High-power PPTC (Polymeric Positive Temperature Coefficient) material and generation method

Abstract

The invention provides a high-power PPTC (Polymeric Positive Temperature Coefficient) material which comprises the following components in parts by weight: 35-60 parts of a polymer matrix; 35-60 parts of a conductive filler, wherein the conductive filler is carbon black with an oil absorption value of 100-200; the particle size of the nano-scale oxide additive is 1-100 nm, and the preparation method comprises the following steps: S1, mixing and granulating: mixing the polymer matrix, the conductive filler, the nano-scale oxide additive and other auxiliaries, and carrying out melt mixing and granulating by adopting a reciprocating single-screw extruder; s2, extruding, laminating and forming: after melting the composite master batch, extruding to form a film through a mold, and compounding the film with nickel-plated copper foil between a pair of laminating rollers; s3, irradiation crosslinking: performing irradiation treatment on the sheet; and S4, product packaging: packaging the PPTC material subjected to irradiation treatment, so that the technical requirements of 3.0 A through-current capability and 30V withstand voltage level are met at the same time under the 1812 packaging size, and the technical problem that high through-current capability and high withstand voltage level are difficult to achieve at the same time in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of PPTC technology, specifically relating to a high-power PPTC material and its generation method. Background Technology

[0002] PPTC (Polymer Positive Temperature Coefficient) material is an important circuit protection component. When overcurrent or overheating occurs in a circuit, its resistance increases sharply, thus protecting the circuit. Traditional PPTC materials are usually composed of a polymer matrix and conductive fillers, where the selection and proportion of the conductive filler play a crucial role in the material's electrical properties.

[0003] In the prior art, various technical solutions for PPTC materials have been proposed. CN112094449A discloses a PTC polymer conductive composite material with adjustable Curie point, comprising 30-70% polymer matrix, 35-60% conductive filler, 1-3% antioxidant, 0.1-4% lubricant, and 2-8% voltage-resistant reinforcing filler. The Curie point can be controlled between 60-110℃ by changing the composition of the polymer matrix. CN109016731B describes a high-temperature PTC circuit protection element, using a trapezoidal conjugated polymer material as a crosslinking agent to improve the high-temperature performance of the material. CN118254432A proposes a five-layer composite structure polymer-based PTC composite material, which combines the advantages of low room temperature resistivity and high voltage resistance through structural design. CN118271724A discloses a polymer-based PTC material with high room temperature conductivity, using conductive fillers with multi-size particle configuration to improve room temperature conductivity. CN116948286A relates to a high-voltage resistant PPTC polymer composition, which improves voltage resistance through a combination of particulate conductive fillers and needle-like conductive fillers.

[0004] However, existing PPTC materials still have some technical limitations. First, while polymer-based conductive composites using carbon black as a conductive filler exhibit good resistivity, the conductivity of commonly used carbon black is limited, failing to meet the requirements of high-power applications. In an 1812 package, the withstand voltage of a 3A product typically only reaches 6V. Second, while existing technologies using metal powder or carbides as fillers can achieve a current carrying capacity of 3A, their withstand voltage is generally limited to below 24V, and the products exhibit poor environmental stability, making them unsuitable for high-reliability applications. Therefore, there is currently a lack of PPTC materials and their preparation methods that can simultaneously meet the requirements of high current carrying capacity (3A) and high withstand voltage (30V or higher), which limits the application of PPTC materials in high-power electronic devices. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-power PPTC material, comprising the following components in parts by weight: 35-60 parts of polymer matrix; 35-60 parts of conductive filler, wherein the conductive filler is carbon black with an oil absorption value between 100-200; 0.1-5 parts of nano-sized oxide additive, wherein the particle size of the nano-sized oxide additive is 1nm-100nm.

[0006] Furthermore, the oil absorption value of the carbon black is above 120.

[0007] Furthermore, the nanoscale oxide additive is selected from at least one of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, or zirconium oxide.

[0008] Furthermore, the polymer matrix is ​​polyethylene.

[0009] Furthermore, it also includes 0.1-3 parts by weight of antioxidant and / or 0.01-1 parts by weight of PPA processing aid.

[0010] A method for preparing a high-power PPTC material, the method comprising the following steps: S1. Mixing and granulation: The polymer matrix, conductive filler, nano-sized oxide additives and other auxiliaries are mixed and then melt-mixed and granulated using a reciprocating single-screw extruder to obtain composite masterbatch; S2. Extrusion Coating: The composite masterbatch is melted, extruded into a film through a die, and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PTC core material-nickel-plated copper foil", wherein the coating rollers are rubber rollers; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material.

[0011] Furthermore, in step S1, the reciprocating single-screw extruder has a mixing screw block on the screw and a corresponding mixing pin on the inner liner of the barrel. The mixing screw block breaks at least once within one screw pitch.

