JPH0294411A - Manufacture of plastic magnet - Google Patents

Abstract

PURPOSE:To increase tensile strength, bending strength, hardness, residual magnetic flux density, coerceive force and maximum energy product by a method wherein, when magnetic powder previously coated with a surface modifying agent, resin and solvent are mixed and blended to form a plastic magnet, the magnet is formed by injection molding after the blended material is made powder. CONSTITUTION:The surface of Ba ferrite magnetic powder 1 whose grain diameter is about 1-5mum is covered with material containing surface modifying agent of 0.5-1.3wt.%, and coated by heating. This powder 1, and inbricant composed of nylon 2 of 6-11.8wt.%, and zinc stearate of 0.3-1wt.% are mixed by a high speed mixer. Desired powder 3 is obtained by blending them with a dual-axis extruder in the state of heating at 200-300 deg.C. Nylon of 2-3.9wt.% is again added to the power, which is mixed by the dual-axis extruder and heated and blended at 200-300 deg.C. Next the powder is subjected to injection-molding in a magnetic field. Thereby, the fluidity of the powder is improved, and the irregularity of characteristics is reduced.

Description

[Detailed description of the invention] A0 Purpose of the invention [Industrial application field] The present invention relates to the manufacture of plastic magnets.

[Conventional technology]

In recent years, with the development of electronics, plastic magnets have been used in industrial equipment such as home appliances, OA equipment, and FA equipment. Lamb cobalt-based plastic magnets are usually made by thoroughly mixing various magnetic powders, binder resin, and lubricant, and then heating them at 200 to 300°C.
The powder was softened by heating, kneaded, hardened and pulverized at room temperature to form a granular powder, and the powder was then extruded or injection molded in a heated magnetic field.

It was thought that the finer the magnetic powder, the worse its fluidity, but it is now known that it actually has better fluidity during injection molding (increases density and hardness, and improves mechanical properties).

The magnetic powder of ferrite plastic magnets is 1 to 5 μmm.
The magnetic powder of the samarium cobalt plastic magnet has a particle diameter of 3 to 10 μmm, and the particle size of the samarium cobalt plastic magnet is 5ffi2GO+7.
Thread plastic magnets are injection molded to a particle size of 3 to 100 μmm. In general, the thinner the better, and the fluidity is not much different with the thinner one than with the coarser one, so the density increases.
The mechanical properties such as bending strength kg/co+2, tensile strength kg/cm2, hardness (Rockwell R), and density are increased, but the workability is not so high as to deteriorate.

The conventional process involves adding resin to magnetic powder to coat the surface, adding nylon resin and lubricant to the magnetic powder-coated powder, and mixing with a high-speed mixer. After that, ferrite type and samarium cobalt type plastic magnets have a
Heat and knead at 300°C.

Thereafter, the kneaded material was crushed and injection molded in a magnetic field.

To write this process simply, (magnetic powder coating) → (
Plastic magnet products were manufactured through the following steps: (mixing powder, resin, and lubricant) → (mixing) → (crushing) → (injection molding in a magnetic field).

An example using a conventional manufacturing method will be described.
It would be difficult to describe all the manufacturing methods for ferrite plastic magnets, Sm r Coa system, and Sm2Co+7 thread plastic magnets, so we will focus on Sm2Co+. The manufacturing method of plastic magnets is described below. According to the conventional manufacturing method of Sm2GO+7 thread plastic magnets, for example, 10 kg of magnetic powder is mixed with 30 g of isoprobyl triisostearoyl titanate as a surface modifier and coated around the magnetic powder. After that, 600 g of nylon-12 as a nylon resin and 60 g of zinc stearate as a lubricant were mixed into the coated powder, and then
After heating and kneading at 300° C., the mixture was cured at room temperature, pulverized with a pulverizer, and used as a powder for injection molding and extrusion molding, and the powder was injection molded in a magnetic field of 15 MKOe.

These manufacturing methods can be applied to Ba ferrite threads, Sr ferrite plastic magnets, and Sm, Co5 fifth thread plastic magnets.Generally speaking, magnetic powder is coated with a surface modifier, After that, the powder was mixed with nylon thread resin and a lubricant, and heated to 200 to 300℃.
After kneading, the powder was cured at room temperature and pulverized, and the pulverized powder was injection molded in a magnetic field.

Table 2 shows the compounding amounts of the surface modifier, nylon thread resin, and lubricant in each conventional process in weight percent.

Blank space below [Problem to be solved by the invention] In the conventional manufacturing method of plastic magnets using injection molding, when trying to manufacture plastic magnets with high magnetic properties, the content of powder is increased to increase the density. However, as the content of the powder increases, the fluidity deteriorates and molding becomes difficult, and as a matter of course, the mechanical properties such as bending strength and tensile strength also deteriorate.

