JP2011213771A - Method of manufacturing polyacrylonitrile copolymer using tubular continuous reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a polyacrylonitrile copolymer suitable for the manufacture of a high-grade carbon fiber and to provide a method of manufacturing a carbon fiber using the polyacrylonitrile copolymer.SOLUTION: The method of manufacturing a polyacrylic copolymer comprises (a) a first polymerization step of feeding a raw material mixture comprising at least monomers containing acrylonitrile, a chain transfer agent and a polymerization initiator to a circulation line (I) having incorporated therewith at least one tubular reactor 24 having a structure for static mixing to continuously polymerize it at 30-150°C with a temperature nonuniformity in the reactor controlled within 5°C, (b) a solution-feeding step of feeding the solution from a branched part of the circulation line (I) used in the first polymerization step to a second polymerization step, and (c) a second polymerization step of continuously polymerizing the solution fed from the solution-feeding step at 30-150°C with a temperature nonuniformity in the tubular reactor controlled within 5°C while passing the solution through a non-circulation line (II) having a structure for static mixing so as to attain a polymerization rate of 80-95% at an outlet of the non-circulation line (II).

Description

The present invention relates to a high-quality carbon fiber precursor fiber, a polyacrylonitrile copolymer suitable for the production of carbon fiber, a method for producing the same, and a method for producing carbon fiber using the polyacrylonitrile copolymer.

  Carbon fiber has high specific strength and specific elastic modulus compared to other fibers. For this reason, as a reinforcing fiber for composite materials, in addition to conventional sports and aerospace applications, it is also widely used in general industrial applications such as automobiles, civil engineering / architecture, pressure vessels and windmill blades. There is a high demand for improved productivity and stable production.

  Among the carbon fibers, the most widely used polyacrylonitrile (hereinafter sometimes abbreviated as PAN) carbon fiber is a PAN copolymer that is a precursor of wet spinning, dry spinning or dry wet spinning. To obtain a carbon fiber precursor fiber, which is then heated in an oxidizing atmosphere at a temperature of 200 to 400 ° C. to convert to a flame-resistant fiber, and heated in an inert atmosphere at a temperature of at least 1000 ° C. It is manufactured industrially by carbonization.

  The productivity and quality improvement of PAN-based carbon fibers are performed from the viewpoints of spinning, flame resistance or carbonization of carbon fiber precursor fibers. Above all, improvement of the productivity of polyacrylonitrile was difficult due to the following problems. That is, the production of a polyacrylonitrile copolymer according to the prior art is carried out using a tank reactor (see Patent Documents 1 and 2). In such a tank reactor, it is first considered to increase the size of the reactor in order to improve productivity. However, it is known that simply increasing the size of the reactor will increase the temperature spot inside the reactor, and if the temperature spot increases, the quality stability will decrease, improving the productivity of the larger reactor size. I can't do it. In order to improve productivity without increasing the size of the reactor, it is conceivable to increase the polymerization rate. However, in this case as well, a problem occurs in heat removal, resulting in a large temperature spot in the reactor and stable quality. Therefore, there is a problem that it is difficult to achieve both improvement in productivity and stabilization of quality.

  On the other hand, in the polymerization of acrylic-styrene copolymer or the like, a production method using a tubular reactor having a static mixing part inside is known. This production method is known as a technology that has high heat removal capability, small temperature spots in the polymerization reactor, and can increase productivity without destabilizing the quality even if the polymerization rate is increased. (See Patent Documents 3 and 4).

JP 2001-146502 A JP-A-1-26615 Japanese Patent Laid-Open No. 9-12638 Japanese Patent Laid-Open No. 10-45811

  However, when a polyacrylonitrile copolymer is polymerized using such a continuous polymerization method, the reaction heat is 1.5 to 2 times that of an acrylic-styrene copolymer, resulting in defects in heat removal and poor quality. It was found to stabilize. Accordingly, an object of the present invention is to provide a production method by a continuous polymerization method using a tubular reactor that can achieve both the quality stability and equipment productivity of a polyacrylonitrile copolymer suitable for producing a carbon fiber precursor fiber. There is to do.

In order to solve this problem, the present invention has the following configuration. That is, a process for producing a polyacrylonitrile copolymer,
(a) A circulation line (I) in which one or more tubular reactors having a static mixing structure are incorporated into a raw material mixture containing at least a monomer containing acrylonitrile, a chain transfer agent, and a polymerization initiator (I A first polymerization step in which temperature fluctuations in the tubular reactor are controlled within 5 ° C. at 30 to 150 ° C., and continuous polymerization is performed.
(b) a liquid feeding step for sending from the branch portion of the circulation line (I) used in the first polymerization step to the second polymerization step;
(c) While passing the solution sent from the liquid feeding process through a non-circulation line (II) having a static mixing structure inside, the temperature spots in the tubular reactor are kept within 5 ° C. at 30 to 150 ° C. It is a method for producing a polyacrylic copolymer having a second polymerization step of controlling and continuously polymerizing the polymerization rate at 80 to 95% at the outlet of the non-circulation line (II).

