JP7188905B2 - Cellulose nanofiber manufacturing method and manufacturing apparatus - Google Patents

Description

The present invention relates to a method and apparatus for producing cellulose nanofibers.

Nano-order fibers, so-called nanofibers, which are made by making fibers as thin as possible, are attracting a great deal of attention. Cellulose nanofibers, which are among this type of nanofibers, are derived from plant fibers produced from wood fibers, so they are a renewable resource and have a low environmental impact in terms of production and disposal, so they are attracting attention in various fields. It is

Cellulose nanofibers are fibers having nano-level fiber diameters of 1000 nm or less, and their dispersions have high transparency. Therefore, it is expected to be applied to applications requiring transparency, such as optical films, coating agents for films, compounding with glass, and the like.

The cellulose nanofibers can generally be obtained by defibrating chemically modified cellulose fibers with a mechanical shearing force (see Patent Document 1). As for the method for producing cellulose nanofibers, various production methods including the production method described in Patent Document 1 have been investigated.

Cellulose fibers are made from natural cellulose isolated from softwood or broadleaf tree wood pulp, cotton pulp, straw pulp or other non-wood pulp, etc., and are oxidized to obtain reactant fibers. It is obtained by a refining step of removing and obtaining reactant fibers impregnated with water, and a dispersing step of dispersing the water-containing reactant fibers in a solvent. Moreover, it is preferable that the natural cellulose used as a raw material is generally available, and since it is generally available, it may contain various impurities. In Patent Document 1, in the refining process, water washing and filtration are repeated using a device such as a strainer to obtain a dispersion of high-purity reactant fibers and water.

Further, Patent Document 2 proposes a papermaking chest provided with a transport section having a foreign matter removing function for removing foreign matter mixed in raw materials, fillers, or stock during the paper manufacturing process. .

Japanese Unexamined Patent Application Publication No. 2008-1728 JP 2016-132848 A

However, if impurities or other foreign substances are mixed in, the quality of the product is naturally degraded. There is a risk that clogging will stop operation or damage the device. Even in the case of filtering as described above, the size of the opening of the strainer cannot be such that the pulp fibers can pass through. It becomes impossible to remove the foreign matter containing the magnetic substance or the magnetic substance having a particle size.

In addition, it is inconvenient to divert the method of removing foreign matter in the papermaking process in which fibers of millimeter order are processed to the process of manufacturing cellulose nanofibers, which requires processing of nano-order fibers. Cellulose nanofibers manufactured by a device equipped with a foreign matter removing function are inevitably contaminated with foreign matter.

Therefore, the present invention provides a method and apparatus for producing cellulose nanofibers that remove even fine magnetic substances or foreign substances containing magnetic substances as much as possible so that the operation of the defibration device is not affected. It is intended to

As a technical means for achieving the above object, the method for producing cellulose nanofibers according to the present invention uses natural cellulose as a raw material to prepare a cellulose fiber dispersion in which fine cellulose fibers are dispersed in a desired solvent. In the method for producing cellulose nanofibers obtained, the inside of a raw material tank in which raw material slurry of cellulose nanofibers is stored is stirred by a stirring device, and the raw material slurry discharged from the raw material tank is discharged by a circulation pump connected to the raw material tank. The raw material slurry is returned to the raw material tank through a return pipe connected to the discharge side of the circulation pump, the raw material slurry is circulated between the circulation pump and the raw material tank, and a magnetic substance adsorption means having a magnet in the middle of the return pipe is arranged to adsorb magnetic substances or foreign substances containing magnetic substances mixed in the raw material slurry, and the raw material slurry to be treated is circulated between the circulation pump and the raw material tank for a desired time to remove the foreign substances. The raw material slurry is discharged and supplied to the next step, the raw material slurry to be processed next is supplied to the raw material tank, and the raw material slurry is transferred between the raw material tank and the circulation pump through the return pipe as desired. It is characterized in that magnetic substances or foreign substances containing magnetic substances are removed by batch processing by repeating time circulation to remove foreign substances and supply to the next process .

In carrying out this manufacturing method, a branching portion is provided in the middle of the return pipe to branch the supply pipe, and after circulation for a desired time, the raw material slurry can be supplied to the next step through the supply pipe.

