Composite conductive filler, conductive paint and preparation method and application thereof

Abstract

The present application belongs to the field of conductive paint, and relates to a composite conductive filler, a preparation method and application thereof. The composite conductive filler comprises a plurality of conductive particles, each of which independently comprises a plurality of conductive particles I and a plurality of conductive particles II. The conductive particle I comprises a conductive core I and polyvinylpyrrolidone and acid attached to the surface of the conductive core I. The conductive particle II comprises a conductive core II and polyvinylpyrrolidone and alkaline carbonate (hydrogen) salt attached to the surface of the conductive core II. The conductive particle I and the conductive particle II in the same conductive particle are bonded together by the polyvinylpyrrolidone attached thereto. The composite conductive filler provided by the present application has good dispersibility in a solvent, and can significantly improve the conductivity when used in conductive paint.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of conductive paint, and particularly relates to a composite conductive filler, a conductive paint and a preparation method and application thereof. BACKGROUND

[0002] Conductive paint has gradually replaced part of metal circuits due to its advantages of good conductivity, firm adhesion to the substrate, low cost, etc., and has a wide application in the fields of printed circuit, electromagnetic shielding material, biosensor, etc. The conductive filler in the conductive paint plays a conductive role and directly determines the conductivity of the conductive paint. Common conductive fillers include metal fillers such as silver powder, nickel powder, copper powder, etc.; metal oxide fillers such as tin oxide, zinc oxide, etc.; and carbon fillers such as graphite, carbon black, graphene, carbon nanotube, etc. Graphene and carbon nanotube in carbon fillers are two-dimensional conductive materials, and the characteristics of large diameter-thickness ratio or high length-diameter ratio of the two-dimensional conductive materials endow them with more excellent conductivity. The advantages of graphene and carbon nanotube are good conductivity and low addition amount, but due to the poor dispersibility of graphene and carbon nanotube, they need to be dispersed in a solvent in advance to prepare a slurry before being added to the active component. However, the solid content of the slurry is generally only about 5%, and the solid content is the effective ingredient. The solvent will generally be volatilized in the subsequent use process, and the viscosity of the slurry will become large or even stratified and cannot be used after long storage time.

[0003] In order to solve the problem of dispersibility of graphene and carbon nanotube, many methods have been used in the prior art to modify them. For example, CN114976001A discloses a composite conductive filler and a preparation method thereof. The composite conductive filler contains graphene, carbon nanotube, conductive carbon black, non-ionic high molecular superdispersant and non-ionic surfactant. The non-ionic high molecular superdispersant is hydrolyzed after being uniformly dispersed with graphene, carbon nanotube and conductive carbon black, and is mixed and dried with the non-ionic surfactant. The non-ionic high molecular superdispersant is polyvinylpyrrolidone (PVP) and / or polyvinyl alcohol, and the non-ionic surfactant is lecithin and / or Tween 80. The combination of non-ionic high molecular superdispersant and non-ionic surfactant can reduce the number of adsorbed groups exposed on the surface of the obtained composite conductive filler particles after drying, and can make the composite conductive filler particles have charge repulsion, effectively reducing the agglomeration of the composite conductive filler and ensuring the dispersion effect of the composite conductive filler in use. Although this method can improve the dispersion effect of the composite conductive filler to some extent, the dispersion performance still needs to be further improved, and the conductivity cannot be effectively exerted when the composite conductive filler is used as a conductive filler. SUMMARY

[0004] One of the purposes of the present application is to overcome the defects of poor dispersion performance of existing graphene / carbon nanotube and the inability to effectively improve the conductive performance when used as a conductive filler in paint, and to provide a composite conductive filler with good dispersion effect, which can significantly improve the conductive performance of paint when used as a conductive particle.

[0005] The second purpose of the present application is to provide a preparation method of the composite conductive filler.

[0006] The third purpose of the present application is to provide the use of the composite conductive filler in conductive paint.

[0007] The fourth purpose of the present application is to provide a conductive paint containing the composite conductive filler.

[0008] The present inventors have found through in-depth and extensive research that when polyvinylpyrrolidone is used as an additive to prepare a conductive material in the prior art (for example, CN114976001A), the dispersion effect cannot be significantly improved and the conductive performance of the paint cannot be significantly improved. The main reason is that the existing composite conductive filler is generally obtained by directly drying the slurry, and the water content decreases during the drying process. Polyvinylpyrrolidone is prone to form insoluble gel, causing the same graphene / carbon nanotube to entangle due to "bonding" and the different graphene / carbon nanotubes to "bond" together to form a solid agglomerated ball. This agglomerated ball is not easy to dissolve. In view of this, the so-called dispersion can only achieve the dispersion between the agglomerated balls, and cannot achieve the re-dispersion inside the agglomerated balls. At the same time, during the dissolution process, part of the polyvinylpyrrolidone is dissolved out of the agglomerated ball, and the graphene and carbon nanotube are still entangled into a spherical shape. Conventional stirring cannot open the agglomerated ball, so the graphene and carbon nanotube cannot take advantage of their large diameter-thickness ratio and high length-diameter ratio as two-dimensional conductive materials, and their conductive performance is poor, which is closer to zero-dimensional materials. Therefore, when used as a conductive filler, the conductive performance cannot be significantly improved.

