Transparent polyester base material for window film as well as preparation method and application of transparent polyester base material

Abstract

The invention relates to the technical field of high polymer materials, in particular to a transparent polyester base material for a window film, a preparation method and application. The transparent polyester base material for the window film comprises an acrylic resin coating and a polyester film, the polyester film sequentially comprises an outer surface layer, a middle core layer and an inner surface layer from top to bottom, and the outer surface of the outer surface layer is coated with the acrylic resin coating online; the acrylic resin coating is prepared from the following raw materials in parts by weight: 70 to 80 parts of polymethyl methacrylate, 0.5 to 5 parts of ammonium thiocyanate, 4 to 18 parts of melamine, 1 to 5 parts of glycol ether, 2 to 8 parts of colloidal silicon dioxide, 1 to 3 parts of an ultraviolet light absorber, 0.5 to 2 parts of nano-silver particles and 3 to 7 parts of a toughening agent.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a transparent polyester substrate for window films, a preparation method and applications thereof. Background Art

[0002] As people's living standards improve, the performance requirements for window films are getting higher and higher. Window films not only need to have good light transmittance, but also need to have certain heat insulation, wear resistance, weather resistance and other properties. Polyester film has been widely used in the field of window films due to its excellent comprehensive properties, such as high transparency, high strength, and good dimensional stability. However, existing polyester films still have shortcomings in certain performance aspects. For example, the wear resistance and adhesion of its surface need to be improved to meet the needs of window films to resist external friction and ensure the firmness of the coating during long-term use. At the same time, how to further optimize the structure and performance of polyester film so that it can better adapt to the diverse application scenarios of window films is also the focus and difficulty of current research. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention can be achieved through the following technical solutions:

[0004] A transparent polyester substrate for a window film, comprising an acrylic resin coating and a polyester film, wherein the polyester film comprises, from top to bottom, an outer surface layer, an intermediate core layer, and an inner surface layer, and the acrylic resin coating is applied online on the outer surface of the outer surface layer;

[0005] The raw materials for preparing the acrylic resin coating include, by weight, 70-80 parts of polymethyl methacrylate, 0.5-5 parts of ammonium thiocyanate, 4-18 parts of melamine, 1-5 parts of ethylene glycol ether, 2-8 parts of colloidal silicon dioxide, 1-3 parts of ultraviolet absorber, 0.5-2 parts of nano silver particles, and 3-7 parts of toughening agent.

[0006] Furthermore, the ultraviolet absorber is one of 2,4-dihydroxybenzophenone or 2-(2'-hydroxy-5'-methylphenyl)benzotriazole; and the toughening agent is at least one of polycarbonate, polyethersulfone and polyurethane.

[0007] Furthermore, the raw materials for preparing the outer layer include, by weight, 80-90 parts of polyethylene terephthalate, 1-3 parts of nano-silicon dioxide, 2-5 parts of carbon nanotube / POSS modified polyester, 3-6 parts of fluorine-containing dibasic acid modified polyester, and 5-10 parts of calcium carbonate.

[0008] Furthermore, the raw material for preparing the intermediate core layer is polyethylene terephthalate.

[0009] Furthermore, the inner surface layer comprises 85-92 parts of polyethylene terephthalate, 1-2 parts of a lubricant, and 0.5-1 part of an antioxidant.

[0010] Furthermore, the lubricant is one of erucamide or oleamide, and the antioxidant is antioxidant 1010 or antioxidant 1076.

[0011] A method for preparing a transparent polyester substrate for window film, the method comprising the following steps:

[0012] S1, adding the raw materials of the outer layer, the middle core layer and the inner layer into the corresponding extruders respectively, melting, co-extruding, casting, biaxially stretching, heat setting and winding to obtain a polyester film;

[0013] S2. Weigh the raw materials for preparing the acrylic resin coating according to the above parts by weight, first add polymethyl methacrylate and ethylene glycol ether into a reaction kettle, stir evenly, then add ammonium thiocyanate, melamine, colloidal silica, ultraviolet absorber, nanosilver particles, and toughening agent in sequence, continue stirring and reacting, to obtain an acrylic resin coating material;

[0014] S3. Evenly coating the prepared acrylic resin coating material on one side of the polyester film, and drying and curing the film to obtain a transparent polyester substrate for the window film.

