JP2710815B2 - Gel substrate - Google Patents

Description

The present invention relates to a gel base comprising polyvinyl alcohol and a water-soluble high molecular polysaccharide.

The gel base material of the present invention is excellent in abrasion resistance, and the biocatalyst such as microorganisms and enzymes entrapped and immobilized therein can efficiently exhibit its activity. It is useful as a carrier for immobilizing a biocatalyst.

B. Prior Art Research has been made for a long time to efficiently utilize enzymes and functions of microorganisms as a biocatalyst by immobilizing the microorganisms. In particular, it is described in detail in "Wastewater treatment by the microorganism immobilization method" (June 10, 1988, published by the Industrial Water Research Society), pages 192 to 214. Abstracts of the 20th Fall Meeting of the Society of Chemical Engineers, pp. 267-269 show that polyvinyl alcohol (abbreviated as PVA) in wastewater treatment with immobilized activated sludge is gelled with boric acid. There is a review of the use of such carriers. Also, "Water and Wastewater" Vol. 30, No. 6, pp. 36-42 (Showa
A similar report was made on anaerobic fermentation bacteria immobilized by gelling PVA with boric acid in 1963.

One of the methods for immobilizing biocatalysts such as enzymes and microorganisms is a comprehensive immobilization method in which a biocatalyst is directly wrapped using a polymer material, and carrageenan, poly is commonly used as a polymer material in this method. There are acrylamide, PVA, photocurable resin and the like. Among them, PVA is -5
After freezing at a temperature below ℃ and thawing at room temperature, a highly water-containing gel having excellent water resistance, elasticity and flexibility was obtained (Japanese Patent Publication No. 47-12854). By including microorganisms, it can be used as an excellent immobilization carrier. This PVA gel can be obtained by repeating freezing and thawing, or by performing vacuum dehydration after freezing to obtain a high-strength gel not found in conventional polymer materials. (Japanese Unexamined Patent Publication No. 58-47492) The polymer material used for immobilizing the biocatalyst must itself be non-toxic and not adversely affect the activity of the biocatalyst. Since no chemicals are used in gel molding, it has high stability to living organisms, and has a high water-containing and porous structure, so that it is an excellent immobilized carrier for culturing and growing microorganisms.

Reaction vessels for immobilizing the biocatalyst by this entrapping immobilization method and performing a biological reaction include a fixed bed (packed bed), a fluidized bed, a stirring tank, and the like. The shape of the carrier is desirably spherical or fibrous from the viewpoint that the active surface can be widened, the fluidity and the filling efficiency are good, and the handling is easy.

In particular, in terms of industrial practical use, it is important that a high-strength immobilized carrier can be easily and inexpensively produced.

 It has been widely used as a carrier for immobilizing enzymes and microorganisms.
Alginates are sodium alginate aqueous solution at room temperature.
The solution, Ca , Al Water containing polyvalent metal ions such as
An inexpensive and easy-to-use gel that forms a gel when dropped on a liquid.
You. However, alginate gels are not phosphated.
Gels are destroyed or gels are used in wastewater treatment, etc.
May erode and dissolve. Also, make sure the mechanical strength
Is not sufficient, resulting in long-term use in the reaction tank.
Often destroyed.

Also, gels made from photocurable resin or acrylamide are also very expensive in raw material prices compared to PVA gels,
As an entrapping immobilization carrier for a biocatalyst, it is limited to application to a bioreaction with high practical value. (Japanese Patent Application Laid-Open No. 61-216688) C. Problems to be Solved by the Invention The following conditions must be satisfied for a gel base material as a carrier for immobilizing a biocatalyst to be used in a practically advantageous manner. It is as follows.

(1) Easy manufacturing.

(2) The activity of the comprehensive biocatalyst must not be lost. or,
The ability to restore the dormant state of live cells.

(3) Bacterial cell growth in the carrier is possible.

(4) High affinity for biocatalysts. Also, the water content must be high.

(5) Good permeability of external substrates and oxygen.

