Conductive filler, ptfc composite resin and method for producing the same

Abstract

This invention provides a conductive filler, a PTFE composite resin, and a method for preparing the same. The method for preparing the conductive filler includes the following steps: mixing and heating conductive carbon black, water, ethanol, and a pH adjuster to obtain a mixture; performing solid-liquid separation on the mixture to obtain a solid phase; and drying the solid phase to obtain the conductive filler. The conductive filler of this invention can be uniformly dispersed in a polytetrafluoroethylene emulsion, and the prepared PTFE composite resin exhibits excellent mechanical and antistatic properties.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a conductive filler, a PTFE composite resin, and a method for preparing the same. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is a high-performance solid self-lubricating material with excellent microwave electrical properties, extremely low coefficient of friction, good chemical and thermal stability. Materials prepared from PTFE exhibit high tensile strength, high lubricity, high temperature resistance, corrosion resistance, and UV resistance. Adding fillers to PTFE emulsions can further improve its physical properties, such as electrical conductivity, thermal conductivity, low dielectric constant, and antistatic properties. Therefore, filler-modified PTFE resins are widely used in the research and preparation of specialty materials in environmental protection, chemical, mechanical, electrical, construction, and medical fields.

[0003] Conductive carbon black possesses characteristics such as high conductivity, high structural properties, irregular and extremely small aggregate size (nanoscale), large and rough specific surface area, clean surface (few compounds), and easy homogeneity with other materials. It can effectively form a three-dimensional network structure in PTFE resin, significantly improving the resin's conductivity and imparting conductive or antistatic properties to resin products. The dispersion of conductive carbon black in a material determines its conductivity or antistatic properties. Especially when carbon black particles reach the nanoscale, the large specific surface area makes flocculation during dissolution easy. Therefore, to ensure uniform dispersion of conductive carbon black in resin materials and achieve good conductivity or antistatic effects, carbon black modification treatment is often necessary. Patent document CN109096661A discloses a polytetrafluoroethylene (PTFE) antistatic film and its preparation method. The method involves mixing N-(benzocyclobutene-4-yl)maleimide or a mixture of N-(benzocyclobutene-4-yl)maleimide and N-phenylmaleimide with carbon black and subjecting the mixture to a Diels-Alder reaction, followed by drying to obtain modified carbon black. The modified carbon black is then mixed with PTFE in a high-speed mixer. The mixture is then pressed, sintered, and flaked to obtain the PTFE antistatic film. However, due to the relatively large particle size and good hydrophobic and oleophobic properties of PTFE resin, the modified carbon black prepared by this method is difficult to disperse evenly when mixed with PTFE, potentially leading to low uniformity of the antistatic film. Furthermore, the PTFE resin is prone to fibrosis during high-speed mixing, which may affect its antistatic properties. Summary of the Invention

[0004] To address one of the aforementioned technical problems in the prior art, this invention provides a conductive filler that can be uniformly dispersed in polytetrafluoroethylene (PTFE) resin, thereby improving the resin material's electrical conductivity and antistatic properties while simultaneously enhancing its mechanical properties. This invention also provides a method for preparing the conductive filler and its applications. Furthermore, this invention provides a PTFE composite resin and its preparation method.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a conductive filler, comprising the following steps:

[0007] Conductive carbon black, water, ethanol, and a pH adjuster are mixed and heated to obtain a mixture;

[0008] The mixture is subjected to solid-liquid separation to obtain a solid phase, which is then dried to obtain a conductive filler.

[0009] According to some embodiments of the present invention, the pH adjuster includes one or more of ammonium carbonate, ammonium bicarbonate, and ammonia water. In some embodiments, the pH adjuster includes ammonium carbonate. In the preparation process of the conductive filler of the present invention, the use of pH adjusters such as ammonium carbonate not only adjusts the pH value of the solution, but these pH adjusters can also be effectively removed during the subsequent drying process, avoiding the introduction of impurities.

[0010] According to some embodiments of the present invention, the amount of the pH adjuster is such that the pH value of the mixture is 7.0-10.0, for example 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0 or any value between them, preferably 8.0-9.0.

[0011] According to some embodiments of the present invention, the heating temperature is 50-80°C. According to some embodiments of the present invention, the heating time is 6-10 hours. In the present invention, stirring is preferably performed simultaneously with heating, which is beneficial to the dispersion of carbon black particles.

