Double-layer PETG heat shrinkage film battery label and preparation method thereof

Abstract

The invention relates to the field of thermal shrinkage label films, in particular to a double-layer PETG thermal shrinkage film battery label and a preparation method thereof.The double-layer PETG thermal shrinkage film battery label is formed by sequentially stacking a release layer, a pressure-sensitive adhesive layer, a bottom film layer, a composite adhesive layer and a top film layer from bottom to top, and an aluminum layer is stacked on the upper layer or the lower layer of the bottom film layer; the ink layer is overlaid on the upper layer or the lower layer of the top film layer; the raw material for preparing the composite adhesive layer is a solvent-free type environment-friendly polyurethane adhesive. The prepared double-layer PETG heat shrinkage film battery label is not prone to layering, the barrier property is excellent, the preparation method is simple, and materials are environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of heat-shrinkable label films, specifically to a double-layer PETG heat-shrinkable film battery label and its preparation method. Background Technology

[0002] Battery labels are essential for recording crucial information such as battery model, performance, production details, and warnings. PETG heat-shrink film battery labels represent the most promising product category in the current battery label market. Traditional single-layer films are prone to uneven shrinkage during heat shrinkage, leading to label wrinkles and pattern deformation. Double-layer PETG heat-shrink film, however, precisely controls the heat shrinkage temperature of both layers. Furthermore, as the functional requirements for battery labels in home settings become increasingly diverse, in addition to basic performance, they also need anti-counterfeiting, weather resistance, and easy-to-tear properties. Double-layer PETG heat-shrink film can achieve functional integration through its layered design. Therefore, double-layer PETG heat-shrink film has become the mainstream development direction for battery label materials, driving the industry towards "high performance, environmental friendliness, and high efficiency."

[0003] Patent CN113257109A discloses a double-layer PETG heat-shrinkable film battery label, comprising release paper, an outer layer coated with a pressure-sensitive adhesive layer, an outer layer coated with a flame-retardant layer, an outer layer coated with a noise-reducing layer, an outer layer coated with a top film layer, an inner layer coated with a thermally conductive layer, an inner layer coated with a protective layer, an inner layer coated with an alkali-resistant coating, and an inner layer coated with a bottom film layer. This battery label exhibits good flame retardancy, making it less prone to spontaneous combustion when heated. It also provides excellent sound insulation and noise reduction, minimizing noise pollution caused by battery vibration within the product. Furthermore, its smooth surface facilitates quick viewing of battery performance and production information, and it is resistant to scratches from sharp objects. However, its thermally conductive layer, made of thermally conductive graphite, may affect the shrinkage and adhesion between the layers of the double-layer PETG heat-shrinkable film battery label.

[0004] Therefore, there is an urgent need in the market for a double-layer PETG heat-shrinkable film battery label with strong adhesion between the layers. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to obtain a double-layer PETG heat-shrinkable film battery label with strong adhesion between layers, excellent barrier properties, and a simple preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a double-layer PETG heat-shrinkable film battery label, which consists of a release layer, a pressure-sensitive adhesive layer, a bottom film layer, a composite adhesive layer, and a top film layer stacked sequentially from bottom to top. An aluminum layer is stacked on top of or below the bottom film layer; an ink layer is stacked on top of or below the top film layer; and the raw material for preparing the composite adhesive layer is a solvent-free environmentally friendly polyurethane adhesive.

[0007] In some embodiments, the raw material for preparing the pressure-sensitive adhesive layer is one of solvent-free polyacrylate pressure-sensitive adhesive, water-based polyacrylate pressure-sensitive adhesive, solvent-based polyacrylate pressure-sensitive adhesive, and UV-based polyacrylate pressure-sensitive adhesive.

[0008] In some embodiments, the raw materials for the bottom and top film layers are PETG heat-shrinkable milky white film or PETG heat-shrinkable transparent film.

[0009] In some embodiments, the material used to prepare the ink layer is one of water-based ink, solvent-based ink, or UV-based ink.

[0010] Preferably, the material used to prepare the ink layer is water-based polyurethane ink or water-based acrylic ink.

