JPH10204204A - Porous spherical particles and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce simply and in a high productivity porous spherical particles that have high mechanical strength and abrasion resistance and affinity with microorganisms, and can be suitably used as a carrier for carrying microorganisms. SOLUTION: This production of porous spherical particles, which are formed of a skeleton of polyvinyl acetal-based resin, and have porosity of 50-90% and degree of acetalization of 30-85mol.%, comprises dropping an aqueous solution in which polyvinyl alcohol, a water-soluble polymer having property of gelling by an ion exchange reaction, and aldehydes are mixed and dissolved, into an acidic solution, and solidifying the liquid drops by the reaction of polyvinyl alcohol and aldehydes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porous spherical particle and a method for producing the same. More particularly, the present invention relates to a porous spherical particle having a skeleton of a polyvinyl acetal resin suitably used as a carrier for a fluidized bed type microorganism carrier, and a method for producing the same.

[0002]

2. Description of the Related Art A method of filling a reactor with microorganisms and enzymes and obtaining a product by utilizing the reaction of the microorganisms and enzymes is called a bioreactor, and is used for producing foods, pharmaceuticals, and chemicals. It has been used industrially in the field and in the fields of treatment of sewage, wastewater, exhaust gas and the like. In recent years, in order to make processing capacity more efficient,
Various means have been studied for filling the microbial biocatalyst into a reaction vessel at a high density.

[0003] As one of the means, the most typical one is a method of obtaining a microorganism carrier by supporting microorganisms on a granular carrier, and roughly comprises a method of supporting microorganisms on the surface of a carrier and a method of mounting microorganisms inside a carrier. There is a method of immobilization. The former is a biofilm method in which microorganisms are used as a so-called biofilm, and the latter is called an entrapping immobilized microorganism method.

[0004] Materials for the granular carrier include organic polymer substances and inorganic substances. The form of use of the microorganism carrier may be a fixed bed type in which the microorganism carrier is immobilized in the reaction tank or a fluidized bed type in which the microorganism carrier is used while flowing. As the carrier of the microorganism carrier used in the fluidized bed type, fluidity and specific gravity are important, so that organic polymer-based granular carriers are generally used rather than inorganic carriers. As a material for this carrier,
For example, a method using a gel-like granular material such as polyvinyl alcohol gel (PVA gel), acrylamide gel, or polyethylene glycol gel, or a method using a porous granular material such as polyethylene, polyurethane, polyvinylidene chloride, or cellulose is exemplified.

Heretofore, organic polymer-based granules have been produced as follows. That is, a mixture obtained by kneading additives such as a pore-forming agent, a cross-linking agent, and a catalyst into an aqueous solution in which raw materials are dissolved is poured into a large-sized reaction type, and reacted in a hot water bath or an air bath to be insolubilized. Further, the pore-forming agent is removed by washing with water to obtain a block-shaped porous polymer. Next, this block-shaped polymer porous body is sliced to a thickness of several millimeters to obtain a sheet-shaped polymer porous body, and this sheet is further cut into several millimeters to form a string-shaped high-porosity body. A cubic particle of several mm square is manufactured by cutting the string-like polymer porous body into a length of several millimeters as a molecular porous body. Alternatively, a granular porous body can be obtained by punching the sheet-shaped polymer porous body in a unit of several millimeters using a punching die.

[0006]

The desired properties of a carrier for a microorganism carrier include, in addition to affinity with microorganisms, fluidity, specific gravity, abrasion resistance, weather (light) resistance, and microorganism resistance. These properties are different depending on the type of the carrier. Although the gel-like carrier has excellent affinity for microorganisms, it has low mechanical strength, and in particular, has extremely poor abrasion resistance.It wears due to friction between carriers generated when the carrier flows and friction with the inner wall of the reaction tank. And the carrier life is short. In addition, porous granular materials such as polyethylene and polyurethane do not have very high weather resistance. Cellulose itself has a problem that it is susceptible to biodegradation, the carrier is easily broken down during long-term use, and the life is short. In addition, conventional porous granular materials are cubic particles, and thus have problems in filling properties into containers, abrasion resistance, and fluidity as a fluidized bed type microbial carrier, and these problems have been solved. It is important to obtain a porous granular material having a uniform particle diameter as close as possible to a true sphere, but this problem has not been solved yet.

Further, since the conventional porous granular material is manufactured by the above-described manufacturing method, it takes several hours for the reaction, requires three stages of forming steps after the reaction, and obtains a uniform granular material of several millimeters. It took at least two or more days to produce. In the case of punching with a die, particles of about several millimeters are often clogged in the die, and a post-treatment for removing the particles is required. Furthermore, since the block-shaped porous body is sliced, cut, or punched by post-processing, the yield is low.

As a means for greatly reducing the post-processing time and improving the yield, there is a method in which a block-shaped polymer is pulverized without being sliced by a pulverizer or the like. However, according to this method, although the processing time can be greatly reduced and the yield can be increased, it has been difficult to obtain porous spherical particles having a uniform particle diameter.

[0009] Further, in each of the above methods, since the reaction is performed for each mold, it is necessary to increase the space of the reaction tank in proportion to the increase in the production amount. There was also a problem that productivity was poor as well.

An object of the present invention is to provide a porous material which has high mechanical strength and abrasion resistance and also has an affinity for microorganisms, and which can be suitably used as a carrier for a microorganism carrier, particularly a fluidized bed type microorganism carrier. To provide globular particles.
Another object of the present invention is to provide a method for producing porous spherical particles, which can easily produce porous spherical particles having a uniform particle diameter as close as possible to a true sphere with high production.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found that porous spherical particles having a skeleton of a polyvinyl acetal resin, particularly porous spheres having a skeleton of a polyvinyl formal resin. It has been found that when is used, a material excellent in abrasion resistance, weather (light) resistance, microbial decomposition resistance, fluidity and microbial affinity can be obtained.

Such porous spherical particles can be used not only as a carrier for a microorganism carrier, but also as a solution holding material and a plant supporting material in hydroponic cultivation of agricultural crops, a culture pond for animal and plant cells, artificial moss, a soil improving material, It is suitably used as a pipe cleaning member, a filtering material, a water absorbing material, and the like. In addition, as a special use example, it can be used as a submersible fluid type cleaning member or a submersible fluid type massage member. The underwater fluid cleaning member is used to wash vegetables with delicate surfaces or vegetables with many irregularities.Put them together with vegetables in the water, generate bubbles from the bottom of the water tank, and bubbling and stirring the whole, so that they come into contact with vegetables, etc. And a cleaning member for cleaning the surface of vegetables. In addition, the underwater flowable massaging member is a member that obtains a massage effect on the human body, and stimulates the skin by contacting the particles with the human body while flowing the particles in a water tank such as a bathtub, thereby giving a massage effect. Refers to a member for obtaining.

