WO2008090938A1

WO2008090938A1 - Method for producing activated carbon and recycle system of waste film

Info

Publication number: WO2008090938A1
Application number: PCT/JP2008/050928
Authority: WO
Inventors: Masayoshi Nagata; Ryou Takeda; Noboru Ishibashi; Kazuyoshi Yamamoto; Yoshio Hara
Original assignee: Fujifilm Corporation
Priority date: 2007-01-24
Filing date: 2008-01-17
Publication date: 2008-07-31
Also published as: KR20090103997A; KR101434285B1; TW200838798A; JP2008201664A; JP5084024B2; CN101588991A

Abstract

An activated carbon production apparatus (10) has a carbonization device (12) and an activation device (13). The carbonization device (12) has a carbonization furnace (20). The activation device (13) has a rotary kiln (30) and a gas supply source (31). In the carbonization furnace (20), a waste film (15) is carbonized into a carbonized film (24). Inside the rotary kiln (30) is heated to a temperature of not less than 750°C and not more than 950°C using an electric heater (43). A carbon dioxide gas (45) is fed from the gas supply source (31) to the rotary kiln (30). The carbonized film (24) is put in the rotary kiln (30), and activated while being stirred by rotation of the rotary kiln (30). Thus, an activated carbon (50) is produced from the carbonized film (24).

Description

DESCRIPTION

METHOD FOR PRODUCING ACTIVATED CARBON

AND RECYCLE SYSTEM OF WASTE FILM

Technical Field

The present invention relates to a method for producing activated carbon wherein a waste cellulose acylate film is reused as a raw material of the activated carbon, and a recycle system of the waste film.

Background Art

Polymer films have excellent optical transmittance and flexibility and are capable of forming thin and lightweight films. Owing to this, the polymer films are widely used as optical functional films. In particular, a cellulose acylate film (hereinafter referred to as a film) formed of cellulose acylate and the like has toughness and low birefringence in addition to the above properties. The film is used as a protection film for a polarizing filter incorporated in a panel, namely, a liquid crystal display (LCD) whose market is recently expanding.

In a polarizing filter production process, in which the polarizing filters are produced, approximately 30% of the total amount of supplied films is discarded. The discarded films (hereinafter referred to as waste films) are rapidly increasing in accordance with rapid market expansion of the polarizing filters. However, reuse and recycle systems, such as a reuse system of wastepaper and a recycle resin forming system of waste plastics, have not been developed for the waste films. Waste films have been burned or disposed of in landfills at additional waste-processing expense.

However, reusing of the waste films is desired from the viewpoint of recent environmental problems and resource saving trends. As methods to reuse the waste films, there are a method to selectively isolate cellulose acylate which is the raw material of the films from the waste films, a method in which the waste films are used as raw materials for molding, and the like. However, in the former method, it is difficult to selectively isolate only the cellulose acylate from the waste films since several additives are added during the film production. In the latter method, the waste films cannot be used as the raw material for molding, since cellulose acylate does not have a melting point and is decomposed by heat.

It is well known that paper and wood, which are biomass, and thermosetting resin represented by phenol resin become porous structures by heating without causing liquefaction. On the contrary, the thermoplastic resin is melted by heating, but does not become a porous structure by carbonization. Carbonization behaviors of cellulose acylate which is melted and decomposed by heating has not been clarified.

A method which reuses wastepaper such as old newspaper and the like as a raw material of activated carbon is known (see, Japanese Patent Laid-Open Publication No. 11-171524). Furthermore, a method which reuses phenol resin-based wastes as raw materials of activated carbon is known (see, Japanese Patent Laid-Open Publication No. 7-172808) . As described above, there have been no references or researches describing whether the waste films can be the raw material of the activated carbon. Japanese Patent Laid-Open Publication No. 11-171524 discloses a method to use pulps such as newspaper as the raw material of the activated carbon. However, in many cases, carbides generated by carbonization of waste materials do not have high adsorption property due to the above reasons. Accordingly, most of such carbides are used as soil improvement agents, fuels or the like, but not as adsorbents.

