JPH02133468A - Resin composition for speaker diaphragm - Google Patents

Abstract

PURPOSE:To obtain the title composition which can give a speaker diaphragm of good tone and surface appearance in producing a speaker diaphragm by injection molding, by mixing a specified thermoplastic liquid crystal polymer with a carbon fiber. CONSTITUTION:The title composition is obtained by mixing at least 10wt.% thermoplastic liquid crystal polymer having a melt viscosity <=500P (at a temperature <=330 deg.C and a shear rate of 1000sem<-1>) and showing a liquid crystal property at 330 deg.C or below [e.g., NOVACCURATE resin (E-322: trademark) which is a thermoplastic liquid crystal polyester partially copolymerized with aliphatic groups, a product of Mitsubishi Kasei] with 1-25wt.% carbon fiber. This composition can be formed into a diaphragm of good tone and surface appearance in producing a speaker diaphragm by injection molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a resin composition comprising a specific thermoplastic liquid crystal polymer blended with carbon fibers.

Specifically, the present invention relates to a resin composition for a speaker diaphragm that provides a diaphragm with good sound quality and surface appearance in the technology of manufacturing a speaker m/moving plate by an injection molding method.

[Conventional technology and problems]

The speaker diaphragm has a specific elastic modulus, E/ρ (E: elastic modulus, ρ
It is important that the material has a large specific gravity) and a large internal loss during vibration deformation, and to achieve this purpose, conventionally, for example, paper pulp mixed with fibers with a very high modulus of elasticity has been used. It's here. However, in recent years, plastic materials have advantages such as relatively large internal loss, the ability to improve the elastic modulus relatively easily by incorporating carbon fiber, and ease of molding. Carbon fiber filled plastic composites are being used. However, such plastic composites generally have a high melt viscosity (injection molding technology cannot be used to mold thin structures such as speaker diaphragms). Showa 1.
The use of liquid crystalline polymer composites has been proposed in Japanese Patent No. 2-1119291 and the like.

Liquid crystalline polymers not only have extremely good fluidity, but also have a relatively large internal loss compared to plastic in the flow direction of the resin, making it the best speaker diaphragm at the current technological level. It can be said to be a material. However, when a speaker diaphragm is injection molded using a carbon fiber composite liquid crystal polymer filled with carbon fibers, the surface appearance of the molded product is thought to be due to the flow behavior of the liquid crystal polymer, but it is Moreover, the degree of blackness was uneven over the surface compared to the expected appearance, and the commercial value was low as it was.

Furthermore, although the melt viscosity of such liquid crystalline polymers is low,
The value is relative, and it is obvious that it depends on the polymerization degree of the polymer itself or the skeletal structure of its molecules.As is well known, the lower the polymerization degree, the lower the mechanical properties of the polymer. Therefore, the degree of polymerization cannot be lowered unnecessarily.Also, since the flow length of the resin depends on the capacity of the injection molding machine used, it is difficult to reduce the polymerization degree unnecessarily. In order to mold a molded product with a flow length of SO ~ / 0, an injection molding machine with a very large mold clamping force is required. However, since it is preferable for the speaker diaphragm to be lightweight, the injection capacity must be extremely small. - Molding machines with large mold clamping force for boat fishing are made with large injection capacity, and when molding small molded products such as subicars, the residence time of the resin is long (and the resin Melt heat stability is a problem. This problem can be solved by using a special molding machine, but the fixed cost is large and it cannot be said to be industrially advantageous.

[Means for solving problems]

As a result of intensive studies in view of the above problems, the present inventors discovered that a specific thermoplastic liquid crystal polymer composition is suitable for a speaker diaphragm, and arrived at the present invention.

That is, the gist of the present invention is that the melt viscosity at shear rate/0005eC-1 at a temperature of 330°C or lower is SOO
A resin composition for a speaker diaphragm containing 10% by weight or more of a thermoplastic liquid crystal polymer having a void temperature of less than 330° C. and exhibiting liquid crystallinity at 330° C. or less, and more than 7% by weight (less than 25% by weight of carbon n and fibers). Exists.

