WO2020137012A1 - Method for manufacturing chemically modified cellulose fiber - Google Patents

Abstract

Through the present invention, a method for manufacturing a sulfuric-acid-esterified cellulose fiber having a cellulose-I-type crystal structure can be provided. The present invention provides a method for manufacturing a chemically modified cellulose fiber, including steps (a) and (b). Step (a): a step for adjusting the moisture content of cellulose fibers to 2% by mass to 200% by mass. Step (b): a step for treating the cellulose fibers with sulfamic acid and thereby reacting sulfamic acid and cellulose fibers, which are constituent elements of the cellulose fibers, and substituting a portion of hydroxyl groups of the cellulose with a substituent represented by structural formula (1) (where M in structural formula (1) represents a univalent to trivalent cation).

Description

Method for producing chemically modified cellulose fiber

The present invention relates to a method for producing a chemically modified cellulose fiber.

Cellulose fiber is used as an industrial raw material for foods, cosmetics, functional papers, resin reinforcements, etc. In addition, the chemically modified cellulose fiber obtained by chemically modifying the surface of the cellulose fiber can be easily dispersed in water, so that the range of application as an industrial raw material is widened and it is considered promising.

There is sulfated cellulose as chemically modified cellulose, and for example, there is particulate sulfated cellulose obtained by sulfate-esterifying cellulose using sulfuric acid anhydride as a sulfating reagent (for example, Patent Document 1). Further, there is a technique of producing a sulfated cellulose having a cellulose II type crystal structure with a degree of polymerization of 60 or less by using an aqueous sulfuric acid solution as a sulfating agent (for example, Patent Document 2).

However, conventionally, sulfuric acid having a high acidity or a high-concentration sulfuric acid aqueous solution has been used as a sulfating agent for sulfuric acid esterification of cellulose, and it is known that sulfamic acid is used for sulfuric acid esterification. Moreover, it is not known to defibrate the cellulose fibers together with the sulfuric acid esterification reaction.

JP, 2007-92034, A JP 2012-526156

An embodiment of the present invention aims to provide a novel method for producing a sulfated cellulose fiber.

（但し、式（１）中、Ｍは１～３価の陽イオンを表す。） The embodiment of the present invention relates to a method for producing a chemically modified cellulose fiber, which includes the following steps (a) and (b).
Step (a): Step of adjusting water content of cellulose fiber to 2% by mass or more and 200% by mass or less Step (b): Treatment of cellulose fiber with sulfamic acid to obtain sulfamic acid and constituent elements of the cellulose fiber. A step of reacting a certain cellulose fine fiber and substituting a part of hydroxyl groups of cellulose with a substituent represented by the following structural formula (1).

(However, in the formula (1), M represents a monovalent to trivalent cation.)

According to this embodiment, it is possible to provide a sulfated esterified cellulose fiber having a cellulose type I crystal structure.

Graphs plotting the introduction amount of sulfate groups hourly after the start of the reaction in Examples 1 to 4 and Comparative Examples 1 and 2.

The method for producing the chemically modified cellulose fiber according to the present embodiment,
Step (a): Step of adjusting the water content of the cellulose fiber to 2% by mass or more and 200% by mass or less (water content adjusting step)
Step (b): relates to a method for producing a sulfated cellulose fiber through a step (chemical modification step) of converting a cellulose fiber into a sulfuric acid ester by treating with sulfamic acid.

[Cellulose fiber]
Specific examples of the cellulose fiber (ie, cellulose raw material) used in the chemical modification step include plants (for example, wood, cotton, bamboo, hemp, jute, kenaf, agricultural land waste, cloth, pulp, recycled pulp, waste paper), animals ( Examples include those originating from ascidians), algae, microorganisms (for example, acetic acid bacteria), microbial products, and the like. Among these, plant-derived pulp is mentioned as a preferable raw material.

Examples of the pulp include chemical pulp (kraft pulp (KP), sulfite pulp (SP)), semi-chemical pulp (which is obtained by pulping a plant raw material chemically or mechanically, or a combination of both. SCP), chemi-ground pulp (CGP), chemi-mechanical pulp (CMP), groundwood pulp (GP), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermo-mechanical pulp (CTMP) are preferred. ..

Also, the cellulose fibers may be chemically modified within a range that does not impair the purpose of the present embodiment, that is, chemically modified pulp may be used. For example, a part or most of the hydroxyl groups present on the surface of the cellulose fiber or the surface of the cellulose fine fiber are esterified with acetic acid ester, nitric acid ester, methyl ether, hydroxyethyl ether, hydroxypropyl ether, hydroxybutyl ether, An etherified product containing carboxymethyl ether or cyanoethyl ether, or a TEMPO oxidation-treated pulp obtained by oxidizing primary hydroxyl groups can be included.

