JPS5854488B2 - ferrite composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improved ferrite compositions, and more particularly to compositions comprising polyalkylene terephthalate and ferrite.

Ferrite has magnetic properties and radio wave absorption properties, and by utilizing these properties, it is applied to, for example, magnets and radio wave shielding materials.

However, in order to mold ferrite itself into a specific shape, it is usually sintered using a powder metallurgy method and must be molded at high temperature and high pressure.

That is, a large amount of thermal energy is expended due to long-time molding at high temperatures, and if dimensional accuracy is required due to shrinkage in the firing process, it is necessary to polish the harder ceramic blade.

Furthermore, yield defects such as chips and cracks occur, which impairs mass productivity, which is a major drawback.

In order to improve these drawbacks, many methods have been proposed in which ferrite is contained in rubber or thermosetting or thermoplastic resin and a ferrite composition is molded according to general molding methods.

Among these, when a thermoplastic resin is used as the matrix of the ferrite composition, the molding cycle by injection molding can be shortened and objects with complicated shapes can be easily molded.

Conventionally, polyvinyl chloride and the like have been used as this type of thermoplastic resin, and there are examples that have actually been put into practical use as plastic magnets, but there have been problems with heat resistance etc., which has limited its use.

In order to overcome these problems, the present inventors & L focused on the excellent properties of polyethylene terephthalate, such as heat resistance, electrical properties, and high melt fluidity, and as a result of studying the use of polyethylene terephthalate as a matrix, the above-mentioned In order to maximize the characteristics of ferrite, it is preferable to use a composition with as high a ferrite content as possible, but in that case, the problem of low thermal shock resistance of the molded product formed from the iron composition becomes a problem. I found out.

That is, when a molded product is suddenly exposed to a low temperature or high temperature state from a high temperature or low temperature state, cracks occur on the surface of the molded product, and especially when the molded product is thin, phenomena such as fracture tend to occur.

This phenomenon occurs when the content of ferrite in the composition is 5.
This phenomenon is particularly likely to occur when the ferrite content is 0% or more, and it tends to become more pronounced as the ferrite content increases.

This phenomenon is probably caused by the difference in linear expansion coefficient between polyethylene terephthalate and ferrite, and it is presumed that the difference in volume change between polyethylene terephthalate and ferrite due to rapid temperature changes causes electric heating.

Therefore, when polyethylene terephthalate is used as a ferrite matrix, if the ferrite content is increased in order to more efficiently express the magnetic properties or radio wave absorption properties of ferrite, the thermal shock resistance of the molded product will inevitably increase. The properties of polyethylene terephthalate deteriorate, and as a result, the range of applications of the composition under high-temperature conditions is considerably restricted, and as a result, the properties of polyethylene terephthalate, which has excellent heat resistance, are not fully utilized.

As a result of further intensive studies to overcome this problem, the present inventors found that a specific composition consisting of polyalkylene terephthalate, particularly polyethylene terephthalate, a polyepoxy compound, and ferrite has excellent moldability and improved thermal shock resistance. The present invention has been achieved based on the discovery that a molded article having the following properties can be provided.

That is, the present invention uses 100 parts by weight of polyalkylene terephthalate, 0.5 to 10 parts by weight of polyepoxy compound, and ferrite, particularly of the general formula IVfO-nFe203 (where M is a divalent metal atom and n is a number of 1 or more). It relates to a ferrite composition consisting of 100 parts by weight to 1000 parts by weight of ferrite represented by:

The polyalkylene terephthalate used in the present invention is polymerized using terephthalic acid or an ester-forming derivative of terephthalic acid as the acid component and an alkylene glycol having 2 to 6 carbon atoms or an ester-forming derivative of the alkylene glycol as the glycol component. refers to polymers that have been

The ester-forming derivatives of terephthalic acid include lower alkyl esters, aryl esters,
Examples include acid halides and the like.

In addition, alkylene glycols include ethylene glycol, propylene glycol, tetramethylene glycol,
Examples include hexamethylene glycol.

Among these, ethylene glycol is particularly preferred.

Furthermore, examples of the ester-forming derivative of alkylene glycol include lower fatty acid esters of the alkylene glycol, ethylene oxide, and the like.

It is preferable that one type of glycol component accounts for 80 moles or more of the glycol component.

Further, the acid component or glycol component of the polyalkylene terephthalate may be copolymerized with other types of dicarboxylic acids or other types of glycols, each of which has a mole or less of 20 or less.

Examples of such other copolymerization components include isophthalic acid, naphthalene-2,6-dicarboxylic acid, adipic acid,
trimethylene glycol, tetramethylene glycol,
neopentyl glycol, hexamethylene glycol,
Diethylene glycol, cyclohexanediol, 1.
4-bisoxyethoxybenzene, bisphenol-A
etc.

