Preparation method of silver-coated mica powder

Abstract

The invention relates to a preparation method of silver-coated mica powder, and belongs to the technical field of conductive powder materials, the silver-coated mica powder comprises modified mica powder and a silver coating layer coating the modified mica powder; wherein a silane coupling agent structure in the Schiff base polymer intermediate can react with hydroxyl on the surface of the mica powder, so that on one hand, the mica powder can be modified, and on the other hand, an organic polymer transition layer is formed on the surface of the mica powder; silver ions are enriched through sulfur and nitrogen multi-reaction active sites in a Schiff base polymer intermediate, so that an organic polymer transition layer and chelated silver ions can be stably attached to the surface of mica powder, and a compact coating layer is formed. And after high-temperature calcination, the silver elementary substance promotes the coating layer to be connected into a sheet through a metal bond between Ag and Ag, the mica powder can be completely coated, and the oxidation resistance of the silver-coated mica powder is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive powder materials, and specifically relates to a preparation method of silver-coated mica powder. Background Art

[0002] As antistatic materials, conductive powders for electromagnetic wave shielding materials have long been widely used. Moreover, conductive powders can enhance the mechanical strength of plastics. Among conductive powders, silver has the advantages of good conductivity, stable chemical properties, low resistance, and high thermal conductivity. However, the high price of silver limits its wide application in daily life.

[0003] Traditionally, silver is usually plated on the surface of ordinary powders, which can not only retain the advantages of silver as a conductive powder but also save the amount of silver used. If the surface coating is relatively complete, it can also replace silver powder to a certain extent. In the prior art, mica powder is often used as a non-metallic matrix material to prepare composite silver powder as a conductive filler. Such conductive fillers have the advantages of light weight and good conductivity. However, in the prior art, the amount of coating of the prepared composite silver powder is small, resulting in a low density of the silver coating layer, which in turn leads to structural defects such as gaps and microcracks easily appearing between the mica powder matrix and the silver coating layer, further affecting the decline of its conductivity. During long-term use, the oxidation process is also prone to oxidize from the surface of the coating layer to the inside, resulting in a decrease in its antioxidant ability and further limiting its application in conductive fillers. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background art, the purpose of the present invention is to provide a preparation method of silver-coated mica powder; The purpose of the present invention can be achieved by the following technical solutions: A silver-coated mica powder, comprising a modified mica powder and a silver coating layer coated outside the modified mica powder; Preparation of modified mica powder: Step A1: Take 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF and mix them into a reaction kettle. Control the stirring reaction rate at 200 - 300 r / min, heat up to 40 - 50 °C, stir and react for 2 - 3 h, then wash with water 3 times and dry to obtain a benzenedicarboxaldehyde derivative intermediate; Furthermore, the dosage ratio of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF is 1 mol: 2 mol: 5 - 8 g: 500 mL; In the above reaction, 2,5-dihydroxy-1,4-phthalaldehyde reacts with 3-chloropropyltriethoxysilane to graft 3-chloropropyltriethoxysilane onto the 2,5-dihydroxy-1,4-phthalaldehyde molecule, introducing the structure of the silane coupling agent. The specific reaction process is as follows:

[0005] Step A2: Take the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid and n-butanol, mix and feed them into a reaction kettle. Control the stirring reaction rate at 300 - 400 r / min, heat up to 85 - 90 °C, stir and react for 3 - 4 h, then carry out rotary evaporation under reduced pressure, and then put it into an oven for drying to obtain the Schiff base polymer intermediate; Furthermore, the dosage ratio of the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid and n-butanol is 1 mol : 1 mol : 10 - 13 mL : 800 mL; In the above reaction, intermediate 1 reacts with thiourea to form an organic polymer with Schiff base; the specific reaction process is as follows:

[0006] Step A3: Take mica powder and ethanol solution, mix and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min, stir for 30 min, then add the Schiff base polymer intermediate, continue to stir for 1 h, then transfer it to an oven, control the oven temperature at 70 °C, dry for 5 h to obtain the modified mica powder; Furthermore, the dosage ratio of mica powder, Schiff base polymer intermediate and ethanol solution is 10 g : 20 - 30 g : 200 mL; the mass fraction of the ethanol solution is 60%; In the above reaction, the silane coupling agent in the Schiff base polymer intermediate reacts with the hydroxyl groups on the surface of mica powder to graft-modify mica powder and form a coated modification on mica powder to obtain the modified mica powder.

