Inner layer adhesive and application thereof in aluminum plastic film

Abstract

The invention belongs to the technical field of adhesives, and provides an inner layer adhesive and application thereof in an aluminum plastic film. The product comprises the following components in parts by mass: 5-25 parts of modified unsaturated polyolefin, 40-100 parts of modified saturated polyolefin, 300-750 parts of an organic solvent, 2-25 parts of a first curing agent, 5-20 parts of a second curing agent and 0-0.05 part of a photoinitiator. By introducing the modified unsaturated polyolefin, the integral grafting rate of the modified polyolefin is improved, the polarity of the inner-layer adhesive is improved, and the bonding strength between the inner-layer adhesive and the aluminum foil is enhanced; the modified unsaturated polyolefin is introduced to construct a modified unsaturated polyolefin-modified saturated polyolefin dual polymer network, so that the strength and stability of a cured cross-linked network are greatly improved, and the adhesive shows excellent heat resistance while having better deep punching resistance, electrolyte corrosion resistance and deep punching resistance.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, in particular to an inner layer adhesive and application thereof in aluminum-plastic films. Background Art

[0002] As a packaging material for soft-pack lithium batteries, aluminum-plastic film needs to meet strict requirements in terms of barrier properties, chemical resistance, mechanical properties, etc. These properties are directly related to the interlayer adhesive. Commercially available soft-pack aluminum-plastic film products are usually divided into three layers, with the inner layer substrate being a polyolefin film, the middle layer being an aluminum foil, and the outer layer being usually a nylon film. The various layers of materials are bonded together using different types of adhesives to give the aluminum-plastic film good processing performance and stability.

[0003] As the inner layer adhesive for bonding aluminum foil and polyolefin film, it needs to meet the performance requirements of high peel strength, electrolyte corrosion resistance, no impact on punching depth, heat resistance, etc. At present, the inner layer adhesive on the market is still monopolized by a few Japanese companies, and the existing domestic technology or products cannot meet the performance requirements of electrolyte corrosion resistance and heat resistance at the same time. Therefore, it is of great significance to provide an aluminum-plastic film inner layer adhesive that has both electrolyte corrosion resistance and heat resistance. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems existing in the prior art and provide an inner layer adhesive and its application in aluminum-plastic film.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides an inner layer adhesive comprising the following components in parts by weight:

[0007] 5 to 25 parts of modified unsaturated polyolefin, 40 to 100 parts of modified saturated polyolefin, 300 to 750 parts of organic solvent, 2 to 25 parts of first curing agent, 5 to 20 parts of second curing agent and 0 to 0.05 parts of photoinitiator.

[0008] Preferably, the preparation method of the modified unsaturated polyolefin comprises the following steps:

[0009] Under an inert atmosphere, unsaturated polyolefin, unsaturated modifier, antioxidant and solvent are mixed and grafted to obtain modified unsaturated polyolefin.

[0010] Preferably, the unsaturated polyolefin includes one or more of polybutadiene, polyisoprene, styrene-butadiene copolymer, isobutylene-isoprene copolymer, styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer;

[0011] The unsaturated modifier includes one or more of α,β-unsaturated carboxylic acid and α,β-unsaturated anhydride;

[0012] The antioxidant includes one or more of 2,6-di-tert-butyl-p-cresol, 9,9-dimethylacridine and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0013] The solvent includes one or more of xylene, terphenyl, dodecane, α-chloronaphthalene and sulfolane.

[0014] Preferably, the mass ratio of the unsaturated polyolefin, the unsaturated modifier, the antioxidant and the solvent is 0.3-2: 0.4-2: 0.005-0.04: 6-25;

[0015] The temperature of the graft modification is 170 to 260° C., and the time of the graft modification is 0.2 to 10 hours;

[0016] The grafting rate of the modified unsaturated polyolefin is 4-9%.

