EP0780849A2 - Process of manufacturing a PTC resistor material - Google Patents

Process of manufacturing a PTC resistor material Download PDF

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Publication number
EP0780849A2
EP0780849A2 EP96810818A EP96810818A EP0780849A2 EP 0780849 A2 EP0780849 A2 EP 0780849A2 EP 96810818 A EP96810818 A EP 96810818A EP 96810818 A EP96810818 A EP 96810818A EP 0780849 A2 EP0780849 A2 EP 0780849A2
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Prior art keywords
kgy
filler
polyethylene
melt
matrix material
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EP96810818A
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German (de)
French (fr)
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EP0780849A3 (en
Inventor
Ralf Dr. Strümpler
Andreas Garbin
Joachim Dr. Glatz-Reichenbach
Jörgen Dr. Skindhoj
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ABB Research Ltd Switzerland
ABB Research Ltd Sweden
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ABB Research Ltd Switzerland
ABB Research Ltd Sweden
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    • 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

Definitions

  • the invention relates to a method for producing a material for PTC resistors according to the preamble of claim 1. Such a method is known from US-A-5 313 184.
  • PTC resistors made from a semicrystalline thermoplastic polymer such as polyethylene, polypropylene and the like. a. as a matrix material, to which a powdery filler made of electrically conductive material, in particular carbon black, is admixed, by ionizing radiation, in particular by electron radiation.
  • US-A-3 858 144 and US-A-3 861 029 a range of 20 kGy to 1.5 MGy for possible radiation doses is given for materials with carbon black as filler, but a dose of 1.2 MGy is recommended .
  • the method according to the invention permits the production of PTC resistors which not only have very good cold-conducting properties due to the high conductivity of the filler, but also good tensile strength and very high stability of the characteristic curve.
  • the relatively low radiation doses have the advantage of short throughput times and generally lower manufacturing costs compared to the usual higher doses.
  • the HD polyethylene Lupolen 5231X from BASF was melted and TiB 2 powder with a particle size ⁇ 45mm, which had previously been etched to clean the particle surfaces of oxides, was added as a filler.
  • the proportion of filler in the mixture was 50% by volume. After mixing, the material was extruded through a slit and sheets 160 mm long, 40 mm wide and 1.3 mm - 2.5 mm thick were produced and irradiated in the direction of minimum expansion with electrons with an energy of 2 MeV.
  • the tensile strength both at 25 ° C (white bars, reference value of the unirradiated Sample 11 MPa) as well as at 100 ° C (hatched bars, reference value 3.15 MPa) was significantly higher with irradiation doses of 25 kGy and 50 kGy than with the unirradiated and with 100 kGy irradiated sample.
  • the material described, irradiated with 10-75 kGy, preferably 25-50 kGy, is therefore excellently suitable for producing stable PTC resistors with good cold-conducting properties or also more complex components with a PTC component.
  • the contacting and possibly also the assembly with other components can take place after the completion of the PTC material or even before the irradiation thereof.
  • the production of plates or other shaped parts can also be done by injection molding or pressing instead of extrusion.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermistors And Varistors (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Treatments Of Macromolecular Shaped Articles (AREA)

Abstract

This novel procedure makes a resistance material with positive temperature coefficient (PTC). A powder filler is admixed into a polymeric melt of matrix material. The powder filler contains one or more of a boride, carbide, nitride, oxide or silicide. The material is solidified and the matrix cross linked, using electron irradiation. In this new procedure, the radiation dose is 10kGy-75kGy preferably 25kGy-50kGy. The material thickness is 3 mm at most, preferably 1.3-2.5 mm. The material includes a polyethylene or ethylene copolymer, and may be a high density polyethylene. The filler is preferably titanium boride. Filler particle size is 50 mm at most. The filler is etched before mixing in. The mixture is extruded, sprayed or pressed from the melt, into plates.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung eines Materials für PTC-Widerstände gemäss dem Oberbegriff des Anspruchs 1. Ein derartiges Verfahren ist aus der US-A-5 313 184 bekannt.The invention relates to a method for producing a material for PTC resistors according to the preamble of claim 1. Such a method is known from US-A-5 313 184.

