JPS591803B2 - Method for manufacturing activated carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing activated carbon fiber (ACF) with a high activation yield and excellent adsorption performance from flame-resistant fibers obtained using acrylonitrile fibers as raw materials. .

Conventionally, raw materials for ACF production include cellulose fibers, fibers made by melting pitch, novolac fibers,
Acrylonitrile fibers are known.

When using cellulose fiber as raw material, AC with high adsorption
Although it is easy to obtain F, there is a problem in that the activation yield is low.

When using novolac fiber as a raw material, ACF has a high activation yield and excellent adsorption properties, but the raw material cost is high.

On the other hand, manufacturing from acrylonitrile fibers has advantages such as the raw materials are relatively inexpensive to obtain, and since ACF contains nitrogen atoms, it is excellent at adsorbing mercaptans, sulfur oxides, and nitrogen oxides. However, it is not necessarily satisfactory from the point of view of activation yield.

As for improving adsorption properties, JP-A-40-116332 proposes a method in which raw acrylonitrile fibers are oxidized in an oxidizing atmosphere without tension, and then gas is activated under tension.

However, although this method improves adsorption properties, ACF has very poor mechanical properties and cannot be used.

The present inventors previously disclosed in Japanese Unexamined Patent Publication No. 51-132193 a method for sufficiently oxidizing acrylonitrile fibers to make them flame resistant (oxidation) in an oxidizing atmosphere, and a method for adhering zinc chloride to flame resistant fibers. We proposed that ACF with excellent adsorption and mechanical properties could be obtained by the following method.

As a result of further research, we found that with high activation yield,
Moreover, they succeeded in obtaining fibers with excellent adsorption performance and mechanical properties, leading to the present invention.

That is, the present invention uses Mg, Zn, Sb, and Ca obtained by flame-retardant treatment under tension using acrylonitrile fiber as a raw material.
or a flame-resistant fiber containing 0.01 to 1% (weight) of one or more compounds containing P in terms of the metal,
This is a method for producing ACF in which heat treatment is performed at 300 to 800°C in an inert atmosphere, and then gas activation is performed under tension at a temperature of 700 to 1000°C.

Conventionally, as a method for attaching metals to acrylonitrile fibers, Japanese Patent Publication No. 48-42813 describes
A method has been proposed to make it easier to make acrylonitrile fibers containing sodium and potassium coexisting flame resistant by treating them with a phosphorus compound, but if this method is used to make them flame resistant and then activated, the activation yield of ACF is extremely low. , and the adsorption performance is low.

Further, JP-A-50-72892 proposes a method of activating ACF using a large amount of zinc chloride, but it is extremely difficult to maintain the fibrous state of ACF obtained by this method.

According to the present invention, magnesium (Mg) is added to the flame-resistant fiber.
Zinc (Zn), antimony (Sb), calcium (C
a) or phosphorus (P) in a specific amount, and heat it in an inert gas at 300 to soo'c higher than the flameproofing temperature, preferably at an activation temperature within this range. Heat treated at low temperature and then under tension 700~10
By performing gas activation at 00°C, high activation yield is achieved.
Moreover, ACF with excellent adsorption performance can be obtained.

The acrylonitrile fiber used in the present invention means a homopolymer or copolymer containing 60% by weight or more of acrylonitrile, or a mixture of these polymers, and the copolymer component is an ethylene-based fiber that can be copolymerized with acrylonitrile. It is a saturated compound.

The forms of acrylonitrile fibers include felt, tow, knit, and woven fabrics.

After flame-retardant or further activation of the IJ-based woven fibers, they can be made into these forms using a nonwoven fabric manufacturing device.

Acrylonitrile fiber has 200-30% in oxidizing atmosphere.
Oxidized (flame resistant) at a temperature of 0°C.

