A heat-shrinkable film for battery packaging, a preparation method and application thereof

Abstract

The application discloses a heat-shrinkable film for battery packaging, a preparation method and application, and relates to the technical field of packaging materials. The application selects polyethylene terephthalate-1,4-cyclohexane dimethanol ester, polyethylene terephthalate, polybutylene terephthalate, acrylonitrile-styrene-butadiene copolymer, hydrogenated styrene-butadiene block copolymer-maleic anhydride, MBS impact modifier, halogen-free reactive flame retardant master batch, modified barrier material, antioxidant, light stabilizer, polyethylene wax and calcium montanate according to a proportioning ratio, and the materials are put into a high-speed mixer to be mixed to obtain premix, the premix is extruded and granulated by a twin-screw extruder to obtain blended granules, the blended granules are crosslinked by a casting base film and irradiation to obtain a cured film, and the cured film is two-dimensionally stretched and formed and cut to obtain the heat-shrinkable film for battery packaging, which has excellent flame-retardant, barrier, impact-resistant and puncture-resistant properties.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, specifically to a heat-shrinkable film for battery packaging and its preparation method. Background Technology

[0002] In the field of battery packaging, heat-shrinkable film, as a key insulating and protective material, has long faced multiple technical challenges: While traditional polyolefin-based heat-shrinkable films possess good shrinkage properties, their high-temperature resistance is insufficient, making them prone to softening and deformation under the heat accumulation of battery charging and discharging or in external high-temperature environments, leading to insulation failure. Halogen-free flame-retardant systems often experience migration and precipitation due to poor compatibility with the substrate, not only reducing long-term flame-retardant efficiency but also potentially corroding the battery's metal current collector. Furthermore, conventional barrier fillers such as silica or clay are difficult to construct a continuous and dense barrier in thin film layers, allowing moisture penetration to accelerate electrolyte decomposition, and electrostatic accumulation on the surface of the insulating material can easily induce short-circuit risks. Although existing technologies attempt to improve heat resistance through polyester alloys, the mechanical weaknesses caused by defects at the ABS / PET multiphase interface, and the contradiction between radiation crosslinking and the thermal decomposition of flame retardants, remain unresolved, hindering the development of high-safety, long-life battery packaging. Summary of the Invention

[0003] The purpose of this invention is to provide a heat-shrinkable film for battery packaging, its preparation method, and its application, in order to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0006] 25-35 parts of polyethylene terephthalate-1,4-cyclohexanediol ester (PETG);

[0007] 10-15 parts of polyethylene terephthalate (PET);

[0008] 15-20 parts of polybutylene terephthalate (PBT);

[0009] 10-18 parts of acrylonitrile-styrene-butadiene copolymer (ABS);

[0010] 10-15 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride (SEBS-g-MAH);

[0011] 6-9 parts of MBS impact modifier;

[0012] 18-22 parts of halogen-free reactive flame retardant masterbatch;

[0013] 3-5 parts of modified barrier material;

[0014] 0.4-0.8 parts of 1010 antioxidant;

[0015] 0.3-0.5 parts of antioxidant 626;

[0016] Light stabilizer 770, 0.2-0.4 parts;

[0017] Polyethylene wax 1.6-2.4 parts;

[0018] 0.5-1 part of calcium lignite.

[0019] Furthermore, the preparation steps of the halogen-free reactive flame retardant masterbatch are as follows:

[0020] A1. Nano-MgAl-LDH two-dimensional layered bimetallic hydroxide was added to anhydrous ethanol, ultrasonically dispersed at 60℃ for 30 min, molten stearic acid was added in a 70℃ water bath and stirred for 2 h, centrifuged and separated, and vacuum dried at 80℃ to obtain hydrophobic LDH.

[0021] The mass ratio of the nano-MgAl-LDH two-dimensional layered bimetallic hydroxide, anhydrous ethanol, and stearic acid is 5:(17.5-22.5):(0.4-0.6).

[0022] A2. Start the twin-screw extruder, with a screw speed of 200-250 r / min. Set the first feeding section to 80-100℃ and add 50 parts of cyclic phosphate ester and 5 parts of hydrophobic LDH. Set the second reaction section to 160-170℃ and add 35 parts of melamine polyphosphate. Set the third dispersion section to 140-150℃ and add 10 parts of zinc borate. Set the fourth homogenization section to 130-140℃. After water cooling and pelletizing at 25℃, dry at 40℃ to obtain halogen-free reactive flame retardant masterbatch.

[0023] The mass ratio of the cyclic phosphate ester, hydrophobic LDH, melamine polyphosphate and zinc borate is 50:(4.8-5.2):(33-37):(9-11).

[0024] It should be noted that surface hydrophobic modification of nanolayered double hydroxide (LDH) with stearic acid significantly improves its dispersibility and interfacial compatibility in the polymer matrix. During twin-screw extrusion melt blending, cyclic phosphate oligomers undergo in-situ transesterification with melamine polyphosphate, forming a thermally stable cross-linked network. During combustion, the B2O3 generated from the decomposition of zinc borate synergistically catalyzes the formation of char with the decomposition products of LDH layers, generating a dense borophosphate ceramic layer. This ceramic layer functions to isolate oxygen, suppress dripping, absorb combustion heat, dilute combustible gases, and reduce the heat release rate. When applied to battery heat-shrink films, it not only meets flame retardant requirements, but its halogen-free properties also prevent corrosion of battery metal components. Furthermore, the hydrophobic LDH can form hydrogen bonds with the maleic anhydride groups of SEBS-g-MAH, anchoring the flame retardant molecules at the compatibilization interface and effectively preventing migration and precipitation during high-temperature processing and long-term use.

