WO2021132303A1

WO2021132303A1 - Ink for hydrogel shaping, and hydrogel using same

Info

Publication number: WO2021132303A1
Application number: PCT/JP2020/048098
Authority: WO
Inventors: 祐貴立花; 雄介天野; 明士藤田; 一彦前川
Original assignee: 株式会社クラレ
Priority date: 2019-12-24
Filing date: 2020-12-23
Publication date: 2021-07-01
Also published as: JPWO2021132303A1

Abstract

An ink for hydrogel shaping, the ink including a modified vinyl alcohol polymer (A) including vinyl ester units represented by formula (1), and an initiator (B), the sulfur content in the ink being 0.001-2000 ppm. This ink has low odor due to the sulfur content thereof being a fixed value or less, and because variation in viscosity of the ink is kept within a fixed range, stable gel strength is realized. The ink also has "stimulation curing properties" whereby the ink rapidly gels in a single step in response to stimulation such as active energy rays or heat, and it is therefore possible to obtain a hydrogel by a simple operation. [In formula (1), X represents a carbon-carbon bond or a divalent saturated hydrocarbon group which may have a C1-10 branched structure, Y represents a hydrogen atom or a saturated hydrocarbon group which may have a C1-6 branched structure, and Z represents a hydrogen atom or a methyl group.]

Description

Hydrogel modeling ink and hydrogel using it

The present invention relates to a hydrogel containing a crosslinked product of ink and polyvinyl alcohol used for modeling a hydrogel.

Hydrogel (hereinafter sometimes abbreviated as gel) is a material composed of crosslinked hydrophilic polymer and water, and has been used for various purposes such as daily life, medical care, food, civil engineering, specifically, high water absorption. Super Absorbent Polymer (SAP), contact lenses, organ models, drug delivery substrates, adsorption carriers for metal ions, enzyme-immobilized carriers, affinity carriers, capsule carriers used for encapsulation of cells and microorganisms, wastewater It is used for treatment carriers, vascular embolizing materials, shock absorbing materials, vibration damping materials, soundproofing materials, ground improvement materials, water blocking materials, antifouling paints, etc. Among them, polyvinyl alcohol is a water-soluble synthetic polymer having excellent hydrophilicity, reactivity, biodegradability, biocompatibility, low toxicity, etc., and a hydrogel obtained by cross-linking it in an aqueous solution is flexible. And it is known that the gel strength is high (Patent Document 1).

Conventionally, as a method of cross-linking polyvinyl alcohol to obtain a hydrogel, (1) a method of physically cross-linking polyvinyl alcohol by repeatedly freezing and thawing an aqueous solution of polyvinyl alcohol (Patent Document 1) and (2) glutaraldehyde. A chemical cross-linking method using a typified aldehyde compound or boric acid as a cross-linking agent is known. However, in the polyvinyl alcohol-based hydrogels obtained by these methods, the physical cross-linking points disappear or the acetal bonds and borate ester bonds are hydrolyzed due to the influence of changes in the external environment such as temperature changes and pH changes. There is a problem that the usage environment is limited because the crosslinks are cut and the hydrogel is disintegrated due to the reaction. Further, the method (1) above requires repeated freezing and thawing of the polyvinyl alcohol aqueous solution, which poses a problem in terms of productivity.

On the other hand, in recent years, the development of a material modeling method called Adaptive Manufacturing represented by a 3D printer has become active, and a material suitable for these has been sought. In particular, in order to apply gel to a 3D printer, it is required that the ink used has "stimulation curability" such that it quickly gels in one step by stimulation with active energy rays or the like. Furthermore, in the medical field, practical application of a method of treating an affected area of a patient by gelling stimulating curable ink (Patent Document 2), surgical practice of a hydrogel model produced using a 3D printer, etc. It is expected to be applied to organ models used in surgery and precision scaffolds for regenerative medicine (Non-Patent Document 1).

To address these issues, Patent Document 3 describes a hydrogel obtained by using an ink containing a modified vinyl alcohol-based polymer having a predetermined crosslinkable group. Since the modified vinyl alcohol-based polymer is excellent in stimulus curability, a high-strength hydrogel can be easily obtained without going through the above-mentioned complicated operations.

JP-A-2010-204131 Japanese Patent Application Laid-Open No. 2008-50021 Japanese Unexamined Patent Publication No. 2019-35043

However, as a result of the studies by the present inventors, the hydrogel containing the crosslinked product of the modified vinyl alcohol-based polymer described in Patent Document 3 has a gel strength that changes depending on the state of the ink before gelation. It was discovered that it may partially cause poor gelation. In addition, it has become clear that there is a problem that odors caused by residual components are generated over time, and there is a concern about adverse effects on the safety of workers and the environment. No hydrogel has been found so far that has a low odor and is highly resistant to changes in temperature and pH.

The present invention has been made to solve the above problems, and is an ink for hydrogel molding capable of obtaining a hydrogel by a simple operation, having a low odor, and stably exhibiting a high gel strength. The purpose is to provide. Another object of the present invention is to provide a hydrogel containing a crosslinked product of polyvinyl alcohol having high resistance and low odor that can be used in a wide range of temperatures and pH.

As a result of diligent studies to solve the above problems, the present inventors have found that the cause of the odor is the sulfur content in the solvent used when modifying polyvinyl alcohol. Furthermore, by reducing the sulfur content, not only the odor of the ink is reduced, but also the change in the viscosity of the ink can be suppressed to a low level, so that high gel strength is stably exhibited and the following hydro They have found that gels are highly resistant to a wide range of temperatures and pH, completing the invention.

That is, the above-mentioned problem includes a modified vinyl alcohol-based polymer (A) containing a vinyl ester unit represented by the following formula (1) and an initiator (B), and has a sulfur content of 0.001 to 2000 ppm. , The solution is to provide an ink for hydrogel modeling.

[In the formula (1), X represents a divalent saturated hydrocarbon group which may have a carbon-carbon bond or a branched structure having 1 to 10 carbon atoms, and Y represents a hydrogen atom or a branched structure having 1 to 6 carbon atoms. It represents a saturated hydrocarbon group which may have a branched structure, and Z represents a hydrogen atom or a methyl group. ]

The content of the vinyl alcohol unit in the modified vinyl alcohol-based polymer (A) with respect to all the constituent units is preferably 60 to 99.99 mol%. It is also preferable that the ratio of the vinyl ester units present in three or more chains to the total vinyl ester units in the modified vinyl alcohol polymer (A) is 20 mol% or less. It is also preferable that the content of the vinyl ester unit represented by the formula (1) in the modified vinyl alcohol-based polymer (A) with respect to all the constituent units is 0.01 to 10 mol%.

In formula (1), it is preferable that Y is a hydrogen atom. It is also preferable that X is a carbon-carbon bond.

It is preferable that the ink further contains the strength-imparting agent (C). The strength-imparting agent (C) is preferably inorganic particles.

It is also preferable that the ink further contains a polymerization inhibitor (D).

It is also preferable that the ink is an ink for a 3D printer. The ink is an organ model, contact lens, drug delivery base material, adsorption carrier, enzyme-immobilized carrier, affinity carrier, capsule carrier, wastewater treatment carrier, vascular embolic material, shock absorber, vibration damping material, soundproofing material, ground. It is also preferably used in the production of improved materials, water blocking materials or antifouling paints.

The above-mentioned problem is a hydrogel containing a crosslinked product of the hydrogel molding ink, and all of them have an elution rate when immersed in water at 100 ° C. having a pH of 0.5, 5, 10 or 14 for 1 hour. It is also solved by providing a hydrogel which is 50% by weight or less.

At this time, the initial moisture content W1 (mass%) of the hydrogel and the hydrogel were vacuum-dried at 40 ° C. for 8 hours, further vacuum-dried at 120 ° C. for 1 hour, and then immersed in water at 40 ° C. for 48 hours. It is preferable that the subsequent water content W2 (mass%) satisfies the following formula (I).
0.8 <(W1 / W2) <1.4 (I)

It is preferable that the hydrogel further contains the strength-imparting agent (C).

Organ model, contact lens, drug delivery base material, adsorption carrier, enzyme-immobilized carrier, affinity carrier, capsule carrier, wastewater treatment carrier, vascular embolizing material, shock absorber, vibration damping material composed of the hydrogel. , Soundproofing material, ground improving material, water blocking material or antifouling paint are preferred embodiments of the present invention.

The hydrogel molding ink of the present invention containing a modified vinyl alcohol-based polymer containing a predetermined vinyl ester unit has a sulfur content of a certain level or less, and therefore has a low odor and a constant viscosity change. Since it is suppressed within the range, stable gel strength is developed. Further, since the ink of the present invention has "stimulation curability" such that it quickly gels in one step by a stimulus such as active energy rays or heat, a hydrogel can be obtained by a simple operation. Taking advantage of these characteristics, the hydrogel modeling ink of the present invention is suitably used as an ink for a 3D printer. Further, since the hydrogel of the present invention has high resistance to a wide range of temperatures and pH and has a low odor, it is suitably used as a medical organ model or the like.

