Transparent coating agent

Abstract

To provide a transparent coating agent having excellent coatability.SOLUTION: A transparent coating agent contains a resin precursor or a resin, and modified cellulose fibers. The modified cellulose fibers have an average fiber length of 500 nm or less and are one or more selected from modified cellulose fibers (A) and / or modified cellulose fibers (B). The modified cellulose fibers (A): cellulose fibers having ionic groups, or modified cellulose fibers with modifying groups bound to the ionic groups. Modified cellulose fibers (B): modified cellulose fibers with modifying groups bound to hydroxy groups of cellulose fibers.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a clear coating agent. [Background technology]

[0002] Coating layers are applied to various substrates to protect their surfaces, improve their functionality, and enhance their aesthetics. For example, hard coat layers are applied to optical displays, eyeglasses, window glass, and the surface of automobile bodies to prevent scratches. Furthermore, smooth, transparent clear coat layers are applied to pharmaceutical labels and packaging containers to improve aesthetics and visibility.

[0003] For example, Patent Document 1 discloses a coating agent characterized by containing specific fine fibrous cellulose and a monomer, with the objective of providing a coating agent that is excellent in properties such as a low linear thermal expansion coefficient.

[0004] Furthermore, Patent Document 2 describes a hard coat film that is produced by applying a coating liquid made of an ionizing radiation-curable resin composition onto a support, drying, photo-curing, and then peeling it off from the support, with the objective of providing a film made of an ionizing radiation-curable resin composition that has high mechanical properties such as breaking strength and breaking strain. The hard coat film is characterized by containing cellulose nanofibers, and is produced by applying the coating liquid containing cellulose nanofibers onto a support, drying, photo-curing, and then peeling it off from the support. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-044098 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-200815 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the coating agents described in these patent documents are not satisfactory in terms of coatability, that is, the appearance of the coating film after application.

[0007] The present invention relates to a transparent coating agent having excellent coatability. [Means for solving the problem]

[0008] The present invention relates to the following [1]. [1] A transparent coating agent containing a resin precursor or resin and modified cellulose fibers, wherein the modified cellulose fibers have an average fiber length of 500 nm or less and are one or more types selected from the group consisting of the following modified cellulose fibers (A) and (B): Modified cellulose fiber (A): Cellulose fiber containing ionic groups, or modified cellulose fiber in which a modifying group is bonded to the ionic group. Modified cellulose fiber (B): Modified cellulose fiber in which a modifying group is bonded to the hydroxyl group of the cellulose fiber. [Effects of the Invention]

[0009] According to the present invention, a transparent coating agent having excellent coatability can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] As a result of intensive research into the above-mentioned problems, the inventors of the present invention have found that a transparent coating agent containing modified cellulose fibers having a specific fiber length has excellent coatability while satisfying the functions of a transparent coating agent, such as surface hardness and transparency. This is thought to be due to the excellent dispersibility of the modified cellulose fibers in the transparent coating agent.

[0011] [Transparent coating agent] The transparent coating agent of the present invention comprises a resin precursor or resin and modified cellulose fibers. In this specification, the transparent coating agent refers to a coating agent that, when applied to a substrate, produces a transparent film. It is an agent that is applied to the substrate for the purposes of protecting the substrate, improving its functionality, and enhancing its aesthetics. It is also sometimes called a varnish. Examples of substrates include transparent components such as optical displays, eyeglasses, and window glass, as well as automotive body surfaces, paper-based materials, wood-based materials, and packaging materials and labels such as plastic films.

[0012] [Resin precursor or resin] Examples of the resin precursor contained in the transparent coating agent of the present invention include curable monomers, prepolymers, and oligomers.

[0013] Examples of monomers that can be suitably used in the transparent coating agent of the present invention include acrylic acid-based monomers, methacrylic acid-based monomers, and epoxy-based monomers.

[0014] The acrylic acid monomer and the methacrylic acid monomer are not particularly limited, but examples thereof include acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, and methacrylamide. More specifically, examples thereof include methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, lauryl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, isobutyl acrylate, 2-methoxyethyl acrylate, cyclohexyl acrylate, dimethylaminoethyl acrylate, phenoxyethyl acrylate, acryloylmorpholine, and ethoxydiethyleneglycol. acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol acrylate, phenyl glycidyl ether acrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

[0015] Among the acrylic acid monomers and methacrylic acid monomers, from the viewpoint of improving the coatability of the transparent coating agent of the present invention, monofunctional or polyfunctional acrylic acid esters or methacrylic acid esters are preferred, polyfunctional acrylic acid esters or methacrylic acid esters are more preferred, and trifunctional or higher functional acrylic acid esters or methacrylic acid esters are even more preferred. The trifunctional or higher functional acrylic acid esters or methacrylic acid esters are not particularly limited, but specific examples include trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

[0016] Examples of epoxy monomers include butyl glycidyl ether, hexyl glycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Examples of suitable epoxy resins include glycidyl ether, trimethylolpropane triglycidyl ether, 3-glycidoxypropyltrimethoxysilane, 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2,2-bis(hydroxymethyl)-1-butanol, 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct, ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl, 3,4-epoxycyclohexanecarboxylate, 1,2-epoxy-4-vinylcyclohexane, and limonene dioxide.

[0017] Examples of prepolymers and oligomers that serve as resin precursors include polymerizable compounds having reactive groups that can be cured by a crosslinking reaction. Preferred reactive groups include, for example, epoxy groups, carboxy groups, amino groups, isocyanate groups, aldehyde groups, hydroxy groups, vinyl groups, acryloyl groups, allyl groups, and silanol groups, and these can be used alone or in combination of two or more. The type of resin obtained by polymerizing the polymerizable compound can be selected depending on the application and desired characteristics or physical properties, and may be any of a thermosetting resin, a photocurable resin, and a thermoplastic resin.

[0018] Examples of thermosetting resins obtained by polymerizing a polymerizable compound include epoxy resins, unsaturated polyester resins, vinyl ester resins, acrylic resins, phenoxy resins, phenolic resins, urea resins, melamine resins, aniline resins, polyimide resins, bismaleimide resins, silicone resins, and urethane resins. Among these, epoxy resins, acrylic resins, phenoxy resins, phenolic resins, and urethane resins are preferred because they provide dispersions with excellent dispersibility, and acrylic resins are more preferred. The acrylic resin may be one obtained by copolymerizing acrylic acid or methacrylic acid with other monomers such as styrene or succinic anhydride.

[0019] The transparent coating agent of the present invention may further contain a curing agent or a curing accelerator in addition to the resin precursor. That is, the composition containing the resin precursor may be composed of the resin precursor, the modified cellulose fiber described below, and a curing agent or a curing accelerator for the resin precursor.

[0020] The curing agent can be appropriately selected depending on the type of resin precursor, and examples of curing agents for heat curing include amine-based curing agents, phenolic resin-based curing agents, acid anhydride-based curing agents, polymercaptan-based curing agents, latent curing agents (boron trifluoride-amine complex, dicyandiamide, carboxylic acid hydrazide, etc.), etc. Furthermore, examples of curing agents for ultraviolet curing include benzyl, benzophenone and derivatives thereof, thioxanthones, benzyl dimethyl ketals, α-hydroxyalkylphenones, α-hydroxyacetophenones, hydroxyketones, aminoalkylphenones, acylphosphine oxides, etc. Specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, benzyl methyl ketone, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, benzophenone, and the like. Commercially available products include "IRGACURE651", "IRGACURE184", "IRGACURE500", "IRGACURE1000", "IRGACURE2959", "DAROCUR1173", "IRGACURE127", "IRGACURE907", "IRGACURE369", "IRGACURE379", "IRGACURE1700", "IRGACURE1800", "IRGACURE819", and "IRG Examples of curing agents include "ACURE784" (the above IRGACURE series and DAROCUR series are trade names manufactured by BASF Japan Ltd.), "KAYACUREITX", "KAYACUREDETX-S", "KAYACUREBP-100", "KAYACUREBMS", and "KAYACURE2-EAQ" (the above KAYACURE series are trade names manufactured by Nippon Kayaku Co., Ltd.). The curing agent may be used alone or in combination of two or more types. In addition, the curing agent may also act as a curing accelerator in some cases.

[0021] The proportion of the curing agent can be appropriately selected depending on the type of resin precursor and curing agent, and is preferably 0.1 to 300 parts by mass, for example, per 100 parts by mass of the resin precursor.

[0022] The curing accelerator can also be appropriately selected depending on the type of resin precursor. For example, curing accelerators for epoxy resins include phosphines, amines, ureas, etc. Curing accelerators for acrylic resins include tertiary amines (dialkylaminobenzoic acid esters, etc.), phosphine accelerators, tin compounds, metal salts, bases, etc. The curing accelerators may be used alone or in combination of two or more.

[0023] The proportion of the curing accelerator can be appropriately selected depending on the type of curing agent, and is preferably 0.01 to 100 parts by mass, for example, per 100 parts by mass of the resin precursor.

[0024] Resins contained in the transparent coating agent of the present invention include acrylic resins, urethane resins, vinyl resins such as water-soluble vinyl acetate, polyvinyl alcohol, cyanoacrylate, ethylene vinyl acetate, vinyl chloride, and vinyl chloride-vinyl acetate copolymers; cellulose resins such as ethyl cellulose, cellulose acetate, and nitrocellulose; polyamide resins, polyvinyl acetal resins, diallyl phthalate resins, alkyd resins, rosin-modified alkyd resins, petroleum resins, urea resins, and rubber-based resins such as butadiene-acrylonitrile copolymers; and acrylic resins or urethane resins are preferred from the viewpoint of dispersibility of the modified cellulose fibers described below. The acrylic resin may be obtained by copolymerizing a monofunctional or polyfunctional acrylic acid ester or methacrylic acid ester. It may also be obtained by copolymerizing acrylic acid or methacrylic acid with other monomers such as styrene or succinic anhydride.

