Fibrous cellulose, aqueous dispersion of fibrous cellulose, rubber composition, and crosslinked rubber product

Abstract

An object of the present application is to provide a fibrous cellulose and a fibrous cellulose aqueous dispersion containing the same, which, when added to a rubber component to crosslink the same, can obtain a crosslinked rubber product in which a decrease in water resistance is inhibited and in which physical properties such as hardness and / or tensile properties after crosslinking are excellent, as compared with the case where a conventional fibrous cellulose is added. The fibrous cellulose of the present application is a fibrous cellulose having an anionic group and a fiber width of 100 μm or less, and the counter ion of the aforementioned anionic group is an ammonium ion (NH4 + ).

Description

Technical Field

[0001] This invention relates to fibrous cellulose, fibrous cellulose aqueous dispersions, rubber compositions, and cross-linked rubber articles. Background Technology

[0002] In recent years, materials utilizing renewable natural fibers have gained attention due to the substitution of petroleum resources and increased environmental awareness. Among natural fibers, fibrous cellulose with a fiber diameter of 10μm or more but less than 50μm, especially fibrous cellulose derived from wood (pulp), has been widely used primarily for paper products to date.

[0003] As fibrous cellulose, microfibrillated cellulose with an average fiber width of less than 1000 nm is also known. Microfibrillated cellulose has attracted attention as a new raw material with diverse applications. For example, the development of sheet and / or resin composites containing microfibrillated cellulose, and thickeners, is underway. Furthermore, composite materials made by combining microfibrillated cellulose with resin emulsions and / or rubber latex have been investigated.

[0004] In prior art document 1, a composition containing a base rubber, a maleic anhydride-modified polymer, and non-chemically modified and unmodified cellulose nanofibers is disclosed with the aim of providing a composition for defibrillating and dispersing cellulose nanofibers and manufacturing cross-linked rubber with excellent tensile properties.

[0005] In addition, Patent Document 2 discloses a polymer composition comprising: (I) a polymer; (II) a nanocellulose dispersion composition (NDC) comprising: (i) an anti-agglomerating agent comprising carbon black filler, elastomer latex, wax, or any combination thereof; (ii) nanocellulose; and (III) a carbon black additive.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-123639

[0009] Patent Document 2: Japanese Patent Publication No. 2022-508946 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] Prior art documents 1 and 2 disclose compositions comprising cellulose nanofibers, elastomers, and / or base rubbers. However, prior art documents 1 and 2 do not investigate the physical properties and composability of the compositions, leaving room for improvement. Furthermore, the physical properties of the crosslinked rubber require further improvement.

[0012] The object of this invention is to provide fibrous cellulose and an aqueous dispersion of fibrous cellulose containing the fibrous cellulose, wherein when the fibrous cellulose is added to a rubber component and crosslinked thereto, a crosslinked rubber article is obtained in which the reduction of water resistance is suppressed, and the deterioration of strength and / or tensile properties after crosslinking due to water absorption is suppressed, compared with the case of adding conventional fibrous cellulose. Furthermore, the object of this invention is to provide a rubber composition containing the aforementioned fibrous cellulose, and a crosslinked rubber article formed by crosslinking and molding a rubber mixture containing the rubber composition and a crosslinking agent.

[0013] Solution for solving the problem

[0014] The inventors have discovered that, through the presence of anionic groups and the counter ion of the anionic groups being NH4, + The fibrous cellulose can solve the above problems.

[0015] This invention relates to the following <1> ~ <12> .

[0016] <1> A fibrous cellulose, comprising anionic groups and a fiber width of less than 100 μm, wherein the counterion of the aforementioned anionic groups is ammonium ion (NH4+). + ).

[0017] <2> according to <1> The fibrous cellulose mentioned above is microfiber cellulose with a fiber width of less than 1000 nm.

[0018] <3> according to <1> The fibrous cellulose is microfibrillated cellulose with a fiber width exceeding 1 μm and less than 100 μm.

[0019] <4> according to <1> ~ <3> The fibrous cellulose according to any one of the following, wherein the anionic group is at least one selected from the group consisting of a phosphorus oxyacid group, a substituent derived from a phosphorus oxyacid group, a sulfur oxyacid group, and a substituent derived from a sulfur oxyacid group.

[0020] <5> according to <1> ~ <4> The fibrous cellulose described in any one of the above is a rubber modifier.

[0021] <6> A fibrous cellulose aqueous dispersion containing <1> ~ <5> The fibrous cellulose described in any one of the above.

[0022] <7> A rubber composition, which is formulated in rubber components <1> ~ <5> It is made from fibrous cellulose as described in any one of the above.

[0023] <8> according to <7> The rubber composition wherein, relative to 100 parts by weight of rubber components, the content of fibrous cellulose is 0.1 parts by weight or more and 60 parts by weight or less.

[0024] <9> according to <7> or <8> The rubber composition wherein the aforementioned rubber component is a diene-based rubber.

[0025] <10> A cross-linked rubber product, which contains <7> ~ <9> The rubber composition described in any one of the above statements is crosslinked with a rubber mixture containing a crosslinking agent and then molded.

[0026] <11> according to <10> The cross-linked rubber product mentioned above is a tire.

[0027] <12> A method for manufacturing a rubber composition, comprising the following steps (I) and (II).

[0028] (I) containing <1> ~ <5> The mixing process described above, in which an aqueous dispersion of fibrous cellulose is mixed with rubber latex to obtain mixture A.

[0029] (II) Heating process of heating and drying the aforementioned mixture A to obtain the rubber composition

[0030] The effects of the invention

[0031] According to the present invention, the object is to provide fibrous cellulose and an aqueous dispersion of fibrous cellulose containing the fibrous cellulose, wherein when the fibrous cellulose is added to a rubber component and crosslinked thereto, a crosslinked rubber article is obtained in which the reduction of water resistance is suppressed, and the deterioration of strength and / or tensile properties after crosslinking due to water absorption is suppressed, compared with the case of adding conventional fibrous cellulose. Furthermore, the object of the present invention is to provide a rubber composition containing the above-mentioned fibrous cellulose, and a crosslinked rubber article formed by crosslinking and molding a rubber mixture containing the rubber composition and a crosslinking agent. Attached Figure Description

[0032] Figure 1 This is a graph showing the relationship between the amount of NaOH added and pH for fibrous cellulose pulp containing phosphorus oxyacid groups.

[0033] Figure 2 This is a graph showing the relationship between the amount of NaOH added and pH for a slurry containing fibrous cellulose with carboxyl groups.

[0034] Figure 3This is a side cross-sectional view of a double drum dryer, which is an example of a heated cylindrical dryer.

[0035] Figure 4 This is a side view of a drum dryer, which is an example of a heated cylindrical dryer. Detailed Implementation

[0036] [Fibrous cellulose]

[0037] The fibrous cellulose (hereinafter also simply referred to as "fibrous cellulose") in this embodiment has anionic groups and the fiber width is less than 100 μm. Furthermore, the counter ion of the aforementioned anionic groups is ammonium ion (NH4+). + ).

[0038] When the fibrous cellulose of this embodiment is added to the rubber component and crosslinked, compared with the case of adding conventional fibrous cellulose, a crosslinked rubber product in which the reduction of water resistance is suppressed and the deterioration of crosslinked strength and / or tensile properties due to water absorption is suppressed.

[0039] The detailed reasons for achieving the above-mentioned effects are not yet clear, but alkali metal ions, especially sodium ions, have been conventionally used as counterions for fibrous cellulose with anionic groups. The inventors have discovered that while cross-linked rubber products obtained by compounding fibrous cellulose with sodium ions as counterions into rubber components exhibit excellent mechanical properties such as tensile strength, they suffer from increased water absorption and reduced water resistance. Therefore, in-depth research was conducted to suppress the decrease in water resistance, and it was found that using ammonium ions (NH4+) as counterions... + The fibrous cellulose from this study showed a suppressed decrease in water resistance compared to previous fibrous cellulose formulations. This is attributed to the high degree of ionization when the counterion is an alkali metal ion, resulting in the fibrous cellulose with anionic groups becoming more hydrophilic. On the other hand, it is believed that the counterion is ammonium ions (NH4+). + When the degree of ionization is low, the decrease in water resistance is suppressed compared to the case where the counter ion is an alkali metal ion. Furthermore, it is believed that during the manufacture of a rubber composition in which fibrous cellulose of this embodiment is compounded into a rubber component, during the preparation of a rubber mixture in which at least a crosslinking agent is added, and during heating for the manufacture of a crosslinked rubber article, at least a portion of the ammonium ions, which are counter ions of the anionic groups of fibrous cellulose having anionic groups, dissociate, and the counter ion becomes a proton (H). + This results in cross-linked rubber products where the reduction in water resistance is further suppressed, and the deterioration caused by water absorption is further suppressed.

[0040] The fibrous cellulose in this embodiment has a fiber width (average fiber width) of 100 μm or less. The fibrous cellulose can be microfibrillated cellulose with a fiber width of 1000 nm or less, or it can be microfibrillated cellulose with a fiber width exceeding 1 μm but less than 100 μm. Furthermore, the fibrous cellulose in this embodiment may contain both microfibrillated cellulose with a fiber width of 1000 nm or less and microfibrillated cellulose with a fiber width exceeding 1 μm but less than 100 μm. It should be noted that the term "fibrous cellulose" includes both "microfibrillated cellulose" and "microfibrillated cellulose".

[0041] When the fibrous cellulose in this embodiment is microfiber cellulose, the upper limit of the fiber width is 1000 nm or less, preferably 100 nm or less, more preferably 50 nm or less, further preferably 20 nm or less, and even more preferably 10 nm or less.

[0042] It should be noted that when the fibrous cellulose in this embodiment is microfiber cellulose, as described later, cellulose fibers with a fiber width exceeding 1 μm (1000 nm) (hereinafter also referred to as "coarse cellulose fibers") may also be blended into the rubber composition.

[0043] The average fiber width of the microfibrillated cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and even more preferably 2 nm or more and 10 nm or less. It should be noted that the microfibrillated cellulose is, for example, monofibrous cellulose.

[0044] The fiber width of the fine fibrous cellulose was measured, for example, using an electron microscope as follows. First, an aqueous suspension of fine fibrous cellulose with a concentration of 0.05% by mass or more and 0.1% by mass or less was prepared. This suspension was then cast onto a hydrophilically treated carbon film-coated mesh to create a sample for TEM observation. In the case of wide fibers, a SEM image of the surface cast on the glass could be observed. Next, observation based on the electron microscope image was performed at any magnification of 1000x, 5000x, 10000x, or 50000x, depending on the width of the fiber being observed. The sample, observation conditions, and magnification were adjusted in a manner that satisfied the following conditions.

[0045] (1) Draw a straight line X at any point in the observed image, with more than 20 fibers intersecting the straight line X.

[0046] (2) Draw a straight line Y that intersects the line perpendicularly within the same image, with more than 20 fibers intersecting the line Y.

[0047] For the observation images that meet the above conditions, the widths of the fibers intersecting lines X and Y are visually read. This yields at least three sets of observation images showing at least non-overlapping surface portions. Next, for each image, the widths of the fibers intersecting lines X and Y are read. This results in at least 20 × 2 × 3 = 120 fiber widths being read. The average of the read fiber widths is then taken as the number-average fiber width of the fine fibrous cellulose.

[0048] The fiber length of the microfibrillary cellulose is not particularly limited, but is 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 setting the fiber length within the above range, the destruction of the crystalline regions of the microfibrillary cellulose can be suppressed. It should be noted that the fiber length of the microfibrillary cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

[0049] In this embodiment, the fibrous cellulose is microfibrillated cellulose, with a fiber width exceeding 1 μm and less than 100 μm. From the viewpoint of dispersibility in the rubber composition and the desired physical properties of the crosslinked rubber article, the fiber width of the microfibrillated cellulose is preferably 3 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and preferably 75 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, and even more preferably 30 μm or less.

[0050] Fiber width can be adjusted by the conditions of the defibering process, such as the degree of defibering, the time of defibering, and the number of defibering processes. For the degree of defibering, for example, when using a disc mill as the defibering device, it can be adjusted by changing the gap or the number of processes; in the case of a homogenizer, it can be adjusted by pressure.

[0051] The fiber width of the microfibrillated cellulose was determined using the method described in the examples.

[0052] Fibrous cellulose preferably has a type I crystal structure. Here, the type I crystal structure of fibrous cellulose can be identified by the diffraction pattern obtained from a wide-angle X-ray diffraction photograph using graphite-monochromated CuKα (λ=1.5418Å). Specifically, it can be identified by the presence of characteristic peaks at two positions: near 2θ=14° to 17° and near 2θ=22° to 23°. The proportion of the type I crystal structure in fibrous cellulose is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. Regarding crystallinity, the X-ray diffraction pattern is measured, and the pattern is determined by conventional methods (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0053] The axial ratio (fiber length / fiber width) of the fibrous cellulose is not particularly limited, but is preferably 50 or more and 10,000 or less, more preferably 100 or more and 1,000 or less. By setting the axial ratio to the lower limit or above, it is easy to form a rubber composition containing fibrous cellulose. Setting the axial ratio to the upper limit or below is preferable, for example, when processing the fibrous cellulose into a dispersion, as it facilitates operations such as dilution.

[0054] In this embodiment, the fibrous cellulose has, for example, both crystalline and amorphous regions. The fibrous cellulose having both crystalline and amorphous regions and an axial ratio within the aforementioned range is achieved by the manufacturing method of the fibrous cellulose described later.

[0055] In this embodiment, the fibrous cellulose has anionic groups. Furthermore, the anionic groups are preferably introduced by direct oxidation of the hydroxyl groups substituted in cellulose, or by introduction into the fibrous cellulose via ester or ether bonds, more preferably by introduction into the fibrous cellulose via ester bonds. In this case, the ester bond is preferably formed by dehydration condensation of the fibrous cellulose with the compound that becomes the anionic group. By introducing the anionic group via ester bonds, the counterion NH4+ can be readily incorporated. + The anionic groups are introduced into cellulose, therefore it is preferred.

[0056] Examples of anionic groups that are ionic groups include phosphorus oxyacid groups or substituents derived from phosphorus oxyacid groups (sometimes simply referred to as phosphorus oxyacid groups), carboxyl groups or substituents derived from carboxyl groups (sometimes simply referred to as carboxyl groups), sulfur oxyacid groups or substituents derived from sulfur oxyacid groups (sometimes simply referred to as sulfur oxyacid groups), xanthate groups or substituents derived from xanthate groups (sometimes simply referred to as xanthate groups), phosphonic acid groups or substituents derived from phosphonic acid groups, hypophosphonic acid groups or substituents derived from hypophosphonic acid groups, sulfonic acid groups or substituents derived from sulfonic acid groups, carboxylalkyl groups, etc. The anionic group is preferably selected from at least one group chosen from the group consisting of a phosphorus oxyacid group, a substituent derived from a phosphorus oxyacid group, a carboxyl group, a sulfur oxyacid group, a substituent derived from a sulfur oxyacid group, carboxymethyl, carboxyethyl, and sulfonic acid groups. More preferably, it is selected from at least one group chosen from the group consisting of a phosphorus oxyacid group, a substituent derived from a phosphorus oxyacid group, a carboxyl group, a sulfur oxyacid group, and a substituent derived from a sulfur oxyacid group. From the viewpoint of introduction via ester bond, it is further preferred to have a phosphorus oxyacid group, a substituent derived from a phosphorus oxyacid group, a sulfur oxyacid group, and a substituent derived from a sulfur oxyacid group. Even more preferably, it is a phosphorus oxyacid group. By introducing a phosphorus oxyacid group as an anionic group, for example, even under alkaline or acidic conditions, the dispersibility of fibrous cellulose can be further improved, resulting in the easy acquisition of cross-linked rubber products with excellent hardness, strength, and elongation.

[0057] The phosphorus oxyacid group or a substituent derived from the phosphorus oxyacid group is, for example, the substituent shown in formula (1) below. Multiple substituents shown in formula (1) below may be introduced into each fibrous cellulose. In this case, the multiple introduced substituents shown in formula (1) below may be the same or different from each other.

[0058]

[0059] In equation (1), a, b, and n are natural numbers, and m is any number (where a = b × m). At least one of the n α and α' is 0. - The rest are R or OR. It should be noted that all α and α' can also be O. - The n α values ​​can be all the same, or they can be different from each other. β b+ It consists of at least ammonium ions (NH4) + A cation with a valence of 1 or higher, composed of organic or inorganic matter.

[0060] R is each 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. Furthermore, in formula (1), n ​​is preferably 1.

[0061] Examples of saturated linear hydrocarbon groups include methyl, ethyl, n-propyl, or n-butyl, without particular limitation. Examples of saturated branched hydrocarbon groups include isopropyl or tert-butyl, without particular limitation. Examples of saturated cyclic hydrocarbon groups include cyclopentyl or cyclohexyl, without particular limitation. Examples of unsaturated linear hydrocarbon groups include vinyl or allyl, without particular limitation. Examples of unsaturated branched hydrocarbon groups include isopropenyl or 3-butenyl, without particular limitation. Examples of unsaturated cyclic hydrocarbon groups include cyclopentenyl, cyclohexenyl, etc., without particular limitation. Examples of aromatic groups include phenyl or naphthyl, without particular limitation.

