JP6977798B2 - Method for Producing Phosphorylated Cellulose Fiber and Cellulose Containing Material - Google Patents

Description

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

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

Further, as the fibrous cellulose, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. Fine fibrous cellulose can be used as a constituent raw material for sheets and complexes. It is known that when fine fibrous cellulose is used, the contact points between the fibers are remarkably increased, so that the tensile strength and the like are greatly improved. In addition, fine fibrous cellulose is also being considered for use in applications such as thickeners.

Fine fibrous cellulose can be produced by mechanically treating conventional cellulose fibers, but the cellulose fibers are strongly bonded to each other by hydrogen bonds. Therefore, a huge amount of energy is required to obtain fine fibrous cellulose by simply performing mechanical treatment.

It is known that pretreatment such as chemical treatment and 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 cationic group, a phosphoric acid group, etc.) is introduced into a hydroxyl group on the surface of cellulose by chemical treatment, electrical repulsion between ions occurs and the ion is hydrated. By doing so, the dispersibility in an aqueous solvent is significantly improved. Therefore, the energy efficiency of miniaturization is higher than that in the case of no chemical treatment.

For example, Patent Documents 1 and 2 disclose methods for producing phosphorylated fine fibrous cellulose and phosphorylated fine fibrous cellulose in which a phosphoric acid group forms an ester with a hydroxyl group of cellulose. In Patent Document 2, it is studied that the phosphorylation reaction step is carried out in the presence of urea and that the phosphorylation reaction step is carried out a plurality of times to increase the amount of phosphorylation group introduced.

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

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

As a result of diligent studies to solve the above problems, the present inventors have produced phosphorylated cellulose fibers by setting the initial water content of the reaction system in the step of phosphorylating cellulose fibers to a predetermined value or less. We have found that it can increase efficiency.
Specifically, the present invention has the following configurations.

[1] A method for producing a phosphorylated cellulose fiber, which comprises a step of phosphorylating the 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 a step of mixing a cellulose fiber, an organic solvent, and a phosphorylating agent.
[3] Organic solvents include dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dioxane and The method for producing a phosphorylated cellulose fiber according to [2], which comprises 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 dehydration condensed phosphoric acid, anhydrous phosphoric acid and phosphoric acid.
[5] The phosphorylation step includes a heating step, and when heated at 140 ° C. in the heating step, the phosphorylation reaction rate from the start of heating to the elapse of 60 minutes is 0.018 mmol / g. -The method for producing a phosphorylated cellulose fiber according to any one of [1] to [4], which is min or more.
[6] The specific viscosity measured according to Tappi T230 of the cellulose-containing material before the phosphorylation step is set to ∨1, and Tappi T230 of the cellulose-containing material obtained in the phosphorylation step is set. The method for producing a phosphorylated cellulose fiber according to any one of [1] to [5], wherein the value of ∨2 / ∨1 is 0.74 or more, where ∨2 is the specific viscosity measured according to the above.
[7] The phosphorylation according to any one of [1] to [6], wherein the specific viscosity measured according to Tappi T230 of the cellulose-containing material obtained in the step of phosphorylation is 8.0 or more. Method for producing cellulose fiber.
[8] A cellulose-containing material containing cellulose fibers having a fiber width of 1000 nm or less, which is obtained by diluting the cellulose-containing material with water so that the solid content concentration becomes 0.4% by mass, at 3 rpm. A cellulose-containing material having a viscosity of 14500 mPa · s or more as measured by a B-type viscometer under the condition of a liquid temperature of 25 ° C.
[9] A cellulose-containing substance containing a cellulose fiber having a phosphoric acid group of 0.1 mmol / g or more and having a specific viscosity of 8.0 or more as measured according to Tappi T230.
[10] The cellulose-containing substance according to [9], wherein the degree of polymerization obtained by measuring according to Tappi T230 is 870 or more.
[11] The cellulose-containing substance 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 NaOH dropped and the electrical conductivity with respect to a fiber raw material having a phosphoric acid group.

