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WO2008046047A1 - Éléments chauffants basse puissance utilisant des composés exothermiques de sulfure de polyphénylène - Google Patents

Éléments chauffants basse puissance utilisant des composés exothermiques de sulfure de polyphénylène Download PDF

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Publication number
WO2008046047A1
WO2008046047A1 PCT/US2007/081242 US2007081242W WO2008046047A1 WO 2008046047 A1 WO2008046047 A1 WO 2008046047A1 US 2007081242 W US2007081242 W US 2007081242W WO 2008046047 A1 WO2008046047 A1 WO 2008046047A1
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WIPO (PCT)
Prior art keywords
heating element
electrically conductive
conductive particles
exothermic
compound
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PCT/US2007/081242
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English (en)
Inventor
Maziyar Bolourchi
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Avient Corp
Original Assignee
Polyone Corp
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/08—Materials not undergoing a change of physical state when used
    • C09K5/14—Solid materials, e.g. powdery or granular

Definitions

  • This invention concerns the use of polyphenylene sulfide compositions as high efficiency heating elements.
  • Thermoplastic polymers have many advantages in material science, as compared with metals: relatively low cost, relative ease of manufacturing to final form, lack of oxidation which leads to corrosion. Heating elements such as metal rods or plates are commonly used to provide resistive heating, whether within an oven or as a cooking surfaces. [0005] U.S. Pat. No.
  • 6,086,791 discloses coatings and films of a non-metallic electrically conductive coating composition effective in emitting heat without break-down when connected to a source of electricity, which comprises: (a) a binder; (b) electrically conductive flake carbon black of particle size between about 5 and 500 micrometers; (c) electrically conductive flake graphite of particle size between about 5 and 500 micrometers; (d) a volatile solvent; wherein the weight amount of (b) and (c) together ranges from between about 10 and 75 weight percent based on the non-volatile solids content of the coating composition.
  • U.S. Pat. No. 6,818,156 also discloses coating and films using carbon-based materials having particle sizes in the nanometric and micrometric range for emitting heat.
  • U.S. Patent Application Publication 2005/0070658 discloses electrically conductive compositions that contain a greater amount of graphite than nanosized conductive filler or carbon fibers, between 6 and 80 times as much.
  • Miller are present only at the surface of an article. Such films and coatings can chip, delaminate, or flake leaving the article untreated.
  • the present invention solves that problem in the art by providing a polypheny! ene sulfide compound that is exothermic throughout its bulk when connected to a source of electrical energy. [00011] Unexpectedly, it has been found that the polyphenylene sulfide compound is very efficient in its use of electrical energy, making it a new type of heating element for consumer and industrial devices.
  • One aspect of the present invention is a heating element comprising a polymer compound having an energy efficiency of at least about 80 percent, wherein the compound comprises polyphenylene sulfide and an exothermic additive comprising electrically conductive particles and, optionally, less electrically conductive particles, wherein the amount of electrically conductive particles in the compound is same or greater than the amount of less electrically conductive particles, if any are present.
  • Another aspect of the present invention is an electrical appliance having a heating element of the polymer compound described above that can operate at plateau temperatures ranging from about 30 0 C to about 250 0 C.
  • An advantage of the present invention is that the heating element can achieve those temperatures efficiently, generally more than about 80% efficiency.
  • Heating element for purposes of the present invention means a component of a device, made from a polymer compound comprising polyphenylene sulfide, that is designed to operate at a temperature greater than ambient temperature to perform work, including without limitation, heating an enclosed space, altering chemical or physical properties of a substance, cooking food, etc.
  • Exothermic additive for purposes of this invention means one type of electrically conductive particles or a combination of that type of electrically conductive particles and less electrically conductive particles that can be engineered to provide a specific temperature when the polyphenylene sulfide compound is formed into a heating element and is powered by electricity.
  • the less electrically conductive particles comprise graphite.
  • Platinum temperature means the temperature after resistive heating in which the compound reaches a steady state of heat dissipation vs. power consumption while functioning in ambient conditions.
  • thermoplastic article of the present invention Because the melting or other degradation point of polyphenylene sulfide is higher than the temperature desired for the components of the electronic device, it is possible to engineer any specific temperature of heat emitted from a thermoplastic article of the present invention.
