GB1605005A - Electrical heating strip - Google Patents
Electrical heating strip Download PDFInfo
- Publication number
- GB1605005A GB1605005A GB428281A GB428281A GB1605005A GB 1605005 A GB1605005 A GB 1605005A GB 428281 A GB428281 A GB 428281A GB 428281 A GB428281 A GB 428281A GB 1605005 A GB1605005 A GB 1605005A
- Authority
- GB
- United Kingdom
- Prior art keywords
- carbon black
- weight
- heating element
- strip according
- polymeric matrix
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000010438 heat treatment Methods 0.000 title claims description 40
- 239000006229 carbon black Substances 0.000 claims description 42
- 239000000203 mixture Substances 0.000 claims description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 18
- 239000011159 matrix material Substances 0.000 claims description 17
- 239000011231 conductive filler Substances 0.000 claims description 14
- -1 polyethylene Polymers 0.000 claims description 8
- 229920000573 polyethylene Polymers 0.000 claims description 7
- 229920000089 Cyclic olefin copolymer Polymers 0.000 claims description 6
- 239000004698 Polyethylene Substances 0.000 claims description 6
- 239000004615 ingredient Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- 239000000155 melt Substances 0.000 claims description 4
- CGPRUXZTHGTMKW-UHFFFAOYSA-N ethene;ethyl prop-2-enoate Chemical compound C=C.CCOC(=O)C=C CGPRUXZTHGTMKW-UHFFFAOYSA-N 0.000 claims description 3
- 229920000642 polymer Polymers 0.000 claims description 3
- 229920000098 polyolefin Polymers 0.000 claims description 3
- 239000003381 stabilizer Substances 0.000 claims description 3
- 229920001897 terpolymer Polymers 0.000 claims description 3
- JJWLMSCSLRJSAN-TYYBGVCCSA-L (e)-but-2-enedioate;lead(2+) Chemical compound [Pb+2].[O-]C(=O)\C=C\C([O-])=O JJWLMSCSLRJSAN-TYYBGVCCSA-L 0.000 claims description 2
- ZNRLMGFXSPUZNR-UHFFFAOYSA-N 2,2,4-trimethyl-1h-quinoline Chemical compound C1=CC=C2C(C)=CC(C)(C)NC2=C1 ZNRLMGFXSPUZNR-UHFFFAOYSA-N 0.000 claims description 2
- BJELTSYBAHKXRW-UHFFFAOYSA-N 2,4,6-triallyloxy-1,3,5-triazine Chemical compound C=CCOC1=NC(OCC=C)=NC(OCC=C)=N1 BJELTSYBAHKXRW-UHFFFAOYSA-N 0.000 claims description 2
- 229920001577 copolymer Polymers 0.000 claims description 2
- 150000001993 dienes Chemical class 0.000 claims description 2
- HQQADJVZYDDRJT-UHFFFAOYSA-N ethene;prop-1-ene Chemical group C=C.CC=C HQQADJVZYDDRJT-UHFFFAOYSA-N 0.000 claims description 2
- 239000006232 furnace black Substances 0.000 claims description 2
- YJOMWQQKPKLUBO-UHFFFAOYSA-L lead(2+);phthalate Chemical compound [Pb+2].[O-]C(=O)C1=CC=CC=C1C([O-])=O YJOMWQQKPKLUBO-UHFFFAOYSA-L 0.000 claims description 2
- 229920000058 polyacrylate Polymers 0.000 claims description 2
- 235000019241 carbon black Nutrition 0.000 description 33
- 238000011068 loading method Methods 0.000 description 5
- 239000004709 Chlorinated polyethylene Substances 0.000 description 3
- 239000000945 filler Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920001342 Bakelite® Polymers 0.000 description 1
- 229910001369 Brass Inorganic materials 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229920001328 Polyvinylidene chloride Polymers 0.000 description 1
- 229920006355 Tefzel Polymers 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 239000004637 bakelite Substances 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- QHSJIZLJUFMIFP-UHFFFAOYSA-N ethene;1,1,2,2-tetrafluoroethene Chemical compound C=C.FC(F)=C(F)F QHSJIZLJUFMIFP-UHFFFAOYSA-N 0.000 description 1
- SUPCQIBBMFXVTL-UHFFFAOYSA-N ethyl 2-methylprop-2-enoate Chemical compound CCOC(=O)C(C)=C SUPCQIBBMFXVTL-UHFFFAOYSA-N 0.000 description 1
- VXNZUUAINFGPBY-UHFFFAOYSA-N ethyl ethylene Natural products CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 description 1
- 229920001684 low density polyethylene Polymers 0.000 description 1
- 239000004702 low-density polyethylene Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000005033 polyvinylidene chloride Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
- H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
- H05B3/146—Conductive polymers, e.g. polyethylene, thermoplastics
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
- H01C7/027—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient consisting of conducting or semi-conducting material dispersed in a non-conductive organic material
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Ceramic Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Description
(54) ELECTRICAL HEATING STRIP
(71) We, RAYCHEM LIMITED, a British Company, formerly of Moor House,
London Wall, London EC2 and now of Rolls House, 7 Rolls Buildings, Fetter Lane,
London EC4, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:
This invention relates to electrical heaters comprising a heating element which is composed of a polymeric matrix having carbon black dispersed therein.
