WO2017000899A1 - 导电聚合物组合物、导电聚合物片材、电气器件以及它们的制备方法 - Google Patents

导电聚合物组合物、导电聚合物片材、电气器件以及它们的制备方法 Download PDF

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WO2017000899A1
WO2017000899A1 PCT/CN2016/087896 CN2016087896W WO2017000899A1 WO 2017000899 A1 WO2017000899 A1 WO 2017000899A1 CN 2016087896 W CN2016087896 W CN 2016087896W WO 2017000899 A1 WO2017000899 A1 WO 2017000899A1
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conductive
transition metal
conductive powder
carbide
powder
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English (en)
French (fr)
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傅英松
陈建华
金铭俊
周志勇
郑伟
胡成
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Littelfuse Electronics Shanghai Co Ltd
TE Connectivity Corp
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Raychem Electronics Shanghai Ltd
Tyco Electronics Corp
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Priority to US15/739,909 priority Critical patent/US10280279B2/en
Priority to KR1020187001744A priority patent/KR102044107B1/ko
Priority to JP2018500690A priority patent/JP6831830B2/ja
Publication of WO2017000899A1 publication Critical patent/WO2017000899A1/zh
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    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
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    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/10—Homopolymers or copolymers of propene
    • C08L23/12—Polypropene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/16—Ethylene-propylene or ethylene-propylene-diene copolymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
    • C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
    • H01C7/028—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient consisting of organic substances
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2500/00—Characteristics or properties of obtained polyolefins; Use thereof
    • C08F2500/17—Viscosity
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    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2500/00—Characteristics or properties of obtained polyolefins; Use thereof
    • C08F2500/19—Shear ratio or shear ratio index
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/001—Conductive additives
    • C—CHEMISTRY; METALLURGY
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    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/002—Physical properties
    • C08K2201/003—Additives being defined by their diameter
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/002—Physical properties
    • C08K2201/005—Additives being defined by their particle size in general
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
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    • C08K2201/014—Additives containing two or more different additives of the same subgroup in C08K
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2207/00—Properties characterising the ingredient of the composition
    • C08L2207/06—Properties of polyethylene
    • C08L2207/062—HDPE

Definitions

  • the invention relates to a conductive polymer composition, a conductive polymer sheet, an electrical device and a preparation method thereof, in particular to a method for preparing air stability, ultra low resistance, and polymer positive temperature coefficient (PPTC).
  • PPTC is an overcurrent protection device with positive temperature coefficient characteristics. Its function is to be connected in series in the circuit. When the circuit current is normal, the PPTC is in a low resistance state. When the circuit is short-circuited or overloaded, the PPTC transitions to a high-impedance state, thus the circuit Fast, accurate limits and protections are made, and when troubleshooting, the PPTC automatically returns to a low-impedance state.
  • PPTC components For low-resistance PPTC components, there are two main types of PPTC materials currently in use.
  • the first type is metal-based (such as nickel powder, copper powder, etc.) PPTC material, metal-based PPTC components have low resistance, easy processing, etc., but metal-based PPTC materials are prone to oxidation during production and subsequent use, resulting in The increase in resistance of the PPTC component causes the PPTC component to fail (keeping current is reduced).
  • the second type is a carbide-based (such as titanium carbide, tungsten carbide, etc.) PPTC material.
  • the metal carbide-based PPTC component has the advantages of low resistance, stability in air (not easily oxidized in air), but carbide-based PPTC material. Poor processing performance and the production of PPTCs with stable quality and ultra-low resistance (resistivity less than 200u ⁇ cm) still pose great challenges.
  • the present invention is directed to solving the problems of the carbide-based PPTC material, thereby obtaining a PPTC device having ultra-low resistance, excellent processing performance, and stable electrical properties.
  • an aspect of the invention provides a conductive polymer composition
  • a conductive polymer composition comprising a polymer and a conductive powder in a volume ratio of from 65:35 to 35:65, wherein the polymer includes at least one a semi-crystalline polymer selected from the group consisting of polyolefins, at least one olefin and at least one non-olefin monomer copolymerizable therewith, and a thermoformable fluoropolymer comprising a transition metal carbide, At least one powder of a transition metal carbon silicide, a transition metal aluminide, and a transition metal carbon tin compound, and the size distribution of the conductive powder satisfies: 20>D 100 /D 50 >6, wherein D 50 represents a conductive powder The particle size corresponding to the cumulative particle size distribution percentage reached 50%, and D 100 represents the maximum particle size.
  • the present invention also provides a conductive polymer sheet obtained by melt extrusion molding of the conductive polymer composition of the present invention.
  • the present invention also provides an electrical device comprising a first electrode, a second electrode, and a conductive polymer layer sandwiched between the first and second electrodes, the conductive polymer layer being formed of the conductive polymer composition of the present invention .
  • Another aspect of the present invention provides a method for obtaining an air-temperature-stabilized ultra-low resistance positive temperature coefficient polymer material, the method comprising a total of a polymer having a volume ratio of 65:35 to 35:65 and a conductive powder Mixed, the polymer comprising at least one copolymer selected from the group consisting of polyolefins, at least one olefin and at least one non-olefin monomer copolymerizable therewith, and a semi-crystalline polymer of a thermoformable fluoropolymer,
  • the conductive powder includes at least one of a transition metal carbide, a transition metal carbon silicide, a transition metal aluminide, and a transition metal carbon tin compound, and the size distribution of the conductive powder satisfies: 20>D 100 /D 50 > 6, wherein D 50 represents a particle diameter corresponding to 50% of the particle size distribution, and D 100 represents the maximum particle diameter.
  • the present invention also relates to a method of preparing an air-stable overcurrent protection device having a positive temperature coefficient characteristic, the method comprising extruding a positive temperature coefficient polymer material obtained by the above method, and with a first electrode and Two electrode laminate.
  • the carbide PPTC has poor processing properties and high electrical resistance, and it is possible to prepare an ultra-low resistance PPTC device which can be stabilized in air without an oxygen barrier coating.
  • Figure 1 shows an SEM image of three conductive powders.
  • FIG. 2 is a rheological graph of the three conductive powders and polyethylene composite materials shown in FIG. 1.
  • Figure 3 shows the resistivity and size distribution of six tungsten carbide powders.
  • Figure 4 shows the relationship between D 100 /D 50 and resistivity after two batches of tungsten carbide powder.
  • Figure 5 shows the relationship between the compounding rate and resistivity of two different specifications of tungsten carbide powder from the same manufacturer.
  • Figure 6 shows the effect of the same size distribution but different total carbon (C.T.) content on resistivity.
