WO2023234129A1

WO2023234129A1 - Method for producing fine fibrous cellulose and method for fibrillating cellulose

Info

Publication number: WO2023234129A1
Application number: PCT/JP2023/019240
Authority: WO
Inventors: 裕介杉村; 丈史中谷; 啓吾渡部
Original assignee: 日本製紙株式会社
Priority date: 2022-05-31
Filing date: 2023-05-24
Publication date: 2023-12-07

Abstract

The method has a surplus water circulation step that takes up a dispersion of chemically modified cellulose or unmodified cellulose stored in a storage unit from a suction port of a plunger pump that constitutes part of the high-pressure washer via the water inlet of a high-pressure washer having a surplus water discharge mechanism comprising a pressure-regulating valve, and the dispersion ejected from the ejection port of the plunger pump is discharged from the surplus water port of the high-pressure washer into the storage unit.

Description

Method for producing fine fibrous cellulose and method for fibrillating cellulose

The present invention relates to a method for producing fine fibrous cellulose and a method for defibrating cellulose.

Cellulose nanofibers and microfibrillated cellulose (hereinafter collectively referred to as "fine fibrous cellulose") obtained by refining cellulose are fine fibers with fiber diameters on the nano to micro order, and have high strength and high elasticity. It is expected to be used in a variety of fields as a new material that has functions not found in ordinary pulp, such as thixotropic properties.

Conventionally, fine fibrous cellulose has been produced in a state in which it is stably dispersed in water by defibrating chemically modified pulp using a high-pressure homogenizer (see, for example, Patent Document 1), and is usually produced at a predetermined concentration. It is transported as a fine fibrous cellulose dispersion to user factories, where it is used for various purposes as an industrial material or as an additive material for foods and cosmetics.

If the manufactured dispersion of fine fibrous cellulose at a predetermined concentration is transported as it is to a user's factory, etc., this leads to increased costs for storage, transportation, etc. On the other hand, when transporting a fine fibrous cellulose dispersion in a dried state, a large amount of electric power is required to dry the fine fibrous cellulose dispersion, leading to an increase in costs. Additionally, it was necessary to install new equipment at the user's factory to dilute and redisperse dried fine fibrous cellulose and adjust it to a concentration suitable for use.

Japanese Patent Application Publication No. 2018-44274

Conventional methods such as those disclosed in Patent Document 1 require a high-pressure homogenizer to defibrate the pulp, and since high-pressure homogenizers are expensive and large equipment, it is sometimes difficult for users to install them. .

An object of the present invention is a method for producing fine fibrous cellulose that is inexpensively available, easy to introduce, and capable of efficiently defibrating cellulose using equipment normally used by users. and a method for defibrating cellulose.

As a result of intensive studies to solve the above-mentioned problems, the present inventor found that the above-mentioned object can be achieved by defibrating using a specific high-pressure washer, and completed the present invention.

The present invention provides the following.
(1) A method for producing fine fibrous cellulose, in which a dispersion of chemically modified cellulose or unmodified cellulose stored in a storage section is passed through a water intake port of a high-pressure washer having a surplus water discharge mechanism consisting of a pressure regulating valve. The dispersion liquid taken in from the suction port of a plunger pump that constitutes a part of the high pressure washer and discharged from the discharge port of the plunger pump is discharged from the spill port of the high pressure washer to the storage section. A method for producing fine fibrous cellulose including a residual water circulation step.
(2) The method for producing fine fibrous cellulose according to (1), wherein the outlet pressure of the pressure regulating valve of the high-pressure washer is 0.5 to 25 MPa.
(3) The method for producing fine fibrous cellulose according to (1) or (2), wherein the solid content concentration of the dispersion is 0.1 to 10.0% by weight.
(4) The method for producing fine fibrous cellulose according to (1) or (2), wherein the chemically modified cellulose is carboxylated cellulose or carboxymethylated cellulose.
(5) The method for producing fine fibrous cellulose according to (1) or (2), wherein the surplus water circulation step is performed 1 to 100 times.
(6) A method for defibrating cellulose, which involves dispersing a dispersion of chemically modified cellulose or unmodified cellulose stored in a storage section through a water intake port of a high-pressure washer having a surplus water discharge mechanism consisting of a pressure regulating valve. , the dispersion liquid taken in from the suction port of a plunger pump that constitutes a part of the high pressure washer and discharged from the discharge port of the plunger pump is discharged from the spill port of the high pressure washer to the storage section; A cellulose defibration method that includes a water circulation process.

According to the present invention, a method for producing fine fibrous cellulose allows cellulose to be efficiently defibrated using equipment that is inexpensively available, easy to introduce, and commonly used by users. and a method for defibrating cellulose.

1 is a schematic diagram showing the configuration of a high-pressure washer that can be used in the present invention. FIG. 2 is a schematic diagram showing the configuration of the pressure regulating valve shown in FIG. 1. FIG. 1 is a graph showing viscosity characteristics of fine fibrous cellulose dispersions obtained in Example 1, Comparative Example 1, and Reference Example 1.