The hydrogel molding ink of the present invention contains a modified vinyl alcohol-based polymer (A) containing a vinyl ester unit represented by the following formula (1) and an initiator (B), and has a sulfur content of 0.001. It is ~ 2000 ppm.

Since the sulfur content of the ink is below a certain level, it has a low odor and the change in viscosity is suppressed below a certain level, so that stable gel strength is exhibited. Further, the modified vinyl alcohol polymer (A) is quickly crosslinked in one step by stimulation with active energy rays or heat to obtain a hydrogel. Since the ink has stimulus curability as described above, a hydrogel can be obtained by a simple operation. Taking advantage of these characteristics, the hydrogel modeling ink of the present invention is suitably used as an ink for a 3D printer or the like. Then, the obtained modeled product is suitably used as a medical organ model or the like.

Since the ink of the present invention has a stimulating curability by containing the modified vinyl alcohol polymer (A) containing the vinyl ester unit represented by the formula (1), a hydrogel can be obtained by a simple operation.

X in the formula (1) represents a divalent saturated hydrocarbon group which may have a carbon-carbon bond or a branched structure having 1 to 10 carbon atoms. It is preferable that X is a carbon-carbon bond from the viewpoint of further improving the stimulus curability.

The saturated hydrocarbon group used as X has 1 to 10 carbon atoms. When the number of carbon atoms exceeds 10, the water solubility deteriorates. The carbon number is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less.

Examples of the divalent saturated hydrocarbon group used as X include an alkylene group and a cycloalkylene group. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group and a decylene group. Examples of the cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group and the like. The alkylene group and the cycloalkylene group used as X may have an alkyl group such as a methyl group or an ethyl group as a branched structure.

Y in the formula (1) represents a hydrogen atom or a saturated hydrocarbon group which may have a branched structure having 1 to 6 carbon atoms. It is preferable that Y is a hydrogen atom.

The saturated hydrocarbon group used as Y has 1 to 6 carbon atoms. If the number of carbon atoms exceeds 6, the water solubility may deteriorate. The carbon number is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less.

Examples of the saturated hydrocarbon group used as Y include an alkyl group and a cycloalkyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, and a hexyl group. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group and the like. The alkyl group and cycloalkyl group used as Y may have an alkyl group such as a methyl group or an ethyl group as a branched structure.

The content of the vinyl ester unit represented by the formula (1) with respect to all the structural units in the modified vinyl alcohol polymer (A) is preferably 0.01 to 10 mol%. If the content is less than 0.01 mol%, the aqueous solution of the modified vinyl alcohol polymer (A) may not easily gel. The content is more preferably 0.05 mol% or more, further preferably 0.1 mol% or more, particularly preferably 0.3 mol% or more, and most preferably 0.5 mol% or more. On the other hand, if the content exceeds 10 mol%, the water solubility of the modified vinyl alcohol-based polymer (A) may deteriorate. The content is more preferably 8 mol% or less, further preferably 5 mol% or less, particularly preferably 3 mol% or less, and most preferably 2 mol% or less. The content of the vinyl ester unit represented by the formula (1) can be determined by a method using ^{1 H-NMR measurement described in Examples described later.}

The content of the vinyl alcohol unit with respect to all the constituent units in the modified vinyl alcohol-based polymer (A) is preferably 60 to 99.99 mol%. If the content of the vinyl alcohol unit is less than 60 mol%, the water solubility of the modified vinyl alcohol polymer (A) may deteriorate and a hydrogel may not be obtained, and the gel strength may decrease. is there. The content of the vinyl alcohol unit is more preferably 70 mol% or more, further preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more. On the other hand, when the content of the vinyl alcohol unit exceeds 99.99 mol%, it may be difficult to industrially produce the modified vinyl alcohol-based polymer (A). The content of the vinyl alcohol unit is more preferably 99.9 mol% or less, further preferably 99.5 mol% or less, particularly preferably 99 mol% or less, and most preferably 98 mol% or less. The content of the vinyl ester unit represented by the formula (1) can be determined by a method using ^{1 H-NMR measurement described in Examples described later.}

The viscosity average degree of polymerization of the modified vinyl alcohol polymer (A) is preferably 100 to 5000, more preferably 200 to 4000. If the viscosity average degree of polymerization is less than 100, the gel strength of the modified vinyl alcohol-based polymer (A) may decrease. On the other hand, when the viscosity average degree of polymerization exceeds 5000, industrial production of the modified vinyl alcohol-based polymer (A) may become difficult. The viscosity average degree of polymerization of the modified vinyl alcohol polymer (A) is measured according to JIS K6726.

The vinyl alcohol unit of the modified vinyl alcohol polymer (A) can be derived from the vinyl ester unit by hydrolysis, alcohol decomposition, or the like. Therefore, the vinyl ester unit may remain in the modified vinyl alcohol-based polymer (A) depending on the conditions for converting the vinyl ester unit to the vinyl alcohol unit.

Examples of the vinyl ester of the vinyl ester unit include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatic acid, vinyl caproate, vinyl caprylate, vinyl laurate, and palmitin. Examples thereof include vinyl acetate, vinyl stearate, vinyl oleate, vinyl benzoate, and the like, and among these, vinyl acetate is preferable from an industrial point of view.

The method for producing the modified vinyl alcohol-based polymer (A) is a method for producing a modified vinyl alcohol-based polymer in which a mixed medium containing an unsaturated carboxylic acid, an acid catalyst and water and a vinyl alcohol-based polymer are mixed. Therefore, it is preferable that the unsaturated carboxylic acid is represented by the following formula (2).

[X, Y, Z in the formula (2) are synonymous with the formula (1). ]

In this method, since it is not necessary to use a liquid medium containing sulfur, there is no problem that the sulfur content derived from the liquid medium or the like remains in the modified vinyl alcohol polymer (A). Further, in the obtained modified vinyl alcohol-based polymer (A), the proportion of vinyl ester units present in three or more chains can be reduced.

By mixing the mixed medium and the vinyl alcohol-based polymer, the unsaturated carboxylic acid and the vinyl alcohol-based polymer are reacted. The mixing method at this time is not particularly limited as long as the two can be mixed uniformly. Specifically, (a) a method of preparing the mixed medium and then mixing the mixed medium with the vinyl alcohol-based polymer, and (b) a part of the vinyl alcohol-based polymer and the mixed medium. After mixing with, a method of mixing the obtained mixture with the remaining components of the mixing medium, (c) a method of simultaneously mixing each component of the mixing medium with the vinyl alcohol polymer, and the like can be mentioned. Of these, (a) is preferable.

It is preferable that the vinyl alcohol-based polymer to be reacted with the unsaturated carboxylic acid is particles. By mixing the mixed medium and the vinyl alcohol-based polymer particles and dispersing the vinyl alcohol-based polymer particles in the mixed medium, the unsaturated carboxylic acid and the vinyl alcohol-based polymer particles are reacted. The method of causing is preferable. As described above, by carrying out the reaction while maintaining the particle shape of the raw material vinyl alcohol-based polymer particles, the operation of precipitating the reaction product using a large amount of poor solvent becomes unnecessary. Specifically, a method of reacting the unsaturated carboxylic acid with the vinyl alcohol-based polymer particles by mixing the mixed medium and the vinyl alcohol-based polymer particles to form a slurry or a dispersion liquid can be mentioned. Be done. Further, a method of reacting the unsaturated carboxylic acid with the vinyl alcohol-based polymer particles by uniformly blending the mixed medium with the vinyl alcohol-based polymer particles can also be mentioned.

As the unsaturated carboxylic acid, the one represented by the formula (2) is used. X, Y, and Z in the formula (2) are synonymous with the formula (1). Specific examples of the unsaturated carboxylic acid when X is a carbon-carbon bond include methacrylic acid, acrylic acid, crotonic acid and the like.

Specific examples of the unsaturated carboxylic acid represented by the formula (2) include methacrylic acid, acrylic acid, crotonic acid, 3-methyl-3-butenoic acid, 4-pentenoic acid, 2-methyl-4-pentenoic acid, and 5 -Hexenoic acid, 3,3-dimethyl-4-pentenoic acid, 7-octenoic acid, trans-3-pentenoic acid, trans-4-decenoic acid, 10-undecenoic acid and the like can be mentioned. Among them, methacrylic acid, acrylic acid, 4-pentenoic acid, 10-undecenoic acid are preferable, methacrylic acid, acrylic acid and 4-pentenoic acid are more preferable, and methacrylic acid and Acrylic acid is more preferred, and methacrylic acid is particularly preferred.

An acid catalyst is used as a catalyst for the reaction between the unsaturated carboxylic acid and the vinyl alcohol polymer. This promotes the reaction between the unsaturated carboxylic acid and the vinyl alcohol polymer. The acid catalyst may be any acid catalyst as long as it catalyzes the dehydration esterification reaction between the unsaturated carboxylic acid represented by the formula (2) and the hydroxyl group of the vinyl alcohol-based polymer, and either an organic acid or an inorganic acid can be used. is there. Examples of the organic acid include methanesulfonic acid, benzenesulfonic acid, trifluoromethanesulfonic acid and paratoluenesulfonic acid, and examples of the inorganic acid include sulfuric acid, hydrochloric acid and nitric acid. Of these, methanesulfonic acid, paratoluenesulfonic acid and sulfuric acid are preferable, and paratoluenesulfonic acid is particularly preferable.