[0062] In addition, as a derivative group in R, examples of addition or substitution of the main chain or side chain of the above-mentioned hydrocarbon groups include carboxyl groups and carboxylate groups (-COO). - The functional group is in the state of at least one of the functional groups such as hydroxyl, amino, and ammonium groups, and is not particularly limited. In addition, the number of carbon atoms in the main chain constituting R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms in the main chain constituting R within the above range, the molecular weight of the phosphorus oxyacid group can be set within an appropriate range, and the penetration into the fibrous raw material can be made easier, thereby improving the yield of fibrous cellulose. It should be noted that when there are multiple Rs in formula (1) or when multiple substituents shown in formula (1) are introduced into fibrous cellulose, the multiple Rs may be the same or different from each other.

[0063] β b+ Contains ammonium ions (NH4) + It should be noted that, as β b+ It does not rule out the possibility of having NH4+. + Other cations, in this case, β b+ Except for NH4 + Cations with a valence of 1 or higher, other than those composed of organic or inorganic substances. Examples of cations with a valence of 1 or higher composed of organic substances include organonium ions. Examples of organonium ions include organoammonium ions and / or organophosphorus ions. Examples of organoammonium ions include aliphatic ammonium ions and aromatic ammonium ions. Examples of organophosphorus ions include aliphatic phosphorus ions and aromatic phosphorus ions. Examples of cations with a valence of 1 or higher composed of inorganic substances include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, and hydrogen ions. It should be noted that multiple β-ions exist in formula (1). b+ In the case of introducing multiple substituents as shown in formula (1) into fibrous cellulose, there are multiple β-type substituents. b+ They can be the same or different.

[0064] It should be noted that the counter ion is ammonium ion (NH4+).+ ")" refers to the fact that the main counter ion (more than 50 mol% of the counter ion) is ammonium ion (NH4+). + This does not exclude the inclusion of other cations as counterions. That is, β b+ It contains at least ammonium ions (NH4) + It may also contain other cations, but from the viewpoint of obtaining crosslinked rubber products with excellent water resistance, it is preferable that the counterion is NH4+ at 50 mol% or more. + More preferably, 70 mol% or more, and even more preferably 90 mol% or more, is NH4. + The upper limit is not specifically limited, but is 100 mol%.

[0065] It should be noted that the above β b+ ammonium ions (NH4) in + The content of ammonium ions (NH4+) is the content in fibrous cellulose, and is found in fibrous cellulose aqueous dispersions prepared by dispersing the aforementioned fibrous cellulose in a solvent containing water, rubber compositions prepared by blending the aforementioned fibrous cellulose in rubber components, rubber mixtures described later, and cross-linked rubber products. + Dissociation allows counterions to be replaced by protons (H+). + )wait.

[0066] More specifically, examples of substituents derived from or derived from phosphorus oxyacid groups include phosphate groups (-PO3H2), salts of phosphate groups, phosphite groups (phosphonite groups (-PO2H2), and salts of phosphite groups). Additionally, phosphorus oxyacid groups or substituents derived from or derived from phosphorus oxyacid groups can also be groups formed by the condensation of phosphate groups (e.g., pyrophosphate groups), groups formed by the condensation of phosphonic acids (e.g., polyphosphonic acid groups), phosphate ester groups (e.g., monomethyl phosphate groups, polyoxyethylene alkyl phosphate groups), alkyl phosphonic acid groups (e.g., methylphosphonic acid groups), etc.

[0067] In addition, the sulfur-oxygenated acid group (or a substituent derived from the sulfur-oxygenated acid group) is, for example, the substituent shown in formula (2) below. Various substituents shown in formula (2) below can be introduced into each fibrous cellulose. In this case, the multiple introduced substituents shown in formula (2) below may be the same or different from each other.

[0068]

[0069] In equation (2), b and n are natural numbers, p is 0 or 1, and m is any number (where 1 = b × m). It should be noted that when n is 2 or more, multiple ps can be the same number or different numbers. In equation (2), β b+ It consists of at least ammonium ions (NH4) +A cation with a valence of 1 or higher, composed of organic or inorganic matter.

[0070] β b+ Contains ammonium ions (NH4) + Additionally, as β b+ It does not rule out the possibility of having NH4+. + Other cations, in this case, are those other than NH4. + Other than cations with a valence of 1 or higher composed of organic matter, β b+ Organonium ions can be cited as examples. Examples of organonium ions include organoammonium ions and / or organophosphorus ions. Examples of organoammonium ions include aliphatic ammonium ions and aromatic ammonium ions. Examples of organophosphorus ions include aliphatic phosphorus ions and aromatic phosphorus ions. Examples of cations with a valence of more than one valence composed of inorganic substances include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, and hydrogen ions. It should be noted that when multiple substituents as shown in formula (2) are introduced into fibrous cellulose, multiple β-type substituents exist. b+ They can be the same or different.

[0071] It should be noted that the counter ion is ammonium ion (NH4+). + ")" refers to the fact that the main counter ion (more than 50 mol% of the counter ion) is ammonium ion (NH4+). + This does not exclude the inclusion of other cations as counterions. That is, β b+ It contains at least ammonium ions (NH4) + It may also contain other cations, but from the viewpoint of obtaining crosslinked rubber products with excellent water resistance, it is preferable that the counterion is NH4+ at 50 mol% or more. + More preferably, 70 mol% or more, and even more preferably 90 mol% or more, is NH4. + The upper limit is not specifically limited, but is 100 mol%.

[0072] It should be noted that the above β b+ ammonium ions (NH4) in + The content of ammonium ions (NH4+) is the content in fibrous cellulose, and is found in fibrous cellulose aqueous dispersions prepared by dispersing the aforementioned fibrous cellulose in a solvent containing water, rubber compositions prepared by blending the aforementioned fibrous cellulose in rubber components, rubber mixtures described later, and cross-linked rubber products. + Dissociation allows counterions to be replaced by protons (H+). + )wait.

[0073] The amount of ionic substituent introduced relative to fibrous cellulose is preferably 0.10 mmol / g or more and 5.20 mmol / g or less per 1 g (mass) of fibrous cellulose, more preferably 0.20 mmol / g or more, further preferably 0.40 mmol / g or more, even more preferably 0.60 mmol / g or more, more preferably 3.65 mmol / g or less, even more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, and even more preferably 2.00 mmol / g or less. Here, the denominator in the unit mmol / g indicates that the counter ion of the ionic substituent is hydrogen ion (H+). + The quality of fibrous cellulose at that time. By setting the amount of ionic substituents introduced within the above range, the defibrillation of the fibrous raw material can be made easier, and the stability of fibrous cellulose can be improved.

[0074] The amount of ionic substituent introduced relative to fibrous cellulose can be determined, for example, by neutralization titration after the cellulose fibers have undergone defibrillation treatment. In the determination using neutralization titration, an alkali such as an aqueous solution of sodium hydroxide is added to the resulting slurry containing fibrous cellulose, and the change in pH is measured to determine the amount introduced.

[0075] It should be noted that the change in the amount of ionic substituents introduced by the defibrillation treatment is very small. Therefore, the amount of ionic substituents introduced into cellulose fibers before defibrillation treatment can also be used as the amount of ionic substituents introduced into fibrous cellulose.

[0076] Figure 1 This is a graph showing the relationship between the amount of NaOH added and pH for a slurry containing fibrous cellulose with phosphorus oxyacid groups. The amount of phosphorus oxyacid groups introduced relative to the fibrous cellulose was determined, for example, as follows.

[0077] First, ion-exchanged water is added to the cellulose fiber (e.g., fibrous cellulose as defibrinated cellulose fiber) to prepare a slurry with a solid content concentration of 0.2% by mass. Then, the slurry is treated with a strong acid ion-exchange resin.

[0078] Next, while adding sodium hydroxide solution, the pH change was observed, and the results were as follows: Figure 1 The titration curve is shown on the upper side. Figure 1 In the titration curve shown on the upper side, the pH value measured relative to the amount of alkali added is plotted. Figure 1In the titration curve shown on the lower side, the pH increment (differential value) (1 / mmol) relative to the amount of alkali added is plotted. In this neutralization titration, in the pH curve measured relative to the amount of alkali added, two points where the increment (differential value of pH relative to the amount of alkali added) is maximized are identified. The point where the increment is maximized first when alkali is added is called the first endpoint, and the point where the increment is maximized next is called the second endpoint. The amount of alkali required from the start of titration to the first endpoint is equal to the first dissociative acid amount of 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 second dissociative acid amount of fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the start of titration to the second endpoint is equal to the total dissociative acid amount of fibrous cellulose contained in the slurry used for titration. Then, the value obtained by dividing the amount of alkali required from the start of titration to the first endpoint by the solids content (g) in the slurry to be titrated is the phosphorus oxyacid group introduction amount (mmol / g). It should be noted that when referred only to the amount of phosphorus oxyacid group introduced (or the amount of phosphorus oxyacid group), it indicates the amount of the first dissociated acid.

[0079] It should be noted that, Figure 1 In this titration, the region from the start of the 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, when the phosphorus oxyacid group is a phosphate group and this phosphate group undergoes condensation, the apparent amount of weak acidic groups in the phosphorus oxyacid group (also referred to as the amount of second dissociated acid in this specification) decreases, and the amount of base required in the second region is less than that required in the first region. On the other hand, the amount of strong acidic groups in the phosphorus oxyacid group (also referred to as the amount of first dissociated acid in this specification) is consistent with the amount of phosphorus atoms, regardless of whether condensation occurs. Furthermore, when the phosphorus oxyacid group is a phosphorous acid group, there are no weak acidic groups in the phosphorus oxyacid group, so sometimes the amount of base required in the second region is less, or the amount of base required in the second region is zero. In this case, the point where the pH increment is extremely large in the titration curve becomes a single point.

[0080] It should be noted that the above-mentioned phosphorus oxyacid group introduction amount (mmol / g) represents the amount of phosphorus oxyacid groups (hereinafter referred to as phosphorus oxyacid group amount (acid type)) in the acid type fibrous cellulose since the denominator represents the mass of the acid type fibrous cellulose. On the other hand, when the counter ion of the phosphorus oxyacid group is replaced by any cation C in a charge equivalent manner, the amount of phosphorus oxyacid groups (hereinafter referred to as phosphorus oxyacid group amount (C type)) in the fibrous cellulose with cation C as the counter ion can be calculated by converting the denominator to the mass of the fibrous cellulose with cation C as the counter ion. That is, it can be calculated by the following formula.

[0081] Phosphorus oxyacid content (Type C)

[0082] =Phosphorus oxyacid content (acid type) / {1 + (W-1) × P / 1000}

[0083] P [mmol / g]: The total anionic content of phosphorus oxyacid groups (total dissociated acid content of phosphorus oxyacid groups) derived from fibrous cellulose.

[0084] W: The formula weight of each monovalent cation C (e.g., 23 for Na, 9 for Al).

[0085] Figure 2 A graph showing the relationship between the amount of NaOH added and pH relative to a fibrous cellulose dispersion having a carboxyl group as an ionic substituent is presented. The amount of carboxyl group introduced relative to the fibrous cellulose was determined, for example, as follows.

[0086] First, ion-exchanged water is added to the cellulose fiber (e.g., fibrous cellulose as defibrinated cellulose fiber) to prepare a slurry with a solid content concentration of 0.2% by mass. Then, the slurry is treated with a strong acid ion-exchange resin.

[0087] Next, while adding sodium hydroxide solution, the pH change was observed, and the results were as follows: Figure 2 The titration curve is shown on the upper side. Figure 2 In the titration curve shown on the upper side, the pH value measured relative to the amount of alkali added is plotted. Figure 2 In the titration curve shown on the lower side, the increment (differential value) of pH relative to the amount of alkali added (1 / mmol) is plotted. In this neutralization titration, in the curve of pH measured relative to the amount of alkali added, a point is identified where the increment (differential value of pH relative to the amount of alkali added) is extremely large; this maximum point is called the first endpoint. Here, Figure 2 The region from the start of titration to the first endpoint is called the first region. The amount of alkali required for the first region is equal to the amount of carboxyl groups in the dispersion used for titration. Then, the amount of alkali (mmol) required for the first region of the titration curve is divided by the solid content (g) in the dispersion containing fibrous cellulose of the titrant, thereby calculating the amount of carboxyl groups introduced (mmol / g).

[0088] It should be noted that the above-mentioned carboxyl group introduction amount (mmol / g) is the mass of acid-type fibrous cellulose in the denominator, and therefore represents the amount of carboxyl groups possessed by acid-type fibrous cellulose (hereinafter referred to as carboxyl group amount (acid type)). On the other hand, when the counter ion of the carboxyl group is replaced by any cation C in a charge equivalent manner, the amount of carboxyl groups possessed by fibrous cellulose with cation C as the counter ion can be determined by converting the denominator to the mass of fibrous cellulose with cation C as the counter ion (hereinafter, carboxyl group amount (C type)). That is, it can be calculated by the following formula.

[0089] Carboxyl group content (C type)

[0090] =Carboxyl group content (acid type) / {1 + (W-1) × (Carboxyl group content (acid type)) / 1000}

[0091] W: The formula weight of each monovalent cation C (e.g., 23 for Na, 9 for Al).

[0092] In the determination of the amount of ionic substituents based on titration, if too much sodium hydroxide aqueous solution is added or the titration interval is too short, the amount of ionic substituents may be lower than it should be, making it impossible to obtain an accurate value. As an appropriate amount of solution and titration interval, it is preferable to titrate 10-50 μL of 0.1N sodium hydroxide aqueous solution every 5-30 seconds. Furthermore, to eliminate the influence of dissolved carbon dioxide in the fibrous cellulose dispersion, it is preferable to perform the measurement while blowing an inactive gas such as nitrogen into the slurry, for example, from 15 minutes before the start of the titration until the end of the titration.

[0093] In addition, regarding the amount of sulfate ester groups and sulfonic acid groups introduced relative to fibrous cellulose, the obtained fibrous cellulose was wet-ashed with perchloric acid and concentrated nitric acid, diluted at an appropriate ratio, and the sulfur content was determined by ICP emission spectroscopy.

[0094] The value obtained by dividing the sulfur content by the absolute dry mass of the tested fibrous cellulose is taken as the sulfur oxyacid group · sulfonic acid group content (unit: mmol / g).

[0095] The degree of polymerization of fibrous cellulose is preferably 100 or more and 1000 or less. If the degree of polymerization is 100 or more, sufficient reinforcing effect can be obtained, for example, when added to a rubber component, and therefore it is preferred. Furthermore, if the degree of polymerization is 1000 or less, the dispersibility is better, for example, when added to a rubber component, and therefore it is preferred.

[0096] The degree of polymerization of fibrous cellulose is more preferably 150 or more, further preferably 300 or more, even more preferably 400 or more, and more preferably 900 or less.

[0097] The degree of polymerization of fibrous cellulose is calculated from the pulp viscosity determined according to Tappi T230. Specifically, after measuring the viscosity (denoted as η1) obtained by dispersing the fibrous cellulose of the test object in an aqueous solution of copper ethylenediamine and the blank viscosity (denoted as η0) obtained using only the dispersion medium, the specific viscosity (ηsp) and intrinsic viscosity ([η]) are determined according to the following formula.

[0098] ηsp=(η1 / η0)-1

[0099] [η] = ηsp / (c(1+0.28×ηsp))

[0100] Here, c in the formula represents the concentration (g / mL) of fibrous cellulose during viscosity measurement.

[0101] Then, the degree of aggregation (DP) is calculated using the following formula.

[0102] DP = 1.75 × [η]

[0103] This degree of polymerization is the average degree of polymerization determined by the viscosity method, and is therefore sometimes referred to as the "viscosity-average degree of polymerization".

[0104] In order to obtain fibrous cellulose with anionic groups (anionic substituents) introduced as described above, it is preferable to have an anionic substituent introduction step, a washing step, and a defiberization step in sequence, wherein the anionic substituent is introduced into the cellulose-containing cellulose fiber raw material. Alternatively, an acid treatment step may be included instead of the washing step, or an acid treatment step may be included in addition to the washing step.

[0105] Additionally, depending on the requirements, counterions can be replaced with NH4 before or after the defiberization process. + The process.

[0106] Examples of anionic substituent introduction processes include phosphorus oxyacid group introduction, carboxyl group introduction, sulfur oxyacid group introduction, xanthic acid group introduction, phosphonic acid or hypophosphonic acid group introduction, and sulfonic acid group introduction. These will be described separately below.

[0107] <Fiber Raw Materials>

[0108] Fiber raw materials are fibrous materials containing cellulose. There are no particular limitations on what constitutes a fiber raw material; examples include wood pulp, non-wood pulp, and deinking pulp. Wood pulp is not specifically limited to any particular type; examples include chemical pulps such as broadleaf kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), alkaline pulp (AP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP); semi-chemical pulps such as SCP and CGP; and mechanical pulps such as GP and thermomechanical pulps (TMP, BCTMP). Non-wood pulp is not specifically limited to any particular type; examples include cotton pulps such as cotton linters and cotton lint, and non-wood pulps such as hemp, wheat straw, bamboo, and bagasse. Deinking pulp is not specifically limited to any particular type; examples include deinking pulp made from waste paper. The pulp raw material in this embodiment can be one of the above-mentioned materials alone, or two or more materials can be used in combination.

