A method for recovering multiple materials, including superabsorbent polymers and pulp fibers, from used absorbent items.

Abstract

The present invention provides a method of recovering materials of a used absorbent article, capable of reducing the burden of wastewater treatment of a treatment liquid, and capable of reducing the burden of hygiene in maintenance of an apparatus. The present method is a method of recovering a plurality of materials including a superabsorbent polymer and pulp fibers from a used absorbent article to which dirt has adhered and which has absorbed moisture. The present method includes a pretreatment step (S01) in which a pretreatment of removing dirt and moisture from the used absorbent article in a deactivation aqueous solution that deactivates a superabsorbent polymer and discharging the deactivation aqueous solution containing the dirt and moisture is performed, and a main treatment step (S02) in which water is injected to the used absorbent article from which the dirt and moisture have been removed, at least one of the plurality of materials is separated and recovered from the used absorbent article.

Description

Technical Field

[0001] This invention relates to a method for recovering various materials, including superabsorbent polymers and pulp fibers, from used absorbent articles. Background Technology

[0002] Methods for recycling materials from used absorbent articles are known. For example, Patent Document 1 discloses a method for recovering pulp fibers from used absorbent articles containing pulp fibers and superabsorbent polymers. This method includes: a receiving step of placing a collection bag containing the used absorbent articles into a container; a crushing step of transferring the collection bag from the container to a crushing device connected to the container, while simultaneously crushing the used absorbent articles in the collection bag along with the collection bag in an inactivating aqueous solution using the crushing device; and a separation step of separating the pulp fibers, superabsorbent polymer, and inactivating aqueous solution from the crushed material obtained in the crushing step using a separation device.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-85686 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Patent Document 1 describes a method capable of recovering various materials, such as films / nonwoven fabrics, pulp fibers, and superabsorbent polymers, from used absorbent articles. In each step of this method, multiple materials are treated in treated water. An acidic aqueous solution is cited as an example of this treated water. This acidic aqueous solution is reused by circulating it within multiple devices that perform consecutive multiple steps.

[0008] However, in this method, in order to adjust the pH of the acidic aqueous solution and to remove the acidic aqueous solution containing impurities that have not been completely removed, it is necessary to partially or completely replace the acidic aqueous solution at appropriate times. Therefore, since some amount of wastewater containing acidic aqueous solution may be generated, the burden of wastewater treatment such as neutralization of the acidic aqueous solution may become greater.

[0009] Furthermore, in this method, waste such as excrement contained in the used absorbent materials is ultimately removed, but it passes through multiple devices. Therefore, when maintaining multiple devices, it is necessary to ensure that the waste does not adversely affect the external environment or workers, potentially increasing the hygiene burden.

[0010] The purpose of this invention is to provide a method for recycling used absorbent materials, in which the burden of wastewater treatment of the treatment liquid can be reduced, and the hygiene burden of equipment maintenance can be reduced.

[0011] Methods for solving problems

[0012] One aspect of the present invention is a method for recovering multiple materials, including superabsorbent polymers and pulp fibers, from used absorbent articles that are contaminated and have absorbed moisture. The method includes: a pretreatment step in which contaminants and moisture are removed from the used absorbent articles in an inactivating aqueous solution that inactivates the superabsorbent polymer, and the inactivating aqueous solution containing the contaminants and moisture is discharged; and a main treatment step in which water is injected into the used absorbent articles from which the contaminants and moisture have been removed, and at least one of the multiple materials is separated and recovered from the used absorbent articles.

[0013] The effects of the invention

[0014] According to the method of the present invention, a method for recycling used absorbent materials can be provided, in which the burden of wastewater treatment of the treatment liquid can be reduced, and the hygiene burden of device maintenance can be reduced. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating a method for recycling used absorbent materials according to an embodiment.

[0016] Figure 2 This is a flowchart illustrating the preprocessing steps of the implementation method.

[0017] Figure 3 This is a schematic diagram illustrating an apparatus for implementing a pretreatment process.

[0018] Figure 4 This is a flowchart illustrating the main processing steps of the implementation method. Detailed Implementation

[0019] This implementation method involves the following approaches.

[0020] [Method 1]

[0021] A method for recovering multiple materials, including superabsorbent polymers and pulp fibers, from used absorbent articles that are contaminated and have absorbed moisture, wherein the method comprises: a pretreatment step in which contaminants and moisture are removed from the used absorbent articles in an inactivating aqueous solution that inactivates the superabsorbent polymer, and the inactivating aqueous solution containing the contaminants and moisture is discharged; and a main treatment step in which water is injected into the used absorbent articles from which the contaminants and moisture have been removed, and at least one of the multiple materials is separated and recovered from the used absorbent articles.

[0022] In this method, firstly, in a pretreatment step, contaminants and moisture are removed from the used absorbent material by inactivating the superabsorbent polymer with an inactivating aqueous solution (e.g., a strongly acidic aqueous solution), thereby dehydrating the superabsorbent polymer. Then, in the main treatment step, water is injected into the used absorbent material, which has been cleaned of contaminants and moisture, and is now lightweight and has a low volume, to separate and recover at least one material.

[0023] Therefore, the pretreatment steps with fewer steps are carried out in the inactivation aqueous solution, while the main treatment steps, such as decomposition, separation, and recovery, which involve more steps, are carried out in water, not in the inactivation aqueous solution. This reduces the amount of inactivation aqueous solution used, thus controlling the amount of wastewater generated. Consequently, this method reduces the burden of wastewater treatment in the recovery of used absorbent materials.

[0024] Furthermore, since water is used in the main processing steps, which involve numerous steps and a large number of devices, the adverse effects of contaminants on the external environment and workers can be minimized during device maintenance. Therefore, this method reduces the hygiene burden in the recycling of used absorbent materials.

[0025] Therefore, this method reduces the burden of wastewater treatment for processing solutions (such as inactivated aqueous solutions) and also reduces the hygiene burden of maintaining multiple devices. Furthermore, through the pretreatment process, used absorbent materials are cleaned of impurities and moisture, achieving lightweight and low-volume processing, thus reducing the amount of water used in the main treatment process. Therefore, this method reduces the environmental burden in the recycling of used absorbent materials.

[0026] [Method 2]

[0027] According to the method of method 1, the inactivating aqueous solution comprises a strongly acidic aqueous solution.

[0028] In this method, an acidic aqueous solution containing strong acidity is used as the inactivation solution in the pretreatment step. By using the strong acidic aqueous solution, the inactivation (dehydration) of the superabsorbent polymer is further promoted. This further removes contaminants and moisture from the used absorbent materials. Furthermore, the used absorbent materials are sterilized or disinfected through the bactericidal or disinfecting effect of the acidic aqueous solution. Then, in the main treatment step, since the used absorbent materials, which have been further cleaned of contaminants and moisture, are lighter and have a lower volume, and have been sterilized or disinfected, are treated in water (not in the acidic aqueous solution), the volume of wastewater from the acidic aqueous solution can be further reduced. Furthermore, since other inactivating agents (e.g., lime, calcium chloride, magnesium sulfate, magnesium chloride, aluminum sulfate, aluminum chloride, etc.), bactericides, disinfectants, and other chemicals are not used, their usage can be reduced. This reduces the burden of treating this wastewater. Therefore, this method can reduce the burden of wastewater treatment of the treatment liquid and reduce the hygiene burden of maintaining multiple devices.

[0029] [Method 3]

[0030] According to the method of method 2, the pretreatment step includes the step of maintaining the used absorbent article in the state at which it was recycled in the acidic aqueous solution and performing the pretreatment.

[0031] In this method, during the pretreatment step, the used absorbent material remains in the same state as when it was recycled, removing contaminants and moisture without decomposing into multiple materials. Therefore, during the pretreatment step, it is difficult for materials to be finely decomposed and leave large amounts of residue within the equipment, allowing operators to maintain the equipment extremely easily and hygienically. Furthermore, since the used absorbent material does not decompose into multiple materials, it is difficult for materials to enter the wastewater containing the treatment liquid (acidic aqueous solution, etc.). This reduces the hygiene burden in the wastewater treatment of the treatment liquid (acidic aqueous solution, etc.). Therefore, this method reduces the burden of wastewater treatment of the treatment liquid (acidic aqueous solution, etc.) and also reduces the hygiene burden in the maintenance of multiple equipment.

[0032] [Method 4]

[0033] According to method 2 or 3, the pretreatment step includes: an introduction step, in which the used absorbent material and the acidic aqueous solution are introduced into a treatment tank, the surface of the acidic aqueous solution being lower than the uppermost part of the unfloating used absorbent material; an inactivation step, in which the acidic aqueous solution is allowed to permeate the used absorbent material by repeatedly applying and easing pressure to the used absorbent material in the treatment tank and in the acidic aqueous solution; and a removal step, in which dirt and moisture are removed from the used absorbent material.

[0034] In this method, during the pretreatment step, the level of the acidic aqueous solution is lower than the top of the multiple used absorbent materials, thus the amount of acidic aqueous solution is very small. This further reduces the volume of wastewater containing the acidic aqueous solution. Simultaneously, it prevents the used absorbent materials from separating and disintegrating due to the force of the acidic aqueous solution flow during the inactivation step, thereby improving hygiene during operator maintenance and suppressing material contamination in the wastewater of the treatment solution (acidic aqueous solution).

[0035] Furthermore, in the inactivation process, during the initial action, pressure is applied to release the gas (e.g., air) inside the used absorbent article to the outside. Then, as the pressure is released, the external liquid (e.g., acidic aqueous solution) is absorbed into the inside under the attraction of the used absorbent article's shape recovery. In subsequent actions, pressure is applied to release the gas and liquid (e.g., moisture released by the inactivation of the superabsorbent polymer based on the acidic aqueous solution) inside the used absorbent article to the outside. Then, as the pressure is released, the external liquid (e.g., acidic aqueous solution) is absorbed into the inside. Thus, even with a small amount of acidic aqueous solution, it is possible to efficiently penetrate the interior of the used absorbent article.

[0036] Furthermore, since a strongly acidic aqueous solution is used, even a small amount of the acidic aqueous solution can reliably inactivate the superabsorbent polymers inside the used absorbent article, allowing internal moisture (e.g., urine) to be released to the outside, thus achieving dehydration. Therefore, by finally removing moisture from the used absorbent article in the removal process, the used absorbent article can be made lighter.

[0037] Here, during the inactivation process, along with the gas and liquid released from the used absorbent material by applying pressure, the excrement attached to the used absorbent material can also be squeezed out to the outside, making the used absorbent material lighter.

[0038] Thus, in this method, during the pretreatment process, a small amount of acidic aqueous solution can be used to reduce the dirt and moisture in the used absorbent materials, thereby preventing the dirt and moisture from being carried to the main treatment process.

[0039] Therefore, it can reduce the burden of wastewater treatment of treatment liquids (such as acidic aqueous solutions) and reduce the hygiene burden of maintenance of multiple devices.

[0040] [Method 5]

[0041] According to the method of method 4, the inactivation step includes the step of applying and mitigating the pressure by causing the used absorbent article to collide with other used absorbent articles.

[0042] In this method, the inactivation step in the pretreatment process includes applying and mitigating pressure by causing each of the multiple used absorbent articles in the treatment tank to collide with each other. Thus, in the inactivation step, the separation and disintegration of the used absorbent articles due to the force of the acidic aqueous solution flow can be easily and reliably suppressed, and the application and mitigation of pressure on the used absorbent articles allows the acidic aqueous solution to permeate them.