The mass ratio [polymer / mixed medium] of the vinyl alcohol-based polymer to the mixed medium when mixing the mixed medium and the vinyl alcohol-based polymer is preferably 3/97 to 90/10. If the mass ratio [polymer / mixed medium] is less than 3/97, the reactivity may be significantly reduced. The mass ratio [polymer / mixed medium] is preferably 10/90 or more. On the other hand, when the mass ratio [polymer / mixed medium] exceeds 90/10, the mixed medium and the vinyl alcohol-based polymer may not be uniformly mixed or the reactivity may be significantly lowered. The mass ratio [polymer / mixed medium] is more preferably 80/20 or less, and even more preferably 50/50 or less.

The water content in the mixed medium is preferably 1 to 30% by mass. When the water content is less than 1% by mass, the obtained modified vinyl alcohol-based polymer (A) may be easily colored. The water content is more preferably 3% by mass or more, further preferably 5% by mass or more, and particularly preferably 8% by mass or more. On the other hand, the water content is more preferably 20% by mass or less, further preferably 18% by mass or less.

The amount of the acid catalyst added when the unsaturated carboxylic acid is reacted with the vinyl alcohol polymer is preferably 0.0001 to 0.1 mol with respect to 1 mol of the hydroxyl group in the vinyl alcohol polymer. .. The addition amount is more preferably 0.0005 mol or more. On the other hand, the addition amount is more preferably 0.08 mol or less.

The content of the unsaturated carboxylic acid in the mixed medium is preferably 5 to 2000 parts by mass with respect to 100 parts by mass of the vinyl alcohol polymer. If the amount of unsaturated carboxylic acid added is less than 5 parts by mass, the reactivity may decrease. The content of the unsaturated carboxylic acid is more preferably 10 parts by mass or more, further preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more. On the other hand, when the content of the unsaturated carboxylic acid exceeds 2000 parts by mass, the unreacted unsaturated carboxylic acid may increase and the cost may increase. The content of the unsaturated carboxylic acid is more preferably 1500 parts by mass or less, further preferably 1000 parts by mass or less, and particularly preferably 700 parts by mass or less.

In order to control the content of the vinyl acetate unit of the modified vinyl alcohol polymer (A), the mixed medium may further contain acetic acid. The content of acetic acid in the mixed medium is preferably 1 to 1000 parts by mass with respect to 100 parts by mass of water. The content of acetic acid is more preferably 5 parts by mass or more, further preferably 10 parts by mass or more. On the other hand, the content of acetic acid is more preferably 800 parts by mass or less, and further preferably 600 parts by mass or less.

The mixed medium may contain an unsaturated carboxylic acid represented by the formula (2), the acid catalyst, water and other additives other than acetic acid. Other additives include, for example, surfactants, organic solvents, UV absorbers, light stabilizers, antioxidants, plasticizers, defoamers. The content of the other additive in the mixed medium is preferably 50% by mass or less, more preferably 35% by mass or less. Further, it is preferable that the mixed medium does not contain a liquid medium containing sulfur.

The temperature at which the unsaturated carboxylic acid is reacted with the vinyl alcohol-based polymer is preferably 10 to 120 ° C. The temperature is more preferably 30 ° C. or higher, and even more preferably 50 ° C. or higher. On the other hand, the temperature is more preferably 100 ° C. or lower, and even more preferably 90 ° C. or lower. The reaction time for reacting the unsaturated carboxylic acid with the vinyl alcohol polymer is usually 0.5 to 72 hours.

When the modified vinyl alcohol polymer (A) is obtained as particles, it is preferable to further wash the particles. Specific examples of the cleaning method include a method of cleaning the particles with a solvent. Specifically, a method of immersing the particles in a solvent and then removing the liquid, a method of contacting the particles with the particles while flowing the solvent in a washing tower for washing, and a washing solvent while flowing the particles. Examples include a method of spraying. Examples of the solvent used include alcohols such as methanol, ethanol, propanol and butanol; aliphatic or alicyclic hydrocarbons such as n-hexane, n-pentane and cyclohexane; aromatic carbides such as benzene and toluene. Hydrogens; nitriles such as acetonitrile and benzonitrile; ethers such as diethyl ether, diphenyl ether, anisole, 1,2-dimethoxyethane and 1,4-dioxane; ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone and methyl isobutyl ketone Kind: Esters such as methyl acetate, ethyl acetate, ethyl propionate and the like. Among them, alcohols, ethers, ketones and esters are more preferable, methanol, ethanol, propanol, diethyl ether, 1,2-dimethoxyethane, acetone, methyl ethyl ketone, methyl acetate and ethyl acetate are more preferable, and methanol, propanol, Acetone, methyl ethyl ketone, methyl acetate and ethyl acetate are particularly preferred. These organic solvents may be used alone or in combination of two or more.

It is preferable to wash the modified vinyl alcohol polymer (A) after the reaction, if necessary, and then dry it. At this time, the drying temperature is usually 20 to 150 ° C., and the drying time is 1 to 72 hours. Further, the modified vinyl alcohol polymer (A) may be dried under atmospheric pressure or under reduced pressure.

The modified vinyl alcohol-based polymer (A) may contain a monomer unit other than the vinyl alcohol unit and the vinyl ester unit as long as the effect of the present invention is not impaired. Examples of such other monomer units include those derived from ethylenically unsaturated monomers copolymerizable with vinyl ester. Examples of such ethylenically unsaturated monomers include α-olefins such as ethylene, propylene, n-butyl, isobutylene, and 1-hexene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, and acrylic acid. Acrylic acid esters such as n-propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid And salts thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, methacrylate Methacrylate esters such as dodecyl and octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salts, acrylamidepropyldimethylamine and its salts. (For example, quaternary salt); methacrylamide, N-methylmethacrylate, N-ethylmethacrylate, methacrylicamidepropanesulfonic acid and its salt, methacrylamidepropyldimethylamine and its salt (for example, quaternary salt); methylvinyl ether, ethyl. Vinyl ethers such as vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane; acrylonitrile , Vinyl cyanide such as methacrylonitrile; Vinyl halides such as vinyl chloride and vinyl fluoride; Vinylidene halides such as vinylidene chloride and vinylidene fluoride; Allyl acetate, 2,3-diacetoxy-1-allyloxy Allyl compounds such as propane and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid and salts thereof or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like can be mentioned.

The content of other monomer units in the modified vinyl alcohol-based polymer (A) with respect to all the constituent units is usually 10 mol% or less, preferably 5 mol% or less, and more preferably 1 mol% or less.

From the viewpoint of improving the viscosity stability of the ink, it is preferable that the ratio of the vinyl ester units present in three or more chains to the total vinyl ester units in the modified vinyl alcohol polymer (A) is 20 mol% or less. The ratio is more preferably 18 mol% or less, further preferably 16 mol% or less, and particularly preferably 15 mol% or less. On the other hand, the proportion of vinyl ester units present in three or more chains is usually 0.1 mol% or more. The proportion of vinyl ester units present in three or more chains can be determined by the method using ^{1 1 H-NMR measurement described in Examples described later.}

The content of the modified vinyl alcohol polymer (A) in the ink of the present invention is preferably 1 to 70% by mass. If the content is less than 1% by mass, the gel strength may be insufficient. The content is more preferably 3% by mass or more, further preferably 5% by mass or more, particularly preferably 7% by mass or more, and most preferably 8% by mass or more. On the other hand, if the content exceeds 70% by mass, the viscosity of the ink may become too high and it may be difficult to handle. The content is more preferably 50% by mass or less, further preferably 40% by mass or less, particularly preferably 30% by mass or less, and most preferably 20% by mass or less.

The sulfur content in the ink needs to be 0.001 to 2000 ppm. When the sulfur content is below a certain level in this way, the odor of the ink and the obtained hydrogel is reduced. Such hydrogels are not only highly safe but also environmentally friendly. Furthermore, when the sulfur content is below a certain level, the viscosity stability of the ink is surprisingly improved. Then, by improving the viscosity stability of the ink, a hydrogel having high gel strength can be stably obtained. The sulfur content is preferably 1500 ppm or less, more preferably 1000 ppm or less, further preferably 500 ppm or less, particularly preferably 300 ppm or less, and most preferably 200 ppm or less. On the other hand, if the sulfur content is less than 0.001 ppm, it may be difficult to industrially produce the modified vinyl alcohol-based polymer (A). The sulfur content is more preferably 0.01 ppm or more, further preferably 0.1 ppm or more, and particularly preferably 1 ppm or more.

