JP2011026731A - Method for producing precursor for carbon fiber production - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precursor for carbon fiber production, having improved flame-retardant rate and giving a carbon fiber having high quality and high productivity in carbon fiber production process. <P>SOLUTION: The method for producing the precursor for carbon fiber production comprises: compounding 0.1-5.0 wt.% of cellulose nanofibers having an average diameter of 1-500 nm to an acrylonitrile-based polymer containing <15 mol% and ≥0.01 mol% of a polymerizable monomer copolymerizable with acrylonitrile, and solution spinning the product. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a precursor that improves the productivity of carbon fibers by improving the flameproofing speed of carbon fibers.

  In recent years, carbon fiber has been pioneered as a material having both high strength and high elastic modulus. In particular, carbon fiber, a promising material, is attracting attention because it is effective to reduce the weight of structural materials for the purpose of reducing transportation costs associated with rising raw fuel prices and equipment costs on production lines. .

  Under such circumstances, the method for producing polyacrylonitrile (PAN) -based carbon fiber includes a flameproofing process and a carbonization process that require a large amount of energy. In particular, in the flameproofing step, since the reaction of oxidizing and extracting hydrogen in the molecular chain becomes rate-limiting, this treatment takes a long time. In order to shorten this time and improve productivity, Patent Document 1 discloses the use of a copolymer component. This technique has good productivity and a uniform flameproofing reaction, but has a problem of hindering the orientation of the molecular chain, such as softening the molecular chain or creating strong entanglement within the molecule.

JP 05-195324 A (paragraph 0012 on page 2)

  The present invention provides a method for producing a precursor for producing carbon fiber, which can improve productivity and reduce production costs in the production process of carbon fiber.

  An object of the present invention is to produce a carbon fiber characterized in that 0.1% to 5.0% by weight of cellulose nanofibers having an average diameter of 1 to 500 nm are blended with an acrylonitrile-based polymer, and solution spinning is performed. This is solved by a method for manufacturing a precursor.

  According to the present invention, carbon fibers having a short flame resistance time and good product quality can be supplied at low cost.

  The acrylonitrile-based polymer of the present invention is preferable because it can improve the physical properties and yield of the obtained carbon fiber. The composition of the acrylonitrile-based polymer is such that the acrylonitrile component is 85 mol% or more, particularly 15 mol% of the polymerizable unsaturated monomer copolymerizable with acrylonitrile, from the viewpoint of physical properties, process balance, and yield when making the carbon fiber. It is preferably a polymer containing less than 0.01 mol%, more preferably less than 5 mol% and 0.1 mol%.

  Examples of the polymerizable unsaturated monomer include unsaturated carboxylic acids or alkali metal salts, ammonium salts, alkyl esters, acrylamide, methacrylamide or derivatives thereof, allyl sulfonic acid, methallyl sulfonic acid or salts thereof. And alkyl esters.

  Of these, unsaturated carboxylic acids are preferred because they promote the flameproofing reaction. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, ethacrylic acid, maleic acid, and mesaconic acid.

  It is important that the precursor for producing carbon fibers of the present invention contains 0.1 to 5.0% by weight of cellulose nanofibers. Cellulose nanofibers are rigid fibers mainly composed of cellulose, and an effect of accelerating the molecular orientation of the acrylonitrile-based polymer can be obtained by being dispersed in a solution by flowing in the die. Although the details of the mechanism by which the flameproofing reaction proceeds in a short time due to this effect are unknown, the nitrile group in the polymer has a close structure and the main chain of the molecular chain is aligned. It is considered that the activation energy when the hydrogenation or dehydrogenation occurs is lowered.

  Moreover, since the average fiber diameter of a cellulose nanofiber is small, it is hard to act as a foreign material also in a precursor, and is excellent in process passage property. In addition, since cellulose contains a large amount of oxygen in the molecule, cellulose in the fiber is the oxygen supply source in the dehydrogenation reaction, particularly in the flameproofing reaction, and the flameproofing reaction time can be greatly shortened. It becomes possible to increase. The flameproofing reaction in the production process of carbon fiber mainly consists of hydrogen extraction from the molecular chain and cyclization reaction, and diffusion of oxygen molecules and water molecules involved in the reaction is an important factor. For this reason, by adding cellulose nanofibers to the precursor, oxygen can be supplied also from cellulose inside the fibers, so that the diffusion rate can be increased in a pseudo manner. In order to obtain these effects, it is important that 0.1% by weight or more of cellulose nanofibers are contained.

