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JP2002159093

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DESCRIPTION JP2002159093
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker diaphragm edge material used for an edge portion or the like outside the diaphragm of a
speaker and a method of manufacturing the same. In particular, the sound pressure is high in the
low to mid range and the sound at around 1000 Hz. The present invention relates to a foam
speaker diaphragm edge material excellent in flat characteristics with less pressure drop (dip)
and a method of manufacturing the same.
[0002]
2. Description of the Related Art In order to improve the acoustic characteristics of the edge
portion provided on the outer peripheral portion of a speaker diaphragm, vibration of the
diaphragm is suppressed, excess vibration is attenuated, and vibration of the diaphragm is also
performed. It is necessary to fully exhibit the characteristics of the diaphragm without giving
excessive stress to the
[0003]
For this reason, various characteristics such as internal loss are required as needed without
causing the edge itself to cause abnormal vibration due to resonance etc., and even if it is placed
under severe environment (water resistance, moisture resistance, cold resistance, heat resistance,
light resistance etc) It is necessary to have strength that can exhibit characteristics and withstand
strong vibrations.
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In order to meet these demands, the following materials are mainly raised as members
conventionally adopted.
[0004]
<Cross-edge material> This is a natural fiber, synthetic fiber, non-woven fabric, woven fabric,
impregnated with thermosetting resin, heat-pressed and molded material, or depending on the
application, dump material (damping resin) And so on), etc., and it is a fiber-based material.
[0005]
<Urethane Edge Material> This is a material obtained by forming a urethane foam which has
been foamed about 30 times by heat pressing, and a resin which is formed by heat pressing.
[0006]
<Rubber edge material> This is a material formed by mixing a chemical such as a vulcanizing
agent with a rubber raw material and vulcanizing with a heat press.
[0007]
<Foam rubber edge material> This is a material formed by mixing a rubber material with
chemicals such as a vulcanizing agent and a foaming agent, and vulcanizing with a heat press.
It is intended to improve the speaker sensitivity and the acoustic characteristics by reducing the
specific gravity and increasing the internal loss rate by foaming the rubber edge.
[0008]
<Elastomer Edge Material> As the elastomer edge material, a material obtained by vacuum
molding or hot press molding a urethane elastomer, an ethylene polypropylene rubber elastomer,
or an olefin elastomer is mainly adopted.
[0009]
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2
However, the above-described conventional materials have the following problems.
<Cross-edge material> The fiber-based material has problems with processability, strength,
characteristics, etc. of non-woven fabric, and mainly woven fabric is adopted, but the woven
fabric mainly has vertical and horizontal direction and weave directionality Yes, the vibration
from the diaphragm is absorbed and damped, and the balance is likely to be lost (Ekbo
phenomenon), and it is difficult to summarize the characteristics depending on the speaker shape
and aperture.
The fibers are mainly impregnated with a thermosetting resin, and depending on the state of the
fabric, the resin permeability varies widely, and it is difficult to match the lowest resonance
frequency (fo).
There is also a problem with waterproofness and recycling is impossible.
[0010]
<Urethane Edge Material> When urethane foam is molded by a heat press, a gas with an
unpleasant odor is generated, which is a serious problem as a working environment. The molded
articles have high evaluation of acoustic properties, but there are problems with weatherability,
water resistance, such as hydrolysis, and recycling is impossible.
[0011]
<Rubber edge material> The edge material with heavy specific gravity is limited in its application
as an edge material by reducing the sensitivity of the speaker. Then, after molding, a blooming
phenomenon (state in which an antiaging agent or the like blows white powder) tends to occur,
which may adversely affect the appearance and adhesion, and because of the vulcanized molded
article, recycling is also impossible. Mainly NBR and SBR systems.
[0012]
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<Foam Rubber Edge Material> The gas generated at the time of foam molding is a serious
problem as a working environment, and the gas also contains a strong acid substance, and the
mold also requires maintenance for corrosion resistance. Even as a molded edge material, high
foaming (about 2 times) is made for weight reduction etc., but a large defect is seen in strength
such as cracking due to high power / strong vibration etc., and to give strength Although low
foam may be considered, weight reduction can not be expected with low foam. In addition, it is
easy to produce the blooming phenomenon after shaping | molding, and a bad influence may
arise on an external appearance and adhesiveness. Because of the vulcanized molded articles,
recycling is also impossible. In this manufacturing method, simultaneous bonding with the
diaphragm is also possible during molding, and there are few members that will be lost, and
there are advantages, but the upper and lower molds are required, costing at the time of design,
and many defects at the time of demolding Nowadays, there are many problems.
[0013]
<Elastomer edge material> This has problems in heat resistance and cold resistance, high
hardness and specific gravity, etc., but the type of use is limited but recycling is possible. In
particular, ester-based urethane elastomers are hydrolyzed and can not maintain their shape in
about 5 years in a general environment in Japan. In particular, the olefin-based elastomer type
was tried to improve by foaming because the strength was satisfactory but it was too flexible and
the sound was hard, but it was not possible to retain the mixed gas, and the sample of the surface
state with a cracked appearance. I only got
[0014]
A resin composed of an olefin-based elastomer generally has a low melt viscosity in the melt
processing area in non-crosslinking, so that it can not hold a gas, and a phenomenon called foam
breakage occurs where the foam cell membrane is broken. At the same time as the pressure was
released, the gas was released and only a sheet with poor surface and no bubbles mixed in was
obtained. Further, even if bubbles are mixed to some extent and foamed, the bubbles become
defects, and when stretched, there is a problem that the thin sheet-like foam-formed article can
not be formed due to tearing or opening.
