JP6935451B2 - How to manufacture recycled fiber and recycled fiber - Google Patents

Description

The present invention relates to a method for producing recycled fibers from a mixture of fibers and a superabsorbent polymer, and recycled fibers.

Techniques for recycling used disposable diapers and other absorbent articles are known. For example, Patent Document 1 discloses a method for producing recycled pulp from used hygiene products. This method is a process of decomposing used sanitary products into pulp fibers and other materials by applying a physical force to the used sanitary products in an acidic aqueous solution, a mixture of pulp fibers and other materials. A step of separating the pulp fiber from the pulp fiber and a step of treating the separated pulp fiber with an ozone-containing aqueous solution are provided. The reason for treating pulp fibers with an ozone-containing aqueous solution is to remove the superabsorbent polymer remaining in the separated pulp fibers from the pulp fibers by decomposing, reducing the molecular weight, and solubilizing the polymer. be. Examples of the method for treating pulp fibers with an ozone-containing aqueous solution include a method in which an ozone-containing aqueous solution is placed in a treatment tank and the separated pulp fibers are placed in the ozone-containing aqueous solution. During the treatment, it is preferable to appropriately stir the ozone-containing aqueous solution to create a water stream. Alternatively, ozone gas may be blown into the aqueous solution contained in the container, and a water stream may be generated in the ozone-containing aqueous solution by raising the bubbles of the ozone gas.

Japanese Unexamined Patent Publication No. 2016-881

In Patent Document 1, in order to remove as much superabsorbent polymer remaining in pulp fibers as possible, it is necessary to generate a water stream in an ozone-containing aqueous solution to increase the area of pulp fibers in contact with ozone as much as possible. On the other hand, in order to improve the efficiency of pulp fiber processing, it is necessary to add as much pulp fiber as possible to the ozone-containing aqueous solution. However, when a large amount of pulp fibers are put into an ozone-containing aqueous solution, the speed of water flow due to stirring or ozone gas decreases in the ozone-containing aqueous solution, and in some cases, water flow may be difficult to occur. In that case, it becomes difficult to increase the area of the pulp fibers in contact with ozone, so that the treatment of the pulp fibers becomes uneven, that is, the removal of the super absorbent polymer becomes insufficient. Even if the ozone concentration in the ozone-containing aqueous solution is increased, if the speed of the water flow is reduced or the water flow is unlikely to occur, the removal of the superabsorbent polymer is still insufficient. As a result, the purity of the recycled pulp fiber, that is, the recycled pulp is lowered, and the use for reuse is limited, which makes it difficult to reuse. On the other hand, if the treatment time is lengthened to sufficiently remove the superabsorbent polymer, the efficiency of pulp fiber treatment is lowered, and it becomes difficult to efficiently produce recycled pulp. And such a thing can occur not only in the case of producing recycled pulp from the pulp fiber containing a super absorbent polymer, but also in the case of producing a recycled fiber from another fiber containing a superabsorbent polymer.

An object of the present invention is to remove a superabsorbent polymer from a fiber containing a superabsorbent polymer to produce a recycled fiber, in which the superabsorbent polymer is appropriately removed from the fiber and the recycled fiber is efficiently removed. The purpose is to provide a method that can be manufactured.

The method for producing recycled fiber from the mixture of fiber and superabsorbent polymer in the present invention is as follows. (1) A method for producing recycled fibers from a mixture of fibers and a highly water-absorbent polymer, wherein a mixed solution containing fibers containing the highly water-absorbent polymer and water is used as a treatment liquid capable of dissolving the highly water-absorbent polymer. The treatment liquid containing the fibers from which the highly water-absorbent polymer has been dissolved and removed while being continuously supplied into the treatment tank having the first flow rate is placed outside the treatment tank by a second. A method comprising a continuous processing step of continuously discharging at a flow rate of.
In this method, a mixed solution containing a superabsorbent polymer and fibers is continuously supplied at a first flow rate (volume or mass / hour) into a treatment tank having a treatment solution capable of dissolving the superabsorbent polymer. At the same time, a treatment liquid containing fibers from which the superabsorbent polymer has been removed and containing a low molecular weight organic substance produced by oxidative decomposition of the superabsorbent polymer is placed outside the treatment tank at a second flow rate (volume). Or mass / hour) to discharge continuously. Therefore, a continuous and stable fluid flow can be forcibly generated from the supply port for supplying the mixed liquid in the treatment tank to the discharge port for discharging the mixed liquid or the treatment liquid. Due to the flow of the fluid, that is, the water flow, the area of the fibers in contact with the treatment liquid can be increased even if the treatment amount of the fibers is increased, and the fibers can be evenly contacted with the treatment liquid. Therefore, even if the treatment amount of the fiber is increased, the unevenness of the fiber treatment can be suppressed, and the superabsorbent polymer can be appropriately dissolved and removed in the treatment liquid. As a result, the purity of the recycled fiber, that is, the recycled fiber can be increased, and the recycled fiber that can be easily reused can be produced. Therefore, the super absorbent polymer can be appropriately removed from the fiber, and the recycled fiber can be efficiently produced.

In this method, (2) the continuous treatment step is a step of continuously supplying the mixed liquid from the upper part of the treatment tank and continuously discharging the treatment liquid from the lower part of the treatment tank. The method according to (1) above may be included.
Since the fiber containing the superabsorbent polymer in the mixture usually has a higher specific gravity than the treatment liquid, gravity prevails in the treatment liquid over buoyancy and naturally sinks. Therefore, even if the mixed liquid, that is, the fiber is supplied from the lower part to the upper part in the treatment tank, it may return to the lower part again. Further, when the flow of the fluid generated in the treatment tank is a flow from the lower part to the upper part, there is a possibility that a portion of the fluid loses gravity and stays in a corner of the bottom of the treatment tank. In those cases, the efficiency of the process of removing the superabsorbent polymer from the fibers is reduced. Therefore, in this method, in the treatment liquid, the mixed liquid is supplied from the upper part of the treatment tank so that the fibers containing the superabsorbent polymer are moved from the upper part to the lower part, and the treatment liquid is discharged from the lower part of the treatment tank. Thereby, a continuous and stable fluid flow can be generated from the upper part to the lower part in the treatment tank. As a result, the fibers containing the superabsorbent polymer move more smoothly from the upper part to the lower part of the treatment tank without staying at the corners or edges in the treatment tank due to gravity and the flow of the fluid, and are treated with the treatment liquid. Can receive. Therefore, the fibers that have been treated with the treatment liquid can be discharged to the outside from the lower part of the treatment tank as they are. That is, the fiber containing the super absorbent polymer can be efficiently treated. Therefore, it becomes possible to efficiently produce recycled fibers.

In this method, (3) the treatment liquid capable of dissolving the superabsorbent polymer is an aqueous solution containing a gaseous substance that dissolves the superabsorbent polymer in a soluble manner, and the continuous treatment step is carried out in the gaseous state. The method according to (2) above may further include a delivery step of continuously delivering a plurality of bubbles of the substance from the lower part to the upper part of the treatment liquid.
In this method, in the treatment liquid, the gaseous substance moves from the lower part to the upper part, and the fibers containing the super absorbent polymer move from the upper part to the lower part, that is, countercurrent. Thereby, the contact probability between the super absorbent polymer contained in the fiber and the gaseous substance can be increased. In addition, the deeper the fibers containing the superabsorbent polymer settle, the higher the concentration of gaseous substances can be contacted. Therefore, the superabsorbent polymer that could not be completely dissolved in the treatment liquid only by the gaseous substance in contact with the shallow part in the treatment liquid can be brought into contact with the high concentration gaseous substance in the deep part in the treatment liquid. As a result, the super absorbent polymer can be reliably dissolved in the treatment liquid. Therefore, the super absorbent polymer contained in the fiber can be reliably dissolved in the treatment liquid and removed from the fiber.

The method may be the method according to (3) above, wherein (4) the delivery step includes a step of delivering the gaseous substance in the state of microbubbles or nanobubbles.
In this method, a gaseous substance having fine bubbles such as microbubbles or nanobubbles is sent from the lower part to the upper part of the treatment liquid in the treatment tank. Since the rising rate of fine bubbles is slow, the probability that the bubbles come into contact with the fibers can be increased. Further, since the fine bubbles occupy a small area on the surface of the fiber, more bubbles can come into contact with the surface of the fiber. As a result, the fiber containing the super absorbent polymer can be evenly wrapped with fine bubbles, and the contact area between the fiber containing the superabsorbent polymer and the gaseous substance can be further increased. Furthermore, as more bubbles come into contact with the surface of the fiber, the buoyancy of the fine bubbles reduces the sedimentation rate of the fiber containing the superabsorbent polymer, and the fiber containing the superabsorbent polymer and the gaseous substance The contact time can be further increased. As a result, the super absorbent polymer contained in the fiber can be more reliably dissolved in the treatment liquid and removed from the fiber.

The present method may be (5) the method according to (3) or (4) above, wherein the gaseous substance contains ozone.
In this method, the super absorbent polymer contained in the fiber is supplied to the ozone-containing aqueous solution. As a result, the superabsorbent polymer contained in the fiber can be oxidized and decomposed by ozone, so that the product of the oxidation and decomposition can be surely dissolved in the aqueous solution. That is, the super absorbent polymer can be appropriately removed from the fiber. As a result, the purity of the recycled fiber, that is, the recycled fiber can be increased. Further, by using the ozone-containing aqueous solution, the fibers can be bleached, and the color of the recycled fibers can be made closer to white. Further, by using the ozone-containing aqueous solution, the fibers can be sterilized and the recycled fibers can be made cleaner. Therefore, recycled fibers that are easy to reuse can be produced. Therefore, the super absorbent polymer can be appropriately removed from the fiber, and the recycled fiber can be efficiently produced.