[0012] According to some embodiments of the present invention, the drying temperature is 100-150°C. According to some embodiments of the present invention, the drying time is 8-16 hours.

[0013] According to some embodiments of the present invention, the average particle size of the conductive carbon black is 1-10 nm.

[0014] According to some embodiments of the present invention, the mass ratio of water to conductive carbon black is 100:(1-5), for example 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, 100:5 or any value between them, preferably 100:(3-5).

[0015] According to some embodiments of the present invention, the mass ratio of water to ethanol is 10:(1-5), for example 10:1, 10:2, 10:3, 10:4, 10:5 or any value between them, preferably 10:(3-5).

[0016] According to some embodiments of the present invention, the mass ratio of the water to the pH adjuster is 1000:(1-10), for example, 1000:1, 1000:2, 1000:3, 1000:4, 1000:5, 1000:6, 1000:7, 1000:8, 1000:9, 1000:10 or any value between them, preferably 1000:(3-8), more preferably 1000:(3-5).

[0017] In a second aspect, the present invention provides a conductive filler prepared by the preparation method described in the first aspect of the present invention.

[0018] Thirdly, the present invention provides the application of the conductive filler described in the second aspect of the present invention in the preparation of PTFE composite resin.

[0019] Fourthly, the present invention provides a PTFE composite resin, the composite resin comprising polytetrafluoroethylene and the conductive filler described in the second aspect of the present invention.

[0020] In some embodiments, the conductive filler in the composite resin accounts for 1-20% of the mass of polytetrafluoroethylene, for example 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20% or any value between them, preferably 10-20%, more preferably 10-15%.

[0021] In some embodiments, the tensile strength of the composite resin is 25-30 MPa.

[0022] In some embodiments, the elongation at break of the composite resin is 300%-400%, preferably 350%-400%.

[0023] In some embodiments, the relative density of the composite resin is 2.17-2.19.

[0024] In some embodiments, the surface resistivity of the composite resin is (3.5–13.0) × 10⁻⁶. 5Ω, preferably (3.5~9.0)×10 5 Ω, more preferably (3.5~6.0)×10 5 Ω.

[0025] Fifthly, the present invention provides a method for preparing the PTFE composite resin described in the fourth aspect of the present invention, comprising the following steps:

[0026] (1) The PTFE polymer emulsion is mixed with the conductive filler, dispersant and water and heated to obtain a dispersion;

[0027] (2) The dispersion is mixed with a coagulant and coagulated. After coagulation, solid-liquid separation is performed. The solid phase obtained after solid-liquid separation is dried to obtain the composite resin.

[0028] In some embodiments, in step (1), the solid content of the PTFE polymer emulsion is 28-32%. In some embodiments, in step (1), the average particle size of the primary particles of the PTFE polymer emulsion is 0.15-0.25 μm. In some embodiments, in step (1), the average molecular weight of polytetrafluoroethylene in the PTFE polymer emulsion is 1,000,000 to 4,000,000.

[0029] Commercially available PTFE emulsions typically contain a large amount of emulsifier to improve the stability of the PTFE polymer emulsion and prevent demulsification during transportation. If this application uses such a commercially available PTFE emulsion containing a large amount of emulsifier, the emulsifier is difficult to remove and will have a significant impact on the mechanical properties of the final composite resin product. Therefore, the PTFE polymer emulsion in step (1) of this invention preferably uses freshly prepared PTFE polymer stock solution. This invention does not impose any special limitations on the preparation method of the PTFE polymer emulsion. Conventional polymerization methods in the art can be used for preparation, such as solution polymerization. As a non-limiting example, the PTFE polymer emulsion is prepared by a method including the following steps: homopolymerizing tetrafluoroethylene monomer in the presence of deionized water, stabilizer, dispersant, anti-sticking agent and initiator to obtain the PTFE polymer emulsion.

[0030] In some embodiments, the stabilizer used in the preparation of the PTFE polymer emulsion includes, but is not limited to, paraffin wax. The present invention does not impose a particular limitation on the amount of stabilizer used; those skilled in the art can select it based on conventional amounts of stabilizers used in the field.

[0031] In some embodiments, the dispersant used in the preparation of the PTFE polymer emulsion includes, but is not limited to, ammonium perfluorooctanoate substitutes, such as perfluoroether carbonate surfactants, perfluorohexanoic acid, etc. This invention does not impose a particular limitation on the amount of dispersant used; those skilled in the art can select it based on conventional amounts of dispersants used in the field.

