Graphene conductive adhesive and preparation method thereof

Abstract

The invention discloses a graphene conductive adhesive and a preparation method thereof, and relates to the technical field of adhesives. When the graphene conductive adhesive is prepared, polyethylene glycol diglycidyl ether and an ultraviolet absorbent react to prepare a functionalized epoxy monomer; the preparation method comprises the following steps: polymerizing a dihydroxy diphenyl phosphorus-containing monomer and phenyl dichlorosilane, and coating graphene with the polymerized dihydroxy diphenyl phosphorus-containing monomer and phenyl dichlorosilane to prepare pre-modified graphene; the pre-modified graphene and allyl glycidyl ether are subjected to a reaction, and modified graphene is prepared; carrying out polymerization growth on 5, 6-dihydroxyindole and 6-aminomethylindole on the pre-modified cellulose to prepare modified cellulose; and uniformly mixing epoxy resin, a functionalized epoxy monomer, the modified graphene, the modified cellulose, isophorone diamine and acetone to prepare the graphene conductive adhesive. The graphene conductive adhesive prepared by the invention has excellent anti-aging, flame-retardant, conductive and adhesive properties and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, in particular to a graphene conductive adhesive and a preparation method thereof. Background Art

[0002] Conductive adhesives are usually composed of base resin, conductive particles, crosslinking agents, solvents, etc. They are a type of adhesive that has both bonding and conductive properties. Conductive adhesives are widely used in the electronics industry, such as packaging and bonding of liquid crystal displays, light-emitting diodes, integrated circuit chips, printed circuit board components, etc. With the miniaturization and micro-miniaturization of electronic components and the high density and high integration of printed circuit boards, conductive adhesives are gradually replacing traditional soldering due to their simple process, easy operation, improved production efficiency, and environmental protection, becoming an ideal choice for achieving conductive connections.

[0003] The development of conductive adhesives has also had some limitations. The first is the use environment restrictions. As an organic material, conductive adhesives are flammable and easy to age. Over time, they will become powdery, yellow, and have reduced bonding performance. Secondly, compared with metal conductors, the conductivity of conductive adhesives is relatively low and cannot fully meet market demand. Therefore, it is necessary to develop conductive adhesive materials that are flame retardant, anti-aging, and have better conductivity. Summary of the invention

[0004] The purpose of the present invention is to provide a graphene conductive adhesive and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[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; reacting pre-modified graphene and allyl glycidyl ether to obtain modified graphene; polymerizing and growing 5,6-dihydroxyindole and 6-aminomethylindole on pre-modified cellulose to obtain modified cellulose; and uniformly mixing epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isophorone diamine, and acetone to obtain the graphene conductive adhesive.

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

[0008] The pre-modified graphene is prepared by polymerizing dihydroxydiphenyl phosphorus-containing monomers and phenyldichlorosilane and coating them on graphene;

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

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

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

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

[0013] (2) Graphene and N,N-dimethylacetamide were mixed uniformly at a mass ratio of 1:(78-82), and ultrasonically dispersed for 1-1.2 hours. Triethylamine (0.5-0.6 times the mass of graphene) and dihydroxydiphenyl phosphorus-containing monomer (3-4 times the mass of graphene) were added. The mixture was stirred at 100-200 r / min for 20-22 minutes at room temperature. The mixture was heated to 80-90°C. Phenyldichlorosilane solution (9-11 times the mass of dihydroxydiphenyl phosphorus-containing monomer) was added dropwise at a uniform rate within 15 minutes. The mixture was stirred for 7-9 hours, filtered, and washed with anhydrous ethanol and deionized water for 3-5 times each. , under vacuum conditions, dried at 50-60° C. for 10-12 hours to obtain pre-modified graphene; the pre-modified graphene and toluene were mixed uniformly at a mass ratio of 1:(60-70), ultrasonically dispersed for 20-30 minutes, allyl glycidyl ether in an amount of 2-3 times the mass of the pre-modified graphene and chloroplatinic acid in an amount of 0.08-0.1 times the mass of the pre-modified graphene were added, stirred at 70-80° C. and 100-200 r / min for 4-5 hours, filtered, washed with anhydrous ethanol for 3-5 times, and dried at 60-70° C. for 10-12 hours under vacuum conditions to obtain modified graphene;

