Detachable heat-conducting epoxy structural adhesive, preparation method thereof and application of detachable heat-conducting epoxy structural adhesive in new energy battery

Abstract

The invention belongs to the field of new energy batteries, and particularly discloses a detachable heat-conducting epoxy structural adhesive and a preparation method and application thereof in new energy batteries, the detachable heat-conducting epoxy structural adhesive comprises the following raw materials by mass: 10%-25% of an epoxy prepolymer, 8%-15% of a curing agent, 0.05%-0.5% of a catalyst, 45%-75% of a heat-conducting filler, 2%-10% of a flexibilizer, 2%-5% of a diluent, and 0-4% of an auxiliary agent; the catalyst is a tertiary amine or imidazole catalyst, and the curing agent contains a semi-aromatic imine bond or an aromatic imine bond. The detachable heat-conducting epoxy structural adhesive disclosed by the invention is high in bonding strength, relatively good in heat-conducting property, good in insulating property, good in degumming effect, high in thermal stability of a bonding layer, good in damp-heat aging resistance, free of volatile solvents, free of by-product release in a curing reaction process and simple in operation process.

Description

Technical Field

[0001] The present invention relates to the field of new energy batteries, and specifically to a dismountable thermal conductive epoxy structural adhesive for new energy batteries and a preparation method thereof. Background Art

[0002] New energy batteries mainly include power batteries and energy storage batteries. A battery pack generally consists of multiple modules, and each module consists of multiple battery cells. Damage to any one battery cell will cause damage to the entire battery pack. The battery cells are mainly fixed inside the box by structural adhesive. During the process of replacing or recycling the battery cells, it is necessary to peel the battery cells from the adhesive layer. In related technologies, the debonding process mainly adopts a violent forced disassembly mode, which not only has potential safety hazards, but also causes varying degrees of damage to the structure of the battery pack. Summary of the Invention

[0003] The purpose of the present invention is to provide a dismountable thermal conductive epoxy structural adhesive and its application in new energy batteries.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A dismountable thermal conductive epoxy structural adhesive, calculated by mass percentage, comprises the following raw materials: 10% - 25% of epoxy prepolymer, 8% - 15% of curing agent, 0.05% - 0.5% of catalyst, 45% - 75% of thermal conductive filler, 2% - 10% of toughening agent, 2% - 5% of diluent, and 0 - 4% of auxiliary agent; the catalyst is a tertiary amine or imidazole catalyst, and the curing agent contains a semi-aromatic imine bond or an aromatic imine bond.

[0006] Preferably, the epoxy prepolymer contains more than two epoxy groups; the epoxy prepolymer is one or more of glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, and glycidyl amine type epoxy resin; the curing agent is one or more of aliphatic diamine containing semi-aromatic imine bond, cycloaliphatic diamine containing semi-aromatic imine bond, and aromatic diamine containing aromatic imine bond.

[0007] Preferably, the epoxy prepolymer is any one or more of bisphenol A glycidyl ether, bisphenol F glycidyl ether, resorcinol diglycidyl ether, phenolic glycidyl ether, phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, 1,2 - epoxycyclohexane - 4,5 - dicarboxylic acid diglycidyl ester, p - aminophenol glycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerol diglycidyl ether, trimethylolpropane glycidyl ether.

[0008] Preferably, the curing agent includes any one or more of the following structures:

[0009]

[0010] Preferably, the catalyst is one or a mixture of two or more of 2,4,6-tris(dimethylaminomethyl)phenol, tris(2-ethylhexanoate) of 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, triethanolamine, benzyldimethylamine, o-hydroxybenzyldimethylamine, 2-ethyl-4-methylimidazole, 1-benzyl-2-ethylimidazole, and 1-aminoethyl-2-methylimidazole.

[0011] Preferably, the heat-conducting filler is one or a mixture of two or more of alumina, magnesia, zinc oxide, silica, aluminum nitride, boron nitride, silicon nitride, and silicon carbide.

[0012] Preferably, the toughening agent is one or two or more of phenoxy resin powder, polyvinyl butyral powder, polyurethane powder, methyl methacrylate block copolymer powder, liquid nitrile rubber, liquid polysulfide rubber, and liquid silicone rubber.

