PET decorative film and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a PET decorative film and a preparation method thereof. The preparation method comprises the following steps: synthesizing hydroxyl-terminated hyperbranched polyester by taking pentaerythritol and 2, 2-dimethylolpropionic acid as raw materials, and reacting with polyol glycidyl ether to prepare an epoxy-terminated organic modifier; silver-loaded nano silicon dioxide subjected to surface treatment by an amino silane coupling agent is used as inorganic functional particles; pET resin, an organic modifier and inorganic functional particles are subjected to melt blending and extrusion granulation, and modified PET is prepared; the modified PET is prepared into the film through a two-way stretching process. Epoxy groups of the organic modifier chemically react with amino groups at the tail end of a PET molecular chain and on the surfaces of inorganic particles respectively, a stable organic-inorganic hybrid network is constructed, synergistic improvement of reinforcement, toughening and long-acting antibiosis is achieved, and the technical problems that functional particles are not uniform in dispersion, interface bonding is weak, and antibacterial components are prone to migration are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a PET decorative film and its preparation method. Background Technology

[0002] Polyethylene terephthalate (PET) decorative films are widely used for surface decoration and protection in building materials, home appliances, and automotive interiors due to their excellent mechanical strength, dimensional stability, and processability. With the upgrading of consumption, the market has placed higher demands on the appearance, durability, and functionality of decorative films. Currently, PET is mainly functionalized and its performance improved through processes such as resin blending, surface coating, and multilayer lamination. These technologies have formed a relatively mature production and application system.

[0003] Existing technical approaches can be summarized as follows: First, physical blending modification, which involves adding elastomers, inorganic fillers, or functional additives to improve toughness, heat resistance, or impart antibacterial functions. However, this method suffers from uneven dispersion of modified components and poor interfacial compatibility, easily leading to loss of mechanical properties, decreased transparency, and migration of functional components, affecting the durability and stability of performance. Second, chemical grafting modification, such as grafting reactive monomers onto the PET molecular chain to introduce functional groups. However, this method often faces problems such as poor controllability of grafting rate and molecular structure, and potential damage to the bulk properties of PET. Third, modification based on hyperbranched polymers, utilizing their multi-terminal group characteristics as toughening agents or carriers. However, existing technologies are mostly limited to physical blending. Hyperbranched polymers lack strong chemical bonds with the PET matrix and inorganic functional particles, failing to fully utilize their potential for molecular bridging and stress transfer. Furthermore, inorganic particles are prone to aggregation, resulting in weak interfacial interactions. In addition, while surface coating with functional coatings or multilayer composites can improve certain properties, they generally suffer from limitations such as insufficient adhesion, easy peeling between layers, complex processes, or poor environmental friendliness. Existing technologies struggle to achieve a systematic balance among multiple objectives, such as significant toughening, efficient and long-lasting antibacterial properties, and good processability, resulting in poor functional synergy.

[0004] Therefore, developing a new method for preparing PET decorative films that can achieve strong interfacial bonding between organic and inorganic components, have both long-lasting antibacterial and significant toughening effects, and whose process is controllable, has clear technical necessity and important application value. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a PET decorative film and its preparation method to solve the problems in the prior art, such as the difficulty in synergistically improving mechanical properties and functionality due to the weak interfacial bonding between organic and inorganic components, as well as the easy migration and uneven dispersion of functional components.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a PET decorative film includes the following steps: Step 1: Mix pentaerythritol, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid, and heat to the set temperature under nitrogen protection to react. After the reaction is completed, purify to obtain hydroxyl-terminated hyperbranched polyester. Hydroxyl-terminated hyperbranched polyester was mixed with polyol glycidyl ether, a catalyst was added, and the mixture was reacted. After the reaction was completed, the mixture was purified to obtain an organic modifier. Step 2: Mix PET resin with organic modifier and Ag@SiO2 inorganic functional particles, melt blend, and extrude granulate to obtain modified PET; Step 3: The modified PET is melt-extruded and cast into sheets. The cast sheets are then subjected to longitudinal stretching, transverse stretching, and heat setting to obtain the PET decorative film.