The electrical heating strips of the present invention comprise a heating element composed of a carbon-black-loaded polymeric composition and a pair of elongate electrodes which are electrically connected by said heating element, the heating element being composed of a polymeric matrix having dispersed therein
(i) a first carbon black which is a relatively conductive filler (as hereinafter defined) and
(ii) a second carbon black which is a relatively less conductive filler (as hereinafter defined)
In the heating element of the present invention, the weight of the second carbon black is greater than the weight of the first carbon black.
The term "relatively conductive filler" is used herein to denote a filler which, when dispersed in polyethylene having a density 0.916 g/cm3 and a melt flow index of 2, exhibits a curve of impedance versus loading which falls steeply in the range of specific impedance values from 109 to 106 ohm.cm and reaches a specific impedance of less than 5 x 106 ohm.cm, preferably less than 106 ohm.cm, at a loading of 60 parts by weight per 100 parts by weight of polyethylene, the specific impedances being measured at 50 H2 with a field strength of 4 kV/cm.The term "relatively less conductive filler" is used herein to denote a filler which, when dispersed in polyethylene having a density of 0.916 g/cm3 and a melt flow index of 2, exhibits a curve of impedance versus loading having a relatively shallow slope with no steep sections and which has a specific impedance greater than 10g ohm. cm, and preferably less than 10'0 ohm.cm, at a loading of 60 parts by weight per 100 parts by weight of polythene, the specific impedances being measured at 50Hz with a field strength of 4 kV/cm.
The specific impedances referred to in this specification are measured by the procedure given in Example 1 (i.e. by mixing the ingredients in a Banbury mixer, pressing the mixture into a slab, and measuring the impedance of the unannealed slab at room temperature at 50HZ and a field strength of 4 kV/cm).
The polymeric matrix in the heating strips of the present invention preferably comprises a thermoplastic resin, especially a polyolefin, e.g. polyethylene or polypropylene; an olefin copolymer, e.g. an ethylene/ethyl acrylate or ethylene/ethyl methacrylate polymer; a halogen-substituted olefin copolymer, e.g. Tefzel (a ter polymer of ethylene, tetrafluoroethylene and a fluorinated monomer manufactured by Du Pont) or polyvinylidene chloride; or a mixture of two or more of these. "Teftel" is a trade mark.
The first carbon black (which is a relatively good conductive filler) may have an average particle size of 10 to 100 millimicrons, preferably 2() to 60 millimicrons, and an average specific surface area greater than 30 m2/g, preferably greater than 1(X) m2/g, as measured by the method of ASIM D3037-76.Suitable carbon blacks can be chosen from carbon blacks which are commercially available as Types HAF, SKI, EPC, FEF and ECF, e.g. those manufactured by Cabot under the trade names Vulcan XC72, Vulcan P, and Vulcan 3; by
Columbian under the trade names Statex 160, Statex 125 and Conductex 950; by AK ZO Chemie under the trade name Kctjen Black EC; and by Degussa under the trade names
Corax L and Corax P. ["Vulcan", "Statex", "Ketjen" and "Corax" are Trade Marksj The second carbon black (which is a relatively less conductive filler) is preferably one of the so-called low structure carbon blacks.Suitable carbon blacks include commercially available Thermal blacks, e.g. those manufactured by Vanderbilt under the trade names
Thermax and P-33; by Sevalco under the trade name Sevacarb MT;; and by Columbian under the trade name Statex MT. ["Thermax" is a Trade Mark.] The second carbon black may have an average particle size of at least 30 millimicrons and an average specific surface area of less than 2() m2/g.
