An inner adhesive for an aluminum-plastic film with high peeling strength, a preparation method and application thereof

Abstract

The present application relates to a kind of inner layer adhesive for high peel strength of aluminium plastic film and its preparation method, application, it is composed of main agent and curing agent, wherein, the main agent includes the following weight percentage content of each component: maleic anhydride silane modified polyolefin 10%-20%, solvent A 80-90%;The curing agent uses isocyanate curing agent.The maleic anhydride silane modified polyolefin is mixed with polyolefin, maleic anhydride, double bond silane coupling agent, diisopropylbenzene peroxide, solvent B, is obtained under the condition of stirring in inert gas, heating reaction.Gains the following beneficial effects compared with prior art: 1, high firmness with aluminium foil;2, high peel strength;3, high liquid resistance.

Description

Technical Field

[0001] This invention relates to the field of aluminum-plastic film inner layers, and particularly to an inner layer adhesive for aluminum-plastic films with high peel strength, its preparation method, and its application. Background Technology

[0002] Lithium-ion battery soft-pack packaging offers advantages such as superior safety, light weight, large capacity, and excellent cycle performance, gradually replacing traditional square and cylindrical battery packaging. Furthermore, soft-pack batteries are environmentally friendly and durable, leading to rapid growth in the 3C and power battery industries. Generally, aluminum-plastic film is composed of polypropylene, aluminum foil, and nylon. However, the commonly used aluminum-plastic film for lithium batteries comes into direct contact with highly corrosive electrolytes and generates heat during use in high-temperature environments. If the aluminum-plastic film is not corrosion-resistant, problems such as aluminum foil perforation, leakage, and short circuits can occur, significantly impacting battery life. The inner adhesive layer, which bonds the stretched polypropylene film and aluminum foil, must possess high-temperature and corrosion resistance.

[0003] However, most of the inner layer adhesives on the market currently focus on electrolyte resistance at 85°C, while their ultra-high temperature peel strength above 100°C is relatively low and cannot meet the requirements for high-temperature use. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high peel strength inner layer adhesive for aluminum-plastic films, its preparation method, and its application. It is a two-component adhesive composition that is resistant to electrolyte corrosion and maintains high peel strength even at high temperatures.

[0005] The objective of this invention can be achieved through the following methods:

[0006] This invention provides an inner layer adhesive for aluminum-plastic film that is resistant to high temperature and corrosion, comprising a main agent and a curing agent, wherein the mass ratio of the main agent to the curing agent is 100:3-10; The main agent comprises the following components in weight percentages: Maleic anhydride silane modified polyolefin 10%-20% Solvent A: 80%-90%.

[0007] As one embodiment of the present invention, the maleic anhydride silane-modified polyolefin is prepared by the following method: The polyolefin, maleic anhydride, double-bonded silane coupling agent, diisopropyl peroxide, and solvent B are mixed and heated under stirring in an inert gas atmosphere to obtain the product.

[0008] The raw materials used, by weight, are as follows: 40-80 parts polyolefin, 3-10 parts maleic anhydride, 3-5 parts double bond silane coupling agent, 0.1-1 parts diisopropyl peroxide, and 4-53.9 parts solvent B.

[0009] Preferably, per 100 parts, the composition is 40-80 parts polyolefin, 3-10 parts maleic anhydride, 3-5 parts double bond silane coupling agent, 0.1-1 parts diisopropyl peroxide, and 4-53.9 parts solvent B.

[0010] The polyolefin includes one or more of polypropylene (PP), polypropylene-butene polymer (PP-PB), and chlorinated polypropylene (CPP).

[0011] The double-bonded silane coupling agent includes one or more of γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and allyltrimethoxysilane.

[0012] Solvent B includes one or more of toluene, xylene, cyclohexane, and methylcyclohexane.

[0013] The stirring speed is 100-500 r / min.

[0014] The inert gas includes nitrogen.

[0015] The heating reaction is carried out at a temperature of 100-180℃ for 2-10 h. The reaction is continued until a precipitate is completely formed, the filtrate is released, and the product is dried under vacuum to obtain maleic anhydride silane-modified polyolefin.

[0016] In one embodiment of the present invention, solvent A is solvent A1 or a mixed solvent containing solvent A1. In the mixed solvent, the mass fraction of solvent A1 is not less than 60%. The mixed solvent includes solvent A2 (solvent A is 60-100% solvent A1 and 0-40% solvent A2 by mass fraction).

[0017] Solvent A1 includes one or more of toluene, xylene, cyclohexane, and methylcyclohexane.

[0018] Solvent A2 includes one or more of butanone and ethyl acetate.

[0019] As one embodiment of the present invention, the curing agent includes one or more of 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), isophthalic dimethyl isocyanate (XDI), and cyclohexanedimethyl diisocyanate (HXDI).

