JP2019035043A - Stimulus-curable gel - Google Patents

Abstract

To provide a stimulus-curable gel excellent in curability and safety, high in mechanical strength, and applicable to a wide range of applications.SOLUTION: A stimulus-curable gel contains a water-soluble polymer having a crosslinkable group, and polymer particles having a glass transition temperature of 25°C or lower. The crosslinkable group is selected from a vinyl group, a (meth) acryloyloxy group, a (meth) acryloylamino group, a vinylphenyl group, and derivatives thereof. An introduction ratio of the crosslinkable group is 0.01-10 mol% based on a repeating unit of the water-soluble polymer having the crosslinkable group.SELECTED DRAWING: None

Description

  The present invention relates to a stimulus-curable gel that hardens upon stimulation.

  A hydrogel (hereinafter sometimes abbreviated as a gel) is a material composed of a crosslinked hydrophilic polymer and water. Conventionally, a superabsorbent polymer (SAP), a contact lens, and a drug delivery group are used. It is used in various applications such as life, medical care, food, and civil engineering, such as materials, shock absorbing materials, vibration control and soundproofing materials. However, the conventional gel has a problem that the mechanical strength is low and the application range is limited. In order to solve this problem, a double network gel in which a network structure of two types of water-soluble polymers enters each other has been proposed (Patent Document 1).

  In recent years, a material modeling method called Additive Manufacturing typified by a 3D printer has been actively developed, and a demand for a material adapted to these methods is increasing. In particular, in order to make a gel correspond to a 3D printer, “stimulus sclerosis” is required such that the gel is quickly cured in one step by stimulation such as active energy rays. Furthermore, in the medical field, a method of curing and treating an affected area of a patient using a stimulus-curable gel (Patent Document 2), an organ model used for surgical practice using a 3D printer, and a precision scaffold for regenerative medicine ( Application to the production of non-patent document 1) is expected.

  Since the double network gel can produce an unprecedented gel having both strength and flexibility, it can be used as a gel for a 3D printer, for example. However, the double network gel has problems in applicability to 3D printers, such as the gel that has been polymerized must be swollen with a monomer solution, and the monomer is polymerized, so that the curability is lacking.

  In order to solve the above-mentioned problems of the double network gel, an attempt has been made to improve the stimulus curability by adding crosslinked gel particles to the gel. This produces cross-linked gel particles consisting of the first hydrophilic polymer among the two types of hydrophilic polymers that make up the double network gel, and the monomers that make up the cross-linked gel particles and the second hydrophilic polymer It is the method of making it mix and gelatinize (patent documents 3-5, nonpatent literature 2-4). If this method is used, a double network gel can be produced in one step, so that it is considered that the applicability to a 3D printer is higher. From such an idea, it has recently been proposed to apply a gel to which crosslinked gel particles are added to a 3D printer (Patent Document 6, Non-Patent Document 5).

International Publication No. 2003/093337 Special table 2008-510021 JP 2008-163055 A JP 2010-260929 A Japanese Patent Laying-Open No. 2015-96560 JP 2017-26680 A Japanese National Patent Publication No. 10-513408 Special table 2002-50613 gazette

Chemical Reviews 116 (2016) 1496-1539 Macromolecules 44 (2011) 7775-7781 Macromolecules 45 (2012) 5218-5228 Macromolecules 45 (2012) 9445-9451 Journal of Solid Mechanics and Materials Engineering 7 (2013) 163-168

  In the gels described in Patent Documents 3 to 6 and Non-Patent Documents 2 to 5, it is possible to produce a double network gel excellent in mechanical strength in one step by mixing the crosslinked gel fine particles and the monomer. There was still a problem with curability due to the polymerization of the monomers. In addition, acrylamide is often used as a monomer, and since the toxicity of the monomer itself is very high, there is a problem that it cannot be used for medical purposes.

  On the other hand, a water-soluble polymer having a crosslinkable group (hereinafter sometimes abbreviated as a macromer) is less toxic than the monomer, and is used in various applications including medical applications (Patent Document 7, Patent Document). 8). However, there is a problem that only a gel having low mechanical strength can be produced only by curing the macromer.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a stimulus-curable gel that is excellent in curability and safety, has high mechanical strength, and can be applied to a wide range of uses.

  As a result of intensive studies by the present inventors, a gel having high mechanical strength can be obtained by adding polymer particles to a water-soluble polymer having a crosslinkable group even if double networking does not occur sufficiently. The present invention was completed through further studies based on the findings.

That is, the present invention
[1] A stimulus-curable gel containing a water-soluble polymer having a crosslinkable group and polymer particles (x) having a glass transition temperature of 25 ° C. or lower;
[2] The stimulus-curable gel according to [1], wherein the crosslinkable group is at least one selected from a vinyl group, a (meth) acryloyloxy group, a (meth) acryloylamino group, a vinylphenyl group, and derivatives thereof. ;
[3] The stimulus-curable gel according to [1] or [2], wherein the introduction rate of the crosslinkable group is 0.01 to 10 mol% with respect to the repeating unit of the water-soluble polymer having a crosslinkable group;
[4] The stimulus-curable gel according to any one of [1] to [3], wherein the polymer particles (x) have an average particle size of 0.01 to 10 μm;
[5] The stimulus-curable gel according to any one of the above [1] to [4], wherein the stimulus is at least one selected from active energy rays, heat and mixing;
[6] The stimulus-curable gel according to any one of the above [1] to [5], wherein the polymer particles (x) are coated polymer particles;
About.

  According to the present invention, a stimulus-curable gel that is excellent in curability and safety, has high mechanical strength, and can be applied to a wide range of uses can be obtained.

Hereinafter, the present invention will be described in detail.
In the present specification, “(meth) acryl” means a generic name of “methacryl” and “acryl”.

  The stimulus-curable gel of the present invention includes a water-soluble polymer having a crosslinkable group and polymer particles (x) having a glass transition temperature of 25 ° C. or lower.

The stimulus curable property in the present invention refers to curing by at least one kind of stimulus selected from active energy rays, heat and mixing. The water-soluble polymer having a crosslinkable group can be cured by the addition of a photopolymerization initiator or a thermal polymerization initiator by stimulating active energy rays or heat, respectively. In the case of a redox polymerization initiator among the thermal polymerization initiators, it is possible to cure by mixing a peroxide polymerization initiator and a reducing agent as a stimulus.
In addition, in this specification, an active energy ray means a light beam, electromagnetic waves, particle beams, and a combination thereof. Examples of light rays include far ultraviolet rays, ultraviolet rays (UV), near ultraviolet rays, visible rays, and infrared rays, electromagnetic waves include X-rays and γ rays, and particle beams include electron beams (EB) and proton rays (α Line) and neutron beam. Among these active energy rays, ultraviolet rays and electron beams are preferable, and ultraviolet rays are more preferable, from the viewpoints of curing speed, availability of the irradiation apparatus, price, and the like.

<Water-soluble polymer having a crosslinkable group>
The water-soluble polymer having a crosslinkable group refers to a polymer containing a crosslinkable group in the side chain or terminal of the water-soluble polymer serving as a base material. As a water-soluble polymer serving as a substrate of a water-soluble polymer having a crosslinkable group, any of a synthetic polymer and a natural polymer can be used.

(Water-soluble polymer)
Examples of synthetic polymers include polyvinyl alcohol (hereinafter sometimes abbreviated as PVA), poly (meth) acrylic acid, poly (meth) acrylamide, poly (N, N-dimethyl (meth) acrylamide), poly (N , N-diethyl (meth) acrylamide), poly (N-isopropyl (meth) acrylamide), polyvinylpyrrolidone, polyhydroxyethyl (meth) acrylamide, polyhydroxyethyl (meth) acrylate, polyethylene oxide, polypropylene oxide, polyethyleneimine, poly Examples include allylamine and derivatives thereof. These synthetic polymers may be copolymerized with other monomers as long as water solubility is not impaired. The content of other monomers is preferably less than 50 mol%, more preferably less than 30 mol%, based on all structural units constituting the synthetic polymer.

