JP7554664B2 - Resin composition - Google Patents

Description

The present invention relates to a resin composition and molded article containing modified cellulose fibers, as well as a method for producing a cured resin.

Traditionally, plastic materials derived from petroleum, a finite resource, have been widely used, but in recent years, technologies with less environmental impact have been attracting attention. Against this technological background, cellulose fiber, a biomass that exists in abundance in nature, is attracting attention because it can be recycled, can be biodegraded by microorganisms, has a low environmental impact, and has excellent mechanical properties.

Cellulose fibers have a large number of hydrogen bonds and their surface is hydrophilic, so if the resin is hydrophobic, the cellulose fibers tend to aggregate and their dispersibility in the resin decreases. Therefore, in order to blend cellulose fibers into a resin and enhance its mechanical properties, it is necessary to improve the dispersibility and storage stability of the cellulose fibers.

Various proposals have been made as techniques relating to the dispersibility and storage stability of cellulose fibers in resins.
For example, Patent Document 1 discloses a non-aqueous dispersion containing a fine cellulose fiber composite that can improve the strength and toughness of a resin composition; as a resin composition, a fine cellulose fiber composite in which modifying groups are bonded to cellulose fibers containing ionic groups; and a resin composition that contains a resin and has little foreign matter having a length of 1 μm or more.
Patent Document 2 discloses an adhesive composition using cellulose nanofibers that has heat resistance and high adhesive strength, and that contains fine fibrous cellulose having anionic functional groups and a cellulose I type crystal structure, a number average fiber diameter of 2 to 500 nm, an average aspect ratio of 10 to 1,000, and a specific polyetheramine bonded to some or all of the anionic functional groups, and a matrix resin.
Patent Document 3 discloses a curable resin composition for printed wiring boards that can give a cured product having low thermal expansion and good adhesion to a metal conductor, the resin composition comprising fine cellulose fibers obtained by modifying the carboxyl groups of cellulose fibers having carboxyl groups with an amine compound or the like to make the fibers hydrophobic, and a curable resin, wherein the fine cellulose fibers have an average fiber diameter of 0.1 to 200 nm, an average fiber length of 600 nm or less, and an average aspect ratio of 1 to 200.

JP 2019-119880 A JP 2018-44097 A JP 2018-24878 A

However, the techniques of Patent Documents 1 to 3 do not provide fully satisfactory dispersibility and storage stability of the resulting resin compositions.
In addition, in a curable resin composition, a long pot life is desirable from the viewpoint of workability after mixing the resin and the curing agent.
The present invention relates to a resin composition containing modified cellulose fibers, which has excellent storage stability and a long pot life, a molded article, and a method for producing a cured resin product.

The present inventors have found that the above problems can be solved by combining a curable resin, modified cellulose fiber, and a polyaddition type curing agent to form a composite.
That is, the present invention relates to the following [1] to [3].
[1] A resin composition comprising a curable resin (A), a modified cellulose fiber (B), and a polyaddition type curing agent (C).
[2] A molded article obtained by molding the resin composition described in [1] above.
[3] A method for producing a cured resin, comprising polymerizing a curable resin (A) in the presence of a modified cellulose fiber (B) and a polyaddition-type curing agent (C).

The present invention provides a resin composition and molded article containing modified cellulose fibers that have excellent storage stability and a long pot life, as well as a method for producing a cured resin product.

[Resin composition]
The resin composition of the present invention contains a curable resin (A), modified cellulose fibers (B), and a polyaddition-type curing agent (C).
The resin composition of the present invention has excellent storage stability and a long pot life. The reason for this is not clear, but is thought to be as follows.
In general, when cellulose fibers are blended with a resin, the interface fracture is likely to occur due to the low compatibility between the resin and the cellulose fibers, and the molded body tends to become hard and brittle. Here, when a curable resin (A), a modified cellulose fiber (B), and a polyaddition type curing agent (C) are blended, it is considered that the polyaddition type curing agent (C) acts to moderately bond both the curable resin (A) and the modified cellulose fiber (B). As a result, it is considered that the compatibility with the curable resin (A) is improved without the modified cellulose fiber (B) agglomerating, and the storage stability is improved.
In addition, it is believed that the modified cellulose fiber (B) and the polyaddition type hardener (C) interact with each other and compete with the hardening reaction, thereby lengthening the pot life. However, since this interaction is reversible, it is believed that it does not affect the final hardening degree.

<Curable resin (A)>
The curable resin (A) used in the present invention includes photocurable resins and thermosetting resins. Among these, epoxy resins, (meth)acrylic resins, phenolic resins, unsaturated polyester resins, polyurethanes, etc. Preferably, the resin is at least one selected from the group consisting of polyimide resins, cyanate ester resins, and polyimide resins, more preferably at least one selected from the group consisting of epoxy resins and phenol resins, and even more preferably an epoxy resin.
The (meth)acrylic resin means a methacrylic resin and an acrylic resin.

Depending on the type of the curable resin, a photocuring process and/or a heat curing process can be performed.
In the photocuring treatment, a polymerization reaction proceeds by using a photopolymerization initiator that generates radicals or cations when irradiated with active energy rays such as ultraviolet rays or electron beams.
Examples of the photopolymerization initiator include acetophenones, benzophenones, ketals, anthraquinones, thioxanthones, azo compounds, peroxides, 2,3-dialkyldione compounds, disulfide compounds, thiuram compounds, and fluoroamine compounds.
A photopolymerization initiator can be used to polymerize monofunctional monomers, polyfunctional monomers, oligomers and resins having reactive unsaturated groups, and the like.

Examples of epoxy resins that can be used as the curable resin (A) include bisphenol type epoxy resins and novolac type epoxy resins.
Examples of bisphenol type epoxy resins include 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.
Examples of the novolac type epoxy resin include bisphenol A novolac type epoxy resin, phenol novolac type epoxy resin, and cresol novolac type epoxy resin.
Other examples of the epoxy resins include biphenyl type, biphenyl aralkyl type, aryl alkylene type, tetraphenylol ethane type, naphthalene type, anthracene type, phenoxy type, dicyclopentadiene type, norbornene type, adamantane type, fluorene type, and glycidyl methacrylate copolymer epoxy resins, as well as copolymer epoxy resins of cyclohexylmaleimide and glycidyl methacrylate, epoxy-modified polybutadiene rubber derivatives, and CTBN-modified epoxy resins.
Among the above epoxy resins, bisphenol type epoxy resins and novolac type epoxy resins are preferred, bisphenol type epoxy resins are more preferred, and bisphenol A type epoxy resins are even more preferred.

Examples of phenolic resins include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin, as well as resol-type phenolic resins such as unmodified resol phenolic resin and oil-modified resol phenolic resin.

