A stampable profiled film, its production and use

Abstract

This invention relates to the field of composite film technology, specifically to a stampable and shape-retaining film, its preparation method, and its application. It comprises a base film and a tin foil layer bonded to its surface. The base film is co-extruded from top to bottom by a printed composite layer, an impact-resistant molding layer, and an adhesive backing layer. This invention combines a matrix resin with a multifunctional interface compatibilizer for reactive three-layer co-extrusion and hot-pressing. Its core lies in utilizing a modifier with a hyperbranched polyester backbone as the molecular chain core and end-group grafted epoxy and siloxane groups to provide significant branching steric hindrance, intralayer ring-opening crosslinking, and interfacial covalent bonding effects. This invention overcomes the problems of deformation recovery and metal layer separation that commonly occur under high tensile strain during stamping of polymer films. By utilizing a specific modified anchoring structure, it effectively releases and locks in the internal stress of the structure, achieving overall structural lightweighting while endowing the film with excellent shape retention, reliable peel resistance, and impact toughness.

Description

Technical Field

[0001] This invention relates to the field of composite film technology, specifically to a stampable and shaped film, its preparation method, and its application. Background Technology

[0002] In applications such as electronic devices, home appliances, and automotive interiors, solid metal marking components suffer from limitations such as excessive weight, high processing energy consumption, and difficulty in achieving complex curved surface bonding. The industry often uses composite materials combining polymer base films and metal foils as an alternative. However, conventional polymer materials experience strong stress rebound during stamping, making it easy for the material to deform and recover, thus making it difficult to maintain the three-dimensional macroscopic dimensions and edge details.

[0003] Furthermore, when a metal layer with a thickness of micrometers is bonded to the surface of a thin film, the large strain and stretching generated during the stamping stage can easily cause interfacial delamination and separation between the metal layer and the base film. Current conventional solutions usually involve increasing the thickness of the material itself or physically blending inorganic fillers to improve the material's rigidity. However, this leads to increased brittleness and reduced impact resistance, and still cannot cope with the interfacial delamination phenomenon under large deformation during stamping. Summary of the Invention

[0004] The purpose of this invention is to provide a stampable and shaped thin film, its preparation method, and its application. This aims to solve the problems in existing technologies where polymer composite films are prone to stress rebound and deformation recovery during stamping, metal layer and base film are prone to delamination under deep stamping deformation, and conventional stiffening treatments lead to increased material brittleness and deterioration of impact resistance. Specifically, the technical solution of this invention is as follows:

[0005] A stampable and shaped film includes a base film and a tin foil layer bonded to the surface of the base film; the base film is co-extruded from top to bottom by a printed composite layer, an impact-resistant molding layer and an adhesive backing layer; wherein the printed composite layer, or the printed composite layer and the impact-resistant molding layer, contains a multifunctional interface compatibilizer; the molecular chain core of the multifunctional interface compatibilizer is a hyperbranched polyester skeleton, and the end groups of the hyperbranched polyester skeleton are grafted with epoxy groups and siloxane groups.

[0006] Preferably, the preparation steps of the multifunctional interface compatibilizer include:

[0007] Step 1: Trimethylolpropane, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid are mixed in a molar ratio of 1:(5-15):(0.01-0.1) and melt polycondensed for 4-6 hours under stirring conditions at 140℃ and absolute pressure ≤0.01MPa to obtain hydroxyl-terminated hyperbranched polyester.

[0008] Step 2: Dissolve the hydroxyl-terminated hyperbranched polyester in toluene, add epichlorohydrin and tetrabutylammonium bromide, wherein the molar ratio of epichlorohydrin to the hydroxyl groups in the hydroxyl-terminated hyperbranched polyester is (0.4-2.5):1, and the amount of tetrabutylammonium bromide added is 1-5% of the mass of the hydroxyl-terminated hyperbranched polyester. Under stirring conditions at 60℃, add a 30% sodium hydroxide aqueous solution dropwise at a uniform rate over 1-2 hours, and continue the reaction at this temperature for 5 hours. The molar ratio of sodium hydroxide to epichlorohydrin in the sodium hydroxide aqueous solution is (1.0-1.2):1. After washing with water and rotary evaporation under reduced pressure, the hyperbranched polyester intermediate is obtained.

[0009] Step 3: Dissolve the hyperbranched polyester intermediate in anhydrous dichloromethane, add dibutyltin dilaurate, wherein the amount of dibutyltin dilaurate added is 0.1-0.5% of the mass of the hyperbranched polyester intermediate, and react with 3-isocyanate-propyltriethoxysilane dropwise at 40°C for 3 hours under nitrogen protection, wherein the molar ratio of 3-isocyanate-propyltriethoxysilane to the remaining hydroxyl groups in the hyperbranched polyester intermediate is (0.1-0.5):1. After precipitation purification and vacuum drying, a multifunctional interface compatibilizer is prepared.