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

(Manufacturing method of phosphorylated cellulose fiber)
The present invention relates to a method for producing a phosphorylated cellulose fiber, which comprises a step of phosphorylating the cellulose fiber (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 less than a predetermined value. In the present invention, it is possible to reduce the energy cost required for producing the phosphorylated cellulose fiber. In addition, the phosphorylation reaction time in the phosphorylation reaction step can be shortened. This makes it possible to increase the production efficiency of the phosphorylated cellulose fiber.
The phosphorylation reaction of cellulose fibers proceeds in the absence of substantially water. However, conventionally, it has been considered that the solvent for the cellulose fibers in the phosphorylation reaction step is preferably an aqueous solvent in order to increase the solubility of the phosphorylating agent and facilitate 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, the start time of the phosphorylation reaction of the cellulose fiber is accelerated, and further, the phosphorylation group introduction rate during the phosphorylation reaction is accelerated. It was a success. In particular, since the rate of the phosphorylation reaction can be increased from the start of the phosphorylation reaction to the lapse of a predetermined time, 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 fibers and the phosphorylating agent required for the phosphorylation reaction in the phosphorylation reaction step, and is substantially before the phosphorylation reaction starts. The water content of the mixture of. The initial water content of the reaction system can be calculated from the water content of various components initially mixed in the phosphorylation reaction step. For example, when only the cellulose fiber and the phosphorylating agent are mixed in the phosphorylation reaction step, 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 of the fiber and the water content of the solvent. Further, when the cellulose fiber is mixed as a cellulose-containing substance containing hemicellulose or the like, the water content of the cellulose-containing material and the water content of other components such as a phosphorifying agent can be calculated to obtain the initial water content. ..

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, still more preferably 10% by mass or less. It is more preferably 5% by mass or less, particularly preferably 3.5% by mass or less, and most preferably 1% by mass or less. By setting the initial water content of the reaction system within the above range, the rate of introduction of phosphoric acid groups during the phosphorylation reaction can be increased, and the production efficiency of phosphorylated cellulose fibers can be increased.

In the present invention, cellulose fibers can be phosphorylated, for example, by carrying out a phosphorylation reaction of a cellulose-containing material containing cellulose fibers. The cellulose-containing substance may be composed of cellulose fibers, but may also contain other components such as polysaccharides in which two or more monosaccharides are bound by glycosidic bonds, in addition to the cellulose fibers. Examples of the monosaccharide include glucose, galactose, mannose, fructose, xylose and the like. Polysaccharides also include disaccharides and oligosaccharides in which two of these monosaccharides are bound. Examples of polysaccharides other than cellulose fibers include hydroxyethyl cellulose, methyl hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, hemicellulose and the like. Further, 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 to be subjected to 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 fiber contained in the cellulose-containing material is not particularly limited and may be, for example, 100% by mass. Examples of the cellulose-containing substance include pulp described later.

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

<Phosphorylation reaction process>
The phosphorylation reaction step is a step of introducing a phosphate group or a substituent derived from a phosphate group (sometimes referred to simply as a phosphate group) into a cellulose fiber. The phosphoric acid group is a divalent functional group obtained by removing the hydroxyl group from phosphoric acid. 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 decomposing a phosphoric acid group, a salt of a phosphoric acid group, and a phosphoric acid ester group, and even if it is an ionic substituent, it is a nonionic substituent. It may be a group.

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

In equation (1), a, b, m and n each independently represent an integer (where a = b × m); α ⁿ (an integer of 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 chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched chain hydrocarbon group. , An aromatic group, or an inducing group thereof; β is a monovalent or higher cation consisting of an organic or inorganic substance.

The raw material for the cellulose fiber (hereinafter, also referred to as a fiber raw material) is not particularly limited, but it is preferable to use pulp because it is easily available and inexpensive. Examples of the pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), and oxygen bleached craft. Examples thereof include chemical pulp such as pulp (OKP). Examples thereof include semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), mechanical pulp such as crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), but are not particularly limited. Examples of the non-wood pulp include cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, cellulose isolated from sea squirts and seaweed, chitin, chitosan and the like, but are not particularly limited. .. Examples of the deinked pulp include deinked pulp made from recycled paper, but the pulp is not particularly limited. As the pulp of this embodiment, one of the above may be used alone, or two or more of them may be mixed and used. Among the above pulps, wood pulp containing cellulose and deinked pulp are preferable in terms of availability. Among wood pulps, chemical pulp has a large cellulose ratio and is preferable in that long fine fibrous cellulose having a high degree of polymerization can be obtained. Of these, kraft pulp and sulfite pulp are most preferably selected. High viscosity tends to be obtained when fine fibrous cellulose having a high degree of polymerization is used.