[0025] Furthermore, the preparation steps of the modified barrier material are as follows:

[0026] B1. Add graphene oxide to tris(hydroxymethyl)aminomethane buffer, sonicate for 30 min, and let stand for 1 h to obtain a dispersion.

[0027] The graphene oxide sheets have a diameter of 5-20 μm;

[0028] The pH of the tris(hydroxymethyl)aminomethane buffer solution is 8.3-8.7, and the concentration of tris(hydroxymethyl)aminomethane is 0.1 mol / L.

[0029] The ratio of graphene oxide to tris(hydroxymethyl)aminomethane buffer is 1 g:(40-60) mL;

[0030] B2. Add dopamine hydrochloride to the dispersion obtained in step B1, transfer to a light-protected reaction vessel, and stir at 120-180 r / min for 12 h at room temperature. After the reaction is completed, centrifuge at 8000-12000 r / min for 8-12 min, discard the supernatant, wash the precipitate 3 times with deionized water, and freeze-dry to obtain GO@PDA powder.

[0031] The ratio of the dispersion to dopamine hydrochloride is (460-540) mL: 3 g;

[0032] B3. Sodium montmorillonite was added to a cetyltrimethylammonium bromide solution at 80°C and stirred at a constant speed at 78-82°C for 24 hours. The mixture was then filtered through a 0.22 μm microporous membrane, washed with deionized water, dried for 24 hours, and ground through a 200-mesh sieve to obtain cationic montmorillonite.

[0033] The deionized water washing should continue until no precipitate is detected by 0.1 mol / L AgNO3.

[0034] The hexadecyltrimethylammonium bromide solution is prepared by dissolving hexadecyltrimethylammonium bromide in deionized water, and the ratio of hexadecyltrimethylammonium bromide to deionized water is (8.2-8.8) g:(480-520) mL;

[0035] The volume ratio of sodium montmorillonite to hexadecyltrimethylammonium bromide solution is 1 g:(40-60) mL;

[0036] B4. Disperse the GO@PDA powder obtained in step B2 in deionized water and ultrasonically disperse to obtain a GO@PDA dispersion; disperse the cationic montmorillonite obtained in step B3 in deionized water and ultrasonically disperse to obtain a cationic montmorillonite dispersion; add the cationic montmorillonite dispersion dropwise to the GO@PDA dispersion, stir magnetically at 400-600 r / min for 1-2 h at room temperature, add ascorbic acid solution, stir and react at 58-62℃ for 1-2 h, filter with a 0.22 μm microporous membrane, wash with deionized water, dry the filter cake for 24-48 h, freeze-pulverize, and sieve through a 5-20 μm sieve to obtain the modified barrier material;

[0037] The GO@PDA dispersion was prepared by mixing GO@PDA powder and deionized water in a ratio of 1g:(90-110)mL.

[0038] The cationic montmorillonite dispersion was prepared by using cationic montmorillonite and deionized water in a ratio of 1g:(80-120)mL.

[0039] The ascorbic acid solution is prepared by using ascorbic acid and deionized water in a ratio of (0.8-1.2)g:20mL.

[0040] The volume ratio of the GO@PDA dispersion, the cationic montmorillonite dispersion, and the ascorbic acid solution is (9.5-10.5):(4.7-5.3):1.

[0041] It should be noted that after graphene oxide is coated with polydopamine, the abundant phenolic hydroxyl and amino groups on its surface significantly enhance its interfacial reactivity. Cationic montmorillonite expands the interlayer spacing through organic intercalation and forms an alternating layered structure with the polydopamine-modified graphene oxide through electrostatic self-assembly. The partial reduction of graphene oxide by ascorbic acid constructs conductive pathways between the layers, endowing the material with antistatic properties. When applied to battery heat-shrink films, the nanosheets are oriented along the film plane during biaxial stretching, forcing water vapor and oxygen to traverse extremely long and tortuous paths, creating a maze effect that significantly improves barrier performance. During heat shrinking, polydopamine enhances interfacial bonding with PETG / PBT through physical interactions such as hydrogen bonding. The conductive network effectively suppresses the accumulation of localized static charge and the generation of micro-arcs within the battery.

[0042] A method for preparing heat-shrink film for battery packaging is as follows:

[0043] Step 1: Add the raw materials to a high-speed mixer according to the formula and mix at 800-1200 r / min for 20-30 min to obtain the premix.

[0044] Step 2: Add the premixed material to the twin-screw extruder at 170°C in the feeding section, 200°C in the melting section, 245°C in the mixing section, 210°C in the venting section, 265°C in the homogenization section, and 185°C in the die. The screw speed is 200-300 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain the blended granules.

[0045] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1-1.5mm through a T-die, and set it with a cooling roller at 25℃ to obtain the base film;

[0046] Step 4: The base film is subjected to gradient irradiation using an electron accelerator. After irradiation, the film material is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0047] The specific parameters of the irradiation operation are: 5 kGy dose in the pre-irradiation zone, 15 kGy dose in the main cross-linking zone, and 3 kGy dose in the surface curing zone.

