JPS5820883B2 - Activated carbon fiber manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention uses acrylonitrile fiber as a raw material.

The present invention relates to a method for obtaining activated carbon fibers with excellent mechanical fiber performance and high adsorption performance in a high yield by subjecting the carbon fibers to oxidation treatment and activation treatment.

The activated carbon fibers herein refer to carbonaceous fibers that have adsorption performance as activated carbon, and structures such as felts and woven fabrics made from the same.

Activated carbon has long been known as a very useful adsorbent.

Particularly in recent years, interest in pollution problems has increased rapidly, and adsorption functions are important as a means of preventing water pollution, air pollution, etc.

Activated carbon as the adsorbent used here has an advantage over other adsorbent materials in terms of performance, cost, etc.

Conventionally, activated carbon has been produced in the form of powder or granules using mainly coconut shells, wood materials, tar, and the like as raw materials.

A method using an acrylonitrile polymer as a raw material has also been proposed.

Activated carbon made from these raw materials has characteristics that depend on the raw materials.

However, since conventional activated carbon is usually in the form of powder or granules, it does not have shape retention and is inconvenient in handling depending on the application.

As a result of research into the production of activated carbon fibers using acrylonitrile fibers as raw materials, the present inventor discovered a method for obtaining activated carbon fibers with high yields that are processable as fibers and have excellent adsorption properties. .

That is, the present invention provides acrylonitrile fibers with a free shrinkage rate of 5 at a temperature of 200 to 300°C in an oxidizing atmosphere.
Activated carbon fibers are obtained by oxidizing the fibers while applying tension such that the fiber has a saturated oxygen bond amount of 80 or more, and then activating in a steam atmosphere. .

According to such a method, activated carbon fibers with high fiber strength and excellent adsorption performance can be obtained.

Conventionally, the production of activated carbon using acrylonitrile fiber as a raw material has also been proposed (Japanese Patent Application Laid-Open No. 116332/1989).
Publication No.).

In this method, acrylonitrile fibers are subjected to flameproofing treatment (oxidation treatment) and then activation treatment under no tension.

Normally, when acrylonitrile fibers are heat-treated, they shrink due to relaxation of molecular orientation, and their strength decreases accordingly.

According to the above-mentioned known method, the activated carbon fiber obtained not only has low strength and is brittle, but also loses its most important characteristic, processability, due to the stress-free treatment during the flame-retardant treatment process, making it difficult to use. The surface is the same as normal activated carbon, so there is no point in making it fibrous.

On the other hand, according to the present invention, there is no such problem, and it has excellent adsorption performance and strength necessary for processing, and has the form of long fibers, short fibers, and woven fabrics made of these.
It can be processed and used as nonwoven fabric, felt, etc., and can be used more functionally than conventional activated carbon.

In the present invention, acrylonitrile fibers are fibers made of a polymer whose main component is acrylonitrile, and the copolymerization components include, for example, vinyl chloride, vinylidene chloride, vinyl bromide, acrylic acid or methacrylic acid, and derivatives thereof.
A fiber made of a polymer copolymerized with one or more of acrylamide, N-methylolacrylamide, allylsulfonic acid, metaallylsulfonic acid, or salts thereof.

Acrylonyl l-IJ type woven fibers are produced by spinning using various organic and inorganic solvents, but when organic solvents are used, the residual solvent in the fibers undergoes plasticizing action during oxidation treatment, causing the fibers to deteriorate. May become vulnerable.

For this reason, it is best to use an inorganic solvent as the solvent.
In particular, when a zinc chloride-based aqueous solution is used, the oxidation and activation time is shortened due to the residual normal lead content, and even higher strength fibers can be obtained.

This acrylonitrile fiber is oxidized at a temperature of 200 to 300° C. in an oxidizing atmosphere while applying tension.

The tension during the oxidation treatment is adjusted so that the shrinkage at the flame resistance temperature (oxidation treatment temperature) is 50 to 90% of the free shrinkage rate at that temperature.

If the shrinkage ratio is less than 50 times the free shrinkage ratio, the tension will be too high and the orientation of the fibers will progress after oxidation, making it difficult to react with the activation gas in the activation process. As the activation yield decreases and the activation conditions become harsher.

Fiber strength decreases.

On the other hand, if the shrinkage ratio is 90 or higher, only activated carbon fibers with low strength and no workability can be obtained.

Furthermore, if the oxidation treatment at this time is not sufficient, the activation yield will be high and a product with excellent adsorption performance will not be obtained.

Further, the oxidation treatment must be carried out in an oxidizing atmosphere at 200 to 300° C. until the amount of saturated oxygen bonds reaches 80 or more.

When acrylonitrile fiber is oxidized, it has a specific amount of saturated oxygen bonding depending on its copolymer composition.

When fibers are oxidized at 200 to 300°C, this saturated oxygen binding amount gradually increases when measuring the oxygen binding amount over time, but after a certain treatment time it becomes constant, and the oxygen binding amount at this time ( % by weight) is called the saturated oxygen bond amount.

The treatment time required until the amount of oxygen bonds reaches saturation varies depending on the treatment temperature and copolymer composition, but is 2 to 24 hours.

In the production of activated carbon fibers using an acrylonitrile polymer as a raw material, the amount of oxygen bonded into the polymer molecular chain in the oxidation step has a large influence on the subsequent performance of the activated carbon fibers.