[0010] A method for preparing a stampable and shaped thin film includes the following preparation steps:

[0011] Step 1, Vacuum pretreatment of raw materials: The multifunctional interface compatibilizer and the matrix resin of the printing composite layer, the impact-resistant molding layer and the adhesive backing layer are placed in a vacuum drying oven and dried for 4-6 hours at 90-100℃ and absolute pressure ≤0.01MPa. Then, according to the material ratio of each layer, the corresponding matrix resin and multifunctional interface compatibilizer are placed in a high-speed mixer and stirred and mixed at a speed of 700-800r / min for 12-15min to obtain the co-extrusion raw materials of each layer.

[0012] Step 2, reactive three-layer co-extrusion: The co-extrusion raw materials for each layer are fed into independent extruders for reactive co-extrusion. The extrusion temperature of the printed composite layer is 220-240℃, the extrusion temperature of the impact-resistant molding layer is 225-245℃, and the extrusion temperature of the adhesive layer is 220-240℃. The extruded melt is filtered through a sintered metal mesh with a pore size of 10-20μm and then merged according to the thickness ratio.

[0013] Step 3, pressure casting: After the merged extruded melt is extruded through the die, it is subjected to pressure cooling casting between a mirror roller and a silicone roller with a surface roughness Ra of 1.0-2.0μm and nano silica filler to obtain a base film with one side being mirror and the other side being frosted.

[0014] Step 4, Surface activation and hot-pressing lamination: The mirror surface of the base film is subjected to corona treatment, and a tin foil layer is hot-pressed onto the corona-treated mirror surface to obtain a stampable and shaped film.

[0015] The present invention also provides the application of the above-mentioned stampable and shaped film in the preparation of signs for computer, communication and consumer electronics products, home appliances or automotive interiors.

[0016] The present invention has the following beneficial effects:

[0017] 1. This invention utilizes a hyperbranched polyester skeleton with a multifunctional interface compatibilizer, which can stably maintain the three-dimensional dimensions and edge details of the film after deep stamping deformation; by effectively releasing and locking the internal stress of the structure, spontaneous deformation recovery is avoided, thus meeting the manufacturing requirements of complex curved surfaces and high-precision appearance parts.

[0018] 2. This invention enriches the siloxane groups in the multifunctional interface compatibilizer on the mirror surface of the base film, enabling the tin foil layer and the base film to be bonded by silicon-oxygen-metal covalent bonds. This stable anchoring structure ensures dense adhesion between film layers, avoids local blistering or overall separation under strain and tension, provides excellent interface adhesion protection, and extends the service life of the overall structure.

[0019] 3. This invention utilizes the ring-opening crosslinking structure formed by the epoxy groups in the multifunctional interface compatibilizer and the end groups of the matrix resin to construct an internal crosslinking network in the material, which can effectively absorb and disperse energy when subjected to external impact, reducing the risk of brittle fracture; thus, the film achieves overall structural lightweighting while significantly improving the impact toughness and physical protection capability of the matrix. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below; the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Example 1:

[0022] This embodiment provides a stampable and shaped film, specifically including the following steps;

[0023] Preparation of S1 hyperbranched polyester backbone: 13.4 g of trimethylolpropane, 134.1 g of 2,2-dimethylolpropionic acid and 0.86 g of p-toluenesulfonic acid were weighed and added to a four-necked flask equipped with a mechanical stirrer, thermometer and vacuum interface. The temperature was raised to 140 °C under nitrogen protection, the stirrer was turned on and the vacuum was gradually reduced to 0.005 MPa, and the reaction was maintained for 5 h. During the reaction, the water generated by polycondensation was continuously removed. After the reaction was completed, the temperature was lowered to obtain hydroxyl-terminated hyperbranched polyester. This hydroxyl-terminated hyperbranched polyester serves as the molecular chain core of the subsequent multifunctional interface compatibilizer. Its highly branched structure can provide significant branching steric hindrance and chain segment interlocking effect for the film, thereby improving the shape retention ability of the film after stamping deformation.

[0024] S2 epoxy group grafting: The hydroxyl-terminated hyperbranched polyester obtained in S1 was dissolved in toluene based on the total amount of hydroxyl groups, and the solid content was controlled at 35 wt%. Epichlorohydrin was added to make the molar ratio of epichlorohydrin to hydroxyl groups in the hydroxyl-terminated hyperbranched polyester 2.2:1. Then tetrabutylammonium bromide was added, and the amount added was 3 wt% of the mass of the hydroxyl-terminated hyperbranched polyester. The system was heated to 60℃, and a 30% sodium hydroxide aqueous solution was added dropwise under stirring. The addition was controlled to be completed at a uniform rate within 1-2 hours. The molar ratio of sodium hydroxide to epichlorohydrin in the sodium hydroxide aqueous solution was 1.1:1. The reaction was kept at this temperature for 5 hours.