[0007] Preferably, in step one, when preparing the hydroxyl-terminated hyperbranched polyester, the molar ratio of pentaerythritol to 2,2-dimethylolpropionic acid is 1:12, and the amount of p-toluenesulfonic acid added is 0.4%-0.6% of the total mass of pentaerythritol and 2,2-dimethylolpropionic acid. The reaction conditions are as follows: first, under nitrogen protection, react at a set temperature for 3-6 hours, then stop the nitrogen flow, and maintain the set temperature at a pressure of -0.06 to -0.09 MPa until no more water distills out. The set temperature is 140-150℃.

[0008] Preferably, in step one, when preparing the organic modifier, the molar ratio of the terminal hydroxyl hyperbranched polyester to the polyol glycidyl ether is 1:8, the amount of catalyst added is 0.5%-1.5% of the mass of the polyol glycidyl ether, and the reaction conditions are under nitrogen protection and at a temperature of 75-85℃ for 4-8 hours. The polyol glycidyl ether includes ethylene glycol diglycidyl ether; The catalyst includes triethylamine.

[0009] Preferably, the polyol glycidyl ether may also be selected from any one of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol glycidyl ether.

[0010] Preferably, the catalyst may also be selected from tetramethylammonium chloride and tetraethylammonium bromide.

[0011] Preferably, in step two, the mass ratio of PET resin, organic modifier, and Ag@SiO2 inorganic functional particles is 100:(8-12):(3-6), and the melt blending temperature is 260-280℃.

[0012] Preferably, the Ag@SiO2 inorganic functional particles in step two are prepared by the following steps: S1. Nano-silica was added to deionized water, ultrasonically dispersed, and then silver ammonia solution was added. After stirring, centrifugation and washing, silver ion-loaded nano-silica (Ag) was obtained. + (@SiO2); S2. Disperse silver ion-loaded nano-silica in deionized water, add reducing agent solution, react, and after the reaction is complete, centrifuge and wash to obtain silver-loaded nano-silica (Ag@SiO2). S3. Add silver-loaded nano-silica to an ethanol aqueous solution, add an aminosilane coupling agent, and react. After the reaction is complete, centrifuge, wash, and dry to obtain the Ag@SiO2 inorganic functional particles.

[0013] Preferably, in S1, the mass ratio of nano-silica, deionized water, and silver ammonia solution is (2-4):100:(200-300), and the stirring condition is stirring at room temperature for 3-5 hours; The concentration of the silver ammonia solution is 0.5-0.8 mol / L.

[0014] Preferably, in S2, the mass ratio of silver ion-loaded nano-silica, deionized water, and reducing agent solution is 1:(6-10):(3-5), and the reaction conditions are stirring at 30-50℃ for 1-2 hours. The concentration of the reducing agent solution is 0.1-0.3 mol / L; The reducing agent solution includes an aqueous fructose solution.

[0015] Preferably, in S3, the mass ratio of silver-loaded nano-silica, aqueous ethanol solution, and aminosilane coupling agent is 1:(80-120):(0.5-1.5), and the reaction conditions are stirring at room temperature (25°C) for 24-36 hours. The aminosilane coupling agent includes silane coupling agent KH-550 (γ-aminopropyltriethoxysilane).

[0016] Preferably, in step three, the extrusion die temperature is 255-265℃, the preheating temperature for longitudinal stretching is 80-100℃, the stretching temperature is 105-115℃, and the stretching ratio is 4-4.4 times; the preheating temperature for transverse stretching is 90-100℃, the stretching temperature is 105-115℃, and the stretching ratio is 3.8-4.2 times; and the heat setting temperature is 235-245℃.

[0017] Preferably, the thickness of the PET decorative film obtained in step three is 25-35 μm.

