JPS61179506A - Magnetic material composition - Google Patents

Abstract

PURPOSE:To obtain a resin magnet having desirable magnetic characteristics with its good heat resistance preserved and further having desirable flow properties which enable it to be shaped easily, by forming the magnet of a polyamide resin composition containing polyamide and a stabilizer and of magnetic powder. CONSTITUTION:A magnetic composition consists of a polyamide resin composition of 5-30wt%, in which 1-75wt% polyamide having a number-average molecular weight of 3,000-15,000 is mixed with 99-25wt% polyamide having a number-average molecular weight of 15,000-30,000, and of magnetic powder of 70-95wt%. The magnetic powder is composed of an oxide of a ferrous group element (MFe2O4 in which M is iron and/or a ferrous element), for example Mn-ferrite. The magnetic powder preferably in an amount of 85-95wt% is mixed in the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic composition. More specifically, the present invention relates to a magnetic composition that has good moldability and high magnetic properties.

[Conventional technology]

polyethylene, chlorinated polyethylene, polyvinyl chloride,
It is well known that synthetic rubber, nylon, polypropylene, ethylene-vinyl acetate copolymer, etc., mixed with magnetic powder, are injection molded or extruded and used as plastic magnets.

It is also well known to mix magnetic powder into natural rubber or synthetic rubber and produce rubber magnets by hot rolling, extrusion molding, or the like.

[Problem that the invention seeks to solve]

In order to improve the magnetic properties of such plastic magnets or rubber magnets, it is necessary to increase the content of magnetic powder and to distribute the magnetic powder in a certain direction to provide anisotropy. . However, increasing the content of magnetic powder causes problems in that the mechanical properties of the molded product deteriorate and moldability becomes extremely difficult.

In addition, when ethylene-vinyl sulfate copolymer, polyethylene, polypropylene, etc. are used together with ferrite as a magnetic composition, the heat resistance is insufficient, and deformation occurs when left at temperatures of 100°C or higher. It's not as good as you'd expect, and its impact strength is weak (・.Also, if polyamide is used in the same way, the heat resistance during use is good, but due to molding processing
Since a molding temperature condition near Q O'C is required and the molding condition is near the decomposition point of polyamide, the range of molding conditions is narrow and molding processability cannot be said to be sufficient.

[Means for solving problems]

The present invention solves the above-mentioned drawbacks of plastic magnets, and by using polyamide, it maintains good heat resistance, has good magnetic properties, and has good fluidity during molding, making it easy to mold. This provides an easy-to-use resin magnet.

That is, the present invention has a number average molecular weight of 3,000 to 15.
000 polyamide with a number average molecular weight of 1 to 75% by weight
5,000-30,000 polyamide 99-25
Pertains to a magnetic composition with good fluidity during molding, consisting of 5-30% by weight of a polyamide resin composition containing 0-2.0% by weight of a stabilizer and 70-95% by weight of magnetic powder. It is something.

The magnetic resin composition of the present invention will be explained in detail below.

The magnetic powder used in the present invention is composed of an oxide of an iron group element (molecular formula: MF e 204, M is iron and/or an iron group element), which is commonly called ferrite in the art, such as Mn-ferrite. , N1-ferrite, Zn-ferrite, and their solid solution Mn-Zn-Fujii), Mn-Zn-Fe ferrite, N1-Zn ferrite, or Co-Fe7 ferrite, Ba-ferrite, Sr-ferrite, Mn-
There are Mg-Al ferrite, Cr-ferrite, etc.

Furthermore, examples include those in which various characteristics are added by adding trace amounts of oxides of various elements to these ferrites.

In addition, RFeO, which combines rare earth elements in addition to iron group elements,
3 (R is Tm, Lu, Yb, Er, Ho, Y
, Nd.

Examples include rare earth orthoferrites such as rare earth elements such as Sm and Eu.

Also included are magnetic materials made of a combination of iron group elements that do not contain iron.