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

Further, the phosphorylation reaction step more preferably includes a step of mixing the cellulose fiber, the phosphorylating agent, and the solvent. Here, the solvent may be a solvent contained in the cellulose fiber slurry, or may be a solvent added separately from the cellulose fiber 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, still more 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 only an organic solvent.

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

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

As an example of the method of allowing the compound A to act on the cellulose fibers in the coexistence of the compound B, there is a method of mixing the powder or the aqueous solution of the compound A and the compound B with the cellulose fibers in a dry state or a wet state. Another example is a method of adding a powder or an aqueous solution of compound A and compound B to a slurry of cellulose fibers. Of these, since the reaction uniformity is high, a method of adding an aqueous solution of compound A and compound B to a dry cellulose fiber, or a method of adding a powder or an aqueous solution of compound A and compound B to a wet cellulose fiber. The method is preferred. Further, compound A and compound B may be added at the same time or separately. Further, the compound A and the compound B to be tested in the reaction may be added as an aqueous solution first, and the excess chemical solution may be removed by pressing. The form of the cellulose fiber is preferably cotton-like or thin sheet-like, but is not particularly limited.

The phosphorylating agent (Compound A) is at least one selected from a compound having a phosphoric acid group and a salt thereof. Examples of the phosphoric acid agent include lithium salt of phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, ammonium salt of phosphoric acid, dehydration condensed phosphoric acid, anhydrous phosphoric acid, phosphoric acid and the like. Among them, the phosphoric acid agent is preferably at least one selected from dehydration-condensed phosphoric acid, anhydrous phosphoric acid and phosphoric acid. As the phosphoric acid, those having various puritys can be used, and for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Orthophosphoric acid can be obtained, for example, by reacting diphosphorus pentoxide with phosphoric acid. Specifically, it can be obtained by slowly dropping 85% phosphoric acid with respect to diphosphorus pentoxide in an ice bath. The dehydration-condensed phosphoric acid is a phosphoric acid that has become an inorganic polymer by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of anhydrous phosphoric acid include diphosphorus pentoxide.

The phosphorylating agent (Compound A) is preferably used as an aqueous solution because the uniformity of the reaction is improved and the efficiency of introducing the phosphate group is higher. The pH of the aqueous solution of the phosphorylating agent (Compound A) is not particularly limited, but is preferably 7 or less because the efficiency of introducing a phosphate group is high, and pH 3 or more and pH 7 or less from the viewpoint of suppressing hydrolysis of pulp fibers. Is even more preferable. The pH of the aqueous solution of the compound A may be adjusted, for example, by using a compound having a phosphoric acid group in combination with an acidic compound and an alkaline compound, and changing the amount ratio thereof. 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 an acid group and exhibiting acidity.

The amount of the phosphorylating agent (Compound A) added to the fiber raw material is not particularly limited, but when the amount of the phosphorylating agent (Compound A) added is converted into the phosphorus atomic weight, the amount of the phosphorus atom added 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 atom added to the fiber raw material is within the above range, the yield of phosphorylated cellulose fiber can be further improved. By adding the phosphorus atom to the fiber raw material in an amount of 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 setting the addition amount of the phosphorus atom to the fiber raw material to be equal to or higher than the above lower limit value.

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

Compound B is preferably used as an aqueous solution like compound A. Further, since the uniformity of the reaction is enhanced, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved. The amount of compound B added 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 or less. It is more preferably 150% by mass or more, and particularly preferably 300% by mass or less.

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

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

The phosphorylation reaction step preferably includes 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 and hydrolysis reaction of the cellulose fibers. 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, and a microwave heating device may be used for heating.

During the heat treatment, when the cellulose fiber slurry containing the compound A contains water and the cellulose fibers are allowed to stand for a long time, the water molecules and the dissolved compound A move to the surface of the fiber raw material as it dries. do. Therefore, the concentration of the compound A in the fiber raw material may be uneven, and the introduction of the phosphoric acid group to the fiber surface may not proceed uniformly. In order to suppress the occurrence of uneven concentration of 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 compound A are kneaded or stirred with a kneader or the like and dried by heating or under reduced pressure. You can take the method.

The heating device used for the heat treatment is preferably a device that can always discharge the water retained by the slurry and the water generated by the addition reaction of the fiber such as a phosphoric acid group to the hydroxyl group to the outside of the device system. Etc. are preferable. If the water in the apparatus system is constantly discharged, not only the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphate esterification, can be suppressed, but also the acid hydrolysis of the sugar chain in the fiber can be suppressed. , Fine fibers having a high degree of polymerization can be obtained.

