JP2015157729A - Carbon particle-containing slurry and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide carbon particle-containing slurry having excellent flowability.SOLUTION: Carbon particle-containing slurry comprises carbon particles, silica particles the volume average particle diameter of which is smaller than that of the carbon particles and in the range of 5 nm or more and 200 nm or less, and a dispersion medium. By mixing the carbon particles and silica particles, the carbon particle-containing slurry having excellent flowability can be obtained.

Description

  The present invention relates to a carbon particle-containing slurry having a low viscosity and a method for producing the same.

  Carbon particles are materials with excellent chemical stability, and are applied to the formation of black matrices in liquid crystal filters, secondary battery conductive materials, pigments (for writing instruments, paints, etc.), etc. (Patent Literature) 1-4). In these applications, carbon black is used in the form of a slurry dispersed in an appropriate solvent.

JP 2004-289696 A JP 2012-212054 A JP 2006-53548 A JP 2011-195803 A

  However, a slurry in which carbon particles are dispersed tends to have a high viscosity, and it is difficult to increase the concentration. One of the causes may be the high cohesiveness of the carbon particles. The slurry in which the aggregated carbon particles are dispersed has a high viscosity.

  The present invention has been completed in view of the above circumstances, and it is an object to be solved to provide a carbon particle-containing slurry having improved carbon particle dispersion in a slurry in which carbon particles are dispersed and having a low viscosity, and a method for producing the same. And

  The use of an organic dispersant is indispensable for producing a slurry in which an organic solvent and a resin are mixed using carbon black. In addition, since the pigments have become finer and the surface area has increased, organic dispersants tend to be used in large quantities. However, there are cases where physical properties are lowered due to an increase in the amount of the dispersant, and a reduction in the amount used is desired. The present invention provides a carbon particle-containing organic solvent slurry and a method for producing the same without using an organic dispersant.

(A) The carbon particle-containing slurry of the present invention that solves the above-mentioned problems is composed of carbon particles, silica particles having a volume average particle size smaller than that of the carbon particles and not less than 5 nm and not more than 200 nm, and primary particle-like silica particles. And a dispersion medium.
The viscosity of the carbon particle-containing slurry obtained by dispersing carbon particles in a dispersion medium together with silica particles in which primary particles are dispersed can be reduced.

(B) The carbon particle-containing slurry of the present invention that solves the above-mentioned problems is a carbon particle, a volume average particle size smaller than the carbon particle and 5 nm or more and 200 nm or less, primary silica particles, an amine-based slurry It is obtained by mixing a silane coupling agent and a dispersion medium for dispersing them.

  The viscosity of the slurry obtained by reacting the amine-based silane coupling agent is lowered.

  In particular, when the carbon black is neutral or basic carbon black, the effect of the amine-based silane coupling agent is remarkable.

The carbon particle-containing slurry disclosed in the above (a) and (b) can be added with one or more components of (c) to (e) described below.
(C) The silica particles are
The volume average particle size of the primary particles is 200 nm or less, the bulk density is 450 g / L or less,
Sintered ^{one having} a functional group represented by the formula (1): -OSiX ¹ X ² X ³ and a functional group represented by the formula (2): -OSiY ¹ Y ² Y ³ on the surface It is characterized by being.

Silica particles having such a functional group on the surface have particularly low agglomeration properties and can maintain a state of being dispersed to the state of primary particles, so that the surface of the carbon particles can be coated almost without gaps.
(In the above formulas (1) and (2); X ¹ is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group; X ² , X ³ Are independently selected from —OSiR ₃ and —OSiY ⁴ Y ⁵ Y ⁶ ; Y ¹ is R; Y ² and Y ³ are each independently selected from R and —OSiY ⁴ Y ⁵ Y ⁶ .Y ⁴ is an R; ^{Y 5} and ^{Y 6} is selected from R and -OSiR ₃ independently;. R is independently selected from alkyl groups of 1 to 3 carbon atoms Incidentally, ^{X 2} , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ are any of the adjacent functional groups X ² , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ , and —O—. May be combined with each other.)
(D) substantially does not contain an organic dispersant. Here, the “organic dispersant” in the present specification is an organic substance having a large molecular weight. For example, a substance having a molecular weight of 1000 or more. Organic dispersants can be classified into resin-type dispersants and surfactants. In particular, a resin type dispersant is preferably used. The resin-type dispersant is a resin composed of a part adsorbed on the pigment and a part having high affinity with the solvent, and disperses the pigment due to steric hindrance.
(E) The carbon particles have a volume average particle diameter of 200 μm or less and 0.5 μm or more.
(F) A method for producing a carbon particle-containing slurry that solves the above-mentioned problem is a pulverization in which the primary particles have a volume average particle size of 200 nm or less and are crushed so that the bulk density is 450 g / L or less. Process,
A mixing step of mixing the silica particles obtained in the crushing step and carbon particles having a volume average particle size larger than the primary particles of the silica particles;
Have
The raw silica particles are
A surface treatment step of surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water;
Removing the liquid medium;
It is processed in the pretreatment process with
The silane coupling agent has three alkoxy groups, a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group,
The molar ratio of the silane coupling agent to the organosilazane is characterized in that the silane coupling agent: the organosilazane = 1: 2 to 1:10.

  By adopting such a process, the silica particles can be firmly bonded to the surface of the carbon particles without agglomeration.

In the manufacturing method (f) described above, the following components (g) can be added.
(G) The surface treatment step includes:
A first treatment step of treating with the silane coupling agent;
A second treatment step of treating with the organosilazane,
The second processing step is performed after the first processing step.

  The carbon particle-containing slurry of the present invention can provide a carbon particle-containing slurry having a low viscosity and a method for producing the same by containing silica particles in the form of primary particles.

