Gel-forming compositions and gel materials

Abstract

The present invention provides a gel-forming composition that can produce a gel material with excellent flexibility, extensibility, and toughness. [Solution] The gel-forming composition of the present invention contains an acrylic monomer having a specific structure, an aqueous medium, silica particles, and a polymerization initiator. The polymer produced by polymerizing the acrylic monomer can stably retain the aqueous medium and silica particles inside due to the polarity caused by the amide bond (-C=ON-). Therefore, the gel material produced by polymerizing and curing the gel-forming composition has excellent flexibility, extensibility, and toughness.

Description

[Technical Field]

[0001] This invention relates to gel-forming compositions and gel materials. [Background technology]

[0002] In recent years, hydrogels have attracted attention due to their excellent properties such as flexibility and water retention, and are expected to have applications in a wide range of fields, including medicine, pharmaceuticals, food, civil engineering, bioengineering, and sports.

[0003] One challenge in using hydrogels is improving their mechanical strength. Gel materials with improved mechanical strength have been proposed.

[0004] Patent Document 1 discloses a topological gel in which crosslinking points move along the main chain.

[0005] Patent Document 2 discloses a polymer composite in which an organic polymer (A) consisting of a polymer of (meth)acrylic acid ester (a), or a copolymer of (meth)acrylamide and at least one N-substituted (meth)acrylamide (b) and (meth)acrylic acid ester (a), and a water-swellable clay mineral (B) form a three-dimensional network.

[0006] Patent Document 3 discloses a semi-interpenetrating network hydrogel or interpenetrating network hydrogel obtained by introducing a second monomer component into a network structure formed by polymerizing and crosslinking a first monomer component, and then polymerizing and optionally crosslinking the second monomer component. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 3475252 [Patent Document 2] Japanese Patent Publication No. 2004-143212 [Patent Document 3] WO2003 / 093337 Summary of the Invention Problem to be Solved by the Invention

[0008] However, the topological gel of Patent Document 1 has problems of low tensile modulus and low tensile breaking strength, as well as a complicated production process.

[0009] The polymer composite of Patent Document 2 also has a problem of low mechanical strength such as low tensile modulus and low tensile breaking strength.

[0010] The present invention provides a gel-forming composition capable of producing a gel material excellent in flexibility, stretchability and toughness. Means for Solving the Problem

[0011] The gel-forming composition of the present invention is characterized by comprising an acrylic monomer represented by formula (1), an aqueous medium, silica particles and a polymerization initiator.

[0012] [Chemical Formula] Provided that in formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents a hydrogen atom or a methyl group, R 3 represents a hydrogen atom or a hydroxyl group, and Z represents an alkylene group having 1 to 6 carbon atoms.

[0013] The gel material of the present invention is a gel material characterized by comprising a polymerization product of the above gel-forming composition. Effect of the Invention

[0014] The gel-forming composition of the present invention contains an acrylic monomer represented by the above formula (1), an aqueous medium, and silica particles. The polymer produced by polymerizing the acrylic monomer can stably retain an aqueous medium therein due to the polarity derived from the amide bond (-C=ON-). Furthermore, an interaction derived from hydrogen bonding can be exerted between the polarity derived from the amide bond of the acrylic monomer component of the produced polymer and the hydroxyl groups (-OH) of the silica particles.

[0015] Therefore, the gel material produced by polymerizing the gel-forming composition of the present invention has excellent flexibility, and when an external force is applied to the gel material, the external force can be absorbed by releasing the interaction between the polymer formed by polymerization of the acrylic monomer and the silica particles, so that the gel material has excellent stretchability and toughness. MODE FOR CARRYING OUT THE INVENTION

[0016] In the numerical ranges described stepwise in the present specification, the upper limit or lower limit of the numerical range in one step can be arbitrarily combined with the upper limit or lower limit of the numerical range in another step. In the numerical ranges described in the present specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples or a value that can be uniquely derived from the examples. In the present specification, a numerical value connected by "~" means a numerical range including the numerical values before and after "~" as the lower limit and the upper limit.

[0017] The gel-forming composition of the present invention comprises an acrylic monomer represented by formula (1), an aqueous medium, silica particles, and a polymerization initiator.

[0018] (Acrylic Monomer) The gel-forming composition contains an acrylic monomer represented by formula (1).

[0019]

Chemical Formula

[0020] The polymer produced by polymerizing the acrylic monomer shown in formula (1) exhibits excellent interaction with aqueous media due to amide bonds, and stably retains aqueous media. Furthermore, the polymer exhibits moderately strong interaction with silica particles at the amide bond portion, resulting in excellent flexibility and extensibility. It can also smoothly absorb external forces by severing the interaction with silica particles, and possesses excellent toughness. In this invention, an amide bond refers to the structure shown in the following formula (A). * represents a bond, and signifies a single bond.

