Method for manufacturing conductive material compositions

Abstract

The present invention provides a method for producing a conductive material composition that can shorten the dissolution time required to dissolve carboxymethylcellulose (CMC) in water. [Solution] A method for manufacturing a conductive material composition, comprising: a first step of preparing a CMC solution in which CMC is dissolved in an aqueous medium containing water; and a second step of preparing a conductive material composition by adding a carbon-based conductive material to the CMC solution, wherein the first step comprises: a) adding the aqueous medium to a circulating system for circulating liquid and circulating the aqueous medium; b) adding the CMC to the circulating system, mixing the aqueous medium and the CMC, and circulating the resulting mixture; c) continuously applying a shear force to the mixture circulating in the circulating system to prepare the CMC solution; and d) determining the end of step c based on the determination viscosity of the mixture becoming below a predetermined value.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a conductive material composition.

Background Art

[0002] Conductive materials impart functions such as antistatic properties, conductivity, heat conductivity, and electromagnetic wave shielding properties to various materials. From the perspective of processability, conductive materials may be used by mixing them with various materials and applying them as a conductive material composition dispersed wetly. Carbon nanotubes or carbon black, which are carbon-based conductive materials with a large specific surface area, are suitably used as conductive materials from the perspectives of light weight and high conductivity. However, since these conductive materials have strong cohesive forces and extremely low hydrophilicity, it is necessary to devise methods for dispersing them well in an aqueous medium containing water.

[0003] JP-A-2024-65983 (Patent Document 1) describes using carboxymethyl cellulose as a dispersant for a conductive material composition. Carboxymethyl cellulose has the property of easily forming lumps (clumps, nodules) when introduced into water. Therefore, when introducing carboxymethyl cellulose into water, it is necessary to devise methods such as introducing it little by little over time.

[0004] JP-A-2007-63427 (Patent Document 2) describes that by setting the concentration of magnesium ions in water within a predetermined range, the dissolution time when dissolving carboxymethyl cellulose in water can be shortened.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The method disclosed in Patent Document 2 requires the addition of magnesium ions. Magnesium ions may degrade the performance of the conductive material composition when it is used in specific applications such as battery materials. The present invention provides a method for producing a conductive material composition that can shorten the dissolution time of carboxymethylcellulose in water without requiring additives. [Means for solving the problem]

[0007] [1] A first step is to prepare a carboxymethylcellulose solution in which carboxymethylcellulose is dissolved in an aqueous medium containing water, The process includes a second step of preparing a conductive material composition by adding a carbon-based conductive material to the carboxymethylcellulose solution, The first step described above is, a) A step of introducing the aqueous medium into a circulation system that circulates liquid and circulating the aqueous medium, b) A step of introducing the carboxymethylcellulose into the circulation system, mixing the aqueous medium and the carboxymethylcellulose, and circulating the resulting mixture, c) A step of preparing the carboxymethylcellulose solution by continuously applying a shear force to the mixed liquid circulating in the circulation system, d) A step of determining the end of step c based on the fact that the viscosity of the mixed liquid has fallen below a predetermined value, a method for producing a conductive material composition.

[0008] By circulating a mixture containing an aqueous medium and carboxymethylcellulose, and continuously applying a shear force to the mixture, a carboxymethylcellulose solution can be prepared in a short time, and as a result, a conductive material composition can be obtained in a short time. Generally, it is effective to determine whether carboxymethylcellulose is sufficiently dissolved in the aqueous medium based on the viscosity of the mixture. The inventors have reduced the complexity of the determination process by determining the end of step c based on the viscosity of the mixture falling below a predetermined value, and by making an appropriate determination, excessive preparation time in step c can be reduced, allowing a conductive material composition to be obtained in a short time. The carboxymethylcellulose solution obtained in this way is of good quality with reduced clumping of carboxymethylcellulose, and as a result, a conductive material composition with excellent storage stability can be obtained.

