JP2009242544A - Magnet material composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that conventional magnet rollers react to applied magnetic fields and deform due to the use of a ferromagnetic body powder during molding magnet pieces, thereby causing crack, etc., it is difficult to carry out continuous extrusion molding by rupture of molded articles, it is difficult to carry out lamination with sufficient accuracy by generation of meandering when laminating magnet pieces on a shaft periphery surface, which may result in image degradation, and in particular, when a ferromagnetic powder is used on the basis of a rare earth-based magnetic powder, conventional magnet rollers are very easy to react to applied magnetic fields and it is more difficult to carry out continuous extrusion molding, due to the high residual magnetic flux density, and so on. <P>SOLUTION: A magnet material composition for extrusion molding is used wherein, in a mixture based on a ferromagnetic powder and resin binder, the weight ratio of a ferromagnetic powder in the mixture is 50-95 wt.%, the melt viscosity of the mixture is 30-45 N×m, and the bending strength after molding is 150×10<SP>5</SP>-250×10<SP>5</SP>N/m<SP>2</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnet material composition for a magnet roller incorporated in an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

As a magnet roller incorporated in an image forming apparatus using powdered toner in a copying machine, a printer, a facsimile machine or the like, a magnet roller having a plurality of magnet pieces arranged on the outer periphery of a metal shaft is typical. Conventionally, (1) As a magnetic material composition, a binder or roller made of resin or rubber, a mixture of magnetic powder, and fine particles having a particle size of 1 μm or less, or a kneaded product, which is extruded in a magnetic field, is a magnet roller (low deformation and high magnetic force). Patent Document 1) or (2) In a resin magnet material for extrusion using a ferromagnetic powder and a resin binder, the resin binder is mainly composed of an ethylene ethyl acrylate resin, and hydrogenated styrene is added to the resin binder. By adding 20 to 40 parts of the thermoplastic elastomer, the magnetic flux density is reduced. Ku magnet roller can be prevented cracking of the magnet pieces (Patent Document 2) are known.
JP-A-9-283315 JP 2006-199804 A

  However, since conventional magnet rollers use a ferromagnetic powder such as ferrite magnetic powder, they deform in response to an applied magnetic field during molding of the magnet piece, which causes cracks or the molded product to break. Thus, there is a problem that continuous extrusion molding is difficult. Further, when the magnet piece is bonded to the outer peripheral surface of the shaft, meandering is generated, and it is difficult to bond the magnetic piece to the outer peripheral surface with high accuracy, which may cause variations in the magnetic pole position and reduce the image quality. Further, the magnet piece may be warped due to environmental changes (temperature, humidity, etc.). In particular, when rare earth magnetic powder is mainly used as a ferromagnetic powder for the purpose of obtaining a magnet piece having a high magnetic flux density, it is very easy to react to an applied magnetic field because of its high residual magnetic flux density (Br). Deformation at the time of application is much larger than that of ferrite magnetic powder, making continuous extrusion more difficult.

  Even in Patent Document 1, particularly when a large amount of rare earth magnetic powder having a high residual magnetic flux density (Br) is used as a ferromagnetic powder, it reacts strongly to the applied magnetic field because of the high Br, and as a result, forming during magnetic field extrusion molding. The product may be greatly deformed, the molded product may be cracked or torn, and the extrusion moldability may be reduced.

  Also in Patent Document 2, the addition of a hydrogenated styrene-based thermoplastic elastomer improves the cracks of the molded product, but a particularly large amount of anisotropic rare earth magnetic powder having a high residual magnetic flux density (Br) is used. In such a case, the deformation due to the applied magnetic field increases, and cracks may occur.

According to the present invention, in a mixture mainly composed of ferromagnetic powder and resin binder, the weight ratio of the ferromagnetic powder in the mixture is 50 wt% or more and 95 wt% or less, and the melt viscosity of the mixture is 30 N · m or more and 45 N · m or less. The extrusion molding magnet material composition has a bending strength after molding of 150 × 10 ⁵ N / m ² or more and 250 × 10 ⁵ N / m ² or less.

