Dust dispersion suppressant and dust dispersion suppression method

Abstract

To provide an agent for preventing scattering of dust that is effective in preventing scattering of dust.SOLUTION: An agent for preventing scattering of dust has a solvent, and fibrous cellulose with a fiber width of 1000 nm or less. There is also provided a method for preventing scattering of dust with the agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dust dispersion inhibitor and a dust dispersion inhibitor. [Background technology]

[0002] Traditionally, construction sites, waste disposal sites, and land development areas have faced problems with dust generation due to wind, which negatively impacts the surrounding environment. Therefore, various measures such as water-spraying dust suppression and covering dust suppression have been considered to prevent dust generation.

[0003] For example, Patent Document 1 describes a dust dispersion suppressant containing a chitosan solution. Patent Document 1 describes the use of a solution obtained by diluting chitosan and acetic acid in a weight ratio of 6:4, where the concentration of the chitosan solution is 5,000 ppm to 20,000 ppm, as a dust dispersion suppressant.

[0004] Furthermore, Patent Document 2 discloses a dust suppressant comprising a mixture of latex: 0.1-7%, modified starch / modified cellulose: 0.1-6%, sodium alginate: 0.1-5%, polyvinyl alcohol: 0.1-8%, sodium silicate: 0-8%, glycerin: 10-60%, surfactant: 0.01-5%, with the remainder being water. Note that the modified cellulose in Patent Document 2 is an amorphous, water-soluble cellulose derivative. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-190398 [Patent Document 2] Special Publication No. 2019-513155 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] When the inventors examined conventional dust scattering preventives, they found that there was room for improvement in the dust scattering prevention effect. Therefore, in order to solve such problems of the prior art, the inventors proceeded with studies aiming to provide a dust scattering preventive capable of exhibiting an excellent dust scattering prevention effect.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the inventors have found that a dust scattering preventive capable of exhibiting an excellent dust scattering prevention effect can be obtained by blending fibrous cellulose having a fiber width of 1000 nm or less into the dust scattering preventive. Specifically, the present invention has the following constitution.

[0008] [1] A dust scattering preventive comprising a solvent and fibrous cellulose having a fiber width of 1000 nm or less. [2] The dust scattering preventive according to [1], wherein the aspect ratio of the fibrous cellulose is 10 or more. [3] The dust scattering preventive according to [1] or [2], wherein an ionic substituent is introduced into the fibrous cellulose. [4] The dust scattering preventive according to [3], wherein the ionic substituent is an anionic group. [5] The dust scattering preventive according to [3], wherein the ionic substituent is at least one selected from the group consisting of a phosphoxo acid group, a substituent derived from a phosphoxo acid group, a carboxy group, a substituent derived from a carboxy group, a carboxymethyl group, a carboxyethyl group, a sulfur oxo acid group, a substituent derived from a sulfur oxo acid group, a sulfone group, a substituent derived from a sulfone group, and an ammonium group. [6] The dust scattering preventive according to any one of [1] to [5], wherein the solid content concentration of the fibrous cellulose is 1.0 mass% or less. [7] The dust scattering preventive according to any one of [1] to [6], wherein the pH is 5.0 or more and 9.0 or less. [8] The dust scattering preventive according to any one of [1] to [7], wherein the solvent is a solvent mainly composed of water. A method for preventing dust scattering, comprising a step of spraying the dust scattering preventive agent according to any one of [1] to [8] onto a dust generation target object.

Advantages of the Invention

[0009] According to the present invention, a dust scattering preventive agent capable of exhibiting an excellent dust scattering prevention effect can be obtained.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and the pH of a fibrous cellulose-containing slurry having a phosphoric acid group. [Figure 2] FIG. 2 is a graph showing the relationship between the amount of NaOH dropped and the pH of a fibrous cellulose-containing slurry having a carboxy group.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.

[0012] (Dust Scattering Preventive Agent) The present invention relates to a dust scattering preventive agent containing a solvent and fibrous cellulose having a fiber width of 1000 nm or less. In this specification, fibrous cellulose having a fiber width of 1000 nm or less may also be referred to as microfibrillated cellulose or CNF.

[0013] The dust dispersion suppressant of the present invention, having the above-described structure, exhibits excellent dust dispersion suppression effects. Specifically, when the dust dispersion suppressant of the present invention is sprayed onto dust-generating objects such as soil and sand, which are dust sources, it can bind the soil and sand together. As a result, dust generation can be suppressed. This is presumed to be because, by scattering fine fibrous cellulose onto the dust-generating objects, the particles of the dust-generating objects are firmly bound together by the crystalline fine fibrous cellulose. Furthermore, the dust dispersion suppressant of the present invention can also suppress the dispersion of ultrafine particles such as PM2.5.

[0014] The dust dispersion prevention effect can be confirmed, for example, by evaluating the binding strength of the silica sand using the following method. First, 5g of silica sand No. 6 (manufactured by Toyo Materan Co., Ltd.) is used as a model material for generating dust, and it is laid in a circular shape with a diameter of 50mm. Next, 7g of dust dispersion suppressant is sprayed onto the dust-generating object made of silica sand, and it is dried at room temperature for 24 hours. Then, when the center of the dust-generating object is pressed with a load of 2N, if the surface of the silica sand does not crumble and the occurrence of cracks is suppressed, it can be determined that the silica sand is well bound. If the silica sand is well bound, dust will not scatter even when air is blown onto the binding body, and it can be determined that the dust dispersion prevention effect was achieved by spraying the dust dispersion suppressant.

[0015] Furthermore, because the dust dispersion suppressant of the present invention has the above-described structure, it also exhibits excellent spray characteristics (aerosol characteristics). Since the dust dispersion suppressant of the present invention contains fine fibrous cellulose with a fiber width of 1000 nm or less, solid matter does not clog the nozzle when spraying the dust dispersion suppressant, thereby enabling uniform and continuous spray coating (aerosol coating) of dust-generating objects.

[0016] Furthermore, since the dust dispersion suppressant of the present invention contains fine fibrous cellulose derived from plant-derived cellulose, the dust dispersion suppressant contains plant-derived raw materials. For this reason, even if the dust dispersion suppressant of the present invention is sprayed into natural environments such as soil, it will not chemically contaminate the soil or adversely affect the properties of the soil. Thus, the dust dispersion suppressant of the present invention has a low environmental impact and can be said to be an environmentally friendly agent.

[0017] In this embodiment, the pH of the dust dispersion suppressant is preferably 5.0 or higher, more preferably 5.5 or higher, and even more preferably 6.0 or higher. Furthermore, the pH of the dust dispersion suppressant is preferably 9.0 or lower. Thus, it is preferable that the pH of the dust dispersion suppressant be in the near-neutral range. By setting the pH of the dust dispersion suppressant to the near-neutral range, even if the dust dispersion suppressant is sprayed into a natural environment such as soil, for example, it will not change the pH of the soil, and adverse effects on the ecosystem can be suppressed.

[0018] In this embodiment, the solid content concentration of the fine fibrous cellulose is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.6% by mass or less, relative to the total mass of the dust dispersion suppressant. Furthermore, the solid content concentration of the fine fibrous cellulose is preferably 0.01% by mass or more, relative to the total mass of the dust dispersion suppressant. Thus, the solid content concentration of the fine fibrous cellulose in the dust dispersion suppressant may be low. Even with a low concentration of the active ingredient, the dust dispersion suppressant of the present invention can exhibit excellent dust dispersion suppression effects.

[0019] In this embodiment, the dust dispersion suppressant is preferably a water-based dust dispersion suppressant. Here, a water-based dust dispersion suppressant refers to one that contains water as the main component as a solvent. By containing water as the main component as a solvent, even if the dust dispersion suppressant is sprayed into a natural environment such as soil, for example, it will not change the properties of the soil and it is possible to suppress adverse effects on the ecosystem.

[0020] (Fine fibrous cellulose) The dust dispersion suppressant of the present invention contains fibrous cellulose (fine fibrous cellulose) with a fiber width of 1000 nm or less. In this specification, fibrous cellulose (fine fibrous cellulose) with a fiber width of 1000 nm or less also includes cellulose nanocrystals (CNC).

[0021] The fiber width of the fibrous cellulose should be 1000 nm or less, preferably 100 nm or less, more preferably 20 nm or less, and even more preferably 8 nm or less. Furthermore, the number-average fiber width of the fibrous cellulose contained in the dust dispersion suppressant is preferably 1000 nm or less. The number-average fiber width of the fibrous cellulose is preferably, for example, 2 nm to 1000 nm, more preferably 2 nm to 100 nm, even more preferably 2 nm to 50 nm, and particularly preferably 2 nm to 10 nm. Note that the fibrous cellulose is, for example, monocrystalline cellulose.

[0022] The fiber width of fibrous cellulose can be measured, for example, using an electron microscope as follows: First, an aqueous suspension of fibrous cellulose with a concentration of 0.05% to 0.1% by mass is prepared, and this suspension is cast onto a hydrophilic carbon film-coated grid to prepare a sample for TEM observation. If the sample contains wide fibers, an SEM image of the surface cast on glass may be observed. Next, observation of the electron microscope image is performed at a magnification of 1000x, 5000x, 10000x, or 50000x, depending on the width of the fiber to be observed. However, the sample, observation conditions, and magnification should be adjusted to meet the following conditions.

[0023] (1) A straight line X is drawn at any point in the observed image, and 20 or more fibers intersect with this straight line X. (2) A line Y is drawn perpendicular to the line in the same image, and 20 or more fibers intersect with line Y.

[0024] For observation images that satisfy the above conditions, the width of the fibers intersecting with lines X and Y is visually read. In this way, at least three sets of observation images of surface areas that do not overlap are obtained. Next, for each image, the width of the fibers intersecting with lines X and Y is read. This allows for the reading of at least 20 × 2 × 3 = 120 fiber widths. The average of the read fiber widths is then taken as the number-average fiber width of the fibrous cellulose.

[0025] The fiber length of fibrous cellulose is not particularly limited, but is preferably between 0.1 μm and 1000 μm, more preferably between 0.1 μm and 800 μm, and even more preferably between 0.1 μm and 600 μm. By keeping the fiber length within the above range, the fracture of the crystalline region of the fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fibrous cellulose within an appropriate range. The fiber length of fibrous cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

[0026] It is preferable that the fibrous cellulose has a type I crystalline structure. The presence of a type I crystalline structure in fibrous cellulose can be identified in the diffraction profile obtained from a wide-angle X-ray diffraction photograph using graphite-monochromatized CuKα (λ=1.5418Å). Specifically, it can be identified by the presence of typical peaks at two locations: around 2θ=14° to 17° and around 2θ=22° to 23°. The proportion of type I crystalline structure in the fine fibrous cellulose is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. This allows for even better performance in terms of heat resistance and low linear thermal expansion coefficient. Furthermore, because the fibrous cellulose has a type I crystalline structure, natural cellulose can be used as a raw material, resulting in a dust dispersion suppressant with less environmental impact. The degree of crystallinity can be determined by measuring the X-ray diffraction profile and analyzing its pattern using conventional methods (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0027] The aspect ratio of the fibrous cellulose is preferably 10 or more, more preferably 20 or more, even more preferably 30 or more, even more preferably 40 or more, and particularly preferably 50 or more. Furthermore, the aspect ratio of the fibrous cellulose is preferably 10000 or less, and more preferably 1000 or less. In this specification, the aspect ratio of the fibrous cellulose is the value of the axial ratio (fiber length / fiber width) of the fibrous cellulose. By setting the aspect ratio of the fibrous cellulose within the above range, the particles of the dust-generating object are more easily bound together, and the dust dispersion prevention effect of the dust dispersion suppressant can be more effectively enhanced. In addition, by setting the aspect ratio of the fibrous cellulose within the above range, the spray characteristics (aerosol characteristics) of the dust dispersion suppressant can be further enhanced.

[0028] The fibrous cellulose in this embodiment, for example, has both crystalline and amorphous regions. Fine fibrous cellulose having both crystalline and amorphous regions and having an aspect ratio within the above range can be realized by the fine fibrous cellulose manufacturing method described later.

[0029] The fibrous cellulose of the present invention preferably has an ionic substituent. The ionic substituent may include, for example, either an anionic group or a cationic group, or both. In this embodiment, it is particularly preferable that the ionic substituent is an anionic group. Furthermore, the ionic substituent is preferably a group introduced into the fibrous cellulose via an ester bond or an ether bond, and more preferably a group introduced into the fibrous cellulose via an ester bond. In this case, the ester bond is preferably formed by the dehydration condensation of the fibrous cellulose and the compound that will become the ionic substituent.