[0007] A silver-coated mica powder is prepared by the following method: Mix the modified mica powder and silver ammonia solution and feed them into a stirrer. Control the stirring reaction rate at 800 - 1000 r / min, stir and react for 2 h, then add the reducing solution, continue to stir for 10 min to obtain a mixed solution, and then dropwise add 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 11 - 12; then react in the stirrer for 1 - 1.5 h, vacuum dry to obtain the silver-coated mica powder semi-finished product, and finally calcine the silver-coated mica powder semi-finished product at 700 °C for 1 h and then cool it naturally to obtain the silver-coated mica powder.

[0008] Furthermore, the dosage ratio of the modified mica powder, the silver ammonia solution and the reducing solution is 5g:25-30mL:200mL; the reducing solution is a glucose solution with a mass fraction of 5%; the mass fraction of the silver ammonia solution is 5g / L; Beneficial effects of the present invention: The invention discloses a preparation method of silver-coated mica powder, comprising modified mica powder and a silver coating layer coated on the modified mica powder; compared with the existing silver-coated mica powder, the silver coating layer disclosed by the invention is more compact, has better electrical conductivity and stronger antioxidant capacity; wherein the silane coupling agent structure of the Schiff base polymer intermediate can react with the hydroxyl group on the surface of the mica powder, on the one hand, can be grafted and modified with the mica powder to improve the compatibility between the Schiff base polymer intermediate and the mica powder, and on the other hand, can also form an organic polymer transition layer on the surface of the mica powder; and the sulfur and nitrogen reaction active sites on the Schiff base polymer intermediate can react with the silver ions Chelation is carried out to "enrich" the silver ions in the silver ammonia solution on the organic polymer transition layer to form an organic polymer-silver ion composite coating system, so that it can be firmly attached to the surface of the mica powder. After reduction by the reducing solution, a dense silver coating layer is formed on the surface of the mica powder; the conductive properties of the silver-coated mica powder are effectively improved; and after high-temperature calcination, the organic polymer transition layer decomposes and disappears, and the silver element in the composite system causes the coating layer to be connected into sheets through the metal bond between Ag-Ag, which can completely coat the mica powder, thereby inhibiting the oxidation process from the surface of the coating layer to the inside, and effectively improving the antioxidant capacity of the silver-coated mica powder. DETAILED DESCRIPTION

[0009] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0010] Example 1 The specific implementation process of preparing a silver-coated mica powder in this embodiment is as follows: Preparation of modified mica powder a1: 2,5-dihydroxy-1,4-benzenedicaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide and DMF were mixed and added into a reactor, the stirring reaction rate was controlled to be 200r / min, the temperature was raised to 40°C, and the mixture was stirred for reaction for 2h, and then washed with water 3 times and dried to obtain a benzaldehyde derivative intermediate; in the above reaction, the amount ratio of 2,5-dihydroxy-1,4-benzenedicaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide and DMF was 1mol:2mol:5g:500mL; a2: Mix the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol and charge them into a reaction kettle. Control the stirring reaction rate at 300 r / min, heat up to 85 °C, stir and react for 3 h, then perform rotary evaporation under reduced pressure, and then place it in an oven for drying to obtain the Schiff base polymer intermediate; in the above reaction, the dosage ratio of the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol is 1 mol: 1 mol: 10 mL: 800 mL; a3: Mix mica powder and an ethanol solution with a mass fraction of 60% and charge them into a stirrer. Control the stirring reaction rate at 1000 r / min, stir for 30 min, then add the Schiff base polymer intermediate, continue to stir for 1 h, and then transfer it to an oven. Control the oven temperature at 70 °C, dry for 5 h to obtain the modified mica powder; in the above reaction, the dosage ratio of mica powder, Schiff base polymer intermediate, and ethanol solution is 10 g: 20 g: 200 mL; Preparation of silver-coated mica powder s1: Mix 25 mL of a 5% silver ammonia solution and 5 g of modified mica powder and charge them into a stirrer. Control the stirring reaction rate at 800 r / min, stir and react for 2 h, then add 200 mL of a 5% glucose solution, continue to stir for 10 min to obtain a mixed solution, and then dropwise add a 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 11; after reacting in the stirrer for 1 h, perform vacuum drying to obtain a semi-finished product of silver-coated mica powder. Finally, calcine the semi-finished product of silver-coated mica powder at 700 °C for 1 h and then naturally cool it to obtain silver-coated mica powder.

