JP2636911B2 - Speaker diaphragm - Google Patents

Description

The present invention relates to a speaker diaphragm represented by a speaker cone and the like.

(Prior Art) Conventionally, as a material for a speaker cone, paper or a polyolefin-based polymer film and a material obtained by mixing an inorganic material with them have been used.
JP-A-57-154994, JP-A-62-205127, JP-A-62-205127
-149296, JP-A-62-101281, JP-A-62-101281
As seen in Japanese Patent Publication No. 149296, liquid crystal films have begun to be used.

(Problems to be Solved by the Invention) However, a speaker cone using paper or a polyolefin-based polymer film has the advantages of high internal loss tamδ and low price, but paper and polyolefin have a specific elastic modulus E / ρ. (E is the elastic modulus, ρ is the density), the balance of the performance as the speaker cone is insufficient. For this reason, inorganic materials, such as paper and polyolefin,
In particular, a method of increasing the specific elastic modulus by mixing mica and carbon fiber is used, but the amount of inorganic materials mixed is limited, and the specific elastic modulus has not yet reached a satisfactory level. . In addition, polyolefin is disadvantageous in terms of heat resistance and is not suitable for car stereos or high-output speakers.
In the case of a speaker diaphragm using a liquid crystal polymer, although high specific modulus, internal loss, and heat resistance can be obtained, the liquid crystal polymer is expensive and has a highly anisotropic and heterogeneous structure. I can't get a satisfactory speaker cone.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a speaker diaphragm having both high heat resistance and an appropriate specific elastic modulus, internal loss, and economy.

(Means for Solving the Problems) That is, the present invention relates to (a) inorganic compound 5 having an average particle diameter of 50 μ or less per 100 parts by weight of polyethylene terephthalate or polyester having at least 80 mol% or more of ethylene terephthalate repeating units. 50 parts by weight, (b) maleic anhydride graft-modified polyolefin
Using an extruded sheet containing 0.5 to 10 parts by weight, heat it to 80 to 180 ° C and vacuum form, vacuum / pneumatic, or vacuum / pneumatic plug assisted to crystallize to a crystallinity of 10% or more. It is a speaker diaphragm characterized by being hampered.

The polyethylene terephthalate used in the present invention is:
It is obtained by a usual melt polymerization method from terephthalic acid or an ester of terephthalic acid and ethylene glycol, or obtained by subjecting it to solid-state polymerization. The polyester having at least 80 mol% or more of ethylene terephthalate repeating units means a copolymer comprising at least 80 mol% of ethylene terephthalate repeating units and another repeating unit, that is, another copolymer component. As other copolymerization components, various acid components and glycol components can be used.

For example, acid components include isophthalic acid, naphthalenedicarboxylic acid, diphenylether dicarboxylic acid, diphenylmethane dicarboxylic acid, diphenylsulfondicarboxylic acid, p- (2-hydroxyethoxy) benzoic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, Sebacic acid, dodecane-1,12-dicarboxylic acid, tetradecane-1,14-dicarboxylic acid, hexadecane-1,16-
Dicarboxylic acid, octadecane-1,18-dicarboxylic acid, 6-
Ethyl-hexadecane-1,16-dicarboxylic acid and the like can be mentioned.

Examples of the glycol component include propylene glycol, diethylene glycol, butylene glycol, pentyl glycol, neopentyl glycol, hexamethylene glycol, polyethylene glycol, and polyalkylene glycol such as polytetramethylene glycol.

The inorganic compound used as the component (A) of the present invention includes:
Depending on the particle size and shape, smoothing agent, reinforcing material,
The effect as a moderator of anisotropy of mechanical properties and a nucleating agent is different. When the average particle size exceeds about 50μ, the effect is reduced. Therefore, inorganic compounds having an average particle size of 50μ or less are generally useful.

Specific examples of the inorganic compound having an average particle size of 50 μm or less include carbon black, silica, calcium carbonate, synthetic silicic acid and silicate, zinc white, halocytoclay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, Examples include wollastonite, dolomite powder, titanium oxide, barium sulfate, calcium sulfate, and alumina.
One or more of these inorganic compounds can be used. Among them, talc, mica and wollastonite are particularly effective in the present invention.

Polyethylene is preferable as the polyolefin as a base of the maleic anhydride-grafted modified polyolefin used as the component (b) of the present invention, but a copolymer containing a small amount of polypropylene or polybutylene as long as the properties of polyethylene are not impaired. It may be united. The amount of maleic anhydride grafted was 100 parts by weight of the copolymer.
If it is 0.05 part by weight or more, the compatibility with the thermoplastic polyester is sufficient.

The component (A) in the resin composition of the present invention, that is, an inorganic compound having an average particle diameter of 50 μm or less, has a multi-functionality of a sheet surface smoothing agent, a reinforcing agent, a mechanical property anisotropy reducing agent, and a crystal nucleating agent. Have. If the blending ratio of component (a) is less than 5 parts by weight with respect to 100 parts by weight of polyester component, the effect as a sheet surface smoothing agent, an anisotropic agent for mechanical properties, and a reinforcing material is insufficient. Conversely, if the amount is more than 50 parts by weight, the mechanical properties are remarkably deteriorated. Therefore, the amount of the component (a) is 5 to 50 parts by weight, preferably 10 to 30 parts by weight, per 100 parts by weight of the polyester component.