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

The amount of the phosphoric acid group introduced into the cellulose fiber 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 or less. 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. By setting the amount of the phosphoric acid group introduced within the above range, it is possible to facilitate the miniaturization of the cellulose fibers and enhance the stability of the fine fibrous celluloses when the phosphorylated cellulose fibers are subjected to the defibration treatment.

The amount of the phosphoric acid group introduced into the cellulose fiber can be measured by the conductivity titration method. Specifically, the introduced amount 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. The above measurement may be performed using a phosphorylated cellulose fiber that has been subjected to a defibration treatment. When the method for producing a phosphorylated cellulose fiber of the present invention includes a defibration treatment step, the amount of phosphoric acid groups introduced may be measured using the slurry obtained after the defibration treatment step, and the phosphorylated cellulose fiber may be measured. If the production method of No. 1 does not include the defibration treatment step, the defibration treatment may be performed before the above measurement.

In the conductivity titration, the addition of alkali gives the curve shown in FIG. Initially, the electrical conductivity drops sharply (hereinafter referred to as the "first region"). After that, the conductivity begins to increase slightly (hereinafter referred to as "second region"). After that, the increment of conductivity increases (hereinafter referred to as "third region"). That is, three regions appear. Of these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is equal to the amount of weakly acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid group causes condensation, the weakly acidic group is apparently lost, and the amount of alkali required for the second region is smaller than the amount of alkali required for 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, it is simply referred to as the amount of phosphoric acid group introduced (or the amount of phosphoric acid group) or the amount of substituent introduced (or the amount of substituent). When it is 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 substituent introduced (mmol / g).

The method for producing a phosphorylated cellulose fiber 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 heated at 140 ° C., the phosphorylation reaction rate from the start of heating to the elapse of 60 minutes is preferably 0.018 mmol / g · min or more, preferably 0.020 mmol / min. It is more preferably g · min or more, and 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 lapse of a predetermined time is sufficiently high, whereby the energy efficiency in the manufacturing process of the phosphorylated cellulose fiber can be enhanced.

In the heat treatment step, when heating is performed at 140 ° C., the phosphorylation reaction rate from the start of heating to the elapse of 60 minutes can be calculated by the following method. First, the amount of phosphoric acid group introduced at each time of 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60 minutes from the start of heating is calculated by the above method. Measure. Next, the vertical axis represents the amount of phosphate group introduced (mmol / g) and the horizontal axis represents the reaction time (min), and the obtained data are plotted on 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 was set to ∨1 as measured according to Tappi T230, and the cellulose-containing material containing the cellulose fibers obtained in the phosphorylation reaction step (hereinafter referred to as phosphorylated cellulose). When the specific viscosity measured according to Tappi T230 (also referred to as an inclusion) is ∨2, the value of ∨2 / ∨1 is preferably 0.74 or more, and more preferably 0.80 or more. , 0.81 or more is more preferable. Further, the value of ∨2 / ∨1 is preferably 1.5 or less. The present invention is characterized in that the specific viscosity of the phosphorylated cellulose-containing material does not decrease even after undergoing the phosphorylation reaction step, and the cellulose-containing material thus obtained exhibits excellent thickening properties. Can be done. 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 viscosities of the cellulose-containing material and the phosphorylated cellulose-containing material can be measured by the following methods according to Tappi T230. First, the viscosity of the slurry in which the cellulose-containing substance or the phosphorylated cellulose-containing substance before phosphorylation is dispersed in a dispersion medium (referred to as η ₁ ) and the blank viscosity measured only in the dispersion medium (referred to as η ₀ ) are measured. 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 indicates the concentration of the cellulose-containing substance or the phosphorylated cellulose-containing substance at the time of measuring the viscosity.

The specific viscosity of the cellulose-containing material before phosphorylation is preferably 8.0 or more, more preferably 9.0 or more, and even more 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. It is preferably 0.93 or more, more preferably 0.94 or more, and even more preferably 0.94 or more. Further, the value of DPb / DPa is preferably 1.5 or less. The present invention is characterized in that the degree of polymerization of the phosphorylated cellulose-containing material does not decrease much after the phosphorylation reaction step. It is presumed that this is because the hydrolysis of the cellulose-containing substance is suppressed in the phosphorylation reaction step.

