Graphene conductive adhesive and preparation method thereof

Abstract

The application discloses graphene conductive glue and a preparation method thereof, and relates to the technical field of adhesives.The functionalized epoxy monomer is prepared by reacting polyethylene glycol diglycidyl ether and an ultraviolet absorber when the graphene conductive glue is prepared; the pre-modified graphene is prepared by polymerizing and coating a dihydroxydiphenyl phosphorus monomer and phenyldichlorosilane on graphene; the modified graphene is prepared by reacting the pre-modified graphene and allyl glycidyl ether; the modified cellulose is prepared by polymerizing and growing 5,6-dihydroxyindole and 6-aminomethylindole on the pre-modified cellulose; and the graphene conductive glue is prepared by uniformly mixing epoxy resin, the functionalized epoxy monomer, the modified graphene, the modified cellulose, isophorone diamine and acetone.The graphene conductive glue prepared by the application has excellent anti-aging, flame-retardant, conductive, bonding and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a graphene conductive adhesive and its preparation method. Background Technology

[0002] Conductive adhesives are typically composed of a base resin, conductive particles, crosslinking agents, and solvents. They are a type of adhesive that possesses both bonding and conductive properties. Conductive adhesives have wide applications in the electronics industry, such as the encapsulation and bonding of liquid crystal displays, light-emitting diodes, integrated circuit chips, and printed circuit board assemblies. With the miniaturization and micro-miniaturization of electronic components, as well as the high density and high integration of printed circuit boards, conductive adhesives are gradually replacing traditional soldering and becoming the ideal choice for achieving conductive connections due to their advantages such as simple processing, ease of operation, improved production efficiency, and environmental friendliness.

[0003] The development of conductive adhesives has reached a point where some limitations remain. Firstly, there are environmental constraints. As organic materials, conductive adhesives are flammable and prone to aging, exhibiting powdering, yellowing, and decreased adhesion over time. Secondly, compared to metallic conductors, the conductivity of conductive adhesives is relatively low, failing to fully meet market demands. Therefore, it is necessary to develop conductive adhesive materials that are flame-retardant, anti-aging, and possess superior conductivity. Summary of the Invention

[0004] The purpose of this invention is to provide a graphene conductive adhesive and its preparation method to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A graphene conductive adhesive, characterized in that the graphene conductive adhesive is prepared by reacting polyethylene glycol diglycidyl ether and an ultraviolet absorber to obtain a functionalized epoxy monomer; by reacting pre-modified graphene and allyl glycidyl ether to obtain modified graphene; by polymerizing and growing 5,6-dihydroxyindole and 6-aminomethylindole on pre-modified cellulose to obtain modified cellulose; and by uniformly mixing epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isoflurane diamine, and acetone.

[0007] The ultraviolet absorber is prepared by reacting 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde.

[0008] The pre-modified graphene is prepared by polymerizing and coating graphene with dihydroxydiphenyl phosphorus-containing monomers and phenyl dichlorosilane.

[0009] The dihydroxydiphenyl phosphorus-containing monomer is prepared by reacting 4,4'-dihydroxybenzophenone and methylphenyl-phosphorus oxide.

[0010] The pre-modified cellulose is prepared by reacting cellulose and indole-6-carboxylic acid.

[0011] A method for preparing graphene conductive adhesive, the method comprising the following preparation steps:

[0012] (1) Polyethylene glycol diglycidyl ether, ultraviolet absorber and p-toluenesulfonic acid monohydrate are mixed evenly at a mass ratio of 100:(6~8):(1.1~1.3). Under nitrogen protection, the mixture is stirred at 78~80℃ and 100~150r / min for 30~40min. The temperature is increased to 128~130℃ at a heating rate of 10℃ / h, and stirring is continued for 20~30min. The mixture is cooled to room temperature and extracted with deionized water 3~5 times. The organic phase is taken and dried at 50~60℃ for 8~10h under vacuum to obtain the functionalized epoxy monomer.

[0013] (2) Mix graphene and N,N-dimethylacetamide at a mass ratio of 1:(78-82) until homogeneous, and ultrasonically disperse for 1-1.2 h. Add 0.5-0.6 times the mass of graphene triethylamine and 3-4 times the mass of graphene dihydroxydiphenylphosphine-containing monomer. Stir at 100-200 r / min for 20-22 min at room temperature. Raise the temperature to 80-90℃ and add 9-11 times the mass of dihydroxydiphenylphosphine-containing monomer phenyl dichlorosilane solution dropwise over 15 min. Continue stirring for 7-9 h. Filter and wash 3-5 times each with anhydrous ethanol and deionized water. Pre-modified graphene was prepared by drying at 50–60°C for 10–12 h under vacuum conditions. The pre-modified graphene and toluene were mixed evenly at a mass ratio of 1:(60–70), ultrasonically dispersed for 20–30 min, and then allyl glycidyl ether (2–3 times the mass of the pre-modified graphene) and chloroplatinic acid (0.08–0.1 times the mass of the pre-modified graphene) were added. The mixture was stirred at 70–80°C and 100–200 r / min for 4–5 h. After filtration, the mixture was washed 3–5 times with anhydrous ethanol and dried at 60–70°C for 10–12 h under vacuum conditions to obtain modified graphene.