It is a graph which shows the viscosity of the test samples C1 and C2 in an Example. It is an optical microscope photograph of the test sample C1 in an Example. It is an optical microscope photograph of the test sample C2 in an Example. It is a graph which shows the particle size distribution of the test sample D1 in an Example. It is a graph which shows the particle size distribution of the test sample D2 in an Example. It is a graph which shows the viscosity of the test samples D1 and D2 in an Example. It is a SEM photograph of test sample D1 in an example. It is a SEM photograph of test sample D2 in an example. It is a graph which shows the particle size distribution of the test sample E1 in an Example. It is a graph which shows the particle size distribution of the test sample E2 in an Example. It is a graph which shows the viscosity of the test samples E1 and E2 in an Example. It is a SEM photograph of test sample E1 in an example. It is a SEM photograph of test sample E2 in an example.

  Hereinafter, the carbon particle-containing slurry of the present invention and the production method thereof will be described in detail based on embodiments. The carbon particle-containing slurry of the present invention can be used for applications to which carbon particles can be applied. For example, formation of a black matrix in a liquid crystal filter, a conductive material of a secondary battery, and a pigment (for writing instruments, paints, etc.). Note that the black matrix shields a gap between adjacent pixels in order to improve contrast in a liquid crystal display. The conductive material of the secondary battery is a material mixed in order to improve the conductivity between the active materials. For example, the conductive path between the positive electrode active materials in the lithium battery or between the positive electrode active material and the current collector In order to form the electrode, an electrode paste is formed by mixing with a positive electrode active material, and an active material layer is formed by coating on a current collector. Pigments are a comprehensive concept that includes the materials that form the black matrix described above, and are derived from general paints (those that cover the surface of products such as automobiles, and those used in printing), and carbon conductivity. There is an electromagnetic shielding paint that does.

(Carbon particle-containing slurry)
The carbon particle-containing slurry of this embodiment has carbon particles, silica particles, and a dispersion medium. Silica particles are contained in the form of primary particles. Furthermore, an amine-based silane coupling agent can be contained. It is considered that the amine-based silane coupling agent reacts with one or both of the surfaces of carbon particles and silica particles.

  The content of silica particles can adopt the upper limit of about 40%, 30%, 20%, 10%, 7.5%, 5%, 3%, 1% as a preferred range based on the mass of the carbon particles. However, about 0.001%, 0.005%, and 0.0001% can be adopted as a preferable range.

  The carbon particles have a volume average particle size larger than the primary particles of the silica particles. Here, it is desirable that the silica particles substantially exist as primary particles in the slurry. Here, the presence of primary particles means particles in a state in which the particles can change relative positions with each other in the slurry. In order to say that the particles are primary particles, 80% or more, preferably 90% or more of the particles may be primary particles based on the mass of the entire silica particles.

  The carbon particles only need to be composed of simple carbon as a main component. Examples thereof include carbon black, graphite (artificial and natural), fullerene, and carbon nanotube (nanohorn). Carbon particles include acidic, neutral, and basic carbon particles depending on the pH value when suspended in water. The pH is measured by suspending 3.5 g of carbon particles in 35 mL of pure water and shaking for 30 minutes. In general, channel black is acidic and furnace black is neutral or basic.

  The particle size of the carbon particles is not particularly limited. For example, as a desirable upper limit of the volume average particle diameter, 200 μm, 150 μm, 100 μm, 80 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, and 15 μm can be adopted. Examples of the lower limit of the particle size of the carbon particles include 0.5 μm, 1.0 μm, 2.0 μm, 3.0 μm, and 5.0 μm. In particular, the carbon particles may take a bead-like form, but such a bead-like form may also be used.

  Silica particles have a volume average particle size of primary particles of 5 nm to 200 nm. In particular, the bulk density is desirably 450 g / L or less. As a volume average particle diameter, 100 nm, 70 nm, 50 nm, 30 nm, and 20 nm are mentioned as a preferable upper limit. Moreover, 10 nm is mentioned as a preferable minimum. The silica particles preferably have a particle size of 300 nm or less.

  The measurement of the bulk density in this specification is performed using the Tsutsui-Rikagakuki Co., Ltd. product: electromagnetic vibration type | mold beak density measuring device (MVD-86 type | mold). Specifically, after the sample to be measured is put into the upper 500 μm sieve as the sample tank, the sample is dispersed through the two upper and lower 500 μm sieves under electromagnetic acceleration conditions, and dropped into a 100 mL sample container. The mass was measured, and the bulk density was calculated from the mass and volume. In order to prevent a decrease in bulk density due to its own weight, measurement should be performed within 1 hour after dropping.

  Preferred upper limits for the bulk density include 400 g / L, 370 g / L, 350 g / L, 300 g / L, 280 g / L, and 250 g / L. A preferred lower limit is 100 g / L. By setting the bulk density to a value below these upper limits, primary particles can be separated more reliably. Moreover, when the bulk density is set to a value higher than these lower limits, the bulk is small and the handling becomes easy.

  The dispersion medium is not particularly limited. Either an organic solvent or water may be used. For example, propylene glycol monomethyl ether acetate, alcohol such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, terpenes such as α- or β-terpineol, acetone, methyl ethyl ketone, cyclohexanone, N-methyl- Ketones such as 2-pyrrolidone, aromatic hydrocarbons such as toluene, xylene, tetramethylbenzene, cellosolve, methyl cellosolve, ethyl cellosolve, carbitol, methyl carbitol, ethyl carbitol, butyl carbitol, propylene glycol monomethyl ether , Propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene Glycol ethers such as glycol monomethyl ether and triethylene glycol monoethyl ether, ethyl acetate, butyl acetate, cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, carbitol acetate, ethyl carbitol acetate, butyl carbitol acetate, propylene glycol monoethyl Examples thereof include single or mixed solvents such as acetates such as ether acetate. It is desirable to perform surface treatment on the carbon particles and silica particles so as to increase the affinity for the dispersion medium according to the type of the dispersion medium. The amount in which the carbon particles and silica particles are dispersed in the dispersion medium is not particularly limited, and only necessary amounts may be dispersed. For example, the mass of the carbon particles and the silica particles may be 15% or more and 30% or less based on the total mass. In addition, examples of the lower limit include 10%, 5%, and 1%, and examples of the upper limit include 40%, 50%, and 60%. Even when dispersed to such a high concentration, the viscosity is not so high. Therefore, dispersion is possible. Here, in the present specification, being dispersible means that the carbon particles do not aggregate. Whether or not agglomeration occurred was determined at three points arbitrarily selected when the paste used was further diluted for 20 times with the dispersion medium used after observing with an optical microscope after dispersion used and allowing to stand for 1 day. In the above-mentioned 200 μm × 200 μm visual field, it means that there are 3 or less particles each having an equivalent circle diameter of 5 μm or more.