[0011] This application designs a double-layer PETG heat-shrinkable film battery label, consisting of a release layer, a pressure-sensitive adhesive layer, a bottom film layer, a composite adhesive layer, and a top film layer stacked sequentially from bottom to top. An ink layer is stacked on top or below the top film layer. The design of both the top and bottom films being made of PETG heat-shrinkable film ensures that the ink layer and the top and bottom films maintain the same heat shrinkage rate, solving problems such as printing pattern deformation, warping, and unclear images caused by mismatched heat shrinkage rates of the materials. Aluminizing the bottom film layer enhances the barrier properties of the PETG film, thereby improving the stability of battery performance. Furthermore, PETG heat-shrinkable film is a biodegradable green material, the adhesive used is a solvent-free environmentally friendly polyurethane adhesive, the pressure-sensitive adhesive is a solvent-free polyacrylate pressure-sensitive adhesive, and the ink is a water-based ink, making the double-layer PETG heat-shrinkable film battery label environmentally friendly.

[0012] In some embodiments, the method for preparing the solvent-free environmentally friendly polyurethane adhesive includes the following steps: A1. Add 9,9-dibromo-9H-fluorene to triethyl phosphite, heat to 120-140℃ and react for 12-24 h, then distill under reduced pressure and perform column chromatography to obtain the compound; The structural formula of the compound is as follows: Where R= ; A2. Add the compound obtained in step A1 to the polyether polyol, heat to 60-70℃, add 4,4'-diphenylmethane diisocyanate and catalyst, and react under nitrogen protection for 5-7 hours to obtain component A. A3. Add 4,4'-diphenylmethane diisocyanate and catalyst to a reaction vessel, heat to 55-65℃, add 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene and polyether polyol, react under nitrogen protection for 7-9 h to obtain component B; A4. Add component A obtained in step A2 to component B obtained in step A3, stir at 20-35℃ for 20-30 minutes to obtain solvent-free environmentally friendly polyurethane adhesive.

[0013] This application introduces 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene into the polyurethane chain. On the one hand, the large number of rigid structures on 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene can increase the glass transition temperature of the polyurethane chain, thereby improving the heat resistance of the solvent-free environmentally friendly polyurethane adhesive and making the double-layer PETG heat-shrinkable film battery label less prone to delamination during heat shrinking. On the other hand, the 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene chain can interact with the compound formed by adding 9,9-dibromo-9H-fluorene to triethyl phosphite through π-π bonds, promoting the dispersibility of the phosphate-containing compound in the solvent-free environmentally friendly polyurethane adhesive. The introduction of phosphate ester is beneficial to improving the adhesion between the solvent-free environmentally friendly polyurethane adhesive and the aluminum layer. Furthermore, the strong π-π interaction force in the solvent-free environmentally friendly polyurethane adhesive system enhances the interaction force between the polyurethane chain segments, thereby improving the adhesion and heat resistance of the solvent-free environmentally friendly polyurethane adhesive.

[0014] In some embodiments, the ratio of 9,9-dibromo-9H-fluorene to triethyl phosphite is 1 g: (12-16) ml.

[0015] In some embodiments, the molar ratio of the compound described in step A2, the hydroxyl groups in the polyether polyol, and 4,4'-diphenylmethane diisocyanate is (0.5-0.8):(15-17):1.

[0016] Preferably, the polyether polyol is a composition of polyether diol and polyether triol, with a molar ratio of 1:(6-9).

[0017] In some embodiments, the molar ratio of 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene, the hydroxyl group in the polyether diol, and 4,4'-diphenylmethane diisocyanate in step A3 is (0.05-0.1):(0.2-0.3):1.

[0018] In some embodiments, the mass ratio of component A to component B is 1:(1.4-1.7).

