WO2018025500A1

WO2018025500A1 - Method for recovering pulp fibers from used absorbent article

Info

Publication number: WO2018025500A1
Application number: PCT/JP2017/021540
Authority: WO
Inventors: 孝義小西; 利夫平岡; 八巻　孝一; 範朋亀田
Original assignee: ユニ・チャーム株式会社
Priority date: 2016-08-05
Filing date: 2017-06-09
Publication date: 2018-02-08

Abstract

A method is provided which, by a simple process, separates and recovers pulp fibers from a used absorbent article that contains pulp fibers and a superabsorbent polymer. A used absorbent article is treated with an aqueous solution that contains greater than or equal to 0.05 mass% of at least one kind of terpene selected from the group comprising terpene hydrocarbons, terpene aldehydes, and terpene ketones and that contains a deactivating agent that can deactivate the superabsorbent polymer; the superabsorbent polymer is deactivated, the adhesive that bonds together the constituent materials of the absorbent article is dissolved with the terpene to decompose the absorbent article, the pulp fibers are discharged to outside of the absorbent article, and the pulp fibers are separated from the absorbent article and recovered.

Description

Method for recovering pulp fibers from used absorbent articles

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

[Attempts have been made to recycle absorbent articles such as used disposable diapers. In order to recycle a used absorbent article, usually, the used absorbent article is decomposed in water, separated into components of the absorbent article, and collected. However, the superabsorbent polymer contained in the absorbent article absorbs moisture and increases its mass, and also becomes a gel and loses fluidity, thereby reducing the processing capability of the processing apparatus.

Therefore, JP 2010-84031 A introduces lime, hypochlorous acid and used paper diapers into a treatment tank, and stirs for a predetermined time while supplying a minimum amount of water that can be stirred in the treatment tank. A treatment method for used paper diapers characterized by discharging the liquid in the treatment tank to the outside of the treatment tank and dehydrating it, collecting the discharged waste water, performing water quality treatment, and discarding it is proposed.

JP 2010-84031 A

However, in the method disclosed in Japanese Patent Application Laid-Open No. 2010-84031, lime, hypochlorous acid, and used paper diaper are put into a treatment tank, and stirring is performed for a predetermined time while supplying a minimum amount of water that can be stirred in the treatment tank. After that, since the used paper diaper maintains the original form with the top sheet and the back sheet adhered, the pulp fibers cannot be easily separated and collected from the used paper diaper.

The present inventors pay attention to such conventional problems, and add terpene to an aqueous solution when the used absorbent article is treated with an aqueous solution containing an inactivating agent capable of inactivating the superabsorbent polymer. By dissolving the hot melt adhesive that bonds the constituent materials of absorbent articles such as paper diapers at room temperature, the absorbent article is decomposed into components, and the pulp fibers inside the used paper diaper are in the treatment tank It was found that the pulp fibers can be easily separated and collected from the absorbent article, and the present invention has been completed.

That is, the present invention is a method for recovering pulp fibers from a used absorbent article containing pulp fibers and a superabsorbent polymer, the method comprising converting a used absorbent article into a terpene hydrocarbon, a terpene aldehyde, and a terpene. A step of inactivating the superabsorbent polymer by treating with an aqueous solution containing at least one terpene selected from the group consisting of ketones in an amount of 0.05% by mass or more and containing an inactivating agent capable of inactivating the superabsorbent polymer. It is characterized by including.

The present invention includes the following aspects.
[1] A method for recovering pulp fibers from a used absorbent article containing pulp fibers and a superabsorbent polymer, wherein the method comprises a terpene hydrocarbon, a terpene aldehyde, and a terpene ketone. Including a step of inactivating the superabsorbent polymer by treating with 0.05% by mass or more of a terpene selected from the group and an aqueous solution containing an inactivating agent capable of inactivating the superabsorbent polymer. Feature method.
[2] The method according to [1], further comprising a step of separating pulp fibers and inactivated superabsorbent polymer from the used absorbent article after being treated with the aqueous solution.
[3] The method further includes a step of treating the mixture containing separated pulp fibers and inactivated superabsorbent polymer with an oxidizing agent, decomposing the inactivated superabsorbent polymer, reducing the molecular weight, and solubilizing [2]. The method described in 1.
[4] The method according to [3], further comprising separating pulp fibers from the mixture treated with the oxidizing agent.
[5] The method according to any one of [1] to [4], wherein the aqueous solution containing an inactivating agent capable of inactivating the superabsorbent polymer is an aqueous organic acid solution having a pH of 2.5 or lower.
[6] The method according to [5], wherein the organic acid is citric acid.
[7] The method according to [6], wherein the citric acid concentration of the organic acid aqueous solution is 2% by mass or more.
[8] The method according to any one of [1] to [7], wherein the terpene is a terpene hydrocarbon.
[9] The method according to [8], wherein the terpene hydrocarbon is limonene.
[10] The method according to any one of [1] to [9], wherein the concentration of the terpene in the aqueous solution is 0.05 to 1.0% by mass.
[11] The used absorbent article includes a material made of a thermoplastic resin, and the method dries the residue after separating the pulp fiber and the inactivated superabsorbent polymer from the used absorbent article, The method according to any one of [2] to [10], further comprising a step of separating a material comprising a thermoplastic resin from the residue.
[12] The used absorbent article includes a thermoplastic resin film, and the method is used to dry the residue after separating the pulp fibers and the inactivated superabsorbent polymer from the used absorbent article, and to obtain a dried residue. The method according to any one of [2] to [10], further comprising a step of separating the thermoplastic resin film from the film.
[13] Any one of [1] to [12], wherein the absorbent article is at least one selected from the group consisting of a disposable diaper, a urine absorbing pad, a bed sheet, a sanitary napkin, and a pet sheet. The method described in 1.