[0009] [2] In step b, the carboxymethylcellulose is added such that the concentration of carboxymethylcellulose in the resulting mixture is 0.6 ± 0.05% by mass. The manufacturing method according to [1], wherein in step d, the predetermined value is set to a value within the range of 62 to 96.5 [mPa·s]. [3] The manufacturing method according to [1] or [2], wherein in step d, the determination viscosity is a measured value or a predicted value. [4] The circulation system comprises a circulation channel through which liquid circulates and a shear force application section provided within the circulation channel, The shear force application section comprises a stator having a plurality of slits through which the liquid passing through the circulation channel passes, The manufacturing method according to any one of [1] to [3], wherein in step c, the shear force is applied when the mixed liquid passes through the slit. [5] The carbon-based conductive material is a single-walled carbon nanotube, the manufacturing method according to any one of [1] to [4]. [Brief explanation of the drawing]

[0010] [Figure 1]FIG. 1 is a schematic flowchart of a method for manufacturing a conductive material composition according to the present embodiment. [Figure 2] FIG. 2 is a diagram showing an outline of an example of a manufacturing apparatus used in the method for manufacturing a conductive material composition according to the present embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing a schematic configuration of a CMC storage unit and a first mixing unit. [Figure 4] FIG. 4 is a cross-sectional view showing the relationship between a rotating shaft, a stator, and a rotor in a case. [Figure 5] FIG. 12 is a perspective view of a stator. [Figure 6] FIG. 15 is a perspective view of a rotor. [Figure 7] FIG. 18 is a diagram plotting the predicted viscosity of Test Example 1 and the measured viscosity of Test Example 2. [MODE FOR CARRYING OUT THE INVENTION]

[0011] Hereinafter, embodiments of the present disclosure (hereinafter also referred to as "the present embodiment") and examples of the present disclosure (hereinafter also referred to as "the present examples") will be described. The present embodiment and the present examples do not limit the technical scope of the present disclosure.

[0012] The conductive material composition manufactured in the present embodiment is suitably used, for example, as a conductive material composition to be blended with a material used for forming a layer which is a component of a secondary battery, particularly as a conductive material composition to be blended with a material used for forming a negative electrode composite layer for a non-aqueous electrolyte secondary battery.

[0013] [Method for Manufacturing Conductive Material Composition] FIG. 1 is a schematic flowchart of a method for manufacturing a conductive material composition according to the present embodiment. Hereinafter, "the method for manufacturing a conductive material composition according to the present embodiment" may be abbreviated as "the present manufacturing method". The present manufacturing method includes a first step S10 of preparing a carboxymethylcellulose solution (hereinafter also referred to as "CMC solution") in which carboxymethylcellulose (hereinafter also referred to as "CMC") is dissolved in an aqueous medium containing water, and a second step S20 of preparing a conductive material composition by introducing a carbon-based conductive material into the CMC solution.

[0014] The first step S10 includes: Step a: introducing an aqueous medium into a circulation system for circulating a liquid (the "aqueous medium introduction step S11" in FIG. 1) and circulating the aqueous medium; Step b: introducing CMC into the circulation system (the "CMC introduction step S13" in FIG. 1), mixing the aqueous medium and CMC (the "first mixing step S14" in FIG. 1), and circulating the resulting mixture; Step c: continuously applying a shear force to the mixture being circulated in the circulation system to prepare the carboxymethyl cellulose solution (the "shearing step S15" in FIG. 1); and Step d: determining the end of step c based on the fact that the measured viscosity of the mixture becomes not more than a predetermined value. It has:

[0015] Simultaneously with the start of the CMC introduction step S13, the preparation of the mixture by the first mixing step S14 is carried out. Also, step b of circulating the resulting mixture and the shearing step S15 of continuously applying a shear force to the circulating mixture are carried out in parallel with the first mixing step S14. In step b, taking the time point when the introduction of CMC starts as a reference, if the time required for the introduction of CMC is x and the time for circulating the mixture is t, then the time x is made shorter than the time t. In this manufacturing method, it is preferable to shorten the time x within the range acceptable to the apparatus. That is, it is preferable to introduce CMC at once. In this manufacturing method, by shortening the time x, it is also possible to shorten the time t. After the introduction of CMC is completed (after the time x has elapsed), the CMC introduction step S13 is not carried out in step b. On the other hand, the application of the shear force to the mixture by the shearing step S15 is continued, the dissolution of CMC in the aqueous medium and the crushing of the CMC mass proceed, and an aqueous CMC solution in which CMC is sufficiently dissolved in the aqueous medium can be obtained. The time t depends on the amount of the CMC solution to be prepared, but according to this manufacturing method, it can be, for example, not more than 30 minutes, and can also be 20 minutes or less, 10 minutes or less, 5 minutes or less.