  The amine of the amine-based silane coupling agent that is desirably mixed may be any of primary to quaternary amines, and examples thereof include silane coupling agents having an amino group. The amount of the amine-based silane coupling agent to be contained is the amount of silica particles (for example, related to the surface area. Further, the amount of OH groups present on the surface (for example, an amount capable of reacting all OH groups). Can be determined). Amine-based silane coupling agents are expected to react mainly with silica particles. The amount of the amine-based silane coupling agent is desirably less than 10% by mass based on the mass of the silica particles. The amine-based silane coupling agent is desirably added after both the carbon particles and the silica particles are dispersed in the dispersion medium. The amine-based silane coupling agent is desirably added when the carbon black is neutral or basic.

  In the silica particles of this embodiment, functional groups containing carbon are introduced on the surface. Since the specific structure of the functional group containing carbon and the method of introducing it onto the surface of the silica particles will be described in detail in the production method described later, description thereof is omitted here.

(Method for producing carbon particle-containing slurry)
The method for producing a carbon particle-containing slurry of the present embodiment is a method in which silica particles produced by performing a crushing step on raw silica particles are mixed (mixing step) with carbon particles. This is a method that can be suitably used for producing the carbon particle-containing slurry of the present embodiment described above. The raw material silica particles have a large proportion of primary particles bonded together, but the bonds can be separated in the crushing step. Further, an amine-based silane coupling agent may be added. In particular, when neutral or basic carbon black is employed, the effect of an amine-based silane coupling agent is remarkable.

  The mixing step is a step of mixing silica particles and carbon particles, and is not particularly limited. However, as described above, silica particles crushed to primary particles in a dry state can be dispersed in a dispersion medium as they are. The dispersion in the dispersion medium may be performed after mixing with the carbon particles, may be performed before the carbon particles, or may be performed after the carbon particles. The method for performing dispersion is not particularly limited. A general stirrer can be used. Furthermore, ultrasonic waves may be applied to improve the degree of dispersion. Prior to the dispersion, or after the dispersion, the surface treatment can be performed with the surface treatment agent.

  The method for the crushing step is not particularly limited. Preferably, a method of adding an effect of separating the aggregates of the aggregates is preferable, and a method that does not destroy the primary particles constituting the aggregates is preferable. For example, it can be performed by a method similar to pulverization performed in a dry state, and examples thereof include a jet mill, a pin mill, and a hammer mill. It is particularly desirable to use a jet mill. The final stage of the process is judged from the value of the bulk density of the raw silica particles. After the proper bulk density, it can be selected from the range described above. The jet mill is a device that performs pulverization by placing raw material silica particles in an air stream. Any type of jet mill is acceptable. Crushing by a jet mill is desirably performed by a dry method.

  The raw material silica particles have a primary particle size volume average particle size of 200 nm or less. In addition, examples of the upper limit include 100 nm, 70 nm, and 50 nm. The method for producing the raw material silica particles is not particularly limited. For example, a water glass method, an alkoxide method, and a VMC method can be exemplified, and it is desirable to employ the water glass method. The water glass method is a method of precipitating raw material silica particles by performing ion exchange, introduction / desorption of substituents by chemical reaction, control of pH, temperature, and the like on water glass. For example, an aqueous slurry in which nanometer order silica particles are dispersed can be prepared by ion exchange of water glass with an ion exchange resin. The particle diameter of the secondary particles constituting the raw silica particles is not particularly limited, but the volume average particle diameter may be 10 μm or more, 100 μm or more. Furthermore, the raw material silica particles can be produced by dissolving metal silicon in an alkali solution or the like and then depositing it (a method similar to the water glass method).

  A pretreatment process is applied to the preparation of the raw silica particles. The pretreatment process includes a surface treatment process and a process for removing the liquid medium (solidification process). The surface treatment step is a step of performing a surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water (water, one containing alcohol in addition to water). The silane coupling agent has three alkoxy groups and a phenyl group, vinyl group, epoxy group, methacryl group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group. The molar ratio of the silane coupling agent to the organosilazane is (silane coupling agent) :( organosilazane) = 1: 2 to 1:10.

  The surface treatment step includes a first treatment step for treating with the above-described silane coupling agent and a second treatment step for treating with organosilazane thereafter.

In the surface treatment step, the functional group represented by the formula (1): -OSiX ¹ X ² X ³ and the formula (2): -OSiY ¹ Y ² Y are applied to the silica particles obtained by the above-described method. ³ is a step of obtaining raw material silica particles in which the functional group represented by ³ is bonded to the surface. Hereinafter, the functional group represented by the formula (1) is referred to as a first functional group, and the functional group represented by the formula (2) is referred to as a second functional group.

X ¹ in the first functional group is a phenyl group, vinyl group, epoxy group, methacryl group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group. X ² and X ³ are —OSiR ₃ or —OSiY ⁴ Y ⁵ Y ⁶ , respectively. Y ⁴ is R. Y ⁵ and Y ⁶ are each R or —OSiR ₃ .

Y ¹ in the second functional group is R. Y ² and Y ³ are each —OSiR ₃ or —OSiY ⁴ Y ⁵ Y ⁶ .

The more —OSiR ₃ contained in the first functional group and the second functional group, the more R on the surface of the raw silica particles. As the R (the alkyl group having 1 to 3 carbon atoms) contained in the first functional group and the second functional group increases, the raw silica particles are less likely to aggregate.

Regarding the first functional group, when X ² and X ³ are each —OSiR ₃ , the number of R is minimized. Further, ^{X 2} and ^{X 3} is -OSiY ⁴ Y ⁵ Y ^6, respectively, ^and, if Y 5, ^{Y 6} is -OSiR ₃ respectively, the number of R is maximized.

