JP2020079423A - Method for producing phosphorylated cellulose fiber and cellulose-containing material - Google Patents

Abstract

To improve the production efficiency of phosphorylated cellulose fibers.SOLUTION: The present invention relates to a method for producing phosphorylated cellulose fibers including a step for phosphorylating cellulose fibers, where an initial moisture content of a reaction system is less than 40 mass%. The present invention also relates to a cellulose-containing material produced by such a production method and a cellulose-containing material containing fibrous cellulose with a fiber width of 1000 nm or less.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing phosphorylated cellulose fiber and a cellulose-containing material.

  In recent years, materials that use reproducible natural fibers have been attracting attention due to the substitution of petroleum resources and increasing environmental awareness. Among natural fibers, fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, in particular, fibrous cellulose (pulp) derived from wood has been widely used as paper products until now.

  As the fibrous cellulose, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. The fine fibrous cellulose can be used as a constituent raw material for a sheet or a composite. It is known that when fine fibrous cellulose is used, the number of contact points between fibers remarkably increases, so that the tensile strength and the like are greatly improved. Further, the use of fine fibrous cellulose in applications such as thickeners is also under study.

  The fine fibrous cellulose can be produced by mechanically treating conventional cellulose fibers, but the cellulose fibers are strongly bonded to each other by hydrogen bonding. Therefore, enormous energy is required to obtain fine fibrous cellulose simply by performing mechanical treatment.

  It is known that pretreatment such as chemical treatment or biological treatment is effective in addition to mechanical treatment in order to produce fine fibrous cellulose with smaller mechanical treatment energy. In particular, when a hydrophilic functional group (for example, a carboxyl group, a cation group, a phosphate group, etc.) is introduced into the hydroxyl group on the surface of cellulose by chemical treatment, electric repulsion between the ions occurs and the ions are hydrated. By doing so, the dispersibility in an aqueous solvent is remarkably improved. Therefore, the energy efficiency of miniaturization is higher than that in the case where no chemical treatment is applied.

  For example, Patent Documents 1 and 2 disclose a phosphorylated fine fibrous cellulose in which a phosphoric acid group forms an ester with a hydroxyl group of cellulose and a method for producing phosphorylated fine fibrous cellulose. In Patent Document 2, it is considered to carry out the phosphorylation reaction step in the presence of urea or to increase the phosphate group introduction amount by carrying out the phosphorylation reaction step a plurality of times.

International Publication No. 2013/073652 International Publication No. 2014/185505

  The present inventors have conducted studies for the purpose of providing a method for more efficiently producing phosphorylated cellulose fibers.

As a result of intensive studies to solve the above problems, the present inventors, by setting the initial water content of the reaction system in the step of phosphorylating the cellulose fiber to a predetermined value or less, the production of phosphorylated cellulose fiber It has been found that the efficiency can be increased.
Specifically, the present invention has the following configurations.

[1] A method for producing a phosphorylated cellulose fiber, which comprises a step of phosphorylating a cellulose fiber, wherein the initial water content of the reaction system is less than 40% by mass.
[2] The method for producing phosphorylated cellulose fiber according to [1], wherein the step of phosphorylating includes the step of mixing the cellulose fiber, an organic solvent, and a phosphorylating agent.
[3] The organic solvent is dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethylsulfoxide (DMSO), dioxane and The method for producing a phosphorylated cellulose fiber according to [2], which contains at least one selected from urea.
[4] The method for producing a phosphorylated cellulose fiber according to [2] or [3], wherein the phosphorylating agent contains at least one selected from dehydrated condensed phosphoric acid, phosphoric anhydride, and phosphoric acid.
[5] The phosphorylation step includes a heating step, and when heating at 140° C. in the heating step, the phosphorylation reaction rate from the start of heating to the time of 60 minutes is 0.018 mmol/g. -The manufacturing method of the phosphorylated cellulose fiber in any one of [1]-[4] which is min or more.
[6] The specific viscosity measured according to Tappi T230 of the cellulose-containing material containing the cellulose fibers before undergoing the phosphorylation step is set to ∨1, and the cellulose-containing material Tappi T230 containing the cellulose fibers obtained in the phosphorylation step. The method for producing phosphorylated cellulose fibers according to any one of [1] to [5], wherein the value of ∨2/∨1 is 0.74 or more, where the specific viscosity measured according to the above is ∨2.
[7] The phosphorylation according to any one of [1] to [6], wherein the cellulose-containing material containing cellulose fibers obtained in the phosphorylation step has a specific viscosity of 8.0 or more as measured according to Tappi T230. Method for producing cellulose fiber.
[8] A cellulose-containing material containing cellulose fibers having a fiber width of 1000 nm or less, and 3 rpm of a slurry obtained by diluting the cellulose-containing material with water to a solid content concentration of 0.4% by mass, A cellulose-containing material having a viscosity of 14500 mPa·s or higher as measured by a B-type viscometer at a liquid temperature of 25°C.
[9] A cellulose-containing material containing cellulose fibers having a phosphoric acid group of 0.1 mmol/g or more and having a specific viscosity of 8.0 or more measured according to Tappi T230.
[10] The cellulose-containing material according to [9], which has a degree of polymerization of 870 or more, which is obtained by measurement according to Tappi T230.
[11] The cellulose-containing material according to [9] or [10], which contains an organic solvent component.

  According to the production method of the present invention, the production efficiency of phosphorylated cellulose fibers can be increased.

FIG. 1 is a graph showing the relationship between the amount of dropped NaOH and the electrical conductivity with respect to a fiber raw material having a phosphate group.

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

(Method for producing phosphorylated cellulose fiber)
The present invention relates to a method for producing phosphorylated cellulose fibers, which includes a step of phosphorylating cellulose fibers (hereinafter, also referred to as a phosphorylation reaction step). The initial water content of the reaction system in the method for producing a phosphorylated cellulose fiber of the present invention is less than 40% by mass.

In the present invention, the phosphorylated cellulose fiber can be efficiently produced by setting the initial water content of the reaction system to be less than the predetermined value. In the present invention, the energy cost required for producing phosphorylated cellulose fibers can be reduced. In addition, the phosphorylation reaction time in the phosphorylation reaction step can be shortened. Thereby, the production efficiency of the phosphorylated cellulose fiber can be increased.
The phosphorylation reaction of cellulose fibers proceeds under the condition that water is substantially absent. However, conventionally, it has been considered that the solvent of the cellulose fiber in the phosphorylation reaction step is preferably an aqueous solvent in order to enhance the solubility of the phosphorylating agent and facilitate the uniform dispersion. Therefore, there is a problem that it takes time for the phosphorylation reaction to proceed. In the present invention, by intentionally lowering the initial water content of the solvent in the phosphorylation reaction step, to accelerate the start point of the phosphorylation reaction of the cellulose fiber, and further to accelerate the phosphate group introduction rate during the phosphorylation reaction. It was successful. In particular, since the rate of the phosphorylation reaction from the start of the phosphorylation reaction to the elapse of a predetermined time can be increased, the time required for the phosphorylation reaction step can be significantly shortened. Thereby, the production efficiency of the phosphorylated cellulose fiber can be effectively increased.

