JP7481812B2 - Carboxymethylcellulose or its salt and composition thereof - Google Patents

Description

The present invention relates to carboxymethylcellulose (hereinafter, simply referred to as CMC) or a salt thereof, an aqueous composition containing CMC or a salt thereof and water, and a method for preparing CMC or a salt thereof into granules having a predetermined particle size distribution to improve its solubility in water.

CMC is one of the most representative water-soluble polymer materials, and is used in a wide range of applications, including food, cosmetics, pharmaceuticals, and negative electrode materials for lithium-ion batteries. Although CMC is usually used in the form of an aqueous solution, it is prone to form aggregates (aggregates or sticky floccules) when mixed with water, which inhibits the penetration of water into the aggregates. Once aggregates are formed, it takes a long time to dissolve the CMC, preventing improvement in product productivity. For this reason, methods are being investigated for efficiently dissolving CMC in a short time.

JP 59-36941 A (Patent Document 1) discloses that CMC-Na obtained by adding a predetermined amount of water-soluble salt and water to CMC sodium salt (hereinafter simply referred to as CMC-Na) with a purity of 95% or more, followed by granulation and sieving, exhibits easy water dispersibility. In the examples of this document, a predetermined amount of water-soluble salt such as anhydrous sodium sulfate or its aqueous solution, table salt, and sodium L-glutamate and water is added to CMC powder with a purity of 99%, which is then granulated and sieved to prepare CMC granules that pass through a 20 mesh but not an 80 mesh.

In addition, Japanese Patent No. 3516358 (Patent Document 2) discloses a method of spray-drying and granulating a solvent-water-containing slurry of CMC alkali salt by atomizing it by flowing it down onto a rotating disk or by spraying it from a nozzle under a specified gas atmosphere. It is described that the obtained CMC powder has excellent solubility because 80% or more of the total has a particle size within the range of 70 to 200 μm, and the proportion of fine powder with a particle size of 20 μm or less is small, at 2.0% or less of the total.

Japanese Patent Publication No. 59-36941 Japanese Patent No. 3516358

However, in Patent Document 1, the product contains relatively large particles that pass through a 20 mesh screen, which may take a long time to dissolve, and the purity is reduced by the addition of water-soluble salts, which are essential components, so there is a risk that the product's uses may be limited.

In Patent Document 2, although the proportion of fine powder of 20 μm or less is small, depending on conditions such as the pressure of the spray injection, the particles of the atomized CMC solution may become small, and the particle size of the resulting CMC powder may also be relatively small. Also, perhaps because the proportion of particles with relatively small particle sizes is high, it may take a long time to dissolve.

In addition, neither Patent Document 1 nor Patent Document 2 discloses any information about the relationship between the particle size, such as the specific median size (D50), of CMC-Na and the dissolution rate.

The object of the present invention is therefore to provide CMC or a salt thereof that can be efficiently dissolved in water (has excellent immediate solubility) even with gentle stirring, an aqueous composition thereof, and a method for preparing the CMC or a salt thereof to improve water solubility.

Another object of the present invention is to provide CMC or a salt thereof that can be efficiently dissolved in water even if the viscosity of the aqueous solution is high (or even if the molecular weight of the CMC or a salt thereof is large), an aqueous composition thereof, and a method for preparing the CMC or a salt thereof to improve the water solubility.

Yet another object of the present invention is to provide CMC or its salt, an aqueous composition thereof, and a method for preparing the CMC or its salt to improve the water solubility, which can improve the productivity of negative electrodes for lithium ion batteries.

As a result of intensive research into achieving the above object, the inventors discovered that carboxymethylcellulose or a salt thereof having a specific particle size distribution (or particle diameter distribution) can be efficiently dissolved in water, and thus completed the present invention.

In other words, the carboxymethylcellulose or salt thereof of the present invention is granular, and when the particle size at the cumulative 10%, cumulative 50% and cumulative 90% from the small particle size side in the volume-based cumulative distribution (or cumulative frequency distribution) of particle sizes is defined as D10, D50 and D90, respectively, D10 is about 90 μm or more, D50 is about 120 to 470 μm, and D90 is about 500 μm or less.

The D10 may be about 100 μm or more, the D50 may be about 150 to 200 μm, and the D90 may be about 250 μm or less.