  In the present invention, preferably, the ferromagnetic powder includes at least an anisotropic rare earth magnetic powder and a ferrite magnetic powder, and the anisotropic rare earth magnetic powder: the ferrite magnetic powder = 100 to 50: 0 to 50. It is a magnet material composition for extrusion molding.

  Furthermore, it is a magnet material composition for extrusion molding, wherein the resin binder is preferably a polyolefin resin having a melt mass flow rate (MFR) of 2 g / 10 min to 5 g / 10 min.

  According to the present invention, deformation at the time of applying a magnetic field can be prevented, cracks can be prevented and continuous extrusion molding can be performed, and a magnet piece having a desired high magnetic flux density can be obtained. It can be pasted together, and high image quality is possible. Furthermore, even in the case of magnetic powder having a high residual magnetic flux density (Br) such as anisotropic rare earth magnetic powder, the content of magnetic powder in the resin can be increased without sacrificing extrusion moldability and magnetic properties. In addition, the strength of the molded product can be improved and the extrusion moldability can be stabilized.

  Next, the magnet material composition for extrusion molding of the present invention will be described in detail with examples.

The present invention provides a mixture mainly composed of ferromagnetic powder and resin binder, wherein the weight ratio of the ferromagnetic powder is 50 wt% or more and 95 wt% or less, the melt viscosity is 30 N · m or more and 45 N · m or less, and It is a magnet material composition for extrusion molding with a bending strength of 150 × 10 ⁵ N / m ² or more and 250 × 10 ⁵ N / m or less.

  The resin binder is 5 to 50% by weight of polyolefin resin (including lubricants, stabilizers, etc.), and the ferromagnetic powder is anisotropic ferrite magnetic powder of 95 to 50% by weight. As a surface treatment agent for magnetic powder, coupling agents such as silane and titanate, polystyrene and fluorine lubricants that improve fluidity, stabilizers, plasticizers, flame retardants, etc. are added, mixed and dispersed, Melt-knead and form into pellets.

  The pellets are melted and extruded using a molding apparatus (die) as shown in FIG. 1 while applying a magnetic field of 150 K · A / m to 2400 K · A / m, as shown in FIG. An orientationally magnetized magnet piece (3) is obtained. The orientation magnetization magnetic field applied at the time of molding may be appropriately selected according to the magnetic flux density specification required for each magnetic pole. Further, depending on the required magnetic properties, the orientation magnetization magnetic field may not be applied at the time of molding, and may be magnetized after molding.

  The magnet piece (3) obtained above is bonded to the outer periphery of the shaft (5) to form a magnet roller as shown in FIG.

By adjusting the molecular weight of the resin binder, addition of elastomer, addition amount of plasticizer (hydrocarbon), particle size distribution and content of ferrite, molding conditions (molding temperature, etc.), etc., the pellets have a melt viscosity. The bending strength of the magnet molded product after molding is set to 150 × 10 ⁵ N / m ² or more and 250 × 10 ⁵ N / m or less at 170 to 180 ° C. at 30 N · m to 45 N · m. The melt viscosity increases as the molecular weight of the resin binder is increased, the amount of plasticizer added is decreased, or the molding temperature is lowered. The bending strength increases when an elastomer is added or when an ethylene ethyl acrylate resin is selected as a resin binder and the number of ethylene ethyl groups (EA groups) is increased.

  When the melt viscosity is less than 30 N · m, deformation due to the applied magnetic field of the magnet piece extruded from the mold (extrusion die) during extrusion in a magnetic field becomes large, and a desired shape cannot be obtained, or cracks due to deformation May occur, and the molded product may be torn and continuous extrusion molding may not be possible. If it exceeds 45 N · m, the degree of orientation of the magnetic particles in the magnet piece will decrease and the desired magnetic properties will not be obtained. Moreover, the extrusion torque at the time of extrusion molding becomes large, which may lead to breakage of the extruder.

When the bending strength of the magnet piece is less than 150 × 10 ⁵ N / m ² , when the magnet piece is bonded to the outer peripheral surface of the shaft, meandering occurs, causing variation in the magnetic pole position and image quality can be degraded. If it exceeds 250 × 10 ⁵ N / m ² , it can be bonded to the outer peripheral surface of the shaft with high precision, but the magnet piece warps due to environmental changes (temperature, humidity, etc.) It may cause peeling from the shaft or warping of the entire magnet roller.

