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JP2005341465

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DESCRIPTION JP2005341465
PROBLEM TO BE SOLVED: To provide a speaker diaphragm having excellent features such as
excellent workability at the time of molding and high strength. SOLUTION: A powder 5 of an
unfoamed acrylic resin containing a foaming agent is put into a mold 4 for a speaker diaphragm,
which is obtained by foaming. The “non-foamed acrylic resin containing a foaming agent” is,
for example, one or two or more monomers selected from the group consisting of acrylamide,
methacrylamide, acrylic acid and methacrylic acid, if necessary, the single amount It is obtained
by polymerizing the monomer in a state in which the copolymerizable monomer and the blowing
agent are at least mixed. As temperature at the time of foaming in the metal mold | die 4 for
speaker diaphragms, 100-300 degreeC is especially preferable, Especially preferably, it is 150250 degreeC. [Selected figure] Figure 2
Speaker diaphragm
[0001]
The present invention relates to a speaker diaphragm, for example, to a speaker diaphragm
having excellent features such as excellent workability at the time of molding and high strength.
[0002]
As a reinforcing material of the speaker diaphragm or the speaker diaphragm (with a skin layer
on both sides or one side), it is possible to use a rigid foam made of a continuous foam acrylic
foam which is shaped by heat press molding (See, for example, Patent Document 1).
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1
For example, the outline of the cross section of the acrylic foam 1 is shown to (a) of FIG. In FIG.
1A, 2 is an acrylic resin portion, and 3 is an open cell portion. Such acrylic foam 1 is processed
into the speaker diaphragm 10 by a manufacturing process including preheating, mold lowering,
molding, mold opening, inside and outside diameter cutting, etc. as shown in FIG. 1B. The
Numeral 4 in FIG. 1 (b) is a mold used for press molding.
[0003]
JP-A-61-19299 (page 3)
[0004]
However, although acrylic foam is a hard and rigid material, it has the disadvantage of being
brittle.
For example, as shown in FIG. 1C, the acrylic foam 1 is easily broken even when the amount of
deformation is small. In addition, shrinkage of the material (deformation of cells) occurs due to
preheating. Therefore, when the speaker diaphragm 10 is processed from the acrylic foam 1 by
the process as shown in FIG. 1 (b), the workability at the time of molding is bad, and even if the
inner and outer diameters are removed in the later process Possibilities are mentioned as an
example. Inherent thickness reduction and strength decrease.
[0005]
That is, the invention according to claim 1 is characterized in that the powder or bead of an
unfoamed acrylic resin containing a foaming agent is obtained by putting it in a mold for a
speaker diaphragm and causing it to foam.
[0006]
Hereinafter, the speaker diaphragm of the present invention will be described in more detail.
First, “powder of non-foamed acrylic resin containing a foaming agent” used in the production
of the speaker diaphragm of the present invention will be described. The “non-foamed acrylic
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2
resin containing a foaming agent” is not particularly limited, and for example, one or more
monomers selected from the group consisting of acrylamide, methacrylamide, acrylic acid and
methacrylic acid And those obtained by polymerizing the acrylic monomer in a state where at
least the acrylic monomer and the foaming agent are mixed.
[0007]
As the above-mentioned foaming agent, all of the foaming agents which are vaporized by heating
to become gas or are decomposed to generate gas are used, but in addition, urea which is not
well known as a conventional foaming agent Substances which decompose to generate gas at a
temperature at which heating and foaming occur, such as citric acid and itaconic acid, are also
used. However, preferred blowing agents used are dinitrosopentamethylenetetramine,
amidoguanidine, trimethylene triamine, paratoluene sulfone hydrazine, azodicarbonamide,
itaconic acid, maleic anhydride, urea, thiourea, ammonium chloride, dicyandiamide, There are
dioxane, hexane, chloral hydrate and citric acid, etc., among which urea, itaconic acid, maleic
anhydride, thiourea, chloral hydrate and citric acid are preferable.
[0008]
Such a foaming agent is similarly used for any monomer of acrylic acid, methacrylic acid,
acrylamide or methacrylamide, but when the foaming agent and the monomer are compatible,
both of them are simply used. If only mixing is performed, mixing is uniform, and if they are not
compatible, mixing is performed uniformly using a suitable medium or the like. Furthermore,
with respect to the addition amount of the above-mentioned foaming agent, generally, the
expansion ratio of the foaming agent is proportionally increased if the addition amount of the
foaming agent is increased until the addition amount of the foaming agent is increased to some
extent. When the expansion ratio is reached, the expansion ratio hardly changes even if the
addition amount of the foaming agent is further increased. Therefore, industrially, it is
meaningless to add more than the amount of the foaming agent at the maximum expansion ratio.
The amount of the foaming agent at this time varies depending on the type of monomer, the type
of the foaming agent, the pressure at the time of foaming, the temperature, etc., but usually 60%
by weight or less, preferably 0.1 -30 (weight)% is used and is used suitably according to the use.