As the cellulose fiber, it is preferable to use one having a cellulose type I crystal and a crystallinity of 50% or more. The cellulose I-type crystallinity value of the cellulose fiber is more preferably 60% or more, and further preferably 70% or more. The upper limit of the cellulose type I crystallinity of the cellulose fiber is not particularly limited, but may be, for example, 98% or less, 95% or less, or 90% or less.

In the present specification, the crystallinity of cellulose is the cellulose I type crystallinity calculated by the Segal method from the diffraction intensity value by the X-ray diffraction method, and is defined by the following formula.
Cellulose type I crystallinity (%)=[(I _22.6 -I _18.5 )/I _22.6 ]×100
In the formula, I _22.6 is the diffraction intensity of the lattice plane (002 plane) (diffraction angle 2θ=22.6°) in X-ray diffraction, and I _18.5 is the diffraction intensity of the amorphous part (diffraction angle 2θ=18.5°). Indicates. The cellulose type I is a crystalline form of natural cellulose, and the cellulose type I crystallinity means the ratio of the amount of crystalline region in the whole cellulose.

The shape of the cellulose fiber used in the present embodiment is not particularly limited, but from the viewpoint of handling, a fiber shape, a sheet shape, a cotton shape, a powder shape, a chip shape, and a flake shape are preferable.

[Water content adjustment process]
In the water content adjusting step, the water content of the cellulose fiber is adjusted to 2% by mass or more and 200% by mass or less by adding a predetermined amount of water to the cellulose fiber or adjusting the humidity. The water content is 2% by mass or more and 200% by mass or less, preferably 2% by mass or more and 100% by mass or less, and more preferably 2% by mass or more and 50% by mass or less. When the water content is within the above range, it is preferable in that the reaction delay due to the inactivation of the sulfating agent by water and the balance of the appropriate cutting of the cellulose fiber due to the acid formation can be maintained, and in the commercial production, It is preferable from the viewpoint of reducing the amount of use of the sulfating agent, washing the reaction crude product after the sulfation reaction, and reducing labor related to operations such as removal of byproducts. The above water content is measured by the following method. That is, as a test piece, 1 to 2 g of cellulose fiber was weighed in a glass container with a lid, and the temperature was kept at 105°C ± 2°C. Dry with the lid of the container open, cover the glass container in the dryer after a predetermined time, put it in the desiccator and let it cool, then open the container lid halfway to remove the pressure difference inside and outside the container. Then, it is quickly closed again and the mass of the dried test piece is measured. By repeating this operation, the water content is calculated from the difference in mass of the test piece before and after drying when the test piece reaches a constant weight. The constant weight of the test piece means that the constant weight is reached when the difference between the two consecutive weighing values is 0.1% or less of the mass of the test piece before drying.

[Chemical modification process]
In the chemical modification step, the reaction between cellulose fibers and sulfamic acid (that is, sulfuric acid esterification reaction) can be performed by immersing the cellulose fibers in a chemical solution containing sulfamic acid. Further, it is an effective means to increase the contact efficiency between the chemical liquid and the cellulose fiber by operations such as stirring, mixing, and shaking by a known method, and it can be applied to the present invention.

The method of the chemical modification step is not particularly limited, but from the viewpoint of commercial production, for the purpose of increasing the reaction efficiency in the sulfation reaction of the present invention, it is a sulfating agent for the cellulose fiber raw material particularly limited in the present invention. A preferable embodiment is also a method of adding sulfamic acid in multiple stages, a method of changing the ratio of sulfamic acid and a solvent to perform a multi-stage reaction, a method of continuously changing the ratio of sulfamic acid and a solvent, and the like.

In the chemical modification reaction of cellulose fibers, at the initial stage of the reaction, the operation of promoting the breakage of hydrogen bonds between fibers peculiar to the cellulose raw material and the swelling of the cellulose fiber, and the operation of micronizing and defibrating fibers by mechanical force in parallel are It is rational in chemical modification reactions. Further, it is rational to increase the relative concentration of sulfamic acid as much as possible after the middle stage of the reaction to accelerate the reaction. In addition, the present invention particularly includes a hydrous cellulose raw material in a limited range also in view of suppressing the breakage of the cellulose fiber and the breakage of the molecular chain beyond the desired degree due to the mechanical force at the initial stage of the reaction due to the lubricity of water. It is valid.

In this embodiment, sulfamic acid is used as the sulfating agent. Sulfamic acid not only has a low cellulose solubility as compared with sulfuric acid anhydride or a sulfuric acid aqueous solution, but also has a low acidity, so that it can retain the degree of polymerization and can retain the crystallinity of cellulose fibers. Also, with respect to sulfuric acid and sulfuric acid aqueous solutions that have strong acidity and high corrosiveness, there is no limitation on handling, the corrosion effect of production equipment is small, and since it is not specified as a specific substance under the Air Pollution Control Act The load on the environment is small.