[0030] Examples of anionic groups as ionic substituents include phosphorus oxoacid groups or substituents derived from phosphorus oxoacid groups (sometimes simply referred to as phosphorus oxoacid groups), carboxyl groups or substituents derived from carboxyl groups (sometimes simply referred to as carboxyl groups), carboxymethyl groups, carboxyethyl groups, sulfur oxoacid groups or substituents derived from sulfur oxoacid groups, xantate groups or substituents derived from xantate groups, phosphonone groups or substituents derived from phosphonone groups, phosphine groups or substituents derived from phosphine groups, sulfone groups or substituents derived from sulfone groups, carboxyalkyl groups, etc. Examples of cationic groups as ionic substituents include ammonium groups, phosphonium groups, sulfonium groups, etc. In particular, the ionic substituent is preferably at least one selected from the group consisting of phosphorus oxoacid group, substituents derived from phosphorus oxoacid group, carboxyl group, substituents derived from carboxyl group, carboxymethyl group, carboxyethyl group, sulfur oxoacid group, substituents derived from sulfur oxoacid group, sulfone group, substituents derived from sulfone group, and ammonium group; more preferably at least one selected from the group consisting of phosphorus oxoacid group, substituents derived from phosphorus oxoacid group, carboxyl group, substituents derived from carboxyl group, carboxymethyl group, sulfur oxoacid group, and substituents derived from sulfur oxoacid group; even more preferably at least one selected from the group consisting of phosphorus oxoacid group, substituents derived from phosphorus oxoacid group, carboxyl group, and substituents derived from carboxyl group; and particularly preferably at least one selected from phosphorus oxoacid group and substituents derived from phosphorus oxoacid group. By introducing a phosphorus oxoacid group as an anionic group, for example, the dispersibility of fibrous cellulose can be further improved even under alkaline or acidic conditions, and as a result, the dust dispersion prevention effect of the dust dispersion suppressant can be more effectively enhanced.

[0031] A phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group is, for example, a substituent represented by the following formula (1). Multiple substituents represented by the following formula (1) may be introduced into each fibrous cellulose. In this case, the multiple substituents represented by the following formula (1) may be the same or different.

[0032] [ka]

[0033] In equation (1), a, b, and n are natural numbers, and m is any number (where a = b × m). Of the n α and α', at least one is O - The rest are R or OR. Note that all of each α and α' are O - It is acceptable for this to be the case. The n αs may all be the same, or they may all be different. β b+ It is a cation with one or more valencies, composed of organic or inorganic substances.

[0034] R is a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an unsaturated cyclic hydrocarbon group, an aromatic group, or a derivative thereof. In formula (1), n ​​is preferably 1.

[0035] Examples of saturated linear hydrocarbon groups include, but are not limited to, methyl, ethyl, n-propyl, or n-butyl groups. Examples of saturated branched hydrocarbon groups include, but are not limited to, i-propyl or t-butyl groups. Examples of saturated cyclic hydrocarbon groups include, but are not limited to, cyclopentyl or cyclohexyl groups. Examples of unsaturated linear hydrocarbon groups include, but are not limited to, vinyl or allyl groups. Examples of unsaturated branched hydrocarbon groups include, but are not limited to, i-propenyl or 3-butenyl groups. Examples of unsaturated cyclic hydrocarbon groups include, but are not limited to, cyclopentenyl or cyclohexenyl groups. Examples of aromatic groups include, but are not limited to, phenyl or naphthyl groups.

[0036] Furthermore, as derivative groups in R, carboxyl groups and carboxylate groups (-COO) are added to the main chain or side chain of the various hydrocarbon groups mentioned above. - Examples of functional groups include, but are not particularly limited to, a functional group in which at least one selected from functional groups such as hydroxyl groups, amino groups, and ammonium groups is added or substituted. Furthermore, the number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphorus oxoacid group can be set within an appropriate range, which facilitates penetration into the fiber raw material and can also increase the yield of fibrous cellulose. Note that if there are multiple Rs in formula (1) or if multiple substituents represented by formula (1) are introduced into fibrous cellulose, the multiple Rs may be the same or different.

[0037] β b+β is a cation with one or more valencies composed of organic or inorganic substances. Examples of cations with one or more valencies composed of organic substances include organic onium ions. Examples of organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of cations with one or more valencies composed of inorganic substances include alkali metal ions such as sodium, potassium, or lithium, divalent metal ions such as calcium or magnesium, hydrogen ions, and ammonium ions. Note that β is included in formula (1). b+ If multiple β atoms exist, or if multiple substituents represented by formula (1) above are introduced into fibrous cellulose, then multiple β atoms exist. b+ These may be the same or different. As a monovalent or more cation consisting of organic or inorganic material, β b+ Sodium or potassium ions are preferred because they do not easily yellow when the fiber raw material containing them is heated and are readily available for industrial use, but the material is not particularly limited.

[0038] More specifically, substituents derived from a phosphorus oxoacid group include a phosphate group (-PO3H2), a salt of a phosphate group, a phosphonotic group (phosphonic acid group) (-PO2H2), and a salt of a phosphonotic group (phosphonic acid group). Furthermore, substituents derived from a phosphorus oxoacid group may also be groups formed by condensation of a phosphate group (e.g., a pyrophosphate group), groups formed by condensation of a phosphonic acid (e.g., a polyphosphonic acid group), phosphate ester groups (e.g., monomethyl phosphate group, polyoxyethylene alkyl phosphate group), alkylphosphonic acid groups (e.g., a methylphosphonic acid group), and the like.

[0039] Further, the sulfur oxoacid group (sulfur oxoacid group or a substituent derived from the sulfur oxoacid group) is, for example, a substituent represented by the following formula (2). A plurality of substituents represented by the following formula (2) may be introduced into each fibrous cellulose. In this case, the substituents represented by the following formula (2) introduced in plurality may be the same or different from each other.

[0040]

Chemical formula

[0041] In the above structural formula, b and n are natural numbers, p is 0 or 1, and m is an arbitrary number (provided that 1 = b × m). When n is 2 or more, the plurality of p's may be the same number or different numbers. In the above structural formula, β b+ is a cation of monovalent or higher valence composed of an organic or inorganic substance. Examples of the cation of monovalent or higher valence composed of an organic substance include organic onium ions. Examples of the organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of the organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of the organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of the cation of monovalent or higher valence composed of an inorganic substance include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, ammonium ions, and the like. When a plurality of substituents represented by the above formula (2) are introduced into the fibrous cellulose, the plurality of βs b+ may be the same or different from each other. As the cation of monovalent or higher valence composed of an organic or inorganic substance, sodium or potassium ions, which are less likely to cause yellowing when heating a fiber raw material containing β b+ and are easy to use industrially, are preferable, but not particularly limited.

[0042] The amount of ionic substituent introduced into fibrous cellulose is preferably, for example, 0.10 mmol / g or more per 1 g (mass) of fibrous cellulose, more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, and particularly preferably 0.60 mmol / g or more. Furthermore, the amount of ionic substituent introduced into fibrous cellulose is preferably, for example, 5.20 mmol / g or less per 1 g (mass) of fibrous cellulose, 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, even more preferably 2.00 mmol / g or less, even more preferably 1.50 mmol / g or less, and particularly preferably 1.00 mmol / g or less. Here, the denominator in the unit mmol / g is the amount of the counterion of the ionic substituent being a hydrogen ion (H + This indicates the mass of fibrous cellulose when ). By keeping the amount of ionic substituents within the above range, it is possible to easily refine the fiber raw material and improve the stability of fibrous cellulose. As a result, the dust dispersion prevention effect of the dust dispersion suppressant can be more effectively enhanced.

[0043] The amount of ionic substituent introduced into fibrous cellulose can be measured, for example, by neutralization titration. In neutralization titration, the amount introduced is determined by measuring the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the resulting slurry containing fibrous cellulose.

[0044] Figure 1 is a graph showing the relationship between the amount of NaOH added to a slurry containing fibrous cellulose with phosphorus oxoacid groups and the pH. The amount of phosphorus oxoacid groups introduced into the fibrous cellulose can be measured, for example, as follows. First, the slurry containing fibrous cellulose is treated with a strong acid ion exchange resin. If necessary, a defibration treatment similar to the defibration treatment process described later may be performed on the sample to be measured before treatment with the strong acid ion exchange resin. Next, the pH change is observed while adding an aqueous sodium hydroxide solution, and a titration curve like the one shown in the upper part of Figure 1 is obtained. In the titration curve shown in the upper part of Figure 1, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of Figure 1, the increment (derivative value) (1 / mmol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, two points are observed in the curve plotting the measured pH against the amount of alkali added where the increment (derivative value of pH with respect to the amount of alkali added) is maximum. Of these, the first maximum increment obtained after starting to add alkali is called the first endpoint, and the next maximum increment obtained is called the second endpoint. The amount of alkali required from the start of the titration to the first endpoint is equal to the amount of the first dissociated acid from the fibrous cellulose contained in the slurry used for titration. The amount of alkali required from the first endpoint to the second endpoint is equal to the amount of the second dissociated acid from the fibrous cellulose contained in the slurry used for titration. The amount of alkali required from the start of the titration to the second endpoint is equal to the total amount of dissociated acid from the fibrous cellulose contained in the slurry used for titration. The value obtained by dividing the amount of alkali required from the start of the titration to the first endpoint by the solid content (g) of the slurry being titrated is the amount of phosphorus oxoacid groups introduced (mmol / g). Note that when simply referred to as the amount of phosphorus oxoacid groups introduced (or amount of phosphorus oxoacid groups), it refers to the amount of the first dissociated acid. In Figure 1, the region from the start of titration to the first endpoint is called the first region, and the region from the first endpoint to the second endpoint is called the second region. For example, if the phosphorus oxoacid group is a phosphate group and this phosphate group undergoes condensation, the amount of weakly acidic group in the phosphorus oxoacid group (also referred to as the amount of the second dissociated acid in this specification) appears to decrease, and the amount of alkali required in the second region becomes less than the amount of alkali required in the first region. On the other hand, the amount of strongly acidic group in the phosphorus oxoacid group (also referred to as the amount of the first dissociated acid in this specification) is equal to the amount of phosphorus atoms, regardless of whether condensation occurs or not. Also, if the phosphorus oxoacid group is a phosphite group, there is no weakly acidic group in the phosphorus oxoacid group, so the amount of alkali required in the second region becomes less, or in some cases, the amount of alkali required in the second region becomes zero. In this case, there is only one point on the titration curve where the pH increment is maximum.

[0045] The amount of phosphorus oxoacid groups introduced (mmol / g) mentioned above represents the amount of phosphorus oxoacid groups present in acid-type fibrous cellulose (hereinafter referred to as phosphorus oxoacid group amount (acid type)), since the denominator represents the mass of acid-type fibrous cellulose. On the other hand, if the counterion of the phosphorus oxoacid group is substituted with an arbitrary cation C such that it is equivalent in charge, the amount of phosphorus oxoacid groups present in fibrous cellulose with cation C as the counterion can be determined by converting the denominator to the mass of fibrous cellulose when cation C is the counterion (hereinafter referred to as phosphorus oxoacid group amount (C type)). In other words, it is calculated using the following formula. Phosphorus oxoacid group amount (C type) = Phosphorus oxoacid group amount (acid type) / {1 + (W - 1) × A / 1000} A [mmol / g]: Total amount of anions derived from the phosphorus oxoacid group in fibrous cellulose (total amount of dissociated acids from the phosphorus oxoacid group) W: Formula weight per unit charge of the cation C (for example, Na is 23, Al is 9)

[0046] Figure 2 is a graph showing the relationship between the amount of NaOH added to a dispersion containing fibrous cellulose having a carboxyl group as an ionic substituent and the pH. The amount of carboxyl group introduced into the fibrous cellulose can be measured, for example, as follows. First, a dispersion containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, a defibration treatment similar to the defibration treatment process described later may be performed on the sample before treatment with the strongly acidic ion exchange resin. Next, the pH change is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in the upper part of Figure 2. In the titration curve shown in the upper part of Figure 2, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of Figure 2, the increment (derivative value) (1 / mmol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, one point is identified in the curve plotting the measured pH against the amount of alkali added where the increment (derivative value of pH with respect to the amount of alkali added) is maximum, and this maximum point is called the first endpoint. Here, the region from the start of titration to the first endpoint in Figure 2 is called the first region. The amount of alkali required in the first region is equal to the amount of carboxyl groups in the dispersion used for titration. Then, the amount of alkali required in the first region of the titration curve (mmol) is divided by the solid content (g) in the dispersion containing the fibrous cellulose to be titrated to calculate the amount of carboxyl groups introduced (mmol / g).