[0015] Furthermore, the specific process parameters in step S1 are as follows: melting temperature is 270-290°C, co-extrusion pressure is 10-15 MPa, casting temperature is 25-35°C, longitudinal stretching ratio of biaxial stretching is 3-5 times, transverse stretching ratio is 3-5 times, and heat setting temperature is 220-240°C.

[0016] Furthermore, in step S3, the coating thickness of the acrylic resin coating material is controlled to be 0.05-1 μm, and the drying and curing temperature is 80-100°C.

[0017] The transparent polyester substrate for window film is used on the surface of automobile windows or building windows.

[0018] Beneficial effects of the present invention:

[0019] 1. The amino groups (-NH2) of melamine and the carboxyl groups (-COOH) of PMMA form an amide bond crosslinking network through dehydration condensation, transforming the linear PMMA molecular chains into a three-dimensional network. This increases the coating's tensile strength by over 40% and its impact resistance by 35%. The thiocyanate (SCN-) of ammonium thiocyanate forms hydrogen bonds with the polar groups of PMMA, promoting the orderly arrangement of the molecular chains, reducing internal porosity and defects, and further enhancing the coating's resistance to cracking. These three factors work together to create a "rigid-flexible balance" of properties: it possesses the rigid support of PMMA while also enhancing toughness through the crosslinking network and hydrogen bonding, making it less susceptible to damage from external impact or deformation.

[0020] 2. Melamine, as a nitrogen-based flame retardant, decomposes at high temperatures to release nitrogen (N2) and ammonia (NH3), diluting the oxygen concentration and capturing combustion free radicals (such as OH·), inhibiting the spread of flames; at the same time, it generates a nitrogen-containing carbonized layer to block heat and oxygen. Ammonium thiocyanate decomposes under heat to produce sulfur oxides (SO x ) and sulfur-containing free radicals, which react with nitrogen-containing products of melamine to form a "nitrogen-sulfur synergistic flame retardant system," accelerating char formation and enhancing the thermal stability of the char layer (raising its temperature resistance to over 350°C). Experiments show that the oxygen index (OI) of the resulting coating increases from 17.3% to 29.1%, achieving UL94 V-0 in vertical burning tests, and reducing smoke emissions by 25%, meeting flame retardancy standards for automotive interiors and architectural films.

[0021] 3. The rigid ring structure of melamine is embedded in the PMMA molecular chain, inhibiting crystal orientation and the formation of large crystals, reducing the coating haze from 3.5% to below 1.0%. Ammonium thiocyanate regulates phase separation behavior, prompting PMMA to form a uniform nanoscale dispersed phase (particle size <50nm), reducing light scattering and increasing light transmittance from 88% to 93%, approaching the level of optical-grade PMMA, making it suitable for high-definition window films. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 Schematic diagram of the structure of the window film substrate of the present invention.

[0024] Reference numerals: 1, acrylic resin coating; 2, polyester film; 21, outer surface layer; 22, middle core layer; 23, inner surface layer. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] Example 1

[0027] Preparation of raw materials:

[0028] Raw materials of the outer layer 21 (by weight): 80 parts of polyethylene terephthalate, 1 part of nano-silicon dioxide, 2 parts of carbon nanotube / POSS modified polyester, 3 parts of fluorine-containing dibasic acid modified polyester, and 5 parts of calcium carbonate.

[0029] The raw material of the middle core layer 22 is 100 parts of polyethylene terephthalate.

[0030] Raw materials of the inner surface layer 23 (by weight): 85 parts of polyethylene terephthalate, 1 part of erucamide, and 0.5 parts of antioxidant 1010.

[0031] Acrylic resin coating 1 (by weight): 70 parts of polymethyl methacrylate, 0.5 parts of ammonium thiocyanate, 4 parts of melamine, 1 part of ethylene glycol ether, 2 parts of colloidal silica, 1 part of 2,4-dihydroxybenzophenone, 0.5 parts of nanosilver particles, and 3 parts of polycarbonate.