[0021] [ka]

[0022] In formula (1), Z is an alkylene group having 1 to 6 carbon atoms. In the present invention, an alkylene group is a divalent atomic group formed by abstracting one hydrogen atom each from different carbon atoms in an aliphatic saturated hydrocarbon, or a divalent atomic group formed by abstracting two hydrogen atoms from methane, and includes both linear and branched atomic groups.

[0023] Examples of alkylene groups include methylene group [-CH2-], ethylene group [-CH2-CH2-], propylene group [-CH(CH3)-CH2-], trimethylene group [-CH2-CH2-CH2-], butylene group, amylene group [-(CH2)5-], and hexylene group.

[0024] The number of carbon atoms in the alkylene group is preferably 1 to 4, more preferably 1 to 3, and more preferably 1 or 2. When the number of carbon atoms in the alkylene group is within the above range, the interaction between the polymer produced by polymerizing the monomer represented by formula (1) and the aqueous medium can further stably retain the aqueous medium in the polymer.

[0025] The acrylic monomer represented by Formula (1) is preferably an acrylic monomer represented by any one of Formulas (2) to (4), provided that in Formula (4), R 4 is an alkyl group having 1 to 6 carbon atoms. In Formulas (2) to (4), R 1 , R 2 , R 3 and Z are as described for the acrylic monomer represented by Formula (1), so descriptions thereof are omitted.

[0026]

Chemical Formula

[0027] R 4 With respect to the alkyl group having 1 to 6 carbon atoms for R, there is no particular limitation. Examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. A methyl group, an ethyl group, and a propyl group are preferred; a methyl group or an ethyl group is more preferred; and a methyl group is even more preferred.

[0028] The acrylic monomer represented by Formula (2) has polarity derived from the amide bond moiety (-C=ON-) and the terminal hydroxyl group (-OH), exhibits further excellent interaction with an aqueous medium and the hydroxyl groups on the surface of silica particles, and a gel material produced from the gel-forming composition has excellent flexibility, stretchability, and toughness.

[0029] The acrylic monomer represented by Formula (3) has high polarity derived from the amide bond moiety (-C=ON-), exhibits further excellent interaction with an aqueous medium and the hydroxyl groups on the surface of silica particles, and a gel material produced from the gel-forming composition has excellent flexibility, stretchability, and toughness.

[0030] The acrylic monomer represented by Formula (4) is characterized in that R 2 and R 4Due to its electron-donating properties, it possesses high polarity and exhibits excellent interaction with aqueous media and hydroxyl groups on the silica particle surface, resulting in gel materials produced from gel-forming compositions that have excellent flexibility, extensibility, and toughness.

[0031] The acrylic monomer represented by formula (1) is preferably N-(2-hydroxyethyl)acrylamide, N-(2-hydroxyethyl)methacrylamide, N,N-dimethylacrylamide, or N,N-dimethylmethacrylamide, more preferably N-(2-hydroxyethyl)acrylamide or N,N-dimethylacrylamide, and even more preferably N-(2-hydroxyethyl)acrylamide.

[0032] (aqueous medium) The gel-forming composition includes an aqueous medium. The aqueous medium contains water as an essential component. Examples of water include pure water such as ion-exchanged water, limit filtered water, reverse osmosis water, and distilled water, as well as ultrapure water.

[0033] The aqueous medium preferably contains a water-soluble organic solvent. The water-soluble organic solvent is miscible with water and, when mixed with water, dissolves in it to form a single phase. The water-soluble organic solvent is not particularly limited and includes, for example, glycerin derivatives of glycerin and polyglycerin (e.g., diglycerin, triglycerin, etc.); polyhydric alcohols such as alkanediols (e.g., 1,3-butanediol, 2,3-butanediol, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, etc.) and polyalkylene glycols (e.g., diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol); sugar alcohols; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, isopropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether Examples of glycol ethers include diethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol monoisopropyl ether, and tripropylene glycol monomethyl ether. Note that the water-soluble organic solvent may be used alone or in combination of two or more types.

[0034] As the water-soluble organic solvent, polyhydric alcohols are preferred, glycerin, polyglycerin, alkanediols, and polyalkylene glycols are more preferred, glycerin, polyglycerin, and polyalkylene glycols are even more preferred, and glycerin and polyglycerin are even more preferred. When the aqueous medium contains a polyhydric alcohol, the polar groups derived from the multiple hydroxyl groups contained in the polyhydric alcohol allow the aqueous medium to be stably retained within the polymer contained in the gel material. Furthermore, the interaction between the multiple hydroxyl groups contained in the polyhydric alcohol and the hydroxyl groups on the surface of the silica particles allows for uniform dispersion of silica particles in the aqueous medium. Therefore, the gel material produced from the gel-forming composition has excellent flexibility, extensibility, and toughness.

[0035] Polyglycerin is preferably linear. Linear polyglycerin can be produced, for example, by a dehydration condensation reaction of glycerin or a polyaddition reaction of epichlorohydrin. Linear polyglycerin is the polyglycerin represented by formula (5), where n is the number of repeating units and is an integer of 2 or more.