The method may be (6) the method according to any one of (1) to (5) above, wherein the fiber is a pulp fiber.
In this method, the fibers are pulp fibers. Therefore, by dissolving the super absorbent polymer contained in the pulp fiber in the treatment liquid, the superabsorbent polymer can be appropriately removed from the pulp fiber. As a result, the purity of the recycled pulp fiber, that is, the recycled pulp can be increased. As a result, recycled pulp that is easy to reuse can be produced. Therefore, the super absorbent polymer can be appropriately removed from the pulp fiber, and recycled pulp can be efficiently produced.

This method may be the method according to any one of (1) to (6) above, wherein (7) the treatment liquid is an acidic aqueous solution.
In this method, the treatment liquid is an acidic aqueous solution (example: pH 5 or less). Even when the superabsorbent polymer contained in the fiber has a partial water absorption capacity, the water absorption expansion of the superabsorbent polymer can be suppressed. Thereby, the super absorbent polymer can be dissolved in the treatment liquid in a short time, and the superabsorbent polymer can be more reliably removed from the fiber. In particular, when the treatment liquid is an ozone-containing aqueous solution, ozone in the ozone-containing aqueous solution can be hardly deactivated, so that the superabsorbent polymer can be oxidized and decomposed in a short time and can be dissolved, and the superabsorbent polymer can be made into fibers. Can be removed more reliably from.

In this method, (8) before the continuous treatment step, the mixture is treated with an aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer, and the water absorption performance of the superabsorbent polymer in the mixture is treated. (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) to (1) The method according to any one of 7) may be used.
In this method, in the inactivation step, the water absorption performance of the superabsorbent polymer is suppressed by an aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer. The super absorbent polymer can be dissolved in the treatment liquid in a short time. That is, the super absorbent polymer can be removed more reliably from the fiber.

In this method, (9) the method according to (8) above, wherein the aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer in the inactivation step is an acidic aqueous solution.
In this method, the aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer is an acidic aqueous solution (example: pH 2.5 or less), and the acidic aqueous solution has a high effect of inactivating the superabsorbent polymer. At this stage, the water absorption performance of the superabsorbent polymer can be suppressed more reliably. As a result, the superabsorbent polymer can be more easily dissolved in the treatment liquid for a short time at the stage of the continuous treatment step of the subsequent step. That is, the super absorbent polymer can be removed more reliably from the fiber.

The method according to any one of (1) to (9) above, wherein (10) the treatment tank includes at least a first treatment tank and a second treatment tank connected in series with each other. The method may be.
In this method, the treatment tank includes at least a first treatment tank and a second treatment tank connected in series with each other. In that case, for example, the first treatment tank is supplied with the mixed liquid, the first treated liquid (mixed liquid or the treatment liquid of the first treatment tank) is discharged, and the second treatment tank is the first. The mixed liquid is treated in multiple stages, such that the treated liquid of No. 1 is supplied and the second treated liquid (the first treated liquid or the treated liquid in the second treatment tank) is discharged. In that case, since the treatment is performed with a new treatment liquid for each tank as compared with the case where one treatment tank having a large capacity is provided, for example, the treatment cannot be completely dissolved in the first treatment tank (first stage treatment tank). The super absorbent polymer can be more reliably dissolved and removed from the fiber, for example, the superabsorbent polymer can be easily dissolved in the second treatment tank (next-stage treatment tank).

According to the method of the present invention, in a method for producing a recycled fiber by removing the superabsorbent polymer from the fiber containing the superabsorbent polymer, the recycled fiber is produced while appropriately removing the superabsorbent polymer from the fiber. It becomes possible to manufacture efficiently.

It is a flowchart which shows the embodiment which concerns on the method of this invention. It is the schematic which shows the structural example of the apparatus of the oxidant treatment process of FIG. It is the schematic which shows the other structural example of the apparatus of the oxidant treatment step of FIG. It is the schematic which shows still another structural example of the apparatus of the oxidant treatment step of FIG.

Hereinafter, a method for producing recycled fibers from a mixture of fibers and a super absorbent polymer according to an embodiment will be described. In this embodiment, an example will be described in which the fibers are pulp fibers and the mixture of fibers and superabsorbent polymer is a mixture of pulp fibers and superabsorbent polymer obtained from a used absorbent article. However, the present invention is not limited to the present embodiment, and can be appropriately modified without departing from the spirit of the present invention. For example, the fiber may be a fiber other than pulp fiber, and a mixture of the fiber and a super absorbent polymer may be obtained from a fiber other than the used absorbent article. The used absorbent article is an absorbent article used by the user, and includes an absorbent article in a state of absorbing the liquid excrement of the user, and is used but absorbs the excrement. It also includes unused and unused items.

First, a configuration example of the absorbent article will be described. The absorbent article includes a front surface sheet, a back surface sheet, and an absorber arranged between the front surface sheet and the back surface sheet. Absorbent articles include, for example, disposable diapers, urine absorbing pads, sanitary napkins, bed sheets, and pet sheets. An example of the size of the absorbent article is a length of about 15 to 100 cm and a width of 5 to 100 cm.

Examples of the constituent members of the surface sheet include non-woven fabrics or films, and specific examples thereof include liquid-permeable non-woven fabrics, synthetic resin films having liquid-permeable holes, and composite sheets thereof. Examples of the constituent members of the back sheet include non-woven fabrics or films, and specific examples thereof include liquid-impermeable non-woven fabrics, liquid-impermeable synthetic resin films, and composite sheets of these non-woven fabrics and synthetic resin films. Here, the material of the non-woven fabric or the synthetic resin film is not particularly limited as long as it can be used as an absorbent article, but for example, an olefin resin such as polyethylene or polypropylene, or a polyamide such as 6-nylon or 6,6-nylon. Examples thereof include polyester resins such as polyethylene tale phthalate (PET) and polybutylene teletalate (PBT). In the present embodiment, an absorbent article in which the constituent member of the back surface sheet is a film and the constituent member of the front surface sheet is a non-woven fabric will be described as an example.

Examples of the constituent members of the absorber include absorber materials, that is, pulp fibers and superabsorbent polymers. The pulp fiber is not particularly limited as long as it can be used as an absorbent article, and examples thereof include cellulosic fibers. Examples of cellulosic fibers include wood pulp, crosslinked pulp, non-wood pulp, regenerated cellulose, semi-synthetic cellulose and the like. The superabsorbent polymer (SAP) is not particularly limited as long as it can be used as an absorbent article, and examples thereof include polyacrylate-based, polysulfone-based, and maleic anhydride-based water-absorbing polymers. Can be mentioned.

One surface and the other surface of the absorber are bonded to the front surface sheet and the back surface sheet, respectively, via an adhesive. In a plan view, the portion of the front surface sheet that extends outside the absorber so as to surround the absorber (peripheral portion) is outside the absorber so as to surround the absorber in the back sheet. It is joined to the extended portion (peripheral portion) via an adhesive. Therefore, the absorber is wrapped inside the joint between the front surface sheet and the back surface sheet. The adhesive is not particularly limited as long as it can be used as an absorbent article and the bonding strength is lowered by softening or the like due to warm water described later, and examples thereof include a hot melt type adhesive. Examples of the hot melt type adhesive include rubber-based adhesives such as styrene-ethylene-butadiene-styrene, styrene-butadiene-styrene, and styrene-isoprene-styrene, or olefin-based pressure-sensitive adhesives such as polyethylene, or heat-sensitive adhesives. Agents can be mentioned.

Next, a method for producing recycled pulp fiber from a mixture of pulp fiber and super absorbent polymer obtained from a used absorbent article will be described. In the present embodiment, the used absorbent article is collected / acquired from the outside for reuse (recycling) and used. Each used absorbent article is rolled or folded with the surface sheet on which the excrement is excreted inside so that the excrement is not exposed to the front side and the odor does not diffuse to the surroundings. It is collected in the state of being excreted. The used absorbent article does not have to be in a rolled state or the like.

A method for producing recycled pulp fibers from a mixture of pulp fibers obtained from a used absorbent article and a superabsorbent polymer is included in a material separation method for separating a used absorbent article into constituent materials. FIG. 1 is a flowchart showing a material separation method for separating a used absorbent article into constituent materials. This material separation method is a method for separating a used absorbent article into a film, a non-woven fabric, a pulp fiber, and a super absorbent polymer. This material separation method includes a pretreatment step S11, a decomposition step S12, and a separation step S13. In the pretreatment step S11, the used absorbent article is swollen with water. In the decomposition step S12, the swollen used absorbent article is physically impacted to decompose the used absorbent article into a film, a non-woven fabric, and an absorbent material (pulp fiber and super absorbent polymer). In the separation step S13, the film, the non-woven fabric, the pulp fibers, and the super absorbent polymer are separated. A method for producing recycled pulp fiber from a mixture of pulp fiber and superabsorbent polymer is included in the separation step S13 of this material separation method. When the mixture of pulp fiber and highly water-absorbent polymer is obtained in advance by some method, recycled pulp is obtained from the mixture of pulp fiber and highly water-absorbent polymer in the pretreatment step S11, the decomposition step S12 and the separation step S13. The step prior to the method of producing the fiber does not need to be carried out. Hereinafter, each step will be described.

The pretreatment step S11 is in the state when a plurality of used absorbent articles are collected from the outside, that is, in the rolled state or the folded state without breaking or cutting. It absorbs water and swells without inactivating the superabsorbent polymer of the absorber. In the present embodiment, the used absorbent article is made to absorb hot water and swell, or the absorbed water is heated after absorbing and expanding the water to make hot water. Hot water refers to water having a temperature higher than room temperature (20 ° C ± 15 ° C (5-35 ° C): JIS Z 8703).

Normally, the amount of liquid excrement actually absorbed by a used absorbent article is very small compared to the maximum absorption that the absorbent article can absorb (eg, about 10 to 20 of the maximum absorption). mass%). In the present embodiment, in the pretreatment step S11, by immersing the used absorbent article in warm water, water is reduced to an amount close to the maximum absorption amount of the used absorbent article (example: 80% by mass or more of the maximum absorption amount). To absorb. Alternatively, the used absorbent article is immersed in water at room temperature to absorb water to an amount close to the maximum absorption amount of the used absorbent article, and then the entire used absorbent article is heated to the temperature of warm water. Thereby, the used absorbent article can be made into a very expanded state with warm water or water at room temperature (hereinafter, also simply referred to as "warm water"). As a result, a very high internal pressure is generated in the used absorbent article. The purpose of making the water hot is mainly to weaken the adhesive force of the adhesive as described later.

