JP2003064535A - Active carbon cloth or active carbon sheet of polyvinyl alcohol, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture fibrous active carbon cloth or a fibrous active carbon sheet free from shrinkage unevenness and quality unevenness by using a PVA fiber in an industrially advantageous method. SOLUTION: A polyvinyl alcohol fiber is subjected to a hydration treatment, the dehydrated fiber is processed into a cloth or a sheet, and subsequently, it is carbonized and activated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyvinyl alcohol-based activated carbon cloth or activated carbon sheet and a method for producing them. The activated carbon cloth or activated carbon sheet according to the present invention,
It is suitable for applications such as water purification, air purification, gas adsorption, water treatment, decolorization, cigarette filters, clean room filters, etc., and also useful as an electrode material for secondary batteries, electrolytic capacitors, electric double layer capacitors, etc. .

[0002]

2. Description of the Related Art Conventionally, activated carbon has been used in food industry, chemical industry,
Widely used in the pharmaceutical industry and various other industries. As the activated carbon used for such an application, coconut shell, wood powder, activated carbonaceous materials such as coal with steam, gas, etc. are generally used, but in the field of adsorbents, the adsorption rate is Fibrous activated carbon is often used because of its speed and small pressure loss. In this case, the shape of the fibrous activated carbon is appropriately selected depending on the application, but for example, for the adsorption of gas, a sheet-shaped fibrous activated carbon is preferably used, and specifically, gas such as NOx and SOx is used. An example of using a polyacrylonitrile-based fibrous activated carbon sheet to adsorb is disclosed in JP-A-53-133591.

On the other hand, in recent years, electric double layer capacitors have been attracting attention as a backup power source and an auxiliary power source, and development focusing on the performance of activated carbon as an electrode of the electric double layer capacitor has been widely made and industrialized. . Conventionally, as activated carbon for electric double layer capacitor electrodes,
(1) Activated carbon obtained by activating resin material, palm shell, pitch, coal, etc. with steam, gas, etc. (See Large-capacity capacitor technology and materials, CMC Publishing (1998)),
(2) Activated carbon moldings obtained by carbonizing and activating a phenol resin foam (Japanese Patent Laid-Open No. 2-279915) and the like have been reported, but a fibrous activated carbon cloth is used because of its low resistance. In many cases, for example, Japanese Patent Application Laid-Open No. 64-82514 discloses an electrode made of activated carbon fiber cloth in which phenol fiber cloth or pitch fiber cloth is activated by carbonization.

As a method for producing a fibrous activated carbon sheet, a method in which a raw material fiber is preliminarily processed into a felt or sheet shape and then carbonized and activated is generally used. For example, JP-A-49-125665 discloses a pitch-based fibrous activated carbon sheet, and JP-A-51-198118 discloses a cellulose-based fibrous activated carbon sheet. JP-A-53-133591 discloses a polyacrylonitrile-based fibrous activated carbon sheet.

Among these, as for the pitch-based fibrous activated carbon sheet, the method for producing a raw material sheet or a raw material felt by melt spinning of pitch (hereinafter, the sheet or felt may be referred to as a sheet, etc.) is complicated, and particularly, When producing thin sheets, it is difficult to produce uniform and homogeneous sheets. Since the homogeneity and homogeneity of the raw material sheet and the like are directly reflected in the fibrous activated carbon sheet and the like as the final product, this method is difficult to adopt, particularly when it is used in applications where the homogeneity and homogeneity affect. Further, the manufacturing cost of the raw material sheet and the like is relatively high, and as a result, the cost of the fibrous activated carbon sheet and the like, which is the final product, becomes high.

On the other hand, in the case of producing a cellulosic or polyacrylonitrile-based fibrous activated carbon, the production of raw material sheets and the like is easier than that of pitch, but generally the weight yield during carbonization and activation is low, and as a result, This will increase the cost of the final fibrous activated carbon sheet. Further, since the shrinkage at the time of carbonization and activation is severe, even if the raw material sheet or the like is homogeneous, the fibrous activated carbon sheet or the like finally obtained is likely to have thickness unevenness or quality unevenness.

As a method for producing a fibrous activated carbon cloth, there is known a method in which a raw material fiber is preliminarily processed into a cloth shape and then carbonized and activated (for example, regarding a polyacrylonitrile-based material, Japanese Patent Laid-Open No. 62- No. 133124, and JP-A No. 60-35509 for phenol resin).
However, regarding the polyacrylonitrile-based, like the sheet, carbonization, it is likely to cause uneven thickness and quality unevenness of the final product due to shrinkage during activation, and in the case of the pitch-based, it is very difficult to produce the raw material cloth in the first place. is there. Also,
In the case of phenolic resin type fibrous activated carbon, the strength of the raw material fiber is generally weak and it is difficult to process it into a cloth.
Since the raw material cloth is very expensive, there is a problem that the fibrous activated carbon cloth finally obtained becomes expensive. As described above, at present, a method for industrially producing an inexpensive and excellent quality fibrous activated carbon sheet or fibrous activated carbon cloth has not been established.

As mentioned above, as the raw material of the fibrous activated carbon, cellulose type fiber, phenol resin type fiber, polyacrylonitrile type fiber and the like are known.
An example using a polyvinyl alcohol fiber as an inexpensive and high performance fibrous activated carbon raw material has been reported. Polyvinyl alcohol fiber (hereinafter, polyvinyl alcohol is referred to as P
(Abbreviated as VA) is promising as a raw material for a new activated carbon in terms of strength, price, texture, adsorption performance, and the like, and is drawing attention. Up to now, fibrous activated carbon made from PVA-based fibers has been mainly used in JP-A-53-114925 and 59-59.
As disclosed in JP-A-187624 and JP-A-61-47827, it is obtained by a method of activating after applying or impregnating a dehydration catalyst to a PVA-based fiber and heat-treating it.