[0015]
In addition, as a low to medium sound speaker, a speaker diaphragm edge material excellent in
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flat characteristics with a large low sound pressure and a small tendency (dip) in which the
sound pressure decreases near 1000 Hz is required. The speaker diaphragm edge material of the
characteristic which fully satisfy | fills the request | requirement was not proposed.
[0016]
In view of the above circumstances, the inventors have obtained a sheet-like foam molded article
excellent in heat resistance, cold resistance, moisture resistance, durability which is not easily
broken even when given a large volume, appearance without surface whitening, and recyclability.
Using this, various experiments were carried out to realize a speaker diaphragm edge material
with characteristics meeting the above requirements.
[0017]
The objects of the present invention are heat resistance, cold resistance, moisture resistance,
durability that can not be broken even with a large volume, excellent appearance without surface
whitening, and excellent recyclability, and can be used for a long time even under harsh
environments such as automobile interiors. It is an object of the present invention to provide a
foam speaker diaphragm edge material capable of obtaining a good sound quality over a wide
range.
[0018]
The other objects of the present invention are heat resistance, cold resistance, moisture
resistance, durability which is not easily broken even if a large volume is given, excellent
appearance without surface whitening, and excellent recyclability, even in a harsh environment
such as an automobile interior. It is an object of the present invention to provide a method for
producing a foam speaker diaphragm edge material which can obtain good sound quality over a
long period of time and which can be manufactured at low cost and low energy without requiring
a special foaming machine.
[0019]
SUMMARY OF THE INVENTION In order to achieve the above object, the foamed speaker
diaphragm edge material of the present invention comprises (1) an olefin-based thermoplastic
elastomer, a styrene-based thermoplastic elastomer, and an ethylene α-olefin copolymer. A
foamed sheet containing three components of a polymer, having a Shore-A hardness of 30 to 70,
a density of 0.70 to 0.89 g / cm 3, a thickness of 0.2 to 1.0 mm, and cells on the cut surface It is
characterized by using wood.
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[0020]
(2) The olefinic thermoplastic elastomer of (1) is produced by a dynamic crosslinking method in
which an organic peroxide treatment is performed while kneading at least two or more of EPDM
and PP, and the melt index is 230 ° C. * 10 kg load at 10 g / 10 min or more and 230 ° C *
2.16 kg load at 50 g / 10 min or less, density at 0.93 g / cm 3 or less at 0.87 g / cm 3 or more,
maximum melting peak temperature by DSC: It is characterized in that Tm (° C.) is in the range
of 130 to 170 ° C.
[0021]
(3) The styrenic thermoplastic elastomer of (1) or (2) is a block copolymer containing styrene
and is characterized by having a Shore-A hardness of 90 or less.
[0022]
Furthermore, (4) the ethylene α-olefin copolymer of (1) to (3) has a comonomer having a carbon
number of at least 5 or more and a melt index of 0.5 to 10 under the conditions of 190 ° C. *
2.16 kg. .0 g / 10 min, density is 0.90 / cm 3 or less, maximum melting peak temperature by
DSC: Tm (° C.) is in the range of 55 to 100 ° C., comonomer ratio to ethylene is 20% or more It
is characterized by certain things.
[0023]
(5) In the above (1) to (4), 20 to 80% by weight of the olefin-based thermoplastic elastomer, 1 to
50% by weight of the styrene-based thermoplastic elastomer, and 1 of the ethylene α-olefin
copolymer It is characterized by containing about 50 wt%.
[0024]
The method for producing a foamed speaker diaphragm edge material of the present invention
comprises (6) a compound containing an olefin thermoplastic elastomer, a styrene thermoplastic
elastomer, and an ethylene α-olefin copolymer, and comprising a screw, a cylinder and a die The
method comprises the steps of forming a sheet-like foam by heating melt foaming extrusion
using an extruder, and heating and vacuum-suctioning the sheet-like foam to form an edge-like
mold. There is.
[0025]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Summary of the Invention) As a
result of further investigations from the material surface, molding surface, etc., the inventor has
developed an olefin-based plastic elastomer compound having good foamability and good gas
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retention. We found that a sheet-like foam-molded product obtained by an extruder had good
vacuum formability and after shaping, it could be a speaker diaphragm edge material with good
shape retention and developed its manufacturing method.
[0026]
Specifically, the olefin-based thermoplastic elastomer is used in combination with a specific
styrene-based thermoplastic elastomer and a specific ethylene α-olefin copolymer without using
the olefin-based thermoplastic elastomer alone to retain the foaming gas. As a result, the
compounding composition suitable for producing thin-walled sheet-like foamed molded products
is drawn during extrusion processing, and the gas generated by the thermal decomposition of the
foaming agent is sufficiently and uniformly held in the melt. Fine and uniform cells are uniformly
distributed throughout the foam, and there are few bubbles in the foam inside and on the surface
of the foam, and the product is completed in one step (extrusion foam molding) It has been found
that an energy-saving, low-loss sheet-like thermoplastic elastomer extrusion-molded article can
be obtained.
This sheet-like thermoplastic elastomer extrusion-molded article can be effectively used in a wide
range of fields by taking advantage of these various properties.
[0027]
The present invention uses the sheet-like thermoplastic elastomer extrusion-molded article
obtained as described above as a speaker diaphragm edge material.
The sheet-like thermoplastic elastomer extruded foam molded body is excellent in mechanical
characteristics at vacuum molding pressure by a good foamed cell structure, and forms a skin
layer, so that a speaker diaphragm edge material is manufactured by vacuum molding Are
particularly advantageous.
The speaker diaphragm edge material obtained in this manner has a soft soft feeling, good cold
resistance, excellent thinning, excellent recyclability, tear resistance that is not easily broken
even when strong earthquakes are added, and it is only at low cost. Instead, they have found that
they have very good acoustic characteristics (low to medium sound pressure, flat characteristics)
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as a speaker.
