JP2009260063A - Electret composes of polyphenylene ether system foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin foam electret which can convert electric energy into mechanical energy, or convert the mechanical energy into the electric energy, is excellent in charge retention nature at high temperature, and can easily be manufactured. <P>SOLUTION: The electret is obtained by charging denatured polyphenylene ether system resin foam, and preferably, by charging denatured polyphenylene ether system resin foam of which the ratio A/B between average cell diameter A in the thickness direction and average cell diameter B of a plane perpendicular to the thickness direction is ≤1, and the number of cells in the thickness direction is ≥2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electret obtained by charging a modified polyphenylene ether resin foam.

  An electret is known as one that converts electrical energy into mechanical energy or mechanical energy into electrical energy. Electrets are used for acoustic devices such as speakers and microphones, pressure sensors, and the like.

Conventionally, a charged polyvinylidene fluoride film has been used as an electret made of an organic material. However, there is a problem that the piezoelectricity is low. In recent years, it has been found that a charged polypropylene foam film exhibits high piezoelectricity, but there is a problem that the piezoelectric performance deteriorates at 60 ° C. due to insufficient charge retention at high temperatures (non- Patent Document 1). Fluoropolymer foams such as polytetrafluoroethylene and tetrafluoroethylene-hexafluoroethylene copolymer are known as foams excellent in charge retention even at high temperatures (Patent Document 1). However, the fluororesin foam has excellent charge retention at high temperatures, but has a problem that the foam is not easy to produce.
JP 2007-231077 A Ferroelectrics, 2006, 331, 189-199

  An object of the present invention is to provide a resin foam electret that is excellent in charge retention at high temperatures and can be easily manufactured.

  As a result of intensive research to solve the above-mentioned problems, the inventors of the present invention have shown that a charged product of a modified polyphenylene ether-based resin foam that can be easily produced exhibits good piezoelectricity and retains charge at high temperatures. As a result, the present invention has been completed.

  That is, the present invention relates to an electret obtained by charging a modified polyphenylene ether resin foam.

  As a preferred embodiment, the ratio A / B between the average cell diameter A in the thickness direction of the modified polyphenylene ether-based resin foam and the average cell diameter B in the plane perpendicular to the thickness direction is 1 or less. As a more preferred embodiment, the above-mentioned electret is characterized in that the number of cells in the thickness direction of the modified polyphenylene ether resin foam is 2 or more.

  By using a modified polyphenylene ether resin foam as a foam and charging it, an electret having excellent durability, good piezoelectricity, and excellent charge retention at high temperatures can be easily obtained.

  The modified polyphenylene ether resin, which is a material resin of the modified polyphenylene ether resin foam in the present invention, includes a styrene / phenylene ether copolymer obtained by polymerizing a styrene monomer to a polyphenylene ether resin, and a polyphenylene ether resin. And a resin obtained by mixing a polystyrene resin and the like.

  Among these modified polyphenylene ether resins, it is low-cost, and by changing the mixing ratio, it is possible to easily obtain a product with excellent quality such as heat resistance and rigidity, and with changed workability. A resin obtained by mixing a polyphenylene ether resin and a polystyrene resin is preferable.

  The modified polyphenylene ether resin preferably comprises 10% by weight to 70% by weight of the polyphenylene ether resin and 30% by weight to 90% by weight of the polystyrene resin in the modified polyphenylene ether resin, more preferably polyphenylene ether. 30% by weight or more and 60% by weight or less of the resin and 40% by weight or more and 70% by weight or less of the polystyrene resin.

  Specific examples of the polyphenylene ether resin include poly (2,6-dimethylphenylene-1,4-ether), poly (2-methyl-6-ethylphenylene-4-ether), and poly (2,6 -Diethylphenylene-1,4-ether), poly (2,6-diethylphenylene-1,4-ether), poly (2-methyl-6-n-propylphenylene-1,4-ether), poly (2 -Methyl-6-n-butylphenylene-1,4-ether), poly (2-methyl-6-chlorophenylene-1,4-ether), poly (2-methyl-6-bromophenylene-1,4-ether) Ether) and poly (2-ethyl-6-chlorophenylene-1,4-ether). These may be used alone or in combination of two or more.