  The quality stability and equipment productivity of a polyacrylonitrile copolymer suitable for producing a carbon fiber precursor fiber can be achieved.

It is process drawing which shows the outline of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  The raw material mixture used in the method for producing a polyacrylonitrile (hereinafter sometimes referred to as PAN) copolymer of the present invention contains at least a monomer containing acrylonitrile, a chain transfer agent, and a polymerization initiator.

  As a monomer for obtaining the polyacrylonitrile copolymer in the raw material mixture used in the method for producing the polyacrylonitrile copolymer of the present invention, it is necessary to include acrylonitrile (hereinafter sometimes referred to as AN), Those containing AN of 98 to 100 mol% and containing 0 to 2 mol% of monomers copolymerizable with AN are preferably used.

  Examples of monomers copolymerizable with AN include, for example, acrylic acid, methacrylic acid, itaconic acid and alkali metal salts thereof, ammonium, from the viewpoint of accelerating the treatment in the flameproofing process, which is the first process of carbon fiber production. Salts and lower alkyl esters, acrylamide and derivatives thereof, allyl sulfonic acid, methallyl sulfonic acid and salts or alkyl esters thereof can be used.

  The polymerization initiator in the raw material mixture used in the method for producing the polyacrylonitrile copolymer of the present invention has a radical generation temperature (in the present invention, the 10-hour half-life temperature is defined as the radical generation temperature) of 30 to 150 ° C. is there. From the viewpoints of handling from a safety aspect and industrially efficient polymerization, a polymerization initiator having a radical generation temperature in the range of 30 to 100 ° C. is preferable. As such a polymerization initiator, oil-soluble azo compounds, water-soluble azo compounds, peroxides, and the like are preferable. Among them, an azo compound that does not cause the generation of oxygen that inhibits polymerization at the time of decomposition is preferably used, and in the case of polymerization by solution polymerization, an oil-soluble azo compound is preferably used from the viewpoint of solubility. Specific examples of the oil-soluble azo compounds include 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (radical generation temperature 30 ° C.), 2,2′-azobis (2,4′- Dimethylvaleronitrile) (radical generation temperature 51 ° C.), 2,2′-azobisisobutyronitrile (radical generation temperature 65 ° C.), and 1,1′-azobis (cyclohexane-1-carbonitrile) (radical generation temperature) 88.degree. C.) as specific examples of water-soluble azo compounds such as 2,2′azobis (2,2′imidazolinyl) propane, (radical generation temperature 61 ° C.), and specific examples of peroxides as dibenzoyldioxidane ( Radical generation temperature 80 ° C.). Further, the content of the polymerization initiator is preferably 0.1 to 5.0 parts by weight per 100 parts by weight of the monomer. When the amount is less than 0.1 parts by weight, the polymerization rate may decrease and the productivity may decrease. When the amount exceeds 5.0 parts by weight, the reaction heat generated at the initial stage of the polymerization reaction increases, and heat removal is performed. May cause problems.

  As the chain transfer agent in the raw material mixture used in the method for producing the polyacrylonitrile copolymer of the present invention, a known compound having a chain transfer action such as octyl mercaptan and dodecyl mercaptan can be used. The chain transfer agent content is preferably 0.00 to 0.100 parts by weight per 100 parts by weight of the monomer. This is because if the molecular weight exceeds 0.10, the molecular weight may decrease and the carbon fiber elastic modulus may decrease.

  In the method for producing a polyacrylonitrile copolymer of the present invention, the raw material mixture is polymerized by applying the following steps (a) to (c). By applying this process, both high quality stability and equipment productivity can be achieved. The polymerization method can be selected from known polymerization methods such as bulk polymerization, solution polymerization, and saponification polymerization, and is preferably solution polymerization from the viewpoint of productivity and quality stability.

 (a) In the first polymerization step, a polymerization initiation reaction and a part of the growth reaction are performed. In (c) the second polymerization step, a growth reaction and a termination reaction are performed. By combining these steps, a polyacrylonitrile polymer having the target molecular weight is obtained. (b) The liquid feeding step is a step of feeding a liquid from the first polymerization step to (c) the second polymerization step and adding a polymerization initiator or a chain transfer agent as necessary.

  Each step will be described in detail below.

