JP4384801B2 - Method for producing polyacrylonitrile-based carbonized product - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The technology for flame-retardant treatment of polyacrylonitrile has been addressed as a flame-retardant fiber in the form of fibers.
[0002]
The obtained flame-retardant fiber is also positioned as an intermediate for producing carbon fiber, and technical development has been made for the purpose of obtaining higher-performance carbon fiber by further firing the flame-retardant fiber.
[0003]
In the specification of the present application, the flameproofing process means a process for imparting self-extinguishing properties to the target, and usually involves various chemical reactions such as oxidation, cyclization, and crosslinking. Moreover, the thing which has such a self-digestibility is called an incombustible body.
[0004]
As a technique for producing carbonized fibers that have been addressed so far, for example, in JP-A-5-339813, a homopolymer consisting only of polyacrylonitrile has a slow oxidation, cyclization and crosslinking reaction, and thus acrylic acid. And a method of efficiently obtaining an incombustible fiber by copolymerizing a carboxylic acid group-containing vinyl monomer such as the above to promote the reaction.
[0005]
However, the oxidation reaction naturally requires oxygen or air, and still requires a high temperature close to 300 ° C., and the physical properties of the fiber and the physical properties of the subsequent carbon fiber are due to copolymer components other than acrylonitrile. There are concerns about adverse effects. Furthermore, since the reaction in the presence of oxygen or air is essential, it is a factor for lowering the yield in the subsequent carbon fiber formation.
[0006]
For the same purpose as described above, for example, Carbon Vol. 29, no. 8, pp. 1081-1090 (1991) introduces a method for promoting cyclization by treating polyacrylonitrile with a basic substance or a nucleophilic agent as a cyclization aid.
[0007]
For example, J. et al. Mats. Sci. Letts. 7, pp. 628 (1988) reports that polyacrylonitrile fiber is treated with an aqueous potassium permanganate solution to promote cyclization.
[0008]
However, the actual situation is that no effective method for practical use has been found.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for efficiently producing a carbonized product of acrylonitrile resin.
[0010]
[Means for Solving the Problems]
As a result of diligent research on the above-mentioned issues in a series of studies on the incombustibility and carbonization of polyacrylonitrile, first, polyacrylonitrile homopolymer was promptly developed under a lower temperature condition than before. I found a way to make it flame-retardant. Furthermore, by calcining the flame retardant, it has been found that the carbonization yield is high as a characteristic that the conventional carbonized material production method does not have, and the present invention has been reached.
[0011]
That is, the present invention is a method for producing a polyacrylonitrile-based carbonized product characterized by bringing a polyacrylonitrile resin into contact with a gas containing iodine gas and oxygen as described below.
[0012]
1. Production of a polyacrylonitrile-based carbonized product, which is obtained by bringing a polyacrylonitrile resin into contact with a gas containing iodine gas and oxygen to form an incombustible material, and then firing in an inert gas atmosphere at 300 to 3000 ° C. Method.
[0013]
2. 2. The method for producing a polyacrylonitrile-based carbonized product as described in 1 above, wherein the gas containing iodine gas and oxygen is substantially composed of iodine gas and air.
[0014]
3. 3. The method for producing a polyacrylonitrile-based carbonized product according to 1 or 2 above, wherein the acrylonitrile monomer component in the polyacrylonitrile resin is 80 to 100 mol%.
[0015]
4). 4. The method for producing a polyacrylonitrile-based carbonized product according to any one of 1 to 3 above, wherein the polyacrylonitrile resin has a fibrous form.
[0016]
5. 4. The method for producing a polyacrylonitrile-based carbonized product as described in any one of 1 to 3 above, wherein the polyacrylonitrile resin is in the form of a film.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0018]
In the present invention, first, the polyacrylonitrile resin is present in a gas containing iodine gas and oxygen and subjected to an incombustible treatment, so that the polyacrylonitrile-based incombustible material that is a precursor of the carbonized product is obtained at a low temperature. It can be manufactured efficiently.
[0019]
As the polyacrylonitrile resin used in the present invention, a polymer prepared by a known method and having an acrylonitrile monomer component of 80 to 100 mol% can be used. Moreover, in order to give the oxidation promotion effect of a prior art, the copolymerization polyacrylonitrile obtained by copolymerizing 20-0 mol% of another monomer other than an acrylonitrile monomer can also be used.
[0020]
A polyacrylonitrile resin prepared by polymerization from 100 mol% of acrylonitrile is preferred.
[0021]
In the present invention, the polyacrylonitrile resin is contact-treated with a gas containing iodine gas and oxygen.
[0022]
The iodine gas used in the present invention can be a gas prepared by a known method, but it is desirable to use iodine with high purity.