[0025] The content of the resin precursor or resin in the transparent coating agent of the present invention is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, even more preferably 10% by mass or more, and even more preferably 30% by mass or more, from the viewpoint of reducing the workload for drying and the like, and is preferably 99.5% by mass or less, more preferably 99% by mass or less, even more preferably 98% by mass or less, even more preferably 90% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of obtaining a cured film.

[0026] [Modified cellulose fiber] The modified cellulose fiber contained in the transparent coating agent of the present invention is one or more types selected from the group consisting of modified cellulose fiber (A) and modified cellulose fiber (B) below. From the viewpoint of coatability, the modified cellulose fiber (A) preferably contains one or more modifying groups selected from the group consisting of (a) hydrocarbon groups, (b) silicone chains, and (c) alkylene oxide chains. From the viewpoints of specific puncture strength and water resistance, unmodified cellulose fibers containing ionic groups are preferred. Modified cellulose fiber (A): Cellulose fiber containing ionic groups, or modified cellulose fiber in which a modifying group is bonded to the ionic group. Modified cellulose fiber (B): Modified cellulose fiber in which a modifying group is bonded to the hydroxyl group of the cellulose fiber.

[0027] From the viewpoint of environmental load, natural cellulose fibers are preferably used as the raw material for the modified cellulose fibers. Examples of natural cellulose fibers include wood pulps such as softwood pulp and hardwood pulp, cotton pulps such as cotton linter and cotton lint, non-wood pulps such as straw pulp and bagasse pulp, and bacterial cellulose. These fibers may be used alone or in combination of two or more.

[0028] The average fiber diameter and average fiber length of the raw cellulose fibers are not particularly limited. The average fiber diameter is, for example, preferably 1 μm or more from the viewpoint of availability, and from the same viewpoint, preferably 100 μm or less. The average fiber length is, for example, preferably 1,000 μm or more from the viewpoint of availability, and from the same viewpoint, preferably 10,000 μm or less. The average fiber diameter and average fiber length of the raw cellulose fibers can be measured by the method described in the Examples below.

[0029] <Modified cellulose fiber (A)> The modified cellulose fiber (A) in the present invention is a cellulose fiber containing an ionic group, or a modified cellulose fiber in which a modifying group is bonded to the ionic group.

[0030] (ionic group) The cellulose fibers containing ionic groups are cellulose fibers that have been modified so as to contain ionic groups.

[0031] Examples of ionic groups include anionic groups and cationic groups. In this specification, cellulose fibers having anionic groups are also referred to as "anion-modified cellulose fibers." Examples of anionic groups include carboxyl groups, sulfonic acid groups, and phosphate groups, and examples of cationic groups include groups having an onium group such as ammonium, phosphonium, or sulfonium within the group. From the viewpoint of incorporation efficiency into the modified cellulose fiber (A), anionic groups are preferred as ionic groups, and carboxyl groups are more preferred as anionic groups.

[0032] When the ionic group is an anionic group, the counter ion of the anionic group is one or more selected from the group consisting of metal ions and protons. The metal ion is preferably a monovalent cation, such as an alkali metal ion such as a lithium ion, a sodium ion, or a potassium ion. From the viewpoint of reaction efficiency to form modified cellulose fibers, a proton is preferred.

[0033] The content of ionic groups in cellulose fibers containing ionic groups is preferably 0.1 mmol / g or more, more preferably 0.4 mmol / g or more, and even more preferably 0.6 mmol / g or more, from the viewpoint of stable micronization and introduction of modifying groups. From the same viewpoint, the upper limit is preferably 3.0 mmol / g or less, more preferably 2.0 mmol / g or less, and even more preferably 1.8 mmol / g or less. When the ionic groups are anionic groups, the content of the anionic groups can be measured by the method described in the Examples below.

[0034] (modifying group) The modified cellulose fibers (A) may have modifying groups bonded to the ionic groups of the cellulose fibers, such as ionic bonds and covalent bonds (e.g., amide bonds, ester bonds, and urethane bonds).

[0035] The modifying group in the modified cellulose fiber (A) preferably contains one or more modifying groups selected from the group consisting of (a) hydrocarbon groups, (b) silicone chains, and (c) alkylene oxide chains. These groups may be introduced into the modified cellulose fiber (A) either alone or in combination of two or more.

[0036] From the viewpoints of coatability, surface hardness, and transparency, the number of carbon atoms in the hydrocarbon group as the modifying group is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, and from the same viewpoints, is preferably 30 or less, more preferably 24 or less, and even more preferably 18 or less. Unless otherwise specified, the number of carbon atoms in the hydrocarbon group means the number of carbon atoms in one modifying group.

[0037] Specific examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, a pentyl group, a tert-pentyl group, an isopentyl group, a hexyl group, an isohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a tetradecyl group, an octadecyl group, a docosyl group, and an octacosanyl group.

[0038] Specific examples of the chain unsaturated hydrocarbon group include an ethylene group, a propylene group, a butene group, an isobutene group, an isoprene group, a pentene group, a hexene group, a heptene group, an octene group, a nonene group, a decene group, a dodecene group, a tridecene group, a tetradecene group, and an octadecene group.

[0039] Specific examples of the cyclic saturated hydrocarbon group include a cyclopropane group, a cyclobutyl group, a cyclopentane group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cyclododecyl group, a cyclotridecyl group, a cyclotetradecyl group, and a cyclooctadecyl group.

[0040] The aromatic hydrocarbon group is, for example, selected from the group consisting of an aryl group and an aralkyl group. In the aryl group and the aralkyl group, the aromatic ring itself may be substituted or unsubstituted.

[0041] 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, and groups in which these groups are substituted with the substituents described below.

[0042] Examples of aralkyl groups include benzyl, phenethyl, phenylpropyl, phenylpentyl, phenylhexyl, phenylheptyl, and phenyloctyl groups, as well as groups in which the aromatic group of these groups is further substituted with a substituent.

[0043] When the modifying group is a hydrocarbon group and the hydrocarbon group has a substituent, the substituent may be, for example, a linear or branched alkoxy group having 1 to 6 carbon atoms; a linear or branched alkoxycarbonyl group having 1 to 6 carbon atoms in the alkoxy group; a halogen atom such as a bromine atom or an iodine atom; an acyl group having 1 to 6 carbon atoms; an aralkyl group; an aralkyloxy group; an alkylamino group having 1 to 6 carbon atoms; a dialkylamino group having 1 to 6 carbon atoms in the alkyl group; a hydroxy group, an ether, an amide, etc. The above-mentioned various hydrocarbon groups may themselves be bonded to another hydrocarbon group as a substituent.

[0044] The silicone chain is a monovalent group having a siloxane bond as the main chain, and may further include an alkylene group. The silicone chain may further include a substituent.

[0045] Examples of alkylene oxide chains include ethylene oxide / propylene oxide (EO / PO) copolymerization moieties. The (EO / PO) copolymerization moiety refers to a structure in which ethylene oxide (EO) and propylene oxide (PO) are polymerized randomly or in a block form. Examples of groups in which an (EO / PO) copolymerization moiety is bonded to an alkyl group include groups represented by the following formula (i'), which can be introduced using a compound represented by the following formula (i):

[0046] [ka]

[0047] [In the formula, R 1 represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or an aminoalkyl group thereof, EO and PO are present randomly or in blocks, a is a positive number indicating the average number of moles of EO added, and b is a positive number indicating the average number of moles of PO added. Here, "the aminoalkyl group" means a group in which one of the hydrogen atoms constituting the linear or branched alkyl group having 1 to 6 carbon atoms is substituted with an amino group. In formula (i), an alkylene group having 1 to 3 carbon atoms may be present between the amino group and EO or PO.]

[0048] R 1 is preferably a hydrogen atom from the viewpoints of coatability, surface hardness, and transparency. 1 When 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 a sec-propyl group.

[0049] From the viewpoints of coatability, surface hardness, and transparency, a is preferably 1 or more, more preferably 3 or more, even more preferably 6 or more, even more preferably 11 or more, even more preferably 15 or more, even more preferably 20 or more, even more preferably 25 or more, and even more preferably 30 or more. From the same viewpoints, a is preferably 100 or less, more preferably 70 or less, even more preferably 60 or less, even more preferably 50 or less, and even more preferably 40 or less.

[0050] From the viewpoints of coatability, surface hardness, and transparency, b is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more. From the same viewpoints, b is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, even more preferably 25 or less, even more preferably 20 or less, even more preferably 15 or less, and even more preferably 10 or less.

[0051] Examples of the alkylene group having 1 to 3 carbon atoms include a methylene group, an ethylene group, and a propylene group.

[0052] The PO content (mol %) in the (EO / PO) copolymerization moiety can be calculated based on the above a and b, specifically, by b × 100 / (a + b). From the viewpoints of coatability, surface hardness, and transparency, the PO content is preferably 1 mol % or more, more preferably 5 mol % or more, even more preferably 7 mol % or more, and even more preferably 10 mol % or more. From the same viewpoints, the PO content is preferably 100 mol % or less, more preferably 90 mol % or less, even more preferably 85 mol % or less, even more preferably 75 mol % or less, even more preferably 60 mol % or less, even more preferably 50 mol % or less, even more preferably 40 mol % or less, and even more preferably 30 mol % or less.

[0053] From the viewpoints of coatability, surface hardness, and transparency, the molecular weight of the (EO / PO) copolymerization portion is preferably 100 or more, more preferably 200 or more, even more preferably 300 or more, even more preferably 500 or more, even more preferably 1,000 or more, and even more preferably 1,500 or more. From the same viewpoints, the molecular weight is preferably 10,000 or less, more preferably 7,000 or less, even more preferably 5,000 or less, even more preferably 4,000 or less, even more preferably 3,500 or less, and even more preferably 2,500 or less.

[0054] The amine having an EO / PO copolymerization moiety represented by formula (i) is a modifying compound for introducing a modifying group represented by formula (i'), and details of the amine are described in, for example, Japanese Patent No. 6105139.

