polymer with an aqueous solution containing an oxidizing agent.

This method is a method of crushing a gel-like (block-like or substantially spherical) super absorbent polymer remaining after water absorption of pulp fibers (for example, crushing the super absorbent polymer with a pressure equal to or higher than the gel strength) to reduce the thickness of the super absorbent polymer and form the super absorbent polymer into a flat shape or a finely divided shape. That is, according to the present method, by crushing the block-shaped or substantially spherical super absorbent polymer, the surface area of the super absorbent polymer can be increased, and the exposed portion can be increased, such as exposing the portion inside the super absorbent polymer to the surface side. Therefore, in the case of a block-shaped or substantially spherical superabsorbent polymer in the oxidizing agent treatment step, the contact area of the superabsorbent polymer with the oxidizing agent can be increased by, for example, contacting the inner portion of the superabsorbent polymer that is less likely to contact the oxidizing agent with the oxidizing agent. This enables the oxidative decomposition of the super absorbent polymer to be more efficiently performed, and the time for the oxidizing agent treatment to be shortened. Thus, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved. Examples of the oxidizing agent include ozone, chlorine dioxide, peracetic acid, sodium hypochlorite, and hydrogen peroxide.

The method may be (2) the method according to the above (1), wherein the solid-liquid separation step includes a crushing step of crushing the superabsorbent polymer remaining in the pulp fibers by treating the inactivated aqueous solution containing the pulp fibers and the superabsorbent polymer by a pressure-type dewatering method.

The method crushes the superabsorbent polymer remaining in the pulp fiber by the pressure-type dewatering method, and thus can simultaneously, efficiently and reliably perform solid-liquid separation and crushing of the superabsorbent polymer on the pulp fiber. That is, the method can efficiently and reliably enlarge the surface area of the super absorbent polymer on the pulp fiber. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers. The super absorbent polymer remaining in the pulp fiber is exemplified by a super absorbent polymer adhering to the surface of the pulp fiber.

The method may be (3) the method according to the above (2), wherein a pressure at the time of pressurization in the pressurized dehydration method in the crushing step is 0.02MPa or more and 0.5MPa or less.

The method sets the pressure in the pressurization dehydration method to be more than 0.02MPa and less than 0.5 MPa. Therefore, the method can sufficiently crush the superabsorbent polymer remaining in the pulp fibers without damaging the pulp fibers, and can sufficiently enlarge the surface area of the superabsorbent polymer. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers. However, if the pressure is less than 0.02MPa, the super absorbent polymer cannot be sufficiently crushed, and hence the time for the oxidizing agent treatment cannot be shortened excessively, and if the pressure is more than 0.5MPa, the super absorbent polymer can be sufficiently crushed, but pulp fibers may be damaged.

The method may be (4) the method according to any one of (1) to (3) above, further comprising a step of separating the superabsorbent polymer and a part of the inactivated aqueous solution from the inactivated aqueous solution containing the pulp fibers and the superabsorbent polymer, before the solid-liquid separation step.

The method separates a quantity of superabsorbent polymer from an aqueous deactivation solution comprising pulp fibers and superabsorbent polymer prior to a solid-liquid separation process. Therefore, the method can suppress the proportion of the super absorbent polymer in the material (pulp fiber, super absorbent polymer and inactivated aqueous solution) supplied to the solid-liquid separation step to be low. Thus, the super absorbent polymer attached to the pulp fibers can be crushed more efficiently in the solid-liquid separation step, and the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers can be improved.

The method may be (5) the method according to any one of (1) to (4) above, wherein the proportion of the superabsorbent polymer in the inactivated aqueous solution supplied to the solid-liquid separation step is 50% or less.

In the method, the proportion of the super absorbent polymer in the inactivated aqueous solution to be separated is 50% or less in the solid-liquid separation step. This eliminates the need to crush an excessive amount of the super absorbent polymer, and thus the super absorbent polymer can be crushed more reliably and efficiently. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers.

The method according to any one of (1) to (5) above, wherein the method further comprises, before the solid-liquid separation step: breaking the used absorbent article in an aqueous deactivation solution; and separating an aqueous inactivation solution containing pulp fibers and a superabsorbent polymer from the aqueous inactivation solution containing the crushed material obtained in the crushing step.

In the method, an inactivated aqueous solution containing pulp fibers and a super absorbent polymer separated from a used absorbent article and supplied in the solid-liquid separation step is produced through a crushing step and a separation step. This can prevent foreign matter (materials other than pulp fibers and superabsorbent polymers of the disposable absorbent article (exemplified by films (back sheets and the like), nonwoven fabrics (surface sheets and the like), and elastomers (rubber for leakage barriers and the like)) from being mixed into the inactivation aqueous solution.

The method may be (7) the method according to any one of (1) to (6), wherein the aqueous inactivation solution is an acidic aqueous solution.

In the method, since the inactivating aqueous solution is an acidic aqueous solution, the superabsorbent polymer in the used absorbent article can be reliably dehydrated to a predetermined size (exemplified by particle diameter) or less. This makes it possible to crush the super absorbent polymer while easily performing solid-liquid separation in the solid-liquid separation step. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

The method according to (8) above (7), wherein the acidic aqueous solution has a pH of 2.5 or less.

In this method, the acidic aqueous solution has a pH of 2.5 or less, and therefore, the super absorbent polymer in the used absorbent article can be dehydrated more reliably to a predetermined size (exemplified by particle diameter) or less. This makes it possible to crush the super absorbent polymer while more easily performing solid-liquid separation in the solid-liquid separation step. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved. Further, since the superabsorbent polymer is set to a predetermined size or less in the gel state, the superabsorbent polymer can be easily crushed.

The method may be (9) the method according to (7) or (8) above, wherein the acidic aqueous solution contains citric acid.

In the method, since the acidic aqueous solution contains citric acid (exemplified as a concentration of 0.5 to 2.0 mass%), the superabsorbent polymer in the used absorbent article can be reliably dehydrated to a predetermined particle size or less. This makes it possible to crush the super absorbent polymer while easily performing solid-liquid separation in the solid-liquid separation step. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

The system used for recovering pulp fibers from a used absorbent article containing pulp fibers and a super absorbent polymer of the present invention is as follows. (10) A system for recovering pulp fibers from a used absorbent article comprising pulp fibers and a superabsorbent polymer, wherein the system comprises: a solid-liquid separation device that separates an inactivated aqueous solution containing pulp fibers and a superabsorbent polymer separated from used absorbent articles into a solid containing the pulp fibers and the superabsorbent polymer and a liquid containing the superabsorbent polymer and the inactivated aqueous solution, and crushes the superabsorbent polymer contained in the solid; and an oxidizing agent treatment device for treating the pulp fibers contained in the separated solids and the crushed superabsorbent polymer with an aqueous solution containing an oxidizing agent.

In this system, the thickness of the super absorbent polymer is reduced by crushing the gel-like (block-like or substantially spherical) super absorbent polymer remaining after the water absorption of the pulp fibers (exemplified by crushing with a pressure equal to or higher than the gel strength), and the super absorbent polymer is formed into a flat shape or a finely divided shape. That is, in the present system, by crushing the super absorbent polymer, the surface area of the block-shaped or substantially spherical super absorbent polymer can be enlarged to a large extent, and the exposed portion can be increased such as exposing the portion originally inside the super absorbent polymer to the surface side. Therefore, in the case of a block-shaped or substantially spherical superabsorbent polymer in the oxidizing agent treatment apparatus, the contact area of the superabsorbent polymer with the oxidizing agent can be increased by, for example, contacting the inner portion of the superabsorbent polymer that is less likely to contact the oxidizing agent with the oxidizing agent. This enables the oxidative decomposition of the super absorbent polymer to be more efficiently performed, and the time for the oxidizing agent treatment to be shortened. Thus, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

The present system may be (11) the system according to (10) above, wherein the solid-liquid separation device includes a screw press dehydrator that crushes the superabsorbent polymer remaining in the pulp fibers by treating the inactivated aqueous solution containing the pulp fibers and the superabsorbent polymer by a pressurized dehydration method.

The system crushes the superabsorbent polymer remaining in the pulp fibers by a pressure dewatering method using a screw press dehydrator, and thus can simultaneously, efficiently and reliably perform solid-liquid separation and crushing of the superabsorbent polymer on the pulp fibers. That is, the system can efficiently and reliably enlarge the surface area of the superabsorbent polymer on the pulp fibers to a large extent. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers. The super absorbent polymer remaining in the pulp fiber is exemplified by a super absorbent polymer adhering to the surface of the pulp fiber.

The present system may be (12) the system according to the above (11), wherein a pressure at the time of pressurization in the pressure dewatering method of the screw press dehydrator is 0.02MPa or more and 0.5MPa or less.

The system sets the pressure at the time of pressurization in the pressurized dehydration method to 0.02MPa or more and 0.5MPa or less. Therefore, the present system can sufficiently crush the superabsorbent polymer remaining in the pulp fibers without damaging the pulp fibers, and can sufficiently enlarge the surface area of the superabsorbent polymer. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers. However, if the pressure is less than 0.02MPa, the super absorbent polymer cannot be sufficiently crushed, and hence the time for the oxidizing agent treatment cannot be shortened too much, and if the pressure is more than 0.5MPa, the super absorbent polymer can be sufficiently crushed, but pulp fibers may be damaged.

The present system may be (13) the system according to any one of (10) to (12) above, further comprising a trommel dehydrator for separating the superabsorbent polymer and a part of the aqueous inactivation solution from the aqueous inactivation solution containing the pulp fibers and the superabsorbent polymer, before the solid-liquid separation device.

The system utilizes a trommel dehydrator to separate a certain amount of superabsorbent polymer from an aqueous inactivation solution containing pulp fibers and superabsorbent polymer before a solid-liquid separation device. Therefore, the present system can suppress the proportion of the super absorbent polymer in the material (pulp fiber, super absorbent polymer, and inactivated aqueous solution) supplied to the solid-liquid separation step to be low. Thus, the screw press dehydrator can crush the super absorbent polymer attached to the pulp fibers more efficiently, and the efficiency of the treatment of removing the super absorbent polymer from the pulp fibers can be improved.

The present system may be (14) the system according to any one of (10) to (13) above, wherein the proportion of the super absorbent polymer in the inactivated aqueous solution supplied to the solid-liquid separator is 50% or less.

In this system, the solid-liquid separator is configured such that the proportion of the super absorbent polymer in the inactivated aqueous solution to be separated is 50% or less. This eliminates the need to crush an excessive amount of the super absorbent polymer, and thus the super absorbent polymer can be crushed more reliably and efficiently. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers.

The system according to any one of (10) to (14) above, wherein the aqueous inactivation solution is an acidic aqueous solution, and (15) is provided.

