A kind of graphene conductive carbon slurry with high thixotropy and preparation method thereof

Abstract

The invention discloses a highly thixotropic graphene conductive carbon slurry and a preparation method thereof, wherein the raw materials are composed of 10 to 20 parts of filler, 30 to 40 parts of organic solvent, 1 to 10 parts of binder, 20 to 30 parts of dispersant, and 30 to 40 parts of auxiliary agent by weight; wherein the filler is a mixture of graphite, carbon black and graphene. The invention uses carbon black, graphite and graphene as fillers, so that the obtained slurry has excellent conductive properties and thixotropic properties. The method of the invention is simple to operate and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of conductive carbon paste, and in particular to a highly thixotropic graphene conductive carbon paste and a preparation method thereof. Background Art

[0002] The development of printed electronics in the fields of wearable transistors, display devices, radio frequency (RF) electronics, and energy management has urged the research on smart electronic textiles. The further integration of smart electronic systems requires low-loss and high-reliability smart textiles to provide electronic functions for the human body. The formulation of high-performance conductive functional carbon paste is a key part of smart textiles. Various carbon pastes have been developed and used for printing flexible electronics. A large number of printing technologies are used in the manufacture of flexible printed electronics. Screen printing is one of the most widely used contact printing technologies, which can achieve highly scalable production.

[0003] The screen printing properties of the paste are mainly optimized by adjusting the thixotropy of the paste, and high thixotropic conductive carbon paste has a wide range of application prospects in the manufacture of electronic products. For example, in the field of radio frequency (RF) electronics, high thixotropic conductive carbon paste can be used to shield electromagnetic interference and radio frequency interference to ensure the compatibility of equipment; in the field of display devices, high thixotropic conductive carbon paste can be used as a conductive material for touch screens to improve touch sensitivity and response speed. Therefore, the improvement of thixotropy is a crucial parameter for the application of pastes and is also an urgent problem to be solved.

[0004] At present, there have been many studies on the thixotropy of slurries, such as: Patent CN102964762A discloses a highly thixotropic ink binder resin composition for screen printing water transfer, which not only has high rheological properties, but also has very good printability of the ink. At the same time, it is very effective in reducing mesh blockage during printing and residues generated during firing. Patent CN116003142A discloses a debonding agent that can improve the thixotropy of mud and its preparation method. It adopts a polymer cross-linking structure and a variety of functional raw materials to improve the thixotropy, and has a very excellent debonding effect. Patent CN115910426A discloses a highly thixotropic conductive silver paste and its preparation method, which mainly adopts a low-viscosity resin system to enhance the thixotropy of the conductive silver paste itself, so as to solve the phenomenon of conductive lines falling off from the substrate.

[0005] The commonly used method for measuring the thixotropy of slurry is the 3ITT test (three-stage thixotropy test), because it can well simulate the process of carbon slurry screen printing, so as to have a deeper understanding of the structural decomposition and recovery of the slurry in the process. The test is carried out in three intervals. First, in the first interval, it is maintained at a low shear rate for a period of time, representing the slurry on the fabric screen before screen printing. Next, the shear rate is increased to reproduce the scraper stroke during the printing process. Finally, in the third interval, the shear rate is reduced to the same low shear rate as the first interval, and maintained for a period of time to simulate structural recovery. Based on this test method, the present invention proposes a highly thixotropic conductive carbon slurry and a preparation method thereof to solve the problems existing in the prior art. Summary of the invention

[0006] The purpose of the present invention is to provide a highly thixotropic graphene conductive carbon slurry and a preparation method thereof, so as to make it have the advantage of improving the thixotropy by relying on its own material and solve the problems existing in the prior art.

[0007] To achieve the purpose, the present invention adopts the following technical solution:

[0008] A highly thixotropic graphene conductive carbon slurry, wherein the raw materials thereof are composed of 10 to 20 parts of filler, 30 to 40 parts of organic solvent, 1 to 10 parts of binder, 20 to 30 parts of dispersant and 30 to 40 parts of auxiliary agent in parts by weight; the filler is a mixture of graphite, carbon black and graphene.

[0009] Furthermore, the weight proportion of graphene is 0.01 to 1 part, and the mass ratio of graphite (1000 mesh) to carbon black (industrial grade) is 1:0.5-2.

[0010] Furthermore, the organic solvent is a mixture of isopropanol, ethylene glycol and N,N-dimethylacetamide, and the mass ratio of the three is preferably 0.5-1.5:1:2.5-4.

[0011] Furthermore, the binder is at least one of polyurethane, ethyl cellulose and epoxy resin.

[0012] Furthermore, the dispersant is at least one of polyvinyl pyrrolidone, Triton and polyvinyl acetate.

[0013] Furthermore, the auxiliary agent is a mixture of deionized water, a thickener and a defoamer, and the mass ratio of the three is most preferably 15-150:1:4-5.

[0014] Furthermore, the thickener is at least one of carboxymethyl cellulose, organic bentonite and fumed silica, and the defoamer is BYK-066N organosilicon defoamer.

