HK1221329B - High temperature thermal cutoff device - Google Patents

Description

High temperature thermal cutoff device

This application is a divisional application of a patent application filed on August 5, 2009, with application number 200910211606.9 and invention name “High-temperature thermal cutoff device”.

Technical Field

The present invention relates to electrical current interruption devices and, more particularly, to high temperature current interruption safety devices or thermal cut-offs that provide protection against overheating conditions.

Background Art

The descriptions in this section merely provide background information related to the present disclosure and may not constitute prior art.

The operating temperature of electrical appliances, electronic devices, motors, and other electrical devices generally has an optimal range. The temperature range at which system components may be damaged or a device may become a potential safety hazard in the appliance or to the end user serves as an important detection limit. A variety of devices are capable of sensing this over-temperature threshold. Specific devices that can sense over-temperature thresholds and interrupt current flow include thermal fuses, which operate only within a very narrow temperature range. For example, tin-lead alloys, indium-tin alloys, or other metal alloys that form eutectic metals are not suitable for electrical appliances, electronic devices, electrical and motor equipment because they have an undesirably wide temperature response threshold and/or a detection temperature outside the required safety range.

Summary of the Invention

One type of device particularly well-suited for overheat detection is a current-interrupting safety device known as a thermal cutoff (TCO), which is capable of both temperature detection and simultaneous current interruption when necessary. Such TCO devices are typically installed between the current source and the electrical component in electrical equipment so that if a potentially harmful or dangerous overheat condition occurs, the TCO can interrupt circuit continuity. TCOs are typically designed to irreversibly interrupt the flow of current to the equipment. High-temperature electrical appliances and equipment require the use of robust overheat detection devices with high holding temperatures exceeding the operating temperature and/or the holding temperatures of conventional TCO designs. Thus, in various aspects, the present invention provides stable, reliable, and robust high-temperature TCO devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG1 is an enlarged cross-sectional view of an exemplary thermal cutoff device structure;

FIG2 depicts the thermal cutoff device structure of FIG1 after the thermal pellet has undergone a physical transformation and the current interruption activation assembly has caused the electrical switch to break continuity and change the operating conditions of the thermal cutoff device;

FIG3 is a side perspective view illustrating a current interruption initiating assembly;

4 is a side view of a sliding contact member of the current interruption activation assembly switch structure of FIG. 1 ;

FIG5 is a side view of a spring of the current interrupt activation assembly of FIG1 ;

FIG6 is a cross-sectional view of the ceramic bushing of FIG1;

FIG7 is a front view of the thermal particle of FIG1 .

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

Many safety circuit-breaker devices, including thermal cutoff circuit breakers (TCOs), meet requirements for a wide range of application temperatures and interrupt current flow above a threshold temperature or rating (typically from approximately 60°C up to approximately 235°C). However, for higher temperature applications, such as those greater than or equal to 240°C, conventional TCO devices are unsuitable. In other words, conventional TCO devices no longer meet the performance standards, particularly stability and robustness, required for long-term use as safety devices in high-temperature applications.

In various aspects, the present invention provides a high-temperature thermal cutoff device (hereinafter referred to as "HTTCO"). Such an HTTCO device is capable of switching the continuity of an electrical circuit or electrical communication when the ambient or operating temperature reaches a predetermined threshold temperature. The term "high-temperature" thermal cutoff device is used to indicate that the device has a threshold or activation temperature greater than about 235°C, optionally greater than or equal to 240°C, optionally greater than or equal to about 245°C, optionally greater than or equal to 250°C, optionally greater than or equal to about 255°C, optionally greater than or equal to 260°C, optionally greater than or equal to about 265°C, optionally greater than or equal to 270°C, optionally greater than or equal to about 275°C, optionally greater than or equal to 280°C, optionally greater than or equal to about 285°C, optionally greater than or equal to 290°C, optionally greater than or equal to about 295°C, optionally greater than or equal to 300°C, and in specific aspects, greater than or equal to about 305°C. In certain aspects, the HTTCO exhibits switching characteristics at a threshold or activation temperature of greater than or equal to about 240°C to less than or equal to about 270°C, optionally greater than or equal to about 240°C to less than or equal to about 265°C, greater than or equal to about 240°C to less than or equal to about 260°C, optionally greater than or equal to about 240°C to less than or equal to about 255°C, greater than or equal to about 240°C to less than or equal to about 250°C, optionally greater than or equal to about 240°C to less than or equal to about 245°C, optionally greater than or equal to about 240°C to less than or equal to about 243°C. In certain approaches, at about 240°C, optionally about 241°C, optionally about 242°C, optionally about 243°C, optionally about 244°C, optionally about 245°C, optionally about 246°C, optionally about 247°C, optionally about 248°C, optionally about 249°C, optionally about 250°C, optionally about 251°C, optionally about 252°C, optionally about 253°C, optionally about 254°C, optionally about 255°C, optionally about 256°C, HTTCO exhibits switching characteristics at a threshold or activation temperature of, optionally, about 257°C, optionally about 258°C, optionally about 259°C, optionally about 260°C, optionally about 261°C, optionally about 262°C, optionally about 263°C, optionally about 264°C, optionally about 265°C, optionally about 266°C, optionally about 267°C, optionally about 268°C, optionally about 269°C, and in certain embodiments, optionally about 270°C.

Illustrative testing to demonstrate the performance of a high-temperature thermal pellet composition includes aging an HTTCO device formed according to the teachings of the present invention for at least 1000 hours at a continuous temperature of 235°C. Although the HTTCO ideally meets or exceeds the criteria of the above illustrative experiments, it will be understood by those skilled in the art that the composition is expected to be applicable to both low-pressure and high-pressure applications. Moreover, in some embodiments, the high-temperature thermal pellet composition meets or exceeds the standards of Underwriter Laboratory test UL1020 or IEC/EN 60691, each of which is incorporated herein by reference. In certain embodiments, the HTTCO device meets one or more such standards at the preselected rated high temperature of the device. Although the performance criteria are fully summarized in each of these standards, the outstanding embodiments of the performance tests consistent with the IEC 60691, third edition standard are summarized in Table 1.

In various embodiments, the HTTCO of the present invention includes a sealed housing in which a high-temperature thermal pellet is disposed, the high-temperature thermal pellet having a transition temperature greater than or equal to about 240°C. The transition temperature of the high-temperature thermal pellet is related to the threshold temperature at which the HTTCO device switches or starts, as will be described in more detail below. The high-temperature thermal pellet includes at least one organic compound, which generally has a melting point or melting point range close to a preselected or desired transition temperature. Moreover, the HTTCO has a high-temperature seal disposed in a portion of at least one opening of the housing, the high-temperature seal substantially sealing the housing up to the transition temperature of the high-temperature thermal pellet. The HTTCO also includes a current interruption assembly at least partially disposed within the housing. The current interruption assembly establishes electrical continuity under a first operating condition of the HTTCO and disconnects electrical continuity when the operating temperature exceeds the transition temperature, wherein the first operating condition corresponds to an operating temperature lower than the transition temperature of the high-temperature thermal pellet.

By way of background, an exemplary TCO device is described herein, as illustrated in Figures 1 and 2. Generally, TCO 10 includes a conductive metal housing or casing 11 having a first metallic electrical conductor 12 in electrical contact with a closed end 13 of housing 11. An insulating bushing 14 (e.g., a ceramic bushing) is disposed within an opening 15 of housing 11. Housing 11 also includes a retainer edge 16 that secures ceramic bushing 14 to the end of housing 11. A current interrupt assembly 25, which responds to high-temperature activation, such as by breaking the continuity of an electrical circuit, includes an electrical contact 17 (e.g., a metallic electrical conductor) at least partially disposed within housing 11 through opening 15. Electrical contact 17 extends through insulating bushing 14 and has an enlarged terminal end 18 disposed relative to a side 19 of insulating bushing 14 and a second end 20 extending beyond an outer end 21 of insulating bushing 14. A seal 28 is disposed over the opening 15 and is capable of creating sealing contact with the housing 11 and the exposed portions of the shutter edge 16, the insulating bushing 14, and the second end 20 of the electrical contact 17. In this manner, the interior 29 of the housing 11 is substantially sealed from the external environment 30. "Substantially sealed" means that, although the barrier seal is optionally porous at a microscopic level, the barrier is capable of preventing a significant amount of loss of the thermal pellet material, e.g., the seal retains at least about 95% by mass of the initial thermal pellet, optionally about 96% by mass of the initial thermal pellet, optionally about 97% by mass of the initial thermal pellet, optionally about 98% by mass of the initial thermal pellet, optionally about 99% by mass of the initial thermal pellet, optionally about 99.5% by mass of the initial thermal pellet, and in certain aspects, optionally about 99.9% by mass of the initial thermal pellet, within the housing through continuous operation at 235°C for 1000 hours.

