JP7207391B2 - Nickel paste and method for producing nickel paste - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nickel paste that can be suitably used, for example, for internal electrodes of laminated ceramic capacitors, and a method for producing the nickel paste.

In general, nickel paste used for internal electrodes of multilayer ceramic capacitors (hereinafter also referred to as "MLCC") is produced by kneading nickel powder into a vehicle and contains many aggregates of nickel powder. In the final stage of the nickel powder manufacturing process, it is common to have a drying process regardless of the metal powder manufacturing method (dry method or wet method), and the drying treatment in this drying process promotes aggregation of nickel particles. Therefore, the obtained nickel powder generally contains agglomerates generated during drying.

In recent years, multilayer ceramic capacitors are required to increase the number of laminated ceramic green sheets with internal electrode layers from several hundred to about 1,000 layers in order to achieve small size and large capacity. For this reason, studies have been made to reduce the thickness of the internal electrode layer from the conventional level of several microns to the submicron level. there is

However, the smaller the particle size, the larger the surface area of the nickel powder, which in turn increases the surface energy and facilitates the formation of agglomerates. In addition, metal ultrafine powder such as nickel ultrafine powder has poor dispersibility, and if agglomerates exist, the nickel powder penetrates the ceramic sheet layer when sintered in the firing process during the production of the ceramic capacitor. It becomes a defective product with shorted electrodes. In addition, even if the ceramic sheet layer is not penetrated, the shortened distance between the electrodes causes partial current concentration, which causes deterioration of the life of the multilayer ceramic capacitor.

As a nickel ultrafine powder slurry used for the internal electrode of MLCC, there is a slurry disclosed in Patent Document 1, for example. Specifically, Patent Document 1 discloses the following technique. That is, first, 0.3 parts by mass of a specific anionic surfactant is added to 100 parts by mass of the ultrafine metal powder to an aqueous slurry of ultrafine metal powder (concentration of ultrafine metal powder: 50% by mass), and a process homogenizer or the like is used. is carried out for a predetermined period of time to disperse aggregates of ultrafine metal powder in water to primary particles. After that, 10 parts by mass of terpineol, for example, as an organic solvent is added to 100 parts by mass of the ultrafine metal powder. As a result, the terpineol layer containing the metal powder becomes a continuous layer and forms a precipitate, and the water is separated as a supernatant to obtain a metal ultrafine powder organic solvent slurry.

In addition, the present inventors have found that in the technique disclosed in Patent Document 1, a specific anionic surfactant is added directly to the nickel ultrafine powder water slurry, so that the surfactant is micellized and the metal is efficiently Although it is described that it may be difficult to adsorb to the powder surface and the conditions for obtaining an organic solvent slurry, there is no description of what kind of effect can be obtained when it is made into a nickel paste. Further studies have been conducted, and a technique for obtaining the nickel paste described in Patent Document 2 has been proposed.

Specifically, the technique described in Patent Document 2 uses the molecular cross-sectional area (adsorption cross-sectional area) per molecule of the dispersion-transfer accelerator to determine the amount of the dispersion-transfer accelerator to be added. The total surface area of the nickel powder (m ² )×mass per unit molecular cross-sectional area of the dispersion transfer accelerator (g/m ² )”. This theoretically calculated amount can be regarded as the amount equivalent to the minimum amount of the dispersion transfer accelerator required to uniformly adsorb and cover the entire surface area of the nickel powder, so the dispersion transfer accelerator can be used efficiently. It can be said that it is a nickel paste production technology that can be used.

JP-A-2006-63441 JP 2015-46256 A

However, in the method of Patent Document 1, in order to prepare the nickel powder organic slurry, first, a specific anionic surfactant is added to the nickel powder aqueous slurry, and then mixed with an organic solvent to replace the nickel powder. In this method, an organic slurry of nickel powder is obtained by sintering, and the process becomes complicated and efficient treatment cannot be performed. Also, in the method of Patent Document 2, as in the method of Patent Document 1, first, a specific dispersion transfer accelerator and an organic solvent are added to the aqueous nickel slurry to obtain an organic nickel powder slurry. After that, the nickel powder organic slurry is further required to be kneaded with an organic vehicle. In order to obtain the nickel paste, the nickel powder organic slurry is once obtained as an intermediate product, and then the nickel paste is formed. This is a two-step process. Is required.

In recent years, there has been an increasing demand for smaller diameter nickel ultrafine powders used in internal electrodes and for multi-layered MLCCs. There is a demand for the development of a nickel paste having such a property, and a demand for a method for producing it in an extremely simple process.

The present invention has been proposed in view of such circumstances, and provides a nickel paste in which nickel ultrafine powder is dispersed in a state of less aggregation, and a nickel paste that can be produced by a simple process. The object is to provide a manufacturing method.