[0032] In some embodiments, the anti-sticking agent in the preparation of the PTFE polymer emulsion includes, but is not limited to, succinic acid. This invention does not impose a specific limitation on the amount of anti-sticking agent used; those skilled in the art can select it based on conventional amounts of anti-sticking agents used in the field.

[0033] In some embodiments, the initiator used in the preparation of the PTFE polymer emulsion includes, but is not limited to, persulfate initiators, such as potassium persulfate, sodium persulfate, and ammonium persulfate. This invention does not impose a specific limitation on the amount of initiator used; those skilled in the art can select the appropriate amount based on conventional initiator usage.

[0034] In some embodiments, the homopolymerization reaction is carried out at a temperature of 80-90°C during the preparation of the PTFE polymer emulsion.

[0035] In some embodiments, the homopolymerization reaction is carried out at a pressure of 2.0-3.0 MPa during the preparation of the PTFE polymer emulsion.

[0036] According to some embodiments of the present invention, in step (1), the dispersant comprises a nonionic surfactant, preferably a polyether nonionic surfactant. Examples of dispersants used in step (1) of the present invention include, but are not limited to, one or more of TMN-10, TMN-6, and E1310.

[0037] According to some embodiments of the present invention, in step (1), the mass ratio of the conductive filler to the PTFE polymer emulsion is (3-5):100, for example, 3:100, 3.5:100, 4.0:100, 4.5:100, 5:100 or any value between them, preferably (3-4.5):100, more preferably (4-4.5):100.

[0038] According to some embodiments of the present invention, in step (2), the mass ratio of the dispersant to the PTFE polymer emulsion is (0.3-0.9):1000, for example, 0.3:1000, 0.4:1000, 0.5:1000, 0.6:1000, 0.7:1000, 0.8:1000, 0.9:1000 or any value between them.

[0039] According to some embodiments of the present invention, in step (2), the mass ratio of water to the PTFE polymer emulsion is (2-6):1, for example, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1 or any value between them.

[0040] According to some embodiments of the present invention, in step (1), the heating temperature is 40-90°C, preferably 60-80°C. According to some embodiments of the present invention, in step (2), the coagulant includes one or more of ammonium bicarbonate, ammonium carbonate, and ammonia water.

[0041] According to some embodiments of the present invention, in step (2), the temperature of the coagulation is 40-90°C, preferably 60-80°C.

[0042] In this application, the temperature of condensation in step (2) is preferably the same as the heating temperature in step (1).

[0043] According to some embodiments of the present invention, in step (2), the coagulation time is 15-30 min.

[0044] According to some embodiments of the present invention, in step (2), the mass ratio of the coagulant to the PTFE polymer emulsion is (2-4):10.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] (1) By dispersing conductive carbon black in a mixed solvent of water and ethanol and adjusting the pH value, the present invention can increase the charge carried by the conductive carbon black particles, so that the carbon black particles repel each other and maintain a stable separation state, while improving the compatibility and bonding force between conductive carbon black and polytetrafluoroethylene resin.

[0047] (2) The conductive filler of the present invention can be uniformly dispersed in polytetrafluoroethylene, and the prepared polytetrafluoroethylene composite resin has excellent mechanical properties and antistatic properties. Attached Figure Description

[0048] Figure 1 A photograph of the PTFE composite resin prepared in Example 1 of this application.

[0049] Figure 2 A photograph of the PTFE composite resin prepared in Comparative Example 5 of this application. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0051] Unless otherwise specified, all reagents used in the following experiments of this invention are commercially available products or reagents prepared according to conventional methods. Unless otherwise specified, all methods used in the experiments are conventional experimental methods. Unless otherwise specified, all instruments used in the experiments are commercially available.

[0052] The average particle size of the conductive carbon black used in the following embodiments and comparative examples of the present invention is 5 nm.

