KR20210017888A - Method for preparing acrylonitrile based fiber - Google Patents

Abstract

The present invention relates to an acrylonitrile-based fiber manufacturing method, which comprises the steps of: preparing an acrylonitrile-based fiber precursor by applying moisture to acrylonitrile-based dry yarn using a kissing roller; and preparing an acrylonitrile-based fiber by flame-proofing the acrylonitrile-based fiber precursor, wherein a surface of the kissing roller contains alumina, and has an average roughness in a range of 0.3-1.3 μm. According to the present invention, an appropriate amount of moisture is evenly applied onto the entire area of the acrylonitrile-based fiber precursor so as to further improve unwinding properties, and during the flame-proofing process, heat is evenly transferred to the acrylonitrile-based fiber precursor, such that mechanical properties of the acrylonitrile-based fiber can be further improved.

Description

Manufacturing method of acrylonitrile fiber {METHOD FOR PREPARING ACRYLONITRILE BASED FIBER}

The present invention relates to a method for producing an acrylonitrile fiber, and to a method for producing an acrylonitrile fiber in which an appropriate amount of moisture can be uniformly applied to an acrylonitrile fiber precursor.

Acrylonitrile-based fibers are fibers most commonly used as carbon fiber precursors, and are manufactured through a wet spinning process including processes such as coagulation, washing, stretching, drying, normalizing, and winding. The normalizing process is a process of cooling the temperature of an acrylonitrile-based drying yarn that has been overheated after thermal drying and giving moisture to prevent static electricity. If the acrylonitrile-based fiber precursor does not contain sufficient moisture over the entire area, the storage performance is deteriorated because the fiber cannot be evenly wound around the bobbin during winding. In addition, as the possibility of generating static electricity during maritime increases for use in the firing process, maritime properties may be reduced, resulting in excessive wool generation, and the quality of carbon fibers may deteriorate. The ideal moisture content of the acrylonitrile fiber precursor is evaluated as around 2.0% by weight on average in various literatures, and it is said that the basic quality control is that the acrylonitrile fiber precursor uniformly contains an appropriate amount of moisture over the entire area. I can. In general, in order to impart moisture to the acrylonitrile-based fiber precursor, a process of contacting the acrylonitrile-based fiber precursor by moistening water on a kissing roller in the normalizer process is used. At this time, the moisture content was controlled by adjusting the speed of the kissing roller and the contact area with the acrylonitrile fiber precursor. However, using the above-described process, it was difficult for the acrylonitrile-based fiber precursor to contain uniform moisture over the entire area.

JP2011-021302A

It is an object of the present invention to provide a method for producing an acrylonitrile-based fiber with improved maritime properties since the acrylonitrile-based fiber precursor can uniformly contain an appropriate amount of moisture as a whole.

In addition, an object of the present invention is to provide a method for producing acrylonitrile-based fibers capable of producing carbon fibers with improved mechanical properties.

In order to solve the above-described problems, the present invention provides a step of producing an acrylonitrile fiber precursor by imparting moisture to the acrylonitrile-based dry yarn using a kissing roller; And preparing an acrylonitrile-based fiber by chlorinating the acrylonitrile-based fiber precursor, wherein the surface of the kissing roller includes alumina, and the surface of the kissing roller has an average roughness of 0.3 to 1.3 µm. It provides a method for producing a phosphorus acrylonitrile fiber.

According to the method for producing an acrylonitrile fiber of the present invention, an appropriate amount of moisture can be uniformly provided over the entire area of the acrylonitrile fiber precursor, so that an acrylonitrile fiber precursor having excellent seamability can be prepared. have. In addition, heat can be uniformly transferred over the entire area of the fiber during the chlorination of the acrylonitrile fiber precursor and the carbonization process of the acrylonitrile fiber, so that the mechanical properties of the final product carbon fiber can be improved. .

1 is a view showing a method of manufacturing an acrylonitrile-based fiber precursor.

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

The terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

In the present invention, the average roughness of the surface of the kissing roller can be measured using AFM (Atomic Force Microscopes) by measuring the centerline average roughness (Ra) suggested in the KS B 0161 standard.