  If the content of the ferromagnetic powder shown above is less than 50% by weight, the magnetic properties of the magnet piece are reduced due to the lack of magnetic powder, making it difficult to obtain a desired magnetic force, and the content of the ferromagnetic powder is 95. If it exceeds wt%, the binder becomes insufficient and the moldability may be impaired.

  Here, the ferrite magnetic powder may be either isotropic or anisotropic, but anisotropic ferrite magnetic powder is preferred in view of contribution to magnetic properties.

Examples of the ferrite magnetic powder include ferrite magnetic powder having a chemical formula represented by MO.nFe ₂ O ₃ (n is a natural number). As M in the formula, one or more of Sr, Ba, lead and the like are appropriately selected and used.

  In the present invention, the ferromagnetic powder includes at least an anisotropic rare earth magnetic powder and a ferrite magnetic powder, and the anisotropic rare earth magnetic powder: the ferrite magnetic powder = 100 to 50: 0 to 50. It is preferably a magnet material composition for extrusion molding.

  When the ratio of the anisotropic rare earth magnetic powder is less than 50 wt%, a magnet piece that satisfies a desired high magnetic flux density may not be obtained.

  In order to obtain a magnet piece having a higher magnetic flux density, it is desirable that the anisotropic rare earth magnetic powder is usually contained 90% by weight or more, preferably 95% by weight or more.

  The resin binder is 5 to 50% by weight of polyolefin resin (including lubricants, stabilizers, etc.), and the ferromagnetic powder is 95 to 50% by weight. An anisotropic rare earth magnetic powder (SmFeN type or the like) in the ferromagnetic powder. ) Of 100 to 50 wt%, and if necessary, as a surface treatment agent for the ferromagnetic powder, a coupling agent such as a silane or titanate, a polystyrene or fluorine lubricant for improving fluidity, and the like. An agent, a plasticizer, or a flame retardant is added, mixed and dispersed, melted and kneaded, and formed into a pellet.

  The pellets are melted and extruded using a molding apparatus (die) as shown in FIG. 1 while applying a magnetic field of 150 K · A / m to 2400 K · A / m, as shown in FIG. An orientationally magnetized magnet piece (3) is obtained. The orientation magnetization magnetic field applied at the time of molding may be appropriately selected according to the magnetic flux density specification required for each magnetic pole. Further, depending on the required magnetic properties, the orientation magnetization magnetic field may not be applied at the time of molding, and may be magnetized after molding.

  The magnet piece (3) obtained above is bonded to the outer periphery of the shaft (5) to form a magnet roller as shown in FIG.

  The melt viscosity at the time of molding and the bending strength of the molded product are adjusted in the same manner as described above.

  In addition, if the content of the ferromagnetic powder including at least the anisotropic rare earth magnetic powder and the ferrite magnetic powder shown above is less than 50% by weight, the magnetic characteristics of the magnet roller are deteriorated due to a lack of magnetic powder, and the desired properties are obtained. When it becomes difficult to obtain a magnetic force and the content thereof exceeds 95% by weight, the binder is insufficient and the moldability may be impaired.

  Examples of the anisotropic rare earth magnetic powder include NdFeB system and the like in addition to SmFeN system. Further, the residual magnetic flux density (Br) of the anisotropic rare earth magnetic powder is preferably 1T or more.

  In particular, in the case of a high residual magnetic flux density (Br) such as anisotropic rare earth magnetic powder, it is very easy to react to the applied magnetic field, and as a result, the deformation at the time of applying the magnetic field is much larger than that of the ferrite magnetic powder.

  As described above, in the extrusion method in the magnetic field according to the conventional method, the deformation of the molded product due to the application of the magnetic field is large, and the deformation may cause a crack in the molded product, and continuous extrusion molding may not be performed. Further, it may take time to adjust the extrusion die (extrusion die) in order to correct the deformation. Furthermore, when the extrusion molding magnetic material composition is adjusted so as to reduce deformation during molding by the conventional method, a desired magnetic flux density may not be obtained (lower than desired).