The porous spherical particles (hereinafter referred to as “porous spherical particles”) of the present invention having continuous pores and having a skeleton of a polyvinyl acetal resin.
It is referred to as the porous spherical particles of the present invention. ) Can be optimally used for fluidized bed applications because it has both affinity for microorganisms and excellent fluidity. In particular, porous spherical particles having a uniform particle size close to a true sphere and having a skeleton of a polyvinyl acetal resin are more excellent in mechanical strength and abrasion resistance, and can be filled into a container or flow as a microorganism carrier. The properties are further improved.

The present invention relates to porous spherical particles having continuous pores and having a skeleton of a polyvinyl acetal resin. In a preferred embodiment, the interconnected vents are 2-4 μm
Is the size of

In a preferred embodiment, the polyvinyl acetal resin is polyvinyl formal, and has a formalization degree of 30 to 85 mol%. In a preferred embodiment, the porosity of the porous spherical particles is 5%.
0 to 98%.

[0016] In a preferred embodiment, the porous spherical particles are hollow.

Further, in a preferred embodiment, the porous spherical particles have pores on the surface, and the inside of the particles has a porous structure. In a preferred embodiment, the apparent specific gravity of the porous spherical particles in a water-containing state is 1.0.
~ 1.2. In a preferred embodiment, the size of the porous spherical particles in a water-containing state has a diameter of 1 to 20.
mm.

The present invention also relates to a microorganism carrier having microorganisms fixed to porous spherical particles having the above-mentioned polyvinyl acetal resin as a skeleton.

In a preferred embodiment, the microorganism is fixed on the surface and / or in the pores of the porous spherical particles. In a preferred embodiment, the microorganism is immobilized by a microorganism fixing agent. I have.

[0020] In a preferred embodiment, the microorganism immobilizing agent is sodium alginate.

Further, the present invention relates to a bioreactor using the above-mentioned microorganism carrier.

Further, the present invention provides the following steps: a step of dropping a droplet of a mixed aqueous solution of a water-soluble polymer having a property of gelling in an acidic solution, polyvinyl alcohol and aldehydes into the acidic solution; And a step of reacting polyvinyl alcohol and aldehydes in the droplets with a skeleton of a polyvinyl acetal resin.

Furthermore, the present invention is a method for producing porous spherical particles having a skeleton of a polyvinyl acetal resin, comprising the following steps: a water-soluble polymer having a property of gelling by an ion exchange reaction; Dropping a droplet of the mixed solution of (1) into an aqueous solution of a polyvalent metal salt, and gelling the droplet to form gel-like spherical particles containing polyvinyl alcohol; and acetalizing the gel-like spherical particles. A method.

In a preferred embodiment, the mixed solution contains 0.5 to 5% by weight of a water-soluble polymer having a property of gelling by an ion exchange reaction and 5 to 20% by weight of polyvinyl alcohol.

The present invention also provides the following steps: Drops of an aqueous solution of a polyvalent metal salt are dropped into a mixed solution of a water-soluble polymer having a property of gelling by ion exchange reaction and polyvinyl alcohol. The present invention relates to a method for producing hollow porous spherical particles, which includes a step of forming gel-like spherical particles on an outer peripheral portion of a droplet; and a step of acetalizing the gel-like particles.

[0026]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to porous spherical particles having a skeleton of a polyvinyl acetal resin. The porous spherical particles made of the polyvinyl acetal-based resin of the present invention have open pores. The size of the continuous vent is about 2
４4 μm is preferred.

The porosity of the porous spherical particles of the present invention may be set according to the intended use and is not limited.
% Is a preferable range. When the porosity is less than 50%, it becomes difficult for the individual pores to be adjacent to each other, so that a tendency for the existence of closed cells is observed, thereby significantly impairing the water permeability. When the porosity exceeds 98%, mechanical strength such as abrasion resistance is reduced, so that there may be a disadvantage that the use is restricted depending on the use.

The degree of acetalization of the polyvinyl acetal-based porous material is not particularly limited. If the degree of acetalization is 30 to 85 mol%, it is good in terms of resistance to microbial erosion and excellent in strength. High friction fastness.
Preferably it is 45 to 70 mol%. The same applies to the degree of formalization.

By adjusting the degree of acetal in this way, it is possible to obtain a flexible and wear-resistant carrier for a microorganism carrier. When the degree of acetalization is less than 30 mol%, the degree of molecular crosslinking is low, the strength is inferior, and the fastness to friction is low. Therefore, particularly when the carrier is used as a carrier for microorganisms in a fluidized bed type, the carrier is liable to be worn due to friction between the carriers generated at the time of carrier flow and friction with the inner wall of the reaction tank, and the carrier life is shortened. Further, it is not preferable in that the microbial erosion resistance is reduced. Further, there is a problem that it is difficult to handle in a manufacturing process. On the other hand, if it exceeds 85 mol%, the porosity decreases, and the apparent specific gravity increases, and the water content decreases. Especially when used as a carrier for microorganisms in a fluidized bed type, sedimentation is easy but it is difficult to float. Therefore, the fluidity in the processing tank is reduced. Further, in particular, the hydrophilicity decreases with a decrease in the amount of hydroxyl groups in the polyvinyl acetal resin, which is not preferable. Further, the rebound resilience when wet becomes low, which is not preferable in terms of water absorption and durability.

The apparent specific gravity of the porous spherical particles of the present invention in a water-containing state is preferably from 1.0 to 1.2.
In this range, especially when used as a fluidized bed type granular porous body, appropriate fluidity can be exhibited well.
When the apparent specific gravity in the water-containing state is smaller than 1.0, the carrier is only floated even if it is put into the treatment tank, which is not suitable for the fluidized bed type. If the apparent specific gravity exceeds 1.2, sedimentation is likely to occur, and this point also lacks fluidity.

