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JP2004269756

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DESCRIPTION JP2004269756
An object of the present invention is to make it possible to easily manufacture a thin speaker
edge or other damping material having a thickness of 10 to 300 μm, which is used for a small
speaker, with a small thickness unevenness by sheet forming. A sheet is formed of a
thermoplastic elastomer mainly composed of a mixture of polypropylene and a styrenic
elastomer, wherein the vulcanizing agent content of the styrenic elastomer is 0.2% by weight or
less, and a polypropylene and a styrenic system. The weight mixing ratio of the thermoplastic
elastomer is 90/10 to 30/70, the thickness of the sheet is 10 to 300 μm, and tan δ at 25 ° C.
is 0.09 or more. [Selected figure] None
Vibration control sheet
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sheet for damping material made of a thermoplastic elastomer, for example, for thermoforming a
thin damping material or damper such as a small speaker edge with a heating mold. It relates to a
suitable sheet material. [0002] As a thermoplastic elastomer composition that can be used to
form a speaker edge, a thermoplastic resin (A having a softening point of 80 ° C. or higher)
comprising a matrix phase and a dispersed phase, as described above And a polymer (B) having a
peak temperature of 0 to 50 ° C. and a peak temperature of tan δ, and the above dispersed
phase is formed of an elastomer (C) having a glass transition point of −20 ° C. or less What was
formed with the elastomer composition containing is known (refer Unexamined-Japanese-Patent
No. 2001-59057). The above-mentioned thermoplastic elastomer composition is prepared by
melt-kneading the above-mentioned thermoplastic resin composition and elastomer composition
in advance and dispersing the elastomer composition as a dispersed phase in the thermoplastic
resin composition forming the matrix phase. And, the vulcanizing agent is added under the
above-mentioned kneading, and the elastomer composition is produced by dynamic
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vulcanization. Then, the obtained thermoplastic elastomer composition is processed into an edge
of a supporting member of a vibration system, for example, a speaker cone by injection molding,
press molding or the like. However, in the above-mentioned thermoplastic elastomer
composition, the elastomer composition forming the dispersed phase in the matrix phase
comprising the thermoplastic resin composition is vulcanized, and the speaker edge is directly
produced by injection molding. It is difficult to form a thin speaker edge with a thickness of 200
μm or less, which is used for small-sized speakers such as in-vehicle AV equipment, personal
computers, mobile phones, etc. There was a problem with SUMMARY OF THE INVENTION The
damping material sheet according to the present invention is a sheet of a thin speaker edge
having a thickness of 10 to 300 μm, which is used for the above-mentioned small-sized speaker,
and other damping material, which is heat using a mold. By molding, it can be easily
manufactured with small thickness unevenness. The sheet for vibration damping materials
according to the present invention is a sheet molded of a thermoplastic elastomer containing a
mixture of polypropylene and a styrene elastomer as a main component, and the abovementioned styrene elastomer Content of the vulcanizing agent is 0.2% by weight or less, the
weight mixing ratio of polypropylene and styrene thermoplastic elastomer is 90/10 to 30/70,
the thickness of the sheet is 10 to 300 μm, and tan δ at 25 ° C. is 0 .09 or more.
The sheet for damping material described above is melt-blended by feeding the above-mentioned
polypropylene and styrenic elastomer in a predetermined ratio to a single- or twin-screw
extruder, and after extruding into strands, it is given By long cutting into pellets, the resulting
pellets are formed into a sheet by a T-die extruder, or the above-mentioned polypropylene and
styrenic elastomer are supplied directly to the T-die extruder at a predetermined ratio, and melt
mixed It can be produced by extruding in the form of a sheet and can be made thinner by
stretching immediately after extrusion. And since it is a sheet which consists of a thermoplastic
elastomer, damping materials, such as a speaker edge, can be shape | molded by secondary
molding using a heating metal mold, and thickness is thin compared with injection molding,
compression molding, etc. The damping material can be easily manufactured without thickness
unevenness. Further, since polypropylene is used which is excellent in heat resistance and water
resistance, even when the speaker edge of an automotive AV apparatus is molded, the physical
property is deteriorated due to thermal deformation or the influence of moisture and humidity.
