JPH01170011A - Electret forming device - Google Patents

Abstract

PURPOSE:To make it possible to uniformly and easily mass-produce a highly efficient electret sheet in a short period by a method wherein a humidifier, to be used to humidify the space between electrodes, is provided. CONSTITUTION:A sheet 1 passes through guide rolls 2 and 8, it is sent to the humidifying chamber 3a, the degree of moisening of which is controlled by a humidifier 3, the sheet 1 is contacted to the drum-shaped opposing electrode (earth electrode) 4 to be used for high voltage application, and after the cathode or the anode high voltage of a non-contact type discharge electrode 5 has been applied thereon, it is rolled up as an electret sheet 7 through guide rolls 6 and 9. By discharging a corona in a humidified atmosphere through the abovementioned procedures, the hindrance of repulsion and the like of the injected electrons and ions can be eliminated, and the sheet formed by high voltage into the state of uniform electret continuously and uniformly can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a manufacturing apparatus for manufacturing an electret sheet by using corona discharge on a polymer 7-sheet.
More specifically, the present invention relates to a high performance electret sheet 1 - an apparatus that can be mass-produced uniformly and easily in a very short period of time.

[Conventional technology]

Electrets are currently in practical use as diaphragms and bias voltage application materials in acoustic transducer devices such as microphones, speakers, and cartridges.
Applications are also being considered for switches, air filters, etc.

There are many types of electrets depending on the manufacturing method, such as 1) thermal electret, 2) electroelectret, 3) radio electret, 4) mechanoelectret, and 5) magnetoelectret. (For example, see Physical Properties, September issue (1971, pp.516-527)) Among these manufacturing methods, the 4EHC general method, the electroelectret method, and the 9 corona method are used to produce dielectric sheets, which are materials to be made into various electrets. , is a method of forming an electret by applying a DC high voltage at room temperature and causing a corona discharge to the surface of the 'nl#L body (for example, JP-A-60-168511 [Problem to be solved by the invention]) In general, the corona method This may be due to the advantages that the obtained electret has a large amount of initial charge and can be made into an electret in a short time using a simple method.If the applied voltage is low and the material is thick, the electrons injected by corona discharge and Ions are distributed only near the p-plane.Also, there is a problem that the injected electrons and ions at the beginning of corona discharge repel and inhibit subsequent electrons and ions, making it impossible to achieve sufficient electret formation.To avoid this, the applied voltage When the temperature rises, the electrons or ions injected into the sheet cause the insulation RZ&
There was a pause where something happened.

An object of the present invention is to provide an electret-forming device m that can eliminate the above-mentioned drawbacks without impairing the advantages of electret produced by the corona method.

[Means for resolving intervening points]

The electretization apparatus of the present invention is an apparatus that converts a sheet-like material into electret by continuously applying high pressure while moving the material using opposing electrodes, and is provided with a humidifying device for humidifying the space between the electrodes. Features.

[Examples and effects]

Next, embodiment 1i of the present invention will be explained with reference to the drawings.

The drawing shows an example of the embodiment of the present invention, in which a rolled sheet 1 is sent through guide rolls 8 and 2 to a humidifying chamber 3aK where humidification is adjusted by a humidifying device It3. After contacting the drum-shaped counter electrode (earth electrode) 4 for applying high voltage installed at 3a17-3 and applying a high voltage of negative or positive polarity to the non-contact type discharge electrode 5, the guide roll 6 and The electret sheet 7 is wound through 9 as the electret sheet 7.

It is preferable that the humidifying device 3 used in the present invention has a capacity that allows the relative humidity in the humidifying chamber 3a to be set within the range of 60% to 100%. A structure is used. Further, it is more preferable to have a structure in which a humidity detector is provided and the humidity can be set.

As the discharge electrode 5, a needle electrode, a wire electrode, etc. are used, but these IT electrode materials have a volume resistivity of 1.
It is preferable to use conductive gold ingots of 0″ Ω·α or less. Also,
The drum-shaped counter electrode 4 is preferably made of the same metal as the electrode 5, although the material is not specified in terms of percentage.

Sheets to be made into electrets include films, paper-like materials, etc. made of polyolefin polymers such as polyethylene and polypropylene, polyesters, polycarbonates, fluorine-based resins, inorganic materials, and other materials with a volume resistivity of 10 μm 3 Ω or more. Nonwoven fabrics, woven fabrics, knitted fabrics, foams, etc. can be used.

