A polyester film and a method for producing the same

Abstract

The application provides a polyester film, which comprises a first functional layer, a barrier core layer, a second functional layer, a bonding layer, a PET base film layer and a glue layer arranged in sequence; the barrier core layer comprises the following components in percentage by mass: 80-88% of polyester and 12-20% of a second barrier additive; the second barrier additive is a first barrier additive modified by an organic ultraviolet barrier; the first barrier additive comprises the following components in percentage by mass: 52-58% of nano-silicon dioxide, 25-30% of nano-vanadium dioxide and 14-20% of nano-titanium dioxide; the first functional layer and the second functional layer each comprise the following components in percentage by mass: 65-73% of polyester, 24-32% of an anti-blocking master batch and 3-5% of the second barrier additive. The application is helpful to improve production efficiency, and although the heat insulation and ultraviolet shielding performance slightly decreases, the process cost is low, and the application is very suitable for factory batch production.

Description

Technical Field

[0001] This invention belongs to the field of polyester film technology, and specifically refers to a polyester film used as an automotive window film and its preparation method. Background Technology

[0002] Applying window film to the front and rear windows of a car can provide a certain degree of privacy protection, heat insulation, sun protection, and UV protection. Traditional car window films are one-way transparent films, which do not affect driving safety, but their heat insulation, sun protection, and UV protection functions are not significant. As for the industry-claimed effects of reducing interior temperature, reducing air conditioning use, and reducing fuel consumption, these are negligible. Chinese invention patent application number 201911170208.7 discloses a high-transmittance, high-definition, explosion-proof polyester film and its preparation method (application publication number CN 111004585 A). The polyester film sequentially includes a coating layer, a first functional layer, a core layer, a second functional layer, a metal heat insulation layer, an adhesive layer, a PET base film layer, and an adhesive layer. Compared with existing polyester films, this film offers high light transmittance, low haze, and good UV protection, providing the driver with a more comfortable field of vision. Furthermore, this film has high infrared blocking rate, high tensile strength, and high peel strength, exhibiting excellent heat insulation and explosion-proof performance. However, this film involves an eight-layer structure, requiring the following steps during preparation: (1) preparing a first functional layer, a core layer, and a second functional layer to form a three-layer co-extruded film; (2) preparing a coating layer on the first functional layer; (3) preparing a metal heat insulation layer on the second functional layer; (4) preparing a PET base film layer; (5) coating an adhesive on the upper surface of the PET base film layer to form an adhesive layer, which is then bonded to the metal heat insulation layer; and (6) coating an adhesive on the lower surface of the PET base film layer to form an adhesive layer. These multi-step operations are not only cumbersome but also severely impact production efficiency. Furthermore, the formation of the coating layer using the PEVCD method and the metal heat insulation layer using vacuum magnetron sputtering technology both involve high process costs, and the metal heat insulation layer also blocks visible light, which is detrimental to mass production in factories. Therefore, this application is submitted. Summary of the Invention

[0003] To address the shortcomings of the prior art, this invention proposes a polyester film and its preparation method.

[0004] This invention proposes a polyester film comprising, in sequence: a first functional layer, a barrier core layer, a second functional layer, an adhesive layer, a PET base film layer, and an adhesive layer;

[0005] The barrier core layer comprises the following components by mass percentage: 80%-88% polyester and 12%-20% second barrier additive. The second barrier additive is a first barrier additive modified with an organic ultraviolet blocker. The preparation method of the second barrier additive is to add an organic ultraviolet blocker with a mass of 2-5 times that of the first barrier additive to the first barrier additive and mix them evenly.

[0006] The first barrier additive comprises the following components by weight percentage: 52%-58% nano-silica, 25%-30% nano-vanadium dioxide, and 14%-20% nano-titanium dioxide;

[0007] Both the first and second functional layers comprise the following components by weight percentage: 65%-73% polyester, 24%-32% anti-blocking masterbatch, and 3%-5% second barrier additive. The anti-blocking masterbatch is hollow and spherical nano-silica (which can be commercially available or made in-house using existing technology).

[0008] Nano-silica, nano-vanadium dioxide, and nano-titanium dioxide are preferably spherical or layered structures. Spherical and layered structures have superior reflective and diffuse reflective properties, which can enhance infrared light blocking performance at the microscale and also help to obtain good organic ultraviolet blocking material modification effects.

[0009] Polyesters include one or more of polyethylene terephthalate, propylene terephthalate, and butylene terephthalate.