(6) Excellent mechanical performance (strength, durability in water, abrasion resistance).

(7) Having microbial resistance (not biodegradable).

(8) Be economical.

However, at present, a gel base material that can sufficiently satisfy the above conditions has not been found yet.

Accordingly, an object of the present invention is to provide a gel base material that can satisfy the above conditions.

D. Means for Solving the Problems According to the present invention, the object described above comprises an inner film and an outer film made of polyvinyl alcohol and a water-soluble polymer polysaccharide, and the average thickness of the inner film in a dry state is reduced.
0.005 to 0.20 μm, the average thickness of the outer coating is 0.1 to 10 μm, and the average maximum diameter of the inner coating or the space formed by the inner coating and the outer coating is
This is achieved by providing a gel substrate characterized by being in the range of 0.1 to 10 μm.

The gel base material of the present invention is composed of PVA and a water-soluble polymer polysaccharide, and as such PVA, the average degree of polymerization is 1000 or more,
Preferably, the fully saponified PVA having a saponification degree of 98.5% or more, preferably a saponification degree of 99.85 mol% or more is PVA of 1700 or more.
Desirable for gel formation. As described below, the gel base material of the present invention is formed through a freezing step.However, when the degree of saponification of the PVA used decreases, the freezing conditions for gel molding become severe, and in order to obtain a gel having the required strength, Since a lower freezing temperature and a lower freezing time are required, it is not preferable in terms of productivity. As the PVA, various known modified PVAs can be used as long as the object of the present invention is not impaired. As the water-soluble polymer polysaccharide which is another polymer component constituting the gel base material of the present invention, specifically, an alkali metal salt of alginic acid, carrageenan, mannan, contact with cations such as chitosan, etc. And water-soluble high-molecular-weight polysaccharides capable of gelling. The water-soluble polymer polysaccharide includes alkaline earth metal ions such as magnesium ion, calcium ion, strontium ion and barium ion; other polyvalent metal ions such as aluminum ion, cerium ion and nickel ion; potassium ion; ammonium ion And the like, and may coexist with a cation capable of gelling the above water-soluble polymer polysaccharide. The polymerization ratio of PVA to the water-soluble polysaccharide is preferably in the range of 35:65 to 95: 5. The gel base material of the present invention further comprises a component of a microorganism culture medium, a reinforcing material for increasing the strength of the immobilized carrier, a filler for adjusting the specific gravity of the produced gel, a protective agent against freezing damage of microorganisms by freezing treatment, and the like. It may be contained.

The gel base material of the present invention is covered with an outer coating, has a network structure inside, and in a dry state, 0.005 to 0.20 μm.
m and an outer coating having an average thickness in the range of 0.1 to 10 μm and formed by the inner coating or the outer coating and the outer coating having an average thickness in the range of 0.1 to 10 μm. The average maximum diameter of the space is in the range of 0.1 to 10 μm in a dry state. These dimensions are determined by observing the cross section of the gel base in a dry state with an electron microscope. Here, the dry state means, for example, that the water in the gel is replaced with ethanol by sequentially immersing the hydrogel in an aqueous ethanol solution and ethanol, the ethanol-containing gel obtained is frozen in liquid nitrogen, and then dried under vacuum. This is the state achieved by doing so. The average maximum diameter of the space is determined by arbitrarily picking up 50 places in the space that has appeared in an electron micrograph of the cross section of the gel base material, measuring the maximum diameter in each space, and taking the arithmetic average of the numerical values. The average thickness of the inner coating is
For each of the above-mentioned fifty spaces, one point of the internal film forming the space is arbitrarily selected, the thickness of the film at that part is measured, and an arithmetic average of the numerical values is determined. The average thickness of the outer coating is determined by taking 50 arbitrary locations of the outer coating, measuring the thickness of the outer coating at those positions, and taking the arithmetic average of the values.