[0032] A method for preparing a transparent polyester substrate for window film:

[0033] S1, respectively adding the raw materials for the outer surface layer 21, the intermediate core layer 22 and the inner surface layer 23 into the corresponding extruders, melting, co-extruding and casting at a melt temperature of 270°C, a co-extrusion pressure of 10 MPa and a casting temperature of 25°C, then biaxially stretching with a longitudinal stretching ratio of 3 times and a transverse stretching ratio of 3 times, finally heat-setting at a heat-setting temperature of 220°C and winding to obtain a polyester film 2;

[0034] S2, adding polymethyl methacrylate and ethylene glycol ether into a reaction kettle, stirring evenly at 60° C., then adding other raw materials in sequence, and continuing to stir and react for 2 hours to obtain an acrylic resin coating 1 material;

[0035] S3. Evenly coat the acrylic resin coating 1 material on one side of the polyester film 2 with a coating thickness of 0.55 μm, and dry and solidify at 80° C. to obtain a transparent polyester substrate for the window film.

[0036] Example 2

[0037] Preparation of raw materials:

[0038] Raw materials of the outer layer 21 (by weight): 85 parts of polyethylene terephthalate, 2 parts of nano-silicon dioxide, 3 parts of carbon nanotube / POSS modified polyester, 4 parts of fluorine-containing dibasic acid modified polyester, and 6 parts of calcium carbonate.

[0039] The raw material of the middle core layer 22 is 100 parts of polyethylene terephthalate.

[0040] Raw materials of the inner surface layer 23 (by weight): 88 parts of polyethylene terephthalate, 1.5 parts of erucamide, and 0.8 parts of antioxidant 1010.

[0041] Acrylic resin coating 1 (by weight): 75 parts of polymethyl methacrylate, 2 parts of ammonium thiocyanate, 10 parts of melamine, 3 parts of ethylene glycol ether, 5 parts of colloidal silica, 2 parts of 2,4-dihydroxybenzophenone, 1 part of nanosilver particles, and 5 parts of polycarbonate.

[0042] A method for preparing a transparent polyester substrate for window film:

[0043] S1, respectively adding the raw materials for the outer surface layer 21, the intermediate core layer 22 and the inner surface layer 23 into the corresponding extruders, melting, co-extruding and casting at a melt temperature of 280°C, a co-extrusion pressure of 12 MPa and a casting temperature of 30°C, then biaxially stretching with a longitudinal stretching ratio of 4 times and a transverse stretching ratio of 4 times, finally heat-setting at a heat-setting temperature of 230°C and winding to obtain a polyester film 2;

[0044] S2, adding polymethyl methacrylate and ethylene glycol ether into a reactor, stirring at 65° C., then adding other raw materials in sequence, and continuing to stir and react for 2.5 hours to obtain an acrylic resin coating 1 material;

[0045] S3. Evenly coat the acrylic resin coating 1 material on one side of the polyester film 2 with a coating thickness of 0.7 μm, and dry and solidify it at 90° C. to obtain a transparent polyester substrate for the window film.

[0046] Example 3

[0047] Preparation of raw materials:

[0048] Raw materials of the outer layer 21 (by weight): 90 parts of polyethylene terephthalate, 3 parts of nano-silicon dioxide, 5 parts of carbon nanotube / POSS modified polyester, 6 parts of fluorine-containing dibasic acid modified polyester, and 8 parts of calcium carbonate.

[0049] The raw material of the middle core layer 22 is 100 parts of polyethylene terephthalate.

[0050] Raw materials of the inner surface layer 23 (by weight): 92 parts of polyethylene terephthalate, 2 parts of erucamide, and 1 part of antioxidant 1010.

[0051] Acrylic resin coating 1 (by weight): 80 parts of polymethyl methacrylate, 5 parts of ammonium thiocyanate, 18 parts of melamine, 5 parts of ethylene glycol ether, 8 parts of colloidal silica, 3 parts of 2,4-dihydroxybenzophenone, 2 parts of nanosilver particles, and 7 parts of polycarbonate.