The sound quality is stable and effective for weight reduction. In addition, since a styrenic
elastomer having excellent damping properties is used, a sheet for damping materials having
good damping properties can be obtained. In addition, since the styrene-based elastomer used in
the present invention has a vulcanizing agent content of 0.2% by weight or less, dynamic
vulcanization of the styrene-based elastomer is hardly carried out during melt mixing. Thus, a
combination of extrusion and stretching readily provides a 10-300 μm thick sheet. And, the
thinness of the sheet can make the sheet flexible and prevent the curing associated with the lack
of the flexible dispersed phase. However, if the thickness of the sheet is less than 10 μm, the
sheet is likely to be broken. Conversely, if it exceeds 300 μm, the flexibility is lost. On the other
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hand, when the vulcanizing agent content exceeds 0.2% by weight with respect to the blending
amount of the styrene-based elastomer, dynamic vulcanization proceeds at the time of meltkneading, and it becomes difficult to form a thin sheet. When the weight mixing ratio of
polypropylene and styrene elastomer exceeds 90/10, the tan δ at 25 ° C. of the thermoforming
damping sheet is less than 0.09, and it is molded as an edge or other damping material. In the
case of the speaker edge, in particular, resonance occurs and the sound quality is degraded. In
addition, when the weight mixing ratio of polypropylene and styrenic elastomer is less than
30/70, heat resistance is insufficient, and deformation occurs at a temperature of 80 ° C.
The sheet for vibration damping materials according to the present invention is mainly composed
of a mixture of polypropylene and a styrene-based elastomer, but the above-mentioned
polypropylene is a homopolymer of propylene and a copolymer of propylene and ethylene. If the
ethylene content exceeds 20% by weight, including those having an ethylene content of 20% by
weight or less, it is not preferable because the heat resistance decreases. Further, examples of the
above-mentioned styrenic elastomer include polystyrene / polybutadiene / polystyrene triblock
copolymer, polystyrene / polyisoprene / polystyrene triblock copolymer, and hydrogenated
products thereof. As long as tan δ at 25 ° C. of the material sheet is 0.09 or more, any triblock
copolymer and its hydrogenated substance can be used alone or in combination of two or more.
When the above-mentioned tan δ is less than 0.09, the damping property is insufficient and it
can not be used as a damping material. In the above-described triblock copolymer, the
polystyrene / polyisoprene / polystyrene triblock copolymer and the hydrogenated product
thereof have a tan δ at 25 ° C. of 0.3 or more, and the triblock copolymer described above.
Highest in coalescence, ie in styrenic elastomers. Therefore, even when the above-described
polystyrene / polyisoprene / polystyrene triblock copolymer or its hydrogenated substance is
used alone or when it is mixed with other triblock copolymers, the polystyrene / polyisoprene /
polystyrene triblock When the blending amount of the copolymer is 10% by weight or more
based on the total amount of the polymer, ie, the total amount of the polypropylene and the
styrenic elastomer, the tan δ at 25 ° C. of the sheet for vibration damping materials can be
easily 0.09 It can be more than. As described above, the sheet for vibration damping materials
according to the present invention is mainly composed of a mixture of polypropylene and a
styrenic elastomer, but as additives, coloring agents, lubricants, anti-aging agents and anti-static
agents One or more of them can be contained as needed. In particular, by adding a fatty acid
ester, a fatty acid amide or any other optional lubricant, a nonionic, an anionic, a cationic or any
other antistatic agent, the sheet is formed or the resulting sheet is subjected to thermoforming
for secondary processing. Occurrence of wrinkles is prevented, releasability is improved, and
processability is further improved.
As the above-mentioned additive, a masterbatch diluted with a polymer or a filler can be used.