(a) In the first polymerization step, the raw material mixture is supplied to a circulation line (I) incorporating one or more tubular reactors having a static mixing structure therein, at 30 to 150 ° C. In this step, temperature fluctuations in the tubular reactor are controlled within 5 ° C., and continuous polymerization is performed. By having the tubular reactor having the structure for static mixing inside, the internal heat exchange surface area is increased and high heat conduction is achieved. In addition, in the circulation line (I) incorporating one or more tubular reactors having a structure for static mixing therein, continuous polymerization is performed while performing static mixing in the tubular reactor. Thus, continuous polymerization can be performed under conditions in which temperature spots are controlled to be small. Preferably, the hydrostatic mixer has a compound curved tube. The heat transfer area per unit volume of the tubular reactor is preferably 10 m ² / m ³ or more, more preferably 30 m ² / m ³ or more, and even more preferably 50 m ² / m ³ or more.

  The tubular reactor having the static mixing structure therein is preferably a tubular reactor having a static mixing element therein. As the mixing element, for example, there is an element that mixes the polymerization liquid by forming a turbulent flow by changing the flow of the polymerization liquid flowing into the pipe and changing the flow direction and repeating the division and merging.

  As a tubular reactor having a static static mixing structure inside, a tubular reaction having a Sulzer type SMR type tubular mixer (manufactured by Sulzer) excellent in stirring efficiency and heat transfer area. It is preferable to use a vessel. Such a continuous line may have a plurality of static mixing structures of the same or different types.

  The polymerization temperature in the first polymerization step is 30 to 150 ° C, more preferably 40 to 120 ° C, and further preferably 90 to 120 ° C. As described above, in radical polymerization, the higher the polymerization temperature, the higher the polymerization rate tends to increase. In addition, the viscosity of the reaction solution decreases, which is advantageous for productivity, but the polyacrylonitrile polymer has a cyclization reaction. It is also important that the reaction is not too high because side reactions such as and crosslinking reactions become significant. When the polymerization temperature is lower than 30 ° C., the polymerization rate is decreased, and measures such as increasing the concentration of the polymerization initiator may be necessary, which is not preferable. On the other hand, if the temperature is higher than 150 ° C., the side reaction that the reaction solution undergoes during polymerization becomes significant, which is not preferable. When the polymerization temperature is in the range of 40 to 120 ° C., results in which productivity and polymer property stability are particularly excellent are obtained. Furthermore, by setting the polymerization temperature to 90 to 120 ° C., productivity is significantly higher than that of batch type solution polymerization under normal pressure or slight pressure generally used in the production of polyacrylonitrile polymers. Can be increased. At this time, it is preferable to perform polymerization by pressurizing the monomer mixture or solvent supplied in the polymerization step to a pressure equal to or higher than the saturated vapor pressure at the polymerization temperature. When the polymerization is carried out at or below the saturation vapor pressure of each raw material, the raw material evaporates and the raw material composition changes, so the quality may not be stable.

  In the continuous polymerization, the temperature in the tubular reactor in the circulation line (I) needs to be controlled within 5 ° C. This is because when the temperature spots exceed 5 ° C., the quality becomes unstable and the productivity decreases. From this viewpoint, it is more preferably within 3 ° C.

  Further, it is preferable to set the type, concentration and polymerization temperature of the polymerization initiator so that the polymerization rate in the first polymerization step is 5 to 20% / hr. If it is less than 5% / hr, the productivity is lowered, and if it is 20% / hr, there is a large amount of heat of reaction, which may cause problems in heat removal.

  (b) The liquid feeding step is a step of sending the branched portion of the circulation line (I) used in the first polymerization step to the second polymerization step. In this liquid feeding step, it is also a preferred form to add a monomer, a polymerization initiator, and a chain transfer agent as necessary. For example, a polymerization initiator is added when the polymerization rate is below the target at the outlet of the first polymerization step, a chain transfer agent is added when Mz is above the target, and the polymer concentration is below the target. When they match, it is preferable to add a monomer and a polymerization initiator.

  (c) In the second polymerization step, the polyacrylonitrile polymer supplied from the liquid feeding step is a non-circulation line (II) incorporating one or more tubular reactors having a static mixing structure therein. ), Temperature fluctuations in the tubular reactor at 30 to 150 ° C. are controlled within 5 ° C., and continuous polymerization is performed.

  As the static mixing structure portion of the tubular reactor incorporated in the non-circulation line of the second polymerization step, a Sulzer type SMR having excellent stirring efficiency and heat transfer area as in the first polymerization step. It is preferable to use a type of tubular mixer (manufactured by Sulzer). Such continuous lines may have the same or different types of static mixing structures at a plurality of locations.

