US4775778A
Expired / Lapsed
US
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PTC compositions and devices comprising them
Assignee: Tyco International Ltd Bermuda
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Filing: 1985-05-14
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Granted: 1988-10-04
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Expires: 2005-05-14
Abstract
Abstract Novel conductive polymer compositions which exhibit useful PTC behavior are produced by cross-linking processes. By correlating the polymer, the conductive filler dispersed therein, and the cross-linking conditions, PTC compositions having desired resistance/temperature characteristics can be prepared. In particular the cross-linking can be carried out so as to provide compositions having a switching temperature around the cross-linking temperature. The invention is applicable to both elastomeric and thermoplastic polymers, and provides for the first time a method of making PTC compositions exhibiting useful PTC behavior from elastomers.
Inventors
- 👤 Peter H. van Konynenburg
- 👤 Bernard J. Lyons
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 10:49
CPC Classifications
H; H05; H05B; H05B3/00; H05B3/40; H05B3/54; H05B3/56; C; C08; C08K; C08K3/00; C08K3/02; C08K3/04; H01; H01B; H01B1/00; H01B1/20; H01B1/24; H01C; H01C7/00; H01C7/02; H01C7/027; H05B3/10; H05B3/12; H05B3/14; H05B3/146; H05B3/565
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
131 words
An electrical device which comprises two or more electrodes and a PTC composition in contact therewith, the PTC composition comprising: (1) a cross-linked elastomer prepared by cross-linking an elastomeric gum having a tensile stress of less than 10 psi at 20% elongation; and (2) conductive particles enclosed with the cross-linked network of said elastomer, the particles having a size of at least 18 millimicrons: which composition (a) has a gel fraction of at least 0.6; (b) exhibits PTC behavior with an R 14 value of at least 2.5 or an R 100 value of at least 10, and at least one T s within the temperature range from room temperature to +250° C.; and (c) has a volume resistivity at temperatures below said T s between 25 and 10 5 ohm.cm.
Claim 2
Dependent Claim
131 words
An electrical device which comprises two or more electrodes and a PTC composition in contact therewith, the PTC composition comprising: (1) a cross-linked elastomer prepared by cross-linking an elastomeric gum having a tensile stress of less than 10 psi at 20% elongation; and (2) conductive particles enclosed with the cross-linked network of said elastomer, the particles having a size of at least 18 millimicrons: which composition (a) has a gel fraction of at least 0.6; (b) exhibits PTC behavior with an R 14 value of at least 2.5 or an R 100 value of at least 10, and at least one T s within the temperature range from room temperature to +250° C.; and (c) has a volume resistivity at temperatures below said T s between 25 and 10 5 ohm.cm.
Claim 3
Dependent Claim
20 words
A device according to claim 1 wherein the elastomer has been crosslinked with the aid of a chemical cross-linking agent.
Claim 4
Dependent Claim
56 words
A device according to claim 1 wherein the PTC composition is one whose T s remains substantially unchanged when repeatedly subjected to thermal cycling which comprises heating the composition from a temperature below T s to a temperature above T s but below the peak temperature, followed by cooling to a temperature below T s .
Claim 5
Dependent Claim
22 words
A device according to claim 1 wherein the conductive particles are carbon black particles having a size of 22 to 80 millimicrons.
Claim 6
Dependent Claim
12 words
A device ccording to claim 1 wherein the elastomer is a polysiloxane.
Claim 7
Dependent Claim
18 words
A device according to claim 5 wherein the PTC composition comprises a polysiloxane having silica particles dispersed therein.
Claim 8
Dependent Claim
38 words
A device according to claim 5 which is a strip heater comprising an elongate element of said PTC composition, two longitudinally extending, parallel electrodes embedded in said composition, and an outer layer of a protective and insulating composition.
Claim 9
Dependent Claim
115 words
A PTC composition comprising: (1) a cross-linked elastomer prepared by cross-linking an elastomeric gum having a tensile stress of less than 10 psi at 20% elongation; and (2) conductive particles enclosed within the cross-linked network of said elastomer, the particles having a size of at least 18 millimicrons; which composition (a) has a gel fraction of at least 0.6; (b) exhibits PTC behavior with an R 14 value of at least 2.5 or an R 100 value of at least 10, and at least one T s within the temperature range from room temperature to +250° C.; and (c) has a volume resistivity at temperatures below said T s between 25 and 10 5 ohm.cm.
Claim 10
Dependent Claim
115 words
A PTC composition comprising: (1) a cross-linked elastomer prepared by cross-linking an elastomeric gum having a tensile stress of less than 10 psi at 20% elongation; and (2) conductive particles enclosed within the cross-linked network of said elastomer, the particles having a size of at least 18 millimicrons; which composition (a) has a gel fraction of at least 0.6; (b) exhibits PTC behavior with an R 14 value of at least 2.5 or an R 100 value of at least 10, and at least one T s within the temperature range from room temperature to +250° C.; and (c) has a volume resistivity at temperatures below said T s between 25 and 10 5 ohm.cm.