[0013] Preferably, the diluent is one or two or more of n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, tolyl glycidyl ether, glycidyl benzoate, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, 1,2-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0014] Preferably, the auxiliary agent is one or two or more of flame retardant, thixotropic agent, coupling agent, defoaming agent, and pigment. The above auxiliary agents are all commonly used commercially available products.

[0015] The preparation method of the disassemblable heat-conducting epoxy structural adhesive includes the following steps:

[0016] (1) Dispersing the epoxy prepolymer, heat-conducting filler, toughening agent, diluent, and auxiliary agent uniformly to obtain a mixture;

[0017] (2) Adding a curing agent and a catalyst to the mixture and further mixing uniformly to obtain the disassemblable heat-conducting epoxy structural adhesive.

[0018] The application of the disassemblable heat-conducting epoxy structural adhesive in a new energy battery is to evenly apply the disassemblable heat-conducting epoxy structural adhesive on the construction site and cure it. The curing conditions are: curing at 20-80°C for 0.5-24h.

[0019] The debonding method of the disassemblable thermally conductive epoxy structural adhesive uses an amine solution to degrade the adhesive layer. The solute of the amine solution is one or a mixture of two or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, m-xylenediamine, diethylaminopropylamine, menthanediamine, N-aminoethylpiperazine, 1-methyl-2,4-cyclohexanediamine, 1,3-bis(aminomethyl)cyclohexane; the solvent of the amine solution is one or a mixture of two or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, isobutanol, cyclohexanone, methylcyclohexanone, acetone, butanone, ethyl acetate, butyl acetate, and cellosolve.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) The present invention uses an amine curing agent containing a semi-aromatic or aromatic imine bond in the molecular structure to react with an epoxy prepolymer. The epoxy group can endow the adhesive with high bonding strength. The prepared disassemblable thermally conductive epoxy structural adhesive has high bonding strength (tensile shear strength of 29.9 - 34.2 MPa), good thermal conductivity (thermal conductivity of 1.4 - 2.8 (W / (m·K))), good insulation performance (volume resistivity of 1.2 - 1.8×10 14 Ω), good flame retardant effect (UL94V-0 level), high thermal stability of the adhesive layer (glass transition temperature of 80 - 130 °C), and good resistance to damp and heat aging.

[0022] (2) The epoxy structural adhesive of the present invention does not contain volatile solvents. The imine dynamic covalent bond structure formed during the curing reaction endows the adhesive with a degradable function and no by-products are released. While improving the bonding strength of the epoxy structural adhesive, it still has a good debonding effect. The average debonding speed is 0.3 - 3 cm within the range of -50 to 60 °C 2 / h.

[0023] (3) The structure and performance of the disassemblable thermally conductive epoxy structural adhesive prepared by the present invention can be adjusted arbitrarily, which is beneficial for the rapid detachment of the battery core and the box body of new energy batteries; and the preparation method of the present invention is simple and easy to scale up production. Specific Embodiments

[0024] The following further illustrates the present invention with specific embodiments, but the content of the present invention is not limited to the following embodiments.

[0025] Example 1

[0026] 9 parts of bisphenol F diglycidyl ether (Epikote 862), 5 parts of resorcinol diglycidyl ether, 4 parts of 1,2-cyclohexanedicarboxylic acid diglycidyl ester, 3 parts of n-butyl glycidyl ether, 4 parts of liquid nitrile rubber, 40 parts of alumina powder, 20 parts of boron nitride powder, 2.2 parts of flame retardant phenoxycyclophosphazene, 0.5 part of coupling agent 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 0.2 part of defoamer BYK-1765 (BYK) were added to a stirring kettle and mixed evenly. 12 parts of curing agent A and 0.1 part of 2,4,6-tris(dimethylaminomethyl)phenol were added and rapidly stirred for 5 minutes, then degassed to obtain a disassemblable thermally conductive structural adhesive mixture. According to the method of GB / T 7124-2008 Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material) in the national standard, the tensile shear strength of the adhesive was tested, and stainless steel test pieces were used to simulate the bonding effect between the battery cell housing and the box. The structural adhesive was evenly applied to the bonding part of the stainless steel test pieces, the steel sheets were closely fitted, the excess adhesive at the edges was removed, fixed with a reverse tail clip, and cured at room temperature for 24 h. 5 samples were tested in each group and the average value was taken. The samples were subjected to an aging experiment according to GB / T 2423.50-2012 in the national standard. According to GB / T 31838.2-2019 in the national standard, the volume resistivity of the samples in this example was 1.3×10 14 Ω, with good insulation performance. According to the ANSI UL94-2018 standard, the flame retardancy of the samples in this example reached V-0 level, with high flame retardancy. The samples were immersed in a degradation solution to test the debonding speed of the adhesive. The samples in this example were immersed in a mixed solution of 10 parts of m-xylenediamine, 20 parts of tetrahydrofuran, and 70 parts of N,N-dimethylacetamide at room temperature to test the debonding speed of the adhesive.

