Photocurable composition and molded article

Abstract

The present invention provides a photocurable composition and molded article that can produce organogels with excellent flexibility and toughness. [Solution] The photocurable composition of the present invention comprises a liquid organic medium, a water-insoluble monomer, a mineral, and a polar group-containing monomer. Due to the electrical interaction between the polar groups of the polar group-containing monomer component contained in the polymer produced by curing the photocurable composition and the ions of the mineral, the mineral is well dispersed in the polymer, and the organogel obtained by curing the photocurable composition has excellent flexibility and toughness.

Description

[Technical Field]

[0001] The present invention relates to a photocurable composition and a molded article. [Background technology]

[0002] Organogels are gel-like materials in which a liquid organic medium is incorporated into a three-dimensional network. Compared to hydrogels, which use water as a solvent, organogels are less prone to drying and have higher stability, making them widely used in applications such as parts for precision equipment like robots, sensor materials, 3D printed parts, bearings and interlayers that come into contact with metal, cushioning materials, shock absorbers, and cushions.

[0003] On the other hand, organogels are generally inflexible and brittle materials, which can make them difficult to handle depending on the application. Therefore, development is underway to create organogels with improved physical properties such as flexibility and toughness.

[0004] Patent Document 1 discloses a polymer organogel containing a liquid organic medium and a modified water-swellable layered silicate compound within a polymer having a three-dimensional crosslinked structure. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-191260 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the above-mentioned polymer organogels still suffer from insufficient flexibility and toughness, and there is a need for organogels with superior flexibility and toughness.

[0007] The present invention provides a photocurable composition that can produce organogels with excellent flexibility and toughness. [Means for solving the problem]

[0008] The photocurable composition of the present invention is characterized by comprising a liquid organic medium, a water-insoluble monomer, a mineral, and a polar group-containing monomer.

[0009] The molded article of the present invention is characterized by containing a cured product of the above-mentioned photocurable composition. [Effects of the Invention]

[0010] The photocurable composition of the present invention comprises a liquid organic medium, a water-insoluble monomer, a mineral, and a polar group-containing monomer. The mineral is well dispersed in the polymer produced by curing this photocurable composition due to the electrical interaction between the polar groups of the polar group-containing monomer component and the ions of the mineral. The organogel obtained by curing the photocurable composition has excellent flexibility and toughness. [Modes for carrying out the invention]

[0011] In the numerical ranges described stepwise in this specification, the upper or lower limit of one step in the numerical range can be arbitrarily combined with the upper or lower limit of another step in the numerical range. In the numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with values ​​shown in the examples or values ​​that can be uniquely derived from the examples. In this specification, numbers connected by "~" mean a numerical range that includes the numbers before and after "~" as the lower and upper limits.

[0012] The photocurable composition of the present invention comprises a liquid organic medium, a water-insoluble monomer, a mineral, and a polar group-containing monomer.

[0013] [Liquid organic medium] The photocurable composition contains a liquid organic medium. The liquid organic medium only needs to be liquid during the curing of the photocurable composition and at the time of use after curing. Note that "liquid" refers to a form that has a certain volume and is fluid.

[0014] The liquid organic medium is incorporated into the polymer formed by curing the photocurable composition to impart a gel-like form to the cured product. The liquid organic medium is preferably excellent in compatibility with the water-insoluble monomers contained in the photocurable composition.

[0015] The liquid organic medium is not particularly limited, and examples thereof include carboxylic acid esters such as citrate, phthalate, trimellitate, aliphatic dibasic acid ester, adipate, etc., phosphate esters, glycol ethers, sulfonamides, castor oil, etc. Since the photocurable composition can cure to produce an organogel having further excellent flexibility and toughness as a cured product, ester compounds of polyvalent carboxylic acids and alcohols, and ester compounds of polyhydric alcohols and carboxylic acids are preferred. A carboxylic acid is an organic acid having at least one carboxy group (-COOH) in the molecule. In the ester compound of a polyvalent carboxylic acid and an alcohol, it is only necessary that at least one carboxy group in the molecule is esterified. In the ester compound of a polyhydric alcohol and a carboxylic acid, it is only necessary that at least one hydroxyl group (-OH) in the molecule is esterified. The liquid organic medium may be used alone or in combination of two or more.

[0016] The liquid organic medium preferably has the structure shown in Formula 1 in the molecule, more preferably has a plurality of the structures shown in Formula 1 in the molecule, still more preferably has 2 to 4 of the structures shown in Formula 1 in the molecule, and still more preferably has 2 or 3 of the structures shown in Formula 1 in the molecule. In Formula 1, * is a bond and means a single bond. The liquid organic medium exhibits an electrical interaction between the polar group-containing monomer component in the polymer formed by curing the photocurable composition and the ions possessed by the mineral, and the liquid organic medium can be incorporated into the polymer without phase separation from the polymer and contained in a state where the mineral is uniformly dispersed.