[0025] After the reaction is completed, the mixture is allowed to stand and separate into layers. It is then washed with water until neutral and removed by rotary evaporation under reduced pressure to remove toluene and unreacted epichlorohydrin, thus obtaining a hyperbranched polyester intermediate. The epoxy groups grafted onto this hyperbranched polyester intermediate can undergo ring-opening crosslinking reactions with the end groups of the matrix resin during the subsequent film forming process, thereby enhancing the chemical anchoring and intralayer stress transfer capabilities between the multifunctional interface compatibilizer and the resin matrix.

[0026] S3 siloxane group grafting: The hyperbranched polyester intermediate obtained from S2 was dissolved in anhydrous dichloromethane, and the solid content was controlled at 25 wt%. Dibutyltin dilaurate was added, and the amount added was 0.3 wt% of the mass of the hyperbranched polyester intermediate. Under nitrogen protection, 3-isocyanate-propyltriethoxysilane was added dropwise at 40 °C, so that the molar ratio of 3-isocyanate-propyltriethoxysilane to the remaining hydroxyl groups in the hyperbranched polyester intermediate was 0.30:1. The reaction was maintained at this temperature for 3 h. The reaction solution was poured into anhydrous diethyl ether for precipitation and purification. After filtration, it was vacuum dried at 50 °C for 12 h to prepare a multifunctional interface compatibilizer.

[0027] Gel permeation chromatography determined that the number-average molecular weight of this multifunctional interface compatibilizer was 3200 g / mol, and the molecular weight distribution was 1.45. Infrared spectroscopy showed that at 910 cm⁻¹... -1 A distinct characteristic absorption peak of epoxy groups appears at 1080 cm⁻¹. -1 A silicon-oxygen-silicon bond stretching vibration peak appears at 3300-3500 cm⁻¹. -1The hydroxyl peak at the position was significantly weakened; the 1H NMR spectrum showed a proton peak on the epoxy ring at 2.6-2.8 ppm and a methylene proton peak bonded to silicon atoms at 0.6 ppm; the epoxy equivalent was determined to be 450 g / eq by chemical titration; the synthesis yield of the multifunctional interface compatibilizer was 85%, and the purity was determined to be 98% by liquid chromatography.

[0028] S4 Raw Material Pretreatment and Batching: The printing composite layer uses polyethylene terephthalate (PET) resin with an intrinsic viscosity of 0.80 dL / g. The impact-resistant molding layer uses a blend of polycarbonate resin and thermoplastic polyurethane elastomer resin at a mass ratio of 80:20. The polycarbonate resin has a melt flow rate of 9 g / 10 min at 300℃ / 1.2 kg, and the thermoplastic polyurethane elastomer resin has a melt flow rate of 15 g / 10 min at 210℃ / 5 kg. The adhesive layer uses the same brand of thermoplastic polyurethane elastomer resin.

[0029] The multifunctional interface compatibilizer and the base resins of the printing composite layer, impact-resistant molding layer, and backing adhesive layer were placed in a vacuum drying oven and dried for 5 hours at 95℃ and an absolute pressure ≤0.01MPa. The multifunctional interface compatibilizer was added to the printing composite layer and the impact-resistant molding layer respectively, with 3wt% added to the printing composite layer and 3wt% added to the impact-resistant molding layer, and no multifunctional interface compatibilizer added to the backing adhesive layer. The materials of each layer were placed in a high-speed mixer and stirred and mixed at a speed of 750r / min for 13 minutes to obtain the co-extrusion raw materials of each layer.

[0030] S5 Three-Layer Reactive Co-Extrusion: The raw materials for each co-extrusion layer are fed into an independent extruder for reactive co-extrusion; the extrusion temperature of the printing composite layer is set to 228℃, the extrusion temperature of the impact-resistant molding layer is set to 233℃, and the extrusion temperature of the adhesive layer is set to 228℃; the extruded melt is precisely filtered through a sintered metal mesh with a pore size of 10-20μm and then merged at a thickness ratio of 18:64:18.

[0031] S6 Pressure Casting: The merged extruded melt is extruded through a die and then subjected to pressure cooling casting between a mirror roller and a silicone roller with a surface roughness Ra of 1.0-2.0μm and nano-silica filler. The temperature of the mirror roller is set to 70℃ and the temperature of the nano-silica roller is set to 72℃, resulting in a base film with one side being mirrored and the other side being frosted. The total thickness of the base film is 150μm.

[0032] S7 Surface Activation and Hot Pressing: The mirror surface of the base film is subjected to corona treatment at a voltage of 20kV and a frequency of 10kHz; a 12μm tin foil layer is hot-pressed onto the corona-treated mirror surface at a temperature of 110°C, a pressure of 0.35MPa, and a speed of 8m / min to obtain a stampable and shaped film.

[0033] Example 2:

[0034] This embodiment provides a stampable and shaped film, specifically including the following steps;

[0035] Preparation of S1 multifunctional interface compatibilizer: Trimethylolpropane, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid were mixed in a molar ratio of 1:5:0.02 and melt polycondensed for 4 hours under stirring conditions of 140℃ and 0.008MPa absolute pressure to obtain hydroxyl-terminated hyperbranched polyester.