In the present invention, a polyaddition type curing agent (C) is used to cure the curable resin (A).
When an epoxy resin is used as the curable resin (A), it is preferable to use, as the polyaddition type curing agent (C), one or more selected from dicyandiamide, acid anhydrides, and polymercaptan compounds, as described later.

<Modified cellulose fiber (B)>
As the modified cellulose fiber (B) used in the present invention, from the viewpoint of improving the storage stability and usable life of the resin composition, it is preferable to use a modified cellulose fiber in which a modifying group is bonded to the ionic group of a cellulose fiber having an ionic group.

As the cellulose fiber that is the raw material for the modified cellulose fiber, it is preferable to use natural cellulose fiber from the viewpoint of environmental load. Examples of natural cellulose fibers include wood pulp such as coniferous pulp and broadleaf pulp; cotton pulp such as cotton linter and cotton lint; non-wood pulp such as straw pulp and bagasse pulp; bacterial cellulose, etc. The raw cellulose fiber can be one of the above types alone or two or more types in combination.

From the viewpoints of availability and cost reduction, the average fiber length of the raw cellulose fibers is preferably 1,000 μm or more, more preferably 1,200 μm or more, even more preferably 1,500 μm or more, and is preferably 10,000 μm or less, more preferably 5,000 μm or less, even more preferably 3,000 μm or less.
From the viewpoints of availability and cost reduction, the average fiber diameter of the raw cellulose fibers is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, and is preferably 300 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less.
From the viewpoints of availability and cost reduction, the aspect ratio of the raw cellulose fibers is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and is preferably 200 or less, more preferably 100 or less, even more preferably 80 or less.

(Cellulosic Fibers Having Ionic Groups)
The cellulose fibers having ionic groups refer to cellulose fibers that have been modified so as to contain ionic groups.
Ionic groups include anionic groups and cationic groups.
Examples of the anionic group include a carboxy group, a sulfonic acid group, and a (phosphorous) phosphorus group, and examples of the cationic group include groups having an onium group such as ammonium, phosphonium, or sulfonium within the group.
From the viewpoint of efficiency of introduction into the modified cellulose fiber, the ionic group is preferably an anionic group, and the anionic group is preferably a carboxy group.

When the ionic group is an anionic group, the ion paired with the anionic group (counter ion) is preferably one or more selected from a metal ion and a proton.
The metal ion is preferably a monovalent cation, such as a lithium ion, a sodium ion, a potassium ion, etc. Among these, a proton is preferred from the viewpoint of reaction efficiency with the modified cellulose fiber.

From the viewpoint of the efficiency of introduction into the modified cellulose fiber, the content of ionic groups in the cellulose fiber having ionic groups is preferably 0.1 mmol/g or more, more preferably 0.4 mmol/g or more, even more preferably 0.6 mmol/g or more, and is preferably 3.0 mmol/g or less, more preferably 2.0 mmol/g or less, even more preferably 1.8 mmol/g or less.
When the ionic group is an anionic group, the content of the anionic group can be measured by the method described in the Examples.

As a method for introducing anionic groups into cellulose fibers, for example, a method in which hydroxyl groups of cellulose are oxidized to convert them into carboxyl groups can be mentioned.
The method for oxidizing the hydroxyl groups of cellulose is not particularly limited. For example, there is a method of oxidizing the hydroxyl groups of cellulose by reacting an oxidizing agent such as sodium hypochlorite and a bromide such as sodium bromide with 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) as a catalyst. For more details, the method described in JP 2011-140632 A can be referred to.
By performing an oxidation treatment of cellulose fibers using TEMPO as a catalyst, the hydroxymethyl group (-CH ₂ OH) at the C6 position of the cellulose structural unit is selectively converted to a carboxy group. This method is particularly advantageous in that it has excellent selectivity for the hydroxy group at the C6 position, which is the target of oxidation on the surface of the raw cellulose fibers, and the reaction conditions are mild.

(Modifying Group for Ionic Group)
In the modified cellulose fiber, a modifying group is bonded to the ionic group of the cellulose fiber having an ionic group. The modifying group may be one or more selected from (i) a hydrocarbon group and (ii) a group in which a copolymerization site is bonded to an alkyl group. These groups may be introduced into the modified cellulose fiber (B) alone or in combination of two or more.

(i) Hydrocarbon Group The hydrocarbon group may be at least one selected from a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, an aromatic hydrocarbon group, and the like.
From the viewpoint of improving the storage stability and pot life of the resin composition, the carbon number of the hydrocarbon group as the modifying group is 1 or more, preferably 2 or more, more preferably 3 or more, and is preferably 30 or less, more preferably 24 or less, and even more preferably 18 or less. The carbon number of the hydrocarbon group means the number of carbon atoms in one modifying group.
Examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a docosyl group having 22 carbon atoms.
Examples of the chain unsaturated hydrocarbon group include an ethylene group, a propylene group, a butene group, an isobutene group, and an octadecene group having 18 carbon atoms.
Examples of the cyclic saturated hydrocarbon group include a cyclopropane group having 3 carbon atoms, a cyclopentane group having 5 carbon atoms, and a cyclooctadecyl group having 18 carbon atoms.

The aromatic hydrocarbon group includes an aryl group and an aralkyl group, in which the aromatic ring itself may be substituted or unsubstituted.
Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a biphenyl group, a triphenyl group, a terphenyl group, etc., and examples of the aralkyl group include a benzyl group, a phenethyl group, a phenylpropyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, etc. The aromatic group in these groups may be further substituted with a substituent described later.
When the hydrocarbon group has a substituent, examples of the substituent include a linear or branched alkoxy group having 1 to 6 carbon atoms, an acyl group having 1 to 6 carbon atoms, a halogen atom such as a bromine atom, an aralkyl group, an aralkyloxy group, an alkylamino group having 1 to 6 carbon atoms, a dialkylamino group having 2 to 12 carbon atoms, and a hydroxy group.

(ii) Group in which a copolymerization moiety is bonded to an alkyl group Examples of the copolymerization moiety in the group in which a copolymerization moiety is bonded to an alkyl group include a polyoxyalkanediyl group, and preferred examples include an ethylene oxide/propylene oxide (EO/PO) copolymerization moiety described below.

(Compound having a modifying group)
From the viewpoint of improving storage stability, the bond between the ionic group and the modifying group can be achieved by ionic and/or covalently bonding (e.g., amide bond, ester bond, urethane bond, etc.) a compound having a modifying group to an ionic group present on the surface of a cellulose fiber having an ionic group, preferably an anion-modified cellulose fiber.
The compound having a modifying group can be appropriately selected depending on the bonding mode with the ionic group. Examples of the compound having a modifying group include amine compounds, quaternary ammonium compounds, phosphonium compounds, acid anhydrides, isocyanate compounds, etc., and amine compounds are more preferred.

