Anti-ultraviolet BOPET window film and preparation method thereof

Abstract

The invention discloses an anti-ultraviolet BOPET window film and a preparation method thereof, and belongs to the technical field of BOPET window films. Comprising the following raw materials in parts by weight: 80-90 parts of polyester chips, 6-8 parts of dioctyl phthalate, 3-5 parts of nano zinc oxide, 2-8 parts of an anti-ultraviolet agent and 0.2-0.6 part of an antioxidant. The anti-ultraviolet agent disclosed by the invention can act together with the nano zinc oxide, so that the anti-ultraviolet performance of the window film is improved, the heat resistance of the window film can be improved, and the service life of the window film is prolonged; nano zinc oxide is modified by a silane coupling agent, so that the compatibility with a polyester matrix is improved, agglomeration is avoided, and the negative influence on the window film is reduced; in conclusion, the window film prepared by the invention has excellent ultraviolet resistance and heat resistance, and is suitable for outdoor scenes such as automobile window films, building glass films and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of BOPET window films, and in particular relates to an anti-ultraviolet BOPET window film and a preparation method thereof. Background Art

[0002] With the rapid development of modern architecture and the automotive industry, the demand for high-performance window film materials is growing. Biaxially oriented polyester film (BOPET) has become an important substrate in the window film industry due to its excellent mechanical properties, transparency, and chemical stability.

[0003] In practical applications, whether it's for cars exposed to the sun for extended periods or for creating a comfortable indoor environment in buildings, window films must possess multiple key properties. Among these, UV protection is particularly crucial. It not only effectively blocks UV radiation from reaching vehicle occupants or people indoors, reducing damage to human skin and eyes, but also reduces the risk of aging and fading of furniture and decorative materials due to UV exposure, extending their service life.

[0004] In order to give window films effective anti-UV properties, the current common technical means is to add a small amount of ultraviolet light absorbers to the base resin. Commonly used inorganic ultraviolet light absorbers, such as titanium dioxide, have long-lasting and stable characteristics, but they are prone to agglomeration in the base resin. The agglomerated titanium dioxide particles will not only reduce the compatibility with organic matter, but also have a negative impact on the light transmittance of the window film, causing the window film to become turbid, uneven in light transmittance, and other problems. At the same time, it will also damage the mechanical properties of the window film, reducing its strength and flexibility, and it is prone to cracking and delamination during use. Organic ultraviolet light absorbers, such as benzotriazole ultraviolet light absorbers, have high compatibility with the base resin and can better play the role of absorbing ultraviolet rays. However, the anti-UV performance of a single benzotriazole ultraviolet light absorber is insufficient. After long-term ultraviolet radiation, its molecular structure is prone to depolymerization and failure, resulting in a gradual decline in anti-UV performance. In addition to the above-mentioned anti-ultraviolet properties, the surface temperature of the window film will rise when it is exposed to direct sunlight outdoors for a long time. Excessive temperature will cause thermal degradation of the window film, affecting its service life. Based on the above problems, there is an urgent need to invent a BOPET window film that has both anti-ultraviolet and heat-resistant properties. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide an anti-ultraviolet BOPET window film and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing an ultraviolet-resistant BOPET window film comprises the following steps: A1. Place the polyester chips in a vacuum drying oven to dry them and remove moisture from the chips to avoid bubbles in the subsequent processing. A2, mixing the dried polyester chips, dioctyl phthalate, nano zinc oxide, anti-ultraviolet agent and antioxidant, and melt-blending them through a twin-screw extruder to form a uniform melt; A3. First, the melt is extruded from the die head, then rapidly cooled by cold rollers to form a cast sheet, which is then stretched longitudinally and transversely, and finally heat-set, cooled and rolled to obtain the UV-resistant BOPET window film.

[0007] Optionally, the drying temperature is 120-140° C. and the drying time is 4-6 hours.

[0008] Optionally, the temperature of the twin-screw extruder is 250-270°C.

[0009] Optionally, the temperature of the cold roller is 20-30°C.

[0010] Optionally, the heat setting temperature is 180-200° C. and the time is 3-5 minutes.

[0011] Optionally, the raw materials of the anti-ultraviolet BOPET window film are as follows in parts by mass: 80-90 parts of polyester chips, 6-8 parts of dioctyl phthalate, 3-5 parts of nano zinc oxide, 2-8 parts of anti-ultraviolet agent and 0.2-0.6 parts of antioxidant.