[0047] The above-mentioned amount of carboxyl groups introduced (mmol / g) represents the amount of carboxyl groups present in acidic fibrous cellulose (hereinafter referred to as carboxyl group amount (acidic type)), since the denominator is the mass of acidic fibrous cellulose. On the other hand, if the counterion of the carboxyl group is substituted with an arbitrary cation C such that it is equivalent in charge, the amount of carboxyl groups present in fibrous cellulose with cation C as the counterion (hereinafter referred to as carboxyl group amount (C type)) can be determined by converting the denominator to the mass of fibrous cellulose when the cation C is the counterion. That is, it is calculated using the following formula. Carboxylate group weight (C type) = Carboxylate group weight (acid type) / {1 + (W - 1) × (Carboxylate group weight (acid type)) / 1000} W: Formula weight per unit charge of the cation C (for example, Na is 23, Al is 9)

[0048] In measuring the amount of ionic substituents by titration, if the amount of sodium hydroxide aqueous solution added is too large or the titration interval is too short, accurate values ​​may not be obtained, resulting in a lower-than-actual amount of ionic substituents. Appropriate titration volumes and intervals include, for example, titrating with 10-50 μL of 0.1N sodium hydroxide aqueous solution every 5-30 seconds. Furthermore, to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, it is desirable to blow an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration until the end of the titration while performing the measurement.

[0049] Furthermore, the amount of sulfur oxoacid groups or sulfone groups introduced into fibrous cellulose can be calculated by freeze-drying a slurry containing fibrous cellulose and then measuring the sulfur content of the pulverized sample. Specifically, the slurry containing fibrous cellulose is freeze-dried, and the pulverized sample is subjected to pressurized thermal decomposition using nitric acid in a sealed container. After appropriate dilution, the sulfur content is measured by ICP-OES. The value obtained by dividing by the oven-dry mass of the fibrous cellulose is taken as the amount of sulfur oxoacid groups or sulfone groups of the fibrous cellulose (unit: mmol / g).

[0050] To obtain fine fibrous cellulose with the ionic substituents described above, it is preferable to have an ionic substituent introduction step, a washing step, an alkali treatment step (neutralization step), and a defibration treatment step in this order, and an acid treatment step may be included instead of the washing step, or in addition to the washing step. Examples of ionic substituent introduction steps include a phosphorus oxo acid group introduction step, a carboxyl group introduction step, a sulfur oxo acid group introduction step, a xantate group introduction step, a phosphone group or phosphine group introduction step, a sulfone group introduction step, and a cationic group introduction step. Each of these will be described below.

[0051] (Method for producing microfiber cellulose) <Fiber raw materials> Fine fibrous cellulose is produced from cellulose-containing fiber raw materials. The cellulose-containing fiber raw materials are not particularly limited, but pulp is preferred because it is readily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp are not particularly limited, but include chemical pulps such as hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP); semi-chemical pulps such as semi-chemical pulp (SCP) and chemigroundwood pulp (CGP); and mechanical pulps such as crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP). Examples of non-wood pulp are not particularly limited, but include cotton-based pulps such as cotton linters and cotton lint, and non-wood-based pulps such as hemp, straw, and bagasse. The deinked pulp is not particularly limited, but examples include deinked pulp made from recycled paper. The pulp in this embodiment may be one of the above types used alone, or two or more types may be used in mixture. Among the above pulps, wood pulp and deinked pulp are preferred from the viewpoint of ease of availability. Among wood pulps, chemical pulp is more preferred from the viewpoint of having a high cellulose ratio and a high yield of fine fibrous cellulose during defibration treatment, and from the viewpoint of obtaining long-fiber fine fibrous cellulose with a large axial ratio due to minimal cellulose decomposition in the pulp. Kraft pulp and sulfite pulp are even more preferred.

[0052] As fiber raw materials containing cellulose, for example, cellulose contained in sea squirts or bacterial cellulose produced by acetic acid bacteria can be used. Alternatively, instead of fiber raw materials containing cellulose, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can be used.

[0053] <Phosphorus oxoacid group introduction process> The manufacturing process for fine fibrous cellulose preferably includes an ionic substituent introduction step, such as a phosphorus oxoacid group introduction step. The phosphorus oxoacid group introduction step involves reacting the cellulose-containing fiber raw material with at least one compound (hereinafter also referred to as "compound A") selected from compounds capable of introducing phosphorus oxoacid groups by reacting with hydroxyl groups present in the cellulose-containing fiber raw material. This step yields phosphorus oxoacid group-introduced fibers.

[0054] In the phosphorus oxoacid group introduction step according to this embodiment, the reaction of the cellulose-containing fiber raw material with compound A may be carried out in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as "compound B"). Alternatively, the reaction of the cellulose-containing fiber raw material with compound A may be carried out in the absence of compound B.

[0055] One example of a method for reacting compound A with compound B to a fiber raw material is to mix compound A and compound B with the fiber raw material in a dry, wet, or slurry state. Of these, it is preferable to use a fiber raw material in a dry or wet state, and particularly preferable to use a fiber raw material in a dry state, due to the high uniformity of the reaction. The form of the fiber raw material is not particularly limited, but for example, it is preferably in the form of cotton or a thin sheet. Compounds A and B can be added to the fiber raw material in the form of powder, a solution dissolved in a solvent, or after being heated above the melting point and melted. Of these, it is preferable to add them in the form of a solution dissolved in a solvent, particularly an aqueous solution, due to the high uniformity of the reaction. Compounds A and B may be added to the fiber raw material simultaneously, separately, or as a mixture. The method of adding compounds A and B is not particularly limited, but if compounds A and B are in solution form, the fiber raw material may be immersed in the solution and then removed, or the solution may be added dropwise to the fiber raw material. Alternatively, the required amounts of compound A and compound B may be added to the fiber raw material, or excess amounts of compound A and compound B may be added to the fiber raw material, and then the excess compound A and compound B may be removed by pressing or filtration.

[0056] Compound A used in this embodiment may be any compound having a phosphorus atom and capable of forming an ester bond with cellulose, and is not particularly limited to, but includes phosphoric acid or its salts, phosphorous acid or its salts, dehydrated condensed phosphoric acid or its salts, and phosphoric anhydride (phosphorus pentoxide). As phosphoric acid, various purities can be used, for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. As phosphorous acid, 99% phosphorous acid (phosphonic acid) can be used. Dehydrated condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid through a dehydration reaction, and examples include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphites, and dehydrated condensed phosphates include lithium salts, sodium salts, potassium salts, and ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid, and these can be neutralized to various degrees. Of these, phosphoric acid, sodium phosphoric acid, potassium phosphoric acid, ammonium phosphoric acid, or phosphorous acid, sodium phosphorous acid, potassium phosphorous acid, or ammonium phosphorous acid are preferred from the viewpoint of having high efficiency in introducing phosphate groups, easily improving the defibration efficiency in the defibration process described later, being low cost, and being easily applicable industrially. More preferably, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, or phosphorous acid or sodium phosphorous acid are preferred.

[0057] The amount of compound A added to the fiber raw material is not particularly limited, but for example, when the amount of compound A added is converted to the amount of phosphorus atoms, it is preferable that the amount of phosphorus atoms added to the fiber raw material (oven-dry mass) be 0.5% by mass or more and 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 30% by mass or less. By keeping the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by keeping the amount of phosphorus atoms added to the fiber raw material below the above upper limit, it is possible to balance the effect of improving yield with cost.

[0058] As described above, compound B used in this embodiment is at least one selected from urea and its derivatives. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea. From the viewpoint of improving the uniformity of the reaction, it is preferable to use compound B as an aqueous solution. Furthermore, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

[0059] The amount of compound B added to the fiber raw material (absolute dry weight) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and even more preferably 100% by mass or more and 350% by mass or less.

[0060] In the reaction of cellulose-containing fiber raw materials with compound A, in addition to compound B, other substances such as amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, and dimethylacetamide. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, triethylamine is known to act as a particularly good reaction catalyst.

[0061] In the phosphorus oxoacid group introduction process, it is preferable to add or mix compound A or the like to the fiber raw material and then subject the fiber raw material to heat treatment. The heat treatment temperature is preferably selected to efficiently introduce phosphorus oxoacid groups while suppressing thermal decomposition and hydrolysis reactions of the fibers. The heat treatment temperature is preferably, for example, 50°C to 300°C, more preferably 100°C to 250°C, and even more preferably 130°C to 200°C. Furthermore, various heat transfer devices can be used for the heat treatment, such as agitation dryers, rotary dryers, disc dryers, roll-type heaters, plate-type heaters, fluidized bed dryers, airflow dryers, vacuum dryers, infrared heaters, far-infrared heaters, and microwave heaters.

[0062] In the heat treatment according to this embodiment, for example, a method can be employed in which compound A is added to a thin sheet-like fiber raw material by impregnation or other methods, and then heated, or a method can be employed in which the fiber raw material and compound A are kneaded or stirred while heating. This makes it possible to suppress uneven concentration of compound A in the fiber raw material and to introduce phosphorus oxoacid groups more uniformly to the surface of the cellulose contained in the fiber raw material. This is thought to be because, as water molecules move to the surface of the fiber raw material during drying, dissolved compound A is attracted to the water molecules by surface tension and similarly moves to the surface of the fiber raw material (i.e., uneven concentration of compound A is produced), and this can be suppressed.

[0063] Furthermore, the heating device used for the heat treatment is preferably one that can constantly discharge, for example, the moisture held in the slurry and the moisture generated by the dehydration condensation (phosphate esterification) reaction between compound A and hydroxyl groups contained in cellulose, etc., in the fiber raw material, to the outside of the device system. Examples of such heating devices include a forced-air oven. By constantly discharging moisture from the device system, it is possible to suppress the hydrolysis reaction of phosphate ester bonds, which is the reverse reaction of phosphate esterification, as well as the acid hydrolysis of sugar chains in the fibers. As a result, it becomes possible to obtain fine fibrous cellulose with a high axial ratio.

[0064] The heating time is preferably between 1 second and 300 minutes, more preferably between 1 second and 1000 seconds, and even more preferably between 10 seconds and 800 seconds, after substantially all moisture has been removed from the fiber raw material. In this embodiment, the amount of phosphorus oxoacid groups introduced can be kept within a preferred range by setting the heating temperature and heating time within an appropriate range.

[0065] The phosphorus oxoacid group introduction step only needs to be performed at least once, but it can also be repeated two or more times. By performing the phosphorus oxoacid group introduction step two or more times, a large number of phosphorus oxoacid groups can be introduced into the fiber raw material. In this embodiment, one example of a preferred embodiment is the case in which the phosphorus oxoacid group introduction step is performed twice.

[0066] The amount of phosphorus oxoacid groups introduced into the fiber raw material is preferably 0.10 mmol / g or more per gram (mass) of fiber raw material, more preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 1.00 mmol / g or more. Furthermore, the amount of phosphorus oxoacid groups introduced into the fiber raw material is preferably 5.20 mmol / g or less per gram (mass) of fiber raw material, more preferably 3.65 mmol / g or less, and even more preferably 3.00 mmol / g or less. By keeping the amount of phosphorus oxoacid groups introduced within the above range, the micronization of the fiber raw material can be facilitated, and the stability of the fine fibrous cellulose can be enhanced.

[0067] <Carboxyloid introduction process> The manufacturing process for fine fibrous cellulose may include, for example, a carboxyl group introduction step as an ionic substituent introduction step. The carboxyl group introduction step is carried out by treating the cellulose-containing fiber raw material with an oxidation treatment such as ozono-oxidation, Fenton oxidation, or TEMPO oxidation treatment, or with a compound having a carboxylic acid-derived group or a derivative thereof, or with an acid anhydride or a derivative thereof of a compound having a carboxylic acid-derived group.

[0068] Compounds having a carboxylic acid-derived group are not particularly limited, but examples include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. Furthermore, derivatives of compounds having a carboxylic acid-derived group are not particularly limited, but examples include imidides of acid anhydrides of compounds having a carboxyl group, and derivatives of acid anhydrides of compounds having a carboxyl group. Imidides of acid anhydrides of compounds having a carboxyl group are not particularly limited, but examples include imidides of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

[0069] Acid anhydrides of compounds having a carboxylic acid-derived group are not particularly limited, but examples include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Furthermore, derivatives of acid anhydrides of compounds having a carboxylic acid-derived group are not particularly limited, but examples include acid anhydrides of compounds having a carboxyl group, such as dimethyl maleic anhydride, diethyl maleic anhydride, and diphenyl maleic anhydride, in which at least some of the hydrogen atoms are substituted with substituents such as alkyl groups and phenyl groups.

[0070] In the carboxyl group introduction step, when performing TEMPO oxidation treatment, it is preferable to carry out the treatment under conditions where the pH is between 6 and 8. Such treatment is also called neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment can be carried out, for example, by adding pulp as the fiber raw material, a nitroxyl radical such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst, and sodium hypochlorite as a sacrificial reagent to a sodium phosphate buffer (pH=6.8). Furthermore, by including sodium chlorite, the aldehyde generated during the oxidation process can be efficiently oxidized to the carboxyl group. Alternatively, the TEMPO oxidation treatment may be carried out under conditions where the pH is between 10 and 11. Such treatment is also called alkaline TEMPO oxidation treatment. Alkaline TEMPO oxidation treatment can be carried out, for example, by adding a nitroxyl radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as the fiber raw material.

