JP2013237746A - Method for producing acrylonitrile-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an acrylonitrile-based polymer by suppressing the increase of a viscosity of a reaction liquid while keeping the mixing of the reaction liquid well by properly controlling coagulated particle diameters of the polymer under the polymerization reaction.SOLUTION: The stirring power for stirring a reaction liquid in a reactor is regulated so as to be ≥2.3 kW/mand ≤6 kW/mfrom the start of the feed of a monomer to the reactor to X hours, so as to be ≥3.0 kW/mand ≤6 kW/mfrom over X hours to Y hours, and so as to be ≥2.3 kW/mand ≤2.7 kW/mfrom over Y hours (wherein, 1≤X≤3, and 4≤Y≤6) when producing an acrylonitrile-based polymer by continuously feeding a monomer containing ≥40 mass% of acrylonitrile, a redox-type polymerization initiator and water into a mixture obtained by charging the polymerization initiator and water to an overflow port of the reactor, and continuously taking out the reaction liquid from the reactor.

Description

  The present invention relates to a method for producing an acrylonitrile polymer, particularly an acrylonitrile polymer suitable for acrylonitrile fibers.

  The acrylonitrile-based polymer is generally produced by aqueous precipitation polymerization or solution polymerization. In particular, the aqueous precipitation polymerization method enables continuous production with a shorter residence time than solution polymerization, and is extremely excellent in productivity because it uses a simple reactor.

  Generally, in the case of continuous production by aqueous precipitation polymerization, water and a polymerization initiator are charged in advance to the overflow port of the reactor at the start of polymerization, and the polymerization initiator, monomer and water are continuously added at a predetermined ratio. And the overflowed polymer suspension is recovered. From the start of polymerization to the steady state, the polymer contained in the overflowed polymer suspension greatly changes in particle shape and concentration.

  That is, immediately after the start of polymerization, the water in the reactor is in an extremely excessive state with respect to the monomer. And, immediately after starting the supply of monomers and the like, the polymer suspension begins to overflow from the reactor, so the resulting polymer suspension contains almost no polymer, The polymer contained in a very small amount is very fine.

  As the polymerization reaction proceeds, the polymer particle concentration in the overflowed polymer suspension gradually increases, and the polymer particles grow while repeating aggregation and destruction, and the particle shape and concentration are steady. To the state. Until this steady state is reached, the viscosity of the polymer suspension varies greatly. That is, as the concentration of the polymer increases and the agglomeration progresses, the viscosity of the reaction solution once increases, then the viscosity decreases and then becomes constant, but if the viscosity increases too much, stirring becomes impossible and the production is interrupted. Become.

  One solution to the above problem is to start supplying the monomer and polymerization initiator continuously to the reactor from a state where less water than the reactor overflow start capacity is charged. A method is known in which the concentration of the polymer is improved and the polymer particles have a predetermined average particle size (Patent Document 1).

  However, in this method, the initial concentration is low, and as the polymerization progresses, the viscosity of the reaction solution becomes high and cannot be stirred before it reaches a steady state due to the increase in concentration or the progress of aggregation.

JP 2000-26512 A

  An object of the present invention is to produce an acrylonitrile-based polymer while suitably controlling the agglomerated particle size of the polymer during the polymerization reaction, thereby suppressing an increase in the viscosity of the reaction solution and maintaining good mixing of the reaction solution. Is to provide a method.

  The problem is solved by the following.

In the present invention, a polymerization initiator and water are charged to the overflow port of the reactor, a monomer containing 40% by mass or more of acrylonitrile, a polymerization initiator and water are continuously supplied to the reactor, and a reaction liquid is supplied to the reactor. A process for producing an acrylonitrile-based polymer continuously taken out from
Stirring power for stirring the reaction liquid in the reactor is, the from the start supplying monomer to the reactor until the X time is 2.3 kW / m ³ or more 6 kW / m ³ or less, X times greater than the Y Time until 3.0 kW / m ³ or more 6 kW / m ³ or less, from the Y time is a manufacturing method of 2.3 kW / m ³ or more 2.7 kW / m ³ or less is acrylonitrile polymer (where, 1 ≦ X ≦ 3, 4 ≦ Y ≦ 6).
(Here, the agitation power is the electric power per unit volume (1 m ³ ) received by agitation of the reaction liquid filled up to the overflow port in the reactor, specifically, the reactor is empty. The difference between the power value when the stirrer is operated and the power value when the stirrer is operated in a state where the reaction liquid is filled up to the overflow port of the reactor is the volume to the overflow port of the reactor. (It is specified as a divided and standardized numerical value.)

