Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/10—Printing inks based on artificial resins
  • C09D11/102—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions other than those only involving unsaturated carbon-to-carbon bonds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/10—Printing inks based on artificial resins
  • C09D11/106—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/52—Electrically conductive inks
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
  • F16L53/00—Heating of pipes or pipe systems; Cooling of pipes or pipe systems
  • F16L53/30—Heating of pipes or pipe systems
  • F16L53/35—Ohmic-resistance heating
  • F16L53/38—Ohmic-resistance heating using elongate electric heating elements, e.g. wires or ribbons
• • 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
  • H05B3/145—Carbon only, e.g. carbon black, graphite
• • 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
  • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
  • H05B3/26—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
  • H05B3/267—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base the insulating base being an organic material, e.g. plastic
• • 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
• • 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
  • H05B3/342—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater flexible, e.g. heating nets or webs heaters used in textiles
• • 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
  • H05B3/40—Heating elements having the shape of rods or tubes
  • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
  • H05B3/44—Heating elements having the shape of rods or tubes non-flexible heating conductor arranged within rods or tubes of insulating material
• • 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
  • H05B3/40—Heating elements having the shape of rods or tubes
  • H05B3/54—Heating elements having the shape of rods or tubes flexible
  • H05B3/58—Heating hoses; Heating collars
• • 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
  • H05B2203/013—Heaters using resistive films or coatings
• • 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
  • H05B2203/02—Heaters using heating elements having a positive temperature coefficient
• • 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
  • H05B2203/026—Heaters specially adapted for floor 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
  • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
  • H05B2203/037—Heaters with zones of different power density
• • 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
  • H05B2214/00—Aspects relating to resistive heating, induction heating and heating using microwaves, covered by groups H05B3/00, H05B6/00
  • H05B2214/02—Heaters specially designed for de-icing or protection against icing

Definitions

• the present invention is directed to an electrically conductive ink and relates to a method of making a PTC screen printable ink with double switching temperatures and applications thereof in flexible, screen-printable polymeric PTC heaters.
• the present invention related to a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range.
• the substrate is a flexible substrate. In some embodiments the substrate is a rigid substrate. In some embodiment, the substrate is deformable to generate a three-dimensional structure.
• the substrate is selected from the group consisting of: polyester, polyimide, polyamide, polypropylene, thermoplastic polyurethane, fiberglass, cement board, carbon composite materials, polyethylene terephthalate, polyethylene, aluminum, steel, glass composite, molded plastic, high-density polyethylene and styrene ethylene butyl ene styrene.
• the first resin is selected from the group consisting of: polyethylene glycol and polycaprolactone and the first temperature range is from 20 °C to 35 °C.
• the first resin is selected from the group consisting of: polycaprolactone diol and ethylene-vinyl acetate copolymer and the first temperature range is from 36 °C to 50 °C.
• the first resin is selected from the group consisting of: low-density polyethylene and maleic acid grafted polyvinyl chloride and the first temperature range is from 51 °C to 70 °C.
• the second resin is selected from the group consisting of: polyvinylidene fluoride, poly vinyl chloride, high-density polyethylene, and polyacrylate compounds and the second temperature range is from 70 °C to 160 °C.
• the heater is encapsulated by an encapsulation material.
• the encapsulation material is selected from the group consisting of: polyester, polyimide, polypropylene, rubber, silicone, thermoplastic polyurethane, laminates, ethylene-vinyl acetate (EVA) adhesive film, acrylate adhesive film and silicon adhesive film, fabric, silicone, and polyethylene terephthalate (PET).
• the heater demonstrates temperature fluctuations of 5 degrees at an operating temperature of 48 °C.
• the heater demonstrates temperature fluctuations of 2 degrees at an operating temperature above 48 °C.
• the heater demonstrates substantially no degradation in relative resistance over multiple operating cycles.
• the heater includes a plurality of resistors in parallel.
• the heater includes electrical interconnects comprising one or more of: metal paste, metal foils, alloys, aluminum, copper, nickel and high-conductivity electronic polymers.
• the heater includes a sensor positioned proximal to the heater and a feedback loop to regulate operating temperature.
• the present invention is directed to a radiant-heated flooring material comprising a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range, wherein the double-switching heater is disposed between a flooring material and a sub-flooring material.
• the present invention is directed to a flooring textile comprising a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range, wherein the double-switching heater is bonded to the underside of the flooring textile.
• the present invention is directed to a fluid pipe comprising a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range.