The current interrupt assembly 25, which is activated or switched to change the continuity of the circuit, further includes a sliding contact member 22 formed of a conductive material, such as a metal, disposed within the interior of the housing 11 and having resilient peripheral fingers 23 ( FIG. 4 ) configured to slideably engage an internal peripheral surface 24 of the housing 11 to provide electrical contact therebetween. Furthermore, the sliding contact member 22 is configured to electrically contact the terminal 18 of the electrical contact 17 when the operating temperature of the TCO is below a predetermined threshold set point temperature of the TCO device.

The current interrupt assembly 25 also includes a tensioning mechanism, which may include multiple tensioning mechanisms. The tensioning mechanism 25 biases the sliding contact member 22 toward the terminal end 18 relative to the electrical contact 17 to establish electrical contact under a first operating condition (where the operating temperature is below the threshold temperature of the TCO device, as described below). As shown in Figures 1 and 2, the tensioning mechanism includes a pair of springs 31, each disposed on opposite sides of the sliding contact member 22. The springs 31 include a compression spring 26 and an expansion trip spring 27.

As shown in FIG3 , a thermally responsive pellet or thermoparticle 25 is disposed within the housing 11 relative to the end wall 13 of the housing 11. A compression spring 26 is positioned in a compressed state between the solid thermoparticle 25 and the sliding contact member 22. In the exemplary arrangement shown, the compression force of the compression spring 26 is generally greater than the force of an expansion release spring 27 disposed between the contact member 22 and the insulating bushing 14, causing the sliding contact member 22 to bias toward and electrically contact the enlarged end 18 of the electrical contact 17. In this manner, an electrical circuit is established between the first electrical conductor 12 and the electrical contact 17 via the conductive housing 11 and the sliding contact member 22.

As described above, the TCO device is designed to include a thermal pellet 25 that is reliably stable under a first operating condition (where the operating temperature, such as the temperature of the ambient environment 30, is below a threshold temperature), but reliably transitions to a different physical state under a second operating condition when the operating temperature meets or exceeds the threshold temperature. Under such conditions, when the operating temperature meets or exceeds the threshold temperature, as shown in FIG. 2 , the thermal pellet 25 melts, liquefies, softens, volatilizes, or otherwise transitions to a different physical state under adverse heating conditions.

The spring 31 is adapted to expand and release, as shown by the expansion release spring 27 in FIG5 , and through the relationship between a specific force and the length of the compression spring 26 and the expansion release spring 27, the sliding contact member 22 moves out of electrical contact with the end 18 of the electrical contact 17 in the manner shown in FIG2 , thereby interrupting and breaking the circuit between the terminal conductor 12 and the electrical contact 17 connected by the thermal fuse structure 10 (through the housing 11 and the sliding contact member 22), and maintaining the circuit open, as shown in FIG2 .

The thermal cutoff device described herein is for illustrative purposes only and is exemplary and should not be construed as limiting in certain embodiments. In certain embodiments, various components, designs, or operating principles may vary in number or design. Many other thermal switches or fuse devices are known in the art and are also contemplated.

In various embodiments, the high-temperature thermal pellet composition taught by the present invention is thermally and chemically stable, reliable, and robust for use in HTTCO applications. Preferably, the high-temperature thermal pellet composition will include one or more organic compounds, such as crystalline organic compounds. In various embodiments, the high-temperature thermal pellet composition is designed to have a transition temperature that allows the HTTCO device to have a final temperature (Tf) (also known as the activation or threshold temperature), at which the internal contacts (internal contacts) break electrical continuity due to structural changes in the thermal pellet composition, which in turn causes, for example, the opening of the tension adjustment mechanism. The transition temperature of the high-temperature thermal pellet thus directly corresponds to the threshold temperature _Tf of the HTTCO device, thereby initiating the switching of continuity. As described above, the transition temperature generally refers to the temperature at which the thermal pellet melts, liquefies, softens, volatilizes, or otherwise transforms into a different physical state, thereby transforming from a solid state with structural rigidity to a form or state that loses structural rigidity through contraction, displacement, or other physical change, which causes the internal electrical contacts to separate from the tension adjustment mechanism due to applied tension. Thus, as used herein, once a thermal particle material reaches its transition temperature, it means that the material no longer has the structural rigidity required to maintain a tension regulating structure, such as, for example, a switch in a held open or held closed position according to an HTTCO device.

As referred to herein, this transition temperature is also referred to as the "melting point"; however, the compounds in the thermal pellet components do not need to completely melt in the conventional sense to achieve separation of electrical contacts, thereby disconnecting the internal furnace and electrical continuity. As those skilled in the art will appreciate, the melting point temperature is the temperature at which a compound or component transitions from a solid to a liquid state, which may occur over a range of temperatures rather than at a single, discrete temperature point. In some embodiments, by way of non-limiting example, the high-temperature thermal pellet may soften or sublime rather than melt to achieve separation of electrical contacts, thereby disconnecting the circuit. Melting point temperatures can be measured using a variety of instruments, such as those manufactured by Thomas Hoover, Mettler, and Fisher-Johns. Differential scanning calorimetry (DSC) is also commonly used. Different measurement techniques may yield different melting points. For example, optical analysis methods such as the Fisher-Johns method determine the transition from solid to liquid by measuring the light transmittance of a sample. Earlier optical methods may be subject to more severe observation errors than more modern light beam transmittance melt point indicators. Additionally, early techniques for determining melting points (before the availability of digital high-speed scanning capabilities) allowed for a wider range of results for melting points and other transitions. Similarly, before the advent of HPLC and other precise analytical techniques for determining purity, for example, the melting point of a sample measured by DSC (which measures, for example, changes in crystallinity (solid-solid) and thermal flow behavior of solid to liquid phase changes) may indicate solid-solid phase transitions (such as dehydration or hydroxyl bond cleavage) of impurities that may have been reported as melting points, as well as solid-liquid phase transitions at the melting point of the material of interest. Thus, in various embodiments, ingredients may be selected for use in thermal pellets that empirically exhibit desirable physical changes that will enable the thermal pellets to undergo physical changes without necessarily being associated with an expected melting point range.

In some embodiments, the thermal pellet 25 has a relatively rapid and repeatable collapse rate, meaning that once the environment 30 reaches the threshold temperature, the rate of physical collapse of the thermal pellet component 25 is relatively high. For example, one method for testing the thermal pellet collapse rate is through thermomechanical analysis (TMA), in which the thermal pellet is rapidly heated to a temperature within a range of 10°C-15°C from the expected melting point, and then the heating rate is selected, for example, to be approximately 0.5°C/min over the entire expected melting point temperature range. Simultaneously, at the beginning of the test and throughout the heating process, the physical height of the thermal pellet is measured, thereby measuring the displacement from the upper surface of the thermal pellet to the underlying substrate (on which the thermal pellet is initially located). The thermal pellet height collapse rate measured in microns/°C from the beginning to the end of the transition temperature is related to the thermal pellet collapse rate, for example, a 75% reduction in pellet height from the threshold temperature within approximately 100 microns/°C, optionally approximately 500 microns/°C, and optionally approximately 1000 microns/°C. In various embodiments, the solid-liquid phase transition temperature and the thermal bead collapse rate are both significant characteristics of the thermal bead 25. This rapidity of the thermal bead collapse ensures sufficient separation of the electrical contacts in the HTTCO, thereby avoiding unwanted arcing, which could melt various components and potentially affect HTTCO performance. Methods for measuring and quantifying this thermal bead collapse rate are further detailed below.

In some embodiments, the thermal pellets include one or more organic compounds having a melting point temperature (mp) that occurs within a certain temperature range corresponding to a desired transition temperature. For example, in some embodiments, the high-temperature thermal pellets include one or more organic compounds having a melting point temperature (mp) that is within about 5°C below the transition temperature and within about 2°C above the transition temperature (that is, where T-5°C ≤ mp ≤ T+2°C), where T is the transition temperature.

In various embodiments, the high-temperature thermal pellet component includes an organic compound or material selected to meet one or more of the following criteria. In certain embodiments, the organic component selected for the high-temperature thermal pellet has a relatively high chemical purity. For example, in certain embodiments, ideal candidate chemicals for the high-temperature thermal pellet component have a purity grade ranging from approximately 95% to 99+%. In certain embodiments, the organic component selected for the high-temperature thermal pellet is particularly suitable for handling, processing, and toxicity characteristics. In certain embodiments, the organic compound or chemical component selected for the high-temperature thermal pellet component has a median lethal dose ( _LD50 ) of less than or equal to approximately 220 mg/kg (ppm) for mice; less than or equal to approximately 400 mg/kg (ppm) for rabbits; and less than or equal to approximately 350 mg/kg (ppm) for rats. Additionally, in certain embodiments, the organic chemical component selected for the high-temperature thermal pellet ideally does not have documented carcinogenic, mutagenic, neurotoxic, reproductive, teratogenic, and/or other adverse health or epidemiological effects. In other embodiments, the organic component used in the high-temperature thermal pellet composition is selected so that other reactive residues, reaction products formed during the manufacturing process, decomposition products, or decomposition products or other species that may be formed during manufacturing, storage or use are absent, minimized or can be purified and removed.