  On the other hand, if a large amount of cellulose nanofiber is present in the precursor, it may cause a defect in the product quality of the carbon fiber or cause a single yarn breakage in the drawing process. Moreover, it is important to set it as 5.0 weight% or less from a viewpoint of the quality of the carbon fiber obtained and process stabilization. For these reasons, the content of cellulose nanofibers is preferably 0.2 to 4.0% by weight, and more preferably 0.3 to 2.0% by weight.

  Since the precursor for carbon fiber production of the present invention has a structure in which the flameproofing reaction easily proceeds due to the inclusion of cellulose nanofibers, the flameproofing reaction time can be set to 70 minutes or less to increase productivity. . The flameproofing reaction time usually takes about 80 to 100 minutes, but as a result of extensive studies, the inventors succeeded in shortening the flameproofing reaction time and improving the productivity. Although the flameproofing time is preferably as short as possible in order to improve productivity, it is sufficient if it can be shortened to about 40 minutes in order to achieve the objects and effects of the present invention.

  Cellulose nanofibers used in the present invention may be those produced by a conventionally known method, but the cellulose fibers used are bacterial cellulose produced by bacterial cellulose, even if they are separated from plants. However, it can be suitably used.

  The pulp used as the raw material of the cellulose nanofiber of the present invention is a pulp obtained by a mechanical method (eg, groundwood pulp, refiner ground pulp, thermomechanical pulp, semichemical pulp, chemiground pulp), or a chemical method. Pulp (craft pulp, sulfite pulp, etc.) obtained in (1) can be used. As the pulp, wood pulp, linter pulp, waste paper pulp and the like are usually used. In addition, materials containing cellulose can be widely used, for example, refined pulp subjected to delignification treatment such as bamboo pulp and bagasse pulp, or cellulose type such as cotton fiber, cotton linter and hemp fiber Natural fibers, or purified natural fibers obtained by subjecting them to delignification, or regenerated cellulose moldings such as viscose, rayon, tencel, polynosic fibers, or dietary fibers derived from grains or fruits (for example, Wheat bran, oat bran, corn hull, rice bran, beer lees, soybean meal, pea fiber, okara, apple fiber, etc.), or lignocellulosic materials such as wood and rice straw.

  Further, non-wood fibers such as kenaf, shiogusa, esparto, cocoon, cocoon, husk, ramie, etc. may be used, and microorganism-produced cellulose, valonia cellulose, squirt cellulose, etc. can also be used.

  In the above, it is preferable to use wood pulp as a main raw material, and synthetic pulp such as polypropylene may be added as necessary. Preferably used are inorganic-supported pulps. Cellulose pulps used for the production thereof include, for example, chemical pulps such as sulfite pulps, alkali pulps, and kraft pulps obtained from hardwoods and softwoods, semi-chemical pulps, Examples thereof include mechanical pulp and mechanical pulp.

  Further, the pulp can be used without distinction between unbleached pulp, bleached pulp and beating, and unbeaten. Hardwood bleached kraft pulp or softwood bleached kraft pulp is most suitable due to its quality and cost.

  In addition, a method in which natural cellulose is used as a raw material, an N-oxyl compound is used as an oxidation catalyst and is oxidized using a co-oxidant and then dispersed in a solvent is also a preferable embodiment because the average diameter of the fibers can be very small.

  It is important that the cellulose nanofiber of the present invention has an average diameter of 1 to 500 nm. The average diameter is obtained by cutting out a cross section of the precursor with a microtome method, photographing the surface with a transmission electron microscope, and randomly extracting and measuring 50 fiber diameters in the obtained image. And the average value. The average diameter needs to be 500 nm or less so as not to act as a foreign substance in the precursor. The average diameter of the fiber is preferably as small as possible, but the fiber diameter is preferably 1 nm or more in order to reduce the energy cost for miniaturization. For these reasons, the average diameter is more preferably 5 to 400 nm, and most preferably 10 to 300 nm.