If the average thickness of the inner coating is less than 0.005 μm, it will be inflexible because of lack of elasticity as a gel molded body, and the space created by this coating will be very small, as a space where the biocatalyst is comprehensively immobilized Is not preferred. On the other hand, if it exceeds 0.20 μm, the film becomes thick and the skeleton of the gel structure becomes large, so that it lacks the permeability of the substrate and oxygen, and the growth of microorganisms and the activity as a biocatalyst are not preferable.

If the average maximum diameter of the space formed by the inner film or the inner film and the outer film is less than 0.1 μm, the permeability of the substrate and oxygen to the inside of the gel base material is impaired, and the living space for microorganisms is not preferable because it is too small. . On the other hand, if the thickness exceeds 10 μm, the space is too large, which impairs the mechanical strength of the gel and results in low gel strength, which is not preferable. In addition, if the space has the dimensions specified in the present invention, the space containing the microorganisms can contain 8 to 15 times the amount of water, and the affinity for the microorganisms is imparted.

If the average thickness of the outer coating is less than 0.1 μm, the mechanical performance of the gel is inferior in the strength and elasticity of the gel, and the collision between the gel particles in the fluidized bed and the inner wall of the packed bed and abrasion are severe, resulting in long-term durability. Be impaired. Further, the biocatalyst in the gel wrapped at a high concentration may leak to the external environment, which is not preferable. On the other hand, when covered with an outer coating exceeding 10 μm, the permeability of the substrate and oxygen deteriorates extremely, so that the microorganisms gather on the surface portion of the gel, and the substrate and oxygen do not pass through to the inside of the gel, so that it is preferable as a biocatalyst. Absent.

The shape of the gel base material of the present invention is not particularly limited, and an arbitrary shape such as a spherical shape, a fibrous shape, and a film shape can be appropriately selected.

The biocatalyst in which the gel substrate of the present invention can be used for entrapping and immobilizing is not particularly limited, such as microorganisms, enzymes, animal and plant cells. The microorganism may be any of bacteria, actinomycetes, molds, yeasts, and the like, and may be obtained by pure culture, obtained by mixed culture, or activated sludge. As the microorganism, for example, Mucol (Mu
genus ccor), genus Fusarium, genus Cladothrix, sphaerotilus
Genus, Zoogloea, Leptomus
genus itus, genus Aspergillus, genus Rhizopus, Pseudomonas
Genus, Acetobacter, Streptomyces, Escherichia
a) Microorganisms belonging to genera such as genera, genus Saccharomyces, and genus Candida, including sulfur bacteria, methane bacteria, butyric acid bacteria, lactic acid bacteria, Bacillus subtilis,
Examples include deformed bacteria, defective bacteria, nitric acid bacteria, and nitrite bacteria.
For the purpose of wastewater treatment, it is desirable to immobilize bacteria that produce proteases, carbohydrate degradation enzymes, and lipolytic enzymes. Regarding the enzyme, regardless of its origin, an enzyme derived from an animal or a microorganism can be arbitrarily selected. Representative examples of the enzyme include lactate dehydrogenase (1.1.2.3), lactate oxidase (1.1.3.2), and glucose oxidase (1.1.3.
4), formate dehydrogenase (1.2.1.2), aldehyde dehydrogenase (1.2.1.3), aldehyde oxidase (1.2.3.1), xanthine oxidase (1.2.3.
2), pyruvate oxidase (1.2.3.3), pyruvate reductase (1.2.4.1), cortisone-α-reductase (1.3.1.4), acyl CoA-dehydrogenase (13.9
9.3), 3-ketosteroid △ ¹ -dehydrogenase (1.3.99.4), 3-ketosteroid △ ⁴ -dehydrogenase (1.3.99.5), L-alanine dehydrogenase (1.3.99.5)
4.1.1), L-glutamate dehydrogenase (1.4.1.
3), L-amino acid oxidase (1.4.3.2), D-amino acid oxidase (1.4.3.3), pyridoxal phosphate oxidase (1.4.3.5), catalase (1.11.1.6),
Catechol methyltransferase (2.1.1.6), carnitine acetyltransferase (2.3.1.7), acetyl-CoA acetyltransferase (2.3.1.9), asperate aminotransferase (2.6.1.1),
Alanine aminotransferase (2.6.1.2), pyridoxamine pyruvate transerase (2.6.1),
Hexokinase (2.7.11), glucokinase (2.7.1.
2), fructokinase (2.7.1.4), phosphoglucokinase (2.7.1.10), phosphofructokinase (2.7.1.1)
1), pyruvate kinase (2.7.1.40), carboxylesterase (3.1.1.1), arylesterase (3.1.
1.2), lipase (3.1.1.3), phospholipase A (3.1.
1.4), acetylesterase (3.1.1.6), cholesterol esterase (3.1.1.13), glucoamylase (3.
2.1.3), cellulase (3.2.1.4), inulase (3.2.1.
7), α-glucosidase (3.2.1.20), β-glucosidase (3.2.1.21), α-galactosidase (3.2.1.2
2), β-galactosidase (3.2.1.23), invertase (3.2.1.26), pepsin (3.4.4.1), trypsin (3.4.4.4), chymotrypsin A (3.4.4.5), cathepsin A (3.4), papain (3.4) 4.10), thrombin (3.
4.4.13), amidase (3.5.1.4), urease (3.5.
1.5), penicillin acidase (3.5.1.11), aminoacylase (3.5.1.14), adenine deaminase (3.5.4.
2), ATPase (3.6.1.3), pyruvate decarboxylase (4.1.1.1), oxalate decarboxylase (4.1.1.2), tryptophan decarboxylase (4.1.1.27), aldolase (4.1.2.13), Murray Tosidase (4.1.3.2), tryptophan synthase (4.
2.1.20), asperase (4.3.1.1), lysine racemase (5.1.1.5), glucose-6-phosphate isomerase (5.3.1.9), steroid △ -isomerase (5.3.3.
1), maxinyl-CoA synthetase (6.2.1.5) [(Note)
Numbers in katzko represent enzyme numbers. And the like. As animal and plant cells, growth point cells,
Examples include calli and embryos.