  Among the synthetic polymers, for example, poly (meth) acrylamide derivatives such as polyacrylamide, poly (N, N-dimethyl (meth) acrylamide), poly (N, N-diethylacrylamide), poly (N-isopropylacrylamide); and polyvinyl Synthetic polymers that do not contain functional groups for introducing crosslinkable groups such as amino groups, hydroxyl groups, and carboxyl groups, such as pyrrolidone, are monomers having functional groups for introducing crosslinkable groups, such as hydroxyethyl methacrylate and methacrylic methacrylate. It is necessary to copolymerize with an acid or the like and introduce a functional group for introducing a crosslinkable group into the side chain. The content of the monomer having a functional group for introducing a crosslinkable group is preferably less than 20 mol%, more preferably less than 10 mol%, based on all structural units constituting the synthetic polymer.

  As natural polymers, water-soluble polysaccharides and water-soluble proteins can be used. Examples of water-soluble polysaccharides include water-soluble cellulose derivatives such as alginic acid, propylene glycol alginate, agarose, hydroxyethylcellulose, carboxymethylcellulose; guar gum, carrageenan, agar, chitosan, gellan gum, dextran, starch, hyaluronic acid, pullulan, heparin Etc. Examples of water-soluble proteins include collagen, gelatin, albumin and the like.

  Among the water-soluble polysaccharides exemplified above, for example, alginic acid gels by adding calcium ions. In addition, agarose, gellan gum, gelatin and the like are dissolved in hot water and gelled by cooling. In this way, it is possible to take advantage of the gelling properties of the natural polymer itself, but considering the selection of stimuli for curing and the degree of freedom of molding, application to 3D printers, the crosslinkable group is bound to the natural polymer. It is essential.

(Crosslinkable group)
Examples of the crosslinkable group include a vinyl group, a (meth) acryloyloxy group, a (meth) acryloylamino group, a vinylphenyl group and derivatives thereof that can be expected to be highly efficient in water. The vinyl group in the present invention includes not only unsaturated hydrocarbons but also allyl groups and vinyl ester groups. Of the unsaturated hydrocarbons, an unsaturated hydrocarbon having a terminal double bond is preferable in consideration of reactivity.

  Such a crosslinkable group can be introduced via a side chain or a terminal functional group of the water-soluble polymer, such as a hydroxyl group, an amino group, a carboxyl group, a 1,2-diol group, or a 1,3-diol group. For a hydroxyl group or amino group, a (meth) acryloyloxy group can be introduced, for example, by reacting acrylic anhydride or glycidyl methacrylate in the presence of a base. That is, a (meth) acryloyloxy group can be introduced into the hydroxyl group by esterification, and a (meth) acryloylamino group can be introduced into the amino group by amidation. For the hydroxyl group and amino group, for example, an allyl ether group which is a kind of vinyl group can be introduced by reacting allyl glycidyl ether in the presence of a base. For the amino group, for example, a vinyl ester group which is a kind of vinyl group can be introduced by reacting divinyl adipate in the presence of a base. For the carboxyl group, for example, a methacryloyloxy group can be introduced by esterification by reacting glycidyl methacrylate under acidic conditions. Furthermore, for 1,2-diol groups and 1,3-diol groups, for example, acrolein, 5-norbornene-2-carboxaldehyde, 7-octenal and the like are reacted in the presence of an acid catalyst to form a vinyl group by acetalization. Can be introduced. Similarly, by acetalization, 3-vinylbenzaldehyde, 4-vinylbenzaldehyde, and the like are reacted to react the vinylphenyl group with N- (2,2-dimethoxyethyl) (meth) acrylamide and the like (meth) acryloyl. An amino group can be introduced. The introduction of the crosslinkable group into the water-soluble polymer can be used other than the exemplified reactions, and two or more kinds of reactions may be used in combination.

  Examples of the water-soluble polymer having a crosslinkable group include PVA having a crosslinkable group; polyacrylamide having a crosslinkable group, poly (N, N-dimethyl (meth) acrylamide), poly (N, N-diethylacrylamide), poly Polyacrylamide derivatives such as (N-isopropylacrylamide); polyhydroxyethyl (meth) acrylate having a crosslinkable group; polyethylene glycol having a crosslinkable group; a water-soluble cellulose derivative having a crosslinkable group is preferred, and the crosslinkable group is ( A meth) acryl group, a vinyl group and a (meth) acryloylamino group are preferred.

  However, since it may be difficult to cure when a vinyl group is used among the crosslinkable groups, for example, a polythiol having two or more thiol groups in one molecule is added to a water-soluble polymer having a vinyl group. -An ene reaction may be used. As said polythiol, what shows water solubility is preferable, For example, the terminal thiolation thing of 3, 6- dioxa- 1, 8-octane dithiol, dithiothreitol, polyethyleneglycol dithiol, and multi-arm polyethyleneglycol etc. are mentioned. In the thiol-ene reaction, since the vinyl group and the thiol group react one-on-one, it is necessary to add the polythiol so that the thiol group is equimolar or less with respect to the vinyl group. If it is this addition amount, in order to control gel strength etc., the addition amount of the said polythiol can be controlled arbitrarily.

  The introduction rate of the crosslinkable group is preferably 10 mol% or less, more preferably 5 mol% or less, and further preferably 3 mol% or less with respect to the repeating unit of the water-soluble polymer having a crosslinkable group. Moreover, Preferably it is 0.01 mol% or more, More preferably, it is 0.1 mol% or more. If the introduction ratio of the crosslinkable group becomes too high, the mechanical strength of the gel after curing is improved while it becomes very brittle.

  The degree of polymerization, which is the number of repeating units contained in the polymer chain, for both the synthetic polymer and the natural polymer in the present invention is not particularly limited, and those having various degrees of polymerization can be used. However, if the degree of polymerization is too small for both synthetic and natural polymers, the gel when cured tends to become brittle. Further, when the polymerization degree is too high for both the synthetic polymer and the natural polymer, the viscosity of the aqueous solution becomes high and the processing tends to be difficult. Therefore, the polymerization degree of the synthetic polymer and the natural polymer is preferably 4 or more, more preferably 9 or more, and still more preferably 14 or more. Moreover, 30000 or less are preferable, 10,000 or less are more preferable, and 5000 or less are more preferable.

Here, the degree of polymerization in the present invention can be determined by measuring the intrinsic viscosity [η] and dividing the viscosity average molecular weight calculated from the Mark-Houink equation by the molecular weight of the repeating unit contained in the polymer chain. For example, the polymerization degree of PVA exemplified as a water-soluble polymer is measured according to JISK6726: 1994. That is, after re-saponifying and purifying PVA, it is calculated | required by following Formula from intrinsic viscosity [(eta)] measured in 30 degreeC water.
Degree of polymerization = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

  The water-soluble polymer having a crosslinkable group in the present invention preferably contains an ionic group, and the content thereof is preferably 20 mol% or less with respect to the repeating unit of the polymer. If it contains more than 20 mol% of ionic groups, the water absorption is increased, and the gel strength and dimensional stability may be reduced.