[0071] The amount of carboxyl groups introduced into the fiber raw material varies depending on the type of substituent. For example, when introducing carboxyl groups by TEMPO oxidation, it is preferable to have 0.10 mmol / g or more per gram (mass) of fiber raw material, more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, and particularly preferable to have 0.60 mmol / g or more. Furthermore, the amount of carboxyl groups introduced into fibrous cellulose is preferably 3.65 mmol / g or less, more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, even more preferably 2.00 mmol / g or less, even more preferably 1.50 mmol / g or less, and particularly preferable to have 1.00 mmol / g or less. In addition, when the substituent is a carboxymethyl group, the amount of carboxyl groups introduced may be 5.8 mmol / g or less per gram (mass) of fine fibrous cellulose. By keeping the amount of carboxyl groups introduced within the above range, it is possible to facilitate the refinement of the fiber raw material and improve the stability of the fibrous cellulose.

[0072] <Sulfur oxoacid group introduction process> The manufacturing process for fine fibrous cellulose may include, for example, a sulfur oxoacid group introduction step as an ionic substituent introduction step. In the sulfur oxoacid group introduction step, a cellulose fiber having a sulfur oxoacid group can be obtained by the reaction of a sulfur oxoacid with a hydroxyl group present in the cellulose-containing fiber raw material.

[0073] In the sulfur oxoacid group introduction step, instead of compound A in the <phosphorus oxoacid group introduction step> described above, at least one compound (hereinafter also referred to as "compound C") selected from compounds that can introduce sulfur oxoacid groups by reacting with hydroxyl groups present in the cellulose-containing fiber raw material is used. Compound C can be any compound that has a sulfur atom and can form an ester bond with cellulose, and examples include sulfuric acid or its salts, sulfurous acid or its salts, and sulfuric acid amides, but is not particularly limited. Sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. As sulfurous acid, 5% sulfurous acid water can be used. As sulfates or sulfurous acid salts, examples include lithium salts, sodium salts, potassium salts, and ammonium salts of sulfates or sulfurous acid salts, and these can be neutralized to various degrees. As sulfuric acid amides, sulfamic acid can be used. In the sulfur oxoacid group introduction step, it is preferable to use compound B in the <phosphorus oxoacid group introduction step> described above in the same manner.

[0074] In the sulfur oxoacid group introduction step, it is preferable to mix the cellulose raw material with an aqueous solution containing sulfur oxoacid and urea and / or a urea derivative, and then heat-treat the cellulose raw material. The heat treatment temperature is preferably selected to efficiently introduce sulfur oxoacid groups while suppressing thermal decomposition and hydrolysis reactions of the fibers. The heat treatment temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 150°C or higher. Furthermore, the heat treatment temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0075] In the heat treatment process, it is preferable to heat until substantially all moisture is removed. Therefore, the heat treatment time varies depending on the amount of moisture contained in the cellulose raw material, the amount of sulfur oxoacid and aqueous solution containing urea and / or urea derivatives added, but it is preferable to heat for at least 10 seconds and no more than 10,000 seconds. Various heat transfer devices can be used for the heat treatment, such as stirring dryers, rotary dryers, disc dryers, roll-type heaters, plate-type heaters, fluidized bed dryers, band-type dryers, filtration dryers, vibrating fluidized bed dryers, airflow dryers, vacuum dryers, infrared heaters, far-infrared heaters, microwave heaters, and high-frequency dryers.

[0076] The amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 0.50 mmol / g or more, more preferably 0.70 mmol / g or more, and even more preferably 1.00 mmol / g or more. Furthermore, the amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 5.00 mmol / g or less, and more preferably 3.00 mmol / g or less. By keeping the amount of sulfur oxoacid groups introduced within the above range, it is possible to facilitate the refinement of the fiber raw material and improve the stability of the fibrous cellulose.

[0077] <Oxidation process using chlorine-based oxidizing agent (second carboxyl group introduction process)> The ionic substituent introduction step may include an oxidation step using a chlorine-based oxidizing agent. In the oxidation step using a chlorine-based oxidizing agent, a carboxyl group is introduced into the fiber raw material by adding the chlorine-based oxidizing agent to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out the reaction.

[0078] Examples of chlorine-based oxidizing agents include hypochlorous acid, hypochlorite, chlorous acid, chlorite, chloric acid, chlorate, perchloric acid, perchlorate, and chlorine dioxide. From the standpoint of substituent introduction efficiency, and consequently defibration efficiency, cost, and ease of handling, sodium hypochlorite, sodium chlorite, and chlorine dioxide are preferred as chlorine-based oxidizing agents. When adding a chlorine-based oxidizing agent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be dissolved in a suitable solvent before being added.

[0079] In the oxidation process using a chlorine-based oxidizing agent, the concentration of the chlorine-based oxidizing agent in the solution is preferably 1% by mass or more and 1,000% 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, when converted to an effective chlorine concentration. The amount of chlorine-based oxidizing agent added per 100 parts by mass of 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.

[0080] The reaction time with the chlorine-based oxidizing agent in the oxidation step may vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 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. Furthermore, it is preferable to maintain a constant pH (for example, pH 11) at the start of the reaction and during the reaction by appropriately adding hydrochloric acid or sodium hydroxide. After the reaction, excess reaction reagents, by-products, etc. may be washed off with water by filtration or the like.

[0081] <Xanthogenic group introduction process (xanthogenic acid esterification process)> The ionic substituent introduction step may include, for example, a xantate group introduction step (hereinafter also referred to as the xantate formation step). In the xantate formation step, xantate groups are introduced into the fiber raw material by adding carbon disulfide and an alkali compound to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out the reaction. Specifically, carbon disulfide is added to a fiber raw material that has been alkali-celluloseized by the method described later and the reaction is carried out.

[0082] <<Alkaline Cellulose Treatment>> When introducing ionic substituents to fiber raw materials, it is preferable to react the cellulose contained in the fiber raw material with an alkaline solution to alkalize the cellulose. This treatment causes some of the hydroxyl groups of the cellulose to ionically dissociate, thereby increasing its nucleophilicity (reactivity). The alkaline compound contained in the alkaline solution is not particularly limited and may be an inorganic alkaline compound or an organic alkaline compound. For their versatility, it is preferable to use, for example, sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, or tetrabutylammonium hydroxide. Alkalicelluloseization may be performed simultaneously with the introduction of ionic substituents, as a preliminary step, or at both timings.

[0083] The solution temperature at which alkali cellulose formation is initiated is preferably 0°C to 50°C, more preferably 5°C to 40°C, and even more preferably 10°C to 30°C.

[0084] The alkali concentration in the alkaline solution is preferably 0.01 mol / L or more and 4 mol / L or less as a molar concentration, more preferably 0.1 mol / L or more and 3 mol / L or less, and even more preferably 1 mol / L or more and 2.5 mol / L or less. In particular, when the processing temperature in alkali cellulose formation is less than 10°C, the alkali concentration is preferably 1 mol / L or more and 2 mol / L or less.

[0085] The alkali cellulose treatment time is preferably 1 minute or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. The alkali treatment time is preferably 6 hours or less, more preferably 5 hours or less, and even more preferably 4 hours or less.

[0086] By adjusting the type of alkaline solution, treatment temperature, concentration, and immersion time as described above, the penetration of the alkaline solution into the crystalline regions of cellulose can be suppressed, making it easier to maintain the type I cellulose crystalline structure and increasing the yield of fine fibrous cellulose.

[0087] When the introduction of ionic substituents and alkali cellulose are not performed simultaneously, alkali cellulose is preferably performed before the introduction of ionic substituents. In this case, it is preferable to separate the alkali cellulose obtained from the alkali cellulose treatment into solid and liquid by general deliquidation methods such as centrifugation or filtration to remove moisture. This improves the reaction efficiency in the subsequent ionic substituent introduction step. The cellulose fiber concentration after solid-liquid separation is preferably 5% to 50%, more preferably 10% to 40%, and even more preferably 15% to 35%.

[0088] <Phosphozone group or phosphine group introduction process (phosphoalkylation process)> The ionic substituent introduction step may include a phosphone group or phosphine group introduction step (phosphoalkylation step). In the phosphoalkylation step, a compound having a reactive group and a phospho group or phosphine group (compound E) is used as an essential component. A ) , by adding an alkaline compound, compound B selected from the aforementioned urea and its derivatives as an optional component, to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out the reaction, a phosphone group or phosphine group is introduced into the fiber raw material.

[0089] Examples of reactive groups include alkyl halides, vinyl groups, and epoxy groups (glycidyl groups). Compound E A Examples include vinylphosphonic acid, phenylvinylphosphonic acid, and phenylvinylphosphinic acid. Compound E is chosen from the standpoint of substituent introduction efficiency, and consequently defibrillation efficiency, cost, and ease of handling. A It is preferable that it is vinylphosphonic acid. Furthermore, it is also preferable to use compound B from the <phosphorus oxoacid group introduction step> described above as an optional component, and the amount added is also preferably as described above.

[0090] Compound E A When adding the reagent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be added after being dissolved in a suitable solvent. It is preferable that the fiber raw material be alkali-cellulosed beforehand or simultaneously with the reaction. The method of alkali-cellulosed treatment is as described above.

[0091] The reaction temperature is preferably, for example, 50°C to 300°C, more preferably 100°C to 250°C, and even more preferably 130°C to 200°C.

[0092] Compound E A The amount added per 100 parts by mass of fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0093] The reaction time may vary depending on the reaction temperature, but is preferably between 1 minute and 1,000 minutes, more preferably between 10 minutes and 500 minutes, and even more preferably between 20 minutes and 400 minutes. After the reaction, excess reaction reagents, by-products, etc., may be washed away with water by filtration or other means.

[0094] <Sulfone group introduction process (sulfoalkylation process) (second sulfone group introduction process)> The ionic substituent introduction step may include a sulfone group introduction step (sulfoalkylation step). In sulfoalkylation, a compound having a reactive group and a sulfone group (compound E) is used as an essential component. B ) and compound B, selected from an alkaline compound and the aforementioned urea and its derivatives, are added to a hydroxyl-containing fiber raw material in a wet or dry state and reacted to introduce sulfone groups into the fiber raw material.

[0095] Examples of reactive groups include alkyl halides, vinyl groups, and epoxy groups (glycidyl groups). Compound E B Examples include sodium 2-chloroethanesulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, and 2-acrylamido-2-methylpropanesulfonic acid. Among these, compound E is considered to have the efficiency of substituent introduction, and consequently the efficiency of defibrillation, cost, and ease of handling. B It is preferable that it be sodium vinyl sulfonate. Furthermore, it is also preferable to use compound B from the <phosphorus oxoacid group introduction step> described above as an optional component, and the amount added is also preferably as described above.

[0096] Compound E B When adding the reagent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be added after being dissolved in a suitable solvent. It is preferable that the fiber raw material be alkali-cellulosed beforehand or simultaneously with the reaction. The method of alkali-cellulosed treatment is as described above.

[0097] The reaction temperature is preferably, for example, 50°C to 300°C, more preferably 100°C to 250°C, and even more preferably 130°C to 200°C.

[0098] Compound E BThe amount added per 100 parts by mass of fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0099] The reaction time may vary depending on the reaction temperature, but is preferably between 1 minute and 1,000 minutes, more preferably between 10 minutes and 500 minutes, and even more preferably between 15 minutes and 400 minutes. After the reaction, excess reaction reagents, by-products, etc., may be washed away with water by filtration or other means.

[0100] <Carboxyalkylation process (third carboxyl group introduction process)> The ionic substituent introduction step may include a carboxyalkylation step. An essential component is a compound having a reactive group and a carboxyl group (compound E). C ) ) A carboxyl group is introduced into the fiber raw material by adding an alkaline compound, compound B selected from the aforementioned urea and its derivatives as an optional component, to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out the reaction.

[0101] Examples of reactive groups include alkyl halides, vinyl groups, and epoxy groups (glycidyl groups). Compound E C From the viewpoint of substituent introduction efficiency, and consequently defibration efficiency, cost, and ease of handling, monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, 3-chloropropionic acid, sodium 2-chloropropionate, and sodium 3-chloropropionate are preferred. Furthermore, it is also preferable to use compound B from the <phosphorus oxoacid group introduction step> described above as an optional component, and the amount added is also preferably as described above.

[0102] Compound E CWhen adding the reagent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be added after being dissolved in a suitable solvent. It is preferable that the fiber raw material be alkali-cellulosed beforehand or simultaneously with the reaction. The method of alkali-cellulosed treatment is as described above.

