WO2023210528A1

WO2023210528A1 - Method for producing plastic material derived from used sanitary product suitable for material recycling or chemical recycling, and plastic material derived from used sanitary product

Info

Publication number: WO2023210528A1
Application number: PCT/JP2023/015928
Authority: WO
Inventors: 孝義小西; 宜秀石川; 美彦松本
Original assignee: ユニ・チャーム株式会社
Priority date: 2022-04-27
Filing date: 2023-04-21
Publication date: 2023-11-02

Abstract

Provided is a method for producing a plastic material derived from a used sanitary product suitable for material recycling or chemical recycling, wherein impurities in the produced plastic material can be suppressed. The method comprises: a first separation step S2 for separating a used sanitary product including excreta, a plastic material, a superabsorbent polymer, and pulp fibers into a first fraction containing the plastic material and a second fraction containing the excreta, the superabsorbent polymer, which has been deactivated, and the pulp fibers; a second separation step S3 for applying a physical impact to separate the first fraction into the plastic material and excreta, a superabsorbent polymer, and a pulp fibers remaining in the first fraction due to not being separated in the first separation step; and an aqueous solution treatment step for spraying an aqueous solution onto the separated plastic material.

Description

Method for producing plastic material derived from used sanitary products suitable for material recycling or chemical recycling, and plastic material derived from used sanitary products

The present invention relates to a method for producing a plastic material derived from used sanitary products, which is suitable for material recycling or chemical recycling, and a plastic material derived from used sanitary products.

Technology for producing recyclable plastic materials from used sanitary products is known. For example, Patent Document 1 discloses a method for recovering constituent members from used absorbent articles. This method is a method for recovering the component films and absorbent material from used absorbent articles. This method includes a pre-treatment step in which the used absorbent article is swollen with water, and a physical impact is applied to the swollen used absorbent article so that at least the film and absorbent material of the used absorbent article are The method includes a decomposition step of decomposing the film and a separation step of separating the decomposed film from the absorbent material. The separated film can be used as a recyclable plastic material.

Japanese Patent Application Publication No. 2018-171589

In Patent Document 1, a plastic material such as a film or nonwoven fabric and an absorbent material such as a superabsorbent polymer or pulp fiber are separated from each other in a separation step. However, it is difficult to completely separate excrement and absorbent material from the separated plastic material, and there is a risk that the separated plastic material may contain some amount of excrement and absorbent material, that is, a certain amount of impurities. be.

Such impurities include, for example, odor-producing sulfur compounds (e.g., hydrogen sulfide) and nitrogen compounds (e.g., ammonia) derived from excreta (e.g., urine, feces) contained in used sanitary products, and absorbent materials. Examples include sodium derived from superabsorbent polymers in the material. If these impurities are contained in plastic materials, when plastic materials are applied to material recycling or chemical recycling to produce recycled products, there is a risk that they may have an adverse effect on the catalysts used in production, or they may cause damage to the recycled products produced. May cause unpleasant odors. Therefore, with respect to obtaining plastic materials suitable for material recycling or chemical recycling, there is room for improvement in terms of reducing these impurities.

The purpose of the present invention is to provide a method for manufacturing plastic materials derived from used sanitary products suitable for material recycling or chemical recycling, which can suppress impurities in the manufactured plastic materials, and a method in which impurities can be suppressed. The objective is to provide plastic materials derived from used sanitary products.

One aspect of the present invention is a method for producing plastic materials derived from used sanitary products suitable for material recycling or chemical recycling, wherein the used sanitary products include excrement, plastic materials, super absorbent a first fraction comprising the plastic material and a second fraction comprising the excreta, the inactivated superabsorbent polymer, and the pulp fibers; a first separation step of separating the first fraction into two parts; and the excrement remaining in the first fraction that could not be completely separated in the first separation step by applying a physical impact to the first fraction; A method comprising: a second separation step of separating the superabsorbent polymer and the pulp fibers from the plastic material; and an aqueous solution treatment step of spraying an aqueous solution onto the separated plastic material. .

Another aspect of the present invention is a plastic material derived from used sanitary products, wherein the proportion of sulfur contained in the plastic material is 500 ppm or less, and the proportion of nitrogen contained in the plastic material is 2000 ppm or less, The proportion of sodium contained in the plastic material is 500 ppm or less.

According to the present invention, in a method for producing plastic materials derived from used sanitary products suitable for material recycling or chemical recycling, there is provided a method capable of suppressing impurities in the produced plastic materials, and a method in which impurities are suppressed. It is possible to provide plastic materials derived from used sanitary products.

1 is a flowchart illustrating a method for manufacturing plastic material derived from used sanitary products according to an embodiment.

This embodiment relates to the following aspects.
[Aspect 1]
A method for producing plastic materials derived from used sanitary products suitable for material recycling or chemical recycling, wherein the used sanitary products contain excrement, plastic materials, superabsorbent polymers and pulp fibers. and separating the used sanitary product into a first fraction containing the plastic material and a second fraction containing the excrement, the inactivated superabsorbent polymer, and the pulp fibers. 1 separation step, and the first fraction is subjected to physical impact to remove the excrement, the superabsorbent polymer, and the superabsorbent polymer that were not completely separated in the first separation step and remained in the first fraction. A method comprising: a second separation step of separating pulp fibers and the plastic material from each other; and an aqueous solution treatment step of injecting an aqueous solution to the separated plastic material.

In this method, a first fraction is separated in a first separation step. At this time, the superabsorbent polymer that had been absorbing urine and the like has been inactivated, so sodium and nitrogen compounds are released (dehydrated) to the outside along with water and become granular. Therefore, in the second separation step, the superabsorbent polymer of the first fraction can be easily separated from the plastic material by physical impact. In addition, even if there is a superabsorbent polymer that cannot be separated from the plastic material, the content of sodium and nitrogen compounds in the superabsorbent polymer can be reduced. Also, other excreta and pulp fibers can be easily separated from the plastic material by physical impact.
Thereafter, an aqueous solution treatment step is performed in which an aqueous solution is injected onto the plastic material separated in the second separation step. However, examples of the aqueous solution include water and an oxidizing agent aqueous solution containing an oxidizing agent. At this time, by supplying the aqueous solution to the plastic material by spraying, the force of the spray can wash away sulfur compounds, nitrogen compounds, etc. adhering to the surface of the plastic material. Further, by spraying the aqueous solution into fine particles and supplying it to the plastic material, it is possible to make it easier for the aqueous solution to penetrate into the finer details of the plastic material. Furthermore, compared to the case where the plastic material is immersed in an aqueous solution, a fresh aqueous solution can always be supplied to the surface of the plastic material, and variations in the cleaning effect can be reduced.
In this manner, impurities containing sodium, sulfur, and nitrogen are separated and removed in the plastic material produced by the present method, so that impurities in the plastic material can be suppressed. When applying the plastic material to material recycling or chemical recycling to manufacture recycled products, since the impurities in the plastic material are suppressed, the impact on the catalyst used in the manufacturing process can be reduced, and undesirable odors can be eliminated. It can be made difficult to cause.

[Aspect 2]
The method according to aspect 1, wherein the aqueous solution treatment step includes an oxidizing agent treatment step of injecting an oxidizing agent aqueous solution containing an oxidizing agent as the aqueous solution onto the separated plastic material.
In this method, in the aqueous solution treatment step, an oxidizing agent treatment step is performed in which an oxidizing agent aqueous solution containing an oxidizing agent is injected onto the plastic material separated in the second separation step. As a result, sulfur compounds and nitrogen compounds derived from excrement that were not completely separated in the second separation step and remained in the plastic material are oxidized, and other odorless substances such as sulfur (S) and nitrogen (N) are oxidized. ₂ )), and part or all of the substance mixes with the aqueous oxidizing agent solution and flows out, and/or is released as a gas. That is, sulfur compounds and nitrogen compounds remaining in the plastic material are further removed. In this way, the odor-producing sulfur and nitrogen compounds are converted into other odorless substances and are generally removed, thereby making the plastic material less likely to produce bad odors. The oxidizing agent can also sterilize plastic materials. At this time, the oxidizing agent aqueous solution can be made fine by spraying and supplied to the plastic material, thereby making it easier for the oxidizing agent aqueous solution to enter the fine details of the plastic material. As a result, compared to the case where the plastic material is immersed in an oxidizing agent aqueous solution, a fresh oxidizing agent aqueous solution can be constantly supplied to the surface of the plastic material, and variations in the sterilization effect can be reduced.
In this way, in the plastic material produced by the present method, impurities containing sodium, sulfur, and nitrogen are decomposed and removed in greater amounts, so that impurities in the plastic material can be further suppressed. Moreover, sterilization can be performed at the same time. When the plastic material is applied to material recycling or chemical recycling to manufacture recycled products, since the impurities in the plastic material are further suppressed, the impact on the catalyst used in the manufacturing process can be further reduced, which may be undesirable. It is possible to make it difficult to cause odor.

