JP7583407B2 - Fiber material, curable resin composition, dry film, and cured product - Google Patents

Description

The present invention relates to a fiber material, a curable resin composition, a dry film, and a cured product thereof.

In recent years, cellulose nanofibers, which are made from wood, have been attracting attention. Because cellulose nanofibers have characteristics such as high crystallinity, mixing them into resins as a reinforcing material can improve mechanical strength and heat resistance.

For example, Patent Document 1 discloses a curable resin composition that contains an epoxy compound, a phenolic compound as a curing agent for the epoxy compound, and cellulose nanofibers having a specific fiber diameter, and describes that a cured product with excellent breaking elongation and flame retardancy can be obtained.

When using cellulose nanofibers as such a reinforcing material, it is known that the reinforcing effect can be improved by first preparing a fiber material in which the cellulose nanofibers are uniformly dispersed in a solvent or other material that has affinity for the cellulose nanofibers, and then mixing the fiber material with a resin.

For example, Patent Document 2 discloses a fiber material containing a polyhydric alcohol, a cationic surfactant, and cellulose nanofibers. It has been shown that by compounding this fiber material with a resin, the dispersibility of the cellulose nanofibers is maintained, and a composite material with excellent mechanical strength and thermal properties can be obtained.

Patent Publication 2014-220344 Patent Publication 2019-173253

However, in the curable resin composition described in Patent Document 1, the affinity between the cellulose nanofibers and the resin components is not high, so aggregation of the cellulose nanofibers occurs in the resin, which may reduce the reinforcing effect. Further improvements are needed to stably obtain an excellent reinforcing effect.

In addition, in the composite material using the fiber material described in Patent Document 2, due to the high hydrophilicity of the polyhydric alcohol, a redispersion process was required during compounding depending on the type of resin component. Furthermore, Patent Document 2 does not specifically evaluate the curable resin composition in which the curable resin and fiber material are compounded, and the inventors have newly discovered that, depending on the type of polyhydric alcohol used, new problems arise, such as the generation of air bubbles in the cured product and the re-aggregation of cellulose nanofibers in the fiber material.

The object of the present invention is to provide a fiber material that has excellent dispersibility of cellulose nanofibers in resin and can be particularly suitably used in curable resin compositions, and a curable resin composition that can give a good cured product that has excellent mechanical strength and heat resistance and is free of air bubbles, and the cured product.

As a result of thorough research based on the recognition of this new problem, the inventors have unexpectedly found that by adopting a cationic surfactant and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule and having a hydroxyl group equivalent of 200 g/eq or less as components in a fiber material, a fiber material with excellent dispersibility of cellulose nanofibers in resin can be obtained, and a curable resin composition containing such a fiber material can give a good cured product with excellent mechanical strength and heat resistance and no air bubbles, thereby completing the present invention.
That is, the present invention provides
A fiber material comprising a dispersion of cellulose nanofibers, the dispersion containing cellulose nanofibers, a cationic surfactant, and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule,
The compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule is a fiber material characterized in that the compound has a hydroxyl group equivalent of 200 g/eq or less.

In one embodiment, the fiber material is characterized in that the weight loss after heating at 100°C for 1 hour is less than 5% by mass.

In one embodiment, the compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule is characterized by having a viscosity of 10,000 mPa·s or less at 25°C.

The present invention provides a curable resin composition comprising a fiber material comprising a dispersion of cellulose nanofibers containing cellulose nanofibers, a cationic surfactant, and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule, and a curable resin,
The compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule is a curable resin composition characterized in that the compound has a hydroxyl group equivalent of 200 g/eq or less.

As one embodiment, the curable resin composition is applied to a film and dried to form a dry film having a resin layer,
The dry film is characterized in that the weight loss of the dry film after heating at 100° C. for 1 hour is less than 5% by mass.

In one embodiment, the curable resin composition or the resin layer of the dry film is cured to form a cured product.

The present invention provides a fiber material with excellent dispersibility of cellulose nanofibers that can be particularly suitably used in curable resin compositions, a curable resin composition that has excellent mechanical strength and heat resistance and can give a good cured product, and the cured product.

The fiber material and curable resin composition of the present invention will be described in more detail below.

<Textile materials>
The fiber material of the present invention is a fiber material consisting of a dispersion of cellulose nanofibers containing cellulose nanofibers, a cationic surfactant, and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule, and is characterized in that the hydroxyl group equivalent of the compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule is 200 eq/g or less.

The fiber material of the present invention contains, in addition to a cationic surfactant, a compound that has a hydroxyl group and a reactive group other than a hydroxyl group in one molecule and has a hydroxyl group equivalent of 200 eq/g or less, making it possible to obtain a fiber material with excellent dispersibility of cellulose nanofibers in resin. Furthermore, a resin composition obtained by compounding such a fiber material with a resin component such as a curable resin or a thermoplastic resin has excellent mechanical strength and heat resistance.

Below, we explain each component of the fiber material.

[Cellulose nanofiber]
The cellulose nanofibers constituting the fiber material of the present invention are not particularly limited, but for example, cellulose nanofibers obtained by subjecting pulp obtained from wood or the like to mechanical or chemical fiberization treatment can be used. Among these, cellulose nanofibers obtained by chemical fiberization treatment (chemically defibrated cellulose nanofibers) are preferred because they have strong interactions between cellulose nanofibers and can provide a composition with superior heat resistance and mechanical strength.