Here, the used absorbent article is absorbed by being immersed in warm water when it is initially rolled or folded with the back sheet on the outside (the front sheet is hidden inside). The absorber of the sex article absorbs the hot water and expands in the warm water. As a result, the internal pressure of the used absorbent article increases, and a force acting to open the used absorbent article outward causes the used absorbent article in the rolled or folded state to move outward. It opens toward you and becomes almost flat. That is, the used absorbent article can be flattened in warm water. At this time, since the absorbent body of the used absorbent article absorbs a large amount of hot water and expands very much, the front surface of the used absorbent article, that is, either the front surface sheet or the back surface sheet surrounding the absorbent body is easily formed. It is in a state where it is about to break. That is, in the pretreatment step S11, one of the surfaces of the used absorbent article can be torn and cut. When the used absorbent article is unfolded flat from the beginning, any part of the surface is likely to be easily torn off in that state. This state cannot occur when the used absorbent article is broken or the like.

Furthermore, the used absorbent article is immersed in warm water and / or absorbs the hot water to soften the adhesive (eg, hot melt adhesive) used for joining between the constituent members by the heat of the hot water. It is possible to reduce the bonding force of the adhesive. For example, the adhesive that joins the peripheral portion of the front surface sheet and the peripheral portion of the back surface sheet can be softened by the heat of warm water to reduce the bonding force of the adhesive. Further, the adhesive for joining the front surface sheet and the absorber and the adhesive for joining the back surface sheet and the absorber can be softened by the heat of warm water, and the bonding force of these adhesives can be reduced.

As described above, in the pretreatment step S11, due to the expansion of the absorber of the used absorbent article, any part of the surface of the used absorbent article is likely to be torn off, and the bonding force of the adhesive is reduced. A state, can occur. When the used absorbent article is in such a state, the used absorbent article can be reliably decomposed in the decomposition step described later.

The temperature of the hot water in the pretreatment step S11 is not particularly limited as long as the adhesive of the used absorbent article can be softened, but is, for example, 60 ° C. or higher, preferably 70 ° C. or higher and 98 ° C. or lower. By setting the temperature of the hot water to 70 ° C. or higher, the adhesive for joining the constituent members can be further softened by the heat of the hot water, and the bonding force of the adhesive can be further reduced. By setting the temperature of the hot water to 98 ° C. or lower, the hot water surely exists as a liquid, so that the used absorbent article can more reliably absorb the hot water. Due to the expansion of the absorber and the heat of the hot water, it is possible to more reliably generate a state in which the surface of the used absorbent article is likely to be torn off and a state in which the bonding force of the adhesive is reduced. For temperature measurement, measure the temperature of hot water in which the used absorbent article is immersed, or measure the temperature 5 mm inside the surface of the used absorbent article that has absorbed water to an amount close to the maximum absorption amount ( Insert the tip of the temperature sensor).

In addition, sterilization of constituent materials is extremely important in the reuse of used absorbent articles. By setting the temperature of the hot water to 70 ° C. or higher, it is possible to exert the effect of sterilizing (disinfecting) the used absorbent article, which is preferable.

The treatment time in the pretreatment step S11, that is, the time for immersing the used absorbent article in warm water is not particularly limited as long as the absorber of the used absorbent article can expand, but is preferably 2 to 60 minutes, for example. 4 to 30 minutes. If the time is too short, the absorber cannot expand sufficiently, and if it is too long, the time is wasted and the processing cost increases unnecessarily.

The amount of hot water absorbed by the absorber in the pretreatment step S11 is not particularly limited as long as the absorber can expand to the extent that the used absorbent article can be decomposed in the decomposition step described later. The maximum absorption amount is 80% by mass or more, preferably 90% by mass or more. Thereby, the used absorbent article can be fully inflated with water. As a result, an extremely high internal pressure can be generated in the absorber of the used absorbent article.

However, the maximum absorption amount is measured by the following procedure.
(1) An unused absorbent article is dried in an atmosphere of 100 ° C. or higher, and the mass of the absorbent article is measured.
(2) If an elastic material (eg, elastic member around the legs or waist) that can form a pocket that makes it difficult for water to reach the absorber is placed in the absorbent article, a cut is made in the elastic member. Flatten the absorbent article by adding.
(3) Immerse the absorbent article in a water bath filled with sufficient tap water with the surface sheet facing down, and leave it for 30 minutes.
(4) After being left to stand, the absorbent article is placed on a net with the surface sheet facing down, drained for 20 minutes, and then the mass of the absorbent article is measured.
Then, the mass difference before and after immersion in tap water is defined as the maximum absorption amount.

Next, in the decomposition step S12, the plurality of used absorbent articles developed and swollen in the pretreatment step S11 are physically impacted to form the plurality of used absorbent articles into a film (back sheet) and a non-woven fabric (front surface). It decomposes into a sheet) and an absorber material (absorbent and superabsorbent polymer: absorber).

The used absorbent article is unfolded and flat by the pretreatment step S11, and any part of the surface is likely to be torn off due to expansion. The bonding strength of the is reduced. Therefore, in the disassembling step S12, by applying a physical impact to the used absorbent article in that state, the front sheet (nonwoven fabric) and the back sheet (nonwoven fabric) and the back sheet (nonwoven fabric) whose bonding strength is particularly reduced in any part of the surface surface. The joint with the film) is torn off. Thereby, the joint portion can be torn (peeled). The physical impact is not particularly limited, but for example, a method of striking a used absorbent article on a surface made of a material harder than the used absorbent article, or a method of arranging used absorbent articles face-to-face with each other. An example is a method of pressing from both sides while sandwiching the roll between a pair of rolls and passing the roll.

In the present embodiment, the disassembling step S12 includes a step of charging a plurality of swollen used absorbent articles into the bottom of a rotating drum having a horizontal rotating shaft, and rotating the rotating drum around the rotating shaft. It involves pulling a plurality of used absorbent articles to the top of the rotating drum and tapping them against the bottom. Thereby, a physical impact can be stably, continuously (continuously) and easily applied to a plurality of used absorbent articles. Examples of the rotating drum include a rotating drum in the washing tub of a horizontal washing machine, so that the disassembling step S12 can be carried out using an existing horizontal washing machine (example: ECO-22B manufactured by Inamoto Manufacturing Co., Ltd.). The size of the rotating drum is not particularly limited as long as the above impact can be realized, but the inner diameter and depth are, for example, 50 to 150 cm and 30 to 120 cm. The rotation speed of the rotating drum is not particularly limited as long as the above impact can be realized, and examples thereof include 30 times / minute to 100 times / minute.

Further, the temperature of the used absorbent article is kept relatively high by the hot water absorbed in the used absorbent article, but from the viewpoint of suppressing the temperature decrease of the adhesive and maintaining the sterilizing effect, the temperature of the used absorbent article is kept relatively high. The temperature of the atmosphere in the rotating drum is preferably 70 ° C. or higher, more preferably 75 ° C. or higher. The temperature inside the rotating drum is preferably 98 ° C. or lower, more preferably 90 ° C. or lower, from the viewpoint of handling used absorbent articles. The amount of water in the rotating drum is preferably as small as possible, and preferably so small that the used absorbent article is not below the water surface, at least at the bottom. When the used absorbent article is below the water surface, the impact on the used absorbent article is absorbed by the water, and it becomes difficult to give a desired impact to the used absorbent article. The time for rotating the rotating drum is not particularly limited as long as the front surface sheet and the back surface sheet and the absorber material can be decomposed, but is, for example, 2 to 40 minutes, preferably 4 to 20 minutes.

In the used absorbent article, the joint portion between the front surface sheet (nonwoven fabric) and the back surface sheet (film) is torn and torn by a physical impact. At the same time, the absorbent material (pulp fiber and water-absorbing polymer) in the used absorbent article is ejected (jumped out) through the crevice due to the internal pressure of the absorber. Thereby, the used absorbent article can be reliably decomposed by the front surface sheet (nonwoven fabric) and the back surface sheet (film) and the absorbent material (pulp fiber and water-absorbent polymer).

Next, in the separation step S13, the plurality of films (back sheet), the plurality of non-woven fabrics (front sheet), and the absorber material (pulp fiber and water-absorbent polymer: absorber) are separated. However, the non-woven fabric may be bonded to the film. At this time, the back surface sheet (film) and the front surface sheet (nonwoven fabric) generally maintain the same shape as that of the absorbent article, that is, the original shape. Therefore, the size, shape, and mass of the front sheet (nonwoven fabric) and the back sheet (film) are clearly different from the size, shape, and shape of the absorber material, as compared with the case where the front sheet (nonwoven fabric) and the back sheet (film) are broken into pieces before decomposition. Therefore, in the separation step S13, the front surface sheet (nonwoven fabric) and the back surface sheet (film) can be easily separated from the absorber (pulp fiber and water-absorbent polymer). The separation method is not particularly limited, and examples thereof include a method using a sieve through which the absorber material is passed without passing through the front surface sheet and the back surface sheet. As a result, the constituent member such as a film can be easily separated from other constituent members while maintaining the same shape without breaking or the like.

In the present embodiment, the separation step S13 includes an inactivation step S31 that inactivates the superabsorbent polymer with an aqueous solution containing an inactivating agent before separating the film and the non-woven fabric from the absorber material, and the film and the non-woven fabric. , A first separation step S32 for separating the pulp fiber, the inactivated superabsorbent polymer and the mixture containing the sewage discharged from the superabsorbent polymer by inactivation, may be included.

In the inactivation step S31, the front sheet (nonwoven fabric), the back sheet (film) and the absorber (pulp fiber and superabsorbent polymer) can be inactivated before the first separation step S32. Immerse in an aqueous solution containing an inactivating agent. Thereby, the super absorbent polymer adhering to the front surface sheet, the back surface sheet and the pulp fiber can be inactivated. Thereby, the superabsorbent polymer in a high viscosity state before inactivation can be made into a superabsorbent polymer in a low viscosity state by dehydration by inactivation.