[0109] Of the aforementioned pulps, wood pulp and deinked pulp are preferred from the viewpoint of easy availability. Furthermore, among wood pulps, from the viewpoint of a high cellulose ratio and a high yield of fibrous cellulose during defibrillation, and from the viewpoint of obtaining fibrous cellulose with low cellulose decomposition and high axial ratio in long fibers, chemical pulp is preferred, and kraft pulp and sulfite pulp are even more preferred. It should be noted that when using fibrous cellulose with a high axial ratio of long fibers, there is a tendency for the viscosity to increase.

[0110] <Phosphorus-containing oxyacid group introduction process>

[0111] When obtaining cellulose fibers with ionic substituents, it is preferable to perform an ionic substituent introduction step before the defiberization process. For example, a phosphorus oxyacid group introduction step can be described as an ionic substituent introduction step. The phosphorus oxyacid group introduction step involves applying at least one compound (hereinafter also referred to as "Compound A") selected from compounds capable of introducing phosphorus oxyacid groups by reacting with hydroxyl groups present in the cellulose-containing fiber raw material. Through this step, cellulose fibers with phosphorus oxyacid groups are obtained.

[0112] In the phosphorus oxyacid group introduction process of this embodiment, the reaction of the cellulose-containing fiber raw material with compound A can be carried out in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as "compound B"). On the other hand, the reaction of the cellulose-containing fiber raw material with compound A can also be carried out in the absence of compound B. From the viewpoint of reactivity and obtaining fibrous cellulose with ammonium ions as counterions, it is preferable to carry out the reaction in the presence of compound B.

[0113] As an example of a method for applying compound A to a fiber raw material in the presence of compound B, a method of mixing compound A and compound B in a dry, wet, or slurry-like state of the fiber raw material can be cited. Since the reaction has high uniformity, it is preferable to use a dry or wet state of the fiber raw material, and particularly preferable to use a dry state of the fiber raw material. The form of the fiber raw material is not particularly limited; for example, cotton-like or sheet-like forms are preferred. Methods can be used to add compound A and compound B to the fiber raw material in the form of powder, solution dissolved in a solvent, or melted by heating above their melting point. Since the reaction has high uniformity, it is preferable to add them in the form of a solution dissolved in a solvent, particularly an aqueous solution. Furthermore, compound A and compound B can be added to the fiber raw material simultaneously, separately, or as a mixture. As for the method of adding compound A and compound B, there is no particular limitation; when compound A and compound B are in solution form, the fiber raw material can be immersed in the solution and allowed to absorb the liquid before being removed, or the solution can be added dropwise to the fiber raw material. Alternatively, the necessary amounts of compound A and compound B can be added to the fiber raw material, or excess compounds A and B can be removed by pressing and filtering after adding excess compounds A and B to the fiber raw material.

[0114] Compound A used in this embodiment can be any compound having a phosphorus atom and capable of forming an ester bond with cellulose. Examples include phosphoric acid or its salts, phosphorous acid or its salts, dehydrated condensed phosphoric acid or its salts, and phosphoric anhydride (phosphorus pentoxide), etc., without particular limitation. Phosphoric acid can be of various purities, such as 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid. Phosphorous acid can be 99% phosphorous acid (phosphonic acid). Dehydrated condensed phosphoric acid is formed by the condensation of two or more molecules of phosphoric acid through a dehydration reaction; examples include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphites, and dehydrated condensed phosphates can be lithium, sodium, potassium, or ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid, and they can have various degrees of neutralization. From the perspective of high efficiency of phosphate group introduction, easier improvement of defiberization efficiency in the defiberization process described later, low cost and easy industrial application, phosphoric acid, sodium salt of phosphate, potassium salt of phosphate, ammonium salt of phosphate or phosphorous acid, sodium salt of phosphorous acid, potassium salt of phosphorous acid, ammonium salt of phosphorous acid are preferred, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate or phosphorous acid, sodium phosphite are more preferred, phosphoric acid, ammonium dihydrogen phosphate or phosphorous acid are even more preferred, and ammonium dihydrogen phosphate or phosphorous acid are even more preferred.

[0115] The amount of compound A added relative to the fiber raw material is not particularly limited. For example, when converting the amount of compound A added to phosphorus atomic weight, the amount of phosphorus atoms added relative to the fiber raw material (absolute dry weight) is preferably 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 relative 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 relative to the fiber raw material below the above upper limit, a balance can be achieved between the yield improvement effect and the cost.

[0116] In this embodiment, compound B is selected from at least one of 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 reactivity and ease of acquisition, urea is preferred as compound B. From the viewpoint of improving the uniformity of the reaction, compound B is preferably used in the form of an aqueous solution. Furthermore, from the viewpoint of further improving the uniformity of the reaction, an aqueous solution containing both compound A and compound B is preferred.

[0117] The amount of compound B added relative to the fiber raw material (absolute dry weight) is not particularly limited, for example, preferably 1% or more and 500% or less by mass, more preferably 10% or more and 400% or less by mass, and even more preferably 100% or more and 350% or less by mass.

[0118] In the process of introducing phosphorus-containing oxyacid groups, it is preferable to heat-treat the fiber raw material after adding or mixing compound A, etc. As the heat treatment temperature, it is preferable to select a temperature that can suppress the thermal decomposition and hydrolysis reaction of the fiber and efficiently introduce the phosphorus-containing oxyacid groups. The heat treatment temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower. Furthermore, in the heat treatment, equipment with various heat media can be used, such as hot air drying devices, stirred drying devices, rotary drying devices, disc drying devices, roller heating devices, plate heating devices, fluidized bed drying devices, belt drying devices, filter drying devices, vibrating fluidized bed drying devices, airflow drying devices, reduced pressure drying devices, infrared heating devices, far-infrared heating devices, microwave heating devices, and high-frequency drying devices.

[0119] In this embodiment, the heat treatment can be performed by, for example, adding compound A to the sheet-like fiber material through impregnation and then heating, or by mixing or stirring the fiber material and compound A using a kneader while heating. This suppresses uneven concentrations of compound A in the fiber material and allows for more uniform introduction of phosphoric oxyacid groups onto the surface of the cellulose fibers contained within the fiber material. This is believed to be because, as water molecules move towards the surface of the fiber material during drying, it prevents dissolved compound A from being pulled towards the fiber material surface by water molecules due to surface tension (i.e., preventing uneven concentrations of compound A).

[0120] Furthermore, the heating device used in the heat treatment is preferably one capable of continuously removing the moisture held in the slurry and the moisture generated by the dehydration condensation (phosphorylation) reaction of the accompanying compound A with hydroxyl groups contained in cellulose and other fiber raw materials to the outside of the device system. Examples of such heating devices include, for instance, an oven with a forced-airflow mechanism. By continuously removing moisture from the device system, not only can the reverse reaction of phosphorylation, i.e., the hydrolysis of phosphate ester bonds, be suppressed, but also the acid hydrolysis of sugar chains in the fiber can be suppressed. Therefore, fibrous cellulose with a high axial ratio can be obtained.

[0121] The heat treatment time, calculated from the point at which the moisture in the fiber raw material is substantially removed, is preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and even more preferably 10 seconds or more and 800 seconds or less. In this embodiment, by setting the heating temperature and heating time to an appropriate range, the amount of phosphorus oxyacid groups introduced can be set to a preferred range.

[0122] The phosphorus oxyacid group introduction process can be performed at least once, or it can be repeated more than twice. By performing the phosphorus oxyacid group introduction process more than twice, a large number of phosphorus oxyacid groups can be introduced into the fiber raw material.

[0123] The amount of phosphorus oxyacid groups introduced relative to the cellulose raw material is preferably 0.10 mmol / g or more and 5.20 mmol / g or less per 1g (mass) of cellulose fiber, more preferably 0.20 mmol / g or more, further preferably 0.50 mmol / g or more, even more preferably 1.00 mmol / g or more, and more preferably 3.65 mmol / g or less, even more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, and even more preferably 2.00 mmol / g or less. By setting the amount of phosphorus oxyacid groups introduced within the above range, the defibrillation of cellulose fibers in the defibrillation process can be facilitated, and the stability of fibrous cellulose can be improved.

[0124] <Carboxyl group introduction process>

[0125] As an ionic substituent introduction process, a carboxyl group introduction process may be included. The carboxyl group introduction process involves oxidizing cellulose-containing fiber raw materials as follows: ozone oxidation, Fenton-based oxidation, TEMPO oxidation, etc.; or treating them with a compound having a group derived from a carboxylic acid or a derivative thereof, or with an anhydride of a compound having a group derived from a carboxylic acid or a derivative thereof.

[0126] The term "compound having a group derived from a carboxylic acid" is not particularly limited, and 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, the term "derivative of a compound having a group derived from a carboxylic acid" is not particularly limited, and examples include imides of the anhydrides of compounds having a carboxyl group, and derivatives of the anhydrides of compounds having a carboxyl group. The term "imide of the anhydrides of compounds having a carboxyl group" is also not particularly limited, and examples include imides of dicarboxylic acid compounds such as maleimide, succinimidide, and phthalimide.

[0127] An anhydride, as a compound having a group derived from a carboxylic acid, is not particularly limited, and examples include anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Furthermore, derivatives of anhydrides of compounds having a group derived from a carboxylic acid are not particularly limited, and examples include compounds formed by substituting at least some hydrogen atoms of anhydrides of carboxyl compounds such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride, which are substituted with substituents such as alkyl or phenyl groups.

[0128] When TEMPO oxidation is performed in the carboxyl group introduction process, it is preferable to perform the treatment under conditions where the pH is between 6 and 8. Such a treatment is also called neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment can be performed, for example, by adding pulp as a fiber raw material, nitrogen-oxygen radicals such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxo radical) as a catalyst, and sodium hypochlorite as a sacrificial agent to a sodium phosphate buffer (pH=6.8). Furthermore, by coexisting with sodium chlorite, the aldehydes generated during the oxidation process can be efficiently oxidized to carboxyl groups.

[0129] Furthermore, TEMPO oxidation treatment can be carried out under conditions where the pH is above 10 and below 11. Such treatment is also known as alkaline TEMPO oxidation treatment. Alkaline TEMPO oxidation treatment can be carried out, for example, by adding nitric oxide radicals such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidant to pulp, which is a fibrous raw material.

[0130] The amount of carboxyl group introduced relative to cellulose fibers varies depending on the type of substituent. For example, when the carboxyl group is introduced via TEMPO oxidation, the amount relative to 1 g (mass) of cellulose fibers is preferably 0.10 mmol / g or more and 3.65 mmol / g or less, more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.60 mmol / g or more, and more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, and even more preferably 2.00 mmol / g or less. Furthermore, when the substituent is carboxymethyl, the amount of carboxyl group introduced relative to 1 g (mass) of cellulose fibers can be 5.8 mmol / g or less. By setting the amount of carboxyl group introduced within the above range, the defibrillation of cellulose fibers in the defibrillation process can be facilitated, and the stability of fibrous cellulose can be improved.

[0131] <Sulfonic Acid Group Introduction Process>

[0132] As an ionic substituent introduction process, a sulfonic acid group introduction process may be included. The sulfonic acid group introduction process reacts the hydroxyl groups of the cellulose fiber raw material with sulfur-containing oxyacids to obtain cellulose fibers with sulfonic acid groups (sulfonic acid group introduced fibers).

[0133] In the sulfonic acid group introduction process, instead of compound A in the above-described <phosphorus oxyacid group introduction process>, at least one compound selected from compounds capable of introducing sulfonic acid groups through reaction with hydroxyl groups present in cellulose-containing fiber raw materials (hereinafter also referred to as "compound C") is used. As compound C, any compound having a sulfur atom and capable of forming an ester bond with cellulose can be used; examples include sulfuric acid or its salts, sulfurous acid or its salts, sulfonic acid amines, etc., without particular limitation. As sulfuric acid, sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid). As sulfurous acid, 5% sulfurous acid water can be used. As sulfates or sulfites, examples include lithium salts, sodium salts, potassium salts, ammonium salts, etc., of sulfates or sulfites, which can have various degrees of neutralization. As sulfonic acid amines, aminosulfonic acid, etc., can be used. In the sulfonic acid group introduction process, compound B from the above-described <phosphorus oxyacid group introduction process> is preferably used in the same manner.

[0134] In the sulfonic acid group introduction process, it is preferable to heat-treat the cellulose raw material after mixing it with an aqueous solution containing a sulfur-containing oxyacid and urea and / or urea derivatives. The heat treatment temperature is preferably selected to suppress the thermal decomposition and hydrolysis of the fiber and to efficiently introduce the sulfonic acid groups. The heat treatment temperature is preferably 100°C or higher and 300°C or lower, more preferably 120°C or higher, further preferably 150°C or higher, and even more preferably 250°C or lower, and even more preferably 200°C or lower.

[0135] In the heat treatment process, it is preferable to heat until substantially free of moisture. Therefore, the heat treatment time varies depending on the moisture content of the cellulose raw material and the amount of aqueous solution containing sulfur-containing oxyacids and urea and / or urea derivatives added, and is preferably 10 seconds or more and 10,000 seconds or less. Various heat media can be used in the heat treatment, such as hot air drying devices, stirred drying devices, rotary drying devices, disc drying devices, roller heating devices, plate heating devices, fluidized bed drying devices, belt drying devices, filter drying devices, vibrating fluidized bed drying devices, airflow drying devices, reduced pressure drying devices, infrared heating devices, far-infrared heating devices, microwave heating devices, and high-frequency drying devices.

[0136] The amount of sulfonic acid groups introduced relative to the cellulose raw material is preferably 0.05 mmol / g or more and 5.00 mmol / g or less, more preferably 0.10 mmol / g or more, even more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, and more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, and even more preferably 2.00 mmol / g or less. By setting the amount of sulfonic acid groups introduced within the above range, the defibrillation of cellulose fibers in the defibrillation process can be facilitated, and the stability of fibrous cellulose can be improved.

[0137] <Oxidation process using chlorine-based oxidants (second carboxyl group introduction process)>

[0138] As an ionic substituent introduction process, an oxidation process utilizing a chlorine-based oxidant may be included. In the oxidation process utilizing a chlorine-based oxidant, a carboxyl group is introduced into the fiber raw material by reacting the chlorine-based oxidant with a hydroxyl group in a wet or dry state.

[0139] Examples of chlorine-based oxidants include hypochlorous acid, hypochlorite, chlorite, chlorite, chloric acid, chlorate, perchloric acid, perchlorate, and chlorine dioxide. Considering the efficiency of substituent introduction, fiber dissociation efficiency, cost, and ease of processing, sodium hypochlorite, sodium chlorite, and chlorine dioxide are preferred chlorine-based oxidants. When adding chlorine-based oxidants, they can be added directly to the fiber raw material in reagent form (solid or liquid), or they can be dissolved in a suitable solvent before addition.

[0140] In the oxidation process using chlorine-based oxidants, the concentration of the chlorine-based oxidant solution, converted to an effective chlorine concentration, is preferably 1% by mass or more and 1000% by mass or less, more preferably 5% by mass or more and 500% by mass or less, and even more preferably 10% by mass or more and 100% by mass or less. The amount of chlorine-based oxidant added relative to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 10 parts by mass or more and 10,000 parts by mass or less, and even more preferably 100 parts by mass or more and 5,000 parts by mass or less.

[0141] The reaction time with the chlorine-based oxidant in the oxidation process can be varied depending on the reaction temperature. For example, it is preferably 1 minute or more and 1000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. The pH during the reaction is preferably 5 or more and 15 or less, more preferably 7 or more and 14 or less, and even more preferably 9 or more and 13 or less. In addition, the pH at the start of the reaction and during the reaction is preferably kept constant (e.g., pH 11) while appropriately adding hydrochloric acid and sodium hydroxide. Furthermore, after the reaction, excess reaction reagents and byproducts can be removed by washing with water, such as by filtration.

[0142] <Xanthate group introduction process>

[0143] The manufacturing process of fibrous cellulose may include a xanthate group introduction process as an ionic substituent introduction process. The xanthate group introduction process can obtain cellulose fibers with xanthate groups (xanthate group introduced fibers) by replacing the hydroxyl groups of the cellulose-containing cellulose raw material with xanthate groups as shown in the following formula (3).

[0144] -OCSS - M + ……(3)

[0145] Here, M + It is selected from at least one of hydrogen ions, monovalent metal ions, ammonium ions, aliphatic or aromatic ammonium ions.

[0146] In the xanthate group introduction process, firstly, the cellulose fiber raw material containing the above-mentioned cellulose is treated with an alkaline solution to obtain alkali cellulose. Examples of alkaline solutions include aqueous solutions of alkali metal hydroxides and aqueous solutions of alkaline earth metal hydroxides. Preferably, the alkaline solution is an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, more preferably an aqueous solution of sodium hydroxide. When the alkaline solution is an aqueous solution of an alkali metal hydroxide, the concentration of the alkali metal hydroxide in the aqueous solution is preferably 4% by mass or more and 9% by mass or less, more preferably 5% by mass or more. By setting the concentration of the alkali metal hydroxide to the lower limit or above, the mercerization of cellulose can be fully carried out, reducing the amount of byproducts generated during subsequent xanthate treatment, and as a result, the yield of xanthate group introduced into the fiber can be improved. This allows for more efficient implementation of the defibrillation process described later. Furthermore, by setting the concentration of the alkali metal hydroxide to the upper limit or below, the penetration of the aqueous solution of the alkali metal hydroxide into the crystalline region of cellulose can be suppressed during mercerization, thus easily maintaining the type I crystal structure of cellulose and further improving the yield of fibrous cellulose.