The present inventors have made extensive studies to solve the above-described problems. As a result, a dispersion transfer accelerator is added to and mixed with a vehicle prepared by dissolving a specific binder resin in an organic solvent in advance, and a nickel powder water slurry is added to the vehicle containing the dispersion transfer accelerator. The present inventors have completed the present invention based on the finding that a nickel paste in which nickel powder is dispersed in a state of less aggregation can be obtained by a simple process of kneading. That is, the present invention provides the following.

(1) A first aspect of the present invention contains at least nickel powder, a dispersion transfer accelerator, and a vehicle, wherein the vehicle has an acid amount of the raw material binder resin of 20 to 300 μmol/g, The content of the dispersion transfer accelerator is 0.16 to 3.0 parts by mass with respect to 100 parts by mass of the nickel powder, the nickel concentration is 50 to 70% by mass, and the viscosity of the paste is 8 to 150 Pa · s, nickel paste.

(2) A second aspect of the present invention is the first aspect, wherein the dispersion-transfer accelerator is a dispersion-transfer accelerator having an anionic surfactant structure or a dispersion-transfer accelerator having a polymer structure. , nickel paste.

（ただし、式（１）、（２）において、ｎは、１０～２０の整数である。式（３）において、ｍ、ｎは、ｍ＋ｎ＝１２～２０の関係を満たす。） (3) A third aspect of the present invention is the first or second aspect, wherein the dispersion-transfer accelerator is a dispersion-transfer accelerator having an anionic surfactant structure, and is represented by the following general formula (1): A nickel paste which is one or more selected from the compounds shown in (3).

(However, in formulas (1) and (2), n is an integer of 10 to 20. In formula (3), m and n satisfy the relationship m+n=12 to 20.)

(4) A fourth aspect of the present invention is a method for producing a nickel paste containing at least nickel powder, a dispersion transfer accelerator, and a vehicle, and having a nickel concentration of 50 to 70% by mass, wherein the vehicle a first step of obtaining a vehicle containing the dispersion transfer accelerator by adding and mixing a dispersion transfer accelerator to the first step, and adding a nickel powder water slurry to the vehicle obtained in the first step and kneading and a second step of separating and removing water.

(5) A fifth aspect of the present invention is the fourth aspect, wherein in the first step, a vehicle in which the raw material binder resin has an acid amount of 20 to 300 μmol/g is used, and the dispersion transfer is performed in the vehicle. A method for producing a nickel paste with the addition of an accelerator.

(6) A sixth invention of the present invention is the fourth or fifth invention, wherein in the first step, the content of the dispersion migration accelerator in the nickel paste is added in the second step. The method for producing a nickel paste, wherein the dispersion migration accelerator is added to the vehicle so as to be 0.16 to 3.0 parts by mass with respect to 100 parts by mass of the nickel powder contained in the nickel powder slurry.

(7) A seventh invention of the present invention is any one of the fourth to sixth inventions, wherein in the first step, a vehicle having a binder resin content of 5% by mass or more as a raw material is used, A paste manufacturing method.

ADVANTAGE OF THE INVENTION According to this invention, the nickel paste which disperse|distributes nickel ultrafine powder in the state with few aggregations, and can be suitably used, for example for internal electrodes of a laminated ceramic capacitor, etc. can be provided. Moreover, according to the production method according to the present invention, such a nickel paste can be produced in a simple process.

Specific embodiments of the present invention (hereinafter referred to as "present embodiments") will be described in detail below. In addition, the present invention is not limited to the following embodiments, and various modifications are possible without changing the gist of the present invention. Further, in this specification, the notation "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less" unless otherwise specified.

≪1. Nickel paste≫
The nickel paste according to the present embodiment is a nickel paste containing at least nickel powder, a dispersion transfer accelerator, and a vehicle. This nickel paste has a nickel concentration of 50 to 70% by mass and a viscosity of 8 to 150 Pa·s.

In this nickel paste, the vehicle has an acid amount of 20 to 300 μmol/g of the binder resin as a raw material, and the content of the dispersion transfer accelerator is 0.16 to 3.0 μmol/g with respect to 100 parts by mass of the nickel powder. It is in the range of 0 parts by mass.

According to such a nickel paste, nickel powder, which is a constituent component, is dispersed in a less agglomerated state, so that it can be suitably used for internal electrodes of high-layer ceramic capacitors, for example.

[Nickel powder]
Nickel powder is a constituent component of the nickel paste, and various nickel powders can be used regardless of manufacturing methods such as a wet method and a dry method. For example, nickel powder obtained by a so-called dry method such as a CVD method, a quenching method, or a hydrogen reduction method using a nickel salt or nickel hydroxide may be used. Nickel powder obtained by a so-called wet method such as the wet reduction method used may also be used. Among them, it is preferable to use nickel powder obtained by a so-called wet method such as a wet reduction method.

