JP3361780B2 - Ferrite molding granules and molded bodies thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to ferrite molding.
The present invention relates to granules, and particularly relates to molding granules from which a ferrite molded product having excellent processability can be obtained.

[0002]

2. Description of the Related Art Ferrite is widely used in electronic parts, and the ferrite is obtained by molding a ferrite material and firing the molded body. Conventionally,
Various methods have been adopted as a method for producing a ferrite molded body, but among them, a dry pressure molding method is generally widely used. For example, an aqueous slurry is prepared with a ferrite raw material powder, a binder, and water, and granules produced by spray-drying this with a spray dryer, or by stirring and mixing the ferrite raw material powder and a binder solution, drying and oscillating extrusion granulation. A ferrite molded body is manufactured by pressure-molding the granules that are repeatedly manufactured. Then, a sintered body is obtained by firing the molded body.

By the way, when a complicated shape is required, such as a drum core for a coil, or when high dimensional accuracy is required, it is not possible to obtain a predetermined component by simply firing the molded body. Therefore, processing steps such as cutting, grinding, polishing, and cutting are required. Generally, depending on where the processing step is provided in the process of obtaining a ferrite product, (1) a method of processing a densely fired ferrite fired body into a predetermined size or a predetermined shape (2) a temperature for densifying the ferrite From 100 ° C to 50
There is a method of processing a semi-sintered ferrite molded body that is fired at a temperature lower by 0 ° C., that is, near the sintering start temperature. (3) There is a method of directly processing the ferrite molded body without firing.

In the method (1) of processing a sintered body, since the hardness of ferrite itself is extremely high, the wear of the processing tool increases, so that the dimensional accuracy of the processed product decreases, and further, during processing. The impact is large and chipping and the like are likely to occur.

The method (2) for processing the semi-sintered body is as follows:
Since the ferrite is not completely densified, the hardness and wear resistance are low, and the workability is improved, but the firing at the temperature brought by the semi-sintered state causes the dough to be in the shrinking process, so processing in this shrinked state After that, if the remaining baking is attempted, the dimensions change greatly. Moreover, when the ferrite molded body is fired in a semi-sintered state to form a ferrite molded body, the temperature distribution in the furnace greatly varies depending on the installation position of the ferrite molded body in the furnace and the number of ferrite molded bodies.
The dimensional accuracy of the semi-sintered ferrite compact in the shrinking process is reduced.

For these reasons, the processing of the ferrite molded body is generally performed in the above (3) except for special cases.
The method of (3), that is, the method of processing after molding without sintering is adopted.

[0007]

When the ferrite molded body is processed by the method (3), the mechanical strength of the molded body is weaker than that of the sintered or semi-sintered ferrite molded body. Therefore, defects such as cracks and chips are likely to occur. Therefore, conventionally, a method has been used in which the ferrite compact is made to have a high compact density, or the compact is dried to increase its mechanical strength and then processed. However, a ferrite molded body whose mechanical strength is increased by drying or the like has a high surface hardness, wear of a grinding machine such as a diamond wheel becomes large, and the accuracy of the surface machined in a short time or the chipping of the surface is reduced. Processing defects are likely to occur. Therefore, defective products are likely to occur and the yield is reduced.
Further, in order to improve the yield, it is necessary to frequently clean a processing tool such as a diamond wheel, which requires a complicated maintenance work.

In view of the above-mentioned problems, the present invention provides a ferrite compact which is less likely to wear a tool for the ferrite compact and which does not cause chipping of the ferrite compact or reduction in precision of the machined surface due to impact of a tool during machining. Obtained ferrite molding
The purpose is to provide a granule for use .

[0009]

The granules for ferrite molding according to claim 1 contain a ferrite raw material powder, polyvinyl alcohol as a binder, and polyethylene glycol having a molecular weight of 2000 or more and 4000 or less, which is added as a plasticizer. For 100 parts by weight of alcohol,
Polyethylene glycol is added in an amount of 5 parts by weight or more and 50 parts by weight or less, mixed, and granulated to improve the Vickers hardness of the molded body.
When Y and the density of the molded body is X (gcm-3),
The relationship between Y and X is Y = 19X-A, and X = 3.
0-3.9 g-cm-3, A = 44-56
It is characterized in that a molded product of ellite is obtained .