The chemically defibrated cellulose nanofibers are obtained by subjecting the pulp to an oxidation treatment to oxidize the primary hydroxyl group at C6 in the glucopyranose ring of natural cellulose, and then defibrating the cellulose using a high-pressure homogenizer or the like. In such a chemical defibration treatment, the primary hydroxyl group at C6 in the glucopyranose ring of cellulose is modified to an anionic group, and as a result, the cellulose can be easily defibrated due to the mutual repulsion of the anionic groups. Examples of anionic groups include a carboxyl group, a phosphate group, a phosphite group, and a sulfate group. Among these, it is preferable to use cellulose nanofibers having a phosphate group, since a resin composition having excellent mechanical strength can be obtained. Specifically, examples of the cellulose nanofibers include TEMPO-oxidized cellulose nanofibers in which the oxidation treatment is performed with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and phosphate-esterified cellulose nanofibers in which the oxidation treatment is performed with a phosphate salt.

The fiber shape of the cellulose nanofibers constituting the fiber material of the present invention is not particularly limited, but the number average fiber diameter is preferably 3 to 1000 nm, more preferably 3 to 500 nm, and even more preferably 3 to 200 nm. The number average fiber length is preferably 100 nm to 2000 nm, more preferably 150 nm to 1000 nm, and even more preferably 200 to 800 nm. By making the fiber shape of the cellulose nanofiber within the above range, the resin composition obtained by compounding such a fiber material with a resin component such as a curable resin or a thermoplastic resin has superior mechanical strength and heat resistance.

In addition, the number average fiber diameter and number average fiber length of the cellulose nanofibers in the present invention are the arithmetic average values measured for at least 50 cellulose nanofibers within the field of view of an observation photograph using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

The amount of cellulose nanofibers contained in the fiber material of the present invention is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass, based on the total amount of non-volatile components of the fiber material. When the amount of cellulose nanofibers is 0.1% by mass or more, a resin composition with superior mechanical strength can be obtained, and when the amount is 20% by mass or less, the dispersibility of the cellulose nanofibers in the resin composition is superior.

[Cationic Surfactant]
The cationic surfactant constituting the fiber material of the present invention suppresses the aggregation of cellulose nanofibers contained in the fiber material. Such cationic surfactants are not particularly limited, but are preferably primary to tertiary amine salts and quaternary ammonium salts, and more preferably quaternary ammonium salts. Furthermore, the cationic surfactant preferably has an alkyl group having 1 to 40 carbon atoms, more preferably has an alkyl group having 2 to 20 carbon atoms, and even more preferably has an alkyl group having 8 to 18 carbon atoms. The cationic surfactant has a more excellent effect of suppressing the aggregation of cellulose nanofibers as the number of carbon atoms in the alkyl group increases.

Examples of cationic surfactants include trimethylammonium salts such as octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and octadecyltrimethylammonium chloride; pyridinium salts such as octylpyridinium chloride, decylpyridinium chloride, dodecylpyridinium chloride, tetradecylpyridinium chloride, hexadecylpyridinium chloride, and octadecylpyridinium chloride; benzalkonium chloride, benzethonium chloride, benzyltrialkylammonium chloride, dialkyldimethylammonium chloride, trimethylstearylammonium chloride, dodecyltrimethylammonium bromide, and hexadecyltrimethylammonium bromide. Two or more of these cationic surfactants can also be used in combination.

The amount of cationic surfactant blended is preferably 10 to 200% by mass, more preferably 20 to 100% by mass, relative to the amount of cellulose nanofiber blended in the fiber material. If the amount of cationic surfactant blended is 10% by mass or more, a fiber material with excellent dispersibility of cellulose nanofiber in resin can be obtained, and if the amount is 200% by mass or less, the processability during production of the fiber material is good.

[Compounds containing a hydroxyl group and a reactive group other than a hydroxyl group in one molecule]
The compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule constituting the fiber material of the present invention has a hydroxyl group equivalent of 200 g/eq or less, which suppresses aggregation due to hydrogen bonding between cellulose nanofibers and maintains excellent dispersibility of the cellulose nanofibers in the fiber material. In the fiber material of the present invention, by blending a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule together with a cationic surfactant, re-aggregation of the cellulose nanofibers in the resin composition can be suppressed when the fiber material and the resin are composited. The hydroxyl group equivalent of the compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule is preferably 80 to 200 g/eq, more preferably 100 to 195 g/eq, and even more preferably 120 to 190 g/eq. By having the hydroxyl group equivalent in the above range, the dispersibility of the cellulose nanofibers in the fiber material and the resin composition is more stabilized.

In addition, the compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule can obtain a fiber material that has excellent compatibility with the resin component by having a reactive group other than a hydroxyl group, and can obtain a resin composition that has excellent dispersibility of cellulose nanofibers.

In the present invention, the reactive group is a functional group that can react with other sites by chemical reaction, and for example, it means a functional group that can react with each other to form a crosslinked structure, or react with a functional group of the curable resin described later to form a crosslinked structure. By having such a reactive group, it is possible to suppress the generation of bubbles when curing a curable resin composition using such a fiber material. Specifically, but not limited to, for example, cyclic ether groups, amino groups, mercapto groups, carboxyl groups, ester groups, vinyl groups, methacryl groups, acrylic groups, etc., can be mentioned, and any one or more reactive groups are included. Among these reactive groups, it is more preferable to have a cyclic ether group in order to obtain a fiber material with excellent reactivity and compatibility with the resin component, and a cured product with excellent heat resistance and mechanical strength.