[0012] Optionally, the antioxidant is one of antioxidant 1135, antioxidant 1076, antioxidant 168 and antioxidant 626.

[0013] Optionally, the nano zinc oxide is nano zinc oxide modified with a silane coupling agent, which is prepared by the following steps: B1. Add nano zinc oxide powder to anhydrous ethanol and ultrasonically disperse for 20-30 minutes to destroy agglomerates and form a uniform suspension; B2. Add a silane coupling agent to the suspension, and adjust the pH to 4-5 with acetic acid solution. Stir magnetically for 30-50 minutes to fully hydrolyze the silane. Heat to 60-65°C and stir at a constant temperature for 2-3 hours. After the reaction is complete, centrifuge for 10-20 minutes, collect the precipitate, wash it with ethanol several times, and dry it to obtain nano zinc oxide modified with a silane coupling agent.

[0014] Optionally, the mass ratio of the nano zinc oxide powder to the silane coupling agent is 10g:0.4-1.1g.

[0015] Optionally, the silane coupling agent is one of KH-550, KH-560, KH-570, KH-792, and KH-590.

[0016] Optionally, the anti-ultraviolet agent is prepared by the following steps: C1. First, 4,4'-dihydroxybenzophenone and p-aminophenol were placed in a flask, followed by the addition of xylene as a solvent. Then, a formaldehyde aqueous solution (37% by mass) was added to the flask, and mechanically stirred at 100-110°C, and refluxed under condensation for 4-5 hours. After the reaction was complete, the mixture was cooled and transferred to a separatory funnel. The mixture was washed three times with ethanol, dilute hydrochloric acid, and deionized water in sequence. After separating the organic layer, it was rotary evaporated and dried to obtain the first product. C2, first tetramethyl piperidinol, methyl 4-chlorobutyrate, and p-hydroxyanisole are put into a flask, followed by adding petroleum ether as a solvent, under nitrogen protection, mechanical stirring, and preheating to 110-120 ° C, then tetraethyl titanate is added dropwise to the flask, after the dropwise addition is completed, the reaction is kept warm for 10-12h, and the reaction process is accompanied by the steaming of methanol. The reaction terminates, and after cooling, the mixture is washed 3 times with deionized water, and after separating the organic layer, it is distilled under reduced pressure to obtain the second product; C3. First, put the first product and the second product into a flask, then add xylene as a solvent, then mix sodium hydroxide with distilled water, stir to dissolve the sodium hydroxide, and slowly add it dropwise to the flask through a dropping funnel. After the addition is complete, heat to 70-80°C, keep the temperature for reaction for 6-8h, and after the reaction is complete, post-process to obtain an anti-ultraviolet agent.

[0017] In the preparation process of the anti-ultraviolet agent, the reaction formulas of steps C1 and C2 are as follows: Step C1: Step C2: The preparation principle of the anti-ultraviolet agent is as follows: first, in step C1, p-aminophenol and formaldehyde (paraformaldehyde decomposes upon heating) first generate an imine intermediate, which then reacts with 4,4'-dihydroxybenzophenone to obtain a first product; secondly, in step C2, tetramethylpiperidinol and methyl 4-chlorobutyrate undergo an ester exchange reaction under the catalysis of tetraethyl titanate to obtain a second product; and then in step C3, the first product and the second product undergo a nucleophilic substitution reaction under the catalysis of sodium hydroxide to obtain an anti-ultraviolet agent. Finally, it should be noted that the ratio of the amount of 4,4'-dihydroxybenzophenone to p-aminophenol in step C1 of the present invention is 1:2, wherein the excess p-aminophenol ensures complete reaction. Similarly, the ratio of the amount of the first product to the second product in step C3 is also 1:2.

[0018] The performance of the anti-UV agent is as follows: First, the anti-UV agent contains ketone groups as ultraviolet absorption components and hindered amines as light stabilizing components. Among them, the ketone group can form a conjugated system with the adjacent benzene ring and has certain ultraviolet absorption properties, while the hindered amine can capture the active free radicals produced by photodegradation, interrupt the free radical chain reaction, and thus inhibit photodegradation. Therefore, from the perspective of the working principle of the two, the ketone group can play a synergistic role with the hindered amine to greatly improve the anti-UV performance of the matrix. In addition, the anti-UV agent also contains benzoxazine components, which can improve the heat resistance of the matrix to a certain extent.

