JP4191889B2 - 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 has also been positioned as an intermediate for producing carbon fiber, and technology has been developed 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, JP-A-5-339813 discloses that a homopolymer composed only of polyacrylonitrile has a slow oxidation, cyclization, and cross-linking reaction, so A method is described in which a flame-retardant fiber is efficiently obtained by copolymerizing a carboxylic acid group-containing vinyl monomer such as an acid to accelerate the reaction.
[0005]
However, oxygen or air is required for the oxidation reaction, and a high temperature close to 300 ° C. is still required, and the physical properties of the fiber and the properties of the subsequent carbon fiber are adversely affected by copolymer components other than acrylonitrile. Is concerned.
[0006]
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.
[0007]
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.
[0008]
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.
[0009]
However, the actual situation is that no effective method for practical use has been found.
[0010]
[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.
[0011]
[Means for Solving the Problems]
As a result of diligent research on the above-mentioned issues during the series of studies on the flame retardancy and carbonization of polyacrylonitrile, we first brought the polyacrylonitrile homopolymer into contact with iodine gas under low temperature conditions. Below, I found a method that can quickly incombust. 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.
[0012]
That is, the present invention is a method for producing a polyacrylonitrile-based carbonized product characterized by bringing a polyacrylonitrile resin into contact with iodine gas as described below.
[0013]
1. A method for producing a polyacrylonitrile-based carbonized product, characterized in that a polyacrylonitrile resin is brought into contact with iodine gas to make an incombustible material, and then fired in an inert gas atmosphere at 300 to 3000 ° C.
[0014]
2. 2. The method for producing a polyacrylonitrile-based carbonized product according to 1 above, wherein the acrylonitrile monomer component in the polyacrylonitrile resin is 80 to 100 mol%.
[0015]
3. 3. The method for producing a polyacrylonitrile-based carbonized product according to 1 or 2 above, wherein the polyacrylonitrile resin is fibrous.
[0016]
4). 3. The method for producing a polyacrylonitrile-based carbonized product according to 1 or 2 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, an incombustible body, which is a precursor of a carbonized body, can be efficiently produced at a low temperature by causing a polyacrylonitrile resin to exist in iodine gas and incombusting it.
[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.
[0020]
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.
[0021]
A polyacrylonitrile resin prepared by polymerizing from 100 mol% of acrylonitrile is preferred.
[0022]
In the present invention, the polyacrylonitrile resin is contact-treated with iodine gas.
[0023]
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.
[0024]
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.
[0025]
It is desirable to introduce solid iodine into a system in which a polyacrylonitrile resin is present by gasification by heating.
[0026]
Hereinafter, conditions for treating polyacrylonitrile resin with iodine gas will be described in detail.
[0027]
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.
[0028]
There is no problem even if iodine gas is used in a mixed gas state with an inert gas, oxygen, air, etc., but in this case, the iodine gas concentration is 1 to 100 mol% with respect to the molar amount of the whole gas. It is preferable to keep between. 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.
[0029]
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.
[0030]
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 assumed 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.
[0031]
In the present invention, the carbonized product is obtained by firing the polyacrylonitrile flame-retardant obtained as described above in an atmosphere filled with an inert gas at 300 to 3000 ° C.
[0032]
The firing temperature is preferably 300 to 3000 ° C. More preferably, it is 400-2900 degreeC, More preferably, it is the range of 500-2800 degreeC. 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.
[0033]
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.
[0034]
As the inert gas used for firing, argon, nitrogen, or the like is preferably used.
[0035]
Although there is no restriction | limiting in the form in manufacture of the carbonization body of this invention, this invention is useful as a manufacturing method for obtaining the polyacrylonitrile type | system | group carbonization body of a fiber form or a film form.
[0036]
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.
[0037]
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.
[0038]
【The invention's effect】
According to the present invention, first, a polyacrylonitrile resin is brought into contact with iodine gas, whereby an incombustible body can be obtained efficiently even at a low temperature.
[0039]
This is presumably because iodine gas causes the polyacrylonitrile resin to rapidly oxidize, cyclize and crosslink.
[0040]
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.
[0041]
【Example】
Examples of the present invention will be described in detail below. However, the present invention is not limited to these.
[0042]
<Combustion test>
The flame of the gas burner is adjusted to a size of 2 cm, and an incombustible body test sample cut out there is sandwiched between tweezers and brought close to the flame.
[0043]
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”.
[0044]
A polyacrylonitrile resin manufactured by Aldrich was used.
[0045]
Iodine manufactured by Kanto Chemical Co., Ltd. (purity 99.8% by weight) was used after purification by sublimation purification or the like.
[0046]
<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.
[0047]
[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.
[0048]
[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.
[0049]
[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 nitrogen substitution 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.
[0050]
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.
[0051]
For non flames of body obtained above, firing furnace filled with a nitrogen gas flow rate of 100 mL / min (Siliconit manufactured electric furnace "1800SpUSH") in a 700 ° C., then stepwise calcination under conditions of 1300 ° C., The results of the carbonized products obtained after each firing are summarized in Table 1.
[0052]
[Examples 3 and 4]
The same treatment as in Examples 1 and 2 was carried out except that the temperature was changed to 200 ° C. for 2 hours and 250 ° C. for 1 hour. The results of the carbonized products obtained after each firing are summarized in Table 1.
[0053]
[Comparative Examples 1 and 2]
Implementation was carried out except that the polyacrylonitrile fibers and films obtained in Reference Examples 1 and 2 were each placed in a hot air dryer at 200 ° C. as they were (that is, without the operation of putting solid iodine and replacing nitrogen). The same treatment as in Examples 1 and 2 was performed. The results of the carbonized products obtained after each firing are summarized in Table 1.
[0054]
[Comparative Examples 3 and 4]
The polyacrylonitrile fiber and film obtained in Reference Examples 1 and 2 were each put in a pressure-resistant glass bottle (capacity 420 mL), and the same as in Examples 1 and 2 except that the solid iodine was replaced with nitrogen and sealed. Treatment was performed. The results of the carbonized products obtained after each firing are summarized in Table 1.
[0055]
[Comparative Examples 5 and 6]
Implementation was carried out except that the polyacrylonitrile fiber and film obtained in Reference Examples 1 and 2 were each put into a hot air dryer at 250 ° C. as they were (that is, without performing an operation of adding solid iodine and replacing nitrogen). The same treatment as in Examples 1 and 2 was performed. The results of the carbonized products obtained after each firing are summarized in Table 1.
[0056]
In addition, in the column of the carbonization yield in the table, “−” indicates that the carbonization yield is low because the flame resistance is insufficient by the combustion test, and therefore, even if the carbonization treatment is performed later, yarn breakage, breakage, etc. occur. It means that the measurement was impossible.
[0057]
[Table 1]

Claims (4)

A method for producing a polyacrylonitrile-based carbonized product, comprising: making a polyacrylonitrile resin in contact with iodine gas in the absence of oxygen to make an incombustible material, followed by firing in an atmosphere of an inert gas at 300 to 3000 ° C. .   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%.   The method for producing a polyacrylonitrile-based carbonized product according to claim 1 or 2, wherein the polyacrylonitrile resin is fibrous.   The method for producing a polyacrylonitrile-based carbonized product according to claim 1 or 2, wherein the polyacrylonitrile resin is in the form of a film.