JP4653992B2 - Polyvinyl alcohol-based hydrogel, adsorption separation agent and adsorption separation method using the same - Google Patents

Description

The present invention is polyvinyl alcohol hydrogel, its Re Adsorption separating agent and adsorption separation method was used.

A hydrogel made of polyvinyl alcohol (hereinafter abbreviated as PVA) is a biomaterial such as a water-retaining material for agriculture and horticulture, a cold-retaining agent, a vitreous body, and an artificial joint because of its high water content, strength, and affinity to living organisms. It is used in a wide range of applications such as medical materials such as contact lenses, drug delivery systems and wound dressings, separation membranes, and microbial carriers.
As a method for producing this PVA-based hydrogel, freeze drying of a PVA aqueous solution, a method using a microcrystalline portion generated by repeated freezing and thawing as a crosslinking point, a method using complex formation between a PVA aqueous solution and a boron compound, In addition, as a method for obtaining a hydrogel molded product having excellent strength and water resistance, a mixed aqueous solution of PVA and a high molecular weight polysaccharide is contacted with a cationic compound and formed into a spherical shape. There is a known method (for example, see Patent Document 1).

Such a PVA-based hydrogel has the property that the volume and the amount of adsorbed organic matter change according to changes in the environmental temperature. In particular, as an application using the latter property, the PVA-based hydrogel is used in a temperature range higher than its phase transition temperature. There has been proposed a method for removing organic matter in an aqueous solution in which the organic matter is adsorbed by contacting with an aqueous solution in which the organic matter is dissolved, and after separation, the adsorbed organic matter is desorbed by bringing the gel to a temperature lower than its phase transition temperature. (For example, refer to Patent Document 2).
JP 9-316271 A JP 2001-096104 A

The organic substance removal method from the aqueous solution using the PVA-based hydrogel described in Patent Document 2 reversibly adsorbs and desorbs the organic substance with a slight temperature swing, and continuously separates the organic substance by repeating the cycle. This is a very good method in that it can be removed. However, since the separation and removal efficiency depends on the difference in the amount of adsorption before and after the phase transition of the PVA hydrous gel used, it has been found that there is room for further improvement in order to improve the processing efficiency.
That is, in order to improve the processing efficiency of organic substance separation / removal from an organic substance-dissolved aqueous solution using the PVA-based hydrogel, a PVA-based hydrogel having a large change in the amount of adsorbed organic substance before and after the phase transition is desired.

However, as a result of intensive studies in view of such circumstances, the present inventor has obtained a mixed aqueous solution containing a PVA resin (A) containing a 1,2-diol component in the side chain and a water-soluble polycarboxylate (C). A PVA water-containing product obtained by reacting a gel-like molded product obtained by contacting an aqueous solution containing a polyvalent metal ion (D) with a waterproofing agent (B) selected from an aldehyde compound and a boron compound The present invention was completed by finding that the gel meets the above-mentioned purpose.
The PVA resin (A) containing a 1,2-diol component in the side chain is a PVA resin (A) containing a 1,2-diol structural unit represented by the general formula (1). favored arbitrariness.

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an alkyl group, and R ⁴ represents a C 1-3 alkylene group which may have a single bond or an alkyl group. N is 0 or a positive integer]

The PVA water-containing gel of the present invention has a large change in the amount of organic matter adsorbed due to a change in environmental temperature, and the phase transition temperature can be arbitrarily shifted to the high temperature side according to the content of 1,2-diol structural units. It is possible, and is suitable as a PVA-based hydrous gel used for removal of organic substances from a treatment target liquid in which organic substances are dissolved.
In addition, the PVA water-containing gel of the present invention includes agricultural and horticultural water retaining materials, cryogens, biomaterials such as vitreous bodies and artificial joints, medical materials such as contact lenses, drug delivery systems, and wound dressings, separation membranes (benzene / It can also be applied to separation of azeotropic solvents such as hexane, isolation of natural antioxidants, and microbial carriers.

  The PVA resin (A) containing a 1,2-diol component in the side chain used in the present invention will be described in detail.

The PVA-based resin (A) used in the present invention contains a 1,2-diol component in the side chain of the PVA-based resin. More specifically, the 1,2-diol represented by the following general formula (1) It is a PVA resin having a diol structural unit.

In the above general formula (1), R ¹ , R ² and R ³ are each independently hydrogen or an alkyl group. Although it does not specifically limit as this alkyl group, For example, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, are preferable. Such an alkyl group may have a substituent such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, if necessary. R ⁴ represents a single bond or an alkylene group having 1 to 3 carbon atoms which may have an alkyl group, and n represents 0 or a positive integer.

In obtaining such a PVA resin (A), although not particularly limited, (i) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a vinyl ethylene carbonate represented by the following general formula (2) ,

[However, R ¹ , R ² and R ³ are each independently hydrogen or an alkyl group. ]

(Ii) a method of saponifying and deketalizing a copolymer of a vinyl ester monomer and a 2,2-dialkyl-4-vinyl-1,3-dioxolane represented by the following general formula (3):

[However, R ¹ , R ² , R ³ , R ⁵ , R ⁶ are each independently hydrogen or an alkyl group. ]

(Iii) a method of saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (4),

[However, R ¹ , R ² , R ³ are each independently hydrogen or an alkyl group, R ⁴ is a C 1-3 alkylene group that may have a single bond or an alkyl group, ⁷ and R ⁸ are each independently hydrogen or R ⁹ —CO— (wherein R ⁹ is an alkyl group). ]

(Iv) A method of saponifying a copolymer of a vinyl ester monomer and glycerol monoallyl ether is preferably used.
Hereinafter, the methods (i), (ii), (iii) and (iv) will be described.

