Aluminum-plastic film adhesive for lithium battery soft pack and preparation method thereof

Abstract

The present invention relates to the technical field of adhesives, and in particular to an aluminum-plastic film adhesive for lithium battery soft packs and a preparation method thereof. The adhesive comprises the following components in parts by weight: 100 parts of a polyolefin resin, 1-5 parts of a boric acid ester, 0.5-1 parts of a borane, 0.5-1 parts of a boric acid, 0.5-2 parts of an allyl diepoxypropyl isocyanate, and 0.1-0.5 parts of a peroxide initiator. The allyl diepoxypropyl isocyanate in the present invention can greatly improve the adhesion between the polyolefin resin and polypropylene (PP) and aluminum foil. Under the initiation of the initiator, the double bonds of the allyl diepoxypropyl isocyanate undergo a grafting reaction with the polyolefin, thereby grafting the allyl diepoxypropyl isocyanate onto the polyolefin. Simultaneously, the epoxy bonds react with the boric acid, the boric acid ester, and the borane. Furthermore, the carbonyl groups and N atoms on the allyl diepoxypropyl isocyanate molecules both increase the polarity of the polyolefin, and can generate weak bonding reactions with the boron atoms and the aluminum foil.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, in particular to an aluminum-plastic film adhesive for lithium battery soft packages and a preparation method thereof. Background Art

[0002] The aluminum-plastic film used in lithium battery soft packs is made of PP, nylon, and aluminum foil. The bonding between PP and aluminum foil is very difficult, mainly because 1) the surface of aluminum foil is smooth and not easy to adhere to objects; the surface of PP is hydrophobic and has low surface energy, which is also difficult to bond; 2) PP's extremely low surface tension and low melting point make it difficult to combine with other materials.

[0003] In order to achieve effective bonding between PP and aluminum foil, the following methods can be used:

[0004] 1. Surface treatment:

[0005] 1) Mechanical grinding: By grinding the PP surface to increase its roughness, the bonding effect is improved. However, this method may not be suitable for all cases and may damage the material surface.

[0006] 2) Primer treatment: Apply a layer of primer to the PP surface. This primer can produce a good bonding effect with both PP and aluminum foil. This method is relatively simple and effective, but it requires the selection of a suitable primer.

[0007] 3) Plasma treatment: Utilizes the high energy of plasma to modify the PP surface, increasing its surface energy and thus enhancing the bonding effect. This method is suitable for large-scale production, but the cost is relatively high.

[0008] 2. Heating and pressing:

[0009] Glue the PP and aluminum foil together according to the bonding position and heat and press them together to make them tightly bonded. The heating temperature should be determined according to the different PP and aluminum foil. It should not be too high or too low to avoid affecting the performance of the product or causing loose bonding.

[0010] The adhesives currently used in the industry mainly come from Toa Synthetics of Japan. With the development of the industry, the bonding strength and electrolyte resistance need to be further improved. Summary of the Invention

[0011] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an aluminum-plastic film adhesive for lithium battery soft packs and a preparation method thereof.

[0012] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0013] An aluminum-plastic film adhesive for lithium battery soft packs, comprising the following components by weight:

[0014] 100 parts of polyolefin resin,

[0015] 1-5 parts of borate ester,

[0016] 0.5-1 part of borane,

[0017] 0.5-1 part of boric acid,

[0018] Allyl diepoxypropyl triisocyanate 0.5-2 parts,

[0019] Peroxide initiator 0.1-0.5 parts.

[0020] Furthermore, the polyolefin resin is selected from one of PP, PE, TPO and POE.

[0021] Furthermore, the borate ester is selected from one or more of trimethyl borate, triethyl borate, tributyl borate, triisopropyl borate, and triethanolamine borate.

[0022] Furthermore, the borane is tributylborane.

[0023] Furthermore, the peroxide initiator is selected from at least one of a bis-25 initiator and a TBEC initiator, wherein the bis-25 initiator is also known as DBPH (2,5-dimethyl-2,5-peroxy)hexane).