In some embodiments, the ingredients selected for use in high-temperature thermal pellets exhibit long-term stability. For example, the ingredients are optionally selected to be temperature-stable or thermally stable. In other words, the following compounds may be rejected as viable candidates: they exhibit decomposition or volatility characteristics within a temperature range of about 10°C, optionally about 20°C, optionally about 30°C, optionally about 40°C, optionally about 50°C, optionally about 60°C, optionally about 75°C, and in some embodiments, optionally about 100°C from the transition temperature or melting point of the organic compound. In addition, in some embodiments, chemical ingredients suitable for use as high-temperature thermal pellet components will not exhibit a strong potential for oxidation or decomposition that is induced by heat and promoted by aging.

In addition, compositions suitable for use as high-temperature thermal pellets include those that are "non-conductive," meaning that the composition can withstand a 240-volt, 60-Hz sinusoidal potential between two electrodes for at least 1 minute at a temperature at least 5°C higher than the _Tf final temperature without conducting more than 250 mA. In certain embodiments, the selected composition can withstand a 240-volt, 60-Hz sinusoidal potential between two electrodes for at least 1 minute at a temperature at least 10°C higher than the _Tf final temperature without conducting more than 250 mA. In other embodiments, the high-temperature thermal fuse composition is optionally capable of withstanding a 240-volt, 60-Hz sinusoidal potential between two electrodes for at least 1 minute at a temperature at least 50°C higher than the _Tf final transition temperature without conducting more than 250 mA.

In various approaches, the organic chemical composition selected for the high temperature thermal composition has an initial melting point temperature of at least about 240°C, optionally about 241°C, optionally about 242°C, optionally about 243°C, optionally about 244°C, optionally about 245°C, optionally about 246°C, optionally about 247°C, optionally about 248°C, optionally about 249°C, optionally about 250°C, optionally about 251°C, optionally about 252°C, Optionally about 253°C, optionally about 254°C, optionally about 255°C, optionally about 256°C, optionally about 257°C, optionally about 258°C, optionally about 259°C, optionally about 260°C, optionally about 261°C, optionally about 262°C, optionally about 263°C, optionally about 264°C, optionally about 265°C, optionally about 266°C, optionally about 267°C, optionally about 268°C, optionally about 269°C 9°C, optionally about 270°C, optionally about 271°C, optionally about 272°C, optionally about 273°C, optionally about 274°C, optionally about 275°C, optionally about 276°C, optionally about 277°C, optionally about 278°C, optionally about 279°C, optionally about 280°C, optionally about 281°C, optionally about 282°C, optionally about 283°C, optionally about 284°C, optionally about 285°C, optionally About 286°C, optionally about 287°C, optionally about 288°C, optionally about 289°C, optionally about 290°C, optionally about 291°C, optionally about 292°C, optionally about 293°C, optionally about 294°C, optionally about 295°C, optionally about 296°C, optionally about 297°C, optionally about 298°C, optionally about 299°C, optionally about 300°C, and in certain embodiments, optionally about 301°C. In certain embodiments, the melting point of the organic component used in the high-temperature thermal pellets is greater than 275°C, and in certain embodiments, optionally greater than about 300°C. In certain embodiments, organic compounds that meet the above selection criteria and can remain solid at a temperature range of 50°C to at least 235°C are ideal. In certain aspects, compounds that can maintain a stable solid state up to 236°C are desirable, optionally up to about 237°C, optionally up to about 238°C, optionally up to about 239°C, optionally up to about 240°C, optionally up to about 245°C, optionally up to about 250°C, optionally up to about 255°C, optionally up to about 260°C, optionally up to about 265°C, optionally up to about 270°C, optionally up to about 275°C, optionally up to about 280°C, optionally up to about 285°C, optionally up to about 290°C, optionally up to about 295°C, and in certain aspects optionally up to or exceeding about 300°C.

Suitable candidate organic compounds for the high-temperature thermal pellets of the HTTCO devices of the present invention optionally include the following additional characteristics. In certain embodiments, the use of organic chemicals with acidic structures (e.g., structures with multiple hydroxyl groups or structures that may be ionically active in an electric field) can be avoided or minimized. Furthermore, certain organic compounds with sulfur-containing side groups can be avoided in certain applications because they have bond structures that are easily broken in an electric field.

In certain embodiments, the organic compound that can be used as the thermal fuse component here can be selected based on the chemical behavior of the chemicals related to and interacting with the sealing material used for the HTTCO housing, which is typically a porous polymer structure. Suitable organic compounds for high-temperature thermal particles include those with relatively large molecular sizes, such as organic molecules with cyclic structures, such as those that occupy dimensional space due to bending or side groups. In certain schemes, appropriate candidate chemicals with flat or unbent configurations or chemical structures should be avoided, which may have shear mobility or relatively lossless navigation through the pores in the sealing material. Similarly, in certain schemes, the organic compounds selected for high-temperature thermal particle components have relatively large molecular complexity, such as organic polycyclic structures with complex bond orientations that can produce irregular dimensional space filling configurations or structures. For example, certain chemical structures that "entangle" in high-energy states are ideal because they are relatively large organic species with complex side chains.

In addition, suitable compounds for the high temperature thermal components of the present invention include those compounds with high molecular bond strength, for example, in ring structures (such as polyaromatic rings, polyalkyl rings, heteroalkyl rings, including condensed ring structures sharing one or more common bonds). Chemical structures with high in-bond strength (introbond strength) between other rings or side groups are also suitable organic species. Moreover, compounds with intermolecular bond strength (intermolecular bond strength) (including structures with non-polar or relatively low polarity strength with high instantaneous polarity) are also suitable. For example, structures with side groups having "bond affinity" to the parent rings or side groups of other molecular groups are ideal.

High melting point aromatic compounds have been shown to provide unique bond strength, relatively large molecular size, and electronegativity characteristics that are desirable for use as high temperature thermally-fuse organic compounds when formulated into solid forms such as pellets. In certain embodiments, the thermally-fuse component may include one or more aromatic compounds, one or more five-membered ring compounds, polymers, copolymers, and mixtures thereof.

In certain embodiments, the high-temperature thermal pellet may include multiple organic compounds as primary components. Therefore, the high-temperature thermal pellet composition used in the HTTCO device of the present invention optionally includes one or more organic compounds that provide a transition temperature greater than or equal to approximately 240°C. In certain embodiments, multiple such organic components may be used so that the melting point of the resulting mixture provides a predetermined ideal transition temperature for the thermal pellet composition. As known to those skilled in the art, the combination of different organic components or other ingredients will produce a thermal pellet transition temperature, _Tx , represented by the following relationship: where _Xn is the mass fraction of each individual component present in the thermal pellet composition (where n is greater than 1), and " _mpn " is the initial melting point temperature of each individual component. In this way, the transition temperature of the thermal pellet can be predicted based on the melting points of the various organic compounds present in the thermal pellet composition. In certain embodiments, the thermal pellet composition may include a single organic component as the primary component to achieve a _Tx greater than or equal to approximately 240°C. In other embodiments, the thermal pellet composition may include multiple organic components, such as two or more organic compounds, to achieve a _Tx greater than or equal to approximately 240°C. Such organic compounds may have different melting temperatures or other properties and may be mixed by co-precipitation, co-crystallization, mixing, blending, grinding, or other suitable means known in the art.

In some embodiments, the high-temperature thermal pellet component includes one or more compounds, including compounds having a chemical structure containing one or more six-membered rings, the chemical structure having a basic carbon skeleton with constituent side groups. In some embodiments, the thermal cutoff component may include one or more chemical entities generally described by the structural repeating unit (SRU): (-PhRR'-) _n , where R and R' can be the same or different constituent side groups, and where n can also be a value greater than or equal to 1, indicating the repetition of the structural repeating unit (SRU). In some embodiments, the high-temperature thermal pellet component may include one or more five-membered ring structures, where the side groups and/or SRU may have or can be the same or different entities (e.g., having different constituent side groups), such as, as an example, where the thermal cutoff component is described by the standard SRU formula (-Ph- ^RR1 ) _n -(-Ph ^{- R2R3} ) _m , where R and ^R1 are different side groups from ^R2 and ^R3 . In some embodiments, R and ^R1 can be the same or different, and similarly, ^R2 and ^R3 can be the same or different.