[Method (i)]
Examples of vinyl ester monomers used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, benzoate. Vinyl acid, vinyl versatate and the like can be mentioned, but vinyl acetate is preferably used from the economical viewpoint.

The vinyl ethylene carbonate is not particularly limited as long as it has a structure represented by the general formula (2). In the general formula (2), R ¹ , R ² and R ³ are the same as those in the general formula (1). The same thing is mentioned. Among these, vinyl ethylene carbonate in which R ¹ , R ² , and R ³ are hydrogen is preferable because it is easily available and has good copolymerizability.

In copolymerizing such a vinyl ester monomer and vinyl ethylene carbonate, known methods such as bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization, or emulsion polymerization can be employed. Is done.
The method for charging the monomer component at the time of polymerization is not particularly limited, and any method such as batch charging, split charging, continuous charging, etc. can be adopted, but vinyl ethylene carbonate is uniformly distributed in the molecular chain of the polyvinyl ester polymer. In view of the above, drop polymerization is preferred, and a polymerization method based on the HANNA method [reactivity ratio: r (vinyl ethylene carbonate) = 5.4, r (vinyl acetate) = 0.85] is particularly preferred.

Examples of the solvent used for such polymerization include lower alcohols such as methanol, ethanol, propanol and butanol, and ketones such as acetone and methyl ethyl ketone. Methanol is preferably used from an economical viewpoint.
The amount of the solvent used may be appropriately selected in consideration of the chain transfer constant of the solvent in accordance with the degree of polymerization of the target copolymer. For example, when the solvent is methanol, S (solvent) / M ( Monomer) = 0.01 to 10 (weight ratio), preferably 0.05 to 3 (weight ratio).

For the copolymerization, a polymerization catalyst is used. Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauryl peroxide, azobisdimethylvaleronitrile, azo Examples include low-temperature active radical polymerization catalysts such as bismethoxydimethylvaleronitrile, and the amount of the polymerization catalyst used varies depending on the polymerization catalyst and is not generally determined, but is arbitrarily selected according to the polymerization rate. For example, when azobisisobutyronitrile or acetyl peroxide is used, 0.01 to 0.2 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0.15 mol% is particularly preferable.
Further, the reaction temperature of the copolymerization reaction is preferably 40 ° C to 200 ° C, more preferably 40 ° C to 180 ° C, and particularly preferably about 40 ° C to 72 ° C.

  In the present invention, the content of vinyl ethylene carbonate is not particularly limited, but is preferably 0.1 to 20 mol% (more preferably 0.5 to 15 mol%, particularly 1 to 10 mol%), and such If the content of vinyl ethylene carbonate is less than 0.1 mol%, the effect of modification is not recognized so much. Conversely, if the content exceeds 20 mol%, the degree of polymerization cannot be increased or the polymerization rate is decreased. It is not preferable.

The copolymer of vinyl ester monomer and vinyl ethylene carbonate thus obtained is then saponified and decarboxylated.
In the saponification, the copolymer is dissolved in an alcohol or a hydrous alcohol, and an alkali catalyst or an acid catalyst is used. Examples of the alcohol include methanol, ethanol, propanol, tert-butanol and the like, and methanol is particularly preferably used. The concentration of the copolymer in the alcohol is appropriately selected depending on the viscosity of the system, but is usually selected from the range of 10 to 60% by weight. Catalysts used for saponification include alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, lithium methylate, etc., sulfuric acid, Examples include acid catalysts such as hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin.

The amount of the saponification catalyst used is appropriately selected depending on the saponification method, the target degree of saponification, and the like. When an alkali catalyst is used, it is usually 0.05 to 1 mol per 1 mol of the vinyl ester monomer. A proportion of 30 mmol, preferably 0.5-15 mmol, is suitable.
Moreover, although the reaction temperature of saponification reaction is not specifically limited, 10-60 degreeC is preferable, More preferably, it is 20-50 degreeC.

As for decarboxylation, usually, without any special treatment after saponification, decarboxylation is performed together with the saponification under the above saponification conditions, and the ethylene carbonate ring is opened to form a 1,2-diol component. Converted.
Thus, a PVA resin having a 1,2-diol component in the side chain is obtained.
In addition, decarboxylation can be performed without saponifying the vinyl ester moiety under a constant pressure (normal pressure to 100 kg / cm ² ) and at a high temperature (50 to 200 ° C.). The above saponification can also be carried out after the above.

[Method (ii)]
The 2,2-dialkyl-4-vinyl-1,3-dioxolane used in the present invention is not particularly limited as long as it has a structure represented by the general formula (3). In the general formula (3), , R ¹ , R ² , and R ³ are the same as those in the general formula (1), and R ⁵ and R ⁶ are each independently hydrogen or an alkyl group, and the alkyl group is not particularly limited. For example, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group is preferable. Such an alkyl group may have a substituent such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, if necessary. Among them, 2,2-dimethyl-4-vinyl-1, in which R ¹ , R ² and R ³ are hydrogen and R ⁵ and R ⁶ are methyl groups in terms of easy availability and good copolymerizability. 3-dioxolane is preferred.

  The copolymerization of the vinyl ester monomer and 2,2-dialkyl-4-vinyl-1,3-dioxolane is carried out in the same manner as in the above method (i).

  In the present invention, the content of 2,2-dialkyl-4-vinyl-1,3-dioxolane is not particularly limited, but it is preferably 0.1 to 20 mol% for the same reason as in (i) above. More preferably, it is 0.5-15 mol%, Most preferably, it is 1-10 mol%.