[0010] Principle: Silica and vanadium dioxide both possess excellent infrared blocking capabilities, while titanium dioxide exhibits excellent ultraviolet (UV) blocking capabilities. Nano-silica, nano-vanadium dioxide, and nano-titanium dioxide are combined in the aforementioned proportions to form the first barrier additive. This first barrier additive possesses good infrared blocking capabilities and a certain degree of UV blocking capability. The second barrier additive, modified with organic UV blockers, combines both good infrared and UV blocking capabilities. Ultimately, this results in a first functional layer, a barrier core layer, and a second functional layer that synergistically perform infrared and UV blocking functions. The first functional layer forms the initial barrier, the barrier core layer performs the primary blocking function, and the second functional layer forms the final barrier defense. The synergistic effect of these three infrared blocking layers and the synergistic interaction of the organic and inorganic UV absorbers significantly enhance the UV resistance and heat insulation performance of the polyester film.

[0011] Preferably, the first and second functional layers have the same thickness, both 5-8 μm, and the barrier core layer has a thickness of 10-15 μm. Adding a second barrier additive to the first and second functional layers not only blocks infrared and ultraviolet light but also prevents glare, improving the driver's visual experience. The adhesive layer is specifically composed of at least one of EVA adhesive and polyamide adhesive, with a thickness not exceeding that of the first or second functional layer. The PET base film layer is extruded from 95%-98% PET and 2%-5% inorganic anti-adhesion particles by weight, which can improve the tensile strength of the polyester film. The adhesive layer is specifically composed of at least one of polyurethane adhesive and acrylate adhesive, with a thickness not exceeding that of the first or second functional layer. The adhesive layer, PET base film layer, and adhesive layer work together to effectively mitigate external impact forces.

[0012] Further preferably, the organic ultraviolet blocking material comprises the following components in weight percentage: 60%-75% benzotriazole organic compound and 25%-40% bis-ethylhexyloxyphenol methoxyphenyl triazine. The benzotriazole organic compound is capable of effectively absorbing ultraviolet light at 350-400 nm, specifically at least one of 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, and 2-(2'-hydroxy-3'-tert-butyl-5'-methoxyphenyl)5-amino-benzotriazole; bis-ethylhexyloxyphenol methoxyphenyl triazine is a broad-spectrum UV absorber.

[0013] This invention proposes a method for preparing the above-mentioned polyester film, comprising the following steps:

[0014] (1) A three-layer co-extrusion process is used to prepare the first functional layer (layer A), the barrier core layer (layer B), and the second functional layer (layer A) to form an ABA three-layer co-extrusion film;

[0015] (2) Preparation of PET base film layer;

[0016] (3) An adhesive is applied to the upper surface of the PET base film to form an adhesive layer, and the adhesive layer is bonded to the second functional layer.

[0017] (4) Apply adhesive to the lower surface of the PET base film to form an adhesive layer.

[0018] Compared with existing technologies, the polyester film preparation method proposed in this invention is relatively simple and helps to improve production efficiency. Although the heat insulation and UV protection performance are slightly reduced, it does not require coating, does not involve PEVCD method and vacuum magnetron sputtering technology, has low process cost, and is suitable for mass production in factories.

[0019] Specifically, the preparation method of the first barrier additive is as follows: nano-silica, nano-vanadium dioxide, and nano-titanium dioxide are mixed in proportion, dispersed in ethanol, and silane is added. The resulting mixture is then ball-milled under the following conditions: the diameter of the milling balls is 1-3 mm, the milling speed is 800-1000 r / min, and the milling time is not less than 6 hours. Ball milling can further improve the dispersibility of nano-silica, nano-vanadium dioxide, and nano-titanium dioxide in polyester. Adding silane during ball milling can also modify the surface of each substance, enhancing its interfacial bonding with the polyester, ultimately achieving uniform dispersion in the polyester film. The preferred silane is a mixture of vinyltrimethoxysilane and vinyltriethoxysilane in a mass ratio of 3:2. Single silanes have poor surface modification effects and are not conducive to modification. The silane mixture of the above components can reduce the surface energy of each substance, exhibiting strong hydrophobic and oleophilic effects, which helps in the subsequent modification of organic UV blockers, ultimately achieving the best dispersion effect. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a polyester film proposed in this invention.

