WO1984000461A1 - Lamine conducteur d'electricite possedant une stabilite amelioree de la resistance et son utilisation dans le chauffage - Google Patents

Lamine conducteur d'electricite possedant une stabilite amelioree de la resistance et son utilisation dans le chauffage Download PDF

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Publication number
WO1984000461A1
WO1984000461A1 PCT/US1983/001038 US8301038W WO8400461A1 WO 1984000461 A1 WO1984000461 A1 WO 1984000461A1 US 8301038 W US8301038 W US 8301038W WO 8400461 A1 WO8400461 A1 WO 8400461A1
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WO
WIPO (PCT)
Prior art keywords
electrically conductive
conductive layer
layer
process according
laminate
Prior art date
Application number
PCT/US1983/001038
Other languages
English (en)
Inventor
Victor E Althouse
Original Assignee
Tvi Energy 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
Application filed by Tvi Energy Corp filed Critical Tvi Energy Corp
Priority to AU18232/83A priority Critical patent/AU1823283A/en
Publication of WO1984000461A1 publication Critical patent/WO1984000461A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B32B27/365—Layered products comprising a layer of synthetic resin comprising polyesters comprising polycarbonates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D13/00—Electric heating systems
    • F24D13/02—Electric heating systems solely using resistance heating, e.g. underfloor heating
    • 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
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/34—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater flexible, e.g. heating nets or webs
    • H05B3/36—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater flexible, e.g. heating nets or webs heating conductor embedded in insulating material
    • H05B3/38—Powder conductors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
    • B32B2307/202—Conductive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/702—Amorphous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2313/00—Elements other than metals
    • B32B2313/04—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2367/00—Polyesters, e.g. PET, i.e. polyethylene terephthalate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2369/00—Polycarbonates
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/002—Heaters using a particular layout for the resistive material or resistive elements
    • H05B2203/005—Heaters using a particular layout for the resistive material or resistive elements using multiple resistive elements or resistive zones isolated from each other
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/011—Heaters using laterally extending conductive material as connecting means
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/017—Manufacturing methods or apparatus for heaters
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/032—Heaters specially adapted for heating by radiation heating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]