[0014] (3) Mix cellulose and N,N-dimethylformamide at a mass ratio of 1:(26-30), disperse ultrasonically for 30-40 min, adjust the pH to 3-4 with hydrochloric acid aqueous solution, add 0.4-0.6 times the mass of cellulose indole-6-carboxylic acid, stir at 100-200 r / min at 120-122℃ for 40-50 min, filter, wash 3-5 times with deionized water, and dry at 50-60℃ under vacuum for 7-8 h to obtain pre-modified cellulose; mix the pre-modified cellulose and 5,6-dihydroxyindole... 6-Aminomethylindole and anhydrous ethanol were mixed evenly in a mass ratio of 1:(3-4):(1-1.2):(22-24) and ultrasonically dispersed for 20-30 min to prepare a mixed reaction solution. Under nitrogen protection, at 0-2℃ and stirring at 100-200 r / min, the oxidant solution was added dropwise to the mixed reaction solution at a uniform rate over 15 min. The reaction was continued to be stirred for 3-4 h. The mixture was filtered, washed 3-5 times each with anhydrous ethanol and deionized water, and dried at 60-70℃ under vacuum for 8-10 h to obtain modified cellulose.

[0015] (4) Weigh 30-36 parts of epoxy resin, 58-60 parts of functionalized epoxy monomer, 4-5 parts of modified graphene, 6-7 parts of modified cellulose, 6-8 parts of isoflurane diamine, and 22-24 parts of acetone by mass. Mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 1800-2200 cps with acetone to obtain graphene conductive adhesive.

[0016] As an optimization, the preparation method of the ultraviolet absorber in step (1) is as follows: 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde are added to toluene at a molar ratio of 1:1 to 12-14 times the mass of 5-aminonaphthalene-1-carboxylic acid, stirred at 100-200 r / min for 3-4 h at 60-66 °C, and dried at 50-60 °C under vacuum for 8-10 h to obtain the ultraviolet absorber; the reaction process is as follows:

[0017]

[0018] As an optimization, the molecular weight of the polyethylene glycol diglycidyl ether in step (1) is 1000.

[0019] As an optimization, the reaction process of the functionalized epoxy monomer in step (1) is as follows:

[0020]

[0021] As an optimization, the preparation method of the dihydroxydiphenyl phosphorus-containing monomer in step (2) is as follows: 4,4'-dihydroxybenzophenone and methylphenyl-oxyphosphine are mixed evenly at a molar ratio of 1:1, stirred at 100-200 r / min for 3-3.2 h at 188-192℃, cooled to 99-101℃, and toluene (10-12 times the mass of 4,4'-dihydroxybenzophenone) is added and mixed evenly. The mixture is filtered, and dried at 50-60℃ under vacuum for 10-12 h to obtain the dihydroxydiphenyl phosphorus-containing monomer. The reaction process is as follows:

[0022]

[0023] As an optimization, the preparation method of the phenyl dichlorosilane solution in step (2) is as follows: phenyl dichlorosilane and N,N-dimethylacetamide are mixed evenly at a mass ratio of 1:(8-10) to prepare a phenyl dichlorosilane solution.

[0024] As an optimization, the particle size of the graphene in step (2) is 3 to 9 nm.

[0025] As an optimization, the molecular weight of the cellulose in step (3) is 20,000.

[0026] As an optimization, the concentration of the hydrochloric acid aqueous solution in step (3) is 1 mol / L.

[0027] As an optimization, the epoxy resin used in step (4) is of type E51.

[0028] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0029] In preparing the graphene conductive adhesive, the present invention involves reacting 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde to obtain an ultraviolet absorber; reacting polyethylene glycol diglycidyl ether and the ultraviolet absorber to obtain a functionalized epoxy monomer; reacting 4,4'-dihydroxybenzophenone and methylphenyl-phosphorus oxide to obtain a dihydroxydiphenylphosphine-containing monomer; polymerizing and coating the dihydroxydiphenylphosphine-containing monomer and phenyl dichlorosilane onto graphene to obtain pre-modified graphene; reacting the pre-modified graphene and allyl glycidyl ether to obtain modified graphene; reacting cellulose and indole-6-carboxylic acid to obtain pre-modified cellulose; polymerizing and growing 5,6-dihydroxyindole and 6-aminomethylindole on the pre-modified cellulose to obtain modified cellulose; and mixing epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isoflurane diamine, and acetone uniformly to obtain the graphene conductive adhesive.

[0030] First, a UV absorber is prepared by reacting 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde, and a carboxyl group is introduced onto the UV absorber. Then, the hydroxyl groups on the side chain of polyethylene glycol diglycidyl ether are esterified with the carboxyl groups on the UV absorber to prepare a functionalized epoxy monomer. The epoxy groups on the functionalized epoxy monomer can participate in the curing process of the graphene conductive adhesive, introducing the UV absorber monomer into the graphene conductive adhesive. Under UV irradiation, the UV absorber monomer undergoes a cis-trans isomerization change, transforming from an enol form to a ketone form. Under visible light or heating conditions, a reverse reaction occurs. This reversible enol-ketone tautomerism can absorb UV light and release it in a harmless form, thereby improving the anti-aging properties of the graphene conductive adhesive. The mechanism of action is as follows:

[0031]

[0032] Secondly, 4,4'-dihydroxybenzophenone and methylphenyl-oxyphosphorus were reacted to prepare a dihydroxydiphenylphosphine-containing monomer; the dihydroxydiphenylphosphine-containing monomer and phenyl dichlorosilane were polymerized and coated onto graphene to prepare pre-modified graphene; organophosphorus, organosilicon, and Si-H bonds were introduced into the pre-modified graphene; the introduction of organophosphorus and organosilicon can improve the flame retardant properties of the graphene conductive adhesive; the Si-H bonds introduced into the pre-modified graphene were reacted with the carbon-carbon double bonds on allyl glycidyl ether to prepare modified graphene, and epoxy groups were introduced into the modified graphene; the modified graphene... The introduction of epoxy groups on graphene allows modified graphene to participate in the curing process of graphene conductive adhesive, forming a cross-linked network structure, thereby improving the mechanical properties of the graphene conductive adhesive. Graphene is a high-performance conductive material, and adding graphene to conductive adhesive can improve its conductivity. However, graphene is an inorganic material, and direct addition to adhesives can lead to uneven dispersion and agglomeration. Surface modification of graphene can improve the compatibility between graphene and adhesive, allowing graphene to be uniformly dispersed in the conductive adhesive and fully utilizing its conductive properties.