[0028]
The sheet-like thermoplastic elastomer extrusion-foamed article to be a material of the speaker
diaphragm edge material of the present invention comprises (A) an olefin-based thermoplastic
elastomer, (B) a styrene-based thermoplastic elastomer, and (C) ethylene α-olefin A sheet-like
thermoplastic elastomer extruded foam molded article for a speaker diaphragm edge material,
which comprises a copolymer, and has a hardness Shore-A hardness of 70 or less, a density of
0.85 g / cm 3 or less, and a thickness of 1 mm or less is there.
[0029]
Moreover, the method for producing a sheet-like thermoplastic elastomer extrusion-molded
article according to the present invention comprises (A) an olefin-based thermoplastic elastomer,
(B) a styrene-based thermoplastic elastomer, and (C) an ethylene α-olefin copolymer. A method
of adding 0.1 to 10 parts by weight of one or two or more kinds of a foaming agent selected from
the group consisting of bicarbonate, citrate, diazocarbonamide and hydrazine to 100 parts by
weight of a resin composition containing There is.
[0030]
As another method, there is also a method of injecting an odorless liquefied butane gas, a carbon
dioxide gas or a fluorocarbon gas at the tip of the extruder to obtain a foaming gas.
It is a method for producing a thermoplastic elastomer extrusion-foamed product characterized
in that it is heated, melt-foamed, and extruded using an extruder comprising a screw, a cylinder
and a die.
When liquefied butane is used, a special screw structure having a stirring function for dispersing
the gas in the resin is required.
[0031]
Hereinafter, preferred embodiments of the present invention will be described in detail.
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The extruded foam molded article used for the foamed speaker diaphragm edge material
according to the present invention comprises at least (A) an olefin-based thermoplastic
elastomer, (B) a styrene-based thermoplastic elastomer, and (C) an ethylene α-olefin copolymer
And contains.
Each component will be described below.
[0032]
(A) Olefin-based thermoplastic elastomer As the olefin-based thermoplastic elastomer, for
example, known ethylene α-olefin copolymer rubber as disclosed in JP-B-53-21021, a partially
crosslinked product, and an olefin-based resin Of a continuous kneading mixture, a co-kneaded
partially crosslinked product of a known ethylene .alpha.-olefin and an olefin resin, for example, a
known ethylene .alpha.-olefin copolymer rubber and a portion as disclosed in JP-B-62-59139.
Examples thereof include partially co-crosslinked products of a cross-linked product and an
ethylene-based resin, and mixtures of a rubber-like product and an olefin-based resin.
As an olefin-based thermoplastic elastomer, a dynamic crosslinking method in which organic
peroxide treatment is performed while kneading at least two or more of EPDM (ethylenepropylene-non-conjugated gen terpolymer rubber) and PP (polypropylene) What is obtained is
particularly preferred.
[0033]
The olefin thermoplastic elastomer has an MI of 230 g * 10 kg for 10 g / 10 min or more and
230 g * 2.16 kg for 50 g / 10 min or less, preferably 230 g * 10 kg for 15 g More than 10
minutes, 230 g * 2.16 kg load, 30 g / 10 minutes or less, more preferably 230 g C * 10 kg load,
more than 20 g / 10 minutes, 230 g * 2.16 kg load, 20 g / g It is less than 10 minutes.
[0034]
If the melt index MI is less than 10 g / 10 min at a load of 230 ° C. * 10 kg, the resin flow may
be deteriorated and the extrusion processability may be deteriorated, and the appearance of the
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molded article may be deteriorated. Needs to be processed by
In some cases, the decomposition of the blowing agent can not be controlled, making it difficult
to produce a molded article.
In the case of a load of 230 g * 2.16 kg and 51 g / 10 min or more, the viscosity is too low to
hold the foaming gas, and the cells are broken so that the surface is roughly broken and pinholes
are generated.
The melt index MI mentioned here is a scale representing the fluidity of the thermoplastic resin
at the time of melting, and is a value measured under the conditions of 230 ° C., 10 kg and 2.16
kg load by the method shown in ASTM D1238. is there.
[0035]
The olefin thermoplastic elastomer has a density of 0.93 g / cm 3 or less and 0.87 g / 10
minutes or more, preferably 0.92 to 0.89 g / cm 3.
When the density exceeds 0.93 g / cm 3, the olefin-based thermoplastic elastomer can not retain
the generated gas by the expansion force of the gas, which makes it difficult to expand greatly,
which is not preferable.
[0036]
Furthermore, olefin thermoplastic elastomers have a maximum melting peak temperature by DSC
(Differential Scanning Calorimeter): Tm (° C.) is 130 to 150 from the viewpoint of imparting
heat resistance and strength to the resulting foam sheet 170 degreeC is preferable, More
preferably, it is 130-160 degreeC.
Maximum melting peak temperature by DSC of olefinic thermoplastic elastomer: Tm (° C) less
than 130 ° C can not be used for automobile interior parts because of insufficient heat
resistance, and the resulting foam sheet is less flexible and hard Or the foamability may
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deteriorate, and if the temperature exceeds 170 ° C., the foaming agent begins to be
decomposed in that temperature range, and the sea layer (matrix layer) of the thermoplastic
elastomer is not completed because it enters the gas release temperature range. In the molten
state, it may be difficult to foam.
[0037]
As olefinic thermoplastic elastomers, commercially available products include, for example,
"Milastomer 4010N (trademark)" and "Milastomer 5030N (trademark)" manufactured by Mitsui
Chemicals, Inc. and "Sumitomo TPE Santo Plain (trademark)" manufactured by Sumitomo
Chemical Co., Ltd. , "Santoplane 111-5 (trademark)", "Santoplane 111-55 (trademark)" of
"Santoplane (trademark)" series manufactured by AES, and "CATALLOY (trademark)" series
(Montel, Inc.) KS353P (trademark) etc. are mentioned.