  • Figure 7 is a schematic illustration of a general process flow for preparing a PPTC device.
  • Figure 8 shows a PPTC device and its resistance-temperature (RT) graph in accordance with the present invention.
  • the present invention is intended to provide an ultra-low-resistance PPTC material excellent in processability and air-stable, a preparation method thereof, and a PPTC sheet and a PPTC device prepared therewith.
  • the PPTC device is formed by welding a PPTC sheet (combined by a conductive powder and a semi-crystalline polymer, granulating, and extruding) after irradiation.
  • a PPTC sheet combined by a conductive powder and a semi-crystalline polymer, granulating, and extruding
  • the choice of conductive powder is critical.
  • Conductive carbon black, carbide powder and metal powder are commonly used conductive powders of PPTC, and their powder resistivities are -1.0 ⁇ 10 -3 ohm ⁇ cm to 1.0 ⁇ 10 -5 ohm ⁇ cm and ⁇ 1.0 ⁇ 10 -6 ohm, respectively. ⁇ cm.
  • carbides and metal powders can be used as conductive materials to achieve low electrical resistance. Ultra-low initial resistance can be obtained with metal powder as the conductive powder.
  • Ultra-low resistivity PPTC sheets (resistivity less than 200 ⁇ cm) can be obtained by blending nickel powder Inco255 with conductive powder (nickel powder volume ratio of 40%) and polyethylene, and the processing property is excellent. During the extrusion process, the size and morphology of the powder will change greatly.
  • Nickel powder Inco255 is a tree before processing The dendritic structure is processed into a spherical structure due to the softness of nickel powder. Nickel powder may oxidize during processing, storage, and use, resulting in increased resistance of the PPTC device. Although the coating of the exposed area of the chip is shielded from oxygen by using an excellent coating of oxygen barrier, the oxidation of the metal powder can be prevented, but the process of coating the coating is complicated, and the device that is not perfectly coated is difficult to detect.
  • Transition metal carbides have a very high melting point, low coefficient of friction, chemical inertness, oxidation resistance and good thermal and electrical conductivity. They are increasingly used in the electronics industry and gradually play an important role.
  • a composite of a polyolefin material (such as titanium carbide, tungsten carbide, etc.) and a general-purpose polyolefin (such as high-density polyethylene HDPE, low-density polyethylene LDPE, ethylene vinyl acetate EVA, etc.) can obtain a PPTC which is stable in air.
  • the ordinary carbide is polygonal (such as titanium carbide), its hardness is high (the hardness of carbide is about 10 times that of nickel), and it will be difficult to process during dry mixing, extrusion and lamination, which is represented by screw and The barrel is seriously worn, the thickness of the finished product is difficult to control, and the powder is partially dispersed unevenly in the resin matrix, resulting in large batch-to-product variation and unstable performance.
  • the resistivity of the conductive powder can be controlled by adjusting the size distribution of the conductive powder, wherein it is surprisingly found that a wider size distribution is more advantageous for obtaining a lower average size.
  • the resistance For example, D 100 /D 50 >6 can achieve an ultra-low resistivity (less than 200 ⁇ cm), where D 100 represents the maximum particle diameter, and D 50 represents the corresponding percentage of the cumulative particle size distribution in the conductive powder of 50%. Particle size.
  • the physical meaning of D 50 is that the particle size is larger than 50% of the particles, and the particles smaller than it also account for 50%.
  • the D 50 is also called the median diameter or the median diameter.
  • the surface morphology of the conductive powder also has a significant influence on the fluidity of the carbide powder and the processing property upon compounding with the polymer, and when the spherical-like conductive powder is selected, compared with the non-spherical carbide It can significantly improve the processing performance, and under the same processing conditions, can increase the filling amount of the conductive powder, thereby reducing the electrical resistance of the PPTC sheet.
  • the magnitude of the electrical resistance is directly related to the carbon content of the carbide.
  • the carbide having a lower carbon content has a lower resistivity.
  • the carbon content in the tungsten carbide is T.C. ⁇ 6.0%, in particular, when the content of T.C. is about 5.90%, a low electric resistance can be obtained.
  • T.C.>6.0% the resistivity is high.
  • the present invention provides a conductive polymer composition, a conductive polymer sheet, an electrical device, and a method of preparing the same.
  • a conductive polymer composition comprising a polymer and a conductive powder in a volume ratio of from 65:35 to 35:65, wherein the polymer comprises at least one selected from the group consisting of poly a copolymer of an olefin, at least one olefin, and at least one non-olefin monomer copolymerizable therewith, and a semi-crystalline polymer of a thermoformable fluoropolymer, the conductive powder comprising a transition metal carbide, a transition metal carbon At least one of a silicide, a transition metal aluminide, and a transition metal carbonitride, and the size distribution of the conductive powder satisfies: 20>D 100 /D 50 >6.
  • the polymer of the composition according to one embodiment of the present invention comprises at least one copolymer selected from the group consisting of polyolefins, at least one olefin and at least one non-olefin monomer copolymerizable therewith, and thermoformable fluorine-containing polymerization.
  • the polyolefin comprises polypropylene, polyethylene (including high density polyethylene, medium density polyethylene, low density polyethylene and linear low density polyethylene), or a copolymer of ethylene and propylene;
  • the copolymer comprises an ethylene-vinyl acetate copolymer, an ethylene-vinyl alcohol copolymer, an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-acrylic acid copolymer, an ethylene-butyl acrylate copolymer;
  • the thermoformable fluoropolymers include polyvinylidene fluoride, and ethylene/tetrafluoroethylene copolymers and the like.
  • the conductive powder according to an embodiment of the present invention includes at least one of a transition metal carbide, a transition metal carbon silicide, a transition metal aluminide, and a transition metal carbon tin compound.
  • a transition metal carbide titanium carbide, tungsten carbide, titanium carbonitride, titanium aluminide, titanium tin carbide, and the like.
  • Titanium carbonitride, titanium aluminide, titanium tin carbide, and the like have properties similar to those of tungsten carbide.
  • the above conductive powder is preferably a spheroidal shape.
  • sphere-like includes an ideal sphere and a shape similar thereto.
  • spherical and “spherical” are used interchangeably.
  • the conductive powder having a spheroidal shape of the present invention can be obtained by various methods including, but not limited to, centrifugal rotation, rotary atomization, centrifugal rotary condensation, induction or resistance heating spheroidization, plasma spheroidization, gas Atomization method, etc.
  • the conductive powder may have an average particle size of 0.1 to 50 ⁇ m.
  • the size of the conductive powder satisfies: D 50 ⁇ 5 ⁇ m, D 100 ⁇ 50 ⁇ m.
