Positive temperature coefficient polymer composition and circuit protection device

Abstract

A positive temperature coefficient polymer composition and a circuit protection device are disclosed. The positive temperature coefficient polymer composition comprises a first polymer, a second polymer, and a conductive filler dispersed in the first polymer and the second polymer. The first polymer has a melting point of 100°C to 200°C, and the second polymer has a melting point greater than 200°C. The weight ratio of the first polymer to the second polymer ranges from 1:5 to 5:1. The circuit protection device comprises a polymer positive temperature coefficient (PPTC) element and two electrodes, which are respectively disposed on opposite sides of the PPTC element. The PPTC element comprises a polymer substrate and a conductive filler dispersed in the polymer substrate. The polymer substrate comprises the first polymer and the second polymer as described above. The circuit protection device comprising this positive temperature coefficient polymer composition can withstand higher voltages and has better stability and durability.

Description

Technical Field

[0001] The present invention relates to a positive temperature coefficient (PTC) polymer composition, and more particularly to a positive temperature coefficient polymer composition comprising a first polymer and a second polymer, and a circuit protection device comprising the first polymer and the second polymer. Background Technology

[0002] A positive temperature coefficient (PTC) element exhibits the PTC effect, enabling its use as a circuit protection device (e.g., a resettable fuse). The PTC element may include a PTC polymer unit and first and second electrodes formed on two opposite surfaces of the PTC polymer unit. The PTC polymer unit includes a polymer substrate containing crystalline and amorphous regions, and particulate conductive filler. The particulate conductive filler is dispersed in the amorphous regions of the polymer substrate, forming a continuous conductive path for electrically connecting the first and second electrodes. The PTC effect refers to a phenomenon where, when the temperature of the polymer substrate in the crystalline region is raised to its melting point, the crystals in the crystalline region begin to melt, thereby creating new amorphous regions. As the number of new amorphous regions increases to the point of merging with the original amorphous regions, the conductive path of the particulate conductive filler gradually becomes an open circuit, and the resistance of the PTC polymer unit increases sharply, causing a loss of electrical conductivity between the first and second electrodes.

[0003] The aforementioned circuit protection device can be used as a protective device in electronic devices. The material of this circuit protection device is designed according to its operating temperature; for example, polyolefin with an operating temperature between -40°C and 85°C is commonly used as the polymer base material. Furthermore, polyvinylidene fluoride (PVDF) with an operating temperature between -40°C and 125°C is also commonly used as the polymer base material.

[0004] In overcurrent protection applications, circuit protection devices with higher operating temperatures can be used at higher rated voltages, and are therefore highly sought after in the industry. Summary of the Invention

[0005] The purpose of this invention is to provide a positive temperature coefficient polymer composition that can overcome at least one of the disadvantages of the prior art.

[0006] The positive temperature coefficient polymer composition of the present invention comprises a first polymer, a second polymer, and a conductive filler dispersed in the first polymer and the second polymer. The first polymer has a melting point of 100°C to 200°C, the second polymer has a melting point greater than 200°C, and the weight ratio of the first polymer to the second polymer ranges from 1:5 to 5:1.

[0007] The positive temperature coefficient polymer composition of the present invention has a second polymer having a melting point at least 50°C higher than that of the first polymer.

[0008] The positive temperature coefficient polymer composition of the present invention has a weight ratio of the first polymer to the second polymer ranging from 1:4 to 4:1.

[0009] The positive temperature coefficient polymer composition of the present invention has a weight ratio of the first polymer to the second polymer ranging from 1:3 to 3:1.

[0010] The positive temperature coefficient polymer composition of the present invention has a weight ratio of the first polymer to the second polymer ranging from 1:2 to 2:1.

[0011] The positive temperature coefficient polymer composition of the present invention has a weight ratio of the first polymer to the second polymer of 1:1.

[0012] The positive temperature coefficient polymer composition of the present invention has a total weight of 100 wt%, and the content of at least one of the first polymer and the second polymer ranges from 11 to 46 wt%.

[0013] The positive temperature coefficient polymer composition of the present invention has a first polymer with a melting point of 140°C to 180°C and a second polymer with a melting point greater than 200°C to 280°C.

[0014] The positive temperature coefficient polymer composition of the present invention has a first polymer with a melt flow index of 0.5-30 g / 10 min at 230 °C and a second polymer with a melt flow index of 3-40 g / 10 min at 297 °C.