In the granular CMC or salt thereof, the proportion of particles with a circularity of 50% or more may be about 90% by volume or more relative to the total, and the proportion of particles with a circularity of 70% or more may be about 70% by volume or more relative to the total. In addition, the proportion of particles with a circularity of 50% or more may be about 95% by volume or more relative to the total, and the proportion of particles with a circularity of 70% or more may be about 80% by volume or more relative to the total.

The viscosity of a 1% by mass aqueous solution of the CMC or its salt may be about 1500 to 3000 mPa·s at a temperature of 25°C. The CMC or its salt may be an electrode material.

The present invention includes an aqueous composition containing the CMC or a salt thereof and water, and a method for producing the aqueous composition by mixing the CMC or a salt thereof with water, and also includes a method for preparing the CMC or a salt thereof in the above-mentioned granular form to improve its solubility in water.

In the present invention, since the CMC or its salt has a predetermined particle size distribution, the generation of maltose can be effectively suppressed, and it can be efficiently dissolved in water even with gentle stirring. In addition, even if the viscosity of the aqueous solution is high (or even if the molecular weight of the CMC or its salt is large), it can be efficiently dissolved in water in a short time. Furthermore, when the CMC or its salt of the present invention is used in the negative electrode of a lithium ion battery, the CMC or its salt dissolves efficiently, so that the time required for the process of preparing an aqueous composition (or a slurry composition) for forming an electrode can be shortened, and the generation of maltose, which causes product defects, can be suppressed, so that the productivity (or yield) of the lithium ion battery can be effectively improved.

FIG. 1 is a graph showing the transition of the maximum torque achievement rate of the stirrer in the dissolution time measurement of CMC-Na obtained in the Examples, Comparative Examples, and Reference Examples. FIG. 2 shows the volume-based particle size distribution of the CMC-Na obtained in the Examples, Comparative Examples, and Reference Examples. FIG. 3 shows the distribution of the volumetric circularity of the CMC-Na obtained in the examples, comparative examples, and reference examples.

[CMC or its salt]
The granular CMC or salt thereof of the present invention exhibits a predetermined particle size distribution. That is, D10 can be selected from a range of about 90 μm or more (e.g., 95 to 250 μm), and may be, for example, about 100 μm or more (e.g., 105 to 200 μm), preferably about 110 μm or more (e.g., 115 to 150 μm), and more preferably about 120 μm or more (e.g., 120 to 140 μm, preferably 120 to 130 μm).

D50 can be selected from the range of about 120 to 470 μm (e.g., 130 to 400 μm), and may be, for example, about 140 to 350 μm (e.g., 155 to 300 μm), preferably about 145 to 250 μm (e.g., 150 to 200 μm), and more preferably about 160 to 190 μm (e.g., 165 to 185 μm, preferably 170 to 180 μm).

D90 can be selected from a range of about 500 μm or less (e.g., 180 to 400 μm), and may be, for example, about 450 μm or less (e.g., 190 to 400 μm), preferably about 350 μm or less (e.g., 200 to 300 μm), and more preferably about 250 μm or less (e.g., 210 to 240 μm, preferably 220 to 230 μm).

In this specification and claims, D10, D50 and D90 are particle sizes based on volume and can be measured by the method described in the examples below.

In addition, since it is preferable that the particle size of CMC or its salt has a narrow distribution width and high uniformity, D10, D50 and D90 may be, for example, D10 is 90 μm or more, D50 is 130 to 400 μm, and D90 is 450 μm or less; preferably D10 is 100 μm or more, D50 is 140 to 350 μm, and D90 is 450 μm or less; more preferably D10 is 100 μm or more, D50 is 150 to 200 μm, and D90 is 250 μm or less; particularly preferably D10 is 110 μm or more, D50 is 160 to 190 μm, and D90 is 250 μm or less; and particularly preferably D10 is 120 μm or more, D50 is 165 to 185 μm, and D90 is 210 to 240 μm.

The mode diameter (the most frequent diameter or most frequent particle diameter) in the particle size distribution of CMC or its salt can be selected from the range of, for example, about 120 to 470 μm (for example, 130 to 400 μm), and may be, for example, about 140 to 350 μm (for example, 145 to 300 μm), preferably about 150 to 250 μm (for example, 150 to 200 μm), and more preferably about 160 to 190 μm.