Commercially available compounds having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule that can be used in the present invention include, for example, Denacol EX521, Denacol EX512, Denacol EX614, Denacol EX614B, Denacol EX612, and Denacol EX622, all manufactured by Nagase ChemteX Corporation.

The viscosity of the compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule, which constitutes the fiber material of the present invention, is preferably 10,000 mPa·s or less at 25°C, more preferably 9000 mPa·s or less, and even more preferably 8000 mPa·s or less, from the viewpoints of processability during the production of the fiber material and maintaining dispersibility of the cellulose nanofibers when composited with resin components such as curable resins and thermoplastic resins.

In the present invention, the viscosity is measured in accordance with JIS Z8803:2011, 10, using a cone-plate type rotational viscometer at 25°C, 100 rpm, and 30 seconds using a cone rotor of 1°34' x R24 (TVE-33H, manufactured by Toki Sangyo Co., Ltd.).

The amount of the compound having a hydroxyl group and a reactive group other than hydroxyl groups in one molecule, which constitutes the fiber material of the present invention, is preferably 100 to 5000% by mass, more preferably 200 to 4000% by mass, and even more preferably 300 to 3000% by mass, relative to the amount of cellulose nanofibers in the fiber material. By setting the amount of the compound having a hydroxyl group and a reactive group other than hydroxyl groups in one molecule within the above range, the dispersibility of the cellulose nanofibers in the fiber material and resin composition is more stabilized, and the resin composition using such a fiber material and its cured product have excellent heat resistance.

[Other ingredients]
In addition to cellulose nanofibers, cationic surfactants, and compounds having hydroxyl groups and reactive groups other than hydroxyl groups in one molecule, the fiber material of the present invention can contain components other than the curable resin described below, provided the effects of the invention are not impaired. Examples of such components include thermoplastic resins such as polyvinyl alcohol and polyacrylic acid, coupling agents such as silane-based, titanate-based, and aluminate-based coupling agents, additive components such as flame retardants and thixotropic agents, and inorganic fillers such as silica, barium sulfate, and titanium oxide.

<Method of manufacturing fiber material>
The method for producing a fiber material of the present invention includes a dispersion step of mixing a cellulose nanofiber solvent dispersion, a cationic surfactant, and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule to obtain a cellulose nanofiber dispersion, and a drying step of removing solvents such as water and organic solvents from the cellulose nanofiber dispersion to obtain a fiber material consisting of a cellulose nanofiber dispersion.

[Dispersion process]
The dispersion process is a process in which a cellulose nanofiber solvent dispersion in which cellulose nanofibers are dispersed in water or an organic solvent is mixed with a cationic surfactant and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule to obtain a cellulose nanofiber dispersion.

In the dispersion process, a predetermined amount of cationic surfactant and a predetermined amount of a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule are added to the cellulose nanofiber solvent dispersion, and the mixture is mixed using a known, commonly used stirring means to obtain a cellulose nanofiber dispersion. The stirring means is not particularly limited, but examples that can be used include a disintegrator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a roll mill, a jet mill, a single-screw extruder, a twin-screw extruder, an ultrasonic stirrer, and a household juicer mixer. In addition, water or an organic solvent may be added appropriately to adjust the viscosity during stirring, within a range that does not impair the effects of the present invention.

[Drying process]
The drying step is a step of removing water and organic solvent from the cellulose nanofiber dispersion obtained in the dispersion step to obtain a fiber material consisting of a cellulose nanofiber dispersion. The method of removing water and organic solvent from the cellulose nanofiber dispersion can be a known and commonly used method, for example, a method of drying by heating can be used.

Specifically, for example, the cellulose nanofiber dispersion is poured into a polyethylene container, and the container is placed in an air dryer and heated to 30 to 100°C to evaporate the water and organic solvent.

In the drying process, it is preferable to substantially remove water and the organic solvent from the cellulose nanofiber dispersion. In the present invention, substantially removed means that the weight loss of the obtained fiber material after heat treatment at 100°C for 10 minutes is less than 5% by weight.

<Curable resin composition>
The curable resin composition of the present invention comprises a fiber material comprising a dispersion of cellulose nanofibers containing cellulose nanofibers, a cationic surfactant, and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule; and a curable resin, wherein the compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule has a hydroxyl group equivalent of 200 g/eq or less. .

The curable resin composition of the present invention can be obtained by mixing a fiber material consisting of a cellulose nanofiber dispersion that has been pre-treated with a cationic surfactant and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule, a curable resin, and, as necessary, optional components.
As such, the curable resin composition of the present invention uses a fiber material made of a cellulose nanofiber dispersion unique to the present invention, and therefore, compared to a curable resin composition in which a fiber material made of a cellulose nanofiber dispersion previously treated with a cationic surfactant and a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule are mixed with a curable resin, or a curable resin composition in which the above three components are mixed individually with a curable resin, the curable resin composition has excellent dispersibility of cellulose nanofibers in the curable resin composition, and further, a cured product having excellent mechanical strength and heat resistance can be obtained.

[Textile materials]
As described above, the fiber material constituting the curable resin composition of the present invention contains a cationic surfactant and also contains a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule. By having the compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule have a reactive group other than a hydroxyl group, the reactive groups can react with each other or with a functional group of the curable resin described later, and the generation of bubbles during curing of the curable resin composition can be suppressed.

The fiber materials constituting the curable resin composition of the present invention can be those described above.