[0017] Preferably, the modified saturated polyolefin includes α,β-unsaturated carboxylic acid grafted polypropylene, α,β-unsaturated acid anhydride grafted polypropylene, α,β-unsaturated carboxylic acid grafted α-olefin / propylene copolymer or α,β-unsaturated acid anhydride grafted α-olefin / propylene copolymer; the grafting rate of the modified saturated polyolefin is 0.5-3%.

[0018] Preferably, the organic solvent comprises one or more of benzene, toluene, xylene, cyclohexane, n-heptane, methylcyclohexane, acetone, butanone, ethyl acetate and ethyl propionate.

[0019] Preferably, the first curing agent includes one or more of polymer isocyanate and epoxy resin.

[0020] Preferably, the second curing agent includes one or more of polyols and polythiols.

[0021] The invention also provides application of the inner layer adhesive in the aluminum-plastic film.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides an inner layer adhesive, comprising the following components in parts by mass: 5-25 parts of modified unsaturated polyolefin, 40-100 parts of modified saturated polyolefin, 300-750 parts of organic solvent, 2-25 parts of first curing agent, 5-20 parts of second curing agent and 0-0.05 parts of photoinitiator. By introducing modified unsaturated polyolefin, the overall grafting rate of modified polyolefin is improved, the polarity of inner layer adhesive is improved, and the bonding strength between inner layer adhesive and aluminum foil is strengthened; by introducing modified unsaturated polyolefin, a double polymer network of modified unsaturated polyolefin-modified saturated polyolefin is constructed, which greatly improves the strength and stability of the cross-linked network after curing, so that the adhesive has good deep impact resistance, electrolyte corrosion resistance, deep impact resistance and excellent heat resistance. By using the inner layer adhesive of the present invention, the initial peel strength of the obtained aluminum-plastic film material at room temperature reaches 16-18N / 15mm, the peel strength reaches 11-12N after being immersed in 85°C electrolyte for 7 days, the high-temperature peel strength at 120°C is greater than 5.5N / 15mm, and the punching depth can reach 8mm without delamination. DETAILED DESCRIPTION

[0024] The present invention provides an inner layer adhesive comprising the following components in parts by weight:

[0025] 5 to 25 parts of modified unsaturated polyolefin, 40 to 100 parts of modified saturated polyolefin, 300 to 750 parts of organic solvent, 2 to 25 parts of first curing agent, 5 to 20 parts of second curing agent and 0 to 0.05 parts of photoinitiator.

[0026] In the present invention, the modified unsaturated polyolefin, the modified saturated polyolefin and the organic solvent are used together as the main agent of the inner layer adhesive; the first curing agent and the second curing agent are used together as the curing agent of the inner layer adhesive.

[0027] In the present invention, the mass fraction of the modified unsaturated polyolefin is 5 to 25 parts, preferably 6 to 23 parts, more preferably 8 to 20 parts, and even more preferably 10 to 15 parts.

[0028] In the present invention, the mass fraction of the modified saturated polyolefin is 40 to 100 parts, preferably 50 to 90 parts, more preferably 60 to 80 parts, and even more preferably 65 to 70 parts.

[0029] In the present invention, the mass fraction of the organic solvent is 300 to 750 parts, preferably 350 to 700 parts, more preferably 400 to 650 parts, and even more preferably 500 to 550 parts.

[0030] In the present invention, the mass fraction of the first curing agent is 2 to 25 parts, preferably 5 to 20 parts, more preferably 10 to 15 parts, and even more preferably 12 to 13 parts.

[0031] In the present invention, the mass fraction of the second curing agent is 5 to 20 parts, preferably 7 to 18 parts, more preferably 10 to 16 parts, and even more preferably 12 to 15 parts.

[0032] In the present invention, the mass fraction of the photoinitiator is 0 to 0.05 parts, preferably 0.01 to 0.04 parts, more preferably 0.015 to 0.035 parts, and even more preferably 0.02 to 0.03 parts.

