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The present invention relates to a speaker diaphragm represented by a speaker cone or the like.
(Conventional art) Conventionally, as a material of a speaker cone, a cocoon or polyolefin
polymer film and a material in which an inorganic material is mixed with them are used in many
cases. Also, recently, see JP-A-57-1571994, JP-A-62-205127, JP-A-62-149296, JP-A-62-100128,
JP-A-62-149296, etc. Liquid crystal films are also beginning to be used. (Problems to be Solved
by the Invention) However, a speaker cone using two papers or a polyolefin polymer film has an
advantage that the internal loss tan δ is high and the price is low. Paper and polyolefin have
poor specific elastic modulus E / ρ (巳 is elastic modulus and ρ is density), so the performance
balance as a speaker cone is insufficient. For this reason, there is a method of mixing inorganic
materials, especially mica and carbon fibers, in paper and polyolefin to raise the specific elastic
modulus, but there is a limit to the mixing amount of the inorganic materials, and the sufficiently
specific elastic modulus It is 1 present condition that it has not reached. In addition, polyolefin is
disadvantageous at one point of heat resistance, and is not suitable for car stereos and speakers
for high output. Also, in the case of a speaker diaphragm using a liquid crystal polymer, a high
specific elastic modulus. Although internal loss and heat resistance can be obtained, the liquid
crystal polymer is expensive and has a highly anisotropic and heterogeneous structure, so that a
sufficiently satisfactory speaker cone can not be obtained. The present invention has been made
to solve such problems, and it is an object of the present invention to obtain a speaker diaphragm
having high heat resistance, appropriate specific elastic modulus, internal loss and economy.
(Means for Solving the Problems) That is, the present invention relates to (i) an inorganic
compound having an average particle size of 50 μm or less with respect to 100 parts by weight
of polyester having polyethylene terephthalate or ethylene terephthalate repeating unit of at
least 80 mol% (B) using an extrusion-formed sheet containing 5 to 50 parts by weight and (b) 0.5
to 10 parts by weight of a maleic anhydride graft-modified polyolefin, vacuum forming while
vacuuming this to 80 to 180 ° C. Alternatively, it is a speaker diaphragm characterized in that
vacuum pressure plug A-I is molded and crystallized to a crystallinity of 10% or more. The
polyethylene terephthalate used in the present invention is one obtained from terephthalic acid
or an ester of terephthalic acid and ethylene glycol by a usual melt polymerization method, or
one obtained by solid phase polymerization treatment thereof.
And, polyester having at least 80 mol% or more of ethylene terephthalate repeating units means
80 mol% or more of ethylene terephthalate repeating units and other repeating units. That is, it
means a copolymer composed of other copolymer components, and various acid components and
glycol components can be used as the above-mentioned other copolymer components. For
example, as an acid component, isophthalic acid, tic-dicarboxylic acid, diphenyl ether dicarboxylic
acid. Diphenylmethanedicarboxylic acid, diphenylsulfonedicarboxylic acid, p- (2-hydroxyethoxy)
benzoic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecane1,12-dicarboxylic acid, tetradecane-1,14 And -dicarboxylic acid, hexadecane-1,16-dicarboxylic
acid, octadecane-1,18-dicarboxylic acid, 6-ethyl-hexadecane-1,16-dicarboxylic acid and the like.
Examples of the glycol component include polyalkylene glycols such as propylene glycol,
diethylene glycol, butylene glycol, pentyl glycol, neopentyl glycol, hexamethylene glycol,
polyethylene glycol and polytetramethylene glycol. The inorganic compound used as the
component (i) of the present invention has different effects as an anisotropic relaxation agent
and crystal nucleating agent of the smoothing agent 1 reinforcing material 5 mechanical
property of the sheet surface depending on the particle size and shape. In general, inorganic
compounds having an average particle size of 50 μm or less are useful because the effect is
reduced when the average particle size exceeds about 50 μ. Specific examples of inorganic
compounds having an average particle size of 50 μm or less are carbon blanks, silica and
calcium carbonate. Synthetic silicas and silicates, zinc flower, halosite clay, kaolin, basic
magnesium carbonate, mica, kurku 1 quartz powder, wollastonite, dolomite powder titanium
dioxide, barium sulfate, calcium sulfate, alumina etc. And one or more of these inorganic
compounds can be used. Among them, talc, mica and wollastonite are particularly effective in the
present invention. As a polyolefin which becomes a basis of maleic anhydride graft modification
polyolefin used as (ii) ingredient of the present invention, although polyethylene is desirable, it is
a copolymer which contained a small amount of polypropylene or polybutylene in the range
which does not impair the property of polyethylene. But it is good. If the grafting amount of
maleic anhydride is 0.05 parts by weight or more with respect to 100 parts by weight of the
copolymer, the compatibility with the thermoplastic polyester is sufficient.
