TWI744625B - PTC circuit protection device - Google Patents

Abstract

A PTC circuit protection device includes a positive temperature coefficient polymer material and two electrodes attached to the positive temperature coefficient polymer material. The positive temperature coefficient polymer material includes a polymer substrate and a particulate conductive filler dispersed in the polymer substrate. The polymer substrate is made of a polymer composition containing a non-grafted polyolefin. The particulate conductive filler includes first tungsten carbide particles, the first tungsten carbide particles having a first average Fischer microsieve particle size less than 2.5 μm, and a first particle size distribution. The D10 particle size is less than 2.0 μm, and the D100 particle size of the first particle size distribution is less than 10.0 μm. The PTC circuit protection device of the present invention has excellent electrical stability under high voltage.

Description

PTC circuit protection device

The present invention relates to a positive temperature coefficient (PTC) circuit protection device, in particular to a PTC circuit protection device with excellent electrical stability under high voltage.

A positive temperature coefficient (PTC) element exhibits a positive temperature coefficient effect equivalent to a circuit protection device (such as a resettable fuse). The PTC element includes a PTC polymer material, and a first electrode and a second electrode attached to two opposite surfaces of the PTC polymer material.

The PTC polymer material includes a polymer substrate containing a crystalline region and an amorphous region, and a particulate conductive filler. The particulate conductive filler is dispersed in the amorphous region of the polymer matrix and forms a continuous conductive path for electrically connecting the first electrode and the second electrode. The positive temperature coefficient effect refers to a phenomenon in which when the temperature of the crystalline region is increased to its melting point, the crystals in the crystalline region begin to melt, thereby generating a new amorphous region. When the new amorphous region is increased to the extent that it merges into the original amorphous region, the conductive path of the particulate conductive filler will become discontinuous and the resistance of the PTC polymer material will increase significantly, resulting in the first There is no electrical conduction between one electrode and the second electrode.

Although the conductivity of the PTC polymer material can be significantly improved by using granular non-carbon particles (such as metal particles), the high conductivity of the conductive non-carbon particles can easily lead to the use of the PTC polymer material. An undesirable arc is generated. The electric arc will deteriorate the molecular structure of the PTC polymer material and cause the electrical instability of the PTC element, and reduce the service life of the PTC element.

US patent US 10,147,525 B1 discloses a PTC polymer material. The PTC polymer material includes a polymer substrate and tungsten carbide particles dispersed in the polymer substrate. Based on the total weight of the tungsten carbide particles, the total carbon content of the tungsten carbide particles ranges from 5.0 to 6.0 wt%, so the device containing the PTC polymer material can be operated at 12 Vdc and the electrical stability can be improved. However, there is still a need to further improve the electrical stability at higher voltages (for example, 30 Vdc).

Therefore, the purpose of the present invention is to provide a PTC circuit protection device that can overcome at least one of the above-mentioned disadvantages of the prior art.

Therefore, the PTC circuit protection device of the present invention includes a positive temperature coefficient polymer material and two electrodes attached to the positive temperature coefficient polymer material. The positive temperature coefficient polymer material includes a polymer substrate and a particulate conductive filler dispersed in the polymer substrate.

The polymer substrate is made of a polymer composition containing a non-grafted polyolefin. The particulate conductive filler includes first tungsten carbide particles, the first tungsten carbide particles having a first average Fisher sub-sieve particle size (Fisher sub-sieve particle size, FSSS) less than 2.5 μm, and a first particle Diameter distribution, the D10 particle size of the first particle size distribution is less than 2.0 μm, and the D100 particle size of the first particle size distribution is less than 10.0 μm.

The effect of the present invention is that the PTC circuit protection device of the present invention has excellent electrical stability under high voltage.

The content of the present invention will be described in detail below:

In certain embodiments, the non-grafted polyolefin is non-grafted polyethylene. In certain embodiments, the non-grafted polyolefin is high density polyethylene (HDPE).

In some embodiments, the polymer composition further includes a grafted polyolefin. In certain embodiments, the grafted polyolefin is polyethylene grafted with carboxylic anhydride. The polyethylene grafted with carboxylic anhydride may be high-density polyethylene grafted with carboxylic anhydride. In this embodiment, the high-density polyethylene grafted with carboxylic anhydride is a high-density polyethylene grafted with maleic anhydride.

In some embodiments, the first average Fischer microsieve particle size of the first tungsten carbide particles is greater than 1.9 μm. In some embodiments, the first average Fischer microsieve particle size of the first tungsten carbide particles is less than 2.0 μm.