It is preferable that the porous spherical particles of the present invention have a specific gravity closer to the specific gravity of the liquid to be treated when the liquid to be treated is filled in the pores of the particles. When the liquid to be treated is converted to water, the apparent specific gravity in a water-containing state is 1.
Ideally, a value of 0 or more and infinitely close to 1.0 is ideal, but practically 1.01 to 1.1 is optimal. The true specific gravity of the material itself is in the range of 1.24 to 1.28, preferably in the range of 1.25 to 1.26. When a polyvinyl acetal-based porous material having a specific gravity within these ranges is used as a carrier for a microorganism support, particularly when used as a fluidized-bed granular porous material, good fluidity is exhibited.

Although the specific gravity of the porous spherical particles of the present invention can be generally controlled by the porosity, the specific gravity of the particles may be further reduced, that is, further reduced, depending on the application. In particular, in the case of a carrier for a microorganism carrier used in a fluidized bed or the like, since fluidity is an important factor, a wide range of specific gravity control is important. Therefore, if the inside of the porous spherical particles having a skeleton of a polyvinyl acetal resin having excellent wear resistance and mechanical strength is made into hollow particles, depending on the degree of the hollow, the particles are combined with the porous structure to form the particles. Can be controlled over a wide range.

The porous spherical particles of the present invention are desirably spherical with a diameter of 1 mm to 20 mm in a water-containing state. Thereby, the fluidity is improved, and the microorganism processing ability can be exhibited. Even when used in a sewage treatment apparatus or the like in which a recovery filter for a microorganism carrier is installed, the wastewater passes through the recovery filter and is treated. The microorganism concentration can be maintained at a high level without fear of flowing out of the exhaust port.

When the size of the spherical particles exceeds 20 mm in diameter, it may be disadvantageous when the porous spherical particles of the present invention are used as a carrier for a microorganism carrier. That is,
Not only does the fluidity of the particles decrease, but the effective surface area supporting the microorganisms becomes poor, so that it becomes difficult to maintain a high concentration of the microorganisms, and the treatment capacity of the microorganisms decreases. In this regard, the smaller the particle size, the better the flowability, and in the fluidized bed reactor, the energy for flowing the microorganism carrier is small, and the processing performance is improved.
If it is smaller than m, it may pass through the recovery filter of the microorganism carrier, and may flow out of the outlet of the processing wastewater,
It becomes difficult to maintain the microorganism concentration at a high concentration. In this respect, it is conceivable to make the slit (pore diameter) of the recovery filter, for example, the recovery filter installed at the treatment liquid outlet smaller. However, fine particles, microorganisms, viscous products of microorganisms and the like in the wastewater adhere to the slits and block the slits, which naturally limits the size of the filter slits. From the relationship, the optimum size of the porous spherical particles of the present invention is determined.

As will be described later, the size of the porous spherical particles of the present invention can be easily controlled by the size of the droplet to be dropped. Specifically, particles having an arbitrary particle size can be obtained by arbitrarily adjusting the discharge amount of the droplets and the diameter of the nozzle required for the dropping.

The porous spherical particles of the present invention have a water content of 50%
At a 50% compressive stress in a state of swelling with water,
It has a moderate elasticity of about × 10 ³ N / m ² . This elasticity provides good wear resistance when the carrier flows.

In order to improve the abrasion resistance and mechanical strength of the porous spherical particles, it is desirable that the particles have pores on the surface and the inside of the particles has a porous structure. Spherical particles produced by the production method of the present invention described later have pores on the surface and have excellent mechanical strength.

As described above, when the porous spherical particles of the present invention are used as a carrier for a fluidized bed type microorganism carrier, a suitable porosity that facilitates floating and settling in the treatment tank and an apparent specific gravity of a water-containing state are obtained. And has excellent hydrophilicity, so that it exhibits excellent flow performance. Also, the rebound resilience when wet is increased.

The porous spherical particles of the present invention can be satisfactorily floated and flowed in the treatment tank by aeration or the like as a water-containing porous body simply by being put into a fluidized bed type treatment tank, and furthermore, the material is incompatible with microorganisms. Because of the good affinity of the microorganisms, microorganisms can be attached to perform excellent biological treatment. In addition, since the abrasion resistance is good, the abrasion hardly occurs due to the friction between the carriers generated during the flow of the carriers and the friction with the inner wall of the reaction tank. Furthermore, the mechanical strength is high, the weather (light) resistance and the microbial decomposition resistance are excellent, and the life of the carrier is prolonged. Thus, the porous spherical particles of the present invention are also excellent as carriers for microorganism carriers.

The porous spherical particles of the present invention are, as described above,
It is suitable for adhering microorganisms to the surface of the carrier including the inside of the pores of the porous spherical particles, has excellent fluidity, and is most suitable for fluidized bed applications. On the other hand, the comprehensive immobilized microbial method
1) High-concentration microorganisms can be maintained and high-speed treatment of wastewater can be achieved. 2) By immobilizing specific microorganisms,
Processing of specific substances or recovery of organic substances becomes possible. 3)
Since the amount of sludge generated can be reduced, it is also desirable that the method can be applied as an entrapping immobilized microorganism method together with the above-mentioned microorganism membrane method.

Various microorganism immobilizing agents can be employed.
Although not limited, a microorganism immobilizing agent containing sodium alginate as a main component is preferable. When sodium alginate is used as the main component, it is easily filled and fixed to polyvinyl acetal-based porous spherical particles, particularly, polyvinyl formal porous spherical particles, and has good compatibility. In addition, it is particularly good in terms of wear resistance.

For entrapping and immobilizing microorganisms using a microorganism immobilizing agent, for example, porous spherical particles are impregnated with a mixed solution of a microorganism and a microorganism immobilizing agent, and the microorganism immobilizing agent is impregnated with the porous material. May be insolubilized in the pores.

As a result, the abrasion resistance, weather (light) resistance, microbial decomposition resistance, fluidity and microbial affinity are excellent, the microorganisms can be maintained at a high concentration, and the wastewater can be treated at high speed. By immobilizing the microorganisms, it becomes possible to treat specific substances or recover valuable resources, and it is possible to reduce the amount of sludge generated. That is, it is possible to provide a microorganism carrier that can take advantage of the advantages of the microbial membrane method and the entrapping immobilized microorganism method, and also overcome the disadvantages of both the microbial membrane method and the entrapping immobilized microorganism method.

The porous spherical particles of the present invention can be used as a carrier in either a fluidized bed or a fixed bed irrespective of the above-mentioned entrapping fixed type (entrapping immobilization method) and the above-mentioned non-entrapping immobilization type (microbial membrane method). The present invention is also applied to various bioreactor applications including a sewage treatment apparatus. Especially in the processing tank,
It can be suitably used as a fluidized bed type sewage treatment apparatus for treating the particulate microorganism carrier of the present invention by floating and convection.