The properties of the gel substrate of the present invention are generally as follows.
The water content of the gel (percentage of water in the total amount of gel) is 80-90%
It is very expensive. The amount of water to PVA is 8 to 15 times. Regarding the permeability of the substrate, the hydrated gel comprising the gel base material of the present invention is immersed in an aqueous solution in which a constant concentration of the substrate is dissolved, the solvent is sampled at regular intervals, and the concentration of the substrate is determined by gas chromatography. The concentration of the substrate in the gel at the time of equilibrium was determined. The partition coefficient (substrate concentration in gel / substrate concentration) was determined from this value. 0.97 ethanol, 0.98 methanol, 0.98 cane sugar, 0.9 glucose
8. Synthetic sewage was very high at 0.89, close to 1.

Regarding the mechanical strength of the hydrogel comprising the gel base material of the present invention, a gel having a thickness of 1 mm, a width of 1 cm, and a length of 3 cm was prepared, and the tensile strength and the breaking strength were measured using an Autograph IM-100 manufactured by Shimadzu Corporation. The elongation was determined. Its tensile strength is 1-10
kg / cm ² , and the breaking elongation at that time was 100 to 300%. On the other hand, the abrasion resistance in water was set at a filling rate of 10%, and the mixture was put into an aeration tank by a standard activated sludge method, and the weight change after each day was examined (the water temperature was 10 to 20 ° C). The change in weight within 30 days from the start of the test showed a decrease of about 10 to 18% with respect to the total weight, but after that, the rate of decrease after 360 days was as small as 1 to 2%, and no breakage of the gel was observed. Alginic acid-only gels tested for comparison had completely disappeared after 30 days.

