JP4970836B2 - Method for stabilizing ceramic powders and slurries by introducing chemical working groups - Google Patents

Description

  The present invention provides a method for producing a ceramic powder in which a high-density amine group-containing polymer layer is formed, a method for producing a slurry in which the ceramic powder produced by the above method is stably highly dispersed in a dispersion solvent, and each of the above It relates to ceramic powders and slurries produced by the method.

  Conventionally, various methods for highly dispersing ceramic powder so as to be stable on a solution have been proposed. However, attempts have been made mainly by a physical method. For example, Patent Document 1 discloses a high-pressure slurry dispersion method for producing a slurry in which ceramic powder particles are uniformly dispersed without excessively damaging the crystallinity of the ceramic powder particles. However, although the above-mentioned Patent Document 1 applies a medium-type dispersion method using a dispersion medium such as a ball or a bead, there is an inconvenience that it must be dispersed under high-pressure conditions.

  Patent Document 2 describes a technique relating to a method of polymerizing a vinyl monomer to make a slurry of ceramic powder on water and an organic solvent. Here, too, ceramic powder and solvent are used for dispersion of the powder. Inconvenient work to obtain a dispersed slurry by mixing and polishing for a long time with a ball-mill equipment.

  Furthermore, Patent Document 3 discloses stabilization of a ceramic suspension in which an organic compound having at least one functional group such as a hydroxyl group and a carboxyl group is added to a reactive, water-soluble ceramic suspension as a chemical method. Although a method is described, the above method is to stabilize a colloidal ceramic particle by adding a specific substance to a ceramic suspension, and does not describe a specific treatment of the ceramic particle.

Recent developments in nanotechnology have made it possible to produce ceramic particles whose size can be controlled at the nanometer level, but evenly disperse the powder particles of micrometer and nanometer level sizes throughout the dispersion medium. It is not easy to apply to the production process of various products.
US Pat. No. 6,579,394 JP 1997-11212 JP JP 1996-47917

  The first object of the present invention is to provide a method of coating ceramic powder having amine groups coated on the surface of the ceramic powder.

  The second object of the present invention is to provide a method for improving the dispersibility of ceramic particles with a dispersion solvent by forming a positive charge in the ceramic powder coated with the amine group.

  The third object of the present invention is to provide ceramic powders and slurries produced by the above methods.

  Furthermore, the fourth object of the present invention is to provide a ceramic slurry green sheet and a multilayer ceramic electronic component using the above ceramic slurry composition.

  More specifically, the ceramic nanoparticle powder can be uniformly dispersed in the dispersion medium without a mechanical mixing / polishing step such as a milling step in the process of obtaining a uniform dispersion of the ceramic particles at the nanometer level. An object of the present invention is to provide a high-density surface charge generated by changing the chemical environment of a solvent after introducing a chemical functional group onto the surface of a nanometer-sized ceramic particle. The present invention relates to a method of stably dispersing particles on a solution using electrostatic repulsion between them. In addition, the use of an organic solvent can be reduced by using water as a dispersion medium, and an environmentally friendly method is provided.

  As a first embodiment of the present invention, a step of forming a nucleophilic functional group on the surface of a washed ceramic powder, and a chain polymerization reaction of an aziridine equivalent on the surface of the ceramic powder on which the nucleophilic functional group is formed, an amine Coating a group, and a method for coating a ceramic powder is provided.

  According to a second embodiment of the present invention, there is provided a ceramic powder slurry, wherein an acid catalyst is added to a surface of a ceramic powder coated with an amine group formed according to the first embodiment under a polar solvent to form a positive charge. A stabilization method is provided.

  As a third embodiment of the present invention, there is provided a ceramic powder in which the surface of ceramic particles having a nucleophilic functional group is coated with a polyethyleneimine polymer layer.

  As a fourth embodiment of the present invention, there is provided a ceramic slurry in which a positive charge is formed on an amine group at the end of a polyethyleneimine polymer coating ceramic particles coated with a polyethyleneimine polymer layer.

  As a fifth embodiment of the present invention, a ceramic slurry green sheet using the above ceramic powder slurry composition and a multilayer ceramic electronic component using the same are provided.

