US3957573A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing insulating paper where the paper is frictionally calendered
Assignee: Dainichi Nippon Cables Ltd
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Filing: 1972-11-08
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Granted: 1976-05-18
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Expires: 1992-11-08
Abstract
Abstract Polyolefin fibers containing at least 70% by weight of polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 are formed into a sheet. The sheet is then frictionally calendered in the dry state at a frictional ratio of at least 15% and at a temperature in the range from 90°C to 160°C whereby an insulating paper having excellent air-impermeability and oil-resistance is obtained.
Inventors
- 👤 Haruo Miyamoto
- 👤 Ikuo Igami
- 👤 Masaru Uehara
- 👤 Hideo Fujita
- 👤 Hirotaka Itoh
- 👤 Zyozi Kan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:40
CPC Classifications
D; D21; D21H; D21H5/00; D21H5/12; D21H5/20; D21H5/202; D21H13/00; D21H13/10; D21H13/12; D21H13/14
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
86 words
A process for producing an insulating paper having high air-impermeability and high oil resistance suitable for use in an oil-filled electrical device which comprises forming a sheet of polyolefin fibers containing at least 70% by weight of polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 , and frictionally calendering said sheet in the dry state at a frictional ratio of at least 15% and at a temperature in the range from 90°C to 160°C.
Claim 2
Dependent Claim
86 words
A process for producing an insulating paper having high air-impermeability and high oil resistance suitable for use in an oil-filled electrical device which comprises forming a sheet of polyolefin fibers containing at least 70% by weight of polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 , and frictionally calendering said sheet in the dry state at a frictional ratio of at least 15% and at a temperature in the range from 90°C to 160°C.
Claim 3
Dependent Claim
22 words
A process according to claim 1, wherein said frictional ratio is at least 20% and said temperature ranges from 115° to 160°C.
Claim 4
Dependent Claim
75 words
A process according to claim 2, wherein said sheet comprises a mixture of: (1) 30% by weight, or less, of polypropylene microfibers having a diameter less than 10 μ prepared from a polypropylene whose extractable contents in decalin at 77°C is less than 15% by weight; and (2) at least 70% by weight of polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 .
Claim 5
Dependent Claim
44 words
A process according to claim 1, said sheet of polyolefin comprises polypropylene-polyethylene bicomponent fibers containing at least 70% by weight of a polypropylene fiber portion having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 .
Claim 6
Dependent Claim
88 words
A process according to claim 1, wherein said sheet of polyolefin fibers comprises a mixture of: (1) polypropylenepolyethylene bicomponent fibers containing a polypropylene fiber portion having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 ; and (2) polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 , the total amount of said polypropylene fibers portion being at least 70% by weight of the total weight of said sheet.
Claim 7
Dependent Claim
61 words
A process according to claim 1, wherein said sheet of polyolefin fibers comprises a mixture of: (1) 30% by weight, or less, of polyethylene fibers having a denier of at least 0.5; and (2) at least 70% by weight of polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 .
Claim 8
Dependent Claim
20 words
A process according to claim 4, wherein said polyethylene has a density in the range of from 0.955 to 0.97.
Claim 9
Dependent Claim
20 words
A process according to claim 5, wherein said polyethylene has a density in the range of from 0.955 to 0.97.
Claim 10
Dependent Claim
20 words
A process according to claim 6, wherein said polyethylene has a density in the range of from 0.955 to 0.97.
Claim 11
Dependent Claim
14 words
A process according to claim 2, wherein said frictional ratio is at least 25%.
Claim 12
Dependent Claim
22 words
A process according to claim 2, wherein said polypropylene fiber has a birefringence of at least 3.0 × 10 - 2 .
Claim 13
Dependent Claim
36 words
A process according to claim 11, wherein said polypropylene fibers are formed from a polypropylene having a density of at least 0.89 and an intrinsic viscosity in the range of from about 1.0 to about 3.0.
Claim 14
Dependent Claim
33 words
A process according to claim 2, wherein said sheet of polyolefin fibers has a basis weight in the range of from 20 to 400 g/m 2 before being subjected to said frictional calendering.
Claim 15
Dependent Claim
26 words
A process according to claim 2, wherein said sheet of polyolefin fibers is washed with a solvent before and/or after being subjected to said frictional calendering.
Claim 16
Dependent Claim
18 words
A process according to claim 14, wherein said solvent is water at a temperature of at least 40°C.
Claim 17
Dependent Claim
13 words
A process according to claim 14, wherein said solvent is a hydrophilic solvent.
Claim 18
Dependent Claim
13 words
A process according to claim 14, wherein said solvent is a lipophilic solvent.
Claim 19
Dependent Claim
20 words
A process according to claim 14, wherein said solvent is a mixture of a hydrophilic solvent and a lipophilic solvent.
Claim 20
Dependent Claim
31 words
A process according to claim 14, wherein said washing is conducted first with water, then with deionized water and finally with a mixture of a hydrophilic solvent and a lipophilic solvent.
Claim 21
Dependent Claim
22 words
The process of claim 4 wherein the polyethylene comprises at least about 5% by weight of the balance of the bicomponent fiber.
Claim 22
Dependent Claim
22 words
The process of claim 20 wherein the polyethylene comprises from 10 to 20% by weight of the balance of the bicomponent fiber.
Claim 23
Dependent Claim
17 words
The process of claim 6 wherein the sheet comprises at least about 5% by weight polyethylene fibers.
Claim 24
Dependent Claim
17 words
The process of claim 22 wherein the sheet comprises from 10 to 20% by weight polyethylene fibers.
Claim 25
Dependent Claim
18 words
A process according to claim 1 wherein said polypropylene is formed into a sheet by a dry processing.
Claim 26
Dependent Claim
18 words
A process according to claim 1 wherein said polypropylene is formed into a sheet by a wet processing.
Claim 27
Dependent Claim
45 words
A process according to claim 25, wherein said polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 have a cut length of 0.5 to 20 mm, and said insulating paper exhibits a uniform air-impermeability.
Claim 28
Dependent Claim
23 words
A process according to claim 25 wherein a binder is used to form said sheet, said binder being removed prior to frictional calendering.
Claim 29
Dependent Claim
25 words
A process according to claim 25 wherein an organic solvent is used to form said sheet, said organic solvent being removed prior to frictional calendering.
Claim 30
Dependent Claim
43 words
A process according to claim 1, wherein said sheet consists essentially of polyolefins, at least 70% by weight of which are said polypropylene fibers having a denier of at least 0.5 and a birefringence of at least 2.5 × 10 - 2 .
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-05-18 | 1979-11-17 | 1980-05-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-05-18 | 1983-11-17 | 1984-05-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-05-18 | 1987-11-17 | 1988-05-18 | $7700.00 | Window Closed / Lapsed |