The polymerization temperature in the second polymerization step is 30 to 150 ° C, more preferably 40 to 150 ° C, and further preferably 90 to 150 ° C. As described above, in radical polymerization, the higher the polymerization temperature, the higher the polymerization rate tends to increase. In addition, the viscosity of the reaction solution decreases, which is advantageous for productivity, but the polyacrylonitrile polymer has a cyclization reaction. It is also important that the reaction is not too high because side reactions such as and crosslinking reactions become prominent. When the polymerization temperature is lower than 30 ° C., the polymerization rate is decreased, and measures such as increasing the concentration of the polymerization initiator may be necessary, which is not preferable. On the other hand, if the temperature is higher than 150 ° C., the side reaction that the reaction solution undergoes during polymerization becomes significant, which is not preferable. When the polymerization temperature is in the range of 40 to 120 ° C., results in which productivity and polymer property stability are particularly excellent are obtained. At this time, it is preferable to perform polymerization by pressurizing the monomer mixture or solvent supplied in the polymerization step to a pressure equal to or higher than the saturated vapor pressure at the polymerization temperature. When the polymerization is carried out at or below the saturation vapor pressure of each raw material, the raw material evaporates and the raw material composition changes, so the quality may not be stable. Furthermore, by setting the polymerization temperature to 90 to 120 ° C., productivity is significantly higher than that of batch type solution polymerization under normal pressure or slight pressure generally used in the production of polyacrylonitrile polymers. Can be increased.
In the continuous polymerization, the temperature in the tubular reactor in the non-circulation line (II) needs to be controlled within 5 ° C. This is because when the temperature spots exceed 5 ° C., the quality becomes unstable and the productivity decreases. From this viewpoint, it is more preferably within 3 ° C.
Further, the polymerization rate in the first polymerization step is preferably 5 to 20% / hr, and if it is less than 5% / hr, the productivity is lowered, and if it is 20% / hr, reaction heat is generated. In many cases, problems may occur in heat removal. The polymerization rate at the outlet of the second polymerization step is preferably 80 to 95%. When the polymerization rate is less than 80%, the productivity is lowered. On the other hand, when the polymerization rate exceeds 90%, the polymerization rate is lowered. Therefore, in order to obtain a polymerization rate of 95% or more, the polymerization reaction time is increased and the productivity is lowered.

  Next, the manufacturing method of the carbon fiber precursor fiber using the PAN-type polymer obtained with the manufacturing method of this invention is demonstrated.

  After the PAN copolymer obtained by the production method of the present invention is introduced into a coagulation bath and coagulated to form a coagulated yarn, it is subjected to a water washing step, an in-bath drawing step, an oil agent application step, and a drying step, and then carbon fiber. Precursor fibers are obtained. Moreover, you may add a dry heat extending process and a steam extending process to said process. The solidified yarn may be directly stretched in the bath without the water washing step, or may be stretched in the bath after removing the solvent by the water washing step. Usually, the stretching in the bath is preferably performed in a single or a plurality of stretching baths adjusted to a temperature of 30 to 98 ° C. The draw ratio at that time is preferably 1 to 5 times, and more preferably 1 to 3 times.

  After the stretching step in the bath, it is preferable to apply an oil agent made of silicone or the like to the stretched fiber yarn for the purpose of preventing adhesion between single fibers. As the silicone oil, it is preferable to use a silicone oil containing a modified silicone such as amino-modified silicone having high heat resistance.

  As the drying step, for example, a drying condition in which a drying temperature is 70 to 200 ° C. and a drying time is 10 seconds to 200 seconds gives preferable results. As an improvement in productivity and an improvement in the degree of crystal orientation, it is preferable to stretch in a heating heat medium after the drying step. As the heating heat medium, for example, pressurized steam or superheated steam is suitably used in terms of operational stability and cost, and the draw ratio is usually 1.5 to 10 times.

  Next, the manufacturing method of the carbon fiber of this invention is demonstrated.

In the present invention, the carbon fiber precursor fiber obtained as described above is flame-resistant in which the carbon fiber precursor fiber is flame-resistant in air at a temperature of 200 to 300 ° C., and the fiber obtained in the flame resistance process is 300 to 800 ° C. Carbon fiber through a preliminary carbonization step of precarbonizing in an inert atmosphere at a temperature of 5 and a carbonization step of carbonizing the fiber obtained in the preliminary carbonization step in an inert atmosphere at a temperature of 1,000 to 3,000 ° C. Can be obtained.
The carbon fiber obtained by the present invention is a carbon fiber reinforced composite material excellent in various mechanical properties such as post-impact compressive strength by various molding methods such as autoclave molding as a prepreg and molding by resin transfer molding as a preform such as a woven fabric. Therefore, it can be suitably used as a carbon fiber reinforced composite material having excellent post-impact compressive strength for aircraft structural materials, automotive applications, marine applications, sports applications and other general industrial applications.