Es ist seit langem bekannt, die mechanische und elektrische Stabilität von PTC-Widerständen aus einem semikristallinen thermoplastischen Polymer wie Polyethylen, Polypropylen u. a. als Matrixmaterial, dem ein pulverförmiger Füllstoff aus elektrisch leitendem Material, insbesondere Russ, beigemischt ist, durch ionisierende Strahlung, insbesondere durch Elektronenbestrahlung, zu verbessern.It has long been known that the mechanical and electrical stability of PTC resistors made from a semicrystalline thermoplastic polymer such as polyethylene, polypropylene and the like. a. as a matrix material, to which a powdery filler made of electrically conductive material, in particular carbon black, is admixed, by ionizing radiation, in particular by electron radiation.

In US-A-3 351 882 und US-A-4 534 889, in denen neben Russ auch Graphit, Metallpulver, Metallsalze und -oxide sowie bor- und phosphordotiertes Silizium und Germanium als mögliche Füllstoffe erwähnt werden, werden Bestrahlungsdosen von 500 kGy bis 1 MGy empfohlen.In US-A-3 351 882 and US-A-4 534 889, in which not only carbon black but also graphite, metal powder, metal salts and oxides as well as boron and phosphorus-doped silicon and germanium are mentioned as possible fillers, radiation doses of 500 kGy to 1 MGy recommended.

In der US-A-3 858 144 und der US-A-3 861 029 ist für Materialen mit Russ als Füllstoff ein Bereich von 20 kGy bis 1,5 MGy für mögliche Bestrahlungsdosen angegeben, doch wird eine Dosis von 1,2 MGy empfohlen.In US-A-3 858 144 and US-A-3 861 029 a range of 20 kGy to 1.5 MGy for possible radiation doses is given for materials with carbon black as filler, but a dose of 1.2 MGy is recommended .

In bekannten konkreten Beispielen (s. z. B. WO-A-90/00825, EP-B-198 598) betragen die Bestrahlungsdosen für Materialien mit Füllstoffen auf Kohlenstoffbasis durchwegs mindestens 100 kGy, meist liegen sie beträchtlich darüber. Gemäss EP-A-0 311 142 wurden Versuche mit einem Material auf der Basis von Polyethylen mit Russ als Füllstoff gemacht, die zeigten, dass Bestrahlungsdosen von 800 kGy und 1,6 MGy zu höherer Stabilität des Ansprechverhaltens des PTC-Widerstands führten als eine Dosis von 200 kGy.In known concrete examples (see, for example, WO-A-90/00825, EP-B-198 598), the radiation doses for materials with fillers based on carbon are consistently at least 100 kGy, in most cases they are considerably higher. According to EP-A-0 311 142 tests with a material on the Made of polyethylene with carbon black as filler, which showed that radiation doses of 800 kGy and 1.6 MGy resulted in higher stability of the response of the PTC resistor than a dose of 200 kGy.

Materialien, die nicht auf Kohlenstoff, sondern auf Metall basierende Füllstoffe enthalten, werden seit längerem in der Literatur erwähnt und ihre Verwendung ist z. B. in der bereits erwähnten US-A-5 313 184 konkret beschrieben. Wegen der hohen Leitfähigkeit des Füllmaterials haben derartige Materialien sehr gute Kaltleiteigenschaften, doch ist die Kennlinienstabilität, d. h. die Stabilität der Widerstands-Temperatur-Charakteristik, bekannter derartiger Materialien im allgemeinen eher prekär. Versuche mit Vernetzung durch Elektronenbestrahlung scheinen bisher nicht in grösserem Umfang durchgeführt worden zu sein.Materials that do not contain carbon, but metal-based fillers have long been mentioned in the literature and their use is e.g. B. specifically described in the aforementioned US-A-5 313 184. Because of the high conductivity of the filling material, such materials have very good cold-conducting properties, but the stability of the characteristic curve, i. H. the stability of the resistance-temperature characteristic, known materials of this type are generally rather precarious. Attempts with crosslinking by electron radiation do not appear to have been carried out on a large scale so far.

