JP2014201728A - Acrylonitrile-based copolymer particle, and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dissolubility of acrylonitrile-based copolymer particles, and to achieve reduction in load when filtering an acrylonitrile-based copolymer solution, and stability improvement of a manufacturing process and a quality of carbon fiber precursor acrylonitrile-based fibers, the reduction in load and the stability improvement accompanying the improvement of the dissolubility of the acrylonitrile-based copolymer particles.SOLUTION: A production method of acrylonitrile-based copolymer particles is that the acrylonitrile-based copolymer particles are produced by a redox aqueous precipitation polymerization in which a monomer, a redox initiator and deionization exchange water are continuously supplied to a reaction vessel, and a reaction liquid is continuously taken out from the reaction vessel. In this production method, a reaction vessel agitation power defined in the specification is at least 3.0 kW/mand at most 7.0 kW/m.

Description

  The present invention relates to acrylonitrile-based copolymer particles used as a raw material for a carbon fiber precursor acrylonitrile-based fiber and a method for producing the same.

  It is known that carbon fibers have a high specific strength and specific elastic modulus compared to other fibers. For this reason, in addition to conventional sports and aerospace applications, composite fibers are being widely deployed in general industrial applications such as automobiles, civil engineering, architecture, pressure vessels, and windmill blades. Furthermore, there is a high demand for higher strength and higher elastic modulus in sports and aerospace applications that have been used in the past.

  Among the carbon fibers, acrylonitrile-based carbon fibers are the most widely used. Acrylonitrile-based carbon fiber is, for example, made from acrylonitrile-based copolymer particles as a raw material, carbon fiber precursor acrylonitrile-based fiber as a carbon fiber precursor, and heating the carbon fiber precursor in an oxygen-existing atmosphere at 200 to 400 ° C. By processing, it can be converted into flame-resistant fiber and subsequently carbonized under an inert atmosphere of 1000 ° C. or higher.

  As an industrial production method of acrylonitrile copolymer particles, an aqueous precipitation polymerization method and a solution polymerization method are known, but an aqueous precipitation continuous polymerization method in which an aqueous precipitation polymerization is continuously performed is compared with a continuous solution polymerization method. In addition, continuous production is possible with a short residence time, and a simple polymerization reactor can be used.

  To obtain the carbon fiber precursor acrylonitrile fiber industrially from acrylonitrile copolymer particles produced by the aqueous precipitation continuous polymerization method, first, the suspension containing the acrylonitrile copolymer particles is washed, dehydrated and dried. Thus, acrylonitrile copolymer particles are obtained. Next, the acrylonitrile copolymer particles are dissolved in a solvent to prepare an acrylonitrile copolymer solution, which is then spun.

  Undissolved acrylonitrile copolymer particles present in the acrylonitrile copolymer solution not only adversely affect the production process of the carbon fiber precursor acrylonitrile fiber, but also foreign matter in the carbon fiber precursor acrylonitrile fiber. In general, the acrylonitrile-based copolymer solution is filtered through a filter before spinning, because it remains as a defect and results in a decrease in strength of the acrylonitrile-based carbon fiber.

  However, as the number of undissolved acrylonitrile copolymer particles present in the acrylonitrile copolymer solution increases, the frequency of replacement of the filter for filtering the acrylonitrile copolymer solution increases, and the work load increases. Further, since the pressure increase in the filter is accelerated, the foreign matter trapped in the filter is pushed out, resulting in an increase in the amount of foreign matter present in the acrylonitrile copolymer solution, and the carbon fiber precursor. In addition to adversely affecting the production process and quality of the acrylonitrile fiber, it causes a reduction in strength of the resulting acrylonitrile carbon fiber.

Therefore, the acrylonitrile copolymer particles used as the raw material for the carbon fiber precursor acrylonitrile fiber are required to have excellent solubility in a solvent.
In order to solve these problems, Patent Document 1 improves solubility by controlling the bulk specific gravity, pore distribution average, crystallization index, and the like of acrylonitrile-based copolymer particles.

  In Patent Document 2, the solubility is improved by controlling the bulk specific gravity of the acrylonitrile copolymer particles, the porosity of the surface layer portion, and the average particle diameter. In Patent Document 3, the solubility is improved by controlling the bulk specific gravity of the acrylonitrile-based copolymer particles and the porosity of the central portion and the outer peripheral portion. In Patent Document 4, not only the average particle diameter of acrylonitrile-based copolymer particles is controlled, but the solubility is improved by setting the volume ratio of particles having a particle diameter of 80 μm or more to 10% or less.

JP-A-11-140131 JP 2009-185273 A JP 2009-203317 A JP 2009-275202 A

  However, the methods described in Patent Documents 1 to 4 have not always been sufficient to improve solubility and dispersibility. The present invention has been made in view of the above circumstances, further improving the solubility of acrylonitrile-based copolymer particles, reducing the load during filtration of the acrylonitrile-based copolymer solution, and the carbon fiber precursor acrylonitrile-based fibers. It aims to improve the stability of the manufacturing process and quality.

