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JPS62197411

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DESCRIPTION JPS62197411
[0001]
Technical Field> The present invention relates to a damping material for a speaker, and more
particularly to a radiation / ultraviolet curable damping material composition having a high tan
δ (loss coefficient) at a high temperature and a low elastic modulus. <Prior Art> A damping
material for a speaker is applied to the edge of a cone of a speaker for the purpose of braking
and reinforcement. This edge part plays an important role, and the quality of the speaker
changes with the quality of this part. That is, when the edge portion of the corn paper is of paper
quality, mechanical vibration transmitted from the central portion of the corn paper along with
the vibration of the corn paper causes reflection at the edge and causes it to be a peak or dip of
the characteristic curve. Come. In order to improve such poor frequency characteristics and to
absorb the reflected wave at the edge, a damping material for a speaker is applied to the entire
surface or edge of the cone paper. Heretofore, as this type of damping material for speakers, one
in which an acrylic polymer is dissolved in an organic solvent such as toluene, acetic acid ester or
the like to adjust the solid content to about 30 to 60% by weight is used. However, since organic
solvents are used, it is necessary to dry after application, and generally it takes a long time to dry
because it is drying at normal temperature, and the risk of fire etc. 1 Hazard to human body, etc.
Due to problems with occupational safety and health, it has been desired to develop a solventfree, short-time drying or curing material. <Object of the invention> The object of the present
invention is to provide a speaker damping material having a high elastic modulus at a high
temperature, which can be cured in a short time without solvent, and has a high elastic modulus.
Used for the edge part. The inventors of the present invention have studied various radiation /
ultraviolet curable materials as a solvent-free, short-curing material, and as a damping material
for speakers, the radiation / ultraviolet curable damping satisfies the following characteristics.
The material composition could be obtained. The damping material composition is required to
have a high tan δ (loss coefficient) of the material of the cured product and an appropriate
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elastic modulus, for the purpose of damping and reinforcing. It is desirable that Tan δ be as high
as possible as high as possible from low temperature to high temperature and from low
frequency region to high frequency region as high as possible, and generally at least 0.7 at
normal temperature and 0-1 or more at high temperature. is there. The elastic modulus is
preferably as low as possible, but from about 10 @ 5 to 10 Adyne / C 112 is desirable from the
viewpoint of reinforcement, and generally about 10 @ 5 to 10 @ 6 dyne / cm @ 2 at normal
temperature is used.
Furthermore, in view of coating workability, it is necessary to have an appropriate viscosity, and
generally, about 500 to 20000 cps is desired. In order to satisfy these properties, a composition
of the present invention comprising a combination of an oligomer and a monomer which is a
radiation / ultraviolet curable material described below was obtained. That is, the present
invention is a copolymer (PO / THF (molar ratio) = 8072Q or less) of propylene oxide
(hereinafter abbreviated as PO) and tetrahydrofuran (hereinafter abbreviated as T) IF having
hydroxyl groups at both ends in molecule 1soo-10000 The following formula is a urethane
acrylate (hereinafter referred to as "work") obtained by reacting diisocyanates at both ends of the
compound and then reacting the compound having only a hydroxyl group with a compound
having a hydroxyl group and an acryloyl group (or methacryloyl group) respectively. (R +: H,
CH3, R2: aliphatic group, aromatic group) with 20 to 70 wt% of all acrylate components, and ■
with all acrylate components. Also provided is a radiation / ultraviolet curable damping material
composition characterized by containing 30 to 80 wt%. It is. Hereinafter, the present invention
will be described in detail. (1) A modified product of a copolymer of propylene oxide and
tetrahydrofuran as shown in the construction In a copolymer having hydroxyl groups at both
ends of the construction, the copolymer having a PO / T) (F molar ratio of 80/20 or less is It is
preferably used. When PO alone, i.e., polypropylene glycol, is used in the same manner to obtain
a cured product, only those having poor heat aging resistance are obtained, and at least 20 mol%
or more of THF is required. The molecular weight is determined in the range having a straight
elastic modulus, but since the finally obtained urethane acrylate may be dominated by
monoacrylate rather than diacrylate, in this case the diacrylate is Molecular weight does not
affect the elastic modulus as compared to affecting the elastic modulus. For this reason, the
molecular weight range can be quite broad, but those less than 500 and those exceeding 1 oooo
are not practical because they are expensive as a copolymer in production. MDI (methylene
diisocyanate), hydrogenated MDI, TDI (tolylene diisocyanate), isophorone diisocyanate,
hexamethylene diisocyanate, chlorophenylene as the diisocyanate to be reacted with the
hydroxyl groups at both ends of this copolymer Di-isocyanate, tetramethylene di-isocyanate, XDI
(xylylene di-isocyanate), etc. are preferably used, and in a usual reaction, for example, using
dibutyltin dilaurate as a catalyst, 80 ° C. The reaction product (urethane-modified product)
having isocyanate groups at both ends can be obtained by reacting for about 4 hours.
