Composition, molded article, structure, electrolyte membrane for solid polymer fuel cell, and method for producing molded article

Abstract

Provided is a composition comprising fibrous cellulose, said composition having a low water absorption rate.　The present invention provides a composition comprising fibrous cellulose, wherein an infrared absorption spectrum obtained by analyzing the composition using infrared spectroscopy has an absorption peak derived from a urethane bond.

Description

Composition, molded article, structure, electrolyte membrane for polymer electrolyte fuel cell, and method for manufacturing the molded article

[0001] The present invention relates to a composition, a molded article, a structure, an electrolyte membrane for a polymer electrolyte fuel cell, and a method for manufacturing the molded article.

[0002] In recent years, due to the need for alternatives to petroleum resources and growing environmental awareness, materials made from renewable natural fibers have attracted attention. Among natural fibers, fibrous cellulose, particularly fibrous cellulose with a fiber diameter of 10 μm to 50 μm, and wood-derived fibrous cellulose (pulp), have been widely used, mainly in paper products.

[0003] As a type of fibrous cellulose, fine fibrous cellulose with a fiber diameter of 1 μm or less is also known, and composite sheets containing fine fibrous cellulose and resins or oily components have been developed.

[0004] For example, Patent Document 1 discloses a sheet having a fiber layer and a coating layer on the fiber layer, wherein the fiber layer contains 60% by mass or more of fine fibrous cellulose with a fiber diameter of 1000 nm or less, the haze of the sheet is 20% or less, and the water contact angle of the surface of the sheet on the coating layer side after 30 seconds of dropping distilled water is 70 degrees or more.

[0005] Japanese Patent Publication No. 2021-46658

[0006] However, conventional sheets containing fibrous cellulose have low water resistance and high water absorption. Furthermore, as disclosed in Patent Document 1, it has been proposed to provide a resin layer on the surface of the sheet to improve water resistance, but such sheets have the problem that the fibrous cellulose is exposed at the edges, resulting in insufficient water resistance.

[0007] According to the present invention, a composition containing fibrous cellulose is provided, wherein the infrared absorption spectrum obtained by analyzing the composition by infrared spectroscopy has an absorption peak originating from urethane bonds.

[0008] Through diligent research, the inventors discovered that by giving a composition containing fibrous cellulose an absorption peak derived from urethane bonds, a composition with low water absorption can be obtained, leading to the completion of the present invention.

[0009] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other. [1] A composition containing fibrous cellulose, wherein the infrared absorption spectrum obtained by analyzing the composition by infrared spectroscopy has an absorption peak derived from a urethane bond. [2] The composition according to [1], wherein the fibrous cellulose comprises a urethaneized product of fibrous cellulose. [3] The composition according to [2], wherein the urethaneized product comprises a urethane bond, and the urethane bond is derived from the hydroxyl group of the fibrous cellulose and the isocyanate group of the isocyanate compound. [4] The composition according to [3], wherein the isocyanate compound comprises a polyisocyanate compound, and the urethaneized product comprises a structure in which the fibrous cellulose is crosslinked by a crosslinked portion containing the urethane bond. [5] The composition according to any one of [1] to [4], comprising a water-soluble resin. [6] The composition according to any one of [1] to [5], wherein the fibrous cellulose has an ionic functional group. A composition according to any one of [7] [1] to [6], which is for use as an electrolyte membrane for a polymer electrolyte fuel cell. A molded article of a composition according to any one of [8] [1] to [7]. A molded article according to [9] [8], wherein the water absorption rate when the molded article is immersed in water is 150% or less. A molded article according to

[10] [8] or [9], wherein the haze is less than 4%. A molded article according to any one of [8] to

[10] , wherein the tensile modulus is 5.0 GPa or more. A molded article according to any one of [8] to

[11] , wherein the tensile strength is 65.0 MPa or more. A molded article according to any one of

[13] , [8] to

[12] , wherein YI1 is the yellowness of the molded article measured in accordance with JIS K7373:2006, YI2 is the yellowness of the molded article after heating it at 160°C for 6 hours, and T μm is the thickness of the molded article, and the value of ΔYI per 25 μm of the molded article calculated by the following formula (2) is 10.0 or less. ΔYI = (YI2 - YI1) / T × 25 (2) A structure comprising a molded article according to any one of

[14] , [8] to

[13] .An electrolyte membrane for a solid polymer fuel cell comprising at least one selected from the group consisting of the composition described in

[15] [1] to [6] and a molded body of the composition. A method for producing a molded body, the production method includes a water dispersion preparation step and a molding step. In the water dispersion preparation step, a water dispersion containing fibrous cellulose, an isocyanate compound, a surfactant, and water is prepared. In the molding step, at least a part of water is removed from the water dispersion and molded to obtain a molded body containing a urethanized product of the fibrous cellulose formed by the reaction of the fibrous cellulose and the isocyanate compound.

[0010] According to the present invention, a composition containing fibrous cellulose and having a low water absorption rate can be provided. Further, the molded body and the structure of the composition according to an embodiment of the present invention contain fibrous cellulose and have a low water absorption rate. Furthermore, according to the method for producing a molded body according to an embodiment of the present invention, a molded body containing fibrous cellulose and having a low water absorption rate is provided.

[0011] FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and the pH of a slurry containing fibrous cellulose having a phosphonooxy group. FIG. 2 shows the infrared absorption spectra of the sheets of Example 2 and Comparative Example 3 measured by the ATR method using a Fourier transform infrared spectrophotometer (FT-IR).

[0012] Hereinafter, embodiments of the present invention will be described. Each feature shown in the following embodiments can be combined with each other. Further, the invention is established independently for each feature. Furthermore, among the following embodiments, elements not defined in the claims are optional elements and can be omitted. At the end of the numerical values disclosed in the following description, an arbitrary number (for example, one or two) of "0" may be added. For example, one or two "zeros" may be added after "1.4" to make it "1.40" or "1.400".

[0013] 1. Composition The composition according to the present invention contains fibrous cellulose.

[0014] 1.1 Fibrous Cellulose The fiber diameter of fibrous cellulose is not particularly limited, but fibrous cellulose according to one embodiment of the present invention can have an average fiber diameter of 2 nm to 50 μm. The average fiber diameter of fibrous cellulose can be, for example, 2 nm, 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 500 nm, 1000 nm, 2 μm, 3 μm, 5 μm, 10 μm, 30 μm, or 50 μm, and may be within the range of any two of the values ​​exemplified herein.

[0015] The fibrous cellulose according to one embodiment of the present invention may include fine fibrous cellulose. The average fiber diameter of the fine fibrous cellulose can be, for example, 1000 nm or less. The average fiber diameter of the fine fibrous cellulose is preferably, for example, 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, even more preferably 2 nm or more and 50 nm or less, and particularly preferably 2 nm or more and 10 nm or less. The average fiber diameter of the fine fibrous cellulose can be, for example, 2 nm, 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 500 nm, and 1000 nm, and may be within the range of any two of the values ​​exemplified herein. The composition according to one embodiment of the present invention may have a fine fibrous cellulose content of 10% by mass or more relative to 100% by mass of fibrous cellulose in the composition, preferably exceeding 20% ​​by mass, and more preferably exceeding 30% by mass. The content of fine fibrous cellulose relative to 100% by mass of fibrous cellulose in the composition is, for example, 10, 15, 21, 25, 30, 31, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0016] The fibrous cellulose according to one embodiment of the present invention may also include fibrous cellulose having an average fiber diameter exceeding 3 μm (3000 nm). In the composition according to one embodiment of the present invention, the content of microfibrillar cellulose having an average fiber diameter exceeding 3 μm with respect to 100% by mass of the fibrous cellulose in the composition can be 90% by mass or less. The content of fibrous cellulose having an average fiber diameter exceeding 3 μm with respect to 100% by mass of the fibrous cellulose in the composition is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90% by mass, and may be within the range between any two of the numerical values exemplified here. By setting the content of microfibrillar cellulose and / or fibrous cellulose having an average fiber diameter exceeding 3 μm in the fibrous cellulose within the above numerical range, in addition to reducing the water absorption rate of the molded body of the composition, optical properties (for example, haze), and mechanical properties (tensile modulus and tensile strength) can be improved.

[0017] The fiber diameter of the fibrous cellulose can be measured, for example, using a scanning electron microscope (SEM), a transmission electron microscope (TEM), an atomic force microscope (AFM), or the like. The fiber diameter of the fibrous cellulose can also be measured using a fiber image analysis device (manufactured by Valmet Co., Ltd., Valmet FS5), a Kajaani fiber length measuring instrument (manufactured by Kajaani Automation Co., Ltd., FS-200 type), or an optical microscope according to the width of the fiber. For example, the fiber diameter of fibrous cellulose having a fiber diameter exceeding 1000 nm can be measured using a fiber image analysis device, a Kajaani fiber length measuring instrument, or an optical microscope. When using an electron microscope, it is measured as follows. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast onto a carbon film-coated grid subjected to a hydrophilic treatment to obtain a sample for TEM observation. When including wide fibers, the SEM image of the surface cast on glass may be observed. Next, observation is performed on the electron microscope image at any magnification of 1000 times, 5000 times, 10000 times, or 50000 times according to the width of the fiber to be observed. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions (1) and (2).

[0018] Condition (1) A straight line X is drawn at any point in the observed image, and 20 or more fibers intersect with this line X. Condition (2) A straight line Y is drawn perpendicular to the line X in the same image, and 20 or more fibers intersect with this line Y.

[0019] For observation images that satisfy the above conditions (1) and (2), the width of the fibers intersecting with lines X and Y is visually read. In this way, at least three sets of observation images of surface portions that do not overlap are obtained. Next, for each image, the width of the fibers intersecting with lines X and Y is read. This allows for the reading of at least 20 × 2 × 3 = 120 fiber diameters. The average of the read fiber diameters is then taken as the number-average fiber diameter of the fibrous cellulose.

[0020] The fiber length of fibrous cellulose is not particularly limited, but for example, it can be 0.1 μm or more and 30 mm or less, preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and even more preferably 0.1 μm or more and 600 μm or less. By keeping the fiber length within the above range, the destruction of the crystalline region of the fibrous cellulose can be suppressed. The fiber length of fibrous cellulose can be determined, for example, by image analysis using TEM, SEM, AFM, or optical microscope.

[0021] It is preferable that the fibrous cellulose has a type I crystalline structure. Here, the presence of a type I crystalline structure in fibrous cellulose can be identified in the diffraction profile obtained from a wide-angle X-ray diffraction photograph using graphite-monochromatized CuKα (λ = 1.5418 Å). Specifically, it can be identified by the presence of typical peaks at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°. The proportion of type I crystalline structure in the fibrous cellulose is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. The degree of crystallinity can be determined by measuring the X-ray diffraction profile and analyzing its pattern using a conventional method (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0022] The axial ratio (fiber length / fiber diameter) of fibrous cellulose is not particularly limited, but is preferably 50 to 10,000, and more preferably 100 to 1,000. Setting the axial ratio above the lower limit makes it easier to form molded articles containing fibrous cellulose. Setting the axial ratio below the upper limit is preferable in that it makes handling easier, such as dilution, when handling fibrous cellulose as a dispersion.

[0023] Fibrous cellulose may have ionic functional groups. The ionic substituent may include, for example, either an anionic group or a cationic group, or both, and it is particularly preferable that the ionic substituent be an anionic group. Furthermore, the ionic substituent is preferably a group introduced into the fibrous cellulose via an ester bond or an ether bond, and more preferably a group introduced into the fibrous cellulose via an ester bond. In this case, the ester bond is preferably formed by the dehydration condensation of the fibrous cellulose and the compound that will become the ionic substituent. In this specification, the ester group can be a structure produced by the dehydration condensation of a hydroxyl group with various acid groups such as acids (e.g., oxo acids such as organic acids and inorganic acids).

[0024] Examples of anionic groups as ionic groups include phosphorus oxoacid groups or substituents derived from phosphorus oxoacid groups (sometimes simply referred to as phosphorus oxoacid groups), carboxyl groups or substituents derived from carboxyl groups (sometimes simply referred to as carboxyl groups), sulfur oxoacid groups or substituents derived from sulfur oxoacid groups (sometimes simply referred to as sulfur oxoacid groups), xantate groups or substituents derived from xantate groups (sometimes simply referred to as xantate groups), phosphone groups or substituents derived from phosphone groups, phosphine groups or substituents derived from phosphine groups, sulfone groups or substituents derived from sulfone groups, carboxyalkyl groups, and the like. In particular, the anionic group is preferably at least one selected from the group consisting of a phosphorus oxoacid group, a substituent derived from a phosphorus oxoacid group, a carboxyl group, a sulfur oxoacid group, a substituent derived from a sulfur oxoacid group, a carboxymethyl group, a carboxyethyl group, and a sulfone group; more preferably at least one selected from the group consisting of a phosphorus oxoacid group, a substituent derived from a phosphorus oxoacid group, a carboxyl group, a sulfur oxoacid group, and a substituent derived from a sulfur oxoacid group; and particularly preferably a phosphorus oxoacid group. By introducing a phosphorus oxoacid group as the anionic group, for example, the dispersibility of the fibrous cellulose can be further improved even under alkaline or acidic conditions, and as a result, it becomes easier to obtain a high-strength and highly transparent sheet. Examples of cationic groups as ionic groups include ammonium groups, phosphonium groups, and sulfonium groups. Among these, the cationic group is preferably an ammonium group. The fibrous cellulose according to one embodiment of the present invention may also exclude those containing a methyl group, a hydroxypropyl group, or a hydroxyethyl group.

[0025] In this embodiment, the fibrous cellulose preferably has a phosphorus oxoacid group. In this specification, the "phosphorus oxoacid group" includes substituents derived from the phosphorus oxoacid group. Furthermore, the "counterion" of the phosphorus oxoacid group includes a dissociable proton. As a counterion, for example, the β of the substituent represented by formula (1) described later. ｂ＋ (Proton (H) ＋)(or a monovalent or higher cation composed of an organic or inorganic substance). As described later, the composition according to one embodiment of the present invention can be used for an electrolyte membrane for a solid polymer fuel cell. In particular, from the viewpoint of improving proton conductivity when used as an electrolyte membrane for a solid polymer fuel cell, the counter ion is H ＋ and at least one selected from the group consisting of ions of an alkali metal (such as sodium, potassium, or lithium, etc.) is preferably included, and H ＋ and / or sodium ion (Na ＋ ) is more preferably included. From the viewpoints of improving the proton conductivity of the electrolyte membrane for a solid polymer fuel cell, reducing the temperature dependence of the proton conductivity, and reducing the activation energy of proton conduction, it is even more preferable that the counter ion contains H ＋ .

