EP0311142B1 - Radiation cross-linking of ptc conductive polymers - Google Patents

Radiation cross-linking of ptc conductive polymers

Info

Publication number
EP0311142B1
EP0311142B1 EP19880117360 EP88117360A EP0311142B1 EP 0311142 B1 EP0311142 B1 EP 0311142B1 EP 19880117360 EP19880117360 EP 19880117360 EP 88117360 A EP88117360 A EP 88117360A EP 0311142 B1 EP0311142 B1 EP 0311142B1
Authority
EP
Grant status
Grant
Patent type
Prior art keywords
conductive
ptc
cross
electrodes
gy
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 - Lifetime
Application number
EP19880117360
Other languages
German (de)
French (fr)
Other versions
EP0311142A2 (en )
EP0311142A3 (en )
Inventor
Stephen M. Jacobs
Mary Sandra Mctavish
James Michael Taylor
Frank Anthony Doljack
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raychem Corp
Original Assignee
Raychem Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Grant date

Links

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01CRESISTORS
    • H01C7/00Non-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
    • H01C7/02Non-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
    • H01C7/027Non-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

Description

  • [0001]
    Conductive polymer compositions exhibiting PTC behavior, and electrical devices comprising them, have been described in published documents and in our earlier specificatons. Reference may be made, for example, to U. S. Patents Nos. 2,952,761, 2,978,665, 3,243,753, 3,351,882, 3,571,777, 3,757,086, 3,793,716, 3,823,217, 3,858,144, 3,861,029, 4,017,715, 4,072,848, 4,085,286, 4,117,312, 4,177,376, 4,177,446, 4,188,276, 4,237,441, 4,242,573, 4,246,468, 4,250,400, 4,255,698, 4,272,471, 4,276,466 and 4,314,230; J. Applied Polymer Science 19, 813-815 (1975), Klason and Kubat; Polymer Engineering and Science 18, 649-653 (1978), Narkis et al; German OLS 2,634,999, 2,746,602, 2,755,076, 2,755,077, 2,821,799 and 3,030,799; European Published Applications Nos. 0028142, 0030479, 0038713, 0038714, 0038715 and 0038718; pending European Applications No. 81,301,767.0, 81,301,768.8 and 81,302,201.9; and pending U.S. Applications Nos. 176,300, 184,647, 254,352, 272,854 and 300,709. The disclosures of these patents, publications and applications are incorporated herein by reference.
  • [0002]
    It is known to cross-link PTC conductive polymers by radiation, and in practice the dosages employed have been relatively low, e.g. 100,000 to 200,000 Gy (10-20 Mrads). Higher dosages have, however, been proposed for some purposes. Thus OLS 2,634,999 recommends a dose of 200,000 to 450,000 Gy (20-45 Mrads); U.K. Specification No. 1,071,032 describes irradiated compositions comprising a copolymer of ethylene and a vinyl ester or an acrylate monomer and 50-400% by weight of a filler, e.g. carbon black, the radiation dose being about 20,000 to about 1,000,000 Gy (about 2 to about 100 Mrads), preferably about 20,000 to about 200,000 Gy (about 2 to about 20 Mrads), and the use of such compositions as tapes for grading the insulation on cables; and US-A-3 351 882 discloses the preparation of electrical devices by embedding electrodes having a considerable area and an irregular surface, e.g. a metal mesh, in a resistor composed of a PTC conductive polymer, followed by cross-linking of the conductive polymer. The stated purpose of using electrodes of considerable area is to avoid excessive current concentrations and consequent damage to the conductive polymer. The stated purposes of the radiation are (a) to cross-link the conductive polymer adjacent the electrodes, so that the electrodes are firmly gripped, and (b) to cross-link the bulk of the conductive polymer so that it will resist softening. The cross-linking can be effected by radiation, and the patent discloses subjecting the entire resistor to a dose of 500,000 to 1,000,000 Gy (50 to 100 megarads) of radiation of one or two million electron volt electrons. As shown by US-A-3 858 144 and 3 861 029, a dose of 20,000 to 150,000 Gy (2-15 megarads) is sufficient to prevent softening of PTC conductive polymers, and higher doses are regarded as disadvantageous because they reduce crystallinity.
  • [0003]
    The higher the voltage applied to an electrical device comprising a PTC conductive polymer, the more likely it is that intermittent application of the voltage will cause the device to fail. This has been a serious problem, for example, in the use of circuit protection devices where the voltage dropped over the device in the "tripped" (i.e. high resistance) condition is more than about 200 volts. [Voltages given herein are DC values or RMS values for AC power sources.] We have now discovered that the likelihood of such failure can be substantially reduced by irradiating the conductive polymer so that it is very highly cross-linked.
  • [0004]
    Our experiments indicate that the higher the radiation dose, the greater the number of "trips" (i.e. conversions to the tripped state) a device will withstand without failure. The radiation dose is, therefore at least 600,000 Gy (60 Mrads), particularly at least 800,000 Gy (80 Mrads), with yet higher dosages, e.g. at least 1,200,000 Gy 120 Mrads or at least 1,600,000 Gy (160 Mrads), being preferred when satisfactory PTC characteristics are maintained and the desire for improved performance outweighs the cost of radiation.
  • [0005]
    The present invention provides a process for the preparation of an electrical device comprising (1) a cross-linked PTC conductive polymer element comprising a polymeric component consisting essentially of one or more polymers, and (2) two substantially planar, parallel, metal electrodes which can be connected to a power source to cause current to flow through the PTC element, which process comprises cross-linking the PTC element by irradiating it after the electrodes have been secured thereto, characterized in that the electrodes are metal foil electrodes and the essential parts of the PTC element are irradiated to a dosage of at least 600,000 Gy (60 Mrads).
  • [0006]
    When reference is made herein to an electrode being "substantially planar", we mean an electrode whose shape and position in the device are such that substantially all the current enters (or leaves) the electrode through a surface which is substantially planar.
  • [0007]
    The present invention is particularly useful for circuit protection devices, but is also applicable to heaters, particularly laminar heaters.
  • [0008]
    In this invention, each of the electrodes is substantially planar and is a metal foil. Since the metal foil electrodes are applied to the PTC element before it is irradiated, there is a danger that gases evolved during irradiation will be trapped.
  • [0009]
    PTC conductive polymers suitable for use in this invention are disclosed in the patents and applications referenced above. Their resistivity at 23°C is preferably less than 1250 ohm.cm, eg. less than 750 ohm.cm, particularly less than 500 ohm.cm, with values less than 50 ohm.cm being preferred for circuit protection devices. The polymeric component should be one which is cross-linked and not significantly degraded by radiation. The polymeric component is preferably free of thermosetting polymers and often consists essentially of one or more crystalline polymers. Suitable polymers include polyolefins, eg. polyethylene, and copolymers of at least one olefin and at least one olefinically unsaturated monomer containing a polar group. The conductive filler is preferably carbon black. The composition may also contain a non-conductive filler, eg. alumina trihydrate. The composition can, but preferably does not, contain a radiation cross-linking aid. The presence of a cross-linking aid can substantially reduce the radiaton dose required to produce a particular degree of cross-linking, but its residue generally has an adverse effect on electrical characteristics.
  • [0010]
    Shaping of the conductive polymer will generally be effected by a melt-shaping technique, eg. by melt-extrusion or molding.