[0033] In the present invention, the preparation method of the modified unsaturated polyolefin preferably comprises the following steps:

[0034] Under an inert atmosphere, unsaturated polyolefin, unsaturated modifier, antioxidant and solvent are mixed and grafted to obtain modified unsaturated polyolefin.

[0035] In the present invention, the inert atmosphere is preferably nitrogen.

[0036] In the present invention, the unsaturated polyolefin is a polyolefin containing unsaturated double bonds in the polymer main chain; the unsaturated polyolefin preferably includes one or more of polybutadiene, polyisoprene, styrene-butadiene copolymer, isobutylene-isoprene copolymer (CAS No. 9010-85-9), styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer (hydrogenated styrene-butadiene-styrene block copolymer is an incompletely hydrogenated styrene-butadiene-styrene block copolymer, preferably YH-533 of Baling Petrochemical) and styrene-isoprene-styrene block copolymer, more preferably polyisoprene and / or isobutylene-isoprene copolymer.

[0037] In the present invention, the unsaturated modifier preferably includes one or more of α, β-unsaturated carboxylic acids and α, β-unsaturated anhydrides; the α, β-unsaturated carboxylic acids preferably include maleic acid, itaconic acid or citraconic acid, more preferably maleic acid; the α, β-unsaturated anhydrides preferably include maleic anhydride, itaconic anhydride or citraconic anhydride, more preferably maleic anhydride.

[0038] In the present invention, the antioxidant preferably includes one or more of 2,6-di-tert-butyl-p-cresol, 9,9-dimethylacridine and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and more preferably 2,6-di-tert-butyl-p-cresol.

[0039] In the present invention, the solvent preferably includes one or more of xylene, terphenyl, dodecane, α-chloronaphthalene and sulfolane.

[0040] In the present invention, the mass ratio of the unsaturated polyolefin, the unsaturated modifier, the antioxidant and the solvent is preferably 0.3-2:0.4-2:0.005-0.04:6-25, more preferably 0.5-1.5:0.8-1.8:0.01-0.03:8-22, and more preferably 1-1.2:1-1.2:0.02-0.025:10-15.

[0041] In the present invention, the temperature of the grafting modification is preferably 170-260°C, more preferably 190-250°C, and more preferably 200-220°C; the time of the grafting modification is preferably 0.2-10h, more preferably 0.4-8h, and more preferably 0.5-6h.

[0042] In the present invention, after the grafting modification is completed, the obtained system is naturally cooled to room temperature, then washed and purified with butanone, and finally dried to obtain the modified unsaturated polyolefin.

[0043] In the present invention, the grafting rate of the modified unsaturated polyolefin is preferably 4 to 9%, more preferably 5 to 8%, and even more preferably 6 to 7%.

[0044] In the present invention, the modified saturated polyolefin preferably includes α,β-unsaturated carboxylic acid grafted polypropylene, α,β-unsaturated anhydride grafted polypropylene, α,β-unsaturated carboxylic acid grafted α-olefin / propylene copolymer or α,β-unsaturated anhydride grafted α-olefin / propylene copolymer; α,β-unsaturated carboxylic acid grafted polypropylene is preferably maleic acid grafted polypropylene; α,β-unsaturated anhydride grafted polypropylene is preferably maleic anhydride grafted polypropylene; α,β-unsaturated carboxylic acid grafted α-olefin / propylene copolymer is preferably ADI-1021 purchased from Shenyang Sinochem New Material Technology Co., Ltd.; α,β-unsaturated anhydride grafted α-olefin / propylene copolymer is preferably ADI-1011 purchased from Shenyang Sinochem New Material Technology Co., Ltd.; the grafting rate of the modified saturated polyolefin is preferably 0.5-3%, more preferably 1-2.5%, and more preferably 1.2-2%.

[0045] In the present invention, the organic solvent preferably includes one or more of benzene, toluene, xylene, cyclohexane, n-heptane, methylcyclohexane, acetone, butanone, ethyl acetate and ethyl propionate.