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Next, a compound having a urethane acrylate can be obtained by respectively reacting a
compound having a hydroxyl group and no other functional group and a compound having a
hydroxyl group and an acryloyl group in the above urethane-modified product. In addition, an
acryloyl group shall mean an acryloyl group or a methacryloyl group here. Also in this reaction,
either of the compounds may be reacted first and then the other compound may be reacted, or
both compounds may be reacted simultaneously. The reaction can be almost completed in about
4 hours at a reaction temperature of 80 ° C. It is possible to raise various alcohols, phenols, etc.
with the compound which has a hydroxyl group used here and does not take other functional
groups, but it does not react with an isocyanate group, even if there is a functional group which
does not react with light. In the present invention, since there is no problem in the present
invention, in the present invention, an isocyanate group or a functional group reactive to light
refers to one other than a hydroxyl group. For example, amino group, thiol group, epoxy group,
acryloyl group (or methacryloyl group) and the like. Moreover, although the compound which
has a hydroxyl group and an acryloyl group is 2-hydroxyethyl acrylate (or methacrylate), 2hydroxypropyl acrylate (or methacrylate) etc., for example, it is not limited to these. A molar ratio
of a compound having a hydroxyl group and not having another functional group to a compound
having a hydroxyl group and an acryloyl group is preferably 80720 or less. If this molar ratio is
exceeded, the tackiness of the cured product of the composition obtained by compounding is
increased, the subsequent work becomes difficult, and the properties after heat aging deteriorate.
That is, by reacting the above-described urethane-modified product with the above-described
compound having a hydroxyl group and no other functional group with a compound having a
hydroxyl group and an acryloyl group, both terminals are not acrylates, either partially or A
urethane acrylate is obtained which has ends which are largely insensitive to light. (2) The
monofunctional acrylate represented by {circle over (1)} with respect to the monoacrylate
represented by {circle over (2)} can give a cured product with high Tan δ even when used alone.
However, the modulus of elasticity of the cured product of (1) is considerably high, and the
viscosity of the uncured product is also very low, so there is a problem in coating workability
alone. Therefore, the composition of the present invention is to mix the highly viscous urethane
acrylates in order to lower the elastic modulus to a preferable range without lowering Tan δ and
to give a suitable viscosity.