[0012] Furthermore, in step S2, the nickel-plated copper foil is a single-sided nickel-plated copper foil.

[0013] The beneficial effects of this invention are as follows: compared with the prior art, the addition of nano-sized oxides can improve the withstand voltage rating, and nanoparticles can suppress space charge, thereby improving the breakdown field strength of the composite material and achieving a withstand voltage rating of 30V or higher; combined with a specific reciprocating single-screw extruder mixing method, the screw simultaneously performs axial reciprocating oscillation during rotation, enhancing the mixing effect and ensuring optimal dispersibility and distribution; in the coating process, the use of rubber rollers to replace the original steel rollers effectively reduces the impact on the performance of PPTC materials during production, improves crystallization conditions, reduces internal stress, thereby reducing resistivity by about 30% and improving current carrying capacity; it achieves the technical requirements of simultaneously meeting the 3.0A current carrying capacity and 30V withstand voltage rating within the 1812 package size, solving the technical problem of the difficulty in achieving both high current carrying capacity and high withstand voltage rating in the prior art. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the production method of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] To address the problems existing in the relevant prior art, please refer to Figure 1 This invention proposes a high-power PPTC material, comprising the following components in parts by weight: 35-60 parts of polymer matrix, specifically polyethylene is selected as the polymer matrix; 35-60 parts of conductive filler, wherein the conductive filler is carbon black with an oil absorption value between 100 and 200.

[0018] 0.1-5 parts of nano-sized oxide additive, wherein the particle size of the nano-sized oxide additive is 1nm-100nm, and the nano-sized oxide additive is selected from at least one of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide or zirconium oxide.

[0019] In the above scheme, preferably, the oil absorption value of the carbon black is above 120.

[0020] The composition also includes 0.1-3 parts by weight of antioxidant and / or 0.01-1 parts by weight of PPA processing aid.

[0021] Based on the same concept, this invention also proposes a method for preparing high-power PPTC materials, comprising the following steps: S1. Mixing and Granulation: The polyethylene matrix, conductive filler, nano-sized oxide additives and other auxiliaries are mixed and then melt-mixed and granulated using a reciprocating single-screw extruder to obtain composite masterbatch. Specifically, the reciprocating single-screw extruder is used with a mixing speed of 500-1500 RPM, a mixing time of 3-5 min, a screw temperature of 160-220℃, and a rotation speed of 50-150 RPM. The screw of the reciprocating single-screw extruder is equipped with a mixing screw block, and the inner liner of the barrel is equipped with a corresponding mixing pin. The mixing screw block is broken at least once within one screw pitch.

[0022] S2. Extrusion Coating: The composite masterbatch is melted and extruded into a film through a die. It is then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PPTC core material-nickel-plated copper foil". The nickel-plated copper foil is single-sided nickel-plated copper foil. The coating rollers are rubber rollers, which specifically refer to pressure rollers with a certain thickness of rubber wrapped around the outer layer of a steel roller. The coating temperature is 180-250℃, the roller speed is 0.1-1.0m / min, and the roller gap is 0.1-0.5mm. S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrads; S4. Product Packaging: Packaging the irradiated PPTC material.

[0023] In the packaging process, insulating grooves are etched into the conductive electrodes of the PPTC sheet using inner layer pattern transfer etching technology. Then, two insulating layers are stacked on the two surfaces of the etched composite sheet and covered with metal foil. The sheets are then pressed together at high temperature. After that, the pressed substrate undergoes subsequent steps such as tin plating of the outer metal foil, etching of the outer layer pattern, printing of solder resist ink, curing of solder resist ink, drilling, copper plating, and encapsulation to obtain a polymer PTC overcurrent protection element with excellent environmental stability. The pressing temperature is 150-210℃.

[0024] The following are specific examples: Example 1

[0025] Select the following components by weight: Carbon black N500 46 parts, nano-alumina 1.5 parts, polyethylene 52.35 parts, antioxidant 0.1 parts and PPA 0.05 parts.

[0026] The above components are produced through the following steps: S1. Mixing and granulation: The above-mentioned polyethylene matrix, carbon black N500, nano-alumina, antioxidant and PPA are mixed and blended, and then melt-mixed and granulated using a reciprocating single screw extruder to obtain composite masterbatch; S2. Extrusion Coating: After melting the composite masterbatch, it is extruded into a film through a die and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PPTC core material-nickel-plated copper foil", wherein at least one of the coating rollers is a rubber roller; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material. Example 2

[0027] Select the following components by weight: Carbon black N500 46 parts, nano-grade zirconium oxide 1.5 parts, polyethylene 50.5 parts, antioxidant 1 part and PPA 1 part.