  Here, the initial water content of the reaction system is the water content immediately after mixing the cellulose fiber and the phosphorylating agent necessary for the phosphorylation reaction in the phosphorylation reaction step, and substantially before the phosphorylation reaction starts. Is the water content of the mixture. The initial water content of the reaction system can be calculated from the water content of various components that are first mixed in the phosphorylation reaction step. For example, in the phosphorylation reaction step, when only the cellulose fiber and the phosphorylating agent are mixed, the initial water content of the reaction system can be calculated from the water content of the cellulose fiber and the water content of the phosphorylating agent. . Further, in the phosphorylation reaction step, when the cellulose fiber, the phosphorylating agent, and the solvent are mixed, or when the cellulose fiber is in the form of a slurry dispersed in the solvent, the water content of the cellulose fiber and the phosphorylating agent The initial water content of the reaction system can be calculated from the water content contained in and the water content of the solvent. Furthermore, when the cellulose fibers are mixed as a cellulose-containing material containing hemicellulose and the like, the initial water content can be calculated by calculating the water content of the cellulose-containing material and the water content of other components such as a phosphorylating agent. .

  The initial water content of the reaction system may be less than 40% by mass, preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, 5 The content is more preferably not more than mass%, particularly preferably not more than 3.5 mass%, and most preferably not more than 1 mass%. By setting the initial water content of the reaction system within the above range, the rate of introduction of phosphate groups during the phosphorylation reaction can be increased, and the production efficiency of phosphorylated cellulose fibers can be increased.

In the present invention, the cellulose fibers can be phosphorylated by, for example, performing a phosphorylation reaction of a cellulose-containing substance containing cellulose fibers. The cellulose-containing material may be composed of cellulose fibers, but may contain other components such as polysaccharides in which two or more monosaccharides are bonded by glycoside bonds, in addition to the cellulose fibers. Examples of monosaccharides include glucose, galactose, mannose, fructose, xylose and the like. Polysaccharides also include disaccharides and oligosaccharides in which two of these monosaccharides are linked. Examples of polysaccharides other than cellulose fibers include hydroxyethyl cellulose, methyl hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, hemicellulose and the like. In addition, as the above-mentioned other components, components other than polysaccharides derived from raw materials such as pulp may be contained.
In the present embodiment, the cellulose-containing material used in the phosphorylation reaction step preferably contains, for example, 75% by mass or more of cellulose fibers, more preferably 80% by mass or more, and further preferably 85% by mass or more. preferable. This makes it possible to more effectively improve the production efficiency of the phosphorylated cellulose fiber. On the other hand, the upper limit of the content of the cellulose fibers contained in the cellulose-containing material is not particularly limited, and may be 100% by mass, for example. In addition, as the cellulose-containing material, for example, pulp described later can be mentioned.

  The method for producing a phosphorylated cellulose fiber can further include a defibration treatment step after the phosphorylation reaction step, for example. By passing through such a defibration treatment step, the phosphorylated cellulose fibers are miniaturized, and fibrous cellulose having a fiber width of 1000 nm or less (fine fibrous cellulose) can be obtained.

<Phosphorylation reaction step>
The phosphorylation reaction step is a step of introducing a phosphoric acid group or a substituent derived from a phosphoric acid group (sometimes simply referred to as a phosphoric acid group) into the cellulose fiber. The phosphoric acid group is a divalent functional group corresponding to phosphoric acid from which a hydroxyl group has been removed. Specifically, it is a group represented by —PO ₃ H ₂ . Substituents derived from a phosphoric acid group include substituents such as a group obtained by polycondensing a phosphoric acid group, a salt of a phosphoric acid group, and a phosphoric acid ester group. It may be a group.

In the present invention, the phosphoric acid group or the substituent derived from the phosphoric acid group may be a substituent represented by the following formula (1).

In the formula (1), a, b, m and n each independently represent an integer (where a=b×m); α ⁿ (n=1 or more and n or less) and α′ are independent of each other. Represents R or OR. 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 aromatic group, or a derivative group thereof; β is a monovalent or higher cation composed of an organic substance or an inorganic substance.

  The raw material of cellulose fiber (hereinafter, also referred to as fiber raw material) is not particularly limited, but it is preferable to use pulp because it is easily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of the wood pulp include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), oxygen bleaching kraft. Examples include chemical pulp such as pulp (OKP). Further, semi-chemical pulp such as semi-chemical pulp (SCP), chemi-groundwood pulp (CGP), mechanical pulp such as ground wood pulp (GP), thermomechanical pulp (TMP, BCTMP), etc. are mentioned, but are not particularly limited. Examples of the non-wood pulp include cotton-based pulp such as cotton linter and cotton lint, non-wood-based pulp such as hemp, straw and bagasse, cellulose isolated from ascidian and seaweed, chitin, chitosan and the like, but are not particularly limited. . Examples of the deinked pulp include deinked pulp made from waste paper, but are not particularly limited. The pulp of this embodiment may be used alone or as a mixture of two or more kinds. Among the above pulps, wood pulp containing cellulose and deinked pulp are preferable from the viewpoint of easy availability. Among the wood pulps, the chemical pulp is preferable in that it has a high cellulose ratio and can obtain long fibrous cellulose having a high degree of polymerization. Of these, kraft pulp and sulfite pulp are most preferably selected. If fine fibrous cellulose having a high degree of polymerization is used, high viscosity tends to be obtained.

  In the phosphorylation reaction step, it is carried out by reacting the cellulose fiber with at least one compound selected from a compound having a phosphoric acid group and a salt thereof (hereinafter, also referred to as “phosphorylating agent” or “compound A”). You can Such a phosphorylating agent may be mixed with dry or wet cellulose fibers in the form of powder or aqueous solution. As another example, a phosphoric acid powder or an aqueous solution may be added to a slurry of cellulose fibers. That is, the phosphorylation reaction step includes at least a step of mixing the cellulose fiber and the phosphorylating agent.

  It is more preferable that the phosphorylation reaction step includes a step of mixing the cellulose fiber, the phosphorylating agent, and the solvent. Here, the solvent may be a solvent contained in the slurry of cellulose fibers, or may be a solvent added separately from the cellulose fibers or the cellulose fiber slurry. The water content of the solvent is preferably less than 40% by mass, more preferably 30% by mass or less, further preferably 20% by mass or less, further preferably 10% by mass or less, It is particularly preferably 5% by mass or less, more preferably 3.5% by mass or less, and most preferably 1% by mass or less. Among them, the solvent is particularly preferably an organic solvent, and most preferably composed of only the organic solvent.

