Degradable and Recyclable Epoxy Conductive Adhesive as well as Preparing, Degrading and Recycling Methods therefor

Abstract

The present invention provides a degradable and recyclable epoxy conductive adhesive, which comprises the following raw materials in percentage by weight: 15% to 30% of epoxy resin, 1% to 10% of a curing agent, 0.1% to 2% of a reaction diluent and 15% to 85% of a conductive filler, wherein the curing agent comprises a breakable molecular structure. According to the epoxy conductive adhesive of the present invention, after the epoxy resin in the conductive adhesive is cured by using the recyclable and degradable epoxy resin curing agent of a specific molecular structure, the conductive adhesive can be degraded in normal pressure, mild and specific conditions, the process is simple and the operation is convenient, no contamination is brought to the environment, the recycling cost is largely reduced, and the recycling of the conductive adhesive has enormous economic and environmental advantages. By using the recyclable and degradable epoxy resin curing agent of a specific molecular structure, the shear strength of the conductive adhesive is greatly increased, and the reliability and the service life of the conductive adhesive are largely improved.

Claims

1. A degradable and recoverable epoxy conductive adhesive comprising the following raw materials in weight percentage: 15-30% of an epoxy resin, 1-10% of a curing agent, 0.1-2% of a reactive diluent and 15-85% of a conductive filler, the curing agent comprising a breakable molecular structure shown as follows: ##STR00012## wherein R.sub.1 and R.sub.2 are independently anyone selected from the group consisting of hydrogen atom, alkyl group, cycloalkyl group, heterocyclic group, heterocycloalkyl group, alkenyl group, cycloalkenyl group, aromatic group, heteroaromatic group, alkyl heteroalkyl group, alkynyl group, alkylene group, alkylene heteroalkylene, alkenylene group, alkylene heteroalkenylene, alkynylene group and alkylene heteroalkynylene; R.sub.3 and R.sub.4 are independently anyone selected from the group consisting of alkylene group, alkylene heteroalkylene, alkenylene group, alkenylene heteroalkenylene, alkylene heteroalkenylene, alkynylene group, cycloalkylene group, alkylene cycloalkylene, alkylene cycloalkylene alkylene, alkenylene cycloalkylene, alkenylene cycloalkylene alkenylene, alkylene cycloalkylene alkenylene, alkynylene cycloalkylene, alkynylene cycloalkylene alkynylene, heterocycloalkylene group, alkylene heterocycloalkylene, alkylene heterocycloalkyl alkylene, alkenylene heterocycloalkylene, alkenylene heterocycloalkyl alkenylene, alkylene heterocycloalkyl alkenylene, alkynylene heterocycloalkylene, alkynylene heterocycloalkyl alkynylene, cycloalkenylene, alkylene cycloalkenylene, alkylene cycloalkenylene alkylene, alkenylene cycloalkenylene, alkenylene cycloalkenylene alkenylene, alkylene cycloalkenylene alkenylene, alkynylene cycloalkenylene, alkynylene cycloalkenylene alkynylene, heterocycloalkenylene, alkylene heterocycloalkenylene, alkylene heterocycloalkenyl alkylene, alkenylene heterocycloalkenylene, alkenylene heterocycloalkenyl alkenylene, alkylene heterocycloalkenyl alkenylene, alkynylene heterocycloalkenylene, alkynylene heterocycloalkenyl alkynylene, arylene group, alkylene arylene group, alkylene arylene alkylene, alkenylene arylene group, alkenylene arylene alkenylene, alkylene arylene alkenylene, alkynylene arylene group, alkynylene arylene alkynylene, heteroarylene group, alkylene heteroarylene group, alkylene heteroarylene alkylene, alkenylene heteroarylene group, alkenylene heteroarylene alkenylene, alkylene heteroarylene alkenylene, alkynylene heteroarylene group, alkynylene heteroarylene alkynylene, 1,4-alkyl substituted piperazine, carbonyl group and thiocarbonyl group.

2. The epoxy conductive adhesive according to claim 1, wherein R.sub.1 and R.sub.2 are in the same ring structure together with the co-adjacent carbon atoms.

3. The epoxy conductive adhesive according to claim 1, wherein the epoxy resin is anyone selected from the group consisting of glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl ammonia type epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin and nitrogen-containing epoxy resin, or a mixture of at least two selected therefrom.