  The precursor for producing carbon fiber of the present invention may contain other polymers as long as the properties of the acrylonitrile polymer are not significantly changed. As the polymer, 1 selected from the group consisting of cellulose or derivatives thereof, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, polyvinyl chloride, polyvinylidene chloride, polybutadiene, ABS resin, AS resin, AB resin, phenol resin, furan resin Species or two or more are used.

Examples of cellulose or its derivatives include cellulose acetate, nitrocellulose, carboxymethylcellulose and the like. Examples of polyvinyl acetal include polyvinyl butyral and polyvinyl formal. Examples of the phenol resin include novolac type phenol resins.

  However, if the yield of the polymer suitably mixed with the acrylonitrile polymer upon firing is low, not only the modification effect of the obtained carbon fiber is small, but also the generation of voids increases, and the physical properties of the carbon fiber are inferior. Since only a product may be obtained, the yield at 600 ° C. of the polymer to be mixed with the acrylonitrile polymer is preferably 5% by weight or more, more preferably 10% by weight or more, and further preferably 20% by weight or more. Here, the yield at 600 ° C. is 600 ° C. when measured at a heating rate of 20 ° C./min and a nitrogen flow rate of 30 mL / min using a differential thermal balance (TG-DTA) CN8078B1 manufactured by Rigaku Corporation. Is the weight retention with respect to the weight of the sample before measurement.

  The precursor for carbon fiber production obtained in the present invention preferably has a specific gravity of 1.30 to 1.50 after the flameproofing reaction is performed in an air atmosphere, 260 ° C., and a residence time of 60 minutes. The specific gravity after the flame resistance becomes an index for measuring the progress of the flame resistance reaction. If the specific gravity is within this range even if the treatment is performed in a short time, it indicates that the flameproofing reaction has progressed, which is also an indicator of productivity. If the specific gravity after flame resistance is 1.30 or more, carbon fiber can be obtained without breaking the yarn in the next carbonization step, and if it is 1.50 or less, the strength of the carbon fiber can be increased. preferable. For this reason, the specific gravity of the precursor after the flameproofing reaction is more preferably 1.32 to 1.45, and most preferably 1.34 to 1.40, from the viewpoint of process passability and ensuring the quality of the carbon fiber.

  Moreover, it is preferable that the strand strength of the carbon fiber obtained by carbonizing the precursor for producing carbon fiber of the present invention is 3 GPa or more. The higher the strand strength of the carbon fiber, the higher the strength when it is made into a structure. From this, the strand strength of the carbon fiber does not particularly define an upper limit, but if it is about 10 GPa, it is sufficient to achieve the object and effect of the present invention.

  Moreover, it is preferable that the strand elastic modulus of the carbon fiber obtained by carbonizing the precursor for carbon fiber production of the present invention is 200 GPa or more. Since the elasticity modulus of carbon fiber contributes to the elasticity modulus at the time of making it a composite material, it is so preferable that it is high. From this, the elastic modulus of the carbon fiber is not particularly limited, but 500 GPa is sufficient to achieve the objects and effects of the present invention.

  A preferred example for obtaining the precursor for producing carbon fiber of the present invention is shown below.

  The main component constituting the precursor for producing carbon fiber is the acrylonitrile-based polymer described above, and cellulose nanofibers are added to the polymer in an amount of 0.10 to 5.0% by weight.

  Conventional polymerization methods such as suspension polymerization, solution polymerization, and emulsion polymerization can be employed as the polymerization method for the acrylonitrile-based polymer. For the purpose of obtaining a high molecular weight polymer, suspension polymerization or emulsion polymerization is used. In applications where high molecular weight is not required, it is preferable to select solution polymerization in which the polymerization solution can be used as a spinning stock solution as it is.

  As the solvent for dissolving the acrylonitrile-based polymer and the cellulose nanofiber, any of organic and inorganic solvents can be used, but it is preferable to appropriately select from dimethyl sulfoxide, dimethylformamide, and dimethylacetamide. In particular, when solution polymerization is selected as the polymerization method, it is preferable to use dimethyl sulfoxide as a solvent because the monomer can be dissolved.

  A solution in which an acrylonitrile polymer and cellulose nanofibers are dissolved and finely dispersed in a selected solvent is used as a spinning dope.