[Aspect 3]
In the second separation step, a physical impact is applied to the first fraction while injecting an acidic aqueous solution to separate the excrement, the superabsorbent polymer, the pulp fibers, and the plastic material from each other. The method according to aspect 1 or 2, comprising the step of separating.
In this method, in the second separation step, an acidic aqueous solution is injected into the first fraction, so that the superabsorbent polymer remaining in the plastic material is further inactivated by the acidic aqueous solution, and is further inactivated by sodium and nitrogen. The compound is released to the outside (dehydrated) and becomes finer particles. Therefore, the superabsorbent polymer can be more easily separated (washed off) from the plastic material by physical impact or by a flow of acidic aqueous solution. In addition, even if there is a superabsorbent polymer that cannot be separated from the plastic material, the content of sodium and nitrogen compounds in the superabsorbent polymer can be further reduced. Also, other excreta and pulp fibers can be more easily separated (washed off) from the plastic material by physical impact or a stream of acidic aqueous solutions. Additionally, plastic materials can be sterilized with acidic aqueous solutions.

[Aspect 4]
The method according to any one of aspects 1 to 3, further comprising a compression dehydration drying step of compressing dehydration drying the plastic material treated in the aqueous solution treatment step.
In this method, the plastic material treated in the aqueous solution treatment step is compressed and dried while being dehydrated, so that the water content in the plastic material can be further reduced. Thereby, impurities (for example, substances containing sulfur or nitrogen) mixed in water (aqueous solution) during an aqueous solution treatment process can be discharged from the plastic material along with the water.

[Aspect 5]
The method according to any one of aspects 1 to 4, further comprising a conveyance step of conveying the plastic material separated in the second separation step to the aqueous solution treatment step by air.
In this method, the plastic material separated in the second separation step is transported by air to the aqueous solution treatment step, so that the water in the plastic material can be blown away by the air flow, thereby reducing the amount of moisture in the plastic material. water content can be further reduced. Therefore, impurities (for example, sodium, nitrogen compounds, and sulfur compounds) mixed into the water (aqueous solution) can be removed together with the water in the first and second separation steps. In addition, since the plurality of plastic materials can be separated into pieces by the air flow, the aqueous solution can be almost uniformly supplied to the entire surface of each plastic material in the next aqueous solution treatment step.

[Aspect 6]
The method according to aspect 2, wherein the oxidizing agent in the oxidizing agent treatment step includes at least one of ozone and hydrogen peroxide.
In this method, the oxidizing agent in the oxidizing agent treatment step contains at least one of ozone and hydrogen peroxide. Therefore, the excrement-derived substances remaining in the plastic material can be reliably oxidized and converted into other substances. In addition, since the oxidizing agent does not contain chlorine, chlorine is unlikely to remain as an impurity in the plastic material, and the dechlorination step can be omitted in the manufacturing process of recycled products, reducing the impact on the catalyst used in the manufacturing process.

[Aspect 7]
The first separation step includes a step of separating the used sanitary product into the first fraction and the second fraction while inactivating the superabsorbent polymer in an acidic aqueous solution. 7. The method according to any one of aspects 1 to 6.
In this method, the used sanitary products are separated in an acidic aqueous solution even in the first separation step, so that the superabsorbent polymer that has absorbed urine etc. can be more reliably inactivated. Thereby, the sodium and nitrogen compounds in the superabsorbent polymer can be released to the outside together with the moisture.

[Aspect 8]
Any one of aspects 1 to 7, wherein the physical impact in the second separation step is applied to the first fraction by collision of rotating blades in an impeller that stirs the first fraction in air. The method described in.
In this method, a physical shock is applied to the first fraction by the impingement of rotating blades in an impeller to agitate the first fraction in air. Thereby, physical impact can be more reliably applied to the first fraction in air. Therefore, the excreta, superabsorbent polymers and pulp fibers remaining in the first fraction can be more easily removed from the plastic material.

[Aspect 9]
9. The method according to any one of aspects 1 to 8, wherein the plastic material obtained in the aqueous solution treatment step is for chemical recycling.
In this method, the plastic material obtained in the aqueous solution treatment step can be used for chemical recycling. In other words, since the plastic material obtained by this method is a plastic material with suppressed impurities, its reuse is limited to oil conversion (decomposition of plastic material derived from used products using heat or a catalyst). It will be possible to expand this technology to chemical recycling, such as technology for producing liquid products.

[Aspect 10]
The method according to any one of aspects 1 to 8, wherein the plastic material obtained in the aqueous solution treatment step is for material recycling.
In this method, the plastic material obtained in the aqueous solution treatment step can be used for material recycling. In other words, the plastic material obtained by this method is a plastic material with suppressed impurities, so its reuse can be recycled (a technology that turns plastic materials derived from used products into plastic raw materials or plastic products). This makes it possible to expand the scope of material recycling.

[Aspect 11]
Any of Aspects 1 to 10, wherein the plastic material after the aqueous solution treatment step contains sulfur at a rate of 500 ppm or less, nitrogen at a rate of 2000 ppm or less, and sodium at a rate of 500 ppm or less. The method described in paragraph (1).
In this method, the plastic material produced has a sulfur content of 500 ppm or less, a nitrogen content of 2000 ppm or less, and a sodium content of 500 ppm or less, even though it is derived from used sanitary products. It is. That is, since the manufactured plastic material is a plastic material with suppressed impurities, it can be applied to various uses (eg, material recycling, chemical recycling).

[Aspect 12]
A plastic material derived from used sanitary products, wherein the proportion of sulfur contained in the plastic material is 500 ppm or less, the proportion of nitrogen contained in the plastic material is 2000 ppm or less, and the proportion of sodium contained in the plastic material is 500 ppm or less. Plastic material, the proportion of which is less than 500 ppm.
Although this plastic material is derived from used sanitary products, the proportion of sulfur it contains is 500 ppm or less, the proportion of nitrogen it contains is 2000 ppm or less, and the proportion of sodium it contains is 500 ppm or less. That is, since the present plastic material is a plastic material with suppressed impurities, it can be said to be a recycled plastic material that is applied to various uses (eg, material recycling, chemical recycling).

[Aspect 13]
13. The plastic material according to aspect 12, wherein the plastic material is for chemical recycling.
Since this plastic material is a plastic material with suppressed impurities such as sulfur, nitrogen, and sodium, its reuse is reduced to oil (plastic material derived from used products is decomposed using heat or catalysts). This makes it possible to extend this technology to chemical recycling, such as technology for producing liquid products.

[Aspect 14]
13. The plastic material according to aspect 12, wherein the plastic material is for material recycling.
This plastic material is a plastic material with suppressed impurities such as sulfur, nitrogen, and sodium, so its reuse can be recycled (a technology that turns plastic materials derived from used products into plastic raw materials or plastic products). ) can be extended to material recycling such as

[Aspect 15]
The plastic material according to any one of aspects 12 to 14, comprising 10% by mass or less of a superabsorbent polymer and pulp fiber.
The present plastic material contains 10% by mass or less of superabsorbent polymers and pulp fibers derived from used sanitary products. In other words, although the plastic material is derived from used sanitary products, impurities such as sulfur, nitrogen and sodium as well as superabsorbent polymers and pulp fibers are suppressed. Therefore, this plastic material can be said to be a recyclable plastic material applied to various uses.

Hereinafter, a method for manufacturing a plastic material derived from used sanitary products suitable for material recycling or chemical recycling according to the present embodiment, and a plastic material derived from used sanitary products will be described.

However, used sanitary products are sanitary products that have been used by users, but may also include some unused but discarded sanitary products. Examples of sanitary products include disposable diapers, incontinence pads, sanitary napkins, disposable shorts, bed sheets, and pet sheets. Used sanitary products include sanitary products that have absorbed and retained the user's excrement (eg, urine, feces). Chemical recycling is the process of chemically processing and recycling waste plastic materials. For example, it is a technology that decomposes used plastic materials using heat or catalysts to produce liquid products. In addition to oil conversion, other methods include gasification and monomerization. Material recycling is the production and reuse of new plastic products using waste plastic materials as raw materials.For example, used plastic materials can be used as raw materials for plastics, or used plastic raw materials can be used to make other plastics. Examples include manufacturing products.

First, a configuration example of the sanitary products targeted in this embodiment will be described. The sanitary product includes a top sheet, a back sheet, and an absorbent body disposed between the top sheet and the back sheet. Examples of the size of sanitary products include, but are not limited to, approximately 15 to 100 cm in length and 5 to 100 cm in width. Note that the sanitary product may further include other members included in common sanitary products, such as a diffusion sheet, a leak-proof wall, a side sheet, an exterior sheet, and an elastic member.