Regarding the second functional group, when Y ² and Y ³ are each —OSiR ₃ , the number of R is minimized. Further, ^{Y 2} and ^{Y 3} are -OSiY ⁴ Y ⁵ Y ^6, respectively, ^and, if Y 5, ^{Y 6} is -OSiR ₃ respectively, the number of R is maximized.

The number of X ¹ contained in the first functional group, the number of R contained in the first functional group, and the number of R contained in the second functional group are the abundance ratio of R and X ¹ What is necessary is just to set suitably according to the particle size and use of a silica particle.

^{Incidentally, X 2, X 3, Y} 2, Y 3, Y 5, and any of ^{Y 6, X} 2 of the adjacent ^{functionality, X 3, Y 2, Y} 3, Y 5, and any ^{Y 6} You may combine with heel -O-. For example, any one of the first functional group X ² , X ³ , Y ⁵ , and Y ⁶ is the first functional group adjacent to the first functional group X ² , X ³ , Y ⁵ , and It may be bonded to any of Y ⁶ by —O—. Similarly, any of Y ² , Y ³ , Y ⁵ , and Y ⁶ of the second functional group is replaced with Y ² , Y ³ , Y ⁵ , Y ² of the second functional group adjacent to the second functional group. And Y ⁶ may be bonded to each other by —O—. Furthermore, any one of the first functional groups X ² , X ³ , Y ⁵ , and Y ⁶ is the second functional group adjacent to the first functional group, Y ² , Y ³ , Y ⁵ , And Y ⁶ may be bonded to each other by —O—.

In the raw material silica particles, the presence ratio of the first functional groups and second functional groups is 1: 12-1: if 60, the surface of the raw material silica particles and X ¹ and R are present good balance. For this reason, the raw material silica particle whose abundance ratio of the first functional group and the second functional group is 1:12 to 1:60 is particularly excellent in the affinity for the resin and the aggregation suppressing effect. Further, if X ¹ is 0.5 to 2.5 per unit surface area (nm ² ) of the raw silica particles, a sufficient number of first functional groups are bonded to the surface of the raw silica particles, and the first There are also a sufficient number of Rs derived from the functional group and the second functional group. Therefore, also in this case, the affinity for the resin and the aggregation suppressing effect of the raw silica particles are sufficiently exhibited.

In any case, R per unit surface area (nm ² ) of the raw silica particles is preferably 1 to 10. In this case, the balance between the number of X ¹ present on the surface of the raw silica particles and the number of R is improved, and both the affinity for the resin and the aggregation suppressing effect of the raw silica particles are exhibited in a well-balanced manner.

In the raw material silica particles, it is preferable that all of the hydroxyl groups present on the surface of the silica particles are substituted with the first functional group or the second functional group. If the sum of the first functional group and the second functional group is 2.0 or more per unit surface area (nm ² ) of the raw silica particles, the raw silica particles were present on the surface of the silica particles. It can be said that almost all of the hydroxyl groups are substituted with the first functional group or the second functional group.

The raw silica particles have R on the surface. This can be confirmed by an infrared absorption spectrum. Specifically, when the infrared absorption spectrum of the raw silica particles is measured by the solid diffuse reflection method, there is a maximum absorption of C—H stretching vibration at 2962 ± 2 cm ⁻¹ .

  Further, as described above, the raw material silica particles hardly aggregate.

  Note that the raw silica particles can be dispersed again by ultrasonic treatment even if they are slightly agglomerated. Specifically, the raw silica particles can be substantially dispersed to primary particles by irradiating the raw silica particles dispersed in methyl ethyl ketone with ultrasonic waves having an oscillation frequency of 39 kHz and an output of 500 W. The ultrasonic irradiation time at this time may be 10 minutes or less. Whether or not the raw material silica particles are dispersed to the primary particles can be confirmed by measuring the particle size distribution. Specifically, when the methyl ethyl ketone dispersion material of the raw material silica particles is measured with a particle size distribution measuring device such as a microtrack device, and there is a particle size distribution of the raw material silica particles, it can be said that the raw material silica particles are dispersed to primary particles.

  Since the raw silica particles hardly aggregate, they can be provided as raw silica particles that are not dispersed in a liquid medium such as water or alcohol. In this case, since no liquid medium is brought in, it is preferably used as a filler for a resin material.

  Further, since the raw silica particles are difficult to aggregate, they can be easily washed with water.

The raw material silica particles are treated in a step of treating the silica particles with a silane coupling agent and an organosilazane (surface treatment step) in a liquid medium containing water. The silane coupling agent has three alkoxy groups and a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group (that is, X ¹ described above).

By performing the surface treatment with the silane coupling agent, the hydroxyl group present on the surface of the silica particles is substituted with a functional group derived from the silane coupling agent. The functional group derived from the silane coupling agent is represented by the formula (3); —OSiX ¹ X ⁴ X ⁵ . The functional group represented by the formula (3) is referred to as a third functional group. X ¹ in the third functional group is the same as X ¹ in the functional group represented by the formula (1). X ⁴ and X ⁵ are each an alkoxy group. By surface-treating with organosilazane, the third functional group X ⁴ and X ⁵ are derived from organosilazane —OSiY ¹ Y ² Y ³ (the functional group represented by the formula (2), the second functional group ). When all of the hydroxyl groups present on the surface of the silica particles are not substituted with the third functional group, the hydroxyl groups remaining on the surface of the silica particles are substituted with the second functional group. For this reason, on the surface of the surface-treated raw material silica particles, a functional group represented by the formula (1): -OSiX ¹ X ² X ³ (that is, the first functional group) and a formula (2): -OSiY ^The functional group represented by ¹ Y ² Y ³ is bonded to the functional group (that is, the second functional group). In addition, since the molar ratio of the silane coupling agent and the organosilazane is silane coupling agent: organosilazane = 1: 2 to 1:10, the first functional group and the second functional group in the obtained raw material silica particles are used. The abundance ratio with the functional group is theoretically from 1:12 to 1:60.