[0033] Finally, some hydroxyl groups on cellulose were reacted with carboxyl groups on indole-6-carboxylic acid to prepare pre-modified cellulose, and indole groups were introduced onto the pre-modified cellulose. 5,6-dihydroxyindole and 6-aminomethylindole were polymerized and grown on the pre-modified cellulose to prepare modified cellulose. Polyindole was generated on the modified cellulose, and amino groups were introduced. Polyindole is a conductive polymer material that can improve the conductivity of graphene conductive adhesive. The 5,6-dihydroxyindole in polyindole contains a diphenol structure, which can form hydrogen bonds, coordinate bonds, and covalent bonds with various substrate surfaces, thereby enhancing the adhesion of the graphene conductive adhesive. The amino groups introduced onto the modified cellulose can participate in the curing process of the graphene conductive adhesive, increase crosslinking sites, and improve the mechanical properties of the graphene conductive adhesive. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1:

[0036] A method for preparing graphene conductive adhesive, the method comprising the following preparation steps:

[0037] (1) 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde were added to toluene at a molar ratio of 1:1 to 12 times the mass of 5-aminonaphthalene-1-carboxylic acid. The mixture was stirred at 100 r / min for 4 h at 60 °C and dried at 50 °C for 10 h under vacuum to obtain an ultraviolet absorber. Polyethylene glycol diglycidyl ether, ultraviolet absorber and p-toluenesulfonic acid monohydrate were mixed evenly at a mass ratio of 100:6:1.1. The mixture was stirred at 100 r / min for 40 min at 78 °C under nitrogen protection. The temperature was increased to 128 °C at a heating rate of 10 °C / h and stirred for another 30 min. The mixture was cooled to room temperature and extracted three times with deionized water. The organic phase was collected and dried at 50 °C for 10 h under vacuum to obtain a functionalized epoxy monomer.

[0038] (2) Mix 4,4'-dihydroxybenzophenone and methylphenyl-phosphorus oxide at a molar ratio of 1:1 until homogeneous, stir at 100 r / min for 3.2 h at 188 °C, cool to 99 °C, add toluene at 10 times the mass of 4,4'-dihydroxybenzophenone and mix until homogeneous, filter, and dry at 50 °C for 12 h under vacuum to obtain dihydroxydiphenylphosphorus-containing monomer; mix phenyldichlorosilane and N,N-dimethylacetamide at a mass ratio of 1:8 until homogeneous to prepare phenyldichlorosilane solution; mix graphene and N,N-dimethylacetamide at a mass ratio of 1:78 until homogeneous, ultrasonically disperse for 1.2 h, add triethylamine at 0.5 times the mass of graphene and dihydroxydiphenylphosphorus-containing monomer at 3 times the mass of graphene, and react at room temperature. The mixture was stirred at 100 rpm for 22 min, heated to 80 °C, and a phenyl dichlorosilane solution (9 times the mass of the phosphorus-containing monomer of dihydroxydiphenyl) was added dropwise at a uniform rate over 15 min. The reaction was continued with stirring for 9 h, filtered, and washed three times each with anhydrous ethanol and deionized water. The mixture was then dried at 50 °C for 12 h under vacuum to obtain pre-modified graphene. The pre-modified graphene and toluene were mixed evenly at a mass ratio of 1:60, ultrasonically dispersed for 30 min, and then allyl glycidyl ether (2 times the mass of the pre-modified graphene) and chloroplatinic acid (0.08 times the mass of the pre-modified graphene) were added. The mixture was stirred at 100 rpm for 5 h at 70 °C, filtered, washed three times with anhydrous ethanol, and dried at 60 °C for 12 h under vacuum to obtain modified graphene.

[0039] (3) Cellulose and N,N-dimethylformamide were mixed evenly at a mass ratio of 1:26, ultrasonically dispersed for 40 min, and the pH was adjusted to 3 with 1 mol / L hydrochloric acid aqueous solution. Indole-6-carboxylic acid (0.4 times the mass of cellulose) was added, and the mixture was stirred at 100 r / min for 50 min at 120 °C. After filtration, the mixture was washed three times with deionized water and dried at 50 °C for 8 h under vacuum to obtain pre-modified cellulose. The pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole, and anhydrous ethanol were mixed at a mass ratio of 1: The mixture of 3:1:22 was thoroughly mixed and ultrasonically dispersed for 30 min to prepare a mixed reaction solution. Ammonium persulfate (0.06 times the mass of 5,6-dihydroxyindole) and deionized water were mixed thoroughly at a mass ratio of 1:6 to prepare an oxidizing agent solution. Under nitrogen protection, at 0℃ and with stirring at 100 r / min, the oxidizing agent solution was added dropwise to the mixed reaction solution over 15 min. The reaction was continued with stirring for 4 h. After filtration, the mixture was washed three times each with anhydrous ethanol and deionized water, and dried at 60℃ for 10 h under vacuum to obtain modified cellulose.