[0018] The present invention also discloses a PET decorative film prepared by the PET decorative film preparation method described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, rigid particles Ag@SiO2 are used as an inorganic modifier, which can effectively bear stress and provide reinforcement and stiffness. Hyperbranched polymers are used as organic modifiers, which have good compatibility with PET resin. The hyperbranched three-dimensional dendritic network structure forms chain entanglement with PET molecular chains, which plays a good role in toughening and improving the mechanical properties of PET film materials. The synergistic effect of inorganic and organic modifiers can overcome the traditional contradiction between strength and toughness, and achieve simultaneous improvement of the strength, modulus and impact toughness of PET film. In addition, the introduction of silver particles in the inorganic modifier can effectively improve the antibacterial properties of PET film. In this invention, the hyperbranched polymer-type organic modifier is epoxy-terminated, which can react with the terminal carboxyl or hydroxyl groups of the PET molecular chain to form a stable chemical bond with the PET resin matrix. At the same time, the organic modifier can form a chemical bond with Ag@SiO2 particles functionalized by aminosilane coupling agent through the reaction of epoxy groups. The hyperbranched polymer establishes a strong chemical bond bridge between the PET matrix and inorganic functional particles, realizing efficient stress transfer. This not only effectively solves the fundamental problem of weak interfacial bonding between hyperbranched polymer and PET matrix and inorganic particles, but also avoids the aggregation of inorganic particles and the migration of functional components. In this invention, silver particles in Ag@SiO2 are firmly loaded onto the SiO2 support and further anchored in the polymer network through the subsequent chemical bonding of amino groups on the SiO2 surface with the epoxy groups of the organic modifier. This ensures the long-lasting and slow release of the antibacterial components, achieving a highly efficient and durable antibacterial effect and preventing the rapid loss or aggregation of silver particles. In addition, the organic-inorganic network also improves the thermal stability and aging resistance of the material. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the hydroxyl-terminated hyperbranched polyester obtained in Example 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the organic modifier prepared in Example 1 of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0022] Example 1 This embodiment discloses a method for preparing a PET decorative film, including the following steps: Step 1: Mix pentaerythritol, 2,2-dimethylolpropionic acid, and p-toluenesulfonic acid. The molar ratio of pentaerythritol to 2,2-dimethylolpropionic acid is 1:12. The amount of p-toluenesulfonic acid added is 0.5% of the total mass of pentaerythritol and 2,2-dimethylolpropionic acid. Under nitrogen protection, heat to 145°C and react for 4.5 hours at 145°C under nitrogen protection. Then stop the nitrogen flow and maintain the reaction at 145°C under a pressure of -0.075 MPa until no more water distills out. Cool to room temperature and add acetone with a mass equal to 3 times the mass of the reaction mixture to the reaction mixture. After stirring to dissolve, add the dissolved mixture to ether with the same mass as acetone, stir to precipitate, filter, and place the precipitate in a vacuum drying oven at 50°C to dry to constant weight to obtain hydroxyl-terminated hyperbranched polyester. Hydroxyl-terminated hyperbranched polyester and ethylene glycol diglycidyl ether were mixed at a molar ratio of 1:8. Triethylamine was added as a catalyst at 1% of the mass of ethylene glycol diglycidyl ether. The mixture was reacted at 80°C for 6 hours under nitrogen protection. After the reaction, acetone (3 times the mass of the mixture) was added to the reaction mixture for dilution. The mixture was then rotary evaporated at -50°C and -0.095 MPa to remove most of the acetone and triethylamine. When the mixture began to thicken, acetone (2 times the mass of the viscous substance) was added to dissolve it. The mixture was then added dropwise to ice water (0°C) (5 times the mass of the viscous substance) at a stirring speed of 1000 r / min for precipitation. The precipitate was filtered, washed five times with ice water, and then dried in a vacuum drying oven at 50°C to constant weight to obtain the organic modifier. Step 2: Mix PET resin with organic modifier and Ag@SiO2 inorganic functional particles. The mass ratio of PET resin, organic modifier and Ag@SiO2 inorganic functional particles is 100:8:3. After melt blending at a temperature of 260℃, the mixture is extruded and granulated to obtain modified PET. The Ag@SiO2 inorganic functional particles are prepared by the following steps: S1. Add nano-silica to deionized water and ultrasonically disperse at 50kHz for 30min. Then add 0.65mol / L silver ammonia solution. The mass ratio of nano-silica, deionized water and 0.7mol / L silver ammonia solution is 3:100:250. Stir at room temperature for 4h, centrifuge, remove the supernatant, and wash the centrifuged precipitate with deionized water 5 times to obtain silver ion-loaded nano-silica. S2. Disperse silver ion-loaded nano-silica in deionized water, add 0.2 mol / L fructose aqueous solution, the mass ratio of silver ion-loaded nano-silica, deionized water and 0.2 mol / L fructose aqueous solution is 1:8:4, stir and react at 40℃ for 1.5 h, after the reaction is completed, centrifuge, remove the supernatant, and wash the centrifuged precipitate with deionized water 5 times to obtain silver-loaded nano-silica; S3. Add silver-loaded nano-silica to 95wt% ethanol aqueous solution, add silane coupling agent KH-550, the mass ratio of silver-loaded nano-silica, 95wt% ethanol aqueous solution and silane coupling agent KH-550 is 1:100:1, stir and react at room temperature for 30h, after the reaction is completed, centrifuge, remove the supernatant, wash the centrifuged precipitate with deionized water 5 times, place it in a 50℃ vacuum drying oven and dry to constant weight to obtain the Ag@SiO2 inorganic functional particles. Step 3: The modified PET is melt-extruded at a die temperature of 255°C, and cast into a sheet. The sheet is then subjected to longitudinal stretching, transverse stretching, and heat setting to obtain the PET decorative film. The preheating temperature for longitudinal stretching is 90℃, the stretching temperature is 110℃, and the stretching ratio is 4.2 times; the preheating temperature for transverse stretching is 95℃, the stretching temperature is 110℃, and the stretching ratio is 4 times; the heat setting temperature is 240℃. The thickness of the PET decorative film is 12 μm.

