JP2013150976A - Method for treating used sanitary article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating used sanitary articles reducing adverse effects on the environment and capable of efficiently performing the separation and recovery of a material such as fiber or SAP.SOLUTION: A method for treating used sanitary articles includes at least a process for macerating the sanitary article to disperse the same in water and a process for separating and recovering a fiber and SAP and, in the process for macerating the sanitary article to disperse the same in water, a crosslinking agent and an acidic substance are added.

Description

  The present invention relates to a method for treating used sanitary goods. In particular, the present invention relates to a processing method for separating and recovering a material from a used sanitary product in a reusable manner.

  Sanitary articles such as disposable paper diapers typically include an absorbent body made of pulp fibers, an SAP (super absorbent polymer) that retains moisture absorbed by the absorbent body, and a non-woven fabric as a wrapping material It consists of materials such as plastic. These sanitary products were not used repeatedly, but were discarded and incinerated after use. However, in recent years, due to environmental considerations, the need to collect and recycle constituent materials has increased. Yes.

  For example, Patent Document 1 discloses that a physiological paper product containing a superabsorbent polymer is treated in at least one bath of an aqueous solution to dissolve soluble substances from the product, and the superabsorbent polymer is alkali metal or alkaline earth metal. A processing method is described which includes steps of treating with at least one water soluble compound of aluminum, copper (II), iron (III) and zinc to reduce swelling of the superabsorbent polymer in an aqueous solution. .

  Further, in Patent Document 2, after the used paper diaper is crushed, the crushed used paper diaper is put into a polymer decomposition tank in which the polymer decomposing agent is mixed and stirred, and discharged from the polymer decomposition tank. The water containing the polymer decomposing agent is purified in a septic tank that purifies using microorganisms, part or all of the purified water is returned to the polymer decomposing tank, and the polymer decomposing agent is circulated and used in the polymer decomposing tank. Describes a regeneration treatment method in which a water-absorbing polymer contained in a paper diaper is decomposed into monomers and then a pulp component contained in the paper diaper is separated and recovered.

JP-T 6-502454 JP 2000-84533 A

  Specifically, the method of Patent Document 1 uses an apparatus similar to a washing machine, and the washing tub is a continuous batch type, in which washing with chemicals and rinsing with water are repeated. Therefore, a large amount of water is required, and there is a problem from the viewpoint of resource saving.

  In the method of Patent Document 2, a polymer decomposing agent is added to the decomposition tank, and in this case, a large amount of addition is required. Further, since the polymer is decomposed, the polymer cannot be recovered, and it is considered difficult to recycle both the fiber containing pulp and the polymer. Furthermore, when SAP is decomposed and eluted into wastewater, there is a concern that the load of wastewater treatment will increase.

  Therefore, an object of the present invention is to provide a method for treating used sanitary goods, which has less adverse effects on the environment than before, and can efficiently separate and collect materials such as fibers and SAP.

  First, the present inventors have found that the separation and recovery efficiency of a material can be increased by adding a crosslinking agent and an acidic substance in a step of disaggregating used sanitary goods and dispersing them in water. The invention has been completed.

The present invention includes, but is not limited to, the following inventions.
(1) A method for treating used sanitary goods, comprising at least a step of disaggregating sanitary products and dispersing them in water, and a step of separating and collecting fibers and SAP contained in the sanitary products, and disaggregating the sanitary products Then, in the step of dispersing in water, a crosslinking agent and an acidic substance are added.
(2) The method according to (1), wherein a bleaching disinfectant is further added in the disaggregation dispersion step.
(3) The method according to (1) or (2), wherein calcium chloride is added as a cross-linking agent and acidification is added after disaggregation at a concentration of 3.0 to 20.0%.
(4) The method according to any one of (1) to (3), wherein the acidic substance is added after diluting the slurry concentration to 2% or less after disaggregation.
(5) The method according to any one of (1) to (4), wherein the acidic substance is added to adjust the pH of the slurry to 6 or less.
(6) The method according to any one of (1) to (5), which comprises adding a reducing agent in advance before adding the acidic substance.
(7) The method according to any one of (1) to (6), comprising heating at one or more locations in the process.
(8) The method according to any one of (1) to (7), wherein a tab-type pulper is used for disaggregation of sanitary goods.
(9) The method according to (8), wherein the tab-type pulper has a separation pulper and / or a detractor immediately after.
(10) The method according to (8) or (9), wherein the tab-type pulper has a rope plugger.
(11) The method according to any one of (1) to (10), wherein the separation and recovery step is performed using a screen and / or a cleaner.
(12) In any of the separation and recovery steps, the dispersion liquid containing fibers is washed and dehydrated using a vertical washer, and the dehydrated water is used as in-process water. The method of crab.
(13) The method according to any one of (1) to (12), wherein a secondary or higher cascaded or forwarded separation apparatus is used in the separation and recovery step.

  According to the treatment method of the present invention, it is possible to efficiently separate and collect materials such as fibers and SAP from used sanitary goods. Therefore, it is possible to obtain high-quality and reusable fibers and SAP and improve operability.

It is a flowchart which shows one embodiment of the processing method of this invention. It is a flowchart which shows one embodiment of the processing method of this invention.

1. The sanitary article in the present invention includes fibers and SAP (super absorbent polymer), and examples thereof include disposable paper diapers, incontinence products, feminine physiological products, bed pads, etc. It is not limited. Hereinafter, the present invention may be described by taking a disposable diaper as an example, but the present invention is not limited thereto.

  In the present invention, the fiber refers to synthetic fibers (polypropylene, polyethylene, etc.) such as pulp fibers and nonwoven fabrics among materials constituting sanitary goods such as paper diapers. SAP is a superabsorbent polymer, and examples thereof include sodium polyacrylate, carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), and PVA / sodium polyacrylate. The most commonly used is cross-linked sodium polyacrylate.