[0036] Hydroxyl-terminated hyperbranched polyester was dissolved in toluene, and epichlorohydrin and tetrabutylammonium bromide were added. The molar ratio of epichlorohydrin to hydroxyl groups in the hyperbranched polyester was 0.4:1, and the amount of tetrabutylammonium bromide added was 1 wt% of the mass of the hyperbranched polyester. A 30% sodium hydroxide aqueous solution was added dropwise at a uniform rate over 1-2 hours at 60°C with stirring. The reaction was continued at this temperature for 5 hours. The molar ratio of sodium hydroxide to epichlorohydrin in the sodium hydroxide aqueous solution was 1.0:1. After washing with water and rotary evaporation under reduced pressure, the hyperbranched polyester intermediate was obtained.

[0037] The hyperbranched polyester intermediate was dissolved in anhydrous dichloromethane, and dibutyltin dilaurate was added, wherein the amount of dibutyltin dilaurate added was 0.1 wt% of the mass of the hyperbranched polyester intermediate. Under nitrogen protection, 3-isocyanate-propyltriethoxysilane was added dropwise at 40°C and reacted for 3 h, wherein the molar ratio of 3-isocyanate-propyltriethoxysilane to the remaining hydroxyl groups in the hyperbranched polyester intermediate was 0.15:1. After precipitation purification and vacuum drying, a multifunctional interface compatibilizer was prepared.

[0038] Testing revealed that this multifunctional interface compatibilizer has a number-average molecular weight of 2800 g / mol and a PDI of 1.38; the 910 cm⁻¹ region was confirmed in the Fourier transform infrared spectrum. -1 Epoxy groups and 1080cm -1 Characteristic peaks of silicon-oxygen-silicon bonds were observed; corresponding characteristic proton peaks were observed at 2.6-2.8 ppm and 0.6 ppm in the proton NMR spectrum; the epoxy equivalent was 580 g / eq, the synthesis yield was 82%, and the purity was 97%.

[0039] S2 Raw Material Pretreatment and Batching: The printing composite layer uses PET resin with an intrinsic viscosity of 0.80 dL / g; the impact molding layer uses polycarbonate resin with a melt flow rate of 9 g / 10 min; and the backing layer uses thermoplastic polyurethane elastomer resin with a melt flow rate of 15 g / 10 min. The multifunctional interface compatibilizer and the base resins of the printing composite layer, impact molding layer, and backing layer are placed in a vacuum drying oven and dried for 4 hours at 90℃ and an absolute pressure ≤0.01 MPa. The mixture is then placed in a high-speed mixer, with the multifunctional interface compatibilizer added only to the printing composite layer at a rate of 2 wt%. The mixture is stirred at 700 r / min for 12 minutes to obtain the co-extrusion raw materials for each layer.

[0040] S3 Three-Layer Reactive Co-Extrusion: The raw materials for each co-extrusion layer are fed into an independent extruder for reactive co-extrusion. The extrusion temperature of the printing composite layer is 225℃, the extrusion temperature of the impact-resistant molding layer is 230℃, and the extrusion temperature of the adhesive backing layer is 225℃. The extruded melt is then finely filtered through a sintered metal mesh with a pore size of 10-20μm and merged at a thickness ratio of 15:70:15.

[0041] S4 Pressure Casting and Hot Press Lamination: The merged extruded melt is extruded through a die and then pressure-cooled and cast between a mirror roller and a silicone roller with a surface roughness Ra of 1.0-2.0μm and nano-silica filler. The temperature of both the mirror roller and the nano-silica roller is set to 60℃, resulting in a base film with one side being mirrored and the other side being frosted. The total thickness of the base film is 140μm. The mirror surface of the base film is corona treated with a voltage of 10kV and a frequency of 1kHz. A 12μm tin foil layer is then hot-pressed onto the corona-treated mirror surface at a temperature of 105℃, a linear pressure of 0.30MPa, and a lamination speed of 6m / min to obtain the finished film.

[0042] Example 3:

[0043] This embodiment provides a stampable and shaped film, specifically including the following steps;

[0044] Preparation of S1 multifunctional interface compatibilizer: Trimethylolpropane, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid were mixed in a molar ratio of 1:15:0.08 and melt polycondensed for 6 hours under stirring conditions at 140℃ and an absolute pressure of less than 0.01MPa to obtain hydroxyl-terminated hyperbranched polyester.

[0045] Hydroxyl-terminated hyperbranched polyester was dissolved in toluene, and epichlorohydrin and tetrabutylammonium bromide were added. The molar ratio of epichlorohydrin to hydroxyl groups in the hyperbranched polyester was 0.8:1, and the amount of tetrabutylammonium bromide added was 5 wt% of the mass of the hyperbranched polyester. A 30% sodium hydroxide aqueous solution was added dropwise at a uniform rate over 1-2 hours at 60°C with stirring. The reaction was continued at this temperature for 5 hours. The molar ratio of sodium hydroxide to epichlorohydrin in the sodium hydroxide aqueous solution was 1.2:1. After washing with water and rotary evaporation under reduced pressure, the hyperbranched polyester intermediate was obtained.

