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
• • 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
  • H05B3/28—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material
  • H05B3/286—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material the insulating material 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
  • 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
  • H05B2214/00—Aspects relating to resistive heating, induction heating and heating using microwaves, covered by groups H05B3/00, H05B6/00
  • H05B2214/04—Heating means manufactured by using nanotechnology

Definitions

• the present invention refers to heated panels produced by conventional plastics transformation processes and based on conductive thermoplastic compounds.
• the panel is heated thanks to the Joule effect by which an electrical conductive material is heated by applying an electric current.
• These panels can be used as a heating system in different sectors such as automotive, construction, aerospace and packaging.
• the panels can be obtained by extrusion, injection or compression molding and subsequently shaped to adapt to different geometries.
• the invention ES2574622 uses as a heating material an additive thermoset elastomer with a high percentage of carbon nanotubes (NTC) (between 20-45% by weight). This elastomer is used as a coating on different substrates.
• NTC carbon nanotubes
• the invention indicates the importance of copper electrodes, which are deposited by electrochemical electrodeposition on the conductive material.
• WO 2007089118 a high conductivity film capable of being heated is obtained by spraying an aqueous solution of carbon nanotubes (NTC) onto a polymeric sheet.
• the invention DE102011086448 (A1) also bases its invention on the deposition of layers of an aqueous solution of carbon nanotubes (NTC) to obtain a heated coating.
• the invention W02002076805 A1 describes a heated flywheel by applying conductive coatings based on carbon particles. They also work with different layers of conductive coatings in the invention ES2402034B1, which also contemplates the encapsulation of the heating elements and the electrodes.
• US2005172950 and WO 2009011674 refer to heated fabrics or garments. The first is based on the impregnation of fabrics with conductive coatings and the second obtains the conductive fabric from long carbon nanotube fibers.
• ES 2537400 B1 conductive coatings are applied on heating elements of automobiles, in particular in mirrors.
• thermostable polymer in the example the use of a silicone is specified.
• thermoplastic polymers can be partially crosslinked to obtain an extruded sheet, but in that case they cannot be re-melted so they cannot be recycled.
• the materials do not intersect in any case, being recyclability a characteristic of the panel of great novelty.
• it refers to soft materials, such as silicone, while the materials of the present invention are rigid panels.
• the resistivity of the materials developed in the present invention is much lower, being much more conductive than the materials specified in said German invention DE102011003012.
• the low conductivity determines the design of the electrodes, causing them to be relatively close and of a large size (similar to the geometry of the heated sheet).
• the process of obtaining a film with high conductivity is very different from the one developed in the present invention. It is based on the annealing annealing that is made to the polymer after extrusion of the film. This annealing can last up to 24 hours.
• the present invention does not contemplate this technology since good conductivity is achieved by dispersing the conductive load well and correctly processing the material to obtain the final film or piece with the desired conductive properties. Therefore, a PTC plastic is obtained by conventional processes thanks to the good dispersion of the conductive particles which are achieved by applying specific and specific processing conditions, which also allows to produce larger geometries with greater distance from the electrodes.
• the invention CN201610317174 refers to solvent-based conductive pastes without being thermoplastic polymers.
• the polymeric material that is produced by extrusion is the substrate (non-conductive) on which the conductive paste is applied. It is a functional printing process of inks, very different from thermoplastic processing.
• the inventions found are based on the application of conductive paints or varnishes that finally make up a conductive coating or are based on the extrusion of materials with worse electrical conductivities, which subsequently complicates and complicates the configuration of the electrodes.
• the application of coatings is a manual process and the final behavior of the heating element depends on different factors, such as: number of layers of the paint or conductive solution, worker who applies the paint, homogeneity of the solution, since if the conductive particles They decant over time, the first applied layer may have a concentration of conductive particles much greater than the last applied layer. Therefore, the heating homogeneity and reproducibility of the heating elements produced is not stable.
• the conductive particles are dispersed in the thermoplastic matrix in a co-rotating twin screw extruder.
• a homogeneous nanocomposite of high electrical conductivity is obtained, allowing the electrodes to be positioned at a great distance.
• this material is melted to obtain a conductive sheet.
• Said process can be an extrusion, a compression or an injection.
• the piece obtained will have a concentration of homogeneous conductive particles ensuring a reproducible and homogeneous behavior.