[0016] The second step S20 includes a carbon-based conductive material addition step S21 in which a carbon-based conductive material is added to the CMC solution obtained in the first step 10, a second mixing step S22 in which the added carbon-based conductive material is stirred and mixed to obtain a conductive material composition, and a conductive material composition storage step S23 in which the obtained conductive material composition is stored.

[0017] The decision to terminate the aqueous media circulation process (process a) and start the CMC input process S13 is made in process S12. The method of decision in process S12 is not limited and may include, for example, a method of decision based on whether the operation of a specific operating part has reached a predetermined level, or a method of decision based on whether a predetermined time has elapsed.

[0018] The decision to terminate the first step S10 and start the second step S20 is made in step S16. The decision in step S16 is based on whether the viscosity of the mixed solution has fallen below a predetermined value (step d). It is known that the degree to which clumps of CMC remain in the CMC solution is negatively correlated with the amount that passes through the filter in the CMC solution filter passage evaluation test described below. The inventors have found that there is a negative correlation between the amount that passes through in this filter passage evaluation test and the viscosity of the CMC solution, that is, the lower the viscosity of the CMC solution, the greater the amount that passes through and the lower the degree to which clumps of CMC remain, leading to step d. The lower the degree to which clumps of CMC remain, the higher the quality of the CMC solution. The longer the time t for circulating the CMC solution and applying continuous shear force, the less clumps of CMC remain, but from the viewpoint of shortening the manufacturing time, a shorter time t is preferable. In step d of this manufacturing method, time t is determined based on the viscosity of the mixed CMC solution, that is, the end of step c is determined, thereby enabling the shortening of time t while maintaining appropriate quality for forming the conductive material composition.

[0019] The specific method for the filter passage amount evaluation test described above is explained below. 15 g of CMC solution is filtered through a #150 mesh filter (manufactured by Yutoriyama Co., Ltd.), and the filter is shaken to allow it to settle and the liquid droplets to be observed. When the interval between droplets reaches 1 minute or more, filtration is stopped, and the amount of filtrate that has passed through is measured. In this measurement method, it is preferable that the amount of filtrate be 7.2 g or more for the formation of a conductive material composition.

[0020] In step d, the viscosity of the mixture may be a measured value or a predicted value. In the case of a predicted value, it may be, for example, the upper limit of the predicted value that falls within the 90% confidence interval. An example of how to calculate the predicted value will be explained in the example described later.

[0021] The predetermined value in step d can be appropriately determined by preliminary experiments. For example, in the filter passage amount evaluation test described above, the viscosity at which the amount of filtrate is a suitable value can be determined in advance and that value can be used. In step b, when the carboxymethylcellulose is administered so that the concentration of carboxymethylcellulose in the resulting mixture is 0.6 ± 0.05% by mass, and the ambient temperature of the circulation system is tw [°C], the predetermined value can be A(tw) [mPa·s] calculated from the following formula (3), and the predetermined value can also be a value less than or equal to A. Formula (3): A(tw)=96.5×exp(-0.01×(tw-13.5))

[0022] When the ambient temperature tw of the circulation system is 13.5°C, A(tw) calculated by equation (3) is 96.5 [mPa·s]. Also, when the ambient temperature tw of the circulation system is 31°C, A(tw) calculated by equation (3) is 62 [mPa·s]. Since the ambient temperature tw of the circulation system is usually within the range of 13.5°C to 31°C, the predetermined value in process d may be, for example, a value within the range of 62 to 96.5 [mPa·s].

[0023] Figure 2 is a schematic cross-sectional view of an example of a manufacturing apparatus used in this manufacturing method. The manufacturing apparatus shown in Figure 2 has a first process section 10 for performing the first process S10 and a second process section 20 for performing the second process S20. The first process section 10 has a circulation pipe (circulation channel) 101, an aqueous medium storage section 11, a CMC storage section 13, and a first mixing section 14. The second process section 20 has a pipe (channel) 201, a carbon-based conductive material storage section 21, a second mixing section 22, and a conductive material composition storage section 23.