Definitions

  • This invention relates to an electrically conductive laminate having improved resistance stability, and in particular its use in a heating element for conductive, convective and radiant heating.
  • radiant heating panels have been fabricated by embedding resistive wires in an insulating substrate, such as gypsum board, or by applying the wires directly to the insulating substrate.
  • insulating substrate such as gypsum board
  • wires directly to the insulating substrate.
  • etched or pierced aluminum and other metal foil heating elements have also been proposed.
  • a commercially available unit comprises a metal foil laid between two layers of clear polyester film.
  • Resistive wire heaters and metal foil heaters suffer a major deficiency in that all of the current is usually carried by a single continuous conductor. A break anywhere in the electrically conductive path renders the entire heater inoperable.
  • the substrate interposes an additional insulative layer between the heating element and the intended receptor and thereby reduces the effectiveness of heat transmission.
  • Metallic powders, transparent vapor-deposited metals or metal oxides, and binders which contain conductive carbon black or graphite have been proposed for use as electrically conductive films in radiant heaters. These materials may be deposited between layers of silicone rubber, polyester film or asbestos-like paper.
  • the electrical stability of conductive plastic matrices containing conductive carbon black or graphite tends to be difficult to control. Generally, this is manifested by changes in the resistance of the conductive matrix through various manufacturing processes (to form the matrix or specific end products), and through the life-cycle of these specific end-products. In many types of applications and end-uses, high levels of stability in such conductive matrices are not critical - e.g., anti-static applications. However, in other applications, and particularly when these conductive matrices form the basis for heating element systems, the constancy of the output (constant wattage) of the heater during constant or cyclical use, or flexing or oh thermal shock is critically dependent on the resistance stability of the system.
  • constant wattage heaters are based on conductive carbon black (or graphite) coating or impregnation technology, and these systems are difficult to maintain in a constant output mode (stable resistance, constant wattage, constant temperature) under a range of practical operating conditions.
  • an electrically conductive layer having improved resistance stability which can be employed in a laminated article useful, for example, as a radiant, conductive or convective heater.
  • the electrically conductive layer should enable the manufacture of a laminated article useful at relatively low operating temperatures, such as about 250°F or less, and also at higher temperatures, if desired.
  • the article When used as a heating element, the article should be of a unitary structure making it unnecessary to cut or otherwise open or separate the lamina in order to install the article in its intended location. It should also be possible to make electrical connections to the article without damaging or destroying the external laminae.
  • the article should be water-proof and substantially impermeable to moisture and harmful gases and vapors.
  • the device should exhibit a stable resistivity. Moreover, the resistivity should be controllable, reproducible and predictable over a range of operating conditions.
  • the article should be fire-resistant and safe if accidentally punctured. It should also be capable of being operated at 110 volts AC or other voltages. The article should have good aesthetic qualities and be capable of being produced at relatively high speed using conventional equipment.
  • the invention provides an electrically conductive layer having improved resistance stability which can be employed in a laminated article useful, for example, as a radiant conductive or connective heater, or as an infrared radiating device. More specifically, the electrically conductive layer comprises an amorphous, solvent-cast thermoplastic film and conductive carbon black, the carbon black being dispersed in the film, such that the electrically conductive laminate has improved resistance stability.
  • the laminated article in which the electrically conductive layer can be employed is a unitary, composite laminated article of manufacture comprising an electrically insulating top layer having an inner surface and an outer surface. An electrically insulating bottom layer having an inner surface and an outer surface is also provided.
  • the aforesaid electrically conductive layer is substantially continuous and of substantially uniform thickness, and is interposed between the inner surfaces of the top and bottom layers.
  • Electrical conductor means are provided in contact with the electrically conductive layer.
  • the electrically conductive layer is capable of emitting electromagnetic radiation when an electric current is passed therethrough.
  • the top layer and the bottom layer have edges that are sealed together to thereby form an enclosed laminate. More particularly, the electrical conductor means are enclosed between the top and bottom layers which have been secured together.
  • the laminated article is characterized by an improved resistance stability, and the article is particularly useful as a radiant heat source.
  • This invention also provides a process for preparing the unitary, composite laminated article of this invention.
  • the process comprises substantially covering an inner surface " of an electrically insulating top layer having an inner surface and an outer surface with the previously described substantially continuous electrically conductive layer of substantially uniform thickness.