• the sheet can be crushed and reprocessed ensuring recycling at the end of the product's life. Recycling is not contemplated in the state of the art since different materials and thermosetting coatings that do not allow recycling are combined.
• the materials developed and the manufacturing process carried out in the present invention provide a lower resistivity of the conductive sheet being 10 1 Ohm.cm, much lower compared to the patent DE102011003012A1, which mentions resistances between 10 3 to 10 6 ohm.cm, which implies a greater conduction through the developed panel.
• the present invention has been devised as a heating panel that uses electrical energy as a power source to be converted into thermal energy.
• the novelty lies in the type of material that makes up the heating panel and in its manufacturing process.
• the solution conceived is based on obtaining a conductive, lightweight and recyclable polymer sheet to be used in a wide variety of designs depending on the sizes and geometries required according to the application.
• Polymeric materials are usually insulating, however, thanks to the addition of conductive additives, they can change their thermal and electrical properties and replace metallic heat-generating resistors when this type of heating is required.
• the heating panel produces thermal energy when an electric current is applied, so that, to carry out this process, the panel comprises:
• thermoplastic material additive with temperature conductive particles that provide the sheet with PTC (Possitive Temperature Coefficient) behavior, where the geometry of the sheet can be adaptable by the processes of thermoforming or used in its manufacture and where said sheet is recyclable;
• metal electrodes mechanically connected to the sheet and configured to apply an electric current flowing through said sheet
• a first temperature and electricity insulating layer configured to avoid losses of heat energy in the opposite direction to the desired one
• a second electrical insulating layer configured to avoid direct contact with the sheet
• thermocouple sensor attached to the sheet configured to measure the internal temperature of the heating panel
• thermocouple sensor is joined in the central part of the sheet.
• thermocouple sensor All these components that form the heating panel, the sheet, the first insulating layer, the second insulating layer, the thermocouple sensor and the metal electrodes, are reusable to be part of another heated panel or to be part of another system.
• the sheet Since the sheet has a PTC thermistor behavior, when an electric current is applied to the metal electrodes, the sheet works by increasing the electrical resistance with increasing temperature. That is, once the desired temperature is reached it stabilizes and no temperature peaks are generated, being a safe heating system. This feature gives it the particularity of being self-regulating, regardless of the need for thermostats, necessary in other heating systems.
• the conductive particles that add the thermoplastic material of the sheet have percentages directly proportional in the mixture with the thermoplastic material, depending on the final temperature required by the heating panel and the type of conductive particles used. Once the material has been formulated, the temperature of the panels can be regulated by adapting the input voltage or cutting off the power supply, without adapting the formulation to each of the applications.
• These conductive particles of sheet temperature can be carbon nanotubes, graphene, graphite, carbon black or a combination of the above.
• the conductive particles that add the thermoplastic material of the sheet are carbon nanotubes and have a concentration between 5-5 10% with respect to the total weight of the sheet.
• the concentration is between 20-40%, when they are carbon black, the concentration is between 10-30%, when they are graphene, between 3 -10%, all these percentages being with respect to the total weight of the mixture that forms the sheet.
• thermoplastic materials of the sheet can be polyolefins, polyesters, polyamides, thermoplastic elastomers, polysulfones, polyetherimides or a combination of all of the above, since they all allow mixing with the conductive temperature particles and have adequate structural and mechanical characteristics for the use of the heated panel, although preferably one type of polyolefin, polypropylene, is used.
• the "composite" layer can take multiple forms by thermoforming, obtaining a lightweight final compound, allowing its use for spaces with special geometries.
• machining operations can be applied to adjust with other elements.
• the heating panel also comprises a covering fabric that partially or totally covers the panel, said covering fabric being an electrical insulating material resistant to temperature changes and which is selected according to the characteristics of the installation of the panel.
• the conductive materials of the metal electrodes can be made of copper or silver, although other metallic materials that can be mechanically attached to the sheet can be selected to be reused.
• the manufacturing process of the sheet, made of thermoplastic material, additive with temperature conductive particles, is carried out through processes of transformation of plastics and thermoplastics.
• the conductive particles, in powder form and of the thermoplastic material, preferably polypropylene, in the form of pellets are introduced into a heated tank of a co-rotating twin-screw extruder.
