EP0522228A1 - Electric heater - Google Patents
Electric heater Download PDFInfo
- Publication number
- EP0522228A1 EP0522228A1 EP92100534A EP92100534A EP0522228A1 EP 0522228 A1 EP0522228 A1 EP 0522228A1 EP 92100534 A EP92100534 A EP 92100534A EP 92100534 A EP92100534 A EP 92100534A EP 0522228 A1 EP0522228 A1 EP 0522228A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- electric heater
- ferrite
- polymer material
- heater according
- volume
- 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.)
- Withdrawn
Links
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 23
- 239000002861 polymer material Substances 0.000 claims abstract description 18
- 229920000620 organic polymer Polymers 0.000 claims abstract description 13
- 239000000843 powder Substances 0.000 claims abstract description 10
- 239000000203 mixture Substances 0.000 claims abstract description 8
- 239000004696 Poly ether ether ketone Substances 0.000 claims description 9
- 229920002530 polyetherether ketone Polymers 0.000 claims description 9
- -1 polyethylene Polymers 0.000 claims description 6
- 239000004698 Polyethylene Substances 0.000 claims description 4
- 239000004734 Polyphenylene sulfide Substances 0.000 claims description 4
- 229920000573 polyethylene Polymers 0.000 claims description 4
- 229920000069 polyphenylene sulfide Polymers 0.000 claims description 4
- 229920006015 heat resistant resin Polymers 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 3
- 230000008018 melting Effects 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 239000004952 Polyamide Substances 0.000 claims description 2
- 239000004695 Polyether sulfone Substances 0.000 claims description 2
- 239000004697 Polyetherimide Substances 0.000 claims description 2
- 239000004743 Polypropylene Substances 0.000 claims description 2
- 229920001643 poly(ether ketone) Polymers 0.000 claims description 2
- 229920001652 poly(etherketoneketone) Polymers 0.000 claims description 2
- 229920002647 polyamide Polymers 0.000 claims description 2
- 229920000728 polyester Polymers 0.000 claims description 2
- 229920006393 polyether sulfone Polymers 0.000 claims description 2
- 229920001601 polyetherimide Polymers 0.000 claims description 2
- 229920001155 polypropylene Polymers 0.000 claims description 2
- 229920000915 polyvinyl chloride Polymers 0.000 claims description 2
- 239000004800 polyvinyl chloride Substances 0.000 claims description 2
- 239000011701 zinc Substances 0.000 description 13
- 239000006229 carbon black Substances 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 229910002804 graphite Inorganic materials 0.000 description 8
- 239000010439 graphite Substances 0.000 description 8
- JUPQTSLXMOCDHR-UHFFFAOYSA-N benzene-1,4-diol;bis(4-fluorophenyl)methanone Chemical compound OC1=CC=C(O)C=C1.C1=CC(F)=CC=C1C(=O)C1=CC=C(F)C=C1 JUPQTSLXMOCDHR-UHFFFAOYSA-N 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229920006038 crystalline resin Polymers 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- WJZHMLNIAZSFDO-UHFFFAOYSA-N manganese zinc Chemical compound [Mn].[Zn] WJZHMLNIAZSFDO-UHFFFAOYSA-N 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
Images
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
Definitions
- the present invention relates to an electric heater useful for various heating equipments or devices.
- Heaters which comprise an organic polymer material and a fine powder of e.g. carbon black or graphite having a volume resistivity of at most about 10 ⁇ 2 ⁇ cm, kneaded and dispersed in the polymer material.
- heaters containing such fine powders had the following problems.
- Mn-Zn ferrite as conductive fine powder for a resisting element of an electric heater.
- the present invention provides an electric heater comprising a resisting element composed essentially of a composition comprising an organic polymer material and a conductive fine powder dispersed in the polymer material and adapted to be heated by application of a voltage to the resisting element, wherein the conductive fine powder is Mn-Zn ferrite.
- the Mn-Zn ferrite has a higher volume resistivity than carbon black or graphite, and its content will accordingly be large, whereby a variation in the resistivity due to a fluctuation in the content can be minimized, and the ferrite itself is not inflammable and thus it is free from a danger of burning.
- Figure 1 is a graph showing the relation between the contents of various conductive fine powders and the volume resistivities (logarithmic values).
- Figure 2 is a view illustrating a state in which a voltage is applied in the thickness direction to a thin heater.
- FIG. 1 will be described.
- carbon black, graphite or Mn-Zn ferrite is incorporated thereto.
