KR20190063221A - Method for preparing polyacrylonitrile based fiber - Google Patents

Abstract

The present invention relates to a production method of polyacrylonitrile-based fibers capable of improving dry densification efficiency. The production method comprises the steps of: spinning and coagulating a spinning liquid containing a polyacrylonitrile-based polymer; primarily elongating the coagulated polyacrylonitrile-based polymer; drying the primarily elongated polyacrylonitrile-based polymer while passing through a Nelson-type hot roll; and secondarily elongating the dried polyacrylonitrile-based polymer.

Description

METHOD FOR PREPARING POLYACRYLONITRILE BASED FIBER Technical Field [1] The present invention relates to a method for producing polyacrylonitrile-

The present invention relates to a method for producing polyacrylonitrile-based fibers, and more particularly, to a method for producing polyacrylonitrile-based fibers using Nelson-type hot rolls.

The polyacrylonitrile (hereinafter, referred to as PAN) fiber, which is a carbon fiber precursor, can be prepared by spinning, primary drawing, drying, secondary drawing, and heat setting of a spinning solution containing PAN. Here, the first stretching step is a stretching step subsequent to the spinning step in the above-described series of steps, and is usually referred to as hydrothermal stretching or bath stretching because stretching is performed in a bath. The secondary stretching means a stretching step in which the yarn is dried once after the first stretching step, and steam stretching is mainly performed. As described above, in spinning of the PAN fiber which is a carbon fiber precursor, stretching is generally performed twice, and the first stretching is referred to as a first or previous stretching, and the latter is referred to as a second stretching or a subsequent stretching.

On the other hand, in the general drying process, the fiber is conveyed through the spreading roller and dried using a heating plate or a Godet roller. The most commonly used drying process is a drying process using straight hot rolls in which high-defect type rollers are arranged in a line. The straight-line hot-roll drying process can adjust the shrinkage of the fiber by 4 to 15%, thereby optimizing drying efficiency and stretching ratio. More specifically, the straight-line hot-roll drying process is performed at 100 to 150 ° C. When the tension is increased due to the contraction of the fibers due to evaporation of water and residual stress during drying, the speed of the hot- The shrinkage ratio can be controlled.

However, since the straight hot-roll drying process requires a large number of hot rolls and the fiber shrinks due to moisture evaporation and residual stress, there is a problem that the speed of the rollers must be constantly controlled. Further, even if the control of the speed of the roller is finely performed, there is a problem that the fiber shrinks.

JP2004-225191A

An object of the present invention is to provide a method for producing a polyacrylonitrile-based fiber capable of improving the densification of dryness without causing shrinkage of the fiber in the drying step.

In order to solve the above-described problems, the present invention provides a method for producing a polyacrylonitrile-based polymer, comprising: spinning and coagulating a spinning solution containing a polyacrylonitrile-based polymer; Wherein the coagulated polyacrylonitrile-based polymer is firstly elongated; The first stretched polyacrylonitrile-based polymer is dried while passing through a Nelson-type hot roll; And a step of secondarily drawing the dried polyacrylonitrile-based polymer. The present invention also provides a method for producing polyacrylonitrile-based fibers.

According to the method for producing a polyacrylonitrile-based fiber of the present invention, shrinkage does not occur at all in a drying step, and dry densification can be improved while minimizing damage to fibers. In addition, not only the drying process can be performed using a small number of hot rolls, but the process efficiency can be increased because there is no need to control the speed of the hot roll every time the fiber shrinks. Further, the strength, modulus of elasticity and crystal orientation of the polyacrylonitrile-based fiber can be enhanced.

FIG. 1 is a schematic view of a Nelson type roller used in a drying step of a method of producing polyacrylonitrile-based fibers according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

A method for producing a polyacrylonitrile-based fiber according to an embodiment of the present invention includes the steps of: (1) spinning and coagulating a spinning solution containing a polyacrylonitrile-based polymer; (2) a step in which the solidified polyacrylonitrile-based polymer is firstly elongated; (3) drying the primary elongated polyacrylonitrile-based polymer through a Nelson-type hot roll; And (4) secondarily drawing the dried polyacrylonitrile-based copolymer.

Hereinafter, each step of the production method of the present invention will be described in more detail.

(1) Radiation and solidification step

First, a spinning solution containing a polyacrylonitrile-based polymer (hereinafter referred to as "PAN-based polymer") is prepared.

The PAN-based polymer may be a homopolymer obtained by singly polymerizing a (meth) acrylonitrile-based monomer, and may be selected from the group consisting of (meth) acrylonitrile-based monomers, carboxylic acid-based monomers and (meth) May be a PAN-based copolymer that is copolymerized with at least one comonomer.