[0009] The inventors of the present application surprisingly found during the research that, first, two kinds of conductive particles were prepared separately by using polyvinylpyrrolidone-acid and polyvinylpyrrolidone-alkali carbonate (hydrogen) salt as the adhesion agent respectively, then the two kinds of conductive particles were attached by means of stirring and spraying during the coating process, and finally the two kinds of conductive particles were mixed and granulated by dry granulation, which can significantly improve the dispersibility of the composite conductive filler and effectively improve the conductive performance of the coating. The reason is probably that: on the one hand, polyvinylpyrrolidone can play a role in adhesion during the dry granulation process and can play a role in dispersion during the dissolution process, and the polyvinylpyrrolidone is attached to the surface of the conductive particles by means of stirring and spraying, the polyvinylpyrrolidone does not form a gel to make the composite conductive filler form an agglomerated ball which is not easy to dissolve, and the polyvinylpyrrolidone on the surface of the conductive particles is deformed and adhered together under pressure, which is easily dispersed during the dissolution process; on the other hand, the conductive particles in the composite conductive filler and the conductive particles are easily adhered together to form conductive particles, but the surface of the conductive particles is attached with acid and alkali carbonate (hydrogen) salt and polyvinylpyrrolidone, when the composite conductive filler is placed in the solvent, the conductive particles exposed to the solvent are quickly dispersed in the solvent under the action of polyvinylpyrrolidone, and at the same time, due to the capillary action, the solvent enters the inside of the conductive particles along the gap, the conductive particles contain many small conductive particles, the acid and alkali carbonate (hydrogen) salt on the surface of the small conductive particles reacts to produce carbon dioxide under the action of the solvent to make the inside of the conductive particles expand, and under the cooperation of the capillary action, the expansion and the gas production, the conductive particles are quickly disintegrated and dispersed, and then the graphene and / or carbon nanotube are fully stretched and exposed to effectively play the advantages of the two-dimensional conductive material, thereby improving the conductive performance of the coating. Based on this, the present application is completed.

[0010] Specifically, the composite conductive filler provided by the present application comprises a plurality of conductive particles, each of which independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particle I comprises a conductive core I and polyvinylpyrrolidone and acid attached to the surface of the conductive core I, and the conductive particle II comprises a conductive core II and polyvinylpyrrolidone and alkali carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particle I and the conductive particle II in the same conductive particle are adhered together by the polyvinylpyrrolidone attached thereto.

[0011] In a preferred embodiment, the mass ratio of the conductive core I, polyvinylpyrrolidone and acid in the conductive particle I is (800-1200):100:(30-80).

[0012] In a preferred embodiment, the mass ratio of the conductive core II, polyvinylpyrrolidone and alkali carbonate (hydrogen) salt in the conductive particle II is (800-1200):100:(30-80).

[0013] In a preferred embodiment, the ratio of the conductive particles I and the conductive particles II in the composite conductive filler is such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the basic carbonate (hydrogen) salt is 1:(0.8-1.2).

[0014] In a preferred embodiment, the conductive core I and the conductive core II are each independently graphene and / or carbon nanotube.

[0015] In a preferred embodiment, the acid is at least one selected from tartaric acid, citric acid, malic acid, fumaric acid, boric acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0016] In a preferred embodiment, the basic carbonate (hydrogen) salt is at least one selected from sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

[0017] In a preferred embodiment, the D50 of the conductive particles I is 1-70 μm, and the D50 of the conductive particles II is 1-70 μm. 90 In a preferred embodiment, the D50 of the conductive particles I is 1-70 μm, and the D50 of the conductive particles II is 1-70 μm. 90 In a preferred embodiment, the average diameter of the conductive particles is 0.2-3 mm.

[0018] The method for preparing the composite conductive filler provided by the present application comprises the following steps:

[0019] S1. Spraying a water solution of polyvinylpyrrolidone and an acid on the conductive core I under high-speed stirring, and then drying to make the polyvinylpyrrolidone and the acid adhere to the surface of the conductive core I, to obtain the conductive particles I; and spraying a water solution of polyvinylpyrrolidone and a basic carbonate (hydrogen) salt on the conductive core II under high-speed stirring, and then drying to make the polyvinylpyrrolidone and the basic carbonate (hydrogen) salt adhere to the surface of the conductive core II, to obtain the conductive particles II;

[0020] S2. Mixing the conductive particles I and the conductive particles II, and then dry granulating to obtain the composite conductive filler.

[0021] In a preferred embodiment, in the preparation of the conductive particles I and the conductive particles II in step S1, the rotation speed of the high-speed stirring is independently 100-600 rpm.

[0022] In a preferred embodiment, in the preparation of the conductive particles I and the conductive particles II in step S1, the drying condition independently comprises a temperature of 90-110°C and a time of 2-8 h.