• the heater is disposed on the inside of the fluid pipe. In some embodiments, the heater is disposed on the outside of the fluid pipe.
• the present invention is directed to a mold comprising a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range, wherein the heater is disposed on the proximal to a cavity of the mold.
• the present invention is directed to an ice cube tray comprising a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range.
• the present invention is directed to a cooking appliance comprising a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range.
• the present invention is directed to an article of clothing comprising a double-switching heater comprising a double-switching PTC ink deposited on a substrate to form one or more resistors, the double-switching PTC ink having a first resin that provides a first PTC effect at a first temperature range and a second resin that provides a second PTC effect at a second temperature range, wherein the second temperature range is higher than the first temperature range.
• PTC positive temperature coefficient
• PTCR positive temperature coefficient of resistivity
• the polymer resins which are dissolved in suitable solvents, are the binders and the conductive particles are dispersed in the binders to obtain the inks/coatings.
• Various polymeric PTC compositions have been developed, however, most PTC compositions exhibit Negative Temperature Coefficient (NTC) characteristics of resistivity immediately after the PTC characteristics. This change from PTC behaviour to a strong NTC behaviour is often undesirable, and may cause self-burning in some cases.
• Figure 1 shows a typical curve of the PTC composition described above.
• the NTC temperature region is a potential safety risk temperature region.
• U.S. Pat. No. 8,496,854 discloses a method to reduce the NTC effect without cross-linking the material.
• Their PTC compositions include a thermoplastic base resin, an electrically conductive filler and particles of a polymeric additive dispersed in the PTC composition; wherein the polymeric additive has a melting or softening temperature greater than the melting temperature of the thermoplastic resin, which helps reduce the NTC effect.
• the above PTC composition was produced by melt-extruding technology not like the ink/coating technology used in the present invention.
• the NTC effect is only reduced and not completely eliminated by the above method.
• PTC materials are commonly used in a class of flexible heaters comprising an electrical resistor that is encapsulated between two polymer films.
• the resistor is typically an etched metal foil or, alternatively, an electrically conductive material, or ink, with fixed resistance and suitable properties for printing onto the polymer film.
• the foil is usually composed of Ni-Cr alloy; the ink is usually composed of an electrically insulating polymer with a dispersed, electrically conductive powder additive.
• the conductive powder can be composed of metals such as Ag, Au or Sn, electro-conductive ceramics such as WC, or carbon in various forms such as graphite or carbon black. Carbon is the most common.
• the powder additive dispersed three-dimensionally throughout the polymer, has sufficient volume fraction in the polymer to reach its percolation threshold so as to form a contiguous, conductive network for electrical current to flow throughout the polymer.
• Both flexible heater types often have an adhesive on at least one outer side of the encapsulating film for affixing the heater to the part to be heated.
• Polymeric PTC heaters form a subclass of the second type of flexible heaters described above. These flexible heaters are typically encapsulated in a polymer film like other heaters of the type and generate heat with an applied voltage, but have printed conductive polymer elements that can control current, hence control heating power.
• the temperature at which the electrical resistance starts to increase sharply is referred to as the switch temperature.
• a "switch temperature” or “switching temperature” as used herein refers to the temperature at which the PTC heater generates power only sufficient to maintain thermal equilibrium with its environment, i.e. the point at which the heater temperature neither rises nor lowers under its own power. Typical resistance magnification factors range from 5-15 at the switch temperature. Therefore, they are self-regulating.
• the switching mechanism is due to the polymer undergoing a phase change at around the switch temperature from its normal crystalline molecular structure to an amorphous molecular structure. Because the amorphous material phase has greater volume than the crystalline phase, its volume and thermal expansion interrupts the web of conductors dispersed throughout the polymer. Upon cooling below the switch temperature, the reverse phase- transformation takes place and the conductive network is re-established.
• Polymeric PTC flexible heaters are used for a wide variety of applications where low temperature, controlled thermal gradients, uniform heating and localized temperature control are crucial, without requiring complex electronic controllers or feedback loops.
• PTC-based heater solutions can be found in many aspects of daily life from automotive applications (such as external mirror heaters, seat heaters, etc.), to structural home systems (including floor heaters, bed heaters, etc.) to small appliances (like rice or vegetable cookers).
• Polymeric PTC flexible heaters are most commonly composed of a polymer with carbonaceous conductor in the form of carbon black or graphite. This is because polymeric PTC heaters with metal or conductive ceramics are more expensive and more difficult to deposit as films.
• carbon based polymeric PTC heaters suffer from several important operational technical problems.