[0019] Optionally, in step C1, the ratio of 4,4'-dihydroxybenzophenone, p-aminophenol and formaldehyde aqueous solution is 21.4 g: 22.1-23.3 g: 30-35 mL.

[0020] Optionally, in step C2, the ratio of tetramethylpiperidinol, methyl 4-chlorobutyrate, p-hydroxyanisole and tetraethyl titanate is 15.7 g:13.6 g:0.29 g:0.62 g.

[0021] Optionally, in step C3, the ratio of the first product, the second product and sodium hydroxide is 47.9 g: 52.8-54.1 g: 8.3-9.1 g.

[0022] Beneficial effects of the present invention: Advantages 1. The anti-ultraviolet agent of the present invention can work together with nano zinc oxide (modified with a silane coupling agent) to not only improve the anti-ultraviolet performance of the window film, but also solve the problems of insufficient anti-ultraviolet performance and easy failure of single organic ultraviolet absorbers, and the problem that inorganic ultraviolet absorbers are easy to agglomerate and affect compatibility and light transmittance; Advantage 2: The anti-ultraviolet agent of the present invention can also improve the heat resistance of the window film to a certain extent, reduce the thermal degradation of the window film caused by long-term exposure to the outdoors and direct sunlight, and extend the service life of the window film; Advantage 3: Nano zinc oxide modified with silane coupling agent improves compatibility with polyester matrix, avoids agglomeration, and reduces negative impact on window film; In summary, the window film prepared by the present invention has excellent anti-ultraviolet and heat resistance, and is suitable for outdoor scenes such as automobile window film and architectural glass film. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0024] Example 1 Preparation of UV protection agent: C1. First, 21.4 g of 4,4'-dihydroxybenzophenone and 22.1 g of p-aminophenol were placed in a flask. Then, 120 mL of xylene was added as a solvent. Then, 30 mL of formaldehyde aqueous solution (mass fraction 37%) was added to the flask. The mixture was mechanically stirred at 100°C and refluxed for 4 h. After the reaction was completed, the mixture was cooled and transferred to a separatory funnel. The mixture was washed three times with ethanol, dilute hydrochloric acid, and deionized water in sequence. After separating the organic layer, it was rotary evaporated and dried to obtain the first product. C2, first 15.7g tetramethyl piperidinol, 13.6g4-chlorobutyric acid methyl ester, 0.29g p-Hydroxyanisole are put in flask, secondly add 100mL sherwood oil as solvent, under nitrogen protection condition, mechanical stirring, and be preheated to 110 ℃, then in flask, drip 0.62g tetraethyl titanate, after being added dropwise to complete, insulation reaction 10h, steaming with methyl alcohol in the reaction process, reaction terminates, after cooling, wash 3 times with deionized water, after isolating organic layer, carry out underpressure distillation, obtain the second product; C3. First, 47.9 g of the first product and 52.8 g of the second product were put into a flask, followed by adding 150 mL of xylene as a solvent, and then 8.3 g of sodium hydroxide was mixed with 20 mL of distilled water, stirred to dissolve the sodium hydroxide, and slowly added dropwise to the flask through a dropping funnel. After the addition was complete, the temperature was raised to 70° C. and the reaction was kept at this temperature for 6 hours. After the reaction was complete, the product was purified on a silica gel column (eluent: dichloromethane / methanol = 20:1) to obtain an anti-ultraviolet agent; Preparation of nano zinc oxide modified with silane coupling agent: B1. Add 10g of nano zinc oxide powder to anhydrous ethanol and ultrasonically disperse for 20-30min to destroy the agglomerates and form a uniform suspension; B2. Add 0.4 g of KH-560 to the suspension, adjust the pH to 4 with acetic acid solution, stir magnetically for 30 min to fully hydrolyze the silane, heat to 60° C., stir at constant temperature for 2 h, complete the reaction, centrifuge for 10 min, collect the precipitate, wash it with ethanol several times, and dry it to obtain nano zinc oxide modified with a silane coupling agent; A method for preparing an ultraviolet-resistant BOPET window film comprises the following steps: A1. Place 80g of polyester chips in a vacuum drying oven and dry at 120°C for 4 hours to remove moisture from the chips and avoid bubbles during subsequent processing. A2. Mix the dried polyester chips, 6 g of dioctyl phthalate, 3 g of nano zinc oxide modified with a silane coupling agent, 2 g of an anti-ultraviolet agent, and 0.2 g of antioxidant 1135, and melt-blend them through a twin-screw extruder at 250° C. to form a uniform melt; A3. First, the melt is extruded from the die head, and then rapidly cooled by a cold roller at 20°C to form a cast sheet. The cast sheet is then stretched longitudinally and transversely, and finally heat-set at 180°C for 3 minutes, cooled and rolled to obtain an anti-UV BOPET window film.