  In addition, the volume average particle diameter of the polymer particles contained in the overflowing reaction solution is 50 μm or less until 8 hours from the start of supplying the monomer to the reactor, and the volume average particles after 8 hours or more. The method for producing an acrylonitrile-based polymer according to claim 1, wherein the diameter is 30 μm or more and 40 μm or less.

  According to the present invention, it is possible to suppress the increase in the viscosity of the reaction liquid, to keep the reaction liquid mixed well, and to produce a particulate acrylonitrile-based polymer excellent in detergency.

  Hereinafter, the present invention will be described in detail.

  In this invention, the monomer which has acrylonitrile as a main component, a polymerization initiator, and water are continuously supplied in a reactor, and a monomer is polymerized. In the present invention, since the polymerization of this monomer is performed by redox aqueous precipitation polymerization using a redox initiator as a polymerization initiator, it is compared with other polymerization methods such as suspension polymerization, solution polymerization, and emulsion polymerization. It is excellent in productivity and the amount of unnecessary components such as residual monomers can be reduced.

  Since the present invention is a method in which a monomer is continuously polymerized by a redox aqueous precipitation polymerization method, for example, water (polymerization medium) is previously charged in a reactor, and an oxidizing agent, a reducing agent, a redox auxiliary agent, It is preferable that water and the monomer are continuously supplied and the polymerization reaction proceeds while stirring. In addition, as water, what was refine | purified to such an extent that it does not become a disorder | damage | failure of superposition | polymerization is used, and deionized water is usually preferable.

  In redox aqueous precipitation polymerization, an oxidizing agent and a reducing agent are used in pairs as a polymerization initiator. As the oxidizing agent, generally, an inorganic oxidizing agent such as ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide, methyl ethyl ketone peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, Suitable are organic peroxides such as cumene hydroperoxide, succinic acid peroxide, and di (2-ethoxyethyl) peroxydicarbonate. The amount of the oxidizing agent used is determined by the molecular weight of the target polymer, and is usually set so that the oxidizing agent / monomer is 0.005 to 0.05 mass%.

  Moreover, as a reducing agent, generally sodium sulfite, ammonium sulfite, sodium bisulfite, ammonium bisulfite, sodium thiosulfate, ammonium thiosulfate, sodium dithionite, sodium formaldehyde sulfoxylate (SFS), L- Examples include alcorbic acid and dextrose. In addition, the usage-amount of a reducing agent is determined by the molecular weight of the target polymer, and is normally set so that a reducing agent / monomer may be 0.005-0.05 mass%.

  Moreover, it is preferable to use a redox-type auxiliary agent together with the oxidizing agent and the reducing agent. Examples of the auxiliary agent include ferrous sulfate and copper sulfate. In particular, it is preferable to use a combination of ammonium persulfate-ammonium hydrogen sulfite-ferrous sulfate. The concentration of the auxiliary agent is not particularly defined, but is preferably 0.01 ppm or more in the reaction solution from the viewpoint of more efficiently proceeding the polymerization, and preferably 1000 ppm or less from the point that remaining in the polymer does not cause a problem.

  In the present invention, the monomer contains acrylonitrile as a main component, but usually preferably contains acrylonitrile in an amount of 40% by mass or more. When the resulting polymer is for fibers, its heat resistance and the like are taken into consideration. Then, it is still more preferable that 90 mass% or more of acrylonitrile is contained.