The copolymer of the vinyl ester monomer thus obtained and 2,2-dialkyl-4-vinyl-1,3-dioxolane is then saponified and deketalized.
The saponification is performed in the same manner as the method (i) above.

Regarding the deketalization of the saponification product of the copolymer, when the saponification is carried out using an alkali catalyst, after saponification, an aqueous solvent (water, water / acetone, water / Deketalization is performed in a mixed solvent of lower alcohol such as methanol) and the like, and converted into a 1,2-diol component. Examples of the acid catalyst used for deketalization include acetic acid, hydrochloric acid, sulfuric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin.
When the saponification is carried out using an acid catalyst, the deketalization is usually carried out together with the saponification under the above saponification conditions without any special treatment after saponification. Converted to diol component.

[Method (iii)]
In the compound represented by the general formula (4) used in the present invention, examples of R ¹ , R ² and R ³ are the same as those in the general formula (1), and R ⁴ has a single bond or an alkyl group. R ⁷ and R ⁸ are each independently hydrogen or R ⁹ —CO— (wherein R ⁹ is an alkyl group, preferably a methyl group, A propyl group, a butyl group, a hexyl group or an octyl group, and the alkyl group may optionally have a substituent such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group) It is.
Examples of the compound represented by the formula (4) include 3,4-dihydroxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-hydroxy-1-butene, and 4-acyloxy-3-hydroxy. -1-butene, 3,4-diasiloxy-2-methyl-1-butene, 4,5-dihydroxy-1-pentene, 4,5-diasiloxy-1-pentene, 4,5-dihydroxy-3-methyl-1 -Pentene, 4,5-diacyloxy-3-methyl-1-pentene, 5,6-dihydroxy-1-hexene, 5,6-diacyloxy-1-hexene and the like. Among them, R ¹ , R ² and R ³ are hydrogen, R ⁴ is a single bond, R ⁷ and R ⁸ are R ⁹ —CO—, and R ⁹ is excellent in copolymerization reactivity and industrial handling. 3,4-diacyloxy-1-butene in which is an alkyl group is preferable, and 3,4-diacetoxy-1-butene in which R ⁹ is a methyl group is particularly preferable.
For 3,4-diacetoxy-1-butene, products of Eastman Chemical Co. and Acros Co. can be obtained from the market.

  The copolymerization of the vinyl ester monomer and the compound represented by the formula (4) is carried out in the same manner as the above method (i).

  In the present invention, the content of the compound represented by the formula (4) is not particularly limited, but it is preferably 0.1 to 20 mol% for the same reason as the above (i), more preferably 0.5. It is -15 mol%, Most preferably, it is 1-10 mol%.

The copolymer of the vinyl monomer thus obtained and the compound represented by the formula (4) is then saponified.
The saponification is performed in the same manner as the method (i) above.
The amount of the saponification catalyst used is appropriately selected depending on the saponification method, the target degree of saponification, and the like. When an alkali catalyst is used, the vinyl ester monomer and the compound represented by the formula (4) are usually used. Is used in a proportion of 0.1 to 30 mmol, preferably 2 to 17 mmol, per 1 mol of the total amount.
A PVA resin (A) containing a 1,2-diol component in the side chain obtained by saponifying a copolymer of a vinyl ester monomer and a compound represented by formula (4) Since it is produced by simultaneously converting the ester part of the monomer and the acyloxy part of the compound represented by the formula (4) into a hydroxyl group, a by-product such as dimethyl carbonate, which is a disadvantage when using vinyl ethylene carbonate, is not generated. It has the characteristics.

[Method (iv)]
In the above method (i), it can be obtained by using glycerin monoallyl ether in place of vinyl ethylene carbonate. As a method for charging the monomer component at the time of polymerization, batch charging, divided charging, continuous charging, etc. Is preferably employed, and dropping polymerization can also be performed.
In the present invention, the content of glycerin monoallyl ether is not particularly limited, but it is preferably 0.1 to 20 mol% for the same reason as (i) above, and more preferably 0.5 to 15 mol%. Especially preferably, it is 1-10 mol%.
The amount of the polymerization catalyst used is preferably 0.05 to 0.7 mol% with respect to the vinyl ester monomer, especially when azobisisobutyrotitryl or acetyl peroxide is used. It is preferable to set it as 1-0.5 mol%. In addition, when glycerol monoallyl ether is used as a copolymerization monomer, the PVA-type resin (A) containing the 1, 2- diol component can be obtained without decarboxylation naturally.

  In the PVA resin (A) used in the present invention, other unsaturated monomers can be copolymerized as a copolymerizable component as long as the object of the present invention is not impaired. Examples of the unsaturated monomer include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-olefins such as α-octadecene, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride , Unsaturated acids such as itaconic acid or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as diacetone acrylamide, acrylamide and methacrylamide, ethylene sulfonic acid, allyl sulfonic acid, methallyl Olefin sulfonic acids such as sulfonic acids or their salts, alkyl vinyl ethers, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxyp Polyoxyalkylene (meth) allyl ether such as pyrene (meth) allyl ether, polyoxyalkylene (meth) acrylate such as polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, Polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene Examples include allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

  Further, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidopropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 2-hydroxy-3- Cationic group-containing monomers such as methacryloyloxypropyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, 3-butenetrimethylammonium chloride, dimethyldiallylammonium chloride, diethyldiallylammonium chloride, acetoacetyl group-containing monomers And so on. In addition, by setting the polymerization temperature to 100 ° C. or higher, it is possible to use a product in which 1,2-diol is introduced into the PVA main chain.

