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JP2001103595

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DESCRIPTION JP2001103595
[0001]
The present invention relates to a foamable composition for an electroacoustic transducer used
for an edge portion or the like which is a supporting system member of an acoustic transducer
such as a speaker, and a member for an electroacoustic transducer using the same. is there.
[0002]
2. Description of the Related Art As a condition required for an edge which is one of the support
system components of an electroacoustic transducer such as a speaker, it is required to have
good linearity, to be lightweight, to have high internal loss, It does not produce an inherent
sound, has sufficient reliability, and is easy and inexpensive to manufacture.
[0003]
Under such circumstances, the fixed edge, in which the diaphragm and the edge are integrated,
can simplify the manufacturing process and has an advantage of being able to provide an
inexpensive diaphragm because the material yield of the edge portion is good. have.
However, due to its structure, it is difficult to obtain the above ideal function as an edge because
the same material as the diaphragm, ie, a material having a relatively high elastic modulus, is also
used for the edge.
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[0004]
On the other hand, in order to improve the functional defect of the fixed edge, various free edges
in which the diaphragm body and the edge portion are formed of different materials have
conventionally been proposed and put to practical use. For example, a sheet material obtained by
coating a relatively flexible material having a large internal loss such as rubber or acrylic on a
woven fabric of natural fibers or synthetic fibers, and further, if necessary, impregnated with a
thermosetting resin for controlling hardness. Coating fabric edge urethane foam sheet which is
heat molded into a predetermined edge shape Heat molded into a predetermined edge shape a
rubber mixture mainly composed of a urethane foam raw material rubber and a vulcanizing
agent which is heat molded into a predetermined edge shape Vulcanized rubber edge
thermoplastic elastomer (TPE) sheet molded into a predetermined edge shape TPE sheet edge
pelletized thermoplastic elastomer (TPE) molded into a predetermined edge shape by injection
molding method TPE edge These free edges also have various disadvantages. In recent years, was
remedy these drawbacks vulcanized foam rubber edge is being used is proposed.
[0005]
However, the above-mentioned vulcanized foam rubber edge also has the following
disadvantages. That is, those using styrene-butadiene rubber (SBR) have good moldability and
large internal loss, so it can be said that the material is excellent in these respects, but the
weather resistance (especially heat resistance and cold resistance) ) Is bad and there is a problem
in terms of durability. Those having ethylene-propylene-terpolymer rubber (EPT) as a main
component are excellent in weather resistance, but have a problem that the internal loss is small.
[0006]
For example, in the embodiment described in JP-A-7-240994, there is almost no difference in
internal loss between the one containing EPT as the main component and the one containing SBR
as the main component, but this measurement was performed at a frequency of 1 Hz. The
conditions are largely different from the frequency band in which the present invention is
concerned.
[0007]
In general, the internal loss is frequency dependent, and it has the same high value at frequencies
in other different bands just as it has a high internal loss at a very low frequency of 1 Hz as
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2
described above. Not necessarily.
[0008]
Usually, the reproduction frequency band of the speaker system is about 50 Hz to 30 kHz, and
particularly in the vicinity of the mid band where the present invention is concerned, the range of
about 500 Hz to 2 kHz is problematic.
Therefore, in the present invention, the internal loss of one having EPT as the main component
and one having SBR as the main component was measured and compared at a frequency close to
the frequency in question as much as possible.
The results are shown in Table 1 below.
[0010]
For example, since the mechanical resistance decreases when the internal loss is small, the Q
(resonance sharpness) represented by the following equation (1) becomes high, and the
frequency band from the piston motion region of the speaker to the divided vibration region The
resonance and reverse resonance of the diaphragm and the edge that occur in the middle range
will be sharpened in general full range speakers, and as a result, large peaks and valleys will be
generated in the frequency-sound pressure characteristics of this band. .
[0011]
In addition, since the mechanical resistance increases when the internal loss is large, the Q
(resonance acuity) shown by the following equation (1) becomes low, and the resonance and
reverse resonance become dull, resulting in a frequency in this band -The peaks and valleys of
the sound pressure characteristic become smaller, and a flatter frequency-sound pressure
characteristic can be obtained.
[0013]
However, since the internal loss is frequency dependent as described above, just because it is
high internal loss near the midrange, it is not necessarily high internal loss at other frequencies.