FIGS. 1 to 4 show electron micrographs of a cross section of the gel base material of the present invention obtained in Example 1 described later in a dry state. That is, the gel on which the microorganisms obtained in Example 1 were fixed was repeatedly immersed and replaced in an ascending series of aqueous solutions of 10, 20, 30, 40, 50, 60, 80 and 90% ethanol each day, and finally, After immersion replacement in ethanol, the mixture was frozen in liquid nitrogen and dried under vacuum to obtain a dried gel base material. After the gel base material was freeze-fractured, it was vapor-deposited with a gold-palladium alloy, and observed with a scanning electron microscope of type HSF-2 manufactured by Hitachi, Ltd. The electron micrographs are shown in FIGS. FIG. 1 is a photograph of a cross section of an outer film and an inner film, and FIG.
4 are photographs of the cross section of the internal coating. The average thickness of the observed coating was 1.5 μm for the outer coating and 0.1 μm for the inner coating.
It is 5 μm, and the size of the space is 1.7 μm in average maximum diameter when viewed from the cross section, and it is recognized that the space is uniformly distributed.

The gel composed of the gel base material of the present invention is rich in affinity with a biocatalyst, has strength and durability applicable to various reaction tank types, and is excellent in water resistance and chemical resistance. It has desirable characteristics as an entrapping and immobilizing carrier for biocatalysts.
In addition, the gel base material can be manufactured by a simple operation of freezing treatment as described later, and without using any chemical solution harmful to the biocatalyst.

The gel base material of the present invention having the above-mentioned properties is a public sewage drainage, household or building night drainage, household wastewater, agriculture, livestock, fishery, fishpond drainage, horticulture, garden, golf course, It can be used as a substrate for water treatment in a pond or the like, and can also be used as a substrate for drainage during production of food, production of enzymes, and the like.

Hereinafter, the method for producing the gel base material of the present invention will be described in detail.

The gel base material of the present invention is a mixed aqueous solution containing a water-soluble polymer polysaccharide capable of gelling by contact with PVA and a cation in a spherical, fibrous, or film-shaped arbitrary shape.
The surface of the mixed aqueous solution is solidified by contact with an aqueous solution containing a compound containing a cation capable of gelling the water-soluble high molecular polysaccharide, and the obtained molded product is cooled to -5 ° C.
It can be obtained by gelling PVA by subjecting the PVA to at least one operation of the following freezing and subsequent thawing. As the water-soluble polymer polysaccharide, various ones can be used as described above, but it is preferable to use sodium alginate. Sodium alginate not only serves as a molding aid for the PVA aqueous solution, but also has an effect of increasing the gel strength and eliminating the stickiness of the gel surface, as compared with the case where sodium alginate is not added. This further simplifies the freezing conditions such as the freezing temperature, the freezing holding time, and the number of freeze-thaw treatments, so that the time required for the biocatalyst immobilization treatment using the gel can be significantly reduced. When sodium alginate is used, it is preferable to use calcium chloride (hereinafter sometimes abbreviated as CaCl ₂ ) as a compound containing a cation that can gel it.

The concentration of PVA in the PVA mixed aqueous solution can be from 3 to 40% by weight from the range of the PVA gel forming ability. As the PVA concentration increases, a stronger gel is generated, but if the required gel strength is obtained, The lower the PVA concentration, the higher the affinity of the gel substrate for the biocatalyst, the higher the water content, and the better the permeability of the substrate and oxygen. It is necessary to select an appropriate concentration depending on the type and concentration of the additive component other than PVA, the liquid temperature of the PVA mixed aqueous solution, and the like.For example, when the PVA mixed aqueous solution is dropped at room temperature to the cation-containing compound aqueous solution, When the PVA concentration is 5 to 10% by weight, spheroidization is easy, and practically sufficient gel strength can be obtained.

