Aluminum-plastic film outer layer structure and aluminum-plastic film production process

Abstract

The present application belongs to the technical field of aluminum-plastic film, and particularly relates to an aluminum-plastic film outer layer structure and a production process of the aluminum-plastic film. The aluminum-plastic film outer layer structure can be a two-layer or three-layer structure. The two-layer structure comprises a support layer on the outer side and a water barrier layer on the inner side of the support layer. The three-layer structure further comprises a bonding layer between the support layer and the water barrier layer on the basis of the two-layer structure. The present application effectively improves the bonding strength and the waterproof performance by redesigning the aluminum-plastic film outer layer structure and the bonding mechanism, and the risk problem caused by the failure of the polyurethane adhesive due to water vapor intrusion is solved. Even in a high-temperature and high-humidity environment, the bonding strength can still be maintained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum-plastic film, and particularly relates to an aluminum-plastic film outer layer structure and a production process of the aluminum-plastic film. BACKGROUND

[0002] Lithium battery packaging has become a widely used packaging form, and its main structure is in the order from inside to outside: an inner protective layer, an aluminum foil layer and an outer protective layer, wherein the main material of the outer protective layer is polyamide (PA). Polyamide has high requirements on impact resistance, puncture resistance, heat resistance, friction resistance and the like, and its role is to protect the aluminum foil layer from being scratched and to provide sufficient deformation strength for the aluminum foil to ensure that the aluminum foil is not broken in the forming process.

[0003] However, polyamide itself has strong hygroscopicity, which leads to poor water resistance, so that water vapor easily passes through the polyamide layer to reach the polyurethane adhesive layer. Water vapor can cause the polyurethane adhesive to hydrolyze, resulting in adhesion failure and causing the outer protective layer to fall off, greatly increasing the use risk of the battery. At the same time, a high-temperature environment can further accelerate the hydrolysis process of the polyurethane adhesive.

[0004] To overcome the above problems, the prior art uses a polyamide layer combined with a PET film to slow down the process of water vapor intrusion. However, the addition of PET can also lead to a decrease in the adhesion strength of the polyurethane, and under a high-temperature and high-humidity test environment, the outer layer still falls off due to local failure of the polyurethane adhesive, indicating that the addition of PET can only slow down the process, but cannot completely solve the fundamental problem of adhesion failure caused by water vapor intrusion. SUMMARY

[0005] The purpose of the present application is to provide an aluminum-plastic film outer layer structure and a production process of the aluminum-plastic film to solve the risk problem caused by the failure of the polyurethane adhesive due to water vapor intrusion, that is, to maintain a certain adhesion strength even in a high-temperature and high-humidity environment.

[0006] To solve the above technical problems, the present application provides an aluminum-plastic film outer layer structure, which comprises a support layer on the outer side and a water barrier layer on the inner side of the support layer; wherein the support layer is made of polyamide; and the water barrier layer is made of polyolefin.

[0007] Further, the water barrier layer is an anhydride grafted polyolefin, and the anhydride grafting rate is 0.5-1.5%.

[0008] Further, the anhydride grafted polyolefin is maleic anhydride grafted linear low-density polyethylene.

[0009] Further, the outer layer structure of the aluminum-plastic film further comprises an adhesive layer between the support layer and the water barrier layer; the adhesive layer comprises one or a combination of ethylene-vinyl alcohol, EVA, olefin-hydroxyl copolymer, olefin-carboxylic acid copolymer, olefin-amine copolymer, maleic anhydride grafted polyolefin, epoxy grafted polyolefin, and carboxylic acid grafted polyolefin.

[0010] Further, the adhesive layer is ethylene-vinyl alcohol.

[0011] In another aspect, the application further provides an aluminum-plastic film, comprising: an inner layer and an aluminum foil, and an outer layer structure of the aluminum-plastic film as described above on the outer side of the aluminum foil; wherein the aluminum foil is an aluminum foil with a surface modified by one of an amino silane coupling agent, an isocyanate silane coupling agent, and an amino resin adhesive.

[0012] In another aspect, the application further provides a lithium battery packaged by the aluminum-plastic film as described above.

[0013] In another aspect, the application further provides a production process of the aluminum-plastic film, comprising: producing the outer layer of the aluminum-plastic film in the form of co-extrusion; modifying the surface of the aluminum foil; and pasting the water barrier layer of the outer layer of the aluminum-plastic film and the treated surface of the aluminum foil together, and then pressing them together by a high-temperature hot roller at 160°C and cooling and rolling them up.