[0147] The preferred alkali treatment time is 30 minutes or more and 6 hours or less, more preferably 1 hour or more and 5 hours or less. By keeping the alkali treatment time within the above range, the final yield can be improved, and productivity can be increased.

[0148] The alkali cellulose obtained by the above-described alkali treatment is preferably subjected to solid-liquid separation to remove as much aqueous solution as possible. This reduces the water content during the subsequent xanthate treatment and promotes the reaction. Common dehydration methods such as centrifugation and filtration can be used for solid-liquid separation. It should be noted that, relative to the total mass of the alkali cellulose after solid-liquid separation, the concentration of alkali metal hydroxides in the alkali cellulose after solid-liquid separation is preferably 3% by mass or more and 8% by mass or less.

[0149] In the xanthate introduction process, a xanthate treatment step is performed after alkali treatment. In the xanthate treatment step, carbon disulfide (CS2) reacts with alkali cellulose to form (-O... - Na + )base becomes (-OCSS - Na + Xanthate-based fibers are obtained by introducing xanthate groups into alkali cellulose. It should be noted that, in the above, the metal ions introduced into alkali cellulose are representatively represented by Na+. + It is described, but other alkali metal ions also undergo the same reaction.

[0150] In the xanthan acidification process, it is preferable to supply at least 10% by mass of carbon disulfide relative to the absolute dry weight of cellulose in alkali cellulose. Furthermore, the contact time between carbon disulfide and alkali cellulose in the xanthan acidification process is preferably at least 30 minutes, more preferably at least 1 hour. By contacting carbon disulfide with alkali cellulose, xanthan acidification proceeds rapidly, but it takes time for carbon disulfide to penetrate into the interior of the alkali cellulose; therefore, the reaction time is preferably within the aforementioned range. On the other hand, a contact time of 6 hours or less between carbon disulfide and alkali cellulose is sufficient to ensure adequate penetration into the dehydrated alkali cellulose mass, thereby largely completing the reactive xanthan acidification.

[0151] The reaction temperature in the xanthate treatment is preferably below 46°C. By keeping the reaction temperature within this range, the decomposition of alkali cellulose is easily suppressed. In addition, by setting the reaction temperature within this range, the reaction is easily and uniformly carried out, thus suppressing the formation of by-products and, consequently, suppressing the removal of the generated xanthate groups.

[0152] In the xanthate group introduction process, the amount of xanthate groups introduced relative to 1 g (mass) of the fiber raw material is preferably 0.60 mmol / g or more and 5.00 mmol / g or less, more preferably 0.70 mmol / g or more, further preferably 0.80 mmol / g or more, even more preferably 1.00 mmol / g or more, even more preferably 1.20 mmol / g or more, and more preferably 3.00 mmol / g or less. By setting the amount of xanthate groups introduced within the above range, the defibrillation of the fiber raw material can be facilitated, and the stability of the fibrous cellulose can be improved.

[0153] <Phosphonic acid or phosphonoside introduction process (phosphine alkylation process)>

[0154] As an ionic substituent introduction process, it may include a phosphonic acid group or a phosphonoside group introduction process (phosphonylation process). In the phosphonylation process, a compound (compound E) having a reactive group and having a phosphonic acid group or a phosphonoside group as an essential component is introduced. A Compound B, selected from alkali compounds, urea and its derivatives, is added as an arbitrary component to a hydroxyl-containing fiber raw material in a moist or dry state to react and thereby introduce phosphonic acid groups or hypophosphonic acid groups into the fiber raw material.

[0155] Examples of reactive groups include haloalkyl groups, vinyl groups, and epoxy groups (glycidyl groups).

[0156] As compound E AExamples include vinylphosphonic acid, phenylvinylphosphonic acid, and phenylvinylphosphonic acid. Considering the efficiency of substituent introduction, fiber debonding efficiency, cost, and ease of processing, compound E... A Vinylphosphonic acid is preferred.

[0157] Furthermore, as an optional component, it is also preferable to use compound B from the above-described <phosphorus oxyacid group introduction process>, and the amount added is also preferably as described above.

[0158] Add compound E A The reagent can be added directly to the fiber raw material in the form of a reagent (solid or liquid), or it can be dissolved in a suitable solvent before addition. Preferably, the fiber raw material is pre-treated with alkali cellulose, or alkali cellulose is applied simultaneously with the reaction. The method of alkali cellulose treatment is as described above.

[0159] The reaction temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0160] Compound E A The amount added relative to 100 parts by weight of fiber raw material is preferably 1 part by weight or more and 100,000 parts by weight or less, more preferably 2 parts by weight or more and 10,000 parts by weight or less, and even more preferably 5 parts by weight or more and 1,000 parts by weight or less.

[0161] The reaction time can vary depending on the reaction temperature, and is preferably 1 minute or more and 1000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. Furthermore, after the reaction, excess reaction reagents and byproducts can be removed by filtration or other methods by washing with water.

[0162] <Sulfonic acid group introduction process (sulfonylation process) (second sulfonic acid group introduction process)>

[0163] As an ionic substituent introduction process, a sulfonic acid group introduction process (sulfonylation process) may be included. In sulfonylation, a compound (compound E) having reactive groups and sulfonic acid groups as essential components is introduced. B Compound B, selected from alkali compounds, urea and its derivatives, and as an arbitrary component, is added to a hydroxyl-containing fiber raw material in a wet or dry state to react and thereby introduce sulfonic acid groups into the fiber raw material.

[0164] Examples of reactive groups include haloalkyl groups, vinyl groups, and epoxy groups (glycidyl groups).

[0165] As compound E BExamples include sodium 2-chloroethane sulfonate, sodium vinyl sulfonate, sodium p-styrene sulfonate, and 2-acrylamide-2-methylpropanesulfonic acid. Among these, compound E... (The sentence is incomplete and requires further context to translate accurately.) B Sodium vinyl sulfonate is preferred.

[0166] Furthermore, as an optional component, it is also preferable to use compound B from the above-described <phosphorus oxyacid group introduction process>, and the amount added is also preferably as described above.

[0167] Add compound E B The reagent can be added directly to the fiber raw material in the form of a reagent (solid or liquid), or it can be dissolved in a suitable solvent before addition. Preferably, the fiber raw material is pre-treated with alkali cellulose, or alkali cellulose is applied simultaneously with the reaction. The method of alkali cellulose treatment is as described above.

[0168] The reaction temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0169] Compound E B The amount added relative to 100 parts by weight of fiber raw material is preferably 1 part by weight or more and 100,000 parts by weight or less, more preferably 2 parts by weight or more and 10,000 parts by weight or less, and even more preferably 5 parts by weight or more and 1,000 parts by weight or less.

[0170] The reaction time can vary depending on the reaction temperature, and is preferably 1 minute or more and 1000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 15 minutes or more and 400 minutes or less. Furthermore, after the reaction, excess reaction reagents and byproducts can be removed by filtration or other methods of washing with water.

[0171] <Carboxylation process (third carboxyl group introduction process)>

[0172] As an ionic substituent introduction process, a carboxylation process may be included. This involves introducing a compound (compound E) with reactive groups and a carboxyl group as an essential component. C Compound B, selected from alkali compounds, urea and its derivatives, is added as an arbitrary component to a hydroxyl-containing fiber raw material in a moist or dry state to react and thereby introduce carboxyl groups into the fiber raw material.

[0173] Examples of reactive groups include haloalkyl groups, vinyl groups, and epoxy groups (glycidyl groups).

[0174] As compound E CBased on the factors of substituent introduction efficiency, fiber debonding efficiency, cost, and ease of processing, monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, 3-chloropropionic acid, sodium 2-chloropropionate, and sodium 3-chloropropionate are preferred.

[0175] Furthermore, as an optional component, it is also preferable to use compound B from the above-described <phosphorus oxyacid group introduction process>, and the amount added is also preferably as described above.

[0176] Add compound E C The reagent can be added directly to the fiber raw material in the form of a reagent (solid or liquid), or it can be dissolved in a suitable solvent before addition. Preferably, the fiber raw material is pre-treated with alkali cellulose, or alkali cellulose is applied simultaneously with the reaction. The method of alkali cellulose treatment is as described above.

[0177] The reaction temperature is preferably 50°C or higher and 300°C or lower, more preferably 70°C or higher and 200°C or lower, and even more preferably 90°C or higher and 150°C or lower.

[0178] Compound E C The amount added relative to 100 parts by weight of fiber raw material is preferably 1 part by weight or more and 100,000 parts by weight or less, more preferably 2 parts by weight or more and 10,000 parts by weight or less, and even more preferably 5 parts by weight or more and 1,000 parts by weight or less.

[0179] The reaction time can vary depending on the reaction temperature, and is preferably 1 minute or more and 1000 minutes or less, more preferably 3 minutes or more and 500 minutes or less, and even more preferably 5 minutes or more and 400 minutes or less. Furthermore, after the reaction, excess reaction reagents and byproducts can be removed by filtration or other methods by washing with water.

[0180] <Cleaning Process>

[0181] In the process of obtaining cellulose fibers with anionic substituents, a cleaning process can be performed on the fibers to which the anionic substituents have been introduced, as needed. The cleaning process can be performed, for example, by washing the fibers with water and / or an organic solvent. Alternatively, the cleaning process can be performed after the processes described later, and there is no particular limitation on the number of cleaning cycles performed in each cleaning process.

[0182] In this embodiment, the counter ion of the anionic groups in fibrous cellulose is ammonium ion (NH4+). + When anionic groups are introduced into cellulose fibers through esterification using the aforementioned compound B, the counter ion of the introduced anionic group is NH4+. + Therefore, there is no need for the process of replacing counterions.

[0183] On the other hand, when anionic groups are introduced through TEMPO oxidation, hypochlorous acid oxidation, carboxymethylation, etc., it is necessary to replace the counter ion of the anionic group with NH4+. + The process involves, in this case, preferably, acid treatment of the cellulose fibers incorporating anionic groups and replacement of the counterions with NH4. + The process involves acid treatment and the replacement of counterions with NH4+. + The defiberization process can be performed before or after the defiberization process described later. From the viewpoint of ease of manufacturing, it is preferable to perform it before the defiberization process. The fibrous cellulose after the defiberization process has high water absorption and high viscosity, thus increasing the load on the washing process.

[0184] <Acid Treatment Process>

[0185] In the process of obtaining cellulose fibers with anionic substituents, an acid treatment step can be set between the anionic substituent introduction step and the defiberization step. For example, the anionic substituent introduction step, the acid treatment step, and the replacement of the counter ion with NH4 can be performed sequentially. + The process includes the fiber unwinding process.

[0186] Through an acid treatment process, the counter ion of the anionic group becomes a hydrogen ion.

[0187] The method of acid treatment is not particularly limited; for example, impregnating the fiber raw material in an acidic solution containing acid can be cited. The concentration of the acidic solution used is not particularly limited; for example, it is preferably 10% by mass or less, more preferably 5% by mass or less. Furthermore, the pH of the acidic solution used is not particularly limited; for example, it is preferably 0 or higher and 4 or lower, more preferably 1 or higher and 3 or lower. The acid contained in the acidic solution can be, for example, inorganic acids, sulfonic acids, carboxylic acids, etc. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorite, 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, tartaric acid, etc. Of these, hydrochloric acid or sulfuric acid is particularly preferred.

[0188] The temperature of the acid solution used in the acid treatment is not particularly limited, but is preferably 5°C or higher and 100°C or lower, more preferably 20°C or higher and 90°C or lower. The immersion time in the acid solution during acid treatment is not particularly limited, but is preferably 5 minutes or higher and 120 minutes or lower, more preferably 10 minutes or higher and 90 minutes or lower. The amount of acid solution used in the acid treatment is not particularly limited, but is preferably 100 parts by weight or higher and 100,000 parts by weight or lower, more preferably 1,000 parts by weight or higher and 10,000 parts by weight or lower, relative to the absolute dry weight of the fiber raw material.

[0189] Replace the counter ion with NH4 + Process >

[0190] As a way to replace counterions with NH4 + The method is not particularly limited; for example, a method of impregnating fibers with anionic groups introduced through the above-mentioned acid treatment process in ammonia water can be cited. The concentration of the ammonia water used is not particularly limited; for example, it is preferably 5N or more, more preferably 10N or more, and even more preferably 14N or more.

[0191] The temperature of the ammonia solution is not particularly limited, but is preferably 5°C or higher and 100°C or lower, more preferably 20°C or higher and 90°C or lower. The immersion time in the ammonia solution is not particularly limited, but is preferably 5 minutes or higher and 120 minutes or lower, more preferably 10 minutes or higher and 90 minutes or lower.

[0192] <Fiber Debonding Process>

[0193] Fiber-like cellulose can be obtained by introducing anionic groups into fibers and then performing a defiberization process. Depending on the degree of defiberization, the obtained fibrous cellulose can be processed into microfiber-like cellulose with a fiber width of less than 1000 nm, or into microfibrillated cellulose with a fiber width exceeding 1 μm but less than 100 μm. In the defiberization process, for example, a defiberization apparatus can be used. The defiberization apparatus is not particularly limited; for example, a high-speed defiberizer, a mill (mortar-type grinder), a high-pressure homogenizer, an ultra-high-pressure homogenizer, a high-pressure impact mill, a ball mill, a bead mill, a disc mill, a conical mill, a twin-shaft mixer, a vibratory mill, a high-speed rotating homogenizer, an ultrasonic disperser, or a pulper can be used.

[0194] In order to obtain fine fibrous cellulose, the above-mentioned defibrillation processing apparatus is more preferably equipped with a high-speed defibrillator, a high-pressure homogenizer, or an ultra-high-pressure homogenizer, which have less influence from the pulverizing medium and less possibility of contamination.

[0195] Furthermore, in order to obtain microfibrillated cellulose, from the viewpoint of obtaining microfibrillated cellulose with the desired fiber width, a fine mill is preferred, a disc mill is more preferred, and a single-disc mill is even more preferred. In addition to the disc mill mentioned above, a high-speed defibrillator, a high-pressure homogenizer, or an ultra-high-pressure homogenizer can also be used in combination. In this case, the defibrillation process using one of the group consisting of the high-speed defibrillator, the high-pressure homogenizer, and the ultra-high-pressure homogenizer can be performed once to three times, preferably once to two times, and more preferably once.

[0196] In the fiber disintegration process, for example, it is preferable to use a dispersion medium to introduce anionic groups into the fiber and dilute it to form a slurry. As the dispersion medium, one or more organic solvents selected from water and polar organic solvents can be used. There are no particular limitations on the polar organic solvent; for example, alcohols, polyols, ketones, ethers, esters, and aprotic polar solvents are preferred. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutanol. Examples of polyols include ethylene glycol, propylene glycol, and glycerol. 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 monobutyl 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-pyrrolidone (NMP).

[0197] The concentration of solid components in the fibrous cellulose during the defibrillation process can be appropriately set. Furthermore, the slurry obtained by dispersing anionic groups into fibers in a dispersion medium may also contain solid components other than the anionic group-introduced fibers, such as urea, which has hydrogen bonding properties.

[0198] <Low Polymerization Treatment>

[0199] In addition to the steps described above, the method for manufacturing fibrous cellulose according to this embodiment may also include a step of performing a degree-low polymerization treatment to obtain fibrous cellulose with a desired degree of polymerization. Specifically, as described above, it may include: a step of performing a defibrillation treatment on cellulose fibers incorporating anionic groups to obtain fibrous cellulose with a fiber width of 100 μm or less; and a step of performing a degree-low polymerization treatment on the fibrous cellulose. It should be noted that the order of the defibrillation treatment step and the degree-low polymerization treatment step may be either step first, but it is preferable to perform the degree-low polymerization treatment after the defibrillation treatment step. That is, the method for manufacturing fibrous cellulose according to this embodiment may, for example, include a step of performing a degree-low polymerization treatment after performing a defibrillation treatment on cellulose fibers incorporating anionic groups. In the following description, the case where the degree-low polymerization treatment step is performed after the defibrillation treatment step will be described in detail. However, in the case where the degree-low polymerization treatment step is performed before the defibrillation treatment step, the dispersion containing fibrous cellulose is replaced with a dispersion of cellulose fibers (preferably cellulose fibers incorporating anionic groups) before the defibrillation treatment step.

[0200] It should be noted that even after low degree of polymerization treatment, the amount of anionic substituents in fibrous cellulose remains almost unchanged. Therefore, the amount of anionic substituents in fibrous cellulose before low degree of polymerization treatment can be approximated as the amount of anionic substituents in fibrous cellulose after low degree of polymerization treatment.