  The organic solvent used in the phosphorylation reaction step is dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethylsulfoxide (DMSO). ), dioxane and urea. Among them, the organic solvent is preferably at least one selected from dimethylformamide (DMF), dimethylsulfoxide (DMSO) and urea. As the organic solvent, only one kind of the above-mentioned organic solvent may be used, or an organic solvent obtained by mixing two or more kinds may be used. In this case, it is preferable to mix urea with the organic solvent. Urea is used as an organic solvent in the phosphorylation reaction step, but may function as a phosphorylating agent described later.

  The phosphorylation reaction step can be performed by reacting a cellulose fiber with a phosphorylating agent, and this reaction is the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “compound B”). You may go down.

  As an example of the method of allowing the compound A to act on the cellulose fiber in the coexistence of the compound B, a method of mixing the powder or the aqueous solution of the compound A and the compound B to the dry or wet cellulose fiber can be mentioned. Another example is a method of adding powders or aqueous solutions of Compound A and Compound B to a slurry of cellulose fibers. Among these, since the reaction is highly uniform, a method of adding an aqueous solution of the compound A and the compound B to the cellulose fiber in a dry state, or a method of adding a powder or an aqueous solution of the compound A and the compound B to the cellulose fiber in a wet state. The method is preferred. Further, the compound A and the compound B may be added simultaneously or separately. Alternatively, the compound A and the compound B to be tested in the reaction may be first added as an aqueous solution, and the excessive chemical solution may be removed by pressing. The form of the cellulose fiber is preferably cotton or thin sheet, but is not particularly limited.

  The phosphorylating agent (compound A) is at least one selected from compounds having a phosphoric acid group and salts thereof. Examples of the phosphorylating agent include lithium salts of phosphoric acid, sodium salts of phosphoric acid, potassium salts of phosphoric acid, ammonium salts of phosphoric acid, dehydrated condensed phosphoric acid, phosphoric anhydride, phosphoric acid and the like. Among them, the phosphorylating agent is preferably at least one selected from dehydrated condensed phosphoric acid, phosphoric anhydride, and phosphoric acid. As the phosphoric acid, those having various purities can be used, and for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. Orthophosphoric acid can be obtained, for example, by reacting phosphorus pentoxide with phosphoric acid. Specifically, it can be obtained by slowly adding 85% phosphoric acid to diphosphorus pentoxide in an ice bath. The dehydrated condensed phosphoric acid is phosphoric acid converted into an inorganic polymer by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of phosphoric anhydride include diphosphorus pentoxide and the like.

  It is preferable to use the phosphorylating agent (Compound A) as an aqueous solution because the homogeneity of the reaction is enhanced and the efficiency of introducing the phosphate group is further enhanced. The pH of the aqueous solution of the phosphorylating agent (Compound A) is not particularly limited, but it is preferably 7 or less because the efficiency of introducing the phosphate group is high, and pH 3 or more and pH 7 or less from the viewpoint of suppressing hydrolysis of pulp fiber. Is more preferable. The pH of the aqueous solution of the compound A may be adjusted by, for example, using a compound having an acid group and a compound having an alkalinity among the compounds having a phosphoric acid group and changing the amount ratio. The pH of the aqueous solution of the phosphorylating agent (Compound A) may be adjusted by adding an inorganic alkali or an organic alkali to a compound having a phosphoric acid group and showing an acidity.

  The addition amount of the phosphorylating agent (Compound A) to the fiber raw material is not particularly limited, but when the addition amount of the phosphorylating agent (Compound A) is converted into the phosphorus atom amount, the addition amount of the phosphorus atom to the fiber raw material (absolute dry mass) Is preferably 0.5% by mass or more and 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and most preferably 2% by mass or more and 30% by mass or less. When the amount of phosphorus atoms added to the fiber raw material is within the above range, the yield of phosphorylated cellulose fibers can be further improved. By adjusting the amount of phosphorus atoms added to the fiber raw material to 100% by mass or less, the effect of improving the yield and the cost can be balanced. On the other hand, the yield can be increased by adjusting the amount of phosphorus atoms added to the fiber raw material to the above lower limit or more.

  Examples of the compound B used in this embodiment include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea and 1-ethylurea.

  Like the compound A, the compound B is preferably used as an aqueous solution. Further, it is preferable to use an aqueous solution in which both the compound A and the compound B are dissolved because the uniformity of the reaction is enhanced. The addition amount of the compound B to the fiber raw material (absolute dry mass) 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 100% by mass or more and 350% by mass. It is more preferable that the amount is 150% by mass or more and 300% by mass or less.

  In addition to the compounds A and B, amides or amines may be included in the reaction system. Examples of the amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, triethylamine is known to work particularly as a good reaction catalyst.

  In the present embodiment, for example, the phosphorylation reaction step may be a step of phosphorylating a cellulose-containing material containing cellulose fibers. In this case, the phosphorylation reaction step includes a step of mixing, for example, a cellulose-containing material, a solvent, compound A, and optionally compound B. As the cellulose-containing material, for example, the fiber raw materials exemplified above can be used.

  The phosphorylation reaction step preferably has a step of further heating (hereinafter, also referred to as a heat treatment step). As the heat treatment temperature in the heat treatment step, it is preferable to select a temperature at which the phosphate group can be efficiently introduced while suppressing the thermal decomposition or hydrolysis reaction of the cellulose fiber. Specifically, it is preferably 50° C. or higher and 300° C. or lower, more preferably 100° C. or higher and 250° C. or lower, and further preferably 130° C. or higher and 200° C. or lower. Further, a vacuum dryer, an infrared heating device, or a microwave heating device may be used for heating.

  During the heat treatment, while the cellulose fiber slurry to which the compound A is added contains water, if the time for which the cellulose fibers are allowed to stand is prolonged, the compound A dissolved in water molecules and the water molecules moves to the fiber raw material surface with drying. To do. Therefore, the concentration of the compound A in the fiber raw material may be uneven, and the phosphoric acid group may not be uniformly introduced into the fiber surface. In order to suppress the occurrence of uneven concentration of the compound A in the fiber raw material due to drying, a very thin sheet-shaped fiber raw material is used, or the fiber raw material and the compound A are heated or dried under reduced pressure while kneading or stirring the fiber raw material and the compound A. Just take the method.

  The heating device used for the heat treatment is preferably a device that can always discharge the water held by the slurry and the water generated by the addition reaction of the fibers such as phosphate groups to the hydroxyl groups of the fiber to the outside of the system, for example, a blower type oven. Etc. are preferred. If water in the device system is constantly discharged, in addition to suppressing the hydrolysis reaction of the phosphoric acid ester bond, which is the reverse reaction of phosphoric acid esterification, it is also possible to suppress the acid hydrolysis of sugar chains in the fiber. Therefore, fine fibers having a high degree of polymerization can be obtained.