Hereinafter, the present invention will be described in detail with reference to the drawings. In the present invention, "~" includes extreme values. That is, "X~Y" includes the values X and Y at both ends.

The method for producing fine fibrous cellulose of the present invention involves dispersing a dispersion of chemically modified cellulose or unmodified cellulose stored in a storage section through a water intake port of a high-pressure washer having a surplus water discharge mechanism consisting of a pressure regulating valve. , the dispersion liquid taken in from the suction port of a plunger pump that constitutes a part of the high pressure washer and discharged from the discharge port of the plunger pump is discharged from the spill port of the high pressure washer to the storage section; It has a water circulation process.

A plunger pump is a pump that reciprocates a plunger (rod-shaped piston) to change the volume of liquid inside the pump and expel it to a discharge port. In the manufacturing method of the present invention, the plunger pump constitutes a part of a high-pressure washer having a surplus water discharge mechanism.

FIG. 1 is a schematic diagram showing the configuration of a high-pressure washer that can be used in the present invention. Note that the high-pressure washer that can be used in the present invention is not limited to the one shown in FIG.

The high-pressure washer 2 that can be used in the present invention includes a water intake port 8 that takes the dispersion liquid 6 stored in the storage part 4 into the high-pressure washer 2, and a plunger that applies pressure to the taken-in dispersion liquid 6. A pump 10, a discharge port 12 that discharges the high-pressure dispersion liquid 6, a nozzle 16 connected to the discharge port 12 via a discharge hose 14, a pressure regulating valve 18 that adjusts the discharge pressure, and a discharge port 12 that discharges the high-pressure dispersion liquid 6. The water outlet 20 is provided for discharging the dispersion liquid 6 to the storage section 4 when the pressure exceeds a set value. Here, a water suction hose 22 is attached to the water suction port 8 so as to be able to absorb the dispersion liquid 6 from the bottom of the storage section 4 . Further, a spill water hose 24 is attached to the spill water outlet 20 so that the excess water in the high-pressure washer 2 can be discharged to the storage section 4. Note that in FIG. 1, arrows indicate the direction in which the dispersion liquid passes when the nozzle is in a closed state.

When the plunger pump 10 is driven, the dispersion liquid 6 stored in the storage section 4 is taken into the high-pressure washer 2 via the water absorption hose 22. This dispersion liquid 6 is taken in from the suction port 9 of the plunger pump 10 and pressurized within the pump, and the pressurized dispersion liquid 6 is passed from the discharge port 11 of the plunger pump 10 via the pressure regulating valve 18. , is discharged from the discharge port 12 or spill port 20 of the high-pressure washer 2. When the nozzle 16 is opened, the high-pressure dispersion liquid 6 is injected from the nozzle 16, and when the nozzle 16 is closed, the high-pressure water is cut off. When the nozzle is closed, the pressure of the dispersion liquid 6 between the plunger pump 10 and the pressure regulating valve 18 increases, so the pressure regulating valve 18 works to maintain the pressure between the pressure regulating valve 18 and the nozzle 16 at the set pressure. Then, the entire amount of the dispersion liquid 6 in the plunger pump 10 is discharged from the spillway port 20 to the storage section 4 via the spillwater hose 24.

Next, the operation of the pressure regulating valve 18 will be explained using FIG. 2. The pressure regulating valve 18 includes a pressure regulating screw 26 for regulating the discharge pressure, a pressure regulating spring 28, a piston 30, and a relief valve 32. The discharge pressure is adjusted by rotating the pressure adjustment screw 26. When the nozzle 16 is open, the dispersion liquid 6 discharged from the discharge port 11 of the plunger pump 10 enters from the pressure regulating valve inlet 36 and is discharged from the pressure regulating valve outlet 38 (discharge port 12 side). At this time, if the pressure of the dispersion liquid 6 exceeds the set pressure, the relief valve 32 opens according to the pressure, and some percentage of the dispersion liquid 6 flows to the surplus water outlet 40.

Next, the mechanism of pressure adjustment will be explained. The dispersion liquid 6 entering from the pressure regulating valve inlet 36 of the pressure regulating valve 18 is discharged from the pressure regulating valve outlet 38. At the same time, pressure is transmitted to the space below the piston 30. When the pressure of the dispersion liquid 6 exceeds the set pressure, the piston 30 is pushed up and the relief valve 32 is also raised, so the dispersion liquid 6 that entered from the pressure regulating valve inlet 36 also flows to the surplus water outlet 40 and flows to the pressure regulating valve outlet 38. pressure (discharge pressure) is maintained at the set pressure. When the pressure adjustment screw 26 above the piston 30 is tightened, the piston 30 is strongly pushed down via the pressure adjustment spring 28, thereby making it possible to adjust the discharge pressure.