The (meth) acrylonitrile monomer may be at least one member selected from the group consisting of acrylonitrile and methacrylonitrile, of which acrylonitrile is preferable.

The carboxylic acid-based monomer may be at least one member selected from the group consisting of itaconic acid, acrylic acid and methacrylic acid, and itaconic acid is preferable.

The (meth) acrylate monomer may be at least one selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate and propyl methacrylate, The rate is preferred.

As the polymerization method of the PAN-based polymer, known polymerization methods such as solution polymerization, suspension polymerization and emulsion polymerization can be used, and solution polymerization is preferable in consideration of process convenience. Examples of the solvent used in the solution polymerization include dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide and the like. In consideration of the productivity, that is, the solidification rate, dimethylsulfoxide Lt; / RTI >

The spinning solution may be prepared by adding the PAN-based polymer to a solvent capable of dissolving the PAN-based polymer such as dimethylsulfoxide, dimethylformamide, dimethylacetamide or the like, or dissolving the PAN-based polymer, or using a PAN-based polymer solution prepared by solution polymerization .

The concentration of the PAN-based polymer in the spinning solution may be 10 to 40% by weight, preferably 15 to 35% by weight, more preferably 20 to 30% by weight. When the above-mentioned range is satisfied, the viscosity of the spinning solution can be maintained at a level at which the fibrosis process can be easily performed. Further, stability of the spinning solution can be improved because the viscosity of the spinning solution is not changed with the passage of time.

In addition, it may be preferable to remove the impurities contained in the raw materials of the polymerization reaction and the respective steps by performing a process of filtering the filter solution having a pore size of about 1 탆 or less before spinning the solution. In this case, The strength of the final product, carbon fiber, can be improved.

The radiation may be dry radiation, wet radiation or dry-wet radiation, and it may be desirable to apply wet or dry-wet radiation. For the purpose of improving the compactness of PAN-based fibers and improving mechanical properties, it may be preferable to use dry-wet spinning.

The spinning can be carried out while passing the spinning solution through the spinneret. The shape, diameter and number of holes in the spinneret can be adjusted to suit the end product carbon fiber. The material of the spinneret is not particularly limited, but examples thereof include stainless steel, gold, and platinum.

The solidification can be performed by discharging the spinning solution through the spinneret into the coagulation bath. The coagulation bath may include a coagulation solution containing an organic solvent such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, etc., and a coagulation promoter which is the same as the solvent of the spinach solution. As the coagulation promoting agent, those having compatibility with the solvent used in the spinning solution without dissolving the PAN-based polymer may be used, for example, water may be applied.

The temperature of the solidifying solution can be determined in consideration of the solidification point of the solidifying solution, the boiling point, the density of the PAN-based fibers, and the balance of the strength of the carbon fiber as a final product. Specifically, the temperature of the solidifying solution may be 40 to 60 캜. More specifically, the temperature of the solidifying solution may be the same as the temperature of the spinning solution. This is because high quality PAN-based fibers are produced only when the temperature and viscosity are kept constant or the temperature and viscosity gradient are minimized in the entire process until the spinning solution becomes a fiber.

After the coagulation process, a washing process may be further performed.

(2) Primary elongation step

Next, the coagulated PAN-based polymer is firstly drawn.

The primary elongation may be a hydrothermal extrusion. The hydrothermal stretching may be carried out in a single or a plurality of stretching baths. The temperature of the stretching bath may be 60 to 100 ° C, preferably 70 to 100 ° C, more preferably 80 to 100 ° C have. The stretching ratio may be 1.5 to 10 times, preferably 2 to 6 times, more preferably 3 to 5 times, the total length of the coagulated PAN-based polymer.

Although not essential, a step of adding an emulsifier composed of silicone or the like may be additionally performed after the first drawing step to prevent adhesion between the first drawn PAN-based polymers. The silicone emulsifier may use modified silicone and it may be preferable to add an amino-modified silicone emulsifier having high heat resistance.

(3) Drying step

Next, the first stretched PAN-based polymer is dried while passing through a Nelson-type hot roll.

FIG. 1 is a view for explaining a drying process according to the present invention.

As shown in Fig. 1, the drying process according to the present invention is carried out using a Nelson-type hot roll 100 including a pair of hot rolls arranged up and down. 1, three Nelson-type hot rolls 100 are disposed, but the present invention is not limited thereto. The number of Nelson-type hotrolls can be appropriately adjusted as needed. The first stretched PAN polymer is fed to the Nelson-type hot roll 100 through a feed roller 200, and the first-stretched PAN-based polymer is dried in a state of being wound several times on the Nelson-type hot roll have. In addition, the dried PAN-based polymer can be taken out through the spreading roller 300.

