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JP2000217190

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2000217190
[0001]
TECHNICAL FIELD The present invention relates to a speaker edge and a method of
manufacturing the same. More particularly, the present invention relates to a speaker edge
having simultaneously excellent heat resistance, weather resistance, internal loss and excellent
formability and productivity, and a simple manufacturing method thereof. 2. Description of the
Related Art In general, a speaker edge for supporting a speaker diaphragm is required to have
three characteristics: supporting the center of the diaphragm (supportability), air tightness, and
vibration absorbability. As the material for the edge, resin-coated woven fabric, urethane foam,
thermoplastic elastomer, vulcanized rubber and the like are usually used. The resin-coated woven
fabric is insufficient in supportability because of its small thickness and low rigidity. Foamed
urethane and thermoplastic elastomers are excellent in productivity because they can be
prepared in large amounts in advance and can be heat-pressed to form the sheets. Furthermore,
thermoplastic elastomers have insufficient heat resistance and internal loss. Although the
vulcanized rubber is excellent in heat resistance and weather resistance, moldability and
productivity are insufficient. That is, since a vulcanized rubber can not be molded after
vulcanization, it is necessary to mold an indefinite rubber mixture (a mixture containing a rubber
raw material and a vulcanizing agent) into a mold. Moreover, such a mixture is chemically
unstable and the reaction between the rubber raw material and the vulcanizing agent gradually
progresses, so that the degree of vulcanization varies, and even if it is molded, the desired
internal loss Is often not obtained. Furthermore, vulcanized rubber has a problem that it takes a
long time for vulcanization and costs increase. As described above, a speaker edge having
simultaneously excellent heat resistance, weather resistance and internal loss, and excellent
formability and productivity has not yet been obtained. SUMMARY OF THE INVENTION The
present invention has been made to solve the above-mentioned conventional problems, and the
object of the present invention is to provide excellent heat resistance, weather resistance, internal
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loss and excellent formability. It is an object of the present invention to provide a speaker edge
having at the same time and productivity and a simple manufacturing method thereof. [Means for
Solving the Problems] As a result of intensive studies on the material for the speaker edge and
the molding method thereof, the present inventors have found that the heat resistance is
excellent by dispersing and using a specific thermoplastic resin in a specific rubber. It has been
found that a speaker edge having weatherability and internal loss at the same time as excellent
formability and productivity can be obtained, and the present invention has been completed. The
speaker edge of the present invention includes a vulcanized rubber and thermoplastic resin fine
particles which are incompatible with the vulcanized rubber dispersed in the vulcanized rubber.
In a preferred embodiment, the rubber component of the vulcanized rubber is at least one
selected from EPDM, SBR, NBR, CR, IR, IIR, and SR, and the thermoplastic resin is polypropylene,
polybutene-1 And at least one selected from polyethylene. In a preferred embodiment, the
thermoplastic resin fine particles have a rod-like shape. According to another aspect of the
present invention, a method of manufacturing a speaker edge is provided. This method comprises
the steps of dispersing a thermoplastic resin in the rubber, vulcanizing the rubber in which the
thermoplastic resin is dispersed, and simultaneously forming it into a sheet, and making the
obtained vulcanized rubber sheet into a predetermined shape. And a forming step. DETAILED
DESCRIPTION OF THE INVENTION The speaker edge of the present invention comprises a
vulcanized rubber and thermoplastic resin fine particles which are incompatible with the
vulcanized rubber dispersed in the vulcanized rubber. Examples of the rubber component to be
vulcanized include EPDM, SBR, NBR, CR, IR, IIR, SR and the like. Preferred rubber components are
EPDM and SBR. The rubber component may be vulcanized under any suitable conditions using
any suitable amount (for example, 0.5 parts by weight based on 100 parts by weight of the
rubber component) of a vulcanizing agent (sulfur). If necessary, vulcanization accelerators (eg,
MBT, ZnBDC, DPTT) are used. The thermoplastic resin is incompatible with the vulcanized
rubber. As such a thermoplastic resin, polypropylene (PP), polybutene-1 (PB), polyethylene (PE)
etc. are mentioned, for example. The preferred thermoplastic resin is PP. The thermoplastic resin
is in the form of fine particles and is dispersed in the vulcanized rubber. Preferably, the
thermoplastic resin is dispersed in the vulcanized rubber as rod-like fine particles. In the present
specification, the rod-like shape includes, in addition to a normal rod-like shape, an elongated
three-dimensional shape (e.g., oval spherical shape, peanut shape) in general. The rod-like fine
particles typically have a length of about 0.5 to 1.2 μm and a width (diameter) of about 0.2 to
0.3 μm. The thermoplastic resin is contained in a proportion of typically 10 to 60 parts by
weight, preferably 10 to 30 parts by weight, and more preferably about 20 parts by weight with
respect to 100 parts by weight of the rubber component. When the content of the thermoplastic
resin exceeds 60 parts by weight, the tensile modulus is often insufficient. If it is less than 10
parts by weight, molding is often impossible. Next, an example of a method of manufacturing a
speaker edge according to the present invention will be described with reference to FIGS. 1 (a) to
1 (e).