  • power consumption As a first approximation, will be described as Watts, also known as Joules/second. It is true that with alternating current, a power factor may be needed to convert volt*amps to Watts. However, using the equipment to conduct the experiments of this invention and report the results, the alternating current in volt*amps does approximate Watts because the power factor has been addressed.
  • Fig. 1 is an image showing a heating element of the present invention before a raw egg is placed on its surface, wherein the heating element is electrified to be at a temperature of 121°C.
  • Fig 2. is an image captured from a video at time zero (To), showing the raw egg being placed on the surface of the heating element.
  • Fig 3. is an image captured from a video at To plus thirty seconds
  • Fig 4. is an image captured from a video at To plus one hundred fifty seconds (T 150 sees. ) showing the raw egg as it cooks on the surface of the heating element.
  • Fig 5. is an image captured from a video at To plus two hundred ten seconds (T 21 0 sees.) showing the fully cooked fried egg on the surface of the heating element.
  • EMBODIMENTS OF THE INVENTION [00026] Polvphenylene Sulfides
  • Polyphenylene sulfides are polymers containing a phenyl moiety and one or more sulfides bonded thereto.
  • PPS polyphenylene sulfides
  • Non-limiting examples of such commercially available polyphenylene sulfides include Ryton brand PPS powders in various grades from Chevron Phillips Chemical Co. of The Woodlands, Texas. Any of the patents in the literature known to those skilled in the art are appropriate for determining a suitable choice, without undue experimentation.
  • the exothermic additive for the present invention can be a single form of carbon, preferably carbon black or substitutes for carbon black. In this embodiment, no graphite is needed or desired. [00030] An acceptable commercially available carbon black is Printex
  • XE2 super conductive carbon black particles having a particle size of about 35 run, from Degussa of Akron, Ohio, among other locations.
  • Other types of carbon black particles include, without limitation, Corax ®' and Purex ® brand carbon blacks, also from Degussa, Ketjenblack ® brand carbon blacks from Akzo Nobel, Black Pearls ® brand carbon blacks from Cabot Corporation.
  • Useful grades of carbon black as described in RUBBER TECHNOLOGY 59-85 (1995) range from Nl 10 to N990.
  • average diameter particle size of the carbon black can be any size within the nanometric region, and more particularly from about 15 to about 900 nm. and preferably from about 20 to about 80nm.
  • the aspect ratio of the carbon black can be any range customarily found, preferably ranging from about 1 :1 for spherical particles to about 5:1.
  • Non-limiting examples of substitutes for carbon black include nanotubes (single- walled and multi -walled), nanofibers, and other forms of carbon that have a high aspect ratio and are electrically conductive.
  • the cumulative amount of carbon black or its substitute as the exothermic additive can range from about 1 to about 75 weight percent of the total thermoplastic compound, and desirably less than about 18 weight percent, preferably less than about 15 weight percent, and most preferably less than about 10 weight percent. Generally, the greater the concentration of carbon black, the more exothermic the thermoplastic compound at a given amount of applied electrical energy.
  • the exothermic additive can be a combination of two different forms of carbon, preferably a combination of particles of carbon black and particles of graphite.
  • the carbon black is more electrically conductive than graphite.
  • the amount of carbon black exceeds the amount of graphite, in order to maximize the electrical efficiency of heating elements made from this embodiment.
  • an acceptable commercially available graphite is No. 2939 Thermally Pur. Flake graphite having a particle size of less than about 20 microns, from Superior Graphite
  • the size of the two different forms of carbon can be any size within the nanometric or micrometric region.
  • the aspect ratio of the two different forms of carbon can be any range customarily found in the various forms of carbon useful for the present invention, such as almost 1:1 for spherical particles to about 20,000:1 for nanotubes.
  • a balance of carbon black particles and graphite particles can provide both electrical conductivity via the carbon black particles to transport electrical energy throughout the bulk of the polyphenylene sulfide and while also generating heat because of the less conductive or resistive nature of the graphite particles.
  • the combination of two different forms of carbon can be dispersed into bulk of an article formed from a polyphenylene sulfide compound to provide electrical conductivity and exothermic properties.
  • the Miller patents do not disclose polyphenylene sulfide as a suitable binder for his coatings and films.
  • the ratio of more conductive: less conductive portions of carbon forms in the exothermic additive can range from about 1.1 :1 to about 3:1. Generally at a constant ratio of more conductive/less conductive carbonaceous particles, the greater the concentration of exothermic additive, the more exothermic the thermoplastic compound at a given amount of applied electrical energy.
  • the cumulative amount of exothermic additive can range from about 1 to about 75 weight percent of the total thermoplastic compound. Generally at a constant ratio of more conductive/less conductive carbonaceous particles, the greater the concentration of exothermic additive, the more exothermic the thermoplastic compound at a given amount of applied electrical energy. [00042] Optional Other Polymers