  • the process includes providing electrical conductor means in contact with the electrically conductive layer.
  • An electrically insulating bottom layer is provided in contact with the electrically conductive layer.
  • the top layer and bottom layer have edges, which are bonded together to thereby form an enclosed laminate containing the electrically conductive layer.
  • this invention provides a method of using the unitary, composite, laminated article of the present invention. More particularly, the electrically conductive layer in the article of this invention is connected to an electric power supply. An electric current is passed through the electrically conductive layer, which results in the article radiating infra-red energy.
  • Figure 1 is a plan view of a laminate of the invention in a three-busbar configuration comprised of a central hot line and two lateral neutral lines; the various layers are progressively peeled away to illustrate their relationship; and
  • Figure II is a view through section A-A of Figure I.
  • a unitary, composite laminated article useful as a radiant heating panel is comprised of an electrically insulating bottom layer 1, such as a polyester sheet.
  • the electrically conductive layer 3 is deposited on the inner surface of layer 1.
  • Adhesive layer 4 contacts the electrically conductive layer 3 and is applied to the inner surface of electrically insulating top layer 6. It will be understood that an adhesive layer can be applied to either or both of the inner surfaces of the top and bottom layers.
  • Busbars 7 and 8 are shown as having been laid on top of the conductive layer 3.
  • a transverse interconnecting line 9 between the outer busbar 8 is positioned outside the electrically conductive layer 3 so as not to interfere with the conductive paths between central busbar 7 and lateral busbars 8.
  • the transverse interconnecting line 9 could be laid over the electrically conductive layer 3 if line 9 is electrically isolated from layer 3, such as by a strip of high-dielectric film.
  • Lead wires 12 and 13 are connected to the busbars at 10 and 11.
  • transverse interconnecting line 9 can be omitted and wire pigtails can be directly connected to busbars 7 and 8, such as by the use of crimped connectors secured to the busbars.
  • Decorative layer 18 is an optional layer applied to either side of the article. Since the function of the decorative layer 18 is to mask the usual black color of the electrically conductive layer 3 and the busbars 7 and 8 from view, or to match the decor of the surrounding area in which the article is used, it is between the viewer and these parts .
  • the water-tight, sealed construction of the laminate can be more fully appreciated from Figure II showing a cross-section of a heating panel near one of the lateral edges of the panel.
  • a compression seal 14 is formed by laminating under pressure or pressure and heat various layers comprising the article. By sealing all of the exposed edges of the article, the electrically conductive layer and internal electrical circuitry are protected from the elements. It will also be understood that the laminate can be waterproofed and protected with a second insulating or protective layer heat sealed to encase the laminate.
  • a solder bead 15 which bonds the transverse connector 9 to one of the longitudinal busbars 8.
  • Adhesive layers 16 bond the busbars 8 and 9 to the layers with which they are in contact.
  • the top layer and the bottom layer are each electrically insulating layers. They can be comprised of the same material or can be of different materials. Preferably, the top and bottom layers are each comprised of a polymeric film, especially a flexible polymeric film.
  • Typical of such material are films comprised of polyesters, acrylics, ABS, cellulosics, fluorocarbons, polyethylene, polypropylene, polystyrenes, silicones, polyvinylidene chloride, polyvinylidene fluoride, other fluorine-containing thermoplastics, polyether-imide, styrene-acrylonitrile polymer, polycarbonate, chlorosulfonated polyethylene, polyetherether ketone, polysulfone, polyether sulfone, polyamide-imide, and related alloys and blends of the above.
  • Preferred polymeric films are polyesters.
  • a particularly preferred polyester is polyethylene terephthalate, such as Mylar (manufactured by E. I. DuPont de Nemours and Co.).
  • the top and bottom layers can have thicknesses up to about 30 mils, but generally have thicknesses of about 0.35 to about 14 mils, preferably about 0.5 to about 5 mils.
  • the thickness of the layers will depend upon where the laminated article is to be used. For instance, the top and bottom layers can each be about 2 mils if a panel is ceiling-mounted as a radiant heating device or about 5 mils if wall mounted. Layers less than 5 mils thickness can even be employed in wall mounted radiant heaters, but an additional layer or facing may be required for safety purposes to protect the laminate of the invention from mechanical damage.
  • the preferred range of thickness gives the desired resiliency, bending properties and resistance to tearing required for most uses.
  • the top and bottom layers must each be electrically insulating. These layers are characterized by dielectric strengths of at least about 400 volts AC per mil, preferably at least about 1000 volts AC per mil. Dielectric strengths of at least about 7500 volts AC per mil are particularly preferred. Dielectric strength as referred to herein is determined according to ASTM D 149.
  • the top and bottom layers will exhibit volume resistivities of at least about 4.5 x 10 13, preferably about 1 x 10 15 to about 1 x 1018. Volume resistivity is expressed as ohm-cm and is determined by ASTM D 257.
  • the dielectric constants for the top and bottom layers as determined by ASTM D 150 will be at least about 2.0 at 10 cps, at least about 2.0 at 10 6 cps, and at least about 2.0 at 10 9 cps.
  • Preferred values are at least about 3.2 at 10 3 cps, 3.0 at 10 6 cps, and 2.8 at 10 9 cps.