[0023] In a preferred embodiment, in step S2, the method for dry granulation is to roll the mixture, and then to make conductive particles through a crushing and granulating process.

[0024] The present application also provides the use of the composite conductive filler in conductive paint.

[0025] Furthermore, the present application also provides a conductive paint, which contains resin and conductive particles, and the conductive particles are the composite conductive filler described above.

[0026] The composite conductive filler provided by the present application has good dispersibility in solvent, and when it is used in conductive paint, the conductivity can be significantly improved. In addition, the composite conductive filler provided by the present application can be stored for a long time, and its properties do not change substantially even after being placed for six months or even twelve months. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of the surface of the composite conductive filler obtained in Example 1;

[0028] Figure 2 SEM image of the surface of the composite conductive filler obtained in Comparative Example 1. DETAILED DESCRIPTION

[0029] It should be noted that in the present application, all numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about". The term "about" generally refers to a range of values, which those of ordinary skill in the art would consider equivalent to the stated value to produce substantially the same properties, functions, results, etc. A range of values indicated by a lower value and an upper value is defined to include all values included in the range of values and all sub-ranges included in the range of values.

[0030] The composite conductive filler provided by the present application includes a plurality of conductive particles, each of which independently includes a plurality of conductive particles I and a plurality of conductive particles II, and the conductive particles I and the conductive particles II in the same conductive particle are adhered together through the polyvinylpyrrolidone adhered on the surface thereof. The D 90 The particle size is preferably 1-70 μm, such as 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm or any value therebetween. The D 90The particle size is preferably 1 to 70 μm, such as 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, or any value therebetween. The average diameter of the conductive particles is preferably 0.2 to 3 mm, such as 0.2 mm, 0.5 mm, 0.8 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, or any value therebetween.

[0031] In the present application, the conductive particle I includes a conductive core I and polyvinylpyrrolidone and acid attached to the surface of the conductive core I. The mass ratio of the conductive core I, polyvinylpyrrolidone and acid in the conductive particle I is preferably (800-1200): 100: (30-80), at which point the polyvinylpyrrolidone can be well attached to the surface of the conductive particle I, and the acid can also be uniformly dispersed in the polyvinylpyrrolidone, which is more conducive to improving the dispersibility and conductivity of the composite conductive filler. Specifically, taking the content of polyvinylpyrrolidone in the conductive particle I as 100 parts by weight, the content of the conductive core I can be 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200 parts by weight, or any value therebetween, and the content of the acid can be 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight, or any value therebetween. The content of each component in the conductive particle I can be any point value within the above range, which is not enumerated here.

[0032] In the present application, the conductive particle I includes a conductive core I and polyvinylpyrrolidone and acid attached to the surface of the conductive core I. The mass ratio of the conductive core I, polyvinylpyrrolidone and acid in the conductive particle I is preferably (800-1200): 100: (30-80), at which point the polyvinylpyrrolidone can be well attached to the surface of the conductive particle I, and the acid can also be uniformly dispersed in the polyvinylpyrrolidone, which is more conducive to improving the dispersibility and conductivity of the composite conductive filler. Specifically, taking the content of polyvinylpyrrolidone in the conductive particle I as 100 parts by weight, the content of the conductive core I can be 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200 parts by weight, or any value therebetween, and the content of the acid can be 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight, or any value therebetween. The content of each component in the conductive particle I can be any point value within the above range, which is not enumerated here.

[0033] In the present application, the ratio of the conductive particle I and the conductive particle II in the composite conductive filler is preferably such that the ratio of the molar amount of the carboxylate in the acid to the molar amount of the carbonate in the basic carbonate (hydrogen carbonate) is 1:(0.8-1.2), at which time the acid and the basic carbonate (hydrogen carbonate) can be fully reacted, and the effects of the swelling and the gas production are optimal, and correspondingly, the dispersibility and the conductivity of the composite conductive filler are both better. The ratio of the molar amount of the carboxylate in the acid to the molar amount of the carbonate in the basic carbonate (hydrogen carbonate) in the composite conductive filler can exemplarily be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, or any value therebetween. The ratio of the acid and the basic carbonate (hydrogen carbonate) can be any point value in the above range, which is not enumerated here.

[0034] In the most preferred embodiment, the mass ratio of the conductive core I, the polyvinylpyrrolidone, and the acid in the conductive particle I is (800-1200):100:(30-80), the mass ratio of the conductive core II, the polyvinylpyrrolidone, and the basic carbonate (hydrogen carbonate) in the conductive particle II is (800-1200):100:(30-80), and the ratio of the conductive particle I and the conductive particle II in the composite conductive filler is such that the ratio of the molar amount of the carboxylate in the acid to the molar amount of the carbonate in the basic carbonate (hydrogen carbonate) is 1:(0.8-1.2), at which time the optimal ratio is achieved among the raw materials, and when under pressure, the conductive particle I and the conductive particle I, the conductive particle I and the conductive particle II, and the conductive particle II and the conductive particle II can be easily bonded together under the action of the polyvinylpyrrolidone, and the acid and the basic carbonate (hydrogen carbonate) can be easily and uniformly dispersed in the polyvinylpyrrolidone; when dissolved, the acid and the basic carbonate (hydrogen carbonate) can be easily dispersed under the adhesive action of the polyvinylpyrrolidone, and the capillary action, the swelling, and the gas production can all be brought to the extreme, and the dissolution effect is optimal, and the graphene and / or the carbon nanotube can also be most fully stretched and exposed, and the conductivity is better.