[0040] (4) Weigh out 30 parts of epoxy resin, 58 parts of functionalized epoxy monomer, 4 parts of modified graphene, 6 parts of modified cellulose, 6 parts of isoflurane diamine, and 22 parts of acetone by mass. Mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 1800 cps with acetone to obtain graphene conductive adhesive.

[0041] Example 2:

[0042] A method for preparing graphene conductive adhesive, the method comprising the following preparation steps:

[0043] (1) 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde were added to toluene at a molar ratio of 1:1 to 13 times the mass of 5-aminonaphthalene-1-carboxylic acid. The mixture was stirred at 63°C and 150 r / min for 3.5 h, and dried at 55°C under vacuum for 9 h to obtain an ultraviolet absorber. Polyethylene glycol diglycidyl ether, ultraviolet absorber and p-toluenesulfonic acid monohydrate were mixed evenly at a mass ratio of 100:7:1.2. The mixture was stirred at 79°C and 125 r / min for 35 min under nitrogen protection. The temperature was increased to 129°C at a heating rate of 10°C / h, and stirring was continued for 25 min. The mixture was cooled to room temperature and extracted with deionized water 4 times. The organic phase was collected and dried at 55°C under vacuum for 9 h to obtain a functionalized epoxy monomer.

[0044] (2) 4,4'-dihydroxybenzophenone and methylphenyl-phosphorus oxychloride were mixed evenly at a molar ratio of 1:1 and stirred at 150 r / min for 3.1 h at 190 °C. The mixture was then cooled to 100 °C, and toluene (11 times the mass of 4,4'-dihydroxybenzophenone) was added and mixed evenly. The mixture was filtered and dried at 55 °C for 11 h under vacuum to obtain the dihydroxydiphenyl phosphorus-containing monomer. Phenylated dichlorosilane and N,N-dimethylacetamide were mixed evenly at a mass ratio of 1:9 to prepare a phenyllated dichlorosilane solution. Graphene and N,N-dimethylacetamide were mixed evenly at a mass ratio of 1:80 and ultrasonically dispersed for 1.1 h. Triethylamine (0.55 times the mass of graphene) and dihydroxydiphenyl phosphorus-containing monomer (3.5 times the mass of graphene) were added and the mixture was dried at room temperature. The mixture was stirred at 150 rpm for 21 min, heated to 85 °C, and a phenyl dichlorosilane solution with a mass of 10 times that of the phosphorus-containing monomer of dihydroxydiphenyl was added dropwise over 15 min. The reaction was continued with stirring for 8 h, filtered, and washed 4 times each with anhydrous ethanol and deionized water. The mixture was then dried at 55 °C for 11 h under vacuum to obtain pre-modified graphene. The pre-modified graphene and toluene were mixed evenly at a mass ratio of 1:65 and ultrasonically dispersed for 25 min. Allyl glycidyl ether with a mass of 2.5 times that of the pre-modified graphene and chloroplatinic acid with a mass of 0.09 times that of the pre-modified graphene were added. The mixture was stirred at 150 rpm for 4.5 h at 75 °C, filtered, and washed 4 times with anhydrous ethanol. The mixture was then dried at 65 °C for 11 h under vacuum to obtain modified graphene.

[0045] (3) Cellulose and N,N-dimethylformamide were mixed evenly at a mass ratio of 1:28, ultrasonically dispersed for 35 min, and the pH was adjusted to 3.5 with 1 mol / L hydrochloric acid aqueous solution. Indole-6-carboxylic acid (0.5 times the mass of cellulose) was added, and the mixture was stirred at 121℃ and 150 r / min for 45 min. The mixture was filtered, washed four times with deionized water, and dried at 55℃ for 7.5 h under vacuum to obtain pre-modified cellulose. The pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole, and anhydrous ethanol were mixed at a mass ratio of 1: Mix 3.5:1.1:23 thoroughly and ultrasonically disperse for 25 min to prepare a mixed reaction solution; mix ammonium persulfate (0.07 times the mass of 5,6-dihydroxyindole) and deionized water at a mass ratio of 1:7 to prepare an oxidizing agent solution; under nitrogen protection, at 1℃ and 150 r / min stirring, add the oxidizing agent solution dropwise to the mixed reaction solution at a uniform rate over 15 min, continue stirring and react for 3.5 h, filter, wash 4 times each with anhydrous ethanol and deionized water, and dry at 65℃ for 9 h under vacuum to obtain modified cellulose;

[0046] (4) Weigh out 33 parts of epoxy resin, 59 parts of functionalized epoxy monomer, 4.5 parts of modified graphene, 6.5 parts of modified cellulose, 7 parts of isoflurane diamine, and 23 parts of acetone by mass. Mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 2000 cps with acetone to obtain graphene conductive adhesive.

[0047] Example 3:

[0048] A method for preparing graphene conductive adhesive, the method comprising the following preparation steps:

[0049] (1) 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde were added to toluene at a molar ratio of 1:1 to 14 times the mass of 5-aminonaphthalene-1-carboxylic acid. The mixture was stirred at 200 r / min for 3 h at 66 °C and dried at 60 °C for 8 h under vacuum to obtain an ultraviolet absorber. Polyethylene glycol diglycidyl ether, ultraviolet absorber and p-toluenesulfonic acid monohydrate were mixed evenly at a mass ratio of 100:8:1.3. The mixture was stirred at 150 r / min for 30 min at 80 °C under nitrogen protection. The temperature was increased to 130 °C at a heating rate of 10 °C / h and stirred for another 20 min. The mixture was cooled to room temperature and extracted with deionized water 5 times. The organic phase was collected and dried at 60 °C for 8 h under vacuum to obtain a functionalized epoxy monomer.