[0046] The hyperbranched polyester intermediate was dissolved in anhydrous dichloromethane, and dibutyltin dilaurate was added, wherein the amount of dibutyltin dilaurate added was 0.5 wt% of the mass of the hyperbranched polyester intermediate. Under nitrogen protection, 3-isocyanate-propyltriethoxysilane was added dropwise at 40°C and reacted for 3 h, wherein the molar ratio of 3-isocyanate-propyltriethoxysilane to the remaining hydroxyl groups in the hyperbranched polyester intermediate was 0.50:1. After precipitation purification and vacuum drying, a multifunctional interface compatibilizer was prepared.

[0047] Testing revealed that this multifunctional interface compatibilizer has a number-average molecular weight of 4500 g / mol and a PDI of 1.52; the 910 cm⁻¹ region was confirmed in the Fourier transform infrared spectrum. -1 Epoxy groups and 1080cm -1 Characteristic peaks of silicon-oxygen-silicon bonds were observed; corresponding characteristic proton peaks were observed at 2.6-2.8 ppm and 0.6 ppm in the proton NMR spectrum; the epoxy equivalent was 320 g / eq, the synthesis yield was 88%, and the purity was 99%.

[0048] S2 Raw Material Pretreatment and Batching: The printing composite layer uses polycarbonate resin with a melt flow rate of 9g / 10min. The impact-resistant molding layer uses the above-mentioned polycarbonate resin and thermoplastic polyurethane elastomer resin with a melt flow rate of 15g / 10min and a mass ratio of 70:30. The backing layer uses the above-mentioned thermoplastic polyurethane elastomer resin of the same grade.

[0049] The multifunctional interface compatibilizer and the base resin of the printing composite layer, the impact-resistant molding layer and the backing layer were placed in a vacuum drying oven and dried at 100℃ and absolute pressure ≤0.01MPa for 6 hours. The mixture was then placed in a high-speed mixer, and the multifunctional interface compatibilizer was added to the printing composite layer and the impact-resistant molding layer respectively, with an addition amount of 5wt% for each layer. The mixture was stirred and mixed at a speed of 800r / min for 15 minutes to obtain the co-extrusion raw materials of each layer.

[0050] S3 Three-Layer Reactive Co-Extrusion: The raw materials for each co-extrusion layer are fed into an independent extruder for reactive co-extrusion. The extrusion temperature of the printing composite layer is 230℃, the extrusion temperature of the impact-resistant molding layer is 235℃, and the extrusion temperature of the adhesive backing layer is 230℃. The extruded melt is then finely filtered through a sintered metal mesh with a pore size of 10-20μm and merged at a thickness ratio of 20:60:20.

[0051] S4 Pressure Casting and Hot Press Lamination: The merged extruded melt is extruded through a die and then pressure-cooled between a mirror roller and a silicone roller with a surface roughness Ra of 1.0-2.0μm and nano-silica filler. The temperature of both the mirror roller and the nano-silica roller is set to 80℃, resulting in a base film with one side being mirrored and the other side being frosted. The total thickness of the base film is 160μm. The mirror surface of the base film is corona treated with a voltage of 30kV and a frequency of 20kHz. A 12μm tin foil layer is then hot-pressed onto the corona-treated mirror surface at a hot-pressing temperature of 115°C, a linear pressure of 0.40MPa, and a lamination speed of 10m / min to obtain the finished film.

[0052] Example 4:

[0053] This embodiment provides a stampable and shaped film, specifically including the following steps;

[0054] Preparation of S1 modifier: The molar ratio of trimethylolpropane, 2,2-dimethylolpropionic acid, and p-toluenesulfonic acid was 1:10:0.05. Polycondensation was carried out at 140℃ and 0.006MPa for 5 hours to obtain a hydroxyl-terminated hyperbranched polyester. The molar ratio of epichlorohydrin to the hydroxyl groups in the hydroxyl-terminated hyperbranched polyester was 2.5:1. The amount of tetrabutylammonium bromide added was 4wt% of the mass of the hydroxyl-terminated hyperbranched polyester. The reaction was carried out at 60℃ for 5 hours to obtain a hyperbranched polyester intermediate. The molar ratio of 3-isocyanate-propyltriethoxysilane to the remaining hydroxyl groups was 0.40:1. The amount of dibutyltin dilaurate added was 0.3wt% of the mass of the hyperbranched polyester intermediate. The reaction was carried out at 40℃ for 3 hours to obtain the modifier.

[0055] S2 Raw Material Pretreatment and Batching: The printing composite layer uses a blend of PET and polycarbonate resin at a mass ratio of 60:40; the impact-resistant molding layer uses a blend of polycarbonate resin and thermoplastic polyurethane elastomer resin at a mass ratio of 75:25; and the adhesive layer uses thermoplastic polyurethane elastomer resin. Each layer of resin and modifier is dried at 95℃ and an absolute pressure ≤0.01MPa for 5 hours. Modifiers are added to both the printing composite layer and the impact-resistant molding layer, with 4wt% added to the printing composite layer and 3wt% added to the impact-resistant molding layer. High-speed mixing conditions are 760r / min for 14 minutes.