[0043] [Method 6]

[0044] According to the method of method 5, the treatment tank is a horizontal rotating drum, and the inactivation process includes a process in which the used absorbent articles collide with other used absorbent articles by rotating the rotating drum.

[0045] In this method, since the treatment tank is a horizontal rotating drum in the pretreatment step, the rotation of the drum in the deactivation step allows each of the multiple used absorbent materials inside the drum to easily and reliably collide with each other. This makes it easier and more reliable to suppress the separation and disintegration of the used absorbent materials due to the force of the acidic aqueous solution flow, and the application and easing of pressure on the used absorbent materials allows the acidic aqueous solution to penetrate them.

[0046] [Method 7]

[0047] According to any one of methods 4 to 6, the surface of the acidic aqueous solution in the introduction step is located at the position where the used absorbent article is immersed in the treatment tank at 3 / 5 to 4 / 5.

[0048] In this method, during the pretreatment step, the level of the acidic aqueous solution introduced in the process is such that 3 / 5 to 4 / 5 (of the number of) of the multiple used absorbent materials in the treatment tank are immersed. That is, 1 / 5 to 2 / 5 of the multiple used absorbent materials may not be immersed. In this way, by using a smaller amount of acidic aqueous solution on the multiple used absorbent materials, the amount of wastewater can be further suppressed. Furthermore, by using a smaller amount of acidic aqueous solution, the separation and disintegration of the used absorbent materials from their recycling state due to the force of the water flow of the acidic aqueous solution during the inactivation step can be further suppressed.

[0049] [Method 8]

[0050] According to any one of methods 4 to 7, in the introduction step, the weight of the acidic aqueous solution is 2 to 3 times the weight of the used absorbent article in the treatment tank.

[0051] In this method, during the pretreatment step, the weight of the acidic aqueous solution introduced into the process is 2 to 3 times the weight of the multiple used absorbent materials in the treatment tank. This way, by using a small amount of acidic aqueous solution on the multiple used absorbent materials, the amount of wastewater can be suppressed. Furthermore, by using a small amount of acidic aqueous solution, the separation and disintegration of the used absorbent materials from their original state during the inactivation step due to the force of the acidic aqueous solution flow can be prevented.

[0052] [Method 9]

[0053] According to any one of methods 4 to 8, in the introduction step, the pH of the acidic aqueous solution is below 2.0.

[0054] In this method, the pH of the acidic aqueous solution introduced in the pretreatment step is below 2.0. Therefore, even if the acidic aqueous solution is in small amounts relative to the multiple used absorbent materials, the inactivation step of this method can more reliably inhibit the separation and disintegration of the multiple used absorbent materials, and perform inactivation and dehydration.

[0055] [Method 10]

[0056] According to any one of methods 4 to 9, in the introductory step, the acidic aqueous solution contains sulfuric acid.

[0057] In this method, the acidic aqueous solution introduced in the pretreatment step contains sulfuric acid. Therefore, even if the acidic aqueous solution is in small amounts relative to the multiple used absorbent materials, the inactivation step of this method can more reliably inhibit the separation and disintegration of the multiple used absorbent materials, and perform inactivation and dehydration.

[0058] [Method 11]

[0059] According to any one of methods 4 to 10, the dehydration rate of the used absorbent article after the removal process is 60% or more.

[0060] In this method, during the pretreatment step, the dehydration rate of multiple used absorbent materials after the previous step is over 60%. Therefore, this method can suppress the separation and disintegration of multiple used absorbent materials, and can achieve extremely good inactivation and dehydration, resulting in very effective weight reduction.

[0061] [Method 12]

[0062] According to any one of methods 1 to 11, the main processing step includes: a separation step in which water, including the used absorbent article from which dirt and moisture have been removed, is separated into superabsorbent polymer, pulp fibers, and water, and other materials; and a recycling step in which superabsorbent polymer and pulp fibers are separated and recycled from the separated superabsorbent polymer, pulp fibers, and water, respectively.

[0063] In this method, the main treatment processes are carried out in water, not in acidic aqueous solutions. Therefore, the amount of acidic aqueous solution used can be reduced, thereby reducing the amount of acidic wastewater and lowering the burden of wastewater treatment. Furthermore, since water is used in the main treatment processes, which involve many steps, the adverse effects of contaminants on the external environment and workers can be minimized during equipment maintenance, reducing hygiene burdens.

[0064] [Method 13]

[0065] According to the method of method 12, the main processing step further includes a crushing step of crushing the used absorbent material before the separation step.

[0066] In this method, the main processing steps also include a crushing step that breaks down the used absorbent material before the separation step. Therefore, by means of the crushing step, the constituent materials of the used absorbent material can be easily separated from each other before the separation step. This allows for a more efficient separation process and facilitates the recovery of the materials (constituent materials) of the used absorbent material.

[0067] [Method 14]

[0068] According to the method of method 1 or 2, the pretreatment step includes: a crushing step of crushing the used absorbent article; and an inactivation step of immersing the crushed fragments of the used absorbent article in the inactivation aqueous solution.

[0069] In this method, the used absorbent material is crushed in a crushing step before the inactivation step in the pretreatment process. This allows for easier contact between the inactivation aqueous solution and the superabsorbent polymer in the used absorbent material through the cross-section of the crushed material. Therefore, the superabsorbent polymer can be efficiently inactivated (dehydrated), thus reducing the amount of inactivation aqueous solution or the concentration of the inactivating agent in the solution. This, in turn, reduces the environmental burden.

[0070] [Method 15]

[0071] According to method 1 or 2, the pretreatment step includes an inactivation and crushing step of crushing the used absorbent article together with the inactivation aqueous solution.

[0072] In this method, during the pretreatment step, the used absorbent material is crushed and the superabsorbent polymers within it are inactivated almost simultaneously through the inactivation and crushing process. Therefore, the inactivation solution can more easily contact the superabsorbent polymers through the cross-section of the crushed material, and the pretreatment time can be shortened. Consequently, the superabsorbent polymers can be efficiently inactivated (dehydrated), thus reducing the amount of inactivation solution or the concentration of the inactivating agent in the solution, and decreasing the energy consumed in the process. Therefore, the environmental burden can be reduced.

[0073] [Method 16]

[0074] According to method 1 or 2, the pretreatment step includes: an inactivation step of immersing the used absorbent article in the inactivation aqueous solution; and a crushing step of crushing the used absorbent article containing the inactivated superabsorbent polymer.

[0075] In this method, the superabsorbent polymer (SAP) in the used absorbent material is deactivated (dehydrated) during the inactivation step of the pretreatment process, prior to the crushing step. This reduces the swelling of the SAP before the crushing step. Consequently, the SAP is less likely to be damaged during the crushing step, thus reducing the amount of SAP that is difficult to reuse. Therefore, the SAP recovery rate is improved, and the amount of inactivating aqueous solution or the concentration of the inactivating agent in the inactivating aqueous solution required for SAP recovery is reduced. This reduces the environmental burden.

[0076] [Method 17]

[0077] According to any one of methods 1 to 16, the amount of the inactivating aqueous solution used in the pretreatment step is less than the amount of water injected in the main treatment step.

[0078] If a method is to recover multiple materials from used absorbent articles solely through a main treatment process without a pretreatment step, the main treatment process requires the use of an inactivating aqueous solution. In this case, the amount of inactivating aqueous solution is approximately the same as the amount of water injected into the main treatment process when both a pretreatment and a main treatment process are performed (described later). Therefore, compared to the method of recovering multiple materials from used absorbent articles solely through a main treatment process without a pretreatment step—that is, the case where the main treatment process is performed without water but using an inactivating aqueous solution—this method can reduce the amount of inactivating aqueous solution. This, in turn, reduces the environmental burden.

[0079] (First Implementation)

[0080] The following describes a method for recovering various materials, including superabsorbent polymers and pulp fibers, from used absorbent articles according to the first embodiment. However, used absorbent articles include not only those used by a user, i.e., those that absorb and retain the user's excrement, but also unused but discarded absorbent articles. Examples of absorbent articles include disposable diapers, diaper pads, sanitary napkins, bed sheets, and pet pads.

[0081] First, an example of the structure of an absorbent article will be described. An absorbent article includes a surface sheet, a back sheet, and an absorbent body disposed between the surface sheet and the back sheet. As an example of the size of an absorbent article, a length of approximately 15 to 100 cm and a width of 5 to 100 cm can be given. It should be noted that absorbent articles may also include other components commonly found in absorbent articles, such as diffuser sheets, leak-proof walls, side sheets, and outer sheaths.

[0082] The material for the surface sheet is not particularly limited, and known surface sheet materials can be used. Examples include liquid-permeable nonwoven fabrics, synthetic resin membranes with liquid-permeable pores, and composite sheets thereof. The material for the back sheet is not particularly limited, and known back sheet materials can be used. Examples include liquid-impermeable nonwoven fabrics, liquid-impermeable synthetic resin membranes, and composite sheets thereof. The material for the diffuser sheet is not particularly limited, and known diffuser sheet materials can be used. Examples include liquid-permeable nonwoven fabrics. The material for the leak-proof wall and side sheets is not particularly limited, and known leak-proof wall and side sheet materials can be used. Examples include waterproof nonwoven fabrics, and the leak-proof wall may further include elastic components such as rubber threads. The material for the outer sheath is not particularly limited, and known outer sheath materials can be used. Examples include liquid-impermeable and breathable nonwoven fabrics, liquid-impermeable and breathable synthetic resin membranes, and composite sheets thereof.

[0083] There are no particular limitations on the types of nonwoven fabrics mentioned above. Examples include meltblown nonwoven fabrics, spunbond nonwoven fabrics, thermally bonded nonwoven fabrics, air-laid nonwoven fabrics, and hot-air nonwoven fabrics. Similarly, there are no particular limitations on the types of synthetic resin films; known film materials can be used. Here, the materials used for nonwoven fabrics and synthetic resin films are simply those suitable for use in absorbent articles; there are no particular limitations. Examples include olefin resins such as polyethylene and polypropylene, polyamide resins such as 6-nylon and 6,6-nylon, and polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). These nonwoven fabrics or synthetic resin films are made of synthetic resins and can be referred to as plastic materials. In this embodiment, an absorbent article in which the back sheet is a film and the surface sheet is a nonwoven fabric will be described as an example.

[0084] Examples of absorbent materials include pulp fibers and superabsorbent polymers. Examples of pulp fibers include cellulose fibers. Examples of cellulose fibers include wood pulp, cross-linked pulp, non-wood pulp, regenerated cellulose, and semi-synthetic cellulose. Regarding the size of pulp fibers, the average long diameter can be, for example, tens of μm (20–40 μm), and the average fiber length can be, for example, several mm (2–5 mm). Examples of superabsorbent polymers (SAP) include polyacrylate-based, polysulfonate-based, and maleic anhydride-based superabsorbent polymers. Regarding the size of superabsorbent polymers (when dry), the average particle size can be, for example, hundreds of μm (200–500 μm). The absorbent may also be encapsulated within a core layer formed of a liquid-permeable sheet.