  In the present invention, the melt viscosity at the time of magnetic field extrusion molding, and the bending strength of the molded product are each in a specific range, so that deformation at the time of magnetic field application can be prevented, cracks do not occur, and continuous extrusion molding is possible, and Thus, a magnet piece having a desired high magnetic flux density can be obtained, and the magnet piece can be bonded to the outer peripheral portion of the shaft with high accuracy, so that high image quality can be achieved.

  As a magnet piece material, the above pellets may be used for all magnet pieces, but considering the required magnetic flux density specifications and costs, the above pellets are used only for magnetic pieces for magnetic poles that require high magnetic flux density. For other magnet pieces, a conventional anisotropic ferrite resin magnet material or the like may be used and may be appropriately designed. The molding method other than the pellet may be injection molding, compression molding, or the like.

As the resin binder of the magnet piece material, the polyolefin resin has been described above. However, the present invention is not limited to this, and when the magnetic powder is mixed, the melt viscosity of the mixture is 30 N · m to 45 N · m. and that the bending strength after molding is 150 × ¹⁰ 5 N / ^{m 2} or more 250 × ¹⁰ 5 N / ^{m 2} or less, can be generally used.

  Usually, as the resin binder, polyolefin resin, polyamide resin, polystyrene resin, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), EVA (ethylene-vinyl acetate copolymer), EVOH ( 1 type or 2 or more types such as ethylene-vinyl alcohol copolymer) and PVC (polyvinyl chloride), or heat such as epoxy resin, phenol resin, urea resin, melamine resin, furan resin, unsaturated polyester resin and polyimide resin One kind or two or more kinds of curable resins can be mixed and used. Of these, polyolefin resins having a melt mass flow rate (MFR) of 2 g / 10 min or more and 5 g / 10 min or less are preferable.

  The melt mass flow rate (MFR) is based on JIS K-6922-2, and a certain amount of synthetic resin is heated and pressurized at a predetermined temperature in a heated cylindrical container to It is measured by the amount of resin extruded per 10 minutes from the provided opening (nozzle).

  By using a polyolefin-based resin having a melt mass flow rate (MFR) of 2 g / 10 min or more and 5 g / 10 min or less, the above-described melt viscosity at the time of magnetic field extrusion molding and the bending strength of the molded product can be easily in a specific range, respectively. Can be adjusted.

  This melt mass flow rate is hereinafter abbreviated as MFR.

  Further, in the present specification, the description has been given of the five-pole magnet roll, but the present invention is not limited to the five-pole magnet roll. That is, the number of magnetic poles and the magnetic pole position may be set as appropriate according to the desired magnetic flux density and magnetic field distribution.

  Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
The N1 magnet piece material in FIG. 4 is composed of 90% by weight of anisotropic ferrite magnetic powder (NF-350 manufactured by Dowa Electronics Co., Ltd.) as a ferromagnetic powder, and ethylene ethyl acrylate resin (Nihon Unicar Co., Ltd.) as a resin binder. NCU-6220 manufactured, MFR = 4g / 10min) 10% by weight (including plasticizer, lubricant, stabilizer), these are mixed, melt-kneaded, formed into pellets, and the pellets are melted. Extrusion molding was performed at 160 ° C. using No. 1 molding apparatus (mold).

The melt viscosity of the pellets was 38 N · m at 175 ° C., and the bending strength of the magnet piece after extrusion was 200 × 10 ⁵ N / m ² .

  The magnet piece obtained above was bonded to the outer periphery of a SUM22 shaft having an outer diameter of 6 mm and a length of 370 mm to obtain a magnet roller as shown in FIG. The outer diameter of the magnet roller main body was 13.6 mm, and the length of the magnet main body (magnet piece) was 320 mm.

Melt viscosity, using a laboplastomill (manufactured by Toyo Seiki 30C150), the pellet was charged so as to satisfy 80% of the mixer space 60cm ^3, 175 ° C., and stirred for 10 minutes at a screw speed 25 rpm, the minimum torque value Measured and used as the melt viscosity.

  The bending strength was measured according to ASTM D790.