  The content of the 1,2-diol component present in the side chain of the PVA resin (A) thus obtained is not particularly limited, but is preferably 0.1 to 20 mol%, more preferably 0.5 to 15 mol%, particularly preferably 1 to 10 mol%. When the content of the 1,2-diol component is less than 0.1 mol%, the effect of modification is not recognized so much. Conversely, when the content exceeds 20 mol%, the degree of polymerization of the PVA resin hardly increases. Or the polymerization rate is lowered, which is industrially disadvantageous, which is not preferable.

  The average degree of polymerization (measured in accordance with JIS K6726) of the PVA resin (A) of the present invention is preferably 300 to 4000 (more preferably 300 to 3500, particularly 300 to 3000), and the average degree of polymerization is 300. If the ratio is less than 4,000, the strength of the gel is insufficient. On the other hand, if it exceeds 4,000, the viscosity is too high, and the stirring and mixing properties during the production of the gel are lowered, and the productivity is lowered.

  Further, the saponification degree of the PVA-based resin (A) is 70 mol% or more (more preferably 78 mol% or more, particularly 88 mol% or more, and if the saponification degree is less than 70 mol%, it is water-soluble. Is not preferable because it is difficult to produce a gel.

Next, the waterproofing agent (B) will be described.
The water-proofing agent used in the present invention (B), aldehydes compound, a boron compound is a low-cost, preferred in terms of strength of the resulting gel is high, more is more preferably a water-soluble compound .

  Examples of the aldehyde compound include formaldehyde, acetaldehyde, glutaraldehyde, benzaldehyde, terephthalaldehyde, succinaldehyde, nonane dial, malondialdehyde, adipine aldehyde and the like. From the viewpoint of high, formaldehyde and glutaraldehyde are preferably used.

  Examples of the boron compound include boric acid, sodium borate, borax, calcium borate, magnesium borate, etc. Among them, boric acid and borax are preferably used in terms of cost.

Next, the manufacturing method of the PVA-type water-containing gel of this invention is demonstrated.
Method for producing the PVA hydrogel of the present invention, a mixed aqueous solution containing P VA resin (A) and the water-soluble polycarboxylate (C), is contacted with an aqueous solution containing polyvalent metal ions (D) after the gel-like molding, waterproofing agent by (B) to crosslink the PVA-based resin (a), the are needed use is how to impart water resistance.

Examples of the water-soluble polycarboxylate (C) used in the above method include poly (meth) acrylic acid, polyitaconic acid, polyfumaric acid, polymaleic acid, poly (p-styrenecarboxylic acid), and styrene / maleic acid copolymer. and a modified product thereof, polyaspartic acid, polyglutamic acid, polylysine, synthetic polymers such as polymalic acid, alginic acid, pectic acid, and salts of natural polymer multi etc., etc., such as carboxymethyl cellulose row scan, especially sodium alginate Preferably used.

  Moreover, as polyvalent metal ions (D), alkaline earth metal ions such as magnesium ions, calcium ions, strontium ions and barium ions, transition metal ions such as aluminum ions, nickel ions and zirconium ions, cerium ions and the like And rare earth metal ions, among which calcium ions and magnesium ions are preferably used.

It will be described in detail above Symbol methods below.
In producing the PVA-based hydrogel, first, a mixed aqueous solution of the PVA-based resin (A) and the water-soluble polycarboxylate (C) is prepared, but the mixing ratio of both in the mixed aqueous solution is not particularly limited. However, (C / A) is preferably 1/100 to 100/100 (weight ratio), more preferably 2/100 to 50/100, and particularly preferably 3/100 to 30/100. In such a mixing ratio (C / A), if the blending amount of the water-soluble polycarboxylate (C) exceeds 100/100, the gel strength decreases, or conversely, the blending of the water-soluble polycarboxylate (C). When the amount is less than 1/100, the gel moldability is lowered or the gel strength is lowered, which is not preferable.

  The concentration of the mixed aqueous solution containing the PVA resin (A) and the water-soluble carboxylate (C) is preferably 3 to 30% by weight, more preferably 5 to 25% by weight, particularly 7 to It is preferably 20% by weight. If the concentration exceeds 30% by weight, the viscosity may become high and handling of the aqueous solution may be difficult.

  Next, by bringing the mixed aqueous solution of the PVA resin (A) and the water-soluble carboxylate (C) obtained as described above into contact with an aqueous solution containing a polyvalent metal ion (D), gel-like molding is performed. A desired gel shape can be obtained by such a contact method.

  For example, when obtaining a spherical gel-like molded product, a mixed aqueous solution of a PVA resin (A) and a water-soluble carboxylate (C) is transferred from a tubular die to an aqueous solution surface containing a polyvalent metal ion (D). The droplets of the mixed aqueous solution are formed by dropping or extruding into the liquid, and this instantaneously gels upon contact with the polyvalent metal ion (D) to obtain a spherical shaped product. The particle size of the spherical molded product can be controlled by the concentration of the mixed aqueous solution, the viscosity, the discharge speed, the diameter of the die, and the like.

  In the case of a fibrous molded product, a mixed aqueous solution of PVA resin (A) and water-soluble carboxylate (C) is continuously discharged from a tubular die into an aqueous solution containing polyvalent metal ions (D). And after this gelatinizes, a fibrous molding is obtained by winding up continuously. As in the case of the spherical molded product, the thickness of the fibrous molded product can be controlled by the concentration of the mixed aqueous solution, the viscosity, the discharge speed, the diameter of the die, and the winding speed.