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First, a rubber raw material mixture 4 is prepared by mixing the rubber component (rubber raw
material) 1, the thermoplastic resin 2 and a vulcanizing agent (not shown) in the above ratio (see
FIGS. b). As a mixing method, a roll kneader, a kneader, etc. are mentioned, for example. The
mixing conditions may vary depending on the type of rubber and thermoplastic resin used. For
example, when EPDM is used as a rubber raw material, PP is used as a thermoplastic resin, and a
roll kneader is used as a mixing means, the front roll temperature of the roll kneader is 50 to 60
° C., and the rear roll temperature is 60 to 70 The kneading time is 10 to 20 minutes. Various
additives 3 may be added as needed. Representative examples of the additives include the abovementioned vulcanization accelerators, reinforcing agents (for example, pigments such as carbon
black), mold release agents (for example, stearic acid), acceleration activators (for example, zinc
oxide), A plasticizer (for example, process oil) etc. are mentioned. These additives may be added
in any appropriate amount depending on the purpose. Then, by extruding the rubber material
mixture 4 with an extruder, the rubber is vulcanized and at the same time, the rubber material
mixture is formed into a sheet 5 (FIG. 1 (c)). The die temperature of the extruder may vary
depending on the type of rubber and thermoplastic resin used, but is typically 160 to 180 ° C,
preferably 170 ° C. The thickness of the resulting sheet may vary depending on the purpose,
but is typically 0.2 to 0.3 mm. The resulting vulcanized rubber sheet 5 is formed into a
predetermined shape by heat pressing, whereby the speaker edge 6 of the present invention is
obtained (FIGS. 1 (d) and (e)). The conditions of heat pressing may vary depending on the type of
rubber and thermoplastic resin used. Typically, the heating temperature is 170 to 190 ° C., the
heating time is 20 to 40 seconds, and the pressure at pressing is 5 to 10 kg / cm 2. Hereinafter,
the operation of the present invention will be described. According to the present invention, by
combining and using a specific rubber and a thermoplastic resin incompatible with the rubber, it
is possible to further form a vulcanized rubber sheet, unlike the case where the rubber alone is
vulcanized. The mechanism is as follows: The thermoplastic resin incompatible with the rubber is
dispersed in the form of fine particles in the unvulcanized rubber as shown in FIG. 1 (b) by
kneading. When vulcanization and sheet formation are simultaneously performed on a mixed
material having such a dispersed state, a sheet in which thermoplastic resin fine particles are
dispersed in a vulcanized rubber is obtained. When this vulcanized rubber sheet is hot-pressed at
a temperature above the melting point of the thermoplastic resin, the fine particles of the
thermoplastic resin dispersed in the vulcanized rubber are melted and deformed into a rod shape
by pressing, and deformed by cooling after pressing Solidify and determine the shape.
By utilizing the deformation of the thermoplastic resin fine particles by such a press, a vulcanized
rubber sheet which can not be molded alone can be molded by a heat press. Therefore, the
productivity is significantly improved as compared with the conventional speaker edge in which
the unvulcanized rubber raw material has to be placed in a mold and subjected to batch
processing. Furthermore, by preparing the vulcanized rubber sheet in advance as described
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above, not only the productivity but also the quality of the obtained speaker edge is significantly
improved. That is, since the vulcanized rubber sheet has already been vulcanized, the rubber and
the vulcanizing agent do not react with time. In other words, the vulcanized rubber sheet is much
more chemically stable than an amorphous rubber blend containing unvulcanized rubber and a
vulcanizing agent. Therefore, by forming the edge from the vulcanized sheet, an edge having a
uniform degree of vulcanization and excellent quality can be obtained. In addition, as is apparent
from the results of the examples described later, the moldability is dramatically improved by
using a combination of a rubber and a thermoplastic resin. In addition, even when rubber and
thermoplastic resin are used in combination, excellent weather resistance, heat resistance and
internal loss are maintained as in the case of rubber alone. As described above, according to the
present invention, it is possible to obtain a speaker edge simultaneously having excellent heat
resistance, weather resistance and internal loss, and excellent formability and productivity.
Further, according to the manufacturing method of the present invention, by forming a
vulcanized rubber sheet, it is possible to perform the above-described excellent speaker edge
without performing complicated and skillful operations or increasing the number of
manufacturing steps. It can be obtained simply and inexpensively. EXAMPLES The present
invention will be explained specifically by the following examples, but the present invention is
not limited to these examples. Example 1 The components shown in Table 1 below were kneaded
using a roll kneader (front roll temperature 50 ° C., rear roll temperature 60 ° C.) to prepare a
raw rubber mixture. The raw rubber mixture was extruded into a sheet while being vulcanized
using an extruder (160 ° C. in this example) to prepare a rubber sheet having a thickness of
0.25 mm. The rubber sheet was heat-pressed at 180 ° C. for 30 seconds to obtain roll edges.
This roll edge was subjected to the following evaluation. The evaluation results are shown in
Table 2 below together with the results of Examples 2 to 9 and Comparative Examples 1 to 8.