[0019] Another aspect of the present invention provides a method for preparing a double-layer PETG heat-shrinkable film battery tag, comprising the following steps: S1. Vacuum aluminum deposition is performed on the upper or lower layer of the base film with a thickness of 10-30 μm, with a vacuum degree of 1×10⁻⁶. -4 Pa ~ 1×10 -5 Pa, winding speed of 280-320m / min, evaporation boat heating temperature of 1300-1400℃, to obtain aluminum layer with thickness of 20-40nm and aluminum layer uniformity index of ±5%; S2. Apply pressure-sensitive adhesive to the bottom film layer or the aluminum layer, and then cure and mature it. The maturity temperature is 35-45℃ and the maturity time is 12-48h to form a pressure-sensitive adhesive layer with a thickness of 15-25μm. Combine the pressure-sensitive adhesive layer with a release layer with a thickness of 23±2μm and roll it up to obtain composite layer 1. S3. Print ink on the upper or lower layer of the top film layer with a thickness of 10-30μm to form an ink layer with a thickness of 0.5-2.5μm, thus obtaining composite layer 2; S4. Apply a solvent-free environmentally friendly polyurethane adhesive between composite layer 1 and composite layer 2. After application, cure at 55-65℃ to form a composite adhesive layer with a thickness of 0.5-2.5μm. Then, roll up and press to obtain a double-layer PETG heat shrink film battery label.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a release layer, a pressure-sensitive adhesive layer, a bottom film layer, a composite adhesive layer and a top film layer to be stacked sequentially from bottom to top. The bottom film layer is stacked with an aluminum layer on top or below the bottom film layer and the top film layer is stacked with an ink layer on top or below the top film layer. This makes the prepared double-layer PETG heat shrink film battery label have clear printing patterns, excellent barrier performance, good adhesion of each layer and green environmental protection.

[0021] (2) By introducing 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene into the polyurethane chain, the present invention can, on the one hand, increase the glass transition temperature of the polyurethane chain by introducing a large number of rigid structures, thereby making it less likely for the double-layer PETG heat shrink film battery label to delaminate during the heat shrinking process; on the other hand, the 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene chain can interact with the 9,9-dibromo-9H-fluorene chain in the compound through π-π bonds, thereby promoting the dispersion of the phosphate ester group-containing compound in the solvent-free environmentally friendly polyurethane adhesive.

[0022] (3) The present invention prepares a solvent-free environmentally friendly polyurethane adhesive containing fluorene groups and phosphate groups by reacting 9,9-dibromo-9H-fluorene with triethyl phosphite. The introduction of phosphate groups further improves the adhesion between the composite adhesive layer and the aluminum layer. Furthermore, the fluorene groups generate strong π-π interaction forces with the 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene segments on the solvent-free environmentally friendly polyurethane adhesive, thereby enhancing the interaction forces of each polyurethane segment and thus improving the adhesion and heat resistance of the solvent-free environmentally friendly polyurethane adhesive. Detailed Implementation

[0023] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0024] In the following examples and comparative examples, except for the solvent-free environmentally friendly polyurethane adhesive, all other compounds and related reagents and raw materials used were commercially available. The bottom and top film layers were PETG heat-shrinkable transparent films with a thickness of 25 μm, purchased from Shijiazhuang Dajia New Material Technology Co., Ltd.; the polyether diol was PPG-210; the polyether triol was N-310, purchased from Nanjing Zhongshan Chemical Co., Ltd.; the water-based acrylic ink was LA-6169A, purchased from Zhaoqing Xinguangli Chemical Industry Co., Ltd.; the solvent-free polyacrylate pressure-sensitive adhesive was 3808-1A, purchased from Dongguan Wanjiang Jianda Adhesive Products Co., Ltd.; and the release layer had a thickness of 23±2 μm, purchased from Dongguan Zhongshu New Material Technology Development Co., Ltd.

[0025] Preparation Example 1 The preparation method of solvent-free environmentally friendly polyurethane adhesive-1 includes the following steps: A1. 1 g of 9,9-dibromo-9H-fluorene was added to 15 ml of triethyl phosphite, and the mixture was heated to 130 °C and reacted for 18 h. After vacuum distillation, column chromatography was performed (the eluent was a mixture of n-hexanol, methanol, and triethylamine in a volume ratio of 100:10:2) to obtain the compound. The structural formula of the compound is Where R= ; A2. Add 0.0065 mol of the compound obtained in step A1 to 0.019 mol of polyether diol (calculated as hydroxyl groups) and 0.141 mol of polyether triol (calculated as hydroxyl groups), heat to 65°C, add 0.01 mol of 4,4'-diphenylmethane diisocyanate and 0.01 g of dibutyltin dilaurate, react under nitrogen protection for 6 h to obtain component A; A3. Add 0.08 mol of 4,4'-diphenylmethane diisocyanate and 0.01 g of dibutyltin dilaurate to a reaction vessel, heat to 60 °C, add 0.006 mol of 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene and 0.02 mol of polyether diol (based on hydroxyl groups), and react for 8 h under nitrogen protection to obtain component B; A4. Add 10g of component A obtained in step A2 to 16g of component B obtained in step A3, stir at 30℃ for 25min to obtain solvent-free environmentally friendly polyurethane adhesive-1.