[0201] In this specification, the step of performing the degree of polymerization reduction treatment is a process of reducing the degree of polymerization of the dispersion containing fibrous cellulose to a suitable range. Specifically, the step of performing the degree of polymerization reduction treatment is a process in which the degree of polymerization of fibrous cellulose containing anionic groups with a fiber width of 100 μm or less is preferably 100 or more and 500 or less. It should be noted that the degree of polymerization of the fibrous cellulose obtained in the step of performing the degree of polymerization reduction treatment is more preferably 110 or more, further preferably 130 or more, even more preferably 150 or more, and more preferably 450 or less, further preferably 400 or less, and even more preferably 350 or less.

[0202] Examples of processes for implementing low-polymerization treatment include ozone treatment, enzyme treatment, hypochlorous acid treatment, subcritical water treatment, and radiation irradiation treatment. Preferably, the process for implementing low-polymerization treatment is selected from at least one of the following: ozone treatment, enzyme treatment, hypochlorous acid treatment, subcritical water treatment, and radiation irradiation treatment; ozone treatment is particularly preferred. It should be noted that the common element among ozone treatment, enzyme treatment, hypochlorous acid treatment, subcritical water treatment, and radiation irradiation treatment is the reduction of polymerization degree.

[0203] In the ozone treatment process, ozone is added to a fibrous cellulose dispersion (slurry). When adding ozone, it is preferable to add it as an ozone / oxygen mixture. In this case, the ozone addition rate is preferably 1.0 × 10⁻¹¹ g of fibrous cellulose contained in the fibrous cellulose dispersion (slurry). -4 g or more, more preferably 1.0 × 10 g. -3 More than g. It should be noted that, relative to 1g of fibrous cellulose, the preferred ozone addition rate is 1.0 × 10⁻⁶ g. 1 g or less, more preferably 1.0 × 10 g. 0 g or less, more preferably 1.0 × 10 g. -1 Below g, more preferably 3.0 × 10 g. -2 Below g, more preferably 1.5 × 10 g. - 2 Below g, more preferably 1.0 × 10 g. -2 g or less, particularly preferred is 6.0 × 10 g. -3 less than g. After adding ozone to the fibrous cellulose dispersion (slurry), it is preferable to stir for more than 10 seconds and less than 10 minutes at a temperature of 10°C or higher and less than 50°C, and then let it stand for more than 1 minute and less than 100 minutes.

[0204] In the enzyme treatment process, an enzyme is added to the fibrous cellulose dispersion (slurry). The enzyme used here is preferably a cellulase. Cellulases are classified as a family of glycoside hydrolases with higher-order structures based on catalytic domains that function in the hydrolysis of cellulose. Cellulases are broadly classified into endo-glucanases and cellobiohydrolases based on their cellulose-decomposing properties. Endo-glucanases are highly hydrolytic to the amorphous portions of cellulose, soluble cellulose oligosaccharides, or cellulose derivatives such as carboxymethyl cellulose, randomly cleaving their molecular chains from the inside, thus reducing the degree of polymerization. In contrast, cellobiohydrolases decompose the crystalline portions of cellulose, providing cellobiose. Additionally, cellobiohydrolases hydrolyze from the ends of cellulose molecules and are also called exo-glucanases or progressive enzymes. The enzyme used in the enzyme treatment process is not particularly limited, but endo-glucanases are preferred.

[0205] In the enzyme treatment process, the preferred enzyme addition rate is 1.0 × 10⁻¹⁰ relative to 1 g of fibrous cellulose. -7 g or more, more preferably 1.0 × 10 g -6 g or more, preferably 5.0 × 10 g -6 g or more, and more preferably 1.0 × 10 g. -5g or more. Furthermore, the enzyme addition rate is preferably 1.0 × 10⁻¹¹ relative to 1 g of fibrous cellulose. -2 Below g. After adding the enzyme to the fibrous cellulose dispersion (slurry), it is preferable to stir for more than 1 minute and less than 10 hours at a temperature of 30°C or higher and 70°C or lower, and then place it at a temperature of 90°C or higher to deactivate the enzyme.

[0206] In the hypochlorous acid treatment process, sodium hypochlorite is added to the fibrous cellulose dispersion (slurry). The preferred addition rate of sodium hypochlorite is 1.0 × 10⁻⁶ g relative to 1 g of fibrous cellulose. -4 g or more, more preferably 1.0 × 10 g. -3 g or more, more preferably 1.0 × 10 g. -2 More than g. Furthermore, the preferred sodium hypochlorite addition rate is 1.0 × 10⁻⁶ g relative to 1 g of fibrous cellulose. 2 g or less, more preferably 1.0 × 10 g. 1 g or less, more preferably 3×10 g 0 less than g. After adding sodium hypochlorite to the fibrous cellulose dispersion (slurry), it is preferable to stir for more than 1 minute and less than 10 hours at a temperature of 10°C or higher and 50°C or lower.

[0207] In the subcritical water treatment process, a fibrous cellulose dispersion (slurry) is subjected to high temperature and high pressure treatment to form a subcritical state. The fibrous cellulose is hydrolyzed in the subcritical state. Specifically, after the fibrous cellulose dispersion (slurry) is placed in a reaction vessel, the temperature is raised to 150°C or higher and 500°C or lower, preferably 150°C or higher and 350°C or lower, and the pressure inside the reaction vessel is increased to 10 MPa or higher and 80 MPa or lower, preferably 10 MPa or higher and 20 MPa or lower. The heating and pressurization time is preferably 0.1 seconds or higher and 100 seconds or lower, more preferably 0.3 seconds or higher and 50 seconds or lower.

[0208] Following the degree of polymerization reduction treatment described above, a further defibrillation process can be performed. This further defibrillation process can be the same as the defibrillation process described above when obtaining fibrous cellulose.

[0209] [Fibrous cellulose aqueous dispersion]

[0210] This embodiment also relates to an aqueous dispersion of fibrous cellulose (also referred to as a slurry or paste containing fibrous cellulose) obtained by dispersing the above-mentioned fibrous cellulose in a solvent containing water. The aqueous dispersion of fibrous cellulose can be, for example, a rubber modifier for addition to rubber components.

[0211] Relative to the total mass of the fibrous cellulose aqueous dispersion, the content of fibrous cellulose in the fibrous cellulose aqueous dispersion is preferably 0.1% by mass or more and 8.0% by mass or less, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, and more preferably 7.0% by mass or less, even more preferably 6.0% by mass or less, and even more preferably 5.0% by mass or less. When the content of fibrous cellulose is at or above the above lower limit, the mixing amount of the aqueous dispersion is small, and it is also suitable for storage and transportation. Therefore, it is preferable that when it is at or below the above upper limit, the ease of manufacture is excellent, and the viscosity is within an appropriate range.

[0212] The fibrous cellulose aqueous dispersion may contain other additives in addition to the solvent containing water and the fibrous cellulose of this embodiment. Examples of other additives include, for instance, defoamers, lubricants, ultraviolet absorbers, dyes, pigments, stabilizers, surfactants, and preservatives (e.g., phenoxyethanol).

[0213] Compared to conventional fibrous cellulose with alkali metal ions as counterions, the fibrous cellulose of this embodiment exhibits reduced water resistance when blended. Therefore, it can be applied to various applications where reduced water resistance is a problem when fibrous cellulose is added. Specifically, it is preferably used as a reinforcing material to improve mechanical properties such as tensile strength, and more preferably as a rubber modifier added to rubber components.

[0214] [Rubber Composition]

[0215] The rubber composition of this embodiment contains fibrous cellulose and rubber components of this embodiment.

[0216] <Rubber Composition>

[0217] In this embodiment, the rubber composition contains rubber components in addition to the aforementioned fibrous cellulose.

[0218] As a rubber component, natural rubber (NR) or synthetic rubber can be used, for example.

[0219] Examples of synthetic rubbers include styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene propylene diene monomer (EPDM), butyl rubber (IIR), chlorinated butyl rubber (CIIR), acrylate rubber (ACM), silicone rubber (Q), fluororubber (FKM), butadiene rubber (BR), epoxidized butadiene rubber (EBR), epichlorohydrin rubber (CO,CEO), polyurethane rubber (U), and polysulfide rubber (T). Examples of nitrile rubbers include hydrogenated nitrile rubber, carboxyl-modified nitrile rubber, silicone-modified nitrile rubber, maleic acid-modified nitrile rubber, hydroxyl-modified nitrile rubber, and other modified nitrile rubbers, or rubbers made by hydrogenating these; and acrylonitrile-butadiene-isoprene copolymers in which a portion of the butadiene is replaced with isoprene. Hydrogenated nitrile rubber (H-NBR) is sometimes referred to as hydrogenated nitrile rubber or hydrogenated acrylonitrile-butadiene rubber. Hydrogenated nitrile rubber can be obtained by hydrogenating the double bonds contained in nitrile rubber.

[0220] In addition to natural rubber (NR), other natural rubbers that can be cited as examples include epoxidized natural rubber (ENR), modified natural rubber such as methyl methacrylate (MMA) grafted polymerized natural rubber, hydrogenated natural rubber, and deproteinized natural rubber.

[0221] These rubber components can be used alone or in combination of two or more. Furthermore, these rubber components can be pre-crosslinking raw materials without a crosslinking structure, or they can be rubber components with a crosslinking structure.

[0222] Among these, the rubber component is preferably diene rubber, preferably selected from at least one of natural rubber, nitrile rubber, butadiene rubber, and styrene-butadiene rubber, more preferably selected from at least one of natural rubber, nitrile rubber, and styrene-butadiene rubber, and even more preferably selected from at least one of natural rubber, carboxylated nitrile rubber, and styrene-butadiene rubber.

[0223] Alternatively, the rubber component can also be a pre-crosslinking raw material. The rubber component is preferably a latex of these rubber components. By using a latex containing a rubber component, the dispersibility of fibrous cellulose is improved, making it easier to obtain a composite material with excellent tensile properties.

[0224] When using latex with rubber components, solid rubber components can be further mixed in. It should be noted that the solid rubber components can be added during the plasticizing of the rubber composition or during the preparation of the rubber mixture, but it is preferred to add them during the preparation of the rubber mixture.

[0225] In the rubber composition of this embodiment, from the viewpoint of good compatibility, the content of fibrous cellulose relative to 100 parts by weight of rubber component is preferably 0.1 parts by weight or more and 200 parts by weight or less, more preferably 1 part by weight or more, further preferably 3 parts by weight or more, even more preferably 5 parts by weight or more, even more preferably 10 parts by weight or more, even more preferably 15 parts by weight or more, and more preferably 150 parts by weight or less, further preferably 100 parts by weight or less, even more preferably 80 parts by weight or less, even more preferably 60 parts by weight or less, and even more preferably 40 parts by weight or less.

[0226] It should be noted that the content of fibrous cellulose in the rubber composition of this embodiment relative to 100 parts by mass of rubber component may be different from the content of fibrous cellulose relative to 100 parts by mass of rubber component when making cross-linked rubber products. Specifically, in the rubber composition, the content of fibrous cellulose can be increased in advance, and the content of fibrous cellulose relative to rubber component can be adjusted by adding rubber component when preparing rubber mixture.

[0227] The total amount of fibrous cellulose and rubber components in the rubber composition is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and the upper limit is not particularly limited, but is 100% by mass or less.

[0228] In this embodiment, the rubber composition may contain other components in addition to the fibrous cellulose and rubber components described above.

[0229] When the fibrous cellulose is microfibrillated cellulose, other examples include coarse cellulose fibers with a fiber width exceeding 1 μm (1000 nm). It should be noted that the aforementioned coarse cellulose fibers can be the microfibrillated cellulose of this embodiment, or they can be coarse cellulose fibers that do not belong to this category, such as those lacking anionic groups, or those possessing anionic groups and whose counterion is not NH4. + The rubber composition of this embodiment contains coarse cellulose fibers. The fiber width of the coarse cellulose fibers is not particularly limited, but is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more, further preferably 10 μm or more, and even more preferably 50 μm or less, and even more preferably 40 μm or less. It should be noted that the fiber width of the coarse cellulose fibers can be determined using a fiber length distribution measuring device (e.g., Valmet FS5, ABB L&W Fiber Tester Plus).

[0230] From the viewpoint of improving dispersibility in rubber compositions, coarse cellulose fibers preferably have ionic substituents, and more preferably have anionic substituents. The preferred morphology of the anionic substituents is the same as that of the microfibrillary cellulose, and the preferred ranges for their types and amounts are also the same.

[0231] When the rubber composition contains coarse cellulose fibers, the content of coarse cellulose fibers is preferably 0.5 parts by mass or more and 80 parts by mass or less relative to 100 parts by mass of rubber components, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, and more preferably 50 parts by mass or less, and even more preferably 20 parts by mass or less.

[0232] Furthermore, when the rubber composition contains coarse cellulose fibers, the content of coarse cellulose fibers is preferably 1 part by mass or more and 95 parts by mass or less, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 90 parts by mass or less, more preferably 85 parts by mass or less, relative to a total of 100 parts by mass of fine fibrous cellulose and coarse cellulose fibers.

[0233] When the content of coarse cellulose fibers is within the above range, coarse cellulose fibers can be manufactured at a lower cost than fine cellulose fibers. Therefore, rubber compositions can be manufactured at a lower cost, and rubber compositions with excellent mixing properties and excellent cross-linked physical properties can be obtained. Therefore, it is preferred.

[0234] The rubber composition of this embodiment may contain zinc oxide, vulcanization accelerator, anti-aging agent, reinforcing agent, etc. as other components, which can be added at any step of the manufacturing process.

[0235] <Method for manufacturing rubber composition>

[0236] There are no particular limitations on the method of manufacturing the rubber composition. It is preferred to prepare a dispersion containing at least rubber components and fibrous cellulose, and remove the dispersion medium from the dispersion to manufacture the rubber composition.

[0237] In the above manufacturing method, it is preferable to first mix fibrous cellulose with the rubber component to prepare a dispersion of the mixture in an aqueous medium (hereinafter also simply referred to as "dispersion of the mixture"). That is, the manufacturing method of the rubber composition of this embodiment preferably includes the following steps (I) and (II).

[0238] (I) A mixing process in which an aqueous dispersion containing fibrous cellulose according to this embodiment is mixed with rubber latex to obtain mixture A.

[0239] (II) Heating process of heating and drying the aforementioned mixture A to obtain the rubber composition

[0240] Specifically, fibrous cellulose and rubber components can be mixed and dispersed in an aqueous medium to obtain a dispersion of the mixture. Alternatively, an aqueous dispersion of fibrous cellulose (such as the fibrous cellulose aqueous dispersion described above) can be mixed with an aqueous dispersion of rubber components (rubber latex) to obtain a mixture. Preferably, the dispersion of fibrous cellulose (fibrous cellulose aqueous dispersion) is mixed with the aqueous dispersion of rubber components (rubber latex) to obtain a dispersion containing fibrous cellulose and rubber components (mixture A).

[0241] Mixing can be carried out using known devices such as dispersers, Three-One Motors, CLEARMIX mixers, homogenizers, homogenizers, and propeller mixers (e.g., Tornado mixers). The mixing temperature is not limited, but room temperature (20–30°C) is preferred. The mixing time can also be adjusted appropriately.

[0242] When preparing a dispersion of the mixture, there is a tendency for improved physical properties after cross-linking by thoroughly mixing the fibrous cellulose and rubber components.

[0243] The rubber latex is preferably a dispersion of rubber components in an aqueous medium. The aqueous medium is primarily composed of water, and the water content relative to the total aqueous medium is preferably 50% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and even more preferably 95% by mass or more. There is no particular upper limit, but it is 100% by mass or less. In addition to water, it may contain known organic solvents, etc., to the extent that it does not impair the effects of this disclosure.

[0244] The solid content concentration (by mass) of the dispersion of the mixture is preferably 0.5% by mass or more and 50% by mass or less, more preferably 1% by mass or more, further preferably 3% by mass or more, and even more preferably 40% by mass or less, and even more preferably 30% by mass or less. By keeping the solid content concentration of the dispersion of the mixture within the above range, the energy required for water removal can be reduced, and the resulting rubber composition is less prone to aggregation of fibrous cellulose fibers, resulting in excellent composability and crosslinking properties of the obtained rubber composition.

[0245] The concentration of solid components in the dispersion of the mixture can be calculated by drying a specified amount of the dispersion to a constant weight using a dryer at 105°C, using the mass of the dried product and the mass of the dispersion of the mixture supplied for drying, according to the following formula (I).

[0246] Concentration of solids in the dispersion of the mixture (mass %)

[0247] =Mass of dried product [g] / Mass of dispersion of mixture supplied for drying [g] × 100 (I)

[0248] As shown in step (II) above, the rubber composition is obtained by heating and drying the dispersion of the resulting mixture (mixture A).

[0249] There are no particular limitations on the heating and drying method. Examples include methods such as coating a dispersion of a mixture onto a substrate and drying using a rotary drum dryer.

[0250] In coating methods, for example, a dispersion containing a mixture of fibrous cellulose and rubber components is coated onto a substrate. Furthermore, by using a coating apparatus and a strip of substrate, sheets can be produced continuously.