[0015] The positive temperature coefficient polymer composition of the present invention, wherein the first polymer is selected from polypropylene or polyvinylidene fluoride.

[0016] The positive temperature coefficient polymer composition of the present invention, wherein the second polymer is selected from polyethylene terephthalate, perfluoroalkoxyalkane, polyamide, polyacrylonitrile, polystyrene or ethylene-tetrafluoroethylene copolymer.

[0017] Another object of the present invention is to provide a circuit protection device comprising a polymeric positive temperature coefficient (PPTC) element and two electrodes disposed on opposite sides of the PPTC element. The PPTC element comprises a polymer substrate and a conductive filler dispersed in the polymer substrate. The polymer substrate comprises a first polymer and a second polymer as described above. The first polymer has a melting point of 100°C to 200°C, the second polymer has a melting point greater than 200°C, and the weight ratio of the first polymer to the second polymer ranges from 1:5 to 5:1.

[0018] In the circuit protection device of the present invention, the melting point of the second polymer is at least 50°C higher than that of the first polymer.

[0019] In the circuit protection device of the present invention, the weight ratio of the first polymer to the second polymer ranges from 1:4 to 4:1.

[0020] In the circuit protection device of the present invention, the weight ratio of the first polymer to the second polymer ranges from 1:3 to 3:1.

[0021] In the circuit protection device of the present invention, the weight ratio of the first polymer to the second polymer ranges from 1:2 to 2:1.

[0022] In the circuit protection device of the present invention, the total weight of the polymer positive temperature coefficient element is 100 wt%, and the content of at least one of the first polymer and the second polymer ranges from 11 to 46 wt%.

[0023] In the circuit protection device of the present invention, the first polymer has a melting point of 140°C to 180°C, and the second polymer has a melting point of greater than 200°C to 280°C.

[0024] In the circuit protection device of the present invention, the first polymer is selected from polypropylene or polyvinylidene fluoride.

[0025] In the circuit protection device of the present invention, the second polymer is selected from polyethylene terephthalate, perfluoroalkoxyalkane, polyamide, polyacrylonitrile, polystyrene, or ethylene-tetrafluoroethylene copolymer.

[0026] The beneficial effects of the present invention are that the circuit protection device including the positive temperature coefficient polymer composition can withstand higher voltages and has better stability and durability. Attached Figure Description

[0027] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, wherein:

[0028] Figure 1 This is a cross-sectional schematic diagram of an embodiment of the circuit protection device of the present invention. Detailed Implementation

[0029] Before the invention is described in detail, it should be noted that similar elements are represented by the same numbers in the following description.

[0030] See Figure 1 An embodiment of the circuit protection device of the present invention includes a polymer positive temperature coefficient element (PPTC element) 2 and two electrodes 31, 32, which are respectively disposed on opposite sides of the PPTC element 2. The PPTC element 2 includes a polymer substrate 21 and a conductive filler 22 dispersed in the polymer substrate 21. The polymer substrate 21 includes a first polymer and a second polymer. The first polymer has a melting point of 100°C to 200°C, the second polymer has a melting point greater than 200°C, and the weight ratio of the first polymer to the second polymer ranges from 1:5 to 5:1.

[0031] In some embodiments of the present invention, the melting point of the second polymer is at least 50°C higher than that of the first polymer. In some embodiments of the present invention, the melting point of the first polymer is 140°C to 180°C, and the melting point of the second polymer is greater than 200°C to 280°C. In a specific embodiment of the present invention, the melting point of the first polymer is 170°C, and the melting point of the second polymer is 220°C to 223°C.

[0032] In some embodiments of the present invention, the weight ratio of the first polymer to the second polymer ranges from 1:4 to 4:1. In some embodiments of the present invention, the weight ratio of the first polymer to the second polymer ranges from 1:3 to 3:1. In some embodiments of the present invention, the weight ratio of the first polymer to the second polymer ranges from 1:2 to 2:1. In some embodiments of the present invention, the weight ratio of the first polymer to the second polymer is 1:1.

[0033] In some specific embodiments of the present invention, the total weight of the positive temperature coefficient polymer composition is 100 wt%, and the content of the first polymer and the second polymer each ranges from 11 to 46 wt%. In some specific embodiments of the present invention, the content of the first polymer and the second polymer each ranges from 19 to 38 wt%. In some specific embodiments of the present invention, the content of the first polymer and the second polymer each is 28.5 wt%.