In particular, the above-mentioned "Milastomer 5030N (trademark)" is obtained by a dynamic
crosslinking method in which organic peroxide treatment is carried out while kneading at least
two or more of EPDM and PP, as in a car interior material Is suitable for applications where heat
resistance, strength and texture are required.
[0038]
(B) Styrene-Based Thermoplastic Elastomer The styrene-based thermoplastic elastomer is a block
copolymer containing styrene and preferably has a Shore-A hardness of 90 or less, preferably 50
to 80. The block copolymer containing styrene is preferably a hydrogenated styrene-ethylenepropylene block copolymer called SEPS or a hydrogenated styrene / isobutylene block copolymer
called SEBS. In addition, when the styrene-based thermoplastic elastomer has a Shore-A hardness
of 90, the sheet-like foam molded article becomes hard, and it is difficult to obtain a flexible
speaker diaphragm edge material. Examples of commercial products of styrenic thermoplastic
elastomers include “SeptonTM” series manufactured by Kuraray Co., Ltd., “LavaronTM”
series manufactured by Mitsubishi Chemical Corp., “DynalonTM” series manufactured by JSR,
The “Tuftec (trademark)” series manufactured by Asahi Kasei Co., Ltd. and “Kraton G series
(trademark)” manufactured by Shell Chemical Co., Ltd. can be mentioned.
[0039]
[Ethylene-α-olefin copolymer] As the ethylene-α-olefin copolymer, an ethylene-pentene
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copolymer synthesized under a metallocene catalyst or an ethylene-octene copolymer
synthesized under a metallocene catalyst, etc. preferable.
[0040]
The density of the ethylene / α-olefin copolymer is preferably 0.90 g / cm 3 or less, and
particularly preferably 0.88 g / cm 3 or less.
When the density exceeds 0.90 g / cm 3, the gas generated by the foaming agent can not be
held, which may make it difficult to expand greatly, which is not preferable. In addition, the
sound quality becomes hard due to the hardness. On the other hand, if the density is in the
preferable range of 0.90 g / cm 3 or less, it is preferable in that there is no defect and processing
is possible in a wide temperature range.
[0041]
The MI of the ethylene / α-olefin copolymer is preferably 0.5 to 10 g / 10 min, more preferably
1.0 to 7.0 g / 10 min, and 1.0 to 5.0 g / 10 minutes is particularly preferred. If the MI is less
than 0.5 g / 10 min, the resin flow may be deteriorated and the extrusion processability may be
deteriorated, and the appearance of the molded article may be deteriorated. Therefore, it is
necessary to process at a high temperature. As a result, the decomposition of the blowing agent
can not be controlled and the production of a molded article may become difficult. Furthermore,
if it exceeds 10.0 g / 10 min, there is also a problem that the melt tension necessary for holding
the bubbling gas can not be obtained, and the bubbling gas will escape.
[0042]
On the other hand, when the MI is in the preferable range, it is preferable in that the foam
molding processability can be improved because the above-mentioned defects do not occur. In
addition, MI of ethylene alpha-olefin in the present invention is a scale showing fluidity at the
time of melting of a thermoplastic resin, and is measured under conditions of 190 ° C. and 2.16
kg by a method shown in ASTM D1238. Value.
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[0043]
The highest melting peak temperature by DSC of the ethylene / α-olefin copolymer: Tm (° C.) is
preferably 60 to 100 ° C., and more preferably 60 to 80 ° C. When the maximum melting peak
temperature by the DSC exceeds 100 ° C., it becomes hard and difficult to process and the
obtained foamed sheet becomes hard. On the other hand, if the maximum melting peak
temperature by the DSC is within the above-mentioned numerical range, it is preferable from the
viewpoint of energy saving since it can be processed at a low temperature while being free from
the above-mentioned defects.
[0044]
In the ethylene / α-olefin copolymer, examples of comonomers to ethylene include butene,
pentene, hexene, octene, etc. The ratio of these comonomers is 20% or more, preferably 21 to
30%, more preferably Is preferably 22 to 26%. If the ratio of comonomer to ethylene is less than
20%, sufficient steric hindrance effect of the comonomer can not be obtained, and the degree of
crystallinity increases and the composition becomes hard. The higher the comonomer ratio, the
lower the degree of crystallinity and the greater the flexibility. In addition, since the molecules
are entangled and the viscosity can be maintained even at high temperature, and the foaming gas
retention property is improved, the foaming ratio can be increased. However, if it exceeds 30%, it
is rubbery, and there is a possibility that the motor load may be increased and stopped at the
time of processing of the sheet-like foam molded body by the extruder.
[0045]
As said ethylene-alpha-olefin copolymer, what was synthesize | combined suitably may be used,
and a commercial item may be used. These may be used alone or in combination of two or more.
The ethylene / α-olefin copolymer uses, for example, a geometrically constrained catalyst
containing a metallocene compound, more specifically, a geometrically constrained catalyst (CGC)
which is a kind of single site catalyst (SSC) centering on a metallocene compound It is suitably
obtained by solution polymerization.
[0046]
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When the geometrically constrained catalyst is used, molecular chain structure is not disturbed
even if the amount of comonomer is large, and a large amount of comonomer can be uniformly
introduced, as compared with the case of using the conventional Ziegler catalyst etc., Further,
since the molecular weight distribution can be made in a narrow range, as a result, the
dependency of the melt viscosity on the shear rate is large, which is advantageous in that a
copolymer having high melt tension and excellent moldability can be obtained. Further, among
the geometrically constrained catalysts, the ethylene-octene copolymer produced by a unique
catalyst technology called in-situ technology is the most flexible and viscous and has a good foam
gas retention property.