[0048] Step 5: Soften the curing film with a 95°C preheating roller, stretch it biaxially, and then cut it to obtain heat shrink film for battery packaging.

[0049] The specific parameters of the biaxial stretching molding operation are as follows: the longitudinal stretching is 3 times the stretching ratio, and the film is transferred to the transverse stretching frame. The film is expanded to 3 times the width at 120-130℃, and the size is locked in the heat setting zone at 150℃ for 10 seconds. The film is then rapidly cooled by a 25℃ cooling roller, and after molding, it is slit to obtain heat shrink film for battery packaging.

[0050] Furthermore, the heat-shrinkable film for battery packaging and its preparation method are applied in the fields of power battery module packaging, cylindrical lithium battery casing protection, energy storage battery system sealing, and consumer electronics irregular battery packing.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The heat-shrinkable film for battery packaging prepared in this scheme improves the overall performance of the film through the preparation of halogen-free reactive flame retardant masterbatch and modified barrier material, combined with multi-component synergistic design. In the flame retardant masterbatch, hydrophobic layered bimetallic hydroxide, cyclic phosphate ester, and melamine polyphosphate form a thermally stable cross-linked network during the melting process. During combustion, LDH decomposes, absorbs heat, and releases flame-retardant gas, forming a dense ceramic layer that effectively isolates oxygen and inhibits dripping. The modified barrier material forms an alternating layered structure through polydopamine-bridged graphene oxide / montmorillonite, which, during biaxial stretching, forms a tortuous barrier path, delaying the penetration of water vapor and oxygen. The constructed conductive network reduces electrostatic charge and prevents static accumulation. Flame retardant migration is inhibited through physical mechanisms such as hydrogen bond anchoring. Electron beam gradient irradiation induces controllable cross-linking of molecular chains, combined with biaxial stretching orientation locking, resulting in excellent heat shrinkage memory, puncture resistance, and high-temperature dimensional stability. The heat-shrinkable film for battery packaging prepared by this invention provides long-term protection for power batteries, combining flame retardancy, barrier properties, mechanical protection, and resistance to aging and weathering. Detailed Implementation

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0054] Preparation Example 1

[0055] The preparation steps of halogen-free reactive flame retardant masterbatch are as follows:

[0056] A1. Nano-MgAl-LDH two-dimensional layered bimetallic hydroxide was added to anhydrous ethanol, ultrasonically dispersed at 60℃ for 30 min, molten stearic acid was added in a 70℃ water bath and stirred for 2 h, centrifuged and separated, and vacuum dried at 80℃ to obtain hydrophobic LDH.

[0057] The mass ratio of the nano-MgAl-LDH two-dimensional layered bimetallic hydroxide, anhydrous ethanol, and stearic acid is 5:20:0.5.

[0058] A2. Start the twin-screw extruder, screw speed 250 r / min. Set the first feeding section to 90℃ and add cyclic phosphate ester and hydrophobic LDH; set the second reaction section to 165℃ and add melamine polyphosphate; set the third dispersion section to 145℃ and add zinc borate; set the fourth homogenization section to 135℃, then cool with water at 25℃, pelletize, and dry at 40℃ to obtain halogen-free reactive flame retardant masterbatch.

[0059] The mass ratio of the cyclic phosphate ester, hydrophobic LDH, melamine polyphosphate, and zinc borate is 50:5:35:10.

[0060] The MgAl-LDH two-dimensional layered bimetallic hydroxide used in this preparation example is from Nanjing Xianfeng Nanomaterials Technology Co., Ltd. The cyclic phosphate used in this preparation example is from Wuhan Maikairui Chemical Co., Ltd., model number 255-263-6, methylphosphonic acid (5-ethyl-2-methyl-2-oxo-1,3,2-dioxophosphazenecyclohexyl-5-yl) methyl methyl ester (CAS No. 41203-81-0). The melamine polyphosphate used in this preparation example is from Hubei Xinyuhong Biomedical Technology Co., Ltd., product number xyh001, melamine pyrophosphate (CAS No. 15541-60-3).

[0061] Preparation Example 2

[0062] The preparation steps of the modified barrier material are as follows:

[0063] B1. Add graphene oxide with an average sheet diameter of 10 μm to tris(hydroxymethyl)aminomethane buffer, sonicate for 30 min, and let stand for 1 h to obtain a dispersion.

[0064] The pH of the tris(hydroxymethyl)aminomethane buffer solution is 8.5, and the concentration of tris(hydroxymethyl)aminomethane is 0.1 mol / L.

[0065] The ratio of graphene oxide to tris(hydroxymethyl)aminomethane buffer is 1 g: 50 mL.

[0066] B2. Add dopamine hydrochloride to the dispersion obtained in step B1, transfer to a light-protected reactor, and stir at 150 r / min for 12 h at room temperature. After the reaction is completed, centrifuge at 10000 r / min for 10 min, discard the supernatant, wash the precipitate three times with deionized water, and freeze-dry to obtain GO@PDA powder.