[0046] In the present invention, the first curing agent preferably includes one or more of polymer isocyanate and epoxy resin; the polymer isocyanate is preferably HDI trimer (CAS No. 3779-63-3), and the epoxy resin is preferably bisphenol A epoxy resin E51 (purchased from Baling Petrochemical).

[0047] In the present invention, the second curing agent preferably includes one or more of a polyol and a polythiol; the polythiol is preferably 1,10-decanedithiol, and the polyol is preferably 1,6-hexanediol.

[0048] In the present invention, the type of photoinitiator is preferably 2-hydroxy-2-methylphenylpropane-1-one, and the purpose of adding the photoinitiator is to promote the curing of the modified unsaturated polyolefin.

[0049] The invention also provides application of the inner layer adhesive in the aluminum-plastic film.

[0050] In the present invention, the application preferably comprises the following steps: applying an inner layer adhesive to the inner surface of the aluminum foil which has been laminated with an outer layer nylon film and cured, wherein the thickness of the adhesive layer after drying is 2 to 5 μm; then, laminating with a polypropylene film, and curing after laminating, and obtaining an aluminum-plastic film after curing.

[0051] In the present invention, the specific curing method is determined according to the type of base film by conventional means in the art; whether the photoinitiator is added is determined according to the curing method; preferably, the present invention provides a curing method: first, the polypropylene film layer is irradiated under ultraviolet light (365nm) for 10 minutes for photocuring, and then heated at 50-80°C for 3-5 days for thermal curing.

[0052] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0053] Example 1

[0054] Add 9 parts by mass of cis-polyisoprene (Mw=35000), 15 parts by mass of maleic anhydride, 0.05 parts by mass of 2,6-di-tert-butyl-p-cresol, and 160 parts by mass of xylene into a reactor, mix well, replace the air in the reaction system with nitrogen, stir and heat to 220°C, keep warm for 0.75h, and after the grafting modification is completed, naturally cool to room temperature, then wash and purify with butanone, and finally vacuum dry to obtain a modified unsaturated polyolefin (grafting rate is 7.1%);

[0055] Take 6 parts by mass of modified unsaturated polyolefin, 18 parts by mass of modified saturated polyolefin (purchased from Shenyang Sinochem New Material Technology Co., Ltd., model ADI-1021, grafting rate 1.3%) and 176 parts by mass of organic solvent (123 parts by mass of methylcyclohexane and 53 parts by mass of ethyl acetate) and mix them. After fully dissolving, add 8 parts by mass of the first curing agent (HDI trimer), 6 parts by mass of the second curing agent (1,10-decanedithiol) and 0.03 parts by mass of the photoinitiator (2-hydroxy-2-methylphenylpropane-1-one) to obtain an inner layer adhesive.

[0056] Example 2

[0057] Add 18 parts by mass of cis-polyisoprene (Mw=35000), 5 parts by mass of maleic anhydride, 0.05 parts by mass of 2,6-di-tert-butyl-p-cresol, and 160 parts by mass of xylene into a reactor, mix well, replace the air in the reaction system with nitrogen, stir and heat to 220°C, keep warm for 0.75h, and after the grafting modification is completed, naturally cool to room temperature, then wash and purify with butanone, and finally vacuum dry to obtain a modified unsaturated polyolefin (grafting rate is 4.2%);

[0058] Take 6 parts by mass of modified unsaturated polyolefin, 18 parts by mass of modified saturated polyolefin (purchased from Shenyang Sinochem New Material Technology Co., Ltd., model ADI-1021, grafting rate 1.3%) and 176 parts by mass of organic solvent (123 parts by mass of methylcyclohexane and 53 parts by mass of ethyl acetate) and mix them. After fully dissolving, add 8 parts by mass of the first curing agent (HDI trimer), 6 parts by mass of the second curing agent (1,10-decanedithiol) and 0.03 parts by mass of the photoinitiator (2-hydroxy-2-methylphenylpropane-1-one) to obtain an inner layer adhesive.