[0055] The amine having an EO / PO copolymerization moiety (also referred to as "EOPO amine") may be, for example, a commercially available product. Specific examples thereof 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, and XTJ-508, manufactured by HUNTSMAN; and Jeffamine M3000, Jeffamine ED-900, Jeffamine ED-2003, Jeffamine D-2000, Jeffamine D-4000, XTJ-510, and Jeffamine ED-2003, manufactured by BASF. Examples include T-3000, Jeffamine T-5000, XTJ-502, XTJ-509, and XTJ-510.

[0056] From the viewpoints of coatability, surface hardness, and transparency, the average bond amount of modifying groups in the modified cellulose fiber (A) 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, even more preferably 0.3 mmol / g or more, and even more preferably 0.5 mmol / g or more. From the same viewpoints, it is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, even more preferably 2.0 mmol / g or less, even more preferably 1.8 mmol / g or less, and even more preferably 1.5 mmol / g or less. When any two or more types of modifying groups are simultaneously introduced into the modified cellulose fiber (A), the average bond amount of the modifying groups is preferably such that the total amount of the introduced modifying groups is within the above-mentioned range.

[0057] From the viewpoints of coatability, surface hardness, and transparency, the introduction rate of the modifying group in the modified cellulose fiber (A) is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, even more preferably 60 mol% or more, and even more preferably 70 mol% or more, and from the same viewpoints, it is preferably 99 mol% or less, more preferably 97 mol% or less, even more preferably 95 mol% or less, and even more preferably 90 mol% or less. When any two or more types of modifying groups are simultaneously introduced as the modifying group, it is preferable that the total introduction rate be within the above range, provided that it does not exceed the upper limit of 100 mol%.

[0058] The average bond amount and introduction rate of the modifying group can be adjusted by the amount and type of compound used to introduce the modifying group, i.e., the modifying compound, the reaction temperature, the reaction time, the type of solvent, etc. The average bond amount (mmol / g) and introduction rate (mol %) of the modifying group refer to the amount and rate of the modifying group introduced (bonded) to the ionic group in the modified cellulose fiber (A). For example, when the ionic group is anionic, the average bond amount and introduction rate of the modifying group are calculated by the method described in the Examples below.

[0059] (Method for producing modified cellulose fiber (A)) The modified cellulose fiber (A) can be produced by any known method, without particular limitation, as long as it is possible to prepare cellulose fibers containing ionic groups or to introduce modifying groups into the ionic groups. For example, when the ionic group is a carboxyl group, the modified cellulose fiber (A) can be produced by referring to paragraphs 0017 to 0106 of JP 2018-024967 A. When the ionic group is a sulfonic acid group, a method for introducing the sulfonic acid group into the cellulose fiber can be exemplified by adding sulfuric acid to the cellulose fiber and heating the cellulose fiber. When the ionic group is a phosphate group, a method for introducing the phosphate group into the cellulose fiber can be exemplified by mixing a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative with dry or wet cellulose fiber, or by adding an aqueous solution of phosphoric acid or a phosphoric acid derivative to a dispersion of cellulose fiber. A method for introducing a modifying group can be exemplified by mixing a compound having a modifying group with cellulose fiber having a phosphate group. When the ionic group is a cationic group, a method for introducing the cationic group into the cellulose fiber can be exemplified by treating the cellulose fiber with a cationizing agent in the presence of an alkali. When producing the modified cellulose fiber (A), the aspect ratio reduction treatment and the micronization process described in JP 2018-024967 A can be omitted.

[0060] <Modified cellulose fiber (B)> The modified cellulose fiber (B) in the present invention is a modified cellulose fiber in which a modifying group is bonded to a hydroxy group of a cellulose fiber.

[0061] (modifying group) In the modified cellulose fiber (B), the cellulose fiber and the modifying group are bonded via an ether bond. In this specification, "bonded via an ether bond" means that the modifying group reacts with the hydroxy group of the cellulose fiber to form an ether bond.

[0062] The modifying group in the modified cellulose fiber (B) is preferably a hydrocarbon group which may have a substituent. Examples of the hydrocarbon group which may have a substituent include saturated or unsaturated, straight-chain or branched-chain aliphatic hydrocarbon groups, aromatic hydrocarbon groups such as phenyl groups, and alicyclic hydrocarbon groups such as cyclohexyl groups. Examples of the substituent in the hydrocarbon group which may have a substituent in the present invention include halogen atoms, oxyalkylene groups such as oxyethylene groups, and hydroxy groups.

[0063] A preferred embodiment of such modified cellulose fiber (B) (referred to as "embodiment 1") is, for example, a cellulose fiber having one or more modifying groups selected from the group consisting of the modifying group represented by the following general formula (1) and the modifying group represented by the following general formula (2) bonded to the cellulose fiber via an ether bond, and having a cellulose type I crystal structure. -CH2-CH(R 0 )-R 1 (1) -CH2-CH(R 0 )-CH2-(OA) n -OR 1 (2) [wherein R in general formula (1) and general formula (2) 0 represents a hydrogen atom or a hydroxy group, and R 1 each independently represents a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms, preferably 3 to 30 carbon atoms, and in general formula (2), n is a number of 0 to 50, and A is a linear or branched divalent saturated hydrocarbon group having 1 to 6 carbon atoms.

[0064] A specific example of the first aspect is a modified cellulose fiber represented by the following general formula (3).

[0065] [ka]

[0066] [In the formula, R may be the same or different and represent hydrogen or a modifying group selected from the modifying group represented by the general formula (1) and the modifying group represented by the general formula (2), except for the case where all R are simultaneously hydrogen. m is preferably an integer of 20 to 3000.]

[0067] The modified cellulose fiber (B) represented by general formula (3) has a repeating structure of cellulose units into which the above-mentioned modifying group has been introduced. The number of repeating units, m, in general formula (3) is preferably an integer of 20 to 3000 from the viewpoints of coatability, surface hardness, and transparency.

[0068] (Optionally substituted hydrocarbon group) The modified cellulose fiber (B) of aspect 1 is introduced with one or more modifying groups selected from the modifying groups represented by the above general formula (1) and the following general formula (2), either singly or in any combination. Note that even when the modifying group introduced is only one of the above groups, the same modifying group may be introduced within each group, or two or more types may be introduced in combination.

[0069] From the viewpoint of coatability, surface hardness, and transparency, R in general formula (1) and general formula (2) 0 is preferably a hydroxy group.

[0070] R in general formula (1) 1 From the viewpoints of coatability, surface hardness, and transparency, the number of carbon atoms is preferably 25 or less. Specific examples include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a hexadecyl group, an octadecyl group, an isooctadecyl group, an icosyl group, a triacontyl group, a phenyl group, and a methylphenyl group.

[0071] R in general formula (2) 1The number of carbon atoms in R in the general formula (1) is preferably 4 or more from the viewpoints of coatability, surface hardness, and transparency, and is preferably 27 or less from the viewpoints of availability and improved reactivity. 1 The same can be mentioned.

[0072] In general formula (2), A forms an oxyalkylene group together with the adjacent oxygen atom. From the viewpoints of availability and cost, the number of carbon atoms in A is preferably 2 or more, and from the same viewpoints, preferably 4 or less. Specific examples include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group.

[0073] In general formula (2), n represents the number of moles of alkylene oxide added, and is preferably 3 or more from the viewpoints of dispersibility, availability, and cost, and is preferably 40 or less from the same viewpoints.

[0074] From the viewpoints of coatability, surface hardness, and transparency, the combination of A and n in general formula (2) is preferably such that A is a linear or branched divalent saturated hydrocarbon group having from 2 to 3 carbon atoms, and n is a number from 0 to 20.

[0075] Specific examples of the modifying group represented by general formula (1) include, for example, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, an isooctadecyl group, an icosyl group, a hydroxyethyl group, a methylhydroxyethyl group, an ethylhydroxyethyl group, a propylhydroxyethyl group, a butylhydroxyethyl group, a pentylhydroxyethyl group, a hexylhydroxyethyl group, a heptylhydroxyethyl group, an octylhydroxyethyl group, a 2-ethylhexylhydroxyethyl group, a nonylhydroxyethyl group, a decylhydroxyethyl group, a undecylhydroxyethyl group, a dodecylhydroxyethyl group, a hexadecylhydroxyethyl group, an octadecylhydroxyethyl group, an isooctadecylhydroxyethyl group, an icosylhydroxyethyl group, and a triacontylhydroxyethyl group.

[0076] Specific examples of the modifying group represented by general formula (2) include, for example, a 3-butoxy-2-hydroxypropyl group, a 3-hexoxyethyleneoxide-2-hydroxypropyl group, a 3-hexoxy-2-hydroxypropyl group, a 3-octoxyethyleneoxide-2-hydroxypropyl group, a 3-octoxy-2-hydroxypropyl group, a 6-ethyl-3-hexoxy-2-hydroxypropyl group, a 6-ethyl-3-hexoxyethyleneoxide-2-hydroxypropyl group, a 3-detoxyethyleneoxide-2-hydroxypropyl group, a 3-detoxy-2-hydroxypropyl group, a 3-detoxy-2-hydroxypropyl group, a 3-detoxy-2-hydroxypropyl group, a 3-butoxy-2-hydroxypropyl group, a 3-hexoxyethyleneoxide ... -propyl group, 3-undethoxyethyleneoxide-2-hydroxypropyl group, 3-undethoxy-2-hydroxypropyl group, 3-dodethoxyethyleneoxide-2-hydroxypropyl group, 3-dodethoxy-2-hydroxypropyl group, 3-hexadethoxyethyleneoxide-2-hydroxypropyl group, 3-hexadethoxy-2-hydroxypropyl group, 3-octadethoxyethyleneoxide-2-hydroxypropyl group, 3-octadethoxy-2-hydroxypropyl group, 3-o-methylphenoxy-2-hydroxypropyl group, etc. The number of moles of alkylene oxide added may be from 0 to 50, and examples thereof include the above-mentioned substituents having an oxyalkylene group such as ethylene oxide, with the number of moles added being 10, 12, 13, or 20 moles.