As to the degree of improvement of the range, the problem is how large the internal loss of the
high range is.
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[0014]
The present invention has been made in view of such circumstances, and by having sufficient
durability and high internal loss, good characteristics with few peaks and valleys in frequencysound pressure characteristics and severe conditions such as the inside of an automobile etc. It is
an object of the present invention to provide a foamable composition for an electroacoustic
transducer that can be provided over a long period of time under various circumstances and a
member for an electroacoustic transducer using the same.
[0015]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
provides a foamable composition for an electroacoustic transducer, which comprises the
following components (A) and (B) as essential components: I assume.
(A) A copolymer comprising the following (a1) to (a3):
(a1)エチレン。
(A2) α-olefin.
(A3) A cyclic polyene having a nonconjugated double bond or an acyclic polyene having a
nonconjugated double bond. (B) A thermoplastic elastomer obtained by hydrogenating a block
copolymer consisting of polystyrene and polyisoprene.
[0016]
Then, a member for an electroacoustic transducer, which is formed into a predetermined shape
by foaming and vulcanization using the foamable composition for an electroacoustic transducer,
is taken as a second aspect.
[0017]
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That is, in order to achieve the said objective, the present inventors repeated research about the
essential component which comprises a foamable composition.
As a result, when the specific three-component copolymer (component A) and the specific
thermoplastic elastomer (component B) are used as essential components, the effect of improving
the durability based on the component A can be obtained. It has been found and found that good
frequency-sound pressure characteristics can be obtained in a frequency band near the
midrange, which can not be obtained conventionally, and that it has both high internal loss and
excellent durability, which is the intended purpose. The invention has been reached.
[0018]
Further, in the above essential components, by setting the compounding amount of the B
component to be a specific ratio with respect to 100 parts by weight (hereinafter abbreviated as
"part") of the A component, the higher internal loss and the superior It was found that durability
was obtained.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention
will be described in detail.
[0020]
The foamable composition for an electroacoustic transducer of the present invention (hereinafter
referred to as "foamable composition") comprises a specific three-component copolymer
(component A) and a specific thermoplastic elastomer (component B). It is obtained.
[0021]
The specific three-component copolymer (component A) comprises ethylene (a1), α-olefin (a2)
and a cyclic polyene having a nonconjugated double bond or an acyclic polyene having a
nonconjugated double bond. It is a terpolymer consisting of three components of (a3).
[0022]
Examples of the α-olefin (a2) include propylene and butene-1.
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[0023]
Examples of the cyclic polyene having a nonconjugated double bond or the noncyclic polyene
(a3) having a nonconjugated double bond include dicyclopentadiene, 1,5-cyclooctadiene, 1,1cyclooctadiene, and 1,6. -Cyclododecadiene, 1,7-cyclododecadiene, 1,5,9-cyclododecatriene, 1,4cycloheptadiene, 1,4-cyclohexadiene, norbornadiene, ethylene norbornene, 2-methylpentadiene1, Examples include 4,1,5-hexadiene, 1,6-heptadiene, 1,4-hexadiene, methyl-tetrahydroindene
and the like.
[0024]
In each of the monomers (a1) to (a3) constituting the above-mentioned copolymer (component
A), ethylene (a1), propylene (a2) and dicyclopentadiene or ethylene norbornene from the
viewpoint that an appropriate vulcanization rate can be obtained. The combination with (a3) is
preferred.
[0025]
The copolymerization ratio of each of the above monomers is preferably such that 30 to 80% by
weight of ethylene (a1), 0.1 to 20% by weight of polyene (a3), and the balance to α-olefin (a2) It
is.
It is particularly preferable that 50 to 70% by weight of ethylene (a1), 5 to 12% by weight of
polyene (a3), and the remainder be in the range of α-olefin (a2).
[0026]
The specific thermoplastic elastomer (component B) used as an essential component together
with the component A is obtained by hydrogenating a block copolymer composed of polystyrene
and polyisoprene.
Among such thermoplastic elastomers, those having a styrene content in the range of 10 to 65%
by weight are preferable.
Particularly preferably, the styrene content is 13 to 35% by weight.