The raw material powder of the ferrite molding granules of the present invention is not particularly limited, but is, for example, Fe2O.
3, NiO, CuO, ZnO as a main component or Fe2O3, NiO, MnO as a main component, and if necessary, Mg, Co as another metal oxide as a subcomponent or an irreversible impurity. , W, Bi, Si, B,
An oxide such as Zr may be included.

The average particle size of the ferrite raw material powder is preferably 0.01 to 5 μm, more preferably 0.1.
It is 1 to 1.5 μm. In order to obtain a preferable average particle diameter, a pulverizing method such as a ball mill, a stirring mill, or an attritor may be used, and either wet pulverization or dry pulverization may be used.

Polyvinyl alcohol, which is the first essential component, functions as a binder for primary particles, that is, a binder between raw material powders and raw material powders, and the degree of saponification and the degree of polymerization are appropriately selected from known ones. Can be used. The addition amount of this polyvinyl alcohol is 1
It is usually 0.2 to 10 parts by weight, and more preferably 0.5 to 3 parts by weight, relative to 00 parts by weight. If the addition amount of polyvinyl alcohol is less than 0.2 parts by weight, ferrite particles cannot be granulated, which is not preferable. On the other hand, if the amount exceeds 10 parts by weight, the ferrite granules become too hard and the crushing becomes worse, leaving a large number of grain boundaries to cause defective molding. In addition, capacity defects increase, which is not preferable.

Polyethylene glycol, which is the second essential component, functions as a plasticizer in the ferrite compact granules, reduces the surface hardness of the compact appropriately, and improves the processability. The preferred molecular weight of polyethylene glycol is 1000 to 6000, more preferably 20.
It is from 00 to 4000. If the molecular weight is less than 1000, the surface hardness of the molded product will be improved by the addition, but since it has a high hygroscopicity, powder such as shavings generated during processing is processed by grinding machines such as diamond wheels, drills, and cutting tools. It adheres to tools and reduces workability. On the other hand, if the molecular weight is more than 6000, the effect of improving the surface hardness of the molded product by addition is small, and cracks are likely to occur due to the decrease in the strength of the molded product.

The ferrite molding granules according to the present invention can be obtained by granulating ferrite powder by a conventionally known method such as a spray granulation method using a spray dryer or an oscillating extrusion granulation method. The average particle size of the ferrite granules thus obtained is usually 50 to 500 μm, preferably 70 to 300 μm, and more preferably 80 to 150 μm. Average particle size is 50
When it is less than μm, the fluidity and the filling into the mold are deteriorated, so that the size and the unit weight of the molded product vary greatly. In addition, the adhesion of fine powder (sticking) to the mold easily occurs, which is not preferable. Conversely 500
If it exceeds μm, many grain boundaries are left and molding defects occur. In addition, variations in the size and unit weight of the molded body also increase. In particular, a molded product having a diameter of 2 mm or less is not preferable because the variation becomes large.

Further , the ferrite molding granules of the present invention
If the amount of polyethylene glycol added exceeds 50 parts by weight, cracks are likely to occur due to a decrease in strength of the molded body. On the other hand, if it is less than 5 parts by weight, the effect of improving the surface hardness of the molded product by the addition is insufficient.

In order to produce a ferrite compact having excellent workability according to the present invention, the ferrite molding granules are subjected to dry pressure molding using a mold. At this time, the pressing pressure is usually 0.5 to 5 t / cm 2, preferably 1 to 4 t / cm.
It is selected in the range of 2.

When a ferrite compact is obtained from the granules
In this case, the relationship between the Vickers hardness Y and the density X of the molded body is as described above.
If it is within the range of satisfying the relationship of
For example, in continuous grinding of 100,000 or 200,000 pieces,
No or little dust adhesion, chipping, and breakage
be able to. Vickers hardness is the same as
If the value is smaller than the relationship, shavings will not adhere or break due to grinding.
Vickers hardness is increased in density.
On the other hand, if the value becomes larger than the above relation,
Chips are likely to occur.

