JP7014485B2 - Polyvinyl alcohol-based mutual penetration type gel - Google Patents

Description

The present invention relates to a high-strength polyvinyl alcohol-based interpenetrating gel that cures with a specific stimulus.

Polyvinyl alcohol is a water-soluble synthetic polymer having excellent features such as biodegradability, biocompatibility, and low toxicity. The hydrogel material made of polyvinyl alcohol is a material made of polyvinyl alcohol and water crosslinked by various methods, and is a contact lens (for example, Patent Document 1), a medical device coating (for example, Patent Document 2), and an organ model (for example, Patent Document). 3), artificial spinal disc nucleus (for example, Patent Document 4), ground improving material (for example, Patent Document 5), etc. are used for various purposes.

In recent years, the development of material modeling methods called Additive Manufacturing Technology represented by 3D printers has become active, and the demand for hydrogel materials adapted to these has been increasing. For example, in the medical field, attempts have been made to manufacture an organ model used for surgical practice and the like and a precision scaffold for regenerative medicine (for example, Non-Patent Document 1) using a 3D printer.

Here, in order to apply the polyvinyl alcohol hydrogel material to additional manufacturing technology such as 3D printers, stimulus curability (hereinafter, also abbreviated as "stimulus curability") such that it is rapidly cured by stimuli such as light and heat is required. Desired.
The most classic method for producing a hydrogel of polyvinyl alcohol is the freeze-thaw method, but this method has a problem that it cannot be applied to a 3D printer because it does not have stimulatory curability and has low heat resistance. Therefore, as a polyvinyl alcohol hydrogel that can be crosslinked by light or heat, polyvinyl alcohol macromer pendant with a polymerizable group has been proposed (Patent Documents 1, 2, and 4).

On the other hand, in order to expand the applications of hydrogel materials, it is also desired to improve their mechanical strength. As a method for improving the mechanical strength of a hydrogel material, a mutual penetration type gel in which a network structure of two types of water-soluble polymers penetrates into each other has been proposed (for example, Patent Document 6). In Patent Document 6, the first monomer is polymerized together with a cross-linking agent to obtain a first polymer network, and the first polymer network is further impregnated with the second monomer and a cross-linking agent to polymerize the second polymer. The polymer network of the above is formed to produce a cross-linking gel. In addition, as a method for controlling the mechanical properties of the hydrogel material and enhancing its applicability to 3D printers, a gel material using acrylamides, in which prefabricated crosslinked gel particles are added to a monomer solution, has also been proposed (). For example, Patent Document 7).

Special Table No. 10-513408 Gazette Special Table 2002-506813 Gazette Japanese Unexamined Patent Publication No. 2011-0018213 Japanese Patent Publication No. 2008-50021 JP-A-2007-246770 International Publication No. 2003/0933227 Japanese Unexamined Patent Publication No. 2017-26680

Chemical Reviews, 2016, Vol. 116, p. 1496-1539

The polyvinyl alcohol macromers described in Patent Documents 1, 2 and 4 show biocompatibility and low toxicity, and have stimulatory curability, so that they can be applied to 3D printers, but the mechanical strength of the cured gel is high. Low and limited in use. Further, the mutual penetration type gel described in Patent Document 6 is manufactured in two steps of forming the first and second polymer networks by the same polymerization method, so that the process is complicated.
On the other hand, the gel material described in Patent Document 7 is manufactured in one step and has excellent mechanical strength, but since it is a technique using an acrylamide-based monomer, it has low stimulus curability by light, and there is a concern about toxicity due to residual monomers. Yes, for example, not suitable for medical use.
Further, no interpenetrating gel technique containing polyvinyl alcohol macromer having stimulatory curability has been known so far.

An object of the present invention is to provide a high-strength polyvinyl alcohol-based mutual penetration type gel which is excellent in stimulant curability and safety, has high mechanical strength, and can be applied to a wide range of applications.

As a result of diligent studies, the present inventors have found a cross-penetrating gel containing a first polymer network and a second polymer network, in which the first polymer network is a polyvinyl alcohol having a radically polymerizable group. The above is a polyvinyl alcohol-based mutual penetration type gel, which is a cross-linked polyvinyl alcohol cross-linked product, and the second polymer network is a water-soluble polymer cross-linked product obtained by cross-linking a water-soluble polymer having a carboxyl group with metal ions. We have found that the problem can be solved, and based on the findings, further studies have been carried out to complete the present invention.

That is, the present invention relates to the following [1] to [5].
[1] A polyvinyl alcohol-based mutual intrusive gel containing a first polymer network and a second polymer network.
The first polymer network is a polyvinyl alcohol crosslinked product (1) formed by cross-linking polyvinyl alcohol (1') having a radically polymerizable group.
A polyvinyl alcohol-based mutual penetration type gel in which the second polymer network is a water-soluble polymer crosslinked body (2) formed by cross-linking a water-soluble polymer (2') having a carboxyl group with metal ions.
[2] The radically polymerizable group is at least one selected from the group consisting of a vinyl group, a (meth) acryloyloxy group, a (meth) acryloylamino group, a vinylphenyl group, a norbornenyl group and derivatives thereof. The polyvinyl alcohol-based mutual penetration type gel of the above [1].
[3] The polyvinyl alcohol-based mutual penetration type according to the above [1] or [2], wherein the introduction rate of the radically polymerizable group is 0.1 to 10 mol% with respect to the repeating unit of the polyvinyl alcohol (1'). gel.
[4] Any of the above [1] to [3], wherein the water-soluble polymer (2') is at least one selected from the group consisting of alginic acid, carboxymethyl cellulose, LM pectin, carboxymethyl starch and derivatives thereof. Polyvinyl alcohol-based mutual penetration type gel.
[5] The value of the mass ratio [first polymer network / second polymer network] between the first polymer network and the second polymer network is 1000 to 0.01 in the interpenetrating gel, as described above. The polyvinyl alcohol-based mutual penetration type gel according to any one of [1] to [4].

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a high-strength polyvinyl alcohol-based interpenetrating gel which is excellent in stimulant curability and safety, has high mechanical strength, and can be applied to a wide range of applications.

Hereinafter, the present invention will be described in detail.
In the present specification, "(meth) acrylic" means a general term for "methacrylic" and "acrylic", and "(meth) acryloyl" means a general term for "methacrylic acid" and "acryloyl". do.

[Polyvinyl alcohol-based mutual penetration type gel]
The polyvinyl alcohol (hereinafter, also abbreviated as “PVA”)-based interpenetrating gel (hereinafter, also abbreviated as “interpenetrating gel”) of the present invention is a PVA containing a first polymer network and a second polymer network. A polyvinyl alcohol cross-linking in which a first polymer network is cross-linked with polyvinyl alcohol (1') having a radically polymerizable group (hereinafter, also abbreviated as "PVA (1')"), which is a system-based interpenetrating gel. It is a body (1) (hereinafter, also abbreviated as “PVA crosslinked body (1)”), and the second polymer network is a water-soluble polymer (2') having a carboxyl group (hereinafter, “water-soluble polymer (2 ′)”. ) ”) Is crosslinked with metal ions to form a water-soluble polymer cross-linked product (2) (hereinafter, also abbreviated as“ water-soluble polymer cross-linked product (2) ”).
In the present invention, the "interpenetrating gel" means a gel having an interpenetrating polymer network (IPN) structure.