  • the conductive powder according to an embodiment of the present invention preferably has a wide size distribution.
  • D 100 /D 50 >6.
  • the upper limit of D 100 /D 50 may be 20, preferably 10.
  • the present invention also draws similar conclusions when the two conductive powders are mixed to satisfy D 100 /D 50 >
  • the transition metal since the transition metal generally has a variable valence state, in its carbide, there may be an M x C phase (M represents a transition metal, x is greater than 1), and the presence of such an M x C phase reduces the total carbon in the carbide. content.
  • M represents a transition metal, x is greater than 1
  • M x C phase reduces the total carbon in the carbide. content.
  • W tungsten carbide
  • W 2 C is metastable phase
  • WC contains a small amount of W 2 C.
  • the carbon content will decrease.
  • the present inventors have found that carbides having a lower carbon content have a lower resistivity under conditions similar to the particle size distribution.
  • the carbon content in the tungsten carbide is TC ⁇ 6.0% (where TC is 100% by mass ⁇ C/WC), in particular, when the content of TC is about 5.90%, a low electric resistance can be obtained.
  • TC>6.0% the resistivity is high.
  • TiC titanium carbide
  • the total carbon content should be 20.03% in stoichiometric ratio, and the resistance will be lower when the total carbon content is between 19.0 and 19.5. Therefore, a total carbon content ratio of 3% to 5% lower than the stoichiometric ratio is advantageous for obtaining a low resistance system.
  • the carbon content in the transition metal carbide is 2% to 5% lower than the theoretical total carbon content of the stoichiometric transition metal carbide MC (M is a transition metal element), preferably 3% lower. 5%.
  • Free carbon the content should be as low as possible, generally requires F.C. ⁇ 0.3%, preferably less than 0.05%.
  • the volume ratio of the polymer to the conductive powder may be from 65:35 to 35:65, preferably from 60:40 to 40:60. More preferably, 55:45 to 45:55, most preferably the polymer and the electrically conductive powder are mixed in substantially equal volume ratio. .
  • the conductive polymer composition according to an embodiment of the present invention may contain components other than the above polymer and conductive powder, for example, inorganic fillers or other polymer materials, and additives such as processing aids and lubricants, provided that Does not impair the low electrical resistance and processability of the conductive polymer composition of the present invention can.
  • the present invention also provides a conductive polymer sheet obtained by melt extrusion molding of the conductive polymer composition of the present invention.
  • a conductive polymer sheet according to an embodiment of the present invention can be used as a PPTC sheet for preparing a PPTC device.
  • a conductive polymer sheet can be obtained by compound blending, granulating, and then extrusion processing various components of the conductive polymer composition according to one embodiment of the present invention.
  • the conductive polymer sheet according to an embodiment of the present invention has a resistivity of less than 200 ⁇ cm.
  • the present invention also provides an electrical device comprising a first electrode, a second electrode, and a conductive polymer layer sandwiched between the first and second electrodes, the conductive polymer layer being formed of the conductive polymer composition of the present invention .
  • the above conductive polymer layer may be formed of the conductive polymer sheet of the present invention, and further, the conductive polymer sheet has a resistivity of less than 200 ⁇ cm.
  • Conductive polymer compositions in accordance with one embodiment of the present invention can be used to make electrical devices such as circuit protection devices, heaters, resistors, and thermal indicators. While the circuit protection device can have any shape, a particularly useful circuit protection device comprises two layered electrodes, preferably metal foil electrodes, and a layer of conductive polymer sandwiched between the electrodes.
  • the device typically includes a lead that is fastened, for example soldered or fused to the electrode.
  • the lead is suitable for insertion into a printed circuit board or for surface mounting on a printed circuit board.
  • Circuit protection devices are particularly suitable for applications such as battery protection where the leads are in the form of strips or strips and are electrically connected to a substrate such as a battery terminal (as shown in Figure 8A).
  • the electrical device is an overcurrent protection device having a positive temperature coefficient characteristic, and the overcurrent protection device is in an unprotected state (at this time, the device The resistivity at the normal operating temperature is less than 200 ⁇ cm.
  • Electrical devices in accordance with one embodiment of the present invention are particularly suitable for use in spot welding and lead-free reflow soldering processes.
  • a method for obtaining an air temperature ultra low resistance positive temperature coefficient polymer material comprising polymerizing and conducting a volume ratio of 65:35 to 35:65 Powder blending, the polymer comprising at least one copolymer selected from the group consisting of polyolefins, at least one olefin and at least one non-olefin monomer copolymerizable therewith, and semi-crystalline polymerization of a thermoformable fluoropolymer
  • the conductive powder includes at least one of a transition metal carbide, a transition metal carbon silicide, a transition metal aluminide, and a transition metal carbon tin compound, and the size distribution of the conductive powder satisfies: 20>D 100 / D 50 >6.
  • the polymer and the conductive powder used in the above method according to one embodiment of the present invention are the same as those described in the conductive polymer composition of the present invention.
  • the conductive powder is preferably spheroidal.
  • the spherical conductive powder is prepared by a centrifugal rotation method, a rotary atomization method, a centrifugal rotary condensation method, an induction or resistance heating spheroidization method, a plasma spheroidization method, or a gas atomization method.
  • the size distribution of the conductive powder preferably satisfies: 20 > D 100 / D 50 > 6.
  • Such a size distribution can be obtained by air flow screening.
  • a cyclone separator can be used to divide the tungsten carbide powder into products of different sizes and sizes.
  • lower resistivity can be obtained by controlling the carbon content therein.
  • tungsten carbide WC
  • the carbon atoms are intercalated into the gap of the tungsten metal lattice, and the interstitial solid solution is formed without destroying the original metal lattice, which gives the tungsten carbide a good electrical conductivity.
  • the theoretical total carbon content of pure WC is 6.18%, but the WC phase usually contains W 2 C (W 2 C is a metastable phase), and the total carbon content decreases when WC contains a small amount of W 2 C. Under the condition that the particle size distribution is similar, the carbide having a lower carbon content has a lower resistivity.
  • the carbon content in tungsten carbide is TC ⁇ 6.0%, low resistance is obtained, and when TC>6.0%, the electrical resistivity is high.
  • the total carbon content should be 20.03% in stoichiometric ratio, and the resistance should be lower when the total carbon content is between 19.0 and 19.5. Therefore, in the present invention, the carbon content in the transition metal carbide can be controlled to be 2% to 5% lower than the theoretical total carbon content of the stoichiometric transition metal carbide MC (M is a transition metal element), To get a lower resistivity.
