JPH04345298A - Speaker vibration diaphragm - Google Patents

Abstract

PURPOSE:To obtain a speaker vibration diaphragm with large inner loss and a satisfactory acoustic characteristic. CONSTITUTION:A diaphragm consists of (a) 40-93wt.% propylene polymer, (b) 40-2wt.% the block sharing polymer of vinyl aroma group where glass transition temperatures is within the range of -20 deg.C-50 deg.C with conjugate diene or its hydrogenation and (c) 40-5wt.% graphite.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker diaphragm with large internal loss and excellent acoustic characteristics.

0002

[Prior Art] Conventionally, materials for speaker diaphragms include paper,
They are selected from a wide variety of materials such as mixed paper, ceramics, and resin. Among these materials, resin-based materials have come into widespread use in recent years because they are easier to balance the elastic modulus and loss coefficient of the material than other materials.

0003

[Problems to be Solved by the Invention] Such resin materials inherently have a large loss coefficient compared to other materials, and the loss coefficient differs depending on the molecular structure. Among them, polypropylene is an excellent material in terms of the balance between price, mechanical properties, and loss coefficient. Among materials using such resins, carbon fiber reinforced plastic is a typical material with a well-balanced elastic modulus and loss coefficient. However, in recent years, it has become necessary to produce "sound" of higher quality, and to make this possible, materials with even higher loss coefficients are required. Therefore, there is a need for a material that is inexpensive and has high mechanical properties and loss coefficient. Note that the speaker diaphragm needs to have an appropriate elastic modulus to faithfully transmit vibrations and an appropriate internal loss to absorb unnecessary vibrations such as reflected vibrations. Generally, elastic modulus and internal loss are in an inversely proportional relationship. Therefore, in order to improve the sound quality, it is a technical challenge to increase the internal loss while maintaining the elastic modulus appropriately, that is, to increase the loss coefficient of the material.

0004

[Means to solve the problem]

[Summary of the Invention] As a result of intensive research in view of the above problems, the present inventors have discovered that
By blending specific materials with propylene polymer,
It is believed that a speaker diaphragm formed from a composition using a polypropylene material with a significantly increased loss coefficient can achieve the above objectives without degrading the various characteristics possessed by this propylene polymer. This knowledge led to the completion of the present invention. That is, the speaker diaphragm of the present invention contains (a) 40 to 93% by weight of a propylene polymer, (b)
Consisting of 40 to 2% by weight of a block copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated substance thereof having a glass transition temperature in the range of -20°C to 50°C, and (c) 40 to 5% by weight of graphite. It is characterized by:

[Detailed Description of the Invention] [I] Production of propylene polymer composition (1) Constituent component (a) component: Propylene polymer The propylene polymer as component (a) used in the present invention is as follows: It is crystalline, specifically a single polymer of propylene, or a random, block or graft copolymer of propylene and other α-olefins, etc., or other vinyl monomers. , mixtures of these polymers and copolymers. Among these, a propylene/ethylene block copolymer having an ethylene content of 1 to 20% by weight, particularly 1.5 to 15% by weight is preferred. The MFR (melt flow rate; 230°C, 2.16 kg load) of these propylene polymers is 0.01 to 4.
00 (g/10min), especially 0.1 to 200
It is preferable that it is within the range of . If the MFR is less than 0.01, there will be difficulties in molding and it will be difficult to obtain a product with commercial value. Moreover, when the MFR exceeds 400, the mechanical strength level becomes low, which is not preferable.

Component (b): A block copolymer of a vinyl aromatic compound and a conjugated diene or a hydrogenated product thereof A block copolymer of a vinyl aromatic compound and a conjugated diene as the component (b) used in the present invention Alternatively, the hydrogenated product has a structure having at least one chain block "A" of a vinyl aromatic compound and at least one chain block "B" of a conjugated diene, and the chain block "A" has at least one chain block "B" of a conjugated diene.
” and “B” include those that form a linear structure or those that form a so-called radial teleblock structure that forms a branched structure. Specific examples of the vinyl aromatic compound constituting the chain block "A" include styrene, α-methylstyrene, vinylxylene, vinyltoluene, vinylnaphthalene, and the like. Among these, it is more preferable to use styrene. Further, specific examples of the conjugated diene constituting the chain block "B" include 2-methyl-1,3-butadiene, 1,3
-butadiene, or a combination type of 2-methyl-1,3-butadiene and 1,3-butadiene is used. The proportion of the chain blocks "A" and "B" in the polymer molecular chain is 30% or more, preferably 40 to 30%.
95% is used. If “B” is less than 30%,
It is difficult to obtain sufficient vibration damping performance within the normal operating temperature range.