  By improving the dispersibility when acrylonitrile copolymer particles are dispersed in a solvent, it is possible to reduce undissolved acrylonitrile copolymer particles in the acrylonitrile copolymer solution, acrylonitrile copolymer particles It is well known from the prior literature that the dispersibility when dispersed in a solvent can be improved by controlling the bulk specific gravity of the acrylonitrile copolymer particles, the structure of the particles, and the volume average particle diameter.

  As a result of earnest study on the improvement in solubility of further acrylonitrile-based copolymer particles, the present inventor has found that the acrylonitrile-based copolymer is controlled by controlling the particle size distribution in addition to the volume average particle size of the acrylonitrile-based copolymer particles. Dispersibility is improved when the particles are dispersed in a solvent, and the solubility of the acrylonitrile copolymer particles can be further improved. The particle size distribution of the acrylonitrile copolymer particles is controlled by the reactor stirring power. I found out that I can do it. That is, the present invention has the following configuration.

The method for producing acrylonitrile-based copolymer particles of the present invention is a redox aqueous precipitation in which a monomer, a redox initiator and deionized water are continuously supplied to a reactor, and a reaction liquid is continuously taken out from the reactor. by polymerization, a method for producing acrylonitrile copolymer particles, reactor stirring power is less than 3.0 kW / ^{m 3} or more 7.0 kW / ^{m 3.}

  However, the reactor agitation power in the present invention is the net electric power per unit volume received by the agitation of the water filled up to the overflow port in the reactor, specifically, the reactor is empty. The difference between the power value when the stirring blade is rotated and the power value when the stirring blade is rotated while the reactor is filled with water up to the overflow port is calculated. The number divided by the amount of water filled.

The method for producing acrylonitrile-based copolymer particles according to the present invention includes a mol concentration A (mol / l) of an acrylonitrile monomer contained in a supply liquid to be supplied to a reactor, and a total single amount contained in the supply liquid. It is preferable that the mol concentration B (mol / l) of the body satisfies the following formula.
0.95 ≦ A / B ≦ 0.995

The method for producing acrylonitrile-based copolymer particles according to the present invention includes a molar concentration C (mol / l) of a redox initiator contained in a feed solution supplied to a reactor, and all monomers contained in the feed solution. It is preferable that the mol concentration B (mol / l) satisfies the following formula.
0.20 ≦ C / B × 100 ≦ 0.65

In the method for producing acrylonitrile-based copolymer particles of the present invention, the ion exchange water W (kg) in the feed liquid supplied to the reactor and the amount M (kg) of the total monomers in the feed liquid are expressed by the following equations. It is preferable to satisfy.
1.5 ≦ W / M ≦ 5.5

  The acrylonitrile copolymer particles of the present invention have a volume average particle diameter of 30 μm or more and 40 μm or less, and a standard deviation σ of the volume average particle diameter obtained by the following formula is 0.25 or less.

  The acrylonitrile-based copolymer particles of the present invention preferably have a volume ratio of particles having a volume-converted particle diameter of 10 μm or less of 1.5% or less.

  The acrylonitrile-based copolymer particles of the present invention preferably have a volume ratio of particles having a volume conversion particle diameter of 200 μm or more of 1.0% or less.

  The acrylonitrile-based copolymer particles of the present invention preferably have a volume ratio of particles having a volume-converted particle diameter of 300 μm or more of 0.1% or less.

  According to the present invention, acrylonitrile copolymer particles having excellent solubility can be obtained. In addition, by using the acrylonitrile copolymer solution using the acrylonitrile copolymer particles of the present invention, the load during filtration of the acrylonitrile copolymer solution is reduced, and the carbon fiber precursor has high process and quality stability. A body acrylonitrile fiber can be produced. Further, by using this carbon fiber precursor acrylonitrile fiber, it is possible to produce acrylonitrile carbon fiber with few foreign matters and defects that cause a decrease in strength.

Details of the present invention will be described below.
The acrylonitrile-based copolymer particles of the present invention preferably have an acrylonitrile monomer unit content of 95.0 mol% or more and 99.5 mol% or less, and 97.0 mol% or more and 99.5 mol% or less. It is more preferable that In the firing step for converting the carbon fiber precursor acrylonitrile fiber to acrylonitrile carbon fiber by setting the acrylonitrile monomer unit in the acrylonitrile copolymer particles to 95.0 mol% or more, the fibers are fused. The excellent quality and performance of the acrylonitrile-based carbon fiber can be maintained without incurring any damage. In addition, the heat resistance of the acrylonitrile copolymer particles does not decrease, and drying can be suppressed when the carbon fiber precursor acrylonitrile fiber is spun. Furthermore, adhesion between single fibers can be avoided in processing such as stretching with a heating roller or pressurized steam.

  Further, by setting the acrylonitrile monomer unit in the acrylonitrile copolymer particles to 99.5 mol% or less, sufficient solubility in the solvent can be secured, and the acrylonitrile copolymer particles in the acrylonitrile copolymer solution Precipitation into can be prevented.

  As the monomer other than acrylonitrile in the acrylonitrile copolymer particles, a vinyl monomer that can be copolymerized with acrylonitrile can be suitably selected, and vinyl that improves the hydrophilicity of the acrylonitrile copolymer particles. A monomer based on vinyl and a monomer based on flame resistance are preferred.