[0017]

Chemical formula

[0018] As the liquid organic medium, it is preferable to have a structure of any of the following formulas 2 to 4. When the liquid organic medium has a structure of any of the following formulas 2 to 4, the photocurable composition can be cured to produce an organogel having excellent flexibility and toughness as a cured product.

[0019]

Chemical formula

[0020] However, in formula 2, R 1 is a hydrogen atom or an acetyl group (-COCH3), and R 2 ~R 4 are each independently a hydrogen atom or an alkyl group having 1 to 22 carbon atoms. The alkyl group may be either linear or branched.

[0021] In formula 2, R 1 is preferably a hydrogen atom. R 2 ~R 4 are each independently preferably an alkyl group having 1 to 15 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, still more preferably an alkyl group having 1 to 8 carbon atoms, still more preferably an alkyl group having 1 to 6 carbon atoms, still more preferably an alkyl group having 1 to 4 carbon atoms, and still more preferably an alkyl group having 1 to 3 carbon atoms.

[0022] As the liquid organic medium represented by formula 2, citrate esters such as acetyltriethyl citrate, acetyltributyl citrate, isodecyl citrate, isopropyl citrate, triethyl citrate, triethylhexyl citrate, tributyl citrate, 2-ethylhexyl acetyl citrate, etc. are preferable, trialkyl citrate esters are more preferable, in formula 2, trialkyl citrate esters in which R 1 is a hydrogen atom are more preferable, and triethyl citrate (in formula 2, R 1 is a hydrogen atom and R 2 ~R 4It is more preferable that the group is an ethyl group.

[0023] [ka]

[0024] However, in equation 3, R 5 and R 6 Each of these is independently either a hydrogen atom or an acetyl group (-COCH3).

[0025] Examples of the liquid organic medium represented by formula 3 include monoacetin, diacetin, and triacetin, with triacetin being preferred.

[0026] [ka]

[0027] However, in equation 4, R 7 and R 8 Each of these is independently either a hydrogen atom or an alkyl group having 1 to 22 carbon atoms. The alkyl group may be linear or branched. n is an integer between 2 and 10.

[0028] In Equation 4, R 7 and R 8 Each of these is independently preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 2 to 4 carbon atoms.

[0029] In formula 4, n is preferably 2 to 10, more preferably 2 to 8, more preferably 2 to 6, more preferably 2 to 4, and more preferably 3 or 4.

[0030] Examples of liquid organic media represented by Formula 4 include dimethyl adipate, dibutyl adipate, diisostearyl adipate, diisodecyl adipate, diisononyl adipate, diisobutyl adipate, diisopropyl adipate, diethylhexyl adipate, dioctyl adipate, dioctyldodecyl adipate, dicapryl adipate, dihexyldecyl adipate, bis(2-methoxyethyl) adipate, bis[2-(2-methoxyethoxy)ethyl] adipate, and bis[2-(2-butoxyethoxy)ethyl] adipate.

[0031] In this invention, an alkyl group refers to the remaining atomic group obtained by removing one hydrogen atom from an aliphatic saturated hydrocarbon, and may be linear or branched. In formulas 2 and 4, the alkyl group is not particularly limited and examples include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, and tetradecyl groups. The multiple alkyl groups in formulas 2 and 4 may be the same or different.

[0032] In the photocurable composition, the content of the liquid organic medium is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, more preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and more preferably 28 parts by mass or more, per 100 parts by mass of the non-water-soluble monomer described later. In the photocurable composition, the content of the liquid organic medium is preferably 130 parts by mass or less, more preferably 120 parts by mass or less, more preferably 110 parts by mass or less, more preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and more preferably 85 parts by mass or less, per 100 parts by mass of the non-water-soluble monomer described later. When the content of the liquid organic medium is 10 parts by mass or more, the flexibility and toughness of the organogel, which is the cured product of the photocurable composition, are improved. When the content of the liquid organic medium is 130 parts by mass or less, the organogel, which is the cured product of the photocurable composition, can stably maintain the desired shape due to the excellent retention of the liquid organic medium by the polymer generated from the photocurable composition.

[0033] [Non-water soluble monomers] The photocurable composition contains a water-insoluble monomer. A "water-insoluble monomer" refers to a monomer whose mass when dissolved in 100 g of a saturated aqueous solution at 20°C is less than 1.0 g.

[0034] When a non-water-soluble monomer is irradiated with an active light as described later, as shown in the photocurable composition, it copolymerizes with a polar group-containing monomer, as described later, to produce a polymer. The non-water-soluble monomer is selected so that the resulting polymer and the liquid organic medium do not undergo phase separation during and after the polymerization process.

[0035] It is preferable that the water-insoluble monomer has at least one aromatic ring in its molecule. The presence of at least one aromatic ring in the water-insoluble monomer improves the toughness of the organogel produced by curing the photocurable composition. Although the mechanism is not clearly understood, it is presumed to be due to the following mechanism.

