Method for producing fibrous material, cellulose-containing material, and acid treatment agent for treating fiber raw material

Abstract

To provide a fibrous material in which coloring is suppressed even when a heating reaction is carried out in a metal container.SOLUTION: The present invention relates to a method for producing a fibrous material comprising the step (A) of adding an oxo acid and a corrosion inhibitor to a fiber raw material and heating the fiber raw material, wherein the value of b / a is 0.32 or more when the amount of oxo acid added is a pts.mass and the amount of the corrosion inhibitor added is b pts.mass.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing fibrous materials, a cellulose-containing material, and an acid treatment agent for treating fiber raw materials.

Background Art

[0002] In recent years, due to the substitution of petroleum resources and the increasing environmental awareness, materials using renewable natural fibers have attracted attention. Among natural fibers, cellulose fibers with a fiber diameter of 10 to 50 μm, especially cellulose fibers (pulp) derived from wood, have been widely used mainly as paper products.

[0003] As cellulose fibers, microfibrillar cellulose with a fiber diameter of 1 μm or less is also known. As microfibrillar cellulose, cellulose nanofibers (CNF) and cellulose nanocrystals (CNC) are mainly known.

[0004] Cellulose nanofibers (CNF) are produced by mechanically treating cellulose fibers. However, cellulose fibers are strongly bonded to each other by hydrogen bonds. Therefore, simply performing mechanical treatment alone requires a large amount of energy to obtain fine cellulose fibers. For this reason, in order to produce fine cellulose fibers with smaller mechanical treatment energy, performing chemical treatment in combination with mechanical treatment has been studied. For example, when an ionic substituent such as an anionic group or a cationic group is introduced into the hydroxy group on the cellulose surface, the electrical repulsive force between the ions facilitates fibrillation, and the energy efficiency of fibrillation increases. For example, Patent Document 1 discloses phosphorylated fine cellulose fibers (cellulose nanofibers). Here, urea, sodium dihydrogen phosphate dihydrate, and disodium hydrogen phosphate are dissolved in water to form a phosphorylation reagent, and this phosphorylation reagent is impregnated into pulp and then heated to perform a phosphorylation reaction.

[0005] Cellulose nanocrystals (CNC) are usually produced by acid hydrolysis of cellulose fibers followed by sonication. For example, Patent Document 2 discloses a method of adding an acid solution to cellulose fibers, performing acid hydrolysis of the cellulose fibers using an extruder screw, and obtaining cellulose nanocrystals (CNC). Specifically, in the production method of Patent Document 2, a sulfuric acid solution is added to cellulose fibers, and hydrolysis is carried out under high temperature conditions of 200 to 230 °C.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in conventional production methods of cellulose nanofibers (CNF) and cellulose nanocrystals (CNC), when the fiber raw material is subjected to oxo-oxidation treatment, the reaction product may be colored during the process. In particular, when the oxo-oxidation reaction of the fiber raw material is carried out in a metal container, coloring of the reaction product is observed, and improvement has been demanded.

[0008] Therefore, in order to solve such problems of the prior art, the present inventor has proceeded with studies for the purpose of providing a fibrous material with suppressed coloring even when a heating reaction is carried out in a metal container.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that when oxo-oxidizing a fiber raw material, in addition to an oxo acid, a corrosion inhibitor is added, and by setting the addition amounts of the oxo acid and the corrosion inhibitor to a predetermined ratio, even when a heating reaction is carried out in a metal container, a fiber-like material with suppressed coloring can be obtained. Specifically, the present invention has the following configuration.

[0010] [1] A method for producing a fiber-like material, comprising a step (A) of adding an oxo acid and a corrosion inhibitor to a fiber raw material and heating it, wherein when the addition amount of the oxo acid is a parts by mass and the addition amount of the corrosion inhibitor is b parts by mass, the value of b / a is 0.32 or more. [2] The method for producing a fiber-like material according to [1], wherein the step (A) is carried out in a metal container. [3] The method for producing a fiber-like material according to [1] or [2], wherein the fiber raw material is a cellulose-based material. [4] After the step (A), further comprising a defibrination treatment step (B), The method for producing a fiber-like material according to any one of [1] to [3], wherein the fiber-like material contains fibrous cellulose having a fiber width of 1000 nm or less. [5] The method for producing a fiber-like material according to any one of [1] to [4], wherein the corrosion inhibitor is a compound represented by the following formula (1); [Chemical formula] In the above formula (1), X represents an oxygen atom or a sulfur atom, and R 1 represents an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group or -NHR 11 , and R 2 represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group or an aryl group; in -NHR 11 , R 11 is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group or an aryl group. [6] The method for producing a fiber-like material according to any one of [1] to [5], wherein the corrosion inhibitor is at least one selected from urea and urea derivatives. [7] The method for producing a fibrous material according to any one of [1] to [6], wherein the oxo acid is phosphoric acid, the value of b / a is 0.32 or more and 1.0 or less, and the heat treatment temperature in the heating step (A) is 145°C or more and 185°C or less. [8] A cellulose-containing material containing fibrous cellulose having a fiber width of 1000 nm or less and containing a group derived from an oxo acid, The cellulose-containing material, wherein the content of the polyvalent metal in the cellulose-containing material is 50 to 1000 ppm. [9] The cellulose-containing material according to [8], wherein the oxo acid is phosphoric acid and the polyvalent metal is at least one selected from the group consisting of Fe, Cu, Cr, Ni, Mo, and Mn.

[10] An acid treatment agent for treating a fiber raw material, which contains an oxo acid and a compound represented by the following formula (1), When the content of the oxo acid contained in the acid treatment agent for treating a fiber raw material is c parts by mass and the content of the compound is d parts by mass, the value of d / c is 0.32 or more; the acid treatment agent for treating a fiber raw material;

Chemical formula

Advantages of the Invention

[0011] According to the present invention, even when a heating reaction is carried out in a metal container, a fibrous material with suppressed coloring can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments.

[0014] (Method for Producing Fiber-Like Material) The present invention relates to a method for producing a fibrous material including a step (A) of adding an oxo acid and a corrosion inhibitor to a fiber raw material and heating it. Here, in step (A), when the addition amount of the oxo acid is a parts by mass and the addition amount of the corrosion inhibitor is b parts by mass, the value of b / a is 0.32 or more. In addition, in the production method of the present invention, step (A) may be carried out in a metal container. In the present invention, even when step (A) is carried out in a metal container, a fibrous material with suppressed coloring can be obtained.

[0015] Here, regarding the coloring of the fibrous material, it can be evaluated by visually observing the fibrous material obtained through step (A). Specifically, the degree of coloring of the fibrous material obtained after the reaction is evaluated, and when it is white, it can be determined that the coloring is suppressed and it is good. Thus, in the present invention, even when step (A) is carried out in a metal container, a fibrous material with suppressed coloring can be obtained, and such a fibrous material can be said to have an excellent appearance.

