Adhesive film, method for manufacturing the same, and battery protection plate

Abstract

The present application relates to the technical field of bonding materials, in particular to a bonding adhesive film, a preparation method thereof and a battery protection plate. The bonding adhesive film comprises 20-50 parts of polypropylene, 10-30 parts of polypropylene graft, 5-15 parts of thermoplastic elastomer, 2-6 parts of styrene-butadiene-styrene block copolymer, 10-20 parts of high-temperature-resistant particles, 2-10 parts of tackifier and 0.1-0.5 parts of antioxidant. The polypropylene graft is mainly prepared from a polypropylene matrix, graft monomers and an initiator. The polypropylene matrix comprises 60-80% of random copolymerized polypropylene and / or block copolymerized polypropylene and 20-40% of homopolymerized polypropylene by mass percentage. In the bonding adhesive film, the components are compounded to ensure excellent bonding strength of the continuous fiber reinforced thermoplastic material and the metal substrate of the battery protection plate, realize high-temperature heat dissipation and low-temperature heat preservation, and have fast bonding speed and high processing efficiency.

Description

Technical Field

[0001] This invention relates to the field of adhesive materials technology, and in particular to an adhesive film, its preparation method, and a battery guard plate. Background Technology

[0002] A pure electric vehicle (EV) is a car that uses a single battery as its energy storage and power source. The battery provides electrical energy to the electric motor, driving its operation. Currently, pure electric vehicles are developing rapidly and becoming increasingly common, gaining wider acceptance and attention. Because the battery is the power source of a pure electric vehicle, it is generally quite large. Batteries typically suffer from issues such as susceptibility to impacts, overheating damage, and low charge levels in low temperatures. Currently, most batteries are installed in the lower center of the vehicle, making them vulnerable to impacts and suffering from poor heat dissipation. Current battery underbody protection plates are often made of thick steel plates, which, while providing good support, offer poor insulation in low temperatures and poor heat dissipation in high temperatures. Furthermore, when designing the battery underbody protection plate, excessively thick steel plates increase the overall weight of the vehicle, wasting power and resulting in poor fuel economy; conversely, insufficiently thick steel plates provide poor protection and can easily damage the battery.

[0003] Continuous fiber reinforced thermoplastic materials have the characteristics of being lightweight, high-strength, and heat-insulating. By combining a metal substrate with continuous fiber reinforced thermoplastic materials and using steel plates partially embedded in the continuous fiber reinforced thermoplastic composite board, not only can the amount of steel plates used be reduced and the corrosion of the steel plates be minimized, but also higher impact resistance and puncture resistance can be obtained.

[0004] Existing technologies use PUR hot melt adhesive to bond continuous fiber-reinforced thermoplastic materials and metal substrates. However, this construction process is relatively complicated and has a long processing cycle, involving processes such as removing the dustproof film, applying adhesive, attaching the film, and drying. At the same time, PUR hot melt adhesive has very high requirements for environmental temperature and humidity, and there is also a risk of embrittlement at high temperatures after the material has cured, making it difficult to guarantee the stability of the battery protection plate quality.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an adhesive film, its preparation method, and a battery guard plate. When used for bonding battery guard plates, the adhesive film of this invention can achieve high-temperature heat dissipation and low-temperature heat preservation, and can also achieve rapid bonding of steel plates and continuous fiber-reinforced thermoplastic materials, with good bonding stability.

[0007] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides an adhesive film comprising the following components in parts by weight:

[0008] 20-50 parts polypropylene, 10-30 parts polypropylene graft, 5-15 parts thermoplastic elastomer, 2-6 parts styrene-butadiene-styrene block copolymer, 10-20 parts high-temperature resistant particles, 2-10 parts tackifier and 0.1-0.5 parts antioxidant;

[0009] The polypropylene graft is mainly prepared from a polypropylene matrix, grafting monomers and an initiator; the polypropylene matrix comprises 60% to 80% by mass of random copolymer polypropylene and / or block copolymer polypropylene and 20% to 40% by mass of homopolymer polypropylene.

[0010] In a specific embodiment of the present invention, the relative grafting rate of the grafted monomers in the polypropylene graft is 0.15% to 0.25%. Further, the melt flow index of the polypropylene graft at 230°C and 2.16 kg is 80 to 150 g / 10 min.

[0011] In a specific embodiment of the present invention, the grafting monomer includes at least one of maleic anhydride, diethyl maleate, and butyl acrylate.

[0012] In a specific embodiment of the present invention, the amount of the grafting monomer is 1 wt% to 2 wt% of the polypropylene matrix; the amount of the initiator is 0.05 wt% to 0.2 wt% of the polypropylene matrix.