  Although the time of the heat treatment is affected by the heating temperature, it is preferably 1 second or more and 300 minutes or less and more preferably 1 second or more and 60 minutes or less after the water is substantially removed from the fiber raw material slurry. It is preferably 10 seconds or more and 1500 seconds or less. In the present invention, by introducing the heating temperature and the heating time in appropriate ranges, the amount of phosphate groups introduced can be kept within the preferred range.

  The amount of the phosphate group introduced into the cellulose fibers is preferably 0.1 mmol/g or more and 3.65 mmol/g or less, more preferably 0.14 mmol/g or more and 3.5 mmol/g or less, and 0.2 mmol/g. It is more preferably g or more and 3.2 mmol/g or less, particularly preferably 0.4 mmol/g or more and 3.0 mmol/g or less, and most preferably 0.6 mmol/g or more and 2.5 mmol/g or less. When the amount of the phosphate group introduced is within the above range, it is possible to facilitate the micronization of the cellulose fibers when the phosphatized cellulose fibers are subjected to the defibration treatment, and to enhance the stability of the microfibrous cellulose.

  The amount of phosphate groups introduced into the cellulose fibers can be measured by the conductivity titration method. Specifically, the amount introduced can be measured by treating the slurry obtained after the phosphorylation reaction step with an ion exchange resin and then determining the change in electrical conductivity while adding an aqueous sodium hydroxide solution. In addition, you may perform the said measurement using the phosphating cellulose fiber which performed the defibration process. When the method for producing a phosphorylated cellulose fiber of the present invention includes a defibration treatment step, the introduction amount of the phosphate group may be measured using the slurry obtained after the defibration treatment step. When the manufacturing method of 1 does not include a defibration process step, a defibration process may be performed before the measurement.

  In conductivity titration, the addition of alkali gives the curve shown in FIG. At first, the electrical conductivity is sharply reduced (hereinafter, referred to as "first region"). After that, the conductivity starts to slightly increase (hereinafter, referred to as “second region”). After that, the increment of conductivity increases (hereinafter, referred to as “third region”). That is, three areas appear. Of these, the amount of alkali required in the first region is equal to the amount of strong acidic groups in the slurry used for titration, and the amount of alkali required in the second region is equal to the amount of weak acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid groups undergo condensation, apparently weak acidic groups are lost, and the amount of alkali required in the second region is smaller than the amount of alkali required in the first region. On the other hand, since the amount of strongly acidic group is the same as the amount of phosphorus atom regardless of the presence or absence of condensation, simply the amount of introduced phosphate group (or amount of phosphate group) or the introduced amount of substituent group (or amount of substituent group) When said, it means the amount of strongly acidic groups. That is, the amount of alkali (mmol) required in the first region of the curve shown in FIG. 1 is divided by the solid content (g) in the slurry to be titrated to obtain the amount of introduced substituent (mmol/g).

  The method for producing phosphorylated cellulose fibers of the present invention is also characterized in that the phosphorylation reaction rate is high in the heat treatment step. For example, in the heat treatment step, when heating at 140° C., the phosphorylation reaction rate from the start of heating to the time of 60 minutes is preferably 0.018 mmol/g·min or more, and 0.020 mmol/g It is more preferably g·min or more, further preferably 0.022 mmol/g·min or more. In the present invention, the initial phosphorylation reaction rate from the start of heating to the elapse of a predetermined time is sufficiently high, whereby the energy efficiency in the production process of phosphorylated cellulose fibers can be increased.

  In the heat treatment step, when heating is performed at 140° C., the phosphorylation reaction rate from the start of heating to the time of 60 minutes can be calculated by the following method. First, the amount of phosphate group introduced at each time of 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60 minutes from the start of heating by the method described above. taking measurement. Next, the vertical axis represents the amount of introduced phosphate group (mmol/g) and the horizontal axis represents the reaction time (min), and the obtained data is plotted in a graph. An approximate straight line is created from the plotted graph, and the slope of the approximate straight line is defined as the reaction rate a (mmol/g·min).

  The specific viscosity of the cellulose-containing material containing cellulose fibers before the phosphorylation reaction step measured according to Tappi T230 is set to ∨1, and the cellulose-containing material containing the cellulose fibers obtained in the phosphorylation reaction step (hereinafter referred to as phosphorylated cellulose (Also referred to as inclusions), where the specific viscosity measured according to Tappi T230 is ∨2, the value of ∨2/∨1 is preferably 0.74 or more, more preferably 0.80 or more. , 0.81 or more is more preferable. The value of ∨2/∨1 is preferably 1.5 or less. The present invention is characterized in that the decrease in specific viscosity of the phosphorylated cellulose-containing product is small even after the phosphorylation reaction step, and the cellulose-containing product thus obtained exhibits excellent thickening properties. You can The cellulose-containing material preferably contains, for example, 75% by mass or more of cellulose fibers, more preferably 80% by mass or more, and further preferably 85% by mass or more. The cellulose-containing material may be composed of cellulose fibers, or may contain other components such as the above-mentioned polysaccharides.

The specific viscosity of the cellulose-containing material and the phosphorylated cellulose-containing material can be measured by the following method according to Tappi T230. First, the viscosity of the slurry in which the cellulose-containing material before phosphorylation or the phosphorylated cellulose-containing material is dispersed in the dispersion medium (η ₁ ) and the blank viscosity measured only in the dispersion medium (η ₀ ) are measured. To do. Then, the specific viscosity (η _sp ) and the intrinsic viscosity ([η]) are calculated according to the following formulas.
η _sp =(η ₁ /η ₀ )-1
[Η]=η _sp /(c(1+0.28×η _sp ))
Here, c in the formula represents the concentration of the cellulose-containing material or the phosphorylated cellulose-containing material at the time of viscosity measurement.

  The specific viscosity of the cellulose-containing material before phosphorylation is preferably 8.0 or more, more preferably 9.0 or more, and further preferably 10.0 or more. Further, the specific viscosity of the phosphorylated cellulose-containing material is preferably 8.0 or more, more preferably 8.5 or more, and further preferably 8.8 or more.

  When the degree of polymerization of the cellulose-containing material before the phosphorylation reaction step is DPa and the degree of polymerization of the phosphorylated cellulose-containing material obtained in the phosphorylation reaction step is DPb, the value of DPb/DPa is 0.92 or more. Preferably, it is preferably 0.93 or more, more preferably 0.94 or more. The value of DPb/DPa is preferably 1.5 or less. The present invention is characterized in that the decrease in the degree of polymerization of the phosphorylated cellulose-containing product after the phosphorylation reaction step is small. It is presumed that this is because the hydrolysis of the cellulose-containing material is suppressed in the phosphorylation reaction step.

The degree of polymerization of the cellulose-containing material and the phosphorylated cellulose-containing material can be measured according to Tappi T230. First, the specific viscosity (η _sp ) and the intrinsic viscosity ([η]) are calculated by the method described above. Then, the degree of polymerization (DP) is calculated from the following formula.
DP=1.75×[η]
Since such a degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as a “viscosity average degree of polymerization”.