In some embodiments, the term "hydrocarbyl" is generally used here to represent an organic group comprising a carbon chain to which hydrogen and optionally other elements are attached. The CH ₂ or CH group and the C atom of the hydrocarbyl carbon chain can be replaced with one or more heteroatoms (i.e., non-carbon atoms). Suitable heteroatoms include, but are not limited to, O, S, P, and N atoms. Exemplary hydrocarbyl groups may include, but are not limited to, alkyl, alkenyl, alkynyl, ether, polyether, thioether, straight or cyclic sugars, ascorbic acid, aminoalkyl, hydroxyalkyl, sulfanyl, aryl and heteroaryl, optionally substituted tricyclic molecules, amino acids, polyols, glycols, groups with a mixture of saturated and unsaturated bonds, carbocycles, and combinations of these groups. The term also includes straight, branched, and cyclic structures or combinations thereof. Hydrocarbyl groups are optionally substituted. Hydrocarbyl substitution includes substitution of one or more carbons in the group with a molecular moiety containing heteroatoms.

Suitable substituents for the hydrocarbon group include, but are not limited to, halogen, including chlorine, fluorine, bromine, and iodine; OH; SH; -N-OH; NH; NH ₂ ; -C-NH ₂ =S; CH; -CH-O; C=N; -CN=O; -C-NH ₂ =O; C=O; COH; -C-NH ₂ =S; CO ₂ ; H; -CHBN; -CHP; OR ¹ ; SR ¹ ; NR ¹ ; R ″ ; CONR ¹ R ² ; and combinations thereof, wherein R ¹ and R ² is independently an alkyl, an unsaturated hydrocarbon or an aryl. The term alkyl takes its ordinary meaning in the art and is intended to include straight chain, branched chain and cycloalkyl groups. The term includes, but is not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, 2-methylbutyl, 1-methylbutyl, 1-methylpropyl, 1,1-dimethylpropyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2-ethylbutyl, 1-ethylbutyl, 1,3-dimethylbutyl, n-heptyl, 5-methylhexyl , 4-methylhexyl, 3-methylhexyl, 2-methylhexyl, 1-methylhexyl, 3-ethylpentyl, 2-ethylpentyl, 1-ethylpentyl, 4,4-dimethylpentyl, 3,3-dimethylpentyl, 2,2-dimethylpentyl, 1,1-dimethylpentyl, n-octyl, 6-methylheptyl, 5-methylheptyl, 4-methylheptyl, 3-methylheptyl, 2-methylheptyl, 1-methylheptyl, 1-ethylhexyl, 1-propylpentyl, 3-ethylhexyl, 5,5-dimethylhexyl, 4,4-dimethylhexyl, 2,2-diethylbutyl, 3,3-diethylbutyl and 1-methyl-1-propylbutyl. Alkyl groups are optionally substituted. Lower alkyl groups are C ₁ -C ₆ alkyls and include methyl, ethyl, n-propyl and isopropyl, etc.

The term "cycloalkyl" refers to an alkyl group having a hydrocarbon ring, particularly those having 3 to 7 carbon atoms. Cycloalkyl groups include those having an alkyl substitution on the ring. Cycloalkyl groups may include straight and branched molecular moieties. Cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclononyl. Cycloalkyl groups may be optionally substituted.

The aryl group may be substituted with one, two or more simple substituents including, but not limited to, _{lower alkyl, such as C1-C4 alkyl} , methyl, ethyl, propyl, butyl; halogen, such as chlorine, bromine; nitro; sulfato; sulfonyloxy; carboxyl; carbonyl-lower alkoxy, such as carbomethoxy, carboethoxy; amino; mono- and di-lower alkylamines, such as methylamino, ethylamino, dimethylamino, methylethylamino; amide; hydroxy; lower alkoxy, such as methoxy, ethoxy; and lower alkanoyloxy, such as acetoxy.

The term "unsaturated alkyl" is used herein to include alkyl groups in which one or more individual carbon-carbon bonds are double or triple bonds. The term includes alkenyl and alkynyl in its most common sense. The term is intended to include groups having more than one double or triple bond or a combination of double and triple bonds. Unsaturated alkyl groups include, without limitation, unsaturated straight, branched, or cyclic alkyl groups. Unsaturated alkyl groups include, without limitation, vinyl, allyl, propenyl, isopropenyl, butenyl, pentenyl, hexenyl, hexadienyl, heptenyl, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, cyclopentadienyl, 1-propynyl, 2-butynyl, 2-methyl-2-butynyl, ethynyl, propynyl, 3-methyl-1-propynyl, and 2-heptynyl. Unsaturated alkyl groups are optionally substituted.

Substitution of alkyl, cycloalkyl and unsaturated alkyl groups includes substitution with heteroatom-containing molecular moieties on one or more carbon atoms of the group. Suitable substituents for these groups include, but are not limited to, OH, SH, NH ₂ , COH, CO ₂ H, OR ³ , SR ³ , P, PO, NR ³ R ⁴ , CONR ³ R ⁴ and halogen (especially chlorine and bromine), wherein R ³ and R ⁴ are independently alkyl, unsaturated alkyl or aryl. Suitable alkyl and unsaturated alkyl groups are lower alkyl, alkenyl or alkynyl groups having 1 to about 5 carbon atoms.

The term "aryl" is generally used herein to refer to an aromatic group having at least one ring containing a conjugated π electron system, including, without limitation, carbocyclic aryl, aralkyl, heterocyclic aryl, biaryl, and heterocyclic biaryl, all of which are optionally substituted. Preferred aryl groups have one or two aromatic rings. "Carbocyclic aryl" refers to an aryl group in which the aromatic ring atoms are all carbon atoms, including, without limitation, phenyl, biphenyl, and naphthyl.

"Aralkyl" refers to an alkyl group substituted with an aryl group. Suitable aralkyl groups include benzyl, phenethyl, and the like, and may be optionally substituted, for example, pyridylmethyl substituted with nitrogen. Aralkyl groups include those having aromatic moieties including heterocyclic and carbocyclic rings.

"Heteroaryl" refers to a group having at least one heteroaromatic ring with 1 to 3 heteroatoms in the heteroaromatic ring, the remainder being carbon and hydrogen atoms. Suitable heteroatoms include, without limitation, oxygen, sulfur, and nitrogen. Heteroaromatic groups include furyl, thienyl, pyridyl, pyrrolyl, N-alkylpyrrolo, pyrimidinyl, pyrazinyl, imidazolyl, benzofuranyl, quinolyl, and indole, and the like, all of which are optionally substituted.

"Heterocyclic biaryl" refers to a heterocyclic aryl group in which a phenyl group is substituted with a heterocyclic aryl group at the ortho, meta, or para position to the point of attachment of the phenyl ring to decalin or cyclohexane. Heterocyclic biaryl groups include groups having a phenyl group substituted with a heteroaryl ring, etc. The aromatic ring of the heterocyclic aryl group may be optionally substituted.

"Biaryl" refers to a carbocyclic aromatic group in which a phenyl group is substituted with a carbocyclic aromatic group in the ortho, meta, or para position at the point of attachment of the phenyl ring to the decalin or cyclohexane structure. Biaryl groups include a first phenyl group substituted with a second phenyl ring in the ortho, meta, or para position at the point of attachment of the first phenyl ring to the decalin or cyclohexane structure. Para substitution is preferred. The aromatic ring of the biphenyl group may be optionally substituted.

Aryl substitution includes substitution with non-aryl groups (excluding H) on one or more carbons of the aromatic ring _or , if applicable, on one or more heteroatoms in the aromatic group. In contrast, unsubstituted aryl refers to an aryl group in which all aromatic ring carbons are replaced with H, such as unsubstituted phenyl ( _-C6H5 ) or naphthyl _{( -C10H7} ). Suitable substituents for aryl include alkyl, unsaturated alkyl, halogen, OH, SH, NH2, _COH , _CO2H , ^OR5 , ^SR5 , ^NR6 , ^R6 , ^CONR5R6 , wherein ^{R5 and R6} are independently alkyl, unsaturated alkyl, or aryl. Preferred substituents are OH, SH, ^OR5 , and ^SR5 , wherein ^R5 is lower alkyl, i.e., an alkyl group having 1 to about 5 carbon atoms. Other preferred substituents are halogen (more preferably chlorine or bromine), and lower alkyl and unsaturated lower alkyl groups having 1 to about 5 carbon atoms. Substituents include bridging groups between aromatic rings in an aryl group, such as _-CO2- , -CO-, -O-, -S-, -P-, -NH-, -CH=CH-, and -( _CH2 ) _l- (where l is an integer from 1 to about 5), especially _-CH2- where l is 1. Examples of aryl groups having bridging substituents include phenylbenzoate. Substituents also include molecular moieties, such as -( _CH2 ) _J- , -O-( _CH2 ) _J- , or -OCO( _CH2 ) _J- , where J is an integer from about 2 to 7, which are suitable for molecular moieties that bridge two ring atoms in a single aromatic ring (e.g., in a 1,2,3,4-tetralinyl group). Alkyl and unsaturated alkyl substituents of aryl groups may also be optionally substituted, as described above for substituted alkyl and unsaturated alkyl groups.

