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JPH02133468

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DESCRIPTION JPH02133468
[0001]
FIELD OF THE INVENTION The present invention relates to a resin composition comprising a
specific thermoplastic liquid crystal polymer blended with carbon fiber. More specifically, the
present invention relates to a resin composition for a speaker diaphragm, which provides a
diaphragm having good sound quality and surface appearance in a technology for manufacturing
a speaker m and a moving plate by an injection molding method. [Prior art and problems] It is
important that the speaker diaphragm has a large specific modulus, E / ρ (E: modulus, :: specific
gravity), and a large internal loss in vibrational deformation, and such purpose is achieved.
Conventionally, for example, a material obtained by mixing a fiber having a very large modulus of
elasticity with paper pulp has been used as a material for the purpose. However, in recent years,
plastic materials have relatively high internal loss, and the elastic modulus can be relatively easily
improved by mixing carbon fibers, and further, they are easy to form and process, etc. Carbon
fiber filled plastic composites are being used. However, such plastic composites generally have
high melt viscosities (the injection molding technique can not be used to form thin leaf structures
such as speaker diaphragms). To address this problem, it has been proposed to use a liquid
crystalline polymer composite, for example, in Japanese Patent Application Laid-Open No. 1.21119291. The liquid crystalline polymer not only has very good fluidity of the resin itself, but
also has a relatively large internal loss compared to the plastic in the flow direction of the resin,
and is most excellent for the speaker diaphragm as the current technical level It can be said that
it is a material. However, when such a liquid crystal polymer is filled with a carbon fiber into a
carbon fiber composite liquid crystal polymer and the speaker diaphragm is injection molded, the
surface appearance of the molded product is considered to be due to the flow behavior of the
liquid crystal polymer. The degree of blackness was uneven across the surface as compared to
the expected appearance, and as such was of low commercial value. Also, although the melt
viscosity of such a liquid crystalline polymer is low, its value is relative, and it is obvious that it
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depends on the degree of polymerization of the polymer itself or the backbone structure of the
molecule. As is well known, the smaller the degree of polymerization, the lower the mechanical
properties of the polymer, and therefore the degree of polymerization can not be lowered. In
addition, since the flow length of the resin depends on the ability of the injection molding
machine used, it forms a molded product with a thickness of a2 to o, pmW and a flow length of
SO to / 0 on the left like a speaker diaphragm. In order to do this, an injection molding machine
with a very large clamping force is required.
However, since the speaker diaphragm is preferably light, the emission capacity needs to be
extremely small. -A molding machine with a large clamping force for fishing is also made with a
large injection capacity, and when molding a molded product with a small fabric weight such as
such a swinger, the residence time of the resin is long (and the melting heat stability of the resin
Sex is a problem. Although this problem is solved by using a dedicated molding machine, the
fixed cost burden is large and it can not be said to be industrially advantageous. [Means for
Solving the Problems] As a result of intensive investigations in view of the problems as described
above, the present inventors have found that a specific thermoplastic liquid crystal polymer
composition is suitable for a speaker diaphragm, The invention has been reached. That is, the gist
of the present invention is 10% by weight or more of a thermoplastic liquid crystal polymer
having a melt viscosity at shear rate / 0005eC-1 at a temperature of 330 ° C. or less and a SOO
Boise or less and exhibiting liquid crystallinity at 330 ° C. or less And a carbon n, a resin
composition for a speaker diaphragm containing more than 7% by weight of fiber (less than 25%
by weight). The object of the present invention is to provide a carbon fiber composite liquid
crystal polymer in which, when forming a speaker diaphragm by an injection molding machine
marketed for fishing, the E / ρ is large, the internal loss is large, the flowability is good, and the
vibration is An object of the present invention is to provide a resin composition capable of
obtaining a molded article having an excellent plate surface appearance. Hereinafter, the present
invention will be described in detail. The thermoplastic liquid crystal polymer used in the present
invention can be arbitrarily selected from the group of polyesters or polyesteramides comprising
segments having the following structure. /: Polyester-O-R-O-CO-I '(-CO-I-4-CO-, 2: polyester
amide-O-R-O-CO-R-CO-I-O-4- CO--NH--R--CO--NH--R--NH--In this structural formula, R can be
optionally selected from the following group. -CH2- (CH232 (CH2) 4 (C1-T2) 6- The
thermoplastic liquid crystal polymer of the present invention was measured at a shear rate /
0005eC- 'at a temperature of 330 ° C or less, preferably 27s to 330 ° C. The melt viscosity is
less than 00 Boise. When a speaker diaphragm is injection-molded with a carbon fiber composite
liquid crystal polymer, the clamping force of the injection molding machine used is also
determined by the aromatic ring, aliphatic group, alicyclic group etc. It may be substituted by
various substituents selected from the group of It is preferable to use an injection molding
machine having a clamping force of not more than / sO, because B "-C1, -COOH, CONH2-CH3,
etc."