  Examples of the monomer that improves the hydrophilicity of the acrylonitrile-based copolymer particles include a vinyl compound having a hydrophilic functional group such as a carboxyl group, a sulfo group, an amino group, an amide group, or a hydroxyl group. Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, ethacrylic acid, maleic acid, mesaconic acid and the like, among which acrylic acid, methacrylic acid, and itaconic acid are preferable. Examples of the monomer having a sulfo group include allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, and sulfopropyl methacrylate. Acid, methallylsulfonic acid, styrenesulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid are preferred. Examples of the monomer having an amino group include dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, tertiary butylaminoethyl methacrylate, allylamine, o-aminostyrene, and p-aminostyrene. Of these, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, and diethylaminoethyl acrylate are preferable. As the monomer having an amide group, acrylamide, methacrylamide, dimethylacrylamide, and crotonamide are preferable. Examples of the monomer having a hydroxyl group include hydroxymethyl methacrylate, hydroxymethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 3-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2- And hydroxypropyl acrylate.

  By blending such a monomer, the hydrophilicity of the acrylonitrile-based copolymer particles is improved. When the hydrophilicity is improved, the denseness of the obtained carbon fiber precursor acrylonitrile-based fiber is improved, and generation of microvoids in the surface layer portion can be suppressed. The above-mentioned monomers can be used alone or in combination of two or more. The blending amount of the monomer for improving the hydrophilicity of such acrylonitrile-based copolymer particles is preferably 0.5 to 5.0 mol% in the acrylonitrile-based copolymer particles, and 0.5 to 3 More preferably, the content is 0.0 mol%.

  Monomers having an effect of promoting flame resistance include acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid, mesaconic acid or their lower alkyl esters, alkali metal salts, ammonium salts or acrylamides. , Methacrylamide and the like. Among these, from the viewpoint of obtaining a higher flame resistance-promoting effect with a small amount, a monomer having a carboxyl group is preferable, and vinyl monomers such as acrylic acid, methacrylic acid, and itaconic acid are particularly preferable. By blending such a monomer, the time for the firing process can be shortened, and the manufacturing cost can be reduced. The above-mentioned monomers can be used alone or in combination of two or more. The blending amount of the monomer having the effect of promoting flame resistance is preferably 0.5 to 5.0 mol% in the acrylonitrile-based copolymer particles, and is 0.5 to 3.0 mol%. It is more preferable.

  The acrylonitrile-based copolymer particles of the present invention preferably have a volume average particle diameter of 30 μm or more and 40 μm or less, and a standard deviation σ of the volume average particle diameter obtained by the following formula is 0.25 or less.

  In addition, the particle size distribution of the acrylonitrile-based copolymer particles was measured using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Horiba, Ltd., product name: LA-910) using ion-exchanged water as a dispersion medium. The refractive index was measured as 1.14. The volume average particle diameter means a median diameter in terms of volume average in this measurement.

  In general, when acrylonitrile-based copolymer particles having a small particle diameter are dispersed in a solvent, dissolution rapidly proceeds and the viscosity of the dispersion increases. When the viscosity of the dispersion increases, polymer particles that are in the middle of dissolution are partially aggregated, resulting in poor dispersion that is difficult to dissolve. In addition, the acrylonitrile copolymer particles having a large particle diameter are difficult to dissolve because the solvent does not easily penetrate to the center.

  By reducing the volume average particle diameter of the acrylonitrile copolymer particles to 30 μm or more and the standard deviation σ to 0.25 or less, the ratio of acrylonitrile copolymer particles having a small particle diameter that causes poor dispersion is greatly reduced. As a result, it is possible to obtain acrylonitrile-based copolymer particles having good dispersibility in a solvent and excellent solubility.

  In addition, by setting the volume average particle diameter of acrylonitrile copolymer particles to 40 μm or less and the standard deviation σ to 0.25 or less, the ratio of acrylonitrile copolymer particles having a large particle diameter that is difficult to dissolve is greatly reduced. Acrylonitrile-based copolymer particles having excellent solubility can be obtained.

  From the viewpoint of obtaining acrylonitrile-based copolymer particles having excellent solubility, it is more preferable that the volume average particle diameter of the acrylonitrile-based copolymer particles be 30 μm or more and 35 μm or less. The standard deviation σ of the volume average particle diameter is more preferably 0.22 or less, and further preferably 0.20 or less.

  The acrylonitrile-based copolymer particles of the present invention preferably have a volume ratio of particles having a volume-converted particle diameter of 10 μm or less of 1.5% or less. Since the ratio of particles having a volume-converted particle diameter of 10 μm or less is 1.5% or less, the ratio of acrylonitrile-based copolymer particles having a small particle diameter that causes poor dispersion can be greatly reduced. As a result, it is possible to obtain acrylonitrile-based copolymer particles having excellent dispersibility.

  From the viewpoint of obtaining acrylonitrile-based copolymer particles having excellent solubility, the ratio of particles having a volume conversion particle diameter of 10 μm or less is more preferably 1.0% or less, and more preferably 0.5% or less. Further preferred.