[0059] Comparative Example 1

[0060] Take 12 parts by mass of modified saturated polyolefin (purchased from Shenyang Sinochem New Material Technology Co., Ltd., model ADI-1021, grafting rate 1.3%) and 88 parts by mass of organic solvent (61.6 parts by mass of methylcyclohexane and 26.4 parts by mass of ethyl acetate), mix them, add 3 parts by mass of curing agent (HDI trimer) after fully dissolving, and obtain the inner layer adhesive.

[0061] Comparative Example 2

[0062] The modified unsaturated polyolefin was prepared in the same manner as in Example 1;

[0063] Take 6 parts by mass of modified unsaturated polyolefin and 44 parts by mass of organic solvent (31 parts by mass of methylcyclohexane and 13 parts by mass of ethyl acetate) and mix them. After fully dissolving, add 6.4 parts by mass of the first curing agent (HDI trimer), 6 parts by mass of the second curing agent (1,10-decanedithiol) and 0.03 parts by mass of the photoinitiator (2-hydroxy-2-methylphenylpropane-1-one) to obtain an inner layer adhesive.

[0064] Comparative Example 3

[0065] The modified unsaturated polyolefin was prepared by the same method as in Example 1;

[0066] Take 6 parts by mass of modified unsaturated polyolefin, 6 parts by mass of modified saturated polyolefin (purchased from Shenyang Sinochem New Material Technology Co., Ltd., model ADI-1021, grafting rate 1.3%) and 88 parts by mass of organic solvent (61.6 parts by mass of methylcyclohexane and 26.4 parts by mass of ethyl acetate) and mix them. After fully dissolving, add 7.2 parts by mass of the first curing agent (HDI trimer), 3 parts by mass of the second curing agent (1,10-decanedithiol) and 0.03 parts by mass of the photoinitiator (2-hydroxy-2-methylphenylpropane-1-one) to obtain an inner layer adhesive.

[0067] Comparative Example 4

[0068] The other conditions in Example 1 were kept unchanged, and the second curing agent and the photoinitiator were not added to obtain an inner layer adhesive.

[0069] Comparative Example 5

[0070] The other conditions in Example 1 were kept unchanged, and the amount of maleic anhydride used in the preparation of the modified unsaturated polyolefin was changed to 1 part by mass to obtain an inner layer adhesive.

[0071] The inner layer adhesives prepared in Examples 1 to 2 and Comparative Examples 1 to 5 were respectively coated on the inner surface of the aluminum foil that had been compounded with the outer layer nylon film and cured (the outer layer adhesive used was ADE-1522 from Shenyang Zhonghua New Material Technology Co., Ltd.), and the thickness of the inner layer dry adhesive was 2.5 μm. Then, the aluminum foil and the inner layer polypropylene film were compounded. After compounding, they were irradiated under an ultraviolet lamp (365 nm) for 10 minutes, and then heated at 60° C. for 4 days. After curing, an aluminum-plastic film was obtained. The aluminum-plastic film was subjected to performance tests, and the performance test results of different aluminum-plastic films were obtained, as shown in Table 1.

[0072] Among them, the room temperature peel strength test refers to "GB-T2791-1995 Adhesive T peel strength test method flexible material to flexible material", the aluminum-plastic film is cut into 15mm×20cm strips, and the inner layer of polypropylene film and the unbonded section of the aluminum foil layer are clamped on the upper and lower fixtures of the universal testing machine respectively. Start the testing machine and separate the upper and lower clamps at a speed of 100±10mm / min. The sample peeling length is at least 125mm. The high-temperature peel strength test refers to the normal temperature peel strength test method. The specimen is placed in a high-temperature universal testing machine for testing. The temperature is set to 120℃. The specimen is kept at 120℃ for 5 minutes before testing. The deep punching performance test uses an 18350 mold to observe whether delamination or even aluminum cracking occurs after deep punching, and the maximum punching depth without any abnormalities is recorded. The electrolyte resistance performance refers to the normal temperature peel strength test method. The specimen is placed in an 85℃ electrolyte and immersed for 7 days. After taking it out, wash it with clean water and wipe off the residual liquid, and then a peel strength test is performed. The electrolyte used is a 1.0 mol / LLiPF6 dimethyl carbonate-diethyl carbonate-ethylene carbonate (volume ratio 1:1:1) solution, and 1000ppm water is additionally added.