<Polymer particles (x)>
The polymer constituting the polymer particles (x) may be a polymer composed of one kind of monomer unit or a copolymer composed of plural kinds of monomer units. Moreover, the mixture of a some polymer may be sufficient.
Examples of the monomer include conjugated dienes 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, ( (Meth) ethyl acrylate, (meth) acrylic acid n-propyl, (meth) acrylic acid n-butyl, (meth) acrylic acid isopropyl, dicyclopentanyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (Meth) acrylic acid esters such as (meth) acrylate; (meth) acrylamide; (meth) acrylamide derivatives such as N-methyl (meth) acrylamide and N-ethyl (meth) acrylamide; nitriles such as (meth) acrylonitrile; methyl Vinyl ether, ethyl vinyl ether, -Vinyl ethers such as butyl vinyl ether and isobutyl vinyl ether; vinyl esters such as vinyl acetate, vinyl n-propionate, vinyl butyrate and vinyl pivalate; unsaturated dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride; ethene, propene, monoolefins such as n-butene and isobutene; halogenated ethylenes such as vinyl bromide, vinylidene bromide, vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid, Unsaturated dicarboxylic acids such as fumaric acid and itaconic acid and salts thereof; unsaturated dicarboxylic esters such as maleic acid ester and itaconic acid ester; vinylsilyl compounds such as trimethoxysilane; cyclic dienes such as cyclopentadiene and norbornadiene; Indene such as trahydroindene; cyclic ether such as ethylene oxide, propylene oxide, oxetane and tetrahydrofuran; cyclic sulfide such as thiirane and thietan; cyclic amine such as aziridine and azetidine; 1,3-dioxolane and 1,3,5-trioxane Cyclic acetals such as spiro orthoesters; cyclic imino ethers such as 2-oxozaline and imino ether; lactones such as β-propiolactone, δ-valerolactone and ε-caprolactone; cyclic carbonates such as ethylene carbonate and propylene carbonate; hexa And cyclic siloxanes such as methylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and the like.
Among these, at least one monomer selected from the group consisting of a conjugated diene, an aromatic vinyl compound, and a (meth) acrylic acid ester is preferable from the viewpoint of productivity.

  The glass transition temperature of the polymer particles (x) is 25 ° C. or less and preferably 0 ° C. or less in order to efficiently relax and / or dissipate external stress on the stimulus-curable gel of the present invention. More preferably, it is −10 ° C. or lower. Moreover, it is preferable that it is -80 degreeC or more. In the present specification, the glass transition temperature can be determined by differential scanning calorimetry.

  When the water-soluble polymer having a crosslinkable group is cured, if the polymer particles (x) having a glass transition temperature of 25 ° C. or lower are contained therein as in the stimulus-curable gel of the present invention, the gel is externally applied. The polymer particles (x) can be sacrificially deformed when stress is applied to relax and / or collapse the stress and dissipate the stress to stop the development of minute cracks generated in the gel. . For this reason, it is estimated that the whole gel is prevented from collapsing and the toughness of the gel is increased.

The polymer particles (x) having a glass transition temperature of 25 ° C. or lower are not particularly limited as long as these conditions are satisfied, but are dispersed in water because they are mixed with a water-soluble polymer having a crosslinkable group in an aqueous solvent. Preferably it can be done. As polymer particles (x), for example, hard particles having a glass transition temperature above room temperature, such as acrylic particles, or crosslinked acrylamide gel particles containing an ionic group described in JP-A-2004-285203 are stimulated. Although improvement in the elastic modulus and rupture strength of the curable gel may be observed, it is difficult to improve flexibility.
As the polymer particles (x) of the present invention, from the viewpoint of dispersibility in water, polymer particles whose surfaces are hydrophilized with a surfactant or the like, and coated polymer particles are preferable, and coated polymer particles are more preferable. preferable. Specific examples of the coated polymer particles include coated polymer particles having a polymer coating (y) that covers at least a part of the polymer particles (x) as described later.

(Coated polymer particles)
The polymer particles (x) are preferably coated polymer particles having a polymer coating (y) that covers at least a part of the polymer particles (x). The polymer constituting the polymer film (y) may be a polymer composed of one kind of monomer unit or a copolymer composed of plural kinds of monomer units. Moreover, the mixture of a some polymer may be sufficient.
Examples of the monomer include those listed for the polymer particles (x), and preferred examples are also the same.

  The glass transition temperature of the polymer coating (y) is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, from the viewpoint of preventing fusion between particles and dispersion stability in water. . Moreover, it is preferable that it is 250 degrees C or less.

The content of the polymer coating (y) in the coated polymer particles is based on the total weight of the coated polymer particles from the viewpoint of efficiently relieving and / or dissipating external stress on the stimulus-curable gel of the present invention. 1 wt% or more is preferable, 3 wt% or more is more preferable, and 5 wt% or more is more preferable. Moreover, it is preferable that it is 80 wt% or less, It is more preferable that it is 60 wt% or less, It is further more preferable that it is 50 wt% or less.
Moreover, it is preferable that a polymer film (y) coat | covers the whole polymer particle (x).

The average particle diameter of the polymer particles (x), and when the polymer particles (x) are coated polymer particles, the average particle diameter of the entire coated polymer particles including the polymer coating (y) is preferably 0.01. It is 10-10 micrometers, More preferably, it is 0.02-1 micrometer, More preferably, it is 0.04-0.5 micrometer. When the average particle diameter is large, the gel itself tends to become cloudy and the transparency tends to be lost, and the particles are liable to settle. However, an improvement in gel strength can be expected even with a small content. On the other hand, when the average particle size is small, it is necessary to increase the content in order to improve the gel strength, but there is a tendency that a gel having high transparency is obtained.
In addition, the average particle diameter in this invention refers to the average dispersed particle diameter measured with the dynamic light scattering measuring apparatus mentioned later.

(Production method of polymer particles (x))
Although the manufacturing method of polymer particle (x) is not specifically limited, For example, it can manufacture by emulsion polymerization, suspension polymerization, self-emulsification of resin, mechanical emulsification, etc.

  In the emulsion polymerization according to the production method of the polymer particles (x), an emulsifier is usually used. Examples of the emulsifier include anionic surfactants such as sodium alkylbenzene sulfonate, sodium lauryl sulfate, higher fatty acid sodium, and rosin soap; nonionic surfactants such as alkyl polyethylene glycol and nonylphenol ethoxylate; distearyldimethylammonium chloride Cationic surfactants such as benzalkonium chloride; amphoteric surfactants such as cocamidopropyl betaine and cocamidopropylhydroxysultain can be used. Polymeric surfactants such as partially saponified PVA (saponification degree 70-90 mol%), mercapto group-modified PVA (saponification degree 70-90 mol%), β-naphthalene sulfonic acid formalin condensate salt, ethyl (meth) acrylate copolymer, etc. It is also possible to use. Here, the polymer surfactant can function in the same manner as the polymer coating (y) for coating the polymer particles (x) after the completion of the emulsion polymerization. These emulsifiers may be used alone or in combination of two or more. The use amount of such an emulsifier is preferably 0.01 to 40 wt%, more preferably 0.05 to 20 wt% with respect to water.

  In the emulsion polymerization according to the production method, a radical polymerization initiator is usually used. Examples of such radical polymerization initiators include water-soluble inorganic polymerization initiators, water-soluble azo polymerization initiators, oil-soluble azo polymerization initiators, and organic peroxides. A redox polymerization initiator may be used as the radical polymerization initiator.

  Examples of the water-soluble inorganic polymerization initiator include hydrogen peroxide, sodium peroxodisulfate, and potassium persulfate. Examples of water-soluble azo initiators include 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl). Propane] disulfate dihydrate, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, 2, , 2′-azobis [2- (2-imidazolin-2-yl) propane], 2-2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis [ 2-methyl-N- (2-hydroxyethyl) propionamide] and the like.