It is preferable that the ink further contains the strength-imparting agent (C). Examples of the strength-imparting agent (C) include organic particles (C-1) other than the vinyl alcohol-based polymer and inorganic particles (C-2), and the latter is preferable.

Examples of the organic particles (C-1) include polymer particles, cellulose nanofibers, graphene oxide, bamboo charcoal, particles of carbon material such as activated carbon, and the like. The polymer constituting the polymer particles may be a polymer composed of one kind of monomer unit or a copolymer composed of a plurality of types of monomer units. It may also be a mixture of a plurality of polymers.

Examples of the monomer unit include conjugated diene such as butadiene and isoprene; aromatic vinyl compounds such as styrene, α-methylstyrene and tert-butylstyrene; (meth) acrylic acid and salts thereof; methyl (meth) acrylate, Ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isopropyl (meth) acrylate, dicyclopentanyl (meth) acrylate, trimethylpropanthry (meth) acrylate, (Meta) acrylic acid esters such as allyl (meth) acrylate; (meth) acrylamide; (meth) acrylamide derivatives such as N-methyl (meth) acrylamide and N-ethyl (meth) acrylamide; nitriles such as (meth) acrylonitrile; Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether; vinyl esters such as vinyl acetate, vinyl n-propionate, vinyl butyrate, vinyl pivalate; unsaturated dicarboxylic acids such as maleic anhydride and itaconic anhydride. Anhydrous; monoolefins such as ether, propene, n-butene, isobutene; ethylene halides such as vinyl bromide, vinylidene bromide, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, etc .; allyl acetate, allyl chloride, etc. Allyl compounds; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid and salts thereof; unsaturated dicarboxylic acid esters such as maleic acid ester and itaconic acid ester; vinylsilyl compounds such as trimethoxysilane; cyclopentadiene, norbornadien, etc. Cyclic diene; indens such as inden and tetrahydroinden; cyclic ethers such as ethylene oxide, propylene oxide, oxetane and tetrahydrofuran; cyclic sulfides such as thirane and thietan; cyclic amines such as allyl and azetidine; 1,3-dioxolane, 1, Cyclic acetals such as 3,5-trioxane and spiroorthoester; cyclic iminoethers such as 2-oxozarin and iminoether; lactones such as β-propiolactone, δ-valerolactone and ε-caprolactone; ethylene carbonate, propylene carbonate and the like. (Cyclic carbonate); Cyclic siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane; and the like. Among these, from the viewpoint of productivity, a monomer unit derived from at least one selected from the group consisting of conjugated diene, aromatic vinyl compound and (meth) acrylic acid ester is preferable, and derived from (meth) acrylic acid ester. The monomer unit to be used is more preferable.

The polymer particles are preferably particles having a core-shell structure. As the polymer constituting the core and the shell, the above-mentioned polymer is used as the polymer constituting the polymer particles.

The polymer particles are produced by the method described in JP-A-2019-35043 or the like.

Examples of the inorganic particles (C-2) include silica such as colloidal silica, precipitated silica, gelled silica, and vapor phase silica; ceramics such as alumina, hydroxyapatite, zirconia, zinc oxide, and barium titanate; smectite, bentonite, and the like. Minerals such as zeolite, talc, montmorillonite (including compounds); gypsum such as calcium sulfate; metal oxides such as calcium oxide and iron oxide; metal carbonates such as calcium carbonate and magnesium carbonate; Examples thereof include sand and gravel, and among them, colloidal silica, smectite and bentonite are preferable.

The average particle size of the strength-imparting agent (C) is preferably 0.001 to 100 μm. The average particle size is more preferably 50 μm or less, further preferably 10 μm or less, particularly preferably 5 μm or less, and most preferably 1 μm or less.

The content of the strength-imparting agent (C) in the ink is preferably 0.1 to 50% by mass. If the content is less than 0.1% by mass, the effect of improving the gel strength may not be obtained. The content is more preferably 0.5% by mass or more, further preferably 1.0% by mass or more, particularly preferably 2.0% by mass or more, and most preferably 3.0% by mass or more. On the other hand, if the content exceeds 50% by mass, gelation may be difficult. The content is more preferably 40% by mass or less, further preferably 30% by mass or less, particularly preferably 20% by mass or less, and most preferably 10% by mass or less.

The ink usually contains water. The content of water in the ink is preferably 30% by mass or more, more preferably 50% by mass or more, and further preferably 70% by mass or more. The ink may contain a solvent other than water. Other solvents include monoalcohols such as methanol, ethanol, propanol and isopropanol; and water-soluble solvents such as polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol and glycerin. The content of the other solvent in the ink is preferably 10% by mass or less, and it is more preferable that the hydrogel does not substantially contain a solvent other than water from the viewpoint of safety and the environment.

The ink contains an initiator (B). Examples of the initiator (B) include a photoinitiator, a heat initiator, a redox initiator and the like. The amount of the initiator (B) added is usually 0.01 to 10 parts by mass with respect to 100 parts by mass of the modified vinyl alcohol polymer (A).

As the photoinitiator, any one that initiates a radical reaction with light rays such as ultraviolet rays (UV) and visible light can be used without any particular problem. Specifically, for example, α-ketoglutaric acid, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one (trade name "Irgacure2959", BASF Japan). , 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.), eodin Y, and other photoinitiators with relatively high water solubility can be mentioned.

When the ink contains a light initiator, the ink may further contain a light absorber. By containing a light absorber, a modeled product having a more precise shape can be obtained when a hydrogel is modeled by a stereolithography method using a 3D printer or the like. The light absorber is not particularly limited as long as it exhibits water solubility, but is "KEMISORB111" and "KEMISORB11S" manufactured by Chemipro Kasei Co., Ltd. and "Tinuvin 477-DW", "UVA805" and "Tinuvin 1130" manufactured by BASF Japan Ltd. And so on.

As the heat initiator, an azo-based initiator or a peroxide-based initiator, which is generally used as a radical reaction initiator, can be used, but it does not generate gas and has more excellent transparency and gel strength. A peroxide-based initiator is preferable from the viewpoint of obtaining a hydrogel having.

Examples of the peroxide-based polymerization initiator include inorganic peroxides such as ammonium persulfate, potassium persulfate, and sodium persulfate.

As an azo-based initiator, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (trade name "VA-044", manufactured by Wako Pure Chemical Industries, Ltd.), 2 , 2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate (trade name "VA-044B", manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'- Azobis [2-methylpropion amidine] dihydrochloride (trade name "V-50", manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropion Amidine] tetrahydrate (trade name "VA-057", manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] (trade name "VA" -061 ", manufactured by Wako Pure Chemical Industries, Ltd., 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] (trade name" VA-086 ", Wako Pure Chemical Industries, Ltd. ( (Manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis (4-cyanopentanoic acid) (trade name "V-501", manufactured by Wako Pure Chemical Industries, Ltd.) Be done.

As the redox-based initiator, a combination of the above-mentioned peroxide-based initiator and reducing agent is used, and the radical reaction (crosslinking reaction) is started by mixing the two. As the reducing agent, a reducing agent having relatively high water solubility such as N, N, N', N'-tetramethylethylenediamine, sodium sulfite, sodium hydrogen sulfite, and sodium hydrosulfite is used.

It is preferable that the ink further contains a polymerization inhibitor (D). The polymerization inhibitor (D) is not particularly limited, but a polymerization inhibitor (D) having a relatively high water solubility such as methquinone and hydroquinone is preferable, and methquinone is more preferable. When the ink contains a polymerization inhibitor (D) to further enhance the viscosity stability of the ink, or when a hydrogel is formed by a stereolithography method using a 3D printer or the like, a modeled product having a precise shape. Can be obtained. The amount of the polymerization inhibitor (D) added is usually 0.001 to 1 part by mass with respect to 100 parts by mass of the modified vinyl alcohol-based polymer (A).

The ink may contain a cross-linking agent. Such cross-linking agents preferably exhibit water solubility, and are radically reactive, for example, N, N'-methylenebisacrylamide, ethylene glycol di (meth) acrylate, N, N'-diethylene glycol di (meth) acrylate. Examples thereof include compounds having two or more ethylenic double bonds.

The ink may contain additives such as dyes, preservatives and fungicides as long as the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

The method for producing the ink is not particularly limited, but the method of adding other components to the aqueous solution obtained by dissolving the modified vinyl alcohol polymer (A) in water, the modified vinyl alcohol polymer (A) and the like. Examples thereof include a method of dissolving the modified vinyl alcohol-based polymer (A) after adding other components to water.

Since the ink of the present invention thus obtained has a low sulfur content, the odor is reduced and the change in viscosity is suppressed within a certain range, so that stable gel strength is exhibited. Further, since the ink of the present invention has excellent stimulus curability, a hydrogel can be obtained by a simple operation. Taking advantage of these characteristics, the hydrogel modeling ink of the present invention is used in a hydrogel modeling method using a conventional mold, and is also suitably used in applications such as 3D printers.

