JPH05271425A - Production of pva gel molding - Google Patents

Abstract

PURPOSE:To obtain the title molding having high strengths, water resistance and chemical resistance and a high affinity for a biocatalyst by bringing a mixed aqueous solution of PVA and a water-soluble polysaccharide into contact with a liquid containing borate ions and cations to form particles and treating the particles for insolubilizing the PVA. CONSTITUTION:A spherical polyvinyl alcohol gel molding is produced by bringing an aqueous solution containing polyvinyl alcohol and a water-soluble polysaccharide capable of gelling upon contact with cations into contact with a liquid containing borate ions and cations to form spherical particles and treating the particles for insolubilizing the PVA. According to this process, the spherical polyvinyl alcohol gel molding can be easily obtained, has a high affinity for a biocatalyst, and therefore can be used as a bioreactor, a carrier for wastewater treatment, a water retentive, a low-temperature insulation, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyvinyl alcohol gel molding having a high affinity with biocatalysts such as enzymes and microorganisms.

[0002]

Polymer hydrogels are used as a carrier for immobilizing biocatalysts, water retention materials, cold insulation materials, substitutes for biogels for eyes, skin, joints, etc.
In recent years, research has been active. As a polymer material which is a raw material of these hydrogels, agar, alginate, carrageenan, polyacrylamide, polyvinyl alcohol,
There are photo-curable resins and the like. Among these, polyvinyl alcohol (hereinafter abbreviated as PVA) hydrogel has a high water content, excellent oxygen / substrate permeability, high affinity with living organisms, and is particularly excellent among high molecular hydrogels. This PVA
The shape of the hydrous gel is often required to be spherical in consideration of fluidity, filling effect, and handleability.

Conventionally, as a method of forming PVA gel into a spherical shape, a method of bringing an aqueous solution of PVA into contact with a saturated aqueous solution of boric acid to form a gel (Sewerage Society, 23, 41 (1986),
Irrigation and wastewater, 30, 36 (1986). ); Method of contacting a mixed aqueous solution of PVA and sodium alginate with a mixed aqueous solution of calcium chloride and boric acid to form a spherical gel (JP-A-62-138193); Contacting a mixed aqueous solution of PVA and sodium alginate with an aqueous calcium chloride solution After spherical molding, freeze and thaw
A method for gelating VA (Japanese Patent Laid-Open No. 64-43188) is known.

[0004]

In the method of dropping the PVA aqueous solution into the boric acid aqueous solution, the dropped droplets stick to each other and a spherical molded article cannot be obtained. Also, PV
A method of dropping a mixed aqueous solution of A and sodium alginate into a mixed aqueous solution of calcium chloride and boric acid, and performing no subsequent treatment is to bring the dropped product into contact with the aqueous boric acid solution for a long time, and to form a gel up to the center of the spherical molded article. Therefore, when the biocatalyst is immobilized, boric acid adversely affects the biocatalyst and the activity of the biocatalyst does not appear. Further, gelation with boric acid is a reversible reaction, and the gel is easily dissolved due to a change in pH, etc., which makes practical application difficult. In addition, a method of gelating PVA by contacting a mixed aqueous solution of PVA and sodium alginate with a calcium chloride aqueous solution to form a spherical shape, and then freezing and thawing, is a method in which only the alginate is gelated when forming the spherical shape. Since PVA does not gel, PVA is eluted into the calcium chloride aqueous solution, the calcium chloride aqueous solution is contaminated, and the viscosity increases, so that the calcium chloride aqueous solution cannot be repeatedly used. Further, there was a problem that the PVA exudes to the surface even when it is frozen, and the spherical gels stick to each other.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, a mixed aqueous solution containing an aqueous solution polysaccharide (B) capable of gelling upon contact with PVA (A) and a cation (hereinafter , Abbreviated as PVA mixed aqueous solution)
Is formed into a spherical shape by contacting with a liquid containing borate ions and cations (hereinafter abbreviated as coagulation liquid), and then PVA insolubilization treatment is carried out. The manufacturing method was found and the present invention was completed.