  In addition, it is preferable to finely disperse cellulose nanofibers in the spinning dope. The state in which the cellulose nanofibers are finely dispersed in the spinning dope is a state in which coarse aggregates having a diameter of 2 μm or more are not present in the spinning dope. This is because one drop of the spinning dope is put on a slide glass and passed through a cover glass. This can be confirmed by observing with an optical microscope.

  The method of fine dispersion here is not particularly limited, but the cellulose nanofibers are once stirred and mixed in dimethyl sulfoxide and dispersed, and then the acrylonitrile polymer is dissolved, or the cellulose nanofibers and the acrylonitrile polymer are dissolved simultaneously. It is also a preferred embodiment that stirring and mixing.

  Filtration can also be performed to remove coarse fibers in the cellulose nanofibers. A conventionally known method can be used as a filtration method, and it is not particularly limited. However, a method of passing a filter through a solution transport step, a method of filtering a cellulose nanofiber dispersion while stirring a spinning stock solution, etc. Is suitable because of high production efficiency.

  In addition, since the cellulose nanofibers to be added are refined by applying physical force, in order to reduce the average diameter, for example, high-speed stirring at 3000 rpm or more, or refinement by ultrasonic waves, etc. Is also a preferred embodiment.

  A spinning dope containing an acrylonitrile-based polymer and cellulose nanofibers is discharged from a die through a metering facility to obtain fibers. The spinning method at this time is not particularly limited, but wet spinning, dry spinning, dry wet spinning, and the like are preferable embodiments.

  The fiber discharged from the die is solidified by solvent replacement or evaporation. When solvent substitution is performed, it is preferable to use a coagulation bath, and it is also a preferable aspect to add a coagulation accelerator to the coagulation bath. As the coagulation accelerator, one that does not dissolve the acrylonitrile copolymer and is compatible with the solvent used in the spinning dope can be used. Specifically, it is preferable to use water.

  The solidified fiber is heated and stretched through one or a plurality of heating steps with hot air or hot water, and then subjected to a drying and densification step, followed by stretching with pressurized steam.

  The drawn fiber is subjected to a flameproofing treatment in an air atmosphere heated to a temperature of 200 ° C. or higher to obtain a flameproof yarn in which cyclization has progressed.

  The obtained flame resistant yarn is subsequently carbonized in a carbonization furnace at 1000 to 2000 ° C. kept in an inert gas atmosphere to form carbon fibers. Moreover, it can graphitize further using a 2000-3000 degreeC furnace, and it can also be set as a graphitized fiber with a high elasticity modulus.

  The preferable example for manufacturing the precursor for carbon fiber manufacture of this invention below is shown.

Moreover, the measuring method of the main physical property value in an Example was described below.
(1) Specific gravity The specific gravity of the flame resistant fiber was measured according to the method described in JIS R7601 (2006). As a reagent, ethanol (special grade manufactured by Wako Pure Chemical Industries, Ltd.) was used without purification. 1.0 to 1.5 g of flameproof fiber bundle was collected and dried at 120 ° C. for 2 hours. After the absolute dry weight (A) was measured, it was impregnated with ethanol having a known specific gravity (specific gravity ρ), and the flame-resistant fiber bundle weight (B) in ethanol was measured. Specific gravity was calculated according to the following.
Flameproof yarn specific gravity = (A × ρ) / (A−B)
(2) Strand tensile strength and tensile elastic modulus Strand tensile strength and tensile elastic modulus are determined in accordance with JIS R7601 (2006) after impregnating a resin having the following composition into a carbon fiber bundle and curing at 130 ° C. for 35 minutes. It can be determined by a tensile test. The tensile modulus can be determined from the slope of the load-elongation curve obtained by the test.
(Resin composition)
• 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexane-carboxylate 100 parts by weight • boron trifluoride monoethylamine 3 parts by weight • acetone 4 parts by weight (3) Stretching process passability In the steam stretching process, 5 Check the running of the yarn for a minute, ◎ if there is no single yarn breakage ◎, slightly seen ○, obviously there is a lot of single yarn breakage or all yarn breakage has occurred The thing was set as x, and ○ or more was set as the pass.