[0073] Table 1 Performance test results of different aluminum-plastic films

[0074]

[0075] As can be seen from Table 1, the inner layer adhesive of the aluminum-plastic film of a lithium battery prepared by the present invention with modified unsaturated polyolefin, modified saturated polyolefin, organic solvent, first curing agent and second curing agent exhibits good peel strength, resistance to electrolyte corrosion, resistance to deep impact and heat resistance. When the proportion of modified unsaturated polyolefin is too high, the film is relatively hard and brittle. Although it has high heat resistance, it loses deep impact resistance. When the grafting rate is too low, the introduction of modified unsaturated polyolefin may even make the product performance inferior to the performance of another component alone. Under specific conditions, the components of the embodiment of the present invention are well matched, the application performance is excellent and stable, and the heat resistance requirements of the inner layer adhesive of the aluminum-plastic film of lithium batteries can be met.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An inner layer adhesive, characterized in that: Contains the following components in parts by weight: 5 to 25 parts of modified unsaturated polyolefin, 40 to 100 parts of modified saturated polyolefin, 300 to 750 parts of organic solvent, 2 to 25 parts of first curing agent, 5 to 20 parts of second curing agent and 0 to 0.05 parts of photoinitiator.

2. The inner layer adhesive according to claim 1, characterized in that: The preparation method of the modified unsaturated polyolefin comprises the following steps: Under an inert atmosphere, unsaturated polyolefin, unsaturated modifier, antioxidant and solvent are mixed and grafted to obtain modified unsaturated polyolefin.

3. The inner layer adhesive according to claim 2, characterized in that: The unsaturated polyolefin includes one or more of polybutadiene, polyisoprene, styrene-butadiene copolymer, isobutylene-isoprene copolymer, styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer; The unsaturated modifier includes one or more of α,β-unsaturated carboxylic acid and α,β-unsaturated anhydride; The antioxidant includes one or more of 2,6-di-tert-butyl-p-cresol, 9,9-dimethylacridine and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; The solvent includes one or more of xylene, terphenyl, dodecane, α-chloronaphthalene and sulfolane.

4. The inner layer adhesive according to claim 2 or 3, characterized in that: The mass ratio of the unsaturated polyolefin, the unsaturated modifier, the antioxidant and the solvent is 0.3-2: 0.4-2: 0.005-0.04: 6-25; The graft modification temperature is 170-260°C, and the graft modification time is 0.2-10h; The grafting rate of the modified unsaturated polyolefin is 4-9%.

5. The inner layer adhesive according to claim 1, characterized in that: The modified saturated polyolefin includes α,β-unsaturated carboxylic acid grafted polypropylene, α,β-unsaturated acid anhydride grafted polypropylene, α,β-unsaturated carboxylic acid grafted α-olefin / propylene copolymer or α,β-unsaturated acid anhydride grafted α-olefin / propylene copolymer; the grafting rate of the modified saturated polyolefin is 0.5-3%.

6. The inner layer adhesive according to claim 1 or 5, characterized in that: The organic solvent includes one or more of benzene, toluene, xylene, cyclohexane, n-heptane, methylcyclohexane, acetone, butanone, ethyl acetate and ethyl propionate.

7. The inner layer adhesive according to claim 6, characterized in that: The first curing agent includes one or more of polymer isocyanate and epoxy resin.

8. The inner layer adhesive according to claim 7, characterized in that: The second curing agent includes one or more of polyol and polythiol.

9. Use of the inner layer adhesive according to any one of claims 1 to 8 in aluminum-plastic films.

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