(Amine Compound)
The amine compound, which is a compound having a modifying group, may be one or more selected from primary monoamines, secondary monoamines, and tertiary monoamines, and has preferably 2 or more, more preferably 6 or more, and preferably 30 or less, more preferably 24 or less, and even more preferably 18 or less.
Examples of primary monoamines include aliphatic monoamines, aromatic monoamines, heterocycle-containing monoamines, alicyclic monoamines, polyoxyethylene amines, polyoxypropylene amines, polyoxyethylene/polyoxypropylene (EO/PO) amines, and the like.
Among these, from the viewpoints of reactivity and improving storage stability, primary or secondary monoamines are preferred, primary monoamines are more preferred, and aliphatic primary monoamines having one or more groups selected from a hydrocarbon group and a polyether group are more preferred.

Specific examples of aliphatic monoamines include propylamine, dipropylamine, butylamine, dibutylamine, diallylamine, hexylamine, 2-ethylhexylamine, dihexylamine, trihexylamine, octylamine, dioctylamine, trioctylamine, dodecylamine, didodecylamine, distearylamine, oleylamine, aniline, octadecylamine, dimethylbenzylamine, etc., with diallylamine, hexylamine, 2-ethylhexylamine, dihexylamine, dodecylamine, oleylamine, etc. being preferred.

From the viewpoint of improving the storage stability and pot life of the resin composition, the monoamine is preferably an aliphatic primary monoamine having a polyoxyalkanediyl group such as (EO/PO), and even more preferably a compound represented by the following formula (1).

[In the formula, R ¹ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, x represents the average number of moles of ethylene oxide (EO) added and is 5 to 100, and y represents the average number of moles of propylene oxide (PO) added and is 1 to 50.]
EO and PO are present randomly or in a block form, and an alkylene group having 1 to 3 carbon atoms may be present between the amino group and EO or PO.]

From the viewpoint of improving storage stability, R ¹ is preferably at least one selected from a hydrogen atom, an amino group and an aminoalkyl group, and more preferably a hydrogen atom.
When R ¹ is a straight or branched alkyl group having 1 to 6 carbon atoms, the alkyl group is preferably a methyl group, an ethyl group, an n-propyl group, or an isopropyl group.
Examples of the alkylene group having 1 to 3 carbon atoms include a methylene group, an ethylene group, and a propylene group.

From the viewpoint of improving storage stability, the average number of moles of EO added, x, is preferably 2 or more, more preferably 5 or more, even more preferably 10 or more, still more preferably 15 or more, still more preferably 20 or more, and is preferably 90 or less, more preferably 70 or less, and still more preferably 50 or less.
From the viewpoint of improving storage stability, the average number of moles of PO added, y, is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and is preferably 40 or less, more preferably 30 or less, even more preferably 20 or less.
In addition, from the viewpoint of improving storage stability, the ratio of the average number of moles added (y/x) is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, and is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less.

From the viewpoint of improving storage stability, the weight average molecular weight of the (EO/PO) copolymerization portion in formula (1) is preferably 100 or more, more preferably 200 or more, even more preferably 300 or more, still more preferably 500 or more, still more preferably 1,000 or more, still more preferably 1,500 or more, and is preferably 10,000 or less, more preferably 7,000 or less, still more preferably 5,000 or less, still more preferably 4,000 or less, still more preferably 3,500 or less, and still more preferably 2,500 or less.
Details of the above amines are described, for example, in paragraphs [0030] to [0041] of JP-A-2018-44101.

Examples of commercially available amines having the (EO/PO) copolymerization moiety include Jeffamine M-2070, Jeffamine M-2005, Jeffamine M-2095, Jeffamine M-1000, Jeffamine M-600, Surfoamine B200, Surfoamine L100, Surfoamine L200, Surfoamine L207, Surfoamine L300, XTJ-501, XTJ-506, XTJ-507, XTJ-508, Jeffamine ED-900, Jeffamine ED-2003, Jeffamine D-2000, Jeffamine D-4000, XTJ-510, Jeffamine T-3000, and Jeffamine ED-2003 manufactured by Huntsman, USA. Examples include T-5000, XTJ-502, XTJ-509; and M3000 manufactured by BASF.

From the viewpoint of improving storage stability, the average bonding amount of the modifying group in the modified cellulose fiber (B) is preferably 0.01 mmol/g or more, more preferably 0.05 mmol/g or more, even more preferably 0.1 mmol/g or more, still more preferably 0.2 mmol/g or more, and is preferably 3 mmol/g or less, more preferably 2 mmol/g or less, and even more preferably 1 mmol/g or less.
From the viewpoint of improving storage stability, the introduction rate of the modifying group in the modified cellulose fiber (B) is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and preferably 95 mol% or less, more preferably 85 mol% or less, even more preferably 75 mol% or less.
The above-mentioned average bond amount (mmol/g) and introduction rate (mol%) of the modifying group refer to the amount and ratio of the modifying group introduced (bonded) to the ionic group in the modified cellulose fiber (B). The average bond amount and introduction rate of the modifying group can be adjusted by the amount and type of compound added for introducing the modifying group, the reaction temperature, the reaction time, the type of solvent, etc.
When the ionic group is an anionic group, the average bond amount and introduction rate of the modifying group are calculated by the method described in the Examples.

In the modified cellulose fiber (B), the amount of modifying group introduced (addition amount) to the cellulose fiber is, from the viewpoint of improving storage stability, preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and preferably 200% by mass or less, more preferably 150% by mass or less, even more preferably 100% by mass or less.
The amount of modifying group introduced into the cellulose fiber is calculated by the method described in the Examples.
The amount of modifying group introduced into the cellulose fibers is calculated assuming that all of the modifying groups of the added compound having a modifying group are introduced into the cellulose fibers to modify them, for example, by adding an amine compound having a modifying group to the carboxyl groups of TEMPO-oxidized cellulose fibers and converting them into amine salts (neutralization reaction), thereby introducing the modifying group into the cellulose fibers.

(Production of modified cellulose fiber (B))
The modified cellulose fibers (B) may be prepared by any method that can introduce modifying groups into the ionic groups of the cellulose fibers containing ionic groups, and there are no particular limitations on the method.
For example, when the ionic group is a carboxy group, modified cellulose fibers can be produced by referring to paragraphs [0017] to [0106] of JP 2018-24967 A.
When the ionic group is a sulfonic acid group, a method for introducing the sulfonic acid group into the cellulose fibers includes a method in which sulfuric acid is added to the cellulose fibers and then the fibers are heated.
When the ionic group is a (phosphate) group, methods for introducing the (phosphate) group into cellulose fibers include a method for mixing a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative with cellulose fibers in a dry or wet state, a method for adding an aqueous solution of phosphoric acid or a phosphoric acid derivative to a dispersion of cellulose fibers, etc. A method for introducing a modifying group includes a method for mixing a compound having a modifying group with cellulose fibers having a phosphoric acid group, etc.
When the ionic group is a cationic group, a method for introducing a cationic group into a cellulose fiber includes treating the cellulose fiber with a cationizing agent in the presence of an alkali. In addition, when producing the modified cellulose fiber (B), the aspect ratio reduction treatment and the fineness process in JP-A-2018-24967 can be omitted.