[0013] In a specific embodiment of the present invention, the mass ratio of styrene to butadiene in the styrene-butadiene-styrene block copolymer is (32-40): (60-68).

[0014] In a specific embodiment of the present invention, the high-temperature resistant particles include thermally conductive fillers and phase change material microcapsules with a mass ratio of 1:(0.8 to 1.2).

[0015] In a specific embodiment of the present invention, the thermally conductive filler includes at least one of aluminum nitride and boron nitride. Further, the average particle size of the thermally conductive filler is 50–100 nm.

[0016] In a specific embodiment of the present invention, the phase change material microcapsule comprises a polymer shell and a phase change material disposed within the polymer shell; the phase change temperature of the phase change material is 45–60°C. Further, the phase change material comprises at least one of paraffin wax and fatty acids; the polymer shell comprises at least one of melamine-formaldehyde resin, urea-formaldehyde resin, polyurethane, and polymethyl methacrylate.

[0017] In a specific embodiment of the present invention, the average particle size of the phase change material microcapsules is 10–50 μm.

[0018] In a specific embodiment of the present invention, the phase change material accounts for no less than 80% of the mass of the phase change material microcapsule.

[0019] In a specific embodiment of the present invention, the thermoplastic elastomer includes at least one of ethylene propylene diene monomer (EPDM) rubber, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, and ethylene-octene copolymer.

[0020] In a specific embodiment of the present invention, the thermoplastic elastomer has a melt index of 1–10 g / 10 min at 190°C and a weight of 2.16 kg, a melting point of 80–100°C, and a density of 0.87–0.94 g / cm³. 3 .

[0021] In a specific embodiment of the present invention, the polypropylene includes at least one of homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene.

[0022] In a specific embodiment of the present invention, the tackifier includes at least one of rosin resin, petroleum resin, terpene resin and phenolic resin.

[0023] In a specific embodiment of the present invention, the thickness of the adhesive film is 0.05 to 0.4 mm.

[0024] The second aspect of the present invention provides a method for preparing the adhesive film provided in the first aspect of the present invention, comprising the following steps: mixing the components of the adhesive film in proportion, extruding and granulating to obtain hot melt adhesive particles, and then casting or calendering to obtain the adhesive film.

[0025] A third aspect of the present invention provides a battery guard plate, comprising the adhesive film described in the first aspect of the present invention.

[0026] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0027] (1) The adhesive film of the present invention exhibits strong interfacial bonding force between the continuous fiber-reinforced thermoplastic material and the metal substrate with significant polarity difference in the battery guard plate through the synergistic effect of components such as polypropylene grafts; the test roller peel strength of the obtained guard plate is above 180 (N·mm) / mm, and the failure mode is ideal cohesive failure; and the structure has excellent integrity, with a compressive strength of over 320MPa and a quasi-static puncture force peak of 4500N, which can effectively resist collision, scraping and stone impact, and provide top passive safety protection for the battery pack.

[0028] (2) By introducing high-temperature resistant particles formed by the combination of thermally conductive fillers and phase change material microcapsules, the adhesive film transcends the single function of traditional adhesive layers. When the battery generates heat during operation, the adhesive film can accelerate the lateral diffusion of heat. Combined with the phase change heat absorption mechanism, it can reduce the temperature of the hot spot area by 10-15°C at 85°C. In low-temperature environments, it can also play a role in heat insulation and heat preservation, slowing down the internal temperature drop rate by more than 40%. This significantly smooths out the temperature fluctuation of the battery pack, extends the battery life, and improves the performance under extreme climate conditions.

[0029] (3) The adhesive film of the present invention is made of thermoplastic materials. The adhesive film can be melted, impregnated and bonded quickly by hot pressing at 160-180°C for a short time (30-90s) without a long curing time. Compared with liquid adhesives or reactive adhesive films that require several hours to cure, the production efficiency can be increased by tens of times. The process is stable, environmentally friendly and solvent-free, which perfectly meets the needs of the new energy vehicle industry for efficient and automated manufacturing of parts. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] Currently, hot melt adhesives used to bond continuous fiber reinforced thermoplastic materials (such as polypropylene) to metal substrates have complicated construction procedures, long processing cycles, and become brittle after curing. They also have difficulty achieving both heat insulation and heat dissipation effects.

[0032] Based on this, the first aspect of the present invention provides an adhesive film comprising the following components in parts by weight:

[0033] 20-50 parts polypropylene, 10-30 parts polypropylene graft, 5-15 parts thermoplastic elastomer, 2-6 parts styrene-butadiene-styrene block copolymer, 10-20 parts high-temperature resistant particles, 2-10 parts tackifier and 0.1-0.5 parts antioxidant;

[0034] The polypropylene graft is mainly made of polypropylene matrix, graft monomer and initiator; the polypropylene matrix includes 60% to 80% random copolymer polypropylene and / or block copolymer polypropylene and 20% to 40% homopolymer polypropylene by mass percentage.