  As the oil-soluble azo polymerization initiator, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 ′ -Azobis (isobutyronitrile), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methyl Ethyl) azo] formamide, 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2′-azobis (N-butyl-2-methylpropionamide), dimethyl 2,2 -Azobis (isobutyrate) and the like.

Examples of organic peroxides include diacyl peroxides such as bis-3,5,5-trimethylhexanoyl peroxide, dilauroyl peroxide, and dibenzyl peroxide; 1,1,3,3-tetramethylbutyl hydroperoxide , Cumene hydroperoxide, hydroperoxide such as t-butyl hydroperoxide; dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 1,3-bis (t Dialkyl peroxides such as -butylperoxyisopropyl) benzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3; 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane, 1,1-di-tert-butyl Peroxyketals such as peroxycyclohexane and 2,2-di-t-butylperoxybutane; 1,1,3,3-tetramethylbutylperoxyneodecanoate, α-cumylperoxyneodecanoate, t-butylperoxyneodecanoate, t-butylperoxyneoheptanoate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t -Amyl peroxy 2-ethyl hexanoate, t-butyl peroxy 2-ethyl hexanoate, di-t-butyl peroxy hexahydroterephthalate, t-amyl peroxy 3,5,5-trimethyl hexanoate, t-butylperoxy 3,5,5-trimethylhexanoate, t-butylperoxyacetate, t- Alkyl peroxyesters such as butyl peroxybenzoate; di-2-ethylhexyl peroxydicarbonate, diisopropyl peroxydicarbonate, t-butylperoxyisopropyl carbonate, t-butylperoxy 2-ethylhexyl carbonate, 1,6-bis And peroxycarbonates such as (t-butylperoxycarbonyloxy) hexane.
The amount of the radical polymerization initiator used is preferably 0.0001 to 1 wt%, more preferably 0.001 to 0.5 wt% with respect to water.

Further, from the viewpoint of productivity, a redox polymerization initiator may be used, and the redox polymerization initiator is preferably a combination of the organic peroxide and the transition metal salt.
Examples of transition metal salts used in combination with organic peroxides include iron (II) sulfate, iron (II) thiosulfate, iron (II) carbonate, iron (II) chloride, iron (II) bromide, and iron iodide. Iron compounds such as (II), iron hydroxide (II) and iron oxide (II); copper sulfate (I), copper thiosulfate (I), copper carbonate (I), copper chloride (I), copper bromide ( Copper compounds such as I), copper iodide (I), copper hydroxide (I), copper oxide (I), or hydrates thereof can be used.
Among these, from the viewpoint of productivity, the combined use of cumene hydroperoxide and an iron compound is preferable, and the combined use of cumene hydroperoxide and iron (II) sulfate hydrate is more preferable.

A reducing agent may be used together with the radical polymerization initiator. Examples of the reducing agent include iron compounds such as ferrous chloride and ferrous sulfate; sodium salts such as sodium hydrogen sulfate, sodium bisulfite, sodium sulfite, sodium hydrogen sulfite, and sodium hydrogen carbonate; ascorbic acid, longgarit, diiotin Examples thereof include organic reducing agents such as sodium acid, triethanolamine, glucose, fructose, glyceraldehyde, lactose, arabinose, and maltose. Among these, it is preferable to use an iron compound and an organic reducing agent in combination.
The amount of the reducing agent used is preferably in the range of 0.0001 to 1 wt%, more preferably in the range of 0.001 to 0.5 wt% with respect to water.

  In the production method, a metal ion chelating agent may be added to the emulsion polymerization system as necessary. Specifically, metal ion chelating agents, such as ethylenediaminetetraacetic acid dihydrogen disodium, are mentioned.

  In the production method, an electrolyte may be added as a thickening inhibitor to the emulsion polymerization system as necessary. Specific examples include electrolytes such as sodium chloride, sodium sulfate, and trisodium phosphate. In the said manufacturing method, when using an emulsifier and a thickening inhibitor together, the usage-amount of a thickening inhibitor is 20 wt% or less with respect to an emulsifier from a viewpoint of the stability of the micelle in an emulsion, and 10 wt%. The following is more preferable, and 5 wt% or less is still more preferable.

  The reducing agent, metal ion chelating agent and electrolyte may be added during the polymerization reaction, but are preferably added to water from the beginning of the emulsion polymerization.

  In the production method, a chain transfer agent may be added to the emulsion polymerization system as necessary. As chain transfer agents, mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, hexadecyl mercaptan, n-octadecyl mercaptan; mercaptoacetic acid, 2-ethylhexyl mercaptoacetate, methoxybutyl mercaptoacetate, β-mercapto Thiols such as propionic acid, methyl β-mercaptopropionate, 2-ethylhexyl β-mercaptopropionate, 3-methoxybutyl β-mercaptopropionate, mercaptoethanol, 3-mercapto-1,2-propanediol; α-methyl Hydrocarbon compounds having a large chain transfer constant such as styrene dimer can be used.

  When using a water-soluble radical polymerization initiator, it may be added as an aqueous solution, but when using a radical polymerization initiator that is sparingly soluble in water, an emulsion of the radical polymerization initiator is prepared in advance using water and an emulsifier. This may be added. In this case, the emulsifier used may be the same as or different from that used in the emulsion polymerization. Two or more emulsifiers may be combined.

  The polymerization temperature for emulsion polymerization is usually preferably in the range of 0 to 100 ° C, and preferably 50 to 90 ° C from the viewpoint of increasing the polymerization rate.

  In the present invention, the emulsion after emulsion polymerization may be used as it is, or the polymer particles (x) may be recovered and used by a known method such as salting out, aciding out, freezing, or addition of a solvent. The polymer particles (x) thus recovered may be further purified by a known method such as washing, reprecipitation, steam stripping or the like.

  In the present invention, from the viewpoint of suppressing the deterioration of the polymer particles (x), an anti-aging agent may be added to the emulsion liquid after the emulsion polymerization, or the polymer particles (x) after the recovery treatment or the purification treatment. . From the viewpoint of suppressing deterioration in the recovery process and purification process of the polymer particles (x) after the polymerization reaction, the antioxidant is added to the emulsion liquid after the emulsion polymerization, and then the polymer particles (x ) May be recovered or purified. Further, from the viewpoint of suppressing deterioration during use of the obtained polymer particles (x), an anti-aging agent is added to the polymer particles (x) after the recovery treatment or purification treatment of the polymer particles (x). It may be added. However, when the anti-aging agent is added to the emulsion after emulsion polymerization, the added anti-aging agent may be removed by the recovery or purification treatment of the polymer particles (x). It is desirable to add it again after the recovery process or purification process of x).

  A general material can be used as an anti-aging agent. Specifically, hydroquinone, hydroquinone monomethyl ether, 2,5-di-t-butylphenol, 2,6-di (t-butyl) -4-methylphenol, mono (or di, or tri) (α-methylbenzyl) ) Phenolic compounds such as phenol; 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 4,4'-thiobis Bisphenol compounds such as (3-methyl-6-tert-butylphenol); benzimidazole compounds such as 2-mercaptobenzimidazole and 2-mercaptomethylbenzimidazole; 6-ethoxy-1,2-dihydro-2,2, 4-trimethylquinoline, reaction product of diphenylamine and acetone, 2,2,4-trimethyl-1 Amine-ketone compounds such as 2-dihydroquinoline polymers; N-phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine, p- (p -Toluenesulfonylamido) aromatic secondary amine compounds such as diphenylamine and N, N'-diphenyl-p-phenylenediamine; thioureas such as 1,3-bis (dimethylaminopropyl) -2-thiourea and tributylthiourea Series compounds can be used.