[0036] It is believed that when a photocurable composition is cured, the aromatic rings within the polymer chains form a physical cross-linking structure through π-π stacking. This physical cross-linking structure can be easily deformed while maintaining its cross-linking structure when an external force is applied, thus providing the organogel with excellent flexibility. On the other hand, when an external force exceeding a certain magnitude is applied, the physical cross-linking structure due to π-π stacking can easily collapse and absorb the external force, preventing the polymer chain from breaking, and the organogel has excellent toughness. After the external force applied to the organogel is removed, the physical cross-linking structure due to π-π stacking between the aromatic rings can be regenerated, and the organogel can maintain its excellent toughness. Furthermore, the formation of a physical cross-linking structure between the polymer chains allows the liquid organic medium to be stably incorporated into the spaces formed between the polymer chains, and the cured organogel has excellent retention of the liquid organic medium.

[0037] The aromatic rings contained in the molecule of the water-insoluble monomer are not particularly limited and include, for example, benzene rings (which may be benzene rings that constitute part of a phenoxy structure, a biphenyl structure, or a fluorene structure), fused rings (e.g., naphthalene rings, indene rings, azulene rings, anthracene rings, phenanthrene rings), heterocycles (e.g., pyridine rings, pyrimidine rings, pyridazine rings, pyrazine rings, triazine rings, pyrrole rings, pyrazole rings, imidazole rings, triazole rings, oxazole rings, isoxazole rings, thiazole rings, thiophene rings, etc.), with benzene rings being preferred, benzene rings being more preferred, and benzene rings constituting a phenoxy structure (-OPh) or a biphenyl structure being even more preferred. Heteroatoms included as ring constituent atoms in the heterocycle include, for example, nitrogen atoms, sulfur atoms, and oxygen atoms, with nitrogen atoms and sulfur atoms being preferred. The water-insoluble monomer may have a structure in which one or more carbon rings and one or more heterocycles are fused, such as the dinaphthothiophene structure.

[0038] The aromatic ring may be unsubstituted or may have one or more substituents on the ring constituent atoms. When the aromatic ring has substituents, such substituents are not particularly limited and include, for example, alkyl groups, alkoxy groups, aryloxy groups, hydroxyl groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), hydroxyalkyl groups, hydroxyalkyloxy groups, glycidyloxy groups, etc., with alkyl groups, alkoxy groups, and halogen atoms being preferred. When the substituent of the aromatic ring contains carbon atoms, the number of carbon atoms in the substituent is preferably 1 to 4, more preferably 1 to 3, and more preferably 1 or 2.

[0039] The number of aromatic rings in the water-insoluble monomer is preferably one or more, and more preferably two or more. The number of aromatic rings in the water-insoluble monomer is preferably 12 or less, more preferably 8 or less, more preferably 6 or less, more preferably 5 or less, more preferably 4 or less, more preferably 3 or less, and more preferably 2 or less. When the number of aromatic rings in the water-insoluble monomer is within the above range, the organogel, which is the cured product of the photocurable composition, has excellent flexibility and toughness.

[0040] The water-insoluble monomer is preferably 3-phenoxybenzyl acrylate (Formula 5) or 2-hydroxy-3-phenoxypropyl acrylate (Formula 6), with 3-phenoxybenzyl acrylate (Formula 5) being more preferred, because the organogel, which is the cured product of the photocurable composition, has excellent flexibility and toughness. When the water-insoluble monomer contains 3-phenoxybenzyl acrylate (Formula 5) or 2-hydroxy-3-phenoxypropyl acrylate (Formula 6), the organogel, which is the cured product of the photocurable composition, has excellent flexibility and toughness.

[0041] [ka]

[0042] The non-water-soluble monomer preferably has an unsaturated double bond at its first end and an aromatic ring at its second end; more preferably has an unsaturated double bond at its first end and a benzene ring at its second end; and even more preferably has an unsaturated double bond at its first end and a phenoxy structure at its second end. When the non-water-soluble monomer has an unsaturated double bond at its first end and an aromatic ring at its second end, the aromatic ring is located at the end of a branched chain that branches off from the main chain of the polymer produced by curing the photocurable composition, making it easier to form physical crosslinks by the π-π stacking described above, and improving the flexibility and toughness of the organogel, which is the cured product of the photocurable composition.

[0043] In the water-insoluble monomers, the content of water-insoluble monomers having at least one aromatic ring in the molecule is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, more preferably 99% by mass or more, and more preferably 100% by mass.

[0044] [Polar group-containing monomers] The photocurable composition contains a polar group-containing monomer. The polar group-containing monomer is copolymerizable with a water-insoluble monomer, and during the curing of the water-insoluble monomer, the polar group-containing monomer copolymerizes with the water-insoluble monomer and is incorporated into the resulting polymer while being uniformly dispersed. The polar group-containing monomer is obtained by removing the water-insoluble monomer.