[0050] (2) Mix 4,4'-dihydroxybenzophenone and methylphenyl-phosphorus oxychloride at a molar ratio of 1:1, stir at 192℃ and 200r / min for 3h, cool to 101℃, add 12 times the mass of toluene of 4,4'-dihydroxybenzophenone, mix well, filter, and dry at 60℃ for 10h under vacuum to obtain dihydroxydiphenylphosphorus-containing monomer; mix phenyldichlorosilane and N,N-dimethylacetamide at a mass ratio of 1:10 to prepare phenyldichlorosilane solution; mix graphene and N,N-dimethylacetamide at a mass ratio of 1:82, ultrasonically disperse for 1h, add 0.6 times the mass of triethylamine and 4 times the mass of dihydroxydiphenylphosphorus-containing monomer of graphene, and stir at room temperature. The mixture was stirred at 200 rpm for 20 min, heated to 90 °C, and a phenyl dichlorosilane solution with a mass of 11 times the phosphorus-containing monomer of dihydroxydiphenyl was added dropwise over 15 min. The reaction was continued with stirring for 7 h, filtered, and washed 5 times each with anhydrous ethanol and deionized water. The mixture was then dried at 60 °C for 10 h under vacuum to obtain pre-modified graphene. The pre-modified graphene and toluene were mixed evenly at a mass ratio of 1:70 and ultrasonically dispersed for 20 min. Allyl glycidyl ether with a mass of 3 times the pre-modified graphene and chloroplatinic acid with a mass of 0.1 times the pre-modified graphene were added. The mixture was stirred at 200 rpm for 4 h at 80 °C, filtered, and washed 5 times with anhydrous ethanol. The mixture was then dried at 70 °C for 10 h under vacuum to obtain modified graphene.

[0051] (3) Cellulose and N,N-dimethylformamide were mixed evenly at a mass ratio of 1:30, ultrasonically dispersed for 30 min, and the pH was adjusted to 4 with 1 mol / L hydrochloric acid aqueous solution. Indole-6-carboxylic acid (0.6 times the mass of cellulose) was added, and the mixture was stirred at 122℃ and 200 r / min for 40 min. The mixture was filtered, washed 5 times with deionized water, and dried at 60℃ for 7 h under vacuum to obtain pre-modified cellulose. Pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole, and anhydrous ethanol were mixed at a mass ratio of 1: Mix the ingredients in a 4:1.2:24 ratio until homogeneous, and ultrasonically disperse for 20 min to prepare a mixed reaction solution. Mix ammonium persulfate (0.08 times the mass of 5,6-dihydroxyindole) and deionized water at a mass ratio of 1:8 until homogeneous to prepare an oxidizing agent solution. Under nitrogen protection, at 2℃ and with stirring at 200 r / min, add the oxidizing agent solution dropwise to the mixed reaction solution at a uniform rate over 15 min. Continue stirring and react for 3 h. Filter the solution, wash it 5 times each with anhydrous ethanol and deionized water, and dry it at 70℃ for 8 h under vacuum to obtain modified cellulose.

[0052] (4) Weigh out 36 parts of epoxy resin, 60 parts of functionalized epoxy monomer, 5 parts of modified graphene, 7 parts of modified cellulose, 8 parts of isoflurane diamine, and 24 parts of acetone by mass. Mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 2200 cps with acetone to obtain graphene conductive adhesive.

[0053] Comparative Example 1:

[0054] The preparation method of the graphene conductive adhesive in Comparative Example 1 differs from that in Example 2 in that step (1) is omitted, and step (4) is modified as follows: Weigh 33 parts of epoxy resin, 59 parts of polyethylene glycol diglycidyl ether, 4.5 parts of modified graphene, 6.5 parts of modified cellulose, 7 parts of isoflurane diamine, and 23 parts of acetone by mass; mix the epoxy resin, polyethylene glycol diglycidyl ether, modified graphene, modified cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 2000 cps with acetone to obtain the graphene conductive adhesive. The remaining steps are the same as in Example 2.

[0055] Comparative Example 2:

[0056] The difference between the preparation method of the graphene conductive adhesive in Comparative Example 2 and Example 2 lies in step (2). Step (2) is modified as follows: 4,4'-dihydroxybenzophenone and methylphenyl-oxyphosphine are mixed evenly in a molar ratio of 1:1, stirred at 150 r / min for 3.1 h at 190 °C, cooled to 100 °C, and toluene (11 times the mass of 4,4'-dihydroxybenzophenone) is added and mixed evenly. The mixture is filtered and dried at 55 °C for 11 h under vacuum to obtain the dihydroxydiphenyl phosphorus-containing monomer; phenyl dichlorosilane and N,N-dimethylacetamide are mixed evenly in a mass ratio of 1:9, and then... A phenyldichlorosilane solution was prepared. Graphene and N,N-dimethylacetamide were mixed uniformly at a mass ratio of 1:80 and ultrasonically dispersed for 1.1 h. Triethylamine (0.55 times the mass of graphene) and dihydroxydiphenylphosphine-containing monomer (3.5 times the mass of graphene) were added. The mixture was stirred at 150 r / min for 21 min at room temperature, then heated to 85 °C. A phenyldichlorosilane solution (10 times the mass of dihydroxydiphenylphosphine-containing monomer) was added dropwise at a uniform rate over 15 min. The reaction was continued with stirring for 8 h. The mixture was filtered, washed four times each with anhydrous ethanol and deionized water, and dried at 55 °C for 11 h under vacuum to obtain modified graphene. The remaining steps were the same as in Example 2.