If the proportion of small particles is too high, the particles may easily aggregate and the formation of agglomerates may not be suppressed, and if the proportion of large particles is too high, the area (surface area) available for contact with water may decrease, causing the large particles themselves to become agglomerated, which may lengthen the dissolution time. The CMC or salt thereof of the present invention has a well-balanced, uniform particle size that suppresses the formation of agglomerates between particles while increasing the contact area with water, allowing the dissolution time to be significantly shortened.

The shape of the particles of CMC or its salt is preferably approximately spherical. The approximately spherical shape provides a good balance between inhibiting particle aggregation and increasing the contact area with water, and thus the dissolution time can be significantly shortened. For this reason, it is preferable that the CMC or its salt of the present invention has a high proportion of particles with high circularity (or area circularity). Note that although the particle size of CMC or its salt is often discussed, no attention has been paid to its circularity, probably because CMC or its salt usually has a powdery appearance.

In CMC or a salt thereof, the proportion of particles with a circularity of 50% or more may be, for example, 85% by volume or more, preferably 90% by volume or more (e.g., 90 to 100% by volume), and more preferably 95% by volume or more (e.g., 95 to 100% by volume) relative to the total volume of the particles.

The proportion of particles with a circularity of 70% or more may be, for example, 50% by volume or more, preferably 60% by volume or more (e.g., 70 to 100% by volume), and more preferably 75% by volume or more (e.g., 80 to 100% by volume) relative to the total volume of the particles.

Furthermore, the proportion of particles with a circularity of 90% or more may be, for example, 5% by volume or more (e.g., 10 to 100% by volume) and preferably 13% by volume or more (e.g., 15 to 100% by volume) relative to the total volume of the particles.

In this specification and claims, "roundness" is defined as follows:

Circularity [%] = 4π × A/P ² × 100
(In the formula, π represents the circular constant, A represents the area (projected area) of the particle, and P represents the perimeter of the particle.)

In addition, in the specification and claims of the present invention, the circularity distribution is a volume-based distribution, and can be measured by the method described in the examples below.

When the percentages of particles with a circularity of 50% or more, 70% or more, and 90% or more are respectively designated as C50, C70, and C90, for example, C50 may be about 90% by volume or more relative to the entire particles, and C70 may be about 70% by volume or more relative to the entire particles; preferably C50 may be about 95% by volume or more relative to the entire particles, and C70 may be about 80% by volume or more relative to the entire particles; more preferably C50 may be about 95% by volume or more relative to the entire particles, C70 may be about 80% by volume or more relative to the entire particles, and C90 may be about 15% by volume or more relative to the entire particles. If the percentage of particles with low circularity is too high, it may not be possible to shorten the dissolution time. It should be noted that even if C90 is relatively low, if the values of C70 and C50 are high, it seems that solubility can be effectively improved.

The average degree of substitution (degree of etherification or DS) of CMC or its salt can be selected from the range of, for example, about 0.1 to 3 (for example, 0.3 to 2.5), preferably about 0.4 to 2 (for example, 0.5 to 1.5), more preferably about 0.6 to 1.3 (for example, 0.7 to 1.2), and particularly about 0.8 to 1.1 (for example, 0.85 to 1, preferably 0.85 to 0.95). If the degree of substitution is too low, the solubility or immediate solubility may decrease, and if the degree of substitution is too high, the water-soluble portion increases and it is difficult to form mamako, but when used as an electrode material, it is difficult to form hydrophobic interactions with the active material, and the coating strength may decrease. In this specification and claims, the average degree of substitution (degree of etherification) can be measured by the method described below.

1.000 g of sample is weighed out precisely and placed in a porcelain crucible. After carbonization, it is completely incinerated at 630°C and allowed to cool at room temperature (1). Approximately 250 mL of ion-exchanged water and 40 mL of 0.05 mol/L sulfuric acid are precisely weighed and added to a beaker (2). (1) is added to (2), loosely covered, boiled for 30 minutes, and then cooled in cold water. After cooling, 5 drops of phenolphthalein solution are added and neutralized by titration with 0.1 mol/L sodium hydroxide aqueous solution. A blank test is performed in the same manner, and the degree of etherification is calculated using the following formula.