The amount of the fiber material that constitutes the curable resin composition of the present invention is not particularly limited, but is preferably 10% by mass to 200% by mass, more preferably 20% by mass to 150% by mass, and even more preferably 30% by mass to 100% by mass, relative to the amount of the curable resin in the curable resin composition.

[Hardening resin]
The curable resin constituting the curable resin composition of the present invention may be a thermosetting resin, a photocurable resin, a photocurable thermosetting resin, or the like, and any known and commonly used resin may be used, excluding compounds that have a hydroxyl group and a reactive group other than a hydroxyl group in one molecule constituting the fiber material.

The thermosetting resin is not particularly limited, and a resin having a functional group capable of undergoing a curing reaction by heat can be used. Examples of the thermosetting resin include resins having a cyclic ether group, phenol resins, phenoxy resins, amino resins, active ester resins, bismaleimide resins, diallyl phthalate resins, silicone resins, resins having a benzoxazine ring, norbornene resins, cyanate resins, isocyanate resins, urethane resins, maleimide resins, bismaleimide triazine resins, polyazomethine resins, and polyimide resins. Among these, resins having a cyclic ether group are preferably used because they provide crosslinking reactivity between a hydroxyl group and a compound having a reactive group other than a hydroxyl group in one molecule. These thermosetting resins can be used alone or in combination of two or more.

Resins having cyclic ether groups include, for example, bisphenol type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol E type epoxy resins, bisphenol M type epoxy resins, bisphenol P type epoxy resins, and bisphenol Z type epoxy resins; novolac type epoxy resins such as bisphenol A novolac type epoxy resins, phenol novolac type epoxy resins, and cresol novolac epoxy resins; biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, aryl alkylene type epoxy resins, tetraphenylol ethane type epoxy resins, naphthalene type epoxy resins, anthracene type epoxy resins, phenoxy type epoxy resins, dicyclopentadiene type epoxy resins, and novolac type epoxy resins. Examples of epoxy resins include arylbornene type epoxy resins, adamantane type epoxy resins, fluorene type epoxy resins, glycidyl methacrylate copolymer epoxy resins, cyclohexylmaleimide and glycidyl methacrylate copolymer epoxy resins, epoxy-modified polybutadiene rubber derivatives, CTBN-modified epoxy resins, trimethylolpropane polyglycidyl ether, phenyl-1,3-diglycidyl ether, biphenyl-4,4'-diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol or propylene glycol diglycidyl ether, sorbitol polyglycidyl ether, tris(2,3-epoxypropyl)isocyanurate, and triglycidyl tris(2-hydroxyethyl)isocyanurate. These resins having cyclic ether groups can be used alone or in combination of two or more.

The photocurable resin is not particularly limited, and may be any known, commonly used resin having a reactive group capable of undergoing a curing reaction upon irradiation with active energy rays, and the curing reactivity may be either radically polymerizable or cationic polymerizable. Examples of photocurable resins include compounds having one or more ethylenically unsaturated bonds in the molecule, alicyclic epoxy compounds, and oxetane compounds, and compounds having one or more ethylenically unsaturated bonds in the molecule are preferably used.

There are no particular limitations on the photocurable thermosetting resin composition, and any composition that has photocurability and thermosetting properties can be used, and it may be a mixture containing the photocurable resin and thermosetting resin described above.

Among these curable resins, it is particularly preferable to use a curable resin that is liquid at 25°C, as this makes it easier to compound with fiber materials, and it is even more preferable to use a resin that has a cyclic ether group and is liquid at 25°C.

The curable resin composition used in the present invention can contain other commonly used components in addition to the fiber material and curable resin, depending on the application.

Other commonly used components include, for example, thermoplastic resins, curing catalysts, inorganic fillers, organic solvents, coupling agents, photopolymerization initiators, defoamers/leveling agents, thixotropic agents, and flame retardants, and any other commonly known components can be used.

Examples of thermoplastic resins include general-purpose plastics such as acrylic, modified acrylic, low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polypropylene, modified polypropylene, polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, and polylactic acid; engineering plastics such as polyamide, thermoplastic polyurethane, polyacetal, polycarbonate, ultra-high molecular weight polyethylene, polybutylene terephthalate, modified polyphenylene ether, polysulfone, polyphenylene sulfide, polyether sulfone, polyether ether ketone, polyarylate, polyetherimide, polyamideimide, liquid crystal polymer, polyamide 6T, polyamide 9T, polytetrafluoroethylene, polyvinylidene fluoride, polyesterimide, and thermoplastic polyimide; and thermoplastic elastomers such as olefins, styrenes, polyesters, urethanes, amides, vinyl chlorides, and hydrogenated types.

Examples of curing catalysts include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, and 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid dihydrazide and sebacic acid dihydrazide; phosphorus compounds such as triphenylphosphine; and dimethylaminopyridine. Commercially available products include, for example, 2MZ-A, 2MZ-OK, 2PHZ, 2P4BHZ, 2P4MHZ (manufactured by Shikoku Kasei Corporation), U-CAT3503N, U-CAT3502T, DBU, DBN, U-CATSA102, and U-CAT5002 (manufactured by San-Apro Co., Ltd.), and may be used alone or in combination of two or more. Similarly, S-triazine derivatives such as guanamine, acetoguanamine, benzoguanamine, melamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine-isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine-isocyanuric acid adduct can also be used.

Inorganic fillers include barium sulfate, barium titanate, amorphous silica, crystalline silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, etc.

The organic solvent is used to adjust the viscosity of the curable resin composition and improve its processability. An appropriate organic solvent can be selected and used to the extent that it can be removed in the dry film formation process described below. Examples of organic solvents include ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as toluene, esters such as ethyl acetate, and alcohols such as ethanol and propanol.