The object of the present invention is to provide a carbon fiber composite liquid crystal polymer,
- When molding a speaker diaphragm using an injection molding machine commercially available for boat fishing, it is possible to obtain a molded product with a large E/ρ, large internal loss, good fluidity, and a good diaphragm surface appearance. An object of the present invention is to provide a resin composition.

The present invention will be explained in detail below.

The thermoplastic liquid crystal polymer used in the present invention can be arbitrarily selected from the group of polyesters or polyesteramides consisting of segments having the following structure.

/: Polyester -〇-R-0--CO-1'
(-CO- 10-4-CO-, 2: Polyesteramide -o -R-0--C0-
R-CO- 10-4-CO- -NH-R-CO- -NH-R-NH- In this structural formula, R can be selected from any two groups below.

-CH2-(CH232(CH2)4 (C1
-T2)6-The thermoplastic liquid crystal polymer of the present invention is 330
The melt viscosity measured at a shear rate/0005 eC-' at a temperature of 0.degree. C. or less, preferably from 27 s to 330.degree. When injection molding a speaker diaphragm using carbon fiber composite liquid crystal polymer, the mold clamping force of the injection molding machine used is also as follows: may be substituted with various substituents selected from the group of

B" -C1, -COOH, CONH2 -CH3, Therefore, it is preferable to use an injection molding machine with a mold clamping force of /sO) or less. However, if the melt viscosity of the liquid crystal polymer is higher than the SOO poise Therefore, the mold clamping force is insufficient to mold a speaker diaphragm of a desired shape using such a molding machine.

Therefore, the solution viscosity of the thermoplastic liquid crystal polymer of the present invention must be less than SOO poise. As a thermoplastic liquid crystal polymer having such a melt viscosity and also having mechanical properties suitable for use as a molding material, it is preferable to use a polymer containing a portion of an aliphatic group or an alicyclic group in its main chain. A wholly aromatic liquid crystal polymer containing neither an aliphatic group nor an alicyclic group in its main chain is not preferred because it is extremely difficult to reduce the melt viscosity to 100 poise or less under the present conditions.

The content of the aliphatic group or alicyclic group in the thermoplastic liquid crystal polymer can be selected as desired within the range that exhibits liquid crystallinity in the molten state, but is preferably 2 to !ro mol%. Regarding this content, it is preferable to select this content by considering the high elastic modulus after molding, which is also an important factor as a material for a speaker diaphragm.

Examples of the aliphatic group or alicyclic group include those containing an aliphatic group or an alicyclic group among the vine groups selected as R of the segment forming the thermoplastic liquid crystal polymer of the present invention described above. . Specifically, the following can be mentioned.

CH2 (CHz)2 (CH2)4
(CH2)6-- (CH2-O-(CH2)2
- -CH2minCH2-CH3 When molding a speaker using such resin,
Liquid crystal polymer is oriented in the flow direction of the resin, and has a high elastic modulus in that direction, but in a direction perpendicular to this direction, its elastic modulus is about the same as that of ordinary plastic, so it is not suitable as a speaker diaphragm as it is. In order to solve this problem and to improve the surface appearance and weather resistance, it is important to fill this material with carbon fiber. However, when such a thin-sheet molded article is molded using a composition in which the thermoplastic liquid crystal polymer of the present invention is filled with a fibrous substance, the distribution density of the fibers is extremely non-uniform, and when carbon fiber is selected as the fiber, Its exterior color is black, and its nonuniformity appears as a black and gray mottled pattern, making it impossible to obtain a molded product with commercial value. In the present invention, the filling amount of carbon fiber is 7
It is more than 25% by weight, preferably more than 1% by weight and less than 0% by weight. If the carbon fiber filling amount is less than 3 wt%, the appearance will be good even when the resin of the present invention is used, and the non-uniform black and gray mottled pattern will be replaced by alternating black and white patterns as shown in Figure 1. , changes to a radial pinch pattern consisting of gray. Its appearance is extremely beautiful;
It has an excellent appearance as a speaker diaphragm. In the present invention, the thermoplastic liquid crystal polymer may be further copolymerized or blended with other thermoplastic polymer components, but the thermoplastic liquid crystal polymer in the present invention must be contained in an amount of at least 70% by weight. If it is less than 70% by weight, the liquid crystallinity will decrease and it will be difficult to obtain a speaker imaging plate with excellent performance, which is the goal of the present invention. Other thermoplastic polymers that may be copolymerized or blended include polyesters, polyamides, polycarbonates, polysulfides, polysulfones, or polythioethers.