(Short fiber processing)
In the present invention, when the fiber length of the raw cellulose fibers is 1,000 μm or more, it is preferable to subject the raw cellulose fibers to a fiber shortening treatment.
The fiber shortening process can be carried out by subjecting the raw cellulose fibers to one or more treatment methods selected from the group consisting of alkali treatment, acid treatment, heat treatment, ultraviolet treatment, electron beam treatment, mechanical treatment, and enzyme treatment.
The average fiber length of the modified cellulose fiber (B) after the shortening treatment is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and is preferably 900 μm or less, more preferably 800 μm or less, even more preferably 700 μm or less.
The average fiber diameter of the modified cellulose fiber (B) after the shortening treatment is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and is preferably 300 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less.
The aspect ratio of the modified cellulose fiber (B) after the fiber shortening treatment is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and is preferably 200 or less, more preferably 100 or less, even more preferably 80 or less.
The average fiber length, average fiber diameter, and aspect ratio of the shortened cellulose fibers can be measured by the method described in the Examples.

(Characteristics of modified cellulose fiber (B))
The modified cellulose fiber (B) uses natural cellulose fibers as its raw material, and therefore has a cellulose I type crystal structure.
From the viewpoint of improving storage stability, the cellulose I type crystallinity of the modified cellulose fiber (B) is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, and even more preferably 45% or more, and is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.
Cellulose type I crystals refer to the crystalline form of natural cellulose, and the degree of cellulose type I crystallinity refers to the proportion of cellulose type I crystalline regions in the entire cellulose.
The presence or absence of cellulose type I crystal structure can be determined by the presence of a peak at 2θ=22.6° in X-ray diffraction measurement, and the cellulose type I crystallinity can be measured by the method described in the Examples.

(Micronization process)
The modified cellulose fiber (B) of the present invention may be further subjected to a microfine treatment, if necessary.
The micronization process is a mechanical process, and by carrying out the micronization process, it is possible to convert the cellulose into fine cellulose fibers (nanofibers) having a nanoscale fiber length and fiber diameter.
The device used for micronizing the cellulose fibers is not particularly limited. Examples of the device include a disintegrator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a single-screw extruder, a twin-screw extruder, and an ultrasonic agitator. Among these, from the viewpoint of the micronization efficiency, it is preferable to use a wet-type high-pressure homogenizer capable of applying a strong shear force.
From the viewpoint of the efficiency of the fine particle size reduction, the pressure applied to the dispersion using the high-pressure homogenizer is preferably 50 MPa or more, more preferably 100 MPa or more, and even more preferably 120 MPa or more, and the number of processing passes is 1 or more, preferably 2 or more, and preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

From the viewpoint of improving dispersion stability, the average fiber length of the modified cellulose fiber (B) after the above-mentioned micronization treatment is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 100 nm or more, and is preferably 1000 nm or less, more preferably 800 nm or less, even more preferably 500 nm or less.
The average fiber diameter of the modified cellulose fiber (B) after the micronization treatment is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 2.5 nm or more, and preferably 50 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less.
The average aspect ratio (average fiber length/average fiber diameter) of the modified cellulose fiber (B) after the micronization treatment is preferably 5 or more, more preferably 10 or more, even more preferably 20 or more, and preferably 200 or less, more preferably 150 or less, even more preferably 80 or less.
The average fiber length, average fiber diameter, and average aspect ratio of the modified cellulose fiber (B) after the microfibrillation treatment can be measured using an atomic force microscope (AFM) by the method described in the Examples.

<Polyaddition-type curing agent (C)>
The polyaddition type curing agent (C) has a function of reacting with the curable resin (A) to cure the resin composition. Examples of the curing agent include polyaddition type and catalyst type curing agents, but in the present invention, the polyaddition type curing agent (C) is used from the viewpoint of improving the storage stability and usable life of the obtained resin composition.
Examples of the polyaddition type curing agent (C) include dicyandiamide, acid anhydrides, phenolic resin curing agents, polyamine compounds, polymercaptan compounds, isocyanate compounds, organic acids, and the like. In the present invention, one or more selected from dicyandiamide, acid anhydrides, polyamine compounds, and polymercaptan compounds are preferred.

(Dicyandiamide)
Dicyandiamide is represented by H ₂ N--C(NH ₂ )=N--CN, and its melting point is usually 205 to 215°C, and 207 to 212°C for those with high purity.
Dicyandiamide is a crystalline substance, and its purity is preferably 98% or more, more preferably 99% or more, and even more preferably 99.4% or more.
Dicyandiamide may be a derivative thereof. The derivative of dicyandiamide is a compound obtained by bonding various compounds to dicyandiamide, and examples of the derivative include a reaction product with an epoxy resin, a reaction product with a vinyl compound, or an acrylic compound.
Dicyandiamide or a derivative thereof can be blended in the resin composition as a powder. In this case, the average particle size of the powder is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, and even more preferably 5 μm or less.

Commercially available dicyandiamide products include DICY-7 (average particle size 3 μm) and DICY-15 manufactured by Mitsubishi Chemical Corporation, DICY-15 manufactured by Nippon Carbide Industries Co., Ltd., Tokyo Chemical Industry Co., Ltd., Kishida Chemical Co., Ltd., and Nacalai Tesque, Inc.
Dicyandiamide may be used alone or in combination with a dicyandiamide curing accelerator or other curing agents. Examples of dicyandiamide curing accelerators that can be combined include ureas, imidazoles, Lewis acid catalysts, etc., and examples of other curing agents include aromatic amine curing agents, alicyclic amine curing agents, acid anhydride curing agents, etc. Among these, it is preferable to use ureas as the curing accelerator.
Examples of the ureas include 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), toluene bis(dimethylurea), 4,4'-methylene bis(phenyl dimethylurea), 3-phenyl-1,1-dimethylurea, dichlorodimethylurea, and phenyl dimethylurea.
Examples of commercially available products include "DCMU99" manufactured by Hodogaya Chemical Co., Ltd., and Omicure24, Omicure52, and Omicure94 manufactured by CVC Specialty Chemicals, Inc.

Examples of commercially available imidazoles include "2MZ", "2PZ", and "2E4MZ" manufactured by Shikoku Kasei Corporation.
Examples of the Lewis acid catalyst include complexes of boron halides and bases, such as boron trifluoride-piperidine complex, boron trifluoride-monoethylamine complex, boron trifluoride-triethanolamine complex, and boron trichloride-octylamine complex.