[0016] Further, in the present invention, even when step (A) is carried out in a metal container, it is difficult for metal components to be mixed into the resulting fibrous material. In step (A), since an oxo-acid is used to carry out an oxo-oxidation reaction, depending on the acid used and the reaction conditions, polyvalent metals derived from the metal container may be mixed into the fibrous material which is the reaction product. In particular, when a strong acid is used as the oxo-acid and the oxo-oxidation reaction is carried out under high-temperature conditions, polyvalent metals derived from the metal container tend to be mixed into the fibrous material which is the reaction product. However, in the present invention, in step (A), by using an oxo-acid and a corrosion inhibitor in combination and further setting the addition amount ratio of the oxo-acid and the corrosion inhibitor to a predetermined ratio, the amount of polyvalent metals mixed into the fibrous material can be reduced. Thereby, a fibrous material with higher purity can be obtained.

[0017] The method for producing the fibrous material of the present invention preferably further includes a defibrillation treatment step (B) after step (A). By including step (B) in the method for producing the fibrous material of the present invention, the resulting fibrous material will contain fibrous cellulose with a fiber width of 1000 nm or less. Thus, the method for producing the fibrous material of the present invention is preferably a method for producing fibrous cellulose with a fiber width of 1000 nm or less. In this specification, fibrous cellulose with a fiber width of 1000 nm or less is also referred to as microfibrillated cellulose, and microfibrillated cellulose includes cellulose nanofiber (CNF) and cellulose nanocrystal (CNC).

[0018] <Step (A)> Step (A) is a step of adding an oxo-acid and a corrosion inhibitor to a fiber raw material and heating it. In this specification, step (A) is also referred to as an oxo-acid group introduction step or an oxo-oxidation step.

[0019] The fiber raw materials used in Project (A) are not particularly limited, and examples include inorganic fibers, organic fibers, synthetic fibers, etc., semi-synthetic fibers, and regenerated fibers. Examples of inorganic fibers include glass fibers, rock fibers, metal fibers, etc. Examples of organic fibers include fibers derived from natural products such as cellulose, carbon fibers, pulp, chitin, chitosan, etc. Examples of synthetic fibers include nylon, vinylon, vinylidene, polyester, polyolefin (e.g., polyethylene, polypropylene, etc.), polyurethane, acrylic, polyvinyl chloride, aramid, etc. Examples of semi-synthetic fibers include acetate, triacetate, promix, etc. Examples of regenerated fibers include rayon, cupra, polynosic rayon, lyocell, tencel, etc. The fiber raw materials used in the present invention are not particularly limited, but it is preferable to contain a hydroxyl group or an amino group because it facilitates the introduction of substituents described later.

[0020] Among them, the fiber raw material used in step (A) is preferably a fiber raw material containing cellulose. That is, the fiber raw material is preferably a cellulosic material. The fiber raw material containing cellulose is not particularly limited, but pulp is preferably used from the viewpoints of easy availability and low cost. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp are not particularly limited, and include, for example, chemical pulps such as hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving 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 groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP). Examples of non-wood pulp are not particularly limited, and include, for example, cotton-based pulps such as cotton linter and cotton lint, and non-wood-based pulps such as hemp, wheat straw, and bagasse. Examples of deinked pulp are not particularly limited, and include, for example, deinked pulp made from waste paper. The pulp of this embodiment may be used alone or in combination of two or more of the above. Among the above pulps, from the viewpoint of easy availability, for example, wood pulp and deinked pulp are preferable. Among wood pulps, from the viewpoint of a large cellulose ratio and a high yield of microfibrillar cellulose during fibrillation treatment, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are even more preferable.

[0021] As the fiber raw material containing cellulose, for example, cellulose contained in jellyfish or bacterial cellulose produced by acetic acid bacteria can also be used. Further, instead of the fiber raw material containing cellulose, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can also be used.

[0022] Step (A) is a step of allowing an oxo acid and a corrosion inhibitor to act on a fiber raw material containing cellulose. By this step, oxo acid group-introduced fibers can be obtained.

[0023] The oxo acid used in step (A) is an acid having a structure in which an oxo group (=O) and a hydroxy group (-OH) are bonded to a central atom. The oxo acid used in step (A) is preferably at least one selected from phosphorous oxo acids, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, carbonic acid, silicic acid, and carboxylic acid, more preferably at least one selected from phosphorous oxo acids, sulfuric acid, sulfurous acid, and carboxylic acid, still more preferably at least one selected from phosphorous oxo acids, sulfuric acid, and sulfurous acid, and particularly preferably a phosphorous oxo acid. The phosphorous oxo acid is preferably at least one selected from phosphoric acid and phosphorous acid, more preferably phosphoric acid or phosphorous acid, and still more preferably phosphoric acid. The phosphorous oxo acid may be pyrophosphoric acid or polyphosphoric acid. The oxo acid may be one kind or two or more kinds.

[0024] Examples of the corrosion inhibitor used in step (A) include nitrogen-containing organic compounds and sulfur-containing organic compounds. Examples of the nitrogen-containing organic compounds include imidazolium-based quaternary ammonium salts and polyamine compounds. The nitrogen-containing organic compound is preferably a compound represented by the following formula (1). By using the compound represented by the following formula (1) as the nitrogen-containing organic compound, the coloring of the fibrous material can be more effectively suppressed, and in addition, the production cost of the fibrous material can be reduced.

Chemical formula

[0025] In the above formula (1), X represents an oxygen atom or a sulfur atom, and R 1 represents an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, or -NHR 11 represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, or an aryl group; in -NHR 2 11 11 ​​is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group or an aryl group. In formula (1), R 1 and R 2 each group represented by may further have a substituent. Such substituents include, for example, a halogen atom, a halogenated alkyl group, an alkyl group, an alkenyl group, an acyl group, a hydroxy group, a hydroxyalkyl group, an alkoxy group, an aryl group, a heteroaryl group, an alicyclic group, a cyano group, an epoxy group, an oxetanyl group, a mercapto group, an amino group, a (meth)acryloyl group and other substitutable substituents that can be selected. Each group represented by R 11 may also further have a substituent, and as the substituent, the same substituents as described above can be enumerated.