[0035] The adhesive film of this invention employs a compound formulation of its components, ensuring excellent bonding strength between the continuous fiber-reinforced thermoplastic material and the metal substrate of the battery guard plate, while achieving high-temperature heat dissipation and low-temperature heat preservation, and exhibiting excellent water resistance. Simultaneously, it boasts fast bonding speed, high processing efficiency, and suitability for continuous production. The adhesive film of this invention, used in film form, makes battery guard plate processing more convenient and faster, improving the overall production efficiency and reducing costs of the battery guard plate industry.

[0036] The adhesive film of this invention uses polypropylene as the main material, and one of its core innovations lies in the use of a polypropylene graft with a specific composition. This graft introduces polar functional groups into the polypropylene molecular chain through chemical grafting, playing the following key roles: (1) Bridging heterogeneous interfaces: effectively improving the compatibility and affinity between the non-polar polypropylene matrix and the polar continuous fiber-reinforced thermoplastic materials (such as CFRP) and metal (such as aluminum alloy) surfaces, thereby achieving high-strength and high-reliability interfacial bonding. (2) Enhancing system compatibility: as a polymer compatibilizer, it significantly improves the interfacial interaction between high-temperature resistant particles and the polypropylene matrix, ensuring that the high-temperature resistant particles are well and stably dispersed in the film and form a firm bond with it, preventing agglomeration or interfacial debonding during processing or use, thereby fully utilizing its functions such as reinforcement, thermal conductivity, or phase change. To achieve the above dual effects, this invention has creatively designed the matrix composition of the polypropylene graft. The polypropylene matrix is ​​composed of random copolymer polypropylene and / or block copolymer polypropylene and homopolymer polypropylene in a specific ratio. Based on the total mass of the polypropylene matrix as 100%, the mass percentage of random copolymer polypropylene and / or block copolymer polypropylene can be 60%, 65%, 70%, 75%, 80%, or any two of these components; the mass percentage of homopolymer polypropylene can be 20%, 25%, 30%, 35%, 40%, or any two of these components.

[0037] This invention reveals that the synergistic effect of the above components is crucial: The copolymer polypropylene component, due to the ethylene units introduced into its chain segments, exhibits better flexibility and lower crystallinity, which facilitates the grafting reaction and improves the wetting and penetration ability of the grafted material on polar surfaces, thus ensuring excellent adhesion. The homopolymer polypropylene component, due to its high crystallinity and regular structure, provides the grafted material with higher cohesive strength, rigidity, and heat resistance, ensuring sufficient dimensional stability and support under stress or heat, and preventing creep.

[0038] By melt-extruding, reacting, and granulating the polypropylene matrix, grafted monomers (such as maleic anhydride), and initiator in a specific ratio using a twin-screw extruder, the core functional component of this invention—the polypropylene graft—can be obtained. This component ultimately achieves a perfect balance between strong and tough adhesion to heterogeneous materials and stable dispersion of functional fillers, which is the foundation for the excellent comprehensive performance of the adhesive film of this invention.

[0039] This invention introduces a certain amount of thermoplastic elastomer into the adhesive film to improve its initial adhesive strength and bonding speed under low-temperature conditions. Simultaneously, it introduces a certain amount of styrene-butadiene-styrene block copolymer to adjust the material's viscosity, thereby improving processing efficiency and enhancing both the adhesive film's adhesive strength and the overall material compatibility. The introduction of an appropriate amount of tackifier improves the wetting effect of the adhesive film on continuous fiber-reinforced thermoplastic materials.

[0040] In different implementation methods, the amounts of each component in the adhesive film, by weight, can be as follows:

[0041] The amount of polypropylene can be 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any combination thereof.

[0042] The amount of polypropylene graft can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, or any combination thereof.

[0043] The amount of thermoplastic elastomer can be 5 parts, 8 parts, 10 parts, 12 parts, 15 parts or any combination thereof; adjusting the amount of thermoplastic elastomer within the above range helps to improve the initial bond strength at low temperatures, improve workability, and at the same time ensure bond strength.

[0044] The amount of styrene-butadiene-styrene block copolymer can be 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, or any combination thereof; adjusting the amount of styrene-butadiene-styrene block copolymer within the above range helps to improve processing efficiency and bond strength.