The reason for this is that powder coated with resin, which is a surface modifier, is sprinkled with nylon resin and lubricant, then kneaded, and then the kneaded material is crushed to produce powder, which is then used for injection molding. We observed the plastic magnets and powder particles under a microscope and investigated the state of powder clogging.As shown in Figure 2, we mixed the coated powder with nylon resin and a lubricant. When the kneaded material is pulverized by softening and heating at 300°C and cooling and hardening, the pulverized powder 3 becomes angular particles with many sharp angles, the resin 2 falls off from the powder, and the clogging is worse than that of the powder of the present invention. , that is, there was a drawback that the variation became large.

In addition, as shown in Figure 3, areas where the magnetic powder 1 was tightly packed (high density) and areas where the magnetic powder 1 was sparse with respect to the resin were observed.Even if the overall density is the same, the magnetic The occurrence of places where the powder is densely packed and places where the powder is coarsely and sparsely packed means that there are places where the powder is filled with a lot of resin and places where the powder is packed with a lot of magnetic powder, and the fluidity during injection molding is affected. The problem was that the filling was insufficient and the density was not constant in some areas, resulting in poor magnetic properties.

In order to improve the magnetic properties, we want to increase the density by increasing the amount of magnetic powder, but if the content of powder coated with magnetic powder increases, it will be heated in the furnace and softened before being injected into the mold. The more powder there is, the worse the flow becomes, making it impossible to avoid insufficient filling and internal defects, and the orientation of the powder, that is, the magnetic anisotropy, which is treated in a magnetic field that impairs magnetic properties, is also extremely degraded.

For this reason, considering mass production, we determined the particle size, found the best blend of nylon resin and lubricant, and kept the injection molding pressure constant.In this state, we manufactured plastic magnets and coated them for injection molding. Provided is a method for producing a plastic magnet that has good magnetic compounding properties with uniform density so that the powder is uniformly clogged, and does not become overcrowded or sparsely packed, and therefore has good magnetic and mechanical properties. The purpose is to

Structure of the Invention [Means for Solving the Problems] In order to achieve the above object, if a nylon resin is sufficiently coated around the magnetic powder with the same thickness, the flow of the powder becomes denser and denser. As a result of our efforts to improve the powder for injection molding, we found that the powder is as compact as the conventional one (magnetic powder coating) → (powder It was found that the following steps could be used as the next step: (mixing of 10 resins and 10 lubricants) → (mixing) → (crushing) → (injection molding in a magnetic field).

(magnetic powder coating) → (mix powder ten resin ten lubricant,
However, the blending ratio of resin lubricant is reduced to a certain ratio and mixed)
It has been confirmed that the desired powder can be obtained by improving the process of + (kneading) 10 (grinding) + (mixing powder 10 resin 10 lubricant) 10 (kneading) + (grinding) 10 (injection molding in a magnetic field) It was done.

That is, the present invention provides a plastic magnet in which magnet powder coated in advance with a surface modifier, a resin, and a lubricant are mixed and kneaded. This method of manufacturing a plastic magnet is characterized in that injection molding is performed through a step of forming the kneaded material into a shape, and a step of mixing and kneading the pulverized material obtained by pulverizing the kneaded material with a resin.

[Effect]

The conventional manufacturing process (coating) → (mixing) → (mixing) → (pulverization) → (injection molding in a magnetic field) is now (coating)
→ (Mixing) → (Mixing) → (Crushing) → (Mixing) → (Crushing)
→ (injection molding in a magnetic field), the powder crushed in the conventional process had a lot of nylon resin falling off, but this powder was coated with nylon thread resin again and crushed. As a result, the adhesion of the nylon-based resin is increased, and almost no magnetic powder falls off, resulting in a spherical shape with no coating visible. This is clearly due to the fact that the first bond between the nylon resin and the magnetic powder is repeated in the second coating, which makes the bond better and stronger.
The nylon resin penetrates around the magnetic powder, making it more spherical, producing powder with good fluidity and no clogging, which improves magnetic and mechanical properties. By connecting, you can achieve your goal.

[Example] Example 1 The Ba ferrite plastic magnet in Table 1 will be described. The particles of the magnetic powder of Ba ferrite are about 1 to 5 μmm. Conventional Ba ferrite plastic magnets have a residual magnetic flux density of 2500 to 2700G,
1300-16000e, maximum energy product: 13-1
6MGOe, density: 3.4-3.6, fluidity MFR:
0.8-1.5g 710 minutes (MRF is meltflow
It is an interpretation of rate, and represents the fluidity of a plastic magnet, and when an acceleration of 10 kg/cm2 is applied at 270°C, 1
It indicates how many grams of softened powder flows out in 0 minutes, and the unit is 8710 minutes. ), hardness = 85-130, Rockwell R1 tensile strength = 600-700 kg/cm2, and bending strength: 800-1200 kg/cm2.