  The vinyl monomer used together with acrylonitrile is not particularly limited as long as it is copolymerizable with acrylonitrile, but when the resulting polymer is for fibers, as a copolymerizable vinyl monomer, for example, (Meth) acrylic esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, vinyl chloride, vinyl bromide, vinylidene chloride, etc. Vinyl halides, acids such as (meth) acrylic acid, itaconic acid, crotonic acid and their salts, maleic imide, phenylmaleimide, (meth) acrylamide, styrene, α-methylstyrene, vinyl acetate, (meth) allyl Sodium sulfonate, (meth) allyloxybenzenesulfone Sodium, sodium styrene sulfonate, and the like 2-acrylamido-2-methylpropanesulfonic acid and salts thereof.

  The reactor used in the present invention is, for example, a device that circulates a reaction liquid in the reactor, a supply port that supplies each component, a polymerization heat removal device, and an overflow port. As the circulation device, a stirrer is preferably used from the viewpoint of promptly diffusing each component in the solution.

  The temperature of the reaction liquid in the reactor is not particularly limited as long as the monomer can be polymerized. However, it is preferably 80 ° C. or less, more preferably 60 ° C. or less, from the viewpoint of preventing acrylonitrile from evaporating and being dispersed outside the reaction system. Moreover, it is preferable to keep the temperature of the reaction liquid constant from the viewpoint of stabilizing the molecular weight of the polymer.

  The average residence time of the monomer in the reactor is not particularly limited, and the time employed when producing the acrylonitrile polymer by aqueous precipitation polymerization is appropriate. That is, the average residence time is preferably 200 minutes or less from the viewpoint of productivity, and preferably 20 minutes or more from the viewpoint of sufficiently completing the polymerization.

  The amount of monomer supplied to the reactor is determined in consideration of the residence time, and is determined together with the supply of water, a polymerization initiator, a pH regulator and the like to be supplied at the same time. It is made to become 40 mass%.

  The hydrogen ion concentration in the reactor may be a concentration such that the initiator promptly causes an oxidation / reduction reaction, and an acidic region having a pH of 2.0 to 3.5 is preferable.

  In the present invention, while the monomer is polymerized in the reactor as described above, the reaction liquid containing the polymer particles is continuously taken out from the overflow port of the reactor.

  The polymerization is stopped by adding, for example, a polymerization terminator dissolved in deionized exchange water to the reaction solution. As the polymerization terminator, a polymerization terminator used when the acrylonitrile polymer is produced by aqueous precipitation polymerization can be used without any trouble.

  Subsequently, the unreacted monomer is recovered from the polymer aqueous dispersion. As a method for recovering the unreacted monomer, there are a method of directly distilling from the polymer dispersion, and a method of once dehydrating and separating the unreacted monomer from the polymer and then distilling. In the present invention, both methods Both can be adopted. As the dehydration washer used in the latter method, a generally known filter dehydrator can be used. For example, a rotary vacuum filter, a centrifugal dehydrator, or the like can be used. From the viewpoint of efficiency, a flocculant such as ammonium sulfate, aluminum sulfate, or sodium sulfate can be added when separating the polymer from the reaction solution using these apparatuses, and further from the viewpoint of promoting the aggregation of the polymer. Operations such as raising the temperature of the polymer dispersion can also be performed. Further, water remaining in the polymer can be removed by a normal drying method.

  The polymer particles are typically polymer particles (aggregates of primary particles) formed by agglomerating particles having a volume average particle size of 0.1 μm or more and 10 μm or less deposited in an aqueous phase in aqueous precipitation polymerization. is there. Such polymer particles grow while repeating aggregation and destruction in the reactor, and reach a steady state.

  In other words, polymer particles precipitated in the aqueous phase aggregate while colliding with other polymer particles by the circulation of stirring, and the particle size increases. However, when a certain particle size is reached, destruction by shearing of the stirring becomes dominant. The particle size becomes smaller. Finally, a steady state is obtained with a particle diameter in which aggregation and shear are balanced.

  In the unsteady state, the polymer particles grown under conditions where shearing by stirring is weak has a sparse structure because it aggregates slowly. The sparse polymer particles have a large amount of dispersion medium adsorbed in the polymer particles, become bulky particles, and increase the viscosity of the reaction solution.

  The time at which the particle diameter of the polymer particles becomes maximum can be controlled by arbitrarily selecting the polymerization conditions. Generally, the volume average particle diameter is maximum by 8 hours after the start of supplying the monomer to the reactor. Then, it gradually becomes smaller and becomes a steady state. In the present invention, the time when the monomer starts to be supplied to the reactor is regarded as the start of polymerization. Hereinafter, for the sake of simplicity, the period after the start of supplying the monomer to the reactor is referred to as “after the start of polymerization”.

