KR102351984B1 - Polyacrylonitrile based oxidized fiber - Google Patents

Abstract

The present invention relates to polyacrylonitrile-based flame-resistant fibers having a specific range of cyclization reactivity, which can provide carbon fibers having excellent physical properties.

Description

Polyacrylonitrile-based oxidized fiber {Polyacrylonitrile based oxidized fiber}

The present invention relates to polyacrylonitrile-based flame-resistant fibers having a specific range of cyclization reactivity, which can provide carbon fibers having excellent physical properties.

Carbon fiber is widely used in civil engineering and construction fields such as building materials, concrete structures, earthquake-resistance reinforcement, CNG tanks, blades for wind power generation, centrifugal rotors, Alternative energy such as fly foil, green energy, high-speed transportation equipment such as ships and vehicles, offshore development, deep-sea oil field mining, high-performance equipment, medical welfare equipment, electrical conduction applications, and aerospace applications such as ultra-heat-resistant construction It is a situation in which the range of application fields is expanding for various industrial fields ranging from industry to industry. Carbon fiber is growing as a material that creates the foundation for a new era as a third general-purpose material that can replace iron and aluminum by taking advantage of its unique characteristics. In particular, with the application of carbon fiber as an aircraft component material for the recently developed supersonic aircraft, the Boeing 787 and Airbus 380, the use of carbon fiber is expected to increase in various advanced material fields.

In general, a high heat treatment temperature of about 1300° C. or higher is applied to carbon fiber, and its properties may vary greatly depending on the setting of carbonization process factors. In addition, the process is complicated, the productivity is low, and the production cost is high, so the price of the product is relatively high.

Polyacrylonitrile-based precursor fiber (hereinafter, PAN fiber), known as the most suitable precursor for producing carbon fiber, is a series of stabilization (Stabi1ization or Oxidation), carbonization, and optionally graphitization process steps and a series of surface treatment (Surface treatment). ) and sizing, it can be finally converted into carbon fiber or graphite fiber.

The stabilization process (or flame-resistant process, or oxidation stabilization process) refers to a heat treatment process performed at a temperature of about 200° C. to 400° C. while applying a certain tension in an oxidizing or air atmosphere. In this process, the PAN fiber is chemically As a result, a large change occurs, and the structure is chemically, physically, and thermally stable even at a high heat treatment temperature such as partial carbonization or graphitization conditions that are subsequently performed.

On the other hand, looking at the price structure of carbon fiber, PAN fiber occupies the largest proportion at 43%, and the stabilization stage, a process that consumes a lot of energy due to a very slow reaction rate, occupies 18%. Therefore, it is essential to secure low-cost PAN fiber technology for carbon fiber cost reduction, and stabilization and carbonization process technology with low energy consumption are required.

In the stabilization reaction, a cyclization reaction, a dehydrogenation reaction, an aromatization reaction, an oxidation reaction, and a crosslinking reaction occur, and a ladder structure of a conjugated structure having heat resistance is formed through these reactions.

The cyclization reaction is an exothermic reaction, and it is preferable to proceed at a low temperature to reduce side reactions (degradation) and to be economically advantageous, and it is important to easily disperse the amount of emitted heat to prevent damage to the fibers (low shrinkage).

Republic of Korea Patent Publication No. 10-2011-0078246

The present invention has been devised to solve the problems of the prior art, and an object of the present invention is to provide a polyacrylonitrile-based flame-resistant fiber having a specific cyclization reactivity.

In addition, the present invention provides a carbon fiber having excellent physical properties manufactured using the polyacrylonitrile-based flame-resistant fiber.