[0034] In some specific embodiments of the present invention, the first polymer has a melt flow index (MFI) of 0.5-30 g / 10 min at 230 °C, and the second polymer has a melt flow index of 3-40 g / 10 min at 297 °C.

[0035] In some specific embodiments of the present invention, the glass transition temperature (Tg) of the second polymer g The glass transition temperature of the first polymer is higher than that of the second polymer. In a specific embodiment of the present invention, the glass transition temperature of the first polymer is not lower than -40°C, and the glass transition temperature of the second polymer is not lower than 50°C.

[0036] In some embodiments of the present invention, the first polymer is selected from polypropylene (PP) or polyvinylidene fluoride (PVDF). In some embodiments of the present invention, the first polymer is PVDF. In some embodiments of the present invention, the second polymer is selected from polyethylene terephthalate (PET), perfluoroalkoxyalkane (PFA), polyamide (PA), polyacrylonitrile (PAN), polystyrene (PS), or ethylene-tetrafluoroethylene copolymer (ETFE). In some embodiments of the present invention, the second polymer is ETFE.

[0037] In some specific embodiments of the present invention, the total weight of the positive temperature coefficient polymer composition is 100 wt%, and the content of the conductive filler ranges from 30-55 wt%. The conductive filler may be carbon black powder, carbon nanotubes, graphene, metal powder, or conductive ceramic powder. In a specific embodiment of the present invention, the conductive filler is carbon black powder.

[0038] In some specific embodiments of the present invention, the positive temperature coefficient polymer composition further comprises a non-conductive filler dispersed in the first polymer and the second polymer. With a total weight of 100 wt% for the positive temperature coefficient polymer composition, the content of the non-conductive filler ranges from 1-5 wt%, for example, 3 wt%. In a specific embodiment of the present invention, the non-conductive filler is calcium carbonate.

[0039] In a specific embodiment of the present invention, the operating temperature range of the circuit protection device is -40°C to 125°C, and it can operate at temperatures above 16V. dc Used at the rated voltage.

[0040] The present invention also provides a positive temperature coefficient polymer composition for forming the PPTC element 2. The positive temperature coefficient polymer composition comprises a first polymer, a second polymer, and a conductive filler dispersed in the first polymer and the second polymer. The weight ratio of the first polymer to the second polymer ranges from 1:5 to 5:1. The positive temperature coefficient polymer composition may further comprise a non-conductive filler dispersed in the first polymer and the second polymer.

[0041] The present invention will be further described with reference to the following embodiments, but it should be understood that the embodiments are for illustrative purposes only and should not be construed as limiting the implementation of the present invention.

[0042] Example

[0043] <Example 1 (E1)>

[0044] 22.8g of PVDF [purchased from Arkema S.A., product name:] 761, Melting point: 170℃, T g [35℃, MFI: 0.5g / 10min (230℃)], 5.7g ETFE [purchased from Daikin Industries, Ltd., product name: EP-610, melting point: 223℃, T g [80℃, MFI: 30g / 10min (297℃)], 20g carbon black powder (purchased from Birla Carbon, product name: 430 Ultra) and 1.5g of calcium carbonate (purchased from Merlin White Stone Co., Ltd.) were used as ingredients and mixed in a mixer (Brabender) at a temperature of 250°C and a speed of 30rpm for 10 minutes to obtain the ingredient mixture.

[0045] The above-mentioned mixture of ingredients was placed in a mold and hot-pressed at a temperature of 200°C and a pressure of 80 kg / cm². 2 The PPTC element 2 with a thickness of 0.35 mm was obtained by hot pressing for 4 minutes under the following conditions. The PPTC element 2 was then sandwiched between two nickel-plated copper foils (as electrodes 31 and 32) and heated at 200°C and 80 kg / cm². 2 The PTC laminate was hot-pressed for 4 minutes to obtain a PTC laminate with a thickness of 0.42 mm. This PTC laminate was then cut into multiple 8 mm × 8 mm semi-finished products, which were subsequently irradiated with Co-60 gamma rays at a total radiation dose of 50 kGy to obtain the desired product. Figure 1 The circuit protection device shown.

[0046] <Examples 2 to Examples 7 (E2-E7)>

[0047] The process conditions for circuit protection devices of E2-E7 are similar to those of E1, with the difference being the content of PVDF and ETFE (i.e., the weight ratio of the first polymer to the second polymer, as shown in Table 1).