Hereinafter, the present invention will be described more specifically with reference to examples. The measurement method used in this example will be described next.
<Reactor temperature spots>
Five contact-type thermometers are installed at equal intervals from the reactor wall in the longitudinal center of the tubular reactor to the center of the reactor, and the temperature in the center of the reactor in the longitudinal center of the tubular reactor in the first polymerization step. The temperature distribution was measured a total of 5 times after 1 hour, 3 hours, 6 hours, 9 hours and 12 hours had elapsed since the polymerization temperature of Production Condition I was reached. The difference between the maximum value and the minimum value of the temperature distribution at each elapsed time was determined, and the average of these was taken as the reactor temperature spot.
<Weight average molecular weight (Mw); GPC method>
Sampling was performed 1 hour after the temperature of the reactor center in the longitudinal center of the tubular reactor in the first polymerization step reached the polymerization temperature of Production Condition I, and the concentration of the polymer to be measured was A sample solution was obtained by dissolving in dimethylformamide (0.01N-lithium bromide added) so as to be 0.1% by weight. About the obtained sample solution, the molecular weight distribution curve was calculated | required from the GPC curve measured on the following conditions using GPC apparatus, and Mw was computed. The measurement was performed three times, and Mz values were averaged.
・ Column: Column for polar organic solvent GPC ・ Flow rate: 0.5 ml / min
・ Temperature: 70 ℃
・ Sample filtration: Membrane filter (0.45μm cut)
・ Injection volume: 200 μl
・ Detector: Differential refractive index detector Molecular weight is based on at least 6 types of monodisperse polystyrenes with different molecular weights and known molecular weights, and a calibration curve of elution time-molecular weight is created, and corresponding to the corresponding elution time on the calibration curve. It was determined by reading the molecular weight in terms of polystyrene.

In this example, CLASS-LC2010 manufactured by Shimadzu Corporation as a GPC apparatus, TSK-GEL-α-M (× 2) manufactured by Tosoh Corporation as a column, Wako Pure Chemical Industries as dimethylformamide and lithium bromide Made by Millipore Corporation 0.45μ-FHLP FILTER as a membrane filter, Shimadzu Corporation RID-10AV as a differential refractive index detector, and monodispersed polystyrene for preparing a calibration curve, molecular weight 184000, 427,000, 791000, 1300000, 1810000 and 4240000 were used, respectively.
<Viscosity ηt of polyacrylonitrile mixed solution>
The viscosity ηt (Pa · s) of the PAN-based polymer solution was measured with a B-type viscometer. Specifically, the PAN-based polymer solution that was sampled 1 hour after the temperature of the reactor center in the longitudinal center of the tubular reactor in the first polymerization step reached the polymerization temperature of Production Condition I was measured. After placing in a beaker and immersing in a warm water bath adjusted to the measurement temperature t (K) and adjusting the temperature, use a B8L viscometer manufactured by Tokyo Keiki Co., Ltd., and use rotor No. 4. The range of the viscosity of the PAN-based polymer solution from 0 to 100 Pa · s is that the rotor rotational speed is 6 r. p. m. The viscosity of the PAN-based polymer solution is in the range of 100 to 1000 Pa · s. p. m. Measured with
<Polymerization rate>
The polymerization rate was determined by sampling the reaction solution from each position of the continuous reactor, obtaining the polymer concentration c by the above method, dividing by the charged monomer concentration [M], and c / [M] × 100 ( %).
<Polymerization rate>
The polymerization rate was calculated by dividing each polymerization by the reaction time, that is, the average residence time in the first polymerization step and / or the second polymerization step, using the above polymerization rate. The average residence time is the average arrival time from the input to each polymerization step to the outlet of each polymerization step, and was calculated by dividing the volume of the polymerization apparatus in each polymerization step by the input amount per time.
Example 1
AN 100 parts by weight, itaconic acid 1 part by weight, 2,2′-azobisisobutyronitrile (AIBN, 10 hour half-life temperature = 65 ° C.) 0.40 part by weight as a polymerization initiator, octyl mercaptan 0 as a chain transfer agent A raw material mixture in which 0.01 parts by weight is uniformly dissolved in 400 parts by weight of dimethyl sulfoxide, a flow rate of 10.0 t / hr using a plunger pump so that the average residence time in the first polymerization step is 2 hours. Into the first polymerization step, polymerization was carried out at a temperature of 63 ° C. while circulating with a gear pump. At this time, the polymerization rate at the outlet of the first polymerization step was 60%, the polymerization rate in the first polymerization step was 30% / hr, and Mw was 380,000. The reaction solution was continuously introduced from the first polymerization step to the second polymerization step, and the polymerization was completed at 80 ° C. over 3 hours to obtain a polyacrylonitrile mixed solution (PAN-based polymer solution). At this time, the polymerization rate at the outlet of the second polymerization step was 92%, the polymer concentration was 19.3 wt%, the Mw was 300,000, and the viscosity at 75 ° C. was 23.5 Pa · s.
The temperature spot in the reactor in the first polymerization step was 4.8 ° C., and the temperature spot causing the deterioration of quality stability was smaller than that in the tank reactor.