- carbon black or graphite only a small amount at a level of not more than 20% by volume is required to obtain a volume resistivity of from 102 to 105 ⁇ cm required for an electric heater. Accordingly, it is difficult to disperse it uniformly in the organic polymer. If the dispersion is non-uniform, the volume resistivity varies substantially.
- Mn-Zn (manganese-zinc) ferrite has a volume resistivity of its own at a level of e.g. about 100 ⁇ cm. Accordingly, its content in an electric heater will be at least 30% by volume, whereby uniform dispersion is easy. Further, as is evident from the small inclination of the curve in Figure 1, even when there is a some fluctuation in the dispersion, the variation in the volume resistivity attributable to the fluctuation in the dispersion, is small.
- the Mn-Zn ferrite preferably has a volume resistivity of from 100 to 103 ⁇ cm. Further, its particle size is preferably from 0.1 to 10 ⁇ m, more preferably from 1 to 5 ⁇ m.
- the organic polymer material for the electric heater there is no particular restriction as to the organic polymer material for the electric heater.
- polyethylene, polypropylene, polyvinyl chloride, polyamide, polyester, polyphenylene sulfide, polyetherimide, polyether ether ketone, polyether sulfone, or a mixture thereof may be mentioned.
- a crystalline heat resistant resin having a melting point of at least 200°C, particularly at least 250°C, such as polyphenylene sulfide, polyether ether ketone, polyether ketone ketone, polyether ketone, or a mixture thereof.
- the crystalline resin has a low melt viscosity, whereby incorporation of the Mn-Zn ferrite is easy.
- the Mn-Zn ferrite is added usually in an amount of from 30 to 70% by volume, preferably from 40 to 60% by volume, based on the total amount by volume of the organic polymer material and the Mn-Zn ferrite.
- Mixing of the organic polymer material and the Mn-Zn ferrite can be conducted, for example, by an extruder.
- the variation in the volume resistivity is small.
- the variation in the volume resistivity was evaluated in the same manner as above except that polyether ether ketone (PEEK, melting point: 330°C) was used as the organic polymer material, whereby similar effects were obtained. Further, the plate adhesion and the heat resistance were evaluated. The plate adhesion was evaluated in such a manner that the surface was subjected to etching with a solution of a mixture of chromic acid and sulfuric acid for 3 minutes and then copper was chemically plated, and a cooling and heating cycle between 23°C and 200°C was repeated ten times. With the product having carbon black incorporated to PEEK, peeling of the plated layer was observed.
- PEEK polyether ether ketone
- the product of the present invention having the Mn-Zn ferrite incorporated to PEEK no peeling of the plated layer was observed, thus indicating excellent plating properties for the formation of an electrode. Further, the product of the present invention having the Mn-Zn ferrite incorporated to PEEK was useful at a heating temperature of 220°C without any deformation, and thus was superior to the one wherein polyethylene was used.
- the present invention it is possible to obtain an electric heater having a minimum variation in the resistivity and being free from burning.
- the electric heater of the present invention is useful particularly for an application where a voltage is applied in the thickness direction of a thin heater.
Landscapes
- Resistance Heating (AREA)
Abstract
An electric heater comprising a resisting element composed essentially of a composition comprising an organic polymer material and a conductive fine powder dispersed in the polymer material and adapted to be heated by application of a voltage to the resisting element, wherein the conductive fine powder is Mn-Zn ferrite.
Description
- The present invention relates to an electric heater useful for various heating equipments or devices.
- Heaters are known which comprise an organic polymer material and a fine powder of e.g. carbon black or graphite having a volume resistivity of at most about 10⁻² Ω·cm, kneaded and dispersed in the polymer material.
- However, heaters containing such fine powders had the following problems.
- 1) Carbon black and graphite have a low volume resistivity at a level of 10⁻² Ω·cm. Accordingly, to obtain a volume resistivity of from 10² to 10⁵ Ω·cm required for an electric heater, it is sufficient to incorporate carbon black or graphite in such a low amount as not more than 20% by volume to an organic polymer material. Therefore, a high level of kneading and dispersing technique is required in order to obtain a heater having a minimum variation in the resistivity, or it is unavoidable to have a variation in the resistivity to some extent.
- 2) Carbon black and graphite are inflammable by themselves and will burn when they undergo burning. A possibility of danger of burning tends to be high when a voltage is applied in the thickness direction particularly in the case of a thin heater element.
- According to the present invention, the above problems have been solved by employing Mn-Zn ferrite as conductive fine powder for a resisting element of an electric heater.
