JPH08207043A - Production of pellet composed of magnetic resin composition - Google Patents

Abstract

PURPOSE: To obtain pellets having a uniform shape by kneading a powder of an oxide magnetic material wherein water content is a predetermined value or less and the generation amt. of carbon dioxide at the time of heating in nitrogen at predetermined temp. for a predetermined time is a predetermined amt. or less with a thermoplastic resin and pelletizing the resulting kneaded matter. CONSTITUTION: Pellets of a magnetic resin composn. are formed by kneading a powder of an oxide magnetic material characterized by that moisture content is 1000ppm or less and the generation amt. of carbon dioxide at the time of heating in nitrogen at 400 deg.C for 2hr is 400ppm or less with a thermoplastic resin and pelletizing the molten kneaded compsn. by a known pelletizing method such as hot cutting method, a mist-cut method or a strand cutting method. Herein, water content is calculated by a Karl Fischer coulometric titration method and the generation amt. of carbon dioxide is calculated by a method wherein 20mg of a powder of a magnetic material is put in a 1000ml combustion tube to be heated at 400 deg.C for 2hr in nitrogen gas within an electric crucible oven and the generated gas is collected through a calcium chloride tube and the amt. thereof is calculated by a gas chromatograph.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing pellets of a magnetic resin composition comprising a thermoplastic resin and an oxide magnetic material.

[0002]

BACKGROUND OF THE INVENTION Magnetic substance compositions containing various oxide magnetic substance powders using a thermoplastic resin as a binder have been attempted to be applied to electric and electronic parts, automobile parts and the like. Not only in these fields, it is economically very important to mold a product efficiently.

[0003]

2. Description of the Related Art Conventionally, a composition containing an oxide magnetic substance powder with a thermoplastic resin as a binder often has a variable extrusion amount at the time of melt-kneading, and particularly the content of the magnetic substance powder increases. Therefore, this tendency was remarkable. Usually, the melt-kneaded composition is hot cut method, mist cut method,
It is formed into a pellet shape by a pelletizing method such as a strand cut method. After that, it is supplied into a mold such as an injection molding machine, molded into a shape to be used, and incorporated into a product. However, when these molded product pellets are obtained by the melt-kneading method, there are cases where the pellet shape becomes extremely uneven due to a change in the extrusion amount. When the pellet shape of the composition becomes non-uniform, for example, when molding a product by an injection molding method, there are problems such as unstable metering, poor filling, and increased load on the molding machine. For this reason, there are cases where it affects various characteristics of the obtained molded product.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pellet having a uniform shape in a composition containing a binder made of a thermoplastic resin and an oxide magnetic powder.

[0005]

The present invention was obtained while investigating what is causing the variation of the extrusion amount as described above, and its basic idea is as follows.
The metal oxide magnetic powder has a high affinity with water,
Moreover, the water once bound to the magnetic powder cannot be easily removed. There is also the fact that carbon dioxide is generated from the metal oxide magnetic powder. This is presumed to have been adsorbed on the surface during the manufacturing process of the magnetic substance or after crushing it. As a result, when the composition of the thermoplastic resin and the magnetic powder is kneaded, both water and carbon dioxide, which are considered to be generated from the magnetic powder, rapidly increase the pressure inside the kneader, and the fluctuation of the extrusion rate. It is considered that the pellet shape changes due to the above. On the other hand, it has been found that the problems of the present invention can be solved by setting the water content and the carbon dioxide content to be equal to or less than the predetermined amounts.

That is, the gist of the present invention is that the water content is 1000 ppm or less, and the amount of carbon dioxide generated when heated in nitrogen at 400 ° C. for 2 hours is 400 ppm or less and an oxide magnetic powder and thermoplasticity. A method for producing a magnetic material composition, which comprises kneading a resin to form a pellet. Hereinafter, the present invention will be described in detail.

In the present invention, the water content is 1000 ppm or less, preferably 500 ppm or less, more preferably 30 ppm.
0ppm or less, carbon dioxide generation is 400ppm
Hereinafter, the oxide magnetic material powder having a content of 300 ppm or less, more preferably 300 ppm or less, more preferably 250 ppm or less is used. When the water content of the oxide magnetic powder exceeds 1000 ppm, when kneading with the thermoplastic resin in the extruder, water is generated, the amount of extrusion changes, and the pellet shape becomes nonuniform, which is preferable. Because there is no. When the amount of carbon dioxide generated in the oxide magnetic powder exceeds 400 ppm,
This is because when kneading in an extruder, carbon dioxide is generated, the amount of extrusion varies, and the pellet shape becomes significantly uneven, which is not preferable.