[0024] Figure 3 is a perspective view showing the schematic configuration of the CMC housing section 13 and the first mixing section 14. The first mixing section 14 comprises a rotating shaft 141, a screw 142, a stator 151, a rotor 152, and a case 146. The case 146 houses the rotating shaft 141, the screw 142, the stator 154, and the rotor 155, and has a first opening 146a, a second opening 146b, and a third opening 146c. The screw 142 is helically mounted on the rotating shaft 141. The first mixing section 14 includes a shear force application section 15, which comprises a stator 151 and a rotor 152. Figure 4 is a cross-sectional view showing the relationship between the rotating shaft 141, the stator 151, and the rotor 152 within the case 146. The rotor 152 is fixed to the rotating shaft 141. The stator 151 is fixed to the case 146.

[0025] The CMC storage section 13 illustrated in Figure 3 is a hopper. When the CMC 13a is stored in the hopper and the valve 102 provided at the lower end of the hopper is opened and closed, the CMC is supplied to the first mixing section 14 from the second opening 146b.

[0026] Figure 5 is a perspective view of the stator 151. The stator 151 has a base body 1511 and an annular slit blade 1512. The base body 1511 is formed in a disc shape, and a through hole 1513 is formed in the center of the base body 1511. The annular slit blade 1512 is erected on one surface of the base body 1511 so as to surround the through hole 1513. The annular slit blade 1512 has a plurality of slits 1512a extending perpendicularly to the base body 1511 at predetermined intervals. The slit width w in the inner wall of the slits 1512a of the annular slit blade 1512 can be appropriately selected. By reducing the slit width w, the shear force applied to the mixed liquid can be increased. From the viewpoint of the shear force applied to the mixed liquid, the slit width w is preferably 15 mm or less, more preferably 10 mm or less, and even more preferably 8 mm or less. The slit width w is usually 3 mm or more.

[0027] Figure 6 is a perspective view of the rotor 152. The rotor 152 has a base 1521 and an annular wall 1522. The base 1521 is formed in a disc shape, and a through hole 1523 is formed in the center of the base 1521. The annular wall 1522 is erected on one side of the base 1521 so as to surround the through hole 1523. The annular wall 1522 has a plurality of slits 1522a extending perpendicularly to the base 1521 at predetermined intervals.

[0028] In the shear force application section 15 of the first mixing section 14, the stator 151 is fixed to the case 146 with the side where the annular slit blade 1512 is not erected, so that the rotating shaft 141 passes through the through hole 1513 of the base body 1511. The rotor 152 is fixed to the rotating shaft 141 with the rotating shaft 141 passing through the through hole 1523 of the base body 1521, and with the side where the annular wall 1522 of the base body 1521 is erected facing the stator 151. The diameter of the inner surface of the annular slit blade 1512 of the stator 151 is larger than the diameter of the outer surface of the annular wall 1522 of the rotor 152. The annular slit blade 1512 of the stator 151 and the annular wall 1522 of the rotor 152 are arranged such that the inner surface of the annular slit blade 1512 and the outer surface of the annular wall 1522 face each other and form a gap (hereinafter also referred to as the "facing region"). The shear force applied to the mixed liquid can be adjusted by the distance d between the inner surface of the annular slit blade 1512 and the annular wall 1522. By reducing the distance d, the shear force applied to the mixed liquid can be increased. From the viewpoint of the shear force applied to the mixed liquid, the distance d is preferably 5 mm or less, more preferably 3 mm or less, and even more preferably 1 mm or less. The distance d is usually 0.5 mm or more.