[0011] Example 2 The specific implementation process for preparing a silver-coated mica powder in this example is as follows: Preparation of modified mica powder a1: Mix 2,5-dihydroxy-1,4-phthalaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF and charge them into a reaction kettle. Control the stirring reaction rate at 220 r / min, heat up to 42 °C, stir and react for 3 h, then wash with water 3 times and dry to obtain the phthalaldehyde derivative intermediate; in the above reaction, the dosage ratio of 2,5-dihydroxy-1,4-phthalaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF is 1 mol: 2 mol: 6 g: 500 mL; a2: Mix the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol and charge them into a reaction kettle. Control the stirring reaction rate at 320 r / min, heat up to 86 °C, stir and react for 3 h, then perform rotary evaporation under reduced pressure, and then place it in an oven for drying to obtain the Schiff base polymer intermediate; in the above reaction, the dosage ratio of the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol is 1 mol: 1 mol: 11 mL: 800 mL; a3: Mix mica powder and an ethanol solution with a mass fraction of 60% and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring for 30 min, add the Schiff base polymer intermediate. Continue stirring for 1 h and then transfer it to an oven. Control the oven temperature at 70 °C and dry for 5 h to obtain modified mica powder. In the above reaction, the dosage ratio of mica powder, Schiff base polymer intermediate and ethanol solution is 10 g: 22 g: 200 mL; Preparation of silver-coated mica powder s1: Mix 26 mL of a silver ammonia solution with a mass fraction of 5% and 5 g of modified mica powder and feed them into a stirrer. Control the stirring reaction rate at 900 r / min. After stirring and reacting for 2 h, add 200 mL of a glucose solution with a mass fraction of 5%. Continue stirring for 10 min to obtain a mixed solution. Then add 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 11. After reacting in the stirrer for 1 h, vacuum dry to obtain a semi-finished product of silver-coated mica powder. Finally, calcine the semi-finished product of silver-coated mica powder at 700 °C for 1 h and then cool it naturally to obtain silver-coated mica powder.

[0012] Example 3 The specific implementation process of preparing a silver-coated mica powder in this example is as follows: Preparation of modified mica powder a1: Mix 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide and DMF and feed them into a reaction kettle. Control the stirring reaction rate at 240 r / min and heat up to 44 °C. After stirring and reacting for 3 h, wash with water 3 times and dry to obtain a benzene dicarboxaldehyde derivative intermediate. In the above reaction, the dosage ratio of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide and DMF is 1 mol: 2 mol: 7 g: 500 mL; a2: Mix the benzene dicarboxaldehyde derivative intermediate, thiourea, hydrochloric acid and n-butanol and feed them into a reaction kettle. Control the stirring reaction rate at 340 r / min and heat up to 87 °C. After stirring and reacting for 3 h, carry out rotary evaporation under reduced pressure and then place it in an oven to dry to obtain a Schiff base polymer intermediate. In the above reaction, the dosage ratio of benzene dicarboxaldehyde derivative intermediate, thiourea, hydrochloric acid and n-butanol is 1 mol: 1 mol: 12 mL: 800 mL; a3: Mix mica powder and an ethanol solution with a mass fraction of 60% and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring for 30 min, add the Schiff base polymer intermediate. Continue stirring for 1 h and then transfer it to an oven. Control the oven temperature at 70 °C and dry for 5 h to obtain modified mica powder. In the above reaction, the dosage ratio of mica powder, Schiff base polymer intermediate and ethanol solution is 10 g: 24 g: 200 mL; Preparation of silver-coated mica powder S1: Mix 27 mL of silver ammonia solution with a mass fraction of 5% and 5 g of modified mica powder and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring and reacting for 2 h, add 200 mL of glucose solution with a mass fraction of 5%. Continue to stir for 10 min to obtain a mixed solution, and then dropwise add 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 11. After reacting in the stirrer for 1.5 h, vacuum dry to obtain a semi-finished product of silver-coated mica powder. Finally, calcine the semi-finished product of silver-coated mica powder at 700 °C for 1 h and then naturally cool to obtain silver-coated mica powder.