Further, it is preferable that the nickel powder is ultrafine particles having an average particle size of 0.05 to 0.5 μm. The ultrafine nickel powder can be suitably used, for example, for internal electrodes of laminated ceramic capacitors. From the standpoint of meeting the recent demand for thinner layers for internal electrodes of MLCCs, it is necessary to preferably use nickel powder having an average particle size of about 0.05 to 0.3 μm, and in particular, the internal thickness of 1000 layers. In order to form an electrode, nickel powder with an average particle size of submicrons is required, and it is more preferable to use nickel powder with an average particle size of 0.05 to 0.1 μm.

[Dispersion transfer accelerator]
The dispersion transfer accelerator is adsorbed and coated on the surface of the nickel powder, and acts to improve the dispersibility in the nickel paste. As the dispersion-transfer accelerator, a dispersion-transfer accelerator having an anionic surfactant structure or a dispersion-transfer accelerator having a polymer structure can be used. Here, the surface of the nickel powder has basic properties. Therefore, by using a dispersion-transfer accelerator having an anionic surfactant structure or a dispersion-transfer accelerator having a polymer structure as a dispersion-transfer accelerator, it can be efficiently adsorbed on the surface of the nickel powder, and dispersed. can improve sexuality.

(Dispersion transfer accelerator having an anionic surfactant structure)
Specifically, as the dispersion transfer accelerator having an anionic surfactant structure, for example, any one of compounds (1) to (3) having a specific structure represented by the following general formula can be used. .

Here, “n” in the formulas is an integer of 10-20 with respect to the compounds represented by the general formulas (1) and (2). If the number of n is less than 10, the hydrophilicity becomes strong, and it may become difficult to remove water during kneading in the preparation of the nickel paste. On the other hand, if the number of n is more than 20, it becomes lipophilic and easily removes water, but it is difficult to dissolve in an organic solvent and may not efficiently coat the surface of the nickel powder.

For example, the compound represented by the above general formula (1), which is represented by a structural formula where n=10, is specifically a compound represented by the following structural formula (1-1). The compound represented by this structural formula (1-1) has a chemical name of "lauroyl sarcosine" (molecular formula = C ₁₅ H ₂₉ NO ₃ , CAS No. = 97-78-9), and is commercially available as an interface is an active agent.

Further, as other compounds, the chemical name "lauroylmethyl-β-alanine" (structural formula: (2-1) below, molecular formula: C ₁₆ H ₃₁ NO ₃ , CAS No. 21539-57-1) and the chemical name "Myristoylmethyl-β-alanine" (structural formula: (2-2) below, molecular formula: C ₁₈ H ₃₅ NO ₃ , CAS No. 21539-71-9). In addition, cocoyl sarcosinate (general formula (1), molecular formula: C ₁₆ H ₃₁ NO ₃ ), myristoyl sarcosinate (general formula (1), molecular formula: C ₁₇ H ₃₃ NO ₃ ), palmitoyl sarcosine (general formula ( 1), molecular formula: C ₁₉ H ₃₇ NO ₃ ), stearoyl sarcosine (general formula (1), molecular formula: C ₂₁ H ₄₁ NO ₃ ), and the like.

Further, regarding the compound represented by the general formula (3), "m" and "n" in the formula satisfy the relationship m+n=12-20. If m+n is less than 12, the lipophilicity may be insufficient, resulting in insufficient water separation. On the other hand, when m+n is more than 20, it may become difficult to dissolve in an organic solvent.

Specifically, the compound represented by the above general formula (3) has a molecular formula of C ₂₁ H ₃₉ NO ₃ and has the following structural formula (3-1) (provided that in general formula (3), m= 7, n=7), and the molecular formula is C ₁₉ H ₃₅ NO ₃ (provided that m=7, n=5 in general formula (3) The chemical name is "N-palmitolein-N-methylglycine", and the chemical formula is C ₂₁ H ₃₉ NO ₃ (where m=9 and n=5 in general formula (3)). The name "N- _{Vacsen -} N-methylglycine" and the chemical name "N- _Nervone- N-methylglycine” and the like.

(Dispersion transfer accelerator having a polymer structure)
Further, as the dispersion transfer accelerator having a polymer structure, for example, a dispersion transfer accelerator having a polymer structure having a functional group (acid group) such as a carboxylic acid at the terminal or in the molecule is used. be able to.

Specifically, examples of dispersion transfer accelerators having a polymer structure with a functional group (acid group) such as carboxylic acid at the end include urethane-based polymer dispersants. As the urethane polymer dispersant, trade name: Solsperse 55000 (average molecular weight 55000), trade name: Solsperse 36000 (average molecular weight 36000), trade name: Solsperse 21000 (average molecular weight 21000), etc. manufactured by Lubrizol) can be preferably used. A single carboxylic acid type product name: Solsperse 3000 (manufactured by Nippon Lubrizol Co., Ltd.) can also be effectively used.

