JPH06132692A - Noise absorber and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a noise absorber which is flexible and can be cut into an appropriate length to be used by composing that noise absorber of a complex magnetic layer formed of a soft-magnetic ferrite powder and a thermoplastic polymer and a protective layer formed of a heat shrinking sheet or heat shrinking tube. CONSTITUTION:To 100wt.% low-density polyethylene, 5wt.% carbon black, 1.5wt.% of dicumyl peroxide are added, mixed and molded. Then the molded item is heated at 140 deg.C for 20 minites to effect bridging process. Thereafter it is heated to 160 deg.C and expanded to obtain a heat shrinking sheet 1. Then, to an Ni-Zn ferrite calsined powder, etylene-vinyl acetate copolymer in which content of vinyl acetate is 14% is mixed as a space factor of powder becomes 65% to obtain a mixture 2. The mixture 2 is applied to the heat shrinking sheet 1 and thus a noise absorber 3 is obtained. Accordingly, this absorber can be cut into a desired length easily by a simple cutting jig.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise absorbing device mounted on an input / output cable of an electronic device for use.

[0002]

2. Description of the Related Art In an electronic device such as a measuring instrument, various problems are caused by noise entering through an input / output cable or noise radiated from the device to the outside through the input / output cable. In order to absorb and remove this on the input / output side of the electronic device, for example, as shown in FIG. 1, a tubular noise absorbing device made of a magnetic material such as ferrite is attached to the input / output cable of the electronic device.

[0003]

Among the noises of electronic equipment, a cable routing portion is a major one of the noise generating portion and the portion easily affected by the outside (the weak portion to the noise). The noise generation level and the tolerance level in such a part are often unknown at the time of designing a device, and various noise tests are often performed on an actual machine, and countermeasures and treatments thereof are often applied.

In this case, noise countermeasures are taken by mounting the above-described noise absorbing device having various impedance-frequency characteristics according to the noise level.
When a ferrite magnetic material is used, the factor that determines the frequency band is the frequency characteristics of the permeability μ and the complex permeability μ ″ of the ferrite itself, and the impedance level is the It is determined by the cross-sectional area of the magnetic path of the body and the length of penetration, ie the length of the tube.

Since the conventional noise absorbing device is formed of a tube having a constant length as described above, its impedance is constant, and if one absorbing device is insufficient, it is additionally mounted. There must be. Therefore, the impedance value takes a discrete value, and it is not always possible to mount the one having an appropriate length. For this reason, there is a method of preparing and placing absorbing devices of various lengths and appropriately using them, but it is inefficient in terms of workability and economy.

Most of the ferrite magnetic bodies used in the conventional noise absorbing device are provided as sintered bodies, but they are poor in flexibility as compared with cables, which is a hindrance in routing.

The present invention provides a noise absorbing device for solving the problems of the conventional absorbing device.

[0008]

The noise absorbing device of the present invention comprises a composite magnetic layer made of soft magnetic ferrite powder and a thermoplastic polymer, and a protective layer made of a heat-shrinkable sheet or a heat-shrinkable tube. It is characterized by

According to the noise absorbing device of the present invention,
The occupation ratio of the ferrite powder in the composite magnetic layer is 30 to 80% of the whole mixture for the composite magnetic layer.

Further, according to the noise absorbing device of the present invention, the protective layer is made of polyolefin, polysiloxane,
It is configured to include any one of polyvinyl chloride.

Further, according to the noise absorbing device of the present invention, the thermoplastic polymer of the composite magnetic layer is configured to contain an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5% by weight or more. There is.

Further, the thermoplastic polymer of the composite magnetic layer may be configured to include an ethylene-ethyl acrylate copolymer having an ethyl acrylate content of 5% by weight or more.

Further, the thermoplastic polymer of the composite magnetic layer comprises ethylene-containing methacrylic acid having a content of 5% by weight or more.
You may comprise so that a methacrylic acid copolymer may be included.

Further, the thermoplastic polymer of the composite magnetic layer may be constituted so as to include a polymer composed of a monomer composed of a salt of acrylic acid or methacrylic acid and a divalent metal ion, and another monomer. Good.

In the method of manufacturing a noise absorbing device according to the present invention, the protective layer is obtained by subjecting the protective layer to a molding treatment, a crosslinking treatment and a stretching treatment in advance, and then applying the composite magnetic layer to the protective layer.

In the method for manufacturing a noise absorbing device according to the present invention, the protective layer and the composite magnetic layer are integrally molded, and only the protective layer is crosslinked, and then the molded body is stretched. It is obtained by applying.

[0017]

EXAMPLES Examples of the present invention will be described below. First, as a first embodiment, a method for manufacturing a noise absorbing device containing a polyolefin in a protective layer and an ethylene-vinyl acetate copolymer in a thermoplastic polymer will be specifically described.