[0009]

The fibrous activated carbon made of PVA-based fiber has not been used in a sheet or cloth in the past, but as its use as an electrode for an electric double layer capacitor has recently received attention, There is an increasing demand for sheets or fabrics. However, as described above, although there are many reports on sheets or cloths made of industrially useful fibrous activated carbon, they have problems such as high price or complexity of industrial manufacturing method, while, Fibrous activated carbon made of PVA fiber is known as a raw material for new fibrous activated carbon in terms of strength, price, texture, adsorption performance, etc., but no report has been made on a cloth or sheet made of this. Is the actual situation. Therefore, an object of the present invention is to manufacture PV that is inexpensive and industrially easy to manufacture.
It is intended to provide a fibrous activated carbon cloth or a fibrous activated carbon sheet made of A-based fibers as a raw material and a method for producing them.

[0010]

Means for Solving the Problems In producing a sheet or cloth made of fibrous activated carbon using PVA-based fiber as a raw material, the present inventors have preferably dehydrated the PVA-based fiber as a raw material in advance. After that, after forming into a cloth or sheet,
It has been found that the target fibrous activated carbon cloth or sheet can be efficiently and easily obtained by carbonizing and activating this. That is, the present invention is an activated carbon cloth or activated carbon sheet made of fibrous activated carbon produced by using PVA-based fibers as a raw material.

Another invention of the present invention is PV.
A method for producing an activated carbon cloth or activated carbon sheet, which comprises carbonizing and activating after processing an A-based fiber into a cloth or sheet. Still another invention of the present invention is an activated carbon cloth or activated carbon sheet obtained by such a production method.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The PVA-based fiber used in the present invention is obtained from a PVA-based resin obtained by saponifying polyvinyl acetate or a copolymer thereof which is usually used in the production of PVA. Further, it can be obtained by decomposing a bulky vinyl ester having a side chain such as vinyl pivalate or vinyl formate or a highly polar vinyl ester, or a homopolymer or copolymer of vinyl ether such as t-butyl vinyl ether, trimethylsilyl vinyl ether or benzyl vinyl ether. You may use PVA type resin.

Here, the comonomer unit of the copolymer can be divided into a unit which produces a vinyl alcohol unit by saponification or decomposition and a unit other than the unit. The latter comonomer unit is mainly used for modification. It is copolymerized and is used within a range not impairing the gist of the present invention. Examples of such a unit include olefins such as ethylene, propylene, 1-butene, and isobutene,
Acrylic acid and its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate,
Acrylic esters such as t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid and its salts, methyl methacrylate, ethyl methacrylate, n methacrylate
-Propyl, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-methacrylic acid
-Methacrylic acid esters such as butyl, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetyl acrylamide Acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts and quaternary salts, acrylamide derivatives such as N-methylolacrylamide and its derivatives, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N, N-dimethyl methacrylamide, diacetone methacrylamide, methacrylamide propane sulfonic acid and its salts, methacrylamide propyldimethylamine and its salts and quaternary salts,
Methacrylamide derivatives such as N-methylol methacrylamide and its derivatives, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t
-Butyl vinyl ether, benzyl vinyl ether, dodecyl vinyl ether, vinyl ethers such as stearyl vinyl ether, acrylonitrile, nitriles such as methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl fluoride, vinyl halides such as vinylidene fluoride, allyl acetate, Examples thereof include allyl compounds such as allyl chloride, maleic acid and salts and esters thereof, itaconic acid and salts and esters thereof, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate.

The degree of saponification of the PVA resin is preferably 70 mol% or more, more preferably 90 to 99.99 mol%. Here, the degree of saponification is the ratio of vinyl alcohol units after saponification to units that can be converted to vinyl alcohol units by saponification in a vinyl acetate homopolymer or copolymer, and the residue is vinyl acetate. It is a unit.
The degree of polymerization of the PVA-based resin is preferably 1000 or more, more preferably 1700 or more. However, PVA-based resins having a degree of polymerization of more than 30,000 are generally difficult to produce, and are not necessarily suitable from the viewpoint of industrial production.

The method for producing the PVA fiber is not particularly limited, but a known wet spinning method, dry wet spinning method or dry spinning method can be adopted. What is the wet spinning method?
This is a method in which a spinning solution containing a polymer solution obtained by dissolving a PVA-based resin in an organic solvent or an aqueous solution obtained by dissolving the PVA-based resin in water is directly spun from a spinning nozzle into a coagulation bath, which is a dry-wet spinning method. Is a spinning method in which a gas space (air-gap) such as air or an inert gas is provided between a spinning nozzle and a coagulation bath, the gas is run for a specific distance, and then spun into the coagulation bath. .

The wet spinning method in which the spinning nozzle is brought into direct contact with the coagulation bath for spinning is suitable for spinning using a multi-hole nozzle because fibers can be spun without sticking even if the nozzle hole pitch is narrowed. On the other hand, in the case of the dry-wet spinning method in which an air gap is provided between the coagulation bath and the spinning nozzle, and spinning is performed from the spinning nozzle through the gas, high elongation is achieved due to the large elongation in the air gap. Are suitable. The dry spinning method is a spinning method in which a spinning dope, which is an aqueous solution obtained by dissolving a PVA-based resin in water, is spun directly into a gas from a spinning nozzle, and does not require a coagulation bath. . The spinning method as described above may be appropriately selected and adopted according to the purpose and use.