The above problem is a hydrogel containing a crosslinked product of polyvinyl alcohol (E), which has a sulfur content of 0.001 to 2000 ppm and a pH of 0.5, 5, 10 or 14 at 100 ° C. It is also solved by providing a hydrogel having an elution rate of 50% by mass or less when immersed in water for 1 hour. Such hydrogels have a low odor due to their low sulfur content. Therefore, the hydrogel is highly safe and has little impact on the environment. Moreover, the hydrogel has a low elution rate when immersed in water having a wide range of temperatures and pH, and has high resistance to temperature changes and pH changes, so that it is suitably used for various purposes.

It is preferable that the content and viscosity average degree of polymerization of the vinyl alcohol unit with respect to all the constituent units in the polyvinyl alcohol (E) are the same as those of the modified vinyl alcohol-based polymer (A) described above.

The vinyl alcohol unit of polyvinyl alcohol (E) can be derived from the vinyl ester unit by hydrolysis, alcohol decomposition, or the like. Therefore, the vinyl ester unit may remain in the polyvinyl alcohol (E) depending on the conditions for converting the vinyl ester unit to the vinyl alcohol unit. Examples of such a vinyl ester unit include those similar to the above-mentioned modified vinyl alcohol-based polymer (A).

It is preferable that the polyvinyl alcohol (E) contains a crosslinkable group from the viewpoint of improving the resistance to temperature change and pH change and the re-swelling property of the obtained hydrogel. As the crosslinkable group, a (meth) acryloyloxy group, a (meth) acryloylamino group, an allyl group, a vinyl ether group, a vinyl ester group, a vinylphenyl group, a vinylidene group, a vinylene group and these can be expected to react highly efficiently even in water. A group having an ethylenic double bond, such as a derivative of the above, is preferable.

As long as the effect of the present invention is not impaired, the polyvinyl alcohol (E) contains a vinyl alcohol unit, a vinyl ester unit, and a monomer unit other than a monomer having a crosslinkable group or a derivative thereof. You may. Examples of such other monomer units include those described above as other monomer units other than the vinyl alcohol unit and the vinyl ester unit that may be contained in the modified vinyl alcohol-based polymer (A). ..

The content of other monomer units in the polyvinyl alcohol (E) with respect to all the constituent units is usually 10 mol% or less, preferably 5 mol% or less, and more preferably 1 mol% or less.

From the viewpoint of improving the re-swelling property of the hydrogel, it is preferable that the ratio of the vinyl ester units present in three or more chains to the total vinyl ester units in the polyvinyl alcohol (E) is 20 mol% or less. The ratio is more preferably 18 mol% or less, further preferably 16 mol% or less, and particularly preferably 15 mol% or less. On the other hand, the proportion of vinyl ester units present in three or more chains is usually 0.1 mol% or more.

As a method for producing polyvinyl alcohol (E) having a crosslinkable group, a method of reacting polyvinyl alcohol with a compound having a crosslinkable group or a derivative thereof, or a monomer having a crosslinkable group or a derivative thereof is vinyl. Examples thereof include a method of cross-linking with an ester and then cross-linking.

As the polyvinyl alcohol (E) having a crosslinkable group, the above-mentioned modified vinyl alcohol-based polymer (A) is more preferable. That is, it is preferable that the hydrogel contains a crosslinked product of the ink of the present invention containing the modified vinyl alcohol polymer (A) and the initiator (B) described above.

The content of the crosslinkable group with respect to all the structural units in the polyvinyl alcohol (E) is the same as the content of the vinyl ester unit represented by the above formula (1) in the above-mentioned modified vinyl alcohol-based polymer (A). Is preferable.

The content of polyvinyl alcohol (E) in the hydrogel of the present invention is preferably 1 to 70% by mass. If the content is less than 1% by mass, the gel strength may be insufficient. The content is more preferably 3% by mass or more, further preferably 5% by mass or more, particularly preferably 7% by mass or more, and most preferably 8% by mass or more. On the other hand, if the content exceeds 70% by mass, the viscosity of the obtained aqueous solution may become too high, making it difficult to handle. The content is more preferably 50% by mass or less, further preferably 40% by mass or less, particularly preferably 30% by mass or less, and most preferably 20% by mass or less.

It is preferable that the hydrogel further contains the strength-imparting agent (C). As the strength-imparting agent (C), those described above are used as those contained in the ink of the present invention.

The content of the strength-imparting agent (C) in the hydrogel is preferably 0.1 to 50% by mass. If the content is less than 0.1% by mass, the effect of improving the gel strength may not be obtained. The content is more preferably 0.5% by mass or more, further preferably 1.0% by mass or more, particularly preferably 2.0% by mass or more, and most preferably 3.0% by mass or more. On the other hand, if the content exceeds 50% by mass, gelation may be difficult. The content is more preferably 40% by mass or less, further preferably 30% by mass or less, particularly preferably 20% by mass or less, and most preferably 10% by mass or less.

The method for producing the hydrogel is not particularly limited, but after obtaining an aqueous solution containing polyvinyl alcohol (E), a strength-imparting agent (C) if necessary, and other additives, the polyvinyl alcohol in the aqueous solution ( The method of cross-linking E) is preferable.

The content of water in the hydrogel is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more. The hydrogel may contain a solvent other than water. Other solvents include monoalcohols such as methanol, ethanol, propanol and isopropanol; and water-soluble solvents such as polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol and glycerin. The content of the other solvent in the hydrogel is preferably 10% by mass or less, and it is more preferable that the hydrogel does not substantially contain a solvent other than water from the viewpoint of safety and the environment.

The method for producing the aqueous solution is not particularly limited, but a method of adding other components to the aqueous solution obtained by dissolving polyvinyl alcohol (E) in water, polyvinyl alcohol (E) and other components are added to water. After that, a method of dissolving the polyvinyl alcohol (E) and the like can be mentioned.

When a polyvinyl alcohol (E) having the above-mentioned crosslinkable group is used, it is preferable that the aqueous solution contains the initiator (B). As the initiator (B), the above-mentioned one contained in the ink of the present invention is used. The amount of the initiator (B) added is usually 0.01 to 10 parts by mass with respect to 100 parts by mass of polyvinyl alcohol (E). The ink of the present invention described above is preferably used as an aqueous solution containing polyvinyl alcohol (E) having a crosslinkable group and an initiator (B) used in the production of the hydrogel.

When the aqueous solution contains the initiator (B), it is preferable that the aqueous solution further contains the polymerization inhibitor (D). The polymerization inhibitor is not particularly limited, but those described above are preferable as those contained in the ink of the present invention. When the aqueous solution contains a polymerization inhibitor (D) to enhance the storage stability of the solution, or when a hydrogel is formed by a stereolithography method using a 3D printer or the like, a modeled product having a precise shape can be obtained. Obtainable. The amount of the polymerization inhibitor (D) added is usually 0.001 to 1 part by mass with respect to 100 parts by mass of polyvinyl alcohol (E).

The aqueous solution may contain a cross-linking agent. Examples of such a cross-linking agent include those described above as those contained in the ink of the present invention.

The aqueous solution may contain additives such as pigments, preservatives and fungicides as long as the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

A hydrogel can be obtained by cross-linking the polyvinyl alcohol (E) in the aqueous solution. The method at this time is not particularly limited, but an aqueous solution containing polyvinyl alcohol (E) having a crosslinkable group, an initiator (B), and if necessary, other additives, preferably the above-mentioned ink of the present invention. On the other hand, a method of irradiating or heating with active energy rays is preferable. The active energy beam is not particularly limited as long as it can cleave the photoinitiator to generate a radical, and is a ray of far ultraviolet rays, ultraviolet rays (UV), near ultraviolet rays, visible rays, infrared rays, X-rays, etc. Examples thereof include electromagnetic waves such as γ-rays, electron beams (EB), proton beams (α rays), and particle beams such as neutron rays. Among them, ultraviolet rays and electron beams are preferable, and ultraviolet rays are more preferable, from the viewpoints of starting efficiency, availability of an irradiation device, price, and the like.

The hydrogel molding method includes (a) a method of pouring the aqueous solution into a predetermined mold and the like, and then cross-linking polyvinyl alcohol (E), and (b) molding the hydrogel using a 3D printer. The method and the like can be mentioned.

The specific method of (b) will be described below. As the modeling ink, an aqueous solution containing polyvinyl alcohol (E) having a crosslinkable group, an initiator (B), and if necessary, other additives, preferably the ink of the present invention described above is used. Examples of the 3D printer method include a material extrusion deposition method, an inkjet method, and a stereolithography method. In the material extrusion deposition method, the hydrogel is deposited by repeating a step of ejecting the ink to a desired position using a syringe or the like and a step of irradiating the ejected ink with active energy rays. A model is obtained. In the inkjet method, a modeled product is obtained by performing a step of ejecting the ink from the inkjet head to a desired position and a step of irradiating the ejected ink with active energy rays. In the stereolithography method, a step of irradiating a desired portion of the liquid surface of the ink filled in a container with active energy rays to gel the portion, and a step of immersing the gelled portion in the ink are used. A modeled product is obtained by repeating the step of covering the upper surface with the ink and depositing the hydrogel.