The amount of sulfamic acid used can be appropriately adjusted in consideration of the amount of the substituent introduced into the cellulose fiber. Sulfamic acid can be used, for example, in an amount of preferably 0.01 to 50 mol, more preferably 0.1 to 30 mol, per mol of anhydroglucose unit in the cellulose molecule.

The sulfating agent for the sulfuric acid esterification reaction is a mixture of sulfamic acid and a solvent, and may or may not further contain a catalyst. Examples of the catalyst include urea, amides, tertiary amines and the like. The amount of the catalyst used is not particularly limited, but is preferably 0.001 to 5 mol, more preferably 0.005 to 2.5 mol, and more preferably 0.01 to 2 per 1 mol of anhydroglucose unit in the cellulose molecule. 0.0 mol is more preferred. The catalyst having a high concentration may be used as it is, or may be diluted with a solvent in advance and used. In addition, although not particularly limited, batch addition, divided addition, continuous addition, or a combination thereof can be performed. However, from the viewpoint of environmental load and industrial viewpoint, it is preferable that the catalyst is not used during the reaction.

The solvent used for the sulfating agent is not particularly limited, but a known solvent may be used. Known solvents include, in addition to water, straight-chain or branched saturated hydrocarbons or unsaturated hydrocarbons having 1 to 6 carbon atoms or alcohols, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, toluene, xylene and the like. Aromatic hydrocarbons, halogenated hydrocarbons such as methylene chloride and chloroform, lower alkyl ethers having 2 to 5 carbon atoms, dioxane, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, Examples thereof include solvents such as N-methylpyrrolidone and pyridine. These may be used alone or in admixture of two or more. Among the above organic solvents, for example, water or a polar organic solvent is more preferable from the viewpoint of promoting swelling of the cellulose raw material. In addition, the said solvent may be used individually and may be used in combination of 2 or more type. The amount of the solvent used is not particularly limited, but for example, the solvent content of the cellulose fibers (that is, the ratio of the mass of the solvent to the dry mass of the cellulose fibers) is 10% by mass or more, preferably 10 to 10000% by mass, and more preferably Is used in an amount of 20 to 1000% by mass, more preferably 20 to 500% by mass. The smaller the amount of the solvent, the more rational in terms of production efficiency such as reaction promotion and convenience of washing process.

The temperature of the sulfuric acid esterification reaction is 0 to 100°C, preferably 10 to 80°C, more preferably 20 to 70°C. If the reaction temperature is too low, it takes a long time to complete the reaction, and if the reaction temperature is too high, the glycoside bond in the cellulose molecule is cleaved, which is not preferable. The sulfuric acid esterification reaction time is usually 30 minutes to 5 hours to complete the reaction.

In order to obtain a product with less coloring, an inert gas such as nitrogen gas, neon gas, argon gas, or helium gas or carbon dioxide gas may be introduced during the sulfuric acid esterification reaction. As a method of introducing these inert gases, a method of carrying out the reaction while blowing an inert gas into the reaction tank, a method of replacing the inside of the reaction tank with an inert gas before the reaction, and then carrying out a reaction by sealing the reaction tank or Any other method may be used.

The method for producing a sulfated cellulose fiber according to this embodiment preferably has a step (c) of defibrating at the same time as the step (b), in addition to the steps (a) and (b). Cellulose fibers are a bundle of cellulose fine fibers as a constituent element. In the present embodiment, it is preferable to chemically modify the surface of the cellulose fine fibers with sulfamic acid while maintaining the shape of the cellulose fibers, which is the fiber bundle of the cellulose fine fibers, while defibrating, that is, while unraveling the fiber bundle. .. Since the esterification treatment is performed while defibrating the cellulose fine fibers in this manner, there is no need to perform a defibration process in a subsequent step, and efficiency and productivity can be improved.

Also, the sulfated cellulose fibers can be taken out in the fibrous state within the range of conditions limited by the present invention. Since the sulfated cellulose fiber obtained in the present invention can be handled in a solid state, it is useful in product distribution or in processing in a later step. Further, the sulfated cellulose fiber is useful in that the fibrillation of the cellulose fiber proceeds in water even with a general-purpose stirring device.

[Neutralization/washing process]
In the present embodiment, the sulfated cellulose fibers can be taken out as ammonium sulfate after the sulfation reaction with sulfamic acid. Moreover, you may provide the process of neutralizing a sulfated cellulose fiber as needed. Sulfated cellulose fibers have a concern about storage stability of the crude product under acidic conditions due to a decrease in the pH of the crude product during washing and purification steps, and the pH value can be increased by neutralizing by adding a basic compound. It is preferably adjusted to be neutral or alkaline. The basic compound used for neutralization is not particularly limited, but examples thereof include alkali metal hydroxides, alkaline earth metal hydroxides, other inorganic salts, and amines. Specifically, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium acetate, calcium lactate, calcium oxalate, magnesium hydroxide, magnesium acetate, magnesium lactate, magnesium oxalate, basic aluminum lactate, basic Examples thereof include aluminum chloride, ammonia, methylamine, dimethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine and pyridine. In addition, in this embodiment, it can neutralize using 1 or more types of basic compounds.