[0009]
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In the mixture before polymerization of the acrylic monomer, in addition to the acrylic monomer
and the foaming agent, a monomer copolymerizable with the acrylic monomer (hereinafter, also
simply referred to as another monomer) May be contained. In this case, any other monomer may
be used as long as it can be copolymerized with the above-mentioned acrylic monomer, and it is
suitably selected according to the physical properties required for the foam, but it is particularly
preferable to use styrene. Compounds such as acrylonitrile, vinyl acetate, various acrylic esters,
and methacrylic esters and diallyl phthalates, triallyl cyanurate, triallylamine, diallylamine, diallyl
citraconate, triallyl phosphonate, diallyl itaconate, triallyl Preferred are compounds having two or
more double bonds, such as acetolate, divinylbenzene, ethylene glycol dimethacrylate and the
like.
[0010]
A publicly known method is utilized as a method of polymerizing the above-mentioned acrylic
monomer and, if necessary, other monomers in the state where the foaming agent is mixed.
Examples of known polymerization methods include catalytic polymerization, thermal
polymerization, ionizing radiation, polymerization by irradiation with ultraviolet light or light,
polymerization by the action of ultrasonic waves, etc. A method or catalyst by which
polymerization is performed by ionizing radiation irradiation The method of first polymerization
by polymerization and irradiation with ionizing radiation is the best result.
[0011]
As other examples of the above-mentioned "non-foamed acrylic resin containing a foaming
agent", those described in Japanese Patent Publication No. 40-24387, Japanese Patent
Publication No. 40-24388, and Japanese Patent Publication No. 40-29020 can be mentioned.
Although it does not specifically limit as a particle size of the said "powder of the unfoamed
acrylic resin containing a foaming agent", The range of 0.1-5 mm is preferable.
[0012]
As shown in FIG. 2, the above-mentioned “powder of non-foamed acrylic resin containing a
foaming agent (hereinafter, also simply referred to as non-foamed acrylic resin powder)” 5 is
supplied to a die 4 for a speaker diaphragm, Then, by being heat-molded, the foaming agent
contained therein is foamed. After the non-foamed acrylic resin powder 5 is thermally molded
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4
and foamed, the mold is opened to obtain the speaker diaphragm 10. At this time, the powder
may be blended with a fiber-based filler such as glass fiber (GF) or carbon fiber (CF), or a platelike filler such as mica, and simultaneously molded to form a composite. Alternatively, a cross
molded article, a non-woven molded article, or the like may be placed in a mold in advance, and
then powder of non-foamed acrylic resin may be placed and molded.
[0013]
The temperature at the time of heat molding varies depending on the properties of the nonfoamed acrylic resin powder, the type of the foaming agent, etc., but usually 100 to 300 ° C.,
particularly preferably 150 to 250 ° C. The outline of the cross section of the speaker
diaphragm of the present invention obtained by the above manufacturing process is shown in
FIG. The speaker diaphragm of the present invention has a structure in which non-foamed acrylic
resin powder foams (hereinafter also referred to as foamed acrylic resin) 6 are in close contact
with each other, and among the foamed acrylic resin. There are a large number of air bubbles 7
in.
[0014]
Therefore, the above speaker diaphragm has an advantage that the process of removing the inner
and outer diameters after molding becomes unnecessary in the manufacturing process. Further,
since the above-mentioned speaker diaphragm is obtained by foaming from bead-like (powderlike) non-foamed acrylic resin, a wall is formed between adjacent bead-like acrylic resins, so that
the strength is high. It becomes.
[0015]
EXAMPLES The present invention will be more specifically described below by way of Examples,
but the scope of the present invention is of course not limited by these. [Example 1] 100 parts of
acrylamide, 100 parts of acrylic acid, 60 parts of maleic anhydride, 100 parts of acrylonitrile, 50
parts of methyl methacrylate, 50 parts of styrene, 30 parts of urea, 35 parts of concentrated
sulfuric acid are mixed, and 1% tasha The solution is mixed with isobutyl hydroperoxide and 1%
dimethylaniline to form a uniform solution, which is polymerized at 35 ° C for 40 hours, and a
powder of an unfoamed acrylic resin powder containing a foaming agent having an average
particle diameter of 1.0 mm. I got The powder was filled in a die for a speaker diaphragm as
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shown in FIG. 2 and was molded while being heated to 200.degree. After that, the mold was
opened to obtain a speaker diaphragm made of acrylic foam.
[0016]
It is a manufacturing-process schematic of the conventional speaker diaphragm which consists of
acrylic foams. It is a manufacturing-process schematic of the speaker diaphragm of this
invention. It is the cross-sectional schematic of the speaker diaphragm of this invention.
Explanation of sign
[0017]
Reference Signs List 1 acrylic foam 2 acrylic resin portion 3 continuous bubble portion 4 mold
for speaker diaphragm 5 unfoamed acrylic resin powder 6 foamed acrylic resin 7 bubble 10
speaker diaphragm
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