- Thus, the present invention provides an electric heater comprising a resisting element composed essentially of a composition comprising an organic polymer material and a conductive fine powder dispersed in the polymer material and adapted to be heated by application of a voltage to the resisting element, wherein the conductive fine powder is Mn-Zn ferrite.
- The Mn-Zn ferrite has a higher volume resistivity than carbon black or graphite, and its content will accordingly be large, whereby a variation in the resistivity due to a fluctuation in the content can be minimized, and the ferrite itself is not inflammable and thus it is free from a danger of burning.
- Now, the present invention will be described in detail with reference to the accompanying drawings.
- Figure 1 is a graph showing the relation between the contents of various conductive fine powders and the volume resistivities (logarithmic values).
- Figure 2 is a view illustrating a state in which a voltage is applied in the thickness direction to a thin heater.
- Figure 1 will be described. Using polyethylene as the organic polymer material, carbon black, graphite or Mn-Zn ferrite is incorporated thereto. In the case of carbon black or graphite, only a small amount at a level of not more than 20% by volume is required to obtain a volume resistivity of from 10² to 10⁵ Ω·cm required for an electric heater. Accordingly, it is difficult to disperse it uniformly in the organic polymer. If the dispersion is non-uniform, the volume resistivity varies substantially.
- Accordingly, if a voltage is applied in the thickness direction by an
electrode 2 to a thin heater (sheet-shaped heater) 1 as shown in Figure 2, there will be a locally excessively heated portion, and there is a possible of danger of burning. - Whereas, Mn-Zn (manganese-zinc) ferrite has a volume resistivity of its own at a level of e.g. about 10⁰ Ω·cm. Accordingly, its content in an electric heater will be at least 30% by volume, whereby uniform dispersion is easy. Further, as is evident from the small inclination of the curve in Figure 1, even when there is a some fluctuation in the dispersion, the variation in the volume resistivity attributable to the fluctuation in the dispersion, is small. The Mn-Zn ferrite preferably has a volume resistivity of from 10⁰ to 10³ Ω·cm. Further, its particle size is preferably from 0.1 to 10 µm, more preferably from 1 to 5 µm.
- There is no particular restriction as to the organic polymer material for the electric heater. For example, polyethylene, polypropylene, polyvinyl chloride, polyamide, polyester, polyphenylene sulfide, polyetherimide, polyether ether ketone, polyether sulfone, or a mixture thereof may be mentioned. Preferred is a crystalline heat resistant resin having a melting point of at least 200°C, particularly at least 250°C, such as polyphenylene sulfide, polyether ether ketone, polyether ketone ketone, polyether ketone, or a mixture thereof. The crystalline resin has a low melt viscosity, whereby incorporation of the Mn-Zn ferrite is easy.
- As is apparent from Figure 1, the Mn-Zn ferrite is added usually in an amount of from 30 to 70% by volume, preferably from 40 to 60% by volume, based on the total amount by volume of the organic polymer material and the Mn-Zn ferrite.
- Mixing of the organic polymer material and the Mn-Zn ferrite can be conducted, for example, by an extruder.
- When the volume resistivity is adjusted substantially to a level of 10⁴ Ω·cm using the materials shown in Figure 1, the required contents (% by volume) of the respective materials and variations in the volume resistivity ρν (Ω.cm) were as shown in Table 1. The variations in ρν were represented by 3σ/x (σ is a standard deviation, and x is an average value).
Table 1 Content (% by volume) 4 ρν (x 10⁴) variations in ρν Carbon black 3 8.2 0.18 Graphite 15 7.5 0.12 Mn-Zn ferrite 45 4.0 0.05 - Thus, according to the present invention, the variation in the volume resistivity is small.
- Further, the variation in the volume resistivity was evaluated in the same manner as above except that polyether ether ketone (PEEK, melting point: 330°C) was used as the organic polymer material, whereby similar effects were obtained. Further, the plate adhesion and the heat resistance were evaluated. The plate adhesion was evaluated in such a manner that the surface was subjected to etching with a solution of a mixture of chromic acid and sulfuric acid for 3 minutes and then copper was chemically plated, and a cooling and heating cycle between 23°C and 200°C was repeated ten times. With the product having carbon black incorporated to PEEK, peeling of the plated layer was observed. Whereas, with the product of the present invention having the Mn-Zn ferrite incorporated to PEEK, no peeling of the plated layer was observed, thus indicating excellent plating properties for the formation of an electrode. Further, the product of the present invention having the Mn-Zn ferrite incorporated to PEEK was useful at a heating temperature of 220°C without any deformation, and thus was superior to the one wherein polyethylene was used.