[0014] Further, the outer layer of the aluminum-plastic film is a two-layer or three-layer structure; the two-layer structure comprises: a support layer on the outer side and a water barrier layer on the inner side of the support layer; wherein the support layer is made of polyamide, and the water barrier layer is maleic anhydride grafted linear low-density polyethylene; the three-layer structure further comprises an adhesive layer between the support layer and the water barrier layer on the basis of the two-layer structure; wherein the adhesive layer comprises one or a combination of ethylene-vinyl alcohol, EVA, olefin-hydroxyl copolymer, olefin-carboxylic acid copolymer, olefin-amine copolymer, maleic anhydride grafted polyolefin, epoxy grafted polyolefin, and carboxylic acid grafted polyolefin.

[0015] Further, the modification of the surface of the aluminum foil comprises: dissolving the amino silane coupling agent in an alcohol-water solvent and mixing them uniformly, wherein the alcohol is 60-80%, the water is 5-15%, and the amino silane coupling agent is 15-25%; and then spraying or coating the mixed solution on the surface of the aluminum foil at a dispersion of 10-15 g / m2, and then entering a 110-130°C air duct for baking for 15-20 seconds, and then rolling up after drying.

[0016] The beneficial effects of this invention are that, by redesigning the outer layer structure and bonding mechanism of the aluminum-plastic film, the bonding strength is effectively improved and the waterproof performance is significantly improved compared with the existing process solutions; it solves the risk problem caused by the failure of polyurethane adhesive due to moisture intrusion, and can still maintain a certain bonding strength even in high temperature and high humidity environments.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the outer layer structure of the two-layer aluminum-plastic film according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the outer layer structure of the three-layer aluminum-plastic film according to an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1 As shown, this embodiment 1 provides a two-layer aluminum-plastic film outer layer structure, including: a support layer located on the outer side and a waterproof layer located on the inner side of the support layer; wherein the support layer is made of polyamide material; and the waterproof layer is made of polyolefin material.

[0025] In this embodiment, preferably, the support layer is made of polyamide material, which provides performance requirements such as impact resistance, puncture resistance, heat resistance, and abrasion resistance.

[0026] Further preferably, the waterproof layer is preferably an anhydride-grafted polyolefin; wherein, the anhydride grafting rate is 0.5-1.5%. If the grafting rate is too low, the reaction with the aluminum foil is insufficient and the bonding strength is low; if the grafting rate is high, the water absorption of the waterproof layer is too high. Optionally, the grafting rate can be 0.5%, 0.8%, 1.0%, 1.3%, or 1.5%.

[0027] Further preferably, in order to meet the requirements of water resistance, stress, tear resistance, and weather resistance after deep drawing, the waterproof layer can preferably be linear low-density polyethylene (LLDPE), which can be maleic anhydride-grafted linear low-density polyethylene.

[0028] Example 2

[0029] like Figure 2 As shown in the figure, based on Embodiment 1, Embodiment 2 provides a three-layer aluminum-plastic film outer layer structure, which further includes an adhesive layer located between the support layer and the waterproof layer.

[0030] In this embodiment, optionally, the adhesive layer includes one or a combination of several of the following: ethylene-vinyl alcohol, EVA, olefin-hydroxy copolymer, olefin-carboxylic acid copolymer, olefin-amine copolymer, maleic anhydride grafted polyolefin, epoxy grafted polyolefin, and carboxylic acid grafted polyolefin.

[0031] In order to enhance the tensile strength of the outer layer and thus increase the drawing depth, the adhesive layer is preferably ethylene-vinyl alcohol.

[0032] Further preferably, to ensure the adhesive layer can effectively react onto the aluminum foil, the waterproof layer is preferably an anhydride-grafted polyolefin; wherein, the anhydride grafting rate is 0.5% to 1.5%. If the grafting rate is too low, the reaction with the aluminum foil will be insufficient and the bonding strength will be low; if the grafting rate is too high, the water absorption of the waterproof layer will be too high. Optionally, the grafting rate can be 0.5%, 0.8%, 1.0%, 1.3%, or 1.5%. Further preferably, to meet the requirements for water resistance, stress, tear resistance, and weather resistance after deep drawing, the waterproof layer can preferably be linear low-density polyethylene (LLDPE), which can be maleic anhydride-grafted linear low-density polyethylene.