The degree of oxidation is shown in JP-A-50-57762 and JP-A-53-
As proposed in each publication of No. 45426, it is preferable to oxidize to 75 to 85% of the saturated oxygen bond amount at the oxidation temperature in order to obtain activated carbon fibers having excellent adsorption properties.

Oxidation also reduces the free shrinkage rate from 50 to 90 at the oxidation temperature.
% tension is desirable from the viewpoint of increasing the strength of the fibers and increasing the production efficiency of the oxidation process.

In the present invention, there are roughly two methods for attaching a metal compound containing a metal to the flame-resistant fibers.

The first method is to apply it to the spinning solution before producing the raw material acrylonitrile fiber or to the raw material fiber after producing it.

That is, the metal compound is added to the polymerization solution before spinning, or the metal compound is attached during the yarn production process such as spinning, water washing, or subsequent treatment steps, or after the yarn production.

When metal is added during the manufacturing process, the metal compound can be uniformly adhered to the yarn, which has the advantage that the amount of adhesion can be small.

The second method is to impregnate flame-resistant fibers obtained by flame-resistant fibers or secondary forms thereof with a solution of a metal compound containing a metal.

This method does not have metal compounds attached to the raw yarn, which may cause the yarn to stick together when making it flame resistant.The first method is preferable, but the first method and the second method may be combined. This can also prevent sticking.

Furthermore, when a metal-reactive functional group, such as a sulfonic acid or carboxylic acid group, is present in the copolymer of acrylonitrile fibers, it is also preferable to bond the metal thereto, since this allows the metal to be introduced uniformly.

In the present invention, metals are introduced in the form of various compounds, generally chlorides, oxides, nitrates, sulfates, carbonates, etc.

In addition, phosphorus compounds include phosphoric acid, metaphosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, polyphosphoric acid,
Hydrogen phosphate, ammonia, organic phosphoric acid, etc. are used.

The amount of the metal compound deposited varies depending on the type of metal, but is in the range of 0.05 to 1% by weight in terms of metal, based on the flame-resistant fiber.

If it deviates from this range, the desired effect will not be obtained (see Table 1 below).

In this case, two or more types of metal compounds may be combined.

For example, a combination of zinc and phosphorus, a combination of zinc, phosphorus, calcium, etc.

In particular, a combination of phosphorus and zinc or phosphorus and calcium has the advantage of improved thermal oxidation resistance.

The flame-resistant fiber to which the metal compound containing one or more metals is attached in this way is then heat-treated in an inert gas atmosphere.

The inert gas atmosphere is nitrogen gas, argon gas, helium gas, etc., or a combination thereof.

Flame-resistant fibers containing metal are treated in such an inert gas atmosphere at a temperature of 300 to 800°C for usually 10 minutes to 180 minutes.

This heat treatment step has a very important meaning in the present invention.

That is, it is thought that through this heat treatment, pores are not immediately formed, but the metal acts catalytically to change the fiber structure, resulting in a structure that is easily activated.

In the case of ordinary chemical activation of activated carbon, pores are developed by impregnating it with chemicals and heat-treating it, resulting in a specific surface area of 800~
1000 rri:/f? However, even when the flame-resistant fiber containing the metal of the present invention was heat-treated at 300 to 800°C in an inert gas atmosphere, pores did not develop and the specific surface area was zero.

FIG. 1 shows the influence of heat treatment temperature in the present invention.

This figure shows that the amount of zinc is controlled* in the water washing process during the acrylonitrile fiber manufacturing process, and zinc chloride is deposited at 0.15% as zinc, and the raw material fibers are 93% acrylonitrile, 5% methyl acrylate, and acrylamide. Fibers made of 2% copolymer were used, and after flame-retardant treatment, they were heat-treated in a nitrogen stream for 20 minutes at varying temperatures in the range of about 300 to 800°C, and then the specific surface area was about 1000rn.
:/? Adjust the time so that
/min) after activation treatment at 800°C.

FIG. 1 shows the relationship between the heat treatment temperature and the activation yield at this time.