[0025] Example 2 Preparation of UV protection agent: C1. First, 21.4 g of 4,4'-dihydroxybenzophenone and 23.3 g of p-aminophenol were placed in a flask. Then, 120 mL of xylene was added as a solvent. Then, 35 mL of formaldehyde aqueous solution (mass fraction 37%) was added to the flask. The mixture was mechanically stirred at 110°C and refluxed under condensation for 4-5 hours. After the reaction was completed, the mixture was cooled and transferred to a separatory funnel. The mixture was washed three times with ethanol, dilute hydrochloric acid, and deionized water in sequence. After separating the organic layer, it was rotary evaporated and dried to obtain the first product. C2, first 15.7g tetramethyl piperidinol, 13.6g4-chlorobutyric acid methyl ester, 0.29g p-Hydroxyanisole are put in flask, secondly add 100mL sherwood oil as solvent, under nitrogen protection condition, mechanical stirring, and be preheated to 120 ℃, then in flask, drip 0.62g tetraethyl titanate, after being added dropwise to complete, insulation reaction 12h, steaming with methyl alcohol in the reaction process, reaction terminates, after cooling, wash 3 times with deionized water, after isolating organic layer, carry out underpressure distillation, obtain the second product; C3. First, 47.9 g of the first product and 54.1 g of the second product were put into a flask, followed by adding 150 mL of xylene as a solvent, and then 9.1 g of sodium hydroxide was mixed with 20 mL of distilled water, stirred to dissolve the sodium hydroxide, and slowly added dropwise to the flask through a dropping funnel. After the addition was complete, the temperature was raised to 80° C. and the reaction was kept at this temperature for 8 hours. After the reaction was complete, the product was purified on a silica gel column (eluent: dichloromethane / methanol = 20:1) to obtain an anti-ultraviolet agent; Preparation of nano zinc oxide modified with silane coupling agent: B1. Add 10g of nano zinc oxide powder to anhydrous ethanol and ultrasonically disperse for 30min to destroy the agglomerates and form a uniform suspension; B2. Add 1.1 g of KH-550 to the suspension, adjust the pH to 5 with acetic acid solution, and stir magnetically for 50 min to fully hydrolyze the silane. Heat to 65° C. and stir at this constant temperature for 3 h. After the reaction is complete, centrifuge for 20 min, collect the precipitate, wash it with ethanol several times, and dry it to obtain nano-zinc oxide modified with a silane coupling agent; A method for preparing an ultraviolet-resistant BOPET window film comprises the following steps: A1. Place 85g of polyester chips in a vacuum drying oven at 130°C for 5 hours to remove moisture from the chips and avoid bubbles during subsequent processing. A2. The dried polyester chips, 7 g of dioctyl phthalate, 4 g of nano zinc oxide modified with a silane coupling agent, 5 g of an anti-ultraviolet agent, and 0.4 g of antioxidant 1076 were mixed and melt-blended in a twin-screw extruder at 260° C. to form a uniform melt. A3. First, the melt is extruded from the die head, and then rapidly cooled by a cold roller at 30°C to form a cast sheet. The cast sheet is then stretched longitudinally and transversely, and finally heat-set at 200°C for 4 minutes, cooled and rolled to obtain an anti-UV BOPET window film.

[0026] Example 3 The only difference between this embodiment and the second embodiment is that, in this embodiment, a method for preparing an anti-ultraviolet BOPET window film comprises the following steps: A1. Place 90g of polyester chips in a vacuum drying oven and dry at 140°C for 6 hours to remove moisture from the chips and avoid bubbles during subsequent processing. A2. The dried polyester chips, 8 g of dioctyl phthalate, 5 g of nano zinc oxide modified with a silane coupling agent, 8 g of an anti-ultraviolet agent, and 0.6 g of antioxidant 1076 were mixed and melt-blended through a twin-screw extruder at 270° C. to form a uniform melt; A3. First, the melt is extruded from the die head, and then rapidly cooled by a cold roller at 30°C to form a cast sheet. The cast sheet is then stretched longitudinally and transversely, and finally heat-set at 200°C for 5 minutes, cooled and rolled to obtain an anti-UV BOPET window film.