[0023] Example 2 This embodiment discloses a method for preparing a PET decorative film, including the following steps: Step 1: Prepare organic modifiers; The preparation method of the organic modifier is the same as in Example 1; Step 2: Mix PET resin with organic modifier and Ag@SiO2 inorganic functional particles. The mass ratio of PET resin, organic modifier and Ag@SiO2 inorganic functional particles is 100:12:6. After melt blending at a temperature of 280℃, the mixture is extruded and granulated to obtain modified PET. The preparation method of Ag@SiO2 inorganic functional particles is the same as in Example 1; Step 3: The modified PET is melt-extruded at a die temperature of 265°C, and cast into a sheet. The sheet is then stretched longitudinally, stretched laterally, and heat-set to obtain the PET decorative film. The preheating temperature for longitudinal stretching is 90℃, the stretching temperature is 110℃, and the stretching ratio is 4.2 times; the preheating temperature for transverse stretching is 95℃, the stretching temperature is 110℃, and the stretching ratio is 4 times; the heat setting temperature is 240℃. The thickness of the PET decorative film is 12 μm.

[0024] Example 3 This embodiment discloses a method for preparing a PET decorative film, including the following steps: Step 1: Prepare organic modifiers; The preparation method of the organic modifier is the same as in Example 1; Step 2: Mix PET resin with organic modifier and Ag@SiO2 inorganic functional particles. The mass ratio of PET resin, organic modifier and Ag@SiO2 inorganic functional particles is 100:9:4. After melt blending at a temperature of 270℃, the mixture is extruded and granulated to obtain modified PET. The preparation method of Ag@SiO2 inorganic functional particles is the same as in Example 1; Step 3: The modified PET is melt-extruded at a die temperature of 260°C, and cast into a sheet. The sheet is then stretched longitudinally, stretched laterally, and heat-set to obtain the PET decorative film. The preheating temperature for longitudinal stretching is 90℃, the stretching temperature is 110℃, and the stretching ratio is 4.2 times; the preheating temperature for transverse stretching is 95℃, the stretching temperature is 110℃, and the stretching ratio is 4 times; the heat setting temperature is 240℃. The thickness of the PET decorative film is 12 μm.

