Anti-UV TAC film and preparation method thereof

Abstract

The invention discloses an anti-UV TAC film and a preparation method thereof, and belongs to the technical field of TAC optical films. The anti-UV TAC film is prepared from the following raw materials in parts by mass: 100 parts of cellulose triacetate, 10 to 20 parts of cellulose p-formyl benzoate, 650 to 700 parts of solvent, 70 to 120 parts of cosolvent, 15 to 25 parts of plasticizer and 1 to 3 parts of ultraviolet absorbent, the cellulose p-formylbenzoate is prepared by carrying out transesterification reaction on cellulose and methyl p-formylbenzoate; the ultraviolet absorbent is prepared by carrying out condensation reaction on 4-carboxyl benzotriazole and amino at one end of a diamine derivative of phenylphosphoryl. According to the invention, a halogen-free high-molecular-weight ultraviolet absorbent is designed and synthesized, and the halogen-free high-molecular-weight ultraviolet absorbent and cellulose p-formyl benzoate form a synergistic effect, so that anti-ultraviolet active components are not easy to physically migrate, and the cellulose triacetate film is ensured to have high light transmittance and good ultraviolet barrier property.

Description

Technical Field

[0001] This invention belongs to the field of TAC optical film technology, specifically relating to a UV-resistant TAC thin film and its preparation method. Background Technology

[0002] Triacetyl cellulose acetate film (TAC), as a protective film for polarizers, possesses excellent optical properties, mechanical strength, and optical isotropy, making it an indispensable functional optical film in liquid crystal displays.

[0003] When LCD monitors are used outdoors, prolonged exposure to sunlight can reduce their display quality and lifespan. Therefore, the TAC film on the surface of the polarizer needs to have UV resistance to prevent damage from ultraviolet rays. Currently, there are two main methods to improve the UV resistance of TAC films: one is to add UV absorbers to the raw materials used in film preparation, and the other is to use the TAC film as a substrate and coat its surface with an UV-resistant coating.

[0004] Compared to adding an anti-UV coating, adding UV absorbers is obviously simpler and easier to implement. The commonly used UV absorbers in TAC films are benzotriazole compounds, whose anti-UV mechanism is to absorb the energy of ultraviolet rays and convert it into heat. However, existing benzotriazole UV absorbers have problems with poor thermal stability and easy migration, which will adversely affect the haze and transmittance of the final product. Summary of the Invention

[0005] The purpose of this invention is to provide a UV-resistant TAC film and its preparation method, which can solve the problem of easy migration of UV absorbers in existing TAC films.

[0006] The objective of this invention can be achieved through the following technical solutions: A UV-resistant TAC film, comprising the following raw materials by weight: 100 parts of cellulose triacetate, 10-20 parts of cellulose p-aldehyde benzoate, 650-700 parts of solvent, 70-120 parts of cosolvent, 15-25 parts of plasticizer, and 1-3 parts of ultraviolet absorber; The cellulose p-formaldehyde benzoate is prepared by transesterification of cellulose with methyl p-formylbenzoate. The ultraviolet absorber is prepared by condensation reaction of 4-carboxybenzotriazole with a diamine derivative of phenylphosphine and one of its terminal amino groups.

[0007] Conventional benzotriazole UV absorbers have relatively small molecular weights. The UV absorber designed and prepared in this invention contains both benzotriazole and phenylphosphine structures in its molecular structure. The phenylphosphine structure itself enhances the UV absorber's resistance to thermo-oxidative decomposition, and the multi-benzene ring structure increases the molecular weight, resulting in high thermal stability. The UV absorber added in this invention has a larger molecular weight, improving its physical migration within the film and reducing its precipitation on the film surface, thus mitigating its adverse effects on the transmittance of the TAC film. This invention also incorporates cellulose p-formaldehyde benzoate along with the UV absorber. Unlike conventional cellulose, the introduction of the p-formaldehyde benzoate structure reduces water absorption and promotes UV absorber compatibility through the conjugation of benzene rings. The aldehyde group at its outer end can condense with the amino group on the UV absorber during subsequent processing to form a Schiff base, firmly locking the UV absorber within the cellulose triacetate ester, thereby improving UV protection efficiency and durability.

[0008] Furthermore, the preparation steps of the cellulose-based aldehyde benzoate are as follows: S1. Add DMSO as a solvent to the reactor, then add 1,8-diazabicycloundec-7-ene and cellulose. Under a carbon dioxide atmosphere, maintain a pressure of 0.3-0.4 MPa, stir for 10-30 min, then raise the temperature to 50℃ and maintain a pressure of 0.2 MPa for 3-4 h to activate. S2. Add the activated solution to a flask, heat to 110-120℃, add methyl p-formylbenzoate, and stir the reaction under a carbon dioxide atmosphere for 12-24 hours. After the reaction is completed, remove the solvent by rotary evaporation under reduced pressure, wash with deionized water and dry under vacuum to obtain cellulose p-aldehyde benzoate.