An sich wäre zu erwarten gewesen, dass wegen der höheren Dichte derartiger Füllstoffe die Streuung der Elektronen grösser und ihre Eindringtiefe geringer wäre als etwa bei russgefüllten Materialien und dass dies höhere Bestrahlungsdosen bedingen würde. Offenbar ist letzteres jedoch nicht der Fall.As such, it would have been expected that due to the higher density of such fillers, the scattering of the electrons would be greater and their penetration depth would be less than, for example, with soot-filled materials and that this would result in higher radiation doses. However, the latter is obviously not the case.

Es hat sich im Gegenteil herausgestellt, dass bei einer Bestrahlungsdosis in einem Bereich von ca. 10 kGy bis 60 kGy die Zugfestigkeit günstige Werte erreicht und auch die Kennlinienstabilität sehr hoch ist. Erstere sinkt anschliessend bis zu einer Bestrahlungsdosis von 100 kGy etwas ab, steigt aber dann, vor allem bei höheren Probentemperaturen, wieder an, doch die Kennlinienstabilität erreicht ihre Höchstwerte bei Dosen von 25 kGy bis 50 kGy und sinkt bei noch höheren Dosen ab.On the contrary, it has been found that with an irradiation dose in a range from approximately 10 kGy to 60 kGy the tensile strength reaches favorable values and the stability of the characteristic curve is also very high. The former then drops somewhat up to an irradiation dose of 100 kGy, but then increases again, especially at higher sample temperatures, but the stability of the characteristic curve reaches its maximum at doses from 25 kGy to 50 kGy and decreases at even higher doses.

Auf der Grundlage dieser Erkenntnis wurde das in den Ansprüchen gekennzeichnete Verfahren zur Herstellung von Materialien für gattungsgemässe PTC-Widerstände entwickelt.On the basis of this knowledge, the method characterized in the claims for the production of materials for generic PTC resistors was developed.

Das erfindungsgemässe Verfahren erlaubt die Herstellung von PTC-Widerständen, die nicht nur wegen der hohen Leitfähigkeit des Füllstoffs sehr gute Kaltleiteigenschaften aufweisen, sondern auch eine gute Zugfestigkeit und eine sehr hohe Kennlinienstabilität. Ausserdem haben die verhältnismässig tiefen Bestrahlungsdosen gegenüber den üblichen höheren Dosen den Vorteil kurzer Durchlaufzeiten und allgemein geringeren Herstellungsaufwands.The method according to the invention permits the production of PTC resistors which not only have very good cold-conducting properties due to the high conductivity of the filler, but also good tensile strength and very high stability of the characteristic curve. In addition, the relatively low radiation doses have the advantage of short throughput times and generally lower manufacturing costs compared to the usual higher doses.

Im folgenden wird die Erfindung anhand eines Ausführungsbeispiels im einzelnen dargestellt und anhand von Figuren erläutert. Es zeigen