  Specific examples of the styrene monomer that is polymerized to polyphenylene ether resin, preferably graft polymerized, include, for example, styrene, α-methylstyrene, 2,4-dimethylstyrene, monochlorostyrene, dichlorostyrene, p- Examples include methyl styrene and ethyl styrene. These may be used alone or in combination of two or more. Of these, styrene is preferable in terms of versatility and cost.

  Specific examples of the polystyrene-based resin include resins having the styrene-based monomer as a main component. The polystyrene resin is not limited to a homopolymer composed of only styrene or a styrene derivative, but may be a copolymer made by copolymerizing with another monomer.

  The modified polyphenylene ether-based resin foam in the present invention is, for example, after melt-kneading the modified polyphenylene ether-based resin and the foaming agent in an extruder at 150 to 300 ° C., and adjusted to a foaming temperature of 130 to 200 ° C. in the extruder, Using a circular die having an annular lip, extrusion is performed from the lip of the die into atmospheric pressure to obtain a cylindrical foam, and then cooled by molding with a cooling cylinder (mandrel) while taking the cylindrical foam. Thereafter, it can be produced by a slitting method. Further, it is also produced by a method in which a foam is obtained in the form of a film using a T die instead of a circular die and taken up with a roll or the like. Further, the obtained foam may be cut by cutting or the like.

  Examples of the foaming agent used in the production of the modified polyphenylene ether-based resin foam in the present invention include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, and isopentane, cyclobutane, cyclopentane, and cyclohexane. Inorganic gases such as alicyclic hydrocarbons, nitrogen, carbon dioxide and air. You may use these individually or in mixture of 2 or more types.

  The amount of the foaming agent varies depending on the type of foaming agent and the target density, but is preferably 1 part by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the modified polyphenylene ether resin.

  In the present invention, in order to control the number of cells in the thickness direction of the modified polyphenylene ether-based resin foam within the above range, a nucleating agent such as talc may be used in combination as necessary. The addition amount of the nucleating agent used as necessary is not particularly limited, but is usually preferably 0.01 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the modified polyphenylene ether resin. .

  Furthermore, in the present invention, in the production of the modified polyphenylene ether resin foam, a thermoplastic resin, an antioxidant, a metal deactivator, and a phosphorus processing stabilizer are within the range that does not impair the foamability of the modified polyphenylene ether resin. , UV absorbers, UV stabilizers, fluorescent brighteners, metal soaps, antacid adsorbent stabilizers, or crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments Additives such as dyes and flame retardants may be added.

  The modified polyphenylene ether resin foam in the present invention can be obtained in this manner.

  The ratio A / B of the average cell diameter A in the thickness direction of the modified polyphenylene ether-based resin foam in the present invention to the average cell diameter B in the plane perpendicular to the thickness direction is preferably 1 or less, more preferably 0.5. It is as follows. Here, the thickness of the modified polyphenylene ether-based resin foam refers to a direction parallel to a direction in which a high voltage is applied in electretization.

  The average cell diameter A in the thickness direction of the modified polyphenylene ether resin foam in the present invention is not particularly limited as long as it does not exceed the thickness of the modified polyphenylene ether resin foam, but the number of cells in the thickness direction is 2 or more. Preferably there is. The number of cells in the thickness direction is read by observing the cross-section magnified 150 times with a microscope.

The average cell diameter A in the thickness direction of the modified polyphenylene ether resin foam in the present invention and the average cell diameter B in the plane perpendicular to the thickness direction are two orthogonal directions parallel to the thickness direction of the modified polyphenylene ether resin foam. The cross section to be enlarged is magnified 150 times with a microscope, and the cell diameter in the direction perpendicular to the thickness direction and the thickness direction is read for each of 20 cells using a scale attached to the microscope, and is calculated by arithmetic average. Read the major and minor diameters of the cell diameter in the vertical direction.

  The thickness of the modified polyphenylene ether resin foam in the present invention is not particularly limited, but is usually 0.05 to 2 mm. If it is this range, the performance as an electret can be shown.

  An electret can be obtained by applying a high voltage to the modified polyphenylene ether-based resin foam obtained by the above method and charging it. As a method of applying a high voltage, there are a method using a corona discharge device and a method of attaching an electrode to a foam and connecting it to a high voltage power source. Since it is not necessary to attach an electrode, a method in which a high voltage is applied and charged by a corona discharge device is preferable. If the applied voltage is too low, charging becomes insufficient, and it is preferable to apply a voltage of 0.5 kV or more.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” are based on mass.

