JP2002155428A - Method for producing carbonized polyacrylonitrile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a carbonized material of an acrylonitrile resin. SOLUTION: Carbonized polyacrylonitrile is produced by bringing a polyacrylonitrile resin into contact with iodine gas and baking the product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The art of flame retarding polyacrylonitrile has been addressed as fiberized fibers in the form of fibers.

[0002] The obtained non-flammable fiber is also regarded as an intermediate for producing carbon fiber, and its technology has been developed for the purpose of obtaining high-performance carbon fiber by further firing the non-flammable fiber. Was.

[0003] In the specification of the present application, the flameproofing treatment means a treatment for imparting self-extinguishing property to the object, and usually involves various chemical reactions such as oxidation, cyclization, and crosslinking. In addition, a substance having such self-digestibility is referred to as an inflammable substance.

[0004] As a technique for producing carbonized fiber which has been addressed so far, for example, Japanese Unexamined Patent Publication No. 5-339913
According to the publication, a homopolymer consisting of only polyacrylonitrile has a slow oxidation, cyclization and cross-linking reaction, so that a carboxylic acid group-containing vinyl monomer such as acrylic acid is copolymerized to promote the reaction and efficiently produce a flame retardant. A method for obtaining modified fibers is described.

[0005] However, the oxidation reaction requires oxygen or air, and still requires a high temperature close to 300 ° C. The copolymerization component other than acrylonitrile causes the physical properties of the fiber and the carbon fiber It is feared that physical properties are adversely affected.

Further, since the reaction in the presence of oxygen or air is indispensable, this is a factor that lowers the yield in the subsequent carbon fiber formation.

For the same purpose as described above, for example, Carbon
Vol. 29, No. 8, pp. 1081-1090
(1991) introduces a method of promoting cyclization by treating polyacrylonitrile with a basic substance or a nucleophile as a cyclizing aid.

For example, in J. Mats. Sci. Lett
s. 7, pp. 628 (1988) reports that a polyacrylonitrile fiber is treated with an aqueous solution of potassium permanganate to promote cyclization.

However, in reality, no effective method for practical use has been found.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for efficiently producing a carbonized acrylonitrile resin.

[0011]

Means for Solving the Problems In a series of studies on the nonflammability and carbonization of polyacrylonitrile, we conducted intensive studies on the above-mentioned problems, and as a result, we first obtained a homopolymer of polyacrylonitrile. The present inventors have found a method capable of promptly making a flame non-flammable under low temperature conditions by contacting with iodine gas. Further, by calcining the nonflammable body, it has been found that a carbonization yield is high as a feature not found in the conventional carbonized body production method, and the present invention has been achieved.

That is, the present invention is a method for producing a polyacrylonitrile-based carbonized material, which comprises contacting a polyacrylonitrile resin with iodine gas as described below.

1. The polyacrylonitrile resin is brought into contact with iodine gas to form a non-flammable body, and then 300 to 3000
A method for producing a polyacrylonitrile-based carbonized material, characterized by firing in an atmosphere of an inert gas at a temperature of ° C.

2. 2. The method for producing a polyacrylonitrile-based carbonized product according to the above item 1, wherein the acrylonitrile monomer component in the polyacrylonitrile resin is 80 to 100 mol%.

3. 3. The method for producing a polyacrylonitrile-based carbonized product according to the above item 1 or 2, wherein the form of the polyacrylonitrile resin is fibrous.

4. 3. The method for producing a polyacrylonitrile-based carbonized product according to the above item 1 or 2, wherein the polyacrylonitrile resin is in the form of a film.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the present invention, first, a polyacrylonitrile resin is made to exist in iodine gas and subjected to a nonflammable treatment to efficiently produce a nonflammable body which is a precursor of a carbonized substance at a low temperature. it can.

As the polyacrylonitrile resin used in the present invention, a polymer prepared by a known method and containing 80 to 100 mol% of an acrylonitrile monomer component can be used.

In addition to the acrylonitrile monomer, a copolymerized polyacrylonitrile obtained by copolymerizing 20 to 0 mol% of another monomer other than the acrylonitrile monomer can be used in order to have the oxidation promoting effect of the prior art.

Preferably, acrylonitrile 100 mol%
Is a polyacrylonitrile resin prepared by polymerization from

In the present invention, the above-mentioned polyacrylonitrile resin is subjected to contact treatment with iodine gas.

As the iodine gas used in the present invention, a gas prepared by a known method can be used, but it is preferable to use iodine having high purity.