In order to solve the above problems, the present invention is a polyacrylonitrile-based flame-resistant fiber having a cyclization reactivity of 0.37 to 0.55 according to the following Equation 1, which is defined according to the peak height of the infrared spectral spectrum to which the attenuation pre-reflection technique is applied. to provide:

[Equation 1]

In Equation 1 above,

I ₀ is the corrected value of the C≡N peak height in the infrared spectral spectrum before the cyclization reaction of the flame-resistant fiber,

I ₁ is the corrected value of the C≡N peak height in the infrared spectral spectrum of the flame-resistant fiber,

The correction value of each peak height is calculated by the following Equations 2 and 3,

[Equation 2]

[Equation 3]

In Equations 2 and 3 above,

A ₀ , A ₁ , A ₂ , B ₁ and B ₂ are the peak height measurements of the infrared spectral spectrum, respectively,

A ₀ is the CH peak height of the nonvolatile liquid material, A ₁ is the CH peak height of the fiber, A ₂ is the CH peak height of the fiber impregnated with the nonvolatile liquid material, B ₁ is the C≡N peak height of the fiber and B ₂ is C≡N peak height of the fiber impregnated with the nonvolatile liquid material, wherein the nonvolatile liquid material is at least one selected from paraffin oil, aliphatic ester-based compound, aliphatic ether-based compound, and aliphatic alcohol-based compound to be.

In addition, the present invention provides a carbon fiber prepared by carbonizing the polyacrylonitrile-based flame-resistant fiber, and having a strength of 2.8 GPa or more.

The polyacrylonitrile-based flame-resistant fiber according to the present invention can provide carbon fibers having excellent physical properties by having a cyclization reactivity within a specific range.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the above-described content of the invention, so the present invention is limited to the matters described in those drawings It should not be construed as being limited.
1 shows a spectrum obtained by IR-ATR measurement of Example 1 and a first sample according to an embodiment of the present invention.
2 shows spectra obtained by IR-ATR measurement of samples 1 and 2 according to an embodiment of the present invention.
3 shows spectra obtained by IR-ATR measurement of samples 1 and 3 according to an embodiment of the present invention.
4 shows spectra obtained by IR-ATR measurement of samples 1 and 4 according to an embodiment of the present invention.
5 shows spectra obtained by IR-ATR measurement of samples 1 and 5 according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail to help the understanding of the present invention.

The terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor may properly define the concept of the term in order to describe his invention as the best invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

The term “polyacrylonitrile-based precursor fiber” used in the present invention refers to a polyacrylonitrile-based copolymer fiberized by a spinning process, etc., and “polyacrylonitrile-based flame-resistant fiber” refers to the polyacrylonitrile-based copolymer It is prepared by stabilizing the precursor fibers.

The present invention provides a polyacrylonitrile-based flame-resistant fiber having a specific range of cyclization reactivity, which is used in the production of carbon fiber.

Polyacrylonitrile-based flame-retardant fiber is the most widely used material for the production of carbon fibers, usually by polymerizing an acrylonitrile-based monomer and a carboxylic acid-based comonomer to prepare an acrylonitrile-based copolymer, and the copolymer It is manufactured by stabilizing it after fiberization. Here, the stabilization is a process of cyclization, oxidation, dehydrogenation, etc. which is performed by oxidizing the copolymer or heat-treating it while applying a certain tension in an air atmosphere in order to obtain a polyacrylonitrile-based flame-resistant fiber to which heat resistance is imparted. , a large chemical change occurs in the copolymer during this process. Of these, the cyclization reaction in which the C≡N bond in the copolymer molecule changes to C=N to form a ring may be the most important reaction, and the heat resistance may vary depending on the degree of this cyclization reaction, and as a result, finally manufactured It affects the physical properties of carbon fiber.

Therefore, in order to obtain carbon fibers having excellent physical properties, it may be important to use polyacrylonitrile-based flame-resistant fibers prepared by appropriately controlling stabilization, particularly, cyclization.

Accordingly, the inventors of the present invention obtained an infrared spectral spectrum by measuring by an attenuation pre-reflection technique using an infrared spectrometer before and after the cyclization reaction during the production of polyacrylonitrile-based flame-resistant fiber, and the obtained equation was derived from the spectrum To provide the polyacrylonitrile-based flame-resistant fiber by confirming through a number of experiments that the physical properties of the finally produced carbon fiber in a specific range of the cyclization reactivity defined as 1 are excellent.

The term "cyclization reactivity" used in the present invention refers to a change in the amount of C≡N bonds in a cyclization reaction in which a C≡N bond is changed to a C=N bond through the cyclization reaction as in Scheme 1 below. will be.

