JPS63182698A - Composition for preventing acoustic resonance and acoustic resonance preventing molded product - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention ■ Background Technical Field of the Invention The present invention relates to a composition for preventing acoustic resonance used in audio equipment such as a speaker box, a speaker back chamber, a record player housing, a turntable for a record player, and a case for a cassette recorder. The present invention relates to a molded body for preventing acoustic resonance, such as a housing for an audio device, molded from this composition.

Prior Art and Its Problems Wood-based materials, resins, fiber-reinforced resins, metals, and the like have conventionally been used for housings for audio equipment such as speaker boxes, record player housings, and cassette recorder cases.

However, when resin or fiber-reinforced resin is used, it is superior in terms of moldability and weight reduction, but because of its light weight, it has the disadvantage of being susceptible to resonance and being susceptible to external vibrations. When wood-based materials are used, internal loss is large and unnecessary resonance can be suppressed, but there are problems such as laborious assembly and high costs.

In addition, when metals such as aluminum are used, the density is high and the Young's modulus is small, so when used as the surrounding material of a speaker, the sound velocity becomes low. There are problems in that it is difficult to remove it from the outside, and because the resonance acuity (Q) value is large, high-frequency resonance cannot be sufficiently attenuated, and resonance is likely to occur at specific frequencies. Furthermore, there were cases where sufficient mechanical strength could not be obtained.

In order to deal with such problems, synthetic resins such as polyethylene and polypropylene were kneaded with graphite powder, and casings for audio equipment were formed using this mixed wire material (Special Publication Publication No. 58-5
6316), a ceramic molded body using thermosetting resin or rubber as a binder (JP-A-55-79597), an acoustic product made by depositing fibrous metal pieces and then compressing them to bond them together. Material (Unexamined Japanese Patent Publication No. 57-79796)
etc. are disclosed.

However, graphite powder and synthetic resin have low Young's modulus and density, making it impossible to sufficiently prevent resonance, and ceramic molded bodies using binders are expensive, and the molding method is inefficient, resulting in cost problems. Also, because the density of compressed fibrous metal pieces deposited is low, even though they are suitable for speaker diaphragms, they cannot sufficiently suppress resonance in applications such as speaker boxes. Further improvements are desired.

■ Purpose of the Invention The purpose of the present invention is to provide a material that has good characteristics such as resonance sharpness, Young's modulus, density, and sound wave propagation characteristics, prevents acoustic resonance, has sufficient acoustic characteristics, and is advantageous in terms of processability and cost. An object of the present invention is to provide a composition for preventing acoustic resonance and a molded body for preventing acoustic resonance.

■ Disclosure of invention These objects are achieved by the invention described below.

That is, the first invention of the present invention is a composition for preventing acoustic resonance characterized by containing iron, an iron-based alloy, an iron-based oxide powder, and a polyolefin-based resin.

A second invention is a composition for preventing acoustic resonance, characterized by containing iron, an iron-based alloy, an iron-based oxide powder, a polyolefin resin, and a pigment.

A third invention is a molded article for preventing acoustic resonance, characterized in that a composition containing iron, an iron-based alloy, an iron-based oxide powder, and a polyolefin resin is molded and a coating layer is formed on the surface.

A fourth invention is a molded article for preventing acoustic resonance, characterized in that a composition containing iron, an iron-based alloy, an iron-based oxide powder, a polyolefin resin, and a pigment is molded, and a coating layer is formed on the surface. It is.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The composition for audio equipment, etc. of the present invention contains powder of iron, iron-based alloy, or iron-based oxide.

Examples of the iron powder include reduced iron powder and atomized iron powder.

In addition, various types of stainless steel powder, C
Examples include alloy steel powder containing r, Cu, Ni, Mo, V%Co, and the like.

These may be partially oxidized.

Further, examples of the iron-based oxide powder include various iron oxide powders.

The term "powder" as used herein broadly includes granules, flakes, fibrous materials, etc., and when it is necessary to increase the filling rate, granules or flakes are particularly preferred.

In the case of granules, the average particle diameter (d) is 10~tsoIj! f
i, especially preferably 50 to 100 voices.

The reason for having such an average particle size is that if d is less than 10, there will be problems in handling such as mixing and dispersing the filler with the resin, and if it exceeds 150, it will be difficult to use the extruder or injection molding when making a compound or injection molding. This is because damage may occur to the screw, housing, etc. of the molding machine.

In the case of flakes, the aspect ratio [average particle diameter (d)/average thickness 1)] is preferably 100 or less.

Such an aspect ratio is used because if d/l exceeds 100, a sufficient filling rate of the resin cannot be ensured.