[0026] Preparation Example 2 The preparation method of solvent-free environmentally friendly polyurethane adhesive-2 is the same as that of preparation example 1, except that the amount of compound added in step A2 is 0.009 mol.

[0027] Preparation Example 3 The preparation method of solvent-free environmentally friendly polyurethane adhesive-3 is the same as that of preparation example 1, except that the amount of 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene added is 0.0096 mol.

[0028] Preparation Example 4 The preparation method of solvent-free environmentally friendly polyurethane adhesive-4 is the same as that of preparation example 1, except that the amount of component B added is 20g.

[0029] Preparation Example 5 The preparation method of solvent-free environmentally friendly polyurethane adhesive-5 includes the following steps: A1. 1 g of 9,9-dibromo-9H-fluorene was added to 15 ml of triethyl phosphite, and the mixture was heated to 130 °C and reacted for 18 h. After vacuum distillation, column chromatography was performed (the eluent was a mixture of n-hexanol, methanol, and triethylamine in a volume ratio of 100:10:2) to obtain the compound. The structural formula of the compound is Where R= ; A2. Add 0.0065 mol of the compound obtained in step A1 to 0.019 mol of polyether diol (calculated as hydroxyl groups) and 0.141 mol of polyether triol (calculated as hydroxyl groups), heat to 65°C, add 0.01 mol of 4,4'-diphenylmethane diisocyanate and 0.01 g of dibutyltin dilaurate, react under nitrogen protection for 6 h to obtain component A; A3. Add 0.08 mol of 4,4'-diphenylmethane diisocyanate and 0.01 g of dibutyltin dilaurate to a reaction vessel, heat to 60°C, add 0.02 mol of polyether diol (based on hydroxyl groups), and react for 8 h under nitrogen protection to obtain component B; A4. Add 10g of component A obtained in step A2 to 16g of component B obtained in step A3, stir at 30℃ for 25min to obtain solvent-free environmentally friendly polyurethane adhesive-5.

[0030] Preparation Example 6 The preparation method of solvent-free environmentally friendly polyurethane adhesive-6 includes the following steps: A1. 0.019 mol of polyether diol (calculated as hydroxyl groups) and 0.141 mol of polyether triol (calculated as hydroxyl groups) were heated to 65°C, and 0.01 mol of 4,4'-diphenylmethane diisocyanate and 0.01 g of dibutyltin dilaurate were added. The mixture was reacted under nitrogen protection for 6 h to obtain component A. A2. Add 0.08 mol of 4,4'-diphenylmethane diisocyanate and 0.01 g of dibutyltin dilaurate to a reaction vessel, heat to 60 °C, add 0.006 mol of 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene and 0.02 mol of polyether diol (based on hydroxyl groups), and react for 8 h under nitrogen protection to obtain component B; A3. Add 10g of component A obtained in step A1 to 16g of component B obtained in step A2, stir at 30℃ for 25min to obtain solvent-free environmentally friendly polyurethane adhesive-6.

[0031] Preparation Example 7 The preparation method of solvent-free environmentally friendly polyurethane adhesive-7 includes the following steps: A1. In a mixture of 10g polyether diol and 78.5g polyether triol, the temperature was raised to 65℃, and 0.01mol of 4,4'-diphenylmethane diisocyanate and 0.01g of dibutyltin dilaurate were added. The mixture was reacted under nitrogen protection for 6h to obtain component A. A2. Add 0.08 mol of 4,4'-diphenylmethane diisocyanate and 0.01 g of dibutyltin dilaurate to a reaction vessel, heat to 60°C, add 16 g of polyether diol, and react for 8 h under nitrogen protection to obtain component B. A3. Add 10g of component A obtained in step A1 to 16g of component B obtained in step A2, stir at 30℃ for 25min to obtain solvent-free environmentally friendly polyurethane adhesive-7.