[0025] Example 4 This embodiment discloses a method for preparing a PET decorative film, including the following steps: Step 1: Prepare organic modifiers; The preparation method of the organic modifier is the same as in Example 1; Step 2: Mix PET resin with organic modifier and Ag@SiO2 inorganic functional particles. The mass ratio of PET resin, organic modifier and Ag@SiO2 inorganic functional particles is 100:10:4.5. After melt blending at a temperature of 270℃, the mixture is extruded and granulated to obtain modified PET. The preparation method of Ag@SiO2 inorganic functional particles is the same as in Example 1; Step 3: The modified PET is melt-extruded at a die temperature of 260°C, and cast into a sheet. The sheet is then stretched longitudinally, stretched laterally, and heat-set to obtain the PET decorative film. The preheating temperature for longitudinal stretching is 90℃, the stretching temperature is 110℃, and the stretching ratio is 4.2 times; the preheating temperature for transverse stretching is 95℃, the stretching temperature is 110℃, and the stretching ratio is 4 times; the heat setting temperature is 240℃. The thickness of the PET decorative film is 12 μm.

[0026] Example 5 This embodiment discloses a method for preparing a PET decorative film, including the following steps: Step 1: Prepare organic modifiers; The preparation method of the organic modifier is the same as in Example 1; Step 2: Mix PET resin with organic modifier and Ag@SiO2 inorganic functional particles. The mass ratio of PET resin, organic modifier and Ag@SiO2 inorganic functional particles is 100:11:5. After melt blending at a temperature of 270℃, the mixture is extruded and granulated to obtain modified PET. The preparation method of Ag@SiO2 inorganic functional particles is the same as in Example 1; Step 3: The modified PET is melt-extruded at a die temperature of 260°C, and cast into a sheet. The sheet is then stretched longitudinally, stretched laterally, and heat-set to obtain the PET decorative film. The preheating temperature for longitudinal stretching is 90℃, the stretching temperature is 110℃, and the stretching ratio is 4.2 times; the preheating temperature for transverse stretching is 95℃, the stretching temperature is 110℃, and the stretching ratio is 4 times; the heat setting temperature is 240℃. The thickness of the PET decorative film is 12 μm.

[0027] Comparative Example 1 This comparative example discloses a method for preparing a PET decorative film, including the following steps: Step 1: Preparation of Ag@SiO2 inorganic functional particles; The preparation method of Ag@SiO2 inorganic functional particles is the same as in Example 1; Step 2: Mix PET resin with Ag@SiO2 inorganic functional particles at a mass ratio of 112:6. Melt blend at a temperature of 280°C, then extrude and granulate to obtain modified PET. Step 3: The modified PET is melt-extruded at a die temperature of 265°C, and cast into a sheet. The sheet is then stretched longitudinally, stretched laterally, and heat-set to obtain the PET decorative film. The process parameters for longitudinal stretching, transverse stretching, and heat setting are the same as in Example 1; The thickness of the PET decorative film is 12 μm.

[0028] Comparative Example 2 This comparative example discloses a method for preparing a PET decorative film, including the following steps: Step 1: Prepare organic modifiers; The preparation method of the organic modifier is the same as in Example 1; Step 2: Mix PET resin with organic modifier at a mass ratio of 106:12, melt blend at a temperature of 280°C, and then extrude and granulate to obtain modified PET. Step 3: The modified PET is melt-extruded at a die temperature of 265°C, and cast into a sheet. The sheet is then stretched longitudinally, stretched laterally, and heat-set to obtain the PET decorative film. The process parameters for longitudinal stretching, transverse stretching, and heat setting are the same as in Example 1; The thickness of the PET decorative film is 12 μm.

[0029] Comparative Example 3 This comparative example discloses a method for preparing a PET decorative film, including the following steps: Step 1: Preparation of hydroxyl-terminated hyperbranched polyester; The preparation method of the hydroxyl-terminated hyperbranched polyester is the same as in Example 1; Step 2: Mix PET resin with hydroxyl-terminated hyperbranched polyester and silver-loaded nano-silica. The mass ratio of PET resin, hydroxyl-terminated hyperbranched polyester and silver-loaded nano-silica is 105.6:7:5.4. After melt blending at a temperature of 280℃, the mixture is extruded and granulated to obtain modified PET. The preparation method of silver-loaded nano-silica is the same as in Example 1; Step 3: The modified PET is melt-extruded at a die temperature of 265°C, and cast into a sheet. The sheet is then stretched longitudinally, stretched laterally, and heat-set to obtain the PET decorative film. The process parameters for longitudinal stretching, transverse stretching, and heat setting are the same as in Example 1; The thickness of the PET decorative film is 12 μm.