[0251] The material of the substrate used in the coating method is not particularly limited. A substrate with high wettability to the dispersion of the mixture can suppress shrinkage of the sheet during drying, etc. However, it is preferable to choose a substrate that allows the sheet formed after drying to be easily peeled off. Among them, resin films and / or sheets, or metal films and / or sheets, are preferred, without particular limitation. For example, films and / or sheets made of resins such as acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polypropylene, polycarbonate, polyvinylidene chloride, etc., films and / or sheets made of metals such as aluminum, zinc, copper, iron plates, and films and / or sheets with their surfaces oxidized, films and / or sheets made of stainless steel, films and / or sheets made of brass, etc., can be used.

[0252] In coating methods, when the viscosity of the dispersion of the mixture is low and it spreads on the substrate, a frame for fixing a barrier can be used to obtain a sheet of a specified thickness and basis weight. Alternatively, a substrate with grooved barriers can also be used. The frame for the barrier is not particularly limited; for example, a frame that allows for easy peeling from the ends of the sheet after drying is preferred. From this viewpoint, it is more preferable to mold a resin sheet or a metal sheet. In this embodiment, for example, frames molded from resin sheets such as acrylic sheets, polyethylene terephthalate sheets, vinyl chloride sheets, polystyrene sheets, polypropylene sheets, polycarbonate sheets, and polyvinylidene chloride sheets, as well as metal sheets such as aluminum sheets, zinc sheets, copper sheets, and iron sheets, and sheets with their surfaces anodized, stainless steel sheets, and brass sheets can be used.

[0253] There are no particular limitations on the coating machine used to apply the dispersion of the mixture to the substrate; for example, roller coaters, gravure coaters, die coaters, curtain coaters, and air knife coaters can be used. From the perspective of enabling more uniform sheet thickness, die coaters, curtain coaters, and spray coaters are particularly preferred.

[0254] The dispersion temperature and ambient temperature (hereinafter, both the dispersion temperature and ambient temperature are collectively referred to as "coating temperature") of the mixture when it is coated onto a substrate are not particularly limited. For example, it is preferably 5°C or higher and 80°C or lower, more preferably 10°C or higher and 60°C or lower, even more preferably 15°C or higher and 50°C or lower, and particularly preferably 20°C or higher and 50°C or lower. When the coating temperature is above the lower limit mentioned above, the dispersion of the mixture can be coated more easily. When the coating temperature is below the upper limit mentioned above, the volatilization of the dispersion medium in the coating can be suppressed.

[0255] There are no particular limitations on the drying equipment used; for example, an explosion-proof dryer can be cited.

[0256] In the coating process, it is preferable to coat the dispersion of the mixture onto the substrate in such a way that the finished basis weight and thickness of the sheet fall within the aforementioned preferred range.

[0257] The dispersion of the mixture can be dried by heating in a cylindrical dryer to obtain a rubber composition.

[0258] Figure 3 This is a side cross-sectional view of a drum dryer 10, which is an example of a heated cylindrical dryer. Figure 4 This is a side view of the drum dryer 10.

[0259] First, a heating medium (usually steam) is introduced into the interior of the rotating cylinder 1 (drum), and a dispersion of the mixture is introduced into the feed section 2. The introduced dispersion of the mixture forms a sheet-like mixture 3 on the surface of the heated cylinder 1 and adheres to it, and is rapidly heated and dried. The sheet-like mixture 3 is scraped off by a scraper 4 fixed by the rotating cylinder 1, thus obtaining a rubber composition 5 (heat-dried product).

[0260] The lower limit of the surface temperature of the heated cylindrical dryer is preferably 80°C or higher, more preferably 90°C or higher. Furthermore, the upper limit of the surface temperature is preferably 250°C or lower, more preferably 200°C or lower.

[0261] Furthermore, the surface temperature of the heated cylindrical dryer refers to the temperature of the cylindrical surface in contact with the mixture. The surface temperature of the heated cylindrical dryer can be, for example, 80~250℃, 90~200℃, or 95~180℃. By maintaining the surface temperature of the heated cylindrical dryer within these ranges, production efficiency is high, and rubber compositions with excellent mixing properties and superior crosslinking properties can be obtained.

[0262] The lower limit of the heating and drying time using a heated cylindrical dryer is preferably 2 seconds or more, and more preferably 4 seconds or more. Furthermore, the upper limit of the heating and drying time is preferably 1800 seconds or less, and more preferably 600 seconds or less.

[0263] It should be noted that the heating and drying time [sec] in a heated cylindrical dryer refers to the contact time [sec] between the mixture and the surface of the cylinder. The heating and drying time can be, for example, 2~1800 seconds, 4~600 seconds, or 6~400 seconds. By keeping the heating and drying time within the above range, a dried product that is neither undried nor over-dried can be obtained, exhibiting excellent peelability from the drum.

[0264] The lower limit of the cylinder width w of the heated cylindrical dryer is preferably 0.1m or more, and more preferably 0.2m or more. Furthermore, the upper limit of the cylinder width w is not particularly limited, and is typically 7m or less.

[0265] The cylinder width w can be, for example, 0.1~7m or 0.2~5m. By keeping the cylinder width w within the above range, a dried product of uniform thickness can be obtained.

[0266] The lower limit of the cylinder rotation speed v of the heated cylindrical dryer is preferably 0.001 m / sec or more, and more preferably 0.002 m / sec. In addition, the upper limit of the cylinder rotation speed v is not particularly limited, and is usually 35 m / sec or less.

[0267] The cylinder rotation speed v can be, for example, 0.001~3.5 [m / sec] or 0.002~0.2 [m / sec]. By keeping the cylinder rotation speed v within the above range, the contact time between the mixture and the heated drum can be within an appropriate range, and a dried product with excellent mixing properties and cross-linking properties can be obtained.

[0268] The heated cylindrical dryer used in the manufacturing method of the rubber composition can be any conductive heating type dryer that introduces a heat medium into the interior of a cylinder, causing the mixture to contact the surface of the heated cylinder for heating and drying. Examples include rotary drum dryers such as double-drum dryers, single-drum dryers, and twin-drum dryers, as well as rotary drum dryers and Yankee dryers. From the viewpoint of heating and drying efficiency, a double-drum dryer or a rotary drum dryer is preferred.

[0269] In the preparation of rubber compositions, it is believed that some or all of the ammonium ions present in fibrous cellulose as counterions of anionic groups are dissociated by heating or the like, and thus some or all of the counterions can be replaced by protons (H). + ).

[0270] [Rubber compound]

[0271] In this embodiment, the rubber mixture refers to the composition in its pre-crosslinking state, formed by mixing rubber compositions.

[0272] The rubber compound preferably contains at least a crosslinking agent. In addition to the crosslinking agent, it may also contain additives that can be used as additives in the rubber industry, such as zinc oxide, vulcanization accelerators, fillers, softeners, fatty acids, anti-aging agents, plasticizers, colorants, pH adjusters, and curing resins. Furthermore, in addition to the rubber components used in preparing the rubber composition, solid rubber may be added separately.

[0273] When adding solid rubber, the solid rubber is the same as the substance exemplified as a rubber component, but it is not added in latex form; only solid rubber (solid rubber) is added.

[0274] It should be noted that examples of crosslinking agents include sulfur-based crosslinking agents (e.g., sulfur powder, sulfur bloom, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, etc.; sulfur-containing compounds such as amine disulfide, polymeric polysulfides, sulfur olefin adducts, sulfur chloride, sulfur dichloride, etc.; insoluble polymeric sulfur, etc.), peroxide-based crosslinking agents (e.g., dicumyl peroxide, dichlorobenzoyl peroxide, benzoyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 4,4-bis(tert-butylperoxy)valerate, di-tert-butylperoxy-diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane), and quinone-based crosslinking agents (e.g., p-quinone dioxime, p,p'-dibenzoylquinone dioxime), among which sulfur-based crosslinking agents or peroxide-based crosslinking agents are preferred.

[0275] The amount of crosslinking agent added is not particularly limited, but is preferably 0.1 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of rubber component, more preferably 0.5 parts by mass or more, even more preferably 1.0 parts by mass or less, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

[0276] Alternatively, it may contain a crosslinking accelerator that promotes crosslinking based on the crosslinking agent. In the case of using a sulfur-based crosslinking agent, it is preferable to contain a crosslinking accelerator (vulcanization accelerator).

[0277] When using a sulfur-based crosslinking agent (vulcanizing agent) as the crosslinking agent, the preferred crosslinking accelerators (vulcanization accelerators) are sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators.

[0278] Examples of fillers mentioned above include carbon black and silica. These fillers can be used individually or in combination of two or more. There are no particular limitations on the content of the fillers, but preferably 10 parts by weight or more and 150 parts by weight or less, more preferably 20 parts by weight or more and 100 parts by weight or less, relative to 100 parts by weight of the rubber component.

[0279] Examples of softeners mentioned above include: aromatic oils, paraffin oils, naphthenic oils, vegetable oils other than castor oil, low-PCA oils such as MES, TDAE, and SRAE, and heavy naphthenic oils. Preferred low-PCA oils include various plant-derived oils harvested from vegetables, nuts, and seeds. Plant-derived oils include soybean oil, sunflower oil, safflower oil, corn oil, flaxseed oil, cottonseed oil, rapeseed oil, cashew oil, sesame oil, camellia oil, jojoba oil, macadamia oil, coconut oil, and palm oil.

[0280] Relative to 100 parts by weight of rubber component, the content of the softener is preferably 1 part by weight or more and 35 parts by weight or less, more preferably 5 parts by weight or more, even more preferably 10 parts by weight or more, and even more preferably 30 parts by weight or less, and even more preferably 25 parts by weight or less.

[0281] Examples of the aforementioned fatty acids include stearic acid, palmitic acid, arachidic acid, oleic acid, linoleic acid, and arachidonic acid. Among these, stearic acid is preferred.

[0282] The content of the aforementioned fatty acids is not particularly limited, but is preferably 0.1 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the rubber component, more preferably 1 part by mass or more and 4 parts by mass or less.

[0283] Examples of antioxidants mentioned above include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), N,N'-diphenyl-p-phenylenediamine (DPPD), and 2-mercaptobenzimidazole (MBI). Antioxidants can be used alone or in combination of two or more.

[0284] There is no particular limitation on the content of the anti-aging agent, but it is preferably 0.1 parts by mass and 5 parts by mass and more preferably 1 part by mass and 3 parts by mass and less, relative to 100 parts by mass of the rubber component.

[0285] The content of zinc oxide (zinc white) is not particularly limited, but is preferably 1 part or more and 10 parts or less, more preferably 2 parts or more and 8 parts or less, relative to 100 parts by mass of the rubber component.

[0286] [Method for manufacturing rubber compounds]

[0287] There are no particular limitations on the method for manufacturing the rubber mixture, but it is preferable to have at least a mixing step of mixing the rubber composition of this embodiment.

[0288] In the mixing process, it is preferable to add at least a crosslinking agent and mix after plasticizing the rubber composition of this embodiment. In addition to the aforementioned crosslinking agent, the aforementioned additives may also be mixed in. Furthermore, in addition to the rubber components contained in the rubber composition, solid rubber may also be mixed in the mixing process.

[0289] In this embodiment, from the viewpoint of improving water resistance and improving mechanical properties, the content of fibrous cellulose in the rubber mixture and the crosslinked rubber and crosslinked rubber articles described later is preferably 0.1 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of rubber component, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, and more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0290] The method for manufacturing the rubber compound is not particularly limited, but a step of plasticizing the rubber composition of this embodiment is preferred. Plasticizing improves the dispersibility of subsequently compounded crosslinking agents and the like. Plasticizing can be performed using conventional methods, such as low-temperature mixing using a rolling mill or similar mill, or high-temperature mixing using a Banbury mixer or similar equipment. From the viewpoint of dispersibility of fibrous cellulose in the rubber composition, low-temperature mixing is preferred. The temperature for low-temperature mixing is preferably 15°C or higher and 70°C or lower, more preferably 20°C or higher and 65°C or lower, and even more preferably 25°C or higher and 60°C or lower. Conversely, the temperature for high-temperature mixing is preferably 80°C or higher and 200°C or lower.

[0291] Furthermore, a rubber compound is manufactured by adding additives such as crosslinking agents to a plasticized rubber composition and then mixing it.

[0292] Mixing is the process of uniformly dispersing crosslinking agents and other compounding agents in a rubber composition (preferably a plasticized rubber composition). Mixing can be carried out as is known, for example using a Banbury mixer, kneader, open mill, etc. Examples of crosslinking agents include sulfur and peroxides. Examples of other compounding agents include the additives mentioned above and solid rubber.

[0293] [Cross-linked rubber and cross-linked rubber products]

[0294] The crosslinked rubber of this embodiment is formed by crosslinking a rubber mixture containing a crosslinking agent. Furthermore, by molding during crosslinking, crosslinked rubber products can be manufactured. That is, crosslinked rubber products are formed by crosslinking and molding a rubber mixture prepared from a rubber composition containing fibrous cellulose of this embodiment.

[0295] The method for manufacturing cross-linked rubber products of the present invention may further include a step of molding the rubber mixture obtained through the above-described mixing process into a desired shape (molding step). Molding in this molding step can be performed using various molding methods such as extrusion molding machines, calendering rolls, presses, injection molding machines, transfer molding machines, blow molding machines, and foam molding machines. The appropriate method can be selected based on the shape, intended use, and molding method of the final product.

[0296] It should be noted that the above-mentioned mixing process and the above-mentioned molding process can be carried out independently or continuously.

[0297] Regarding crosslinking, there are no particular limitations on temperature as long as the conditions for the crosslinking reaction are met. Generally, a crosslinked rubber composition can be obtained by heating an uncrosslinked rubber composition obtained from mixing to perform crosslinking (also called vulcanization when sulfur is involved). The heating temperature is preferably 140°C or higher, preferably 200°C or lower, and more preferably 180°C or lower. Therefore, the heating temperature is preferably around 140~200°C, and more preferably around 140~180°C. Crosslinking can be performed, for example, using vulcanization equipment for mold vulcanization, tank vulcanization, continuous vulcanization, etc.

[0298] In this embodiment, the water absorption rate of the crosslinked rubber composition and the crosslinked rubber article is preferably low, specifically, preferably 24.0% or less, more preferably 22.0% or less, even more preferably 20.0% or less, even more preferably 18.0% or less, even more preferably 16.0% or less, even more preferably 14.0% or less, and the lower limit is not particularly limited, but is 0% or more.

[0299] The water absorption rate was determined using the method described in the examples.

[0300] <Applications>

[0301] The cross-linked rubber product of this embodiment can be used for applications such as automotive rubber components, hose materials, gaskets, rubber rollers, industrial cables, industrial conveyor belts, shoe soles (foot soles), vibration damping rubber, and other rubber parts, without particular limitation. Examples of automotive rubber components include tires, automotive gaskets, automotive oil seals, automotive sealing rings, automotive rubber hoses, V-belts, and automotive vibration damping rubber.

[0302] Example

[0303] The following examples and comparative examples further illustrate the features of the present invention. The materials, amounts, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as limited by the specific examples shown below.

[0304] <Manufacturing Example 1>

[0305] [Phosphorus Oxygen Acidification Treatment]

[0306] As the raw material pulp, we use coniferous kraft pulp (93% solids by mass, 245 g / m³) manufactured by Oji Paper Co., Ltd. 2 The product was in flake form, dissociated, and the Canadian standard free fraction (CSF) determined according to JIS P 8121-2:2012 was 700 mL.

[0307] The raw pulp was subjected to phosphoric acidification treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by weight (absolute dry weight) of the raw pulp to adjust the composition to 45 parts by weight of ammonium dihydrogen phosphate, 120 parts by weight of urea, and 150 parts by weight of water, resulting in a chemically impregnated pulp. Next, the 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, resulting in phosphoric acid pulp.

[0308] Next, the obtained phosphorylated pulp was washed. The washing process was carried out as follows: a pulp dispersion obtained by adding 100g (absolute dry weight) of phosphorylated pulp to 10L of ion-exchanged water was stirred to ensure uniform dispersion of the pulp, and then the process of filtration and dewatering was repeated. The washing endpoint was defined as the point at which the conductivity of the filtrate reached below 100μS / cm.

[0309] The infrared absorption spectrum of the obtained phosphorylated pulp was determined using FT-IR. The results showed that the absorption spectrum was within the range of 1230 cm⁻¹. -1 Absorption at P=O based on phosphate groups was observed nearby, confirming the addition of phosphate groups to the pulp. Furthermore, the resulting phosphorylated pulp was tested and analyzed using X-ray diffraction. Characteristic peaks were identified at two locations: approximately 2θ = 14° to 17° and 2θ = 22° to 23°, confirming the presence of cellulose type I crystals. It should be noted that the amount of phosphate groups (first dissociated acid content), determined by the method described later, was 1.45 mmol / g. The total dissociated acid content was 2.45 mmol / g.

[0310] Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a pulp with a solids content of 2.2% by mass. This pulp was then treated twice using a wet micronization apparatus (SUGINO MACHINE LIMITED, Starburst) at a pressure of 200 MPa to obtain a microfibrillated cellulose dispersion A containing fine fibrous cellulose. It should be noted that the fiber width of the obtained microfibrillated cellulose was measured using a transmission electron microscope, and the result was 3–5 nm.

[0311] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. It should be noted that the amount of phosphate (first dissociated acid) determined by the method described later in the section on [Determination of Phosphorus Oxyacid Content] was 1.45 mmol / g. It should also be noted that the total dissociated acid content was 2.45 mmol / g.