Degree of etherification=162×A ₁ /(10000−80×A ₁ )
[In the formula, A ₁ is the amount (mL) of 0.05 mol/L sulfuric acid consumed by the bound alkali in 1 g of sample calculated as a dry matter, and is represented by the following formula.
A ₁ = (B ₁ - S ₁ ) × F ₁ / (W ₁ × (1 - M ₁ / 100)) - alkalinity (wherein B ₁ is the amount (mL) of 0.1 mol/L sodium hydroxide aqueous solution consumed in the blank test, S ₁ is the amount (mL) of 0.1 mol/L sodium hydroxide aqueous solution consumed in the actual test, W ₁ is the amount of sample (g), M ₁ is the drying loss of the sample (mass %), and F ₁ is the factor of the 0.1 mol/L sodium hydroxide aqueous solution).

The loss on drying was measured in accordance with JIS P 8203:2010 (ISO 638:2008), "Paper, paperboard and pulp - Determination of absolute dryness - Dryer method."
The alkalinity can be measured by the method described below.

Place approximately 250 mL of ion-exchanged water in a beaker, add 1.000 g of precisely weighed sample little by little while stirring until dissolved, then add 5 mL of 0.05 mol/L sulfuric acid. Cover loosely and boil for 10 minutes, then cool in cold water. After cooling, add 5 drops of phenolphthalein solution and neutralize with 0.1 mol/L sodium hydroxide aqueous solution. Perform a blank test in the same way, and calculate the alkalinity using the following formula.

Alkalinity = (B ₂ - S ₂ ) x F ₂ / (W ₂ x (1 - M ₂ / 100))
(In the formula, _B2 is the consumption amount (mL) of 0.1 mol/L aqueous sodium hydroxide solution required in the blank test, _S2 is the consumption amount (mL) of 0.1 mol/L aqueous sodium hydroxide solution required in the actual test, _W2 is the sample weight (g), _M2 is the drying loss of the sample (mass %), and _F2 is the factor of the 0.1 mol/L aqueous sodium hydroxide solution.)

The loss on drying can be measured in the same manner as described in the section on average degree of substitution.

Examples of salts of CMC include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt, and ammonium salt. These salts may be used alone or in combination of two or more. Of these salts, sodium salt or ammonium salt is usually used, and sodium salt is preferred. Note that CMC or its salts may be used in combination, but usually, a salt of CMC (preferably CMC-Na) is used alone.

The viscosity of a 1% by mass aqueous solution of CMC or its salt at a temperature of 25°C may be selected from a range of, for example, about 10 to 20,000 mPa·s (for example, 100 to 15,000 mPa·s) depending on the application, and may be, for example, about 1,000 to 10,000 mPa·s (for example, 1,100 to 8,000 mPa·s), preferably about 1,200 to 6,000 mPa·s (for example, 1,300 to 5,000 mPa·s), more preferably about 1,400 to 4,000 mPa·s (for example, 1,500 to 3,000 mPa·s), and particularly about 1,600 to 2,000 mPa·s (for example, 1,700 to 1,900 mPa·s). If the viscosity is too low, it may not be usable, particularly for applications such as electrode materials.

For example, when used as a negative electrode material (such as a thickener, dispersion stabilizer, or binder (binding agent or binder)) for lithium ion batteries, CMC or its salt itself becomes a resistor, and adding a large amount of it reduces battery performance, so a high-viscosity product is required so that it can exert the desired function (such as a thickening effect) even when added in a small amount. On the other hand, from the viewpoint of improving productivity, CMC or its salt is required to have less undissolved matter (such as 'mako') that causes product defects and can be dissolved quickly in a short time. However, the higher the viscosity in the aqueous solution, the more likely it is that 'mako' will occur and the longer the dissolution time will be, so these characteristics are in a trade-off relationship, and it has been difficult to satisfy all of them. The CMC or its salt of the present invention can be suitably used as an electrode material (such as a thickener, dispersion stabilizer, and/or binder) because it can effectively shorten the dissolution time by suppressing the occurrence of 'mako' even when the viscosity is high in the aqueous solution.

In this specification and claims, viscosity can be measured by the method described below.

100 mL of ion-exchanged water is placed in a dissolution bottle for viscosity measurement (hereinafter referred to as "viscosity bottle"), and a separately weighed sample (2.50 x X ₃ ) g is added little by little so as not to form lumps, and lightly crushed with a glass rod. After sufficient swelling, the amount of additional water V ₃ (mL) corrected for ion-exchanged water calculated by the following formula is added, and completely dissolved while stirring occasionally with a glass rod. After dissolution, the solution is degassed under reduced pressure, and the viscosity bottle is placed in a thermostatic water bath until the liquid temperature reaches 25°C, and the sample solution is stirred uniformly, and then measured at 60 rpm with a B-type viscometer.