[0057] Comparative Example 3:

[0058] The preparation method of the graphene conductive adhesive in Comparative Example 3 differs from that in Example 2 in that step (2) is omitted, and step (4) is modified as follows: Weigh 33 parts of epoxy resin, 59 parts of functionalized epoxy monomer, 4.5 parts of graphene, 6.5 parts of modified cellulose, 7 parts of isoflurane diamine, and 23 parts of acetone by mass; mix the epoxy resin, functionalized epoxy monomer, graphene, modified cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 2000 cps with acetone to obtain the graphene conductive adhesive. The remaining steps are the same as in Example 2.

[0059] Comparative Example 4:

[0060] The preparation method of the graphene conductive adhesive in Comparative Example 4 differs from that in Example 2 only in step (3). Step (3) is modified as follows: cellulose and N,N-dimethylformamide are mixed evenly at a mass ratio of 1:28, ultrasonically dispersed for 35 min, the pH is adjusted to 3.5 with 1 mol / L hydrochloric acid aqueous solution, indole-6-carboxylic acid (0.5 times the mass of cellulose) is added, and the mixture is stirred at 121℃ and 150 r / min for 45 min. After filtration, the mixture is washed four times with deionized water and dried at 55℃ for 7.5 h under vacuum to obtain pre-modified cellulose. The pre-modified cellulose and 5,6-dihydroxy... Indole, indole, and anhydrous ethanol were mixed evenly in a mass ratio of 1:3.5:1.1:23 and ultrasonically dispersed for 25 min to prepare a mixed reaction solution. Ammonium persulfate (0.07 times the mass of 5,6-dihydroxyindole) and deionized water were mixed evenly in a mass ratio of 1:7 to prepare an oxidizing agent solution. Under nitrogen protection, at 1°C and with stirring at 150 r / min, the oxidizing agent solution was added dropwise to the mixed reaction solution at a uniform rate over 15 min. The reaction was continued with stirring for 3.5 h. After filtration, the mixture was washed four times each with anhydrous ethanol and deionized water, and dried at 65°C for 9 h under vacuum to obtain modified cellulose. The remaining steps were the same as in Example 2.

[0061] Comparative Example 5:

[0062] The preparation method of the graphene conductive adhesive in Comparative Example 5 differs from that in Example 2 only in step (3). Step (3) is modified as follows: cellulose and N,N-dimethylformamide are mixed evenly at a mass ratio of 1:28, ultrasonically dispersed for 35 min, the pH is adjusted to 3.5 with 1 mol / L hydrochloric acid aqueous solution, indole-6-carboxylic acid (0.5 times the mass of cellulose) is added, and the mixture is stirred at 121℃ and 150 r / min for 45 min. After filtration, the mixture is washed four times with deionized water and dried at 55℃ for 7.5 h under vacuum to obtain pre-modified cellulose. The pre-modified cellulose and indole-6-carboxylic acid are then mixed. 6-Aminomethylindole and anhydrous ethanol were mixed evenly in a mass ratio of 1:3.5:1.1:23 and ultrasonically dispersed for 25 min to prepare a mixed reaction solution. Ammonium persulfate (0.07 times the mass of indole) and deionized water were mixed evenly in a mass ratio of 1:7 to prepare an oxidizing agent solution. Under nitrogen protection, at 1°C and with stirring at 150 r / min, the oxidizing agent solution was added dropwise to the mixed reaction solution at a uniform rate over 15 min. The reaction was continued with stirring for 3.5 h. After filtration, the mixture was washed four times each with anhydrous ethanol and deionized water, and dried at 65°C for 9 h under vacuum to obtain modified cellulose. The remaining steps were the same as in Example 2.

[0063] Comparative Example 6:

[0064] The preparation method of the graphene conductive adhesive in Comparative Example 6 differs from that in Example 2 in that step (3) is omitted, and step (4) is modified as follows: Weigh 33 parts of epoxy resin, 59 parts of functionalized epoxy monomer, 4.5 parts of modified graphene, 6.5 parts of cellulose, 7 parts of isoflurane diamine, and 23 parts of acetone by mass; mix the epoxy resin, functionalized epoxy monomer, modified graphene, cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 2000 cps with acetone to obtain the graphene conductive adhesive. The remaining steps are the same as in Example 2.

[0065] Test Example 1

[0066] Electrical conductivity testing

[0067] Test method: The examples and comparative examples were poured into molds and cured at 50°C for 5 hours. After curing, the volume resistivity of the examples and comparative examples was tested according to ASTM D257-2007. The results are shown in Table 1.

[0068] Table 1

[0069]

[0070] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-6 in Table 1 reveals that the graphene conductive adhesive prepared in this invention has excellent conductivity.

[0071] By comparison, the volume resistivity of Examples 1-3 is lower than that of Comparative Example 3, indicating that pre-modified graphene is prepared by polymerizing and coating graphene with dihydroxydiphenyl phosphorus-containing monomers and phenyl dichlorosilane; modified graphene is prepared by reacting the Si-H bonds introduced on the pre-modified graphene with the carbon-carbon double bonds on allyl glycidyl ether; graphene is a high-performance conductive material, and adding graphene to conductive adhesives can improve the conductivity of the adhesives. However, graphene is an inorganic material, and direct addition to adhesives will result in uneven dispersion and agglomeration. Surface modification of graphene can improve the compatibility between graphene and adhesives, so that graphene is uniformly dispersed in the conductive adhesive and fully exerts the conductive properties of graphene.