[0036] [ka]

[0037] In formula (5), the degree of polymerization n of polyglycerin is preferably 2 or higher, and more preferably 3 or higher. In formula (5), the degree of polymerization n of polyalkylene glycol is preferably 20 or lower, more preferably 15 or lower, more preferably 10 or lower, more preferably 8 or lower, and more preferably 6 or lower. When the degree of polymerization n of polyglycerin is within the above range, the aqueous medium can be stably held in the polymer contained in the gel material, and silica particles can be uniformly dispersed in the aqueous medium, and the gel material produced from the gel-forming composition has excellent flexibility, extensibility, and toughness.

[0038] The average molecular weight of linear polyglycerin is preferably 200 to 5000 g / mol, and more preferably 230 to 3000 g / mol. The average molecular weight of linear polyglycerin refers to the value measured by GPC (gel permeation chromatography). Specifically, it refers to the molecular weight in terms of polystyrene, measured using one of the following as the eluent: chloroform, dimethylformamide, tetrahydrofuran (THF), acetone, or a combination of these solvents, preferably tetrahydrofuran. For example, the average molecular weight of linear polyglycerin can be measured under the following conditions.

[0039] For example, the average molecular weight of linear polyglycerin can be measured by gel permeation chromatography (GPC) under the following conditions. Sample: Approximately 5 mg of linear polyglycerin dissolved in 1.5 g of THF. Equipment: Shimadzu Corporation, Semi-micro GPC system Prominence 504 RI detector: RI-504, manufactured by Shoko Science Co., Ltd. Columns: KF-802, KF-803 Guard Column KF-G 4A Column oven temperature: 40℃ Solvent: THF (manufactured by Kanto Chemical Co., Ltd., HPLC grade) Flow rate: 0.6mL / min

[0040] The hydroxyl value of linear polyglycerin is preferably 500 to 2000 KOH mg / g, and more preferably 800 to 1200 KOH mg / g.

[0041] In this invention, the hydroxyl value of a polyol refers to the number of milligrams of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl groups when 1 g of polyol is acetylated (JIS K0070:1992 2.1(5)). Specifically, it can be measured by acetylating the hydroxyl groups in the polyol with acetic anhydride, and then titrating the unused acetic anhydride with potassium hydroxide (JIS K0070:1992 3.1 (neutralization titration method)).

[0042] Linear polyglycerin can be purchased from Sakamoto Pharmaceutical Co., Ltd. under the product names "Diglycerin S," "Polyglycerin #310," "Polyglycerin #500," and "Polyglycerin #750," or from NOF Corporation under the product name "Uniglycerin G-6."

[0043] The content of the water-soluble organic solvent in the aqueous medium is preferably 5% by mass or more, more preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, and more preferably 45% by mass or more. The content of the water-soluble organic solvent in the aqueous medium is preferably 90% by mass or less, more preferably 85% by mass or less, and more preferably 76% by mass or less. When the content of the water-soluble organic solvent is within the above range, the gel material produced from the gel-forming composition has excellent flexibility, extensibility, and toughness.

[0044] The total content of glycerin and polyglycerin in the aqueous medium is preferably 5% by mass or more, more preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, and more preferably 45% by mass or more. The total content of glycerin and polyglycerin in the aqueous medium is preferably 90% by mass or less, more preferably 85% by mass or less, and more preferably 76% by mass or less.

[0045] The water content in the aqueous medium is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 30% by mass or more. The water content in the aqueous medium is preferably 95% by mass or less, more preferably 80% by mass or less, more preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less.

[0046] The content of the aqueous medium in the gel-forming composition is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and more preferably 60 parts by mass or more, per 100 parts by mass of the acrylic monomer represented by formula (1). The content of the aqueous medium in the gel-forming composition is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, and more preferably 70 parts by mass or less, per 100 parts by mass of the acrylic monomer represented by formula (1). When the content of the aqueous medium is 30 parts by mass or more, the flexibility of the gel material produced from the gel-forming composition is improved. When the content of the aqueous medium is 80 parts by mass or less, the extensibility and toughness of the gel material produced from the gel-forming composition are improved.

[0047] (Silica particles) The gel-forming composition contains silica particles. Within the gel material produced from the gel-forming composition, the silica particles are dispersed within an aqueous medium held within the polymer, interacting with the polymer and forming electrical bonds. Therefore, when an external force is applied to the gel material produced from the gel-forming composition, the force can be absorbed by changing the relative position of the polymer and the silica particles. If the force cannot be absorbed by changing the relative position of the polymer and silica particles, the force can be absorbed by breaking the interaction between the polymer and the silica particles. Thus, the gel material exhibits excellent conformability to external forces and possesses superior flexibility, extensibility, and toughness.

[0048] The shape of the silica particles is not particularly limited as long as it does not impair the effects of the present invention, but it is preferable that they be spherical in order to impart excellent extensibility and toughness to the gel material. In the present invention, "spherical" means a perfect sphere, a nearly spherical shape, or a spheroid, excluding rod-shaped or plate-shaped particles, and may have irregularities on its surface.