[0312] <Manufacturing Example 2>

[0313] [TEMPO oxidation treatment]

[0314] As the raw material pulp, we used undried coniferous kraft pulp manufactured by Oji Paper Co., Ltd. The raw material pulp was subjected to alkali TEMPO oxidation treatment as follows.

[0315] First, 100 parts by weight of the above-mentioned raw material pulp, 1.6 parts by weight of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxy radical), and 10 parts by weight of sodium bromide were dispersed in 10,000 parts by weight of water. Next, a 13% by weight aqueous solution of sodium hypochlorite was added at a rate of 10 mmol per 1.0 g of pulp to initiate the reaction. During the reaction, a 0.5 M aqueous solution of sodium hydroxide was added dropwise to maintain the pH above 10 and below 10.5. The reaction was considered complete when no change in pH was observed.

[0316] Next, the obtained TEMPO oxidized pulp was cleaned. The cleaning process was as follows: the TEMPO oxidized pulp was dewatered to obtain dewatered sheets, and then 5000 parts by weight of ion-exchanged water was added. After stirring to ensure uniform dispersion, the filtration and dewatering process was repeated. The cleaning endpoint was defined as the point at which the conductivity of the filtrate reached below 100 μS / cm.

[0317] The dehydrated sheet was subjected to additional oxidation treatment to remove residual aldehyde groups. 100 parts by weight of the dehydrated sheet (dry weight) were dispersed in 10,000 parts by weight of 0.1 mol / L acetate buffer (pH 4.8). Then, 113 parts by weight of 80% sodium chlorite were added, and the mixture was immediately sealed and reacted at room temperature for 48 hours with magnetic stirring at 500 rpm to obtain pulp.

[0318] Next, the TEMPO oxidized pulp that has undergone additional oxidation is cleaned. The cleaning process is as follows: the oxidized pulp is dewatered to obtain dewatered sheets, then 5000 parts by weight of ion-exchanged water is added, stirred to ensure uniform dispersion, and the filtration and dewatering process is repeated. The cleaning endpoint is defined as when the conductivity of the filtrate reaches below 100 μS / cm.

[0319] The TEMPO oxidized pulp was treated to replace the counterions of carboxyl groups with hydrogen ions. The washed TEMPO oxidized pulp was impregnated with 12N hydrochloric acid and reacted at room temperature for 60 minutes. The hydrochloric acid-impregnated pulp was then dehydrated to obtain dehydrated sheets. 5000 parts by weight of 1N hydrochloric acid were then injected, stirred to ensure uniform dispersion, and then filtered for further dehydration.

[0320] Next, the obtained TEMPO oxidized pulp was washed. The washing process was carried out as follows: 100g (absolute dry weight) of TEMPO oxidized pulp was added to 10L of ion-exchanged water to obtain a pulp dispersion, which was stirred to ensure uniform dispersion of the pulp. Then, the pulp was repeatedly filtered and dehydrated. The washing endpoint was defined as the point at which the conductivity of the filtrate reached below 100μS / cm.

[0321] Next, the obtained hydrogen ion-exchanged TEMPO oxidized pulp was treated to replace the carboxyl counterions with ammonium ions. The washed hydrogen ion-exchanged TEMPO oxidized pulp was impregnated with 15N ammonia water and reacted at room temperature for 60 minutes. The ammonia-impregnated pulp was then dehydrated to obtain dehydrated sheets. 5000 parts by weight of ion-exchanged water were then added, stirred to ensure uniform dispersion, and the filtration and dehydration process was repeated. The washing process ended when the conductivity of the filtrate fell below 100 μS / cm.

[0322] The obtained TEMPO oxidized pulp was found to have a carboxyl content of 1.80 mmol / g, as determined by the method described later. Furthermore, the obtained TEMPO oxidized pulp was tested and analyzed using X-ray diffraction. Characteristic peaks were identified at two positions: approximately 2θ = 14° to 17° and approximately 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0323] Ion-exchanged water was added to the obtained TEMPO oxidized pulp to prepare a pulp with a solids content of 2% by mass. The pulp was then treated twice with a wet micronization device at a pressure of 200 MPa to obtain a microfibrillated cellulose dispersion B containing microfibrillated cellulose.

[0324] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained type I cellulose crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using transmission electron microscopy, yielding a result of 3–5 nm. It should be noted that the carboxyl group content of the obtained fine fibrous cellulose, determined using the method described later, was 1.80 mmol / g.

[0325] <Manufacturing Example 3>

[0326] Using 33 parts by mass of phosphorous acid (phosphonic acid) instead of ammonium dihydrogen phosphate, the same procedure as in Manufacturing Example 1 was performed to obtain a microfibrillated cellulose dispersion C containing phosphorylated pulp and microfibrillated cellulose.

[0327] The infrared absorption spectrum of the obtained phosphorylated pulp was determined using FT-IR. The results showed that the absorption spectrum was within 1210 cm⁻¹. -1 The absorption of the P=O group of the phosphonate group, which is a tautomer of the phosphorous group, was observed nearby, confirming the presence of phosphorous groups (phosphonate groups) in the pulp. Furthermore, the obtained phosphorylated pulp was tested and analyzed using an X-ray diffraction apparatus. Characteristic peaks were identified at two positions: approximately 2θ = 14° to 17° and approximately 2θ = 22° to 23°, confirming the presence of cellulose type I crystals. It should be noted that the amount of phosphorous groups (first dissociated acid content) determined by the method described later in the section on "Determination of Phosphorus Oxyacid Content" was 1.51 mmol / g. The total dissociated acid content was 1.54 mmol / g.

[0328] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using transmission electron microscopy, and the result was 3–5 nm. It should be noted that the amount of phosphite (first dissociated acid) in the obtained fine fibrous cellulose, determined by the method described later in the section on "Determination of Phosphorus Oxyacid Content," was 1.51 mmol / g. Additionally, the total dissociated acid content was 1.54 mmol / g.

[0329] <Manufacturing Example 4>

[0330] Using 38 parts by mass of sulfamic acid (aminosulfonic acid) instead of ammonium dihydrogen phosphate, the heating time was extended to 20 minutes. Otherwise, the operation was carried out in the same manner as in Manufacturing Example 1 to obtain a microfibrillated cellulose dispersion D containing sulfated pulp and microfibrillated cellulose.

[0331] The infrared absorption spectrum of the obtained sulfated pulp was determined using FT-IR. The results showed that the absorption spectrum was within the range of 1220-1260 cm⁻¹. -1Absorption at S=O based on sulfate groups was observed nearby, confirming the addition of sulfate groups in the pulp. Furthermore, the obtained sulfated pulp was tested and analyzed using X-ray diffraction. Characteristic peaks were identified at two locations: approximately 2θ = 14° to 17° and 2θ = 22° to 23°, confirming the presence of cellulose type I crystals. It should be noted that the sulfate group content, determined by the method described later in the section on "Determination of Sulfate Group Content," was 1.47 mmol / g.

[0332] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using transmission electron microscopy, and the result was 3–5 nm. It should be noted that the sulfate group content of the obtained fine fibrous cellulose, determined using the method described later, was 1.47 mmol / g.

[0333] <Manufacturing Example 5>

[0334] [Carboxymethylation]

[0335] As the raw material pulp, we use coniferous kraft pulp (93% solids by mass, 245 g / m³) manufactured by Oji Paper Co., Ltd. 2 The product was in flake form, dissociated, and the Canadian standard free fraction (CSF) determined according to JIS P 8121-2:2012 was 700 mL.

[0336] A chemical solution consisting of 83 parts by mass of 12N NaOH aqueous solution, 175 parts by mass of sodium monochloroacetate, and 313 parts by mass of deionized water (totaling 571 parts by mass) was added to 100 parts by mass (absolute dry weight) of the raw pulp to obtain chemically impregnated pulp. Next, the pulp impregnated with the chemical solution was heated in a hot water bath at 95°C for 60 minutes to introduce carboxylmethyl groups (carboxyl groups) into the cellulose in the pulp, resulting in carboxylmethyl-infused pulp.

[0337] Next, the obtained carboxymethyl-infused pulp was washed. The washing process was as follows: the pulp dispersion obtained by injecting ion-exchanged water into the obtained carboxymethyl-infused pulp was stirred to ensure uniform dispersion of the pulp, and then repeatedly filtered and dehydrated to perform washing. The washing endpoint was defined as the point at which the conductivity of the filtrate reached below 100 μS / cm.

[0338] The carboxymethyl-introduced pulp was treated in the same way as in Manufacturing Example 2, replacing the counter ion of the carboxyl group with an ammonium ion.

[0339] The amount of carboxyl-infused pulp obtained was determined to be 1.21 mmol / g by the method described later. Furthermore, carboxymethyl-infused pulp was tested and analyzed using X-ray diffraction. Characteristic peaks were confirmed at two positions: approximately 2θ = 14° to 17° and approximately 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0340] Ion-exchanged water was added to the obtained carboxymethyl-infused pulp to prepare a pulp with a solids content of 2% by mass. The pulp was then treated twice with a wet micronization apparatus at a pressure of 200 MPa to obtain a microfibrillated cellulose dispersion E containing microfibrillated cellulose.

[0341] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using transmission electron microscopy, and the result was 3–5 nm. It should be noted that the carboxyl group content of the obtained fine fibrous cellulose, determined using the method described later, was 1.21 mmol / g.

[0342] <Manufacturing Example 6>

[0343] [Hypochlorous acid oxidation]

[0344] Using a manual mixer (Labo Millser PLUS, Osaka Chemical Co., Ltd.), sheets of bleached coniferous kraft pulp (NBKP) (90% by mass solids) were treated at 20,000 rpm for 15 seconds to produce a cotton-like fluff pulp (90% by mass solids). Next, sodium hypochlorite pentahydrate was added to ion-exchanged water to prepare an aqueous solution with a sodium hypochlorite solids concentration of 22% by mass. 9000 parts by mass of the 22% by mass sodium hypochlorite aqueous solution were added to 100 parts by mass of the cotton-like fluff pulp, and the reaction was carried out in a warm bath at 30°C for 2 hours to obtain carboxyl-introduced pulp. An appropriate amount of 1N sodium hydroxide aqueous solution was added during the reaction to maintain the pH at 11.

[0345] Next, the obtained carboxyl-infused pulp was washed. The washing process was as follows: the pulp dispersion obtained by injecting ion-exchanged water into the obtained carboxyl-infused pulp was stirred to ensure uniform dispersion of the pulp, and then repeatedly filtered and dehydrated to perform washing. The washing endpoint was defined as the point at which the conductivity of the filtrate reached below 100 μS / cm.

[0346] The carboxyl group introduced into the pulp was treated in the same way as in Manufacturing Example 2, replacing the counter ion of the carboxyl group with an ammonium ion.

[0347] The amount of carboxyl groups in the obtained carboxyl-infused pulp was determined to be 0.70 mmol / g by the method described later. Furthermore, the obtained carboxyl-infused pulp was tested and analyzed using an X-ray diffraction apparatus. Characteristic peaks were confirmed at two positions: approximately 2θ = 14° to 17° and approximately 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0348] Ion-exchanged water was added to the obtained carboxyl-introduced pulp to prepare a pulp with a solid content concentration of 2% by mass. The pulp was then treated twice with a wet micronization device at a pressure of 200 MPa to obtain a microfibrillated cellulose dispersion F containing microfibrillated cellulose.

[0349] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained type I cellulose crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using transmission electron microscopy, yielding a result of 3–5 nm. It should be noted that the carboxyl group content of the obtained fine fibrous cellulose, determined using the method described later, was 0.70 mmol / g.

[0350] <Manufacturing Example 7>

[0351] In Manufacturing Example 1, the washed phosphorylated pulp was neutralized as follows. First, the washed phosphorylated pulp was diluted with 10 L of deionized water, and then 1 N of sodium hydroxide aqueous solution was added little by little while stirring, thereby obtaining a phosphorylated pulp with a pH of 12 or higher and 13 or lower. Next, the phosphorylated pulp was dehydrated and washed to obtain a neutralized phosphorylated pulp. In addition to using this phosphorylated pulp, a fine fibrous cellulose dispersion G was obtained in the same manner as in Manufacturing Example 1.

[0352] <Manufacturing Example 8>

[0353] In Manufacturing Example 2, except for the hydrogen ion replacement treatment and the ammonium ion replacement treatment, a fine fibrous cellulose dispersion H was obtained in the same manner as in Manufacturing Example 2.

[0354] <Manufacturing Example 9>

[0355] In Manufacturing Example 3, the same neutralization treatment as in Manufacturing Example 7 was performed, and otherwise, the same fine fibrous cellulose dispersion I was obtained as in Manufacturing Example 3.

[0356] <Manufacturing Example 10>

[0357] In Manufacturing Example 4, the same neutralization treatment as in Manufacturing Example 7 was performed, and otherwise, a fine fibrous cellulose dispersion J was obtained in the same manner as in Manufacturing Example 4.

[0358] <Manufacturing Example 11>

[0359] In Manufacturing Example 7, a tetrabutylammonium hydroxide solution was used instead of an aqueous sodium hydroxide solution. Otherwise, the same as in Manufacturing Example 7, a fine fibrous cellulose dispersion K was obtained.

[0360] <Manufacturing Example 12>

[0361] In Manufacturing Example 1, ion-exchanged water was added to the washed phosphorylated pulp to prepare a pulp with a solids content of 2% by mass. This pulp was then treated 20 times using a single-disc refiner with a gap set to 600 μm for defibrillation, yielding a microfibrillated cellulose dispersion A. The microfibrillated cellulose in dispersion A had a fiber width of 25.3 μm.

[0362] <Manufacturing Example 13>

[0363] The microfibrillated cellulose dispersion A obtained in Manufacturing Example 12 was treated once using a wet micronization apparatus (Starburst, manufactured by SUGINO MACHINE LIMITED) at a pressure of 150 MPa to obtain microfibrillated cellulose dispersion B. The microfibrillated cellulose in dispersion B has a fiber width of 20.3 μm.

[0364] <Manufacturing Example 14>

[0365] Except for using the phosphorylated pulp obtained in Manufacturing Example 7, the same treatment as in Manufacturing Example 12 was performed to obtain a microfibrillated cellulose dispersion C. The microfibrillated cellulose in this dispersion C has a fiber width of 17.4 μm.

[0366] [Measurement]

[0367] The methods for determining the content of each ionic group and the fiber width are as follows.

[0368] (Determination of phosphorus oxyacid content)

[0369] In the determination of the phosphorus oxyacid content (phosphate content or phosphite content) of fibrous cellulose, firstly, ion-exchanged water is added to the fibrous cellulose to prepare a slurry with a solid content concentration of 0.2% by mass. The resulting fibrous cellulose dispersion is then treated with an ion-exchange resin, and the content is determined by titration with an alkali.

[0370] The treatment using ion exchange resin is carried out as follows: 1 / 10 by volume of a strong acid ion exchange resin (Amberjet 1024; Organo Corporation, after adjustment) is added to the above fibrous cellulose dispersion, and after shaking for 1 hour, it is poured onto a 90 μm mesh screen to separate the resin from the slurry.

[0371] Additionally, the titration using alkali was performed as follows: In a cellulose slurry treated with ion exchange resin, 10 μL of a 0.1N sodium hydroxide aqueous solution was added every 5 seconds, while the change in pH value displayed by the slurry was measured. It should be noted that the titration was performed while nitrogen gas was blown into the slurry starting 15 minutes before the titration began. In this neutralization titration, in the pH curve plotted relative to the amount of alkali added, two points were observed where the increment (the differential value of pH relative to the amount of alkali added) was extremely large. The point where the increment was most large at the beginning of alkali addition is called the first endpoint, and the point where the increment was most large afterward is called the second endpoint. Figure 1 The amount of alkali required from the start of titration to the first endpoint is equal to the amount of the first dissociated acid in the slurry used for titration. Furthermore, the amount of alkali required from the start of titration to the second endpoint is equal to the amount of total dissociated acid in the slurry used for titration. It should be noted that the value obtained by dividing the amount of alkali required from the start of titration to the first endpoint (mmol) by the solids content (g) of the slurry being titrated is taken as the amount of phosphorus oxyacid (first dissociated acid) (mmol / g). Additionally, the value obtained by dividing the amount of alkali required from the start of titration to the second endpoint (mmol) by the solids content (g) of the slurry being titrated is taken as the amount of total dissociated acid (mmol / g).

[0372] (Determination of carboxyl group content)

[0373] The carboxyl content of fibrous cellulose was determined as follows: ion-exchanged water was added to a fibrous cellulose dispersion containing the fibrous cellulose to a content of 0.2% by mass, and the dispersion was treated with an ion-exchange resin and then titrated with an alkali.

[0374] The treatment using ion exchange resin is carried out as follows: 1 / 10 by volume of a strong acid ion exchange resin (Amberjet 1024; manufactured and adjusted by Organo Corporation) is added to a slurry containing 0.2% by mass of fibrous cellulose. After shaking for 1 hour, the resin is poured onto a 90μm mesh screen to separate it from the slurry.