A fluidized bed type bioreactor is, for example,
The present invention can be applied as long as it carries out biological treatment and chemical treatment by bringing the microorganism carrier into contact with the liquid to be treated. In particular,
In addition to decomposition of organic substances, etc., oxidation reduction such as nitrification and denitrification,
The present invention can be applied to an apparatus for performing a chemical reaction such as addition, substitution, conversion, and elimination.

The carrier for the microbial carrier of the porous spherical particles of the present invention can be used in a known microorganism treatment apparatus, for example, a single-tank type or a multi-tank type.
It is effectively used in any of the aerobic treatments.

The method for producing the porous spherical particles of the present invention will be described below.

As one production method, a droplet of a mixture of a water-soluble polymer having a property of gelling in an acidic solution, polyvinyl alcohol and aldehydes is dropped into the acidic solution, and the droplet is added to the acidic solution. A method for producing porous spherical particles, which comprises reacting polyvinyl alcohol and aldehydes in the droplets simultaneously with gelation to obtain porous spherical particles having a polyvinyl acetal resin as a skeleton. .

Further, according to the production method of the present invention, since the liquid droplets of the stock solution forming the particles are brought into contact with the reaction solution and directly become particles, the acetalization treatment and the process of forming the spherical particles can be performed simultaneously. it can. In addition, since the aqueous polymer solution contains an aqueous solution polymer that gels when it comes into contact with an acid which is a catalyst for acetalization, the shape of the droplet is not distorted. Therefore, it is possible to easily produce porous spherical particles having a uniform particle diameter close to a true sphere, without requiring multiple steps as in the related art, with high productivity.

In this production method, a solution containing polyvinyl alcohol is reacted with an acidic solution to form droplets, and at the same time, the acetalization of polyvinyl alcohol and aldehydes contained in the droplets is performed by the action of the acidic solution as a catalyst. Are started at the same time. That is,
While the polyvinyl alcohol and aldehydes in the solution do not react with the acidic solution as a catalyst, they do not react and maintain the solution state, but upon contact with the acidic solution, the acetalization reaction starts and starts to solidify. In addition, since the water-soluble polymer that has a property of gelling in an acidic solution contained in the solution becomes a gel-like substance due to the action of an acid and has viscosity, a spherical form is formed until the reaction between the polyvinyl alcohol and the aldehyde is completed. Plays a role in preventing deformation. In the production method of the present invention, depending on the purpose of use, for example, it is possible to form a comprehensive immobilized support by kneading microorganisms in an aqueous solution comprising polyvinyl alcohol, a water-soluble polymer, and aldehydes. The formulation can also be adjusted.

A water-soluble polymer having a property of gelling in an acidic solution (the same applies to other production methods described below).
Is not particularly limited, and examples thereof include sodium alginate, carrageenan, and sodium polyacrylate.

The raw material polyvinyl alcohol is not particularly limited, but has an average degree of polymerization of 500 to 500.
The polyvinyl alcohol of 3800 is desirable, and it may be completely saponified, or may be a mixture of a partially saponified product and a low-polymerized product. When the average degree of polymerization is less than 500, it is difficult to obtain a material having a high porosity, and when the average degree of polymerization exceeds 3800, the viscosity becomes too high when dissolved in water. It becomes difficult to handle in the step.
Polyvinyl alcohol raw materials having different degrees of polymerization can be blended and used, and there is no problem if a mixture having a degree of polymerization of 300 and a degree of polymerization of 300 is used instead of the above range. Especially elastic, flexible,
To obtain texture, porosity adjustment, improved water absorption, etc.
You may use the polyvinyl alcohol resin of a low polymerization degree.

The concentration of polyvinyl alcohol is 5 to 20.
% By weight, more preferably 7 to 15% by weight. Generally, when the polyvinyl alcohol concentration is high, spherical particles are easily formed, and when the polyvinyl alcohol concentration is low, a hydrogel is easily formed. The difference in the physical properties of these particles does not depend solely on the polyvinyl alcohol concentration, but is also affected by other factors, but the polyvinyl alcohol concentration is an important factor in forming a resin skeleton in spherical particles. . Therefore, in the present invention, the compounding amount is important. In the present invention, when the concentration of polyvinyl alcohol exceeds 20% by weight, not only the viscosity of the solution becomes too high, which makes handling difficult, but also droplet-like particles are formed as if the liquid were dropped. Thus, it is difficult to form a spherical material having a uniform diameter or a nearly uniform diameter. On the other hand, if the concentration is lower than 5% by weight, the strength of the spherical particles obtained by the acetylation reaction after dropping becomes low, which is not preferable. The temperature of the mixture of the polyvinyl alcohol, the aldehyde and the water-soluble polymer is not particularly limited, and there is no problem at room temperature as long as the temperature can maintain fluidity without denaturing each other.

Examples of the aldehydes include aliphatic and aromatic aldehydes such as formaldehyde, benzaldehyde, acetaldehyde, butyraldehyde, acrylaldehyde and glyoxal. Acetals which can be easily converted to aldehydes by the coexisting acid may be used. However, reactivity with polyvinyl alcohol, water solubility, price, handleability, strength of reaction product, rebound resilience and post-reaction treatment Formaldehyde is particularly excellent in view of the ease of processing.

The concentration of the aldehyde is not particularly limited, but is important because it affects the degree of acetalization of the resin skeleton particles. In the present invention,
It is necessary to appropriately select an appropriate concentration of the aldehyde according to the concentration of the coexisting acid catalyst and the reaction temperature. The higher the aldehyde concentration, the shorter the time required to reach the desired degree of acetalization. However, if the aldehyde concentration is too high, the reaction rate is so high that it is difficult to control the degree of acetalization. In general, those having a high degree of acetalization improve the strength, but too high a porosity decreases when producing a porous body, and the apparent specific gravity increases to decrease the water content. In addition, the hydrophilicity decreases as the residual hydroxyl groups decrease. Also, the rebound resilience of the particles decreases.

On the other hand, the degree of acetalization was 3
0 to 85 mol% is a suitable range. In particular, when it is suitably used as a fluidized bed type microbial carrier requiring rubber-like elasticity and relatively high hardness, it must be set to 55 to 85 mol%. The concentration of the aldehyde at this time varies depending on the type, but when formaldehyde is used, it is preferable to set the concentration to about 3 to 10% by weight.