1. Manufacturing method of acrylonitrile fiber

A method of manufacturing an acrylonitrile-based fiber according to an embodiment of the present invention includes: 1) preparing an acrylonitrile-based fiber precursor by imparting moisture to the acrylonitrile-based dry yarn using a kissing roller; And 2) preparing an acrylonitrile-based fiber by chlorinating the acrylonitrile-based fiber precursor to prepare an acrylonitrile-based fiber, wherein the surface of the kissing roller includes alumina, and the surface of the kissing roller has an average roughness of 0.3 to It is 1.3 μm.

The inventors of the present invention can control the moisture content and relative deviation of the moisture content of the acrylonitrile fiber precursor by controlling the material and the average roughness of the surface of the kissing roller, and thus, the maritime properties of the acrylonitrile fiber as well as the final product It was found that the mechanical properties of the phosphorus carbon fiber were improved, and thus the present invention was completed.

Hereinafter, each step of the method of manufacturing an acrylonitrile fiber according to an embodiment of the present invention will be described in detail.

1) preparing an acrylonitrile fiber precursor

First, an acrylonitrile-based fiber precursor is prepared by imparting moisture to the acrylonitrile-based dry yarn using a kissing roller.

Since the surface of the kissing roller contains alumina, it has excellent hydrophilicity. Accordingly, even if moisture is given to the surface of the kissing roller and then the kissing roller is rotated for a certain period of time, the residual amount of moisture is significantly higher than that of a kissing roller made of another material. When such a kissing roller and the acrylonitrile-based drying yarn are in contact, moisture present on the surface of the kissing roller is imparted to the acrylonitrile-based drying yarn, and an acrylonitrile-based fiber precursor containing sufficient moisture can be prepared. .

In addition, the average roughness of the surface of the kissing roller may be 0.3 to 1.3 µm, and preferably 0.6 to 1.0 µm. If the above conditions are satisfied, moisture present on the surface of the kissing roller is uniformly imparted over the entire area of the acrylonitrile-based drying yarn, and thus, acrylonitrile containing sufficient moisture uniformly over the entire area. Drying sand can be prepared. In addition, the acrylonitrile-based drying yarn can be wound in an ideal shape on the bobbin, and the amount of wool generated during maritime can be significantly reduced. If it is less than the above-described conditions, the kissing roller cannot impart sufficient moisture to the acrylonitrile-based dry yarn. When it exceeds the above-described range, moisture cannot be uniformly applied to the acrylonitrile-based dry yarn over the entire area. Therefore, the winding property and the spinning property of the acrylonitrile-based fiber precursor may be remarkably deteriorated.

Meanwhile, the material of the kissing roller may be alumina or aluminum having alumina formed thereon. The aluminum with alumina formed on the surface may be prepared by anodizing aluminum, that is, prepared by immersing aluminum in a sulfuric acid solution and then using a low-temperature electrolysis method. If manufactured by the above method, due to the microstructure of the alumina film formed on the surface of the kissing roller, it is possible to finely control the content and distribution of moisture present on the surface of the kissing roller, so that the moisture imparted to the acrylonitrile-based dry sand The content and distribution of can also be finely controlled. In addition, the alumina film formed on the surface of the kissing roller has the advantage of improving the wear resistance and impact resistance of the kissing roller.

Meanwhile, FIG. 1 is a diagram showing a method of manufacturing an acrylonitrile-based fiber precursor.

Referring to FIG. 1, the kissing roller 1 receives moisture from the water tank 2 through rotation, and the kissing roller 1 and the acrylonitrile-based drying yarn 3 contact each other, so that the kissing roller ( Moisture present on the surface of 1) may be imparted to the acrylonitrile-based dry sand (3).

Meanwhile, the acrylonitrile-based drying yarn may be prepared by coagulating, stretching, and drying a spinning solution containing an acrylonitrile-based polymer.