The intrinsic viscosity of polyalkylene terephthalate (when measured at 35°C using a dichlorophenol solvent, is 0.35 or more, more preferably in the range of 0.35 to 2.01, especially in the range of 0.5 to 1.5) This is desirable.

In particular, in the case of polyethylene terephthalate, its intrinsic viscosity is preferably in the range of 0.35 to 1.0, more preferably 0.5 to 0.8.

For example, if polyethylene terephthalate with an intrinsic viscosity of less than 0.35 is used, the strength of the molded product of the obtained composition will be low, making it impractical, while on the other hand, if polyethylene terephthalate with an intrinsic viscosity of more than 1.0 is used, At times, the fluidity of the composition deteriorates, and conversely, if you try to increase the fluidity, you must necessarily reduce the amount of ferrite in the composition, and as a result, the characteristics of ferrite cannot be fully expressed. This is not desirable because it will cause a condition.

If polyethylene terephthalate having a higher intrinsic viscosity is used, the resulting molded product will lose its glossy appearance, which may be considered a fatal defect depending on the application, so care must be taken.

The polyepoxy compound used in the present invention is a compound having at least two epoxy groups in the molecule,
For example, bisphenol-A type epoxy compounds obtained by reacting bisphenol-A and epichlorohydrin, novolac type epoxy compounds obtained from novolak resin and epichlorohydrin, aromatic carboxylic acid type epoxy compounds obtained from aromatic carboxylic acids and epichlorohydrin, fatty acids, etc. Aliphatic ether type epoxy compounds obtained from glycols (e.g. ethylene glycol, phlopylene gelylcol, diethylene glycol, etc.) and glycerin, fatty acids (e.g. succinic acid, maleic acid, adipic acid,
Examples include aliphatic ester-type epoxy compounds obtained from aliphatic esters (sebacic acid, etc.), and alicyclic compound-type epoxy compounds obtained from alicyclic compounds (for example, cyclohexene, dicyclopentadiene, cyclopentadiene, etc.).

Among these polyepoxy compounds, jepoxy compounds are preferred, and particularly preferred compounds include bisphenol A type epoxy compounds, diglycidyl ethers of low molecular weight polyethylene glycol, and diglycidyl esters of aromatic carboxylic acids.

The amount of the polyepoxy compound added is 0.5 to 10 parts by weight based on 100 parts by weight of polyalkylene terephthalate in the composition.
Parts by weight.

If the amount added is less than 0.5 parts by weight, the effect of improving the thermal shock resistance of the molded product will be weak, and if it exceeds 10 parts by weight, partial gelation will occur during melt molding, resulting in poor melt flowability of the composition. The appearance of the obtained molded product tends to deteriorate, and the physical properties also deteriorate.

The ferrite used in the present invention is a solid solution of Fe2O3 and a metal oxide, and includes both so-called hard magnetic ferrite and soft magnetic ferrite.

A preferable ferrite has the general formula MO-nF
Examples include ferrite represented by e203 (where M is a divalent metal atom and n is a number of 1 or more).

The metal atom of M in the general formula is M n e F e
x N 1sCu, Mg, Co, ZntPb, Ba,
Examples include Sr.

Also, n is 6 when M is Pb, Ba, and Sr;
n s F e x N 1 s Cu s Mg
In the case of sCo and Zn, the number is preferably 1.

The amount of ferrite used is 100 to 1000 parts by weight per 100 parts by weight of polyalkylene terephthalate.

If the amount used is less than 100 parts by weight, it will not be possible to obtain a molded product that can effectively take advantage of the magnetic properties or radio wave shielding properties of ferrite, and if it is more than 1000 parts by weight, the fluidity of the composition during molding will be impaired. This is undesirable because not only does it become impossible to mold depending on the shape, but also the dispersion of ferrite in the molded product becomes poor, resulting in uneven properties and further loss of elasticity and flexibility.

In the present invention, there is no particular restriction on the means for blending each component, and any method can be used.

Generally, it is preferable to disperse these ingredients more uniformly, and it is preferable to mix and homogenize the raw material mixture using, for example, a blender, kneader, co-kneader, roll, or extruder.

The most common method is to melt and knead the ingredients in a heated extruder, homogenize them, extrude them into wires, and then cut them into pellets.

The ferrite composition thus produced is usually kept sufficiently dry before being subjected to molding.

Additionally, this composition can be processed by injection molding, extrusion molding, compression molding,
It can be easily molded by any method such as calenthane molding.

At this time, it is not necessary to particularly heat the mold temperature, but in the case of polyethylene terephthalate, molding in a mold preheated to 120 to 150°C will yield a molded product with excellent gloss in appearance.

