JP2009280760A - Production method of porous polymer particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining porous polymer particles in a high yield by efficiently filtering and washing a reaction mixture obtained by suspension polymerization so as to effectively eliminate impurities. <P>SOLUTION: The porous polymer particles are obtained through steps of: (a) leaving to stand a reaction mixture obtained by suspension polymerization, and removing a water phase to obtain a cake of porous polymer particles; (b) pulverizing the cake, suspending the porous polymer particles in water, leaving the suspension to stand and removing the water phase; (c) pulverizing the obtained cake of the porous polymer particles, suspending the porous polymer particles in water, filtering the porous polymer particles by using a filtering medium; and (d) pulverizing the obtained cake of the porous polymer particles, suspending the porous polymer particles in an organic solvent, and filtering the particles by using a filtering medium to obtain the porous polymer particles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a process for producing porous particles mainly composed of an aromatic vinyl monomer and an aromatic divinyl monomer, preferably a copolymer of styrene and divinylbenzene.

  Conventionally, polystyrene-based porous polymer particles have been used as ion exchange resins, adsorbents in various applications, carriers for protein synthesis, etc. In recent years, antisense oligo DNAs and siRNAs used as pharmaceuticals, etc. Therefore, there is a need for a method for more efficiently producing porous polymer particles with fewer impurities.

  Under such circumstances, conventionally, suspension polymerization, which is relatively easy to operate, has been preferably used as a means for producing porous polymer particles. However, according to suspension polymerization, porous polymer particles having an arbitrary average particle diameter can be easily obtained. On the other hand, the obtained particles have a relatively wide particle size distribution, and thus can be obtained by suspension polymerization. There is a problem that labor and time are required for the separation of the target porous polymer particles from the reaction mixture thus obtained and the washing for removing impurities, and the production cost is increased.

  Conventionally, means such as centrifugal separation and centrifugal filtration have been used to separate the desired porous polymer particles from the reaction mixture obtained by suspension polymerization, and in particular, suction filtration and pressurization using a filter medium. Filtration is advantageous because it does not require a large-scale and complicated structure and the power cost is low.

However, in the production of porous polymer particles by suspension polymerization, a fine particle polymer is unnecessarily generated in the aqueous phase, and the target porous polymer particles are filtered using a filter medium. Viscosity of the reaction mixture obtained by suspension polymerization of a dispersant composed of a water-soluble polymer such as polyvinyl alcohol or polyvinylpyrrolidone added to the aqueous phase in suspension polymerization. In order to increase the filtration resistance during filtration of the target porous polymer particles, and the filtration efficiency of the target porous polymer particles is reduced due to various reasons, and the target porous It takes a very long time to separate the polymer particles by filtration. Moreover, in order to remove impurities in the porous polymer particles, it is necessary to repeat the washing and filtration. When the filter medium is clogged in the middle, the filter medium must be replaced each time. It ’s cumbersome.
Japanese Patent Laid-Open No. 03-068593

  The present invention has been made to solve the above-described problems in the filtration and separation of porous polymer particles from a reaction mixture obtained by suspension polymerization. The reaction mixture is efficiently filtered and washed to remove impurities. An object of the present invention is to provide a method of effectively removing the target porous polymer particles with a high yield.

According to the present invention, a monomer mixture containing an aromatic vinyl monomer and an aromatic divinyl monomer as main components and a polymerization initiator are dissolved in an organic solvent to form a monomer solution, which is used as a dispersant. The above-mentioned monomer is subjected to suspension polymerization in a suspension polymerization system dispersed in water to form porous polymer particles, and then the porous polymer particles are separated from the obtained reaction mixture. In the method for producing porous polymer particles,
(A) standing the reaction mixture, separating the porous polymer particles from the aqueous phase, then removing the aqueous phase and separating the cake of porous polymer particles from the reaction mixture;
(B) The cake of the porous polymer particles obtained in the step (a) is crushed, and the porous polymer particles are suspended in water, and then left to stand, and the porous polymer particles are washed with water. Separating the aqueous phase and then removing the aqueous phase to obtain a porous polymer cake;
(C) After pulverizing the cake of the porous polymer particles obtained in the step (b), suspending the porous polymer particles in water, washing the porous polymer particles, and then using a filter medium. Filtering to obtain a cake of porous polymer particles,
(D) After pulverizing the cake of porous polymer particles obtained in the step (c), suspending the porous polymer particles in an organic solvent, washing the porous polymer particles, and then filtering the filter medium. And filtering to obtain a cake of porous polymer particles,
Are provided in this order to obtain porous polymer particles.