Similarly, when producing carbon fibers for use in composite materials, it is effective to shift to the carbonization process at a stage when the amount of oxygen bonding in the oxidation process does not become too high in order to obtain high-performance carbon fibers. Moreover, the tension at this time promotes crystallization of the fibers and increases the degree of orientation.
It is preferable to carry out the oxidation treatment under as high a tension as possible.

However, in the production of activated carbon fiber as an adsorbent,
In order to obtain high-performance activated carbon fibers, it is preferable to bind sufficient oxygen to the acrylonide IJ polymer in the oxidation step and oxidize it almost to the saturation point.

For example, the relationship between oxidation treatment conditions and activated carbon fibers is shown in the following table.

The table below shows the relationship between the amount of oxygen bonded in the oxidation stage and the performance of activated carbon fibers.

However, copolymer fiber oxidation treatment of 89.7% acrylonitrile, 9 parts methyl acrylate, 1.3 parts sodium methalylsulfonate, 75 parts free shrinkage activation conditions, 40 minutes treatment in 800°C Steach The surface area was measured using Shibata Chemical Instruments ■5AL00, and the amount of benzene adsorption was measured according to JIS K-1112.

As mentioned above, the amount of oxygen binding and tension in the oxidation process directly affect the performance of activated carbon fibers, and 80% of the saturated oxygen binding amount
When the adsorption capacity exceeds 100%, extremely high adsorption capacity is exhibited.

Activation treatment is performed by heating the oxidized fibers at 800 to 1000℃.
The treatment is carried out by treatment in an atmosphere containing water vapor for 20 minutes to 3 hours.

The oxidized fibers shrink by 15-30% during this process.

Therefore, the activation process is carried out under sufficient tension to correspond to the contraction.

Preferably, the coefficient of free shrinkage in the activation process is 40 or more.

In this case, if the shrinkage rate of the fibers to be treated is less than 40 times the free shrinkage rate, the fibers are likely to break during the activation process, and activation will be difficult, resulting in poor adsorption ability.

As described above, activated carbon fibers can be obtained by oxidation treatment and activation treatment of acrylonyl l-IJ type woven fibers.According to the present invention, activated carbon fibers have processability as fibers, so they must be treated before activation treatment. Alternatively, it can be later woven or felted and used not only in the form of fibers but also as a structure.

Examples will be shown below.

Example 1 A solution consisting of 90 parts of a 60% zinc chloride-based aqueous solution, 9.7 parts of AkuIJO nitrile, and 0.3 parts of methyl acrylate was subjected to homogeneous solution polymerization, and the resulting polymer solution was used as a spinning stock solution.
The fibers were spun in a 30% zinc chloride aqueous solution at 5°C using a nozzle with a pore diameter of o, osmmu and 1000 holes, washed with water while being stretched, dried in a dryer at 120°C, and then spun in steam at 130°C for 50 minutes. The fiber was stretched twice to obtain a 1.5 denier fiber.

This fiber was sufficiently processed in an electric furnace in air at 250° C. while applying tension to give a contraction of 70 times the free shrinkage rate until the amount of oxygen bonds became 90 times the amount of saturated oxygen bonds. .

Next, at 850°C, water vapor was supplied at a rate of 0.7 g/min per 1 g of fiber for 40 minutes, and the free shrinkage rate was 80
The activation process was carried out under tension giving a contraction of %.

The obtained activated carbon fiber has a diameter of 4.0 parts and a strength of 1.81 g.
(strength: 8.6 g/d), elongation ratio: 1.52, and has sufficient mechanical strength, surface area is L 400 m2/g, and benzene adsorption amount is 46.11%, so it has satisfactory activity. did.

On the other hand, the fibers subjected to the oxidation treatment without tension had a diameter of 5 μm, a strength of 0.5 to 0, and a strength of 6 g (strength of 1.5 to 1.8 g/d), and were too brittle to be used as fibers.

Example 2 The raw material acrylonitrile fiber used in Example 1 was oxidized at 260°C with different shrinkage rates, and then 1,200 m
Activation treatment was performed in steam at 900° C. to obtain a surface area of 2/g.

The yield and fiber strength at this time were as follows.

The amount of oxygen bonded during the oxidation treatment was set to be 90 times the amount of saturated oxygen bonded.

1 consisting of a polymer composition of 92 parts acrylonitrile, 7 parts methyl methacrylate, and sodium allylsulfonate lfo.
．． An acrylonitrile fiber bundle consisting of 5 denier and 30,000 filaments was used as a raw material.

This acrylonyl l-IJ fiber bundle was subjected to oxidation treatment at a shrinkage rate of 60% relative to free shrinkage in air at 250° C. by changing the amount of oxygen bonding by changing the treatment time.

Next, this oxidized fiber was made into a nonwoven fabric by needle punching, and activated in steam at 850° C. for 30 minutes.

The surface area, yield, and amount of benzene adsorbed at this time were as follows.

Claims (1)

[Claims] 1 Acrylonitrile fibers in an oxidizing atmosphere of 200~
While applying tension at a temperature of 300°C so that the shrinkage rate is 50 to 90 times the free shrinkage rate, oxidation treatment is performed until the saturated oxygen bond amount of the fiber becomes 80 times or more, and then activated in a steam atmosphere. A method for producing activated carbon fiber characterized by: