US4874659A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electret fiber sheet and method of producing same
Assignee: Toray Industries Inc
•
Filing: 1985-10-23
•
Granted: 1989-10-17
•
Expires: 2005-10-23
Abstract
Abstract An electret fiber sheet has polarized charges on its surface and preferably has charges in ordered orientation across it. The polarized charges are present in an amount of at least 7×10 -11 C/cm 2 . Such sheets are formed to have a dust collecting efficiency. Sheets having an amount of polarized charge even as high as this are nevertheless stable when they have a maximum orientation energy of depolarization of at least 0.2 eV. Such an electret sheet can be obtained by a process comprising placing a fiber sheet between a non-contact type voltage-application electrode and an earth electrode confronting each other and supplying electricity (voltage>3 kV; current density>1×10 -6 mA/cm 2 ) between the electrodes, provided that the fiber sheet has a weight less than 80 g/m 2 and a covering factor at least 60%. The electret fiber sheet is useful in a variety of applications, such as filter materials, especially for collection of micro dust; clothing and furniture apparel for industrial clean rooms; adsorbing materials; and medical materials such as masks and collectors of bacillus.
Inventors
- 👤 Katsutoshi Ando
- 👤 Yo Ogawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:24
CPC Classifications
B; B01; B01D; B01D39/00; B01D39/08; B01D39/083; B01D39/086; B01D39/14; B01D39/16; B01D39/1607; B01D39/1623; B01D39/20; B01D39/2003; B01D39/2017; B03; B03C; B03C3/00; B03C3/28; H; H01; H01G; H01G7/00; H01G7/02; H01G7/021; H01G7/023; B01D2239/00; B01D2239/02; B01D2239/0216; B01D2239/0233; B01D2239/0241; B01D2239/04; B01D2239/0407; B01D2239/0435; B01D2239/06; B01D2239/0604; B01D2239/0622; B01D2239/12; B01D2239/1291; Y; Y10; Y10S; Y10S55/00; Y10S55/39; Y10T; Y10T428/00; Y10T428/249921
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
59 words
An electret fiber sheet having polarized charges of ordered orientation on the surfaces thereof, said electric fiber sheet being made from a sheet having a weight of 80 g/cm 2 or less and a covering factor of 60% or higher, wherein said electret fiber sheet has at least one measurable activation energy of depolarization of at least 0.2 eV.
Claim 2
Dependent Claim
59 words
An electret fiber sheet having polarized charges of ordered orientation on the surfaces thereof, said electric fiber sheet being made from a sheet having a weight of 80 g/cm 2 or less and a covering factor of 60% or higher, wherein said electret fiber sheet has at least one measurable activation energy of depolarization of at least 0.2 eV.
Claim 3
Dependent Claim
65 words
An electret fiber sheet having polarized charges of ordered orientation on opposite surfaces thereof, said fiber sheet being made from a sheet having a weight of 80 g/cm 2 or less and a covering factor of 60% or higher, wherein the said electret fiber sheet has a total amount of polarized charge per unit area of at least [7×10 -11 ]2×10 -10 C/cm 2 .
Claim 4
Dependent Claim
65 words
An electret fiber sheet having polarized charges of ordered orientation on opposite surfaces thereof, said fiber sheet being made from a sheet having a weight of 80 g/cm 2 or less and a covering factor of 60% or higher, wherein the said electret fiber sheet has a total amount of polarized charge per unit area of at least [7×10 -11 ]2×10 -10 C/cm 2 .
Claim 5
Dependent Claim
27 words
An electret fiber sheet as claimed in claim 2, wherein said total amount of polarized charge per unit area is at least 5×10 -10 C/cm 2 .
Claim 6
Dependent Claim
29 words
An electret fiber sheet as claimed in claim 1, wherein the total charge per unit area of the sheet is at least [7×10 -11 ]2×10 -10 C/cm 2 .
Claim 7
Dependent Claim
21 words
An electret fiber sheet as claimed in claim 1, wherein the peak temperature of the depolarization is at least 50° C.
Claim 8
Dependent Claim
20 words
An electret fiber sheet according to claim 4, wherein the peak temperature of the depolarization is at least 80° C.
Claim 9
Dependent Claim
18 words
An electret fiber sheet as claimed in claim 1, wherein the fiber sheet is a non-woven fiber sheet.
Claim 10
Dependent Claim
19 words
An electret fiber sheet as claimed in claim 7, wherein the non-woven fiber sheet is a melt-blown fiber sheet.
Claim 11
Dependent Claim
22 words
An electret fiber sheet as claimed in claim 1, wherein said one measurable activation energy of depolarization is at least 0.5 eV.
Claim 12
Dependent Claim
25 words
A material comprising a laminate of electret fiber sheets, each of which comprises an electret fiber sheet according to any of claim 1 to 9.
Claim 13
Dependent Claim
138 words
A process for producing an electret fiber sheet having polarized charges of ordered orientation and having either at least one measurable activation energy of depolarization of at least 0.2 eV or a total amount of polarized charge per unit area of at least 2×10 -10 C/cm 2 said process comprising the steps of: placing a fiber sheet having a weight of 80 g/m 2 or less and a covering factor of 60% or higher between a non-contact type voltage-application electrode and an earth electrode facing one another; placing a supplemental material having a volume resistivity higher than that of said earth electrode and lower than that of said fiber sheet between said earth electrode and said fiber sheet; and applying voltage of at least 3kV at an electric current density of at least 1×10 -6 mA/cm 2 .
Claim 14
Dependent Claim
138 words
A process for producing an electret fiber sheet having polarized charges of ordered orientation and having either at least one measurable activation energy of depolarization of at least 0.2 eV or a total amount of polarized charge per unit area of at least 2×10 -10 C/cm 2 said process comprising the steps of: placing a fiber sheet having a weight of 80 g/m 2 or less and a covering factor of 60% or higher between a non-contact type voltage-application electrode and an earth electrode facing one another; placing a supplemental material having a volume resistivity higher than that of said earth electrode and lower than that of said fiber sheet between said earth electrode and said fiber sheet; and applying voltage of at least 3kV at an electric current density of at least 1×10 -6 mA/cm 2 .
Claim 15
Dependent Claim
41 words
A process as claimed in claim 11, wherein a supplemental material having a volume resistivity higher than that of said earth electrode and lower than that of said fiber sheet is additionally disposed between said earth electrode and said fiber sheet.
Claim 16
Dependent Claim
27 words
A process as claimed in claim 11, wherein the volume resistivity of the supplemental material is in a range from 10 -1 to 10 10 Ω.cm inclusive.
Claim 17
Dependent Claim
17 words
A process as claimed in claim 11 or claim 13, wherein said supplemental material is a liquid.
Claim 18
Dependent Claim
21 words
A process as claimed in claim 11, wherein said fiber sheet has an apparent density of at least 0.05 g/cm 3
Claim 19
Dependent Claim
30 words
A process as claimed in any of claim 11, which is carried out at a temperature between the glass-transition temperature and melt point of the material of the fiber sheet.
Claim 20
Dependent Claim
25 words
A process as claimed in any of claim 11, wherein the distance between the fiber sheet and the voltage-application electrode is at least 5 mm.
Claim 21
Dependent Claim
101 words
A process as claimed in any of claim 11, which includes the steps of (a) placing the fiber sheet between the voltage-application and the opposite face of the fiber sheet faces the earth electrode, (b) applying a voltage of a given polarity between the voltage-application and earth electrodes, (c) reversing the fiber sheet so that the said one face thereof faces the earth electrode and the said opposite face thereof faces the voltage-application electrode, and (d) applying a voltage of a polarity opposite to that of the said given polarity applied in step (b) between the voltage application and earth electrodes.
References Cited (Backward Citations)
US31285A
Cited
US32171A
Cited
US30782A
Cited
US3379811A
Cited
US3571679A
Cited
US3978185A
Cited
US3998916A
Cited
USRE30782E
Cited
USRE32171E
Cited
US4091140A
Cited
USRE31285E
Cited
US4215682A
Cited
JPS57101073A
Cited
US4375718A
Cited
JPS5915168A
Cited
US4588537A
Cited
US4456648A
Cited
US4623438A
Cited
US4592815A
Cited
US4789504A
Cited
JPH05341369A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-10-16 | 1993-04-17 | 1993-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-16 | 1997-04-17 | 1997-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-16 | 2001-04-17 | 2001-10-17 | $7700.00 | Window Closed / Lapsed |