  • the compound of the present invention can include additional polymer resins to alter the morphology or rheology of the compound.
  • the other polymers can be compatible with PPS in order to form blends or incompatible with PPS in order to form a continuous/discontinuous two-phase polymeric system.
  • Non-limiting examples of other optional polymers include polyolefins, polyamides, polyesters, polyhalo-olefins, and polyurethanes.
  • polyolefins such as polyethylenes, and more preferably high density polyethylenes (HDPE), in order to reduce brittleness of molded parts made from compounds of the present invention.
  • HDPE high density polyethylenes
  • the cumulative amount of optional other polymers can range from 0 to about 50 weight percent of the total thermoplastic compound.
  • the compound of the present invention can include conventional plastics additives in an amount that is sufficient to obtain a desired processing or performance property for the compound.
  • the amount should not be wasteful of the additive nor detrimental to the processing or performance of the compound.
  • compounding PPS other compounding ingredients are desirably incorporated into the PPS to produce compounding formulas.
  • Other compounding ingredients can include fillers, pigments and colorants if desired, processing lubricants, impact modifiers, uv-stabilizers, other processing aids, as well as other additives such as biocides or flame retardants.
  • Fillers ordinarily are used to reduce cost and gloss and can include conventional calcium carbonates, clay, talc, mica, and diatomaceous earth fillers.
  • Useful pigments and colorants can be organic, but preferably mineral such as titanium dioxide (which also serves as a uv-stabilizer).
  • Impact modifiers are useful in PPS to increase toughness and can include chlorinated polyethylenes, ABS, acrylic polymers and copolymers, or methacrylic copolymers such as methylmethacrylate-butadiene-styrene (MBS) or olefins functionalized with carboxylic acids anhydrides or epoxides.
  • MVS methylmethacrylate-butadiene-styrene
  • Other processing aids for extruding PPS in complex profiles include acrylic or styrene-acrylonitrile copolymers to prevent edge tear in the extrusion of complex profiles or configurations.
  • Lubricants can be used to reduce sticking to hot processing metal surfaces and can include polyethylene, paraffin oils, and paraffin waxes in combination with metal stearates. Other lubricants include metal carboxylates, and carboxylic acids.
  • the cumulative amount of optional additives can range from 0 to about 40 weight percent of the total thermoplastic compound, depending on the type of additive and desired processing or performance property to be changed from the compound without such additive(s) therein. Without undue experimentation, one skilled in the art can determine the appropriate amounts using statistical techniques such as Design of Experiments. [00054] Processing
  • the preparation of compounds of the present invention is uncomplicated to those skilled in the art of thermoplastic compounding.
  • the compound of the present can be made in batch or continuous operations.
  • Mixing in a continuous process typically occurs in an extruder that is elevated to a temperature that is sufficient to melt the polymer matrix with addition either at the head of the extruder or downstream in the extruder of the solid ingredient additives.
  • Extruder speeds can range from about 50 to about 500 revolutions per minute (rpm), and preferably from about 100 to about 300 rpm.
  • the output from the extruder is pelletized for later extrusion or molding into polymeric articles.
  • the ingredients Prior to extruding at temperatures sufficient to melt the PPS, the ingredients are physically mixed together using a Henschel mixer. Contrary to the disclosures of the Miller patents which teach grinding the carbon black particles with the graphite particles, the processing of the present invention begins with mixing of carbon black with the PPS followed by addition of the graphite. This order of mixing improves dispersion of both constituents of the exothermic additive within and throughout the bulk of the extruded PPS article.
  • Mixing in a batch process typically occurs in a Banbury mixer that is also elevated to a temperature that is sufficient to melt the polymer matrix to permit addition of the solid ingredient additives of any optional additive.
  • the mixing speeds range from 60 to 1000 rpm and temperature of mixing can be ambient. Also, the output from the mixer is chopped into smaller sizes for later extrusion or molding into polymeric articles.
  • Compounds can be formed into powder, cubes, or pellets for further extrusion or molding into polymeric heating elements of the present invention.
  • resistive heating can be represented by the following equation (I):
  • V voltage applied to the heating element
  • R resistance within the heating element
  • m the mass of the item to be heated.
  • C p heat capacity of the heating element
  • Tp final or plateau temperature of the heating element.
  • the geometry of the heating element influences its plateau temperature and efficiencies including such factors as its various aspect ratios, overall physical dimensions, distance between electrodes, surface area, and the like.
  • Equation II which expresses a steady state condition, assumes no essential change in ambient temperature either by the heating element or some outside influence.