[0029] In the first mixing section 14, the flow path connecting the first opening 146a and the third opening 146c constitutes part of the flow path of the circulation piping 101 of the first process section 10, and the second opening 146b communicates with the CMC housing section 130. When a motor (not shown) is driven in the first mixing section 14, the rotating shaft 141 rotates, causing the screw 142 and rotor 152 to rotate together. The rotation of the screw 142 transfers the aqueous medium in the circulation piping 101. When CMC is supplied from the second opening 146b, the rotation of the screw 142 mixes the aqueous medium and CMC, and the mixture is transferred to the shear force application section 15. In the shear force application section 15, centrifugal force is applied to the mixed liquid by the rotation of the rotor 152, and the mixed liquid passes through the slit 1522a of the annular wall 1522 of the rotor 152 and the slit 1512a of the annular slit blade 1512 of the stator 151, and is discharged from the third opening 146c.

[0030] The mixture, having passed through the slit 1522a of the annular wall 1522 of the rotor 152, is subjected to a strong shear force in the opposing region where it is sandwiched between the rotating annular wall 1522 and the stationary annular slit blade 1512. This crushes the clumps 13b of CMC in the mixture. While the circulation of the mixture continues, a continuous shear force is applied to the mixture in the shear force application section 15. In this manufacturing method, by continuously applying a shear force to the mixture in the shear force application section 15, even if the CMC forms clumps 13b when it is introduced into the aqueous solvent all at once, the CMC can be dissolved in the aqueous solvent in a short time. The shear rate of the mixture in the shear force application section 15 is such that the flow velocity is Q(m 3 If the peripheral speed of the rotor 152 is v (m / sec) and the number of slits in the stator 151 is S, then we can assume that the value will be proportional to Q / (v × S).

[0031] At the start of the first step S10, the motor that applies rotational force to the rotating shaft 141 of the first mixing unit 14 is started to drive. In the aqueous medium input step S11, the aqueous medium stored in the aqueous medium storage unit 11 is introduced into the circulation piping 101. In step S12, if it is determined that the introduction of CMC should be started, the process moves to the CMC input step S13. In step S12, for example, it can be determined to move to the CMC input step S13 based on the rotational speed of the rotor 145 in the first mixing unit 14 reaching a predetermined value. In the CMC input step S13, the valve 102 connected to the CMC storage unit 13 is opened and CMC is introduced into the first mixing unit 14. The first mixing step S14 is performed in the first mixing unit 14. The shearing step S15 is performed in the shearing force application unit 15 in the first mixing unit 14.

[0032] In step S16, if it is determined that the first step is complete, the process proceeds to the second step S20. In step S16, for example, the decision to proceed to the second step S20 can be made based on the amount of remaining CMC clumps. The transition to the second step S20 is performed by adjusting the opening and closing of valve 104 to stop the circulation in circulation piping 101 and to supply the CMC solution in circulation piping 101 to piping 201 of the second step section 20. In the carbon-based conductive material input step S21, valve 202 connected to the carbon-based conductive material storage section 21 is opened and the carbon-based conductive material is introduced into the second mixing section 22. In the second mixing section 22, the carbon-based conductive material is mixed into the CMC solution to obtain a conductive material composition. The second mixing section 22 is exemplified by a configuration that includes, for example, a stirrer. The conductive material composition is sent from the second mixing section 22 to the conductive material composition storage section 23 where it is stored.

[0033] This manufacturing method may include steps other than those described above, such as a step to remove clumps of CMC from the CMC solution, a step to remove air bubbles from the conductive composition, and so on. These steps may be performed by adding additives, by mechanical treatment, or by a combination of these methods. The additives are not limited as long as they do not impair the effects of this manufacturing method.

[0034] (aqueous medium) The aqueous medium used in this manufacturing method contains at least water and may optionally contain other media that are compatible with water, as long as it does not impair the effects of the present invention. There are no particular limitations on the water, and examples include tap water, distilled water, and deionized water. Examples of other media besides water include methanol, ethanol, ethylene glycol, propylene glycol, and glycerin. In one embodiment, the aqueous medium may consist only of water. The volume of the aqueous medium circulated in the first step S10 is, for example, 1 L or more and 1000 L or less, and may be 50 L or more and 500 L or less.

[0035] (CMC) The CMC added to the aqueous medium in this manufacturing method may be CMC itself or a salt of CMC. The degree of etherification of the CMC is preferably 0.3 to 0.9, more preferably 0.4 to 0.8, and even more preferably 0.5 to 0.6. By having the degree of etherification of the CMC within the above range, the balance between the intermolecular forces between CMC and the conductive material, and between CMC and water, is improved, allowing the conductive material to be well dispersed in the conductive material composition and maintaining a well dispersed state of the conductive material.