[0035] In the present application, the conductive inner core I and the conductive inner core II are preferably each independently graphene and / or carbon nanotube, that is, can be graphene, can be carbon nanotube, and can also be a mixture of graphene and carbon nanotube. Among them, the thickness of the graphene is preferably 1.5-3 nm, such as 1.5 nm, 1.6 nm, 1.8 nm, 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm, 3 nm or any value between them; the flake diameter is preferably 5-10 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any value between them. The aspect ratio of the carbon nanotube is preferably 500-2000, such as 500, 800, 1000, 1200, 1500, 1800, 2000 or any value between them. Specific examples of the acid include but are not limited to at least one of tartaric acid, citric acid, malic acid, fumaric acid, boric acid, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. The term "alkali carbonate (hydrogen) salt" includes alkali carbonate and / or alkali bicarbonate. Specific examples of the alkali carbonate (hydrogen) salt include but are not limited to at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate and ammonium bicarbonate. In addition, the number average molecular weight of polyvinylpyrrolidone (PVP) is preferably 2000-15000, such as 2000, 4000, 6000, 8000, 10000, 12000, 14000, 15000 or any value between them.

[0036] In the present application, the terms "I" and "II" are only used to distinguish different conductive particles and conductive inner cores for the purpose of description, and have no other special meanings.

[0037] In the present application, polyvinylpyrrolidone is in the form of powder. Compared with gelatinous polyvinylpyrrolidone, powder-like polyvinylpyrrolidone is easy to be dispersed in the dissolving process.

[0038] The present application provides a preparation method of the conductive material, which comprises the following steps:

[0039] S1, the aqueous solution of polyvinylpyrrolidone and acid is sprayed on the conductive inner core I under high-speed stirring, and then dried to make the polyvinylpyrrolidone and acid adhere to the surface of the conductive inner core I, to obtain the conductive particle I; the aqueous solution of polyvinylpyrrolidone and alkali carbonate (hydrogen) salt is sprayed on the conductive inner core II under high-speed stirring, and then dried to make the polyvinylpyrrolidone and alkali carbonate (hydrogen) salt adhere to the surface of the conductive inner core II, to obtain the conductive particle II;

[0040] S2, the conductive particle I and the conductive particle II are mixed, and then dry granulation is adopted, to obtain the composite conductive filler.

[0041] In the present application, in step S1, during the preparation of the conductive particle I and the conductive particle II, the rotation speed of the high-speed stirring can be independently 100-600 rpm, such as 100, 200, 300, 400, 500, 600 rpm or any value between them.

[0042] In the present application, in step S1, during the preparation of the conductive particle I and the conductive particle II, the drying conditions preferably independently include a temperature of 90-110℃, such as 90℃, 95℃, 100℃, 105℃, 110℃ or any value between them; a time of 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h or any value between them.

[0043] In the present application, when the conductive core I and / or the conductive core II adopts carbon nanotubes, it is preferred to sand the carbon nanotubes in advance, the purpose of which is to reduce the aspect ratio of the carbon nanotubes, so as to avoid the entanglement due to too large aspect ratio in the subsequent use process and affect the performance of the conductive property.

[0044] In the present application, in step S2, the dry granulation method is to roll the mixture and then crush and granulate to obtain the conductive particles, in which process the polyvinylpyrrolidone on the surface of graphene and carbon nanotubes is deformed and bonded together under pressure, and the crushing and granulation process can make it not float on the surface of the solution during the dissolution process.

[0045] The present application also provides the use of the above-mentioned composite conductive filler in conductive paint.

[0046] In addition, the present application also provides a conductive paint, which contains resin and conductive particles, and the conductive particles are the above-mentioned composite conductive filler. The main improvement of the conductive paint provided by the present application is to use a new conductive filler, and the type of resin, the content between the resin and the conductive filler can be the same as the prior art, which is known to those skilled in the art, and will not be described here.

[0047] The present application will be described in detail below through examples.

[0048] Example 1

[0049] S1, 1000 g of graphene / carbon nanotube (the mass ratio of graphene and carbon nanotube is 1:1, the average thickness of graphene is 1.5 nm and the average flake diameter is 5 μm, and the average aspect ratio of carbon nanotube is 800:1) is put into a high-speed mixer, 100 g of PVP (Mn is 5000) and 50 g of tartaric acid are dissolved in 1000 g of water to obtain a PVP / tartaric acid solution, the PVP / tartaric acid solution is sprayed onto the graphene / carbon nanotube through a spray head under high-speed stirring (the stirring speed is 400 rpm) so that the PVP and tartaric acid are attached to the surface of the graphene / carbon nanotube through high-speed stirring, and then the mixture is put into an oven and baked at 100°C for 4 h to obtain D 90 The conductive particles I have a particle size of 11.3 μm.