The PVA-based mutual penetration type gel of the present invention is excellent in stimulus curability and safety, has high mechanical strength, and can be applied to a wide range of applications. The reason for this is not clear, but it is presumed as follows.
A PVA crosslinked product (1) obtained by cross-linking PVA (1') having a radically polymerizable group is used as a first polymer network, and a water-soluble polymer (2') having a carboxyl group is cross-linked by metal ions. The sex polymer crosslinked product (2) is used as a second polymer network, and the first and second polymer networks are intertwined with each other at the molecular chain level, that is, an interpenetrating polymer network (IPN) structure. By forming the above, the mechanical strength is improved.
Further, since the first polymer network is formed by curing macromer, it has excellent stimulus curability even if the introduction rate of radically polymerizable groups is low as compared with the case where it is formed by polymerizing a monomer. Can be maintained. Therefore, it is considered that the original properties of PVA can be easily maintained, high biocompatibility and low toxicity can be exhibited, and safety can be improved. On the other hand, since the second polymer network is formed by cross-linking metal ions, the curing operation itself is simple and the curing rate is high. Further, when an impact is applied to the mutual intrusive gel, the crosslinks due to metal ions are broken, the impact energy can be absorbed, and it is considered that the mechanical strength is increased.

<Polyvinyl alcohol having a radically polymerizable group (1')>
The interpenetrating gel of the present invention contains a PVA crosslinked product (1) obtained by cross-linking PVA (1') (PVA (1')) having a radically polymerizable group as a first polymer network. The PVA crosslinked product (1) has a crosslinked structure in which PVA chains are crosslinked with each other by a structural unit derived from a radically polymerizable group.
PVA (1') contains a radically polymerizable group at the side chain or the terminal of the PVA chain as a base material. The PVA chain contains at least vinyl alcohol units and may further contain vinyl ester units. The total amount of the vinyl alcohol unit and the vinyl ester unit with respect to all the structural units constituting the PVA chain is more than 50 mol%, preferably more than 80 mol%, more preferably more than 90 mol%, still more preferably more than 95 mol%.

The radically polymerizable group is a group capable of forming a crosslink between PVA chains by a radical polymerization reaction. Examples of the radically polymerizable group include a cyclic group such as a vinyl group, a (meth) acryloyloxy group, a (meth) acryloylamino group, a vinylphenyl group, a cyclohexenyl group, a cyclopentenyl group, a norbornenyl group and a dicyclopentenyl group. Examples include unsaturated hydrocarbon groups and derivatives thereof.
The "vinyl group" in the present invention includes not only an ethenyl group but also a chain unsaturated hydrocarbon group such as an allyl group and an unsaturated carbon bond obtained by removing one hydrogen atom from ethylene such as a vinyloxycarbonyl group. Also includes functional groups including. Among them, from the viewpoint of improving the stimulus curability and mechanical strength of the mutual penetration type gel, a group consisting of a vinyl group, a (meth) acryloyloxy group, a (meth) acryloylamino group, a vinylphenyl group, a norbornenyl group and derivatives thereof. At least one selected from the above is preferable. From the viewpoint of reactivity, a functional group having a terminal unsaturated carbon bond is preferable, and a (meth) acryloyloxy group is more preferable. Further, from the viewpoint of improving the alkali resistance of the mutual penetration type gel, a (meth) acryloylamino group and a vinylphenyl group are preferable.

As a method for producing PVA (1'), a method for introducing a radically polymerizable group via a side chain or a terminal functional group of polyvinyl alcohol (hereinafter, also abbreviated as “raw material PVA”) as a raw material, and a method for producing PVA. Examples thereof include a method of introducing a radically polymerizable group by copolymerizing a vinyl ester-based monomer and a monomer other than the vinyl ester-based monomer in the process.

The raw material PVA can be produced by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester-based monomer and converting the ester group in the polyvinyl ester into a hydroxyl group.
Examples of the vinyl ester-based monomer include vinyl formate, vinyl acetate, vinyl propionate, n-vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatic acid, vinyl caproate, vinyl caprilate, and vinyl caprate. , An aliphatic vinyl ester such as vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl oleate; and aromatic vinyl ester such as vinyl benzoate. One of these may be used alone or in combination of two or more. Among them, an aliphatic vinyl ester is preferable, and vinyl acetate is more preferable from an economical viewpoint, that is, the polyvinyl acetate is preferably polyvinyl acetate obtained by polymerizing vinyl acetate.

Further, the polyvinyl ester may contain a structural unit derived from a monomer other than the vinyl ester-based monomer, if necessary, as long as the effect of the present invention is not impaired. Examples of the other monomer include α-olefins such as ethylene, propylene, n-butyl and isobutylene; acrylic acid or a salt thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-acrylate. Acrylic acid alkyl esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid or a salt thereof; methyl methacrylate , Ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, etc. Alkyl methacrylate esters; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamide propanesulfonic acid or its salts, acrylamidepropyldimethylamine or its salts or quaternary salts, N -Acrylamide derivatives such as methylolacrylamide or derivatives thereof; methacrylamide, N-methylmethacrylate, N-ethylmethacrylate, methacrylamidepropanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or a salt thereof or a quaternary salt, N- Methylamide derivatives such as methylolmethacrylamide or derivatives thereof; N-vinylamide derivatives such as N-vinylformamide and N-vinylacetamide; methylvinyl ether, ethylvinyl ether, n-propylvinyl ether, i-propylvinyl ether, n-butylvinyl ether, i -Vinyl ethers such as butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; halogens such as vinylidene chloride and vinylidene fluoride Vinylidene hydride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or salts thereof, esters or acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like can be mentioned. One of these may be used alone or in combination of two or more. When the polyvinyl ester contains a structural unit derived from another monomer, the content of the structural unit derived from the other monomer is less than 20 mol% with respect to all the structural units constituting the polyvinyl ester. It is preferably less than 10 mol%, more preferably less than 5 mol%.

The saponification reaction of the polyvinyl ester is not particularly limited and can be carried out by the same method as before, and for example, an alcohol-added decomposition method using an alkali catalyst or an acid catalyst, a hydrolysis method and the like can be applied. Above all, a saponification reaction using methanol as a solvent and a caustic soda (NaOH) catalyst is convenient and preferable.

The degree of polymerization of the raw material PVA is not particularly limited, and those having various degrees of polymerization can be used. The degree of polymerization of the raw material PVA is preferably 100 or more, more preferably 200 or more, still more preferably 300 or more, from the viewpoint of suppressing embrittlement of the mutual penetration type gel. Then, from the viewpoint of suppressing the increase in viscosity of the uncured gel solution described later and improving the ease of processing, the amount is preferably 10,000 or less, more preferably 5,000 or less, still more preferably 3,000 or less. Further, as the raw material PVA, two or more kinds having different degrees of polymerization may be mixed and used.
The degree of polymerization of PVA in the present specification refers to the degree of polymerization measured according to JIS K 6726: 1994, and can be obtained from the extreme viscosity measured in water at 30 ° C. after PVA is saponified again and purified.

The saponification degree of the raw material PVA is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 65 mol% or more, from the viewpoint of improving the water solubility of the raw material PVA.
Further, as the raw material PVA, it is preferably 95 mol% or less, more preferably 90 mol% or less, from the viewpoint of suppressing the increase in viscosity of the uncured gel solution described later and improving the storage stability of the uncured gel solution. PVA may be used.
The degree of saponification of PVA in the present specification is the molar number of the vinyl alcohol units with respect to the total number of moles of the structural units (for example, vinyl acetate units) and the vinyl alcohol units constituting the PVA, which can be converted into vinyl alcohol units by saponification. It means the ratio (mol%) occupied by the number, and can be measured according to JIS K 6726: 1994.