A step of washing the sulfated cellulose fibers in a wet state may be provided for the purpose of stopping the reaction and/or for removing the sulfating agent residue, residual catalyst, solvent and the like. At this time, washing conditions are not particularly limited, but it is preferable to wash the sulfated cellulose fibers after the reaction with an organic solvent or a water-containing organic solvent.

The method for removing the solvent is not particularly limited, but a centrifugal sedimentation method, filtration, press treatment or the like can be used. Here, the sheet made of chemically modified cellulose fibers may be kept wet with the organic solvent without completely removing the organic solvent. The organic solvent content of the sulfated cellulose fibers (that is, the ratio of the mass of the organic solvent to the dry mass of the sulfated cellulose fiber aggregate) is preferably 1 to 500% by mass, more preferably 10 to 100% by mass. %, and more preferably 10 to 50% by mass.

[Chemically modified cellulose fiber]
The chemically modified cellulose fiber according to the present embodiment obtained by the above production method has a cellulose type I crystal, and a part of the hydroxyl groups in the glucose unit constituting the cellulose is a substituent represented by the following formula (1). Has been replaced by.

　式中、Ｍは１～３価の陽イオンを表す。

In the formula, M represents a monovalent to trivalent cation.

(Cellulose type I crystal)
The chemically modified cellulose fiber has a cellulose type I crystal structure, and its crystallinity is preferably 50% or more. When the crystallinity is 50% or more, the properties derived from the cellulose crystal structure can be exhibited, and the thickening property and mechanical strength can be improved. The crystallinity is more preferably 60% or more, further preferably 65% or more, and may be 70% or more. The upper limit of the crystallinity is not particularly limited, but from the viewpoint of improving the reaction efficiency of the sulfate esterification reaction, it is preferably 98% or less, more preferably 95% or less, further preferably 90% or less, 85% It may be the following.

(Substituent)
The substituent represented by the above formula (1) is a sulfate group, and as shown by the following formula, the wavy portion is a cellulose molecule, and instead of a hydrogen atom to an oxygen atom of a hydroxyl group in cellulose, It has a structure in which SO ₃ M is bonded, and a sulfate group is introduced into the cellulose fiber.

Examples of the monovalent to trivalent cation represented by M in the formula (1) include a hydrogen ion, a metal ion and an ammonium ion. In the case of a divalent or trivalent cation, the cation forms an ionic bond with two or three —OSO ^{3 −} .

The metal ions include alkali metal ions, alkaline earth metal ions, transition metal ions, and other metal ions. Here, examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium. Examples of alkaline earth metals include calcium and strontium. Examples of the transition metal include iron, nickel, palladium, copper and silver. Other metals include beryllium, magnesium, zinc, aluminum and the like.

Examples of ammonium ions include not only NH ⁴⁺ but also ammonium ions derived from various amines formed by replacing one or more hydrogen atoms of NH ⁴⁺ with an organic group, and examples thereof include NH ⁴⁺ , quaternary ammonium cations, and alkanolamines. Ions, pyridinium ions and the like.

The cation represented by M is preferably sodium ion, potassium ion, calcium ion, or quaternary ammonium cation from the viewpoint of storage stability. The cations listed above may be used alone or in combination of two or more.

(Amount of introduced substituents)
In the sulfated cellulose fiber of the present invention, the introduced amount of the substituent represented by the formula (1) per 1 g of the obtained cellulose fiber is preferably 0.1 to 3.0 mmol. When the amount introduced is 3.0 mmol/g or less, the effect of retaining the cellulose crystal structure can be enhanced. The amount introduced is more preferably 2.0 mmol/g or less. In addition, from the viewpoint of covering the entire surface of the cellulose fine fiber which is a constituent element of the cellulose fiber with a substituent, it is preferably 0.1 mmol/g or more, more preferably 0.2 mmol/g or more, and further preferably 0. It is 0.4 mmol/g or more.

In the present specification, the introduced amount of the substituent is a value calculated by potentiometric measurement, for example, the denaturing agent used as a raw material by washing, or after removing by-products such as hydrolysates thereof, It can be calculated by conducting a potentiometric analysis. Specifically, it can be measured by the method described in Examples below.

[Function and effect]
The sulfated cellulose fiber according to the present embodiment, since the cellulose surface is sulfated, can be used as a thickener or a water-absorbing material, for example, food, cosmetics, functional paper, resin reinforcing material, etc. It can be used for various purposes other than the industrial raw materials.