Fig. 1
die Zugfestigkeit eines nach dem erfindungsgemässen Verfahren hergestellten Materials bei 25°C und 100°C als Funktion der Bestrahlungsdosis,
Fig. 2a
den spezifischen Widerstand eines nach dem erfindungsgemässen Verfahren hergestellten, mit 25 kGy bestrahlten Materials als Funktion der Temperatur bei mehreren aufeinanderfolgenden Schaltungen,
Fig. 2b
eine Darstellung entsprechend Fig. 2a, wobei die Bestrahlungsdosis 50 kGy beträgt und
Fig. 3
eine Darstellung entsprechend Fig. 2a, wobei die Bestrahlungsdosis ausserhalb des erfindungsgemässen Bereichs bei 100 kGy liegt.
The invention is illustrated in detail below using an exemplary embodiment and explained using figures. Show it
Fig. 1
the tensile strength of a material produced by the process according to the invention at 25 ° C. and 100 ° C. as a function of the radiation dose,
Fig. 2a
the specific resistance of a material produced by the method according to the invention and irradiated with 25 kGy as a function of the temperature in several successive circuits,
Fig. 2b
a representation corresponding to Fig. 2a, wherein the radiation dose is 50 kGy and
Fig. 3
a representation corresponding to FIG. 2a, the radiation dose outside the range according to the invention being 100 kGy.

Das HD-Polyethylen Lupolen 5231X der Firma BASF wurde geschmolzen und TiB2-Pulver mit einer Partikelgrösse <45mm, das vorher zur Reinigung der Partikeloberflächen von Oxiden geätzt worden war, als Füllmaterial beigemischt. Der Anteil des Füllmaterials an der Mischung betrug 50 Vol.-%. Nach Durchmischung wurde das Material durch einen Schlitz extrudiert und Platten von 160 mm Länge, 40 mm Breite und einer Dicke von 1,3 mm - 2,5 mm hergestellt und in der Richtung der geringsten Ausdehnung mit Elektronen einer Energie von 2 MeV bestrahlt.The HD polyethylene Lupolen 5231X from BASF was melted and TiB 2 powder with a particle size <45mm, which had previously been etched to clean the particle surfaces of oxides, was added as a filler. The proportion of filler in the mixture was 50% by volume. After mixing, the material was extruded through a slit and sheets 160 mm long, 40 mm wide and 1.3 mm - 2.5 mm thick were produced and irradiated in the direction of minimum expansion with electrons with an energy of 2 MeV.

Es wurden mehrere Proben hergestellt und zur Erzielung unterschiedlicher Vernetzungsgrade des Matrixmaterials unterschiedlichen Bestrahlungsdosen ausgesetzt, nämlich 25 kGy, 50 kGy und 100 kGy. Eine weitere Probe wurde mit 100 kGy bestrahlt, dann auf 100°C erwärmt und 5 min auf dieser Temperatur gehalten und nach Abkühlung nochmals mit einer Dosis von 400 kGy bestrahlt. Zwecks Erzielung eines möglichst homogenen Vernetzungsprofils wurde jeweils die Hälfte der Bestrahlungsdosis auf die eine und die andere Hälfte auf die andere Seite der Platte aufgebracht. Bei Zugbelastung der Proben sowie einer unbestrahlten Vergleichsprobe bis zur Reissgrenze wurden die in Fig. 1 dargestellten Resultate erzielt. Die Reissfestigkeit sowohl bei 25°C (weisse Balken, Referenzwert der unbestrahlten Probe 11 MPa) als auch bei 100°C (schraffierte Balken, Referenzwert 3,15 MPa) lag bei Bestrahlungsdosen von 25 kGy und 50 kGy deutlich höher als bei der unbestrahlten und der mit 100 kGy bestrahlten Probe. Bei der mit insgesamt 500 kGy bestrahlten Probe lag sie dann wiederum höher als bei der mit 100 kGy bestrahlten, bei 100°C Probentemperatur sogar beträchtlich.Several samples were produced and exposed to different radiation doses, namely 25 kGy, 50 kGy and 100 kGy, in order to achieve different degrees of cross-linking of the matrix material. Another sample was irradiated with 100 kGy, then heated to 100 ° C. and kept at this temperature for 5 min and, after cooling, irradiated again with a dose of 400 kGy. In order to achieve the most homogeneous crosslinking profile possible, half of the radiation dose was applied to one side and the other half to the other side of the plate. The results shown in FIG. 1 were achieved when the samples were subjected to tensile loads and an unirradiated comparative sample up to the tear limit. The tensile strength both at 25 ° C (white bars, reference value of the unirradiated Sample 11 MPa) as well as at 100 ° C (hatched bars, reference value 3.15 MPa) was significantly higher with irradiation doses of 25 kGy and 50 kGy than with the unirradiated and with 100 kGy irradiated sample. For the sample irradiated with a total of 500 kGy, it was again higher than for the sample irradiated with 100 kGy and even considerably at a sample temperature of 100 ° C.