[0014] (3) cellulose and N,N-dimethylformamide are mixed uniformly at a mass ratio of 1:(26-30), ultrasonically dispersed for 30-40 minutes, the pH is adjusted to 3-4 with a hydrochloric acid aqueous solution, 0.4-0.6 times the mass of cellulose is added with indole-6-carboxylic acid, stirred at 120-122° C. and 100-200 r / min for 40-50 minutes, filtered, washed with deionized water for 3-5 times, and dried at 50-60° C. under vacuum conditions for 7-8 hours to obtain pre-modified cellulose; the pre-modified cellulose and 5,6-dihydroxyindole , 6-aminomethylindole, and anhydrous ethanol are mixed uniformly in a mass ratio of 1:(3-4):(1-1.2):(22-24), and ultrasonically dispersed for 20-30 minutes to prepare a mixed reaction liquid; under nitrogen protection, at 0-2°C, 100-200r / min stirring conditions, the oxidant solution is uniformly added dropwise to the mixed reaction liquid within 15 minutes, and the stirring reaction is continued for 3-4 hours, filtered, washed with anhydrous ethanol and deionized water for 3-5 times respectively, and dried at 60-70°C for 8-10 hours under vacuum conditions 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 isophorone diamine, and 22-24 parts of acetone by mass; mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isophorone diamine, and acetone evenly, and then adjust the viscosity to 1800-2200 cps with acetone to obtain a graphene conductive adhesive.

[0016] As an optimization, the preparation method of the ultraviolet absorber in step (1) is: adding 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde in a molar ratio of 1:1 to toluene with a mass of 12 to 14 times that of 5-aminonaphthalene-1-carboxylic acid, stirring at 60 to 66° C. and 100 to 200 r / min for 3 to 4 hours, and drying at 50 to 60° C. under vacuum conditions for 8 to 10 hours 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: 4,4'-dihydroxybenzophenone and methylphenyl-phosphine are mixed uniformly in a molar ratio of 1:1, stirred at 188-192°C and 100-200r / min for 3-3.2h, cooled to 99-101°C, toluene with a mass of 10-12 times that of 4,4'-dihydroxybenzophenone is added, mixed uniformly, filtered, and dried at 50-60°C for 10-12h under vacuum conditions to obtain the dihydroxydiphenyl phosphorus-containing monomer; the reaction process is as follows:

[0022]

[0023] As an optimization, the preparation method of the phenyldichlorosilane solution in step (2) is: phenyldichlorosilane and N,N-dimethylacetamide are uniformly mixed in a mass ratio of 1:(8-10) to prepare a phenyldichlorosilane 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 model of the epoxy resin in step (4) is E51.

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

[0029] When preparing graphene conductive adhesive, the present invention comprises the following steps: reacting 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde to obtain an ultraviolet absorber; reacting polyethylene glycol diglycidyl ether and an ultraviolet absorber to obtain a functionalized epoxy monomer; reacting 4,4'-dihydroxybenzophenone and methylphenyl-phosphine oxide to obtain a dihydroxydiphenyl phosphorus-containing monomer; polymerizing and coating the dihydroxydiphenyl phosphorus-containing monomer and phenyldichlorosilane on 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 uniformly mixing epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isophorone diamine and acetone to obtain the graphene conductive adhesive.

[0030] First, 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde are reacted to obtain a UV absorber, and a carboxyl group is introduced into the UV absorber; the hydroxyl group on the side chain of the polyethylene glycol diglycidyl ether molecule is esterified with the carboxyl group on the UV absorber to obtain a functionalized epoxy monomer; the epoxy group on the functionalized epoxy monomer can participate in the curing process of the graphene conductive adhesive, and the UV absorbing monomer is introduced into the graphene conductive adhesive; the UV absorbing monomer undergoes cis-trans isomerization under UV irradiation, from the enol form to the keto form, and a reverse reaction occurs under visible light or heating conditions. This reversible enol-keto tautomerism can absorb UV light and release the UV light in a harmless form, thereby improving the anti-aging performance of the graphene conductive adhesive. The mechanism of action is as follows:

[0031]

[0032] Secondly, 4,4'-dihydroxybenzophenone and methylphenyl-phosphine oxide are reacted to obtain dihydroxydiphenyl phosphorus-containing monomers; dihydroxydiphenyl phosphorus-containing monomers and phenyldichlorosilane are polymerized and coated on graphene to obtain pre-modified graphene; organic phosphorus, organic silicon and Si-H bonds are introduced into the pre-modified graphene; the introduction of organic phosphorus and organic silicon can improve the flame retardant properties of graphene conductive adhesive; the Si-H bond introduced into the pre-modified graphene is reacted with the carbon-carbon double bond of allyl glycidyl ether to obtain modified graphene, and epoxy groups are introduced into the modified graphene; the modified graphene The epoxy group introduced on the graphene allows the modified graphene to participate in the curing process of the graphene conductive adhesive, forming a cross-linked network structure, thereby improving the mechanical properties of the graphene conductive adhesive; graphene is a conductive material with excellent performance. Adding graphene to the conductive adhesive can improve the conductivity of the conductive adhesive, but graphene is an inorganic material. Directly adding graphene to the adhesive will result in uneven dispersion and agglomeration. Surface modification of graphene can improve the compatibility between graphene and the adhesive, allowing the graphene to be evenly dispersed in the conductive adhesive and give full play to the conductive properties of graphene.