[0026] The phosphoacid group or the substituent derived from the phosphoacid group is, for example, a substituent represented by the following formula (1). A plurality of substituents represented by the following formula (1) may be introduced into each fibrous cellulose. In this case, the plurality of substituents represented by the following formula (1) introduced may be the same or different from each other. The substituent represented by the following formula (1) is preferably bonded directly to the carbon atoms at the 2-position, 3-position, and / or 6-position of cellulose through "-O-".

[0027]

[0028] In formula (1), a, b, and n are natural numbers, and m is an arbitrary number (provided that a = b × m). At least one of the n α and α' is O － and the rest are R or OR. Note that all of each α and α' may be O － . The n α may all be the same or different from each other. β ｂ＋ is a monovalent or higher cation composed of an organic or inorganic substance.

[0029] R is a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an unsaturated cyclic hydrocarbon group, an aromatic group, or a derivative thereof. In formula (1), n ​​is preferably 1.

[0030] Examples of saturated linear hydrocarbon groups include, but are not limited to, methyl, ethyl, n-propyl, or n-butyl groups. Examples of saturated branched hydrocarbon groups include, but are not limited to, i-propyl or t-butyl groups. Examples of saturated cyclic hydrocarbon groups include, but are not limited to, cyclopentyl or cyclohexyl groups. Examples of unsaturated linear hydrocarbon groups include, but are not limited to, vinyl or allyl groups. Examples of unsaturated branched hydrocarbon groups include, but are not limited to, i-propenyl or 3-butenyl groups. Examples of unsaturated cyclic hydrocarbon groups include, but are not limited to, cyclopentenyl or cyclohexenyl groups. Examples of aromatic groups include, but are not limited to, phenyl or naphthyl groups.

[0031] Furthermore, the derivative group in R is a functional group obtained by adding or substituting at least one functional group selected from carboxyl groups, carboxylate groups (-COO-), hydroxyl groups, amino groups, and ammonium groups to the main chain or side chain of the various hydrocarbon groups mentioned above, but is not particularly limited. Also, the number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphorus oxoacid group can be set within an appropriate range, which facilitates penetration into the fiber raw material and can also increase the yield of fibrous cellulose. Note that when there are multiple Rs in formula (1) or when multiple substituents represented by formula (1) are introduced into fibrous cellulose, the multiple Rs may be the same or different.

[0032] β ｂ＋β is a cation with one or more valencies composed of organic or inorganic substances. Examples of cations with one or more valencies composed of organic substances include organic onium ions. Examples of organic onium ions include organic ammonium ions and organic onium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic onium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of cations with one or more valencies composed of inorganic substances include alkali metal ions such as sodium, potassium, or lithium, divalent metal ions such as calcium or magnesium, hydrogen ions, and ammonium ions. Note that β is included in formula (1). ｂ＋ If multiple β atoms exist, or if multiple substituents represented by formula (1) are introduced into fibrous cellulose, then multiple β atoms exist. ｂ＋ These may be the same or different. As a monovalent or greater cation consisting of organic or inorganic material, β ｂ＋ Sodium or potassium ions are preferred, but are not particularly limited, as they do not easily yellow when the fiber raw material containing them is heated and are readily available for industrial use. From the viewpoint of improving the proton conductivity of electrolyte membranes for polymer electrolyte fuel cells, β ｂ＋ H ＋ Preferably, it contains at least one selected from the group consisting of alkali metal ions, H ＋ and / or sodium ions (Na ＋ It is more preferable to include β, from the viewpoint of improving the proton conductivity of the electrolyte membrane for polymer electrolyte fuel cells, reducing the temperature dependence of the proton conductivity, and reducing the activation energy of proton conduction. ｂ＋ H ＋ It is even more preferable to include

[0033] More specifically, a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group is a phosphate group (-PO ３ H ２ ), phosphate group salt, phosphite group (phosphonic acid group) (-PO ２ H ２Examples include phosphate groups and phosphonic acid groups (phosphonic acid groups). Furthermore, substituents derived from phosphate groups or phosphate groups may be groups formed by condensation of phosphate groups (e.g., pyrophosphate groups), groups formed by condensation of phosphonic acid (e.g., polyphosphonic acid groups), phosphate ester groups (e.g., monomethyl phosphate groups, polyoxyethylene alkyl phosphate groups), alkylphosphonic acid groups (e.g., methylphosphonic acid groups), etc.

[0034] The presence of each ionic functional group in fibrous cellulose can be confirmed by measuring the infrared absorption spectrum using FT-IR, although this depends on the amount of each ionic functional group. For example, the presence or absence of a phosphate group can be determined at 1230 cm⁻¹. －１ This can be confirmed based on the absorption of the phosphate group based on P=O in the vicinity.

[0035] Furthermore, the sulfur oxoacid group (sulfur oxoacid group or substituent derived from a sulfur oxoacid group) can be, for example, a substituent represented by the following formula (2). Multiple substituents represented by the following formula (2) may be introduced into each fibrous cellulose. In this case, the substituents represented by the following formula (2) that are introduced may be the same or different.

[0036]

[0037] In equation (2), b and n are natural numbers, p is 0 or 1, and m is any number (where 1 = b × m). Note that if n is 2 or greater, the multiple p values ​​may be the same number or different numbers. In equation (2), β ｂ＋ This is β in equation (1). ｂ＋ The same can be done. Furthermore, when multiple substituents represented by formula (2) are introduced into fibrous cellulose, multiple β ｂ＋ These may be the same or different. As a monovalent or greater cation consisting of organic or inorganic material, β ｂ＋ Sodium or potassium ions are preferred because they do not easily yellow when the fiber raw material containing them is heated and are readily available for industrial use, but the material is not particularly limited.

[0038] The amount of ionic substituent introduced per gram of fibrous cellulose can be 0.10 to 3.65 mmol / g or less, and more preferably 0.10 to 1.50 mmol or 0.10 to 0.9 mmol / g. The amount of ionic substituent per gram of fibrous cellulose can be, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.80, 2.00, 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.40, 3.60, or 3.65 mmol / g, and may be within the range of any two of the values ​​exemplified here. Here, the denominator in the unit mmol / g is the counterion of the ionic substituent being a hydrogen ion (H ＋ This shows the mass of fibrous cellulose when ).

[0039] A fibrous cellulose according to one embodiment of the present invention has phosphorus oxoacid groups. The amount of phosphorus oxoacid groups introduced per gram of fibrous cellulose can be 0.10 to 3.65 mmol / g or less, and more preferably 0.10 to 1.50 mmol or 0.10 to 0.9 mmol / g. The amount of phosphorus oxoacid groups per gram of fibrous cellulose is, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.80, 2.00, 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.40, 3.60, and 3.65 mmol / g, and may be within the range of any two of the values ​​exemplified here. From the viewpoint of improving the proton conductivity of electrolyte membranes for polymer electrolyte fuel cells, the amount of phosphorus oxoacid groups introduced into fibrous cellulose is preferably, for example, 0.50 mmol / g or more and 2.50 mmol / g or less per 1 g (mass) of fibrous cellulose, more preferably 0.80 mmol / g or more, even more preferably 1.00 mmol / g or more, particularly preferably 1.20 mmol / g or more, more preferably 2.30 mmol / g or less, and even more preferably 2.10 mmol / g or less. From the viewpoint of improving the proton conductivity of electrolyte membranes for polymer electrolyte fuel cells, it is preferable that the amount of phosphorus oxoacid groups introduced is above the lower limit, and from the viewpoint of improving the strength, rigidity, and dimensional stability of electrolyte membranes for polymer electrolyte fuel cells, it is preferable that the amount of phosphorus oxoacid groups introduced is below the upper limit.

[0040] By setting the content of ionic functional groups such as phosphorus oxoacid groups above the above lower limit, the fineness of the fiber raw material can be facilitated, and the stability of fibrous cellulose can be enhanced. Furthermore, according to one embodiment of the present invention, by setting the content of ionic functional groups such as phosphorus oxoacid groups within the above numerical range, particularly below the upper limit, the increase in hydrophilicity can be suppressed by keeping the amount of ionic functional groups below a certain level, thereby reducing water absorption. In addition, for example, by removing some of the substituents such as phosphate groups and replacing them with hydroxyl groups, the water resistance and strength of the composition, molded article, and structure can be further improved. This is presumed to be because urethane bonds derived from the hydroxyl groups of fibrous cellulose and the isocyanate groups of the isocyanate compound are more easily formed.

[0041] The fibrous cellulose according to one embodiment of the present invention can also have its ionic functional group content adjusted by manufacturing it using a manufacturing method that includes a substituent removal step, as described later. For example, by the substituent removal step, the fibrous cellulose according to one embodiment of the present invention can have an ionic substituent content of 0.01 mmol or more and less than 0.50 mmol / g, and 0.01 mmol or more and 0.10 mmol or less per gram. The amount of ionic substituents per gram of fibrous cellulose can be, for example, 0.01, 0.02, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50 mmol / g, and may be within the range of any two of the values ​​exemplified here.

[0042] The amount of ionic substituents introduced into fibrous cellulose can be measured, for example, by neutralization titration, after the cellulose fibers have been subjected to micronization treatment. In the neutralization titration method, the amount introduced is determined by measuring the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the slurry containing the obtained fibrous cellulose.

[0043] As an example, let's explain how to determine the amount of phosphorus oxoacid groups. Figure 1 is a graph showing the relationship between the amount of NaOH added to a slurry containing fibrous cellulose with phosphorus oxoacid groups and pH. The amount of phosphorus oxoacid groups introduced into the fibrous cellulose can be measured, for example, as follows. First, ion-exchanged water is added to the target cellulose fibers to prepare a slurry with a solid content of 0.2% by mass. This slurry is processed four times at a pressure of 200 MPa using a wet atomizing device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion (slurry) containing fibrous cellulose. Then, the fibrous cellulose dispersion is treated with a strongly acidic ion exchange resin. Next, the change in pH is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in the upper part of Figure 1. In the titration curve shown in the upper part of Figure 1, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of Figure 1, the increment (derivative value) (1 / mol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, two points are observed in the curve plotting the measured pH against the amount of alkali added, where the increment (the derivative of pH with respect to the amount of alkali added) is maximum. Of these, the first maximum increment obtained after starting to add alkali is called the first endpoint, and the next maximum increment obtained is called the second endpoint. The amount of alkali required from the start of titration to the first endpoint is equal to the amount of the first dissociated acid of the fibrous cellulose contained in the slurry used for titration. The amount of alkali required from the first endpoint to the second endpoint is equal to the amount of the second dissociated acid of the fibrous cellulose contained in the slurry used for titration. The amount of alkali required from the start of titration to the second endpoint is equal to the total amount of dissociated acid of the fibrous cellulose contained in the slurry used for titration. The value obtained by dividing the amount of alkali required from the start of titration to the first endpoint by the solid content (g) of the slurry being titrated is the amount of phosphorus oxoacid group introduced (mol / g). Note that when simply referring to the amount of phosphorus oxoacid group introduced (or the amount of phosphorus oxoacid group), it refers to the amount of the first dissociated acid. In Figure 1, the region from the start of titration to the first endpoint is called the first region, and the region from the first endpoint to the second endpoint is called the second region.For example, if the phosphorus oxoacid group is a phosphate group and this phosphate group undergoes condensation, the amount of weakly acidic group in the phosphorus oxoacid group (also referred to as the amount of the second dissociated acid in this specification) appears to decrease, and the amount of alkali required in the second region becomes less than the amount of alkali required in the first region. On the other hand, the amount of strongly acidic group in the phosphorus oxoacid group (also referred to as the amount of the first dissociated acid in this specification) is equal to the amount of phosphorus atoms, regardless of whether condensation occurs or not. Also, if the phosphorus oxoacid group is a phosphorous acid group, there is no weakly acidic group in the phosphorus oxoacid group, so the amount of alkali required in the second region becomes less, or in some cases, the amount of alkali required in the second region becomes zero. In this case, there is only one point on the titration curve where the pH increment is maximum.

[0044] The amount of phosphorus oxoacid groups introduced (moles / g) mentioned above represents the amount of phosphorus oxoacid groups present in acid-type fibrous cellulose, since the denominator represents the mass of acid-type fibrous cellulose (hereinafter referred to as phosphorus oxoacid group amount (acid-type)). On the other hand, if the counterion of the phosphorus oxoacid group is substituted with an arbitrary cation C such that it is equivalent in charge, the amount of phosphorus oxoacid groups present in fibrous cellulose with cation C as the counterion can be determined by converting the denominator to the mass of fibrous cellulose when cation C is the counterion (hereinafter referred to as phosphorus oxoacid group amount (C-type)). That is, it is calculated using the following formula. Phosphorus oxoacid group amount (C type) = Phosphorus oxoacid group amount (acid type) / {1 + (W - 1) × P / 1000} P [mol / g]: Total amount of anions derived from phosphorus oxoacid groups in fibrous cellulose (total amount of dissociated acids from phosphorus oxoacid groups) W: Formula weight per unit of cation C (for example, Na is 23, Al is 9)

[0045] In measuring the amount of ionic substituents by titration, if the amount of sodium hydroxide aqueous solution added is too large or the titration interval is too short, accurate values ​​may not be obtained, resulting in a lower-than-actual amount of ionic substituents. Appropriate titration volumes and intervals include, for example, titrating 10 to 50 μL of 0.1 N sodium hydroxide aqueous solution every 5 to 30 seconds.

[0046] The amount (content) of anionic functional groups such as phosphate groups introduced into fibrous cellulose can be controlled by adjusting the manufacturing process and conditions for the fibrous cellulose manufacturing method, particularly by adjusting the presence and conditions of the ionic substituent introduction step, washing step, alkali treatment step (neutralization step), defibration treatment step, and substituent removal step.

[0047] 1.2 Method for Producing Fibrous Cellulose The method for producing fibrous cellulose according to the present invention is not particularly limited. A method for producing fibrous cellulose according to one embodiment of the present invention may include an ionic substituent introduction step, a washing step, an alkali treatment step (neutralization step), and a defibration treatment step. Furthermore, a method for producing fibrous cellulose according to one embodiment of the present invention may include a substituent removal step, a post-substituent removal washing step, and a post-substituent removal dispersion step.