[0072] By comparison, the volume resistivity of Examples 1-3 is less than that of Comparative Example 6, indicating that pre-modified cellulose is prepared by reacting some of the hydroxyl groups on cellulose with the carboxyl groups on indole-6-carboxylic acid, and indole groups are introduced onto the pre-modified cellulose; modified cellulose is prepared by polymerizing and growing 5,6-dihydroxyindole and 6-aminomethylindole on the pre-modified cellulose, and polyindole is generated on the modified cellulose; polyindole is a conductive polymer material that can improve the conductivity of graphene conductive adhesive.

[0073] Test Example 2

[0074] Testing of mechanical properties and anti-aging properties

[0075] Test method: The examples and comparative examples were poured into molds and cured at 50°C for 5 hours. After removal, standard specimens were prepared according to GB / T1040-92, and their tensile strength X was tested. The standard specimens were irradiated with a xenon arc lamp for 14 days, and their tensile strength Y was tested. The change rate of tensile strength of the examples and comparative examples before and after UV aging treatment was calculated as follows: tensile strength change rate = (XY) / X × 100%. The results are shown in Table 2.

[0076] Table 2

[0077]

[0078]

[0079] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-6 in Table 2 reveals that the graphene conductive adhesive prepared by this invention possesses excellent mechanical properties and anti-aging properties.

[0080] By comparison, the tensile strength of Examples 1-3 is greater than that of Comparative Examples 2-3, indicating that pre-modified graphene is prepared by polymerizing and coating dihydroxydiphenyl phosphorus-containing monomers and phenyl dichlorosilane onto graphene; Si-H bonds are introduced into the pre-modified graphene; the Si-H bonds introduced into the pre-modified graphene react with the carbon-carbon double bonds on allyl glycidyl ether to obtain modified graphene; epoxy groups are introduced into the modified graphene; the epoxy groups introduced into the modified graphene enable the modified graphene to participate in the curing process of graphene conductive adhesive, forming a cross-linked network structure, thereby improving the mechanical properties of graphene conductive adhesive.

[0081] By comparison, the tensile strength of Examples 1-3 is greater than that of Comparative Examples 4 and 6, indicating that pre-modified cellulose is prepared by reacting some of the hydroxyl groups on cellulose with the carboxyl groups on indole-6-carboxylic acid, and indole groups are introduced onto the pre-modified cellulose; modified cellulose is prepared by polymerizing and growing 5,6-dihydroxyindole and 6-aminomethylindole on the pre-modified cellulose, generating polyindole on the modified cellulose, and introducing amino groups; the amino groups introduced on the modified cellulose can participate in the curing process of graphene conductive adhesive, increase crosslinking sites, and improve the mechanical properties of graphene conductive adhesive.

[0082] By comparison, the tensile strength change rate of Examples 1-3 is less than that of Comparative Example 1, indicating that the UV absorber is prepared by reacting 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde, and a carboxyl group is introduced onto the UV absorber; the hydroxyl group on the side chain of polyethylene glycol diglycidyl ether molecule undergoes an esterification reaction with the carboxyl group on the UV absorber to prepare a functionalized epoxy monomer; the epoxy group on the functionalized epoxy monomer can participate in the curing process of graphene conductive adhesive, introducing the UV absorber monomer into the graphene conductive adhesive; the UV absorber monomer undergoes a cis-trans isomerization change under UV irradiation, changing from the enol form to the ketone form, and then undergoes a reverse reaction under visible light or heating conditions. This reversible enol-ketone tautomerism can absorb UV light and release it in a harmless form, thereby improving the anti-aging performance of the graphene conductive adhesive.

[0083] Test Example 3

[0084] Flame retardant performance testing

[0085] Test method: The samples from the examples and comparative examples were poured into molds and cured at 50°C for 5 hours. After curing, they were removed and cut into standard specimens according to GB / T2406.2. The limiting oxygen index of the standard specimens was then tested. The results are shown in Table 3.

[0086] Table 3

[0087] Limiting oxygen index (%) Limiting oxygen index (%) Example 1 29.16 Comparative Example 1 28.34 Example 2 29.51 Comparative Example 2 28.52 Example 3 28.99 Comparative Example 3 21.19 Comparative Example 4 28.76 Comparative Example 5 28.91 Comparative Example 6 28.98

[0088] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-6 in Table 3 reveals that the graphene conductive adhesive prepared in this invention has good flame retardant properties.

[0089] By comparison, the limiting oxygen index of Examples 1-3 is greater than that of Comparative Example 3, indicating that the dihydroxydiphenyl phosphorus-containing monomer is prepared by reacting 4,4'-dihydroxybenzophenone and methylphenyl-phosphorus oxide; the pre-modified graphene is prepared by polymerizing and coating the dihydroxydiphenyl phosphorus-containing monomer and phenyl dichlorosilane onto graphene; organophosphorus and organosilicon are introduced into the pre-modified graphene; the introduction of organophosphorus and organosilicon can improve the flame retardant properties of graphene conductive adhesive.

[0090] Test Example 4

[0091] Testing of bonding performance

[0092] Test method: According to the national standard GB / T2791-1995, the peel strength of the examples and comparative examples was tested using a BLD-200N electronic peel tester. The results are shown in Table 4.

[0093]

[0094]

[0095] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-6 in Table 4 reveals that the graphene conductive adhesive prepared in this invention has excellent bonding properties.

[0096] By comparison, the peel strength of Examples 1-3 is greater than that of Comparative Example 5, indicating that pre-modified cellulose is prepared by reacting some of the hydroxyl groups on cellulose with the carboxyl groups on indole-6-carboxylic acid, and indole groups are introduced onto the pre-modified cellulose; modified cellulose is prepared by polymerizing and growing 5,6-dihydroxyindole and 6-aminomethylindole on the pre-modified cellulose, and polyindole is generated on the modified cellulose; the 5,6-dihydroxyindole in the polyindole contains a diphenol structure, which can form hydrogen bonds, coordination bonds and covalent bonds with the surface of various substrates, thereby enhancing the adhesion of the graphene conductive adhesive.