To 100 parts by weight of low-density polyethylene having a number average molecular weight of about 210,000, 5 parts by weight of carbon black and 1.5 parts by weight of dicumyl peroxide were added,
The mixture is kneaded using a biaxial kneading roll to obtain a mixture for the protective layer. This mixture is molded into the shape shown in FIG. 1 using a steam press. Next, by heating at 140 ° C. for 20 minutes, the molded body is subjected to a cross-linking treatment, this molded body is heated to 160 ° C., stretched to a length of 4 times in the direction of the arrow in FIG. 1, and then cooled to room temperature. Then, the heat shrinkable sheet 1 is obtained.

Next, Ni--Zn having an average particle size of 0.35 μm
The content of vinyl acetate is 14 with respect to the calcined ferrite powder.
%, An ethylene-vinyl acetate copolymer having a number average molecular weight of about 100,000 was mixed so as to have a powder space factor of 65%, and the mixture was kneaded using a biaxial kneading roll to obtain a composite. A mixture 2 for the magnetic layer is obtained.

As shown in FIG. 2, the mixture 2 is applied to the heat shrinkable sheet 1 to obtain the noise absorbing device 3.

Further, the noise absorbing device 3 is connected to the cable 4
After it is wrapped around, it is heated and shrunk using a hair dryer or the like, and both ends of the noise absorbing device 3 are fixed with clips 5.
It is mounted and fixed in the state shown in FIG.

Next, as a second embodiment, a method for manufacturing a noise absorbing device containing polyvinyl chloride in the protective layer and ethylene-ethyl acrylate copolymer in the thermoplastic polymer will be specifically described.

100 parts by weight of vinyl chloride having a number average molecular weight of about 140,000, 40 parts by weight of trioctyl trimellitate as a plasticizer, 1.5 parts by weight of trimethylolpropane triacrylate as a crosslinking aid, and carbon black 5 as a colorant. A mixture of parts by weight is kneaded using a biaxial kneading roll to obtain a mixture for a protective layer. Next, the heat-shrinkable sheet 1 is obtained in the same manner as in the first embodiment described above (see FIG. 1).

Next, ethylene-ethyl acrylate having a content of ethyl acrylate of 17% and a number average molecular weight of about 110,000 with respect to the calcined powder of Ni-Zn ferrite having an average particle size of 0.41 μm. The copolymer has a powder space factor of 70.
% To be mixed, and the mixture is kneaded using a biaxial kneading roll to obtain a mixture 2 for the composite magnetic layer. Next, the noise absorbing device 3 is obtained and fixed to the cable 4 by the same method as in the first embodiment (see FIG. 2).

Next, as a third embodiment, a method of manufacturing a noise absorbing device in which the protective layer contains polysiloxane and the thermoplastic polymer contains ethylene-methacrylic acid copolymer will be specifically described.

To 100 parts by weight of polydimethylsiloxane containing 5% by weight of vinylmethylsiloxane and having a number average molecular weight of about 240,000, 1.5 parts by weight of tylper oxide was added and kneaded using a biaxial kneading roll. A mixture for the protective layer is obtained. This mixture is molded into the shape shown in FIG. 1 by using an electrothermal press. Next, the heat-shrinkable sheet 1 is heated at 180 ° C. for 20 minutes to subject the molded body to a crosslinking treatment, heated to 180 ° C., stretched in the direction of the arrow in FIG. 1, and then cooled to room temperature. To get

Next, 11% by weight of methacrylic acid was added to the same calcined powder of Ni-Zn ferrite of 0.35 μm as used in the first embodiment, and the number average molecular weight was about 110,
000 ethylene-methacrylic acid copolymers were mixed so as to have a powder space factor of 65%, and the mixture was kneaded using a biaxial kneading roll to obtain a mixture 2 for the composite magnetic layer.

The mixture 2 was applied to the heat shrinkable sheet 1 as shown in FIG. 2 to obtain a noise absorbing device 3.

Furthermore, after the noise absorbing device 3 is wound around the cable 4, it is heated and shrunk by using a hair dryer or the like, and both ends of the noise contracting device 3 are fixed with the clips 5 and mounted and fixed in the state shown in FIG. .

Next, as a fourth embodiment, the protective layer is
The thermoplastic polymer includes any one of those used in the above-mentioned first to third embodiments, wherein the thermoplastic polymer contains a monomer of a salt of acrylic acid or methacrylic acid and a divalent metal ion, and other monomers. A method for manufacturing the noise absorbing device containing the polymer will be specifically described.

The heat shrinkable sheet 1 is obtained in the same manner as in the case of any one of the first, second and third embodiments.