Examples of coupling agents include silane-based, titanate-based, and aluminate-based coupling agents, and can be used that have alkoxy groups such as methoxy groups, ethoxy groups, and acetyl groups, and reactive functional groups such as vinyl, methacryl, acrylic, epoxy, cyclic epoxy, mercapto, amino, diamino, acid anhydride, ureido, sulfide, and isocyanate.

The photopolymerization initiator may be either a photoradical polymerization initiator or a photocationic polymerization initiator.

Examples of photoradical polymerization initiators include benzoin and benzoin alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether; acetophenones such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, and 1,1-dichloroacetophenone; aminoalkylphenones such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone; 2-methylanthraquinone, 2-ethyl Examples of the initiator include anthraquinones such as anthraquinone, 2-tertiary butyl anthraquinone, and 1-chloro anthraquinone; thioxanthones such as 2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone, 2-chloro thioxanthone, and 2,4-diisopropyl thioxanthone; ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenones such as benzophenone; or xanthones; phosphine oxides such as (2,6-dimethoxybenzoyl)-2,4,4-pentyl phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenyl phosphine oxide, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, and ethyl-2,4,6-trimethylbenzoyl phenyl phosphineate; various peroxides, and titanocene initiators. These may be used in combination with photosensitizers such as tertiary amines such as N,N-dimethylaminobenzoic acid ethyl ester, N,N-dimethylaminobenzoic acid isoamyl ester, pentyl-4-dimethylaminobenzoate, triethylamine, and triethanolamine.

Examples of photocationic polymerization initiators include onium salts such as diazonium salts, iodonium salts, bromonium salts, chloronium salts, sulfonium salts, selenonium salts, pyrylium salts, thiapyrylium salts, and pyridinium salts; halogenated compounds such as tris(trihalomethyl)-s-triazine and its derivatives; 2-nitrobenzyl esters of sulfonic acid; iminosulfonates; 1-oxo-2-diazonaphthoquinone-4-sulfonate derivatives; N-hydroxyimide sulfonates; tri(methanesulfonyloxy)benzene derivatives; bissulfonyldiazomethanes; sulfonylcarbonylalkanes; sulfonylcarbonyldiazomethanes; and disulfone compounds.

These photopolymerization initiators can be used alone or in combination of two or more.

When the curable resin composition of the present invention as described above is used as a development-type curable resin composition using an alkaline aqueous solution, it is preferable that the curable resin contains a carboxyl group-containing resin.

The carboxyl group-containing resin is not particularly limited, and may be either a photosensitive carboxyl group-containing resin having one or more photosensitive unsaturated double bonds or a carboxyl group-containing resin having no photosensitive unsaturated double bonds. In particular, the following resins may be preferably used:
(1) A carboxyl group-containing resin obtained by copolymerizing an unsaturated carboxylic acid with a compound having an unsaturated double bond, and a carboxyl group-containing resin obtained by modifying the copolymer to adjust the molecular weight or acid value.
(2) A carboxyl group-containing photosensitive resin obtained by reacting a carboxyl group-containing (meth)acrylic copolymer resin with a compound having an oxirane ring and an ethylenically unsaturated group in one molecule.
(3) A carboxyl group-containing photosensitive resin obtained by reacting an unsaturated monocarboxylic acid with a copolymer of a compound having one epoxy group and one unsaturated double bond in each molecule and a compound having an unsaturated double bond, and then reacting the secondary hydroxyl group produced by this reaction with a saturated or unsaturated polybasic acid anhydride.
(4) A carboxyl group-containing photosensitive resin obtained by reacting a polyfunctional epoxy compound, a compound having in one molecule two or more hydroxyl groups and one reactive group other than a hydroxyl group that reacts with an epoxy group, and an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.
(5) A carboxyl group-containing photosensitive resin obtained by reacting a reaction product of a resin having a phenolic hydroxyl group with an alkylene oxide or a cyclic carbonate with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.
(6) A carboxyl group-containing photosensitive resin obtained by reacting a polyfunctional epoxy compound, a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule, and an unsaturated group-containing monocarboxylic acid, and then reacting the alcoholic hydroxyl group of the resulting reaction product with an anhydride group of a polybasic acid anhydride.

<Method for producing curable resin composition>
The method for producing a curable resin composition according to the present invention includes a compounding step of mixing the fiber material obtained by the above-mentioned method for producing a fiber material with a curable resin to obtain a curable resin composition.

[Combination process]
The compounding step is a step of mixing the fiber material obtained in the drying step with a curable resin to obtain a curable resin composition. The mixing method is not particularly limited, and can be mixed by a known and commonly used mixing means. For example, a disintegrator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a roll mill, a jet mill, a single-screw extruder, a twin-screw extruder, an ultrasonic agitator, a household juicer mixer, etc. can be used.

The curable resin composition of the present invention has excellent mechanical strength and heat resistance when cured, and can therefore be suitably used as structural materials such as automobile and aircraft bodies, and insulating layers for printed wiring boards, etc.

When the curable resin composition of the present invention is used as an insulating material for printed wiring boards and the like, it may be used in the form of a dry film or in the form of a one-component or two-component or more liquid form. Of these, it is preferable to use it as a dry film from the viewpoint of processability.

<Dry film>
The dry film of the present invention is a dry film including a resin layer made of the curable resin composition, and is characterized in that the resin layer has a weight loss of less than 5% by mass after heating for 1 hour at 100° C. The weight loss of less than 5% by mass can prevent air bubbles from being generated during curing, which can prevent defects in the cured film.