[0026] In formula (1), when R 1 is an alkyl group, the alkyl group may be a branched alkyl group. The number of carbon atoms of the alkyl group is preferably 1 to 4, more preferably 1 to 2. Among them, the alkyl group is preferably a methyl group or an ethyl group. In formula (1), when R 1 is an alkenyl group, the alkenyl group may be a branched alkenyl group. The number of carbon atoms of the alkenyl group is preferably 2 to 4, more preferably 2 to 3. Among them, the alkenyl group is preferably a vinyl group, an allyl group or an isopropyl group. In formula (1), when R 1 is a cycloalkyl group, the number of carbon atoms of the cycloalkyl group is preferably 3 to 6, more preferably 3 to 5. Among them, the cycloalkyl group is preferably a cyclopropyl group, a cyclobutyl group, a cyclopentyl group or a cyclohexyl group. Note that the cycloalkyl group may have a spiro structure. In formula (1), when R 1When it is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 to 4, more preferably 1 to 2. Among them, the alkoxy group is preferably a methoxy group or an ethoxy group. In addition, the alkoxy group may be a phenoxy group, an allyloxy group, or a cyclohexyloxy group.

[0027] In formula (1), R 2 When it is an alkyl group, the alkyl group may be a branched alkyl group. The number of carbon atoms of the alkyl group is preferably 1 to 4, more preferably 1 to 2. Among them, the alkyl group is preferably a methyl group or an ethyl group. In formula (1), R 2 When it is an alkenyl group, the alkenyl group may be a branched alkenyl group. The number of carbon atoms of the alkenyl group is preferably 2 to 4, more preferably 2 to 3. Among them, the alkenyl group is preferably a vinyl group, an allyl group, or an isopropyl group. In formula (1), R 2 When it is a cycloalkyl group, the number of carbon atoms of the cycloalkyl group is preferably 3 to 6, more preferably 3 to 5. Among them, the cycloalkyl group is preferably a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group. In addition, the cycloalkyl group may have a spiro structure. In formula (1), R 2 When it is an aryl group, R 2 is preferably a phenyl group or a naphthyl group.

[0028] Among them, in formula (1), X is preferably an oxygen atom. Also, R 1 is preferably -NHR 11 Also, R 11 is preferably at least one selected from a hydrogen atom and a methyl group, more preferably a hydrogen atom. Further, R 2 is also preferably at least one selected from a hydrogen atom and a methyl group, more preferably a hydrogen atom

[0029] Specifically, the corrosion inhibitor is preferably at least one selected from urea and urea derivatives, more preferably at least one selected from the group consisting of urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea, and particularly preferably urea.

[0030] The addition amount of the oxo acid to the fiber raw material is preferably 4 parts by mass or more, more preferably 8 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the fiber raw material. Also, the addition amount of the oxo acid to the fiber raw material is preferably 8700 parts by mass or less, more preferably 4350 parts by mass or less, and still more preferably 1740 parts by mass or less with respect to 100 parts by mass of the fiber raw material. By setting the addition amount of the oxo acid within the above range, it becomes easy to set the amount of oxo acid groups with respect to the fiber raw material within a desired range.

[0031] The addition amount of the corrosion inhibitor to the fiber raw material (dry mass) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the fiber raw material. Also, the addition amount of the corrosion inhibitor to the fiber raw material is preferably 15960 parts by mass or less, more preferably 7980 parts by mass or less, and still more preferably 3192 parts by mass or less with respect to 100 parts by mass of the fiber raw material. By setting the addition amount of the corrosion inhibitor within the above range, it becomes easy to obtain a fiber-like material with suppressed coloring.

[0032] In step (A), when the addition amount of the oxo acid is a parts by mass and the addition amount of the corrosion inhibitor is b parts by mass, the value of b / a may be 0.32 or more, preferably 0.64 or more, more preferably 0.94 or more, and even more preferably 1.30 or more. Note that the value of b / a is preferably 30 or less, more preferably 1.0 or less, and even more preferably 0.95 or less. By setting the value of b / a in step (A) within the above range, a fiber-like material with suppressed coloring can be obtained. Furthermore, by setting the value of b / a in step (A) within the above range, the amount of polyvalent metal mixed into the fiber-like material can be reduced, and a fiber-like material with higher purity can be obtained.

[0033] In step (A), when the addition amount of the oxo acid is a' moles and the addition amount of the corrosion inhibitor is b' moles, the value of b' / a' is preferably 0.15 or more, more preferably 0.30 or more, and even more preferably 0.75 or more. Note that the value of b' / a' is preferably 52 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. By setting the value of b' / a' in step (A) within the above range, a fiber-like material with suppressed coloring can be obtained. Furthermore, by setting the value of b' / a' in step (A) within the above range, the amount of polyvalent metal mixed into the fiber-like material can be reduced, and a fiber-like material with higher purity can be obtained.

[0034] As an example of a method of allowing an oxo acid to act on a fiber raw material in the coexistence of a corrosion inhibitor, a method of mixing the oxo acid and the corrosion inhibitor with the fiber raw material in a dry state, a wet state or a slurry state can be mentioned. Among these, since the uniformity of the reaction is high, it is preferable to use the fiber raw material in a dry state or a wet state, and it is particularly preferable to use the fiber raw material in a dry state. The form of the fiber raw material is not particularly limited, but for example, it is preferably in a cotton-like or thin sheet-like form. Examples of methods of adding the oxo acid and the corrosion inhibitor to the fiber raw material include adding them in a powdery form, in a solution form dissolved in a solvent, or in a molten state heated to a temperature above the melting point. Among these, since the uniformity of the reaction is high, it is preferable to add them in a solution form dissolved in a solvent, particularly in an aqueous solution state. Further, the oxo acid and the corrosion inhibitor may be added to the fiber raw material simultaneously, separately, or as a mixture. The method of adding the oxo acid and the corrosion inhibitor is not particularly limited, but when the oxo acid and the corrosion inhibitor are in a solution state, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the solution may be dropped onto the fiber raw material. Further, a necessary amount of the oxo acid and the corrosion inhibitor may be added to the fiber raw material, or after adding an excessive amount of the oxo acid and the corrosion inhibitor to the fiber raw material respectively, the excess oxo acid and corrosion inhibitor may be removed by pressing or filtration.

[0035] In step (A), after adding or mixing the oxo acid and the corrosion inhibitor to the fiber raw material, heat treatment (also referred to as heating) is performed on the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which the oxo acid group can be efficiently introduced. The heat treatment temperature is preferably, for example, 30°C or higher and 300°C or lower, more preferably 40°C or higher and 250°C or lower, still more preferably 45°C or higher and 200°C or lower, and particularly preferably 145°C or higher and 185°C or lower.

[0036] In the heat treatment according to this embodiment, for example, after adding an oxo acid to a thin sheet-like fiber raw material by a method such as impregnation, a method of heating or a method of heating while kneading or stirring the fiber raw material and the oxo acid with a kneader or the like can be adopted. Thereby, it is possible to suppress the unevenness in the concentration of the oxo acid in the fiber raw material and introduce oxo acid groups more uniformly onto the surface of the cellulose fibers contained in the fiber raw material. This is presumably because when water molecules move to the surface of the fiber raw material during drying, the dissolved oxo acid is attracted to the water molecules by surface tension and also moves to the surface of the fiber raw material (that is, unevenness in the concentration of the oxo acid is caused), which can be suppressed.