[0045] The amount of high-temperature resistant particles can be 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, or any combination thereof. Adjusting the amount of high-temperature resistant particles within the above range can ensure that the high-temperature resistant particles are well and uniformly dispersed in the polypropylene matrix, thereby effectively constructing a thermally conductive / phase change functional network or reinforcing skeleton, significantly improving the heat resistance, dimensional stability, and thermal management capability of the film, while maintaining stable adhesive performance. Within the above range, the function of the high-temperature resistant particles can be fully utilized, and the effective wetting and adhesion of the film matrix (especially the polypropylene graft) to the metal and composite material interface can be ensured, avoiding excessive dilution of the matrix resin or obstruction of interfacial contact due to excessive filler, thereby preventing the deterioration of adhesive strength (especially shear strength).

[0046] The amount of tackifier can be 2 parts, 5 parts, 8 parts, 10 parts, or any combination thereof;

[0047] The amount of antioxidant can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, or any combination thereof.

[0048] In a specific embodiment of the present invention, the relative grafting rate of the grafted monomers in the polypropylene graft is 0.15% to 0.25%, for example, it can be a range of 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, or any combination thereof. Further, the melt index of the polypropylene graft at 230°C and 2.16 kg is 80 to 150 g / 10 min, for example, it can be a range of 80 g / 10 min, 100 g / 10 min, 120 g / 10 min, 140 g / 10 min, 150 g / 10 min, or any combination thereof.

[0049] In a specific embodiment of the present invention, the grafting monomer includes at least one of maleic anhydride, diethyl maleate, and butyl acrylate.

[0050] In a specific embodiment of the present invention, the amount of graft monomer used is 1 wt% to 2 wt% of the polypropylene matrix, for example, it can be 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt% or any combination thereof; the amount of initiator used is 0.05 wt% to 0.2 wt% of the polypropylene matrix, for example, it can be 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt% or any combination thereof.

[0051] In a specific embodiment of the present invention, the initiator includes at least one selected from dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, tert-butyl peroxylaurate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, bis(tert-butylperoxyisopropyl)benzene, tert-butylisopropylphenyl peroxide, tert-butyl peroxybenzoate, and tert-butyl peroxyacetate.

[0052] In a specific embodiment of the present invention, the mass ratio of styrene to butadiene in the styrene-butadiene-styrene block copolymer is (32-40):(60-68), for example, it can be a range of 32:68, 34:66, 35:65, 36:64, 38:62, 40:60 or any two of these. This helps to further improve the overall viscosity of the adhesive material, improve the processing performance, and ensure the bonding strength and impact resistance of the adhesive film.

[0053] In a specific embodiment of the present invention, the high-temperature resistant particles include thermally conductive fillers and phase change material microcapsules in a mass ratio of 1:(0.8 to 1.2). Specifically, the mass ratio of thermally conductive fillers and phase change material microcapsules can be 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, or any combination thereof.

[0054] In a specific embodiment of the present invention, the thermally conductive filler includes at least one of aluminum nitride and boron nitride. Further, the average particle size of the thermally conductive filler is 50–100 nm, for example, it can be a range of 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any combination thereof.

[0055] In a specific embodiment of the present invention, the phase change material microcapsule comprises a polymer shell and a phase change material disposed within the polymer shell; the phase change temperature of the phase change material is 45–60°C, specifically 45°C, 48°C, 50°C, 55°C, 60°C, or any combination thereof. Further, the phase change material comprises at least one of paraffin wax and fatty acids; the polymer shell comprises at least one of melamine-formaldehyde resin, urea-formaldehyde resin, polyurethane, and polymethyl methacrylate. The specific method for preparing the phase change material microcapsule is not limited.

[0056] In a specific embodiment of the present invention, the average particle size of the phase change material microcapsules can be 10 to 50 μm, for example, it can be a range of 10 μm, 20 μm, 30 μm, 40 μm, 50 μm or any combination thereof.

[0057] In a specific embodiment of the present invention, the phase change material accounts for no less than 80% of the mass of the phase change material microcapsule.

[0058] In a specific embodiment of the present invention, the phase change material microcapsules can be further subjected to surface silane coupling treatment to improve their dispersibility and interfacial bonding in the polypropylene matrix.

[0059] In a specific embodiment of the present invention, the thermoplastic elastomer includes at least one of ethylene propylene diene monomer (EPDM) rubber, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, and ethylene-octene copolymer.

[0060] In a specific embodiment of the present invention, the melt index of the thermoplastic elastomer at 190°C and 2.16 kg is 1–10 g / 10 min, for example, it can be 1 g / 10 min, 3 g / 10 min, 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, or any combination thereof; the melting point is 80–100°C, for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, or any combination thereof; and the density is 0.87–0.94 g / cm³. 3 For example, it can be 0.87 g / cm³. 3 0.89 g / cm 3 0.9g / cm 3 0.91g / cm 3 0.94g / cm 3 Or a range consisting of any two of them.

