Electrical transmission or interconnection systems – Electrets
Patent
1990-01-11
1991-10-15
Pellinen, A. D.
Electrical transmission or interconnection systems
Electrets
G11C 1302
Patent
active
050577107
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to electret materials having thermal stability and high amounts of trap electric charge and being stable for a long time and the method for preparing them.
The electret materials obtained by the present invention are most suitably used for, for example, various filter materials, wiping materials, absorbing materials, mask materials, materials for dust-protecting clothes and so on and can be used in wide ranges of applications by utilizing the good electret characteristics.
2. Background Art
Up to this time, various methods were described on the page 155 of the Handbook of Static Electricity (Ohm-Sha, published on May 30, 1981) and Japanese Patent Laid-Open No. 61-289177 as the methods for preparing electret of polymers. And, in these methods, polarization is carried out by generating implantation of electrons, movement of ions, orientation of dipoles and so on and electric charge is given in consequence.
Moreover, as one of the electretification technologies for obtaining high electretification effect, a technology which gave an electretification effect by adding a compounded material to a polymer and thereby prepared an electret material, was proposed. For example, there is a method described on Japanese Patent Laid-Open No. 60-196922.
However, by the method described on the above described Japanese Patent Laid-Open No. 60-196922 where a metal salt of an aliphatic acid was compounded in polypropylene and a corona treatment was carried out, the amount of trap electric charge increased in some extent and electretification effect was recognized, but this was not an enough level for a sufficient electret material.
DISCLOSURE OF INVENTION
The technological problems to be solved by the present invention are to offer an electret material having no defect which the above described conventional materials have and especially to offer an electret material having high amount of electric charge at high temperature and thereby being capable of having high heat resistance and holding stably the electric charge for a long time.
The present invention has the following constitutions.
Namely, the electret materials of the present invention are electret materials characterized by compounding 0.01 parts by weight or more and 2 parts by weights or less of at least one stabilizer selected from stabilizers of hindered amines, nitrogen-containing hindered phenols and metal-containing hindered phenol against 100 parts by weight of polypropylene and by using, at least as a part, a polypropylene whose molecular weight distribution is 5.5 or less in the ratio of Mw/Mn (Mw:weight average molecular weight, Mn:number average molecular weight).
Moreover, the method for preparing the electret materials of the present invention is the method for preparing the electret materials characterized by using a polypropylene containing 0.01 parts by weight or more and 2 parts by weight or less of at least one stabilizer selected from stabilizers of hindered amines, nitrogen-containing hindered phenols and metal-containing hindered phenol, reducing the molecular weight distribution of the polypropylene to 5.5 or less in its ratio of Mw/Mn (Mw:weight average molecular weight, Mn:number average molecular weight), molding the compound in a desired shape and applying thereon an electret treatment.
The electret materials of the present invention, as described above, can have high amounts of trap electric charge and it is therefore offer electret materials having high heat stability on said electric charge and being capable of exhibiting electret characteristics stably for a long time.
The electret materials of the present invention like this are most suitable for various filter materials, wiper materials, absorbing materials, materials for dust-protecting clothes and so on by utilizing the above described characteristics and the present invention therefore has such practical excellent effects that it is possible to use electret materials in various wide range of applications and fields.
B
REFERENCES:
patent: 4086499 (1978-04-01), Mishra
patent: 4527218 (1985-07-01), von Seggern
patent: 4626263 (1986-12-01), Inoue et al.
patent: 4789504 (1988-12-01), Ohmori et al.
Ando Katsutoshi
Nishiura Eiichi
Gaffin Jeffrey A.
Pellinen A. D.
Toray Industries Inc.
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