[0048] The fibrous cellulose raw material for obtaining fibrous cellulose according to one embodiment of the present invention is not particularly limited, but it is preferable to use pulp because it is readily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), oxygen-bleached kraft pulp (OKP), and other chemical pulps. Other examples include semi-chemical pulp (SCP), chemiground wood pulp (CGP), and mechanical pulp (GP), but are not particularly limited. Examples of non-wood pulps include cotton pulps such as cotton linters and cotton lint, non-wood pulps such as hemp, straw, and bagasse, and cellulose, chitin, and chitosan isolated from sea squirts and seaweed, but are not particularly limited. Examples of deinked pulps include deinked pulps made from recycled paper, but are not particularly limited. One type of pulp may be used alone, or two or more types may be used in mixture. Among the above pulps, wood pulp containing cellulose and deinked pulp are preferred in terms of availability. Among wood pulps, chemical pulp is preferred because it has a high cellulose ratio, resulting in a high yield of fibrous cellulose during fiber refinement (defibration), and because the decomposition of cellulose in the pulp is small, allowing for the production of long-fiber fibrous cellulose with a high axial ratio. Among these, kraft pulp and sulfite pulp are the most preferred selections. Sheets containing long-fiber fibrous cellulose with a high axial ratio tend to yield high strength.

[0049] 1.2.1 Ionic Substituent Introduction Process Examples of ionic substituent introduction processes include phosphorus oxoacid group introduction, carboxyl group introduction, sulfur oxoacid group introduction, xantate group introduction, phosphone group or phosphine group introduction, sulfone group introduction, and cationic group introduction. Each introduction process can employ known methods, such as those described in Japanese Patent Application Publication No. 2024-92412. The phosphorus oxoacid group introduction process will be described below.

[0050] <Phosphorus Oxoacid Group Introduction Step> When obtaining cellulose fibers having ionic substituents, it is preferable to include an ionic substituent introduction step before the defibration treatment step. An example of an ionic substituent introduction step is a phosphorus oxoacid group introduction step. The phosphorus oxoacid group introduction step is a step in which at least one compound (hereinafter also referred to as "compound A") selected from compounds that can introduce phosphorus oxoacid groups by reacting with hydroxyl groups present in the cellulose-containing fiber raw material is reacted with the cellulose-containing fiber raw material. This step results in obtaining cellulose fibers having phosphorus oxoacid groups.

[0051] In the phosphorus oxoacid group introduction step, the reaction of the cellulose-containing fiber raw material with compound A may be carried out in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as "compound B"). Alternatively, the reaction of the cellulose-containing fiber raw material with compound A may be carried out in the absence of compound B.

[0052] One example of a method for reacting compound A with compound B to a fiber raw material is to mix compound A and compound B with the fiber raw material in a dry, wet, or slurry state. Of these, it is preferable to use a fiber raw material in a dry or wet state, and particularly preferable to use a fiber raw material in a dry state, due to the high uniformity of the reaction. The form of the fiber raw material is not particularly limited, but for example, it is preferably in the form of cotton or a thin sheet. Compounds A and B can be added to the fiber raw material in the form of powder, a solution dissolved in a solvent, or after being heated above the melting point and melted. Of these, it is preferable to add them in the form of a solution dissolved in a solvent, particularly an aqueous solution, due to the high uniformity of the reaction. Compounds A and B may be added to the fiber raw material simultaneously, separately, or as a mixture. The method of adding compounds A and B is not particularly limited, but if compounds A and B are in solution form, the fiber raw material may be immersed in the solution and then removed, or the solution may be added dropwise to the fiber raw material. Alternatively, the required amounts of compound A and compound B may be added to the fiber raw material, or excess amounts of compound A and compound B may be added to the fiber raw material, and then the excess compound A and compound B may be removed by pressing or filtration.

[0053] Compound A can be any compound having a phosphorus atom and capable of forming an ester bond with cellulose, such as phosphoric acid or its salts, phosphorous acid or its salts, dehydrated condensed phosphoric acid or its salts, or phosphoric anhydride (phosphorus pentoxide), but is not particularly limited. As phosphoric acid, various purities can be used, for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. As phosphorous acid, 99% phosphorous acid (phosphonic acid) can be used. Dehydrated condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid through a dehydration reaction, and examples include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphites, and dehydrated condensed phosphates include lithium salts, sodium salts, potassium salts, and ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid, and these can be neutralized to various degrees. Of these, phosphoric acid, sodium phosphoric acid, potassium phosphoric acid, ammonium phosphoric acid, or phosphorous acid, sodium phosphorous acid, potassium phosphorous acid, or ammonium phosphorous acid are preferred from the viewpoint of having high efficiency in introducing phosphate groups, easily improving the defibration efficiency in the defibration process described later, being low cost, and being easily applicable industrially. Phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, or phosphorous acid or sodium phosphorous acid are more preferred.

[0054] The amount of compound A added to the fiber raw material is not particularly limited, but for example, when the amount of compound A added is converted to the amount of phosphorus atoms, it is preferable that the amount of phosphorus atoms added to the fiber raw material (oven-dry mass) be 0.5% by mass or more and 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 30% by mass or less. By keeping the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fibrous cellulose can be further improved. On the other hand, by keeping the amount of phosphorus atoms added to the fiber raw material below the above upper limit, it is possible to balance the effect of improving yield with cost.

[0055] Compound B is at least one selected from urea and its derivatives, as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea. From the viewpoint of improving the uniformity of the reaction, it is preferable to use compound B as an aqueous solution. Furthermore, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

[0056] The amount of compound B added to the fiber raw material (absolutely dry mass) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and even more preferably 100% by mass or more and 350% by mass or less.

[0057] In the reaction of cellulose-containing fiber raw materials with compound A, in addition to compound B, other substances such as amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, and dimethylacetamide. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, triethylamine is known to act as a particularly good reaction catalyst.

[0058] In the phosphorus oxoacid group introduction step, it is preferable to add or mix compound A or the like to the fiber raw material and then subject the fiber raw material to heat treatment. The heat treatment temperature is preferably selected to efficiently introduce phosphorus oxoacid groups while suppressing thermal decomposition and hydrolysis reactions of the fibers. The heat treatment temperature is preferably, for example, 50°C to 300°C, more preferably 100°C to 250°C, and even more preferably 130°C to 200°C. Furthermore, various heat transfer devices can be used for the heat treatment, such as agitation dryers, rotary dryers, disc dryers, roll-type heaters, plate-type heaters, fluidized bed dryers, band-type dryers, filtration dryers, vibrating fluidized bed dryers, airflow dryers, vacuum dryers, infrared heaters, far-infrared heaters, microwave heaters, and high-frequency dryers.

[0059] In the heat treatment, for example, a method can be employed in which compound A is added to a thin sheet-like fiber raw material by impregnation or other methods, and then heated, or a method can be employed in which the fiber raw material and compound A are kneaded or stirred while heating. This makes it possible to suppress uneven concentration of compound A in the fiber raw material and to introduce phosphorus oxoacid groups more uniformly to the surface of the cellulose fibers contained in the fiber raw material. This is thought to be because, as water molecules move to the surface of the fiber raw material during drying, dissolved compound A is attracted to the water molecules by surface tension and similarly moves to the surface of the fiber raw material (i.e., uneven concentration of compound A is created), and this can be suppressed.

[0060] Furthermore, the heating device used for the heat treatment is preferably one that can constantly discharge, for example, the moisture held in the slurry and the moisture generated by the dehydration condensation (phosphate esterification) reaction between compound A and hydroxyl groups contained in cellulose, etc., in the fiber raw material, to the outside of the device system. Examples of such heating devices include a forced-air oven. By constantly discharging moisture from the device system, it is possible to suppress the hydrolysis reaction of phosphate ester bonds, which is the reverse reaction of phosphate esterification, as well as the acid hydrolysis of sugar chains in the fibers. As a result, it becomes possible to obtain fibrous cellulose with a high axial ratio.

[0061] The heating time is preferably between 1 second and 300 minutes, more preferably between 1 second and 1000 seconds, and even more preferably between 10 seconds and 800 seconds, after substantially all moisture has been removed from the fiber raw material. In this embodiment, by setting the heating temperature and heating time within an appropriate range, the amount of phosphorus oxoacid group introduced can be kept within a preferred range.

[0062] The phosphorus oxoacid group introduction process only needs to be performed at least once, but it can also be repeated two or more times. By performing the phosphorus oxoacid group introduction process two or more times, a large number of phosphorus oxoacid groups can be introduced into the fiber raw material.

[0063] The amount of phosphorus oxoacid groups introduced into the fiber raw material can be adjusted so that the phosphorus oxoacid group content falls within the numerical range described above.

[0064] <Carboxyloid Group Introduction Step> The ionic substituent introduction step may include a carboxyloid group introduction step. The carboxyloid group introduction step is carried out by treating the cellulose-containing fiber raw material with an oxidation treatment such as ozone oxidation, oxidation by the Fenton method, or TEMPO oxidation treatment, or with a compound having a carboxylic acid-derived group or a derivative thereof, or with an acid anhydride or a derivative thereof of a compound having a carboxylic acid-derived group.

[0065] Compounds having a carboxylic acid-derived group are not particularly limited, but examples include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. Furthermore, derivatives of compounds having a carboxylic acid-derived group are not particularly limited, but examples include imidides of acid anhydrides of compounds having a carboxyl group, and derivatives of acid anhydrides of compounds having a carboxyl group. Imidides of acid anhydrides of compounds having a carboxyl group are not particularly limited, but examples include imidides of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

[0066] Acid anhydrides of compounds having a carboxylic acid-derived group are not particularly limited, but examples include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Furthermore, derivatives of acid anhydrides of compounds having a carboxylic acid-derived group are not particularly limited, but examples include acid anhydrides of compounds having a carboxyl group, such as dimethyl maleic anhydride, diethyl maleic anhydride, and diphenyl maleic anhydride, in which at least some of the hydrogen atoms are substituted with substituents such as alkyl groups and phenyl groups.

[0067] In the carboxyl group introduction step, when performing TEMPO oxidation treatment, it is preferable to carry out the treatment under conditions where the pH is between 6 and 8. Such treatment is also called neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment can be carried out, for example, by adding pulp as the fiber raw material, a nitroxy radical such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst, and sodium hypochlorite as a sacrificial reagent to a sodium phosphate buffer (pH = 6.8). Furthermore, by including sodium chlorite, the aldehyde generated during the oxidation process can be efficiently oxidized to the carboxyl group. Alternatively, the TEMPO oxidation treatment may be carried out under conditions where the pH is between 10 and 11. Such treatment is also called alkaline TEMPO oxidation treatment. Alkaline TEMPO oxidation treatment can be carried out, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as the fiber raw material.

[0068] <Sulfone Group Introduction Step> The ionic substituent introduction step may include a sulfone group introduction step. In the sulfone group introduction step, a hydroxyl group present in the cellulose-containing fiber raw material reacts with a sulfur oxoacid to obtain cellulose fibers having sulfone groups (sulfone group introduced fibers).

[0069] In the sulfone group introduction step, instead of compound A in the <phosphorus oxoacid group introduction step> described above, at least one compound (hereinafter also referred to as "compound C") selected from compounds that can introduce sulfone groups by reacting with hydroxyl groups present in the cellulose-containing fiber raw material is used. Compound C can be any compound having a sulfur atom and capable of forming an ester bond with cellulose, and examples include sulfuric acid or its salts, sulfite or its salts, and sulfuric acid amide, but is not particularly limited. Sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. As sulfite, 5% sulfurous acid water can be used. As sulfates or sulfites, lithium salts, sodium salts, potassium salts, and ammonium salts of sulfates or sulfites can be used, and these can be neutralized to various degrees. As sulfuric acid amide, sulfamic acid can be used. In the sulfone group introduction step, it is preferable to use compound B in the <phosphorus oxoacid group introduction step> described above in the same manner.

[0070] In the sulfone group introduction step, it is preferable to mix the cellulose raw material with an aqueous solution containing sulfur oxoacid and urea and / or a urea derivative, and then heat-treat the cellulose raw material. The heat treatment temperature is preferably selected to efficiently introduce sulfone groups while suppressing thermal decomposition and hydrolysis reactions of the fibers. The heat treatment temperature is preferably 100°C or higher and 200°C or lower. In the heat treatment step, it is preferable to heat until substantially all moisture is removed.

[0071] <Oxidation step with chlorine-based oxidizing agent (second carboxyl group introduction step)> The ionic substituent introduction step may include an oxidation step with a chlorine-based oxidizing agent. In the oxidation step with a chlorine-based oxidizing agent, a carboxyl group is introduced into the fiber raw material by adding the chlorine-based oxidizing agent to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out the reaction.

[0072] Examples of chlorine-based oxidizing agents include hypochlorous acid, hypochlorite, chlorous acid, chlorite, chloric acid, chlorate, perchloric acid, perchlorate, and chlorine dioxide. From the standpoint of substituent introduction efficiency, and consequently defibration efficiency, cost, and ease of handling, sodium hypochlorite, sodium chlorite, and chlorine dioxide are preferred as chlorine-based oxidizing agents. When adding a chlorine-based oxidizing agent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be dissolved in a suitable solvent before being added.

[0073] <Xantate Group Introduction Step> The manufacturing process of fibrous cellulose may include a xantate group introduction step as an ionic substituent introduction step. The xantate group introduction step involves substituting the hydroxyl groups in the cellulose-containing fiber raw material with xantate groups represented by the following formula to obtain cellulose fibers having xantate groups (xantate group-introduced fibers). -OCS － M ＋ Here, M ＋ is at least one selected from hydrogen ions, monovalent metal ions, ammonium ions, aliphatic or aromatic ammonium ions.