  In addition to these shapes, the shape of a rectangular parallelepiped, cubic, hollow fiber, film, etc. can be controlled by controlling the shape of the die that discharges the mixed aqueous solution of the PVA resin (A) and the water-soluble carboxylate (C). It is also possible to do.

The concentration of the polyvalent metal ion (D) -containing aqueous solution used above is preferably 1% by weight or more. If the concentration is less than 1%, sufficient gel forming ability cannot be obtained, which is not preferable. Moreover, the upper limit is not specifically limited, A saturated aqueous solution may be used.
Moreover, there is no restriction | limiting in particular in the temperature at the time of making this mixed aqueous solution contact polyvalent metal ion (D) containing aqueous solution, but it is about 10-50 degreeC normally.

  Next, the PVA water-containing gel of the present invention is obtained by allowing the water-resistant agent (B) to act on the gel-like product thus obtained. Although the water-resistant treatment method by the water-resistant agent (B) in the present invention is not particularly limited, it is usually carried out by bringing the gel-shaped product into contact with an aqueous reaction solution containing the water-resistant agent (B).

  When an aldehyde compound is used as the water-proofing agent (B), it is preferable to use an acid catalyst in combination in order to utilize the PVA acetalization reaction. Examples of such acids include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and organic acids such as acetic acid, trichloroacetic acid, oxalic acid, formic acid, maleic acid, and paratoluenesulfonic acid. Some sulfuric acid and hydrochloric acid are preferred. In addition, it is also preferable to add a sulfate such as sodium sulfate or ammonium sulfate to the reaction solution for the purpose of suppressing gel swelling.

  The rate and the degree of acetalization of the acetalization reaction can be controlled by the concentration of the aldehyde compound, the strength and concentration of the acid, the reaction temperature, the reaction time, and the like. The concentration of the aldehyde compound in the reaction solution is preferably 0.01 to 20% by weight, more preferably 0.1 to 15% by weight, and particularly preferably 1 to 10% by weight. If the concentration is less than 0.01% by weight, the strength of the obtained hydrogel may be reduced, or the degree of swelling may be too high. Since it is not, it is not preferable. The acid concentration is preferably 0.1 to 15% by weight, more preferably 0.5 to 10% by weight, and particularly preferably 1 to 10% by weight. If the concentration is less than 0.1% by weight, sufficient gel strength cannot be obtained, and if it exceeds 15% by weight, there is no particular effect, which is not preferable. The temperature of the reaction solution is preferably 20 to 80 ° C., and the reaction time is not particularly limited. The degree of acetalization is preferably 10 to 80 mol%, more preferably 10 to 70 mol%, and particularly preferably 20 to 60%. When the degree of acetalization is less than 10 mol%, the gel strength is reduced or the temperature sensitivity before and after the phase transition temperature becomes insensitive, and when it exceeds 80%, the volume change rate of the gel becomes slow, This is not preferable because the difference in the amount of adsorption of organic substances and other substances is not recognized.

  Moreover, also when using a boric acid compound as this water-proofing agent (B), the reaction rate and the elasticity, strength, durability, etc. of the obtained PVA water-containing gel are the concentration and temperature of the boric acid compound in the reaction solution. The reaction time can be controlled. Usually, the concentration of the boric acid compound in the reaction solution is preferably 0.1% by weight or more, and may be a saturated aqueous solution. If the concentration is less than 0.1% by weight, the gel strength is insufficient, such being undesirable. Moreover, it is also possible to add an alkaline substance to this reaction liquid and to adjust pH, and the preferable pH range in this case is 5-12. The temperature of the reaction solution is preferably 2 to 50 ° C., and the reaction time is preferably 5 to 300 minutes.

  After the water resistance treatment, the PVA water-containing gel of the present invention can be obtained by removing acid, aldehyde compound or boric acid compound contained in the product by washing or the like. Such PVA water-containing gel is a reinforcement selected from inorganic fillers or organic fillers in a range that does not inhibit gelation by contact with the polyvalent metal ion (D) or water resistance by reaction with the water-resistant agent (B). A material, a filler for adjusting specific gravity, a biocatalyst, a biocatalyst protective agent, a water-soluble substance such as starch or polysaccharide may be contained. These additives are preferably added to a mixed aqueous solution of the PVA resin (A) and the water-soluble polycarboxylate (C).

  The thus obtained PVA water-containing gel of the present invention shows temperature dependency in the water content in an aqueous medium and the adsorption amount of organic matter or metal ions. That is, the moisture content is low in the temperature region higher than the phase transition temperature, and the adsorption amount of organic matter or metal ions is large. Conversely, in the region lower than the phase transition temperature, the moisture content is high and the adsorption amount is small. Therefore, it is possible to efficiently adsorb these removal objects by bringing the PVA-based hydrogel into contact with a treatment object liquid containing organic substances or metal ions to be removed in a temperature range higher than its phase transition temperature. is there. In addition, since the PVA resin (A) containing a 1,2-diol component in the side chain used in the present invention has a primary hydroxyl group in the PVA molecule, compared to a PVA composed of a normal secondary hydroxyl group, It may be possible to arbitrarily shift the phase transition temperature to the high temperature side depending on the content of the 1,2-diol component, probably because hydrogen bonds with water molecules become stronger.