Claims (2)

  1. A process for the preparation of an electrical device comprising (1) a cross-linked PTC conductive polymer element comprising a polymeric component consisting essentially of one or more polymers, and (2) two substantially planar, parallel, metal electrodes which can be connected to a power source to cause current to flow through the PTC element, which process comprises cross-linking the PTC element by irradiating it after the electrodes have been secured thereto, characterized in that the electrodes are metal foil electrodes and the essential parts of the PTC element are irradiated to a dosage of at least 600,000 Gy (60 Mrads).
  2. A process according to claim 1 characterized in that the essential parts of the device are irradiated to a dosage of at least 800,000 Gy (80 Mrads).
EP19880117360 1981-04-02 1982-04-02 Radiation cross-linking of ptc conductive polymers Expired - Lifetime EP0311142B1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US25049181 true 1981-04-02 1981-04-02
US250491 1981-04-02
US06254352 US4426633A (en) 1981-04-15 1981-04-15 Devices containing PTC conductive polymer compositions
US254352 2002-09-25

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
EP82301765.2 Division 1982-04-02

Publications (3)

Publication Number Publication Date
EP0311142A2 true EP0311142A2 (en) 1989-04-12
EP0311142A3 true EP0311142A3 (en) 1989-04-26
EP0311142B1 true EP0311142B1 (en) 1993-12-15

Family

ID=26940917

Family Applications (2)

Application Number Title Priority Date Filing Date
EP19880117360 Expired - Lifetime EP0311142B1 (en) 1981-04-02 1982-04-02 Radiation cross-linking of ptc conductive polymers
EP19820301765 Expired EP0063440B1 (en) 1981-04-02 1982-04-02 Radiation cross-linking of ptc conductive polymers

Family Applications After (1)

Application Number Title Priority Date Filing Date
EP19820301765 Expired EP0063440B1 (en) 1981-04-02 1982-04-02 Radiation cross-linking of ptc conductive polymers

Country Status (4)