  The degree of polymerization of the cellulose-containing material before phosphorylation is preferably 500 or more, more preferably 600 or more, further preferably 800 or more, particularly preferably 900 or more. The degree of polymerization of the phosphorylated cellulose-containing material is preferably 500 or more, more preferably 600 or more, further preferably 800 or more, and particularly preferably 870 or more.

  The above-mentioned phosphorylation reaction step may be performed at least once, but may be repeated a plurality of times. In the present invention, since the phosphorylation reaction rate is high and the phosphorylation efficiency is enhanced, it is possible to reduce the number of phosphorylation reaction steps. For example, the number of phosphorylation reaction steps is preferably 1 or more and 3 or less, and may be 1 or more. In the present invention, a sufficient amount of phosphoric acid groups can be introduced into cellulose fibers even when the number of phosphorylation reaction steps is small.

<Alkali treatment step>
The method for producing a phosphorylated cellulose fiber of the present invention includes a phosphorylation reaction step and may further include a defibration treatment step. When the method for producing a phosphorylated cellulose fiber includes a defibration treatment step, it is preferable to provide an alkali treatment step between the phosphorylation reaction step and the defibration treatment step described below. The method of alkali treatment is not particularly limited, and examples thereof include a method of immersing phosphorylated cellulose fibers in an alkaline solution. In addition, what is provided to the said alkali process may be the phosphorylated cellulose containing material obtained by the phosphorylation reaction process.

  The alkaline compound contained in the alkaline solution is not particularly limited, but may be an inorganic alkaline compound or an organic alkaline compound. The solvent in the alkaline solution may be either water or an organic solvent. The solvent is preferably a polar solvent (water or a polar organic solvent such as alcohol), and may be an aqueous solvent. Further, among the alkaline solutions, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is particularly preferable because of its high versatility.

The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5°C or higher and 80°C or lower, more preferably 10°C or higher and 60°C or lower.
The immersion time in the alkali solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less.
The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less, based on the absolute dry mass of the phosphorylated cellulose fiber. Is more preferable.

  In order to reduce the amount of the alkaline solution used in the alkali treatment step, the phosphorylated cellulose fiber may be washed with water or an organic solvent before the alkali treatment step. After the alkali treatment, in order to improve the handling property, it is preferable to wash the alkali-treated phosphorylated cellulose fibers with water or an organic solvent before the defibration treatment step.

<Acid treatment step>
When the method for producing phosphorylated cellulose fibers of the present invention includes a defibration treatment step, an acid treatment step may be provided between the phosphorylation reaction step and the defibration treatment step described below. Further, the phosphorylation reaction step, the acid treatment, the alkali treatment and the defibration treatment may be performed in this order.

  The method of acid treatment is not particularly limited, and examples thereof include a method of immersing the phosphorylated cellulose fiber in an acidic liquid containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less. As the acid contained in the acidic liquid, for example, an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, boric acid and the like. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid and the like. Of these, hydrochloric acid is preferably used as the acid. Moreover, what is provided to the said acid treatment may be the phosphorylated cellulose-containing material obtained by the phosphorylation reaction step.

The temperature of the acid solution in the acid treatment step is not particularly limited, but is preferably 5°C or higher and 80°C or lower, more preferably 10°C or higher and 60°C or lower.
The immersion time in the acid solution in the acid treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less.
The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less based on the absolute dry mass of the phosphorylated cellulose fiber. Is more preferable.

<Defibration process>
The phosphorylated cellulose fiber may be defibrated in a defibration process step, for example. In the defibration treatment step, usually, a defibration treatment device is used to defibrate the fibers to obtain a fine fibrous cellulose-containing slurry, but the treatment device and the treatment method are not particularly limited. The defibration treatment may be a phosphorylated cellulose-containing material obtained in the phosphorylation reaction step.

  As the defibration treatment device, a high-speed defibration machine, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill and the like can be used. Alternatively, as the defibration treatment device, use a device such as 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, for wet pulverization. You can also The defibration processing device is not limited to the above. Preferred defibration treatment methods include a high-speed defibrator, a high-pressure homogenizer, and an ultrahigh-pressure homogenizer, which are less affected by grinding media and less likely to cause contamination.

  At the time of the defibration treatment, it is preferable to dilute the phosphorylated cellulose or the phosphorylated cellulose-containing material alone or in combination with water and the organic solvent to form a slurry, but it is not particularly limited. As the dispersion medium, a polar organic solvent can be used in addition to water. Preferred polar organic solvents include alcohols, ketones, ethers, dimethylsulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), etc., but are not particularly limited. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, and t-butyl alcohol. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether and tetrahydrofuran (THF). The dispersion medium may be one type or two or more types. Further, the dispersion medium may contain a solid content other than the phosphorylated cellulose or the phosphorylated cellulose-containing material, such as urea having hydrogen bonding property.

  In the present invention, the fibrillation treatment may be performed after the phosphorylated cellulose fiber is concentrated and dried. In this case, the method of concentration and drying is not particularly limited, and examples thereof include a method of adding a condensing agent to a slurry containing phosphorylated cellulose fibers, a commonly used dehydrator, a press, and a method of using a dryer. In addition, known methods, for example, methods described in WO2014/024876, WO2012/107642, and WO2013/121086 can be used. Further, the concentrated phosphorylated cellulose fiber may be formed into a sheet. The sheet may be crushed and defibrated.

  As a device used for crushing the phosphorylated cellulose fiber, a high-speed defibrator, a grinder (stone mill type crusher), a high pressure homogenizer, an ultra-high pressure homogenizer, a high pressure collision type crusher, a ball mill, a bead mill, a disc type refiner, a conical A wet milling device such as a refiner, a twin-screw kneader, a vibration mill, a homomixer under high speed rotation, an ultrasonic disperser, or a beater can also be used, but is not particularly limited. Further, the treatment condition is not particularly limited as long as a preferable degree of polymerization is obtained.

  In the present invention, it becomes easy to control the average degree of polymerization of the phosphorylated cellulose fiber within a preferable range by appropriately selecting the raw material and the production conditions of the phosphorylated cellulose fiber. Such manufacturing conditions are not particularly limited, for example, adjusting the conditions in the phosphate group introduction step, adjusting the defibration processing conditions in the defibration processing step, or selecting the type of manufacturing apparatus And so on. For example, in the case of using a defibration treatment device (Clearmix-2.2S, manufactured by M Technique Co., Ltd.), defibration treatment may be performed for 10 minutes or more and 60 minutes or less under conditions of 10,000 rotations/minute or more and 21500 rotations/minute or less preferable.