Activation yield is the rate at which ACF is obtained from flame-resistant fibers, and is expressed by the following formula.

The activation yield decreases as the ACF with a larger specific surface area is obtained, and the activation yield fluctuates, so the activation yields are compared between those with approximately the same specific surface area (see Table 2 below).

As is clear from this figure, the heat treatment temperature is 300~8
00°C, especially 500-700°C gives desirable results.

The treatment time varies depending on the temperature, but 5 to 60 minutes is sufficient.

FIG. 2 shows the influence of the amount of metal deposited.

The metal deposition method and processing conditions were set to be the same as in FIG.

In the figure, 1 is for fibers that are not heat treated, and 2 is for fibers that are heated to 600℃.
The graph shows the relationship between the amount of metal added and the activation yield for fibers heat-treated in nitrogen gas for 20 minutes.

As is clear from the results shown in Figures 1 and 2 above, simply attaching metal to flame-resistant fibers and activating them has little effect; in addition, heat treatment at 300 to 800°C before activation It turns out that the effect is very strong.

Next, the effects of various metals are shown in Table 1 below.

The results in Table 1 show that acrylonitrile 93 was used as the raw material fiber.
%, 5% methyl acrylate, and 2% acrylamide copolymer, and zinc chloride, phosphoric acid, magnesium oxide, antimony oxide, and calcium chloride were added in Table 1 in the water washing process during the manufacturing process of the raw fiber. The fibers were made flame resistant and activated by adhering them in the amount shown (metal equivalent).

As can be seen from Table 1, if the amount of attached metal compound is outside the range of 0.05 to 1% by weight in terms of metal, or if heat treatment at 300 to 800°C is not performed even within this range, the It is not possible to obtain an ACF with high performance.

Activation is performed at 700 to 1000° C. in an atmosphere containing steam gas, carbon dioxide gas, and ammonia gas, but it is desirable to perform activation at a temperature higher than the inert gas treatment temperature in the previous stage.

The activation time is usually 10 to 120 minutes.

If the activation temperature is lower than 700°C, it will take time and 1
If the temperature is higher than 000°C, activation spots will occur, which is not preferable.

In this way, activated carbon fibers with high activation yield and excellent adsorption performance can be obtained.

The present invention will be explained below with reference to Examples.

Example 1 90 parts of 60% zinc chloride aqueous solution, 9.3 parts of acrylonitrile
A polymer solution obtained by homogeneous solution polymerization of a solution consisting of 0.7 parts of methyl acrylate,
By controlling the water washing process, the amount of zinc chloride in the fiber was changed to 0.3% by weight of zinc to obtain a fiber.

The fibers were oxidized at 270°C for 6 hours in air under a tension that caused a contraction of 70% of the free contraction and until the amount of oxygen binding became 85% of the saturated oxygen binding amount. did.

Next, it was heat treated at 600°C for 20 minutes in a nitrogen gas atmosphere, and then activated at 850°C in steam gas under tension to give a shrinkage of 80% of the free shrinkage rate.

The results are shown in Table 2.

For comparison, Table 2 also shows the case where fibers containing no zinc chloride were similarly flame-retardant treated and then activated.

In the case of the present invention, the obtained ACF has a specific surface area of 85Qm”/
The activation yield was as high as 35.0% in the case of the comparative example, whereas in the case of the comparative example, the specific surface area was almost the same, 900 m/? When this happens, the activation yield is as low as 19.3%.

Similarly, the specific surface area is 1100 (1120), 1400 (13
60), 1s2o (1s1o) m/P, the activation yield in the present invention is higher than that in the comparative example.

The fiber strength of the product of the present invention was excellent: a 0.9 kg/m4 for a product with a specific surface area of s5 om''/l, and 42.8 kg/- for a product with a specific surface area of 1100 m/P.

