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JPH02206999

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DESCRIPTION JPH02206999
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
loudspeaker diaphragm of a propylene-based polymer containing inorganic hollow spheres. More
particularly, the present invention relates to a speaker diaphragm of a propylene-based polymer
containing inorganic hollow spheres which are lightweight, high in rigidity and excellent in
acoustic characteristics. (Conventional art) Although the speaker diaphragm has been
manufactured from paper and pulp as a raw material, the speaker diaphragm which uses
aluminum foil as a raw material is also manufactured recently. In addition, a method of
manufacturing a speaker diaphragm by thermoforming after injection molding or sheet molding
of a composition in which a synthetic resin or a synthetic fiber containing an inorganic filler such
as mica, talc, graphite or carbon fiber is used. Many have been proposed. In fact, some of the
present inventors have previously proposed a speaker diaphragm using a composition in which a
fibrous filler is mixed with a propylene-based polymer (Japanese Patent Application Nos. 62223127 and 52-252445). . Furthermore, a speaker diaphragm using a composition in which
hollow microspheres having a specific gravity of 0.05 to 0.6 are mixed with a propylene-based
polymer has been proposed (JP-A-55-6982, JP-A-63-109698). issue). [Problems to be Solved by
the Invention] In the case of the speaker diaphragm made of paper and pulp as the raw material,
there is a problem in terms of rigidity. Moreover, when using metal foils, such as aluminum, as a
raw material, shaping | molding is difficult. Furthermore, with the synthetic resin alone, the
rigidity is insufficient, the diaphragm is deformed in a certain frequency range, and the
reproduced sound is distorted. Further, in the case of the composition containing the inorganic
filler, although the rigidity is good, it is not desirable because the output sound pressure level is
reduced because the specific gravity or the weight is increased. Furthermore, in the case of the
composition which mix | blended the fibrous filler, although rigidity improved, the significant
improvement was not recognized in the sound quality. Moreover, in the composition containing
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hollow microspheres, the microspheres are broken during preparation by mixing / kneading in
order to make the composition uniform because the specific gravity of the hollow microspheres
is small, as originally thought. It was not possible to obtain a speaker diaphragm that is
lightweight, has high rigidity, and sufficiently exhibits acoustic characteristics. Furthermore, in
the case of metal foils such as aluminum, there is a disadvantage that it is difficult to form. From
the above, it is an object of the present invention to obtain a speaker diaphragm which is free of
these drawbacks (i.e., light in weight, high in rigidity and excellent in acoustic characteristics).
[Means for Solving the Problems] According to the invention, according to the invention, these
problems can be obtained by using an apparent density of 0.70 to 1.00 g / (B) with respect to
100 parts by weight of (A) a propylene-based polymer. It can be solved by a speaker diaphragm
formed by molding a composition comprising 5.0 to 70 parts by weight of inorganic hollow
spheres of cm ′ ′ and having an average particle diameter of 5 to 400 μm. Hereinafter, the
present invention will be specifically described. (A) Propylene-based polymer The propylenebased polymer used to produce the speaker diaphragm of the present invention may be a
propylene homopolymer, or a small amount of propylene (-generally at most 25% by weight,
Preferably up to 20% by weight, preferably 0.1 to 15% by weight) of ethylene and / or carbon
number or at most 124 N <desirably 4 to 8 α-olefins (eg Latin-1, 4 -Melt index of the propylenebased polymer which may be a random or block copolymer with methylpentene-1 and hexene-1)
(measured according to JIS K 7210 under the condition 14; hereinafter referred to as "MIJ") is
usually 0 1 to 100 g 710 minutes, preferably 0.2 to 80 g / 10 minutes, particularly preferably
0.3 to 70 g / 10 minutes . When a propylene-based polymer having an MI of less than 0.1 g / 10
min is used, the set is not good in formability. On the other hand, when using a propylene-based
polymer exceeding tug / 10 minutes, the mechanical strength of the resulting speaker diaphragm
is not good. The propylene-based polymer described above may be used to manufacture the
speaker diaphragm of the present invention. Furthermore, the propylene-based polymer is
modified in the presence of a radical initiator (usually organic peroxide) to modify unsaturated
carboxylic acid and / or its anhydride (eg acrylic acid, maleic acid, maleic anhydride ##) The
modified propylene polymer obtained by the above can also be used. These propylene-based
polymers and modified propylene-based polymers are both industrially produced and widely
used, and their production methods are well known. (8) Inorganic hollow spheres Further, the
inorganic hollow spheres used in the present invention have an apparent density of 0.70 to 1.00
g / cm ", preferably 0.70 to 0.95 g / crn, In particular, 0.70 to 0.90 g / cm 'is preferable. When
the apparent density is less than 0.70 g / cm ′ ′, the breakage rate at the time of mixed wire
formation and molding is large.