[0061] In a specific embodiment of the present invention, the polypropylene includes at least one selected from homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene. Further, the density of the polypropylene is 0.88–0.92 g / cm³. 3 For example, it can be 0.88 g / cm³. 3 0.89 g / cm 3 0.9g / cm 3 0.91g / cm 3 0.92g / cm 3 Or a range of any two of them; the melt index at 230℃ and 2.16kg is 2 to 30 g / 10min, for example, it can be 2 g / 10min, 5 g / 10min, 10 g / 10min, 15 g / 10min, 20 g / 10min, 25 g / 10min, 30 g / 10min or a range of any two of them.

[0062] In a specific embodiment of the present invention, the tackifier includes at least one of rosin resin, petroleum resin, terpene resin and phenolic resin.

[0063] In a specific embodiment of the present invention, the antioxidant includes at least one of antioxidant B215, antioxidant B245 and antioxidant 1010.

[0064] In a specific embodiment of the present invention, the thickness of the adhesive film is 0.05 to 0.4 mm, for example, it can be a range of 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm or any combination thereof, and can be adjusted according to actual application requirements.

[0065] The second aspect of the present invention provides a method for preparing the adhesive film provided in the first aspect of the present invention, comprising the following steps: mixing the components of the adhesive film in proportion, extruding and granulating to obtain hot melt adhesive particles, and then casting or calendering to obtain the adhesive film.

[0066] In a specific embodiment of the present invention, the extrusion temperature is 210–230°C during extrusion granulation. In actual operation, the raw materials can be premixed in proportion using a high-speed mixer for 20–30 minutes, and then extruded and granulated using a twin-screw extruder to obtain hot melt adhesive granules.

[0067] In a specific embodiment of the present invention, the temperature during casting or calendering is 230–240°C.

[0068] A third aspect of the present invention provides a battery protection plate, including the adhesive film of the first aspect of the present invention.

[0069] The battery guard plate may include a continuous fiber reinforced thermoplastic material and a metal substrate, with an adhesive film disposed between the continuous fiber reinforced thermoplastic material and the metal substrate to bond the two together.

[0070] Example 1

[0071] This embodiment provides an adhesive film comprising the following components in parts by weight:

[0072] The adhesive film contains 50 parts polypropylene, 20 parts polypropylene graft, 5 parts thermoplastic elastomer, 3 parts styrene-butadiene-styrene block copolymer, 10 parts high-temperature resistant particles, 5 parts tackifier, and 0.5 parts antioxidant; the thickness of the adhesive film is 0.1 mm.

[0073] The polypropylene in this product is a random copolymer polypropylene with a melt index of 8 g / 10 min at 190℃ / 2.16 kg and a density of 0.89 g / cm³. 3 The thermoplastic elastomer is an ethylene-butene copolymer with a melt index of 8 g / 10 min at 190℃ / 2.16 kg, a melting point of 80℃, and a density of 0.878 g / cm³. 3In the styrene-butadiene-styrene block copolymer, the mass ratio of styrene to butadiene is 32:68; the tackifier is rosin resin; the high-temperature resistant particles are a mixture obtained by physical blending of nano-sized aluminum nitride with an average particle size of 50 nm and 20 μm phase change material microcapsules with a mass ratio of 1:1, wherein the phase change material microcapsules are FSM-PCM56 (Fossmann Technology (Beijing) Co., Ltd., the phase change material is a fatty acid with a phase change temperature of 55℃, and the shell is urea-formaldehyde resin); the antioxidants are antioxidant B215 and antioxidant B245 with a mass ratio of 1:1.

[0074] The polypropylene graft is mainly prepared by homopolymer polypropylene (melt index of 3 g / 10 min at 230℃ / 2.16 kg), random copolymer polypropylene (melt index of 10 g / 10 min at 230℃ / 2.16 kg), maleic anhydride, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in a mass ratio of 40:60:1.5:0.1. The specific preparation includes: weighing each material according to the proportion, premixing in a high-speed mixer, and after uniform dispersion, extruding and granulating through a reactive twin-screw extruder; in the extrusion granulation: the length-to-diameter ratio of the extruder is 36:1, the main engine speed is 320 rpm, and the extrusion processing temperature range is 220~230℃; the relative grafting rate of the obtained polypropylene graft is 0.15%, and the melt index at 230℃ / 2.16 kg is 90 g / 10 min.