4. The epoxy conductive adhesive according to claim 1, wherein the reactive diluent is anyone selected from the group consisting of allyl glycidyl ether, butyl glycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol glycidyl ether, trimethylolpropane glycidyl ether and polyethylene glycol diglycidyl ether, or a mixture of at least two selected therefrom.

5. The epoxy conductive adhesive according to claim 1, wherein the conductive filler is anyone selected from the group consisting of flaky metallic silver, micron silver powder, flaky gold, micron gold, flaky metallic copper, micron copper powder, flaky metallic nickel and micron nickel powder, or a mixture of at least two selected therefrom.

6. The epoxy conductive adhesive according to claim 1, wherein the conductive filler is surface-modified by graphene which is in an amount of 0.2-2% by weight of the conductive filler.

7. A process for preparing the degradable and recoverable epoxy conductive adhesive according to claim 1, comprising the steps of dissolving the reactive diluent, curing agent and epoxy resin in an organic solvent, stirring at 20-50° C. for 5-30 min, adding optionally a graphene solution, continuing to stir for 10-30 min, then adding the conductive filler, dispersing for 30-120 min to obtain the degradable and recoverable epoxy conductive adhesive.

8. The process according to claim 7, wherein the dispersion is ultrasonic dispersion or stirring dispersion, wherein the ultrasonic dispersion is conducted at 20-60° C., and the stirring dispersion is conducted in a three-roll or double-planetary hybrid mixer.

9. A process for degrading and recovering the degradable and recoverable epoxy conductive adhesive according to claim 1, in addition to degrading the epoxy conductive adhesive by using acids and solvents under heating conditions, further comprising neutralizing with an alkali solution the solution obtained after degradation and adjusting the pH of the solution.

10. The process according to claim 9, wherein the process further comprises recovering the degraded polymer after the degradation step and neutralization steps.

11. The process according to claim 9, wherein the acid is anyone selected from the group consisting of hydrochloric acid, hydrobromic acid, hydrofluoric acid, acetic acid, trifluoroacetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, perchloric acid, benzoic acid, salicylic acid and phthalic acid, or a mixture of at least two selected therefrom.

12. The process according to claim 9, wherein the alkali is anyone selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate and ammonia, or a mixture of at least two selected therefrom.

13. The epoxy conductive adhesive according to claim 6, wherein a a coupling agent is added while the conductive filler is surface modified by graphene, wherein the coupling agent is anyone selected from the group consisting of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane and vinyltriethoxysilane, or a mixture of at least two selected therefrom.

14. The epoxy conductive adhesive according to claim 13, wherein the coupling agent is in an amount of from 0.5% to 1% by weight of the conductive filler.

15. The process according to claim 7, wherein the graphene solution is prepared by oxidizing natural flake graphite by Hummers method to obtain graphite oxide, dissolving the coupling agent in an organic solvent, then mixing the graphene with the organic solvent in a mass ratio of 2-10:50-200, stirring the mixed solution in a magnetic stirrer and heating for 0.5-2 hours to control the temperature to be 20-50° C., subjecting the mixed solution to ultrasonic processing for 1-3 h after magnetic stirring, standing still for 1-12 h, centrifugalizing the upper suspension of the mixed solution, distilling to obtain a graphene solution.

16. The process according to claim 15 wherein the organic solvent is anyone selected from the group consisting of acetone, butanone, N,N-dimethylformamide, tetrahydrofuran, dimethylsulfoxide and N-methylpyrrolidone, or a mixture of at least two selected therefrom.

17. The process according to claim 9, wherein the solvent is anyone selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, benzyl alcohol, phenethyl alcohol, p-dimethylol benzene, m-dimethylol benzene, o-dimethylol benzene, p-dihydroxyethyl benzene, m-dihydroxyethyl benzene, o-dihydroxyethylbenzene, water, N,N-dimethyl-formamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, tetrahydrofuran, methyltetrahydrofuran, glycerol and dioxane, or a mixture of at least two selected therefrom.

18. The process according to claim 9, wherein the acid has a mass concentration of 0.1-100% in the solvent; optionally, the heating temperature ranges from 15° C. to 400° C.; and optionally, the heating lasts for 1-120 h.