[0077] (Molar substitution (MS)) In the modified cellulose fiber (B) of Aspect 1, the molar amount of modifying groups introduced per mole of anhydroglucose unit of cellulose (molar substitution: MS) cannot be generally limited depending on the type of modifying group. However, from the viewpoints of coatability, surface hardness, and transparency, it is preferably 0.0001 moles or more, more preferably 0.01 moles or more, and even more preferably 0.1 moles or more. Furthermore, when the modified cellulose fiber (B) has a cellulose type I crystal structure, from the viewpoints of coatability, surface hardness, and transparency, it is preferably 1.5 moles or less, more preferably 1.2 moles or less, and even more preferably 1 mole or less. Here, when the bonded modifying groups are composed of multiple types of modifying groups, the MS of the bonded modifying groups is the sum of the MS of each modifying group. In this specification, the MS of the modifying groups in the modified cellulose fiber (B) can be measured according to the method described in the Examples below.

[0078] <Method for producing modified cellulose fiber (B)> In the modified cellulose fiber (B) of the present invention, as described above, a modifying group, preferably a hydrocarbon group optionally having the modifying group, is bonded to the cellulose fiber via an ether bond, and the introduction of the modifying group can be carried out according to any known method without particular limitation. Specific examples of methods for producing the modified cellulose fiber (B) of embodiment 1 are described below.

[0079] (Method for producing modified cellulose fiber (B) of embodiment 1) A specific example of the method for producing the modified cellulose fiber (B) of Aspect 1 is a method in which a specific compound is reacted with raw cellulose fiber in the presence of a base.

[0080] In order to reduce the number of manufacturing steps, pre-micronized cellulose fibers may be used as the raw cellulose fibers, and in this case, the average fiber diameter is preferably 1 nm or more from the viewpoints of availability and cost. Although there is no particular upper limit, it is preferably 500 nm or less from the viewpoint of handleability.

[0081] (base) The base is not particularly limited, but from the viewpoint of promoting the etherification reaction, one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, primary to tertiary amines, quaternary ammonium salts, imidazole and its derivatives, pyridine and its derivatives, and alkoxides are preferred. Specific examples include the bases described in paragraphs 0053 to 0058 of JP 2017-053077 A.

[0082] The amount of base is preferably 0.01 equivalents or more relative to the anhydroglucose units of the raw cellulose fiber from the viewpoint of proceeding with the etherification reaction, and is preferably 10 equivalents or less from the viewpoint of production costs.

[0083] The raw cellulose fibers and the base may be mixed in the presence of a solvent, which is not particularly limited and includes, for example, water, isopropanol, t-butanol, dimethylformamide, toluene, methyl isobutyl ketone, acetonitrile, dimethyl sulfoxide, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, hexane, 1,4-dioxane, and mixtures thereof.

[0084] There are no particular limitations on the temperature or time for mixing the raw material cellulose fiber and base, provided that they can be mixed uniformly.

[0085] Next, a modifying compound (also referred to herein as an "etherifying agent"), preferably a compound for introducing an optionally substituted hydrocarbon group, is added to the mixture of the raw cellulose fibers and base obtained above, and the raw cellulose fibers are reacted with the compound. As such a compound, it is preferable to use a compound having a reactive cyclic structural group, and it is more preferable to use a compound having an epoxy group.

[0086] Examples of compounds to which the modifying group represented by general formula (1) can be bonded via an ether bond include the alkylene oxide compounds described in paragraphs 0079 to 0084 of JP-A No. 2017-053077.

[0087] Examples of compounds to which the modifying group represented by general formula (2) can be bonded via an ether bond include the glycidyl ether compounds described in paragraphs 0085 to 0091 of JP-A No. 2017-053077.

[0088] The amount of the modifying compound can be determined based on the desired introduction rate of the modifying group in the resulting modified cellulose fiber (B), but from the standpoint of reactivity, it is preferably 0.01 equivalents or more relative to the anhydroglucose units of the raw cellulose fiber, and from the standpoint of production costs, it is preferably 10 equivalents or less.

[0089] (Etherification reaction) The etherification reaction between the compound and the raw cellulose fiber can be carried out by mixing them in the presence of a solvent. The solvent is not particularly limited, and the solvents exemplified as those usable in the presence of the base can be used. For details of the etherification reaction, please refer to paragraphs 0070 to 0075 of JP 2017-053077 A.

[0090] The modified cellulose fibers (B) of embodiment 1 thus obtained may be subjected to a known pulverization treatment, for example, treatment using a high-pressure homogenizer in an organic solvent.

[0091] In either case of the modified cellulose fibers (A) and (B), the modified cellulose fibers can be used in the form of a dispersion, or the solvent can be removed from the dispersion by drying or other treatment to obtain dried powdery modified cellulose fibers, which can then be used. Here, "powdered" refers to a powder in which the modified cellulose fibers are agglomerated, and does not mean cellulose particles.

[0092] Examples of powdered modified cellulose fibers include a dried product obtained by directly drying the cellulose fiber dispersion, a dried product powdered by mechanical processing, a cellulose fiber dispersion powdered by a known spray drying method, and a cellulose fiber dispersion powdered by a known freeze drying method. The spray drying method is a method in which the cellulose fiber dispersion is sprayed in the atmosphere and dried.

[0093] <Characteristics of modified cellulose fiber> Modified cellulose fibers have a cellulose type I crystalline structure due to the use of natural cellulose fibers as their raw material. Cellulose type I refers to the crystalline form of natural cellulose, and cellulose type I crystallinity refers to the proportion of cellulose type I crystalline regions in the total cellulose. The presence or absence of cellulose type I crystalline structure can be determined by the presence of a peak at 2θ = 22.6° in X-ray diffraction measurements.

[0094] The cellulose type I crystallinity of the modified cellulose fiber is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, and even more preferably 45% or more, from the viewpoint of surface hardness. Furthermore, from the viewpoint of the cost of the cellulose raw material used, it is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, and even more preferably 80% or less. In this specification, the cellulose type I crystallinity of cellulose fiber, modified cellulose fiber, etc. is specifically measured by the method described in the Examples below.

[0095] From the viewpoint of production efficiency, the average fiber length of the modified cellulose fiber is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 50 nm or more, and from the viewpoint of coatability, it is 500 nm or less, preferably 400 nm or less, more preferably 300 nm or less, even more preferably 250 nm or less, even more preferably 200 nm or less, and even more preferably 150 nm or less. The average fiber length of the modified cellulose fiber can be measured by the method described in the examples below.

[0096] The average fiber diameter of the modified cellulose fiber is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 3 nm or more from the viewpoint of production efficiency, and is preferably 30 nm or less, more preferably 10 nm or less, and even more preferably 5 nm or less from the viewpoint of coatability. The average fiber diameter of the modified cellulose fiber can be measured by the method described in the Examples below.

[0097] From the viewpoint of production efficiency, the average aspect ratio of the modified cellulose fiber is preferably 1 or more, more preferably 5 or more, and even more preferably 8 or more, and from the viewpoint of coatability, it is preferably 150 or less, more preferably 100 or less, even more preferably 80 or less, even more preferably 60 or less, and even more preferably 50 or less. The average aspect ratio of the modified cellulose fiber can be measured by the method described in the examples below.

[0098] Examples of methods for adjusting the average aspect ratio of modified cellulose fibers to 150 or less include a method of subjecting modified cellulose fibers that have been shortened to an average fiber length of 1 μm to 1,000 μm to micronization. The average fiber length of such short cellulose fibers is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and even more preferably 25 μm or more, and is preferably 1,000 μm or less, more preferably 800 μm or less, even more preferably 500 μm or less, and even more preferably 400 μm or less. The average fiber diameter is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 15 μm or more, and is preferably 300 μm or less, more preferably 100 μm or less, and even more preferably 60 μm or less.

[0099] Known methods can be used for the fiber shortening treatment, and the target cellulose fibers can be shortened by alkaline hydrolysis treatment, acid hydrolysis treatment, hydrogen peroxide treatment, ultraviolet treatment, electron beam treatment, hot water decomposition treatment, mechanical treatment, enzyme treatment, etc. Note that the modified cellulose fibers to be subjected to the micronization treatment may be shortened before or after the introduction of the above-mentioned modifying groups or ionic groups. For example, there is a production mode in which ionic groups are introduced into the raw cellulose fibers, followed by the fiber shortening treatment, and then modifying groups are introduced, and the resulting shortened, modified cellulose fibers are micronized.

[0100] Suitable examples of equipment that can be used in the micronization treatment include known dispersers. For example, a stirrer equipped with stirring blades, a disintegrator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a roll mill, a single-screw kneader, a twin-screw kneader, a single-screw extruder, a twin-screw extruder, an ultrasonic agitator, a household juicer mixer, etc. can be used. The operating conditions of the equipment can be set appropriately by referring to the attached instruction manual.

[0101] The amount of modified cellulose fiber in the transparent coating agent of the present invention, calculated in terms of cellulose (not including modifying groups, etc.), is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, from the viewpoint of improving hardness, while from the viewpoint of maintaining transparency, it is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, even more preferably 7% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0102] The mass ratio of modified cellulose fiber / resin precursor or resin to the total amount in the transparent coating agent of the present invention is, in terms of the blending amount, converted into cellulose (not including modifying groups, etc.), from the viewpoint of improving hardness, preferably 0.01 / 100 or more, more preferably 0.05 / 100 or more, even more preferably 0.1 / 100 or more, even more preferably 0.3 / 100 or more, even more preferably 0.5 / 100 or more, and even more preferably 1 / 100 or more; on the other hand, from the viewpoint of maintaining transparency, it is preferably 30 / 100 or less, more preferably 20 / 100 or less, even more preferably 15 / 100 or less, even more preferably 10 / 100 or less, even more preferably 7 / 100 or less, even more preferably 5 / 100 or less, even more preferably 4 / 100 or less, and even more preferably 3 / 100 or less.