[0047]
Examples of commercial products of such ethylene / α-olefin copolymers include “Engage
(trademark)” manufactured by DuPont Dow Elastomers, “EXACT (trademark)” series
manufactured by Exxon Chemical Co., Ltd., Mitsui Chemicals, Inc. "Evolue (trademark)" made
from is preferable.
[0048]
In the resin to be foamed, the (A) olefin-based thermoplastic elastomer is 20 to 80% by weight,
preferably 40 to 70% by weight, and more preferably 50 to 65% by weight.
The (B) styrenic thermoplastic elastomer is 1 to 50% by weight, preferably 5 to 20% by weight,
more preferably 5 to 15% by weight. The amount of (C) ethylene α-olefin copolymer is 1 to 50%
by weight, preferably 5 to 40% by weight, and more preferably 20 to 40% by weight.
[0049]
(A) 20 to 80% by weight of an olefin-based thermoplastic elastomer, (B) 1 to 50% by weight of a
styrene-based thermoplastic elastomer, and (C) 1 to 50% by weight of an ethylene α-olefin
copolymer If this is not the case, all four qualities of foamability, flexibility, heat resistance and
processability can not be well balanced, which is not preferable.
[0050]
In the case of foaming using a foaming agent> The foaming agent can be appropriately selected
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according to the type of base resin to be foamed, but for example, if it is a single substance of
ethylene / α-olefin copolymer, foaming is Examples thereof include citric acid-based "EE207
(trademark)" manufactured by Eiwa Kasei Kogyo Co., Ltd. and "Unifine P-3 (trademark)"
manufactured by Otsuka Chemical Co., Ltd. which release carbon dioxide as a gas.
In the case of mixing a heat-resistant thermoplastic elastomer, a nitrogen gas release type having
a high foaming gas pressure and a large amount of gas is preferable. For example, "AZ-H
(trademark)" manufactured by Otsuka Chemical Co., Ltd. is preferably used. The blowing agent is
preferably added in an amount of 0.01 to 10% by weight, more preferably 0.5 to 5% by weight,
based on the entire resin to be foamed.
[0051]
<When foaming gas is injected into the molten resin at the tip of the extruder> Generally, it is a
liquid or gas such as odorless liquefied butane, carbon dioxide gas, fluorocarbon gas, nitrogen
gas, etc., but recently it is more compatible with resin It is also possible to use a good
supercritical fluid. In general, it is better to use carbon dioxide as the supercritical fluid so that it
dissolves in the resin well and fine cells are obtained, and the decrease in strength due to
foaming can be minimized.
[0052]
<Other Additives> In the composition of the present invention, in addition to the above materials,
a lubricant for preventing adhesion during pellet production, a light stabilizer for improving light
resistance, an inorganic material for improving heat resistance and rigidity Fillers, pigments for
coloring and the like can be added as appropriate.
[0053]
As the lubricant, it is preferable to use a high melting point type lubricant having little bleeding
and blooming and having excellent fogging properties.
For example, ethylene stearylamide is suitable. The lubricant is preferably added in an amount of
0.1 to 2% by weight, more preferably 0.2 to 0.5% by weight, based on the base resin.
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[0054]
As a light stabilizer, a benzotriazole ring-containing compound of an ultraviolet light absorber is
already formulated as a foam retarder, so it has a light stabilization effect, but when it needs a
stabilization effect, it has a synergy effect with this Light stabilizers based on high hindered
amines (HALS) are preferred. As a light stabilizer of HALS type, “Tinubin 770 (trademark)”,
“Tinubin 622LD (trademark)”, “Kimasorb 944LD (trademark)” manufactured by Ciba Geigy,
and “LA-77 (trademark)” manufactured by Asahi Denka Kogyo Co., Ltd. ", LA-62 (trademark)"
is preferred. The light stabilizer of the HALS system is preferably added in an amount of 0.05 to
1% by weight, more preferably 0.1 to 0.3% by weight, based on the base resin.
[0055]
As the inorganic filler, calcium carbonate, talc, mica and the like can be mentioned. These
inorganic fillers can be suitably added in the range which does not inhibit foaming. As the
coloring agent, titanium white, carbon black, phthalocyanine blue, watching red, quinacridone
red, titanium yellow and the like can be used.
[0056]
<Method of Forming Sheet-like Extruded Foamed Product> The thermoplastic elastomer extruded
foam according to the present invention can be obtained by a known extrusion foam molding
method. As the extrusion foam molding method, (A) an olefin-based thermoplastic elastomer, (B)
a styrene-based thermoplastic elastomer, (C) an ethylene α-olefin copolymer, and a foaming
agent, a foaming gas, and the like are optionally blended. The compounded composition
containing the components is melt-kneaded / foamed from a screw and a cylinder by an extruder,
rolled into a plate shape by a die called a T-die, and stretched by a nip roll.
[0057]
FIG. 1 is a view showing the entire apparatus configuration for forming a sheet (film) -like
extruded foam-formed body, which comprises an extruder 1, a film forming machine 2, and a
winding machine 3. In the present example, an extruder "FS65-30 (trademark)" manufactured by
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Ikegami Co., Ltd. was used as the extruder 1. The extruder 1 is comprised from the extruder main
body 11 and T-die 12, as shown in FIG. Furthermore, the extruder main body 11 is composed of
a screw 111 and a cylinder 112.