[0050] 1000 g of graphene / carbon nanotube (the mass ratio of graphene and carbon nanotube is 1:1, the average thickness of graphene is 1.5 nm and the average flake diameter is 5 μm, and the average aspect ratio of carbon nanotube is 800:1) is put into a high-speed mixer, 100 g of PVP (Mn is 5000) and 50 g of sodium bicarbonate are dissolved in 1000 g of water to obtain a PVP / sodium bicarbonate solution, the PVP / sodium bicarbonate solution is sprayed onto the graphene / carbon nanotube through a spray head under high-speed stirring (the stirring speed is 400 rpm) so that the PVP / sodium bicarbonate is attached to the surface of the graphene / carbon nanotube through high-speed stirring, and then the mixture is put into an oven and baked at 100°C for 4 h to obtain D 90 The conductive particles II have a particle size of 11.2 μm.

[0051] S2, the conductive particles I and the conductive particles II are uniformly mixed, and the content of the conductive particles I and the conductive particles II is such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the basic carbonate (hydrogen) salt is 1:1, and then the obtained mixture is rolled and crushed into conductive particles with an average diameter of 1.1 mm to obtain a composite conductive filler. The SEM image of the composite conductive filler is shown in Figure 1 It can be seen from Figure 1 that the conductive substances in the composite conductive filler are in an extended state and do not appear to be agglomerated.

[0052] The composite conductive filler comprises a plurality of conductive particles, each of which independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particles I comprise a conductive core I and polyvinylpyrrolidone and an acid attached to the surface of the conductive core I, the conductive particles II comprise a conductive core II and polyvinylpyrrolidone and a basic carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are bonded together by the polyvinylpyrrolidone attached to their surfaces.

[0053] Example 2

[0054] S1, 1000 g of graphene (average thickness of graphene is 3 nm and average flake diameter is 10 μm) is put into a high-speed mixer, 100 g of PVP (Mn is 8000) and 50 g of citric acid are dissolved in 1000 g of water to obtain a PVP / citric acid solution, the PVP / citric acid solution is sprayed onto the graphene through a spray head while high-speed stirring (stirring speed is 400 rpm) so that PVP and citric acid are attached to the surface of graphene through high-speed stirring, and then it is put into an oven and baked at 100°C for 4 h to obtain D 90 The conductive particles I have a particle size of 11.5 μm.

[0055] 1000 g of graphene (average thickness of graphene is 3 nm and average flake diameter is 10 μm) is put into a high-speed mixer, 100 g of PVP (Mn is 8000) and 50 g of sodium carbonate are dissolved in 1000 g of water to obtain a PVP / sodium carbonate solution, the PVP / sodium carbonate solution is sprayed onto the graphene through a spray head while high-speed stirring (stirring speed is 400 rpm) so that PVP / sodium carbonate is attached to the surface of graphene through high-speed stirring, and then it is put into an oven and baked at 100°C for 4 h to obtain D 90 The conductive particles II have a particle size of 11.3 μm.

[0056] S2, the conductive particles I and the conductive particles II are uniformly mixed, the content of the conductive particles I and the conductive particles II is such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the basic (hydrogen) carbonate is 1:1, and then the obtained mixture is rolled and crushed into conductive particles with an average diameter of 1.1 mm to obtain a composite conductive filler.

[0057] The composite conductive filler comprises a plurality of conductive particles, each of the conductive particles independently comprises a plurality of the conductive particles I and a plurality of the conductive particles II, the conductive particles I comprise a conductive core I and polyvinylpyrrolidone and an acid attached to the surface of the conductive core I, the conductive particles II comprise a conductive core II and polyvinylpyrrolidone and a basic (hydrogen) carbonate attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are bonded together through the polyvinylpyrrolidone attached to the surface thereof.

[0058] Example 3

[0059] S1, 1000 g of carbon nanotubes (average aspect ratio is 1500:1) is put into a high-speed mixer, 100 g of PVP (Mn is 12000) and 50 g of fumaric acid are dissolved in 1000 g of water to obtain a PVP / fumaric acid solution, the PVP / fumaric acid solution is sprayed onto the carbon nanotubes through a spray head while high-speed stirring (stirring speed is 400 rpm) so that PVP and fumaric acid are attached to the surface of the carbon nanotubes through high-speed stirring, and then it is put into an oven and baked at 100°C for 4 h to obtain D90 Conductive particles I with a particle size of 11.8 μm.

[0060] 1000 g of carbon nanotubes (average aspect ratio of 1500:1) were placed in a high-speed mixer, 100 g of PVP (Mn of 12000) and 50 g of ammonium bicarbonate were dissolved in 1000 g of water to obtain a PVP / ammonium bicarbonate solution, and the PVP / ammonium bicarbonate solution was sprayed onto the carbon nanotubes through a spray head while being stirred at high speed (stirring speed of 400 rpm) so that the PVP / ammonium bicarbonate was attached to the surface of the carbon nanotubes by high-speed stirring. After that, the mixture was placed in an oven and baked at 100°C for 4 h to obtain D 90 Conductive particles II with a particle size of 11.9 μm.