Viscosity (mPa·s) = scale reading × conversion factor V ₃ = 2.5 × (100 - X ₃ - _{M 3} ) - 100
(In the formula, _V3 is the amount of water added (mL) corrected for ion-exchanged water, _X3 is the measured concentration (mass%), and _M3 is the sample drying loss (mass%).

The loss on drying can be measured in the same manner as described in the section on average degree of substitution.

The dissolution time when preparing a 0.8% by mass aqueous solution of CMC or a salt thereof may be, at a temperature of 25°C and a stirring speed of 300 rpm, for example, 10 minutes or less (e.g., 10 seconds to 8 minutes), preferably 6 minutes or less (e.g., 30 seconds to 5 minutes), more preferably 4 minutes or less (e.g., 1 to 3 minutes), and particularly 3 minutes or less (e.g., 1.5 to 2.5 minutes). In this specification and claims, the dissolution time can be measured by the method described in the Examples below.

[Production method]
The method for producing CMC or a salt thereof of the present invention is not particularly limited. Usually, the method includes at least a granulation step of granulating CMC or a salt thereof.

(Granulation process)
The CMC or a salt thereof used in the granulation step can be a commercially available product, and is usually formed into a fine powder and/or fiber form.

The granulation method may be a conventional granulation method, such as rolling granulation, fluidized bed granulation, stirring granulation (mixing and stirring granulation), crushing or crushing granulation (crushing and crushing granulation), compression granulation (compression molding granulation), extrusion granulation, spray granulation (melt granulation), or spray drying granulation. The granulation method may be a dry method, but is usually a wet method. Of these granulation methods, stirring granulation is often used. Granulation may be performed under normal pressure, reduced pressure, or increased pressure.

A binder may be added to CMC or its salt depending on the granulation method. The binder may be an organic solvent, but is usually water (e.g., pure water, etc.). For example, in agitation granulation, water (e.g., pure water) as a binder may be sprayed while agitating CMC or its salt in a granulator (or agitator).

The amount of binder (especially water) sprayed may be, for example, about 10 to 1000 parts by mass (e.g., 30 to 800 parts by mass), preferably about 50 to 500 parts by mass (e.g., 60 to 300 parts by mass), and more preferably about 70 to 200 parts by mass (e.g., 80 to 100 parts by mass) per 100 parts by mass of CMC or its salt.

(Drying process)
The granular CMC or its salt obtained in the granulation step is often dried in a drying step to adjust the amount of remaining binder (especially water). The drying method may be natural drying, or drying under heating and/or reduced pressure. Usually, drying is often performed by heating, and the heating temperature may be, for example, about 50 to 200°C (e.g., 60 to 150°C), preferably about 70 to 100°C (e.g., 80 to 90°C).

The amount of remaining binder may be, for example, about 30% by mass or less (e.g., 20% by mass or less) relative to the total amount of granular CMC or its salt after drying, and may be adjusted to preferably about 15% by mass or less (e.g., 10% by mass or less), and more preferably about 5% by mass or less (e.g., 1% by mass or less).

(Crushing process)
After drying, the obtained CMC or its salt may be pulverized in a pulverization step to adjust the particle size, if necessary. For pulverization, a conventional pulverizer, such as a roll crusher, a cone crusher, a cutter mill, a stamp mill, an autogenous pulverizer, a stone mill, a mortar, a mortar mill, a ring mill, or the like, capable of pulverizing to about several hundred μm (or a medium pulverizer); a roller mill, a jet mill, a high-speed rotary mill (hammer mill, pin mill, etc.), a container-driven pulverizer (a ball mill, a tube mill, a rod mill, or the like, a vibration mill, a planetary mill, etc.), a media-agitation pulverizer (attritor, bead mill, etc.), or the like, capable of pulverizing to several hundred μm or less (a fine pulverizer or an ultrafine pulverizer), may be used. These pulverizers may be used alone or in combination of two or more. Among these pulverizers, a medium pulverizer such as a cutter mill is often used.

When a cutter mill is used, the rotation speed may be, for example, 100 to 1,000,000 rpm (e.g., 1,000 to 100,000 rpm), preferably 5,000 to 50,000 rpm (e.g., 10,000 to 30,000 rpm), and more preferably about 15,000 to 25,000 rpm.