If the purity is low, the desired non-flammable product cannot be obtained, or the mechanical properties of the non-flammable product deteriorate, which is not preferable. Preferably at least 99% by weight, more preferably 9% by weight.
Iodine having a purity of 9.5% by weight or more, more preferably 99.9% by weight or more, is used.

It is desirable that the solid iodine be gasified by heating and introduced into the system in which the polyacrylonitrile resin is present.

Hereinafter, conditions for treating the polyacrylonitrile resin with iodine gas will be described in detail.

The temperature conditions of the non-flammable treatment are from 0 to 50.
A temperature condition of 0 ° C. is preferred. If the temperature is out of this range, the desired non-flammable body cannot be obtained, or the mechanical properties of the non-flammable body deteriorate, which is not preferable. It is more preferably in the range of 100 to 450 ° C. More preferably 200
~ 400 ° C.

There is no problem if the iodine gas is used in a mixed gas state with an inert gas, oxygen, air or the like.
It is preferred to keep it between 1 and 100 mol%. If the concentration is outside this range, the desired non-flammable product cannot be obtained, or the mechanical properties of the non-flammable product deteriorate, which is not preferable.

The pressure condition at that time depends on the kind of the mixed gas used, but is substantially 1% as the total pressure.
The range is from Pa to 100 MPa. The contact time is not particularly limited, but is preferably 1 second to 10 hours.

The above-mentioned temperature means the temperature of both the polyacrylonitrile resin and the gas, but it is not necessary that they are the same, and for example, one of the temperatures may deviate from the preferable temperature range before contacting the two. Even if it does, it is sufficient that the temperature falls within a preferable temperature range as a result of the contact between the two. Rather, for example, even if one of the temperatures deviates from the preferable temperature range before the contact between the two, if the non-flammable body is obtained as a result of the contact between the two, it can be inferred that the temperature has entered the preferable temperature range. Therefore, by bringing the heated iodine gas into contact with the non-heated polyacrylonitrile, it is also possible to obtain an excellent non-flammable body.

In the present invention, the carbonized product is obtained by firing the non-flammable polyacrylonitrile obtained as described above in an atmosphere filled with an inert gas at 300 to 3000 ° C.

The firing temperature is preferably from 300 to 3000.degree. The temperature is more preferably in the range of 400 to 2900 ° C, and still more preferably in the range of 500 to 2800 ° C. In addition, there is no problem in raising the temperature either stepwise or continuously. In order to obtain a more uniform carbonized product, it is often preferable to continuously increase the carbonized product.

When the desired form of the carbonized product is a fiber, it is possible to control the degree of contraction or expansion by applying a tensile stress at the time of raising the temperature without any problem.

As the inert gas used for firing, it is preferable to use argon, nitrogen, or the like.

The form in the production of the carbonized product of the present invention is not limited, but the present invention is useful as a production method for obtaining a polyacrylonitrile-based carbonized product in a fibrous or film form.

That is, after the polyacrylonitrile resin is once dissolved in a soluble organic solvent, it is molded into a fibrous, film or other form, and this is treated with iodine gas to obtain the desired fibrous or film form. A carbonized product can be obtained.

The organic solvent to be used is not particularly limited as long as polyacrylonitrile is soluble, but the following organic solvents, that is, halogenated hydrocarbons and aprotic polar solvents can be preferably used. 1,1,
2,2-tetrachloroethane, chloroform, dimethyl chloride, tetrahydrofuran, N-methylpyrrolidone, dimethylacetamide, dimethylformamide and dimethylsulfoxide are more preferred, and N-methylpyrrolidone, dimethylacetamide and dimethylformamide are even more preferred.

[0038]

According to the present invention, first, a polyacrylonitrile resin is brought into contact with iodine gas,
Even at a low temperature, an inflammable body can be obtained efficiently.

This is presumably because the iodine gas rapidly oxidized, cyclized and crosslinked the polyacrylonitrile resin.

Further, the carbonized product obtained by firing through the obtained non-flammable polyacrylonitrile has a higher carbonization yield than the conventional method, and a carbon fiber excellent in strength can be stably obtained. Thus, by developing it into a prepreg or a composite material, a product having excellent mechanical strength can be obtained at a low cost.

[0041]

Embodiments of the present invention will be described below in detail. However, the present invention is not limited to these.

<Combustion Test> The flame of the gas burner was adjusted to a size of 2 cm, and the cut nonflammable body test sample was pinched with tweezers to approach the flame.