The method for producing the spherical PVA-based gel molded article of the present invention will be described in more detail below. First, the components used in the present invention will be described. P used in the present invention
The average degree of polymerization of VA (A) is preferably 1000 or more, and 1
700 or more is more preferable. The degree of saponification of PVA is 98.
5 mol% or more is preferable, and 99.85 mol% or more of completely saponified PVA is more preferable from the viewpoint of gel formation. Further, as the PVA of the present invention, various known modified PVA can be used as long as the object of the present invention is not impaired. The higher the concentration of PVA, the stronger the gel formed,
If the required gel strength can be obtained, it is advantageous from the viewpoint of raw material cost that the PVA concentration is low. Although 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 droplet formation method, P at room temperature
When dropping the VA mixed aqueous solution, the PVA concentration is 0.3 to
40 wt% is easy to be spheroidized, and practically sufficient gel strength can be obtained. The aqueous solution polysaccharide (B) having the ability to gel upon contact with a cation used in the present invention includes:
Examples thereof include alginate, carrageenan, mannan, chitosan, etc., and sodium alginate is particularly preferable. Examples of the cations in the present invention include calcium ions, magnesium ions, strontium ions, barium ions, aluminum ions, potassium ions, cerium ions, metal ions such as nickel ions, and cations such as ammonium ions. Metal cations are preferred. Compounds containing at least one of these cations, especially calcium chloride, are preferred. The cation concentration is preferably 0.1 to 10% by weight. Examples of the compound containing a borate ion in the present invention include boric acid, borate, and borate ester. The borate ion concentration is preferably 1 g / liter or more, more preferably 10 g / liter or more, and a saturated solution may be used. Further, the pH may be adjusted by adding an alkaline substance to the borate ion-containing aqueous solution.

This PVA mixed aqueous solution contains biocatalysts such as microorganisms and enzymes within a range that does not inhibit gelation of PVA.
Microbial medium, reinforcing material to increase the strength of spherical gel,
You may add the filler etc. which adjust the specific gravity of a gel molding. For example, the PVA mixed aqueous solution obtained by the above method is dropped from a tubular die or sprayed from a spray die to form droplets, which are then brought into contact with a coagulating liquid. The droplets of the PVA mixed aqueous solution become spherical due to the surface tension when they come into contact with the coagulating liquid. The diameter of the spherical molded product can be arbitrarily changed by adjusting the diameter of the die, the spraying pressure, and the viscosity of the PVA aqueous solution. The coagulation liquid may be allowed to stand still, but by forcibly stirring it with a stirrer or the like, the reaction between the PVA mixed aqueous solution and the coagulation liquid can be promoted, and the sticking of the spherical molded products can be completely prevented. In practice, when a large amount of PVA-based gel molded product is produced, the diameter of the spherical molded product can be made uniform by using a pump or the like for the extrusion for dropping the PVA mixed aqueous solution.
The PVA-based molded product spheroidized in the coagulating liquid is subjected to insolubilization treatment of PVA after being separated from the coagulating liquid. The following two methods are preferable for the insolubilization treatment of PVA. The operation of freezing at −5 ° C. or lower, preferably −10 ° C., holding for at least 1 hour or longer, preferably 10 hours or longer, and then thawing is repeated at least once or more, preferably 2 or more times. The PVA is brought into contact with a liquid containing a compound having a syneresis action. The immersion time is 10 minutes or longer, preferably 30 minutes or longer. Examples of the compound having a synergic action of PVA include sodium sulfate, ammonium sulfate, potassium sulfate, magnesium sulfate, aluminum sulfate, sodium citrate, ammonium citrate, potassium citrate, magnesium citrate, aluminum citrate, sodium tartrate, and ammonium tartrate. Examples include liquids containing at least one of compounds such as potassium tartrate, magnesium tartrate, and aluminum tartrate, with sodium sulfate aqueous solution being particularly preferable. The concentration is 100 g / liter or more, and a saturated aqueous solution is particularly preferable, and the above methods and may be used in combination. The spherical PVA-based gel molded product thus obtained has strength that does not deform or damage over a long period of time, and can be continuously used without being attacked by water or various chemicals. Is expressed.

[0008]