According to the method of the present invention, pulp fibers can be separated and recovered from a used absorbent article containing pulp fibers and a superabsorbent polymer by a simple process.

FIG. 1 is a photograph of the paper diaper used in Examples 3 to 7 before processing. FIG. 2 shows a photograph of the washing tub after the treatment of Example 3, a photograph of a nonwoven fabric and a film collected after the treatment, and a photograph of the superabsorbent polymer deactivated with the pulp fibers collected after the treatment. FIG. 3 shows a photograph of the washing tub after the treatment of Example 4, a photograph of the nonwoven fabric and film recovered after the treatment, and a photograph of the superabsorbent polymer deactivated with the pulp fibers collected after the treatment. FIG. 4 shows a photograph of the washing tub after the treatment of Example 5, a photograph of a nonwoven fabric and a film collected after the treatment, and a photograph of the superabsorbent polymer deactivated with the pulp fibers collected after the treatment. FIG. 5 shows a photograph of the washing tub after the treatment of Example 6, a photograph of a nonwoven fabric and a film collected after the treatment, and a photograph of the superabsorbent polymer deactivated with the pulp fibers collected after the treatment. FIG. 6 shows a photograph of the washing tub after the treatment of Example 7, a photograph of a nonwoven fabric and a film collected after the treatment, and a photograph of the superabsorbent polymer deactivated with the pulp fibers collected after the treatment.

The present invention is a method for recovering pulp fibers from a used absorbent article containing pulp fibers and a superabsorbent polymer.

The absorbent article is not particularly limited as long as it contains pulp fibers and a superabsorbent polymer, and examples thereof include paper diapers, urine absorbing pads, bed sheets, sanitary napkins, pet sheets, and the like. . These absorbent articles are usually composed of constituent materials such as pulp fibers, superabsorbent polymers, nonwoven fabrics, thermoplastic resin films, hot melt adhesives and the like.

Although it does not specifically limit as a pulp fiber, A fluffy pulp fiber, a chemical pulp fiber, etc. can be illustrated.

Superabsorbent polymer, also called SAP, has a three-dimensional network structure in which water-soluble polymers are appropriately cross-linked. It absorbs water several hundred to thousand times but is essentially insoluble in water. The water once absorbed does not release even when a certain pressure is applied, and examples thereof include starch-based, acrylic acid-based, amino acid-based particulate or fibrous polymers.

In the method of the present invention, the used absorbent article contains 0.05% by mass or more of at least one terpene selected from the group consisting of terpene hydrocarbons, terpene aldehydes and terpene ketones, and can inactivate superabsorbent polymers. And a step of inactivating the superabsorbent polymer (hereinafter also simply referred to as “inactivation step”). In this process, the superabsorbent polymer is inactivated, and the hot melt adhesive that adheres the constituent material of the absorbent article is dissolved by the terpene, and the absorbent article is made into the constituent material by the force of stirring and washing. Decompose and disperse the pulp fibers inside the absorbent article in the treatment tank. Also, terpenes have a high oil stain cleaning effect. In addition to the effect of dissolving hot melt adhesive, when printing is performed on a leak-proof film that is one of the constituent materials of the absorbent article, the printing ink is also decomposed and removed. The printed leak-proof film can also be collected as a high-purity plastic material.

The inactivating agent that can inactivate the superabsorbent polymer is not limited, and examples include organic acids, lime, calcium chloride, magnesium sulfate, magnesium chloride, aluminum sulfate, and aluminum chloride. preferable.