The structure of the dispersion transfer accelerator is not particularly limited, but a comb-shaped polymer is particularly preferred. The dispersion transfer accelerator having a comb structure has a carboxylic acid group in the anchor portion and a polyoxyalkylene group in the graft portion, and has a structure such that the balance between hydrophobicity and hydrophilicity varies depending on the composition. As a polymeric dispersant that is a comb-shaped polymer, for example, NOF Corporation's Marialim AWC series and SC series are commercially available.

In the nickel paste according to the present embodiment, the content of this dispersion transfer accelerator is in the range of 0.16 to 3.0 parts by mass with respect to 100 parts by mass of the nickel powder. If the content of the dispersion transfer accelerator is less than 0.16 parts by mass with respect to 100 parts by mass of the nickel powder, water is not efficiently separated during kneading to prepare the nickel paste, and more residual moisture. On the other hand, even if the content of the dispersion transfer accelerator exceeds 3.0% by mass, the effect of separating water is not further improved. Impact may occur.

[Vehicle]
The vehicle is obtained by dissolving the raw material binder resin in an organic solvent. As the vehicle used in the present embodiment, it is important to select and use a resin having an acid amount of 20 to 300 μmol/g in the binder resin that is the raw material.

The present inventors have found that not only the dispersion transfer accelerator described above, but also the binder resin having the acid amount in the range described above is efficiently adsorbed on the surface of the nickel powder. As a result, the nickel paste according to the present embodiment contains the above-described dispersion transfer accelerator and contains a vehicle containing a binder resin having an acid amount in the above range, so that the surface of the nickel powder The adsorbed dispersion transfer accelerator and the binder resin contained in the vehicle can effectively improve the dispersibility of the nickel powder, and the ultrafine nickel powder can be dispersed in a state of extremely low aggregation. In addition, by containing a vehicle containing such a binder resin, the content of the dispersion transfer accelerator can also be reduced.

In addition, by containing a dispersion migration accelerator and containing a vehicle containing a specific binder resin, it is possible to more efficiently adsorb the surface of the nickel powder as described above. Water based on the nickel powder water slurry to be kneaded can be separated and removed more efficiently, and the manufacturing process can be simplified. Although details will be described later, the nickel paste according to the present embodiment is prepared by adding and mixing a dispersion transfer accelerator to a vehicle containing this specific binder resin, and adding the obtained dispersion transfer accelerator to the vehicle containing the dispersion transfer accelerator. can be obtained by adding nickel powder water slurry and kneading. In such a production method, unlike the prior art, an organic slurry of nickel powder is not produced as an intermediate product, so production can be performed through simple steps.

Here, regarding the acid amount of the binder resin, if the acid amount is lower than 20 μmol / g, the amount of adsorption to the nickel powder is insufficient, and water is not sufficiently separated during kneading to prepare the nickel paste. The amount of residual moisture in the On the other hand, when the acid amount of the binder resin exceeds 300 μmol / g, although the adsorption with the nickel powder is efficiently performed, the viscosity of the nickel paste to be produced becomes too high due to the excessive amount of acid, and for example, the inside of the MLCC Appropriate viscosity cannot be obtained when used as an electrode. For this reason, it is necessary to use a binder resin having an acid amount in an appropriate range. Specifically, as described above, a binder resin having an acid amount in the range of 20 to 300 μmol/g is used.

Specifically, the binder resin has a structure selected from, for example, a cellulose structure, a cellulose ester structure, and a cellulose ether structure, and has a functional group (acid group) such as a carboxyl group introduced therein. can be used.

Thus, for example, a binder resin into which a functional group (acid group) such as a carboxylic acid is introduced and an acid amount of 20 to 300 μmol/g is selected, and this binder resin is dissolved in an organic solvent. The vehicle can be made by

Although the concentration of the binder resin in the vehicle is not particularly limited, it is preferably 5% by mass or more. If the concentration of the binder resin in the vehicle is less than 5% by mass, the viscosity may be low, torque may not be applied during kneading, and the effect of separating and removing water may be low.

The organic solvent is not particularly limited as long as it dissolves the binder resin described above, and those commonly used for conductive pastes can be used. For example, a terpene alcohol-based solvent, an aliphatic hydrocarbon-based solvent, or the like can be used. Specific examples of terpene alcohol-based organic solvents include terpineol (terpineol), dihydroterpineol, terpineol acetate, borneol, geraniol, and linalool. Examples of aliphatic hydrocarbon-based organic solvents include n-decane, n-dodecane, and mineral spirits. About these organic solvents, you may use individually by 1 type and may use 2 or more types together.

[others]
In addition, the nickel paste according to the present embodiment can contain various additives as necessary within a range that does not impair the action of the paste. Specifically, a dispersant for further improving the dispersibility of the nickel powder, a viscosity modifier for adjusting the viscosity, a rheology control agent for increasing the thixotropy, and the like can be added.