[0067] The ratio of the dispersion to dopamine hydrochloride is 500 mL: 3 g;

[0068] B3. Sodium montmorillonite was added to a cetyltrimethylammonium bromide solution at 80°C and stirred at a constant speed at 80°C for 24 hours. The mixture was then filtered through a 0.22 μm microporous membrane, washed with deionized water, dried for 24 hours, and ground through a 200-mesh sieve to obtain cationic montmorillonite.

[0069] The deionized water washing should continue until no precipitate is detected by 0.1 mol / L AgNO3.

[0070] The hexadecyltrimethylammonium bromide solution is prepared by dissolving hexadecyltrimethylammonium bromide in deionized water, with a volume ratio of hexadecyltrimethylammonium bromide to deionized water of 8.5 g: 500 mL; the volume ratio of sodium montmorillonite to hexadecyltrimethylammonium bromide solution is 1 g: 50 mL.

[0071] B4. Disperse the GO@PDA powder obtained in step B2 in deionized water and ultrasonically disperse to obtain a GO@PDA dispersion; disperse the cationic montmorillonite obtained in step B3 in deionized water and ultrasonically disperse to obtain a cationic montmorillonite dispersion; add the cationic montmorillonite dispersion dropwise to the GO@PDA dispersion, stir magnetically at 500 r / min for 2 h at room temperature, add ascorbic acid solution, stir and react at 60℃ for 1 h, filter with a 0.22 μm microporous membrane, wash with deionized water, dry the filter cake for 24 h, freeze pulverize, and sieve through a 10 μm sieve to obtain the modified barrier material;

[0072] The GO@PDA dispersion was prepared by mixing GO@PDA powder and deionized water in a ratio of 1g:100mL.

[0073] The cationic montmorillonite dispersion was prepared by using cationic montmorillonite and deionized water in a ratio of 1g:100mL.

[0074] The ascorbic acid solution is prepared by using ascorbic acid and deionized water in a ratio of 1g:20mL.

[0075] The volume ratio of the GO@PDA dispersion, the cationic montmorillonite dispersion, and the ascorbic acid solution is 10:5:1.

[0076] Example 1

[0077] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0078] 30 parts of polyethylene terephthalate-1,4-cyclohexanediol ester;

[0079] 12 parts of polyethylene terephthalate;

[0080] 18 parts of polybutylene terephthalate;

[0081] 14 parts of acrylonitrile-styrene-butadiene copolymer;

[0082] 13 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride;

[0083] 7.5 parts of MBS impact modifier;

[0084] 20 parts of halogen-free reactive flame retardant masterbatch;

[0085] Four portions of modified barrier material;

[0086] 0.6 parts of 1010 antioxidant;

[0087] 0.4 parts of 626 antioxidant;

[0088] Light stabilizer 770, 0.3 parts;

[0089] 2 parts polyethylene wax;

[0090] 0.8 parts of calcium lignite.

[0091] A method for preparing heat-shrink film for battery packaging is as follows:

[0092] Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix at 1000 r / min for 25 min to obtain the premix.

[0093] Step 2: Add the premixed material to a twin-screw extruder with the following temperatures: feed section 170°C, melting section 200°C, mixing section 245°C, venting section 210°C, homogenization section 265°C, die head 185°C, and screw speed 250 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain blended pellets.

[0094] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1.2 mm through a T-die, and set it with a cooling roller at 25°C to obtain the base film;

[0095] Step 4: The base film is subjected to gradient irradiation using an electron accelerator, with a dose of 5 kGy in the pre-irradiation area, 15 kGy in the main crosslinking area, and 3 kGy in the surface curing area. After irradiation, the film is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0096] Step 5: Soften the curing film with a 95°C preheating roller, stretch it longitudinally at a 3x stretch ratio, transfer it to a transverse stretching frame, expand it to 3x width at 125°C, hold it in a 150°C heat setting zone for 10 seconds to lock the size, cool it rapidly with a 25°C cooling roller, and after forming, cut it to obtain heat shrink film for battery packaging.

[0097] The halogen-free reactive flame retardant masterbatch and modified barrier material used in this embodiment are the same substances obtained in Preparation Examples 1-2, and the same applies to other embodiments.

[0098] The polyethylene terephthalate-1,4-cyclohexanediol ester used in this embodiment is from Eastman Chemical Company, USA, product number GN077. The polyethylene terephthalate used in this embodiment is from DuPont, USA, product number FR530. The polybutylene terephthalate used in this embodiment is from Polyplastics Plastics Co., Ltd., Japan, product number 3226. The acrylonitrile-styrene-butadiene copolymer used in this embodiment is from TECHNO, Japan, product number ABS 830, distributed by Dongguan Chengyu Hui New Materials Co., Ltd. The hydrogenated styrene-butadiene block copolymer-maleic anhydride used in this embodiment is from TSRC Corporation Limited, Dongguan Xinxin New Materials Co., Ltd., product number SEBS 6150. The MBS impact modifier used in this embodiment is from Kanekachi, Japan, product number M724, distributed by Shenzhen Pasteur New Materials Technology Co., Ltd. The polyethylene wax used in this embodiment is from Dongguan Xinghong Chemical Materials Co., Ltd., product number A-3052. The calcium lignite used in this embodiment is from Hubei Weishi Chemical Reagent Co., Ltd., product number HBWS-149. The same raw materials are used in other embodiments.