[0056] S3 three-layer reactive co-extrusion: the printing composite layer is extruded at 227℃, the impact-resistant molding layer is extruded at 232℃, and the adhesive backing layer is extruded at 227℃; the thickness ratio is 17:66:17.

[0057] S4 pressure casting and lamination: The mirror roller temperature is 68℃ and the nano-silicone roller temperature is 70℃ to obtain a base film with a total thickness of 150μm; the corona treatment voltage is 18kV and the frequency is 8kHz, and a 12μm tin foil layer is hot-pressed to obtain the finished film.

[0058] Comparative Example 1:

[0059] The difference between this comparative example and Example 1 is that the multifunctional interface compatibilizer obtained in S3 is omitted, and no modifier is added to the printed composite layer and the impact-resistant molding layer. Other operating steps and process parameters are exactly the same as in Example 1.

[0060] Comparative Example 2:

[0061] The difference between this comparative example and Example 1 is that the multifunctional interface compatibilizer in Example 1 is replaced with a hyperbranched polyester intermediate. That is, the modifier used contains only a hyperbranched polyester skeleton and epoxy groups, and does not contain siloxane groups. Other operating steps and process parameters are exactly the same as in Example 1.

[0062] Comparative Example 3:

[0063] The difference between this comparative example and Example 1 is that the multifunctional interface compatibilizer in Example 1 is replaced with a modifier containing only a hyperbranched polyester backbone and siloxane groups. This modifier is prepared by reacting a terminal hydroxyl hyperbranched polyester with 3-isocyanate-propyltriethoxysilane without epoxy grafting. Other operating steps and process parameters are exactly the same as in Example 1.

[0064] Comparative Example 4:

[0065] The difference between this comparative example and Example 1 is that the corona treatment step in S7 is omitted, and the base film is directly hot-pressed to form a composite tin foil layer after it is prepared. Other operation steps and process parameters are exactly the same as in Example 1.

[0066] Comparative Example 5:

[0067] The difference between this comparative example and Example 1 is that the amount of multifunctional interface compatibilizer added in Example 1 is changed from 3wt% to 1wt%, and the amount added in the printed composite layer and the impact-resistant molding layer is 1wt%. Other operating steps and process parameters are exactly the same as in Example 1.

[0068] Performance Testing and Datasheets

[0069] The dimensional change rate after 3D deep drawing and placement at 85℃ for 72 hours was used to evaluate the resilience performance; the lower the value, the better the shape retention. A 180° peel test was used to test the peel strength between the tin foil layer and the base film, with a test width of 15 mm and a peel speed of 300 mm / min. A drop hammer impact test was used to evaluate the impact resistance performance. The thermal shock test conditions were -40℃ and 85℃ alternating cycles for 100 times, with each temperature zone held for 2 hours.

[0070] Table 1. Performance test results of each embodiment and comparative example.

[0071] Example 1 0.80% 4.6 62 No bubbling, no delamination Example 2 1.00% 4.1 56 No bubbling, no delamination Example 3 0.90% 4.3 58 No bubbling, no delamination Example 4 0.90% 4.4 60 No bubbling, no delamination Comparative Example 1 5.80% 1.6 44 Large-area delamination Comparative Example 2 1.70% 1.9 57 Edge delamination Comparative Example 3 1.40% 3 39 Localized blistering, accompanied by interlayer cracking Comparative Example 4 0.90% 2.4 61 Localized blistering Comparative Example 5 2.60% 3.1 52 Edge delamination

[0072] As can be seen from the comparison of the test results of Example 1 and Comparative Example 1 in Table 1, after omitting the multifunctional interface compatibilizer, the rebound rate, peel strength and impact strength all decreased significantly.

[0073] The underlying mechanism is that the lack of branching steric hindrance and chain segment interlocking effect brought by the hyperbranched polyester skeleton in the film system makes the molecular chains after stamping deformation more likely to undergo elastic recovery, resulting in an increased resilience. At the same time, the lack of migratable siloxane groups at the interface means that the tin foil layer and the base film mainly rely on physical contact and a small amount of polar interaction. During thermal cycling, the interfacial stress is difficult to release, resulting in large-area delamination. In this comparative example, there is also no reactive bonding between epoxy groups and resin end groups, which reduces the stress transmission capacity within the layer and leads to a decrease in drop hammer impact strength.

[0074] As can be seen from the comparison of the test results of Example 1 and Comparative Example 2 in Table 1, the lack of siloxane groups will significantly reduce the peel strength and the interface stability after thermal shock.