Since the organic acid is less likely to damage the pulp fiber, the use of the organic acid makes it possible to recover the pulp fiber with less damage, that is, the pulp fiber having a high water absorption ratio and a high water retention ratio. When an organic acid is used as the inactivating agent, the pH of the aqueous organic acid solution is 2.5 or less. That is, the aqueous solution containing an inactivating agent capable of inactivating the superabsorbent polymer is preferably an organic acid aqueous solution having a pH of 2.5 or less.

Examples of the organic acid include citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, ascorbic acid, and the like, and citric acid is particularly preferable. Due to the chelate effect of citric acid, metal ions and the like in excreta can be trapped and removed, and a high dirt component removal effect can be expected due to the cleaning effect of citric acid.

The pH of the organic acid aqueous solution is 2.5 or less, preferably 1.3 to 2.4, and more preferably 1.5 to 2.1. If the pH is too high, the water absorption ability of the superabsorbent polymer cannot be sufficiently reduced. Moreover, there exists a possibility that the disinfection ability may fall and it cannot disinfect. If the pH is too low, there is a concern that the equipment will be corroded and the service life will be reduced, or a lot of alkaline chemicals may be required for the neutralization treatment during the wastewater treatment.
In addition, since pH changes with water temperature, pH in this invention shall mean pH measured by aqueous solution temperature 20 degreeC.

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 2% by mass or more, More preferred is 2.0 to 4.0% by mass, and further more preferred is 2.0 to 3.0% by mass.

The aqueous solution containing an inactivating agent capable of inactivating the superabsorbent polymer contains at least one terpene selected from the group consisting of terpene hydrocarbons, terpene aldehydes and terpene ketones.
Terpene hydrocarbons include myrcene, limonene, pinene, camphor, sapinene, ferrandlene, paracymene, osymene, terpinene, karen, gingivalene, caryophyllene, bisabolene, cedrene, among others, limonene, pinene, terpinene, caren. Is preferred.
Examples of the terpene aldehyde include citronellal, citral, cyclocitral, safranal, ferrandral, perillaldehyde, geranial, and neral, among which citral is preferable.
Examples of terpene ketones include camphor and tsuyoshi.
Among the terpenes, terpene hydrocarbons are preferable, and a particularly preferable terpene is limonene. There are three types of limonene: d-limonene, l-limonene, and dipentene (dl-limonene), and any of them can be preferably used.
Terpenes can be used singly or in combination of two or more.

The concentration of terpene in the aqueous solution is 0.05% by mass or more, preferably 0.05 to 1.0% by mass, and more preferably 0.075 to 0.5% by mass. If the concentration of the terpene is too low, the disposable diaper may not be efficiently decomposed into its constituent materials. If the terpene concentration is too high, the cost may increase.

The aqueous solution may further contain a detergent or the like.

The treatment temperature, that is, the temperature of the aqueous solution is not particularly limited and may be heated, but may be room temperature, for example, 15 to 30 ° C.

The treatment time is not limited as long as it can inactivate the superabsorbent polymer and decompose the used absorbent article into a constituent material, but it is preferably 5 to 60 minutes, more preferably 10 to 30 minutes. .

The amount of the aqueous solution is not limited as long as it can inactivate the superabsorbent polymer and decompose the used absorbent article into a constituent material, but is preferably 300 to 3000 mass with respect to 100 parts by mass of the used absorbent article. Part, more preferably 500 to 2500 parts by weight, still more preferably 1000 to 2000 parts by weight.

The method of treating the used absorbent article with the aqueous solution is not particularly limited. For example, a predetermined amount of the used absorbent article is put into a cleaning facility, and then contains 0.05% by mass or more of terpene and has a high water absorption property. An aqueous solution containing an inactivating agent capable of inactivating the polymer is added and stirred as necessary. A detergent or the like may be added to the aqueous solution as necessary.

The method of the present invention further includes a step of separating pulp fibers and inactivated superabsorbent polymer from the used absorbent article after being treated with the aqueous solution (hereinafter also simply referred to as “separation step”). Can do. The method for separating the pulp fiber and the inactivated superabsorbent polymer is not limited. For example, the mixture produced by the inactivation step is preferably 5 to 100 mm, more preferably 10 to 80 mm. By discharging while passing through the screen, the pulp fiber and the inactivated superabsorbent polymer remain in the waste water, and other large shapes such as the nonwoven fabric and the thermoplastic resin film remain on the screen and can be separated.