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Moreover, that whose glass transition temperature in the temperature increase rate of 10 degreeC / min by DSC method (differential-heat method) is -25-20 degreeC is used suitably.
Specifically, the polyisoprene moiety contains vinyl isoprene (3.4 bonds) rather than being
composed only of the normal 1.4-linked isoprene.
[0027]
It is preferable to set the compounding quantity of the said B component so that it may become
0.5 to 100 parts of B components with respect to 100 parts of A components.
More preferably, it is 1 to 80 parts, particularly preferably 5 to 55 parts.
That is, when the compounding amount of the B component is too small, such as less than 0.5
part, a sufficiently high internal loss is difficult to obtain, and conversely, when the B component
exceeds 100 parts, the workability at the time of heat and pressure molding It is because there is
a tendency that the moldability is deteriorated and the releasability from the mold is lowered.
[0028]
In the foamable composition of the present invention, in addition to the above-mentioned
essential components A and B, a softener, a foaming agent, a vulcanizing agent, a vulcanization
accelerator, a filler, a rubber reinforcing agent, and ultraviolet light absorption Various assistants
such as an agent, an antiaging agent, a natural resin, a synthetic resin, a foaming assistant and
the like can be appropriately blended as required.
[0029]
Examples of the softeners include low molecular weight plasticizers such as dioctyl phthalate and
dibutyl phthalate, polymer plasticizers such as polyester plasticizers, lubricating oils such as
spindle oil, machine oil and cylinder oil, paraffin process oil, naphthenic oil Process oil such as
process oil, petroleum softener such as paraffin such as liquid paraffin and petroleum jelly, coal
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tar softener such as coal tar and coal tar pitch, aliphatic softener such as castor oil and
cottonseed oil Examples thereof include waxes such as beeswax and lanolin, resins which are
liquid or solid at normal temperature, and other liquid rubbers such as polybutene.
These may be used alone or in combination of two or more. And it is preferable to set the
compounding quantity of the said softening agent to 200 parts or less with respect to 100 parts
of A components, especially the range of 1 to 150 parts.
[0030]
As the above-mentioned foaming agent, nitroso compounds such as N, N'dinitrosopentamethylenetetramine, N, N'-dimethyl-N, N'-dinitrosotephthalamide,
azodicarbosoamide, azobisisobutylonitrile, diazoamino Examples include azo compounds such as
benzene; sulfonyl hydrazide compounds such as benzene sulfonyl hydrazide and toluene sulfonyl
hydrazide; p-toluene sulfonyl azide; 4,4'-diphenyl sulfonyl azide; 4,4'- oxybis benzoso sulfonyl
hydrazide and the like. These may be used alone or in combination of two or more. And it is
preferable to set the compounding quantity of the said foaming agent to the range of 0.1-30
parts with respect to 100 parts of A components, More preferably, it is 1-20 parts.
[0031]
Examples of the vulcanizing agent include sulfur, sulfur compounds such as sulfur chloride and
sulfur dichloride, oximes such as p-quinone dioxime, carbamates such as hexadiamine carbamate
and ethylene diamine carbamate, and others such as selenium and lithium surge. . These may be
used alone or in combination of two or more. And it is preferable to set the compounding
quantity of the said vulcanizing agent in the range of 0.01-10 parts with respect to 100 parts of
A components, Especially preferably, it is 0.1-5 parts.
[0032]
Examples of the vulcanization accelerator include guanidine compounds such as
diphenylguanidine and triphenylguanidine, thiazole compounds such as 2-mercaptobenzothiazole
and dibenzothiazole disulfide, thiourea compounds such as thiocarbanilide and diethylthiourea,
and tetramethylthiuram mono Thiuram compounds such as sulfide and tetramethylthiuram
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disulfide, and dithiocarbamate compounds such as zinc dimethyldithiocarbamate and sodium
dimethyldithiocarbamate. These may be used alone or in combination of two or more. And it is
preferable to set the compounding quantity of the said vulcanization accelerator to the range of
0.1-20 parts with respect to 100 parts of A components.
[0033]
Examples of the filler include calcium carbonate, talc, clay, asbestos, pumice powder, glass fibers,
inorganic fillers such as mica, silica and hollow beads, and organic fillers such as regenerated
rubber, shellac, wood powder and cork powder. And fibers such as polyester, acrylic, nylon,
aramid and cellulose. These may be used alone or in combination of two or more. And it is
preferable to set the compounding quantity of the said filler in the range of 10-200 parts with
respect to 100 parts of A components.