[0099] Example 2

[0100] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0101] 25 parts of polyethylene terephthalate-1,4-cyclohexanediol ester;

[0102] 10 parts of polyethylene terephthalate;

[0103] 15 parts of polybutylene terephthalate;

[0104] 10 parts of acrylonitrile-styrene-butadiene copolymer;

[0105] 10 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride;

[0106] 6 parts MBS impact modifier;

[0107] 18 parts of halogen-free reactive flame retardant masterbatch;

[0108] Three portions of modified barrier material;

[0109] 0.4 parts of 1010 antioxidant;

[0110] 0.3 parts of 626 antioxidant;

[0111] Light stabilizer 770, 0.2 parts;

[0112] 1.6 parts of polyethylene wax;

[0113] 0.5 parts of calcium lignite.

[0114] A method for preparing heat-shrink film for battery packaging is as follows:

[0115] Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix at 1000 r / min for 25 min to obtain the premix.

[0116] Step 2: Add the premixed material to a twin-screw extruder with the following temperatures: feed section 170°C, melting section 200°C, mixing section 245°C, venting section 210°C, homogenization section 265°C, die head 185°C, and screw speed 250 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain blended pellets.

[0117] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1.2 mm through a T-die, and set it with a cooling roller at 25°C to obtain the base film;

[0118] Step 4: The base film is subjected to gradient irradiation using an electron accelerator, with a dose of 5 kGy in the pre-irradiation area, 15 kGy in the main crosslinking area, and 3 kGy in the surface curing area. After irradiation, the film is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0119] Step 5: Soften the curing film with a 95°C preheating roller, stretch it longitudinally at a 3x stretch ratio, transfer it to a transverse stretching frame, expand it to 3x width at 125°C, hold it in a 150°C heat setting zone for 10 seconds to lock the size, cool it rapidly with a 25°C cooling roller, and after forming, cut it to obtain heat shrink film for battery packaging.

[0120] Example 3

[0121] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0122] 35 parts of polyethylene terephthalate-1,4-cyclohexanediol ester;

[0123] 15 parts of polyethylene terephthalate;

[0124] 20 parts of polybutylene terephthalate;

[0125] 18 parts of acrylonitrile-styrene-butadiene copolymer;

[0126] 15 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride;

[0127] 9 parts of MBS impact modifier;

[0128] 22 parts of halogen-free reactive flame retardant masterbatch;

[0129] Five parts of modified barrier material;

[0130] 0.8 parts of 1010 antioxidant;

[0131] 0.5 parts of 626 antioxidant;

[0132] Light stabilizer 770, 0.4 parts;

[0133] 2.4 parts of polyethylene wax;

[0134] 1 part of calcium lignite.

[0135] A method for preparing heat-shrink film for battery packaging is as follows:

[0136] Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix at 1000 r / min for 25 min to obtain the premix.

[0137] Step 2: Add the premixed material to a twin-screw extruder with the following temperatures: feed section 170°C, melting section 200°C, mixing section 245°C, venting section 210°C, homogenization section 265°C, die head 185°C, and screw speed 250 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain blended pellets.

[0138] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1.2 mm through a T-die, and set it with a cooling roller at 25°C to obtain the base film;

[0139] Step 4: The base film is subjected to gradient irradiation using an electron accelerator, with a dose of 5 kGy in the pre-irradiation area, 15 kGy in the main crosslinking area, and 3 kGy in the surface curing area. After irradiation, the film is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0140] Step 5: Soften the curing film with a 95°C preheating roller, stretch it longitudinally at a 3x stretch ratio, transfer it to a transverse stretching frame, expand it to 3x width at 125°C, hold it in a 150°C heat setting zone for 10 seconds to lock the size, cool it rapidly with a 25°C cooling roller, and after forming, cut it to obtain heat shrink film for battery packaging.

[0141] Comparative Example 1

[0142] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0143] 30 parts of polyethylene terephthalate-1,4-cyclohexanediol ester;

[0144] 12 parts of polyethylene terephthalate;

[0145] 18 parts of polybutylene terephthalate;

[0146] 14 parts of acrylonitrile-styrene-butadiene copolymer;

[0147] 13 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride;

[0148] 7.5 parts of MBS impact modifier;

[0149] 20 parts of melamine polyphosphate;

[0150] Four portions of modified barrier material;

[0151] 0.6 parts of 1010 antioxidant;

[0152] 0.4 parts of 626 antioxidant;

[0153] Light stabilizer 770, 0.3 parts;

[0154] 2 parts polyethylene wax;

[0155] 0.8 parts of calcium lignite.

[0156] A method for preparing heat-shrink film for battery packaging is as follows:

[0157] Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix at 1000 r / min for 25 min to obtain the premix.

[0158] Step 2: Add the premixed material to a twin-screw extruder with the following temperatures: feed section 170°C, melting section 200°C, mixing section 245°C, venting section 210°C, homogenization section 265°C, die head 185°C, and screw speed 250 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain blended pellets.

[0159] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1.2 mm through a T-die, and set it with a cooling roller at 25°C to obtain the base film;

[0160] Step 4: The base film is subjected to gradient irradiation using an electron accelerator, with a dose of 5 kGy in the pre-irradiation area, 15 kGy in the main crosslinking area, and 3 kGy in the surface curing area. After irradiation, the film is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0161] Step 5: Soften the curing film with a 95°C preheating roller, stretch it longitudinally at a 3x stretch ratio, transfer it to a transverse stretching frame, expand it to 3x width at 125°C, hold it in a 150°C heat setting zone for 10 seconds to lock the size, cool it rapidly with a 25°C cooling roller, and after forming, cut it to obtain heat shrink film for battery packaging.