  • the blending of the polymer and the conductive powder can be achieved by physical blending in a high speed mixer or in an extruder (including a twin screw extruder and a reciprocating single screw extruder).
  • an extruder including a twin screw extruder and a reciprocating single screw extruder.
  • the melt blending temperature depends on the specific kind of the polymer used.
  • the present invention also relates to a method of preparing an air-stable overcurrent protection device having a positive temperature coefficient characteristic, the method comprising extruding a positive temperature coefficient polymer material obtained by the above method, and with a first electrode and Two electrode laminate.
  • the method of preparing an overcurrent protection device according to an embodiment of the present invention may further include a step of slicing after lamination, and a post-assembly step such as punching and cutting.
  • Figure 7 shows the general process flow for preparing a PPTC device.
  • a transition metal carbide as a conductive powder is classified, for example, by gas flow screening to obtain a spherical carbide powder satisfying a D 100 /D 50 >6 size distribution.
  • the carbide powder was mixed with the polymer powder (dry blending) to obtain a blended powder.
  • the blended powder is melt blended and extruded into pellets under the action of twin screw or single screw.
  • the obtained particulate material is extrusion-formed, formed into a sheet, and laminated with an electrode material.
  • a PPTC device such as a PPTC chip is obtained.
  • the conductive powder by making the conductive powder have a wide size distribution, for example, 20>D 100 /D 50 > 6, an ultra-low resistivity (less than 200 ⁇ ) can be obtained with substantially the same average size.
  • an ultra-low resistivity (less than 200 ⁇ ) can be obtained with substantially the same average size.
  • the spherical conductive powder by selecting the spherical conductive powder, the problem that the ordinary transition metal carbide is difficult to process and unevenly dispersed in the polymer resin matrix is overcome, the processing property of the conductive powder can be remarkably improved, and the filling amount of the conductive powder can be increased, thereby reducing The resistance of the PPTC sheet.
  • the present invention can provide an ultra-low-resistance PPTC material having excellent processability and air stability. With such a PPTC material, an ultra-low-resistance PPTC device which can be air-stable without an oxygen barrier coating can be prepared.
  • Fig. 3A shows the relationship between the resistivity and the WC size distribution
  • Fig. 3B shows the size distribution of the corresponding WC particles.
  • the three powders of D 100 /D 50 > 6 obtained ultra low resistance.
  • the powder resistivity which is small in average particle size but narrow in size distribution is inversely increased.
  • D 50 < 5 ⁇ m when D 100 / D 50 < 6, the resistivity exceeds 200 ⁇ ⁇ cm.
  • tungsten carbide powders (WC-15 and WC-50) of Japan New Metal Co., Ltd. were selected, and they were compounded at different ratios, and the relationship between the compounding ratio and the electrical resistivity was measured.