  The polymer particles (x) can be produced by natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, isobutylene-isoprene copolymer, styrene-isoprene copolymer, styrene-isoprene-butadiene copolymer. Polymers such as rubbers such as polymers, halogenated isobutylene-isoprene copolymers, ethylene-propylene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylonitrile-butadiene copolymer partial hydrogenated products, polychloroprene They can also be produced by a method of producing them, emulsifying or suspending them in water and taking them out by spray drying or the like. When polymer particles having a glass transition temperature of 25 ° C. or less are produced by the above-described method, the particles are fused with each other and are difficult to redisperse in water or the like. For example, partially saponified PVA that is a polymer surfactant is used as an emulsifier. And emulsifying is a preferred method.

<Coexisting monomer>
The stimulus-curable gel of the present invention may further contain a coexisting monomer. Coexisting monomers include water-soluble radical polymerizable monomers 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, N, N-dimethylacrylamide, (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid N-isopropylacrylamide, vinyl pyridine, hydroxyethyl (meth) acrylate, styrene sulfonic acid, polyethylene glycol mono (meth) acrylate, and the like.

<Crosslinking agent>
The stimulus-curable gel of the present invention may further contain a crosslinking agent. As the crosslinking agent, water-soluble ones are particularly preferable, and N, N′-methylenebisacrylamide, ethylene glycol di (meth) acrylate, N, N′-diethylene glycol di (2) having two or more radical polymerizable unsaturated groups are preferred. And (meth) acrylate.

<Inorganic fine particles>
The stimulus-curable gel of the present invention may contain water-insoluble inorganic fine particles. Examples of water-insoluble inorganic fine particles include silica such as precipitated silica, gel-like silica, gas phase method silica and colloidal silica; ceramics such as alumina, hydroxyapatite, zirconia, zinc oxide and barium titanate; zeolite, talc, montmorillonite and the like Minerals such as calcium sulfate, metal oxides such as iron oxide; metal carbonates such as calcium carbonate and magnesium carbonate; diatomaceous earth, soil, clay, sand, gravel and the like. These inorganic fine particles may be used alone or in combination of two or more. By adding water-insoluble inorganic fine particles, it is possible to impart functions such as high mechanical properties and magnetism to the gel. It is also possible to obtain a molded inorganic sintered body by drying and further sintering the molded stimulus-curable gel containing inorganic fine particles.
The content of the inorganic fine particles in the stimulus curable gel is not particularly limited, but is preferably 99.5 wt% or less, more preferably 99 wt% or less, and still more preferably 95 wt% or less. Furthermore, in order to obtain the addition effect of inorganic fine particles, the content of inorganic fine particles is 0.01 wt% or more, more preferably 0.05% or more, and further preferably 0.1% or more.

<Uncured gel solution>
The stimulus curable gel of the present invention prepares an uncured gel solution by mixing the water-soluble polymer having the crosslinkable group and the polymer particles (x) in a solvent, and the crosslinkable group is formed by the curing method. It is obtained by curing and gelling the water-soluble polymer.

  The concentration of the water-soluble polymer having a crosslinkable group in the uncured gel solution is preferably 1 wt% or more, more preferably 3 wt% or more, and further preferably 5 wt% or more with respect to the uncured gel solution. Moreover, 70 wt% or less is preferable, 60 wt% or less is more preferable, and 50 wt% or less is more preferable. If the concentration of the water-soluble polymer having a crosslinkable group is less than 1 wt%, the strength of the gel obtained is low, and if it exceeds 70 wt%, the viscosity of the uncured gel solution tends to be high and molding tends to be difficult.

  The content of the polymer particles (x) in the uncured gel solution is preferably 1 wt% or more, more preferably 5 wt% or more with respect to the water-soluble polymer having a crosslinkable group. Moreover, 300 wt% or less is preferable and 200 wt% or less is more preferable. If the content of the polymer particles (x) is 1 wt% or more, the toughness of the gel tends to increase, and if it is 300 wt% or less, the gel is formed without inhibiting the curing of the water-soluble polymer having a crosslinkable group. There is a tendency to be able to.

  The solvent for the uncured gel solution is preferably water. In addition, aprotic polar solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone; monoalcohols such as methanol, ethanol, propanol, isopropanol; and multivalents such as ethylene glycol, diethylene glycol, triethylene glycol, and glycerin You may mix and use water-soluble solvents, such as alcohol.

  The uncured gel solution preferably contains a polymerization initiator. The stimulus-curable gel of the present invention is obtained by adding a thermal polymerization initiator and / or a photopolymerization initiator as a polymerization initiator to the uncured gel solution, pouring it into a predetermined mold, etc., and then applying a stimulus. . In addition, when using a material extrusion deposition method or an inkjet method as in a 3D printer, an uncured gel solution can be ejected from a syringe or printer head and then cured by stimulation to be formed into a desired shape. Furthermore, in the optical modeling method, an uncured gel solution containing a photopolymerization initiator can be placed in a bathtub-shaped container and molded into a desired shape by optical modeling.

  As thermal polymerization initiators, azo polymerization initiators and peroxide polymerization initiators that are common in radical polymerization can be used, but in order to obtain gels with excellent transparency and physical properties, peroxide is not generated. A physical polymerization initiator is preferred. A redox polymerization initiator combined with a reducing agent may be used. As described above, a redox polymerization initiator can be cured by stimulation of mixing a peroxide polymerization initiator and a reducing agent.

  When an aqueous solvent is used for the uncured gel solution, a highly water-soluble peroxide polymerization initiator is preferable. Specific examples include inorganic peroxides such as ammonium persulfate, potassium persulfate, and sodium persulfate. As the reducing agent to be combined as a redox polymerization initiator, known reducing agents can be used. Among them, N, N, N ′, N′-tetramethylethylenediamine, sodium sulfite, sodium bisulfite, hydrosal, which have high water solubility, can be used. Phyto sodium etc. are mentioned as a preferable example.

  As already mentioned, a peroxide-based polymerization initiator that does not generate gas is preferably used, but a water-soluble azo polymerization initiator may be used particularly when the transparency and physical properties of the gel are not questioned. . Specifically, for example, 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-Methylpropionamidine] dihydrochloride (trade name “V-50”, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine ] 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- ( -Hydroxyethyl) propionamide] (trade name “VA-086”, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2′-azobis (4-cyanopentanoic acid) (trade name “V-501”, Wako Pure) Yakuhin Kogyo Co., Ltd.).

  As the photopolymerization initiator, any photopolymerization initiator can be used without any problem as long as the polymerization is initiated by light rays such as ultraviolet rays (UV) and visible rays, but those exhibiting water solubility are preferred. Specifically, for example, α-ketoglutaric acid, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (trade name “Irgacure 2959”, BASF Corporation ), Phenyl (2,4,6-trimethylbenzoyl) phosphinic acid lithium salt (trade name “L0290”, manufactured by Tokyo Chemical Industry Co., Ltd.), 2,2′-azobis [2-methyl-N- (2- Hydroxyethyl) propionamide] (trade name “VA-086”, manufactured by Wako Pure Chemical Industries, Ltd.), Eosin Y and the like.

  When the uncured gel solution containing the photopolymerization initiator is cured, the uncured gel solution may include a light absorber. In many cases, the light absorbing agent is required to ensure precision in the modeling by the 3D printer of the optical modeling method. The light absorbing agent is not particularly limited as long as it shows water solubility, but “KEMISORB111”, “KEMISORB11S” manufactured by Chemipro Kasei Co., Ltd., “Tinuvin477-DW”, “UVA805”, “Tinuvin1130” manufactured by BASF, etc. Is mentioned.