[0103] The reaction temperature is preferably, for example, 50°C to 300°C, more preferably 100°C to 250°C, and even more preferably 130°C to 200°C.

[0104] Compound E C The amount added per 100 parts by mass of fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0105] The reaction time may vary depending on the reaction temperature, but is preferably between 1 minute and 1,000 minutes, more preferably between 3 minutes and 500 minutes, and even more preferably between 5 minutes and 400 minutes. After the reaction, excess reaction reagents, by-products, etc., may be washed away with water by filtration or other means.

[0106] <Cationic group introduction process (cationization process)> As an essential component, a compound having a reactive group and a cationic group (compound E D ) A cation group is introduced into the fiber raw material by adding an alkaline compound, compound B selected from the aforementioned urea and its derivatives as an optional component, to a hydroxyl-containing fiber raw material in a wet or dry state and carrying out a reaction.

[0107] Examples of reactive groups include alkyl halides, vinyl groups, and epoxy groups (glycidyl groups). Examples of cationic groups include ammonium groups, phosphonium groups, and sulfonium groups. Among these, ammonium groups are preferred as the cationic group. Compound E D As such, glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, etc. are preferred in terms of substituent introduction efficiency, and consequently defibration efficiency, cost, and ease of handling. Furthermore, it is also preferable to use compound B from the <phosphorus oxoacid group introduction step> described above as an optional component. The amount added is also preferably as described above.

[0108] Compound E D When adding the reagent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be added after being dissolved in a suitable solvent. It is preferable that the fiber raw material be alkali-cellulosed beforehand or simultaneously with the reaction. The method of alkali-cellulosed treatment is as described above.

[0109] The reaction temperature is preferably, for example, 50°C to 300°C, more preferably 100°C to 250°C, and even more preferably 130°C to 200°C.

[0110] Compound E D The amount added per 100 parts by mass of fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0111] The reaction time may vary depending on the reaction temperature, but is preferably between 1 minute and 1,000 minutes, more preferably between 5 minutes and 500 minutes, and even more preferably between 10 minutes and 400 minutes. After the reaction, excess reaction reagents, by-products, etc., may be washed away with water by filtration or other means.

[0112] <Washing process> In the method for producing fine fibrous cellulose according to this embodiment, a washing step can be performed on the ionic substituent-introduced fibers as needed. The washing step is performed, for example, by washing the ionic substituent-introduced fibers with water or an organic solvent. Furthermore, the washing step may be performed after each of the steps described later, and the number of washing steps performed in each washing step is not particularly limited.

[0113] <Alkali treatment process> When producing fine fibrous cellulose, an alkaline treatment may be performed on the fiber raw material between the ionic substituent introduction step and the defibration treatment step described later. The method of alkaline treatment is not particularly limited, but one example is immersing the ionic substituent-introduced fibers in an alkaline solution.

[0114] The alkali compound contained in the alkaline solution is not particularly limited and may be an inorganic alkali compound or an organic alkali compound. In this embodiment, it is preferable to use sodium hydroxide or potassium hydroxide as the alkali compound due to its high versatility. The solvent contained in the alkaline solution may be either water or an organic solvent. In particular, the solvent contained in the alkaline solution is preferably water or a polar solvent including a polar organic solvent such as alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferred due to its high versatility.

[0115] The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably, for example, 5°C to 80°C, and more preferably 10°C to 60°C. The immersion time of the ionic substituent-introduced fiber in the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably, for example, 5 minutes to 30 minutes, and more preferably 10 minutes to 20 minutes. The amount of alkaline solution used in the alkaline treatment is not particularly limited, but is preferably, for example, 100% by mass to 100,000% by mass, and more preferably 1,000% by mass to 10,000% by mass, relative to the absolute dry mass of the ionic substituent-introduced fiber.

[0116] To reduce the amount of alkaline solution used in the alkaline treatment process, the ionic substituent-introduced fibers may be washed with water or an organic solvent after the ionic substituent introduction process and before the alkaline treatment process. After the alkaline treatment process and before the defibration process, it is preferable to wash the alkaline-treated ionic substituent-introduced fibers with water or an organic solvent to improve handling.

[0117] <Acid treatment process> When producing fine fibrous cellulose, the fiber raw material may be treated with acid between the step of introducing ionic substituents and the defibration treatment step described later. For example, the ionic substituent introduction step, acid treatment, alkali treatment, and defibration treatment may be performed in this order.

[0118] The method of acid treatment is not particularly limited, but one example is immersing the fiber material in an acidic solution containing an acid. The concentration of the acidic solution used is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic solution used is not particularly limited, but is preferably 0 to 4, and more preferably 1 to 3. Examples of acids that can be included in the acidic solution include inorganic acids, sulfonic acids, carboxylic acids, etc. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, and boric acid. Examples of sulfonic acids include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. Examples of carboxylic acids include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Among these, the use of hydrochloric acid or sulfuric acid is particularly preferred.

[0119] The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5°C to 100°C, and more preferably 20°C to 90°C. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes to 120 minutes, and more preferably 10 minutes to 60 minutes. The amount of acid solution used in the acid treatment is not particularly limited, but is preferably 100% to 100,000% by mass, and more preferably 1,000% to 10,000% by mass, relative to the absolute dry mass of the fiber raw material.

[0120] <Fibrillation treatment> Fine fibrous cellulose can be obtained by defibrating ionic substituent-introduced fibers in a defibration process. In the defibration process, for example, a defibration apparatus can be used. The defibration apparatus is not particularly limited, but for example, a high-speed defibrator, grinder (stone mill type grinder), high-pressure homogenizer or ultra-high-pressure homogenizer, high-pressure impact grinder, ball mill, bead mill, disc refiner, conical refiner, twin-screw kneader, vibrating mill, homomixer under high-speed rotation, ultrasonic disperser, or beater can be used. Among the above defibration apparatuses, it is more preferable to use a high-speed defibrator, high-pressure homogenizer, or ultra-high-pressure homogenizer, which have less influence from the grinding media and less risk of contamination.

[0121] In the defibration process, for example, it is preferable to dilute the ionic substituent-introduced fibers with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and organic solvents such as polar organic solvents can be used. The polar organic solvent is not particularly limited, but for example, alcohols, polyhydric alcohols, ketones, ethers, esters, and aprotic polar solvents are preferred. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, and glycerin. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, and propylene glycol monomethyl ether. Examples of esters include ethyl acetate and butyl acetate. Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidinone (NMP).

[0122] The solid content concentration of the fine fibrous cellulose during the defibration process can be set as appropriate. Furthermore, the slurry obtained by dispersing the ionic substituent-introduced fibers in a dispersion medium may contain solid components other than the ionic substituent-introduced fibers, such as hydrogen-bonding urea.

[0123] (solvent) The dust dispersion suppressant of the present invention contains a solvent. In addition to aqueous solvents, organic solvents can be used as the solvent. A mixed solvent of aqueous solvent and organic solvent may also be used.

[0124] In particular, the solvent is preferably a water-based solvent. That is, the solvent is preferably an aqueous solvent. In this specification, a water-based solvent is a solvent that contains 50% by mass or more of water relative to the total mass of the solvent. The water content is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to the total mass of the solvent. By using a water-based solvent, the environmental burden can be reduced. Furthermore, by using a water-based solvent, greater consideration can be given to the safety of workers who spray the dust dispersion suppressant.

[0125] When using an organic solvent, examples of organic solvents include lower aliphatic alcohols such as methanol, ethanol, isopropanol, n-butanol, and isobutanol; ethylene glycol derivatives such as ethylene glycol, ethylene glycol monobutyl ether, and ethylene glycol acetate monoethyl ether; diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether; and diacetone alcohol. Furthermore, as organic solvents, pyrrolidone compounds such as 2-pyrrolidone, 3-pyrrolidone, N-alkyl-2-pyrrolidone (e.g., N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone), 5-alkyl-2-pyrrolidone (e.g., 5-methyl-2-pyrrolidone, 5-ethyl-2-pyrrolidone, 5-propyl-2-pyrrolidone), N-vinyl-2-pyrrolidone, N-alkyl-3-pyrrolidone (e.g., N-methyl-3-pyrrolidone, N-ethyl-3-pyrrolidone, N-propyl-3-pyrrolidone), nitrogen-containing solvents such as formamide, N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide; methyl alcohol, ethyl Examples of alcoholic solvents include chloroform, propyl alcohol, butyl alcohol, 1-propanol, 2-propanol, isopropyl alcohol, ethylene glycol, salicylic alcohol, cinnamyl alcohol, beraryl alcohol, cinnabyl alcohol, diphenylmethanol, vanillyl alcohol, benzyl alcohol, 2-methylbenzyl alcohol, 3-methylbenzyl alcohol, 3-nitrile benzyl alcohol, 4-methylbenzyl alcohol, α-methylbenzyl alcohol, allyl alcohol, propagyl alcohol, phenethyl alcohol, hydroxybenzyl alcohol, and hydroxyphenethyl alcohol; and chlorine-based solvents such as chloroform, carbon tetrachloride, methylene chloride, trichloroethylene, or tetrachloroethylene.

[0126] The solvent content is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total mass of the dust dispersion suppressant. Furthermore, the solvent content is preferably 99.99% by mass or less, more preferably 99.95% by mass or less, and even more preferably 99.90% by mass or less, based on the total mass of the dust dispersion suppressant. By setting the solvent content within the above range, it becomes easier to obtain a dust dispersion suppressant with superior dust dispersion suppression effect.

[0127] (optional ingredient) The dust dispersion suppressant of the present invention may contain optional components in addition to the components described above. Examples of optional components include surfactants, inorganic layered compounds, inorganic acicular minerals, defoaming agents, inorganic particles, organic particles, lubricants, antioxidants, ultraviolet absorbers, stabilizers, plasticizers, crosslinking agents, and thickeners. The dust dispersion suppressant may also contain hydrophilic polymers, hydrophilic low molecular weight molecules, organic ions, and the like as optional components.

[0128] Examples of surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. Among these, anionic surfactants include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, polyoxyethylene sodium lauryl sulfate, phosphate esters, α-olefin sulfonates, higher alcohol ethoxysulfates, and dialkyl sulfosuccinates. Cationic surfactants include lauryldimethylbenzylammonium chloride, and nonionic surfactants include polyoxyethylene nonylphenol ether and polyoxyethylene oleyl ether.

[0129] The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the fibrous cellulose mentioned above). Examples of oxygen-containing organic compounds include polyethylene glycol, polyethylene oxide, casein, dextrin, starch, modified starch, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates, alkyl acrylate copolymers, urethane copolymers, and cellulose derivatives (hydroxyethylcellulose, carboxyethylcellulose, carboxymethylcellulose, etc.).

[0130] The hydrophilic low molecular weight is preferably a hydrophilic oxygen-containing organic compound, and more preferably a polyhydric alcohol. Examples of polyhydric alcohols include glycerin, sorbitol, and ethylene glycol.

[0131] Examples of organic ions include tetraalkylammonium ions and tetraalkylphosphonium ions. Examples of tetraalkylammonium ions include tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, tetrabutylammonium ions, tetrapentylammonium ions, tetrahexylammonium ions, tetraheptylammonium ions, tributylmethylammonium ions, lauryltrimethylammonium ions, cetyltrimethylammonium ions, stearyltrimethylammonium ions, octyldimethylethylammonium ions, lauryldimethylethylammonium ions, didecyldimethylammonium ions, lauryldimethylbenzylammonium ions, and tributylbenzylammonium ions. Examples of tetraalkylphosphonium ions include tetramethylphosphonium ions, tetraethylphosphonium ions, tetrapropylphosphonium ions, tetrabutylphosphonium ions, and lauryltrimethylphosphonium ions. In addition, examples of tetrapropylonium ions and tetrabutylonium ions include tetra-n-propylonium ions and tetra-n-butylonium ions, respectively.

[0132] The content of optional components is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total mass of the dust dispersion suppressant.

[0133] (Method of manufacturing a dust dispersion suppressant) As a dust dispersion inhibitor, the dispersion obtained in the defibration process in the above-described method for producing fine fibrous cellulose can be used as is. The dispersion obtained in the defibration process contains water in addition to fibrous cellulose with a fiber width of 1000 nm or less. Thus, in the present invention, a dust dispersion inhibitor can be produced in the process for producing fine fibrous cellulose, making it possible to prevent dust dispersion in a simpler way. If the dust dispersion inhibitor contains any optional components as described above, the optional components may be mixed into the dispersion obtained in the defibration process.