≪2. Manufacturing method of nickel paste≫
Next, a method for producing the nickel paste will be described. The nickel paste according to this embodiment can be manufactured by the following two procedures.
[Procedure A] A dispersion transfer accelerator is added to a vehicle and mixed to obtain a vehicle containing a dispersion transfer accelerator. then
[Procedure B] A nickel aqueous slurry is added to a vehicle containing a dispersion transfer accelerator, kneaded, and water is separated and removed to obtain a nickel paste having a nickel concentration of 50 to 70% by mass.

<2-1. About Procedure A>
In the nickel paste manufacturing method according to the present embodiment, first, the dispersion-transfer accelerator is added to the vehicle, and the mixture is stirred and mixed to obtain the vehicle containing the dispersion-transfer accelerator.

(Preparation of vehicle)
The vehicle used can be made by dissolving the binder resin in an organic solvent. Here, as the binder resin constituting the vehicle, a resin having an acid content of 20 to 300 μmol/g is selected as described above. As the organic solvent, a terpene alcohol-based solvent, an aliphatic hydrocarbon-based solvent, or the like can be used.

As the vehicle, it is preferable to use one prepared by dissolving the binder resin in an organic solvent so that the concentration of the binder resin is 5% by mass or more. If the concentration of the binder resin is less than 5% by mass, the viscosity will be low, making it difficult to apply torque during kneading.

(Addition/Mixing of Dispersion Transfer Accelerator)
As the dispersion-transfer accelerator, as described above, a dispersion-transfer accelerator having an anionic surfactant structure or a dispersion-transfer accelerator having a polymer structure can be used. Since the surface of the nickel powder is basic, the use of these dispersion transfer accelerators enables efficient adsorption on the surface of the nickel powder. In the present embodiment, a vehicle containing a dispersion transfer accelerator is obtained by adding these dispersion transfer accelerators to a vehicle and mixing them.

When adding the dispersion-transfer accelerator to the vehicle, the content of the dispersion-transfer accelerator in the resulting nickel paste is 100 nickel powder contained in the aqueous nickel powder slurry to be kneaded in the following procedure (procedure B). It is preferable to calculate and add so as to be in the range of 0.16 parts by mass to 3.0 parts by mass with respect to parts by mass.

That is, when the dispersion transfer accelerator is added so that the content in the nickel paste is less than 0.16 parts by mass with respect to 100 parts by mass of the nickel powder, water is efficiently separated during kneading to prepare the nickel paste. However, the nickel paste obtained contains a large amount of residual water. On the other hand, even if the dispersion transfer accelerator is added so that the content exceeds 3.0% by mass with respect to 100 parts by mass of the nickel powder, the water separation effect is not further improved, and rather nickel The viscosity of the paste may be affected.

As a method of mixing after adding the dispersion transfer accelerator to the vehicle, for example, it can be carried out using a known kneading device such as a stirrer, a rotation/revolution mixer, a planetary mixer, and the like.

As described above, in the method for producing a nickel paste according to the present embodiment, first, a dispersion transfer accelerator is added at a predetermined ratio to a vehicle made of a specific binder resin as a raw material, and stirred and mixed. , to obtain a vehicle containing a dispersion migration enhancer.

<2-2. Regarding Procedure B>
In the method for producing a nickel paste according to the present embodiment, next, a nickel water slurry is added to the vehicle containing the dispersion transfer accelerator obtained by procedure A and kneaded.

Thus, by adding the aqueous nickel powder slurry to the vehicle containing the dispersion transfer accelerator and kneading the mixture, water in the nickel powder slurry can be efficiently separated and removed. In the present embodiment, by using a vehicle containing a dispersion transfer accelerator, the dispersion transfer accelerator is efficiently adsorbed to the surface of the nickel powder, and the binder resin having a specific acid amount contained in the vehicle Since the nickel powder is also adsorbed on the surface of the nickel powder, the nickel powder can be effectively dispersed, and water based on the added nickel powder water slurry can be efficiently separated. As a result, a nickel paste with extremely little residual moisture can be produced in a simple process. Specifically, a nickel paste having a moisture content of less than 1% can be obtained by the Karl Fischer method.

(Nickel powder water slurry)
As for the nickel powder contained in the nickel powder water slurry, as described above, various kinds of nickel powder can be used regardless of the manufacturing method such as the wet method or the dry method. In addition, as the average particle size, ultrafine particles of about 0.05 μm to 0.5 μm, preferably 0.05 μm to 0.3 μm, more preferably 0.05 μm to 0.1 μm can be used. Such ultrafine nickel powder is suitably used for internal electrodes of laminated ceramic capacitors.

The nickel powder aqueous slurry can be obtained by dispersing the above ultrafine nickel powder in water by a conventionally known method. The nickel content in the nickel powder water slurry is not particularly limited.

In addition, as nickel powder water slurry, the thing which added the dispersion|distribution migration accelerator may be used. In this case, as the dispersion transfer accelerator, the same one added to the vehicle in Procedure A can be used as described above.

