JP5267775B2 - Dispersion of fine barium titanate powder and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion of barium titanate fine powder excellent in storage stability and a method for producing the same, wherein barium titanate fine powder is uniformly dispersed in a dispersion medium as fine particles of nanometer order having a narrow particle size distribution and does not cause problems such as thickening, gelation and sedimentation separation in long-term storage. <P>SOLUTION: The dispersion of barium titanate fine powder in which barium titanate fine powder is dispersed in a dispersion medium and the barium titanate in the dispersion has a number-reduced average particle diameter of &le;100 nm is obtained through a first step of preliminarily dispersing barium titanate fine powder having an average primary particle diameter of &le;100 nm in a dispersion medium, a second step of dispersing a dispersion medium containing barium titanate fine powder obtained at the first step by stirring with media, and a third step of after-dispersing a dispersion medium containing barium titanate fine powder obtained at the second step. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  In the present invention, the barium titanate fine particle powder is uniformly dispersed as nano-order fine particles having a narrow particle size distribution in the dispersion medium, and does not cause thickening, gelation, sedimentation separation, etc. during long-term storage. The present invention relates to a dispersion of barium titanate fine particles having excellent storage stability and a method for producing the same.

  Barium titanate is an insulating ferroelectric compound having a perovskite structure, and is widely used as a dielectric material for electronic components such as multilayer capacitors, positive thermistors, piezoelectric materials, and high-frequency vibrators. In recent years, with the reduction in size, performance, and weight of various electronic devices, barium titanate particles used in dielectric materials for electronic components are also required to be excellent in dispersibility without agglomeration. Yes.

  In addition, when the particle diameter of the barium titanate fine particle powder is 100 nm or less in the dispersion medium, that is, a particle diameter sufficiently smaller than the wavelength in the visible region, the light scattering intensity is remarkably reduced and the transparency is increased. Therefore, it is used in optical materials such as optical inks and liquid crystal spacers, and is dispersed in the dispersion medium as nano-order primary particles with a narrow particle size distribution. In addition, it is required to have excellent storage stability without causing sedimentation separation or the like.

  So far, an ultrafine particle dispersion type optical ink (Patent Document 1) in which ultrafine particles of metal oxide powder pulverized so as to have a particle diameter of 5 to 100 nm are dispersed in a resin binder using cyclohexanone as a main solvent has been disclosed. Proposed.

  Moreover, a dispersion liquid (Patent Document 2) in which inorganic particles having an average particle diameter of 50 nm or less are uniformly dispersed by adjusting the pH of the dispersion liquid has been proposed.

  In addition, a method for producing a barium titanate dispersion in which a suspension of barium titanate is treated with a wet jet mill has been proposed (Patent Document 3).

  Further, barium titanate dispersions (Patent Document 4 and Patent Document 5) in which the ratio of the average primary particle diameter to the average secondary particle diameter is limited to a range of 0.7 to 6.0 have been proposed.

JP 2000-26773 A JP 2007-23131 A JP 2000-189830 A JP 2005-289668 A JP 2007-137759 A

  Barium titanate fine particle powder is uniformly dispersed as nano-order fine particles with a narrow particle size distribution in the dispersion medium, and does not cause thickening, gelation or sedimentation separation during long-term storage, storage stability An excellent dispersion of barium titanate fine particles and a method for producing the same are currently in great demand, but have not yet been obtained.

  That is, Patent Document 1 describes a method in which ultrafine particles of metal oxide powder pulverized to have a particle diameter of 5 to 100 nm are dispersed in a resin binder containing cyclohexanone as a main solvent. Is limited to cyclohexanone and requires a resin binder, and pulverization and dispersion processing is performed using a pulverizer, which is industrially disadvantageous because it takes 50 to 350 hours for the processing. . Furthermore, since no further dispersion has been performed after fine dispersion to a nano-order particle size by this dispersion, it is difficult to obtain a dispersion of fine barium titanate powder having excellent storage stability.

  Patent Document 2 describes a method for uniformly dispersing inorganic particles having an average particle diameter of 50 nm or less by adjusting the pH of the dispersion liquid. Since further dispersion is not performed after finely dispersing to the particle size, it is difficult to obtain a dispersion of barium titanate fine particles having excellent storage stability. Moreover, since a solvent is limited to an organic solvent and it is necessary to adjust pH, it is industrially disadvantageous.