[0085] One side and the other side of the absorbent are bonded to the surface sheet and the back sheet, respectively, via adhesives. In a top view, the portion of the surface sheet extending outwards from the absorbent (peripheral portion) in a manner surrounding the absorbent is bonded to the portion of the back sheet extending outwards from the absorbent (peripheral portion) in a manner surrounding the absorbent via adhesive. Thus, the absorbent is enclosed within the bonded body of the surface sheet and the back sheet. No particular limitation is made to the adhesive; for example, a hot-melt adhesive can be cited. Examples of hot-melt adhesives include pressure-sensitive or heat-sensitive adhesives with rubber-based or olefin-based substrates such as styrene-ethylene-butadiene-styrene, styrene-butadiene-styrene, and styrene-isoprene-styrene.

[0086] Next, a method for recovering various materials, including superabsorbent polymers and pulp fibers, from used absorbent articles that are soiled and have absorbed moisture will be specifically described. For example, used absorbent articles that are soiled and have absorbed moisture can be collected from external sources (hospitals, nursing homes, private residences, etc.). It should be noted that by separating and recovering superabsorbent polymers and pulp fibers from used absorbent articles to obtain reusable superabsorbent polymers and pulp fibers, this method can be described as a method for manufacturing reusable superabsorbent polymers and regenerated pulp fibers, since reusable recycled superabsorbent polymers and recycled pulp fibers are generated.

[0087] Figure 1 This is a flowchart illustrating a method for recycling used absorbent materials according to an embodiment. The method includes a pretreatment step S01 and a main treatment step S02.

[0088] Pretreatment step S01 is a pretreatment process in which contaminants and moisture are removed from the used absorbent material in an inactivation solution (e.g., a strongly acidic aqueous solution), and the inactivation solution containing contaminants and moisture is discharged. For example, used absorbent materials with contaminants and absorbed moisture are placed in a treatment tank containing the inactivation solution. Then, the inactivation solution inactivates and dehydrates the superabsorbent polymer, and the moisture released from the superabsorbent polymer to the outside and the contaminants and moisture removed from the used absorbent material by the inactivation solution are removed. Therefore, used absorbent materials with very little contaminants and moisture, are lightweight, and have a low volume can be obtained.

[0089] The inactivating aqueous solution is an aqueous solution containing an inactivating agent that inactivates (dehydrates) the superabsorbent polymer. Examples of inactivating aqueous solutions include strongly acidic aqueous solutions. It should be noted that aqueous solutions containing other known inactivating agents (e.g., lime, calcium chloride, magnesium sulfate, magnesium chloride, aluminum sulfate, aluminum chloride, etc.) may also be used as the inactivating aqueous solution. In this embodiment, a strongly acidic aqueous solution is used as the inactivating aqueous solution.

[0090] Here, a strongly acidic aqueous solution inactivates and dehydrates the superabsorbent polymer contained in the used absorbent articles. The pH of the strongly acidic aqueous solution is preferably 2.0 as the upper limit and 0.5 as the lower limit. Even if the used absorbent articles are prevented from separating or disintegrating, or even if the amount of acidic aqueous solution is small, an acidic aqueous solution with a pH of 2.0 or lower can sufficiently inactivate and dehydrate the superabsorbent polymer, thereby achieving high bactericidal ability. That is, even in situations where the acidic aqueous solution is difficult to distribute widely, such as when treating multiple used absorbent articles, the superabsorbent polymer can be sufficiently inactivated and dehydrated. Acidic aqueous solutions with a pH of 0.5 or higher are less likely to corrode equipment, reducing the amount of alkaline chemicals required for neutralization treatment during wastewater treatment. It should be noted that pH varies with water temperature; therefore, the pH in this invention is the pH measured at an aqueous solution temperature of 20°C.

[0091] Examples of acidic aqueous solutions include aqueous solutions of inorganic acids and organic acids. Examples of inorganic acids include sulfuric acid, hydrochloric acid, and nitric acid, but sulfuric acid is preferred from the viewpoints of being chlorine-free and cost-effective. It should be noted that examples of organic acids include citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, and ascorbic acid, but citric acid is preferred. Through the chelating effect of citric acid, metal ions and other substances in excrement can be captured and removed, and through the cleaning effect of citric acid, a high level of dirt removal can be expected. In this embodiment, sulfuric acid, an inorganic acid, is used. Therefore, even if the amount of acidic aqueous solution is relatively small compared to the number of used absorbent materials, the pretreatment step S01 (deactivation step S12: described later) can more reliably suppress the separation and disintegration of the multiple used absorbent materials, and inactivation and dehydration can be performed.

[0092] The acid concentration of the acidic aqueous solution is not particularly limited as long as the pH value described above is met. The acid concentration of the acidic aqueous solution containing an inorganic acid is not particularly limited, but when the inorganic acid is sulfuric acid, it is preferably 0.1 to 2.0% by mass, more preferably 0.15 to 1.5% by mass. The acid concentration of the acidic aqueous solution containing an organic acid is not particularly limited, but when the organic acid is citric acid, it is preferably 0.5 to 4% by mass, more preferably 0.8 to 3% by mass.

[0093] In this embodiment, since a strong acidic aqueous solution is used as the deactivating agent (dehydrating agent) for the water-absorbing polymer in the pretreatment step S01, other deactivating agents (dehydrating agents) (e.g., lime, calcium chloride, magnesium sulfate, magnesium chloride, aluminum sulfate, aluminum chloride, etc.) are not used in this embodiment. Furthermore, the strong acidic aqueous solution has bactericidal or sterilizing effects; therefore, bactericides, sterilizing agents, disinfectants, and other chemicals are not used in the pretreatment step S01 and are not used in this embodiment.

[0094] In the pretreatment step S01, physical forces can also be applied to multiple used absorbent items. For example, a flow can be created by stirring an acidic aqueous solution, allowing the acidic solution to easily reach the superabsorbent polymer and wash away the dirt from the used absorbent items. Alternatively, for example, the used absorbent items can be agitated in an acidic aqueous solution, allowing the acidic solution to easily reach the superabsorbent polymer and wash away the dirt from the used absorbent items.

[0095] The main processing step S02 is as follows: water is injected into a used absorbent material from which contaminants and moisture have been removed, and at least one of several materials is separated and recovered from the used absorbent material. Here, the water is not particularly limited as long as its pH is 5.8 or higher and 8.6 or lower; examples include industrial water, tap water, and groundwater. In the main processing step S02, the method for separating and recovering materials from the used absorbent material is not particularly limited as long as it is carried out in water; for example, known methods can be used. Thus, the materials of the used absorbent material (e.g., film / nonwoven fabric, superabsorbent polymer, pulp fiber) are recovered as recycled materials.

[0096] In the main processing step S02, the superabsorbent polymer that was inactivated and dehydrated by the strongly acidic aqueous solution in the pretreatment step S01 will not reabsorb water and swell. The reason is as follows: If a superabsorbent polymer (e.g., sodium polyacrylate cross-linked polymer) used in absorbent items such as diapers is immersed in a strongly acidic aqueous solution with a high electrolyte concentration, Na is neutralized, and the degree of Na substitution decreases to near zero. [Polyacrylate] - Na + The chemical change is [polyacrylic acid]-H. As a result, even if the superabsorbent polymer is subsequently placed in water again, it will not exhibit superabsorbency. It should be noted that for other inactivated aqueous solutions containing other inactivating agents, the situation is the same as for acidic aqueous solutions, except that the ions incorporated into the superabsorbent polymer are different.

[0097] In this method, as described above, firstly, in the pretreatment step S01, dirt and moisture are removed from the used absorbent article by the action of inactivating (dehydrating) the superabsorbent polymer using an inactivating aqueous solution (e.g., a strongly acidic aqueous solution) that inactivates the superabsorbent polymer. Then, in the main treatment step S02, water is injected into the used absorbent article, which has been cleaned of dirt and moisture, and is now lightweight and has a low volume, to separate and recover at least one material.

[0098] Therefore, the pretreatment step S01, which involves fewer steps, is carried out in the inactivation aqueous solution, while the main treatment step S02, which involves more steps such as decomposition, separation, and recovery, is carried out in water, not in the inactivation aqueous solution. This reduces the amount of inactivation aqueous solution used, thus suppressing the amount of wastewater generated from it. Consequently, this method reduces the burden of wastewater treatment in the recovery of used absorbent materials.

[0099] Furthermore, since water is used in the main processing step S02, which involves numerous steps and a large number of devices, the adverse effects of contaminants on the external environment and workers can be minimized during device maintenance. Therefore, this method reduces the hygiene burden in the recycling of used absorbent materials.

[0100] Therefore, this method reduces the burden of wastewater treatment for the treatment solution (such as an inactivated aqueous solution) and also reduces the hygiene burden during the maintenance of multiple devices. Furthermore, through the pretreatment step S01, used absorbent materials are cleaned of impurities and moisture, achieving lightweight and low-volume processing; thus, the amount of water used in the main treatment step S02 can also be reduced. Therefore, this method reduces the environmental burden in the recycling of used absorbent materials.

[0101] In this embodiment, in the pretreatment step S01, an acidic aqueous solution containing a strong acid is used as the inactivation aqueous solution. By using the strong acidic aqueous solution, the inactivation (dehydration) of the superabsorbent polymer can be further promoted. This further removes dirt and moisture from the used absorbent articles. Furthermore, the used absorbent articles can be sterilized or disinfected through the bactericidal or disinfecting effect based on the strong acidic aqueous solution. Then, in the main treatment step S02, since the used absorbent articles, which have been further cleaned of dirt and moisture, are lighter and have a lower volume, and have been sterilized or disinfected, are treated in water (not in the acidic aqueous solution), the volume of wastewater from the acidic aqueous solution can be further reduced. Furthermore, since other inactivating agents (e.g., lime, calcium chloride, magnesium sulfate, magnesium chloride, aluminum sulfate, aluminum chloride, etc.), bactericides, disinfectants, and other chemicals are not used, their usage can be reduced. This reduces the burden of treating this wastewater. Therefore, this method can reduce the burden of wastewater treatment of the treatment liquid and reduce the hygiene burden of maintaining multiple devices.

[0102] Next, the pretreatment step S01 will be further explained. In this embodiment, as described above, the pretreatment step S01 is a pretreatment step in which dirt and water are removed from the used absorbent material in a strongly acidic aqueous solution, which is an inactivation aqueous solution, and the inactivation aqueous solution containing dirt and water is discharged. Figure 2 This is a flowchart illustrating the pretreatment step S01 of the embodiment. In this embodiment, the pretreatment step S01 includes an introduction step S11, an inactivation step S12, and a removal step S13. The introduction step S11 is a step of introducing used absorbent materials and a strongly acidic aqueous solution into a treatment tank. The surface of the acidic aqueous solution is lower than the top of the unfloating used absorbent materials. Next, in the inactivation step S12, the acidic aqueous solution permeates the used absorbent materials by repeatedly applying and easing pressure in the acidic aqueous solution within the treatment tank. Next, in the removal step S13, moisture is removed from the multiple used absorbent materials.

[0103] In the introduction process S11, the amount of acidic aqueous solution introduced into the treatment tank is sufficient so that the surface of the acidic aqueous solution is lower than the top of the unfloating used absorbent materials. Here, the top of the used absorbent materials refers to the uppermost portion of the used absorbent material that is not floating in the acidic aqueous solution within the treatment tank. It should be noted that the position of the top of the used absorbent materials and the liquid surface is determined when the used absorbent materials are considered as a group, provided that the used absorbent materials constituting the upper surface of that group are arranged in a roughly horizontal manner. "Roughly horizontal" means that the unevenness of the upper surface of the group of used absorbent materials is within ±2 of the used absorbent materials 2.