[0049] As silica particles, for example, powdered spherical silica particles, colloidal silica (silica sol), etc., can be used.

[0050] The average particle diameter of the primary silica particles is preferably less than 300 nm, more preferably less than 280 nm, more preferably 260 nm or less, more preferably 150 nm or less, more preferably 100 nm or less, more preferably 80 nm or less, more preferably 60 nm or less, more preferably 40 nm or less, more preferably 30 nm or less, more preferably 25 nm or less, and more preferably 20 nm or less. The average particle diameter of the silica particles is preferably 0.5 nm or more, more preferably 1 nm or more, more preferably 3 nm or more, and more preferably 5 nm or more. When the average particle diameter of the silica particles is less than 300 nm, a fine network-like interaction can be formed between the polymer contained in the gel material and the silica particles, and the gel material has excellent flexibility as well as excellent extensibility and toughness. When the average particle diameter of the silica particles is 0.5 nm or more, the interaction between the polymer contained in the gel material and the silica particles can be strengthened, and the toughness of the gel material is improved.

[0051] The average particle diameter of primary silica particles refers to the value measured by a transmission electron microscope (TEM). Specifically, primary silica particles are photographed at 20,000x magnification using a transmission electron microscope (TEM). Fifty primary silica particles are arbitrarily selected from the obtained TEM image, and the diameter of each primary particle is measured. The arithmetic mean of the primary particle diameters is taken as the average particle diameter of the primary silica particles. Note that the diameter of a primary particle is defined as the diameter of the smallest circle that can enclose the primary particle in the TEM image.

[0052] The specific surface area of ​​silica particles is 100 m². 2 Preferably 130m / g or more. 2 More preferably 150m / g or more, 2 More preferably 160m / g or more, 2 A value of 300 m² or more is more preferable. The specific surface area of ​​the silica particles is 300 m². 2 Preferably less than / g, 290m 2 It is more preferable to have a value of 280m or less. 2 / g or less is more preferable, 260m 2 Less than / g is preferable, 240m 2Less than / g is more preferable. The specific surface area of ​​the silica particles is 100m². 2 When the silica content is 300 m² or higher, a fine network of interactions can be formed between the polymer and silica particles contained in the gel material, resulting in a gel material with excellent flexibility, as well as excellent extensibility and toughness. 2 When the silica content is less than / g, the interaction between the polymer and silica particles in the gel material can be strengthened, improving the toughness of the gel material. The specific surface area of ​​the silica particles refers to the value measured by the nitrogen adsorption method (BET).

[0053] The silica particle content in the gel-forming composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and more preferably 1.0 part by mass or more, per 100 parts by mass of the acrylic monomer represented by formula (1). The silica particle content in the gel-forming composition is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the acrylic monomer represented by formula (1). When the silica particle content is 0.1 parts by mass or more, the interaction between the polymer and silica particles in the gel material can be increased, thereby imparting excellent toughness to the gel material. When the silica particle content is 30 parts by mass or less, excellent flexibility and extensibility can be imparted to the gel material.

[0054] (Polymerization initiator) The gel-forming composition contains a polymerization initiator. The gel-forming composition generates a gel material by radical polymerization of a monomer composition containing an acrylic monomer represented by formula (1).

[0055] A polymerization initiator is contained to radically polymerize the gel-forming composition. The polymerization initiator only needs to be able to initiate the radical polymerization of the monomer composition containing the acrylic monomer represented by formula (1), and may be either a photopolymerization initiator or a thermal polymerization initiator.

[0056] The photopolymerization initiator can be any agent that generates radicals upon irradiation with light and initiates polymerization of a monomer composition containing an acrylic monomer represented by formula (1). While there are no particular limitations on the photopolymerization initiator, those that generate radicals upon irradiation with ultraviolet light are preferred. Preferably, the photopolymerization initiator absorbs light with a wavelength of 360 to 470 nm to generate radicals.

[0057] Examples of photopolymerization initiators include 2-hydroxy-2-methylpropiophenone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 2-[4-(methylthiobenzoyl)]-2-(4-morpholinyl)propane, 2-hydroxy-1-{4-[4-(2-hydroxy- Examples include 2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 1-hydroxycyclohexylphenyl ketone, [4-[4-methylphenyl]thio]phenyl]phenylmethanone, 4-(dimethylamino)benzoate ethyl, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 4,4'-bis-(dimethylamino)benzophenone, 4,4'-diethylaminobenzophenone, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-[(4-methylphenyl)sulfonyl]propan-1-one, (methylimino)diethane-2,1-diyl(4-dimethylamibenzoate), lithium phenyl(2,4,6-trimethylbenzoyl)phosphinate, and bis(4-methoxybenzoyl)diethylgermanium. Furthermore, the photopolymerization initiator may be used alone or in combination of two or more types.