According to the present embodiment, the sulfated cellulose fiber can be produced with environmental compatibility, efficiency and high productivity, which is industrially advantageous. Specifically, by chemically reacting the cellulose fiber with sulfamic acid, it is possible to easily and inexpensively obtain the chemically modified cellulose fiber while suppressing the environmental load.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. The measurement/evaluation methods in each example and each comparative example are as follows.

(1) Cellulose Type I Crystallinity The X-ray diffraction intensities of the cellulose fibers and the chemically modified cellulose fibers were measured by the X-ray diffraction method, and the measurement results were calculated by the following formula using the Segal method.
Cellulose type I crystallinity (%)=[(I _22.6 -I _18.5 )/I _22.6 ]×100
In the formula, I _22.6 is the diffraction intensity of the lattice plane (002 plane) (diffraction angle 2θ=22.6°) in X-ray diffraction, and I _18.5 is the diffraction intensity of the amorphous part (diffraction angle 2θ=18.5°). Indicates. The X-ray diffraction intensity of the sample was measured using "RINT2200" manufactured by Rigaku Co., Ltd. under the following conditions:
X-ray source: Cu/Kα-radiation
Tube voltage: 40Kv
Tube current: 30mA
Measuring range: Diffraction angle 2θ=5~35°
X-ray scan speed: 10°/min

(2) Measurement of Substituent Introduction Amount of Sulfated Cellulose Fiber The sulfate group introduction amount was calculated by potentiometric measurement. Specifically, 60 mL of an aqueous dispersion of the cellulose fiber prepared to have a solid content of 0.5% by mass was prepared from a sulfated modified cellulose fiber sample whose dry weight was precisely weighed, and the pH was adjusted to about pH with 0.1 M hydrochloric acid aqueous solution. After adjusting to 2.5, the mixture was filtered and washed with water, the fiber was redispersed in 60 mL of water again, and a 0.1 M aqueous potassium hydroxide solution was added dropwise to adjust the pH to about 11. A 0.1 M hydrochloric acid aqueous solution was added dropwise to this slurry for potentiometric titration. The amount of sulfate groups introduced into the sulfated cellulose fibers was calculated from the amount of the 0.1 M hydrochloric acid aqueous solution added by the end point.

(3) Sulfation reaction curve in each example of the present invention In the examples and comparative examples of the present invention, sampling was carried out every hour from the start of the reaction, and the amount of sulfate group was measured by the method described in (2) above. The relationship between the reaction time and the amount of sulfate group introduced was plotted to compare the example with the comparative example.

(4) Evaluation of Fiber Shape of Sulfated Cellulose Fiber The shape of the sulfated cellulose fiber was evaluated by optical microscope observation and evaluated according to the following criteria.
○: It has been defibrated.
Δ: Some undisentangled parts remain.
X: The fiber shape is not retained and the fibers are dissolved or shortened.
=: Many coarse fibers are seen in the visual field.

(5) Disentanglement treatment The water content of the sulfated cellulose fiber of the present invention obtained above is adjusted so that the solid concentration is 0.5% by mass, and the cellulose fiber aqueous dispersion is 10,000 rpm using a homomixer. Was treated for 20 minutes to obtain a gelled aqueous dispersion of sulfated cellulose fibers, and the following evaluation was performed.

(6) Evaluation of water dispersibility after defibration treatment Each of the sulfated cellulose fiber aqueous dispersions after defibration treatment was prepared by diluting by adding water while stirring so that the solid content concentration becomes 0.2% by mass. After allowing the aqueous dispersion sample to stand at 25° C. for 1 week, the dispersed state of the cellulose fibers was visually observed and evaluated according to the following criteria.
Good: No syneresis or nonuniformity of cellulose fibers is observed, and good dispersibility in water is exhibited.
Δ: No water separation is observed, but undisentangled fibers and fibers in a swollen state are seen.
X: Water separation and aggregation of cellulose fibers are observed.

(7) Viscosity measurement The viscosity of an aqueous dispersion of sulfated cellulose fibers prepared to a solid content of 0.5% by mass was measured using a B-type viscometer at a rotation speed of 6.0 rpm and 25°C.

(8) Spinnability The sulfated cellulose fiber aqueous dispersion having a solid content concentration of 0.5 mass% prepared by the defibration operation in (6) above was transferred to a 100 ml sample bottle with a lid and allowed to stand at 25°C for 24 hours. After that, the tip 2 cm of a glass rod having a diameter of 7 mm was inserted into the cellulose fiber aqueous dispersion, and then the spinnability of the liquid was measured when the tip of the glass rod was pulled up to a water surface of 5 cm at a constant speed. It was evaluated according to the standard.
◯: No spinnability is observed when the glass rod is pulled up.
Δ: The spinnability is less than 5 mm when the glass rod is pulled up.
X: When the glass rod is pulled up, the spinnability is 5 mm or more.