Noch wichtiger als dieses Resultat sind jedoch die Ergebnisse, die bezüglich der Kennlinienstabilität ermittelt wurden. So ergibt sich aus Fig. 2a, dass bei einer mit 25 kGy bestrahlten Probe der spezifische Widerstand als Funktion der Temperatur bei einer Reihe hintereinander ausgeführter Schaltungen (die Zyklen 1, 3, 5, 7 sind durch verschiedene Stricharten kenntlich gemacht) nur geringfügig streut und keine systematische Verschiebung nach tieferen Schalttemperaturen hin auftritt. Das gleiche günstige Resultat ergibt sich für eine mit 50 kGy bestrahlte Probe aus Fig. 2b. Dagegen zeigte, wie aus Fig. 3 ersichtlich, ein Vergleichsversuch mit einer Probe, die mit 100 kGy bestrahlt wurde, ein verhältnismässig ausgeprägtes systematisches Sinken der Schalttemperatur und auch eine ausgeprägtere Hysterese bei den einzelnen Schaltungen.Even more important than this result are the results that were determined with regard to the stability of the characteristic curve. It follows from Fig. 2a that in a sample irradiated with 25 kGy, the specific resistance as a function of temperature in a series of circuits carried out in series (cycles 1, 3, 5, 7 are indicated by different line types) is only slightly scattered and there is no systematic shift towards lower switching temperatures. The same favorable result is obtained for a sample irradiated with 50 kGy from FIG. 2b. In contrast, as can be seen from FIG. 3, a comparison test with a sample which was irradiated with 100 kGy showed a relatively pronounced systematic decrease in the switching temperature and also a more pronounced hysteresis in the individual circuits.

Das beschriebene Material, bestrahlt mit 10-75 kGy, vorzugsweise 25-50 kGy, eignet sich also hervorragend zur Herstellung von stabilen PTC-Widerständen mit guten Kaltleiteigenschaften oder auch komplexeren Bauteilen mit einem PTC-Anteil. Die Kontaktierung und eventuell auch der Zusammenbau mit anderen Bestandteilen können nach der Fertigstellung des PTC-Materials oder auch vor der Bestrahlung desselben erfolgen.The material described, irradiated with 10-75 kGy, preferably 25-50 kGy, is therefore excellently suitable for producing stable PTC resistors with good cold-conducting properties or also more complex components with a PTC component. The contacting and possibly also the assembly with other components can take place after the completion of the PTC material or even before the irradiation thereof.

Die Herstellung von Platten oder auch anders geformter Teile kann statt durch Extrudieren auch durch Spritzen oder Pressen erfolgen.The production of plates or other shaped parts can also be done by injection molding or pressing instead of extrusion.

Claims (10)