Examples of the constituent members of the topsheet include liquid-permeable nonwoven fabrics, synthetic resin films having liquid-permeable holes, composite sheets thereof, and the like. Examples of the constituent members of the backsheet include liquid-impermeable nonwoven fabrics, liquid-impermeable synthetic resin films, and composite sheets thereof. Examples of the constituent members of the diffusion sheet include liquid-permeable nonwoven fabric. The leak-proof wall and the side sheet may be made of, for example, a water-repellent nonwoven fabric, and the leak-proof wall may include an elastic member such as rubber. Examples of the constituent members of the exterior sheet include liquid-impermeable and breathable nonwoven fabrics, liquid-impermeable and breathable synthetic resin films, and composite sheets thereof. Examples of the constituent members of the elastic member include rubber-based synthetic resin. The type of nonwoven fabric is not particularly limited, and examples thereof include meltblown nonwoven fabric, spunbond nonwoven fabric, airlaid nonwoven fabric, air-through nonwoven fabric, and the like. There are no particular restrictions on the type of synthetic resin film, and known film materials can be used. There are no particular restrictions on the materials for nonwoven fabrics and synthetic resin films as long as they can be used for sanitary products, but examples include olefin resins such as polyethylene and polypropylene, polyamide resins such as 6-nylon and 6,6-nylon, Examples include polyester resins such as polyethylene talphthalate and polybutylene terethalate. The materials of these nonwoven fabrics and synthetic resin films are synthetic resins and can be called plastic materials. In this embodiment, a sanitary product in which the constituent members of the back sheet are made of a synthetic resin film and the constituent members of the top sheet is made of a nonwoven fabric will be described as an example.

Components of the absorbent body include absorbent materials, ie, pulp fibers and superabsorbent polymers. Examples of pulp fibers include cellulose fibers. Examples of cellulosic fibers include wood pulp, crosslinked pulp, non-wood pulp, regenerated cellulose, and semi-synthetic cellulose. As for the size of the pulp fibers, the average length of the fibers is, for example, several tens of μm, preferably 20 to 40 μm, and the average fiber length is, for example, several mm, preferably 2 to 5 mm. Examples of the super absorbent polymer (SAP) include polyacrylate-based, polysulfonate-based, and maleic anhydride-based water-absorbing polymers. As for the size of the superabsorbent polymer (when dry), the average particle size is, for example, several hundred μm, preferably 200 to 500 μm. The absorbent body may include a core wrap formed of a liquid permeable sheet.

One side and the other side of the absorber are bonded to a top sheet and a back sheet, respectively, via an adhesive. In plan view, the part of the topsheet that extends outside the absorbent body so as to surround the absorbent body (peripheral part) is the part of the backsheet that extends outside the absorbent body so as to surround the absorbent body. It is joined to the extended portion (peripheral portion) via an adhesive. Therefore, the absorbent body is wrapped inside the joined body of the top sheet and the back sheet. The adhesive is not particularly limited, and examples thereof include hot melt adhesives. Examples of hot melt adhesives include pressure-sensitive adhesives or heat-sensitive adhesives that are mainly rubber-based such as styrene-ethylene-butadiene-styrene, styrene-butadiene-styrene, styrene-isoprene-styrene, or olefin-based adhesives such as polyethylene. Examples include agents.

Next, a method for manufacturing a plastic material derived from used sanitary products suitable for material recycling or chemical recycling according to the present embodiment will be specifically described. In this embodiment, a disposable diaper will be described as an example of a sanitary product.

FIG. 1 is a flowchart illustrating a method for producing plastic material derived from used sanitary products suitable for material recycling or chemical recycling according to an embodiment. This method includes a first separation step S2, a second separation step S3, and an aqueous solution treatment step as steps for manufacturing plastic material derived from used sanitary products. However, in this embodiment, the first oxidizing agent treatment step S5 is performed as the aqueous solution treatment step.

In this embodiment, the method further includes a crushing step S1, an air conveying step S4, and a compression dehydration drying step S6. In addition, in this embodiment, in relation to this method, a dust removal step S7 for recovering pulp fibers and superabsorbent polymers separated in the first separation step S2 and/or second separation step S3 to pulp fibers is described. A separation step S10 is further performed. Each step will be explained below.

In this embodiment, used sanitary products are collected from outside for reuse (recycling). At that time, multiple used sanitary products are sealed in collection bags to prevent excrement, fungi, and odors from leaking outside. Each used sanitary product in a collection bag is rolled up, for example, with the top sheet from which excreta is excreted on the inside, so that excrement and fungi are not exposed on the outside and odors are not spread to the surrounding area. It is collected in a folded state. Note that the used sanitary products do not need to be enclosed in a collection bag or rolled up.

The crushing step S1 is a step of crushing used sanitary products in an inactivating aqueous solution containing an inactivating agent. In this embodiment, in the crushing step S1, a collection bag containing used sanitary products is supplied to a receiving tank that receives the collection bags (used sanitary products). The collection bags are delivered from the receiving tank to a crushing device (eg, a two-shaft crusher, such as a two-shaft rotary crusher, a two-shaft differential crusher, a two-shaft shear crusher). The collection bag is crushed together with the collection bag by a crushing device. During crushing, the crushing device is supplied with an inactivated aqueous solution, whereby the used sanitary products in the collection bag are crushed together with the collection bag in the inactivated aqueous solution to produce crushed products. The crushed material alone or together with the inactivating aqueous solution is sent to the first separation step S2. However, the inactivating aqueous solution may be stored in advance in the receiving tank before receiving the collection bag.

Here, in the crushing step S1, the used sanitary products are preferably crushed so that the size of the crushed products is approximately 20 to 150 mm, preferably 25 to 100 mm. If the length is 20 mm or more, materials other than pulp fibers and superabsorbent polymers (examples: films, nonwoven fabrics, elastic bodies, etc.) will be cut into large pieces, and these materials will be combined with pulp fibers and superabsorbent polymers in the subsequent process. Can be easily separated. If the length is 150 mm or less, the materials of used sanitary products will not easily get entangled with each other, making it easier for larger materials to disintegrate, and also making it easier to separate pulp fibers and superabsorbent polymers sandwiched between these materials. .

When used sanitary products are treated in an inactivated aqueous solution, the superabsorbent polymers contained or contained in the used sanitary products are inactivated and dehydrated to become small particle sizes. Therefore, handling (separation and recovery) of the superabsorbent polymer becomes easier in subsequent steps, improving processing efficiency. Moreover, at that time, the sodium and nitrogen compounds contained in the superabsorbent polymer are released (dehydrated) to the outside along with the water. Therefore, even if the superabsorbent polymer remains in the plastic material obtained by this method, the amount of sodium and nitrogen compounds in the plastic material can be suppressed. As the inactivating agent, it is preferable to use an aqueous solution of an inorganic acid and an organic acid, that is, an acidic aqueous solution. When using an acidic aqueous solution, compared to using an aqueous solution of lime or calcium chloride, it is difficult for ash and chlorine to remain in plastic materials and pulp fibers, and the degree of inactivation (particle size and specific gravity) can be easily adjusted by adjusting the pH.

Examples of organic acids include citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, ascorbic acid, and the like, with citric acid being preferred. Citric acid can trap and remove metal ions in excrement due to its chelating effect, and can also remove dirt components due to its cleaning effect. On the other hand, examples of inorganic acids include sulfuric acid, hydrochloric acid, and nitric acid, with sulfuric acid being preferred. Sulfuric acid does not contain chlorine, so chlorine does not easily remain in plastic materials, etc., and is low cost.

The pH of the acidic aqueous solution is preferably 1.0 to 4.0. When the pH is set to 1.0 or higher, equipment is less likely to corrode, and the amount of alkaline chemicals required for neutralization during wastewater treatment can be reduced.When the pH is set to 4.0 or lower, the superabsorbent polymer can be made sufficiently small. Sterilization ability is also enhanced. Since pH changes depending on water temperature, pH in the present invention refers to pH measured at an aqueous solution temperature of 20°C.

The organic acid concentration of the organic acid aqueous solution is not particularly limited, but when the organic acid is citric acid, it is preferably 0.5% by mass or more and 4% by mass or less. The inorganic acid concentration of the inorganic acid aqueous solution is not particularly limited, but when the inorganic acid is sulfuric acid, it is preferably 0.1% by mass or more and 0.5% by mass or less. In this embodiment, a case will be described in which an aqueous solution of an inorganic acid sulfuric acid (dilute sulfuric acid), that is, an acidic aqueous solution is used as the inactivating aqueous solution.

Note that the used sanitary products that are fed into the twin-shaft crusher do not need to be placed in a collection bag. Moreover, the collection bag containing the used sanitary products or the used sanitary products not contained in the collection bag may be thrown into the biaxial crusher without passing through the solution tank. Moreover, crushing with a twin-screw crusher does not need to be carried out in an acidic aqueous solution, and may be carried out, for example, in air. In that case, the subsequent steps, the first separation step S2 and/or the second separation step S3, are performed in an acidic aqueous solution.

In this way, in the crushing step S1, each component of the used sanitary product is crushed into approximately a predetermined size. At that time, the bonding force of the adhesive (for example, hot melt adhesive) between each component is reduced by the heat generated during crushing and/or the heat of the acidic aqueous solution, so that each component can easily disintegrate from each other. is also possible.