[0033] In this embodiment, the three-layer structure can achieve high drawing depth (≥6.5mm) by adjusting the thickness ratio of the three layers, but the cost is relatively high; the two-layer structure has a low cost and is suitable for low drawing depth.

[0034] Example 3

[0035] Based on the above embodiments, this embodiment 3 provides an aluminum-plastic film, including: an inner layer and an aluminum foil, and an outer layer structure of aluminum-plastic film as described above located outside the aluminum foil; wherein the aluminum foil is an aluminum foil that has been surface modified using one of amino silane coupling agents, isocyanate silane coupling agents, and amino resin adhesives.

[0036] In this embodiment, the outer layer structure of the aluminum-plastic film can be produced by co-extrusion. In order to better bond the waterproof layer with the aluminum foil and improve the bonding strength and weather resistance, relying solely on anchoring force and non-covalent bond force is far from sufficient to meet the performance requirements. Therefore, it is necessary to modify the surface of the aluminum foil to give it functional groups that can react with acid anhydrides. Preferred materials include amino silane coupling agents, isocyanate silane coupling agents, and amino resin adhesives.

[0037] In this embodiment, considering price and water resistance, an amino-based silane coupling agent is further preferred. The siloxane hydrolyzes and reacts with the aluminum foil surface, while the active amino group at the other end reacts chemically with the acid anhydride to form a covalent bond.

[0038] In this embodiment, the inner layer can be CPP.

[0039] Example 4

[0040] Based on the above embodiments, this embodiment 4 provides a lithium battery that is packaged in aluminum-plastic film as described above.

[0041] Example 5

[0042] Based on the above embodiments, this embodiment 5 provides a production process for aluminum-plastic film, including: producing the outer layer of aluminum-plastic film by co-extrusion in an extruder; modifying the surface of aluminum foil; bonding the water-proof layer of the outer layer of aluminum-plastic film and the treated surface of aluminum foil together, pressing them together with a hot roller at 160°C, and then cooling and winding them up.

[0043] In this embodiment, optionally, the outer layer of the aluminum-plastic film has a two-layer or three-layer structure; wherein

[0044] The two-layer structure includes: an outer support layer and an inner waterproof layer; and

[0045] The three-layer structure is based on a two-layer structure, and also includes an adhesive layer located between the support layer and the waterproof layer.

[0046] In this embodiment, preferably, the support layer is made of polyamide and the waterproof layer is made of polyolefin.

[0047] In this embodiment, preferably, the support layer is made of polyamide, the adhesive layer is made of ethylene-vinyl alcohol, and the waterproof layer is made of maleic anhydride-grafted linear low-density polyethylene.

[0048] In this embodiment, preferably, the modification treatment of the aluminum foil surface includes: dissolving the amino silane coupling agent in an alcohol-water solvent and mixing it thoroughly and evenly, wherein the ethanol content is 60-80%, the water content is 5-15%, and the amino silane coupling agent content is 15-25%; dispersing the mixture on the aluminum foil surface at a rate of 10-15 g / m² by spraying or coating, then baking it in an air duct at 110-130°C for 15-20 seconds, and then winding it up after drying.

[0049] In this embodiment, preferably, the modification treatment of the aluminum foil surface includes: dissolving the amino silane coupling agent in an alcohol-water solvent and mixing it thoroughly and evenly, wherein the ethanol is 70%, the water is 10%, and the amino silane coupling agent is 20%; dispersing the mixture on the aluminum foil surface at 10-15 g / m² by spraying or coating, then baking it in a 120°C air duct for 15-20 seconds, and then winding it up after drying.

[0050] In this embodiment, the outer waterproof layer and the modified aluminum foil are laminated together and pressed at a high temperature of 160°C using hot rollers. This causes the linear low-density polyethylene to soften and be fully anchored to the aluminum foil through pressing. At the same time, the grafted maleic anhydride undergoes an acylation reaction with the amino groups on the surface of the aluminum foil to form stable covalent bonds, further improving the bonding strength and stability. Finally, the mixture is cooled and wound up.

[0051] The following describes specific preparation examples and comparative examples.

[0052] Example 6

[0053] The outer structure of the aluminum-plastic film is produced and wound in the form of three-layer co-extrusion in an extruder. The support layer is made of polyamide, the adhesive layer is made of ethylene-vinyl alcohol, and the waterproof layer is made of maleic anhydride-grafted linear low-density polyethylene with a grafting rate of 1.2%. The support layer is 15µm, the adhesive layer is 6µm, and the waterproof layer is 4µm.