In some specific embodiments, the D10 particle size of the first particle size distribution is greater than 0.9 μm. In some specific embodiments, the D10 particle size of the first particle size distribution is less than 1.0 μm.

In some specific embodiments, the D100 particle size of the first particle size distribution is greater than 7.0 μm. In some specific embodiments, the D100 particle size of the first particle size distribution is less than 8.0 μm.

Preferably, the first tungsten carbide particles have a total carbon content, and based on the total weight of the first tungsten carbide particles, the total carbon content ranges from 5.0 to 6.1 wt%. In some embodiments, the first tungsten carbide particles have a total carbon content, and based on the total weight of the first tungsten carbide particles, the total carbon content ranges from 5.6 to 6.1 wt%. In some embodiments, the first tungsten carbide particles have a total carbon content, and based on the total weight of the first tungsten carbide particles, the total carbon content ranges from 5.6 to 5.9 wt%.

In some specific embodiments, based on the total weight of the positive temperature coefficient polymer material, the content of the polymer substrate ranges from 4 to 6 wt%, and the content of the particulate conductive filler ranges from 94 to 96 wt%. In some embodiments, based on the total weight of the positive temperature coefficient polymer material, the content of the first tungsten carbide particles is at least 48 wt%.

In some embodiments, the particulate conductive filler further includes second tungsten carbide particles, and the second tungsten carbide particles have a second average Fischer microsieve particle size larger than the first average Fischer microsieve particle size Diameter, and a second particle size distribution, the D10 particle size of the second particle size distribution is greater than the D10 particle size of the first particle size distribution, and the D100 particle size of the second particle size distribution is greater than the first particle size distribution The D100 particle size.

In some embodiments, the content of the first tungsten carbide particles is greater than or equal to the content of the second tungsten carbide particles. In some embodiments, as mentioned above, based on the total weight of the positive temperature coefficient polymer material, the content of the first tungsten carbide particles is at least 48 wt%.

The present invention will be further described with the following examples, but it should be understood that these examples are for illustrative purposes only and should not be construed as limitations to the implementation of the present invention.

Referring to FIG. 1, an embodiment of the PTC circuit protection device of the present invention includes a positive temperature coefficient polymer material 2 and two electrodes 3 attached to two opposite surfaces of the positive temperature coefficient polymer material 2 respectively.

The positive temperature coefficient polymer material 2 includes a polymer substrate 21 and a particulate conductive filler 22 dispersed in the polymer substrate 21. The polymer substrate 21 is made of a polymer composition containing a non-grafted polyolefin.

According to the present invention, the particulate conductive filler includes first tungsten carbide particles, the first tungsten carbide particles having a first average Fischer microsieve particle size less than 2.5 μm, and a first particle size distribution. The D10 particle size of the particle size distribution is less than 2.0 μm, and the D100 particle size of the first particle size distribution is less than 10.0 μm.

Example

＜ Example 1 (E1) ＞

9 g HDPE (purchased from Taiwan Plastics Industry Co., Ltd., model HDPE 9002) was mixed in a Brabender mixer as a non-grafted polyolefin, and 9 g of HDPE grafted with maleic anhydride (purchased from Dupont , The model is MD100D) as the grafted polyolefin, and 282 g tungsten carbide particles (WC-1 particles) as the first tungsten carbide particles of the particulate conductive filler.

As shown in Table 1, the average Fischer microsieve particle size of the WC-1 particles is 1.96 μm, the total carbon content is 5.6 wt%, the D10 particle size of the particle size distribution is 0.97 μm, and the D100 particle size of the particle size distribution is It is 7.09 μm. The WC-1 particles are made by contacting tungsten metal and carbon particles, carbonizing at about 1750°C in the presence of hydrogen, and then pulverizing into particles with high-pressure air. The mixing temperature is 200°C, the stirring speed is 50 rpm, the pressurized weight is 5 kg, and the mixing time is 10 min.

The obtained mixed mixture was pressed into a sheet of the positive temperature coefficient polymer material 2 by hot pressing, the thickness of which was 0.28 mm. The hot pressing temperature is 200° C., the hot pressing time is 4 min, and the hot pressing pressure is 80 kg/cm ² . Two copper foil sheets (as electrodes) are attached to the two opposite sides of the sheet, and are hot-pressed under an environment where the hot-pressing temperature is 200℃, the hot-pressing time is 4 min, and the hot-pressing pressure is 80 kg/cm ² A positive temperature coefficient laminate with a thickness of 0.35 mm sandwich structure is formed. The positive temperature coefficient laminate was cut into multiple test samples with dimensions of 4.5 mm×3.2 mm×0.35 mm, and irradiated with Co-60 γ rays with a total radiation dose of 150 kGy.