[0097] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a graphene conductive adhesive, characterized in that, The preparation method of the graphene conductive adhesive includes the following preparation steps: (1) Polyethylene glycol diglycidyl ether, ultraviolet absorber and p-toluenesulfonic acid monohydrate are mixed evenly at a mass ratio of 100:(6~8):(1.1~1.3). Under nitrogen protection, the mixture is stirred at 78~80℃ and 100~150r / min for 30~40min. The temperature is increased to 128~130℃ at a heating rate of 10℃ / h, and stirring is continued for 20~30min. The mixture is cooled to room temperature and extracted with deionized water 3~5 times. The organic phase is taken and dried at 50~60℃ for 8~10h under vacuum to obtain the functionalized epoxy monomer. (2) Mix graphene and N,N-dimethylacetamide at a mass ratio of 1:(78~82) until homogeneous, and ultrasonically disperse for 1~1.2h. Add 0.5~0.6 times the mass of graphene triethylamine and 3~4 times the mass of graphene dihydroxydiphenyl phosphorus-containing monomer. Stir at 100~200r / min for 20~22min at room temperature, raise the temperature to 80~90℃, and uniformly add 9~11 times the mass of dihydroxydiphenyl phosphorus-containing monomer phenyl dichlorosilane solution over 15min. Continue stirring and react for 7~9h. Filter and wash 3~5 times each with anhydrous ethanol and deionized water. Pre-modified graphene was prepared by drying at 50-60℃ for 10-12 hours under vacuum conditions. The pre-modified graphene and toluene were mixed evenly at a mass ratio of 1:(60-70), ultrasonically dispersed for 20-30 minutes, and then allyl glycidyl ether (2-3 times the mass of the pre-modified graphene) and chloroplatinic acid (0.08-0.1 times the mass of the pre-modified graphene) were added. The mixture was stirred at 70-80℃ and 100-200 r / min for 4-5 hours. After filtration, the mixture was washed 3-5 times with anhydrous ethanol and dried at 60-70℃ for 10-12 hours under vacuum conditions to obtain modified graphene. (3) Mix cellulose and N,N-dimethylformamide at a mass ratio of 1:(26~30), disperse by ultrasonication for 30~40 min, adjust the pH to 3~4 with hydrochloric acid aqueous solution, add indole-6-carboxylic acid at 0.4~0.6 times the mass of cellulose, stir at 100~200 r / min for 40~50 min at 120~122℃, filter, wash with deionized water 3~5 times, and dry at 50~60℃ for 7~8 h under vacuum to obtain pre-modified cellulose; Pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole, and anhydrous ethanol were mixed evenly in a mass ratio of 1:(3~4):(1~1.2):(22~24) and ultrasonically dispersed for 20~30 min to prepare a mixed reaction solution. Under nitrogen protection, at 0~2℃ and stirring at 100~200 r / min, the oxidant solution was added dropwise to the mixed reaction solution at a uniform rate over 15 min. The reaction was continued to be stirred for 3~4 h. The mixture was filtered, washed 3~5 times each with anhydrous ethanol and deionized water, and dried at 60~70℃ for 8~10 h under vacuum to obtain modified cellulose. (4) Weigh 30-36 parts of epoxy resin, 58-60 parts of functionalized epoxy monomer, 4-5 parts of modified graphene, 6-7 parts of modified cellulose, 6-8 parts of isoflurane diamine, and 22-24 parts of acetone by mass. Mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isoflurane diamine, and acetone evenly, and then adjust the viscosity to 1800-2200 cps with acetone to obtain graphene conductive adhesive.

2. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The method for preparing the ultraviolet absorber in step (1) is as follows: 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butylsalicylaldehyde are added to toluene at a molar ratio of 1:1 to 12-14 times the mass of 5-aminonaphthalene-1-carboxylic acid. The mixture is stirred at 100-200 r / min for 3-4 h at 60-66 °C and dried at 50-60 °C for 8-10 h under vacuum to obtain the ultraviolet absorber.

3. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The molecular weight of the polyethylene glycol diglycidyl ether mentioned in step (1) is 1000.

4. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The preparation method of the dihydroxydiphenyl phosphorus-containing monomer in step (2) is as follows: 4,4'-dihydroxybenzophenone and methylphenyl-oxyphosphine are mixed evenly in a molar ratio of 1:1, stirred at 100-200 r / min for 3-3.2 h at 188-192℃, cooled to 99-101℃, and toluene with a mass of 10-12 times that of 4,4'-dihydroxybenzophenone is added and mixed evenly. The mixture is filtered and dried at 50-60℃ for 10-12 h under vacuum to obtain the dihydroxydiphenyl phosphorus-containing monomer.

5. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The method for preparing the phenyl dichlorosilane solution in step (2) is as follows: phenyl dichlorosilane and N,N-dimethylacetamide are mixed evenly at a mass ratio of 1:(8~10) to prepare a phenyl dichlorosilane solution.

6. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The graphene in step (2) has a particle size of 3~9 nm.

7. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The molecular weight of the cellulose in step (3) is 20,000.

8. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The concentration of the hydrochloric acid aqueous solution in step (3) is 1 mol / L.

9. The method for preparing a graphene conductive adhesive according to claim 1, characterized in that, The epoxy resin used in step (4) is of type E51.

10. A graphene conductive adhesive prepared by the method of any one of claims 1 to 9.

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