[0028] The above components are produced through the following steps: S1. Mixing and granulation: The above-mentioned polyethylene matrix, carbon black N500, nano-grade zirconium oxide, antioxidant and PPA are mixed, melt-mixed and granulated using a reciprocating single screw extruder to obtain composite masterbatch; S2. Extrusion Coating: After melting the composite masterbatch, it is extruded into a film through a die and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PPTC core material-nickel-plated copper foil", wherein at least one of the coating rollers is a rubber roller; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material. Example 3

[0029] Select the following components by weight: Carbon black N500 46 parts, nano-grade silica 1.5 parts, polyethylene 49 parts, antioxidant 3 parts and PPA 0.5 parts.

[0030] The above components are produced through the following steps: S1. Mixing and granulation: The above-mentioned polyethylene matrix, carbon black N500, nano-grade silica, antioxidant and PPA are mixed, melt-mixed and granulated using a reciprocating single screw extruder to obtain composite masterbatch; S2. Extrusion Coating: After melting the composite masterbatch, it is extruded into a film through a die and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PPTC core material-nickel-plated copper foil", wherein at least one of the coating rollers is a rubber roller; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material. Example 4

[0031] Select the following components by weight: Carbon black N660 48 parts, nano-alumina 0.8 parts, polyethylene 49.7 parts, antioxidant 1 part and PPA 0.5 parts.

[0032] The above components are produced through the following steps: S1. Mixing and granulation: The above-mentioned polyethylene matrix, carbon black N660, nano-alumina, antioxidant and PPA are mixed, melt-mixed and granulated using a reciprocating single screw extruder to obtain composite masterbatch; S2. Extrusion Coating: After melting the composite masterbatch, it is extruded into a film through a die and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PPTC core material-nickel-plated copper foil", wherein at least one of the coating rollers is a rubber roller; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material. Example 5

[0033] Select the following components by weight: Carbon black N660 50 parts, nano-grade zirconium oxide 1.2 parts, polyethylene 47.3 parts, antioxidant 1 part and PPA 0.5 parts.

[0034] The above components are produced through the following steps: S1. Mixing and granulation: The above-mentioned polyethylene matrix, carbon black N660, nano-grade zirconium oxide, antioxidant and PPA are mixed, melt-mixed and granulated using a reciprocating single screw extruder to obtain composite masterbatch; S2. Extrusion Coating: After melting the composite masterbatch, it is extruded into a film through a die and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PPTC core material-nickel-plated copper foil", wherein at least one of the coating rollers is a rubber roller; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material. Example 6

[0035] Select the following components by weight: Carbon black N660 52 parts, nano-alumina 2 parts, polyethylene 44.5 parts, antioxidant 1 part and PPA 0.5 parts.

[0036] The above components are produced through the following steps: S1. Mixing and granulation: The above-mentioned polyethylene matrix, carbon black N660 52 parts, nano-alumina, antioxidant and PPA are mixed, and melt-mixed and granulated using a reciprocating single screw extruder to obtain composite masterbatch; S2. Extrusion Coating: After melting the composite masterbatch, it is extruded into a film through a die and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PPTC core material-nickel-plated copper foil", wherein at least one of the coating rollers is a rubber roller; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material.

[0037] In the above six embodiments, the mixing equipment used is a reciprocating single-screw extruder manufactured by Xinda Company, with a mixing speed of 500-1500 RPM, a mixing time of 3-5 min, a screw temperature of 160-220℃, and a rotation speed of 50-150 RPM. The reciprocating single-screw extruder has a mixing screw block on the screw and a corresponding mixing pin on the inner liner of the barrel. The mixing screw block breaks once within one screw pitch.

[0038] The products of the above six embodiments were tested under the following specific conditions: First, the power input was 30V / 40A. After the product was triggered and started working, a 30V voltage was applied across the PPTC terminals for 168 hours. Second, a current-resistance cycle switch test was performed: under a 30V / 40A input, the device operated for 6 seconds, then disconnected for 120 seconds, for a total of 1000 cycles. The final test results are summarized in the table below: Example Carbon black type <![CDATA[Oil absorption value Cm 3 / 100g]]> Nano-additive types Nanoparticle size (nm) Nano-additive content (parts by weight) Sheet thickness (mm) Number of sheet layers Flow capacity Pressure rating Did it ignite, spew carbon, or burn? 1 N550 125 Alumina 50 1.5 0.20 4 3.0 30 no 2 N550 125 Zirconia 30 1.5 0.18 4 3.0 30 no 3 N550 125 silicon dioxide 20 1.5 0.18 4 3.0 30 no 4 N660 102 Alumina 50 0.8 0.22 4 3.0 30 no 5 N660 102 Zirconia 30 1.2 0.18 4 3.2 30 no 6 N660 102 silicon dioxide 20 2.0 0.20 4 3.4 36 no The results above show that by selecting carbon black with a high oil absorption value, increasing the oil absorption value of the carbon black can significantly reduce the resistivity of the finished product, thereby improving its current carrying capacity. However, it will reduce the product's withstand voltage. The main reason is that under fault current conditions, carbon black particles with a high oil absorption value are difficult to separate in the polymer matrix, making it difficult to increase the resistance when a sharp increase is needed. At this time, the voltage will be applied to both ends of the PPTC product, causing arc discharge due to the difficulty in separating the carbon black particles in the PPTC composite material, thus damaging the device. To increase the current, carbon black with a high oil absorption value must be used. Therefore, semiconductor oxide nanoparticles with a size comparable to that of carbon black are added to the material formulation. In this way, the oxide nanoparticles can occupy the positions of carbon black in the polymer. When voltage is applied, the band gap of the nanoparticles can absorb the energy generated by the arc discharge, thereby suppressing space charge and improving the breakdown field strength of the composite material.

