Patent US4591700A successfully refreshed from Google Patents.
US4591700A
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PTC compositions
Assignee: Tyco International Ltd
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Filing: 1984-03-12
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Granted: 1986-05-27
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Expires: 2004-03-12
Abstract
Abstract Novel PTC conductive polymer compositions contain a mixture of two crystalline polymers of different melting points, the higher melting of the polymers having a melting point which is at least 160 DEG C. and at least 25 DEG C. higher than the melting point of the other polymer. The compositions do not increase in resistivity by a factor more than 2 when maintained at 150 DEG C. for 1000 hours, and are therefore particularly suitable for self-limiting heaters which can be used on apparatus which is periodically subjected to high temperatures, e.g. during steam-cleaning thereof.
Inventors
- 👤 Umesh K. Sopory
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 13:36
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; H01C7/027; H05; H05B; H05B3/00; H05B3/10; H05B3/12; H05B3/14; H05B3/146; H05B3/40; H05B3/54; H05B3/56
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
226 words
A self-limiting heater suitable for use at line voltages of about 120 volts or more which comprises (a) a PTC element composed of a PTC conductive polymer composition which exhibits PTC behavior, which has a resistivity at 25° C. of at least 10 2 ohm.cm and which comprises (i) 50 to 85%, by weight of the composition, of a polymer component which comprises a mixture of a first crystalline fluorinated polymer having a first melting point, T 1 , which is from 100° C. to 175° C. and a second crystalline fluorinated polymer having a second melting point, T 2 , which is at least 200° C., the ratio by weight of said first polymer to said second polymer being from 1:3 to 3:1, and (ii) a particulate filler component which has been dispersed in said polymer component and which comprises carbon black in amount 8 to 40% by weight of the composition; and (b) two electrodes which are are in electrical contact with said PTC element and which can be connected to a source of electrical power to cause current to flow through the PTC element; said heater having a resistance at 25° of R 25 ohms. and a resistance at 25° C. after being maintained at a temperature of 160° C. for 1000 hours, R 1000 , which is less than 2×R 25 .
Claim 2
Dependent Claim
226 words
A self-limiting heater suitable for use at line voltages of about 120 volts or more which comprises (a) a PTC element composed of a PTC conductive polymer composition which exhibits PTC behavior, which has a resistivity at 25° C. of at least 10 2 ohm.cm and which comprises (i) 50 to 85%, by weight of the composition, of a polymer component which comprises a mixture of a first crystalline fluorinated polymer having a first melting point, T 1 , which is from 100° C. to 175° C. and a second crystalline fluorinated polymer having a second melting point, T 2 , which is at least 200° C., the ratio by weight of said first polymer to said second polymer being from 1:3 to 3:1, and (ii) a particulate filler component which has been dispersed in said polymer component and which comprises carbon black in amount 8 to 40% by weight of the composition; and (b) two electrodes which are are in electrical contact with said PTC element and which can be connected to a source of electrical power to cause current to flow through the PTC element; said heater having a resistance at 25° of R 25 ohms. and a resistance at 25° C. after being maintained at a temperature of 160° C. for 1000 hours, R 1000 , which is less than 2×R 25 .
Claim 3
Dependent Claim
13 words
A heater according to claim 1 wherein the first polymer is polyvinylidene fluoride.
Claim 4
Dependent Claim
14 words
A heater according to claim 2 wherein the second polymer is an ethylene/tetrafluoroethylene copolymer.
Claim 5
Dependent Claim
15 words
A heater according to claim 3 wherein the PTC element is substantially free from cross-linking.
Claim 6
Dependent Claim
23 words
A heater according to claim 1 wherein the ratio by weight of the first polymer to the second polymer is 1:2 to 2:1.
Claim 7
Dependent Claim
13 words
A heater according to claim 5 wherein said ratio is 0.5 to 1.
Claim 8
Dependent Claim
13 words
A heater according to claim 6 wherein said ratio is 0.6 to 0.8.
Claim 9
Dependent Claim
38 words
A heater according to claim 1 wherein said PTC composition contains 65 to 75% by weight of said polymer component, 10 to 15% by weight of carbon black and 10 to 25% by weight of non-conductive particulate filler.
Claim 10
Dependent Claim
15 words
A heater according to claim 1 wherein T 2 is at least (T 1 +70)°C.
Claim 11
Dependent Claim
15 words
A heater according to claim 9 wherein T 2 is at least (T 1 +90)°C.
Claim 12
Dependent Claim
19 words
A heater according to claim 1 wherein the carbon black is the sole conductive filler in the PTC composition.
Claim 13
Dependent Claim
18 words
A heater according to claim 1 wherein the amount of carbon black is 10 to 15% by weight.
Claim 14
Dependent Claim
20 words
A heater according to claim 1 wherein the PTC composition contain 10 to 25% by weight of a non-conductive filler.
Claim 15
Dependent Claim
17 words
A heater according to claim 1 wherein the first and second polymers are incompatible with each other.
Claim 16
Dependent Claim
49 words
A heater according to claim 1 which is a flexible elongate heating strip in which the PTC strip is elongate and flexible and has a resistivity of 10 2 to 10 5 ohm.cm, and the electrodes are elongate, parallel, flexible metal wires which are embedded in the PTC element.
Claim 17
Dependent Claim
17 words
A heater according to claim 15 wherein the first and second polymers are incompatible with each other.
Claim 18
Dependent Claim
38 words
A heater according to claim 1 wherein the conductive polymer composition has a resistivity at 25° C. of 10 2 to 10 5 ohm.cm, the first polymer is polyvinylidene fluoride and the second polymer is an ethylene/tetrafluoroethylene copolymer.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1989-05-26 | 1989-11-25 | 1990-05-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-05-26 | 1993-11-25 | 1994-05-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-05-26 | 1997-11-25 | 1998-05-27 | $7700.00 | Window Closed / Lapsed |