After confirming that the flame had burned to the test sample, the sample was moved away from the flame, and the appearance afterward was observed.
The case where the flame continued to burn as it was kept away was marked as "x".

As the polyacrylonitrile resin, a resin manufactured by Aldrich was used.

Iodine was manufactured by Kanto Chemical (purity 99.
8% by weight) was used after purification by sublimation purification or the like.

<Carburization Yield> The weight of the carbonized product obtained after the calcination with respect to the weight of the dried polyacrylonitrile resin before the flameproofing treatment is defined as a “carbonization yield” of 100.
Shown in fractions.

Reference Example 1 Polyacrylonitrile Powder 3
4 kg was dissolved in 166 kg of N-methylpyrrolidone to prepare a 17% by weight solution. The resulting solution was wet-spun to obtain polyacrylonitrile fiber having a single yarn of 0.11 tex and a fiber bundle of 333 tex.

Reference Example 2 Polyacrylonitrile Powder 3
4 g was dissolved in 166 g of N-methylpyrrolidone, and 1
A 7% by weight solution was prepared. The resulting solution is formed into a film by a film casting method and dried to obtain a film having a thickness of 5 mm.
A 0 μm polyacrylonitrile film was obtained.

[Examples 1 and 2] The polyacrylonitrile fibers and the films obtained in Reference Examples 1 and 2 were each placed in a pressure-resistant glass bottle (capacity: 420 mL), and 1.066 g of solid iodine was added. And sealed. The pressure bottle was put into a hot air drier at 200 ° C., taken out after 2 hours, and allowed to cool.

The samples taken out were subjected to a combustion test. As a result, all of the fibers and films were non-flammable, exhibiting self-extinguishing properties.

The non-flammable body obtained above was heated at 700 ° C. in a firing furnace (siliconit electric furnace “1800 SpUSH”) filled with a nitrogen gas flow rate of 100 mL / min.
Next, firing was carried out stepwise at 1300 ° C., and the results of the carbonized bodies obtained after each firing were summarized in Table 1.

[Examples 3 and 4] Examples 1 and 2 except that the conditions of 200 ° C. and 2 hours were changed to 250 ° C. and 1 hour.
The same treatment was performed. Table 1 summarizes the results of the carbonized products obtained after each firing.

[Comparative Examples 1 and 2] The polyacrylonitrile fibers and films obtained in Reference Examples 1 and 2 were each heated as they were (ie, without the operation of adding solid iodine and replacing with nitrogen) at 200 ° C. The same treatment as in Examples 1 and 2 was carried out except that it was placed in a dryer. Table 1 summarizes the results of the carbonized products obtained after each firing.

[Comparative Examples 3 and 4] The polyacrylonitrile fiber and the film obtained in Reference Examples 1 and 2 were respectively placed in pressure-resistant glass bottles (capacity: 420 mL), replaced with nitrogen without containing solid iodine, and sealed. Other than Examples 1 and 2
The same treatment was performed. Table 1 summarizes the results of the carbonized products obtained after each firing.

[Comparative Examples 5 and 6] The polyacrylonitrile fibers and films obtained in Reference Examples 1 and 2 were each heated as they were (ie, without the operation of adding solid iodine and purging with nitrogen) at 250 ° C. The same treatment as in Examples 1 and 2 was carried out except that it was placed in a dryer. Table 1 summarizes the results of the carbonized products obtained after each firing.

In the column of carbonization yield in the table, "-" indicates that the flame resistance was insufficient in the combustion test, and even if carbonization was performed later, thread breakage and breakage would occur. It means that the yield could not be measured.

[0057]

[Table 1]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F073 AA12 BA18 BB01 DA02 GA01 HA04 4L035 BB03 BB06 BB11 FF01 MB00 4L037 CS03 PA53 PC10 PC11 PS03

Claims (4)

[Claims] 1. A method for producing a polyacrylonitrile-based carbonized material, comprising: bringing a polyacrylonitrile resin into contact with iodine gas to form a non-flammable body; and firing the resultant in an inert gas atmosphere at 300 to 3000 ° C. . 2. The method for producing a polyacrylonitrile-based carbonized product according to claim 1, wherein the acrylonitrile monomer component in the polyacrylonitrile resin is 80 to 100 mol%. 3. The method for producing a polyacrylonitrile-based carbonized product according to claim 1, wherein the form of the polyacrylonitrile resin is fibrous. 4. The method for producing a polyacrylonitrile-based carbonized product according to claim 1, wherein the polyacrylonitrile resin is in the form of a film.