2. Process flow, equipment <Process flow>
As the processing flow of used paper diapers, for example, the following flow can be used according to the required quality and processing cost.

  In the separation and recovery process according to the present invention, fibers and materials such as SAP are collected. For example, in a cleaner or a screen, fibers are collected as accepts, and materials other than fibers (such as SAP) can be collected as rejects. it can. In the present specification, a material other than the fiber may be referred to as a foreign material, but a material such as SAP can be further separated and recovered from the foreign material (material other than the fiber) recovered as a reject.

・ Flow 1 (low quality, low cost):
Disaggregation → Cleaner and / or screen → Dehydrator / Concentrator → Washer ・ Flow 2 (medium quality / medium cost):
Disaggregation → Cleaner and / or screen → Dehydration / concentrator → High concentration treatment device → Washer ・ Flow 3 (high quality, high cost):
Disaggregation → Coarse screen → Cleaner → Dehydration / concentrator → High concentration treatment device → Selection screen → Washing / dehydrator ・ Flow 4 (high quality, high cost):
Disaggregation → Dehydration / concentrator → High-concentration treatment device → Rough selection screen → Cleaner → Selection screen → Washing / dehydration machine FIG. 1 shows a specific example of the processing flow, but the present invention is not limited to this. In the figure, first, as a process of disaggregating sanitary goods and dispersing them in water, used paper diapers as raw materials are put into a pulper and dispersed in water. At this time, a bleach disinfectant and a crosslinking agent are added to the pulper. Further, the dispersion is diluted to adjust the concentration, and a reducing agent and an acidic substance are sequentially added to adjust the pH. Next, as a process of separating and collecting the fibers and SAP contained in the paper diaper, processing is performed using a screen and a cleaner, and the SAP component is first collected. On the other hand, the dispersion containing fibers is subsequently washed and dehydrated by a dehydrator or the like. Here, the dehydrated water can be returned to the process and reused. Furthermore, the dispersion liquid containing fibers is processed by a high concentration apparatus. And although not shown in figure, a fiber part is collect | recovered by performing washing | cleaning, spin-drying | dehydration, and a screen process as needed. Moreover, although not shown in the figure, in addition to the fiber component, the plastic component contained in the nonwoven fabric is also separated and recovered.

<Pulper>
In the present invention, a pulper is preferably used as a device that disperses used paper diapers and disperses them in water. The pulper is preferably a pulper used for the disaggregation of waste paper. Utilization of a system comprising a low-density pulper or a batch-type vertical tab type high-density pulper, followed by a secondary pulper (separation pulper) and / or a detrusor Is preferred. Since the tab type (tab type) has a higher disaggregation capability than the drum type, the used paper diaper as a raw material can be efficiently crushed.

Examples of the low-concentration pulper include a vertical tab type continuous low-concentration pulper manufactured by Maruishi Seisakusho, and a low-medium concentration pulper manufactured by Aikawa Tekko, which are disaggregated at a concentration of about 3.0 to 8.0%.
Examples of the high-concentration pulper include a vertical tab-type batch-type high-concentration pulper manufactured by Aikawa Tekko. As the rotor shape inside the pulper, a spiral type or a helicopter type can be used. The disaggregation concentration is about 8.0 to 20.0%.

Moreover, in order to remove foreign matters such as vinyl efficiently at an early stage, a low-medium and low-medium concentration pulper can use a foreign matter collecting device called a rope plugger.
Examples of the secondary pulper include a PAL sorter and a pair pulper manufactured by Aikawa Tekko. These devices have the function of performing mechanical disaggregation and rough foreign matter removal (rough selection process) using a round hole strainer basket, etc., to shorten the disaggregation time with the pulper and promote the separation of foreign matters. Can do. In particular, the pair pulper has a round hole strainer with a diameter of about 7.00 mm and a slit screen with a diameter of about 3.50 mm, and is therefore suitable for high foreign matter removal efficiency.

  As the detractor, a screw separator manufactured by Aikawa Iron Works or a drum-type separator can be used, and a MAX drum manufactured by Aikawa Tekko Co., Ltd. with a detrasher having a disaggregation ability can also be used as appropriate.

  In the recycling process of paper diapers, since there are many non-woven fabrics contained in diapers and vinyl used for collection, the processing time in the pulper can be shortened by using a secondary pulper in particular. Moreover, since the fluidity of the diaper disintegration suspension is high, even when a high-concentration pulper is used, the removal efficiency of vinyl or the like is further improved and workability is improved by using a lager.

  The detractor can dehydrate and select the raw material discharged without being disaggregated by the pulper, and can reduce the volume of the discharged soot. Therefore, it is effective to treat the used paper diaper that has been disaggregated by the pulper with a secondary pulper and then treat it with a detractor.

  For example, the MAX drum manufactured by Aikawa Tekko has the ability to disintegrate in addition to the dewatering and deselecting function of the detrusor, so it can process the raw material that has been dissociated by the pulper and recover the fiber and SAP. Therefore, it is effective to improve the fiber and SAP recovery rate and reduce waste, and it is more effective to perform the fiber recovery process with the MAX drum after the pulper.

  In the present invention, if the disaggregation concentration is too low, the amount of moisture tends to swell easily, and the amount of paper diapers that can be processed at one time is reduced. If the disaggregation concentration is too high, the disaggregation efficiency in the pulper decreases, and the paper diaper Therefore, it is preferable to disaggregate so that the concentration in the pulper is 3.0 to 20.0%. More preferably, the concentration is 3.0 to 15.0%, and still more preferably 3.0 to 8.0%. After disaggregation, the dispersion is diluted in a tank, a mixer, etc. in order to make it difficult to entrain the fibers when SAP is precipitated, and the concentration is 0.3 to 2.0%, preferably 0.3 to 1.5%. More preferably, it may be adjusted to 0.3 to 1.2%.