Examples of the water-soluble polymer having a property of gelling by an ion exchange reaction include sodium alginate, carrageenan, sodium polyacrylate and the like. Then, sodium alginate is most excellent, and it is preferable to use this. The molecular weight of sodium alginate is not particularly limited, but the higher the molecular weight, the faster the gelation rate and the easier the production of clean particles. However, if the molecular weight is too high, the viscosity of the solution is excessively increased, and thus it is not preferable because it tends to become droplet-shaped particles. For example, sodium alginate having a viscosity of about 30 dPa · sec at a concentration of 4% at 20 ° C. is preferably used, but is not limited thereto.

The water-soluble polymer contained in the polyvinyl alcohol solution, for example, having a property of gelling by an ion exchange reaction, plays a role as a pore-forming agent and a shape maintaining agent as described above. The concentration is not particularly limited. In general, when these concentrations are high, the viscosity of the solution increases, which often hinders dripping. On the other hand, when the concentration is low, the reaction rate of gel formation becomes slow, and it becomes difficult to obtain spherical particles. In consideration of such handling, the concentration depends on the molecular weight of sodium alginate, but is preferably 0.5 to 5% by weight, and particularly preferably 1 to 5% by weight. In particular, when the concentration of sodium alginate is less than 0.5% by weight, the dispersing force becomes stronger than the surface tension of the water-soluble polymer itself on the water surface or in water, so that water cannot be retained and diffuses on the water surface. On the other hand, the concentration of sodium alginate was 5% by weight.
If it exceeds 50, it is difficult to obtain spherical particles having a uniform diameter as a result of injecting the yarn into the solution while pulling the yarn from the supply port.

To promote the reaction between polyvinyl alcohol and aldehydes, it is preferable to use an acidic solution. Although these acids are not particularly limited, for example, inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, and organic acids such as maleic acid can be used. Particularly, a strong acid is preferable, and sulfuric acid is most suitable for handling.

Although the aqueous solution of the polyvalent metal salt is not particularly limited, calcium chloride, zinc chloride, aluminum sulfate and the like are preferred. The concentration varies somewhat depending on the type of metal salt selected and the temperature of the aqueous solution, but when calcium chloride is used, the optimum concentration is about 1 to 20% by weight. If the concentration of calcium chloride is higher than 20%, the generated gel particles become large, and the phenomenon of fusing with other adjacent particles tends to occur, which is not preferable. When a small amount of a polyvalent metal salt such as calcium chloride is added to an acidic aqueous solution, spherical particles having a uniform diameter can be produced without collapsing the spherical particles.

The polyvinyl acetal-based spherical particles produced by the method of the present invention do not contain polyvinyl acetal in the hydrogel of the water-soluble polymer, but contain water-soluble such as sodium alginate in the resin skeleton of the polyvinyl acetal. Obtained in a state in which a hydrogel of a conductive polymer is contained. Then, the dried resin particles shrink from a gel of a water-soluble polymer such as sodium alginate, and become porous with a fine pore diameter. Thereby, rubbery elastic or relatively hard porous spherical resin particles are obtained. Also, when put into water, the gel of the contracted water-soluble polymer such as sodium alginate is substantially restored as a water-containing gel, and can be used as a dwelling place for microorganisms as a porous structure. When the gel contained in the particles is removed, porous spherical particles that open to the outside are obtained.

Further, according to the method for producing spherical particles of the present invention, an aqueous solution obtained by mixing and dissolving a water-soluble polymer having a property of gelling by ion exchange reaction and polyvinyl alcohol is added to a polyvalent metal salt aqueous solution. And the droplets are gelled by an ion exchange reaction to form gel-like spherical particles containing polyvinyl alcohol. Thereafter, the gel-like particles are added to an acidic solution containing aldehyde, and the gel-like particles are added to the gel-like particles. By reacting the contained polyvinyl alcohol with aldehydes, it is possible to obtain porous spherical particles having a degree of acetalization of 30 to 85% by mole of a polyvinyl acetal resin.

In this production method, the hydrogel of the water-soluble polymer is not used as the main component of the spherical particles, but is used as a shape retaining means of the spherical particles. And a polyvinyl acetal-based spheroidal particle having an almost uniform diameter can be easily and mass-produced. That is, the respective mixing ratios of polyvinyl alcohol, which is a main component of the skeleton particles to be polyvinyl acetal, and a water-soluble polymer such as sodium alginate which performs a shape-retaining action and a pore-forming action of spherical particles in the production process, and polyvinyl alcohol By adjusting the degree of acetalization to the above blending ratio, polyvinyl acetal skeleton spherical particles having physical properties such as rubber elasticity and relatively hardness and having a uniform particle diameter close to a true sphere can be easily and in large quantities. It is possible to manufacture. This method is preferable in that the degree of acetalization can be easily adjusted as compared with a method in which a mixture of polyvinyl alcohol, a water-soluble polymer, and an aldehyde is dropped into an acidic solution. The acetalization degree can be controlled by adjusting the amount of aldehydes in the reaction solution, the temperature of the reaction solution, and the reaction time.

On the other hand, as a method for producing hollow porous spherical particles having a skeleton of polyvinyl acetal resin having excellent wear resistance and mechanical strength, an aqueous polyvalent metal salt solution is prepared by an ion exchange reaction. A water-soluble polymer having a gelling property and polyvinyl alcohol are dropped into an aqueous solution obtained by mixing and dissolving, and solidified by the reaction between the droplet of the polyvalent metal salt and the water-soluble polymer, and on the outer periphery of the droplet, Form a gel-like spherical particle in which a water-soluble polymer gel reacted with a polyvalent metal salt and polyvinyl alcohol are mixed, and then add the gel-like particle to an acidic aqueous solution containing aldehydes to form a gel-like particle. A method of reacting polyvinyl alcohol contained in the body with aldehydes may be mentioned.

In this production method, the aqueous solution of the polyvalent metal salt is dropped into the polyvinyl alcohol solution, so that the outer peripheral portion of the droplet gels, whereby the polyvinyl alcohol solution cannot enter the inside of the droplet. Instead, the product is hollow particles.

The pore diameter, porosity and degree of acetalization of the present invention, including the examples described below, are based on the following measuring methods.

(Measurement of pore diameter) The measurement of the pore diameter was performed according to ASTM.
(Designation: D4404-84). Specifically, the average pore diameter was determined by mercury intrusion porosimetry using a porosimeter manufactured by POROUS MATERIALS, INC.