An object of the present invention is to provide a method for producing activated carbon wherein the waste film is reused as a raw material of the activated carbon, and a recycle system of the waste film.

Disclosure of Invention

In order to achieve the above and other objects, in a producing method of activated carbon according to the present invention, carbide is generated by carbonizing an organic substance which contains cellulose acylate as a main component.

The activated carbon is produced by activating the carbide.

It is preferable that the organic substance is a waste film cut into chips. It is preferable that the carbide is activated at a temperature of not less than 750⁰C and not more than 950⁰C.

It is preferable to use an oxidizing gas for the activation of the carbide. It is preferable that the carbide is activated while being stirred.

A recycle system of the waste film according to the present invention produces the activated carbon from the waste film by using the above activated carbon producing method. The activated carbon produced from the waste film has adsorption property equivalent to that of activated carbon produced from palm shell and coconut shell. The produced activated carbon is used as, for example, an adsorbent for solvents generated during the film production.

According to the present invention, activated carbon having adsorption property is produced from the waste film.

Brief Description of Drawings

Fig. 1 is a schematic diagram of an activated carbon production apparatus and a recycle system including the activated carbon production apparatus according to the present invention.

Best Mode for Carrying Out the Invention

In Fig. 1, an activated carbon production apparatus 10 includes a hopper 11, a carbonization device 12, and an activation device 13. A discarded film (hereinafter referred to as waste film) 15 is put into the hopper 11. The waste film 15 may be from, for example, a film production apparatus, a polarizing filter production apparatus, and the like. A rotary cutter 16 is attached to the hopper 11. The rotary cutter 16 cuts the waste film 15 into chips about 1 cm square. The chips of the waste film 15 are sent to the carbonization device 12.

A film is produced from the following raw materials in the film production apparatus. Unnecessary portions of the film become the waste film 15. Triacetyl cellulose (TAC) is preferable as cellulose acylate which is a main component of the film. The main component is a component having the largest weight ratio among the components contained in the film.

Aromatic hydrocarbons (for example, benzene, toluene and the like) , hydrocarbon halides (for example, dichloromethane, chlorobenzene and the like) , alcohols (for example, methanol, ethanol, n-propanol, n-butanol, diethyleneglycol and the like) , ketones (for example, acetone, methylethyl ketone and the like) , esters (for example, methyl acetate, ethyl acetate, propyl acetate and the like) may be used as solvents to dissolve cellulose acylate.

A dope is prepared from the above described cellulose acylate and the solvent (s) . The film is produced from the dope. At the time of dope preparation, additives such as plasticizers, deterioration inhibitors, UV-absorbers, optical anisotropy controllers, retardation controllers, dyes, matting agents, peeling agents, peeling improvers and the like, are added to the dope in accordance with the type of the film to be produced. The cellulose acylate is detailed in paragraphs [0140] to [0195] of Japanese Patent Laid-Open Publication No. 2005-104148. The above described solvents and additives are detailed in paragraphs [0196] and [0516] of Japanese Patent Laid-Open Publication No. 2005-104148.