The degree of polymerization of the cellulose-containing substance and the phosphorylated cellulose-containing substance can be measured according to Tappi T230. First, the specific viscosity (η _sp ) and the intrinsic viscosity ([η]) are calculated by the above-mentioned method. 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 is sometimes 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, and 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 phosphorylation reaction step as described above 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 time. In the present invention, a sufficient amount of phosphorylation group can be introduced into the cellulose fiber even when the number of phosphorylation reaction steps is small.

<Alkaline treatment process>
The method for producing a phosphorylated cellulose fiber of the present invention includes a phosphorylation reaction step and can further include a defibration treatment step. When the method for producing 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 later. The method of alkaline treatment is not particularly limited, and examples thereof include a method of immersing phosphorylated cellulose fibers in an alkaline solution. It should be noted that what is subjected to the alkali treatment may be a phosphorylated cellulose-containing substance obtained by the phosphorylation reaction step.

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, a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution 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, and more preferably 10 ° C. or higher and 60 ° C. or lower.
The immersion time in the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and 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 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less with respect to 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 alkaline treatment step, the phosphorylated cellulose fibers may be washed with water or an organic solvent before the alkaline treatment step. After the alkali treatment, it is preferable to wash the alkali-treated phosphorylated cellulose fibers with water or an organic solvent before the defibration treatment step in order to improve the handleability.

<Acid treatment process>
When the method for producing a phosphorylated cellulose fiber 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 later. 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 phosphorylated cellulose fibers 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, and more preferably 5% by mass or less. As the acid contained in the acidic solution, 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, chloric 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. Above all, it is preferable to use hydrochloric acid as the acid. Further, what is subjected to the acid treatment may be a phosphorylated cellulose-containing substance 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, and 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, and 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 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less with respect to the absolute dry mass of the phosphorylated cellulose fiber. Is more preferable.

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

As the defibration processing device, 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 and the like can be used. Alternatively, as the defibration processing device, a wet pulverizing device such as a disc type refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater shall be used. You can also. The defibration processing apparatus is not limited to the above. Preferred defibration treatment methods include a high-speed defibrator, a high-pressure homogenizer, and an ultra-high-pressure homogenizer, which are less affected by crushed 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 substance alone or in combination with water and an 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, but are not limited to, alcohols, ketones, ethers, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butyl alcohol and the like. Examples of the ketone include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether and tetrahydrofuran (THF). The dispersion medium may be one kind or two or more kinds. Further, the dispersion medium may contain a solid content other than phosphorylated cellulose or a phosphorylated cellulose-containing substance, for example, urea having a hydrogen-bonding property.

In the present invention, the phosphorylated cellulose fiber may be concentrated and dried, and then the defibration treatment may be performed. In this case, the method of concentration and drying is not particularly limited, and examples thereof include a method of adding a concentrating agent to a slurry containing phosphorylated cellulose fibers, a method of using a commonly used dehydrator, a press, and a dryer. Also known methods, such as those described in WO2014 / 024876, WO2012 / 107642, and WO2013 / 121086, can be used. Further, the concentrated phosphorylated cellulose fiber may be made into a sheet. The sheet can also be crushed for defibration treatment.

Devices used for crushing phosphorylated cellulose fibers include high-speed crushers, grinders (stone mill type crushers), high-pressure homogenizers, ultra-high pressure homogenizers, high-pressure collision type crushers, ball mills, bead mills, disc-type refiners, and conicals. Wet pulverizers such as refiners, twin-screw kneaders, vibration mills, homomixers under high-speed rotation, ultrasonic dispersers, beaters, etc. can also be used, but are not particularly limited. Further, the treatment conditions are not particularly limited as long as the conditions are such that a preferable degree of polymerization can be obtained.

In the present invention, the average degree of polymerization of the phosphorylated cellulose fiber can be easily controlled 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, but for example, the conditions in the phosphate group introduction step may be adjusted, the defibration treatment conditions in the defibration treatment step may be adjusted, and the type of manufacturing equipment may be selected. And so on. For example, when a defibration processing device (Clearmix-2.2S manufactured by M-Technique Co., Ltd.) is used, the defibration processing can be performed for 10 minutes or more and 60 minutes or less under the 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 substance with water so that the solid content concentration becomes 0.4% by mass is measured by a B-type viscometer under the conditions of 3 rpm and a liquid temperature of 25 ° C. , 14500 mPa · s or more. The viscosity measurement time is 3 minutes. The viscosity of the slurry is more preferably 15,000 mPa · s or more, and even more 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. As described above, the cellulose-containing material may or may not contain other components such as hemicellulose.