[0023]
If the purity is low, the intended flame retardant cannot be obtained, and the mechanical properties of the flame retardant are not preferred. Preferably, iodine having a purity of 99% by weight or more, more preferably 99.5% by weight or more, and further preferably 99.9% by weight or more is used.
[0024]
It is desirable to introduce the solid iodine into the system in which the polyacrylonitrile resin is present by gasification by heating.
[0025]
The “gas containing iodine gas and oxygen” in the present invention may be prepared by mixing iodine gas and gas containing oxygen, but may be produced by a method of vaporizing iodine in a gas containing oxygen.
[0026]
In addition, other gases such as nitrogen, argon and carbon dioxide may coexist in the “gas containing oxygen”.
[0027]
The simplest “gas containing oxygen” is air. That is, a method of vaporizing iodine in the air is preferable as a method for producing the “gas containing iodine gas and oxygen” according to the present invention.
[0028]
The “air” that can be used in the present invention means the atmosphere in a normal environment. However, a modification such as further adding nitrogen gas may be added.
[0029]
The air is preferably dry air, that is, air that does not contain much moisture and moisture. If it contains moisture, the target flame-retardant cannot be obtained, or the mechanical properties of the flame-retardant are reduced, which is not preferable. The less moisture, the better.
[0030]
Hereinafter, conditions for treating the polyacrylonitrile resin with a gas containing iodine gas and oxygen will be described in detail.
[0031]
As a temperature condition for the flame-retardant treatment, a temperature condition of 0 to 500 ° C. is preferable. If the temperature is outside this range, the target flame-retardant cannot be obtained, or the mechanical properties of the flame-retardant are reduced, which is not preferable. More preferably, it is the range of 100-450 degreeC. More preferably, it is the range of 200-400 degreeC.
[0032]
It is preferable to keep iodine gas between 1 to 100 mol% with respect to the molar amount of the whole gas. If the concentration is outside this range, the target flame-retardant cannot be obtained, or the mechanical properties of the flame-retardant are reduced, which is not preferable.
[0033]
Further, the pressure condition at that time is substantially in the range of 1 Pa to 100 MPa as the total pressure, although it depends on the kind of the mixed gas to be used. The contact time is not particularly limited, but is preferably 1 second to 10 hours.
[0034]
In addition, although the said temperature means the temperature of both polyacrylonitrile resin and gas, both need not be the same, for example, one temperature has deviated from the preferable temperature range before both contact. However, it is sufficient to enter the preferred temperature range as a result of the contact between the two. Rather, for example, even if one temperature deviates from the preferred temperature range before the contact between the two, if an incombustible material is obtained as a result of the contact between the two, it can be inferred that the temperature has entered the preferred temperature range. Therefore, it is possible to obtain an excellent flame retardant by bringing heated iodine gas into contact with unheated polyacrylonitrile.
[0035]
In the present invention, the carbonized product is obtained by firing the polyacrylonitrile flame-retardant obtained as described above in an inert gas atmosphere at 300 to 3000 ° C.
[0036]
The firing temperature is preferably 300 to 3000 ° C. More preferably, the range of 400 to 2900 ° C., more preferably 500 to 2800 ° C. is desirable as the firing temperature. Moreover, there is no problem even if the temperature raising method is raised stepwise or continuously. In order to obtain a more uniform carbonized product, it is often preferable to raise it continuously.
[0037]
When the target carbonized form is fiber, it is possible to control the degree of shrinkage or expansion by applying a tensile stress at the time of temperature rise without any problem. As the inert gas used for firing, argon, nitrogen, or the like is preferably used.
[0038]
Although there is no restriction | limiting in the form in manufacture of the carbonization body of this invention, this invention is effective as a manufacturing method for obtaining the polyacrylonitrile type | system | group carbonization body in the form of a fiber or a film.
[0039]
That is, after the polyacrylonitrile resin is once dissolved in a soluble organic solvent, it is formed into a fibrous, film-like or other form, and this is treated with iodine gas to obtain the desired fibrous or film-like carbonized product. Can be obtained.
[0040]
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 preferable, and N-methylpyrrolidone, dimethylacetamide, and dimethylformamide are more preferable.
[0041]
【The invention's effect】
According to the present invention, first, by bringing the polyacrylonitrile resin into contact with a gas containing iodine gas and oxygen, an incombustible body can be obtained efficiently even at a low temperature, and a conventionally used incombustible flame. At the crystallization temperature, the flame retardant can be made in a shorter time than the treatment time.
[0042]
This is presumably because the gas containing iodine gas and oxygen causes the polyacrylonitrile resin to rapidly oxidize, cyclize and crosslink.