  The acrylonitrile-based copolymer particles of the present invention preferably have a volume ratio of particles having a volume conversion particle diameter of 200 μm or more of 1.0% or less. By setting the ratio of particles having a volume-converted particle diameter of 200 μm or more to 1.0% or less, the ratio of acrylonitrile copolymer particles having a large particle diameter that is difficult to dissolve can be greatly reduced, so that the solubility is excellent. Acrylonitrile copolymer particles can be obtained.

  From the viewpoint of obtaining acrylonitrile-based copolymer particles having excellent solubility, the volume ratio of particles having a volume-converted particle size of 200 μm or more is more preferably 0.5% or less, and 0.1% or less. More preferably.

  The acrylonitrile-based copolymer particles of the present invention preferably have a volume ratio of particles having a volume-converted particle diameter of 300 μm or more of 0.1% or less. By setting the ratio of particles having a volume-converted particle diameter of 300 μm or more to 0.1% or less, the ratio of acrylonitrile-based copolymer particles having a large particle diameter that is difficult to dissolve can be greatly reduced, so that the solubility is excellent. In addition, acrylonitrile-based copolymer particles can be obtained.

  From the viewpoint of obtaining acrylonitrile-based copolymer particles having excellent solubility, it is more preferable that the volume ratio of particles having a volume-converted particle diameter of 300 μm or more is 0.05% or less.

  The acrylonitrile copolymer particles of the present invention are obtained by redox aqueous precipitation polymerization in which a monomer, a redox initiator and deionized exchange water are continuously supplied to the reactor, and the reaction liquid is continuously taken out from the reactor. be able to.

  The hydrogen ion concentration in the polymerization reaction vessel may be within a range where the initiator used promptly causes an oxidation / reduction reaction, and an acidic region having a pH of 2.0 to 3.5 is preferable. Known redox initiators can be used.

  The temperature of the reaction solution in the reactor is preferably 30 to 80 ° C. By setting the reaction liquid temperature to 80 ° C. or less, the polymerization conversion rate is improved without acrylonitrile evaporating and being dispersed outside the reaction system. Further, by setting the reaction liquid temperature to 30 ° C. or higher, not only the polymerization rate is increased and the productivity is improved, but also the polymerization stability is increased.

In order to prevent radical deactivation due to oxygen, the inside of the reactor is preferably in an inert gas atmosphere, and more preferably nitrogen is used from the viewpoint of cost.
It is preferred reactor agitation power of the present invention is less than 3.0 kW / ^{m 3} or more 7.0 kW / ^{m 3.}

  In general, the smaller the reactor stirring power, the larger the proportion of particles having a large particle size contained in the acrylonitrile copolymer particles in the reactor, resulting in acrylonitrile copolymer particles that are difficult to dissolve. End up. Further, the flow state in the reactor is increased in spots, the particle size distribution of the acrylonitrile-based copolymer particles to be generated is widened, and the process stability is also lowered.

  On the other hand, as the reactor stirring power increases, the proportion of particles having a small particle size contained in the acrylonitrile copolymer particles in the reactor increases, resulting in acrylonitrile copolymer particles that tend to be poorly dispersed. In addition, since the liquid at the reaction liquid level in the reactor becomes easy to splash, the splashed liquid adheres to the upper part of the reactor and is generated by polymerization with a monomer in the gas phase. The molecular weight is higher than that of acrylonitrile-based copolymer particles, and the amount of abnormal polymer that is difficult to dissolve increases.

By setting the reactor stirring power to 3.0 kW / m ³ or more, it is possible to reduce the proportion of acrylonitrile-based copolymer particles having a large particle diameter that is difficult for the solvent to permeate to the central portion and difficult to dissolve. Further, the flow state in the reactor becomes uniform, the particle size distribution of the acrylonitrile-based copolymer particles to be produced can be narrowed, and the process stability is also improved.

By setting the reactor stirring power to 7.0 kW / m ³ or less, it is possible to suppress an increase in the proportion of acrylonitrile-based copolymer particles having a small particle diameter that causes poor dispersion. It becomes possible to suppress.

From the viewpoint of obtaining excellent acrylonitrile copolymer particles in solubility, the reactor stirring power, more preferably to 3.5 kW / ^{m 3} or more 6.5 kW / ^{m 3} or less, 3.5 kW / ^{m 3} or more More preferably, it is 6.0 kW / m ³ or less. However, the reactor agitation power in the present invention is the net electric power per unit volume received by the agitation of the water filled up to the overflow port in the reactor, specifically, the reactor is empty. The difference between the power value when the stirring blade is rotated and the power value when the stirring blade is rotated while the reactor is filled with water up to the overflow port is calculated. The number divided by the amount of water filled.

The method for producing acrylonitrile-based copolymer particles according to the present invention includes a mol concentration A (mol / l) of an acrylonitrile monomer contained in a supply liquid to be supplied to a reactor, and a total single amount contained in the supply liquid. It is preferable that the mol concentration B (mol / l) of the body satisfies the following formula.
0.95 ≦ A / B ≦ 0.995

  By setting A / B to 0.95 or more, it is possible to obtain acrylonitrile-based copolymer particles having an acrylonitrile monomer unit content of 95.0 mol% or more. Therefore, the heat resistance of acrylonitrile-based copolymer particles Therefore, drying can be suppressed when the carbon fiber precursor acrylonitrile fiber is spun. Furthermore, adhesion between single fibers can be avoided in processing such as stretching with a heating roller or pressurized steam. Further, in the firing step for converting the carbon fiber precursor acrylonitrile-based fiber into acrylonitrile-based carbon fiber, the excellent quality and performance of the acrylonitrile-based carbon fiber can be maintained without causing fusion between the fibers.