  • Fig. 5B is a size distribution diagram of two types of tungsten carbide powder, and Fig. 5A shows a change in electrical resistivity with the ratio of two kinds of tungsten carbide.
  • two kinds of tungsten carbide powders are compounded according to a certain ratio, when the ratio of WC-15/WC-50 exceeds 5:5 (for example, WC-15/WC-50>6:4), A resistivity of less than 200 ⁇ cm can be obtained.
  • tungsten carbide powders (Xiamen-20 and Xiamen-46) from Xiamen Jinlu Special Alloy Co., Ltd. and two tungsten carbide powders (Guangdong-17 and Guangdong-18) from Guangdong Xianglu Tungsten Co., Ltd. were selected and measured separately. Its size distribution, carbon content and electrical resistivity.
  • Fig. 6A shows the size distribution of the above four kinds of tungsten carbide
  • Fig. 6B shows the relationship between the carbon content and the specific resistance.
  • the total carbon content in the WC is lower than the theoretical total carbon content (6.18%) due to the small amount of W 2 C.
  • the carbide having a lower carbon content has a lower resistivity.
  • the carbon content in the tungsten carbide is TC ⁇ 6.0% (TC is 100% by mass ⁇ C / WC)
  • TC is 100% by mass ⁇ C / WC
  • the content of TC is about 5.90
  • TC>6.0 the resistivity is high.

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Abstract

本发明提供一种导电聚合物组合物、导电聚合物片材、电气器件以及它们的制备方法。本发明的导电聚合物组合物包含体积比为35∶65至65∶35的聚合物粉末和导电粉末，其中所述聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，所述导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种粉末，并且所述导电粉末的尺寸分布满足：20＞D100/D50＞6，其中D50表示导电粉末中的累计粒度分布百分比达到50％时所对应的粒径，D100表示最大粒径。所述导电聚合物组合物具有优异的加工性能，可以用于制备无需氧气阻隔涂层就可在空气中稳定的超低电阻PPTC器件。

Description

导电聚合物组合物、导电聚合物片材、电气器件以及它们的制备方法 技术领域
本发明涉及导电聚合物组合物、导电聚合物片材、电气器件以及它们的制备方法，尤其涉及可用于制备具有空气稳定性、超低电阻、聚合物正温度系数(Polymer Positive Temperature Coefficient，PPTC)特征的器件的导电聚合物组合物，以及由其形成的导电聚合物片材和电气器件。
背景技术
PPTC是具有正温度系数特征的过流保护器件，其作用为串联在电路中，当电路电流正常时，PPTC处于低阻状态，当电路发生短路或者过载时，PPTC跃迁至高阻状态，从而对电路进行快速，准确的限制和保护，当故障排除后，PPTC自动恢复至低阻状态。
现代电子产业的发展，对PPTC元器件的要求也越来越高，小型化、低电阻化、性能稳定化是PPTC元器件发展的趋势。对于低电阻PPTC元器件，目前使用的PPTC材料主要有两大类。第一类为金属基(如镍粉，铜粉等)PPTC材料，金属基PPTC元器件具有低电阻，易加工等优点，但金属基PPTC材料在生产加工以及后续使用过程中易发生氧化，导致PPTC元器件电阻升高造成PPTC元器件失效(保持电流降低)。第二类为碳化物基(如碳化钛，碳化钨等)PPTC材料，金属碳化物基PPTC元器件具有低电阻，在空气中稳定(在空气中不易氧化)的优点，但碳化物基PPTC材料加工性能差，生产出质量稳定且超低电阻(电阻率低于200uΩ·cm)的PPTC仍具有较大的挑战。
发明内容
本发明旨在解决碳化物基PPTC材料存在的问题，从而在获得超低电阻，加工性能优异，电性能稳定的PPTC器件。
为了实现本发明的上述目的，本发明的一个方面提供一种导电聚合物组合物，其包含体积比为65∶35至35∶65的聚合物和导电粉末，其中所述聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，所述导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种粉末，并且所述导电粉末的尺寸分布满足：20＞D100/D50＞6，其中D50表示导电粉末中的累计粒度分布百分比达到50％时所对应的粒径，D100表示最大粒径。
本发明还提供一种导电聚合物片材，其通过本发明的导电聚合物组合物熔融挤出成型而获得。
本发明还提供一种电气器件，其包括第一电极、第二电极和夹在第一、第二电极之间的导电聚合物层，所述导电聚合物层由本发明的导电聚合物组合物形成。
本发明的另一个方面提供一种用于获得空气稳定性超低电阻的正温度系数聚合物材料的方法，所述方法包括将体积比为65∶35至35∶65的聚合物和导电粉末共混，所述聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，所述导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种粉末，并且所述导电粉末的尺寸分布满足：20＞D100/D50＞6，其中D50表示粒径分布中占50％所对应的粒径，D100表示最大粒径。
本发明还涉及一种制备具有正温度系数特征的空气稳定性过电流保护器件的方法，所述方法包括将通过上述方法获得的正温度系数聚合物材料挤出成型，并且与第一电极和第二电极层压。
根据本发明，可以解决碳化物PPTC加工性能差，电阻偏高的问题，并且能够制备无需氧气阻隔涂层就可在空气中稳定的超低电阻PPTC器件。
附图说明
参考以下附图对本发明的多个实施例进行详细说明，以便于更全面地理解本发明，其中：