For comparison (no tension), in Example 1, the flame retardant treatment and the activation treatment were performed under no tension, and the other treatments were performed under the same conditions, and the activation yield of ACF was 1100.
rri:/? It was 28%.

This product had an excellent benzene adsorption amount of 48%, but the fiber strength was 10.6 kg/ln7? It was as low as L.

For comparison (not containing metal), the zinc chloride in Example 1 was simultaneously washed completely with water to obtain fibers containing no zinc chloride.

After flame-proofing the fibers, they were heat-treated at 700°C for 10 minutes in a nitrogen gas atmosphere and activated in steam gas at 850°C. The activation yield was 17.4% and the specific surface area was 110.
An ACF of 0 rrl/g and a benzene adsorption amount of 41% was obtained.

This product has a particularly low activation yield compared to the examples of the present invention.

Example 2 (a) Instead of controlling the amount of zinc deposited in the washing step in Example 1, after washing, stretching, and relaxing, the fibers were immersed in an aqueous zinc chloride solution to deposit the same amount of zinc as in Example 1.

(b) Instead of controlling the amount of zinc deposited in the washing step in Example 1, the fibers were immersed in an aqueous zinc chloride solution after washing, stretching, relaxing, and drying, and the same amount of zinc as in Example 1 was deposited.

( ) → Acrylonitrile fibers were obtained by a normal method without metal attachment in the water washing step as in Example 1.

Next, it was oxidized in air at 270° C. to the same degree of flame resistance as in Example 1, and then zinc chloride in the same amount as in Example 1 was deposited.

In the cases of (A) and (O) above, Example 1 is continued.
It was treated under the same flame-retardant conditions.

And (a), (b) and e→ are all Example 1
The specific surface area is approximately 1000m'/
? I got something like that.

The activation yield and the state of ACF are shown in Table 3 together with Example 1.

The ACF of these (a) ~ e → is 29.6 kg/mA
It had a fiber strength of ~31.2 kg/ma.

Example 3 90 parts of 60% zinc chloride aqueous solution, 9.4 parts of acrylonitrile
0.59 parts of methyl acrylate, and 0.01 part of sodium metaallylsulfonate were subjected to homogeneous solution polymerization, and the obtained polymer solution was used as a spinning stock solution for spinning, and the amount of Zn was 0.59 parts.
It was an acrylonitrile fiber containing 4% ZnCl2.

This fiber was immersed in a phosphoric acid aqueous solution to adhere 0.1% phosphoric acid as phosphorus.

Then, in air at 270°C for 5 hours, the free shrinkage rate was 8
It was sufficiently oxidized under tension to give 0% shrinkage and until the amount of bound oxygen was 80% of the saturated amount of bound oxygen.

Thereafter, it was heat-treated at 550° C. for 22 minutes in a nitrogen gas atmosphere, and then activated at 850° C. in steam gas under tension to give a shrinkage of 80% of the free shrinkage rate.

The activation yield was 27.6%, the obtained ACFO specific surface area was 1030 g''/guzen adsorption amount was 48.1%, and the fiber strength was 3.
It was 1 kg/-.

The thermal oxidation resistance of this material was measured using a thermogravimetric analyzer (manufactured by Rigaku Denki Co., Ltd.)
As a result of measurement in air at 400° C. for 3 hours, the weight loss rate was 12%.

[Brief explanation of drawings]

FIG. 1 shows the relationship between heat treatment temperature and activation yield. FIG. 2 shows the relationship between the amount of metal added and the activation yield.

Claims (1)

[Claims] 1 Any one or two or more compounds containing Mg1zn, sb, Ca or P obtained by flame-retardant treatment under tension using acrylonitrile fiber as a raw material are 0 in terms of the metal.
．． Flame-resistant fiber containing 05-1% (weight) at 300-800℃
heat treated in an inert gas atmosphere and then heated under tension for 70 minutes.
A method for producing activated carbon fiber, characterized by gas activation at a temperature of 0 to 1000°C.