  When the uncured gel solution containing the photopolymerization initiator is cured, the uncured gel solution may further contain a polymerization inhibitor. Examples of the polymerization inhibitor include water-soluble hydroquinone and p-methoxyphenol, but other polymerization inhibitors can also be used. By adding a polymerization inhibitor, the storage stability of the uncured gel solution can be enhanced.

  The uncured gel solution may contain additives such as pigments, preservatives, and antifungal agents 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 stimulus-curable gel of the present invention can be used as it is, but it may be used after being immersed in a solvent such as water to obtain an equilibrium swelling state. The effect of removing unreacted raw materials and non-crosslinked polymer components by an immersion operation can also be expected. In order to further remove the unreacted raw material and the non-crosslinked polymer component, the immersion operation may be repeated by exchanging the solvent. However, since the stimulus-curable gel of the present invention uses a water-soluble polymer having a crosslinkable group, there is a feature that even if it is used as it is, the toxicity usually exhibited by the monomer is hardly exhibited.

  The use of the stimulus-curable gel of the present invention is not limited to hygiene products such as disposable diapers and sanitary products, medical devices used outside the body such as contact lenses and wound dressings, shock absorbing materials, vibration-damping / sound-proofing materials, etc. , More advanced medical devices such as surface coatings and artificial organs for medical devices, civil engineering and building materials such as soil improvement materials that require on-site construction, agricultural materials such as water retention materials, and curing for 3D printers molded on demand Material.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by these examples.

Each component used in the examples and comparative examples is as follows.
(Monomer)
・ N-butyl acrylate: Nippon Shokubai Co., Ltd. ・ Trimethylolpropane trimethacrylate: Trade name “Light Ester TMP”, Kyoeisha Chemical Co., Ltd. ・ Allyl methacrylate: Tokyo Chemical Industry Co., Ltd. ・ Dicyclopentanyl Methacrylate: Trade name “Fancryl FA-513M”, manufactured by Hitachi Chemical Co., Ltd., butadiene: manufactured by JSR Co., Ltd., styrene: manufactured by Kishida Chemical Co., Ltd. (water-soluble polymer)
・ Polyvinyl alcohol: Trade name “PVA117”, manufactured by Kuraray Co., Ltd. ・ Polyvinyl alcohol: Trade name “PVA105”, manufactured by Kuraray Co., Ltd. (crosslinking agent)
・ N, N′-methylenebisacrylamide: manufactured by Tokyo Chemical Industry Co., Ltd. (chain transfer agent)
・ Dodecyl mercaptan: Aldrich Japan Co., Ltd. (emulsifier)
-Trade name "Eleminol JS-20" manufactured by Sanyo Chemical Industries, Ltd.-Mercapto group-modified PVA: manufactured by Kuraray Co., Ltd.-Sodium lauryl sulfate: trade name "Emar 2FG", manufactured by Kao Corporation (radical polymerization initiator)
-Sodium peroxodisulfate: Wako Pure Chemical Industries, Ltd.-Hydrogen peroxide solution: Wako Pure Chemical Industries, Ltd.-Cumene hydroperoxide: Trade name "Park Mill H-80", NOF Corporation ( Transition metal salt)
Iron (II) sulfate (7 hydrate): Wako Pure Chemical Industries, Ltd. (metal ion chelating agent)
・ Ethylenediaminetetraacetic acid disodium dihydrogen: manufactured by Kanto Chemical Co., Ltd. (thickening inhibitor)
・ Sodium chloride: Wako Pure Chemical Industries, Ltd. ・ Sodium acetate: Wako Pure Chemical Industries, Ltd. (anti-aging agent)
・ Oligomer type hindered phenol: Trade name “Cerosol K-840”, manufactured by Chukyo Yushi Co., Ltd. (solvent)
-Ion exchange water: Ion exchange water having an electric conductivity of 0.08 × 10 ⁻⁴ S / m or less.

  In the examples and comparative examples, various analysis conditions were performed according to the following methods.

[Average dispersion particle size in emulsion]
Using a dynamic light scattering measurement device (device name: FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.), a mixture of polymer particle (x) emulsion (0.1 mL) and ion-exchanged water (10 mL) The particle size distribution was measured on a volume basis, and the median diameter was measured as the average dispersed particle diameter.

[Polymerization degree of water-soluble polymer having a crosslinkable group]
The degree of polymerization of the water-soluble polymer having a crosslinkable group obtained in the following synthesis example was measured according to JIS K6726: 1994.

[Introduction rate of crosslinkable group]
The introduction rate of the crosslinkable group of the water-soluble polymer having a crosslinkable group obtained in the following synthesis example was measured by proton NMR. The introduction rate is determined from the ratio of the integral value of the signal of the crosslinkable group and the signal of the water-soluble polymer.
(Proton NMR measurement conditions)
Equipment: Nuclear magnetic resonance equipment “JNM-ECX400” manufactured by JEOL Ltd.
Temperature: 25 ° C

  Evaluation in Examples and Comparative Examples was performed according to the following method.

[Stimulus curing]
Regarding the gels produced by the following examples and comparative examples, those that formed a gel with a sense of unity were “O”, those that were weak but somehow formed a gel that showed a sense of unity were “△”, and the whole did not cure as a gel Items that could not be handled were marked with “x”.

[Evaluation of gel tensile strength]
The tensile strength of the gel obtained in Examples 1-7 and Comparative Examples 1-5 was measured by the following procedure. Using a JISK-6251-3 standard dumbbell cutter according to the method described in JP-A-2015-004059, a test piece was cut out from each gel sheet prepared with a thickness of 2 mm. Two test marks were attached to the test piece using the food red, and the distance between the test marks was measured with a caliper. A micrometer was used to measure the width and thickness of the specimen. A test piece was set in a tensile tester manufactured by Easton Co., Ltd., and breaking stress and breaking strain were measured while acquiring image data. The initial elastic modulus was simply obtained from the respective stresses corresponding to strains of 1% and 100%. The results are shown in Table 2.

[Synthesis Example 1]
(N-butyl acrylate (BA) / dicyclopentanyl methacrylate (TCDMA) particles)
(Process 1)
After adding 240 g of ion exchange water, 91.368 g of “Eleminol JS-20” and 1.08 g of sodium peroxodisulfate to the dried 2 L pressure-resistant polymerization tank, deoxygenation treatment was performed by bubbling with nitrogen gas for 30 minutes. To obtain an aqueous solution.
After raising the temperature of the aqueous solution to 60 ° C., a monomer mixture for forming polymer particles (x) (n-butyl acrylate: trimethylolpropane trimethacrylate: allyl methacrylate = 360: 1.8: 3.6 ( (Weight ratio)) 365.4 g was deoxygenated and then continuously added at a rate of 10 mL / min.

(Process 2)
When it was confirmed that the total monomer conversion rate exceeded 99 wt%, 45 g of dicyclopentanyl methacrylate forming the polymer film (y) was deoxygenated in the emulsion obtained in Step 1 above. Thereafter, it was continuously added at a rate of 10 mL / min.

(Process 3)
When it was confirmed that the total monomer conversion rate exceeded 99 wt%, the emulsion obtained in Step 2 was heated to 100 ° C. and stirred for 2 hours to decompose the residual polymerization initiator. went. The polymerization tank was cooled to 25 ° C., and an emulsion of coated polymer particles (BA / TCDMA particles) was taken out. The average dispersed particle size in the emulsion was 47.4 nm, and the solid content concentration was 28 wt%. The glass transition temperature of the polymer particles (x) was −55 ° C.