＜ Example 2 and 3 (E2 and E3) ＞

The process conditions of the test samples of Examples 2 and 3 (E2 and E3) are similar to those of Example 1. The difference is that the usage amounts of the first tungsten carbide particles, HDPE and grafted HDPE are changed as shown in Table 1. Shown.

＜ Example 4 and 5 (E4 and E5) ＞

The process conditions of the test samples of Examples 4 and 5 (E4 and E5) are similar to those of Example 3. The difference is that the types of the tungsten carbide particles as the first tungsten carbide particles are changed to WC-2 particles and WC- particles, respectively. 3 particles.

As shown in Table 1, the average Fischer microsieve particle size of the WC-2 particles is 2.45 μm, the total carbon content is 5.9 wt%, the D10 particle size of the particle size distribution is 1.90 μm, and the D100 particle size of the particle size distribution is It is 9.86 μm. The average Fischer microsieve particle size of the WC-3 particles is 2.40 μm, the total carbon content is 6.1 wt%, the D10 particle size of the particle size distribution is 1.52 μm, and the D100 particle size of the particle size distribution is 8.92 μm.

＜ Example 6 and 7 (E6 and E7) ＞

The process conditions of the test samples of Examples 6 and 7 (E6 and E7) are similar to those of Example 3. The difference is that the particulate conductive filler also includes different amounts of tungsten carbide particles (WC-4 particles) as the second tungsten carbide Particles.

As shown in Table 1, the average Fischer microsieve particle size of the WC-4 particles is 3.10 μm, the total carbon content is 5.6 wt%, the D10 particle size of the particle size distribution is 2.56 μm, and the D100 particle size of the particle size distribution is It is 18.50 μm. The WC-4 particles are made by contacting tungsten metal and carbon particles and carbonizing at about 1750°C in the presence of hydrogen. The usage amounts of HDPE, grafted HDPE, the first tungsten carbide particles and the second tungsten carbide particles are shown in Table 1, respectively.

＜Compare example 1 to 5 (CE1 to CE5) ＞

The process conditions of the test samples of Comparative Examples 1 to 5 (CE1 to CE5) are similar to those of Examples 1 to 5, respectively. The difference is that Comparative Examples 1 to 3 change the types of tungsten carbide particles as the first tungsten carbide particles to WC-4 particles, Comparative Examples 4 and 5 changed the types of the tungsten carbide particles as the first tungsten carbide particles to WC-5 particles and WC-6 particles, respectively.

As shown in Table 1, the average Fischer microsieve particle size of the WC-5 particles is 2.93 μm, the total carbon content is 5.9 wt%, the D10 particle size of the particle size distribution is 2.45 μm, and the D100 particle size of the particle size distribution is It is 16.21 μm. The average Fischer microsieve particle size of the WC-6 particles is 2.91 μm, the total carbon content is 6.1 wt%, the D10 particle size of the particle size distribution is 2.08 μm, and the D100 particle size of the particle size distribution is 15.34 μm. 【Table 1】 Polymer substrate Granular conductive filler The first tungsten carbide (WC) particles Second tungsten carbide particles HDPE (wt%) Grafted HDPE (wt%) type wt% FSSS (μm) D10 (μm) D100 (μm) Total W/C content (wt%) type wt% FSSS (μm) D10 (μm) D100 (μm) Total W/C content (wt%) E1 3.0 3.0 WC-1 94.0 1.96 0.97 7.09 94.4/5.6 E2 2.5 2.5 WC-1 95.0 1.96 0.97 7.09 94.4/5.6 E3 2.0 2.0 WC-1 96.0 1.96 0.97 7.09 94.4/5.6 E4 2.0 2.0 WC-2 96.0 2.45 1.90 9.86 94.1/5.9 E5 2.0 2.0 WC-3 96.0 2.40 1.52 8.92 93.9/6.1 E6 2.0 2.0 WC-1 72.0 1.96 0.97 7.09 94.4/5.6 WC-4 24.0 3.10 2.56 18.50 94.4/5.6 E7 2.0 2.0 WC-1 48.0 1.96 0.97 7.09 94.4/5.6 WC-4 48.0 3.10 2.56 18.50 94.4/5.6 CE1 3.0 3.0 WC-4 94.0 3.10 2.56 18.50 94.4/5.6 CE2 2.5 2.5 WC-4 95.0 3.10 2.56 18.50 94.4/5.6 CE3 2.0 2.0 WC-4 96.0 3.10 2.56 18.50 94.4/5.6 CE4 2.0 2.0 WC-5 96.0 2.93 2.45 16.21 94.1/5.9 CE5 2.0 2.0 WC-6 96.0 2.91 2.08 15.34 93.9/6.1