Here, the inactivating agent is not particularly limited, and examples thereof include inorganic acids, organic acids, lime, calcium chloride, magnesium sulfate, magnesium chloride, aluminum sulfate, and aluminum chloride. Of these, inorganic acids and organic acids are preferable because they do not leave ash in the pulp fibers. When an inorganic acid or an organic acid is used as the inactivating agent, the pH of the inorganic acid aqueous solution or the organic acid aqueous solution is 2.5 or less, preferably 1.3 to 2.4. Therefore, the aqueous solution containing the inactivating agent can be said to be an acidic aqueous solution. If the pH is too high, the water absorption capacity of the super absorbent polymer cannot be sufficiently reduced. In addition, the bactericidal ability may be reduced. If the pH is too low, there is a risk of equipment corrosion, and a large amount of alkaline chemicals are required for neutralization treatment during wastewater treatment. Examples of the inorganic acid include sulfuric acid, hydrochloric acid, and nitric acid, but sulfuric acid is preferable from the viewpoint of not containing chlorine and cost. On the other hand, examples of the organic acid include citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, ascorbic acid, etc., but hydroxycarbonate-based organic acids such as citric acid, tartaric acid, gluconic acid, etc. are particularly preferable. preferable. The chelating effect of citric acid traps and removes metal ions and the like in excrement, and the cleaning effect of citric acid is expected to have a high effect of removing dirt components. Since the pH changes depending on the water temperature, the pH in the present invention refers to the pH measured at an aqueous solution temperature of 20 ° C. The inorganic acid concentration of the inorganic acid aqueous solution is not limited as long as the pH of the inorganic acid aqueous solution is 2.5 or less, but when the inorganic acid is sulfuric acid, the concentration of sulfuric acid is preferably 0.1% by mass or more and 0.5. It is less than or equal to mass%. The organic acid concentration of the organic acid aqueous solution is not limited as long as the pH of the organic acid aqueous solution is 2.5 or less, but when the organic acid is citric acid, the concentration of citric acid is preferably 0.8% by mass or more 4 It is less than or equal to mass%.

The treatment temperature of the inactivating step S31, that is, the temperature of the aqueous solution containing the inactivating agent is not particularly limited as long as the inactivating reaction proceeds. The treatment temperature may be room temperature or higher than room temperature, and examples thereof include 15 to 30 ° C. The treatment time of the inactivating step S31, that is, the time for immersing the front sheet, the back sheet and the absorber material in the aqueous solution containing the inactivating agent is not particularly limited as long as the superabsorbent polymer is inactivated and dehydrated. For example, 2 to 60 minutes, preferably 5 to 30 minutes. Further, the amount of the aqueous solution in the inactivating step S31, that is, the amount of the aqueous solution containing the inactivating agent is not particularly limited as long as the inactivating reaction proceeds. The amount of the aqueous solution is, for example, preferably 300 to 3000 parts by mass, more preferably 500 to 2500 parts by mass, and further preferably 1000 to 2000 parts by mass with respect to 100 parts by mass of the used absorbent article.

In the first separation step S32, a mixture containing a front sheet (nonwoven fabric) and a back sheet (film), pulp fibers, an inactivated superabsorbent polymer, and sewage discharged from the superabsorbent polymer due to inactivation, To separate. However, the sewage is sewage containing water released from the superabsorbent polymer by dehydration with an aqueous solution containing an inactivating agent in the inactivating step S31, that is, liquid derived from excrement and water derived from warm water.

In the first separation step S32, the method for separating the front surface sheet and the back surface sheet from the pulp fiber, the super absorbent polymer and the sewage is not particularly limited. For example, the product produced by the inactivation step (front surface sheet, back surface sheet, pulp fiber, super absorbent polymer, sewage, etc.) is discharged while passing through a screen having an opening of 5 to 100 mm, preferably an opening of 10 to 60 mm. .. Thereby, the pulp fibers, the superabsorbent polymer and the sewage remain in the wastewater, and the front sheet and the back sheet remain on the screen, so that their products can be separated. In addition, other large-shaped objects such as non-woven fabrics and films may remain on the screen. In particular, since the superabsorbent polymer is in a highly viscous state before inactivation, it is not easy to separate the superabsorbent polymer attached to the front surface sheet, the back surface sheet and the pulp fiber. However, after inactivation, the superabsorbent polymer becomes low in viscosity due to dehydration. Therefore, the superabsorbent polymer adhering to the front sheet, the back sheet and the pulp fiber is removed from the front sheet, the back sheet and the pulp fiber. It can be easily separated. Therefore, the constituent members of the absorbent article can be efficiently separated and recovered.

In the present embodiment, the separation step S13 may further include a second separation step S33 in which the adhesive at the joint portion is removed with a solvent that dissolves the adhesive at the joint portion between the film and the other member. In the present embodiment, the adhesive at each joint is removed with a solvent that dissolves the adhesive at each joint between the film, the non-woven fabric, and the absorber material.

In the second separation step S33, the adhesive at the joint portion between the film (back surface sheet) and other members (nonwoven fabric of the front surface sheet, absorber material of the absorber remaining on the surface of the front surface sheet or the back surface sheet, etc.) is used as a solvent. Removed by. As a result, the film and other members can be separated from each other while maintaining the same shape without breaking or the like. Therefore, a constituent member such as a film of an absorbent article can be efficiently recovered. Further, since the film and other members can be separated without leaving an adhesive on the film, the film can be reused as a high-purity resin. As a result, it is possible to prevent the adhesive from adversely affecting the film when it is reused. The same applies to the non-woven fabric as well as the film.

The solvent used in the second separation step S33 is not particularly limited as long as it can dissolve the adhesive, and for example, a terpene containing at least one of a terpene hydrocarbon, a terpene aldehyde, and a terpene ketone can be used. Can be mentioned. In this step, an aqueous solution containing Tempel is used, and the concentration of Tempel in the aqueous solution is, for example, 0.05% by mass or more and 2% by mass or less. It is preferably 0.075 to 1% by mass. If the concentration of terpenes is too low, the adhesive at the joint may not be able to dissolve. If the concentration of terpenes is too high, the cost can be high. In addition, Tempel not only dissolves adhesives such as hot melt adhesives, but also has an oil stain cleaning effect. Therefore, when printing is performed on a constituent member of an absorbent article such as a back sheet, Tempel can also decompose and remove the printing ink.

Examples of terpene hydrocarbons include myrcene, limonene, pinene, camphor, sapinene, phellandrene, parasimene, ocimene, terpinene, kalen, gingiberene, cariophyllene, bisabolen and sedrene. Of these, limonene, pinene, terpinene, and karen are preferable. Examples of the terpene aldehyde include citronellal, citral, cyclocitral, safranal, ferlandral, perillaldehyde, geranial, and neral. Examples of the terpene ketone include camphor and tsuyoshi. Among the terpenes, terpene hydrocarbons are preferable, and limonene is particularly preferable. There are three types of limonene, d-limonene, l-limonene, and dipentene (dl-limonene), and any of them can be preferably used. One type of terpene can be used alone, or two or more types can be used in combination.

The treatment temperature of the second separation step S33, that is, the temperature of the aqueous solution containing the solvent is not particularly limited as long as the adhesive is dissolved and the used absorbent article is decomposed into constituent members. The treatment temperature may be room temperature or higher than room temperature, and examples thereof include 15 to 30 ° C. Further, during the processing time of the second separation step S33, that is, the time for immersing the front sheet, the back sheet and the absorber material in the aqueous solution containing the solvent, the adhesive dissolves and the used absorbent article is decomposed into constituent members. As long as it is not particularly limited. The processing time is, for example, 2 to 60 minutes, preferably 5 to 30 minutes. The amount of the aqueous solution in the second separation step S33, that is, the amount of the aqueous solution containing the solvent is not particularly limited as long as the adhesive is dissolved and the used absorbent article is decomposed into constituent members. The amount of the aqueous solution is, for example, preferably 300 to 3000 parts by mass, and more preferably 500 to 2500 parts by mass with respect to 100 parts by mass of the used absorbent article. By the second separation step S33, the amount of the adhesive remaining on the film, the non-woven fabric or the absorbent material can be reduced to 1% by mass or less with respect to the film, the non-woven fabric or the absorbent material.

In the present embodiment, as another preferable embodiment, the second separation step S33 may be performed together with the inactivation step S31. That is, the adhesive attached to the front sheet, the back sheet and the pulp fiber may be dissolved while inactivating the super absorbent polymer attached to the front sheet, the back sheet and the pulp fiber. In this case, as the aqueous solution for immersing the front surface sheet, the back surface sheet, the pulp fiber and the super absorbent polymer, an aqueous solution containing both an inactivating agent and a solvent is used. As a result, in the inactivation step S31, the back sheet (film), the front sheet (nonwoven fabric), and the absorber (pulp fiber and superabsorbent polymer) can be substantially separated in the aqueous solution. Then, in the subsequent first separation step, the back sheet (film) and front sheet (nonwoven fabric) and the absorber (pulp fiber and superabsorbent polymer) can be separated, and the second separation step S33 can be omitted. .. In this case, the back sheet (film) and the front sheet (nonwoven fabric) are substantially separated by removing the adhesive.

In the present embodiment, the separation step S13 further includes a first drying step S34 in which the film is dried in an atmosphere or hot air having a temperature higher than room temperature to remove the solvent after the step of removing the adhesive at the joint portion. It may be included. In the present embodiment, the non-woven fabric is also dried in this step.

Sterilization is extremely important in the reuse of used absorbent articles. In the first drying step S34, a step of drying the separated film (back surface sheet) and non-woven fabric (front surface sheet) in a high temperature atmosphere or hot air is performed. The drying temperature is, for example, 105 to 210 ° C, preferably 110 to 190 ° C. The drying time depends on the drying temperature, but is, for example, 10 to 120 minutes, preferably 15 to 100 minutes. Thereby, not only the solvent remaining on the surface of the film and the non-woven fabric can be evaporated and removed, but also the film and the non-woven fabric can be sterilized by a high temperature atmosphere or hot air. As a result, it is possible to exert the effect of sterilization (disinfection) while removing the solvent.