[0020] The present invention also provides a method for preparing the inner layer adhesive for the aluminum-plastic film, comprising the following steps: S1. Maleic anhydride silane modified polyolefin and solvent A are mixed and reacted under stirring conditions to obtain the main agent; S2. Mix the main agent and the curing agent to obtain the inner layer adhesive for aluminum-plastic film.

[0021] In one embodiment of the present invention, in step S1, the stirring speed is 100-500 r / min.

[0022] In one embodiment of the present invention, in step S1, the temperature of the heating reaction is 40-70°C and the time is 1-4 hours.

[0023] When using the inner layer adhesive for aluminum-plastic film of the present invention, the prepared main agent is simply mixed with the curing agent.

[0024] The present invention also provides the application of the inner layer adhesive for the aluminum-plastic film in the preparation of lithium battery soft packs.

[0025] As one embodiment of the present invention, the application is to use an inner layer adhesive for aluminum-plastic film for interfacial bonding between aluminum foil and stretched polypropylene film.

[0026] The present invention relates to a novel high-temperature corrosion resistant inner layer adhesive for aluminum-plastic film. The inner layer adhesive combination is used for bonding aluminum foil to stretched polypropylene film, and is resistant to high temperature and electrolyte corrosion, thus applicable to 3C and power fields such as lithium battery soft packs.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) Maleic anhydride can be copolymerized with double bond silane coupling agents to increase the grafting rate of maleic anhydride. Compared with traditional maleic anhydride grafted modified polyolefins, it can achieve a higher grafting rate. The copolymerization reaction can also reduce the residual maleic anhydride monomer and avoid the consumption of initiator due to the residual monomer in the system. (2) The curing agent is an isocyanate curing agent, which has a fast reaction rate and is not easily hydrolyzed. It can be cured with maleic anhydride to form a polyimide structure with high strength and has good resistance to electrolyte corrosion. (3) The other end of the double-bonded silane coupling agent is a siloxane group, and each silane coupling agent monomer contains 3 siloxane groups, which can hydrolyze and condense with each other and undergo rapid cross-linking and curing reactions with the hydroxyl groups on the aluminum foil to form a dense cross-linked network. The non-polar polyolefin backbone is connected to the aluminum foil through chemical bonds via silane side chains, which can significantly improve the adhesion between the inner layer adhesive and the aluminum foil surface. In addition, the double bonds in the silane coupling agent monomers selected in this invention have high reactivity, and the siloxane groups are all methoxy groups, which have a faster hydrolysis rate and better stability within the system. Moreover, the chemical bond energy of the silane cross-linked network is high, and it is very stable at high temperatures, still having high peel strength under high temperature conditions. Although the subsequent addition of silane coupling agent can also achieve cross-linking with the aluminum foil, there is no chemical bond link with the backbone of the inner layer adhesive. Even if reactive groups are added, there are limiting factors such as steric hindrance, polarity difference, and reaction rate, which cannot achieve high peel strength. Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0029] Example 1 A novel high-temperature corrosion resistant inner layer adhesive for aluminum-plastic films comprises an inner layer adhesive and a curing agent, and its preparation method is as follows: (1) Maleic anhydride silane modified polyolefin: Modified polyolefin 1 was prepared by reacting 50g of polypropylene, 5g of maleic anhydride, 3g of γ-methacryloyloxypropyltrimethoxysilane, 0.1g of diphenylpropane peroxide, and 41.9g of toluene at 120℃ for 3h under nitrogen protection and a rotation speed of 100r / min, followed by precipitation and drying.

[0030] (2) Main ingredient: Maleic anhydride silane modified polyolefin 1 17g, cyclohexane 49.2g, and butanone 32.8g were stirred at 40℃ for 1h at a speed of 100r / min to obtain the product. (3) Adhesive: Add 5g of HDI as a curing agent to the prepared main agent and mix well to obtain the inner layer adhesive for aluminum-plastic film.

[0031] Examples 2-7 A novel high-temperature corrosion resistant inner layer adhesive for aluminum-plastic film differs from that in Example 1 in that its maleic anhydride silane modified polyolefin composition, functional additives, solvent composition, type and amount of curing agent are all different, as shown in Table 1. Otherwise, the operation is the same as in Example 1, and then a lithium battery soft packaging aluminum-plastic film is prepared.

[0032] Table 1 Components and dosages of the examples

[0033] The modified polyolefin raw materials used are shown in Table 2.

[0034] Table 2. Components and dosage of modified polyolefins

[0035] Comparative Example 1 The formulation and method of this comparative example are basically the same as those of Example 1, except that the content of the double bond silane coupling agent is 0.

[0036] Comparative Example 2 The formulation and method of this comparative example are basically the same as those of Example 1, except that the content of double bond silane coupling agent is 0, and 3g of γ-methacryloyloxypropyltrimethoxysilane is added to the main agent.