In the present system, since the inactivating aqueous solution is an acidic aqueous solution, the superabsorbent polymer in the used absorbent article can be reliably dehydrated to a predetermined particle size or less. This makes it possible to crush the super absorbent polymer while easily performing solid-liquid separation in the solid-liquid separator. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

The system according to (16) above (15), wherein the acidic aqueous solution has a pH of 2.5 or less.

In this system, since the acidic aqueous solution has a ph of 2.5 or less, the superabsorbent polymer in the used absorbent article can be dehydrated more reliably to a predetermined particle diameter or less. This makes it possible to crush the super absorbent polymer while more easily performing solid-liquid separation in the screw press dehydrator. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved. Further, the superabsorbent polymer is reduced in particle size to a predetermined value or less in the gel state, and therefore, the superabsorbent polymer can be easily crushed.

The system may be (17) the system according to (15) or (16) above, wherein the acidic aqueous solution contains citric acid.

In this system, since the acidic aqueous solution contains citric acid (exemplified as a concentration of 0.5 to 2.0 mass%), it is possible to reliably dehydrate the super absorbent polymer in the used absorbent article to a predetermined particle size or less. This makes it possible to crush the super absorbent polymer while easily performing solid-liquid separation in the screw press dehydrator. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the method and system of the present invention, the super absorbent polymer can be removed from the pulp fiber having the super absorbent polymer remaining therein, which is separated from the used absorbent article, with high treatment efficiency.

Drawings

Fig. 1 is a block diagram showing an example of a system according to the embodiment.

Fig. 2 is a schematic diagram showing a configuration example of the bag-breaking device and the breaking device in fig. 1.

FIG. 3 is a schematic diagram showing a configuration example of the 3 rd separating apparatus of FIG. 1.

Fig. 4 is a schematic diagram showing a configuration example of the oxidizing agent treatment apparatus of fig. 1.

Fig. 5 is a partially enlarged view showing another configuration example of the oxidizing agent treatment device of fig. 1.

Fig. 6 is a flowchart showing an example of the method according to the embodiment.

Fig. 7 is a graph showing the relationship between the pressure and the processing time in the 3 rd separation step.

Detailed Description

Hereinafter, a method of recovering pulp fibers from a used absorbent article including pulp fibers and a super absorbent polymer according to an embodiment will be described. The term "used absorbent article" as used herein means an absorbent article used by a user, including an absorbent article in a state of absorbing and retaining excrement of the user, and also includes an absorbent article which has been used but has not absorbed and retained excrement, and an absorbent article which has not been used but has been discarded. Examples of the absorbent article include disposable diapers, urine absorbent pads, sanitary napkins, bed sheets, and pet sheets. In the method of recovering pulp fibers from a used absorbent article according to the present embodiment, recycled pulp fibers are produced, and therefore, the method can be said to be a method of producing recycled pulp fibers from a used absorbent article. Further, the method of recovering pulp fibers from a used absorbent article of the present embodiment recovers a super absorbent polymer together with pulp fibers in the middle and produces a recycled super absorbent polymer by separation, and thus can be said to be a method of recovering a super absorbent polymer from a used absorbent article or a method of producing a recycled super absorbent polymer. Here, a method of recovering pulp fibers from a used absorbent article will be described.

First, a configuration example of the absorbent article will be described. The absorbent article includes a front sheet, a back sheet, and an absorber disposed between the front sheet and the back sheet. Examples of the size of the absorbent article include a length of about 15cm to 100cm and a width of 5cm to 100 cm. The absorbent article may include further other members, such as a diffusion sheet and a leakage preventing wall, which are included in a general absorbent article.

Examples of the structural member of the top sheet include a liquid-permeable nonwoven fabric, a liquid-permeable synthetic resin film having liquid-permeable pores, and a composite sheet thereof. Examples of the structural member of the back sheet include a liquid-impermeable nonwoven fabric, a liquid-impermeable synthetic resin film, and a composite sheet thereof. Examples of the structural member of the diffusion sheet include liquid-permeable nonwoven fabrics. The structural member of the leakage preventing wall may be, for example, a liquid impermeable nonwoven fabric, or may include an elastic member such as rubber. Here, the material of the nonwoven fabric and the synthetic resin film is not particularly limited as long as it can be used as an absorbent article, but examples thereof include olefin-based resins such as polyethylene and polypropylene, polyamide-based resins such as 6-nylon and 6, 6-nylon, and polyester-based resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). In the present embodiment, an absorbent article in which the structural member of the back sheet is a film and the structural member of the front sheet is a nonwoven fabric will be described as an example.

As the structural member of the absorbent body, absorbent body materials, that is, pulp fibers and super absorbent polymers can be cited. The pulp fiber is not particularly limited as long as it can be used as an absorbent article, but for example, a cellulose fiber is exemplified. Examples of the cellulose-based fibers include wood pulp, crosslinked pulp, non-wood pulp, regenerated cellulose, and semi-synthetic cellulose. The pulp fiber has an average length of several tens of micrometers, preferably 20 to 40 micrometers, and an average fiber length of several mm, preferably 2 to 5 mm. The Super Absorbent Polymer (SAP) is not particularly limited as long as it can be used as an absorbent article, but examples thereof include polyacrylate-based, polysulfonate-based, and maleic anhydride-based water absorbent polymers. The average particle size of the superabsorbent polymer (when dry) is, for example, several hundred microns, preferably 200 to 500 microns.

One surface and the other surface of the absorbent body are bonded to the front sheet and the back sheet, respectively, with an adhesive. In a plan view, a portion (peripheral portion) of the front sheet that extends outward of the absorber so as to surround the absorber is joined to a portion (peripheral portion) of the back sheet that extends outward of the absorber so as to surround the absorber via an adhesive. Therefore, the absorbent body is enclosed in the joined body of the front sheet and the back sheet. The adhesive is not particularly limited as long as it can be used as an absorbent article and the adhesive strength is reduced by softening with warm water or the like described later, but examples thereof include a hot-melt adhesive. Examples of the hot-melt adhesive include a pressure-sensitive adhesive or a heat-sensitive adhesive containing a rubber-based body such as styrene-ethylene-butadiene-styrene, styrene-butadiene-styrene, or styrene-isoprene-styrene, or an olefin-based body such as polyethylene.

Next, a method of recovering pulp fibers from a used absorbent article including pulp fibers and a super absorbent polymer according to an embodiment will be described. In the present embodiment, the used absorbent article is recovered/taken from the outside and used for reuse (recycling). At this time, a plurality of used absorbent articles are enclosed in a collecting bag (hereinafter, also referred to as "collecting bag") so that dirt (excrement, etc.), fungi, and odor do not leak to the outside. In order to prevent the excrement from being exposed to the front surface side and prevent the odor from diffusing to the surroundings, each used absorbent article in the collecting bag is collected mainly in a state of being rolled up or in a folded state so that the front surface sheet on which the excrement is excreted is positioned inside.

First, a system 1 used in a method of recovering pulp fibers from a used absorbent article will be described. The system 1 is a system for recovering pulp fibers (and preferably also superabsorbent polymer) from used absorbent articles to produce recycled pulp fibers (and preferably also recycled superabsorbent polymer). Fig. 1 is a block diagram showing an example of a system 1 according to the present embodiment. The system 1 comprises a 3 rd separating device 18 and an oxidant treatment device 19, and preferably comprises a bag breaking device 11, a crushing device 12, a 1 st separating device 13, a 1 st dust removing device 14, a 2 nd dust removing device 15, a 3 rd dust removing device 16, a 2 nd separating device 17 and a 4 th separating device 20. The following description will be made in detail.

First, the bag breaker 11 and the breaker 12 will be described. The bag breaking device 11 opens a collecting bag containing used absorbent articles in the inactivating aqueous solution. The breaking device 12 breaks up used absorbent articles that have fallen in the inactivating water solution below the water surface of the inactivating water solution together with the collecting bag. Wherein the inactivation aqueous solution is an aqueous solution in which the super absorbent polymer is inactivated, and the water absorption performance of the super absorbent polymer is reduced by inactivation. Thus, the super absorbent polymer releases water to an amount that can be tolerated by the water absorption properties, i.e., dehydrates, while absorbing more water than the reduced water absorption properties. Hereinafter, a case of using an acidic aqueous solution as the inactivation aqueous solution will be described as an example.

Fig. 2 is a schematic diagram showing a configuration example of the bag breaker 11 and the breaker 12 in fig. 1.

The bag-breaking device 11 stores an acidic aqueous solution B supplied through, for example, a pipe having a valve, and opens a hole in a collection bag a put in the acidic aqueous solution B. The bag-breaking device 11 includes a solution tank V and an opening portion 50. The solution tank V is for storing the acidic aqueous solution B. The opening portion 50 is provided in the solution tank V, and opens a hole in the surface of the collection bag a that comes into contact with the acidic aqueous solution B when the collection bag a is placed in the solution tank V.

The opening portion 50 includes the feeding portion 30 and the bag breaking portion 40. The sending unit 30 sends (introduces) the collection bag a (physically and forcibly) into the acidic aqueous solution B in the solution tank V. The feeding portion 30 is, for example, a mixer, and includes a mixing blade 33, a support shaft (rotation shaft) 32 for supporting the mixing blade 33, and a driving device 31 for rotating the support shaft 32 along an axis. The stirring blade 33 is rotated about a rotation shaft (support shaft 32) by the driving device 31, thereby generating a vortex in the acidic aqueous solution B. The feeding unit 30 draws the collection bag a in the bottom direction of the acidic aqueous solution B (solution tank V) by a vortex.

The bag breaking portion 40 is disposed at a lower portion (preferably, a bottom portion) of the solution tank V, and includes a bag breaking blade 41, a support shaft (rotation shaft) 42 for supporting the bag breaking blade 41, and a driving device 43 for rotating the support shaft 42 along an axis. The bag breaking blade 41 is rotated about a rotation shaft (support shaft 42) by a driving device 43 to open a hole in the collection bag a moved to the lower portion of the acidic aqueous solution B (solution tank V). The lower portion of the solution tank V represents a portion below a position half way in the height direction of the solution tank V.

The bag breaking blade 41 of the hole portion 50 of the bag breaking device 11 may be movable in the vertical direction in the solution tank V while rotating around a rotation shaft (support shaft 42). In this case, the bag-breaking blade 41 moves upward, so that the collection bag a can be perforated even if the collection bag a does not move to the lower portion of the acidic aqueous solution B (solution tank V).