Some pressure regulating valves have an additional mechanism that keeps the high-pressure dispersion liquid 6 pushing up the piston 30 when the nozzle 16 is closed. When this mechanism works, the relief valve 32 is fully opened and the entire amount of the dispersion liquid 6 flows to the surplus water outlet 40.
The defibrating effect of the present invention is obtained when the high-pressure dispersion liquid 6 passes through the relief valve 32 that is not fully open, so when using a pressure regulating valve having the holding mechanism, the holding mechanism is disabled. Things are good.

(Leftwater circulation process)
When carrying out the method for producing fine fibrous cellulose of the present invention, a dispersion liquid 6 of chemically modified cellulose or unmodified cellulose stored in the storage section 4 is provided with a surplus water discharge mechanism as shown in FIG. The dispersion liquid 6 taken in from the suction port 9 of the plunger pump via the water suction port 8 of the high-pressure washer 2 and discharged from the discharge port 11 of the plunger pump is discharged from the overflow port 20 of the high-pressure washer 2 to the storage section 4. Perform the surplus water circulation process. By operating the plunger pump 10 with the nozzle 16 closed using the high-pressure washer 2 having a surplus water discharge mechanism, the cellulose dispersion 6 stored in the storage section 4 is discharged through the water absorption hose 22. The dispersion liquid 6 is taken in from the water intake port 8 and pressurized by the plunger pump 10, flows out from the spill water outlet 40 of the pressure regulating valve 18, and is discharged from the spill water port 20 via the spill water hose 24 to the storage section 4. be done. The residual water circulation step may be performed only once, or may be performed multiple times. The number of times the residual water circulation step is performed is preferably 1 to 100 times, more preferably 1 to 50 times, from the viewpoint of efficiently defibrating. In addition, the number of times of the residual water circulation process may be set to an optimal value according to the setting value of the discharge pressure of the high-pressure washer 2. For example, if the discharge pressure is 20 MPa or more, the number of times of the residual water circulation process may be set to 1 to 10. It is preferable to carry out the process twice, more preferably from 1 to 5 times, and even more preferably from 3 to 5 times. Further, when the discharge pressure is 10 MPa or more and less than 20 MPa, the number of times of the residual water circulation process is preferably 1 to 10 times, more preferably 3 to 8 times, and even more preferably 5 to 8 times. preferable. Further, when the discharge pressure is 5 MPa or more and less than 10 MPa, the number of times of the residual water circulation process is preferably 3 to 100 times, more preferably 10 to 50 times, and even more preferably 20 to 50 times. preferable.

The set value of the discharge pressure (outlet pressure of the pressure regulating valve) of the high-pressure washer 2 is not particularly limited, but from the viewpoint of efficient defibration, it is preferably 0.5 to 25 MPa, and 5 to 25 MPa. is more preferable, and even more preferably 10 to 20 MPa. The setting of the discharge pressure can be controlled by a surplus water discharge mechanism, and specifically can be performed using the pressure regulating screw 26 of the pressure regulating valve 18.

The amount of dispersion liquid 6 processed using the high-pressure washer 2 depends on the capacity of the machine. When used, from the viewpoint of production volume, it is preferably 10 to 20 L/min, more preferably 12 to 20 L/min.

The high-pressure washer that can be used in the present invention can be used without any particular restriction as long as it is equipped with a pressure regulating valve 18 and has a surplus water discharge mechanism. Examples include a washing machine (product name: TRY high-pressure washer, model number: TRY-10200), a high-pressure washing vehicle manufactured by Isuzu Motors (product name: Isuzu Achumat, 4t vehicle), and the like.

(Fine fibrous cellulose)
The fine fibrous cellulose used in the present invention is a fine fiber made from cellulose. The average fiber diameter of the fine fibrous cellulose is not particularly limited, but is approximately 1 nm to 10 μm. The average fiber diameter and average fiber length of fine fibrous cellulose are obtained from the results of observing each fiber using a scanning electron microscope (SEM), atomic force microscope (AFM), or transmission electron microscope (TEM). It can be obtained by averaging the fiber diameter and fiber length. Fine fibrous cellulose can be produced by defibrating cellulose.

The average aspect ratio of the fine fibrous cellulose used in the present invention is usually 50 or more. The upper limit is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated by the following formula:
Aspect ratio = average fiber length / average fiber diameter

The cellulose raw material is not particularly limited as long as it contains cellulose, but includes, for example, plants (for example, wood, bamboo, hemp, jute, kenaf, agricultural residue, cloth, pulp (softwood unbleached kraft pulp (NUKP), Softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), bleached kraft pulp (BKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP) Examples include thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g. ascidians), algae, microorganisms (e.g. acetic acid bacteria), microbial products, etc. As cellulose raw materials, any of these The cellulose raw materials derived from plants or microorganisms (e.g., cellulose fibers) are preferably used, and the cellulose raw materials derived from plants (e.g., cellulose fibers) are preferably used. ).