In the case of a fibrous body, the value of average length 1)/average diameter (d) is 200 or less, usually 10 to 200, particularly 100 to 200.
It is preferable that

If this value (JZ/d) exceeds 200, the state of dispersion in the resin will become non-uniform, which is not preferable. Further, if it is less than 10, a sufficient filling rate to the resin cannot be ensured.

When using these powders, especially easily oxidizable iron powders, if oxidation is a problem, it is preferable to perform various surface treatments to prevent oxidation.

The composition for audio equipment, etc. of the present invention contains a polyolefin resin.

As the polyolefin resin, polypropylene and polyethylene are suitable, and these are usually homopolymers, but may be copolymers or modified products.

The polyolefin resin used may be in the form of a powder or a pellet, but in order to improve dispersibility, it is preferable to use a powder.

The content of iron, iron-based alloy, or iron-based oxide powder to be mixed with the polyolefin resin is 40 to 90 wt%, preferably 60 to 90 wt%.

This content is determined when the proportion of iron, iron-based alloy, or iron-based oxide powder is smaller than the above value.
This is because the density and Young's modulus are low, making it impossible to obtain the desired acoustic effect, and if the value exceeds the above value, the filler may not be sufficiently kneaded into the resin and a portion of the filler may separate.

Polyolefin resins such as polypropylene (PP) and polyethylene (PE) may be used alone or in combination as described above, but if necessary, polyolefin resins such as polymethyl methacrylate (PMMA) etc. may be used. It may be used by mixing with resin, and furthermore, butyl rubber, nitrile butadiene rubber (NBR), styrene butadiene rubber (S
A rubber material such as BR) may be added and mixed for use.

When mixed with other synthetic resins or rubber-based materials, the mixing ratio with iron, iron-based alloy, or iron-based oxide powder should be such that the content of these metal powders is as described above. In addition, the polyolefin resin may be replaced with a synthetic resin or a rubber material, and the mixing ratio of the polyolefin resin and other synthetic resin or rubber material may be determined as appropriate depending on the purpose.

The composition of the invention may further contain a pigment.

Examples of the pigment include various organic and inorganic pigments such as carbon black, phthalocyanine blue, cadmium pigment, red iron oxide, and titanium white.

Further, the amount of the pigment added is usually about 1 to 6 wt% of the total amount of iron, iron-based alloy, or iron-based oxide powder and the resin component.

When pigments are added in this way, it may not be necessary to paint. The effect of such pigment addition is remarkable when copper powder such as stainless steel is used. This is because it becomes possible to hide color unevenness due to powder orientation caused by injection molding, which will be described later.

The composition of the present invention further includes various stabilizers and dispersants (
For example, a silane coupling agent, a titanium coupling agent, etc.) may be included.

The molded body as a housing for an audio device or the like of the present invention is formed from the above-mentioned composition.

First, a powder of iron, an iron-based alloy, or an iron-based oxide, a polyolefin resin, a pigment, and, if necessary, additives such as a stabilizer and a dispersant are added, mixed, and kneaded.

Kneading may be performed using a kneading extruder, a pressure kneader, or the like.

The crosstalk composition thus obtained can be used to form various molded objects such as speaker boxes, record player housings, record player turntables, cassette recorder cases, voice coil bobbins, and other intended audio equipment casings. Various desired molded bodies are obtained. Although any method such as injection molding, compression molding, press molding, or cast molding may be applied to the molding, injection molding can be applied in the present invention and is advantageous in terms of manufacturing.

Furthermore, the molded product of the present invention is very effective when used as ceilings, walls, etc. of concert halls, listening rooms, etc. In this case, even if plywood or other materials are attached to the front and back surfaces of the molded body, it can be used satisfactorily.

The molded body formed from the composition of the present invention has a resonance sharpness (Q
) is 20 to 40, especially about 20 to 30, Young's modulus (E)
is approximately (4,0 to 9.0)xl 0 ION/m2, density (ρ) is approximately 19oO to 3000 Kg/m3, and sound velocity is approximately 140θ to 1800m5-', making it suitable for use in molded bodies for audio equipment, etc. Shows favorable properties.

Although the casing etc. can be of various shapes,
Its thickness is usually about 1 to 6 mm.

Further, the composition of the present invention can also be used as a magnetic shield in places where magnetic shielding is required, such as the back chamber of television speakers. In this case, the content of iron, iron-based alloy, or iron-based oxide powder mixed with the polyolefin resin is 50%
~90wt%, preferably 70-90wt% binding, iron,
The filling rate may be increased by increasing the proportion of iron-based alloy or iron-based oxide powder.

By using the composition of the present invention, there is no need to use a canceling magnet used in the back chamber of the speaker, and the screen and the speaker can be installed close to each other, allowing the speaker and the television to be made more compact.