[0104] In the inactivation step S12, pressure is repeatedly applied and relaxed on the used absorbent article. Specifically, in the initial action, by applying pressure, the gas (e.g., air) inside the used absorbent article is released to the outside, and along with the released gas, excrement adhering to the used absorbent article is squeezed outwards. Next, by easing the pressure, under the attraction of the used absorbent article's shape recovery, external liquid (e.g., acidic aqueous solution) is absorbed into the interior. Furthermore, in subsequent actions, by applying pressure, the gas and liquid (e.g., moisture released during inactivation based on the acidic aqueous solution) inside the used absorbent article are released to the outside, and along with the released gas and liquid, excrement adhering to the used absorbent article is squeezed outwards. Next, by easing the pressure, external liquid (e.g., acidic aqueous solution) is absorbed into the interior. This process maintains the used absorbent material in the same state as when it was recycled, and allows the acidic aqueous solution to penetrate the interior of the used absorbent material, expelling the internal waste to the outside. During this process, along with the gas and liquid released from the used absorbent material under pressure, the waste adhering to the used absorbent material is also expelled to the outside.

[0105] In the removal step S13, the acidic aqueous solution (containing water discharged from the used absorbent articles) inside the treatment tank is discharged, and the acidic aqueous solution (containing water discharged from the used absorbent articles) contained in the nonwoven fabric or pulp fibers of the used absorbent articles is discharged using, for example, centrifugal force or pressure. At this time, along with the acidic aqueous solution (containing water discharged from the used absorbent articles), the excrement attached to the used absorbent articles can also be squeezed out to the outside. Furthermore, at least one step can be performed as follows: washing the used absorbent articles in water, and then removing the water from the used absorbent articles.

[0106] In this embodiment, during the pretreatment step S01, the surface of the acidic aqueous solution is positioned lower than the top of the multiple used absorbent materials, thus the amount of acidic aqueous solution is very small. This further reduces the volume of wastewater containing the acidic aqueous solution. Simultaneously, it prevents the used absorbent materials from separating and disintegrating due to the force of the acidic aqueous solution flow during the inactivation step S12, thereby improving hygiene during operator maintenance and suppressing material contamination in the wastewater of the treatment solution (acidic aqueous solution).

[0107] Furthermore, in the inactivation step S12, during the initial operation, pressure is applied to release the gas (e.g., air) inside the used absorbent article to the outside. Then, as the pressure is eased, external liquid (e.g., acidic aqueous solution) is absorbed into the inside under the attraction of the used absorbent article's shape recovery. In subsequent operations, pressure is applied to release the gas and liquid (e.g., moisture released by the inactivation of the superabsorbent polymer based on the acidic aqueous solution) inside the used absorbent article to the outside. Then, as the pressure is eased, external liquid (e.g., acidic aqueous solution) is absorbed into the inside. Thus, even with a small amount of acidic aqueous solution, it is possible to efficiently penetrate the interior of the used absorbent article.

[0108] Furthermore, since a strongly acidic aqueous solution is used, even a small amount of the acidic aqueous solution can reliably inactivate the superabsorbent polymers inside the used absorbent article, allowing internal moisture (e.g., urine) to be released to the outside, thus achieving dehydration. Therefore, by finally removing moisture from the used absorbent article in the removal process, the used absorbent article can be made lighter.

[0109] Here, in the inactivation process S12, along with the gas and liquid released from the used absorbent material by applying pressure, the excrement attached to the used absorbent material can also be squeezed out to the outside, which can make the used absorbent material lighter.

[0110] Thus, in this method, in the pretreatment step S01, a small amount of acidic aqueous solution can be used to reduce the dirt and moisture in the used absorbent materials, thereby preventing the dirt and moisture from being carried to the main treatment step S02.

[0111] Therefore, it can reduce the burden of wastewater treatment of treatment liquids (such as acidic aqueous solutions) and reduce the hygiene burden of maintenance of multiple devices.

[0112] In this embodiment, as a preferred approach, the pretreatment step S01 includes a step of pretreating multiple used absorbent articles in an acidic aqueous solution while maintaining them in the state they were in when they were recycled. In other words, multiple used absorbent articles are maintained in the state they were in when they were recycled, and the above-described introduction step S11, inactivation step S12, and removal step S13 are performed.

[0113] Here, the term "state at the time of recycling" for used absorbent materials refers to a state in which the used absorbent materials remain unchanged in shape from their place of use (e.g., hospital, nursing home, home, etc.) or recycling location (e.g., dedicated recycling station, street garbage collection station, etc.) to the location where this method is implemented. Specifically, it refers to a state in which the used absorbent materials and their components have not been damaged (e.g., broken, shattered, shredded), separated, or disintegrated from the time of recycling. Therefore, it does not include shrinkage, enlargement, or deformation, such as those accompanying compression, adhesion, or discharge (release) of absorbed excrement. It should be noted that the "state at the time of recycling" for used absorbent materials includes a "rolled-up state." Being in a "rolled-up state" means that, in order to prevent excrement from adhering to the surroundings or its odor from spreading to the surroundings, the used absorbent materials are rolled or folded with the surface containing the excrement facing inwards, resulting in a roughly rolled-up state. There are no particular limitations on the rolling method, such as winding or folding. It is preferable that the strip attached to the absorbent material maintains these states while it is rolled up. It should be noted that if the absorbent material is partially damaged when removed from the wearer, it is also considered to be in the "state when being recycled" if it is not damaged afterward. In addition, if the "rolled-up state" is simply expanded (unrolled), it can also be considered to be in the "state when being recycled".

[0114] In this embodiment, in the pretreatment step S01, the used absorbent material is maintained in the state it was in when it was recycled, and dirt and moisture are removed without decomposing into multiple materials. Therefore, in the pretreatment step S01, it is difficult for materials to be finely decomposed and leave a large amount of residue in the device, allowing operators to maintain the device extremely easily and hygienically. Furthermore, since the used absorbent material does not decompose into multiple materials, it is difficult for materials to enter the wastewater of the treatment liquid (acidic aqueous solution, etc.). This reduces the hygiene burden in the wastewater treatment of the treatment liquid (acidic aqueous solution, etc.). Therefore, in this method, the burden of wastewater treatment of the treatment liquid (acidic aqueous solution, etc.) can be reduced, and the hygiene burden in the maintenance of multiple devices can also be reduced.

[0115] It should be noted that in this case, not all of the multiple used absorbent articles need to be in the state they were in when they were recycled. From the viewpoint of suppressing the impact of used absorbent articles that are not in the state they were in when they were recycled on the used absorbent articles that were in the state they were in when they were recycled (e.g., suppressing damage to the used absorbent articles), the proportion of used absorbent articles in the state they were in when they were recycled is preferably 90% or more, more preferably 95% or more. In this embodiment, it is 100%. It should be noted that the proportion of used absorbent articles in the rolled-up state is not particularly limited; in this embodiment, it is 100%.

[0116] In this embodiment, as a preferred method, in the deactivation step S12, the pressure is applied and eased by repeatedly applying pressure to each of the plurality of used absorbent articles by colliding each of the plurality of used absorbent articles with each other. That is, the used absorbent articles are made to collide with each other. There is no particular limitation on the method for colliding each of the plurality of used absorbent articles with each other; for example, methods such as stirring the acidic aqueous solution in the treatment tank or swinging or rotating the treatment tank can be used. As a result, in the deactivation step S12, it is easy and reliable to prevent the used absorbent articles from separating or disintegrating due to the force of the acidic aqueous solution flow (preferably, maintaining them in the state when they were recycled), and the application and easing of pressure on the used absorbent articles allows the acidic aqueous solution to permeate the used absorbent articles.

[0117] Figure 3 This is a schematic diagram illustrating an example of the structure of the pretreatment apparatus 1 in the embodiment. The means for performing the pretreatment steps S01 (introduction step S11, inactivation step S12, and removal step S13) are not particularly limited; in this embodiment, the pretreatment apparatus 1 shown in this figure is used.

[0118] The pretreatment device 1 is a cleaning device having a horizontal (or inclined relative to the horizontal) rotating drum as a treatment tank 10. The rotating drum (treatment tank 10) includes: an outer tank 12 having a horizontal plane CH containing its rotation axis X and a vertical plane CV containing its rotation axis X, capable of holding / draining liquid; and an inner tank 11, rotatably disposed inside the outer tank 12 about the rotation axis X, having a plurality of holes (not shown) on its peripheral wall. An example of such a device is a fully automatic washing and dewatering machine (inner diameter of the inner tank 11: 1000 mm φ).

[0119] As described above, in the pretreatment step S01, since the treatment tank 10 is a horizontal rotating drum, in the deactivation step S12, the rotation of the rotating drum allows each of the multiple used absorbent articles to easily and reliably collide with each other. That is, the used absorbent articles can collide with other used absorbent articles. As a result, it is easier and more reliable to suppress the separation and disintegration of the used absorbent articles due to the force of the acidic aqueous solution flow (preferably maintaining a recycled state), and the application and easing of pressure on the used absorbent articles allows the acidic aqueous solution to permeate the used absorbent articles.

[0120] In the introduction process S11 of the pretreatment device 1 of this embodiment, an acidic aqueous solution WA is introduced into the inner tank 11 and the outer tank 12 of the treatment tank 10, and a plurality of used absorbent materials 2 are introduced into the inner tank 11.

[0121] The placement of multiple used absorbent items 2 within the inner slot 11 is not particularly restricted, but as... Figure 3 As shown, when considered as a group, the multiple used absorbent articles constituting the upper surface of this group are preferably arranged in a manner that is substantially parallel to the horizontal plane CH. "Substantially parallel to the horizontal plane CH" means that the unevenness or depression of its upper surface is within ±2 of the used absorbent articles 2. This is based on the viewpoint of applying pressure to the multiple used absorbent articles 2 in substantially the same manner and easing the pressure during the deactivation step S12.

[0122] Furthermore, the amount of multiple used absorbent items 2 in the inner tank 11 is not particularly limited, but such as Figure 3 As shown, it is preferable to arrange the amount of absorbent material 2 in a manner that is located below the horizontal plane CH. If a large number of used absorbent materials 2 exceeding the horizontal plane CH are arranged in the inner tank 11, then in the deactivation step S12, it is difficult to apply pressure to the multiple used absorbent materials 2 in a substantially uniform manner and to ease the pressure, and it is also difficult to spread the acidic aqueous solution WA to the multiple used absorbent materials 2 in a substantially uniform manner.

[0123] The amount of acidic aqueous solution WA is sufficient to ensure that the surface level WL of the acidic aqueous solution WA is lower than the uppermost part 2TE of the plurality of unfloated used absorbent articles 2. Here, the uppermost part 2TE of the plurality of used absorbent articles 2 refers to the uppermost portion of the uppermost used absorbent article 2T among the plurality of used absorbent articles 2 that are not floating in the acidic aqueous solution WA within the inner tank 11. In other words, when the plurality of used absorbent articles 2 are considered as a group, its uppermost part refers to the uppermost portion of the uppermost used absorbent article 2T among the unfloated plurality of used absorbent articles 2 constituting the upper surface of that group of used absorbent articles.