In the surface treatment step, the silica particles may be simultaneously surface treated with a silane coupling agent and an organosilazane. Alternatively, the silica particles may first be surface treated with a silane coupling agent and then surface treated with organosilazane. Alternatively, the silica particles may be first surface treated with organosilazane, then surface treated with a silane coupling agent, and then surface treated with organosilazane. In any case, the amount of organosilazane may be adjusted so that all the hydroxyl groups present on the surface of the silica particles are not substituted with the second functional group. The hydroxyl groups present on the surface of the silica particles may all be substituted with the third functional group, or only a part may be substituted with the third functional group, and the other part may be substituted with the second functional group. It may be replaced. All of X ⁴ and X ⁵ contained in the third functional group may be substituted with the second functional group.

A part of organosilazane may be replaced with the second silane coupling agent. As the second silane coupling agent, one having three alkoxy groups and one alkyl group can be used. In this case, X ⁴ and X ⁵ contained in the third functional group are substituted with the fourth functional group derived from the second silane coupling agent. The fourth functional group has the formula (4); - represented by OSiY ¹ X ⁶ X ^7. Y ¹ is the same R as ^{Y 1} in the second functional ^{group, X 6,} X ⁷ is an alkoxy group or a hydroxyl group, respectively. X ⁶ and X ⁷ contained in the fourth functional group are substituted with the second functional group derived from organosilazane, or are substituted with another fourth functional group. In this case, the amount of R present on the surface of the raw silica particles can be further increased. When a part of the organosilazane is replaced with the second silane coupling agent, it is necessary to surface-treat with the organosilazane again after the surface treatment with the second silane coupling agent. This is because X ⁶ and X ⁷ contained in the fourth functional group are finally substituted with the second functional group derived from organosilazane.

When a part of the organosilazane is replaced with the second silane coupling agent, X ⁴ and X ⁵ contained in the first functional group described above are substituted with the second functional group derived from the organosilazane, Substitution with a fourth functional group derived from the second silane coupling agent. When X ⁴ and X ⁵ are substituted with the fourth functional group, X ⁶ and X ⁷ contained in the fourth functional group are substituted with the second functional group or another fourth functional group. Is replaced by If X ^6, X ⁷ contained in the fourth functional group has been replaced by another fourth functional group, X ^6, X ⁷ contained in the fourth functional groups is substituted with the second functional group The For this reason, the second silane coupling agent is an organosilazane set when the surface treatment is performed only with the first coupling agent and the organosilazane (when the organosilazane is not replaced with the second silane coupling agent). A maximum of 5a / 3 mol can be substituted for the amount (a) mol. The amount of organosilazane required in this case is 8a / 3 mol.

  The alkoxy groups of the silane coupling agent and the second silane coupling agent are not particularly limited, but those having a relatively small carbon number are preferred, and those having 1 to 12 carbon atoms are preferred. Considering the hydrolyzability of the alkoxy group, the alkoxy group is more preferably any one of a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

  Specific examples of silane coupling agents include phenyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane. 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3 -Aminopropyltrimethoxysilane.

  Any organosilazane may be used as long as it can replace the hydroxyl group present on the surface of the silica particles and the alkoxy group derived from the silane coupling agent with the second functional group described above. preferable. Specific examples include tetramethyldisilazane, hexamethyldisilazane, pentamethyldisilazane, and the like.

  Examples of the second silane coupling agent include methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, and hexyltriethoxysilane.

  In the surface treatment step, a polymerization inhibitor may be added in order to suppress polymerization of the silane coupling agent or polymerization of the second silane coupling agent. As the polymerization inhibitor, common ones such as 3,5-dibutyl-4-hydroxytoluene (BHT) and p-methoxyphenol (methoquinone) can be used.

  The raw silica particles may be provided with a solidification step after the surface treatment step. The solidification step is a step in which the raw material silica particles after the surface treatment are precipitated with a mineral acid, and the precipitate is washed with water and dried to obtain a solid material of the raw material silica particles. As described above, since general silica particles are very likely to aggregate, it is very difficult to disperse once solidified silica particles. However, since the raw silica particles are difficult to agglomerate, they are difficult to agglomerate even if solidified, and are easily redispersed even if agglomerated. In the washing step, washing is preferably repeated until the electrical conductivity of the extraction water of the raw silica particles (specifically, the water in which the silica particles are immersed at 121 ° C. for 24 hours) becomes 50 μS / cm or less.

  Examples of the mineral acid used in the solidification step include hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, and hydrochloric acid is particularly desirable. The mineral acid may be used as it is, but is preferably used as a mineral acid aqueous solution. The concentration of the mineral acid in the aqueous mineral acid solution is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. The amount of the mineral acid aqueous solution can be about 6 to 12 times based on the mass of the raw silica particles to be cleaned.

  The cleaning with the mineral acid aqueous solution can be performed a plurality of times. The washing with the mineral acid aqueous solution is preferably performed after the raw silica particles are immersed in the mineral acid aqueous solution and then stirred. Further, it can be left in the immersed state for 1 to 24 hours, and further for about 72 hours. When it is allowed to stand, stirring can be continued or not stirred. When washing in the mineral acid-containing liquid, it can be heated to room temperature or higher.

  Thereafter, the raw silica particles washed and suspended are collected by filtration and then washed with water. It is desirable that the water used does not contain ions such as alkali metals (for example, 1 ppm or less on a mass basis). For example, ion exchange water, distilled water, pure water and the like. Washing with water is the same as washing with an aqueous mineral acid solution, after the raw silica particles are dispersed and suspended, they can be filtered, or by continuously passing water through the filtered raw silica particles. Is possible. The end of washing with water may be determined by the electrical conductivity of the extracted water described above, or may be the time when the alkali metal concentration in the waste water after washing the raw silica particles becomes 1 ppm or less, It is good also as the time of the alkali metal concentration of extraction water becoming 5 ppm or less. When washing with water, it can be heated to a room temperature or higher.

  Drying of the raw silica particles can be performed by a conventional method. For example, heating or leaving under reduced pressure (vacuum).