The molded product of the present invention is preferably coated with various types of paint on its surface, subjected to two-color molding, laminated with other materials, or formed with various films on a portion of its surface.

In addition to improving the appearance, such a coating layer is effective in preventing oxidation, especially when oxidation of easily oxidizable iron powder is a problem. Particularly when producing a molded body by injection molding, it is preferable to provide a coating layer in a range including at least the gate position.

■Specific effects of the invention According to the present invention, since it contains iron, iron-based alloy, or iron-based oxide powder and polyolefin resin, it has high resonance sharpness, high rigidity, and high density, and also has excellent sound wave propagation characteristics. It is possible to obtain a composition for preventing acoustic resonance, such as for an audio device, and a molded body, such as a casing for an audio device, which has sufficient acoustic properties such as good performance and prevention of acoustic resonance.

It also has good processability, such as being able to be injection molded.
Since iron-based powder is used, it is also advantageous in terms of cost.

Furthermore, if a pigment is included in addition to the above components, there is no need for painting at all. Even if color unevenness occurs due to powder orientation due to molding, this can be concealed.

Furthermore, by forming a coating layer on the molded product, if oxidation prevention becomes a problem when using easily oxidizable powder, oxidation prevention can be achieved and appearance defects due to aging can be prevented. This is particularly effective when using easily oxidizable iron or alloy steel powder.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

Example 1 A flaky stainless steel powder (SUS304) having an average particle size of 30-1 and an average aspect ratio of 100 was mixed with 100 parts by weight of polypropylene in the proportions shown in Table 1 and kneaded using a kneading extruder.

The crosstalk composition thus obtained was injection molded to give a 150X
A plate of 150 x 3 mm was prepared and designated as samples 1 to 4.

Separately, Sample 5 made of only polypropylene was obtained for comparison.

Also, in sample 1, instead of stainless steel flakes,
Sample 6 was obtained using reduced iron powder with an average particle size of 50 particles.

Further, Sample 7 was obtained by replacing the stainless steel flakes in Sample 1 with graphite flakes.

Resonance sharpness (Q), Young's modulus (
E), density (ρ) and sound velocity (C) were investigated. The results are shown in Table 1.

From the results in Table 1, Samples 1 to 3 and 6 of the present invention have a high Young's modulus, a high specific gravity, good sound wave (longitudinal wave) propagation characteristics, and have a Q value that is lower than that of Sample 5, which is made only of polypropylene. You can see that it doesn't change.

On the other hand, in sample 4.5, although the Q value is small, the Young's modulus and specific gravity are low, indicating that it is insufficient for practical use.

Furthermore, it can be seen that Sample 6 has a large Q value and a small Young's modulus and specific gravity.

Next, using the same composition as each of these samples, a thickness of 4
A III+ speaker box was fabricated to form a 3-way speaker system. When a listening test was conducted using this speaker system, each sample 1 of the present invention
~3.6 was confirmed to exhibit extremely good acoustic characteristics.

On the other hand, as mentioned above, samples 4 and 5 have a small Young's modulus and specific gravity, and sample 6 has a large Q value and a small Young's modulus and specific gravity. -3 and 6, the acoustic properties were much poorer.

In addition, in sample 6, when the iron powder was replaced with AJZ powder, the Young's modulus was low, the Q value was large, and the results of the viewing test were also far inferior.

Example 2 Samples were prepared in the same manner as in Example 1, except that 2 wt% of carbon black was further added to Samples 1 to 3 and 6 (invention) of Example 1.

Each of these samples exhibited properties almost equivalent to those of Example 1.

Furthermore, there was no color unevenness due to powder orientation during injection molding.

Example 3 A 20-thick coating layer of acrylic paint was formed on the surface of Sample 6 of Example 1. This is designated as sample 6B.

When a salt spray test was conducted, in sample 6, the iron powder at the gate position was oxidized and red rust appeared, but in sample 6B, no oxidation occurred at all.

From the above, the effects of the present invention are clear.

Claims (4)

[Claims] (1) A composition for preventing acoustic resonance, characterized by containing iron, an iron-based alloy, an iron-based oxide powder, and a polyolefin resin. (2) A composition for preventing acoustic resonance, characterized by containing iron, an iron-based alloy, an iron-based oxide powder, a polyolefin resin, and a pigment. (3) A molded article for preventing acoustic resonance, characterized in that a composition containing iron, an iron-based alloy, an iron-based oxide powder, and a polyolefin resin is molded and a coating layer is formed on the surface. (4) A molded article for preventing acoustic resonance, characterized in that a composition containing iron, an iron-based alloy, an iron-based oxide powder, a polyolefin resin, and a pigment is molded, and a coating layer is formed on the surface.