  Patent Document 3 describes a method for producing a barium titanate dispersion in which a suspension of barium titanate is treated with a wet jet mill. Since further dispersion is not performed after finely dispersing to the particle size, it is difficult to obtain a dispersion of barium titanate fine particles having excellent storage stability. Further, the barium titanate dispersed in Patent Document 3 is in the submicron order of 0.41 μm to 0.69 μm, which is different from the dispersion in which the nano-order barium titanate fine particles of the present invention are uniformly dispersed. Is.

  Patent Document 4 and Patent Document 5 describe a dispersion using barium titanate in which the ratio of the average primary particle diameter to the average secondary particle diameter is limited to a range of 0.7 to 6.0. ing. However, the average secondary particle size is measured in a very dilute system in which barium titanate is dispersed in an aqueous solution to which a dispersant (sodium hexametaphosphate) is added (“NIKKISO MICROTRAC UPA150: manufactured by Nikkiso Co., Ltd.). "Is not possible to measure the particle size distribution in a dense system), so the average secondary particle size in the actually produced dispersion has not been evaluated. Further, the dispersion method is not particularly taken into consideration, and a dispersion of barium titanate fine particle powder excellent in storage stability that does not cause thickening, gelation, and sedimentation separation in long-term storage simply by dispersing. It is difficult to get.

  Therefore, the present invention is that the barium titanate fine particle powder is uniformly dispersed as nano-order fine particles having a narrow particle size distribution in the dispersion medium, and has such functions as thickening, gelation and sedimentation separation during long-term storage. An object of the present invention is to provide a dispersion of barium titanate fine particle powder that does not occur and has excellent storage stability and a method for producing the same.

  The technical problem can be achieved by the present invention as follows.

  That is, the present invention is a dispersion of barium titanate fine particle powder in which barium titanate fine particle powder is dispersed in a dispersion medium, and the number-average particle diameter of barium titanate in the dispersion is 100 nm or less. This is a dispersion of fine barium titanate powder (Invention 1).

  Further, in the present invention, the dispersion reach of the barium titanate fine particle powder in the dispersion of the present invention 1 is such that the number-average dispersion average particle diameter of the barium titanate fine particle powder in the dispersion and the average primary of the barium titanate fine particle powder. A dispersion of fine barium titanate powder having a particle diameter ratio of 1.50 or less (Invention 2).

  The present invention also includes a first step of pre-dispersing barium titanate fine particle powder having an average primary particle diameter of 100 nm or less in a dispersion medium, and the barium titanate fine particle powder obtained in the first step. A book comprising: a second step of stirring and dispersing the dispersion medium together with the medium; and a third step of post-dispersing the dispersion medium containing the barium titanate fine particle powder obtained in the second step. This is a method for producing a dispersion of barium titanate fine particles according to Invention 1 or Invention 2 (Invention 3).

  Further, the present invention is the method for producing a dispersion of barium titanate fine particle powder according to the present invention 3, wherein the media used in the second step has an average particle diameter of less than 100 μm (the present invention 4).

  According to the present invention, the barium titanate fine particle powder is uniformly dispersed as nano-order fine particles having a narrow particle size distribution in the dispersion medium, as well as thickening, gelation and sedimentation separation during long-term storage. A barium titanate fine particle powder dispersion that does not occur and has excellent storage stability can be obtained.

  The dispersion of barium titanate fine particles according to the present invention will be described below.

  The number-average dispersion average particle diameter of the barium titanate fine particle powder in the dispersion of the barium titanate fine particle powder according to the present invention is 100 nm or less, preferably depending on the average primary particle diameter of the barium titanate fine particle powder. It is 90 nm, more preferably 80 nm or less.

  The dispersion attainment degree of the barium titanate fine particle powder in the dispersion of the barium titanate fine particle powder according to the present invention is determined by the number-average dispersion average particle diameter of the barium titanate fine particle powder in the dispersion and the average primary of the barium titanate fine particle powder. The particle size ratio is 1.50 or less, preferably 1.45 or less, more preferably 1.40 or less.

  The particle size distribution of the barium titanate fine particle powder in the dispersion of the barium titanate fine particle powder according to the present invention is preferably 2.0 or less, more preferably 1 as the geometric standard deviation value of the volume-converted dispersion average particle diameter. .8 or less, still more preferably 1.6 or less.