(Acid anhydride)
The acid anhydride is preferably an acid anhydride of an unsaturated dicarboxylic acid having a radically polymerizable unsaturated bond, more preferably at least one selected from an aromatic acid anhydride, a cyclic aliphatic acid anhydride, and an aliphatic acid anhydride, and further preferably an acid anhydride that is liquid at 25°C.
Specific examples of the acid anhydride include acid anhydrides of fumaric acid, maleic acid, succinic acid, dodecenylsuccinic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, itaconic acid, citraconic acid, and the like. Of these, preferred are acid anhydrides of maleic acid, tetrahydrophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and methylhexahydrophthalic acid, and more preferred are one or more selected from tetrahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.
These acid anhydrides can be used alone or in combination of two or more.
In addition, it is also preferable to dissolve an acid anhydride that is solid at room temperature (about 25° C.), such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, or methylcyclohexene dicarboxylic anhydride, in an acid anhydride that is liquid at room temperature (about 25° C.) and use the resulting mixture in a liquid state.

In the present invention, acid components other than the above-mentioned acid anhydrides can be used.
Examples of the other acid component include polyvalent carboxylic acids or derivatives thereof, and preferably include divalent and trivalent non-radical reactive carboxylic acids having 4 to 40 carbon atoms. Examples of the other acid components include divalent carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, dimer acid, alkenylsuccinic acid (having 4 to 20 carbon atoms), cyclohexanedicarboxylic acid, and naphthalenedicarboxylic acid, and trivalent carboxylic acids such as 1,2,4-benzenetricarboxylic acid, and anhydrides thereof.
The content of the acid anhydride in the total acid components is preferably 40 mol % or more, more preferably 50 mol % or more, even more preferably 70 mol % or more, and still more preferably 90 mol % or more, and 100 mol % or less.
Examples of commercially available acid anhydrides include those manufactured by New Japan Chemical Co., Ltd. under the trade names "RIKACID MH" and "RIKACID MH-700G," and those manufactured by Hitachi Chemical Co., Ltd. under the trade name "HN-5500."

When an acid anhydride is used, a tertiary amine, a tertiary amine salt, an imidazole, an organic phosphorus compound, a quaternary ammonium salt, a quaternary phosphonium salt, an organic metal salt, a boron compound, or the like can be used as a curing accelerator having a function of accelerating the curing reaction.
Examples of tertiary amines include lauryldimethylamine, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, N,N-dimethylaniline, (N,N-dimethylaminomethyl)phenol, 2,4,6-tris(N,N-dimethylaminomethyl)phenol, 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), and 1,5-diazabicyclo[4.3.0]nonene-5 (DBN).
Examples of the tertiary amine salt include carboxylates, sulfonates, and inorganic acid salts of the above tertiary amines.
Examples of the imidazoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole.

Examples of the organic phosphorus compounds include triphenylphosphine, and examples of the quaternary ammonium salts include tetraethylammonium bromide and tetrabutylammonium bromide.
Examples of the quaternary phosphonium salt include tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, tetrabutylphosphonium myristate, tetrabutylphosphonium palmitate, and salts of the tetrabutylphosphonium cation with an anion such as bicyclo[2.2.1]heptane-2,3-dicarboxylic acid, methylbicyclo[2.2.1]heptane-2,3-dicarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 4-chlorobenzenesulfonic acid, and dodecylbenzenesulfonic acid.
Examples of the organic metal salt include tin octylate, zinc octylate, dibutyltin dilaurate, and aluminum acetylacetone complex. Examples of the boron compound include boron trifluoride and triphenylborate.
The amount of the curing accelerator to be added is not particularly limited, but from the viewpoint of curing acceleration and color hue, it is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, and even more preferably 0.2 to 3 parts by mass, relative to 100 parts by mass of the polyaddition type curing agent (C).

(Polyamine Compound)
The polyamine compound may be a diamine compound, a triamine compound, or the like, and is preferably at least one selected from an aliphatic diamine, an aromatic diamine, and a dialicyclic amine.

(Polymercaptan Compound)
Examples of the polymercaptan compound include polyhydric alcohol esters of mercaptocarboxylic acids, esters of monomercaptan monohydric alcohols containing polycarboxylic acids, compounds having a mercaptan group at the end of a polypropylene glycol or polyethylene glycol chain, other ester-containing polymercaptans described in U.S. Pat. No. 4,126,505, propoxylated ether polythiols described in U.S. Pat. No. 4,092,293, polymercaptan-containing resins having a molecular weight of 750 to 7000 described in U.S. Pat. No. 3,258,495, dimercaptopolysulfide polymers described in U.S. Pat. No. 2,919,255, and thiolated oligomeric triglycerides.
Of these, polyhydric alcohol esters of mercaptocarboxylic acids are preferred.
Preferred examples of the polyhydric alcohol ester of a mercaptocarboxylic acid include trimethylolpropane trimercaptopropionate, trimethylolpropane trithiogluconate, pentaerythritol tetramercaptopropionate, pentaerythritol tetrathiogluconate, and trimethylolethane trimercaptopropionate.

(Content of each component in resin composition)
The content of each component in the resin composition varies depending on the type of resin, but is as follows.
From the viewpoint of improving the storage stability and usable life of the obtained resin composition, the content of the curable resin (A) in the resin composition is preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, and is preferably 99.5 mass% or less, more preferably 99 mass% or less, even more preferably 98 mass% or less.
From the viewpoint of improving the storage stability and usable life of the resulting resin composition, the content of the modified cellulose fiber (B) in the resin composition is, in terms of mass ratio ((B)/(A)) to the curable resin (A), preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.01 or more, and preferably 0.5 or less, more preferably 0.3 or less, even more preferably 0.2 or less, and even more preferably 0.1 or less.

From the viewpoint of improving the storage stability and pot life of the resulting resin composition, the content of the polyaddition type curing agent (C) in the resin composition is, in terms of a mass ratio ((C)/(A)) to the curable resin (A), preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.01 or more, and is preferably 1.1 or less, more preferably 1.0 or less, even more preferably 0.9 or less.
When the polyaddition type curing agent (C) is dicyandiamide, the mass ratio ((C)/(A)) is preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.01 or more, and is preferably 0.5 or less, more preferably 0.3 or less, even more preferably 0.2 or less.
When the polyaddition type curing agent (C) is an acid anhydride, the mass ratio ((C)/(A)) is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, still more preferably 0.2 or more, and is preferably 1.1 or less, more preferably 1.0 or less, even more preferably 0.9 or less.