(Measurement of porosity) In a wet state, the sample was measured at three places with calipers using a vernier caliper, and was measured using an apparent volume (Va) and a dry type automatic density meter Acubic 1330 (trade name) manufactured by Shimadzu Corporation. Measure the volume (V). Using this value, the porosity ε (%) was calculated by the following equation.

Ε = (1−V / Va) × 100 Va: Apparent volume of sample V: True volume

(Measurement of the degree of acetalization) The degree of acetalization F (%) was calculated from the proton NMR measurement in an aqueous solution of deuterated chloroform and trifluoroacetic acid by the following formula.

F = (a / c) × 100 c: methine proton (for example, 4.153, 4.442)
ppm) sum of peak intensities a: methylene protons adjacent to the ether group (eg,
4.667, 5.150, 5.313, 5.326 pp
m) sum of peak intensities

[0072]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. In the following Examples and Comparative Examples,% means% by weight.

(Example 1) (Drip solution) Polyvinyl alcohol 7.5% Sodium alginate 1.0% Formaldehyde 4.0% Water 87.5% (Reaction liquid) Sulfuric acid 10.0% Water 90.0% Average polymerization A completely saponified polyvinyl alcohol resin having a degree of 1500 was dissolved in hot water and then cooled. An aqueous solution of sodium alginate separately prepared was added thereto, and an aqueous formaldehyde solution was further added and mixed uniformly. Next, this mixture was dropped into a 10% aqueous sulfuric acid solution. The liquid temperature of this aqueous sulfuric acid solution was 60 ° C. The droplet formed in the aqueous sulfuric acid solution gelled in about 5 minutes, and was reacted in this state for about 15 minutes, and then the particles were separated. As a result, an elastic particle body having polyvinyl acetal as a resin skeleton was obtained. This was sufficiently washed with water and dried to obtain polyvinyl acetal porous spherical particles having a uniform particle diameter close to a true sphere having a particle diameter of 3 to 4 mm.

(Example 2) (Drip solution) Polyvinyl alcohol 7.5% Sodium alginate 1.0% Water 91.5% (Reaction solution) Sulfuric acid 5.0% Formaldehyde 4.0% Water 91.0% Average polymerization A polyvinyl alcohol resin having a saponification degree of 1500 and completely saponified was dissolved in hot water and then cooled, and a separately prepared aqueous solution of sodium alginate was added thereto and mixed. This mixture was dropped into a mixture of a separately prepared aqueous solution of formaldehyde and an aqueous solution of sulfuric acid. The liquid temperature of this acidic formalin solution was 60 ° C. The dropped droplet is 5
Gelation took about 30 minutes, and the reaction was carried out for about 30 minutes in this state, whereby elastic particles having a resin skeleton of polyvinyl acetal were generated. This was almost the same as that obtained in Example 1.

(Comparative Example 1) (Drip solution) Polyvinyl alcohol 7.5% Formaldehyde 4.0% Water 88.5% (Reaction liquid) Sulfuric acid 10.0% Water 90.0% The average degree of polymerization is 1500 and complete quenching The polyvinyl alcohol resin was dissolved in hot water and cooled, and an aqueous formaldehyde solution was added thereto and mixed uniformly. Next, this mixture was dropped into a 10% aqueous sulfuric acid solution at a liquid temperature of 60 ° C. However, the dropped mixture does not remain as droplets but gradually diffuses into the acidic aqueous solution, and at the same time, the reaction proceeds, so that only a cloudy solid is generated, and spherical particles can be obtained. Did not.

(Comparative Example 2) (Drip solution) Polyvinyl alcohol 8.0% Water 92.0% (Reaction liquid) Sulfuric acid 5.0% Formaldehyde 4.0% Water 91.0% The average polymerization degree is 1500 and complete polymerization The polyvinyl alcohol resin was dissolved in hot water and then cooled. Next, this mixture was dropped into a mixture of a separately prepared aqueous formaldehyde solution and a sulfuric acid aqueous solution. The liquid temperature of this acidic formaldehyde aqueous solution was 60 ° C. However, the same phenomenon as in Comparative Example 1 occurred, and spherical particles could not be obtained.

(Example 3) (Drip solution) Calcium chloride 2.0% Water 98.0% (First reaction solution) Polyvinyl alcohol 3.0% Sodium alginate 0.5% Water 96.5% (Second reaction) Liquid) formaldehyde 8.0% sulfuric acid 10.0% water 82.0% A completely alcoholized polyvinyl alcohol resin having an average degree of polymerization of 1500 was dissolved in hot water, cooled and cooled, and a sodium alginate aqueous solution separately prepared 2000
ml of the mixed solution. The temperature of this mixed solution was room temperature. When an aqueous solution of calcium chloride was slowly dropped, the droplets began to solidify and completely gelled after about 5 minutes, producing translucent spherical particles. Next, the gel particles were separated and collected, and further added to a mixed solution of formalin and sulfuric acid at a liquid temperature of 60 ° C. Simultaneously with the addition, the translucent gel-like particles began to become cloudy, and after about 10 minutes, completely whitened, and spherical particles having rubber elasticity and having polyvinyl acetal as a resin skeleton were obtained. Wash this thoroughly with water,
Polyvinyl acetal hollow particles having a uniform particle diameter close to a true sphere having a particle diameter of 3 to 4 mm were obtained.

Comparative Example 3 (Drip solution) Polyvinyl alcohol 7.5% Calcium chloride 5.0% Water 87.5% (First reaction liquid) Sodium alginate 0.5% Water 99.5% (Second reaction) Liquid) Formaldehyde 8.0% Sulfuric acid 10.0% Water 82.0% A completely saponified polyvinyl alcohol resin having an average degree of polymerization of 1500 is dissolved in hot water, then cooled, and a separately prepared calcium chloride aqueous solution is added thereto. Thus, a mixed solution having a total volume of 2000 ml was obtained. When the solution was slowly dropped into an aqueous sodium alginate solution, the solution settled and gelled, producing a translucent string-like gel. Next, the string-like gel is separated and recovered, and further, a liquid temperature of 60 ° C. comprising formalin and sulfuric acid.
Was added to the mixed aqueous solution. At the same time as the addition, the translucent gel-like particles began to become cloudy and completely whitened after about 10 minutes, and a rubber-elastic one was obtained.
It was not hollow.