[0036] The weight-average molecular weight of CMC, expressed as pullulan equivalent, is preferably 10,000 or more, more preferably 15,000 or more. It is also preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 30,000 or less.

[0037] The mass of CMC introduced into the circulating aqueous medium in the first step S10 is not limited, but may be, for example, 10g or more and 100kg or less, or 100g or more and 1kg or less.

[0038] (CMC solution) The CMC solution obtained in the first step S10 contains at least an aqueous medium and CMC, and may also contain other components. The CMC concentration of the CMC solution obtained in the first step S10 is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.05% by mass or more and 5% by mass or less.

[0039] (Carbon-based conductive material) The carbon-based conductive material used in this manufacturing method is a conductive material whose main component is carbon. Examples of carbon-based conductive materials include carbon nanotubes (hereinafter sometimes referred to as "CNT"), carbon black, carbon fiber, and graphite. Among these, CNT is preferred from the viewpoint of conductivity and density.

[0040] CNTs have a cylindrical shape formed by winding planar graphite, and include single-walled CNTs and multi-walled CNTs, which may be mixed together. CNTs of different diameters may also be mixed. Single-walled CNTs have a structure in which one layer of graphite is wound. Multi-walled CNTs have a structure in which two or more layers of graphite are wound. It is preferable that the CNTs include single-walled CNTs. The shape of the CNTs is not limited. Examples of CNT shapes include needle-shaped, cylindrical tube-shaped, fishbone-shaped, playing card-shaped, and coil-shaped.

[0041] (Conductive material composition) The conductive material composition produced by this manufacturing method comprises at least an aqueous dispersion medium, CMC, and a carbon-based conductive material, and may also contain other components. Examples of other components include defoaming agents and binders. The conductive material concentration of the conductive material composition is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.2% by mass or more and 5% by mass or less. [Examples]

[0042] <Test Example 1: Predicted Viscosity Value> The CMC solution was prepared using the first process section 10 of the manufacturing apparatus shown in Figure 2. First, the motor in the first mixing section 14 was started, and B[L] of water was introduced from the aqueous medium storage section 11 into the circulation pipe 101, and the water was circulated within the circulation pipe 101. When the peripheral speed of the rotor 152 of the shear force application section 15 reached v[m / sec], the valve 102 was opened, and an amount of CMC such that the CMC concentration reached 0.6±0.05 mass% was added to the water circulating in the circulation pipe 101 at an input rate of Va[g / sec]. After that, the circulation of the mixed liquid was continued for t[min] from the start of input to obtain the CMC solution. During the circulation of the mixed liquid, the peripheral speed of the rotor 152 was maintained at v[m / sec].

[0043] As the first mixing unit 14, a flash mix (model: FMX-25) manufactured by Silverson Nippon was used. The stator model was BD3472, with a slit width w of 5 mm and a distance d between the stator and rotor of 1 mm. The following materials were assumed to be used in the preparation of the CMC solution. • Water-based medium: Water (high-purity water conforming to or exceeding the Battery Industry Standard (S0404)) • CMC: Carboxymethylcellulose ammonium (DN400H manufactured by Daicel Mirise, degree of etherification 0.5-0.6, weight-average molecular weight 1.0 × 10⁻⁶) 6 )

[0044] In the above-described hypothetical test, the viscosity of the CMC solution at a reference temperature t0 [°C] was expected to be the predicted viscosity η(t0) [mPa·s] calculated by equation (1) below, based on Andrade's equation, which is derived from Arrhenius's equation as an approximation of viscosity in liquids. In equation (1) below, the reference temperature t0 [°C] is 13.5°C.

[0045] Formula (1): η(t0)={-(4.7Va+10.3)ln(t)(B / 100)+(-10.3y+245.2) In equation (1), y is the shear rate and is the value calculated using equation (2) below.

[0046] Formula (2): y = Q / (v × S) In equation (2), Q[m 3 [m / sec] is the flow velocity, v [m / sec] is the peripheral speed of rotor 152, and S is the number of slits in stator 151. In this test, the shear rate y was set to 18.2, which is the fastest possible condition.