The number average fiber diameter of the cellulose raw material is not particularly limited, but in the case of softwood kraft pulp, which is a common pulp, it is about 30 to 60 μm, and in the case of hardwood kraft pulp, it is about 10 to 30 μm. In the case of other pulps, those that have undergone general refining have a diameter of about 50 μm. For example, in the case of refined chips or the like that are several centimeters in size, it is preferable to mechanically process them using a disintegrator such as a refiner or a beater to adjust the size to about 50 μm.

Cellulose has three hydroxyl groups per glucose unit, and can be chemically modified to produce chemically modified cellulose. In the present invention, chemically modified cellulose or unmodified cellulose is used as a raw material for fine fibrous cellulose, and from the viewpoint of promoting the progress of fibrillation, a cellulose raw material obtained by chemical modification (chemically modified cellulose) is used as a raw material for fine fibrous cellulose. ) is preferably used.

Examples of chemically modified cellulose include cellulose that has undergone chemical modification such as carboxymethylation, carboxylation (oxidation), cationization, and esterification. Among these, carboxymethylated cellulose and carboxylated (oxidized) cellulose are more preferred.

(chemical denaturation)
(carboxymethylation)
In the present invention, when carboxymethylated fine fibrous cellulose obtained by fibrillating carboxymethylated cellulose is used, the carboxymethylated cellulose can be obtained by carboxymethylating the above-mentioned cellulose raw material by a known method. Alternatively, a commercially available product may be used. In either case, the cellulose preferably has a degree of substitution of carboxymethyl groups per anhydroglucose unit of 0.01 to 0.50. An example of a method for producing such carboxymethylated cellulose is the following method. Cellulose is used as the base material, and as a solvent 3 to 20 times the weight of water and/or lower alcohol, specifically water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary alcohol. A single medium such as butanol or a mixture of two or more types is used. Note that when lower alcohols are mixed, the mixing ratio of lower alcohols is 60 to 95% by weight. As the mercerizing agent, alkali metal hydroxide, specifically sodium hydroxide and potassium hydroxide, is used in an amount of 0.5 to 20 times the mole per anhydroglucose residue of the bottom starting material. The bottom starting material, a solvent, and a mercerization agent are mixed, and mercerization treatment is performed at a reaction temperature of 0 to 70°C, preferably 10 to 60°C, and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, a carboxymethylating agent is added in a mol amount of 0.05 to 10.0 times per glucose residue, and the reaction temperature is 30 to 90°C, preferably 40 to 80°C, and the reaction time is 30 minutes to 10 hours, preferably 1 hour. The etherification reaction is carried out for ~4 hours.

In addition, in this specification, "carboxymethylated cellulose", which is a type of chemically modified cellulose used for preparing fine fibrous cellulose, maintains at least part of its fibrous shape even when dispersed in water. say something Therefore, it is distinguished from carboxymethyl cellulose, which is a type of water-soluble polymer. When an aqueous dispersion of "carboxymethylated cellulose" is observed with an electron microscope, fibrous substances can be observed. On the other hand, when observing an aqueous dispersion of carboxymethylcellulose, which is a type of water-soluble polymer, no fibrous material is observed. Furthermore, when "carboxymethylated cellulose" is measured by X-ray diffraction, a peak of cellulose type I crystals can be observed, but cellulose type I crystals are not observed in the water-soluble polymer carboxymethylcellulose.

(carboxylation)
In the present invention, when using oxidized fine fibrous cellulose obtained by fibrillating carboxylated (oxidized) cellulose, carboxylated cellulose (also referred to as oxidized cellulose) is obtained by carboxylating the above-mentioned cellulose raw material by a known method. (oxidation). Although not particularly limited, during carboxylation, the amount of carboxy groups is adjusted to 0.6 to 2.0 mmol/g based on the absolute dry weight of the chemically modified fine fibrous cellulose. It is preferable, and more preferably adjusted to 1.0 mmol/g to 2.0 mmol/g.

As an example of a carboxylation (oxidation) method, a cellulosic raw material is carboxylated in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides or mixtures thereof. Here are some ways to do it. Through this carboxylation reaction, the C6 position of the glucopyranose ring on the cellulose surface is selectively carboxylated, producing cellulose fibers having an aldehyde group and a carboxy group (-COOH) or a carboxylate group (-COO ^- ) on the surface. Obtainable. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by weight or less.

The N-oxyl compound refers to a compound that can generate nitroxy radicals. As the N-oxyl compound, any compound can be used as long as it promotes the desired carboxylation reaction. Examples include 2,2,6,6-tetramethylpiperidine-1-oxyradical (TEMPO) and its derivatives (eg, 4-hydroxyTEMPO).

The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can carboxylate cellulose as a raw material. For example, it is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and even more preferably 0.05 to 0.5 mmol, per 1 g of bone dry cellulose. Further, it is preferably about 0.1 to 4 mmol/L to the reaction system.