Among the methods for producing PVA-based fibers, the method for producing PVA-based fibers by a solvent system using a polymer solution prepared by dissolving a PVA-based resin in an organic solvent as a spinning stock solution will be described in more detail. P that constitutes the spinning solution
Examples of the solvent for the VA-based resin include polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, butanediol, and organic solvents selected from dimethyl sulfoxide (DMSO), dimethylformamide, diethylenetriamine, and the like.
Alternatively, a mixed solvent of two or more kinds of these, and a mixed solvent of these organic solvents and water can be used.

From the viewpoint of spinnability, fiber performance, etc., the concentration of the PVA resin in the spinning dope is preferably 5 to 25% by weight, and the temperature of the spinning dope is generally 80 to 230 ° C. Further, boric acid, a surfactant, a decomposition inhibitor, a dye, a pigment and the like may be added to the spinning dope, as long as the effects of the present invention are not impaired. The spinning dope thus prepared is wet-spun or dry-wet spun in a coagulation bath through a spinning nozzle.

As the coagulating liquid for coagulating the spinning dope and making it into fibers, alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone are preferred organic solvents having a coagulating ability for PVA. . From the viewpoint of spinnability, fiber performance, etc., the coagulation bath is
It is preferable to include the same solvent as the spinning solution in the coagulating liquid,
For example, when DMSO is used as the solvent of the spinning dope, it is preferable that DMSO is contained in alcohol such as methanol or ethanol as a coagulation bath. In this case, the concentration of the spinning dope solution solvent in the coagulation bath is preferably 20 to 70% by weight, more preferably 25 to 65% by weight. Further, the ratio of the solvent used in the coagulating liquid / spinning stock solution is preferably 25/75 to 85/15 in weight ratio. Other additives may be added as long as the effects of the present invention are not impaired.

Further, from the viewpoint of reducing the coagulation reaction rate to form a sufficiently uniform gel structure inside the fiber, the temperature of the coagulation bath is preferably 30 ° C. or lower, more preferably 20 ° C. or lower, and 15 It is more preferable that the temperature is not higher than ° C. By adopting such a method, gelation becomes uniform in the cross-sectional direction, and a fiber with high crystallinity can be obtained without heat treatment or the like. From the viewpoint of reducing the sticking between fibers and facilitating the subsequent dry heat drawing, the Shinobu that has been separated from the coagulation bath contains the organic solvent at 20 to 60 ° C.
It is preferable to carry out wet heat stretching at a temperature of 2 to 10 times.

Next, the fiber is immersed in an extraction bath to extract the solvent. As the extractant, methanol, ethanol,
Alcohols such as propanol, acetone, methyl ethyl ketone, ether and water can be used. continue,
If necessary, an oil agent or the like may be added and dried. From the viewpoint of increasing the strength of the PVA-based fiber that is the raw material of the activated carbon, it is preferable to further carry out dry heat drawing, and especially the total draw ratio is 6 times or more, preferably 8 times or more, more preferably 9 times or more. It is preferable to stretch by dry heat. The total draw ratio is represented by the product of the wet heat draw ratio and the dry heat draw ratio.

As a method for producing PVA-based fibers, a method for producing PVA-based fibers by an aqueous solution system in which an aqueous solution of PVA-based resin is used as a spinning stock solution may be adopted. That is, a method of producing a PVA-based fiber by wet spinning or dry-wet spinning a spinning stock solution containing a PVA-based resin aqueous solution in a coagulation bath containing a concentrated electrolyte aqueous solution, and washing with water, drying, and dry heat drawing to produce a PVA-based fiber is also suitably used. If necessary, wet heat drawing may be performed as in the case of wet spinning, or an oil agent may be added.

In this case, the concentration of the PVA-based resin in the spinning dope varies depending on the degree of polymerization of the PVA-based resin, but is 5 to 5.
It is preferably 30% by weight, especially 10 to 20% by weight. If the concentration of the PVA-based resin is too high, the viscosity of the undiluted solution may increase, which may make stable spinning difficult.
If the concentration is too low, the productivity will decrease, and the variation in single fiber thickness (denier unevenness) is likely to occur.
It is preferable to adjust the concentration of the PVA resin within the above range.

If desired, other additives may be added to the spinning dope. For example, one or more surfactants or inorganic substances may be added to the spinning dope in order to extend the life of the spinneret during spinning and enhance the stability of the drawing process. The additive is preferably added in an amount of 20% by weight or less, particularly 0.1 to 5% by weight in order to suppress defective dehydration and coagulation of Ishino. The types of surfactants are nonionic, anionic,
Any cation type or amphoteric type may be used, but 2
When more than one kind is used in combination, it is better to avoid a combination that causes precipitation (for example, anionic and cationic). It is particularly preferable to use a nonionic surfactant.

It is also possible to form a crosslinked structure when the polymer solution is discharged from the spinneret into the coagulation bath to make the structure of the fiber cross section uniform. For example, boric acid or boric acid may be added to the stock solution. Such a crosslinked structure can be formed by adding a salt. In this case, the total addition amount of boric acid and borate salts in the spinning dope is 0.03 to 0.2% by weight / total weight of the spinning dope, particularly 0.05 to 0.15% by weight.
The total weight of the spinning dope is preferably.