The method of the present invention further comprises a step of treating the mixture containing separated pulp fibers and inactivated superabsorbent polymer with an oxidizing agent, decomposing the inactivated superabsorbent polymer, reducing the molecular weight, and solubilizing ( Hereinafter, it may be simply referred to as an “oxidant treatment step”. By treating the mixture containing pulp fibers and inactivated superabsorbent polymer with an oxidizing agent, the inactivated superabsorbent polymer can be oxidized and decomposed, reduced in molecular weight and solubilized. Subsequent sterilization, bleaching and deodorization can be performed. Here, the state in which the superabsorbent polymer is decomposed, reduced in molecular weight, and solubilized refers to a state of passing through a 2 mm screen. That is, in this step, the superabsorbent polymer is decomposed to such an extent that it passes through a screen having a mesh opening of 2 mm.

Examples of the oxidizing agent include, but are not limited to, chlorine dioxide, ozone, sodium hypochlorite and the like, as long as the inactivated superabsorbent polymer can be decomposed, reduced in molecular weight, and solubilized. Among these, ozone is preferable from the viewpoint of high decomposition ability and environmental impact.

The method of treating with an oxidizing agent is not limited as long as the deactivated superabsorbent polymer can be decomposed, reduced in molecular weight, and solubilized, but for example, pulp fibers obtained after separation through a screen in the separation step and Add oxidizing agent to waste water containing inactivated superabsorbent polymer. Or, further, the pulp fiber and the deactivated superabsorbent polymer are separated from the drainage through a screen that is fine enough to prevent the pulp fiber and the deactivated superabsorbent polymer from passing through, and the separated pulp fiber and An inactivated superabsorbent polymer may be added to the aqueous oxidizing agent solution.

When ozone is used as the oxidizer, the mixture containing pulp fibers and inactivated superabsorbent polymer is brought into contact with ozone, more specifically, the wastewater containing pulp fibers and inactivated superabsorbent polymer is treated with ozone. The oxidant treatment can be performed by blowing. Ozone can be generated using, for example, an ozone water generator (such as an ozone water exposure tester ED-OWX-2 manufactured by Ecodesign Corporation, an ozone generator OS-25V manufactured by Mitsubishi Electric Corporation).

When ozone is blown into wastewater containing pulp fibers and inactivated superabsorbent polymer, the ozone concentration in the wastewater is not particularly limited as long as it can decompose the superabsorbent polymer, but preferably 1 to It is 50 ppm by mass, more preferably 2 to 40 ppm by mass, and further preferably 3 to 30 ppm by mass. If the concentration is too low, the superabsorbent polymer cannot be completely solubilized and the superabsorbent polymer may remain in the recovered pulp fiber. On the other hand, if the concentration is too high, the oxidizing power is also increased, which may damage the pulp fiber and may cause a problem in safety.

The time for the ozone treatment is not particularly limited as long as it is a time during which the superabsorbent polymer can be decomposed. The treatment time may be short if the ozone concentration is high, and a long time is required if the ozone concentration is low.
The product of ozone concentration (ppm) and treatment time (min) (hereinafter also referred to as “CT value”) is preferably 100 to 6000 ppm · min, more preferably 200 to 4800 ppm · min, and even more preferably 300. ~ 3600 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 fiber. On the other hand, if the CT value is too large, it may lead to damage of pulp fibers, a decrease in safety, and an increase in manufacturing costs.
As described above, the treatment time depends on the ozone concentration, but is preferably 20 to 120 minutes, more preferably 30 to 100 minutes, and further preferably 40 to 80 minutes.

The temperature during the ozone treatment is not particularly limited as long as it is a temperature at which the superabsorbent polymer can be decomposed. When ozone is blown into wastewater containing pulp fibers and inactivated superabsorbent polymer, the wastewater may be heated but may remain at room temperature.

In the oxidant treatment step, the superabsorbent polymer is subjected to oxidative decomposition action by the oxidizer, the three-dimensional network structure of the superabsorbent polymer is destroyed, and the superabsorbent polymer loses water retention, has a low molecular weight, and is solubilized.

When ozone is blown into wastewater containing pulp fiber and inactivated superabsorbent polymer, the wastewater is preferably acidic. More preferably, the pH of the waste water is 2.5 or less, and more preferably 1.5 to 2.4. By treating in an acidic state, the effect of decomposing and removing the superabsorbent polymer by ozone is improved, and the superabsorbent polymer can be decomposed in a short time.

When chlorine dioxide is used as the oxidizing agent, the pulp fiber and the deactivated superabsorbent polymer are more specifically brought into contact with chlorine dioxide by contacting the mixture containing the pulp fiber and the deactivated superabsorbent polymer with chlorine dioxide. The oxidant treatment can be performed by blowing chlorine dioxide into the waste water. Commercially available chlorine dioxide can be used.

