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JPH07179755

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DESCRIPTION JPH07179755
[0001]
FIELD OF THE INVENTION This invention relates to thermoplastic polyimide films. Specifically, it
is a thermoplastic polyimide film obtained by adding a specific amount of graphite to a
thermoplastic polyimide having a specific structure, which has excellent heat resistance and
elastic modulus, and is mainly suitable as a material film of a speaker diaphragm The present
invention relates to a thermoplastic polyimide film.
[0002]
2. Description of the Related Art Aromatic polyimides are used in various fields taking advantage
of these properties because they are excellent in heat resistance, mechanical properties, electrical
insulation, solvent resistance and the like. For example, JP-B-56-49040 discloses a diaphragm
obtained by heating and compression-molding a polyimide film obtained from pyromellitic
dianhydride and diaminodiphenyl ether. However, although this polyimide film is high in heat
resistance, it is difficult to melt-mold it, so there is a disadvantage that the film must be formed
by solution casting, and compression molding can not be performed at temperatures of 400 ° C.
or higher. Besides, there is a problem that the molding time is long. Japanese Patent Publication
No. 4-68839 discloses a diaphragm formed of a polyetherimide film. Since the polyetherimide
film has a heat deformation temperature of 200 ° C., it is characterized in that it has good
formability and can be deep drawn. However, since the elastic modulus changes rapidly at
temperatures exceeding 200 ° C., the heat resistance is insufficient as a high power diaphragm.
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[0003]
Recently, a diaphragm formed of polyimide has been proposed. For example, JP-A-63-7099
comprises an aromatic polyimide obtained from a tetracarboxylic acid component containing
biphenyltetracarboxylic acids as a main component and a diamine component containing
diaminodiphenyl ethers as a main component, and A diaphragm for an acoustic device is
disclosed in which an aromatic polyimide film having a second order transition temperature of
250 to 400 ° C. is heated and pressed to form a sheet. This diaphragm has heat resistance of
250 ° C. or higher, has a relatively high propagation speed, and is excellent in performance as a
diaphragm, but is difficult to melt and form, and a solution of polyamic acid which is a precursor
of polyimide The sheet must be formed by solution casting. Therefore, there is a problem that the
process such as recovery of the solvent is complicated and the productivity is inferior, and most
of 300 ° C. or more is required to form the obtained sheet into a diaphragm, and the forming
time Has a problem of poor productivity because it is long.
[0004]
In order to ameliorate such a drawback, a polyimide sheet obtained by melt-molding a
thermoplastic polyimide has been proposed. For example, JP-A-2-209924 discloses a polyimide
sheet obtained by heating and melting a thermoplastic polyimide having a specific structure at
300 to 400 ° C. by an extruder and a method for producing the same. ing. However, the
polyimide sheet is a sheet having good moldability and excellent heat resistance, but has a low
elastic modulus and is not suitable for applications requiring a high elastic modulus.
[0005]
SUMMARY OF THE INVENTION The object of the present invention is to solve the above
problems and to provide a thermoplastic polyimide film which has excellent heat resistance and
is excellent in elastic modulus and deep drawability and which can be melt-formed. It is to do.
Another object of the present invention is to provide a thermoplastic polyimide film suitable as a
material for a speaker diaphragm.
[0006]
[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the
present inventors melt-mold a resin composition in which a specific amount of graphite is added
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to a thermoplastic polyimide having a specific structure. It has been finally found that the
thermoplastic polyimide film obtained as described above is a film having excellent heat
resistance, elastic modulus, deep drawability and the like.
[0007]
That is, the present invention is a thermoplastic polyimide film obtained by melt-molding a resin
composition containing 100 parts by weight of a thermoplastic polyimide and 5 to 25 parts by
weight of graphite, and having an elastic modulus of 450 kg / mm 2 or more at room
temperature. It is a thermoplastic polyimide film characterized by being.
[0008]
The feature of the thermoplastic polyimide film of the present invention is that it is a meltformed thermoplastic polyimide film containing a specific amount of graphite, and has excellent
heat resistance, elastic modulus, deep drawability, and the like.