The particle size of these magnetic powders is desirably 0.5 to 10 μm, and from a cost standpoint, 1 to 5 μm is preferable, considering the blending during injection molding and the manufacturing process of the magnetic powders. The amount of magnetic powder mixed in the magnetic resin composition of the present invention is 70 to 9
5 wt%, and a preferable mixing amount is 85 to 95 wt%. If the amount is less than 70 wt%, the magnetic performance will not be sufficient, and if it exceeds 95 wt%, the moldability will be significantly deteriorated.

The polyamide used in the composition of the present invention includes Ce
Homopolyamide or copolyamide or Ckl whose main component is a lactam or aminocarboxylic acid of ``-12''
There are homopolyamides and copolyamides whose main components are diamine No. 2 and C6-I2 dicarboxylic acid.

Specifically, nylon 6, nylon 6.6, nylon 6
-10, nylon 6/12, nylon 11, nylon 2, nylon 10/12, nylon 8/12, and copolymers thereof.

The number average molecular weight of these polyamides is 3. OOO~15
．． 000 and the number average molecular weight is 15. OOO~3
0.000, but preferably one with a number average molecular weight of 3,500 to 15,000 and one with a number average molecular weight of 15,000.
5,000 to 26,000. A polyamide with a number average molecular weight lower than 3.000 has no resistance to impact, and although it has good fluidity, it cannot maintain mechanical properties. In addition, the number average molecular weight is 30,
Polyamides with a molecular weight exceeding 0.000 will maintain sufficient mechanical properties, but will have poor fluidity when mixed with magnetic powder, making molding difficult.

When the above blend is compared with a polyamide having a standard molecular weight distribution in which the number average molecular weight of polyamide numbers is a standard distribution, there is no change in the number average molecular weight and fluidity when viewed as a polyamide. However, when it is made into a composition with magnetic powder, compared to a magnetic composition that combines polyamide with a standard molecular weight distribution and magnetic powder, magnetic powder is produced by combining polyamides with different number average molecular weights. In the case of a magnetic composition containing the above, less force is required during kneading, and the fluidity of the magnetic composition is also good. The reason for this is that the polyamide with a low number average molecular weight exerts a plasticizing effect on the polyamide with a high number average molecular weight, and in the region where the resin component is small in the load, that is, in the region where the magnetic powder is 70 to 95%, the fluidity is reduced. It is estimated that it will appear in a significantly improved form.

The mixed polyamide according to the present invention, which is a combination of polyamides having different number average molecular weights, has even higher heat resistance due to the presence of a stabilizer.

Stabilizers include copper compounds such as copper iodide, metal soaps, lead stabilizers, organotin stabilizers, epoxy compounds, bisphenol stabilizers, and phosphite stabilizers. These can be used alone or in a mixture of two or more. Any stabilizer may be used as long as it is compatible with the polyamide.

There is no need to add more stabilizer than necessary to 100 parts by weight of the polyamide component; 2. Although there is not much difference in the stabilizing effect, the addition of the stabilizer at a higher level than the oxygen level is not preferable because it increases the price.

The following properties can be obtained by appropriately blending the polyamide low-molecular weight, high-molecular weight, and stabilizer described above and using them as a binder resin for a plastic magnet.

1) Frictional wear between the magnetic powder and the resin during kneading is reduced, and when injection molding is performed while applying an external magnetic field, orientation of the magnetic powder becomes easier, improving magnetic properties.

2) When performing kneading, extrusion, and injection molding, the fluidity of the mixture becomes high, and molding can be performed even if it contains a large amount of magnetic powder.

3) Friction and wear on the surfaces of the molding machine and screw are reduced, making it possible to reduce the amount of impurities mixed into the molded product. Furthermore, the life of the device can be extended.

The composition of the present invention is produced by melt-mixing magnetic powder with a high molecular weight polyamide, a low molecular weight polyamide, and a stabilizer, usually using a spindle or twin screw extruder. Further, kneading may be carried out using a kneader. At this time, it is also possible to use a small amount of lubricant.