Claim 11
Dependent Claim
21 words
A PTC composition according to claim 8 wherein the elastomer has been cross-linked with the aid of a chemical cross-linking agent.
Claim 12
Dependent Claim
19 words
A PTC composition according to claim 9 wherein the elastomer has been cross-linked with the aid of a peroxide.
Claim 13
Dependent Claim
51 words
A PTC composition according to claim 1 whose T s remains substantially unchanged when repeatedly subjected to thermal cycling which comprises heating the composition from a temperature below T s to a temperature above T s but below the peak temperature, followed by cooling to a temperature below T s .
Claim 14
Dependent Claim
23 words
A PTC composition according to claim 1 wherein the conductive particles are carbon black particles having a size of 22 to 80 millimicrons.
Claim 15
Dependent Claim
20 words
A PTC composition according to claim 8 which further comprises non-conductive particles enclosed within the cross-linked network of the elastomer.
Claim 16
Dependent Claim
19 words
A PTC composition according to claim 13 wherein the polymer is a polysiloxane and the non-conductive filler is silica.
Claim 17
Dependent Claim
13 words
A PTC composition according to claim 8 wherein the elastomer is a polysiloxane.
Claim 18
Dependent Claim
19 words
A PTC composition according to claim 15 wherein the conductive particles consist essentially of at least one carbon black.
Claim 19
Dependent Claim
143 words
A process for the preparation of a PTC composition which comprises: (1) dispersing conductive particles having a size of at least 18 millimicrons in an elastomeric gum having a tensile stress of less than 10 psi at 20% elongation; and (2) cross-linking the dispersion from step (1) to obtain a composition which has a gel fraction of at least 0.6 and which comprises conductive particles enclosed with the elastomer resulting from said cross-linking; the particles, the elastomeric gum, and the cross-linking conditions being such that the cross-linked composition (a) exhibits PTC behavior with an R 14 value of at least 2.5 or an R 100 value of at least 10, and at least one T s within the temperature range from room temperature to +250° C.; and (b) has a volume resistivity at temperatures below T s between 25 and 10 5 ohm.cm.
Claim 20
Dependent Claim
143 words
A process for the preparation of a PTC composition which comprises: (1) dispersing conductive particles having a size of at least 18 millimicrons in an elastomeric gum having a tensile stress of less than 10 psi at 20% elongation; and (2) cross-linking the dispersion from step (1) to obtain a composition which has a gel fraction of at least 0.6 and which comprises conductive particles enclosed with the elastomer resulting from said cross-linking; the particles, the elastomeric gum, and the cross-linking conditions being such that the cross-linked composition (a) exhibits PTC behavior with an R 14 value of at least 2.5 or an R 100 value of at least 10, and at least one T s within the temperature range from room temperature to +250° C.; and (b) has a volume resistivity at temperatures below T s between 25 and 10 5 ohm.cm.
Claim 21
Dependent Claim
13 words
A process according to claim 17 wherein the conductive particles comprise carbon black.
Claim 22
Dependent Claim
12 words
A process according to claim 17 wherein the elastomer is a polysiloxane.
Claim 23
Dependent Claim
14 words
A process according to claim 19 wherein the polysiloxane contain silica as a filler.
Claim 24
Dependent Claim
18 words
A process according to claim 19 wherein the conductive particles consist essentially of one or more carbon blacks.
Claim 25
Dependent Claim
14 words
A process according to claim 17 wherein the elastomeric gum is cross-linked by irradiation.
Claim 26
Dependent Claim
20 words
A process according to claim 17 wherein the elastomeric gum is cross-linked with the aid of a chemical cross-linking agent.
Claim 27
Dependent Claim
31 words
A process according to claim 17 wherein the cross-linking temperature is above 20° C. and the conductive filler is a carbon black having a particle size of at least 20 millimicrons.
Claim 28
Dependent Claim
31 words
A process according to claim 17 wherein the cross-linking temperature is above 100° C. and the conductive filler is a carbon black having a particle size of at least 30 millimicrons.
Claim 29
Dependent Claim
31 words
A process according to claim 17 wherein the cross-linking temperature is above 150° C. and the conductive filler is a carbon black having a particle size of at least 40 millimicrons.
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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) | 1991-10-04 | 1992-04-04 | 1992-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-04 | 1996-04-04 | 1996-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-04 | 2000-04-04 | 2000-10-04 | $7700.00 | Window Closed / Lapsed |