  Next, itaconic acid was neutralized by blowing ammonia gas into the obtained PAN-based polymer solution until the pH reached 8.5 to prepare a spinning solution. The polymer production in the spinning solution was 46.4 t / day.

Spinning, firing and evaluation were performed using the above spinning solution.
First, the spinning solution is spun by a dry and wet spinning method, coagulated, washed with water, and bath-stretched, then provided with an amino-modified silicone-based silicone oil, dried using a roller heated to a temperature of 165 ° C., and subjected to pressurized steam stretching. The carbon fiber precursor fiber having a single fiber fineness of 0.8 dtex and a filament number of 12,000 was obtained.

  The processability of the yarn making process was good. The number of yarn breaks per unit polymer production was 0.04 times / t-polymer.

The obtained carbon fiber precursor fiber was flameproofed for 90 minutes while being stretched at a stretch ratio of 1.0 in air having a temperature distribution of 240 to 260 ° C. to obtain flameproofed fibers. Subsequently, in the nitrogen atmosphere having a temperature distribution of 300 to 700 ° C., the obtained flame-resistant fiber is subjected to a preliminary carbonization treatment while being drawn at a draw ratio of 1.0, and further in a nitrogen atmosphere having a maximum temperature of 1500 ° C. The carbonization treatment was performed to obtain continuous carbon fibers. The process passability of the firing process was good, and the quality of the obtained carbon fiber was good. When the strand physical property of the obtained carbon fiber bundle was measured, the strength was 5.0 GPa and the elastic modulus was 300 GPa.
(Example 2)
100 parts by weight of AN, 1 part by weight of itaconic acid, 0.22 parts by weight of 2,2′-azobisisobutyronitrile (AIBN, 10 hour half-life temperature = 65 ° C.) as a polymerization initiator, 0 octyl mercaptan as a chain transfer agent A flow rate of 2.9 t / hr using a plunger pump so that a raw material mixture in which 0.05 parts by weight is uniformly dissolved in 400 parts by weight of dimethyl sulfoxide is used so that the average residence time in the first polymerization step is 7 hours. Into the first polymerization step, polymerization was carried out at a temperature of 50 ° C. while circulating with a gear pump. At this time, the polymerization rate at the outlet of the first polymerization step was 42%, the polymerization rate in the first polymerization step was 6% / hr, and Mw was 580,000. The reaction solution was continuously introduced from the first polymerization step to the second polymerization step, and the polymerization was completed at 80 ° C. for 8 hours to obtain a polyacrylonitrile mixed solution (PAN-based polymer solution). At this time, the polymerization rate at the outlet of the second polymerization step was 81%, the polymer concentration was 17.0 wt%, the Mw was 420,000, and the viscosity at 75 ° C. was 25.8 Pa · s. The polymer production amount was 11.7 t / day.
The temperature variation in the reactor in the first polymerization step is 2.0 ° C., which is small with respect to the temperature difference of 6.0 ° C. between the central portion of the polymerization tank and the wall surface in the tank reactor having the same polymer production capability. There were small temperature spots that caused quality variations. Thereafter, yarn production and firing were performed in the same manner as in Example 1 to obtain continuous carbon fibers. When the strand physical property of the obtained carbon fiber bundle was measured, the strength was 5.0 GPa and the elastic modulus was 300 GPa.
The processability of the yarn making process was good. The number of yarn breaks per unit polymer production was 0.01 times / t-polymer.
(Example 3)
100 parts by weight of AN, 1 part by weight of itaconic acid, 0.22 parts by weight of 2,2′-azobisisobutyronitrile (AIBN, 10 hour half-life temperature = 65 ° C.) as a polymerization initiator, 0 octyl mercaptan as a chain transfer agent A raw material mixture prepared by uniformly dissolving 0.02 parts by weight in 400 parts by weight of dimethyl sulfoxide and substituting with nitrogen so that the dissolved oxygen concentration becomes 1 ppm is obtained. The average residence time in the first polymerization step is 5 hours. Thus, it was introduced into the first polymerization step at a flow rate of 4.0 t / hr using a plunger pump, and polymerization was carried out at a temperature of 60 ° C. while circulating through a gear pump. At this time, the polymerization rate at the outlet of the first polymerization step was 55%, the polymerization rate in the first polymerization step was 11% / hr, and Mw was 500,000. The reaction solution was continuously introduced from the first polymerization step to the second polymerization step, and the polymerization was completed at a temperature of 75 ° C. over 6 hours to obtain a polyacrylonitrile mixed solution (PAN-based polymer solution). At this time, the polymerization rate at the outlet of the second polymerization step was 90%, the polymer concentration was 18.9 wt%, the Mw was 380,000, and the viscosity at 75 ° C. was 26.4 Pa · s. The polymer production amount was 18.1 t / day.
The temperature variation in the reactor of the first polymerization step was 2.4 ° C. Thereafter, yarn production and firing were performed in the same manner as in Example 1 to obtain continuous carbon fibers. When the strand physical property of the obtained carbon fiber bundle was measured, the strength was 5.0 GPa and the elastic modulus was 300 GPa.
The processability of the yarn making process was good. The number of yarn breaks per unit polymer production was 0.01 times / t-polymer.
(Example 4)
100 parts by weight of AN, 1 part by weight of itaconic acid, 0.30 part by weight of 2,2′-azobisisobutyronitrile (AIBN, 10 hour half-life temperature = 65 ° C.) as a polymerization initiator, 0 octyl mercaptan as a chain transfer agent A flow rate of 6.7 t / hr was obtained by using a plunger pump so that a raw material mixture in which 0.01 parts by weight was uniformly dissolved in 400 parts by weight of dimethyl sulfoxide was used so that the average residence time in the first polymerization step was 3 hours. Into the first polymerization step, polymerization was carried out at a temperature of 63 ° C. while circulating with a gear pump. At this time, the polymerization rate at the outlet of the first polymerization step was 60%, the polymerization rate in the first polymerization step was 20% / hr, and Mw was 450,000. The reaction solution was continuously introduced from the first polymerization step to the second polymerization step, and the polymerization was completed at 75 ° C. for 5 hours to obtain a polyacrylonitrile mixed solution (PAN-based polymer solution). At this time, the polymerization rate at the outlet of the second polymerization step was 91%, the polymer concentration was 19.1 wt%, the Mw was 350,000, and the viscosity at 75 ° C. was 26.8 Pa · s. The polymer production amount was 30.6 t / day.
The temperature difference between the reactor center and the reactor wall surface in the circulation line (I) was 3.0 ° C. Thereafter, yarn production and firing were performed in the same manner as in Example 1 to obtain continuous carbon fibers. When the strand physical property of the obtained carbon fiber bundle was measured, the strength was 5.0 GPa and the elastic modulus was 300 GPa.