(Kneading of Vehicle and Nickel Powder Water Slurry)
As described above, by adding the nickel powder aqueous slurry to the vehicle containing the dispersion transfer accelerator and performing kneading treatment, the water contained in the nickel powder aqueous slurry is efficiently separated, and the residual water content is small. A nickel paste can be obtained.

The method for kneading the vehicle and the nickel powder water slurry is not particularly limited, and a known method can be used. Specifically, it can be carried out by a method using a kneading device such as a roll mill, ball mill, homogenizer, lykai machine, kneader, planetary mixer and the like. In addition, if necessary, the pressure may be reduced using a vacuum pump or an aspirator, defoaming or dehydration treatment may be performed, or heat treatment may be performed. Thereby, the moisture content of the resulting nickel paste can be more effectively reduced, and the moisture content according to the Karl Fischer method can be more efficiently reduced to less than 1% by mass.

Moreover, in this kneading treatment, the nickel concentration of the obtained nickel paste is treated to be 50% by mass or more and less than 70% by mass. When the nickel concentration in the paste is less than 50% by mass, it becomes difficult to apply torque during kneading, and water separation is insufficient, resulting in a large amount of residual water in the nickel paste. On the other hand, when the nickel concentration in the paste exceeds 70% by mass, the nickel concentration is too high and the paste loses fluidity. Also, if the nickel concentration is too high, it becomes difficult to dilute the paste with an organic solvent.

In the nickel paste obtained in this way, after separating and removing moisture, for example, barium titanate or the like as a dielectric component, which is a component of a laminated ceramic capacitor, may be mixed. In addition, a dispersant may be added to further improve the dispersibility of nickel in the paste, and an organic solvent may be added to adjust the viscosity. Further, rheology control agents and the like may be added and kneaded to enhance thixotropy.

As described above, in the method for producing a nickel paste according to the present embodiment, first, the dispersion-transfer accelerator is added to the vehicle and mixed, and then the obtained vehicle containing the dispersion-transfer accelerator is A nickel paste with a nickel concentration of 50 to 70% by mass is obtained by adding and kneading a nickel powder water slurry and removing the separated water.

According to such a production method, water can be effectively separated and removed, and a nickel paste can be obtained in which the amount of residual water is small and the nickel powder is dispersed in a state of extremely low agglomeration. In addition, it is not necessary to prepare an organic slurry of nickel powder as an intermediate product as in the conventional method, and the nickel paste can be prepared by an extremely simple process. The obtained nickel paste can be suitably used, for example, for internal electrodes of highly laminated ceramic capacitors for which there is an increasing demand for miniaturization.

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

≪Evaluation method≫
Nickel pastes obtained under the production conditions shown in Examples and Comparative Examples below were evaluated by the following evaluation methods.

(Evaluation of residual moisture content)
A coulometric Karl Fischer moisture meter (manufactured by Kyoto Electronics Industry Co., Ltd.) was used to measure the residual moisture content (% by mass) of the nickel paste at 180°C.

(Evaluation of dry film density)
A nickel paste was applied on a PET film to a thickness of 200 μm using an applicator, dried at 120° C. for 40 minutes, cut out to a diameter of 40 mm, and the area, film thickness, and mass were measured. , and the dry film density (g/cm ³ ) of the nickel paste was calculated from the measurement data.

(Evaluation of viscosity)
Using a rheometer (MCR-501, manufactured by Anton Paar), the viscosity (Pa·s) of the nickel paste was measured at a shear rate of 4.0 s ^-1 and 25°C.

≪Preparation of nickel paste≫
[Example 1]
First, 10.5 g of ethyl cellulose (standard name: STD300, manufactured by Dow Chemical Co., Ltd.) was added to 120 g of dihydroterpineol (manufactured by Nippon Koryo Co., Ltd.) as an organic solvent, and 10.5 g of ethyl cellulose (standard name: STD300, manufactured by Dow Chemical Co., Ltd.) was added as an organic solvent. was prepared. Next, 3.0 g of N-oleyl-N-methylglycine (trade name: oleoyl sarcosine 221P) as a dispersion transfer accelerator was dissolved in the prepared vehicle, and 133.5 g of the vehicle containing the dispersion transfer accelerator was added. Obtained.

Next, the entire amount of the vehicle containing the dispersion transfer accelerator is put into a planetary mixer (Hibismix 2P-1 type, manufactured by PRIMIX), and further nickel powder water slurry manufactured by Sumitomo Metal Mining Co., Ltd. (water content: 80%) ) (ultrafine Ni powder by wet reduction method, average particle size 0.07 μm) was added and kneaded for 15 minutes at 30 rpm to remove water separated from the kneaded product. After that, 500 g of the same nickel powder water slurry (water content 80%) was added again, kneaded under the same conditions (rotational speed 30 rpm, 15 minutes), and separated water was removed. This operation was repeated, and a total of 1.5 kg of nickel powder aqueous slurry (water content: 80%) was added to obtain a kneaded product containing a total of 300 g of nickel powder.