Here, the water content is obtained by the Karl Fischer coulometric titration method. In addition, the amount of carbon dioxide generated was such that 20 mg of magnetic powder was placed in a 100 ml combustion tube and heated in an electric crucible furnace at 400 ° C for 2 hours in nitrogen gas. It is what I asked for.

In order to obtain an oxide magnetic powder having a water content of 1000 ppm or less and a carbon dioxide generation amount of 400 ppm or less, the following method is preferably adopted. This is a method in which the calcined oxide magnetic material is pulverized and then heated at a temperature higher than the kneading temperature by 20 ° C. or higher and at a temperature lower than the calcining temperature of the magnetic material for 1 hour or longer, preferably 3 hours or longer. The heating temperature is preferably 50 rather than the kneading temperature.
It is performed at a temperature higher than ℃ and lower than the firing temperature of the magnetic material. Here, the kneading temperature is a display with a thermometer which is usually measured in a kneading device, because the temperature of the resin itself cannot be clearly measured in reality.

Instead of the display by the kneading temperature, it may be expressed as follows. That is, when the thermoplastic resin is a crystalline thermoplastic resin, the oxide magnetic material is heated at a temperature 100 ° C. or higher higher than the crystalline melting point of the crystalline thermoplastic resin and not higher than the firing temperature of the magnetic material. Body powder,
When the thermoplastic resin is an amorphous thermoplastic resin, an oxide heated at a temperature higher than the glass transition temperature of the amorphous thermoplastic resin by 150 ° C. or more and at a temperature not higher than the firing temperature of the magnetic material. It is a magnetic powder. In the case of a crystalline thermoplastic resin, the heating temperature is preferably a temperature higher than the crystal melting point by 120 ° C. or higher and a temperature lower than the firing temperature of the magnetic material, and more preferably a temperature higher than the crystal melting point by 150 ° C. or higher. A temperature that is lower than or equal to the firing temperature of the magnetic material is used. In the case of an amorphous thermoplastic resin, the heating temperature is preferably 170 ° C. or higher higher than the glass transition temperature and lower than the firing temperature of the magnetic material, and more preferably 200 ° C. or higher glass transition temperature. High temperature,
Moreover, a temperature lower than the firing temperature of the magnetic material is adopted.

The atmosphere in the dehydration step may be atmospheric air, and although it is not particularly limited, nitrogen or an inert gas is preferable, but dry air is used in the cooling process at 100 ° C. or lower. Is also preferably used. After heating, it is cooled, and the container is hermetically stored in a gas barrier container that has an atmosphere containing substantially no water and carbon dioxide,
Appropriate for kneading with the resin, or if necessary, after cooling, kneading with the resin. In the latter case, when it is heat-treated at a temperature higher than the decomposition temperature of the resin, it is cooled to a temperature lower than the kneading temperature and then kneaded with a thermoplastic resin. It may be kneaded with a resin. The magnetic resin composition can be obtained by kneading such an oxide magnetic powder and a thermoplastic resin by a known method and pelletizing.

The atmosphere in the gas barrier container is optional as long as it does not substantially contain water and carbon dioxide, but nitrogen gas or an inert gas is usually used. Here, "substantially" means that the water content of the oxide magnetic powder is 1000 pp.
m or less, and means that it may contain water and carbon dioxide to the extent that the amount of carbon dioxide generated when heated in nitrogen at 400 ° C. for 2 hours is 400 ppm or less, and its allowable value. The content rate depends on the storage period, the type of magnetic powder, the particle size distribution, and the like.

Further, as the oxide magnetic powder, the general formula MO · Fe ₂ O ₃ (where, M is a divalent metal element) spinel ferrite represented by the general formula 3M ₂ O ₃ · 5Fe ₂ O
Garnet type ferrite represented by ₃ (however, M is yttrium or trivalent rare earth element), general formula MO ・ 6Fe
Ferrite-based magnetic powder such as magnetoplumbite ferrite represented by ₂ O ₃ (M is a divalent metal element) is used.

A spinel type ferrite represented by the general formula MO.Fe ₂ O ₃ (where M is a divalent metal element) is M
n-Zn ferrite, Ni-Zn ferrite, Mg
-Zn ferrite, Cu-Zn ferrite, Li-
Zn-based ferrite, composite ferrite such as Ni-Cu-Co-based ferrite, Mn ferrite, Co ferrite,
Examples include unitary ferrites such as Ni ferrite.

The garnet-type ferrite represented by the general formula 3M ₂ O ₃ .5Fe ₂ O ₃ (where M is yttrium or a trivalent rare earth element) is yttrium iron garnet (YIG-based material) or Ho-substituted garnet. Examples thereof include a system ferrite and a Gd-substituted garnet system ferrite.

Examples of the magnetoplumbite type ferrite represented by the general formula MO.6Fe ₂ O ₃ include strontium ferrite and barium ferrite.