[0103] (Solvent or dispersion medium) The transparent coating agent of the present invention can further contain a solvent or dispersion medium. Examples of solvents or dispersion mediums that can be added include water, ethyl acetate, methyl methacrylate, methanol, ethanol, isopropanol, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide, tetrahydrofuran (THF), propylene glycol monomethyl ether, a diester of succinic acid and triethylene glycol monomethyl ether, acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, acetonitrile, dichloromethane, chloroform, toluene, and acetic acid. These can be used alone or in combination of two or more. When a solvent or dispersion medium is used, the amount thereof is, for example, preferably 30 parts by weight or more, more preferably 50 parts by weight or more, and even more preferably 70 parts by weight or more, per 100 parts by weight of the resin precursor or resin. It is also preferably 5,000 parts by weight or less, more preferably 1,000 parts by weight or less, and even more preferably 500 parts by weight or less.

[0104] (wax) The transparent coating agent of the present invention may further contain a wax, such as a synthetic wax, a plant-derived wax, an animal-derived wax, or a petroleum-derived wax such as paraffin wax. Examples of the synthesized wax include polyolefin waxes such as polyethylene waxes that are liquid at 25°C.

[0105] The transparent coating agent of the present invention may optionally contain additives such as stabilizers, dehydrating agents, leveling agents, thickeners, and ultraviolet absorbers. Examples of dehydrating agents include methyl orthoformate, ethyl orthoformate, methyl orthoacetate, and ethyl orthoacetate. Examples of leveling agents include various polyether-modified silicone oils. Furthermore, by adding various pigments, colorants such as dyes, carbon black, charge control agents, aluminum paste, talc, glass frit, metal powder, and the like to the transparent coating agent of the present invention, it can also be used as a paint.

[0106] The transparent coating agent of the present invention has excellent coatability for modified cellulose fibers and can therefore be suitably used as a transparent coating agent for transparent materials such as glass, optical displays, and eyeglass lenses; as a clear coating for automobile body surfaces; and as an overcoat (varnish) for packaging materials such as paper-based materials, wood-based materials, and plastic films, and labels. The transparent coating agent before application is in a liquid, emulsion, or solid form (e.g., pellets or powder) at room temperature (25°C). If the agent is solid, it can be converted into a paste, solution, or dispersion by adding an appropriate medium. It can also be heated as needed before use to form a fluid.

[0107] Furthermore, additives other than those mentioned above can be appropriately selected as components of the transparent coating agent of the present invention depending on the substrate to be coated and the intended use, provided that the effects of the present invention are not impaired.

[0108] Examples of substrates to which the transparent coating agent of the present invention can be applied include metals such as iron, stainless steel, aluminum, anodized aluminum, and duralumin; metal oxides such as iron oxide, ferrite, alumina, and zinc oxide; inorganic substrates such as mortar, slate, concrete, glass, and ceramic; wood, plywood; paper-based materials such as cardboard, paperboard, wrapping paper, and coated paper; and resins such as thermosetting resins, thermoplastic resins, and FRP. Examples of the shape of the substrate include plate, sheet, block, film, particulate, and powder.

[0109] [Method for producing transparent coating agent] The transparent coating agent of the present invention can be produced by mixing the above-mentioned components. The method for mixing the components is not particularly limited, and includes common methods such as using a stirrer, an ultrasonic homogenizer, a high-pressure homogenizer, etc.

[0110] [Method for applying transparent coating agent] The transparent coating agent of the present invention can be applied by a known method using a bar coater, applicator, spin coater, etc., or by brush coating, hand coating, spray coating, dip coating, etc. After application, the agent can also be cured using a UV irradiator, etc.

[0111] [Transparent coating film] The film after application (transparent coating film) is transparent so as not to impair the appearance of the substrate, and the haze value is preferably 50 or less, more preferably 10 or less, and even more preferably 3 or less. Furthermore, the dry thickness of the coating film is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more from the viewpoint of protecting the substrate, and is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less from the viewpoint of transparency. From the viewpoint of protecting the substrate, the surface hardness of the coating film is preferably 6B or more, more preferably HB or more, even more preferably H or more, and even more preferably 2H or more in pencil hardness. The upper limit can be, for example, 10H or less. From the viewpoint of good appearance, the arithmetic mean roughness of the coating film surface is preferably 50 μm or less, more preferably 10 μm or less, even more preferably 6 μm or less, and even more preferably 3 μm or less. The lower limit can be, for example, 0.3 μm or more. The specific puncture strength of the coating film cannot be generalized because it depends on the type of resin used and the coating thickness, but from the viewpoint of protecting the substrate, it is, for example, preferably 20 N / mm or more, more preferably 25 N / mm or more, and even more preferably 30 N / mm or more. There is no particular upper limit, but it can be, for example, 1000 N / mm or less. The haze value, surface hardness, arithmetic mean roughness of the surface, and specific puncture strength of the coating film can be measured by the methods described in the Examples below. [Example]

[0112] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Note that "normal pressure" refers to 101.3 kPa and "normal temperature" refers to 25°C.

[0113] [Average fiber diameter, average fiber length and average aspect ratio of anion-modified cellulose fibers and modified cellulose fibers] Deionized water or DMF is added to the cellulose fibers to be measured to prepare a dispersion with a content of 0.0001% by mass. The dispersion is dropped onto mica and dried to serve as an observation sample. An atomic force microscope (AFM) (Digital Instruments, Nanoscope II Tapping mode AFM; Nanosensors, Point Probe (NCH) probe) is used to measure the fiber height (height difference between where fibers are present and where fibers are absent) of the cellulose fibers in the observation sample. In this case, 100 cellulose fibers are extracted from a microscopic image in which the cellulose fibers can be seen, and the average fiber diameter is calculated from their fiber height. The average fiber length is calculated from the distance in the fiber direction. The average aspect ratio is calculated by dividing the average fiber length by the average fiber diameter. The height analyzed in the AFM image can be considered the fiber diameter.

[0114] [Average fiber diameter and average fiber length of raw cellulose fibers] Deionized water is added to the cellulose fibers to be measured to prepare a dispersion containing 0.01% by mass of cellulose. The dispersion is measured using a wet dispersion image analysis particle size distribution analyzer (manufactured by Jusco International, 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: 500 μm, image recognition mode: ghost, threshold: 8, analysis sample volume: 1 mL, and sampling: 15%. One hundred cellulose fibers are measured, and the average ISO fiber diameter and average ISO fiber length are calculated as the average fiber diameter and average fiber length, respectively.

[0115] [Solid content in dispersion] The measurement is performed using a halogen moisture meter (Shimadzu Corporation; product name "MOC-120H"), with 1 g of sample measured every 30 seconds at a constant temperature of 150°C, and the value when the mass loss is 0.1% or less of the initial amount of the sample is taken as the solid content.

[0116] [Anionic Group Content of Anion-Modified Cellulose Fibers and Modified Cellulose Fibers] A dry mass of 0.5 g of the cellulose fiber to be measured is placed in a beaker and mixed with deionized water or a 2:1 (volume ratio) methanol / water mixture to a total volume of 55 mL. 5 mL of 0.01 M aqueous sodium chloride solution is then added to prepare a dispersion. The dispersion is stirred until the cellulose fiber to be measured is fully dispersed. 0.1 M hydrochloric acid is added to the dispersion to adjust the pH to 2.5-3. Using an automatic titrator (manufactured by DKK-TOA Corporation, product name "AUT-701"), 0.05 M aqueous sodium hydroxide solution is added dropwise to the dispersion with a waiting time of 60 seconds, and the conductivity and pH values ​​are measured every minute. Measurements are continued until the pH reaches approximately 11, and a conductivity curve is obtained. The sodium hydroxide titration amount is determined from this conductivity curve, and the anionic group content of the cellulose fiber to be measured is calculated using the following formula: Anionic group content (mmol / g) = [Titer of aqueous sodium hydroxide solution (mL) × Concentration of aqueous sodium hydroxide solution (0.05 M)] / [Mass of cellulose fiber to be measured (0.5 g)]

[0117] [Average bond amount and introduction rate of modifying groups in modified cellulose fiber (A)] The average bond amount of the modifying group is determined by the following IR measurement method, and the average bond amount and introduction rate are calculated using the following formula. Specifically, the IR measurement involves measuring the infrared absorption spectrum of the dried modified cellulose fiber by the ATR method using an infrared absorption spectrometer (IR) (Nicolet 6700, manufactured by Thermo Fisher Scientific), and the average bond amount and introduction rate of the modifying group are calculated using formulas A and B. The following describes the case where the anionic group is a carboxy group, i.e., the case of oxidized cellulose fiber. The following "1720 cm" -1 The "peak intensity" is the peak intensity derived from the carbonyl group. In the case of an anionic group other than a carboxy group, the wave number value may be appropriately changed to calculate the average bond amount and introduction rate of the modifying group. <Formula A-1 (Ionic bond)> Average binding amount of modifying group (mmol / g) = a × (bc) ÷ b a: Carboxylic group content of oxidized cellulose fiber (mmol / g) b: 1720 cm of oxidized cellulose fiber -1Peak intensity of c: 1720 cm of modified cellulose fiber -1 Peak intensity of <Formula A-2 (in the case of an amide bond)> Average bond amount of modifying group (mmol / g) = de d: Carboxylic group content of oxidized cellulose fiber (mmol / g) e: Carboxylic group content of modified cellulose fiber (mmol / g) <Formula B> Modification group introduction rate (mol%) = 100 × f / g f: Average binding amount of the modification group (mmol / g) g: Carboxylic group content of oxidized cellulose fiber (mmol / g)

[0118] [Cellulose fiber (equivalent amount) in modified cellulose fiber (A)] The cellulose amount (equivalent amount) in a modified cellulose fiber is the amount of cellulose in the modified cellulose fiber excluding the modifying group. In the modified cellulose fiber of the present invention, the formula weight of the modifying group may be considerably larger (for example, than the molecular weight of glucose). Therefore, in this specification, when it is appropriate to explain the difference in formula weight of the modifying group without considering the difference, the amount of cellulose constituting the modified cellulose fiber (equivalent amount) is expressed rather than the amount of modified cellulose fiber. The cellulose fiber (equivalent amount) in the modified cellulose fiber is measured by the following method.