The hydrogel thus obtained 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.

In the present invention, the elution rate when the hydrogel is immersed in water at 100 ° C. having a pH of 0.5, 5, 10 or 14 for 1 hour is required to be 50% by mass or less. Hydrogels that satisfy such conditions have high resistance to a wide range of temperatures and pH, and are therefore suitably used in various applications. Water having a pH of 0.5 or 5 is obtained by adding sulfuric acid to water to adjust the pH to a predetermined value, and water having a pH of 10 or 14 is obtained by adding sodium hydroxide to water. Is obtained by adjusting to a predetermined value. After heating each water whose pH has been adjusted to a predetermined value to 100 ° C., the test piece of the hydrogel is immersed in the water for 1 hour, and the elution rate is obtained from the mass (dry mass) of the hydrogel before and after the immersion. Specifically, the method described in the examples is adopted.

The sulfur content in the hydrogel of the present invention needs to be 0.001 to 2000 ppm. When the sulfur content is below a certain level in this way, the odor of the obtained hydrogel is reduced. Therefore, the hydrogel of the present invention is not only highly safe but also environmentally friendly. The sulfur content is preferably 1500 ppm or less, more preferably 1000 ppm or less, further preferably 500 ppm or less, particularly preferably 300 ppm or less, and most preferably 200 ppm or less. On the other hand, if the sulfur content is less than 0.001 ppm, it may be difficult to industrially produce polyvinyl alcohol (A). The sulfur content is more preferably 0.01 ppm or more, further preferably 0.1 ppm or more, still more preferably 1 ppm or more.

The initial moisture content W1 (mass%) of the hydrogel of the present invention and the hydrogel were vacuum-dried at 40 ° C. for 8 hours, further vacuum-dried at 120 ° C. for 1 hour, and then immersed in water at 40 ° C. for 48 hours. It is preferable that the water content W2 (mass%) of the above satisfies the following formula (I). Since such a hydrogel has excellent re-swelling property, it is suitably used in applications such as a water blocking material in which drying and swelling are repeatedly performed. The initial water content W1 and the water content W2 of the hydrogel after re-swelling are determined by the methods described in the examples. The ratio (W1 / W2) of the initial water content W1 to the water content W2 after re-swelling is more preferably 1 or more. On the other hand, the ratio (W1 / W2) is more preferably 1.35 or less.
0.8 <(W1 / W2) <1.4 (I)

The hydrogel of the present invention has high resistance to a wide range of temperatures and pH. In addition, the hydrogel has a sulfur content of a certain level or less and has a low odor, so that it is highly safe and environmentally friendly. Furthermore, the hydrogel has high gel strength. Therefore, the hydrogel is suitably used in various applications. Organ model, contact lens, drug delivery base material, adsorption carrier, enzyme-immobilized carrier, affinity carrier, capsule carrier, wastewater treatment carrier, vascular embolizing material, shock absorber, vibration damping material composed of the hydrogel. , Soundproofing material, ground improving material, water blocking material or antifouling paint are preferred embodiments of the present invention, and the ink of the present invention is suitably used for their production.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "%" and "parts" in Examples and Comparative Examples represent "% by mass" and "parts by mass", respectively.

[Calculation of vinyl alcohol unit content]
Using a nuclear magnetic resonance apparatus "LAMBDA 500" manufactured by Nippon Denshi Co., Ltd., ¹ H-NMR of a modified vinyl alcohol polymer was measured in a DMSO-d6 solvent at room temperature, and a peak derived from a methine proton to which a hydroxyl group was bonded (3). The content of the vinyl alcohol unit of the polymer was calculated from the integrated value of (4.4 to 4.0 ppm) and the integrated value of the peak (4.7 to 5.3 ppm) derived from the methine proton of the vinyl ester group.

[Calculation of denaturation rate]
Using a nuclear magnetic resonance apparatus "LAMBDA 500" manufactured by Nippon Denshi Co., Ltd., ¹ H-NMR of a modified vinyl alcohol polymer was measured in a DMSO-d6 solvent at room temperature, and peaks derived from olefin protons (5.0 to 7) were measured. From the integrated value of (5.5 ppm), the modification rate of the polymer [content of vinyl ester unit represented by the above formula (1) with respect to all constituent units (mol%)] was calculated. For example, in Example 1, the denaturation rate was calculated from the integral value of the peaks derived from olefin protons appearing at 5.6 ppm and 6.0 ppm.

[Calculation of the proportion of vinyl ester groups present in three or more chains]
Using a nuclear magnetic resonance apparatus "LAMBDA 500" manufactured by JEOL Ltd., ¹ H-NMR of a modified vinyl alcohol polymer was measured at 80 ° C. in a DMSO-d6 solvent. (A) 4.7 to 4.9 ppm (hydroxyl-vinyl ester group-methine proton in the middle of the hydroxyl group), (b) 4.9 to 5.05 ppm (hydroxyl-vinyl ester group-methine proton in the middle of the vinyl ester group) ), (C) From the integrated value of 5.05 to 5.25 ppm (methine proton in the middle of the three vinyl ester group chains), according to the following formula, the vinyl ester groups existing in three or more chains with respect to all vinyl ester units. The ratio was calculated.

Percentage of vinyl ester groups present in three or more chains (%)
= (C) / {(a) + (b) + (c)} × 100

[Evaluation of sulfur content]
The modified vinyl alcohol-based polymer obtained in Examples or Comparative Examples was dried at 80 ° C. for 12 hours, and then the sulfur content in the modified vinyl alcohol-based polymer was contained using an organic element analyzer 2400II manufactured by PerkinElmer. The amount was measured. From this value, the sulfur content in the ink was calculated. The sulfur content in the hydrogels obtained in Examples or Comparative Examples was also measured by the same method as for the modified vinyl alcohol polymer.

[Evaluation of viscosity stability]
Using the Brookfield viscometer "LVDV-2 + PRO", the viscosity η _{0 of} _{the ink obtained in Example or Comparative Example immediately after preparation and the viscosity η 7} after standing at 20 ° C. for 7 days after preparation. After each measurement, the viscosity ratio η ₇ / η ₀ was calculated and the viscosity stability was evaluated according to the following criteria. The larger the value of the viscosity ratio η ₇ / η ₀ , the worse the viscosity stability.
A: η ₇ / η ₀ is less than 1.7 B: η ₇ / η ₀ is 1.7 or more and less than 1.9 C: η ₇ / η ₀ is 1.9 or more and less than 2.1 D: η ₇ / η ₀ is 2.1 or more

[Evaluation of gel strength of hydrogel]
A test piece was cut out from the hydrogel sheet obtained in Example or Comparative Example 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 Instron tensile tester, and the breaking stress and breaking strain were measured while acquiring image data. The initial elastic modulus was simply obtained from each stress when the strain was 1% or 100%. The results are shown in Table 2.

[Evaluation of stimulus curability]
Regarding the hydrogels obtained in Examples or Comparative Examples, those having a sense of unity were evaluated as A, those that were weak but somehow showed a sense of unity were evaluated as B, and those that were only partially gelled and could not be treated as a gel were evaluated as C.

[Evaluation of odor]
When the hydrogels obtained in Examples or Comparative Examples were smelled, those with almost no odor were evaluated as A, and those with odor were evaluated as B.

[Evaluation of hydrolysis resistance of hydrogel]
A 10 g test piece was taken from the hydrogel obtained in the Example or Comparative Example, and the test piece was vacuum dried at 80 ° C. for 12 hours, and then the mass (W3) was measured. Sulfuric acid was added to obtain 1000 g of water having pH 0.5 and 5, respectively. Further, sodium hydroxide was added to obtain 1000 g of water having pH 10 and 14, respectively. To each of these boiling waters, 10 g of a separately collected test piece was added, heated at 100 ° C. for 1 hour, and then taken out. The test piece was washed with running water for 10 minutes, vacuum dried at 80 ° C. for 12 hours, and the mass (W4) was measured. The elution rate of the hydrogel when immersed in water at 100 ° C. having a predetermined pH for 1 hour was calculated according to the following formula, and this elution rate was used as an index of hydrolysis resistance. The lower the elution rate, the higher the hydrolysis resistance.
Elution rate (mass%) = 100 × ([W3]-[W4]) / [W3]

[Evaluation of re-swelling property of hydrogel]
The mass (W5) of the hydrogel immediately after cross-linking obtained in Examples or Comparative Examples was measured, vacuum dried at 80 ° C. for 12 hours, and the mass (W6) was measured again. The initial water content W1 (mass%) was calculated according to the following formula.
Initial moisture content W1 (mass%) = (W5-W6) / W5 × 100

The hydrogels obtained in Examples or Comparative Examples were vacuum dried at 40 ° C. for 8 hours and then vacuum dried at 120 ° C. for 1 hour. The obtained dried product was immersed in water at 40 ° C. for 48 hours to re-swell, and then the mass (W7) of the obtained re-swelling hydrogel was measured. After vacuum-drying the re-swelling hydrogel at 80 ° C. for 12 hours, the mass (W8) was measured, and the water content W2 (mass%) after the re-swelling was calculated according to the following formula.
Moisture content after re-swelling W2 (mass%) = (W7-W8) / W7 × 100

The ratio of the initial water content W1 to the water content W2 after re-swelling (W1 / W2) was used as an index of re-swelling property. When the ratio (W1 / W2) is larger than 1, the re-swelling property is low, and once dried, it is difficult to restore the original gel. When the ratio (W1 / W2) is smaller than 1, the re-swelling property is excessive and the gel swells more than the original gel. Indicates that it becomes a gel.