  As the volume average particle diameter increases, the volume ratio of the polymer particles in the reaction liquid increases, the viscosity of the reaction liquid increases, and the mixing state in the reactor deteriorates. On the other hand, when the particle size is reduced, the cake layer of polymer particles formed by a dehydration washing machine becomes too dense, so that the washing water is difficult to pass and the washing property is deteriorated.

  From the viewpoint of maintaining a good mixed state in the reactor, the volume average particle diameter of the polymer particles up to 8 hours after the start of polymerization is 50 μm or less, more preferably 45 μm or less. Furthermore, the volume average particle diameter gradually increases from the start of polymerization, and after 8 hours, preferably falls within the following volume average particle diameter range. The volume average particle size is 10 μm or more from 1 hour to 2 hours from 2 hours in order to prevent the cake layer of polymer particles formed by the dehydration washing machine from becoming too dense even up to 8 hours. It is preferable that it is 20 micrometers or more. If the volume average particle diameter of the polymer particles is 10 μm or more, the filter is not clogged and the cleaning property is not deteriorated.

  In the present invention, based on the value obtained by measuring the volume average particle diameter of the polymer particles contained in the polymer suspension collected from the reactor overflow port every hour until 8 hours after the start of polymerization. The volume average particle diameter of the polymer particles up to 8 hours after the start of monomer supply was determined.

  Further, from the viewpoint of maintaining good cleaning properties of the polymer particles, the volume average particle diameter of the polymer particles after 8 hours from the start of polymerization is preferably 30 μm or more, and from the viewpoint of maintaining a good mixed state in the reactor, 40 μm The following is preferable, and 36 μm or less is more preferable.

  In the present invention, the average value of the volume average particle diameter of the polymer particles after 8 hours from the start of polymerization is the volume average particle diameter of the polymer particles contained in the polymer suspension collected from the reactor overflow port. Calculation was based on the diameter. That is, a value obtained by arithmetically averaging the measured values of the volume average particle diameter for 1 hour before and after the time of calculation was adopted.

  The particle size of the polymer particles can be controlled by arbitrarily selecting the polymerization conditions, but is preferably controlled by stirring power because it can be carried out without impairing the productivity. By increasing the stirring power, the aggregated particles of the polymer due to the shearing of the stirring are broken, so that the particle size of the polymer particles is reduced. On the contrary, by reducing the stirring power, the aggregation of the polymer particles is superior to the destruction, so that the particle size of the polymer particles is increased.

In the present invention, the stirring power is the net power per unit volume received by the contents of the reactor by stirring. Specifically, when stirring is performed with a stirring blade, the power value when the stirring blade is rotated while the reactor is empty and the stirring blade is rotated with the reaction liquid filled to the overflow port of the reactor. The difference in power value is calculated, and the numerical value converted per 1 m ^{3 of the} reaction liquid in the reactor is used as the stirring power. In the case of using an external circulation device, the power value when the external circulation device is operated in an empty state and the power value when the external circulation device is operated with the reaction liquid filled to the overflow port of the reactor. The stirring power is obtained from the difference. The reactor internal volume is the total volume of the supply liquid and the reaction liquid. In the present invention, the power value was measured using a compact power meter MODEL 6300 (trade name) manufactured by Kyoritsu Electric Instruments Co., Ltd.

  In the present invention, as the average value of the stirring power, a value obtained by arithmetically averaging the stirring power collected every 10 seconds for 30 minutes before and after the calculation time point was adopted.

  Since the monomer concentration is small immediately after the start of polymerization, the resulting polymer tends to be fine particles. Therefore, it is preferable to set the stirring power low so that the aggregation of the polymer easily proceeds until 1 to 3 hours (X hours) after the start of polymerization, but even if it is high, the polymer concentration is low. The polymer particles do not become too small without undergoing excessive shearing.