  • the particularly preferred polyethylene terephthalate polyester film employed in this invention exhibits a volume resistivity of 10 ohm/cm 3 at 50% RH and 23°C, is void free and has a relatively low dielectric constant of about 2.8 to 3.2 at from 10 3 to 109 cps. It also has a very high arc resistance (121-200 seconds) when tested by ASTM D 495. It exhibits a dielectric strength of about 7500 VAC/(1-mil).
  • top and bottom layers will depend upon the conditions to which the laminate is exposed.
  • each of these layers will have a tensile strength
  • each layer is about 50%.
  • the laminated article is flexible.
  • This invention fulfills a need in the art for a light-weight heating element that can be rolled into the form of a tube for compactness in shipping and ease of handling and installation.
  • the top and bottom layers should both be flexible. Therefore, the folding endurance for each of these layers should be at least about 400 folds, preferably at least 10,000 folds, as determined by ASTM D 2176.
  • the thermal resistance of each of the top and bottom layers will be dependent upon the conditions under which the laminate of the invention is used. If the laminate is used as a radiant heater in extremely cold climates, it is desirable for the components to resist embrittlement at the low temperatures to which it will be exposed.
  • the preferred polyester film of this invention is capable of withstanding - 100°F when tested by ASTM D 759.
  • a preferred 1200 watt heating panel generally will not exceed about 160°F in normal operation. Other panels, however, when insulated, may attain temperatures of about 200° to about 250°F.
  • the heat resistance of the top and bottom layers when tested by ASTM d 759 will preferably be at least about 275°F without degradation. In certain circumstances, it may be necessary to go as high as 300°F in order to assure long term aging resistance at maximum operating temperatures.
  • the preferred polyethylene terephthalate film is capable of withstanding 300°F.
  • top and bottom layers of the laminate of this invention will generally be exposed to the surrounding atmosphere in which the laminate is used, these layers should possess the required chemical resistance.
  • their resistance to acids, alkalies, greases, oils and organic solvents should be rated as good when tested according to ASTM D 543. This is an indication that there is no adverse chemical reaction when the films are in contact with these materials.
  • the top and bottom layers should also be resistant to water, and thus will exhibit water adsorption values (ASTM D 570) of about 0.8 to about 2.9% in 24 hours, preferably less than about 0.8% in 24 hours.
  • the rate of water vapor transmission (ASTM E 96-E) expressed as gm/100 sq in/24 hr/mil at 37.8°C will be about 1 to about 5.4 preferably not more than about 1.
  • Permeability to gases (ASTM D 1434) expressed as cc/100 sq in/mil/24hrs/atm at 25°C should not exceed about:
  • the top and bottom layers are bonded to each other in order to enclose the electrically conductive layer and electrical conductor means.
  • the layers are bonded by adhesive means.
  • a large number of adhesives can be suitable for bonding the top and bottom layers together to form an enclosed laminate.
  • the adhesive must be effective at performance temperatures, and can be selected from a group consisting of most pressure sensitive adhesives (acrylics, silicones, etc.), most thermosets, i.e., curable systems such as polyesters, polyurethanes, etc., and thermoplastics having melting points above operating temperatures. Silicone adhesives are preferred.
  • the laminated article of the present invention When the laminated article of the present invention is employed as a heating panel, it is important to consider the flammability characteristics of the top and bottom layers.
  • the layers will be nonflammable or at least self-extinguishing as determined by ASTM D 1433-58.
  • secondary flame retardant layers can be employed.
  • the electrically conductive layer employed in the laminate of this invention comprises carbon or graphite and is capable of emitting electromagnetic radiation in the middle infra-red range (i.e., about 3 to about 30 microns in wavelength) when electric current is passed therethrough, It is employed in a layer of substantially uniform thickness, which is important in order to ensure uniform electrical and thermal characteristics in the layer.
  • One of the problems encountered with laminated articles having electrically conductive layers comprising carbon is that the electrical resistivity of the electrically conductive layer varies over a period of time in different types of environments. This is unacceptable when the articles are used as radiant heaters. Specifically, such heaters must usually be approved or certified by recognized testing laboratories or by Government agencies. One of the requirements is that resistivity be maintained within relatively narrow limits over extended periods of time.
  • the present invention overcomes the problem of varying electrical resistivity of electrically conductive layers that comprise carbon.
  • Important characteristics of the electrically conductive film of the present invention are its amorphous polymer structure and the fact that the film is produced by a solvent casting technique.
  • a preferred film layer having these characteristics is marketed by the Schweitzer Division of the Kimberly-Clark Corporation under the trademark KIMFLO.
  • the electrically conductive layer possesses greatly improved resistance stability under a variety of operating conditions, relative to layers which do not possess the important characteristics of the conductive layer.
  • thermoplastic materials comprising polymer of amorphous structure are suitable for use in the electrically conductive layer.