[0032] Example 1 A double-layer PETG heat-shrinkable film battery label comprises, from bottom to top, a release layer, a pressure-sensitive adhesive layer, a bottom film layer, an aluminum layer, a composite adhesive layer, an ink layer, and a top film layer; the raw material for preparing the composite adhesive layer is a solvent-free environmentally friendly polyurethane adhesive-1.

[0033] The method for preparing the double-layer PETG heat-shrinkable film battery tag in this embodiment includes the following steps: S1. Vacuum aluminum deposition is performed on the top layer of the 25μm thick base film, with a vacuum degree of 1×10⁻⁶. -4 Pa, winding speed of 300m / min, evaporation boat heating temperature of 1350℃, to obtain aluminum layer with a thickness of 30nm and aluminum layer uniformity index of ±5%; S2. A solvent-free polyacrylate pressure-sensitive adhesive is coated on the underside of the base film layer. After coating, it is cured and aged at a temperature of 40°C for 24 hours to form a pressure-sensitive adhesive layer with a thickness of 20μm. The pressure-sensitive adhesive layer is then combined with a release layer with a thickness of 23±2μm and wound up to obtain composite layer 1. S3. A water-based acrylic ink is printed under a top film layer with a thickness of 25 μm to form an ink layer with a thickness of 1.5 μm, thus obtaining composite layer 2; S4. Apply solvent-free environmentally friendly polyurethane adhesive-1 between composite layer 1 and composite layer 2. After application, cure at 60°C to form a composite adhesive layer with a thickness of 1.5μm. Then, roll up and press to obtain a double-layer PETG heat shrink film battery label.

[0034] Example 2 A double-layer PETG heat-shrinkable film battery label comprises, from bottom to top, a release layer, a pressure-sensitive adhesive layer, a bottom film layer, an aluminum layer, a composite adhesive layer, an ink layer, and a top film layer; the raw material for preparing the composite adhesive layer is a solvent-free environmentally friendly polyurethane adhesive-1.

[0035] The method for preparing the double-layer PETG heat-shrinkable film battery tag in this embodiment includes the following steps: S1. Vacuum aluminum deposition is performed on the top layer of the 25μm thick base film, with a vacuum degree of 1×10⁻⁶. -4 Pa, winding speed of 280m / min, evaporation boat heating temperature of 1300℃, to obtain an aluminum layer with a thickness of 30nm and an aluminum layer uniformity index of ±5%; S2. A solvent-free polyacrylate pressure-sensitive adhesive is coated on the underside of the base film layer. After coating, it is cured and aged at a temperature of 35°C for 48 hours to form a pressure-sensitive adhesive layer with a thickness of 15μm. The pressure-sensitive adhesive layer is then combined with a release layer with a thickness of 23±2μm and wound up to obtain composite layer 1. S3. A water-based acrylic ink is printed under a top film layer with a thickness of 25 μm to form an ink layer with a thickness of 1.5 μm, thus obtaining composite layer 2; S4. Apply solvent-free environmentally friendly polyurethane adhesive-1 to composite layer 1 and composite layer 2, and cure at 55°C to form a composite adhesive layer with a thickness of 1.5μm. Then, roll up and press to obtain a double-layer PETG heat shrink film battery label.

[0036] Example 3 A double-layer PETG heat-shrinkable film battery label comprises, from bottom to top, a release layer, a pressure-sensitive adhesive layer, a bottom film layer, an aluminum layer, a composite adhesive layer, an ink layer, and a top film layer; the raw material for preparing the composite adhesive layer is a solvent-free environmentally friendly polyurethane adhesive-1.