[0037] Further, the heating device used for the heat treatment may be a device that can always discharge the moisture held by the slurry and the moisture generated by the dehydration condensation (phosphoric esterification) reaction between the oxo acid and the hydroxyl groups contained in cellulose or the like in the fiber raw material to the outside of the device system. Examples of such heating devices include a blower-type oven, a stirring dryer, a rotary dryer, a disk dryer, a roll-type heating device, a plate-type heating device, a fluidized bed dryer, a band-type dryer, a filtration dryer, a vibration fluidized dryer, a pneumatic dryer, a vacuum dryer, an infrared heating device, a far-infrared heating device, a microwave heating device, a high-frequency dryer, and the like. By always discharging the moisture in the device system, for example, when phosphoric acid or phosphorous acid is used as the oxo acid, in addition to suppressing the hydrolysis reaction of the phosphoric ester bond, which is the reverse reaction of phosphoric esterification, it is also possible to suppress the acid hydrolysis of the sugar chain in the fiber. Therefore, it is possible to obtain microfibrillar cellulose having a high axial ratio.

[0038] The heat treatment time is preferably, for example, 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and even more preferably 10 seconds or more and 800 seconds or less, in the case of a reaction for removing moisture from the system, i.e., after substantially removing moisture from the fiber raw material. On the other hand, in the case of a reaction carried out in an aqueous solution, for example, it is preferably 360 seconds or more and 36000 seconds or less, more preferably 720 seconds or more and 18000 seconds or less, and even more preferably 1800 seconds or more and 7200 seconds or less, from the start of heating.

[0039] The step (A) as described above may be carried out in a metal container. Examples of the metal container include stainless steel containers (such as SUS304, SUS316, SUS316L, etc.), iron containers, copper containers, and the like. Conventionally, when an oxo oxidation treatment is carried out in a metal container, there has been a problem that the metal constituting the metal container elutes during the reaction process and the eluted metal component mixes into the reaction product. For this reason, although it is conceivable to carry out the oxo oxidation treatment in a non-metal material, there is also a demand to use a metal container from the viewpoints of durability and the like. In the present invention, even when the oxo oxidation treatment is carried out in the metal container as described above, it is possible to suppress the mixing of metal components derived from the container. Thereby, an oxo-oxidized fibrous material with higher purity can be obtained.

[0040] The introduction amount of the oxo acid group with respect to the fiber raw material is preferably, for example, 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, even more preferably 0.05 mmol / g or more, and particularly preferably 0.10 mmol / g or more, per 1 g (mass) of the fiber raw material. Also, the introduction amount of the oxo acid group with respect to the fiber raw material is preferably, for example, 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and even more preferably 3.00 mmol / g or less, per 1 g (mass) of the fiber raw material. By setting the introduction amount of the oxo acid group within the above range, for example, the refinement of the fiber raw material in the step (B) described later can be facilitated, and the stability of the microfibrillar cellulose can be enhanced.

[0041] The amount of oxo acid groups introduced into the fiber raw material can be measured, for example, by a neutralization titration method. In the measurement by the neutralization titration method, the amount of introduction is measured by determining the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the slurry containing the obtained fiber raw material.

[0042] Figure 1 is a graph showing the relationship between the amount of NaOH dropped and the pH for a slurry containing a fiber raw material having a phosphorous oxo acid group. The amount of phosphorous oxo acid groups introduced into the fiber raw material is measured, for example, as follows. First, the slurry containing the fiber raw material is treated with a strongly acidic ion exchange resin. Incidentally, if necessary, before the treatment with the strongly acidic ion exchange resin, a defibrillation treatment similar to the defibrillation treatment process described later may be performed on the measurement target. Next, while observing the change in pH while adding an aqueous sodium hydroxide solution, a titration curve as shown in the upper part of FIG. 1 is obtained. In the titration curve shown in the upper part of FIG. 1, the pH measured with respect to the amount of alkali added is plotted, and in the titration curve shown in the lower part of FIG. 1, the increment (differential value) (1 / mmol) of the pH with respect to the amount of alkali added is plotted. In this neutralization titration, in the curve obtained by plotting the pH measured with respect to the amount of alkali added, two points where the increment (differential value of the pH with respect to the amount of alkali dropped) becomes maximum are confirmed. Among these, the first maximum point of the increment obtained first after starting to add the alkali is called the first end point, and the next maximum point of the increment obtained is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the first dissociation acid amount of the fiber raw material contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point is equal to the second dissociation acid amount of the fiber raw material contained in the slurry used for titration, and the amount of alkali required from the start of titration to the second end point is equal to the total dissociation acid amount of the fiber raw material contained in the slurry used for titration. And the value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the titration target slurry becomes the amount of phosphorous oxo acid group introduced (mmol / g). Incidentally, when simply referring to the amount of phosphorous oxo acid group introduced (or the amount of phosphorous oxo acid group), it represents the amount of the first dissociation acid. In FIG. 1, the region from the start of titration to the first end point is referred to as the first region, and the region from the first end point to the second end point is referred to as the second region. For example, when the oxoacid group is a phosphate group and this phosphate group undergoes condensation, apparently, the amount of weak acid groups in the oxoacid group (also referred to as the second dissociation acid amount in this specification) decreases, 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 strong acid groups in the oxoacid group (also referred to as the first dissociation acid amount in this specification) coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation. Further, when the oxoacid group is a phosphite group, since there are no weak acid groups in the oxoacid group, the amount of alkali required in the second region may decrease, or the amount of alkali required in the second region may be zero. In this case, in the titration curve, there is only one point where the increment of pH becomes maximum.