<Screen>
As the screen, an inward or outward round hole and / or slit screen can be used. It is also possible to use a screen called a reject screen or tail screen, which is suitable for conditions with a large amount of foreign matter, and is unlikely to cause problems due to foreign matter clogging or entanglement. It is a composite that has both a round hole screen and a basket type slit screen. A screen (ADS double separator: manufactured by Aikawa Tekko) can also be used.

  By using a multistage screen in which screen rejection is further processed by a screen, fiber loss can be suppressed and foreign matter separation efficiency can be increased. In the case of a multistage screen system, a forward process in which the acceptance after the secondary screen is forwarded to the next process may be performed, or a cascade process to return to the previous stage may be performed.

  Moreover, it is good also as a series (tandem) system which combined the slit screen immediately after the round hole screen. As the hole diameter of the round hole screen, those having a diameter of φ3.00 to 0.50 mm can be used. When the diameter is larger than 3.00 mm, the foreign matter removal efficiency is deteriorated. Further, since SAP has a specific gravity heavier than that of fibers and easily swells in a gel state, when it is smaller than φ0.5 mm, the gelled SAP is easily clogged and the operability is deteriorated.

  As the slit screen, a cutting type or bar type basket can be used, and a slit width of 0.30 to 0.10 mm can be used, and a 0.25 to 0.15 mm is preferable. When it is larger than 0.30 mm, the gel-like SAP easily passes and the separation efficiency from the fiber is deteriorated. When it is smaller than 0.10 mm, the gel polymer is easily clogged and the operability is deteriorated.

  As operating conditions of the screen in the present invention, the solid content concentration is preferably 0.3 to 1.2%, more preferably 0.4 to 0.8%. If it is higher than 1.5%, the screen is likely to be clogged, resulting in a decrease in separation efficiency. Not only is waste increased, but also the dehydration load after the screen is increased, which is not preferable.

  As a screen passage flow rate, the range of 0.6-2.0 m / s is preferable, and the range of 1.0-1.5 m / s is more preferable. Further, the peripheral speed of the agitator inside the screen is preferably 10 to 20 m / s, and more preferably 14 to 18 m / s. If the passing flow velocity or the peripheral speed is too low, gel deposition on a basket or the like occurs, which is not preferable. On the other hand, when the passing flow velocity or the peripheral speed is too high, the shearing force becomes too large, the gel-like SAP polymer is refined, and the separation efficiency from the fiber is lowered, which is not suitable.

  In the recycling process of a disposable diaper, a cascade and / or forward process including two or more slit screens is preferable, and a cascade process is more preferable from the viewpoint of improving SAP removal efficiency.

<Cleaner>
As the cleaner in the present invention, a heavy foreign matter cleaner using centrifugal force can be used,
A low concentration / high differential pressure type cleaner or a low concentration / low differential pressure type cleaner is suitable.

  The diameter of the reject cone of the cleaner in the present invention is preferably 7.0 to 30.0 mm. If it is smaller than 6.0 mm, it will be difficult to collect a stable raw material due to clogging of the reject cone. If it is larger than 30.0 mm, it will be difficult to control the pressure difference between the inlet pressure and the outlet pressure of the reject cone, and the separation efficiency will be significantly reduced. This is not preferable.

  As operating conditions of the cleaner, the solid content concentration is preferably 0.3 to 1.2%, and more preferably 0.3 to 0.8%. If the concentration is higher than 1.5%, the reject corn is clogged and a stable raw material cannot be collected. Even if the sample can be collected, it is not preferable because the separation from the foreign matter becomes insufficient, and if it is less than 0.3%, the amount of liquid to be processed increases, the processing takes time, and not only energy is wasted. This is not preferable because the dehydration load after the screen increases.

  By using a multistage process in which the reject of the cleaner is further processed by the cleaner, the fiber loss can be suppressed and the foreign matter separation efficiency can be increased. In the case of a multistage cleaner system, forward processing for accepting the secondary cleaner or later may be forwarded to the next process, or cascade processing may be performed to return to the previous stage, from the viewpoint of yield improvement and equipment compactness. The forward process is more preferable.

  In addition, it is also preferable to use a combination of a cleaner and a screen, and processing with a round hole screen and / or slit screen and a centrifugal cleaner is more preferable, and a combination of two or more is more preferable. It is more preferable to process in the order of the screen.

<Dehydrator / Concentrator / Washer>
In the present invention, dehydration / concentration / washing may be performed by an apparatus having these functions, or may be performed separately by individual apparatuses.

  Medium to high concentration dehydrators include screw thickeners, inclined extractors, screw presses, power presses, and other devices that dehydrate pulps with a concentration of around 2.0-3.0% to around 10.0%. % Is not particularly limited as long as it is a device that dehydrates pulp having a concentration of around% to about 25.0 to 30.0%.

  The low concentration concentrator is a preliminary dehydration device that dehydrates and concentrates pulp having a concentration of around 1.0% to a concentration of 3.0% or more, and is not particularly limited. For example, a device that performs filtration and dewatering using a pulp mat such as a disk extract or a disk thickener, or a device that performs natural dewatering using a filter or dewatering element such as an SP filter or a trommel may be used.

  As the washing machine, a high-speed washing and dehydrating machine such as a wire and roll type DNT washer, a horizontal drum type trommel or fall washer, or a vertical type zuku can be used.