[0037] The method for preparing the double-layer PETG heat-shrinkable film battery tag in this embodiment includes the following steps: S1. Vacuum aluminum deposition is performed on the underlayer with a thickness of 25 μm, with a vacuum degree of 1×10⁻⁶. -5 Pa, winding speed of 320m / min, evaporation boat heating temperature of 1400℃, to obtain an aluminum layer with a thickness of 30nm and an aluminum layer uniformity index of ±5%; S2. A solvent-free polyacrylate pressure-sensitive adhesive is coated on the underside of the aluminum layer. After coating, it is cured and aged at a temperature of 45°C for 12 hours to form a pressure-sensitive adhesive layer with a thickness of 25μm. The pressure-sensitive adhesive layer is then combined with a release layer with a thickness of 23±2μm and wound up to obtain composite layer 1. S3. A water-based acrylic ink is printed on the top film layer with a thickness of 25 μm to form an ink layer with a thickness of 1.5 μm, thus obtaining composite layer 2; S4. Apply solvent-free environmentally friendly polyurethane adhesive-1 between composite layer 1 and composite layer 2. After application, cure at 65°C to form a composite adhesive layer with a thickness of 1.5μm. Then, roll up and press to obtain a double-layer PETG heat shrink film battery label.

[0038] Example 4 A double-layer PETG heat-shrinkable film battery label and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that solvent-free environmentally friendly polyurethane adhesive-1 is replaced with solvent-free environmentally friendly polyurethane adhesive-2 in equal amounts.

[0039] Example 5 A double-layer PETG heat-shrinkable film battery label and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that solvent-free environmentally friendly polyurethane adhesive-1 is replaced with solvent-free environmentally friendly polyurethane adhesive-3 in equal amounts.

[0040] Example 6 A double-layer PETG heat-shrinkable film battery label and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that solvent-free environmentally friendly polyurethane adhesive-1 is replaced with solvent-free environmentally friendly polyurethane adhesive-4 in equal amounts.

[0041] Example 7 A double-layer PETG heat-shrinkable film battery label and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that solvent-free environmentally friendly polyurethane adhesive-1 is replaced with solvent-free environmentally friendly polyurethane adhesive-5 in equal amounts.

[0042] Example 8 A double-layer PETG heat-shrinkable film battery label and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that solvent-free environmentally friendly polyurethane adhesive-1 is replaced with solvent-free environmentally friendly polyurethane adhesive-6 in equal amounts.

[0043] Example 9 A double-layer PETG heat-shrinkable film battery label and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that solvent-free environmentally friendly polyurethane adhesive-1 is replaced with solvent-free environmentally friendly polyurethane adhesive-7 in equal amounts.

[0044] Performance testing The double-layer PETG heat-shrinkable film battery labels obtained in the above embodiments were tested: (1) Peel strength: The peel strength of the double-layer PETG heat shrink film battery labels obtained in each embodiment was tested in accordance with GB / T 2791-1995.

[0045] (2) Heat resistance: The double-layer PETG heat shrink film battery labels obtained in each embodiment were wrapped on a glass rod and aged at 70°C for one week. The ink layer and aluminum layer were observed to see if they were separated from the composite adhesive layer.

[0046] The test results are shown in Table 1: Table 1 As shown in Table 1, the double-layer PETG heat-shrinkable film battery labels of Examples 1-3 of this application exhibit excellent adhesion and heat resistance between their layers. A comparison of Examples 4, 5, and Example 1 shows that changing the ratio of the compound to 4,4'-diphenylmethane diisocyanate in step A2 or the ratio of 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene to 4,4'-diphenylmethane diisocyanate in step A3 may increase the brittleness of the adhesive, thereby worsening the adhesion and heat resistance of the double-layer PETG heat-shrinkable film battery labels. A comparison of Example 6 and Example 1 shows that changing component A... When mixing with component B, unreacted component B may react with water in the air, resulting in poor adhesion and heat resistance of the double-layer PETG heat-shrinkable film battery label. A comparison of Examples 7 and 8 with Example 1 shows that without the addition of the compound or 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene, the adhesion and heat resistance of the double-layer PETG heat-shrinkable film battery label deteriorate. A comparison of Examples 9 and 1 shows that the solvent-free two-component polyurethane synthesized by conventional methods has poor heat resistance and poor adhesion to the aluminum layer, resulting in poor adhesion and heat resistance of the double-layer PETG heat-shrinkable film battery label.

[0047] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A double-layer PETG heat-shrinkable film battery label, comprising, from bottom to top, a release layer, a pressure-sensitive adhesive layer, a bottom film layer, a composite adhesive layer, and a top film layer, characterized in that, An aluminum layer is superimposed on the upper or lower layer of the bottom film layer; an ink layer is superimposed on the upper or lower layer of the top film layer; the raw material for preparing the composite adhesive layer is a solvent-free environmentally friendly polyurethane adhesive.