The introduction of the radically polymerizable group into the raw material PVA is preferably carried out via a side chain of the raw material PVA, a terminal functional group, or the like, and a radical is applied to the hydroxyl group of the side chain of the raw material PVA or the 1,3-diol group of the raw material PVA. It is more preferable to react with a compound containing a polymerizable group (hereinafter, also abbreviated as "radical polymerizable group-containing compound").
For the hydroxyl group, which is the side chain of the raw material PVA, examples of the radically polymerizable group-containing compound include (meth) acrylic acid, (meth) acrylic acid anhydride, (meth) acrylic acid halide, and (meth) acrylic acid ester. The (meth) acryloyl group can be introduced by subjecting the above (meth) acrylic acid or a derivative thereof to an esterification reaction or an ester exchange reaction in the presence of a base.
Further, for the hydroxyl group which is a side chain of the raw material PVA, a method of subjecting a compound containing a radically polymerizable group and a glycidyl group in the molecule as a radically polymerizable group-containing compound to an etherification reaction in the presence of a base can be mentioned. .. Examples of the compound containing a radically polymerizable group and a glycidyl group in the molecule include glycidyl (meth) acrylate and allyl glycidyl ether. This makes it possible to introduce a (meth) acryloyl group or an allyl group.
For the 1,3-diol group of the raw material PVA, examples of the radically polymerizable group-containing compound include acrylic aldehyde (acrolein), methacryl aldehyde (methacrolein), 5-norbornen-2-carboxyaldehyde, and 7-octenal. , 3-Vinylbenzaldehyde, 4-vinylbenzaldehyde and the like, a method of acetalizing a compound containing a radically polymerizable group and an aldehyde group in the molecule in the presence of an acid catalyst can also be mentioned. For example, a vinylphenyl group can be introduced by acetalizing a 3-vinylbenzaldehyde, 4-vinylbenzaldehyde, or the like. Further, it is possible to introduce a (meth) acryloylamino group by reacting with N- (2,2-dimethoxyethyl) (meth) acrylamide or the like. The method of introducing a radically polymerizable group using the raw material PVA can be used in addition to the above-mentioned reactions exemplified above, and two or more kinds of reactions may be used in combination.

As another method for introducing the radically polymerizable group, a vinyl ester-based monomer and a polymerizable monomer other than the vinyl ester-based monomer are copolymerized in the process of producing PVA, and then saponified. Then, a method of obtaining a copolymer-modified polyvinyl alcohol (hereinafter, also abbreviated as "copolymer-modified PVA") can be mentioned. Examples of the copolymerized PVA include carboxylic acid-modified PVA and amino-modified PVA.
Examples of the monomer constituting the carboxylic acid-modified PVA include α, β-unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, fumaric acid and itaconic acid; methyl (meth) acrylate and (meth) acrylic acid. Examples thereof include (meth) acrylic acid alkyl esters such as ethyl; α, β-unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride, and derivatives thereof. In the carboxylic acid-modified PVA, for example, a vinyl ester-based monomer is copolymerized with α, β-unsaturated carboxylic acid anhydride or a derivative thereof, and then saponified, and the introduced carboxyl group is subjected to, for example, glycidyl methacrylate. Can be reacted under acidic conditions to form an ester bond and introduce a methacryloyl group.
Further, in the amino-modified PVA, a vinyl ester-based monomer and N-vinylformamide or the like are copolymerized and then saponified, and for the introduced amino group, for example, acrylic acid anhydride is amidated in the presence of a base. An acryloylamino group can be introduced by reacting. Further, a vinyloxycarbonyl group can be introduced by, for example, amidating a divinyl adipate with the amino group of the amino-modified PVA. The method of introducing a radically polymerizable group via the copolymerized PVA can be used in addition to the above-mentioned reactions exemplified above, and two or more kinds of reactions may be used in combination.

As the PVA (1'), a PVA having a radically polymerizable group introduced via a hydroxyl group of the side chain of the raw material PVA or a 1,3-diol group is preferable from the viewpoint of ease of production, and a hydroxyl group of the side chain of the raw material PVA is preferable. PVA obtained by subjecting (meth) acrylic acid or a derivative thereof to an esterification reaction or an ester exchange reaction, a compound containing a radically polymerizable group and an aldehyde group in the molecule with respect to the 1,3-diol group of the raw material PVA. PVA obtained by acetalizing the above is more preferable.

The introduction rate of the radically polymerizable group with respect to the repeating unit of PVA (1') is preferably 10 mol% or less, more preferably 5 mol% or less, from the viewpoint of suppressing embrittlement while improving the elastic modulus of the mutual penetration type gel. , More preferably 3 mol% or less. Then, from the viewpoint of promoting the cross-linking reaction and satisfactorily forming the mutual penetration type gel and improving the elastic modulus of the mutual penetration type gel, the content is preferably 0.01 mol% or more, more preferably 0.1 mol% or more. be.

PVA (1') generates radicals by heat or light by addition of a radical polymerization initiator, that is, a thermal radical polymerization initiator or a photoradical polymerization initiator, respectively, to polymerize the radical polymerizable group, and crosslink the PVA chain. It is preferable that the PVA crosslinked product (1) is obtained by curing it. Further, a redox-based initiator may be used as the thermal radical polymerization initiator, and when the redox-based initiator is used, the mixture of the peroxide-based initiator and the reducing agent can be used as a stimulus for curing.

Further, in the case of PVA (1') having a vinyl group as the radically polymerizable group, for example, a polythiol having two or more thiol groups is added in the molecule from the viewpoint of promoting curing to carry out a thiol-ene reaction. It may be used for cross-linking. As such a polythiol, one showing water solubility is preferable, for example, a polythiol having a hydroxyl group such as dithiothreitol; a terminal such as 3,6-dioxa-1,8-octanedithiol, polyethylene glycol dithiol, multi-arm polyethylene glycol or the like. Examples thereof include polythiol containing an ether bond such as a thiol compound.
Since the thiol-ene reaction has a one-to-one reaction between a vinyl group and a thiol group, it is preferable to add the polythiol so that the thiol group is equal to or less than the equivalent amount of the vinyl group. Within the range of the addition amount, the addition amount of the polythiol can be arbitrarily adjusted from the viewpoint of controlling the mechanical strength and the like of the mutual penetration type gel. Curing by thiol-ene reaction may also be used for PVA (1') having a vinyloxycarbonyl group.

<Water-soluble polymer with carboxyl group (2')>
The mutual penetration type gel of the present invention contains a water-soluble polymer crosslinked body (2) formed by cross-linking a water-soluble polymer (2') having a carboxyl group with metal ions as a second polymer network. The water-soluble polymer crosslinked body (2) has a crosslinked structure in which water-soluble polymer chains having a carboxyl group are crosslinked with metal ions. In the present invention, the "water-soluble polymer" means a polymer in which the carboxyl group is 100% neutralized with sodium hydroxide and the dissolved amount exceeds 0.1 g when dissolved in 100 g of water at 25 ° C.
The first polymer network is cross-linked by a radical polymerization reaction, but when an attempt is made to form a second polymer network by the same method of cross-linking by a radical polymerization reaction, after the first polymer network is formed. The process of impregnating the raw material of the second polymer network is required, the process becomes complicated, and it takes a long time to manufacture. Therefore, in the present invention, the first polymer network is formed by cross-linking the water-soluble polymer (2') by a cross-linking method using a metal ion different from that of the first polymer network to form the second polymer network. Even before, the raw materials of the second polymer network can be mixed in advance, and the process of producing the interpenetrating gel can be greatly simplified.
Further, since the mutual penetration type gel of the present invention can be produced in an aqueous medium, the crosslinking reaction proceeds very efficiently in the aqueous medium by forming the second polymer network by crosslinking with metal ions. do. Therefore, it is not necessary to use an excessive amount of additives and raw materials, and a gel cleaning step for removing residual additives and unreacted raw materials is not required.