The method for producing this dry film is not particularly limited, but for example, a method is available in which a resin layer made of the curable resin composition of the present invention is formed on a carrier film, a film having a release property such as a polytetrafluoroethylene (PTFE) film or a surface release-treated film is laminated on the resin layer, and a uniform thickness is obtained by heat pressing or vacuum pressing, and then the release film is peeled off to form a resin layer made of the curable resin composition on the carrier film in a film shape. In addition, a method is available in which the curable resin composition of the present invention is diluted with the organic solvent to adjust the viscosity to an appropriate level, and then coated on a carrier film in a uniform thickness using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, or the like, and then dried at a temperature of 40 to 130°C for 1 to 30 minutes to form a resin layer. There is no particular limit to the thickness of the resin layer of the dry film of the present invention, but the thickness after drying is generally appropriately selected within a range of 3 to 150 μm, preferably 5 to 100 μm.

As the carrier film, a plastic film is used, for example, a polyester film such as polyethylene terephthalate (PET), a polyimide film, a polyamideimide film, a polypropylene film, a polystyrene film, etc. can be used. There is no particular restriction on the thickness of the carrier film, but it is generally selected appropriately in the range of 10 to 150 μm. It is more preferably in the range of 15 to 130 μm.

After forming a resin layer made of the curable resin composition of the present invention on the carrier film, it is preferable to further laminate a film having releasability, such as a PTFE film or a surface release-treated film, on the surface of the resin layer in order to prevent dust from adhering to the surface of the resin layer. Examples of the peelable cover film that can be used include polyethylene film, polytetrafluoroethylene film, polypropylene film, and surface-treated paper. It is preferable that the adhesive strength between the cover film and the resin layer when peeled off is smaller than the adhesive strength between the resin layer and the carrier film.

<Cured Product>
When the curable resin composition has thermosetting properties, the cured product of the present invention can be formed by heating the curable resin composition to a temperature of 100 to 180° C. using a hot air circulation drying oven, a heat press machine, or the like to thermally cure the composition.

When the resin composition is photocurable, the cured product of the present invention can be obtained by irradiating the curable resin composition with active energy rays using an exposure device, etc. A high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a mercury short arc lamp, etc., is used as the light source of the exposure device, and active energy rays having a wavelength of 350 to 450 nm are irradiated at an integrated light amount of 10 to 1000 mJ/ ^cm2 , preferably 20 to 800 mJ/ ^cm2 , to cause curing.

The present invention will be described in more detail below using examples. Note that all compounding amounts in the following tables are in parts by weight unless otherwise specified.

<Textile materials>
Example 1
To 500 g of an aqueous dispersion of TEMPO oxidized cellulose nanofiber (CNF) (solid content concentration 1%), 50 g (10 times the solid content of the cellulose nanofiber) of Denacol EX521 (manufactured by Nagase ChemteX Corporation) was added as a compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule, and the mixture was stirred for 15 seconds using a juicer mixer (Twinbird Corporation, KC-4850R) to mix.
Next, an aqueous solution of 2.5 g of trimethyldodecylammonium chloride (0.5 times the solid content of the cellulose nanofiber) was added as a cationic surfactant, and the mixture was stirred for 15 seconds using a juicer mixer.

The aqueous dispersion containing the cellulose nanofiber dispersion thus obtained was poured into a polyethylene tray and dried at 40°C for 24 hours using a precision thermostatic chamber (DF612, manufactured by Yamato Scientific Co., Ltd.) to produce fiber material 1 consisting of a cellulose nanofiber dispersion.

(Examples 2 to 8)
Fiber materials 2 to 8 were prepared in the same manner as fiber material 1, except that the cellulose nanofibers, cationic surfactant, and compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule were used in the amounts shown in Table 1.
(Comparative Examples 1 and 2)
Fiber materials 9 and 10 were prepared in the same manner as fiber material 1, except that the cellulose nanofibers, cationic surfactant, compound having a hydroxyl group and a reactive group other than a hydroxyl group in one molecule, and organic solvent were used in the amounts shown in Table 1.

※１ ナガセケムテックス(株)製、水酸基当量１６１～１８９ｇ／ｅｑ、粘度４４００ｍＰａ・ｓ
※２ ナガセケムテックス(株)製、水酸基当量１８０～１９０ｇ／ｅｑ、粘度１３００ｍＰａ・ｓ
※３ ナガセケムテックス(株)製、水酸基当量１１０～１１５ｇ／ｅｑ、粘度５０００ｍＰａ・ｓ
※４ ナガセケムテックス(株)製、水酸基当量１１０～１１５ｇ／ｅｑ、粘度１１９００ｍＰａ・ｓ
※５ ナガセケムテックス(株)製、水酸基当量３５０～３６０ｇ／ｅｑ、粘度１３０ｍＰａ・ｓ
※６ ＴＥＭＰＯ酸化セルロースナノファイバー水分散液（表１中の数値は固形分（ＣＮＦ）の量を表す）
※７ リン酸エステル化セルロースナノファイバー水分散液（表１中の数値は固形分（ＣＮＦ）の量を表す）