[0053] The PTFE polymerization solution used in the following embodiments and comparative examples of this invention was prepared by the following method:

[0054] In a 100L horizontal high-pressure reactor equipped with a stirrer and jacket, add 60L of deionized water, 3Kg of paraffin wax as a stabilizer, 150g of perfluorohexanoic acid as a dispersant, and 15g of succinic acid as an anti-sticking agent. Start stirring. After the oxygen analysis is qualified, start heating and introduce tetrafluoroethylene monomer to the reaction pressure of 2.5MPa. When the temperature rises to 80℃, add initiator solution (1g of ammonium persulfate dissolved in 50g of deionized water) through a metering pump. Start the homopolymerization reaction in the range of 80-90℃. During the reaction, continuously add 400g of perfluorohexanoic acid as a dispersant until the reaction is completed. Stop the reaction when the solid content reaches 28-32%. Obtain PTFE polymerization stock solution with a primary particle size of 0.15-0.25μm and a molecular weight of 1 million-4 million.

[0055] Example 1

[0056] Step 1: Add 5000g deionized water, 200g conductive carbon black, 2000g anhydrous ethanol and 20g ammonium carbonate to a pressure-resistant device in sequence. Set the temperature to 80℃ and the speed to 60rpm, and stir continuously for 8 hours to obtain a mixture with a pH value of 8.6.

[0057] Step 2: After filtering the material stirred in Step 1, dry it at 120℃ for 12 hours to obtain the conductive filler.

[0058] Step 3: Add 1200g of PTFE polymerization stock solution with a solid content of 30% to a 10L coagulation tank equipped with a temperature control system and mechanical stirring. Add 2400g of deionized water for dilution, then add 54g of conductive filler and 0.36g of dispersant TMN-10. Start stirring at 60rpm, raise the temperature to 80℃, and continue stirring for 10min to ensure that the conductive filler is evenly dispersed in the solution.

[0059] Step 4: Add 480g of coagulant ammonium bicarbonate to the coagulation tank, set the rotation speed to 400rpm, coagulate at 80℃ for 20min, after the lower layer solution becomes clear, filter it, and dry it at 120℃ for 12h to obtain the composite resin.

[0060] Photographs of the resin prepared in Example 1 are shown below. Figure 1 As shown in the figure, the resin is evenly dispersed.

[0061] After the composite resin is made into sheets, its tensile strength, elongation at break, relative density, surface resistivity and other properties are tested.

[0062] Example 2

[0063] The difference from Example 1 is that:

[0064] Step 1: Add 5000g deionized water, 200g conductive carbon black, 2000g anhydrous ethanol and 20g ammonium carbonate to a pressure-resistant device in sequence. Set the temperature to 50℃ and the speed to 60rpm, and stir continuously for 8 hours to obtain a mixture.

[0065] Step 2: After filtering the material stirred in Step 1, dry it at 120℃ for 12 hours to obtain the conductive filler.

[0066] Step 3: Add 1200g of PTFE polymerization stock solution with a solid content of 30% to a 10L coagulation tank equipped with a temperature control system and mechanical stirring. Add 2400g of deionized water for dilution, then add 54g of conductive filler and 0.36g of dispersant TMN-10. Start stirring at 60rpm, raise the temperature to 60℃, and continue stirring for 10min to ensure that the conductive filler is evenly dispersed in the solution.

[0067] Step 4: Add 480g of ammonium bicarbonate coagulant to the coagulation tank, set the rotation speed to 400rpm, coagulate at 60℃ for 20min, and after the lower layer solution becomes clear, filter it and dry it at 120℃ for 12h to obtain the composite resin. After the composite resin is made into sheets, its tensile strength, elongation at break, relative density, surface resistivity and other properties are tested.

[0068] Example 3

[0069] The difference from Example 1 is that in step 3, 36g of conductive filler and 0.36g of dispersant TMN-10 are added.

[0070] Example 4

[0071] The difference from Example 1 is that in step 3, 36g of conductive filler and 1.08g of dispersant TMN-10 are added.

[0072] Example 5

[0073] The difference from Example 1 is that:

[0074] In step 3, add 4800g of deionized water for dilution; heat to 60℃.

[0075] In step 4, 240g of ammonium bicarbonate coagulant was added to the coagulation tank. The rotation speed was set to 400 rpm, and coagulation was carried out at 60℃ for 40 minutes. After the lower layer solution became clear, it was filtered and dried at 120℃ for 12 hours to obtain the composite resin. After the composite resin was made into sheets, its tensile strength, elongation at break, relative density, and surface resistivity were tested.

[0076] Comparative Example 1

[0077] The difference from Example 1 is that:

[0078] In step 1, the conductive filler is prepared by adding 5000g of deionized water, 200g of conductive carbon black, 2000g of anhydrous ethanol and 200g of ammonium carbonate into a pressure-resistant device in sequence. The temperature is set to 80℃, the speed is set to 60rpm, and the mixture is stirred continuously for 8 hours to obtain a mixture with a pH value of 10.3.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that in step 3, 36g of conductive filler and 18g of dispersant TMN-10 are added.