[0124] exist Figure 3 In the example, the uppermost part 2TE of the used absorbent material 2T, located at the top, is at a height d1 from the deepest part of the inner tank 11. On the other hand, the surface WL of the acidic aqueous solution WA is at a height d2 from the deepest part of the inner tank 11. Therefore, d1>d2, and the surface WL of the acidic aqueous solution WA is located lower than the uppermost part 2TE of the multiple unfloating used absorbent materials 2. By reducing the amount of acidic aqueous solution WA, it is possible to suppress the used absorbent materials 2 from separating and disintegrating from their state when being recycled due to the force of the water flow of the acidic aqueous solution WA. It should be noted that, relative to the inner diameter D1 of the inner tank 11, the horizontal plane CH is located at a height D1 / 2 from the deepest part of the inner tank 11, and D1 / 2>d1, meaning that the multiple used absorbent materials 2 are located below the horizontal plane CH. It is possible to apply / relax pressure to the multiple used absorbent materials 2 in approximately the same manner, and it is possible to easily distribute the acidic aqueous solution WA.

[0125] The surface level (WL) of the acidic aqueous solution WA is preferably located at approximately 3 / 5 to 4 / 5 (of the number) of the multiple used absorbent articles 2, where they are immersed. That is, 1 / 5 to 2 / 5 (of the number) of the multiple used absorbent articles 2 may not be immersed. In this way, by using a smaller amount of acidic aqueous solution WA on the multiple used absorbent articles 2, the amount of wastewater can be further suppressed. Furthermore, by using a smaller amount of acidic aqueous solution WA, the separation and disintegration of the used absorbent articles 2 from their recycled state due to the force of the water flow of the acidic aqueous solution WA during the inactivation step S12 can be further suppressed (preferably maintaining the recycled state). Thus, the multiple used absorbent articles 2 can be maintained in their recycled state while inactivating and dehydrating these superabsorbent polymers, thereby reducing the weight of the multiple used absorbent articles 2.

[0126] It should be noted that if the liquid level WL of the acidic aqueous solution WA is too low, the acidic aqueous solution may not be able to adequately cover the multiple used absorbent materials 2, and may not be able to adequately inactivate the multiple used absorbent materials 2. On the other hand, if the liquid level WL of the acidic aqueous solution WA is too high, the used absorbent materials 2, which are rolled up due to the large amount of water flow, may collapse and separate or disintegrate.

[0127] exist Figure 3 In the example, when the used absorbent articles 2 are prepared at approximately the same quantity density (number per unit volume), the liquid level WL of the acidic aqueous solution WA is located at approximately 2 / 3 (number) of the used absorbent articles 2 that are immersed (immersed).

[0128] The weight of the acidic aqueous solution WA is preferably 2 to 5 times the weight of the multiple used absorbent articles 2 (including excrement), more preferably 2 to 3 times the weight. This way, by using a relatively small amount of acidic aqueous solution WA on the multiple used absorbent articles 2, the amount of wastewater can be suppressed. Furthermore, by using a small amount of acidic aqueous solution WA, the separation and disintegration of the used absorbent articles 2 from their recovered state due to the force of the water flow of the acidic aqueous solution WA during the inactivation step S12 can be suppressed (preferably maintaining the recovered state). This allows for a lighter weight for the multiple used absorbent articles 2. If the amount of acidic aqueous solution WA is too small, it may not be able to adequately cover the multiple used absorbent articles 2, and may not be able to adequately inactivate them. On the other hand, if the amount of acidic aqueous solution WA is too large, it is easy for them to separate and disintegrate due to the water flow, leading to an increase in the alkaline chemicals required for neutralization treatment during wastewater treatment.

[0129] The temperature of the acidic aqueous solution WA is not particularly limited as long as the inactivation reaction takes place in the inactivation step S12. The temperature can be room temperature or higher, for example, 15–30°C. Furthermore, the treatment time of the used absorbent article in the acidic aqueous solution in the inactivation step S12 is not particularly limited as long as the superabsorbent polymer is inactivated and dehydrated; for example, 1–60 minutes, preferably 5–30 minutes.

[0130] Next, the deactivation step S12 using the pretreatment device 1 in this embodiment will be described. In the deactivation step S12, the inner tank 11 is rotated at a predetermined speed in a forward direction (which may be paused midway) or in a forward-reverse direction relative to the plurality of used absorbent articles 2 disposed in the inner tank 11, thereby moving the plurality of used absorbent articles 2 within the inner tank 11. That is, the deactivation step S12 includes a step in which each of the plurality of used absorbent articles collides with each other due to the rotation of the rotating drum. Figure 3 In the example, before the action, the position of the liquid level WL of the acidic aqueous solution WA is the position where about 2 / 3 (number) of the multiple used absorbent items 2 are immersed. However, during the action, by moving the multiple used absorbent items 2 and the acidic aqueous solution WA in the inner tank 11, the used absorbent items 2 are immersed in the acidic aqueous solution WA in a roughly periodic manner, although not simultaneously.

[0131] In this case, the inner tank 11 of the processing tank 10 is roughly divided into three regions in the vertical direction: an upper region, a middle region, and a lower region (the width in the vertical direction is the same). At this time, for example, in the initial stage of operation, multiple used absorbent items 2 are accumulated in the lower region of the inner tank 11. Then, each used absorbent item 2 repeatedly performs the following action: by rotating the inner tank 11, it rolls against the inner wall of the inner tank 11 and reaches a height near the middle region, then rolls onto other multiple used absorbent items 2 located in the lower region. Thus, while rolling against the inner wall of the inner tank 11 and reaching a height near the middle region, adjacent used absorbent items 2 collide with each other, or when rolling onto multiple used absorbent items 2 located in the lower region, adjacent used absorbent items collide with each other. Through these collisions and other actions, pressure is repeatedly applied to and relieved on the used absorbent items 2. It should be noted that at this time, the rotation speed of the inner tank 11 should be adjusted appropriately so that the used absorbent material 2 does not reach the upper area and then fall freely (impact) to the lower area due to gravity. This is because if it falls freely due to excessive rotation speed, the pressure on the used absorbent material 2 will be too great, and the used absorbent material 2 will easily separate and disintegrate.

[0132] Here, the cycle of applying and easing pressure is not particularly limited as long as the used absorbent material 2 is difficult to separate or disintegrate (preferably able to maintain its state when recycled). For example, when rotating the inner tank 11 (inner diameter 1000mmφ) in the forward direction, a rotational speed greater than 20 rpm and less than 35 rpm can be used. In this case, the cycle of applying and easing pressure in the used absorbent material 2 is not necessarily clear and is not particularly limited (it may not be constant). For example, if the cycle is considered to be the time it takes for the inner tank 11 to rotate approximately one revolution, it can be considered to be about 1.7 to 2.4 seconds. Alternatively, for example, when rotating the inner tank 11 (inner diameter 1000mmφ) by reciprocating in both directions, a rotational speed greater than 20 rpm and less than 35 rpm can be used, and the cycle of the reciprocating rotation of the inner tank 11 in both directions can be about 2 to 6 seconds. In this case, the repeated cycle of pressure application and easing in the used absorbent material 2 is not necessarily clear and is not particularly limited (it may not be constant). For example, if the cycle is considered to be the time it takes for the inner tank 11 to perform a reciprocating rotational motion in both directions, it can be considered to be approximately 2 to 6 seconds. It should be noted that the time in the forward direction and the time in the reverse direction can also be different within one cycle of the reciprocating rotational motion of the inner tank 11. For example, the time in one direction can be approximately 1.2 to 2 times the time in the other direction.

[0133] In this way, multiple used absorbent materials 2 are maintained in their original state when being recycled within the acidic aqueous solution WA in the treatment tank 10, and pressure is repeatedly applied and relaxed on each used absorbent material 2, thereby allowing the acidic aqueous solution to penetrate into the interior of each used absorbent material 2. This dehydrates the superabsorbent polymer in each used absorbent material 2. Furthermore, along with the dehydration of the superabsorbent polymer, excrement adhering to each used absorbent material 2 can be discharged.

[0134] Next, the removal step S13 using the pretreatment device 1 in this embodiment will be further explained. In the previous inactivation step S12, the moisture (e.g., urine) contained in the superabsorbent polymer of each used absorbent article 2 is removed, thus dehydrating the superabsorbent polymer. However, each used absorbent article 2 as a whole is in a state containing moisture (e.g., acidic aqueous solution, moisture removed from the superabsorbent polymer). For example, the pulp fibers and nonwoven fabrics of each used absorbent article are in a state containing moisture. Therefore, in the removal step S13, the moisture contained in each used absorbent article 2 is removed.

[0135] In the removal step S13, specifically, an acidic aqueous solution WA is discharged from the treatment tank 10 (outer tank 12), and then the treatment tank (inner tank 11) is rotated about the rotation axis X (e.g., 100 rpm). This allows centrifugal force to remove the moisture contained in each used absorbent article 2 via the outer tank 12. Thus, not only can the moisture in the superabsorbent polymer be dehydrated in the inactivation step S12, but the moisture in multiple used absorbent articles 2 can also be removed entirely in the removal step S13, resulting in lightweight multiple used absorbent articles 2.

[0136] Here, the dehydration rate of the multiple used absorbent articles after step S13 is preferably 40% or more, more preferably 60% or more, and even more preferably 65% ​​or more. The dehydration rate is calculated using the following formula.

[0137] Dehydration rate (%)

[0138] = {1 - (mass of multiple used absorbent materials after pretreatment - mass of multiple unused absorbent materials) / (mass of multiple used absorbent materials before pretreatment - mass of multiple unused absorbent materials)} × 100

[0139] = {1 - (mass of moisture in multiple used absorbent materials after the pretreatment process) / (mass of moisture in multiple used absorbent materials before the pretreatment process)} × 100.

[0140] Thus, in the pretreatment step S01, the dehydration rate of the multiple used absorbent items 2 after removal step S13 is over 40%. Therefore, through the pretreatment step S01, the multiple used absorbent items 2 can be effectively inactivated and dehydrated in their recycled state, resulting in very efficient weight reduction. This allows for hygienic transfer and storage of the used absorbent items 2 to the main treatment step S02. Furthermore, it suppresses the amount of wastewater and the spread of excrement, achieving more hygienic recycling treatment with less environmental impact. It should be noted that in the removal step S13, water can also be added to the treatment tank containing the multiple used absorbent items 2, causing the tank to rotate around the rotation axis X, and the multiple used absorbent items 2 can be washed with water.

[0141] The lightweight multiple used absorbent articles 2 obtained after the removal step S13 in the pretreatment step S01 are transferred to the main treatment step S02.

[0142] It should be noted that, in this embodiment, the method for performing the inactivation step S12 is not particularly limited as long as pressure can be repeatedly applied and eased on each of the plurality of used absorbent articles in an acidic aqueous solution. For example, the following method can be considered as such a method.