The processability of the yarn making process and the firing process was good, the quality of the obtained precursor fiber and carbon fiber was good, and the number of yarn breaks in the yarn making process was 0.02 times / t-polymer.
(Comparative Example 1)
100 parts by weight of AN, 1 part by weight of itaconic acid, 0.22 parts by weight of 2,2′-azobisisobutyronitrile (AIBN, 10 hour half-life temperature = 65 ° C.) as a polymerization initiator, 0 octyl mercaptan as a chain transfer agent A first raw material mixture having a capacity of 20 M3 at a flow rate of 2.9 t / hr is added to a raw material mixture in which 0.05 part by weight is uniformly dissolved in 400 parts by weight of dimethyl sulfoxide using a plunger pump so that the average residence time is 7 hours. It introduce | transduced into the tank reactor and superposed | polymerized at the temperature of 50 degreeC, extracting to a 2nd tank reactor. In this case, the polymerization rate in the first tank reactor was 42%, the polymerization rate was 6.0% / hr, and Mw was 600,000. The reaction solution was introduced into a second tank reactor having the same capacity, and the polymerization was completed at a temperature of 80 ° C. over 7 hours to obtain a polyacrylonitrile mixed solution (PAN-based polymer solution). The polymerization rate at this time was 79%, the polymer concentration was 16.6 wt%, the Mw was 430,000, and the viscosity at 75 ° C. was 21.7 Pa · s. At this time, the reactor temperature spot in the tank reactor (I) was 6 ° C. The polymer production amount was 11.4 t / day. Thereafter, yarn production and firing were performed in the same manner as in Example 1 to obtain continuous carbon fibers. When the strand physical property of the obtained carbon fiber bundle was measured, the strength was 5.0 GPa and the elastic modulus was 300 GPa.
The processability of the yarn making process was good. The number of yarn breaks per unit polymer production was 0.04 times / t-polymer.
(Comparative Example 2)
100 parts by weight of AN, 1 part by weight of itaconic acid, 0.22 parts by weight of 2,2′-azobisisobutyronitrile (AIBN, 10 hour half-life temperature = 65 ° C.) as a polymerization initiator, 0 octyl mercaptan as a chain transfer agent A raw material mixture in which 0.02 parts by weight is uniformly dissolved in 400 parts by weight of dimethyl sulfoxide is mixed with a first pump having a capacity of 20 M3 at a flow rate of 4.0 t / hr using a plunger pump so that the average residence time is 5 hours. It introduce | transduced into the tank reactor and superposed | polymerized at the temperature of 60 degreeC, extracting to a 2nd tank reactor. At this time, the polymerization rate in the first tank reactor was 55%, the polymerization rate was 10.3% / hr, and Mw was 510,000. The reaction solution was introduced into a second tank reactor having the same capacity, and the polymerization was completed at a temperature of 75 ° C. over 6 hours to obtain a polyacrylonitrile mixed solution (PAN-based polymer solution). At this time, the polymerization rate was 90%, the polymer concentration was 18.9 wt%, the Mw was 390,000, and the viscosity at 75 ° C. was 26.7 Pa · s. At this time, the reactor temperature spot was 8 ° C. in the tank reactor (I). Moreover, the polymer production amount was 18.1 t / hr. Thereafter, yarn production and firing were performed in the same manner as in Example 1 to obtain continuous carbon fibers. When the strand physical property of the obtained carbon fiber bundle was measured, the strength was 5.0 GPa and the elastic modulus was 300 GPa.
The processability of the yarn making process was good. The number of yarn breaks per unit polymer production was 0.06 times / t-polymer.
(Comparative Example 3)
100 parts by weight of AN, 1 part by weight of itaconic acid, 0.30 part by weight of 2,2′-azobisisobutyronitrile (AIBN, 10 hour half-life temperature = 65 ° C.) as a polymerization initiator, 0 octyl mercaptan as a chain transfer agent A raw material mixture prepared by uniformly dissolving 0.01 parts by weight in 400 parts by weight of dimethyl sulfoxide was used at a flow rate of 6.7 m 3 / hr using a plunger pump so that the average residence time was 3 hours. It introduce | transduced into the 1st tank type reactor and superposed | polymerized at the temperature of 63 degreeC, extracting to a 2nd tank type reactor. Immediately after the start of the reaction, the heat removal was insufficient, and the reactor temperature significantly exceeded the control range, so the polymerization was stopped.
The production conditions of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 1, the properties of the obtained polyacrylonitrile copolymer are shown in Table 2, and the carbon fiber precursor produced using the polyacrylonitrile polymer. The properties of the fibers and carbon fibers are summarized in Table 3.