[0074] In the xantate group introduction process, first, the fiber raw material containing the cellulose is treated with an alkaline solution to obtain alkaline cellulose. Examples of alkaline solutions include aqueous alkali metal hydroxide solutions and alkaline earth metal hydroxide solutions. Among these, the alkaline solution is preferably an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide, and is particularly preferably an aqueous sodium hydroxide solution. The alkali metal hydroxide concentration in the aqueous alkali metal hydroxide solution is preferably 4% by mass or more and 9% by mass or less. By setting the alkali metal hydroxide concentration above the lower limit, mercellation of cellulose can be sufficiently advanced, the amount of by-products generated during subsequent xantate formation can be reduced, and as a result, the yield of xantate group-introduced fibers can be increased. This allows the defibration treatment described later to be carried out more effectively. Furthermore, by setting the alkali metal hydroxide concentration below the upper limit, mercellation can be advanced while suppressing the penetration of the aqueous alkali metal hydroxide solution into the crystalline region of cellulose, so that the cellulose type I crystalline structure is more easily maintained, and the yield of fibrous cellulose can be further increased.

[0075] It is preferable to remove as much of the aqueous solution as possible from the alkali cellulose obtained by the above alkali treatment by solid-liquid separation. This reduces the water content during the subsequent xantate treatment and promotes the reaction. As for the solid-liquid separation method, general dehydration methods such as centrifugation or filtration can be used. It is preferable that the concentration of alkali metal hydroxide in the alkali cellulose after solid-liquid separation is 3% by mass or more and 8% by mass or less of the total mass of the alkali cellulose after solid-liquid separation.

[0076] In the xantate group introduction process, an alkali treatment is followed by a xantate treatment process. In the xantate treatment process, carbon disulfide (CS) is added to the alkali cellulose. ２ ) reacts to form (-O-Na ＋ ) base (-OCS － Na ＋) A xantate group-introduced fiber is obtained using this group. In the above, the metal ions introduced into alkali cellulose are, representatively, Na ＋ As described above, similar reactions proceed with other alkali metal ions.

[0077] <Phosphozone or phosphine group introduction step (phosphoalkylation step)> The ionic substituent introduction step may include a phosphozone or phosphine group introduction step (phosphoalkylation step). In the phosphoalkylation step, a compound having a reactive group and a phospho group or phosphine group (compound E) is used as an essential component. Ａ ), by adding an alkaline compound, compound B selected from the aforementioned urea and its derivatives as an optional component, to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out a reaction, a phosphone group or phosphine group is introduced into the fiber raw material.

[0078] Examples of reactive groups include alkyl halides, vinyl groups, and epoxy groups (glycidyl groups). Compound E Ａ Examples include vinylphosphonic acid, phenylvinylphosphonic acid, and phenylvinylphosphinic acid. Compound E is chosen from the standpoint of substituent introduction efficiency, and consequently defibrillation efficiency, cost, and ease of handling. Ａ It is preferable that the compound is vinylphosphonic acid. Furthermore, it is also preferable to use compound B from the <phosphorus oxoacid group introduction step> described above as an optional component, and the amount added is also preferably as described above.

[0079] Compound E Ａ When adding the reagent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be added after being dissolved in a suitable solvent. It is preferable that the fiber raw material be alkali-cellulosed beforehand or alkali-cellulosed simultaneously with the reaction. The method of alkali-cellulosed treatment is as described above.

[0080] <Sulfone group introduction step (sulfoalkylation step) (second sulfone group introduction step)> The ionic substituent introduction step may include a sulfone group introduction step (sulfoalkylation step). In sulfoalkylation, a compound having a reactive group and a sulfone group (compound E) is used as an essential component. Ｂ ) and compound B, selected as an optional component from an alkaline compound, the aforementioned urea and its derivatives, are added to a hydroxyl-containing fiber raw material in a wet or dry state, and a reaction is carried out to introduce sulfone groups into the fiber raw material.

[0081] Examples of reactive groups include alkyl halides, vinyl groups, and epoxy groups (glycidyl groups). Compound E Ｂ Examples include sodium 2-chloroethanesulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, and 2-acrylamido-2-methylpropanesulfonic acid. Among these, compound E is considered to have the efficiency of substituent introduction, and consequently the efficiency of defibration, cost, and ease of handling. Ｂ It is preferable that this is sodium vinyl sulfonate. Furthermore, it is also preferable to use compound B from the <phosphorus oxoacid group introduction step> described above as an optional component, and the amount added is also preferably as described above.

[0082] Compound E Ｂ When adding the reagent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be added after being dissolved in a suitable solvent. It is preferable that the fiber raw material be alkali-cellulosed beforehand or alkali-cellulosed simultaneously with the reaction. The method of alkali-cellulosed treatment is as described above.

[0083] <Carboxyalkylation step (third carboxyl group introduction step)> The ionic substituent introduction step may include a carboxyalkylation step. An essential component is a compound having a reactive group and a carboxyl group (compound E Ｃ ), by adding an alkaline compound, compound B selected from the aforementioned urea and its derivatives as an optional component, to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out a reaction, a carboxyl group is introduced into the fiber raw material.

[0084] Examples of reactive groups include alkyl halides, vinyl groups, and epoxy groups (glycidyl groups). Compound E Ｃ From the viewpoint of substituent introduction efficiency, and consequently defibration efficiency, cost, and ease of handling, monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, 3-chloropropionic acid, sodium 2-chloropropionate, and sodium 3-chloropropionate are preferred. Furthermore, as an optional component, compound B from the <phosphorus oxoacid group introduction step> described above may also be used in the same manner.

[0085] Compound E Ｃ When adding the reagent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be added after being dissolved in a suitable solvent. It is preferable that the fiber raw material be alkali-cellulosed beforehand or alkali-cellulosed simultaneously with the reaction. The method of alkali-cellulosed treatment is as described above.

[0086] The amount of each ionic substituent introduced into the fiber raw material can be adjusted so that the content of the ionic substituent falls within the numerical range described above.

[0087] <Washing Process> In the process of obtaining cellulose fibers having ionic substituents, a washing process may be performed on the ionic substituent-introduced fibers as needed. The washing process is carried out, for example, by washing the ionic substituent-introduced fibers with water or an organic solvent. Furthermore, the washing process may be performed after each of the processes described later, and the number of washing cycles performed in each washing process is not particularly limited.

[0088] <Alkali Treatment Process (Neutralization Process)> In the process of obtaining cellulose fibers having ionic substituents, an alkali treatment process may be provided between the ionic substituent introduction process and the micronization process. The alkali treatment method is not particularly limited, but one example is immersing the ionic substituent-introduced fibers in an alkaline solution.

[0089] The alkali compound contained in the alkaline solution is not particularly limited and may be an inorganic alkali compound or an organic alkali compound. In this embodiment, it is preferable to use sodium hydroxide or potassium hydroxide as the alkali compound due to its high versatility. The solvent contained in the alkaline solution may be either water or an organic solvent. In particular, the solvent contained in the alkaline solution is preferably water or a polar solvent including a polar organic solvent such as alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferred due to its high versatility.

[0090] The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably, for example, 5°C to 80°C, and more preferably 10°C to 60°C. The immersion time of the ionic substituent-introduced fiber in the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably, for example, 5 minutes to 30 minutes, and more preferably 10 minutes to 20 minutes. The amount of alkaline solution used in the alkaline treatment is not particularly limited, but is preferably, for example, 100% by mass to 100,000% by mass, and more preferably 1,000% by mass to 10,000% by mass, relative to the absolute dry mass of the ionic substituent-introduced fiber.

[0091] To reduce the amount of alkaline solution used in the alkaline treatment process, the ionic substituent-introduced fibers may be washed with water or an organic solvent after the ionic substituent introduction process and before the alkaline treatment process. After the alkaline treatment process and before the micronization process, it is preferable to wash the alkaline-treated ionic substituent-introduced fibers with water or an organic solvent to improve handling.

[0092] <Acid Treatment Step> In the step of obtaining cellulose fibers having ionic substituents, an acid treatment step may be provided between the ionic substituent introduction step and the micronization treatment step. For example, the ionic substituent introduction step, acid treatment, alkali treatment, and micronization treatment may be performed in this order. The concentration of the acidic solution used is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic solution used is not particularly limited, but is preferably 0 to 4, and more preferably 1 to 3. Examples of acids that can be included in the acidic solution include inorganic acids, sulfonic acids, carboxylic acids, etc. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, boric acid, etc. Examples of sulfonic acids include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, etc. Examples of carboxylic acids include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Among these, hydrochloric acid or sulfuric acid is particularly preferred.

[0093] <Fibrillation Process> By fibrillating the fiber raw material or ionic group-introduced fiber in the fibrillation process, fibrous cellulose, particularly fine fibrous cellulose, can be obtained. The fibrillation process is also called the micronization process. In the fibrillation process, for example, a fibrillation processing device can be used. The fibrillation processing device is not particularly limited, but for example, a high-speed fibrillator, grinder (stone mill type grinder), high-pressure homogenizer or ultra-high-pressure homogenizer, high-pressure impact grinder, ball mill, bead mill, disc type refiner, conical refiner, twin-screw kneader, vibrating mill, homomixer under high-speed rotation, ultrasonic disperser, or beater can be used. Among the above fibrillation processing devices, it is more preferable to use a high-speed fibrillator, high-pressure homogenizer, or ultra-high-pressure homogenizer, which have less influence from the grinding media and less risk of contamination.

[0094] In the defibration process, it is preferable to dilute, for example, the fiber raw material or ionic group-introduced fiber with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and organic solvents such as polar organic solvents can be used. The polar organic solvent is not particularly limited, but preferred examples include alcohols, polyhydric alcohols, ketones, ethers, esters, and aprotic polar solvents. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, and glycerin. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, and propylene glycol monomethyl ether. Examples of esters include ethyl acetate and butyl acetate. Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidinone (NMP).

[0095] The solid content concentration of fibrous cellulose during the defibration process can be set as appropriate. Furthermore, the slurry obtained by dispersing ionic group-introduced fibers in a dispersion medium may contain solid components other than ionic group-introduced fibers, such as hydrogen-bonding urea.

[0096] <Substituent Removal Process> A method for producing fibrous cellulose may include a substituent removal process in which at least a portion of substituents are removed from fibrous cellulose having substituents. In this specification, the process of removing at least a portion of substituents from fibrous cellulose obtained in the above-described process is also referred to as a substituent removal process.

[0097] Examples of substituent removal processes include heat treatment, enzymatic treatment, acid treatment, and alkali treatment of the substituted fibrous cellulose. These may be performed individually or in combination. Among these, the substituent removal process is preferably a heat treatment or an enzymatic treatment. By going through the above treatment process, at least a portion of the substituents can be removed from the substituted fibrous cellulose, and fibrous cellulose with a substituent amount of, for example, less than 0.5 mmol / g can be obtained.

[0098] The substituent removal process is preferably carried out in slurry form. Specifically, the substituent removal process is preferably a process of heat treatment, enzymatic treatment, acid treatment, alkali treatment, etc., of a slurry containing substituent-containing fibrous cellulose. By carrying out the substituent removal process in slurry form, it is possible to prevent the formation of coloring substances caused by heating during substituent removal, as well as the residue of added or generated acids, alkalis, salts, etc. This makes it possible to suppress the coloring of the fibrous cellulose. Furthermore, if a treatment to remove salts derived from the substituents removed after substituent removal is carried out, it is possible to improve the efficiency of salt removal.

[0099] When performing substituent removal treatment on a slurry containing fibrous cellulose having substituents, the concentration of fibrous cellulose in the slurry is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more. Furthermore, the concentration of fibrous cellulose in the slurry is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. By keeping the concentration of fibrous cellulose in the slurry within the above range, the substituent removal treatment can be performed more efficiently. In addition, by keeping the concentration of fibrous cellulose in the slurry within the above range, it is possible to prevent the residue of coloring substances generated by heating during the substituent removal treatment, as well as added or generated acids, alkalis, salts, etc. This makes it possible to suppress the coloring of the resulting fibrous cellulose. Furthermore, when performing a salt removal treatment for salts derived from substituents after the substituent removal treatment, it is also possible to improve the efficiency of salt removal.

[0100] When the substituent removal process is a process of heat-treating fibrous cellulose having substituents, the heating temperature in the heat treatment process is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. Furthermore, the heating temperature in the heat treatment process is preferably 250°C or lower, more preferably 230°C or lower, and even more preferably 200°C or lower. In particular, when the substituents on the fibrous cellulose subjected to the substituent removal process are phosphorus oxoacid groups or sulfone groups, the heating temperature in the heat treatment process is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher.

[0101] If the substituent removal process is a heat treatment process, the heating equipment that can be used in the heat treatment process is not particularly limited, but may include hot air heaters, steam heaters, electric heaters, hydrothermal heaters, thermal heaters, infrared heaters, far-infrared heaters, microwave heaters, high-frequency heaters, stirring dryers, rotary dryers, disc dryers, roll-type heaters, plate-type heaters, fluidized bed dryers, band-type dryers, filtration dryers, vibrating fluidized bed dryers, airflow dryers, and vacuum dryers. From the viewpoint of preventing evaporation, heating is preferably carried out in a closed system, and from the viewpoint of increasing the heating temperature, it is preferable to carry out the heating in a pressure-resistant device or container. The heat treatment may be a batch process, a batch continuous process, or a continuous process.

[0102] If the substituent removal process involves enzymatically treating fibrous cellulose having substituents, it is preferable to use phosphate hydrolase, sulfate hydrolase, etc., in the enzymatic treatment process.

[0103] In the enzyme treatment step, it is preferable to add enzymes so that the enzyme activity is 0.1 nkat or more per 1 g of fibrous cellulose, more preferably 1.0 nkat or more, and even more preferably 10 nkat or more. Furthermore, it is preferable to add enzymes so that the enzyme activity is 100,000 nkat or less per 1 g of fibrous cellulose, more preferably 50,000 nkat or less, and even more preferably 10,000 nkat or less. After adding enzymes to the fibrous cellulose dispersion (slurry), it is preferable to treat the material for 1 minute to 100 hours under conditions of 0°C to less than 50°C.

[0104] A step to deactivate the enzyme after the enzymatic reaction may be included. Methods for deactivating the enzyme include adding an acidic or alkaline component to the enzyme-treated slurry to deactivate the enzyme, or raising the temperature of the enzyme-treated slurry to 90°C or higher to deactivate the enzyme.

[0105] If the substituent removal step is a step of acid-treating fibrous cellulose having substituents, it is preferable to add an acid compound that can be used in the acid treatment step described above to the slurry during the acid treatment step.

[0106] If the substituent removal step is a step of alkali treatment of fibrous cellulose having substituents, it is preferable to add an alkali compound that can be used in the alkali treatment step described above to the slurry during the alkali treatment step.

