JPH05255537A - Resin composition for acoustic material - Google Patents

Abstract

PURPOSE:To provide a resin composition having both high vibration-damping properties and a high modulus and excellent in strength, impact resistance, and moldability, which properties are required of an acoustic material. CONSTITUTION:The title composition comprises, as the essential ingredients, a thermoplastic resin and a flaky inorganic filler having an average particle size of 10-300mum and an aspect ratio of 5 or higher and has a lower strength than that of the resin itself.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition suitable for audio equipment.

[0002]

2. Description of the Related Art Audio equipment, such as speaker boxes, player housings, radio-cassette housings, etc., have good performance in addition to general performances such as strength, elastic modulus, impact strength and heat resistance. Characteristics are required. Naturally, the acoustic characteristics greatly depend on the shape of the equipment, but on the other hand, it is said that the molding material used must have both a high elastic modulus and a high vibration damping property. Since it is extremely difficult to satisfy all of these many required functions with a single polymer, although technological development of alloying various polymers and compounding with inorganic fillers and inorganic fibers is underway, these No composition has hitherto been found that satisfies the performance in a well-balanced manner. In particular, the vibration damping property and the elastic modulus are mutually contradictory performances, and it has been extremely difficult to obtain a composition having a good balance between the two.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composition suitable for audio equipment such as a speaker box, a player housing, a radio-cassette housing, in other words, having a high vibration damping property and a high elastic modulus. An object of the present invention is to provide a resin composition having excellent strength, impact resistance, and moldability required for audio equipment.

[0004]

According to the present invention, the above objects are (a) a thermoplastic resin and (b) an average particle size of 10:
To provide a resin composition for audio equipment, which comprises a flaky inorganic filler having an aspect ratio of 5 to 300 μm and an aspect ratio of 5 or more as an essential component, and has a strength lower than that of a thermoplastic resin. Achieved by.

In the present invention, examples of the thermoplastic resin (a) include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, ABS,
Examples thereof include styrene resins such as AS, polyamides, polyphenylene ethers, polyacetals, polycarbonates, copolymers containing these as the main components, and a mixture of two or more thereof, but a softening point of about 70 ° C. or higher or The resin is not particularly limited as long as it has a heat distortion temperature.

In the present invention, it is preferable to have a glass transition temperature (hereinafter abbreviated as Tg) near room temperature in terms of weight reduction, molding processability, cost, etc. of the audio equipment. Polyolefin resins and copolymers containing them as the main component are preferable, and polypropylene and ethylene copolymer polypropylene are particularly preferably used. A nonpolar resin component such as a silicone resin or a fluorine resin may be added to these resins in order to weaken the affinity with the inorganic filler.
The thermoplastic resin (a) has only to have excellent moldability,
The degree of polymerization, the average molecular weight, and the melt index are not limited at all.

The flake-like inorganic filler (b) used in the present invention is used in combination with a resin, but it is necessary to secure the vibration damping property and elastic modulus required for the performance of audio equipment, Mica, flake graphite, glass flake, etc. are used. Two or more of these may be used in combination, but flake graphite is preferably used alone. Further, in the present invention, flake graphite having excellent damping properties is used in combination with mica which imparts a high elastic modulus, and by changing the blending ratio of each, molding having damping properties and elastic modulus according to the purpose. You can get things. When the shape of the inorganic filler is not flake, the elastic modulus is often improved, but it is not preferable because it does not have the effect of improving the vibration damping property. Since the proportion of fixed carbon in commonly used naturally occurring graphite varies widely, a fixed carbon content of at least 70% is preferred in the present invention. Impurities present in graphite, such as silicic acid, alumina or iron oxides, can be used as long as they do not affect the stability of the resin composition. Particularly preferred in the present invention is graphite with a high fixed carbon content, containing at least 90% fixed carbon.