  According to the present invention, a separate milling process for uniformly dispersing the ceramic particles is not required, and the ceramic powder particles can be uniformly dispersed without damaging the crystallinity of the ceramic powder in producing the ceramic slurry. Thus, an excellent effect of producing a high-quality ceramic slurry can be obtained.

  In addition, the use of water as a dispersion medium can reduce the use of an organic solvent, so that an environmentally friendly effect can be obtained.

  Further, a slurry in which ceramic powder is highly dispersed can be used, and an excellent effect that a high-quality ceramic slurry green sheet and multilayer ceramic electronic component can be produced can be obtained.

  Hereinafter, embodiments of the present invention will be described in more detail.

  As one embodiment of the present invention, a nucleophilic functional group is formed on the surface of a cleaned ceramic powder, and an aziridine equivalent is chain-polymerized on the surface of the ceramic powder on which the nucleophilic functional group is formed. The powder surface can be coated with amine groups.

  The ceramic powder used in the present embodiment can be used without any particular limitation as long as it contains oxygen atoms. For example, but not limited to, dielectric ceramic powder such as barium titanate, strontium titanate or lead titanate, insulator ceramic powder such as alumina or silica, magnetic ceramic powder such as ferrite Alternatively, piezoelectric ceramic powder or the like can be used.

  In the present embodiment, the average particle size of the ceramic particles is not particularly limited. Usually, the average particle size (average primary particle size measured with an electron microscope) of the ceramic powder used for the production of the ceramic electronic component is preferably in the range of 0.001 to 1.0 μm. The present invention can also be applied when the average particle size does not fall outside the range of 0.001 to 1.0 μm.

  In this embodiment, a mechanical treatment process (such as a milling process) for the ceramic powder is not required. However, when the ceramic powder is agglomerated from the beginning, simple mechanical processing can be performed.

  In one aspect of the present embodiment, the step of forming a nucleophilic functional group on the surface of the ceramic powder is performed by washing the ceramic powder surface with an organic solvent and / or an acidic solution and then drying. Can be formed.

For example, the organic solvent as the cleaning solution is not limited to this, but any organic solvent containing oxygen atoms such as acetone containing a ketone group, ethanol containing a hydroxyl group, or methanol can be used without limitation. Further, in the above acidic solution hydrochloric, nitric acid, an inorganic acid or acetic acid, butyric acid, palmitic acid, such as sulfuric acid, oxalic acid, can be used organic acids such as tartaric acid (carboxy acid), if the solution showing an acidic pH It can be used in a wide range regardless of. In this embodiment, an acidic solution can be more preferably used as the cleaning liquid.

  By washing and drying the ceramic powder having oxygen atoms using such an organic solvent or an acidic solution, the nucleophilic functional group is activated on the surface of the ceramic powder as shown in FIG. In this case, the nucleophilic functional group can include a functional group selected from the group consisting of a hydroxyl group (—OH), a thiol group (—SH), and an amine group (—NH 2). Nucleophilic functional groups that can be used more suitably in form include hydroxyl groups (—OH).

  The ceramic powder having nucleophilic functional groups formed on the surface by the washing and drying steps as described above is subjected to chain polymerization reaction with an aziridine equivalent in a reaction solvent, and the particle surface is coated with amine groups. At this time, an acid catalyst can be added to promote the reaction.

Examples of the above-mentioned aziridine equivalent include aziridine represented by the following chemical formula [Chemical Formula 1] or a haloethylamine represented by the following chemical formula [Chemical Formula 2]. Here, in the following chemical formula [Chemical Formula 2], X is Cl, Br or I.

  A solution selected from the group consisting of dichloromethane, chloroform, hexene, toluene and the like can be used as the reaction solvent used in the polymerization reaction of the nucleophilic functional group and the aziridine equivalent, and more preferably dichloromethane is used. It can be used as a reaction solvent. The nucleophilic functional group formed on the surface of the ceramic powder particles in the reaction solvent as described above reacts with the nitrogen atom of the aziridine equivalent, and the aziridine equivalent subsequently reacts in a chain-opening polymerization reaction. It becomes like this. As a result of such a polymerization reaction, branched chains are formed on the surface of the ceramic powder. In particular, the above-mentioned branching occurs in a chain reaction with a nitrogen atom to form a highly branched polymer, that is, a polyethylimine having an amine group at the terminal.