  The dispersion stability of the dispersion of the barium titanate fine particles according to the present invention is preferably 10% or less, more preferably 8% or less, in the rate of change in viscosity described below. When the rate of change in viscosity is greater than 10%, it becomes difficult to store for a long time in a stable dispersion state.

  Next, a method for producing a dispersion of fine barium titanate powder according to the present invention will be described.

  The barium titanate fine particle powder dispersion according to the present invention is obtained in the first step of predispersing the barium titanate fine particle powder having an average primary particle diameter of 100 nm or less in a dispersion medium, and the first step. The second step of stirring and dispersing the dispersion medium containing the fine barium titanate powder with the medium, and the third step of post-dispersing the dispersion medium containing the fine barium titanate powder obtained in the second step Consists of.

  The average primary particle diameter of the barium titanate fine particle powder in the present invention is preferably 100 nm or less, more preferably 5 to 80 nm, and still more preferably 6 to 60 nm.

The BET specific surface area value of the barium titanate fine particle powder in the present invention is preferably 5 m ² / g or more, more preferably 5 to 110 m ² / g.

  As the dispersion medium in the present invention, either an aqueous system or a solvent system can be used.

  As a dispersion medium of the aqueous dispersion, water or alcohol solvents such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol; glycol ether solvents such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, and butyl cellosolve; Oxyethylene or oxypropylene addition polymers such as diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol; alkylene glycols such as ethylene glycol, propylene glycol, and 1,2,6-hexanetriol; glycerin Water-soluble organic solvents such as 2-pyrrolidone can be used. These dispersion media for aqueous dispersions can be used alone or in combination of two or more depending on the intended application.

  Dispersion media for solvent-based dispersions include aromatic hydrocarbons such as toluene and xylene; ketones such as methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone Ether glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl Ether acetates such as ether acetate and propylene glycol monoethyl ether acetate; ethyl acetate Acetic acid esters such as butyl acetate and isobutyl acetate; Lactic acid esters such as lactate methyl ester, lactate ethyl ester and lactate propyl ester; Cyclic esters such as ethylene carbonate, propylene carbonate and γ-butyrolactone and various monomers may be used. it can. These dispersion media for solvent-based dispersions can be used alone or in combination of two or more depending on the intended application.

  The disperser used in the first step of pre-dispersing the barium titanate fine particle powder of the present invention in a dispersion medium is not particularly limited, but shearing force, impact force, compressive force, and / or frictional force are applied to the powder layer. Is preferable, for example, a roller mill, a high-speed rotary mill, a high-speed rotary mill with a built-in classifier, a ball mill, a medium agitating mill, an airflow-type crusher, a consolidation shear mill, a colloid mill, a roll mill, etc. Can do.

  When using a media agitating mill in the first step, the grinding media may be stainless steel, steel ball beads such as steel, depending on the mill material; alumina, steatite, zirconia, zircon, silica, silicon carbide, nitriding Ceramic beads such as silicon; glass beads such as soda glass and high bee; carbide beads such as WC can be used, and the size is preferably in the range of 0.1 to 1.5 mm.

  As the disperser used in the second step of stirring and dispersing the dispersion medium containing the barium titanate fine particle powder obtained in the first step of the present invention together with the medium, a medium stirring mill can be suitably used. Particularly preferred is a vertical bead mill.

  As the grinding media used in the second step, depending on the mill material, steel ball beads such as stainless steel and steel; ceramic beads such as alumina, steatite, zirconia, zircon, silica, silicon carbide, and silicon nitride; soda Glass beads such as glass and high bee; carbide beads such as WC can be used, the size is less than 100 μm, and the lower limit is 1 μm.

  As the disperser used in the third step of post-dispersing the dispersion medium containing the barium titanate fine particle powder obtained in the second step of the present invention, it is preferable to use other than the medium stirring mill, particularly preferably A sonic disperser can be used.

  The dispersion of the barium titanate fine particle powder obtained by the production method of the present invention contains 0.1 to 60 parts by weight, preferably 0.5 to 0.5 parts by weight of the barium titanate fine particle powder with respect to 100 parts by weight of the dispersion-constituting substrate. -50 parts by weight, more preferably 1-40 parts by weight. The base material of the dispersion of the barium titanate fine particle powder includes a dispersion medium in addition to the above-mentioned barium titanate fine particle powder, and if necessary, a dispersant, an additive (resin, antifoaming agent, auxiliary agent, etc.) Etc. can also be added.