  According to the method of the present invention, the step (a) can effectively remove the fine particle polymer that is unnecessarily generated in the aqueous phase in the suspension polymerization, and thus the porous polymer using the subsequent filter medium. The main cause of clogging the filter medium in the filtration of particles can be removed. In the step (b), the porous polymer particles are efficiently washed to remove the dispersant, the fine particle polymer and other impurities efficiently. Furthermore, in step (c) and step (d), it is filtered while effectively removing the dispersant still remaining in the porous polymer particles and the organic solvent used for suspension polymerization. The intended porous polymer particles can be obtained.

The present invention provides a monomer solution obtained by dissolving a monomer mixture mainly composed of an aromatic vinyl monomer and an aromatic divinyl monomer and a polymerization initiator in an organic solvent, and this is a water solution containing a dispersant. A porous polymer comprising a suspension polymerization system in which the above monomer is subjected to suspension polymerization to form porous polymer particles, and then the porous polymer particles are separated from the resulting reaction mixture. In the method for producing polymer particles,
(A) standing the reaction mixture, separating the porous polymer particles from the aqueous phase, then removing the aqueous phase and separating the cake of porous polymer particles from the reaction mixture;
(B) The cake of the porous polymer particles obtained in the step (a) is crushed, and the porous polymer particles are suspended in water, and then left to stand, and the porous polymer particles are washed with water. Separating the aqueous phase and then removing the aqueous phase to obtain a porous polymer cake;
(C) After pulverizing the cake of the porous polymer particles obtained in the step (b), suspending the porous polymer particles in water, washing the porous polymer particles, and then using a filter medium. Filtering to obtain a cake of porous polymer particles,
(D) After pulverizing the cake of porous polymer particles obtained in the step (c), suspending the porous polymer particles in an organic solvent, washing the porous polymer particles, and then filtering the filter medium. And filtering to obtain a cake of porous polymer particles,
In this order, porous polymer particles are obtained.

  In the present invention, styrene or a substituted product thereof is used as the aromatic vinyl monomer, preferably styrene mainly composed of styrene and having various functional groups depending on the required characteristics of the obtained porous polymer particles. Mixtures containing substitutions are used.

  Examples of such styrene substitution products include alkyl groups having 1 to 5 carbon atoms, halogen atoms, amino groups, carboxyl groups, sulfonic acid groups, cyano groups, alkoxy groups having 1 to 5 carbon atoms, nitro groups, and acyloxy groups. And the like having a substituent as the substituent. For example, porous polymer particles having a hydroxyl group by hydrolyzing polymer particles obtained by suspension copolymerization with alkali or acid using p-acetoxystyrene as styrene as an aromatic vinyl monomer Can be obtained efficiently.

  In particular, in the present invention, aromatic vinyl monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, pt-butylstyrene, and the like. Examples thereof include α-alkyl-substituted styrenes such as nuclear alkyl-substituted styrene, α-methylstyrene and α-methyl-p-methylstyrene, halogenated styrenes such as chlorostyrene, and p-acetoxystyrene. It is not limited.

  Examples of the aromatic divinyl monomer include divinylbenzene and divinylbenzene compounds having various substituents as in the above-mentioned styrene-substituted product, but usually a nuclear alkyl such as divinylbenzene or methyldivinylbenzene. Substituted divinylbenzene is preferably used, and among them, divinylbenzene is preferably used. As divinylbenzene, o-, m- or p-divinylbenzene or a mixture thereof is used.

  In the present invention, the monomer mixture contains the above-described aromatic vinyl monomer and aromatic divinyl monomer as main components. That is, in the present invention, 50% by weight or more of the monomer mixture is composed of the above-mentioned aromatic vinyl monomer and aromatic divinyl monomer, and the remainder is composed of other monomers. Also good. Further, the monomer mixture may occupy 100% by weight with the aromatic vinyl monomer and the aromatic divinyl monomer.