[0054] KH550 was dissolved in an alcohol-water solvent, with 70% ethanol, 10% water, and 20% KH550, and thoroughly mixed. The mixture was then spread onto the surface of aluminum foil at a rate of 15 g / m² using a coating method. The foil was then baked in a 120°C air duct for 20 seconds, dried, and then wound up.

[0055] The waterproof layer of the outer structure of the aluminum-plastic film and the treated surface of the aluminum foil are laminated together, pressed together by a hot roller at a high temperature of 160°C, and then cooled and rolled up.

[0056] The semi-finished aluminum-plastic film, which is used to bond the outer layer structure of the aluminum-plastic film, is dry-bonded with 80um CPP to obtain the finished product.

[0057] Example 7

[0058] The outer layer structure of the aluminum-plastic film is produced and wound in the form of three-layer co-extrusion by an extruder. The support layer is made of polyamide, the adhesive layer is made of ethylene-vinyl alcohol, and the waterproof layer is made of maleic anhydride-grafted linear low-density polyethylene with a grafting rate of 1.2%. The support layer is 15µm, the adhesive layer is 3µm, and the waterproof layer is 7µm.

[0059] KH550 was dissolved in an alcohol-water solvent, wherein 70% ethanol, 10% water and 20% KH550 were thoroughly mixed; the mixture was then dispersed on the surface of aluminum foil at 15g / ㎡ by coating, baked in a 120℃ air duct for 20s, and then wound up after drying.

[0060] The waterproof layer of the outer structure of the aluminum-plastic film and the treated surface of the aluminum foil are laminated together, pressed together by a hot roller at a high temperature of 160°C, and then cooled and rolled up.

[0061] The semi-finished aluminum-plastic film, which is used to bond the outer layer structure of the aluminum-plastic film, is dry-bonded with 80um CPP to obtain the finished aluminum-plastic film.

[0062] Example 8

[0063] The outer layer structure of the aluminum-plastic film is produced and wound in the form of two-layer co-extrusion in an extruder. The support layer is made of polyamide, and the waterproof layer is made of maleic anhydride-grafted linear low-density polyethylene with a grafting rate of 1.2%. The support layer is 20µm and the waterproof layer is 5µm.

[0064] KH550 was dissolved in an alcohol-water solvent, wherein 70% ethanol, 10% water and 20% KH550 were thoroughly mixed; the mixture was then dispersed on the surface of aluminum foil at 15g / ㎡ by coating, baked in a 120℃ air duct for 20s, and then wound up after drying.

[0065] The waterproof layer of the aluminum-plastic film outer structure and the treated surface of the aluminum foil are bonded together, pressed together by a hot roller at 160°C, and then cooled and rolled up.

[0066] The semi-finished aluminum-plastic film, which is used to bond the outer layer structure of the aluminum-plastic film, is dry-bonded with 80um CPP to obtain the finished product.

[0067] Example 9

[0068] The outer layer structure of the aluminum-plastic film is produced and wound in the form of two-layer co-extrusion in an extruder. The support layer is made of polyamide, and the waterproof layer is made of maleic anhydride-grafted linear low-density polyethylene with a grafting rate of 1.2%. The support layer is 17µm and the waterproof layer is 8µm.

[0069] KH550 was dissolved in an alcohol-water solvent, wherein 70% ethanol, 10% water and 20% KH550 were thoroughly mixed; the mixture was then dispersed on the surface of aluminum foil at 15g / ㎡ by coating, baked in a 120℃ air duct for 20s, and then wound up after drying.

[0070] The waterproof layer of the outer structure of the aluminum-plastic film and the treated surface of the aluminum foil are laminated together, pressed together by a hot roller at a high temperature of 160°C, and then cooled and rolled up.

[0071] The semi-finished aluminum-plastic film, which is used to bond the outer layer structure of the aluminum-plastic film, is dry-bonded with 80um CPP to obtain the finished product.

[0072] Comparative Example 1

[0073] The outer layer of the aluminum-plastic film is a conventional pure polyamide layer with a thickness of 25um, which is bonded to the aluminum foil with polyurethane adhesive. The aluminum-plastic film semi-finished product with the outer layer is then bonded to 80um CPP using a dry method to obtain the finished product.