Comparative Example 4 (Drip solution) Polyvinyl alcohol 5.0% Calcium chloride 2.0% Formaldehyde 3.0% Sulfuric acid 4.0% Water 86.0% (First reaction liquid) Sodium alginate 0.5 % Water 99.5% (second reaction liquid) water A mixture of a completely saponified polyvinyl alcohol resin having an average degree of polymerization of 1500 and calcium chloride, formaldehyde, and sulfuric acid is slowly dropped into an aqueous sodium alginate solution. It gelled while settling.
These particles were separated, added to a hot water bath at 60 ° C., and reacted for 30 minutes to obtain elastic particles. However, the particles were not hollow particles and were inferior in strength to those obtained in Example 3. In addition, it turned out that the dripping liquid which dripped and remained had solidified after 15 minutes, and it had to be used up very early after preparing a dripping liquid.

Example 4 (Drip solution) Polyvinyl alcohol 7.5% Sodium alginate 1.0% Water 91.5% (First reaction solution) Calcium chloride 3.0% Water 97.0% (Second reaction) Liquid) formaldehyde 3.0% sulfuric acid 4.0% water 93.0% A completely saponified polyvinyl alcohol resin having an average degree of polymerization of 1500 was dissolved in hot water, cooled, and then a separately prepared aqueous sodium alginate solution was added thereto. 2000m
1 mixed solution. This is added to an aqueous calcium chloride solution 50
As soon as the solution was slowly dropped into 00 ml, the droplets began to solidify and lost fluidity, and after about 3 minutes completely gelled to produce translucent spherical particles. Next, the gel particles were separated and recovered, and further added to a mixed aqueous solution having a formaldehyde concentration of 4% and a sulfuric acid concentration of 5%. At the same time as the addition, the translucent gel-like particles started to become cloudy and completely whitened after about 3 minutes, and spherical particles having rubber elasticity were obtained. This was sufficiently washed with water to obtain polyvinyl acetal porous spherical particles having a uniform particle diameter close to a true sphere having a particle diameter of 3 to 4 mm. After drying the spherical particles, the internal structure was observed with a scanning electron microscope, and had many pores of 2 to 4 μm.
All were continuous vents.

(Example 5) (Drip solution) Polyvinyl alcohol 7.5% Sodium alginate 1.0% Water 91.5% (First reaction solution) Calcium chloride 3.0% Water 97.0% (Second reaction) Liquid) formaldehyde 8.0% sulfuric acid 10.0% water 82.0% After gel-like particles were obtained by the same operation as in Example 4, the gel-like particles were separated and collected, and then formaldehyde 8% and sulfuric acid 10% Was added to a mixed aqueous solution at 80 ° C. When the reaction was carried out for 5 minutes in this state, 3 to 4 mm spherical particles having no elasticity were obtained. The spherical particles had fine creter-like irregularities. After thoroughly washing this with water and drying, and observing the internal structure with an operation electron microscope,
It had many pores of 2 to 4 μm, all of which were communicating holes.

(Example 6) (Drip solution) Polyvinyl alcohol 7.5% Sodium alginate 1.0% Water 91.5% (First reaction solution) Calcium chloride 3.0% Water 97.0% (Second reaction) Liquid) Formaldehyde 8.0% Sulfuric acid 10.0% Water 82.0% In the same manner as in Example 5, the gel particles were added to a mixed solution of 8% formaldehyde and 10% sulfuric acid at 20 ° C. for 15 hours. When reacted, hard spherical particles similar to those in Example 2 were obtained, but the particle surfaces were smoother than the particles obtained in Example 5.

(Comparative Example 5) (Drip solution) Polyvinyl alcohol 10.0% Sodium alginate 1.0% Water 89.0% (Reaction liquid) Calcium chloride 3.0% Water 97.0% Average polymerization degree is 1500 A completely saponified polyvinyl alcohol resin is dissolved in hot water and then cooled, and a separately prepared aqueous sodium alginate solution is added thereto to give a total amount of 2,000.
ml of the mixed solution. When this was slowly dropped into 5000 ml of a 3% aqueous solution of calcium chloride, the droplets immediately began to solidify, lost fluidity and gelled completely after about 3 minutes, but the particles were in the form of drops, It was not a true sphere.

(Comparative Example 6) (Drip liquid) Polyvinyl alcohol 8.0% Water 92.0% (Reaction liquid) Calcium chloride 3.0% Water 97.0% Polyvinyl alcohol completely saponified with an average polymerization degree of 1500 When an 8% aqueous solution obtained by dissolving a resin in water is slowly dropped into 5000 ml of a 3% aqueous solution of calcium chloride, the droplet spreads on the surface of the aqueous solution of calcium chloride, and the solution is left standing for 10 minutes even in this state. Did not solidify, and no kerides were obtained.

The apparent specific gravity of the porous spherical particles obtained in each example in a water-containing state was about 1.0 per 10 samples.
17 to 1.019. The specific gravity of the hollow particles of Example 3 was smaller than this, and was about 1.008. The water content after centrifugal dehydration was 50.4%, and the 50% compressive stress was 20 × 10 ³ N / m ² . When 20 grains were put into the water of a beaker and shaken, all the grains gently sank below the water surface in 3 minutes and 28 seconds after floating on the water surface for a while.

(Microbial Degradability Test of Carrier) Also, about 10% of the particles obtained in the examples were filled in a polypropylene container having a large number of holes of 2 mm mesh and immersed in an activated sludge aeration tank. Crushed. One year later, the container was taken out, and the polyvinyl acetal particles in the container were observed. As a result, no dimensional change due to abrasion was observed. In addition, aerobic microorganisms adhered to the particle surface at high density, and erosion of the carrier by these microorganisms was not confirmed.

(Production of entrapping immobilized carrier)
A mixture of activated sludge concentrated to about 0 g / liter and 2% sodium alginate at a volume ratio of 1: 1 was separately prepared and impregnated into the porous spherical particles obtained in each of the examples. . The mixed solution was flowed under reduced pressure to increase the amount of impregnation to obtain a microorganism carrier.

Then, the obtained microorganism carrier was impregnated with a 5% calcium chloride aqueous solution, stirred, and reacted for about 3 hours. As a result, the sodium alginate contained in the polyvinyl acetal-based porous material was insolubilized and immobilized in a state in which the microorganisms were included.