In the ferrite molding granules of claim 2, the addition amount of polyethylene glycol to polyvinyl alcohol is more preferably 20 to 40 parts by weight .

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION In Table 1, a PVA aqueous solution N
o. For those other than 5 to 7, 17 parts by weight of various polyvinyl alcohol aqueous solutions with or without polyethylene glycol were added to 100 parts by weight of Ni-Cu-Zn ferrite powder, and the mixture was stirred and granulated by TM mixer (Mitsui Mining Co., Ltd.). (Manufactured by the company) was mixed and granulated with stirring to prepare granulated powder.

In Table 1, PVA aqueous solution No. 5, 6
In the case of No. 1, 66 parts by weight of Ni-Cu-Zn ferrite powder, 28 parts by weight of water, 6 parts by weight of a polyethylene glycol-added polyvinyl alcohol aqueous solution having a solid content concentration of 12% by weight, and a polycarboxylic acid ammonium salt of 0. A ferrite slurry was prepared by wet-milling and mixing 25 parts by weight. PVA aqueous solution No. 7 is
PVA except that polyethylene glycol is not added
Aqueous solution No. It adjusted like 5 and 6.

Here, as shown in Table 1, the polyvinyl alcohol has a saponification degree of 98.5 and a polymerization degree of 2400 (PVA aqueous solution Nos. 1 to 4, 8 to 13, 17 to 2).
0) and a saponification degree of 88.0 and a polymerization degree of 500 (P
VA aqueous solution No. 5 to 7) and a saponification degree of 88.0 and a polymerization degree of 1700 (PVA aqueous solution Nos. 14 to 16,
21-23) was used.

Polyethylene glycol having a molecular weight of 600 (PVA aqueous solution No. 3, 20, 22)
And having a molecular weight of 1000 (PVA aqueous solution No. 12
~ 14, 23), those having a molecular weight of 2000 (PVA aqueous solution Nos. 1, 6, 8, 15 to 18, 21) and those having a molecular weight of 4000 (PVA aqueous solutions No. 2, 5, 9, 1).
9) with a molecular weight of 6000 (PVA aqueous solution No.
10), having a molecular weight of 10,000 (PVA aqueous solution N
o. 11) was used, and the addition amount of polyethylene glycol was changed variously as shown in the right column of Table 1 with respect to 100 parts by weight of polyvinyl alcohol.

[0023]

[Table 1]

Aqueous PVA solution No. For those of 1 to 4 and 8 to 23, as shown in Table 2, the granulated powder is dried by a belt dryer, extruded by an oscillating granulator and granulated, and sized by a shifter. And average particle size 200
μm granules were obtained. In addition, the PVA aqueous solution No. Nos. 5 to 7 were granulated with a spray atomizer to obtain spherical granules having an average particle size of 125 μm.

[0025]

[Table 2]

Then, a cylindrical core (PVA aqueous solution Nos. 1 to 4, having a diameter of 3.0 mm and a length (L) of 2.5 mm,
11-13, 19), or a cylindrical core having a diameter of 1.3 mm and a length of 1.5 mm (PVA aqueous solution No. 5).
7), or a cylindrical core having a diameter of 4.0 mm and a length of 3.0 mm (PVA aqueous solution No. 8 to 10, 17, 18),
Alternatively, a cylindrical core (PVA aqueous solution Nos. 14 to 16 and 20 to 23) having a diameter of 1.5 mm and a length of 1.8 mm was continuously molded.

The Vickers hardness H of the molded body obtained in FIG.
The relationship between v, the density of the compact and the workability level is shown. The Vickers hardness is a load of 100 gf (PVA aqueous solution Nos. 1 to 4 and 8 to 2) using a Shimadzu micro hardness meter HMV-2000 type.
3) or a load of 300 gf (PVA aqueous solution No.
In the case of 5 to 7), the measurement was performed.