Finally, heating under reduced pressure (pressure: 0.098 MPa, heating temperature: 60° C.) was performed for 20 minutes to volatilize and remove the remaining moisture to obtain a nickel paste.

The "residual moisture content", "dry film density", and "viscosity" of the prepared nickel paste samples were measured and evaluated based on the evaluation methods described above.

As a result, the residual moisture content of the nickel paste was extremely low at 0.84% by mass. Also, the dry film density was 5.5 g/cm ³ , and a high film density was obtained. Further, the viscosity was 131.2 Pa·s, which was a viscosity that could be used as a paste as it was.

[Example 2]
Regarding the amount of dispersion transfer accelerator added to the vehicle, except that the amount of N-oleyl-N-methylglycine (trade name: oleoyl sarcosine 221P) added as a dispersion transfer accelerator was changed to 4.5 g, A nickel paste was prepared in the same manner as in Example 1.

[Example 3]
Regarding the amount of dispersion transfer accelerator added to the vehicle, except that the amount of N-oleyl-N-methylglycine (trade name: oleoyl sarcosine 221P) added as a dispersion transfer accelerator was changed to 9.0 g, A nickel paste was prepared in the same manner as in Example 1.

[Example 4]
First, 120 g of dihydroterpineol (manufactured by Nippon Koryo Co., Ltd.) as an organic solvent and 10.5 g of an acrylic resin (standard name: LC #9176, manufactured by Toei Kasei Co., Ltd.) as a binder resin are added and heated to 80 ° C. while stirring. Vehicle was prepared by dissolution. Next, 1.8 g of N-oleyl-N-methylglycine (trade name: oleoyl sarcosine 221P) as a dispersion transfer accelerator was dissolved in the prepared vehicle, and 132.3 g of the vehicle containing the dispersion transfer accelerator was added. Obtained.

Next, the entire amount of the vehicle containing the dispersion transfer accelerator is put into a planetary mixer (Hibismix 2P-1 type, manufactured by PRIMIX), and further nickel powder water slurry manufactured by Sumitomo Metal Mining Co., Ltd. (water content: 80%) ) (ultrafine Ni powder by wet reduction method, average particle size 0.1 μm) was added and kneaded for 15 minutes at a rotation speed of 30 rpm to remove water separated from the kneaded product. After that, 500 g of the same aqueous slurry of nickel powder (80% water content) was added again, kneaded under the same conditions (rotation speed: 30 rpm, 15 minutes), and separated water was removed. This operation was repeated, and a total of 1.5 kg of nickel powder aqueous slurry (water content: 80%) was added to obtain a kneaded product containing a total of 300 g of nickel powder.

Finally, heating under reduced pressure (pressure: 0.098 MPa, heating temperature: 60° C.) was performed for 20 minutes to volatilize and remove the remaining moisture to obtain a nickel paste.

[Example 5]
Regarding the amount of dispersion transfer accelerator added to the vehicle, except that the amount of N-oleyl-N-methylglycine (trade name: oleoyl sarcosine 221P) added as a dispersion transfer accelerator was changed to 4.5 g, A nickel paste was prepared in the same manner as in Example 4.

[Example 6]
As the binder resin, changed to 10.5 g of an acrylic resin that is a standard name: PC#5984 manufactured by Toei Kasei Co., Ltd., and N-oleyl-N-methylglycine (trade name : A nickel paste was prepared in the same manner as in Example 4, except that the amount of oleoyl sarcosine 221P) added was changed to 1.8 g.

[Example 7]
The dispersion transfer accelerator added to the vehicle was changed to 1.5 g of a polymer dispersant having a structure having an acid group at the end (Solsperse 55000, manufactured by Nippon Lubrizol Co., Ltd.). ), a nickel paste was prepared in the same manner as in Example 1, except that it contained Ni ultrafine powder having an average particle size of 0.2 μm by a wet reduction method manufactured by Sumitomo Metal Mining Co., Ltd.

[Example 8]
Nickel in the same manner as in Example 7, except that the dispersion transfer accelerator added to the vehicle was changed to 1.5 g of a polymer dispersant having a structure having an acid group at the end (Solsperse 21000, manufactured by Lubrizol Japan Co., Ltd.). A paste was made.

[Example 9]
A nickel paste was prepared in the same manner as in Example 8, except that 270 g of dihydroterpineol (manufactured by Nippon Koryo Co., Ltd.) was used as the amount of organic solvent.

[Example 10]
The binder resin was changed to 10.5 g of ethyl cellulose, which is a standard name: STD4 manufactured by Dow Chemical Co., Ltd., and the dispersion transfer accelerator added to the vehicle was lauroyl, an anionic surfactant manufactured by Kawaken Fine Chemicals Co., Ltd. It was changed to 0.48 g of sarcosine (trade name: Soypon SLA). Also, the nickel powder aqueous slurry (water content 20%) was changed to one containing Ni ultrafine powder having an average particle size of 0.3 μm by a wet reduction method manufactured by Sumitomo Metal Mining Co., Ltd. A nickel paste was prepared in the same manner as in Example 1 except for these matters.