[0134] Furthermore, the dust dispersion suppressant may be manufactured by redispersing a concentrate or solid body of fibrous cellulose with a fiber width of 1000 nm or less, contained in the dispersion obtained in the defibration process described above, into a solvent. If the dust dispersion suppressant is obtained through a process of redispersing a concentrate or solid body of fibrous cellulose with a fiber width of 1000 nm or less into a solvent, then a step of first obtaining a concentrate of fibrous cellulose with a fiber width of 1000 nm or less is provided. Examples of steps for obtaining a concentrate of fibrous cellulose with a fiber width of 1000 nm or less include adding a flocculant such as a polyvalent metal salt to the fine fibrous cellulose-containing dispersion obtained in the defibration process, or adding an organic onium ion or a compound that forms an organic onium ion by neutralization.

[0135] If the step of obtaining a concentrated fibrous cellulose with a fiber width of 1000 nm or less involves adding a flocculant such as a polyvalent metal salt, the step includes adding a flocculant such as a polyvalent metal salt to the fine fibrous cellulose-containing dispersion obtained in the defibration treatment step. In this case, it is preferable to add the polyvalent metal salt as an aqueous solution containing the polyvalent metal salt. Examples of polyvalent metal salts include aluminum sulfate, aluminum chloride, polyaluminum chloride, calcium chloride, magnesium chloride, calcium sulfate, magnesium sulfate, copper chloride, copper sulfate, iron chloride, iron sulfate, lead chloride, and lead sulfide.

[0136] The step of adding a polyvalent metal salt is also called the flocculation step because it floccates the fine fibrous cellulose with the metal component. In the flocculation step, it is preferable to add a metal salt containing a polyvalent metal in an amount of 1 part by mass or more, and more preferably 5 parts by mass or more, per 100 parts by mass of fine fibrous cellulose contained in the dispersion. Furthermore, it is preferable to add a metal salt containing a polyvalent metal in an amount of 100 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of fine fibrous cellulose contained in the dispersion.

[0137] The flocculation step preferably includes a filtration step after adding a polyvalent metal salt and stirring. By including such a filtration step, a concentrate can be obtained. The filter material used in the filtration step is not particularly limited, but filter materials such as stainless steel, filter paper, polypropylene, nylon, polyethylene, and polyester can be used. Since acid may also be used, polypropylene filter material is preferred. The lower the air permeability of the filter material, the higher the yield, so 30 cm is preferable. 3 / cm 2 • sec or less, more preferably 10 cm 3 / cm 2 • sec or less, more preferably 1 cm 3 / cm 2 It is less than 2 seconds.

[0138] The filtration process may further include a compression process. A compression device can be used in the compression process. Such a device can be a general press device such as a belt press, screw press, or filter press, and the device is not particularly limited. The compression pressure is preferably 0.2 MPa or higher, and more preferably 0.4 MPa or higher.

[0139] Furthermore, if the step of obtaining a concentrated fibrous cellulose with a fiber width of 1000 nm or less involves adding an organic onium ion or a compound that forms an organic onium ion by neutralization, the step includes adding an organic onium ion or a compound that forms an organic onium ion by neutralization to the fine fibrous cellulose-containing dispersion obtained in the defibration treatment step. Specifically, an organic onium ion or a compound that forms an organic onium ion by neutralization is added to the fine fibrous cellulose-containing dispersion obtained in the defibration treatment step described above. In this case, it is preferable to add the organic onium ion as a solution containing the organic onium ion, and more preferable to add it as an aqueous solution containing the organic onium ion.

[0140] Aqueous solutions containing organic onium ions typically contain both organic onium ions and their counterions (anions). When preparing an aqueous solution of organic onium ions, if the organic onium ions and their corresponding counterions have already formed a salt, they can simply be dissolved in water. When preparing an aqueous solution of organic onium ions, if the organic onium ions and their corresponding counterions have already formed a salt, it is preferable to dissolve them in water or hot water.

[0141] Furthermore, organic onium ions can sometimes only be formed after neutralization with an acid, such as with dodecylamine. In this case, the organic onium ion is obtained by the reaction of a compound that forms an organic onium ion upon neutralization with an acid. Examples of acids used for neutralization in this case include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as lactic acid, acetic acid, formic acid, and oxalic acid.

[0142] The step of adding organic onium ions or compounds that form organic onium ions by neutralization to a fine fibrous cellulose-containing slurry preferably further includes a stirring step. In the stirring step, the liquid temperature of the fine fibrous cellulose-containing slurry to which the organic onium ions have been added (hereinafter also referred to as the stirring temperature) is preferably 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower, and particularly preferably 30°C or lower. In the present invention, by keeping the stirring temperature within the above range, the mobility of the organic onium ions can be controlled within an appropriate range, thereby allowing sufficient counterion exchange in the fine fibrous cellulose to proceed.

[0143] The amount of organic onium ions added is preferably 2% by mass or more, more preferably 10% by mass or more, even more preferably 50% by mass or more, and particularly preferably 100% by mass or more, relative to the total mass of the fine fibrous cellulose. Furthermore, the amount of organic onium ions added is preferably 1000% by mass or less, relative to the total mass of the fine fibrous cellulose. Furthermore, the number of moles of organic onium ions to be added is preferably 0.2 times or more the value obtained by multiplying the amount (in moles) of phosphorus oxoacid groups contained in the fine fibrous cellulose by its valence, more preferably 1.0 times or more, and even more preferably 2.0 times or more. It is also preferable that the number of moles of organic onium ions to be added is 10 times or less the value obtained by multiplying the amount (in moles) of phosphorus oxoacid groups contained in the fine fibrous cellulose by its valence.

[0144] When organic onium ions are added and the mixture is stirred, aggregates form in the fine fibrous cellulose-containing slurry. These aggregates are formed from fine fibrous cellulose that has organic onium ions as counterions. The fine fibrous cellulose aggregates can be recovered by filtering the slurry containing the aggregates under reduced pressure.

[0145] The resulting fine fibrous cellulose aggregates may be washed with deionized water. By repeatedly washing the fine fibrous cellulose aggregates with deionized water, excess organic onium ions and other substances contained in the fine fibrous cellulose aggregates can be removed.

[0146] The fibrous cellulose content relative to the total mass of the fine fibrous cellulose concentrate obtained through the process described above is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit of the fibrous cellulose content relative to the total mass of the fine fibrous cellulose concentrate is preferably 99% by mass.

[0147] If the manufacturing process of a dust dispersion suppressant includes the step of obtaining the concentrate described above, a redispersion step is provided after the step of obtaining the concentrate. In the redispersion step, the fine fibrous cellulose concentrate is redispersed in a solvent. The solvent used for redispersion is preferably selected appropriately considering the flocculant used in the concentrate step. For example, when a concentrate is obtained by adding a polyvalent metal salt, an aqueous solution containing tetraalkylonium hydroxide is preferred as the redispersion solution, tetraalkylammonium hydroxide and tetraalkylphosphonium hydroxide are particularly preferred, and a solution containing tetraalkylammonium hydroxide is more preferred. Examples of tetraalkylammonium hydroxides include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, triethylmethylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, tetraheptylammonium hydroxide, lauryltrimethylammonium hydroxide, cetyltrimethylammonium hydroxide, stearyltrimethylammonium hydroxide, octyldimethylethylammonium hydroxide, lauryldimethylethylammonium hydroxide, didecyldimethylammonium hydroxide, lauryldimethylbenzylammonium hydroxide, tributylbenzylammonium hydroxide, methyltri-n-octylammonium hydroxide, alkyldimethylbenzylammonium hydroxide, di-n-alkyldimethylammonium hydroxide, and behenyltrimethylammonium hydroxide.As the tetraalkylphosphonium hydroxide, it is preferable to select tetramethylphosphonium hydroxide, tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, tetrabutylphosphonium hydroxide, triethylmethylphosphonium hydroxide, tetraphenylphosphonium hydroxide, tetraoctylphosphonium hydroxide, acetonyltriphenylphosphonium hydroxide, allyltriphenylphosphonium hydroxide, amyltriphenylphosphonium hydroxide, benzyltriphenylphosphonium hydroxide, ethyltriphenylphosphonium hydroxide, etc. Furthermore, when a concentrate is obtained by adding organic onium ions, examples of redispersants include water, methanol, ethanol, n-propyl alcohol, isopropyl alcohol (IPA), 1-butanol, m-cresol, glycerin, acetic acid, pyridine, tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), ethyl acetate, aniline, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), hexane, cyclohexane, benzene, toluene, p-xylene, and diethyl ether chloroform. These solvents may be used in mixtures. In the redispersion step, redispersion may be carried out using the defibration treatment apparatus used in the defibration treatment step described above.

[0148] The above-mentioned optional components may be mixed in the process after the concentrate has been redispersed, or during the process of redispersing the concentrate.

[0149] (Method for preventing dust scattering) The present invention also relates to a method for preventing dust dispersion, which includes the step of spraying the above-mentioned dust dispersion inhibitor onto a dust-generating object. In this dust dispersion prevention method, the dust dispersion inhibitor is sprayed onto a dust-generating object such as soil or sand that is a source of dust. Thus, the present invention can prevent dust dispersion in a simple manner by including the step of spraying the above-mentioned dust dispersion inhibitor onto a dust-generating object.

[0150] There are no particular restrictions on the amount of dust dispersion suppressant to be applied, but the amount should be 500 g / m² relative to the surface area of ​​the dust-generating object. 2 It is preferable to spread it in such a manner that the amount is 1000g / m². 2 It is preferable to spray the dust in the above manner. By keeping the amount of dust dispersion suppressant applied within the above range, the dust dispersion suppression effect will be more pronounced.

[0151] It is preferable to include a drying step after spraying a dust-dispersing inhibitor onto the dust-generating object. This allows the soil and other materials constituting the dust-generating object to be more firmly bound together. While there are no particular limitations on drying conditions, in normal weather conditions other than rainy weather, it is sufficient to allow 24 hours after spraying. [Examples]

[0152] The features of the present invention will be further described below with reference to examples and comparative examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples.

[0153] <Manufacturing example A> [Phosphate esterification] The raw material pulp is softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solids content 93% by mass, basis weight 208 g / m²). 2 A sheet-like material with a Canadian standard filtration efficiency (CSF) of 700 ml (measured according to JIS P 8121 after disintegration) was used.

[0154] The raw pulp was subjected to phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (oven-dry mass) of the raw pulp to adjust the mixture to 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water to obtain chemically impregnated pulp. Next, the obtained chemically impregnated pulp was heated in a hot air dryer at 165°C for 200 seconds to introduce phosphate groups into the cellulose in the pulp, thereby obtaining phosphorylated pulp.

[0155] Next, the obtained phosphorylated pulp was subjected to a washing treatment. The washing treatment was carried out by repeatedly adding 10 L of deionized water to 100 g (oven-dry mass) of phosphorylated pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0156] Next, the washed phosphorylated pulp was subjected to a neutralization treatment as follows. First, the washed phosphorylated pulp was diluted with 10 L of deionized water, and then a 1N sodium hydroxide aqueous solution was gradually added while stirring to obtain a phosphorylated pulp slurry with a pH of 12 to 13. Next, the phosphorylated pulp slurry was dehydrated to obtain phosphorylated pulp that had undergone neutralization treatment. Then, the phosphorylated pulp that had undergone neutralization treatment was subjected to the washing treatment described above.

[0157] The resulting phosphorylated pulp was subjected to infrared absorption spectroscopy using FT-IR. The result showed that 1230 cm⁻¹ -1 Absorption based on phosphate groups was observed in the vicinity, confirming that phosphate groups were added to the pulp. Furthermore, when the obtained phosphorylated pulp was analyzed using an X-ray diffractometer, typical peaks were found at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0158] Deionized water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0159] X-ray diffraction confirmed that this fine fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Additionally, image analysis using AFM extracted 100 strands of the fine fibrous cellulose and calculated the numerical average aspect ratio, which was found to be 300. The amount of phosphate groups (strongly acidic groups) measured using the method described later was 1.45 mmol / g.

[0160] The fine fibrous cellulose-containing dispersion obtained in this manufacturing example was diluted with deionized water to adjust the solid content concentration of the fine fibrous cellulose to 0.4% by mass. This dispersion was used as dust dispersion suppressant A.

[0161] <Manufacturing example B> [Phosphate esterification] Phosphorylated pulp was obtained in the same manner as in Production Example A. Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content concentration of 2% by mass. The slurry was processed once at a pressure of 100 MPa using a high-pressure homogenizer (Beryu-Mini, manufactured by Biryu Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose. When the obtained dispersion containing fine fibrous cellulose was observed with an optical microscope, a large number of fibrous cellulose fibers with a fiber width of 20 μm or more were observed. On the other hand, when the obtained dispersion containing fine fibrous cellulose was measured using a transmission electron microscope, a large number of fine fibrous cellulose fibers of 3-5 nm were also observed. Furthermore, when 100 strands of fine fibrous cellulose were extracted from image analysis by AFM and the numerical mean of the aspect ratio was calculated, the numerical mean of the aspect ratio was 225.