[Synthesis Example 2]
(BA / mercapto group-modified PVA particles)
(Process 1)
In a dried 2 L glass polymerization tank, 537.12 g of a 2 wt% aqueous solution of mercapto group-modified PVA (polymerization degree 500, saponification degree 88 mol%), iron (II) sulfate (7 hydrate) 0.0059 g, sodium acetate 0.145 g was added and adjusted to pH 5.0 with a 1 N aqueous sulfuric acid solution, and then deoxygenated by bubbling with nitrogen gas for 30 minutes to obtain an aqueous solution.
After the temperature of the aqueous solution was raised to 70 ° C., a mixture consisting of 133.16 g of n-butyl acrylate and 0.66 g of dodecyl mercaptan was deoxygenated and then added all at once. Thereafter, 86.74 g of 0.9 wt% aqueous hydrogen peroxide solution was continuously added at a rate of 2.48 mL / min, and polymerization was carried out with stirring until the addition was completed over 40 minutes.

(Process 2)
To the emulsion obtained in Step 1, 107.42 g of a 10 wt% aqueous solution of mercapto group-modified PVA adjusted to pH 5.0 with a 1 N aqueous sulfuric acid solution was deoxygenated and added all at once. Subsequently, a mixture consisting of 133.16 g of n-butyl acrylate and 0.66 g of dodecyl mercaptan was subjected to deoxygenation treatment and then added all at once. Thereafter, 86.74 g of 0.9 wt% aqueous hydrogen peroxide solution was continuously added at a rate of 2.48 mL / min, and polymerization was carried out with stirring until the addition was completed over 40 minutes.

(Process 3)
The same operation as in Step 2 was performed on the emulsion obtained in Step 2.

(Process 4)
The emulsion obtained in Step 3 was subjected to the same operation as in Step 3, and then stirred for 4 hours. When it was confirmed that the total monomer conversion exceeded 99.5%, the polymerization tank Was cooled to 25 ° C., and an emulsion of polymer particles (BA / mercapto group-modified PVA particles) was taken out. The average dispersed particle size in the emulsion was 306.3 nm, and the solid content concentration was 33 wt%. The glass transition temperature of the polymer particles (x) was −55 ° C.

[Synthesis Example 3]
(Butadiene / styrene particles)
The emulsion composed of 3.45 g of cumene hydroperoxide, 3.75 g of sodium lauryl sulfate and 150 g of ion-exchanged water was subjected to deoxygenation treatment to obtain a radical polymerization initiator emulsion.
In a dried 0.5 L pressure-resistant polymerization tank, 200 g of ion-exchanged water, 5 g of sodium lauryl sulfate, 0.032 g of iron (II) sulfate (7 hydrate), 0.02 g of disodium ethylenediaminetetraacetate, 0.02 g of sodium chloride After adding 2 g, deoxygenation was performed by bubbling with nitrogen gas for 30 minutes to obtain an aqueous solution.
After raising the temperature of the aqueous solution to 60 ° C., 78 g of butadiene for forming deoxidized polymer particles (x) was added. Next, the polymerization was started by continuously adding the radical polymerization initiator emulsion at a rate of 0.02 mL / min. When it was confirmed that the monomer conversion rate exceeded 95 wt%, the polymer was deoxygenated while feeding the radical polymerization initiator emulsion to the obtained emulsion at a rate of 0.02 mL / min. Monomer mixture (butadiene: styrene: trimethylolpropane trimethacrylate = 2.8: 19: 0.2 (weight ratio)) 22 g forming the coating (y) was continuously added at a rate of 1.7 mL / min. did. After the addition of the monomer mixture, when it was confirmed that the monomer conversion rate exceeded 95 wt%, the addition of the radical polymerization initiator emulsion was stopped, and a deoxygenated aqueous solution of hydroquinone as a polymerization terminator was added. Added. The polymerization tank was cooled to 25 ° C., and an emulsion of coated polymer particles (butadiene / styrene particles) was taken out.
The polymerization time from the start of polymerization to the addition of the polymerization terminator was 10 hours. 0.5 g of K-840 as an anti-aging agent was added to the emulsion, the average dispersed particle size in the emulsion was 48 nm, and the solid content concentration was 34 wt%. The glass transition temperature of the polymer particles (x) was −76 ° C.

[Synthesis Example 4]
[Synthesis of water-soluble polymer having a crosslinkable group 1]
40 g (monomer repeat 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. The temperature was raised to 80 ° C. with a water bath and stirring was continued for 4 hours. It confirmed visually that PVA melt | dissolved, 1.2 g (10.8 mmol) of vinyl methacrylate was added directly, heating and stirring, and also it stirred at 80 degreeC for 3 hours. After allowing to cool, the reaction solution was poured into 2 L of methanol while stirring. Stirring was stopped and left for 1 hour. After the obtained solid was recovered, it was further washed by being immersed in 1 L of methanol for 1 hour. This washing operation was performed three times in total. The collected solid was vacuum-dried overnight at room temperature to obtain methacryloyloxylated PVA. The introduction ratio of methacryloyloxy group was 1.2 mol% with respect to the monomer repeating unit of PVA (hereinafter abbreviated as MA-PVA117 (1.2)). Using the same method, methacryloyloxylated PVA with various changes in the polymerization degree and methacryloyloxy group introduction rate of PVA was produced (Table 1).

注１）けん化度は約９８．０〜９９．０ｍｏｌ％
注２）ＰＶＡ重合度は、ＪＩＳＫ６７２６：１９９４年に準拠して測定した

Note 1) Degree of saponification is about 98.0-99.0 mol%
Note 2) The degree of polymerization of PVA was measured according to JIS K6726: 1994.

[Synthesis Example 5]
[Synthesis of water-soluble polymer having a crosslinkable group 2]
60 g (monomer repeat 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. The temperature was raised to 80 ° C. with a water bath and stirring was continued for 4 hours. It was visually confirmed that PVA was dissolved, and the temperature was lowered to 40 ° C. While stirring at 40 ° C., 2.5 g (20.5 mmol) of 5-norbornene-2-carboxaldehyde and 22 mL of 10 vol% sulfuric acid aqueous solution were directly added, followed by further stirring at 40 ° C. for 4 hours. After allowing to cool, 80 mL of 1N NaOH aqueous solution was added for neutralization, and the mixture was desalted by placing it in a dialysis membrane with a molecular weight cut off of 3500 (executed 4 times for 5 L of ion exchange water). The aqueous solution after desalting was poured into 2 L of methanol while stirring, and left for 1 hour. After the obtained solid was recovered, it was further washed by being immersed in 1 L of methanol for 1 hour. The collected solid was vacuum-dried overnight at room temperature to obtain norbornene PVA. The norbornene introduction rate was 1.3 mol% with respect to the monomer repeating unit of PVA (hereinafter abbreviated as Nor-PVA117 (1.3)).

[Example 1]
To 20 g of MA-PVA117 (1.2), 80 mL of ion-exchanged water was added and dissolved with stirring at 80 ° C. for 4 hours. To 15 g of this MA-PVA solution, 4.5 g of an emulsion of BA / TCDMA particles of Synthesis Example 1 (solid content concentration 28 wt%) and 10.5 g of ion-exchanged water were added and stirred. Subsequently, “Irgacure 2959”, which is a water-soluble photopolymerization initiator, was added to a concentration of 0.1 wt% to prepare an uncured gel solution.
Next, this solution is poured between glass plates sandwiching a spacer of 2 mm thickness, and GS Yuasa metal halide lamp is used for 30 seconds (irradiation energy amount: 1200 mJ / cm ² ) of ultraviolet rays (UV) at 145 mW / cm ² . When irradiated, it was fully cured and a tough, unity gel was obtained.