Regarding the compounding ratio of each component in the resin composition of the present
invention, (a) Component, that is, an inorganic compound having an average particle diameter of
5077 or less is an sheet surface smoothing agent 1 reinforcing material It is an additive that aims
for multiple functions such as a crystal nucleating agent. If it is less than 5 parts by weight with
respect to 100 parts by weight of the polyester component, the effect as a sheet surface
smoothing agent, mechanical property of the anisotropic relaxation agent 1 as a reinforcing
material is insufficient, and conversely more than 50 parts by weight Mechanical properties are
significantly degraded when compounded. Accordingly, the blending amount of the component
(i) is 5 to 50 parts by weight with respect to 100 ffKffi part of the polyester component.
Preferably, it is 10 to 30 parts by weight. When the amount of maleic anhydride graft modified
polyolefin is less than 0.5 parts by weight based on 100 parts by weight of the (mouth)
component, that is, the thermoplastic polyester, the crystallization speed is slow and the
economy of molding process Problems occur. On the other hand, even if it is added in excess of
10 parts by weight, the improvement effect of the crystallization rate increase is saturated, and
the heat resistance and elastic modulus begin to decrease, so maleic anhydride is added to 100
parts by weight of thermoplastic polyester The amount of graft modified polyolefin is 0.5 to 10
parts by weight, preferably 1 to 5 parts by weight. The resin composition in the present
invention may further contain a heat stabilizer, an oxidation stabilizer, a light stabilizer, and a
lubricant as required. You may mix | blend additives, such as a pigment, a flame retardant, and a
plasticizer. Further, if the heating temperature of the sheet is lower than 80 ° C., the softening is
insufficient, so that the ripe-forming becomes difficult, and conversely, when heated to a
temperature higher than 180 ° C., the sheet is too soft and deformation of the sheet occurs.
Therefore, the heating temperature of the sheet is 80 to 180 "C, preferably 100 to 160" C. The
forming method may be any of vacuum forming, vacuum pressure forming, or vacuum pressure
plug assist forming generally used widely, but other forming methods such as, for example,
matching or the like may be adopted. The thermoformed article produced by this method has a
crystallinity of 10% or more, and thus has a further high elastic modulus and extremely high heat
resistance. The crystallinity degree mentioned here is calculated | required by an infrared total
reflection absorption spectrum method. The method is described below. A polyester film having a
thickness of 100 μm was subjected to heat treatment at different temperatures and times to
prepare ten kinds of standard samples for measuring crystallinity, and FT-IR-ATII spectra were
measured. The absorbance ratio (P) of the crystallization buff 11341 cm 'and the normalized
band 1409 cm' is determined.
For the crystallinity dependence of these two bands of polyester resin, J.
VOL、12. P, 13 (1974), described in detail. If this absorbance ratio (P) is plotted against
the crystallinity (Xc) determined by the density method for 10 types of samples, the following
linear relationship can be obtained. (Relational Formula I) Xc = 37.8IP-7, 44C%) The relationship
between the degree of crystallinity (Xc) and the density () X) of a polyester resin is well known.
(Relational formula 2) (However, CC is 1.455 g / cJ in the density of the crystallized polyester
resin, and aa is 1.335 g / 'c in the density of the amorphous polyester resin. It can be obtained by
the relational expression of Therefore, the crystallinity of the unknown sample can be
determined from the absorbance ratio of the 1341 cm- 'band and the 1409 cm-' band by using
the above-mentioned relational expression I. If the degree of crystallinity measured by this
method does not reach 10%, the modulus of elasticity and heat resistance of the thermoformed
article are insufficient, and thermal deformation occurs due to heat generation during operation
of the speaker, so the degree of crystallinity is 10% or more , Preferably 18% or more. Examples
1 to 3 100 parts by weight of polyethylene terephthalate resin having an intrinsic viscosity of
0.98 was blended with a part by weight of mica having an average particle diameter of 40 μ
shown in Table 1, and maleic anhydride graft modified low density polyethylene 3 The placed
portion was melt-kneaded using a twin-screw pressure ratio machine to make a billet, and this
was used to produce a 0.4 mm thick sheet with an extrusion sheet forming apparatus using a Tdie. The obtained sheet is subjected to a vacuum pressure air plug assist molding machine having
a molding die of 150'C. It was preheated to the sheet temperature shown in Table 1, and a
speaker diaphragm was molded with a cycle time of 6 seconds / cycle. As shown in Table 2, the
formability is good and the crystallinity is also high. The specific elastic modulus and internal
loss were also suitable, and a good speaker diaphragm was obtained. Comparative Examples 1 to
6 Under the same conditions as Example 1, the mixing ratio of mica and maleic anhydride graft
modified low density PE and the sheet temperature before molding were changed as shown in
Table 1 to prepare a speaker diaphragm. Physical properties and the like of the speaker
diaphragm are shown in Table 2. Table 1 Second Table (Effects of the Invention) The speaker
diaphragm of the present invention has heat resistance, specific modulus, and internal loss as
compared with polymers such as polypropylene polyethylene, nylon 6, and polystyrene. It has
become possible to use a mass production method of producing a sheet by an extrusion method
using a polymer excellent in dimensional stability and low in cost.
Further, by performing vacuum forming, vacuum pressure forming, vacuum pressure air plug
assist forming or the like, high speed forming becomes possible with a degree of crystallization of
10% or more, and the economic effect is also great. Patent Applicant Unitika Co., Ltd.
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