An enhanced aluminum laminate

Abstract

The application discloses an enhanced aluminum-plastic film, which is a multilayer composite film, and comprises a wear-resistant surface layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer and a heat-seal layer; the heat-seal layer comprises a heat-seal surface layer and an enhanced core layer, and the enhanced core layer is arranged between the second adhesive layer and the heat-seal surface layer; the heat-seal surface layer and the enhanced core layer are both polypropylene layers, the enhanced core layer contains an enhanced phase, and the enhanced phase is at least one selected from rod-shaped microcrystalline cellulose and silicon compound whiskers. The enhanced aluminum-plastic film uses the microcrystalline cellulose and / or silicon compound whiskers in the enhanced core layer as the enhanced phase, and the microcrystalline cellulose and / or silicon compound whiskers can effectively improve the tensile strength of the aluminum-plastic film at the heat-seal position; the enhanced aluminum-plastic film is used in lithium ion battery packaging, and is beneficial to improving the use safety factor of the battery.

Description

Technical Field

[0001] This invention relates to the field of aluminum-plastic film technology, and specifically to an enhanced aluminum-plastic film. Background Technology

[0002] Aluminum-plastic film is a multi-layer composite film. Its typical structure includes a wear-resistant surface layer, an adhesive layer, an aluminum layer, another adhesive layer, and a heat-sealing layer. The wear-resistant surface layer is commonly made of PA (nylon) or PET (polyethylene terephthalate), or a composite layer of PA and PET. Aluminum-plastic film possesses excellent insulation, sealing properties, wear resistance, and acid and alkali resistance, making it suitable for use as containers for soft-pack lithium-ion batteries.

[0003] The tensile strength, tear resistance, and other mechanical properties of the heat-sealed area of ​​the aluminum-plastic film directly determine the safety of pouch batteries. In the event of thermal runaway in the battery cell, the heat-sealed edge of the aluminum-plastic film is the first to break. Current technologies primarily reinforce the aluminum-plastic film through two methods: the wear-resistant surface layer and the heat-sealing layer, such as adding lignocellulose to the heat-sealing layer. However, how to select reinforcing materials that exhibit good compatibility with the polypropylene material of the heat-sealing layer remains a critical technical challenge for engineers in the aluminum-plastic film field. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects in the prior art and provide an enhanced aluminum-plastic film in which microcrystalline cellulose and silicon compound whiskers can be uniformly dispersed in the polypropylene substrate of the reinforcing core layer. The heat-sealing layer, which is a composite of the heat-sealing surface layer and the reinforcing core layer, is beneficial to improving the tear resistance and tensile strength of the heat-sealed edges and the heat-sealed parts of the aluminum-plastic film.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: an enhanced aluminum-plastic film, which is a multilayer composite film, wherein the multilayer composite film includes a wear-resistant surface layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a heat-sealing layer. The heat-sealing layer includes a heat-sealing surface layer and a reinforcing core layer, wherein the reinforcing core layer is disposed between the second adhesive layer and the heat-sealing surface layer; both the heat-sealing surface layer and the reinforcing core layer are polypropylene layers, and the reinforcing core layer contains a reinforcing phase, wherein the reinforcing phase is at least one selected from microcrystalline cellulose and silicon compound whiskers.

[0006] The preferred technical solution is that, by mass, the main components of the raw materials of the reinforcing core layer are: 80-90 parts of polypropylene, 0.5-4 parts of coupling agent, and 1.3-4.5 parts of reinforcing phase.

[0007] A preferred technical solution is that the reinforcing phase is composed of microcrystalline cellulose and silicon compound whiskers, and the mass ratio of microcrystalline cellulose to silicon compound whiskers is 1:(0.03~0.07).

[0008] A preferred technical solution is that the coupling agent is at least one selected from silane coupling agents or titanate coupling agents.

[0009] A preferred technical solution is that the thickness of the heat-sealed surface layer is 20–40 μm, and the thickness of the reinforcing core layer is 10–16 μm.

[0010] The preferred technical solution is that the polypropylene is a blend of block copolymer polypropylene and random copolymer polypropylene, wherein the content of random copolymer polypropylene in the polypropylene is not less than 80%.

[0011] A preferred technical solution is that the length of the silicon compound whiskers of the microcrystalline cellulose is 5-30 μm, and / or the length of the microcrystalline cellulose is 50-500 nm.

[0012] A preferred technical solution is that the raw material composition of the heat-sealed surface layer and the heat-sealed core layer further includes at least one selected from opening agents and slip agents.

[0013] A preferred technical solution is that the opening agent is fumed silica, and the slip agent is at least one selected from erucamide and oleamide.

[0014] The preferred technical solution is that the heat-sealed surface layer and the reinforcing core layer are composite by casting, and the wear-resistant surface layer, the first adhesive layer, the aluminum foil layer, the second adhesive layer and the heat-sealing layer are obtained by dry composite.