Moreover, since it contains graphite, it has a color tone suitable as a material for speaker cones.
The thermoplastic polyimide film of the present invention having such properties is a film
particularly suitable as a material for a speaker diaphragm.
[0009]
The thermoplastic polyimide film of the present invention is made into a resin composition by
adding a specific amount of graphite to a thermoplastic polyimide, and the resin composition is
kneaded and melted using a molding machine such as an extruder, and molded into a film. It is
obtained by
[0010]
Hereinafter, the thermoplastic polyimide film of the present invention will be described in detail.
The thermoplastic polyimide used in the present invention is represented by the formula (8)
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[Formula 8]
[0011]
(Wherein, R and R 1 each represent an aliphatic group having 2 or more carbon atoms, a cyclic
aliphatic group, a monocyclic aliphatic group, a fused polycyclic aliphatic group, or an aromatic
group mutually or directly depending on the crosslinking member) R is a group selected from the
group consisting of linked non-condensed polycyclic aliphatic groups, R is a tetravalent group, R
1 is a divalent group, and those having a repeating structural unit represented by It is a
polyimide having thermoplasticity.
[0012]
Among the above-mentioned polyimides, the thermoplastic polyimide preferably used in the
present invention is represented by the formula (1) [Formula 9]
[0013]
(Wherein R is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a
monocyclic aromatic group, a fused polycyclic aromatic group, or an aromatic group mutually
linked by a direct or bridge member) A tetravalent group selected from the group consisting of
non-fused polycyclic aromatic groups is shown, and X is a single bond, a sulfur atom, a sulfone
group, a carbonyl group, an isopropylidene group or a divalent group of
hexafluoroisopropylidene group Is a thermoplastic polyimide having a repeating structural unit
represented by
[0014]
Among these thermoplastic polyimides, those which are more preferably used in view of
moldability, heat resistance and the like are those in which R is a structural formula (2) in the
formula (1) [formula 8]
[0015]
Formula (3) [formula 11]
[0016]
Formula (4) [formula 12]
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[0017]
Formula (5) [formula 13]
[0018]
Or Formula (6) [Formula 14]
[0019]
And thermoplastic polyimids.
[0020]
Among the above thermoplastic polyimides, those most preferably used in the present invention
are represented by the formula (7) [Formula 15]
[0021]
The thermoplastic polyimide which has a repeating structural unit represented by these is
mentioned.
[0022]
The polyimide used in the present invention can be obtained by the dehydration condensation
reaction of an aromatic tetracarboxylic acid dianhydride and an aromatic diamine.
Examples of the aromatic tetracarboxylic acid dianhydride used to obtain this polyimide include
pyromellitic acid dianhydride, ethanetetracarboxylic acid dianhydride, butanetetracarboxylic acid
dianhydride, and cyclopentanetetracarboxylic acid dianhydride. 1,2,3,4-benzenetetracarboxylic
acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-Naphthalenetetracarboxylic dianhydride,
3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,
2,7,8-phenanthrene tetracarboxylic acid dianhydride, 3,3 ', 4,4'-biphenyl tetracarboxylic acid
dianhydride, 2,2', 3,3'-biphenylate Carboxylic acid dianhydride, 3,3 ′, 4,4′benzophenonetetracarboxylic acid dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic acid
dianhydride, 2,2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl)
propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (2,3 -Dicarboxyphenyl)
ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (2,3-dicarboxyphenyl)
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sulfone dianhydride, 2,2-bis (3,4-) Dicarboxyphenyl) 1,1,1,3,3,3-hexafluoropropane dianhydride,
2,2-bis (3,4-dicarboxyphenyl) 1,1,1,3,3,3-hexachloro Professional Dianhydride, 1,1-bis (2,3dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4dicarboxyphenyl) methane Dianhydride, 4,4 '-(p-phenylenedioxy) diphthalic dianhydride, 4,4'-(mphenylenedioxy) diphthalic dianhydride, 4,4'-diphenyl sulfide dioxybis (4-phthalic acid)
dianhydride, 4,4'-diphenyl sulfonedioxybis (4-phthalic acid) dianhydride, methylene bis- (4phenylene oxy-4-phthalic acid) dianhydride, ethylidene bis -(4-phenylene oxy-4-phthalic acid)
dianhydride, isopropylidene bis- (4-phenylene oxy-4-phthalic acid) dianhydride,
hexafluoroisopropylidene bis- (4- And phenyleneoxy-4-phthalic acid) dianhydride and the like.