In addition, heating the acidic aqueous solution (temperature: 70 to 95°C) softens the adhesive (e.g., hot melt adhesive) used to bond the constituent parts of used sanitary products. Bonding force can be reduced. Thereby, the constituent members can be easily disaggregated naturally or by a small impact. It also becomes possible to further sterilize (disinfect) used sanitary products.

In addition, when the crushing step S1 is not used, for example, the used sanitary products are immersed in a heated oxidizing agent aqueous solution, and the bonding strength of the adhesive between each component is reduced by physical impact such as stirring. The respective constituent members may be disintegrated from each other.

The first separation step S2 is a step of separating the used sanitary products into a first fraction containing plastic material and a second fraction containing excrement, inactivated superabsorbent polymer, and pulp fibers. It is. That is, in the first separation step S2, the plastic material (first fraction containing) and the mixture of the plastic material, excrement, inactivated superabsorbent polymer, and pulp fiber obtained by decomposing used sanitary products are separated. , excrement, superabsorbent polymer and pulp fiber (a second fraction comprising) are separated.

In the present embodiment, in the first separation step S2, a mixture of the crushed material generated in the crushing step S1 and an acidic aqueous solution that is an inactivated aqueous solution is supplied to a pulper separator (first separation device). The pulper separator is equipped with a stirring separation tank that functions as both a washing tank for washing the mixture and a sieving tank for separating the mixture. Note that another acidic aqueous solution that is not used in the crushing step S1 may be supplied to the first separation step S2 as the acidic aqueous solution.

The mixture is agitated and washed by a pulper separator to remove dirt from the crushed material, while a screen separates the first fraction containing collection bags, films, non-woven fabrics, etc. from the pulp fibers and inactivated high-quality materials. It is separated into a second fraction containing water-absorbing polymers, excreta, acidic aqueous solutions, and the like. That is, the pulp fibers, superabsorbent polymer, excreta, and acidic aqueous solution are separated from the mixture through a screen and delivered from the pulper separator. On the other hand, other materials such as collection bags, films, and non-woven fabrics that could not pass through the screen remain in the pulper separator and are then sent to the second separation step S3. At this time, a portion of the pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution may not pass through the screen and may remain on the screen together with other materials. Also, some of the other materials may pass through the screen.

Further, as in the present embodiment, when the superabsorbent polymer is previously inactivated and granulated to suppress its water absorption ability before the first separation step S2 (in the crushing step S1, etc.), In the first separation step S2, the inactivating aqueous solution (acidic aqueous solution) may not be used, and water (aqueous solution) containing no inactivating agent may be used.

In addition, if the superabsorbent polymer is not inactivated in advance before the first separation step S2 (such as in the crushing step S1), the first separation step S2 is performed by first removing the used sanitary products from an inactivating aqueous solution (acidic aqueous solution). ), that is, a step of inactivating the superabsorbent polymer. In that case, processing methods include, for example, immersing the used sanitary products in an inactivated aqueous solution (acidic aqueous solution), or spraying the used sanitary products with an inactivated aqueous solution (acidic aqueous solution). . The acidic aqueous solution is as described above. The first separation step S2 is followed by a step of separating the used sanitary products into a first fraction and a second fraction.

However, other materials such as collection bags, films, and non-woven fabrics are made of synthetic resin and can be considered plastic materials. Therefore, in the first separation step S2, the plastic material and a small amount of residual material (pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution) become residues (rejects) on the screen, and the separated pulp fibers and superabsorbent Polymers, excreta, and acidic aqueous solutions become what passes through the screen (accept).

In this embodiment, the first separation step S2 is performed in one of the two first separation devices connected in parallel. For example, if two pulper separators are connected in parallel and one pulper separator is operated, and that pulper separator requires maintenance, then that pulper separator is stopped and the other pulper separator is operated. operate the machine. Thereby, the first separation step S2 can be performed continuously. Note that three or more first separation devices may be connected in parallel.

In this embodiment, in the first separation step S2, the pH of the acidic aqueous solution is adjusted to be maintained within a predetermined range. The predetermined pH range is a range within which the pH fluctuation is within ±1.0. Thereby, the difference between the specific gravity and size of the superabsorbent polymer and the specific gravity and size of the pulp fibers can be kept within a predetermined range. In this case, the difference within a predetermined range means, for example, that one is within a range of 0.2 to 5 times the other. Thereby, the difference between the pulp fiber and the superabsorbent polymer is that the specific gravity is within a predetermined range and the size is within a predetermined range. As a result, we have found that pulp fibers and superabsorbent polymers can be used to make use of the differences in size and specific gravity from other materials (mainly plastic materials) used in used sanitary products other than pulp fibers and superabsorbent polymers. can be easily separated. The pH can be adjusted using an acidic aqueous solution or an alkaline aqueous solution based on the pH value measured by a pH sensor. Note that the pH may be adjusted in the second separation step S3 as well in the same manner as in the first separation step S2.

Furthermore, when an inactivating aqueous solution (acidic aqueous solution) is used in the crushing step S1, the pH of the acidic aqueous solution may be adjusted as in the first separation step S2.

In the second separation step S3, the first fraction is subjected to physical impact to separate the plastic material, the excrement that was not completely separated in the first separation step S2 and remained in the first fraction, and the super absorbent polymer. and pulp fibers. That is, in the second separation step S3, the plastic material, the remaining excrement, the superabsorbent polymer, and the pulp fiber are separated from the mixture of the plastic material, the remaining excrement, the superabsorbent polymer, and the pulp fiber. and are separated, thereby recovering the plastic material.

In the present embodiment, the second separation step S3 performs separation by applying a physical impact to the first fraction while treating the first fraction with an acidic aqueous solution. Specifically, first, in the second separation step S3, the mixture (plastic material and residue) from which excrement, pulp fibers, superabsorbent polymers, etc. have been separated in the first separation step S2 is supplied to a separation device. Ru. The separation device consists of a cylindrical part installed on its side, a plurality of impellers provided in the cylindrical part, a plurality of acidic aqueous solution supply parts provided on the upper outer circumferential surface of the cylindrical part, and a cylindrical part installed on its side. A screen (sieve) provided on the lower outer peripheral surface. A mixture supply port is provided at one end of the cylindrical portion, and a discharge port is provided at the other end. The plurality of impellers are arranged at intervals along the direction of the central axis of the cylindrical part so that their rotation axes and the central axis of the cylindrical part overlap. The plurality of impellers rotate about the central axis of the cylindrical portion, and the direction of the blades is adjusted so as to cause air to flow from one end of the cylindrical portion to the other end. The plurality of acidic aqueous solution supply sections are lined up at intervals along the central axis direction, and spray the acidic aqueous solution toward the bottom of the cylindrical section. It is preferable that the acidic aqueous solution supply unit sprays the acidic aqueous solution in the form of a spray. The individual openings in the screen are sized to allow pulp fibers and superabsorbent polymers to pass through, but not to allow plastic materials to pass through.

In the air inside the cylindrical part of the separation device, the mixture is injected with an acidic aqueous solution from each of the plurality of acidic aqueous solution supply parts, stirred by the blades of a rotating impeller, and subjected to physical impact by collision of the blades of the impeller. It moves (flows) from one end side of the cylindrical part to the other end side while being During this time, the mixture is washed away from dirt and/or sterilized and bleached by the sprayed acidic aqueous solution. At the same time, the pulp fibers in the mixture are removed from the plastic materials in the mixture due to physical impact, and the superabsorbent polymers in the mixture are removed from the plastic materials in the mixture due to further inactivation with an acidic aqueous solution or physical impact. It will be done. The removed pulp fibers and superabsorbent polymers pass through a screen below the cylindrical part and are separated (removed) together with the acidic aqueous solution.

On the other hand, the plastic material in the mixture from which pulp fibers, superabsorbent polymers, etc. have been removed is discharged from the discharge port at the other end of the cylindrical portion without passing through the screen. That is, the superabsorbent polymer and pulp fibers remaining without being separated in the first separation step S2 are separated from the plastic material, and a plastic material with suppressed impurities is produced and recovered. However, although the amount is not necessarily large, sulfur compounds and nitrogen compounds derived from excrement that could not be completely removed in the second separation step S3 remain in the plastic material. Note that the separated acidic aqueous solution may be reused in the first separation step S2 or the crushing step S1. Note that the acidic aqueous solution is as described above.

The amount of the acidic aqueous solution to be supplied is not particularly limited as long as it can achieve the desired function, but for example, the weight of the acidic aqueous solution may be 5 to 100 times the weight of the plastic material, and 10 to 50 times the weight of the plastic material. preferable. The supply rate of the acidic aqueous solution is not particularly limited as long as it can achieve the desired function, but examples include 50 to 500 cm ³ /min, preferably 80 to 200 cm ³ /min. If the supply amount or supply rate is small, it will be difficult to obtain the desired effect, and if the supply rate is large, equipment, materials, etc. may be damaged.