On the other hand, if it exceeds 1.00 g / crn, not only the weight reduction effect of the speaker
diaphragm is low, but also the acoustic effect is lowered. The average particle diameter is 5 to
400 p-m, preferably 5 to 300 JL11, and more preferably 5 to 2501 Ls. When the average
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particle size is less than 51 Lm, it is difficult to produce hollow spheres, and it is difficult to
obtain hollow spheres having the above-mentioned density even if they are obtained by weight,
while those exceeding 400 end are Not only the appearance of the resulting product is bad, but
also the mechanical properties are greatly reduced. The inorganic hollow spheres of the
invention consist essentially of silica and alumina, the proportion of silica generally being from
50 to 75% by weight, preferably from 55 to 75% by weight, preferably from 55 to 70% by
weight. The inorganic hollow spheres contain as oxides an oxide of a metal such as iron oxide
(for example, iron trioxide), but the proportion of said impurities is usually at most 9% by weight.
This inorganic hollow sphere has an appearance shape and a hollow structure close to a true
sphere. Furthermore, the thickness of the hollow spheres is generally 1/12 to 1/8 of the particle
size in terms of damageability and weight. The inorganic hollow spheres may be surface or
untreated, may be surface-treated with a coupling agent such as aminosilane, or may be surfaced
with metals such as iron, copper, aluminum, zinc, silver and the like. It can also use what was
processed. By performing these surface treatments, the dispersibility of the inorganic hollow
spheres is improved. (4) Composition ratio In the composition for producing the speaker
diaphragm of the present invention, the composition ratio of the inorganic hollow spheres is 5.0
to 70 parts by weight with respect to 100 parts by weight of the propylene-based polymer, and
5.0 to G5 Parts by weight are desirable, in particular 10 to 65 parts by weight. If the composition
ratio of the inorganic hollow spheres to 100 parts by weight of the propylene-based polymer is
less than 5.0 parts by weight, the effect of improving the rigidity is small, while if it exceeds 70
parts by weight, it is difficult to obtain uniform f & materials. Even if a uniform composition is
obtained. Poor improvement of sound effects. (D) Production of Composition To produce the
composition of the present invention, the above-mentioned propylene-based polymer and non411 quality hollow spheres may be mixed uniformly. At this time, if necessary, additives
generally used in the field of propylene polymers, such as stabilizers for oxygen and light or heat,
flame retardants, processability improvers, lubricants, antistatic agents and pigments. Of course,
it may be added. To make the compositions of the present invention, they may be tri-blended
using mixers such as tumbler ribbon blenders and Henschel mixers.
Alternatively, the kneader may be melted and kneaded using a kneader such as a batch-type
mixture 1 sal + (for example, a Banbury mixer) or a continuous kneader (for example, a screwtype extruder). Furthermore, mixing can be performed more uniformly by using these mixing
methods together (for example, after tri-blending and continuously kneading). The composition
thus obtained is usually formed into a beret shape and is used for the production of a speaker
diaphragm described later. (E) Production of Speaker Diaphragm The composition thus obtained
(usually, beret) is thermoformed by injection molding generally practiced in the field of
thermoplastic resins, and a sheet previously obtained by extrusion molding. The speaker
diaphragm of the present invention can be manufactured by any of the methods. Whether meltkneaded in manufacturing the composition or injection acid or extrusion molding in forming the
speaker diaphragm, any of propylene polymers or modified propylene polymers used either It is
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important to carry out at a temperature higher than the melting point or in a temperature range
in which S decomposition does not occur. Therefore, it is generally carried out at 180 to 280 ° C
(preferably 200 to 260 ° C). When the inorganic hollow spheres of the present invention and a
propylene-based polymer are kneaded to produce a composition, and when the composition is
molded to produce a speaker diaphragm, breakage of the inorganic hollow spheres or the abovementioned may occur. There is less increase in density due to less breakage compared to hollow
microspheres, and thus the speaker diaphragm is lightweight. Furthermore, it is considered that
there is no sound attenuation in the space inside the inorganic hollow sphere, and as a result, the
speaker diaphragm of the present invention has good sound elongation and excellent sound
separation and reproduction effects. Presumed. EXAMPLES AND COMPARATIVE EXAMPLES The
present invention will be further described in detail by the following examples. In the examples
and comparative examples, the flexural modulus was measured according to ASTM D790. Also,
the density was measured in accordance with JIS K 6758. The physical properties, production
and the like of the propylene-based polymer or the modified propylene-based polymer, the
inorganic hollow spheres and the other inorganic fillers used in Examples and Comparative
Examples are shown below. ((A) Propylene-based polymer) The copolymerization ratio of a
propylene homopolymer having a MI of 20 g / 10 min (hereinafter referred to as r PP (a) J) and
ethylene as a propylene-based polymer is 17 wt% And a propylene-ethylene block copolymer
(hereinafter referred to as rPP (b) J) having an MI of 0.5 g / 10 min.