  The magnetic flux density of the obtained magnet roller is a probe (Bell magnetic flux density sensor) at a position (on the sleeve) 8 mm away from the center of the magnet roller while rotating the magnet roller while supporting the shafts on both ends of the magnet roller. , And measure the circumferential magnetic flux density in the axial direction with a gauss meter at three locations (10 mm from the both ends of the magnet toward the central portion and the axial central portion), and the main pole (the pole with the highest magnetic flux density) The magnetic flux density value of the N1 pole and the magnetic pole position were obtained. The twist of the magnetic pole position is a value obtained by subtracting the minimum magnetic pole position (angle) from the maximum magnetic pole position (angle) at the magnetic pole positions measured at the three locations. If the N1 pole magnetic flux density is 85 mT or more and the twist at the magnetic pole position is 3 ° or less, there is no practical problem.

Extrudability was evaluated by the following four stages by observation. ◎: Good formability, ○: No problem in practical use, △: Slightly poor formability (shape cannot be retained, fine cracks, etc.), ×: Poor formability (cracks, cracked, etc.)
As shown in FIG. 5, the deflection amount was measured by holding only the axial end (20 mm) of the magnet piece (total length 320 mm). If the amount of deflection is 140 mm or less, there is no practical problem.

  Table 1 shows the evaluation results of the melt viscosity and bending strength, extrusion moldability, N1 pole magnetic flux density and twist of the pole position, and the deflection of the molded product (magnet piece) of the N1 pole raw material which is the main pole.

（実施例２）
樹脂バインダーとしてエチレンエチルアクリレート樹脂（日本ユニカー株式会社製ＮＣ
Ｕ−６２２５、ＭＦＲ＝５ｇ／１０ｍｉｎ）を用い、上記ペレットの溶融粘度を１７５℃
で３０Ｎ・ｍとし、押出成形後のマグネットピースの曲げ強度を１５０×１０^５Ｎ／ｍ^２とする以外はすべて実施例１と同様に行なった。

(Example 2)
Ethylene ethyl acrylate resin as resin binder (NC manufactured by Nihon Unicar Co., Ltd.
U-6225, MFR = 5 g / 10 min) and the pellets have a melt viscosity of 175 ° C.
The same procedure as in Example 1 was conducted except that the bending strength of the magnet piece after extrusion was set to 150 × 10 ⁵ N / m ² .

(Example 3)
Using ethylene ethyl acrylate resin (NCU-6221 manufactured by Nihon Unicar Co., Ltd., MFR = 3 g / 10 min) as the resin binder, the melt viscosity of the above pellets is 45 N · m at 175 ° C., and the bending strength of the magnet piece after extrusion molding is The same procedure as in Example 1 was performed except that 250 × 10 ⁵ N / m ² was applied.

Example 4
The same procedure as in Example 1 was performed except that the anisotropic rare earth magnetic powder (SFN alloy fine powder B manufactured by Sumitomo Metal Mining) was 90% by weight as the ferromagnetic powder of the N1 magnet piece material of FIG.
The evaluation results are shown in Table 1. The N1 magnetic flux density is 120 mT or more, which is practically preferable.

(Example 5)
The same procedure as in Example 2 was performed except that 90 wt% of anisotropic rare earth magnetic powder (SFN alloy fine powder B manufactured by Sumitomo Metal Mining) was used as the ferromagnetic powder of the N1 magnet piece material of FIG.
The evaluation results are shown in Table 1. The N1 magnetic flux density is 120 mT or more, which is practically preferable.

(Example 6)
The same procedure as in Example 3 was performed except that the anisotropic rare earth magnetic powder (SFN alloy fine powder B manufactured by Sumitomo Metal Mining) was 90% by weight as the ferromagnetic powder of the N1 magnet piece material of FIG.
The evaluation results are shown in Table 1. The N1 magnetic flux density is 120 mT or more, which is practically preferable.

(Example 7)
As a ferromagnetic powder of the N1 magnet piece material of FIG. 4, anisotropic rare earth magnetic powder (SFN alloy powder B manufactured by Sumitomo Metal Mining): anisotropic ferrite magnetic powder (NF-350 manufactured by Dowa Electronics Co., Ltd.) = 95 wt% : 5 wt% was mixed in the same manner as in Example 2 except that the mixed magnetic powder was changed to 90 wt%.
The evaluation results are shown in Table 1. The N1 magnetic flux density is 120 mT or more, which is practically preferable.