[Scheme 1]

The term "before the cyclization reaction of the flame-resistant fiber" used in the present invention refers to the polyacrylonitrile-based precursor fiber before the cyclization reaction to prepare the flame-resistant fiber.

In addition, in the present invention, _{the fibers in A 1} , A ₂ , B ₁ and B ₂ are polyacrylonitrile-based flame-resistant fibers, or before the cyclization of the flame-resistant fibers, that is, polyacrylonitrile-based precursor fibers. it could be

The polyacrylonitrile-based flame-resistant fiber according to an embodiment of the present invention has a cyclization reactivity according to Equation 1, which is defined according to the peak height of an infrared spectral spectrum to which an attenuated total reflection technique is applied, of 0.37 to 0.55.

[Equation 1]

I ₀ is the correction value of the C≡N peak height in the infrared spectral spectrum before the cyclization reaction of the flame-resistant fiber, I ₁ is the correction value of the C≡N peak height in the infrared spectrum of the flame-resistant fiber, and each peak height The correction value of is calculated by Equation 2 and Equation 3 below,

[Equation 2]

[Equation 3]

In Equations 2 and 3, A ₀ , A ₁ , A ₂ , B ₁ and B ₂ are respectively peak height measurement values of the infrared spectral spectrum, A ₀ is the CH peak height of the nonvolatile liquid material, A ₁ is CH peak height of the fiber, A ₂ is the CH peak height of the fiber impregnated with a non-volatile liquid substance, B ₁ is the C≡N peak height of the fiber, and B ₂ is C≡ of the fiber impregnated with a non-volatile liquid substance N peak height, wherein the nonvolatile liquid material is at least one selected from paraffin oil, aliphatic ester-based compounds, aliphatic ether-based compounds and aliphatic alcohol-based compounds.

Here, the aliphatic ester-based compound may be vegetable oil such as soybean oil and corn oil, dioctyl adipate, dioctyl sebacate or dioctyl azelate, and the aliphatic ether The compound may be dioctyl ether, dihexyl ether or dibutyl ether, and the aliphatic alcohol compound may be octanol, hexanol or butanol.

Specifically, the polyacrylonitrile-based flame-resistant fiber according to an embodiment of the present invention may exhibit a cyclization reactivity of 0.40 to 0.50.

In one embodiment of the present invention, the infrared spectral spectrum is obtained by measuring a total of five samples by an attenuation pre-reflection technique using an infrared spectrometer, respectively, and each sample is obtained before the cyclization reaction of the flame-resistant fiber. 1 sample, a second sample in which the first sample is impregnated with a non-volatile liquid material, a third sample collected from the flame-resistant fiber, a fourth sample in which the third sample is impregnated with a non-volatile liquid material, and a non-volatile liquid material The phosphorus may be a fifth sample. In this case, the nonvolatile liquid material may specifically be paraffin oil.

In addition, the infrared spectral spectrum for each sample is measured by contacting the sample with the reflection crystal before attenuation, irradiating light to the sample through the reflection crystal before attenuation, and detecting the light emitted from the reflection crystal before attenuation. and the reflective crystal before attenuation may be, for example, germanium.

Meanwhile, the infrared spectral spectrum of the fifth sample may be obtained by directly applying (dropping) the fifth sample to the pre-attenuation reflective crystal and bringing the pre-attenuating reflective crystal into contact with the fifth sample.

In addition, the infrared spectral spectrum according to an embodiment of the present invention is attenuated by a pre-reflection technique with a resolution of 8 cm ^{-1 and a scan number of 64 in a wavenumber region of 600 to 4000 cm -1 using an infrared spectrometer.} It may be obtained by measuring.

According to a specific embodiment of the present invention, the infrared spectral spectrum is obtained by using a microscope infrared spectrometer (Lumos, Bruker) for the subject, resolution 8 cm ^-1 and integration count 64, ATR tip The pressure was selected as Medium, and the CH peak height ^{was measured at 2923 cm -1} , the baseline was drawn as a straight line at ^{2600 cm -1} and 3155 cm ^{-1 , and the C≡N peak height was measured at 2243 cm -1} , and the baseline was Measurements were made in a straight line at 2100 cm ^-1 and 2280 cm ^{-1 .}

In the present invention, the attenuation pre-reflection technique is a method of measuring a change occurring in an internally reflected beam when an infrared beam hits a sample. Specifically, a transparent material with a large refractive index is brought into close contact with the sample. Total reflection occurs when incident light is irradiated from the side, but the reflected light is absorbed by a small portion of the sample near the contact surface, so the absorption characteristics of the sample must be reflected.