As the water-soluble polymer (2'), naturally-derived polysaccharides are preferable from the viewpoint of safety, and examples thereof include alginic acid, carboxymethyl cellulose, LM pectin, carboxymethyl starch and derivatives thereof. Examples of the derivative include salts and esters. For example, the carboxyl group of the water-soluble polymer (2') may be a metal salt or an ammonium salt bonded to an alkali metal ion such as sodium or potassium or an ammonium ion. Further, the carboxyl group of the water-soluble polymer (2') may be esterified, such as propylene glycol alginate. The water-soluble polymer (2') may be used alone or in combination of two or more. Of these, alginic acid and its derivatives are preferable from the viewpoint of improving the stimulatory curability and mechanical strength of the mutual penetration type gel. As the water-soluble polymer (2'), various commercially available products can be used.
The solution viscosity of the water-soluble polymer (2') can be freely selected according to the purpose. For example, when the water-soluble polymer (2') is sodium alginate, the viscosity (20 ° C.) of the 1% by mass aqueous solution thereof penetrates into each other. From the viewpoint of increasing the mechanical strength of the mold gel, it is preferably 10 to 1,500 mPa · s, more preferably 30 to 1,300 mPa · s, still more preferably 50 to 1,000 mPa · s, still more preferably 100. It is about 700 mPa · s, particularly preferably 200 to 500 mPa · s.

As the metal ion, a multivalent metal ion is preferable. The polyvalent metal ion is not particularly limited, and is, for example, a divalent metal ion such as magnesium, calcium, barium, strontium, copper (II), iron (II), manganese, zinc; trivalent such as aluminum and iron (III). Examples include metal ions. These polyvalent metal ions are organic acid salts such as acetates, lactates, tartrates and citrates; inorganic acid salts such as carbonates, sulfates and phosphates; halides such as chlorides; or hydroxides. It can be used in the state of things. Of these polyvalent metal ions, calcium, iron and aluminum are preferable, and calcium is more preferable.

(Inorganic fine particles)
The mutual penetration type gel of the present invention may further contain water-insoluble inorganic fine particles. Examples of water-insoluble inorganic fine particles include silica such as precipitated silica, gelled silica, vapor phase silica, colloidal silica; ceramics such as alumina, hydroxyapatite, zirconia, zinc oxide and barium titanate; zeolite, talc, montmorillonite and the like. Minerals; gypsum such as calcium sulfate; metal oxides such as calcium oxide and iron oxide; metal carbonates such as calcium carbonate and magnesium carbonate; These inorganic fine particles may be used alone or in combination of two or more. By containing water-insoluble inorganic fine particles, it is possible to impart functions such as higher mechanical properties and magnetism to the gel. Further, it is also possible to obtain a molded inorganic sintered body by drying and further sintering a molded mutual penetration type gel containing inorganic fine particles.
The content of the inorganic fine particles is not particularly limited, and is preferably 99.5% by mass or less, more preferably 99% by mass or less, still more preferably 95% by mass or less in the mutual penetration type gel. Further, from the viewpoint of obtaining the effect of adding the inorganic fine particles, the content of the inorganic fine particles is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more.

The mutual penetration type gel of the present invention contains water as a solvent, but may further contain a water-soluble organic solvent. Examples of the water-soluble organic solvent include aprotonic polar solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone, and monoalcohols such as methanol, ethanol, propanol and isopropanol; ethylene glycol, diethylene glycol and triethylene glycol. Examples thereof include polyhydric alcohols such as glycerin.
The content of the solvent in the mutual penetration type gel of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass, from the viewpoint of improving the flexibility of the mutual penetration type gel. The above is even more preferably 30% by mass or more. The upper limit of the solvent content is not particularly limited, but from the viewpoint of improving the mechanical strength of the mutual penetration type gel, it is preferably 99% by mass or less, more preferably 98% by mass or less, still more preferably 95% by mass or less. Is. When a water-soluble organic solvent is contained as the solvent, the content of the solvent is the total amount of water and the water-soluble organic solvent.
The content of the solvent in the interpenetrating gel can be measured using a drying method. Specifically, the sample can be heated and kept for a certain period of time, the solvent can be evaporated and dried from the sample, and the amount of decrease in the sample mass before and after heating and drying can be determined as the content of the solvent.

The value of the mass ratio [first polymer network / second polymer network] between the first polymer network and the second polymer network in the interpenetrating gel of the present invention sufficiently exerts the interpenetrating effect. From the viewpoint, it is preferably 1000 to 0.01, more preferably 500 to 0.03, still more preferably 100 to 0.1, still more preferably 50 to 1, and particularly preferably 35 to 3.
The total content of the first polymer network and the second polymer network in the interpenetrating gel of the present invention is preferably 1% by mass or more, more preferably, from the viewpoint of improving the mechanical strength of the interpenetrating gel. It is preferably 2% by mass or more, more preferably 5% by mass or more. From the viewpoint of improving the flexibility of the mutual penetration type gel, it is preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 80% by mass or less, still more preferably 70% by mass or less.

[Manufacturing method of polyvinyl alcohol-based mutual intrusive gel]
The interpenetrating gel of the present invention comprises a step of cross-linking PVA (1') having a radically polymerizable group to form a first polymer network to obtain a PVA crosslinked product (1), and a water-soluble polymer having a carboxyl group. It can be produced by a production method including a step of forming a second polymer network in which (2') is crosslinked with metal ions to obtain a water-soluble polymer crosslinked product (2).
In the production of the interpenetrating gel of the present invention, the order of forming the first polymer network and the second polymer network is not particularly limited, and after forming the first polymer network, the second polymer network is formed. Alternatively, the first polymer network may be formed after the second polymer network is formed. Further, the first polymer network and the second polymer network may be formed at the same time. "Molding at the same time" means that the cross-linking of PVA (1') having a radically polymerizable group and the cross-linking of a water-soluble polymer (2') having a carboxyl group by a metal ion are performed at the same time.

From the viewpoint of ease of production, the interpenetrating gel is produced by mixing a PVA (1') having a radically polymerizable group and a water-soluble polymer (2') having a carboxyl group in an uncured gel solution (2'). Hereinafter, it is preferable to simply prepare a "uncured gel solution").
The mass ratio [PVA (1') / water-soluble polymer (2')] of PVA (1') and the water-soluble polymer (2') in the uncured gel solution is the first and second values. From the viewpoint of sufficiently exerting the mutual penetration effect without excessively reducing the content in the mutual penetration type gel of either one of the polymer networks, it is preferably 1000 to 0.01, more preferably 500 to 0.03. It is more preferably 100 to 0.1, still more preferably 50 to 1, and particularly preferably 35 to 3.

The total content of PVA (1') and the water-soluble polymer (2') in the uncured gel solution is preferably 1% by mass or more, preferably 2% by mass, from the viewpoint of improving the mechanical strength of the mutual penetration type gel. % Or more is more preferable, and 5% by mass or more is further preferable. The content of PVA (1') is preferably 50% by mass or less, more preferably 45% by mass or less, and more preferably 40% by mass, from the viewpoint of suppressing the increase in viscosity of the uncured gel solution and obtaining good moldability. More preferably, it is by mass or less.

Water is contained as the solvent of the uncured gel solution. The uncured gel solution may further contain a water-soluble organic solvent, such as an aprotic polar solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone, and a monopoly such as methanol, ethanol, propanol and isopropanol. Alcohol: A water-soluble organic solvent such as a polyhydric alcohol such as ethylene glycol, diethylene glycol, triethylene glycol, or glycerin may be mixed and used. The content of the water-soluble organic solvent in the uncured gel solution is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less.
The content of the solvent in the uncured gel solution is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more. The content of the solvent is preferably 99% by mass or less, more preferably 98% by mass or less, and further preferably 95% by mass or less.

It is preferable to use a radical polymerization initiator for the cross-linking reaction of PVA (1'). Examples of the radical polymerization initiator include a thermal radical polymerization initiator and a photoradical polymerization initiator, and among them, a photoradical polymerization initiator is preferable.
The thermal radical polymerization initiator is not particularly limited as long as it initiates radical polymerization by heat, and examples thereof include an azo-based initiator and a peroxide-based initiator generally used in radical polymerization. From the viewpoint of improving the transparency and physical properties of the mutual penetration type gel, a peroxide-based initiator that does not generate gas is preferable, and from the viewpoint that the uncured gel solution is an aqueous solvent, a peroxide-based initiator having high water solubility is preferred. The agent is more preferred. Specific examples thereof include inorganic peroxides such as ammonium persulfate, potassium persulfate and sodium persulfate.
Further, a redox-based initiator combined with a reducing agent may be used. If it is a redox-based initiator, the first polymer network can be formed and cured by the stimulation of mixing the peroxide-based initiator and the reducing agent. Known reducing agents can be used as the reducing agent to be combined as the redox-based initiator. Among these, highly water-soluble N, N, N', N'-tetramethylethylenediamine, sodium sulfite, sodium hydrogen sulfite, and hydro Sodium sulfite and the like are preferable.