- According to the present invention, it is possible to obtain an electric heater having a minimum variation in the resistivity and being free from burning. The electric heater of the present invention is useful particularly for an application where a voltage is applied in the thickness direction of a thin heater.
Claims (10)
- An electric heater comprising a resisting element composed essentially of a composition comprising an organic polymer material and a conductive fine powder dispersed in the polymer material and adapted to be heated by application of a voltage to the resisting element, wherein the conductive fine powder is Mn-Zn ferrite.
- The electric heater according to Claim 1, wherein the resisting element has a volume resistivity of from 10² to 10⁵ Ω·cm.
- The electric heater according to Claim 1, wherein the Mn-Zn ferrite has a volume resistivity of from 10⁰ to 10³ Ω·cm.
- The electric heater according to Claim 1, wherein the Mn-Zn ferrite has a particle size of from 0.1 to 10 µm.
- The electric heater according to Claim 1, wherein the Mn-Zn ferrite has a particle size of from 1 to 5 µm.
- The electric heater according to Claim 1, wherein the polymer material is polyethylene, polypropylene, polyvinyl chloride, polyamide, polyester, polyphenylene sulfide, polyetherimide, polyether ether ketone, polyether sulfone, or a mixture thereof.
- The electric heater according to Claim 1, wherein the polymer material is a crystalline heat resistant resin having a melting point of at least 200°C.
- The electric heater according to Claim 7, wherein the crystalline heat resistant resin is polyphenylene sulfide, polyether ether ketone, polyether ketone ketone, polyether ketone, or a mixture thereof.
- The electric heater according to Claim 1, wherein the Mn-Zn ferrite is from 30 to 70% by volume based on the total amount by volume of the organic polymer material and the Mn-Zn ferrite.
- The electric heater according to Claim 1, wherein the Mn-Zn ferrite is from 40 to 60% by volume based on the total amount by volume of the organic polymer material and the Mn-Zn ferrite.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3194754A JPH04357693A (en) | 1990-07-11 | 1991-07-09 | Conductive heater body |
| JP194754/91 | 1991-07-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0522228A1 true EP0522228A1 (en) | 1993-01-13 |
Family
ID=16329681
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP92100534A Withdrawn EP0522228A1 (en) | 1991-07-09 | 1992-01-14 | Electric heater |
Country Status (1)
| Country | Link |
|---|---|
| EP (1) | EP0522228A1 (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2186801A1 (en) * | 1972-05-29 | 1974-01-11 | Pilato Maurice | |
| US3852566A (en) * | 1972-05-25 | 1974-12-03 | Stackpole Carbon Co | Fail-safe electric water heater |
| US4107387A (en) * | 1976-03-15 | 1978-08-15 | U.S. Philips Corporation | Resistance material |
| EP0172302A1 (en) * | 1984-03-02 | 1986-02-26 | Tokyo Cosmos Electric Co., Ltd. | Planar resistance heating element |
| EP0250905A2 (en) * | 1986-06-06 | 1988-01-07 | Fujii Kinzoku Kako Co., Ltd. | Resistive paste, electric heating resistance and preparation process using this paste |
| US4818439A (en) * | 1986-01-30 | 1989-04-04 | Sunbeam Corporation | PTC compositions containing low molecular weight polymer molecules for reduced annealing |
-
1992
- 1992-01-14 EP EP92100534A patent/EP0522228A1/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3852566A (en) * | 1972-05-25 | 1974-12-03 | Stackpole Carbon Co | Fail-safe electric water heater |
| FR2186801A1 (en) * | 1972-05-29 | 1974-01-11 | Pilato Maurice | |
| US4107387A (en) * | 1976-03-15 | 1978-08-15 | U.S. Philips Corporation | Resistance material |
| EP0172302A1 (en) * | 1984-03-02 | 1986-02-26 | Tokyo Cosmos Electric Co., Ltd. | Planar resistance heating element |
| US4818439A (en) * | 1986-01-30 | 1989-04-04 | Sunbeam Corporation | PTC compositions containing low molecular weight polymer molecules for reduced annealing |
| EP0250905A2 (en) * | 1986-06-06 | 1988-01-07 | Fujii Kinzoku Kako Co., Ltd. | Resistive paste, electric heating resistance and preparation process using this paste |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
| AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE FR GB IT |
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| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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| 18D | Application deemed to be withdrawn |
Effective date: 19930714 |