A bromide is a compound containing bromine, and examples thereof include alkali metal bromides that can be dissociated and ionized in water. Moreover, iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide to be used can be selected within a range that can promote the carboxylation reaction. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and even more preferably 0.5 to 5 mmol, per 1 g of bone dry cellulose.

As the oxidizing agent, known ones can be used, such as halogen, hypohalous acid, halous acid, perhalogenic acid, or salts thereof, halogen oxides, peroxides, etc. Among these, sodium hypochlorite is preferred because it is inexpensive and has a low environmental impact. The amount of the oxidizing agent used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, and most preferably 3 to 10 mmol, per 1 g of bone dry cellulose. Further, for example, it is preferably 1 to 40 mol per 1 mol of the N-oxyl compound.

Carboxylation of cellulose can proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40°C, and may be room temperature of about 15 to 30°C. As the reaction progresses, carboxy groups are generated in the cellulose, so a decrease in the pH of the reaction solution is observed. In order to efficiently advance the carboxylation reaction, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at about 8 to 12, preferably about 10 to 11. Water is preferable as the reaction medium because of ease of handling and the fact that side reactions are less likely to occur.

The reaction time in the carboxylation reaction can be appropriately set according to the degree of progress of carboxylation, and is usually about 0.5 to 6 hours, for example about 0.5 to 4 hours.

Additionally, the carboxylation reaction may be carried out in two stages. For example, by carboxylated cellulose obtained by filtration after the first stage reaction is carboxylated again under the same or different reaction conditions, the reaction is not inhibited by the salt produced as a by-product in the first stage reaction. , carboxylation can be carried out efficiently.

Another example of the carboxylation (oxidation) method is a method of carboxylating a cellulose raw material by bringing it into contact with a gas containing ozone. Through this carboxylation reaction, the hydroxyl groups at at least the 2- and 6-positions of the glucopyranose ring are carboxylated, and the cellulose chain is decomposed. The ozone concentration in the ozone-containing gas is preferably 50 to 250 g/m ³ , more preferably 50 to 220 g/m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by weight, more preferably 5 to 30 parts by weight, when the solid content of the cellulose raw material is 100 parts by weight. The ozone treatment temperature is preferably 0 to 50°C, more preferably 20 to 50°C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, excessive carboxylation and decomposition of cellulose can be prevented, resulting in a good yield of carboxylated cellulose. After the ozone treatment, additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples thereof include chlorine-based compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, the additional oxidation treatment can be performed by dissolving these oxidizing agents in water or a polar organic solvent such as alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the solution.

The amount of carboxy groups in carboxylated cellulose can be adjusted by controlling reaction conditions such as the amount of the oxidizing agent added and reaction time.

(cationization)
In the present invention, cationized fine fibrous cellulose obtained by defibrating cellulose obtained by further cationizing the carboxylated cellulose can be used. The cation-modified cellulose is produced by adding a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrite or its halohydrin type to the carboxylated cellulose raw material, and alkali hydroxide as a catalyst. It can be obtained by reacting a metal (sodium hydroxide, potassium hydroxide, etc.) in the presence of water or an alcohol having 1 to 4 carbon atoms.

The degree of cation substitution per glucose unit is preferably 0.02 to 0.50. By introducing cationic substituents into cellulose, the cells electrically repel each other. Therefore, cellulose into which cationic substituents have been introduced can be easily nano-fibrillated. If the degree of cation substitution per glucose unit is less than 0.02, sufficient nanofibrillation cannot be achieved. On the other hand, if the degree of cation substitution per glucose unit is greater than 0.50, the nanofibers may not be obtained due to swelling or dissolution. In order to efficiently perform fibrillation, the cationically modified cellulose raw material obtained above is preferably washed. The degree of cation substitution can be adjusted by adjusting the amount of the cationizing agent to be reacted and the composition ratio of water or alcohol having 1 to 4 carbon atoms.

(esterification)
In the present invention, esterified fine fibrous cellulose obtained by defibrating esterified cellulose can be used. The esterified cellulose can be obtained by mixing a powder or aqueous solution of phosphoric acid compound A with the cellulose raw material described above, or by adding an aqueous solution of phosphoric acid compound A to a slurry of the cellulose raw material.

Examples of the phosphoric acid compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, polyphosphonic acid, or esters thereof. These may be in the form of salts. Among these, compounds having phosphoric acid groups are preferred because they are low cost, easy to handle, and can introduce phosphoric acid groups into the cellulose of pulp fibers to improve the defibration efficiency. Compounds with phosphoric acid groups include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, potassium phosphite, sodium hypophosphite, and potassium hypophosphite. , sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate , ammonium pyrophosphate, ammonium metaphosphate, and the like. These can be used alone or in combination of two or more. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid The ammonium salt of is more preferred. Particularly preferred are sodium dihydrogen phosphate and disodium hydrogen phosphate. Further, it is preferable to use the phosphoric acid compound A in the form of an aqueous solution, since the uniformity of the reaction and the efficiency of introducing phosphoric acid groups are increased. The pH of the aqueous solution of the phosphoric acid compound A is preferably 7 or less since this increases the efficiency of introducing phosphoric acid groups, but the pH is preferably 3 to 7 from the viewpoint of suppressing hydrolysis of pulp fibers.

