US3660736A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the production of high-efficient electrets
Assignee: Kureha Corp
•
Filing: 1971-03-10
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Granted: 1972-05-02
•
Expires: 1991-03-10
Abstract
Abstract By heat-treating a polymer-type electret that has been subjected to a polarization treatment at temperatures lower than the melting point of the polymer but higher than the glass transition point of the polymer, an unstable hetero-charge component and the homo-charge component can be reduced and a stable hetero-charge can be sustained.
Inventors
- 👤 Yuriko Igarashi
- 👤 Haruko Kakutani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:46
CPC Classifications
H; H01; H01G; H01G7/00; H01G7/02; H01G7/021; H01G7/023
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
31 words
The process as claimed in claim 1 wherein said crystalline high molecular weight material is selected from the group consisting of polyvinylidene fluoride, polyvinylidene chloride, polyvinyl chloride, polyethylene terephthalate, and polycarbonate.
Claim 2
Dependent Claim
22 words
The process as claimed in claim 1 wherein said high molecular weight material is a mixture of polyvinylidene fluoride and polymethyl methacrylate.
Claim 3
Dependent Claim
29 words
The process of claim 1 wherein said electret is formed by subjecting a crystalline high molecular weight material to a direct current field of from 1 to 200 KV./cm.
Claim 4
Dependent Claim
17 words
The process of claim 1 wherein said period of time varies from 0.5 hour to 1 week.
References Cited (Backward Citations)
US2538554A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-02 | 1975-11-01 | 1976-05-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-02 | 1979-11-01 | 1980-05-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-02 | 1983-11-01 | 1984-05-02 | $7700.00 | Window Closed / Lapsed |