[0075] The method for preparing the adhesive film in this embodiment includes the following steps:

[0076] (1) Weigh polypropylene, polypropylene graft, thermoplastic elastomer, styrene-butadiene-styrene block copolymer, high-temperature resistant particles, tackifier and antioxidant according to the above proportions, premix them for 30 min in a high-speed mixer, and then extrude them through a twin-screw extruder to obtain hot melt adhesive granules; in the extrusion granulation, the length-to-diameter ratio of the extruder is 52:1, the main machine speed is 450 rpm, and the extrusion processing temperature range is 210~220℃.

[0077] (2) The hot melt adhesive particles obtained in step (1) are cast into a film with a thickness of 0.1 mm by casting machine at a casting temperature of 230-240℃.

[0078] Example 2

[0079] This embodiment provides an adhesive film comprising the following components in parts by weight:

[0080] The adhesive film contains 30 parts polypropylene, 30 parts polypropylene graft, 15 parts thermoplastic elastomer, 3 parts styrene-butadiene-styrene block copolymer, 15 parts high-temperature resistant particles, 5 parts tackifier, and 0.5 parts antioxidant; the thickness of the adhesive film is 0.15 mm.

[0081] The polypropylene in this product is a random copolymer polypropylene with a melt index of 8 g / 10 min at 190℃ / 2.16 kg and a density of 0.89 g / cm³. 3 The thermoplastic elastomer is an ethylene-octene copolymer with a melt index of 2 g / 10 min at 190℃ / 2.16 kg, a melting point of 100℃, and a density of 0.90 g / cm³. 3 In the styrene-butadiene-styrene block copolymer, the mass ratio of styrene to butadiene is 32:68; the tackifier is a terpene resin; the high-temperature resistant particles are the same as those in Example 1; and the antioxidant is antioxidant B215.

[0082] The polypropylene graft is mainly prepared by homopolymer polypropylene (melt index of 15 g / 10 min at 230℃ / 2.16 kg), random copolymer polypropylene (melt index of 10 g / 10 min at 230℃ / 2.16 kg), maleic anhydride, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in a mass ratio of 30:70:2:0.15. The specific preparation includes: weighing each material according to the proportion, premixing in a high-speed mixer, and after uniform dispersion, extruding and granulating through a reactive twin-screw extruder; in the extrusion granulation: the length-to-diameter ratio of the extruder is 36:1, the main engine speed is 320 rpm, and the extrusion processing temperature range is 220~230℃; the relative grafting rate of the obtained polypropylene graft is 0.20%, and the melt index at 230℃ / 2.16 kg is 110 g / 10 min.

[0083] The method for preparing the adhesive film in this embodiment is the same as in Example 1.

[0084] Example 3

[0085] This embodiment provides an adhesive film comprising the following components in parts by weight:

[0086] The adhesive film contains 40 parts polypropylene, 27 parts polypropylene graft, 15 parts thermoplastic elastomer, 3 parts styrene-butadiene-styrene block copolymer, 20 parts high-temperature resistant particles, 10 parts tackifier, and 0.5 parts antioxidant; the thickness of the adhesive film is 0.35 mm.

[0087] The polypropylene in this product is a block copolymer polypropylene with a melt flow index of 10 g / 10 min at 190℃ / 2.16 kg and a density of 0.899 g / cm³. 3 The thermoplastic elastomer is an ethylene-vinyl acetate copolymer with a melt index of 8 g / 10 min at 190℃ / 2.16 kg, a melting point of 86℃, and a density of 0.92 g / cm³. 3In the styrene-butadiene-styrene block copolymer, the mass ratio of styrene to butadiene is 40:60; the tackifier is a terpene resin; the high-temperature resistant particles are a mixture obtained by physical blending of boron nitride nanoparticles with an average particle size of 80 nm and phase change material microcapsules with a mass ratio of 1:1, wherein the phase change material microcapsules are the same as those in Example 1; the antioxidant is antioxidant B215.

[0088] The polypropylene graft is mainly prepared by homopolymer polypropylene (melt index of 15 g / 10 min at 230℃ / 2.16 kg), random copolymer polypropylene (melt index of 30 g / 10 min at 230℃ / 2.16 kg), diethyl maleate, and dicumyl peroxide in a mass ratio of 30:70:2:0.15. The specific preparation includes: weighing each material according to the proportion, premixing in a high-speed mixer, and after uniform dispersion, extruding and granulating through a reactive twin-screw extruder; in the extrusion granulation: the length-to-diameter ratio of the extruder is 36:1, the main engine speed is 320 rpm, and the extrusion processing temperature range is 220~230℃; the relative grafting rate of the obtained polypropylene graft is 0.18%, and the melt index at 230℃ / 2.16 kg is 150 g / 10 min.

[0089] The method for preparing the adhesive film in this embodiment is the same as in Example 1.

[0090] Example 4

[0091] This embodiment refers to the adhesive film and its preparation method in Example 3, the only difference being that the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide in the polypropylene graft is different.