[0119] (1) When one type of "modifying compound" is added The amount of cellulose fiber (equivalent amount) is calculated by the following formula E. <Formula E> Amount of cellulose fiber (equivalent amount) (g) = mass of modified cellulose fiber (g) / [1 + molecular weight of modifying compound (g / mol) × bonding amount of modifying group (mmol / g) × 0.001] (2) When two or more types of "modifying compounds" are added The amount of cellulose fiber (equivalent amount) is calculated taking into consideration the molar ratio of each compound (that is, the molar ratio when the total molar amount of the compounds added is taken as 1).

[0120] In addition, when the bonding mode between the cellulose fiber and the modifying compound is an ionic bond, in the above formula, the "molecular weight of the modifying compound" refers to the "molecular weight of the entire modifying compound including the copolymer portion" when the modifying compound is a primary amine, secondary amine, or tertiary amine, and refers to "(molecular weight of the entire modifying compound including the copolymer portion) - (molecular weight of the anionic component)" when the compound having a modifying group is a quaternary ammonium compound or a phosphonium compound. On the other hand, when the bonding mode between the cellulose fiber and the modifying compound is an amide bond, in the above formula, if the modifying compound is a primary amine or a secondary amine, the "molecular weight of the modifying compound" is "(the molecular weight of the entire compound having the modifying group, including the copolymer portion) - 18".

[0121] [Amount and mass of modified groups introduced into modified cellulose fiber (B)] The amount of modified groups introduced into the resulting modified cellulose fiber (B) (molar substitution: MS) was calculated according to the Zeisel method, which is known as a method for analyzing the average number of moles of alkoxy groups added to cellulose ether, as described in Analytical Chemistry, Vol. 51, No. 13, 2172 (1979), "The Japanese Pharmacopoeia, 15th Edition (section on analytical methods for hydroxypropyl cellulose)" and the like. The procedure is as follows:

[0122] (i) 0.1 g of n-octadecane was added to a 200 mL measuring flask, and the flask was filled up to the mark with hexane to prepare an internal standard solution. (ii) 100 mg of the purified and dried modified cellulose fiber and 100 mg of adipic acid were precisely weighed into a 10 mL vial, and 2 mL of hydroiodic acid was added and the vial was sealed. (iii) The mixture in the vial was heated in a block heater at 160°C for 1 hour while being stirred with a stirrer tip. (iv) After heating, 3 mL of the internal standard solution and 3 mL of diethyl ether were sequentially poured into the vial, and the mixture was stirred at room temperature for 1 minute. (v) The upper layer (diethyl ether layer) of the mixture separated into two phases in the vial was analyzed by gas chromatography (Shimadzu Corporation, GC2010Plus) to quantify the amount of the etherifying agent. (vi) Separately, analysis was performed in the same manner as (i) to (v) above, using 5 mg, 10 mg, and 15 mg of the etherification agent used for modification instead of the modified cellulose fiber, and a calibration curve for the etherification agent was created.

[0123] The analysis conditions are as follows. Column: Agilent Technologies DB-5 (12 m, 0.2 mm x 0.33 μm) Column temperature: 100℃ → 10℃ / min → 280℃ (10min hold) Injector temperature: 300°C, detector temperature: 300°C, injection volume: 1 μL The mass (mass%) of the modified group introduced into the modified cellulose fiber was calculated from the prepared calibration curve and the detected amount of the etherification agent used.

[0124] Next, the molar substitution (MS) was calculated from the introduced mass of the obtained substituent using the following mathematical formulas (1) to (3). (When only one type of substituent is introduced) MS=(W / Mw) / ((100-W) / 162.14) (1) W: Mass of substituent introduced into modified cellulose (mass%) Mw: Molecular weight of the introduced etherification agent (g / mol) (When two types of substituents are introduced) MS1=(W1 / Mw1) / ((100-W1-W2) / 162.14) (2) MS2=(W2 / Mw2) / ((100-W1-W2) / 162.14) (3) MS1: Molar substitution of the first substituent MS2: Molar substitution of the second type of substituent W1: Mass of the first type of substituent introduced into the modified cellulose (mass%) W2: Mass of the second type of substituent introduced into the modified cellulose (mass%) Mw1: Molecular weight of the first etherification agent introduced (g / mol) Mw2: Molecular weight of the second etherification agent introduced (g / mol)

[0125] [Cellulose fiber (equivalent amount) in modified cellulose fiber (B)] (When only one type of substituent is introduced) Cellulose fiber (equivalent amount) (g) = mass of modified cellulose fiber (B) (g) × 162.14 / (162.14 + Mw1 × MS1) (When two types of substituents are introduced) Cellulose fiber (equivalent amount) (g) = mass of modified cellulose fiber (B) (g) × 162.14 / (162.14 + Mw1 × MS1 + Mw2 × MS2)

[0126] [Confirmation of crystalline structure in various cellulose fibers] The crystalline structure of various cellulose fibers such as modified cellulose fibers is confirmed by measurement under the following conditions using an X-ray diffractometer (MiniFlexII, manufactured by Rigaku Corporation). The measurement conditions were as follows: X-ray source: Cu / Kα-radiation, tube voltage: 30 kV, tube current: 15 mA, measurement range: diffraction angle 2θ = 5 to 45°, X-ray scan speed: 10° / min. The measurement sample was a cellulose fiber to be measured, with an area of ​​320 mm. 2 The cellulose is compressed into a pellet with a thickness of 1 mm. The degree of crystallinity of the cellulose type I crystal structure is calculated from the obtained X-ray diffraction intensity using the following formula C.

[0127] <Formula C> Cellulose type I crystallinity (%) = [(I 22.6 -I 18.5 ) / I 22.6 ] x 100 [In the formula, I 22.6 is the diffraction intensity of the lattice plane (002 plane) (diffraction angle 2θ = 22.6°) in X-ray diffraction, I 18.5 indicates the diffraction intensity of the amorphous portion (diffraction angle 2θ=18.5°).

[0128] On the other hand, if the crystallinity obtained by the above formula C is 35% or less, in order to improve calculation accuracy, it is preferable to calculate based on the following formula D, in accordance with the description on pages 199-200 of the "Wood Science Experiment Manual" (edited by the Japan Wood Research Society; published in April 2000). Therefore, when the crystallinity obtained by the above formula C is 35% or less, the value calculated based on the following formula D can be used as the crystallinity.

[0129] <Formula D> Cellulose type I crystallinity (%) = [Ac / (Ac+Aa)] x 100 (In the formula, Ac is the sum of the peak areas of the lattice planes (002 plane) (diffraction angle 2θ=22.6°), (011 plane) (diffraction angle 2θ=15.1°), and (0-11 plane) (diffraction angle 2θ=16.2°) in X-ray diffraction, and Aa is the peak area of ​​the amorphous portion (diffraction angle 2θ=18.5°). Each peak area is determined by fitting the obtained X-ray diffraction chart with a Gaussian function.)

[0130] [Preparation of Anion-Modified Cellulose Fibers] Preparation Example 1 Bleached coniferous kraft pulp (manufactured by Westfraser, trade name: Hinton) was used as the natural cellulose fiber. TEMPO was a commercially available product (manufactured by Aldrich, free radical, 98% by mass). Sodium hypochlorite was a commercially available product (manufactured by Wako Pure Chemical Industries, Ltd., 10.5% by mass aqueous solution). Sodium bromide was a commercially available product (manufactured by Wako Pure Chemical Industries, Ltd.).

[0131] First, 10 g of the bleached kraft pulp fiber was thoroughly stirred with 990 g of deionized water, and then 0.13 g of TEMPO, 1.3 g of sodium bromide, and 27 g of a 10.5% by mass sodium hypochlorite aqueous solution were added to the 10 g of pulp fiber in this order. Using an automatic titrator (manufactured by DKK-TOA Corporation, product name: AUT-701) for pH stat titration, 0.5 M aqueous sodium hydroxide was added dropwise to maintain the pH at 10.5. The reaction was carried out at a stirring speed of 200 rpm for 120 minutes (20°C), after which the addition of sodium hydroxide was stopped, yielding anion-modified cellulose fiber.

[0132] The resulting anion-modified cellulose fibers were neutralized with 0.01 M hydrochloric acid, thoroughly washed with deionized water until the conductivity of the filtrate measured with a compact electrical conductivity meter (HORIBA, Ltd., LAQUAtwin EC-33B) was 200 μs / cm or less, and then dehydrated. The anion-modified cellulose fibers had a carboxyl group content of 1.5 mmol / g, an average fiber diameter of 61 μm, and an average fiber length of 952 μm.

[0133] Preparation Example 2 A vial equipped with a magnetic stirrer and a stirring bar was charged with 7.2 g (bone dry mass) of the anion-modified cellulose fiber obtained in Preparation Example 1, and deionized water was added until the mass of the treatment solution reached 360 g. The treatment solution was stirred at 95°C for 24 hours to obtain anion-modified cellulose fiber. The anion-modified cellulose fiber had a carboxy group content of 1.3 mmol / g, an average fiber diameter of 40 μm, and an average fiber length of 93 μm.

[0134] Example 1 A beaker equipped with a magnetic stirrer and a stirring bar was charged with 1.40 g of the anion-modified cellulose fiber (29.3% solids by mass, 0.41 g cellulose fiber) finally obtained in Preparation Example 2 and 10 times the mass of DMF (14.0 g) and stirred for 30 minutes. The mixture was then centrifuged at 5°C and 10,000 × g for 1 minute. The insoluble residue was subjected to the same procedure again to obtain anion-modified cellulose fiber substituted with DMF. Subsequently, DMF was added to the insoluble residue so that the total amount, including the insoluble residue, was 40 g. The mixture was reacted at room temperature (25°C) for 30 minutes, and then subjected to five passes of dispersion treatment at 150 MPa using a high-pressure homogenizer (Yoshida Kikai Co., Ltd., trade name: Nanovaita L-ES) to obtain a DMF dispersion of finely divided anion-modified cellulose fiber (cellulose fiber concentration: 1%, total solids concentration: 1%). 2 g of the resulting dispersion of finely divided anion-modified cellulose fibers (i.e., 0.02 g of cellulose fibers) and 2 g of dipentaerythritol hexamethacrylate (Light Acrylate DPE-6A, manufactured by Kyoeisha Chemical Co., Ltd.) were mixed by stirring at 2000 rpm for 2 minutes using an automatic revolving mixer (Thinky Corporation, Awatori Rentaro). Subsequently, 0.06 g of 1-hydroxycyclohexyl phenyl ketone (Fujifilm Wako Pure Chemical Industries, Ltd.) as a curing agent was added, and the mixture was stirred at 2000 rpm for 1 minute using the automatic revolving mixer, followed by degassing at 2200 rpm for 1 minute, yielding a coating solution with a solids content of approximately 50%. The coating solution was obtained as a highly transparent liquid composition. The coating was applied to a nylon film (film thickness approximately 20 μm) using a bar coater to a thickness of approximately 20 μm, dried at 80°C and atmospheric pressure for 1 minute, and then irradiated twice with a UV irradiator (EYE GRAPHICS, EYE INVERTOR GRANDAGE (4 kW)) at 4 kW, a height of 150 mm, and a speed of 246 cm / min to obtain a coating film. The irradiance was approximately 24 mW / cm. 2 The irradiation dose was approximately 580 mJ / cm 2 It was.