As shown in Table 3, 0.5 to 1.3% by weight of a surface modifier was added to 10 kg of Ba ferrite magnetic powder, and the surface was coated by heating and mixing to form a coated powder. To this powder, 6 to 11.8% by weight of nylon 6 as a nylon resin and 0.3 to 1% by weight of zinc stearate as a lubricant are added and mixed using a high speed mixer. Thereafter, the mixture is heated at 200-300% and kneaded using a twin-screw extruder. The kneaded material thus prepared is cooled to room temperature and hardened, and then ground in a grinder to form a powder. Injection molding was performed using this powder, but in the present invention, 2 to 3.9% by weight of nylon 6 as a nylon resin was further mixed with this powder and mixed again in a twin screw extruder. After that 250-300
% and kneaded with heat. The kneaded material thus obtained is crushed,
This powder was injection molded in a magnetic field, and the following properties as shown in Table 1 were obtained.

That is, residual magnetic flux density: 2800-3000 G, coercion crab 1500-18000e, maximum energy product: 1
．． 5-1.8 MGOe, density: 3.6-3.8, fluidity MER: l-2 g/10 min, hardness: 100-150 Rockwell R1 tensile strength: 650-750 kg/c
m2, bending strength: 900 to 1300 kg/cm2.

It can be seen that the magnetic properties and mechanical properties are improved in this way. As shown in Figure 1, when one ring is observed under a microscope, the magnetic powder 1 is uniformly coated with wood JJFj 2, and the magnetic powder is evenly packed, with very little variation in density. It was found that the magnetic properties and mechanical properties were improved compared to the conventional ones because the particles were composed of packed powder 3.

Example 2 The Sr ferrite plastic magnet in Table 1 will be described. The particle size of the magnetic powder of Sr ferrite is about 1 to 5 μmm. In conventional Sr ferrite plastic magnets,
Residual magnetic flux density: 2500-2700 G, coercive crab
2000~23000e, maximum energy product: 1.6~
1,9MGOe, density: 3,4-3.6, MRF:
0.8-1.5g/10 minutes, hardness: 85-130 Rockwell R1 tensile strength = 600-700kg/am"
, bending strength: 800 to 1200 kg/cm2.

As shown in Table 3, 0.5 to 1.3% by weight of a surface modifier was added to 10 kg of Sr ferrite magnetic powder, and the mixture was heated and mixed to form a surface coated powder. 6 to 11.8% by weight of nylon 6 as a nylon resin and 0.3 to 1% by weight of zinc stearate as a lubricant are mixed into this powder using a high-speed mixer. Thereafter, the mixture is heated at 200 to 300°C and kneaded using a twin-screw extruder. The kneaded material thus prepared is cooled to room temperature and hardened, and then ground in a grinder to form a powder. Injection molding was performed using this powder, but in the present invention, 2 to 3.9% by weight of nylon 6 as a nylon resin was further mixed with this powder, and the mixture was again mixed using a twin-screw extruder. Thereafter, the mixture was heated and kneaded at 200 to 300%.

The thus obtained kneaded material was pulverized and the resulting powder was held in a magnetic field and injection molded to obtain the following resin.

That is, as shown in Table 1, residual magnetic flux density: 2800-3
000 G, coercion crab 2200-25000e, maximum energy product: 1.8-2.1MGOe, density: 3.6
~3.8, fluidity MER: 1-2 g/10 min, hardness = 1
00-150 Rockwell R1 tensile strength: 650
~750kg/cm2, bending strength 900~1300kg
/cm2.

It can thus be seen that both the magnetic properties and mechanical properties are improved.

Example 3 As shown in Table 1, the conventional magnetic properties and mechanical properties of the 5IIllCO5 thread plastic magnet are described.The magnetic properties include residual magnetic flux density: 5500 to 5800G, coercion crab 5000 to 52000e, and maximum energy product. Near to 9MGOe, mechanical properties include tensile strength: 250-350kg/cm', bending strength: 300
~500kg/cm2, hardness: 90-100 Rockwell R, density = 5.2-5.5, MFE near ~
It was 9g/10 minutes.