[0037] Comparative Example 3 The application of this comparative example is basically the same as that of Example 1, except that the inner layer adhesive used is PMA-KH, a product of Toyobo Co., Ltd. of Japan.

[0038] Comparative Examples 4-6 The application of this comparative example is basically the same as that of Example 1, and the composition is shown in Table 3. The difference is that the double bond silane coupling agent is different, as shown in Table 2.

[0039] Table 3

[0040] Application of the novel high-temperature corrosion resistant inner layer adhesive for aluminum-plastic films of this invention: The adhesives prepared in the examples and comparative examples were used to prepare battery packaging materials with an inner resin film / inner adhesive / aluminum foil / outer adhesive / thermoplastic resin film structure by dry lamination. The details of each layer are as follows: Inner resin film: stretched polypropylene film (40μm thick); Inner layer adhesive: A new type of high-temperature corrosion resistant inner layer adhesive for aluminum-plastic film (coating amount 3g / m²) 2 ); Aluminum foil layer: Aluminum foil (40μm thick); Outer adhesive: VN930 / CA-N6 combination, product of Shanghai Weikai Optoelectronic New Materials Co., Ltd. (coating amount 4g / m²) 2 ); Thermoplastic resin film: stretched nylon film (25μm thick).

[0041] The physical properties of the modified polyolefins are shown in Table 4.

[0042] Table 4

[0043] Performance tests are shown in Table 5.

[0044] Table 5 Comparison of Experimental Results

[0045] The test methods are shown in Table 6: Table 6

[0046] As shown in Table 5, under the same experimental conditions, the example is far superior to the comparative example in terms of electrolyte resistance and high-temperature peel strength, and has a significant improvement in the corrosion resistance of aluminum-plastic film.

[0047] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A high-temperature corrosion resistant inner layer adhesive for aluminum-plastic films, characterized in that, It includes a main agent and a curing agent, with a mass ratio of 100:3-10; The main agent comprises the following components in weight percentages: Maleic anhydride silane modified polyolefin 10%-20% Solvent A 80%-90%; The maleic anhydride silane-modified polyolefin was prepared by the following method: The polyolefin, maleic anhydride, double-bonded silane coupling agent, diisopropyl peroxide, and solvent B are mixed and heated under stirring in an inert gas atmosphere to obtain the product. The double-bonded silane coupling agent includes one or more of γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and allyltrimethoxysilane.

2. The inner layer adhesive for aluminum-plastic film as described in claim 1, characterized in that, The raw materials used in the preparation of maleic anhydride silane modified polyolefin are as follows by weight: 40-80 parts polyolefin, 3-10 parts maleic anhydride, 3-5 parts double bond silane coupling agent, 0.1-1 parts diisopropyl peroxide, and 4-53.9 parts solvent B.

3. The inner layer adhesive for aluminum-plastic film as described in claim 1, characterized in that, The polyolefin includes one or more of polypropylene, polypropylene-butene polymer, and chlorinated polypropylene; And / or, the solvent B includes one or more of toluene, xylene, cyclohexane, and methylcyclohexane.

4. The inner layer adhesive for aluminum-plastic film as described in claim 1, characterized in that, The heating reaction is carried out at a temperature of 100-180℃ for 2-10 hours.

5. The inner layer adhesive for aluminum-plastic film as described in claim 1, characterized in that, Solvent A is solvent A1 or a mixed solvent containing solvent A1; in the mixed solvent, the mass fraction of solvent A1 is not less than 60%; Solvent A1 includes one or more of toluene, xylene, cyclohexane, and methylcyclohexane; Solvent A2 includes one or more of butanone and ethyl acetate.

6. The inner layer adhesive for aluminum-plastic film as described in claim 1, characterized in that, The curing agent includes one or more of 1,6-hexamethylene diisocyanate, isophorone diisocyanate, isophthalic dimethyl isocyanate, and cyclohexanedimethyl diisocyanate.

7. A method for preparing the inner layer adhesive for aluminum-plastic film as described in claim 1, characterized in that, Includes the following steps: S1. Maleic anhydride silane modified polyolefin and solvent A are mixed and reacted under stirring conditions to obtain the main agent; S2. Mix the main agent and the curing agent to obtain the inner layer adhesive for aluminum-plastic film.

8. The preparation method according to claim 7, characterized in that, In step S1, the temperature of the heating reaction is 40-70℃, and the time is 1-4 h.

9. The application of the inner layer adhesive for aluminum-plastic film as described in claim 1 in the preparation of lithium battery soft packs.

10. The application as described in claim 9, characterized in that, In the preparation of lithium battery soft packs, the inner layer adhesive of the aluminum-plastic film is used for the interfacial bonding of the aluminum foil of the aluminum-plastic film and the stretched polypropylene film.

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