[0061] S2, the conductive particles I and the conductive particles II were mixed uniformly, and the content of the conductive particles I and the conductive particles II was such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the basic carbonate (hydrogen) salt was 1:1. After that, the obtained mixture was rolled and crushed into conductive particles with an average diameter of 1.1 mm to obtain the composite conductive filler.

[0062] The composite conductive filler comprises a plurality of conductive particles, each of the conductive particles independently comprises a plurality of the conductive particles I and a plurality of the conductive particles II, the conductive particles I comprise a conductive core I and polyvinylpyrrolidone and an acid attached to the surface of the conductive core I, and the conductive particles II comprise a conductive core II and polyvinylpyrrolidone and a basic carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are bonded together by the polyvinylpyrrolidone attached to the surface thereof.

[0063] Example 4

[0064] The composite conductive filler was prepared according to the method of Example 1, except that in step S1, the amount of tartaric acid was 180 g, and the other conditions were the same as in Example 1, to obtain the composite conductive filler.

[0065] The composite conductive filler comprises a plurality of conductive particles, each of the conductive particles independently comprises a plurality of the conductive particles I and a plurality of the conductive particles II, the conductive particles I comprise a conductive core I and polyvinylpyrrolidone and an acid attached to the surface of the conductive core I, and the conductive particles II comprise a conductive core II and polyvinylpyrrolidone and a basic carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are bonded together by the polyvinylpyrrolidone attached to the surface thereof.

[0066] Example 5

[0067] The composite conductive filler was prepared according to the method of Example 1, except that in step S1, the amount of sodium bicarbonate was 150 g, and the other conditions were the same as in Example 1, to obtain the composite conductive filler.

[0068] The composite conductive filler comprises a plurality of conductive particles, each of which independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particles I comprise a conductive core I and polyvinylpyrrolidone and an acid attached to the surface of the conductive core I, and the conductive particles II comprise a conductive core II and polyvinylpyrrolidone and basic carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are adhered together by the polyvinylpyrrolidone attached to their surfaces.

[0069] Example 6

[0070] The composite conductive filler was prepared according to the method of Example 1, except that in step S2, the contents of the conductive particles I and the conductive particles II were such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the basic carbonate (hydrogen) salt was 0.5:1, and the other conditions were the same as in Example 1, to obtain the composite conductive filler.

[0071] The composite conductive filler comprises a plurality of conductive particles, each of which independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particles I comprise a conductive core I and polyvinylpyrrolidone and an acid attached to the surface of the conductive core I, and the conductive particles II comprise a conductive core II and polyvinylpyrrolidone and basic carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are adhered together by the polyvinylpyrrolidone attached to their surfaces.

[0072] Comparative Example 1

[0073] The composite conductive filler was prepared according to the method of Example 1, except that in step S1, both tartaric acid and sodium bicarbonate were replaced by PVP in the same weight fraction, and the other conditions were the same as in Example 1, to obtain the composite conductive filler. The SEM image of the composite conductive filler is shown in Figure 2 From Figure 2 It can be seen that the conductive material in the composite conductive filler has been entangled into a spherical shape and has not been fully stretched out.

[0074] The composite conductive filler comprises a plurality of conductive particles, each of the conductive particles independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particles I comprises a conductive core I and polyvinylpyrrolidone attached to the surface of the conductive core I, the conductive particles II comprises a conductive core II and polyvinylpyrrolidone attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are bonded together by the polyvinylpyrrolidone attached to the surface thereof.

[0075] Comparative Example 2

[0076] The composite conductive filler is prepared according to the method of Example 1, except that spray drying granulation is used, and the specific steps are as follows:

[0077] S1, 1000g graphene / carbon nanotubes (the mass ratio of graphene and carbon nanotubes is 1:1, the average thickness of graphene is 1.5nm and the average flake diameter is 5μm, and the average aspect ratio of carbon nanotubes is 800:1), 100g PVP (Mn is 5000) and 50g tartaric acid are dissolved in 1000g water, and the obtained slurry is spray dried and granulated to obtain D 90 The conductive particles I have a particle size of 25.6μm.

[0078] 1000g graphene / carbon nanotubes (the mass ratio of graphene and carbon nanotubes is 1:1, the average thickness of graphene is 1.5nm and the average flake diameter is 5μm, and the average aspect ratio of carbon nanotubes is 800:1), 100g PVP (Mn is 5000) and 50g sodium bicarbonate are dissolved in 1000g water, and the obtained slurry is spray dried and granulated to obtain D 90 The conductive particles II have a particle size of 25.5μm.

[0079] S2, the conductive particles I and the conductive particles II are uniformly mixed, and the content of the conductive particles I and the conductive particles II is such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the basic carbonate (hydrogen) salt is 1:1, and then the obtained mixture is rolled and crushed into granules to obtain a composite conductive filler with an average diameter of 1.1mm.