[0033] Finally, some hydroxyl groups on cellulose are reacted with carboxyl groups on indole-6-carboxylic acid to obtain pre-modified cellulose, and indole groups are introduced into the pre-modified cellulose; 5,6-dihydroxyindole and 6-aminomethylindole are polymerized and grown on the pre-modified cellulose to obtain modified cellulose, polyindole is generated on the modified cellulose, and amino groups are introduced; polyindole is a conductive polymer material that can improve the conductive properties of graphene conductive adhesive; 5,6-dihydroxyindole in polyindole contains a diphenol structure, which can form hydrogen bonds, coordination bonds and covalent bonds with the surfaces of various substrates, thereby enhancing the adhesion of the graphene conductive adhesive; the amino groups introduced on the modified cellulose can participate in the curing process of the graphene conductive adhesive, increase the cross-linking sites, and improve the mechanical properties of the graphene conductive adhesive. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

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

[0037] (1) 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde were added in a molar ratio of 1:1 to toluene with a mass of 12 times that of 5-aminonaphthalene-1-carboxylic acid, stirred at 60°C and 100 r / min for 4 hours, and dried at 50°C for 10 hours under vacuum conditions to obtain a UV absorber; polyethylene glycol diglycidyl ether, UV absorber, and p-toluenesulfonic acid monohydrate were mixed evenly in a mass ratio of 100:6:1.1, stirred at 78°C and 100 r / min for 40 minutes under nitrogen protection, heated to 128°C at a heating rate of 10°C / h, continued to stir for 30 minutes, cooled to room temperature, extracted with deionized water for 3 times, and the organic phase was taken and dried at 50°C for 10 hours under vacuum conditions to obtain a functionalized epoxy monomer;

[0038] (2) 4,4'-dihydroxybenzophenone and methylphenyl-phosphine oxide were mixed in a molar ratio of 1:1, stirred at 188°C and 100 r / min for 3.2 h, cooled to 99°C, toluene (10 times the mass of 4,4'-dihydroxybenzophenone) was added and mixed evenly, filtered, and dried at 50°C for 12 h under vacuum conditions to obtain a dihydroxydiphenyl phosphorus-containing monomer; phenyldichlorosilane and N,N-dimethylacetamide were mixed in a mass ratio of 1:8 to prepare a phenyldichlorosilane solution; graphene and N,N-dimethylacetamide were mixed in a mass ratio of 1:78 to prepare a phenyldichlorosilane solution; ultrasonically dispersed for 1.2 h, triethylamine (0.5 times the mass of graphene) and dihydroxydiphenyl phosphorus-containing monomer (3 times the mass of graphene) were added, and heated at room temperature. The mixture was stirred at 100 r / min for 22 min, heated to 80°C, and a phenyldichlorosilane solution of 9 times the mass of the dihydroxydiphenyl phosphorus-containing monomer was uniformly added dropwise within 15 min, and the reaction was continued for 9 h under stirring, filtered, washed with anhydrous ethanol and deionized water 3 times each, and dried at 50°C for 12 h under vacuum conditions to obtain pre-modified graphene; the pre-modified graphene and toluene were mixed uniformly at a mass ratio of 1:60, ultrasonically dispersed for 30 min, allyl glycidyl ether of 2 times the mass of the pre-modified graphene and chloroplatinic acid of 0.08 times the mass of the pre-modified graphene were added, stirred at 70°C and 100 r / min for 5 h, filtered, washed with anhydrous ethanol 3 times, and dried at 60°C for 12 h under vacuum conditions to obtain modified graphene;

[0039] (3) Cellulose and N,N-dimethylformamide were mixed at a mass ratio of 1:26, ultrasonically dispersed for 40 minutes, the pH was adjusted to 3 with a 1 mol / L hydrochloric acid aqueous solution, indole-6-carboxylic acid (0.4 times the mass of cellulose) was added, stirred at 120°C and 100 r / min for 50 minutes, filtered, washed with deionized water for 3 times, and dried at 50°C for 8 hours under vacuum conditions to obtain pre-modified cellulose; pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole, and anhydrous ethanol were mixed at a mass ratio of 1:26. 3:1:22 were mixed evenly, and ultrasonic dispersion was performed for 30 minutes to prepare a mixed reaction liquid; ammonium persulfate with a mass ratio of 0.06 times that of 5,6-dihydroxyindole and deionized water were mixed evenly at a mass ratio of 1:6 to prepare an oxidant solution; under nitrogen protection, at 0°C and 100r / min stirring conditions, the oxidant solution was uniformly added dropwise to the mixed reaction liquid within 15 minutes, and the stirring reaction was continued for 4 hours, filtered, washed with anhydrous ethanol and deionized water for 3 times each, and dried at 60°C for 10 hours under vacuum conditions to obtain modified cellulose;