The terms "alkoxy" and "thioalkoxy" (also known as thiolate group (emrcaptide group), sulfur analogs of alkoxy) have their generally accepted meanings. Alkoxy includes, but is not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, tert-butoxy, n-pentoxy, neopentoxy, 2-methylbutoxy, 1-methylbutoxy, 1-ethylpropoxy, 1,1-dimethylpropoxy, n-hexyloxy, 1-methylpentoxy, 2-methylpentoxy, 3-methylpentoxy, 4-methylpentoxy, 3,3-dimethylbutoxy, 2,2-dimethoxybutoxy, 1,1-dimethylbutoxy 1-ethylbutoxy, 2-ethylbutoxy, 1-ethylbutoxy, 1,3-dimethylbutoxy, n-pentoxy, 5-methylhexyloxy, 4-methylhexyloxy, 3-methylhexyloxy, 2-methylhexyloxy, 1-methylhexyloxy, 3-ethylpentoxy, 2-ethylpentoxy, 1-ethylpentoxy, 4,4-dimethylpentoxy, 3,3-dimethylpentoxy, 2,2-dimethylpentoxy, 1,1-dimethylpentoxy, n-octyloxy, 6-methylheptyloxy, 5-methylheptyloxy , 4-methylheptyloxy, 3-methylheptyloxy, 2-methylheptyloxy, 1-methylheptyloxy, 1-ethylhexyloxy, 1-propylpentyloxy, 3-ethylhexyloxy, 5,5-dimethylhexyloxy, 4,4-dimethylhexyloxy, 2,2-diethylbutoxy, 3,3-diethylbutoxy, 1-methyl-1-propylpentyloxy, ethoxymethyl, n-propoxymethyl, isopropoxymethyl, sec-butoxymethyl, isobutoxymethyl, (1-ethylpropoxy)methyl, ( Sulfanyl includes, but is not limited to, sulphur analogs of the alkoxy radicals specifically listed above.

In some embodiments, the R, ^R1 , ^R2 , ^R3 , ^R4 , ^R5 , and ^R6 side groups in the 5- and 6-membered rings can be independently selected from any of the above-described hydrocarbyl substituents, for example, -CH, -CH-O, -CH-OH, _-NH2 , -NH, -CH-N, -CH=O, -N-OH, -CHBN, -CHP, or mixtures thereof.

In certain embodiments, a particularly suitable organic compound for use in the high-temperature thermal pellet composition of the present invention is triptycene (or tryptycene) (9,10-dihydro-9,10-o-benzo-9,10-dihydroanthracene, CAS Registry Number 477-75-8), which has a transition temperature of about 255°C and a melting point temperature range of 255°C to about 257°C. Triptycene is generally classified as a polycyclic aromatic hydrocarbon and is generally represented by the exemplary formula (1):

Triptylene can be prepared by reducing anthraquinone adducts with lithium aluminum hydride or aluminum borohydride, as well as other methods known to those skilled in the art. Triptylene is described in Organic Syntheses, Coll. Vol. 4, pp. 964 (1963), the relevant portion of which is incorporated herein by reference.

In certain other embodiments, a particularly suitable organic compound for use in the high-temperature thermal pellet component is 1-aminoanthraquinone (also known as 1-amino-9,10-anthracenedione, CAS Registry No. 82-45-1), which is classified as a polycyclic aromatic hydrocarbon having pendant groups -C=O and C-NH ₂ , as shown in formula (II):

1-Aminoanthraquinone has an expected transition temperature of about 253°C and a melting point range of 253°C to about 257°C. 1-Aminoanthraquinone (1-AAQ) can be prepared by the reaction of 2-chlorobenzyl chloride and xylene in the presence of a solid acid catalyst or by other methods known in the art. 1-Aminoanthraquinone (also known as 1-amino-9,10-anthracenedione) is described in U.S. Patents 4,006,170 and 4,695,407, the relevant portions of which are incorporated herein by reference.

Based on the criteria discussed above and the estimated melting point temperature ranges set forth below, other representative organic compounds (e.g., the exemplary compounds set forth in Table 2 below) are also considered, by way of example and not limitation, to be very suitable candidates for high-temperature thermal pellet components of the HTTCO device of the present invention. However, the present invention also contemplates a variety of other organic compounds that, although not listed here, meet one or more of the criteria listed above, including melting point data corresponding to a transition temperature greater than about 240°C. As described above, the expected melting point range may vary depending on the analytical technique used (thus, certain compounds have multiple or different melting points), and therefore such ingredients are selected to have an empirical transition temperature that physically transforms and changes point continuity in the thermal pellet at an ideal threshold temperature.

Table 2

In some embodiments, the one or more organic compounds or chemicals are processed to minimize evaporation losses, increase crystallinity, and obtain high purity levels. For example, the one or more organic compounds are processed into a compacted shape such as a pellet or grain by applying pressure in a mold or die. The integrity of the pellet structure is ideally sufficient to withstand the pressure of the HTTCO device, such as withstanding the force applied by the acid and deflecting the springs and sleeves in the HTTCO assembly. The following unique ability of HTTCO is an important feature of the high-temperature thermal sensing component of the present invention: namely, maintaining physical rigidity and spring compression, and thereby maintaining electrical continuity at the TCO operating temperature in a high-temperature device, and further having the ability to physically transform and disconnect the circuit at a rated threshold temperature. For example, as previously described, certain HTTCOs can withstand long-term exposure to the following operating temperatures without disconnecting the electrical continuity of the circuit: the operating temperature is up to a temperature about 5°C lower than the threshold or activation temperature.

The high-temperature thermal particle component can be made into any commercially available form suitable for use in a TCO housing, including particles, pellets, spheres, and any geometric shape known to those skilled in the art. In addition to the organic compounds described above, the high-temperature hot-melt thermal particle component of the present invention may optionally include one or more components selected from the following group: adhesives, pressing aids (pressaid), release agents, pigments, or mixtures thereof. The adhesive component typically softens (melts) at a temperature below the melting point of the organic component, and is mainly used to assist in the production of thermal particles. Although various adhesives known for the formation of thermal particles can be used, suitable adhesives include polyethylene glycol, 1,3-benzenediol, epoxy resins, polyamides, and mixtures thereof. The adhesive is typically present in an amount of up to about 10 wt% of the total ingredients.

In addition, when processing thermal particles, it may be necessary to use lubricants or pressing aids to improve flow and filling properties. For example, many lubricants or pressing aids that have been proven to be useful are calcium stearate, boron nitride, magnesium silicate, and polytetrafluoroethylene. The amount of lubricant present is generally up to about 5wt% of the total thermal particle composition. In some applications, it may also be necessary to add a colorant (such as a pigment) to the thermal melt component to allow for a quick visual inspection of the condition of the thermal particles. In fact, any known pigment that is compatible with the aforementioned thermal melt component can be used. When applied, the amount of pigment present is generally up to about 2wt% of the thermal particle composition.

In certain embodiments, the thermal pellet composition may consist essentially of a single organic component (which is the primary component to achieve a transition temperature of greater than or equal to about 240° C.) and an optional binder, an optional pressing aid, an optional release agent, and/or an optional pigment. Such a thermal pellet composition may include minimal diluents or impurities that do not substantially affect the transition temperature of the thermal pellet composition or the performance of the HTTCO at operating temperatures above the threshold temperature.

Initially, a first high-temperature thermal pellet sample can be prepared with the goal of obtaining a product having a desired transition temperature (e.g., melting point or melt transition temperature) of approximately 240°C. The sample is processed to increase crystallinity and then prepared by mixing approximately 90 wt% to approximately 100 wt% of the chemicals alone or with 10 wt% to approximately 0.25 wt% of an additive (e.g., a binder) in a hammer mill. The amount added to the above-mentioned organic compound can be 5 wt% to 0.25 wt% of a binder (e.g., a polyamide binder, etc.) and 1 wt% to 0.05 wt% of an organic azo pigment. The resulting composition exhibits a transition temperature/melting point of approximately 236°C.

Additional samples can be prepared to produce an HTTCO product having a melting point temperature of approximately 257°C. In this regard, the samples are processed to increase crystallinity and then prepared by mixing between about 90% and about 100% by weight of the chemicals, either alone or with 10% to about 0.25% by weight of an additive (e.g., a binder) in a hammer mill mixer. Added to the organic compounds can be 5% to 0.25% by weight of a binder (e.g., a polyamide binder) and 1% to 0.05% by weight of an organic azo pigment. After blending to homogenize the components, the samples can be analyzed using differential scanning calorimetry (DSC). The resulting composition has a transition temperature/melting point temperature of approximately 257°C.