  For the recycling process of disposable diapers, a vertical washer is particularly suitable because it uses less water. Compared with a horizontal dehydrator, the amount of washing water used can be saved to 1/3 or less. In addition, water can be further saved by reusing the dehydrated water as process water. For example, it can be used as dilution water in the previous stage of the screen cleaner.

<High concentration processing equipment>
The concentration of the high concentration treatment in the present invention is 10.0 to 50.0%. Preferably it is 15.0-45.0%, More preferably, it is 20.0-40.0%. Examples of the high concentration processing apparatus include a low-speed kneader and a high-speed disperser. In the flow 2 described above, it is preferable to use a hot dispersion system having excellent foreign matter dispersibility as a high concentration processing apparatus. In the flow 3, it is preferable to use a kneader as a high-concentration processing apparatus, and it is more preferable to perform screen processing after that, because SAP is thermally denatured to form resin particles and easily separated.

  As a kneader, one, two or four axes can be used, and a kneader having two or more kneading portions can also be used. Treatment temperature is 40-120 ° C, preferably 40-100 ° C, by heating by adding steam to the kneading part or by passing a plurality of kneading parts continuously to generate heat spontaneously by friction of the fibers. More preferably, by heating to 50 to 80 ° C., it is possible to obtain resin-like particles in which SAP is thermally denatured and water contained therein is separated. In addition, in this invention, in order to improve the isolation | separation efficiency of a fiber and SAP also in places other than a high concentration process, it can heat. By heating, the binding force between the carboxyl group of polyacrylic acid of SAP and water molecules is weakened, so it is considered that water separation from SAP is promoted. At the same time, the sewage contained in the SAP can be easily replaced and sterilized, which is preferable. Furthermore, since the moisture content of the SAP decreases, an improvement in drying efficiency after SAP recovery can be expected.

  As the disperser, a disc type or a conical type can be used. By combining a device such as a heating tube immediately before the disperser, so-called hot dispersion can be performed, and SAP can be finely dispersed and made inconspicuous.

3. Added chemicals such as the present invention, in the step of dispersing by macerating the used paper diaper into water, to a method of treating by adding a crosslinking agent and an acidic substance.

<Bleaching fungicide>
In a preferred embodiment, a bleaching disinfectant may be added for the purpose of bleaching, disinfecting and disinfecting materials such as filth contained in the raw material paper diaper, fibers to which the filth adheres, and SAP. The bleaching disinfectant is preferably added to an apparatus for disaggregating used paper diapers such as a pulper. Since raw materials including sewage are collectively subjected to powerful bleaching and sterilization in the previous stage, it is efficient.

  Bleach disinfectants are classified into two types, an oxidized type and a reduced type, and the oxidized type is further classified into a chlorine type and an oxygen type. Among these, the oxidizing power is excellent in the oxidative chlorine system, and sodium hypochlorite is particularly strong and is preferable because it can be efficiently bleached and sterilized.

  In the present invention, since the raw material contains human waste, the pH in the process is considered to be weakly acidic to neutral. However, in the case of sodium hypochlorite, the sterilization bleaching effect in this pH region is high and efficient. On the other hand, Patent Document 1 described above uses hydrogen peroxide (oxidized oxygen bleaching) and a microbicide (peracetic acid), but these are bleached or sterilized compared to sodium hypochlorite. The action is weak. Further, in order to optimize the bleach sterilization effect in Patent Document 1, hydrogen peroxide is effective at pH 11.0 or higher and the microbicide pH 9.0 or higher, so it is necessary to control to alkali. If it is done (pH 11.0 or higher), the effect of the cross-linking agent is reduced due to high sodium ion conditions, and it is assumed that the fiber becomes yellow due to alkali burning and the whiteness is hardly improved. In addition, in acidity (pH 4.0 or less), since the fiber is damaged (the degree of polymerization of cellulose is lowered), the strength of the fiber is lowered, and there is a possibility that troubles may be caused at the time of reuse. In the present invention, by using sodium hypochlorite having a high bactericidal bleaching effect in a neutral to weakly acidic pH range, it is not necessary to control pH (alkali treatment), and the fiber is not adversely affected. can do.

  The addition rate of the bleaching disinfectant is 1 to 100000 ppm, preferably 5 to 30000 ppm, more preferably 10 to 20000 ppm in the dispersion at the time of addition. If it is 1 ppm or less, there is a possibility that a sufficient bleach sterilization effect cannot be expected. If it is 100,000 ppm or more, as will be described later, a large amount of sodium sulfite is required for the reduction of free chlorine in the latter stage, resulting in an increase in waste.

<Crosslinking agent>
A crosslinking agent is added in order to bridge | crosslink the carboxyl groups of polyacrylic acid which is the main component of SAP, and to suppress swelling of SAP. It is effective to add a cross-linking agent to an apparatus for disaggregating used paper diapers such as a pulper as well as a bleaching disinfectant.

  The cross-linking agent may be any polyvalent metal salt, and examples thereof include calcium chloride, calcium nitrate, calcium sulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, sulfate band, and polyaluminum chloride (PAC). Among them, calcium chloride is preferable because it is inexpensive and excellent in the SAP swelling suppression effect.

  The addition rate may be 1.0 to 30.0%, preferably 5.0 to 20.0%, more preferably 10.0 to 20.0% based on the weight of the raw material. If it is 1.0% or less, the effect as a crosslinking agent cannot be sufficiently expected, and if it is 30.0% or more, corrosion of piping in the process due to excessive chloride ions is more than the merit of the suppression effect of SAP swelling due to crosslinking. The disadvantage of increased risk is greater.