Meanwhile, in the present invention, the polyacrylonitrile-based flame-resistant fiber is prepared by polymerizing, for example, an acrylonitrile-based monomer and a carboxylic acid-based comonomer to prepare a polyacrylonitrile-based copolymer, and fiberizing the prepared copolymer into fibers After preparing the polyacrylonitrile-based copolymer, it may be prepared by stabilizing it.

Here, the acrylonitrile-based monomer may be acrylonitrile, and the carboxylic acid-based comonomer is composed of acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid, and mesaconic acid. It may be at least one selected from the group.

In addition, the polyacrylonitrile-based copolymer is 95 wt% to 99 wt% of repeating units derived from acrylonitrile-based monomers; and 1 wt% to 5 wt% of a carboxylic acid-based comonomer-derived repeating unit.

In addition, the fiberized polyacrylonitrile-based copolymer may be prepared to have a fibrous shape by applying the polyacrylonitrile-based copolymer to a spinning process, for example, by dissolving the polyacrylonitrile-based copolymer It can be prepared by dissolving in a solvent that can be used to prepare a spinning solution, and it can be prepared by dry spinning, wet spinning or dry and wet spinning.

The solvent is not particularly limited as being capable of dissolving the polyacrylonitrile-based copolymer, but may be, for example, dimethyl sulfoxide, dimethylformamide or dimethylacetamide, and the spinning solution is the polyacrylonitrile-based copolymer. It may be prepared by adjusting the concentration to be 10 to 40% by weight.

In addition, in the wet or dry spinning, the spinning undiluted solution may be introduced into a coagulation tank to coagulate, and the coagulation tank may include a solvent of the spinning undiluted solution and a coagulation accelerator.

After the solidification, the washing process and the stretching process may be performed, and these two processes may be performed sequentially or continuously, or in the reverse order.

In addition, a process such as dry heat treatment or steam stretching may be further performed, and through this, a fibrous polyacrylonitrile-based copolymer may be prepared.

The stabilization is a process for imparting heat resistance to the fiberized polyacrylonitrile-based copolymer, and may be carried out by heat treatment performed in a temperature range of about 180° C. to 350° C. while applying a certain tension in an oxidizing or air atmosphere, Through this, low-molecular substances among components constituting the fibrous polyacrylonitrile-based copolymer are removed and a large chemical change occurs, whereby a polyacrylonitrile-based flame-resistant fiber having heat resistance can be manufactured.

In addition, the present invention provides a carbon fiber prepared by carbonizing the polyacrylonitrile-based flame-resistant fiber, and having a tensile strength of 2.8 GPa or more.

Specifically, the carbon fiber may have excellent physical properties by being manufactured using a polyacrylonitrile-based flame-resistant fiber having a cyclization reactivity within the specific range, and, for example, may exhibit excellent tensile strength as described above.

In this case, the carbon fiber may be prepared by carbonizing the polyacrylonitrile-based flame-resistant fiber at a temperature of, for example, about 1,000° C. or more, specifically 1,200° C. or more, and 2,000° C. or less in an inert atmosphere.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1

A polyacrylonitrile-based flame-resistant fiber was prepared by controlling the cyclization reaction to have the cyclization reactivity shown in Table 1 below.

Specifically, a polyacrylonitrile-based precursor fiber (Jilin) containing about 96% by weight of acrylonitrile, about 3% by weight of methyl methacrylate, and about 1% by weight of itaconic acid was placed in an oven at 220° C. for 15 minutes, A polyacrylonitrile-based flame-resistant fiber was prepared by sequentially cyclizing for 60 minutes at 240° C. for 15 minutes, at 260° C. for 15 minutes, and at 280° C. for 15 minutes.