[0007] The obtained block copolymer may also be a hydrogenated product obtained by hydrogenation by a known method depending on requirements such as heat resistance and weather resistance. The glass transition temperature of this block copolymer is -20℃
-50°C, preferably -10 to 40°C. This glass transition temperature is desirably set within the operating temperature range of the material; outside this temperature range, it is far from the actual operating temperature and poses a practical problem. Further, the number average molecular weight of the block copolymer is preferably in the range of 3,000 to 500,000, particularly 5,000 to 300,000. When the molecular weight is less than 3,000, mechanical properties are low and practicality is poor. Moreover, if the molecular weight exceeds 500,000, processability deteriorates, which is not preferable.

Component (c): Graphite The graphite used as component (c) in the present invention is suitably in the range of 0.5 to 50 μm, preferably 1 to 20 μm, with an average particle size of 0. If the diameter is less than .5 μm, secondary aggregation of graphite particles tends to occur, making uniform dispersion in the matrix difficult, which is undesirable. Particles exceeding 50 μm are also undesirable because they significantly reduce the impact strength of the resulting composition.

Component (d): Optional component In addition to the essential components (a) to (c) above, if necessary, a homopolymer of other α-olefins such as polyethylene or other α-olefins may be added. and unsaturated monomers, block or random copolymers, ethylene-propylene copolymer rubber, antioxidants, slip agents, weatherability improvers, nucleating agents, pigments, fillers (talc, calcium carbonate,
Mica, etc.), fibrous fillers (carbon fibers, glass fibers, whiskers, etc.), and the like can be blended with arbitrary compounding components.

(2) Amount ratio The blending ratio of the above essential components (a), (b), and (c) is (a) + (b) + (c) = 100% by weight,
Components (a), (b), and (c) satisfy the following condition range. 40≦(a)≦93% by weight, preferably 50≦(a)≦
85% by weight, 2≦(b)≦40% by weight, preferably 5≦(b)≦
40% by weight, 5≦(c)≦40% by weight, preferably 10≦(c)≦4
0% by weight, and component (d), which is added as an optional component, can be added to the components (a) to (d) above to the extent that the effects of the present invention are not significantly impaired. The component (d) is (a) to (
It is generally about 0 to 20% by weight, preferably about 0 to 15% by weight, based on the total amount of component c). If the amount of the propylene polymer (a) is less than the above range, the material will lack rigidity and heat resistance, making it unsuitable for use as a speaker diaphragm, while if it exceeds the above range, the loss factor will be unsatisfactory. If the blending amount of the block copolymer of a vinyl aromatic compound and a conjugated diene or its water additive as component (b) is less than the above range, there will be almost no effect of improving the acoustic properties;
If it exceeds the above range, it is difficult to ensure the quality of the mechanical properties of the produced product. The blending of component (c) graphite is an essential component in terms of the balance between impact strength and rigidity; if the proportion is less than the above range, the stiffness imparting effect will not be sufficient, and if it exceeds the above range, the impact strength will be significantly reduced. I'll let you.

(3) Blending and kneading As a method for obtaining the propylene polymer composition used for the speaker diaphragm of the present invention, the above-mentioned components (a) to (c) and, if necessary, component (d) are added to powder. The granular or granular components are uniformly dispersed into a mixture using a Henschel mixer, super mixer, ribbon blender, etc., and then a melt kneader such as a twin-screw kneader extruder, single-screw kneader extruder, roll, or Banbury mixer is used. be done. Melt kneading is usually carried out at 180 to 350°C, preferably 180 to 280°C.
It is carried out within the range of The resin composition obtained as described above can be extruded into pellets after being melt-kneaded. In the propylene polymer composition thus obtained, the block copolymer of a vinyl aromatic compound and a conjugated diene or its hydrogenated component (b) is three-dimensional in the component (a) constituting the matrix. Distributed in a mesh pattern. That is, although component (b) is finely dispersed in component (a), it is important that it exists in the matrix without being mixed with other components.