And, when the dilution material is not a material of the same component as the above-mentioned
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main component polypropylene or styrenic elastomer, it is preferable to make the addition
amount of the dilution material 1/10 or less of the above-mentioned main component. In
addition, the sheet surface can be processed into a mat to further improve the processability at
the time of the thermoforming. BEST MODE FOR CARRYING OUT THE INVENTION Embodiment
1 A polystyrene / polyisoprene / polystyrene triblock copolymer having a tan δ of 0.3 or more
at 25 ° C. or a hydrogenated product thereof is prepared as a styrenic elastomer, In a singlescrew or twin-screw extruder, polypropylene and the above-mentioned styrenic elastomer are
added at a weight mixing ratio of 90/10 to 30/70, no vulcanizing agent is added, and melt
mixing is carried out at a temperature of 180 to 200 ° C. The mixture is extruded into strands,
which are cut into pellets. The obtained pellet is supplied to a T-die extruder at a temperature of
180 to 200 ° C. to form a sheet for damping material having a thickness of 10 to 300 μm,
preferably 100 μm or less, and the surface is matted. Thereafter, the damping material sheet is
cut into an arbitrary size, and a speaker edge and other damping materials are molded and
cooled by secondary molding using a heating mold, for example, vacuum molding or pressure
molding. Embodiment 2 In the above embodiment 1, the lubricant and the antistatic agent are
added in the form of a master batch containing polyethylene or polypropylene as a dilution
material, and the other sheet is the same as in embodiment 1 as a sheet for damping material.
Then, it is cut into an arbitrary size, and a speaker edge or the like is formed by secondary
molding. Embodiment 3 In the above embodiment 1, 10% by weight or more of polystyrene /
polyisoprene / polystyrene with respect to the total amount of polypropylene and triblock
copolymer of polystyrene / polyisoprene / polystyrene (or a hydrogenated product thereof) (25
° C.) is a portion of the above-mentioned polystyrene / polyisoprene / polystyrene triblock
copolymer (or its hydrogenated substance) so that the triblock copolymer (or its hydrogenated
substance) of Substituting less than 0.3 of polystyrene / polyisoprene / polystyrene triblock
copolymer, polystyrene / polybutadiene / polystyrene triblock copolymer, or any of these
hydrogenated substances Similarly, a sheet for damping material is manufactured, and this sheet
is A speaker edge etc. are manufactured by secondary molding using.
Embodiment 4 In the above-mentioned Embodiment 3, the lubricant and the antistatic agent are
added in the form of a master batch containing polyethylene and polypropylene as dilution
materials, and in the same manner as in Embodiment 1, the sheet for damping material Then, it is
cut into an arbitrary size, and a speaker edge or the like is formed by secondary molding.
EXAMPLES The following were prepared as polypropylene resins. Resin 1: Homopolymer of
propylene, "Idemitsu PP F704NP" manufactured by Idemitsu Petrochemical Co., Ltd. Resin 2:
Propylene / ethylene random copolymer, Grand Polypro F327D manufactured by Grand Polymer,
Inc. Resin 3: Homopolymer of propylene, Grand polymer Co., Ltd. "Grand Polypro F109D" The
following were prepared as styrenic elastomers. E1: Polystyrene / polyisoprene / polystyrene
triblock copolymer (Kuraray's “Hibler 5127”, tan δ at 25 ° C. is 1.100) E2: Polystyrene /
polyisoprene / polystyrene triblock copolymer (Kuraray Co., Ltd. "Hybuller 5125", tan δ at 25 °
C is 0.780) E3: Polystyrene, polyisoprene, polystyrene triblock copolymer hydrogenated
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substance (Kuraray's "Hybuller 7125", at 25 ° C tan δ is 0.450) E4: Hydrogenated substance of
triblock copolymer of polystyrene, polyisoprene and polystyrene (Hylar 7311 manufactured by
Kuraray Co., Ltd., tan δ at 25 ° C. is 0.340) E5: Polystyrene and polyisoprene -Triblock
copolymer of polystyrene (manufactured by Kuraray "CEP Ton 2004 ", tan δ at 25 ° C. is
0.070) E6: Hydrogenated product of styrene butadiene rubber (" Dynalon 1320 P "manufactured
by JS AR, tan δ at 25 ° C. is 0.073) The following were prepared as elastomers of E7: Ethylenepropylene-ethylidene norbornene copolymer ("JSR EP22" manufactured by JS AR Co., Ltd.) E8:
Polyether-based thermoplastic polyester elastomer ("Hytrel 6377" manufactured by Toray
DuPont Co., Ltd.), tan δ at 25 ° C is 0. E5: Polyether-based thermoplastic polyurethane
elastomer ("Kramilon 9180" manufactured by Kuraray Co., Ltd., tan δ at 25 ° C. 0.088).
Examples 1 to 10 and Comparative Examples 1 to 7 Resins and Elastomers Above The sheets for
vibration damping materials of Examples 1 to 10 and Comparative Examples 1 to 7 were
produced by using the above.