[0143] As an example of this method, a method using a vertical rotating drum as a treatment tank can be cited. The treatment tank (rotating drum) has an outer tank capable of holding liquid and an inner tank rotatably disposed inside it and having multiple holes on its peripheral wall. The inner tank is rotated at a predetermined speed in a forward direction (with pauses) or in both directions relative to multiple used absorbent articles disposed in the inner tank, thereby moving the multiple used absorbent articles within the inner tank. In this case, it is not necessary to immerse all the multiple used absorbent articles in the acidic aqueous solution before operation. On the other hand, during operation, by moving the multiple used absorbent articles or the acidic aqueous solution within the treatment tank, the used absorbent articles are immersed in the acidic aqueous solution approximately periodically, although not simultaneously.

[0144] In this case, the processing tank of the vertical rotating drum is roughly divided into an upper region, a middle region, and a lower region in the vertical direction. At this time, for example, initially during operation, multiple used absorbent materials are accumulated in the lower region of the rotating drum. Subsequently, as the inner tank rotates, each used absorbent material moves towards the inner wall of the inner tank under the centrifugal force generated by the rotation. Some further move towards the middle or upper region, where they are pressed by the inner wall or other used absorbent materials, applying pressure. During pauses or reversals in rotation, the centrifugal force disappears, and the pressure is relieved. Thus, through the collisions between the used absorbent materials and the inner wall or other used absorbent materials, pressure is repeatedly applied to and relieved on the used absorbent materials. It should be noted that, at this time, the rotational speed of the rotating drum should be appropriately adjusted to avoid excessive pressure applied to the used absorbent materials, which could lead to separation or disintegration of the used absorbent materials (preferably maintaining their state at the time of recycling).

[0145] Another example of this method is as follows: Pressure is applied periodically by pressing a flat plate-shaped component above multiple used absorbent materials disposed in a processing tank, and the pressure is relieved by lifting the flat plate-shaped component upwards. In this case, it is not necessary to immerse all the used absorbent materials in the acidic aqueous solution before the operation. During the operation, by moving the multiple used absorbent materials or the acidic aqueous solution within the processing tank, the used absorbent materials are immersed in the acidic aqueous solution approximately periodically, although not simultaneously. Thus, the pressure on the used absorbent materials is repeatedly applied and relieved through the collisions between the used absorbent materials and the inner wall, the flat plate-shaped component, or other used absorbent materials. It should be noted that the pressure applied to the flat plate-shaped component should be appropriately adjusted to avoid excessive pressure on the used absorbent materials, which could cause them to separate or disintegrate (preferably maintaining their state at the time of recycling).

[0146] As another example of this method, the following approach can be used: By reciprocating a processing tank containing multiple used absorbent materials in a horizontal direction, the multiple used absorbent materials are pressed against the inner wall of one or more sides, thereby applying pressure. The pressure is then relieved between the inner walls of one side and the other side (midway through the reciprocating motion). In this case, it is not necessary to immerse all the multiple used absorbent materials in the acidic aqueous solution before the operation. During the operation, when applying pressure, the multiple used absorbent materials or the acidic aqueous solution are moved within the processing tank, and the used absorbent materials are immersed in the acidic aqueous solution approximately periodically, although not simultaneously. In this way, the pressure on the used absorbent materials is repeatedly applied and relieved through the collision between the used absorbent materials and the inner wall or other used absorbent materials. It should be noted that the speed of the reciprocating motion of the processing tank should be appropriately adjusted to avoid excessive pressure on the used absorbent materials, which could cause the used absorbent materials to separate or disintegrate (preferably maintaining their state when being recycled).

[0147] As for methods to remove moisture contained in each used absorbent item 2, there are no particular limitations as long as the moisture can be removed.

[0148] For example, when using a vertical rotating drum as the treatment tank, by discharging an acidic aqueous solution from the treatment tank (outer tank) and then rotating the treatment tank (inner tank), centrifugal force can be used to remove the moisture contained in each used absorbent item via the outer tank. When using a treatment tank with a flat plate component, by discharging an acidic aqueous solution from the treatment tank and then pressing multiple used absorbent items against the inner wall of the treatment tank using the flat plate component, the moisture contained in each used absorbent item can be removed. For example, when using a treatment tank that reciprocates in the horizontal direction, by discharging an acidic aqueous solution from the treatment tank and then reciprocating the treatment tank in the horizontal direction, the moisture contained in each used absorbent item can be removed.

[0149] Next, the main treatment step S02 will be further explained. As described above, the main treatment step S02 is the following step: in water, multiple used absorbent materials from which dirt and water have been removed are decomposed, and at least one of multiple materials is separated and recovered from the decomposed multiple used absorbent materials. Figure 4 This is a flowchart illustrating the main processing step S02 of the embodiment. In this embodiment, the main processing step S02 includes a crushing step S21, a film / nonwoven fabric separation step S22, a foreign matter removal step S23, a SAP separation step S24, an ozone treatment step S25, and a rinsing / dehydration step S26.

[0150] The crushing step S21 is a process of crushing used absorbent materials in water. In this embodiment, firstly, in the crushing step S21, multiple used absorbent materials obtained in the pretreatment step S01, after removing impurities and moisture, are supplied to a solution tank containing water (or not containing water). Next, water containing the used absorbent materials (or used absorbent materials and water separately) is fed from the solution tank to a twin-shaft crusher (e.g., a twin-shaft rotary crusher, a twin-shaft differential crusher, or a twin-shaft shear crusher). Then, the used absorbent materials are crushed using the twin-shaft crusher. This generates crushed material of the used absorbent materials. The crushed material is conveyed, alone or together with water, to the film / nonwoven fabric separation step S22. It should be noted that the twin-shaft crusher is, for example, located at the bottom of the solution tank and connected to the solution tank. In this case, the used absorbent materials are transferred to the twin-shaft crusher by gravity or by being drawn in by the twin-shaft crusher. In another embodiment, water is not stored in the solution tank, and the used absorbent material is fed to the twin-shaft crusher along with water to crush the used absorbent material together with water.

[0151] Next, the film / nonwoven fabric separation process S22 is as follows: In water, plastic materials are separated from a mixture of synthetic resin-based plastic materials (e.g., films, nonwoven fabrics, collection bags, etc.) obtained by decomposing used absorbent materials, superabsorbent polymers, and pulp fibers. In this embodiment, firstly, the mixture of crushed material and water generated in the crushing process S21 is fed to a pulp separator. Next, the mixture of crushed material and water is separated into a mixture of plastic materials, pulp fibers, superabsorbent polymers, and water by passing it through a screen in the pulp separator. The pulp fibers, superabsorbent polymers, and water that have passed through the screen are then supplied to the foreign matter removal process S23. On the other hand, the plastic materials that do not pass through the screen are then washed with washing water, dried, and recycled as recycled plastic materials (films, nonwoven fabrics, etc.).

[0152] Next, in the foreign matter removal step S23, foreign matter such as film, nonwoven fabric, and collection bags that were not completely removed are separated from the mixture supplied by the film / nonwoven fabric separation step S22 by at least one separator (e.g., a screen separator with relatively large mesh), a screen separator with relatively small mesh, and a cyclone separator in sequence to separate foreign matter from the mixture. This results in pulp fibers and superabsorbent polymers with fewer foreign matter. The mixture of pulp fibers and superabsorbent polymers with fewer foreign matter and water is then supplied to the SAP separation step S24.

[0153] In the SAP separation step S24, the superabsorbent polymer (SAP) is separated from the mixture (containing pulp fibers with few impurities and SAP) supplied by the foreign matter removal step S23 using at least one separator (e.g., a drum screen separator). In this embodiment, the mixture is separated into SAP and water, and pulp fibers (containing a small amount of SAP) by the drum screen separator. The SAP and water that have passed through the screen are then separated into SAP and an acidic aqueous solution by another separator (e.g., an inclined screen separator). The SAP is washed with washing water, dried, and recycled as a regenerated SAP. Meanwhile, the pulp fibers that have not passed through the screen are supplied to the ozone treatment step S25.

[0154] In the ozone treatment step S25, pulp fibers separated from used absorbent articles are treated with a treatment solution containing ozone (e.g., water containing ozone). This treatment allows highly absorbent polymers or organic impurities (e.g., lignin) that may adhere to the surface or interior of the pulp fibers from used absorbent articles to come into contact with ozone. Thus, the highly absorbent polymers or organic impurities are oxidized and decomposed by ozone, making them soluble in the treatment solution and easily removed from the pulp fibers. Therefore, pulp fibers with fewer impurities can be obtained.

[0155] The ozone treatment apparatus in ozone treatment process S25 is not particularly limited in structure as long as it allows the pulp fibers to come into contact with ozone. For example, the ozone treatment apparatus includes a treatment tank for storing the treatment liquid and an ozone supply device for supplying ozone-containing gas into the treatment tank. In the ozone treatment apparatus, for example, pulp fibers are added to the treatment liquid from the top or bottom of the treatment tank, and ozone-containing gas is supplied to the treatment liquid from the bottom of the treatment tank. The pulp fibers and the ozone-containing gas in the treatment liquid mix and come into contact within the treatment tank. Examples of ozone supply devices include the EcoDesign ED-OWX-2 ozone water exposure tester and the Mitsubishi Electric OS-25V ozone generator. Furthermore, by using the ozone-containing treatment liquid, the pulp fibers can be sterilized and bleached.

[0156] In the ozone treatment step S25, the concentration of pulp fibers contained in the treatment liquid is, for example, 0.5 to 20% by mass of 100% of the treatment liquid, preferably 1 to 10% by mass. If the concentration of pulp fibers is too low, the treatment efficiency will be poor; if it is too high, it will be difficult to remove impurities from the pulp fibers.

[0157] In the ozone treatment step S25, the ozone concentration in the treatment solution is preferably 1 to 200 ppm by mass. If the concentration is too low, it will be difficult to remove impurities from the pulp fibers; if the concentration is too high, it will easily damage the pulp fibers. Furthermore, if the ozone concentration in the treatment solution is high, the treatment time with ozone is short; if the ozone concentration is low, the treatment time with ozone is long, typically 5 to 120 minutes. The product of the ozone concentration (ppm) in the treatment solution and the treatment time (minutes) (hereinafter also referred to as the "CT value") is preferably 100 to 6000 ppm·min. If the CT value is too low, it will be difficult to remove impurities; if the CT value is too high, it will easily damage the pulp fibers.

[0158] The treatment solution is preferably slightly acidic (pH 5.8–7.0), and more preferably more acidic (pH 5.8–6.0), in water (pH 5.8–8.6). By keeping the water slightly acidic, the deactivation and vaporization of ozone in the treatment solution can be suppressed, and the superabsorbent polymer can be oxidized and decomposed in a short time. To maintain the pH of the treatment solution, for example, the pH of the treatment solution can be monitored using a pH sensor, and when the pH changes towards the neutral side, an amount of slightly acidic water corresponding to the magnitude of the change can be added to the treatment solution.

[0159] Ozone treatment in step S25 suppresses the residue of highly absorbent polymers, lignin, and other impurities in the pulp fibers. It also deodorizes, sterilizes, and bleachs the pulp fibers, thereby promoting fibrillation. Therefore, the resulting pulp fibers are characterized by fewer impurities, inhibition of bacterial growth, and increased surface area, making them suitable for various applications.

[0160] Subsequently, the pulp fibers treated with ozone in the ozone treatment step S25 are separated from the treatment liquid by a separation device with a sieve (or mesh) that is set separately from the ozone treatment device (solid-liquid separation) and supplied to the rinsing / dewatering step S26.