[0023]
Moreover, as an aromatic diamine used in order to obtain a polyimide, the bis [4- (3-amino
phenoxy) phenyl] sulfide, bis [4- (3-amino phenoxy) phenyl] sulfone, bis [4- (3) is mentioned, for
example. -Aminophenoxy) phenyl] ketone, 4,4'-bis (3-aminophenoxy) biphenyl, 2,2-bis [4- (3aminophenoxy) phenyl] propane, 2,2-bis [4- (3) -Aminophenoxy) phenyl] -1,1,1,3,3,3hexafluoropropane, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl ether, 4,4'diaminodiphenyl sulfone 4,4'-Diaminodiphenylmethane, 1,1-di (p-aminophenyl) ethane, 2,2-di (paminophenyl) Propane, 2,2-di (p- aminophenyl) -1,1,1,3,3,3-hexafluoropropane, and the like.
[0024]
These aromatic tetracarboxylic acid dianhydrides or aromatic diamines can be used alone or in
combination of two or more.
In producing the thermoplastic polyimide used in the present invention, some of the above
aromatic diamines can be replaced with other aromatic diamines.
Preferably, the aromatic diamine used alternatively is less than 20 mole percent of the total
aromatic diamine.
[0025]
As other aromatic diamines, for example, p-phenylenediamine, m-phenylenediamine, maminobenzylamine, p-aminobenzylamine, 4,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4 'Diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'diaminodiphenylmethane, 1,1-bis (4-aminophenyl) ethane, 1,1-bis (3-) Aminophenyl) ethane, 2,2-
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bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) propane, 2,2-bis (4-aminophenyl) -1,1,1,3 ,
3,3-hexafluoropropane, 2,2-bis (3-aminophenyl) -1,1,1,3,3,3-hexaf Oropropane, 3,3'diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4 ' -Diamino benzophenone etc. are
mentioned.
[0026]
The polyimide used in the present invention can be prepared by using conventional methods
known in the art, such as suspending or dissolving these aromatic tetracarboxylic acid
dianhydrides and aromatic diamines in an organic solvent, It can be obtained by a general
method of heating or chemically dehydrating, separating and purifying the product.
In the thermoplastic polyimide resin as described above, additives such as a lubricant, a heat
resistant stabilizer, an inorganic filler such as a surface modifier, a sliding agent such as a
fluorine resin and the like within the range not impairing the present invention. You may blend.
[0027]
In addition, the particle size of the graphite used in the present invention is 50 to 0.01 μm,
preferably 20 to 0.01 μm, and a material used for general engineering plastics is desirable.
The addition amount of graphite affects the modulus of elasticity and deep drawability of the
obtained film, and when the addition amount is small, the modulus of elasticity of the obtained
film becomes low, and when it is large, the deep drawability deteriorates.
From this viewpoint, the blending amount of graphite used in the present invention is blended in
the range of 5 to 25 parts by weight with respect to 100 parts by weight of polyimide.
Preferably, it is 8 to 18 parts by weight.
[0028]
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There is no particular limitation on the method of mixing the above-mentioned polyimide and
graphite, and a known mixing method is applied.
For example, mixers such as ribbon blenders, Henschel mixers, universal mixers, etc. are used.