Then, the obtained molded body is ground with a diamond foil to prepare a drum-shaped core for a coil having a shape shown in FIG. 2 (A).
The increase in the medium diameter R of the processed core, the state of occurrence of core breakage, and the adhesion of shavings were evaluated. In addition, the processing device with diamond wheel can rotate both ends of the cylinder with many cylinders on the outer circumference and in the cylinder housing around the disk so that the axis of the cylinder is parallel to the center axis of the disk. 2B is supported and set on the disk, and while rotating this disk, the cylinder is brought into contact with the cutting surface of the diamond wheel which is rotated at a high speed to cut a groove in the cylinder in the circumferential direction. A drum type core is manufactured.

FIG. 2B shows the PVA aqueous solution No. 1 (shown as Example 1), PVA aqueous solution No. 2 (Example 2
,), And PVA aqueous solution No. No. 4 (shown as Comparative Example 1) and the grinding time (hr) and the number of grinding (× 104) of the diamond foil of the molded body made of the granules.
The increase in the medium diameter R of the core after grinding shown in FIG. In Examples 1 and 2, that is, using an aqueous polyvinyl alcohol solution containing polyethylene glycol having a molecular weight of 2000 or 4000,
Even when the diamond foil ground for 24 hours was used, the medium diameter R increased only to about R = 0.13 mm, which was much smaller than the practical upper limit R = 0.20 mm. On the other hand, in Comparative Example 1, that is, one containing no polyethylene glycol, after grinding for 8 hours, the upper limit R = 0.
It reached 20 mm, and it was found that the diamond foil was likely to be worn.

3 (a), (b), and (c) show the state of the core formed by grinding with a diamond foil of the molded body granulated and molded using the above-mentioned Example 1 (PVA aqueous solution No. 1). It is a photograph figure shown. FIG. 3A shows a state of a certain core at the start of grinding with a diamond wheel. Figure 3
(B) shows the state of a certain core after 12 hours of continuous grinding with the diamond wheel (after 144,000 continuous grinding). FIG. 3C shows a state of a core after 24 hours of continuous grinding with the diamond foil (after 288,000 pieces are continuously ground). As can be confirmed from these photograph diagrams, according to Example 1, a good drum-shaped core free from chipping of the inner collar as the machined surface and breakage of the core was obtained even after 24 hours of continuous grinding.

4 (a), (b), and (c) show the state of the core formed by grinding with a diamond foil of the molded body granulated and molded using Comparative Example 1 (PVA aqueous solution No. 4). It is a photograph figure shown. FIG. 4A shows a state of a certain core at the start of grinding with a diamond wheel. Figure 4
(B) shows the state of a certain core after 4 hours of continuous grinding with the diamond wheel (after continuous grinding of 48,000 pieces).
FIG. 4C shows the continuous grinding 8 using the diamond wheel.
The state of the core after a certain time (after continuous grinding of 96,000 pieces) is shown. As can be seen from these photographs, a large internal brim chipping had already occurred 4 hours after grinding, and a large chipping was found 8 hours after grinding. In addition, 24 core breakages were also generated.

5 (a), (b), and (c) show PVA aqueous solution No. A molded body obtained by granulating and molding using No. 5 (Example 3
FIG. 4 is a photograph showing a state of a core formed by a grinding process using a diamond wheel (referred to as “”). FIG. 5 (a) shows a state of a core at the start of grinding with a diamond wheel. FIG. 5B shows a state of a core after 4 hours of continuous grinding with the diamond foil (after 36,000 pieces are continuously ground). FIG. 5C shows a state of a core after 16 hours of continuous grinding with the diamond foil (after 144,000 pieces are continuously ground). As can be confirmed from these photograph diagrams, according to Example 3, a good drum-type core free from chipping of the inner collar and broken core, which was the machined surface, was obtained even after 16 hours of continuous grinding.