[0015] The present invention also provides a method for preparing the above-mentioned highly thixotropic graphene conductive carbon slurry, which comprises uniformly dispersing an organic solvent, a dispersant and an auxiliary agent by ultrasonication, pouring the mixture into a ball mill, adding a filler and a binder, and performing ball milling to obtain the graphene conductive carbon slurry.

[0016] Furthermore: the ultrasonic time is 30min-60min; the ball mill speed is 400r / min-600r / min, and the ball milling time is 4h.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention uses carbon black, graphite and graphene as fillers, so that the obtained slurry has excellent electrical conductivity and thixotropic properties. At the same time, the present invention uses a low-viscosity alcohol system and a ball milling blending method to dissolve the agglomeration between particles, thereby better reducing the viscosity of the slurry and ensuring the high thixotropy and good dispersibility of the slurry. The method of the present invention is simple to operate and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The viscosity change curve of the graphene conductive carbon slurry obtained in each embodiment and comparative example is shown in FIG.

[0020] Figure 2 The thixotropic performance diagram of the graphene conductive carbon paste obtained in each embodiment and comparative example.

[0021] Figure 3 The infrared thermal images of the graphene conductive carbon pastes obtained in the embodiments and comparative examples are shown. DETAILED DESCRIPTION

[0022] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0023] The method for preparing graphene conductive carbon slurry in the following embodiment comprises the following steps:

[0024] (1) Add an organic solvent, a dispersant and an additive into a beaker in sequence, and place the beaker into an ultrasonic machine for ultrasonic treatment for 30 min.

[0025] (2) Pour the solution from step 1 into a ball mill, and then add filler and binder.

[0026] (3) The slurry obtained in step 2 is subjected to ball milling treatment, the rotation speed is set to 500 r / min, and the ball mill is set to rotate forward for 2 hours and reverse for 2 hours. After the ball milling is completed, a conductive carbon slurry is obtained.

[0027] Example 1

[0028] A graphene conductive carbon slurry, wherein the raw materials are composed of 10 parts of filler, 30 parts of organic solvent, 5 parts of binder, 20 parts of dispersant and 30 parts of auxiliary agent in terms of weight. Specifically:

[0029] The filler includes 0.01 parts of graphene, 5 parts of carbon black and 4.99 parts of graphite; the organic solvent includes 5 parts of isopropanol, 5 parts of ethylene glycol and 20 parts of N,N-dimethylacetamide; the binder is polyurethane; the dispersant includes 10 parts of polyvinyl pyrrolidone and 10 parts of Triton; the additives include 27 parts of deionized water, 2 parts of carboxymethyl cellulose and 1 part of BYK-066N silicone defoamer.

[0030] Example 2

[0031] A graphene conductive carbon slurry, wherein the raw materials are composed of 10 parts of filler, 30 parts of organic solvent, 5 parts of binder, 20 parts of dispersant and 30 parts of auxiliary agent in terms of weight. Specifically:

[0032] The filler includes 0.02 parts of graphene, 5 parts of carbon black and 4.98 parts of graphite; the organic solvent includes 5 parts of isopropanol, 5 parts of ethylene glycol and 20 parts of N,N-dimethylacetamide; the binder is polyurethane; the dispersant includes 10 parts of polyvinyl pyrrolidone and 10 parts of Triton; the additives include 27 parts of deionized water, 2 parts of carboxymethyl cellulose and 1 part of BYK-066N silicone defoamer.

[0033] Example 3

[0034] A graphene conductive carbon slurry, wherein the raw materials are composed of 10 parts of filler, 30 parts of organic solvent, 5 parts of binder, 20 parts of dispersant and 30 parts of auxiliary agent in terms of weight. Specifically:

[0035] The filler includes 0.03 parts of graphene, 5 parts of carbon black and 4.97 parts of graphite; the organic solvent includes 5 parts of isopropanol, 5 parts of ethylene glycol and 20 parts of N,N-dimethylacetamide; the binder is polyurethane; the dispersant includes 10 parts of polyvinyl pyrrolidone and 10 parts of Triton; the additives include 27 parts of deionized water, 2 parts of carboxymethyl cellulose and 1 part of BYK-066N silicone defoamer.

[0036] Example 4

[0037] A graphene conductive carbon slurry, wherein the raw materials are composed of 10 parts of filler, 30 parts of organic solvent, 5 parts of binder, 20 parts of dispersant and 30 parts of auxiliary agent in terms of weight. Specifically:

[0038] The filler includes 0.04 parts of graphene, 5 parts of carbon black and 4.96 parts of graphite; the organic solvent includes 5 parts of isopropanol, 5 parts of ethylene glycol and 20 parts of N,N-dimethylacetamide; the binder is polyurethane; the dispersant includes 10 parts of polyvinyl pyrrolidone and 10 parts of Triton; the additives include 27 parts of deionized water, 2 parts of carboxymethyl cellulose and 1 part of BYK-066N silicone defoamer.

[0039] Comparative Example 1

[0040] The difference between Comparative Example 1 and Example 1 is that the fillers are only carbon black and graphite, wherein the carbon black is 3 parts and the graphite is 7 parts.