The grinding time may be selected depending on the type of grinder, and may be, for example, 10 seconds to 1 hour (e.g., 30 seconds to 30 minutes), preferably 1 to 10 minutes (e.g., 1 to 3 minutes).

(Classification process)
The obtained granular CMC or its salt is often classified (or sieved) in a classification step to adjust to a desired particle size (and roundness). Classification methods include conventional methods, such as classification using the principles of fluid mechanics [dry classification (gravity classification, inertia classification, centrifugal classification, etc.), wet classification (sedimentation classification, mechanical classification, hydraulic classification, centrifugal classification, etc.)], sieving, etc. These classification methods can be used alone or in combination of two or more. Of these, classification is usually performed by sieving.

When classifying by sieving, the granulated CMC or its salt is usually classified by stacking successively larger mesh sizes of sieves, starting with the smallest mesh size among multiple sieves with different mesh sizes. The particles separated by sieving may be particles that pass through a sieve with a mesh size of, for example, about 500 μm, preferably 400 μm, more preferably 300 μm, even more preferably 200 μm, and particularly preferably about 180 μm, but do not pass through a sieve with a mesh size of, for example, about 90 μm, preferably about 100 μm.

In this manner, the CMC or salt thereof of the present invention can be prepared. The present invention also includes a method for improving the solubility in water by adjusting the particle size distribution (and circularity) of the CMC or salt thereof to a predetermined range by the above-mentioned method.

[Aqueous composition and method for producing same]
The present invention also includes an aqueous composition (liquid, slurry or paste composition) containing the CMC or its salt and water. In the aqueous composition, the ratio of CMC or its salt to the total amount of CMC or its salt and water may be, for example, about 0.01 to 10% by mass (e.g., 0.1 to 5% by mass), preferably about 0.3 to 2% by mass (e.g., 0.5 to 1.5% by mass), and more preferably about 0.6 to 1% by mass (e.g., 0.7 to 0.9% by mass).

The water is usually pure water. The pH of the aqueous composition may be acidic, but is usually neutral or alkaline (especially neutral).

The aqueous composition may contain other components different from CMC or its salt and water. For example, when CMC or its salt is used as an electrode material (such as a thickener and/or dispersion stabilizer), the aqueous composition may contain other electrode materials such as active materials (e.g., carbon materials such as natural graphite, artificial graphite, hard carbon, MCMB (mesophase microspheres), lithium titanate, etc.), binders (such as styrene butadiene copolymers), etc.).

The aqueous composition can be prepared by mixing the CMC or its salt, the water, and, if necessary, the other components. There are no particular limitations on the order or method of mixing, but from the viewpoint of effectively suppressing the formation of mamaco, it is preferable to add the CMC or its salt (particularly slowly or in small amounts) while stirring the water using a stirrer or the like.

The stirring speed (rotation speed of the stirrer or impeller) when CMC or its salt is added to water may be, for example, about 10 to 2000 rpm (for example, 100 to 1500 rpm), preferably about 500 to 1000 rpm (for example, 600 to 900 rpm), and more preferably about 650 to 850 rpm (for example, 700 to 800 rpm). After the addition of CMC or its salt is completed, stirring is usually continued until dissolution is completed (or the stirring torque becomes stable). The stirring speed after the addition may be equal to or higher than the stirring speed during addition, but may also be slow, for example, about 10 to 1000 rpm (for example, 50 to 800 rpm), preferably about 100 to 500 rpm (for example, 150 to 450 rpm), and more preferably about 200 to 400 rpm (for example, 250 to 350 rpm). In the present invention, even if the stirring is slow, the dissolution time can be effectively shortened.

The shape of the impeller of the agitator may be, for example, a turbine impeller (e.g., an edged turbine impeller, a flat or inclined turbine impeller (e.g., a fan turbine impeller, a disk turbine impeller, etc.)), a paddle impeller (e.g., a flat paddle impeller, an inclined paddle impeller), a propeller impeller, a Pfaudle impeller, an anchor impeller (e.g., a gate impeller), a ribbon impeller (or a helical ribbon impeller) (e.g., a multi-strand ribbon impeller such as a double ribbon impeller, a single ribbon impeller, etc.). These impellers may be used alone or in combination of two or more kinds. Of these impellers, the ribbon impeller is preferred.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[material]
CMC-Na: carboxymethylcellulose sodium salt, "CMC Daicel Product No. 2200" manufactured by Daicel FineChem Co., Ltd., degree of etherification (DS) = 0.90, viscosity of 1% by mass aqueous solution (25°C, 60 rpm) = 1800 mPa·s.