(Comparative Example 1)
Using ethylene ethyl acrylate resin (NCU-6170 manufactured by Nihon Unicar Co., Ltd., MFR = 6 g / 10 min) as a resin binder, the pellet has a melt viscosity of 25 N · m at 175 ° C., and the bending strength of the magnet piece after extrusion molding The same procedure as in Example 1 was performed except that 100 × 10 ⁵ N / m ² was applied. The evaluation results are shown in Table 1.

(Comparative Example 2)
Bending of magnet piece after extrusion molding using ethylene ethyl acrylate resin (NCU-6520, manufactured by Nihon Unicar Co., Ltd., MFR = 1.6 g / 10 min) as the resin binder, and the pellet having a melt viscosity of 50 N · m at 175 ° C. The same procedure as in Example 1 was performed except that the strength was 300 × 10 ⁵ N / m ² . The evaluation results are shown in Table 1.

(Comparative Example 3)
Using ethylene ethyl acrylate resin (NCU-6170 manufactured by Nihon Unicar Co., Ltd., MFR = 6 g / 10 min) as a resin binder, the pellet has a melt viscosity of 25 N · m at 175 ° C., and the bending strength of the magnet piece after extrusion molding All operations were performed in the same manner as in Example 4 except that 100 × 10 ⁵ N / m ² was applied. The evaluation results are shown in Table 1.

(Comparative Example 4)
Bending of magnet piece after extrusion molding using ethylene ethyl acrylate resin (NCU-6520, manufactured by Nihon Unicar Co., Ltd., MFR = 1.6 g / 10 min) as the resin binder, and the pellet having a melt viscosity of 50 N · m at 175 ° C. The same procedure as in Example 4 was performed except that the strength was 300 × 10 ⁵ N / m ² . The evaluation results are shown in Table 1.

Examples 1 to 7 are superior to Comparative Examples 1 to 4 in terms of extrudability, magnetic properties (N1 magnetic flux density, N1 magnetic pole twist), and deflection amount.

When Example 2 and Comparative Example 1 are compared, and Example 5 and Comparative Example 3 are compared, Comparative Examples 1 and 3 have an extrudability of Δ or × ˜Δ, the N1 magnetic pole twist exceeds 3 °, and the amount of deflection is 140 mm. Since it exceeds, it turns out that melt viscosity becomes favorable in 30 N * m or more and bending strength in the range of 150 N / m < ² > or more.

When Example 3 and Comparative Example 2 are compared, and Example 6 and Comparative Example 4 are compared, Comparative Examples 2 and 4 have an extrusion moldability of Δ or × ˜Δ and a low N1 magnetic flux density, so the melt viscosity is 45 N · m. Hereinafter, it can be seen that the bending strength is good in the range of 250 N / m ² or less.

Magnet piece molding equipment (mold) Perspective view of magnet piece Perspective view of magnet roller Magnetic pattern of magnet roller The figure explaining the measuring method of the deflection amount of a magnet piece

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Excitation source 2 Yoke 3 Magnet piece 4 Magnetic particle orientation direction 5 Shaft 6 Magnetic flux density pattern 7 N1 pole magnetic flux density peak value and N1 magnetic pole position 8 Sleeve 9 Magnet piece support jig 10 Magnet piece deflection strength measuring device base stand

Claims (3)

In the mixture mainly composed of the ferromagnetic powder and the resin binder, the weight ratio of the ferromagnetic powder in the mixture is 50 wt% or more and 95 wt% or less, and the melt viscosity of the mixture is 30 N · m or more and 45 N · m or less, and A magnet material composition for extrusion molding, wherein the bending strength after molding is 150 × 10 ⁵ N / m ² or more and 250 × 10 ⁵ N / m ² or less.   The ferromagnetic powder contains at least an anisotropic rare earth magnetic powder and a ferrite magnetic powder, and the anisotropic rare earth magnetic powder: the ferrite magnetic powder = 100 to 50: 0 to 50. Item 2. The magnet material composition for extrusion molding according to Item 1.   The magnet material composition for extrusion molding according to claim 1 or 2, wherein the resin binder is a polyolefin resin having a melt mass flow rate (MFR) of 2 g / 10 min to 5 g / 10 min.

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