  The carbon particle-containing slurry of the present invention and the production method thereof will be described based on examples. In this example, when mentioning the particle size, the particle size of the secondary particles is described unless there is a description that the particle size of the primary particles.

[First test]
Test sample preparation Test examples A1 to A5 and B1 to B4
(Test Example A-1)
20 parts by mass of carbon black (specific surface area 65 m ² / g, Conductex 7067 Ultra, Columbian Chemicals Korea, basic carbon black having a pH of 8.6) as carbon particles and silica particles (manufactured by Admatechs; nano silica YA010C-SP3; volume average particle diameter 10 nm; produced by the method of Test Example 1 below) was dispersed in 76 parts by mass of propylene glycol monomethyl ether acetate (PGMAC) as a dispersion medium. After dispersing carbon particles and silica particles in a dispersion medium, 0.08 parts by mass of an amine-based silane coupling agent (KBM903, manufactured by Shin-Etsu Chemical Co., Ltd., 3-aminopropyltriethoxysilane) was mixed (silica particles 1). 0.02 parts by mass with respect to parts by mass). The mixture was stirred for 10 minutes so that the silane coupling agent reacted uniformly. The obtained slurry was used as the carbon particle-containing slurry of this test example.

(Test Example A-2)
This test example is the same as the test example A-1, except that the amount of silica particles is 8 parts by mass, the amount of PGMAC is 72 parts by mass, and the amount of the amine-based silane coupling agent is 0.16 parts by mass. A carbon particle-containing slurry was produced.

(Test Example A-3)
The same steps as in Test Example A-1 except that the amount of silica particles was 10 parts by mass, the amount of PGMAC was 70 parts by mass, and the amount of silane coupling agent of Ami / BR> East N was 0.20 parts by mass. The carbon particle-containing slurry of this test example was manufactured.

(Test Example A-4)
This test example is the same as the test example A-1, except that the amount of silica particles is 12 parts by mass, the amount of PGMAC is 68 parts by mass, and the amount of the amine-based silane coupling agent is 0.24 parts by mass. A carbon particle-containing slurry was produced.

(Test Example A-5)
The carbon particle-containing slurry of this test example was produced in the same process as test example A-3 except that the amount of the amine-based silane coupling agent was 0.50 parts by mass.

(Test Example B-1)
The carbon of this test example is the same as the test example A-1, except that the amount of silica particles is 0 part by mass, the amount of PGMAC is 80 parts by mass, and the amount of the amine-based silane coupling agent is 0 part by mass. A particle-containing slurry was produced.

(Test Example B-2)
The carbon of this test example is the same as the test example B-1, except that the amount of silica particles is 10 parts by mass, the amount of PGMAC is 70 parts by mass, and the amount of the amine-based silane coupling agent is 0 part by mass. A particle-containing slurry was produced.

(Test Example B-3)
The carbon particle-containing slurry of this test example was produced in the same process as test example B-1, except that the amount of the amine-based silane coupling agent was 0.2 parts by mass.

(Test Example B-4)
Except that the amount of the amine-based silane coupling agent was 1.0 part by mass, the carbon particle-containing slurry of this test example was produced in the same process as test example B-2.

(Observation)
About the test sample of Test Example A-1 to A-5 and B-1 to B-4, the external appearance was observed immediately after the preparation and three days after the preparation, respectively. About Test example A-2 and A-3, the outstanding fluidity | liquidity was shown. In particular, Test Example A-3 showed better fluidity (low viscosity). Test Examples A-1, A-4, A-5, and B-2 showed thixotropic flow. Test Examples B-1, B-3, and B-4 were solidified into a lump. There was no difference between any of the test samples immediately after preparation and after 3 days.

  The following knowledge was obtained from the above results. First, improvement in fluidity was observed by incorporating silica particles in a range of 20% to 60% based on the mass of carbon black (Test Examples A-1 to A-5, B-2). Furthermore, fluidity could be improved by including an amine-based silane coupling agent (Test Examples A-1 to A-5). However, even when an amine-based silane coupling agent was added when no silica particles were present, a sufficient fluidity improving effect was not observed (Test Example B-3). Further, in this test system, it was found that when 10% of an amine-based silane coupling agent was added based on the mass of silica particles, the effect of suppressing aggregation of the silica particles could not be sufficiently exhibited (Test Example B-4). Although details are not shown, it has been found that the addition of an amine-based silane coupling agent has a higher effect of improving fluidity when carbon particles and silica particles are added after being dispersed in a dispersion medium.

  For reference, the slurry of Test Examples A-3 and B-3 diluted 20 times with PGMAC was observed with an optical microscope. In the slurry of Test Example A-3, aggregation of carbon particles could not be observed with an optical microscope, whereas in the slurry of Test Example B-3, the presence of aggregates exceeding 20 μm was observed. As a result of measuring the viscosity of the slurry of Test Examples A-3 and B-3, it was found that the slurry of Test Example A-3 was lower in viscosity than the slurry of Test Example B-3 at any share rate.

[Second test: pH of carbon black]
(Evaluation of basic carbon black)
Sample Preparation After 20 parts by mass of basic carbon black (pH 8.6) was dispersed in 80 parts by mass of PGMAC, 0.2 parts by mass of KBM903 was added and further dispersed. A test sample (Test Example C1) was obtained which was allowed to stand for 1 day and then dispersed with an emulsifying disperser.

  20 parts by mass of basic carbon black (pH 8.6) was dispersed in 69.8 parts by mass of PGMAC in which 10 parts by mass of silica particles had been dispersed in advance, and then 0.2 parts by mass of KBM903 was added. Further dispersed. A test sample (Test Example C2) was obtained which was allowed to stand for 1 day and then dispersed with a disperser.

-Evaluation About the obtained test sample of Test Example C1 and C2, while measuring a viscosity, it diluted with PGMAC so that it might become 20 times amount, and observed with the optical microscope. The results are shown in FIG. 1 (viscosity measurement results), FIG. 2 (Test Example C1) and FIG. 3 (Test Example C2).