When the PVA mixed aqueous solution comes into contact with the coagulation liquid, the elution of PVA into the coagulation liquid disappeared because the water-soluble polysaccharide was gelated by the cations and at the same time the PVA was cross-linked with boric acid and the PVA was temporarily suspended. It is thought that this is due to insolubilization.
Further, it is considered that the reason why the spherical molded articles disappeared from each other was due to the temporary insolubilization of PVA due to the cross-linking with boric acid. Further, it is considered that the gel, which was incomplete by only boric acid crosslinking, is improved in strength and durability by the insolubilization treatment of or.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 PVA (average polymerization degree: 4100, saponification degree: 99.85 mol%) manufactured by Kuraray Co., Ltd. was washed with warm water at 40 ° C. for about 1 hour, and water was added to PVA so that the PVA concentration became 10 wt%. The total amount is 500 g, and while stirring this, 110 ° C,
It was treated for 2 hours to dissolve PVA and allowed to cool to room temperature. To this, 250 g of 4 wt% sodium alginate aqueous solution was added and mixed, and further collected from the wastewater treatment tank of the Kuraray Okayama Plant (1-2-1, Kaigandori, Okayama City, Okayama Prefecture).
Activated sludge obtained by subjecting to concentration operation (MLSS 800
250 mg of 00 mg / liter was added and sufficiently stirred. This mixed solution was fed at a rate of 1 ml / min by a roller pump using one vinyl tube having an inner diameter of 2 mmφ with an injection needle having an inner diameter of 1 mm attached to the tip, and stirred with a stirrer to pH 7 to adjust the pH to 7 g of boric acid. And 30
g / l calcium chloride mixed aqueous solution (coagulation liquid)
Water was added dropwise to 10 liters from a height of 5 cm on the water surface. The dropped droplets were immediately spherical in the coagulating liquid. After dropping the whole amount,
These spheroidized molded products were separated from the coagulating liquid and immersed in a saturated Na ↓ 2SO ↓ 4 aqueous solution stirred with a stirrer for 90 minutes to obtain an opaque brown flexible spherical gel. This gel was formed into a spherical shape and was not tacky. The particle size was 3 to 3.5 mmφ. The total organic carbon content (TOC) of the coagulation liquid was measured to be 4 ppm, and the elution of PVA into the coagulation liquid was very small. The PVA gel thus obtained was examined for durability in water. Add 300g of water to 30g of gel and add 3
Stirred at 0 ° C. No change in particle size or strength was observed even after 1 month.

Example 2 The same PVA as in Example 1 was washed with warm water of 40 ° C. for about 1 hour, water was added to PVA so that the concentration of PVA was 10 wt%, and the total amount was 500 g. ,
It was treated for 2 hours to dissolve PVA and allowed to cool to room temperature. To this, 250 g of 4 wt% sodium alginate aqueous solution was added and mixed, and the sludge was collected from the same wastewater treatment tank as in Example 1 and concentrated to obtain activated sludge (MLSS 8).
250 g (0000 mg / liter) was added and sufficiently stirred. This mixed solution was sent at 1 ml / min by a roller pump using one vinyl tube having an inner diameter of 2 mmφ with an injection needle having an inner diameter of 1 mm attached to the tip, and was stirred with a stirrer to adjust the pH to 7 g of boric acid of 10 g / liter. And 3
The mixture was added dropwise to 10 liters of a 0 g / liter calcium chloride mixed aqueous solution (coagulation liquid) from a height of 5 cm on the water surface.
The dropped droplets were immediately spherical in the coagulating liquid. After dropping the whole amount, these spheroidized moldings are separated from the coagulating liquid,
It was frozen at 0 ° C. for 24 hours and thawed at room temperature. Further, this freeze-thaw operation was repeated twice to obtain an opaque brown flexible spherical gel. This gel is formed into a spherical shape and is not sticky. The particle size was 3 to 3.5 mmφ.
When the total organic carbon content (TOC) of the coagulation liquid was measured, it was 3p.
pm, and the elution of PVA into the coagulation liquid was very small. The PVA gel thus obtained was examined for durability in water. 300 g of water was added to 30 g of the gel and stirred at 30 ° C. No change in particle size or strength was observed even after 1 month.

Comparative Example 1 The same PVA as in Example 1 was washed with warm water at 40 ° C. for about 1 hour, then water was added to PVA to a PVA concentration of 10 wt% to make the total amount 500 g, and this was stirred at 110 ° C. ,
It was treated for 2 hours to dissolve PVA and allowed to cool to room temperature. The activated sludge (MLSS 40000 mg / ml) obtained by collecting and collecting the same from the same wastewater treatment tank as in Example 1
Liter) 500 g was added and sufficiently stirred. This liquid has an inner diameter of 2 mm and an injection needle with an inner diameter of 1 mm attached to the tip.
The solution was fed at a rate of 1 ml / min with a roller pump using one vinyl tube of No. 1 and was added dropwise to 10 liters of a 30 g / liter boric acid aqueous solution (coagulation solution) adjusted to pH 7 with a stirrer from a height of 5 cm of water surface. .. The dropped liquid droplets immediately solidified in the solidifying liquid, but the liquid droplets stuck to each other and a spherical molded product could not be obtained.