[0009] Furthermore, the cellulose is 3-7% of the mass of DMSO.

[0010] Furthermore, the mass ratio of the 1,8-diazabicycloundec-7-ene to cellulose is (2.5-3.5):1.

[0011] Furthermore, the mass ratio of methyl paraformylbenzoate to cellulose is (0.2-0.5):1.

[0012] The structural formula of cellulose p-aldehyde benzoate is as follows: , In the above preparation scheme, cellulose reacts with CO2 in DMSO in the presence of 1,8-diazabicycloundec-7-ene (DBU) to generate a reversible polyionic liquid of cellulose. Then, in situ DBU is used as an organic functional catalyst to catalyze the transesterification reaction of cellulose with methyl p-formylbenzoate to form cellulose p-aldehyde benzoate.

[0013] Furthermore, the preparation steps of the ultraviolet absorber are as follows: A1. Under ice bath conditions, phenylphosphoryl dichloride was added dropwise to 1,10-decanediamine at a molar ratio of 1:2. Under nitrogen atmosphere, the temperature was raised to 58-60℃ and the mixture was stirred for 6-8 hours. After the reaction was completed, the mixture was washed with water and dried to obtain the diamine derivative of phenylphosphoryl. A2. Add the diamine derivative of phenylphosphine and 4-carboxybenzotriazole to DMF, stir to dissolve, add triethylamine dropwise while stirring under ice bath conditions, stir evenly and then remove the ice bath, add EDC·HCl and DMAP, remove the ice bath, heat to 30-40℃ and stir to react for 8-12 h, after the reaction is completed, remove the solvent by rotary evaporation, and purify by chromatography to obtain the ultraviolet absorber.

[0014] Further, the mass ratio of the phenylphosphine diamine derivative to 4-carboxybenzotriazole is (2.8-3.2):1.

[0015] Furthermore, the molar ratio of triethylamine to 4-carboxybenzotriazole is (2.8-3.1):1.

[0016] Further, the molar ratio of 4-carboxybenzotriazole, EDC·HCl and DMAP is 1.0:(1.1-1.2):(0.1-0.3).

[0017] The preparation reaction formula for the above-mentioned ultraviolet absorber is as follows: ; .

[0018] In the above preparation method, phenylphosphoryl dichloride is first condensed with 1,10-decanediamine to obtain a phenylphosphoryl diamine derivative containing a long alkyl chain. The terminal amino group reacts with the carboxyl group of 4-carboxybenzotriazole to form an amide bond, thus linking the benzotriazole structure with the phenylphosphoryl diamine derivative. The long-chain alkyl group acts as a bridge between the phenylphosphoryl structure and the benzotriazole structure, which can avoid the steric hindrance effect from hindering the reaction. The resulting ultraviolet absorber has a large molecular weight and good thermal stability.

[0019] Furthermore, the solvent is at least one selected from dichloromethane and trichloromethane; The co-solvent is at least one of methanol, ethanol, and isopropanol.

[0020] Furthermore, the plasticizer is at least one of diethyl phthalate and triacetin.

[0021] This invention also provides a method for preparing a UV-resistant TAC film, which includes the following steps: Step 1: Prepare the raw materials according to the proportions, and mix the solvent and co-solvent to form a mixed solvent; Step 2: Add cellulose triacetate, cellulose p-aldehyde benzoate, plasticizer and UV absorber to the mixed solvent and stir to dissolve and form a homogeneous solution; Step 3: After the solution is cast into a film, it is dried to obtain a UV-resistant TAC film.

[0022] The beneficial effects of this invention are: (1) In this invention, cellulose triacetate is used as the main matrix of TAC film. Based on the existing technology of adding ultraviolet absorbers, a halogen-free high molecular weight ultraviolet absorber is designed and synthesized. The ultraviolet absorber is prepared by condensation reaction of 4-carboxybenzotriazole and the terminal amino group of the diamine derivative of phenylphosphine. By bridging the benzotriazole structure and the phenylphosphine structure with a long-chain alkyl group, the molecular weight is greatly increased, which effectively inhibits its migration in the TAC matrix. The introduced phenylphosphine structure can improve the thermal stability of the ultraviolet absorber, so that the ultraviolet absorber can stably and effectively play an anti-ultraviolet role in the film.