Further, it is preferable that a magnetic substance attracting means is disposed between the circulation pump and the branching portion to attract foreign matter containing a magnetic substance or a magnetic substance.

Alternatively, a return-side switching valve may be arranged in the return pipe on the downstream side of the branched portion, and a magnetic material attracting means may be arranged downstream of the return-side switching valve to attract magnetic substances or foreign substances containing magnetic substances. preferable.

Further, it is preferable that a supply-side switching valve is arranged in the supply pipe, and a magnetic substance attracting means is arranged downstream of the supply-side switching valve so as to attract a magnetic substance or a foreign substance containing a magnetic substance.

Further, the cellulose nanofiber manufacturing apparatus according to the present invention is a cellulose nanofiber manufacturing apparatus that obtains a cellulose fiber dispersion in which fine cellulose fibers are dispersed in a desired solvent using natural cellulose as a raw material. A raw material slurry including a raw material tank for storing raw material slurry for fibers, a stirring device for stirring the raw material slurry in the raw material tank, and a circulation pump and a return pipe for discharging the raw material slurry from the raw material tank and returning it to the raw material tank. It consists of a circulation path and a magnetic adsorption means having a magnet arranged in the middle of the raw material slurry circulation path, and circulates the raw material slurry to be processed between the raw material tank and the circulation pump through the raw material slurry circulation path. While the magnetic substance adsorption means adsorbs a magnetic substance or a foreign substance containing a magnetic substance, the processed raw material slurry is discharged and supplied to the next process, and the next raw material slurry to be processed is supplied to the raw material tank. Circulating the raw material slurry between the raw material tank and the circulation pump through the raw material slurry circulation path to adsorb magnetic substances or foreign substances containing magnetic substances, and repeatedly supplying the material slurry to the next step, and performing batch processing . is characterized by

Further, it is preferable to provide a conduit switching means for switching supply of the raw material slurry discharged from the circulation pump to one or both of the return pipe and the supply pipe.

The pipeline switching means may comprise a return-side switching valve arranged in the return pipe on the downstream side of the branch and a supply-side switching valve arranged in the supply pipe.

Further, the channel switching means can be a three-way valve arranged at the branch.

Further, it is preferable to arrange the magnetic attraction means in one or both of the return pipe and the supply pipe on the downstream side of the pipe line switching means.

According to the method and apparatus for producing cellulose nanofibers according to the present invention, the raw material slurry stored in the raw material tank is stirred and circulated through the raw material slurry circulation path, and the magnetic material is placed in the middle of the raw material slurry circulation path. Since the adsorption means is provided, the magnetic substance or the foreign matter containing the magnetic substance mixed in the raw material slurry flowing through the raw material slurry circulation path is adsorbed and captured by the magnetic substance adsorption means. Moreover, since the magnetic attraction is used, the fibers in the raw material slurry are not damaged, and even fine magnetic substances or foreign substances containing magnetic substances that cannot be removed with a strainer or the like can be removed regardless of the size of the fibers. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a schematic configuration of a cellulose nanofiber manufacturing apparatus for explaining a cellulose nanofiber manufacturing method and manufacturing apparatus according to the present invention; 4 is a table showing the effect of removing foreign substances by the method and apparatus for producing cellulose nanofibers according to the present invention.

Hereinafter, the method and apparatus for producing cellulose nanofibers according to the present invention will be specifically described based on a preferred embodiment schematically shown in FIG.

A cellulose nanofiber production apparatus 1 according to the present invention includes a raw material tank 2 for storing a raw material slurry S to be processed , a circulation pump 3, magnetic adsorption means 4a and 4b, and a stirring device 8 for stirring the inside of the raw material tank 2. It is composed as the subject. Since it is necessary to supply the raw material slurry S processed by the cellulose nanofiber production apparatus 1 to the next step, it is preferable to provide the switching valves 5 and 6 and the magnetic adsorption means 7 as the apparatus.

A raw material slurry S is supplied to and stored in the raw material tank 2 . The stored raw material slurry S is stirred by the stirring device 8 . The stirring device 8 stirs the raw material slurry S by rotating a stirring blade 8a immersed in the raw material slurry S stored in the raw material tank 2 via a rotating shaft 8c of a driving motor 8b. A suction port of a circulation pump 3 is connected to the raw material tank 2 via a suction side pipe 9 .