A mixture of a powder or pellet of polyimide and a predetermined amount of graphite using a
mixing device such as a Henschel mixer or a universal mixer, or a powder or pellet of polyimide
and a predetermined amount of graphite such as a Henschel or universal mixer The mixture is
mixed beforehand, and pelletized by a known kneader or melt extruder or other pelletizing
device, and dispersed relatively uniformly in polyimide pellets, or powder or pellets of polyimide
and graphite of a predetermined amount or more Use as a master batch a material which is
mixed in advance using a mixing apparatus such as a Henschel or a universal mixer, pelletized
using a known kneader or a pelletizing apparatus such as a melt extruder, and relatively
uniformly dispersed in polyimide pellets. It becomes a predetermined amount of graphite content
As a raw material a material obtained by uniformly mixing the urchin polyimide pellets and
mixers low shear, such as the master batch ribbon blender or hand mixing.
[0029]
There is no restriction | limiting in particular in the method to shape | mold powdery polyimide
in pellet form, A well-known method is used.
For example, using a single- or twin-screw extruder equipped with a strand die, kneading is
performed in the temperature range of melting point to melting point + about 50 ° C. of the
used polyimide, and the molten resin is extruded into strands, cooled and cut. And a method of
cutting the molten strand and then cooling it.
[0030]
The method of shape | molding the obtained pellet to a film applies a well-known method.
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For example, using a single- or twin-screw extruder equipped with a T-die, the resin is extruded
from the slit-like resin outlet of the T-die within the temperature range of melting point to
melting point + about 50 ° C of thermoplastic polyimide used, surface temperature A film is
obtained by casting the molten resin with a roll controlled to a temperature below the glass
transition temperature of the resin.
[0031]
The polyimide resin composition having the above composition can be melt-molded, and a film
obtained by melt-molding the composition has a high elastic modulus of 450 kg / mm 2 or more
and excellent heat resistance.
Therefore, this film is excellent in moldability, which is a defect of the polyimide film
conventionally proposed as a material for a speaker diaphragm, but the heat resistance is not
sufficient or the heat resistance is excellent but the thermoformability is difficult. It is a film that
has been solved that is very difficult.
By using this film as a speaker diaphragm material, it is possible to obtain a speaker diaphragm
excellent in high frequency range characteristics.
[0032]
As mentioned above, the amount of graphite added affects the modulus and deep drawability of
the resulting film. The modulus of elasticity of the resulting film increases as the amount of
graphite added increases, but if it is too high, deep drawability is adversely affected. Therefore, in
the present invention, in order to obtain a film having both excellent elastic modulus and deep
drawability, the addition amount of graphite is suppressed to a maximum of 25 parts by weight
with respect to 100 parts by weight of the thermoplastic polyimide. The thickness of the
thermoplastic polyimide film of the present invention obtained as described above is not
particularly limited, but is usually about 25 to 500 μm.
[0033]
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FIG. 1 is a schematic view of a cross section of a diaphragm of a typical speaker. The diaphragm
has a dome portion 1 and a cone portion 2. When the thermoplastic polyimide film of the present
invention is used, the dome portion 1 and the cone portion 2 of the diaphragm can be integrally
formed because the deep drawability is good. Usually, the dome portion 1 and the cone portion 2
of the diaphragm are obtained by vacuum forming and pressure forming a sheet or film, but
when using the thermoplastic polyimide film of the present invention, press forming is possible.
At the time of molding, the thermoplastic polyimide film of the present invention is excellent in
deep drawability of the film, and therefore thickness variation does not occur. Therefore, a
diaphragm having a constant sound quality can be obtained.
[0034]
As described above, since the thermoplastic polyimide film of the present invention is excellent in
heat resistance, it is suitable as a material of a diaphragm for a high output speaker. In addition,
since it has excellent deep drawability, when it is press-formed, vacuum-formed or pressureformed to form, for example, a diaphragm for a speaker or the like, it does not break and
thickness variations may occur. Absent. Moreover, since the addition amount of graphite is
suppressed within the range of a predetermined amount, the heat resistance and mechanical
characteristics which polyimide originally has are not impaired. The color tone is also suitable for
the speaker diaphragm. Therefore, it is most suitable as a material film for a diaphragm of a
speaker.
[0035]
EXAMPLES The present invention will be described more specifically by the following examples.