• transition temperature region between the low resistance state and the high resistance state where only partial current flows.
• the transition region varies in width proportional to ambient temperature and the overall conditions for heat transfer. Therefore, the operational characteristics of the heater are determined by a multitude of design factors involving its physical environment. This affects the heater's power dissipation, the time-to-switch and the heater's hold current.
• the present invention provides a method to completely eliminate the NTC effect of the PTC composition produced by ink/coating technology.
• the present invention provides a PTC ink composition, which is screen printable and has a high PTC characteristic without any NTC behaviour.
• the safety risk temperature region in the application of the PTC composition has been completely eliminated.
• T m melting point
• T s softening point
• the polymeric PTC composition will turn unstable, which usually results in the NTC behaviour.
• two kinds of polymer with different T m or T s are used.
• the first kind of polymer with a lower T m or T s results in the first PTC effect in the working temperature region
• the second kind of polymer with higher T m or T s results in the second PTC effect in the safety risk temperature region. Therefore, the present PTC composition is also called a PTC screen printable ink with double switch temperatures.
• the present invention describes applications of flexible PTC heaters that utilize the novel composition of PTC conductive ink described above that eliminate the NTC effect, offer magnification factors as high as 250 and switch in the range of 30° - 160°C. Applications using this technology therefore are safer, more reliable and dissipate minimal power at switch temperature.
• Figure 1 presents a typical temperature-resistance curve of a typical prior art PTC composition.
• Figure 2a is a cross sectional view of a flexible double-switching heater used in a radiant-heating application according to one embodiment of the present invention.
• Figure 2b is a circuit according to one embodiment of the present invention.
• Figure 3 is a cross sectional view of a flexible double-switching heater used in a radiant-heating application according to one embodiment of the present invention.
• Figure 4 a cross sectional view of a flexible double-switching heater used in a radiant-heating application according to one embodiment of the present invention.
• Figure 5 is a cross sectional view of flexible double-switching heater used in a snow melting, de-icing and/or anti-icing application according to one embodiment of the present invention.
• Figure 6a is a cross sectional view of a flexible double-switching heater used on the exterior of a water pipe in a point-of use water heating application according to one embodiment of the present invention.
• Figure 6b is a cross sectional view of a flexible double-switching heater used on the interior of a water pipe in a point-of use water heating application according to one embodiment of the present invention.
• Figure 7 is a cross sectional view of a double-switching heater used in a molding tool application according to an embodiment of the present invention.
• Figure 8 presents the temperature-resistance curves of the PTC ink discussed in Example 1, Example 2 and Example 3.
• Figure 9 presents the temperature-resistance curves of the PTC ink discussed in Example 4.
• Figure 10 presents the temperature profiles of a double-switching PTC film during operation.
• Figure 11 presents the presents the temperature profiles of a double-switching PTC film during operation.
• Figure 12 presents PTC profile of a double-switching PTC film.
• Figure 13 presents the PTC profile of a double-switching PTC film.
• Figure 14 presents the TCR profile of a double-switching PTC film.
• Figure 15 presents the relative resistance of a double-switching PTC film plotted relative to a control sample.
• the present invention provides an electrically conductive PTC screen- printable ink with double switch temperatures and a method of making the same.
• the electrically conductive PTC ink not only presents an efficient PTC effect at lower temperatures but also shows a PTC effect at higher temperatures.
• the present PTC ink is applied in a self-regulating heating element with low regulated temperatures ( ⁇ 70 °C), the safety risk temperature region is completely eliminated.
• the PTC ink with double switching temperatures is a typical screen-printable ink produced by ink/coating technology, which comprises:
• the conductive particles can be one or a mixture of more than one of metallic powder, metal oxide, carbon black and graphite.
• the polymer resin 1 is a crystalline or semi-crystalline polymer, such as, but not limited to, polyurethane, nylon, and polyester.
• the polymer resin 2 is a non-crystalline polymer, such as, but not limited to, acrylic resin.
• the selection of the solvent is based on its boiling point at STP and the solubility of polymer resins used.
• the polymer resin 1 and resin 2 are completely dissolved in the organic vehicle prior to blending with other components.
• Any organic, inert liquid may be used as the solvent for the medium (vehicle) so long as the polymer is fully solubilized.
• the preferred solvents are selected from Methyl Ethyl Ketone ("MEK”), N- methyl pyrolidone ( MP), toluene, xylene, and the like.
• the other additives include a dispersing/wetting additive and a rheology additive.