6 (a), (b), and (c) are PVA aqueous solution Nos. FIG. 7 is a photograph showing the state of a core formed by grinding a molded body that was granulated and molded using 7 (polyethylene glycol-free polyvinyl alcohol aqueous solution) with a diamond foil. FIG. 6 (a) shows a state of a core at the start of grinding with a diamond wheel. FIG. 6B shows a state of a core after 4 hours of continuous grinding with the diamond wheel (after 36,000 pieces are continuously ground). Figure 6
(C) shows the state of a certain core after 9 hours of continuous grinding with the diamond wheel (after 81,000 continuous grinding).
As can be confirmed from these photographs, the inner brim was chipped after 4 hours of continuous grinding, and a large chip was observed after 9 hours of continuous grinding. In addition, core breakage occurred in 33 out of 81,000 pieces.

[Evaluation] (Presence or absence of addition of polyethylene glycol) As described above, polyethylene glycol as a plasticizer was added to polyvinyl alcohol to obtain granules, and ferrite granules were produced from the granules, and then ground with diamond foil. When the molded body was processed in this manner, the inner collar chipping and core breakage did not occur when continuously grinding for a long time, and a molded body with good workability was obtained.

(Regarding Molecular Weight of Polyethylene Glycol) As described above, FIG. 1 shows the relationship between the density of the molded body and the Vickers hardness and also shows the workability level. Figure 1
The numbers attached to each mark in the above are the PVA aqueous solution No.
Is shown. PVA aqueous solution No. When the molecular weight of polyethylene glycol is 1000 as in Nos. 12 and 14, there is no chipping or breaking even when 100,000 or 200,000 continuous grindings are performed. On the other hand, PVA aqueous solution No. 1 having a molecular weight of polyethylene glycol of 600. Regarding Nos. 3, 20, and 22, No. In No. 3, chipping occurred in 30,000 continuous grinding, No.
In No. 20, continuous grinding of 100,000 pieces caused shavings to adhere to the core and the diamond foil, resulting in poor appearance and poor workability, and 1 to 20 folds. In No. 22, in the continuous grinding of 100,000 pieces, shavings adhered and 20 to 50 pieces were broken. Therefore, the molecular weight of polyethylene glycol is preferably 1000 or more.

On the other hand, a PVA aqueous solution No. 1 having a polyethylene glycol molecular weight of 6000 was used. In the case of 10, there is no chipping or break even if the number of continuous grindings reaches 200,000. However, PVA aqueous solution No. 1 having a polyethylene glycol molecular weight of 10,000 was used. In the case of No. 11, chipping occurred in 30,000 continuous grinding. Therefore, the molecular weight of polyethylene glycol is preferably 6000 or less.

Further, the PVA aqueous solution No. No. 1 having a molecular weight of polyethylene glycol of 2000 or 4000 and an addition amount of polyethylene glycol within the range described below was used.
In Nos. 1, 2, 5, 6, 8, 10, 12, 15, and 21, since 100,000 or 200,000 pieces of continuous grinding are not broken or broken, the molecular weight should be in the range of 2000 to 4000. Is more preferable.

(Regarding Addition Amount of Polyethylene Glycol) A PVA aqueous solution No. 1 having a molecular weight of polyethylene glycol of 2000 and an addition amount of 5 parts by weight with respect to polyvinyl alcohol. In the case of No. 8, there is no chipping or break even when 200,000 pieces of continuous grinding are performed. However, the PVA aqueous solution No. 3 in which the molecular weight of polyethylene glycol was 4000 and the addition amount to polyvinyl alcohol was 3 parts by weight. In the case of 9, a PVA aqueous solution N in which the molecular weight of polyethylene glycol is 1000 and the addition amount to polyvinyl alcohol is 2 parts by weight
o. In the case of 13, the molecular weight of polyethylene glycol is 2
000, and the addition amount to polyvinyl alcohol is 3 parts by weight. In the case of 16, chipping occurred in 30,000 continuous grindings. Therefore, the amount of polyethylene glycol added is preferably 5 parts by weight or more.