*1 Nagase ChemteX Corporation, hydroxyl equivalent 161-189g/eq, viscosity 4400mPa·s
*2 Nagase ChemteX Corporation, hydroxyl equivalent 180-190g/eq, viscosity 1300mPa·s
*3 Nagase ChemteX Corporation, hydroxyl equivalent 110-115g/eq, viscosity 5000mPa·s
*4 Nagase ChemteX Corporation, hydroxyl equivalent 110-115g/eq, viscosity 11,900mPa·s
*5 Nagase ChemteX Corporation, hydroxyl equivalent 350-360g/eq, viscosity 130mPa·s
*6 TEMPO oxidized cellulose nanofiber aqueous dispersion (The numbers in Table 1 indicate the amount of solids (CNF))
*7 Phosphated cellulose nanofiber aqueous dispersion (The numbers in Table 1 indicate the amount of solids (CNF))

<Curable resin composition>
(Examples 9 to 19, Comparative Examples 3 and 4)
Fiber materials 1 to 10, thermosetting resin, and curing catalyst were mixed in the components and compositions shown in Table 2, and then milled using a three-roll mill (EXAKT 50I, manufactured by Nagase Screen Printing Laboratory Co., Ltd.). The dispersion treatment was carried out four times to prepare the thermosetting resin compositions of Examples 9 to 19 and Comparative Examples 3 and 4.

(Examples 20 to 22, Comparative Examples 5 and 6)
Fiber materials 1 and 10, photocurable resin, thermosetting resin, curing catalyst, and photopolymerization initiator were blended and mixed according to the components and compositions shown in Table 3, and then dispersed four times using a three-roll mill (EXAKT 50I, manufactured by Nagase Screen Printing Laboratory Co., Ltd.) to prepare the photocurable resin compositions of Examples 20 and 21, and Comparative Example 5, and the photocurable thermosetting resin compositions of Example 22 and Comparative Example 6.

<Preparation of dry film>
Each of the curable resin compositions prepared in Examples 9 to 22 and Comparative Examples 3 to 6 was applied onto a PET carrier film using an applicator, and then a PTFE release film was laminated onto the curable resin composition. Next, a vacuum laminator was used to perform heat pressing for 60 seconds under conditions of 60 ° C. and a pressure of 0.5 MPa, and the curable resin composition was formed into a film shape. Next, the release film was peeled off to obtain a dry film having each resin composition layer. When the resin composition layer contained a solvent, after peeling off the release film, the layer was heated and dried at 60 ° C. for 10 minutes in a precision thermostatic chamber to produce a dry film having each resin composition layer.

<Preparation of Cured Film Evaluation Sample>
For the thermosetting resin compositions of Examples 9 to 19 and Comparative Examples 3 and 4, each prepared dry film was pressure-bonded to the glossy surface of a copper foil using a vacuum laminator at 60°C and a pressure of 0.5 MPa for 60 seconds, and then the carrier film was peeled off. Next, the composition was heated and cured at 160°C for 30 minutes in a precision thermostatic chamber, and then the copper foil was peeled off to prepare a sample for evaluating the cured film.

For the photocurable resin compositions of Examples 20 and 21 and Comparative Example 5, the prepared dry films were pressed onto the glossy surface of copper foil using a vacuum laminator at 60° C. and a pressure of 0.5 MPa for 60 seconds, and then the carrier film was peeled off. Next, the samples were irradiated with light from a metal halide lamp at a wavelength of 350 nm so that the integrated light amount was 2 J/cm ² , to prepare samples for evaluating the cured film.

For the photocurable thermosetting resin compositions of Example 22 and Comparative Example 6, the dry films prepared were pressed onto the glossy surface of copper foil using a vacuum laminator at 60° C. and a pressure of 0.5 MPa for 60 seconds, and then the carrier film was peeled off. Next, the films were exposed to an integrated light amount of 700 mJ/cm ² using a metal halide lamp. Then, the films were cured in a precision thermostatic chamber at 150° C. for 60 minutes, and then peeled off from the copper foil to obtain a sample for evaluating the cured film.

<Evaluation of film formability of cured film>
For each of the samples for evaluating the cured film obtained above, the film-forming property was evaluated according to the following criteria.
A: A cured film without any defects was obtained.
×: Defects such as air bubbles or holes were present in the cured film.

<Evaluation of cellulose nanofiber dispersibility>
For each of the samples for evaluating the cured film obtained above, the presence or absence of cellulose nanofiber aggregates was observed visually and with an optical microscope, and the dispersibility of the cellulose nanofibers was evaluated according to the following criteria.
⊚: No aggregates were observed by either visual inspection or by optical microscope.
◯: No aggregates were observed with the naked eye, but aggregates were observed with an optical microscope.
x: Aggregates are visible.

<Measurement of glass transition temperature and storage modulus>
Each of the samples for evaluating the cured film obtained above was cut into a test piece having a width of 5 mm and a length of 15 mm. The test piece was heated from -50 to 200°C at a rate of 5°C/min using a DMA (Dynamic Mechanical Analysis) RSA-G2 manufactured by TA Instruments Co., Ltd. under the conditions of a chuck distance of 10 mm, a load of 0.5 N, and a frequency of 1 Hz.

A graph was created with the tan δ values obtained by the measurement on the vertical axis and temperature on the horizontal axis, and the peak temperature of tan δ was taken as the glass transition temperature. The storage modulus value at 120°C was also taken as the storage modulus.

The evaluation results are shown in Tables 2 and 3.
As is clear from the results shown in Tables 2 and 3, it was confirmed that the fiber material of the present invention has excellent dispersibility for cellulose nanofibers, and that a curable resin composition containing such a fiber material can give a cured product having excellent mechanical strength and heat resistance.