[0107] In the substituent removal process, it is preferable that the substituent removal reaction proceeds uniformly. To ensure uniform reaction, for example, the slurry containing fibrous cellulose may be stirred, or the specific surface area of ​​the slurry may be increased. Methods of stirring the slurry include applying external mechanical shear, or promoting self-stirring by increasing the slurry delivery rate during the reaction.

[0108] <pH Adjustment Step> When the substituent removal process is carried out in slurry form, a step to adjust the pH of the slurry containing fibrous cellulose may be provided before the substituent removal process. For example, anionic groups may be introduced into cellulose fibers, and the counterions of these anionic groups may be Na ＋ In this case, the slurry containing fibrous cellulose after defibration will be weakly alkaline. If heated in this state, monosaccharides, which are one of the causes of discoloration, may be generated due to the decomposition of cellulose, so it is preferable to adjust the pH of the slurry to 8 or less, and more preferably to 6 or less. Similarly, monosaccharides may also be generated under acidic conditions, so it is preferable to adjust the pH of the slurry to 3 or more, and more preferably to 4 or more.

[0109] Furthermore, if the fibrous cellulose having substituents is fibrous cellulose having phosphate groups, it is preferable that the phosphorus of the phosphate group is in a state that is easily susceptible to nucleophilic attack, from the viewpoint of improving the efficiency of substituent removal. Cellulose that is easily susceptible to nucleophilic attack is cellulose-O-P(=O)(-O-H ＋ ) (-O-Na ＋This represents a neutralization degree of 1, and to achieve this state, it is preferable to adjust the pH of the slurry to 3 or more and 8 or less, and more preferably to adjust the pH to 4 or more and 6 or less.

[0110] The means of adjusting the pH are not particularly limited, but for example, an acidic or alkaline component may be added to a slurry containing fibrous cellulose. The acidic component may be either an inorganic acid or an organic acid. Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Examples of organic acids include formic acid, acetic acid, citric acid, malic acid, lactic acid, adipic acid, sebacic acid, stearic acid, maleic acid, succinic acid, tartaric acid, fumaric acid, and gluconic acid. The alkaline component may be an inorganic alkali compound or an organic alkali compound. Examples of inorganic alkali compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, lithium bicarbonate, potassium carbonate, potassium bicarbonate, sodium carbonate, and sodium bicarbonate. Examples of organic alkali compounds include ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, and N,N-dimethyl-4-aminopyridine.

[0111] Furthermore, in the pH adjustment process, ion exchange treatment may be performed to adjust the pH. For ion exchange treatment, a strongly acidic cation exchange resin or a weakly acidic ion exchange resin can be used. By treating with an appropriate amount of cation exchange resin for a sufficient amount of time, a slurry containing fibrous cellulose at the desired pH can be obtained. Additionally, the pH adjustment process may be combined with the addition of acidic or alkaline components and ion exchange treatment.

[0112] <Salt Removal Process> After the substituent removal process, it is preferable to remove the salts derived from the removed substituents. Removing the salts derived from the substituents makes it easier to obtain fibrous cellulose that can suppress discoloration. The means for removing the salts derived from the substituents are not particularly limited, but washing is one example. The washing is carried out by washing the fibrous cellulose that has aggregated in the substituent removal process with water or an organic solvent, for example. From the viewpoint of more effectively suppressing yellowing, the washing is preferably carried out by filtration dehydration, centrifugal dehydration, or centrifugation.

[0113] <Uniform Dispersion Treatment Step> A method for producing fibrous cellulose may include a substituent removal treatment step in which at least a portion of substituents are removed from fibrous cellulose having substituents, and a uniform dispersion treatment step after the substituent removal treatment. The uniform dispersion treatment step is a step in which the fibrous cellulose obtained after the substituent removal treatment step is uniformly dispersed. The state in which the fibrous cellulose is uniformly dispersed in the uniform dispersion treatment step means a state in which the fiber diameter of the fibrous cellulose is 100 nm or less. By going through the uniform dispersion treatment step, it becomes easy to make the number average fiber diameter of the fibrous cellulose 100 nm or less, preferably 50 nm or less, even though the amount of substituents introduced is low, less than 0.5 mmol / g.

[0114] In the uniform dispersion process, for example, a high-speed defibrator, grinder (stone mill type grinder), high-pressure homogenizer, high-pressure impact grinder, ball mill, bead mill, disc refiner, conical refiner, twin-screw kneader, vibrating mill, homomixer under high-speed rotation, ultrasonic disperser, or beater can be used. Among the above uniform dispersion processing devices, the use of a high-speed defibrator and a high-pressure homogenizer is more preferable.

[0115] The processing conditions in the uniform dispersion process are not particularly limited, but it is preferable to increase the maximum movement speed of the fibrous cellulose during processing and the processing pressure. In a high-speed defibrator, the peripheral speed is preferably 20 m / sec or more, more preferably 25 m / sec or more, and even more preferably 30 m / sec or more. A high-pressure homogenizer can be used more preferably than a high-speed defibrator because it allows for a higher maximum movement speed of the fibrous cellulose during processing and a higher processing pressure. In high-pressure homogenizer processing, the processing pressure is preferably 1 MPa or more, more preferably 10 MPa or more, even more preferably 50 MPa or more, and particularly preferably 100 MPa or more. Furthermore, in high-pressure homogenizer processing, the processing pressure is preferably 350 MPa or less, more preferably 300 MPa or less, and even more preferably 250 MPa or less.

[0116] 1.3 Isocyanate Compounds An isocyanate compound means a compound having at least one isocyanate group, and a polyisocyanate compound means a compound having at least two or more isocyanate groups. A polyisocyanate compound may contain diisocyanate and may contain three or more isocyanate groups. The isocyanate compound is preferably a water-dispersible isocyanate. Examples of water-dispersible isocyanate compounds include, specifically, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, Examples include aromatic isocyanates such as 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, aliphatic isocyanates such as 1,6-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, and lysine diisocyanate, aromatic aliphatic diisocyanates such as xylylene-1,4'-diisocyanate and xylylene-1,3'-diisocyanate, isophorone diisocyanate, water-added tolylene diisocyanate, water-added xylylene diisocyanate, water-added diphenylmethane diisocyanate, water-added tetramethylxylylene diisocyanate, alicyclic diisocyanates, and NCO-terminated compounds obtained by the reaction of these compounds with active hydrogen group-containing compounds. These isocyanates can be used alone or as a mixture of two or more. The isocyanate compound according to one embodiment of the present invention may be an aliphatic isocyanate or have a structure derived from an aliphatic isocyanate. The isocyanate compound may contain one or more alkylene groups.The alkylene group can have, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, and may be within the range of any two of the values ​​exemplified here. As described later, the isocyanate group of the isocyanate compound is presumed to react with the hydroxyl group contained in the fibrous cellulose and contribute to the urethane formation of the fibrous cellulose. The isocyanate compound may also include a so-called blocked isocyanate compound, which is a compound obtained by substituting the isocyanate group of an isocyanate compound with a blocked group. Blocked isocyanate compounds can be excluded because they can yield sheets with superior water absorption, tensile modulus, tensile strength, yellowing suppression, and haze. On the other hand, blocked isocyanate compounds can also be included because the reaction with fibrous cellulose can be controlled during the manufacturing process. The isocyanate compounds used as raw materials for blocked isocyanate compounds are not particularly limited and include, for example, aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI); aromatic polyisocyanates such as tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI); and modified versions thereof. Furthermore, the above-mentioned water-dispersible isocyanate compounds can also be used. The blocking agents are not particularly limited, but include, for example, alcohols such as methanol and ethanol; phenols such as phenol and cresol; oximes such as methyl ethyl ketoxime (MEKO) and acetooxime; lactams (acid amides) such as ε-caprolactam; active methylenes such as diethyl malonate and acetate acetate; pyrazoles (imidazoles) such as 3,5-dimethylpyrazole; acid imides such as succinimide; amines such as aniline; and the like. These can be used individually or in combination of two or more. The blocked isocyanate compound is preferably water-dispersible for application in the aqueous dispersion system of the present invention. The blocked isocyanate compound is stable at around room temperature, and upon heating, the blocking agent dissociates (deblocks), allowing the isocyanate groups to react with the hydroxyl groups of fibrous cellulose to form urethane bonds.The dissociation temperature of the blocked isocyanate compound is, for example, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200°C, and may be within the range of any two of the values ​​exemplified herein. The isocyanate compound according to one embodiment of the present invention may contain a blocked isocyanate compound and an isocyanate compound other than the blocked isocyanate compound, and the proportion of the blocked isocyanate compound is, for example, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0117] 1.4 Water-soluble resins A composition according to one embodiment of the present invention may contain a water-soluble resin. Examples of water-soluble resins include polyalkylene glycols (e.g., polyethylene glycol, polypropylene glycol), cellulose derivatives (e.g., hydroxyethyl methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, methylcellulose, carboxyethylcellulose, carboxymethylcellulose), proteins such as casein, starches (e.g., dextrin, cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, amylose), polyvinyl alcohol, modified polyvinyl alcohol (e.g., acetoacetylated polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene oxided polyvinyl alcohol), and polyalkylene oxides (e.g., polyethylene oxide). Examples include polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates (e.g., sodium polyacrylate), polycations (e.g., polyacrylamide, polyethyleneimine), polyanions, amphoteric polymers, alkyl acrylate copolymers, urethane copolymers, thickening polysaccharides (e.g., xanthan gum, guar gum, tamarind gum, locust bean gum, quince seed, alginic acid, metal salts of alginic acid, pullulan, carrageenan, sacran, pectin), polyesters, modified polyesters, modified polyimides, glycerins such as polyglycerin, hyaluronic acid, metal salts of hyaluronic acid, carboxyvinyl polymers, alkyl methacrylates, acrylic acid copolymers, and polyacrylates (e.g., sodium polyacrylate). Among these, it is preferable to include one or more selected from polyvinyl alcohol, modified polyvinyl alcohol, and cellulose derivatives. Note that the water-soluble resin may not contain fibrous cellulose. By incorporating a water-soluble resin, optical properties (e.g., suppression of changes in yellowness) and coating properties (e.g., uniformity of the coated surface) can be further improved.

[0118] 1.5 Surfactants A composition according to one embodiment of the present invention may contain a surfactant. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymeric surfactants, reactive surfactants, and the like.

[0119] Examples of anionic surfactants include alkyl carboxylate compounds, alkyl sulfate compounds, alkyl sulfonate compounds, and alkyl phosphates. Examples of nonionic surfactants include ethylene oxide and / or propylene oxide adducts of C1-C18 alcohols, ethylene oxide and / or propylene oxide adducts of alkylphenols, and ethylene oxide and / or propylene oxide adducts of alkylene glycols and / or alkylenediamines. Examples of cationic surfactants include primary to tertiary amine salts, pyridinium salts, alkylpyridinium salts, and quaternary ammonium salts such as alkyl quaternary ammonium halides. The surfactant according to one embodiment of the present invention may contain alkyl sulfonate compounds and may contain dialkyl sulfosuccinate salts (e.g., sodium salts).

[0120] 1.6 Characteristics of the Composition The composition according to the present invention contains the above-mentioned fibrous cellulose, and the infrared absorption spectrum obtained by analyzing the composition by infrared spectroscopy has an absorption peak originating from the urethane bond. Specifically, it is preferable that the infrared absorption spectrum of the composition obtained using a Fourier transform infrared spectrophotometer (FT-IR) has peaks originating from the C=O stretching vibration and NH bending vibration of the urethane bond. The peak originating from the C=O stretching vibration is in the range of 1735 to 1680 cm⁻¹. －１ These can be observed at, for example, 1735, 1730, 1725, 1720, 1715, 1710, 1705, 1700, 1695, 1690, 1685, and 1680 cm. －１It can be observed in the range between any two of the values ​​exemplified here. The peak originating from C=O stretching vibration may have its peak top in this range. The peak originating from NH bending vibration may be in the range of 1550–1510 cm. －１ These can be observed at, for example, 1550, 1545, 1540, 1535, 1530, 1525, 1520, 1515, and 1510 cm. －１ This can be observed and may be within the range between any two of the values ​​exemplified here. Peaks originating from NH bending oscillations may have their peak tops within this range.

[0121] The composition according to the present invention preferably contains a urethaneized fibrous cellulose. A urethaneized fibrous cellulose means that the hydroxyl groups of fibrous cellulose react with the isocyanate groups of an isocyanate compound to form a urethaneized structure (a structure having urethane bonds). That is, the urethaneized material contains urethane bonds, and the urethane bonds can originate from the hydroxyl groups of fibrous cellulose and the isocyanate groups of the isocyanate compound. The urethaneized fibrous cellulose may have a structure represented by the following formula.

[0122]

[0123] In formula (3), *1 can be a bond that leads to a structure derived from fibrous cellulose, and *2 can be a bond that leads to a residue of the isocyanate compound.

[0124] Furthermore, it is preferable that the urethaneized product has at least one structure selected from a structure in which residues of an isocyanate compound are bonded to fibrous cellulose via urethane bonds, and a structure in which fibrous cellulose is crosslinked by a crosslinked portion containing urethane bonds. The structure in which residues of an isocyanate compound are bonded to fibrous cellulose via urethane bonds can be represented by the following formula.

[0125] In formula (4), *11 can be a bond that leads to a structure derived from fibrous cellulose. １This can be a monovalent organic group and can be a residue of an isocyanate compound. An isocyanate compound residue refers to the group that constitutes the portion of an isocyanate compound from which the isocyanate group has been removed. A structure in which fibrous cellulose is cross-linked with cross-linked regions containing urethane bonds can be represented by the following formula. In this case, the isocyanate compound can be a polyisocyanate compound.

[0126]

[0127] In formula (5), *11 and *12 can be binding bonds that lead to a structure derived from fibrous cellulose. The fibrous cellulose to which *11 is bound and the fibrous cellulose to which *12 is bound may be the same or different. ２ This can be a divalent organic group and can be a residue of a polyisocyanate compound. A residue of a polyisocyanate compound refers to a group that constitutes the portion of a polyisocyanate compound from which the isocyanate group has been removed. Although formula (5) illustrates a urethane bond derived from a diisocyanate compound, polyisocyanate compounds are not limited to diisocyanate compounds.