[0058]
In the cylinder 112 of the extruder main body 11, (A) an olefin-based thermoplastic elastomer,
(B) a styrene-based thermoplastic elastomer, (C) an ethylene α-olefin copolymer, a foaming
agent or a foaming gas, etc. as required When the compounded composition (olefin compound)
containing the components to be compounded is added, the compounded composition is meltkneaded and foamed by the rotation of the screw 111 and then rolled into a plate shape by the T
die 12 and released. Furthermore, the film is drawn by the nip roll 21 of the film forming
machine 2, and after the temperature is lowered by the cooling roll 22, the film is taken up by
the winder 3.
[0059]
According to the present invention, Shore-A hardness is 70 or less, preferably Shore-A hardness
20 to 65, preferably Shore-A hardness 20 to 55, and the density is 0.85 g / cm 3 or less,
preferably 0. Sheet-like extrusion of 20 to 0.80 g / cm 3, more preferably 0.20 to 0.70 g / cm 3,
thickness is 1 mm or less, preferably 0.20 to 0.60 mm, more preferably 0.20 to 0.50 mm A foam
can be obtained.
[0060]
<Sheet-like foam molded example> The present invention will be further described in detail by
way of examples, but the present invention is not limited thereto.
In evaluating the example and comparative example of the sheet-like foam-formed body shape |
molded using the raw material of the mixing | blending shown in FIG. 3, extruder foam molding
was performed on condition of the following.
[0061]
The extrusion foam molding was performed using the raw material of the composition of each
Example and each comparative example as shown in FIG. 3 using the extrusion foam molding
machine "FS65-30 (trademark)" by Ikegai Co., Ltd. product.
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[0062]
The environmental conditions for extrusion foam molding are as follows.
(Environmental conditions for extrusion foam molding): Molding machine; “FS65-30
(trademark)” manufactured by Ikegai Co., Ltd. single screw screw; diameter 65 mm, L / D = 30,
compression ratio 2.5, rotation speed 60 rpm lip width; 1250 mm cylinder temperature; 210 °
C. die temperature; 200 ° C. molded article; width 1180 mm, thickness 0.5 mm
[0063]
Example 1 Component (A-1) 60% by weight of an olefin-based thermoplastic elastomer Shore-A
hardness 40 manufactured by Mitsui Chemicals, Inc. and having a MI of 15 g / 10 min (230 ° C.
* 10 kg / cm 2), component (B) -1) Kuraray styrenic thermoplastic elastomer Shore-A hardness
80, MI 100 g / 10 min (200 ° C. * 10 kg / cm 2) 15 wt%, component (C-1) DuPont Dow
Elastomers ethylene Octene copolymer with a density of 0.870 g / cm3 at 25 wt% at 5 g / 10
min (190 ° C * 2.16 kg / cm2) of MI
[0064]
2 parts by weight of a polyethylene kneading masterbatch containing 20% by weight of a citric
acid foaming agent manufactured by EIWA CHEMICAL CO., LTD. And 1 part by weight of a
polyethylene kneading masterbatch containing 20% by weight of pigment carbon black as a
foaming agent at the above resin ratio Did.
As a result, an elastomeric foam having the characteristics shown in FIG. 3 was obtained.
The present invention will be more specifically described by the following experimental
examples.
[0065]
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18
[Evaluation method] (1) Density: The weight of the foam and the weight of the foam in water
were measured to determine the specific gravity. (2) Hardness: Shore-A hardness measurement.
(3) Bubble shape: A cell in a cross section cut out in the drawing direction was observed with a
microscope. The case where it is a spherical air bubble without tearing was made into "(circle)".
When there is a thing in the state in which there was a tear and the next air bubbles connected, it
was set as "x". The evaluation results of Example 1 were the density of 0.817 (g / cm 3), the
hardness of 55 (Shore-A), and the cell shape of “o”.
[0066]
[Example 2] Component (C-1) is an ethylene octene copolymer manufactured by DuPont Dow
Elastomers, which has a low MI of 1.5 g / 10 min (190 ° C * 2.16 kg / cm 2). An elastomeric
foam was obtained in the same manner as in Example 1 except that the density was changed to
0.895 g / cm 3. The evaluation results of Example 2 were the density of 0.8268 (g / cm 3), the
hardness of 65 (Shore-A), and the cell shape of “o”.
[0067]
[Example 3] Component (A-1) was changed to Component (A-2) Olefin-based thermoplastic
elastomer Shore-A hardness 50 manufactured by Mitsui Chemicals, Inc. and MI was 30 g / 10
min (230 ° C. + 10 kg / cm 2) An elastomeric foam was obtained in the same manner as in
Example 1 except for the above. The evaluation results of Example 3 were the density of 0.808 (g
/ cm 3), the hardness of 50 (Shore-A), and the cell shape of “o”.
[0068]
[Example 4] Component (C-1) is an ethylene octene copolymer manufactured by Dupont Dow
Elastomers, which has a low MI of 1.5 g / 10 min (190 ° C * 2.16 kg / cm 2). An elastomeric
foam was obtained in the same manner as in Example 3 except that the density was changed to
0.895 g / cm 3. The evaluation results of Example 4 were the density of 0.8258 (g / cm 3), the
hardness of 62 (Shore-A), and the cell shape of “o”.
[0069]
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19
Example 5 An elastomeric foam was obtained in the same manner as Example 1, except that the
resin composition was the same, but the number of foaming agent parts was increased from 2
parts by weight to 5 parts by weight. The evaluation results of Example 5 were that the density
was 0.7117 (g / cm 3), the hardness was 55 (Shore-A), and the cell shape was “o”.
[0070]
Example 6 An elastomeric foam was obtained in the same manner as in Example 3, except that
the resin composition was the same, but the number of parts of the foaming agent was increased
from 2 to 5 parts by weight. The evaluation result of Example 6 was that the density was 0.7116
(g / cm 3), the hardness was 45 (Shore-A), and the cell shape was “o”.