The coagulating liquid for spinning using an aqueous solution system is not particularly limited as long as it has a coagulating ability with respect to the spinning dope, but in view of processability and cost.
It is preferable to use a coagulating liquid using water as a solvent. Specifically, an aqueous solution of a salt having a dehydrating ability such as sodium sulfate (Glauber's salt), ammonium sulfate and sodium carbonate can be exemplified. The concentration of the aqueous solution can be selected from 300 g / liter or more to a saturated concentration, but it is preferable that the concentration is as close to the saturated concentration as possible because the dehydration coagulation ability is high. Among them, it is preferable to use a saturated aqueous solution coagulating bath from the viewpoints of processability and cost. The temperature of the coagulation bath is 20 to 70 ° C, especially 30 to 50 ° C
Is preferred. Further, when boric acid or a borate is added to the spinning dope, it is necessary to contain a substance such as sodium hydroxide in order to make the coagulation bath alkaline. For example, when sodium hydroxide is used, the concentration in the coagulation bath is preferably 0.5 to 3% by weight.

The spinning dope discharged from the spinneret into the coagulation bath is dehydrated and coagulated in the coagulation bath to form a yarn.
The bath is separated from the coagulation bath, and a roller stretching of about 1 to 4 times is performed. When boric acid or the like is added to the spinning dope and sodium hydroxide or the like is added to the coagulation bath to develop a crosslinked structure, an acid such as sulfuric acid is added to neutralize and remove the alkaline compound attached to the thread. It is necessary to pass a neutralization bath containing In this case, the concentration of sulfuric acid is 5-10
It is preferable to set the content to about% by weight. Next, in order to enhance the morphological stabilization of the thread, it is preferable to perform wet heat drawing in a high temperature saturated aqueous solution bath of salts having the same dehydrating ability as the coagulation bath.
The temperature of the saturated aqueous solution bath is preferably 90 ° C. or higher, and the wet heat stretching ratio is preferably about 1 to 4 times. The total draw ratio in the wet state is preferably set to 2 times or more, preferably 3 times or more and 8 times or less as the base point of the speed of the separating roller from the coagulation bath. When it is 8 times or more, the tension applied to the thread becomes too high, and fluffing or thread breakage may occur.

Next, in order to remove the salts, acids, boric acid, etc. adhering to the Shinoshino by washing, the Shinoshino is introduced into a water washing tank, and these contents in the fiber are washed away by running water. In such a washing step, it is preferable to wash the thread under tension from the viewpoint that the inorganic salts on the fiber surface and inside the fiber can be selectively removed and the swelling of the fiber can be suppressed more effectively. It is preferable to keep the tension constant. In order to more quickly and selectively remove inorganic salts on the fiber surface,
It is also possible to apply ultrasonic vibration to Itoshino in the bath or move it up and down in the bath. The temperature of the cleaning solution is 10 ~ 70 ℃
The swelling and sticking of the fibers can be effectively prevented by controlling the temperature to a constant temperature of 20 to 50 ° C.

Next, in order to suppress inter-fiber sticking that tends to occur after the drying step, an oil agent for preventing sticking may be attached to the thread after the washing step if desired. A conventionally known method, such as a method of impregnating and applying a thread on the oil agent tank, a method of contacting the thread on the surface of the roller with the oil agent, or the like can be adopted as the method of adhesion. PVA as the oil component
Good adhesion to the base fibers and drying temperature (100-150
Those that do not solidify even at (° C.) and do not increase the inter-fiber friction coefficient of PVA-based fibers are preferable. As such an oil agent, for example, a paraffin oil agent can be exemplified. The oil agent adhesion rate is preferably 1.2% by weight or less / PVA, more preferably 0.8% by weight or less, and particularly preferably 0 to 0.5% by weight / PVA.

Next, the wet thread is dried. 80 drying
It is preferably carried out by hot air heating at about 150 to 150 ° C., especially about 100 to 140 ° C. After drying it, it is stretched and wound up. The water content of Itoshino introduced in the drying process is 8
About 0 to 300% by weight / PVA, particularly 90 to 200% by weight / PVA, and more preferably 100 to 150% by weight is preferable from the viewpoint of prevention of sticking and drying efficiency. Then, it is preferable to perform drying until the water content of the shinobi that has undergone the drying step becomes 1% / PVA or less.

The PVA fiber is subjected to a drying step and then further stretched to obtain a PVA fiber having excellent mechanical performance. The method is not particularly limited, and the stretching can be performed in a generally applied stretching step. The total draw ratio is preferably 6 times or more, more preferably 7 times or more, further preferably 8 times or more. Furthermore, after stretching, if necessary, heat treatment, shrinkage treatment,
Various treatments such as oiling treatment and acetalization treatment may be performed.

Next, a dry spinning method which does not use a coagulation bath will be described. A PVA-based resin is made into a water-containing chip having a concentration of 40 to 60% by weight, heated and melted by an extruder, and defoamed. The temperature of the spinning dope is preferably 90 to 140 ° C. Such a PVA spinning dope is pressurized and discharged from the nozzle hole into the air for dry spinning. The nozzle hole may have a circular shape or any other shape other than the circular shape, such as a flat shape, a cross shape, a T shape, a Y shape, an L shape, a triangular shape, a square shape, or a star shape. However, the above-mentioned T-shaped, Y-shaped, L-shaped and other modified cross-section fibers may be broken during the production, but even if the fibers are broken, the purpose and effect of the present invention are not significantly impaired.