  • Energy efficiency of a heating element of the present invention is determined by experimental results using such techniques as bomb calorimetry, which takes into consideration such factors as mass of water, specific heat of water (4.18 J/g-°C), power to the system, initial and final temperature of water, and duration of the experiment. Because there is no heat dissipation into the environment in a bomb calorimetry apparatus, Equation I is transformed into
  • Equation II of between about 0.077 and 4.128 Watts, respectively. Moreover, the temperatures are reached by using voltages that seem far less than power consumption of appliance operating with conventional household voltages of
  • any article that needs to be heated, in whole or in part, can benefit from a heating element of the present invention, especially when considering those articles which presently use metal rods or wires.
  • consumer appliances benefit.
  • Non-limiting examples of consumer appliances include heating blankets, heating ovens, heating dryers, milk warmers, hot plates and grills, etc.
  • any article can be powered via a transformer to reduce voltage from household voltage to any desired lower voltage for powering the heating element to reach a desired plateau temperature according to Equation I above.
  • FIG. 1-5 Demonstration of the practicality of the present invention is shown in Figs. 1-5.
  • Each of the Figs is an image from a digital video showing the process of frying an egg on a surface made from a compound of the present invention.
  • the surface pre-heated to a plateau temperature of 121 0 C
  • a total of 1919.7 Joules was used to fry the egg.
  • the temperature can be controlled by a rheostat which controls electrical energy input to the thermoplastic article.
  • the electrical energy can be alternating current or direct current.
  • Heating elements can be extruded as wires having diameters ranging from about 0.1 to about 0.25 cm or as rods having diameters ranging from about 0.25 to about 1.5 cm. Additionally, because the heating element is a thermoplastic polymer, heating elements can be molded into any desired three dimensional shape to provide a source of high efficiency, low power heat to any other material. It is not inconceivable for the shape of the final molded article to conform around the material to be heated, whether the material be a gas, a liquid, or a solid. Because the heating element is thermoplastic, very complex shapes can be achieved, using molding techniques known to those skilled in the art.
  • any type of current arrestor such as an inline fuse, to assure that no more than a specific amount of electrical energy is to be delivered to the exothermic thermoplastic heating element of the present invention.
  • An inline fuse would forestall excessive electrical energy being delivered to the article that would otherwise generate such heat as to degrade or melt the polyphenylene sulfide in the heating element or harm any component of any device such as an appliance that includes the heating element or a device or article in the vicinity of the heating element.
  • Electrodes Any form of electrode is suitable for connecting articles of the invention to the source of electrical energy. Ranging from alligator metal clips from a consumer retail outlet such as Radio Shack stores to pressure sensitive electrodes from a commercial wholesale outlet such as 3 M Company, the goal of the electrode is to connect the article to the source of electrical energy without excessive loss of energy. Electrodes can be insert-molded as well as integral to the part.
  • the carbon black was dry-mixed in a Henschel mixer for about 2 minutes followed by addition of PPS and mixing for about 2 minutes, followed by addition of the graphite, if any, and continued mixing for about 2 minutes.
  • Table 3 shows the formulations, exothermic properties, and physical properties of the test bars.
  • Table 3 shows several unexpected results based on the following factors. Plateau temperature is dependent on both formulation and voltage. Resistance is nearly constant at a given voltage (15 volts) over the temperature range during resistive heating. Current draw is dependent on resistance at plateau temperature for a given voltage and that voltage. Power consumption is dependent on voltage and current at plateau temperature. [00097] With these factors and viewing especially the results of Example
  • Example 9 The compound of Example 9, having been molded into a plaque was tested for its ability to fry a chicken egg.
  • Fig. 1 shows the image of the test plaque, about 1 1.43 cm in diameter and about 0.32 cm thick, having electrodes attached and energized with 45 volts to reach a plateau temperature of 121 0 C.
  • the current measured at the plateau temperature was 0.47 amps, and the rate of power consumption was
  • Fig. 2 shows an image of the chicken egg being broken and spilled onto the surface of the test plaque operating at the plateau temperature of
  • Fig. 3 shows the cooking of the egg after 30 seconds from the image of Fig. 2. It is apparent that the albumin is beginning to turn opaque white.
  • Fig. 4 shows the cooking of the egg after 150 seconds from the image of Fig. 2. It is apparent that the albumin is fully cooked and the yolk is firm.
  • Fig. 5 shows the completion of the cooking of the egg after 210 seconds from the image of Fig. 2.
  • the compounds of the present invention can replace metallic surfaces to literal])' fry an egg.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Thermal Sciences (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Resistance Heating (AREA)