The carbonization device 12 has a carbonization furnace 20. Installed inside the carbonization furnace 20 are a conveyer 21 and an electric heater 22. The carbonization furnace 20 has an inlet 23 for taking in the waste film 15, and an outlet 25 for discharging a waste film (hereinafter referred to as carbonized film) 24 carbonized in the carbonization furnace 20. An open-close shutter (not shown) is attached to each of the inlet 23 and the outlet 25. The shutters seal the inlet 23 and the outlet 25 to make the carbonization furnace 20 airtight during the carbonization of the waste film 15. In the present invention, carbonization means the conversion of a substance containing carbon into a substance composed of approximately 100% carbon atoms through pyrolysis and heating. The conveyer 21 is driven by a driving mechanism 27, and conveys the waste film 15. The electric heater 22 heats inside the carbonization furnace 20. It is preferable to make the temperature inside the carbonization furnace 20 not less than 450⁰C and not more than 600⁰C using the electric heater 22. It is preferable that the carbonization time is not less than 15 minutes and not more than 60 minutes. The waste film 15 is conveyed with the use of the conveyer 21. However, the conveying method of the waste film 15 is not limited to the above. For example, a rotary kiln 30, which will be described later, may be used. It is also possible to promote carbonization by feeding nitrogen to the carbonization furnace 20 to reduce oxygen concentration therein. By carbonizing the waste film 15 in the carbonization device 12, as described above, generation of dioxin due to burning of the waste film 15 is prevented. Furthermore, emission of carbon dioxide which is the cause of global warming is prevented. The activation device 13 has the rotary kiln 30 and a gas supply source 31. The rotary kiln 30 is a cylindrical pipe having a twisted blade 30a fixed to the inner circumference thereof. The rotary kiln 30 is provided with an inlet 34 and the outlet 35. The inlet 34 takes in the carbonized film 24 from the carbonization device 12. The outlet 35 discharges the carbonized film 24 activated in the rotary kiln 30. An open/close shutter (not shown) is provided to each of the inlet 34 and the outlet 35. The open/close shutters seal the inlet 34 and the outlet 35 to make the rotary kiln 30 airtight during the activation of the carbonized film 24.

An outer surface of the rotary kiln 30 is supported by rollers 36 so as to make the rotary kiln 30 rotatable. A sprocket wheel 40 is attached to the rotary kiln 30. The sprocket wheel 40 is driven by a driving mechanism 41. With a rotation of the sprocket wheel 40, the carbonized film 24 is conveyed through the rotary kiln 30 while being stirred.

An electric heater 43 is installed inside the rotary kiln 30. It is preferable to heat inside the rotary kiln 30 to a temperature of not less than 750⁰C and not more than 950⁰C using the electric heater 43. If the temperature is less than 750⁰C, activation, which is endothermic reaction, is extremely hindered. If the temperature exceeds 950⁰C, activation is excessively advanced, which results in low yield due to carbon volatilization. Moreover, installation cost increases so as to secure heat resistance.

A carbon dioxide (CO₂) gas 45 is fed from the gas supply source 31 to the rotary kiln 30 through a gas inlet tube 47 attached to the rotary kiln 30. The gas to be fed to the rotary kiln 30 is not limited to the CO₂ gas, and any oxidizing gas may be used, for example, water vapor, air, or a mixture of the above gases.

The carbonized film 24 is activated by the activation device 13. Fine carbides are removed from and a plurality of micropores are formed in the carbonized film 24. Owing to the micropores, the activated carbonized film 24 obtains significantly higher adsorption property compared to the carbonized film 24 before the activation. That is, activated carbon 50 is produced from the carbonized film 24 with the use of the activation device 13. The carbonized film 24 is activated while being stirred in the rotary kiln 30, and thus the activated carbon 50 having the adsorption property equivalent to activated carbon produced from palm shell and coconut shell is produced. Thus, a recycle system 71 which produces the activated carbon 50 from the waste film 15 is configured. Even if the waste film has a different additive composition, the recycle system is capable of producing high-adsorption activated carbon 50 regardless of the additive composition. A pulverizer 52 is installed downstream from the activation device 13, and pulverizes the activated carbon 50 into powders. The powdery activated carbon 50 is used as an adsorbent for adsorbing solvent gas generated in the film production apparatus. The solvent gas is evaporated from a volatile organic solvent such as methylene chloride. The activated carbon 50 may be used in a granular form using a sintering agent or a binder in accordance with the uses. The sintering agent bonds and solidifies the activated carbon by melting or causing structure changes through heating. The binder has a polymer structure and bonds and solidifies the activated carbon.

Next, an operation of the activated carbon production apparatus 10 is described. First, the waste film 15 discarded from the film production apparatus, the polarizing filter production apparatus, and the like is put in the hopper 11. The waste film 15 is cut by the rotary cutter 16 into chips. The chips of the waste film 15 are fed to the moving conveyer 21 through the inlet 23 of the carbonization furnace 20. When a certain amount of the waste film 15 is fed to the conveyer 21, the conveyer 21 is stopped and the inlet 23 is sealed by the open/close shutter. Thereby, the carbonization furnace 20 is made airtight, and carbonization of the waste film 15 is started. At this time, it is preferable that the carbonization furnace 20 is heated to a temperature of not less than 450°C and not more than 600⁰C using the electric heater 22. It is preferable that the carbonization time is not less than 15 minutes and not more than 60 minutes.