[0092] In the preparation of the polypropylene graft in this embodiment, the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide was 40:60:2:0.15. The relative grafting rate of the obtained polypropylene graft was 0.24%, and the melt index at 230℃ / 2.16kg was 125g / 10min.

[0093] Example 5

[0094] This embodiment refers to the adhesive film and its preparation method in Example 3, the only difference being that the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide in the polypropylene graft is different.

[0095] In the preparation of the polypropylene graft in this embodiment, the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide was 20:80:2:0.15. The relative grafting rate of the obtained polypropylene graft was 0.22%, and the melt index at 230℃ / 2.16kg was 105g / 10min.

[0096] Example 6

[0097] This embodiment refers to the adhesive film and its preparation method in Example 3, the only difference being that the styrene-butadiene-styrene block copolymer is different.

[0098] In this embodiment, the mass ratio of styrene to butadiene in the styrene-butadiene block copolymer is 30:70.

[0099] Example 7

[0100] This embodiment refers to the adhesive film and its preparation method in Example 3, the only difference being that the styrene-butadiene-styrene block copolymer is different.

[0101] In this embodiment, the mass ratio of styrene to butadiene in the styrene-butadiene block copolymer is 45:55.

[0102] Comparative Example 1

[0103] Commercially available hot melt adhesive film 1 has a single-layer structure and a thickness of 0.2 mm. Its main components are a blend of polypropylene and thermoplastic elastomer. By weight percentage, polypropylene accounts for 80% and thermoplastic elastomer (ethylene-butene copolymer) accounts for 20%.

[0104] Comparative Example 2

[0105] Commercially available hot melt adhesive film 2 has a three-layer structure with a thickness of 0.15mm. Its main components are polypropylene, LLDPE, POE, and tackifier. The first and third layers have the same composition, consisting of polypropylene, LLDPE, POE, and tackifier. By weight percentage, polypropylene accounts for 65%, LLDPE for 20%, POE for 10%, and tackifier for 5%. The second layer is made of pure polypropylene. The thickness ratio of the three layers is 1:2:1.

[0106] Comparative Example 3

[0107] Comparative Example 3 refers to the adhesive film and its preparation method in Example 3, except that the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide in the polypropylene graft is different.

[0108] In the preparation of the polypropylene graft in Comparative Example 3, the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide was 50:50:2:0.15. The relative grafting rate of the obtained polypropylene graft was 0.10%, and the melt index at 230℃ / 2.16 kg was 50 g / 10 min.

[0109] Comparative Example 4

[0110] Comparative Example 4 refers to the adhesive film and its preparation method of Example 3, the difference being that the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide in the polypropylene graft is different.

[0111] In the preparation of the polypropylene graft in Comparative Example 4, the mass ratio of homopolymer polypropylene, random copolymer polypropylene, diethyl maleate, and dicumyl peroxide was 10:90:2:0.15. The relative grafting rate of the obtained polypropylene graft was 0.11%, and the melt index at 230℃ / 2.16kg was 20g / 10min.

[0112] Comparative Example 5

[0113] Comparative Example 5 refers to the adhesive film and its preparation method of Example 3, except that: random copolymer polypropylene is not included in the polypropylene graft.

[0114] In the preparation of the polypropylene graft in Comparative Example 5, the mass ratio of homopolymer polypropylene, diethyl maleate, and dicumyl peroxide was 100:2:0.15. The relative grafting rate of the obtained polypropylene graft was 0.12%, and the melt index at 230℃ / 2.16 kg was 40 g / 10 min.

[0115] Comparative Example 6

[0116] Comparative Example 6 refers to the adhesive film and its preparation method of Example 3, except that: the polypropylene graft does not include homopolymer polypropylene.

[0117] In the preparation of the polypropylene graft in Comparative Example 6, the mass ratio of random copolymer polypropylene, diethyl maleate, and dicumyl peroxide was 100:2:0.15. The relative grafting rate of the obtained polypropylene graft was 0.15%, and the melt index at 230℃ / 2.16kg was 200g / 10min.

[0118] Comparative Example 7

[0119] Comparative Example 7 refers to the adhesive film and its preparation method of Example 3, except that: an equal weight of styrene-isoprene-styrene block copolymer is used to replace the styrene-butadiene-styrene block copolymer in Example 3.

[0120] In the styrene-isoprene-styrene block copolymer of Comparative Example 7, the mass ratio of styrene to isoprene was 40:60.

[0121] Experimental Example

[0122] To compare and illustrate the performance of the adhesive films of different embodiments and comparative examples, the adhesive films of each embodiment and comparative example were subjected to the following tests, and the test results are shown in Table 1.