[0048] <Examples 8 to 12 (E8-E12)>

[0049] The manufacturing processes for circuit protection devices E8-E12 are similar to those for E1, E3-E5, and E7, respectively. The difference lies in the ETFE used in E8-E12 [purchased from Daikin Industries, Ltd., product name:]. EP-620AS, melting point: 220℃, T g [80℃, MFI: 3g / 10min (297℃)] (as shown in Table 1).

[0050] <Comparative Examples 1 to 7 (CE1-CE7)>

[0051] The process conditions for the circuit protection devices of CE1-CE7 are similar to those of E1. The difference lies in the ingredients of CE1-CE7, as shown in Table 1. CE1 contains only the first polymer, while CE4 and CE7 contain only the second polymer.

[0052] Table 1

[0053]

[0054]

[0055] Performance testing

[0056] [Resistance Test]

[0057] Ten circuit protection devices for E1-E12 and CE1-CE7 were selected as test samples. The test samples were heated from 25°C to 250°C in an oven at a heating rate of 2°C / min. The initial resistance (R0) of the test samples at 25°C was measured using a micro-ohmmeter. 25 ,R i Resistance (R) at 180℃ 180 and its resistance (R) at 240℃ 240 The average test results are shown in Table 2.

[0058] Table 2

[0059]

[0060]

[0061] Table 2 shows the average resistance (R0) of the E1-E12 test samples at 240℃. 240The resistance is between 342.9-657.7Ω, which is significantly greater than that of the test samples of CE1-CE7 (between 274.2-298.5Ω), indicating that the circuit protection devices of E1-E12 can withstand higher rated voltages without damage.

[0062] Breakdown voltage test

[0063] Ten circuit protection devices for E1-E12 and CE1-CE7 were selected as test samples, with a starting voltage of 10V. dc The test was conducted by maintaining a current of 100A for 2 minutes. If none of the samples burned out (indicating that the test was passed), another 10 samples were taken, and the voltage was increased by 2V each time. dc The tests were then conducted. The highest voltage (i.e., breakdown voltage) at which all 10 samples of E1-E12 and CE1-CE7 did not burn out after testing was recorded, and the results are shown in Table 2.

[0064] The results in Table 2 show that the breakdown voltage (20-26V) of the test samples E1-E12 is significantly higher than that of the test samples CE1-CE7 (16V). Among them, the test samples E4 and E10 have the highest breakdown voltage (26V), indicating that the circuit protection devices of E1-E12 can withstand higher voltages without burning out (the circuit protection devices have better stability).

[0065] [Switching cycle test]

[0066] Ten circuit protection devices for E1-E12 and CE1-CE7 were selected as test samples, and tested at 16V. dc The voltage and current of 10A were applied to the sample for 60 seconds, then cut off for 60 seconds, and this switching cycle was repeated 6000 times. The resistance (R) of each test sample was measured after the test. f1 And calculate the rate of change of resistance (R) f1 / R i (×100%), and the average values ​​of the test results are shown in Table 2.

[0067] Table 2 shows that the average resistance change rate of the test samples E1-E12 ranges from 167% to 322%. Among them, the test samples E4 and E10 have relatively small resistance change rates (193% and 167%, respectively), which are significantly lower than the average resistance change rates of the test samples CE1-CE7 (589%-715%). This indicates that the circuit protection devices of E1-E12 have better stability and durability.

[0068] [Aging test]

[0069] Ten circuit protection devices for E1-E12 and CE1-CE7 were selected as test samples, and tested at 16V. dc The voltage and current of 10A were continuously applied to the samples for 1000 hours, and the resistance (R) of each test sample was measured after the test. f2 And calculate the rate of change of resistance (R) f2 / R i (×100%), and the average values ​​of the test results are shown in Table 2.

[0070] Table 2 shows that the average resistance change rate of the test samples E1-E12 ranges from 393% to 1039%. Among them, the test samples E4 and E10 have relatively small resistance change rates (490% and 393%), which are significantly lower than the average resistance change rates of the test samples CE1-CE7 (3761%-4005%). This indicates that the circuit protection devices of E1-E12 have better stability and durability.