In each example and each comparative example, 10 samples were tested using a micro-ohmmeter. _{Measure the initial resistance (R i} , ohm) and volume resistivity (VR, ohm-cm) of the test samples of E1~E7 and CE1~CE5 at 25°C. The average values are shown in Table 2.

Performance Testing

Attach two tin foil sheets to the copper foil sheets of each test sample of E1~E7 and CE1~CE5, respectively, to perform the following breakdown test, switching cycle test and aging ( aging) test.

[ Collapse test (Breakdown test)]

Carry out the collapse test on the samples prepared by E1~E7 and CE1~CE5 respectively: each example and each comparative example are tested with 10 samples first, and the starting voltage is 8 Vdc and the constant current 10 A is energized for 60 s and then cut off. Electricity 60 s cycle 10 times to test. If none of the 10 samples are burnt (indicating that the pass rate is 100%), another 10 samples are taken, and the voltage is changed to 12 Vdc for 10 cycles for testing. If none is burnt, the voltage is changed to increase 4 Vdc successively. Record the maximum withstand voltage (ie, collapse voltage) of the test samples of E1~E7 and CE1~CE5 after the test of 10 samples without burning, and the results are shown in Table 2.

It can be seen from Table 2 that the breakdown voltage (40~48 Vdc) of the test samples of E1~E7 is significantly higher than the breakdown voltage (8~12 Vdc) of the corresponding test samples of CE1~CE5. This result shows that a PTC device containing tungsten carbide particles with an average Fischer microsieve particle size of less than 2.5 μm, a particle size distribution of D10 particle size less than 2.0 μm, and a particle size distribution of D100 particle size less than 10.0 μm can effectively withstand higher voltages. In the collapse.

In addition, compared to the test samples of CE3, the test samples of E6 and E7 not only contain WC-4 with a larger particle size, but also contain WC-1 with a smaller particle size (and its content is not less than the content of WC-4) , Showing a higher breakdown voltage.

Therefore, the applicant speculates that tungsten carbide particles with a smaller particle size have less contact with each other (that is, tend to disperse) in high voltage and high current, which can avoid undesirable arcs and flashovers, thereby preventing PTC device damage Or burned.

[ Toggle cycle test (Switching cycle test)]

For each embodiment and each comparative example, 10 samples were tested in a switching cycle. The test samples of E1~E7 and CE1~CE5 were connected with a voltage of 30 Vdc and a current of 10 A respectively for 60 seconds, and then switched off for 60 seconds, thus performing 7200 switching cycles. _{Measure the resistance (R i} and R _f ) of each test sample before the start and after 7,200 cycles, and determine the average resistance change rate (R _f /R _i ×100%) of each example and each comparative example, And calculate the switching cycle pass rate of each embodiment and each comparative example (n/10×100%, n represents the number of test samples that passed the switching cycle test without burning). The results of the switching cycle test are shown in Table 2.

The results show that all test samples from E1 to E7 have passed the switching cycle test (the switching cycle pass rate is 100%). The switching cycle pass rates of the test samples of CE1~CE5 are all below 20%, which means that the test samples of CE1~CE5 are easily damaged under a voltage of 30 Vdc. In addition, the average resistance change rate of the test samples from E1 to E7 is significantly lower than that of CE1 to CE5.

[ Aging test (Aging test)]

Ten samples were subjected to aging test for each example and each comparative example. Apply a voltage of 30 Vdc and a current of 10 A to the test samples of E1~E7 and CE1~CE5 for 1000 hours. _{Measure the resistance (R i} and R _f ) of each test sample before and after 1000 hours of application, and determine the average resistance change rate (R _f /R _i ×100%) of each example and each comparative example, And calculate the aging pass rate of each embodiment and each comparative example (n/10×100%, n represents the number of test samples that passed the aging test without being burnt). The results of the aging test are shown in Table 2.