[0081] Comparative Example 3

[0082] The difference from Example 1 is that:

[0083] In step 3, 108g of conductive filler and 1.08g of dispersant TMN-10 are added.

[0084] In step 4, 480g of ammonium bicarbonate coagulant was added to the coagulation tank. The rotation speed was set to 400 rpm, and coagulation was carried out at 80℃ for 60 minutes. After standing for 10 minutes, a small amount of conductive material was still dispersed in the lower layer of the solution. After filtration, the solution was dried at 120℃ for 12 hours to obtain the composite resin. After the composite resin was made into sheets, its tensile strength, elongation at break, relative density, and surface resistivity were tested.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that:

[0087] In step 3, add 108g of conductive filler and 18g of dispersant TMN-10.

[0088] In step 4, 480g of ammonium bicarbonate coagulant was added to the coagulation tank. The rotation speed was set to 400 rpm, and coagulation was carried out at 80℃ for 60 minutes. After standing for 10 minutes, a small amount of conductive material was still dispersed in the lower layer of the solution. After filtration, the solution was dried at 120℃ for 12 hours to obtain the composite resin. After the composite resin was made into sheets, its tensile strength, elongation at break, relative density, and surface resistivity were tested.

[0089] Comparative Example 5

[0090] The difference from Example 1 is that:

[0091] In step 3, 1200g of PTFE polymer stock solution with a solid content of 30% is added to a 10L coagulation tank equipped with a temperature control system and mechanical stirring. 4800g of deionized water is added for dilution, followed by 54g of conductive filler and 0.36g of dispersant TMN-10. Stirring is started at 60rpm and 20℃ and continued for 10min to ensure that the conductive filler is evenly dispersed in the solution.

[0092] Step 4: Add 480g of coagulant ammonium bicarbonate to the coagulation tank, set the rotation speed to 400rpm, coagulate at 20℃ for 60min, let stand for 10min, and a small amount of conductive material will still be dispersed in the lower layer solution. After filtration, dry at 120℃ for 12h to obtain composite resin.

[0093] Photographs of the resin prepared in Comparative Example 5 are shown. Figure 2 As shown, from Figure 2 It can be seen that the resin is not evenly dispersed.

[0094] After the composite resin is made into sheets, its tensile strength, elongation at break, relative density, surface resistivity and other properties are tested.

[0095] Comparative Example 6

[0096] Step 1: Take 200g of conductive carbon black and dry it at 120℃ for 12h to use as a conductive filler.

[0097] Step 2: Add 1200g of PTFE polymerization stock solution with a solid content of 30% to a 10L coagulation tank equipped with a temperature control system and mechanical stirring. Add 2400g of deionized water for dilution, then add 54g of conductive filler and 0.36g of dispersant TMN-10. Start stirring at 60rpm, raise the temperature to 80℃, and continue stirring for 10min to ensure that the conductive filler is evenly dispersed in the solution.

[0098] Step 3: Add 480g of ammonium bicarbonate coagulant to the coagulation tank, set the rotation speed to 400rpm, coagulate at 80℃ for 60min, then let stand for 10min. A small amount of conductive material is still dispersed in the lower layer of solution. After filtration, dry at 120℃ for 12h to obtain composite resin. After the composite resin is made into sheets, its tensile strength, elongation at break, relative density, surface resistivity and other properties are tested.

[0099] Comparative Example 7

[0100] The difference from Example 1 is that anhydrous ethanol is not added in step 1, and the amount of deionized water used is 7000g.

[0101] Comparative Example 8

[0102] The difference from Example 1 is that ammonium carbonate is not added in step 1.

[0103] Table 1. Detection data for the examples and comparative examples.

[0104]

[0105] Note: The tensile strength, elongation at break, and relative density in Table 1 were tested according to the chemical industry standard HG / T 3028-1999, and the surface resistivity was tested according to the standard GB / T 1410-2006.

[0106] As can be seen from Table 1, the composite resins prepared in Examples 1-5 have better mechanical properties and antistatic properties compared with the composite resins prepared in Comparative Examples 1-8; in particular, the composite resin prepared in Example 1 has good mechanical properties and superior antistatic properties compared with Examples 2-5.