The acrylonitrile-based polymer may be a homopolymer, and may be a copolymer polymerized with an acrylonitrile-based monomer and a comonomer capable of copolymerizing with the acrylonitrile-based monomer. The acrylonitrile-based monomer may be one or more selected from the group consisting of acrylonitrile, methacrylonitrile and 2-ethylacrylonitrile, of which acrylonitrile is preferable. The comonomer may be at least one selected from the group consisting of carboxylic acid-based monomers and acrylonitrile-based monomers. The carboxylic acid-based monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, 2-ethylacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid and mesaconic acid, and itaconic acid is preferred. The acrylate-based monomer may be one or more selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate, of which methyl acrylate is desirable.

The acrylonitrile-based polymer may be prepared using a known polymerization method such as solution polymerization, suspension polymerization, and emulsion polymerization, and solution polymerization is preferable in consideration of process convenience. The solvent used in the solution polymerization may be at least one selected from the group consisting of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, and dimethyl sulfoxide is preferred in consideration of productivity.

The spinning solution is prepared by injecting and dissolving the acrylonitrile-based polymer in at least one selected from the group consisting of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, or prepared by solution polymerization. It may be a solution.

The spinning solution may contain 10 to 40% by weight, 15 to 35% by weight, or 20 to 30% by weight of the acrylonitrile-based polymer, of which 20 to 30% by weight is preferably included. If the above-described range is satisfied, the viscosity of the spinning solution can be maintained at a level at which the fiberization process can be easily performed. In addition, the stability of the spinning solution can be improved because there is little change in the viscosity of the spinning solution over time.

The coagulation may be performed by discharging a spinning solution to a coagulation tank through the spinneret. The coagulation bath may contain a coagulation solution including an organic solvent such as dimethyl sulfoxide, dimethylformamide, dimethyl acetamide, and a coagulation accelerator, which are the same as the solvent of the spinning solution. As the coagulation accelerator, water that does not dissolve the acrylonitrile polymer and is compatible with the solvent used in the spinning solution may be used.

The temperature of the coagulation solution may be determined in consideration of the coagulation point, boiling point of the coagulation solution, the density of the acrylonitrile fiber, and the balance of the strength of the final product carbon fiber. Specifically, the temperature of the coagulation solution may be 40 to 60 ℃. More specifically, the temperature of the coagulation solution may be the same as the temperature of the spinning solution. The reason is that high-quality acrylonitrile fibers are produced only when the temperature and viscosity are kept constant or the temperature and viscosity gradients are minimized throughout the entire process until the spinning solution becomes fibers.

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

On the other hand, the stretching may be hot water stretching and steam stretching in a solidified yarn produced by solidification in a stretching tank. The hot water stretching ratio and the steam stretching ratio may be 2 to 5 or 2.5 to 4.5, respectively, of which 2.5 to 4.5 are preferable. If the above-described conditions are satisfied, the running speed of the coagulated yarn is slowed, and the running direction of the coagulated yarn and the flow direction of water become opposite to each other, so that the occurrence of vortex in the stretching tank can be prevented. Accordingly, it is possible to prevent the focusability and damage of the drawn yarn, and it is possible to prevent deterioration in process runability.

The drying may be to dry the drawn yarn to prepare an acrylonitrile-based dry yarn. The drying may be performed using a hot roll, and the surface temperature of the hot roll may be 100 to 155 °C, 100 to 145 °C, or 110 to 145 °C, of which 110 to 145 °C is preferred. If the above conditions are satisfied, the density of the acrylonitrile-based coagulated yarn can be increased.

2) preparing acrylonitrile fiber

Then, the acrylonitrile-based fiber precursor is flame-resistant to prepare an acrylonitrile-based fiber.

During chlorination, the exothermic reaction due to the cyclization reaction, oxidation reaction, and dehydrogenation reaction occurs suddenly for a short period of time, so it is difficult to control, and such an exothermic reaction is an acrylonitrile polymer contained in the acrylonitrile fiber precursor. It can cause chain breakage, and consequently deteriorate the physical properties of the carbon fiber.

As such, the intermediate step in the production of carbon fibers is chlorination, oxidation, dehydrogenation, etc., through a heat treatment performed in a temperature range of about 180 to 350 ℃ while applying a certain tension in an oxidizing or air atmosphere. Among the components constituting the nitrile-based fiber precursor, low-molecular substances are removed and chemically large changes are made. In addition, this flame resistance is an important process that affects physical properties such as physical and mechanical properties of carbon fiber, as a process that imparts flame retardancy that does not burn even when in contact with a flame.