  As the dispersant in the present invention, it can be appropriately selected and used according to the type of barium titanate fine particle powder and dispersion medium to be used, and organosilicon compounds such as alkoxysilane, silane coupling agent and organopolysiloxane , Surfactants or polymer dispersants can be used, and these can be used alone or in combination of two or more.

  Examples of the organosilicon compound include methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, butyltriethoxysilane, hexyltriethoxysilane, and octyltriethoxy. Silanes, alkoxysilanes such as tetraethoxysilane and tetramethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Emissions, .gamma.-chloropropyl trimethoxy silane silane coupling agent such as a polysiloxane, methyl hydrogen polysiloxane, organopolysiloxane and the like of the modified polysiloxane.

  Examples of the surfactant include anionic surfactants such as fatty acid salts, sulfate ester salts, sulfonate salts and phosphate ester salts; polyethylene glycol type nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene aryl ethers Agents, nonionic surfactants such as polyhydric alcohol type nonionic surfactants such as sorbitan fatty acid esters; chaotic surfactants such as amine salt type cationic surfactants and quaternary ammonium salt type cationic surfactants Agents: amphoteric surfactants such as alkylbetaines such as alkyldimethylaminoacetic acid betaine and alkylimidazolines.

  As the polymer dispersant, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, polycarboxylic acid, its salt, and the like can be used.

  The amount of the dispersant added depends on the total surface area of the barium titanate fine particle powder in the dispersion, and may be appropriately adjusted according to the use of the dispersion of the barium titanate fine particle powder and the type of the dispersant. Specifically, by adding 0.01 to 100% by weight of a dispersant to the barium titanate fine particle powder in the dispersion medium, the barium titanate fine particle powder can be uniformly and finely dispersed in the dispersion medium. At the same time, the dispersion stability can be improved. In addition to directly adding the dispersant to the dispersion medium, the fine particles of barium titanate may be previously treated.

  Hereinafter, the present invention will be described in detail with reference to examples.

  The average particle size of the primary particles of the barium titanate fine particle powder was measured by measuring the particle size of 350 particles shown in the electron micrograph, and the average value was shown.

  The specific surface area value was indicated by a value measured by the BET method.

  The number-converted dispersed average particle size and volume-converted dispersed particle size of the barium titanate fine particle powder in the dispersion were measured using a dynamic light scattering method “ZETA SIZER Nano-ZS” (manufactured by Sysmex Corporation).

  The dispersion reach of the barium titanate fine particle powder in the dispersion of the barium titanate fine particle powder is the ratio of the number-average dispersed average particle size of the barium titanate fine particle powder to the average primary particle size of the barium titanate fine particle powder. Indicated.

  The particle size distribution of the barium titanate fine particle powder in the dispersion of the barium titanate fine particle powder was represented by a geometric standard deviation value determined by the following method.

  That is, the particle diameter on the logarithmic normal probability paper on the logarithmic normal probability paper and the vertical axis belongs to each of the predetermined particle diameter sections according to a statistical method from the volume-converted dispersed particle diameter and number measured using the dynamic light scattering method. Plot the cumulative number of particles (under integrated sieve) as a percentage. Then, from this graph, the particle diameter values corresponding to the number of particles of 50% and 84.13% are read, and the geometric standard deviation value = particle diameter under integrated fluid 84.13% / under integrated fluid 50%. The value was calculated according to the particle diameter (geometric mean diameter). The closer the geometric standard deviation value is to 1, the better the particle size distribution of the barium titanate fine particle powder in the dispersion.

The viscosity change rate of the dispersion of barium titanate fine particle powder was determined by using the “E-type viscometer EMD-R” (manufactured by Tokyo Keiki Co., Ltd.) after allowing the obtained dispersion to stand at 60 ° C. for 1 week. The viscosity value at a shear rate D = 383 sec ⁻¹ was measured at 25 ° C., and the value obtained by dividing the amount of change in viscosity before and after standing by the value before standing was expressed as a percentage as the rate of change.