The tensile strength was measured after the obtained roll edge was left to stand at 70 ° C., 110
° C. and 140 ° C. for 500 hours. The heat resistance was evaluated based on the ratio of the
tensile strength after heating to the tensile strength before heating.
Evaluation criteria are as follows: 割 合 when the ratio is 90% or more; 70% or more and less
than 90% ○; 50% or more and less than 70% 70; less than 50% or less. A strip-like (100 mm ×
10 mm) test piece was cut out from the obtained roll edge, and stretched so that the long side
was doubled (this length is referred to as “initial length”). After heating at 180 ° C. for 5
minutes while maintaining the stretched state, it was cooled in the stretched state. The length of
the long side of the test piece after standing for one day was measured, and the ratio (%) to the
initial length was determined. The closer this ratio is to 100%, the longer the stretched length is
maintained, which means that the formability is better. The tan δ was determined in the usual
manner. Example 2 A roll edge was obtained in the same manner as in Example 1 except that 20
parts of polybutene was used instead of 20 parts of polypropylene. This roll edge was subjected
to the same evaluation as in Example 1. The results are shown in Table 2. Example 3 A roll edge
was obtained in the same manner as in Example 1 except that 20 parts of polyethylene was used
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instead of 20 parts of polypropylene. This roll edge was subjected to the same evaluation as in
Example 1. The results are shown in Table 2. Example 4 A roll edge was obtained in the same
manner as in Example 1 except that 100 parts of EPBR were used instead of 100 parts of EPDM.
This roll edge was subjected to the same evaluation as in Example 1. The results are shown in
Table 2. EXAMPLE 5 A roll edge was obtained in the same manner as in Example 1 except that
100 parts of NBR were used instead of 100 parts of EPDM. This roll edge was subjected to the
same evaluation as in Example 1. The results are shown in Table 2. Example 6 A roll edge was
obtained in the same manner as in Example 1 except that 100 parts of CR was used instead of
100 parts of EPDM. This roll edge was subjected to the same evaluation as in Example 1. The
results are shown in Table 2. Example 7 A roll edge was obtained in the same manner as in
Example 1 except that 100 parts of IR was used instead of 100 parts of EPDM. This roll edge was
subjected to the same evaluation as in Example 1. The results are shown in Table 2. Example 8 A
roll edge was obtained in the same manner as in Example 1 except that 100 parts of IIR was used
instead of 100 parts of EPDM. This roll edge was subjected to the same evaluation as in Example
1. The results are shown in Table 2. Example 9 A roll edge was obtained in the same manner as
in Example 1 except that 100 parts of EPDM was used instead of 100 parts of EPDM. This roll
edge was subjected to the same evaluation as in Example 1.
The results are shown in Table 2. Comparative Example 1 A roll edge was obtained in the same
manner as in Example 1 except that polypropylene was not used. This roll edge was subjected to
the same evaluation as in Example 1. The results are shown in Table 2. Comparative Example 2 A
roll edge was obtained in the same manner as in Example 4 except that polypropylene was not
used. This roll edge was subjected to the same evaluation as in Example 1. The results are shown
in Table 2. Comparative Example 3 A roll edge was obtained in the same manner as in Example 5
except that polypropylene was not used. This roll edge was subjected to the same evaluation as
in Example 1. The results are shown in Table 2. Comparative Example 4 A roll edge was obtained
in the same manner as in Example 6 except that polypropylene was not used. This roll edge was
subjected to the same evaluation as in Example 1. The results are shown in Table 2. Comparative
Example 5 A roll edge was obtained in the same manner as in Example 7 except that
polypropylene was not used. This roll edge was subjected to the same evaluation as in Example 1.
The results are shown in Table 2. Comparative Example 6 A roll edge was obtained in the same
manner as in Example 8 except that polypropylene was not used. This roll edge was subjected to
the same evaluation as in Example 1. The results are shown in Table 2. Comparative Example 7 A
roll edge was obtained in the same manner as in Example 9 except that polypropylene was not
used. This roll edge was subjected to the same evaluation as in Example 1. The results are shown
in Table 2. Comparative Example 8 A roll edge was produced by using a thermoplastic urethane
elastomer alone, and was subjected to the same evaluation as in Example 1. The results are
shown in Table 2. As apparent from Table 2, by using a combination of a rubber and a
thermoplastic resin, the moldability is dramatically improved. Furthermore, internal loss is also
improved. Although heat resistance may decrease depending on the resin used, it is possible to
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dramatically improve formability and internal loss without reducing heat resistance by selecting
an appropriate resin according to the application. . According to the present invention, by using a
thermoplastic resin dispersed in rubber, it becomes possible to form an edge after forming a
vulcanized rubber sheet in advance, and productivity is dramatically improved Be done. In
addition, by using the rubber and the thermoplastic resin in combination, it is possible to
dramatically improve the moldability and the internal loss while maintaining the heat resistance
and the weather resistance. Thus, according to the present invention, a speaker edge is obtained
which simultaneously has excellent heat resistance, weather resistance and internal loss, and
excellent formability and productivity.
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