[0021] In the diagram: 1. First functional layer; 2. Barrier core layer; 3. Second functional layer; 4. EVA adhesive layer; 5. PET base film layer; 6. Adhesive layer. Detailed Implementation

[0022] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the following embodiments, the preparation method of the ABA three-layer co-extruded film is as follows:

[0024] (1) Place the raw materials of the first functional layer, the barrier core layer, and the second functional layer in the corresponding hoppers. Control the mass ratio of the extruded melt of the main extruder and the auxiliary extruder according to the designed thickness of the first functional layer, the barrier core layer, and the second functional layer. The raw materials are melted at 280°C in the main extruder and the auxiliary extruder, vacuumed, and then filtered to remove impurities through a filter with a precision of 10μm. The resulting main extruded melt and auxiliary extruded melt are combined and melted in an ABA-type three-layer die and extruded at 285°C.

[0025] (2) The melt extruded by the three-layer die is attached to the surface of the cold drum by electrostatic attachment to form a casting sheet. The temperature of the cold drum is set to 25°C, and the thickness of the resulting casting sheet is controlled to be 300-400μm. Then, it is stretched longitudinally and then stretched laterally. The longitudinal stretching zone consists of a preheating section at 70-75°C, a stretching section at 75-80°C, and a cooling and forming section at 20-25°C. The longitudinal stretching ratio is preferably 3. The transverse stretching zone consists of a preheating section at 90-100°C, a stretching section at 110-120°C, a forming section at 180-200°C, and a cooling section at 30-40°C. The transverse stretching ratio is preferably 4.3.

[0026] (3) Perform subsequent processing such as thickness measurement, flattening, static electricity removal, and winding in sequence.

[0027] In the following embodiments, the polyester in the first and second functional layers is PET polyester; the anti-adhesion masterbatch in the first and second functional layers is specifically hollow and spherical nano-silica, which, along with the nano-silica in the first barrier additive, is prepared with reference to prior art (Qiyu Yu, Pengpeng Wang, Shi Hu, Junfeng Hui, Jing Zhuang, and Xun Wang, hydrothermal synthesis of hollow silica spheres under acidic conditions, Langmuir 2011, 27, 7185-7191). The nano-titanium dioxide in the first barrier additive is prepared with reference to prior art (Chinese Invention Patent Application No. 201810529196.1, titanium dioxide hollow nanospheres and their preparation method). The nano-vanadium dioxide in the first barrier additive is prepared with reference to prior art (Chinese Invention Patent Application No. 201010177821.4, preparation method and application of rutile phase vanadium dioxide nanowires).

[0028] In the following embodiment, the PET base film layer is prepared by melting 95%-98% by mass of PET and 2%-5% of inorganic anti-adhesion particles (hollow and spherical nano-silica, sourced from the same nano-silica as the first barrier) to form a PET sheet, and then biaxially stretching it to form a PET base film layer.

[0029] In the following embodiments, unless otherwise specified, the parts, including but not limited to reagents and equipment, all adopt existing technologies. Example

[0030] A polyester film includes, in sequence: a first functional layer, a barrier core layer, a second functional layer, an adhesive layer, a PET base film layer, and an adhesive layer. The thickness of the first functional layer and the second functional layer is 5 μm, the thickness of the barrier core layer is 15 μm, the thickness of the adhesive layer is 4 μm, the thickness of the PET base film layer is 6 μm, and the thickness of the adhesive layer is 3 μm.

[0031] The barrier core layer comprises the following components by weight percentage: 80% polyester and 20% second barrier additive. The second barrier additive is a first barrier additive modified with an organic ultraviolet barrier. The organic ultraviolet barrier comprises the following components by weight percentage: 35% 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 40% 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, and 25% bis-ethylhexyloxyphenol methoxyphenyl triazine. The second barrier additive is prepared by adding five times its weight of the organic ultraviolet barrier to the first barrier and mixing them evenly.

[0032] The first barrier additive comprises the following components by weight percentage: 58% nano-silica, 28% nano-vanadium dioxide, and 14% nano-titanium dioxide;

[0033] The first and second functional layers have the same composition, both including the following components by mass percentage: 73% polyester, 24% anti-blocking masterbatch, and 3% second barrier additive.