  Further, by setting A / B to 0.995 or less, it is possible to obtain acrylonitrile-based copolymer particles having an acrylonitrile monomer unit content of 99.5 mol% or less. Therefore, acrylonitrile-based copolymer particles Can be sufficiently secured in the solvent.

  From the viewpoint of reducing the proportion of acrylonitrile copolymer particles having a small particle diameter and acrylonitrile copolymer particles having a large particle diameter, A / B is more preferably 0.965 or more and 0.992 or less.

The method for producing acrylonitrile-based copolymer particles according to the present invention includes a molar concentration C (mol / l) of a redox initiator contained in a feed solution supplied to a reactor, and all monomers contained in the feed solution. It is preferable that the mol concentration B (mol / l) satisfies the following formula.
20 ≦ C / B × 100 ≦ 0.65

  By setting C / B × 100 to 0.65 or less, the repulsive force between acrylonitrile-based copolymer particles exerted by the electrolyte in the reaction solution is prevented from becoming too large, and the acrylonitrile-based copolymer particles are densely packed. Suppresses the increase in the proportion of acrylonitrile copolymer particles having large particle diameters that do not agglomerate and grow into particles having large gaps and large particle diameters, resulting in difficulty in dissolution. be able to.

  Further, by setting C / B × 100 to 0.20 or more, the repulsive force between the acrylonitrile copolymer particles exerted by the electrolyte in the reaction solution is prevented from becoming too small, and the acrylonitrile copolymer in the reaction solution is prevented. The coalesced particles are aggregated and become too dense, the particle size is reduced, and as a result, an increase in the proportion of acrylonitrile copolymer particles having a small particle size that causes poor dispersion can be suppressed.

  From the viewpoint of reducing the ratio of acrylonitrile copolymer particles having a small particle diameter and acrylonitrile copolymer particles having a large particle diameter to obtain acrylonitrile copolymer particles having good solubility, the C / B × 100 is set to 0.00. It is more preferably 30 or more and 0.60 or less, and further preferably 0.35 or more and 0.55 or less.

In the method for producing acrylonitrile-based copolymer particles of the present invention, the ion exchange water W (kg) in the feed liquid supplied to the reactor and the amount M (kg) of the total monomers in the feed liquid are expressed by the following equations. It is preferable to satisfy.
5 ≦ W / M ≦ 5.5

  Since the heat of polymerization in the reactor can be stably removed by setting W / M to 1.5 or more, and the state in the reactor can be made uniform, acrylonitrile copolymer particles having a narrow particle size distribution can be obtained. It becomes easy to obtain. Also, the acrylonitrile copolymer particles are likely to aggregate with each other, and as a result, an increase in the proportion of acrylonitrile copolymer particles having a small particle diameter that causes poor dispersion can be suppressed, and the acrylonitrile system has good solubility. Copolymer particles can be obtained.

  By setting W / M to 5.5 or less, excessive aggregation of acrylonitrile-based copolymer particles can be prevented, and the ratio of acrylonitrile-based copolymer particles that are difficult to dissolve and have a large particle diameter is sufficiently reduced. And acrylonitrile copolymer particles having good solubility can be obtained.

  From the viewpoint of obtaining a acrylonitrile-based copolymer particle having good solubility by reducing the proportion of acrylonitrile-based copolymer particles having a narrow particle size distribution and a large particle size, and a small proportion of acrylonitrile-based copolymer particles. It is preferable to set it as 0.0 or more and 4.0 or less, and it is more preferable to set it as 2.0 or more and 3.0 or less.

  The reaction liquid containing the acrylonitrile-based copolymer particles obtained in the reactor is continuously discharged out of the reactor system, and the reaction is stopped by adding a polymerization terminator to obtain a polymer dispersion. The polymerization reaction terminator is not a problem as long as it is usually used when producing acrylonitrile-based copolymer particles by aqueous suspension polymerization.

  After adding a polymerization terminator, unreacted monomers are recovered from the polymer dispersion. As a method for recovering the unreacted monomer, there are a method of directly distilling the polymer dispersion, and a method of once dehydrating and separating the unreacted monomer from the polymer, followed by distillation. Both methods can be adopted.

  After the unreacted monomer is removed, residues such as redox initiator contained in the acrylonitrile copolymer particles are removed by a known washing method, and the remaining water is removed by a normal drying method.

  After drying, it is pulverized by a known pulverization method to obtain acrylonitrile-based copolymer particles.

  The acrylonitrile-based copolymer particles obtained by the above-described method have excellent dispersibility in a solvent, and an acrylonitrile-based copolymer solution with little undissolved material can be obtained. By using the obtained acrylonitrile copolymer solution, the load during filtration of the acrylonitrile copolymer solution can be reduced, and the production process and quality stability of the carbon fiber precursor acrylonitrile fiber can be improved. Become. Moreover, from the obtained carbon fiber precursor acrylonitrile-based fiber, acrylonitrile-based carbon fiber with less foreign matter and defects and good strength development can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.