In the second separation step S3, in a preferred embodiment, an acidic aqueous solution is injected into the mixture. The force of the jet can wash away residual superabsorbent polymers and pulp fibers adhering to the plastic material. In addition, since the acidic aqueous solution is made finer by spraying, it is possible to make it easier for the acidic aqueous solution to reach the superabsorbent polymer remaining in the details of the plastic material. Moreover, compared to the case where a plastic material is immersed in an acidic aqueous solution, a fresh acidic aqueous solution can always be supplied to the surface of the plastic material, and variations in the effect of the acidic aqueous solution can be suppressed. Furthermore, plastic materials can be sterilized with acidic aqueous solutions.

In the second separation step S3, the separation may be performed by applying physical impact to the first fraction without treating the first fraction with the acidic aqueous solution. The mixture is stirred by the blades of a rotating impeller in the air inside the cylindrical part of the separator, and is moved from one end of the cylindrical part to the other while being subjected to physical impact due to the collision of the impeller blades ( flow). During this time, the mixture is knocked clean of dirt by physical impact. For example, pulp fibers or superabsorbent polymers in the mixture are removed from the plastic material in the mixture by physical impact. The removed pulp fibers and superabsorbent polymers pass through a screen below the cylindrical part and are separated (removed).

Alternatively, in the second separation step S3, instead of the acidic aqueous solution, water or an aqueous solution containing no inactivating agent (hereinafter also simply referred to as "water") may be injected into the first fraction. Water is injected from each of the multiple water supply parts into the mixture in the air inside the cylindrical part of the separator, and the mixture is stirred by the blades of a rotating impeller, and the mixture is subjected to physical impact due to the collision of the blades of the impeller. It moves (flows) from one end side of the cylindrical part to the other end side while being applied. During this time, the mixture is washed clean of dirt by the jetted water and knocked off by the physical impact. For example, pulp fibers and superabsorbent polymers in the mixture are removed from the plastic material in the mixture by water flow, physical impact, etc., respectively. The removed pulp fibers and superabsorbent polymers pass through a screen below the cylindrical part and are separated (removed) along with water.

The air conveyance process S4 (conveyance process) is a process in which the plastic material separated in the second separation process S3 is conveyed by air to the first oxidizing agent treatment process S5, which is an example of an aqueous solution treatment process. That is, in the air conveyance step S4, the separated plastic material is conveyed to the next step while being dried in an air flow.

In this embodiment, in the air conveyance step S4, air flows through the pipe by a blower in a pipe connecting the separation device of the second separation step S3 and the first oxidizer treatment device (described later) of the first oxidizer treatment step S5. Then, the separated plastic material is transported from the separation device to the first oxidizer treatment device. At this time, the moisture contained in the plastic material is evaporated or blown away into the air, so that the moisture content of the plastic material is reduced. The moisture content decreases, for example, from about 95% to about 80%. Moreover, since the plurality of plastic materials can be separated into pieces by the air flow, the oxidizing agent aqueous solution can be supplied almost uniformly to the entire surface of each plastic material in the next first oxidizing agent treatment step S5. Note that the air conveyance step S4 may not be used, and the separated plastic material may be conveyed by other known conveyance means.

The first oxidizing agent treatment step S5 is a step of injecting an oxidizing agent aqueous solution containing an oxidizing agent onto the plastic material separated in the second separating step S3. In the first oxidizing agent treatment step S5, sulfur compounds, nitrogen compounds, and the like derived from excrement that were not completely removed in the second separation step S3 and remain in the plastic material can be removed using the oxidizing agent aqueous solution. .

Note that in this embodiment, as an aqueous solution treatment step after the second separation step S3, a first oxidizing agent treatment step S5 is performed in which an oxidizing agent aqueous solution containing an oxidizing agent is injected onto the plastic material. However, the aqueous solution treatment step after the second separation step S3 is not limited to that example, and water treatment in which water that does not contain an oxidizing agent is injected onto the plastic material instead of an oxidizing agent aqueous solution containing an oxidizing agent. You may perform the process. However, the water may also contain substances that do not become impurities in the plastic material (eg, substances that do not easily adhere to the plastic material, substances that do not cause problems when the plastic material is reused). In this case as well, sulfur compounds, nitrogen compounds, etc. derived from excrement remaining in the plastic material can be removed with water (including cases where only water is used). In the aqueous solution treatment step after the second separation step S3, an aqueous solution containing an oxidizing agent (oxidizing agent treatment step), a water treatment step containing no oxidizing agent (water treatment step), It can be said that it is a process of treating plastic materials using (including the case of ), so it can be said to be an aqueous solution treatment process.

In this embodiment, in the first oxidizer treatment step S5, the plastic material separated in the second separation step S3 (via the air conveyance step S4) is supplied to the first oxidizer treatment device. The first oxidizing agent treatment device includes a conveyor (for example, a screw conveyor) that conveys the plastic material, and a plurality of oxidizing agent aqueous solution supply units that are provided above the conveyor and inject an oxidizing agent aqueous solution onto the plastic material being conveyed. , is provided. The conveyor is inclined upwardly along the conveying direction (e.g. 30°), thereby conveying the aqueous oxidizer solution that has been jetted and spilled from the plastic material to a drain below. The plurality of oxidizing agent aqueous solution supply units are lined up at intervals along the conveyance direction of the conveyor. It is preferable that the oxidizing agent aqueous solution supply section injects the oxidizing agent aqueous solution in the form of a spray.

The plastic material is conveyed from one end to the other end by a conveyor while being sprayed with an oxidizing agent aqueous solution supply section from each of the plurality of oxidizing agent aqueous solution supply sections. During this time, the injected oxidant aqueous solution oxidizes sulfur compounds and nitrogen compounds derived from excrement remaining on the plastic material, and converts them into other odorless substances (e.g. sulfur (S) and nitrogen (N ₂ )). , mixed into the oxidizing agent aqueous solution, and/or released as a gas. That is, sulfur compounds and nitrogen compounds remaining in the plastic material are removed. Furthermore, the plastic material is sterilized by the oxidizing agent aqueous solution.

In the first oxidizing agent treatment step S5, an oxidizing agent aqueous solution is injected onto the plastic material. The force of the jet can wash away sulfur compounds and nitrogen compounds adhering to the surface of plastic materials. Furthermore, since the oxidizing agent aqueous solution becomes finer by spraying, it is possible to make it easier for the oxidizing agent aqueous solution to reach the sulfur compounds and nitrogen compounds remaining in the details of the plastic material. In addition, compared to the case where plastic materials are immersed in an oxidizing agent aqueous solution, a fresh oxidizing agent aqueous solution can always be supplied to the surface of the plastic material, and variations in the effects of the oxidizing agent aqueous solution (for example, cleaning and sterilizing effects) can be suppressed. can do.

Here, the oxidizing agent aqueous solution is an aqueous solution containing an oxidizing agent. The oxidizing agent includes at least one of ozone and hydrogen peroxide. In this embodiment, ozone is used as an oxidizing agent from the viewpoint of oxidizing power, sterilizing power, and bleaching power. Specifically, as the oxidizing agent aqueous solution, ozone water is used, which is water (or aqueous solution) such as pure water or clean water mixed with ozone gas. Note that the oxidizing agent aqueous solution may be acidic from the viewpoint of suppressing deactivation of ozone. Furthermore, in the case where an acidic aqueous solution such as a (dilute) sulfuric acid aqueous solution is used as the inactivation aqueous solution in at least the second separation step S3 of the crushing step S1, the first separation step S2, and the second separation step S3, each step is continuous. It may be acidic from the viewpoint of properties and effective use of the aqueous solution. In that case, an acidic aqueous solution (for example, a dilute sulfuric acid aqueous solution) mixed with ozone gas is used. As the acidic aqueous solution, an acidic aqueous solution used in another process may be reused.

The ozone concentration in the oxidizing agent aqueous solution is not particularly limited as long as it can achieve the desired function, that is, oxidizing power, bactericidal power, and bleaching power against sulfur compounds (including sulfuric acid in acidic aqueous solutions), nitrogen compounds, etc. Its concentration is, for example, 0.2 to 10 ppm, preferably 0.5 to 5 ppm. If the concentration is not too low, the desired function can be achieved, and if the concentration is not too high, corrosion of equipment can be suppressed. The treatment time with the oxidizing agent aqueous solution is not particularly limited as long as it can exhibit the desired function, but the higher the ozone concentration in the oxidizing agent aqueous solution, the shorter the treatment time, and the lower the ozone concentration, the longer the treatment time. ~30 minutes. The product of the ozone concentration (ppm) in the oxidizing agent aqueous solution and the treatment time (minutes) of the treatment process (hereinafter also referred to as "CT value") is, for example, 0.5 to 200 ppm min, and 5 to 100 ppm.・Minutes are preferable. If the CT value is not too small, the desired function can be achieved, and if the CT value is not too large, corrosion of the equipment can be suppressed. Note that, as the oxidizing agent aqueous solution, the oxidizing agent aqueous solution used in the second oxidizing agent treatment step S9, which will be described later, may be reused in this step after lowering its concentration.