Verfahren zur Herstellung eines Materials für PTC-Widerstände, bei welchem einem polymeren Matrixmaterial in Schmelze ein pulverförmiger Füllstoff beigemischt wird, der im wesentlichen aus mindestens einer Metallverbindung aus einer der Gruppen Boride, Karbide, Nitride, Oxide, Silicide besteht, die Mischung verfestigt und das Matrixmaterial durch Elektronenbestrahlung vernetzt wird, dadurch gekennzeichnet, dass die Bestrahlungsdosis zwischen 10 kGy und 75 kGy liegt.Process for producing a material for PTC resistors, in which a polymeric matrix material in the melt is mixed with a powdery filler, which consists essentially of at least one metal compound from one of the groups borides, carbides, nitrides, oxides, silicides, solidifies the mixture and that Matrix material is cross-linked by electron radiation, characterized in that the radiation dose is between 10 kGy and 75 kGy. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Bestrahlungsdosis zwischen 25 kGy und 50 kGy liegt.A method according to claim 1, characterized in that the radiation dose is between 25 kGy and 50 kGy. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Schichtdicke des Materials in Bestrahlungsrichtung höchstens 3 mm beträgt.A method according to claim 1 or 2, characterized in that the layer thickness of the material in the direction of irradiation is at most 3 mm. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass die Schichtdicke des Materials in Bestrahlungsrichtung zwischen 1,3 mm und 2,5 mm liegt.A method according to claim 3, characterized in that the layer thickness of the material in the direction of irradiation is between 1.3 mm and 2.5 mm. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass das Matrixmaterial mindestens ein Polyethylen oder Ethylencopolymer enthält.Method according to one of claims 1 to 4, characterized in that the matrix material contains at least one polyethylene or ethylene copolymer. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass das Matrixmaterial ein HD-Polyethylen ist.A method according to claim 5, characterized in that the matrix material is an HD polyethylene. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass der Füllstoff im wesentlichen aus Titanborid besteht.Method according to one of claims 1 to 6, characterized in that the filler consists essentially of titanium boride. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die Partikelgrösse des Füllstoffs höchstens 50mm beträgt.Method according to one of claims 1 to 7, characterized in that the particle size of the filler is at most 50mm. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass der Füllstoff vor der Beimischung geätzt wird.Method according to one of claims 1 to 8, characterized in that the filler is etched before the admixture. Verfahren nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, dass die Mischung aus der Schmelze zu Platten extrudiert, gespritzt oder gepresst wird.Method according to one of claims 1 to 9, characterized in that the mixture is extruded from the melt into sheets, injected or pressed.
EP96810818A 1995-12-23 1996-11-22 Process of manufacturing a PTC resistor material Withdrawn EP0780849A3 (en)

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DE1995148741 DE19548741A1 (en) 1995-12-23 1995-12-23 Process for the production of a material for PTC resistors
DE19548741 1995-12-23

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Cited By (2)

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EP0932166A1 (en) * 1998-01-22 1999-07-28 Mitsubishi Denki Kabushiki Kaisha Polymeric PTC composition and circuit protection device made therefrom
CN109494035A (en) * 2018-11-13 2019-03-19 昆山聚达电子有限公司 The production method of thermistor

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US3351882A (en) 1964-10-09 1967-11-07 Polyelectric Corp Plastic resistance elements and methods for making same
US3861029A (en) 1972-09-08 1975-01-21 Raychem Corp Method of making heater cable
US3858144A (en) 1972-12-29 1974-12-31 Raychem Corp Voltage stress-resistant conductive articles
US4534889A (en) 1976-10-15 1985-08-13 Raychem Corporation PTC Compositions and devices comprising them
EP0311142A2 (en) 1981-04-02 1989-04-12 Raychem Corporation Radiation cross-linking of ptc conductive polymers
EP0198598B1 (en) 1985-03-14 1991-07-17 RAYCHEM CORPORATION (a Delaware corporation) Process for the preparation of a ptc element by cross-linking conductive polymer compositions, and electrical devices using the product therefrom
WO1990000825A1 (en) 1988-07-15 1990-01-25 Raychem Corporation Assemblies of ptc circuit protection devices
US5313184A (en) 1991-12-21 1994-05-17 Asea Brown Boveri Ltd. Resistor with PTC behavior

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0932166A1 (en) * 1998-01-22 1999-07-28 Mitsubishi Denki Kabushiki Kaisha Polymeric PTC composition and circuit protection device made therefrom
CN109494035A (en) * 2018-11-13 2019-03-19 昆山聚达电子有限公司 The production method of thermistor

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EP0780849A3 (en) 1998-05-13

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