※８ 繊維材料１～８はそれぞれ実施例１～８の繊維材料に対応、繊維材料９は比較例１に対応、繊維材料１０は比較例２の繊維材料に対応
※９ 熱硬化性樹脂、日鉄ケミカル＆マテリアル(株)製、ビスフェノール型液状エポキシ樹脂
※１０ 熱硬化性樹脂、日本化薬(株)製、ビフェニル型固形エポキシ樹脂、シクロヘキサノンで３０ｗｔ％に希釈して使用 （表２中の配合量は固形分量を表す）
※１１ 四国化成工業(株)製、２－エチル４－メチルイミダゾール

*8 Fiber materials 1 to 8 correspond to the fiber materials in Examples 1 to 8, fiber material 9 corresponds to Comparative Example 1, and fiber material 10 corresponds to the fiber material in Comparative Example 2. *9 Thermosetting resin, Nippon Steel Chemical & Material Co., Ltd., bisphenol-type liquid epoxy resin. *10 Thermosetting resin, Nippon Kayaku Co., Ltd., biphenyl-type solid epoxy resin, diluted with cyclohexanone to 30 wt%. (The blending amounts in Table 2 indicate the solid content.)
*11 2-Ethyl 4-methylimidazole, manufactured by Shikoku Chemical Industry Co., Ltd.

※１２ 熱硬化性樹脂、日産化学（株）製、トリアジン骨格含有エポキシ樹脂
※１３ 光硬化性樹脂、ダイセル・オルネクス（株）製、液状エポキシアクリレート
※１４ 光硬化性樹脂、ダイセル・オルネクス（株）製、エポキシアクリレート、シクロヘキサノンで３０ｗｔ％に希釈して使用 （表３中の配合量は固形分量を表す）
※１５ 光硬化性樹脂
※１６ 下記の合成したカルボキシル基含有樹脂 （表３中の配合量は固形分量を表す）
※１７ ＩＧＭ Ｒｅｓｉｎｓ社製、Ｏｍｎｉｒａｄ ９０７

*12 Thermosetting resin, Nissan Chemical Industries, Ltd., triazine skeleton-containing epoxy resin *13 Photocuring resin, Daicel-Allnex Corporation, liquid epoxy acrylate *14 Photocuring resin, Daicel-Allnex Corporation, epoxy acrylate, diluted with cyclohexanone to 30 wt% (The blending amounts in Table 3 indicate the solid content)
*15 Photocurable resin *16 The following synthesized carboxyl group-containing resin (The blending amounts in Table 3 indicate the solid content)
*17 IGM Resins, Omnirad 907

[Synthesis of carboxyl group-containing resin *16]
Diethylene glycol monoethyl ether acetate as a solvent and azobisisobutyronitrile as a catalyst were placed in a flask equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, and the mixture was heated to 80°C under a nitrogen atmosphere, and a monomer mixture of methacrylic acid and methyl methacrylate in a molar ratio of 0.40:0.60 was dropped over about 2 hours. After stirring for 1 hour, the temperature was raised to 115°C and the mixture was deactivated to obtain a resin solution.

After cooling the resin solution, it was subjected to an addition reaction with an equivalent amount of the carboxyl groups of the resin obtained at a molar ratio of 0.40 with butyl glycidyl ether using tetrabutylammonium bromide as a catalyst at 95-105°C for 30 hours, and then cooled.

Further, tetrahydrophthalic anhydride was added to the OH groups of the resin obtained above at a molar ratio of 0.26 for 8 hours at 95 to 105° C. The resulting mixture was cooled and then taken out to obtain a solution containing 50% by mass (non-volatile content) of a carboxyl group-containing resin having a solid acid value of 78.1 mgKOH/g and a mass average molecular weight of 35,000.

Claims (5)

A fiber material comprising a dispersion of cellulose nanofibers, the dispersion containing cellulose nanofibers , a cationic surfactant, and a compound having a hydroxyl group and a cyclic ether group in one molecule (however, the compound is different from the cellulose nanofibers and the cationic surfactant),
the compound having a hydroxyl group and a cyclic ether group in one molecule has a hydroxyl group equivalent of 200 g/eq or less,
A fiber material characterized in that it is used in combination with a resin having a cyclic ether group (excluding the above-mentioned compound having a hydroxyl group and a cyclic ether group in one molecule) and/or a compound having one or more ethylenically unsaturated bonds in the molecule, and optionally any other components as required . 2. The fiber material according to claim 1, wherein the compound having a hydroxyl group and a cyclic ether group in one molecule has a viscosity at 25° C. of 10,000 mPa·s or less. A curable resin composition comprising: a fiber material made of a dispersion of cellulose nanofibers containing cellulose nanofibers, a cationic surfactant, and a compound having a hydroxyl group and a cyclic ether group in one molecule (however, different from the cellulose nanofibers and the cationic surfactant); and a curable resin,
the compound having a hydroxyl group and a cyclic ether group in one molecule has a hydroxyl group equivalent of 200 g/eq or less,
A curable resin composition comprising, as the curable resin, a resin having a cyclic ether group (excluding the compound having a hydroxyl group and a cyclic ether group in one molecule) and/or a compound having one or more ethylenically unsaturated bonds in one molecule . A dry film having a resin layer formed by applying the curable resin composition according to claim 3 onto a film and drying the same,
A dry film, characterized in that the weight loss of the resin layer of the dry film after heating at 100°C for 1 hour is less than 5 mass%. A cured product obtained by curing the curable resin composition according to claim 3 or the resin layer of the dry film according to claim 4.