[0043] Note that since the denominator indicates the mass of the acid-type fiber raw material in the above-mentioned introduced amount of oxoacid group (mmol / g), it represents the amount of oxoacid groups possessed by the acid-type fiber raw material (hereinafter referred to as the amount of oxoacid groups (acid type)). On the other hand, when the counter ion of the oxoacid group is replaced with an arbitrary cation C so as to be charge equivalent, by converting the denominator to the mass of the fiber raw material when the cation C is the counter ion, the amount of oxoacid groups possessed by the fiber raw material in which the cation C is the counter ion (hereinafter referred to as the amount of oxoacid groups (C type)) can be obtained. That is, it is calculated by the following calculation formula. Amount of oxoacid groups (C type) = Amount of oxoacid groups (acid type) / {1 + (W - 1) × A / 1000} A [mmol / g]: Total anion amount derived from oxoacid groups possessed by the fiber raw material (total dissociation acid amount of oxoacid groups) W: Formula weight per monovalent of cation C (for example, Na is 23, Al is 9)

[0044] FIG. 2 is a graph showing the relationship between the amount of NaOH dropped and pH for a dispersion containing a fiber raw material having a carboxy group or a sulfo group as an oxoacid group. The introduced amount of carboxy groups or sulfo groups into the fiber raw material is measured, for example, as follows. First, a dispersion containing a fiber raw material is treated with a strongly acidic ion exchange resin. Optionally, before the treatment with the strongly acidic ion exchange resin, a defibrillation treatment similar to the defibrillation treatment process described below may be performed on the measurement target. Next, while adding an aqueous sodium hydroxide solution, the change in pH is observed to obtain a titration curve as shown in the upper part of FIG. 2. In the titration curve shown in the upper part of FIG. 2, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of FIG. 2, the increment (differential value) (1 / mmol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, in the curve where the measured pH is plotted against the amount of alkali added, one point where the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum is confirmed, and this maximum point is called the first end point. Here, the region from the start of titration to the first end point in FIG. 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, by dividing the amount of alkali (mmol) required in the first region of the titration curve by the solid content (g) in the dispersion containing the fiber raw material to be titrated, the introduction amount (mmol / g) of carboxyl groups or the introduction amount (mmol / g) of sulfonic groups is calculated.

[0045] Note that since the denominator of the above-introduced carboxyl group amount (mmol / g) is the mass of the acid-type fiber raw material, it indicates the amount of carboxyl groups (hereinafter referred to as the carboxyl group amount (acid type)) possessed by the acid-type fiber raw material. On the other hand, when the counter ion of the carboxyl group is replaced with an arbitrary cation C so that the charge equivalent is achieved, by converting the denominator to the mass of the fiber raw material when the cation C is the counter ion, the amount of carboxyl groups (hereinafter referred to as the carboxyl group amount (C type)) possessed by the fiber raw material with the cation C as the counter ion can be obtained. That is, it is calculated by the following calculation formula. Carboxyl group amount (C type) = Carboxyl group amount (acid type) / {1 + (W - 1) × (Carboxyl group amount (acid type)) / 1000} W: Formula weight per valence of cation C (for example, Na is 23, Al is 9)

[0046] In addition, since the denominator of the above-introduced sulfonic acid group amount (mmol / g) is the mass of the acid-form fiber raw material, it indicates the amount of sulfonic acid groups contained in the acid-form fiber raw material (hereinafter referred to as the sulfonic acid group amount (acid form)). On the other hand, when the counter ion of the sulfonic acid group is replaced with an arbitrary cation C so as to be charge equivalent, by converting the denominator to the mass of the fiber raw material when the cation C is the counter ion, the amount of sulfonic acid groups contained in the fiber raw material with the cation C as the counter ion (hereinafter referred to as the sulfonic acid group amount (C form)) can be obtained. That is, it is calculated by the following calculation formula. Sulfonic acid group amount (C form) = Sulfonic acid group amount (acid form) / {1 + (W - 1) × (sulfonic acid group amount (acid form)) / 1000} W: Formula weight per monovalent of cation C (for example, Na is 23, Al is 9)

[0047] In the measurement of the amount of oxo acid groups by titration, accurate values may not be obtained, such as when the dropping amount of one drop of aqueous sodium hydroxide solution is too large or the titration interval is too short, resulting in a lower amount of oxo acid groups than the original. As appropriate dropping amounts and titration intervals, for example, it is desirable to titrate 0.1N aqueous sodium hydroxide solution in 10 - 50 μL portions every 5 - 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the fiber raw material-containing slurry, for example, it is desirable to perform the measurement while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration until the end of titration.

[0048] The oxo acid group introduction step may be performed at least once, but can also be repeated two or more times. By performing the oxo acid group introduction step two or more times, a large amount of oxo acid groups can be introduced into the fiber raw material.

[0049] <Step (B)> The method for producing a fibrous material of the present invention preferably further includes a defibrillation treatment step (B) after the above-described step (A). Step (B) is a step of defibrillating the oxo acid group-introduced fiber. Thereby, microfibrillar cellulose can be obtained. In this specification, microfibrillar cellulose includes cellulose nanofiber (CNF) and cellulose nanocrystal (CNC).

[0050] In step (B), for example, a defibrating device can be used. The defibrating device is not particularly limited, and for example, a high-speed defibrator, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure impact type crusher, a ball mill, a bead mill, a disk type refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater can be used. Among the above defibrating devices, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, or an ultra-high pressure homogenizer, which are less affected by grinding media and have less risk of contamination.

[0051] In step (B), for example, it is preferable to dilute the oxo acid group-introduced fiber with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and organic solvents such as polar organic solvents can be used. The polar organic solvent is not particularly limited, and for example, alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents, etc. are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol, etc. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin, etc. Examples of ketones include acetone, methyl ethyl ketone (MEK), etc. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether, etc. Examples of esters include ethyl acetate, butyl acetate, etc. Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP), etc.

[0052] The solid content concentration of the oxo acid group-introduced fiber during the fibrillation treatment can be set as appropriate. Further, the slurry obtained by dispersing the oxo acid group-introduced fiber in a dispersion medium may contain solids other than the oxo acid group-introduced fiber, such as urea having hydrogen bonding properties.

[0053] <Other processes> -Washing process- In the method for producing a fibrous material according to the present embodiment, a washing process can be performed on the oxo acid group-introduced fiber as necessary. The washing process is performed, for example, by washing the oxo acid group-introduced fiber with water or an organic solvent. Further, the washing process may be performed after each of the processes described below, and the number of washing times performed in each washing process is not particularly limited.

[0054] -Alkali treatment process- In the method for producing a fibrous material, an alkali treatment process may be provided between the oxo acid group-introduction process (Process (A)) and the fibrillation treatment process (Process (B)). The method of alkali treatment is not particularly limited, and examples thereof include a method of immersing the oxo acid group-introduced fiber in an alkali solution. In the present specification, the alkali treatment process is also referred to as a neutralization treatment process.

[0055] The alkali compound contained in the alkali solution is not particularly limited and may be an inorganic alkali compound or an organic alkali compound. In the present embodiment, since it has high versatility, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkali compound. Further, the solvent contained in the alkali solution may be either water or an organic solvent. Among them, the solvent contained in the alkali solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkali solution, since it has high versatility, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferable.