In addition, during the flame-resistant process, the acrylonitrile-based fiber precursor goes through yellow and brown and finally turns to black, and if the holding time in the heat treatment section of the flame-resistant is excessive, the acrylonitrile fiber is caused by peroxidation. Controlling the flame resistance process may be an important factor, such as a problem in which the precursor is burned.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

Specifications of the kissing roller used in the following Examples and Comparative Examples are as follows.

(A) Kissing roller:

(A-1): Alumina ceramic roller (material: alumina, surface average roughness: 0.55 µm) of UDM Co., Ltd. was used.

(A-2): Alumina ceramic roller (material: alumina, surface average roughness: 0.90 µm) of UDM Co., Ltd. was used.

(A-3): Alumina ceramic roller (material: alumina, average surface roughness: 1.50 µm) of UDM Co., Ltd. was used.

(A-4): Anodized roller (material: anodized aluminum, average surface roughness: 0.50 µm) of UDM Co., Ltd. was used.

(A-5): Anodized roller (material: anodized aluminum, surface average roughness: 0.85 µm) of UDM Co., Ltd. was used.

(A-6): Anodized roller (material: anodized aluminum, average surface roughness: 1.32 µm) of UDM Co., Ltd. was used.

(A-7): A stainless steel roller (material: SUS, average surface roughness: 0.40 µm) of UDM Co., Ltd. was used.

(A-8): A stainless steel roller (material: SUS, average surface roughness: 0.78 µm) of UDM Co., Ltd. was used.

(A-9): A stainless steel roller (material: SUS, average surface roughness: 1.0 µm) of UDM Co., Ltd. was used.

(A-10): A stainless steel roller (material: SUS, surface average roughness: 1.2 µm) of UDM Co., Ltd. was used.

(A-11): A stainless roller (material: SUS, average surface roughness: 3.23 µm) of UDM Co., Ltd. was used.

(A-12): A hard chromium plating roller (material: hard chromium plating, average roughness of the surface: 0.7 µm) of UDM Co., Ltd. was used.

(A-13): UDM Co., Ltd.'s hard chromium plating roller (material: hard chromium plating, average roughness of the surface: 0.93 µm) was used.

Example And Comparative example

<Preparation of spinning solution>

A monomer mixture containing 90% by weight of acrylonitrile, 5% by weight of itaconic acid and 5% by weight of methyl acrylate, dimethyl sulfoxide (DMSO) and azobisisobutyronitrile (AIBN) were added to the reactor, followed by solution polymerization to obtain acrylic A ronitrile polymer solution was prepared. The obtained acrylonitrile-based polymer solution and dimethyl sulfoxide were mixed to prepare a spinning solution containing 21% by weight of an acrylonitrile-based polymer.

<Preparation of acrylonitrile fiber precursor>

After raising the temperature of the spinning solution to 50 °C, a coagulation bath containing water and dimethyl sulfoxide in a weight ratio of 50:50 using a spinneret (hole diameter: 65 µm, number of holes: 3,000) (temperature: 60 ℃) and solidified, a solidification draw rate (CDR: Congelation Draw Rate) of 0.6 to prepare a coagulated yarn.

Subsequently, the coagulated yarn was mixed with a first washing tank (temperature: 60 ℃), a second washing tank (temperature: 60 ℃), a third washing tank (temperature: 70 ℃), a fourth washing tank (temperature: 70 ℃), Washing was performed sequentially in a fifth washing tank (temperature: 80° C.) and a sixth washing tank (temperature: 80° C.). The washed coagulated yarn was hot-water-drawn in first and second hot water tanks (temperature: 95° C.) using a roller to prepare a first-drawn yarn having a hot water draw rate (HDR) of 3.6.

Subsequently, the first stretched yarn was subjected to an emulsion treatment and dried at 110 to 140° C. to prepare a first dried yarn having a dry shrinkage of 8.5%. The first dried yarn was drawn with steam to prepare a second drawn yarn having a steam draw rate (SDR) of 3.6.