Since the Nelson type hot roll can be arranged in a dual configuration, unlike the conventional flat type hot roll, the drying process can be performed with a small number of hot rolls.

When the PAN-based polymer is dried by using the Nelson-type hot roll, it is possible to improve the densification of the drying while minimizing damage to the fibers. In addition, it is not necessary to control the speed of the hot roll in accordance with the shrinkage of the fiber, so that the process efficiency can be increased.

The first stretched PAN-based polymer can be dried while passing the Nelson-type hot roll under a tension of 100 cN to 1,000 cN, preferably 200 cN to 1,000 cN, more preferably 300 cN to 900 cN. When the above-mentioned range is satisfied, the Nelson-type hot roll can minimize the shrinkage rate without controlling the speed even if heat is applied by the Nelson-type hot roll to the first-stretched PAN-based polymer to cause shrinkage. This minimizes damage to the fiber and improves the densification of the dry, thereby improving the strength and elastic modulus of the final product, carbon fiber.

The first stretched PAN-based polymer may be dried in the Nelson type hot roll in a wound state 2 to 7 times, preferably 3 to 7 times, more preferably 4 to 6 times. When the above-mentioned range is satisfied, shrinkage does not occur during the drying process, and the process efficiency can be increased.

The first stretched polyacrylonitrile-based copolymer may be dried while passing 2 to 8 sets, preferably 2 to 7 sets, more preferably 3 to 6 sets of the Nelson type hot roll. When the above-mentioned range is satisfied, the dry compactness can be further increased.

The two hot rolls constituting the Nelson-type hotrol may rotate at the same surface velocity. The surface velocity of the hot roll may be 5 to 12 m / min, preferably 5 to 10 m / min, and more preferably 6 to 10 m / min. When the above-mentioned range is satisfied, the first stretched PAN-based polymer can be dried while being transferred.

The surface temperature of the Nelson-type hot roll may be 100 to 155 ° C, preferably 100 to 145 ° C, more preferably 110 to 145 ° C. When the above-mentioned temperature is satisfied, the drying compactness of the first elongated PAN-based polymer can be further increased.

The drying step may be performed for 10 to 120 seconds, preferably 20 to 100 seconds, more preferably 30 to 80 seconds. When the above-mentioned range is satisfied, the drying density of the primary-stretched PAN-based polymer can be further increased.

(4) Second elongation step

Next, the dried PAN-based polymer is subjected to second elongation.

The second stretching may be steam stretching, and the steam stretching may be a step of stretching the dried PAN-based fibers under a pressurized steam atmosphere.

The steam supply pressure may be 1.0 to 3.5 bar, preferably 1.5 to 3.5 bar, more preferably 1.5 to 2.5 bar, and the temperature may be 110 to 150 ° C, preferably 115 to 145 ° C, more preferably 120 To 140 < 0 > C. When the above-mentioned range is satisfied, high temperature is obtained by steam, and at the same time, the presence of moisture enables the plasticizing effect of the fiber polymer to be effected at high magnification in the fiber length direction. As the pressure / temperature of the steam increases, the elongation becomes easy. However, when the temperature exceeds the stretching threshold, the strength between the fiber molecules decreases, resulting in a decrease in the fiber strength and modulus. And can be advantageous for improvement of physical properties.

The method for producing a polyacrylonitrile-based fiber according to an embodiment of the present invention may further include a step of thermally fixing the secondarily stretched PAN-based polymer.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

< PAN system  Preparation of polymer &gt;

Manufacturing example  One

A 3L glass reactor was charged with a monomer mixture containing 85% by weight of acrylonitrile, 10% by weight of itaconic acid and 5% by weight of methyl acrylate, and dimethylsulfoxide (DMSO) as a solvent and azobisisobutyronitrile (AIBN) was used to prepare a PAN - based polymer.

< PAN system  Method of manufacturing fiber>

Example  One

A spinning solution containing the PAN-based polymer of Production Example 1 and dimethyl sulfoxide at a weight ratio of 25:85 was prepared, the spinning solution was heated to 50 ° C, and then spinneret (hole diameter: 0.07 mm, number of holes: 100 ) Was discharged into a coagulation tank (temperature: 50 ° C) containing water and dimethylsulfoxide at a weight ratio of 45:55 and solidified to prepare a coagulated PAN-based polymer. The coagulated PAN-based polymer had a stretch ratio (CDR) of 0.50.