  However, in the present invention, based on the total weight of the aromatic vinyl monomer and the aromatic divinyl monomer, the amount of the aromatic divinyl monomer is in the range of 2 to 30% by weight, preferably 5 It is in the range of ˜20% by weight. When the amount of the aromatic divinyl monomer is out of the above range based on the total weight of the aromatic vinyl monomer and the aromatic divinyl monomer, it is true depending on the combination with the organic solvent described later. It is difficult to obtain spherical porous polymer particles, and the obtained porous polymer particles do not have a uniform porous structure.

  In the present invention, when other monomers are used together with the aromatic vinyl monomer and the aromatic divinyl monomer, the other monomers include, for example, acrylonitrile, acrylic acid, methacrylic acid, methyl methacrylate, etc. (Meth) acrylic monomers can be mentioned.

  According to the present invention, the monomer mixture containing the above-mentioned aromatic vinyl monomer and aromatic divinyl monomer as main components and the polymerization initiator are dissolved in an organic solvent to obtain a monomer solution.

  The polymerization initiator to be used is not particularly limited. For example, dibenzoyl peroxide, dilauroyl peroxide, distearoyl peroxide, 1,1-di (t-butylperoxy) -2-methylcyclohexane, 1,1-di (T-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, 1,1,1-di (t-butylperoxy) cyclohexane, di-t-hexylper Oxide, t-butylcumyl peroxide, di-t-butyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t -Butylperoxy-2-ethylhexanoate, t-butylperoxyisopropylmolybdate Peroxides such as carbonate, azo such as 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile Conventionally known compounds and the like are appropriately used.

  The organic solvent is used for making the resulting polymer particles have a porous structure, that is, a porous agent. As the organic solvent, hydrocarbons or alcohols are preferably used. The hydrocarbon may be either an aliphatic or aromatic hydrocarbon having 5 to 12 carbon atoms, and the aliphatic hydrocarbon may be either a saturated or unsaturated hydrocarbon. Specific examples of such hydrocarbons include toluene, n-hexane, n-heptane, n-octane, isooctane, undecane, dodecane and the like.

  As the alcohol, an aliphatic alcohol is preferably used, and among them, an aliphatic alcohol having 5 to 12 carbon atoms is preferably used. Preferable specific examples include 2-ethylhexanol, t-amyl alcohol, nonyl alcohol, 2-octanol, decanol, lauryl alcohol, cyclohexanol and the like.

  According to the present invention, a mixture of the above hydrocarbon and alcohol is also preferably used as the organic solvent. The weight ratio of hydrocarbon to alcohol in this mixture depends on the specific combination of hydrocarbon and alcohol used, and by adjusting this ratio appropriately, the pore size distribution and specific surface area of the resulting porous polymer particles The porous structure such as can be controlled in various ways.

  The amount of the organic solvent used to obtain the monomer solution is in the range of 0.5 to 2.0 times the total amount of monomers on a weight basis, preferably 0.8 It is the range of -1.5 times. When the amount of the organic solvent used is out of the above range, although it depends on the combination with the monomer used, it is difficult to obtain true spherical polymer particles, and the obtained porous polymer particles are uniform. Does not have a porous structure.

  According to the present invention, the monomer solution is thus dispersed in water together with a dispersant, and suspension polymerization is performed to produce porous polymer particles. The dispersant is not particularly limited. For example, water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, gelatin, starch, carboxymethylcellulose, hydroxyethylcellulose, sodium polyacrylate, and polyvinylpyrrolidone are preferably used. . These may be used alone or in combination of two or more.

  In particular, in the present invention, polyvinyl alcohol is preferably used as the dispersant. Among these, polyvinyl alcohol having a polymerization degree in the range of 500 to 3000 and a saponification degree in the range of 65 to 85 mol% is preferably used. When the degree of polymerization of the polyvinyl alcohol used is less than 500, the dispersion stability of the suspension polymerization system is impaired, a large amount of aggregates are formed, and further, a crosslinking reaction occurs between the porous particles. It is difficult to obtain dispersed porous polymer particles. On the other hand, when the polymerization degree of the polyvinyl alcohol used is larger than 3000, the viscosity of the reaction mixture obtained in the suspension polymerization is high. As a result, the filtration resistance becomes high, and the obtained porous polymer particles are used as the reaction mixture. It becomes difficult to separate from. Regarding the degree of saponification of polyvinyl alcohol, polyvinyl alcohol having a molecular weight lower than 65 mol% is usually difficult to obtain.