[0162] The difference between this comparative example and Example 1 is that halogen-free reactive flame retardant masterbatch was not added; instead, melamine polyphosphate was added.

[0163] Comparative Example 2

[0164] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0165] 30 parts of polyethylene terephthalate-1,4-cyclohexanediol ester;

[0166] 12 parts of polyethylene terephthalate;

[0167] 18 parts of polybutylene terephthalate;

[0168] 14 parts of acrylonitrile-styrene-butadiene copolymer;

[0169] 13 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride;

[0170] 7.5 parts of MBS impact modifier;

[0171] 20 parts of halogen-free reactive flame retardant masterbatch;

[0172] 4 parts of graphene oxide;

[0173] 0.6 parts of 1010 antioxidant;

[0174] 0.4 parts of 626 antioxidant;

[0175] Light stabilizer 770, 0.3 parts;

[0176] 2 parts polyethylene wax;

[0177] 0.8 parts of calcium lignite.

[0178] A method for preparing heat-shrink film for battery packaging is as follows:

[0179] Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix at 1000 r / min for 25 min to obtain the premix.

[0180] Step 2: Add the premixed material to a twin-screw extruder with the following temperatures: feed section 170°C, melting section 200°C, mixing section 245°C, venting section 210°C, homogenization section 265°C, die head 185°C, and screw speed 250 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain blended pellets.

[0181] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1.2 mm through a T-die, and set it with a cooling roller at 25°C to obtain the base film;

[0182] Step 4: The base film is subjected to gradient irradiation using an electron accelerator, with a dose of 5 kGy in the pre-irradiation area, 15 kGy in the main crosslinking area, and 3 kGy in the surface curing area. After irradiation, the film is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0183] Step 5: Soften the curing film with a 95°C preheating roller, stretch it longitudinally at a 3x stretch ratio, transfer it to a transverse stretching frame, expand it to 3x width at 125°C, hold it in a 150°C heat setting zone for 10 seconds to lock the size, cool it rapidly with a 25°C cooling roller, and after forming, cut it to obtain heat shrink film for battery packaging.

[0184] The difference between this comparative example and Example 1 is that no modified barrier material was added; instead, graphene oxide was added.

[0185] Comparative Example 3

[0186] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0187] 30 parts of polyethylene terephthalate-1,4-cyclohexanediol ester;

[0188] 12 parts of polyethylene terephthalate;

[0189] 18 parts of polybutylene terephthalate;

[0190] 14 parts of acrylonitrile-styrene-butadiene copolymer;

[0191] 13 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride;

[0192] 7.5 parts of MBS impact modifier;

[0193] 20 parts of hydrophobic LDH;

[0194] Four portions of modified barrier material;

[0195] 0.6 parts of 1010 antioxidant;

[0196] 0.4 parts of 626 antioxidant;

[0197] Light stabilizer 770, 0.3 parts;

[0198] 2 parts polyethylene wax;

[0199] 0.8 parts of calcium lignite.

[0200] A method for preparing heat-shrink film for battery packaging is as follows:

[0201] Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix at 1000 r / min for 25 min to obtain the premix.

[0202] Step 2: Add the premixed material to a twin-screw extruder with the following temperatures: feed section 170°C, melting section 200°C, mixing section 245°C, venting section 210°C, homogenization section 265°C, die head 185°C, and screw speed 250 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain blended pellets.

[0203] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1.2 mm through a T-die, and set it with a cooling roller at 25°C to obtain the base film;

[0204] Step 4: The base film is subjected to gradient irradiation using an electron accelerator, with a dose of 5 kGy in the pre-irradiation area, 15 kGy in the main crosslinking area, and 3 kGy in the surface curing area. After irradiation, the film is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0205] Step 5: Soften the curing film with a 95°C preheating roller, stretch it longitudinally at a 3x stretch ratio, transfer it to a transverse stretching frame, expand it to 3x width at 125°C, hold it in a 150°C heat setting zone for 10 seconds to lock the size, cool it rapidly with a 25°C cooling roller, and after forming, cut it to obtain heat shrink film for battery packaging.

[0206] The difference between this comparative example and Example 1 is that no halogen-free reactive flame retardant masterbatch was added; instead, hydrophobic LDH was added.

[0207] Comparative Example 4

[0208] A heat-shrink film for battery packaging comprises the following raw materials in parts by weight:

[0209] 30 parts of polyethylene terephthalate-1,4-cyclohexanediol ester;

[0210] 12 parts of polyethylene terephthalate;

[0211] 18 parts of polybutylene terephthalate;

[0212] 14 parts of acrylonitrile-styrene-butadiene copolymer;

[0213] 13 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride;

[0214] 7.5 parts of MBS impact modifier;

[0215] 20 parts of halogen-free reactive flame retardant masterbatch;

[0216] 4 parts of GO@PDA powder;

[0217] 0.6 parts of 1010 antioxidant;

[0218] 0.4 parts of 626 antioxidant;

[0219] Light stabilizer 770, 0.3 parts;

[0220] 2 parts polyethylene wax;

[0221] 0.8 parts of calcium lignite.