[0056] The temperature of the alkaline solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5°C or higher and 80°C or lower, and more preferably 10°C or higher and 60°C or lower. The immersion time of the oxo acid group-introduced fiber in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5 minutes or longer and 30 minutes or shorter, and more preferably 10 minutes or longer and 20 minutes or shorter. The usage amount of the alkaline solution in the alkali treatment is not particularly limited, but is preferably, for example, 100% by mass or more and 100,000% by mass or less based on the absolute dry mass of the oxo acid group-introduced fiber, and more preferably 1,000% by mass or more and 10,000% by mass or less.

[0057] In order to reduce the usage amount of the alkaline solution in the alkali treatment step, the oxo acid group-introduced fiber may be washed with water or an organic solvent after the oxo acid group introduction step and before the alkali treatment step. After the alkali treatment step and before the fibrillation treatment step, from the viewpoint of improving handleability, it is preferable to wash the oxo acid group-introduced fiber subjected to the alkali treatment with water or an organic solvent.

[0058] (Cellulose-containing material) The present invention may relate to a fibrous material produced by the method for producing a fibrous material described above. In this case, the fibrous material preferably contains fibrous cellulose having a fiber width of 1000 nm or less. Further, the present invention may relate to a cellulose-containing material containing a group derived from an oxo acid and containing fibrous cellulose having a fiber width of 1000 nm or less. Here, the cellulose-containing material contains fibrous cellulose having a fiber width of 1000 nm or less and a polyvalent metal, and the content of the polyvalent metal in the cellulose-containing material is 50 to 1000 ppm. The content of the polyvalent metal in the cellulose-containing material may be 50 ppm or more, preferably 60 ppm or more, more preferably 70 ppm or more, and further preferably 80 ppm or more. Also, the content of the polyvalent metal in the cellulose-containing material may be 1000 ppm or less, preferably 900 ppm or less, more preferably 800 ppm or less.

[0059] The content of polyvalent metal in the cellulose-containing material is measured by the following method. First, the cellulose-containing material is dried at 105 °C until it becomes completely dry to obtain a completely dry solid content containing microfibrillar cellulose. After adding 5.0 mL of nitric acid to 0.1 g of this completely dry solid content and performing wet decomposition using a wet decomposition apparatus (manufactured by CEM, MARS5), the amount of polyvalent metal contained in the cellulose-containing material is measured using an ICP emission spectroscopic analyzer (manufactured by Ametek, CIROS120). Note that polyvalent metals include polyvalent metal atoms and polyvalent metal ions. The elements constituting the polyvalent metal are metal elements with a valence of two or more. As metal elements with a valence of two or more, Fe, Cu, Cr, Ni, Mo, Mn, etc. are preferable. That is, the element constituting the polyvalent metal is preferably at least one selected from the group consisting of Fe, Cu, Cr, Ni, Mo, and Mn. The element constituting the polyvalent metal may be one kind or two or more kinds. When step (A) is carried out in a container made of SUS304, as the element constituting the polyvalent metal in the cellulose-containing material in the present embodiment, at least one selected from the group consisting of Fe, Cr, Ni, and Mn can be mentioned. When step (A) is carried out in a container made of SUS316 or SUS316L, as the element constituting the polyvalent metal in the cellulose-containing material in the present embodiment, at least one selected from the group consisting of Fe, Cr, Ni, Mo, and Mn can be mentioned.

[0060] The fibrous cellulose with a fiber width of 1000 nm or less in the cellulose-containing material may further have a group derived from a corrosion inhibitor. Among them, the microfibrillar cellulose preferably has a group derived from at least one selected from urea and urea derivatives, and preferably has a carbamide group.

[0061] The cellulose-containing material contains microfibrillar cellulose with a fiber width of 1000 nm or less. The fiber width of the microfibrillar cellulose is more preferably 100 nm or less, and even more preferably 50 nm or less. When the microfibrillar cellulose is cellulose nanofiber (CNF), the fiber width is particularly preferably 8 nm or less.

[0062] The fiber width of the microfibrillar cellulose can be measured, for example, by electron microscope observation. The average fiber width of the microfibrillar cellulose is, for example, 1000 nm or less. The average fiber width of the fibrillar cellulose is preferably, for example, 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, and even more preferably 2 nm or more and 50 nm or less. When the microfibrillar cellulose is cellulose nanofiber (CNF), the average fiber width of the microfibrillar cellulose is particularly preferably 2 nm or more and 10 nm or less. By setting the average fiber width of the microfibrillar cellulose within the above range, dissolution in water as a cellulose molecule can be suppressed, and the characteristics of the microfibrillar cellulose can be more easily expressed. Note that the microfibrillar cellulose is, for example, single-fiber cellulose.

[0063] The average fiber width of the microfibrillar cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of microfibrillar cellulose with a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast onto a carbon film-coated grid that has been hydrophilized to obtain a sample for TEM observation. When fibers with a wide width are included, the SEM image of the surface cast on glass may be observed. Next, observation is performed on the electron microscope image at any one of magnifications of 1000 times, 5000 times, 10000 times, or 50000 times according to the width of the fiber to be observed. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.

[0064] (1) Draw a straight line X at an arbitrary position within the observation image, and 20 or more fibers intersect the straight line X. (2) Draw a straight line Y that intersects the straight line perpendicularly within the same image, and 20 or more fibers intersect the straight line Y.

[0065] For the observation images satisfying the above conditions, visually read the width of the fibers intersecting the straight line X and the straight line Y. In this way, obtain at least three sets of observation images of surface portions that do not overlap with each other. Next, for each image, read the width of the fibers intersecting the straight line X and the straight line Y. Thereby, read at least 20×2×3 = 120 fiber widths. Then, take the average value of the read fiber widths as the average fiber width of the microfibrillar cellulose.

[0066] The fiber length of the microfibrillar cellulose is not particularly limited, but is preferably, for example, 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and even more preferably 0.1 μm or more and 600 μm or less. When the microfibrillar cellulose is cellulose nanocrystal (CNC), the fiber length of the cellulose nanocrystal (CNC) is preferably 0.05 μm or more and 0.3 μm or less. The fiber length of the microfibrillar cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

[0067] When the microfibrillar cellulose is cellulose nanofiber (CNF), the fiber width of the microfibrillar cellulose is preferably 10 nm or less, and more preferably 5 nm or less. The fiber length is preferably 0.3 μm or more. That is, the aspect ratio (the ratio of fiber length to fiber width) of the cellulose nanofiber (CNF) is preferably 30 or more. On the other hand, when the microfibrillar cellulose is cellulose nanocrystal (CNC), the fiber width of the cellulose nanocrystal (CNC) is preferably greater than 10 nm and 30 nm or less, and the fiber length is preferably 0.3 μm or less. That is, the aspect ratio (the ratio of fiber length to fiber width) of the cellulose nanocrystal (CNC) is preferably 10 or more and less than 30.