The microbial inclusion-immobilized support thus obtained has an alginate-based gel attached in the pores and on the surface of the porous spherical particles described above, similar to the polyvinyl acetal-based porous body. It had good hydrophilicity and was rich in flexibility and elasticity when wet. In addition, since the porous spherical particles are polyvinyl formal and rich in hydrophilicity, the gel easily conforms to the porous spherical particles, and the gel is uniformly present in the carrier. Further, since the porous body has a high porosity and a three-dimensional network structure, the ratio of the gel in the carrier is kept high.

As a simulation test assuming the flow in the bioreactor, the obtained microbial entrapment-immobilized support was filled in a vessel having a diameter of 150 mm and a height of 400 mm, and aerated and flown in water. The carrier was uniformly dispersed and flowed. After running this flow continuously for one month,
The carrier was taken out and observed, but no wear or breakage due to friction was observed at all, and it was confirmed that the carrier had high wear resistance. In addition, the porous spherical particles were not subjected to erosion degradation by microorganisms at all, and it was confirmed that the life of the carrier could be maintained for a long time.

From the results of the above Examples and Comparative Examples, in order to produce porous spherical particles by the production method of the present invention, a water-soluble polymer having a gelling property must be blended at an appropriate concentration. It can be seen that acetalization must be performed to maintain the shape. For example, Example 1 and Comparative Example 1
In addition, in the comparison between Example 2 and Comparative Example 2, since the dropping liquid did not contain sodium alginate, the drop by dropping could not maintain the shape and became cloud-like particles.

As shown in the third embodiment, for example,
It was recognized that hollow particles could be obtained by dropping the first reaction solution and the dropping solution in Example 1 in the opposite manner. In this case, it was found that the smaller the concentration of the polyvinyl alcohol, the more easily the particles became clear.

Further, all of the particles obtained in these examples are excellent in use as a carrier for immobilizing microorganisms,
It had good results in specific gravity, abrasion resistance, weather (light) resistance and microbial degradation resistance. In addition, it has been found that compressing the spherical particles of the present invention improves water permeability and facilitates use. However, when the acetalization degree was as low as 30 mol% or less, the wear resistance was reduced.

[0094]

The porous spherical particles of the present invention have high mechanical strength and abrasion resistance because they have a polyvinyl acetal resin as a skeleton. Therefore, a carrier for a microorganism carrier, a solution holding material and a plant supporting material in hydroponic cultivation of agricultural crops, a culture medium for animal and plant cells, an artificial moss, a soil improvement material, a submerged fluid cleaning member, a submerged fluid mass member, etc. It can be used for various purposes. In particular, in the case of a carrier for a microorganism carrier, in particular, a carrier for a fluidized bed microorganism carrier, the carrier is hardly worn due to friction between carriers generated at the time of carrier flow or friction with the inner wall of the reaction tank, and the life of the carrier is extended. . In addition to its affinity with microorganisms, it has excellent fluidity, specific gravity, weather resistance (light) resistance, and microbial degradation resistance.
Alternatively, it can be suitably used as a carrier for entrapping and immobilizing microorganisms.

In the case of porous spherical particles having a skeleton of a polyvinyl acetal resin having a uniform particle size close to a true sphere,
It can be easily filled into various containers, the abrasion resistance is further improved, and the fluidity as a fluidized bed type microorganism carrier can be improved.

In the method of the present invention for producing spherical particles, the reaction is performed in a single step in the form of droplets, so that the reaction time and post-processing steps can be shortened greatly, and the spherical particles can be produced continuously and in large quantities. it can. Therefore, the production time is greatly reduced, and a material excellent in strength can be obtained. Further, a granular material having an arbitrary particle size and as uniform as possible can be obtained. Further, the yield can be improved with less loss in the post-process as in the conventional method, and the space required for the reaction can be reduced. In addition, hollow polyvinyl acetal-based porous spherical particles can be obtained, and are particularly suitably used as a carrier for a fluidized bed type microorganism carrier.

Claims (16)

[Claims] 1. Porous spherical particles having continuous pores and having a skeleton of a polyvinyl acetal resin. 2. The polyvinyl acetal resin is polyvinyl formal and has a formalization degree of 30 to 85 mol%.
The porous spherical particle according to claim 1, which is: 3. The porosity of the porous spherical particles is 50 to 9.
The porous spherical particles according to claim 1 or 2 which are 8%. 4. The porous spherical particle according to claim 1, wherein the porous spherical particle is a hollow body. 5. The porous spherical particle according to claim 1, wherein the porous spherical particle has pores on the surface, and the inside of the particle has a porous structure. 6. The porous spherical particle according to claim 1, wherein the apparent specific gravity of the porous spherical particle in a water-containing state is 1.0 to 2.2. 7. The porous spherical particle according to claim 1, wherein the size of the porous spherical particle in a water-containing state is 1 to 20 m in diameter. 8. A microorganism carrier in which a living organism is fixed to the porous spherical particles according to claim 1. 9. The microorganism carrier according to claim 8, wherein the microorganisms are fixed on the surface and / or in the pores of the porous spherical particles. 10. The microorganism carrier according to claim 9, wherein the microorganism is comprehensively fixed by a microorganism fixing agent. 11. The microorganism carrier according to claim 10, wherein the microorganism immobilizing agent is sodium alginate. A bioreactor using the microorganism carrier according to any one of claims 8 to 11. 13. The following steps: a step of dropping a droplet of a mixed aqueous solution of a water-soluble polymer having a property of gelling in an acidic solution, polyvinyl alcohol and aldehydes into the acidic solution; Reacting polyvinyl alcohol and aldehydes in the inside thereof, comprising the steps of: 14. A method for producing porous spherical particles having continuous pores and having a skeleton of a polyvinyl acetal resin, comprising the following steps: a water-soluble polymer having a property of gelling by an ion exchange reaction and polyvinyl alcohol. Dropping a droplet of the mixed solution with the above into an aqueous solution of a polyvalent metal salt, and gelling the droplet to form gel-like spherical particles containing polyvinyl alcohol; and acetalizing the gel-like spherical particles. A method comprising: 15. The mixed solution contains 0.5 to 5 water-soluble polymers having a property of gelling by ion exchange reaction.
The method for producing porous spherical particles according to claim 14, comprising 5 to 20% by weight of polyvinyl alcohol. 16. The following step: Drops of an aqueous solution of a polyvalent metal salt are dropped into a mixture of a water-soluble polymer having a property of gelling by an ion exchange reaction and polyvinyl alcohol,
A method for producing hollow porous spherical particles, comprising: forming a gel-like spherical particle on the outer periphery of the droplet; and acetalizing the gel-like particle.