The crushing device 12 crushes the used absorbent articles in the collection bag a that sinks below the water surface of the acidic aqueous solution B together with the collection bag a. The crushing device 12 comprises a crushing section 60 and a pump 63. The crushing unit 60 is connected to the solution tank V by a pipe 61, and crushes the used absorbent article (the mixed liquid 91) in the collection bag a, which is sent out from the solution tank V together with the acidic aqueous solution B, in the acidic aqueous solution B together with the collection bag a. Examples of the crushing section 60 include a twin-shaft crusher (exemplified by a twin-shaft rotary crusher, a twin-shaft differential crusher, and a twin-shaft shear crusher), such as sumituter (manufactured by sumitomo heavy mechanical environment co.). The pump 63 is connected to the crusher 60 by a pipe 62, and the crushed product obtained by the crusher 60 is pumped out from the crusher 60 together with the acidic aqueous solution B (mixed liquid 92) and sent to the next step. The crushed material contains pulp fibers, a super absorbent polymer, and other materials (a raw material of the collection bag a, a film, a nonwoven fabric, an elastomer, and the like). The bag breaking device 11 and the crushing device 12 are preferably different devices from each other.

Referring to fig. 1, the 1 st separator 13 stirs a mixed solution 92 containing the crushed material obtained by the crusher 12 and the acidic aqueous solution, removes dirt (excrement, etc.) from the crushed material, cleans the crushed material, separates pulp fibers, the super absorbent polymer, and the acidic aqueous solution (mixed solution 93) from the mixed solution 92, and sends the separated pulp fibers, the super absorbent polymer, and the acidic aqueous solution to the 1 st dust collector 14.

The 1 st separating device 13 may be, for example, a washing machine having a washing/dewatering tub and a water tub surrounding the washing/dewatering tub. Among them, the washing tank and dehydration tank (rotary drum) is used as a washing tank and sieve tank (separation tank). The size of the through-holes provided in the circumferential surface of the washing tank is set to a size at which pulp fibers and superabsorbent polymer in the crushed material easily pass through and other materials are difficult to pass through. An example of the washing machine is a horizontal washing machine ECO-22B (manufactured by Kagaku corporation).

It should be noted that the used absorbent article may be crushed together with the collecting bag in a gas (for example, in the air) instead of crushing the used absorbent article together with the collecting bag in the inactivating aqueous solution (for example, an acidic aqueous solution). In this case, the bag breaking device 11 is not required, and the breaking device 12 breaks in the air in a state where the aqueous inactivation solution is not present. Thereafter, the crushed material and the aqueous inactivation solution of the crushing apparatus 12 are supplied to the 1 st separation apparatus 13.

In the case where the acidic aqueous solution is not used as the inactivation aqueous solution between the bag-breaking device 11 and the 1 st separation device 13, the acidic aqueous solution may be added from the 1 st dust-removal device 14 to the inactivation aqueous solution so that the inactivation aqueous solution containing the pulp fibers and the super absorbent polymer supplied to the 1 st dust-removal device 14 becomes substantially an acidic aqueous solution. In this case, the specific gravity and size of the super absorbent polymer can be easily adjusted by pH.

The 1 st dust removing device 14 separates the acidic aqueous solution (mixed solution 93) containing pulp fibers and a super absorbent polymer sent from the 1 st separating device 13 into pulp fibers and a super absorbent polymer (mixed solution 94) in the acidic aqueous solution and other materials (foreign substances) by a sieve having a plurality of openings while maintaining the pH within a predetermined range. In order to maintain the pH within a predetermined range, for example, a liquid (exemplified by water) which fluctuates the pH is not added in the middle, or a liquid (exemplified by an acidic aqueous solution) which has substantially the same pH when a liquid is added. The predetermined range is a range in which the variation in pH is within. + -. 1.0.

The first dust removing device 14 may be, for example, a screen separator (coarse screen separator). The openings of the screen (screen) are not particularly limited, and examples thereof include slits, round holes, square holes, and nets, and here, round holes are used. The size of the openings, i.e., the size (diameter) of the circular holes is set to a size through which pulp fibers and super absorbent polymer can pass, and is a size through which other materials (foreign matters) that cannot be removed by the 1 st separator 13 hardly pass, and is a size larger than the width of the slits of the screen of the 2 nd dust collector 15. The size of the circular hole is, for example, 2mm to 5mm in diameter, whereby other materials (foreign matters) at least about 10mm square or more can be removed. In the case of the slit, the size (width) of the slit is, for example, 2mm to 5 mm.

From the viewpoint of improving the efficiency of removing foreign matter, the mixed liquid 93 sent from the 1 st separation device 13 may be pressurized and simultaneously (for example: 0.5 kgf/cm)²～1kgf/cm²) And then supplied to the 1 st dust removing device 14. The first dust removing device 14 is exemplified by a package pulper (manufactured by satomi corporation).

The 2 nd dust removing device 15 separates the acidic aqueous solution (mixed solution 94) containing pulp fibers and a super absorbent polymer sent out from the 1 st dust removing device 14 into pulp fibers and a super absorbent polymer (mixed solution 95) in the acidic aqueous solution and other materials (foreign matters) by a sieve having a plurality of openings while maintaining the pH value within a predetermined range.

The 2 nd dust removing device 15 is exemplified by a screen separator. The openings of the screen (screen) are not particularly limited, and examples thereof include slits, round holes, square holes, and nets, and slits are used herein. The size (width) of the slit is set to a size that pulp fibers and super absorbent polymer can pass through and is a size that other materials (foreign materials) that cannot be removed by the 1 st dust removing device 14 are difficult to pass through. The size of the slit is, for example, 0.2mm to 0.5mm in width, whereby other materials (foreign substances) at least about 3mm square or more can be removed. In the case of a circular hole, the size (diameter) of the circular hole is, for example, 0.2mm to 0.5mm phi in diameter.

From the viewpoint of improving the efficiency of removing foreign matter, the mixed liquid 94 sent from the 1 st dust removing device 14 may be pressurized and simultaneously (for example: 0.5 kgf/cm)²～2kgf/cm²) And supplied to the 2 nd dust removing device 15. From the viewpoint of removing relatively small foreign matters, the pressure is preferably higher than that of the 1 st dust removing device 14. The second dust removing device 15 is, for example, a Lamo sieve (manufactured by Acheki Kaisha).

The 3 rd dust removing device 16 centrifugally separates the acidic aqueous solution (mixed solution 95) containing pulp fibers and a super absorbent polymer, which is sent from the 2 nd dust removing device 15, while maintaining the pH value within a predetermined range, and separates the pulp fibers and the super absorbent polymer (mixed solution 96) in the acidic aqueous solution from other materials (foreign substances having a large weight).

The 3 rd dust removing device 16 is exemplified by a cyclone. An acidic aqueous solution (mixed solution 95) containing pulp fibers and a super absorbent polymer is supplied into an inverted conical casing (not shown) of the 3 rd dust removing device 16 at a predetermined flow rate so that the pulp fibers and the super absorbent polymer in the acidic aqueous solution having a relatively low specific gravity rise and foreign substances (metals, etc.) having a specific gravity higher than that of the pulp fibers and the super absorbent polymer fall. An example of the 3 rd dust removing device 16 is an ACT low concentration cleaner (manufactured by Kogaku K.K.).

The 2 nd separating device 17 separates the acidic aqueous solution (mixed solution 96) containing pulp fibers and a super absorbent polymer sent out from the 3 rd dust removing device 16 into pulp fibers (mixed solution 97) in the acidic aqueous solution and a super absorbent polymer in the acidic aqueous solution by a sieve having a plurality of openings. Therefore, the dehydrator can be considered as a dehydrator for removing the acidic aqueous solution together with the super absorbent polymer from the mixed liquid 96.

The 2 nd separating device 17 is exemplified by a trommel separator. The openings of the trommel (screen) are not particularly limited, and examples thereof include slits, round holes, square holes, and meshes. The size (width) of the slit is set to a size through which the super absorbent polymer can pass, and is a size through which the pulp fibers are difficult to pass. In the case of slits, the size of the slits is, for example, 0.2mm to 0.8mm in width, whereby at least a large amount of the super absorbent polymer can be removed. In the case of a circular hole, the size of the circular hole is, for example, 0.2mm to 0.8mm phi in diameter. The 2 nd separating device 17 may be a trommel dehydrator (manufactured by Toyo Sieve Co., Ltd.).

The 3 rd separating device 18 separates the pulp fibers, the remaining superabsorbent polymer that cannot be separated, and the acidic aqueous solution (mixed solution 97) sent from the 2 nd separating device 17 into a solid (mixture 98) containing the pulp fibers and the superabsorbent polymer and a liquid containing the superabsorbent polymer and the acidic aqueous solution by a sieve having a plurality of openings, and applies pressure to the solid to crush the superabsorbent polymer in the solid. Therefore, the 3 rd separator 18 can be regarded as a dehydration machine of a pressure dehydration system for removing the acidic aqueous solution together with the super absorbent polymer from the mixed liquid 97. Wherein the solids (mixture 98) contain some acidic water solubility.

Fig. 3 is a schematic diagram showing a configuration example of the 3 rd separating apparatus 18 of fig. 1. The 3 rd separating device 18 is exemplified by a screw press dehydrator. The 3 rd separating device 18 includes, for example, a trommel 81, a screw shaft 82, a screw blade 83, a driving device 86, a cover 84, and a pressure adjusting device 85. The trommel 81 is a cylindrical screen (screen) provided in the casing 80. The screw shaft 82 extends along the axis of the cylinder of the drum screen 81, and its diameter gradually increases toward the top end portion of the drum screen 81. The spiral blade 83 is spirally provided outside the spiral shaft 82 and rotates along the inner circumferential surface of the trommel 81. The pitch of the helical blades 83 may also be gradually smaller toward the top end of the trommel 81. The driving device 86 is used to rotate the screw shaft 82. The cover 84 is provided to close the top end of the trommel 81. The pressure adjusting device 85 adjusts the pressing pressure for pressing the cover 84 against the top end of the drum screen 81.

The openings of the trommel (screen)81 are not particularly limited, and examples thereof include slits, round holes, squares, and meshes. The size (width) of the slit is set to a size through which the super absorbent polymer can pass, and is a size through which the pulp fibers are difficult to pass. In the case of the slit, the size of the slit is, for example, 0.1mm to 0.5mm in width, and at least the remaining super absorbent polymer can be removed. The 3 rd separating device 18 sends out the liquid E containing the super absorbent polymer and the acidic aqueous solution from the slit on the side of the trommel 81, and at the same time sends out the solid (mixture 98) containing the pulp fibers and the super absorbent polymer from the gap G between the top end of the trommel 81 and the cover 84. The superabsorbent polymer is crushed as the solids (mixture 98) are delivered. The pressure applied to the lid body for pressing is, for example, 0.01MPa or more and 1MPa or less. The 3 rd separating device 18 is exemplified by a screw press dehydrator (manufactured by kaiko shoji).

The oxidizing agent treatment device 19 treats the pulp fibers (mixture 98) containing the crushed superabsorbent polymer in the solid sent out from the 3 rd separation device 18 with an aqueous solution (treatment liquid) containing an oxidizing agent. Thereby, the super absorbent polymer is oxidized and decomposed and removed from the pulp fibers, and the pulp fibers not containing the super absorbent polymer are sent out together with the treatment liquid (mixed liquid 99).