  As apparent from FIG. 1, the test example C2 to which the silica particles are added has at least a shear rate of 0.01 (1 / s) to 100 (1 / s) compared to the test example C1 to which the silica particles are not added. It was found that the viscosity decreased in the range of. In Test Example C1 (FIG. 2) in which no silica particles were added, rack aggregation was observed in carbon, but in Test Example C2 (FIG. 3) in which silica particles were added, no carbon black aggregation was observed. It was found that the addition of silica particles did not cause aggregation in observation with an optical microscope. That is, the addition of silica particles not only suppressed the aggregation of carbon black, but also reduced the viscosity.

  As described above, it has been found that in basic carbon black, the viscosity improvement is remarkable due to the addition of silica particles and further the addition of KBM903, which is an amine-based silane coupling agent.

(Evaluation of acidic carbon black)
-Preparation of first sample 25 parts by mass of acidic carbon black (pH 4.0) was dispersed in 75 parts by mass of PGMAC to obtain a test sample (Test Example D1).

  25 parts by mass of acidic carbon black (pH 4.0) was dispersed in 71.25 parts by mass of PGMAC in which 3.75 parts by mass of silica particles were previously dispersed to obtain a test sample (Test Example D2).

-Evaluation About the obtained test samples of Test Examples D1 and D2, they were dispersed and emulsified by an emulsifying disperser. Samples with stirring time of 1 minute, 3 minutes, and 10 minutes were prepared, and the particle size distribution was measured with a particle size meter (manufactured by Nikkiso Co., Ltd., model number: Nanotrac 150) (FIG. 4: Test Example D1, FIG. 5: Test Example D2). Moreover, the viscosity was measured about the test sample which made stirring time 10 minutes (FIG. 6).

  As apparent from FIGS. 4 and 5, in Test Example D2 (FIG. 5) to which silica particles are added, the particle size distribution peak can be lowered to a region of 1 μm or less, and further, for 10 minutes. With stirring, the peak of 1 μm or more disappeared and the peak became one. This is considered to be because the aggregates of carbon black aggregated to 1 μm or more were loosened and dispersed uniformly. On the other hand, in Test Example D1 (FIG. 4) in which no silica particles were added, it was found that even if stirring was performed, the peak position did not decrease from 1 μm or more and aggregation could not be eliminated. Further, as is apparent from FIG. 6, the viscosity at a low share rate (about 0.01 (1 / s) to 1 (1 / s)) is different between Test Example D1 and Test Example D2 by almost three orders of magnitude. It was found that Test Example D2 containing silica particles also had a low viscosity.

  And after leaving still for 3 days about each sample which made stirring time 10 minutes, in the example D2 which added the silica particle from the observation result, although the carbon particle was disperse | distributed uniformly, a silica particle was added. In Test Example D1, the transparent dispersion medium (PGMAC) was separated on the upper side, and it was revealed that the precipitation proceeded.

  Regarding the test samples of Test Examples D1 and D2 (stirring for 10 minutes), the PGMAC evaporated was observed by SEM (FIG. 7: Test Example D1, FIG. 8: Test Example D2). As is apparent from the SEM photograph (FIG. 8), it was found that the mixed silica particles were separated and adhered to the primary particle state on the surface of the carbon particles. It was strongly suggested that the decrease in viscosity due to the addition of silica particles was realized by the silica particles present on the surface of the carbon particles.

-Preparation of second sample 20 parts by mass of acidic carbon black (pH 3.5, manufactured by Mitsubishi Chemical Corporation: MA100R) was dispersed in 80 parts by mass of PGMAC to obtain a test sample (Test Example E1).

  A test sample (Test Example E2) was obtained by dispersing 20 parts by mass of acidic carbon black (pH 3.5) in 68 parts by mass of PGMAC in which 12 parts by mass of silica particles had been dispersed in advance.

-Evaluation About the test sample of obtained test example D1 and D2, it stirred with the emulsification stirrer for 10 minutes and was emulsified. Thereafter, the particle size distribution was measured with a particle size meter (manufactured by Nikkiso Co., Ltd., model number: Nanotrac 150) (FIG. 9: Test Example E1, FIG. 10: Test Example E2). Furthermore, the viscosity was measured (FIG. 11).

    As is clear from FIGS. 9 and 12, in the test example E2 (FIG. 10) to which silica particles are added, the peak of the particle size distribution can be reduced to an area of 1 μm or less and the peak becomes one. . That is, it was suggested that there was no aggregation. In contrast, in Test Example E1 (FIG. 9) in which no silica particles were added, it was found that even when stirring was performed, the peak position had two large peaks of 1 μm or more and was agglomerated. As is clear from FIG. 11, the viscosity of Test Example E2 containing silica particles was lower than that of Test Example E1.

  Evaporated PGMAC of the test samples of Test Examples E1 and E2 was observed by SEM (FIG. 12: Test Example E1, FIG. 13: Test Example E2). As apparent from the SEM photograph (FIG. 13), it was found that the mixed silica particles were separated and adhered to the surface of the carbon particles. It was strongly suggested that the decrease in viscosity due to the addition of silica particles was realized by the silica particles present on the surface of the carbon particles.

・ Conclusion From the above results, it was found that carbon particles can be dispersed very well in the slurry containing carbon particles by adding silica particles. Further, it has been found that the dispersibility can be sufficiently improved by adding silica particles without using an amine-based silane coupling agent for acidic carbon.

<Manufacture of silica particles (surface-treated)>
[Test Example 1]
(Manufacture of raw silica particles)
Colloidal silica snowtex OS as an aqueous slurry in which silica particles are dispersed in water as an aqueous medium (silica content 20%: manufactured by Nissan Chemical Co., Ltd .: primary particle size is 10 nm) for 100 parts by mass (surface treatment) Treatment step and drying step).