[0015] The advantages and beneficial effects of this invention are as follows: The present invention uses a composite structure of heat-sealing surface layer and reinforcing core layer in the reinforced aluminum-plastic film as the heat-sealing layer. Microcrystalline cellulose and / or silicon compound whiskers in the reinforcing core layer are used as the reinforcing phase. Microcrystalline cellulose and / or silicon compound whiskers can effectively improve the tensile strength and tear resistance of the heat-sealed part of the aluminum-plastic film. Using reinforced aluminum-plastic film in lithium-ion battery packaging helps improve the safety factor of the battery. Detailed Implementation

[0016] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0017] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0018] It is further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0019] Silicon compound whiskers The silicon compound whiskers can be silicon carbide whiskers or titanium carbide whiskers, with silicon carbide whiskers being preferred. The highly oriented structure of the whiskers endows them with high strength, high modulus, and high elongation.

[0020] Composition of heat sealant In addition to opening agents and slip agents, the additives in the heat seal layer also include known antistatic agents, toughening agents, antioxidants, etc. Example

[0021] The opening agent used in the examples is fumed silica, and the slip agent is erucamide, both of which are commercially available products.

[0022] Silicon carbide whiskers: diameter 0.1–1 μm, length 5–30 μm; Rod-shaped microcrystalline cellulose: diameter 10–100 nm, length 50–500 nm; The laminated structure of the aluminum-plastic film for the soft-pack battery in this embodiment is as follows: a wear-resistant surface layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, a reinforcing core layer, and a heat-sealing surface layer. The wear-resistant surface layer is a 25μm PA layer, the aluminum foil layer is 40μm thick, the dry composite coating thickness of the first and second adhesive layers is 5μm, and the adhesive used is a commercially available two-component polyurethane adhesive for aluminum-plastic film composite. The thickness of the reinforcing core layer is 16μm, and the thickness of the heat-sealing surface layer is 35μm. The composite film structure of the reinforcing core layer and the heat-sealing surface layer is prepared according to the formulation and method of this embodiment.

[0023] Example 1 S1: The raw materials for the reinforcing core layer and heat-sealing surface layer in the examples and comparative examples are prepared according to the following components: Reinforcing core layer: 78 parts random copolymer polypropylene, 12 parts block copolymer polypropylene, 3 parts silane coupling agent, 3.81 parts rod-shaped microcrystalline cellulose, 0.19 parts silicon carbide whiskers, 2.5 parts opening agent, and 0.5 parts slip agent; Heat-sealed surface layer: 97 parts random copolymer polypropylene, 2.5 parts opening agent, and 0.5 parts slip agent; S2: Dry the raw materials. Feed the raw materials for the reinforcing core layer and the heat-sealing surface layer separately, heat and melt them, and plasticize them. After filtering, the melt is co-extruded to the surface of the cooling roller through a two-layer composite casting die in a predetermined ratio. The die temperature is 210℃ and the casting roller speed is 65m / min. Rapid cooling yields a composite heat-sealing film with a reinforcing core layer and a heat-sealing surface layer.

[0024] S3: The aluminum foil surface is cleaned and passivated, and the aluminum-plastic film for soft-pack batteries is prepared by the following process steps: coating the aluminum foil surface with polyurethane adhesive, drying the aluminum foil, dry laminating the PA layer with the aluminum foil, first curing (62℃, 64h), coating the aluminum foil surface with polyurethane adhesive, drying the composite film, dry laminating the heat-sealing layer film with the composite film, and second curing (60℃, 72h).

[0025] Example 2 The reinforced core layer of Example 2 consists of: 78 parts random copolymer polypropylene, 12 parts block copolymer polypropylene, 3 parts silane coupling agent, 3.9 parts rod-shaped microcrystalline cellulose, 0.1 parts silicon carbide whiskers, 2.5 parts opening agent, and 0.5 parts slip agent.

[0026] Example 3 The reinforced core layer of Example 3 consists of: 78 parts random copolymer polypropylene, 12 parts block copolymer polypropylene, 3 parts silane coupling agent, 3.2 parts rod-shaped microcrystalline cellulose, 0.5 parts silicon carbide whiskers, 2.5 parts opening agent, and 0.5 parts slip agent.

[0027] Example 4 The reinforced core layer of Example 4 consists of: 78 parts random copolymer polypropylene, 12 parts block copolymer polypropylene, 3 parts silane coupling agent, 3.5 parts rod-shaped microcrystalline cellulose, 0.1 parts silicon carbide whiskers, 2.5 parts opening agent, and 0.5 parts slip agent.

[0028] Comparative Example 1 The reinforced core layer of Comparative Example 1 consisted of: 78 parts random copolymer polypropylene, 12 parts block copolymer polypropylene, 3 parts silane coupling agent, 4 parts rod-shaped microcrystalline cellulose, 2.5 parts opening agent, and 0.5 parts slip agent.

[0029] Comparative Example 2 The reinforced core layer of Comparative Example 2 consists of: 80 parts random copolymer polypropylene, 12 parts block copolymer polypropylene, 3 parts silane coupling agent, 2 parts silicon carbide whiskers, 2.5 parts opening agent, and 0.5 parts slip agent.

[0030] Comparative Example 3 The reinforced core layer of Comparative Example 3 consisted of: 82 parts random copolymer polypropylene, 12 parts block copolymer polypropylene, 3 parts silane coupling agent, 2.5 parts opening agent, and 0.5 parts slip agent.