[0030] In the above examples and comparative examples, the intrinsic viscosity of the PET resin is 0.83-0.87 dL / g, and the melting point is 247℃; the nano-silica is spherical nano-silica with an average particle size of 50nm.

[0031] Test case The performance of the PET decorative film samples prepared in Examples 1-5 and Comparative Examples 1-3 was tested: (1) Mechanical property testing: Referring to standard GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", a universal testing machine was used to determine the tensile strength, elongation at break, and modulus of elasticity of PET decorative film samples. The tensile speed was 100 mm / min. Five samples were tested for each group of samples, and the average value was taken. The results of the determination of tensile strength, elongation at break, and modulus of elasticity are shown in Table 1. Table 1 As shown in Table 1, the PET decorative film prepared by this invention has good mechanical properties. Compared with Example 2, in Comparative Example 1, due to the lack of bridging and toughening effect of organic modifiers, the added inorganic particles have extremely poor interface bonding with the PET matrix, weakening the effective reinforcing effect of the particles on the PET matrix; in Comparative Example 2, although the elongation at break is high due to the plasticizing effect of organic modifiers, the tensile strength and elastic modulus are significantly reduced due to the lack of rigid support from inorganic particles, and the material is too soft, failing to meet the requirements of decorative film for stiffness and load-bearing capacity; in Comparative Example 3, since the components are only physically mixed and lack chemical bonding bridges, the interfacial compatibility is poor, resulting in a significant decrease in tensile strength, elongation at break, and elastic modulus.

[0032] (2) Antibacterial performance test: The antibacterial rate of PET decorative film against Escherichia coli and Staphylococcus aureus was determined according to the standard GB / T31402-2015 "Test method for antibacterial properties of plastic surfaces". The antibacterial rate was calculated after 24 hours of contact culture using the film-applied method. The results of the antibacterial rate test for Escherichia coli and Staphylococcus aureus are shown in Table 2. Table 2 As shown in Table 2, the PET decorative film prepared by this invention has good antibacterial properties. Compared with Example 2, in Comparative Example 1, although antibacterial particles were present, the lack of an organic bridging phase resulted in poor particle dispersion and easy encapsulation, reducing the effective contact area with bacteria and leading to a decrease in the antibacterial rate. In Comparative Example 2, the surface antibacterial properties of the PET film decreased significantly because no antibacterial components were added. In Comparative Example 3, the inorganic particles were not amination-treated and had no chemical bonding with the matrix, causing silver particles to easily aggregate and potentially migrate and detach, resulting in a reduction and instability of the effective antibacterial components and a decrease in the antibacterial rate.

[0033] (3) Thermal stability test: The thermal stability of PET decorative film was determined according to the standard GB / T12027-2004 "Test method for dimensional change rate of plastic film and sheet under heating". A 100mm×100mm sample was placed in an oven at (150±2)℃ for 30min. After cooling, the dimensional change was measured and the thermal shrinkage rate was calculated. The results of the thermal shrinkage rate test are shown in Table 3. Table 3 As shown in Table 3, the PET decorative film prepared by this invention has good thermal stability. Compared with Example 2, in Comparative Example 1, the inorganic particles have weak interfacial bonding with the PET matrix, which becomes stress defect points when heated, exacerbating the shrinkage of molecular chains and resulting in a high thermal shrinkage rate; in Comparative Example 2, the physical entanglement of the organic modifier alone has limited ability to constrain the molecular chains, and the thermal stability is also reduced; in Comparative Example 3, due to the complete lack of stabilizing effect of chemical bonding, the phases are more prone to relative slippage and shrinkage when heated, exhibiting the worst thermal dimensional stability.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a PET decorative film, characterized in that, Includes the following steps: Step 1: Mix pentaerythritol, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid, and heat to the set temperature under nitrogen protection to react. After the reaction is completed, purify to obtain hydroxyl-terminated hyperbranched polyester. Hydroxyl-terminated hyperbranched polyester was mixed with polyol glycidyl ether, a catalyst was added, and the mixture was reacted. After the reaction was completed, the mixture was purified to obtain an organic modifier. Step 2: Mix PET resin with organic modifier and Ag@SiO2 inorganic functional particles, melt blend, and extrude granulate to obtain modified PET; Step 3: The modified PET is melt-extruded and cast into sheets. The cast sheets are then subjected to longitudinal stretching, transverse stretching, and heat setting to obtain the PET decorative film.