[Composition of acrylonitrile copolymer particles]
The composition of polyacrylonitrile-based copolymer particles (ratio of each monomer unit (mass%)) was measured by ¹ H-NMR method as follows. Using dimethyl sulfoxide -d ₆ solvent as a solvent to dissolve the copolymer, NMR measuring apparatus (manufactured by JEOL Ltd., product name: GSZ-400 type), the number of integration 40 times, measured under the conditions of measurement temperature 120 ° C. The ratio of each monomer unit was determined from the chemical shift integral ratio.

[Particle size of acrylonitrile copolymer particles]
The particle size distribution of the polymer particles was measured using a laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, Ltd., product name: LA-910). Ion exchange water was used as a dispersion medium for the polymer particles, and the refractive index of the polymer particles was 1.14. In addition, the volume average particle diameter in this specification means the median diameter in terms of volume average according to this measurement.

[Filter differential pressure]
The obtained acrylonitrile copolymer particles are dispersed in dimethylformamide at −25 ° C. so that the solid content is 23.2% to obtain an acrylonitrile copolymer particle dispersion. After passing the obtained acrylonitrile-based copolymer particle dispersion through a heating medium of 125 ° C. through one heating multitubular heat exchanger with an inner diameter of 12 mm so that the average residence time is 10 minutes, An acrylonitrile-based copolymer solution was obtained by passing a 65 ° C. refrigerant through a cooling multitubular heat exchanger having an inner diameter of 12 mm so that the average residence time was 6 minutes. The obtained acrylonitrile-based copolymer solution was kept at 65 ° C. and continuously filtered with a filter (model number: NF2-05S, manufactured by Meisei Shokai Co., Ltd.) at a flow rate of 65 L / m ² per minute. . At that time, the change in the pressure applied to the filter until the cumulative flow rate through the filter reached 0 to 0.5 L was determined, and the value was taken as the filter differential pressure.

Example 1
[Production of Acrylonitrile Copolymer Particles]
Place 76.5 liters of deionized water in an aluminum polymerization kettle with a capacity of 80 liters (stirring wing: 240φ, 55 mm x 57 mm, 2 stages, 4 blades) so that the deionized water reaches the polymerization kettle overflow port. 0.01 g of ferrous iron (Fe ₂ SO ₄ .7H ₂ O) was added and the reaction solution was adjusted with sulfuric acid so that the pH was 3.0, and the temperature in the polymerization kettle was maintained at 57 ° C.

Next, from 50 minutes before the start of the polymerization, 0.09 mol% of ammonium persulfate, which is a redox polymerization initiator, 0.32 mol% of ammonium bisulfite, and sulfuric acid with respect to the monomer (100 mol%) to be charged at the start of the polymerization. Ferrous iron (Fe ₂ SO ₄ · 7H ₂ O) was dissolved in deionized water and continuously supplied so that the concentration was 0.3 ppm and sulfuric acid was 0.05 mol%, and the stirring power was 5.4 kW / stirring is carried out for at m ^3, the average residence time of the monomers in the polymerization vessel was set to be 77 minutes.

  Then, at the start of polymerization, a monomer consisting of acrylonitrile (hereinafter abbreviated as AN) monomer unit: methacrylic acid (hereinafter abbreviated as MAA) monomer unit (molar ratio) = 99.1: 0.9 was added to water / The continuous supply of the monomer was started so that the monomer was 2.4 (mass ratio).

  The mol concentration A (mol / l) of the acrylonitrile monomer contained in the supply liquid at this time, the mol concentration B (mol / l) of all monomers, the mol concentration C (mol / l) of the redox initiator, and A / B and C / B × 100 are as shown in Table 1.

  Thereafter, 1 hour after the start of polymerization, the polymerization reaction temperature was lowered to 50 ° C. and the temperature was maintained for 10 hours, and then the polymer slurry was continuously taken out from the polymerization kettle overflow port.

  For the polymer slurry, an aqueous solution of a polymerization terminator in which sodium oxalate 0.37 × 10 −2 mol% and sodium bicarbonate 1.78 × 10 −2 mol% was dissolved in deionized water was used. It added so that it might become 5.5-6.0. The particle diameter of the acrylonitrile copolymer particles was measured using the polymerization slurry at this time. The results are shown in Table 2.

The polymer slurry was dehydrated and washed with an Oliver type continuous filter, and 10 times the amount of deionized water (70 liters) was added to the polymer and dispersed again. The polymer slurry after re-dispersion is again dehydrated with an Oliver type continuous filter, pelletized, dried at 80 ° C. for 8 hours in a hot air circulating dryer, pulverized with a hammer mill, and polyacrylonitrile-based copolymer. Polymer particles were obtained. Table 2 shows the composition of the obtained polyacrylonitrile-based particles and the filter differential pressure.
(Example 2)

From 50 minutes before the start of polymerization, the redox polymerization initiator ammonium persulfate is 0.12 mol% and ammonium bisulfite is 0.41 mol% with respect to the monomer (100 mol%) to be charged at the start of polymerization. Each was dissolved in deionized water and continuously supplied, stirred with a stirring power of 3.4 kW / m ^{3, and} at the start of polymerization, the monomer was water / monomer = 5.0 (mass ratio). In the same manner as in Example 1 except that continuous monomer supply was started. Table 2 shows the composition, particle diameter, and filter differential pressure of the resulting acrylonitrile copolymer particles.
(Example 3)