Example 2

A polyacrylonitrile-based flame-resistant fiber was prepared by controlling the cyclization reaction to have the cyclization reactivity shown in Table 1 below.

Specifically, a polyacrylonitrile-based precursor fiber (Jilin) containing about 96% by weight of acrylonitrile, about 3% by weight of methyl methacrylate, and about 1% by weight of itaconic acid was placed in an oven at 220°C for 10 minutes, A polyacrylonitrile-based flame-resistant fiber was prepared by sequentially cyclizing for 40 minutes at 240° C. for 10 minutes, at 260° C. for 10 minutes, and at 280° C. for 10 minutes.

Example 3

A polyacrylonitrile-based flame-resistant fiber was prepared by controlling the cyclization reaction to have the cyclization reactivity shown in Table 1 below.

Specifically, a polyacrylonitrile-based precursor fiber (Jilin) containing about 96% by weight of acrylonitrile, about 3% by weight of methyl methacrylate, and about 1% by weight of itaconic acid was placed in an oven at 220° C. for 22.5 minutes, A polyacrylonitrile-based flame-resistant fiber was prepared by sequentially cyclizing for 90 minutes at 240° C. for 22.5 minutes, 260° C. for 22.5 minutes, and 280° C. for 22.5 minutes.

Example 4

A polyacrylonitrile-based flame-resistant fiber was prepared by controlling the cyclization reaction to have the cyclization reactivity shown in Table 1 below.

Specifically, a polyacrylonitrile-based precursor fiber (Jilin) containing about 96% by weight of acrylonitrile, about 3% by weight of methyl methacrylate, and about 1% by weight of itaconic acid was placed in an oven at 220° C. for 30 minutes, Polyacrylonitrile-based flame-resistant fibers were prepared by sequentially cyclizing at 240° C. for 30 minutes, 260° C. for 30 minutes, and 280° C. for 30 minutes for 120 minutes.

Comparative Example 1 and Comparative Example 2

A polyacrylonitrile-based flame-resistant fiber was prepared in the same manner as in Example 1, except that the cyclization reaction was differently adjusted so that each had the cyclization reactivity shown in Table 1 below.

division Cyclization Reaction Scheme Example 1 0.40 Example 2 0.44 Example 3 0.50 Example 4 0.50 Comparative Example 1 0.34 Comparative Example 2 0.58

Meanwhile, in Table 1, the cyclization reactivity is a value calculated through Equation 1 below, in which the infrared spectral spectrum to which the attenuation pre-reflection technique is applied is defined according to the peak height.

[Equation 1]

In Equation 1, _{the definitions of I 0} and I ₁ are the same as described above.

In addition, the infrared spectroscopy spectrum is obtained by preparing a total of five samples (first sample, second sample, third sample, fourth sample, and fifth sample) for each Example and Comparative Example, and a microscope infrared spectrometer ( An infrared spectral spectrum was obtained using the attenuated total reflection technique using Lumos, Bruker, Inc. Specifically, Resolution 8 cm ^-1 and 64 scan, ATR tip pressure was selected as Medium, and the CH peak height was 2923 cm ^-1 . Measured, the baseline was ^{a straight line at 2600 cm -1} and 3155 cm ^-1 , the C≡N peak height ^{was measured at 2243 cm -1} , and the baseline was made a straight line at ^{2100 cm -1} and 2280 cm ^{-1 .} Infrared spectroscopy spectra are shown in FIGS. 1 to 5 .

At this time, in each polyacrylonitrile-based flame-resistant fiber, the first sample is taken from the polyacrylonitrile-based precursor fiber before the cyclization reaction, and the second sample is prepared by moistening the collected first sample with paraffin oil, The third sample is obtained from the prepared polyacrylonitrile-based flame-resistant fiber, the fourth sample is prepared by moistening the collected third sample with paraffin oil, and the fifth sample is the paraffin oil itself.

Experimental example

Each of the polyacrylonitrile-based flame-resistant fibers prepared in Examples 1 to 4, Comparative Examples 1 and 2 was carbonized to prepare carbon fibers, and tensile properties of each produced carbon fibers were comparatively analyzed. The results are shown in Table 2 below.