[0027] Example 2

[0028] 12 parts of bisphenol A diglycidyl ether (NPEL-128), 3 parts of phenolic diglycidyl ether (EPALLOY 8240), 3 parts of 1,2-cyclohexanedicarboxylic acid diglycidyl ester, 3 parts of phenyl glycidyl ether, 3 parts of liquid polysulfide rubber, 15 parts of magnesium oxide powder, 50 parts of aluminum nitride powder, 2 parts of flame retardant dimethyl methylphosphonate, 0.5 part of coupling agent γ-aminopropyltriethoxysilane, and 0.2 part of defoamer BYK-1765 (BYK) were added to a stirring kettle and mixed evenly. 8.2 parts of curing agent D and 0.1 part of 2-ethyl-4-methylimidazole were added and rapidly stirred for 10 minutes, then degassed to obtain a disassemblable thermally conductive structural adhesive mixture. The methods for testing the tensile shear strength and aging experiment of the adhesive were the same as in Example 1, and the curing condition of the structural adhesive was 5 h at room temperature. The volume resistivity of the samples in this example was 1.5×10 14Ω, and the flame retardancy reaches V-0 level. The sample of this example was immersed in a mixed solution of 5 parts of ethylenediamine, 10 parts of diethylenetriamine, 30 parts of acetone, and 55 parts of N-methylpyrrolidone at room temperature to test the debonding speed of the adhesive.

[0029] Example 3

[0030] Add 10 parts of diglycidyl 1,2-cyclohexanedicarboxylate, 5 parts of trimethylolpropane glycidyl ether, 5 parts of n-butyl glycidyl ether, 4 parts of liquid silicone rubber, 1 part of polyurethane powder, 60 parts of alumina powder, 2 parts of flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 0.4 part of coupling agent 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 0.2 part of defoaming agent BYK-1765 (BYK) into a stirring kettle and mix evenly. Add 12 parts of curing agent G and 0.2 part of benzyldimethylamine, stir rapidly for 5 minutes, and degas to obtain a disassemblable thermally conductive structural adhesive mixture. The tensile shear strength and aging test methods of the adhesive are the same as those in Example 1, and the curing conditions of the structural adhesive are 40°C for 6 h. The volume resistivity of the sample of this example is 1.2×10 14 Ω, and the flame retardancy reaches V-0 level. The sample of this example was immersed in a mixed solution of 5 parts of ethylenediamine, 10 parts of menthanediamine, and 85 parts of dimethyl sulfoxide at 40°C to test the debonding speed of the adhesive.

[0031] Example 4

[0032] Add 8 parts of resorcinol diglycidyl ether, 5 parts of p-aminophenol glycidyl ether, 2 parts of benzoic acid glycidyl ester, 1 part of liquid nitrile rubber, 1 part of methyl methacrylate block copolymer powder, 30 parts of alumina powder, 10 parts of boron nitride powder, 30 parts of aluminum nitride powder, 1.4 parts of flame retardant 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 0.5 part of coupling agent γ-aminopropyltriethoxysilane, and 0.2 part of defoaming agent BYK-1765 (BYK) into a stirring kettle and mix evenly. Add 6 parts of curing agent A, 5 parts of curing agent L, and 0.1 part of triethanolamine, stir rapidly for 10 minutes, and degas to obtain a disassemblable thermally conductive structural adhesive mixture. The tensile shear strength and aging test methods of the adhesive are the same as those in Example 1, and the curing conditions of the structural adhesive are 60°C for 3 h. The volume resistivity of the sample of this example is 1.8×10 14 Ω, and the flame retardancy reaches V-0 level. The sample of this example was immersed in a mixed solution of 5 parts of 1,3-bis(aminomethyl)cyclohexane, 5 parts of triethylenetetramine, and 80 parts of N,N-dimethylformamide at 60°C to test the debonding speed of the adhesive.