[0013] Example 4 The specific implementation process for preparing a silver-coated mica powder in this example is as follows: Preparation of modified mica powder A1: Take 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF and mix them and feed them into a reaction kettle. Control the stirring reaction rate at 260 r / min, heat up to 46 °C, and after stirring and reacting for 3 h, wash with water 3 times and dry to obtain an intermediate of benzenedicarboxaldehyde derivative; in the above reaction, the dosage ratio of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF is 1 mol: 2 mol: 8 g: 500 mL; A2: Take the intermediate of benzenedicarboxaldehyde derivative, thiourea, hydrochloric acid, and n-butanol and mix them and feed them into a reaction kettle. Control the stirring reaction rate at 360 r / min, heat up to 88 °C, and after stirring and reacting for 3 h, carry out rotary evaporation under reduced pressure, and then place it in an oven to dry to obtain an intermediate of Schiff base polymer; in the above reaction, the dosage ratio of the intermediate of benzenedicarboxaldehyde derivative, thiourea, hydrochloric acid, and n-butanol is 1 mol: 1 mol: 13 mL: 800 mL; A3: Take mica powder and ethanol solution with a mass fraction of 60% and mix them and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring for 30 min, add the intermediate of Schiff base polymer, continue to stir for 1 h, and then transfer it to an oven. Control the oven temperature at 70 °C and dry for 5 h to obtain modified mica powder; in the above reaction, the dosage ratio of mica powder, the intermediate of Schiff base polymer, and ethanol solution is 10 g: 26 g: 200 mL; Preparation rate of silver-coated mica powder; specific test data are shown in Table 1: S1: Mix 28 mL of silver ammonia solution with a mass fraction of 5% and 5 g of modified mica powder and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring and reacting for 2 h, add 200 mL of glucose solution with a mass fraction of 5%. Continue to stir for 10 min to obtain a mixed solution, and then add 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 12. After reacting in the stirrer for 1.5 h, vacuum dry to obtain a semi-finished product of silver-coated mica powder. Finally, calcine the semi-finished product of silver-coated mica powder at 700 °C for 1 h and then cool it naturally to obtain silver-coated mica powder.

[0014] Example 5 The specific implementation process for preparing silver-coated mica powder in this example is as follows: Preparation of modified mica powder A1: Take 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF and mix them and feed them into a reaction kettle. Control the stirring reaction rate at 280 r / min, heat up to 48 °C, and after stirring and reacting for 3 h, wash with water 3 times and dry to obtain a benzenedicarboxaldehyde derivative intermediate. In the above reaction, the dosage ratio of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF is 1 mol: 2 mol: 8 g: 500 mL; A2: Take the benzenedicarboxaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol and mix them and feed them into a reaction kettle. Control the stirring reaction rate at 380 r / min, heat up to 89 °C, and after stirring and reacting for 4 h, carry out rotary evaporation under reduced pressure, and then place it in an oven to dry to obtain a Schiff base polymer intermediate. In the above reaction, the dosage ratio of the benzenedicarboxaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol is 1 mol: 1 mol: 13 mL: 800 mL; A3: Take mica powder and ethanol solution with a mass fraction of 60% and mix them and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring for 30 min, add the Schiff base polymer intermediate. Continue to stir for 1 h and then transfer it to an oven. Control the oven temperature at 70 °C and dry for 5 h to obtain modified mica powder. In the above reaction, the dosage ratio of mica powder, Schiff base polymer intermediate, and ethanol solution is 10 g: 28 g: 200 mL; Preparation of silver-coated mica powder S1: Mix 29 mL of silver ammonia solution with a mass fraction of 5% and 5 g of modified mica powder and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring and reacting for 2 h, add 200 mL of glucose solution with a mass fraction of 5%. Continue to stir for 10 min to obtain a mixed solution, and then add 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 12. After reacting in the stirrer for 1.5 h, vacuum dry to obtain a semi-finished product of silver-coated mica powder. Finally, calcine the semi-finished product of silver-coated mica powder at 700 °C for 1 h and then cool it naturally to obtain silver-coated mica powder.