[0162] The fine fibrous cellulose-containing dispersion obtained in this manufacturing example was diluted with deionized water to adjust the solid content concentration of the fine fibrous cellulose to 0.4% by mass. This dispersion was used as dust dispersion suppressant B.

[0163] <Manufacturing example C> [Phosphite esterification] The procedure was carried out in the same manner as in Production Example A, except that 33 parts by mass of phosphorous acid (phosphonic acid) were used instead of ammonium dihydrogen phosphate, to obtain phosphorylated pulp.

[0164] The obtained phosphorylated pulp was subjected to infrared absorption spectroscopy using FT-IR. The result showed that at 1210 cm⁻¹ -1 Absorption based on P=O of the phosphonic acid group, a tautomer of the phosphite group, was observed in the vicinity, confirming that phosphite groups (phosphonic acid groups) were attached to the pulp. Furthermore, when the obtained phosphite-oxidized pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0165] The obtained phosphite pulp was treated with a wet pulverizer in the same manner as in Production Example A to obtain a dispersion containing fine fibrous cellulose.

[0166] X-ray diffraction confirmed that this fine fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Additionally, 100 strands of the fine fibrous cellulose were extracted from AFM image analysis, and the number-average aspect ratio was calculated to be 280. The amount of phosphite groups (first dissociated acid) measured by the method described later was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0167] The fine fibrous cellulose-containing dispersion obtained in this manufacturing example was diluted with deionized water to adjust the solid content concentration of the fine fibrous cellulose to 0.4% by mass. This dispersion was used as dust dispersion suppressant C.

[0168] <Manufacturing example D> [TEMPO oxidation] As the raw material pulp, softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. was used. 100 parts by mass of the above raw material pulp (equivalent to 100 parts by mass dry weight), 1.6 parts by mass of TEMPO(2,2,6,6-tetramethylpiperidine-1-oxyl), and 10 parts by mass of sodium bromide were dispersed in 10,000 parts by mass of water. Next, a 13% by mass sodium hypochlorite aqueous solution was added to a concentration of 10 mmol per 1.0 g of pulp to initiate the reaction. During the reaction, a 0.5 M sodium hydroxide aqueous solution was added dropwise to maintain the pH between 10 and 10.5, and the reaction was considered complete when no further change in pH was observed.

[0169] Next, the obtained TEMPO-oxidized pulp was subjected to a washing treatment. The washing treatment was carried out by dewatering the pulp slurry after TEMPO oxidation to obtain a dewatered sheet, adding 5000 parts by mass of deionized water, stirring to uniformly disperse the sheet, and then repeating the filtration and dewatering process. The washing was terminated when the electrical conductivity of the filtrate became 100 μS / cm or less.

[0170] Furthermore, when the obtained TEMPO-oxidized pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0171] Deionized water was added to the obtained TEMPO-oxidized pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0172] X-ray diffraction confirmed that this fine fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Additionally, image analysis using AFM extracted 100 strands of the fine fibrous cellulose and calculated the number-average aspect ratio, which was found to be 250. The amount of carboxyl groups, as measured by the method described later, was 1.80 mmol / g.

[0173] The fine fibrous cellulose-containing dispersion obtained in this manufacturing example was diluted with deionized water to adjust the solid content concentration of the fine fibrous cellulose to 0.4% by mass. This dispersion was used as dust dispersion suppressant D.

[0174] <Manufacturing Example E> [carboxymethylation (CMization)] Except for using softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. as the raw material, the carboxymethylated pulp was prepared using the method described in Production Example 1 of International Publication No. 2014 / 088072.

[0175] Next, the obtained carboxymethylated pulp was subjected to a washing treatment. The washing treatment was carried out by dewatering the pulp slurry after carboxymethylation to obtain a dewatered sheet, adding 5000 parts by mass of deionized water, stirring to uniformly disperse the material, and then repeating the filtration and dewatering process. The washing was terminated when the electrical conductivity of the filtrate became 100 μS / cm or less.

[0176] Deionized water was added to the obtained carboxymethylated pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0177] X-ray diffraction confirmed that this fine fibrous cellulose maintains a type I cellulose crystal structure. Furthermore, when 100 strands of the fine fibrous cellulose were extracted from AFM image analysis and the numerical average of the aspect ratios was calculated, the numerical average of the aspect ratios was found to be 190.

[0178] The fine fibrous cellulose-containing dispersion obtained in this manufacturing example was diluted with deionized water to adjust the solid content concentration of the fine fibrous cellulose to 0.4% by mass. This dispersion was used as dust dispersion suppressant E.

[0179] <Manufacturing example F> [Sulfate esterification] Sulfated pulp was obtained by following the same procedure as in Production Example A, except that 38 parts by mass of sulfuric acid amidosulfate were used instead of ammonium dihydrogen phosphate and the heating time was extended to 19 minutes.

[0180] The obtained sulfated pulp was subjected to infrared absorption spectroscopy using FT-IR. The results showed that 1220-1260 cm⁻¹ -1 Absorption based on sulfate groups (sulfur oxoacid groups) was observed in the vicinity, confirming that sulfate groups (sulfur oxoacid groups) were added to the pulp. Furthermore, when the obtained sulfated pulp was tested using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals. The amount of sulfate groups (sulfur oxoacid groups) measured by the measurement method described later was 1.12 mmol / g.

[0181] After adding deionized water to the obtained sulfated pulp, the mixture was stirred to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose. Furthermore, 100 strands of fine fibrous cellulose were extracted from image analysis using AFM, and the numerical mean of the aspect ratio was calculated to be 280.

[0182] The fine fibrous cellulose-containing dispersion obtained in this manufacturing example was diluted with deionized water to adjust the solid content concentration of the fine fibrous cellulose to 0.4% by mass. This dispersion was used as dust dispersion suppressant F.

[0183] <Manufacturing example G> [Unmodified] As the raw material pulp, softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. was used. Deionized water was added to the raw material pulp to dilute it to a solid content concentration of 2% by mass, and then it was subjected to a refiner treatment and beaten (pre-fibrillated) until the Canadian standard filtration efficiency (CSF), measured according to JIS P 8121, was 50 mL or less. Deionized water was further added to the pulp dispersion after pre-fibrillation to dilute it to a solid content concentration of 0.5% by mass, and then it was treated twice at a processing pressure of 200 MPa using a high-pressure homogenizer "Starburst" manufactured by Sugino Machine Co., Ltd. to obtain a dispersion containing fine fibrous cellulose. The number-average fiber width of the fine fibrous cellulose contained in the dispersion was 1000 nm or less, but it was visually confirmed that fibrous material remained because the fineness had not progressed completely. The fine fibrous cellulose contained in the dispersion was considered unmodified fine fibrous cellulose after mechanical fibrillation. Furthermore, when 100 microfiber cellulose fibers were extracted from image analysis using AFM and the numerical average of the aspect ratios was calculated, the numerical average of the aspect ratios was found to be 97.

[0184] The dispersion containing unmodified microfibrous cellulose after mechanical defibration, obtained in this manufacturing example, was diluted with deionized water to adjust the solid content concentration of unmodified microfibrous cellulose after mechanical defibration to 0.4% by mass. This dispersion was used as dust dispersion suppressant G.

[0185] <Manufacturing example H> [Hypochlorite oxidation (NaClO oxidation)] Sheets (solid content 90% by mass) made from bleached coniferous kraft pulp (NBKP) were processed using a hand mixer (Osaka Chemical, Lab Millser PLUS) at 20,000 rpm for 15 seconds to obtain cotton-like fluffy pulp (solid content 90% by mass). Next, sodium hypochlorite pentahydrate was added to deionized water to prepare an aqueous solution with a sodium hypochlorite solid content of 22% by mass. 9,000 parts by mass of the 22% by mass sodium hypochlorite aqueous solution were added to 100 parts by mass of the cotton-like fluffy pulp, and the mixture was reacted for 2 hours while adjusting the temperature to 30°C in a warm bath to obtain carboxyl group-introduced pulp. During the reaction, 1N sodium hydroxide aqueous solution was added as needed to maintain the pH at 11.

[0186] Next, the obtained carboxyl group-introduced pulp was subjected to a washing treatment. The washing treatment involved repeatedly adding deionized water to the obtained carboxyl group-introduced pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0187] When the obtained carboxyl group-introduced pulp was tested and analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0188] Deionized water was added to the obtained carboxyl group-introduced pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0189] X-ray diffraction confirmed that the obtained fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Image analysis using AFM extracted 100 strands of fibrous cellulose, and the number-average aspect ratio was calculated to be 89. The amount of carboxyl groups, measured using the method described later, was 0.70 mmol / g.

[0190] <Manufacturing example I> [Maleic acid esterification] Sheets (solid content 90% by mass) made from bleached coniferous kraft pulp (NBKP) were processed using a hand mixer (Osaka Chemical, Lab Millser PLUS) at a rotation speed of 20,000 rpm for 15 seconds to obtain cotton-like fluffy pulp (solid content 90% by mass). 100 parts by mass of the cotton-like fluffy pulp and 50 parts by mass of maleic anhydride were packed into an autoclave and processed at 150°C for 2 hours to obtain carboxyl group-introduced pulp.

[0191] Next, the obtained carboxyl group-introduced pulp was subjected to a washing treatment. The washing treatment involved repeatedly adding deionized water to the obtained carboxyl group-introduced pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0192] The obtained carboxyl group-introduced pulp was subjected to infrared absorption spectrum measurements using FT-IR. The results showed that the absorption spectra at 1580 and 1720 cm⁻¹ were measured. -1 Absorption based on carboxyl groups was observed in the vicinity, confirming maleate esterification. When carboxyl-introduced pulp was used and analyzed with an X-ray diffractometer, typical peaks were found at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0193] Deionized water was added to the obtained carboxyl group-introduced pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0194] X-ray diffraction confirmed that the obtained fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Image analysis using AFM extracted 100 strands of fibrous cellulose, and the number-average aspect ratio was calculated to be 180. The amount of carboxyl groups, measured using the method described later, was 1.22 mmol / g.

[0195] <Manufacturing example J> [Carboxyethylation (CE conversion)] The raw material pulp used is softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solids content 93% by mass, basis weight 245 g / m²). 2 A sheet-like material was used, which, when disintegrated, had a Canadian standard filtration efficiency (CSF) of 700 ml measured according to JIS P 8121-2:2012.

[0196] To 100 parts by mass (oven-dry mass) of this raw pulp, a chemical solution consisting of 250 parts by mass of 12N NaOH aqueous solution, 163 parts by mass of 2-chloropropionic acid, and 140 parts by mass of ion-exchanged water (total 553 parts by mass) was added to obtain chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165°C for 10 minutes to introduce carboxyethyl groups (carboxyl groups) into the cellulose in the pulp, thereby obtaining carboxyl group-introduced pulp.

[0197] Next, the obtained carboxyl group-introduced pulp was subjected to a washing treatment. The washing treatment involved repeatedly adding deionized water to the obtained carboxyl group-introduced pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0198] Next, the washed carboxyl group-introduced pulp was subjected to neutralization treatment as follows. First, the washed carboxyl group-introduced pulp was diluted with 10 L of deionized water, and then a 1N sodium hydroxide aqueous solution was gradually added while stirring to obtain a carboxyl group-introduced pulp slurry with a pH of 12 to 13. Next, the carboxyl group-introduced pulp slurry was dehydrated and washed to obtain carboxyl group-introduced pulp that had undergone neutralization treatment.

[0199] When carboxyl group-introduced pulp was tested and analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0200] Deionized water was added to the obtained carboxyl group-introduced pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0201] X-ray diffraction confirmed that the obtained fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Image analysis using AFM extracted 100 strands of fibrous cellulose, and the number-average aspect ratio was calculated to be 200. The amount of carboxyl groups measured by the described measurement method was 1.41 mmol / g.

[0202] <Manufacturing example K> [Sulfoethylation] The raw material pulp used is softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solids content 93% by mass, basis weight 245 g / m²). 2 A sheet-like material was used, which, when disintegrated, had a Canadian standard filtration efficiency (CSF) of 700 ml measured according to JIS P 8121-2:2012.

[0203] To 100 parts by mass (oven-dry mass) of this raw pulp, a chemical solution consisting of 180 parts by mass of 2N NaOH aqueous solution and 780 parts by mass of 25% by mass sodium vinyl sulfonate aqueous solution (total 960 parts by mass) was added to obtain chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165°C for 16 minutes to introduce sulfoethyl groups (sulfone groups) into the cellulose in the pulp, thereby obtaining sulfoethyl group-introduced pulp (sulfone group-introduced pulp).