  Thereafter, the stirring power is increased to 4 to 6 hours (Y time) after the start of polymerization to suppress an increase in viscosity and an increase in volume average particle size due to polymer aggregation, and then a predetermined polymer particle size can be maintained. The stirring power can also be adjusted.

That is, the stirring power is set to 2.3 kW / m ³ or more in order to stir the contents of the reactor sufficiently uniformly until X hours after the start of polymerization. In addition, the stirring power is set to 6.0 kW / m ³ or less from the viewpoint of suppressing abrupt aggregation and the prevention of bubble entrainment in the reaction solution.

After the X time, until the polymerization started after Y hours, the stirring power, and 3.0 kW / m ³ or more 6.0 kW / m ³ within the following range. By setting the stirring power to 3.0 kW / m ³ or more, the contents of the reactor can be stirred sufficiently uniformly, and the volume average particle diameter of the polymer particles can be kept sufficiently small. Further, in order to prevent bubbles from being involved in the reaction solution, the stirring power is set to 6.0 kW / m ³ or less. Furthermore, by setting it as 5.0 kW / m < ³ > or less, it is more preferable at the point which can suppress the cullet production | generation by the scattered reaction liquid.

Since the volume average particle diameter of the polymer particles becomes smaller from around Y hours after the start of the polymerization, if the stirring power remains high, the volume average particle diameter of the polymer particles becomes too small, and dewatering washing is performed. Since the cake layer of the polymer particles formed by the machine becomes dense, it becomes difficult for the washing water to pass through and the washing properties deteriorate. Therefore, the stirring power is set to 2.7 kW / m ³ or less in order to maintain good cleaning performance of the polymer particles from the time over Y hours after the start of polymerization. Moreover, in order to stir the contents of the reactor sufficiently uniformly, the stirring power is set to 2.3 kW / m ³ or more.

  The above X time is preferably 1 hour or more in order to appropriately agglomerate the polymer particles precipitated in the aqueous phase at the initial stage of polymerization and to facilitate the recovery of the polymer using a dehydration washing machine, Two hours or more are more preferable. Moreover, in order to acquire the effect of making the maximum value of the volume average particle diameter of a polymer particle small, it is preferable to set it as 3 hours or less.

  Moreover, when Y time is small, the effect which makes the maximum value of the volume average particle diameter of a polymer particle small cannot fully be acquired. If the Y time is large, polymer particles having a small volume average particle diameter are generated, and the cake layer of the polymer particles formed by the dehydration washing machine becomes too dense, so that it is difficult for washing water to pass through and washing. Sex worsens. From this viewpoint, in order to reduce the maximum value of the volume average particle diameter of the polymer particles, the time is set to 4 hours or more. In order to keep the detergency of the polymer particles good, the time is 6 hours or less.

  Hereinafter, the present invention will be described by way of examples. In addition, the evaluation in an Example depended on the following.

[Cleanability (leaf test)]
The detergency of the polymer particles can be evaluated by various methods. In the present invention, as an index of detergency, the speed at which the washing water passes through the cake layer of the polymer particles was measured.

  A polymerization stopper aqueous solution containing 0.5% by mass of sodium oxalate and 1.5% by mass of sodium bicarbonate was added to the reaction solution overflowing from the reactor so that the reaction solution had a pH of 5.5 to 6.0. The reaction solution is filtered using a filter cloth to form a cake layer of polymer particles. Then, the time for a predetermined amount of water to pass through the cake layer is measured. If the cake layer is cracked, the water passage time is measured after filling the crack so that the cake layer is uniform. The measurement conditions are as shown in Table 1 below.

  If the time required for the predetermined amount of water to pass through the cake layer is short, the washing water can be sufficiently passed through the cake layer even if the washing speed of the polymer particles is high, so that the detergency can be kept good. From the above viewpoint, the time for 200 cc of water to pass through the cake layer is 18 seconds or less.

[Reaction liquid viscosity]
The polymerization stopper aqueous solution was added to the overflowing reaction solution so as to have a pH of 5.5 to 6.0, and the reaction solution viscosity was measured with a B-type viscometer. The addition of the polymerization stopper aqueous solution was about 50 ml per 1 m ³ of the reaction solution.