In addition, each characteristic value shown in the Example was measured by the following
method. (1) Elastic modulus (kg / mm 2) It is measured according to the method defined in
ASTM-D-1708 using a tensile tester (manufactured by ORIENTEC Co., Ltd., type: TENSILON RTA100). (2) Deep drawing formability As shown in FIG. 1, a diaphragm in which the dome portion
and the cone portion of the speaker cone are integrally formed is press-formed at 260 ° C. Ten
pieces are molded, and the presence or absence of breakage and thickness variation are observed
for the obtained molded product. ◎ ··· it can be ten molding, yet not a was observed thickness
variation. ○ · · · 10 pieces were able to be molded. ・ ・ ・ ... 1 to 9 pieces were formed. × · · ·
could not be molded even one piece. Using an automatic dynamic viscoelasticity measuring
instrument (manufactured by Toyo Baldwin Co., Ltd., RHEOVIBRON DDV-II-EP), measurement is
made at a temperature rising rate of 2 ° C./min and a frequency of 110 hz, and evaluation is
made at the point where storage elastic modulus starts to fall.
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[0036]
Preparation of Thermoplastic Polyimide 10 kg of m-cresol and 3684 g (10.0 mol) of 4,4'-bis (3aminophenoxy) biphenyl were charged in a reaction vessel equipped with an agitator, a reflux
condenser and a nitrogen introducing pipe. Add a slurry-like mixture of 2074 g (9.51 mol) of
pyromellitic dianhydride and 2 kg of m-cresol under a nitrogen atmosphere carefully in such a
manner that the temperature of the solution does not exceed 60 ° C., Thereafter, 159.6 g (1.078
mol) of phthalic anhydride was further added and the mixture was stirred for 5 hours. Thereafter,
the temperature was raised to 140 ° C. over about 3 hours, and the mixture was stirred at 140
° C. for 2 hours and then cooled to room temperature over 3 hours. The slurry liquid is
separated by filtration, washed with 20 kg of methanol and then with 20 kg of acetone, and dried
at 100 ° C. for 8 hours under a nitrogen atmosphere and subsequently for 4 hours at 300 ° C.
to obtain 5100 g (yield 92 %) Polyimide powder was obtained. This polyimide powder is called
PI-1.
[0037]
Preparation Example 2 Except that as the aromatic diamine, 3315.6 g (9 moles) of 4,4′-bis (3aminophenoxy) biphenyl and 200.2 g (1 mole) of 4,4′-diaminodiphenyl ether were mixed and
used In the same manner as in Preparation Example 1, 4600 g (yield 90%) of polyimide powder
was obtained. This polyimide powder is called PI-2.
[0038]
Examples 1 to 5 and Comparative Examples 1 to 3 100 parts by weight of PI-1 or PI-2 (only for
Example 5) as a powder of a polyimide: Graphite (part by Lonza) Trade name: Graphite Powder
KS-15) is mixed for 5 minutes at room temperature using a universal mixer, and this is melt
extruded at 400 ° C. using a twin-screw extruder equipped with a strand die, cooled and cut. A
thermoplastic polyimide pellet containing a predetermined amount of graphite was obtained. The
obtained polyimide pellet is supplied to a single-screw extruder equipped with a T-die, kneaded
and melted at 410 ° C., extruded from the slit resin outlet of the T-die, and a roll whose surface
temperature is adjusted to 200 ° C. By casting, a thermoplastic polyimide film having a
thickness of 75 μm was obtained. The various characteristics of the obtained film were
evaluated by the above method. The compounding ratio (parts by weight) of the thermoplastic
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polyimide and the graphite, and the evaluation results of the obtained film are shown in [Table
1].
[0040]
The thermoplastic polyimide film of the present invention can be obtained by melt molding, has
excellent elastic modulus and deep drawability, and is also excellent in heat resistance,
mechanical properties and the like. Therefore, it is useful as a material of a molded article for
which excellent heat resistance, elastic modulus, deep drawability, etc. are required, for example,
a material film for a high power speaker diaphragm excellent in high frequency range
characteristics. In forming the speaker diaphragm, the dome portion and the cone portion can be
integrally formed by press forming or the like.
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