Preferably it is polyester or polyamide.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples unless it departs from the gist thereof.

Reference example: N0VACCUR, manufactured by Mitsubishi Kasei ■, is a thermoplastic liquid crystalline polyester partially copolymerized with aliphatic groups.
ATE Ju-Q (E J, 22: trade name) was selected as a fully aromatic polyester resin, Econol resin (trade name) manufactured by Sumitomo Chemical ■, and VECTRA (trade name) manufactured by Celanese Co., Ltd. ) was selected. The melt viscosity of each resin is as shown below.

Polymer A, Polymer B, and Polymer C were injection molded using an injection molding machine with a mold clamping force/Sθ tons at the above resin temperature and with various injection pressures and injection speeds, as shown in Figure 2. A molded product like this was obtained. The results are as follows.

Molding results Polymer A had all short shots within these conditions, and polymer B had a thicker wall than desired, and the mold clamping force was insufficient in this injection molding machine. On the other hand, Polymer C, which is a partially aromatic polyester partially copolymerized with an aliphatic polyester, had a low melt viscosity, and it was possible to obtain a molded article with a desired wall thickness.

Comparative Examples/~5, Examples-/ For Polymer B and Polymer C shown in Reference Examples, resin compositions filled with carbon fibers in the proportions shown in Table 1 were produced, and the same method as in Reference Examples was carried out. The speaker diaphragm was injection molded.

The results are shown in Table 7.

The effect of carbon fiber kneading is almost the same for Polymers B and C, and at 7% by weight, the overall appearance is a little gray, and the contrast between the white and gray radial pitches is very small, and from the viewpoint of appearance design, it is more than 10% by weight. It looked inferior. On the other hand, 25
The speaker diaphragm had a blackish color in terms of weight percentage, but had uneven gray mottled areas and an extremely poor appearance.

Example - A molded article made by molding a resin composition in which Copolymer C is filled with 20% by weight of carbon fibers in the same manner as in the reference example is cut out in the direction of resin flow and in a direction perpendicular thereto, and a Viplon (manufactured by Toyo Boldwin, trade name: DDV-, 2 type) was used to measure the elastic group. The elastic modulus at room temperature is tree II
The ¥1 flow direction was 1λ gigapascal, and the direction perpendicular to it was tag gigapascal. Furthermore, after actually assembling a speaker using the same molded product and conducting a pitch test, it was found that the product had good sound quality up to the high frequency range.

Comparative Example 6 A molded article was obtained in the same manner as in Example A except that Polymer C not filled with carbon fibers was used, and the elastic modulus was measured.

The elastic modulus at room temperature is a resin [Effect of the invention] The composition of the present invention is suitable for molding a speaker diaphragm using a generally commercially available injection molding machine, and has an E/
A molded product with large ρ and internal loss, good fluidity, and good vibration surface appearance can be obtained.

[Brief explanation of drawings]

FIG. 7 is a diagram showing a radial pitch pattern consisting of alternating black and gray as an example of the external appearance of a speaker diaphragm using the resin composition of the present invention. FIG. 2 is a diagram showing the shape of a speaker diaphragm molded in an embodiment of the present invention. In the figure, a is /lIOho, b is 7
0 friends. Further, C indicates the thickness, which is Olympus.

Claims (2)

[Claims] (1) Shear rate 1000s at temperature below 330℃
A speaker vibration containing 10% by weight or more of a thermoplastic liquid crystal polymer having a melt viscosity at ec^-^1 of 500 poise or less and exhibiting liquid crystallinity at 330°C or less, and more than 1% by weight and less than 25% by weight of carbon fiber. Resin composition for boards. (2) The resin composition for a speaker diaphragm according to claim 1, wherein the main chain of the thermoplastic liquid crystal polymer contains a portion of an aliphatic group or an alicyclic group.