On the other hand, in the present embodiment, the separation step S13 may include a third separation step S35 that separates the pulp fibers from the separated mixture. In the third separation step S35, the method for separating the pulp fibers from the separated mixture (including the pulp fibers, the super absorbent polymer and the sewage) is not particularly limited, but for example, the separated mixture is opened at 0. It is discharged while passing through a screen having a size of 1 to 4 mm, preferably a mesh size of 0.15 to 2 mm. Thereby, the superabsorbent polymer and sewage remain in the wastewater, and the pulp fiber (mainly the superabsorbent polymer remaining on the surface) remains on the screen, so that the pulp fiber can be separated from the mixture. Although this pulp fiber contains a lot of impurities, it can be used depending on the application. The separated pulp fibers (mainly a superabsorbent polymer remaining on the surface) are mixed with water in a predetermined ratio and supplied to the oxidizing agent treatment step S36 as a mixed liquid having a predetermined pulp fiber.

In the present embodiment, in the separation step S13, the separated pulp fibers are treated with an aqueous solution containing an oxidizing agent, and the highly water-absorbent polymer remaining in the pulp fibers is treated with an oxidizing agent to reduce the molecular weight, solubilize and remove the polymer. Includes step S36.

In the oxidizing agent treatment step S36, the highly water-absorbent polymer mainly remaining on the surface of the separated pulp fibers is oxidatively decomposed by the oxidizing agent in the aqueous solution to change it into a low molecular weight organic substance soluble in the aqueous solution. , Remove from the surface of pulp fibers. Here, the state in which the superabsorbent polymer is oxidatively decomposed and changed to a low molecular weight organic substance soluble in an aqueous solution means a state in which the superabsorbent polymer passes through a 2 mm screen. As a result, impurities such as a super absorbent polymer contained in the pulp fiber can be removed, and a pulp fiber having high purity can be produced. In addition, the pulp fiber can be secondarily sterilized, bleached, and deodorized by the oxidizing agent treatment.

The oxidizing agent is not particularly limited as long as it can oxidize and decompose an inactivated superabsorbent polymer to reduce its molecular weight and solubilize it, and examples thereof include chlorine dioxide, ozone, and sodium hypochlorite. Of these, ozone is preferable from the viewpoint of high decomposition performance, bleaching performance, sterilization performance, and deodorizing performance, and ozone is used in this embodiment. When ozone is used as an oxidant, it is oxidized by contacting a mixture containing pulp fibers and a highly water-absorbent polymer with ozone, specifically by blowing ozone-containing gas into an aqueous solution containing pulp fibers and a highly water-absorbent polymer. Agent treatment can be performed.

The oxidant treatment step S36 will be further described.
First, an apparatus for executing the oxidizing agent treatment step S36 will be described. FIG. 2 is a schematic view showing an example of the configuration of the apparatus 2 that executes the oxidant treatment step S36. The apparatus 2 treats the mixture storage unit 3 for storing the mixture 51 containing water and the pulp fibers separated in the third separation step S35, and the highly water-absorbent polymer contained in the pulp fibers in the mixture 51. It includes an oxidizing agent treatment unit 4 that is oxidatively decomposed by the liquid 52 and removed from the pulp fibers.

The mixture storage unit 3 includes a mixture tank 12 and a stirrer 13. The mixed liquid tank 12 stores the mixed liquid 51 containing pulp fibers at a constant ratio in the water supplied through the pipe 61. The stirrer 13 stirs the mixed liquid 51 in the mixed liquid tank 12 so that the pulp fibers in the mixed liquid 51 do not separate from water and sink below the mixed liquid 51.

On the other hand, the oxidant processing unit 4 includes a supply pump 21, a processing tank 31, an ozone supply device 41, a delivery pump 22, and an ozone decomposition device 34. The treatment tank 31 has an acidic aqueous solution as the treatment liquid 52. The supply pump 21 continuously supplies the mixed liquid of the mixed liquid tank 12 into the processing tank 31 at the first flow rate via the pipe 62. The ozone supply device 41 supplies the ozone-containing gas 53, which is a gaseous substance, to the treatment tank 31. Examples of the ozone generator 42 of the ozone supply device 41 include an ozone water exposure tester ED-OWX-2 manufactured by Ecodesign Co., Ltd. and an ozone generator OS-25V manufactured by Mitsubishi Electric Corporation. The ozone-containing gas 53 is another type of gas containing ozone, and examples thereof include oxygen gas containing ozone. The nozzle 43 that sends out the ozone-containing gas 53 supplied to the processing tank 31 via the pipe 65 into the processing tank 31 is arranged at the lower part (preferably the bottom) of the processing tank 31. The nozzle 43 continuously supplies the ozone-containing gas 53 as a plurality of fine bubbles into the treatment liquid 52 from the lower part to the upper part of the treatment liquid 52 (treatment tank 31). The delivery pump 22 continuously discharges the processing liquid 52 in the processing tank 31 to the outside of the processing tank 31 at a second flow rate via the pipe 63. The ozone decomposition device 34 receives the ozone-containing gas 53 accumulated in the upper part of the treatment tank 31 via the pipe 64, decomposes ozone, detoxifies it, and releases it to the outside. The treatment liquid 52 in the treatment tank 31 is only the treatment liquid 52 before the start of the oxidizing agent treatment step S36, and after the start, the treatment liquid 52 and the mixed liquid 51 are mixed. In the embodiment, the liquid in the treatment tank 31 is referred to as the treatment liquid 52, including the liquid in which the treatment liquid 52 and the mixed liquid 51 are mixed.

Next, a specific method of the oxidizing agent treatment step S36 will be described.
The pulp fibers separated in the third separation step S35 (mainly a super absorbent polymer remains on the surface) are mixed with water so as to have a preset concentration to form a mixed liquid 51. The concentration of the pulp fibers in the mixed liquid 51 is set to a preset concentration in a state where the pulp fibers are charged into the treatment tank 31 and mixed with the treatment liquid 52. The mixed liquid 51 is supplied to and stored in the mixed liquid tank 12 via the pipe 61. Since the specific gravity of the pulp fiber is larger than 1, the mixed liquid 51 is stirred by the stirrer 13 in the mixed liquid tank 12 so that the pulp fiber and water are not separated.

Then, the mixed liquid 51 (mainly the superabsorbent polymer remaining on the surface) in the mixed liquid tank 12 continuously reaches the processing tank 31 via the pipe 62 at the first flow rate by controlling the flow rate of the supply pump 21. Be supplied. As a result, the pulp fibers are supplied into the treatment liquid 52 from the supply port 32 provided in the upper part of the treatment tank 31. The treatment liquid 52 is an acidic aqueous solution and has a specific gravity of about 1. Therefore, the pulp fibers settle from the upper part to the lower part of the treatment liquid 52.

On the other hand, the ozone-containing gas 53 generated by the ozone generator 42 is supplied to the treatment tank 31 via the pipe 65, and is in the state of fine bubbles in the treatment liquid 52 from the nozzle 43 of the treatment tank 31 (example: microbubbles or It is released in nanobubbles). That is, the ozone-containing gas 53 rises from the lower part to the upper part of the treatment liquid 52. This step can be seen as a delivery step in which a plurality of bubbles of the ozone-containing gas 53 are continuously sent from the lower part to the upper part of the treatment liquid 52.

Then, in the treatment liquid 52, the pulp fibers that settle from the upper part to the lower part and the ozone-containing gas 53 that rises from the lower part to the upper part collide with each other while advancing toward each other. Then, the ozone-containing gas 53 adheres to the surface of the pulp fiber so as to wrap the pulp fiber. At that time, the ozone in the ozone-containing gas 53 reacts with the superabsorbent polymer in the pulp fiber to oxidatively decompose the superabsorbent polymer and dissolve it in the treatment liquid 52. Thereby, the super absorbent polymer on the pulp fiber is removed from the pulp fiber. Then, the pulp fibers settle to the bottom of the treatment tank 31, and the ozone-containing gas 53 escapes to the space above the treatment tank 31.

After that, the treatment liquid 52 (including pulp fibers) at the bottom of the treatment tank 31 has a second flow rate from the discharge port 33 of the treatment tank 31 to the outside of the treatment tank 31 via the pipe 63 by controlling the flow rate of the delivery pump 22. Is continuously discharged. The ozone of the ozone-containing gas 53 accumulated in the upper part of the treatment tank 31 is decomposed by the ozone decomposition device 34, detoxified, and released to the outside.

In this way, the mixed liquid 51 is continuously supplied into the treatment tank 31 from the upper part of the treatment tank 31 at the first flow rate, and the treatment liquid 52 is discharged from the lower part (bottom) of the treatment tank 31 to the outside of the treatment tank 31. It is continuously discharged at the second flow rate. Thereby, a continuous and stable flow of fluid (including pulp fibers) from the upper part to the lower part can be forcibly generated in the treatment tank 31.

The treatment liquid 52 discharged from the treatment tank 31 contains pulp fibers from which the superabsorbent polymer has been removed, and also contains a low molecular weight organic substance produced by oxidative decomposition of the superabsorbent polymer. The pulp fiber is recovered in a step downstream of the delivery pump 22, for example, in a fourth separation step S37 described later. The pulp fiber from which the super absorbent polymer has been removed can be said to be a high-quality pulp fiber (recycled pulp fiber) having extremely few impurities.

In the above-mentioned oxidizing agent treatment step S36, the mixed liquid 51 containing the pulp fiber containing the superabsorbent polymer and water is first placed in the treatment tank 31 having the treatment liquid 52 capable of dissolving the superabsorbent polymer. Continuous treatment in which the superabsorbent polymer is continuously supplied at the flow rate of the above, and the treatment liquid 52 containing the removed fibers is continuously discharged to the outside of the treatment tank 31 at the second flow rate. It can be said that the process is included. That is, it can be said that the oxidant treatment step S36 includes a method for producing recycled pulp fiber from a mixture of pulp fiber and superabsorbent polymer.