Specifically, the tensile properties were analyzed using a single fiber measurement method using FAVIMAT+ equipment (Textechno). The fineness of the fiber was measured with a pretension of 1 cN/tex and a testing speed of 5 mm/min, and the tensile properties were measured at the point where the 90% force was reduced at the condition of pretension 1 cN/tex and testing speed of 5 mm/min as the breaking point of the fiber. It was recognized and measured. At this time, the measurement was measured 25 times for each sample, and the average value was shown as a result.

division Tensile strength (GPa) Example 1 2.8 Example 2 2.8 Example 3 2.8 Example 4 3.1 Comparative Example 1 2.5 Comparative Example 2 2.6

As shown in Table 2 above, the tensile strength of carbon fibers prepared using the polyacrylonitrile-based flame-resistant fibers of Examples 1 to 4 having a cyclization reactivity according to an embodiment of the present invention was a comparative example. It was confirmed that the tensile strength was improved compared to the carbon fiber prepared using the polyacrylonitrile-based flame-resistant fiber of Comparative Example 1 and Comparative Example 2. Through this, it can be seen that in the case of the polyacrylonitrile-based flame-resistant fiber having a cyclization reactivity according to the present invention, a carbon fiber having excellent physical properties can be provided.

Claims (7)

A polyacrylonitrile-based flame-resistant fiber having a cyclization reactivity of 0.37 to 0.55 according to the following Equation 1, which is defined according to the peak height of the infrared spectral spectrum to which the attenuation total reflection technique is applied:
[Equation 1]

In Equation 1 above,
I ₀ is the corrected value of the C≡N peak height in the infrared spectral spectrum before the cyclization reaction of the flame-resistant fiber,
I ₁ is the corrected value of the C≡N peak height in the infrared spectral spectrum of the flame-resistant fiber,
The correction value of each peak height is calculated by the following Equations 2 and 3,
[Equation 2]

[Equation 3]

In Equations 2 and 3 above,
A ₀ , A ₁ , A ₂ , B ₁ and B ₂ are the peak height measurements of the infrared spectral spectrum, respectively,
A ₀ is the CH peak height of the nonvolatile liquid material, A ₁ is the CH peak height of the fiber, A ₂ is the CH peak height of the fiber impregnated with the nonvolatile liquid material, B ₁ is the C≡N peak height of the fiber and B ₂ is the peak height of C≡N of the fiber impregnated with the nonvolatile liquid material, wherein the nonvolatile liquid material is at least one selected from paraffin oil, aliphatic ester oil, and aliphatic ether oil.
The method according to claim 1,
The cyclization reactivity is 0.40 to 0.50 of the polyacrylonitrile-based flame-resistant fiber.
The method according to claim 1,
The non-volatile liquid material is a polyacrylonitrile-based flame-resistant fiber that is paraffin oil.
The method according to claim 1,
The infrared spectral spectrum was obtained by measuring a total of five samples using an infrared spectrometer, respectively, by the attenuation pre-reflection technique,
Each of the samples is a first sample collected before the cyclization reaction of the flame-resistant fiber, a second sample in which the first sample is impregnated with a non-volatile liquid material, a third sample collected from the flame-resistant fiber, and the third sample A fourth sample impregnated with a volatile liquid material, and a fifth sample that is a non-volatile liquid material, the polyacrylonitrile-based flame-resistant fiber.
4. The method according to claim 3,
The infrared spectral spectrum is,
A polyacrylonitrile-based flame-resistant fiber that is measured by contacting a sample with a reflection crystal before attenuation, irradiating light to the sample through the reflection crystal before attenuation, and detecting light emitted from the reflection crystal before attenuation.
4. The method according to claim 3,
The infrared spectral spectrum is obtained by measuring by an attenuated total reflection technique with a resolution of 8 cm ^-1 and an integration number of 64 in a wavenumber range of 600 to 4000 cm ^{-1 using an infrared spectrometer.}
It is prepared by carbonizing the polyacrylonitrile-based flame-resistant fiber according to claim 1,
Carbon fiber with a strength of 2.8 GPa or higher.

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