Subsequently, the second drawn yarn was heat-set at 150 to 180° C. to prepare an acrylonitrile-based dry yarn having a heat-setting shrinkage of 4.8%.

Subsequently, the acrylonitrile-based dry yarn was moistened with a kissing roller described in the following table to prepare an acrylonitrile-based fiber precursor.

<Production of acrylonitrile fiber>

Subsequently, the acrylonitrile-based fiber precursor was heated from 200° C. to 300° C. and a salt-resistant reaction was performed for 2 hours to prepare an acrylonitrile-based fiber.

<Production of carbon fiber>

The acrylonitrile-based fibers were carbonized for 15 minutes while raising the temperature from 400° C. to 1,600° C. in a carbonization furnace, and naturally cooled at room temperature to prepare carbon fibers.

Experimental example One

The physical properties of the acrylonitrile-based fiber precursors of Examples and Comparative Examples were measured by the method described below, and the results are shown in the following table.

① Moisture content (% by weight): Measure the weight of 25 1 m long acrylonitrile-based fiber precursors before drying, dry them at 105°C for 3 hours using a Convection Oven of JEIO TECH, and measure the moisture. The content was derived, and the average value is shown in the table below.

② Moisture Content Relative Deviation (%): Measure the weight of 25 1 m long acrylonitrile fiber precursors before drying, dry them at 105°C for 3 hours using JEIO TECH's Convection Oven, and then measure the weight. The moisture content was derived, and the relative deviation thereof is shown in the table below.

Experimental example 2

The physical properties of the carbon fibers of Examples and Comparative Examples were measured by the method described below, and the results are shown in the following table.

③ Wool amount (㎍/m): After opening the carbon fiber, the opened carbon fiber was passed between the sponges at a constant speed, and the weight of the wool of the carbon fiber on the sponge was measured. The fiber passage speed was 1 m/min, and the fiber passage length was 3 m.

④ Tensile strength (㎬): A bundle of carbon fibers was impregnated with resin and cut into 250 ㎜ length, and a strand specimen was prepared by attaching tabs using resin at both ends. At this time, the amount of impregnation was adjusted so that the resin impregnation rate of the strand specimen was 30 to 60% by weight, and the measurement length of the specimen was 150 mm. The specimen was measured using a tensile strength tester (manufacturer: INSTRON, brand name: 5982). The measurement speed was set to 10 mm/min and measured 7 times. Tensile strength was measured for 7 specimens, and the average value was indicated.

division Example 1 Example 2 Comparative Example 1 Example 3 Example 4 Comparative Example 1 (A) Kissing roller Kinds A-1 A-2 A-3 A-4 A-5 A-6 material Alumina Alumina Alumina Anodized aluminum Anodized aluminum Anodized aluminum Average roughness (㎛) 0.55 0.90 1.50 0.50 0.85 1.32 Acrylonitrile fiber precursor Moisture content
(weight%) 2.13 2.43 2.89 1.52 1.63 1.78 Moisture content relative deviation
(%) 3.77 3.89 4.54 3.10 3.12 3.95 Carbon fiber Rain
(㎍/m) 3,532 3,522 3,973 3,032 3,056 3,647 Intensity (㎬) 3.5 3.7 3.4 3.6 3.9 3.4

division Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 (A) Kissing roller Kinds A-7 A-8 A-9 A-10 A-11 material SUS SUS SUS SUS SUS Average roughness (㎛) 0.40 0.78 1.0 1.2 3.23 Acrylonitrile fiber precursor Moisture content
(weight%) 0.82 1.23 1.19 1.29 1.35 Moisture content relative deviation
(%) 5.33 5.74 5.80 5.92 7.24 Carbon fiber Rain
(㎍/m) 4,866 4,843 4,966 5,139 5,895 Strength (㎬) 3.3 3.4 3.6 3.5 2.9

division Comparative Example 8 Comparative Example 9 (A) Kissing roller Kinds A-12 A-13 material Hard chrome plating Hard chrome plating Average roughness (㎛) 0.7 0.93 Acrylonitrile fiber precursor Moisture content
(weight%) 1.15 1.07 Moisture content relative deviation
(%) 9.13 8.02 Carbon fiber Rain
(㎍/m) 5,200 6,623 Intensity (㎬) 3.4 3.1