In this method, at least the mixed liquid 51 containing the superabsorbent polymer and the pulp fiber is continuously supplied at the first flow rate into the treatment tank 31 having the treatment liquid 52 capable of dissolving the superabsorbent polymer. At the same time, a treatment liquid 52 containing pulp fibers from which the superabsorbent polymer has been removed and containing a low molecular weight organic substance produced by oxidative decomposition of the superabsorbent polymer is discharged to a second flow rate outside the treatment tank 31. Discharge continuously with. With such a configuration, a continuous and stable flow of fluid (including pulp fibers) flows from the supply port 32 for supplying the mixed liquid 51 in the treatment tank 31 toward the discharge port 33 for discharging the treatment liquid 52. Can be forcibly generated. Due to the flow of the fluid, that is, the water flow, the area of the pulp fibers in contact with the treatment liquid can be increased even if the treatment amount of the pulp fibers is increased, and the pulp fibers can be evenly contacted with the treatment liquid. .. Therefore, even if the treatment amount of the pulp fiber is increased, the unevenness of the treatment of the pulp fiber can be suppressed, and the superabsorbent polymer can be appropriately dissolved and removed in the treatment liquid. As a result, the purity of the recycled pulp fiber, that is, the recycled pulp fiber can be increased, and the recycled pulp fiber that can be easily reused can be produced. Therefore, the super absorbent polymer can be appropriately removed from the pulp fiber, and the recycled pulp fiber can be efficiently produced.

Here, it is preferable that the first flow rate and the second flow rate are the same. By making the first flow rate and the second flow rate the same, the amount of the treatment liquid 52 in the treatment tank 31 can be kept constant, and stable and continuous treatment is possible. However, if the amount of the treatment liquid 52 in the treatment tank 31 can be kept substantially constant, that is, unless the amount of the treatment liquid 52 in the treatment tank 31 is significantly increased or decreased, the first flow rate and the second flow rate The flow rate of may fluctuate with time. That is, the first flow rate and the second flow rate do not have to be completely the same at all times, and may be substantially the same on average over time. Here, substantially the same means that the difference is within 5%. In this case as well, stable and continuous processing is possible.

When the ozone-containing gas 53 is supplied to the treatment liquid 52, the ozone concentration in the treatment liquid 52 is not particularly limited as long as it can decompose the highly water-absorbent polymer, and examples thereof include 1 to 50 mass ppm. It is preferably 2 to 40 mass ppm, and more preferably 3 to 30 mass ppm. If the ozone concentration in the treatment liquid 52 is too low, the superabsorbent polymer cannot be completely solubilized, and the superabsorbent polymer may remain in the pulp fibers. On the contrary, if the ozone concentration in the treatment liquid 52 is too high, the oxidizing power is also increased, which may damage the pulp fibers and may cause a problem in safety. The ozone treatment temperature is not particularly limited as long as it can decompose the super absorbent polymer, but may be kept at room temperature or may be higher than room temperature, for example.

However, the concentration of ozone in the treatment liquid 52 (aqueous solution) was measured by the following method.
In a 100 mL graduated cylinder containing about 0.15 g of potassium iodide and 5 mL of a 10% citric acid solution, 85 mL of a treatment solution 52 in which ozone is dissolved is put and reacted. After the reaction, the mixture is transferred to a 200 mL Erlenmeyer flask, a starch solution is added thereto, and the mixture is colored purple, and then titrated with 0.01 mol / L sodium thiosulfate while stirring until it becomes colorless. Then, the concentration of ozone in the aqueous solution is calculated from the titration value using the following formula.
Ozone concentration in aqueous solution (mass ppm) = 0.01 mol / L sodium thiosulfate (mL) required for titration x 0.24 x 0.85 (mL)

The ozone concentration in the ozone-containing gas 53 is preferably 40 to 200 g / m ³ , more preferably 40 to 150 g / m ³ , and even more preferably 40 to 100 g / m ³ . If the ozone concentration in the ozone-containing gas 53 is too low, the superabsorbent polymer cannot be completely solubilized, and the superabsorbent polymer may remain in the pulp fibers. If the concentration in the ozone-containing gas 53 is too high, it may lead to damage to pulp fibers, a decrease in safety, and an increase in manufacturing cost. The ozone concentration in the ozone-containing gas 53 is measured by an ultraviolet absorption type ozone concentration meter (example: manufactured by Ecodesign Co., Ltd .: ozone monitor OZM-5000G).

The concentration of the pulp fiber (including the superabsorbent polymer) in the treatment liquid 52 is not particularly limited as long as it can decompose the super absorbent polymer by ozone in the treatment liquid 52, and is not particularly limited. 1 to 20% by mass is mentioned, preferably 0.2 to 10% by mass, and more preferably 0.3 to 5% by mass. If the concentration of the pulp fiber is too high, the superabsorbent polymer cannot be completely solubilized, and the superabsorbent polymer may remain in the pulp fiber. On the contrary, if the concentration of the pulp fiber is too low, the oxidizing power is also increased, which may damage the pulp fiber and may cause a safety problem. The concentration of the pulp fibers (including the superabsorbent polymer) in the mixture 51 is appropriately set based on the concentration of the pulp fibers in the treatment liquid 52 and the amount of the treatment liquid 52.

When ozone is supplied to the treatment liquid 52 containing the pulp fiber and the super absorbent polymer, the treatment liquid 52 is preferably acidic. More preferably, the pH of the treatment liquid 52 is greater than 0 and 5 or less, and more preferably 1.5 to 2.5. By treating in an acidic state, the deactivation of ozone is suppressed, the effect of decomposing and removing the superabsorbent polymer by ozone is improved, and the superabsorbent polymer can be decomposed in a short time. In order to maintain the pH of the treatment liquid, the pH of the mixture 51 may be the same as the pH of the treatment liquid 52, and the mixture 51 may be supplied to the treatment tank 31. Alternatively, the pH of the treatment liquid 52 may be monitored by a pH sensor, and when the pH fluctuates to the neutral side, a predetermined acidic solution may be added to the treatment liquid 52 in an amount corresponding to the fluctuation range.

The amount of the treatment liquid 52 (including the mixed liquid 51) in the treatment tank 31 is not particularly limited as long as it can decompose the superabsorbent polymer, but the volume V of the treatment liquid 52 in the treatment tank 31 It is preferable that (unit: L) and the mass W (unit: kg) of the pulp fiber satisfy 30 ≦ V / W ≦ 1000. More preferably, it is 50 ≦ V / W ≦ 400, and even more preferably 100 ≦ V / W ≦ 200. If the V / W is too small, the super absorbent polymer contained in the pulp fiber cannot be completely solubilized, and the superabsorbent polymer may remain in the pulp fiber. If the V / W is too large, the manufacturing cost may increase. The volume V of the processing tank 31 is not particularly limited, and examples thereof include 50 to 80 L.

Ozone-containing gas flow rate _{R O} (Unit: L / min) and the volume V (unit: L) of the processing solution 52 in processing tank 31, to meet the 0.01 ≦ _R O /V≦1.5, preferable. More preferably from 0.03 ≦ _R O /V≦1.0, more preferably 0.06 ≦ _R O /V≦0.5. If the _RO / V is too small, the superabsorbent polymer cannot be completely solubilized, and the superabsorbent polymer may remain in the pulp fiber. If _RO / V is too large, it may lead to damage to pulp fibers, reduced safety, and increased manufacturing costs. As the flow rate R _O of the ozone-containing gas is not particularly limited, for example 3～6L / min can be mentioned.

The time during which the pulp fibers are present in the treatment tank 31, that is, the time during which the pulp fibers are treated in the treatment liquid 52 (hereinafter, also referred to as “in-tank treatment time”) can decompose the highly water-absorbent polymer. The time is not particularly limited. The treatment time in the tank may be short if the ozone concentration of the treatment liquid 52 is high, and long if the ozone concentration of the treatment liquid 52 is low. The treatment time in the tank includes, for example, 2 minutes to 60 minutes, preferably 5 minutes to 30 minutes. The product of the ozone concentration (mass ppm) in the treatment liquid 52 and the treatment time (minutes) in the tank (hereinafter, also referred to as “CT value”) is preferably 100 to 6000 ppm · min, more preferably 200 to 4000 ppm. · Minutes, more preferably 300-2000 ppm · min. If the CT value is too small, the superabsorbent polymer cannot be completely solubilized, and the superabsorbent polymer may remain in the recovered pulp fibers. If the CT value is too large, it may lead to damage to pulp fibers, reduced safety, and increased manufacturing costs.

While the pulp fibers are present in the treatment tank 31, the superabsorbent polymer undergoes an oxidative decomposition action by ozone. As a result, the three-dimensional network structure of the super absorbent polymer collapses. As a result, the superabsorbent polymer loses water retention and changes to a low molecular weight material. Then, the low molecular weight material dissolves in the treatment tank 31 in which the pulp fibers are present. The low molecular weight material dissolved in the treatment liquid 52 is discharged together with the treatment liquid 52, but solid particles of the superabsorbent polymer do not remain in the treatment liquid 52. Further, in this step, the used sanitary goods are primarily disinfected by the bactericidal action of ozone.