The resin composition of the present invention may contain, as necessary, other resins than the curable resin (A), plasticizers, crystal nucleating agents, fillers, hydrolysis inhibitors, flame retardants, lubricants, antioxidants, UV absorbers, antistatic agents, antifogging agents, light stabilizers, pigments, mildew inhibitors, antibacterial agents, foaming agents, polysaccharides, fragrances, and the like.
Examples of other resins include thermoplastic resins, cellulose-based resins, and rubber-based resins.
Examples of the plasticizer include polycarboxylic acid esters such as phthalic acid esters, succinic acid esters, and adipic acid esters, and fatty acid esters of aliphatic polyols such as glycerin, and the like. Examples of the plasticizer include those described in JP-A-2008-174718.
In addition, when the resin composition contains a rubber-based resin, other components than those described above may be blended, if desired, in general amounts, with various additives such as reinforcing fillers such as carbon black and silica, various chemicals such as vulcanizing agents, vulcanization accelerators, antioxidants, scorch inhibitors, zinc oxide, stearic acid, process oil, and vegetable oils and fats.

(Preparation of Resin Composition)
The resin composition of the present invention can be prepared by stirring the raw materials containing the curable resin (A), the modified cellulose fiber (B), the polyaddition type curing agent (C), and various additives as necessary, using a Henschel mixer or the like, or by melt-kneading using a known kneader such as an internal kneader, a single-screw or twin-screw extruder, or an open roll type kneader.
(Uses of resin composition)
The resin composition of the present invention is preferably used as a sealant for protecting electronic parts, particularly semiconductors, from light, heat, moisture, dust, physical impact, etc. Furthermore, as described below, the resin composition of the present invention can be suitably used for various applications such as semiconductor-related materials, display-related materials, in-vehicle materials, passive component materials, electromagnetic wave materials, optical materials, and adhesives.

[Method of producing cured resin]
The method for producing a cured resin of the present invention is a method in which a curable resin (A) is polymerized in the presence of a modified cellulose fiber (B) and a polyaddition-type curing agent (C).
The curable resin (A), the modified cellulose fiber (B), and the polyaddition type curing agent (C) can be the same as those described above.
The amount of the modified cellulose fiber (B) used relative to the curable resin (A) is preferably in the same range as the mass ratio ((B)/(A)) relative to the curable resin (A) described above.
The amount of the polyaddition type curing agent (C) used relative to the curable resin (A) is preferably in the same range as the mass ratio ((C)/(A)) relative to the curable resin (A) described above.
The polymerization can be carried out by appropriately adjusting the above-mentioned photocuring and/or heat curing treatment conditions depending on the type of the curable resin (A) that is the raw material.

[Molded body]
The molded article of the present invention is produced by molding the resin composition of the present invention.
As the molding method, known molding methods such as extrusion molding, injection molding, press molding, cast molding, and solvent casting can be used.
The shape of the molded product may be a sheet, a film such as a coating film, or a fiber, and can be any shape appropriate for the application.
The resin composition of the present invention has excellent storage stability and excellent mechanical strength for various resin products, which are molded articles, and can therefore be suitably used for various applications, such as daily necessities, home appliance parts, packaging materials, civil engineering and construction materials, as well as semiconductor-related materials, display-related materials, automotive materials, passive component materials, electromagnetic wave materials, optical materials, adhesives, and the like.

Examples of semiconductor-related materials include sealing materials; power devices such as rectifier diodes, power transistors, thyristors, and triacs; photoresists, buffer coat films, backgrind tapes, dicing tapes, die bond films, underfills, CMP slurries, and CMP pads.
Examples of display-related materials include polarizer protective films, surface treatment films, films for backlights, QD sheets, protective films, transparent conductive films, cover sheets, rear panels, retardation films, substrates and sealing materials for OLEDs, bank materials, and the like.
Examples of automotive materials include millimeter wave radar compatible decorative materials, light sources and interference filters for LiDAR, automotive lens materials, light sources for OCA/OCR and HUD, concave mirrors/flat mirrors, intermediate films, connector terminals, and insulating sheets for motors.
Passive component materials include aluminum electrolytic capacitors, film capacitors, multilayer ceramic capacitors, inductors, varistors, and the like.
Examples of electromagnetic wave materials include electromagnetic wave shielding materials and noise suppression shielding materials. Examples of optical materials include light control glass/films, films for projector screens, graphite sheets, LED phosphor materials, and the like. Examples of adhesives include structural adhesives for various vehicles, aircraft, ships, drones, and the like, instant adhesives, anaerobic adhesives, and the like.

[Measurement of Cellulose I-Type Crystallinity]
The crystal structure of cellulose was confirmed by measurement under the following conditions using an X-ray diffraction apparatus (manufactured by Rigaku Corporation, product name: MiniFlexII).
Measurement pellet preparation conditions: A pressure in the range of 10-20 MPa was applied to the target cellulose using a tablet press to prepare smooth pellets with an area of 320 mm ² × thickness of 1 mm.
X-ray diffraction analysis conditions: step angle 0.01°, scan speed 10°/min, measurement range: diffraction angle 2θ=5 to 40°
X-ray source: Cu/Kα-radiation, tube voltage: 15kv, tube current: 30mA
Peak division conditions: After removing background noise, the peaks were fitted with a Gaussian function so that the error between 2θ=13° and 23° was within 5%.
The cellulose I-type crystallinity was calculated based on the area of the X-ray diffraction peak obtained by the above peak division, according to the following formula.
Cellulose I type crystallinity (%)=[I _cr /(I _cr +I _am )]×100
(In the formula, I _cr represents the area of the diffraction peak of the lattice plane (002 plane) (diffraction angle 2θ=22-23°) in X-ray diffraction, and I _am represents the area of the diffraction peak of the amorphous portion (diffraction angle 2θ=18.5°).)

[Measurement of average fiber length, average fiber diameter, and aspect ratio of shortened modified cellulose fiber (B)]
Ion-exchanged water is added to the cellulose fibers to be measured to prepare a dispersion having a content of 0.01% by mass. The dispersion is measured using a wet dispersion type image analysis particle size distribution meter (manufactured by Jusco International Co., Ltd., product name: IF-3200) under the following conditions: front lens: 2x, telecentric zoom lens: 1x, image resolution: 0.835 μm/pixel, syringe inner diameter: 6515 μm, spacer thickness: 1000 μm, image recognition mode: ghost, threshold: 8, analysis sample amount: 1 mL, sampling: 15%. 10,000 or more cellulose fibers are measured, and the average ISO fiber length is calculated as the average fiber length, the average ISO fiber diameter is calculated as the average fiber diameter, and the aspect ratio is calculated.

[Measurement of average fiber length, average fiber diameter, and aspect ratio of finely divided modified cellulose fiber (B)]
A medium was added to the cellulose fibers to be measured to prepare a dispersion with a concentration of 0.0001% by mass, and the dispersion was dropped onto mica and dried to prepare an observation sample. The fiber height of the cellulose fibers in the observation sample was measured using an atomic force microscope (AFM, manufactured by Digital Instrument, product name: Nanoscope III Tapping mode AFM, and a probe manufactured by Nanosensors, product name: Point Probe (NCH) was used). At that time, 100 or more cellulose fibers were extracted from the microscope image in which the cellulose fibers could be confirmed, and the average fiber length, average fiber diameter, and aspect ratio were calculated.