Referring to the above table, Examples 1 and 2 using a kissing roller made of alumina and having an average roughness of 0.55 µm and 0.90 µm have an appropriate moisture content of an acrylonitrile fiber precursor and a low relative deviation of acrylonitrile. It could be predicted that moisture was uniformly distributed over the entire region of the fiber precursor. In addition, since the amount of wool of the carbon fiber is small and the strength is high, it can be predicted that the appearance quality and mechanical properties are excellent.

Comparative Example 1 using a kissing roller made of alumina and having an average roughness of 1.50 µm has a higher moisture content compared to Examples 1 and 2, but has a high relative variation in moisture content, so that the moisture is uniform throughout the entire area of the acrylonitrile fiber precursor. It could be predicted that it was not distributed properly. In addition, since the amount of wool of the carbon fiber was large and the strength was low, it could be predicted that the appearance quality and mechanical properties were deteriorated.

Examples 3 and 4 using kissing rollers made of anodized aluminum, that is, alumina-formed aluminum and having an average roughness of 0.50 µm and 0.85 µm on the surface, had an appropriate moisture content of the acrylonitrile fiber precursor and low relative deviation. It could be predicted that moisture was uniformly distributed over the entire area of the acrylonitrile fiber precursor. In addition, since the amount of wool of the carbon fiber is small and the strength is high, it can be predicted that the appearance quality and mechanical properties are excellent.

Comparative Example 3 using a kissing roller made of anodized aluminum and having an average roughness of 1.50 µm has a higher moisture content compared to Examples 3 and 4, but has a higher moisture content relative to the entire area of the acrylonitrile fiber precursor. It could be predicted that the moisture was not evenly distributed. In addition, since the amount of wool of the carbon fiber was large and the strength was low, it could be predicted that the appearance quality and mechanical properties were deteriorated.

In Comparative Examples 3 to 7 using a kissing roller made of stainless steel, the moisture content of the acrylonitrile fiber precursor was low compared to the examples, and the relative deviation of the moisture content was high, even though the average roughness of the surface of the kissing roller was appropriate. It could be predicted that the moisture was not uniformly distributed over the entire area of the fiber precursor. In addition, since the amount of wool of the carbon fiber was large and the strength was low, it could be predicted that the appearance quality and mechanical properties were deteriorated.

Comparative Examples 8 and 9 using the kissing roller manufactured by hard chromium plating have a lower moisture content of the acrylonitrile fiber precursor compared to the Examples, and a higher relative deviation of the moisture content compared to the Examples, although the average roughness of the surface of the kissing roller is appropriate. It could be predicted that moisture was not uniformly distributed over the entire region of the fiber precursor. In addition, since the amount of wool of the carbon fiber was large and the strength was low, it could be predicted that the appearance quality and mechanical properties were deteriorated.

Claims (5)

Preparing an acrylonitrile-based fiber precursor by imparting moisture to the acrylonitrile-based dry yarn using a kissing roller; And
Including; preparing an acrylonitrile-based fiber by flame-resistant the acrylonitrile-based fiber precursor,
The surface of the kissing roller includes alumina,
The method of manufacturing an acrylonitrile-based fiber having an average roughness of 0.3 to 1.3 µm on the surface of the kissing roller.
The method according to claim 1,
The material of the kissing roller is alumina or aluminum in which alumina is formed on a surface of the acrylonatrile fiber.
The method according to claim 1,
The method of manufacturing an acrylonitrile-based fiber having an average roughness of 0.6 to 1.0 µm on the surface of the kissing roller.
The method according to claim 2,
The method of manufacturing an acrylonitrile-based fiber, wherein the aluminum having alumina formed on the surface is manufactured by anodizing aluminum.
The method according to claim 1,
The acrylonitrile-based drying yarn
A method for producing an acrylonitrile-based fiber prepared by coagulating, stretching, and drying a spinning solution containing an acrylonitrile-based polymer.

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