The results show that all test samples of E1~E7 have passed the aging test (aging pass rate is 100%). The aging pass rates of the test samples of CE1~CE5 are all below 20%, which means that the test samples of CE1~CE5 are easily damaged under a voltage of 30 Vdc. In addition, the average resistance change rate of the test samples from E1 to E7 is significantly lower than that of CE1 to CE5. 【Table 2】 testing sample Collapse test Switching cycle test (7200 cycles) Aging test (1000 hours) R _i (ohm) VR (ohm-cm) (Vdc) R _f /R _i ×100% Passing rate R _f /R _i ×100% Passing rate E1 0.00452 0.01860 48 2777% 100% 1232% 100% E2 0.00403 0.01658 48 2674% 100% 1259% 100% E3 0.00361 0.01485 48 2886% 100% 1198% 100% E4 0.00385 0.01584 40 2751% 100% 1365% 100% E5 0.00407 0.01675 40 3702% 100% 2012% 100% E6 0.00396 0.01629 36 5730% 100% 2861% 100% E7 0.00426 0.01753 32 6969% 100% 3769% 100% CE1 0.00524 0.02156 12 12029% 20% 8057% 10% CE2 0.00448 0.01843 12 12533% 20% 8869% 20% CE3 0.00405 0.01666 12 13265% 10% 9124% 20% CE4 0.00423 0.01740 12 14572% 10% 12328% 10% CE5 0.00511 0.02102 8 NA 0% NA 0%

In Table 2, "NA" means unavailable.

In summary, by containing tungsten carbide particles with an average Fischer microsieve particle size less than 2.5 μm, a particle size distribution D10 particle size less than 2.0 μm, and a particle size distribution D100 particle size less than 10.0 μm, the PTC circuit protection of the present invention The device can operate at a higher voltage (for example, 30 Vdc) and exhibit good electrical stability, so it can indeed achieve the purpose of the invention.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited by this, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification still belong to This invention patent covers the scope.

2:Positive temperature coefficient polymer material 21: Polymer substrate 22: Granular conductive filler 3: electrode

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, in which: [Figure 1] is a schematic cross-sectional view of an embodiment of the PTC circuit protection device of the present invention.

2:Positive temperature coefficient polymer material

21: Polymer substrate

22: Granular conductive filler

3: electrode

Claims (10)

A PTC circuit protection device, comprising: a positive temperature coefficient polymer material, including a polymer substrate and a granular conductive filler dispersed in the polymer substrate; and attached to the positive temperature coefficient polymer material The two electrodes; wherein, the polymer substrate is made of a polymer composition, the polymer composition contains a non-grafted polyolefin; and wherein, the particulate conductive filler includes the first tungsten carbide Particles, the first tungsten carbide particles have a first average Fischer microsieve particle size smaller than 2.5 μm and larger than 1.9 μm, and a first particle size distribution, the D10 particle size of the first particle size distribution is smaller than 2.0 μm And greater than 0.9 μm, the D100 particle size of the first particle size distribution is less than 10.0 μm and greater than 7.0 μm; based on the total weight of the positive temperature coefficient polymer material, the content of the first tungsten carbide particles ranges from 48 to 96 wt% . The PTC circuit protection device according to claim 1, wherein the first average Fischer microsieve particle size of the first tungsten carbide particles is less than 2.0 μm and greater than 1.9 μm. The PTC circuit protection device according to claim 1, wherein the D10 particle size of the first particle size distribution is less than 1.0 μm and greater than 0.9 μm. The PTC circuit protection device according to claim 1, wherein the D100 particle size of the first particle size distribution is less than 8.0 μm and greater than 7.0 μm. The PTC circuit protection device according to claim 1, wherein, based on the total weight of the positive temperature coefficient polymer material, the content of the polymer substrate ranges from 4 to 6 wt%, and the content of the particulate conductive filler is 94 ~96wt%. The PTC circuit protection device according to claim 1, wherein the non-grafted polyolefin is high-density polyethylene. The PTC circuit protection device according to claim 1, wherein the polymer composition further includes a grafted polyolefin. The PTC circuit protection device according to claim 7, wherein the grafted polyolefin is high-density polyethylene grafted with carboxylic anhydride. The PTC circuit protection device according to claim 1, wherein the first tungsten carbide particles have a total carbon content, and based on the total weight of the first tungsten carbide particles, the total carbon content ranges from 5.0 to 6.1 wt %. The PTC circuit protection device according to claim 1, wherein the first tungsten carbide particles have a total carbon content, and based on the total weight of the first tungsten carbide particles, the total carbon content ranges from 5.6 to 5.9 wt %.

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