On the other hand, the thermoplastic resin is not particularly limited. The molding temperature may be low, for example, about 150 ° C., or the molding temperature is high, for example, 35 ° C.
It does not matter if it is about 0 ° C. This is because water and carbon dioxide are generated regardless of the molding temperature.
However, among them, the polyphenylene sulfide resin, which has a high gas barrier property, does not decompose even when contacted with the oxide magnetic material, and has excellent heat resistance, can be mixed while the oxide magnetic material is still at a high temperature after pulverization. And is excellent in shielding the magnetic powder from water and carbon dioxide after pelletization, which is preferable.

Water content is not particularly limited in ordinary thermoplastic resins other than hygroscopic resins such as polyamide. This is because the thermoplastic resin can be sufficiently removed below the melting point of the thermoplastic resin. On the other hand, in the case of a hygroscopic resin, a pretreatment for removing the absorbed moisture, such as hot air drying, is required.

The composition of the present invention comprises a thermoplastic resin and the above oxide magnetic powder, and the composition is not particularly limited, but 100 to 1900 parts of the oxide magnetic powder per 100 parts of the thermoplastic resin. It is preferably used in the composition containing it.

The composition of the present invention may include any one other than the oxide magnetic powder and the thermoplastic resin as long as the gist of the present invention is not impaired. For example, glass fiber,
Carbon fiber, potassium titanate, asbestos, silicon carbide,
Fibrous reinforcing agents such as ceramic fibers, metal fibers and silicon nitride; barium sulfate, calcium sulfate, kaolin, clay, bentonite, serinite, zeolite, mica,
Mica, nepheline sinite, talc, atalpulgite, wollastonite, calcium silicate, calcium carbonate, magnesium carbonate, dolomite, antimony trioxide, zinc oxide, molybdenum disulfide, graphite, gypsum, glass beads, glass balloons, quartz powder Inorganic substances such as fused silica and crystalline silica; polyamide, polyether ether ketone, polyethylene, polyethylene terephthalate,
Polybutylene terephthalate, wholly aromatic polyester,
Polyoxymethylene, polyoxyethylene, polystyrene, polycarbonate, polyether sulfone, polysulfone, polyphenylene ether, polyarylate,
Thermoplastic resins such as polyetherimide, polyamideimide, polymethylpentene and their modified products; thermosetting resins such as epoxy resins, polydiallyl resins, silicone resins; processing aids for mold release agents, antioxidants, UV absorbers, etc. An agent is illustrated.

The melt-kneaded composition is hot cut,
It is formed into a pellet shape by a known pelletizing method such as a mist cut method or a strand cut method.

[0022]

EXAMPLES First, methods for measuring physical properties shown in Examples will be described. (Measurement method of water content) The measuring device is Hiranuma Trace Moisture Measuring Device A
A Q-5 type was used, and a sample amount of 1 g was weighed and measured.

(Method of measuring carbon dioxide generation amount) 100 ml
20 mg of magnetic substance powder is put into a combustion tube, heated in an electric crucible furnace at 400 ° C. for 2 hours in nitrogen gas, and further, a generated gas is collected through a calcium chloride tube. Then, the evolved gas was introduced into a gas chromatograph (GC-7A manufactured by Shimadzu Corporation), and measured at a column temperature of 120 ° C. using a Unibeas C 60/80 mesh column. The gas used is helium and the flow rate is 50 ml.
/ Min. The detector is TCD and the injection volume is 0.5 ml.

(Measurement of Maximum Length and Minimum Length) From the pelletized composition remaining on the sieve, the pelletized composition was randomly selected from 128 pelletized compositions by a 5 mesh sieve to determine the maximum diameter and the minimum diameter. I asked.

[Example 1] A Ni-Zn-Cu ferrite was dried at 500 ° C for 6 hours and cooled. Its water content is 2
It was 10 ppm and the amount of carbon dioxide generated was 70 ppm. 17 kg of this ferrite and polyphenylene sulfide powder (using "W203" from Kureha Chemical Industry Co., Ltd.) 3
kg was stirred and mixed with a 20 L Hensyl mixer to obtain a mixture. Cylinder temperature of 280 ℃ ~ obtained mixture
It was rapidly supplied to a twin-screw extruder set at 340 ° C., and a pelletized composition was obtained by the mist cut method. The maximum diameter and the minimum diameter of the obtained pelletized composition are each 4 m
m was 3 mm. Table 1 shows the main configurations and effects together with other examples and comparative examples.

[0026]

[Table 1]

[Example 2] Ni-Zn-Cu type ferrite was used in place of the ferrite of Example 1, and the temperature was 500 ° C.
It was dried for 6 hours and cooled. The water content was 210 ppm and the amount of carbon dioxide generated was 210 ppm. Otherwise, when pellets were prepared in the same manner as in Example 1, the maximum diameter and the minimum diameter were 4 mm and 3 mm, respectively.