The following method can be mentioned as an example of the method for producing phosphoric acid esterified cellulose. A phosphoric acid compound A is added to a dispersion of a cellulose raw material having a solid content concentration of 0.1 to 10% by weight while stirring to introduce phosphoric acid groups into the cellulose. When the cellulose raw material is 100 parts by weight, the amount of phosphoric acid compound A added is preferably 0.2 to 500 parts by weight, more preferably 1 to 400 parts by weight as the amount of phosphorus element. If the proportion of phosphoric acid compound A is equal to or higher than the lower limit, the yield of fine fibrous cellulose can be further improved. However, if the above upper limit is exceeded, the effect of improving the yield reaches a ceiling, which is not preferable from a cost standpoint.

At this time, in addition to the cellulose raw material and phosphoric acid compound A, powder or aqueous solution of compound B may be mixed. Compound B is not particularly limited, but is preferably a nitrogen-containing compound that exhibits basicity. "Basic" herein is defined as the aqueous solution exhibiting a pink to red color in the presence of the phenolphthalein indicator, or the pH of the aqueous solution being greater than 7. The basic nitrogen-containing compound used in the present invention is not particularly limited as long as it exhibits the effects of the present invention, but compounds having an amino group are preferred. Examples include, but are not limited to, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, urea is preferred because it is low cost and easy to handle. The amount of compound B added is preferably 2 to 1000 parts by weight, more preferably 100 to 700 parts by weight, based on 100 parts by weight of the solid content of the cellulose raw material. The reaction temperature is preferably 0 to 95°C, more preferably 30 to 90°C. The reaction time is not particularly limited, but is approximately 1 to 600 minutes, more preferably 30 to 480 minutes. When the conditions for the esterification reaction are within these ranges, cellulose can be prevented from being excessively esterified and easily dissolved, and the yield of phosphoric acid esterified cellulose can be improved. After dehydrating the obtained phosphoric acid esterified cellulose suspension, it is preferably heat-treated at 100 to 170° C. from the viewpoint of suppressing hydrolysis of cellulose. Further, during heat treatment, it is preferable to heat at 130° C. or lower, preferably 110° C. or lower while water is contained, and after removing water, heat treatment at 100 to 170° C.

The degree of phosphoric acid group substitution per glucose unit of the phosphoric acid esterified cellulose is preferably 0.001 to 0.40. By introducing phosphate substituents into cellulose, the cellulose cells become electrically repulsive to each other. Therefore, cellulose into which phosphate groups have been introduced can be easily nano-fibrillated. Note that if the degree of phosphate group substitution per glucose unit is less than 0.001, sufficient nanofibrillation cannot be achieved. On the other hand, if the degree of phosphoric acid group substitution per glucose unit is greater than 0.40, the cellulose may swell or dissolve, making it impossible to obtain fine fibrous cellulose. In order to efficiently perform fibrillation, the phosphoric acid esterified cellulose raw material obtained above is preferably boiled and then washed with cold water.

In the present invention, chemically modified cellulose or unmodified cellulose is used in the form of a dispersion liquid dispersed in a dispersion medium. Examples of the dispersion medium include water and organic solvents, and a mixture of these may also be used. The solid content concentration of the cellulose dispersion used in the present invention is 0.1 to 10, because if the concentration is too low, the fibrillation efficiency will be poor, and if the concentration is too high, the viscosity of the dispersion will increase and fibrillation will be difficult. 0% by weight is preferred, 0.1 to 5.0% by weight is more preferred, even more preferably 0.25 to 3.0% by weight, particularly preferably 0.5 to 1.0% by weight.

A dispersion of chemically modified cellulose or unmodified cellulose can be prepared, for example, by diluting the chemically modified cellulose or unmodified cellulose with water.

(defibration)
In the production method of the present invention, a high-pressure washer having a residual water discharge mechanism consisting of a pressure regulating valve is used to wash the dispersion of chemically modified cellulose or unmodified cellulose obtained as described above. A spillwater circulation process in which the dispersion liquid is taken in from the suction port of a plunger pump that constitutes a part of the high-pressure washer through the water suction port and discharged from the discharge port of the plunger pump, and is discharged from the spillwater port of the high-pressure washer to the storage section. By performing this step, cellulose is defibrated and fine fibrous cellulose is obtained.
Specifically, the cellulose is defibrated when the dispersion liquid passes through a narrow gap formed by the relief valve 32 of the pressure regulating valve disposed downstream of the plunger pump and is discharged from the surplus water outlet.