  Organic substances to be removed include organic halogen compounds such as trichloroethylene, dichloroethane, dichloromethane, tribromoethylene, dibromoethane, dibromomethane, and dioxin, and aromatics such as benzene, chlorobenzene, toluene, xylene, parachlorophenol, and orthochlorophenol. Compounds. Examples of metal ions include heavy metal ions such as chromium, copper, iron, zinc, and lead, and metalloid ions such as boron, selenium, and germanium.

  In addition, the PVA hydrogel of the present invention has a high moisture content and excellent strength, so that it can be used for agricultural and horticultural water retention materials, cryogens, biomaterials such as vitreous bodies and artificial joints, contact lenses, drug delivery systems, wounds, etc. It can also be applied to medical materials such as coating materials, separation membranes (separation of azeotropic solvents such as benzene / hexane, isolation of natural antioxidants), microbial carriers and the like.

Hereinafter, the present invention will be specifically described with reference to examples.
In the examples, “%” means weight basis unless otherwise specified.

Production Example 1: PVA resin (A1)
A reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer was charged with 1300 g of vinyl acetate, 190 g of methanol, and 60.5 g of 3,4-diacetoxy-1-butene (2.28 mol%), and azobisisobutyro Nitrile was added in an amount of 0.06 mol% (compared with vinyl acetate), the temperature was increased under a nitrogen stream while stirring, and polymerization was started at 67 ° C., and at the same time, 5.4 of 3,4-diacetoxy-1-butene was added. % Methanol solution was uniformly added dropwise, and 116 ml was charged to a polymerization rate of 85.3%.
When the polymerization rate of vinyl acetate reached 85.3%, the polymerization was terminated. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing methanol vapor to obtain a methanol solution of the copolymer. It was.
The solution was then diluted with methanol to a concentration of 40% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to vinyl acetate and 3,4 in the copolymer. Saponification was carried out by adding 9 mmol per 1 mol of the total amount of diacetoxy-1-butene. When saponification progressed and saponified product was precipitated and became particulate, it was separated by filtration, washed well with methanol and dried in a hot air dryer to obtain PVA resin (A1).

The saponification degree of the obtained PVA-based resin (A1) was 99.6 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate and 3,4-diacetoxy-1-butene. The average degree of polymerization was 1320 when analyzed according to JIS K 6726. Further, the viscosity of a 4% aqueous solution of the polyvinyl alcohol was 18.7 mPa · s (20 ° C.) as measured with a Heppler viscometer, and the content of 1,2-diol structural unit was measured by ¹ H-NMR. As a result, it was 3.2 mol%. For NMR measurement, “AVANCE DPX400” manufactured by Nippon Bruker Co., Ltd. was used.

[ ¹ H-NMR]
Assignment of ¹ H-NMR (internal standard substance: tetramethylsilane, solvent: d6-DMSO) spectrum of the obtained PVA resin (A1) is as follows.
1.2 to 1.5 ppm: methylene proton, 1.8 ppm: methine proton (due to modified species), 3.5 ppm: methylene proton of primary methylol, 3.82 to 3.84 ppm: methine proton, 4.13 to 4.6 ppm: hydroxyl group, 4.25 ppm: diol hydroxyl group

Production Example 2: PVA resin (A2)
In Production Example 1, a sample was extracted during saponification to obtain a PVA resin (A2) [partially saponified product (saponification degree: 88.0 mol%). Assignment of the ¹ H-NMR spectrum of the PVA resin (A2) is as follows.

[ ¹ H-NMR]
1.36 to 1.8 ppm: methylene proton, 1.93 to 1.95 ppm: methyl proton, 3.5 ppm: methylene proton of primary methylol, 3.8 ppm: methine proton, 4.15 to 4.57 ppm: hydroxyl group, 4.3 ppm: hydroxyl group of diol

Production Example 3: PVA resin (A3)
In Production Example 1, the amount of 3,4-diacetoxy-1-butene charged was 15 mol%, the end of polymerization was set to a point when the polymerization rate of vinyl acetate reached 70%, and sodium hydroxide at the time of saponification was 2%. The PVA resin (A3) was prepared in the same manner as in Production Example 1 except that the amount of methanol solution added was 11 mmol per 1 mol of the total amount of vinyl acetate and 3,4-diacetoxy-1-butene in the copolymer. )

  The obtained PVA resin (A3) had a saponification degree of 99.2 mol% and an average polymerization degree of 900. The viscosity of a 4% aqueous solution of the polyvinyl alcohol was 9.5 mPa · s (20 ° C.), and the content of 1,2-diol structural units was 14.9 mol%.

Production Example 4: PVA resin (A4)
Using the same method as in Production Example 1, the saponification degree was 99.4 mol%, the average polymerization degree was 500, the 4% aqueous solution viscosity was 6.0 mPa · s (20 ° C.), 1,2- A PVA resin (A4) having a diol structural unit content of 3.3 mol% was obtained.

Production Example 5: PVA resin (A5)
In a reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer, 1300 g of vinyl acetate, 190 g of methanol, and 40.1 g (2.28 of R ¹ , R ² , and R ³ are all hydrogen). The azobisisobutyronitrile was charged in 0.06 mol% (with respect to the charged vinyl acetate monomer), and the temperature was increased under a nitrogen stream while stirring. Charge of a 10.17% methanol solution of ethylene carbonate was started according to the HANNA method, and 116 ml was charged to a polymerization rate of 85.3%.
It should be noted that the formula of HANNA [reactivity ratio of vinyl ethylene carbonate (r) = 5.4, reactivity ratio of vinyl acetate (r) = 0.85] so that vinyl ethylene carbonate is uniformly polymerized with vinyl acetate. Was charged in accordance with the polymerization rate.
When the polymerization rate of vinyl acetate reached 85.3%, the polymerization was terminated. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing methanol vapor to obtain a methanol solution of the copolymer. It was.
Next, the solution was diluted with methanol to a concentration of 30% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to 1 mol of vinyl acetate in the copolymer. Saponification and decarboxylation were carried out at a ratio of 9 mmol. As saponification and decarboxylation proceeded, saponified substances were precipitated and finally became particles. The produced PVA resin (A5) was filtered off, washed thoroughly with methanol and dried in a hot air dryer to obtain the desired product.