[0023] (2) In this invention, while adding a high molecular weight ultraviolet absorber to the TAC film raw material, cellulose p-aldehyde benzoate is also added. Cellulose p-aldehyde benzoate is prepared by transesterification of cellulose and methyl p-formylbenzoate. It contains aldehyde group and benzene ring. The aldehyde group can undergo Schiff base condensation reaction with the amino group at the end of the ultraviolet absorber during film processing to form a chemical bond. At the same time, the conjugation effect between benzene rings promotes the compatibility of ultraviolet absorber, thereby firmly locking the ultraviolet absorber on the cellulose skeleton. The ultraviolet absorber is uniformly dispersed in the film, so that the prepared TAC film has long-term, high efficiency and stable ultraviolet blocking ability.

[0024] (3) Under the synergistic effect of cellulose benzoate and UV absorber in the raw materials, there is a dual physical and chemical binding mechanism between the UV-resistant active component and the cellulose triacetate matrix, which makes it difficult for the UV-resistant active component to physically migrate and precipitate to the surface during the film processing, thus ensuring that the film has high light transmittance. Detailed Implementation

[0025] 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] Preparation of cellulose p-aldehyde benzoate: S1. Using DMSO as solvent, weigh DMSO and add it to the reactor. Weigh cellulose at 5% of the mass of DMSO. Then weigh 1,8-diazabicycloundec-7-ene at a mass ratio of 3.0:1 to cellulose. Add the prepared 1,8-diazabicycloundec-7-ene and cellulose to the reactor. Under a carbon dioxide atmosphere, maintain a pressure of 0.35-0.4 MPa and stir for 20 min. Then raise the temperature to 50℃ and maintain a pressure of 0.2 MPa for 3 h for activation.

[0028] S2. Transfer the activated solution obtained in step S1 to a flask, heat to 115℃, add methyl p-formylbenzoate, the mass ratio of methyl p-formylbenzoate to cellulose is 0.4:1, stir and react for 24h under carbon dioxide atmosphere, remove the solvent by rotary evaporation under reduced pressure after the reaction is completed, wash with deionized water and dry under vacuum to obtain cellulose p-aldehyde benzoate.

[0029] Preparation of ultraviolet absorbers: A1. Add 1,10-decanediamine to a flask and place it in an ice bath. Add phenylphosphine dichloride dropwise to 1,10-decanediamine at a molar ratio of 1:2. Under a nitrogen atmosphere, heat to 60°C and stir for 6 hours. After the reaction is complete, wash with water and dry to obtain the diamine derivative of phenylphosphine.

[0030] A2. Add DMF to a flask. Weigh 5% of 4-carboxybenzotriazole by mass of DMF and add it to the DMF. Then weigh the phenylphosphine diamine derivative according to a mass ratio of 3.0:1 to 4-carboxybenzotriazole and add it to the DMF. Stir to dissolve. Place the flask in an ice bath and add triethylamine dropwise while stirring. The molar ratio of triethylamine to 4-carboxybenzotriazole is 2.9:1. After stirring evenly, remove the ice bath and add EDC·HCl and DMAP. The molar ratio of 4-carboxybenzotriazole, EDC·HCl and DMAP is 1.0:1.1:0.2. Remove the ice bath and heat to 35℃. Stir and react for 12 hours. After the reaction is complete, remove the solvent by rotary evaporation and purify by chromatography to obtain the ultraviolet absorber.

[0031] Preparation of UV-resistant TAC thin films: Step 1: Prepare the raw materials according to the mass ratio, and mix 680 parts of dichloromethane and 90 parts of methanol to form a mixed solvent; Step 2: Add 100 parts of cellulose triacetate, 15 parts of cellulose p-aldehyde benzoate, 20 parts of diethyl phthalate and 2 parts of UV absorber to the mixed solvent, stir to dissolve and form a homogeneous solution. Step 3: The solution is cast into a film with a thickness of 200 μm. The film is first dried at 20°C and normal pressure for 2 h, and then dried under vacuum at 130°C for 0.5 h to obtain a UV-resistant TAC film.

[0032] Example 2

[0033] The only difference from Example 1 is that the mass ratio of methyl paraben to cellulose was adjusted to 0.2:1 when preparing cellulose paraben.

[0034] Preparation of cellulose p-aldehyde benzoate: S1. Using DMSO as solvent, weigh DMSO and add it to the reactor. Weigh cellulose at 5% of the mass of DMSO. Then weigh 1,8-diazabicycloundec-7-ene at a mass ratio of 3.0:1 to cellulose. Add the prepared 1,8-diazabicycloundec-7-ene and cellulose to the reactor. Under a carbon dioxide atmosphere, maintain a pressure of 0.35-0.4 MPa and stir for 20 min. Then raise the temperature to 50℃ and maintain a pressure of 0.2 MPa for 3 h for activation.