The concentration of the water-soluble polymer polysaccharide added to the aqueous PVA mixed solution is 0.2 to 4% by weight, more preferably 0.5 to 2% by weight based on water.
Is good. If it is less than 0.2 wt%, the surface solidification of the PVA mixed aqueous solution becomes insufficient, and only a thin gel of the inner film and the outer film is obtained, which is not preferable. Conversely, when the concentration of the water-soluble polysaccharide is higher than 4 wt%, a hard molded product is obtained, but not only does the solution viscosity increase,
It is not preferable because the outer coating of the gel becomes thick, the permeability of the substrate and the enzyme is inhibited, and the microbial resistance becomes insufficient. The biocatalyst to be immobilized and immobilized on the gel base material of the present invention is mixed in a PVA mixed aqueous solution. In addition, the PVA mixed aqueous solution contains a biocatalyst medium, a reinforcing material for increasing the strength of the immobilized carrier, a filler for adjusting the specific gravity of the produced gel, and a biotreatment by freezing treatment within a range that does not inhibit gelation of PVA. A protective agent or the like against freezing damage of the catalyst may be added.

By contacting the above PVA mixed aqueous solution with an aqueous solution of a cation-containing compound in an arbitrary shape such as a spherical shape, a fibrous shape, or a film shape, the surface of the PVA mixed aqueous solution is solidified in that shape. When sodium alginate is used as the water-soluble polysaccharide and CaCl ₂ is used as the cation-containing compound, the concentration of the CaCl ₂ aqueous solution is 0.05 to 1.0 mol /
Preferably, from the PVA concentration and sodium alginate concentration, or from the hardness of the molded product of the PVA mixed aqueous solution, usually 0.1%
~ 0.5 mol / is preferred.

For example, when the PVA mixed aqueous solution is filled in a syringe, extruded from a tubular base such as a syringe needle, and dropped into an aqueous solution containing CaCl ₂ , the droplet of the PVA mixed aqueous solution extruded from the base is a CaCl ₂ aqueous solution. When it comes into contact with the sphere, it becomes a sphere due to surface tension, and the outermost surface of the sphere solidifies into a thin film,
It becomes a spherical molded product of the PVA mixed aqueous solution. The diameter of the spherical molded product can be arbitrarily changed to a diameter of 1 mm to 10 mm by adjusting the diameter of the die and the viscosity of the PVA mixed aqueous solution. The CaCl ₂ aqueous solution may be standing water, but by forcibly stirring with a stirrer or the like, the reaction rate between the molded product of the PVA mixed aqueous solution and the CaCl ₂ aqueous solution is promoted, and the fusion of the spherical molded products is almost completely performed. Can be prevented. In practice, when a large amount of PVA gel is produced, a pump or the like can be used to extrude the PVA mixed aqueous solution in order to make the diameter of the spherical molded product uniform. For example, in a roller pump that compresses and feeds a flexible tube, the liquid is intermittently flowed, so that the discharge from the mouthpiece is constant and a uniform spherical molded product is easily obtained.

The PVA mixed aqueous solution molded product surface-solidified in the cation-containing compound aqueous solution is separated from the cation-containing compound aqueous solution and frozen as it is. The freezing temperature may be -5 ° C or lower, but -20 ° C or lower is more preferable to obtain a stronger gel. The freeze-holding time is 2 hours or more, preferably 10 hours or more. By the freezing treatment, the molded product of the PVA mixed aqueous solution is gelled. The PVA gel is obtained by thawing this by leaving it in a temperature range that does not adversely affect the biocatalyst.

The PVA gel can be obtained by one freeze-thaw treatment. However, depending on the composition of the PVA mixed aqueous solution and the freezing conditions, the required strength may not be achieved, and is preferably at least twice, more preferably two or more times. By repeating freezing and thawing three or more times, a gel having sufficiently high strength can be obtained.

E. Examples Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to Examples.

Example 1 PVA manufactured by Kuraray Co., Ltd. (average polymerization degree 1740, saponification degree 99.
85 mol%) with 40 ° C warm water for about 1 hr, PVA concentration 8wt%
Then, water was added to PVA to make the total amount 40 g, and the pH was adjusted to 6. This is treated in an autoclave at 120 ° C for 30 minutes, and PVA
Was dissolved and then allowed to cool to room temperature. After adding 0.4 g of sodium alginate to this aqueous PVA solution and mixing, 0.5 g-wet cell of yeast (Saccharomyces cerevisiae) was further added.
4 ml of sterilized water containing s / ml was added and stirred sufficiently.