Fig. 4 is a schematic diagram showing a configuration example of the oxidizing agent treatment device 19. When ozone is used as the oxidizing agent, the oxidizing agent treatment device 19 includes a pump 121, a treatment tank 123, a pump 125, an ozone generation device 126, an ozone mixing device 127, and an ozone decomposition device 129. The treatment tank 123 has an acidic aqueous solution as the treatment liquid P, and the mixture 98 is supplied from a supply port 122b provided in the upper portion. In the case of using ozone as the oxidizing agent, an acidic aqueous solution is preferable in terms of improving the stability of ozone. The pump 121 discharges the processing liquid P from the delivery port 124a at the bottom of the processing tank 123 via the pipe 132, and supplies the processing liquid P from the supply port 122a at the upper part of the processing tank 123 to the processing tank 123. The pump 125 discharges the processing liquid P from the delivery port 124b at the bottom of the processing tank 123 through the pipe 136, and supplies the processing liquid P to the processing tank 123 from the supply port 122c at the bottom of the processing tank 123. The ozone generator 126 generates an ozone-containing gas Z as a gaseous substance and supplies the gas to the ozone mixer 127. The ozone mixing device 127 is located in the middle of the pipe 136, and mixes the ozone-containing gas Z supplied through the pipe 135 with the treatment liquid P flowing through the supply port 122c toward the lower portion of the treatment tank 123 in the pipe 136. The ozone mixing device 127 supplies the ozone-containing gas Z into the treatment liquid P as a plurality of fine bubbles. The ozone-containing gas Z is another gas containing ozone, and examples thereof include oxygen gas containing ozone and air. Examples of the ozone generator 126 include an ozone water exposure tester ED-OWX-2 manufactured by Eco design corporation and an ozone generator OS-25V manufactured by Mitsubishi Motor corporation. The ozonolysis apparatus 129 receives the ozone-containing gas Z stored in the upper part of the treatment tank 123 through the pipe 134, and decomposes the ozone to make it harmless and discharges it to the outside. Note that the treatment liquid P in the treatment tank 123 is only the treatment liquid P in the initial stage and becomes a liquid in which the treatment liquid P is mixed with the mixture 98 after the start, but in the present embodiment, the treatment liquid P also includes a liquid in which the treatment liquid P is mixed with the mixture 98, and the liquid in the treatment tank 123 is the treatment liquid P.

Fig. 5 is a schematic diagram showing another configuration example of the oxidizing agent treatment device 19. The oxidizing agent treatment device 19 includes: a mixed liquid storage unit 110 that stores the mixture 98 containing pulp fibers together with the treatment liquid Pa; and an oxidizing agent treatment unit 120 for removing the crushed superabsorbent polymer contained in the pulp fibers in the treatment liquid Pa by oxidizing and decomposing the superabsorbent polymer with the treatment liquid P. The mixed liquid storage unit 110 includes a mixed liquid tank 112 and a stirrer 113. The mixture liquid tank 112 stores the mixture 98 containing pulp fibers supplied through the pipe 131 in the treatment liquid Pa. The stirrer 113 stirs the treatment liquid Pa in the mixture tank 112 so that the mixture 98 does not sink downward in the treatment liquid Pa. Meanwhile, the oxidizing agent treatment section 120 includes a pump 121a, a treatment tank 123, an ozone supply device 128, a pump 125a, and an ozone decomposition device 129. The treatment tank 123 has an acidic aqueous solution as the treatment liquid P. The pump 121a continuously supplies the treatment liquid Pa containing the mixture 98 in the mixture liquid tank 112 to the treatment tank 123 at the 1 st flow rate via the pipe 132 a. The ozone supply device 128 generates an ozone-containing gas Z as a gaseous substance by the ozone generation device 126, and supplies the gas to the treatment tank 123 through the pipe 135. The nozzle 127a for sending out the ozone-containing gas Z is disposed at a lower portion (preferably, a bottom portion) of the treatment tank 123, and has, for example, a tubular or flat plate shape. The nozzle 127a continuously supplies the ozone-containing gas Z as a plurality of fine bubbles from the lower portion of the treatment tank 123 toward the upper portion into the treatment liquid P. The pump 125a continuously discharges the treatment liquid P in the treatment tank 123 to the outside of the treatment tank 123 at the 2 nd flow rate via the pipe 133. The ozonolysis apparatus 129 receives the ozone-containing gas Z stored in the upper part of the treatment tank 123 through the pipe 134, and decomposes the ozone to make it harmless and discharges it to the outside.

The oxidizing agent treatment device 19 uses ozone as the oxidizing agent, but other oxidizing agents may be used, and a liquid oxidizing agent or a solid oxidizing agent may be melted into a liquid even if the oxidizing agent is not gaseous. Examples of the oxidizing agent include chlorine dioxide, peracetic acid, sodium hypochlorite, and hydrogen peroxide.

The 4 th separating device 20 separates pulp fibers from the treatment liquid (mixed liquid 99) containing pulp fibers treated by the oxidizing agent treatment device 19 by a screen having a plurality of openings, thereby recovering the pulp fibers to produce recycled pulp fibers.

The 4 th separation device 20 may be, for example, a screen separator. The openings of the screen (screen) are not particularly limited, and examples thereof include slits, round holes, square holes, and nets, and slits are used herein. The size (width) of the slit is a size through which pulp fibers are difficult to pass. The size of the slit is, for example, 0.2mm to 0.8mm in width. In the case of a circular hole, the size of the circular hole is, for example, 0.2mm to 0.8mm phi in diameter.

The system 1 preferably includes an ozone treatment device 22, a pH adjustment device 23, and a water storage tank 24. These apparatuses are apparatuses for regenerating and reusing the acidic aqueous solution used in the system 1. By reusing the acidic aqueous solution, the cost of the acidic aqueous solution can be reduced. The ozone treatment device 22 performs a sterilization treatment of the acidic aqueous solution 101 after further separating the super absorbent polymer from the super absorbent polymer and the acidic aqueous solution separated by the 2 nd separation device 17 with the ozone-containing aqueous solution. The pH adjusting device 23 adjusts the pH of the acidic aqueous solution 102 sterilized with the ozone-containing aqueous solution to generate a regenerated acidic aqueous solution 103. The water storage tank 24 is used for storing the remaining part of the regenerated acidic aqueous solution 103.

Next, a method of recovering pulp fibers from a used absorbent article will be described. This method is a method of recovering pulp fibers (and preferably also superabsorbent polymers) from used absorbent articles to produce recycled pulp fibers (and preferably also recycled superabsorbent polymers). Fig. 6 is a flowchart showing an example of the method according to the present embodiment. The method includes a 3 rd separating step S18 and an oxidizer treating step S19, and preferably includes a drilling step S11, a crushing step S12, a 1 st separating step S13, a 1 st dust removing step S14, a 2 nd dust removing step S15, a 3 rd dust removing step S16, a 2 nd separating step S17, and a 4 th separating step S20. The following description will be made in detail.

The hole forming process S11 is performed by the bag breaking device 11. The collecting bag a in which the used absorbent article is enclosed is put into a solution tank V in which an acidic aqueous solution B is stored, and a hole is formed in the surface of the collecting bag a that is in contact with the acidic aqueous solution B. The acidic aqueous solution B surrounds and seals the periphery of the collection bag a so that when the collection bag a is perforated, dirt, fungus, and odor of the used absorbent article in the collection bag a are not released to the outside. When the acidic aqueous solution enters the collection bag a through the hole, the gas in the collection bag a is discharged to the outside of the collection bag a, the collection bag a has a heavier specific gravity than the acidic aqueous solution B, and the collection bag a settles in the acidic aqueous solution B. In addition, the acidic aqueous solution B inactivates the superabsorbent polymer in the used absorbent article in the collection bag a.

By deactivating the superabsorbent polymer in the used absorbent article, the water absorption capacity thereof is reduced, and the superabsorbent polymer is dehydrated and has a small particle size, so that the subsequent steps can be easily handled, and the handling efficiency can be improved. The reason why an acidic aqueous solution, i.e., an aqueous solution of an inorganic acid and an organic acid is used as the inactivation aqueous solution is that ash does not remain in the pulp fibers as compared with an aqueous solution of lime, calcium chloride, or the like, and that the degree of inactivation (particle size, specific gravity) is easily adjusted 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 absorption capacity of the super absorbent polymer cannot be sufficiently reduced. In addition, the sterilization ability may be lowered. If the pH is too low, the equipment may be corroded, and a large amount of alkaline chemical is required for neutralization treatment in wastewater treatment. In particular, in order to separate pulp fibers and a super absorbent polymer from other materials, it is preferable that the size and specific gravity of the pulp fibers are relatively close to those of the super absorbent polymer. Therefore, by setting the pH of the acidic aqueous solution to 1.0 or more and 4.0 or less, the superabsorbent polymer can be made smaller by inactivation, and the size and specific gravity of the pulp fiber and the size and specific gravity of the superabsorbent polymer can be made relatively close to each other. Examples of the organic acid include citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, ascorbic acid, and the like, and hydroxycarbonate-based organic acids such as citric acid, tartaric acid, gluconic acid, and the like are particularly preferable. Metal ions and the like in excrement can be captured and removed by the chelating effect of citric acid, and a high effect of removing dirt components can be expected by the cleaning effect of citric acid. On the other hand, examples of the inorganic acid include sulfuric acid, hydrochloric acid, and nitric acid, but sulfuric acid is preferable from the viewpoints of chlorine free, cost, and the like. The pH value varies depending on the water temperature, and therefore the pH value in the present invention means a pH value measured at a temperature of 20 ℃ in an aqueous solution. 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 mass% or more and 4 mass% or less. The concentration of the inorganic acid in the aqueous solution of the inorganic acid is not particularly limited, but when the inorganic acid is sulfuric acid, it is preferably 0.1 mass% or more and 0.5 mass% or less.

For example, in the bag-breaking device 11 of fig. 2, first, a vortex is generated in the acidic aqueous solution B by the rotation of the stirring blade 33 around the rotation shaft (support shaft 32), and the collection bag a is physically and forcibly drawn in the bottom direction of the acidic aqueous solution B (solution tank V). Then, by the rotation of the bag breaking blade 41 about the rotation shaft (support shaft 42), the collection bag a moved to the bottom comes into contact with the bag breaking blade 41 to open the hole. In the case where the bag breaking blade 41 is movable in the vertical direction in the solution tank V, even if the collection bag a is not drawn in the bottom direction of the acidic aqueous solution B (solution tank V) by the vortex, the bag breaking blade 41 may be moved upward to open the hole in the collection bag a.

The crushing step S12 is performed by the crushing device 12. The acidic aqueous solution B, i.e., the mixed solution 91, contained in the collection bag a having the opening and sinking to the water surface of the acidic aqueous solution B is discharged from the solution tank V, and the used absorbent articles in the collection bag a are crushed in the acidic aqueous solution B together with the collection bag a.