From 50 minutes before the start of polymerization, the redox polymerization initiator ammonium persulfate is 0.12 mol% and ammonium bisulfite is 0.40 mol% with respect to the monomer (100 mol%) to be charged at the start of polymerization. Each was dissolved in deionized water and continuously supplied, stirred with a stirring power of 3.1 kW / m ^{3, and} at the start of polymerization, the monomer was water / monomer = 4.8 (mass ratio). In the same manner as in Example 1 except that continuous monomer supply was started. Table 2 shows the composition, particle diameter, and filter differential pressure of the resulting acrylonitrile copolymer particles.
Example 4

From 50 minutes before the start of the polymerization, the redox polymerization initiator ammonium persulfate is 0.10 mol% and the ammonium bisulfite is 0.34 mol% with respect to the monomer (100 mol%) to be charged at the start of the polymerization. Each was dissolved in deionized water and continuously supplied, and stirred at a stirring power of 3.0 kW / m ^3. At the start of polymerization, AN monomer unit: MAA monomer unit: acrylamide (hereinafter referred to as AAm) Abbreviation) monomer unit (molar ratio) = 97.1: 0.6: 2.3 monomer to water / monomer = 2.6 (mass ratio) It implemented similarly to Example 1 except having started continuous supply. Table 2 shows the composition, particle diameter, and filter differential pressure of the resulting acrylonitrile copolymer particles.
(Comparative Example 1)

From 50 minutes before the start of polymerization, the redox polymerization initiator ammonium persulfate is 0.12 mol% and ammonium bisulfite is 0.40 mol% with respect to the monomer (100 mol%) to be charged at the start of polymerization. Each was dissolved in deionized water and continuously supplied, and stirred with a stirring power of 1.4 kW / m ^3. At the start of polymerization, the monomer was water / monomer = 4.8 (mass ratio). In the same manner as in Example 1 except that continuous monomer supply was started. The composition, particle diameter, and filter differential pressure of the obtained acrylonitrile copolymer particles are as shown in Table 2, and the standard deviation of the particle size distribution of the acrylonitrile copolymer particles, the volume average particle diameter, 200 μm or more and 300 μm or more. The volume ratio of the particles was larger than that of Example 1. Also, the filter differential pressure was higher than in Example 1, and the particles were more difficult to dissolve than the acrylonitrile copolymer particles in Example 1.
(Comparative Example 2)

From 50 minutes before the start of polymerization, the redox polymerization initiator ammonium persulfate is 0.11 mol% and ammonium bisulfite is 0.36 mol% with respect to the monomer (100 mol%) to be charged at the start of polymerization. Each was dissolved in deionized water and continuously supplied, stirred with a stirring power of 2.7 kW / m ^{3, and} at the start of polymerization, the monomer was water / monomer = 2.4 (mass ratio). Thus, the same procedure as in Example 1 was performed except that continuous supply of a monomer comprising AN monomer unit: MAA monomer unit (molar ratio) = 99.0: 1.0 was started. The composition, particle diameter, and filter differential pressure of the obtained acrylonitrile copolymer particles are as shown in Table 2, and the standard deviation of the particle size distribution of the acrylonitrile copolymer particles, the volume average particle diameter, 200 μm or more and 300 μm or more. The volume ratio of the particles was larger than that of Example 1. Also, the filter differential pressure was higher than in Example 1, and the particles were more difficult to dissolve than the acrylonitrile copolymer particles in Example 1.
(Comparative Example 3)

From 50 minutes before the start of polymerization, the redox polymerization initiator ammonium persulfate is 0.09 mol% and ammonium bisulfite is 0.32 mol% with respect to the monomer (100 mol%) to be charged at the start of polymerization. Each was dissolved in deionized water and continuously supplied, stirred at a stirring power of 8.0 kW / m ^{3, and} at the start of polymerization, the monomer was water / monomer = 2.2 (mass ratio). Other than starting the continuous supply of the monomer consisting of AN monomer unit: MAA monomer unit: AAm monomer unit (molar ratio) = 97.1: 0.6: 2.3 Was carried out in the same manner as in Example 1. The composition, particle diameter, and filter differential pressure of the obtained acrylonitrile copolymer particles are as shown in Table 2, and the standard deviation of the particle size distribution of the acrylonitrile copolymer particles is larger than that of Example 1, and the volume Compared with Example 1, the volume ratio of particles having an average particle diameter of 200 μm or more and 300 μm or more was considerably increased. Also, the filter differential pressure was higher than in Example 1, and the particles were more difficult to dissolve than the acrylonitrile copolymer particles in Example 1.
(Comparative Example 4)