[0033] Example 5

[0034] Add 12 parts of diglycidyl 1,2 - cyclohexanedicarboxylate, 6 parts of phenolic glycidyl ether (EPALLOY8240), 5 parts of 1,2 - propanediol diglycidyl ether, 3 parts of liquid silicone rubber, 3 parts of phenoxy resin powder, 10 parts of alumina powder, 30 parts of boron nitride powder, 10 parts of zinc oxide powder, 3 parts of flame retardant phenoxycyclophosphazene, 0.5 part of coupling agent 3 - (2,3 - epoxypropoxy) propyltrimethoxysilane, and 0.2 part of defoamer BYK - 1765 (BYK) into a stirring kettle and mix evenly. Then add 6 parts of curing agent G, 11 parts of curing agent K, 0.1 part of 2,4,6 - tris(dimethylaminomethyl)phenol, and 0.2 part of 2 - ethyl - 4 - methylimidazole, and stir rapidly for 10 minutes, then degas to obtain a disassemblable thermally conductive structural adhesive mixture. The tensile shear strength and aging test methods of the adhesive are the same as those in Example 1, and the curing conditions of the structural adhesive are 80°C for 0.5 h. The volume resistivity of the sample in this example is 1.6×10 14 Ω, and the flame retardancy reaches V - 0 level. The sample in this example is immersed in a mixed solution of 5 parts of ethylenediamine, 5 parts of N - aminoethylpiperazine, 20 parts of isobutanol, and 70 parts of N - methylpyrrolidone at - 50°C to test the debonding speed of the adhesive.

[0035] Control Example 1

[0036] Use 12 parts of bisphenol F diglycidyl ether (Epikote 862), 6.7 parts of resorcinol diglycidyl ether, 5.3 parts of diglycidyl 1,2 - cyclohexanedicarboxylate, and 6 parts of m - xylylenediamine to replace 9 parts of bisphenol F diglycidyl ether (Epikote 862), 5 parts of resorcinol diglycidyl ether, 4 parts of diglycidyl 1,2 - cyclohexanedicarboxylate, and 12 parts of curing agent A in Example 1 respectively. Others are the same as in Example 1. The volume resistivity of the sample in this control example is 1.2×10 14 Ω, and the flame retardancy reaches V - 1 level.

[0037] Control Example 2

[0038] Use 15.1 parts of bisphenol A diglycidyl ether (NPEL - 128), 3.8 parts of phenolic glycidyl ether (EPALLOY8240), 3.8 parts of diglycidyl 1,2 - cyclohexanedicarboxylate, and 3.5 parts of diethylenetriamine to replace 12 parts of bisphenol A diglycidyl ether (NPEL - 128), 3 parts of phenolic glycidyl ether (EPALLOY 8240), 3 parts of diglycidyl 1,2 - cyclohexanedicarboxylate, and 8.2 parts of curing agent D in Example 2 respectively. Others are the same as in Example 2. The volume resistivity of the sample in this control example is 1.4×10 14 Ω, and the flame retardancy reaches V - 1 level.

[0039] Table 1 Bonding effect and debonding situation of the dismountable thermally conductive epoxy structural adhesive

[0040]

[0041] Note: The thermal conductivity and glass transition temperature of the structural adhesive were tested according to ASTM D5470-17 and GB / T 33061.11-2022 standards; the tensile shear strength of the structural adhesive before and after aging was tested according to GBT2423.50-2012 and GB / T 7124-2008 standards; the average debonding speed was obtained by calculating the bonding area divided by the debonding time; the samples of Comparative Examples 1 and 2 did not degrade completely and could not be debonded.

[0042] The above results show that the dismountable thermally conductive epoxy structural adhesive of the present invention has high bonding strength, good thermal conductivity, high thermal stability of the bonding layer, good insulation performance, good flame retardant effect, fast debonding speed and simple operation process. The molecular structures of the thermal conductive adhesives in Comparative Examples 1 and 2 do not contain semi-aromatic or aromatic imine dynamic covalent bonds. Therefore, compared with Examples 1 to 5, they do not have the debonding function and have poor flame retardant performance under the same conditions.