[Example 1]
A cotton-like softwood kraft pulp that was previously adjusted to a water content of 8.1% by weight as a cellulose fiber raw material in a 1.5 L kneader type reactor equipped with a biaxial stirring blade and a condenser for suppressing volatilization of solvent. (NBKP, cellulose type I crystallinity: 85%) (3.8 g) was added, and then 3.5 g of sulfamic acid and 20 g of N,N-dimethylformamide (DMF) prepared by mixing in advance with stirring. Was stirred for 10 minutes, then the temperature was raised to 50° C., and after reaching 50° C., the reaction was started. At this time, the amount of sulfamic acid used was 1.6 mol per mol of anhydroglucose unit.
Then, the mixture was reacted at 50° C. for 4 hours and then cooled to room temperature. Next, the obtained sulfated cellulose fiber crude product was taken out into a wire net on a bag and centrifuged to remove the drug solution. The following neutralization and washing operations were carried out by immersing the crude sulfated cellulose fiber product in the chemical solution while leaving it in the wire net and shaking it. Neutralization was performed by using a 1N sodium hydroxide aqueous solution as a neutralizing agent, followed by washing with water twice using distilled water, followed by centrifugal separation and dehydration, and the sulfated cellulose of the present invention with a reaction time of 3 hours. Fiber [A4] was obtained. At this time, the recovered amount of the sulfated cellulose fiber [A4] was 6.2 g, the water content was 19% by mass, and the sulfate group amount was 1.1 mmol/g.
In Example 1, sampling was performed 1 hour, 2 hours, 3 hours, and 4 hours after the start of the reaction, and desolvation, neutralization, water washing, and dehydration were performed according to the above method, and each sample was A1, A2, A3. , A4 and the sample name were given.

[Example 2]
Into the same reactor as in Example 1, 3.8 g of the same cellulosic fiber raw material as in Example 1 was charged, and then half of the reaction chemical liquid of 3.5 g of sulfamic acid and 20 g of DMF, which had been mixed and prepared in advance with stirring, was charged. After stirring for 10 minutes, the temperature was raised to 50° C., and after reaching 50° C., the reaction was carried out for 1 hour. Further, the remaining amount of the above reaction chemical liquid was added, and the reaction was continued at 50° C. for 3 hours and then cooled to room temperature. At this time, the total amount of sulfamic acid used was 1.6 mol per mol of anhydroglucose unit.
Thereafter, the same operation as in Example 1 was carried out, and the sulfated cellulose fiber [B4] of the present invention was obtained with a total reaction time of 3 hours. At this time, the recovered amount of the sulfated cellulose fiber [B4] was 6.3 g, the water content was 21% by mass, and the sulfate group amount was 1.2 mmol/g.
In Example 2, after the reaction was started, sampling was performed for 1 hour, 2 hours, 3 hours, and 4 hours, and desolvation, neutralization, washing with water, and dehydration were performed according to the above method, and each sample was subjected to B1, B2, and B3. , B4 and the sample name were given.

[Example 3]
Into the same reactor as in Example 1, 3.8 g of the same cellulose fiber raw material as in Example 1 was charged, and then 1.7 g of sulfamic acid and 20 g of DMF, which had been mixed and prepared in advance with stirring, were charged. The mixture was stirred for 10 minutes, then heated to 50° C., reached a temperature of 50° C., reacted for 1 hour, and then cooled to room temperature.
The sulfated cellulose fiber crude product obtained at this time was once taken out into a bag-shaped wire net, and after centrifuging to remove the chemical liquid, the sulfated cellulose fiber crude product was returned to the reactor again, and further mixed and prepared. The reaction solution of sulfamic acid (1.8 g) and DMF (10 g) were added, the mixture was stirred for 10 minutes, then heated to 50° C., and after reaching 50° C., reacted for 3 hours, and then cooled to room temperature. At this time, the total amount of sulfamic acid used was 1.6 mol per mol of anhydroglucose unit.
Thereafter, through the same operations as in Example 1, the sulfated cellulose fiber [C4] of the present invention was obtained with a total reaction time of 4 hours. At this time, the recovered amount of the sulfated cellulose fiber [C4] was 6.2 g, the water content was 23%, and the sulfate group amount was 1.4 mmol/g.
In Example 3, sampling was performed 1 hour, 2 hours, 3 hours, and 4 hours after the start of the reaction, and desolvation, neutralization, washing with water, and dehydration were performed according to the methods described above, and each sample was subjected to C1, C2, and C3. , C4 and the sample name were given.