• this invention discloses an ink composition having two distinct positive temperature coefficient (PTC) characteristics at two different temperature ranges, comprising:
• thermally active polymer resin- 1 having a melting point of 30-70 °C and providing the first PTC characteristic in the lower temperature range below 70 °C; preferably being a crystalline polymer or a semi-crystalline polymer.
• thermally active polymer resin-2 having a melting point of 70 -140 °C and providing the second PTC characteristic in the higher temperature range above 70 °C; preferably being a non-crystalline polymer
• the invented PTC ink is preferably prepared according to the following steps.
• the mixture is then subjected to a three-roll mill to assure proper dispersion of the carbon black to form a pastelike ink base.
• a rheology additive 1.0-10.0 wt. % based on the total ink base may be added to enhance the screen-printing properties of the ink base.
• the preparation of final PTC ink composition can be obtained by mechanically mixing the above polymer solution and ink base at ratios ranging from 0.5/1 to 1/1. The ratios depend on the needs of the application design such as the desired starting resistance.
• the resulting PTC ink is applied to substrates such as polyester films (e.g. DuPont Teijin films) by the screen-printing process.
• the PTC ink After printing the PTC ink on a polyester film, it is cured in an oven at 120 °C for 10 minutes. In other instances, the film may be cured at different temperatures. Subsequently, a conductive paste, such as DuPont 5025 silver paste, suitable for use on polyester substrates is printed over edges of the PTC ink and cured at 120 °C for 5 minutes. The cured PTC film is tested for resistance change with temperature.
• a conductive paste such as DuPont 5025 silver paste
• the double-switching PTC ink of the present invention may be deposited on a film or other substrate to create a flexible heater comprising the double-switching PTC ink deposited on the film (or other substrate).
• the term "flexible double-switching heater” as used hereinafter refers to a film or other substrate with the double-switching PTC ink deposited on the film (or other substrate).
• different substrates may be used to generate flexible double-switching heaters with different thermal stability properties.
• the polyester substrate described above may be used to generate a flexible double-switching heater.
• a polyimide e.g. DuPont Kapton
• polyamide substrate may be used.
• various substrates may be used depending on other application- dependent parameters, such as toxicity.
• food-grade substrates such as polypropylene may be used; for clothing, where low weight and flexibility is required, thermoplastic polyurethane (TPU) or fabric itself such as polyester blend or nylon is appropriate; for high tensile strength applications such as fiberglass reinforced cement board or carbon composite materials, the strengthening medium, e.g. fiberglass mat, would be used.
• Other substrates can include but are not limited to: polyethylene terephthalate (PET), polyethylene (PE), aluminum, steel, glass composite, molded plastic, high-density polyethylene (HDPE) and styrene ethylene butylene styrene (SEBS).
• PET polyethylene terephthalate
• PE polyethylene
• PE polyethylene
• HDPE high-density polyethylene
• SEBS styrene ethylene butylene styrene
• the flexible-double switching heater will have a top film positioned over the substrate. Suitable materials for a top film include materials suitable for use as a substrate. However, the top film may be composed of a different material than the substrate. [0071] Depending on the embodiment, the double-switching PTC ink of the present invention may be deposited on the substrate to generate a flexible double-switching heater using various techniques. As discussed above, one of the favorable properties of the double- switching PTC ink is that its dispersion allows for screen printing onto a substrate. In addition, the double-switching PTC ink can be deposited on the substrate using gravure or rotogravure (e.g. "doctor blade") techniques. The ink may also be dispensed over simple or complex surfaces using nozzles mounted on programmable robots or embedded in components by 3-D printing. Other methods of depositing PTC ink with substantial accuracy are known in the art.
• silver paste may be deposited on the substrate to create electrical interconnects (e.g. contacts and bus lines) for use in flexible double-switching heater applications.
• electrical interconnects e.g. contacts and bus lines
• other metals e.g. metal foils or pastes
• alloys or electrically conductive materials such as, but not limited to, aluminum, copper, nickel and alloys thereof, or high conductivity electronic polymers may be deposited on the substrate to create interconnects.
• metal foils, inserted or laminated may also be used to create electrical interconnects.
• the flexible double-switching heater may also be encapsulated with a layer of encapsulation material identical to or different from the substrate used to fabricate the PTC film.
• the flexible double-switching heater may be fully or only partially encapsulated.
• Suitable encapsulation materials include, but are not limited to: polyester, polyimide, polypropylene, rubber, silicone, thermoplastic polyurethane, laminates, ethylene-vinyl acetate (EVA) adhesive film, acrylate adhesive film and silicon adhesive film, fabric, silicone, and polyethylene terephthalate (PET).