Country Link
EP (2) EP0311142B1 (en)
JP (1) JPH053101A (en)
DE (3) DE3279970D1 (en)
GB (1) GB2096393B (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5802709A (en) 1995-08-15 1998-09-08 Bourns, Multifuse (Hong Kong), Ltd. Method for manufacturing surface mount conductive polymer devices
US5849137A (en) 1995-08-15 1998-12-15 Bourns Multifuse (Hong Kong) Ltd. Continuous process and apparatus for manufacturing conductive polymer components
US6020808A (en) 1997-09-03 2000-02-01 Bourns Multifuse (Hong Kong) Ltd. Multilayer conductive polymer positive temperature coefficent device
US6228287B1 (en) 1998-09-25 2001-05-08 Bourns, Inc. Two-step process for preparing positive temperature coefficient polymer materials

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1333381C (en) 1986-02-20 1994-12-06 Eric D. Nyberg Method and articles employing ion exchange material
US4924074A (en) * 1987-09-30 1990-05-08 Raychem Corporation Electrical device comprising conductive polymers
US4907340A (en) * 1987-09-30 1990-03-13 Raychem Corporation Electrical device comprising conductive polymers
KR100392572B1 (en) * 1995-03-22 2003-10-17 레이켐 코포레이션 Electrical Device
DE19548741A1 (en) * 1995-12-23 1997-06-26 Abb Research Ltd A process for producing a material for PTC thermistors
US5814264A (en) * 1996-04-12 1998-09-29 Littelfuse, Inc. Continuous manufacturing methods for positive temperature coefficient materials
CA2261895A1 (en) * 1996-08-01 1998-02-12 Raychem Corporation Method of making a laminate comprising a conductive polymer composition
DE10310722A1 (en) 2003-03-10 2004-09-23 Tesa Ag Electrically heatable adhesive composition, useful for adhesive tape in automotive applications such as electrically heated mirrors, comprises an adhesive component and an electrically conductive filler
DE102007007617A1 (en) 2007-02-13 2008-08-14 Tesa Ag Intrinsically heatable hotmelt-adhesive sheet
DE102008034748A1 (en) 2008-07-24 2010-01-28 Tesa Se Flexible heated surface element
DE102008063849A1 (en) 2008-12-19 2010-06-24 Tesa Se Heated surface element and method of attachment
DE102009010437A1 (en) 2009-02-26 2010-09-02 Tesa Se Heated surface element
CN102412094B (en) * 2010-09-20 2014-12-31 胜德国际研发股份有限公司 Protective circuit

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3351882A (en) * 1964-10-09 1967-11-07 Polyelectric Corp Plastic resistance elements and methods for making same
JPS5123543A (en) * 1974-08-22 1976-02-25 Dainippon Printing Co Ltd Dodenseikobunshizairyo
FR2321751A1 (en) * 1975-08-04 1977-03-18 Raychem Corp MATERIALS OF HIGH ELECTRICAL RESISTANCE AT HIGH TEMPS. - comprise crystalline thermoplastic (co)polymer and conducting filler used for heating elements
FR2368127B1 (en) * 1976-10-15 1983-11-18 Raychem Corp
GB1604735A (en) * 1978-04-14 1981-12-16 Raychem Corp Ptc compositions and devices comprising them
US4200973A (en) * 1978-08-10 1980-05-06 Samuel Moore And Company Method of making self-temperature regulating electrical heating cable

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5802709A (en) 1995-08-15 1998-09-08 Bourns, Multifuse (Hong Kong), Ltd. Method for manufacturing surface mount conductive polymer devices
US5849137A (en) 1995-08-15 1998-12-15 Bourns Multifuse (Hong Kong) Ltd. Continuous process and apparatus for manufacturing conductive polymer components
US5849129A (en) 1995-08-15 1998-12-15 Bourns Multifuse (Hong Kong) Ltd. Continuous process and apparatus for manufacturing conductive polymer components
US6020808A (en) 1997-09-03 2000-02-01 Bourns Multifuse (Hong Kong) Ltd. Multilayer conductive polymer positive temperature coefficent device
US6223423B1 (en) 1997-09-03 2001-05-01 Bourns Multifuse (Hong Kong) Ltd. Multilayer conductive polymer positive temperature coefficient device
US6228287B1 (en) 1998-09-25 2001-05-08 Bourns, Inc. Two-step process for preparing positive temperature coefficient polymer materials

Also Published As

Publication number Publication date Type
EP0063440A3 (en) 1983-04-13 application
EP0063440B1 (en) 1989-10-04 grant
DE3280447D1 (en) 1994-01-27 grant
EP0311142A2 (en) 1989-04-12 application
GB2096393A (en) 1982-10-13 application
DE3279970D1 (en) 1989-11-09 grant
GB2096393B (en) 1986-01-02 grant
DE3280447T2 (en) 1994-07-14 grant
EP0063440A2 (en) 1982-10-27 application
JPH053101A (en) 1993-01-08 application
EP0311142A3 (en) 1989-04-26 application

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