[Example 4]
Into the same reactor as in Example 1, 3.8 g of the same cellulose fiber raw material as in Example 1 was charged, then 20 g of DMF was charged with stirring and stirred for 10 minutes, and then the temperature was raised to 50°C. After reaching 50° C., stirring was continued for 1 hour and then cooled to room temperature.
The cellulose fiber which has undergone the above-mentioned operation is once taken out into a bag-shaped wire net, centrifuged to remove DMF, and then the cellulose fiber is returned to the reactor again, and 3.5 g of sulfamic acid prepared and mixed in advance is reacted with 20 g of DMF. The chemical liquid was added, the mixture was stirred for 10 minutes, then heated to 50° C., and after reaching 50° C., reacted for 4 hours and then cooled to room temperature. At this time, the total amount of sulfamic acid used was 1.6 mol per mol of anhydroglucose unit.
Thereafter, the same operations as in Example 1 were carried out, and the sulfated cellulose fiber [D4] of the present invention was obtained in a total reaction time of 4 hours. At this time, the recovered amount of the sulfated cellulose fiber [D4] was 6.5 g, the water content was 26%, and the sulfate group amount was 1.6 mmol/g.
In Example 3, sampling was performed 1 hour, 2 hours, 3 hours, and 4 hours after the start of the reaction, and desolvation, neutralization, water washing, and dehydration were performed according to the above method, and each sample was D1, D2, and D3. , D4 and the sample name were given.

[Example 5]
Water-containing cotton-like softwood kraft pulp (NBKP, cellulose type I crystallinity: 85%, water content 99) obtained by preliminarily immersing in water in the same reactor as in Example 1 and adjusting dehydration operation as a cellulose fiber raw material. (3 wt %) 7.0 g, then 3.5 g of sulfamic acid and 20 g of DMF prepared and mixed in advance with stirring, added, and stirred for 10 minutes, and then heated to 50° C. After reaching 50° C., the reaction was started for 4 hours. At this time, the amount of sulfamic acid used was 1.6 mol per mol of anhydroglucose unit.

When a part of the sulfated cellulose fiber crude product [E4] having a reaction time of 4 hours by the above operation was sampled and the amount of sulfate group was measured, the amount of sulfate group was 0.4 mmol/g. The crude cellulosic fiber crude product "E4" was once taken out into a bag-shaped wire net, centrifuged to remove the drug solution, the sulfated cellulosic fiber crude product was returned to the reactor again, and the sulfamic acid newly mixed and prepared. 3.5 g of DMF and 20 g of DMF were added, the mixture was stirred for 10 minutes, then heated to 50° C., and after reaching 50° C., reacted for 4 hours, and then cooled to room temperature. At this time, the total amount of sulfamic acid used was 3.2 mol per mol of the anhydroglucose unit.

Thereafter, through the same operation as in Example 1, the sulfated cellulose fiber [E8] of the present invention was obtained with a total reaction time of 8 hours. At this time, the recovered amount of the sulfated cellulose fiber [E8] was 5.9 g, the water content was 29%, and the sulfate group amount was 1.4 mmol/g.

In Example 4, sampling was performed 1 to 8 hours after the reaction was started, and desolvation, neutralization, washing with water, and dehydration were performed according to the method described above, and the samples were sequentially labeled with E1 to E8.

[Comparative Example 1]
After softening the same softwood kraft pulp as in Example 1 (NBKP, cellulose type I crystallinity: 85%), the solvent was replaced twice with a large excess of dry methanol, followed by vacuum drying at 50° C. for 1 hour, Further, a dried cellulose fiber raw material (water content 1.3% by weight) obtained by drying under reduced pressure at 70° C. for 1 hour was prepared, and 3.5 g thereof was charged into the same reactor as in Example 1, and then while stirring. After adding 3.5 g of sulfamic acid and 20 g of DMF that had been mixed in advance, the mixture was stirred for 10 minutes, further heated to 50° C., and after the reaction in the reactor reached 50° C., the reaction was performed for 4 hours. , Cooled to room temperature. The amount of sulfamic acid used as a sulfating agent is 1.6 mol per mol of anhydroglucose unit.

After that, through the same operation as in Example 1, a sulfated cellulose fiber [F4] of the present invention was obtained with a reaction time of 4 hours. At this time, the recovered amount of the sulfated cellulose fiber [F4] was 5.0 g, the water content was 15% by mass, and the sulfate group amount was 0.9 mmol/g.

In Example 3, sampling was performed 1 to 4 hours after the reaction was started, desolvation, neutralization, water washing, and dehydration were performed according to the above method, and each sample was given a sample name of F1 to F4.

[Comparative example 2]
Water-containing cotton-like softwood kraft pulp (NBKP, cellulose type I crystallinity: 85%, water content 250) obtained by preliminarily immersing in water in the same reactor as that of Example 1 and adjusting dehydration operation. (1 .4% by weight), then, while stirring, 3.5 g of sulfamic acid and 20 g of DMF prepared and mixed in advance with stirring are added, and the mixture is stirred for 10 minutes and then heated to 50°C. After the temperature reached 50° C., the reaction was started. At this time, the amount of sulfamic acid used was 1.6 mol per mol of anhydroglucose unit.