• one or both of the layers of encapsulation material may have other layers of materials bonded to it such as, but not limited to: materials suitable for use as encapsulation materials, adhesive films, thermal barriers, reflective films, high or low emissivity films, absorptive films, alkaline resistant films, ground planes or EMI/RFI protective layers.
• the PTC film may be flexible, semi-rigid and/or rigid.
• the PTC film may be deformed (e.g. by heating the PTC film) and shaped into a three-dimensional shape.
• the flexible double-switching heater may be positioned proximal to a sensor and may use a feedback loop to adjust its temperature based on the sensor.
• the flexible double-switching heater may have different PTC effects at different temperate ranges. For example, the switching temperature of the first PTC effect (i.e.
• Suitable compounds for use as polymer resin- 1 to achieve a first PTC effect at lower temperatures include: polyethylene glycol (PEG) and polycaprolactone.
• Suitable compounds for use as polymer resin 1 to achieve a first PTC effect at mid-range temperatures include polycaprolactone diol and ethylene-vinyl acetate copolymer such as Elvax 265 (Du Pont Product).
• Suitable compounds for use as polymer resin 1 to achieve a PTC effect at high temperatures include low-density polyethylene (LDPE) and maleic acid grafted polyvinyl chloride (PVC).
• a polymer resin-2 may be selected to provide a second PTC effect that is higher than the first PTC effect, thereby eliminating material degradation due to NTC effect.
• Suitable compounds for use as polymer resin-2 include: polyvinylidene fluoride, poly vinyl chloride (PVC), high-density polyethylene (FIDPE), and a variety of polyacrylate compounds.
• the second PTC effect of the second compound can range from 70 °C to 160 °C.
• the flexible double-switching heaters of the present invention provide various beneficial characteristics such as self- regulation of temperature.
• the flexible double- switching heaters of the present invention demonstrate substantial temperature equilibrium (plus or minus 5 °C) at an operating temperature of approximately 48 °C. At temperatures greater than 48 °C, the flexible double-switching heaters demonstrate minor temperature fluctuations (plus or minus 2 °C).
• the flexible double- switching heaters of the present invention demonstrate durability due to the second PTC effect. Specifically, the flexible double-switching heaters of the present invention demonstrate a negligible reduction in their relative resistance (approximately 1%) over multiple operating cycles with an operating temperature of 65 °C.
• Flexible double-switching heaters may be used for radiant heated floors, walls and ceilings.
• Figure 2a depicts a specific embodiment of a flexible double-switching heater 200 used in a radiant-heated floor or ceiling application.
• the flexible double-switching heater 200 comprises a PTC film including PTC ink of the present invention printed on a substrate.
• Suitable substrates foe radiant-heated floor applications include: polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE) and polyimide (PI).
• the flexible double-switching heater 200 shown in Figure 2a is encapsulated in an encapsulation material 230.
• Suitable encapsulation materials for use in this application include: laminates, ethyl ene-vinyl acetate (EVA) adhesive film, acrylate adhesive film and silicone adhesive film.
• EVA ethyl ene-vinyl acetate
• the encapsulated heater 200 may have an additional material (not shown) added to the outside of the heater. Additional materials may be
• the encapsulated flexible double-switching heater 200 is inserted between flooring/ceiling materials 220 and sub-flooring/ceiling materials 260.
• flooring/ceiling materials 220 used in this application include, but are not limited to: tiles, hardwood, cement, laminate, carpet, vinyl flooring, wallpaper, ceiling tiles or other decorative material.
• Suitable types of sub-flooring/ceiling materials 260 include: flooring underlay, wallboard or ceiling material such as, but not limited to, plywood, cement, cement board, wall board or ceiling tile.
• the encapsulated flexible double-switching heater 200 may be attached to the sub-flooring/ceiling materials 260 and/or the flooring/ceiling materials 220 using any kind of attachment material 250.
• Suitable attachment materials 250 include adhesives (e.g. thinset) and/or mechanical fasteners.
• a ground plane 240 and/or thermal barrier may be optionally placed between the encapsulated flexible double-switching heater 200 and the sub- flooring/ceiling materials 260.
• a ground plane 240 may be required for leakage current monitoring or safety purposes and/or a thermal barrier 270 may be required for greater efficiency.
• the ground plane 240 may be laminated or attached using pressure sensitive adhesive to the outside surface of the encapsulated flexible double-switching heater 200.