When the carbonization of the waste film 15 is completed, the outlet 25 of the carbonization furnace 20 is opened by opening the open/close shutter. The conveyer 21 is driven again and the carbonized film 24 is conveyed from the outlet 25 of the carbonization furnace 20 to the rotary kiln 30 of the activation device 13. The carbonized film 24 is put into the rotating rotary kiln 30 through the inlet 34 thereof. When a certain amount of the carbonized film 24 is put into the rotary kiln 30, the inlet 34 is sealed by the open/close shutter. Thereby, the rotary kiln 30 is made airtight, and activation of the carbonized film 24 is started. It is preferable to heat the inside of the rotary kiln 30 to a temperature of not less than 750⁰C and not more than 950⁰C using the electric heater 43. The CO₂ gas 45 is fed from the gas supply source 31 to the rotary kiln 30. The carbonized film 24 is activated while being stirred by the rotation of the rotary kiln 30. Activation time is adjusted so as to achieve 50% yield of the activated carbon 50. The activation time is also adjusted based on heating capacity of the electric heater 43 and a rotation speed of the rotary kiln 30.

When the activation of the carbonized film 24 is completed, the outlet 35 of the rotary kiln 30 is opened by opening the open/close shutter. The activated carbon 50 is discharged from the outlet 35. The discharged activated carbon 50 is pulverized by the pulverizer 52.

In this embodiment, the waste cellulose acylate film is used as the raw material of the activated carbon 50. However, the raw material is not limited to the above as long as it is an organic substance which contains cellulose acylate as the main component.

In this embodiment, the rotary kiln 30 is used for stirring the carbonized film 24. However, it is not limited to the rotary kiln 30. Any mechanism capable of increasing heat transmission efficiency and contact between the carbonized film 24 and the CO₂ gas 45 may be used. For example, stirring using a gas, that by vibration, or the like may be performed.

In this embodiment, the electric heaters 22 and 43 are used for heating the carbonization furnace 20 and the rotary kiln 30.

However, heating devices are not limited to them. A gas burner or the like may be used. It is also possible to burn an exhaust gas generated during carbonization and/or activation for heating.

In this embodiment, the carbonization device 12 and the activation device 13 are installed as individual devices. However, it is also possible to perform activation inside the carbonization device 12 by introducing the oxidizing gas therein after the carbonization. This configuration is used in a small-sized activated carbon production apparatus.

The activated carbon production apparatus 10 is used as a part of a recycle system 71 in which the waste film 15 is recycled and reused. The recycle system 71 has a solution casting apparatus

73 and the activated carbon production apparatus 10. In the solution casting apparatus 73, a cellulose acylate film (hereinafter referred to as film) 72 is produced from a dope containing cellulose acylate and a solvent. The solution casting apparatus 73 has a film producing section 75 and a solvent recovery section 76. In the film producing section 75, the dope is cast onto a support and peeled, and then the peeled film 72 is dried. In the solvent recovery section 76, the solvent evaporated in the film producing section 75 is recovered and refined, and then returned to the film producing section 75. The solvent refined in the solvent recovery section 76 is reused as a raw material of the dope in the film producing section 75. However, the configuration of the recycle system 71 is not limited to the above.

In the solvent recovery section 76, an adsorbing device (not shown) is installed. The adsorbing device recovers the solvent by adsorbing the solvent vapors and desorbing the adsorbed solvent . A gas containing the solvent vapors is sent from the film producing section 75 to the adsorbing device. The adsorbing device contains the activated carbon 50 which adsorbs the solvent from the gas sent from the film producing section 75. A gas for desorption is sent to the desorption device and comes in contact with the activated carbon 50. Thereby, the adsorbed solvent is desorbed and recovered.