[0068] The microfibrillar cellulose preferably has a type I crystal structure. Here, the fact that the microfibrillar cellulose has a type I crystal structure can be identified from the diffraction profile obtained from a wide-angle X-ray diffraction photograph using monochromatized CuKα (λ = 1.5418 Å) with graphite. Specifically, it can be identified from the presence of typical peaks at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less. The proportion of the type I crystal structure in the microfibrillar cellulose is preferably, for example, 30% or more, more preferably 40% or more, and even more preferably 50% or more. Thereby, further excellent performance can be expected in terms of heat resistance and manifestation of a low linear thermal expansion rate. Regarding the crystallinity, an X-ray diffraction profile is measured, and it is determined by a conventional method from the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959). Note that the microfibrillar cellulose in the present embodiment preferably has, for example, both a crystalline region and an amorphous region.

[0069] (Acid treatment agent for fiber raw material treatment) The present invention may relate to an acid treatment agent for fiber raw material treatment containing an oxo acid and a compound represented by the following formula (1). Here, when the content of the oxo acid contained in the acid treatment agent for fiber raw material treatment is c parts by mass and the content of the compound is d parts by mass, the value of d / c is 0.32 or more. In the present specification, the acid treatment agent for fiber raw material treatment is an agent used when subjecting a fiber raw material to an oxo oxidation treatment. The acid treatment agent for fiber raw material treatment may contain, in addition to the oxo acid and the compound represented by the following formula (1), a solvent and other optional components.

[0070] [Chemical formula]

[0071] In the above formula (1), X represents an oxygen atom or a sulfur atom, and R 1 represents an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, or -NHR 11 and R 2represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group or an aryl group; -NHR 11 In 11 , R

[0072] Note that R in the above (1) 1 and R 2 The specific examples and preferred ranges are as described above.

[0073] The content of the oxo acid is preferably 4 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 20 parts by mass or more with respect to the total mass of the acid treatment agent for treating fiber raw materials. Also, the content of the oxo acid is preferably 8700 parts by mass or less, more preferably 4350 parts by mass or less, and even more preferably 1740 parts by mass or less with respect to the total mass of the acid treatment agent for treating fiber raw materials.

[0074] The content of the compound represented by the formula (1) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more with respect to the total mass of the acid treatment agent for treating fiber raw materials. Also, the content of the compound represented by the formula (1) is preferably 15960 parts by mass or less, more preferably 7980 parts by mass or less, and even more preferably 3192 parts by mass or less with respect to the total mass of the acid treatment agent for treating fiber raw materials.

[0075] When the content of the oxo acid contained in the acid treatment agent for fiber raw material treatment is c parts by mass and the content of the compound is d parts by mass, the value of d / c may be 0.32 or more, preferably 0.64 or more, more preferably 0.94 or more, and even more preferably 1.30 or more. In addition, the value of d / c is preferably 30 or less, more preferably 1.0 or less, and even more preferably 0.95 or less. By setting the value of d / c in the acid treatment agent for fiber raw material treatment within the above range, a fiber-like material with suppressed coloring can be obtained. Furthermore, by setting the value of d / c within the above range, the amount of polyvalent metal mixed into the fiber-like material can be reduced, and a fiber-like material with higher purity can be obtained.

[0076] When the content of the oxo acid contained in the acid treatment agent for fiber raw material treatment is c' moles and the content of the compound is d' moles, the value of d' / c' is preferably 0.15 or more, more preferably 0.30 or more, and even more preferably 0.75 or more. In addition, the value of d' / c' is preferably 52 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. By setting the value of d' / c' in the acid treatment agent for fiber raw material treatment within the above range, a fiber-like material with suppressed coloring can be obtained. Furthermore, by setting the value of d' / c' within the above range, the amount of polyvalent metal mixed into the fiber-like material can be reduced, and a fiber-like material with higher purity can be obtained.

Examples

[0077] The features of the present invention will be further specifically described below with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0078] <Example 1-1> As the raw material pulp, cotton linter pulp manufactured by GAOMI CHEMICAL FIBER (solid content 94% by mass, basis weight 571 g / m 2A sheet-like material was used.

[0079] 2956 parts by mass of a chemical solution consisting of 870 parts by mass of pure sulfuric acid, 1596 parts by mass of urea, and 490 parts by mass of water was prepared. The prepared 2956 parts by mass of the chemical solution and 100 parts by mass (dry mass) of the above raw material pulp were poured into a container made of SUS316L and heated at 45°C for 1 hour.

[0080] Next, the pulp after the reaction was subjected to a washing process. The washing process was carried out by repeating the operation of pouring 10 L of ion-exchanged water into 100 g (dry mass) of the pulp to obtain a pulp dispersion, stirring it so that the pulp was uniformly dispersed, and then filtering and dehydrating. The washing end point was determined when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0081] Next, the neutralization process for the washed pulp was carried out as follows. First, 10 L of ion-exchanged water was poured into 100 g (dry mass) of the washed pulp and diluted, and then a 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a pulp slurry with a pH of 12 or more and 13 or less. Next, the pulp slurry was dehydrated to obtain a pulp subjected to the neutralization process. Further, the above washing process was carried out on the pulp after the neutralization process.

[0082] The infrared absorption spectrum of the pulp thus obtained was measured using FT-IR. As a result, absorption based on the sulfo group was observed at around 1350 cm -1 and 1180 cm -1 , and it was confirmed that the sulfo group was added to the pulp.

[0083] The fibrillation process for the obtained pulp was carried out as follows. First, ion-exchanged water was added to the pulp to prepare a slurry with a solid content concentration of 0.1% by mass. This slurry was treated at 21500 rpm for 2 hours using a rotary high-speed homogenizer (manufactured by M Technique Co., Ltd., Claremix 2.2S) to obtain a microfibrillated cellulose dispersion.

[0084] The obtained microfibrillar cellulose dispersion was centrifuged to obtain a supernatant. When the obtained supernatant was observed with a transmission electron microscope, microfibrillar cellulose having a width of about 20 nm was observed.

[0085] <Comparative Examples 1-1 and 1-2> The chemical solution was prepared by changing the addition amount of urea to 266 parts by mass or 0 parts by mass instead of 1596 parts by mass, respectively. A microfibrillar cellulose dispersion containing microfibrillar cellulose was obtained in the same manner as in Example 1-1, except that 1626 parts by mass or 1360 parts by mass of the prepared chemical solution was used.

[0086] <Reference Example 1-1> A microfibrillar cellulose dispersion containing microfibrillar cellulose was obtained in the same manner as in Comparative Example 1-2, except that a reaction vessel made of Teflon was used instead of the reaction vessel made of SUS316L.