[Example 2]
To 15 g of the MA-PVA solution prepared in Example 1, 9 g of the BA / TCDMA particle emulsion (solid content concentration 28 wt%) of Synthesis Example 1 and 6 g of ion-exchanged water were added and stirred. Subsequently, “Irgacure 2959”, which is a water-soluble photopolymerization initiator, was added to a concentration of 0.1 wt% to prepare an uncured gel solution. When this solution was irradiated with UV in the same manner as in Example 1, it was sufficiently cured and a tough and unity gel was obtained.

[Example 3]
Except for using MA-PVA117 (0.6) instead of MA-PVA117 (1.2), UV irradiation was performed in the same manner as in Example 1 to obtain a gel with a strong and solid sense of unity. It was.

[Example 4]
To 15 g of the MA-PVA solution prepared in Example 1, 0.9 g of an emulsion (solid content concentration 33 wt%) of BA / mercapto group-modified PVA particles of Synthesis Example 2 and 14.1 g of ion-exchanged water were added and stirred. Subsequently, 30 μl of ammonium persulfate (APS) and N, N, N ′, N′-tetramethylethylenediamine (TEMED) as redox polymerization initiators were added and stirred.
After the redox polymerization initiator is added, this solution is quickly poured between glass plates sandwiched with a 2 mm thick spacer and cured at room temperature for 1 hour to obtain a gel with a strong sense of unity. It was.

[Example 5]
To 15 g of the MA-PVA solution prepared in Example 1, 4 g of the butadiene / styrene particle emulsion (Synthesis content 34 wt%) of Synthesis Example 3 and 11 g of ion-exchanged water were added and stirred. Subsequently, “Irgacure 2959”, which is a water-soluble photopolymerization initiator, was added to a concentration of 0.1 wt% to prepare an uncured gel solution. When this solution was irradiated with UV in the same manner as in Example 1, it was sufficiently cured and a tough and unity gel was obtained.

[Example 6]
To 20 g of MA-PVA117 (1.2) and 10 g of MA-PVA105 (1.2), 70 mL of ion-exchanged water was added and dissolved at 80 ° C. with stirring for 4 hours. To 15 g of this PVA solution, 9 g of an emulsion of BA / TCDMA particles (solid content concentration 28 wt%) of Synthesis Example 1 and 6 g of ion-exchanged water were added and stirred. Subsequently, “Irgacure 2959”, which is a water-soluble photopolymerization initiator, was added to a concentration of 0.1 wt% to prepare an uncured gel solution. When this solution was irradiated with UV in the same manner as in Example 1, it was sufficiently cured and a tough and unity gel was obtained.

[Example 7]
To 20 g of Nor-PVA117 (1.3), 80 mL of ion-exchanged water was added and dissolved while stirring at 80 ° C. for 4 hours. 4.5 g of the emulsion of BA / TCDMA particles of Synthesis Example 1 (solid content concentration 28 wt%), 10.5 g of ion-exchanged water, and 3,6-dioxa- as polythiol having a thiol group are added to 15 g of this Nor-PVA solution. 80 mg of 1,8-octanedithiol was added and stirred. Subsequently, “Irgacure 2959”, which is a water-soluble photopolymerization initiator, was added to a concentration of 0.1 wt% to prepare an uncured gel solution. When this solution was irradiated with UV in the same manner as in Example 1, it was sufficiently cured and a tough and unity gel was obtained.

[Comparative Example 1]
To 10 g of MA-PVA117 (1.2), 90 mL of ion-exchanged water was added and dissolved with stirring at 80 ° C. for 4 hours. To this was added 0.1 wt% “Irgacure 2959” as a photopolymerization initiator, and when it was irradiated with UV in the same manner as in Example 1, it was sufficiently cured and a gel with a sense of unity was obtained.

[Comparative Example 2]
Except that MA-PVA117 (0.6) was used instead of MA-PVA117 (1.2), UV was irradiated in the same manner as in Comparative Example 1 to obtain a gel with a sense of unity. .

[Comparative Example 3]
To 10 g of MA-PVA117 (1.2), 90 mL of ion-exchanged water was added and dissolved with stirring at 80 ° C. for 4 hours. When this solution was cured in the same manner as in Example 4, it was sufficiently cured and a gel with a sense of unity was obtained.

[Comparative Example 4]
With reference to Patent Document 6, an interpenetrating gel formed from the first polymer and the second polymer was prepared as follows. 1 mol / L 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 0.04 mol / L N, N′-methylenebisacrylamide (MBAA), and 0.001 mol / L α- as a photopolymerization initiator Polymerization was performed by irradiating 100 mL of an aqueous solution containing ketoglutaric acid with UV irradiation for 7 hours to obtain a polyAMPS gel (PAMPS gel) having a crosslinking degree of 4 mol%. The obtained PAMPS gel was put in a heat dryer for one day, dried, put in a mortar and pulverized to obtain fine particles of the PAMPS gel (hereinafter sometimes referred to as a first polymer).
On the other hand, with respect to 1 mol / L of N, N-dimethylacrylamide (DAAm), 0.01 mol% of MBAA with respect to DAAm as a cross-linking agent and 0.1 wt% of “AA monomer” as a water-soluble photopolymerization initiator. A monomer solution containing “Irgacure 2959” was prepared (hereinafter sometimes referred to as a monomer solution forming a second polymer).
Inject the fine particles of the first polymer into the monomer solution forming the second polymer in such an amount that the ratio of the first polymer and the monomer solution forming the second polymer is 1:30 by weight. did. When this solution was irradiated with UV in the same manner as in Example 1, the whole was not cured and a gel with a sense of unity was not obtained.

[Comparative Example 5]
In Comparative Example 5, an interpenetrating gel formed from the first polymer and the second polymer produced in Comparative Example 4 was prepared using a redox polymerization initiator. A monomer solution containing 0.01 mol% of MBAA as a crosslinking agent with respect to 1 mol / L of DAAm as a crosslinking agent was prepared. The first polymer prepared in Comparative Example 2 and the monomer solution were mixed in such an amount that the ratio by weight was 1:30. When this solution was cured in the same manner as in Example 4, a gel that was weak but somehow showed a sense of unity was obtained.

  Table 2 shows the composition of the water-soluble polymer having a crosslinkable group, the monomer, the polymer particle, the polymerization initiator, and the evaluation results of the stimulus curability in Examples and Comparative Examples.

  According to the present invention, a stimulus-curable gel having excellent curability and safety and high mechanical strength can be obtained. Therefore, it is used outside the body of sanitary products such as disposable diapers and sanitary products, contact lenses and wound dressings. Not only medical equipment, shock-absorbing materials, vibration-damping / sound-proof materials, but more advanced medical equipment such as medical equipment surface coating and artificial organs, civil engineering and building materials such as soil improvement materials that require on-site construction, and water retention Expansion to various fields such as agricultural materials such as materials and curable raw materials for 3D printers molded on demand is expected.

Claims (6)

  A stimulus-curable gel comprising a water-soluble polymer having a crosslinkable group and polymer particles (x) having a glass transition temperature of 25 ° C. or lower.   The stimulus-curable gel according to claim 1, wherein the crosslinkable group is at least one selected from a vinyl group, a (meth) acryloyloxy group, a (meth) acryloylamino group, a vinylphenyl group, and derivatives thereof.   The stimulus-curable gel according to claim 1 or 2, wherein the introduction rate of the crosslinkable group is 0.01 to 10 mol% with respect to the repeating unit of the water-soluble polymer having a crosslinkable group.   The stimulus-curable gel according to any one of claims 1 to 3, wherein the polymer particles (x) have an average particle diameter of 0.01 to 10 µm.   The stimulus-curable gel according to any one of claims 1 to 4, wherein the stimulus is at least one selected from active energy rays, heat, and mixing.   The stimulus curable gel according to any one of claims 1 to 5, wherein the polymer particles (x) are coated polymer particles.