[0128] A composition according to one embodiment of the present invention may include: - Unurethane-treated fibrous cellulose - Urethane-treated fibrous cellulose (urethane-treated fibrous cellulose) - Isocyanate compounds that do not contribute to urethane treatment. In this invention, "fibrous cellulose" includes: - Unurethane-treated fibrous cellulose - Urethane-treated fibrous cellulose (urethane-treated fibrous cellulose). The urethane-treated fibrous cellulose has a structure derived from fibrous cellulose and may further have: - A structure in which residues of the isocyanate compound are bonded via urethane bonds (the portion enclosed by the dotted line in formula (4)) and / or - A structure derived from the isocyanate compound (the crosslinked portion (the portion enclosed by the dotted line in formula (5))). The urethane-treated fibrous cellulose can be composed of a structure derived from fibrous cellulose and a structure derived from the isocyanate compound.

[0129] In one embodiment of the present invention, the total content of (a) unurethane-treated fibrous cellulose and (b) structures derived from fibrous cellulose contained in the urethane-treated fibrous cellulose, relative to 100% by mass of the solid content in the composition, can be 10 to 99% by mass. The total content of unurethane-treated fibrous cellulose and structures derived from fibrous cellulose contained in the urethane-treated fibrous cellulose, relative to 100% by mass of the solid content in the composition, is, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 99% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0130] In one embodiment of the present invention, the total content of (c) structures derived from isocyanate compounds contained in the urethaneized fibrous cellulose (the portion enclosed by the dotted line in formula (4)) and crosslinked portions (the portion enclosed by the dotted line in formula (5)), and (d) isocyanate compounds that do not contribute to urethane formation, relative to 100% by mass of the solid content in the composition, can be 1 to 90% by mass. The total content of structures derived from isocyanate compounds contained in the urethaneized fibrous cellulose and isocyanate compounds that do not contribute to urethane formation, relative to 100% by mass of the solid content in the composition, is, for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, and 90% by mass, and may be within the range of any two of the values ​​exemplified here.

[0131] In one embodiment of the present invention, the composition may have a total content of (c) and (d) of 10 to 150% by mass relative to a total content of (a) and (b) of 100% by mass. The total content of (c) and (d) relative to a total content of (a) and (b) of 100% by mass in the composition may be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150% by mass, and may be within the range of any two of the values ​​exemplified herein. By adjusting the blending amounts of fibrous cellulose and isocyanate compounds and bringing the content of each component within the above numerical range, the water resistance of the molded article can be further improved, and the mechanical properties can be further improved.

[0132] In one embodiment of the present invention, the composition may contain 50% by mass or less of water-soluble resin relative to 100% by mass of solids in the composition. The content of water-soluble resin relative to 100% by mass of solids in the composition may be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0133] In one embodiment of the present invention, the surfactant content relative to 100% by mass of solids in the composition can be 1 to 10% by mass. The surfactant content relative to 100% by mass of solids in the composition may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0134] In one embodiment of the present invention, the total content of unurethane-treated fibrous cellulose, urethane-treated fibrous cellulose (urethane-treated fibrous cellulose), isocyanate compounds that do not contribute to urethane formation, surfactants, and optionally added water-soluble resins, relative to 100% by mass of the solid content in the composition, can be 11 to 100% by mass. For example, it can be 11, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100% by mass, and may be within the range of any two of the values ​​exemplified here.

[0135] A composition according to one embodiment of the present invention may also contain polyol compounds (excluding fibrous cellulose) and structures derived from polyol compounds (excluding fibrous cellulose). The content of polyol compounds (excluding fibrous cellulose) and structures derived from polyol compounds relative to 100% by mass of solids in the composition may be less than 20% by mass, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20% by mass, and may be within the range of any two of the values ​​exemplified herein. A composition according to one embodiment of the present invention may also not contain polyol compounds (excluding fibrous cellulose) and structures derived from polyol compounds (excluding fibrous cellulose).

[0136] The compositions according to the present invention may include powders, pellets, dispersions in a solvent such as water, slurries, pastes, films, sheets, plates, molded articles, and structures, as well as forms prior to being molded into films, sheets, plates, molded articles, and structures. The solid content concentration of the composition according to one embodiment of the present invention can be 0.1 to 100% by mass, for example, 0.1, 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% by mass, and may be within the range of any two of the values ​​exemplified herein. The composition according to one embodiment of the present invention may also be substantially solvent-free.

[0137] The use of the composition according to one embodiment of the present invention is not particularly limited and can be used for various uses described later. For example, the composition according to one embodiment of the present invention can be used for an electrolyte membrane for a polymer electrolyte fuel cell. In the composition according to this embodiment, the fibrous cellulose preferably has ionic functional groups, and the type and amount of ionic functional groups are more preferably as described above. In one embodiment of the present invention, the fibrous cellulose has ionic functional groups and is crosslinked by urethane bonds, thereby providing an electrolyte membrane for a polymer electrolyte fuel cell that maintains proton conductivity while suppressing excessive swelling and exhibiting excellent mechanical strength and dimensional stability. Embodiments of the electrolyte membrane for a polymer electrolyte fuel cell are described later.

[0138] 2. Molded article The molded article according to one embodiment of the present invention may be a molded article of the above composition. The shape of the molded article is not particularly limited. Examples of molded articles include sheets, films, layers formed on a support, for example, three-dimensional structures that have an uneven shape depending on the application, or any three-dimensional shape. The molding method is not particularly limited, but examples include a method of molding by injection molding of the above composition or a method of press molding of a sheet.

[0139] <Water Absorption Rate> The molded article according to one embodiment of the present invention preferably has a water absorption rate of 150% or less when immersed in water. The water absorption rate is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150%, and may be within the range of any two of the values ​​exemplified here.

[0140] The water absorption rate can be measured by the following method. After measuring the weight (dry mass) of a sheet cut to 100 mm x 100 mm, immerse it in water for 24 hours under conditions of 23°C and 50% relative humidity. Place a dry blotting paper on top of the sheet after removing it from the water, remove excess water by rolling a roller back and forth once, then measure the weight (wet mass) of the sheet and calculate the water absorption rate (formula (1) below). Water absorption rate [%] = (m2 - m1) / m1 × 100 (1) m1: Dry mass of the test piece (g) m2: Wet mass of the test piece (g)

[0141] The water absorption rate can be controlled by adjusting the preparation conditions of the molded body (the composition constituting the molded body). For example, it can be controlled by adjusting the type and amount of fibrous cellulose and isocyanate compounds, and the heating (aging) conditions. It is also presumed that the water absorption rate can be controlled by adjusting the amount of urethane bonds (urethaneized product) produced by adjusting the above manufacturing conditions. Furthermore, the water absorption rate of the molded body of the composition can also serve as an indicator of the amount of urethane bonds (urethaneized product) in the composition. By keeping the water absorption rate within the above numerical range, the deterioration of optical and mechanical properties in high-humidity environments or environments where contact with water is possible can be reduced.

[0142] <Transparency (Haze)> The molded article according to one embodiment of the present invention preferably has a haze of less than 4%. For example, the haze may be 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0%, and may be within the range of any two of the values ​​exemplified here.

[0143] Haze can be measured according to JIS K 7136:2000, for example, using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute). Transparency (haze) can be controlled by adjusting the preparation conditions of the molded body (the composition constituting the molded body), for example, by adjusting the type and amount of each component contained in the molded body (the composition constituting the molded body), and in particular, by adjusting the fiber diameter and fiber length of fibrous cellulose.

[0144] <Yellowness> In a molded article according to one embodiment of the present invention, when the yellowness of the molded article measured in accordance with JIS K 7373:2006 is YI1, the yellowness of the molded article after heating the molded article at 160°C for 6 hours is YI2, and the thickness of the molded article is T μm, it is preferable that the value of ΔYI per 25 μm of the molded article, calculated by the following formula (2), is 40 or less. ΔYI = (YI2 - YI1) / T × 25 (2) ΔYI can be 0 to 10.0, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, and may be within the range of any two of the values ​​exemplified here.

[0145] The degree of yellowness (ΔYI per 25 μm) can be controlled by adjusting the preparation conditions of the molded body (the composition constituting the molded body). For example, it can be controlled by adjusting the type and amount of each component contained in the molded body (the composition constituting the molded body), the type and amount of fibrous cellulose and isocyanate compounds, and especially the type and amount of water-soluble resin.

[0146] <Tensile Modulus and Tensile Strength> The molded article according to one embodiment of the present invention preferably has a tensile modulus of 5.0 GPa or more. The tensile modulus is, for example, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0 GPa or more, and may be within the range of any two of the values ​​exemplified here. The molded article according to one embodiment of the present invention preferably has a tensile strength of 65.0 MPa or more. The tensile strength may be, for example, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, 95.0, 100.0, 105.0, 110.0, 115.0, 120.0, 125.0, 130.0, 135.0, 140.0, 145.0, or 150.0 MPa, and may be within the range of any two of the values ​​exemplified here.

[0147] The tensile modulus can be measured using a 180 mm long x 15 mm wide test specimen, in accordance with JIS P 8113:2006, for example, using a Tensilon tensile testing machine (manufactured by A&D Co., Ltd.). The tensile strength (MPa) can be calculated by dividing the measured tensile strength (kN / m) by the specimen thickness (m). When measuring, the test specimen should be conditioned at 23°C and 50% relative humidity for 24 hours, and the span length can be set to 100 mm. The tensile modulus and tensile strength can be controlled by adjusting the preparation conditions of the molded body (the composition constituting the molded body). For example, this can be controlled by adjusting the type and amount of each component contained in the molded body (the composition constituting the molded body), the type and amount of fibrous cellulose and isocyanate compounds, and the type and amount of water-soluble resins.

[0148] The above characteristics can be measured using a sheet-like molded article made from the above composition. The thickness of the sheet-like molded article used for each evaluation can be 15 to 40 μm, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40 μm, and may be within the range of any two of the values ​​exemplified here. In one embodiment of the present invention, it is preferable that when a sheet-like molded article made from the composition is formed by the method described in the examples, the molded article has the above characteristics. Furthermore, the specific measurement method can be as described in the examples.

[0149] A molded article according to one embodiment of the present invention may have a porosity of less than 50%. The porosity may be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 49%, and may be within the range of any two of the values ​​exemplified herein. A molded article according to one embodiment of the present invention has a low porosity, less diffuse reflection of light within the molded article, and excellent optical properties (haze).

[0150] The use of the molded article according to one embodiment of the present invention is not particularly limited and can be used for various applications described later. For example, the molded article according to one embodiment of the present invention can be used as an electrolyte membrane for a polymer electrolyte fuel cell. In the molded article according to this embodiment, the fibrous cellulose preferably has ionic functional groups, and the type and amount of ionic functional groups are more preferably as described above. Embodiments of the electrolyte membrane for a polymer electrolyte fuel cell are described later.

[0151] 3. Structures A structure according to one embodiment of the present invention includes the molded body described above. The configuration and shape of the structure are not particularly limited. Examples of structures include a structure including a laminate including the sheet or film described above, a structure including a support and the layer formed on the support, and other structures including the molded body described above.

[0152] 4. Methods for Manufacturing Compositions, Molded Articles, and Structures A method for manufacturing a molded article according to one embodiment of the present invention may include an aqueous dispersion preparation step and a molding step. In the aqueous dispersion preparation step, an aqueous dispersion containing fibrous cellulose, an isocyanate compound, a surfactant, and water is prepared. In the molding step, at least a portion of the water is removed from the aqueous dispersion and the article is molded to obtain a molded article containing a urethaneized fibrous cellulose produced by the reaction of the fibrous cellulose and the isocyanate compound. A method for manufacturing a molded article according to one embodiment of the present invention may also include a heating step.

[0153] A method for manufacturing a molded article according to one embodiment of the present invention allows for the formation of a molded article through a simple process, such as molding an aqueous dispersion composed of a very small number of raw materials by a coating process, thereby shortening the manufacturing process and reducing labor and costs. A method for manufacturing a molded article according to one embodiment of the present invention may, for example, not include a step of providing a coating layer to a molded article (sheet, film, layer) containing fibrous cellulose, or a step of immersing a molded article (sheet, film, layer) containing fibrous cellulose in a dispersion containing a crosslinking agent.

[0154] <Aqueous Dispersion Preparation Process> In the aqueous dispersion preparation process, an aqueous dispersion containing fibrous cellulose, an isocyanate compound, a surfactant, and water is prepared. The aqueous dispersion may contain 10 to 99% by mass of fibrous cellulose per 100% by mass of solids in the aqueous dispersion. The amount of fibrous cellulose per 100% by mass of solids in the aqueous dispersion is, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99% by mass, and may be within the range of any two of the values ​​exemplified here. The aqueous dispersion may contain 1 to 90% by mass of isocyanate compound per 100% by mass of solids in the aqueous dispersion. The amount of fibrous cellulose relative to 100% by mass of solids in the aqueous dispersion is, for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90% by mass, and may be within the range of any two of the values ​​exemplified here. The aqueous dispersion may contain 10 to 150% by mass of isocyanate compound relative to 100% by mass of fibrous cellulose in the aqueous dispersion. The content of isocyanate compound relative to 100% by mass of fibrous cellulose in the aqueous dispersion is, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150% by mass, and may be within the range of any two of the values ​​exemplified here. By keeping the amount of isocyanate compound blended with fibrous cellulose within the above numerical range, the water resistance of the molded article can be further improved, and its mechanical properties can be further enhanced. As mentioned above, the isocyanate compound may also include a blocked isocyanate compound, and the ratio of the blocked isocyanate compound to 100% by mass of the isocyanate compound may be, for example, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% by mass, and may be within the range of any two of the values ​​exemplified here.

[0155] The aqueous dispersion may contain 1 to 10% by mass of surfactant per 100% by mass of solids in the aqueous dispersion. The surfactant content per 100% by mass of solids in the aqueous dispersion is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10% by mass, and may be within the range of any two of the values ​​exemplified here. The aqueous dispersion may contain 1 to 20% by mass of surfactant per 100% by mass of isocyanate compound in the aqueous dispersion. The surfactant content per 100% by mass of isocyanate compound in the aqueous dispersion is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20% by mass, and may be within the range of any two of the values ​​exemplified here. By keeping the surfactant content within the above numerical range, the uniformity and stability of the dispersion can be improved, and the water resistance, mechanical properties, and optical properties of the molded article can be uniformly improved.