[0045] The polar group-containing monomer components incorporated into the polymer undergo electrical interactions with the ions present in the minerals described later. As a result, the minerals become uniformly dispersed in the liquid organic medium incorporated within the spaces formed between the polymer chains. Furthermore, the minerals dispersed between the polymer chains form a physical cross-linked structure between the polar groups through electrical interactions with the polar groups of the polar group-containing monomer components. Therefore, the organogel, which is the cured product of the photocurable composition, possesses excellent toughness. The physical cross-linked structure formed between the polar groups by the minerals is formed by electrical interactions, so it easily deforms in response to external forces applied to the organogel, exhibiting excellent flexibility. At the same time, it absorbs external forces by breaking down the physical cross-linked structure against external forces exceeding a certain level, preventing damage to the polymer chains, and thus the organogel possesses excellent toughness. After the external force is removed, the physical cross-linked structure can be regenerated, and the organogel can stably maintain its excellent toughness.

[0046] By curing the photocurable composition, a physical cross-linking structure is formed between the polymer chains by minerals, which allows for the stable retention of a liquid organic medium within the spaces between the polymer chains. As a result, organogels have excellent retention capabilities for liquid organic media.

[0047] The polar group contained in the polar group-containing monomer is not particularly limited and includes, for example, a carboxyl group (-COOH), a hydroxyl group (-OH), an amide group (-CO-NH2), an amino group (-NH2), a keto group (-CO-), a nitrogen atom-containing skeleton such as a heterocyclic skeleton having a nitrogen atom as a heteroatom, and an imide group (-CO-NH-CO-). The amide group, hydroxyl group, keto group, and heterocyclic skeleton having a nitrogen atom as a heteroatom are preferred, and the amide group, hydroxyl group, and heterocyclic skeleton having a nitrogen atom as a heteroatom are more preferred. In the amide group and the amino group, either or both of the hydrogen atoms bonded to the nitrogen atom may be substituted with an alkyl group. Such alkyl groups are preferably alkyl groups having 1 to 10 carbon atoms, more preferably alkyl groups having 1 to 7 carbon atoms, more preferably alkyl groups having 1 to 5 carbon atoms, and more preferably alkyl groups having 1 to 3 carbon atoms. The alkyl group is not particularly limited and includes, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. In the imide group, the hydrogen atom bonded to the nitrogen atom may be substituted with other substituents. In the present invention, if a polar group containing a keto group also falls under another polar group, it is classified as that other polar group. The polar group-containing monomer may be used alone or in combination of two or more types.

[0048] The monomers containing a carboxyl group are not particularly limited, and examples include acrylic acid, methacrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. In this invention, (meth)acrylate means acrylate or methacrylate.

[0049] The hydroxyl group-containing monomer is not particularly limited, and examples include N-(2-hydroxyethyl)(meth)acrylamide, N-[tris(hydroxymethyl)methyl]-(meth)acrylamide, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 8-hydroxyoctyl(meth)acrylate, 10-hydroxydecyl(meth)acrylate, 12-hydroxylauryl(meth)acrylate, and 4-(hydroxymethyl)cyclohexylmethyl(meth)acrylate. In this invention, (meth)acrylic means acrylic or methacrylic.

[0050] The hydroxyl group-containing monomer preferably has the structure shown in Formula 7 below, and 2-hydroxyethylacrylamide is more preferred. In Formula 7, R 9 R is a hydrogen atom or a methyl group, 10 R is an alkylene group with 1 to 10 carbon atoms. 10 The alkylene group is preferably one with 1 to 8 carbon atoms, more preferably one with 1 to 6 carbon atoms, more preferably one with 1 to 4 carbon atoms, and more preferably one with 1 to 3 carbon atoms.

[0051] In the present invention, an alkylene group is a divalent atomic group formed by removing (extracting) one hydrogen atom from each of the different carbon atoms bonded to aliphatic saturated hydrocarbons, or a divalent atomic group formed by removing (extracting) two hydrogen atoms from methane, and includes both linear and branched atomic groups.

[0052] 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.

[0053] [ka]

[0054] The monomers containing the amide group are not particularly limited, and examples include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide.

[0055] The amide group-containing monomer preferably has the structure shown in Formula 8 below, and N,N-dimethyl(meth)acrylamide is more preferred. In Formula 8, R 11 R is a hydrogen atom or a methyl group, 12 and R 13 Each of these is an alkyl group having 1 to 10 carbon atoms. 12 and R 13 These may be the same or different. The alkyl group is not particularly limited and includes, for example, a methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, etc.

[0056] In formula 8, R 12 and R 13 Each of these is independently preferably an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms, and preferably an alkyl group having 1 to 3 carbon atoms.