[0052] A method for preparing a transparent polyester substrate for window film:

[0053] S1. The raw materials for the outer surface layer 21, the middle core layer 22 and the inner surface layer 23 are respectively added into the corresponding extruders, and melted, co-extruded and cast under the conditions of a melt temperature of 290°C, a co-extrusion pressure of 15 MPa and a casting temperature of 35°C. Then, biaxial stretching is performed with a longitudinal stretching ratio of 5 times and a transverse stretching ratio of 5 times. Finally, heat setting and winding are performed at a heat setting temperature of 240°C to obtain a polyester film 2.

[0054] S2. Add polymethyl methacrylate and ethylene glycol ether into a reactor, stir evenly at 70° C., then add other raw materials in sequence, continue stirring and react for 3 hours to obtain an acrylic resin coating 1 material.

[0055] S3. Evenly coat the acrylic resin coating 1 material on one side of the polyester film 2 with a coating thickness of 1.0 μm, and dry and solidify at 100° C. to obtain a transparent polyester substrate for the window film.

[0056] Comparative Example 1

[0057] Compared with Example 3, Comparative Example 1 lacks ammonium thiocyanate in the preparation raw materials, and the other components are the same as those in Example 3, and the preparation method is also the same as that in Example 3, to prepare a transparent polyester substrate for a window film.

[0058] Comparative Example 2

[0059] Compared with Example 3, Comparative Example 2 lacks melamine in the raw materials for preparation, and the other components are the same as those in Example 3, and the preparation method is also the same as that in Example 3, to prepare a transparent polyester substrate for a window film.

[0060] The transparent polyester substrates for window films prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were subjected to performance tests.

[0061] The test standards are as follows:

[0062] Tensile strength test: The test standard is GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3: Test conditions for film and sheeting";

[0063] Impact strength test: The test standard is GB / T 8809-2015 "Plastic film resistance to pendulum impact test method";

[0064] Oxygen Index Test: The test standard adopts GB / T 2406.2-2009 "Plastics - Determination of Combustion Behavior by Oxygen Index Method - Part 2: Room Temperature Test"1. This standard is equivalent to ISO 4589-2, which specifies the oxygen index test method for plastics and plastic products at room temperature.

[0065] Smoke emission test: The test standard is GB / T 8323.2-2008, "Plastics - Smoke Generation - Part 2: Single Chamber Method"11. This standard, equivalent to ISO 5692:2006, specifies a method for determining the optical density of smoke generated by the combustion of plastic materials. It is applicable to specimens of sheet materials, composite materials, or assemblies not exceeding 25mm in thickness. During the test, a 75mm x 75mm specimen is placed vertically in a sealed cabinet equipped with a heat radiation source of the specified grade. Smoke generation from the exposed surface is measured with or without a pilot flame. The maximum specific optical density is used as the test result to evaluate the smoke emission performance of the plastic under the specified conditions.

[0066] Coating haze test: The test standard adopts GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics"3. This standard specifies the test method for light transmittance and haze of transparent plastics and is applicable to transparent plastic materials including polyester.

[0067] Light transmittance test: The test standard adopts GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics"1. This standard specifies the test method for light transmittance and haze of transparent plastics and is applicable to transparent plastic materials including polyester.

[0068] The test results are shown in Table 1:

[0069] Table 1

[0070]

[0071] in conclusion:

[0072] 1. The tensile strength of Example 3 reached 103.5 MPa, a 102.5% increase over Comparative Example 2 (no melamine), verifying the reinforcing effect of the melamine cross-linking network. The absence of ammonium thiocyanate (Comparative Example 1) resulted in a 28.6% decrease in strength, indicating its auxiliary effect on molecular chain alignment.

[0073] 2. The impact strength of Example 3 reaches 31.5kJ / m 2 , a 99.4% improvement over Comparative Example 2, embodying a "rigid-flexible balance" design. The synergistic effect of ammonium thiocyanate and melamine increases impact resistance by over 35%.

[0074] 3. The oxygen index of Example 3 reaches 30.5%, meeting UL94 V-0 level.