[0156] The aqueous dispersion may also contain a water-soluble resin. The content of the water-soluble resin relative to 100% by mass of solids in the aqueous dispersion can be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50% by mass, and may be within the range of any two of the values ​​exemplified here.

[0157] The aqueous dispersion may contain a total content of fibrous cellulose, isocyanate compound, and surfactant (and optionally added water-soluble resin) relative to 100% by mass of solids in the aqueous dispersion, ranging from 11% to 100% by mass. For example, it may be 11, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100% by mass, and may be within the range of any two of the values ​​exemplified here. The aqueous dispersion may contain less than 20% by mass of polyol compounds (excluding fibrous cellulose) relative to 100% by mass of solids in the aqueous dispersion. For example, the amounts may be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20% by mass, and may be within the range of any two of the values ​​exemplified here.

[0158] In the aqueous dispersion preparation step, an aqueous dispersion containing fibrous cellulose, an isocyanate compound, and a surfactant is prepared. At this point, at least some of the fibrous cellulose and the isocyanate compound may react to form a urethaneized fibrous cellulose by mixing. The time from the aqueous dispersion preparation step to the start of the molding step (e.g., coating step) may be, for example, less than 1 hour, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 hours, and may be within the range of any two of the values ​​exemplified here. By setting the time from the aqueous dispersion preparation step to the start of the molding step (e.g., coating step) within the above numerical range, a composition with sufficient physical properties such as water absorption can be obtained more reliably.

[0159] <Molding Process> In the molding process, at least a portion of the water is removed from the aqueous dispersion to form a molded article containing a urethaneized fibrous cellulose product formed by the reaction of fibrous cellulose and an isocyanate compound. The molding method is not particularly limited, and known molding methods can be used. As an example, the molding process can be a process of applying the aqueous dispersion onto a substrate, drying it, and peeling the resulting sheet from the substrate to obtain a sheet.

[0160] The quality of the base material is not particularly limited, and known materials can be used. Materials with high wettability to aqueous dispersions are preferable as they can suppress shrinkage of the sheet during drying. It is also preferable to select a material that allows the sheet formed after drying to be easily peeled off. The base material can be a resin or a metal, and for example, resin plates such as acrylic plates, polyethylene terephthalate plates, vinyl chloride plates, polystyrene plates, and polyvinylidene chloride plates, as well as metal plates such as aluminum plates, zinc plates, copper plates, and iron plates, and those whose surfaces have been oxidized, stainless steel plates, brass plates, etc. can be used.

[0161] For coating machines, for example, roll coaters, gravure coaters, die coaters, curtain coaters, and air doctor coaters can be used. Die coaters, curtain coaters, and spray coaters are preferred because they can achieve a more uniform thickness.

[0162] The coating temperature is not particularly limited, but for example, it may be 20, 25, 30, 35, 40, or 45°C, and may be within the range of any two of the values ​​exemplified here. If the coating temperature is above the lower limit, the slurry can be easily coated, and if it is below the upper limit, the volatilization of the dispersion medium during coating can be suppressed.

[0163] The molding process may include a step of drying the aqueous dispersion coated onto the substrate. The drying method is not particularly limited, but may be a non-contact drying method or a method of drying while restraining the sheet, or a combination of these. The drying temperature may be, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150°C, and may be within the range of any two of the values ​​exemplified here. The drying time may be, for example, 10 to 180 minutes, and preferably 30 to 90 minutes. The drying time may be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180 minutes, and may be within the range of any two of the values ​​exemplified here.

[0164] The molding process may also include a papermaking process for the aqueous dispersion. The papermaking process can be carried out using known methods, such as the method disclosed in Japanese Patent Application Publication No. 2020-158939 or the method using the manufacturing apparatus described in WO2011 / 013567. The molding method is not particularly limited, but examples include a method of molding by injection molding of the above composition or a method of press molding of a sheet.

[0165] (Heating step) The sheet manufacturing process preferably includes a heating step after the step of coating the slurry onto the substrate or the step of papermaking the slurry. It is presumed that heating the sheet obtained in the step of coating the slurry onto the substrate or the step of papermaking the slurry in the heating step can further promote the formation of a urethaneized fibrous cellulose by the reaction of fibrous cellulose with an isocyanate compound. Furthermore, if the isocyanate compound contains a blocked isocyanate compound, it is thought that the heating step promotes the dissociation (deblocking) of the blocked groups, thereby efficiently promoting the reaction with the hydroxyl groups of fibrous cellulose.

[0166] In the heating process, the sheet obtained in the process of coating the slurry onto the substrate or in the process of papermaking the slurry can be heated. The heating temperature can be 50 to 150°C, for example, 80 to 100°C. The heating temperature can be, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150°C, and may be within the range of any two of the values ​​exemplified here. The heating time can be 10 minutes to 30 hours, for example, 5 hours to 30 hours, or 12 hours to 20 hours. The heating time can be, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 1 hour, 5 hours, 10 hours, 20 hours, 30 hours, and may be within the range of any two of the values ​​exemplified here. When an isocyanate compound contains a blocked isocyanate compound, the heating temperature and heating time can be set taking into consideration the dissociation temperature (deblocking temperature) and dissociation rate of the blocked isocyanate compound.

[0167] The compositions, molded articles, and structures according to the present invention have low hygroscopicity and excellent water resistance. They also have excellent optical properties, high transparency, low haze, and high strength, and these properties do not deteriorate easily even when used in humid or wet environments. The compositions, molded articles, and structures according to the present invention can be used in applications where these properties are required, such as in display devices such as liquid crystal displays, plasma displays, organic EL displays, field emission displays, and rear projection televisions; light-transmitting substrates for solar cells such as silicon-based solar cells and dye-sensitized solar cells; substrates for electronic devices laminated with barrier films, ITO, and TFTs; components for home appliances; window materials, interior materials, exterior materials, and packaging materials for vehicles such as automobiles and railway cars, and for buildings such as houses, offices, and factories.

[0168] <Electrolyte membrane for polymer electrolyte fuel cell> As an example, the composition, molded body, and structure according to the present invention can be used for an electrolyte membrane for a polymer electrolyte fuel cell. An electrolyte membrane for a polymer electrolyte fuel cell according to one embodiment of the present invention may comprise at least one of the group consisting of the above-mentioned composition, molded body, and structure, and it is preferable that it comprises at least one of the group consisting of the above-mentioned composition and molded body. The composition, molded body, and structure according to the present invention can also be used for an electrolyte membrane for polymer electrolyte water electrolysis. The electrolyte membrane for a polymer electrolyte fuel cell of this embodiment and the electrolyte membrane for polymer electrolyte water electrolysis of this embodiment may have the same configuration as the application.

[0169] The electrolyte membrane for polymer electrolyte fuel cells contains the above-mentioned fibrous cellulose and may also contain other components. The content of fine fibrous cellulose in the solid content of the electrolyte membrane for polymer electrolyte fuel cells is preferably 10% by mass or more and 80% by mass or less. The content of fine fibrous cellulose in the solid content of the electrolyte membrane for polymer electrolyte fuel cells may be, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80% by mass, and may be within the range of any two of the values ​​exemplified here.

[0170] The electrolyte membrane for polymer electrolyte fuel cells of this embodiment may contain a filler material from the viewpoint of mechanical strength and thinness. Examples of fillers include polymers having sulfonic acid groups, sulfonated silica nanoparticles, carbon nanotubes, and MOFs (metal-organic frames), with polymers having sulfonic acid groups being preferred. The electrolyte membrane for polymer electrolyte fuel cells of this embodiment may contain poly(vinylphosphonic acid) coated cellulose nanocrystals from the viewpoint of improving proton conductivity. Poly(vinylphosphonic acid) coated cellulose nanocrystals are those in which part or all of the surface of cellulose nanocrystals is coated with poly(vinylphosphonic acid), and cellulose nanocrystals can be obtained by acid-treating cellulose fibers. Cellulose nanocrystals can be manufactured, for example, by referring to Japanese Patent Application Publication No. 2022-132151.

[0171] The electrolyte membrane for polymer electrolyte fuel cell in this embodiment preferably contains a certain amount of water or more from the viewpoint of improving proton conductivity. The water content in the electrolyte membrane for polymer electrolyte fuel cell is preferably 3% by mass or more and 20% by mass or less. Specifically, for example, it may be 3, 4, 6, 8, 10, 12, 14, 16, 18, or 20% by mass, and may be within the range of any two of the values ​​exemplified here.

[0172] The electrolyte membrane for polymer electrolyte fuel cells of this embodiment may contain fibrous cellulose and other components not described above, as long as the effects of the present invention are not impaired. Examples of such components include hydrophilic polymers, plasticizers, pH adjusters, and crosslinking agents. The content of the above components in the electrolyte membrane for polymer electrolyte fuel cells can be, for example, 5% by mass or less.

[0173] The film thickness of the electrolyte membrane for the polymer electrolyte fuel cell in this embodiment can be appropriately determined according to the size of the membrane electrode assembly incorporating the electrolyte membrane and the polymer electrolyte fuel cell. The film thickness of the electrolyte membrane for the polymer electrolyte fuel cell in this embodiment can be, for example, 10 μm or more and 100 μm or less, specifically, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 μm, and may also be within the range of any two of the values ​​exemplified here.

[0174] The electrolyte membrane for polymer electrolyte fuel cell described above can be used in a membrane electrode assembly. The membrane electrode assembly (MEA) of this embodiment can be formed by joining a positive electrode catalyst layer, the electrolyte membrane for polymer electrolyte fuel cell of this embodiment, and a negative electrode catalyst layer in this order. The membrane electrode assembly of this embodiment can have the same configuration as known membrane electrode assemblies that can be used in polymer electrolyte fuel cells, except that it has the electrolyte membrane for polymer electrolyte fuel cell of this embodiment. For more information on membrane electrode assemblies, see, for example, Japanese Patent Application Publication No. 2022-190524.

[0175] The features of the present invention will be further described below with reference to examples and comparative examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples.

[0176] <Manufacturing Example 1: Production of Substituent-Removed Fine Fibrous Cellulose> (Phosphorus Oxoacid Group Introduction Process (Phosphorus Esterification Treatment)) Hardwood pulp (dry sheet) manufactured by Oji Paper Co., Ltd. was used as the raw material pulp. The phosphate esterification treatment was performed on this raw material pulp as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (oven-dry mass) of the above raw material pulp to adjust the mixture to 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water to obtain chemically impregnated pulp. Next, the obtained chemically impregnated pulp was heated in a hot air dryer at 165°C for 250 seconds to introduce phosphate groups into the cellulose in the pulp and obtain phosphate esterified pulp.

[0177] (Washing Process) Next, the obtained phosphated pulp was subjected to a washing process. The washing process was carried out by repeatedly adding 10 L of deionized water to 100 g (oven-dry mass) of phosphated pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing process was terminated when the conductivity of the filtrate was 100 μS / cm or less.

[0178] (Alkali treatment process (neutralization treatment process)) Next, the washed phosphated pulp was subjected to neutralization treatment as follows. First, the washed phosphated pulp was diluted with 10 L of deionized water, and then a 1N sodium hydroxide aqueous solution was gradually added while stirring to obtain a phosphated pulp dispersion with a pH of 12 to 13. Next, the phosphated pulp dispersion was dehydrated to obtain phosphated pulp that had undergone neutralization treatment. Next, the phosphated pulp that had undergone neutralization treatment was subjected to the washing treatment described above.

[0179] The resulting phosphated pulp was subjected to infrared absorption spectroscopy using FT-IR. The result showed an absorption of 1230 cm⁻¹. －１ Absorption based on the P=O of phosphate groups was observed in the vicinity, confirming that phosphate groups were added to the pulp. Furthermore, when the obtained phosphated pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming that the cellulose type I crystal structure was maintained. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described later was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0180] (Fibraising process (Fibraising of phosphated pulp)) Ion-exchanged water was added to the obtained phosphated pulp to prepare a dispersion with a solid content of 2% by mass. This dispersion was treated six times at a pressure of 200 MPa in a wet atomizing device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose.

[0181] (Substituent removal process (removal of substituents from phosphate-esterified microfibrous cellulose)) A 20% by mass aqueous citric acid solution was added to the above-mentioned microfibrous cellulose dispersion to adjust the pH of the dispersion to 5.5. This microfibrous cellulose dispersion was placed in a pressure vessel and heated at a liquid temperature of 160°C for 15 minutes until the amount of phosphate groups became 0.08 mmol / g. This operation confirmed the formation of microfibrous cellulose aggregates.

[0182] (Salt removal process (washing of microfibrous cellulose after substituent removal)) An equal amount of deionized water was added to the heated dispersion to obtain a dispersion with a solid content of approximately 1% by mass. The dispersion was then stirred and the filtration and dewatering process was repeated to wash the dispersion. When the electrical conductivity of the filtrate became 10 μS / cm or less, deionized water was added again to obtain a dispersion of approximately 1% by mass, and it was left to stand for 24 hours. The filtration and dewatering process was repeated thereafter, and the washing was terminated when the conductivity of the filtrate again became 10 μS / cm or less. Deionized water was added to the obtained microfibrous cellulose aggregates to obtain a dispersion after substituent removal. The solid content of this dispersion was 1.7% by mass.

[0183] (Uniform dispersion step of the dispersion after substituent removal) Ion-exchanged water was added to the obtained substituent removal dispersion to obtain a dispersion with a solid content concentration of 1.0% by mass. This was then processed three times at a pressure of 200 MPa using a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a substituent removal fine fibrous cellulose dispersion containing substituent removal fine fibrous cellulose. Furthermore, the fiber diameter of the substituent removal fine fibrous cellulose was measured using a transmission electron microscope and found to be 2 to 4 nm.