[Measurement of anionic group (carboxy group) content of modified cellulose fiber (B)]
A cellulose fiber to be measured having a dry mass of 0.5 g was placed in a 100 mL beaker, and ion-exchanged water or a mixed solvent of methanol/water = 2/1 was added to make a total of 55 mL, and 5 mL of 0.01 M sodium chloride aqueous solution was added thereto to prepare a dispersion. The dispersion was stirred until the cellulose fiber was sufficiently dispersed. 0.1 M hydrochloric acid was added to this dispersion to adjust the pH to 2.5 to 3, and an automatic titration device (manufactured by DKK-TOA Corporation, product name: AUT-710) was used to drop a 0.05 M sodium hydroxide aqueous solution into the dispersion under the condition of a waiting time of 60 seconds, and the conductivity and pH values were measured every minute. The measurement was continued until the pH reached about 11, and a conductivity curve was obtained. From this conductivity curve, the sodium hydroxide titration amount was determined, and the anionic group content of the cellulose fiber to be measured was calculated by the following formula.
Anionic group content (mmol/g)=sodium hydroxide titration amount×sodium hydroxide aqueous solution concentration (0.05 M)/mass of cellulose fiber to be measured (0.5 g)

[Average bond amount and introduction rate (ionic bond) of modifying groups in modified cellulose fiber (B)]
The amount of modified groups (groups in which an (EO/PO) copolymerization moiety is bonded to an alkyl group) was determined by IR measurement, and the average amount and introduction rate were calculated according to the following formulas.
In the IR measurement, the dried modified cellulose fiber having ionic groups was measured by the ATR method using an infrared absorption spectrometer (IR) (manufactured by Thermo Fisher Scientific, product name: Nicolet 6700), and the average bond amount and introduction rate of the modifying group by ionic bonds were calculated by the following formula. The following shows the case where the ionic group is a carboxy group.
Amount of modified group bonded (mmol/g)=[carboxy group content of cellulose fiber having carboxy group (mmol/g)]×[(peak intensity at 1720 cm ⁻¹ of cellulose fiber having carboxy group−peak intensity at 1720 cm ⁻¹ of modified cellulose fiber)/peak intensity at 1720 cm ⁻¹ of cellulose fiber having carboxy group]
Modification group introduction rate (mol%)=100×(bonding amount of modification group (mmol/g))/(carboxy group content in cellulose fiber having carboxy groups (mmol/g))
The "peak intensity at 1720 cm ^-1 " is the peak intensity derived from a carbonyl group.

[Production of anionically modified cellulose]
Production Example 1 (Production of Anion-Modified Cellulose Fibers)
10 g of bleached coniferous kraft pulp (made by West Fraser, product name: Hinton) as natural cellulose was thoroughly stirred with 990 g of ion-exchanged water, and then 0.13 g of TEMPO (made by Aldrich, product name: Free radical, 98% by mass), 1.3 g of sodium bromide, and 27 g of a 10.5% by mass aqueous solution of sodium hypochlorite (10.5% by mass aqueous solution) were added in this order to 10 g of the pulp. Using pH stat titration with an automatic titrator (made by DKK-TOA, product name: AUT-701), a 0.5 M aqueous solution of sodium hydroxide was added dropwise to maintain the pH at 10.5. After the reaction was carried out for 120 minutes (20° C.) at a stirring speed of 200 rpm, the addition of sodium hydroxide was stopped to obtain an anion-modified cellulose in which the anionic group was a carboxy group.
The anion-modified cellulose obtained was neutralized with 0.01 M hydrochloric acid, and then thoroughly washed with ion-exchanged water until the electrical conductivity of the filtrate measured with a compact electrical conductivity meter (manufactured by Horiba, Ltd., product name: LAQUAtwin EC-33B) was 200 μs/cm or less, and then the anion-modified cellulose was subjected to a dehydration treatment.
The anionically modified cellulose fibers thus obtained had an average fiber length of 594 μm, an aspect ratio of 220, and a carboxy group content of 1.3 mmol/g.

Production Example 2 (Production of resin composition containing modified cellulose fiber)
A predetermined amount of the anion-modified cellulose fiber obtained in Production Example 1 (i.e., 10 g in terms of cellulose), 500 g of acetone, and 6.5 g of monoamine (trade name: Jeffamine M2070, manufactured by Huntsman, USA, PO/EO (molar ratio) = 10/31) were mixed and stirred at 25°C for 1 hour to obtain a dispersion of modified cellulose fiber (average fiber length: 132 nm, aspect ratio: 40).
Thereafter, 500 g of epoxy resin (Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, product name: jER828, viscosity 120-150 P/25°C, epoxy equivalent 184-194) was added and stirred at 25°C for another hour. The resulting mixture was subjected to a dispersion treatment at 150 MPa for five passes using a high-pressure homogenizer (Yoshida Kikai Kogyo Co., Ltd., product name: Nanovater L-ES). The solvent was removed from the resulting dispersion to obtain a resin composition containing modified cellulose fibers and an epoxy resin.
The resulting modified cellulose fiber had a modified group (an alkyl group to which an (EO/PO) copolymerization moiety was bonded) bond amount of 0.34 mmol/g, a modifying group introduction rate of 26 mol%, and a cellulose I type crystallinity of 65%.

[Production of resin composition]
Example A1
To 10 g of the resin composition obtained in Production Example 2, 0.5 g of dicyandiamide (polyaddition type curing agent) and 0.3 g of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (curing accelerator, manufactured by Hodogaya Chemical Co., Ltd., product name: DCMU99) were added, and the mixture was stirred for 2 minutes and degassed for 2 minutes at room temperature (25° C.) using an automatic revolution type mixer (manufactured by Thinky Corporation, product name: Awatori Rentaro) to obtain a resin composition containing modified cellulose fiber and an epoxy resin.

Comparative Example A1
To 10 g of the resin composition obtained in Production Example 2, 0.5 g of 2-ethyl-4-methyl-imidazole (polycondensation type curing agent) was added, and a resin composition containing modified cellulose fiber and an epoxy resin was obtained in the same manner as in Example A1, without using a curing accelerator.

Comparative Example A2
An epoxy resin composition was obtained in the same manner as in Example A1, except that in Example A1, 10 g of an epoxy resin not containing modified cellulose fiber (bisphenol A type epoxy resin, product name: jER828, manufactured by Mitsubishi Chemical Corporation) was used instead of 10 g of the resin composition obtained in Production Example 2.

Comparative Example A3
An epoxy resin composition was obtained in the same manner as in Comparative Example A1, except that 10 g of an epoxy resin not containing modified cellulose fiber (bisphenol A type epoxy resin, product name: jER828, manufactured by Mitsubishi Chemical Corporation) was used instead of 10 g of the resin composition obtained in Production Example 2.