  In the present invention, the amount of the dispersant used is not particularly limited, but is preferably in the range of 0.5 to 3% by weight with respect to the weight of water in the suspension polymerization system. When the amount of the dispersant used is less than 0.5% by weight with respect to the weight of the water of the suspension polymerization system, the dispersion stability of the suspension polymerization system is impaired, and a large amount of aggregates are formed. Furthermore, a crosslinking reaction occurs between the porous polymer particles, and it is difficult to obtain well-dispersed porous polymer particles. Also, when the amount of dispersant used is more than 3% by weight with respect to the weight of water in the suspension polymerization system, the viscosity of the reaction mixture obtained in the suspension polymerization is high, and as a result, the filtration resistance is increased. In addition to the difficulty in separating the obtained porous polymer particles from the reaction mixture, there are disadvantages such as increased costs for removing impurities when washing the obtained porous polymer particles. Arise.

  In the present invention, reaction conditions such as suspension copolymerization temperature and reaction time may be set appropriately. As an example, stirring may be performed at a temperature of 60 to 90 ° C. for about 2 to 48 hours in a nitrogen stream.

  The porous polymer particles produced by the method of the present invention are not particularly limited in the particle diameter, but it is usually preferable that the median particle diameter is in the range of 2 to 200 μm. Porous polymer particles having a median particle diameter larger than 200 μm can obtain good filtration efficiency only by roughening the eyes of the filter medium, and the pores having a median particle diameter smaller than 2 μm are not required in the present invention. The polymer particles are difficult to produce by suspension polymerization.

  According to the present invention, after the monomer mixture is suspension-polymerized in this way to obtain a reaction mixture containing porous polymer particles, first, as the step (a), the reaction mixture is statically treated. Then, the porous polymer particles are levitated due to the difference in specific gravity, and thus the particle phase composed of the porous polymer particles is separated from the lower aqueous phase, and then the aqueous phase is removed to make the porous The polymer particles are separated from the reaction mixture to obtain a porous polymer particle cake.

  In the present invention, after the reaction mixture is allowed to stand and the porous polymer particles are separated from the aqueous phase, “removing the aqueous phase” is particularly limited except for a method of filtering using a filter medium. It is not a thing. For example, the suspension polymerization described above may be performed using a reaction vessel provided with an opening that can be opened and closed in advance at the bottom, and after completion, the lower layer in the reaction vessel may be extracted from the opening. A tube may be inserted into the bottom of the lower layer and pumped out using a pump.

  The standing of the reaction mixture obtained by suspension polymerization may be performed in the reaction vessel in which suspension polymerization was performed, or may be transferred to another vessel, but the former is more efficient. . By allowing the reaction mixture obtained by suspension polymerization to stand, the reaction mixture is separated into a phase of porous polymer particles enclosing an organic solvent that the suspension polymerization system has and an aqueous phase containing a dispersant, Due to the difference in specific gravity, the porous polymer particles float, form an upper layer composed of a particle phase, and separate from a lower layer composed of an aqueous phase. The larger the particle diameter of the porous polymer particles, the more organic solvent is included, and the apparent specific gravity becomes smaller. Therefore, the separation rate is faster than the porous polymer particles having a small particle diameter. That is, the porous polymer particles produced by suspension polymerization have a distribution of particle diameters, and the particle diameter increases toward the upper part of the particle phase and decreases toward the lower part.

  In the aqueous phase of the suspension polymerization system, the unnecessary fine particle polymer has a relatively large apparent specific gravity and therefore remains suspended in the aqueous phase without being separated from the aqueous phase.

  Thus, in step (a), by leaving the reaction mixture containing the porous polymer particles obtained by suspension polymerization, separating the porous polymer particles from the aqueous phase, and then removing the aqueous phase, Including the fine particle polymer produced in the aqueous phase in suspension polymerization, the cause of clogging of the filter medium can be effectively removed in the subsequent filtration step using the filter medium.

  The time for which the reaction mixture obtained by suspension polymerization is allowed to stand is not particularly limited, and may be appropriately selected according to the scale of production.

  Thus, the cake of porous polymer particles obtained by step (a) still contains impurities in the voids between the particles. Therefore, according to the present invention, as the step (b), water is added to the cake of the porous polymer particles, the cake is crushed, the porous polymer particles are suspended in water, and then left standing. Then, after separating the porous polymer particles from the aqueous phase, the aqueous phase is removed and the porous polymer is washed. Also in the step (b), “removing the aqueous phase” is as described above.