For example, in the crushing apparatus 12 of fig. 2, first, the used absorbent articles in the collection bag a fed out from the solution tank V together with the acidic aqueous solution B are crushed in the acidic aqueous solution B together with the collection bag a by the crushing section 60 (in-liquid crushing step). At this time, in the crushing section 60, the mixed liquid 91 is supplied to the rotating cutter head and the liner of the biaxial crusher, which are engaged with each other and rotate inward, and the collection bag a is crushed together with the bag. Then, the acidic aqueous solution B (mixed solution 92) containing the crushed product obtained in the crushing unit 60 (in-solution crushing step) is pumped out from the crushing unit 60 by the pump 63 (pumping step), and is sent to the next step.

Here, in the crushing step S12, it is preferable to crush the used absorbent article together with the collecting bag a so that the average value of the size of the crushed material becomes 50mm to 100 mm. The absorbent article is assumed to have a length of about 150mm to 1000mm and a width of 100mm to 1000 mm. By crushing the crushed material so that the average value of the size of the crushed material is 50mm or more and 100mm or less, it is possible to reliably form slits in the back sheet and/or the front sheet of each used absorbent article. Accordingly, in each used absorbent article, the pulp fibers can be taken out from the slits with substantially no residue, and therefore, the recovery rate of the pulp fibers (total amount of regenerated pulp fibers/total amount of pulp fibers of the used absorbent article supplied) can be increased. When the average value of the sizes is less than 50mm, materials other than pulp fibers (for example, a film (a raw material of the collecting bag a, a back sheet, etc.), a nonwoven fabric (a surface sheet, etc.), an elastic body (a rubber for a leakage preventing wall, etc.)) are excessively cut, and it is difficult to separate these materials from pulp fibers in a subsequent step. As a result, foreign matter (other material) mixed into the regenerated pulp fibers increases, and the recovery rate of the pulp fibers decreases. On the other hand, if the average value of the sizes is larger than 100mm, it is difficult to form a cut in the used absorbent article. As a result, a used absorbent article in which the pulp fibers cannot be taken out is produced, and the recovery rate of the pulp fibers is lowered.

The 1 st separating step S13 is performed by the 1 st separating device 13. The mixed liquid 92 containing the crushed material and the acidic aqueous solution obtained by the crushing device 12 is stirred to wash the crushed material to remove dirt, and the mixed liquid 92 is separated into pulp fibers, a super absorbent polymer, an acidic aqueous solution, and other materials. In this case, an acidic aqueous solution may be additionally added for the purpose of enhancing the washing effect and/or for adjusting the pH. As a result, the pulp fibers, the super absorbent polymer, and the acidic aqueous solution (a part of them including other materials) in the mixed liquid 92 are separated by the through-holes and sent out from the 1 st separator 13 (mixed liquid 93). On the other hand, the materials other than the pulp fibers, the super absorbent polymer, and the acidic aqueous solution in the mixed liquid 92 cannot pass through the through-holes, and remain in the 1 st separating device 13 or are sent out through another path. A part of the other materials is not completely separated and is sent out together with the mixed liquid 93. Here, when a washing machine is used as the first separating device 13, the size of the through-hole of the washing tub functioning as a sieve is 5mm to 20mm in the case of a circular hole, and the size of the through-hole having the same area as the circular hole in the case of a hole having other shape is exemplified.

The method (system) includes at least the hole forming step S11 (bag breaking device 11) and the crushing step S12 (crushing device 12) in the crushing treatment (hole forming step S11 (bag breaking device 11) to the 1 st separating step S13 (1 st separating device 13)) for crushing the used absorbent article as described above. Therefore, the used absorbent article placed in the collecting bag is crushed in the inactivating aqueous solution together with the collecting bag, and therefore contamination of dirt, fungi, or generation of odor in the inactivating aqueous solution hardly occurs at least before the crushing is started. Further, even if dirt, fungi, or odor is mixed in the inactivated aqueous solution when the used absorbent article is crushed, the inactivated aqueous solution in which dirt or fungi are mixed is fed out from the solution tank together with the crushed material substantially simultaneously with the crushing, and therefore, the dirt or fungi can be hardly left in the solution tank and can be flowed away. Further, since the odor can be sealed with the inactivating aqueous solution, the generation of odor is also suppressed to a low level. This makes it possible to prevent dirt and fungus from scattering or to prevent odor from being emitted when the used absorbent article is crushed.

It should be noted that the used absorbent article may be crushed together with the collecting bag in a gas (for example, in the air) instead of crushing the used absorbent article together with the collecting bag in the inactivating aqueous solution (for example, an acidic aqueous solution). In this case, the punching step S11 is not required, and the crushing step S12 is performed in the air without the inactivation aqueous solution. Thereafter, the inactivated aqueous solution is supplied to the 1 st separation step S13 together with the crushed product of the crushing step S12.

In the case where an acidic aqueous solution is not used as the inactivation aqueous solution between the punching step S11 and the 1 st separation step S13, it is preferable that the acidic aqueous solution is added from the 1 st dust removal step S14 so that the inactivation aqueous solution containing the pulp fibers and the super absorbent polymer supplied to the 1 st dust removal step S14 becomes substantially an acidic aqueous solution. In this case, the specific gravity and size of the super absorbent polymer can be easily adjusted by pH.

The 1 st dust removing step S14 is performed by the 1 st dust removing device 14. The mixed liquid 93, which is the acidic aqueous solution containing pulp fibers and a super absorbent polymer and sent from the 1 st separator 13, is separated into an acidic aqueous solution containing pulp fibers and a super absorbent polymer and other materials (foreign materials) by a sieve while maintaining the pH value within a predetermined range. As a result, the pulp fibers, the super absorbent polymer, and the acidic aqueous solution (a part of them including other materials) in the mixed liquid 93 are separated by the screen and sent out from the 1 st dust removing device 14 (mixed liquid 94). On the other hand, the materials other than the pulp fibers, the super absorbent polymer, and the acidic aqueous solution in the mixed liquid 93 cannot pass through the screen and remain in the first dust removing device 14 or are sent out through another route. A part of the other materials is not completely separated and is sent out together with the mixed liquid 94.

It is preferable that the acidic aqueous solution is adjusted in pH at least before the first dust removing step S14 so that the difference between the specific gravity of the super absorbent polymer and the specific gravity of the pulp fibers and the difference between the size of the super absorbent polymer and the size of the pulp fibers are within predetermined ranges. The predetermined range is, for example, 0.2 to 5 times that of the other. In this case, the step before the dust removal step S14 of 1 st can be regarded as an inactivation step of inactivating the superabsorbent polymer by mixing the pulp fibers and the superabsorbent polymer with an acidic aqueous solution having a pH adjusted so that the difference between the specific gravity of the superabsorbent polymer and the specific gravity of the pulp fibers and the difference between the size of the superabsorbent polymer and the size of the pulp fibers fall within predetermined ranges.

The concentration of the pulp fibers and the super absorbent polymer in the acidic solution in the first dust removal step S14 is, for example, 0.1 mass% or more and 10 mass% or less, and preferably 0.1 mass% or more and 5 mass% or less. The ratio of pulp fibers to the super absorbent polymer in the acidic solution is, for example, 50 to 90 mass% and 50 to 10 mass%.

The 2 nd dust removing process S15 is performed by the 2 nd dust removing device 15. The mixed liquid 94, which is the acidic aqueous solution containing pulp fibers and a super absorbent polymer and is sent from the 1 st dust collector 14, is separated into the acidic aqueous solution containing pulp fibers and a super absorbent polymer and other materials (foreign materials) by a sieve while maintaining the pH within a predetermined range. As a result, the pulp fibers, the super absorbent polymer, and the acidic aqueous solution (a part of them including other materials) in the mixed liquid 94 are separated by the screen and sent out from the 2 nd dust removing device 15 (mixed liquid 95). On the other hand, the other materials in the mixed liquid 94 except the pulp fibers, the super absorbent polymer, and the acidic aqueous solution cannot pass through the screen and remain in the second dust removing device 15, or are sent out through another route. Some of the other materials are not completely separated and are sent out together with the mixed liquid 95. The acidic aqueous solution adjusts the pH so that the difference between the specific gravity of the super absorbent polymer and the specific gravity of the pulp fibers and the difference between the size of the super absorbent polymer and the size of the pulp fibers are within predetermined ranges.

The 3 rd dust removing process S16 is performed by the 3 rd dust removing device 16. The mixed liquid 95, which is the acidic aqueous solution containing pulp fibers and a super absorbent polymer and is sent from the 2 nd dust collector 15, is centrifugally separated in the inverted conical casing while maintaining the pH within a predetermined range, and is separated into pulp fibers and a super absorbent polymer in the acidic aqueous solution and other materials (foreign materials having a large weight). As a result, the pulp fibers, the super absorbent polymer, and the acidic aqueous solution in the mixed liquid 95 are sent out from the upper part of the 3 rd dust removing device 16 (cyclone) (mixed liquid 96). On the other hand, the mixed liquid 95 is fed from the lower part of the 3 rd dust removing device 16 (cyclone) with other heavy materials such as pulp fibers, super absorbent polymer, and metals other than the acidic aqueous solution. The acidic aqueous solution adjusts the pH so that the difference between the specific gravity of the super absorbent polymer and the specific gravity of the pulp fibers and the difference between the size of the super absorbent polymer and the size of the pulp fibers are within predetermined ranges.

The method (system) includes at least the 2 nd dust removal process S15 (the 2 nd dust removal device 15) and the 3 rd dust removal process S16 (the 3 rd dust removal device 16) in the dust removal processing (the 1 st dust removal process S14 (the 1 st dust removal device 14) to the 3 rd dust removal process S16 (the 3 rd dust removal device 16)) for removing foreign matters (other materials) as described above. Therefore, the pulp fibers and the super absorbent polymer can be easily separated in size from the resin material, which is the main material of the used absorbent article, other than the pulp fibers and the super absorbent polymer (the 2 nd dust removing step S15 (the 2 nd dust removing device 15)), and easily separated in specific gravity from the material having a higher specific gravity, such as the metal material, among the other materials (the 3 rd dust removing step S16 (the 3 rd dust removing device 16)). Then, the pulp fibers and the super absorbent polymer can be recovered from the used absorbent article by separating them from each other (the 2 nd separation step S17, the 3 rd separation step S18 (the 2 nd separation device 17, the 3 rd separation device 18)). In this case, the number of times of treatment for separating pulp fibers and super absorbent polymers from other materials can be reduced. That is, the efficiency of the process of separating the super absorbent polymer and the pulp fiber can be improved.