图1显示了三种导电粉末的SEM图。
图2为图1所示的三种导电粉末与聚乙烯复合材料的流变曲线图。
图3显示了6种碳化钨粉的电阻率及尺寸分布。
图4显示了两批次碳化钨粉经分选后D100/D50与电阻率关系图。
图5显示了同一厂家两种不同规格碳化钨粉复配率与电阻率间的关系。
图6显示了尺寸分布相同但总碳(C.T.)含量不同对电阻率的影响。
图7为制备PPTC器件的一般工艺流程的示意图。
图8显示了根据本发明的一种PPTC器件及其电阻-温度(RT)曲线图。
具体实施方式
如上所述，本发明旨在提供加工性能优异的、具有空气稳定性的超低电阻PPTC材料，及其制备方法，以及用其制备的PPTC片材和PPTC器件。
PPTC器件是将PPTC片材(通过导电粉与半结晶聚合物复合共混，造粒，挤出加工获得)在辐照后冲片，焊接组装而成。为了获得低电阻PPTC器件，导电粉末的选择非常关键。
导电炭黑，碳化物粉及金属粉是PPTC的常用导电粉末，他们的粉末电阻率分别为～1.0×10-3ohm·cm～1.0×10-5ohm·cm和～1.0×10-6ohm·cm。基于电阻率数据，碳化物和金属粉作为导电材料可以获得低电阻。以金属粉作为导电粉末可以获得超低的初始电阻。
以镍粉Inco255为导电粉末(镍粉体积比40％)和聚乙烯共混可以获得超低电阻率的PPTC片材(电阻率低于200μΩ·cm)，其加工性能优异。在挤出加工过程中，粉末的尺寸及形貌会发生较大的改变。镍粉Inco255在加工前为树 枝状结构，因镍粉软而加工后成为类球形结构。镍粉在加工、储存及使用过程中可能会氧化，从而导致PPTC器件电阻升高。虽然采用氧气阻隔优异的涂料对芯片暴露区域进行涂覆以隔绝氧气，可以防止金属粉体氧化，但涂料涂覆的工艺复杂，未能完美包覆的器件难以检测。
过渡金属碳化物具有极高的熔点，低的摩擦系数，化学惰性，抗氧化和良好的导热和导电性，其在电子工业的应用越来越广泛，并逐渐体现其重要的作用。采用碳化物材料(如碳化钛，碳化钨等)与通用聚烯烃(如高密度聚乙烯HDPE、低密度聚乙烯LDPE，乙烯乙烯乙酸酯EVA等)复合，可以得到在空气中稳定的PPTC。但普通碳化物为多角状(如碳化钛)，其硬度高(碳化物的硬度大约为镍材的10倍)，在干混、挤出及层压过程中会出现加工困难，表现为螺杆和炮筒磨损严重，成品厚度难于控制，且粉末在树脂基体中局部分散不均匀，导致成品间批次性差异大，性能不稳定。
根据本发明的一个实施例，通过调节导电粉末的尺寸分布，可以控制导电粉末的电阻率大小，其中出人意料地发现，在平均尺寸基本相同的情况下，较宽的尺寸分布更有利于获得较低的电阻。例如，D100/D50＞6可获得超低的电阻率(低于200μΩ·cm)，其中D100表示最大粒径，D50表示导电粉末中的累计粒度分布百分比达到50％时所对应的粒径。D50的物理意义是粒径大于它的颗粒占50％，小于它的颗粒也占50％，D50也叫中位径或中值粒径。
根据本发明的一个实施例，导电粉末的表面形貌对碳化物粉末的流动性以及与聚合物复合时的加工性能也有显著影响，当选取类球形导电粉末时，与非球形的碳化物相比，可以显著提高加工性能，而且在同等加工条件下，可以提高导电粉末的填充量，从而降低PPTC片材的电阻。
根据本发明的一个实施例，对于过渡金属碳化物而言，电阻的大小与碳化物中碳含量有直接的关系。在颗粒尺寸分布类似的条件下，具有较低碳含量的碳化物电阻率偏低。例如，碳化钨中碳含量在T.C.＜6.0％时，特别地，T.C.的含量在5.90％左右时可得到低的电阻。而T.C.＞6.0％时，电阻率偏高。
基于上述发现，本发明提供了一种导电聚合物组合物、导电聚合物片材、电气器件以及它们的制备方法。
具体而言，根据本发明的一个方面，提供一种导电聚合物组合物，包含体积比为65∶35至35∶65的聚合物和导电粉末，其中所述聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，所述导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种，并且所述导电粉末的尺寸分布满足：20＞D100/D50＞6。
根据本发明的一个实施例的组合物的聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，其中聚烯烃类包括聚丙烯、聚乙烯(包括高密度聚乙烯、中密度聚乙烯、低密度聚乙烯和线型低密度聚乙烯)、或乙烯和丙烯的共聚物；所述共聚物包括乙烯-醋酸乙烯共聚物、乙烯-乙烯醇共聚物、乙烯-丙烯酸甲酯共聚物、乙烯-丙烯酸乙酯共聚物、乙烯-丙烯酸共聚物、乙烯-丙烯酸丁酯共聚物；所述可热成型含氟聚合物包括聚偏氟乙烯，和乙烯/四氟乙烯共聚物等。
根据本发明的一个实施例的导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种。例如碳化钛、碳化钨、碳硅化钛、碳铝化钛、碳锡化钛等。碳硅化钛、碳铝化钛、碳锡化钛等具有与碳化钨类似的性质。
上述导电粉末优选为类球形形状。此处，术语“类球形”包括理想球形以及与其类似的形状。在本发明中，术语“类球形”与“球形”可以互换使用。
可以采用多种方法获得本发明的具有类球形形状的导电粉末，包括但不限于离心旋转法，旋转雾化法，离心旋转冷凝法，感应或电阻加热球化法，等离子体球化法，气体雾化法等。
根据本发明的一个实施例，导电粉末的平均颗粒大小可以为0.1至50μm。在一些实施方案中，导电粉末的尺寸满足：D50＜5μm，D100＜50μm。
为了获得超低的电阻率(低于200μΩ·cm)，根据本发明的一个实施例的导电粉末优选具有较宽的尺寸分布。优选地，D100/D50＞6。D100/D50的上限值可以为20，优选10。
当将两种导电粉末混合，以满足D100/D50＞6时，本发明也得到类似的结论。
另外，由于过渡金属一般具有可变价态，在其碳化物中，可以存在MxC相(M表示过渡金属，x大于1)，这种MxC相的存在会降低碳化物中的总碳含量。以碳化钨(WC)为例，纯WC的理论总碳含量为6.18％，但WC物相中通常含有W2C(W2C是亚稳态相)，WC中含有少量W2C时总碳含量会降低。本发明发现，在颗粒尺寸分布类似的条件下，具有较低碳含量的碳化物电阻率偏低。例如，碳化钨中碳含量在T.C.＜6.0％时(其中T.C.是以质量计的100％×C/WC)，特别地，T.C.的含量在5.90％左右时可得到低的电阻。而T.C.＞6.0％时，电阻率偏高。对碳化钛(TiC)来讲，按化学计量比总碳含量应该为20.03％，而当总碳含量在19.0～19.5间时，电阻会更低。所以，总碳含量比按化学计量比低3％到5％有利于获得低电阻体系。因此，在本发明中，优选过渡金属碳化物中的碳含量比化学计量比的过渡金属碳化物MC(M为过渡金属元素)的理论总碳含量低2％至5％，优选低3％至5％。
自由碳(F.C.)，含量要尽量低，一般要求F.C.＜0.3％，最好低于0.05％。
本发明中，为了使导电粉末能够均匀地分散在聚合物中并且确保一定的低电阻，聚合物与导电粉末的体积比可以为65∶35至35∶65，优选60∶40至40∶60，更优选55∶45至45∶55，最优选聚合物和导电粉末以大致相等的体积比混合。。
根据本发明的一个实施例的导电聚合物组合物可以包含除上述聚合物和导电粉末之外的组分，例如，无机填料或其他聚合物材料，以及加工助剂和润滑剂等添加剂，前提是不损害本发明的导电聚合物组合物的低电阻和加工性 能。
本发明还提供一种导电聚合物片材，其通过本发明的导电聚合物组合物熔融挤出成型而获得。