• a thermal barrier 270 may be inserted in rigid form or attached to the encapsulated flexible double-switching heater 200 using adhesives or fasteners.
• Figure 2b depicts a printed circuit that regulates temperature independently over each small area covered by the individual resistor 290.
• Each resistor in a row is powered by line voltage busses 290 and interconnects 291.
• R is the resistance of an individual resistor.
• the power is defined and the temperature at each resistor is independently regulated.
• This circuit pattern allows independent temperature control of small areas and temperature uniformity over the surface of the heater regardless of the local thermal load.
• the gap between discrete resistors may also be reduced to zero to form a contiguous line of resistor with identical behavior of the heater, i.e. local self-regulation in response to local thermal load conditions.
• FIG 3 depicts another specific embodiment of a radiant-heated floor/ceiling application of a flexible double-switching heater 300.
• the flexible double-switching heater 300 is positioned between flooring/ceiling materials 320 and sub- flooring/ceiling materials 360.
• the flexible double- switching heater 300 is embedded in the sub-flooring/ceiling materials 360.
• the flexible double-switching heater 300 is perforated and bonded to a strengthening medium 310 by the sub-flooring/ceiling material 360. The perforations allow the sub- flooring/ceiling material 360 to penetrate the flexible double-switching heater 300 in order to anchor the strengthening medium 310 to the material 360. In this way, the heater 300, strengthening medium 310 and sub-flooring/ceiling material 360 become affixed to each other.
• various strengthening mediums 310 may be used including but not limited to: fiberglass mats, polyamide mesh and glass fiber mesh.
• Suitable sub-flooring/ceiling materials 360 for used in this embodiment include: cement, cement board, plywood, composite wood products, and composite polymer products.
• Suitable flooring/ceiling materials 320 for use in this embodiment include: tile, laminate, hardwood, carpet, ceiling tile, plaster and/or other standard flooring/ceiling materials as known in the art.
• a perforated flexible double-switching heater 300 can be embedded in a sub-flooring/ceiling material 360 comprising cement and overlaid with a strengthening medium 310 comprising glass-fiber mesh. A layer of cement (not shown) was poured over the strengthening medium 310 and cured to bond the flexible double- switching heater 300, the sub-flooring/ceiling material 360 and the strengthening medium 310 to each other.
• the perforated flexible double-switching heater 300 is embedded in a sub-flooring/ceiling material 360 comprising layers of plywood and laminated.
• the perforated flexible double-switching heater 300 was created using a substrate comprising a mat used to strengthen cement board (i.e. the double-switching PTC ink was screen printed onto the mat).
• the flexible double-switching heater 300 may be bonded to the underside of the flooring/ceiling material 320 using an attachment material 350 such as those described above with respect to Figure 2.
• Figure 4 depicts another specific embodiment of a flexible double-switching heater in a radiant-heated floor/ceiling application.
• the flexible double-switching heater 400 is encapsulated in an encapsulation material 430.
• Suitable encapsulation materials 430 include but are not limited to rubber, silicone, polyurethane or other polymers.
• the encapsulation material 430 may include its own power supply.
• the encapsulated flexible double-switching heater 400 is bonded to the underside of a flooring textile 490 to form an integral heater.
• exemplary flooring textiles include, but are not limited to, carpets and rugs.
• the encapsulated flexible double-switching heater 400 can be bonded to the flooring textile 490 using attachment materials 450.
• Suitable attachment materials for this embodiment include: a variety of adhesive, double-side adhesive tapes or means of physical fixing including anchoring and stitching.
• the encapsulated flexible double-switching heater 400 that is bonded to the flooring textile 490 is positioned over an underlay 495 for the flooring textile 490.
• the encapsulated flexible double- switching heater 400 may be used as a free-standing floor covering.
• the encapsulated flexible double-switching heater 400 may be used in radiant- heated room application by attaching the encapsulated flexible double-switching heater 400 to a decorative wall hanging (e.g. a picture) and/or an apparatus (e.g. a space heater) for projecting radiant heat into the room.
• Figure 5 depicts a flexible double-switching heater used in a snow melting, de- icing and/or anti-icing application.
• the flexible double-switching heater 500 is encapsulated in an encapsulation material 530.
• Suitable encapsulation materials 530 for this application include but are not limited to rubber, fabric, silicone, polyurethane or other tough polymers.
• encapsulated flexible double-switching heater 500 may comprise its own power supply (not shown).