By the manufacturing method of the present invention, as shown in Table 3, Sm
+ 0.3 to 1.2% by weight of a surface modifier was added to 10 kg of CO5 magnetic powder, and the surface was coated by heating and mixing to obtain a powder coated with Sm + Co5 magnetic powder. After that, this powder is coated with nylon-based resin nylon.
12 (3.4 to 6.4% by weight) and zinc stearate as a lubricant (0.3 to 1'% by weight) are added and mixed using a high speed mixer. Thereafter, the mixture is heated at 200 to 300°C and kneaded using a twin-screw extruder. The kneaded material thus prepared is cooled to room temperature to harden, and then ground into powder using a powder mill. To this pulverization, 1.1 to 2.1% by weight of nylon resin Nylon-12 was further added and mixed, mixed again in a twin screw extruder, and then heated and kneaded at 200 to 300°C.

The kneaded material thus obtained was pulverized, and the powder was injection molded in a magnetic field of 15 KOe. As a result, Table 1
As shown in Figure 2, the following characteristics were obtained.

That is, as shown in Table 1, residual magnetic flux density: 6500-6
800G, coercive force = 5800-60000e, maximum energy product: 8-10MGOe, tensile strength: 300
~400kg, bending strength = 600~800kg/cIf
i2, density: 5.5-5.8, fluidity MFR: 8-10
g/10 minutes, and hardness was 100-110 Rockwell R.

Example 4 As shown in Table 1, the conventional magnetic properties and mechanical properties of Sm2Co+7 plastic magnets are described.The magnetic properties include residual magnetic flux density: 5700 to 6200 G, coercivity crab 3800 to 45000e, and maximum energy product. :8
~10MGOe, and mechanical properties include tensile strength: 250-350 kg/cm2, bending strength: 30
0 to 500 kg/cm2, hardness: 50 to 60 Rockwell R, and density: 5.2 to 5.5, MFE near to
It was 9g/10 minutes.

By the manufacturing method of the present invention, as shown in Table 3, Sm
0.3 to 1.2% by weight was added as a surface modifier to 10 kg of 2GO + □ magnetic powder, and the mixture was heated and mixed to coat the surface, resulting in a powder coated with Sm2Co, □ magnetic powder. After that, this powder is coated with nylon-based resin nylon-12.
3.4 to 6.4% by weight and 0.3 to 1% by weight of zinc stearate as a lubricant are added and mixed with a high speed mixer. Thereafter, the mixture is heated at 200 to 300°C and kneaded using a twin screw extruder. The kneaded material thus prepared is cooled to room temperature to harden, and is ground into powder using a powder mill. In addition to this pulverization, nylon-based resin nylon-12 was added in a weight percent of 1.
1 to 2.1% was added and mixed, mixed again using a twin screw extruder, and then heated and kneaded at 200 to 300°C.

The kneaded material thus obtained was pulverized, and the powder was injection molded in a magnetic field of 15 KOe. As a result, Table 1
As shown in Figure 2, the following characteristics were obtained.

That is, as shown in Table 1, residual magnetic flux density: 6700-7
300G, coercion crab 4400~53000e, maximum energy product: 10~12MGOe, tensile strength:
300-400kg, bending strength: 600-800kg
/cm2, density: 5.5-6.0, fluidity MFR: 8-
10 g/10 minutes, hardness was 60-70 rockwells.

It can thus be seen that both the magnetic properties and mechanical properties are improved.

The following margin is 0 Effects of the invention [Effects of the invention] As mentioned above, (coating) → (mixing) → (kneading) → (
The mechanical properties such as tensile strength, bending strength, and hardness are improved by pulverization → (mixing) → (y-crushing) → (injection molding in a magnetic field), and the magnetic characteristics such as residual magnetic flux density, coercive force,
The maximum energy product also improves. M which is density and fluidity
It can also be seen that the FR has improved.

With this, I was able to achieve my previous goal.

[Brief explanation of drawings]

FIG. 1 is a microscopic view showing the uniform arrangement of spherical particles produced by the manufacturing method of the present invention. Figure 2 is a microscopic view of the arrangement of particles produced by conventional manufacturing methods, with angular shapes, poor density, and coatings that have fallen off. FIG. 3 is a diagram showing that there are areas where the powder is dense and areas where the powder is sparsely dense due to the conventional manufacturing method. 1...Magnetic powder, 2...Nylon resin, and...Powder. 7th 2nd Figure 3

Claims (1)

[Claims] 1. In a plastic magnet in which magnetic powder coated in advance with a surface modifier, a resin, and a lubricant are mixed and kneaded, a step of pulverizing the kneaded product of the plastic magnet mixed and kneaded with the magnetic powder to form a powder; and a method for producing a plastic magnet, comprising injection molding through a step of mixing and kneading a pulverized product obtained by pulverizing the kneaded product with a resin.