[0075] The underlying mechanism is that the hyperbranched polyester intermediate can still undergo ring-opening reactions with the end groups of the matrix resin, so the toughness and shape retention of the layer are still maintained at a certain level, the resilience only increases accordingly, and the impact strength remains at a high level; however, the intermediate does not have low surface energy migration characteristics, so it cannot form an enriched layer on the mirror side, nor can it generate sufficient silanol groups after corona discharge to form a chemical bond with the oxide layer on the tin foil surface. Therefore, the bond between the tin foil layer and the base film mainly relies on mechanical intercalation and polar adsorption, and the peel strength drops to 1.9 N / 15 mm, and edge delamination occurs after thermal shock.

[0076] As can be seen from the comparison of the test results of Example 1 and Comparative Example 3 in Table 1, the lack of epoxy groups will reduce the impact strength and long-term interface stability.

[0077] The underlying mechanism is that the modifier in this comparative example still has a hyperbranched skeleton and siloxane groups. Therefore, the springback control after stamping is still better than that of the system without modifier. Moreover, a certain degree of chemical bonding can still be formed between the tin foil layer and the base film, and the peel strength is higher than that of comparative example 2. However, due to the lack of ring-opening reaction between epoxy groups and the end groups of polycarbonate resin, PET or thermoplastic polyurethane elastomer resin, the chemical anchoring between the modifier and the resin matrix is ​​insufficient. The enriched layer formed near the interface is more likely to undergo cohesive failure with the matrix under impact load and thermal stress. Therefore, the drop hammer impact strength decreases, and local blistering and interlayer cracking occur after thermal shock.

[0078] As can be seen from the comparison of the test results of Example 1 and Comparative Example 4 in Table 1, after omitting the corona treatment, the peel strength decreased significantly, while the rebound rate and impact strength changed little.

[0079] The underlying mechanism is that, in Example 1, the siloxane groups have migrated to the mirror side during the casting stage, thus the internal shaping structure and intralayer mechanical network of the film have been formed. Omitting corona treatment will not significantly change the resilience and impact resistance of the substrate. However, without corona activation, the conversion of alkoxy groups in the surface siloxanes to silanol groups is insufficient, making it difficult to form a high-density chemical bond with the metal oxide layer on the tin foil surface. The interfacial bonding is more of a hot-pressing contact effect, so the peel strength drops from 4.6 N / 15 mm to 2.4 N / 15 mm, and local blistering occurs after thermal shock.

[0080] As can be seen from the comparison of the test results of Example 1 and Comparative Example 5 in Table 1, when the amount of modifier is lower than the set mass percentage, it will simultaneously weaken the resilience, interlayer adhesion and impact resistance.

[0081] The underlying mechanism is that when the modifier is reduced from 3wt% to 1wt%, the distribution density of hyperbranched structures in the printed composite layer and the impact-resistant molding layer decreases, and the number of branched nodes that can participate in chain segment confinement and deformation retention after stamping decreases, resulting in an increase in springback rate to 2.6%. At the same time, the total amount of siloxane groups migrating to the mirror side decreases, the density of silanol groups formed after corona treatment is insufficient, the chemical bonding sites between the tin foil layer and the base film decrease, and the peel strength decreases. In addition, the number of reactive connections formed between epoxy groups and resin end groups decreases, the stress transfer efficiency within the layer decreases, and the drop hammer impact strength decreases simultaneously.

[0082] As can be seen from the various embodiments, within the parameter range defined by the present invention, the modifier simultaneously provides three types of effects: hyperbranching and shaping, epoxy reactive bonding, and siloxane interfacial bonding. Example 1 uses an intermediate ratio and intermediate process window, and the three types of effects are matched to achieve the preset structural requirements or achieve synergistic effects. Therefore, it exhibits comprehensive performance that meets the requirements of various test indicators in terms of springback control, interfacial adhesion, and impact resistance.

[0083] The grafting degree and dosage of the modifier in Example 2 were relatively low, and the performance remained within the preset performance index range. The grafting degree and dosage in Example 3 were relatively high, and the interfacial adhesion and shaping performance were still good, but the impact performance was inferior to that in Example 1 due to the increased rigidity of the system. Example 4 used a mixed resin system to achieve a comprehensive balance between adhesion and impact strength.

[0084] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A punchable and shaped film, characterized in that, It includes a base film and a tin foil layer bonded to the surface of the base film; the base film is prepared by co-extrusion molding from top to bottom in sequence by a printing composite layer, an impact-resistant molding layer and an adhesive layer; wherein, the printing composite layer, or the printing composite layer and the impact-resistant molding layer contain a multifunctional interfacial compatibilizing modifier; the molecular chain core of the multifunctional interfacial compatibilizing modifier is a hyperbranched polyester skeleton, and epoxy groups and siloxane groups are grafted to the end groups of the hyperbranched polyester skeleton.