  The addition method and addition timing of the crosslinking agent are not particularly limited, and may be added when a sanitary product is dispersed in an aqueous solvent to obtain a slurry. The crosslinking agent may be added all at once, may be added in a plurality of times, or may be added continuously.

<Acid substance>
The acidic substance is added to lower the pH and make the dispersion into an acidic solution in order to improve the separation efficiency of the fiber and SAP. Due to the decrease in pH, SAP is made into fine resinous particles such as sand instead of gel, and the separation and recovery efficiency can be increased without clogging the screen. Since the acid dissociation constant pKa of polyacrylic acid, which is the main component of SAP, is about 5.3 to 5.7, by making it lower, the ionic state is changed to the free acid state, and the water contained in the SAP is contained. It is thought that water separation occurs.

  The acidic substance can be added after the addition of the crosslinking agent, and it is effective to add it to the pulper or diluted chest. The concentration is adjusted to 0.3 to 2.0%, preferably 0.3 to 1.5%, more preferably 0.3 to 1.2% in order to make it difficult to entrain the fibers when depositing SAP. Also good.

  The acid that can be used as the acidic substance is not particularly limited and may be either an organic acid or an inorganic acid (mineral acid). However, it is inexpensive and can lower the pH with a small amount of addition, so an inorganic acid is preferable. Sulfuric acid and a sulfuric acid band are particularly preferable.

The addition amount may be adjusted so that the dispersion after the addition has a pH of 6.0 or less, and the addition is preferably performed so that the pH becomes 4.0 to 6.0.
When adjusting pH using a sulfuric acid band, since the effect of lowering the pH with respect to the added amount is small, it is necessary to increase the added amount. As a result, the sulfuric acid ion concentration in the system becomes high, and there is a possibility that a calcium sulfate (gypsum) scale is formed with calcium ions such as calcium chloride added as a crosslinking agent. As a countermeasure, it is effective to use sulfuric acid having a large pH reduction effect with a smaller addition amount.

<Reducing agent>
A reducing agent may be added to reduce free chlorine in the system. When lowering the pH with an acidic substance, chlorine gas is generated if the pH is lowered with the free chlorine (residual chlorine) of sodium hypochlorite added excessively as a bleach sterilant remaining. In order to avoid this, it is desirable to add an acidic substance after previously reducing free chlorine. As the reducing agent, sodium sulfite can be preferably used. In the process of using a reducing agent, the amount of addition can be determined by measuring free chlorine from the supernatant of the dispersion using a kit such as a pack test, and determining the necessity of adding the reducing agent and the amount of reducing agent added. it can. As a guide, 0.0 to 50.0% of a reducing agent can be added to the added sodium hypochlorite, but is not particularly limited thereto.

In one embodiment, the present invention is a method for treating sanitary goods comprising fibers and SAP. According to the present invention, fibers and SAP are efficiently separated from sanitary goods and recovered. Can do.

  As already mentioned, the present invention comprises the step of disaggregating sanitary products and dispersing them in water to obtain a slurry. In this step, a cross-linking agent for cross-linking SAP and an acidic substance for facilitating separation of SAP are added. In a preferred embodiment, a bleach sterilizing agent or a reducing agent may be added to the slurry. This step is preferably carried out using a pulper, and the use of a detractor is also preferred.

  Moreover, this invention is equipped with the process of isolate | separating and collect | recovering the fiber and SAP which are contained in sanitary goods. This step is preferably performed using a screen or a cleaner, and fibers and SAP can be efficiently obtained from the slurry.

Furthermore, in the present invention, the slurry containing the fibers may be dehydrated and the water obtained thereby may be reused.
From another point of view, the present invention can also be considered as a method for producing fibers and / or SAP from sanitary goods. According to the present invention, since fibers and SAP can be efficiently separated and collected from sanitary goods, it is usually possible to obtain fibers and SAP from used sanitary goods as waste.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to these. Unless otherwise specified, parts and% indicate parts by weight and% by weight, and numerical ranges are described as including the end points.

Experiment 1: Evaluation test for SAP particle formation The following experiment was conducted to confirm the effect of promoting water separation (particle formation) due to pH decrease for SAP swollen with water. The SAP used was Aqua Keep SA60S (acrylic acid polymer) manufactured by Sumitomo Seika Co., Ltd. After SAP was diluted 600 times with pure water and sufficiently swollen, calcium chloride (crosslinking agent) was added and reacted sufficiently, and then sulfuric acid or a sulfuric acid band was added and stirred. Thereafter, the pH of the SAP swelling liquid was measured, and the deposition state of the SAP particles was visually confirmed. Table 1 shows the types and amounts of chemicals used in each experimental example and the evaluation results.

  By adding calcium chloride as a crosslinking agent, the fluidity of the SAP swelling liquid was improved (see Test 1 and Test 2). However, the SAP particles formed in Test 2 are gel-like particles of about 2 to 5 mm and have a low specific gravity, so it was difficult to settle.

  In addition, when sulfuric acid band or sulfuric acid, which is an acidic substance, is added, adjustment to pH 6.0 or lower, that is, pKa or lower of polyacrylic acid, which is the main component of SAP, promotes water separation from SAP, and SAP is resinous. It was confirmed that the particles became particles and settled as soon as they were stirred and allowed to stand (Tests 3 to 6: Sulfuric acid band, Tests 7 and 8: Sulfuric acid). However, when the amount of the sulfate band added was large, calcium sulfate was precipitated (Tests 4 to 6).

Experiment 2: Evaluation Test Regarding Separation Efficiency of Fiber and SAP The following experiment was conducted in order to confirm the effect of improving the separation efficiency of fiber and SAP from used sanitary goods. The sanitary article used was an Oshime pad made by Nippon Paper Crecia (SAP component was about 15%, SAP / fiber weight ratio: about 15/85).