When a part of the sulfated cellulose fiber crude product [G4] having a reaction time of 4 hours according to the above operation was sampled and the amount of sulfate group was measured, the amount of sulfate group was 0.2 mmol/g. The cellulose fiber crude product "G4" was once taken out into a bag-shaped wire net, centrifuged to remove the drug solution, and the sulfated cellulose fiber crude product was returned to the reactor again, and further mixed and prepared sulfamic acid 3 0.5 g of DMF and 20 g of DMF were added and the mixture was stirred for 10 minutes, then heated to 50° C., and after reaching 50° C., reacted for 4 hours, and then cooled to room temperature. At this time, the total amount of sulfamic acid used was 3.2 mol per mol of the anhydroglucose unit.

Thereafter, through the same operation as in Example 1, the sulfated cellulose fiber [G8] of the present invention was obtained with a total reaction time of 8 hours. At this time, the recovered amount of the sulfated cellulose fiber [G8] was 5.4 g, the water content was 34%, and the sulfate group amount was 0.5 mmol/g.

Incidentally, in Example 4, after starting the reaction, sampling was carried out in order for 1 to 8 hours, desolvation, neutralization, washing with water and dehydration were carried out in accordance with the above method, and each sample was given a sample name of G1 to G8 in order.

For the above Examples and Comparative Examples, for the cellulose fibers before chemical modification, the crystallinity and water content, and for the chemically modified cellulose fibers after the chemical modification step, the introduction amount of introduced groups, the calculation of the crystallinity, and the fibers The shape was evaluated. The results are shown in Table 1.

*1: Shows the total reaction time until the end of the reaction *2: Shows the total quantity charged until the end of the reaction *3: Amount of sulfamic acid charged per mol of anhydroglucose unit Details of the components in the table are as follows Is.
-DMF: dimethylformamide-NaOH: sodium hydroxide

The results are shown in Table 1 and Figure 1. The chemically modified cellulose fibers of Examples 1 to 5 have good results in fiber shape evaluation, water dispersibility, and spinnability, whereas the water content of the cellulose fiber raw material is less than 2% by mass. In Comparative Example 1 using 1.3% by mass of the cellulose fibers, the swelling of the cellulose fibers was non-uniform and the sulfation reaction and the defibration of the fibers did not proceed uniformly, and after the reaction, coarse fibers were formed in the fiber shape. It can be seen that a fibrous substance is observed when it remains and is dispersed in water, and the viscosity becomes low.

On the other hand, in Comparative Example 2 in which the water content of the cellulose fiber raw material is 250.4 mass that exceeds 200 mass %, the cellulose fibers are shortened in a state where they are not dispersed in water, and the fibers aggregate or precipitate. It was Further, it is understood that the sulfation reaction partially proceeds excessively, part of the sulfated cellulose is dissolved in water, and the spinnability is exhibited.

From FIG. 1, comparing Example 1 with Comparative Example 1, in Comparative Example 1 in which the water content of the cellulose fiber raw material is low, the amount of sulfate groups introduced per reaction time is small and the final amount of sulfate groups introduced is also low. Recognize.

Also, comparing Examples 1 to 4, it can be seen that by changing the sulfamic acid addition method, the amount of sulfate group introduced increases with respect to the reaction time, and the final amount of sulfate group introduced improves.

Comparing Example 5 and Comparative Example 2 in which sulfamic acid was additionally added, in Comparative Example 2 in which the water content of the cellulose fiber raw material was high, the deactivation of the sulfating agent was dominant and the reaction was delayed, resulting in a reaction time. It can be seen that the amount of sulfate group introduced per unit amount is small and the final amount of sulfate group introduced is also low.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and omissions, replacements, and changes thereof are included in the invention described in the claims and equivalents thereof, as well as included in the scope and the gist of the invention.

Claims (3)

A method for producing a chemically modified cellulose fiber, which comprises the following steps (a) and (b).
Step (a): Step of adjusting water content of cellulose fiber to 2% by mass or more and 200% by mass or less Step (b): Treatment of cellulose fiber with sulfamic acid to obtain sulfamic acid and constituent elements of the cellulose fiber. A step of reacting a certain cellulose fine fiber and substituting a part of hydroxyl groups of cellulose with a substituent represented by the following structural formula (1).

(However, in the formula (1), M represents a monovalent to trivalent cation.) The method for producing a chemically modified cellulose fiber according to claim 1, comprising the following step (c).
Step (c): Step of defibrating at the same time as the step (b) The chemically modified cellulose fiber has a cellulose type I crystal structure, a part of the hydroxyl groups of cellulose is substituted with the substituent represented by the structural formula (1), and the introduced amount of the substituent is 1 g of the chemically modified cellulose fiber. The method for producing a chemically modified cellulose fiber according to claim 1 or 2, wherein the amount is 0.1 to 3.0 mmol.

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