[0058] Preferred photopolymerization initiators include 2-hydroxy-2-methylpropiophenone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, lithium phenyl(2,4,6-trimethylbenzoyl)phosphine acid, and bis(4-methoxybenzoyl)diethylgermanium, with 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and 2-hydroxy-2-methylpropiophenone being more preferred.

[0059] The content of the photopolymerization initiator in the gel-forming composition is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and more preferably 0.03 parts by mass or more, per 100 parts by mass of the acrylic monomer represented by formula (1). The content of the photopolymerization initiator in the gel-forming composition is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the acrylic monomer represented by formula (1).

[0060] Any thermal polymerization initiator that generates radicals upon heating and can initiate polymerization of a monomer composition containing the acrylic monomer represented by formula (1) is acceptable.

[0061] Examples of thermal polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane1-carbonnitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, and di-n-propyl peroxydi Examples include carbonates, di(2-ethoxyethyl)peroxydicarbonate, t-butylperoxy2-ethylhexanoate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, diacetylperoxide, ammonium persulfate (hereinafter sometimes referred to as APS), potassium persulfate (hereinafter sometimes referred to as KPS), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (hereinafter sometimes referred to as VA-044), 1,1'-azobis(cyclohexanecarbonilate), di-tert-butylperoxide, tert-butylhydroperoxide, and benzoyl peroxide. The thermal polymerization initiator may be used alone or in combination of two or more types.

[0062] The content of the thermal polymerization initiator in the gel-forming composition is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and more preferably 0.03 parts by mass or more, per 100 parts by mass of the acrylic monomer represented by formula (1). The content of the thermal polymerization initiator in the gel-forming composition is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the acrylic monomer represented by formula (1).

[0063] (Chain transfer agent) The gel-forming composition may contain a chain transfer agent. The presence of a chain transfer agent in the gel-forming composition allows for optimization of the molecular weight of the polymer produced by polymerizing the gel-forming composition, thereby improving the flexibility, extensibility, and toughness of the resulting gel material.

[0064] Examples of chain transfer agents include mercaptocarboxylic acids such as mercaptoacetic acid and 3-mercaptopropionic acid; mercaptocarboxylic acid esters such as methyl mercaptoacetate, methyl 3-mercaptopropionate, 2-ethylhexyl 3-mercaptopropionate, n-octyl 3-mercaptopropionate, methoxybutyl 3-mercaptopropionate, stearyl 3-mercaptopropionate, trimethylolpropanetris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), and dipentaerythritol hexakis(3-mercaptopropionate); ethyl mercaptan, t-butyl mercaptan, and n-dodecyl mercaptan. Examples include alkyl mercaptans such as 1,2-dimercaptoethane; mercapto alcohols such as 2-mercaptoethanol and 4-mercapto-1-butanol; aromatic mercaptans such as benzenethiol, m-toluenethiol, p-toluenethiol, and 2-naphthalenchiol; mercaptoisocyanurates such as tris[(3-mercaptopropionyloxy)-ethyl]isocyanurate; disulfides such as 2-hydroxyethyl disulfide and tetraethyl thiuram disulfide; dithiocarbamates such as benzyl diethyl dithiocarbamate; monomeric dimers such as α-methylstyrene dimer; and alkyl halides such as carbon tetrabromide.

[0065] The content of the chain transfer agent in the gel-forming composition is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and more preferably 0.1 parts by mass or more, per 100 parts by mass of the acrylic monomer represented by formula (1). The content of the chain transfer agent in the gel-forming composition is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the acrylic monomer represented by formula (1).

[0066] (Crosslinking agent) The gel-forming composition preferably contains a crosslinking agent. The presence of a crosslinking agent in the gel-forming composition allows for the introduction of a crosslinked structure into the polymer in the gel material produced by polymerizing the gel-forming composition. This can improve the toughness of the gel material.

[0067] The crosslinking agent is not particularly limited and includes, for example, difunctional acrylate monomers, trifunctional acrylate monomers, and tetrafunctional or more acrylate monomers. Difunctional acrylate monomers are preferred because they improve the toughness of the gel material produced by polymerizing the gel-forming composition. The numbers in parentheses for the crosslinking agents listed below are molecular weights. Note that the crosslinking agent may be used alone or in combination of two or more types.

[0068] Examples of difunctional acrylate monomers include N,N'-methylenebisacrylamide (MBAA) (154.17), ethylene glycol diacrylate (198.22), ethylene oxide-modified bisphenol A diacrylate, 1,4-butanediol diacrylate (198.22), diethylene glycol diacrylate (214.22), 1,6-hexanediol diacrylate (226.27), neopentyl glycol diacrylate (212.25), trimethylolpropane diacrylate (296.32), and polyethylene glycol diacrylate (molecular weight of polyethylene glycol chain: 100-10000).

[0069] Preferred bifunctional acrylate monomers include ethylene glycol diacrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, and N,N'-methylenebisacrylamide, with N,N'-methylenebisacrylamide being more preferred.