(Cellulose-containing material)
<Cellulose-containing material containing fine fibrous cellulose>
The present invention also relates to a cellulose-containing material containing fine fibrous cellulose. Here, the viscosity of the slurry obtained by diluting the cellulose-containing material with water so that the solid content concentration becomes 0.4% by mass under the conditions of 3 rpm and a liquid temperature of 25° C. by a B-type viscometer is , 14500 mPa·s or more. The viscosity measurement time is 3 minutes. The viscosity of the slurry is more preferably 15000 mPa·s or more, and further preferably 15500 mPa·s or more. The upper limit of the viscosity of the slurry is not particularly limited, but can be, for example, 40,000 mPa·s. The cellulose-containing material may or may not contain other components such as hemicellulose, as described above.

As a method for adjusting the viscosity of the slurry obtained by diluting a cellulose-containing material containing fine fibrous cellulose with water so that the solid content concentration becomes 0.4% by mass, for example, phosphorus in fine fibrous cellulose is used. Introducing an acid group may be mentioned. That is, the cellulose-containing material of the present invention preferably contains a cellulose fiber having a phosphoric acid group and having a fiber width of 1000 nm or less.
In the present embodiment, as described above, for example, the defibration step can be performed on the cellulose-containing material containing the phosphorylated cellulose fibers. As a result, a cellulose-containing material containing cellulose fibers (fine fibrous cellulose) having a fiber width of 1000 nm or less obtained by making the phosphorylated cellulose fibers finer is obtained. The amount of phosphoric acid groups in the cellulose fiber having a phosphoric acid group and having a fiber width of 1000 nm or less is preferably 0.1 mmol/g or more.

  The average fiber width of the fine fibrous cellulose is 1000 nm or less as observed with an electron microscope. The average fiber width is preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and still more preferably 2 nm or more and 10 nm or less, but is not particularly limited. When the average fiber width of the fine fibrous cellulose is less than 2 nm, the fine fibrous cellulose is dissolved in water as a cellulose molecule, so that the physical properties (strength, rigidity, dimensional stability) as the fine fibrous cellulose tend not to be easily exhibited. . The fine fibrous cellulose is, for example, a single fibrous cellulose having a fiber width of 1000 nm or less.

  The measurement of the fiber width of the fine fibrous cellulose by observation with an electron microscope is performed as follows. An aqueous suspension of fine fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less was prepared, and this suspension was cast on a hydrophilized carbon film-covered grid to obtain a sample for TEM observation. To do. When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times or 50000 times depending on the width of the constituent fibers. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.

(1) A straight line X is drawn at an arbitrary position in the observed image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.

  The width of the fiber intersecting the straight line X and the straight line Y is visually read from the observed image satisfying the above conditions. In this way, three or more sets of images of the surface portion that do not at least overlap are observed, and the width of the fiber intersecting the straight line X and the straight line Y is read for each image. In this way, the fiber width of at least 20 fibers×2×3=120 fibers is read. The average fiber width of the fine fibrous cellulose (simply referred to as “fiber width”) is the average value of the fiber width thus read.

  The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and particularly preferably 0.1 μm or more and 600 μm or less. By setting the fiber length within the above range, it is possible to suppress the destruction of the crystalline region of the fine fibrous cellulose, and it is possible to set the slurry viscosity of the fine fibrous cellulose in an appropriate range. The fiber length of the fine fibrous cellulose can be determined by image analysis using TEM, SEM, or AFM.

  The fine fibrous cellulose preferably has a type I crystal structure. Here, the fact that the fine fibrous cellulose has the I-type crystal structure can be identified in the diffraction profile obtained from the wide-angle X-ray diffraction photograph using CuKα (λ=1.5418Å) monochromated with graphite. Specifically, it can be identified because it has typical peaks at two positions near 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less.

  The proportion of I-type crystal structure in the fine fibrous cellulose (crystallinity) is not particularly limited in the present invention, but is preferably 30% or more, more preferably 50% or more, further preferably 70%. That is all. In this case, more excellent performance can be expected in terms of heat resistance and low linear thermal expansion coefficient. The crystallinity is determined by measuring the X-ray diffraction profile and using the pattern in a conventional manner (Seagal et al., Textile Research Journal, Vol. 29, page 786, 1959).

  The amount of the phosphate group introduced into the fine fibrous cellulose is preferably 0.1 mmol/g or more and 3.65 mmol/g or less, more preferably 0.14 mmol/g or more and 3.5 mmol/g or less, and 0.1. It is more preferably 2 mmol/g or more and 3.2 mmol/g or less, particularly preferably 0.4 mmol/g or more and 3.0 mmol/g or less, and most preferably 0.6 mmol/g or more and 2.5 mmol/g or less. When the amount of the phosphate group introduced is within the above range, good thickening properties can be exhibited when used as a thickener, for example. The amount of phosphate groups introduced into the fine fibrous cellulose can be measured, for example, in the same manner as the amount of phosphate groups introduced into the cellulose fibers described above.

  The cellulose-containing material containing fine fibrous cellulose may contain, for example, an organic solvent component. This organic solvent component is derived from the organic solvent mixed in the reaction system when phosphorylating the cellulose-containing material. In the method for producing phosphorylated cellulose fiber of the present invention, in the phosphorylation reaction step, it is preferable to use an organic solvent, and a part of this organic solvent may be detected also from the cellulose-containing product as the final product. is there.

<Cellulose-containing material containing cellulose fiber>
In the present specification, the cellulose fibers include fine fibrous cellulose and fibrous cellulose having a fiber width of more than 1000 nm. The present invention may relate to a cellulose-containing material containing a cellulose fiber. That is, the present invention may relate to a cellulose-containing material containing non-micronized cellulose fibers. It is preferable that such a cellulose-containing material contains a cellulose fiber having a phosphoric acid group of 0.1 mmol/g or more, and the specific viscosity measured according to Tappi T230 of the cellulose-containing material is 8.0 or more. .. The specific viscosity is more preferably 9.0 or more, further preferably 10.0 or more. The specific viscosity of the cellulose-containing material containing the cellulose fibers can be measured by the above-described method according to Tappi T230.

  The degree of polymerization obtained by measuring according to Tappi T230 of a cellulose-containing material containing cellulose fibers is preferably 870 or more. The degree of polymerization of the cellulose-containing material can be calculated according to Tappi T230 by the method described above.

  The cellulose-containing material containing cellulose fibers may include, for example, an organic solvent component. This organic solvent component is derived from the organic solvent mixed in the reaction system when phosphorylating the cellulose-containing material.

(Slurry containing fine fibrous cellulose)
The present invention may relate to a slurry containing fine fibrous cellulose. Since the fine fibrous cellulose-containing slurry contains the fine fibrous cellulose described above, it can exhibit high viscosity and further has high transparency.

  The viscosity of the slurry sample obtained by diluting the fine fibrous cellulose-containing slurry with water to a solid concentration of 0.4 mass% is preferably 14500 mPa·s or more, and 15000 mPa·s or more. More preferably, it is more preferably 15500 mPa·s or more. The upper limit of the viscosity of the slurry sample is not particularly limited, but can be, for example, 40,000 mPa·s.