[0135] Example 2 1.40 g of the anion-modified cellulose fiber obtained in Preparation Example 2 (solid content concentration 29.3% by mass, cellulose fiber amount 0.41 g) and 10 times the mass of methanol (14.0 g) were added to a beaker equipped with a magnetic stirrer and a stirring bar, and the mixture was stirred for 30 minutes. The mixture was then centrifuged at 5°C and 10,000 x g for 1 minute. The insoluble residue was subjected to the same procedure again to obtain 0.96 g of anion-modified cellulose fiber substituted with methanol (solid content concentration 41.8% by mass, cellulose fiber amount 0.40 g). To the resulting anion-modified cellulose fibers, EOPO monoamine (Jeffamine M2070, manufactured by Huntsman, USA, EO / PO (molar ratio) = 31 / 10) was added in an amount equivalent to 26 parts by mass per 100 parts by mass of anion-modified cellulose fibers, and 38.9 g of methanol was added. The mixture was reacted at room temperature (25°C) for 30 minutes, and then dispersed three times at 150 MPa using a high-pressure homogenizer (manufactured by Yoshida Kikai Co., Ltd., trade name: Nanovaita L-ES). A methanol dispersion of modified cellulose fibers in which EOPO monoamine was linked to the finely divided anion-modified cellulose fibers via ionic bonds (cellulose fiber concentration 1%, total solids concentration 1.26%) was obtained. 2 g of the resulting modified cellulose fiber dispersion (i.e., 0.02 g of cellulose fiber) and 2 g of dipentaerythritol hexamethacrylate (Kyoeisha Chemical Co., Ltd., Light Acrylate DPE-6A) were mixed using an automatic revolving mixer (Thinky Corporation, Awatori Rentaro) at 2000 rpm for 2 minutes. Next, 0.06 g of 1-hydroxycyclohexyl phenyl ketone (Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a curing agent, and the mixture was stirred at 2000 rpm for 1 minute using an automatic revolving mixer and degassed at 2200 rpm for 1 minute to obtain a coating solution with a solids content of approximately 50%. The coating solution was obtained as a highly transparent liquid composition. The coating was applied to a nylon film using a bar coater to a thickness of approximately 20 μm, dried at 80°C and atmospheric pressure for 1 minute, and then passed twice using a UV irradiator at 4 kW, a height of 150 mm, and a speed of 246 cm / min to obtain a coating film. The irradiance is approximately 24 mW / cm 2 The irradiation dose was approximately 580 mJ / cm 2 It was.

[0136] Example 3 A coating film was obtained in the same manner as in Example 2, except that the amount of EOPO monoamine added was changed to an amount equivalent to 78 parts by mass per 100 parts by mass of anion-modified cellulose fibers.

[0137] Example 4 Six grams of the modified cellulose fiber dispersion (i.e., 0.06 g of cellulose fiber) obtained in the same manner as in Example 3 was mixed with 2 g of dipentaerythritol hexamethacrylate (Light Acrylate DPE-6A, manufactured by Kyoeisha Chemical Co., Ltd.) at 2000 rpm for 2 minutes using an automatic revolving mixer (Thinky Corporation, Awatori Rentaro). Approximately 4 g of methanol was then removed using an evaporator. Next, 0.06 g of 1-hydroxycyclohexyl phenyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a curing agent, and the mixture was stirred at 2000 rpm for 2 minutes using an automatic revolving mixer and degassed at 2200 rpm for 1 minute, yielding a coating solution with a solids content of approximately 50%. The coating solution was obtained as a highly transparent liquid composition. The coating was applied to a nylon film using a bar coater to a thickness of approximately 20 μm, dried at 80°C and normal pressure for 1 minute, and then passed twice through a UV irradiator at 4 kW, a height of 150 mm, and a speed of 246 cm / min to obtain a coating film. The irradiance was approximately 24 mW / cm. 2 The irradiation dose was approximately 580 mJ / cm 2 It was.

[0138] Example 5 A coating film was obtained in the same manner as in Example 2, except that the amount of EOPO monoamine added was changed to an amount equivalent to 260 parts by mass per 100 parts by mass of anion-modified cellulose fibers.

[0139] Preparation Example 3 1.60 g of 6.4 mass% sodium hydroxide solution (NaOH 0.28 equivalents / AGU) was added to 1.50 g of bone-dried NBKP and mixed uniformly. Next, 2.00 g of butylene oxide (Wako Pure Chemical Industries, Ltd., 3 equivalents / AGU) was added as the first etherification agent, and the mixture was sealed and left to react at 50 ° C for 7 hours. After the reaction, the mixture was neutralized with acetic acid, thoroughly washed with water and acetone to remove impurities, and then vacuum dried overnight at 70 ° C to obtain a cellulose raw material (butylene oxide MS 0.23).

[0140] Next, 1.60 g of 6.4 mass% aqueous sodium hydroxide solution (NaOH 0.31 equivalents / AGU) was added to 1.50 g of the resulting cellulose raw material and mixed uniformly. Next, 0.95 g of o-methylphenyl glycidyl ether (o-cresyl glycidyl ether, o-CRGE) (Sigma-Aldrich, 0.7 equivalents / AGU) was added as a second etherification agent, and the mixture was sealed and left to react at 70 °C for 24 hours. After the reaction, the mixture was neutralized with acetic acid, thoroughly washed with water and acetone to remove impurities, and then vacuum dried overnight at 70 °C to obtain modified cellulose fibers (MS of o-methylphenyl glycidyl ether group 0.32). The average fiber diameter of the resulting modified cellulose was 20 μm and the average fiber length was 323 μm.

[0141] To 1.50 g of the resulting modified cellulose fiber, 0.98 g of hydrogen peroxide (45% aqueous solution), 1.24 g of sodium hydroxide, and 13.6 g of water were added, mixed uniformly, and then stirred at 98°C for 12 hours. The mixture was then thoroughly washed with water and acetone to remove impurities, and vacuum dried overnight at 70°C to obtain modified cellulose with a low aspect ratio. The resulting modified cellulose with a low aspect ratio had an average fiber diameter of 18 μm and an average fiber length of 107 μm.

[0142] 0.71 g of the obtained low aspect ratio modified cellulose (0.5 g as the amount of cellulose only without substituents) was added to 49.5 g of DMF and stirred for 30 minutes in a beaker equipped with a magnetic stirrer and a stirring bar. After that, the mixture was treated five times at 150 MPa at room temperature in a high-pressure homogenizer (manufactured by Yoshida Kikai Co., Ltd., product name: Nanovaita L-ES) to obtain a finely modified cellulose dispersion in which the finely modified cellulose was dispersed in DMF (cellulose fiber concentration 1%, total solids concentration 1.42%).

[0143] Example 6 2 g of the dispersion of finely modified cellulose fiber obtained in Preparation Example 3 (i.e., 0.02 g of cellulose fiber) and 2 g of dipentaerythritol hexamethacrylate (Kyoeisha Chemical Co., Ltd., Light Acrylate DPE-6A) were mixed by stirring at 2000 rpm for 2 minutes using an automatic revolutionary mixer (Thinky Corporation, Awatori Rentaro). Next, 0.06 g of 1-hydroxycyclohexyl phenyl ketone (Fujifilm Wako Pure Chemical Industries, Ltd.) as a curing agent was added, and the mixture was stirred at 2000 rpm for 2 minutes using an automatic revolutionary mixer and degassed at 2200 rpm for 1 minute to obtain a coating solution with a solids content of approximately 50%. The coating solution was obtained as a highly transparent liquid composition. The coating was applied to a nylon film using a bar coater to a thickness of approximately 20 μm, dried at 80°C and atmospheric pressure for 2 minutes, and then passed twice through a UV irradiator at 4 kW, a height of 150 mm, and a speed of 246 cm / min to obtain a coating film. The irradiance was approximately 24 mW / cm. 2 The irradiation dose was approximately 580 mJ / cm 2 It was.

[0144] Comparative Example 1 A coating film was obtained in the same manner as in Example 2, except that the anion-modified cellulose fiber obtained in Preparation Example 1 was used and the amount of EOPO monoamine added was changed to 78 parts by mass per 100 parts by mass of anion-modified cellulose fiber.

[0145] Comparative Example 2 A coating film was obtained in the same manner as in Example 2, except that the anion-modified cellulose fiber obtained in Preparation Example 1 was used and the amount of EOPO monoamine added was changed to 300 parts by mass per 100 parts by mass of anion-modified cellulose fiber.

[0146] Comparative Example 3 A coating film was obtained in the same manner as in Example 4, except that the anion-modified cellulose fiber obtained in Preparation Example 1 was used and the amount of EOPO monoamine added was changed to 300 parts by mass per 100 parts by mass of anion-modified cellulose fiber.