A return pipe 10 is connected to the discharge port of the circulation pump 3 , and an open end 10 a of the return pipe 10 faces the raw material tank 2 . Alternatively, this open end 10 a is connected to the raw material tank 2 . Therefore, the raw material slurry S stored in the raw material tank 2 circulates between the raw material tank 2 and the circulation pump 3 so as to be discharged by the circulation pump 3 and returned to the raw material tank through the return pipe 10. It will be. That is, the suction side pipe 9, the circulation pump 3, and the return pipe 10 form a raw material slurry circulation path.

A branch portion 11 is provided in the middle of the return pipe 10 , and a supply pipe 12 is connected to the branch portion 11 . The return-side switching valve 5 of the switching valves 5 and 6 is arranged in the return pipe 10 on the downstream side of the branch portion 11 , and the supply-side switching valve 6 is arranged in the supply pipe 12 . In addition, the raw material slurry S is supplied to the next process such as the disentanglement process 13 through the supply pipe 12 , and is further supplied from the disentanglement process 13 to the subsequent process 14 .

The magnetic material attracting means 4a is the discharge side magnetic material attracting means 4a arranged in the return pipe 10 between the discharge port of the circulation pump 3 and the branch portion 11, and the magnetic material attracting means 4b is the return side switching valve 5. A return-side magnetic attraction means 4b is provided downstream. It is preferable to provide both of these magnetic attraction means 4a and 4b, but either one of them may be provided. Further, the magnetic material attracting means 7 is the supply side magnetic material attracting means 7 arranged downstream of the supply side switching valve 6 .

These magnetic attraction means 4a, 4b and 7 have a structure in which a permanent magnet is housed in a case made of stainless steel or the like. In contact with 4b and 7, magnetic substances or foreign substances containing magnetic substances mixed in the fluid are attracted and captured by magnets. There are various shapes depending on the nominal diameter of the pipe, including rod-shaped and lattice-shaped ones. In addition, as the material of the case, a material having good wear resistance and the like with respect to the properties of the fluid is used. A magnetic substance or a foreign substance containing a magnetic substance captured by the magnet is attracted to the outer surface of the case.

The operation of the apparatus for producing cellulose nanofibers according to the present invention constructed as described above will be explained, and the method for producing cellulose nanofibers by this apparatus will also be explained.

The return side switching valve 5 is opened and the supply side switching valve 6 is closed. The raw material slurry 2 stored in the raw material tank 2 is stirred by the rotation of the stirring blades 8 a of the stirring device 8 . Also, due to the operation of the circulation pump 3, the air is sucked through the suction port through the suction side pipe 9 and discharged to the return pipe 10 through the discharge port. When the raw material slurry S flowing through the return pipe 10 passes through the place where the discharge-side magnetic material adsorption means 4a is arranged, the magnetic material such as iron or the foreign matter containing the magnetic material mixed in the raw material slurry S may The magnetic material or the foreign matter containing the magnetic material is prevented from flowing downstream by being attracted and captured by the magnet of the ejection side magnetic material attracting means 4a. The raw material slurry S reaching the branching portion 11 flows through the return pipe 10 because the supply-side switching valve 6 is closed and the return-side switching valve 5 is open. For this reason, it passes through the place where the return side magnetic substance attracting means 4b is arranged, and the mixed magnetic substance or the foreign substance containing the magnetic substance is also attracted and captured by this return side magnetic substance attracting means 4b. It is separated from the raw material slurry S. The raw material slurry S flowing through the return pipe 10 is returned to the raw material tank 2 from the open end 10a and circulated between the raw material tank 2 and the circulation pump 3 while being stirred by the stirring device 8 in the raw material tank 2. be.