  • these materials include polycarbonates, polysulfones, polyvinylchloride, polyimides (including polyether imides such as Ultem, manufactured by General Electric Company), silicones and other elastomers and various thermosetting resins.
  • the solvent cast material must be capable of producing a film comprising polymer of substantially non-crystalline, amorphous structure.
  • the solvent cast, amorphous plastic can also be formed into a flexible film, so that the resulting heating element can be flexed and/or folded.
  • the electrically conductive layer is produced by a solvent casting method to form an electrically stable, ultra-thin film comprising polymer of amorphous structure.
  • solvent casting involves forming a solution of an appropriate thermoplastic material, which includes carbon black as a disperse phase, and casting the element from solution. Examples of solvent casting techniques are given at pages 238 and 239 of Volume 10 of Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, and in U. S. Patent No. 3,793,716, issued to Smith-Johannsen. Both of these references are hereby incorporated by reference.
  • the electrically conductive layer has substantially uniformly dispersed therethrough finely divided particles of carbon black.
  • the particles can have various configurations and aggregate size, and structure, depending on the process in which they are made.
  • Typical suitable, commercially available conductive carbon blacks are: Conducte SC (Columbia Chemical), acetylene black (Shawinigan), Kjetenblack (Noury), Black Pearls 2000 and Vulcan XC-72 (Cabot).
  • the preferred carbon black is Vulcan XC-72, although others are also acceptable.
  • the carbon black can comprise about 5% to about 50% by weight of the electrically conductive layer, and it is preferable that the carbon black comprise about 15% to about 30% by weight of the layer.
  • the solvent cast electrically conductive layer generally has a thickness of about 0.1 to about 2 mils. Preferably, the thickness is about 0.4 to about 0.8 mils.
  • Additives can be included in the electrically conductive layer, and the selection of these additives is possible by one having ordinary skill in the art. These additives include antioxidants, flame retardants, and other stabilizers or processing aids.
  • barrier layer to the inner surfaces of the top and bottom layers surrounding the electri .cally conductive layer is optional.
  • the barrier layers are substantially impermeable to moisture and water vapor and substantially cover the inner surfaces of the top and bottom layers as described in U. S. Patent 4,250,398.
  • the electrically conductive layer is adhesively bonded to the inner surfaces of the top and bottom layers.
  • the adhesive layer should be substantially non-flammable or at least self-extinguishing, very flexible, elastomeric, thermoplastic or thermosetting, resistant to high temperatures, and free of out-gasing.
  • the adhesive layer can be applied in single or multiple coats. Suitable adhesives include most pressure- sensitive adhesives (acrylics, silicones, and others), most thermosets, i.e., curable systems (polyesters, polyurethanes, and others) , and thermoplastics that have melting points above operating temperatures. Particularly preferred adhesives for use in the present invention are silicone adhesives. Adhesive layers will generally have a thickness of about 0.1 to about 0.5 mils, preferably about 0.1 to about 0.3 mils, but other thickness can be employed.
  • the adhesive should be able to bond the dissimilar layers in which it is in contact; to withstand prolonged exposure to operational temperatures without degrading, outgasing, discoloring or relaxing its tensile bond strength; to stretch under the stresses imposed by the coefficients of expansion of the various layers while still maintaining bond integrity; to form a bond under contact pressure (and heat) after being air dried; and not to migrate into the conductive coating after lamination.
  • Busbars in parallel are utilized to conduct electricity along the length of the electrically conductive layer to present an equidistant path of resistance to the passage of electric current.
  • Non-corroding metal foil busbars are generally employed, but wires or bars, etched copper claddings, and even vapor-deposited or painted metallic coatings can be employed. Any of numerous types of metal foils can be employed, including aluminum, lead, stainless steel, silver, brass, bare copper or tin-plated copper and the like. Electroless copper and nickel busbars are also suitable.
  • copper foil tape is utilized as the busbar material because of its high conductivity and malleability.
  • the tape is backed with a high temperature, electrically conductive heat activated or pressure sensitive adhesive to adhere it to the substrate.
  • Adhesive can be made electrically conductive by dispersing conductive carbon or other conductive particles therethrough.
  • a copper foil tape carries a 0.1-mil thick layer of high temperature, electrically conductive acrylic adhesive. The foil can be applied either underneath the conductive layer or on the top of the conductive layer. When laminated under pressure, the acrylic adhesive offers little resistance to the flow of current.
  • the heater of the preferred design described herein utilizes copper foil 0.001 inches thick, by 0.750 inches wide, to carry the complete 1200-watt load.
  • the copper busbars of this design do not heat significantly above ambient temperature, and thus can safely be employed.
  • the laminate in the form of a conductive, convective or radiant heating panel can be accomplished in a number of ways.
  • the panel can be surrounded by a frame and the frame attached by fasteners to a substrate.
  • the sealed edges surrounding the conductive area of the panel can be stapled directly to the substrate.
  • the panel can be backed with a high-temperature-resistant contact adhesive that will ensure smooth attachment.