  The viscosity of a slurry sample obtained by diluting a fine fibrous cellulose-containing slurry with water to a solid content concentration of 0.4% by mass was measured using a B-type viscometer (Analog viscometer T-LVT manufactured by BLOOKFIELD). Can be measured. The measurement conditions are a liquid temperature of 25° C., a rotation speed of 3 rpm, and a measurement time of 3 minutes.

The haze of the fine fibrous cellulose-containing slurry (fine fibrous cellulose concentration 0.2% by mass) is preferably 20% or less, more preferably 15% or less, and further preferably 10% or less. .. When the haze of the fine fibrous cellulose-containing slurry is within the above range, it means that the fine fibrous cellulose-containing slurry has high transparency and the fine fibrous cellulose is finely refined. In such a slurry containing fine fibrous cellulose, the unique function of fine fibrous cellulose is exhibited.
Here, the haze of the slurry containing fine fibrous cellulose (fine fibrous cellulose concentration of 0.2% by mass) is obtained by adding fine fibrous cellulose to a glass cell for liquid (Fujiwara Seisakusho, MG-40, reverse optical path) having an optical path length of 1 cm. It is a value measured by using a haze meter (HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K 7136 after containing the contained slurry. The zero point measurement is performed with ion-exchanged water contained in the glass cell.

(Use)
The fine fibrous cellulose produced by the method for producing a phosphorylated cellulose fiber of the present invention is suitable for use as a light-transmissive substrate for various display devices, various solar cells, and the like. Further, it is also suitable for use as substrates of electronic devices, members of home appliances, window materials for various vehicles and buildings, interior materials, exterior materials, packaging materials, and the like. Further, in addition to threads, filters, woven fabrics, cushioning materials, sponges, abrasives, etc., it is also suitable for applications where the sheet itself is used as a reinforcing material.
Further, the viscosity of the fine fibrous cellulose-containing slurry is high, and from the viewpoint of utilizing such characteristics, the fibrous cellulose of the present invention is used as a thickener in various applications (for example, foods, cosmetics, cement, paints, inks, etc. Additives, etc.).

  The features of the present invention will be described more specifically below with reference to Examples and Comparative Examples. The materials, usage amounts, ratios, processing contents, processing procedures, and the like 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 limitedly interpreted by the following specific examples.

<Pulp solid content concentration measuring method>
2 g of a pulp sheet or a fluffed raw material obtained by fluffing a pulp sheet was placed in a weighing bottle having a known mass, and dried for 16 hours by a dryer (manufactured by Yamato Scientific Co., Ltd., blower low temperature dryer DK600). After drying, the container was capped in a dryer, placed in a desiccator and allowed to cool. After cooling, in order to remove the pressure difference between the inside and outside of the container, the lid of the container was opened halfway and quickly closed again, and the mass after drying was measured. Using the measured weight, the solid content concentration of pulp was calculated from the following formula (1).
W _dm =m ₁ ÷m ₀ ×100 (1)
W _dm : Drying rate (%) expressed as mass fraction
m ₀ : mass before drying (g)
m ₁ : Mass after drying to constant weight (g)

<Method for adjusting orthophosphoric acid>
In an ice bath, 254 parts by mass of 85% phosphoric acid (manufactured by Kanto Chemical Co., Inc.) was slowly added dropwise to 100 parts by mass of diphosphorus pentoxide (manufactured by Kanto Chemical Co., Ltd.) to prepare orthophosphoric acid.

<Phosphorylation reaction step>
(Example A-1)
As a cellulose-containing material, a pulp sheet made by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 208 g/m ² sheet shape, Canadian standard freeness (CSF) 700 ml which is disaggregated and measured according to JIS P 8121) is used. Used as raw material. 32 parts by mass of orthophosphoric acid, 100 parts by mass of urea (manufactured by Kanto Chemical Co., Inc.), and 150 parts by mass of N,N-dimethylformamide (DMF) (manufactured by Kanto Chemical Co., Ltd.) were added to 100 parts by mass of pulp sheet (absolutely dry mass). , Heat-dried at 140° C. for 30 minutes with an explosion-proof dryer (SPH-200, manufactured by ESPEC), phosphoric acid groups were introduced into the cellulose fibers in the pulp, and phosphorylated cellulose-containing material A was obtained.

<Cleaning and alkali treatment process>
Ion-exchanged water was poured into the obtained phosphorylated cellulose-containing material A, and the mixture was stirred, uniformly dispersed, and then filtered and dehydrated to obtain a dehydrated sheet. By repeating the operation, the surplus chemical solution was sufficiently washed out. Then, it was diluted with ion-exchanged water so that the concentration of the cellulose-containing material was 2% by mass, and 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a pulp slurry having a pH of 12±0.2. After that, the pulp slurry is dehydrated to obtain a dehydrated sheet, and then ion-exchanged water is poured again, and the mixture is stirred and uniformly dispersed, and then filtered and dehydrated to obtain a dehydrated sheet. The sodium oxide was thoroughly washed off to obtain a phosphorylated cellulose-containing material B.

<Machine processing>
Ion-exchanged water was added to the obtained phosphorylated cellulose-containing material B to obtain a suspension having a solid content concentration of 0.5% by mass. This suspension is defibrated for 30 minutes using a defibration treatment device (CLEARMIX-2.2S, manufactured by M Technique Co., Ltd.) under the condition of 21,500 rotations/minute to give a defibration pulp slurry (fine fibrous form). A cellulose-containing slurry) was obtained.

(Example A-2)
A defibrated pulp slurry (slurry containing fine fibrous cellulose) was obtained in the same manner as in Example A-1 except that 300 parts by mass of urea was used instead of 150 parts by mass of N,N-dimethylformamide.

(Example A-3)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) was prepared in the same manner as in Example A-1, except that 85 parts by mass of 85% phosphoric acid (manufactured by Kanto Chemical Co., Inc.) was used instead of 32 parts by mass of orthophosphoric acid. ) Got.

(Comparative Example A-1)
Instead of 150 parts by mass of N,N-dimethylformamide, 150 parts by mass of ion-exchanged water was used, and the heating and drying time was 50 minutes, in the same manner as in Example A-1. A cellulose-containing slurry) was obtained.

(Evaluation)
<Measurement of Amount of Phosphate Group Introduced (Amount of Phosphate Group)>
The amount of phosphate group introduced was measured by the conductivity titration method. Specifically, it is refined by the defibration process step, after treating the resulting fine fibrous cellulose-containing slurry with an ion exchange resin, by determining the change in electrical conductivity while adding an aqueous sodium hydroxide solution, The amount introduced was measured.
In the treatment with an ion exchange resin, a 1/10 volume of a strongly acidic ion exchange resin (Amber Jet 1024; Organo Co., Ltd., already conditioned) is added to a slurry containing 0.2% by mass of fine fibrous cellulose and shaken for 1 hour. Processed. Then, it was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry. In the titration using alkali, a change in the value of electric conductivity exhibited by the slurry was measured while adding a 0.1 N sodium hydroxide aqueous solution to the slurry containing fine fibrous cellulose after ion exchange.