Since the raw material slurry S passes through the locations where the magnetic material adsorption means 4a and 4b are arranged in the course of circulation, the magnetic material or the foreign matter containing the magnetic material is separated each time it passes, and the raw material slurry S is separated. flow with is prevented. When the amount of mixed magnetic material or foreign matter containing a magnetic material is circulated for an appropriate number of times or for an appropriate amount of time and becomes equal to or less than the allowable value for use in the next process, the return-side switching valve 5 is closed and the supply is performed. The side switching valve 6 is opened. As a result, the raw material slurry S discharged from the circulation pump 3 is supplied after the magnetic substance or the foreign matter containing the magnetic substance is attracted and captured when passing through the place where the discharge side magnetic substance adsorption means 4a is arranged. It will flow through tube 12 . When the flow of the supply pipe 12 passes through the location where the supply-side magnetic material attracting means 7 is disposed, the mixed magnetic material or foreign matter containing the magnetic material is attracted, captured and separated. . This raw material slurry S is supplied to the next process such as the fibrillation process 13 . For example, the raw material slurry S supplied to the defibration step 13 is subjected to a fibrillation device such as a high-pressure homogenizer and subjected to mechanical shearing force to fibrillate.

As described above, the supply-side switching valve 6 is closed while the raw material slurry S is being circulated through the return pipe 10 . Slurry S does not flow. Therefore, during this circulating process, the magnetic substance attracting means 7 on the supply side can be removed from the supply pipe 12 and cleaned to remove the trapped magnetic substance or foreign matter containing the magnetic substance. On the other hand, since the return-side switching valve 5 is closed while the raw material slurry S is being supplied to the fibrillation step 13 , the raw material slurry S flows through the return pipe 10 downstream of the return-side switching valve 5 . do not have. Therefore, during this supply process, the return-side magnetic-substance attracting means 4b can be removed from the return pipe 10 and cleaned to remove the captured magnetic substances or foreign substances containing magnetic substances.
In order to take out the return-side magnetic material attracting means 4b and the supply-side magnetic material attracting means 7 in this manner, the pipes where these are arranged are detachable from the return pipe 10 and the supply pipe 12. FIG. That is, the magnetic attraction means 4b and 7 are arranged downstream of the return-side switching valve 5 and downstream of the supply-side switching valve 6, respectively, so that they can be easily cleaned.

Furthermore, since the circulation process for separating magnetic substances or foreign substances containing magnetic substances from the raw material slurry S is a batch type process, the raw material slurry S in the raw material tank 2 is emptied after being supplied to the fibrillation step 13. A new raw material slurry S to be processed is supplied to the raw material tank 2 which has been replaced. Since the circulation pump 3 is stopped while the raw material slurry S is being supplied, the raw material slurry S is not discharged from the circulation pump 3, so that the discharge side magnetic adsorption means 4a can be taken out. Therefore, while the raw material slurry S is being supplied to the raw material tank 2, the ejection side magnetic adsorption means 4a can be taken out and cleaned. When a shutoff valve is installed on the suction side or the discharge side of the circulation pump 3, the magnetic attraction means 4a, 4b and 7 can be cleaned at the same time by closing the shutoff valve.

In the above description, the return-side switching valve 5 is opened or closed, and the supply-side switching valve 6 is closed or opened. Both the side switching valve 5 and the supply side switching valve 6 may be half-opened so that part of the raw material slurry S is circulated and supplied to the defibrating step 13 .

A three-way valve can also be provided in the branch 11 , and the discharge side of the circulation pump 3 can be connected to either the return pipe 10 or the supply pipe 12 . When using a three-way valve, it is not necessary to arrange the return side switching valve 5 and the supply side switching valve 6 .

In the embodiment described above, the circulation pump 3 is used to supply the raw material slurry S both during the circulation process and during the supply process to the next step. A supply pump different from 3 may be connected to the raw material tank 2, and the supply to the defibration step 13 may be performed by this supply pump.

Furthermore, although the case where magnetic substances or foreign substances containing magnetic substances are separated in the previous stage of supplying the raw material slurry S to the fibrillation step 13 has been described, another step, for example, a pulp dissolving step for producing the raw material slurry S It is also possible to separate the magnetic material or the foreign matter containing the magnetic material in the preceding stage or the subsequent stage of the reaction process, the washing process of the produced raw material slurry S, the dehydration process, or the like.