The coagulated PAN-based polymer was washed with water at 60 캜. The washed coagulated solution was hydrothermally stretched in a heat bath of 95 캜 using a roller, and the hydrothermal stretching ratio (HDR) was 3.67.

The hydrothermally stretched PAN-based polymer was passed through three pairs of a pair of Nelson type hot rolls. At this time, the first stretched PAN polymer was wound 12 times in the Nelson type hot roll in a state in which tension of 1,000 cN was applied. The distance between each of the hot rolls constituting the Nelson type hot roll was 50 cm, the surface temperature was 145 占 폚, and the surface velocity was 7 m / min.

Then, the dried PAN-based polymer was subjected to steam-drawing using saturated steam at 2 bar and 130 ° C. The steam draw ratio (SDR) was 3.40. Thus, the production of PAN-based fibers was completed.

1) Method of measuring the stretching ratio (CDR) of the coagulated PAN-based polymer: The CDR was measured by the difference between the discharge linear velocity of the PAN-based polymer discharged from the spinneret and the speed difference of the roller for transporting the coagulated PAN-based polymer coming from the coagulation tank

2) Measuring method of HDR: The difference between the speed of the roller conveying the coagulated PAN-based fibers entering the heat bath (hydrothermal stretching bath) and the speed difference of the roller conveying the hydrothermally stretched PAN-based polymer coming from the heat bath Lt; / RTI &gt;

3) Method of Measuring Steam Drawing Ratio (SDR): The SDR was measured by the difference between the speed of the roller conveying the dried PAN-based polymer entering the steam stretcher and the speed of the roller conveying the PAN-based fibers coming from the steam stretching device.

Example  2

PAN-based fibers were prepared in the same manner as in Example 1, except that the coagulated PAN-based polymer had a draw ratio of 0.45 and a steam-drawn PAN-based polymer had a steam draw ratio of 3.78.

Comparative Example  One

A spinning solution containing the PAN-based polymer of Production Example 1 and dimethyl sulfoxide at a weight ratio of 25:85 was prepared, the spinning solution was heated to 50 ° C, and then spinneret (hole diameter: 0.07 mm, number of holes: 100 ) Was discharged into a coagulation tank (temperature: 50 ° C) containing water and dimethylsulfoxide at a weight ratio of 45:55 and solidified to prepare a coagulated PAN-based polymer. The coagulated PAN-based polymer had a stretch ratio (CDR) of 0.50.

The coagulated PAN-based polymer was washed with water at 60 캜. The washed coagulated solution was subjected to hydrothermal stretching in a heat water bath of 95 using a roller, and the hydrothermal stretching ratio (HDR) was 2.62.

The primary stretched PAN-based polymer was passed through 16 linear hot rolls. At this time, in the 16 linear hot rolls, the first stretched PAN polymer was passed under a tension of 1,500 cN, the distance between each hot roll was 20 cm, the surface temperature was 140 ° C, the surface velocity was 7 m / min .

Then, the dried PAN-based polymer was subjected to steam-drawing at 2 bar and 130 ° C using saturated steam. The steam draw ratio (SDR) was 4.80. Thus, the production of PAN-based fibers was completed.

Comparative Example  2

The tensile force applied to the first PAN drawn on the first hot roll was 500 cN and the tensile force applied on the first drawn PAN polymer was reduced as it passed through the hot roll. PAN-based fibers were prepared in the same manner as in Comparative Example 1 except that the tensile strength was 200 cN.

Comparative Example  3

The tensile force applied to the PAN polymer polymerized first in the first hot roll was 300 cN and the tensile force applied to the PAN polymer polymerized in the first elongated state was decreased as it passed through the hot roll. PAN-based fibers were prepared in the same manner as in Comparative Example 1, except that the tensile strength was 100 cN.

Experimental Example  One

The dried shrinkage ratios of the dried PAN polymers of Examples 1, 2 and Comparative Examples 1 to 3 were measured, and the results are shown in Table 1 below.

4) Method of measuring the shrinkage ratio: The shrinkage ratio was calculated by the roller speed difference before and after drying.

Experimental Example  2

The final draw ratio, strength, elastic modulus, elongation and crystal orientation degree of the PAN fibers of Examples 1, 2 and Comparative Examples 1 to 3 were measured, and the results are shown in Table 1 below.