[0075] 4. The smoke emission of Example 3 was reduced to 55 Dm (optical density), which was 40.2% less than that of Comparative Example 2, verifying the smoke suppression effect of the "nitrogen-sulfur synergistic flame retardant system".

[0076] 5. The haze of Example 3 is as low as 0.7%, close to the optical grade standard, and is 80% higher than that of Comparative Example 2 (3.5%).

[0077] 6. The light transmittance of Example 3 reaches 93.8%, which is 6.6% higher than that of Comparative Example 2, meeting the requirements of high-definition window films.

[0078] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0079] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A transparent polyester substrate for window film, characterized in that: The transparent polyester substrate for the window film comprises an acrylic resin coating (1) and a polyester film (2), wherein the polyester film (2) comprises, from top to bottom, an outer surface layer (21), an intermediate core layer (22), and an inner surface layer (23), and the acrylic resin coating (1) is coated on the outer surface of the outer surface layer (21). The raw materials for preparing the acrylic resin coating (1) include, by weight, 70-80 parts of polymethyl methacrylate, 0.5-5 parts of ammonium thiocyanate, 4-18 parts of melamine, 1-5 parts of ethylene glycol ether, 2-8 parts of colloidal silicon dioxide, 1-3 parts of ultraviolet absorber, 0.5-2 parts of nano silver particles, and 3-7 parts of toughening agent.

2. The transparent polyester substrate for window film according to claim 1, characterized in that: The ultraviolet absorber is one of 2,4-dihydroxybenzophenone and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole; and the toughening agent is at least one of polycarbonate, polyethersulfone and polyurethane.

3. The transparent polyester substrate for window film according to claim 1, characterized in that: The raw materials for preparing the outer layer (21) include, by weight, 80-90 parts of polyethylene terephthalate, 1-3 parts of nano-silicon dioxide, 2-5 parts of carbon nanotube / POSS modified polyester, 3-6 parts of fluorine-containing dibasic acid modified polyester, and 5-10 parts of calcium carbonate.

4. The transparent polyester substrate for window film according to claim 1, characterized in that: The raw material for preparing the intermediate core layer (22) is polyethylene terephthalate.

5. The transparent polyester substrate for window film according to claim 1, characterized in that: The inner surface layer (23) comprises 85-92 parts of polyethylene terephthalate, 1-2 parts of a slip agent, and 0.5-1 part of an antioxidant.

6. The transparent polyester substrate for window film according to claim 5, characterized in that: The lubricant is one of erucamide and oleamide, and the antioxidant is antioxidant 1010 or antioxidant 1076.

7. A method for preparing a transparent polyester substrate for a window film according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1, adding the raw materials of the outer layer (21), the middle core layer (22) and the inner layer (23) into the corresponding extruders respectively, melting, co-extruding, casting, biaxially stretching, heat setting and winding to obtain a polyester film (2); S2. Weigh the raw materials for preparing the acrylic resin coating (1) according to the above-mentioned weight parts, first add polymethyl methacrylate and ethylene glycol ether into a reaction kettle, stir evenly, then add ammonium thiocyanate, melamine, colloidal silica, ultraviolet absorber, nano silver particles, and toughening agent in sequence, continue stirring and reacting, and obtain the acrylic resin coating (1) material; S3. The prepared acrylic resin coating (1) material is evenly coated on one side of the polyester film (2), and after drying and curing, a transparent polyester substrate for the window film is obtained.

8. The method for preparing a transparent polyester substrate for a window film according to claim 7, wherein: The specific process parameters in step S1 are as follows: melting temperature of 270-290°C, co-extrusion pressure of 10-15 MPa, casting temperature of 25-35°C, longitudinal stretching ratio of biaxial stretching of 3-5 times, transverse stretching ratio of 3-5 times, and heat setting temperature of 220-240°C.

9. The method for preparing a transparent polyester substrate for a window film according to claim 7, wherein: In step S3, the coating thickness of the acrylic resin coating (1) material is controlled to be 0.05-1 μm, and the drying and curing temperature is 80-100°C.

10. The transparent polyester substrate for window film according to any one of claims 1 to 6 is used for the surface of automobile windows or building windows.

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