The mixed solution is fed at a rate of 1 ml / min by a roller pump using one vinyl tube having an inner diameter of 2 mm with a syringe needle having an inner diameter of 0.8 mm attached to the tip, and is stirred at 0.5 ml with a stirrer.
5 cm from the water surface in ol / calcium chloride (CaCl ₂ ) aqueous solution
Dropped from the height of. The dropped droplet was immediately spheroidized and settled in a CaCl ₂ aqueous solution. All of the spherical PVA mixed liquid molded product was separated from an aqueous solution of CaCl ₂ , washed lightly with sterile water, and then frozen in a freezer at −27 ° C. ± 3 ° C. After freezing for 20 hours and thawing at room temperature, an opaque yellow-white, highly flexible spherical gel was obtained. This gel is formed into a spherical shape and is not sticky. Further, in order to increase the strength of the gel, the above freeze-thaw treatment was repeated twice.

The spherical PVA gel on which the yeast thus obtained was immobilized had an average diameter of 3.6 mm. Table 1 shows the water content, distribution coefficient, abrasion strength in water, gel strength, average thickness of the inner and outer coatings when dried and average spatial diameter when dried when dried.

Comparative Example 1 The same PVA as used in Example 1 was subjected to the same treatment to obtain a 20 wt% aqueous PVA solution, and the same sodium alginate as used in Example 1 adjusted to a 3% aqueous solution was added 20 times. 60 parts of water were added, and the same yeast as used in Example 1 was added in the same amount as in Example 1. The obtained mixed aqueous solution was mixed with 3% in the same manner as in Example 1.
The solution was added dropwise to a mixed aqueous solution prepared by adding aluminum chloride to a boric acid aqueous solution at 0.2 mol /. Otherwise, processing was performed in the same manner as in Example 1. A PVA particulate gel having a diameter of 3.0 mm was obtained. The physical properties of the obtained gel were measured in the same manner as in Example 1. The results obtained are shown in Table 1.

Comparative Example 2 The same PVA as that used in Example 1 was subjected to the same treatment to obtain a 10 wt% PVA aqueous solution. Otherwise, a mixed aqueous solution was obtained in the same manner as in Example 1. This aqueous solution was dropped into a saturated boric acid aqueous solution under slow stirring in the same manner as in Example 1 to obtain a spherical gel having a diameter of 3 to 4 mm. This spherical gel was slowly stirred in a saturated aqueous solution of boric acid for 24 hours and then washed with tap water for 5 hours to obtain a PVA gel. The physical properties of the obtained gel were measured in the same manner as in Example 1. The results obtained are shown in Table 1.

F. Effects of the Invention According to the present invention, a gel base material having a high water content and a high partition coefficient and high abrasion resistance in water is provided, as is apparent from the above-mentioned examples.

[Brief description of the drawings]

1, 2, 3 and 4 are electron micrographs (60 ×, 600 ×, 6000 ×, and 60 ×, respectively) showing the cross-sectional structure of the gel base particles of the present invention obtained in Example 1. 24000 times).

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroaki Fujii 1-2-1, Kaigandori, Okayama-shi, Okayama Prefecture Kuraray Co., Ltd.Examiner Hiroshi Ueno

Claims (1)

(57) [Claims] 1. An inner coating comprising polyvinyl alcohol and a water-soluble polymer polysaccharide and an outer coating, wherein the average thickness of the inner coating in a dry state is in the range of 0.005 to 0.20 μm, and the average thickness of the outer coating is A gel base material having a thickness within a range of 0.1 to 10 μm, and an average maximum diameter of a space formed by the internal coating or the internal coating and the external coating within a range of 0.1 to 10 μm.