[0161] In the rinsing / dewatering process S26, the ozone-treated pulp fibers are rinsed with cleaning water (e.g., industrial water, tap water, groundwater), and then the cleaning water is removed. In this embodiment, the rinsing function of the washing tank / dewatering tank with rotating drum is used to wash away impurities and treatment liquid (including ozone) present on the surface of the pulp fibers. The dewatering function is used to dewater the pulp fibers to reduce the amount of cleaning water, and the drying function is used to dry the pulp fibers. Thus, the pulp fibers are recycled as recycled pulp fibers.

[0162] In the aforementioned main processing step S02, step S22 can be described as a separation step that separates water, including multiple used absorbent articles from which dirt and moisture have been removed, into superabsorbent polymer, pulp fibers, and water, as well as other materials. Furthermore, steps S23 to S26 can be described as recycling steps that separate and recover superabsorbent polymer and pulp fibers from the separated superabsorbent polymer, pulp fibers, and water, respectively.

[0163] In this method, each step of the main treatment process S02 is carried out in water, not in an acidic aqueous solution. Therefore, the amount of acidic aqueous solution used can be reduced, thereby reducing the amount of wastewater generated from the acidic aqueous solution and thus lowering the burden of wastewater treatment. Furthermore, since water is used in the main treatment process S02, which has a large number of steps, the adverse effects of contaminants on the external environment and operators can be minimized during equipment maintenance, reducing the burden on hygiene.

[0164] Furthermore, in this method, all or part of the water discharged from each step of the main treatment step S02 can be reused as water in other steps (e.g., supplementary water used in other steps preceding this step, water used for material cleaning, etc.). Since each step of the main treatment step S02 is carried out in water rather than in an acidic aqueous solution, it can be reused extremely easily (with almost no special treatment). This reduces wastewater volume and lowers the burden of wastewater treatment. Additionally, all or part of the water discharged from each step of the main treatment step S02 can be reused as water used in the pretreatment step S01 (e.g., water used for concentration or pH adjustment in acidic aqueous solutions, water used for material cleaning, etc.). This reduces the water used in the pretreatment step S01 and lowers the environmental burden.

[0165] In this method, the main processing step S02 includes a crushing step S01 that crushes the used absorbent material before the separation steps (S23-S26). Therefore, by crushing the material before the separation step, the constituent materials of the used absorbent material can be easily separated from each other. As a result, the separation step can be performed more efficiently, and the materials (constituent materials) of the used absorbent material can be easily recovered.

[0166] (Second Implementation)

[0167] The method for recovering various materials, including superabsorbent polymers and pulp fibers, from used absorbent articles according to the second embodiment will be described. In this embodiment, a portion of the pretreatment step S01 differs from that of the first embodiment. Hereinafter, the differences from the first embodiment will be mainly described.

[0168] In this embodiment, the difference from the first embodiment (not shown) lies in that the pretreatment step S01 and Figure 2 The introduction process S11 and the inactivation process S12 shown are different, including a crushing process of crushing used absorbent materials and an inactivation process of immersing the crushed used absorbent materials in an inactivation aqueous solution.

[0169] In the crushing process of pretreatment step S01, in this embodiment, firstly, multiple used absorbent materials, which are covered with dirt and have absorbed moisture, are supplied to a receiving container. Next, the used absorbent materials are fed from the receiving container to a twin-shaft crusher (e.g., a twin-shaft rotary crusher, a twin-shaft differential crusher, or a twin-shaft shear crusher). Then, the used absorbent materials are crushed using the twin-shaft crusher. This produces crushed material of the used absorbent materials. The crushed material is then conveyed to the next step, the deactivation step. It should be noted that the crushed material may also be conveyed to the next step, the deactivation step, together with water or an aqueous deactivation solution.

[0170] The twin-shaft crusher is located, for example, below and communicates with the receiving container. In this case, used absorbent materials are transferred from the receiving container to the twin-shaft crusher by gravity or by the induction of the crusher. This crushing process crushes the used absorbent materials without water. It should be noted that this crushing process can also crush the used absorbent materials together with water (e.g., in water, or while water is being sprayed).

[0171] In the inactivation process performed in the pretreatment step S01, in this embodiment, firstly, the shredded material of the used absorbent article that was shredded in the shredding step is fed into a solution tank containing an inactivation aqueous solution (e.g., an acidic aqueous solution). Next, the shredded material is immersed in the inactivation aqueous solution. As a result, the superabsorbent polymer in the shredded material is inactivated (dehydrated). The shredded material containing the inactivated (dehydrated) superabsorbent polymer is then transferred to the removal step S13 together with the inactivation aqueous solution.

[0172] In this embodiment, the used absorbent material is crushed in the crushing step of the pretreatment step S01 before the inactivation step. Therefore, the inactivation aqueous solution can more easily contact the superabsorbent polymer in the used absorbent material. Thus, the superabsorbent polymer can be efficiently inactivated (dehydrated), thereby reducing the amount of inactivation aqueous solution or the concentration of the inactivating agent in the inactivation aqueous solution. Therefore, this embodiment reduces the environmental burden in the recycling of used absorbent material.

[0173] In this embodiment, since the crushing process is carried out in the pretreatment process S01, the crushing process S21 in the main treatment process S02 can also be omitted.

[0174] (Third Implementation)

[0175] The method for recovering various materials, including superabsorbent polymers and pulp fibers, from used absorbent articles according to the third embodiment will be described. In this embodiment, a portion of the pretreatment step S01 differs from that of the first embodiment. Hereinafter, the differences from the first embodiment will be mainly described.

[0176] In this embodiment, the difference from the first embodiment (not shown) lies in that the pretreatment step S01 and Figure 2 The introduction process S11 and the inactivation process S12 shown are different, including an inactivation crushing process in which the used absorbent material is crushed together with the inactivation aqueous solution.

[0177] In the inactivation and crushing process performed in the pretreatment step S01, in this embodiment, firstly, multiple used absorbent articles with attached contaminants and absorbed moisture are supplied to a receiving container. Next, the used absorbent articles are fed from the receiving container to a twin-shaft crusher (e.g., a twin-shaft rotary crusher, a twin-shaft differential crusher, or a twin-shaft shear crusher), and an inactivation aqueous solution (e.g., an acidic aqueous solution) is supplied to the twin-shaft crusher. Then, the used absorbent articles and the inactivation aqueous solution are crushed together using the twin-shaft crusher. Thus, the used absorbent articles are crushed, and fragments containing the inactivated (dehydrated) superabsorbent polymers in the used absorbent articles are generated. The fragments containing the inactivated (dehydrated) superabsorbent polymers are transferred to the removal step S13 together with the inactivation aqueous solution.

[0178] The twin-shaft crusher is located, for example, below and in communication with the receiving container. In this case, used absorbent material is transferred from the receiving container to the twin-shaft crusher by gravity or by the induction of the crusher. Then, an inactivating aqueous solution is supplied from above the twin-shaft crusher to be sprayed onto the crushing blades of the crusher and / or onto the used absorbent material being transferred to the crusher.

[0179] In this embodiment, during the pretreatment step S01, the used absorbent material is crushed and the superabsorbent polymer in the used absorbent material is inactivated almost simultaneously through the inactivation and crushing step. Therefore, it is easier to bring the inactivation solution into contact with the superabsorbent polymer, and the processing time of the pretreatment step S01 can be shortened. Thus, the superabsorbent polymer can be efficiently inactivated (dehydrated), thereby reducing the amount of inactivation solution or the concentration of the inactivating agent in the inactivation solution, and reducing the energy consumed in the process. Therefore, this embodiment reduces the environmental burden in the recycling of used absorbent material.

[0180] In this embodiment, since the crushing process is carried out in the pretreatment process S01, the crushing process S21 in the main treatment process S02 can also be omitted.

[0181] (Fourth Implementation)

[0182] The method for recovering various materials, including superabsorbent polymers and pulp fibers, from used absorbent articles according to the fourth embodiment will be described. In this embodiment, a portion of the pretreatment step S01 differs from that of the first embodiment. Hereinafter, the differences from the first embodiment will be mainly described.

[0183] In this embodiment, the difference from the first embodiment (not shown) lies in that the pretreatment step S01 and Figure 2 The introduction process S11 and the inactivation process S12 shown are different, including an inactivation process in which the used absorbent material is immersed in the above-mentioned inactivation aqueous solution and a crushing process in which the used absorbent material containing the inactivated superabsorbent polymer is crushed.

[0184] In the inactivation process performed in pretreatment step S01, in this embodiment, firstly, multiple used absorbent articles with attached dirt and absorbed moisture are supplied to a solution tank containing an inactivation aqueous solution (e.g., an acidic aqueous solution). Next, the used absorbent articles are immersed in the inactivation aqueous solution. As a result, the superabsorbent polymer in the used absorbent articles is inactivated (dehydrated). For used absorbent articles containing the inactivated (dehydrated) superabsorbent polymer, the crushed material is conveyed to the next step, the crushing step, either alone or together with the inactivation aqueous solution. It should be noted that this inactivation process can also use... Figure 3 The device shown is used for this purpose.

[0185] In the crushing process of pretreatment step S01, in this embodiment, firstly, the used absorbent article containing the superabsorbent polymer that was deactivated (dehydrated) in the deactivation step is supplied to a receiving container. Next, the used absorbent article is fed from the receiving container to a twin-shaft crusher (e.g., a twin-shaft rotary crusher, a twin-shaft differential crusher, or a twin-shaft shear crusher). Then, the used absorbent article is crushed using the twin-shaft crusher. This generates crushed material containing the deactivated (dehydrated) superabsorbent polymer. The crushed material is then transferred to removal step S13.

[0186] It should be noted that when the used absorbent material is fed from the receiving container to the twin-shaft crusher, an inactivation aqueous solution can also be supplied to the twin-shaft crusher simultaneously. In this case, the used absorbent material is crushed together with the inactivation aqueous solution, and the crushed material containing the inactivated (dehydrated) superabsorbent polymer is transferred to the removal process S13 together with the inactivation aqueous solution.

[0187] The twin-shaft crusher is located, for example, below and communicates with the receiving container. In this case, used absorbent material is transferred from the receiving container to the twin-shaft crusher by gravity or by the induction of the crusher. It should be noted that when crushing used absorbent material with the twin-shaft crusher, inactivating water-soluble substances or water can also be supplied from above the crusher to spray onto the crushing blades and / or onto the used absorbent material being transferred to the crusher.

[0188] In this embodiment, since the superabsorbent polymer in the used absorbent article is deactivated (dehydrated) in the inactivation step of the pretreatment step S01 before the crushing step, the swelling of the superabsorbent polymer can be reduced before the crushing step. Therefore, the superabsorbent polymer is less likely to be damaged during the crushing step, thus reducing the amount of superabsorbent polymer that is difficult to reuse. Therefore, the recovery rate of the superabsorbent polymer can be improved, and the amount of inactivating aqueous solution or the concentration of the inactivating agent in the inactivating aqueous solution required for the recovery of the superabsorbent polymer can be reduced. Thus, this embodiment reduces the environmental burden in the recycling of used absorbent article materials.

[0189] In this embodiment, since the crushing process is carried out in the pretreatment process S01, the crushing process S21 in the main treatment process S02 can also be omitted.

[0190] In a preferred embodiment, the amount of inactivating aqueous solution used in the pretreatment step S01 is less than the amount of water injected in the main treatment step S02.