[0222] A method for preparing heat-shrink film for battery packaging is as follows:

[0223] Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix at 1000 r / min for 25 min to obtain the premix.

[0224] Step 2: Add the premixed material to a twin-screw extruder with the following temperatures: feed section 170°C, melting section 200°C, mixing section 245°C, venting section 210°C, homogenization section 265°C, die head 185°C, and screw speed 250 r / min. After cooling with water at 25°C, the material is pelletized, centrifuged, and sieved to obtain blended pellets.

[0225] Step 3: Feed the blended granules into a single-screw casting machine, extrude a base film with a thickness of 1.2 mm through a T-die, and set it with a cooling roller at 25°C to obtain the base film;

[0226] Step 4: The base film is subjected to gradient irradiation using an electron accelerator, with a dose of 5 kGy in the pre-irradiation area, 15 kGy in the main crosslinking area, and 3 kGy in the surface curing area. After irradiation, the film is cured in a nitrogen atmosphere for 24 hours to obtain a cured film.

[0227] Step 5: Soften the curing film with a 95°C preheating roller, stretch it longitudinally at a 3x stretch ratio, transfer it to a transverse stretching frame, expand it to 3x width at 125°C, hold it in a 150°C heat setting zone for 10 seconds to lock the size, cool it rapidly with a 25°C cooling roller, and after forming, cut it to obtain heat shrink film for battery packaging.

[0228] The difference between this comparative example and Example 1 is that no modified barrier material was added; instead, GO@PDA powder was added.

[0229] test:

[0230] Water resistance test: Samples of heat-shrinkable film for battery packaging prepared in Examples 1-3 and Comparative Examples 1-4, each 100mm × 100mm in size and 80μm thick, were taken and tested for water vapor transmission according to GB / T 1037-2021.

[0231] Puncture strength test: The test method refers to 6.6.13 of GB / T 10004-2008.

[0232] Deep forming performance test: The heat shrink film for battery packaging prepared in Examples 1-3 and Comparative Examples 1-4 was cut into 100mm×200mm film sheets with a thickness of 80μm. The films were stamped on a semi-automatic forming machine with a pressure of 0.3MPa and a holding time of 1.5s (stamping size of 57mm×98mm, Teflon core, and R-angle of 1.5mm) and the maximum forming depth was measured.

[0233] Flame retardant performance test: The heat shrink film for battery packaging prepared in Examples 1-3 and Comparative Examples 1-4 was cut into five strips with a length of 125 mm and a width of 13 mm according to the UL94 standard. The five strips were then subjected to a methane flame test in accordance with the UL94 standard.

[0234] The test results are shown in Table 1.

[0235] Table 1

[0236]

[0237]

[0238] This solution achieves a performance breakthrough through the innovative design of halogen-free flame retardant masterbatch and modified barrier material. Compared with comparative examples 1-3, the hydrophobic LDH in the flame retardant masterbatch forms a three-dimensional cross-linked network with cyclic phosphate esters and melamine polyphosphate during the melting process. At high temperatures, this network synergistically catalyzes the formation of a dense ceramicized carbon layer with zinc borate, significantly improving flame retardant efficiency and anti-aging properties. Compared with comparative examples 2 and 4, the modified barrier material, through a polydopamine-bridged graphene oxide / montmorillonite biomimetic stacked structure, forms an ultra-torsional barrier path during biaxial stretching, alleviating the interlayer stacking defects of single graphene oxide and reducing water vapor permeability to nearly half that of comparative examples 2 and 4. The maleic anhydride groups of SEBS-g-MAH react with the phenolic hydroxyl groups of polydopamine in the barrier material, enhancing the inorganic-organic interface bonding force. This, combined with the topological network formed by irradiation cross-linking, improves puncture strength. The optimization of drawing performance stems from the adaptive orientation of the biomimetic sheets under tensile stress, effectively suppressing local stress concentration and avoiding insufficient forming depth caused by component deficiency in Comparative Examples 3-4. The overall design achieves a multi-level synergistic mechanism of flame retardancy, barrier properties, and toughening.

[0239] As shown in Table 1, compared with Comparative Examples 1-4, the heat-shrinkable films for battery packaging prepared in Examples 1-3 have excellent sealing properties, mechanical properties and flame retardant properties.