Further, the amount of the oxidizing agent aqueous solution to be supplied is not particularly limited as long as it can realize the desired function, but for example, the weight of the oxidizing agent aqueous solution to the weight of the plastic material may be 5 to 100 times, 50 times is preferable. The supply rate of the oxidizing agent aqueous solution is not particularly limited as long as it can achieve the desired function, but examples include 50 to 500 cm ³ /min, preferably 80 to 200 cm ³ /min. If the supply amount or supply rate is small, it will be difficult to obtain the desired effect, and if the supply rate is large, equipment, materials, etc. may be damaged.

Regarding sterilization or sterilization, for example, used paper diapers contain more than 1 billion bacteria/ml, but it cannot be said that they can be completely sterilized with the acidic aqueous solution up to the second separation step S3. Therefore, the plastic material separated in the second separation step S3 (to which a small amount of pulp fibers and superabsorbent polymers are attached) contains a certain amount of general bacteria (eg, 3,400 general bacteria/ml). If this happens, there may be concerns about adverse effects on worker safety and the possibility of rotting or mold growth in the removed plastic materials. There is also a strong odor of excrement that is thought to be caused by common bacteria. However, by performing the first oxidizing agent treatment step S5 using an oxidizing agent aqueous solution, general bacteria from plastic materials can be removed to below the detection limit, similar to E. coli, and sulfur and nitrogen compounds can be decomposed. The odor of excrement can also be reduced to an almost unnoticeable level.

The pressing, dehydrating and drying step S6 is a step of compressing, dehydrating and drying the plastic material treated in the first oxidizing agent treatment step S5. That is, in the compression dehydration drying step S6, a plurality of treated plastic materials are put together, compressed as a whole, dehydrated, and heated and dried.

In this embodiment, in the compression dehydration drying step S6, the plastic material treated in the first oxidizing agent treatment step S5 is supplied to the compression dehydration drying device. A compression dehydration drying device is a device that compresses a plurality of plastic materials together while heating them, squeezes out water, and dehydrates and dries them. The heating temperature may be 120 to 180°C. If the temperature is high, pulp fibers that may be included in the plastic material may be carbonized, and if the temperature is low, it becomes difficult to obtain a drying effect. The heating time depends on the heating temperature, but is, for example, 10 to 120 minutes, preferably 15 to 100 minutes. If the time is long, the drying effect will be saturated, and if the time is short, it will be difficult to obtain the drying effect. The pressing pressure is, for example, 0.2 to 4 MPa, preferably 0.4 to 2 MPa, although it depends on the heating temperature and heating time. If the pressure is low, it is difficult to obtain the dehydration effect, and if the pressure is high, the dehydration effect is saturated. The compression dehydration drying device softens (and/or melts) the plastic material and extrudes it to the outside through a large number of pores (eg, pore diameter: 5 to 15 mm). Thereby, the plastic material can be formed into flakes or pellets, making it easier to pack.

A plurality of plastic materials are put together by a compression dehydration drying device, compressed while being heated, and sent out. Thereby, the water is squeezed out and a evaporated and thus dehydrated, dry plastic material is produced. In this way, a recyclable plastic material is produced. At this time, the moisture content of the plastic material is 5% by mass or less, preferably 3% or less. Note that pressing dehydration and drying may be performed using separate devices.

Note that the dehydration and drying of the plastic material is not limited to the above-mentioned pressing dehydration and drying step S6, and in cases where the shape of the plastic material is not changed, a general dehydration and drying step may be performed. The dehydration/drying process includes, for example, a process of drying the plastic material in a high-temperature atmosphere in a constant temperature bath or with hot air. The drying temperature may be, for example, 80 to 120°C. The drying time is, for example, 10 to 120 minutes, although it depends on the drying temperature.

By the manufacturing method described above, a plastic material derived from used sanitary products suitable for material recycling or chemical recycling according to the present embodiment is manufactured.

In this method, the first fraction is separated in the first separation step S2. At this time, the superabsorbent polymer that had been absorbing urine and the like has been inactivated, so sodium and nitrogen compounds are released (dehydrated) to the outside along with water and become granular. Therefore, in the second separation step S3, the first fraction of the superabsorbent polymer can be easily separated from the plastic material by physical impact. In addition, even if there is a superabsorbent polymer that cannot be separated from the plastic material, the content of sodium and nitrogen compounds in the superabsorbent polymer can be reduced. Also, other excreta and pulp fibers can be easily separated from the plastic material by physical impact.

After that, an aqueous solution treatment step is performed in which an aqueous solution is injected onto the plastic material separated in the second separation step S3. However, the aqueous solution may be a liquid consisting only of water. In that case, the aqueous solution treatment step can be called a water treatment step. At this time, by supplying the aqueous solution to the plastic material by spraying, the force of the spray can wash away sulfur compounds, nitrogen compounds, etc. adhering to the surface of the plastic material. Further, by spraying the aqueous solution into fine particles and supplying it to the plastic material, it is possible to make it easier for the aqueous solution to penetrate into the finer details of the plastic material. Furthermore, compared to the case where the plastic material is immersed in an aqueous solution, a fresh aqueous solution can always be supplied to the surface of the plastic material, and variations in the cleaning effect can be reduced.

However, when implementing the aqueous solution treatment step, an oxidizing agent aqueous solution containing an oxidizing agent may be used as the aqueous solution. In that case, the aqueous solution treatment step can be called a first oxidizing agent treatment step S5. That is, after the second separation step S3, a first oxidant treatment step S5 (oxidant treatment step) of an oxidizing agent aqueous solution containing an oxidizing agent is performed on the plastic material separated in the second separation step S3. At this time, sulfur compounds, nitrogen compounds, etc. derived from excrement that were not completely separated in the second separation step S3 and remained in the plastic material are oxidized, and other odorless substances such as sulfur (S) and nitrogen ( N ₂ )), some or all of which is mixed into the aqueous oxidizer solution and flows out and/or is released as a gas. That is, most of the sulfur compounds and nitrogen compounds remaining in the plastic material are further removed. In this way, the odor-producing sulfur and nitrogen compounds are converted into other odorless substances and are generally removed, thereby making the plastic material less likely to produce bad odors. The oxidizing agent can also sterilize plastic materials. At this time, the oxidizing agent aqueous solution can be made fine by spraying and supplied to the plastic material, thereby making it easier for the oxidizing agent aqueous solution to enter the fine details of the plastic material. As a result, compared to the case where the plastic material is immersed in an oxidizing agent aqueous solution, a fresh oxidizing agent aqueous solution can be constantly supplied to the surface of the plastic material, and variations in the sterilization effect can be reduced.

In this way, in the plastic material produced by the present method, impurities containing sodium, sulfur, and nitrogen are separated or decomposed and removed, so impurities in the plastic material can be suppressed. Moreover, when an oxidizing agent aqueous solution is used as the aqueous solution, sterilization can be performed at the same time. When applying the plastic material to material recycling or chemical recycling to manufacture recycled products, since the impurities in the plastic material are suppressed, the impact on the catalyst used in the manufacturing process can be reduced, and undesirable odors can be eliminated. It can be made difficult to cause.

In this method, in a preferred embodiment, the second separation step S3 includes applying a physical impact to the first fraction while spraying an acidic aqueous solution to separate the excrement, the superabsorbent polymer, the pulp fibers, and the plastic material. , includes a step of separating them from each other. In this way, in the present method, the acidic aqueous solution is injected into the first fraction in the second separation step S3. Therefore, the superabsorbent polymer remaining in the plastic material is further inactivated by the acidic aqueous solution, and releases (dehydrates) sodium and nitrogen compounds to the outside, becoming finer particles. Therefore, the superabsorbent polymer can be more easily separated (washed off) from the plastic material by physical impact or by a flow of acidic aqueous solution. In addition, even if there is a superabsorbent polymer that cannot be separated from the plastic material, the content of sodium and nitrogen compounds in the superabsorbent polymer can be further reduced. Also, other excreta and pulp fibers can be more easily separated (washed off) from the plastic material by physical impact or a stream of acidic aqueous solutions. Additionally, plastic materials can be sterilized with acidic aqueous solutions.

In a preferred embodiment, this method further includes a compression dehydration drying step S6 in which the plastic material treated in the aqueous solution treatment step (or first oxidizing agent treatment step S5) is compressed and dehydrated and dried. That is, since the plastic material treated in the aqueous solution treatment step (or the first oxidizing agent treatment step S5) is dried while being squeezed and dehydrated, the water content in the plastic material can be further reduced. As a result, impurities (e.g., substances containing sulfur and nitrogen that do not cause a bad odor) mixed in moisture (aqueous solution) in the aqueous solution treatment step (or first oxidizing agent treatment step S5) are discharged from the plastic material along with the moisture. be able to.