As is clear from the results of Examples 1 to 4, the production method of the polyacrylonitrile copolymer of the present invention has small temperature spots in the reactor, so that the quality of the obtained polyacrylonitrile is stabilized and the spinning process is performed. The number of thread breaks of has decreased. Compared with the manufacturing methods of Comparative Examples 1 to 3, the production capacity was also improved, and both productivity and quality were excellent. In the production methods of Examples 2 to 4, by reducing temperature spots as compared with Example 1, the number of yarn breaks per unit polymer was remarkably reduced, and the quality stability could be further improved.

(1) Plunger pump (2) Tubular reactor with static mixing structure inside (3) Gear pump (4) Tubular reactor with static mixing structure inside (5) Gear pump (I) Circulation Line (II) Main polymerization line

Claims (6)

A process for producing a polyacrylonitrile copolymer, comprising:
(a) A circulation line (I) in which one or more tubular reactors having a static mixing structure are incorporated into a raw material mixture containing at least a monomer containing acrylonitrile, a chain transfer agent, and a polymerization initiator (I A first polymerization step in which temperature fluctuations in the tubular reactor are controlled within 5 ° C. at 30 to 150 ° C., and continuous polymerization is performed.
(b) a liquid feeding step for sending from the branch portion of the circulation line (I) used in the first polymerization step to the second polymerization step;
(c) While passing the solution sent from the liquid feeding process through a non-circulation line (II) having a static mixing structure inside, the temperature spots in the tubular reactor are kept within 5 ° C. at 30 to 150 ° C. A method for producing a polyacrylic copolymer, comprising a second polymerization step of controlling and continuously polymerizing the polymerization rate at 80 to 95% at the outlet of the non-circulation line (II). The method for producing a polyacrylonitrile copolymer according to claim 1, wherein the polymerization rate defined in the main text in the first polymerization step is 5 to 20% / hr. The polymerization initiator concentration in the raw material mixture containing at least a monomer containing acrylonitrile, a chain transfer agent, and a polymerization initiator to be supplied to the first polymerization step is 0.1 to 5% by weight. A process for producing a polyacrylonitrile copolymer. The first polymerization step and / or the second polymerization step is carried out by pressurizing at a temperature of 40 to 120 ° C. and higher than the saturated vapor pressure at the polymerization temperature of the monomer mixture or solvent supplied in the polymerization step. The manufacturing method of the polyacrylonitrile copolymer in any one of Claims 1-3 performed. A method for producing a carbon fiber precursor fiber, comprising spinning the polyacrylonitrile copolymer according to claim 1. The carbon fiber precursor fiber obtained by the method for producing a carbon fiber precursor fiber according to claim 5 is subjected to flame resistance treatment in air at a temperature of 200 to 300 ° C, and then inert at a temperature of 300 to 800 ° C. A method for producing carbon fiber, characterized by pre-carbonizing in an atmosphere and then carbonizing in an inert atmosphere at a temperature of 1,000 to 3,000 ° C.

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