((B) Modified propylene-based polymer) Further, as a modified propylene-based polymer, 0.6
parts by weight of maleic anhydride and 0.4 parts by weight to 100 parts by weight of a
propylene homopolymer having an MI of 0.6 g / 10 min. After mixing the organic peroxide
(benzoyl peroxide) of the electric resistance part with a Henschel mixer, and then kneading at a
resin temperature or 230 ° C, a maleic anhydride-modified propylene homopolymer
(hereinafter referred to as " Modified PPJ) was used. [(C) Inorganic hollow spheres] Further, as
inorganic hollow spheres, substantially spherical silica having an average particle diameter of
577 zm, a density of 0.75 g / am 3 and a silica content of 61 wt% Alumina hollow spheres
(hereinafter referred to as "hollow spheres (1)"), substantially true, having an average particle
diameter of 90 for a diameter of 90, a density of 0.72 g / crn 'and a silica content of 59% by
weight Spheres silica-alumina hollow spheres (hereinafter referred to as "hollow spheres (2)")
and having an average particle size of 57 JLm, a density of 0.75 g / crn 'and a silica content of
61% by weight Hollow spheres (hereinafter referred to as "hollow spheres (3)") which are
substantially pearls surface-coated with aminosilane were used. [(D) Other Inorganic Fillers] Also,
mica having an average particle diameter of 8 pm was used as another inorganic filler. Examples
1 to 7 and Comparative Examples 1 to 3 100 parts by weight of each propylene-based polymer
(hereinafter referred to as rPPJ) shown in Table 1 and the kind and blending amount are shown
in Table 1 "Inorganic hollow spheres or other inorganic fillers" (hereinafter referred to as
"fillers") were previously tri-blended for 5 minutes using a Henschel mixer. A beret (composition)
was produced while kneading each obtained mixture using a vented extruder (diameter 40 °) at
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a resin temperature or 210 ° C. conditions. Each of the obtained belets was injection molded at
a resin temperature of 230 ° C. using a mold clamping pressure or a 50 ton injection molding
machine to prepare a test piece for measuring flexural modulus. The flexural modulus and
density of each of the obtained specimens were measured. The obtained results are shown in
Table 1. In addition, a speaker diaphragm (thickness 0.4 mm, upper surface diameter 150 mm,
lower surface diameter 405 m, speaker surface at a resin temperature of 280 ° C., using an
injection molding machine with a mold clamping pressure of 100 tons). A height of 35 ° was
molded (Example 1). Comparative example 2). Furthermore, a sheet having a thickness of 0.4 am
was formed at a resin temperature of 200 ° C. using an extruder (diameter 401) equipped with
a T-die, with the obtained belet.
The resulting sheet was manufactured by using vacuum forming at a resin temperature or 160
° C. to produce a Subby-Car diaphragm of the same size as described above (Example 3). The
speaker diaphragms obtained by Example 1 and Comparative Example 2 were respectively
incorporated in the same speaker, and frequency characteristics were measured in an anechoic
chamber. The results are shown in FIG. In this figure, the vertical axis is the output sound
pressure level (dB) and the horizontal axis is the frequency (llz). A curve A is a curve showing the
frequency characteristics of the speaker diaphragm obtained in Example 1, and a curve B is a
curve showing the frequency characteristics of the speaker diaphragm obtained in Comparative
Example 2. The speaker diaphragm of the present invention has a flat frequency characteristic in
the high frequency region, good sound expansion in the middle to high range, and excellent
sound separation and reproduction effects. .
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a drawing showing frequency characteristics of each speaker diaphragm obtained by
Example 1 and Comparative Example 2.
In this figure, the vertical axis is sound pressure (dB) and the horizontal axis is frequency (Hz).
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