A water-soluble azo-based initiator may be used as long as the transparency and physical properties of the mutual penetration type gel are not impaired. Specifically, for example, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (trade name "VA-044"), 2,2'-azobis [2- (2). -Imidazoline-2-yl) propane] disulfate dihydrate (trade name "VA-044B"), 2,2'-azobis [2-methylpropionamidine] dihydrochloride (trade name "V-50") ), 2,2'-Azobis [N- (2-carboxyethyl) -2-methylpropionamidine] tetrahydrate (trade name "VA-057"), 2,2'-azobis [2- (2- (2- (2- (2-) Imidazoline-2-yl) propane] (trade name "VA-061"), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] (trade name "VA-086"), Examples thereof include 4,4'-azobis (4-cyanopentanoic acid) (trade name "V-501") (all manufactured by Wako Pure Chemical Industries, Ltd.).

The photoradical polymerization initiator is not particularly limited as long as it initiates radical polymerization by irradiation with active energy rays such as ultraviolet rays and visible light, and those exhibiting water solubility are preferable. Specifically, for example, α-ketoglutaric acid, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one (trade name "IRGACURE2959", BASF Japan). Co., Ltd.), Phenyl (2,4,6-trimethylbenzoyl) phosphinic acid lithium salt (trade name "L0290", manufactured by Tokyo Kasei Kogyo Co., Ltd.), 2,2'-azobis [2-methyl-N -(2-Hydroxyethyl) propionamide] (trade name "VA-086", manufactured by Wako Pure Chemical Industries, Ltd.), Eodine Y and the like.

The content of the radical polymerization initiator in the uncured gel solution can be appropriately adjusted depending on the type of the radical polymerization initiator, but from the viewpoint of promoting the crosslinking reaction and improving the mechanical strength of the mutual penetration type gel. 5 × 10 ^-6 % by mass or more is preferable, and 1 × 10 ^-5 % by mass or more is more preferable. The content of the radical polymerization initiator is preferably 3% by mass or less, more preferably 1% by mass or less, from the viewpoint of reducing the radical polymerization initiator remaining in the gel and suppressing brittleness of the mutual penetration type gel. It is preferably 0.5% by mass or less, and more preferably 0.5% by mass or less.

The uncured gel solution may further contain a monomer. The monomers include acrylamides such as acrylamide, N-isopropylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N, N-dimethylacrylamide; (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, etc. Α, β-unsaturated carboxylic acid such as fumaric acid; vinylpyridine; hydroxyethyl (meth) acrylate; styrene sulfonic acid; water-soluble radically polymerizable monomer such as polyethylene glycol mono (meth) acrylate, N, N' Examples thereof include cross-linking agents having two or more radically polymerizable groups in the molecule, such as methylenebisacrylamide, ethylene glycol di (meth) acrylate, and N, N'-diethylene glycol di (meth) acrylate.
The content of the monomer in the uncured gel solution is preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less, from the viewpoint of improving the mechanical strength of the mutual penetration type gel. preferable.

The uncured gel solution may further contain additives such as polymer fine particles, a light absorber, a polymerization inhibitor, a chain transfer agent, a colorant, and a preservative, as long as the effects of the present invention are not impaired. .. These may be used alone or in combination of two or more.
When the uncured gel solution contains a photoradical polymerization initiator, the uncured gel solution further absorbs light such as an ultraviolet absorber from the viewpoint of ensuring the precision of the shape at the time of modeling by a 3D printer of the stereolithography method. It may contain an agent. The ultraviolet absorber is not particularly limited as long as it is water-soluble, and is manufactured by Chemipro Kasei Co., Ltd. "KEMISORB111", "KEMISORB11S" (hereinafter, trade name), BASF Co., Ltd. "Tinuvin 477-DW", " Examples include "UVA805" and "Tinuvin1130" (hereinafter referred to as trade names).
When the uncured gel solution containing the photoradical polymerization initiator is cured, the uncured gel solution may further contain a polymerization inhibitor. Examples of the polymerization inhibitor include hydroquinone and p-methoxyphenol which are water-soluble, but other polymerization inhibitors may be used. By containing a polymerization inhibitor, the storage stability of the uncured gel solution can be enhanced.

(Formation of first polymer network)
When PVA (1') having a radically polymerizable group is crosslinked to form a first polymer network by irradiation with active energy rays, examples of active energy rays that can be used for the irradiation treatment include visible light and ultraviolet rays. It is preferably ultraviolet light such as a high-pressure mercury lamp, a low-pressure mercury lamp, a xenon lamp, and a metal halide lamp.
The irradiation energy amount of the active energy ray is preferably 0.1 to 10,000 mJ / cm ² , more preferably 1 to 5,000 mJ / cm ² , and further preferably 10 to 2,000 mJ / cm ² .
When PVA (1') having a radically polymerizable group is crosslinked by heat to form a first polymer network, it is preferable to heat the PVA (1') at a temperature of less than 100 ° C. The heating temperature can be appropriately adjusted depending on the type of the thermal radical polymerization initiator used, and is preferably 40 to 90 ° C, more preferably 50 to 80 ° C.

(Formation of second polymer network)
As a method of allowing a metal ion to act on the water-soluble polymer (2') having a carboxyl group and cross-linking the water-soluble polymer (2') to form a second polymer network, the uncured gel solution itself is used. A method of immersing in a metal ion solution, a method of immersing a first polymer network obtained by cross-linking PVA (1') in the uncured gel solution in a metal ion solution, the uncured gel solution itself or the uncured. Examples thereof include a method of generating metal ions inside a first polymer network obtained by cross-linking PVA (1') in a gel solution. As used herein, the term "immersion" is a concept that includes addition as well as immersion.
The solvent of the metal ion solution used for dipping is preferably water from the viewpoint that the uncured gel solution is an aqueous solvent. The concentration of metal ions in the metal ion solution can be appropriately adjusted depending on the mechanical strength of the mutual penetration type gel, the gelation time, etc., but is preferably 0.005 g / 100 mL or more of water, more preferably 0.01 g. / 100 mL or more of water, more preferably 0.02 g / 100 mL or more of water. The amount is preferably 30 g / 100 mL or less of water, more preferably 10 g / 100 mL or less of water, further preferably 5 g / 100 mL or less of water, and even more preferably 1 g / 100 mL or less of water.

As a method of generating metal ions in the uncured gel solution itself or in the first polymer network, for example, there is a method using a combination of calcium carbonate and glucono lactone. In this combination, glucono lactone is gradually hydrolyzed to acidify the inside of the uncured gel solution and the first polymer network, and calcium carbonate is dissolved to generate calcium ions. Specifically, for example, Progress in Polymer Sciernce, 2012, Vol. 37, p. 106-126, Biomaterials, 2001, Vol. 22, p. The method described in 511 and the like can be mentioned.

The interpenetrating gel of the present invention is preferably produced by a method including the following steps from the viewpoint of ease of production and handleability of the interpenetrating gel.
Step 1-1: A step of cross-linking PVA (1') in an uncured gel solution by a radical polymerization reaction to obtain a PVA cross-linked product (1) to form a first polymer network Step 1-2: Step 1- The water-soluble polymer (2') having a carboxyl group contained in the first polymer network obtained in 1 is crosslinked with metal ions to obtain a water-soluble polymer crosslinked product (2) to form a second polymer network. In step 1-2, the first polymer network obtained in step 1-1 is immersed in a metal ion solution or in step 1-1 from the viewpoint of ease of production. It is preferable to cross-link the water-soluble polymer (2') to obtain the water-soluble polymer cross-linked product (2) by a method of generating metal ions inside the obtained first polymer network.