The 2 nd separating step S17 is performed by the 2 nd separating device 17. The mixed liquid 96, which is the acidic aqueous solution containing pulp fibers and a super absorbent polymer and is sent from the 3 rd dust collector 16, is separated into pulp fibers in the acidic aqueous solution and a super absorbent polymer in the acidic aqueous solution by a trommel. As a result, the acidic aqueous solution containing the super absorbent polymer is separated from the mixed solution 96 by passing through a trommel, and is sent out from the 2 nd separator 17. On the other hand, the acidic aqueous solution containing pulp fibers in the mixed solution 96 is not passed through the trommel, and is sent out from the 2 nd separating device 17 through another path (mixed solution 97). After that, the super absorbent polymer can be separated from the separated super absorbent polymer and acidic aqueous solution by a screen separator or the like. Therefore, the above step can be referred to as a step of separating and recovering the super absorbent polymer, and a step of producing a recycled super absorbent polymer therefrom.

The 3 rd separating step S18 is performed by the 3 rd separating device 18. The mixed liquid 97, which is the pulp fibers, the remaining superabsorbent polymer and the acidic aqueous solution that are not separated, sent from the 2 nd separator 17, is separated into a mixture 98, which is a solid containing the pulp fibers and the superabsorbent polymer, and a liquid E containing the superabsorbent polymer and the acidic aqueous solution by a trommel screen. Then, the superabsorbent polymer in the solid is crushed by applying pressure while separating. As a result, the acidic aqueous solution containing the super absorbent polymer is separated from the mixed solution 97 by passing through a trommel, and is sent out from the 3 rd separator 18. On the other hand, the pulp fibers crushed with the super absorbent polymer in the mixed liquid 97 cannot be fed out to the outside of the 3 rd separation apparatus 18 through the gap of the cover at the tip of the trommel without adding a trommel (mixture 98).

For example, in the 3 rd separator 18 shown in fig. 3, first, the mixed liquid 97 containing the pulp fibers, the super absorbent polymer, and the acidic aqueous solution sent out from the 2 nd separator 17 is put into the trommel 81 and reaches the periphery of the screw shaft 82. When the screw shaft 82 is rotated by the driving device 86, the mixed liquid 97 around the screw shaft 82 is pressed against the side surface of the drum screen 81 by the screw shaft 82 and the screw blade 83, is pressurized, and is conveyed toward the tip end portion of the drum screen 81. At this time, the super absorbent polymer and the acidic aqueous solution pass through the screen on the side of the trommel 81, and are separated from the mixed solution 97, and the pulp fibers and a part of the super absorbent polymer remain in the trommel 81. That is, the mixture 98, which is a solid containing pulp fibers and a super absorbent polymer, is separated from the liquid E containing the super absorbent polymer and an acidic aqueous solution from the mixed liquid 97. Then, the mixture 98 is pressurized and forcibly discharged from a gap G between the top end portion of the trommel 81 and the lid body 84 pressurized in the direction opposite to the conveying direction of the mixture 98. The superabsorbent polymer in the mixture 98 is crushed during conveyance and discharge while being pressurized. On the other hand, the liquid E is sent out from the casing 80. The pressing pressure applied to the lid 84 is, for example, 0.01MPa or more and 1MPa or less, preferably 0.02MPa or more and 0.5MPa or less. If the pressure is set to less than 0.02MPa, it becomes difficult to crush the super absorbent polymer, and the time for the oxidizing agent treatment cannot be shortened too much, whereas if the pressure is set to more than 0.5MPa, the super absorbent polymer is sufficiently crushed, but pulp fibers may be damaged.

The oxidizing agent treatment step S19 is performed by the oxidizing agent treatment device 19. The pulp fibers and the crushed superabsorbent polymer in the solids discharged from the 3 rd separating device 18 are treated in an aqueous solution containing an oxidizing agent. Thereby, the super absorbent polymer is oxidatively decomposed and removed from the pulp fiber. As a result, the super absorbent polymer attached to the pulp fibers (exemplified: remaining on the surfaces of the pulp fibers) of the mixture 98 is oxidatively decomposed by an aqueous solution (treatment liquid) containing an oxidizing agent (exemplified: ozone), and is removed from the pulp fibers by being changed to a low molecular weight organic material soluble in the aqueous solution. Here, the state where the super absorbent polymer is oxidatively decomposed to become an organic substance having a low molecular weight which is soluble in an aqueous solution means a state where the super absorbent polymer passes through a sieve having a size of 2 mm. Thus, impurities such as super absorbent polymers contained in the pulp fibers can be removed, the pulp fibers with high purity can be produced, and sterilization, bleaching and deodorization of the pulp fibers can be performed by the treatment with the oxidizing agent.

For example, in the oxidizing agent treatment apparatus 19 shown in fig. 4, the mixture 98 containing pulp fibers (with superabsorbent polymer remaining therein) separated in the 3 rd separation step S18 is supplied into the treatment liquid P from the supply port 122b provided in the upper portion of the treatment tank 123. The treatment liquid P is an acidic aqueous solution (for the purpose of suppressing inactivation of ozone and inactivation of the super absorbent polymer), and has a specific gravity of approximately 1. Thus, the pulp fibers gradually settle from the upper portion toward the lower portion of the treatment liquid P. On the other hand, the ozone-containing gas Z generated by the ozone generator 126 is mixed with the treatment liquid P in the ozone mixer 127, and is supplied from the supply port 122c to the treatment tank 123 through the pipe 136. The ozone-containing gas Z is continuously discharged from the vicinity of the supply port 122c in the lower part of the treatment tank 123 into the treatment liquid P in the form of fine bubbles (for example, micro bubbles or nano bubbles). That is, the ozone-containing gas Z gradually rises from the lower portion toward the upper portion of the treatment liquid P. Then, in the treatment liquid P, the pulp fibers descending from the upper portion toward the lower portion and the ozone-containing gas Z ascending from the lower portion toward the upper portion relatively advance and collide with each other. Then, the ozone-containing gas Z is attached to the surface of the pulp fibers in such a manner as to wrap the pulp fibers. At this time, ozone in the ozone-containing gas Z reacts with the super absorbent polymer in the pulp fibers to oxidatively decompose the super absorbent polymer, and dissolves in the treatment liquid P. Thereby, the super absorbent polymer on the pulp fiber is removed from the pulp fiber. Because of the relative flow, the probability of contact between the super absorbent polymer contained in the pulp fibers and the ozone-containing gas Z can be increased.

Then, the pulp fibers settle toward the bottom of the treatment tank 123, and the ozone-containing gas Z is discharged into the space above the treatment tank 123. Ozone containing the ozone gas Z stored in the upper part of the treatment tank 123 is decomposed by the ozone decomposition device 129 to be detoxified and released to the outside. Thereafter, the treatment liquid P (including pulp fibers) at the bottom of the treatment tank 123 is supplied to the treatment tank 123 from a supply port 122a provided at the upper portion of the treatment tank 123 through a pipe 132 by a pump 121. Thereby, the pulp fibers of the treatment liquid P can be gradually settled from the upper portion toward the lower portion of the treatment liquid P again, and can be reacted with the ozone-containing gas Z rising from the lower portion toward the upper portion again. In this manner, the treatment liquid P containing pulp fibers treated with the ozone-containing gas Z is supplied from the lower portion (bottom portion) of the treatment tank 123 to the upper portion of the treatment tank 123 again, and a continuous and stable flow of fluid (containing pulp fibers) from the upper portion to the lower portion can be forcibly generated in the treatment tank 123. The probability of contact between the super absorbent polymer contained in the pulp fibers and the ozone-containing gas Z can be further increased. Further, the pulp fibers are repeatedly treated with the ozone-containing gas Z, so that the super absorbent polymer contained in the pulp fibers can be substantially removed, and the purity of the pulp fibers can be greatly improved. When the oxidizing agent treatment apparatus 19 of fig. 4 is used, the oxidizing agent treatment step S19 is preferably performed as a batch process.

When the ozone-containing gas Z is supplied to the treatment liquid P, the concentration of ozone in the treatment liquid P is, for example, 1 to 50 mass ppm. The ozone concentration in the ozone-containing gas Z is, for example, 40g/m³～200g/m³. The concentration of pulp fibers (including a super absorbent polymer) in the treatment liquid P is, for example, 0.1 to 20% by mass. The time for which the pulp fibers are present in the treatment tank 123 is, for example, 2 minutes to 60 minutes. The ozone-containing gas Z is in the form of micro bubbles (diameter of about 1-1000 μm)Bubbles of (2) or nanobubbles (bubbles having a diameter of about 100nm to 1000 nm). That is, the micro-bubbles or nano-bubbles are fine bubbles, have a large surface area per unit volume, and have a slow rising speed in the liquid, so that the probability of the bubbles contacting the pulp fibers can be increased. Also, the fine bubbles can be more in contact with the surface of the pulp fiber. Thus, the pulp fibers can be wrapped with fine bubbles without omission, and the contact area between the pulp fibers and the ozone-containing gas Z can be further increased. Further, by bringing more bubbles into contact with the pulp surface, the settling rate of the pulp fiber containing a super absorbent polymer can be reduced by buoyancy of the bubbles, and the contact time of the pulp fiber with the ozone-containing gas Z can be further increased. This makes it possible to more reliably oxidize and decompose the superabsorbent polymer contained in the pulp fibers and remove the superabsorbent polymer from the pulp fibers.

In the oxidizing agent treatment apparatus 19 shown in fig. 5, the pulp fibers (with the super absorbent polymer remaining therein) separated in the 3 rd separation step S18 are mixed with an acidic aqueous solution to become a treatment liquid Pa. The treatment liquid Pa is supplied to and stored in the mixture liquid tank 112 via the pipe 131. Then, the processing liquid Pa in the mixture liquid tank 112 is continuously supplied to the processing tank 123 at the 1 st flow rate through the pipe 132a by the flow rate control of the pump 121 a. Thereby, the pulp fibers are supplied to the treatment liquid P from the supply port 122 provided in the upper portion of the treatment tank 123. The treatment liquid P is an acidic aqueous solution and has a specific gravity of approximately 1. Thus, the pulp fibers gradually settle from the upper portion toward the lower portion of the treatment liquid P. On the other hand, the ozone-containing gas Z generated by the ozone generator 126 is supplied to the treatment tank 123 through the pipe 135, and is continuously discharged into the treatment liquid P in the form of fine bubbles (for example, micro bubbles or nano bubbles) from the nozzle 127a of the treatment tank 123. That is, the ozone-containing gas Z gradually rises from the lower portion toward the upper portion of the treatment liquid P. Then, in the treatment liquid P, the pulp fibers descending from the upper portion toward the lower portion and the ozone-containing gas Z ascending from the lower portion toward the upper portion relatively advance and collide with each other. Then, the ozone-containing gas Z is attached to the surface of the pulp fibers in such a manner as to wrap the pulp fibers. At this time, ozone in the ozone-containing gas Z reacts with the super absorbent polymer in the pulp fibers to oxidatively decompose the super absorbent polymer, and dissolves in the treatment liquid P. Thereby, the super absorbent polymer on the pulp fiber is removed from the pulp fiber. Because of the relative flow, the probability of contact between the super absorbent polymer contained in the pulp fibers and the ozone-containing gas Z can be increased. Then, the pulp fibers settle toward the bottom of the treatment tank 123, and the ozone-containing gas Z is discharged into the space above the treatment tank 123. Thereafter, the treatment liquid P (including pulp fibers) at the bottom of the treatment tank 123 is continuously discharged from the discharge port 124 of the treatment tank 123 at the 2 nd flow rate to the outside of the treatment tank 123 through the pipe 133 by the flow rate control of the pump 125 a. Ozone containing the ozone gas Z stored in the upper part of the treatment tank 123 is decomposed by the ozone decomposition device 129 to be detoxified and released to the outside. In this manner, the treatment liquid Pa is continuously supplied from the upper portion of the treatment tank 123 into the treatment tank 123 at the 1 st flow rate, and the treatment liquid P is continuously discharged from the lower portion (bottom portion) of the treatment tank 123 to the outside of the treatment tank 123 at the 2 nd flow rate. This can forcibly generate a continuous and stable flow of fluid (including pulp fibers) from the upper portion to the lower portion in the treatment tank 123. The probability of contact between the super absorbent polymer contained in the pulp fibers and the ozone-containing gas Z can be increased. When the oxidizing agent treatment apparatus 19 of fig. 5 is used, the oxidizing agent treatment step S19 is preferably performed as a continuous treatment.