  In order to reproduce the state of a used paper diaper, physiological saline was absorbed into the urine pad. Thereafter, the squeeze pad is cut, heated to a liquid temperature of 60 ° C. with a tab-type high-concentration disintegrator for lab testing, heated to a liquid temperature of 60 ° C., and disaggregated for 6 minutes. Dilute with tap water to a concentration of about 1%. As a result, the urine pad was crushed and dispersed.

Adding a chemical during the disaggregation treatment is referred to as pre-addition, and adding the chemical after dilution after the disaggregation treatment is referred to as post-addition.
Sodium hypochlorite (bleaching disinfectant) and calcium chloride (crosslinking agent) were added in advance, and the pH was adjusted using sulfuric acid or a sulfuric acid band as an acidic substance (Tests 7 and 8). In tests 7 and 8, when the free chlorine of the sample after the pre-addition was measured, no free chlorine was present. In addition, calcium chloride was added before and after (tests 5 and 6). In addition, sodium hypochlorite was added in advance, calcium chloride was added in advance or after, and acidic substances were not added (Tests 1 to 4).

  Thus, each raw material to which the chemicals were added was separated into a fiber component and an SAP component using a test flat screen having a slit width of 6/1000 inches. Each of the accept (passed through the screen) and reject (passed through the screen) was collected, dried and weighed to confirm the properties of the recovered raw material.

  The amount of chemicals used in this experiment (% by weight relative to the solid content weight of the sanitary product) and the evaluation results are shown in the following table. Tests 1 to 6 are examples in which pH adjustment with an acidic substance is not performed. In Test 1, the screen was completely clogged, and subsequent experiments could not be continued. In Tests 2 and 3, although not as much as Test 1, the screen was clogged. Therefore, the flat screen process must be performed while removing the clogging, and the process takes 2 hours or more, and the workability is difficult. In Test 4, the screen was not clogged so much, but not only SAP but also many fibers were mixed on the reject side. Also, SAP was missing on the accept side. This is presumably because the SAP is in a gel form, and the SAP particles are deformed and pass through the slit. Therefore, there is a difficulty in terms of separation efficiency.

  Tests 5 and 6 are examples in which calcium chloride as a crosslinking agent is added separately at the time of disaggregation and after dilution. In this case, as compared with Test 4, almost no clogging of the screen was observed, and almost no fibers were observed on the reject side. From this, it can be seen that when calcium chloride is added in portions, fibers and SAP can be separated efficiently.

  Tests 7 and 8 are examples in which a bleach disinfectant, a crosslinking agent, and an acidic substance are added. In this case, compared to Test 1, since the SAP becomes sandy particles by lowering the pH, the screen is not clogged at all, only the SAP particles are on the reject side, and the fibers are on the accept side. Only was observed. The rejection / acceptance weight ratio is almost the same as the SAP / fiber weight ratio of 15/85 in the product, so it can be said that the separation efficiency was high.

Experiment 3: SAP separation evaluation test 1
Using a high-concentration pulper (Aikawa Tekko, tab type), 400 kg of fiber sheets (total care system, fiber content 86.5%, SAP content 13.5% by weight) regenerated from used paper diapers, After adding water to a solid content concentration of 8.0%, calcium chloride with a solid content concentration of 10.6% (42.4 kg) is added, and the mixture is crushed for 10 minutes at a temperature of 40 ° C. The mixture was adjusted to pH 5.0, and further heated at a temperature of 90 ° C. with a 4-axis kneader (manufactured by Aikawa Tekko) supplied with steam. The slurry obtained by disaggregation in this way was diluted to a solid content concentration of 0.7%, and this was used as Sample A. In this experiment, materials other than fibers are called foreign matters.

(1) Cleaner treatment Sample A was subjected to LCC-150 Ramo Cleaner (manufactured by Aikawa Tekko Co., Ltd.) having a reject nozzle diameter of 8 mm, the pressure in the inlet side pipe was 0.320 MPa, the flow rate was 0.54 m ³ / min, It processed on the conditions whose pressure in outlet side piping is 0.065 Mpa.

  First, in order to confirm the influence of the slurry concentration in the cleaner treatment, the cleaner treatment was performed such that the concentration of the sample A was 1.05 wt%, 0.70 wt%, and 0.31 wt% at the cleaner inlet. (Tests 1-3).

  Further, in order to confirm the influence of the reject nozzle diameter of the cleaner in the cleaner processing, when the slurry concentration at the cleaner inlet was 0.31%, a test was performed in which the reject nozzle diameter was changed to 30 mm (Test 4).

In this experiment, the effect of the cleaner treatment was evaluated according to the following criteria.
<Foreign matter contamination rate>
Foreign matter contamination rate (%) = (foreign matter amount after treatment / foreign matter amount before treatment) × 100
A: Foreign matter contamination rate is 0% or more and less than 1.0%,
○: Foreign matter contamination rate is 1.0% or more and less than 5.0% Δ: Foreign matter contamination rate is 5.0% or more and less than 20.0% ×: Foreign matter contamination rate is 20.0% or more <rejection rate>
Reject rate (%) = (rejected solid content / solid content before processing) × 100
◎: Reject rate is 0% or more and less than 20% ○: Reject rate is 21% or more and less than 40% Δ: Reject rate is 41% or more and less than 60% ×: Reject rate is 61% or more <Operability>
○: Clogging does not occur and stable operation is possible. Δ: Clogging occurs to some extent, but operation is sufficiently possible / decrease in operation efficiency due to increase in treatment flow rate. ×: Clogging is likely to occur, and stable operation is difficult. / Dehydration failure occurs in the latter stage / Reduction in dust removal efficiency due to increased processing flow rate <Comprehensive evaluation>
◎: All evaluation items are ◎ or ○ ○: Overall evaluation is other than ◎ and × ×: One of the above evaluation items has × × The results are shown in the following table. As is clear from the table, when the concentration is 0.70%, there is the least amount of foreign matter mixed into the fiber, and the rejection rate (weight% of the material removed by the cleaner) is also low, from the viewpoint of operability (ease of handling). It was excellent. Further, when the concentration was 0.31%, there was a concern about a decrease in operation efficiency due to an increase in the treatment flow rate, but there was no particular problem and it was good.