[II] Manufacture of speaker diaphragm A speaker diaphragm is usually manufactured into a predetermined shape using an injection molding machine. When using plastics such as those of the present invention, a cone-like shape is common.

[0013]

[Examples] In order to explain the present invention more specifically, Examples and Comparative Examples are shown below. The raw materials and evaluation methods used in Examples and Comparative Examples are as shown below. (1) Raw material (a) component <PE copolymer 1>: ethylene content 2% by weight, MFR
is 30 (manufactured by Mitsubishi Yuka Co., Ltd., the proportion of ethylene/propylene copolymer rubber in the copolymer is 10% by weight) (b) Component <Copolymer 1>: Number average Styrene/isoprene/styrene block copolymer with a molecular weight of 150,000 and a glass transition temperature of 10°C <Copolymer 2>: Styrene/isoprene/styrene block copolymer with a number average molecular weight of 200,000 and a glass transition temperature of -50°C Styrene block copolymer, (c) component <graphite 1>: graphite with an average particle size of 5 μm

(2) Evaluation method <Loss factor> The loss factor was measured using a 16 mm width x 12 mm length
A test piece of 0 mm x 2 mm thickness was used as a sample, and it was determined from the ratio of the resonance frequency measured by a complex elastic modulus measuring device (manufactured by Shobiki Co., Ltd.) and the half width of the resonance peak. <Izod impact strength> ISO R180-1969 (
JIS J7110) (notched Izod impact strength), it was measured using an Izod impact tester manufactured by Toyo Seiki Seisakusho. The measurement atmosphere temperature was 23°C. <Bending elastic modulus>ISO R178-1974 Proc
It was measured using an Instron testing machine according to edure 12 (JIS K7203). <Glass transition temperature> Temperature increase rate 20 deg/min using PerkinElmer differential scanning calorimeter (DSC) type II
The glass transition temperature was measured under the conditions of a cooling rate of 10 deg/min.

Example 1 65% by weight of propylene-ethylene block copolymer (<PE copolymer 1>) as component (a), styrene-isoprene-styrene block copolymer (<PE copolymer 1>) as component (b)
A propylene polymer composition was obtained by kneading a mixture of three types, 15% by weight of <Copolymer 1>) and 20% by weight of graphite (<Graphite 1>), using a twin-screw kneader. The obtained propylene polymer composition was injection molded at 240° C. to make a sheet with a thickness of 2 mm, and this sheet was cut into a size of 16 mm in width x 120 mm in length, which was used as a test piece. The loss coefficient and physical properties (flexural modulus, Izod impact strength) at 23° C. were measured using this test piece. The results are shown in Table 1.

Example 2 Blending ratio of component (a), component (b), and component (c): 90:
A test piece of the propylene polymer composition was prepared in the same manner as in Example 1 except that the ratio was 5:10, and the loss factor and physical properties were measured. The results are shown in Table 1. Comparative Examples 1, 2, 3 and 4 (a), (b), (c) The blending ratio of components (Comparative Example 1)
100:0:0, (Comparative Example 2) 80:20:0, (Comparative Example 3) 80:0:20, (Comparative Example 4) 94:1:5, and the other conditions were the same as in Example 1. A test piece was prepared, and the loss coefficient and physical properties were measured. The results are shown in Table 1.

Comparative Example 5 A test piece was prepared in the same manner as in Example 1 except that the styrene-isoprene-styrene block copolymer was changed to <Copolymer 2> as the component (b), and the loss factor and Physical properties were measured. The results are shown in Table 1.

[0018]

[Table 1]

[0019]

[Effects of the Invention] The speaker diaphragm of the present invention has the excellent mechanical properties of a propylene polymer, and also contains the above-mentioned vinyl aromatic compound, a conjugated diene block copolymer or its hydrogenated product, and graphite. Therefore, it has an extremely large loss coefficient and has excellent acoustic characteristics.

Claims (1)

[Claims] Claim 1: (a) 40 to 93% by weight of a propylene polymer (b) A block copolymer of a vinyl aromatic compound and a conjugated diene or its hydrogen having a glass transition temperature within the range of -20°C to 50°C Additives 40-2% by weight (c)
A speaker diaphragm comprising 40 to 5% by weight of graphite.