• the conductive particles and the thermoplastic material are mixed hot, melting the thermoplastic material in the extruder, to achieve a homogeneous mixture, applying, at the same time as the melting of the thermoplastic material, an energy specific mechanics of at least 0.5 kWh / kg.
• the objective of this process is to disperse the conductive charge in the polymer matrix to achieve optimal electrical properties homogeneously throughout the entire volume of the sheet.
• the melting of the thermoplastic material is carried out at a temperature of 210 ° C, for the preferred case of a polypropylene matrix, and the spindles rotate at a speed greater than 600 rpm, for a material input of 10 kilograms per hour in the co-rotating extruder with a diameter of 25 mm and a ratio of length between diameter equal to 40.
• said mixture of the molten plastic with the conductive particles is passed through an extruder head, configured to generate filaments of thermoplastic material added with conductive particles.
• the calender rollers In order not to lose the electrical conductivity, it is necessary to optimize the processing by ensuring a slow cooling of the material at the head outlet.
• the calender rollers must be at a high temperature ensuring that the carbon nanotubes have enough time to distribute in the polymer matrix and form the conductive network.
• the pellets are melted to obtain the sheet of the heated panel by means of a new extrusion, a drawing, a rolling by rollers, or a combination of these manufacturing processes, all these processes being hot to facilitate the molding of the sheet, although it can also be carried out by injection into plastic dies or compression molding.
• the geometry of the sheet can be adaptable to any geometry depending on the needs of shape and size.
• the conductive sheet thermoplastic material additive with conductive particles can be obtained in one step, by coupling a co-rotary extruder to a flat sheet head. In this way, the panel is cheaper and faster to manufacture.
• the sheet can be crushed, for a new obtaining of pellets, and re-processed ensuring recycling at the end of the product's life. This recycling is not contemplated in the background found since different materials, embedded and thermosetting coatings are combined that do not allow recycling.
• the conductive particles do not cover any material, but are dispersed in the matrix of the twin-screw extruder co-rotating with the thermoplastic material, unlike these inventions mentioned in the background, by what materials developed in the present invention obtain the mentioned resistivity of 10 1 Ohm.cm, and a greater thermal conduction.
• This good conductivity is only achieved by dispersing the conductive load well and correctly processing the conductive particles to obtain the sheet with the desired conductive properties.
• a PTC plastic sheet is achieved by manufacturing processes thanks to the dispersion of the conductive particles, which are achieved by applying specific and specific processing conditions. This also allows to produce geometries larger than those found and with greater distance between the electrodes.
• the construction of the heating panel is carried out by custom machining according to the desired geometry of the final panel or by a thermoforming, connecting the electrodes to the sheet and placing the isolation layers on the sides of said sheet.
• the assembly is covered by the covering fabric, tailored, according to the design and the final application with fabrics resistant to changes in temperatures or possible iterations that may have with the outside to provide a finish suitable for use.
• Figure 1 shows an elevation view and another in profile of the heated panel.
• Figure 2 shows the temperature reached of heated panels with heat conduction sheets of different sizes and geometries.
• Figure 3 shows a graph in which the temperature levels of the material of a sheet made of polypropylene with carbon nanotubes vary, when 48V are applied starting from a temperature of -21 ° C.
• the heating panel of the present invention is composed of a sheet (1), made of thermoplastic material, metal electrodes (6) mechanically connected on the sides to the sheet (1), a first insulating layer (3) located on one side of the sheet (1), which prevents the loss of temperature of the sheet on the opposite side to the desired one, and also prevents the passage of electric current through that side, a second insulating layer (2) of electricity to limit the passage of electric current on the opposite side of the sheet (1) where heat is emitted and a thermocouple sensor (5) attached to the sheet (1) that measures the internal temperature of the heated panel.
• said heating panel is partially or totally covered by a covering fabric (4), of an electrical insulating material, with a double purpose. Prevent a user close to the panel from having unwanted contact with the electrically conductive heating sheet (1) and provide a finish according to the installation site of the panel.
• This covering fabric (4) can be of many types, but preferably a natural fabric is selected.
• the sheet (1) is capable of emitting heat, despite being made of thermoplastic material, because it is additive with electrical conductive particles providing the sheet (1) with a PTC behavior.
• These conductive particles of sheet temperature (1) can be of different types such as carbon nanotubes, graphene, graphite, carbon black and a combination of the above, preferably using carbon nanotubes (NTC, or CTN by its acronym in English) for the heat conduction properties.