根据本发明的一个实施例的导电聚合物片材可以用作PPTC片材，用于制备PPTC器件。
具体地，可以通过将根据本发明一个实施例的导电聚合物组合物的各种组分复合共混，造粒，然后挤出加工，而获得导电聚合物片材。
优选地，根据本发明的一个实施例的导电聚合物片材的电阻率低于200μΩ·cm。
本发明还提供一种电气器件，其包括第一电极、第二电极和夹在第一、第二电极之间的导电聚合物层，所述导电聚合物层由本发明的导电聚合物组合物形成。
优选地，上述导电聚合物层可以由本发明的导电聚合物片材形成，并且进一步地，导电聚合物片材的电阻率低于200μΩ·cm。
根据本发明的一个实施例的导电聚合物组合物可用于制备电气器件，例如电路保护器件，加热器，电阻器，和热指示器。虽然电路保护器件可具有任何形状，但是尤其有用的电路保护器件包括两个层状的电极，优选金属箔电极，和夹在电极之间的导电聚合物层组成。
通常器件包括引线，该引线被紧固例如焊接或熔接到电极。该引线适合于插入到印刷电路板中或适合于表面安装在印刷电路板上。电路保护器件尤其适合于例如电池保护的应用，其中引线以条带或带的形式存在并且电连接到例如电池端子的基板(如图8A所示)。
当根据本发明的一个实施例的电气器件用作如电路保护器件时，所述电气器件是具有正温度系数特征的过电流保护器件，并且过电流保护器件在非保护状态下(此时，器件处于正常工作温度)的电阻率低于200μΩ·cm。
根据本发明的一个实施例的电气器件尤其适用于点焊及无铅回流焊接工艺。
根据本发明的另一方面，提供一种用于获得空气稳定性超低电阻的正温度系数聚合物材料的方法，所述方法包括将体积比为65∶35至35∶65的聚合物和导电粉末共混，所述聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，所述导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种，并且所述导电粉末的尺寸分布满足：20＞D100/D50＞6。
根据本发明一个实施例的上述方法中使用的聚合物和导电粉末与在本发明的导电聚合物组合物中所述的聚合物和导电粉末相同。
其中，导电粉末优选是类球形的。球形导电粉末通过离心旋转法，旋转雾化法，离心旋转冷凝法，感应或电阻加热球化法，等离子体球化法，或气体雾化法制备。
导电粉末的尺寸分布优选满足：20＞D100/D50＞6。这样的尺寸分布可以气流筛选方式获得，例如对于同一种碳化钨粉，可以采用旋风分离器将碳化钨粉体分成不同尺寸及尺寸分布的产品。此外，也可以通过将两种碳化钨粉按照一定的比例复配，来获得D100/D50＞6的尺寸分布。
另外，对于过渡金属碳化物而言，可以通过控制其中的碳含量，来获得更低的电阻率。以碳化钨(WC)为例，碳原子嵌入钨金属晶格间隙，在不破坏原有金属晶格的前提下形成填隙固溶体，其给予碳化钨以良好的导电性。纯WC的理论总碳含量为6.18％，但WC物相中通常含有W2C(W2C是亚稳态相)，WC中含有少量W2C时总碳含量会降低。而在颗粒尺寸分布类似的条件下，具有较低碳含量的碳化物电阻率偏低。例如，碳化钨中碳含量在T.C.＜6.0％时可得到低的电阻，而T.C.＞6.0％时，电阻率偏高。对碳化钨钛(TiC)来讲，按 化学计量比总碳含量应该为20.03％，而总碳含量在19.0～19.5间时，电阻会更低。因此，在本发明中，可以通过控制过渡金属碳化物中的碳含量，使其比化学计量比的过渡金属碳化物MC(M为过渡金属元素)的理论总碳含量低2％-5％，来获得更低的电阻率。
根据本发明一个实施例，聚合物和导电粉末的共混可以通过以下方式实现：在高速混合机中物理共混，或者在挤出机(包括双螺杆挤出机和往复式单螺杆挤出机)中熔融共混挤出。在熔融共混挤出时，熔融共混温度根据所用的聚合物的具体种类而定。
通过上述共混方法，可以获得导电粉末均匀分布在聚合物中的聚合物材料。
本发明还涉及一种制备具有正温度系数特征的空气稳定性过电流保护器件的方法，所述方法包括将通过上述方法获得的正温度系数聚合物材料挤出成型，并且与第一电极和第二电极层压。
根据本发明一个实施例的制备过电流保护器件的方法还可以包括在层压后进行切片的步骤，以及冲片和切割成型等后装配步骤。
图7显示了制备PPTC器件的一般工艺流程。首先，将作为导电粉末的过渡金属碳化物分级，例如以气流筛选方式进行分级，获得满足D100/D50＞6尺寸分布的球形碳化物粉末。然后，将该碳化物粉末与聚合物粉末混合(干混)，获得共混粉末。将该共混粉末在双螺杆或单螺杆作用下熔融共混挤出造粒。将获得的颗粒材料挤出加工成型，形成片材，并且与电极材料层压。然后，经切片，再经冲片和切割成型等后装配步骤，获得PPTC器件，例如PPTC芯片。
根据本发明的一个实施例，通过使导电粉末具有较宽的尺寸分布，例如20＞D100/D50＞6，可以在平均尺寸基本相同的情况下获得超低的电阻率(低于200μΩ·em)。另外，通过选取球形导电粉末，克服了普通过渡金属碳化物难以加 工且在聚合物树脂基体中分散不均匀的问题，可以显著提高导电粉末的加工性能，并且可以提高导电粉末的填充量，从而降低PPTC片材的电阻。而且，对于过渡金属碳化物而言，可以通过控制过渡金属碳化物中的碳含量，使其比化学计量比的过渡金属碳化物MC的理论总碳含量低2％-5％，来获得更低的电阻率。因此，本发明能够提供加工性能优异的、具有空气稳定性的超低电阻PPTC材料，采用这样的PPTC材料，可以制备无需氧气阻隔涂层就可在空气稳定的超低电阻PPTC器件。
具体实施例
以下通过举例说明的方式示出若干具体实施例。应当理解，在不脱离本发明的范围或精神的情况下，设想了其他实施例并可以进行修改。因此，以下的具体实施例不具有限制性意义。
实施例中使用的主要原料总结在表1中。
表1
Figure PCTCN2016087896-appb-000001
实施例1-球形WC的加工性能
选取Inco公司生产的树枝状导电镍粉，株洲三立公司生产的多角状TiC和成都核八五七新材料有限公司生产的类球形WC粉，三者的扫描电子显微镜(SEM)照片如图1所示。将它们分别以相同的体积比(导电粉体的体积比为45％)，在相同的条件下与Petrothene公司生产的PE(聚乙烯)共混并熔融挤出，测量所获得的复合材料的流变曲线。如图2所示，在同样体积比条件下，WC体系(45％WC/55％PE)的动态粘度明显要低于TiC体系(45％TiC/55％PE) 和Ni体系(45％Ni/55％PE)，表明碳化钨/聚乙烯复合物的加工性能优异。
实施例2-碳化物电阻率与颗粒尺寸分布
选取6种平均尺寸基本相同(D50＜5μm)的碳化钨粉体(成都、日本、厦门、在邦、广东和章源)，测量其尺寸分布和电阻率。
图3A显示了电阻率与WC尺寸分布的关系，图3B是相应WC颗粒的尺寸分布图。
如图3A所示，D100/D50＞6的三种粉体获得了超低电阻。
实施例3-碳化物电阻率与颗粒尺寸分布
将获自成都核八五七新材料有限公司的两批次碳化钨粉采用旋风分离器分成不同尺寸及尺寸分布的产品，然后测量D100/D50与电阻率关系。
如图4所示，采用平均粒径小但尺寸分布窄的粉体电阻率反而增加，在D50＜5μm的情况下，当D100/D50＜6时，电阻率超过了200μΩ·cm。
实施例4-碳化物电阻率与颗粒尺寸分布
选取日本新金属有限公司的两种规格的碳化钨粉(WC-15和WC-50)，将它们按不同比率复配，并且测量复配率与电阻率间的关系。
图5B是两种碳化钨粉的尺寸分布图，图5A显示了电阻率随两种碳化钨比例的变化。
如图5A所示，将两种碳化钨粉按照一定的比例复配，当WC-15/WC-50的比例超过5∶5时(例如，WC-15/WC-50＞6∶4)，可以获得低于200μΩ·cm的电阻率。