  In the step (b), water such as ion-exchanged water, purified water, distilled water, and ultrapure water is added to the cake of the porous polymer particles obtained in the previous step (a) and stirred. The cake is crushed and the porous polymer particles are suspended in water, and then left to stand again to separate the phase of the porous polymer particles from the aqueous phase as described above. The aqueous phase is removed and again a cake of porous polymer particles is obtained. Thus, step (b) is preferably repeated several times. That is, in the step (b), a porous polymer particle cake is crushed, the porous polymer particles are suspended in water, left standing, phase-separated, and the aqueous phase is removed to repeat the washing cycle. By washing the polymer particles, it is possible to easily remove impurities, which cause clogging of the filter medium in the subsequent filtration step, such as a dispersant and unnecessary fine particle polymer, and reduce the filtration efficiency. Can do.

  The number of repetitions of the washing cycle is not particularly limited, and an appropriate number of times may be selected in consideration of the particle diameter of the target porous polymer particles and the filtration efficiency using the filter medium.

  In this way, the porous polymer particle cake obtained in the step (b) is then crushed again in the step (c), and the porous polymer particles are suspended in water to obtain a porous material. The polymer particles are washed and then filtered using a filter medium. Although not particularly limited, usually, water is added to the cake of the porous polymer particles obtained in the step (b) in a container, and the cake is crushed to obtain the porous polymer particles. Suspended in water, this suspension is put into a filtration device equipped with a filter medium, and the porous polymer particles are washed and filtered to obtain a cake of porous polymer particles. Step (b) is also preferably repeated several times.

  In the present invention, the filter medium for filtering the suspension of the porous polymer particles is not limited at all. For example, filter paper, stainless sintered filter, glass fiber filter paper, glass sintered filter, polypropylene, A polyethylene filter cloth, nylon mesh or the like is used. Among these, a single-layer nylon mesh has chemical resistance, strength, and good filterability, is thin and lightweight, is easy to handle, and is preferably used. The opening of the nylon mesh is not particularly limited, and may be appropriately selected according to the particle diameter of the porous polymer particles to be produced. The thing of an opening is preferable.

  Also, the filtration device is not particularly limited as long as it uses a filter medium. For example, devices such as centrifugal filtration, vacuum suction filtration, and pressure filtration are used.

  An example of a filtration device preferably used in the present invention is shown in FIG. This filtration device has a drainage port 2 for the filtrate when the dispersion is filtered at the bottom of a cylindrical container 1, and for supplying pressurized air into the container at the top as needed. It has an upper opening 3.

  An annular filter medium support frame 4 is provided along the peripheral wall at the lower part of the container, and a filter medium support 5 through which a solvent can pass is placed on the support frame. The filter medium support is, for example, a metal plate or a metal net having a large number of through holes, but is not limited thereto. The filter medium 6 is placed on this filter medium support.

  The container further includes a stirring device 7 having a shaft body 8 supported at the top of the container so as to be rotatable and movable up and down in the axial direction in the container. A stirring blade 9 extending in the radial direction of the container is provided at the lower end of the shaft body.

  More specifically, the porous polymer particle cake obtained in the step (b) is crushed by adding water, the porous polymer particles are suspended in water, and the resulting suspension is filtered. Charge the above suspension by suction filtration, for example, to obtain a cake of porous polymer particles, then add water to the cake in the container and stir to break up the cake Then, after the porous polymer particles are resuspended in water, stirred and washed, the operation of suction filtration is repeated to obtain a cake. In this way, the dispersion cycle is carried out a plurality of times as necessary by pulverizing the cake of the porous polymer particles, resuspending the porous polymer particles in water, stirring, washing and filtration as necessary. Porous polymer particles from which impurities such as are sufficiently removed are obtained as cakes.

  Next, according to the present invention, as the step (d), an organic solvent is added to the cake of the porous polymer particles obtained in the previous step (c), the cake is crushed, and the porous polymer particles are obtained. After suspending in an organic solvent and washing the porous polymer particles, the mixture is filtered using a filter medium. That is, in this step, in order to remove the organic solvent used in the suspension polymerization, the porous polymer particles obtained in the above step are suspended in the organic solvent, washed, and filtered. This step (c) is also preferably repeated several times.