Furthermore, by using the composition of the present invention, the applicant of the present
application filed on February 14, 1986, in the claims of the "radiation / ultraviolet-curable
dumping material composition" and at both ends shown in the specification. Compared to the
case of using urethane acrylates having acrylates, less change in Tan δ due to changes in
temperature is obtained. That is, Tan δ at high temperature can be increased. In the present
invention, お よ び and を are essential components, ■ is 20 to 70 stomach L% of total acrylate
component, and が is 30 to 80 wt% of total acrylate. When it exceeds 10%, the modulus of
elasticity also increases, which is not preferable. As the amount of work increases, the decrease
in Tan δ is less pronounced compared to the case where all the ends are all acrylates, but again
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Tan δ decreases, so it is not preferable to exceed 70 wL%. In the present invention, it is not
preferable that it is less than 30 wt%. In the present invention, other acrylates may be mixed in
addition to the above-mentioned 、 and ■. For example, it is also possible to add a small amount
of monoacrylate having a very low modulus of elasticity when cured at a low viscosity for
viscosity adjustment or adjustment of the 5 modulus of elasticity. For example, those having a
cured product which has been cured alone can have a Tg of not higher than ordinary
temperature, more preferably not higher than 0 ° C, more effectively. Furthermore, for the
purpose of viscosity adjustment and improvement of workability, thixotropy (ThixoLropy)
imparting agent, for preventing adhesion of the surface of the cured product, releasing agent,
antiblocking agent or photosensitizer, curing accelerator, dispersion of polymerization inhibitor
An agent etc. can also be added suitably as needed. What is obtained by mixing these is a liquid
having a viscosity of 500 to 20,000 cps at normal temperature, and can be applied without
mixing an organic solvent and the like. In addition, they can be cured instantaneously by
irradiation with radiation such as electron beam, but in general, a photoinitiator can be added
and curing can be performed in 10 seconds or less with ultraviolet light. <Examples> The present
invention will be described more specifically using examples. In the composition shown in Table
1, after mixing a photoinitiator and a polymerization inhibitor with monoacrylate, urethane
acrylate was added and sufficiently stirred and mixed to obtain a radiation / ultraviolet curable
damping material composition. The viscosities of these compositions were measured with a Btype rotational viscometer, and the values are shown in Table 1. These compositions were
irradiated with ultraviolet light for 10 seconds at 50 ail / cm 2 using an ultraviolet lamp (80 Vl /
c IKW metal pearlite lamp) to be cured to obtain a sheet of thickness 2 l.
A test piece was cut out from this sheet, and the frequency was made constant, the temperature
was made constant and the temperature was made constant, and the tan δ and the elastic
modulus were measured using a viscoelasticity measuring device. For comparison, acrylic
polymer is dissolved and diluted in organic solvent (toluene), and after applying a material
currently used as a speaker damping material, the solid content is 40%! After drying day and
night, test pieces (comparative examples were cut out and physical properties were similarly
measured. Furthermore, the physical properties in the case where the urethane acrylate
component is a urethane acrylate having an acryloyl group at both ends are also described as
Comparative Example 2. ※ A A mixture of propylene oxide having a hydroxyl group at both ends
of molecular weight 4000 and tetrahydrofuran (PO / THF (molar ratio) = 50750) is used at both
ends of water fiMDI with a slight amount of dibutyltin dilaurate at 80 ° C for 4 hours The
urethane acrylate * B obtained by reacting over a period of time and then reacting 50150 in a
molar ratio of butanol / 2- to doxyethyl acrylate at 80 ° C. for 4 hours, and a hydroxyl group at
both ends of a molecular weight of 4000 The hydrogenated MDI is reacted at both ends of a
copolymer of propylene oxide and tetrahydrofuran (PO / THF (molar ratio) = 50150) with a
slight amount of dibutyltin dilaurate at 80 ° C. for 4 hours, and then And droxyethyl acrylate are
also reacted at 80 ° C. for 4 hours. Urethane acrylate having an acryloyl group at both ends *
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Di-ζ キ シ へ hexyl benzophenone メ ト キ シ E Methoxyhydroquinone <Effect of the invention>
The composition according to the present invention has an appropriate viscosity even without
containing an organic solvent Excellent productivity because it can be cured in a short time by
radiation, ultraviolet light, etc. without requiring a long time for drying time, and there are
problems with occupational safety and health such as fire hazards, harmful effects to human
body, etc. It was resolved. The cured product of the composition of the present invention has a
role of damping and reinforcement because it has high Tan δ from low temperature to high
temperature, low frequency to high frequency region, especially improved Tan δ at high
temperature, and moderately low elastic modulus. Therefore, it can be effectively used as a
speaker damping material.
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