Specifically, a mixture of granular or powdered high-molecular-weight and low-molecular-weight polyamides with a stabilizer and magnetic powder, or a mixture of low-molecular-weight polyamide, high-molecular-weight polyamide, and a stabilizer in advance. Prepare the polyamide mixture in the form of granules or powder,
A method of mixing this with magnetic powder, feeding it into an extruder hopper, heating it, melting it, mixing it, and granulating it. Alternatively, the premixed material is put into a kneader and kneaded, and when the kneading is completed, the material discharged from the discharge port is granulated by cutting or pulverization, or by using an extruder, a polyamide mixture of low molecular weight polyamide and high molecular weight polyamide, and There is a method in which a mixture of stabilizers is charged into a portion of a hopper, heated and melted, and magnetic powder is added and mixed through a hole provided in the middle of the cylinder of an extruder. At this time, a mixture of a polyamide mixture of a low molecular weight polyamide and a high molecular weight polyamide and a stabilizer may be kneaded with heat in an extruder or kneader, and then granulated or a powder thereof may be used.

The pellets thus obtained can be further molded by injection molding or the like while shielding a magnetic field to obtain a plastic magnet. Alternatively, instead of such two-stage molding, a mixture of magnetic powder, low molecular weight polyamide, high molecular weight polyamide, and a stabilizer, or the above-mentioned mixed polyamide and magnetic powder, which have been heated and kneaded with a stabilizer in advance, may be charged into an injection molding machine. By doing so, it is also possible to obtain molded products at once.

In the case of obtaining polyamide injection molded products, polyamides with good fluidity and a low degree of polymerization are sometimes used when trying to obtain very thin-walled molded products. The same flowability and moldability have been obtained with the use of mixtures or with polyamides having a single standard molecular weight distribution, as long as the number average molecular weight is the same.

However, in the composition according to the present invention in which the proportion of magnetic powder is large, it has been found that the state of molecular weight distribution of the resin used as a binder greatly affects the fluidity of the composition containing magnetic powder. The object of the present invention is to use it as a binder resin.

It can be used not only as a binder resin for magnetic compositions, but also as a binder resin component of highly filled inorganic or organic resin mixtures such as glass fiber, glass peas, calcium carbonate, mica, carbon fiber carbon, talc, whiskers, and ceramic raw materials. Combination mixtures of polyamides and high molecular weight polyamides and stabilizers can be applied.

In this way, low polymerization degree polyamide and high polymerization polyamide are combined, stabilizers are added, and lubricants and colorants are added as needed.
Alternatively, the greatest feature of the present invention is that a dispersant is used, and the polyamide mixture is found to have good fluidity that can only be exhibited under conditions of high filling of magnetic material, and is used as a binder for magnetic powder.

Therefore, when obtaining a plastic magnet molded article using the magnetic resin composition of the present invention, a wide range of molding temperatures can be selected even if the magnetic material content is the same. Additionally, improved fluidity allows molding at lower temperatures, extending machine life and saving power consumption.

As described above, according to the magnetic resin composition of the present invention, it is possible to obtain a plastic magnet that has good magnetic properties, no decrease in strength, and good moldability.

Next, the present invention will be described with reference to examples.

(Example) Nylon 12 was selected as the polyamide. Further, as a stabilizer, Irganox 1010 was selected and tested. Examples of low molecular weight polyamides include NYO-3500 (number average molecular weight 3500) and NYO-8100 (number average molecular weight 810) obtained by polymerizing lauryllactam.
(1) was used. As the high-molecular-weight polyamide, Daicel-Hüls■ trade name "Diamide JL-1940" was used. The number average molecular weight of this product was 25,800. These low-molecular-weight polyamides, high-molecular-weight polyamides, and stabilizers are shown in Table 1. Mixed in a predetermined ratio as shown in
Rheocord Type M
A sample of mixed polyamide was obtained by kneading at 50 rm for 15 minutes at a temperature of 210° C. using a blender. Further, the number average molecular weight was measured by a relative viscosity measurement method.