[0080] The composite conductive filler comprises a plurality of conductive particles, each of the conductive particles independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particles I comprises a conductive core I and polyvinylpyrrolidone gel and acid attached to the surface of the conductive core I, the conductive particles II comprises a conductive core II and polyvinylpyrrolidone gel and basic carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are bonded together by the polyvinylpyrrolidone gel attached to the surface thereof.

[0081] Comparative Example 3

[0082] The composite conductive filler was prepared according to the method of Example 1, except that freeze-drying granulation was used, and the specific steps were as follows:

[0083] S1, 1000g graphene / carbon nanotubes (the mass ratio of graphene and carbon nanotubes was 1:1, the average thickness of graphene was 1.5nm and the average flake diameter was 5μm, and the average aspect ratio of carbon nanotubes was 800:1), 100g PVP (Mn was 5000) and 50g tartaric acid were dissolved in 1000g water, and the obtained slurry was freeze-dried and granulated to obtain D 90 The conductive particles I had a particle size of 24.7μm.

[0084] 1000g graphene / carbon nanotubes (the mass ratio of graphene and carbon nanotubes was 1:1, the average thickness of graphene was 1.5nm and the average flake diameter was 5μm, and the average aspect ratio of carbon nanotubes was 800:1), 100g PVP (Mn was 5000) and 50g sodium bicarbonate were dissolved in 1000g water, and the obtained slurry was freeze-dried and granulated to obtain D 90 The conductive particles II had a particle size of 24.7μm.

[0085] S2, the conductive particles I and the conductive particles II were uniformly mixed, and the content of the conductive particles I and the conductive particles II was such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the basic carbonate (hydrogen) salt was 1:1, and then the obtained mixture was rolled and crushed into granules to obtain a composite conductive filler with an average diameter of 1.1mm.

[0086] The composite conductive filler comprises a plurality of conductive particles, each of which independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particles I comprise a conductive core I and a polyvinylpyrrolidone gel and an acid attached to the surface of the conductive core I, and the conductive particles II comprise a conductive core II and a polyvinylpyrrolidone gel and a basic carbonate (hydrogen) salt attached to the surface of the conductive core II, and the conductive particles I and the conductive particles II in the same conductive particle are adhered together by the polyvinylpyrrolidone gel attached to their surfaces.

[0087] Comparative Example 4

[0088] 100g PVP (Mn was 5000) was added to 1000g graphene / carbon nanotubes (the mass ratio of graphene and carbon nanotubes was 1:1, the average thickness of graphene was 1.5nm and the average flake diameter was 5μm, and the average aspect ratio of carbon nanotubes was 800:1) and mixed uniformly to obtain a graphene / carbon nanotube slurry.

[0089] Test Example

[0090] (1) Solubility:

[0091] The composite conductive filler obtained in Examples 1-6 and Comparative Examples 1-3 above was dissolved in 100 g of a polyurethane resin solution having a solid content of 30% under stirring (200 rpm), to obtain a polyurethane conductive slurry. The dissolution speed was observed and the viscosity and particle size of the obtained polyurethane conductive slurry were tested. The graphene / carbon nanotube slurry obtained in Comparative Example 4 was mixed with 100 g of a polyurethane resin solution having a solid content of 30% to obtain a polyurethane conductive slurry. The dissolution speed was observed and the viscosity and particle size of the obtained polyurethane conductive slurry were tested. The results are shown in Table 1.

[0092] (2) Resistivity and mechanical properties:

[0093] The composite conductive filler obtained in Examples 1-6 and Comparative Examples 1-3 above was dissolved in 100 g of a polyurethane resin solution having a solid content of 30% under stirring (200 rpm), and the obtained polyurethane conductive slurry was uniformly coated on a rubber film and dried at 130°C for 4 h to obtain a conductive film having a thickness of 0.2±0.05 mm. The graphene / carbon nanotube slurry obtained in Comparative Example 4 was dissolved in 100 g of a polyurethane resin solution having a solid content of 30% under stirring (200 rpm), and the obtained polyurethane conductive slurry was uniformly coated on a rubber film and dried at 130°C for 4 h to obtain a conductive film having a thickness of 0.2±0.05 mm.

[0094] The resistivity of the conductive film was tested using a M-3 handheld resistivity tester from Suzhou Lattice Electronics Co., Ltd. Five points on each conductive film sample were randomly selected for testing, and the average value was taken as the final result. The results are shown in Table 2.

[0095] The conductive film was cut into dumbbell-shaped samples, and the working area (narrow neck) had a width of 2 mm. The samples were fixed on the clamps of a tensile testing machine and stretched at a rate of 20 mm / min until they broke, to obtain the tensile strength and elongation at break. Each group of samples was repeated 5 times, and the average value after removing the maximum and minimum values was taken as the test result. The results are shown in Table 2.