<Example 1: Production of dispersion of barium titanate fine particle powder>
In a horizontal bead mill (“DISPERMAT SL603” manufactured by VMA-Getzmann, glass media (particle size: 1 mm) is placed so as to be 80 vol% of the stirring vessel, and then barium titanate fine particle powder 1 (average primary particle size: 35 nm) , BET specific surface area value: 31.9 m ² / g) 400 g, 100 g of Solsperse 32500 (manufactured by Nippon Lubrizol Co., Ltd.) as a dispersing agent and PGMEA 1500 g were circulated and dispersed for 4 hours to obtain barium titanate fine particle powder. A first step dispersion was obtained.

  Next, glass media (particle size 50 μm) is placed in a zirconia 0.5 liter stirring vessel of a vertical bead mill (“Ultra Apex Mill UAM-05” manufactured by Kotobuki Giken Kogyo Co., Ltd.) so that the volume becomes 70 vol% of the stirring vessel. Then, the first step dispersion obtained above was dispersed for 1 hour while circulating to obtain a second step dispersion of barium titanate fine particle powder.

  Furthermore, the dispersion obtained in the second step was placed in an ultrasonic disperser (“Sonifier II Model 450D” manufactured by BRANSON) and dispersed for 10 minutes to obtain a dispersion of fine barium titanate powder.

  The number-converted dispersed particle diameter of the barium titanate fine particle powder in the obtained dispersion is 43.4 nm, and the dispersion reachability of the barium titanate fine particle powder in the dispersion (the number of the barium titanate fine particle powder in the dispersion). (Conversion dispersion average particle diameter / average primary particle diameter of barium titanate fine particle powder) is 1.24, the particle size distribution of the barium titanate fine particle powder in the dispersion is 1.23 in terms of geometric standard deviation, and the rate of change in viscosity is 3 9%.

  According to Example 1, a dispersion of barium titanate fine particle powder was prepared. Various production conditions and various properties of the obtained dispersion of barium titanate fine particles are shown.

Barium titanate fine particle powders 1-3:
As barium titanate fine particle powders, barium titanate fine particle powders 1 to 3 having the characteristics shown in Table 1 were prepared.

<Production of dispersion of barium titanate fine particle powder>
Examples 1-3, Comparative Example 1:
Type and amount of fine barium titanate powder in the first step, type of dispersion medium, type and amount of dispersion medium, amount of dispersant, type of dispersion medium in the second step, disperser in the third step A barium titanate fine particle powder dispersion was obtained in the same manner as in Example 1 except that the types were changed.

  The production conditions at this time are shown in Table 2, and the various properties of the obtained barium titanate fine particle powder dispersion are shown in Table 3.

The dispersion of barium titanate fine particles according to the present invention is uniformly dispersed as nano-order fine particles having a narrow particle size distribution in the dispersion medium, and has excellent storage stability. Therefore, it can be used for optical materials such as optical inks and liquid crystal spacers as well as dielectric materials for electronic components such as multilayer capacitors, positive thermistors, piezoelectric materials, and high frequency vibrators.

Claims (3)

A barium titanate fine particle powder dispersion in which a barium titanate fine particle powder is dispersed in a dispersion medium. The barium titanate fine particle powder is added to the dispersion in an amount of 0.1 parts by weight based on 100 parts by weight of the dispersion-constituting substrate. contained 60 parts by weight, number-reduced average particle diameter of the barium titanate of the dispersion is Ri der less 100 nm, the dispersion achievement of barium titanate fine particles in the dispersion is, titanate of the dispersion A dispersion of barium titanate fine particle powder, wherein the ratio of the number-average dispersed average particle size of the barium fine particle powder to the average primary particle size of the barium titanate fine particle powder is 1.50 or less . A first step of pre-dispersing the barium titanate fine particle powder having an average primary particle size of 100 nm or less in the dispersion medium, and the dispersion medium containing the barium titanate fine particle powder obtained in the first step are stirred together with the medium and a second step of dispersing, the third comprising the step claim 1 Symbol placement of barium titanate fine particles to the rear dispersing a dispersion medium comprising a barium titanate fine powder obtained in said second step Dispersion manufacturing method. The method for producing a dispersion of barium titanate fine particle powder according to claim 2 , wherein the average particle size of the media used in the second step is less than 100 µm.