(Surface treatment process)
(1) Preparatory process 40 mass parts of isopropanol was added to 100 mass parts of aqueous slurry, and the dispersion liquid by which a silica particle was disperse | distributed to the liquid medium was obtained by mixing at room temperature (about 25 degreeC).
(2) First Step 1.82 parts by mass of phenyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM103) was added to this dispersion and mixed at 40 ° C. for 72 hours. By this step, the hydroxyl group present on the surface of the silica particles was surface treated with a silane coupling agent. At this time, phenyltrimethoxysilane was calculated and added so that a necessary amount of hydroxyl groups (partially) remained without being surface-treated.
(3) Second Step Next, 3.71 parts by mass of hexamethyldisilazane was added to this mixture and left at 40 ° C. for 72 hours. Through this step, the silica particles were surface-treated to obtain a silica particle material. As the surface treatment progressed, the silica particles that became hydrophobic could no longer exist stably in water and isopropanol, and agglomerated and precipitated. The molar ratio of phenyltrimethoxysilane to mexamethyldisilazane was 2: 5.

(Solidification process)
4.8 parts by mass of 35% aqueous hydrochloric acid solution was added to the mixture obtained in the surface treatment step to precipitate the silica particle material. The precipitate was filtered with a filter paper (5A manufactured by Advantech). The filtration residue (solid content) was washed with pure water and then vacuum-dried at 100 ° C. to obtain a silica particle material solid material (raw material silica particles).

  The obtained silica particles had D10 of 8.8 μm, D50 of 124.5 μm, and D90 of 451.9 μm.

(Crushing process)
A crushing step was performed on the obtained raw material silica particles to obtain silica particles of this test example. The crushing step was carried out under the conditions of a crushing pressure of 0.3 MPa and a supply rate of 10 kg / h using a jet mill (manufactured by Seishin Enterprise Co., Ltd., model number STJ-200). The obtained silica particles had a bulk density of 251.7 g / L, D10 of 0.8 μm, D50 of 1.8 μm, D90 of 4.0 μm, and primary particles having a volume average particle size of 10 nm.

[Test Example 2]
Instead of the crushing step in Test Example 1, what was spray dried by the spray drying method was used as a test sample of this Test Example. Specifically, 100 parts by mass of the raw material silica particles obtained in the solidification step were dispersed in 200 parts by mass of IPA, which was sprayed at a flow rate of 180 ° C. and 5 L / h and dried. The obtained silica particles had a bulk density of 341.3 g / L.

[Test Example 3]
What was obtained in the solidification step without carrying out the crushing step in Test Example 1 was used as the test sample of this Test Example. The obtained silica particles had a bulk density of 769 g / L, D10 of 8.8 μm, D50 of 124.5 μm, D90 of 451.9 μm, and the volume average particle size of the primary particles was 10 nm.

[Test Example 4]
Commercially available silica particles (manufactured by Nippon Aerosil Co., Ltd., AEROSIL R972, so-called Aerosil silica) were used as test samples for this test example. The silica particles of this test example had a bulk density of 41.0 g / L.

[Test Examples 5 to 7]
In the crushing step in Test Example 1, the bulk density was adjusted by adjusting the crushing pressure and the supply amount. The bulk density of the test sample of Test Example 5 was 271.3 g / L, the test sample of Test Example 6 was 364.6 g / L, and the test sample of Test Example 7 was 249.8 g / L. There was a tendency for the bulk density to increase by increasing the crushing pressure. Although detailed results are not shown, it has been clarified that coexistence with carbon particles has the effect of reducing the viscosity of the slurry containing carbon particles as in the above test.

Claims (8)

Carbon particles,
Silica particles having a volume average particle size smaller than the carbon particles and 5 nm or more and 200 nm or less and primary particles,
A dispersion medium for dispersing them,
A carbon particle-containing slurry having Carbon particles,
Silica particles having a volume average particle size smaller than the carbon particles and 5 nm or more and 200 nm or less and primary particles,
An amine-based silane coupling agent;
A dispersion medium for dispersing them,
A carbon particle-containing slurry obtained by mixing these.   The carbon particle-containing slurry according to claim 2, wherein the carbon black is neutral or basic carbon black. The silica particles are
The volume average particle size of the primary particles is 200 nm or less, the bulk density is 450 g / L or less,
Sintered ^{one having} a functional group represented by the formula (1): -OSiX ¹ X ² X ³ and a functional group represented by the formula (2): -OSiY ¹ Y ² Y ³ on the surface The carbon particle-containing slurry according to claim 1 or 2, wherein the slurry is a carbon particle-containing slurry. (In the above formulas (1) and (2); X ¹ is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group; X ² , X ³ Are independently selected from —OSiR ₃ and —OSiY ⁴ Y ⁵ Y ⁶ ; Y ¹ is R; Y ² and Y ³ are each independently selected from R and —OSiY ⁴ Y ⁵ Y ⁶ .Y ⁴ is an R; ^{Y 5} and ^{Y 6} is selected from R and -OSiR ₃ independently;. R is independently selected from alkyl groups of 1 to 3 carbon atoms Incidentally, ^{X 2} , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ are any of the adjacent functional groups X ² , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ , and —O—. May be combined with each other.)   The carbon particle-containing slurry according to any one of claims 1 to 4, which contains substantially no organic dispersant.   The carbon particle-containing slurry according to any one of claims 1 to 5, wherein the carbon particles have a volume average particle size of 200 µm or less and 0.5 µm or more. A crushing step of crushing so that the bulk density is 450 g / L or less with respect to the raw material silica particles having a volume average particle size of the primary particles of 200 nm or less,
A mixing step of mixing the silica particles obtained in the crushing step and carbon particles having a volume average particle size larger than the primary particles of the silica particles;
Have
The raw silica particles are
A surface treatment step of surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water;
Removing the liquid medium;
It is processed in the pretreatment process with
The silane coupling agent has three alkoxy groups, a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group,
The molar ratio of the silane coupling agent to the organosilazane is the silane coupling agent: the organosilazane = 1: 2 to 1:10.
A method for producing a carbon particle-containing slurry. The surface treatment step includes
A first treatment step of treating with the silane coupling agent;
A second treatment step of treating with the organosilazane,
The method for producing a carbon particle-containing slurry according to claim 7, wherein the second treatment step is performed after the first treatment step.