[Volume average particle diameter]
The volume average particle size of the polymer particles is measured using laser scattering techniques such as image analysis of microscopic images, laser diffraction, or focused beam reflectivity mode. In the present invention, the particle size distribution of the polymer particles is adjusted to have a refractive index of 1.330- by using a laser diffraction / scattering particle size distribution analyzer (manufactured by Seisin Corporation, SK Laser Micron Sizer LMS-350 (trade name)). A value of 50% normal distribution measured from 0.01i and a shape factor of 1.000 and calculated from the volume average was taken as the volume average particle size.

<Example 1>
Deionized exchange water in which 0.000013% by mass of ferrous sulfate, 0.07% by mass of ammonium persulfate, and 0.11% by mass of ammonium hydrogen sulfite are dissolved in a 76.5 liter aluminum reactor with a disc turbine stirring blade. Was charged until the water was full, and the internal temperature of the reactor was raised to 57 ° C. Among them, 100 parts by mass of acrylonitrile, 3.61 parts by mass of acrylamide, 0.55 parts by mass of methacrylic acid, 204 parts by mass of deionized water, 0.39 parts by mass of ammonium persulfate, 0.59 parts by mass of ammonium bisulfite, sulfuric acid 0.0003 parts by mass of ferrous iron and 0.06 parts by mass of sulfuric acid were continuously supplied to carry out a polymerization reaction. Components other than acrylonitrile are each dissolved in deionized water, and acrylamide 25% by weight aqueous solution, methacrylic acid 6% by weight aqueous solution, ammonium persulfate 2.75% by weight aqueous solution, ammonium hydrogen sulfite 5% by weight aqueous solution, sulfuric acid first Iron (Fe ₂ SO ₄ .7H ₂ O) 2 ppm aqueous solution and sulfuric acid 0.5 mass% aqueous solution were used.

The reaction solution in the reactor was adjusted with the sulfuric acid supply amount so that the pH was 3.0, the reaction solution temperature was kept at 50 ° C., and the polymerization reaction was continuously carried out while stirring, The reaction solution was continuously taken out from the reactor overflow so that the residence time was 70 minutes. The reaction mixture stirring power until the polymerization initiator after 5 hours 4.0 kW / m ³ per unit volume of, thereafter adjusting the stirring as a 2.7 kW / m ^3.

  A polymerization stopper aqueous solution in which sodium oxalate and sodium bicarbonate were dissolved in deionized exchange water so that the concentration was 0.5% by mass and 1.5% by mass, respectively, was added to the removed reaction solution. The reaction was stopped by adding 5.5 to 6.0.

  The obtained acrylonitrile-based polymer particles were evaluated for volume average particle diameter, detergency, and reaction solution viscosity, and are shown in Table 2.

  Throughout the polymerization reaction, the volume average particle diameter of the polymer particles was kept at 50 μm or less, so the viscosity of the reaction solution was kept low and the fluidity inside the reactor was kept sufficiently. Further, the polymer particles obtained after 8 hours from the start of polymerization also had good detergency.

<Example 2>
Agitation power of per unit volume of the reaction solution, 2.7 kW / m ³ to the polymerization initiator after 3 hours, then the polymerization initiator until after 5 hours 4.0 kW / m ^3, thereafter like a 2.7 kW / m ³ The polymer particles were obtained in the same manner as in Example 1 except that the stirring was adjusted. The results are shown in Table 2.

  Throughout the polymerization reaction, the volume average particle diameter of the polymer particles was kept at 50 μm or less, so the viscosity of the reaction solution was kept low and the fluidity inside the reactor was kept sufficiently. Further, the polymer particles obtained after 8 hours from the start of polymerization also had good detergency.

<Example 3>
The same as in Example 1 except that the stirring power was adjusted so that the stirring power per unit volume of the reaction solution was 5.5 kW / m ³ until 5 hours after the start of polymerization, and 2.4 kW / m ³ thereafter. Polymer particles were obtained and evaluated in the same manner as in Example 1 below. The results are shown in Table 2.

  Throughout the polymerization reaction, the volume average particle diameter of the polymer particles was kept at 50 μm or less, so the viscosity of the reaction solution was kept low and the fluidity inside the reactor was kept sufficiently. Further, the polymer particles obtained after 8 hours from the start of polymerization also had good detergency.