According to the manufacturing method of the present invention, a high-pressure washer having a surplus water discharge mechanism consisting of a pressure regulating valve is provided as equipment that is inexpensively available, easy to introduce, and normally used by users, and includes a plunger pump. By using a material containing as part of the structure, it is possible to efficiently defibrate cellulose and obtain fine fibrous cellulose. Furthermore, the viscosity characteristics of the obtained fine fibrous cellulose are comparable to those of the fine fibrous cellulose obtained using a high-pressure homogenizer, which is expensive and large equipment.

(Application)
The fine fibrous cellulose obtained by the production method of the present invention can be used for various purposes, and is used as a thickener, a gelling agent, a sizing agent, a food additive, Excipients, additives for paints, additives for adhesives, abrasives, compounded materials for rubber and plastics, water retention materials, shape retention agents, muddy water conditioners, filter aids, anti-flooding agents, admixtures, cement-based It can be used as a coating agent for cured products. The fields include food, beverages, cosmetics, pharmaceuticals, paper manufacturing, various chemical supplies, paints, sprays, agricultural chemicals, civil engineering, architecture, electronic materials, flame retardants, household goods, adhesives, cleaning agents, fragrances, and lubricating compositions. Examples include things.

Among the above-mentioned applications, the obtained fine fibrous cellulose can be sprayed and coated directly on a large surface using the high-pressure washer used for defibration, and applications that require spraying and coating on a large surface area. It is particularly suitable for use as a coating agent for cement-based cured products.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. In addition, unless the method of measuring/calculating each numerical value in each example is particularly described, it was measured/calculated by the method described in the specification.

(Example 1)
Carboxymethylated pulp (manufactured by Nippon Paper Industries Co., Ltd., trade name: SLD-F5) was adjusted to a solid content concentration of 1% by weight with water. Pour the obtained dispersion liquid into a tank, turn on the power of the high pressure washer (manufactured by Arimitsu Kogyo Co., Ltd., product name: TRY high pressure washer, model number: TRY-10200), and drain the dispersion liquid in the tank from the water intake port. The dispersion liquid was taken into a high-pressure washer, and the nozzle was kept closed, and the dispersion liquid was discharged from the spill port into a tank. A total of 3 passes were performed at a throughput of 18 L/min to obtain a fine fibrous cellulose dispersion. Note that the processing pressure of the high-pressure washer was 20 MPa.

(Comparative example 1)
Put a dispersion of carboxymethylated pulp prepared in the same manner as in Example 1 into a tank, turn on the same high-pressure washer as in Example 1, take the dispersion in the tank into the high-pressure washer from the water intake port, The nozzle was opened and the dispersion liquid was discharged from the nozzle. One-pass treatment was performed at a throughput of 18 L/min to obtain a fine fibrous cellulose dispersion. Note that the processing pressure of the high-pressure washer was 20 MPa.

(Reference example 1)
A dispersion of carboxymethylated pulp prepared in the same manner as in Example 1 was subjected to 1 to 3 passes of treatment at a pressure of 150 MPa using a high-pressure homogenizer to obtain a fine fibrous cellulose dispersion.

(evaluation)
(viscosity characteristics)
The viscosity characteristics of the fine fibrous cellulose dispersions obtained in Example 1, Comparative Example 1, and Reference Example 1 were measured using a rheometer (Rheometer MCR301, manufactured by Anton Paar) at a shear rate of 10 ^-3 to 10 ³ (1/ s), measured at a temperature of 25°C. A graph of the obtained viscosity characteristics is shown in FIG. The closer the graph is to the viscosity characteristic graph of the dispersion treated with the high-pressure homogenizer of Reference Example 1, the more advanced the fibrillation is.

(result)
As can be seen from FIG. 3, the viscosity of the dispersion liquid of Example 1 discharged from the spillway increased as the number of passes was increased, and the viscosity characteristic graph approached that of Reference Example 1. In other words, it can be seen that the defibration progressed. On the other hand, it can be seen that the viscosity of the dispersion liquid of Comparative Example 1 discharged from the nozzle did not increase as compared to the dispersion liquid of Example 1 which was subjected to one-pass treatment. In the case of Comparative Example 1 in which the dispersion is discharged from a nozzle, it is discharged into the air, and it is considered that the defibrating property is inferior to that in Example 1, which includes a mechanism for discharging into the dispersion liquid from a pressure regulating valve.

(Example 2)
(Manufacture of TEMPO oxidized pulp)
50g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from coniferous trees, 390mg of TEMPO (Sigma Aldrich) (0.05 mmol per 1g of absolutely dry cellulose) and 5.1g of sodium bromide (absolutely dry) 1.0 mmol per 1 g of cellulose) was added to 5 L of an aqueous solution and stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that the sodium hypochlorite concentration was 6.0 mmol/g, and the oxidation reaction was started. During the reaction, the pH in the system decreased, but the pH was adjusted to 10 by successively adding a 3M aqueous sodium hydroxide solution. The reaction was terminated when the sodium hypochlorite was consumed and the pH within the system stopped changing. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain a TEMPO-oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxy groups was 1.6 mmol/g.