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

[0041] Embodiment 2:

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

[0043] (1) 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde were added in a molar ratio of 1:1 to toluene with a mass of 13 times that of 5-aminonaphthalene-1-carboxylic acid, stirred at 63°C and 150 r / min for 3.5 hours, and dried at 55°C for 9 hours under vacuum conditions to obtain a UV absorber; polyethylene glycol diglycidyl ether, UV absorber, and p-toluenesulfonic acid monohydrate were mixed uniformly in a mass ratio of 100:7:1.2, stirred at 79°C and 125 r / min for 35 minutes under nitrogen protection, heated to 129°C at a heating rate of 10°C / h, continued to stir for 25 minutes, cooled to room temperature, extracted with deionized water for 4 times, and the organic phase was taken and dried at 55°C for 9 hours under vacuum conditions to obtain a functionalized epoxy monomer;

[0044] (2) 4,4'-dihydroxybenzophenone and methylphenyl-phosphine oxide were mixed in a molar ratio of 1:1, stirred at 190°C and 150 r / min for 3.1 h, cooled to 100°C, toluene (11 times the mass of 4,4'-dihydroxybenzophenone) was added and mixed evenly, filtered, and dried at 55°C for 11 h under vacuum conditions to obtain a dihydroxydiphenyl phosphorus-containing monomer; phenyldichlorosilane and N,N-dimethylacetamide were mixed in a mass ratio of 1:9 to prepare a phenyldichlorosilane solution; graphene and N,N-dimethylacetamide were mixed in a mass ratio of 1:80, 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 heated at room temperature. The mixture was stirred at 150 r / min for 21 min, heated to 85°C, and a phenyldichlorosilane solution with a mass of 10 times that of the dihydroxydiphenyl phosphorus monomer was uniformly added dropwise within 15 min, and the reaction was continued for 8 h under stirring, filtered, washed with anhydrous ethanol and deionized water 4 times each, and dried at 55°C for 11 h under vacuum conditions to obtain pre-modified graphene; the pre-modified graphene and toluene were mixed uniformly at a mass ratio of 1:65, 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, stirred at 75°C and 150 r / min for 4.5 h, filtered, washed with anhydrous ethanol 4 times, and dried at 65°C for 11 h under vacuum conditions to obtain modified graphene;

[0045] (3) Cellulose and N,N-dimethylformamide were mixed at a mass ratio of 1:28, ultrasonically dispersed for 35 minutes, the pH was adjusted to 3.5 with a 1 mol / L hydrochloric acid aqueous solution, indole-6-carboxylic acid (0.5 times the mass of cellulose) was added, stirred at 121°C and 150 r / min for 45 minutes, filtered, washed with deionized water for 4 times, and dried at 55°C for 7.5 hours under vacuum conditions to obtain pre-modified cellulose; pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole, and anhydrous ethanol were mixed at a mass ratio of 1:28. 3.5:1.1:23 were mixed evenly, and ultrasonic dispersion was performed for 25 minutes to prepare a mixed reaction liquid; ammonium persulfate with a mass ratio of 0.07 times of 5,6-dihydroxyindole and deionized water were mixed evenly at a mass ratio of 1:7 to prepare an oxidant solution; under nitrogen protection, at 1°C, 150r / min stirring conditions, the oxidant solution was uniformly added dropwise to the mixed reaction liquid within 15 minutes, and the stirring reaction was continued for 3.5 hours, filtered, washed with anhydrous ethanol and deionized water for 4 times respectively, and dried at 65°C under vacuum conditions for 9 hours to obtain modified cellulose;

[0046] (4) Weigh 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 isophorone diamine, and 23 parts of acetone by mass; mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isophorone diamine, and acetone evenly, and then adjust the viscosity to 2000 cps with acetone to prepare a graphene conductive adhesive.

[0047] Embodiment 3:

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

[0049] (1) 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde were added in a molar ratio of 1:1 to toluene with a mass of 14 times that of 5-aminonaphthalene-1-carboxylic acid, stirred at 66°C and 200 r / min for 3 hours, and dried at 60°C for 8 hours under vacuum conditions to obtain a UV absorber; polyethylene glycol diglycidyl ether, UV absorber, and p-toluenesulfonic acid monohydrate were mixed evenly in a mass ratio of 100:8:1.3, stirred at 80°C and 150 r / min for 30 minutes under nitrogen protection, heated to 130°C at a heating rate of 10°C / h, continued to stir for 20 minutes, cooled to room temperature, extracted with deionized water for 5 times, and the organic phase was taken and dried at 60°C for 8 hours under vacuum conditions to obtain a functionalized epoxy monomer;