[0034] The preparation method of the above-mentioned polyester film is as follows:

[0035] (1) A first functional layer (A layer), a barrier core layer (B layer) and a second functional layer (A layer) are prepared by a three-layer co-extrusion process to form an ABA three-layer co-extruded film; wherein, the preparation method of the first barrier additive is as follows: nano-silica, nano-vanadium dioxide and nano-titanium dioxide are mixed in proportion, dispersed in ethanol and silane is added, and then the mixture is ball-milled. The specific conditions for ball milling are: the diameter of the grinding ball is 3 mm, the rotation speed of the grinding ball is 900 r / min, and the ball milling time is 6 h.

[0036] (2) Preparation of PET base film layer;

[0037] (3) An adhesive is applied to the upper surface of the PET base film to form an adhesive layer, and the adhesive layer is bonded to the second functional layer;

[0038] (4) Apply adhesive to the lower surface of the PET base film to form an adhesive layer. Example

[0039] A polyester film includes, in sequence: a first functional layer, a barrier core layer, a second functional layer, an adhesive layer, a PET base film layer, and an adhesive layer. The thickness of the first functional layer and the second functional layer is 6 μm, the thickness of the barrier core layer is 12 μm, the thickness of the adhesive layer is 5 μm, the thickness of the PET base film layer is 8 μm, and the thickness of the adhesive layer is 5 μm.

[0040] The barrier core layer comprises the following components by weight percentage: 88% polyester and 12% second barrier additive. The second barrier additive is a first barrier additive modified with an organic UV blocker. The organic UV blocker comprises the following components by weight percentage: 30% 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 30% 2-(2'-hydroxy-3'-tert-butyl-5'-methoxyphenyl)5-amino-benzotriazole, and 40% bis-ethylhexyloxyphenol methoxyphenyl triazine. The second barrier additive is prepared by adding twice its weight of the organic UV blocker to the first barrier additive and mixing them evenly.

[0041] The first barrier additive comprises the following components by weight percentage: 52% nano-silica, 30% nano-vanadium dioxide, and 18% nano-titanium dioxide;

[0042] The first and second functional layers have the same composition, both including the following components by mass percentage: 65% polyester, 30% anti-blocking masterbatch, and 5% second barrier additive.

[0043] The preparation method of the above-mentioned polyester film is as follows:

[0044] (1) A first functional layer (A layer), a barrier core layer (B layer) and a second functional layer (A layer) are prepared by a three-layer co-extrusion process to form an ABA three-layer co-extruded film; wherein, the preparation method of the first barrier additive is as follows: nano-silica, nano-vanadium dioxide and nano-titanium dioxide are mixed in proportion, dispersed in ethanol and silane is added, and then the mixture is ball-milled. The specific conditions for ball milling are: the diameter of the grinding ball is 1 mm, the rotation speed of the grinding ball is 1000 r / min, and the ball milling time is 7 h.

[0045] (2) Preparation of PET base film layer;

[0046] (3) An adhesive is applied to the upper surface of the PET base film to form an adhesive layer, and the adhesive layer is bonded to the second functional layer;

[0047] (4) Apply adhesive to the lower surface of the PET base film to form an adhesive layer. Example

[0048] A polyester film includes, in sequence: a first functional layer, a barrier core layer, a second functional layer, an adhesive layer, a PET base film layer, and an adhesive layer. The thickness of the first functional layer and the second functional layer is 8 μm, the thickness of the barrier core layer is 10 μm, the thickness of the adhesive layer is 2 μm, the thickness of the PET base film layer is 5 μm, and the thickness of the adhesive layer is 2 μm.

[0049] The barrier core layer comprises the following components by mass percentage: 85% polyester and 15% second barrier additive. The second barrier additive is a first barrier additive modified with an organic UV blocker. The organic UV blocker comprises the following components by mass percentage: 20% 2-(2'-hydroxy-3'-tert-butyl-5'-methoxyphenyl)5-amino-benzotriazole, 45% 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, and 35% bis-ethylhexyloxyphenol methoxyphenyl triazine. The second barrier additive is prepared by adding 4 times its mass of the organic UV blocker to the first barrier additive and mixing them evenly.

[0050] The first barrier additive comprises the following components by weight percentage: 55% nano-silica, 25% nano-vanadium dioxide, and 20% nano-titanium dioxide;

[0051] The first and second functional layers have the same composition, both including the following components by mass percentage: 68% polyester, 28% anti-blocking masterbatch, and 4% second barrier additive.