[0047] In equation (1) above, the predicted viscosity η(t0) was calculated based on the water input amount B being 100 L, the input rate Va being 140 [g / sec], and the circulation time t [minutes], and the results were plotted in Figure 7. Figure 7 plots the predicted viscosity η(t0) under conditions where the temperature is 13.5°C, and also shows the range of the 90% confidence interval. When the ambient temperature is different from the reference temperature of 13.5°C (tw [°C]), the predicted viscosity η(tw) changes depending on the temperature tw [°C], and the η(t0) calculated in equation (1) above is corrected by equation (3a) below to obtain η(tw). Formula (3a): η(tw)=η(t0)×exp(-0.01×(tw-13.5))

[0048] <Test Example 2: Measured Viscosity Values> The test was actually carried out as assumed in Test Example 1, and the actual viscosity of the CMC solution was measured when the circulation time was t [minutes]. Specifically, the amount of water input B was set to 100 L, the slit width w of the stator 151 was set to 5 mm, the peripheral speed v of the rotor 152 was set to 11 m / sec, the distance d of the opposing region was set to 1 mm, and the input speed Va was set to 140 [g / sec]. The viscosity of the obtained CMC solution was measured using a viscometer (Toki Sangyo E-type viscometer TV-200E, set value shear rate of 20 m / s, rotor type). The viscosity measurement temperature was 13.5°C. The results are plotted in Figure 7.

[0049] <Consideration> As can be seen from the results shown in Figure 7, the measured viscosity of Test Example 2 falls within the 90% confidence interval of the predicted viscosity of Test Example 1. Therefore, the accuracy of the predicted viscosity is high, and it was confirmed that the termination of process c can be determined in process d based on the predicted viscosity. By being able to determine the termination of process c in process d based on the predicted viscosity, the complexity of the decision can be avoided and the accuracy of the decision can be improved.

[0050] These embodiments and examples are illustrative in all respects. These embodiments and examples are not restrictive. The technical scope of this disclosure includes all modifications in the sense and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from these embodiments and examples and combined in any way. [Explanation of Symbols]

[0051] 11 Aqueous medium storage section, 13 CMC storage section, 14 First mixing section, 15 Shear force application section, 21 Carbon-based conductive material storage section, 22 Second mixing section, 23 Conductive material composition storage section, 141 Rotating shaft, 142 Screw, 143 Propeller, 151 Stator, 152 Rotor.

Claims

1. The first step is to prepare a carboxymethylcellulose solution in which carboxymethylcellulose is dissolved in an aqueous medium containing water, The process includes a second step of preparing a conductive material composition by adding a carbon-based conductive material to the carboxymethylcellulose solution, The first step is, a) A step of introducing the aqueous medium into a circulation system that circulates liquid and circulating the aqueous medium, b) A step of introducing the carboxymethylcellulose into the circulation system, mixing the aqueous medium and the carboxymethylcellulose, and circulating the resulting mixture, c) A step of preparing the carboxymethylcellulose solution by continuously applying a shear force to the mixed liquid circulating in the circulation system, d) A step of determining the end of step c based on the fact that the viscosity of the mixed liquid has fallen below a predetermined value, A method for producing a conductive material composition having the following characteristics.

2. In step b, the carboxymethylcellulose is added such that the concentration of carboxymethylcellulose in the resulting mixture is 0.6 ± 0.05% by mass. The manufacturing method according to claim 1, wherein in step d, the predetermined value is set to a value within the range of 62 to 96.5 [mPa·s].

3. The manufacturing method according to claim 1 or 2, wherein in step d, the determination viscosity is a measured value or a predicted value.

4. The circulation system comprises a circulation channel through which liquid circulates, and a shear force application section provided within the circulation channel. The shear force application section comprises a stator having a plurality of slits through which the liquid passing through the circulation channel passes, The manufacturing method according to claim 1 or 2, wherein in step c, the shear force is applied when the mixed liquid passes through the slit.

5. The manufacturing method according to claim 1 or 2, wherein the carbon-based conductive material is a single-walled carbon nanotube.

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