The ferrite composition of the present invention has new characteristics not found in conventional ferrite compositions, such as vinyl chloride-based ferrite compositions, and is expected to be used in a wide range of applications.

For example, when hard magnetic ferrite is used as the ferrite, it is possible to manufacture molded products such as TV cathode ray tube centering magnets, various micro motor magnets, and magnets for reed switch operation, and when soft magnetic ferrite is used, deflection yokes, It is possible to manufacture magnetic cores for various uses such as intermediate frequency transformers, M-tuned coils, and high-frequency tie yokes, as well as molded products such as covers and shielding plates for the purpose of shielding electromagnetic waves.

Further, other additives can be added to the composition of the present invention within a range that does not impair its purpose.

The present invention will be described in detail below with reference to Examples.

Examples 1 to 5 and Comparative Examples 1 to 4 Preparation of ferrite ■: Manganese carbonate, zinc white, and iron oxide were used, and the composition ratio (molar ratio) of ferrite was MnO: 25, ZnO:
20. The mixture was weighed so as to have a ratio of Fe2O3:55, and mixed in a ball mill for about 4 hours in ethanol.

The resulting mixture was pre-pressed, calcined in the air at 1050° C. for 2 hours, and then rapidly cooled.

After coarsely crushing the obtained calcined product, it was again subjected to a 16-hour ball mill in ethanol, resulting in approximately 70 oKI! The molded product was molded under a pressure of /cd, fired in the air at 1300° C. for 2 hours, and then rapidly cooled.

The ferrite fired product thus obtained was ground in a stang mill to obtain ferrite powder with an average particle size of 150 μm.

Adjustment of ferrite ■: 9. to BaCO310. FezO345Ky was mixed in a Henschel mixer for 2 minutes, and then heated in an electric furnace at 1100 °C.
Barium ferrite was produced by heating at ℃ for 1 hour.

9 to 52 kg of the barium ferrite rough lump and 20 kg of water
The mixture was placed in an attritor pulverizer containing 200 to 11 J diameter steel balls for pulverization, and pulverized at 250 rpm for 6 hours.

A slurry containing pulverized barium ferrite powder was dried at 180°C in a hot air dryer, and then annealed at 1000°C for 1 hour in an electric furnace with an elevator set.

120 in advance with the above ferrite ■ or ferrite ■
Polyethylene terephthalate powder (36 mesh or more) dried at ℃ for 5 hours and a polyepoxy compound were mixed in a tumbler at the compounding ratio shown in the table, and then heated at a cylinder temperature of 270℃ using an extruder with a screw diameter of 3011IJILφ. The mixture was melted and mixed at ℃, and the thread coming out of the die was cooled and cut to obtain pellets for molding.

After drying the pellets in a hot air dryer at 130°C for 5 hours, they were molded into a 3-ounce injection molding machine at a cylinder temperature of 270°C.
℃, injection pressure 800Kti/crL, whole mold temperature 140℃,
A 10 cm square plate with a thickness of 5 U was molded under conditions of a cooling time of 20 seconds.

In addition, for the purpose of comparatively testing the thermal shock resistance of this molded product, the square plate was cut into short strips of 2 cIIL x 10 cIL to prepare test pieces for thermal shock resistance.

The thermal shock resistance test was conducted under the following conditions.

That is, the test piece of scissors was placed in a dryer set at 200°C or 250°C, left for 30 minutes, and then taken out of the dryer. for 5 seconds and visually observe the state of electric heat generation on the surface.

For the test pieces for which no cracks were observed on the surface under these conditions, the same test was repeated three times.

These results are summarized in Table 1 below.

In addition, when the intrinsic viscosity of the resin components of the molded products of Example 1 and Comparative Example 1 was measured at 35°C in an orthochlorophenol solution, they were 0.76 and 0.76, respectively.
It was 55.

Comparative Examples 5 to 7 Molded articles were obtained in the same manner as in Example 1, except that methyl oleate, tri-n-butylamine, or epichlorohydrin was used instead of Epikote #815 in Example 1. We conducted an impact resistance test on
In addition, the intrinsic viscosity of the resin component of the molded product was measured.

These results are shown in Table 2.

From the results in the above table, it is clear that the excellent thermal shock resistance of the present invention is due to the use of a compound having at least two epoxy groups in the molecule.

Claims (1)

[Claims] 1 100 parts by weight of polyalkylene terephthalate, 0.5 to 10 parts by weight of polyepoxy compound, and 10 parts by weight of ferrite
A ferrite composition comprising 0 to 1000 parts by weight. 2. The ferrite according to claim 1, wherein the ferrite is at least one type of ferrite represented by the general formula % (where M is a divalent metal atom and n is a number of 1 or more). Composition.