In addition to exhibiting repeatable transition temperatures, the high temperature thermal cutoff compositions of the present invention are also expected to exhibit clean current interruption characteristics, reduced material and processing costs, and should be flexible to allow custom design of custom thermal cutoffs to meet custom customer needs. In certain aspects, the high melting point organic composition can be formulated using computer software that calculates the melting points of organic compounds, such as, for example, a computer program sold under the trade name TEFLON® manufactured by Daijin Technologies Corp. of South Korea.

In addition, the transition temperatures/melting points of the various ingredients used in the thermal cutoff compositions of the present invention can be measured using a thermogravimetric analyzer coupled with or without mass spectrometry (TGA-MS), differential scanning calorimetry (DSC), and differential thermal analysis (DTA). Equipment for performing these qualitative and quantitative analyses is commercially available, such as the Model Q2000 (DSC) from TA Instruments, New Castle, DE, USA, and the Mettler STARe thermogravimetric analyzer TGA/sDTA851e, coupled to a Balzers ThermoStar mass spectrometer from Mettler-Toledo, Columbus, OH. In addition, for example and without limitation, the ingredients of the present invention can be quantitatively analyzed using known techniques such as proton or carbon nuclear magnetic resonance, mass spectrometry, or Fourier transform infrared spectroscopy.

High temperature sealants

In various embodiments of the present invention, a high-temperature TCO device includes a high-temperature sealant system applied over one or more openings in the housing to provide a barrier between the interior of the HTTCO and the external environment. In various aspects, the high-temperature sealant system or seal is robust, reliable, and maintains integrity even at the high operating temperatures of the HTTCO device. The seal is an important aspect of the reliability and longevity of the HTTCO device because the selection of an appropriate sealing material provides a barrier that maintains the chemical equilibrium within the HTTCO even at the high operating temperatures of the HTTCO and prevents significant loss of thermal pellet material through the seal or barrier.

Thus, in various aspects, the sealing material system provides a secure sealing mechanism over one or more openings in the housing to prevent unwanted sublimation of the thermal pellet and thereby prevent loss of the thermal pellet material. In certain aspects, the reliability of the HTTCO sealing system may be correlated to the life of the HTTCO device, wherein the predetermined life is at least 1000 hours or more at 235°C (reflecting an operating temperature approximately 5°C lower than the rated threshold temperature of 240°C).

In certain aspects, the high temperature sealant system is an epoxy-based system that cures to provide a durable, high temperature, strong seal. A particularly suitable high temperature epoxy system is formed from a precursor comprising one or more diglycidyl ethers of bisphenol A resins, mixed with a hardener such as a modified imidazole hardener or epichlorohydrin.

In various embodiments, the epoxy systems of the present invention are generally prepared according to the manufacturer's recommendations. In certain embodiments, the epoxy systems are prepared in an improved manner that promotes the curing of the epoxy system: that is, a strong mechanical seal is produced between the HTTCO components (metal and ceramic), which can withstand temperatures above about 235°C, optionally above about 240°C, optionally above about 245°C, optionally above about 250°C, optionally above about 260°C, optionally above about 265°C, optionally above about 270°C, optionally above about 275°C, optionally above about 280°C, optionally above about 285°C, optionally above about 290°C, and in certain embodiments, optionally up to about 300°C, by maintaining a stable thermal pellet component and preventing substantial sublimation of the thermal pellet component. In some embodiments, the epoxy systems of the present invention cure to B-stage and/or full advanced or accelerated cure levels under various temperature and relative humidity conditions suitable for producing the desired barrier seal. In certain aspects, a B-stage epoxy cure is a low temperature cure typically conducted at a temperature of about 60°C or less and at a relative humidity of about 0% to about 85%, about 0% to about 85%, optionally about 0 to about 75%, optionally about 0 to about 50%, optionally about 0 to about 40%, and in certain aspects about 0 to about 35%. A polymer seal is generally considered to be B-staged when the seal has a hardness of 75 as indicated by an indentation marked with a Shore D permanent indent. Thus, in certain aspects, curing is performed to achieve a hardness of at least Shore D 75. In certain embodiments, the B-stage cure of the HTTCO device is followed by an accelerated or advanced cure at a higher temperature, for example, at about 150°C to about 175°C for 3 to 5 hours.

Many commercially available epoxy-based systems include at least two or three curable precursors that are mixed together and then cured to form a polymer. In certain embodiments, a suitable high-temperature epoxy-based sealing system for forming a sealant in HTTCO includes a precursor comprising a diglycidyl ether bisphenol A resin and a hardener. In some embodiments, the hardener includes a modified imidazole compound. In certain embodiments, the hardener includes 2-ethyl-4-methyl-1H-imidazole. In certain embodiments, the epoxy sealant is formed by mixing at least two epoxy precursors, wherein the first precursor includes at least one epoxy resin (such as bisphenol A diglycidyl ether), an elastomeric polymer, and neopentyl glycol diglycidyl ether; and the second precursor includes 2-ethyl-4-methyl-1H-imidazole as a hardener. For example, a commercially available diglycidyl ether of bisphenol A and modified imidazole hardener system is available from Henkel Loctite as follows: 210210 Epoxy Resin Part A (Item No. 36745), 210211; Epoxy Hardener Part B (Item No. 36746); and 210209 Epoxy Pigment (Item No. 36745) (this mixed epoxy system is referred to as "C5 Epoxy"). Epoxy Resin Part A of 210211 contains approximately 60-100 wt% of a first patented epoxy resin (which is believed to be a modified bisphenol A diglycidyl ether epoxy resin), 10-30 wt% of a second patented epoxy resin (which is also believed to be a modified bisphenol A diglycidyl ether epoxy resin), 10-30 wt% of neopentyl glycol diglycidyl ether (CAS No. 17557-23-2), 5-10 wt% of a proprietary elastomer, 1-5 wt% of titanium dioxide pigment, and 1-5 wt% of amorphous fumed silica. Epoxy Resin Part B of 210210 contains 60-100 wt% of a proprietary modified imidazole (which is believed to be 2-ethyl-4-methyl-1H-imidazole). 210209 Epoxy Resin Part C contains 30-60 wt% titanium dioxide, 10-30 wt% of a first patented epoxy resin (which is considered to be a modified bisphenol A diglycidyl ether epoxy resin), 10-30 wt% of a second patented epoxy resin (which is also considered to be a modified bisphenol A diglycidyl ether) and 1-5 wt% of a third patented epoxy resin (which is also considered to be a modified bisphenol A diglycidyl ether epoxy resin), 1-5 wt% neopentyl glycol diglycidyl ether, 1-5 wt% alkyl glycidyl ether, 1-5 wt% alumina, 1-5 wt% fumed silica and finally 1-5 wt% of a patented elastomeric polymer.

To prepare the C5 epoxy, mix 80-100 wt% of the resin, Part A, and 0-20 wt% of the hardener, Part B. Part C is optional and can be added at 0-20 wt% to form the final C5 epoxy to be added to a TCO component used to seal a device containing a thermal pellet component.

In another embodiment, the epoxy-based sealant is formed by mixing at least two precursors, wherein the first precursor comprises an epoxy resin or a bisphenol A diglycidyl ether polymer; the second precursor comprises a hardener or curing agent, such as 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; and the third precursor includes a catalyst comprising pyromellitic acid-1,2,4,5-dianhydride, hexahydrophthalic anhydride, and phthalic anhydride.

After applying the curable epoxy material to seal the TCO component and seal one or more openings (as shown in Figures 1-2), the epoxy sealant system is optionally cured. Curing can be performed by any means known in the art, including application of heat, light radiation, etc. In some embodiments, the epoxy sealant material undergoes a B-stage cure, in which the epoxy system is heated to a temperature of about 45°C to about 65°C in a controlled atmosphere with a relative humidity of 0% to 80%. Optionally, a full advanced cure can be performed after the B-stage cure. The advanced cure is optionally performed at a temperature of about 150°C to about 200°C in a controlled atmosphere with a relative humidity of 0% to 5%. In some embodiments, the C5 epoxy sealant is cured by placing the HTTCO device in an oven and heating it at 248°C and 0% relative humidity for about 3 to about 9 hours.

In certain other embodiments, HTTCO can be sealed with a suitable epoxy-based system commercially available from Emerson & Cuming Corp., Billerica, MA USA, which is a bisphenol A diglycidyl ether polymer (Part A), an epichlorohydrin hardener (Part B), and a catalyst (Part C), sold under the trade name 66 Epoxy System (hereinafter referred to as "W66 Epoxy System"). Specifically, the W66 Epoxy System comprises: Part A, which comprises 100 wt% of a bisphenol A diglycidyl ether polymer having an average molecular weight of less than 700; and Part B, which comprises greater than 99 wt% of a 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole hardener in a carrier of less than 0.1 wt% acrylonitrile. Part C of W66 includes a catalyst comprising pyromellitic acid-1,2,4,5-dianhydride (35-50 wt%), hexahydrophthalic anhydride (35-50 wt%), and phthalic anhydride (1-5 wt%).