[0057] [ka]

[0058] The monomers containing a heterocyclic skeleton with a nitrogen atom as a heteroatom are not particularly limited, and examples include acryloylmorpholine and 3-acryloyl-2-oxazolidinone.

[0059] The amino group-containing monomers are not particularly limited and include, for example, primary amino group-containing monomers such as aminomethyl (meth)acrylate and 2-aminoethyl (meth)acrylate, secondary amino group-containing monomers such as 2-(t-butylamino)ethyl (meth)acrylate and 2-(ethylamino)ethyl (meth)acrylate, and tertiary amino group-containing monomers such as 2-(dimethylamino)ethyl (meth)acrylate and 2-(diethylamino)ethyl (meth)acrylate.

[0060] The imide group-containing monomer is not particularly limited, and examples include N-acryloyloxyethylhexahydrophthalimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, and N-butylmaleimide.

[0061] The polar group-containing monomer preferably includes a hydroxyl group-containing monomer, a substituted or unsubstituted amide group-containing monomer, a carboxyl group-containing monomer, or a monomer containing a heterocyclic skeleton having a nitrogen atom as a heteroatom. When the polar group-containing monomer includes a hydroxyl group-containing monomer, a substituted or unsubstituted amide group-containing monomer, a carboxyl group-containing monomer, or a monomer containing a heterocyclic skeleton having a nitrogen atom as a heteroatom, the monomer containing the hydroxyl group, substituted or unsubstituted amide group, carboxyl group, or heterocyclic skeleton having a nitrogen atom as a heteroatom interacts more effectively with the ions of the mineral. As a result, the mineral is uniformly dispersed in the liquid organic medium incorporated into the space formed by the polymer chain produced when the photocurable composition is cured, and the mineral can more stably form a physical crosslink structure between the polar groups of the polar group-containing monomer component in the polymer chain. Therefore, the organogel obtained when the photocurable composition is cured has excellent flexibility and toughness. As described above, one or both of the hydrogen atoms of the amide group (-CO-NH2) in the amide group-containing monomer may be substituted with alkyl groups.

[0062] Furthermore, when the liquid organic medium has the structure shown in Formula 1, the electrical interaction between the polymer and the polar group-containing monomer component of the resulting polymer further improves the polymer's ability to retain the liquid organic medium, allowing for the more stable production of organogels with excellent liquid organic medium retention properties from the photocurable composition.

[0063] The content of hydroxyl group-containing monomers in polar group-containing monomers is preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more.

[0064] In the polar group-containing monomer, the content of substituted or unsubstituted amide group-containing monomers is preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more.

[0065] The content of carboxyl group-containing monomers in polar group-containing monomers is preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more.

[0066] The content of monomers containing a heterocyclic skeleton having a nitrogen atom as a heteroatom in polar group-containing monomers is preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more.

[0067] Among monomers containing hydroxyl groups, substituted or unsubstituted amide groups, carboxyl groups, and heterocyclic skeletons having a nitrogen atom as a heteroatom, the total content of monomers contained in the polar group-containing monomer is more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more.

[0068] The content of polar group-containing monomers in the photocurable composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 15 parts by mass or more, more preferably 18 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of water-insoluble monomer. The content of polar group-containing monomers in the photocurable composition is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, more preferably 32 parts by mass or less, more preferably 30 parts by mass or less, and more preferably 28 parts by mass or less, per 100 parts by mass of water-insoluble monomer. When the content of polar group-containing monomers is 5 parts by mass or more, the flexibility and toughness of the organogel produced by curing the photocurable composition are improved. When the content of polar group-containing monomers is 40 parts by mass or less, the ability of the polymer produced from the photocurable composition to retain liquid organic media is improved, and the retention of liquid organic media in the organogel is improved.

[0069] [mineral] The photocurable composition contains minerals. The inclusion of minerals in the photocurable composition allows for the formation of physical cross-linking structures between the polymer chains generated from the photocurable composition, thereby imparting excellent toughness to the organogel produced from the photocurable composition. Furthermore, the arrangement of minerals between the polymer chains generated by curing the photocurable composition allows for the stable retention of a liquid organic medium in the spaces formed between the polymer chains. This enables the production of an organogel in which separation between the polymer and the liquid organic medium is suppressed, even when external force is applied.

[0070] While not particularly limited, layered clay minerals are preferred. Layered clay minerals are also called plate-like particles. Examples of layered clay minerals are not particularly limited and include smectite minerals such as talc, kaolin, mica, montmorillonite, beiderite, hectorite, saponite, nontronite, stevensite, lucentite, and souconite; layered sodium silicates such as vermiculite, bentonite, kanemite, kenyanite, and makanite; and mica clay minerals such as Na-type tetrasilicic fluorimica, Li-type tetrasilicic fluorimica, Na-type fluorite teniolite, and Li-type fluorite teniolite. The minerals may be obtained from natural sources or chemically synthesized. The minerals may be used individually or in combination of two or more.