After that, it is dried to almost dryness. In order to prevent foaming during drying, it is preferable that the drying is performed at a temperature of 100 ° C. or less, and when the drying is performed to some extent, the drying is further performed at a temperature of 100 ° C. or more. Stretching is performed after drying. The stretching is 200 to 250 ° C.,
It is preferably carried out at a temperature of 220 to 240 ° C. The draw ratio is 5 times or more, preferably 6 times or more.
Stretching is performed in a hot-air type stretching furnace for about 20 seconds to 3 minutes. The fiber thus stretched is subjected to a fixed length heat treatment or a shrinkage treatment, if necessary.
If necessary, crimps or oils may be added to the fibers thus obtained.

Next, the PVA fiber is formed into a cloth or a sheet in the following manner. First, a method for forming a cloth will be described. Since PVA-based fibers can be processed by the same method as general synthetic fibers such as polyester fibers and nylon fibers are processed into woven fabrics and knits, there is no need for a special manufacturing method, It can be processed by the method. The shape of the thread used when processing into woven fabric or knitting is as required, such as when performing from a general filament state or when using a spun yarn manufactured by cutting the thread into a predetermined length. It is possible to respond appropriately. For example, in the case of a woven fabric, the weave design may be any of a plain weave, a twill weave, a twill weave, and the like. The same applies to knitting, and it is possible to appropriately select from various knitting methods such as weft knitting and warp knitting (for example, Raschel knitting and tricot knitting).

As a method for forming a sheet, a general processing method can be used as in the case of woven or knitted fabric. For example, a dry non-woven fabric produced by the hydroentanglement method (raw cotton cut into a predetermined length is formed into a wrap with a predetermined width, length, and weight using a card, and then high-pressure water is injected in the thickness direction of the wrap to produce short fibers. (Manufactured by the method of entanglement) or felt (manufactured by the method of making a predetermined wrap in the same manner as in the case of dry non-woven fabric and passing through a needle punching step to entangle short fibers)
The processing method such as is adopted. Here, as long as the gist of the present invention is not impaired, various binders other than the fibers may be used to maintain the sheet shape.

When the PVA-based fiber is formed into a woven or knitted (cloth) or sheet form, it is preferable to control the fiber density of the formed product as necessary. The reason for this is that when the molded product obtained by the above-mentioned production method is carbonized and activated to be activated carbon, a weight reduction occurs, and at the same time volume contraction also occurs, so that an increase in the fiber density per unit volume is prevented. This is because. The strong entanglement of short fibers in the state of the molded body before carbonization hinders this contraction movement, and in some cases, due to the tension generated by contraction, carbonization,
Since the short fibers may be cut or stuck during the activation process,
It is preferable to set appropriate entanglement (constraint) conditions for the short fibers. Further, since the fiber density per unit volume is the same, it is preferable to set appropriate conditions depending on the fiber specifications and the molding method.

For example, when a molded product after activation treatment is used for a capacitor electrode, the volume density of the molded product after activation treatment is preferably 0.1 g / cc or more, and the weight at the time of molding at the stage of carbonization and activation treatment. It is preferable that the relationship between the decrease and the volume shrinkage is obtained in advance, and the conditions are set at the time of molding the flat body so as to obtain a predetermined fibrous activated carbon.

When PVA-based fibers that have been dehydrated in advance are molded into a cloth or sheet and subjected to carbonization treatment and activation treatment, shrinkage of the fibers during carbonization treatment and / or activation treatment is suppressed. This is preferable because it can suppress unevenness in thickness, unevenness in shape, deterioration of quality, etc. of the finally obtained fibrous activated carbon cloth or fibrous activated carbon sheet. In the present invention, these spots appear in the density spots of the cloth-like or sheet-like material, which leads to variations in the performance of the activated carbon as the cloth-like or sheet-like material. Further, the unevenness of quality refers to disturbance of the surface of a cloth-like or sheet-like material due to fiber fluffs or pills, and fiber sticking. In the activated carbon cloth or activated carbon sheet of the present invention, the density unevenness is ±± of the average density.
It is preferable to be within 7%, and it is desirable to minimize or eliminate the grade unevenness.

The dehydration treatment of PVA fiber is usually carried out by heat treatment. The temperature of the dehydration treatment is appropriately selected depending on the form of the raw material fibers, the presence / absence of addition of a dehydration catalyst, and the intended use of the fibrous activated carbon cloth or sheet finally obtained.
The temperature is preferably 0 ° C or higher and 300 ° C or lower, more preferably 160 ° C or higher and 290 ° C or lower, and further preferably 180 ° C or higher and 280 ° C or lower. The dehydration process is
It may be carried out in one step or may be carried out in two or more steps. Further, it may be carried out under tension, may be carried out under no tension, and may be carried out continuously or batchwise. From the viewpoint of the productivity of the dehydration treatment, it is preferable to continuously dehydrate the raw material PVA fiber under tension.

The dehydration treatment time is appropriately determined depending on the form of the raw material fibers, the presence or absence of addition of a dehydration catalyst, and the intended use of the finally obtained fibrous activated carbon sheet or cloth, but if the treatment time is too short, the weight loss will be sufficient. If it is too long, not only the productivity decreases, but also the pyrolysis reaction, which is a side reaction, accompanies the decrease in weight, and as a result, the weight yield of the finally obtained fibrous activated carbon is increased. May decrease, so it is preferable to carry out in 20 seconds to 2 hours. The atmosphere of the dehydration treatment may be an oxidizing gas atmosphere or a non-oxidizing gas atmosphere.