The acid catalyst is added to promote the polymerization reaction as described above can be cited hydrochloric acid, nitric acid, inorganic acids such as sulfuric acid or acetic acid, butyric acid, palmitic acid, oxalic acid, an organic acid such as tartaric acid, However, the present invention is not limited to this.

  As a condition for the polymerization reaction, the washed and dried ceramic powder particles are mixed with aziridine and, optionally, an acid catalyst in a reaction solvent, and then heated in an inert gas atmosphere. Examples of the inert gas include helium, nitrogen, neon, and argon.

At this time, heating can be performed for about 10 minutes to 30 hours within a temperature range of 50 to 100 ° C. More preferably, it can be heated in the range of 65-75 ° C. for 30 minutes to 10 hours. When the heating temperature is less than 50 ° C., the reactivity is poor, and when it exceeds 100 ° C., the coating property is lowered. Therefore, it is preferable to react within the above-mentioned temperature range. Further, the heating time is not preferable because the same problem occurs when the temperature is out of the above range.

  The ceramic particles coated with polyethyleneimine having amine groups on the surface can be dried to obtain ceramic powder coated with a polymer layer. At this time, it is preferable to dry at room temperature, and the drying method can be performed using a method generally performed in the field to which the present embodiment belongs, and more preferably a vacuum drying method can be used.

  By measuring the surface density of the primary amine, it is possible to determine whether or not branching occurs. A method for confirming whether or not a primary amine can be produced is based on the production of 4-nitrobenzaldiimine by the reaction of 4-nitrobenzaldehyde with a primary amine. By examining the change in absorbance of the produced imine at 284 nm, it can be confirmed whether primary amines can be produced. That is, forming an imine compound and having a high amine density indicates that a branch is formed after the ring-opening reaction of aziridine. At this time, in the case of the ceramic powder particle surface according to the present embodiment, the absorbance at 284 nm of 4-nitrobenzaldiimine has a range of 0.4-0.7. Thus, according to the present embodiment, it can be seen that polyethyleneimine containing amine groups is present at a high density on the surface of the ceramic powder.

  By doing so, the ceramic powder surface can be coated with a polymer layer of polyethyleneimine containing amine groups. By using ceramic powder coated with such a polymer layer, it is possible to achieve another object of the present embodiment in which dispersibility is improved by adding an acid catalyst in a dispersion solvent.

  As another example of the present embodiment, a positive charge is formed at the end of the molecular layer by adding an acid catalyst to the ceramic powder in which the molecular layer having a high-density amine group is formed on the surface in a polar solvent. A stable and highly dispersible ceramic slurry can be obtained.

  In the ceramic slurry, a ceramic powder in which a molecular layer having a high density of amine groups is formed as manufactured according to the present embodiment may be used, and the ceramic powder may be included in a range of 30 to 50% by weight.

  In the ceramic slurry, the polar solvent is not particularly limited as long as it is a polar solvent in which ceramic particles whose surface is coated with a chemical functional group are easily dispersed. For example, a solvent selected from the group consisting of water, alcohols such as methanol, ethanol, isopropyl alcohol, ethers, ketones, and mixtures thereof can be used. Among the polar solvents, water or a mixed solvent of water and the polar solvent can be preferably used. By using water alone or together as a solvent, the use of an organic solvent can be reduced, so that an environmentally friendly effect can be obtained. The polar solvent may be included in the range of 50 to 70% by weight.

The acid catalyst can be used hydrochloric acid, nitric acid, an inorganic acid or acetic acid, butyric acid, palmitic acid, such as sulfuric acid, oxalic acid, an organic acid such as tartaric acid. An inorganic acid can be preferably used, and hydrochloric acid can be particularly preferably used. The acid catalyst can be added within a range of 0.01 to 1.0% by weight, more preferably 0.05 to 0.5% by weight, and particularly preferably 0.07% with respect to 100% by weight of the ceramic slurry. It can be added within the range of -0.3% by weight.