[Synthesis Example 1]
527.3 parts by mass of methacrylic acid, 39.7 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, 7.5 parts by mass of 47 mass% sulfuric acid in a reactor equipped with a stirrer, a reflux tube, and an addition port. , 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average degree of polymerization 1700, saponification degree 88 mol%) was added while stirring at room temperature, and the temperature was raised to 70 ° C. while stirring for 2 hours in a slurry state. It was reacted. The modified vinyl alcohol polymer is cooled to room temperature, the contents are filtered to recover the modified vinyl alcohol polymer, washed with a large amount of methanol, and then dried at 40 ° C. and 1.3 Pa for 20 hours to obtain the modified vinyl alcohol polymer ". PVOH-1 ”was obtained. The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

[Synthesis Example 2]
In a reactor equipped with a stirrer, a reflux tube, and an addition port, 499.0 parts by mass of methacrylic acid, 39.7 parts by mass of acetic acid, 28.4 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, and paratoluene. 9.1 parts by mass of sulfonic acid monohydrate was sequentially charged, 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average polymerization degree 500, saponification degree 88 mol%) was added while stirring at room temperature, and 65 parts by mass was stirred. The temperature was raised to ° C., and the reaction was carried out in a slurry state for 5 hours. Then, it was post-treated in the same manner as in Example 1 to obtain a modified vinyl alcohol-based polymer "PVOH-2". The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

[Synthesis Example 3]
A reactor equipped with a stirrer, a reflux tube, and an addition port contains 454.2 parts by mass of methacrylic acid, 30.0 parts by mass of acetic acid, 56.7 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, and paratoluene. 4.2 parts by mass of sulfonic acid monohydrate was sequentially charged, and 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average polymerization degree 1700, saponification degree 99.5 mol%) was added while stirring at room temperature, and the mixture was stirred. The temperature was raised to 90 ° C., and the mixture was reacted in a slurry state for 3 hours. Then, it was post-treated in the same manner as in Example 1 to obtain a modified vinyl alcohol-based polymer "PVOH-3". The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

[Synthesis Example 4]
A reactor equipped with a stirrer, a reflux tube, and an addition port contains 510.3 parts by mass of methacrylic acid, 28.4 parts by mass of acetic acid, 28.4 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, and paratoluene. 8.1 parts by mass of sulfonic acid monohydrate was sequentially charged, 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average polymerization degree 1700, saponification degree 95 mol%) was added while stirring at room temperature, and 65 parts by mass was stirred. The temperature was raised to ° C., and the reaction was carried out in a slurry state for 5 hours. Then, it was post-treated in the same manner as in Example 1 to obtain a modified vinyl alcohol-based polymer "PVOH-4". The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

[Synthesis Example 5]
A reactor equipped with a stirrer, a reflux tube, and an addition port contains 493.3 parts by mass of acrylic acid, 36.2 parts by mass of acetic acid, 56.7 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, and paratoluene. 4.2 parts by mass of sulfonic acid monohydrate was sequentially charged, and 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity polymerization degree 1000, saponification degree 98.5 mol%) was added while stirring at room temperature, and while stirring. The temperature was raised to 65 ° C., and the reaction was carried out in a slurry state for 5 hours. Then, it was post-treated in the same manner as in Example 1 to obtain a modified vinyl alcohol-based polymer "PVOH-5". The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

[Synthesis Example 6]
In a reactor equipped with a stirrer, a reflux tube, and an addition port, 510.3 parts by mass of 4-pentenoic acid, 56.7 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, and paratoluenesulfonic acid monohydration. 4.2 parts by mass of the product was sequentially charged, 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average polymerization degree 1700, saponification degree 98.5 mol%) was added while stirring at room temperature, and the temperature was raised to 60 ° C. while stirring. It was warmed and reacted in a slurry state for 3 hours. Then, it was post-treated in the same manner as in Example 1 to obtain a modified vinyl alcohol-based polymer "PVOH-6". The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

^{As a result of 1} H-NMR measurement of the obtained modified vinyl alcohol-based polymer particles, the olefin proton peak derived from the unsaturated hydrocarbon group and the methine proton peak of the vinyl ester group overlapped, so that they existed in three or more chains. The ratio of vinyl ester groups to be produced could not be calculated. Therefore, after dissolving the modified vinyl alcohol-based polymer particles in water (content of the modified vinyl alcohol-based polymer is 5% by mass), 1 mol of propanethiol was added to 1 mol of the olefin, and further, light was added. The initiator 2-hydroxy-4'-(2-hydroxyethoxy) -2-methylpropiophenone was added in an amount of 1 mol per 1 mol of propanethiol. The solution thus prepared was irradiated with ultraviolet rays at an intensity of ^{3000 mJ / cm 2.} After adding the obtained solution to a large amount of methanol to precipitate polymer particles, the particles were ^{analyzed by 1} H-NMR. As a result, the olefin proton peak disappeared due to the addition of thiol, resulting in three or more chains. The proportion of vinyl ester groups present could be calculated.

[Synthesis Example 7]
A reactor equipped with a stirrer, a reflux tube, and an addition port is charged with 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average degree of polymerization 1700, saponification degree 95 mol%) and 960 parts by mass of dimethyl sulfoxide, and is heated to 80 ° C. while stirring. The temperature was raised and the mixture was heated and stirred for 4 hours to completely dissolve the polyvinyl alcohol resin. While continuing stirring at 80 ° C., 3.0 parts by mass of vinyl methacrylate was added, and the mixture was further reacted at 80 ° C. for 3 hours. Then, after allowing the contents to cool to room temperature, the contents were poured into a large amount of methanol with stirring to precipitate a modified vinyl alcohol-based polymer. After recovering the obtained modified vinyl alcohol-based polymer, the washing operation of immersing in methanol for 1 hour and filtering is repeated 3 times, and the recovered solid is dried at 40 ° C. and 1.3 Pa for 12 hours to modify vinyl. An alcohol-based polymer "PVOH-7" was obtained. The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

[Synthesis Example 8]
A reactor equipped with a stirrer, a reflux tube, and an addition port is charged with 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average degree of polymerization 1700, saponification degree 98.5 mol%) and 9000 parts by mass of ion-exchanged water, and while stirring. The temperature was raised to 80 ° C., and the mixture was heated and stirred for 4 hours to completely dissolve the polyvinyl alcohol resin. The temperature was lowered to 40 ° C., while stirring was continued, 4.2 parts by mass of 5-norbornene-2-carboxyaldehyde was added, and 36.7 parts by mass of a 10 vol% sulfuric acid aqueous solution was directly added, followed by a reaction at 40 ° C. for 4 hours. I let you. Then, the contents were allowed to cool to room temperature, neutralized by adding 133 parts by mass of a 1 mol / L NaOH aqueous solution, and then placed in a dialysis membrane having a molecular weight cut off of 3500 for desalting (8000 parts by mass). Performed 4 times with ion-exchanged water). The obtained aqueous solution was poured into a large amount of methanol with stirring to precipitate a modified vinyl alcohol-based polymer. After recovering the obtained modified vinyl alcohol-based polymer, the washing operation of immersing in methanol for 1 hour and filtering is repeated 3 times, and the recovered solid is dried at 40 ° C. and 1.3 Pa for 12 hours to modify vinyl. An alcohol-based polymer "PVOH-8" was obtained. The structural analysis results of the obtained modified vinyl alcohol polymer are shown in Table 1.

[Synthesis Example 9]
After adding 240 parts by mass of deionized water, 91.4 parts by mass of emulsifier "Eleminor JS-20" manufactured by Sanyo Kasei Kogyo Co., Ltd., and 1.1 parts by mass of sodium peroxodisulfate to a pressure-resistant polymerization tank equipped with a stirrer, 30 parts by mass. The deoxidizing treatment was performed by bubbling with nitrogen gas for 1 minute. After that, the temperature was raised to 60 ° C., and then the monomer mixture after deoxidation treatment (n-butyl acrylate / trimethylolpropane trimethacrylate / allyl methacrylate = 360 / 1.8 / 3.6 (mass ratio)) 365. 4 parts by mass was continuously added into the polymerization tank at a rate of 10 mL / min. After confirming that the monomer conversion rate exceeded 99%, 45 parts by mass of the deoxidized dicyclopentanyl methacrylate was continuously added into the polymerization tank at a rate of 10 mL / min. After confirming that the monomer conversion rate exceeded 99%, the temperature was raised to 100 ° C. and the mixture was stirred for 2 hours to decompose the residual polymerization initiator. After cooling the polymerization tank to room temperature, acrylic particles having a core-shell structure (emulsion solution, average particle size 0.047 μm) were obtained. The solid content concentration was 28% by mass.