In a preferred embodiment, this method further includes an air conveyance step S4 in which the plastic material separated in the second separation step S3 is conveyed by air to the aqueous solution treatment step (or first oxidizing agent treatment step S5). At this time, the moisture in the plastic material can be blown away by the airflow to the surrounding area, so that the moisture in the plastic material can be further reduced. Therefore, in the first and second separation steps S2, S3, etc., impurities (for example, sodium, nitrogen compounds, and sulfur compounds) mixed into the water (aqueous solution) can be removed together with the water. In addition, since multiple plastic materials can be separated into pieces by air flow, in the next aqueous solution treatment step (or oxidizing agent treatment step S5), the aqueous solution (or oxidizing agent aqueous solution) is applied to the entire surface of each plastic material. Can be supplied evenly.

In a preferred embodiment of this method, the oxidizing agent in the first oxidizing agent treatment step S5 contains at least one of ozone and hydrogen peroxide. Therefore, it is possible to reliably oxidize the excrement-derived substances remaining in the plastic material and convert them into other substances (for example, substances containing sulfur or nitrogen that do not produce bad odors). In addition, since the oxidizing agent does not contain chlorine, chlorine is unlikely to remain as an impurity in the plastic material, and the dechlorination step can be omitted in the manufacturing process of recycled products, reducing the impact on the catalyst used in the manufacturing process.

In a preferred embodiment of this method, the first separation step S2 includes a step of separating the used sanitary product into a first fraction and a second fraction in an acidic aqueous solution. In this way, in the first separation step S2, the used sanitary products are separated in an acidic aqueous solution, so that the superabsorbent polymer that has absorbed urine etc. can be more reliably inactivated. Thereby, the sodium and nitrogen compounds in the superabsorbent polymer can be released to the outside together with the moisture.

In a preferred embodiment of this method, the physical impact in the second separation step S3 is applied to the first fraction by the collision of rotating blades in an impeller that stirs the first fraction in air. Thereby, physical impact can be more reliably applied to the first fraction in air. Therefore, the excreta, superabsorbent polymers and pulp fibers remaining in the first fraction can be more easily removed from the plastic material.

In this method, as a preferred embodiment, the plastic material obtained after the aqueous solution treatment step (or first oxidizing agent treatment step S5) is for chemical recycling or material recycling. In other words, the plastic material obtained by this method is a plastic material with few impurities as will be described later, so its reuse is limited to oil conversion (processing plastic materials derived from used products using heat or catalysts). It will be possible to expand this to chemical recycling, such as technology that decomposes plastic products to produce liquid products, and material recycling, such as reuse (technology that converts plastic materials derived from used products into plastic raw materials or plastic products). .

In a preferred embodiment of this method, the produced plastic material has very few impurities, even though it is derived from used sanitary products. Specifically, the proportion of sulfur contained in the plastic material obtained by this method is 500 ppm or less, preferably 300 ppm, more preferably 100 ppm, and still more preferably 50 ppm or less. Further, the proportion of nitrogen contained in the plastic material obtained by this method is 2000 ppm or less, preferably 1500 ppm, more preferably 1000 ppm, and even more preferably 500 ppm or less. Moreover, the proportion of sodium contained in the plastic material obtained by this method is 500 ppm or less, preferably 300 ppm, more preferably 100 ppm, and still more preferably 50 ppm or less. Therefore, as described above, the plastic material obtained by this method is suitable for material recycling or chemical recycling, and can be applied to various uses (eg, oil conversion, recycling).

However, the method for measuring the content of sulfur, nitrogen, sodium, and chlorine in plastic materials is as follows.
<Method for measuring sulfur, nitrogen, sodium, and chlorine content>
(i) Prepare an energy dispersive X-ray analyzer (EDX: EDX-7200 manufactured by Shimadzu Corporation).
(ii) Dry the plastic material to be measured (120°C x 60 minutes), collect a sufficient amount of sample from the dried plastic material that can be placed on the sample stand of the analyzer, and fix it on the sample stand. do.
(iii) Measure the content of sulfur, nitrogen, sodium, and chlorine in the sample using an analyzer.
(iv) The measurement results of the five samples are averaged to determine the content of sulfur, nitrogen, sodium, and chlorine in the final plastic material.

In this method, as a preferred embodiment, the produced plastic material has extremely low impurities, even though it is a plastic material derived from used sanitary products. Specifically, the plastic material obtained by this method contains a superabsorbent polymer and pulp fibers (total) in an amount of 10% by mass or less, preferably 5% by mass or less. In other words, although the plastic material obtained by this method is derived from used sanitary products, it is not only free from impurities such as sulfur, nitrogen, and sodium, but also contains impurities such as superabsorbent polymers and pulp fibers. . Therefore, the plastic material obtained by this method can be said to be a recycled plastic material that can be applied to various uses.

However, the method for measuring the content of pulp fibers and superabsorbent polymers in plastic materials is as follows.
<Method for measuring pulp fiber and superabsorbent polymer content (mass%)>
(i) Dry the plastic material (120° C. x 60 minutes), weigh about 100 g (measured value A), and use it as sample α1.
(ii) Sample α1 is adjusted to an aqueous solution with a solid concentration of 1%, and ozone gas is blown into the solution while stirring to perform ozone treatment. However, the ozone concentration in the aqueous solution and the treatment time are set to 50 ppm x 30 minutes (CT value 1500) (the super absorbent polymer is decomposed, solubilized, and removed).
(iii) Sample α2 obtained by solid-liquid separation of the ozone aqueous solution in (ii) above is dried (120° C. x 60 minutes) and weighed (measured value A'). As a result, |A'-A| is contained, resulting in a mass D of the superabsorbent polymer.
(iv) Sample α2 is immersed in toluene to dissolve the adhesive (HMA) and separate it into pulp fibers and plastic material. Next, the pulp fibers are air-dried in a draft (60 minutes) and weighed, and the result is the mass C of the pulp fibers.
(v) The mass B of the plastic material itself is calculated by ADC.
therefore,
Plastic material (mass%) = B/A x 100
Pulp fiber (mass%) = C/A x 100
Super absorbent polymer (mass%) = D/A x 100
becomes.

In this method, as a preferred embodiment, the produced plastic material has extremely low impurities, even though it is a plastic material derived from used sanitary products. Specifically, the plastic material obtained by this method contains ash in an amount of 10% by mass or less, preferably 6% by mass or less, and more preferably 4% by mass or less. In other words, although the plastic material obtained by this method is derived from used sanitary products, impurities such as sulfur, nitrogen and sodium as well as ash are suppressed. Therefore, the plastic material obtained by this method can be said to be a recycled plastic material that can be applied to various uses.

However, the method for measuring the ash content in plastic materials is as follows.
<Method for measuring ash content (mass%)>
Ash content refers to the amount of inorganic or non-combustible residue left after organic matter is incinerated, and the ash content (% by mass), or ash content, is the ratio of ash contained in the sample to be measured ( mass ratio). The ash content is measured in accordance with "5. Ash content test method" in "2. General test methods" of the Material Standard for Sanitary Treatment Products. Specifically, the ash content is measured as follows.
(i) In advance, ignite a platinum, quartz, or porcelain crucible (with a lid) at 500 to 550°C for 1 hour, and after cooling, accurately weigh the mass.
(ii) Collect 2 to 4 g of plastic material that has been dried at 120°C for 60 minutes, place it in a crucible, and accurately weigh its mass.
(iii) Remove or shift the lid if necessary and heat the crucible weakly at first, then gradually increase the temperature and ignite it at 500 to 550°C for 4 hours or more to incinerate until no carbide remains. .
(iv) After cooling, accurately weigh the crucible. The residue is incinerated again until it reaches a constant weight, and after cooling, the mass of the crucible is precisely weighed. Based on the measured values of (1), (2), and (4), the ash content (% by mass) is calculated.

In addition, in this embodiment, as shown in FIG. 1, the method includes a dust removal step S7 and a step of separately recovering pulp fibers and superabsorbent polymers (SAP) from used sanitary products. The method may further include a separation step S8, a second oxidizing agent treatment step S9, and a pulp fiber separation step S10.

In the present embodiment, the mixed liquid containing the pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution separated in the first separation step S2 is processed in the dust removal step S7. Note that the pulp fibers, superabsorbent polymer, and the like separated in the second separation step S3 may also be mixed with the liquid mixture and treated in the dust removal step S7.

In the dust removal step S7, dust that could not be completely separated from the mixed liquid supplied from the first separation step S2 (and second separation step S3) by at least one separator (example: screen separator, cyclone separator) Separate foreign objects such as other materials (collection bags, films, non-woven fabrics, elastic bodies, etc.). In the present embodiment, in the dust removal step S7, a screen separator (with a relatively large opening), a screen separator (with a relatively small opening), and a cyclone separator are arranged in this order to remove foreign substances from the mixed liquid. Separated sequentially. As a result, pulp fibers and super absorbent polymers with less foreign matter can be obtained. The mixed liquid of the pulp fibers with few foreign substances, the super absorbent polymer, and the acidic aqueous solution (containing excrement) is supplied to the SAP separation step S8.