[0071]
[Comparative Example 1] Component (A-1) Olefin thermoplastic elastomer manufactured by
Mitsui Chemicals Co., Ltd. Olefin-based thermoplastic elastomer Shore-A hardness is 40 and MI is
15 g / 10 min (230 ° C. * 10 kg / cm 2) 100 wt% The same operation as in Example 1 was
carried out by charging 2 parts by weight of a polyethylene mixing masterbatch containing 20%
by weight of a citric acid foaming agent manufactured by Chemical Co., Ltd. and 1 part by weight
of a polyethylene mixing masterbatch containing 20% by weight of pigment carbon black. In this
example, almost no air bubbles were observed and it was hard. As for the evaluation result of
Comparative Example 1, the density was 0.896 (g / cm 3), the hardness was 63 (Shore-A), and
the cell shape was “x”.
[0072]
Comparative Example 2 Component (A-1) Olefin-based thermoplastic elastomer Shore-A hardness
40 manufactured by Mitsui Chemicals, Inc. and having an MI of 15 g / 10 min (230 ° C. * 10 kg
/ cm 2) as a component (A-2) The same operation as in Comparative Example 1 was carried out
except that the olefin-based thermoplastic elastomer Shore-A hardness 50 manufactured by
Mitsui Chemicals, Inc. and the MI were changed to 30 g / 10 min (230 ° C. * 10 kg / cm 2). As
in Comparative Example 1, almost no air bubbles were observed, and it was harder than
Comparative Example 1. The evaluation result of Comparative Example 2 was that the density
was 0.8956 (g / cm 3), the hardness was 73 (Shore-A), and the cell shape was “x”.
11-05-2019
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[0073]
Comparative Example 3 Component (A-1) Olefin-based thermoplastic elastomer Shore-A hardness
40 manufactured by Mitsui Chemicals, Inc. 85% by weight of MI 30 g / 10 min (230 ° C. * 10
kg / cm 2) (B- 1) Kuraray styrenic thermoplastic elastomer Shoer-A hardness 80, MI 100 g / 10
min (200 ° C. * 10 kg / cm 2) as a foaming agent 15 wt% The same operation as in Comparative
Example 1 was carried out by charging 2 parts by weight of the contained polyethylene kneading
masterbatch and 1 part by weight of the pigment carbon black-containing polyethylene kneading
masterbatch. Almost no bubbles were seen and it became hard. As for the evaluation result of
Comparative Example 3, the density was 0.8954 (g / cm 3), the hardness was 63 (Shore-A), and
the cell shape was “x”.
[0074]
Comparative Example 4 Component (A-1) Olefin-based thermoplastic elastomer Shore-A hardness
40 manufactured by Mitsui Chemicals, Inc. and having an MI of 15 g / 10 min (230 ° C. * 10 kg
/ cm 2) as a component (A-2) A foamable molded article was obtained in the same manner as
Comparative Example 1 except that the olefin-based thermoplastic elastomer Shore-A hardness
50 manufactured by Mitsui Chemicals, Inc. and the MI were changed to 30 g / 10 min (230 ° C.
* 10 kg / cm 2). . As in Comparative Example 1, almost no bubbles were observed and the
product was hard. The evaluation result of Comparative Example 4 was that the density was
0.9029 (g / cm 3), the hardness was 70 (Shore-A), and the cell shape was “x”.
[0075]
FIG. 3 is a diagram summarizing and showing the above evaluation results, whereby the
compounding composition used in each example of the present invention is softer than the one
of each comparative example, and retains spherical air bubbles without breakage. It turned out to
be done.
[0076]
Next, the tear strength will be described.
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The tear strength of Examples 1 to 6 was compared with the non-foamed product of styrene
butadiene rubber which has been proven on the current market. Although the foam products are
on the market, they were compared with the non-foam products of high strength as a
comparison.
[0077]
The measurement of tear strength was performed under the following environmental conditions.
[Environmental conditions for tear strength measurement] Specimen size dumbbell type B.
Sample thickness 0.5 mm. Measured at 20 ° C. Autograph use, speed 200 (mm / min).
[0078]
FIG. 4 is a diagram for explaining the direction in which the tear strength is measured. The tear
strength in the four tear directions as shown in the figure was measured, and the weakest tear
strength was adopted as the tear strength in the case of using Examples 1 to 6 and the
crosslinked SBR sheet.
[0079]
FIG. 5 is a view showing the tear strength of the sheet of each composition thus obtained. As
shown in the figure, while the tear strength of the crosslinked SBR sheet is 4.5 N / mm, the tear
strength in the case of Examples 1 to 6 according to the present invention is the lowest at 9.4 N /
mm. (Example 5) It was found that the highest one was 16.9 N / mm (Example 2), and although it
was foamed, it had a tear strength about twice or more that of the crosslinked SBR sheet.
[0080]
<Vacuum Forming Method of Sheet-like Extruded Foam Formed Material to Speaker Diaphragm
Edge Material> Next, a vacuum forming method for forming the sheet-like extruded foam formed
body as described above into a speaker diaphragm edge material will be described.
[0081]
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22
FIG. 6 is a conceptual view for explaining the vacuum forming method, and FIG. 6 (a) is a view
showing a heater heating step, FIG. 6 (b) is a view showing a vacuum suction step, and FIG. It is a
figure which shows a type | mold process.
In the figure, 4 is the developed product as described above (see Examples 1 to 6), 41 is a
cylinder, 42 is a vacuum mold for forming the developed product into a speaker diaphragm edge
material, and 43 is a developed product 4 Clamp for, 44 is a heater.