[0071] As the mineral, smectite-type minerals are preferred, and hectorite is more preferred. When the mineral contains smectite-type minerals, the smectite-type minerals disperse well in the liquid organic medium while exfoliating, and can be arranged between the polymer chains produced by curing the photocurable composition, forming a physical crosslinked structure throughout the organogel, and the organogel produced by curing the photocurable composition has excellent flexibility and toughness.

[0072] The mineral is preferably surface-modified (surface-treated), preferably surface-modified (surface-treated) with an ammonium salt, more preferably a smectite-based mineral surface-modified (surface-treated) with an ammonium salt, and more preferably a hectorite surface-modified (surface-treated) with an ammonium salt. When the surface of the mineral is modified, the dispersibility into the liquid organic medium is improved through interaction between the water-insoluble monomer component of the polymer in the organogel, which is the cured product of the photocurable composition, and the hydrophobic portion of the liquid organic medium, and a uniform physical crosslinking structure can be formed between the polymer chains. Therefore, the resulting organogel has excellent flexibility and toughness.

[0073] When the mineral is a layered clay mineral whose surface has been modified (surface-treated), the mineral is composed of flaky, plate-like bodies stacked in the thickness direction, but these plates tend to peel off at the interfaces between the layers. The mineral can be uniformly and finely dispersed in a liquid organic medium as a single plate-like body or a laminated sheet of multiple plates stacked together, and a physical cross-linking structure can be formed more uniformly between polymer chains. Therefore, the resulting organogel has superior flexibility and toughness.

[0074] Examples of ammonium salts used to modify the surface of minerals include tetraalkylammonium salts such as trialkylmethylammonium salts (e.g., trioctylmethylammonium chloride), alkyltrimethylammonium salts (e.g., stearyltrimethylammonium chloride), and dialkyldimethylammonium salts (e.g., distearyldimethylammonium chloride), as well as quaternary ammonium salts such as benzalkonium chloride. Tetraalkylammonium salts are preferred, and trialkylmethylammonium salts are more preferred. In tetraalkylammonium salts, the multiple alkyl groups may be the same or different from each other.

[0075] The number of carbon atoms in the alkyl group of the tetraalkylammonium salt is preferably 1 to 25, more preferably 1 to 22, more preferably 1 to 20, more preferably 1 to 18, more preferably 1 to 15, more preferably 1 to 12, and more preferably 1 to 10. When the number of carbon atoms in the alkyl group is within the above range, the dispersibility in the liquid organic medium is further improved due to the interaction between the water-insoluble monomer component of the polymer in the organogel, which is the cured product of the photocurable composition, and the hydrophobic portion of the liquid organic medium, and a more uniform physical crosslinking structure can be formed between the polymer chains. Therefore, the resulting organogel has better flexibility and toughness.

[0076] In the tetraalkylammonium salt, it is preferable that one alkyl group is a methyl group or an ethyl group, and that the three alkyl groups have 3 to 25 carbon atoms (preferably 3 to 22, more preferably 1 to 20, more preferably 1 to 18, more preferably 1 to 15, more preferably 1 to 12, and more preferably 1 to 10).

[0077] Examples of minerals whose surfaces are modified (surface-treated) with ammonium salts include trioctylmethylammonium hectorite, dimethyldistearylammonium hectorite, benzyldimethylstearylammonium hectorite, and dimethyldistearylammonium bentonite.

[0078] In the photocurable composition, the mineral content is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, more preferably 0.4 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of water-insoluble monomer. In the photocurable composition, the mineral content is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, more preferably 16 parts by mass or less, more preferably 14 parts by mass or less, more preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of water-insoluble monomer. When the mineral content is 0.1 parts by mass or more, a physical cross-linking structure is formed between the polymer chains produced by curing the photocurable composition, and the resulting organogel has better flexibility and toughness. When the mineral content is 20 parts by mass or less, the minerals can be well dispersed and arranged between the polymer chains produced by curing the photocurable composition without aggregation, and the resulting organogel has superior flexibility and toughness.

[0079] In the photocurable composition, the mass ratio of the content of polar group-containing monomers to the content of minerals (content of polar group-containing monomers / content of minerals) is preferably 0.1 or more, more preferably 0.5 or more, more preferably 1 or more, more preferably 1.5 or more, more preferably 2 or more, and more preferably 2.5 or more. In the photocurable composition, the mass ratio of the content of polar group-containing monomers to the content of minerals (content of polar group-containing monomers / content of minerals) is preferably 20 or less, more preferably 18 or less, more preferably 16 or less, more preferably 14 or less, more preferably 12 or less, and more preferably 10 or less. When the mass ratio of the content of polar group-containing monomers to the content of minerals is within the above range, the flexibility and toughness of the organogel produced by curing the photocurable composition are improved, and the ability of the polymer produced from the photocurable composition to retain liquid organic media is improved, resulting in improved retention of liquid organic media in the organogel.