As a method for keeping the viscosity of the slurry obtained by diluting the cellulose-containing substance containing fine fibrous cellulose with water so that the solid content concentration becomes 0.4% by mass, for example, phosphorus is added to fine fibrous cellulose. Introducing an acid group can 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, the defibration step can be performed on a cellulose-containing material containing, for example, 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, in which phosphorylated cellulose fibers are refined, can be obtained. The amount of phosphoric acid group in the cellulose fiber having a phosphoric acid group 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, 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, it is dissolved in water as a cellulose molecule, so that the physical properties (strength, rigidity, dimensional stability) of the fine fibrous cellulose tend to be difficult to develop. .. The fine fibrous cellulose is, for example, a single fibrous cellulose having a fiber width of 1000 nm or less.

The fiber width is measured by observing the fine fibrous cellulose with an electron microscope 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-coated grid to form a sample for TEM observation. do. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the constituent fibers. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.

(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly 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 with respect to the observation image satisfying the above conditions. In this way, at least three sets of images of the non-overlapping surface portions are observed, and the widths of the fibers intersecting the straight lines X and Y are read for each image. In this way, at least 20 fibers × 2 × 3 = 120 fibers are read. The average fiber width of the fine fibrous cellulose (sometimes simply referred to as "fiber width") is the average value of the fiber widths read in this way.

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, the destruction of the crystal region of the fine fibrous cellulose can be suppressed, and the slurry viscosity of the fine fibrous cellulose can be set within an appropriate range. The fiber length of the fine fibrous cellulose can be obtained by image analysis by TEM, SEM, or AFM.

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

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

The amount of the phosphoric acid 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. 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. By setting the amount of the phosphoric acid group introduced within the above range, good thickening properties can be exhibited, for example, when used as a thickener. The amount of the phosphoric acid group introduced into the fine fibrous cellulose can be measured in the same manner as the amount of the phosphoric acid group introduced into the cellulose fiber described above, for example.

Further, 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 substance. In the method for producing phosphorylated cellulose fiber of the present invention, it is preferable to use an organic solvent in the phosphorylation reaction step, and a part of this organic solvent may be detected from the cellulose-containing product which is the final product. be.

<Cellulose-containing material containing cellulose fiber>
In the present specification, the cellulose fiber includes 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 cellulose fibers. That is, the present invention may relate to a cellulose-containing material containing unrefined cellulose fibers. Such a cellulose-containing material preferably contains a cellulose fiber having a phosphoric acid group of 0.1 mmol / g or more, and the specific viscosity of the cellulose-containing material measured according to Tappi T230 is preferably 8.0 or more. .. The specific viscosity is more preferably 9.0 or more, and further preferably 10.0 or more. The specific viscosity of the cellulose-containing material containing the cellulose fiber can be measured by the above-mentioned method according to Tappi T230.

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

The cellulose-containing material containing cellulose fibers 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 substance.

(Slurry containing fine fibrous cellulose)
The present invention may relate to a fine fibrous cellulose-containing slurry. Since the fine fibrous cellulose-containing slurry contains the above-mentioned fine fibrous cellulose, 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 so as to have a solid content concentration of 0.4% by mass is preferably 14500 mPa · s or more, and preferably 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 may be, for example, 40,000 mPa · s.

The viscosity of the slurry sample obtained by diluting the fine fibrous cellulose-containing slurry with water so as to have a solid content concentration of 0.4% by mass is determined by 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, still more preferably 10% or less. .. The haze of the fine fibrous cellulose-containing slurry is in the above range, which means that the fine fibrous cellulose-containing slurry has high transparency and the fine fibrous cellulose is finely miniaturized. In such a fine fibrous cellulose-containing slurry, the unique function of the fine fibrous cellulose is exhibited.
Here, the haze of the fine fibrous cellulose-containing slurry (fine fibrous cellulose concentration 0.2% by mass) is formed on a liquid glass cell (manufactured by Fujiwara Seisakusho, MG-40, backlit path) having an optical path length of 1 cm. It is a value measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute) in accordance with JIS K 7136 with the contained slurry. The zero point measurement is performed with ion-exchanged water contained in the same 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 in light-transmitting substrates such as various display devices and various solar cells. It is also suitable for applications such as substrates for electronic devices, materials for home appliances, window materials for various vehicles and buildings, interior materials, exterior materials, and packaging materials. Further, it is suitable for applications such as threads, filters, woven fabrics, cushioning materials, sponges, abrasives, etc., as well as applications in which 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 can be used as a thickener for various uses (for example, foods, cosmetics, cements, paints, inks, etc.). Can be used as an additive, etc.).