[Evaluation method]
(Dissolution time)
220 g of pure water was weighed into a cylindrical glass container with a diameter of 55 mm and a depth of 130 mm, and the temperature was adjusted to 25° C. in a thermostatic bath. A torque meter ("Rotary Torque Meter TYPE YT" manufactured by Shinto Scientific Co., Ltd.) and a stirrer equipped with a helical ribbon-type stirring blade ("Three-One Motor BL1200" manufactured by Shinto Scientific Co., Ltd.) were attached to the cylindrical glass container. The helical ribbon-type stirring blade had a ribbon width of 3 mm, a height of 80 mm, a width (width perpendicular to the rotation axis): 40 mm, a number of blades: single, and a number of spiral turns of the ribbon: 3 times (a shape in which the ribbon turns three times at a height of 80 mm). While stirring the pure water at 750 rpm, a 0.8% by mass amount (about 1.77 g) of the sample was slowly added over 5 to 10 seconds. After the addition, the stirring speed was immediately changed to 300 rpm and the time measurement was started, and the time it took for the torque value to stabilize at a predetermined value was taken as the dissolution time. The maximum torque achievement rate was calculated as a percentage of the torque value stabilized at the above-mentioned predetermined value, which was taken as the reference (100%).

(Particle size distribution and circularity)
Using Malvern's "morphologiG3", the particle size distribution and circularity distribution of the obtained samples were measured, D10, D50 and D90 were calculated from the particle size distribution, and the respective percentages of particles with circularity of 50% or more, 70% or more and 90% or more were calculated from the circularity distribution. The number of samples was N=5000, and a statistical analysis was performed on any particles. The particle size distribution was a volume-based distribution, and the circularity distribution was a volume-based distribution.

Circularity is calculated as follows:

Circularity [%] = 4π × A/P ² × 100
(In the formula, π represents the circular constant, A represents the area (projected area) of the particle, and P represents the perimeter of the particle.)

[Examples 1 to 2 and Reference Examples 1 to 3]
(Preparation of granulated CMC-Na)
After 200 g of CMC-Na was placed in a granulator (Toshiba Corporation's "Mochitsuki Machine AFC-283"), pure water was sprayed while stirring using a spray sprayer (Fulpura Corporation's "No. 503") with the spray nozzle fully throttled and the lever pulled once every 5 seconds. The pure water was added so that the amount was 90% by mass (180 g) relative to the amount of CMC-Na. The mixture was dried at 85°C using a total exhaust dryer (Espec Corporation's "SPH-301S") until the amount of pure water (moisture content) relative to the total amount of CMC-Na and pure water was 10% by mass or less at 85°C. After drying, the obtained sample was pulverized for 2 minutes using Osaka Chemical Corporation's "Force Mill".

(Classification of granulated CMC-Na)
Sieves of 330, 166, 83, 30 and 16 mesh (JIS standard test sieves (JIS Z 8801)) were stacked on a tray in order of the sieve with the smallest mesh size (in the order described above). The granulated sample was added to the top sieve (16 mesh sieve), the lid was closed, and the sieve was subjected to vibration for 5 minutes using a "Microsifter 300" manufactured by Dalton Co., Ltd., for sieving. The classified CMC-Na was taken out as evaluation samples for Examples 1 and 2 and Reference Examples 1 to 3 as shown in Table 2, and evaluated.

[Comparative Example 1]
CMC-Na was evaluated without granulation or sieving.

The relationship between the mesh and the opening of the sieve used is shown in Table 1, and the evaluation results are shown in Table 2 and Figures 1 to 3. In Table 2, "pass" and "on" respectively indicate that the sieve was passed or not passed, so for example, "30 mesh pass, 83 mesh on product" in Example 1 means that the CMC-Na passed a 30 mesh sieve and did not pass an 83 mesh sieve. Also, "Example 1 + Example 2 (combined)" in Figures 2 to 3 shows the results of measuring a mixture of the CMC-Na obtained in Examples 1 and 2 (i.e., 30 mesh pass, 166 mesh on product).

