JPH0224579B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dispersant for soft ferrite raw metal oxide powder. Soft ferrite is made of a metal oxide whose main component is iron oxide, and is particularly useful as a material for the magnetic core of a magnetic coil. Soft ferrite is usually manufactured by the following process. (1) Blend raw materials such as iron oxide, manganese oxide, zinc oxide, and nickel oxide with water, (2) Grind the raw materials to about 0.5μ using a grinder such as a ball mill, sand mill, or attritor, (3) This is spray-dried (4), then press-molded and calcined, (5) water is further added, the powder is ground to about 2-4μ in a grinder, a binder is added, and (6) spray-dried. (7) This is press-formed and sintered. In the grinding steps (2) and (5) above, the raw metal oxide powder is generally ground into a water slurry of about 50% by weight. By increasing this water slurry concentration (which means decreasing the water content in the slurry), the following favorable effects can be achieved. (1) In the pulverization process, the pulverization efficiency increases and the time required to pulverize particles to the desired particle size is shortened. (2) The time required for spray drying is reduced. (3) The bulk density of the spray-dried metal oxide powder is increased, and the press pressure during press molding is reduced. All of the above effects lead to improved productivity and significant savings in power energy. However, if the slurry concentration is increased simply by reducing the water content, the viscosity of the slurry increases, which increases the grinding time and makes it difficult to transport the slurry, making it impossible to improve productivity and save power energy. As a dispersant for inorganic powders such as calcium carbonate powder and titanium oxide powder, sodium polyacrylate,
Sodium lignin sulfonate, sodium salt of naphthalene sulfonate formalin condensate, etc. are commercially available, but when these dispersants are used as dispersants for metal oxide powder as a raw material for soft ferrite, the viscosity of the slurry decreases to a certain extent. However, these dispersants cannot be used because they deteriorate the magnetic permeability of the final ferrite product. For this reason, there is a strong demand in the industry for a dispersant that can form a highly concentrated slurry without degrading the magnetic properties of the final product, ferrite. In view of the current situation, the present inventors have conducted extensive research and found that a dispersion containing one or more ammonium salts or alkanolamine salts of a copolymer of maleic acid and acrylic acid or/and methacrylic acid. The inventors have completed the present invention by discovering that the agent does not deteriorate the magnetic properties of the final product, ferrite, and also makes it possible to form a highly concentrated slurry of metal oxide powder as a raw material for soft ferrite. The copolymer salt according to the present invention has an average molecular weight of 500 to
30000 is preferable, and the average molecular weight is 1000~
15000 is more preferable. Copolymer salts with an average molecular weight of less than 500 and copolymer salts with an average molecular weight of more than 30,000 have insufficient ability to reduce slurry viscosity. Further, there are no particular restrictions on the manufacturing method, and there is no significant difference in performance no matter which method is used to synthesize it. Examples of synthesis methods include the following methods. That is, this is a synthesis method in which acrylic acid and maleic acid are copolymerized in an aqueous solvent in the presence of a persulfate catalyst, and then neutralized with aqueous ammonia or alkanolamine. Examples of the alkanolamine used here include monoethanolamine, diethanolamine, triethanolamine, and the like. It is preferable to add ammonia or alkanolamine in an amount sufficient to completely hydrate maleic acid and acrylic acid or/and methacrylic acid, but not neutralize it to the extent that it does not impair the performance of the copolymer salt. It may be the amount that leaves something behind. The molar ratio of the monomers constituting the copolymer according to the present invention is preferably in the range of maleic acid:acrylic acid or/and methacrylic acid=3:100 to 200:100. When the ratio of maleic acid is less than 3, the thinning effect is equivalent to that of acrylic acid or methacrylic acid alone, and the synergistic effect due to the addition of maleic acid is not achieved. Thinning effect decreases. The above ratio is 3:100
Only within the range of ~200:100, an excellent thinning effect is achieved for the aqueous dispersion of soft ferrite raw metal oxide powder. An aqueous dispersion of metal oxide powder for soft ferrite can be easily produced by mixing the metal oxide powder and water in the presence of the dispersant of the present invention. There are no particular restrictions on the manufacturing procedure; for example, the metal oxide powder is added to an aqueous solution of the copolymer salt and stirred, or a small amount of water is added to the metal oxide powder to form a cake. It can be produced by adding an aqueous solution of a copolymer salt to and stirring the mixture. The amount of the copolymer salt according to the present invention added depends on the particle size of the metal oxide powder, but is in the range of 0.05 to 5%, preferably 0.2 to 4%, based on the weight of the metal oxide powder. is within the range of The dispersant of the present invention makes it possible to obtain a highly concentrated, low viscosity slurry with a solids content of about 75% by weight. The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to these examples. Example 1 40% of ammonium salt of maleic acid/acrylic acid copolymer (molar ratio 30/100, average molecular weight 5000)
Put 18.8 g of the aqueous solution into a stainless steel beaker with an internal volume of 2, add 238.6 g of water, and stir to make the system uniform. Next, soft ferrite raw material metal oxide blended powder (this contains 70% Fe ₂ O ₃ on a weight basis, MnO
It is a powder with an average particle size of 0.8μ containing 23% ZnO and 7% ZnO. ) and stirred with a spatula, and further stirred for 3 minutes at a rotation speed of 3000 revolutions per minute using a homodisper (mixer manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain an aqueous dispersion containing 75% metal oxide powder. I got the liquid. The viscosity of this aqueous dispersion at 25°C was measured using a Bruckfield viscometer. The results are in Table 1
It was hot on the street. 7.5 g of polyvinyl alcohol (average degree of polymerization 1000) was added to this aqueous dispersion, stirred thoroughly with a spatula, and then spray-dried with a small spray dryer to obtain granules with an average particle size of 10 μm. These granules are placed in a form (length x width x depth = 10mm x 40mm x
After pressing under a pressure of 1 t/cm ² and sintering in air at 1200°C, a soft ferrite measuring 8 mm x 30 mm x 5 mm was obtained. The magnetic permeability of this ferrite at 25°C was measured at a frequency of 10KHz. The results were as shown in Table 1. Example 2 10 g of a 40% aqueous solution of the ammonium salt of the maleic acid/acrylic acid copolymer used in Example 1 was added to water.