In the SAP separation step S8, at least one separator (example: drum screen separator) extracts a super absorbent liquid from the mixed liquid (containing pulp fibers and a super absorbent polymer with few foreign substances) supplied from the dust removal step S7. Separate the polymer. In this embodiment, in the SAP separation step S8, the superabsorbent polymer and the acidic aqueous solution (including excrement) are separated from the mixed liquid by a drum screen separator. As a result, a superabsorbent polymer and an acidic aqueous solution with few foreign substances can be obtained. The superabsorbent polymer is separated from the acidic aqueous solution (liquid) and taken out by another separator (eg, an inclined screen separator). On the other hand, pulp fibers with few foreign substances (but containing a small amount of super absorbent polymer) are supplied to the second oxidizing agent treatment step S9.

The second oxidizing agent treatment step S9 oxidizes and decomposes the superabsorbent polymer in the pulp fibers containing few foreign substances (but contains a small amount of superabsorbent polymer) supplied from the SAP separation step S8 using an oxidizing agent aqueous solution, Solubilized and removed from pulp fibers. In the present embodiment, in the second oxidizing agent treatment step S9, pulp fibers are put into a treatment tank that stores an oxidizing agent aqueous solution containing ozone as an oxidizing agent, and the superabsorbent polymer in the pulp fibers is oxidized and decomposed, and the Upon solubilization, pulp fibers with very few impurities are obtained. Pulp fibers containing few impurities (including superabsorbent polymers) are supplied to pulp fiber separation step S10 together with an oxidizing agent aqueous solution.

The type of oxidizing agent in the second oxidizing agent treatment step S9 is the same as the oxidizing agent in the first oxidizing agent treatment step S5. In this embodiment, ozone is used as an oxidizing agent from the viewpoint of oxidizing power, sterilizing power, and bleaching power. The ozone concentration in the oxidizing agent aqueous solution is not particularly limited as long as it is a concentration that can decompose the superabsorbent polymer, and may be, for example, 10 to 50 mass ppm. A concentration that is not too low allows the superabsorbent polymer to be completely solubilized, and a concentration that is not too high does not damage the pulp fibers. The treatment time with the oxidizing agent aqueous solution is not particularly limited as long as it is enough to decompose the superabsorbent polymer, but the higher the ozone concentration in the oxidizing agent aqueous solution, the longer the ozone concentration. The average time is 5 to 300 minutes. The product of the ozone concentration (ppm) in the oxidizing agent aqueous solution and the treatment time (minutes) of the treatment step (hereinafter also referred to as "CT value") is preferably 100 to 15,000 ppm·min. If the CT value is too small, the superabsorbent polymer may not be completely solubilized and the superabsorbent polymer may remain in the pulp fibers, and if the CT value is too large, there is a risk of damaging the pulp fibers.

In the pulp fiber separation step S10, a separator (example: screen separator) separates pulp fibers from the pulp fibers and the oxidizing agent aqueous solution supplied from the second oxidizing agent treatment step S9. The pulp fibers separated and recovered in this manner become so-called recycled pulp fibers. The recycled pulp fibers are washed with washing water and taken out.

Hereinafter, the present invention will be explained based on Examples, but the present invention is not limited to the Examples.

(1) Sample Example 1: Using a used disposable diaper as a raw material, a crushing step S1 to a pressing dehydration drying step S6 were performed to obtain a plastic material sample 1.
However, the acidic aqueous solution in the second separation step S3 is a 0.1% by mass sulfuric acid aqueous solution, and the ozone concentration and treatment time (CT value) in the first oxidizing agent treatment step S5 are 2 ppm x 20 minutes (40 ppm min). did.
Example 2: Using a used disposable diaper as a raw material, a crushing step S1 to a pressing dehydration drying step S6 were performed to obtain a plastic material sample 2.
However, the acidic aqueous solution in the second separation step S3 is a 0.1% by mass sulfuric acid aqueous solution, and instead of the first oxidizing agent treatment step S5 (using an oxidizing agent (ozone) aqueous solution), the water treatment step (using only water) ) was carried out.

(2) Evaluation method (a) Quantitative evaluation The amounts of each of sulfur, nitrogen, sodium, chlorine, pulp fibers, super absorbent polymer, and ash remaining on Sample 1 (Example 1) (mass ppm or mass %) ) was evaluated.
The amounts (mass ppm) of each of sulfur, nitrogen, and sodium adhering to and remaining on Sample 2 (Example 2) were evaluated.
However, each measurement method (calculation method) is as described above.

(3) Evaluation results (a) Quantitative evaluation The amounts of sulfur, nitrogen, sodium, and chlorine remaining in Sample 1 were below the detection limit (however, the detection limit was 10 ppm), 280 ppm, 204 ppm, and 570 ppm, respectively. The amount of pulp fibers and superabsorbent polymer remaining in Sample 1 was 5.0% by mass. The amount of ash remaining in Sample 1 was 3.8% by mass. Therefore, the sulfur, nitrogen, sodium, chlorine, pulp fiber, superabsorbent polymer, and ash remaining in Sample 1 were significantly reduced. That is, the impurities remaining in Sample 1 were significantly reduced.
The amounts of sulfur, nitrogen, and sodium remaining in Sample 2 were 110 ppm, 600 ppm, and 60 ppm, respectively. Therefore, even if the aqueous solution treatment step (using only water) is performed instead of the first oxidizing agent treatment step S5 (using an oxidizing agent (ozone) aqueous solution), the sulfur, nitrogen, and sodium remaining in sample 2 are significantly reduced. It had been reduced. That is, the impurities remaining in Sample 2 were significantly reduced.

The sanitary products of the present invention are not limited to the embodiments described above, and can be combined and changed as appropriate without departing from the purpose and gist of the present invention.

S2 First separation step S3 Second separation step S5 First oxidizing agent treatment step

Claims

A method for producing plastic materials derived from used sanitary products suitable for material recycling or chemical recycling, wherein the used sanitary products contain excrement, plastic materials, superabsorbent polymers and pulp fibers. Ori,
a first separation of the used sanitary product into a first fraction containing the plastic material and a second fraction containing the excrement, the inactivated superabsorbent polymer, and the pulp fibers; process and
The first fraction is subjected to physical impact to remove the excrement, the superabsorbent polymer, and the pulp fibers that were not completely separated in the first separation step and remained in the first fraction; a second separation step of separating the plastic material from each other;
an aqueous solution treatment step of injecting an aqueous solution onto the separated plastic material;
Equipped with
Method.
The aqueous solution treatment step includes an oxidizing agent treatment step of injecting an oxidizing agent aqueous solution containing an oxidizing agent as the aqueous solution onto the separated plastic material.
The method according to claim 1.
In the second separation step, a physical impact is applied to the first fraction while injecting an acidic aqueous solution to separate the excrement, the superabsorbent polymer, the pulp fibers, and the plastic material from each other. including the step of separating;
The method according to claim 1 or 2.
Further comprising a compression dehydration drying step of compressing and dehydrating the plastic material treated in the aqueous solution treatment step.
The method according to claim 1 or 2.
Further comprising a conveyance step of conveying the plastic material separated in the second separation step to the aqueous solution treatment step by air.
The method according to claim 1 or 2.
The oxidizing agent in the oxidizing agent treatment step includes at least one of ozone and hydrogen peroxide.
The method according to claim 2.
The first separation step includes a step of separating the used sanitary product into the first fraction and the second fraction while inactivating the superabsorbent polymer in an acidic aqueous solution.
The method according to claim 1 or 2.
The physical impact in the second separation step is applied to the first fraction by the collision of rotating blades in an impeller that stirs the first fraction in air.
The method according to claim 1 or 2.
The plastic material obtained in the aqueous solution treatment step is for chemical recycling.
The method according to claim 1 or 2.
The plastic material obtained in the aqueous solution treatment step is for material recycling,
The method according to claim 1 or 2.
The plastic material after the aqueous solution treatment step is
The proportion of sulfur contained is 500 ppm or less,
The proportion of nitrogen contained is 2000 ppm or less,
The proportion of sodium contained is 500 ppm or less,
The method according to claim 1 or 2.
A plastic material derived from used sanitary products,
The proportion of sulfur contained in the plastic material is 500 ppm or less,
The proportion of nitrogen contained in the plastic material is 2000 ppm or less,
The proportion of sodium contained in the plastic material is 500 ppm or less,
plastic material.
the plastic material is for chemical recycling;
Plastic material according to claim 12.
the plastic material is for material recycling;
Plastic material according to claim 12.
Contains 10% by mass or less of super absorbent polymer and pulp fiber,
Plastic material according to claim 12.