Example 1
A copolymer consisting of 99.5 mol% of acrylonitrile and 0.5 mol% of itaconic acid is polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent, and further ammonia gas is blown until the pH becomes 8.5. While neutralizing itaconic acid, an ammonium group was introduced into the acrylic copolymer to obtain a spinning dope with a copolymer composition content of 22% by weight. The molecular weight of the copolymer composition was 320,000 as a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography of a solution adjusted to a concentration of 0.1% by weight using dimethylformamide as a solvent. To this spinning dope, cellulose nanofibers with an average diameter of 80 nm (Cerish KY-100G manufactured by Daicel Chemical) were added at a rate of 0.50% by weight, and then mixed for 2 hr using a stirring blade with a rotation speed of 50 rpm. A spinning dope was obtained.

  This spinning dope is passed through a filter having a mesh opening of 0.5 μm, and then discharged at 40 ° C. into air using a spinneret having a single hole diameter of 0.15 mm and a hole number of 6,000, and is about 4 mm. After passing through the space, a coagulated yarn was obtained by a dry and wet spinning method introduced into a coagulation bath composed of an aqueous solution of 35% by weight dimethyl sulfoxide controlled at 3 ° C. The coagulated yarn is washed with water in the usual manner, then stretched 1.5 times in warm water at 80 ° C., further passed through a 3% by weight amino-modified silicone silicone oil bath, and then heated at 180 ° C. Is used to produce a carbon fiber having a total drawing ratio of 5 times, a single fiber fineness of 1.1 dTex, and a filament number of 6,000. A precursor for was obtained.

  The obtained precursor was continuously passed through a furnace in an air atmosphere maintained at 260 ° C. for 50 minutes (flame resistance time) to obtain flame resistant fibers having a specific gravity of 1.38. The carbon fiber was then carbonized in a nitrogen atmosphere at a maximum temperature of 1700 ° C.

  The physical properties of the obtained carbon fibers are shown in Table 1, and fibers excellent in mechanical properties were obtained. In addition, the processing time in the flameproofing process could be greatly shortened, and the productivity was excellent.

Example 2
A precursor for carbon fiber production was produced using a spinning stock solution in which the amount of cellulose nanofiber added to the acrylonitrile-based polymer was 2.5% by weight, and the flameproofing time was 45 minutes. The precursor for carbon fiber manufacture and carbon fiber were obtained by the method. Although a single yarn breakage was slightly observed in the steam drawing process, good processability was shown. Further, the obtained carbon fiber was excellent in mechanical properties, and at the same time, the flameproofing time was significantly shortened, and the productivity could be increased.

Example 3
A precursor for carbon fiber production was produced using a spinning stock solution in which the amount of cellulose nanofiber added to the acrylonitrile-based polymer was 0.25% by weight, and the flameproofing time was 55 minutes. The precursor for carbon fiber manufacture and carbon fiber were obtained by the method. No thread breakage was observed in the steam drawing process, and excellent processability was exhibited. Further, the obtained carbon fiber showed good mechanical properties, and it was possible to improve productivity by shortening the flameproofing treatment time.

Example 4
A precursor for carbon fiber production was produced using a spinning stock solution in which the amount of cellulose nanofiber added to the acrylonitrile-based polymer was 4.5% by weight, and the flameproofing time was 40 minutes. The precursor for carbon fiber manufacture and carbon fiber were obtained by the method. Although some single yarn breakage was observed in the steam drawing process, it showed process passability with no practical problems. Further, the obtained carbon fiber showed good mechanical properties, and it was possible to improve productivity by shortening the flameproofing treatment time.

Example 5
A precursor for carbon fiber production was produced using a spinning stock solution in which the amount of cellulose nanofiber added relative to the acrylonitrile polymer was 0.15% by weight, and the flameproofing time was 60 minutes. The precursor for carbon fiber manufacture and carbon fiber were obtained by the method. No breakage of single yarn was observed in the steam drawing process, and excellent processability was exhibited. Further, the obtained carbon fiber showed excellent mechanical properties, and it was possible to improve productivity by shortening the flameproofing treatment time.

Comparative Example 1
A precursor for carbon fiber production and carbon fibers were obtained in the same manner as in Example 1 except that a spinning solution without adding cellulose nanofibers was used. The obtained carbon fiber was not sufficiently flame-resistant, and yarn breakage occurred frequently in the firing step, and carbon fiber could not be obtained.