  The obtained PVA resin (A5) had a saponification degree of 99.6 mol% and a polymerization degree of 1360. The viscosity of the 4% aqueous solution was 18.5 mPa · s (20 ° C.), and the content of 1,2-diol structural units was 3.1 mol%.

Assignment of ¹ H-NMR spectrum of the obtained PVA resin (A5) is as follows.
[ ¹ H-NMR]
1.376 to 1.538 ppm: methylene proton, 3.528 ppm: methylene proton of primary methylol, 3.849 ppm: methine proton, 4.139 to 4.668 ppm: hydroxyl group

Production Example 6: PVA resin (A6)
To a reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer, 1000 g of vinyl acetate, 100 g of methanol, 2,2-dimethyl-4-vinyl-1,3-dioxolane (R ¹ , R ² , R ³ are all Hydrogen, R ⁴ , and R ⁵ are all methyl groups.) 14.9 g (1 mol%) was charged, and azobisisobutyronitrile (0.045 mol% (compared with vinyl acetate) was charged) and stirred. While increasing the temperature under a nitrogen stream, polymerization was started at 68 ° C. When the polymerization rate of vinyl acetate reached 90%, the polymerization was terminated. Subsequently, unreacted vinyl acetate monomer was removed out of the system by blowing methanol vapor to obtain a methanol solution of the copolymer.
Next, the solution was diluted with methanol and adjusted to a concentration of 30% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to 1 mol of vinyl acetate in the copolymer. Saponification was carried out at a rate of 9 mmol. Saponification progressed as saponification progressed, and finally became particulate. This saponified product is dispersed in 3N hydrochloric acid (water / methanol = 1/1 mixed solvent), deketalized at 60 ° C., and the resulting PVA resin (A6) is filtered off and washed thoroughly with methanol. And it dried in the hot air dryer, and obtained the target object.

  The obtained PVA resin (A6) had a saponification degree of 99.3 mol% and an average polymerization degree of 1110. The viscosity of the 4% aqueous solution was 13.0 mPa · s (20 ° C.), and the content of 1,2-diol structural units was 0.9 mol%.

Assignment of ¹ H-NMR spectrum of the obtained PVA resin (A6) is as follows.
[ ¹ H-NMR]
1.25 ppm: methyl proton (dimethyl ketal methyl), 1.31-1.33 ppm: methyl proton (dimethyl ketal methyl), 1.38-1.66 ppm: methylene proton, 1.87-1.99 ppm : Methyl proton, 3.84 to 3.91 ppm: methine proton, 4.14 to 4.55 ppm: hydroxyl group

Production Example 7: PVA resin (A7)
A reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer was charged with 1300 g of vinyl acetate, 520 g of methanol, and 39.9 g (2 mol%) of glycerol monoallyl ether, and 0.07 mol% of azobisisobutyronitrile. (Various charged vinyl acetate monomer) was charged, and polymerization was carried out by raising the temperature under a nitrogen stream while stirring. 2 hours after the start of polymerization, 0.05 mol% of the polymerization initiator was added, 0.05 mol% after 5.1 hours, and 0.05 mol% after 6 hours. The chain transfer constant of glycerin monoallyl ether is 0.017. When the polymerization rate of vinyl acetate reached 70%, the polymerization was terminated. Subsequently, unreacted vinyl acetate monomer was removed out of the system by blowing methanol vapor to obtain a methanol solution of the copolymer.
Next, the solution was diluted with methanol to a concentration of 40% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to 1 mol of vinyl acetate in the copolymer. Saponification was carried out at a rate of 9 mmol. Saponification progressed as saponification progressed, and finally became particulate. The saponified product was separated by filtration, washed well with methanol, and dried in a hot air dryer to obtain a PVA resin (A7).

  The saponification degree of the obtained PVA resin (A7) was 99.2 mol%, and the polymerization degree was 860. The viscosity of the 4% aqueous solution was 9.2 mPa · s (20 ° C.), and the content of 1,2-diol structural units was 1.7 mol%.

Assignment of ¹ H-NMR spectrum of the obtained PVA resin (A7) is as follows.
[ ¹ H-NMR]
1.363 to 1.508 ppm: methylene proton, 1.8 to 2.0 ppm: methyl proton of residual acetyl group, 3.826 ppm: methine proton, 3.98 to 4 ppm: hydroxyl group derived from 1,2-diol; 140-4.568 ppm: hydroxyl group

Production Example 8: PVA resin (A8)
The same as in Production Example 1, except that 3,4-diacetoxy-1-butene was not charged and only vinyl acetate was polymerized (S / M = 0.5, S: methanol, M: vinyl acetate) and saponified. To obtain a PVA resin (A8). The saponification degree of the obtained PVA-based resin (A8) was 99.5 mol% when analyzed by the alkali consumption required for hydrolysis of the remaining vinyl acetate units, and the polymerization degree was JIS K 6726. According to the same analysis, it was 1200. The viscosity of a 4% aqueous solution of the PVA resin (A8) was 15 mPa · s (20 ° C.) as measured with a Heppler viscometer.