When chlorine dioxide is blown into wastewater containing pulp fibers and inactivated superabsorbent polymer, the concentration of chlorine dioxide in the wastewater is not particularly limited as long as it is a concentration capable of decomposing the superabsorbent polymer, but preferably Is from 150 to 1100 ppm by mass, more preferably from 200 to 1000 ppm by mass, and even more preferably from 300 to 900 ppm by mass. If the concentration is too low, the superabsorbent polymer cannot be completely solubilized and the superabsorbent polymer may remain in the recovered pulp fiber. On the other hand, if the concentration is too high, the oxidizing power is also increased, which may damage the pulp fiber and may cause a problem in safety.
The treatment time is the same as in the case of ozone treatment.

When sodium hypochlorite is used as the oxidant, the pulp fiber and the deactivated mixture are more specifically brought into contact with sodium hypochlorite by contacting the mixture containing the pulp fiber and the deactivated superabsorbent polymer. Oxidation by adding sodium hypochlorite to wastewater containing superabsorbent polymer or by immersing pulp fiber and inactivated superabsorbent polymer separated from wastewater by screen in aqueous sodium hypochlorite solution Agent treatment can be performed. A commercially available thing can be used for sodium hypochlorite.

When adding sodium hypochlorite to wastewater containing pulp fiber and deactivated superabsorbent polymer, or when immersing pulp fiber and deactivated superabsorbent polymer in aqueous sodium hypochlorite solution, The concentration of sodium hypochlorite in the aqueous sodium hypochlorite solution is not particularly limited as long as it is a concentration capable of decomposing the superabsorbent polymer, but is preferably 0.5 to 2% by mass, more Preferably, it is 0.75 to 1.5% by mass. If the concentration is too low, the superabsorbent polymer cannot be completely solubilized and the superabsorbent polymer may remain in the recovered pulp fiber. Further, Bacillus subtilis forming spores cannot be completely sterilized. On the other hand, if the concentration is too high, the oxidizing power is also increased, which may damage the pulp fiber and may cause a problem in safety.
The treatment time is the same as in the case of ozone treatment.

The method of the present invention can further include a step of separating pulp fibers from the mixture treated with the oxidizing agent (hereinafter also simply referred to as “pulp fiber separation step”). The method for separating the pulp fibers is not particularly limited. For example, the pulp fibers can be separated by passing the mixture treated with the oxidizing agent through a screen having an opening of 0.15 to 2 mm. The waste water containing the mixture treated with the oxidizing agent, more specifically, the pulp fiber and the super-absorbent polymer degradation product is passed through a screen having a mesh opening of 0.15 to 2 mm, thereby decomposing the super-absorbent polymer. Waste water containing material passes through the screen, and the pulp fibers remain on the screen.

The separated pulp fibers can be dehydrated, dried and recovered as necessary.
In the case of drying, the drying temperature is preferably 105 to 210 ° C, more preferably 110 to 190 ° C, and further preferably 120 to 180 ° C. Although depending on the drying temperature, the drying time is preferably 10 to 120 minutes, more preferably 15 to 100 minutes, and further preferably 20 to 90 minutes.

When the used absorbent article includes a material made of a thermoplastic resin, the method of the present invention further dries the residue after separating the pulp fibers and the inactivated superabsorbent polymer from the used absorbent article, A step of separating a material made of a thermoplastic resin from the dried residue (hereinafter also simply referred to as a “thermoplastic resin material separation step”) can be included. By drying the residue, secondary sterilization of the residue can be performed. Here, the material made of a thermoplastic resin means a nonwoven fabric, a film, or the like made of a thermoplastic resin such as polyethylene, polypropylene, or polyester. The material made of the separated thermoplastic resin can be made into RPF (solid fuel). Even if an oxidizer treatment process is not provided or ozone is used as an oxidizer even if an oxidizer treatment process is provided, a high-quality RPF that does not damage the furnace because the chlorine-based chemical is not included in the RPF process. Manufacturing is possible.

In the method of the present invention, when the used absorbent article includes a thermoplastic resin film, the residue after separating the pulp fibers and the inactivated superabsorbent polymer from the used absorbent article is further dried and dried. A step of separating the thermoplastic resin film from the residue (hereinafter also simply referred to as “film separation step”) can be included. By drying the residue, secondary sterilization of the residue can be performed. The separated thermoplastic resin film can be regenerated as a plastic bag or film again by pelletizing.