  As described above, when an acid catalyst is added to a chemically coated ceramic powder in a dispersion solvent, a polyethyleneimine-terminated amine group that coats the ceramic particle surface exhibits a positive charge as shown in FIG. . As shown in FIG. 2, the ceramic particles that have become charged on the solvent are dispersed stably on the dispersion solvent by the strong electrostatic repulsion between the particles.

  A binder can be added to the dispersion solvent. The binder component may be added with components usually used in the technical field to which the present embodiment belongs. More specifically, polyvinyl butyral resin, cellulose resin, acrylic resin, vinyl acetate resin, polyvinyl alcohol resin and the like are generally used. Generally, a binder solution prepared by mixing and stirring these binder and the dispersion solvent is used.

  The timing for adding the binder is not particularly limited. That is, the binder may be mixed in advance with a dispersion solvent, or may be mixed when the ceramic powder is dispersed in the dispersion solvent.

FIG. 4 is an SEM photograph showing the agglomerated state of particles which are obtained by dispersing silica powder (a) whose surface is coated and powder (b) whose surface is not coated on an aqueous solution and then drying. In this embodiment, the repulsive force acts between the ceramic particles due to the positive charges formed on the surface of the ceramic powder, and the dispersion is uniformly dispersed in the dispersion solvent, so that the pulverization step with the binder added is not required. Accordingly, as shown in FIG. 4A, the ceramic powder can be uniformly dispersed without damaging the ceramic powder particles, and a high-quality ceramic slurry can be produced. In this embodiment, the dispersion solvent does not require a dispersant other than an acid. However, depending on needs may include other dispersant other than the above acids. At this time, the type and amount of the dispersant that can be added are not particularly limited, and a dispersant that is normally used in the field to which the present embodiment belongs can be appropriately selected and added depending on the target type of the ceramic green sheet. .

  A plasticizer can be added to the ceramic slurry of this embodiment. As the plasticizer, plasticizers usually used in the field to which the present embodiment belongs can be added, and specific examples include polyethylene glycol, phthalic ester, and alkyd resin. However, it is not limited to these. The kind and amount of the plasticizer are preferably selected according to the kind of the target ceramic green sheet.

  The ceramic slurry of this embodiment may further contain an antistatic agent. The antistatic agent used in this embodiment can be any of those generally used in ceramic slurries.

  In addition to the dispersant, plasticizer, and antistatic agent, other additives can be added to the ceramic slurry of this embodiment.

  As an embodiment of the present embodiment, a high quality ceramic slurry green sheet can be manufactured using a stable ceramic slurry in which the ceramic powder is uniformly dispersed. The method for producing the green sheet of the present embodiment is not particularly limited as long as the ceramic slurry is used, and can be produced by a commonly performed method.

As another embodiment of the present embodiment, a ceramic electronic component using the ceramic slurry green sheet can be obtained.
[Example]

  Hereinafter, the present embodiment will be specifically described through examples. The following examples are merely examples of the present embodiment, and the present embodiment is not limited thereto.

  10 g of silica powder was washed thoroughly with an aqueous hydrochloric acid solution having a pH of 2, then washed with water and dried. The ceramic powder was added to a mixture of 2 ml of aziridine, a catalytic amount (0.1% by weight of the total amount of the mixed solution) of acetic acid and 100 ml of dichloromethane, and then the mixture was stirred and a shield tube in a nitrogen atmosphere. (sealed tube) and heated at 70 ° C. for 20 hours.

  The ceramic powder surface-reacted with aziridine was washed with dichloromethane and methanol, and then vacuum-dried at room temperature to obtain a coated ceramic powder by forming a high-density polyethyleneimine layer on the particle surface.

  The same method as in Example 1 was performed except that barium titanate powder was used instead of silica powder.

[Confirmation test of high density amine group-containing molecular layer by ring-opening polymerization reaction]
The silica powder of Example 1 was added to absolute ethanol and reacted with 4-nitrobenzaldehyde using a small amount of acetic acid as a catalyst to form imine on the surface of the ceramic particles. Thereafter, the substrate on which imine was formed was taken out from ethanol, washed cleanly and dried in vacuum, and then immersed in distilled water again and left at 60 ° C. for 6 hours to form 4-nitrobenzaldiimine. The prepared aqueous solution was examined for changes in absorbance at 284 nm of the produced 4-nitrobenzimine using an ultraviolet spectrometer, and the results are shown in FIG. As shown in FIG. 3, a clear absorbance change was expressed at 284 nm.