[Evaluation of thermal stability of electric charge]
The electret was processed in an oven at 60 ° C., and the surface charge was measured and averaged at five points using a surface potentiometer.

[Piezoelectric evaluation]
An aluminum foil was adhered to both sides of the surface perpendicular to the thickness direction of the electret, and the aluminum foil and the voltage measuring device were connected. A 100 g SUS plate (125 mm × 50 mm) was dropped onto the aluminum foil from a height of 1 cm, and the generated voltage was measured.

(Example 1)
57.1 parts by weight of a polyphenylene ether resin (manufactured by GE Japan, EFN-4230: polyphenylene ether component / polystyrene component = 70/30) and polystyrene resin (40% by weight of polyphenylene ether resin and 60% by weight of polystyrene resin) PS Japan, G8102: PS component = 100) 42.9 parts by weight of modified polyphenylene ether resin mixed, talc (manufactured by Hayashi Kasei Co., Ltd., Talcan powder PK) 0.34 parts by weight, stearic acid 0.08 part by weight of magnesium (manufactured by Sakai Chemical Industry Co., Ltd., SM-1000) and 0.05 part by weight of polybutene (manufactured by Nisseki Polybutene, LV-50) were stirred and mixed with a ribbon blender. The obtained blend is supplied to a tandem extruder in which a 115 mmφ extruder (first stage extruder) and a 152 mmφ extruder (second stage extruder) are connected in series so that the resin temperature becomes about 280 ° C. Then, after melt-kneading in the first-stage extruder, a hydrocarbon-based blowing agent (iso-butane / n-butane = 85/15) as a blowing agent is 3.9 with respect to 100 parts by weight of the modified polyphenylene ether resin. Part by weight was press-fitted and mixed. Thereafter, the cylinder temperature of the second stage extruder was cooled to 135 to 145 ° C. and then extruded from a circular die at a rate of 150 kg / hour under atmospheric pressure. While the obtained cylindrical foam is formed using a mandrel (outer diameter of 445 mm, temperature-controlled at 40 ° C. with circulating water) while being taken off at 10.0 m / min, the sheet is cut by a cutter to obtain a sheet. In a state, a length of 200 m was wound using a winding core material having a diameter of 260 mm so as to form a cylindrical roll. The obtained foamed sheet had an expansion ratio of 15 times, a closed cell ratio of 90%, a basis weight of 150 g / m ² , a sheet width of 1400 mm, and a sheet thickness of 2.3 mm.

  The obtained foamed sheet was sliced to obtain a modified polyphenylene ether resin foam having a thickness of 0.3 mm. The average cell diameter in the thickness direction of the obtained modified polyphenylene ether resin foam was 0.05 mm, and the average cell diameter in the plane perpendicular to the thickness direction was 0.12 mm × 0.20 mm.

  A 15 kV voltage was applied to the modified polyphenylene ether resin foam (50 mm × 50 mm × 0.3 mm) by corona discharge for 3 minutes to obtain an electret. The thermal stability of the electric charge and the piezoelectricity were evaluated.

(Comparative Example 1)
Polypropylene foam sheet (50 mm × 50 mm × 1.7 mm, expansion ratio 6.2 times, closed cell ratio 80%, basis weight 240 g / m ² , thickness direction average cell diameter 0.18 mm, average cell in plane perpendicular to thickness direction The diameter was 0.37 mm × 0.46 mm), and a voltage of 15 kV was applied for 3 minutes by corona discharge to obtain an electret. The thermal stability of the electric charge and the piezoelectricity were evaluated.

4 is a graph showing the results of evaluation of thermal stability of charges in Example 1 and Comparative Example 1.

Claims (3)

  An electret obtained by charging a modified polyphenylene ether resin foam.   The electret according to claim 1, wherein a ratio A / B between an average cell diameter A in the thickness direction of the modified polyphenylene ether-based resin foam and an average cell diameter B in a plane perpendicular to the thickness direction is 1 or less.   The electret according to claim 1 or 2, wherein the number of cells in the thickness direction of the modified polyphenylene ether-based resin foam is 2 or more.

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