[0080] [Photopolymerization initiator] The photocurable composition preferably contains a photopolymerization initiator. The presence of a photopolymerization initiator in the photocurable composition can accelerate its curing. The photocurable composition should be able to generate radicals upon irradiation with active light (e.g., visible light, electron beams, ultraviolet light, alpha rays, beta rays, etc.) to initiate radical polymerization of non-water-soluble monomers and polar group-containing monomers.

[0081] The photopolymerization initiator is not particularly limited and includes, for example, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2-(4-(methylthio)benzoyl)-2-(4-morpholinyl)propane, 2-(dimethylamino)-1-(4-morpholinophenyl)-2-benzyl-1-butanone, and 2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl Examples include alkylphenone-based photopolymerization initiators such as butan-1-one; acylphosphine oxide-based photopolymerization initiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; and oxime ester-based photopolymerization initiators such as 1,2-octanedione-1-(4-(phenylthio)-2-(O-benzoyloxime))ethanone and 1-(9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl)-1-(O-acetyloxime). Note that photopolymerization initiators may be used alone or in combination of two or more.

[0082] The content of the photopolymerization initiator in the photocurable composition is preferably 0.1 parts by mass, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, per 100 parts by mass of water-insoluble monomer. The content of the photopolymerization initiator in the photocurable composition is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of water-insoluble monomer. Even more preferably 1.5 parts by mass or less. When the content of the photopolymerization initiator is 0.1 parts by mass or more, the retention of the liquid organic medium in the organogel produced by curing the photocurable composition is improved. When the content of the photopolymerization initiator is 5 parts by mass or less, the flexibility of the organogel produced by curing the photocurable composition is improved.

[0083] [Additives] The photocurable composition may contain additives as long as they do not impair its effects. Additives are not particularly limited and include, for example, crosslinking agents, silane coupling agents, diluent polymers, photosensitizers, fillers, UV blockers, dyes, pigments, leveling agents, fluidity modifiers, defoamers, flame retardants, dispersion stabilizers, preservation stabilizers, antioxidants, metals, metal oxides, metal salts, ceramics, conductivity imparters, thickeners, thermal polymerization initiators, lubricants, and tackifiers. Additives may be used individually or in combination of two or more.

[0084] [Photocurable composition] A photocurable composition can be produced by mixing a liquid organic medium, a water-insoluble monomer, a mineral, a polar group-containing monomer, and optionally included additives in a known manner.

[0085] The photocurable composition, when irradiated with active light, can copolymerize and cure a polymer by which a water-insoluble monomer and a polar group-containing monomer are copolymerized, thereby producing an organogel, a structure that incorporates a liquid organic medium into this polymer and swells.

[0086] As described above, the minerals are well dispersed between the polymer chains formed when the photocurable composition hardens, and the minerals form a physical cross-linking structure. Therefore, the organogel has excellent retention of liquid organic media, and the resulting organogel has excellent flexibility and toughness.

[0087] The photocurable composition can be suitably used as a gel material for 3D printers. The photocurable composition can also be suitably used in 3D printers employing vat polymerization.

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

[0089] As described above, the photocurable composition can be easily cured at a desired location by irradiation with active light, thereby producing a highly accurate cured product, and an organogel molded body having a desired three-dimensional structure and excellent flexibility and toughness can be easily produced.

[0090] The above describes the case where a photocurable composition is used as a gel material for a 3D printer. However, by supplying the photocurable composition into a mold having the desired shape and curing it by irradiating it with active light, it is also possible to easily produce an organogel molded body with the desired shape and excellent flexibility and toughness.

[0091] Organogel molded articles, which are cured products produced from photocurable compositions, can take on various desired forms, including planar forms such as sheets and lines, as well as three-dimensional forms. Organogel molded articles produced from photocurable 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 limbs, and cell culture sheets.

[0092] The tensile breaking strength of the cured product (organogel) produced by curing the photocurable composition is preferably 0.1 MPa or higher, more preferably 0.3 MPa or higher, and even more preferably 0.4 MPa or higher. The tensile breaking strength of the cured product produced by curing the photocurable composition is preferably 6 MPa or lower, and more preferably 5 MPa or lower.

[0093] The tensile elongation at break of the cured product (organogel) produced by curing the photocurable composition is preferably 300% or more, more preferably 400% or more, and even more preferably 500% or more. The tensile elongation at break of the cured product produced by curing the photocurable composition is preferably 1500% or less, and more preferably 1400% or less.

[0094] The tensile breaking strength of the cured product produced by curing the photocurable composition refers to the value measured in the following manner. The cured product produced by curing the photocurable composition is punched out into the shape of a dumbbell-shaped No. 7 test specimen according to JIS K6251:2017 to prepare a test specimen. The tensile breaking strength and tensile breaking elongation of the obtained test specimen are measured in accordance with the provisions of JIS K6251:2017. [Examples]

[0095] 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.