[0070] The bifunctional acrylate monomer preferably has an amide bond [formula (A)] in its molecule. The polymer in the gel material exhibits excellent interaction with the aqueous medium due to the amide bond, and stably retains the aqueous medium. Furthermore, the polymer exhibits an appropriate strength of interaction with silica particles at the amide bond portion, exhibiting excellent flexibility and extensibility, and can smoothly absorb external forces by severing the interaction with the silica particles, thus possessing excellent toughness.

[0071] [ka]

[0072] Examples of trifunctional acrylate monomers include trimethylolpropane triacrylate (296.32) and pentaerythritol triacrylate (298.29).

[0073] Examples of acrylate monomers with four or more functions include pentaerythritol tetraacrylate (352.34), dipentaerythritol pentaacrylate (524.52), dipentaerythritol hexaacrylate (578.57), tripentaerythritol octaacrylate (804.80), tetrapentaerythritol decaacrylate (1031.03), pentapentaerythritol dodecaacrylate (1257.26), and polyglycerin-modified ethylene oxide acrylate, with polyglycerin-modified ethylene oxide acrylate being preferred.

[0074] Examples of polyglycerol-modified ethylene oxide acrylates include acrylate monomers having the structure shown in formula (6) below. m1 to m6 are the number of repeating units and are natural numbers.

[0075] [ka]

[0076] The crosslinking agent preferably has a glycerin skeleton shown in formula (7) in its molecule. It can stably retain the aqueous medium in the polymer within the gel material and uniformly disperse silica particles in the aqueous medium, thereby imparting excellent flexibility, extensibility, and toughness to the gel material. In formula (7), p is an integer from 1 to 20, preferably from 2 to 20. * represents a bond, signifying a single bond.

[0077] [ka]

[0078] The crosslinking agent preferably has a glycerin skeleton in its molecule as shown in formula (8). This allows for stable retention of the aqueous medium within the polymer in the gel material and uniform dispersion of silica particles in the aqueous medium, thereby imparting even greater flexibility, extensibility, and toughness to the gel material. In formula (8), p is an integer between 2 and 20, q1 is an integer between 50 and 200, q2 is an integer between 50 and 200, and q3 is an integer between 50 and 200.

[0079] [ka]

[0080] The crosslinking agent preferably has ethylenically unsaturated bonds (preferably ethylenically unsaturated double bonds) at its molecular ends and a molecular weight of 100 or more. In the polymer in the gel material produced from the gel-forming composition, the distance between crosslinking points is increased, improving the flexibility and toughness of the gel material. The molecular weight of the crosslinking agent is preferably 100 or more, more preferably 125 or more, and even more preferably 150 or more. The molecular weight of the crosslinking agent is preferably 10,000 or less, more preferably 7,500 or less, and even more preferably 5,000 or less.

[0081] In the gel-forming composition, the crosslinking agent content is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, and more preferably 0.08 parts by mass or more, per 100 parts by mass of the acrylic monomer represented by formula (1). In the gel-forming composition, the crosslinking agent content is preferably 0.4 parts by mass or less, more preferably 0.35 parts by mass or less, more preferably 0.30 parts by mass or less, and more preferably 0.25 parts by mass or less, per 100 parts by mass of the acrylic monomer represented by formula (1).

[0082] (Gel-forming composition) A gel-forming composition can be produced by mixing a monomer composition containing an acrylic monomer represented by formula (1) and an optional crosslinking agent with an aqueous medium, silica particles, and a polymerization initiator in a known manner.

[0083] The gel-forming composition may contain additives such as thickeners, electrolytes, conductive fillers, preservatives, antibacterial agents, disinfectants, rust inhibitors, antioxidants, stabilizers, fragrances, colorants, defoamers, UV absorbers, chelating compounds, metal oxides, moisturizing agents, conductivity enhancers, hardness adjusters, and thermal polymerization initiators, to the extent that they do not impair its physical properties.

[0084] The gel-forming composition can be polymerized and cured by irradiating it with active light such as ultraviolet light or visible light, or by heating, by polymerizing a monomer composition containing an acrylic monomer represented by formula (1) and a crosslinking agent added as needed, thereby producing a polymer. At the same time, a gel material (hydrogel), which is a structure in which an aqueous medium is incorporated into this polymer and swells, can be produced as a polymerization product. Silica particles are dispersed in the aqueous medium.

[0085] The gel material produced by polymerizing and curing the gel-forming composition has polarity due to the amide bond portion of the acrylic monomer represented by formula (1), and can stably hold an aqueous medium.

[0086] Silica particles are stably dispersed in an aqueous medium due to the polarity caused by the hydroxyl groups on their surface. Furthermore, the hydroxyl groups on the surface of the silica particles interact with the amide bond portion of the acrylic monomer represented by formula (1) in the polymer through hydrogen bonding and other interactions, forming a pseudo-crosslinked structure with moderate strength. Therefore, the silica particles can easily undergo relative displacement to the polymer in response to external forces applied to the gel material, and the gel material can easily deform while retaining the aqueous medium internally, exhibiting excellent flexibility and extensibility. The pseudo-crosslinked structure formed between the silica particles and the polymer can be easily broken by external forces to absorb them, and the gel material also possesses excellent toughness. Moreover, the pseudo-crosslinked structure between the silica particles and the polymer is easily restored, and the gel material can easily recover its excellent toughness after the external force is removed.