[0082]
As shown to the figure (a), the developed product 4 is clamped by the clamp 43, it heats with a
heater, and it softens. Next, as shown in FIG. 6B, when the temperature reaches a predetermined
temperature or more, the vacuum mold 42 is raised by a cylinder to bring the developed product
4 into close contact with the vacuum mold and vacuum suction from below. The suction heats
and softens the developed product into a vacuum mold. In the case of the present invention, it
goes without saying that the vacuum type is the type of the edge of the speaker diaphragm. At
this time, the heater 44 is retracted. Next, as shown in FIG. 6C, when the temperature drops to a
certain extent, the clamp 43 is removed, and the molded article edge member 5 vacuum-formed
on the edge of the speaker diaphragm is removed. By the above, the speaker diaphragm edge
material can be shape | molded from the developed product shown in Examples 1-6.
[0083]
In fact, 300X (trademark) manufactured by Formesh UK was used as a vacuum forming machine.
As environmental conditions, it was set to 50 mm of single-sided heaters, product heater
distance, a heater temperature of 350 ° C., and a heating time was about 10 seconds.
[0084]
The die of the edge (vacuum die 42) was pushed up in a state where the stretching distortion in
the extruder was removed and the state of being uneven was a pin, and vacuum formed. The
distortion was taken for about 20 seconds with a fan while vacuum forming. This distortion
11-05-2019
23
removal is important, and this distortion removal can reduce the longitudinal and lateral
anisotropy of the speaker diaphragm edge material, and thus can generate a good sound.
[0085]
A 16 cmφ woofer speaker was actually produced using the elastomer foam of the composition of
Example 1, and the frequency-sound pressure characteristics were measured. Acrylonitrile
butadiene rubber (NBR), which is said to have relatively flat stable sound pressure characteristics
from low frequency to high frequency for comparison, was created with exactly the same
specifications except for the edge material, and the frequency-sound pressure characteristics
were measured. .
[0086]
FIG. 7 is a diagram showing frequency-sound pressure characteristics (i) and (ii) obtained as
described above. It was measured by supplying 1 W of power to the speaker and setting the
output voltage to 2 V at 250 Hz. The figure also shows frequency-impedance characteristics (c)
and (d). In the figure, the solid lines (a) and (c) show the characteristics of the olefin-based
thermoplastic elastomer foam (referred to as TPO (Thermoplastic Elastmer Olefin) foam) of the
composition of Example 1, and broken lines (b) and (d). Shows the characteristics of the
conventional acrylonitrile-butadiene-based rubber (referred to as NBR type).
[0087]
As is clear from the figure, the characteristic (b) of the TPO foam according to the present
invention is lower than that of the conventional NBR type (b) from the low frequency range (100
Hz to 800 Hz) to the middle frequency range (800 Hz to 4000 Hz). The sound pressure is
generally high by about 2 db. This is considered to be because specific gravity became small
because it was made into foam.
[0088]
Further, it can be seen that the flat property of the frequency-sound pressure characteristic of
11-05-2019
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the TPO foam according to the present invention is better than that of the conventional NBR type
(ii). The tendency (dip) in the sound pressure to decrease at around 1000 Hz, which is often seen
in other edge materials, is considerably improved in the foam speaker diaphragm edge material
of the present invention as compared to acrylonitrile-butadiene rubber (NBR) There is. The
frequency around 1000 Hz is the most important area in human voice, and the prevention of the
decrease in sound pressure in this frequency area is strongly desired. The foam speaker
diaphragm edge material according to the present invention substantially satisfies this demand,
and is very promising as an edge material for a speaker diaphragm for a low to mid range (100
Hz to 4000 Hz).
[0089]
(Summary) As described above in detail, the sheet-like thermoplastic elastomer extruded foam
molded article used for the speaker diaphragm edge material of the present invention has an
olefin thermal power so that it can be foamed well and stretched and thinned. It is a product that
is designed to be a mixture of three components of a plastic elastomer, a styrenic elastomer, and
an ethylene / α-olefin copolymer, and is lightweight and is recyclable, which is compatible with
environmental problems.
[0090]
The sheet-like thermoplastic elastomer extrusion-foaming molded body can form a skin layer and
can be vacuum-formed in spite of foaming, so that it can be molded in large numbers at one time,
and conventional styrene butadiene rubber and ethylene propylene diethylene glycol can be
molded. The amount of processing energy used can be reduced compared to the in-mold crosslinked foam type using an enter polymer-based rubber, resulting in cost reduction.
There is no harmful gas generation at the time of molding processing, and the working
environment is clean.
[0091]
The raw material used for the foam speaker diaphragm edge material has a specific gravity of
about 0.9 and is lighter than that of a general styrene butadiene rubber and about 1.2, and
further foams to reduce the weight and increase the internal loss rate to improve the sound
quality To improve In general, better results are obtained than the non-foamed acrylonitrile-
11-05-2019
25
butadiene type in which the flatness of the frequency-sound pressure characteristics is said to be
good. In addition, the thickness can be reduced to 0.5 mm or less, and it is stronger than
conventional products despite being foamed, so it can be used for a wide variety of speakers
from small for computer to large for outdoor concerts. .
[0092]
In addition, it has cleared heat resistance (110 ° C) and cold resistant temperature (-30 ° C)
required for the speaker diaphragm edge material in terms of physical properties, and it can
withstand the severe usage conditions such as for automobile interiors. Especially useful as
[0093]
According to the present invention, it is excellent in heat resistance, cold resistance, moisture
resistance, durability which is hard to break even when given a large volume, appearance without
surface whitening and recyclability, and no special foaming machine is required. Low-cost, lowenergy, high-foaming pressure in the low to mid range over a long period of time even in harsh
environments such as automobile interior, and foam having a flat property with little dip (dip)
around 1000 Hz A speaker diaphragm edge material and a method of manufacturing the same
can be realized.
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