Example 1
An aqueous solution containing 2% PVA-based resin (A1) and 0.2% sodium alginate (C) is dropped into a 3% aqueous solution of calcium chloride (D) from the tip of a syringe having a diameter of 2 mm to form a spherical gel A molded product was obtained. The gel-like molded product was put into an aqueous solution adjusted to 60 ° C. containing 4% formaldehyde (B), 7% sulfuric acid and 13% sodium sulfate, and reacted for 1 hour with stirring. The spherical gel was separated by filtration and washed with ion-exchanged water until the washing solution became neutral to obtain a PVA hydrous gel having a diameter of 4 mm.
The following evaluation was performed using the obtained PVA water-containing gel. The results are shown in Table 1.

[Phase transition temperature]
Chemical Engineering, Vol. 27, No. 6, p. Based on the method described in 786-791 (2001), put the obtained PVA hydrogel in water kept at 1 ° C. in a thermostatic bath, and determine the volume of the PVA hydrogel at each temperature while raising the temperature, The temperature at which the volume shrinkage of the gel was completed was defined as the phase transition temperature.

[Amount of organic matter adsorption]
Chemical Engineering, Vol. 27, No. 6, p. 1 in a thermostat adjusted to 55 ° C., which is higher than the phase transition temperature of the PVA water-containing gel, about 0.23 g of PVA water-containing gel by dry weight based on the method described in 786-791 (2001). , 2-dichloroethane aqueous solution (concentration 200 ppm, 100 cm ³ ), shaken at a shaking speed of 150 spm for 1 hour, and then the concentration of 1,2-dichloroethane in the aqueous solution is shown in a capillary gas chromatogram (GC-17A, manufactured by Shimadzu Corporation). The amount of adsorbed q ₅₅ (mmol / g-gel) of 1,2-dichloroethane per gram of PVA water-containing gel was determined from the material balance before and after.
Such an operation is also performed at 25 ° C., which is lower than the phase transition temperature of the PVA-based hydrogel, and the adsorption amount q ₂₅ (mmol / g-gel) of 1,2-dichloroethane at 25 ° C. is obtained. The difference in adsorption amount dq (mmol / g-gel) was determined from the following equation (5).
dq = q ₅₅ −q ₂₅ (5)

Examples 2-7
In Example 1, PVA-type water-containing gel was similarly obtained except having used PVA-type resin (A2-A7) by manufacture example 2-7 as PVA-type resin (A), and evaluated similarly. The results are shown in Table 1.

Example 8
In Example 1, PVA water-containing gel was obtained in the same manner as in Example 1 except that sodium polyacrylate (C) was used instead of sodium alginate (C), and evaluation was performed in the same manner. The results are shown in Table 1.

Example 9
In Example 1, a PVA water-containing gel was obtained in the same manner as in Example 1 except that a magnesium chloride aqueous solution (D) was used instead of the calcium chloride (D) aqueous solution, and evaluation was performed in the same manner. The results are shown in Table 1.

Example 10
In Example 1, a PVA water-containing gel was obtained in the same manner as in Example 1 except that an aqueous solution containing 1% boric acid and 3% calcium chloride was used as the water-proofing agent (B) and evaluated in the same manner. . The results are shown in Table 1.

Comparative Example 1
In Example 1, a PVA water-containing gel was obtained in the same manner except that the PVA resin (A8) according to Production Example 8 was used as the PVA resin (A), and evaluation was performed in the same manner. The results are shown in Table 1.

The PVA water-containing gel of the present invention has a large difference in adsorption amount before and after the phase transition temperature, and the phase transition temperature can be arbitrarily shifted to the high temperature side according to the content of 1,2-diol structural units. In particular, it is particularly useful as a PVA water-containing gel used for removing organic substances and heavy metals from a liquid to be treated in which organic substances and heavy metals are dissolved.
In addition, the PVA water-containing gel of the present invention includes agricultural and horticultural water retaining materials, cryogens, biomaterials such as vitreous bodies and artificial joints, medical materials such as contact lenses, drug delivery systems, and wound dressings, separation membranes (benzene / It is also useful for separation of azeotropic solvents such as hexane, isolation of natural antioxidants, and microbial carriers.

Claims (6)

A mixed aqueous solution containing a polyvinyl alcohol resin (A) containing a 1,2-diol component in the side chain and a water-soluble polycarboxylate (C) is brought into contact with an aqueous solution containing a polyvalent metal ion (D). A polyvinyl alcohol-based water-containing gel obtained by reacting a gel-like molded product obtained with a water resistance agent (B) selected from an aldehyde compound and a boron compound . The polyvinyl alcohol-based hydrogel according to claim 1, wherein the polyvinyl alcohol-based resin (A) contains a 1,2-diol structural unit represented by the general formula (1).

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an alkyl group, and R ⁴ represents a C 1-3 alkylene group which may have a single bond or an alkyl group. N is 0 or a positive integer] The polyvinyl alcohol-based hydrogel according to claim 1 or 2, wherein the content of the 1,2-diol structural unit in the polyvinyl alcohol-based resin (A) is 0.1 to 20 mol%. Water-soluble polycarboxylate (C) is a polyvinyl alcohol-based water gel of claim 1 wherein the alginic acid salt. An adsorption separation agent comprising the polyvinyl alcohol-based hydrogel according to any one of claims 1 to 4 . An adsorptive separation method comprising adsorbing and separating an object to be adsorbed in the adsorption separation agent according to claim 5 in a temperature range higher than a phase transition temperature thereof.