Low resistivity PTC compositions
First Claim
1. A conductive polymer composition which exhibits PTC behavior with a switching temperature Ts above 0°
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
C.; and
which comprises(1) a polymer component having at least 10% crystallinity and(2) a particulate filler component which has been dispersed in said polymer component and which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area, S, in m2 /gram such that S/D is not more than 10;
the amount of said filler component being such that the quantity ##EQU7## is less than 1.
1 Assignment
0 Petitions
Accused Products
Abstract
Compositions which exhibit PTC behavior with a switching temperature (Ts) above 0° C., which have a resistivity at a temperature below Ts of less than 7 ohm. cm, and which comprise a crystalline polymer and a particulate filler component which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area S in m2 /gram such that S/D is not more than 10. The composition preferably has a peak resistivity of at least 1000 ohm. cm and is electrically stable when aged at elevated temperature. The quantity ##EQU1## is preferably less than 1, especially less than 0.5. Shaped articles of such compositions are prepared by a process in which the carbon black is dispersed in the molten polymer and the dispersion is then melt-shaped, the total energy used in preparing and melt-shaping the dispersion being 1 to 300 hp. hr. ft-3, preferably 1 to 100 hp. hr. ft-3, especially 1 to 50 hp. hr. ft-3. The compositions are particularly useful in circuit protection devices.
-
Citations
43 Claims
-
1. A conductive polymer composition which exhibits PTC behavior with a switching temperature Ts above 0°
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
C.; and
which comprises(1) a polymer component having at least 10% crystallinity and (2) a particulate filler component which has been dispersed in said polymer component and which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area, S, in m2 /gram such that S/D is not more than 10;
the amount of said filler component being such that the quantity ##EQU7## is less than 1. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 39)
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
-
15. A conductive polymer composition which exhibits PTC behavior with a switching temperature Ts above 0°
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
C., and which, after having been subjected to a thermal aging treatment which consists of maintaining the composition, by external heating thereof, for 25 hours at a temperature at which the resistivity of the composition is between 100 ohm. cm and the peak resistivity,(a) exhibits PTC behavior, and (b) has a resistivity at at least one temperature between Ts and -40°
C. which is between 0.5 times and 2 times the resistivity of the composition at the same temperature before said thermal aging treatment,and which composition comprises (1) a polymer component having at least 10% crystallinity and (2) a particulate filler component which has been dispersed in said polymer component and which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area, S, in m2 /gram such that S/D is not more than 10. - View Dependent Claims (16, 17, 18, 19, 20, 40)
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
-
21. A conductive polymer composition which exhibits PTC behavior with a switching temperature, Ts, above 0°
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
C. and a peak resistivity of at least 1000 ohm. cm and which comprises(1) a polymer component having at least 10% crystallinity and (2) a particulate filter component which has been dispersed in said polymer component and which comprises carbon black having a particle size, D, which is from 20 to 150 microns and surface area, S, in m2 /gram such that S/D is not more than 10. - View Dependent Claims (22, 23, 24, 25, 41)
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
-
26. An electrical device which comprises a melt-shaped PTC element and at least two electrodes which can be connected to a source of electrical power and which, when so connected, causes current to flow through said PTC element, said PTC element being composed of a PTC conductive polymer composition which comprises a polymer component having at least 10% crystallinity, and, dispersed in said polymer, a particular filler component which comprises a carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area, S, in m2 /gram such that S/D is not more than 10;
- which composition
(a) exhibits PTC behavior with a switching temperature Ts and a peak resitivity of at least 1000 ohm. cm; and (b) has a resistivity of less than 7 ohm. cm in a temperature range which is between Ts and the lower of 0°
C. and (Ts -50)°
C. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
- which composition
-
35. A process for the preparation of shaped article of a conductive polymer composition, which process comprises
(1) providing (a) a polymer component having at least 10% crystallinity; - and
(b) a filler component which comprises a carbon black having a particle size, D, which is from 20 to 150 millimicronsand a surface area, S, in m2 /gram such that S/D is not more than 10, and (2) preparing a composition which comprises a dispersion of said carbon black in said polymer component by a process which comprises dispersing said carbon black in said polymer component while said polymer component is molten; and (3) melt-shaping said dispersion;
the total energy used in preparing and melt-shaping said dispersion being from 1 to 300 hp. hr. ft.-3 and being selected so that the product(a) exhibits PTC behavior with a switching temperature Ts above 0°
C. and a peak resistivity of at least 1000 ohm. cm; and(b) has a resistivity of less that 7 ohm. cm at at least one temperature between Ts and -40°
C. - View Dependent Claims (36, 37, 38)
- and
-
42. A conductive polymer composition which exhibits PTC behavior with a switching temperature Ts above 0°
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
C.; and
which comprises(1) a polymer component having at least 10% crystallinity; and (2) a particulate filler component which has been dispersed in said polymer component and which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area, S, in m2 /grams such that S/D is not more than 10.
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40°
-
43. An electrical device which comprises a melt-shapedPTC element and at least two electrodes which can be connected to a source of electrical power and which, when so connected, cause current to flow through said PTC element, said PTC element being composed of a conductive polymer composition which exhibits PTC behavior with a switching temperature Ts above 0°
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40 C., and which comprises
(1) a polymer component having at least 10% crystallinity; and (2) a particulate filler component which has been dispersed in said polymer component and which comprises carbon black having a particle size D, which is from 20 to 150 millimicrons and a surface area, S, in m2 /grams such that S/D is not more than 10.
- C., which has a resistivity of less than 7 ohm. cm at at least one temperature between Ts and -40 C., and which comprises
Specification