[0034]
Examples of the rubber reinforcing agent include carbon black such as channel black and furnace
black, silicas and the like. These may be used alone or in combination of two or more. And it is
preferable to set the compounding quantity of the said rubber reinforcing agent in the range of
10-100 parts with respect to 100 parts of A components.
[0035]
Further, among the above-mentioned various auxiliary agents, examples of the UV absorber
include benzophenone compounds, benzotriazole compounds and the like. Further, examples of
the above-mentioned antiaging agent include phenol compounds, amine ketone compounds,
aromatic amine compounds and the like. And, as the above-mentioned foaming aid, salicylic acid,
urea and the like can be mentioned. It is preferable to set the total amount of the adjuvant to 0.1
to 100 parts with respect to 100 parts of A components, as for the compounding quantity of the
said various adjuvant.
[0036]
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Examples of the above-mentioned natural resin and synthetic resin include conventionally known
ones such as coumarone resin, phenol resin, terpene resin and hydrogenated petroleum resin.
These may be used alone or in combination of two or more. Preferred are hydrogenated
petroleum resins from the viewpoint of compatibility and durability. The compounding amount of
the resin is preferably set to 100 parts or less, particularly 1 to 60 parts, per 100 parts of the
component A.
[0037]
Among the blending components of the foamable composition, a combination of particularly
preferred blendings is a terpolymer of ethylene-propylene-ethylene norbornene as the
component A, and a glass transition as the component B from the viewpoint that an appropriate
vulcanization rate can be obtained. Hydrogenated product of polystyrene and polyisoprene
copolymer at temperature (Tg) of -20 to 10 ° C (by DSC method), paraffin softener as softener,
azodicarbosoamide as foaming agent, sulfur as vulcanizing agent A combination using zinc oxide
as a vulcanization aid, tetramethylthiuram disulfide as a vulcanization accelerator, talc as a filler,
carbon black as a rubber reinforcing agent, urea as a foaming aid, and a hydrogenated petroleum
resin.
[0038]
The foamable composition of the present invention is produced, for example, as follows.
That is, components A and B, which are the above-mentioned essential components, and, if
necessary, the above-mentioned various additives are appropriately blended and kneaded, and
further sheet-like (about 1 to 3 mm thickness) or film-like using appropriate means It
manufactures by shape | molding (thickness less than 0.1 mm).
[0039]
A member for an electroacoustic transducer made of the foamable composition obtained in this
manner is, for example, charging the foamable composition into a mold having a predetermined
shape, heating and pressurizing it to foam and adding the foamable composition. It can be
produced by vulcanization. In addition, after the foamable composition formed into the sheet
shape or the film shape is punched into a predetermined shape, the punched product may be
heated and pressurized in a molding die.
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[0040]
The heating and pressure molding conditions by the molding die are appropriately set depending
on the composition of the compounding component of the foamable composition, the thickness
of the sheet-like or film-like molding, etc. The pressure is set to 250 ° C., the pressure to 1 to 10
kg / cm 2, and the time to 0.02 to 30 minutes.
[0041]
It is desirable to design the foaming ratio of the member for an electroacoustic transducer
obtained by the above-described heat and pressure molding to be 1.05 to 30 times, particularly
preferably 1.1 to 15 times.
[0042]
Furthermore, the internal loss (tan δ) of the obtained member for an electroacoustic transducer
can be appropriately changed depending on the composition of the compounding component of
the foamable composition.
[0043]
The internal loss (tan δ) is defined as follows.
[0045]
Specific examples of the member for an electroacoustic transducer thus obtained include an edge
member for an electroacoustic transducer and a dustproof cap for an electroacoustic transducer.
[0046]
Next, an example will be described together with a comparative example.
[1712]
[Examples 1 to 7 and Comparative Examples 1 to 2] A foamable composition was prepared by
blending the components shown in Tables 2 and 3 below in the proportions shown in the same
Table.