Comparative Example 2
A precursor for carbon fiber production and carbon fiber were obtained in the same manner as in Example 1 except that a spinning solution without adding cellulose nanofibers was used and the flameproofing time was 80 minutes. Although the obtained carbon fiber showed excellent mechanical properties, the flame resistance time was long and the productivity was poor.

Comparative Example 3
An attempt was made to obtain a precursor for carbon fiber production by the same method as in Example 1 except that a spinning stock solution in which the amount of cellulose nanofibers added to the polymer was 6.0% by weight was used. However, the fiber was highly brittle. Therefore, the single yarn breakage in the steam drawing process was severe, and the whole yarn breakage due to the single yarn breakage occurred, and a sample could not be obtained.

Example 6
A precursor for carbon fiber production and carbon fibers were obtained in the same manner as in Example 1 except that itaconic acid was not added during the polymerization of the acrylonitrile polymer and neutralization with ammonia gas was not performed. The obtained carbon fiber has progressed to a level at which flame resistance is practically acceptable, and exhibited good mechanical properties. In addition, the flameproofing time could be shortened and productivity could be improved.

Example 7
A precursor for carbon fiber production and carbon fiber were obtained in the same manner as in Example 1 except that the weight average molecular weight of the acrylonitrile polymer was 1,200,000 and the stock solution concentration was 10% by weight. The obtained carbon fiber has progressed to a level at which flame resistance is practically acceptable, and exhibited good mechanical properties. In addition, the flameproofing time could be greatly shortened and productivity could be improved.

Example 8
A precursor for carbon fiber production and carbon fibers were obtained in the same manner as in Example 1 except that cellulose nanofibers having an average diameter of 420 nm (Selish KY-100S manufactured by Daicel Chemical Industries) were used as the cellulose nanofibers. Although thread breakage was observed in the steam drawing process, it was at a level of no practical problem. The obtained carbon fiber was sufficiently flame resistant and exhibited good mechanical properties. In addition, the flameproofing time could be greatly shortened and productivity could be improved.

Example 9
A precursor for carbon fiber production and carbon fibers were obtained in the same manner as in Example 1 except that cellulose nanofibers having an average diameter of 350 nm (Cerish KY-100S manufactured by Daicel Chemical Industries) previously pulverized with a homogenizer were used. Slight thread breakage was observed in the steam drawing process, but the drawing process was good. The obtained carbon fiber was sufficiently flame resistant and exhibited good mechanical properties. In addition, the flameproofing time could be greatly shortened and productivity could be improved.

Example 10
A precursor for carbon fiber production and carbon fibers were obtained in the same manner as in Example 1 except that cellulose nanofibers having an average diameter of 250 nm (Cerish KY-100S manufactured by Daicel Chemical Industries) previously pulverized with a homogenizer were used. Although the yarn breakage was slightly observed in the steam drawing process, the passing through the drawing process was good. The obtained carbon fiber was sufficiently flame resistant and exhibited good mechanical properties. In addition, the flameproofing time could be greatly shortened and productivity could be improved.

Example 11
A precursor for carbon fiber production and carbon fibers were obtained in the same manner as in Example 1 except that cellulose nanofibers having an average diameter of 30 nm (Cerish KY-100G manufactured by Daicel Chemical Industries) previously pulverized with a homogenizer were used. No thread breakage was observed in the steam drawing process when obtaining the precursor, and the process passability was good. The obtained carbon fiber was sufficiently flame resistant and exhibited good mechanical properties. In addition, the flameproofing time could be greatly shortened and productivity could be improved.

  Carbon fiber can be supplied with high productivity by the precursor for producing carbon fiber of the present invention.

Claims (2)

  A method for producing a precursor for carbon fiber production, comprising blending 0.1 to 5.0% by weight of cellulose nanofibers having an average diameter of 1 to 500 nm with respect to an acrylonitrile polymer, followed by solution spinning.   The precursor for carbon fiber production according to claim 1, wherein the acrylonitrile polymer is a polymer containing less than 15 mol% and 0.01 mol% or more of a polymerizable unsaturated monomer copolymerizable with acrylonitrile. Manufacturing method.