[0043]
Furthermore, the carbonized product obtained by calcining through the obtained polyacrylonitrile flame retardant has a high carbonization yield compared to conventional methods, and carbon fibers excellent in strength can be stably obtained, By developing to a prepreg or a composite material, it is possible to obtain a product excellent in mechanical strength at a low cost.
[0044]
【Example】
Examples of the present invention will be described in detail below. However, the present invention is not limited to these.
[0045]
<Combustion test>
A flame of a gas burner is prepared to a size of 2 cm, and an incombustible test sample cut into the gas burner is sandwiched with tweezers and brought close to the flame.
[0046]
After confirming that the flame has been transferred to the test sample, move the sample away from the flame and observe the state after that. If the flame disappears naturally and shows self-extinguishing properties, it is indicated as “○”. The case where the flame continued to burn was designated as “x”.
[0047]
A polyacrylonitrile resin manufactured by Aldrich was used.
[0048]
Iodine manufactured by Kanto Chemical Co., Ltd. (purity 99.8% by weight) was used after purification by sublimation purification or the like.
[0049]
<Carbonization yield>
The weight of the carbonized product obtained after calcination with respect to the weight of the dried polyacrylonitrile resin before the incombustion treatment was shown as “carbonization yield” at 100 minutes.
[0050]
[Reference Example 1]
34 kg of polyacrylonitrile powder was dissolved in 166 kg of N-methylpyrrolidone to prepare a 17% by weight solution. The obtained solution was wet-spun to obtain polyacrylonitrile fiber having a single yarn of 0.11 tex and a fiber bundle of 333 tex.
[0051]
[Reference Example 2]
34 g of polyacrylonitrile powder was dissolved in 166 g of N-methylpyrrolidone to prepare a 17% by weight solution. The obtained solution was formed into a film by a film casting method and dried to obtain a polyacrylonitrile film having a thickness of 50 μm.
[0052]
[Examples 1 and 2]
The polyacrylonitrile fibers and 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, followed by air replacement and sealing. The pressure bottle was put in a 200 ° C. hot air dryer, and after 2 hours, it was taken out and allowed to cool.
[0053]
As a result of subjecting the sample taken out to a combustion test, all the fibers and films were non-flammables exhibiting self-extinguishing properties.
[0054]
The flame retardant obtained above was baked stepwise under conditions of 700 ° C. and then 1300 ° C. in a firing furnace (silicon furnace electric furnace “1800 SpUSH”) filled at a nitrogen gas flow rate of 100 mL / min, Table 1 summarizes the results of the carbonized product obtained after firing.
[0055]
[Examples 3 to 6]
The same treatment as in Example 1 was performed except that the conditions shown in Table 1 were used instead of the conditions of 200 ° C. and 2 hours. Table 1 summarizes the results of the combustion test and the carbonized product obtained after firing.
[0056]
[Comparative Examples 1 and 2]
Examples 1 and 2 except that the polyacrylonitrile fibers and films obtained in Reference Examples 1 and 2 were placed in a hot air dryer at 200 ° C. as they were (that is, without the operation of adding solid iodine). Similar treatment was performed. The results are summarized in Table 1.
[0057]
[Comparative Examples 3 to 5]
Each of the polyacrylonitrile fibers and films obtained in Reference Examples 1 and 2 was put into a pressure-resistant glass bottle (capacity 420 mL), and sealed with air alone or nitrogen alone without solid iodine. Otherwise, the same treatment as in Examples 3, 4 and 5 was performed. The results are summarized in Table 1.
[0058]
In addition, in the table of carbonization yield in the table, those indicated with “-” indicate that during the combustion test, the yarn was broken, the sample was broken, or was burned out, and the carbonized product was not obtained or obtained, but the sample was severely damaged. This indicates that the later measurement was impossible.
[0059]
[Table 1]

Claims (5)

Production of a polyacrylonitrile-based carbonized product, which is obtained by bringing a polyacrylonitrile resin into contact with a gas containing iodine gas and oxygen to form an incombustible material, and then firing in an inert gas atmosphere at 300 to 3000 ° C. Method. 2. The method for producing a polyacrylonitrile-based carbonized product according to claim 1, wherein the gas containing iodine gas and oxygen is substantially composed of iodine gas and air. The method for producing a polyacrylonitrile-based carbonized product according to claim 1 or 2, wherein the acrylonitrile monomer component in the polyacrylonitrile resin is 80 to 100 mol%. The method for producing a polyacrylonitrile-based carbonized product according to any one of claims 1 to 3, wherein the polyacrylonitrile resin has a fibrous form. The method for producing a polyacrylonitrile-based carbonized product according to any one of claims 1 to 3, wherein the polyacrylonitrile resin is in the form of a film.