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Then, the foamable composition is molded into a sheet having a thickness of 1.5 mm, and this
sheet-like molded product is cut into a predetermined size, and put into a cavity of a
predetermined speaker edge molding die, 4 kg / cm 2 The mold was clamped at a pressure of 1,
and foaming and vulcanization were performed under heating conditions of 200 ° C. for 1
minute to obtain a foamed rubber edge of a predetermined shape.
[0048]
Next, the obtained foamed rubber edge is punched to a predetermined size, and further bonded
to a cone-shaped paper diaphragm main body (weight: 2.7 g) which has been molded and
punched into a predetermined shape in advance, and has a diameter of about 16 cm. Was
produced.
[0051]
The foaming ratio of the obtained foamed rubber edge was measured and calculated in the
following manner.
That is, the specific gravity was measured according to JIS K 6767, and calculated by the inverse
calculation method from this specific gravity.
The results are shown in Tables 4 to 5 below.
[0052]
Also, the diaphragms of Examples 2, 5 and 6 and Comparative Example 1 obtained as described
above were incorporated into a speaker, and the relationship between frequency and sound
pressure characteristics was measured according to the following method.
The results are shown in FIG. 1 (Example 2 product), FIG. 2 (Example 5 product), FIG. 3 (Example
6 product) and FIG. 4 (Comparative Example 1 product). From the results of FIGS. 1 to 4 above, in
the example product with high internal loss, particularly the mid-range (frequency band 8001500 Hz of the horizontal axis) of the frequency-sound pressure characteristics is more
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compared to the comparative example product with low internal loss. You can see that it is flat.
Next, although measurement was also performed on the example products other than the
example product used for the above measurement, similar results were obtained.
[0053] Further, the speaker incorporating the above diaphragm was subjected to a heat
resistance test at 110 ° C. for 96 hours to measure the rate of change of f 0 (minimum
resonance frequency). Furthermore, the internal loss (tan δ) at a specific frequency was
measured according to the following method. These results are shown in Tables 4 to 5 below.
[0054] [Internal Loss] A foamable composition formed into a sheet having a thickness of 1.5 mm
was foamed and vulcanized under heating conditions of 200 ° C. for 1 minute to prepare a
sheet having a thickness of about 1 mm. Then, the sheet was punched into a predetermined
shape and measured using a dynamic viscoelasticity measuring device (measurement frequency
is described in Tables 4 to 5 below).
[0055] [Press Formability] The mold releasability from the mold and the degree of deformation
after removal from the mold at the time of molding with the speaker edge mold of the above
Examples and Comparative Examples were examined and evaluated as press formability. That is,
as for the releasability, the peeling resistance by human hands was examined, and it was judged
based on the result for mass productivity. Moreover, about the deformation degree, the
dimension was measured and it determined by the pass / fail with respect to drawing dimension
specification (tolerance).
[0058] From the above Tables 4 to 5, it can be seen that the product of Example has excellent
acoustic characteristics and durability because it has a high internal loss and a small f0 change
rate. On the other hand, regarding the comparative example product, although the comparative
example 1 product (EPDM 100%) is excellent in durability, since the internal loss around 1000
Hz is small, the midrange of the frequency-sound pressure characteristic that the present
invention has a problem A mountain-valley is produced near (500 to 2 kHz). Moreover, since the
comparative example 2 product (SBR 100%) has a high internal loss in the vicinity of 1000 Hz,
the frequency-sound pressure characteristics near the middle region (500 to 2 kHz) which the
present invention has a problem have few peaks and valleys. Although excellent, there is a
problem with durability.
[0059] As described above, the present invention is a foamable composition comprising, as
essential components, the specific three component copolymer (component A) and the specific
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thermoplastic elastomer (component B). . For this reason, the member for an electroacoustic
transducer obtained by using this foamable composition is excellent in the durability and has a
high internal loss, so that the frequency-sound pressure characteristics particularly in the middle
band where the present invention is a problem. , Good characteristics with few peaks and valleys
can be provided for a long time even under severe environments.
[0060] Further, in the above essential components, by setting the compounding amount of the B
component to a specific range with respect to 100 parts of the A component, higher internal loss
and excellent durability can be obtained.
[0061] Therefore, the foamable composition of the present invention is most suitable as a
molding material for an electroacoustic transducer edge material or a member for an
electroacoustic transducer that is a dustproof cap for an electroacoustic transducer.
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