[0087] As described above, the gel-forming composition produces an excellent gel material (hydrogel) by polymerization and curing. The gel-forming composition can be suitably used as a gel material for 3D printers by using a photopolymerization initiator as the polymerization initiator. The gel-forming composition can be suitably used in 3D printers employing the vat polymerization method.

[0088] Liquid-level polymerization methods include free-level and restricted-level methods, and gel-forming compositions can be suitably used in either method. In the free-level method, the gel-forming composition is stored in the liquid tank of a 3D printer, and an active light is irradiated onto the liquid surface of the gel-forming composition in the liquid tank to polymerize and harden the gel-forming composition. At the same time, the generated hardened material is gradually moved away from the active light, while the gel-forming composition between the generated hardened material and the liquid surface is sequentially polymerized and hardened, and the resulting layers are sequentially stacked on top of the previously generated hardened material to produce a molded body of any shape. In the restricted-level method, an active light is irradiated onto the gel-forming composition from the bottom of the liquid tank where the gel-forming composition is stored, polymerizing and hardening the gel-forming composition. At the same time, the generated hardened material is gradually moved away from the active light, while the gel-forming composition between the generated hardened material and the bottom of the liquid tank is sequentially polymerized and hardened, and the resulting layers are sequentially stacked on top of the previously generated hardened material to produce a molded body of any shape.

[0089] In the 3D printing process from the start to the end of polymerization, the gel-forming composition allows the acrylic monomer represented by formula (1), the aqueous medium, and the silica particles to interact with each other, thereby incorporating and retaining the aqueous medium in which the silica particles are well dispersed within the resulting polymer. Therefore, the gel material molded from the gel-forming composition can be molded into a desired three-dimensional shape and possesses excellent flexibility, extensibility, and toughness.

[0090] The above describes the case where a gel-forming composition is used as a gel material for a 3D printer. However, by supplying the gel-forming composition into a mold having the desired shape and curing it by irradiating it with active light or heating it, a gel material molded body (hydrogel molded body) with the desired shape and excellent flexibility, extensibility, and toughness can be easily produced.

[0091] Gel materials (hydrogels), which are cured products produced from gel-forming compositions, can take on various desired forms, including planar forms such as sheets and lines, as well as three-dimensional forms. Molded gel materials (hydrogel molded products) produced from gel-forming compositions can be used as sensor materials, bearings and interlayers that come into contact with metal, bandages and packs that come into contact with the human body, and seedbeds. In addition, they can be used in medical applications such as model organs, implant materials, scaffold materials for regenerative medicine, artificial skin, artificial joints, artificial muscles, artificial blood vessels, artificial cartilage, artificial organs, prosthetic arms and legs, and cell culture sheets.

[0092] The tensile breaking strength of the gel material (hydrogel) produced by polymerizing and curing the gel-forming composition is preferably 0.1 MPa or higher, more preferably 0.3 MPa or higher, more preferably 0.5 MPa or higher, more preferably 0.6 MPa or higher, more preferably 0.7 MPa or higher, more preferably 0.8 MPa or higher, more preferably 1.0 MPa or higher, more preferably 1.5 MPa or higher, more preferably 2.0 MPa or higher, and more preferably 3.0 MPa or higher. The tensile breaking strength of the gel material (hydrogel) produced by polymerizing and curing the gel-forming composition is preferably 3 MPa or lower, more preferably 2.5 MPa or lower.

[0093] The tensile fracture strain of the gel material (hydrogel) produced by polymerizing and curing the gel-forming composition is preferably 500% or more, more preferably 600% or more, more preferably 700% or more, more preferably 750% or more, and more preferably 800% or more.

[0094] The tensile breaking strength and tensile breaking strain of the gel material are the values ​​measured according to the following procedure. Specifically, a gel-forming composition is polymerized and cured to produce a gel material, and three dumbbell-shaped test specimens, size 7 as specified in JIS K6251-2017, with a thickness of 0.5 mm are prepared from this gel material. The thickness of the test specimens is measured to the nearest 1 / 100 mm. The thickness of the test specimens can be measured using a "thickness gauge" manufactured by Mitutoyo Corporation.

[0095] Using the above-described test specimen, the "tensile strength at break" and "elongation at break" are measured under the conditions of a gripping distance of 25 mm and a test speed of 100 mm / min. The "tensile strength at break" and "elongation at break" are defined as the "tensile fracture strength" and "tensile fracture strain," respectively. A texture analyzer, "Texture Analyzer TA.XT PLUS" (manufactured by Eiko Seiki Co., Ltd.), can be used for the above measurements.