In the preparation of the W66 epoxy system, 50 wt% to about 80 wt% of Part A is combined and mixed with 50 wt% to about 20 wt% of Part B. Once the W66 epoxy system has been applied to seal the HTTCO component, the W66 epoxy system is optionally cured to a B-stage and/or advanced cure. For example, and not by way of limitation, the W66 sealing system is applied and cured by placing the device in a controlled atmosphere and heating at 40°C and 35% to 85% relative humidity for about 48 to about 96 hours.

Example 1

According to various aspects of the present invention, a high-temperature TCO device is formed as follows. A thermal pellet is formed by mixing 980 g to 1000 g of triptycene (commercially available from Sigma-Aldrich, 95-99% purity) with 20 g to 0.5 g of a colorant, binder, and/or release agent. The homogenized mixture is processed on a standard powder compaction press (commonly available from pharmaceutical equipment suppliers). The powder is fed and evenly distributed on a rotating die table using a gated powder flow control system. The powder fills the die, and the powder in the die is pressed under a pressure of approximately 1 to 4 tons to form a compacted powder pellet having a density of 29 to 50 grains/g. The pellet is placed in a highly conductive metal closed-end cylinder with an inner diameter approximating the outer diameter of the TCO thermal pellet. The closed end of the cylinder is staked shut with an axial conductive metal lead protruding from the cylinder. Other components are loaded in a stacked manner on top of the thermal pellets, depending on the end use requirements of the TCO. The following subassembly is inserted into the open end of the TCO cylinder, the subassembly consisting of a non-conductive ceramic bushing with an axial bore and a conductive metal wire inserted into the bore, the conductive metal wire being mechanically constrained into a permanent integral assembly by deformation of the metal wire. The stacked elements previously noted in paragraph [0018] are compressed into the cylinder by a ceramic, isolated lead assembly, and the edge of the open end of the cylinder is mechanically rolled onto the ceramic bushing to permanently seal the internal components of the TCO cylinder. The enclosed TCO is then sealed with a high temperature epoxy sealant. An epoxy sealant for sealing bushings and isolated leads and for rolling onto the barrel edge on the external termination area of the TCO housing was prepared at 25°C by mixing 200g of 210210 Epoxy Resin Part A (epoxy resin comprising bisphenol A and diglycidyl ether), 14g of 210211 Epoxy Hardener Part B (imidazole hardener), and optionally 13.2g of 210209 Epoxy Pigment Part C (epoxy resin, neopentyl glycol diglycidyl ether, pigment, etc.) in a sealed paddle mixer at 100 RPM under vacuum to 30 mmHg for 10 minutes to form a homogeneous epoxy mixture. The reagents were mixed for a total of 1.5 to 5 minutes, and at the end of the mechanical mixing, a 10-minute no-mix vacuum step was performed to form a single-component base mixture. Apply the epoxy mixture to the bushing and insulated wires to cover the edge of the cylinder rolled onto the TCO device, using an epoxy dispensing bottle with a narrow tip or a mechanical coating device to ensure even coverage.

The assembled TCO coated with epoxy sealing compound is then cured at 48°C to 50°C and 0% to 85% RH for 9 hours. The B-stage TCO assembly is then cured in a controlled atmosphere at a temperature of 150°C to, optionally, 235°C and 0% to 35% RH for 3 to 6 hours.

C5 epoxy resin was studied to demonstrate the high-temperature performance of the sealant system and its ability to retain the polycyclic organic compounds of the thermal pellets used in HTTCO devices. Specifically, high-temperature thermal pellets containing triptycene and a polytetrafluoroethylene release agent were retained by the C5 epoxy sealant when continuously exposed to 247°C. Thermal pellets formed from the smaller molecule pentaerythritol (CAS No. 115-77-5), which has a melting point starting at 259°C, were not retained by the TCO using the C5 sealing system when continuously exposed to 247°C. These two thermal pellet organic compounds, triptycene and pentaerythritol, have similar melting points and are known to have similar volatile emission characteristics. However, the C5 sealing system was significantly better able to retain triptycene within the sealed HTTCO housing than pentaerythritol.

On day 1, the height of the pentaerythritol pellets changed from an initial pellet height of 101 thousandths of an inch to 0.00 thousandths of an inch. Thus, the TCO with pentaerythritol broke continuity or almost immediately exhibited a resistance greater than 200 kOhm (precise). The HTTCO with triptycene-containing pellets had an initial pellet height of approximately 98 thousandths of an inch and maintained a pellet height of at least 80 thousandths of an inch for at least 13 weeks, and 9 of the 10 HTTCO samples did not exhibit a resistance greater than 200 kOhm until 2100 hours.

Assuming that the melting points of the compounds and their volatility caused by TGA are almost the same, it is believed that the difference in retention is attributed to the functionality and/or size of the molecules. Using a simple computer model, the size (radius) of the compounds was calculated. As shown in Table 3 below, triptycene has a radius of 0.46nm, while pentaerythritol has a radius of 0.33nm. Moreover, the triptycene molecule strictly gives the steric hindrance of the three benzene rings. When viewed along the endpoints of the molecule, the three benzene molecules are separated from each other with a maximum interval of 120°. On the other hand, pentaerythritol has a significantly larger molecular freedom to allow it to twist and reorient itself. Unlike the double bonds present in aromatic rings, triptycene has very little functionality. However, aromatic rings have the ability to stack π-π with other aromatic rings in the epoxy structure, which can make them immobilized in the pores and thus block the pores. Pentaerythritol has four polar hydroxyl bonds, which have hydrogen bond accepting/donating capabilities.

Table 3

The performance of 1-aminoanthraquinone [CAS#82-45-1] thermal pellets in a C5 epoxy sealant system was also examined. 1-aminoanthraquinone has the same melting point range as pentaerythritol and triptychene, so size and functionality were again tested to provide an understanding of the interaction between the organic compound and the cured epoxy sealant. 1-aminoanthraquinone molecules lie in a single plane and are rigid molecules, which can be attributed to the benzene rings and the carbonyl bonds that bind them together—both require planar orientation. 1-aminoanthraquinone has a radius of 0.45 nm, which is similar in size to triptychene. However, 1-aminoanthraquinone has the additional advantage of exhibiting more functionality when interacting with the epoxy sealant. The carbonyl bond can accept hydrogen donation, and the amine group can accept/donate hydrogen. Based on the steric similarity of 1-aminoanthraquinone to triptychene and its similarity in functionality to pentaerythritol, 1-aminoanthraquinone has even greater holding power than epoxy sealants using triptychene or pentaerythritol.

Samples of the C5 system were prepared by reacting the components under the temperature and humidity conditions listed below. All samples were exposed to the same temperature program used for the B-stage and advanced cure levels. B-staged samples were heated at 48°C for 5 hours and then at 58°C for 4 hours. B-stages were performed in two different relative humidity environments (0% and 35% RH) to determine the effect of water on the B-stage cure. Samples exposed to 35% RH were B-staged in a humidity chamber maintained at 35% humidity and following the temperature program. Samples prepared at 0% RH were B-staged in an oven. To achieve 0% RH, a compressed air source with two water traps was used to ensure that no water was exposed to the epoxy system during the B-stage. Some samples required advanced curing, which required heating the B-stage samples to 150°C for 3 hours. Humidity was not monitored during the advanced cure, but samples could still be identified by their B-stage humidity level for labeling purposes.

From the surface area data, both cured epoxy seal samples have very low surface areas (about ^0.09m2 /g), and the shape of the adsorption block shows a very nonporous structure. The average pore width is determined by dividing the pore volume by its area and multiplying by 4. To determine the pore width, two different techniques are used - namely, BET values and BJH values. For both techniques, the C5 epoxy sample cured at 35% humidity shows a larger pore width than the C5 epoxy sample cured with 0% humidity (25.53nm vs. 0.312nm measured by BET; 39.53nm vs. 27.16nm measured by BJH). Including water in the B-stage cure shows that it provides a larger pore structure in the cured epoxy polymer. Based on the BET pore width, the smaller pore width of the one cured at 0% humidity, for example, provides the ability to significantly improve the retention of larger triptycene molecules.