[Example 3] Ni-Zn-Cu type ferrite was used in place of the ferrite of Example 1, and the temperature was 600 ° C.
It was dried for 6 hours and cooled. Its water content is 150ppm,
The amount of carbon dioxide generated was 160 ppm. Otherwise, when pellets were prepared in the same manner as in Example 1, the maximum diameter and the minimum diameter were 4 mm and 3 mm, respectively.

[Embodiment 4] Instead of the ferrite of Embodiment 1, the water content is 1300 ppm and the amount of carbon dioxide generated is 45.
Ni-Zn-Cu ferrite of 0 ppm was heated in an electric furnace at a temperature of 700 ° C for 6 hours. The ferrite before heat treatment is the same as the ferrite of Comparative Example 1 described later. The water content after cooling the ferrite and the amount of carbon dioxide generated after the heat treatment were 200 ppm and 20 p, respectively.
pm. After cooling the ferrite after the heat treatment, pellets were prepared immediately in the same manner as in Example 1. Other than that, when pellets were prepared in the same manner as in Example 1, the maximum diameter and the minimum system were 4 mm and 3 mm, respectively.

[Comparative Example 1] As a result of leaving the ferrite of Example 1 after firing without performing the heat treatment of the present invention, the water content was 1300 ppm and the carbon dioxide generation amount was 450 ppm. Example 1 was repeated except that Ni-Zn-Cu based ferrite was used.
The maximum diameter and the minimum diameter were 8 mm and 2 mm, respectively. The firing temperature of ferrite was 1150 ° C.

COMPARATIVE EXAMPLE 2 Instead of the ferrite of Example 1, after firing, it was left without being subjected to the heat treatment of the present invention. As a result, the water content was 900 ppm and the amount of carbon dioxide generated was 500 ppm. When the same procedure as in Example 1 was carried out except that Ni—Zn—Cu ferrite was used, the maximum diameter and the minimum diameter were 7 mm and 2 mm, respectively.

COMPARATIVE EXAMPLE 3 Instead of the ferrite of Example 1, after firing, it was left without being subjected to the heat treatment of the present invention, and as a result, the water content was 1200 ppm, and the amount of carbon dioxide generated was 200 ppm. Example 1 was repeated except that Ni-Zn-Cu based ferrite was used.
The maximum diameter and the minimum diameter were 6 mm and 2 mm, respectively.

[Comparative Example 4] As a result of leaving the ferrite of Example 1 without heat treatment according to the present invention, Ni-Zn having a water content of 220 ppm and a carbon dioxide generation amount of 600 ppm. When the same procedure as in Example 1 was carried out except that a Cu-based ferrite was used, the maximum diameter and the minimum diameter were 7 mm and 2 mm, respectively.

[0034]

The water and carbon dioxide generated from the metal oxide powder are generated even at a temperature above the melting point of the thermoplastic resin, so these are sucked from the kneader unless something like the present invention is used. However, it cannot be sufficiently removed, but in the case of the present invention, there is little variation in the shape of the pellet, and it is more preferable to use an operation such as suction from the kneader together. According to the present invention, a magnetic material composition pellet having a substantially uniform shape having a maximum diameter within twice the minimum diameter can be obtained.

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Claims (5)

[Claims] 1. An oxide magnetic powder having a water content of 1000 ppm or less and a carbon dioxide generation amount of 400 ppm or less when heated in nitrogen at 400 ° C. for 2 hours is kneaded with a thermoplastic resin to form pellets. A method for producing a pellet of a magnetic resin composition, comprising: 2. The method for producing a magnetic resin composition pellet according to claim 1, wherein 100 to 1900 parts of the oxide magnetic powder is contained in 100 parts of the thermoplastic resin. 3. The oxide magnetic substance powder is heated at a temperature higher than the kneading temperature by 20 ° C. or more and lower than the firing temperature of the magnetic substance prior to the kneading with the thermoplastic resin. Item 1. A method for producing a pellet of a magnetic resin composition according to item 1 or 2. 4. Prior to kneading the oxide magnetic powder with the crystalline thermoplastic resin, at a temperature higher than the crystal melting point of the crystalline thermoplastic resin by 100 ° C. or more and lower than the firing temperature of the magnetic material. Claim 1 or claim 2 which has been heated
Of the magnetic resin composition pellets according to claim 1. 5. Prior to kneading the oxide magnetic powder with the amorphous thermoplastic resin, a temperature higher than the glass transition temperature of the amorphous thermoplastic resin by 150 ° C. or more and lower than the firing temperature of the magnetic material. The method for producing the magnetic resin composition pellet according to claim 1 or 2, which is heated at the temperature of.