[0050] (2) 4,4'-dihydroxybenzophenone and methylphenyl-phosphine oxide were mixed in a molar ratio of 1:1, stirred at 192°C and 200 r / min for 3 h, cooled to 101°C, toluene (12 times the mass of 4,4'-dihydroxybenzophenone) was added and mixed evenly, filtered, and dried at 60°C for 10 h under vacuum conditions to obtain a dihydroxydiphenyl phosphorus-containing monomer; phenyldichlorosilane and N,N-dimethylacetamide were mixed in a mass ratio of 1:10 to prepare a phenyldichlorosilane solution; graphene and N,N-dimethylacetamide were mixed in a mass ratio of 1:82, ultrasonically dispersed for 1 h, triethylamine (0.6 times the mass of graphene) and dihydroxydiphenyl phosphorus-containing monomer (4 times the mass of graphene) were added, and heated at room temperature. , stirring at 200r / min for 20min, heating to 90°C, uniformly dropping phenyldichlorosilane solution of 11 times the mass of dihydroxydiphenyl phosphorus-containing monomer within 15min, continuing stirring and reacting for 7h, filtering, washing with anhydrous ethanol and deionized water 5 times each, drying at 60°C for 10h under vacuum conditions to obtain pre-modified graphene; mixing the pre-modified graphene and toluene at a mass ratio of 1:70, ultrasonically dispersing for 20min, adding allyl glycidyl ether 3 times the mass of pre-modified graphene and 0.1 times the mass of pre-modified graphene chloroplatinic acid, stirring and reacting at 80°C, 200r / min for 4h, filtering, washing with anhydrous ethanol 5 times, drying at 70°C for 10h under vacuum conditions to obtain modified graphene;

[0051] (3) Cellulose and N,N-dimethylformamide were mixed at a mass ratio of 1:30, ultrasonically dispersed for 30 minutes, the pH was adjusted to 4 with a 1 mol / L hydrochloric acid aqueous solution, indole-6-carboxylic acid (0.6 times the mass of cellulose) was added, stirred at 122°C and 200 r / min for 40 minutes, filtered, washed with deionized water for 5 times, and dried at 60°C under vacuum conditions for 7 hours to obtain pre-modified cellulose; pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole, and anhydrous ethanol were mixed at a mass ratio of 1: 4:1.2:24, and ultrasonically dispersed for 20 minutes to prepare a mixed reaction liquid; ammonium persulfate with a mass ratio of 0.08 times that of 5,6-dihydroxyindole and deionized water were mixed at a mass ratio of 1:8 to prepare an oxidant solution; under nitrogen protection, at 2°C, 200r / min stirring conditions, the oxidant solution was uniformly added dropwise to the mixed reaction liquid within 15 minutes, and the stirring reaction was continued for 3 hours, filtered, washed with anhydrous ethanol and deionized water for 5 times each, and dried at 70°C for 8 hours under vacuum conditions to obtain modified cellulose;

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

[0053] Comparative Example 1:

[0054] The preparation method of the graphene conductive adhesive of Comparative Example 1 is different from that of Example 2 in that step (1) is not performed, and step (4) is modified as follows: 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 isophorone diamine, and 23 parts of acetone are weighed by mass; the epoxy resin, polyethylene glycol diglycidyl ether, modified graphene, modified cellulose, isophorone diamine, and acetone are uniformly mixed, and then the viscosity is adjusted to 2000 cps with acetone to obtain the graphene conductive adhesive. The remaining steps are the same as those of Example 2.

[0055] Comparative Example 2:

[0056] The difference between the preparation method of the graphene conductive adhesive of Comparative Example 2 and that of Example 2 lies in the difference in step (2). Step (2) is modified as follows: 4,4'-dihydroxybenzophenone and methylphenyl-phosphorus oxide are mixed uniformly in a molar ratio of 1:1, stirred at 190°C and 150r / min for 3.1h, cooled to 100°C, toluene with a mass of 11 times that of 4,4'-dihydroxybenzophenone is added, mixed uniformly, filtered, and dried at 55°C for 11h under vacuum to obtain a dihydroxydiphenyl phosphorus monomer; phenyldichlorosilane and N,N-dimethylacetamide are mixed uniformly in a mass ratio of 1:9, and the mixture is stirred at 150r / min for 3.1h. Prepare a phenyldichlorosilane solution; mix graphene and N,N-dimethylacetamide at a mass ratio of 1:80, ultrasonically disperse for 1.1 hours, add triethylamine 0.55 times the mass of graphene and dihydroxydiphenyl phosphorus monomer 3.5 times the mass of graphene, stir at 150r / min for 21 minutes at room temperature, heat to 85°C, uniformly add phenyldichlorosilane solution 10 times the mass of dihydroxydiphenyl phosphorus monomer within 15 minutes, continue stirring and reacting for 8 hours, filter, wash with anhydrous ethanol and deionized water 4 times each, dry at 55°C for 11 hours under vacuum conditions, and obtain modified graphene. The remaining steps are the same as in Example 2.