Further, the production of the mutual penetration type gel of the present invention is preferably carried out by a method including the following steps from the viewpoint of the simplicity of the curing operation and the curing rate.
Step 2-1: The water-soluble polymer (2') in the uncured gel solution is crosslinked with metal ions to obtain a water-soluble polymer crosslinked body (2) to form a second polymer network. Step 2-2: PVA (1') contained in the second polymer network obtained in step 2-1 is crosslinked by a radical polymerization reaction to obtain a PVA crosslinked product (1) to form a first polymer network, and mutual penetration is performed. Step to obtain mold gel Step 2-1 is a water-soluble polymer (from the viewpoint of ease of production, by immersing the uncured gel solution in a metal ion solution or by generating metal ions in the uncured gel solution. It is preferable to crosslink 2') to obtain a water-soluble polymer crosslinked product (2).

The mutual penetration type gel of the present invention can also be given an arbitrary shape. For example, a method of pouring an uncured gel solution into a predetermined mold or the like, forming either a first polymer network or a second polymer network according to the above method, and then forming the other polymer network, or a method of forming the other polymer network. By forming the first polymer network and the second polymer network at the same time, it is possible to obtain a shape-imparted interpenetrating gel of the present invention.

Further, the mutual penetration type gel of the present invention can be given a precise shape by using a 3D printer. For example, when a material extrusion method or a material injection method is used as the molding method, either the first polymer network or the second polymer network is used after the uncured gel solution is extruded or injected from a nozzle of a syringe or a printer head and deposited. By forming one, forming it into a desired shape, and then forming a polymer network on the other, a cross-penetrating gel can be obtained.
As one of the preferred embodiments of the material extrusion deposition method, a water-soluble polymer (2') having a carboxyl group is crosslinked by discharging an uncured gel solution into a gelatin gel containing metal ions to form a second polymer network. After that, the PVA (1') having a radically polymerizable group contained in the second polymer network can be crosslinked to form the first polymer network. With this method, it becomes easy to stably manufacture a three-dimensional precision shape.
Further, as one of the preferred embodiments of the stereolithography method, an uncured gel solution containing a photoradical polymerization initiator is placed in a bathtub-type container and first stereolithographically formed by crosslinking PVA (1') having a radically polymerizable group. In the present invention, the water-soluble polymer (2') having a carboxyl radical is crosslinked by allowing metal ions to act by immersing the polymer in a gelatin gel containing metal ions after molding into a desired shape. Mutual penetration type gel can be obtained. In all the above-mentioned molding methods, the cross-linking of PVA (1') having a radically polymerizable group and the cross-linking of a water-soluble polymer (2') having a carboxyl group by a metal ion may be performed at the same time.

The mutual intrusive gel of the present invention can be used as it is, but it may also be used after being immersed in a solvent such as water to bring it into an equilibrium swelling state. The effect of removing the unreacted raw material and the non-crosslinked polymer component can be expected by the dipping operation, and the content of the unreacted raw material and the non-crosslinked polymer component can be further reduced. If it is desired to further remove the unreacted raw material and the non-crosslinked polymer component, the dipping operation may be repeated by exchanging the solvent. Since the mutual intrusive gel of the present invention uses macromer, it shows almost no toxicity usually exhibited by a monomer even when used as it is, and from the viewpoint of simplifying the manufacturing process, it is preferable not to have a dipping operation step. Further, the mutual penetration type gel of the present invention can also be used after removing a solvent such as water by drying with hot air or freeze-drying, and then immersing the gel in a solvent such as water again to bring it into an equilibrium swelling state. Once the mutual intrusive gel of the present invention is dried, crystallization of PVA (1') can be induced and the solvent content can be significantly reduced. This makes it possible to significantly increase the mechanical strength of the mutual penetration type gel of the present invention.

The initial elastic modulus of the mutual penetration type gel of the present invention is preferably 0.001 MPa or more, more preferably 0.005 MPa or more, still more preferably 0.01 MPa or more, and more, from the viewpoint of the self-supporting property of the mutual penetration type gel itself. It is more preferably 0.03 MPa or more, and particularly preferably 0.05 MPa or more. From the viewpoint of mechanical properties similar to those of a living body, it is preferably 500 MPa or less, more preferably 200 MPa or less, and further preferably 100 MPa or less.
The tensile strength of the mutual penetration type gel of the present invention is preferably 0.05 MPa or more, more preferably 0.08 MPa or more, still more preferably 0.1 MPa or more, still more, from the viewpoint of the self-supporting property of the mutual penetration type gel itself. It is preferably 0.2 MPa or more. From the viewpoint of mechanical properties similar to those of a living body, it is preferably 500 MPa or less, more preferably 200 MPa or less, and further preferably 100 MPa or less.
The breaking strain of the mutual penetration type gel of the present invention is preferably 10% or more, more preferably 20% or more, still more preferably 50% or more, still more preferably 100% or more, from the viewpoint of the flexibility of the mutual penetration type gel. , Particularly preferably 300% or more. From the viewpoint of mechanical properties similar to those of a living body, it is preferably 3000% or less, more preferably 2000% or less, and further preferably 1000% or less.
The initial elastic modulus, tensile strength and breaking strain are measured by the methods described in the examples.

The interpenetrating gel of the present invention has excellent stimulus curability, safety, and high mechanical strength, so that it is a curable material for 3D printers that are molded on demand, for example; medical models; sanitary products such as paper diapers and sanitary products. Medical devices used outside the body such as contact lenses and wound covering materials; Shock absorbing materials; Anti-vibration or soundproofing materials; Surface coating of medical devices; More advanced medical devices such as artificial organs; Soil improvement materials requiring on-site construction It can be suitably used in various fields such as civil engineering or building materials such as; agricultural materials such as water retention materials.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The main components used in the synthetic examples, examples and comparative examples are shown below.
(Raw material polyvinyl alcohol)
-PVA117: Polyvinyl alcohol (trade name "PVA117", degree of polymerization 1700, degree of saponification of about 98-99 mol%, manufactured by Kuraray Co., Ltd.)
The degree of polymerization of the raw material PVA is measured according to JIS K 6726: 1994.
(Radical polymerizable group-containing compound)
-Vinyl methacrylate: manufactured by Tokyo Chemical Industry Co., Ltd.-5-norbornene-2-carboxyaldehyde: manufactured by Tokyo Chemical Industry Co., Ltd. (water-soluble polymer having a carboxyl group (2'))
-Sodium alginate (NSPMR) (trade name "Duck Algin NSPMR", viscosity of 1% by mass aqueous solution (temperature: 20 ° C.) 300-400 mPa · s, manufactured by Kikkoman Biochemifa Co., Ltd.)
-Sodium alginate (NSPLLR) (trade name "Duck Argin NSPLLR", viscosity of 1% by mass aqueous solution (temperature: 20 ° C.) 40 to 50 mPa · s, manufactured by Kikkoman Biochemifa Co., Ltd.)
(Radical polymerization initiator)
IRGACURE2959: 1- [4- (2-Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one (photoradical polymerization initiator, trade name "IRGACURE2959", BASF Japan Ltd. ) Made)
-Α-Ketoglutaric acid: (photoradical polymerization initiator, manufactured by Wako Pure Chemical Industries, Ltd.)
(Aqueous metal ion solution)
・ Calcium chloride aqueous solution: Concentration 1 g Calcium chloride / 100 mL of water, manufactured by Wako Pure Chemical Industries, Ltd. (Polythiol)
-2,6-Dioxa-1,8-octanedithiol: manufactured by Tokyo Chemical Industry Co., Ltd. (monomer)
・ Acrylamide (AAm): manufactured by Wako Pure Chemical Industries, Ltd. ・ N, N-dimethylacrylamide (DAAm): manufactured by Wako Pure Chemical Industries, Ltd. ・ 2-acrylamide-2-methylpropanesulfonic acid (AMPS): Jun Wako Made by Yakuhin Kogyo Co., Ltd. (crosslinking agent)
-N, N'-methylenebisacrylamide (MBAA): manufactured by Wako Pure Chemical Industries, Ltd.