Hereinafter, the features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

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

<Adjustment method of positive phosphoric 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., Inc.) to prepare positive phosphoric acid.

<Phosphorylation reaction process>
(Example A-1)
As a cellulose-containing substance, a pulp sheet made by Oji Paper (solid content 93% by mass, basis weight 208 g / m ² sheet, separated and measured according to JIS P 8121, Canadian standard drainage degree (CSF) 700 ml) was used. Used as a raw material. To 100 parts by mass of pulp sheet (absolute dry mass), 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., Inc.) are added. , Heat-dried at 140 ° C. for 30 minutes in an explosion-proof dryer (SPH-200, manufactured by ESPEC) to introduce a phosphoric acid group into the cellulose fibers in the pulp to obtain a phosphoric acid cellulose-containing substance A.

<Washing / alkali treatment process>
Ion-exchanged water was poured into the obtained phosphorylated cellulose-containing material A, and the mixture was stirred and uniformly dispersed, and then filtered and dehydrated to obtain a dehydrated sheet. By repeating the operation, the excess chemical solution was sufficiently washed away. Next, the pulp slurry having a pH of 12 ± 0.2 was obtained by diluting with ion-exchanged water so that the concentration of the cellulose-containing substance was 2% by mass and adding a 1N aqueous sodium hydroxide solution little by little while stirring. Then, after dehydrating this pulp slurry to obtain a dehydrated sheet, ion-exchanged water is poured again, and the pulp slurry is stirred and uniformly dispersed, and then filtered and dehydrated to obtain a dehydrated sheet. The sodium oxide was thoroughly washed away to obtain a cellulose phosphate-containing product B.

<Machine processing>
Ion-exchanged water was added to the obtained phosphorylated cellulose-containing material B to prepare a suspension having a solid content concentration of 0.5% by mass. This suspension is defibrated for 30 minutes under the condition of 21500 rpm using a defibration treatment device (Clearmix-2.2S manufactured by M-Technique) to defibrate pulp slurry (fine fibrous form). Cellulose-containing slurry) was obtained.

(Example A-2)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) 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 used in the same manner as in Example A-1 except that 85% phosphoric acid (manufactured by Kanto Chemical Co., Inc.) was used in place of 32 parts by mass of normal phosphoric acid. ) Was obtained.

(Comparative Example A-1)
The same as in Example A-1 except that 150 parts by mass of ion-exchanged water was used instead of 150 parts by mass of N, N-dimethylformamide and the heating and drying time was 50 minutes, the defibrated pulp slurry (fine fibrous form) was used. Cellulose-containing slurry) was obtained.

(evaluation)
<Measurement of introduction amount of phosphoric acid group (amount of phosphoric acid group)>
The amount of phosphoric acid group introduced was measured by the conductivity titration method. Specifically, it is refined by a defibration treatment step, the obtained fine fibrous cellulose-containing slurry is treated with an ion exchange resin, and then the change in electrical conductivity is obtained while adding an aqueous sodium hydroxide solution. The introduction amount was measured.
In the treatment with an ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) with a volume of 1/10 is added to a slurry containing 0.2% by mass fine fibrous cellulose and shaken for 1 hour. Processing was performed. Then, it was poured onto a mesh having an opening of 90 μm, and the resin and the slurry were separated. In the titration using alkali, the change in the electric conductivity value shown by the slurry was measured while adding a 0.1 N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing slurry after ion exchange.

In this conductivity titration, the addition of alkali gives the curve shown in FIG. Initially, the electrical conductivity drops sharply (hereinafter referred to as the "first region"). After that, the conductivity begins to increase slightly (hereinafter referred to as "second region"). After that, the increment of conductivity increases (hereinafter referred to as "third region"). That is, three regions appear. Of these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is equal to the amount of weakly 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 phosphoric acid group introduced (mmol / g).

<How to find the reaction rate>
The reaction rates of Examples A-1 to A-3 and Comparative Example A-1 were measured as follows. First, the phosphorylation group was introduced in the same manner as in the above-mentioned phosphorylation reaction step except that the heating and drying time was set to 60 minutes. At that time, the amount of phosphate group introduced was measured every 10 minutes from 10 minutes to 60 minutes. The vertical axis represents the amount of phosphate group introduced (mmol / g) and the horizontal axis represents the reaction time (min), and the obtained data are plotted on a graph. An approximate straight line was created from the plotted graph, and the slope of the approximate straight line was defined as the reaction rate a (mmol / g · min).