[0375] Additionally, titration using an alkali is performed as follows: While adding a 0.1N aqueous solution of sodium hydroxide to a cellulose-containing slurry treated with an ion exchange resin, the change in pH value of the slurry is measured. If the pH change is observed while adding the sodium hydroxide aqueous solution, the following results are obtained: Figure 2 The titration curve is shown. (As shown in the image.) Figure 2 As shown, in this neutralization titration, a point was observed where the pH increment (the differential value of pH relative to the amount of alkali added) was extremely large in the plotted pH curve relative to the amount of alkali added. This point of maximum increment is called the first endpoint. Here, we will... Figure 2The region from the start of titration to the first endpoint is called the first region. The amount of alkali required for the first region is equal to the amount of carboxyl groups in the slurry used for titration. Then, the amount of alkali (mmol) required for the first region of the titration curve is divided by the solid content (g) in the slurry containing fine fibrous cellulose, thereby calculating the amount of carboxyl groups introduced (mmol / g).

[0376] [Determination of sulfur-containing oxyacid group content or sulfonic acid group content]

[0377] Regarding the sulfur-containing oxyacid group content or sulfonic acid group content of fibrous cellulose, the sulfur content was determined by wet ashing of fibrous cellulose with perchloric acid and concentrated nitric acid, followed by dilution at an appropriate ratio, and then by ICP emission spectroscopy analysis.

[0378] The value obtained by dividing the sulfur content by the absolute dry mass of the tested fibrous cellulose is taken as the sulfur oxyacid group · sulfonic acid group content (unit: mmol / g).

[0379] (Measurement of fiber width)

[0380] The fiber width of microfibrillated cellulose is the number-average fiber width measured using a fiber length measuring machine (FS-5, Valmet). The fiber width of fine fibrous cellulose is the number-average fiber width measured using a transmission electron microscope.

[0381] <Example 1>

[0382] The fine fibrous cellulose dispersion A obtained by manufacturing example 1 was added to a container, such that the solid content of the fine fibrous cellulose was 20 parts by mass. Then, deionized water was added to dilute the concentration of the solid content of the fine fibrous cellulose to 1.0% by mass. As a mixer, a Tornado mixer (general-purpose constrained mixer, PM-202, manufactured by ASONE Co., Ltd.) was used, with 6-inch diameter stirring blades installed, and the mixture was stirred at 1000 rpm for 5 minutes to obtain the diluted fine fibrous cellulose dispersion.

[0383] [Mixed Process]

[0384] A 1.0% by weight microfibrillated cellulose dispersion containing 61% by weight of an aqueous dispersion of natural rubber latex (ULACOL, REGITEX Co., Ltd., with an ammonia content of less than 0.1%) was added to bring the solid content of the rubber component to 100 parts by weight. A Tornado mixer with 6-inch diameter blades was used as the mixer, and the mixture was stirred at 1000 rpm for 5 minutes to obtain a mixture containing microfibrillated cellulose and natural rubber latex.

[0385] [Drying Process]

[0386] The obtained mixture containing microfibrillated cellulose / natural rubber latex was spread out on a tray with a Teflon (registered trademark) coating on the surface, so that the thickness after drying was 0.05 mm. It was then dried in an explosion-proof dryer at 40°C for 48 hours to obtain a sheet-like rubber composition containing microfibrillated cellulose / natural rubber.

[0387] [Preparation of Rubber Compounds]

[0388] The obtained rubber composition containing fine fibrous cellulose / natural rubber was plasticized for 10 minutes without heating using a two-roll mill (6-inch two-roll mill, manufactured by DAIHAN Co., Ltd.) at a speed of 26 / 30 rpm. Next, relative to 100 parts by weight of the rubber component, 2 parts by weight of crosslinking agent (PERCUMYL D, dicumyl peroxide, manufactured by Nippon Oil Co., Ltd.), 3 parts by weight of vulcanization accelerator (two types of zinc oxide, manufactured by Zhengtong Chemical Industry Co., Ltd.), and 1.5 parts by weight each of anti-aging agent (ANTAGE MB, ANTAGERD, manufactured by Kawaguchi Chemical Industry Co., Ltd.) were added, and the mixture was mixed for 6 minutes to obtain a rubber compound with a thickness of approximately 2 mm or more.

[0389] [Cross-linking process]

[0390] The obtained rubber mixture is placed in a mold and pressed and heated at 165°C for 20 minutes to produce a sheet of cross-linked rubber composition with a thickness of 2 mm.

[0391] <Example 2>

[0392] The process was performed in the same manner as in Example 1 to obtain a sheet-like rubber composition containing microfibrillated cellulose / natural rubber. In the [Preparation of the Rubber Mixture] using the obtained rubber composition, 1.5 parts by mass of sulfur (MUCRON OT-20, manufactured by Shikoku Chemical Industry Co., Ltd.), 2 parts by mass of vulcanization accelerator, 2 parts by mass of anti-aging agent (ANTAGE RD), 2 parts by mass of stearic acid (stearic acid 50S, Shin Nippon Rika Co., Ltd.), and 2 parts by mass of vulcanization accelerator (Nocceler MSA-G, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) were added as additives to 100 parts by mass of the rubber component. Otherwise, the rubber mixture was obtained in the same manner as in Example 1. In the [Crosslinking Process], the rubber composition was pressed and heated at 150°C for 10 minutes to produce a sheet of crosslinked rubber composition with a thickness of 2 mm.

[0393] <Example 3>

[0394] Using microfibrillated cellulose dispersion B instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0395] <Example 4>

[0396] Using microfibrillated cellulose dispersion C instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0397] <Example 5>

[0398] Using microfibrillated cellulose dispersion D instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0399] <Example 6>

[0400] Using microfibrillated cellulose dispersion E instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0401] <Example 7>

[0402] Using microfibrillated cellulose dispersion F instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0403] <Example 8>

[0404] Except that an aqueous dispersion of modified natural rubber latex (MG-10, solid content concentration 54% by mass, manufactured by REGITEX Co., Ltd., modified natural rubber latex grafted with methyl methacrylate) was used instead of an aqueous dispersion of natural rubber latex, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0405] <Example 9>

[0406] Except for using an aqueous dispersion of natural rubber latex (LA-LATEX, solid content 61.5% by mass, manufactured by REGITEX Co., Ltd., ammonia content less than 0.3%), the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0407] <Example 10>

[0408] Except for using an aqueous dispersion of natural rubber latex (HA-LATEX, solid content 61.5% by mass, manufactured by REGITEX Co., Ltd., ammonia content of about 0.7%), the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0409] <Example 11>

[0410] Except that microfibrillated cellulose dispersion A was used instead of microfibrillated cellulose dispersion A, the same treatment as in Example 8 was performed to obtain a sheet of crosslinked rubber composition.

[0411] <Example 12>

[0412] Except that microfibrillated cellulose dispersion A was used instead of microfibrillated cellulose dispersion A, the same treatment as in Example 9 was performed to obtain a sheet of crosslinked rubber composition.

[0413] <Example 13>

[0414] Except that microfibrillated cellulose dispersion A was used instead of microfibrillated cellulose dispersion A, the same treatment as in Example 10 was performed to obtain a sheet of crosslinked rubber composition.

[0415] <Example 14>

[0416] Except that microfibrillated cellulose dispersion B was used instead of microfibrillated cellulose dispersion A, the same treatment as in Example 13 was performed to obtain a sheet of crosslinked rubber composition.

[0417] <Example 15>

[0418] Except that an aqueous dispersion of modified natural rubber latex (MG-10, solid content concentration 54% by mass, manufactured by REGITEX Co., Ltd.) was used instead of an aqueous dispersion of natural rubber latex, the same treatment as in Example 2 was performed to obtain a sheet of crosslinked rubber composition.

[0419] <Example 16>

[0420] Except for using an aqueous dispersion of natural rubber latex (HA-LATEX, solids concentration 61.5% by mass, manufactured by REGITEX Co., Ltd.), the same treatment as in Example 2 was performed to obtain a sheet of crosslinked rubber composition.

[0421] <Example 17>

[0422] Instead of microfibrillated cellulose dispersion A, microfibrillated cellulose dispersion A was used, and an aqueous dispersion of natural rubber latex (LA-LATEX, solids concentration 61.5% by mass, manufactured by REGITEX Co., Ltd.) was used. Otherwise, the same treatment as in Example 15 was performed to obtain a sheet of crosslinked rubber composition.

[0423] <Example 18>

[0424] Except that microfibrillated cellulose dispersion A was used instead of microfibrillated cellulose dispersion A, the same treatment as in Example 16 was performed to obtain a sheet of crosslinked rubber composition.

[0425] <Comparative Example 1>

[0426] Using microfibrillated cellulose dispersion G instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0427] <Comparative Example 2>

[0428] Using microfibrillated cellulose dispersion G instead of microfibrillated cellulose dispersion A, the same treatment as in Example 2 was performed to obtain a sheet of crosslinked rubber composition.

[0429] <Comparative Example 3>

[0430] Using microfibrillated cellulose dispersion H instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0431] <Comparative Example 4>

[0432] Using microfibrillated cellulose dispersion I instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0433] <Comparative Example 5>

[0434] Using microfibrillated cellulose dispersion J instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0435] <Comparative Example 6>

[0436] Using microfibrillated cellulose dispersion K instead of microfibrillated cellulose dispersion A, the same treatment as in Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0437] <Comparative Example 7>

[0438] Except for using an aqueous dispersion of natural rubber latex (HA-LATEX, solid content 61.5% by mass, manufactured by REGITEX Co., Ltd.), the same treatment as in Comparative Example 1 was performed to obtain a sheet of crosslinked rubber composition.

[0439] <Comparative Example 8>

[0440] Except that microfibrillated cellulose dispersion C was used instead of microfibrillated cellulose dispersion G, the same treatment as in Comparative Example 7 was performed to obtain a sheet of crosslinked rubber composition.

[0441] <Comparative Example 9>

[0442] Except for using an aqueous dispersion of natural rubber latex (HA-LATEX, solid content 61.5% by mass, manufactured by REGITEX Co., Ltd.), the same treatment as in Comparative Example 2 was performed to obtain a sheet of crosslinked rubber composition.

[0443] <Comparative Example 10>

[0444] Except that microfibrillated cellulose dispersion C was used instead of microfibrillated cellulose dispersion G, the same treatment as in Comparative Example 9 was performed to obtain a sheet of crosslinked rubber composition.

[0445] <Reference Example 1>

[0446] Using natural rubber latex instead of the mixture containing microfibrillated cellulose / natural rubber latex, the same treatment as in Example 1 was performed to obtain a sheet of cross-linked rubber composition.

[0447] <Reference Example 2>

[0448] The same process as in Reference Example 1 was performed to obtain a sheet-like natural rubber composition. Except for using the obtained natural rubber composition, the same process as in Example 2 was performed to obtain a sheet of cross-linked rubber composition.

[0449] <Reference Example 3>

[0450] In Example 1, [Preparation of Rubber Mixture], natural rubber (RSS#3, manufactured by Koshigaya Rubber Industry Co., Ltd.) was used instead of the rubber composition containing microfibrillated cellulose / natural rubber. Otherwise, the same treatment as in Example 1 was performed to obtain a sheet of cross-linked rubber composition.

[0451] [Measurement and Evaluation]

[0452] <Water Absorption Test>

[0453] For the sheets of crosslinked rubber compositions obtained in Examples 1-18, Comparative Examples 1-10, and Reference Examples 1-3, test pieces cut into dumbbell shapes (No. 6 dumbbell shape) as described in JIS K 6251:2017 were weighed at 23°C and 50% RH according to JIS K 7209A:2000, and then immersed in ion-exchange water at 70°C for 48 hours. The weight after wiping off the surface moisture was measured. The water absorption rate was calculated based on the following formula.

[0454] Water absorption rate (%) = (W - Wo) / Wo × 100

[0455] (Here, Wo is the mass at 23℃ and 50%RH, and W is the mass after soaking in ion-exchange water for 48 hours).

[0456] <Tensile Test under Conditioned Humidity Conditions>

[0457] For the sheets of crosslinked rubber compositions obtained in Examples 1-18, Comparative Examples 1-10, and Reference Examples 1-3, tensile tests were conducted using a universal testing machine (manufactured by Shimadzu Corporation) based on JIS K 6251:2017. Test pieces cut into dumbbell (No. 6 dumbbell shape) shapes as described in JIS K 6251:2017 were punched at 23±2°C, with a mark spacing of 20 mm and a tensile speed of 500 mm / min. The 50% modulus (σ50 (MPa)), 100% modulus (σ100 (MPa)), 300% modulus (σ300 (MPa)), strength (tensile strength (MPa)), and breaking strength E (J) were measured. Furthermore, breaking strength E is the area of ​​the SS curve (stress-strain curve).

[0458] <Water Resistance Test>

[0459] After measuring the mass of the impregnated test pieces used in the [water absorption test], a tensile test was quickly conducted using a universal testing machine (manufactured by Shimadzu Corporation) based on JIS K 6251:2017, at 23±2℃, a mark spacing of 20mm, and a tensile speed of 500mm / min. The 50% modulus (σ50 (MPa)), 100% modulus (σ100 (MPa)), 300% modulus (σ300 (MPa)), strength (tensile strength (MPa)), and breaking strength E (J) under water absorption conditions were measured.

[0460] Water resistance is evaluated based on the ratio of each property under water absorption conditions to each property under conditioned conditions.

[0461] It should be noted that low water absorption is preferred. In addition, the ratio of each property under water absorption conditions to each property under conditioning conditions is preferably close to 1.0 for 50% modulus (σ50 (MPa)), 100% modulus (σ100 (MPa)), 300% modulus (σ300 (MPa)), strength (tensile strength (MPa)) and breaking E (J).

[0462] The above measurement results are shown in Table 1 below.

[0463] [Table 1]

[0464]

[0465] In Table 1, "PO" represents dicumyl peroxide and "S" represents sulfur as the crosslinking agent. In addition, "after / before" in the evaluation of physical properties after crosslinking means "the ratio of each physical property under water absorption conditions to each physical property under humidification conditions".

[0466] As shown in Table 1, the crosslinked rubber (crosslinked rubber product) obtained in the examples has lower water absorption and better water resistance compared with the crosslinked rubber of the comparative examples. In addition, the ratios of 50% modulus (σ50 (MPa)), 100% modulus (σ100 (MPa)), 300% modulus (σ300 (MPa)), strength (tensile strength (MPa)), and breaking strength E (J) before and after water absorption are also greater than those of the comparative examples, indicating that the deterioration of physical properties is suppressed.

[0467] It should be noted that the above effects are the same in both peroxide crosslinking and sulfur crosslinking cases. Furthermore, the presence of any one of the following anionic groups—phosphate, carboxyl (TEMPO oxidation, hypochlorous acid oxidation), phosphite, sulfate, or carboxymethyl—has also been confirmed.

[0468] Furthermore, in Reference Example 1, the tensile strength under conditioned conditions was 5.3 MPa, while in Example 1 it was 15.1 MPa. Similarly, in Reference Example 2, the tensile strength under conditioned conditions was 13.8 MPa, while in Example 2 it was 17.5 MPa. Thus, by adding fibrous cellulose, the tensile strength was significantly improved.

[0469] As shown in the comparative example, when the counter ion is sodium ion (Na+) + In this case, the water absorption rate is high, and in addition, the reduction of various physical properties is also significant.

[0470] Industrial availability

[0471] The fibrous cellulose of this embodiment is effective as a rubber modifier, and compared with the conventional addition of fibrous cellulose, it can suppress the deterioration of physical properties caused by water absorption. Therefore, its application as an additive in various rubber products is expected.

[0472] Explanation of reference numerals in the attached figures

[0473] 10… drum dryer, 1… cylinder, 2… feed section, 3… flake mixture, 4… scraper, 5… composite material.

Claims

1. A fibrous cellulose, comprising anionic groups and a fiber width of less than 100 μm, The counter ion of the anionic group is ammonium ion (NH4+). + .

2. The fibrous cellulose according to claim 1 is microfiber cellulose with a fiber width of less than 1000 nm.

3. The fibrous cellulose according to claim 1 is microfibrillated cellulose with a fiber width exceeding 1 μm and less than 100 μm.

4. The fibrous cellulose according to claim 2 or 3, wherein, The anionic group is selected from at least one of the following groups: phosphorus oxyacid group, substituents derived from phosphorus oxyacid group, sulfur oxyacid group and substituents derived from sulfur oxyacid group.

5. A fibrous cellulose aqueous dispersion comprising the fibrous cellulose as described in claim 2 or 3.

6. A rubber composition comprising compounding the fibrous cellulose of claim 2 or 3 into a rubber component.

7. The rubber composition according to claim 6, wherein, The content of fibrous cellulose is 0.1 parts by mass or more and 60 parts by mass or less per 100 parts by mass of rubber component.

8. The rubber composition according to claim 6, wherein, The rubber component is diene-based rubber.

9. A crosslinked rubber article, which is formed by crosslinking and molding a rubber mixture containing the rubber composition of claim 6 and a crosslinking agent.

10. The cross-linked rubber article according to claim 9, wherein it is a tire.

11. A method for manufacturing a rubber composition, comprising the following steps (I) and (II), (I) A mixing step of mixing an aqueous dispersion containing the fibrous cellulose as described in claim 2 or 3 with rubber latex to obtain mixture A; (II) The heating process of heating and drying the mixture A to obtain a rubber composition.

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