[0027] Comparative Example 1 The only difference between this comparative example and Example 2 is that in this comparative example, 5 g of UV-531 is used to replace the anti-ultraviolet agent to prepare the window film.

[0028] Comparative Example 2 The only difference between this comparative example and Example 2 is that in this comparative example, 4 g of nano zinc oxide that has not been modified with a silane coupling agent is used to prepare the window film.

[0029] The anti-ultraviolet and heat resistance performance tests of Examples 1, 2, and 3 and Comparative Examples 1 and 2 were performed; the test methods used are as follows: Use a UV-visible spectrophotometer to scan the window film sample in the wavelength range of 280-400nm to calculate the UV blocking rate; GB / T 1634.2-2019 “Determination of Deflection Temperature of Plastics under Load” was used to measure the heat deformation temperature under a load of 1.82 MPa; The measurement results are shown in the following table: As can be seen from the above table, the window films prepared in the embodiments of the present invention have higher UV blocking rates and heat deformation temperatures than the comparative examples. Therefore, the window films prepared in the present invention have excellent UV resistance and heat resistance, and are suitable for outdoor scenes such as automotive window films and architectural glass films.

[0030] Throughout the 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.

[0031] The above contents are merely examples and explanations of the present invention. Any modifications or additions made by those skilled in the art to the described specific embodiments, or replacements made in a similar manner, shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing an anti-ultraviolet BOPET window film, characterized in that: The following steps are involved: The polyester chips are dried and mixed with dioctyl phthalate, nano zinc oxide, anti-ultraviolet agent and antioxidant, melt-blended in an extruder to form a melt, which is extruded and rapidly cooled by cold rollers to form a cast sheet. The cast sheet is then biaxially stretched, heat-set, cooled and rolled to obtain an anti-ultraviolet BOPET window film.

2. The method for preparing an anti-ultraviolet BOPET window film according to claim 1, wherein: The raw materials are calculated in parts by mass as follows: 80-90 parts of polyester chips, 6-8 parts of dioctyl phthalate, 3-5 parts of nano zinc oxide, 2-8 parts of anti-ultraviolet agent and 0.2-0.6 parts of antioxidant.

3. The method for preparing an anti-ultraviolet BOPET window film according to claim 1, wherein: The anti-ultraviolet agent is prepared by the following steps: C1. Place 4,4'-dihydroxybenzophenone and p-aminophenol into a flask, add xylene, and then add formaldehyde aqueous solution into the flask. Reflux at 100-110°C for 4-5 hours. The reaction is completed to obtain the first product. C2, tetramethylpiperidinol, methyl 4-chlorobutyrate, and p-hydroxyanisole were placed in a flask, petroleum ether was added, and the mixture was stirred under nitrogen protection and preheated to 110-120° C., and then tetraethyl titanate was added dropwise. After the addition was complete, the mixture was kept warm for 10-12 hours to obtain the second product; C3. Put the first product and the second product into a flask, add xylene, then mix sodium hydroxide and distilled water, add them to the flask, and react at 70-80°C for 6-8h. The reaction is completed to obtain an anti-ultraviolet agent.

4. The method for preparing an anti-ultraviolet BOPET window film according to claim 3, wherein: In step C1, the ratio of 4,4'-dihydroxybenzophenone, p-aminophenol and formaldehyde aqueous solution is 21.4 g: 22.1-23.3 g: 30-35 mL.

5. The method for preparing an anti-ultraviolet BOPET window film according to claim 3, wherein: In step C2, the ratio of the amount of tetramethylpiperidinol, methyl 4-chlorobutyrate, p-hydroxyanisole and tetraethyl titanate is 15.7g:13.6g:0.29g:0.62g.

6. The method for preparing an anti-ultraviolet BOPET window film according to claim 3, wherein: The ratio of the first product, the second product and sodium hydroxide used in step C3 is 47.9g:52.8-54.1g:8.3-9.1g.

7. The method for preparing an anti-ultraviolet BOPET window film according to claim 1, wherein: The nano zinc oxide is nano zinc oxide modified by a silane coupling agent.

8. The method for preparing an anti-ultraviolet BOPET window film according to claim 1, characterized in that: The antioxidant is one of antioxidant 1135, antioxidant 1076, antioxidant 168 and antioxidant 626.

9. An anti-ultraviolet BOPET window film, characterized in that: Prepared according to the method according to any one of claims 1 to 8.

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