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However, if the melt viscosity of the liquid crystal polymer is higher than SOO poise, the mold
clamping force is insufficient to form a speaker diaphragm of a desired shape with such a
molding machine. Therefore, the melt viscosity of the thermoplastic liquid crystal polymer of the
present invention needs to be less than SOO poise. As a thermoplastic liquid crystal polymer
having such melt viscosity and also having excellent mechanical properties as a molding material,
those containing an aliphatic group or an alicyclic group in the main chain are preferable. The
wholly aromatic liquid crystal polymer containing neither aliphatic group nor alicyclic group in
the main chain is not preferable because it is extremely difficult to set the melt viscosity to 100
poise or less under the present condition. The content of the aliphatic group or alicyclic group in
the thermoplastic liquid crystal polymer is optional within the range showing liquid crystallinity
in the molten state: (It can be selected, but preferably 2 to! roモル%である。 The content is
preferably selected in consideration of the fact that a high elastic modulus after molding is also
an important factor for a speaker diaphragm material. Examples of the aliphatic group or
alicyclic group include those containing an aliphatic group or an alicyclic group among the
groups selected as R of the segment forming the above-described thermoplastic liquid crystal
polymer of the present invention . Specifically, the following may be mentioned. CH2 (CHz) 2
(CH2) 4 (CH2) 6- (CH2-2-O-(CH2) 2- -CH2 min CH2-CH3) When molding a speaker using such a
resin, the liquid crystal polymer is Although it is oriented in the flow direction and its direction is
high in elastic modulus, the elastic modulus in the direction perpendicular thereto is comparable
to that of ordinary plastic, and as it is, it is not preferable as a speaker diaphragm. In order to
improve the problems such as the surface appearance and the weatherability, it is important to
fill the carbon fiber as this material. However, when such a thin leaf molded product is molded
with a composition in which the thermoplastic liquid crystal polymer of the present invention is
filled with a fibrous material, the distribution density of the fiber is extremely nonuniform, and
carbon fiber is selected as the fiber. Its appearance color is black, its non-uniformity appears as
black and gray spots, and a molded article having commercial value can not be obtained. In the
present invention, the carbon fiber loading is more than 7% by weight and less than 25% by
weight, and preferably not less than co% by weight and not more than θ% by weight. If the
carbon fiber loading is less than 3 wt%, the appearance is good even when the resin of the
present invention is used, and the uneven black and gray spots are as shown in FIG. Change to a
radial pinch pattern consisting of gray.
The appearance is extremely beautiful, and is excellent in appearance as a speaker diaphragm. In
the present invention, the thermoplastic liquid crystal polymer may be further copolymerized or
blended with another thermoplastic polymer component, but the thermoplastic liquid crystal
polymer in the present invention needs to be contained at least 70% by weight or more. If it is
less than 70% by weight, the liquid crystallinity is reduced, and it is difficult to obtain a speaker
imaging plate excellent in performance targeted by the present invention. Other thermoplastic
polymers that may be copolymerized or blended include polyesters, polyamides, polycarbonates,
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polysulfides, polysulfones, or polythioethers, and the like. Preferably, it is polyester or polyamide.
EXAMPLES The present invention will be described in more detail by way of examples, but the
present invention is not limited to these examples without departing from the scope of the
invention. Reference example N0 VACCURATE Q (E J, 22: trade name) coated by Mitsubishi Kasei
■ is selected as a thermoplastic liquid crystal polyester partially copolymerized with aliphatic
groups, and Sumitomo Chemical is selected as a wholly aromatic polyester resin (1) Econol resin
(trade name) sold from ニ ー ズ and VECTRA (trade name) sold from Celanese Corporation were
selected. The melt viscosity of each resin is as follows. For polymer A, polymer B, and polymer C,
injection molding was carried out by changing the injection pressure and injection speed at the
above resin temperature using a mold clamping force / Sθ ton injection molding machine, as
shown in FIG. A similar molded article was obtained. The result is as follows. As a result of
molding, all the shots were short shot in the present conditions, and the polymer B was thicker
than the desired thickness, and the clamping force was insufficient in the present injection
molding machine. On the other hand, polymer C, which is a partially aromatic polyester obtained
by partially copolymerizing an aliphatic polyester, has a low melt viscosity, and it was possible to
obtain a molded article having a desired thickness. A resin composition was prepared in which
carbon fibers were filled in the proportions as shown in Table 1 for polymer B and polymer C
shown in Comparative Example / ~5, Example- / Reference Example, respectively, and the same
method as in the reference example The speaker diaphragm was injection molded. The results
are shown in Table 7. The effect of carbon fiber kneading is almost the same as polymers B and
C. At 7% by weight, the overall grayish appearance, the contrast of the white and gray radial
pitches is very small, and the appearance is more than 10 wt% I missed it. On the other hand, at
25% by weight, only a speaker diaphragm having a blackish appearance but gray spots uniformly
present and having a very poor appearance was obtained.
Example-A molded article obtained by molding a resin composition in which 20% by weight of
carbon fiber is filled in copolymer C is cut out in the resin flow direction and in the direction
perpendicular thereto in the resin flow direction and Viplon (trade name DDV-; The elastic
groups were measured using type 2). The elastic modulus at room temperature was 1 λ
gigapascal in tree II ¥ 1 flow direction, and it was in the direction perpendicular to it. The
speaker was actually assembled using the same molded product, and as a result of a sound
sensitivity test, it was recognized that the sound quality was excellent up to the treble area.
Comparative Example 6 A molded article was obtained in the same manner as Example C except
that the polymer C not filled with carbon fibers was used, and the elastic modulus was measured.
The elastic modulus at room temperature is resin [effect of the invention] The composition of the
present invention is suitable for molding a speaker diaphragm by a commercially available
injection molding machine, and has a large E / ρ and a high internal loss and a good flowability.
And, it is possible to obtain a molded article having a good vibrating surface appearance.
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[0002]
Brief description of the drawings
[0003]
FIG. 7 is a view showing a radial pitch pattern consisting of black and gray alternately as an
example of the appearance of a speaker diaphragm using the resin composition of the present
invention.
FIG. 2 is a view showing the shape of the speaker diaphragm molded in the embodiment of the
present invention. In the figure, a is / lIO 朋 and b is 70 。. Also, C indicates thickness, which is
Olymosis.
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