In the present invention, each material of an absorbent article is bonded to an aqueous solution containing an inactivating agent capable of inactivating a superabsorbent polymer by mixing terpene in an organic acid aqueous solution at a concentration of 0.05% by mass or more. Hot melt adhesive can be dissolved at room temperature, making it easy to disperse absorbent articles easily and cleanly, separating pulp fibers and superabsorbent polymers from absorbent articles, nonwoven fabrics, films, etc. It can be separated and recovered while leaving That is, pulp fibers, films, and nonwoven fabrics can be easily recovered without crushing the paper diaper or without a complicated separation process. When limonene is used as a terpene, as a secondary effect of limonene, there is a refreshing citrus odor. Expected. Limonene is a monoterpene and has a structure similar to that of styrene. Therefore, limonene can dissolve a styrene-based hot melt adhesive generally used in absorbent articles such as disposable diapers. Since cleaning of absorbent articles such as paper diapers is possible at room temperature, energy costs can be reduced and odor generation and diffusion can be suppressed. Terpene is highly effective in cleaning oil stains. In addition to the effect of dissolving hot-melt adhesives, when printing on leak-proof films, the printing ink can be disassembled and removed, and the printed leak-proof film is a high-purity plastic. It can be collected as a material.

When lime is used for the treatment of used absorbent articles as disclosed in JP 2010-84031 A, the lime creates a high pH (12.4) environment in the treatment tank, and the cellulose swells and the pulp fibers become alkali cellulose. However, when an organic acid aqueous solution having a pH of 2.5 or less is used to inactivate the superabsorbent polymer, it is difficult to degrade the pulp fiber. In addition, when citric acid is used as the organic acid, the excrement-derived dirt component removal effect can be expected due to the chelating effect and detergency of citric acid. Moreover, the sterilization effect and the deodorizing effect with respect to alkaline odor can also be expected.

By decomposing and removing the inactivated superabsorbent polymer with an oxidizing agent, it is possible to prevent contamination of the recovered pulp fiber and a sudden increase in sludge due to the superabsorbent polymer water absorption. By adjusting the kind and concentration of the oxidizing agent to be used, the inactivated water-absorbing polymer can be oxidatively decomposed and sterilized at the same time. Also, even if an oxidant treatment process is not provided or ozone is used as an oxidant even if an oxidant treatment process is provided, the non-woven fabric / film material recovery process does not use any chlorine-based chemicals. It is possible to produce high-quality RPF that is not easily damaged. If the film material is collected separately, it can be recycled as a bag or film material. Since salts are not used during the treatment process, there is no remaining in the recovered pulp, and high-quality pulp with a low ash content can be recovered.

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

Example 1
100 g of standard compost (YK-8 manufactured by Yawata Bussan Co., Ltd.) was immersed in 1 L of ion-exchanged water, stirred for 5 minutes, allowed to stand for 30 minutes, and 240 mL of the supernatant solution was sampled to prepare artificial sewage. The prepared artificial sewage was subjected to an ATP inspection using a Lumitester PD-30 manufactured by Kikkoman Corporation as a measuring instrument. The ATP value was 13126.
A commercial paper diaper (Moonie (registered trademark) M size manufactured by Unicharm Co., Ltd.) was allowed to absorb 240 mL of the artificial sewage prepared above, and then the paper diaper was placed in a two-tank small washing machine (Aseis “Sunny” AST -01) was added to the washing tub, and citric acid (manufactured by Fuso Chemical Co., Ltd.) was dissolved in water at a water temperature of 20 ° C. to a concentration of 2.0% by mass. 10 L of an aqueous solution (pH 2.1) in which a reagent grade 1 manufactured by Tesque Co., Ltd. was dissolved so as to have a concentration of 0.05% by mass was charged and washed for 15 minutes. After completion of washing, the top sheet and the back sheet of the diaper were peeled off, and the absorbent body inside was out of the paper diaper, and the pulp fibers were dispersed in the liquid in the washing tub. Large solids such as non-woven fabric and film floating in the liquid in the washing tub are scooped and separated with a colander with a hole of φ10 mm, drained, and the pulp fibers remaining in the tub and the inactivated superabsorbent polymer, In addition, the pulp fibers discharged out of the tank together with the waste water and the inactivated superabsorbent polymer were collected, and ATP inspection was performed. As a result of the ATP test, the ATP value was 0.
Some of the large solids scooped with colander also had a nonwoven fabric with the film still attached, but the film could be easily and cleanly removed from the nonwoven fabric.
Thereafter, the pulp fibers and the inactivated superabsorbent polymer were placed in a nylon net (250 mesh nylon net manufactured by NBC Meshtec Co., Ltd.) bag (250 mm × 250 mm) and dehydrated in a dehydration tank for 5 minutes. The dehydrated pulp fiber and the deactivated superabsorbent polymer are immersed in a 1.0% by weight sodium hypochlorite aqueous solution together with the nylon net bag, washed with stirring for 5 minutes, and dehydrated again for 5 minutes in the dehydration tank. Then, after drying with a hot air dryer at 105 ° C. for 24 hours, the pulp fiber was recovered. When the ash content of the recovered pulp fibers was analyzed, the ash content was 0.28% by mass.