实施例5-碳化物中碳含量对电阻率的影响
选取厦门金鹭特种合金有限公司的两种碳化钨粉(厦门-20和厦门-46)和广东翔鹭钨业股份有限公司的两种碳化钨粉(广东-17和广东-18)，分别测量 其尺寸分布、碳含量和电阻率。
图6A显示了上述四种碳化钨的尺寸分布，图6B显示了碳含量和电阻率的关系。
从图6的结果可以看出，WC中总碳含量由于含有少量W2C而低于理论总碳含量(6.18％)。在颗粒尺寸分布类似的条件下，具有较低碳含量的碳化物电阻率偏低。其中，碳化钨中碳含量在T.C.＜6.0％时(T.C.是以质量计的100％×C/WC)，特别地，T.C.的含量在5.90左右时可得到低的电阻。而T.C.＞6.0时，电阻率偏高。
实施例6-PPTC芯片的RT曲线
将按体积比计为55％的HDPE(高密度聚乙烯，供应商：Marflex)和45％的碳化钨粉(平均颗粒尺寸为3.58μm，D100/D50＝6.30，T.C.＝5.91，供应商：成都核八五七新材料有限公司)，经共混熔融挤出，覆上电极，加工成PPTC片材(电阻率为170μΩ·cm)，制成2.8mm(宽)x3.6mm(长)x0.33mm(高)的芯片，并组装成适合于点焊或无铅回流焊的器件(如图8A)，测量其初始电阻为8.5mohm，并且测量电阻-温度(RT)曲线。如图8B所示，在三次RT曲线中，RT的纵坐标值基本保持恒定，同时发生电阻转折的温度点也基本保持恒定，表明本实施例样品的RT曲线的重复性好。
在不偏离本发明的范围和精神的前提下，对本发明的各种修改和更改对于本领域技术人员将是显而易见的。应当理解，本发明并非意图受本文所给出的示例性实施例和实例的不当限制，这些实例和实施例仅以举例的方式提供，本发明的范围旨在仅受所附权利要求的限制。

Claims (28)

  1. 一种导电聚合物组合物，包含体积比为65∶35至35∶65的聚合物和导电粉末，其中所述聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，所述导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种粉末，并且所述导电粉末的尺寸分布满足：20＞D100/D50＞6，其中D50表示导电粉末中的累计粒度分布百分比达到50％时所对应的粒径，D100表示最大粒径。
  2. 根据权利要求1所述的导电聚合物组合物，其中所述聚烯烃类包括聚丙烯、聚乙烯或乙烯和丙烯的共聚物；所述共聚物包括乙烯-醋酸乙烯共聚物、乙烯-乙烯醇共聚物、乙烯-丙烯酸甲酯共聚物、乙烯-丙烯酸乙酯共聚物、乙烯-丙烯酸共聚物、乙烯-丙烯酸丁酯共聚物；所述可热成型含氟聚合物包括聚偏氟乙烯，或乙烯/四氟乙烯共聚物。
  3. 根据权利要求2所述的导电聚合物组合物，其中所述聚乙烯包括高密度聚乙烯、中密度聚乙烯、低密度聚乙烯或线型低密度聚乙烯。
  4. 根据权利要求1所述的导电聚合物组合物，其中所述导电粉末分散在所述聚合物中。
  5. 根据权利要求1所述的导电聚合物组合物，其中所述导电粉末包括碳化钛、碳化钨、碳硅化钛、碳铝化钛或碳锡化钛。
  6. 根据权利要求1所述的导电聚合物组合物，其中所述导电粉末是类球形的。
  7. 根据权利要求1所述的导电聚合物组合物，其中所述导电粉末的D50＜5μm，D100＜50μm。
  8. 根据权利要求1所述的导电聚合物组合物，其中所述导电粉末的尺寸分布满足：
    10＞D100/D50＞6。
  9. 根据权利要求1至8中任一项所述的导电聚合物组合物，其中所述过渡金属碳化物中的碳含量比化学计量比的过渡金属碳化物MC的理论总碳含量低2％至5％，其中M表示过渡金属元素。
  10. 根据权利要求9所述的导电聚合物组合物，其中所述导电粉末是碳化钨WC，并且WC中碳含量T.C.为5.90％至6.00％，其中T.C.是以质量计的100％×C/WC；或所述导电粉末是碳化钛TiC，并且TiC中碳含量T.C.为19.0％至19.5％，其中T.C.是以质量计的100％×C/TiC。
  11. 一种导电聚合物片材，其通过将根据权利要求1至10中任一项所述的导电聚合物组合物熔融挤出成型而获得。
  12. 一种电气器件，包括第一电极、第二电极和夹在第一、第二电极之间的导电聚合物层，所述导电聚合物层由根据权利要求1至10中任一项所述的导电聚合物组合物形成。
  13. 根据权利要求12所述的电气器件，所述电气器件是具有正温度系数特征的过电流保护器件。
  14. 根据权利要求13所述的电气器件，其中所述过电流保护器件在非保护状态下的电阻率低于200μΩ·cm。
  15. 根据权利要求12至14中任一项所述的电气器件用于点焊及无铅回流焊接工艺的用途。
  16. 一种用于获得空气稳定性超低电阻的正温度系数聚合物材料的方法， 所述方法包括将体积比为65∶35至35∶65的聚合物和导电粉末共混，所述聚合物包括至少一种选自聚烯烃类、至少一种烯烃与至少一种可与其共聚合的非烯烃单体的共聚物和可热成型含氟聚合物的半结晶聚合物，所述导电粉末包括过渡金属碳化物、过渡金属碳硅化物、过渡金属碳铝化物和过渡金属碳锡化物中的至少一种粉末，并且所述导电粉末的尺寸分布满足：20＞D100/D50＞6，其中D50表示导电粉末中的累计粒度分布百分比达到50％时所对应的粒径，D100表示最大粒径。
  17. 根据权利要求16所述的方法，其中所述导电粉末包括碳化钛、碳化钨、碳硅化钛、碳铝化钛或碳锡化钛。
  18. 根据权利要求16所述的方法，其中所述导电粉末是类球形的。
  19. 根据权利要求18所述的方法，其中所述类球形的导电粉末通过离心旋转法，旋转雾化法，离心旋转冷凝法，感应或电阻加热球化法，等离子体球化法，或气体雾化法制备。
  20. 根据权利要求16所述的方法，其中所述导电粉末的尺寸分布满足：10＞D100/D50＞6。
  21. 根据权利要求20所述的方法，其中所述导电粉末通过气流筛选方式获得。
  22. 根据权利要求21所述的方法，其中所述导电粉末通过旋风分离器分离获得。
  23. 根据权利要求20所述的方法，其中所述导电粉末由两种以上的导电粉末复配获得。
  24. 根据权利要求16至23中任一项所述的方法，其中控制过渡金属碳化物中的碳含量，使其比化学计量比的过渡金属碳化物MC的理论总碳含量低2％ 至5％，其中M表示过渡金属元素。
  25. 根据权利要求24所述的方法，其中所述导电粉末是碳化钨WC，并且WC中碳含量T.C.为5.90％至6.00％，其中T.C.是以质量计的100％×C/WC；或者，所述导电粉末是碳化钛TiC，并且TiC中碳含量T.C.为19.0％至19.5％，其中T.C.是以质量计的100％×C/TiC。
  26. 根据权利要求16所述的方法，其中所述共混包括在高速混合机中物理共混或在挤出机中熔融共混挤出。
  27. 一种制备具有正温度系数特征的空气稳定性过电流保护器件的方法，包括将通过权利要求16至26中任一项所述的方法获得的正温度系数聚合物材料挤出成型，并且与第一电极和第二电极层压。
  28. 根据权利要求27所述的方法，还包括在层压后进行切片的步骤，以及任选的后装配步骤，所述后装配包括冲片和切割成型。
PCT/CN2016/087896 2015-06-30 2016-06-30 导电聚合物组合物、导电聚合物片材、电气器件以及它们的制备方法 Ceased WO2017000899A1 (zh)

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