<Example 4>
Agitation power of per unit volume of the reaction solution, 2.7 kW / m ³ to the polymerization initiator after 3 hours, then the polymerization initiator until after 5 hours 5.5 kW / m ^3, thereafter like a 2.4 kW / m ³ The polymer particles were obtained in the same manner as in Example 1 except that the stirring was adjusted. The results are shown in Table 2.

  Throughout the polymerization reaction, the volume average particle diameter of the polymer particles was kept at 50 μm or less, so the viscosity of the reaction solution was kept low and the fluidity inside the reactor was kept sufficiently. Further, the polymer particles obtained after 8 hours from the start of polymerization also had good detergency.

<Comparative Example 1>
Stirring was maintained so that the stirring power was 2.7 kW / m ³ from the beginning, and acrylonitrile-based polymer particles were obtained in the same manner as in Example 1. Evaluation was performed in the same manner as in Example 1 below. The results are shown in Table 2.

  There was time for the volume average particle diameter of the polymer particles to be 50 μm or more by 8 hours after the start of the polymerization. As a result, the viscosity of the reaction solution increased and the flow state inside the reactor deteriorated. In addition, since stirring property recovered | restored by 8 hours after the start of superposition | polymerization, the washability of the polymer particle obtained after 8 hours after the start of reaction was favorable.

<Comparative example 2>
Stirring was maintained so that the stirring power was 4.0 kW / m ³ from the beginning, and acrylonitrile-based polymer particles were obtained in the same manner as in Example 1. Evaluation was performed in the same manner as in Example 1 below. The results are shown in Table 2.

  Since the volume average particle diameter of the polymer particles was kept at 50 μm or less throughout the polymerization reaction, the reaction solution viscosity was kept low and the fluidity inside the reactor was kept sufficiently, but the stirring power was strong. Too much agglomeration of polymer particles and increase in fine powder (volume average particle diameter became less than 28 μm), so that the detergency of polymer particles obtained after 8 hours from the start of the reaction Became worse.

<Comparative Example 3>
When the polymerization reaction was carried out in the same manner as in Example 1 while stirring at a stirring power of 2.0 kW / m ³ from the beginning, the viscosity of the reaction solution increased within 1 hour after the start of polymerization. Since the flow state of the liquid deteriorated, the polymerization was stopped.

<Comparative example 4>
Stirring was performed so that the stirring power was 6.5 kW / m ³ from the beginning, and polymerization was performed in the same manner as in Example 1. Immediately after the start of polymerization, oxygen inside the reactor was involved in the reaction solution, and polymerization was performed. Since it did not progress much, the reactor was turned off in 1 hour.

Claims (2)

A polymerization initiator and water are charged to the overflow of the reactor, a monomer containing 40% by mass or more of acrylonitrile, a redox polymerization initiator and water are continuously supplied to the reactor, and the reaction solution is continuously supplied from the reactor. A process for producing an acrylonitrile-based polymer to be taken out,
Stirring power for stirring the reaction liquid in the reactor is, the from the start supplying monomer to the reactor until the X time is less 2.3 kW / m ³ or more 6 kW / m ^3, from X time than Y until the time is at 3.0 kW / m ³ or more 6 kW / m ³ or less, from the Y time than 2.3 kW / m ³ or more 2.7 kW / m ³ or less is a manufacturing method for acrylonitrile type polymer (however, 1 ≦ X ≦ 3, 4 ≦ Y ≦ 6).
(Here, the stirring power is the electric power per unit volume (1 m ³ ) received by the stirring of the reaction liquid filled up to the overflow port in the reactor. Specifically, the reactor is empty. The difference between the power value when the stirrer is operated and the power value when the stirrer is operated while the reaction liquid is filled up to the overflow port of the reactor is the volume to the overflow port of the reactor. Divided by and specified as a standardized number.)   The volume average particle size of the polymer particles contained in the reaction liquid overflowing from the reactor is 50 μm or less until 8 hours from the start of supplying the monomer to the reactor, and 30 μm or more and 40 μm or less from 8 hours. The method for producing an acrylonitrile-based polymer according to claim 1.