Abstract

Un laminé électro-conducteur possédant une stabilité améliorée de la résistivité électrique comprend des couches supérieure et inférieure isolantes possédant des surfaces internes et externes, une couche électro-conductrice continue entre les surfaces internes des couches supérieure et inférieure et le conducteur électrique en contact avec la couche conductrice. La couche conductrice comprend une pellicule plastique coulée au moyen d'un solvant et se composant d'un polymère de structure amorphe possédant des particules électro-conductrices de carbone ou de graphite dispersées uniformément au travers de la structure. La couche électro-conductrice présente une épaisseur sensiblement uniforme. Les couches supérieure et inférieure possèdent des bords, qui sont reliés ensemble de manière étanche pour former un laminé renfermé contenant la couche conductrice. Le laminé peut émettre une radiation électromagnétique lorsqu'un courant électrique traverse le conducteur et la couche électro-conductrice. Le laminé peut être utilisé notamment dans un élément chauffant permettant un chauffage par conduction, convexion ou rayonnement.
PCT/US1983/001038 1982-07-09 1983-07-07 Lamine conducteur d'electricite possedant une stabilite amelioree de la resistance et son utilisation dans le chauffage WO1984000461A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU18232/83A AU1823283A (en) 1982-07-09 1983-07-07 Electrically conductive laminate having improved resistance stability and its use in heating

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US39655782A 1982-07-09 1982-07-09

Publications (1)

Publication Number Publication Date
WO1984000461A1 true WO1984000461A1 (fr) 1984-02-02

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PCT/US1983/001038 WO1984000461A1 (fr) 1982-07-09 1983-07-07 Lamine conducteur d'electricite possedant une stabilite amelioree de la resistance et son utilisation dans le chauffage

Country Status (2)

Country Link
EP (1) EP0113768A1 (fr)
WO (1) WO1984000461A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991011891A1 (fr) * 1990-01-24 1991-08-08 Hastings Otis Stratifie electroconducteur de regulation de temperature de surfaces
EP0893484A2 (fr) * 1997-07-24 1999-01-27 Sony Chemicals Corporation Adhésif multicouche éléctroconducteur et anisotrope et méthode pour le fabriquer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793716A (en) * 1972-09-08 1974-02-26 Raychem Corp Method of making self limiting heat elements
US3900654A (en) * 1971-07-15 1975-08-19 Du Pont Composite polymeric electric heating element
US3993842A (en) * 1973-04-24 1976-11-23 E. I. Du Pont De Nemours And Company Electrically conductive elastomeric ink
WO1979000705A1 (fr) * 1978-03-03 1979-09-20 Delphic Res Labor Lamelle conductrice solide

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900654A (en) * 1971-07-15 1975-08-19 Du Pont Composite polymeric electric heating element
US3793716A (en) * 1972-09-08 1974-02-26 Raychem Corp Method of making self limiting heat elements
US3993842A (en) * 1973-04-24 1976-11-23 E. I. Du Pont De Nemours And Company Electrically conductive elastomeric ink
WO1979000705A1 (fr) * 1978-03-03 1979-09-20 Delphic Res Labor Lamelle conductrice solide

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991011891A1 (fr) * 1990-01-24 1991-08-08 Hastings Otis Stratifie electroconducteur de regulation de temperature de surfaces
EP0893484A2 (fr) * 1997-07-24 1999-01-27 Sony Chemicals Corporation Adhésif multicouche éléctroconducteur et anisotrope et méthode pour le fabriquer
EP0893484A3 (fr) * 1997-07-24 1999-07-21 Sony Chemicals Corporation Adhésif multicouche éléctroconducteur et anisotrope et méthode pour le fabriquer
US6020059A (en) * 1997-07-24 2000-02-01 Sony Chemicals Corporation Multilayer anisotropic electroconductive adhesive and method for manufacturing same

Also Published As

Publication number Publication date
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