[0191] If a method is to be performed to recover multiple materials from used absorbent articles solely through the main treatment step S02 without a pretreatment step S01, then the main treatment step S02 requires the use of an inactivating aqueous solution. In this case, the amount of inactivating aqueous solution is approximately the same as the amount of water injected into the main treatment step S02 when both pretreatment step S01 and main treatment step S02 are performed (as mentioned above, for the concentration of the inactivating agent in the inactivating aqueous solution, for example, even in a strongly acidic solution, the sulfuric acid concentration is 0.1 to 2.0% by mass, the citric acid concentration is 0.5 to 4% by mass, and the majority (95% by mass or more) of the inactivating aqueous solution is water). Therefore, compared to the method of recovering multiple materials from used absorbent articles solely through the main treatment step S02 without a pretreatment step S01, i.e., performing the main treatment step S02 solely using an inactivating aqueous solution without using water, this method can reduce the amount of inactivating aqueous solution. This reduces the environmental burden.

[0192] Example

[0193] The present invention will be described in more detail below with reference to exemplary embodiments and comparative examples, but the present invention is not limited to these embodiments.

[0194] A. Evaluation related to pretreatment process S01 + main treatment process S02

[0195] (1) Sample

[0196] As samples of absorbent articles, a total of five types were used: two types of unused infant diapers and three types of unused adult diapers. For the multiple diapers used in the examples and comparative examples, five types of diapers were prepared in equal quantities for each example and comparative example. In the infant diapers, the proportion of superabsorbent polymer in the absorbent component of the absorbent body was approximately 50%, and in the adult diapers, the proportion of superabsorbent polymer in the absorbent component of the absorbent body was approximately 30%. Furthermore, to simulate "use," each diaper absorbed 300g of physiological saline, and then the weight of all diapers was measured, resulting in 135kg.

[0197] (2) Evaluation of the treatment

[0198] In the embodiments, the pretreatment step S01 and main treatment step S02 described above were performed on the samples (1) above. A 1% sulfuric acid aqueous solution, which is a strongly acidic aqueous solution, was used as the inactivation aqueous solution in the pretreatment step S01. In the comparative examples, the crushing step S12 to the fourth separation step S20 of the treatment in Patent Document 1 were performed on the samples (1) above. A 0.1% sulfuric acid aqueous solution was used as the acidic aqueous solution in all steps. Furthermore, in the embodiments and comparative examples, the amount of water used and the amount of wastewater to be treated were compared.

[0199] (3) Results

[0200] In this embodiment, the amount of wastewater to be treated is as little as 360L, the amount of water used in the pretreatment step S01, and the amount of sulfuric acid in the wastewater is also as little as 3.6L. Moreover, the amount of water used in the main treatment step S02 is 2700L, and the total amount of water used is as little as 3060L.

[0201] On the other hand, in the comparative example, the amount of wastewater to be treated is very large, reaching 6750L, the total water usage in all processes, and the amount of sulfuric acid in the wastewater is also as high as 6.75L. Moreover, the total water usage in all processes is as high as 6750L.

[0202] Therefore, it can be confirmed that in the embodiments, the amount of wastewater to be treated is small, the amount of strong acid (sulfuric acid) contained therein is also small, and the overall amount of water used is also small.

[0203] [Table 1]

[0204] Example 1 Comparative Example 1 acidic aqueous solution 1% sulfuric acid 0.1% sulfuric acid solution pH 0.96 2.01 Water usage (pretreatment process: L) 360 - Water consumption (main treatment process: L) 2700 6750 Water usage (total: L) 3060 6750 Wastewater volume to be treated (L) 360 6750 The amount of sulfuric acid in the wastewater (L) 3.6 6.75

[0205] B. Evaluation related to pretreatment process S01

[0206] (1) Sample

[0207] Five types of absorbent materials were used as samples: two types of unused infant diapers and three types of unused adult diapers. The weight of each diaper (before use) was then measured. Next, to simulate "use," each diaper was saturated with 300g of saline solution and rolled up. The weight of each diaper was then measured again (after use, before processing). For the multiple diapers used in the examples and comparative examples, five types of diapers were prepared in equal quantities for each example and comparative example. In the infant diapers, the proportion of superabsorbent polymer in the absorbent component of the absorbent body was approximately 50%, and in the adult diapers, the proportion of superabsorbent polymer in the absorbent component of the absorbent body was approximately 30%.

[0208] (2) Evaluation of pretreatment process S01

[0209] A pretreatment step S01 was performed on each embodiment and comparative example using a fully automatic washing and dehydration machine (inner tank inner diameter: 1000 mm φ). For the embodiments and comparative examples, various conditions were varied in the acidic aqueous solution of the pretreatment step S01 and the inactivation step S12. The cases performed according to the conditions of the pretreatment step S01 described above are referred to as embodiments, and the cases performed under conditions partially different from those conditions are referred to as comparative examples.

[0210] (3) Results

[0211] The results are shown in Table 1 below. In Table 1, "Acidic Aqueous Solution" describes the conditions related to the acidic aqueous solution, "Amount Added" indicates the amount of sulfuric acid aqueous solution used, "Sulfuric Acid Concentration" indicates the sulfuric acid concentration in the sulfuric acid aqueous solution, "pH" indicates the pH of the sulfuric acid aqueous solution, and "Immersion Ratio" indicates the proportion of diapers immersed in the sulfuric acid aqueous solution (below the liquid surface) during the introduction process S11.

[0212] Table 1 lists the conditions related to the inactivation process S12, with "rotation speed" indicating the rotation speed of the inner tank. "Processing time" indicates the time for processing the diapers in the sulfuric acid aqueous solution. "Forward or forward-reverse time" indicates the cycles during which the inner tank alternately rotates and stops in the forward direction or alternately rotates in the forward and reverse directions within the processing time.

[0213] In addition, Table 1, under "Diapers," records the results of pretreatment process S01, etc. "Weight before use" indicates the weight of multiple diapers before use, i.e., before absorbing saline solution. "Weight before treatment after use" indicates the weight of multiple diapers after use and before the pretreatment process S01. "Weight after treatment" indicates the weight of multiple diapers after the pretreatment process S01. "Moisture content before treatment" indicates the percentage of water contained in multiple diapers after use and before the pretreatment process S01 (relative to the weight before use). "Dehydration rate" indicates the percentage of water contained in multiple diapers after the pretreatment process S01 (relative to the water contained in multiple diapers before the pretreatment process S01). The term "rolled-up state" is indicated by 〇 to ​​represent a situation where, after pretreatment step S01, more than 90% of the diapers maintain the rolled-up state (the state at the time of recycling) (less than 10% of the diapers are in a partially damaged state), and X to represent a situation where less than 90% (more than 10% of the diapers are in a partially damaged state). It should be noted that "X" in "post-treatment weight" indicates that a portion of the diaper has broken, separated, or disintegrated, making it impossible to properly measure the post-treatment weight, and "X" in "dehydration rate" indicates that it cannot be calculated because the post-treatment weight cannot be measured.

[0214] [Table 2]

[0215]

[0216] In Examples 2-5, after the pretreatment step S01, over 90% (actually 100%) of the diapers remained rolled up. Furthermore, the dehydration rate exceeded 40%. On the other hand, in Comparative Examples 2-3, less than 90% of the diapers remained rolled up after the pretreatment step S01. Moreover, the dehydration rate was low, or most of the used absorbent materials broke or disintegrated during processing, failing to achieve the desired dehydration rate. Specifically, in Comparative Example 2, because the sulfuric acid concentration of the acidic aqueous solution was reduced (increasing the pH), the superabsorbent polymer in the diaper was not completely inactivated. Therefore, the superabsorbent polymer absorbed the acidic aqueous solution diluted with saline solution discharged from the diaper. In Comparative Example 3, by reducing the amount of diapers, the dilution of the acidic aqueous solution was suppressed, but the rolled-up diapers showed almost no dehydration, resulting in a low dehydration rate. It should be noted that, although not shown in the examples and comparative examples, when the surface of the acidic aqueous solution is located above the top of the diaper, that is, when there is too much acidic aqueous solution, a large number of diapers float on the surface, making it difficult to carry out the pretreatment process S01.

[0217] The absorbent articles of the present invention are not limited to the embodiments described above, and can be appropriately combined and modified without departing from the purpose and spirit of the present invention.

[0218] Explanation of reference numerals in the attached figures

[0219] S01 Pretreatment Process

[0220] S02 Main Processing Process

Claims

1. A method for recovering multiple materials, including superabsorbent polymers and pulp fibers, from used absorbent articles, wherein the used absorbent articles are contaminated with dirt and have absorbed moisture, wherein... The method includes: A pretreatment step, wherein the pretreatment involves removing contaminants and moisture from the used absorbent article in an inactivated aqueous solution that inactivates the superabsorbent polymer, and discharging the inactivated aqueous solution containing the contaminants and moisture; and In the main processing step, water is injected into the used absorbent article after the dirt and moisture have been removed, and at least one of the various materials is separated and recovered from the used absorbent article. The inactivation aqueous solution contains a strongly acidic aqueous solution. The pretreatment process includes maintaining the used absorbent material in the state it was in when it was recycled in the acidic aqueous solution and performing the pretreatment.

2. The method as described in claim 1, wherein, The pretreatment process includes: In the import process, the used absorbent material and the acidic aqueous solution are imported into the treatment tank, wherein the liquid level of the acidic aqueous solution is lower than the top of the unfloating used absorbent material. The inactivation process involves repeatedly applying and easing pressure to the used absorbent material in an acidic aqueous solution within the treatment tank, thereby allowing the acidic aqueous solution to permeate the used absorbent material; and The removal process removes dirt and moisture from the used absorbent material.

3. The method as described in claim 2, wherein, The inactivation process includes applying and mitigating the pressure by causing the used absorbent material to collide with other used absorbent materials.

4. The method of claim 3, wherein, The processing tank is a horizontal rotating drum. The inactivation process includes a process in which the used absorbent material collides with other used absorbent materials by rotating the rotating drum.

5. The method of claim 2, wherein, In the importing process, the level of the acidic aqueous solution is located at the position where the used absorbent material in the treatment tank is immersed in 3 / 5 to 4 / 5 of its volume.

6. The method of claim 2, wherein, In the introducing process, the weight of the acidic aqueous solution is 2 to 3 times the weight of the used absorbent material in the treatment tank.

7. The method of claim 2, wherein, In the introductory step, the pH of the acidic aqueous solution is below 2.

0.

8. The method of claim 2, wherein, In the introductory step, the acidic aqueous solution contains sulfuric acid.

9. The method of claim 2, wherein, The dehydration rate of the used absorbent material after the removal process is 60% or more.

10. The method according to any one of claims 1 to 3, wherein, The main processing steps include: A separation process, in which water, including the used absorbent article from which dirt and moisture have been removed, is separated into superabsorbent polymer, pulp fibers and water, and other materials; and The recycling process involves separating and recovering the superabsorbent polymer and pulp fibers from the separated superabsorbent polymer, pulp fibers, and water, respectively.

11. The method of claim 10, wherein, The main processing step also includes a crushing step that crushes the used absorbent material before the separation step.

12. The method according to any one of claims 1 to 3, wherein, The amount of the inactivating aqueous solution used in the pretreatment step is less than the amount of water injected in the main treatment step.

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