On the other hand, a PVA aqueous solution No. 10 containing 50 parts by weight of polyethylene glycol was added. 18 or No. 23
In case of 100, continuous grinding is 100,000 pieces and there is no chipping, and the breakage is 1-2.
0 occurred. However, the PVA aqueous solution No. 6 containing 60 parts by weight of polyethylene glycol was added. 17 or No. 1
In the case of No. 9, continuous grinding was 100,000 pieces and there was no chipping and there were 20 breaks.
Increased to ~ 50. For this reason, the amount of polyethylene glycol added is preferably 50 parts by weight or less.

When the molecular weight of polyethylene glycol is 2000 or 4000, the addition amount of polyethylene glycol to polyvinyl alcohol is within the range of 20 to 40 parts by weight. In the case of 1, 2, 5 and 6, in any case, even in continuous grinding of 200,000 pieces, the inner collar is not chipped or broken, and no shavings are attached. Therefore, the preferable addition amount of polyethylene glycol is 20 to 40 weight. It is a department.

(Relationship between Density of Molded Body and Vickers Hardness) In FIG. 1, when the Vickers hardness of the molded body is Y and the density of the molded body is X (g · cm −3), Y and X If the relation is above Y = 19X−44, a chip occurs in 30,000 continuous grinding. On the other hand, in the region below Y = 19X-56, 100,000 pieces of continuous grinding result in 21 to 5 folds.
The number increases to 0 and shavings adhere. Therefore, it is desirable that the molded body be in the range of Y = 19X-44 or less and Y = 19X-56 or more.

[0042]

The ferrite molding granules according to claim 1 are added with a ferrite raw material powder, polyvinyl alcohol as a binder, and a plasticizer, and have a molecular weight of 2000.
The above-mentioned 4000 or less polyethylene glycol is added to 5 parts by weight or more and 50 parts by weight or less of polyethylene glycol with respect to 100 parts by weight of polyvinyl alcohol, and is mixed and granulated, and the Vickers hardness of the molded body is set to Y, and the molded body is
Relationship between Y and X, where X is the density of X (gcm-3)
Is Y = 19X-A, and X = 3.0 to 3.9 g.
cm-3, A ferrite molded body satisfying A = 44 to 56
As a result, it is possible to obtain a ferrite molded body that is less likely to wear a tool for processing the ferrite molded body and that is free from chipping of the ferrite molded body due to the impact of the tool during processing and deterioration of the precision of the machined surface. Further, as a result, the frequency of maintenance such as cleaning of the processing apparatus is reduced, the yield is improved, quality control is facilitated, and further, product inspection after processing can be eliminated.

The ferrite molding granules according to claim 2 are obtained by adding polyethylene glycol in an amount of 20 parts by weight or more and 40 parts by weight or less to 100 parts by weight of polyvinyl alcohol in the claim 1, so that the effect of claim 1 is further enhanced. Well achieved

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the density, Vickers hardness, and workability of a molded body sample according to the present invention.

FIG. 2A is a side view of a drum core processed according to an embodiment of the present invention, and FIG. 2B is a view showing a relationship between a processing time of the core and a medium diameter R in Examples and Comparative Examples. is there.

FIG. 3 is a photograph showing the state of the drum core in Example 1 of the present invention.

FIG. 4 is a photograph showing the state of a drum core in Comparative Example 1.

FIG. 5 is a photographic diagram showing a state of a drum core according to a second embodiment of the present invention.

FIG. 6 is a photograph showing a state of a drum core in Comparative Example 2.

Claims (2)

(57) [Claims] 1. A ferrite raw material powder and as a binder
Polyvinyl alcohol, added as a plasticizer,
Polyethylene glycol with a molecular weight of 2000 or more and 4000 or less
And 100 parts by weight of polyvinyl alcohol,
5 to 50 parts by weight of polyethylene glycol
Add, mix and granulateBecomes The Vickers hardness of the compact is Y, and the density of the compact is X.
When (g · cm−3), the relationship between Y and X is Y = 19X-A And X = 3.0 to 3.9 g · cm −3, A = 4
A ferrite compact satisfying 4-56 can be obtained. That
Characteristic ferrite molding granules. 2. The ferrite molding granule according to claim 1, wherein 20 parts by weight or more and 40 parts by weight or less of polyethylene glycol is added to 100 parts by weight of polyvinyl alcohol.