[0043] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A detachable thermally conductive epoxy structural adhesive, characterized in that: The invention comprises the following raw materials in percentage by mass: 10% to 25% of epoxy prepolymer, 8% to 15% of curing agent, 0.05% to 0.5% of catalyst, 45% to 75% of thermal conductive filler, 2% to 10% of toughening agent, 2% to 5% of diluent and 0% to 4% of auxiliary agent; the catalyst is a tertiary amine or imidazole catalyst, and the curing agent contains a semi-aromatic imine bond or an aromatic imine bond.

2. The detachable thermally conductive epoxy structural adhesive according to claim 1, characterized in that: The epoxy prepolymer contains two or more epoxy groups.

3. The detachable thermally conductive epoxy structural adhesive according to claim 2, characterized in that: The curing agent includes any one or more of the following structures:

4. The detachable thermally conductive epoxy structural adhesive according to claim 1, 2 or 3, characterized in that: The epoxy prepolymer is one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin; the curing agent is one or more of semi-aromatic imine bond-containing fatty diamine, semi-aromatic imine bond-containing alicyclic diamine and aromatic diamine containing aromatic imine bond.

5. The detachable thermally conductive epoxy structural adhesive according to claim 4, characterized in that: The epoxy prepolymer is any one or more of bisphenol A glycidyl ether, bisphenol F glycidyl ether, resorcinol diglycidyl ether, phenolic glycidyl ether, phthalic acid diglycidyl ether, tetrahydrophthalic acid diglycidyl ether, hexahydrophthalic acid diglycidyl ether, 1,2-epoxycyclohexane-4,5-dicarboxylic acid diglycidyl ether, p-aminophenol glycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerol diglycidyl ether, and trimethylolpropane glycidyl ether.

6. The detachable thermally conductive epoxy structural adhesive according to claim 1, 2 or 3, characterized in that: The catalyst is one or a mixture of two or more of 2,4,6-tris(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol tris(2-ethylhexanoate), triethylamine, triethanolamine, benzyldimethylamine, o-hydroxybenzyldimethylamine, 2-ethyl-4-methylimidazole, 1-benzyl-2-ethylimidazole and 1-aminoethyl-2-methylimidazole.

7. The detachable thermally conductive epoxy structural adhesive according to claim 1, 2 or 3, characterized in that: The thermal conductive filler is one or a mixture of two or more of aluminum oxide, magnesium oxide, zinc oxide, silicon dioxide, aluminum nitride, boron nitride, silicon nitride and silicon carbide; The toughening agent is one or more of phenoxy resin powder, polyvinyl butyral powder, polyurethane powder, methyl methacrylate block copolymer powder, liquid nitrile rubber, liquid polysulfide rubber, and liquid silicone rubber; The diluent is one or more of n-butyl glycidyl ether, 2-ethyl-hexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, benzoic acid glycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, 1,2-propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and neopentyl glycol diglycidyl ether; The auxiliary agent is one or more than two of a flame retardant, a thixotropic agent, a coupling agent, a defoaming agent and a pigment.

8. The method for preparing the disassembled thermally conductive epoxy structural adhesive according to any one of claims 1 to 7, characterized in that: The steps include: (1) uniformly dispersing the epoxy prepolymer, the thermal conductive filler, the toughening agent, the diluent, and the auxiliary agent to obtain a mixture; (2) Add a curing agent and a catalyst to the mixture and further mix them evenly to obtain a disassembled thermally conductive epoxy structural adhesive.

9. Application of the disassembled thermally conductive epoxy structural adhesive according to any one of claims 1 to 7 in new energy batteries, characterized in that: The disassembled thermally conductive epoxy structural adhesive is evenly applied to the construction site and cured. The curing conditions are: curing at 20-80° C. for 0.5 to 24 hours.

10. The debonding method of any one of claims 1 to 7, characterized in that: An amine solution is used to degrade the adhesive layer. The solute of the amine solution is one or a mixture of two or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, meta-xylene diamine, diethylaminopropylamine, menthanediamine, N-aminoethylpiperazine, 1-methyl-2,4-cyclohexanediamine, and 1,3-bis(aminomethyl)cyclohexane; the solvent of the amine solution is one or a mixture of two or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, isobutanol, cyclohexanone, methylcyclohexanone, acetone, butanone, ethyl acetate, butyl acetate, and cellosolve.

Images