2. The punchable and shaped film according to claim 1, characterized in that, The preparation steps of the multifunctional interfacial compatibilizing modifier include: Step 1: Mix trimethylolpropane, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid in a molar ratio of 1:(5-15):(0.01-0.1), and carry out melt polycondensation for 4-6 hours under stirring conditions at 140 °C and an absolute pressure ≤ 0.01 MPa to obtain a hydroxyl-terminated hyperbranched polyester; Step 2: Dissolve the hydroxyl-terminated hyperbranched polyester in toluene, add epichlorohydrin and tetrabutylammonium bromide, wherein the molar ratio of epichlorohydrin to the hydroxyl groups in the hydroxyl-terminated hyperbranched polyester is (0.4-2.5):1, and the addition amount of tetrabutylammonium bromide is 1-5% of the mass of the hydroxyl-terminated hyperbranched polyester. Slowly dropwise add a 30% sodium hydroxide aqueous solution at a constant speed within 1-2 hours under stirring conditions at 60 °C. After the dropwise addition is completed, keep the reaction at a constant temperature for 5 hours. The molar ratio of sodium hydroxide to epichlorohydrin in the sodium hydroxide aqueous solution is (1.0-1.2):

1. After washing with water and rotary evaporation under reduced pressure, a hyperbranched polyester intermediate is obtained; Step 3: Dissolve the hyperbranched polyester intermediate in anhydrous dichloromethane, add dibutyltin dilaurate, wherein the addition amount of dibutyltin dilaurate is 0.1-0.5% of the mass of the hyperbranched polyester intermediate. React by dropwise adding 3-isocyanatopropyltriethoxysilane at 40 °C under nitrogen protection for 3 hours, wherein the molar ratio of 3-isocyanatopropyltriethoxysilane to the remaining hydroxyl groups in the hyperbranched polyester intermediate is (0.1-0.5):

1. After precipitation purification and vacuum drying, a multifunctional interfacial compatibilizing modifier is obtained.

3. The punchable and shaped film according to claim 1, characterized in that, The mass proportion of the multifunctional interfacial compatibilizing modifier in the printing composite layer is 2-5 wt%, and the mass proportion in the impact-resistant molding layer is 0 or 2-5 wt%.

4. The punchable and shaped film according to claim 1, characterized in that, The epoxy groups in the multifunctional interfacial compatibilizing modifier form a ring-opening crosslinked structure with the end groups of the matrix resin in the printing composite layer, or the printing composite layer and the impact-resistant molding layer.

5. A stampable and shaped film according to claim 1, characterized in that, By thickness percentage, the printing composite layer accounts for 15-20% of the total thickness of the base film, the impact-resistant molding layer accounts for 60-70% of the total thickness of the base film, and the adhesive layer accounts for 15-20% of the total thickness of the base film.

6. A punchable and shaped film according to claim 1, characterized in that, One side of the base film that is adhered to the tin foil layer is a mirror surface, the surface roughness of the mirror surface is 0 < Ra ≤ 0.05 μm, and the side of the base film facing away from the tin foil layer is a matte surface.

7. A punchable and shaped film according to claim 6, characterized in that, The siloxane groups in the multifunctional interfacial compatibilizing modifier are enriched on the mirror surface side of the base film, and the tin foil layer is bonded to the mirror surface of the base film through a silicon-oxygen-metal covalent bond.

8. A method for preparing a stampable and shaped film, used to prepare the stampable and shaped film as described in any one of claims 1-7, characterized in that, It includes the following steps: Step 1, Vacuum pretreatment of raw materials: The multifunctional interface compatibilizer and the matrix resin of the printing composite layer, the impact-resistant molding layer and the adhesive backing layer are placed in a vacuum drying oven and dried for 4-6 hours at 90-100℃ and absolute pressure ≤0.01MPa. Then, according to the material ratio of each layer, the corresponding matrix resin and multifunctional interface compatibilizer are placed in a high-speed mixer and stirred and mixed at a speed of 700-800r / min for 12-15min to obtain the co-extrusion raw materials of each layer. Step 2, reactive three-layer co-extrusion: The co-extrusion raw materials for each layer are fed into independent extruders for reactive co-extrusion. The extrusion temperature of the printed composite layer is 220-240℃, the extrusion temperature of the impact-resistant molding layer is 225-245℃, and the extrusion temperature of the adhesive layer is 220-240℃. The extruded melt is filtered through a sintered metal mesh with a pore size of 10-20μm and then merged according to the thickness ratio. Step 3, pressure casting: After the merged extruded melt is extruded through the die, it is subjected to pressure cooling casting between a mirror roller and a silicone roller with a surface roughness Ra of 1.0-2.0μm and nano silica filler to obtain a base film with one side being mirror and the other side being frosted. Step 4, Surface activation and hot-pressing lamination: The mirror surface of the base film is subjected to corona treatment, and a tin foil layer is hot-pressed onto the corona-treated mirror surface to obtain a stampable and shaped film.

9. The method for preparing a stampable and shaped thin film according to claim 8, characterized in that, In step three, both the mirror roller and the silicone roller with added nano-silica filler are controlled at 60-80℃; in step four, the voltage of the corona treatment is 10-30kV and the frequency is 1-20kHz.

10. The use of a stampable film as described in any one of claims 1-7 in the manufacture of signs for computer, communication and consumer electronics products, home appliances or automotive interiors.