[0015] Example 6 The specific implementation process for preparing silver-coated mica powder in this example is as follows: Preparation of modified mica powder A1: Take 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF and mix them and feed them into a reaction kettle. Control the stirring reaction rate at 300 r / min, heat up to 50 °C, and after stirring and reacting for 3 h, wash with water 3 times and dry to obtain a benzenedicarboxaldehyde derivative intermediate. In the above reaction, the dosage ratio of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide, and DMF is 1 mol: 2 mol: 8 g: 500 mL; A2: Take the benzenedicarboxaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol and mix them and feed them into a reaction kettle. Control the stirring reaction rate at 400 r / min, heat up to 90 °C, and after stirring and reacting for 4 h, carry out rotary evaporation under reduced pressure, and then place it in an oven to dry to obtain a Schiff base polymer intermediate. In the above reaction, the dosage ratio of the benzenedicarboxaldehyde derivative intermediate, thiourea, hydrochloric acid, and n-butanol is 1 mol: 1 mol: 13 mL: 800 mL; A3: Take mica powder and ethanol solution with a mass fraction of 60% and mix them and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring for 30 min, add the Schiff base polymer intermediate. Continue to stir for 1 h and then transfer it to an oven. Control the oven temperature at 70 °C and dry for 5 h to obtain modified mica powder. In the above reaction, the dosage ratio of mica powder, Schiff base polymer intermediate, and ethanol solution is 10 g: 30 g: 200 mL; Preparation of silver-coated mica powder S1: Mix 30 mL of a 5% silver ammonia solution and 5 g of modified mica powder and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring and reacting for 2 h, add 200 mL of a 5% glucose solution, continue stirring for 10 min to obtain a mixed solution, and then add 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 12. After reacting in the stirrer for 1.5 h, vacuum dry to obtain a semi-finished product of silver-coated mica powder. Finally, calcine the semi-finished product of silver-coated mica powder at 700 °C for 1 h and then naturally cool to obtain silver-coated mica powder.

[0016] Comparative Example 1 The specific implementation process for preparing a silver-coated mica powder in this comparative example is as follows: S1: Take 50 g of mica powder and mix it with an ethanol solution with a mass fraction of 60% and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring for 30 min, add 0.5 g of 3-chloropropyltriethoxysilane, continue stirring for 1 h, then transfer it to an oven, control the oven temperature at 70 °C, and dry for 5 h to obtain modified mica powder; S2: Mix 29 mL of a 5% silver ammonia solution and 5 g of modified mica powder and feed them into a stirrer. Control the stirring reaction rate at 1000 r / min. After stirring and reacting for 2 h, add 200 mL of a 5% glucose solution, continue stirring for 10 min to obtain a mixed solution, and then add 2.5 mol / L sodium hydroxide solution to adjust the pH of the mixed solution to 12. After reacting in the stirrer for 1.5 h, vacuum dry to obtain silver-coated mica powder.

[0017] Comparative Example 2: This comparative example selects the silver-coated mica powder in CN201710534173; Resistivity test: Measure the compacted surface resistivity of the silver-coated mica powders prepared in Examples 1-6 and Comparative Examples 1-2 using a VC9807A+ digital multimeter (Shenzhen Victory High Electronic Technology Co., Ltd.).