Example 2
The same operation as in Example 1 was carried out except that the concentration of d-limonene was changed to 0.1% by mass. After washing for 15 minutes, the top sheet and the back sheet of the paper diaper in the washing tub were peeled off, the contents of the absorbent body came out of the paper diaper, and the pulp fibers were dispersed in the liquid in the washing tub.

Comparative Example 1
The same operation as in Example 1 was carried out except that the concentration of d-limonene was changed to 0.01% by mass. After washing for 15 minutes, the paper diaper in the washing tub had the top sheet and the back sheet stuck, and the absorbent body was held in the paper diaper.

Comparative Example 2
The same operation as in Example 1 was carried out except that the concentration of d-limonene was changed to 0.03% by mass. After washing for 15 minutes, the paper diaper in the washing tub had the top sheet and the back sheet stuck, and the absorbent body was held in the paper diaper.

Comparative Example 3
The method described in JP 2010-84031 A was additionally tested. Specifically, after a commercial paper diaper (Moonie (registered trademark) M size manufactured by Unicharm Co., Ltd.) was allowed to absorb 240 mL of the artificial sewage prepared previously, the paper diaper was placed in a 2-tank small washing machine (Aluminus) One of them was put into a washing tub of “Harasei” AST-01), and 80 g of CaO (manufactured by Wako Pure Chemical Industries, Ltd.) was put into the washing tub, followed by a sodium hypochlorite aqueous solution having a concentration of 250 mass ppm ( 6.5 L was charged by diluting a product purchased from Wako Pure Chemical Industries, Ltd. After washing for 15 minutes, the paper diapers floating in the liquid in the washing layer were collected, and the diapers were not separated while retaining their form, so the surface material was physically broken by hand, and the inactivated high water absorption inside the diapers The pulp fiber containing the polymer was recovered. When the ash content of the recovered pulp fibers was analyzed, the ash content was 15.9% by mass.

Example 3
One commercially available disposable diaper (“Mooney” (registered trademark) M size manufactured by Unicharm Co., Ltd.) was put into a washing tub of a two-tank type small washing machine (“Haruharu” AST-01 manufactured by Arumis). Next, 200 g of citric acid and 100 g of d-limonene were dissolved in 10 L of water and put into a washing tub. The washing machine was turned on and stirred for 9 minutes. After completion of the stirring, the top sheet and the back sheet of the paper diaper were peeled off, the contents of the absorbent body came out of the paper diaper, and the pulp fibers were dispersed in the liquid in the washing tub. Large solids such as non-woven fabric and film floating in the liquid in the washing tub were scooped with a wire mesh having an opening of 10 mm and collected. Thereafter, drained and recovered the pulp fibers remaining in the washing tub and the inactivated superabsorbent polymer, and the pulp fibers discharged out of the tub together with the drainage and the inactivated superabsorbent polymer.
Fig. 1 shows a photograph of a disposable diaper before treatment, Fig. 2 (a) shows a photograph of a laundry tub after treatment, Fig. 2 (b) shows a photograph of a nonwoven fabric, a film, etc. collected after treatment, Fig. 2 (c). Shows photographs of the pulp fibers recovered after the treatment and the inactivated superabsorbent polymer.
The disposable diaper was decomposed cleanly, and large solids such as nonwoven fabrics and films could be easily separated from the pulp fibers and the inactivated superabsorbent polymer.

Example 4
d-Limonene was changed to 3-carene, and the same procedure as in Example 3 was performed.
The photograph in the washing tub after processing is in FIG. 3 (a), the photograph of the nonwoven fabric, film, etc. recovered after processing in FIG. 3 (b) is inactivated with the pulp fiber recovered after processing in FIG. 3 (c). A photograph of a superabsorbent polymer is shown.
The disposable diaper was decomposed cleanly, and large solids such as nonwoven fabrics and films could be easily separated from the pulp fibers and the inactivated superabsorbent polymer.

Example 5
d-Limonene was changed to α-pinene and the same procedure as in Example 3 was performed.
The photograph in the washing tub after processing is in FIG. 4 (a), the photograph of the nonwoven fabric, film, etc. recovered after processing in FIG. 4 (b) is inactivated with the pulp fiber recovered after processing in FIG. 4 (c). A photograph of a superabsorbent polymer is shown.
The disposable diaper was decomposed cleanly, and large solids such as nonwoven fabrics and films could be easily separated from the pulp fibers and the inactivated superabsorbent polymer.