Example A2
To 10 g of the resin composition obtained in Production Example 2, 8.9 g of acid anhydride (polyaddition type curing agent, manufactured by New Japan Chemical Co., Ltd., product name: Rikacid MH-700G, a mixture of 4-methylhexahydrophthalic anhydride/hexahydrophthalic anhydride = 70/30) and 0.1 g of N,N-dimethylbenzylamine (curing accelerator, manufactured by Kao Corporation, product name: Kao Raiser No. 20: KL-20) were added, and a resin composition containing modified cellulose fiber and epoxy resin was obtained in the same manner as in Example A1.

Comparative Example A4
An epoxy resin composition was obtained in the same manner as in Example A2, except that in Example A2, 10 g of an epoxy resin not containing modified cellulose fiber (bisphenol A type epoxy resin, product name: jER828, manufactured by Mitsubishi Chemical Corporation) was used instead of 10 g of the resin composition obtained in Production Example 2.

[Production of resin molded body]
Example B1
About 10 to 15 mg of the resin composition obtained in Example A1 was weighed into a sealed sample container (made of aluminum, 15 μL) for measurement with a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, product name: DSC7020) to prepare a sample for molding. The sample was then heated in the measuring device at 130° C. for 2 hours to obtain a resin molding containing modified cellulose fiber and epoxy resin.

Comparative Example B1
In Example B1, a resin molding was obtained in the same manner as in Example B1, except that the heating conditions were changed to 80°C for 1 hour and 150°C for 1 hour, for a total of 2 hours, using the resin composition obtained in Comparative Example A1.

Comparative Example B2
A resin molded product was obtained in the same manner as in Example B1, except that the epoxy resin composition obtained in Comparative Example A2 was used.

Comparative Example B3
In Comparative Example B1, a resin molded product was obtained in the same manner as in Comparative Example B1, except that the epoxy resin composition obtained in Comparative Example A3 was used.

Example B2
In Example B1, a resin molding was obtained in the same manner as in Example B1, except that the heating conditions were changed to 1 hour at 120°C and 2 hours at 150°C, for a total of 3 hours, using the resin composition obtained in Example A2.

Comparative Example B4
A resin molded product was obtained in the same manner as in Example B2, except that the epoxy resin composition obtained in Comparative Example A4 was used.

The properties of the resulting resin composition and resin molded body were evaluated using the methods in Test Examples 1 and 2 below. The results are shown in Table 1.

Test Example 1 (Evaluation of storage stability)
The resin molded articles obtained in the examples and comparative examples were measured for the presence or absence of heat generation at 80° C. for 1 hour using a differential scanning calorimeter.
Since the curing reaction is an exothermic reaction, the progress of the curing reaction can be measured based on the presence or absence of an exothermic peak.

Test Example 2 (Evaluation of pot life)
The resin compositions obtained in the examples and comparative examples (sample amount: 10 to 15 mg) were heated at a rate of 5° C./min, and the time from when the curing temperature corresponding to each curing agent was reached to when the curing heat peak reached its peak top was measured, thereby evaluating the pot life of the resin composition (the length of time during which the resin composition can be used after mixing with the curing agent (pot life)).
The curing temperatures for Example B1 and Comparative Example B2 were 130° C., those for Comparative Example B1 and Comparative Example B3 were 80° C., and those for Example B2 and Comparative Example B4 were 120° C., and the time from when the curing temperature was reached to when the curing heat generation peak reached its top was measured.

As can be seen from Table 1, the resin compositions and resin molded articles of Examples A1, B1 and A2, B2 obtained using a polyaddition type curing agent did not undergo curing under conditions of 80°C for 1 hour, and had superior storage stability compared to the resin compositions and resin molded articles of Comparative Examples A1 and B1 obtained using a polycondensation type curing agent.
It is also evident that when modified cellulose fibers are contained in the resin compositions and resin molded articles of Examples A1, B1 and A2, B2, the curing start time is delayed and the pot life is extended.
The difference in pot life between Examples A2 and B2 and Comparative Examples A4 and B4 is 1.7 minutes. However, this difference in pot life occurs with a small sample amount of 10 to 15 mg, and therefore, it can be said that there is a significant difference when handling more practical amounts.

The resin composition containing the modified cellulose fiber of the present invention has excellent storage stability and a long pot life, and various resin products molded from it have excellent mechanical strength. For this reason, it can be suitably used for a variety of applications, including daily necessities, home appliance parts, packaging materials, civil engineering and construction materials, as well as semiconductor-related materials, display-related materials, automotive materials, passive component materials, electromagnetic wave materials, optical materials, and adhesives.

Claims (6)

The composition comprises a curable resin (A), a modified cellulose fiber (B), and a polyaddition type curing agent (C),
The polyaddition type curing agent (C) is dicyandiamide, and the curing accelerator used is a urea.
The modified cellulose fiber (B) is formed by bonding a modifying group to an ionic group of a cellulose fiber having an ionic group,
The ionic group of the modified cellulose fiber (B) is a carboxy group,
The modifying group is a group derived from a compound represented by formula (1).

[In the formula, R1 ^represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, x represents the average number of moles of ethylene oxide (EO) added and is 5 to 100, y represents the average number of moles of propylene oxide (PO) added and is 1 to 50, EO and PO are present randomly or in a block form, and an alkylene group having 1 to 3 carbon atoms may be present between the amino group and EO or PO.]
Resin composition. The resin composition according to claim 1 , wherein the modified cellulose fiber (B) has a fiber length of 1000 nm or less. The resin composition according to claim 1 or 2 , wherein the curable resin (A) is a photocurable resin or a thermosetting resin. The resin composition according to any one of claims 1 to 3 , wherein the curable resin (A) is at least one selected from the group consisting of epoxy resins, (meth)acrylic resins, phenolic resins, unsaturated polyester resins, polyurethane resins, cyanate ester resins, and polyimide resins. A molded article obtained by molding the resin composition according to any one of claims 1 to 4 . A method for producing a cured resin, comprising polymerizing a curable resin (A) in the presence of a modified cellulose fiber (B) and a polyaddition-type curing agent (C),
The polyaddition type curing agent (C) is dicyandiamide, and the curing accelerator used is a urea.
The modified cellulose fiber (B) is formed by bonding a modifying group to an ionic group of a cellulose fiber having an ionic group,
The ionic group of the modified cellulose fiber (B) is a carboxy group,
The modifying group is a group derived from a compound represented by formula (1).

[In the formula, R1 ^represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, x represents the average number of moles of ethylene oxide (EO) added and is 5 to 100, y represents the average number of moles of propylene oxide (PO) added and is 1 to 50, EO and PO are present randomly or in a block form, and an alkylene group having 1 to 3 carbon atoms may be present between the amino group and EO or PO.]
A method for producing a cured resin.