The TEMPO oxidized pulp obtained as described above was adjusted to a solid content concentration of 0.5% by weight with water. Pour the obtained dispersion liquid into a tank, turn on the power of a high-pressure washer (manufactured by Auriko Kogyo Co., Ltd., product name: TRY high-pressure washer, model number: TRY-10200), and take in the dispersion liquid in the tank from the water intake port. The dispersion liquid was discharged into the tank from the spillway with the nozzle kept closed. A total of 5 passes were performed at a throughput of 18 L/min to obtain a fine fibrous cellulose dispersion. Note that the processing pressure of the high-pressure washer was 20 MPa.

(Example 3)
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 2, except that the processing pressure of the high-pressure washer was 15 MPa instead of 20 MPa, and a total of 8 passes were performed instead of 5 passes in total.

(Example 4)
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 2, except that the processing pressure of the high-pressure washer was 10 MPa instead of 20 MPa, and a total of 8 passes were performed instead of 5 passes in total.

(Example 5)
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 2, except that the processing pressure of the high-pressure washer was 5 MPa instead of 20 MPa, and a total of 50 passes were performed instead of 5 passes in total.

(Reference example 2)
The TEMPO oxidized pulp obtained in the same manner as in Example 2 was adjusted to a solid content concentration of 0.5% by weight with water. The obtained dispersion was subjected to 1 to 3 passes of treatment at a pressure of 150 MPa using a high-pressure homogenizer to obtain a fine fibrous cellulose dispersion.

(evaluation)
(Measurement of viscosity)
The fine fibrous cellulose dispersions with a solid content concentration of 0.5% by weight obtained in Examples 2 to 5 and Reference Example 2 were measured at 25°C using a B-type viscometer (manufactured by Eiko Seiki Co., Ltd.). The viscosity was measured after 3 minutes at a rotation speed of 60 rpm, and after 3 minutes at a rotation speed of 6 rpm. The results are shown in Table 1.

(result)
It was confirmed that the dispersion obtained by the one-pass treatment of Reference Example 2 progressed in defibration and had thixotropic properties. It was confirmed that the viscosity decreased significantly after the 2-pass treatment. This is thought to be caused by damage to the fibers due to excessive defibration. It can be said that the closer the viscosity characteristics are to the viscosity characteristics of the dispersion obtained by the one-pass treatment of Reference Example 2, the more preferable it is. In Example 2, preferable results were obtained using 3 to 5 pass treatments. In Example 3, preferable results were obtained with 3 to 8 pass treatments. In Example 4, preferable results were obtained using 5 to 8 pass treatments. In Example 5, preferable results were obtained after 20 to 50 passes of processing.

2...High pressure washer, 4...Storage part, 6...Dispersion liquid, 8...Water inlet, 9...Suction port of plunger pump, 10...Plunger pump, 11...Discharge port of plunger pump, 12...Discharge port, 14...Discharge hose, 16...Nozzle, 18...Pressure regulating valve, 20...Left water port, 22...Water suction hose, 24...Left water hose, 26...Pressure regulating screw, 28...Pressure regulating spring, 30...Piston, 32...Relief valve , 36...pressure regulating valve inlet, 38...pressure regulating valve outlet, 40...surplus water outlet

Claims

A method for producing fine fibrous cellulose, comprising:
A plan that constitutes a part of the high-pressure washer, in which a dispersion of chemically modified cellulose or unmodified cellulose stored in a storage section is passed through a water intake port of a high-pressure washer having a surplus water discharge mechanism consisting of a pressure regulating valve. A method for producing fine fibrous cellulose, comprising a spill water circulation step of discharging the dispersion liquid taken in from a suction port of a plunger pump and discharged from a discharge port of the plunger pump to the storage portion from a spill port of the high-pressure washer.
The method for producing fine fibrous cellulose according to claim 1, wherein the outlet pressure of the pressure regulating valve controlled by the pressure regulating valve of the high-pressure washer is 0.5 to 25 MPa.
The method for producing fine fibrous cellulose according to claim 1 or 2, wherein the solid content concentration of the dispersion is 0.1 to 10.0% by weight.
The method for producing fine fibrous cellulose according to claim 1 or 2, wherein the chemically modified cellulose is carboxylated cellulose or carboxymethylated cellulose.
The method for producing fine fibrous cellulose according to claim 1 or 2, wherein the surplus water circulation step is performed 1 to 100 times.
A method for defibrating cellulose,
A plan that constitutes a part of the high-pressure washer, in which a dispersion of chemically modified cellulose or unmodified cellulose stored in a storage section is passed through a water intake port of a high-pressure washer having a surplus water discharge mechanism consisting of a pressure regulating valve. A method for defibrating cellulose, comprising a residual water circulation step of discharging the dispersion liquid taken in from a suction port of a plunger pump and discharged from a discharge port of the plunger pump to the storage section from a spill port of the high-pressure washer.