On the other hand, when the cleaner inlet concentration was 1.05%, although there was no problem in continuation of operation, clogging with the reject cone occurred, and the rejection rate also deteriorated.
Further, regarding the reject nozzle diameter of the cleaner, in the case of 8.0 mm, there was little foreign matter mixed into the fiber, the rejection rate was low, and it was also excellent from the viewpoint of operability (easy handling). On the other hand, when the cleaner diameter is 30.0 mm, the rejection rate is increased (25.3% → 42.6%) compared to when the cleaner diameter is 8.0 mm, but the operability (ease of handling) is improved. From the point of view, there was no problem.

(2) Screen treatment Using a slit screen (GFC-400, slit width 0.15 mmst, manufactured by Aikawa Tekko Co., Ltd.), the pressure in the inlet side pipe was 0.110 MPa, the flow rate was 0.70 m ³ / min. The treatment was performed under the conditions that the pressure in the outlet side pipe was 0.060 MPa and the flow rate through the screen was 1.0 m / sec.

  At this time, in order to evaluate the influence of the slurry concentration in the screen treatment, the slurry concentration at the screen inlet was changed to 1.05%, 0.70%, and 0.43%, and the screen treatment was performed.

  The results of evaluating the effect of screen processing based on the same criteria as in (1) above are shown below. As is apparent from the table, when the screen inlet concentration was 0.70%, there was the least foreign matter contamination in the fiber, the rejection rate was low, and it was excellent from the viewpoint of operability (ease of handling). When the screen entrance concentration was 0.43%, the rejection rate increased slightly, but there was no particular problem and it was good. On the other hand, when the screen inlet concentration was 1.05%, although there was no problem in operation, clogging with reject cones was observed, and the rejection rate was also deteriorated.

(3) Combination of screen treatment and cleaner treatment Sample A was examined for treatment using a combination of cleaner treatment and screen treatment. Specifically, as shown in the following table, cleaner treatment and screen treatment (slit screen treatment, round hole screen treatment) were performed in combination.

Here, the cleaner process, the slit screen process, and the round hole screen process have different characteristics. That is, the cleaner treatment can effectively remove SAP contained in the used paper diaper raw material, but tends to be clogged with large foreign matters such as wrapping vinyl and nonwoven fabric. On the other hand, the round hole screen is excellent in removing large foreign matters such as wrapping vinyl and non-woven fabric, but tends to pass SAP as it is. In addition, the slit screen is excellent in removing foreign substances other than SAP, wrapping vinyl, and non-woven fabric, and is useful for obtaining good fibers with little foreign matter. However, the wrapping vinyl and non-woven fabric tend to be clogged. Are also prone to clogging.
<< Cleaner >> This is the same as the cleaner process in (1) above. The reject nozzle diameter was 8 mm, and the raw material concentration at the cleaner inlet was adjusted to 0.60%.
<< Slit Screen >> It is the same as the screen processing in (2) above. The raw material concentration at the screen inlet was adjusted to 0.60%.
≪Round hole screen≫ Using a round hole screen (hole diameter 2.2 mm, FR-400 type, manufactured by Aikawa Tekko), the pressure in the inlet side pipe is 0.10 MPa, the flow rate is 1.0 m ³ / min, the outlet side The raw material was processed under operating conditions where the pressure in the pipe was 0.05 MPa. The raw material concentration at the screen inlet was adjusted to 0.80%.

In this experiment, the effects of various treatments were evaluated according to the following criteria.
<Foreign matter contamination rate>
Foreign matter contamination rate (%) = (foreign matter amount after treatment / foreign matter amount before treatment) × 100
◎: 0% or more and less than 1.0% ○: 1.0% or more and less than 5.0% △: 5.0% or more and less than 25.0% ×: 25.0% or more <Operability>
◎: There is almost no possibility of clogging and stable operation is possible. ○: There is concern about the possibility of clogging, but continuous operation is sufficiently possible. △: Some clogging occurs, but operation is possible. Yes x: Clogging occurs and continuous operation is not possible <Comprehensive evaluation>
◎: All evaluations are ◎ or ○ ○: Evaluation is one of ◎ or ○ △: All evaluations are △ ×: One of the above evaluation items is × The results are shown in the table below, and when first treated with a round hole screen, vinyl and non-woven fabric can be removed efficiently, so the subsequent slit screen and cleaner treatment removes SAP without causing clogging. It was possible and was the best from the viewpoints of appearance and operability (Tests 1 to 4). In particular, as in Test 2, after treatment with a round hole screen, treatment with a cleaner and a slit screen sequentially removes the packaging vinyl / nonwoven fabric, SAP, and other foreign matters to obtain good fibers with very few foreign matters. I was able to. Since foreign substances having different sizes and hardnesses are accurately removed, the operation stability is also excellent.

  In addition, when first treated with a cleaner, vinyl and non-woven fabrics may be clogged, and although it is inferior in terms of stability of continuous operation, removal efficiency for foreign substances such as SAP is very high and good fibers are obtained. (Tests 5 to 8).