That is, by dissolving the sample in metacresol to make a 0.5% metacresol solution and measuring the relative viscosity of this solution, each ηrel is determined, and the determined ηrel is substituted into the following formula (%). It was calculated as the number average molecular weight.

Note that the number average molecular weight can also be calculated by measuring the terminal group concentration.

By blending a low molecular weight polyamide and a high molecular weight polyamide at the Re5In blending ratio shown in Table 1, a polyamide mixture having an appropriate number average molecular weight was obtained.

Table 1 also shows the results of measuring the MI value of only these polyamide mixtures. Measurement of MI value is done by MeltInd.
Measurements were performed using an exer. The measurement conditions are 19
At 0°C, a load x 2.1 eng was employed.

As the magnetic powder material, ferrite is used as Nippon Bengara Kogyo's OP-71 (average particle size 1.18 μm).
, compressed density 3.25 g/CTL3).

100 parts by weight of ferrite was prepared in advance by surface treatment with 1 part by weight of Ajinomoto's surface treatment agent "Purenaku N KR-TTS", and was subjected to the following tests and comparative examples. .

When examining the kneading torque using the polyamide mixture and magnetic powder prepared in advance according to the above procedure, we determined the magnetic powder content to be 89.5 wt% and to obtain a measurement sample for the MI value. were mixed so that the magnetic powder content was 88 wt%.

A mixture of these magnetic powders and polyamide (ferrite content: 89.5 wt%) was weighed to have a volume of 50 CG, and the kneading torque during heating and kneading was examined. Pheocord Type M (Ha
The kneading torque was observed 15 minutes after the start of kneading at a kneading temperature of 280° C. and a rotational speed of 100 rpm.

The sample for measuring the MI value was a mixture of magnetic powder and polyamide (ferrite content 88 wt%).
ype M (Haake Inc) at a kneading temperature of 260°C and a rotational speed of 100 rpm.
After continuing kneading for 5 minutes, the kneaded material was taken out and pulverized.

Melt Indexer was used to measure the MI value, and A
According to the method of SThfD1238, a temperature of 250° C. and a load of 10# were adopted as the measurement conditions.

The results of the K measurement as described above are also listed in Table 1, and it can be seen that a magnetic composition with good fluidity was obtained.

(Comparative Example) As in the example, nylon 12 was selected as the polyamide. Moreover, Irganox 1010 was selected as a stabilizer. As polyamides, Daicel Huels IV product names "Diamid JL-1940, L-1700, L-
1600 and L-1500 were used. The number average molecular weights of these are 25,800, 22,000, and 22,000, respectively.
20,200 and 18,400. The number average molecular weight was measured by the relative viscosity measurement method as in the examples.

The MI value of only Re5in was measured using the same device and under the same conditions as in the example.

Moreover, the magnetic powder used in the experiment of the example, which had been surface-treated in advance, was used.

The magnetic powder and polyamide prepared above were mixed in the proportions shown in Table 2, and the kneading torque was observed at a ferrite content of 89.5 wt %, using the same equipment and under the same conditions as in the example. Further, samples for MI values were prepared under the same conditions as in Examples, and MI values were measured using the same equipment and under the same conditions as in Examples.

The results are also listed in Table 2.

As is clear from comparing Tables 1 and 2, polyamides with the same number average molecular weight have the same fluidity when only Re5in is used, but when highly loaded with magnetic powder, they differ from low molecular weight polyamides. It can be seen that the fluidity of the resin using a mixed polyamide of polymeric polyamide as the binder resin is clearly better than that of the resin using a polyamide having a single molecular weight as the binder resin.

Claims (1)

[Claims] 1 to 75% by weight of polyamide with a number average molecular weight of 3,000 to 15,000;
5-30% by weight of a polyamide resin composition blended with 99-25% by weight of 000 polyamide and 70-9% by weight of magnetic powder
A magnetic composition consisting of 5% by weight.