2. The double-layer PETG heat-shrinkable film battery label according to claim 1, characterized in that, The raw material for preparing the pressure-sensitive adhesive layer is one of solvent-free polyacrylate pressure-sensitive adhesive, water-based polyacrylate pressure-sensitive adhesive, solvent-based polyacrylate pressure-sensitive adhesive, and UV-type polyacrylate pressure-sensitive adhesive.

3. The double-layer PETG heat-shrinkable film battery label according to claim 1, characterized in that, The raw materials for the bottom and top film layers are PETG heat-shrinkable milky white film or PETG heat-shrinkable transparent film.

4. The double-layer PETG heat-shrinkable film battery label according to claim 1, characterized in that, The material used to prepare the ink layer is one of water-based ink, solvent-based ink, or UV-based ink.

5. The double-layer PETG heat-shrinkable film battery label according to claim 1, characterized in that, The preparation method of the solvent-free environmentally friendly polyurethane adhesive includes the following steps: A1. Add 9,9-dibromo-9H-fluorene to triethyl phosphite, heat to 120-140℃ and react for 12-24 h, then distill under reduced pressure and perform column chromatography to obtain the compound; A2. Add the compound obtained in step A1 to the polyether polyol, heat to 60-70℃, add 4,4'-diphenylmethane diisocyanate and catalyst, and react under nitrogen protection for 5-7 hours to obtain component A. A3. Add 4,4'-diphenylmethane diisocyanate and catalyst to a reaction vessel, heat to 55-65℃, add 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene and polyether diol, react under nitrogen protection for 7-9 h to obtain component B; A4. Add component A obtained in step A2 to component B obtained in step A3, stir at 20-35℃ for 20-30 minutes to obtain solvent-free environmentally friendly polyurethane adhesive.

6. The double-layer PETG heat-shrinkable film battery label according to claim 5, characterized in that, The ratio of 9,9-dibromo-9H-fluorene to triethyl phosphite is 1 g: (12-16) ml.

7. The double-layer PETG heat-shrinkable film battery label according to claim 5, characterized in that, The molar ratio of the compound mentioned in step A2, the hydroxyl groups in the polyether polyol, and 4,4'-diphenylmethane diisocyanate is (0.5-0.8):(15-17):

1.

8. The double-layer PETG heat-shrinkable film battery label according to claim 5, characterized in that, In step A3, the molar ratio of 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene, the hydroxyl group in the polyether diol, and 4,4'-diphenylmethane diisocyanate is (0.05-0.1):(0.2-0.3):

1.

9. The double-layer PETG heat-shrinkable film battery label according to claim 5, characterized in that, The mass ratio of component A to component B is 1:(1.4-1.7).

10. A method for preparing a double-layer PETG heat-shrinkable film battery label according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Vacuum aluminum deposition is performed on the upper or lower layer of the base film with a thickness of 10-30 μm, with a vacuum degree of 1×10⁻⁶. -4 Pa ~ 1×10 - 5 Pa, winding speed of 280-320m / min, evaporation boat heating temperature of 1300-1400℃, to obtain aluminum layer with thickness of 20-40nm and aluminum layer uniformity index of ±5%; S2. Apply pressure-sensitive adhesive to the bottom film layer or the aluminum layer, and then cure and mature it. The maturity temperature is 35-45℃ and the maturity time is 12-48h to form a pressure-sensitive adhesive layer with a thickness of 15-25μm. Combine the pressure-sensitive adhesive layer with a release layer with a thickness of 23±2μm and roll it up to obtain composite layer 1. S3. Print ink on the upper or lower layer of the top film layer with a thickness of 10-30μm to form an ink layer with a thickness of 0.5-2.5μm, thus obtaining composite layer 2; S4. Apply a solvent-free environmentally friendly polyurethane adhesive between composite layer 1 and composite layer 2. After application, cure at 55-65℃ to form a composite adhesive layer with a thickness of 0.5-2.5μm. Then, roll up and press to obtain a double-layer PETG heat shrink film battery label.

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