19. The process according to claim 9, wherein the solvent of the alkali solution is anyone selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, water, N,N-dimethyl-formamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, tetrahydrofuran, methyltetrahydrofuran, glycerol and dioxane, or a mixture of at least two selected therefrom.

20. The process according to claim 9, wherein the the alkali solution has a mass concentration of 0.1-100%; and optionally, the pH of the solution is adjusted at a temperature of 0-200° C., and adjusted to greater than 6.

Description

EXAMPLE 1

[0058] (1) First dissolving 1.5 g of a vinyltriethoxysilane coupling agent in 20 g of a butanone solvent, then adding 2 g of graphene while adding 40 g of a butanone solvent, and mixing with graphene, placing the mixed solution in a magnetic stirrer, stirring and heating for 1 hour, controlling the heating temperature at 30° C., subjecting the mixed solution to ultrasonic processing for 1 hour after the magnetic stirring, standing still for 12 hours, centrifuging the upper suspension of the mixed solution, distilling to obtain a graphene solution.

[0059] (2) Dissolving 1 g of an allyl glycidyl ether diluent, 5 g of a curing agent A and 15.6 g of a bisphenol F830 epoxy resin in a butanone solvent, stirring at 30° C. for 15 minutes, adding 3 g of a graphene solution, continuing to stir for 20 minutes, adding 80 g of flaky silver (2 μm), subjecting to ultrasonic dispersion at 30° C. for 60 minutes to obtain a conductive adhesive.

##STR00008##

EXAMPLE 2

[0060] (1) First dissolving 1.5 g of a vinyltriethoxysilane coupling agent in 20 g of a butanone solvent, then adding 2 g of graphene while adding 40 g of a butanone solvent, and mixing with graphene, placing the mixed solution in a magnetic stirrer, stirring and heating for 1 hour, controlling the heating temperature at 30° C., subjecting the mixed solution to ultrasonic processing for 1 hour after the magnetic stirring, standing still for 12 hours, centrifuging the upper suspension of the mixed solution, distilling to obtain a graphene solution.

[0061] (2) Dissolving 1 g of a butyl glycidyl ether diluent, 5 g of a curing agent B and 16 g of a bisphenol A828 epoxy resin in a butanone solvent, stirring at 30° C. for 15 minutes, adding 3 g of a graphene solution, continuing to stir for 20 minutes, adding 80 g of flaky silver (2 μm), subjecting to ultrasonic dispersion at 30° C. for 60 minutes to obtain a conductive adhesive.

##STR00009##

EXAMPLE 3

[0062] (1) First dissolving 1.5 g of a vinyltriethoxysilane coupling agent in 20 g of a butanone solvent, then adding 2 g of graphene while adding 40 g of a butanone solvent, and mixing with graphene, placing the mixed solution in a magnetic stirrer, stirring and heating for 1 hour, controlling the heating temperature at 50° C., subjecting the mixed solution to ultrasonic processing for 3 hours after the magnetic stirring, standing still for 1 hours, centrifuging the upper suspension of the mixed solution, distilling to obtain a graphene solution.

[0063] (2) Dissolving 1 g of a butyl glycidyl ether diluent, 5 g of a curing agent C and 16 g of a bisphenol A828 epoxy resin in a butanone solvent, stirring at 50° C. for 10 minutes, adding 3 g of a graphene solution, continuing to stir for 30 minutes, adding 80 g of flaky silver (2 μm), subjecting to ultrasonic dispersion at 30° C. for 120 minutes to obtain a conductive adhesive.

##STR00010##

COMPARISON EXAMPLE 1

[0064] (1) First dissolving 1.8 g of a γ-aminopropyltrimethoxysilane coupling agent in 20 g of a butanone solvent, then adding 2 g of graphene while adding 40 g of a butanone solvent, and mixing with graphene, placing the mixed solution in a magnetic stirrer, stirring and heating for 1 hour, controlling the heating temperature at 30° C., subjecting the mixed solution to ultrasonic processing for 1 hour after the magnetic stirring, standing still for 12 hours, centrifuging the upper suspension of the mixed solution, distilling to obtain a graphene solution.