Next, the conditions for electretization are the applied electric field strength &t
-5 KV/cfIL or more, preferably 7 KV/cm or more, and the gap between the discharge electrode and the counter electrode is preferably at least 105 m or more. If the applied electric field strength is as low as 5KV1cm, it becomes difficult to form a sufficient electret, and the electric field must be placed opposite the discharge electrode! If the gap with the pole is smaller than 10 m, corona discharge will become unstable, and similarly to υ, it will be difficult to make an electret.

The treatment temperature is preferably room temperature; if the treatment fA quality becomes low, cooling becomes necessary, and it takes a long time to form an electret.

The relative humidity when applying corona using the electret conversion device kk of the present invention is preferably 60% or more, more preferably Fi 75% or more.

The effects of the present invention will be explained in more detail below with reference to Examples.

The dust collection efficiency in the examples was calculated from the ratio of particle concentrations before and after the sheet using stearic acid particles with an average particle size of 0.6 μm at a wind speed of 5.3 α/sec. In addition, pressure loss was measured by measuring the pressure difference between the upstream and downstream sides of the sheet using a differential pressure diaphragm.

〔Example〕

Example 1 The average fiber diameter was 1.4μ as a sheet using the device shown in the drawing.
, -N1 soy/m'' was continuously converted into electret by corona discharge under the following conditions.

Electretization conditions: Applied voltage: DC 15xV Distance between electrodes: 201 m Processing temperature: 26°C There was no edge breakage, and the web was operated smoothly without any damage.

The performance of the obtained electl knot web as a filter was measured, and the results are shown in Table 1. For performance measurement, the web was used after 2 hours of operation to stabilize the humidification state and other conditions.

Example 2 Using the apparatus shown in the drawings, the stretching ratio was 6 to 10 times, the width was 10 m,
Several dozen rows of polypropylene flat yarn films having a thickness of 8 to 15 μm were arranged in rows to form an electret under the same conditions as in Example 1.

This electret flat yarn film is defibrated into a mesh shape using a needle-like roll, and then cut into fibers with a fiber length of 20 to 50 using a cutter.
It was cut into m.

The obtained small fibers are fed to a T-card roll, formed into a web, and needle punched to obtain a filter fabric weight of 60.
A filter material of 0g/m'' and 5th edition of Saiji was obtained.

The performance of the obtained electret web as a filter was completely measured, and the results are shown in Table 1.

Comparative Example 1 In the apparatus shown in the drawings, the same test as in Example 1 was carried out with the humidifier completely stopped. When the humidity in the humidifying chamber at this time was measured, it was found to be 40% relative humidity.

The obtained electret web had many dielectric breakdown points and had several U of holes on the web surface. or,
The operating conditions were also unstable as discharge was unstable and continuous processing was not possible. Therefore, the applied voltage was set to 12KV'! I lowered it and turned it into an electret.

The performance of the resulting filter was completely measured, and the results are shown in Table 1.

Comparative Example 2 In the apparatus shown in the drawings, all the same tests as in Example 2 were carried out with the humidifying device stopped and the humidity in the humidifying chamber kept at 40% relative humidity.

The performance of the filtered electret web as a filter was measured, and the results are shown in 0←1.

Table 1: Filter performance [Effects of the invention] When electretization is performed using the electretization device of the present invention, by performing one corona discharge in a humidified atmosphere,
Since there is no inhibition of repulsion of injected electrons and ions, it is possible to obtain a continuous and uniform electret sheet at a high voltage.

Therefore, as shown in Table 1, it can be seen that the obtained electret sheet has a higher dust collection efficiency than the known electret.

[Brief explanation of the drawing]

The drawing is a schematic diagram showing an example of the electretization apparatus of the present invention. 1 Niji? , 2, 6, 8, 98 guide roll, 3: humidifier, 3a=humidifying chamber, 4: counter electrode, 5: discharge electrode, 7:
electret seat

Claims (1)

[Claims] An electret device comprising a discharge electrode and a counter electrode, and forming an electret by placing a sheet material to be formed into an electret between the electrodes, characterized in that a humidifying device is provided for humidifying a space between the electrodes. conversion device.