In order to accelerate the dehydration reaction, it is also effective to add a dehydration catalyst to the PVA fiber, mix it, and apply it on the surface. The dehydration catalyst is not particularly limited, but various acidic compounds are preferably used, for example. The acidic compound can be appropriately selected from known compounds, and specific examples of such compounds include various metal Lewis acids, sulfuric acid, sulfates, hydrochloric acid, hydrochlorides, phosphoric acid, phosphates and the like. You can

In the dehydration treatment, the weight yield of the dehydrated fibers to the raw material fibers is 60 to 85%, preferably 62 to 82.
%, More preferably 65 to 80%. If the weight yield is too low, the thermal decomposition reaction, which is a side reaction, becomes difficult to avoid, and the weight yield of the resulting fibrous activated carbon also decreases. On the other hand, if the weight yield is too high, when the reaction is stopped, the PVA fiber may be easily melted, melted, or stuck in the carbonization treatment and / or activation treatment step described later.

The PVA-based fibers may be dehydrated by a so-called filament, spun yarn or the like, or a tow shape, and then formed into a cloth or sheet. Alternatively, the cotton shape cut in advance to a predetermined length may be dehydrated and then formed into a sheet shape, or may be spun into a cloth shape or a sheet shape. The desired fibrous activated carbon cloth or fibrous activated carbon sheet can be obtained by carbonizing the cloth or sheet made of the dehydrated PVA-based fibers obtained as described above and then activating the cloth or sheet.

The carbonization treatment is not particularly limited as long as the cloth or sheet made of PVA-based fibers does not undergo a significant weight reduction during activation so long as it forms an aromatic ring structure to some extent, but heating to 350 to 650 ° C. is preferable. .
It is more preferable to hold the temperature between 200 and 250 ° C. for about 1 hour to allow the dehydration reaction to proceed. The reason for this is PVA
Has a softening point around 220 to 240 ° C., and when heat treatment is suddenly performed at a high temperature, PVA melts,
The activated carbon performance finally obtained may vary.
It is also effective to hold at 400 ° C to 500 ° C for 1 hour. The reason is that the dehydrogenation reaction is promoted by such an operation. If the heat treatment is stopped at 300 ° C. or lower, the dehydrogenation reaction does not proceed, so the yield after activation may be low.

The carbonization treatment may be carried out in an oxidizing gas atmosphere or a non-oxidizing gas atmosphere, but it is preferably carried out in an oxidizing gas atmosphere. The reason why it is effective to use an oxidizing gas as the atmosphere for carbonization is not necessarily clear, but it is considered that some kind of crosslinked structure is introduced. The atmosphere of the oxidizing gas is not particularly limited as long as it is an atmosphere capable of introducing a sufficient crosslinked structure into the fiber, but an atmosphere containing oxygen gas is usually preferably used.
In this case, the oxygen concentration is usually selected from the range of 3 to 30% by volume, preferably 5 to 25% by volume.

The PVA fiber is carbonized and then activated. When the process of carbonization is transferred to the process of activation, it may be cooled once and then transferred to activation or continuously. The activation is performed with an oxidizing gas. The oxidizing gas used is water vapor,
Carbon dioxide, combustion gas such as LPG, and mixed gas thereof can be used, but the component ratio of the mixed gas is not particularly limited.

The activation temperature is not particularly limited, and the specific surface area can be controlled by this.
Usually, it is carried out in the range of 600 ° C. to 1500 ° C., and usually in the range of 800 ° C. to 1200 ° C. in consideration of the carbon yield and strength of the obtained PVA-based fibrous activated carbon cloth or fibrous activated carbon sheet. The rate of temperature increase up to the activation temperature is not particularly limited, but a rapid temperature increase usually causes strain due to shrinkage of the fiber cloth, etc. It is preferably carried out in the range of 0.1 ° C. to 30 ° C. per minute. The flow rate (linear velocity) of the oxidizing gas at the time of activation varies depending on the reaction equipment used, but is usually 0.
It is carried out in the range of 001 m to 200 m / sec. In consideration of economical efficiency and heat transfer, it is preferable to carry out in the range of 0.01 m to 100 m / sec. The specific surface area 500 meters ² / g or more by this process, preferably 500~3000m ² /
It can be improved to g.

The rate of temperature decrease from the activation temperature is not particularly limited either, and it is possible to allow it to cool or to forcibly cool it. In both the batch system and the continuous system, cooling is usually performed in the range of 0.01 ° C. to 100 ° C./min, and more preferably in the range of 0.1 ° C. to 50 ° C./min. The cooling can be performed in an activated gas atmosphere or in an inert atmosphere such as nitrogen or argon, but in consideration of safety, and in order to suppress the oxidation of the activated carbon cloth obtained, an inert gas atmosphere is used. It is preferably carried out below. Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

[0049]

EXAMPLES Reference Example 1 PVA having a degree of polymerization of 1700 and a degree of saponification of 99.9 mol% or more.
Is added to water, and the mixture is stirred and dissolved at 80 ° C under a nitrogen gas stream,
A spinning dope having a VA concentration of 16% by weight was prepared. The spinning solution was spun through a spinning nozzle having a pore size of 0.12 mm and a number of holes of 300 into a coagulating bath of 40% by weight of a 30 wt% sodium sulfate aqueous solution, and wet spinning was performed. The PVA fiber obtained is immersed in the same coagulation bath for 1 minute and stretched 2.5 times, then immersed in a 35 wt% sodium sulfate aqueous solution at 20 ° C. for 1 minute, and further fully stretched in a saturated sodium sulfate aqueous solution at 90 ° C. The film was stretched to a magnification of 4.5 and immersed in the same bath for 30 seconds at a fixed length. After washing with water at 10 ° C for 2 minutes to remove sodium sulfate, and then drying with hot air at 130 ° C,
I rolled it up. Then, the dried PVA fiber is heated to 170 ° C.
No. 1 furnace and No. 2 furnace at 235 ° C. in a hot-air oven so that the total draw ratio is 17 times, and the fineness is 920 dte.
Got x Itoshino.