[0107] In Comparative Examples 1, 6, 7, and 8, the conductive carbon black was not evenly dispersed in the emulsion, which affected the mechanical properties and antistatic properties.

[0108] The excessive dispersant in Comparative Example 2 resulted in a decrease in antistatic performance.

[0109] In Comparative Examples 3 and 4, too much conductive filler was added, and in Comparative Example 5, the coagulation temperature was too low, which made it difficult for the PTFE emulsion to coagulate and disperse unevenly, thus affecting its mechanical properties and antistatic properties.

[0110] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a conductive filler, comprising the following steps: Conductive carbon black, water, ethanol, and a pH adjuster are mixed and heated to obtain a mixture; The mixture is subjected to solid-liquid separation to obtain a solid phase, which is then dried to obtain a conductive filler.

2. The production method according to claim 1, characterized by, The pH adjuster includes one or more of ammonium carbonate, ammonium bicarbonate, and ammonia water, preferably ammonium carbonate; and / or, The amount of the pH adjuster is such that the pH of the mixture is 7.0-10.0, preferably 8.0-9.0; and / or, The heating temperature is 50-80℃; the heating time is 6-10 hours; and / or, The heating is performed simultaneously with stirring; and / or, The drying temperature is 100-150℃, and the drying time is 8-16 hours.

3. The production method according to claim 1 or 2, characterized by, The conductive carbon black has an average particle size of 1-10 nm; and / or, The mass ratio of water to conductive carbon black is 100:(1-5), preferably 100:(3-5); and / or, The mass ratio of water to ethanol is 10:(1-5), preferably 10:(3-5); and / or, The mass ratio of water to pH adjuster is 1000:(1-10), preferably 1000:(3-8), and more preferably 1000:(3-5).

4. A conductive filler, which is prepared by the preparation method according to any one of claims 1-3.

5. The application of the conductive filler as described in claim 4 in the preparation of PTFE composite resin.

6. A PTFE composite resin comprising polytetrafluoroethylene and the conductive filler of claim 4; Preferably, in the composite resin, the conductive filler accounts for 5-20% of the mass of polytetrafluoroethylene, and more preferably 10-15%.

7. The composite resin according to claim 6, characterized in that, The tensile strength of the composite resin is 25-30 MPa; and / or, the elongation at break of the composite resin is 300%-400%, preferably 350%-400%; and / or, the relative density of the composite resin is 2.17-2.19; and / or, the surface resistivity of the composite resin is (3.5-13.0) x 10 5 Ω, preferably (3.5-9.0) x 10 5 Ω, more preferably (3.5-6.0) x 10 5 Ω.

8. A method for preparing the PTFE composite resin as described in claim 6 or 7, comprising the following steps: (1) The PTFE polymer emulsion is mixed with the conductive filler, dispersant and water and heated to obtain a dispersion; (2) The dispersion is mixed with a coagulant and coagulated. After coagulation, solid-liquid separation is performed. The solid phase obtained after solid-liquid separation is dried to obtain the composite resin.

9. The production method according to claim 8, characterized by, The solid content of the PTFE polymer emulsion is 28-32%; and / or, the average particle size of the primary particles in the PTFE polymer emulsion is 0.15-0.25 μm; and / or, the average molecular weight of polytetrafluoroethylene in the PTFE polymer emulsion is 1,000,000 to 4,000,000; and / or, the dispersant includes a nonionic surfactant, preferably a polyether nonionic surfactant, more preferably one or more of TMN-10, TMN-6, and E1310; and / or, the coagulant includes one or more of ammonium bicarbonate, ammonium carbonate, and ammonia.

10. The production method according to claim 8 or 9, characterized by, The mass ratio of the conductive filler to the PTFE polymer emulsion is (3-5):100, preferably (4-4.5):100; and / or, The mass ratio of the dispersant to the PTFE polymer emulsion is (0.3-0.9):1000; and / or, The mass ratio of water to the PTFE polymer emulsion is (2-6):1; and / or, In step (1), the heating temperature is 40-90℃, preferably 60-80℃; and / or, In step (2), the temperature of the condensation is 40-90℃, preferably 60-80℃; and / or, In step (2), the coagulation time is 15-30 min; and / or, In step (2), the mass ratio of the coagulant to the PTFE polymer emulsion used in step (1) is (2-4):10.

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