In the present embodiment, as a preferred embodiment, the oxidizing agent treatment step S36 (continuous treatment step) continuously supplies the mixed liquid 51 from the upper part of the treatment tank 31 while supplying the treatment liquid 52 to the lower part of the treatment tank 31. Includes a step of continuously discharging from. At this time, the specific gravity of the pulp fiber containing the super absorbent polymer of the mixed liquid 51 is larger than the specific gravity of the treatment liquid 52. Therefore, since gravity is superior to buoyancy in the treatment liquid 52, the pulp fibers containing the super absorbent polymer naturally settle. Therefore, even if the mixed liquid 51, that is, the pulp fiber is supplied from the lower part to the upper part in the processing tank 31, it may return to the lower part again. Further, when the flow of the fluid generated in the processing tank 31 is a flow from the lower part to the upper part, there is a possibility that some of the fluid loses gravity and stays in the corners or ends of the bottom of the processing tank 31. .. In those cases, the efficiency of the process of removing the superabsorbent polymer from the pulp fibers is reduced. Therefore, in the method of the present preferred embodiment, in the treatment liquid 52, the mixed liquid 51 is supplied from the upper part of the treatment tank 31 so as to move the pulp fibers containing the superabsorbent polymer from the upper part to the lower part, and the lower part of the treatment tank 31. The treatment liquid 52 is discharged from. As a result, a continuous and stable fluid flow can be generated from the upper part to the lower part in the processing tank 31. As a result, the pulp fiber containing the superabsorbent polymer is processed while moving more smoothly from the upper part to the lower part of the processing tank 31 without staying at the corner or the end in the processing tank 31 due to gravity and the flow of the fluid thereof. It can be treated with the liquid 52. Therefore, the pulp fibers that have been treated with the treatment liquid 52 can be discharged to the outside from the lower part of the treatment tank 31 as they are. That is, the pulp fiber containing the super absorbent polymer can be efficiently treated. Therefore, it becomes possible to efficiently produce recycled fibers.

In the present embodiment, as a preferred embodiment, the treatment liquid 52 capable of dissolving the superabsorbent polymer is an aqueous solution containing a gaseous substance that dissolves and decomposes the superabsorbent polymer. The oxidant treatment step S36 (continuous treatment step) further includes a delivery step of continuously delivering a plurality of bubbles of the gaseous substance from the lower part to the upper part of the treatment liquid 52. In such a preferred embodiment of the present method, in the treatment liquid 52, the gaseous substance moves from the lower part to the upper part, and the pulp fiber containing the super absorbent polymer moves from the upper part to the lower part, that is, countercurrent. .. Thereby, the contact probability between the super absorbent polymer contained in the pulp fiber and the gaseous substance can be increased. In addition, the deeper the pulp fibers containing the superabsorbent polymer settle, the higher the concentration of gaseous substances can be contacted. Therefore, the superabsorbent polymer that could not be completely dissolved in the treatment liquid 52 only by the gaseous substance that came into contact with the treatment liquid 52 in the shallow part can be brought into contact with the high concentration gaseous substance in the treatment liquid 52 in the deep part. Thereby, the super absorbent polymer can be surely dissolved in the treatment liquid 52. Therefore, the super absorbent polymer contained in the pulp fiber can be reliably dissolved in the treatment liquid and removed from the fiber. Here, when ozone-containing gas is used as the gaseous substance, the embodiment having the above-mentioned delivery step is compared with the case where the treatment liquid which does not have the delivery step and only contains the gaseous substance in advance is used. As a result, the ozone consumption efficiency can be increased by, for example, about 1.5 to 2 times, that is, the consumption amount can be reduced.

In the present embodiment, as a preferred embodiment, the above-mentioned delivery step includes a step of delivering the gaseous substance in the state of microbubbles or nanobubbles. However, the microbubbles are bubbles having a diameter of about 1 to 1000 μm, preferably about 10 to 500 μm, and the nanobubbles are bubbles having a diameter of about 100 to 1000 nm, preferably about 100 to 500 nm. Microbubbles or nanobubbles are such fine bubbles, have a large surface area per unit volume, and have a property that the rate of rise in the liquid is slow. Therefore, in the present method, as a preferred embodiment, such a gaseous substance having fine bubbles is sent from the lower part to the upper part of the treatment liquid 52 in the treatment tank 31. On the other hand, the pulp fiber containing the super absorbent polymer moves from the upper part to the lower part. At this time, since the rising rate of the fine bubbles is slow, the probability that the bubbles come into contact with the pulp fibers can be increased. Further, since the fine bubbles occupy a small area on the surface of the pulp fiber, more bubbles can come into contact with the surface of the pulp fiber. Thereby, the pulp fiber containing the super absorbent polymer can be evenly wrapped with fine bubbles, and the contact area between the pulp fiber containing the superabsorbent polymer and the gaseous substance can be further increased. Furthermore, as more bubbles come into contact with the pulp surface, the buoyancy of the bubbles reduces the sedimentation rate of the pulp fibers containing the superabsorbent polymer, and the contact between the pulp fibers containing the superabsorbent polymer and the gaseous substance. You can increase the time more. As a result, the super absorbent polymer contained in the pulp fiber can be more reliably dissolved in the treatment liquid 52 and removed from the pulp fiber.

In the present embodiment, as a preferred embodiment, the gaseous substance contains ozone, that is, ozone-containing gas 53. Therefore, in the present method, as a preferred embodiment, the superabsorbent polymer contained in the pulp fiber is supplied to the ozone-containing aqueous solution as the treatment liquid. As a result, the super absorbent polymer contained in the pulp fiber can be oxidized and decomposed by ozone, so that the product of the oxidation and decomposition can be surely dissolved in the aqueous solution. That is, the super absorbent polymer can be appropriately removed from the pulp fiber. As a result, the purity of the recycled pulp fiber, that is, the recycled pulp fiber can be increased. Further, by using the ozone-containing aqueous solution, the pulp fibers can be bleached, and the color of the recycled pulp fibers can be made closer to white. Further, by using the ozone-containing aqueous solution, the pulp fibers can be sterilized, and the recycled pulp fibers can be made more clean. Therefore, recycled pulp fibers that are easy to reuse can be produced. Therefore, the super absorbent polymer can be appropriately removed from the pulp fiber, and the recycled pulp fiber can be efficiently produced.

In the present embodiment, as a preferred embodiment, the treatment liquid 52 is an acidic aqueous solution, for example, an acidic aqueous solution having a pH of 2.5 or less. In that case, even if the superabsorbent polymer contained in the pulp fibers in the mixed liquid 51 partially has a water-absorbing ability, the water-absorbing expansion of the superabsorbent polymer can be suppressed. Thereby, the super absorbent polymer can be dissolved in the treatment liquid 52 in a short time, and the superabsorbent polymer can be more reliably removed from the fiber. In particular, when the treatment liquid 52 is an ozone-containing aqueous solution, the ozone in the ozone-containing aqueous solution can be hardly deactivated, so that the superabsorbent polymer can be oxidized and decomposed in a shorter time, can be dissolved, and the superabsorbent polymer can be dissolved. Can be removed more reliably from the fibers.

Further, as another preferred embodiment, the configuration of the treatment tank 31 may be a configuration other than that shown in FIG. FIG. 3 is a schematic view showing another configuration example of the apparatus 2 in the oxidizing agent treatment step of FIG. Compared with the device 2 of FIG. 2, the device 2 of FIG. 3 has a continuous U-shaped tube structure in which the pipe 63 of the oxidant processing unit 4 connects two U-shaped tubes upside down and continuously to each other. , The difference is that the delivery pump 22 is omitted. In that case, the pipe 63 is filled with the treatment liquid 52, and the height of the liquid level of the treatment liquid 52 in the treatment tank 31 is higher than the height of the liquid level in the tank of the next step connected by the pipe 63. If it is high, the treatment liquid 52 is discharged to the tank in the next step via the pipe 63 according to the siphon principle. Therefore, if the height of the liquid level of the treatment liquid 52 in the treatment tank 31 and the height of the liquid level of the liquid in the tank of the next step are initially set to be the same before the start of the treatment, the treatment is started by the start of the treatment. When the mixed liquid 51 is continuously supplied into the tank 31 at the first flow rate, the processing liquid 52 is discharged to the tank of the next step through the pipe 63 at the second flow rate = the first flow rate according to the siphon principle. It will be. However, regarding the height of the liquid level in the tank in the next step, the height before the start of the treatment should be maintained even during the treatment. In this case, the delivery pump 22 is unnecessary, and the control of the second flow rate of the delivery pump 22 becomes unnecessary.

In the present embodiment, the separation step S13 further includes a fourth separation step S37 for separating the pulp fibers from the treatment liquid 52 discharged from the treatment tank 31, and a second drying for drying the separated pulp fibers. Step S38 and may be included.

In the fourth separation step S37, the method for separating the pulp fibers from the treatment liquid 52 discharged from the treatment tank 31 is not particularly limited, but for example, the treatment liquid 52 containing the pulp fibers is opened, for example, 0.15-. A method of passing through a 2 mm screen mesh can be mentioned. When the treatment liquid 52 containing pulp fibers is passed through a screen mesh having an opening of 0.15 to 2 mm, the waste water containing the product due to the oxidative decomposition of the super absorbent polymer passes through the screen. On the other hand, the pulp fibers remain on the screen and are taken out as high-quality pulp fibers (recycled pulp fibers).

In the subsequent second drying step S38, the separated pulp fibers are dried in a high temperature atmosphere or hot air. The drying temperature is, for example, 105 to 210 ° C, preferably 110 to 190 ° C. The drying time depends on the drying temperature, but is, for example, 10 to 120 minutes, preferably 15 to 100 minutes. As a result, the solvent remaining on the surface of the pulp fiber is evaporated and removed, and the pulp fiber having a very low superabsorbent polymer content and a high purity can be recovered. Therefore, the constituent members of the absorbent article can be efficiently recovered. In addition, pulp fibers can be sterilized (disinfected) in a high temperature atmosphere or hot air.

Further, the superabsorbent polymer can be recovered from the wastewater containing the superabsorbent polymer and sewage separated in the third separation step S35. The recovery method is not particularly limited, and examples thereof include a method using a sieve, and examples of a method for recovering the water absorption capacity of the recovered superabsorbent polymer include a method of treating with an aqueous alkali metal salt solution. Further, the residual wastewater (ozone dissolved in a little less than 10 ppm) separated in the fourth separation step S37 may be circulated to the pretreatment step S11. As a result, the pretreatment in the pretreatment step S11 and the sterilization with ozone can be performed at the same time without wasting the wastewater containing ozone.

The method for producing recycled fibers from a mixture of fibers and a superabsorbent polymer further includes the fourth separation step S37 and the second drying step S38 in addition to the oxidant treatment step S36. May be good.