Example 1 Using the PVA fiber obtained in Reference Example 1, a 1.0 m square plain weave cloth (fiber structure: 4 fibers / cm, basis weight: 80 g)
/ M ² , thickness 0.5 mm). Obtained PVA
Cloth in air linearly from 50 ℃ to 300 ℃ 1 ℃ /
The temperature was raised at a rate of minutes to carry out carbonization treatment. The fiber length of the obtained black cloth was shrunk to 40 cm square, and shrinkage unevenness and quality unevenness were observed. The weight yield was 70% by weight based on the raw materials. Then, the obtained black cloth,
The mixture was charged into an activation furnace adjusted to 930 ° C. by a combustion gas of propane (mainly composed of H ₂ O and CO ₂ ) and subjected to activation treatment for 30 minutes. After activation, the cloth was washed with running water and dried to obtain a fibrous activated carbon cloth. The fiber length of the obtained fibrous activated carbon cloth was 20 cm square, and shrinkage unevenness and quality unevenness were observed. The weight yield based on the raw material cloth is 1
0 wt%, BET specific surface area measured by nitrogen adsorption amount is 15
00 m ² / g, I ₂ adsorption amount measured according to JIS K 1474 was 1540 mg / g. From the obtained fibrous activated carbon cloth, an area of 2 cm × 2 cm is arbitrarily set to 5
Point sampling was performed, and the thickness was measured with a micrometer and the weight was measured with a precision balance to calculate the density. The density variation was within ± 15% of the average density.

Example 2 The PVA-based fiber obtained in Reference Example 1 was mechanically crimped and then cut into 54 mm fiber length to obtain a raw cotton for making felt. Then, a felt was formed by a known manufacturing method, and a 1.0 m square felt (thickness 2 mm, density 0.
07 g / cc and basis weight 140 g / m ² ) were cut. Then, the obtained PVA felt is heated in air at 50 ° C to 300 ° C.
The temperature was linearly increased to 1 ° C / min at a rate of 1 ° C / min for carbonization. The fiber length of the obtained black felt was shrunk to 50 cm square, and shrinkage unevenness and quality unevenness were observed. Also,
The weight yield was 70% by weight based on the raw materials.

Then, the obtained black felt was treated with propane combustion gas (mainly composed of H ₂ O and CO ₂ ) 930.
The mixture was placed in an activation furnace adjusted to 0 ° C. and activated for 30 minutes. After activation, the fibers were washed with running water and dried to give a fibrous activated carbon felt. The fiber length of the obtained fibrous activated carbon felt was 27 cm square, and shrinkage unevenness and quality unevenness were observed. Further, the weight yield with respect to the raw material felt was 12% by weight, and the BET specific surface area measured by the nitrogen adsorption amount was 1400.
m ² / g, I measured according to JIS K 1474
_The amount of ₂ adsorption was 1435 mg / g. From the obtained fibrous activated carbon felt, 5 points were arbitrarily sampled in an area of 2 cm × 2 cm, the thickness was measured with a micrometer, and the weight was measured with a precision balance to calculate the density. The density variation was within ± 13% of the average density.

Reference Example 2 PVA having a degree of polymerization of 1700 and a degree of saponification of 99.9 mol% was poured into water and dissolved under stirring at 80 ° C. under a nitrogen gas stream to obtain PVA.
A spinning dope having a concentration of 16% by weight was prepared. The spinning solution is
It was spun through a spinning nozzle having a pore diameter of 0.12 mm and a number of pores of 1000 into a coagulation bath of 40 wt. The PVA fiber obtained was immersed in the same coagulation bath for 1 minute and stretched 2.5 times, then 2
It was dipped in a 35 wt% sodium sulfate aqueous solution at 0 ° C. for 1 minute, further stretched in a saturated sodium sulfate aqueous solution at 90 ° C. so that the total stretching ratio was 4.5 times, and dipped in the same bath for a fixed length of 30 seconds.

After washing with water at 10 ° C. for 2 minutes under running water to remove sodium sulfate, the solution is introduced into a sulfuric acid aqueous solution bath at 25 ° C. and 5% by weight (sulfuric acid and sulfuric acid in the total amount of water) of sulfuric acid.
After being retained for 5 minutes, the surface and inside of the PVA fiber were impregnated with sulfuric acid, dried with hot air at 100 ° C., and wound up. Then, the dried PVA fiber was heated to 170 ° C. in a first furnace, 200
In a hot air oven consisting of a second oven at 0 ° C., hot stretching was performed so that the total stretching ratio was 10 times. The fineness of the obtained Itoshino is 1100 dt.
ex, and the content of sulfuric acid in the fiber was 3 parts by weight with respect to 100 parts by weight of the PVA raw material. The fiber under nitrogen,
The temperature was linearly increased from 50 ° C. to 180 ° C. at a rate of 5 ° C./min, and the temperature was further maintained at 180 ° C. for 30 minutes for dehydration treatment. The obtained fiber was blackish brown, the weight yield based on PVA was 75% by weight, and the shrinkage in the length direction was 4
It was 0% and the fineness was 1380 dtex.