By use of suitable amounts of the first and second carbon blacks, it is possible to prepare conductive compositions having a desired level of specific impedance without undue sensitivity to small changes in the loadings of the carbon blacks. The ratio of weight of the second carbon black to the first carbon black may be, e.g., 2:1 to 8:1 or 3:1 to 6:1. The amount of the first carbon black may be at least 10%, e.g. 10 to 25%, by weight, based on the weight of the polymeric matrix. The amount of the second carbon black may be at least 40% by weight, based on the weight of the polymeric matrix.
The following Examples, in which parts are by weight, illustrate compositions suitable for use in the heating element according to the invention.
Example I
Three sets of compositions were made by blending 62.5 parts of chlorinated polyethylene (CPE 3614 manufactured by Dow Corning), 37.5 parts of low density polyethylene (DYNH 3 manufactured by BXL Bakelite), various amounts of one or both of Vulcan P (a carbon black manufactured by Cabot which is a relatively good conductive filler) and Thermax MT (a carbon black manufactured by Vanderbilt which is a relatively less conductive filler), and small amounts of conventional antioxidants and stabilizers. The ingredients were compounded in a Bridge Banbury internal mixer with a charge weight of 1.2 kg; the mixture was pressed at 1500C into plaque samples 2 mm. thick and the samples cooled to room temperature. Circular electrodes were painted on both sides of each sample which was placed between brass electrodes conforming to BS 2782(201). The specific impedance of the composition was calculated from measurement of both voltage and current at 50 HZ and the known sample dimensions, using a field strength of 4 kV/cm. In the first set of compositions, Vulcan P was the sole carbon black, in amount 10, 20, 30, 40, 50 or 60 parts.
In the second set of compositions, Thermax MT was the sole carbon black, in amount 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 or 120 parts. In the third set of compositions, Vulcan
P and Thermax MT were used together, the ratio by weight in each composition of Vulcan
P to Thermax MT being 1:4 and the total amount of both carbon blacks being 10, 20. 30, 40, 50, 60, 70, 80 or 90 parts.
The results obtained are shown graphically in Figure 1, Curves A, B and C showing the specific impedances of the first, second and third sets of compositions respectively.
Example 2
The procedure described in Example 1 was used to determine the specific impedance of compositions (1) to (8) containing the ingredients and amounts thereof shown in the Table below and in addition (same for each composition) 2.5 parts of a conventional polymer stabilizer (Agerite Resin D), 4.375 parts of dibasic lead phthalate, 1.875 parts of tetrabasic lead fumarate and 1.875 parts of triallyl cyanurate. The various ingredients listed by their trade names in the Table are identified above or as set out below.
DPD 6169 is an ethylene/ethyl acrylate polymer manufactured by Union Carbide and having a melt flow index of 6 and a density of 0.931. Royalene 611 is an ethylene/propylene/ non-conjugated diene terpolymer manufactured by Uniroyal. Philips GPF is a furnace black which is a relatively good conductive filler, manufactured by Philips Petroleum Co.
["Philips" is a Trade Mark.] The specific impedances of the various compositions are also given in the Table.
Composition No. (1) (2) (3) (4) (5) (6) (7) (8)
DYNH 3 37.5 - - 37.5 37.5 37.5 37.5 37 5
CPE 3614 - 100 - 62.5 62.5 62.5 62.5 62.5
DPD 6169 - - 100 - - - - - Royalene 611 62.5 - - - - - - Vulcan P 14 14 14 20 16.6 10 -
Philips GPF - - - - - - 16 20
Thermax MT 56 56 56 40 33.3 60 64 80
Specific Impedance 5.6 3.2 1.6 0.38 2.2 7.6 6.3 0.32
x 10-8 (ohm.cm)
WHAT WE CLAIM IS:
1.An electrical heating strip comprising a heating element composed of a carbon-blackloaded polymeric composition and a pair of elongate electrodes which are electrically connected by said heating element, the heating element being composed of a polymeric matrix having dispersed therein
(i) a first carbon black which is a relatively conductive filler (as hereinbefore defined) and
(ii) a second carbon black which is a relatively less conductive filler (as hereinbefore defined), the weight of the second carbon black being greater than the weight of the first carbon black.