  The organic solvent for washing the porous polymer particles is not particularly limited as long as it is compatible with the organic solvent used in the suspension polymerization. Therefore, although the organic solvent as the washing solvent depends on the organic solvent used for the suspension polymerization, for example, an organic solvent having a relatively low boiling point such as methyl alcohol, ethyl alcohol, propyl alcohol, hexane, toluene, and acetone is used alone. Or in combination of two or more. When it is necessary to dry the obtained porous polymer particle cake after washing, methanol, acetone, hexane or the like is advantageously used from the viewpoint of the cost of the solvent and the power cost at the time of drying.

  More specifically, for example, an appropriate organic solvent, for example, acetone is added as a washing solvent to the cake of the porous polymer particles obtained in the step (c), and the cake is crushed to obtain the porous polymer particles. After suspending in an organic solvent, stirring, washing, suction filtration to obtain a cake of porous polymer particles, and further adding acetone to the cake to crush the cake, the porous polymer particles Is suspended, stirred, washed, and then subjected to suction filtration. By washing with such an organic solvent, the organic solvent used in the suspension polymerization can be effectively removed. Thus, after removing the organic solvent used in the suspension polymerization from the porous polymer particles, filtration, and drying under heating as necessary, the desired porous polymer particles can be obtained. it can.

Example 1
(Suspension copolymerization)
A 500 mL separable flask equipped with a cooling tube, a stirrer and a nitrogen introduction tube is immersed in a constant temperature water bath, and 240 g of purified water and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., average polymerization degree of about 2000, saponification degree of 80 mol%) ) 2.4 g was charged, the temperature of the constant temperature bath was kept at 28 ° C., and while stirring, polyvinyl alcohol was dissolved in water to obtain an aqueous solution.

  Separately, 1 g of dibenzoyl peroxide (containing 25% water) was dissolved in a mixture of 44 g of styrene, 3 g of p-acetoxystyrene and 7 g of divinylbenzene, and further 50 g of 2-ethylhexanol and 20 g of isooctane were added and mixed. The obtained solution was added to the aqueous polyvinyl alcohol solution.

  The obtained mixture was stirred at 470 rpm for 40 minutes under a nitrogen stream, and then the stirring speed was increased to 280 rpm, and the temperature of the constant temperature bath was raised from 28 ° C. to 80 ° C. for 9 hours. Turbid copolymerization reaction was performed. After completion of the reaction, the temperature of the constant temperature water bath was lowered to 28 ° C.

Step (a)
The reaction mixture containing the porous polymer particles obtained by the suspension polymerization and the solvent is allowed to stand in a separable flask used for the polymerization for 15 minutes to float the porous polymer particles, and the particle phase is formed as an upper layer. As separated from the lower aqueous phase. A suction tube was inserted to the bottom of the separable flask, the pressure was reduced with an aspirator, suction was performed, and the aqueous phase was extracted to obtain a cake of porous polymer particles.

Step (b)
Purified water (160 mL) is added into the separable flask and stirred at 280 revolutions per minute to break up the cake of porous polymer particles, and the porous polymer particles are resuspended in water for 10 minutes. On standing, the porous polymer particles floated and separated from the aqueous phase. A suction tube was inserted to the bottom of the separable flask, the pressure was reduced with an aspirator, suction was performed, and the aqueous phase was extracted to obtain a cake of porous polymer particles. This operation was performed three times.

Step (c)
Purified water (160 mL) was added to the separable flask, and the mixture was stirred at 280 rpm, the cake of porous polymer particles was crushed, and the porous polymer particles were resuspended in water.

  As shown in FIG. 1, the filtration device used in this step (c) and the next step (d) is a cylindrical container 1 having an inner diameter of 9 cm and a filter medium (made by NRK, nylon mesh, mesh opening) provided at the bottom thereof. 45 μm) 6, and further has a drain outlet 2 at the bottom of the container for discharging the filtrate that has passed through the filter medium. In addition, the container supports a shaft body 8 that is movable up and down in the axial direction at the top, and a stirring blade 9 is attached to the lower end of the shaft body.

  The entire amount of the porous polymer particles suspended in the water is put into the container of the filtration device, the drain port at the bottom of the container is connected to an aspirator, and suction filtration is performed under reduced pressure to obtain the porous polymer particles. I got a cake. The position of the stirring blade during the filtration is indicated by a solid line in FIG.