[0123] Sample preparation method: The fiberglass board / adhesive film to be tested / steel plate are stacked into a composite structure. The composite structure is pressed at 170℃ for 60s, cooled and held under pressure, and the peel test is performed after complete cooling.

[0124] Roller peel strength: The sample prepared according to the above method is tested according to GB / T 1457-2022 for initial roller peel strength at room temperature, roller peel strength after 1000h high temperature and high humidity (double 85℃), and roller peel strength after high and low temperature (-20℃~60℃) impact.

[0125] High and low temperature impact test requirements: The specimens (metal / film / composite material) prepared by the above method shall be subjected to high and low temperature impact tests from -20℃ to 60℃ in accordance with GB / T2423.22 standard; each temperature point shall be held for 60 minutes, the transition time shall be less than 5 minutes, and a total of 500 cycles shall be performed.

[0126] Water resistance: Cut the prepared sample into 25mm wide and 10cm long samples, immerse the sample in room temperature water, observe the sample interface visually, and record the immersion time corresponding to the occurrence of glue separation. The longest test time is 1000h.

[0127] Table 1 Test results of different adhesive films

[0128]

[0129] The test results above show that the adhesive film of the present invention uses a compounding of various components, which ensures that the adhesive film has excellent bonding strength to the continuous fiber-reinforced thermoplastic material and metal substrate of the battery guard plate, while also having excellent high temperature resistance and water resistance. After 1000h of high temperature and high humidity (double 85℃) test and 500 high and low temperature (-20℃~60℃) impacts, the peel strength of the roller does not decrease significantly and still maintains excellent peel strength. At the same time, the bonding speed is fast, the processing efficiency is high, and it is suitable for continuous production.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adhesive film, characterized by, Includes the following components by weight: 20-50 parts of random copolymer polypropylene and / or block copolymer polypropylene, 10-30 parts of polypropylene graft, 5-15 parts of thermoplastic elastomer, 2-6 parts of styrene-butadiene-styrene block copolymer, 10-20 parts of high-temperature resistant particles, 2-10 parts of tackifier and 0.1-0.5 parts of antioxidant; The polypropylene graft is mainly prepared from a polypropylene matrix, grafting monomers, and an initiator; the polypropylene matrix comprises 60%–80% by mass of random copolymer polypropylene and / or block copolymer polypropylene and 20%–40% by mass of homopolymer polypropylene; in the polypropylene graft, the relative grafting rate of the grafting monomers is 0.15%–0.25%; the melt index of the polypropylene graft at 230°C and 2.16 kg is 80–150 g / 10 min. In the styrene-butadiene-styrene block copolymer, the mass ratio of styrene to butadiene is (32-40):(60-68). The high-temperature resistant particles include thermally conductive fillers and phase change material microcapsules in a mass ratio of 1:(0.8 to 1.2).

2. The adhesive film according to claim 1, wherein The polypropylene graft has at least one of the following characteristics: (1) The grafting monomer includes at least one of maleic anhydride, diethyl maleate and butyl acrylate; (2) The amount of the grafted monomer is 1 wt% to 2 wt% of the polypropylene matrix; (3) The amount of the initiator is 0.05wt% to 0.2wt% of the polypropylene matrix.

3. The adhesive film according to claim 1, wherein The thermally conductive filler includes at least one of aluminum nitride and boron nitride; The phase change material microcapsule includes a polymer shell and a phase change material disposed within the polymer shell; the phase change temperature of the phase change material is 45–60°C.

4. The adhesive film according to claim 1, wherein The thermoplastic elastomer includes at least one of ethylene propylene diene monomer (EPDM) rubber, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, and ethylene-octene copolymer.

5. The adhesive film according to claim 1, wherein The thermoplastic elastomer has at least one of the following characteristics: (1) The melt index of the thermoplastic elastomer at 190℃ and 2.16kg is 1 to 10 g / 10 min; (2) The melting point of the thermoplastic elastomer is 80-100℃; (3) the thermoplastic elastomer has a density of 0.87 to 0.94 g / cm 3 .

6. The adhesive film according to claim 1, wherein The tackifier includes at least one of rosin resin, petroleum resin, terpene resin and phenolic resin.

7. The adhesive film according to claim 1, wherein The thickness of the adhesive film is 0.05 to 0.4 mm.

8. The method of producing the adhesive film according to any one of claims 1 to 7, characterized by, The process includes the following steps: mixing the components of the adhesive film in proportion, extruding and granulating to obtain hot melt adhesive particles, and then casting or calendering to obtain the adhesive film.

9. A battery shield, characterized in that Includes the adhesive film as described in any one of claims 1 to 7.

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