[0039] Furthermore, the granulation process for the masterbatch employs a reciprocating single-screw extruder. On the screw mandrel, the modular screw blocks have a unique design; each block breaks three times within one screw pitch, forming a mixing block. Corresponding to these gaps, three rows of mixing pins are arranged on the inner bushing of the barrel. During screw rotation, it simultaneously undergoes axial reciprocating oscillation. One axial oscillation occurs per revolution. Due to this unique motion, and the action of the mixing blocks and pins, the material is not only sheared between the mixing pins and the irregularly shaped mixing blocks, but also reciprocated. This process differs from that of typical twin-screw extruders. The axial and radial mixing enhances the mixing effect, ensuring optimal dispersion and distribution.

[0040] In the PPTC sheet lamination process, rubber roller lamination is used instead of steel roller lamination. After the PPTC masterbatch is plasticized in a single-screw extruder and extruded through a die, the PPTC material is subjected to stretching, resulting in orientation. However, during sheet lamination, the shearing action of the two rollers generates internal stress in the PPTC material. After the sheet passes through the laminator, the PPTC material rapidly cools and crystallizes; this crystallization process is crucial to the resistivity of PPTC. The material's orientation and internal stress significantly influence crystallization. Compared to steel rollers, rubber rollers reduce strong shearing, improve crystallization conditions, and greatly reduce internal stress in the PPTC material, which is beneficial for reducing resistivity and thus improving the product's current-carrying capacity. Compared to steel roller lamination, rubber roller lamination can reduce resistivity by approximately 30%. In actual production, a 1cm thick layer of high-temperature resistant silicone rubber is wrapped around the steel roller.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-power PPTC material, characterized in that, The components include the following parts by weight: 35-60 parts of polymer matrix; 35-60 parts of conductive filler, wherein the conductive filler is carbon black with an oil absorption value between 100-200; 0.1-5 parts of nano-sized oxide additive, wherein the particle size of the nano-sized oxide additive is 1nm-100nm.

2. The high-power PPTC material according to claim 1, characterized in that, The oil absorption value of the carbon black is above 120.

3. A high-power PPTC material according to claim 1 or 2, characterized in that, The nanoscale oxide additive is selected from at least one of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, or zirconium oxide.

4. A high-power PPTC material according to claim 1 or 2, characterized in that, The polymer matrix is ​​polyethylene.

5. A high-power PPTC material according to claim 1 or 2, characterized in that, It also includes 0.1-3 parts by weight of antioxidants and / or 0.01-1 parts by weight of PPA processing aids.

6. A method for preparing a high-power PPTC material as described in any one of claims 1-5, characterized in that, The method includes the following steps: S1. Mixing and granulation: The polymer matrix, conductive filler, nano-sized oxide additives and other auxiliaries are mixed and then melt-mixed and granulated using a reciprocating single-screw extruder to obtain composite masterbatch; S2. Extrusion Coating: The composite masterbatch is melted, extruded into a film through a die, and then laminated with nickel-plated copper foil between a pair of coating rollers to form a sheet with a structure of "nickel-plated copper foil-PTC core material-nickel-plated copper foil", wherein the coating rollers are rubber rollers; S3. Irradiation crosslinking: The sheet is subjected to irradiation treatment with an irradiation dose of 4-30 Mrad; S4. Product Packaging: Packaging the irradiated PPTC material.

7. The method for preparing a high-power PPTC material according to claim 6, characterized in that, In step S1, the reciprocating single-screw extruder has a mixing screw block on the screw and a corresponding mixing pin on the inner liner of the barrel. The mixing screw block breaks at least once within one screw pitch.

8. The method for preparing a high-power PPTC material according to claim 6, characterized in that, In step S2, the nickel-plated copper foil is a single-sided nickel-plated copper foil.

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