[Synthesis of polyvinyl alcohol (1') having a radically polymerizable group]
[Synthesis Example 1]
40 g (monomer repeating unit: 911 mmol) of PVA117 was placed in a separable flask equipped with a 1 L Dimroth condenser, 350 mL of DMSO was added, and stirring was started with a mechanical stirrer. After raising the temperature to 80 ° C. in a water bath, stirring was continued at 80 ° C. for 4 hours. After visually confirming that the PVA was dissolved, 1.2 g (10.8 mmol) of vinyl methacrylate was added while heating and stirring at 80 ° C., and the mixture was further stirred at 80 ° C. for 3 hours. After allowing to cool, the reaction solution was poured into 2 L of methanol with stirring. Stirring was stopped and the mixture was left as it was for 1 hour. After recovering the obtained solid, it was further immersed in 1 L of methanol for 1 hour for washing. This cleaning work was performed a total of three times. The recovered solid was vacuum dried overnight at room temperature to obtain methacryloylated PVA117. The introduction rate of the radically polymerizable group (methacryloyloxy group) of the methacryloylated PVA117 was 1.2 mol% with respect to the repeating unit of PVA (hereinafter, abbreviated as "MA-PVA117 (1.2)").

[Synthesis Examples 2 to 3]
In Synthesis Example 1, as shown in Table 1, methacryloylated PVA was produced in the same manner as in Synthesis Example 1 except that the introduction rate of the methylenedioxy group was changed.

[Synthesis Example 4]
60 g (monomer repeating unit: 1.36 mol) of PVA117 was placed in a separable flask equipped with a 1 L Dimroth condenser, 540 mL of ion-exchanged water was added, and stirring was started with a mechanical stirrer. After raising the temperature to 80 ° C. in a water bath, stirring was continued at 80 ° C. for 4 hours. After visually confirming that the PVA had dissolved, the temperature was lowered to 40 ° C. While stirring at 40 ° C., 2.5 g (20.5 mmol) of 5-norbornene-2-carboxyaldehyde and 22 mL of a 10% by volume sulfuric acid aqueous solution were added, and the mixture was further stirred at 40 ° C. for 4 hours. After allowing to cool, 80 mL of a 1N NaOH aqueous solution was added to neutralize the mixture, and the mixture was placed in a dialysis membrane having a molecular weight cut off of 3,500 and desalted (performed 4 times for 5 L of ion-exchanged water). The desalted aqueous solution was poured into 2 L of methanol with stirring, and the mixture was left as it was for 1 hour. After recovering the obtained solid, it was further immersed in 1 L of methanol for 1 hour for washing. The recovered solid was vacuum dried overnight at room temperature to obtain norborneneized PVA117. The introduction rate of the radically polymerizable group (norborneneyl group) of the norborneneized PVA117 was 1.3 mol% with respect to the repeating unit of PVA (hereinafter, abbreviated as "Nor-PVA117 (1.3)").

[Example 1]
90 mL of ion-exchanged water was added to 10 g of MA-PVA117 (1.2) as PVA (1'), and the mixture was dissolved at 80 ° C. with stirring for 4 hours. After cooling to room temperature, 1 g of sodium alginate (NSPMR) was added to this MA-PVA aqueous solution, and the mixture was stirred at room temperature for 3 hours. IRGACURE2959, which is a water-soluble photoradical polymerization initiator, was added to and dissolved in a MA-PVA aqueous solution containing sodium alginate in an amount of 0.1% by mass to prepare an uncured gel solution.
Next, this solution was poured between glass plates sandwiching a 2 mm thick spacer, and a metal halide lamp manufactured by GS Yuasa Corporation was used at 145 mW / cm ² for 30 seconds (irradiation energy amount: 1,200 mJ / cm ² ). ) UV light (wavelength 365 nm) was irradiated. The cured gel was taken out from the glass plate and immersed in a calcium chloride aqueous solution (1 g calcium chloride / 100 mL of water) for 30 minutes to obtain a mutual penetration type gel of the present invention. The mutual penetration type gel was sufficiently cured even under the conditions and was a tough gel. The obtained mutual intrusive gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Example 2]
The uncured gel solution prepared in Example 1 was placed in a tray so as to have a thickness of 2 mm, and an aqueous calcium chloride solution (1 g calcium chloride / 100 mL of water) was sprayed from the upper surface of the uncured gel solution layer in the tray. The entire cured gel solution was cured. Then, using a metal halide lamp manufactured by GS Yuasa Corporation, UV light was irradiated at 145 mW / cm ² for 30 seconds (irradiation energy amount: 1,200 mJ / cm ² ) to obtain a mutual penetration type gel. The mutual penetration type gel was sufficiently cured even under the conditions and was a tough gel. The obtained mutual intrusive gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Example 3]
In Example 1, a mutual penetration type gel was obtained by the same method as in Example 1 except that MA-PVA117 (0.6) was used instead of MA-PVA117 (1.2). The mutual penetration type gel was sufficiently cured even under the conditions and was a tough gel. The obtained mutual intrusive gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Example 4]
In Example 1, a mutual penetration type gel was obtained by the same method as in Example 1 except that MA-PVA117 (0.3) was used instead of MA-PVA117 (1.2). The mutual penetration type gel was sufficiently cured even under the conditions and was a tough gel. The obtained mutual intrusive gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Example 5]
In Example 1, a mutual intrusive gel was obtained by the same method as in Example 1 except that sodium alginate (NSPLLR) was used instead of sodium alginate (NSPMR). The mutual penetration type gel was sufficiently cured even under the conditions and was a tough gel. The obtained mutual intrusive gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Example 6]
90 mL of ion-exchanged water was added to 10 g of MA-PVA117 (1.2) as PVA (1'), and the mixture was dissolved at 80 ° C. with stirring for 4 hours. After cooling to room temperature, 2 g of sodium alginate (NSPLLR) was added to this MA-PVA aqueous solution, and the mixture was stirred at room temperature for 3 hours. IRGACURE2959 was added in an amount of 0.1% by mass to an aqueous solution of MA-PVA containing alginic acid and dissolved to prepare an uncured gel solution. This solution was cured under the same conditions as in Example 1 to obtain a mutual intrusive gel. The mutual penetration type gel was sufficiently cured even under the conditions and was a tough gel. The obtained mutual intrusive gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Example 7]
90 mL of ion-exchanged water was added to 10 g of Nor-PVA117 (1.3) as PVA (1'), and the mixture was dissolved at 80 ° C. with stirring for 4 hours. After cooling to room temperature, 1 g of sodium alginate (NSPMR) was added to this Nor-PVA aqueous solution, and the mixture was stirred at room temperature for 3 hours. Further, 0.48 g of 3,6-dioxa-1,8-octanedithiol as polythiol was added and stirred. IRGACURE2959 was added to this solution in an amount of 0.1% by mass and dissolved to prepare an uncured gel solution. This solution was cured under the same conditions as in Example 1 to obtain a mutual intrusive gel. The mutual penetration type gel was sufficiently cured even under the conditions, and a tough gel was obtained. The obtained mutual intrusive gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Comparative Example 1]
90 mL of ion-exchanged water was added to 10 g of MA-PVA117 (1.2) as PVA (1'), and the mixture was dissolved at 80 ° C. with stirring for 4 hours. After cooling to room temperature, IRGACURE2959 was added to this in an amount of 0.1% by mass and dissolved to prepare an uncured gel solution. This solution was cured under the same conditions as in Example 1 to obtain a gel. Since the gel was obtained by curing an uncured gel solution containing no sodium alginate, it does not contain a second polymer network formed by cross-linking with metal ions. The obtained gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Comparative Example 2]
In Comparative Example 1, a gel was obtained in the same manner as in Comparative Example 1 except that MA-PVA117 (0.6) was used.