[Examples 1 to 10]
BASF Japan's "Irgacure2959", which is a water-soluble photopolymerization initiator as an initiator (B), and a strength-imparting agent (C) (Examples 7 to 10) in an aqueous solution in which a modified vinyl alcohol-based polymer (A) is dissolved. Hydrogel modeling ink in which particles of the strength-imparting agent (C) are dispersed in an aqueous solution in which methquinone is mixed as a polymerization inhibitor (D) (Example 10) and a modified vinyl alcohol-based polymer (A) is dissolved. Got Table 2 shows the composition of the ink and the evaluation results. In all the examples and comparative examples, the composition of the ink and the hydrogel obtained by using the ink was substantially the same. In Example 2, the viscosity stability and the stimulus curability were not evaluated. The following compounds were used as the strength-imparting agent (C).
Acrylic particles: Particles according to Synthesis Example 9 Synthetic smectite: "Smecton SA" manufactured by Kunimine Kogyo Co., Ltd., average particle diameter 43 μm
Colloidal silica: Colloidal silica "Snowtex C" manufactured by Nissan Chemical Industries, Ltd., average particle size 0.012 μm

The obtained ink is poured between glass plates sandwiching a 2 mm thick spacer, and irradiated with ultraviolet rays ^{at 145 mW / cm 2 for} 30 seconds (irradiation energy amount: 1200 mJ / cm ^{2) using a metal halide lamp manufactured by GS Yuasa.} , Hydrogel (sheet with a thickness of 2 mm) was obtained, and then evaluated as described above. The composition of the hydrogel and the evaluation results are shown in Table 2.

[Comparative Examples 1 and 2]
Same as in Example 1 except that a commercially available polyvinyl alcohol resin (viscosity average degree of polymerization 1700, saponification degree 98.5 mol%, Comparative Example 1) or PVOH-7 (Comparative Example 2) was used instead of PVOH-1. Inks and hydrogels were prepared and evaluated. Table 2 shows the composition of the ink and the evaluation results. When a commercially available polyvinyl alcohol resin was used (Comparative Example 1), the aqueous solution did not gel even when irradiated with ultraviolet rays, and a hydrogel could not be obtained. Therefore, the gel strength, hydrolysis resistance and reswelling of the hydrogel were not obtained. No sexual evaluation was performed.

[Comparative Example 3]
To 90 parts by mass of ion-exchanged water, 10 parts by mass of a commercially available non-modified polyvinyl alcohol resin (viscosity average degree of polymerization 1700, saponification degree 98.5 mol%) was added and completely dissolved to prepare a 10% by mass aqueous solution. To 50 parts by mass of the obtained aqueous solution, 50 parts by mass of a 4.8% by mass saturated borosand aqueous solution at 25 ° C. was added and sufficiently mixed until uniform to make 5 parts by mass of the modified vinyl alcohol-based polymer (A). An aqueous solution containing 92.6 parts by mass of water and 2.4 parts by mass of boar sand was obtained. This aqueous solution was poured between glass plates sandwiching a spacer having a thickness of 2 mm, and allowed to stand at room temperature for 2 days to obtain a hydrogel, which was then evaluated as described above. Table 2 shows the composition of the ink and the evaluation results.

[Comparative Example 4]
To 40 parts by mass of ion-exchanged water, 10 parts by mass of PVOH-8 was added, and the mixture was completely dissolved by stirring at 80 ° C. for 4 hours. In the obtained aqueous solution, 15 parts by mass of the emulsion of acrylic particles (solid content concentration 28 wt%) described in Synthesis Example 8, 35 parts by mass of ion-exchanged water, and 3,6-dioxa-1,8-octanedithiol as polythiol. Was added by 0.27 parts by mass and stirred. Subsequently, by adding the water-soluble photopolymerization initiator "Irgacure2959" in an amount of 0.1% by mass, PVOH-8 was added in an amount of 10 parts by mass, water was added in an amount of 85 parts by mass, and acrylic particles were added in an amount of 4.2 parts by mass. A hydrogel molding ink containing the mixture was prepared. A hydrogel was obtained in the same manner as in Example 1 except that this solution was used, and then evaluated as described above. Table 2 shows the composition of the ink and the evaluation results.

The ink of the present invention containing a modified vinyl alcohol-based polymer containing a vinyl ester unit represented by the above formula (1) and having a sulfur content of 2000 ppm or less has good viscosity stability and is irritating. The curability was also good (Examples 1, 3 to 10). Further, the hydrogels obtained by using these inks had less odor and high gel strength (Examples 1 to 10). In particular, the hydrogels (Examples 7 to 10) containing the strength-imparting agent (C) had extremely high breaking stress and breaking strain, and had extremely excellent physical properties (gel strength) as a hydrogel. Furthermore, the hydrogel of the present invention has a low elution rate with respect to water (100 ° C.) of any pH, has high resistance to a wide range of temperatures and pH, has little odor, and is excellent in reswelling property. (Examples 1 to 5, 7 to 9).

On the other hand, when unmodified polyvinyl alcohol was used (Comparative Example 1), the aqueous solution did not gel and a hydrogel could not be obtained. Further, the hydrogel (Comparative Example 2) having a high sulfur content and a high proportion of vinyl ester units having three or more chains had a strong odor, low viscosity stability, and poor reswelling property. Further, a hydrogel obtained by cross-linking unmodified polyvinyl alcohol with borax (Comparative Example 3) or a hydrogel containing a cross-linked product of polyvinyl alcohol modified with 5-norbornene-2-carboxyaldehyde (Comparative Example 3). Comparative Example 4) had low resistance to changes in pH.

Claims

Hydrogel molding ink containing a modified vinyl alcohol polymer (A) containing a vinyl ester unit represented by the following formula (1) and an initiator (B), and having a sulfur content of 0.001 to 2000 ppm. ..

[In the formula (1), X represents a divalent saturated hydrocarbon group which may have a carbon-carbon bond or a branched structure having 1 to 10 carbon atoms, and Y represents a hydrogen atom or a branched structure having 1 to 6 carbon atoms. It represents a saturated hydrocarbon group which may have a branched structure, and Z represents a hydrogen atom or a methyl group. ]
The hydrogel molding ink according to claim 1, wherein the content of the vinyl alcohol unit with respect to all the constituent units in the modified vinyl alcohol-based polymer (A) is 60 to 99.99 mol%.
The hydrogel molding ink according to claim 1 or 2, wherein the ratio of the vinyl ester units present in three or more chains to the total vinyl ester units in the modified vinyl alcohol polymer (A) is 20 mol% or less.
The invention according to any one of claims 1 to 3, wherein the content of the vinyl ester unit represented by the formula (1) in the modified vinyl alcohol polymer (A) with respect to all the constituent units is 0.01 to 10 mol%. Hydrogel modeling ink.
The hydrogel modeling ink according to any one of claims 1 to 4, wherein Y is a hydrogen atom.
The hydrogel modeling ink according to any one of claims 1 to 5, wherein X is a carbon-carbon bond.
The hydrogel modeling ink according to any one of claims 1 to 6, further comprising a strength-imparting agent (C).
The hydrogel modeling ink according to claim 7, wherein the strength-imparting agent (C) is inorganic particles.
The hydrogel modeling ink according to any one of claims 1 to 8, further comprising a polymerization inhibitor (D).
The hydrogel modeling ink according to any one of claims 1 to 9, which is an ink for a 3D printer.
Organ model, contact lens, drug delivery base material, adsorption carrier, enzyme-immobilized carrier, affinity carrier, capsule carrier, wastewater treatment carrier, vascular embolization material, shock absorber, vibration damping material, soundproofing material, ground improvement material, The hydrogel molding ink according to any one of claims 1 to 10, which is used for producing a water blocking material or an antifouling paint.
A hydrogel containing a crosslinked product of the hydrogel molding ink according to claim 1, which has an elution rate when immersed in water at 100 ° C. having a pH of 0.5, 5, 10 or 14 for 1 hour. Hydrogel, which is less than 50% by mass.
The initial moisture content W1 (mass%) of the hydrogel and the hydrogel are vacuum dried at 40 ° C. for 8 hours, further vacuum dried at 120 ° C. for 1 hour, and then immersed in water at 40 ° C. for 48 hours. The hydrogel according to claim 12, wherein the rate W2 (% by mass) satisfies the following formula (I).
0.8 <(W1 / W2) <1.4 (I)
The hydrogel according to claim 12 or 13, further comprising a strength-imparting agent (C).
Organ model, contact lens, drug delivery substrate, adsorption carrier, enzyme-immobilized carrier, affinity carrier, capsule carrier, wastewater treatment carrier, blood vessel, which are composed of the hydrogel according to any one of claims 12 to 14. Enzyme material, shock absorber, vibration damping material, soundproofing material, ground improvement material, water blocking material or antifouling paint.