The result of confirming the effect when magnetic substances or foreign substances containing magnetic substances mixed in the raw material slurry S by the above-described cellulose nanofiber production apparatus 1 are captured and separated by the magnetic substance adsorption means 4a, 4b, 7 is shown in FIG. 2. The result was confirmed by the operable time of the fibrillation device used in the fibrillation step 13. For comparison, the data in the case where the treatment for removing the magnetic material or foreign matter containing the magnetic material is not performed without using the cellulose nanofiber manufacturing apparatus 1 is also shown.
As a sample, a raw material slurry S of 1000 kg obtained by diluting pulp having an absolutely dry solid content of 10 kg to a concentration of 1% is put into the raw material tank 2 and stirred by the stirring device 8, and the circulation pump 3 is operated to return it. It was circulated from pipe 10 back to raw material tank 2 . The circulation rate was 15 L/min.
A rod-shaped magnet having a surface magnetic flux density of 10,000 gauss or more was placed in the pipe as the magnetic attraction means.

(Example 1)
The circulation treatment was carried out for 120 minutes, and the magnetic substance adsorption means 4a and 4b adsorbed and captured the foreign substances such as magnetic substances or foreign substances containing magnetic substances. The magnetic substance attracting means 4a and 4b were taken out, and the number of foreign substances attracted and trapped was visually counted. At this time, particles with a size of 0.2 mm ² or more shown in Annex JA "Visual foreign matter comparison chart" in JISP 8145 "Paper and paperboard-Evaluation method of foreign matter" were counted.
As a result, 1200 foreign objects were captured. When the raw material slurry S from which 1,200 foreign substances were removed was supplied to the defibrating device, continuous operation for 120 minutes could be performed.

(Example 2)
After performing the circulation process for 120 minutes and removing the magnetic substance adsorption means 4a and 4b that have adsorbed the magnetic substance or the foreign substance containing the magnetic substance, remove the trapped foreign substance and clean it, attach it to the return pipe 10, and perform the circulation process again. was performed for 120 minutes. When the magnetic attraction means 4a and 4b were taken out and the trapped foreign matter was counted, 200 foreign matter were trapped.
That is, it was circulated for 240 minutes to obtain a raw material slurry S from which a total of 1400 foreign substances were removed. When this raw material slurry S was supplied to the fibrillation device, continuous operation for 120 minutes or longer could be performed.

(Example 3)
The magnetic substance adsorption means 4a and 4b, which have been subjected to circulation treatment for 240 minutes to adsorb and capture magnetic substances or foreign substances containing magnetic substances, are removed, cleaned by removing the captured foreign substances, and attached to the return pipe 10, The circulation treatment was performed again for 120 minutes. When the magnetic attraction means 4a and 4b were taken out and the trapped foreign matter was counted, 50 foreign matter were trapped.
That is, it was circulated for 360 minutes to obtain a raw material slurry S from which a total of 1450 foreign substances were removed. When this raw material slurry S was supplied to the fibrillation device, continuous operation for 120 minutes or more could be performed.

Comparative Examples 1 to 3 all show the case where the above-mentioned sample is subjected to the defibration device without removing the foreign matter, and in Comparative Example 1, clogging occurs in the operation time of 5 minutes. stopped.
Further, in the case of Comparative Example 2, the operation was stopped after 15 minutes, and in the Comparative Example 3, the operation was stopped after 2 minutes.

That is, in the case of the sample, the defibration device could hardly be operated in a state where the foreign matter was not removed, whereas when the foreign matter was removed by arranging the magnetic adsorption means, the defibration device could not be operated. can be operated continuously without almost any trouble.

According to the method and apparatus for producing cellulose nanofibers according to the present invention, magnetic substances or foreign substances containing magnetic substances can be reliably removed from the raw material slurry, contributing to continuous operation of defibration equipment and the like in the next step without hindrance. Therefore, it is effective in improving the productivity of cellulose nanofibers.

1 Cellulose nanofiber manufacturing apparatus 2 Raw material tank 3 Circulation pump 4a Discharge side magnetic material adsorption means 4b Return side magnetic material adsorption means 5 Return side switching valve 6 Supply side switching valve 7 Supply side magnetic material adsorption means 8 Stirring device 8a Stirring blade 8b Drive motor 8c Rotating shaft 9 Suction side pipe 10 Return pipe 11 Branch portion 12 Supply pipe 13 Defibering step (next step)
14 Latter step S raw material slurry

Claims (12)