An aqueous dispersion containing 65% metal oxide powder and ferrite were obtained in the same manner as in Example 1, except that 344 g of metal oxide powder, 650 g of metal oxide blended powder, and 6.5 g of polyvinyl alcohol were used. The viscosity of this dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1. Example 3 Instead of the ammonium salt of the maleic acid/acrylic acid copolymer used in Example 1, maleic acid/acrylic acid copolymer was used.
Using 18.8 g of a 40% aqueous solution of triethanolamine salt of methacrylic acid copolymer (molar ratio 10/100, average molecular weight 5500), otherwise the same procedure as in Example 1 was used to prepare water containing 75% metal oxide powder. A dispersion liquid and ferrite were obtained. The viscosity of this dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1. Example 4 Instead of the ammonium salt of the maleic acid/acrylic acid copolymer used in Example 1, maleic acid/acrylic acid copolymer was used.
Ammonium salt of methacrylic acid copolymer (molar ratio
100/100, average molecular weight 5000) 25% aqueous solution at 30%
An aqueous dispersion containing 75% metal oxide powder and ferrite were obtained in the same manner as in Example 1 except that the amount of water was 227.5 g. The viscosity of this dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1. Comparative Example 1 500 g of the metal oxide blended powder used in Example 1 was added to 500 g of water, and the same procedure as in Example 1 was performed to obtain an aqueous dispersion containing 50% of the metal oxide powder. Next, 5 g of the polyvinyl alcohol used in Example 1 was added to this aqueous dispersion, and a soft ferrite was obtained in the same manner as in Example 1. The viscosity of the aqueous dispersion and the magnetic permeability of the ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1. Comparative Example 2 Instead of the ammonium salt of maleic acid/acrylic acid copolymer used in Example 1, a 40% aqueous solution of polyacrylic acid sodium salt (average molecular weight 4500) was used.
An aqueous dispersion containing 75% metal oxide powder and ferrite were obtained in the same manner as in Example 1, except that 18.8 g was used. The viscosity of this aqueous dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results are in Table 1
It was hot on the street. Comparative Example 3 Instead of the ammonium salt of the maleic acid/acrylic acid copolymer used in Example 1, lignin sulfonic acid sodium salt (trade name Lignaconc, manufactured by Jujo Paper Co., Ltd.) was used.
Co., Ltd.) using 15g of 50% aqueous solution and 242.5g of water.
Other than that, an aqueous dispersion containing 75% metal oxide powder and ferrite were obtained in the same manner as in Example 1. The viscosity of this aqueous dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1. Comparative Example 4 In place of the ammonium salt of the maleic acid/acrylic acid copolymer used in Example 1, powder of naphthalene sulfonic acid formalin condensate sodium salt (42% aqueous solution having a viscosity of 75 centipoise at 20°C) was used. An aqueous dispersion containing 75% metal oxide powder and ferrite were obtained in the same manner as in Example 1, except that 7.5 g of the powder and 250 g of water were used. The viscosity of this aqueous dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1. Comparative Example 5 Instead of the ammonium salt of the maleic acid/acrylic acid copolymer used in Example 1, ligninsulfonic acid ammonium salt (trade name Bolesperse) was used.
The same procedure as in Example 1 was carried out, except that 18.8 g of a 40% aqueous solution of NH (manufactured by Bollegaard in the Netherlands) was used.
An aqueous dispersion containing 75% metal oxide powder and ferrite were obtained. The viscosity of this aqueous dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1. Comparative Example 6 Ammonium salt of maleic acid/methacrylic acid copolymer (molar ratio 250/100, average molecular weight 3500)
% aqueous solution in a stainless steel beaker with an internal volume of 2, and then follow the same procedure as in Example 1 using the same metal oxide blend powder and polyvinyl alcohol as in Example 1, containing 75% metal oxide powder. An aqueous dispersion and ferrite were obtained. The viscosity of this aqueous dispersion and the magnetic permeability of ferrite were measured under the same conditions as in Example 1. The results were as shown in Table 1.

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Claims (1)

[Claims] 1. A dispersant for soft ferrite raw metal oxide powder containing one or more ammonium salts or alkanolamine salts of a copolymer of maleic acid and acrylic acid or/and methacrylic acid. . 2 The molar ratio of monomers constituting the copolymer is
The dispersant for soft ferrite raw metal oxide powder according to claim 1, wherein maleic acid: acrylic acid or/and methacrylic acid = 3:100 to 200:100. 3. The dispersant for soft ferrite raw metal oxide powder according to claim 1 or 2, wherein the copolymer salt has an average molecular weight of 500 to 30,000.