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US4086499A
Expired / Lapsed
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Stable electrets of styrene-type polymers
Assignee: Uniroyal Ltd Canada
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Filing: 1976-11-26
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Granted: 1978-04-25
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Expires: 1996-11-26
Abstract
Abstract An electret made of styrene-type polymer (e.g., polystyrene), having a volume resistivity of at least 1016 ohm-cm and a glass transition temperature above 50 DEG C, and containing not more than 1% by weight of electron-donor impurities and not more than 0.5% by weight of electron-acceptor impurities, said electret being capable of retaining at least 75% of its charge after exposure to a temperature of 50 DEG C and a relative humidity of 100% for 100 days.
Inventors
- 👤 Anupama Mishra
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:25
CPC Classifications
H; H01; H01G; H01G7/00; H01G7/02; H01G7/021; H01G7/023
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
106 words
An electret made of electrostatically polarized, resinous, thermoplastic emulsion-polymerized styrene-type polymer selected from the group consisting of homopolymers of styrene, vinyltoluene or t-butylstyrene, and copolymers of at least two of said monomers, said polymer having a volume resistivity of at least 10 16 ohm-cm, and a glass transition temperature above 50° C, and containing not more than 1% by weight of electron-donor impurities and not more than 0.5% by weight of electron-acceptor impurities, said electret being characterized by the ability to retain at least 75% of its original charge upon exposure to a temperature of 50° C at a relative humidity of 100% for 100 days.
Claim 2
Dependent Claim
106 words
An electret made of electrostatically polarized, resinous, thermoplastic emulsion-polymerized styrene-type polymer selected from the group consisting of homopolymers of styrene, vinyltoluene or t-butylstyrene, and copolymers of at least two of said monomers, said polymer having a volume resistivity of at least 10 16 ohm-cm, and a glass transition temperature above 50° C, and containing not more than 1% by weight of electron-donor impurities and not more than 0.5% by weight of electron-acceptor impurities, said electret being characterized by the ability to retain at least 75% of its original charge upon exposure to a temperature of 50° C at a relative humidity of 100% for 100 days.
Claim 3
Dependent Claim
13 words
An electret as in claim 1, in which the said polymer is polystyrene.
Claim 4
Dependent Claim
13 words
An electret as in claim 1 in which the said polymer is poly(vinyltoluene).
Claim 5
Dependent Claim
13 words
An electret as in claim 1 in which the said polymer is poly(t-butylstyrene).
Claim 6
Dependent Claim
18 words
An electret as in claim 1 in which the said polymer is a copolymer of styrene and vinyltoluene.
Claim 7
Dependent Claim
18 words
An electret as in claim 1 in which the said polymer is a copolymer of styrene and t-butylstyrene.
Claim 8
Dependent Claim
18 words
An electret as in claim 1 in which the said polymer is a copolymer of vinyltoluene and t-butylstyrene.
Claim 9
Dependent Claim
111 words
A charged electret consisting of an electrostatically polarized, resinous, thermoplastic emulsion-polymerized styrene-type polymer selected from the group consisting of (i) homopolymers of styrene, vinyltoluene or t-butylstyrene, and (ii) copolymers of at least two of the said monomers, said polymer having a volume resistivity of at least 10 16 ohm-cm, and a glass transition temperature above 50° C., and containing not more than 1% by weight of electron-donor impurities and not more than 0.5% by weight of electron-acceptor impurities, said electret being characterized by the ability to retain at least 75% of its original charge upon exposure to a temperature of 50° C at a relative humidity of 100% for 100 days.
Claim 10
Dependent Claim
111 words
A charged electret consisting of an electrostatically polarized, resinous, thermoplastic emulsion-polymerized styrene-type polymer selected from the group consisting of (i) homopolymers of styrene, vinyltoluene or t-butylstyrene, and (ii) copolymers of at least two of the said monomers, said polymer having a volume resistivity of at least 10 16 ohm-cm, and a glass transition temperature above 50° C., and containing not more than 1% by weight of electron-donor impurities and not more than 0.5% by weight of electron-acceptor impurities, said electret being characterized by the ability to retain at least 75% of its original charge upon exposure to a temperature of 50° C at a relative humidity of 100% for 100 days.
Claim 11
Dependent Claim
35 words
A method of making the electret of claim 8 comprising sandwiching the said styrene-type polymer between two glass plates and applying a DC voltage of about 20 to 60 KV for 1 to 5 minutes.
References Cited (Backward Citations)
US3755043A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-04-24 | 1981-10-24 | 1982-04-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-04-24 | 1985-10-24 | 1986-04-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-04-24 | 1989-10-24 | 1990-04-25 | $7700.00 | Window Closed / Lapsed |