• the percentage of these particles of carbon nanotubes is between 5 and 10% with respect to the total weight of the sheet, which is completed with thermoplastic materials selected from polyolefins, polyesters, polyamides, thermoplastic elastomers, polysulfone, polyetherimide or a combination of all of the above, although polypropylene, a compound within the group of polyolefins, is preferably used.
• Figure 2 shows the temperature that can reach the heating panel using as an additive particle, carbon nanotubes (CNT) in different percentages and different sizes, so that the higher the percentage of nanotubes, the higher the temperature reached by the panel.
• CNT carbon nanotubes
• thermoplastic material used in this case is a polypropylene in which they have been mixed with different percentages of carbon nanotubes (CNT) from 3% to 10% by weight. Applying a voltage of 48 V to the heating panel, different temperatures are generated in degrees Celsius, reaching up to 100 ° C if the panel has a reduced surface of 15 x 15 cm side.
• CNT carbon nanotubes
• the graph of figure 3 shows the operation of a sheet made of polypropylene with carbon nanotubes to which a voltage of 48 volts has been applied, gradually during the first minute, establishing that constant voltage until minute 6. Due to the applied load, the temperature of the panel begins to heat up in a logarithmic growth, to go from -21 ° C to 75 ° C in those 6 minutes, in which the indicated voltage is applied. When the voltage is removed, the temperature is gradually reduced in an exponential decrease.
• the energy consumption of said heated panel is 120W for a rectangular geometry of 350 cm side by 250 cm on the other side and 2 cm wide, applying 48V and 64W, for the same geometry, applying 24V.
• the power consumption is 20W at 48V and 5W at 24V.
• the sheet (1) is composed of a thermoplastic material and additive particles, first of all, a mixture of both components is made, so that they are joined in a state of pellets and powder, and heated to obtain the melting of the material plastic, where it is removed inside an extruder applying a specific mechanical energy of at least 0.5 kWh / kg.
• thermoplastic material is carried out at a temperature of at least 210 ° C, when polypropylene is used and the spindles rotate at a speed of at least 600 rpm, for a material input of 10 kilograms per hour in a co-extruder Rotary of 25 mm in diameter and length ratio between diameter equal to 40.
• the material is extruded to obtain filaments that are cooled and solidified in rollers, to be subsequently cut by a shear and obtain new pellets but of the mixture of components.
• Said pellets are used to obtain the sheet (1) following one or different processes of transformation of the plastics, such as extrusion, stretching, compression molding, roller lamination or die injection.
• the sheet (1) joins the rest of the components that form the heating panel and is ready for use.
• the present example refers to a sheet of polypropylene and carbon nanotubes obtained by extrusion of flat sheet.
• the plastic material is melted by heat and shear in an extruder and is forced to pass through a head giving it a sheet shape.
• the sheet is passed through a calender or roller system.
• the cooling of the material is controlled by varying the temperature of these rollers.
• Table 1 shows the key parameters for extrusion processing of the sheet with high electrical conductivity.
• the percentage of carbon nanotubes is determined according to the use temperature required by the application. Being the optimum range between 5-10% of nanotubes to reach temperatures between 25-100 ° C.
• Example 2 Heating panel based on polypropylene and graphite
• the sheet is obtained by compression molding.
• the main parameters involved in the process are the pressure exerted on the mold, the cycle time and the temperature during processing.
• Table 2 shows the processing conditions to achieve optimum electrical conductivity in the graphite plates.
• Table 3 shows the temperatures reached in three zones of the heating panel when applying a certain voltage.
• the geometry of the panels in this case is 15 x 15 cm and they were obtained by compression molding.
• Table 3 Thermal behavior of polypropylene panels with graphite

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• Compositions Of Macromolecular Compounds (AREA)
• Surface Heating Bodies (AREA)

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Citations (16)

• 2018
  • 2018-06-18 ES ES201830593A patent/ES2735428B2/es active Active
• 2019
  • 2019-04-23 EP EP19823534.3A patent/EP3809600B1/en active Active
  • 2019-04-23 ES ES19823534T patent/ES2940748T3/es active Active
  • 2019-04-23 WO PCT/ES2019/070276 patent/WO2019243644A1/es active Search and Examination
  • 2019-04-23 PT PT198235343T patent/PT3809600T/pt unknown

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