  The presence of primary amine can be confirmed from the above results, and it can be seen that the amine density is high by converting the density of amine from the intensity of absorbance. This indicates that a high-density amine group-containing polyethyleneimine molecular layer was produced by ring-opening polymerization reaction of aziridine on the silica powder surface of Example 1.

  It can be seen that similar results are obtained for the barium titanate powder of Example 3.

  The silica surface-treated in Example 1 was added to deionized water (pH 5) and dispersed.

  The surface-treated silica in Example 1 was added and dispersed in an aqueous solution (pH 2) obtained by adding hydrochloric acid to deionized water.

[Measurement of particle mobility]
The particle mobility was measured using a light scattering measurement method on silica powder dispersed at pH 5 (Example 4) and pH 2 (Example 5). The results are shown in FIG.

FIG. 5 represents the correlation function over time at pH 2 and pH 5, and Table 1 represents the average particle distribution at pH 2 and pH 5. Correlation intensity at pH 5 represents about 1.0-2.3 in the range of 0-2 seconds, and the average particle size is 750 nm, whereas at pH 2, the correlation strength is in the range of 0-1 seconds. The average particle size is 238 nm. From this, it can be seen that the safety of the particles is improved and the dispersibility is improved at a low pH. Tables 1 and 2 below show distribution analysis.

  It can be seen that the ceramic powder and the slurry stabilized by introducing a chemical functional group as in the above results are excellent in dispersibility.

1 is a diagram schematically showing the surface of a ceramic particle according to the order of formation of a nucleophilic functional group, coating of polyethyleneimine, and formation of a positive charge at an amine group end. 2 is a drawing schematically showing a repulsive force acting between ceramic particles due to a positive charge on a particle surface. It is the graph showing the light absorbency change in 284nm for the production | generation confirmation of the amine group containing molecular layer by ring-opening polymerization reaction. It is a SEM photograph which shows the aggregation state of the particle | grains dried after disperse | distributing the silica powder (a) which coated the surface, and the powder (b) which is not coating the surface on aqueous solution. It is the graph which represented the mobility of the particle | grains obtained by disperse | distributing the surface-coated silica powder at pH2 and pH5 using the light-scattering measuring method with the correlation function by time.

Claims (9)

Washing the surface of the ceramic powder containing oxygen atoms with an organic solvent and / or an acidic solution and then drying to form nucleophilic functional groups on the cleaned ceramic powder surface;
The ceramic powder surface on which the nucleophilic functional group is formed by mixing the ceramic powder in which the nucleophilic functional group is formed and aziridine or haloethylamine in a reaction solvent and then heating in an inert gas atmosphere. Chain-polymerizing the aziridine or the haloethylamine and coating with polyethyleneimine;
A ceramic powder coating method comprising: The ceramic powder coating method according to claim 1, wherein the ceramic powder is a dielectric ceramic powder, a magnetic ceramic powder, a piezoelectric ceramic powder, or an insulating ceramic powder. The nucleophilic functional group is a ceramic powder coating method according to claim 1, characterized in that the hydroxyl (-OH), an thiol group (-SH) or amine group (-NH _2). The ceramic powder coating method according to claim 1, wherein the polyethyleneimine is formed by ring-opening polymerization reaction of aziridine or haloethylamine on a nucleophilic functional group on the surface of ceramic particles. 5. The ceramic powder coating method according to claim 4, wherein during the ring-opening polymerization reaction, a reaction solvent is dichloromethane, chloroform, hexene, or a toluene solution. A method for stabilizing a ceramic slurry, comprising adding a ceramic powder coated by the method according to any one of claims 1 to 5 and an acid catalyst to a polar solvent to form a positive charge. The method for stabilizing a ceramic slurry according to claim 6, wherein the polar solvent is water, alcohols, ethers, or ketones. The method for stabilizing a ceramic slurry according to claim 6, wherein the acid catalyst is an inorganic acid or an organic acid. The method for stabilizing a ceramic slurry according to claim 6, wherein the content of the acid catalyst is 0.01 to 1% by weight.