• the encapsulated flexible double-switching heater 500 can then be disposed over a sub-surface 540 for snow-melting, de-icing and/or anti-icing applications.
• Exemplary sub-surfaces 540 include, but are not limited to, door steps, walkways, parking areas (e.g. a driveway), road ways (e.g. tarmacs), carports, semitrailer tops, vehicle structure (e.g. a car or a boat) or building components (e.g. a deck, ladder, stair, roof or gutter).
• the sub-surface may be comprised of: concrete, asphalt, sand or gravel.
• the encapsulated flexible double- switching heater is disposed above a sub-surface 540 but embedded beneath a surface 545.
• the surface 545 may be comprised of: a composite protective layer (e.g. rubber).
• the encapsulated flexible double- switching heater 500 can be bonded to a rigid, perforated sheet (e.g. a polymer such as PVC sheet).
• a rigid, perforated sheet e.g. a polymer such as PVC sheet.
• the sheet comprising the encapsulated flexible double-switching heater 500 can then attached to a surface 540 for example by embedding the sheet in the surface and/or underlaying the surface with the sheet.
• the encapsulated flexible double-switching heater 500 can comprise an adhesive layer (not shown) on one of its surfaces. Similarly, the encapsulated flexible double-switching heater 500 may comprise a thermal insulation barrier (not shown) on one of its surfaces. In a specific embodiment, the encapsulated flexible double-switching heater 500 may have an adhesive layer (not shown) on one surface and a thermal insulation barrier (not shown) on the opposite surface. In yet another embodiment, a flexible double-switching heater as described above with adhesive layer on one side and thermal insulation barrier on the opposite side is wrapped on to a water pipe, valve or fitting to prevent freezing,
• Figures 6a and 6b depict flexible double-switching heaters for use in point-of- use, on-demand and tank form applications.
• Figure 6a shows a simple point-of-use water pipe 680 which is wrapped in a flexible double-switching heater 600.
• the embodiment depicted in Figure 6a may be used, for example, in a portion of water pipe 680 that is proximal to a faucet, shower head or other dispensing mechanism (not shown).
• Figure 6b shows an alternate embodiment of a water pipe or cavity 681 that has multiple plates comprising flexible double-switching heaters 601, 602, 603 mounted inside the water pipe 681 in a portion of the water pipe 681 that is proximal to a faucet, shower head or other dispensing mechanism (now shown).
• Figure 7 depicts an application of a flexible double-switching heater in a plastics, rubber, silicone, composite material and metal molding application.
• Heating molds during part or all of the molding cycle can promote efficient filling of mold cavities, reduced tonnage of injection molding equipment, controlled cooling during solidification of the part, superior optical properties, elimination of autoclaves and ovens and simplification of heating equipment and controls.
• flexible double-switching heaters increase productivity by eliminating batch oven processing, allow selective application of heat and in some cases eliminate the use of steam.
• a mold 770 comprising a heated hot runner and nozzle 790 has a flexible double-switching heater 700 disposed on the outside of the mold cavity 770.
• the mold 770 may be a large mold 700, e.g. 1.5 meters in diameter and 1.5 meters high, or a small mold 770, e.g 2 cm. x 2 cm.
• the flexible double-switching heater 700 may be disposed on the inside of the mold 700 provided it is fitted with a suitable overlaying material such as metal foil that is compatible with the physical conditions of temperature, pressure and reaction with the melt.
• flexible double-switching heater include, but not limited to, warming drawers, slow cookers, coffee makers, hot potable water supplies, electric teapots, ice cube trays and steam generators.
• Other residential applications are bathtubs, refrigerator defrosters, dishwasher vents, towel warmers, toilet seat warmers and dry sauna heaters.
• the switching temperature of the first PTC effect can range from 30° -70°C.
• Suitable substrates for this application include: polyethylene terephthalate (PET) and polyimide.
• PET polyethylene terephthalate
• EVA ethylene-vinyl acetate
• acrylics acrylics
• Flexible double-sided heaters may also be used for automotive applications such as, but not limited to, seat warmers, electric car battery warmers, mirror warmers, steering wheel warmers, and cold weather accessories such as heaters for fuel piping, oil pans, transmission pans, batteries and engine blocks.
• Suitable substrates for this application include: aluminum, steel, carbon or glass composite, molded plastic, high-density polyethylene (HDPE) and styrene ethylene butylene styrene (SEBS).
• the flexible double-switching heaters may be encapsulated with standard polymers such as polyethylene terephthalate (PET), ethylene-vinyl acetate (EVA), acrylics and silicon.