[0147] Example 7 A methanol dispersion of modified cellulose fibers in which EOPO monoamine was linked via ionic bonds (cellulose fiber concentration: 0.94% by mass, total solids concentration: 1.67% by mass) was obtained by the same procedure as in Example 2, except that the amount of EOPO monoamine used was changed to 78 parts by mass per 100 parts by mass of anion-modified cellulose fibers. 3.0 g of the resulting modified cellulose fiber dispersion (i.e., 0.03 g of cellulose fiber) was mixed with 5.0 g of aqueous acrylic varnish (ROCK Water Varnish H75-0150, manufactured by ROCK Paint Co., Ltd.) and stirred overnight with a magnetic stirrer to obtain a coating solution with a solids content of approximately 30% and containing 3 parts by mass of cellulose fiber per 100 parts by mass of the resin components in the varnish. The coating solution was obtained as a highly transparent liquid composition. The cellulose dispersion varnish solution was applied to a PET film using a bar coater to a thickness of 150 μm and then dried in a vacuum at 80°C for 2 hours to obtain a coating film.

[0148] Example 8 Except for changing the varnish used to an aqueous urethane varnish (clear aqueous urethane varnish, manufactured by Asahipen Co., Ltd.), the same procedure as in Example 7 was carried out to obtain a coating solution with a solids content of approximately 30%, containing 3 parts by mass of cellulose fiber per 100 parts by mass of the resin component in the varnish. The coating solution was obtained as a highly transparent liquid composition. The cellulose dispersion varnish solution was applied to a PET film using a bar coater to a thickness of 150 μm, and then dried in a vacuum at 80°C for 2 hours to obtain a coating film.

[0149] Preparation Example 4 Anion-modified cellulose fibers were obtained by carrying out the same reaction and purification procedures as in Preparation Example 1, except that the amount of 10.5 mass% sodium hypochlorite aqueous solution was changed to 24 g. The anion-modified cellulose fibers had a carboxy group content of 1.3 mmol / g, an average fiber diameter of 55 μm, and an average fiber length of 961 μm.

[0150] Comparative Example 4 A coating film was obtained in the same manner as in Example 7, except that the anion-modified cellulose fibers obtained in Preparation Example 4 were used.

[0151] Comparative Example 5 A coating film was obtained in the same manner as in Example 8, except that the anion-modified cellulose fibers obtained in Preparation Example 4 were used.

[0152] Example 9 Coated paper was obtained by the same procedure as in Example 7, except that the coating target was changed to photo paper (glossy paper) for inkjet printers (KJ-G14B4-10N, manufactured by Kokuyo S&T Co., Ltd.).

[0153] Example 10 Coated paper was obtained by the same procedure as in Example 8, except that the object to be coated was changed to the same photo paper for inkjet printers as in Example 9.

[0154] Comparative Example 6 Coated paper was obtained by the same procedure as in Comparative Example 4, except that the object to be coated was changed to the same photo paper for inkjet printers as in Example 9.

[0155] Comparative Example 7 A coated paper was obtained by carrying out the same operation as in Comparative Example 5, except that the object to be coated was changed to the same photo paper for inkjet printers as in Example 9.

[0156] Example 11 A coated paper was obtained by the same procedure as in Example 9, except that EOPO monoamine was not used.

[0157] Example 12 A coated paper was obtained by the same procedure as in Example 10, except that EOPO monoamine was not used.

[0158] Comparative Example 8 The same procedure as in Comparative Example 6 was carried out except that EOPO monoamine was not used. However, due to poor dispersion, a methanol dispersion of the modified cellulose fiber could not be obtained, and it could not be blended with the aqueous acrylic varnish, so coated paper could not be obtained.

[0159] Comparative Example 9 The same procedure as in Comparative Example 7 was carried out except that EOPO monoamine was not used. However, due to poor dispersion, a methanol dispersion of modified cellulose fiber could not be obtained, and it could not be blended into the aqueous urethane varnish, so coated paper could not be obtained.

[0160] [Evaluation of Coatability] The appearance of the coating film surface after curing was visually inspected and rated as follows, and the results are shown in Tables 1 and 3 to 5. A: The coating surface is smooth with almost no visible roughness. B: The coating surface has a rough texture that can be visually confirmed. C: There are visible cracks and wrinkles on the surface of the coating.

[0161] [Transparency evaluation] The haze value of the cured coating film was measured using a haze meter (HM-150 model, manufactured by Murakami Color Research Laboratory Co., Ltd.). The lower the haze value, the more transparent the film. The results are shown in Tables 1 and 3. The transparency of the coating film on the coated paper was visually inspected and rated as follows. The results are shown in Tables 4 and 5. A: The paper surface covered with the coating film is clearly visible through the coating film. B: The coated paper surface appears blurred through the coating. C: The paper surface covered with the coating cannot be seen at all through the coating.

[0162] [Evaluation of surface hardness] The substrate used in the above Examples 1 to 6 and Comparative Examples 1 to 3 was changed from the nylon film to a PET film (Cosmoshine 100A4300, manufactured by Panac Corporation), and coating films were prepared for each. The hardness was evaluated using a pencil hardness tester (BEVS 1301 Pencil Hardness Tester / 750M) in accordance with JIS K5600-5-4. The results are shown in Table 1. The surface hardness was evaluated in the same manner for the films obtained in Examples 7 and 8 and Comparative Examples 4 and 5. The results are shown in Table 3.

[0163] [Table 1]

[0164] [Measurement of arithmetic mean roughness of film] The arithmetic mean roughness of the film was measured using a laser microscope (Keyence VK-9710) under the following conditions: objective lens: 10x, light intensity: 3%, brightness: 1548, Z pitch: 0.5 μm. The arithmetic mean roughness was measured at five points using the built-in image processing software, and the average value was used. The results are shown in Tables 2 to 5.

[0165] [Table 2]

[0166] [Table 3]

[0167] [Evaluation of water absorption rate] The coated papers obtained in Examples 9 to 12 and Comparative Examples 6 and 7 were cut into 3 cm x 3 cm pieces, and five drops of deionized water were placed on the surface. After leaving the pieces to stand for 5 minutes, the water on the surface was wiped off, and the mass of the coated paper pieces was measured. A lower water absorption rate indicates higher water resistance and superior suitability as a coating film. The results are shown in Tables 4 and 5. The water absorption rate was calculated using the following formula: The water absorption rate of uncoated glossy paper was 12.4%. Water absorption rate (%) = (mass of paper piece after wiping with water - mass of paper piece before dripping water) / mass of dripped water × 100

[0168] [Evaluation of specific puncture strength of coating layer] The coated papers obtained in Examples 9 to 12 and Comparative Examples 6 and 7 were tested using the following method to evaluate the specific puncture strength of the coating layer. A higher specific puncture strength indicates better suitability as a coating film. The results are shown in Tables 4 and 5. The puncture strength of the coated paper was measured in a thermostatic chamber at 25°C using a Shimadzu Autograph Precision Universal Tester (AGS-10kNX) by conducting a five-point puncture test for each sample in accordance with JIS Z1717:2019 General Rules for Plastic Films for Food Packaging (see below). From the puncture strength obtained, the specific puncture strength of the coating layer was calculated using the following formula (I). Formula (I) Specific puncture strength (N / mm) = puncture strength (N) / (thickness of coated paper (mm) - thickness of coated base paper (mm)) *The thickness of the coated paper and the coated base paper was measured at five points using a thickness meter, and the average value was used. JIS Z 1717:2019 General rules for plastic films for food packaging a) The test piece is fixed in a jig and a semicircular needle with a diameter of 1.0 mm and a tip radius of 0.5 mm is pierced at a test speed of 50 mm / min, and the maximum force (N) until the needle penetrates is measured. b) The number of test pieces shall be at least five, and shall be taken so as to be averaged across the entire width of the product. c) If the test result depends on whether the film is penetrated from either side, perform the test on each side. Report values ​​to one decimal place.

[0169] [Table 4]

[0170] [Table 5]

[0171] As can be seen from Tables 1, 3 to 5, the transparent coating agents of the Examples all had excellent coatability and could be used as coating films without any problems in terms of transparency and surface hardness. Furthermore, comparisons of Example 3 and Comparative Example 1, Example 5 and Comparative Example 2, Example 7 and Comparative Example 4, Example 8 and Comparative Example 5, Example 9 and Comparative Example 6, and Example 10 and Comparative Example 7 in Tables 2, 3, and 4 reveal that the surface roughness of the substrates coated with the transparent coating agents of the Examples was low, and smooth coating films could be formed. The coating films of Examples 11 and 12 in Table 5 were also smooth and could be suitably used as coating films. As can be seen from Tables 4 and 5, the transparent coating agents of the examples have no problems with water resistance when used as varnishes on paper. Among these, Examples 11 and 12, which used unmodified anion-modified cellulose fiber, were particularly excellent in puncture strength and water resistance. [Industrial Applicability]

[0172] The transparent coating agent of the present invention can be suitably used as a transparent coating agent for transparent materials such as glass, optical displays, and eyeglass lenses, as a clear coating for the surface of automobile bodies, and as an overcoat agent (varnish) for packaging materials such as paper materials, wood materials, and plastic films, and labels.

Claims

1. A transparent coating agent containing a resin precursor or resin and modified cellulose fibers, wherein the modified cellulose fibers have an average fiber length of less than 150 nm and an average aspect ratio of 1 or more and 150 or less, and are one or more types selected from the group consisting of modified cellulose fibers (A) and modified cellulose fibers (B) below. Modified cellulose fiber (A): Cellulose fiber containing ionic groups, or modified cellulose fiber in which modifying groups are bonded to the ionic groups. Modified cellulose fiber (B): Modified cellulose fiber in which a modifying group is bonded to the hydroxyl group of the cellulose fiber.

2. 2. The transparent coating agent according to claim 1, wherein the ionic group of the modified cellulose fiber is a carboxy group.

3. 3. The transparent coating agent according to claim 1, wherein the modifying group contains at least one selected from the group consisting of (a) a hydrocarbon group, (b) a silicone chain, and (c) an alkylene oxide chain.

4. 4. The transparent coating agent according to claim 1, wherein the resin is an acrylic resin.

5. 5. The transparent coating agent according to claim 1, wherein the haze value of the film coated with the transparent coating agent is 50 or less.

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