2. The method for preparing a PET decorative film according to claim 1, characterized in that, In step one, when preparing the hydroxyl-terminated hyperbranched polyester, the molar ratio of pentaerythritol to 2,2-dimethylolpropionic acid is 1:12, and the amount of p-toluenesulfonic acid added is 0.4%-0.6% of the total mass of pentaerythritol and 2,2-dimethylolpropionic acid. The reaction conditions are as follows: first, under nitrogen protection, react at a set temperature for 3-6 hours, then stop the nitrogen flow, and maintain the set temperature at a pressure of -0.06~-0.09 MPa until no more water distills out. The set temperature is 140-150℃.

3. The method for preparing a PET decorative film according to claim 1, characterized in that, In step one, when preparing the organic modifier, the molar ratio of the terminal hydroxyl hyperbranched polyester to the polyol glycidyl ether is 1:8, the amount of catalyst added is 0.5%-1.5% of the mass of the polyol glycidyl ether, and the reaction conditions are under nitrogen protection and at a temperature of 75-85℃ for 4-8 hours. The polyol glycidyl ether includes ethylene glycol diglycidyl ether; The catalyst includes triethylamine.

4. The method for preparing a PET decorative film according to claim 1, characterized in that, In step two, the mass ratio of PET resin, organic modifier, and Ag@SiO2 inorganic functional particles is 100:(8-12):(3-6), and the melt blending temperature is 260-280℃.

5. The method for preparing a PET decorative film according to claim 1, characterized in that, The Ag@SiO2 inorganic functional particles in step two are prepared by the following steps: S1. Add nano-silica to deionized water, disperse it by ultrasonication, add silver ammonia solution, stir, centrifuge and wash to obtain nano-silica loaded with silver ions. S2. Disperse silver-loaded nano-silica in deionized water, add reducing agent solution, react, and after the reaction is complete, centrifuge and wash to obtain silver-loaded nano-silica. S3. Add silver-loaded nano-silica to an ethanol aqueous solution, add an aminosilane coupling agent, and react. After the reaction is complete, centrifuge, wash, and dry to obtain the Ag@SiO2 inorganic functional particles.

6. The method for preparing a PET decorative film according to claim 5, characterized in that, In S1, the mass ratio of nano-silica, deionized water, and silver ammonia solution is (2-4):100:(200-300), and the stirring conditions are stirring at room temperature for 3-5 hours. The concentration of the silver ammonia solution is 0.5-0.8 mol / L.

7. The method for preparing a PET decorative film according to claim 5, characterized in that, In S2, the mass ratio of silver ion-loaded nano-silica, deionized water, and reducing agent solution is 1:(6-10):(3-5), and the reaction conditions are stirring at 30-50℃ for 1-2 hours. The concentration of the reducing agent solution is 0.1-0.3 mol / L; The reducing agent solution includes an aqueous fructose solution.

8. The method for preparing a PET decorative film according to claim 5, characterized in that, In S3, the mass ratio of silver-loaded nano-silica, aqueous ethanol solution, and aminosilane coupling agent is 1:(80-120):(0.5-1.5), and the reaction conditions are stirring at room temperature for 24-36 hours. The aminosilane coupling agent includes silane coupling agent KH-550; The ethanol aqueous solution is a 95wt% ethanol aqueous solution.

9. The method for preparing a PET decorative film according to claim 1, characterized in that, In step three, the extrusion die temperature is 255-265℃, the preheating temperature for longitudinal stretching is 80-100℃, the stretching temperature is 105-115℃, and the stretching ratio is 4-4.4 times; the preheating temperature for transverse stretching is 90-100℃, the stretching temperature is 105-115℃, and the stretching ratio is 3.8-4.2 times; and the heat setting temperature is 235-245℃.

10. A PET decorative film prepared by the method for preparing a PET decorative film as described in any one of claims 1-9.

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