[0065] (2) Dissolving 1 g of an allyl glycidyl ether diluent, 1 g of a curing agent of dicyandiamide and 15.6 g of a bisphenol F830 epoxy resin in a butanone solvent, stirring at 30° C. for 15 minutes, adding 3 g of a graphene solution, continuing to stir for 20 minutes, adding 80 g of flaky silver (2 μm), subjecting to ultrasonic dispersion at 30° C. for 60 minutes to obtain a conductive adhesive.

COMPARISON EXAMPLE 2

[0066] (1) First dissolving 1.5 g of a vinyltriethoxysilane coupling agent in 20 g of a butanone solvent, then adding 2 g of graphene while adding 40 g of a butanone solvent, and mixing with graphene, placing the mixed solution in a magnetic stirrer, stirring and heating for 1 hour, controlling the heating temperature at 30° C., subjecting the mixed solution to ultrasonic processing for 1 hour after the magnetic stirring, standing still for 12 hours, centrifuging the upper suspension of the mixed solution, distilling to obtain a graphene solution.

[0067] (2) Dissolving 1 g of an allyl glycidyl ether diluent, 1 g of a curing agent of dicyandiamide and 16.5 g of a bisphenol A828 epoxy resin in a butanone solvent, stirring at 30° C. for 15 minutes, adding 3 g of a graphene solution, continuing to stir for 20 minutes, adding 80 g of flaky silver (2 μm), subjecting to ultrasonic dispersion at 30° C. for 60 minutes to obtain a conductive adhesive.

COMPARISON EXAMPLE 3

[0068] (1) First dissolving 1.8 g of a γ-aminopropyltrimethoxysilane coupling agent in 20 g of a butanone solvent, then adding 2 g of graphene while adding 40 g of a butanone solvent, and mixing with graphene, placing the mixed solution in a magnetic stirrer, stirring and heating for 1 hour, controlling the heating temperature at 30° C., subjecting the mixed solution to ultrasonic processing for 1 hour after the magnetic stirring, standing still for 12 hours, centrifuging the upper suspension of the mixed solution, distilling to obtain a graphene solution.

[0069] (2) Dissolving 1 g of a butyl glycidyl ether diluent, 5 g of a curing agent of diaminodiphenyl-methane (DDM) and 15.6 g of a bisphenol F830 epoxy resin in a butanone solvent, stirring at 30° C. for 15 minutes, adding 3 g of a graphene solution, continuing to stir for 20 minutes, adding 80 g of flaky silver (2 μm), subjecting to ultrasonic dispersion at 30° C. for 60 minutes to obtain a conductive adhesive.

[0070] As for the epoxy conductive adhesives prepared above, the conductivities and shear strengthes thereof were tested. The testing results are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Performance testing results of epoxy conductive adhesives Test Testing Comparison Comparison Comparison items conditions Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Volume GB/T1410-2006 37.5 35.4 35.7 39.3 40.2 36.2 resistivity (mΩ .Math. cm) Shear GB/T7124- 28 27 26.8 25.7 24.6 21.3 strength 1986 (MPa)

[0071] It can be seen according to the testing results above that the epoxy conductive adhesives using the curing agent comprising breakable molecular structure of the present invention has excellent conductive property, and maintains better shear strength.

[0072] The methods for the aforesaid performance tests are as follows.

[0073] Volume resistivity: tested according to the testing standard: GB/T1410-2006 by using RT-1000 Resistivity tester from Xiangtan Huafeng Instrument Manufacturing Co., Ltd.

[0074] Shear strength: tested according to the testing standard: GB/T 7124-1986 by using CMT4204 from Meters Industrial Systems (China) Limited.

##STR00011##

[0075] Certainly, the above-described examples are merely preferred examples of the present invention and are not intended to limit the implementation scope of the present invention. Therefore any equivalent change or modification made according to the construction, features and principles within the patent scope of the present invention is included within the patent scope of the present invention.

[0076] The applicant claims that the present invention describes the detailed process of the present invention, but the present invention is not limited to the detailed process of the present invention. That is to say, it does not means that the present invention shall be carried out with respect to the above-described detailed process of the present invention. Those skilled in the art shall know that any improvements to the present invention, equivalent replacements of the raw materials of the present invention, additions of auxiliary, selections of any specific ways all fall within the protection scope and disclosure scope of the present invention.