The average particle size of the inorganic filler of the present invention is 10 to 3
The thickness is 00 μm, preferably 50 to 200 μm. Also,
An aspect ratio of 5 or more, particularly 20 or more is preferable in that the vibration damping property of the obtained molded article is improved.

Further, in order to weaken the affinity between the inorganic filler used in the present invention and the resin component, it is preferable that the inorganic filler, particularly mica, is surface-treated with a non-polar resin or the like. Examples of the non-polar resin include silicon-based resins and fluorine-based resins. The mixing ratio of these nonpolar resins is not particularly limited, but is generally preferably 0.05 to 3% by weight with respect to the weight of the inorganic filler.
There is no limitation on the method of surface-treating an inorganic filler such as a non-polar resin, for example, it can be treated by dissolving it in a solvent or the like, spraying it, and immersing it to dry the inorganic filler.

In the resin composition of the present invention, the compounding ratio of the inorganic filler (b) is usually 10 to 60% by weight, preferably 20 to 40% by weight based on the total weight of the composition. When the compounding ratio of the inorganic filler is less than 10% by weight, the effect of improving the vibration damping property and elastic modulus of the molded product is small, and when the compounding ratio of the inorganic filler exceeds 60% by weight, there is a problem in moldability. Often there is.

In the resin composition of the present invention, it is necessary that the strength of the resin composition is lower than the strength of the thermoplastic resin alone which is the base resin. If the strength is equal to or higher than the strength of the thermoplastic resin alone, it may not be possible to sufficiently satisfy both characteristics of the vibration damping property and the elastic modulus required for the performance of the audio equipment, which is not preferable.

If necessary, a foaming agent, a coloring agent, a plasticizer, a lubricant, or a resin composition may be added to the above resin composition as long as the characteristics of the present invention are not impaired.
Additives such as antioxidants, antistatic agents, flame retardants, heat stabilizers, and ultraviolet absorbers can be added without any problem.

The resin composition of the present invention is generally kneaded with each component by a single-screw extruder, a twin-screw extruder, a roll kneader or the like, but there is no limitation on these kneading methods.

The resin composition for audio equipment thus obtained is produced by various molding methods such as injection molding, foam molding, extrusion molding, compression molding, calender molding, etc. It can be freely molded from small audio equipment to large audio equipment such as housings, cassette tape cases, electronic organ and electronic piano housings, and hand speakers. The resin composition of the present invention is most suitable for use in audio equipment, but can also be molded into applications requiring vibration damping and high elasticity, such as motor housings and gear box covers.

[0015]

The present invention will be described in more detail below with reference to examples, but these examples do not limit the present invention in any way. In addition, each measured value in an Example was calculated | required by the following method.

(1) Flexural strength (kg / cm ↑ 2) and flexural modulus (kg / cm ↑ 2): JIS K 720
Determined according to 7

(2) Heat distortion temperature (° C.): Using a heat distortion tester (manufactured by Toyo Seiki Seisakusho), JIS
Bending stress 18.5 kg / cm according to K 7207
Measured at ↑ 2.

(3) Acoustic characteristics: Leovibron (manufactured by Orientec Co.) frequency 110 HZ, temperature -150.
The peak value of the internal loss (tan δ) that appears near room temperature in the range of ℃ to 150 ℃ was measured (the larger the tan δ value, the better the acoustic characteristics). Also, the reciprocal of this tan δ value was taken as the resonance sharpness.

Example 1 Homopolypropylene (J-115G manufactured by Ube Industries, Ltd.) having a melt flow rate of 15 g / 10 min, and flake graphite having an aspect ratio of 20 and an average particle size of 80 μm were used as raw materials, and polypropylene / graphite was used. =
The mixture was mixed at a ratio of 70/30 (weight ratio), and this mixture was kneaded and pelletized with a single screw extruder under the condition of a cylinder temperature of 250 ° C. The pellets were molded using an injection molding machine under the conditions of a cylinder temperature of 230 ° C. and a thickness of 3 m.
m and 6 mm test pieces were obtained. The bending elastic modulus, bending strength and heat distortion temperature of the obtained test piece were measured, and the results are shown in Table 1. In addition, a speaker box (110 × 9) was prepared by using an injection molding machine (FS160S, manufactured by Nissei Plastic Industry Co., Ltd.) at a cylinder temperature of 230 ° C. using the pellets.
0 × 85 mm, average wall thickness 2 mm) was molded and its acoustic characteristics were evaluated. The results are shown in Table 1.