Example 6
The same procedure as in Example 3 was performed, except that 100 g of d-limonene was changed to 89.4 g (100 mL) of citral.
Fig. 5 (a) shows the photograph in the washing tub after processing, Fig. 5 (b) shows the photograph of the nonwoven fabric, film, etc. recovered after the processing, and Fig. 5 (c) shows the pulp fibers recovered after the processing. A photograph of a superabsorbent polymer is shown.
The disposable diaper was decomposed cleanly, and large solids such as nonwoven fabrics and films could be easily separated from the pulp fibers and the inactivated superabsorbent polymer.

Example 7
The same procedure as in Example 3 was carried out except that 100 g of d-limonene was changed to 91.3 g (100 mL) of γ-terpinene.
The photograph in the washing tub after processing is in FIG. 6 (a), the photograph of the non-woven fabric, film, etc. recovered after processing in FIG. 6 (b) is inactivated with the pulp fiber recovered after processing in FIG. 6 (c). A photograph of a superabsorbent polymer is shown.
The disposable diaper was decomposed cleanly, and large solids such as nonwoven fabrics and films could be easily separated from the pulp fibers and the inactivated superabsorbent polymer.

The ash content analysis method is as follows.

[Analytical analysis method]
Ash refers to the amount of inorganic or incombustible residue left after organic matter has been ashed. Ash content is measured in accordance with “5. Ash test method” in “2. That is, the ash content is measured as follows.
A platinum, quartz, or magnetic crucible is ignited in advance at 500 to 550 ° C. for 1 hour, allowed to cool, and then its mass is accurately measured. Take 2 to 4 g of sample, place in crucible, weigh accurately, remove or shift crucible if necessary, heat gently at first, gradually increase temperature to 500-550 ° C. Ignite for over an hour until no carbides remain. After standing to cool, weigh its mass precisely. The residue is incinerated until it reaches a constant weight, and after standing to cool, its mass is precisely measured to obtain the amount of ash (mass%).

The method of the present invention can be suitably used for recovering pulp fibers from used absorbent articles containing pulp fibers and superabsorbent polymers.

Claims

A method for recovering pulp fibers from a used absorbent article comprising pulp fibers and a superabsorbent polymer, wherein the method is selected from the group consisting of terpene hydrocarbons, terpene aldehydes and terpene ketones. And a step of inactivating the superabsorbent polymer by treating with an aqueous solution containing at least one terpene that is 0.05% by mass or more and containing a deactivator capable of inactivating the superabsorbent polymer. Method.
The method according to claim 1, further comprising a step of separating pulp fibers and inactivated superabsorbent polymer from the used absorbent article after being treated with the aqueous solution.
The method according to claim 2, further comprising a step of treating the mixture containing the separated pulp fibers and the inactivated superabsorbent polymer with an oxidizing agent, decomposing the inactivated superabsorbent polymer, reducing the molecular weight, and solubilizing. Method.
The method according to claim 3, further comprising separating pulp fibers from the mixture treated with the oxidizing agent.
The method according to any one of claims 1 to 4, wherein the aqueous solution containing an inactivating agent capable of inactivating the superabsorbent polymer is an organic acid aqueous solution having a pH of 2.5 or lower.
The method according to claim 5, wherein the organic acid is citric acid.
The method according to claim 6, wherein the citric acid concentration of the organic acid aqueous solution is 2% by mass or more.
The method according to any one of claims 1 to 7, wherein the terpene is a terpene hydrocarbon.
The method according to claim 8, wherein the terpene is at least one selected from the group consisting of limonene, karen, pinene, terpinene and citral.
The method according to any one of claims 1 to 9, wherein the concentration of the terpene in the aqueous solution is 0.05 to 1.0 mass%.
The used absorbent article includes a material made of a thermoplastic resin, and the method is to dry the residue after separating the pulp fiber and the inactivated superabsorbent polymer from the used absorbent article, and from the dried residue The method according to any one of claims 2 to 10, further comprising a step of separating a material made of a thermoplastic resin.
The used absorbent article comprises a thermoplastic resin film, and the method dries the residue after separating the pulp fibers and the inactivated superabsorbent polymer from the used absorbent article, and the thermoplastic from the dried residue. The method according to any one of claims 2 to 10, further comprising a step of separating the resin film.
The absorbent article according to any one of claims 1 to 12, wherein the absorbent article is at least one selected from the group consisting of disposable diapers, urine pads, bed sheets, sanitary napkins and pet sheets. Method.