[0184] (Measurement of Phosphate Group Content) The amount of phosphate groups was measured by adding ion-exchanged water to a dispersion of fine fibrous cellulose containing the target fine fibrous cellulose to prepare a dispersion with a fine fibrous cellulose content of 0.2% by mass. The obtained dispersion was treated with an ion exchange resin and then titrated with an alkali. The treatment with the ion exchange resin was performed by adding 1 / 10 the volume of strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo Corporation, conditioned) to the fine fibrous cellulose-containing dispersion, shaking for 1 hour, and then pouring it onto a mesh with a mesh opening of 90 μm to separate the ion exchange resin from the dispersion. The titration with alkali was performed by adding 10 μL of 0.1 N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing dispersion after treatment with the ion exchange resin at 5-second intervals, and measuring the change in the pH value of the dispersion. In this neutralization titration, two points are observed in the curve plotting the measured pH against the amount of alkali added, where the increment (the derivative of pH with respect to the amount of alkali added) is maximum. Of these, the first maximum increment obtained after starting to add alkali is called the first endpoint, and the next maximum increment obtained is called the second endpoint (Figure 1). The amount of alkali required from the start of the titration to the first endpoint is equal to the amount of the first dissociated acid in the dispersion used for titration. Also, the amount of alkali required from the start of the titration to the second endpoint is equal to the total amount of dissociated acid in the dispersion used for titration. Note that the amount of phosphorus oxoacid groups (mol / g) was defined as the amount of alkali (mol / g) required from the start of the titration to the first endpoint divided by the solid content (g) in the dispersion being titrated. Similarly, the total amount of dissociated acid (mol / g) was defined as the amount of alkali (mol / g) required from the start of the titration to the second endpoint divided by the solid content (g) in the dispersion being titrated. The amount of phosphorus oxoacid groups (amount of phosphorus oxoacid groups introduced) (moles / g) indicates the amount of substituents per gram of mass of fine fibrous cellulose when the counterion of the phosphorus oxoacid group is a hydrogen ion (H+).

[0185] <Production Example 2: Production of Phosphate-Esterified Microfibrous Cellulose> The production was carried out in the same manner as in Production Example 1, except that the steps after the removal of substituents from the defibration-treated phosphate-esterified pulp were omitted. The fiber diameter of the substituent-removed microfibrous cellulose was measured using a transmission electron microscope and was found to be 2 to 4 nm.

[0186] <Production Example 3: Production of Phosphate-Esterified Microfibril Cellulose> Deionized water was added to the neutralized phosphate-esterified pulp obtained in Production Example 1 to prepare a dispersion with a solid content of 2.2% by mass. This dispersion was processed four times in a single-disc refiner set to a clearance of 600 μm to obtain a dispersion of phosphate-esterified microfibril cellulose fibers. The fiber diameter measured with a Kayani fiber length analyzer (FS-200) was 22 μm, and TEM observation confirmed fibers of 1000 nm or less. (Sheet Preparation)

[0187] <Example 1> 50 parts by mass of substituent-removed fine fibrous cellulose produced in Production Example 1 and 50 parts by mass of isocyanate (Asahi Kasei Corporation, Duranate WB40-100, containing polyisocyanate of hexamethylene diisocyanate and containing 7.7% by mass of dioctyl sulfosuccinate sodium salt) were mixed, then diluted with deionized water to a solid content concentration of 1.1%, and stirred. Immediately after preparation, the mixture was coated onto a polyethylene terephthalate substrate (Toray Industries, Inc., Lumirror) to a thickness of 3 mm using an applicator, and dried at 80°C for 1.5 hours. Subsequently, an aging treatment was performed at 90°C for 16 hours. After that, a sheet containing fine fibrous cellulose was obtained by peeling it off the substrate. The thickness of the sheet was 26 μm.

[0188] <Example 2> A sheet was obtained in the same manner as in Example 1, except that the substituent-removed fine fibrous cellulose was mixed in an amount of 70 parts by mass and isocyanate in an amount of 30 parts by mass. The thickness of the sheet was 24 μm.

[0189] <Example 3> A sheet was obtained in the same manner as in Example 1, except that 80 parts by mass of substituent-removed fine fibrous cellulose and 20 parts by mass of isocyanate were mixed. The thickness of the sheet was 25 μm.

[0190] <Example 4> A sheet was obtained in the same manner as in Example 2, except that Duranate WT30-100 (manufactured by Asahi Kasei Corporation, containing polyisocyanate of hexamethylene diisocyanate and containing 2.0% by mass of dioctyl sulfosuccinate sodium salt) was used as the isocyanate. The thickness of the sheet was 24 μm.

[0191] <Example 5> A sheet was obtained in the same manner as in Example 1, except that the mixture consisted of 70 parts by mass of substituent-removed microfibrous cellulose, 10 parts by mass of isocyanate, and 20 parts by mass of hydroxypropyl methylcellulose (HPMC, manufactured by Shin-Etsu Chemical Co., Ltd., Metroze SH65-1500). The thickness of the sheet was 25 μm.

[0192] <Example 6> A sheet was obtained in the same manner as in Example 1, except that the mixture consisted of 70 parts by mass of substituent-removed microfibrous cellulose, 20 parts by mass of isocyanate, and 10 parts by mass of hydroxypropyl methylcellulose (HPMC, manufactured by Shin-Etsu Chemical Co., Ltd., Metroze SH65-1500). The thickness of the sheet was 20 μm.

[0193] <Example 7> A sheet was obtained in the same manner as in Example 6, except that 10 parts by mass of polyvinyl alcohol (Gosenex Z-300, manufactured by Mitsubishi Chemical Corporation) was mixed in place of HPMC. The thickness of the sheet was 22 μm.

[0194] <Example 8> A sheet was obtained in the same manner as in Example 1, except that phosphorylated microfibrous cellulose produced in Production Example 2 was used instead of substituent-removed microfibrous cellulose. The thickness of the sheet was 20 μm.

[0195] <Example 9> A sheet was obtained in the same manner as in Example 2, except that phosphorylated microfiber cellulose was used instead of substituent-removed microfiber cellulose. The thickness of the sheet was 22 μm.

[0196] <Example 10> A sheet was obtained in the same manner as in Example 1, except that instead of substituent-removed microfibrous cellulose, phosphate-esterified microfibril cellulose produced in Production Example 3 was used and mixed to a solid content concentration of 2.4%, and coated to a thickness of 1.4 mm. The thickness of the sheet was 34 μm.

[0197] <Example 11> A sheet was obtained in the same manner as in Example 1, except that unmodified microfibrous cellulose (manufactured by Sugino Machine Co., Ltd., BiNFi-s, IMa-10005, average fiber diameter 10-50 nm) was used instead of substituent-removed microfibrous cellulose, and the mixture was mixed to a solid content concentration of 3.2% and coated to a thickness of 1.0 mm. The thickness of the sheet was 31 μm.

[0198] <Example 12> A sheet was obtained in the same manner as in Example 2, except that phosphate-esterified microfibril cellulose was used instead of substituent-removed microfiber cellulose, mixed to a solid content concentration of 2.4%, and coated to a thickness of 1.4 mm. The thickness of the sheet was 31 μm.

[0199] <Example 13> A sheet was obtained in the same manner as in Example 2, except that unmodified microfibrous cellulose was used instead of substituent-removed microfibrous cellulose, mixed to a solid content concentration of 3.2%, and coated to a thickness of 1.0 mm. The thickness of the sheet was 32 μm.

[0200] <Example 14> A sheet was obtained in the same manner as in Example 1, except that SU-268A (manufactured by Meisei Chemical Co., Ltd., containing 30% by mass of blocked polyisocyanate and 1-10% by mass of propylene glycol monomethyl ether; the blocked polyisocyanate is an adduct of hexamethylene diisocyanate as a blocking agent) was used as the isocyanate, and the aging treatment conditions were changed to 130°C for 20 minutes. The thickness of the sheet was 41 μm.

[0201] <Example 15> A sheet was obtained in the same manner as in Example 14, except that it was coated 6 hours after preparation. The thickness of the sheet was 32 μm.

[0202] <Example 16> A sheet was obtained in the same manner as in Example 14, except that it was coated 24 hours after preparation. The thickness of the sheet was 39 μm.

[0203] <Comparative Example 1> A sheet was obtained in the same manner as in Example 1, except that only substituent-removed microfiber cellulose was used as the coating. The thickness of the sheet was 23 μm.

[0204] <Comparative Example 2> A sheet was obtained in the same manner as in Example 1, except that only HPMC with a solid content concentration of 3% was used as the coating and it was coated to a thickness of 1 mm. The thickness of the sheet was 22 μm.

[0205] <Comparative Example 3> A sheet was obtained in the same manner as in Example 1, except that the substituent-removed fine fibrous cellulose was mixed in an amount of 70 parts by mass and HPMC in an amount of 30 parts by mass. The thickness of the sheet was 18 μm.

[0206] <Comparative Example 4> A sheet was obtained in the same manner as in Example 1, except that HPMC was mixed in an amount of 70 parts by mass and isocyanate in an amount of 30 parts by mass, the solid content concentration was 2.6%, and the mixture was coated to a thickness of 1.15 mm. The thickness of the sheet was 24 μm.

[0207] (Evaluation of sheet characteristics and physical properties) For the following measurements, test specimens were used that had been conditioned at 23°C and 50% relative humidity for 24 hours.

[0208] <Measurement of Infrared Absorption Spectra> Infrared absorption spectra (ATR method (total internal reflection measurement)) were measured using a Fourier transform infrared spectrophotometer (FT-IR) (NEXUS670, manufactured by THERMO SCIENTIFIC). Figure 2 shows the infrared absorption spectra of Example 2 and Comparative Example 3. The infrared absorption spectrum of Example 2 is 1686 cm⁻¹. －１ Nearby and 1524 cm －１ There was a peak in the vicinity. Similarly, the infrared absorption spectra for all of the sheets in the examples were 1686 cm⁻¹. －１ Nearby and 1524 cm －１ It had a peak nearby. 1686 cm －１ The peak observed in the vicinity originates from the C=O stretching vibration of the urethane bond, at 1524 cm². －１The peak observed in the vicinity is thought to originate from NH bending vibrations. On the other hand, the infrared absorption spectrum of Comparative Example 3 did not have the above peak.

[0209] <Transparency (Haze)> The haze of the sheet was measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.) in accordance with JIS K 7136:2000.

[0210] <Water Absorption Rate> After measuring the weight (dry mass) of a sheet (test piece) cut to 100 mm x 100 mm, it was immersed in water for 24 hours under conditions of 23°C and 50% relative humidity. After removing the sheet from the water, a dry blotting paper was placed on top, and excess water was removed by rolling a roller back and forth once, after which the sheet weight (wet mass) was measured. The water absorption rate (formula (1) below) was calculated. Water absorption rate [%] = (m2 - m1) / m1 × 100 (1) m1: Dry mass of the test piece (g) m2: Wet mass of the test piece (g) Samples that dissolved after immersion in water and could not be measured were marked "D".

[0211] <Changes in Transparency After Immersion in Water> The transparency of the sheet was visually evaluated before and after immersion in water at room temperature (23°C) for 24 hours (the state after immersion was evaluated by comparing it with the state before immersion). A: Same B: Slightly worsened (transparency slightly decreased) C: Clearly worsened (transparency clearly decreased, becoming cloudy) D: The sheet collapsed after immersion in water and could not be measured.

[0212] <Yellowness> In accordance with JIS K 7373:2006, the change in yellowness (YI) of the sheet (ΔYI) was measured using Colour Cute i (manufactured by Suga Test Instruments Co., Ltd.). The YI of the sheet was measured before and after heating the sheet at 160°C for 6 hours. The value before heating (YI1) was subtracted from the value after heating (YI2), and this value was divided by the sheet thickness (Tμm) and multiplied by 25 to calculate ΔYI per 25μm thickness (see formula (2) below). ΔYI = (YI2 - YI1) / T × 25 (2)

[0213] <Tensile Modulus and Strength> The tensile modulus of the sheet was measured using a Tensilon tensile testing machine (manufactured by A&D Co., Ltd.), in accordance with JIS P 8113:2006, except that the test specimen size was changed to 180 mm long x 15 mm wide and the test length (span length) was changed to 100 mm. The measured tensile strength (kN / m) was converted to tensile strength (MPa) by dividing the value by the test specimen thickness (m). For the measurement, the test specimen was conditioned at 23°C and 50% relative humidity for 24 hours.

[0214]

Claims

1. A composition containing fibrous cellulose, wherein the infrared absorption spectrum obtained by analyzing the composition by infrared spectroscopy has an absorption peak originating from urethane bonds.

2. The composition according to claim 1, wherein the fibrous cellulose comprises a urethane-treated fibrous cellulose.

3. The composition according to claim 2, wherein the urethaneized body comprises a urethane bond, and the urethane bond is derived from the hydroxyl group of the fibrous cellulose and the isocyanate group of the isocyanate compound.

4. The composition according to claim 3, wherein the isocyanate compound comprises a polyisocyanate compound, and the urethaneized body comprises a structure in which the fibrous cellulose is crosslinked with a crosslinked portion containing the urethane bond.

5. A composition according to any one of claims 1 to 4, comprising a water-soluble resin.

6. A composition according to any one of claims 1 to 4, wherein the fibrous cellulose has an ionic functional group.

7. The composition according to claim 6, wherein the composition is for use as an electrolyte membrane for a polymer electrolyte fuel cell.

8. A molded article of the composition according to any one of claims 1 to 4.

9. A molded article according to claim 8, wherein the water absorption rate when the molded article is immersed in water is 150% or less.

10. A molded article according to claim 8, wherein the haze is less than 4%.

11. A molded article according to claim 8, wherein the tensile modulus is 5.0 GPa or more.

12. A molded article according to claim 8, wherein the tensile strength is 65.0 MPa or more.

13. A molded article according to claim 8, wherein YI1 is the yellowness of the molded article measured in accordance with JIS K 7373:2006, YI2 is the yellowness of the molded article after heating at 160°C for 6 hours, and T μm is the thickness of the molded article, and the value of ΔYI per 25 μm of the molded article calculated by the following formula (2) is 10.0 or less. ΔYI = (YI2 - YI1) / T × 25 (2) 14. A structure comprising the molded article described in claim 8.

15. An electrolyte membrane for a polymer electrolyte fuel cell, comprising at least one from the group consisting of the compositions described in claims 1 to 4 and molded articles of the compositions.

16. A method for manufacturing a molded article, the manufacturing method comprising a step of preparing an aqueous dispersion and a step of molding, wherein in the step of preparing an aqueous dispersion, an aqueous dispersion containing fibrous cellulose, an isocyanate compound, a surfactant, and water is prepared, and in the step of molding, at least a portion of the water is removed from the aqueous dispersion and the article is molded to obtain a molded article containing a urethaneized fibrous cellulose produced by the reaction of the fibrous cellulose and the isocyanate compound.

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