[0024] A method for preparing an aluminum-plastic film adhesive for a lithium battery soft pack, the preparation method being as follows:

[0025] The binder is obtained by mixing a polyolefin resin, borate, borane, boric acid, allyl diglycidyl isocyanate and a peroxide initiator and extruding and granulating the mixture at 150° C.

[0026] The beneficial effects of adopting the technical solution of the present invention are:

[0027] The allyl diepoxypropyl isocyanate in the present invention can greatly improve the adhesion between polyolefin resin and PP and aluminum foil. Under the initiation of an initiator, the double bond of the allyl diepoxypropyl isocyanate undergoes a grafting reaction with the polyolefin, thereby grafting the allyl diepoxypropyl isocyanate onto the polyolefin. At the same time, the epoxy bond reacts with boric acid, boric ester, and borane. The carbonyl group and N atom on the allyl diepoxypropyl isocyanate molecule both increase the polarity of the polyolefin, and can produce weak bonding with the boron atom and the aluminum foil. The allyl diepoxypropyl isocyanate acts as a bridge between the polyolefin and the borane. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific implementation methods and description.

[0029] The polyolefin resin in the present invention is PE resin Sumitomo CB1001.

[0030] An aluminum-plastic film adhesive for lithium battery soft packs, comprising the following components by weight:

[0031] 100 parts of polyolefin resin,

[0032] 1-5 parts of borate ester,

[0033] 0.5-1 part of borane,

[0034] 0.5-1 part of boric acid,

[0035] Allyl diepoxypropyl triisocyanate 0.5-2 parts,

[0036] Peroxide initiator 0.1-0.5 parts.

[0037] Allyl diepoxypropyl isocyanate, namely T1, has the structural formula:

[0038]

[0039] Among them, the polyolefin resin is selected from one of PP, PE, TPO and POE.

[0040] The borate ester is selected from one or more of trimethyl borate, triethyl borate, tributyl borate, triisopropyl borate, and triethanolamine borate.

[0041] Wherein, the borane is tributylborane.

[0042] The peroxide initiator is selected from at least one of a bis-25 initiator and a TBEC initiator, wherein the bis-25 initiator is also known as DBPH (2,5-dimethyl-2,5-peroxy) hexane).

[0043] The preparation method of the aluminum-plastic film adhesive for lithium battery soft packs in the present invention is as follows: polyolefin resin, borate, borane, boric acid, allyl diepoxypropyl triisocyanate and peroxide initiator are mixed and extruded and granulated at 150° C. to obtain the adhesive. Example

[0044] The PE resin Sumitomo CB1001 was used, with 100 parts and 0.3 parts of Bis-25 initiator. The remaining ingredients were as shown in the table below. The pellets were extruded and pelletized at 150°C. The pellets were dissolved in cyclohexane, coated on polypropylene (PP), dried, and heat-laminated at 100°C. The PP adhesion was measured by tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on aluminum foil, drying, heat-laminated at 100°C, and tearing the pellets on a tensile testing machine at 180°C. The aluminum foil adhesion was also measured by tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on PP, drying, heat-laminated at 100°C, and tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on PP, drying, heat-laminated at 100°C, and soaking the pellets in electrolyte for 48 hours to observe whether the aluminum foil and PP separated. See Table 1 for details.