In a method for producing cellulose nanofibers in which natural cellulose is used as a raw material to obtain a dispersion of cellulose fibers in which fine cellulose fibers are dispersed in a desired solvent,
Stir the inside of the raw material tank in which the raw material slurry of cellulose nanofiber is stored with a stirring device,
The raw material slurry discharged from the raw material tank is returned to the raw material tank through the return pipe connected to the discharge side of the circulation pump by the circulation pump connected to the raw material tank. Circulating the raw material slurry between
A magnetic substance adsorption means having a magnet is disposed in the middle of the return pipe to adsorb magnetic substances or foreign substances containing magnetic substances mixed in the raw material slurry,
The raw material slurry to be treated is circulated between the circulation pump and the raw material tank for a desired period of time to discharge the raw material slurry from which foreign substances have been removed and supply it to the next step;
The raw material slurry to be processed next is supplied to the raw material tank, and the raw material slurry is circulated between the raw material tank and the circulation pump through the return pipe for a desired time to remove foreign matter, and the next process. repeatedly supplying to
A method for producing cellulose nanofibers , which comprises removing magnetic substances or foreign substances containing magnetic substances by batch processing . 2. The cellulose nanofiber according to claim 1, wherein a branching portion is provided in the middle of the return pipe to branch the supply pipe, and after circulation for a desired time, the raw material slurry is supplied to the next step through the supply pipe. manufacturing method. 3. The method for producing cellulose nanofibers according to claim 2, wherein a magnetic substance adsorption means is disposed between the circulation pump and the branching portion to adsorb a magnetic substance or a foreign substance containing a magnetic substance. disposing a return-side switching valve in the return pipe on the downstream side of the branched portion;
4. The method for producing cellulose nanofiber according to claim 2 or 3, wherein a magnetic substance adsorption means is arranged downstream of the return-side switching valve to adsorb a magnetic substance or a foreign substance containing a magnetic substance. . Disposing a supply side switching valve in the supply pipe,
5. The cellulose nano-particles according to any one of claims 2 to 4, characterized in that a magnetic substance adsorption means is arranged downstream of the supply side switching valve to adsorb foreign matter containing a magnetic substance or a magnetic substance. How the fiber is made. In a cellulose nanofiber production apparatus that obtains a cellulose fiber dispersion in which fine cellulose fibers are dispersed in a desired solvent using natural cellulose as a raw material,
a raw material tank for storing raw material slurry of cellulose nanofiber;
a stirring device for stirring the raw material slurry in the raw material tank;
a raw material slurry circulation path including a circulation pump and a return pipe for discharging the raw material slurry from the raw material tank and returning the raw material slurry to the raw material tank;
a magnetic material adsorption means having a magnet arranged in the middle of the raw material slurry circulation path,
The raw material slurry to be processed is circulated between the raw material tank and the circulation pump through the raw material slurry circulation path, and the magnetic material absorbing means adsorbs the magnetic material or foreign matter containing the magnetic material, thereby obtaining the processed raw material slurry. Discharge and supply to the next process,
A raw material slurry to be treated next is supplied to a raw material tank, and the raw material slurry is circulated between the raw material tank and the circulation pump through the raw material slurry circulation path to remove magnetic substances or foreign substances containing magnetic substances. An apparatus for producing cellulose nanofibers, characterized in that batch processing is performed by repeatedly adsorbing and supplying to the next step . 7. The cellulose nanofiber according to claim 6, wherein a branching portion is provided in the middle of the return pipe to branch the supply pipe, and after circulation for a desired time, the raw material slurry is supplied to the next step through the supply pipe. manufacturing equipment. 8. The apparatus for producing cellulose nanofibers according to claim 7, wherein the magnetic adsorption means is arranged between the circulation pump and the branch portion. 9. The cellulose nano-particles according to claim 7 or 8, further comprising a conduit switching means for switching supply of the raw material slurry discharged from the circulation pump to one or both of the return pipe and the supply pipe. Fiber manufacturing equipment. 10. The cellulose according to claim 9, wherein the channel switching means comprises a return-side switching valve arranged in the return pipe on the downstream side of the branch and a supply-side switching valve arranged in the supply pipe. Nanofiber manufacturing equipment. 10. The apparatus for producing cellulose nanofiber according to claim 9, wherein the channel switching means is a three-way valve arranged at the branch. 12. The method according to any one of claims 9 to 11, wherein the magnetic attracting means is arranged in one or both of the return pipe and the supply pipe on the downstream side of the pipe line switching means. cellulose nanofiber manufacturing equipment.

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