In this conductivity titration, the addition of alkali gives the curve shown in FIG. At first, the electrical conductivity is sharply reduced (hereinafter, referred to as "first region"). After that, the conductivity starts to slightly increase (hereinafter, referred to as “second region”). After that, the increment of conductivity increases (hereinafter, referred to as “third region”). That is, three areas appear. Of these, the amount of alkali required in the first region is equal to the amount of strong acidic groups in the slurry used for titration, and the amount of alkali required in the second region is equal to the amount of weak acidic groups in the slurry used for titration. Will be equal.
The amount of alkali (mmol) required in the first region of the curve shown in FIG. 1 was divided by the solid content (g) in the slurry to be titrated to obtain the amount of phosphate group introduction (mmol/g).

<How to obtain reaction rate>
The reaction rate was measured as follows for each of Examples A-1 to A-3 and Comparative Example A-1. First, phosphoric acid group introduction was performed in the same manner as in the phosphorylation reaction step described above except that the heating and drying time was 60 minutes. At that time, the phosphate group introduction amount was measured every 10 minutes from 10 minutes to 60 minutes. The vertical axis represents the amount of introduced phosphate group (mmol/g) and the horizontal axis represents the reaction time (min), and the obtained data was plotted in a graph. An approximate straight line was created from the plotted graph, and the slope of the approximate straight line was used as the reaction rate a (mmol/g·min).

  As can be seen from Table 1, in the example, the heating and drying time was shorter than that in the comparative example, but a sufficient amount of phosphate group was introduced. The phosphorylation reaction rate was also fast. That is, it was found that the production efficiency of the phosphorylated fine fibrous cellulose can be more effectively increased in the examples.

(Example B-1)
As a cellulose-containing material, a pulp sheet made by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 208 g/m ² sheet shape, Canadian standard freeness (CSF) 700 ml which is disaggregated and measured according to JIS P 8121) is used. It was fluffed to obtain fluffed pulp, which was used as a raw material. 100 parts by mass of fluffed pulp (absolute dry mass), 167 parts by mass of orthophosphoric acid, 1000 parts by mass of urea (manufactured by Kanto Chemical Co., Inc.), and 1000 parts by mass of N,N-dimethylformamide (DMF) (manufactured by Kanto Chemical Co., Ltd.) The mixture was added to a round bottom flask and heated under reflux at 150° C. for 15 minutes to introduce a phosphoric acid group into the cellulose fibers in the pulp to obtain a phosphorylated cellulose-containing material C. Then, a defibrated pulp slurry (fine fibrous cellulose-containing slurry) was obtained in the same manner as in Example A-1 described above.

(Example B-2)
A defibrated pulp slurry (slurry containing fine fibrous cellulose) was obtained in the same manner as in Example B-1 except that 196 parts by mass of 85% phosphoric acid was used instead of 167 parts by mass of orthophosphoric acid.

(Example B-3)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) was prepared in the same manner as in Example B-1 except that dimethyl sulfoxide (DMSO) (manufactured by Kanto Chemical Co., Inc.) was used instead of N,N-dimethylformamide. Obtained.

(Example B-4)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) was obtained in the same manner as in Example B-1 except that urea was used instead of N,N-dimethylformamide.

(Comparative Example B-1)
The same as Example B-1 except that N,N-dimethylformamide (1000 parts by mass) and urea (1000 parts by mass) were replaced by N,N-dimethylformamide (433 parts by mass), urea (433 parts by mass), and ion-exchanged water (1133 parts by mass). Then, a defibrated pulp slurry (slurry containing fine fibrous cellulose) was obtained.

(Comparative Example B-2)
A defibrated pulp slurry (slurry containing fine fibrous cellulose) was obtained in the same manner as Comparative Example A-1.

(Evaluation)
Fluffed pulp (pre-phosphorylated cellulose-containing material) tested in the phosphorylation reaction step obtained in Examples B-1 to B-4 and Comparative Examples B-1 and B-2, obtained after the washing alkali treatment step The phosphorylated cellulose fibers (containing phosphorylated cellulose) thus obtained were tested, and the specific viscosity and the degree of polymerization were measured by the methods described below. Further, the defibrated pulp slurry after the mechanical treatment was tested, and the amount of introduced phosphate groups was measured by the same method as described above in <Measurement of amount of introduced phosphate groups (amount of phosphate groups)>. Further, the defibrated pulp slurry after mechanical treatment was tested and the viscosity was measured by the method described below.

<Measurement of specific viscosity and degree of polymerization>
The specific viscosity and the degree of polymerization were measured according to Tappi T230. That is, the viscosity (η ₁ ) measured by dispersing the pre-phosphorylated cellulose-containing material or the phosphorylated cellulose-containing material to be measured in a dispersion medium, and the blank viscosity (η ₀ ) measured only in the dispersion medium are After the measurement, the specific viscosity (η _sp ) and the intrinsic viscosity ([η]) were measured according to the following formulas.
η _sp =(η ₁ /η ₀ )-1
[Η]=η _sp /(c(1+0.28×η _sp ))
Here, c in the formula represents the concentration of the cellulose-containing material or the phosphorylated cellulose-containing material at the time of viscosity measurement.
Furthermore, the degree of polymerization (DP) in the present invention was calculated from the following formula.
DP=1.75×[η]
Since this degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as a “viscosity average degree of polymerization”.

<Measurement of viscosity of slurry containing fine fibrous cellulose>
Regarding the viscosity of the fine fibrous cellulose-containing slurry, the fine fibrous cellulose-containing slurry was diluted so that the solid concentration of the fine fibrous cellulose-containing slurry was 0.4% by mass, and then stirred with a disperser at 1500 rpm for 5 minutes. The viscosity of the obtained slurry was measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions were 3 rpm and a liquid temperature of 25°C.

  As can be seen from Table 2, in the examples, it was found that the phosphorylated cellulose fiber-containing slurry after the phosphorylation reaction had a high specific viscosity and that a high solution viscosity could be exhibited even after the fine fibrous cellulose was formed.

Claims (4)

A cellulose-containing material containing a cellulose fiber having a fiber width of 1000 nm or less,
The viscosity of the slurry obtained by diluting the cellulose-containing material with water so that the solid content concentration becomes 0.4 mass% has a viscosity of 14500 mPa·s measured by a B-type viscometer at 3 rpm and a liquid temperature of 25°C. Cellulose-containing material of s or more.   A cellulose-containing material containing 0.1 mmol/g or more of a cellulose fiber having a phosphate group and having a specific viscosity of 8.0 or more measured according to Tappi T230.   The cellulose-containing material according to claim 9, which has a degree of polymerization of 870 or more, which is obtained by measurement according to Tappi T230.   The cellulose-containing material according to claim 9 or 10, which contains an organic solvent component.