In the case where the oxidizing agent is ozone, the treatment liquid is an acidic aqueous solution, whereby inactivation of ozone can be suppressed and the effect of ozone (oxidative decomposition, sterilization, bleaching, deodorization of the super absorbent polymer) can be enhanced. In addition, in addition to the inactivation of the super absorbent polymer, when an acidic aqueous solution is used in the crushing treatment or the dust removal treatment, since continuity is provided between the treatments, there is no fear that the aqueous solution differs between the treatments and any trouble occurs, and the treatment can be stably and reliably performed. In addition, from the viewpoint of reducing the influence of the acid on the workers and the facilities, the organic acid in the acidic aqueous solution is preferable, and among them, citric acid is preferable from the viewpoint of removing the metal.

Here, the 1 st flow rate and the 2 nd flow rate are preferably the same. By making the 1 st flow rate and the 2 nd flow rate the same, the amount of the treatment liquid P in the treatment tank 123 can be kept constant, and continuous treatment can be stably performed. However, the 1 st flow rate and the 2 nd flow rate are not always necessarily the same, and may be approximately the same (within 5% of the error) on average over time.

The 4 th separation step S20 is performed by the 4 th separation device 20, and the mixed liquid 99, which is the treatment liquid containing pulp fibers treated by the oxidizing agent treatment device 19, passes through a screen having a plurality of openings, to separate the pulp fibers and the treatment liquid from the mixed liquid 99. As a result, the treatment liquid 104 is separated from the mixed liquid 99 by passing through a sieve and sent out from the 4 th separation apparatus 20. The separated treatment liquid 104, i.e., the oxidizing agent treatment liquid, may be returned to the oxidizing agent treatment device 19 for reuse. The cost of the oxidizer treatment liquid can be reduced. On the other hand, the pulp fibers in the mixed liquid 99 cannot pass through the screen and remain in the 4 th separator 20, or are sent out through another route. The above step can also be referred to as a step of separating and recovering pulp fibers to produce recycled pulp fibers.

The specific gravity of the super absorbent polymer is measured by the pycnometer method which is a method for measuring the density and specific gravity of a chemical product according to JIS K0061. As a result, the specific gravity of the water-absorbent polymer before water absorption was 1.32 g/ml. The specific gravity was 1.04g/ml when inactivated with an aqueous citric acid solution (pH 2) and 1.01g/ml when inactivated with an aqueous citric acid solution (pH 4).

On the other hand, since the size of the super absorbent polymer (after absorbing water) is difficult to be measured, the size (diameter) of the super absorbent polymer is calculated as follows assuming that the super absorbent polymer is a sphere. That is, the average diameter of the super absorbent polymer before water absorption was set to 200 μm, and the size (diameter) of the super absorbent polymer after water absorption was estimated by volume expansion calculation from the amount of water in the aqueous solution absorbed by the super absorbent polymer. The volume expansion calculation is performed as follows. First, the amount of water absorbed by the super absorbent polymer (per 1 particle) was measured. Then, the volume of water corresponding to the amount of water is assumed to be the volume V of the super absorbent polymer after water absorption, based on V-4/3 pi r³The radius r of the super absorbent polymer after water absorption was determined. Then, the user can use the device to perform the operation,the diameter 2 times the radius r is defined as the size of the super absorbent polymer (after water absorption). As a result, the gel diameter was about 420 μm when inactivated with an aqueous citric acid solution (pH 2) and about 540 μm when inactivated with an aqueous citric acid solution (pH 4).

The proportions of pulp fibers and superabsorbent polymer in the acidic aqueous solution were measured as follows. First, a part of an acidic aqueous solution was collected as a sample, and the sample was put into a 200-mesh filter to measure a sample weight W0. Subsequently, the sample on the filter was lifted for 5 minutes, water was drained, absolute drying was performed by a predetermined absolute drying method (method of heating at 120 ℃ for 10 minutes to dry), and the absolute dry weight W1 of the obtained absolute dried product was measured. Next, the absolute dry matter was immersed in an aqueous solution containing ozone, and the resultant was dried absolutely by the above-described absolute drying method, and the absolute dry weight W2 was measured as pulp fibers. Then, the weight obtained by subtracting the absolute dry weight W2 from the absolute dry weight W1 was defined as the weight of the super absorbent polymer, and the ratio of pulp fibers to the super absorbent polymer in the acidic aqueous solution was calculated according to the following formula. That is, the ratio of (pulp fibers) is (absolute dry weight W2)/(sample weight W0), and the ratio of (superabsorbent polymer) is (absolute dry weight W1 — absolute dry weight W2)/(sample weight W0). In weight proportion, the solid weight of the soil is extremely small and therefore negligible.

The concentration of ozone in the aqueous solution was measured as follows. First, 85mL of an aqueous solution in which ozone was dissolved was added to a 100mL measuring cylinder containing about 0.15g of potassium iodide and 5mL of a 10% citric acid solution. After the reaction, the reaction mixture was transferred to a 200mL Erlenmeyer flask. After adding a starch solution and coloring it to purple, titration was carried out while stirring it with 0.01mol/L sodium thiosulfate until it became colorless. From the titration value, the concentration of ozone in the aqueous solution was calculated using the following formula. The concentration (mass ppm) of ozone in the aqueous solution was 0.01mol/L sodium thiosulfate (mL) × 0.24 × 0.85(mL) required for titration

Preferably, the method includes an ozone treatment step S22 and a pH adjustment step S23. These steps are steps for regenerating and recycling the acidic aqueous solution used in the method. By reusing the acidic aqueous solution, the cost of the acidic aqueous solution can be reduced. The ozone treatment step S22 is a step of sterilizing the acidic aqueous solution 101, which is obtained by further separating the super absorbent polymer from the super absorbent polymer and the acidic aqueous solution separated in the 2 nd separation step S17, with an aqueous ozone-containing solution. The pH adjustment step S23 adjusts the pH of the acidic aqueous solution sterilized with the ozone-containing aqueous solution to generate the regenerated acidic aqueous solution 103. The acidic aqueous solution 103 is supplied to the crusher 11, for example. Alternatively, in the case where the opening step S11 is not performed and the crushing step S12 is performed without using the inactivation solution, the separation step S13 is performed as the 1 st separation step. Alternatively, the acidic aqueous solution may be supplied to another process (apparatus) as needed. The remainder of the acidic aqueous solution 103 is stored in the water reservoir 24.

The above method for recovering pulp fibers from a used absorbent article containing pulp fibers and a super absorbent polymer includes at least a solid-liquid separation step (solid-liquid separation device), that is, a 3 rd separation step S18 (3 rd separation device 18) and an oxidizing agent treatment step S19 (oxidizing agent treatment device 19) in a recovery process for recovering pulp fibers and the like (2 nd separation step S17 (2 nd separation device 17) to 4 th separation step S20 (4 th separation device 20)). In the 3 rd separation step S18 (3 rd separation device 18), the gel-like (block-like or substantially spherical) super absorbent polymer remaining after the water absorption of the pulp fibers is crushed to reduce the thickness of the super absorbent polymer, thereby forming the super absorbent polymer into a flat shape or a finely divided shape. The crushing is exemplified by crushing a gel-like super absorbent polymer under a pressure of gel strength or more. That is, the method or system can enlarge the surface area of the super absorbent polymer to a large extent by crushing the super absorbent polymer in a substantially spherical or block shape, and can increase the exposed portion such as exposing the inside portion of the super absorbent polymer to the surface side. Therefore, in the case of the block-shaped or substantially spherical super absorbent polymer in the oxidizing agent treatment step S19 (oxidizing agent treatment apparatus 19), the contact area of the super absorbent polymer with the oxidizing agent can be increased by, for example, contacting the inner portion of the super absorbent polymer that is less likely to contact the oxidizing agent with the oxidizing agent. This enables the oxidative decomposition of the super absorbent polymer to be more efficiently performed, and the time for the oxidizing agent treatment to be shortened. Thus, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

In a preferred embodiment, the 3 rd separation step S18 (3 rd separation device 18) may include a crushing step (screw press dehydrator) of crushing the superabsorbent polymer remaining in the pulp fibers by treating an aqueous inactivation solution (exemplified by an acidic aqueous solution) containing pulp fibers and superabsorbent polymer by a pressure dehydration method.

The method or system crushes the superabsorbent polymer remaining in the pulp fibers by a pressure-type dewatering method, and thus can simultaneously, efficiently and reliably perform solid-liquid separation and crushing of the superabsorbent polymer on the pulp fibers. That is, the surface area of the super absorbent polymer on the pulp fiber can be enlarged efficiently and reliably. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers.

In a preferred embodiment, the pressure in the pressing step (screw press dehydrator) in the crushing step S18 of the 3 rd separation step S18 may be 0.02MPa or more and 0.5Pa or less.

In the method or system, the pressure in the pressurized dehydration method is set to 0.02MPa or more and 0.5Pa or less. Therefore, the super absorbent polymer remaining in the pulp fibers can be sufficiently crushed without damaging the pulp fibers, and the surface area of the super absorbent polymer can be sufficiently enlarged. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers. However, if the pressure is set to less than 0.02MPa, the super absorbent polymer cannot be sufficiently crushed, and the time for the oxidizing agent treatment cannot be shortened too much, and if the pressure is set to more than 0.5MPa, the super absorbent polymer can be sufficiently crushed, but pulp fibers may be damaged.

In a preferred embodiment, the 3 rd separation step S18 (the 3 rd separation device 18) may be preceded by a step of separating the superabsorbent polymer and a part of the inactivated aqueous solution from the inactivated aqueous solution containing the pulp fibers and the superabsorbent polymer, i.e., a 2 nd separation step S17 (the drum screen dehydrator of the 2 nd separation device 17).

