US4334351A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Novel PTC devices and their preparation
Assignee: Raychem Corp
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Filing: 1980-05-19
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Granted: 1982-06-15
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Expires: 2000-05-19
Abstract
Abstract The flex life of devices comprising a relatively inflexible PTC conductive polymer element is improved by surrounding the PTC element with a layer of a relatively flexible polymeric composition which is melt-fused thereto. Particularly useful devices are self-limiting strip heaters in which the polymeric component of the PTC element comprises a mixture of two crystalline polymers having substantially different melting points, the higher melting polymer having a melting point of at least 160° C., preferably at least 200° C., for example a mixture of polyvinylidene fluoride and a copolymer of ethylene and tetrafluoroethylene. Such devices can be made by melt-extruding a layer of the relatively flexible polymeric composition around the PTC element, and heating to cause melt-fusion of the polymers at the interface of the layer and the PTC element.
Inventors
- 👤 Umesh K. Sopory
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:56
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; B; B29; B29C; B29C48/00; B29C48/03; B29C48/07; B29C48/08; B29C48/12; B29C48/15; B29C48/156; H05; H05B; H05B3/00; H05B3/10; H05B3/12; H05B3/14; H05B3/146; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49083; Y10T29/49101
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
181 words
A method of making a flexible electrical device which comprises (a) an elongate flexible PTC element composed of a PTC conductive polymer composition which exhibits PTC behavior and which comprises (i) a polymer component which comprises a mixture of a first crystalline polymer having a first melting point T 1 and a second crystalline polymer having a second melting point T 2 which is at least (T 1 +25)° C., and (ii) a particulate filler component which has been dispersed in said polymer component and which comprises a conductive filler; and (b) at least one metal electrode; which method comprises (1) forming said PTC element by melt-shaping said conductive polymer composition adjacent said electrode so that the electrode is in electrical contact with said PTC element; (2) forming on the surface of said PTC element a layer of a second polymeric composition having substantially greater flexibility at 23° C. than said PTC composition; and (3) heating said layer to cause melt fusion of said second polymeric composition and said PTC composition at the interface between said layer and said PTC element.
Claim 2
Independent Claim
181 words
A method of making a flexible electrical device which comprises (a) an elongate flexible PTC element composed of a PTC conductive polymer composition which exhibits PTC behavior and which comprises (i) a polymer component which comprises a mixture of a first crystalline polymer having a first melting point T 1 and a second crystalline polymer having a second melting point T 2 which is at least (T 1 +25)° C., and (ii) a particulate filler component which has been dispersed in said polymer component and which comprises a conductive filler; and (b) at least one metal electrode; which method comprises (1) forming said PTC element by melt-shaping said conductive polymer composition adjacent said electrode so that the electrode is in electrical contact with said PTC element; (2) forming on the surface of said PTC element a layer of a second polymeric composition having substantially greater flexibility at 23° C. than said PTC composition; and (3) heating said layer to cause melt fusion of said second polymeric composition and said PTC composition at the interface between said layer and said PTC element.
Claim 3
Dependent Claim
19 words
A method according to claim 1 which comprises melt-extruding the second polymeric composition in contact with the PTC element.
Claim 4
Dependent Claim
23 words
A method according to claim 1 which comprises melt extruding the PTC composition around the electrodes so that the electrodes are embedded therein.
Claim 5
Dependent Claim
16 words
A method according to claim 1 wherein T 2 is at least (T 1 +70)° C.
Claim 6
Dependent Claim
25 words
A method according to claim 1 wherein the second polymeric composition has a melting point of (T 1 -10)° C. to (T 1 +50)° C.
Claim 7
Dependent Claim
16 words
A method according to claim 1 wherein the second polymeric composition comprises said first crystalline polymer.
Claim 8
Dependent Claim
18 words
A method according to claim 6 wherein the second polymeric composition consists essentially of said first crystalline polymer.
Claim 9
Dependent Claim
78 words
A method according to claim 1 wherein in step (3) the device is heated at a temperature which is between (T 1 +5)° C. and (T 2 -10)° C. for a time sufficient to reduce the resistivity at 25° C. of said PTC conductive polymer composition from a first value, e o , prior to said step (3), to a second value, e A , after said step (3), where e A is less than 0.8×e o .
Claim 10
Dependent Claim
15 words
A method according to claim 8 wherein φ A is less than 0.6×e o .
Claim 11
Dependent Claim
16 words
A method according to claim 8 wherein e A is 10 2 to 10 5 ohm.cm.
Claim 12
Dependent Claim
14 words
A method according to claim 1 wherein T 2 is at least 160° C.
Claim 13
Dependent Claim
14 words
A method according to claim 11 wherein T 2 is at least 200° C.
Claim 14
Dependent Claim
14 words
A method according to claim 12 wherein T 1 is 100° to 175° C.
Claim 15
Dependent Claim
20 words
A method according to claim 1 wherein each of the crystalline polymers in the PTC composition is a fluorinated polymer.
Claim 16
Dependent Claim
23 words
A method according to claim 1 wherein the first crystalline polymer is polyvinylidene fluoride and the second crystalline polymer is an ethylene/tetrafluoroethylene copolymer.
Claim 17
Dependent Claim
28 words
A method according to claim 1 wherein said second polymeric composition has substantially greater flexibility than said PTC composition at all temperatures between 0° C. and 100° C.
Claim 18
Dependent Claim
32 words
A method according to claim 1 wherein said second polymeric composition has substantially greater flexibility than said PTC composition at all temperatures between 0° C. and the switching temperature of the composition.
Claim 19
Dependent Claim
18 words
A method according to claim 1 which comprises simultaneously melt-extruding the PTC composition and the second polymeric composition.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-06-14 | 1985-12-14 | 1986-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-06-14 | 1989-12-14 | 1990-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-06-14 | 1993-12-14 | 1994-06-15 | $7700.00 | Window Closed / Lapsed |