[0057] Comparative Example 3:

[0058] The preparation method of the graphene conductive adhesive of Comparative Example 3 is different from that of Example 2 in that step (2) is not performed, and step (4) is modified as follows: 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 isophorone diamine, and 23 parts of acetone are weighed by mass; the epoxy resin, functionalized epoxy monomer, graphene, modified cellulose, isophorone diamine, and acetone are uniformly mixed, and the viscosity is adjusted to 2000 cps with acetone to obtain the graphene conductive adhesive. The remaining steps are the same as those of Example 2.

[0059] Comparative Example 4:

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

[0061] Comparative Example 5:

[0062] The preparation method of the graphene conductive adhesive of Comparative Example 5 is different from that of Example 2 only in step (3). Step (3) is modified as follows: cellulose and N,N-dimethylformamide are mixed uniformly in a mass ratio of 1:28, ultrasonically dispersed for 35 minutes, the pH is adjusted to 3.5 with a 1 mol / L hydrochloric acid aqueous solution, indole-6-carboxylic acid (0.5 times the mass of cellulose) is added, stirred at 121° C. and 150 r / min for 45 minutes, filtered, washed with deionized water 4 times, and dried at 55° C. for 7.5 hours under vacuum conditions to obtain pre-modified cellulose; the pre-modified cellulose and indole , 6-aminomethyl indole, and anhydrous ethanol are mixed in a mass ratio of 1:3.5:1.1:23, and ultrasonically dispersed for 25 minutes to prepare a mixed reaction liquid; ammonium persulfate with a mass ratio of 0.07 times that of indole and deionized water are mixed in a mass ratio of 1:7 to prepare an oxidant solution; under nitrogen protection, at 1°C, 150r / min stirring conditions, the oxidant solution is uniformly added dropwise to the mixed reaction liquid within 15 minutes, and the stirring reaction is continued for 3.5 hours, filtered, washed with anhydrous ethanol and deionized water 4 times each, and dried at 65°C under vacuum conditions for 9 hours to obtain modified cellulose. The remaining steps are the same as those in Example 2.

[0063] Comparative Example 6:

[0064] The preparation method of the graphene conductive adhesive of Comparative Example 6 is different from that of Example 2 in that step (3) is not performed, and step (4) is modified as follows: 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 isophorone diamine, and 23 parts of acetone are weighed by mass; the epoxy resin, functionalized epoxy monomer, modified graphene, cellulose, isophorone diamine, and acetone are uniformly mixed, and then the viscosity is adjusted to 2000 cps with acetone to obtain the graphene conductive adhesive. The remaining steps are the same as those of Example 2.

[0065] Test Example 1

[0066] Conductivity test

[0067] Test method: Pour the examples and comparative examples into a mold, cure at 50° C. for 5 hours, take out, and test the volume resistivity of the examples and comparative examples according to ASTM D257-2007. The results are shown in Table 1.

[0068] Table 1

[0069]

[0070] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 6 in Table 1, it can be found that the graphene conductive adhesive prepared in the present invention has good conductive properties.

[0071] By comparison, the volume resistivity of Examples 1 to 3 is less than that of Comparative Example 3, indicating that pre-modified graphene is prepared by polymerizing and coating dihydroxydiphenyl phosphorus-containing monomers and phenyldichlorosilane on graphene; the Si-H bond introduced on the pre-modified graphene reacts with the carbon-carbon double bond on allyl glycidyl ether to obtain modified graphene; graphene is a conductive material with excellent performance, and adding graphene to conductive adhesive can improve the conductivity of the conductive adhesive, but graphene is an inorganic material, and directly adding it to the adhesive will result in uneven dispersion and agglomeration. Surface modification of graphene can improve the compatibility between graphene and the adhesive, so that the graphene is evenly dispersed in the conductive adhesive, and the conductive properties of the graphene are fully exerted.

[0072] By comparison, the volume resistivity of Examples 1 to 3 is smaller than that of Comparative Example 6, indicating that part of the hydroxyl groups on cellulose react with the carboxyl groups on indole-6-carboxylic acid to obtain pre-modified cellulose, and indole groups are introduced into the pre-modified cellulose; 5,6-dihydroxyindole and 6-aminomethylindole are polymerized and grown on the pre-modified cellulose to obtain modified cellulose, and polyindole is generated on the modified cellulose; polyindole is a conductive polymer material that can improve the conductive properties of graphene conductive adhesive.