First, the above-mentioned resin and elastomer are blended in a predetermined ratio, melt mixed
in a twin-screw extruder, extruded into strands, and cut into pellets. The resulting pellets were
then stretched while being extruded from a T-die extruder. However, in Comparative Example 5,
2,5-dimethyl-2,5-di (t-butylperoxy) hexane ("Perhexa 25B" manufactured by NOF Corp.) was
added as a crosslinking agent. The properties of the resulting sheet were evaluated by the
following and the results are listed in Tables 1 to 3 below along with the formulations. tan δ: A
sheet molded into a thickness of 150 μm was subjected to dynamic viscoelasticity measurement
using a viscoelastic spectrometer (“VES-F-III” manufactured by Iwamoto Seisakusho Co., Ltd.),
and tan δ at 25 ° C. was measured. However, in Table 3, the first digit "0" is omitted. Heat
resistance: A sheet molded to a thickness of 50 μm was left in a gear oven at a temperature of
80 ° C. for 1 hour, and the presence or absence of deformation due to softening was observed.
Hydrolysis resistance: A sheet molded into a thickness of 150 μm is left for 10 days in an
environment of temperature 80 ° C. and humidity 90%, tensile elongation at break of the sheet
before and after the test is measured, and from its retention rate hydrolysis resistance Judge the
quality, and make the retention rate 80% or more good. Sheet formability: When forming a sheet
with a T-die extruder, the take-up speed is gradually increased, the thickness is reduced to 10
μm, the one where 10 μm is obtained is regarded as ○, which is broken in the middle or the
hole is opened Recorded the thickness at that time. <Img class = "EMIRef" id = "19839532200002" /> <img class = "EMIRef" id = "198395322-00003" /> <Img class = "EMIRef" id =
"198395322-00004" /> As seen in Tables 1 and 2 above, each of Examples 1 to 10 has tan δ,
heat resistance and hydrolysis resistance. All of the properties and sheet formability were good.
On the other hand, Comparative Example 1 does not have an elastomer component, so tan δ is
low, and Comparative Example 2 has a low resin component, so heat resistance is low, and
Comparative Examples 3 and 4 have a low tan δ of the used elastomer, so the tan δ of the sheet
is I was short.
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In addition, in Comparative Example 5, EPDM was mixed with the elastomer and vulcanized, so
the sheet formability became worse. Further, in Comparative Example 6, only the polyester
elastomer was used, so tan δ was low and the hydrolyzability was low. Moreover, since only
polyurethane was used in Comparative Example 7, the tan δ and the hydrolyzability were
inferior, and the sheet formability was slightly inferior to that of Examples. Example 11 In
Example 6 described above, 0.2 parts by weight of a lubricant (stearoamide, “Diamid 200”
manufactured by Nippon Kasei Co., Ltd.) as an additive and an antistatic agent (polyhydric
alcohol derivative, first industrial pharmaceutical product) A sheet having a thickness of 50 μm
and a thickness of 300 m (Example 11) is formed in the same manner as in Example 6 except
that 0.1 parts by weight of “Resistat PE139” manufactured by Co., Ltd. is added. Of Example 6
was compared with Example 6, Example 11 had wrinkles while Example 11 had no wrinkles. The
tan δ, heat resistance and hydrolysis resistance were the same as in Example 6. As described
above, the damping material sheet according to the present invention can be molded with a
damping material such as a speaker edge by secondary molding using a heating mold, and
injection molding or the like Compared with the case where the above-mentioned damping
material is molded from an indeterminate composition by compression molding or the like, a
damping material having a small thickness can be easily manufactured without thickness
unevenness. In addition, since the vibration damping material obtained is excellent in heat
resistance and water resistance, it does not undergo thermal deformation or the physical
properties are not affected by the influence of moisture or humidity, which is effective for weight
reduction. And has excellent damping properties. In particular, the invention according to claim 2
can easily make tan δ to be 0.09 or more, which facilitates the production of a sheet for
damping materials, and the invention according to claim 3 is also applicable to the case where
the sheet thickness is thin. Wrinkle generation can be prevented, and in the invention according
to claim 4, the processability at the time of thermoforming of the sheet secondary processing is
further improved.
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