• the advantage of using PTC heaters is the elimination of a temperature sensor, elimination of controller or power supply, excellent temperature uniformity and efficiency.
• the latter advantage arises from the PTC ink being formulated to switch at a desired level.
• compositions for the Examples below are summarized in TABLE 1, where all component concentrations are expressed as percentage by weight based on the total ink composition.
• Example 2 10.0 10.0 21.0 55.0 1.50 2.50
• the PTC ink and film were made following the typical procedure described above.
• the polymer resin-1, polymer resin-2, carbon black, solvent, dispersing additive, and rheology additive used in this Example, Example 2 and Example 3 are respectively polyethylene glycols (Carbowax 1450 from Dow Chemicals) with a melting point ranging from 42-46 °C, polyvinylidene fluoride (PVDF) (Solef460 from Solvay ) with a melting point of 155-160°C, carbon black REGAL 350R, NMP, BYK-220S, and BYK-410, and their contents in the PTC compositions are listed in TABLE-1.
• PVDF polyvinylidene fluoride
• the PTC ink compositions of Examples 1, 2 and 3 were screen -printed onto polyester film to produce four strips, each strip having dimensions of approximately 1 cm by 10 cm. Silver contacts were applied to both ends of each strip in order to measure resistance and experimental error. In addition, a 5cm by 5cm square was printed to evaluate dispersion and uniformity.
• the composition of Example 1 yielded resistivity at 25 °C of the PTC film from this example is 3.9 Kohm/sq.
• Figure 8 show the temperature-resistance curves of it.
• Example 1 The conditions were used as Example 1, but more polymer solution was added into the system.
• the resistivity at 25 °C of the PTC film from this example is 8.0 Kohm/sq.
• Figure 8 shows the temperature-resistance curves generated using this Example.
• the PTC ink and film were made following the procedure as described in Example 1.
• Commercially available polymer Elvax 265 (from DuPont) having a softening point of 49 °C was used as the first thermally active polymer resin- 1.
• Another commercially available polymer BR- 106 (BR- 106, DIANAL resins purchased from Univar Canada Ltd) having a melting point of above 160 °C was used as the thermally active polymer resin-2.
• Commercially available carbon black Monarch 120 (from Cabot) was used as conductive particle.
• Commercially available solvent TEP Triethyl Phosphate from Eastman having a boiling point of about 209 °C was used as the solvent.
• TCR temperature coefficient ratio
• the double-switching PTC ink of Example 4 was printed onto a 500mm by 500 mm square of polyester film to form 64 (in a configuration of 14 x6) PTC heating strips in parallel connection by silver bus lines generated using silver paste (DuPont 5025). Each strip was 2cm by 4cm and the strips were placed at intervals of 1cm.
• the heating element was laminated with a standard EVA/PET film with copper ribbons embedded on both sides as the electrodes and yielded an overall effective initial resistance of 1.4 ⁇ at 27 °C. 220 V/60 Hz of power was supplied to the electrical electrodes and generated an initial heating power of 34.6 watt, which was equal to a power density of 138.4 watt/m2 at 27 °C.
• FIG. 10 demonstrates the temperature profiles observed over the first ten minutes of operation for each probe.
• Figure 11 demonstrates the temperature profiles observed over the first 150 minutes of operation. As shown in Figures 10 and 11, there is some variance in temperature profiles due to the probe's position variation and heat loss associated therewith, i.e., the heat loss was more at the outer edges than at the center. However, both Figures demonstrate that the all of the temperature profiles reach an equilibrium after approximately 60 minutes.
• Figure 14 includes the Temperature Co-efficiency Ratio (TCR) measured over varying temperatures.
• TCR is the ratio between the resistance at a given temperature and the resistance at room temperature (27 °C).
• a flexible double-switching heater made using a double-switching PTC ink of the present invention
• a flexible double-switching heater was made by printing the double-switching PTC ink of Example 4 onto a polyester substrate. Electrical components were made by disposing silver paste (DuPont 5025) onto the substrate after the ink was cured. A reference sample was generated using the same technique but substituting a commercially available PTC ink (DuPont 7282) for the ink of the present invention.
• Figure 16 shows the relative resistance for both samples measured over the 25 operating cycles.
• the relative resistance of the double-switching PTC ink of the present invention suffers only slight degradation due to the elimination of NTC effect obtained by the second PTC effect.
• the reference sample with conventional PTC ink had diminished relative resistance over time, suggesting an NTC effect had caused material degradation.

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• 2017
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