The component (b), namely, thermoplastic polyester 100
If the amount of the maleic anhydride-grafted modified polyolefin is less than 0.5 parts by weight per part by weight, the crystallization rate is low, and there is a problem in the economics of molding. On the other hand, even if the amount is more than 10 parts by weight, the effect of increasing the crystallization rate is saturated, and the heat resistance and elastic modulus begin to decrease. Therefore, maleic anhydride added to 100 parts by weight of the thermoplastic polyester is used. The amount of the graft-modified polyolefin is 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight.

The resin composition of the present invention may further contain additives such as a heat stabilizer, an oxidation stabilizer, a light stabilizer, a lubricant, a pigment, a flame retardant, and a plasticizer, if necessary.

On the other hand, if the heating temperature of the sheet is lower than 80 ° C., the softening is insufficient, so that thermoforming becomes difficult. On the contrary, if the sheet is heated to a temperature higher than 180 ° C., the sheet is excessively softened and the sheet is deformed. Therefore, the heating temperature of the sheet is 80 to 180
° C, preferably 100-160 ° C. The molding method is
Either vacuum forming, vacuum press forming or vacuum press plug assist forming, which is generally widely used, may be used, but other forming methods such as match forming may be employed. The thermoformed body produced by this method is
Since the crystallinity is 10% or more, the elastic modulus becomes even higher,
In addition, heat resistance becomes extremely high.

The crystallinity described here is determined by an infrared total reflection absorption spectrum method. The method is described below.

By changing the temperature and time of heat treatment of a 100 μm thick polyester film, ten kinds of crystallinity measurement standard samples were prepared.
The FT-IR-ATR spectrum was measured and the crystallization band was 1341 cm.
The absorbance ratio (P) between ^-1 and the normalized band 1409 cm ^-1 is determined.
The dependence of these two bands on the crystallinity of the polyester resin is described in Journal Polymer Science, Polymer Lette.
r Edition, VOL. 12, p. 13 (1974). When this absorbance ratio (P) is plotted against the crystallinity (Xc) determined by the density method for ten types of samples, the following linear relationship is obtained.

(Relational formula I) Xc = 37.81P-7.44 (%) The relationship between the crystallinity (Xc) and the density (ρx) of the polyester resin is well known, and (Relational formula II) (However, ρc is the density of the crystallized polyester resin, 1.45.
5g / cm ³ , ρc is the density of amorphous polyester resin 1.335g / cm
³ ). Therefore, the crystallinity of the unknown sample is 1
The crystallinity can be determined from the absorbance ratio between the 341 cm ^-1 band and the 1409 cm ^-1 band by using the above relational expression I.

If the crystallinity measured by this method does not reach 10%,
The elasticity and heat resistance of the thermoformed body are insufficient, and the heat generated during the operation of the speaker causes thermal deformation, so the crystallinity is 10% or more.
Preferably, 18% or more is required.

(Examples) Examples 1 to 3 Polyethylene terephthalate resin 100 having an intrinsic viscosity of 0.98
The mica having an average particle diameter of 40μ was mixed with the parts by weight shown in Table 1 and 3 parts by weight of maleic anhydride graft-modified low density polyethylene was melt-kneaded with a twin screw extruder to prepare pellets. A sheet having a thickness of 0.4 mm was manufactured by an extrusion sheet forming apparatus using a T-die. 150 ° C of the obtained sheet
With a vacuum-pressure pneumatic plug-assist molding machine
The sheet was preheated to the sheet temperature shown in Table 1 and the speaker diaphragm was formed with a cycle time of 6 seconds / time. As shown in Table 2, the formability was good, the crystallinity was high, the specific modulus and the internal loss were low. An appropriate and good speaker diaphragm was obtained.

Comparative Examples 1 to 6 A speaker diaphragm was prepared under the same conditions as in Example 1 except that 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. Table 2 shows the physical properties of the speaker diaphragm.

(Effect of the Invention) The speaker diaphragm of the present invention is superior to polymers such as polypropylene, polyethylene, nylon 6, and polystyrene in terms of heat resistance, specific elastic modulus, internal loss, and dimensional stability. It has become possible to adopt a mass-production method in which sheets are formed by extrusion molding using low-cost polymers. In addition, high-speed molding with a crystallinity of 10% or more becomes possible by performing vacuum molding, vacuum-pressure molding or vacuum-pressure-plug-assist molding, and the economic effect is great.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kiminori Okamoto 23 Uji Kozakura, Uji-city, Kyoto, Japan Examiner in Central Research Laboratory Unitika Ltd. Masahide Kawaguchi (56) References JP-A-57-164697 (JP, A)

Claims (1)

(57) [Claims] (1) 100 parts by weight of polyethylene terephthalate or polyester having at least 80 mol% or more of ethylene terephthalate-based repeating units,
An extruded sheet containing 5 to 50 parts by weight of an inorganic compound having an average particle size of 50 μm or less and 0.5 to 10 parts by weight of (ii) a maleic anhydride graft-modified polyolefin is used.
A speaker diaphragm characterized by crystallizing to a crystallinity of 10% or more by vacuum forming, vacuum / pneumatic forming or vacuum / pneumatic plug assist forming while heating to 180 ° C.