This article includes the identification and characterization of the starting material chemistry for epoxy-based systems, as they are characteristic of cured epoxy-based systems. For the C5 epoxy, Part A epoxy resin has the six components listed above, including two proprietary epoxy resins and a proprietary elastomeric polymer; Part B has a single proprietary imidazole hardener; and Part C is the optional colorant component and includes nine parts: three proprietary epoxy resins and one proprietary elastomer. Materials analysis indicates that the hardener for Part B is 2-ethyl-4-methyl-1H-imidazole. Of the six components listed for the Part A precursor, silica and titanium dioxide are considered relatively inert and do not play a significant role in the cured epoxy chemistry. Part A's neopentyl glycol diglycidyl ether (CAS#17557-23-2) has two epoxy groups, so it does not reduce crosslink density and is believed to provide structural flexibility between the larger, more rigid aromatic epoxy resin. The increased mobility allows the material to flow optimally and increases pot life. The two proprietary epoxy resins are the primary components of the Part A precursor. The elastomeric polymer is not believed to react with the epoxy during the cure process, although the unsaturated double bonds may participate in some crosslinking. Generally, when the elastomeric polymer is unreactive, it forms a separate phase within the epoxy resin that provides greater impact resistance and improved mobility. While not limiting the present invention to any particular theory, it is possible that the elastomeric polymer and the inclusion of neopentyl glycol diglycidyl ether in the epoxy resin backbone impart high temperature reflow capability to the C5 system. The two remaining Part A epoxy resin precursors were determined to be derivatives of the diglycidyl ether of bisphenol A.

In this manner, the present invention provides a high temperature thermal cutoff device and a method of making such a device by forming a high temperature stable seal and a high temperature thermal pellet comprising one or more organic compounds substantially retained by a seal barrier. The HTTCO is very stable, robust, and can be used as a switch device in many high temperature devices that were previously not feasible, such as high temperature clothing irons and hair irons.

Claims (22)

1. A high-temperature thermal fuse device, comprising: High-temperature thermally sensitive particles, having a transition temperature greater than or equal to about 240°C, comprising equal to or more than about 95 wt% of a polycyclic aromatic hydrocarbon compound selected from tripterene, 1-aminoanthraquinone and combinations thereof, and disposed in a shell; A high-temperature sealant disposed in a portion of at least one opening of the housing to substantially seal the housing up to the transition temperature, wherein the high-temperature sealant interacts with and retains the polycyclic aromatic hydrocarbon compound within the housing to prevent sublimation of the high-temperature heat-sensitive particle composition up to the transition temperature, wherein the high-temperature sealant comprises a cured high-temperature epoxy resin formed by curing at least two precursors comprising a first precursor containing bisphenol A and a second precursor containing a hardener; and A current-disconnecting assembly, at least partially disposed within the housing, establishes electrical continuity under a first operating condition corresponding to an operating temperature of at least 235°C and below the transition temperature of the thermally sensitive particles, and disconnects electrical continuity under a second operating condition when the operating temperature exceeds the transition temperature. 2. The high-temperature thermal fuse device as claimed in claim 1, wherein the thermally sensitive particles comprise greater than or equal to about 95 wt% of the triterene. 3. The high-temperature thermal fuse device as claimed in claim 1, wherein the thermally sensitive particles comprise one or more components selected from the group consisting of: adhesives, pressing aids, release agents, pigments, or mixtures thereof. 4. The high-temperature thermal fuse device of claim 1, wherein the high-temperature sealant is formed from a precursor comprising diglycidyl ether bisphenol A resin and the hardener. 5. The high-temperature thermal fuse device as claimed in claim 4, wherein the hardener comprises a modified imidazole compound. 6. The high-temperature thermal fuse device as claimed in claim 4, wherein the hardener comprises 2-ethyl-4-methyl-1H-imidazolium. 7. The high-temperature thermal fuse device of claim 4, wherein the high-temperature seal is formed by combining a first precursor comprising at least one bisphenol A diglycidyl ether, an elastomer, and neopentyl glycol diglycidyl ether with a second precursor comprising 2-ethyl-4-methyl-1H-imidazole. 8. The high-temperature thermal fuse device of claim 4, wherein the high-temperature sealant is formed by combining a first precursor comprising a bisphenol A diglycidyl ether polymer, a second precursor comprising 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, and a third precursor comprising benzoic acid-1,2,4,5-dianhydride, hexahydrophthalic anhydride, and phthalic anhydride. 9. The high-temperature thermal fuse device as claimed in claim 1, wherein the transition temperature is greater than or equal to about 240°C and less than or equal to about 270°C. 10. The high-temperature thermal fuse as claimed in claim 1, wherein the device is capable of operating at a continuous temperature of about 235°C for more than or equal to about 1000 hours. 11. A high-temperature thermal fuse device, comprising: High-temperature thermal sensing particles, wherein the transition temperature of the high-temperature thermal sensing particles is greater than or equal to about 240°C, comprising a single crystalline organic compound selected from tripterene and 1-aminoanthraquinone, and disposed in a shell; A high-temperature sealant disposed in a portion of at least one opening of the housing to substantially seal the housing up to the transition temperature, wherein the high-temperature sealant interacts with and retains the single crystalline organic compound within the housing to prevent sublimation of the high-temperature thermosensitive particle composition up to the transition temperature, wherein the high-temperature sealant comprises a cured high-temperature epoxy resin formed by curing at least two precursors comprising a first precursor containing bisphenol A and a second precursor containing a hardener, wherein the hardener comprises a modified imidazole compound; and A current-disrupting assembly comprising: an electrical contact having electrical continuity with an external current source to establish a circuit under a first operating condition corresponding to an operating temperature of at least 235°C and below the transition temperature of the thermosensitive particle, wherein at least a portion of the electrical contact is disposed within the housing; a sliding contact member disposed within the housing; and a tension adjusting mechanism disposed within the housing to bias the sliding contact member toward the electrical contact to maintain the circuit under the first operating condition, and to release and interrupt the electrical continuity between the sliding contact member and the electrical contact under a second operating condition when the operating temperature is above the transition temperature. 12. The high-temperature thermal fuse device of claim 11, wherein the single crystalline organic compound comprises triterpenesene. 13. The high-temperature thermal fuse device of claim 11, wherein the single crystalline organic compound comprises 1-aminoanthraquinone. 14. The high-temperature thermal fuse device of claim 11, wherein the thermally sensitive particles comprise more than or equal to about 95 wt% of the single crystalline organic compound. 15. The high-temperature thermal fuse device of claim 11, wherein the thermally sensitive particles comprise one or more components selected from the group consisting of: adhesives, pressing aids, release agents, pigments, or mixtures thereof. 16. The high-temperature thermal fuse device of claim 11, wherein the high-temperature sealant comprises an epoxy-based sealant formed from a precursor comprising diglycidyl ether bisphenol A resin and a hardener. 17. The high-temperature thermal fuse device of claim 16, wherein the hardener comprises 2-ethyl-4-methyl-1H-imidazolium. 18. The high-temperature thermal fuse device of claim 16, wherein the epoxy sealant is formed by combining at least two epoxy precursors, wherein the first precursor comprises at least one bisphenol A diglycidyl ether, an elastomer, and neopentyl glycol diglycidyl ether; and the second precursor comprises 2-ethyl-4-methyl-1H-imidazole. 19. The high-temperature thermal fuse device of claim 16, wherein the epoxy sealant is formed by combining at least two epoxy precursors, wherein the first precursor comprises a bisphenol A diglycidyl ether polymer; the second precursor comprises 1-(2-cyanoethyl)-2-ethyl-4-methylimidazolium; and the third precursor comprises benzoic acid-1,2,4,5-dianhydride, hexahydrophthalic anhydride, and phthalic anhydride. 20. The high-temperature thermal fuse device of claim 11, wherein the transition temperature is greater than or equal to about 240°C and less than or equal to about 270°C. 21. The high-temperature thermal fuse as claimed in claim 11, wherein the device is capable of operating at a continuous temperature of about 235°C for more than or equal to about 1000 hours. 22. A method for manufacturing a high-temperature thermal fuse, comprising: A high-temperature thermal sensing particle is disposed in the housing of the thermal fuse device, wherein the high-temperature thermal sensing particle has a transition temperature greater than or equal to about 240°C and comprises equal to or more than about 95 wt% of a crystalline organic compound selected from tripterene, 1-aminoanthraquinone and combinations thereof. The current interruption assembly is at least partially disposed in the housing, wherein the current interruption assembly is capable of establishing electrical continuity under a first operating condition corresponding to an operating temperature of at least 235°C and below the transition temperature of the thermally sensitive particles, and disconnecting electrical continuity under a second operating condition when the operating temperature exceeds the transition temperature. A curable epoxy compound is applied to at least one opening, wherein the curable epoxy compound comprises at least two precursors, the at least two precursors comprising a first precursor containing bisphenol A and a second precursor containing a curing agent; and The curable epoxy compound is cured to form a high-temperature epoxy sealant, and the high-temperature epoxy sealant is used to seal at least one opening in the housing to form a sealed housing, wherein the high-temperature epoxy sealant interacts with the crystalline organic compound and retains it in the housing of the thermal fuse device to prevent sublimation of the high-temperature thermally sensitive particle composition up to the transition temperature.