  In addition, when treated with a slit screen for the first time, the slit screen is clogged with vinyl or non-woven fabric, and when a large amount of raw material is processed continuously, SAP may be clogged. Alternatively, by performing the cleaner treatment, foreign substances such as SAP can be sufficiently removed, and good fibers can be obtained (Tests 9 to 12).

  When the treatment was performed only with the slit screen, the SAP removal efficiency tended to decrease (Test 13). In addition, when the slurry was separated and collected only with a cleaner, when the vinyl was sufficiently removed with a pulper or the like, clogging was not observed so much and the resulting fiber was good (Test 14).

Experiment 4: SAP separation evaluation test 2
A 2 kg (10 pants type, 30 pad type) disposable diaper made by Nippon Paper Crecia is soaked with 4.6 kg of physiological saline (0.9% sodium chloride solution) assuming urine, and a plastic bag for combustible garbage Stuffed.

  110 pieces of this plastic bag, that is, 220 kg of disposable diaper, is packed in high-concentration pulper (Aikawa Tekko: tab-type high-concentration pulper) filled with water (approximately 2,750 L) at a liquid temperature of 40 ° C., and calcium chloride dihydrate. Was added together with 30.0 kg (addition amount of calcium chloride to the solid weight of the disposable diaper: 12.1 wt%) to a solid content concentration of 8%, adjusted to pH 4.7 with concentrated sulfuric acid, and then crushed for 10 minutes did. The crushed slurry was diluted with water to obtain a slurry having a solid content concentration of 4.9% by weight. The fiber content in the solid content of the slurry was 70.2% by weight, and the SAP content was 29.8% by weight.

Next, the slurry was diluted with water so as to have a solid content concentration of 0.7%, and then screened. Specifically, using a 2.20 mm round hole screen (FR-400 type; manufactured by Aikawa Tekko), the pressure in the inlet side pipe is 0.10 MPa, the flow rate is 1.01 m ³ / min, The slurry was screened under a pressure of 0.05 MPa, and Sample B was collected.

(1) Detrusher treatment In order to evaluate the effect of the detrusher treatment, the above-mentioned sample B was further treated with a detrusher. Specifically, Sample B was processed at a rotational speed of 20 rpm using a MAX drum (Detrusher manufactured by Aikawa Tekko Co., Ltd.) to obtain Sample C.

  Sample B and sample C are treated with a round hole strainer (round hole: φ2.20 mm) to remove giant foreign matters, and fibers and SAP contained in the slurry after treatment are quantified and separated from 220 kg of raw paper diaper waste. -Confirmed the percentage of materials recovered (recovery rate).

  The results are shown in the following table, and it was possible to improve the recovery rate of fibers and SAP from disposable diaper waste by 13.5 points (43.6 → 57.1%) by the detrusor treatment. This is probably because the raw material that could not be disaggregated by the pulper alone could be sufficiently disaggregated by processing with the MAX drum, so that the recovery rate was improved.

(2) Quantification of recovered SAP The sample C was treated in the order of “round hole screen, slit screen, cleaner” in the same manner as in test 4 of Experiment 3 (3) to obtain a slurry (sample D ).

SAP was quantified for sample C and sample D. Specifically, after adjusting the raw material to a solid content concentration of 0.7%, 4% cobalt chloride (II) hexahydrate aqueous solution was added to 300 ml of this raw material slurry (corresponding to an absolute dry weight of 2 g), SAP was stained. Thereafter, using this slurry, a hand-made sheet having a basis weight of 60 g / m ² was produced using a round hand-made machine based on JIS P 8209, and was measured with a foreign substance measuring device EasyScan (manufactured by Nippon Paper Unitech). Based on the measurement conditions of JIS P 8208, the number and area per square meter of SAP dyed in indigo were measured.

  The results are shown in the table below. Compared to sample C, sample D has significantly less SAP and selectively separates and recovers fibers from sanitary products by treating the slurry with a screen and cleaner. It was confirmed that it was possible.

Claims (13)

  A method for treating used sanitary goods, comprising at least a step of disaggregating the sanitary products and dispersing them in water, and a step of separating and collecting fibers and SAP contained in the sanitary products, wherein the sanitary products are disaggregated and water is separated. A processing method comprising adding a cross-linking agent and an acidic substance in the step of dispersing in an aqueous solution.   The method according to claim 1, wherein a bleaching disinfectant is further added in the disaggregation dispersion step.   The method according to claim 1 or 2, wherein calcium chloride is added as a crosslinking agent and disaggregation is performed at a concentration of 3.0 to 20.0%, and then an acidic substance is added.   The method according to any one of claims 1 to 3, wherein an acidic substance is added after diluting the slurry concentration to 2% or less after disaggregation.   The method according to claim 1, wherein the acidic substance is added to adjust the pH of the slurry to 6 or less.   The method according to claim 1, comprising adding a reducing agent in advance before adding the acidic substance.   The method in any one of Claims 1-6 including heating in one or more places among processes.   The method according to any one of claims 1 to 7, wherein a tab-type pulper is used to disaggregate sanitary products.   The method according to claim 8, wherein the tab-type pulper has a separating pulper and / or a detractor immediately after.   The method according to claim 8 or 9, wherein the tab-type pulper has a rope plugger.   The method according to claim 1, wherein the separation and recovery step is performed using a screen and / or a cleaner.   The method according to any one of claims 1 to 11, wherein in the separation and recovery step, the dispersion containing fibers is washed and dehydrated using a vertical washer, and the dehydrated water is used as in-process water. .   The method according to any one of claims 1 to 12, wherein in the separation and recovery step, a secondary or higher cascaded or forwarded separation apparatus is used.

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