A number average molecular weight of about 9 consisting of 35 mol% of magnesium methacrylate and 65 mol% of butyl methacrylate.
50,000 copolymers and the same 0.35 μm Ni—Zn-based ferrite calcined powder used in the first example,
A mixture 2 for a composite magnetic layer is obtained by kneading a mixture of powders having a space factor of 65% using a biaxial kneading roll.
To get Next, the noise absorbing device 3 is obtained and attached and fixed to the cable 4 by the same method as in the first embodiment described above (FIG. 2).
See).

In the noise absorbing device formed of the mixture of the protective layer and the mixture of the composite magnetic layers, polyolefin, polysiloxane, polyvinyl chloride,
On the other hand, as the composite magnetic layer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-
A methacrylic acid copolymer, a monomer composed of a salt of acrylic acid or methacrylic acid and a divalent metal ion, and a polymer composed of another monomer are considered. As for the combination of the protective layer and the composite magnetic layer, a total of 3 × 4 = 12 patterns are possible with three kinds of protective layers and four kinds of composite magnetic layers, and similar effects can be obtained.

Further, in FIG. 5, each mixture having any one of the above-mentioned 12 patterns is separately extrusion-molded into a cylindrical shape by using two extruders. This two-layer extruded product is irradiated with an electron beam to carry out a crosslinking treatment. As a result, only the protective layer is crosslinked. further,
This two-layer extruded product was heated to 210 ° C. with an infrared heater, stretched until the diameter doubled by pressurizing it with compressed air, and immediately cooled to room temperature. Obtain tube 6. When it is manufactured by such a method, it can be manufactured to an infinite length, and each time, it can be cut to an appropriate length and used, so that waste can be eliminated.

[0035]

According to the noise absorbing device of the present invention, it is possible to easily obtain the required length with a simple cutting jig such as a knife, the flexibility is high, and noise countermeasures are required. Can be attached in close contact with the part.

Further, according to the noise absorbing device obtained by using the extrusion molding machine, a product of substantially infinite length can be obtained due to the characteristic of the manufacturing method, and it is possible to reduce the waste of the product.

[Brief description of drawings]

FIG. 1 is a perspective view showing a molded body for a protective layer in a noise absorbing device of the present invention.

FIG. 2 is a perspective view showing an embodiment of the noise absorbing device of the present invention.

FIG. 3 is a perspective view showing a state in which the noise absorbing device of the present invention is attached to a cable.

FIG. 4 is a cross-sectional view showing another embodiment of the noise absorbing device of the present invention.

FIG. 5 is a perspective view showing a structure of a conventional noise absorbing device.

[Explanation of symbols]

 1 Heat Shrinkable Sheet (Protective Layer) 2 Compound for Composite Magnetic Layer 3,6 Noise Absorber 4 Cable 5 Clip for Fixing

Claims (9)

[Claims] 1. A noise absorbing device comprising a composite magnetic layer made of soft magnetic ferrite powder and a thermoplastic polymer, and a protective layer made of a heat-shrinkable sheet or a heat-shrinkable tube. 2. The noise absorbing device according to claim 1, wherein the occupation ratio of the ferrite powder in the composite magnetic layer is 30 to 80% of the whole mixture for the composite magnetic layer. . 3. The noise absorbing device according to claim 1, wherein the protective layer contains any one of polyolefin, polysiloxane, and polyvinyl chloride. apparatus. 4. The noise absorbing device according to claim 1, wherein the thermoplastic polymer of the composite magnetic layer comprises an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5% by weight or more. A noise absorbing device including a united body. 5. The noise absorbing device according to claim 1, wherein the thermoplastic polymer of the composite magnetic layer has an ethylene-ethyl acrylate content of 5 wt% or more of ethyl acrylate. A noise absorbing device comprising a copolymer. 6. The noise absorbing device according to claim 1, wherein the thermoplastic polymer of the composite magnetic layer comprises ethylene-methacrylic acid copolymer having a methacrylic acid content of 5% by weight or more. A noise absorbing device including a united body. 7. The noise absorbing device according to claim 1, wherein the thermoplastic polymer of the composite magnetic layer is a monomer composed of a salt of acrylic acid or methacrylic acid and a divalent metal ion. And a polymer composed of other monomers. 8. A method of manufacturing a noise absorbing device comprising a composite magnetic layer comprising soft magnetic ferrite powder and a thermoplastic polymer, and a protective layer comprising a heat-shrinkable sheet or a heat-shrinkable tube. A method for manufacturing a noise absorbing device, wherein the composite magnetic layer is applied to the protective layer after the layer has been subjected to a molding treatment, a crosslinking treatment and a stretching treatment in advance. 9. A method of manufacturing a noise absorbing device, comprising: a composite magnetic layer comprising soft magnetic ferrite powder and a thermoplastic polymer; and a protective layer comprising a heat shrinkable sheet or a heat shrinkable tube. Layer and the composite magnetic layer are integrally molded, and after subjecting only the protective layer to a crosslinking treatment,
A method for manufacturing a noise absorbing device, wherein the molded body is subjected to a stretching treatment.