[0041] Comparative Example 2

[0042] The difference between Comparative Example 2 and Example 1 is that the fillers are only carbon black and graphite, wherein the proportions of carbon black and graphite are both 5 parts.

[0043] The thixotropic properties of the carbon slurries obtained in the above embodiments and comparative examples were tested as follows:

[0044] (1) Use an advanced rheometer and select the 3ITT mode. First, set a low shear stress (1 Pa) for 60 seconds. Then, immediately increase the shear stress to 50 Pa. After 5 seconds of high-speed shear, set the shear stress to 1 Pa again to observe the viscosity recovery state.

[0045] (2) The recovery ratio of the viscosity of the conductive carbon slurry after high-speed shear damage was selected as the evaluation index, and the recovery ratio of the viscosity of the system 2 seconds after the high-speed shear action stopped was obtained and the specific value was recorded.

[0046] The viscosity variation curves of the carbon slurries obtained in the above embodiments and comparative examples were tested as follows: using an advanced rheometer, selecting the shear mode, setting the shear rate variation range to 0.1%-100%, fixing the frequency to 1 Hz, and obtaining a curve of the slurry viscosity varying with the shear rate.

[0047] The square resistance of the carbon slurry obtained in the above embodiments and comparative examples was tested as follows: the slurry was coated on the substrate using a coating machine, and placed in an oven for drying to obtain films of different thicknesses (0.05 mm and 0.06 mm), with the film size fixed at 5 cm*5 cm. A four-probe tester was used, and the equipment test mode was adjusted to square resistance test. The probes were placed vertically on the film surface, and the average value was obtained after multiple tests, and the value was recorded.

[0048] The infrared thermal imaging images of the carbon slurries obtained in the above embodiments and comparative examples were tested as follows: at room temperature, an infrared thermal imaging camera was used to take pictures of the dried film at a voltage of 5V (consistent with the voltage used for commercially available films) after power was applied for 10s, 20s and 30s.

[0049] The test results are shown in Table 1. Figures 1 to 3 shown.

[0050] Table 1

[0051]

[0052] first Figure 1 This shows the shear thinning phenomenon of the slurry, that is, the viscosity decreases with the increase of shear rate, which is the premise for the application of the slurry. In addition, the speed of viscosity recovery reflects the magnitude of the thixotropy of the conductive carbon slurry. Figure 2 The results show that as the amount of graphene added increases, the viscosity of the conductive carbon slurry recovers faster. This may be because the graphene sheets are larger in diameter and are easier to overlap with each other, so the speed of re-forming flocs is fast. From Table 1 and Figure 3 It can be seen that with the addition of graphene, the square resistance of the film formed by the carbon slurry is gradually reduced, and the electrothermal performance is gradually improved. This is because when graphene is added, due to its high electrical conductivity and high thermal conductivity, it can enhance the conductivity of the carbon slurry, thereby reducing the square resistance of the carbon slurry. In addition, the high specific surface area of ​​graphene can also increase the contact area between the carbon slurry particles and the electrode surface, further improving the conductivity of the carbon slurry, thereby reducing the square resistance and improving the electrical conductivity and thermal conductivity.

[0053] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A highly thixotropic graphene conductive carbon paste, characterized in that: The composition of each raw material in parts by weight is: 10-20 parts of filler, 30-40 parts of organic solvent, 1-10 parts of binder, 20-30 parts of dispersant, and 30-40 parts of auxiliary agent; the filler is a mixture of graphite, carbon black and graphene, and the weight portion of graphene is 0.01-1 part, and the mass ratio of graphite to carbon black is 1:0.5-2; The organic solvent is a mixture of isopropanol, ethylene glycol and N,N-dimethylacetamide; the binder is at least one of polyurethane, ethyl cellulose and epoxy resin; the dispersant is at least one of polyvinyl pyrrolidone, Triton and polyvinyl acetate; After the organic solvent, dispersant and additive are uniformly dispersed by ultrasonic, they are poured into a ball mill, and fillers and binders are added for ball milling to obtain graphene conductive carbon slurry. The speed of the ball mill is 400 r / min to 600 r / min, and the ball milling time is 4 hours.

2. The graphene conductive carbon paste according to claim 1, characterized in that: The auxiliary agent is a mixture of deionized water, a thickener and a defoamer.

3. The graphene conductive carbon slurry according to claim 2, characterized in that: The thickener is at least one of carboxymethyl cellulose, organic bentonite and fumed silica.

4. The graphene conductive carbon slurry according to claim 2, characterized in that: The defoamer is BYK-066N organosilicon defoamer.

5. A method for preparing the graphene conductive carbon slurry according to any one of claims 1 to 4, characterized in that: After the organic solvent, dispersant and additive are uniformly dispersed by ultrasonic, they are poured into a ball mill, and fillers and binders are added for ball milling to obtain graphene conductive carbon slurry. The speed of the ball mill is 400 r / min to 600 r / min, and the ball milling time is 4 hours.

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