[0031] Examples 2-4 and Comparative Examples 1-2 were all produced using the aluminum-plastic film production process for soft-pack batteries described in Example 1.

[0032] Detection of Example and Comparative Samples: 1. Observe the shape of the heat-sealing interface of the heat-sealed layer in the heat-sealed area and the non-heat-sealed area of ​​the aluminum-plastic film under magnification; 2. Treat the aluminum-plastic film with electrolyte according to the following steps, and investigate the effect of electrolyte on the tensile strength of the heat-sealed area of ​​the aluminum-plastic film (10 samples, average value): ① Cut the soft-pack battery into the size of a soft-pack battery using aluminum-plastic film, and heat-seal it into a bag shape with an opening at one end; ② The electrolyte is filled into aluminum-plastic film bags. The electrolyte composition is: ethylene carbonate / diethyl carbonate / dimethyl carbonate volume ratio of 1:1.2:1, LiPF6 1mol / L; ③ The aluminum-plastic film bag is placed in a water bath at 85℃ for 24 hours and 30 days to remove the electrolyte from the aluminum-plastic film bag and clean the aluminum-plastic film bag.

[0033] Test the tensile strength of the heat-sealed section of the aluminum-plastic film bag.

[0034] Test results: 1. In both the embodiments and comparative examples, the heat-sealing layer heat-melting interface is a smooth U-shaped arc; 2. The tensile strengths of the aluminum-plastic film bags treated with electrolyte for 24 hours in Examples 1-4 and Comparative Examples 1-3 were tested to be 105 N / 15mm, 101 N / 15mm, 106 N / 15mm, 99 N / 15mm, 92 N / 15mm, 94 N / 15mm, and 81 N / 15mm, respectively. 3. The tensile strengths of the aluminum-plastic film bags treated with electrolyte for 30 days in Examples 1-4 and Comparative Examples 1-3 were tested to be 90 N / 15 mm, 85 N / 15 mm, 89 N / 15 mm, 85 N / 15 mm, 77 N / 15 mm, 78 N / 15 mm, and 62 N / 15 mm, respectively.

[0035] The data above shows that adding rod-shaped microcrystalline cellulose and inorganic silicon compound whiskers to the reinforcing core layer of the heat-sealing layer significantly improves the tensile strength at the heat-sealed area of ​​the aluminum-plastic film heat-sealing bag. When rod-shaped microcrystalline cellulose and silicon carbide whiskers are added simultaneously, and the mass ratio of microcrystalline cellulose to silicon compound whiskers is 1:(0.03~0.07), the heat-sealed area of ​​the aluminum-plastic film heat-sealing bag exhibits even better tensile strength. Based on the above optimal mass ratio of microcrystalline cellulose to silicon compound whiskers, excessive addition of silicon carbide whiskers does not significantly improve the tensile strength at the heat-sealed area.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A reinforced aluminum-plastic film, which is a multilayer composite film, the multilayer composite film comprising a wear-resistant surface layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a heat-sealing layer, characterized in that, The heat-sealing layer includes a heat-sealing surface layer and a reinforcing core layer, wherein the reinforcing core layer is disposed between the second adhesive layer and the heat-sealing surface layer; both the heat-sealing surface layer and the reinforcing core layer are polypropylene layers, and the reinforcing core layer contains a reinforcing phase. The main components of the reinforcing core layer are: 80-90 parts polypropylene, 0.5-4 parts coupling agent, and 1.3-4.5 parts reinforcing phase; the reinforcing phase is composed of rod-shaped microcrystalline cellulose and silicon compound whiskers, with a mass ratio of microcrystalline cellulose to silicon compound whiskers of 1:(0.03-0.07); the polypropylene is a blend of block copolymer polypropylene and random copolymer polypropylene, with the content of random copolymer polypropylene in the polypropylene being not less than 80%; the length of the silicon compound whiskers is 5-30 μm, and / or the length of the microcrystalline cellulose is 50-500 nm, and the second adhesive layer and heat-sealing layer are dry-composite.

2. The reinforced aluminum-plastic film according to claim 1, characterized in that, The coupling agent is at least one selected from silane coupling agents or titanate coupling agents.

3. The reinforced aluminum-plastic film according to claim 1, characterized in that, The thickness of the heat-sealed surface layer is 20–40 μm, and the thickness of the reinforcing core layer is 10–16 μm.

4. The reinforced aluminum-plastic film according to claim 1, characterized in that, The raw material composition of the heat-sealed surface layer and the reinforcing core layer also includes at least one selected from opening agents and slip agents.

5. The reinforced aluminum-plastic film according to claim 4, characterized in that, The opening agent is fumed silica, and the slip agent is at least one selected from erucamide and oleamide.

6. The reinforced aluminum-plastic film according to claim 1, characterized in that, The heat-sealed surface layer and the reinforced core layer are fabricated by casting, and the wear-resistant surface layer, the first adhesive layer, the aluminum foil layer, the second adhesive layer and the heat-sealing layer are obtained by dry lamination.