[0045] Table 1

[0046] As shown in Table 1, triethanolamine borate improves the adhesion of the resin to both PP and aluminum foil. This is because, under heating, the ester bond of triethanolamine borate can remove the amino molecule, generating a transition state of monomolecular boric acid, which reacts with the polyolefin and aluminum foil to form a bond. Tributylborane can also improve the adhesion to PP and aluminum foil, but to a lesser extent. This is because tributylborane, upon contact with water, generates a transition state of monomolecular boric acid, which further reacts with both PP and aluminum foil. However, since tributylborane requires water and has a boiling point of 200°C, it is easily volatile and lost, so its effectiveness is limited. Boric acid significantly improves the adhesion to aluminum foil, but not to PP. This is primarily because boric acid is a solid, aggregated state consisting of numerous boric acid molecules, making it difficult to react uniformly with PP and polyolefins. However, it concentrates the acid on the surface of the aluminum foil, where it corrodes more effectively. T1 can significantly improve the adhesion of polyolefin resins to PP and aluminum foil. This is because, under the influence of an initiator, T1's double bonds undergo a grafting reaction with the polyolefin, thereby grafting T1 onto the polyolefin. Simultaneously, the epoxy bond reacts with boric acid, borate ester, and borane. Furthermore, the carbonyl group and nitrogen atom on the T1 molecule increase the polarity of the polyolefin, enabling weak bonding with boron atoms and aluminum foil. T1 acts as a bridge between the polyolefin and borane. However, excessive T1 increases the polarity of the polyolefin and increases the number of unreacted small T1 molecules, affecting adhesion and electrolyte resistance. A suitable amount is 0.5-2 parts.

[0047] Example 2

[0048] The PE resin Sumitomo CB1001 was used, with 100 parts and 0.3 parts of Bis-25 initiator. The remaining ingredients were as shown in the table below. The pellets were extruded and pelletized at 150°C. The pellets were dissolved in cyclohexane, coated on polypropylene (PP), dried, and heat-laminated at 100°C. The PP adhesion was measured by tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on aluminum foil, dried, heat-laminated at 100°C, and tearing the pellets on a tensile testing machine at 180°C. The aluminum foil adhesion was also measured by tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on PP, dried, heat-laminated at 100°C, and tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on PP, dried, heat-laminated at 100°C, and immersed in electrolyte for 48 hours to observe whether the aluminum foil and PP separated. See Table 2 for details.

[0049] Table 2 Example

[0050] The PE resin Sumitomo CB1001 was used, with 100 parts and 0.3 parts of Bis-25 initiator. The remaining ingredients were as shown in the table below. The pellets were extruded and pelletized at 150°C. The pellets were dissolved in cyclohexane, coated on polypropylene (PP), dried, and heat-laminated at 100°C. The PP adhesion was measured by tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on aluminum foil, drying, heat-laminated at 100°C, and tearing the pellets on a tensile testing machine at 180°C. The aluminum foil adhesion was also measured by tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on PP, drying, heat-laminated at 100°C, and tearing the pellets on a tensile testing machine at 180°C. The PP adhesion was also measured by coating on PP, drying, heat-laminated at 100°C, and soaking the pellets in electrolyte for 48 hours to observe whether the aluminum foil and PP separated. See Table 3 for details.

[0051] Table 3

[0052] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent claim scheme. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. An aluminum-plastic film adhesive for lithium battery soft pack, characterized in that: Its mass composition is as follows: 100 parts of polyolefin resin, 1-5 parts of borate ester, 0.5-1 part of borane, 0.5-1 part of boric acid, Allyl diepoxypropyl triisocyanate 0.5-2 parts, Peroxide initiator 0.1-0.5 parts.

2. The aluminum-plastic film adhesive for lithium battery soft pack according to claim 1, characterized in that: The polyolefin resin is selected from one of PP, PE, TPO and POE.

3. The aluminum-plastic film adhesive for lithium battery soft pack according to claim 1, characterized in that: The borate ester is selected from one or more of trimethyl borate, triethyl borate, tributyl borate, triisopropyl borate, and triethanolamine borate.

4. The aluminum-plastic film adhesive for lithium battery soft pack according to claim 1, characterized in that: The borane is tributylborane.

5. The aluminum-plastic film adhesive for lithium battery soft pack according to claim 1, characterized in that: The peroxide initiator is selected from one of bis-25 initiator and TBEC initiator.

6. A method for preparing an aluminum-plastic film adhesive for lithium battery soft packs according to any one of claims 1 to 5, characterized in that: The preparation method is as follows: The binder is obtained by mixing a polyolefin resin, borate, borane, boric acid, allyl diglycidyl isocyanate and a peroxide initiator and extruding and granulating the mixture at 150° C.

Images