[0204] Next, the obtained sulfoethyl group-introduced pulp was subjected to a washing treatment. The washing treatment involved repeatedly adding deionized water to the obtained sulfoethyl group-introduced pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0205] The amount of sulfoethyl groups (sulfone groups) in the obtained sulfoethyl-introduced pulp, as measured by the method described later, was 1.48 mmol / g. Furthermore, when the sulfoethyl-introduced pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0206] Deionized water was added to the obtained sulfoethyl group-introduced pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0207] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Image analysis using AFM extracted 100 strands of the fine fibrous cellulose, and the numerical average aspect ratio was calculated to be 230.

[0208] <Manufacturing example L> [Cationization treatment] The raw material pulp used is softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solids content 93% by mass, basis weight 245 g / m²). 2 A sheet-like material was used, which, when disintegrated, had a Canadian standard filtration efficiency (CSF) of 700 ml measured according to JIS P 8121-2:2012.

[0209] To 100 parts by mass (oven-dry mass) of this raw pulp, a chemical solution consisting of 180 parts by mass of 1N NaOH aqueous solution and 325 parts by mass of a cationizing agent (Catiomaster G, manufactured by Yokkaichi Gosei Co., Ltd., glycidyltrimethylammonium chloride, purity 73.1% by mass, moisture content 20.2% by mass) (total 505 parts by mass) was added to obtain chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165°C for 12 minutes to introduce cationic groups into the cellulose in the pulp, thereby obtaining cationic group-introduced pulp.

[0210] Next, the obtained cation-introduced pulp was subjected to a washing treatment. The washing treatment involved repeatedly adding deionized water to the obtained cation-introduced pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0211] Next, the washed cation-introduced pulp was subjected to neutralization treatment as follows. First, the washed cation-introduced pulp was diluted with 10 L of deionized water, and then 1N hydrochloric acid was gradually added while stirring to obtain a cation-introduced pulp slurry with a pH of 1 to 2. Next, the cation-introduced pulp slurry was dehydrated and washed to obtain neutralized cation-introduced pulp.

[0212] Trace nitrogen analysis was performed on the obtained cation-introduced pulp, and the amount of cation groups was calculated using the following formula to be 1.45 mmol / g. Furthermore, when the cation-introduced pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals. (Amount of cationic groups) [mmol / g] = (Amount of nitrogen) / 14 × 1000 / (Amount of pulp with cationic groups used in the test)

[0213] Deionized water was added to the obtained cationized pulp to prepare a slurry with a solid content of 2% by mass. This slurry was processed six times at a pressure of 200 MPa using a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a dispersion containing fine fibrous cellulose.

[0214] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3–5 nm. Image analysis using AFM revealed that 100 strands of the fine fibrous cellulose were extracted, and the numerical average aspect ratio was calculated to be 180.

[0215] The fine fibrous cellulose-containing dispersions obtained in production examples H to L were diluted with deionized water to adjust the solid content concentration of the fine fibrous cellulose to 0.4% by mass. These dispersions were designated as dust dispersion suppressants H to L, respectively.

[0216] [Measurement of phosphorus oxoacid group content] In measuring the amount of phosphorus oxoacid groups (phosphate groups or phosphite groups) in fibrous cellulose, first, ion-exchanged water was added to the fibrous cellulose to prepare a slurry with a solid content of 0.2% by mass. The resulting dispersion containing fine fibrous cellulose was then treated with an ion-exchange resin, and the amount was measured by titration using an alkali. The ion exchange resin treatment was performed by adding 1 / 10 the volume of strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the above-mentioned fine fibrous cellulose-containing dispersion, shaking for 1 hour, and then pouring the mixture onto a mesh with a mesh size of 90 μm to separate the resin from the slurry. Furthermore, the alkali titration was performed by adding 10 μL of 0.1 N sodium hydroxide aqueous solution to a dispersion containing fine fibrous cellulose after treatment with ion exchange resin, while measuring the change in the pH value of the slurry. Nitrogen gas was blown into the slurry starting 15 minutes before the start of the titration. In this neutralization titration, two points were observed where the increment (the derivative of pH with respect to the amount of alkali added) was maximum on the curve plotting the measured pH against the amount of alkali added. Of these, the first increment maximum obtained after starting to add alkali is called the first endpoint, and the next increment maximum obtained is called the second endpoint (Figure 1). The amount of alkali required from the start of the titration to the first endpoint is equal to the amount of the first dissociated acid in the slurry used for titration. Also, the amount of alkali required from the start of the titration to the second endpoint is equal to the total amount of dissociated acid in the slurry used for titration. Furthermore, the amount of alkali (mmol) required from the start of the titration to the first endpoint was divided by the solid content (g) in the slurry being titrated to obtain the amount of phosphorus oxoacid groups (mmol / g).

[0217] [Measurement of carboxyl group content] In measuring the carboxyl group content of fibrous cellulose, first, ion-exchanged water was added to the fibrous cellulose to be measured to prepare a slurry with a solid content concentration of 0.2% by mass. The resulting dispersion containing fine fibrous cellulose was then treated with an ion-exchange resin, and the content was measured by titration using an alkali. The ion exchange resin treatment was performed by adding 1 / 10 the volume of strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the above-mentioned fine fibrous cellulose-containing dispersion, shaking for 1 hour, and then pouring the mixture onto a mesh with a mesh size of 90 μm to separate the resin from the slurry. Furthermore, the alkali titration was performed by adding 50 μL of 0.1 N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing dispersion after treatment with ion exchange resin, once every 30 seconds, and measuring the change in the pH value of the dispersion. The amount of carboxyl groups (mmol / g) was calculated by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in Figure 2 by the solid content (g) in the slurry being titrated.

[0218] [Measurement of sulfur oxoacid groups or sulfone groups] The amount of sulfur oxoacid groups or sulfone groups in the fibrous cellulose was measured as follows: The fibrous cellulose obtained in Production Example F was frozen in a freezer and then dried for 3 days in a freeze dryer (FreeZone, manufactured by Labconco). The resulting freeze-dried material was pulverized into a powder using a hand mixer (LaboMillser PLUS, manufactured by Osaka Chemical) at a rotation speed of 20,000 rpm for 60 seconds. The freeze-dried and pulverized samples were subjected to pressurized thermal decomposition using nitric acid in a sealed container. Subsequently, the sulfur content was measured by ICP-OES after appropriate dilution. The value obtained by dividing by the oven-dry mass of the fine fibrous cellulose was defined as the amount of sulfur oxoacid groups or sulfone groups (unit: mmol / g) of the fine fibrous cellulose.

[0219] <Examples 1-12> The dust dispersion prevention effect was evaluated using the dust dispersion prevention agents of the manufacturing examples shown in Tables 1 and 2.

[0220] <pH measurement> The pH at 25°C of the dust scattering preventive agent of each example was measured using a portable water quality meter D52 (manufactured by HORIBA, Ltd.).

[0221] <Preparation of evaluation sample (object generating dust)> As a model substance for generating dust, No. 6 silica sand (manufactured by Toyo Materia Co., Ltd.) was used. 5 g of this silica sand was laid in the center of a filter paper with a diameter of 90 mm so as to form a circular shape with a diameter of 50 mm, and it was used as an evaluation sample (object generating dust).

[0222] <Evaluation of spray characteristics> Approximately 7 g of the dust scattering preventive agent of each example was sprayed onto the evaluation sample (object generating dust) using a commercially available spray. At this time, the spray characteristics of each dust scattering preventive agent were evaluated based on the following criteria. A: Can be sprayed in a mist form and uniform spraying is possible B: Some clogging occurs, but spraying itself is possible C: Cannot be sprayed in a mist form and uniform spraying is difficult In addition, the evaluation sample (object generating dust) after the above spraying was dried at room temperature for 24 hours, and the adhesion force described later was evaluated.

[0223] <Evaluation of adhesion force of silica sand (evaluation of dust scattering prevention effect)> The central part of the evaluation sample (object generating dust) after the above drying was pushed in with a load of 2 N using a force tester MCT1150 (A&D Co., Ltd.), and the adhesion force of the silica sand in each object generating dust was evaluated based on the following criteria. A: The surface of the silica sand does not collapse and no cracks occur B: Some cracks occur, but the surface of the silica sand does not collapse C: A large number of cracks occur and the surface of the silica sand completely collapses When the evaluation was A, the silica sand did not scatter at all even when a commercially available hair dryer was used to blow air on it, demonstrating a dust dispersion prevention effect. When the evaluation was B, a small amount of silica sand scattered when a commercially available hair dryer was used to blow air on it, but a certain degree of dust dispersion prevention effect was observed. On the other hand, when the evaluation was C, the silica sand scattered when a hair dryer was used to blow air on it in the same way.

[0224] <Comparative Example 1> As a dust dispersion suppressant, a 0.4% by mass aqueous solution of sodium carboxymethylcellulose (manufactured by Tokyo Chemical Industry Co., Ltd.) was used, and its dust dispersion suppression effect was evaluated in the same manner as in the examples.

[0225] <Comparative Example 2> As a dust dispersion suppressant, a 0.4% by mass aqueous solution of guar gum (manufactured by Wako Pure Chemical Industries, Ltd.) was used, and its dust dispersion suppression effect was evaluated in the same manner as in the examples.

[0226] <Comparative Example 3> As a dust dispersion inhibitor, a 0.4% by mass aqueous solution of xanthan gum (manufactured by Tokyo Chemical Industry Co., Ltd.) was used, and its dust dispersion inhibitory effect was evaluated in the same manner as in the examples.

[0227] <Comparative Example 4> As a dust dispersion inhibitor, a 0.4% by mass aqueous solution of chitosan (manufactured by Fuji Engineering Co., Ltd.) was used, and its dust dispersion inhibitory effect was evaluated in the same manner as in the examples.

[0228] [Table 1]

[0229] [Table 2]

[0230] [Table 3]

[0231] The dust suppressant used in the examples exhibited excellent spray properties. Furthermore, the dust suppressant used in the examples showed sufficient silica sand binding strength, demonstrating a dust suppression effect. This is presumed to be because, in the examples, the application of fine fibrous cellulose firmly bound the silica sand particles together with the crystalline fine fibrous cellulose, resulting in sufficient silica sand binding strength to obtain a dust suppression effect. In particular, Examples 1, 3-6, and 9-12 showed good spray characteristics and silica sand binding strength, demonstrating their suitability as dust dispersion inhibitors. This is presumed to be due to the finer fiber diameter and larger aspect ratio of the fibrous cellulose contained in Examples 1, 3-6, and 9-12. Furthermore, in the examples, the content of fibrous cellulose in the dust dispersion inhibitor was set to 0.4% by mass, and it was found that a sufficient dust dispersion inhibitory effect could be achieved even at low concentrations of the additive. Thus, the dust dispersion inhibitors of the examples were environmentally friendly dust dispersion inhibitors that could obtain a high dust dispersion inhibitory effect by using only a small amount of fibrous cellulose, which is a fine fiber derived from plants.

[0232] On the other hand, the comparative examples did not exhibit sufficient dust dispersion prevention effects. First, in comparative examples 1 to 3, the silica sand easily disintegrated in the bonding strength evaluation test, and no dust dispersion prevention effect was exhibited at all. On the other hand, when chitosan was used in comparative example 4, the spray characteristics were poor and uniform application was difficult, making it unsuitable as a dust dispersion suppressant. Furthermore, since chitosan only dissolves in weak acids, when using chitosan as a dust dispersion suppressant, it is necessary to spray a weak acidic agent onto the soil. However, from the perspective of environmental impact, it is preferable that the agent sprayed onto the soil has a pH close to neutral, and from the viewpoint of pH, it is not desirable to use chitosan.

Claims

1. It comprises a solvent and fibrous cellulose with a fiber width of 1000 nm or less. A spray coating agent for dust dispersion prevention, wherein the fibrous cellulose is unmodified fine fibrous cellulose, or the fibrous cellulose has at least one ionic substituent selected from the group consisting of a phosphorus oxoacid group, a substituent derived from a phosphorus oxoacid group, a carboxyl group, a substituent derived from a carboxyl group, a carboxyethyl group, a sulfur oxoacid group, a substituent derived from a sulfur oxoacid group, a sulfone group, a substituent derived from a sulfone group, and an ammonium group.

2. The dust scattering prevention spray coating agent according to claim 1, wherein the aspect ratio of the fibrous cellulose is 10 or more.

3. The dust scattering prevention spray coating agent according to claim 1 or 2, wherein the solid content concentration of the fibrous cellulose is 1.0% by mass or less.

4. A dust scattering prevention spray coating agent according to any one of claims 1 to 3, wherein the pH is 5.0 or higher and 9.0 or lower.

5. The dust scattering prevention spray coating agent according to any one of claims 1 to 4, wherein the solvent is a solvent mainly composed of water.

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