5) Total draw ratio: Ratio of coagulated PAN based polymer (CDR) x Ratio of stretched PAN based polymer (HDR) x Steam stretched PAN based polymer (SDR)

6) Strength measurement method (g / denier): The tensile strength of the fiber was measured using Single-Fiber Testers (manufacturer: Textechno, trade name: Favimat +). A group of fibers having a fiber length of 40 to 50 mm was taken from the sample and single fibers were pulled out one by one and attached to the binding apparatus of the tensile tester. The length of the specimen was set to 25 mm and the tensile speed was 10 mm / min. Tensile strength and elastic modulus were measured on 25 test specimens and their average values were shown.

7) Measurement of elastic modulus (g / denier): The tensile modulus of the fiber was measured using Single-Fiber Testers (manufacturer: Textechno, trade name: Favimat +). A group of fibers having a fiber length of 40 to 50 mm was taken from the sample and single fibers were pulled out one by one and attached to the binding apparatus of the tensile tester. The length of the specimen was set to 25 mm and the tensile speed was 10 mm / min. Tensile strength and elastic modulus were measured on 25 test specimens and their average values were shown.

8) Elongation measurement method (%): The elongation of the fiber was measured using Single-Fiber Testers (manufacturer: Textechno, product name: Favimat +). A group of fibers having a fiber length of 40 to 50 mm was taken from the sample and single fibers were pulled out one by one and attached to the binding apparatus of the tensile tester. The length of the specimen was set to 25 mm and the tensile speed was 10 mm / min. Tensile strength and elastic modulus were measured on 25 test specimens and their average values were shown.

9) Crystal orientation (%): The fibers were measured by X-ray diffraction (XRD), and the full width at half maximum (FWHM) at the crystal face (100) And the following equation was used.

Orientation degree = (180 ° - FWHM) / 180 °

10) Steam elongation exit running speed (ea / min): The LED light is illuminated at the steam generator exit, and the number of single fibers broken by the naked eye is counted for 2 minutes and the average value is indicated.

division dry
Contraction ratio
(%) Total stretching cost burglar
(g / denier) Modulus of elasticity
(g / denier) Elongation
(%) decision
Orientation
(%) steam
Stretching
exit
Driving
Mow
(ea / min) Example 1 0% 6.24 7.7 151 10.4 0.883 One Example 2 0% 6.24 7.6 151 11.5 0.882 0 Comparative Example 1 0% 6.68 6.8 127 13.4 0.869 6 Comparative Example 2 4% 6.68 6.6 123 13.1 0.861 One Comparative Example 3 8% 6.68 6.4 127 12.0 0.857 0

In the case of Examples 1 and 2 according to the production method of the polyacrylonitrile-based fiber of the present invention, although the drying shrinkage ratio is 0% and the total draw ratio is lower than that of Comparative Examples 1 to 3, It was confirmed that the fiber had excellent strength, elastic modulus and crystalline orientation. Also, it can be confirmed that the number of occurrences of short fibers (single fibers) generated at the outlet of the steam generator is also good.

However, in the case of Comparative Example 1, it can be confirmed that the drying shrinkage ratio is 0%, but the strength, elastic modulus and crystal orientation degree are lowered, and the running stability of the fiber is lowered there was. In addition, in the case of Comparative Examples 2 and 3, it was confirmed that not only the drying shrinkage but also the strength, the modulus of elasticity and the degree of crystal orientation were both lower than those of Examples 1 and 2.

Claims (8)

A spinning solution containing a polyacrylonitrile-based polymer is spun and coagulated;
Wherein the coagulated polyacrylonitrile-based polymer is firstly elongated;
The first stretched polyacrylonitrile-based polymer is dried while passing through a Nelson-type hot roll; And
Wherein the dried polyacrylonitrile-based polymer is secondarily elongated. The method of producing a polyacrylonitrile-based fiber according to claim 1,
The method according to claim 1,
Wherein the primary stretched polyacrylonitrile-based polymer is dried while passing through a Nelson-type hot roll under a tension of 100 to 1,000 cN.
The method according to claim 1,
Wherein the primary stretched polyacrylonitrile-based polymer is passed through the Nelson-type hot roll two to seven times and then passed.
The method according to claim 1,
Wherein the primary stretched polyacrylonitrile-based polymer is dried while passing through the Nelson type hot rolls 2 to 8.
The method according to claim 1,
Wherein the surface temperature of the Nelson-type hot roll is 100 to 155 占 폚.
The method according to claim 1,
Wherein the drying step is performed for 10 to 120 seconds.
The method according to claim 1,
Wherein the primary drawing is hydrothermal sintering.
The method according to claim 1,
Wherein the secondary drawing is steam drawing.

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