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

(Example B-1)
As a cellulose-containing substance, a pulp sheet made by Oji Paper (solid content 93% by mass, basis weight 208 g / m ² sheet, disassembled and measured according to JIS P 8121, Canadian standard drainage degree (CSF) 700 ml) was used. Fluffing treatment was performed to obtain fluffed pulp, which was used as a raw material. 167 parts by mass of orthophosphoric acid, 1000 parts by mass of urea (manufactured by Kanto Chemical Co., Inc.), 1000 parts by mass of N, N-dimethylformamide (DMF) (manufactured by Kanto Chemical Co., Inc.) in 100 parts by mass of fluffed pulp (absolute dry mass). The mixture was added to a round bottom flask and heat-circulated 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 substance C. Then, a defibrated pulp slurry (slurry containing fine fibrous cellulose) was obtained in the same manner as in Example A-1 described above.

(Example B-2)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) 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 normal phosphoric acid.

(Example B-3)
A defibrated pulp slurry (slurry containing fine fibrous cellulose) 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)
Same as Example B-1 except that instead of 1000 parts by mass of N, N-dimethylformamide and 1000 parts by mass of urea, 433 parts by mass of N, N-dimethylformamide, 433 parts by mass of urea, and 1133 parts by mass of ion-exchanged water were used. To obtain a defibrated pulp slurry (slurry containing fine fibrous cellulose).

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

(evaluation)
Fluffed pulp (cellulose-containing material before phosphorylation) 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 obtained phosphorylated cellulose fiber (phosphorylated cellulose-containing substance) was tested, and the specific viscosity and the degree of polymerization were measured by the method described later. In addition, the machine-treated defibrated pulp slurry was tested and the amount of phosphoric acid group introduced was measured by the same method as described in <Measurement of amount of phosphoric acid group introduced (phosphoric acid group amount)> described above. Further, the defibrated pulp slurry after the machine treatment was tested and the viscosity was measured by the method described later.

<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 measured by dispersing the prephosphoric cellulose-containing substance or the phosphorylated cellulose-containing substance to be measured in a _{dispersion medium (referred to as η 1} ) and the blank viscosity measured using only the dispersion medium (referred to as η ₀ ). 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 indicates the concentration of the cellulose-containing substance or the phosphorylated cellulose-containing substance at the time of measuring the viscosity.
Further, 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 the average degree of polymerization measured by the viscosity method, it is sometimes referred to as "viscosity average degree of polymerization".

<Measurement of viscosity of fine fibrous cellulose-containing slurry>
The viscosity of the fine fibrous cellulose-containing slurry was diluted so that the solid content concentration of the fine fibrous cellulose-containing slurry was 0.4% by mass, and then the mixture was stirred with a disperser at 1500 rpm for 5 minutes. The viscosity of the obtained slurry was measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). 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 specific viscosity of the phosphorylated cellulose fiber-containing slurry after the phosphorylation reaction was high, and that high solution viscosity could be exhibited even after the fine fibrous cellulose was formed.

Claims (5)

Phosphorylated cellulose fibers with a fiber width of 1000 nm or less and
At least one selected from dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dioxane and urea. It is a cellulose-containing substance containing
The viscosity of the slurry obtained by diluting the cellulose-containing substance with water so that the solid content concentration becomes 0.4% by mass is 14500 mPa. Cellulose-containing material that is s or more. The amount of phosphoric acid group contained in the phosphorylated cellulose fiber is 0.1 mmol / g or more , and is
The cellulose-containing product according to claim 1, wherein the specific viscosity measured according to Tappi T230 is 8.0 or more. The cellulose-containing product according to claim 1 or 2, wherein the degree of polymerization obtained by measuring according to Tappi T230 is 870 or more. The viscosity of the slurry obtained by diluting the cellulose-containing substance with water so that the solid content concentration becomes 0.4% by mass is 15600 mPa. The cellulose-containing substance according to any one of claims 1 to 3, which is s or more. The cellulose-containing substance according to any one of claims 1 to 4, wherein the phosphorylated cellulose fiber has a phosphate group amount of 0.73 mmol / g or more.

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