2. A heating strip according to Claim 1, wherein the heating element contains at least 10% by weight, based on the weight of the polymeric matrix, of the first carbon black.
3. A heating strip according to Claim 2, wherein the heating element contains 10 to 25% by weight, based on the weight of the polymeric matrix, of the first carbon black.
4. A heating strip according to any one of claims 1 to 3, wherein the heating element contains at least 40% by weight, based on the weight of the polymeric matrix, of the second carbon black.
5. A heating strip according to any one of claims 1 to 4, wherein the ratio by weight of the second carbon black to the first carbon black is from 2:1 to 8:1.
6. A heating strip according to any one of claims 1 to 5 wherein the polymeric matrix comprises a polyolefin, an olefin copolymer or a halogen-substituted olefin copolymer.
7. A heating strip according to Claim 6, wherein the polymeric matrix comprises polyethylene or an ethylene/ethyl acrylate copolymer or both.
8. A heating strip according to claim 1 wherein the heating element is composed of a composition as specified in either of the Examples herein.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (8)
- **WARNING** start of CLMS field may overlap end of DESC **.Example 2 The procedure described in Example 1 was used to determine the specific impedance of compositions (1) to (8) containing the ingredients and amounts thereof shown in the Table below and in addition (same for each composition) 2.5 parts of a conventional polymer stabilizer (Agerite Resin D), 4.375 parts of dibasic lead phthalate, 1.875 parts of tetrabasic lead fumarate and 1.875 parts of triallyl cyanurate. The various ingredients listed by their trade names in the Table are identified above or as set out below.DPD 6169 is an ethylene/ethyl acrylate polymer manufactured by Union Carbide and having a melt flow index of 6 and a density of 0.931. Royalene 611 is an ethylene/propylene/ non-conjugated diene terpolymer manufactured by Uniroyal. Philips GPF is a furnace black which is a relatively good conductive filler, manufactured by Philips Petroleum Co.["Philips" is a Trade Mark.] The specific impedances of the various compositions are also given in the Table.Composition No. (1) (2) (3) (4) (5) (6) (7) (8) DYNH 3 37.5 - - 37.5 37.5 37.5 37.5 37 5 CPE 3614 - 100 - 62.5 62.5 62.5 62.5 62.5 DPD 6169 - - 100 - - - - - Royalene 611 62.5 - - - - - - Vulcan P 14 14 14 20 16.6 10 - Philips GPF - - - - - - 16 20 Thermax MT 56 56 56 40 33.3 60 64 80 Specific Impedance 5.6 3.2 1.6 0.38 2.2 7.6 6.3 0.32 x 10-8 (ohm.cm) WHAT WE CLAIM IS: 1.An electrical heating strip comprising a heating element composed of a carbon-blackloaded polymeric composition and a pair of elongate electrodes which are electrically connected by said heating element, the heating element being composed of a polymeric matrix having dispersed therein (i) a first carbon black which is a relatively conductive filler (as hereinbefore defined) and (ii) a second carbon black which is a relatively less conductive filler (as hereinbefore defined), the weight of the second carbon black being greater than the weight of the first carbon black.
- 2. A heating strip according to Claim 1, wherein the heating element contains at least 10% by weight, based on the weight of the polymeric matrix, of the first carbon black.
- 3. A heating strip according to Claim 2, wherein the heating element contains 10 to 25% by weight, based on the weight of the polymeric matrix, of the first carbon black.
- 4. A heating strip according to any one of claims 1 to 3, wherein the heating element contains at least 40% by weight, based on the weight of the polymeric matrix, of the second carbon black.
- 5. A heating strip according to any one of claims 1 to 4, wherein the ratio by weight of the second carbon black to the first carbon black is from 2:1 to 8:1.
- 6. A heating strip according to any one of claims 1 to 5 wherein the polymeric matrix comprises a polyolefin, an olefin copolymer or a halogen-substituted olefin copolymer.
- 7. A heating strip according to Claim 6, wherein the polymeric matrix comprises polyethylene or an ethylene/ethyl acrylate copolymer or both.