[0074] Comparative Example 2

[0075] The outer layer of the aluminum-plastic film is a conventional polyamide and PET composite film, which are bonded together with polyurethane. The total thickness is 25um, with polyamide at 15um, adhesive layer at 4um, and PET at 6um. The aluminum foil is bonded with a mass-production polyurethane adhesive. The aluminum-plastic film semi-finished product with the outer layer is then bonded to 80um CPP using a dry method to obtain the finished product.

[0076] Test method:

[0077] Peel strength: The test sample was cut into pieces with a width of 15mm and a length of 100mm, and the outer layer was peeled using a tensile testing machine;

[0078] Molding limit test: Cut the aluminum-plastic film into 200mm*150mm samples and place them in the molding machine for deep punching;

[0079] Forming and floating: Draw to 80% of the drawing depth limit, and place in 50℃ water and 75℃, 90%RH oven for 1 week, 2 weeks, 4 weeks and 9 weeks respectively;

[0080] The test data is shown in the table below:

[0081]

[0082] Note: ○—No abnormality; ▲—Slight delamination; ▲▲—Severe delamination

[0083] As can be seen from Examples 6-9 and the comparative examples, the present invention effectively improves the bonding strength and significantly enhances the waterproof performance compared with existing processes by redesigning the outer layer structure and bonding mechanism of the aluminum-plastic film.

[0084] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An aluminum-plastic film, characterized in that, include: The inner layer and aluminum foil, and the outer aluminum-plastic film structure located outside the aluminum foil; in The outer layer structure of the aluminum-plastic film includes: The outer support layer and the inner waterproof layer; wherein The support layer is made of polyamide; and The waterproof layer is an anhydride-grafted polyolefin with an anhydride grafting rate of 0.5% to 1.5%. The anhydride-grafted polyolefin is maleic anhydride-grafted linear low-density polyethylene. The aluminum foil is a surface-modified aluminum foil using one of the following: amino silane coupling agent, isocyanate silane coupling agent, or amino resin adhesive. The waterproof layer and the surface-modified aluminum foil are bonded together.

2. The aluminum-plastic film as described in claim 1, characterized in that, The outer layer structure of the aluminum-plastic film also includes an adhesive layer located between the support layer and the waterproof layer; The adhesive layer comprises one or a combination of several of the following: ethylene-vinyl alcohol, EVA, olefin-hydroxy copolymer, olefin-carboxylic acid copolymer, olefin-amine copolymer, maleic anhydride grafted polyolefin, epoxy grafted polyolefin, and carboxylic acid grafted polyolefin.

3. The aluminum-plastic film as described in claim 2, characterized in that, The adhesive layer is ethylene-vinyl alcohol.

4. A lithium battery, characterized in that, The aluminum-plastic film packaging as described in claim 1 is used.

5. A production process for aluminum-plastic film as described in claim 1, characterized in that, include: The outer layer of the aluminum-plastic film is produced by co-extrusion using an extruder; The surface of the aluminum foil is modified. The waterproof layer of the aluminum-plastic film and the treated surface of the aluminum foil are laminated together, pressed together by a hot roller at a high temperature of 150-170℃, and then cooled and rolled up. The outer layer of the aluminum-plastic film has a two- or three-layer structure; The two-layer structure includes: The outer support layer and the inner waterproof layer; in The support layer is made of polyamide, and the waterproof layer is made of maleic anhydride-grafted linear low-density polyethylene. The three-layer structure, based on a two-layer structure, further includes an adhesive layer located between the support layer and the waterproof layer; wherein... The adhesive layer comprises one or a combination of several of the following: ethylene-vinyl alcohol, EVA, olefin-hydroxy copolymer, olefin-carboxylic acid copolymer, olefin-amine copolymer, maleic anhydride grafted polyolefin, epoxy grafted polyolefin, and carboxylic acid grafted polyolefin.

6. The production process of aluminum-plastic film as described in claim 5, characterized in that, The surface modification treatment of the aluminum foil includes: The amino-based silane coupling agent is dissolved in an alcohol-water solvent and thoroughly mixed, wherein the solvent comprises 60-80% ethanol, 5-15% water, and 15-25% amino-based silane coupling agent; the mixture is then applied by spraying or coating at a concentration of 10-15 g / m³. 2 Disperse the powder onto the surface of aluminum foil, then bake it in an air duct at 110–130°C for 15–20 seconds, and then roll it up after drying.

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