[0052] The preparation method of the above-mentioned polyester film is as follows:

[0053] (1) A first functional layer (A layer), a barrier core layer (B layer) and a second functional layer (A layer) are prepared by a three-layer co-extrusion process to form an ABA three-layer co-extruded film; wherein, the preparation method of the first barrier additive is as follows: nano-silica, nano-vanadium dioxide and nano-titanium dioxide are mixed in proportion, dispersed in ethanol and silane is added, and then the mixture is ball-milled. The specific conditions for ball milling are: the diameter of the grinding ball is 2 mm, the rotation speed of the grinding ball is 800 r / min, and the ball milling time is 8 h.

[0054] (2) Preparation of PET base film layer;

[0055] (3) An adhesive is applied to the upper surface of the PET base film to form an adhesive layer, and the adhesive layer is bonded to the second functional layer;

[0056] (4) Apply adhesive to the lower surface of the PET base film to form an adhesive layer.

[0057] Comparative Example 1

[0058] The second barrier is the same as the first barrier, i.e., it has not been modified with an organic ultraviolet blocking agent. All other technical parameters are the same as in Example 1.

[0059] Comparative Example 2

[0060] The organic ultraviolet blocker comprises the following components in weight percentage: 35% 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole and 65% 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, with all other technical parameters being the same as in Example 1.

[0061] Comparative Example 3

[0062] The organic UV blocker consists only of bis-ethylhexyloxyphenol methoxyphenyl triazine. All other technical parameters are the same as in Example 1.

[0063] The transmittance, ultraviolet blocking rate, infrared blocking rate, and haze of the films obtained in the above embodiments and comparative examples were tested. The testing methods and standards used were the same as those in Chinese Invention Patent Application No. 201911170208.7, so they will not be described again.

[0064] project Light transmittance (%) UV blocking rate (%) Infrared blocking rate (%) Haze (%) Example 1 65% 98.5 88% 2.36 Example 2 70% 98.7 85% 2.67 Example 3 72% 96.0 84% 2.45 Comparative Example 1 71% 81.4 83% 2.47 Comparative Example 2 69% 80.7 84% 2.58 Comparative Example 3 70% 80.6 83% 2.48

[0065] As shown in the table above, the polyester film proposed in this invention has good light transmittance and relatively high ultraviolet and infrared blocking rates. Although it is slightly different from the prior art mentioned in the background art, it is simple to operate, does not involve costly process operations, and is suitable for mass production in factories.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polyester film, comprising, in sequence: a first functional layer, a barrier core layer, a second functional layer, an EVA adhesive layer, a PET base film layer, and an adhesive layer, characterized in that: The barrier core layer comprises the following components by mass percentage: 80%-88% polyester and 12%-20% second barrier additive. The second barrier additive is a first barrier additive modified with an organic ultraviolet blocker. The preparation method of the second barrier additive is to add 2-5 times its mass of organic ultraviolet blocker to the first barrier additive and mix them evenly. The first barrier additive comprises the following components by weight percentage: 52%-58% nano-silica, 25%-30% nano-vanadium dioxide, and 14%-20% nano-titanium dioxide; The first functional layer and the second functional layer have the same composition, both including the following components by mass percentage: 65%-73% polyester, 24%-32% anti-blocking masterbatch, and 3%-5% second barrier additive; The first functional layer and the second functional layer have the same thickness, both 5-8 μm, and the barrier core layer has a thickness of 10-15 μm. The organic UV blocker comprises the following components by weight percentage: 60%-75% benzotriazole organic compound and 25%-40% bis-ethylhexyloxyphenol methoxyphenyl triazine.

2. A method for preparing a polyester film as described in claim 1, characterized in that: Includes the following steps: (1) A three-layer co-extrusion process is used to prepare the first functional layer (layer A), the barrier core layer (layer B), and the second functional layer (layer A) to form an ABA three-layer co-extrusion film; (2) Preparation of PET base film layer; (3) An adhesive is applied to the upper surface of the PET base film layer to form an adhesive layer, and the adhesive layer is bonded to the second functional layer; (4) Apply adhesive to the lower surface of the PET base film to form an adhesive layer.

3. The method for preparing polyester film according to claim 2, characterized in that: The preparation method of the first barrier additive is as follows: nano-silica, nano-vanadium dioxide and nano-titanium dioxide are mixed in proportion, dispersed in ethanol and silane is added, and then the resulting mixture is subjected to ball milling. The specific conditions for ball milling are: the diameter of the grinding ball is 1-3 mm, the rotation speed of the grinding ball is 800-1000 r / min, and the ball milling time is not less than 6 h.

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