[0071] In summary, by combining the first polymer and the second polymer, which have specific melting point ranges, in a specific weight ratio range, the circuit protection device comprising the positive temperature coefficient polymer composition of the present invention can withstand higher voltages and has better stability and durability. The operating temperature range of this circuit protection device is -40°C to 125°C, and it can operate at voltages above 16V. dc It can be used under the rated voltage, so it can indeed achieve the purpose of this invention.

[0072] The above description is merely an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the present invention shall still fall within the scope of the present invention.

Claims

1. A polymer composition with a positive temperature coefficient, characterized in that, It includes: The first polymer has a melting point of 100°C to 200°C; The second polymer has a melting point greater than 200°C, and the weight ratio of the first polymer to the second polymer is in the range of 1:5 to 5:1; and Conductive filler dispersed in the first polymer and the second polymer.

2. The positive temperature coefficient polymer composition according to claim 1, characterized in that: The melting point of the second polymer is at least 50°C higher than that of the first polymer.

3. The positive temperature coefficient polymer composition according to claim 1, characterized in that: The weight ratio of the first polymer to the second polymer ranges from 1:4 to 4:

1.

4. The positive temperature coefficient polymer composition according to claim 3, characterized in that: The weight ratio of the first polymer to the second polymer ranges from 1:3 to 3:

1.

5. The positive temperature coefficient polymer composition according to claim 4, characterized in that: The weight ratio of the first polymer to the second polymer ranges from 1:2 to 2:

1.

6. The positive temperature coefficient polymer composition according to claim 5, characterized in that: The weight ratio of the first polymer to the second polymer is 1:

1.

7. The positive temperature coefficient polymer composition according to claim 1, characterized in that: The total weight of the positive temperature coefficient polymer composition is 100 wt%, and the content of at least one of the first polymer and the second polymer ranges from 11 to 46 wt%.

8. The positive temperature coefficient polymer composition according to claim 1, characterized in that: The first polymer has a melting point of 140°C to 180°C, and the second polymer has a melting point of greater than 200°C to 280°C.

9. The positive temperature coefficient polymer composition according to claim 1, characterized in that: The first polymer has a melt flow index of 0.5-30 g / 10 min at 230 °C, and the second polymer has a melt flow index of 3-40 g / 10 min at 297 °C.

10. The positive temperature coefficient polymer composition according to claim 1, characterized in that: The first polymer is selected from polypropylene or polyvinylidene fluoride.

11. The positive temperature coefficient polymer composition according to claim 1, characterized in that: The second polymer is selected from polyethylene terephthalate, perfluoroalkoxyalkane, polyamide, polyacrylonitrile, polystyrene, or ethylene-tetrafluoroethylene copolymer.

12. A circuit protection device, characterized in that, It includes: A polymeric positive temperature coefficient element, comprising a polymeric substrate and a conductive filler dispersed in the polymeric substrate, the polymeric substrate comprising a first polymer and a second polymer; and Two electrodes are respectively disposed on opposite sides of the polymer positive temperature coefficient element; The first polymer has a melting point of 100°C to 200°C, the second polymer has a melting point greater than 200°C, and the weight ratio of the first polymer to the second polymer is in the range of 1:5 to 5:

1.

13. The circuit protection device according to claim 12, characterized in that: The melting point of the second polymer is at least 50°C higher than that of the first polymer.

14. The circuit protection device according to claim 12, characterized in that: The weight ratio of the first polymer to the second polymer ranges from 1:4 to 4:

1.

15. The circuit protection device according to claim 14, characterized in that: The weight ratio of the first polymer to the second polymer ranges from 1:3 to 3:

1.

16. The circuit protection device according to claim 15, characterized in that: The weight ratio of the first polymer to the second polymer ranges from 1:2 to 2:

1.

17. The circuit protection device according to claim 12, characterized in that: The total weight of the polymer positive temperature coefficient element is 100 wt%, and the content of at least one of the first polymer and the second polymer ranges from 11 to 46 wt%.

18. The circuit protection device according to claim 12, characterized in that: The first polymer has a melting point of 140°C to 180°C, and the second polymer has a melting point of greater than 200°C to 280°C.

19. The circuit protection device according to claim 12, characterized in that: The first polymer is selected from polypropylene or polyvinylidene fluoride.

20. The circuit protection device according to claim 12, characterized in that: The second polymer is selected from polyethylene terephthalate, perfluoroalkoxyalkane, polyamide, polyacrylonitrile, polystyrene, or ethylene-tetrafluoroethylene copolymer.

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