Example 3 Using the dehydrated fiber obtained in Reference Example 2, a plain weave cloth of 1.0 m square (fiber structure: 6 fibers / cm, fabric weight: 170)
g / m ² , thickness 0.5 mm) was produced. PV obtained
A-Cross linearly 1 ℃ from 50 ℃ to 300 ℃ in air
The temperature was raised at a rate of / minute to carry out a carbonization treatment. The fiber length of the obtained black cloth was shrunk up to 83 cm square, but shrinkage unevenness and quality unevenness were hardly seen. The weight yield was 55% by weight based on the raw materials. Next, the obtained black cloth was charged into an activation furnace adjusted to 930 ° C. with a combustion gas of propane (H ₂ O and CO ₂ were the main components), and activated for 30 minutes. After activation, the fibers were washed with running water and dried to obtain fibrous activated carbon cloth. The fiber length of the obtained fibrous activated carbon cloth was shrunk up to 67 cm square, but shrinkage unevenness and quality unevenness were hardly seen. Further, the weight yield based on the raw material cloth is 15% by weight, the BET specific surface area measured by the nitrogen adsorption amount is 1600 m ² / g, J
The amount of I ₂ adsorption measured according to IS K 1474 is 1
It was 645 mg / g. From the obtained fibrous activated carbon cloth, 5 points were arbitrarily sampled in an area of 2 cm × 2 cm, the thickness was measured with a micrometer, and the weight was measured with a precision balance to calculate the density. Density variation is ± 5 of average density
It was within%.

Example 4 The PVA fiber obtained in Reference Example 2 was mechanically crimped and then cut into 54 mm fiber length to obtain a raw cotton for making a felt. Then, a felt was formed by a known manufacturing method, and a 1.0 m square felt (thickness 2 mm, density 0.
It was cut to 1 g / cc and a basis weight of 200 g / m ² . Then, the obtained PVA-based felt is heated in air at 50 ° C to 30 ° C.
The temperature was linearly increased to 0 ° C. at a rate of 1 ° C./minute to perform carbonization treatment. The fiber length of the obtained black felt was shrunk up to 83 cm square, but shrinkage unevenness and quality unevenness were hardly seen. The weight yield was 55% by weight based on the raw materials. Next, the obtained black felt was charged into an activation furnace adjusted to 930 ° C. by a combustion gas of propane (H ₂ O and CO ₂ were the main components), and activated for 30 minutes. After activation, the fibers were washed with running water and dried to give a fibrous activated carbon felt. The fiber length of the obtained fibrous activated carbon felt was shrunk up to 73 cm square, but shrinkage unevenness and quality unevenness were hardly seen. Further, the weight yield with respect to the raw material felt was 16% by weight, and the BET measured by the nitrogen adsorption
The specific surface area was 1550 m / g, and the I ₂ adsorption amount measured according to JIS K1474 was 1550 mg / g.
From the obtained fibrous activated carbon cloth, 5 points were arbitrarily sampled in an area of 2 cm × 2 cm, the thickness was measured with a micrometer, and the weight was measured with a precision balance to calculate the density. The variation in density was within ± 4% of the average density.

[0057]

Industrial Applicability According to the present invention, a PVA-based fibrous activated carbon cloth or a fibrous activated carbon sheet can be industrially produced from PVA-based fibers as a raw material. The PVA-based fibrous activated carbon cloth or fibrous activated carbon sheet obtained by the present invention is used for water purifiers, air purifiers, gas adsorption, water treatment, decolorization, tobacco filters, clean room filters, and secondary batteries. It is useful as an electrode material, an electrode material for electrolytic capacitors, an electrode material for electric double layer capacitors, and the like.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) D01F 6/14 D01F 6/14 Z 9/21 531 9/21 531 (72) Inventor Hideki Kamata Okayama, Okayama Prefecture Ichikaidori 1-2-1 Kuraray Co., Ltd. (72) Inventor Yu Miyaguchi 1-2-1 Kaigandori, Okayama-shi, Okayama F-Term Co., Ltd. Kuraray 4D019 AA01 BA03 BB02 BB03 BC05 4G046 HA03 HB01 HB03 HC09 HC10 4G066 AA05B AC12A BA03 BA16 CA02 FA18 FA23 FA37 4L035 BB03 BB06 BB15 BB16 BB66 BB69 BB72 BB79 BB82 BB85 BB94 DD20 FF01 FF05 FF10 HH10 4L037 AT18 CS06 FA12 FA15 FA17 PA46 PA46

Claims (7)

[Claims] 1. An activated carbon cloth or activated carbon sheet made of fibrous activated carbon produced by using polyvinyl alcohol fiber as a raw material. 2. The specific surface area of the fibrous activated carbon is 500 to 3
The activated carbon cloth or activated carbon sheet according to claim 1, which has an amount of 000 m ² / g. 3. The activated carbon cloth or activated carbon sheet according to claim 1, wherein the density unevenness of the activated carbon cloth or activated carbon sheet is within ± 7% of the average density. 4. A method for producing an activated carbon cloth or activated carbon sheet, which comprises carbonizing and activating after processing polyvinyl alcohol fibers into a cloth shape or a sheet shape. 5. The method for producing an activated carbon cloth or activated carbon sheet according to claim 4, wherein the polyvinyl alcohol fibers are polyvinyl alcohol fibers that have been dehydrated in advance. 6. The method for producing an activated carbon cloth or activated carbon sheet according to claim 4, wherein the weight yield of the polyvinyl alcohol-based fibers after the dehydration treatment is 60 to 85% by weight based on the raw material fibers. 7. An activated carbon cloth or activated carbon sheet obtained by the production method according to claim 4.