In the film producing section 75, the waste film 15 is generated during the production of the film 72. The waste film 15 is sent to the activated carbon production apparatus 10 and formed into the activated carbon 50. According to the recycle system of the present invention, the activated carbon 50 is produced from the organic substance containing cellulose acylate as the main component, and the produced activated carbon 50 is used as an adsorbent for the solvent vapors generated during the film production. [Example] Hereinafter, Experiments and a Comparative experiment are described as specific examples of the present invention. However, the following Experiments and Comparative experiment do not limit the scope of the present invention.

[Comparative experiment] The inner temperature of the carbonization furnace 20 was set at not less than 350⁰C and not more than 600⁰C. The carbonized film 24 was obtained by carbonizing the chips of the waste film 15 for 15 minutes in the carbonization furnace 20. Activation was not performed to the carbonized film 24. The yield of the carbonized film 24 was 10 wt.%. The yield value is based on the weight of the chips used for carbonization. [Experiment 1]

The carbonized film 24 generated in the Comparative experiment was put in the rotary kiln 30. The inner temperature of the rotary kiln 30 was set at not less than 750 °C and not more than 950⁰C. The CO₂ gas 45 was fed from the gas supply source 31 to the rotary kiln 30 through the gas inlet tube 47 at a flow volume of 1 liter/min. The carbonized film 24 was activated while being stirred at 0.75 rpm in the rotary kiln 30 for 90 minutes. [Experiment 2]

The carbonized film 24 generated in the Comparative experiment was put in an electric furnace (not shown) . The inner temperature of the electric furnace was set at not less than 750⁰C and not more than 950⁰C. A gas inlet tube (not shown) was installed in the electric furnace. The CO₂ gas 45 was fed to the electric furnace through the gas inlet tube at a flow volume of 4 liter/min. The carbonized film 24 was activated in the electric furnace for 75 minutes.

Activated carbon 50 produced in the above Experiments 1 and 2 and the carbonized film 24 produced in the above Comparative experiment were cooled. Cooling means to leave the activated carbon 50 and the carbonized film 24 to cool by themselves without using any cooling devices. After the cooling, adsorption properties were measured by passing iodine and methylene chloride individually through the activated carbon 50 of the Experiments 1 and 2 and the carbonized film 24 of the Comparative experiment. The adsorption amounts of the iodine and the methylene chloride were measured pursuant to JIS (K1474) . The results are shown in Table 1. In the Table 1 and the following description, the activated carbon produced from palm shell and coconut shell is referred to as palm shell and coconut shell activated carbon.

[Table 1]

In the Table 1, the column of "iodine" shows values obtained by dividing an adsorption amount (mg) of iodine by an amount (g) of the activated carbon 50 or the carbonized film 24 used. A column of "methylene chloride" shows values obtained by dividing an adsorption amount (g) of methylene chloride by an amount (g) of the activated carbon 50 or the carbonized film 24 used.

As shown in the Table 1, the activated carbon 50 produced in the Experiments 1 and 2 has the adsorption property equivalent to that of the palm shell and coconut shell activated carbon. The iodine adsorption amount of the palm shell and coconut shell activated carbon was 1064 (mg/g) , and the methylene adsorption amount thereof was 0.55 (g/g) .

Industrial Applicability

The present invention is suitable for the production of the activated carbon using the waste film from the film production apparatus, polarizing filter production apparatus, and the like, and the recycle system of such waste film.

Claims

1. Aproducing method of activated carbon comprising the steps of: generating carbide by carbonizing an organic substance which contains cellulose acylate as a main component; and activating said carbide.

2. The producing method of claim 1, wherein said organic substance is a waste film cut into chips.

3. The producing method of claim 1, wherein said carbide is activated at a temperature of not less than 750⁰C and not more than 950⁰C.

4. The producing method of claim 1, wherein an oxidizing gas is used for said activation of said carbide.

5. The producing method of claim 1, wherein said carbide is activated while being stirred.

6. A recycle system of a waste film, wherein activated carbon is produced from said waste film by using said producing method of activated carbon of claim 2.

7. The recycle system of claim 6, wherein said activated carbon is used as an adsorbent of a solvent generated during production of a film.