[Comparative Example 3]
In Comparative Example 1, a gel was obtained in the same manner as in Comparative Example 1 except that MA-PVA117 (0.3) was used.

[Comparative Example 4]
14 g of acrylamide (AAm) to 86 mL of ion-exchanged water, 0.06 mass% of N, N'-methylenebisacrylamide (MBAA) and 1.7 g of sodium alginate (NSPMR) as a cross-linking agent. Was added and stirred at room temperature to dissolve. IRGACURE2959 was added to this solution in an amount of 0.1% by mass and dissolved to prepare an uncured gel solution. This solution was cured under the same conditions as in Example 1, but no gel was obtained. Therefore, the mechanical strength was not evaluated.

[Comparative Example 5]
14 g of acrylamide (AAm) to 86 mL of ion-exchanged water, 0.06 mass% of N, N'-methylenebisacrylamide (MBAA) and 1.7 g of sodium alginate (NSPMR) as a cross-linking agent. Was added and stirred at room temperature to dissolve. Further, 0.48 g of 3,6-dioxa-1,8-octanedithiol as polythiol was added and stirred. IRGACURE2959 was added to this solution in an amount of 0.1% by mass and dissolved to prepare an uncured gel solution. This solution was cured in the same manner as in Example 1 to obtain a gel. The obtained gel was used to evaluate the mechanical strength. The results are shown in Table 2.

[Comparative Example 6]
A mutual penetration type gel was prepared as follows with reference to Patent Document 7.
1 mol / L 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 0.04 mol / L N, N'-methylenebisacrylamide (MBAA), and 0.001 mol / L α as a photoradical polymerization initiator. -Polymerization was carried out by irradiating 100 mL of an aqueous solution containing ketoglutaric acid with UV light for 7 hours to obtain a polyAMPS gel (PAMPS gel) having a degree of cross-linking of 4 mol%. The obtained PAMPS gel was placed in a heat dryer for one day to dry, and then placed in a mortar and pulverized to obtain fine particles of PAMPS gel.
On the other hand, a monomer solution containing 1 mol / L of N, N-dimethylacrylamide (DAAm), MBAA of 0.01 mol% with respect to DAAm as a cross-linking agent, and IRGACURE2959 of 0.1% by mass with respect to the monomer solution. Prepared.
The fine particles of the PAMPS gel were added to the monomer solution in an amount such that the mass ratio of the fine particles of the PAMPS gel to the monomer solution (fine particles of the PAMPS gel: monomer solution) was 1:30. This solution was cured under the same UV light irradiation conditions as in Example 1, but a tough gel was not obtained. Therefore, the mechanical strength was not evaluated.

[Evaluation of mechanical strength of gel]
The mechanical strengths of the mutual penetration type gels obtained in Examples 1 to 7 and the gels obtained in Comparative Examples 1 to 3 and 5 were subjected to a tensile test according to the following procedure to determine the initial elastic modulus, tensile strength and breaking strain. It was measured.
A test piece was cut out from each gel sheet prepared to have a thickness of 2 mm using a dumbbell cutter of JIS K-6251-3 standard according to the method described in JP-A-2015-004059. Two gauge points were attached to the test piece using food coloring, and the distance between the gauge points was measured with a caliper. The width and thickness of the test piece were measured using a micrometer. The test piece was set on an Easton tensile tester (type 5566), and the test was conducted while acquiring image data. From the obtained image data, a correlation diagram between stress and strain was created, and numerical values of initial elastic modulus, tensile strength and breaking strain were obtained. The results are shown in Table 2.

表２中の各表記は以下のとおりである。
＊１：工程Ａは第１ポリマーネットワークを形成する工程であり、工程Ｂは第２ポリマーネットワークを形成する工程である。
＊２：重合性単量体としてアクリルアミド類と、架橋剤としてＮ，Ｎ’－メチレンビスアクリルアミド（ＭＢＡＡ）を用いて第１のポリマーネットワークを形成した。
＊３：特許文献７を参考に相互貫入型ゲルを作製した。
＊４：全体が硬化していない（ゲルとして取り扱えない）ため機械的強度の評価を行わなかった。

Each notation in Table 2 is as follows.
* 1: Step A is a step of forming the first polymer network, and step B is a step of forming the second polymer network.
* 2: A first polymer network was formed using acrylamides as a polymerizable monomer and N, N'-methylenebisacrylamide (MBAA) as a cross-linking agent.
* 3: A mutual penetration type gel was prepared with reference to Patent Document 7.
* 4: The mechanical strength was not evaluated because the whole was not cured (it cannot be handled as a gel).

From Table 2, it can be seen that Examples 1 to 7 have higher initial elastic moduli and tensile strength than Comparative Examples 1 to 6, and are excellent in mechanical strength.
Since none of Comparative Examples 1 to 3 formed a mutual penetration type gel, the initial elastic modulus and tensile strength were lower than those of Examples 1 to 7, and the mechanical strength was inferior.
In Comparative Examples 4 to 5, an attempt was made to form a gel by polymerizing a polymerizable monomer. However, since the stimulus-curable PVA macromer is not used, the curing is insufficient, and even if the curing is performed, the initial elastic modulus and the tensile strength are lower than those of Examples 1 to 7, and the mechanical strength is inferior. ..
Comparative Example 6 was inferior in curability because the monomer was polymerized, and the curing was insufficient under the same UV light irradiation conditions as in Example 1.

According to the present invention, since it is excellent in stimulus curability and safety and has high mechanical strength, for example, a curable material for a 3D printer to be molded on demand; a medical model; a sanitary product such as a paper diaper and a sanitary product; a contact lens. , Medical equipment used outside the body such as wound dressing; Shock absorbing material; Anti-vibration or soundproofing material; Surface coating of medical equipment; More advanced medical equipment such as artificial organs; Civil engineering such as soil improvement materials that require on-site construction Alternatively, it can be suitably used in various fields such as building materials; agricultural materials such as water retention materials.

Claims (4)

A polyvinyl alcohol-based interpenetrating gel containing a first polymer network and a second polymer network.
The first polymer network is a polyvinyl alcohol crosslinked product (1) formed by cross-linking polyvinyl alcohol (1') having a radically polymerizable group.
The second polymer network is a water-soluble polymer crosslinked body (2) formed by cross-linking a water-soluble polymer (2') having a carboxyl group with metal ions.
The radically polymerizable group is at least one selected from the group consisting of a vinyl group, a (meth) acryloyloxy group, a vinylphenyl group, a norbornenyl group and derivatives thereof .
A polyvinyl alcohol-based mutual penetration type gel in which the introduction rate of the radically polymerizable group is 0.01 to 10 mol% with respect to the repeating unit of the polyvinyl alcohol (1') . The polyvinyl alcohol-based mutual penetration type gel according to claim 1, wherein the introduction rate of the radically polymerizable group is 0.1 to 10 mol% with respect to the repeating unit of the polyvinyl alcohol (1'). The polyvinyl alcohol-based mutual penetration according to claim 1 or 2, wherein the water-soluble polymer (2') is at least one selected from the group consisting of alginic acid, carboxymethyl cellulose, LM pectin, carboxymethyl starch and derivatives thereof. Mold gel. Claims 1 to 0.01, wherein the value of the mass ratio [first polymer network / second polymer network] between the first polymer network and the second polymer network is 1000 to 0.01 in the interpenetrating gel. The polyvinyl alcohol-based mutual penetration type gel according to any one of 3.