[0240] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0241] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A heat-shrink film for battery packaging, characterized in that: Specifically, it includes the following parts by weight of raw materials: 25-35 parts of polyethylene terephthalate-1,4-cyclohexanediol ester; 10-15 parts of polyethylene terephthalate; 15-20 parts of polybutylene terephthalate; 10-18 parts of acrylonitrile-styrene-butadiene copolymer; 10-15 parts of hydrogenated styrene-butadiene block copolymer-maleic anhydride; 6-9 parts of MBS impact retardant; 18-22 parts of halogen-free reactive flame retardant masterbatch; 3-5 parts of modified barrier material. 1010 antioxidant 0.4-0.8 parts; 626 antioxidant 0.3-0.5 parts; Light stabilizer 770 0.2-0.4 parts; polyethylene wax 1.6-2.4 parts; calcium lignite 0.5-1 part; The preparation steps of the modified barrier material are as follows: B1. Add graphene oxide to tris(hydroxymethyl)aminomethane buffer, sonicate for 30 min, and let stand for 1 h to obtain a dispersion. B2. Add dopamine hydrochloride to the dispersion obtained in step B1, transfer to a light-protected reaction vessel, and stir the reaction at room temperature; after the reaction is completed, centrifuge, discard the supernatant, wash with deionized water, precipitate, and freeze-dry to obtain GO@PDA powder; B3. Sodium montmorillonite was added to a cetyltrimethylammonium bromide solution, stirred and reacted, filtered, washed with deionized water, dried, ground and sieved to obtain cationic montmorillonite. B4. Disperse the GO@PDA powder obtained in step B2 in deionized water and sonicate to obtain a GO@PDA dispersion; disperse the cationic montmorillonite obtained in step B3 in deionized water and sonicate to obtain a cationic montmorillonite dispersion; add the cationic montmorillonite dispersion dropwise to the GO@PDA dispersion, stir, add ascorbic acid solution, stir to react, filter, wash with deionized water, dry the filter cake, freeze-pulverize, and sieve to obtain the modified barrier material.

2. The heat-shrink film for battery packaging according to claim 1, characterized in that: The preparation steps of the halogen-free reactive flame retardant masterbatch are as follows: A1. Nano-MgAl-LDH two-dimensional layered bimetallic hydroxide was added to anhydrous ethanol, ultrasonically dispersed, and molten stearic acid was added under a hot water bath and stirred to react. After centrifugation, separation and drying, hydrophobic LDH was obtained. A2. Start the twin-screw extruder. Set the feed section (zone 1) to 80-100℃ and add cyclic phosphate ester and hydrophobic LDH. Set the reaction section (zone 2) to 160-170℃ and add melamine polyphosphate. Set the dispersion section (zone 3) to 140-150℃ and add zinc borate. Set the homogenization section (zone 4) to 130-140℃, cool, pelletize, and dry to obtain halogen-free reactive flame retardant masterbatch.

3. The heat-shrink film for battery packaging according to claim 2, characterized in that: In step A1, the mass ratio of the nano-MgAl-LDH two-dimensional layered double metal hydroxide, anhydrous ethanol and stearic acid is 5:(17.5-22.5):(0.4-0.6); in step A2, the mass ratio of the cyclic phosphate ester, hydrophobic LDH, melamine polyphosphate and zinc borate is 50:(4.8-5.2):(33-37):(9-11).

4. The heat-shrink film for battery packaging according to claim 1, characterized in that: In step B1, the ratio of graphene oxide to tris(hydroxymethyl)aminomethane buffer is 1 g:(40-60) mL; in step B2, the ratio of dispersion to dopamine hydrochloride is (460-540) mL:3 g.

5. The heat-shrink film for battery packaging according to claim 1, characterized in that: In step B3, the hexadecyltrimethylammonium bromide solution is prepared by dissolving hexadecyltrimethylammonium bromide in deionized water, and the ratio of hexadecyltrimethylammonium bromide to deionized water is (8.2-8.8) g:(480-520) mL; the ratio of sodium montmorillonite to hexadecyltrimethylammonium bromide solution is 1 g:(40-60) mL.

6. The heat-shrink film for battery packaging according to claim 1, characterized in that: In step B4, the GO@PDA dispersion is prepared by using GO@PDA powder and deionized water in a ratio of 1g:(90-110)mL; the cationic montmorillonite dispersion is prepared by using cationic montmorillonite and deionized water in a ratio of 1g:(80-120)mL; the ascorbic acid solution is prepared by using ascorbic acid and deionized water in a ratio of (0.8-1.2)g:20mL; and the volume ratio of the GO@PDA dispersion, the cationic montmorillonite dispersion, and the ascorbic acid solution is (9.5-10.5):(4.7-5.3):

1.

7. The method for preparing the heat-shrinkable film for battery packaging according to any one of claims 1-6 is as follows: Step 1: Add the raw materials to a high-speed mixer according to the proportions and mix to obtain a premix; Step 2: Add the premix to a twin-screw extruder, set the temperature to 170-265℃, cool, pelletize, centrifuge, and sieve to obtain blended pellets; Step 3: Feed the blended granules into a single-screw casting machine, extrude the base film, and cool it with a cooling roller to obtain the base film; Step 4: The base film is subjected to gradient irradiation using an electron accelerator. After irradiation, the film material is cured in a nitrogen atmosphere for 24 hours to obtain a cured film. Step 5: Soften the preheating roller of the curing film, stretch it biaxially, and then cut it to obtain heat shrink film for battery packaging.

8. The method for preparing a heat-shrinkable film for battery packaging according to claim 7, characterized in that: In step five, the specific parameters of the biaxial stretching molding operation are as follows: the longitudinal stretching is 3 times the stretching ratio, the film is transferred to the transverse stretching frame, the width is expanded to 3 times the width, the film is held in the heat setting zone for 10 seconds to lock the size, the cooling roller is used for rapid cooling, and after molding, the film is slit to obtain heat shrink film for battery packaging.

9. The application of the heat-shrinkable film or preparation method for battery packaging according to any one of claims 1-8 in the fields of power battery module packaging, cylindrical lithium battery casing protection, energy storage battery system sealing, and consumer electronics irregular battery packaging.

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