[0096] [Non-water soluble monomers] • 3-Phenoxybenzyl acrylate (POB-A, formula 5, manufactured by Kyoeisha Chemical Co., Ltd., product name "Light Acrylate POB-A", mass of 3-phenoxybenzyl acrylate dissolved in 100g of saturated aqueous solution at 20°C: 0g) • 2-Hydroxy-3-phenoxypropyl acrylate (M-600A, Formula 6, manufactured by Kyoeisha Chemical Co., Ltd., product name "Light Acrylate M-600A", mass of 2-hydroxy-3-phenoxypropyl acrylate dissolved in 100g of saturated aqueous solution at 20°C: 0.53g)

[0097] [Polar group-containing monomers] • N-(2-hydroxyethyl)acrylamide (HEAA®, manufactured by KJ Chemicals) • Acryloylmorpholine (ACMO®, manufactured by KJ Chemicals) • N,N-dimethylacrylamide (DMAA®, manufactured by KJ Chemicals)

[0098] [Liquid organic medium] • Triethyl citrate (manufactured by Hikawa Sangyo Co., Ltd., product name "CITROFOL Al Extra") • Triacetin (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0099] [mineral] • Trioctylmethylammonium hectorite (hectorite whose surface is modified (surface-treated) with trioctylmethylammonium chloride salt, manufactured by Kunimine Industries Co., Ltd., product name "Smecton STN")

[0100] [Photopolymerization initiator] • Alkylphenone-based photopolymerization initiator (2-hydroxy-2-methylpropiophenone, manufactured by IGM Resins BV, trade name "Omnirad1173") • Acylphosphine oxide-based photopolymerization initiator (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM Resins BV, trade name "Omnirad819")

[0101] [Chemical crosslinking agent] • Polyethylene glycol dimethacrylate (manufactured by NOF Corporation, product name "PDE-600")

[0102] (Examples 1-8, Comparative Examples 1-4) A photocurable composition was prepared by uniformly mixing the predetermined amounts of water-insoluble monomers, polar group-containing monomers, liquid organic media, minerals, photopolymerization initiators, and chemical crosslinking agents shown in Table 1.

[0103] The obtained photocurable compositions were measured for retention, tensile elongation at break, and tensile strength according to the following procedure, and the results are shown in Table 1.

[0104] (retention) A photocurable composition is supplied into a mold measuring 10 cm (length) x 10 cm (width) x 0.5 mm (depth), and ultraviolet light is applied to this photocurable composition until the cumulative light intensity reaches 6000 mJ / cm². 2 By irradiating and curing the material in such a manner, a rectangular parallelepiped-shaped organogel molded body was produced. The organogel molded body was removed from the mold and evaluated based on the following criteria.

[0105] A. The surface of the organogel molded body was touched with a finger, but no liquid organic medium adhered to the finger. B. When the surface of the organogel molded body was touched with a finger, liquid organic medium adhered to the finger.

[0106] (Tensile elongation at fracture) When ultraviolet light is applied to a photocurable composition, the integrated light intensity is 6000 mJ / cm². 2 An organogel molded body was prepared by irradiating and curing the material in such a manner. The organogel molded body was punched out into the shape of a dumbbell-shaped test piece No. 7 according to JIS K6251:2017 to prepare test pieces. The tensile elongation at break of the obtained test pieces was measured in accordance with the provisions of JIS K6251:2017. In addition, the organogel molded bodies produced from the photocurable compositions of Comparative Examples 2 and 3 had low retention of the liquid organic medium and low toughness, making it impossible to measure the tensile elongation at break.

[0107] (Tensile breaking strength) Test specimens were prepared in the same manner as when measuring the tensile elongation at break. The tensile strength of the obtained test specimens was measured in accordance with the provisions of JIS K6251:2017. However, the organogel molded articles produced from the photocurable compositions of Comparative Examples 2 and 3 had low retention of the liquid organic medium and low toughness, making it impossible to measure their tensile strength.

[0108] [Table 1]

Claims

1. A photocurable composition characterized by comprising a liquid organic medium, a water-insoluble monomer, a mineral, and a polar group-containing monomer.

2. The photocurable composition according to claim 1, characterized in that the above water-insoluble monomer has at least one aromatic ring in the molecule.

3. The photocurable composition according to claim 1 or 2, characterized in that the polar group-containing monomer includes a hydroxyl group-containing monomer, a substituted or unsubstituted amide group-containing monomer, a carboxyl group-containing monomer, or a nitrogen atom-containing monomer, excluding the above-mentioned non-water-soluble monomer.

4. The above mineral is characterized by containing layered clay minerals, as described in claim 1 or 2.

5. A molded article characterized by comprising a cured product of the photocurable composition described in claim 1 or claim 2.

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