[0096] Table 1

[0097]

[0098] Table 2

[0099] Item Appearance of film Resistivity / (Ω-cm) Tensile strength / MPa Elongation at break / % Example 1 Smooth and fine 17.8 10.4 1.2 Example 2 Smooth and fine 17.6 10.5 1.2 Example 3 Smooth and fine 18.6 9.9 1.2 Example 4 Smooth and fine 19.2 9.8 1.1 Example 5 Smooth and fine 19.5 9.6 1.1 Example 6 Smooth and fine 20.1 9.7 1.0 Comparative Example 1 Surface rough 52.8 8.2 0.6 Comparative Example 2 Surface rough 29.6 8.5 0.8 Comparative Example 3 Surface rough 31.5 8.6 0.7 Comparative Example 4 Surface rough 42.3 8.2 0.7

[0100] As can be seen from the results of Table 1 and Table 2, the composite conductive filler provided by the present application has good dispersibility in solvent, and when it is used in conductive paint, the conductivity can be significantly improved. In addition, the composite conductive filler provided by the present application can be stored for a long time, and its properties do not change substantially after being placed for six months.

[0101] As can be seen from the comparison of Example 1 and Examples 4-6, when the amount of acid and / or basic (hydro)carbonate and the ratio between conductive particle I and conductive particle II are controlled within the preferred range of the present application, the conductivity of the composite conductive filler is better.

[0102] As can be seen from the comparison of Example 1 and Comparative Example 1, when tartaric acid and sodium bicarbonate are not added during the preparation of the composite conductive filler, the conductive material is entangled into balls and cannot be fully stretched, and the conductivity is poor.

[0103] As can be seen from the comparison of Example 1 and Examples 2-4, compared with spray drying granulation, freeze drying granulation or conventional dispersion form, the dry granulation method used in the present application is more conducive to the improvement of the conductivity.

[0104] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above embodiments without departing from the principles and purposes of the present application within the scope of the present application.

Claims

1. A composite conductive filler, characterized by, The composite conductive filler comprises a plurality of conductive particles, each of the conductive particles independently comprises a plurality of conductive particles I and a plurality of conductive particles II, the conductive particles I comprises a conductive core I and polyvinylpyrrolidone and acid adhered to the surface of the conductive core I, the conductive particles II comprises a conductive core II and polyvinylpyrrolidone and alkaline carbonate and / or alkaline bicarbonate adhered to the surface of the conductive core II, the conductive particles I and the conductive particles II in the same conductive particle are adhered together by the polyvinylpyrrolidone adhered to the surface thereof; the polyvinylpyrrolidone exists in the form of a powder.

2. The composite conductive filler of claim 1, wherein The mass ratio of the conductive core I, the polyvinylpyrrolidone and the acid in the conductive particles I is (800-1200):100:(30-80).

3. The composite conductive filler of claim 1, wherein The mass ratio of the conductive core II, the polyvinylpyrrolidone, the alkaline carbonate and / or the alkaline bicarbonate in the conductive particles II is (800-1200):100:(30-80).

4. The composite conductive filler of claim 1, wherein The ratio of the conductive particles I and the conductive particles II in the composite conductive filler is such that the ratio of the molar amount of carboxylate in the acid to the molar amount of carbonate in the alkaline carbonate and / or the alkaline bicarbonate is 1:(0.8-1.2).

5. The composite conductive filler according to any one of claims 1 to 4, wherein The conductive core I and the conductive core II are independently graphene and / or carbon nanotube.

6. The composite conductive filler according to any one of claims 1 to 4, wherein The acid is selected from at least one of tartaric acid, citric acid, malic acid, fumaric acid, boric acid, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; the alkaline carbonate and / or the alkaline bicarbonate is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate and ammonium bicarbonate.

7. The composite conductive filler according to any one of claims 1 to 4, wherein D of the conductive particles I 90 D of the conductive particles II 90 D of the conductive particles II D of the conductive particles II 8. A method of producing the composite conductive filler according to any one of claims 1 to 7, characterized by, The method comprises the following steps: S1, after spraying the aqueous solution of polyvinylpyrrolidone and acid on the conductive core I under high-speed stirring and drying, the polyvinylpyrrolidone and the acid are adhered to the surface of the conductive core I to obtain the conductive particles I; after spraying the aqueous solution of polyvinylpyrrolidone and alkaline carbonate and / or alkaline bicarbonate on the conductive core II under high-speed stirring and drying, the polyvinylpyrrolidone and the alkaline carbonate and / or the alkaline bicarbonate are adhered to the surface of the conductive core II to obtain the conductive particles II; S2, after mixing the conductive particles I and the conductive particles II, dry granulation is adopted to obtain the composite conductive filler.

9. The method for preparing the composite conductive filler according to claim 8, characterized in that, In the preparation process of the conductive particles I and the conductive particles II in step S1, the rotating speed of the high-speed stirring is independently 100-600 rpm; the drying condition independently comprises a temperature of 90-110℃ and a time of 2-8h.

10. The method for preparing the composite conductive filler according to claim 8, characterized in that, In step S2, the method of dry granulation is to roll the mixed material and then crush and granulate to obtain the conductive particles.

11. The composite conductive filler in any one of claims 1-7 is applied in conductive paint.

12. An electroconductive paint comprising a resin and electroconductive particles, characterized in that, The conductive particles are the composite conductive filler in any one of claims 1-7.

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