[Example 11]
The dispersion transfer accelerator added to the vehicle was changed to 1.8 g of lauroyl sarcosine (trade name: Soypon SLA), an anionic surfactant manufactured by Kawaken Fine Chemicals Co., Ltd., in the same manner as in Example 10. A nickel paste was prepared.

[Example 12]
A nickel paste was prepared in the same manner as in Example 1, except that the binder resin was changed to 10.5 g of ethyl cellulose (standard name: STD200 manufactured by Dow Chemical Co., Ltd.).

[Example 13]
A nickel paste was prepared in the same manner as in Example 1, except that the binder resin was changed to 10.5 g of ethyl cellulose (standard name: STD20 manufactured by Dow Chemical Co., Ltd.).

[Example 14]
A nickel paste was prepared in the same manner as in Example 1, except that the binder resin was changed to 10.5 g of ethyl cellulose having a standard name of STD4 manufactured by The Dow Chemical Company.

[Comparative Example 1]
First, 4.5 g of ethyl cellulose (manufactured by Dow Chemical Co., Ltd., standard name: STD300) was added to 51.3 g of dihydroterpineol (manufactured by Nippon Koryo Co., Ltd.) as an organic solvent, and the mixture was dissolved by heating to 80°C while stirring to form a vehicle. prepared. Next, 3.0 g of N-oleyl-N-methylglycine (trade name: oleoyl sarcosine 221P) as a dispersion transfer accelerator was dissolved in the prepared vehicle, except that the amount was changed to 3.0 g. An attempt was made to prepare a nickel paste in the same manner as in Example 1.

However, the Ni concentration was too high at 83.6% by mass, making it difficult to separate and remove water, making it impossible to prepare a nickel paste.

[Comparative Example 2]
A vehicle was prepared by adding 42 g of ethyl cellulose (manufactured by Dow Chemical Co., Ltd., standard name: STD300) as a binder resin to 480 g of dihydroterpineol (manufactured by Nippon Koryo Co., Ltd.) as an organic solvent and heating and dissolving at 80 ° C. while stirring. A nickel paste was prepared in the same manner as in Example 1 except for the above.

However, the Ni concentration was as low as 36.36% by mass, and it was difficult to apply torque during kneading. Therefore, the separation and removal of water from the kneaded material was insufficient, and the amount of residual water in the produced nickel paste was large. Also, the dry film density was low.

[Comparative Example 3]
A nickel paste was prepared in the same manner as in Example 4, except that the binder resin was changed to 10.5 g of an acrylic resin having a standard name of YZ#5125 manufactured by Toei Kasei Co., Ltd.

However, the separation and removal of water during kneading was insufficient, and the amount of residual water in the produced nickel paste increased, making it impossible to produce nickel paste.

[Comparative Example 4]
In the same manner as in Example 10, except that 0.27 g of lauroyl sarcosine (trade name: Soypon SLA), an anionic surfactant manufactured by Kawaken Fine Chemicals Co., Ltd., was used as the dispersion transfer accelerator added to the vehicle. I tried to make a nickel paste.

However, since the amount of the dispersion transfer accelerator was too small, the nickel powder water slurry could not be kneaded, and the nickel paste could not be produced.

<<About the acid amount of the binder resin used in Examples and Comparative Examples>>
Table 1 below summarizes the acid amounts of the binder resins used in Examples and Comparative Examples.

<<Evaluation result>>
Table 2 below shows the evaluation results of the nickel paste in each example and comparative example. In addition, in Comparative Examples 1, 3, and 4, since no nickel paste could be produced, the dry film density and viscosity were not evaluated. Moreover, in Comparative Example 4, since the nickel powder water slurry could not be kneaded, the residual water content was not measured.

Claims (2)

containing at least nickel powder, a dispersion transfer accelerator, and a vehicle;
The dispersion transfer accelerator is a dispersion transfer accelerator having an anionic surfactant structure and is a compound represented by the following general formula (3),
In the vehicle, the acid amount of the raw material binder resin is 114.9 to 120.0 μmol/g, the binder resin is ethyl cellulose,
The content of the dispersion transfer accelerator is 0.16 to 3.0 parts by mass with respect to 100 parts by mass of the nickel powder,
The nickel concentration is 50 to 70% by mass, the viscosity of the paste is 8 to 150 Pa s ,
Moisture content by Karl Fischer method is less than 1% by mass
nickel paste.

(However, in formula (3), m and n satisfy the relationship m+n=12 to 20.) The nickel paste according to claim 1, wherein the nickel powder has an average particle size of 0.05 to 0.5 µm.