Comparative Example 2 The same PVA as in Example 1 was washed with warm water at 40 ° C. for about 1 hour, water was added to PVA so that the concentration of PVA was 10 wt%, and the total amount was adjusted to 500 g. ,
It was treated for 2 hours to dissolve PVA and allowed to cool to room temperature. To this, 250 g of 4 wt% sodium alginate aqueous solution was added and mixed, and the sludge was collected from the same wastewater treatment tank as in Example 1 and concentrated to obtain activated sludge (MLSS 8).
250 g (0000 mg / liter) was added and sufficiently stirred. This mixed solution was fed at a rate of 1 ml / min by a roller pump using one vinyl tube having an inner diameter of 2 mmφ with an injection needle having an inner diameter of 1 mm attached to the tip, and stirred at a stirrer to adjust pH to 10 g / liter boric acid. And 30
g / l calcium chloride mixed aqueous solution (coagulation liquid)
Water was added dropwise to 10 liters from a height of 5 cm on the water surface. The dropped droplets were immediately spherical in the coagulating liquid. After dropping the whole amount,
These spheroidized PVA mixed moldings were separated from the coagulation liquid. After that, insolubilization treatment such as freezing was not performed. The particle size was 3 to 3.5 mmφ. The total organic carbon content (TOC) of the coagulation liquid was measured to be 3 ppm, and the elution of PVA into the coagulation liquid was very small. The PVA gel thus obtained was examined for durability in water. 300 g of water was added to 30 g of the gel, and the mixture was stirred at 30 ° C. It was found that the gel was dissolved after 3 days and there was a problem in durability.

Comparative Example 3 The same PVA as in Example 1 was washed with warm water at 40 ° C. for about 1 hour, water was added to PVA so that the concentration of PVA was 10 wt%, and the total amount was adjusted to 500 g. ,
It was treated for 2 hours to dissolve PVA and allowed to cool to room temperature. To this, 250 g of 4 wt% sodium alginate aqueous solution was added and mixed, and the sludge was collected from the same wastewater treatment tank as in Example 1 and concentrated to obtain activated sludge (MLSS 8).
250 g (0000 mg / liter) was added and sufficiently stirred. This mixed solution was delivered at a rate of 1 ml / min by a roller pump using one vinyl tube having an inner diameter of 2 mmφ with an injection needle having an inner diameter of 1 mm attached to the tip, and stirred with a stirrer to adjust the pH to 30 g / liter calcium chloride. It was added dropwise to 10 liters of the aqueous solution (coagulation liquid) from the height of the water surface of 5 cm. The dropped droplets were immediately spherical in the coagulating liquid. After the entire amount was dropped, these spheroidized PVA-mixed molded products were separated from the coagulating liquid, frozen at -20 ° C for 24 hours, and thawed at room temperature. Further, this freeze-thaw operation was repeated twice to obtain an opaque brown flexible spherical gel. The particle size was 3 to 3.5 mmφ. When the total organic carbon content (TOC) of the coagulation liquid was measured, it was 103 ppm.
The elution of A into the coagulation liquid was large. The PVA gel thus obtained was examined for durability in water. 300 g of water was added to 30 g of the gel, and the mixture was stirred at 30 ° C. No change in particle size or strength was observed even after 1 month.

[0014]

[Table 1]

[0015]

As is apparent from the above examples, according to the present invention, a spherical PVA-based gel molded product can be easily obtained.
The obtained PVA-based gel molded product has high strength, sufficient water resistance and chemical resistance, and further has a high affinity with biocatalysts, so that it is a bioreactor / wastewater treatment carrier, water retention material / cooling material, etc. Can be used for.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08L 29/04 LGS 6904-4J LGW 6904-4J (C08L 29/04 5:00) 7415-4J

Claims (2)

[Claims] 1. A mixed aqueous solution containing polyvinyl alcohol (A) and a water-soluble polysaccharide (B) capable of gelling upon contact with a cation is brought into contact with a liquid containing borate ions and cations. A method for producing a spherical polyvinyl alcohol-based gel molded article, which comprises performing insolubilization treatment of polyvinyl alcohol after molding into a spherical shape. 2. A method for insolubilizing polyvinyl alcohol is a method of freezing at −5 ° C. or lower and thawing at least once or a method of contacting with a liquid containing a compound having a syneresis function of polyvinyl alcohol. The method for producing a spherical polyvinyl alcohol-based gel molded article according to claim 1, wherein