Abstract

L'invention concerne des éléments chauffants réalisés avec un additif exothermique dans un composé de sulfure de polyphénylène. Ces éléments chauffants sont très efficaces et utilisent peu de puissance pour produire des températures allant d'environ 30°C à environ 250°C. Ces éléments chauffants peuvent être utilisés dans n'importe quel appareil électrique d'usage industriel ou domestique.
PCT/US2007/081242 2006-10-13 2007-10-12 Éléments chauffants basse puissance utilisant des composés exothermiques de sulfure de polyphénylène Ceased WO2008046047A1 (fr)

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US60/829,505 2006-10-13

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5586214A (en) * 1994-12-29 1996-12-17 Energy Convertors, Inc. Immersion heating element with electric resistance heating material and polymeric layer disposed thereon
US20050070658A1 (en) * 2003-09-30 2005-03-31 Soumyadeb Ghosh Electrically conductive compositions, methods of manufacture thereof and articles derived from such compositions
US7085482B2 (en) * 2004-09-20 2006-08-01 Aquarium Pharmaceuticals, Inc. Aquarium water heater

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5586214A (en) * 1994-12-29 1996-12-17 Energy Convertors, Inc. Immersion heating element with electric resistance heating material and polymeric layer disposed thereon
US20050070658A1 (en) * 2003-09-30 2005-03-31 Soumyadeb Ghosh Electrically conductive compositions, methods of manufacture thereof and articles derived from such compositions
US7085482B2 (en) * 2004-09-20 2006-08-01 Aquarium Pharmaceuticals, Inc. Aquarium water heater

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