[0073] Test Example 2

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

[0075] Test method: pour the embodiment and the comparative example into a mold, cure at 50°C for 5h, take out, prepare the embodiment and the comparative example into standard specimens according to GB / T1040-92, and test its tensile strength X; irradiate the standard specimen with a xenon arc lamp for 14 days, test its tensile strength Y, and calculate the change rate of the tensile strength of the embodiment and the comparative example before and after ultraviolet aging treatment, tensile strength change rate = (XY) / X×100%. The results are shown in Table 2.

[0076] Table 2

[0077]

[0078]

[0079] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 6 in Table 2, it can be found that the graphene conductive adhesive prepared in the present invention has good mechanical properties and anti-aging properties.

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

[0081] By comparison, the tensile strength of Examples 1 to 3 is greater than that of Comparative Examples 4 and 6, indicating that part of the hydroxyl groups on cellulose react with the carboxyl groups on indole-6-carboxylic acid to obtain pre-modified cellulose, and indole groups are introduced into the pre-modified cellulose; 5,6-dihydroxyindole and 6-aminomethylindole are polymerized and grown on the pre-modified cellulose to obtain modified cellulose, polyindole is generated on the modified cellulose, and amino groups are introduced; the amino groups introduced on the modified cellulose can participate in the curing process of the graphene conductive adhesive, increase the cross-linking sites, and improve the mechanical properties of the graphene conductive adhesive.

[0082] By comparison, the change rate of tensile strength of Examples 1 to 3 is less than that of Comparative Example 1, indicating that 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde are reacted to obtain an ultraviolet absorber, and a carboxyl group is introduced into the ultraviolet absorber; the hydroxyl group on the side chain of the polyethylene glycol diglycidyl ether molecule is esterified with the carboxyl group on the ultraviolet absorber to obtain a functionalized epoxy monomer; the epoxy group on the functionalized epoxy monomer can participate in the curing process of the graphene conductive adhesive, and the ultraviolet absorbing monomer is introduced into the graphene conductive adhesive; the ultraviolet absorbing monomer will undergo cis-trans isomerization under ultraviolet light irradiation, from enol form to keto form, and will undergo a reverse reaction under visible light or heating conditions, and this reversible enol-keto tautomerism can absorb ultraviolet light and release the ultraviolet light in a harmless form, thereby improving the anti-aging performance of the graphene conductive adhesive.

[0083] Test Example 3

[0084] Flame retardant performance test

[0085] Test method: Pour the examples and comparative examples into a mold, cure at 50°C for 5 hours, take out, cut into standard specimens according to GB / T2406.2, and test the limiting oxygen index of the standard specimens. 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] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 6 in Table 3, it can be found that the graphene conductive adhesive prepared by the present invention has good flame retardant properties.

[0089] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Example 3, indicating that 4,4'-dihydroxybenzophenone and methylphenyl-phosphine oxide are reacted to obtain a dihydroxydiphenyl phosphorus-containing monomer; dihydroxydiphenyl phosphorus-containing monomer and phenyldichlorosilane are polymerized and coated on graphene to obtain pre-modified graphene; organic phosphorus and organic silicon are introduced into the pre-modified graphene; the introduction of organic phosphorus and organic silicon can improve the flame retardant properties of the graphene conductive adhesive.

[0090] Test Example 4

[0091] Adhesion performance test

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

[0093]

[0094]

[0095] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 6 in Table 4, it can be found that the graphene conductive adhesive prepared by the present invention has good bonding properties.

[0096] By comparison, the peel strength of Examples 1 to 3 is greater than the peel strength of Comparative Example 5, indicating that part of the hydroxyl groups on cellulose react with the carboxyl groups on indole-6-carboxylic acid to obtain pre-modified cellulose, and indole groups are introduced into the pre-modified cellulose; 5,6-dihydroxyindole and 6-aminomethylindole are polymerized and grown on the pre-modified cellulose to obtain modified cellulose, and polyindole is generated on the modified cellulose; 5,6-dihydroxyindole in the polyindole contains a diphenol structure, and this diphenol structure can form hydrogen bonds, coordination bonds and covalent bonds with the surfaces of various substrates, thereby enhancing the adhesion of the graphene conductive adhesive.

[0097] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. 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; reacting pre-modified graphene and allyl glycidyl ether to obtain modified graphene; polymerizing 5,6-dihydroxyindole and 6-aminomethylindole on pre-modified cellulose to obtain modified cellulose; and uniformly mixing epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isophorone diamine and acetone to obtain the conductive adhesive. The ultraviolet absorber is prepared by reacting 5-aminonaphthalene-1-carboxylic acid and 3,5-di-tert-butyl salicylaldehyde; The pre-modified graphene is prepared by polymerizing dihydroxydiphenyl phosphorus-containing monomers and phenyldichlorosilane and coating them on graphene; The dihydroxydiphenyl phosphorus-containing monomer is prepared by reacting 4,4'-dihydroxybenzophenone and methylphenyl-phosphine oxide; The pre-modified cellulose is prepared by reacting cellulose and indole-6-carboxylic acid.