The present method or system is provided with a drum screen dehydrator of the 2 nd separation step S17 (the 2 nd separation device 17) before the 3 rd separation step S18 (the 3 rd separation device 18). Therefore, the present method/system can suppress the proportion of the super absorbent polymer in the material (pulp fibers, super absorbent polymer, and inactivated aqueous solution) supplied to the 3 rd separation step S18 (the 3 rd separation device 18) to be low. Thus, in the 3 rd separating step S18 (the 3 rd separating device 18), the super absorbent polymer adhering to the pulp fibers can be crushed more efficiently, and the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers can be improved.

In a preferred embodiment, the proportion of the super absorbent polymer in the inactivated aqueous solution supplied to the 3 rd separation step S18 (the 3 rd separation device 18) may be 50% or less.

In the present method or system, the ratio of the super absorbent polymer in the inactivated aqueous solution to be separated is 50% or less in the 3 rd separation step S18 (3 rd separation device 18). This eliminates the need to crush an excessive amount of the super absorbent polymer, and thus the super absorbent polymer can be crushed more reliably and efficiently. This can improve the efficiency of the treatment for removing the super absorbent polymer from the pulp fibers.

In a preferred embodiment, the method may further include, before the 3 rd separation step S18 (the 3 rd separation device 18), a step of crushing the used absorbent article in an inactivation aqueous solution (including S12) and a step of separating the inactivation aqueous solution containing the pulp fiber and the super absorbent polymer from the inactivation aqueous solution containing the crushed material obtained in the crushing step (including S12) (including S13, preferably, S14 to S16).

The present method or system is produced by a step of crushing the inactivated aqueous solution containing pulp fibers and superabsorbent polymers separated from used absorbent articles supplied in the 3 rd separation step S18 (3 rd separation device 18) and a separation step of washing. By using the crushing step and the separation step, it is possible to suppress the contamination of foreign matter (materials other than pulp fibers and super absorbent polymers (exemplified by films, nonwoven fabrics, elastomers, etc.) of the disposable absorbent article) into the inactivated aqueous solution. This can crush the super absorbent polymer more reliably without being hindered by foreign matter. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

In a preferred embodiment, the inactivation aqueous solution may be an acidic aqueous solution.

In the present method or system, since the inactivation aqueous solution is an acidic aqueous solution, the superabsorbent polymer in the used absorbent article can be reliably dehydrated to a predetermined size (exemplified by particle diameter) or less. Thus, in the 3 rd separation step S18 (3 rd separation device 18), the super absorbent polymer can be crushed while easily performing solid-liquid separation. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

In a preferred embodiment, the acidic aqueous solution may have a pH of 2.5 or less.

In the method or system, the acidic aqueous solution has a pH of 2.5 or less, and therefore, the superabsorbent polymer in the used absorbent article can be dehydrated more reliably to a predetermined size (exemplified by particle diameter) or less. Thus, in the 3 rd separation step S18 (3 rd separation device 18), the super absorbent polymer can be crushed while the solid-liquid separation is more easily performed. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved. Further, since the superabsorbent polymer is set to a predetermined size or less in the gel state, the superabsorbent polymer can be easily crushed.

In a preferred embodiment, the acidic aqueous solution may contain citric acid.

In the method or system, since the acidic aqueous solution contains citric acid (exemplified as a concentration of 0.5 to 2.0 mass%), the superabsorbent polymer in the used absorbent article can be reliably dehydrated to a predetermined particle size or less. Thus, in the 3 rd separation step S18 (3 rd separation device 18), the super absorbent polymer can be crushed while easily performing solid-liquid separation. As a result, the efficiency of the treatment for removing the super absorbent polymer from the pulp fiber can be improved.

Examples

An example of the above-described method for recovering pulp fibers from a used absorbent article will be described below.

In this example, the absorbent article, from which the pulp fibers and the superabsorbent polymer were removed by crushing, was subjected to the 3 rd separation step S18 and the oxidizing agent treatment step S19 of the above method. Then, the relationship between the pressure applied at the time of pressurization in the 3 rd separation step S18 and the treatment time of the oxidizing agent treatment in the oxidizing agent treatment step S19 was examined. Specifically, as the absorbent article, the mixed liquid 97 in which a plurality of disposable diapers for adults (not used) have been treated in the crushing step S12 to the 2 nd separating step S17 is used. In the 3 rd separation step S18, the pressure applied during the pressurization in the pressure dewatering method (the pressure applied to the cover) is changed to 0 to 3.3kgf/cm²(0 to 0.32 MPa). At this time, the time when the pulp fibers became undetectable with the super absorbent polymer in the oxidizing agent treatment step S19 was measured as the treatment time. The treatment time is a time at which a predetermined amount of pulp fibers are taken out at regular intervals in the oxidizing agent treatment step S19, whether or not the super absorbent polymer is attached to the pulp fibers is detected, and the super absorbent polymer is no longer detected, and is referred to as a treatment time.

In addition, whether or not the super absorbent polymer adheres to the pulp fiber was measured as follows.

After 10g of the pulp fibers were taken out and water was removed, the fibers were disentangled while irradiating with light, and whether or not a polymer was adhered and remained was visually checked with a magnifying glass having a magnification of 20 times. If the polymer remains, light is reflected and emitted, and thus the polymer can be easily found.

Fig. 7 shows the results of examining the relationship between the pressure applied at the time of pressurization and the treatment time of the oxidizing agent treatment. Fig. 7 is a graph showing a relationship between the pressure applied at the time of pressurization and the treatment time of the oxidizing agent treatment. The horizontal axis represents applied pressure (kgf/cm)²) And the vertical axis represents the treatment time (minutes).

As shown in the figure, it was found that the applied pressure was 0kgf/cm²The treatment time of 40 minutes is used as a reference, and when the applied pressure is small, the effect of reducing the treatment time is small, but when the applied pressure is large, the effect of reducing the treatment time is large. In addition, it was also found that the effect of reducing the treatment time was saturated at a certain pressure or more.

Therefore, from the viewpoint of reducing the treatment time, the pressure is preferably 0.2kgf/cm²(0.02MPa) or more. From the viewpoints of saturation of the reducing effect, reliability of the reducing effect, and the like, the pressure is preferably 5kgf/cm²(0.5MPa) or less. The pressure is more preferably 0.5kgf/cm²(0.05MPa) or more, 3kgf/cm²(0.3MPa)。

The above embodiment describes a case where the structural member of the back sheet is a film and the structural member of the front sheet is a nonwoven fabric. However, the embodiment in which the structural member of the back sheet is a nonwoven fabric, the structural member of the front sheet is a film, or the embodiment in which the structural members of both the back sheet and the front sheet are films can be realized by the same method as the above-described embodiment, and the same operational effects can be produced.

The absorbent article of the present invention is not limited to the above-described embodiments, and can be appropriately combined, modified, and the like without departing from the object and spirit of the present invention.

Description of the reference numerals

S18, No. 3 separation step

S19 oxidizing agent treatment step

Claims

1. A method of recovering pulp fibers from a used absorbent article comprising pulp fibers and a superabsorbent polymer, wherein the method comprises:

a solid-liquid separation step of separating an inactivated aqueous solution containing pulp fibers and a superabsorbent polymer separated from a used absorbent article into a solid containing the pulp fibers and the superabsorbent polymer and a liquid containing the superabsorbent polymer and the inactivated aqueous solution, and crushing the superabsorbent polymer contained in the solid; and

and an oxidizing agent treatment step of treating the pulp fibers contained in the separated solids and the crushed superabsorbent polymer with an aqueous solution containing an oxidizing agent.

2. The method according to claim 1, wherein the solid-liquid separation step comprises a crushing step of crushing the superabsorbent polymer remaining in the pulp fibers by treating the inactivated aqueous solution containing the pulp fibers and the superabsorbent polymer by a pressure-type dewatering method.

3. The method according to claim 2, wherein the pressure at the time of pressurization in the pressurized dehydration method in the crushing step is 0.02MPa or more and 0.5MPa or less.

4. The method according to any one of claims 1 to 3, further comprising a step of separating the superabsorbent polymer and a part of the aqueous deactivation solution from the aqueous deactivation solution containing the pulp fibers and the superabsorbent polymer, before the solid-liquid separation step.

5. The method according to any one of claims 1 to 4, wherein the proportion of the super absorbent polymer in the inactivated aqueous solution supplied to the solid-liquid separation step is 50% or less.

6. The method according to any one of claims 1 to 5, further comprising, before the solid-liquid separation step, the step of:

breaking the used absorbent article in an aqueous deactivation solution; and

separating an aqueous inactivation solution containing pulp fibers and a superabsorbent polymer from the aqueous inactivation solution containing the crushed material obtained from the crushing step.

7. The method of any one of claims 1 to 6, wherein the aqueous inactivation solution is an acidic aqueous solution.

8. The method according to claim 7, wherein the acidic aqueous solution has a pH of 2.5 or less.

9. The method of claim 7 or 8, wherein the acidic aqueous solution comprises citric acid.

10. A system for recovering pulp fibers from a used absorbent article comprising pulp fibers and a superabsorbent polymer, wherein the system comprises:

a solid-liquid separation device that separates an inactivated aqueous solution containing pulp fibers and a superabsorbent polymer separated from used absorbent articles into a solid containing the pulp fibers and the superabsorbent polymer and a liquid containing the superabsorbent polymer and the inactivated aqueous solution, and crushes the superabsorbent polymer contained in the solid; and

an oxidizing agent treatment device for treating the pulp fibers contained in the separated solids and the crushed superabsorbent polymer with an aqueous solution containing an oxidizing agent.

11. The system of claim 10, wherein the solid-liquid separation device comprises a screw press dehydrator that crushes the superabsorbent polymer remaining in the pulp fibers by treating the inactivated aqueous solution containing the pulp fibers and the superabsorbent polymer by a pressurized dehydration method.

12. The system according to claim 11, wherein the pressure at the time of pressurization in the pressurized dewatering method of the screw press dehydrator is 0.02MPa or more and 0.5MPa or less.

13. The system of any of claims 10-12, further comprising a trommel dehydrator for separating the superabsorbent polymer and a portion of the aqueous deactivation solution from the aqueous deactivation solution comprising the pulp fibers and the superabsorbent polymer prior to the solid-liquid separation device.

14. The system according to any one of claims 10 to 13, wherein the proportion of the super absorbent polymer in the inactivation aqueous solution supplied to the solid-liquid separation device is 50% or less.

15. The system of any one of claims 10-14, wherein the aqueous inactivation solution is an acidic aqueous solution.

16. The system of claim 15, wherein the acidic aqueous solution is at a ph of 2.5 or less.

17. The system of claim 15 or 16, wherein the acidic aqueous solution comprises citric acid.