[0018] Antioxidant property test: Place the silver-coated mica powders prepared in Examples 1-6 and Comparative Examples 1-2 at room temperature (ambient temperature is 25 ± 2 °C, relative humidity is 45 ± 5%) for 6 months, and then measure their surface resistivity using a VC9807A+ digital multimeter. Antioxidant property test: Oxidize the silver-coated mica powders prepared in Examples 1-6 and Comparative Examples 1-2 in a blast drying oven at 180 °C for 168 h, then cool to room temperature and measure their surface resistivity using a VC9807A+ digital multimeter; the specific test data are shown in Table 1: Table 1

[0019] As can be seen from the data in Table 1, the resistivity of a kind of silver-coated mica powder prepared in this embodiment is 0.083 - 0.087 Ω·cm, which is better than that of the silver-coated mica powder prepared in Comparative Examples 1 - 2. And the resistivities after being placed at room temperature for 6 months and oxidized at 180 °C for 168 h are 0.084 - 0.089 Ω·cm and 0.116 - 0.124 Ω·cm respectively. On the contrary, the resistivities of the silver-coated mica powder in Comparative Examples 1 - 2 after being placed at room temperature for 6 months and oxidized at 180 °C for 168 h are 0.454 / 0.419 Ω·cm and 0.857 / 0.852 Ω·cm respectively; this shows that the silver-coated mica powder prepared in Examples 1 - 6 not only has good electrical conductivity but also has good antioxidant ability.

[0020] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0021] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar ways to replace them. As long as they do not deviate from the invention or exceed the scope defined by the claims of this patent, they should all fall within the protection scope of the present invention.

Claims

1. A silver-coated mica powder, characterized in that: The invention comprises modified mica powder and a silver coating layer coated on the modified mica powder; Preparation of modified mica powder: Step A1: 2,5-dihydroxy-1,4-benzenedicaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide and DMF were mixed and added, the temperature was raised to 40-50°C, stirred for reaction for 2-3h, washed with water 3 times and dried to obtain a benzaldehyde derivative intermediate; Step A2: Mix the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid and n-butanol, raise the temperature to 85-90° C., stir and react for 3-4 hours, then perform vacuum rotary evaporation, and then dry in an oven to obtain a Schiff base polymer intermediate; Step A3: Mix mica powder and ethanol solution, stir for 30 minutes, add Schiff base polymer intermediate, continue stirring for 1 hour, transfer to an oven, and dry to obtain modified mica powder.

2. A silver-coated mica powder according to claim 1, characterized in that: In step A1, the usage ratio of 2,5-dihydroxy-1,4-benzenedicarbaldehyde, 3-chloropropyltriethoxysilane, sodium hydroxide and DMF is 1 mol: 2 mol: 5-8 g: 500 mL.

3. A silver-coated mica powder according to claim 2, characterized in that: In step A2, the usage ratio of the phthalaldehyde derivative intermediate, thiourea, hydrochloric acid and n-butanol is 1 mol: 1 mol: 10-13 mL: 800 mL.

4. A silver-coated mica powder according to claim 3, characterized in that: In step A3, the usage ratio of mica powder, Schiff base polymer intermediate and ethanol solution is 10 g: 20-30 g: 200 mL.

5. The method for preparing a silver-coated mica powder according to claim 4, characterized in that: Prepared by the following method: The modified mica powder and the silver ammonia solution are mixed and fed, and the reducing solution is added after stirring for 2 hours, and the stirring is continued for 10 minutes to obtain a mixed solution, and then sodium hydroxide solution is added dropwise to adjust the pH of the mixed solution to 11-12; thereafter, after reacting in a stirrer for 1-1.5 hours, vacuum drying is performed to obtain a silver-coated mica powder semi-finished product, and finally the silver-coated mica powder semi-finished product is calcined at 700° C. for 1 hour, and naturally cooled to obtain the silver-coated mica powder.

6. The method for preparing a silver-coated mica powder according to claim 5, characterized in that: The dosage ratio of modified mica powder, silver ammonia solution and reducing solution is 5g:25-30mL:200mL.

7. The method for preparing a silver-coated mica powder according to claim 6, characterized in that: The reducing solution is a glucose solution with a mass fraction of 5%.

8. The method for preparing a silver-coated mica powder according to claim 7, characterized in that: The mass fraction of the silver ammonia solution is 5g / L.

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