[0096] The arithmetic mean values ​​of the "tensile breaking strength" and "tensile breaking strain" of the three test specimens are defined as the "tensile breaking strength" and "tensile breaking strain" of the gel material, respectively. [Examples]

[0097] The present invention will be described more specifically below with reference to examples, but the present invention is not limited thereto. Specific numerical values ​​such as blending ratios (content percentages), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to") of the blending ratios (content percentages), physical properties, and parameters described in the "Means for Solving the Problems" and "Modes for Carrying Out the Invention" sections.

[0098] [Acrylic monomer represented by formula (1)] • N-(2-hydroxyethyl)acrylamide (HEAA) [Formula (10)] • N,N-dimethylmethacrylamide (DMAA) [Formula (11)]

[0099] [ka]

[0100] [Aqueous medium] Ion-exchanged water • Glycerin (manufactured by NOF Corporation, product name "Concentrated Glycerin S") • Diglycerin (manufactured by Sakamoto Pharmaceutical Co., Ltd., product name "Diglycerin S") • Triglycerin (manufactured by Sakamoto Pharmaceutical Co., Ltd., product name "PGL-S") • Polyglycerin (manufactured by NOF Corporation, product name "Uniglycerin G-6", linear polyglycerin [formula (5)], degree of polymerization n:6 in formula (5))

[0101] [ka]

[0102] [Photopolymerization initiator] • Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO, manufactured by IGM Resin BV, trade name "Omnirad819", particle size: 0.5~500μm) • 2-Hydroxy-2-methylpropiophenone (manufactured by IGM Resin BV, trade name "Omnirad1173")

[0103] [Silica particles] • Silica particles (manufactured by Nippon Aerosil Co., Ltd., product name "Aerosil 200", average particle diameter of primary particles: 12 nm, specific surface area by BET method: 200 m²) 2 / g)

[0104] [Crosslinking agent] • N,N'-Methylenebisacrylamide (MBAA) (Molecular weight: 154.17) • Polyglycerin-modified ethylene oxide acrylate (Formula (6), m1 to m6: number of repeating units, which are natural numbers, manufactured by Sakamoto Pharmaceutical Co., Ltd., product name "SA-TE60")

[0105] [ka]

[0106] [Examples 1-12, Comparative Example 1] (Preparation of gel-forming compositions) A photopolymerization initiator composition was prepared by dissolving a predetermined amount of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, as shown in Table 1, in a predetermined amount of 2-hydroxy-2-methylpropiophenone, as shown in Table 1. A monomer solution was prepared by adding predetermined amounts of the crosslinking agent and the photopolymerization initiator composition, as shown in Table 1, to the acrylic monomer represented by formula (1) and mixing them.

[0107] A mixed aqueous medium was prepared by mixing predetermined amounts of aqueous media shown in Table 1. A mixed solution was prepared by uniformly mixing the mixed aqueous media into the monomer solution. A predetermined amount of silica particles shown in Table 1 was added to this mixed solution and uniformly dispersed using a stirring and defoaming apparatus to obtain a gel-forming composition.

[0108] (Preparation of gel materials (hydrogels)) Two quartz plates, each with a release-treated polyethylene terephthalate film attached to its surface, were placed with a 0.5 mm gap between them. Furthermore, a spacer member was interposed between the opposing outer edges of the two quartz plates to create a mold.

[0109] The gel-forming composition was supplied into the above-mentioned mold. The gel-forming composition inside the mold was then exposed to ultraviolet irradiation using a JATEC product (product name "J-Cure" model JU-C1500), a metal halide lamp, a retrieval speed of 0.4 m / min, and a peak illuminance of 100 mW / cm². 2 The gel-forming composition was passed through a 3-fold filter, irradiated with ultraviolet light, and cured by photoradical polymerization of the acrylic monomer and crosslinking agent shown in formula (1) to obtain a gel sheet (hydrogel sheet).

[0110] The tensile fracture strength and tensile fracture strain of the obtained gel sheets were measured in accordance with the procedure described above, and the results are shown in Table 1. Note that the tensile fracture strength and tensile fracture strain could not be measured for the gel sheets produced from the gel-forming composition of Comparative Example 1.

[0111] [Table 1]

Claims

1. A gel-forming composition characterized by comprising an acrylic monomer represented by formula (1), an aqueous medium, silica particles, and a polymerization initiator. 【Chemistry 1】 However, in equation (1), R 1 R represents a hydrogen atom or a methyl group. 2 R represents a hydrogen atom or a methyl group. 3 represents a hydrogen atom or a hydroxyl group, and Z represents an alkylene group having 1 to 6 carbon atoms.

2. The gel-forming composition according to claim 1, characterized in that the acrylic monomer represented by formula (1) has the structure represented by formula (2) or (3). 【Chemistry 2】

3. A gel-forming composition according to claim 1 or 2, further comprising a crosslinking agent.

4. A gel material characterized by comprising a polymerization product of the gel-forming composition described in claim 1 or claim 2.

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