In the present embodiment, as a preferred embodiment, before the oxidizing agent treatment step S36 (continuous treatment step), the mixture is treated with an aqueous solution capable of inactivating the water absorption performance of the highly water-absorbent polymer, and the height in the mixture is increased. Before the inactivation step S31 for inactivating the water absorption performance of the water-absorbent polymer and the oxidizing agent treatment step S36 (continuous treatment step), the first step of separating the pulp fiber containing the inactivated highly water-absorbent polymer from the aqueous solution. The separation step S32 is further provided. As described above, in the present method, as a preferred embodiment, in the inactivation step S31, the water absorption performance of the superabsorbent polymer is suppressed by the aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer. At the stage of the treatment step S36 (continuous treatment step), the superabsorbent polymer can be more easily dissolved by the treatment liquid 52 in a short time. That is, the super absorbent polymer can be more reliably removed from the pulp fiber.

In the present embodiment, as a preferred embodiment, the aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer in the inactivation step S31 is an acidic aqueous solution, for example, an acidic aqueous solution having a pH of 2.5 or less. As described above, in the present method, as a preferred embodiment, since the aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer is an acidic aqueous solution, the superabsorbent polymer is more easily inactivated, whereby in the stage of the inactivation step S31. , The water absorption performance of the super absorbent polymer can be suppressed more reliably. As a result, the superabsorbent polymer can be more easily dissolved in the treatment liquid for a short time at the stage of the oxidizing agent treatment step S36 (continuous treatment step) in the subsequent step. That is, the super absorbent polymer can be removed more reliably from the fiber.

Further, as another preferred embodiment, the treatment tank 31 may include at least a first treatment tank 31-1 and a second treatment tank 31-2 connected in series with each other. FIG. 4 is a schematic view showing another configuration example of the apparatus 2 in the oxidizing agent treatment step of FIG. Compared with the device 2 of FIG. 2, the device 2 of FIG. 4 has two oxidant treatment units 4 joined in series, in other words, the first treatment tank 31-1 and the second treatment tank 31-. It differs in that it is joined in series with 2. In that case, for example, the first treatment tank 31-1 is supplied with the mixed liquid 51, the first treated liquid (treatment liquid 52-1 of the first treatment tank 31-1) is discharged, and the second treatment tank 31-1 is discharged. The treatment tank 31-2 is supplied with the first treated liquid, and the second treated liquid (the treatment liquid 52-2 of the second treatment tank 31-2) is discharged, and so on. It is processed in multiple stages. In that case, as compared with the case where one treatment tank 31 having a large capacity is provided, the treatment is performed with new treatment liquids 52-1 and 52-2 for each of the first and second treatment tanks 31-1 and 31-2. Therefore, for example, the superabsorbent polymer that could not be completely dissolved in the first treatment tank (first stage treatment tank) 31-1 can be easily dissolved in the second treatment tank (next stage treatment tank) 31-2. , Etc., the super absorbent polymer can be dissolved more reliably and can be removed from the fiber.

In the present embodiment, as a preferred embodiment, the fiber is a pulp fiber. Therefore, by dissolving the super absorbent polymer contained in the pulp fiber in the treatment liquid 52, the superabsorbent polymer can be appropriately removed from the pulp fiber. As a result, the purity of the recycled pulp fiber, that is, the recycled pulp fiber can be increased. As a result, recycled pulp fibers that are easy to reuse can be produced. Therefore, the super absorbent polymer can be appropriately removed from the pulp fiber, and the recycled pulp fiber can be efficiently produced. However, even if the fiber is a fiber other than the pulp fiber, if the cross-absorbable polymer is attached to the fiber, each embodiment described with reference to FIGS. 1 to 4 above shall be applied. As a result, the purity of the recycled fiber, that is, the recycled fiber can be increased, and the recycled fiber that can be easily reused can be produced. Therefore, the super absorbent polymer can be appropriately removed from the fiber, and the recycled fiber can be efficiently produced.

In the present embodiment, as a preferred embodiment, in the material separation step S1, in the pretreatment step S11, the used absorbent article is kept in the same shape without breaking and the superabsorbent polymer is not inactivated. Can be made very inflated with water. As a result, a very high internal pressure can be generated in the used absorbent article, and any part of the surface thereof can be in a state where it is likely to be torn off. Then, in the decomposition step S12, by applying a physical impact to the used absorbent article in such a state, any part of the surface thereof is torn and the absorbent material inside is ejected to the outside. Can be made to. Thereby, the used absorbent article can be decomposed into at least a film (back sheet) and an absorber material. At this time, since the film generally maintains its original shape, it can be easily separated from the absorber material in the subsequent separation step S13. As a result, the constituent member such as a film can be separated from other constituent members while maintaining the same shape without breaking or the like. Therefore, a constituent member such as a film of an absorbent article can be efficiently recovered.

In the present embodiment, as a preferred embodiment, by using a terpene for removing the adhesive, the hot melt adhesive that adheres the constituent members of the absorbent article can be melted at room temperature. Thereby, the absorbent article can be easily and neatly separated easily, the pulp fiber and the superabsorbent polymer can be separated from the absorbent article, and the non-woven fabric and the film can be separated separately while leaving the member form. That is, the pulp fibers, the film, and the non-woven fabric can be easily recovered separately without crushing the absorbent article or going through a complicated separation process. When limonene is used as a terpene, it has a refreshing citrus odor as a side effect of limonene, so that the odor derived from excrement can be covered to some extent, and the odor burden on the operator and the influence of odor on the neighborhood can be reduced. Limonene is a monoterpene and is similar in structure to styrene, so it can dissolve styrene-based hot melt adhesives commonly used in absorbent articles. Since the absorbent article can be washed at room temperature, the energy cost can be reduced and the generation and diffusion of odor can be suppressed. Terpen has a high oil stain cleaning effect, and in addition to the melting effect of hot melt adhesive, if there is printing on the film, the printing ink can also be decomposed and removed, and the printed film can also be recovered as a high-purity plastic material. Is.

Further, when an organic acid aqueous solution having a pH of 2.5 or less is used for inactivating the super absorbent polymer, the pulp fibers are hardly deteriorated. When citric acid is used as the organic acid, the effect of removing stain components derived from excrement can be expected due to the chelating effect and detergency of citric acid. In addition, a sterilizing effect and a deodorizing effect on alkaline odors can be expected.

Furthermore, by decomposing and removing the superabsorbent polymer with an oxidizing agent, it is possible to prevent contamination of pulp fibers and a rapid increase in sewage due to water absorption of the superabsorbent polymer. By adjusting the type and concentration of the oxidizing agent used, it is possible to simultaneously perform oxidative decomposition and sterilization of the superabsorbent polymer. Further, when ozone is used as the oxidant in the oxidant treatment step, no chlorine-based chemical is used, so that it is possible to produce a high-quality RPF that does not easily damage the combustion furnace from the recovered plastic member. Since no salts are used during the treatment process, there is no residue on the pulp fibers, and high-quality pulp with low ash content can be recovered.

The above-described embodiment describes a case where the constituent member of the back surface sheet is a film and the constituent member of the front surface sheet is a non-woven fabric. However, also in the case where the constituent member of the back surface sheet is a non-woven fabric and the constituent member of the front surface sheet is a film, or the constituent member of both the back surface sheet and the front surface sheet is a film, the above-described embodiment is also used. It can be realized by the same method as the above, and the same action and effect can be obtained.

The absorbent article of the present invention is not limited to the above-described embodiments, and can be appropriately combined or modified as long as it does not deviate from the object and purpose of the present invention.

31 Treatment tank 51 Mixing liquid 52 Treatment liquid S36 Oxidizing agent treatment step

Claims (10)

A device for producing recycled fibers from a mixture of fibers and a super absorbent polymer.
A processing tank having a supply port and a discharge port,
A supply pump connected to the supply port of the processing tank via a pipe,
With
By the supply pump, a mixed liquid containing fibers containing a highly water-absorbent polymer and water is placed in the treatment tank having a treatment liquid capable of dissolving the highly water-absorbent polymer through the supply port. The treatment liquid containing the fibers from which the highly water-absorbent polymer has been dissolved and removed while being continuously supplied at a flow rate of 1 is discharged out of the treatment tank through the discharge port. Configured to be discharged continuously at flow rate,
Device. A delivery pump connected to the discharge port of the processing tank via a pipe is further provided.
The supply pump continuously supplies the mixture from the supply port of the treatment tank, while the delivery pump continuously discharges the treatment liquid from the discharge port of the treatment tank. Consists of,
The device according to claim 1. The treatment liquid capable of dissolving the superabsorbent polymer is an aqueous solution containing a gaseous substance that dissolves and decomposes the superabsorbent polymer.
The device is
Further provided with a gas supply device for supplying the gaseous substance to the treatment tank,
The gas supply device is configured to continuously deliver a plurality of bubbles of the gaseous substance from the lower part to the upper part of the treatment liquid.
The device according to claim 1 or 2. The gas supply device is
The gas generator that generates the gaseous substance and
A nozzle connected to the gas generator, arranged in the processing tank, and delivering the gaseous substance,
Including
The nozzle is configured to deliver the gaseous substance in the form of microbubbles or nanobubbles.
The device according to claim 3. The gaseous substance contains ozone,
The device according to claim 3 or 4. The fiber is a pulp fiber,
The device according to any one of claims 1 to 5. The treatment liquid is an acidic aqueous solution.
The device according to any one of claims 1 to 6. Before supplying the mixture into the treatment tank, the mixture is treated with an aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer, and the water absorption performance of the superabsorbent polymer in the mixture is treated. Inactivation means to inactivate and
Separation means for separating the fiber containing the inactivated superabsorbent polymer from the aqueous solution before supplying the mixed solution into the treatment tank.
Further prepare
The device according to any one of claims 1 to 7. The aqueous solution capable of inactivating the water absorption performance of the superabsorbent polymer is an acidic aqueous solution.
The device according to claim 8. The treatment tank includes at least a first treatment tank and a second treatment tank connected in series with each other.
The device according to any one of claims 1 to 9.

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