As is clear from Table 2 and Figures 1 to 3, in Comparative Example 1 and Reference Example 3, which contain particles that are too small compared to Examples 1 and 2, and Reference Example 1, which contains particles that are too large, the particles were prone to forming lumps and took a long time to dissolve, whereas in Examples 1 and 2 and Reference Example 2, the particles dissolved in a short time compared to Comparative Example 1. In particular, in Examples 1 and 2, no lumps were observed to form, and the dissolution time was reduced to less than 1/6 of that of Comparative Example 1.

In addition, in Comparative Example 1, which had a long dissolution time, the proportion of cotton-like material was high, possibly because granulation was not performed, and in Reference Example 1, although granulation was performed, the proportion of particles with distorted shapes was high, whereas in Examples 1 and 2, which had a short dissolution time, the proportion of particles with high circularity was high compared to the other examples.

The carboxymethylcellulose or salt thereof of the present invention can be efficiently dissolved even with gentle stirring, and therefore can be used in a variety of applications, such as pharmaceuticals (e.g., tablets, laxatives, oral medications (syrups, etc.), poultices, cooling sheets, X-ray contrast agents, denture adhesives, etc.), cosmetics (e.g., hair care products (shampoos, conditioners, etc.), skin care products or basic cosmetics (gels, etc.), hair dyes, etc.), daily necessities (e.g., toothpaste, air fresheners, bath additives, water-dissolvable paper, etc.), foods (e.g., beverages, sherbets, It can be used in raw or chilled noodles, sauces, etc.), electrical and electronic components [for example, electrode (e.g., negative electrode) materials for batteries (secondary batteries such as lithium ion batteries)], civil engineering or construction materials (for example, mud adjustment agents (or mud water adjustment agents) or mud addition agents in construction such as oil or hot spring boring, underground diaphragm walls and cast-in-place piles (foundation piles), and mud pressure shield construction), sizing agents (for example, warp sizing, back sizing), aquaculture feed, firebricks, and thickening or dispersing agents for various slurries.

In particular, since the carboxymethylcellulose or its salt of the present invention can be dissolved in a short time even if it has a large molecular weight (or a high viscosity in a solution state), it can be effectively used, for example, as an electrode material (or additive) for forming electrodes of batteries such as secondary batteries [e.g., thickener, dispersant (dispersion stabilizer or stabilizer), fluidizing agent, binding agent (or binder), suspending agent, etc.], in particular as a negative electrode material for lithium ion batteries (e.g., thickener, dispersant and/or binding agent).

Claims (7)

An electrode material formed of granular carboxymethyl cellulose or a salt thereof, wherein, in a volume-based cumulative distribution of particle diameters, when the particle diameters at 10%, 50% and 90% cumulative from the smallest particle diameter side are defined as D10, D50 and D90, respectively, D10 is 90 μm or more, D50 is 120 to 470 μm and D90 is 500 μm or less,
The ratio of particles having a circularity of 50% or more to the whole particles is 90% by volume or more, and the ratio of particles having a circularity of 70% or more to the whole particles is 70% by volume or more,
The circularity is defined by the following formula:
Circularity [%] = 4π × A/P ² × 100
(In the formula, π represents the circular constant, A represents the area of the particle, and P represents the perimeter of the particle.)
An electrode material formed from carboxymethyl cellulose or a salt thereof, the viscosity of which in a 1% by mass aqueous solution at a temperature of 25° C. is 100 to 15,000 mPa·s. The electrode material according to claim 1, in which D10 is 100 μm or more, D50 is 150 to 200 μm, and D90 is 250 μm or less. An electrode material according to claim 1 or 2, in which the proportion of particles with a circularity of 50% or more is 95% or more by volume relative to the total, and the proportion of particles with a circularity of 70% or more is 80% or more by volume relative to the total. An electrode material according to any one of claims 1 to 3, in which the viscosity of a 1% by mass aqueous solution is 1500 to 3000 mPa·s at a temperature of 25°C. An aqueous composition comprising the electrode material according to any one of claims 1 to 4 and water. A method for producing the aqueous composition according to claim 5 by mixing the electrode material according to any one of claims 1 to 4 with water. A method for improving the solubility in water by preparing carboxymethylcellulose or a salt thereof in the granular form described in any one of claims 1 to 3.

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