  Next, 200 mL of purified water is put into the container and gradually lowered while rotating the shaft of the stirrer from the upper part of the container. Thus, the cake is stirred together with water, and this is crushed to obtain a porous polymer. The particles were well dispersed in water, washed, and then filtered to obtain a cake of porous polymer particles. This operation was repeated 4 times. During the stirring, the stirring blade was lowered from the position indicated by the solid line in FIG. 1 to the position indicated by the broken line while rotating.

Step (d)
Next, 200 mL of acetone is added to the cake of the porous polymer particles thus obtained, and the porous polymer particles are suspended in acetone, washed and filtered in the same manner as in step (c). did. This operation was repeated three times to obtain the desired porous polymer particle cake.

  In any step, the filtration efficiency is excellent, and the obtained porous polymer particles have a median particle size of 92 μm. According to the scanning electron micrograph of the surface, impurities on the surface of the particle can be obtained. No adhesion was observed, and it was confirmed that impurities were sufficiently removed.

Comparative Example 1
In Example 1, after the suspension polymerization, the reaction mixture containing the produced porous polymer particles and the solvent was immediately put into the container of the filtration device without allowing to stand. However, the reaction mixture could not be filtered.

Comparative Example 2
In Example 1, after the suspension polymerization, the reaction mixture containing the produced porous polymer particles and the solvent was subjected to the step (a), then the step (b) was omitted, and the reaction mixture obtained in the step (a) was obtained. A porous polymer particle cake was obtained in the same manner as in Example 1 except that the steps (c) and (d) were performed for the obtained porous polymer particle cake.

  Both the filtration efficiencies in steps (c) and (d) were extremely bad, and the median particle size of the obtained porous polymer particles was 94 μm. According to the scanning electron micrograph of the surface, It was observed that polyvinyl alcohol used as a dispersant was not sufficiently removed and polyvinyl alcohol was deposited on the surface.

In this invention, it is sectional drawing which shows an example of the filtration apparatus preferably used in order to filter the reaction mixture obtained by suspension polymerization.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Container 2 ... Drainage port 3 ... Upper opening 4 ... Filter medium support frame 5 ... Filter medium support body 6 ... Filter medium 7 ... Agitation apparatus 8 ... Shaft body 9 ... Agitation blade

Claims (6)

A monomer mixture composed mainly of an aromatic vinyl monomer and an aromatic divinyl monomer and a polymerization initiator are dissolved in an organic solvent to form a monomer solution, which is dispersed in water containing a dispersant. In the suspension polymerization system, the above-mentioned monomer is subjected to suspension polymerization to form porous polymer particles, and then the porous polymer particles are separated from the obtained reaction mixture. In the manufacturing method,
(A) standing the reaction mixture, separating the porous polymer particles from the aqueous phase, then removing the aqueous phase and separating the cake of porous polymer particles from the reaction mixture;
(B) The cake of the porous polymer particles obtained in the step (a) is crushed, and the porous polymer particles are suspended in water, and then left to stand, and the porous polymer particles are washed with water. Separating the aqueous phase and then removing the aqueous phase to obtain a porous polymer cake;
(C) After pulverizing the cake of the porous polymer particles obtained in the step (b), suspending the porous polymer particles in water, washing the porous polymer particles, and then using a filter medium. Filtering to obtain a cake of porous polymer particles,
(D) After pulverizing the cake of porous polymer particles obtained in the step (c), suspending the porous polymer particles in an organic solvent, washing the porous polymer particles, and then filtering the filter medium. And filtering to obtain a cake of porous polymer particles,
In this order to obtain porous polymer particles.   The method according to claim 1, wherein in the suspension copolymerization system, the amount of the organic solvent is in the range of 0.5 to 2.0 by weight ratio with respect to the total amount of monomers. The method according to claim 1, wherein 50% by weight or more of the monomer mixture is an aromatic vinyl monomer and an aromatic divinyl monomer.   The method according to claim 1, wherein the aromatic vinyl monomer is styrene and the aromatic divinyl monomer is divinylbenzene.   The method of claim 1, wherein the monomer mixture comprises p-acetoxystyrene.   The method of claim 1, wherein the dispersant is a polyvinyl alcohol having an average degree of polymerization in the range of 500 to 3000 and a degree of saponification in the range of 65 to 85 mol%.

Images