- 8. A heating strip according to claim 1 wherein the heating element is composed of a composition as specified in either of the Examples herein.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB428281A GB1605005A (en) | 1978-05-28 | 1978-05-28 | Electrical heating strip |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB428281A GB1605005A (en) | 1978-05-28 | 1978-05-28 | Electrical heating strip |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1605005A true GB1605005A (en) | 1981-12-16 |
Family
ID=9774195
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB428281A Expired GB1605005A (en) | 1978-05-28 | 1978-05-28 | Electrical heating strip |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1605005A (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2561481A1 (en) * | 1984-03-15 | 1985-09-20 | Tokumaru Sennosuke | SHEET HEAT RADIATION ELEMENT |
| GB2173200A (en) * | 1985-03-30 | 1986-10-08 | Charles Romaniec | Conductive materials |
| US4705646A (en) * | 1982-05-24 | 1987-11-10 | Hughes Aircraft Company | Conductive coating |
| GB2191668A (en) * | 1986-06-05 | 1987-12-16 | Kazimierz Czeslaw Cha Romaniec | Electrical heating tape |
| WO1989005230A1 (en) * | 1987-11-16 | 1989-06-15 | Raychem Corporation | Bonding method and devices employing conductive polymers |
| US4910389A (en) * | 1988-06-03 | 1990-03-20 | Raychem Corporation | Conductive polymer compositions |
| US4938820A (en) * | 1987-06-11 | 1990-07-03 | Raychem Corporation | Joining of sheets |
| EP0484138A2 (en) * | 1990-10-31 | 1992-05-06 | Daito Communication Apparatus Co. Ltd. | PTC composition |
| US5266952A (en) * | 1992-03-30 | 1993-11-30 | Hughes Aircraft Company | Feed forward predictive analog-to-digital converter |
| US5286952A (en) * | 1987-06-11 | 1994-02-15 | Raychem Corporation | Methods and devices which make use of conductive polymers to join articles |
| FR2733637A1 (en) * | 1995-04-26 | 1996-10-31 | Gec Alsthom T & D Sa | Electrical appts. with sulphur hexa:fluoride insulation |
| US5747563A (en) * | 1995-03-20 | 1998-05-05 | Cabot Corporation | Polyethylene glycol treated carbon black and compounds thereof |
-
1978
- 1978-05-28 GB GB428281A patent/GB1605005A/en not_active Expired
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4705646A (en) * | 1982-05-24 | 1987-11-10 | Hughes Aircraft Company | Conductive coating |
| FR2561481A1 (en) * | 1984-03-15 | 1985-09-20 | Tokumaru Sennosuke | SHEET HEAT RADIATION ELEMENT |
| GB2173200A (en) * | 1985-03-30 | 1986-10-08 | Charles Romaniec | Conductive materials |
| GB2173200B (en) * | 1985-03-30 | 1989-10-11 | Charles Romaniec | Conductive materials |
| GB2191668A (en) * | 1986-06-05 | 1987-12-16 | Kazimierz Czeslaw Cha Romaniec | Electrical heating tape |
| US5286952A (en) * | 1987-06-11 | 1994-02-15 | Raychem Corporation | Methods and devices which make use of conductive polymers to join articles |
| US4938820A (en) * | 1987-06-11 | 1990-07-03 | Raychem Corporation | Joining of sheets |
| WO1989005230A1 (en) * | 1987-11-16 | 1989-06-15 | Raychem Corporation | Bonding method and devices employing conductive polymers |
| US4910389A (en) * | 1988-06-03 | 1990-03-20 | Raychem Corporation | Conductive polymer compositions |
| EP0484138A3 (en) * | 1990-10-31 | 1992-06-03 | Daito Communication Apparatus Co. Ltd. | Ptc composition |
| US5280263A (en) * | 1990-10-31 | 1994-01-18 | Daito Communication Apparatus Co., Ltd. | PTC device |
| EP0484138A2 (en) * | 1990-10-31 | 1992-05-06 | Daito Communication Apparatus Co. Ltd. | PTC composition |
| US5266952A (en) * | 1992-03-30 | 1993-11-30 | Hughes Aircraft Company | Feed forward predictive analog-to-digital converter |
| US5747563A (en) * | 1995-03-20 | 1998-05-05 | Cabot Corporation | Polyethylene glycol treated carbon black and compounds thereof |
| FR2733637A1 (en) * | 1995-04-26 | 1996-10-31 | Gec Alsthom T & D Sa | Electrical appts. with sulphur hexa:fluoride insulation |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PE20 | Patent expired after termination of 20 years |
Effective date: 19980527 |