[0087] <Reference Example 1-2> The chemical solution was prepared so as to be 11 parts by mass of pure hydrochloric acid, 54 parts by mass of urea, and 153 parts by mass of water. 218 parts by mass of the prepared chemical solution was used, and it was added to 10 parts by mass (dry mass) of raw material pulp. A microfibrillar cellulose dispersion containing microfibrillar cellulose was obtained in the same manner as in Example 1-1, except that the reaction temperature was 95 °C and the heating time was 2 hours.

[0088] <Reference Example 1-3> A microfibrillar cellulose dispersion containing microfibrillar cellulose was obtained in the same manner as in Reference Example 1-2, except that the chemical solution was prepared with 0 parts by mass instead of 54 parts by mass of urea added, and 164 parts by mass of the prepared chemical solution was used.

[0089] <Example 2-1> As the raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content: 93% by mass, basis weight: 245 g / m 2 in the form of a sheet, disintegrated, and the Canadian Standard Freeness (CSF) measured according to JIS P 8121-2:2012 was 700 ml) was used.

[0090] The phosphorylation treatment of this raw material pulp was carried out as follows. First, an aqueous mixed solution of phosphoric acid and urea was added to 100 parts by mass (dry mass) of the above raw material pulp, and it was prepared to contain 38 parts by mass of phosphoric acid, 120 parts by mass of urea, and 150 parts by mass of water to obtain a chemical impregnated pulp. Next, the obtained chemical impregnated pulp was heated in a SUS304 container with a hot air dryer at 165 °C for 600 seconds to introduce phosphate groups into the cellulose in the pulp and obtain a phosphorylated pulp.

[0091] Next, the obtained phosphorylated pulp was subjected to a washing treatment. The washing treatment was performed by repeating the operation of pouring 10 L of ion-exchanged water into 100 g (dry mass) of the phosphorylated pulp to obtain a pulp dispersion, stirring it so that the pulp was uniformly dispersed, and then filtering and dehydrating. The washing end point was determined when the electrical conductivity of the filtrate became 100 μS / cm or less.

[0092] Next, the neutralization treatment of the washed phosphorylated pulp was carried out as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a phosphorylated pulp slurry with a pH of 12 or more and 13 or less. Next, the phosphorylated pulp slurry was dehydrated to obtain a phosphorylated pulp subjected to the neutralization treatment. Next, the above washing treatment was performed on the phosphorylated pulp after the neutralization treatment.

[0093] The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on phosphate groups was observed near 1230 cm -1 −1, and it was confirmed that phosphate groups were added to the pulp. In addition, when the obtained phosphorylated pulp was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals.

[0094] Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content concentration of 2% by mass. This slurry was treated twice at a pressure of 200 MPa using a wet atomization device (manufactured by Sugino Machine, Starburst) to obtain a microfibrillated cellulose dispersion containing microfibrillated cellulose.

[0095] It was confirmed by X-ray diffraction that this microfibrillated cellulose maintained cellulose I-type crystals. Also, when the fiber width of the microfibrillated cellulose was measured using a transmission electron microscope, it was 3 - 5 nm.

[0096] <Example 2-2> A microfibrillated cellulose dispersion containing microfibrillated cellulose was obtained in the same manner as in Example 2-1, except that the addition amount of urea was changed to 12 parts by mass instead of 120 parts by mass.

[0097] <Comparative Example 2-1> A microfibrillated cellulose dispersion containing microfibrillated cellulose was obtained in the same manner as in Example 2-1, except that the addition amount of urea was changed to 0 parts by mass instead of 120 parts by mass.

[0098] <Evaluation Method> [Appearance of Reactants] In the examples, comparative examples, and reference examples, the cellulose fibers obtained after the reaction were visually observed, and the coloring condition was qualitatively evaluated. ○: The cellulose fibers obtained after the reaction are white. △: The cellulose fibers obtained after the reaction are light green or brown. ×: The cellulose fibers obtained after the reaction are dark green or black.

[0099] [Measurement of Polyvalent Metal Amount in Cellulose-containing Substance] The fine fibrous cellulose dispersions obtained in the examples, comparative examples, and reference examples were dried at 105 °C until completely dry to obtain the completely dry solid content of the fine fibrous cellulose. 5.0 mL of nitric acid was added to 0.1 g of this completely dry solid content, and wet decomposition was carried out using a wet decomposition apparatus (manufactured by CEM, MARS5). After that, an ICP emission spectroscopic analyzer (manufactured by Ametek, CIROS120) was used to measure the amount of polyvalent metal contained in the completely dry solid content of the fine fibrous cellulose.

[0100]

Table 1

[0101]

Table 2

[0102] In the examples, the coloring of the reaction product after the heating reaction was suppressed, and cellulose fibers with excellent appearance were obtained. On the other hand, in the comparative examples, the reaction product after the heating reaction was colored.

Claims

1. including a step (A) of adding an oxo acid and a corrosion inhibitor to a fiber raw material and heating it, wherein the fiber raw material is a cellulose-based material, the oxo acid is a phosphorus oxo acid (excluding phosphates), the step (A) is carried out in a metal container, a method for producing a fibrous material, wherein when the addition amount of the phosphorus oxo acid is a parts by mass and the addition amount of the corrosion inhibitor is b parts by mass, the value of b / a is 1.30 or more and 30 or less.

2. further including a defibrillation treatment step (B) after the step (A), the method for producing a fibrous material according to claim 1, wherein the fibrous material includes fibrous cellulose having a fiber width of 1000 nm or less.

3. the method for producing a fibrous material according to claim 1 or 2, wherein the corrosion inhibitor is a compound represented by the following formula (1); 【Chemical 1】 In the above formula (1), X represents an oxygen atom or a sulfur atom, and R １ represents an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, or -NHR １１ , R ２ represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, or an aryl group; in -NHR １１ , R １１ is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, or an aryl group.

4. the method for producing a fibrous material according to any one of claims 1 to 3, wherein the corrosion inhibitor is at least one selected from urea and urea derivatives.

5. the method for producing a fibrous material according to any one of claims 1 to 4, wherein the heat treatment temperature in the heating step (A) is 145°C or more and 185°C or less.

6. an acid treatment agent for treating a fiber raw material, which contains an oxo acid and a compound represented by the following formula (1) and is used in a metal container, wherein the fiber raw material is a cellulose-based material, the oxo acid is a phosphorus oxo acid (excluding phosphates), an acid treatment agent for treating a fiber raw material, wherein when the content of the phosphorus oxo acid contained in the acid treatment agent for treating a fiber raw material is c parts by mass and the content of the compound is d parts by mass, the value of d / c is 1.30 or more and 30 or less. 【Chemical 2】 In the above formula (1), X represents an oxygen atom or a sulfur atom, and R １ represents an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group or -NHR １１ wherein R ２ represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group or an aryl group; in -NHR １１ , R １１ is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group or an aryl group.

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