From 50 minutes before the start of polymerization, the redox polymerization initiator ammonium persulfate is 0.08 mol% and ammonium bisulfite is 0.29 mol% with respect to the monomer (100 mol%) to be charged at the start of polymerization. Each is dissolved in deionized water and continuously supplied, and stirred at a stirring power of 0.9 kW / m ^3. At the start of polymerization, the monomer is water / monomer = 3.0 (mass ratio). Other than starting the continuous supply of the monomer consisting of AN monomer unit: MAA monomer unit: AAm monomer unit (molar ratio) = 97.1: 0.6: 2.3 Was carried out in the same manner as in Example 1. The composition, particle size, and filter differential pressure of the obtained acrylonitrile copolymer particles are as shown in Table 2, and the standard deviation of the particle size distribution of the acrylonitrile copolymer particles, the volume average particle size of particles of 10 μm or less. The volume ratio was larger than that in Example 1. Also, the filter differential pressure was higher than in Example 1, and the particles were more difficult to dissolve than the acrylonitrile copolymer particles in Example 1.
(Comparative Example 5)

From 50 minutes before the start of the polymerization, the redox polymerization initiator ammonium persulfate is 0.10 mol% and the ammonium bisulfite is 0.34 mol% with respect to the monomer (100 mol%) to be charged at the start of the polymerization. Each is dissolved in deionized water and continuously supplied and stirred at a stirring power of 2.2 kW / m ^3. At the start of polymerization, the monomer is water / monomer = 3.0 (mass ratio). In the same manner as in Example 1 except that continuous supply of 100 mol% of the AN single monomer was started. The composition, particle diameter, and filter differential pressure of the obtained acrylonitrile copolymer particles are as shown in Table 2, and the standard deviation of the particle size distribution of the acrylonitrile copolymer particles, the volume average particle diameter, 200 μm or more and 300 μm or more. The volume ratio of the particles was larger than that of Example 1. Further, when the filter differential pressure was measured, the change in the filter pressure was large and could not be measured.
(Comparative Example 6)

From 50 minutes before the start of polymerization, the redox polymerization initiator ammonium persulfate is 0.02 mol% and ammonium bisulfite is 0.16 mol% with respect to the monomer (100 mol%) to be charged at the start of polymerization. Each was dissolved in deionized water and continuously supplied, and stirred with a stirring power of 2.2 kW / m ^3. At the start of polymerization, the monomer was water / monomer = 4.0 (mass ratio). Other than starting the continuous supply of the monomer consisting of AN monomer unit: MAA monomer unit: AAm monomer unit (molar ratio) = 98.0: 0.5: 1.5 Was carried out in the same manner as in Example 1. The composition, particle diameter, and filter differential pressure of the obtained acrylonitrile copolymer particles are as shown in Table 2, and the standard deviation of the particle size distribution of the acrylonitrile copolymer particles, the volume average particle diameter, 200 μm or more and 300 μm or more. The volume ratio of the particles was larger than that of Example 1. Further, when the filter differential pressure was measured, the change in the filter pressure was large and could not be measured.

Claims (8)

This is a method for producing acrylonitrile-based copolymer particles by redox aqueous precipitation polymerization in which a monomer, a redox initiator and deionized water are continuously supplied to a reactor, and a reaction solution is continuously taken out from the reactor. Te method of reactor stirring power is 3.0 kW / ^{m 3} or more 7.0 kW / ^{m 3} or less is acrylonitrile copolymer particles as defined below.
Reactor agitation power is the net power per unit volume received by agitation of water that has been filled to the overflow in the reactor. Specifically, the agitation blades are rotated while the reactor is empty. The amount of water filled in the reactor up to the overflow port is obtained by calculating the difference between the power value in the reactor and the power value in the case where the stirring blade is rotated while the reactor is filled with water up to the overflow port. The number divided by. The mol concentration A (mol / l) of the acrylonitrile monomer contained in the feed liquid supplied to the reactor and the mol concentration B (mol / l) of all monomers contained in the feed liquid are expressed by the following equations. The manufacturing method of the acrylonitrile-type copolymer particle of Claim 1 which satisfy | fills.
0.95 ≦ A / B ≦ 0.995 The molar concentration C (mol / l) of the redox initiator contained in the feed liquid supplied to the reactor and the molar concentration B (mol / l) of all monomers contained in the feed liquid are expressed by the following equations. The manufacturing method of the acrylonitrile-type copolymer particle of Claim 1 or 2 satisfy | filled.
0.20 ≦ C / B × 100 ≦ 0.65 Ion-exchanged water W (kg) in the feed solution and total monomer amount M (k in the feed solution supplied to the reactor
The method for producing acrylonitrile-based copolymer particles according to any one of claims 1 to 3, wherein g) satisfies the following formula.
1.5 ≦ W / M ≦ 5.5 Acrylonitrile copolymer particles having a volume average particle diameter of 30 μm or more and 40 μm or less and a standard deviation σ of volume average particle diameter of 0.25 or less obtained by the following formula.

  The acrylonitrile copolymer particles according to claim 5, wherein the volume ratio of the particles having a volume conversion particle diameter of 10 μm or less is 1.5% or less.   The acrylonitrile-based copolymer particles according to claim 5 or 6, wherein a volume ratio of particles having a volume-converted particle diameter of 200 µm or more is 1.0% or less.   The acrylonitrile copolymer particles according to any one of claims 5 to 7, wherein a volume ratio of particles having a volume-converted particle diameter of 300 µm or more is 0.1% or less.