2. A method for preparing graphene conductive adhesive, characterized in that: The preparation method of the graphene conductive adhesive comprises the following preparation steps: (1) Polyethylene glycol diglycidyl ether, ultraviolet absorber, and p-toluenesulfonic acid monohydrate are uniformly mixed in a mass ratio of 100:(6-8):(1.1-1.3), and stirred at 78-80° C. and 100-150 r / min for 30-40 min under nitrogen protection, and heated to 128-130° C. at a heating rate of 10° C. / h, and stirred for 20-30 min. The mixture is cooled to room temperature, extracted with deionized water for 3-5 times, and the organic phase is taken and dried at 50-60° C. for 8-10 h under vacuum conditions to obtain a functionalized epoxy monomer; (2) Graphene and N,N-dimethylacetamide were mixed uniformly at a mass ratio of 1:(78-82), and ultrasonically dispersed for 1-1.2 hours. Triethylamine (0.5-0.6 times the mass of graphene) and dihydroxydiphenyl phosphorus-containing monomer (3-4 times the mass of graphene) were added. The mixture was stirred at 100-200 r / min for 20-22 minutes at room temperature. The mixture was heated to 80-90°C. Phenyldichlorosilane solution (9-11 times the mass of dihydroxydiphenyl phosphorus-containing monomer) was added dropwise at a uniform rate within 15 minutes. The mixture was stirred for 7-9 hours, filtered, and washed with anhydrous ethanol and deionized water for 3-5 times each. , under vacuum conditions, dried at 50-60° C. for 10-12 hours to obtain pre-modified graphene; the pre-modified graphene and toluene were mixed uniformly at a mass ratio of 1:(60-70), ultrasonically dispersed for 20-30 minutes, allyl glycidyl ether in an amount of 2-3 times the mass of the pre-modified graphene and chloroplatinic acid in an amount of 0.08-0.1 times the mass of the pre-modified graphene were added, stirred at 70-80° C. and 100-200 r / min for 4-5 hours, filtered, washed with anhydrous ethanol for 3-5 times, and dried at 60-70° C. for 10-12 hours under vacuum conditions to obtain modified graphene; (3) cellulose and N,N-dimethylformamide are mixed uniformly at a mass ratio of 1:(26-30), ultrasonically dispersed for 30-40 minutes, the pH is adjusted to 3-4 with a hydrochloric acid aqueous solution, 0.4-0.6 times the mass of cellulose is added with indole-6-carboxylic acid, stirred at 120-122° C. and 100-200 r / min for 40-50 minutes, filtered, washed with deionized water for 3-5 times, and dried at 50-60° C. under vacuum conditions for 7-8 hours to obtain pre-modified cellulose; Pre-modified cellulose, 5,6-dihydroxyindole, 6-aminomethylindole and anhydrous ethanol are mixed uniformly in a mass ratio of 1:(3-4):(1-1.2):(22-24), and ultrasonically dispersed for 20-30 minutes to prepare a mixed reaction liquid; under nitrogen protection, at 0-2°C and 100-200r / min stirring conditions, the oxidant solution is uniformly added dropwise to the mixed reaction liquid within 15 minutes, and the stirring reaction is continued for 3-4 hours, filtered, washed with anhydrous ethanol and deionized water for 3-5 times respectively, and dried at 60-70°C for 8-10 hours under vacuum conditions 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 isophorone diamine, and 22-24 parts of acetone by mass; mix the epoxy resin, functionalized epoxy monomer, modified graphene, modified cellulose, isophorone diamine, and acetone evenly, and then adjust the viscosity to 1800-2200 cps with acetone to obtain a graphene conductive adhesive.

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

4. The method for preparing a graphene conductive adhesive according to claim 2, characterized in that: The molecular weight of the polyethylene glycol diglycidyl ether in step (1) is 1000.

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

6. The method for preparing a graphene conductive adhesive according to claim 2, characterized in that: The preparation method of the phenyldichlorosilane solution in step (2) is: phenyldichlorosilane and N,N-dimethylacetamide are uniformly mixed in a mass ratio of 1:(8-10) to prepare a phenyldichlorosilane solution.

7. The method for preparing a graphene conductive adhesive according to claim 2, characterized in that: The particle size of the graphene in step (2) is 3 to 9 nm.

8. The method for preparing a graphene conductive adhesive according to claim 2, characterized in that: The molecular weight of the cellulose in step (3) is 20,000.

9. The method for preparing a graphene conductive adhesive according to claim 2, characterized in that: The concentration of the hydrochloric acid aqueous solution in step (3) is 1 mol / L.

10. The method for preparing a graphene conductive adhesive according to claim 2, characterized in that: The model of the epoxy resin in step (4) is E51.

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