Examples 2 and 3 In Example 1, phlogopite (Suzorit) surface-treated with silicon resin instead of flake graphite was used.
Emica Products, Szolite Mica 200HK) (Example 2), flakes graphite and phlogopite surface-treated with silicon resin (Example 3) were mixed and pelletized in the same manner. The pellet was molded in the same manner as in Example 1 to obtain a test piece. The flexural modulus, flexural strength, and heat distortion temperature of the obtained test piece were measured to evaluate the acoustic characteristics. The results are shown in Table 1.

Examples 4 and 5 Mixing and pelletization were performed in the same manner as in Example 1 except that the mixing ratios shown in Table 1 were used. The pellet was molded in the same manner as in Example 1 to obtain a test piece. The flexural modulus, flexural strength, and heat distortion temperature of the obtained test piece were measured to evaluate the acoustic characteristics. The results are shown in Table 1. The specific gravity was different from that of the molded product of Example 1, but the performance was well balanced, and there was no problem in practical use.

Example 6 Mixing and pelletization were carried out in the same manner as in Example 1 except that the blending ratio shown in Table 1 was added and a foaming agent was added. The pellet was molded in the same manner as in Example 1 to obtain a test piece. The flexural modulus, flexural strength, and heat distortion temperature of the obtained test piece were measured to evaluate the acoustic characteristics. The results are shown in Table 1. The specific gravity was considerably lighter than that of the molded product of Example 1, but the performance was well balanced and there was no problem in practical use.

Comparative Example 1 Only the polypropylene used in Example 1 was molded in the same manner as in Example 1, various physical properties of the molded product were measured, and the acoustic characteristics were evaluated. The evaluation results are shown in Table 1. It can be seen from Table 1 that tan δ is high, but flexural modulus, flexural strength, and heat distortion temperature are low.

Comparative Example 2 In Example 2, molding was carried out in the same manner as in Example 2 except that the surface treatment of phlogopite was not carried out, various physical properties of the molded article were measured, and acoustic characteristics were evaluated. The evaluation results are shown in Table 1. From Table 1, it can be seen that the flexural modulus, flexural strength, and heat distortion temperature are high, but tan δ is low.

Comparative Examples 3 and 4 In Example 1, chopped strand glass fibers (Y-17 manufactured by Asahi Fiber Glass Co., Ltd.) in which the inorganic filler is not flaky (Comparative Example 3), Wollastonite (Kinsei Kogyo Co., Ltd.) FPW-400) (Comparative Example 4)
Molding was performed in the same manner as in Example 1 except that the above was changed to, and various physical properties of the molded product were measured, and acoustic characteristics were evaluated. The evaluation results are shown in Table 1. From Table 1, it can be seen that the flexural modulus, flexural strength, and heat distortion temperature are high, but tan δ is low.

[0026]

[Table 1]

[0027]

INDUSTRIAL APPLICABILITY The resin composition of the present invention is excellent in mechanical properties such as flexural modulus and flexural strength, and has a large internal loss, and is therefore suitable for an audio equipment having good acoustic characteristics.

Claims (2)

[Claims] 1. A thermoplastic resin comprising (a) a thermoplastic resin and (b) a flaky inorganic filler having an average particle size of 10 to 300 μm and an aspect ratio of 5 or more as essential components and having a strength higher than that of the thermoplastic resin alone. A resin composition for an audio equipment, which is characterized by decreasing. 2. The component (b) is graphite or a mixture of graphite and mica.
The resin composition for an audio equipment described.