[0035] S2. Transfer the activated solution obtained in step S1 to a flask, heat to 115℃, add methyl p-formylbenzoate, the mass ratio of methyl p-formylbenzoate to cellulose is 0.2:1, stir and react for 24h under carbon dioxide atmosphere, remove the solvent by rotary evaporation under reduced pressure after the reaction is completed, wash with deionized water and dry under vacuum to obtain cellulose p-aldehyde benzoate.

[0036] Preparation of ultraviolet absorbers: A1. Add 1,10-decanediamine to a flask and place it in an ice bath. Add phenylphosphine dichloride dropwise to 1,10-decanediamine at a molar ratio of 1:2. Under a nitrogen atmosphere, heat to 60°C and stir for 6 hours. After the reaction is complete, wash with water and dry to obtain the diamine derivative of phenylphosphine.

[0037] A2. Add DMF to a flask. Weigh 5% of 4-carboxybenzotriazole by mass of DMF and add it to the DMF. Then weigh the phenylphosphine diamine derivative according to a mass ratio of 3.0:1 to 4-carboxybenzotriazole and add it to the DMF. Stir to dissolve. Place the flask in an ice bath and add triethylamine dropwise while stirring. The molar ratio of triethylamine to 4-carboxybenzotriazole is 2.9:1. After stirring evenly, remove the ice bath and add EDC·HCl and DMAP. The molar ratio of 4-carboxybenzotriazole, EDC·HCl and DMAP is 1.0:1.1:0.2. Remove the ice bath and heat to 35℃. Stir and react for 12 hours. After the reaction is complete, remove the solvent by rotary evaporation and purify by chromatography to obtain the ultraviolet absorber.

[0038] Preparation of UV-resistant TAC thin films: Step 1: Prepare the raw materials according to the mass ratio, and mix 680 parts of dichloromethane and 90 parts of methanol to form a mixed solvent; Step 2: Add 100 parts of cellulose triacetate, 15 parts of cellulose p-aldehyde benzoate, 20 parts of diethyl phthalate and 2 parts of UV absorber to the mixed solvent, stir to dissolve and form a homogeneous solution. Step 3: The solution is cast into a film with a thickness of 200 μm. The film is first dried at 20°C and normal pressure for 2 h, and then dried under vacuum at 130°C for 0.5 h to obtain a UV-resistant TAC film.

[0039] Example 3

[0040] The only difference from Example 1 is that the mass ratio of methyl paraben to cellulose was adjusted to 0.5:1 when preparing cellulose paraben.

[0041] Preparation of cellulose p-aldehyde benzoate: S1. Using DMSO as solvent, weigh DMSO and add it to the reactor. Weigh cellulose at 5% of the mass of DMSO. Then weigh 1,8-diazabicycloundec-7-ene at a mass ratio of 3.0:1 to cellulose. Add the prepared 1,8-diazabicycloundec-7-ene and cellulose to the reactor. Under a carbon dioxide atmosphere, maintain a pressure of 0.35-0.4 MPa and stir for 20 min. Then raise the temperature to 50℃ and maintain a pressure of 0.2 MPa for 3 h for activation.

[0042] S2. Transfer the activated solution obtained in step S1 to a flask, heat to 115℃, add methyl p-formylbenzoate, the mass ratio of methyl p-formylbenzoate to cellulose is 0.5:1, stir and react for 24h under carbon dioxide atmosphere, remove the solvent by rotary evaporation under reduced pressure after the reaction is completed, wash with deionized water and dry under vacuum to obtain cellulose p-aldehyde benzoate.

[0043] Preparation of ultraviolet absorbers: A1. Add 1,10-decanediamine to a flask and place it in an ice bath. Add phenylphosphine dichloride dropwise to 1,10-decanediamine at a molar ratio of 1:2. Under a nitrogen atmosphere, heat to 60°C and stir for 6 hours. After the reaction is complete, wash with water and dry to obtain the diamine derivative of phenylphosphine.

[0044] A2. Add DMF to a flask. Weigh 5% of 4-carboxybenzotriazole by mass of DMF and add it to the DMF. Then weigh the phenylphosphine diamine derivative according to a mass ratio of 3.0:1 to 4-carboxybenzotriazole and add it to the DMF. Stir to dissolve. Place the flask in an ice bath and add triethylamine dropwise while stirring. The molar ratio of triethylamine to 4-carboxybenzotriazole is 2.9:1. After stirring evenly, remove the ice bath and add EDC·HCl and DMAP. The molar ratio of 4-carboxybenzotriazole, EDC·HCl and DMAP is 1.0:1.1:0.2. Remove the ice bath and heat to 35℃. Stir and react for 12 hours. After the reaction is complete, remove the solvent by rotary evaporation and purify by chromatography to obtain the ultraviolet absorber.

[0045] Preparation of UV-resistant TAC thin films: Step 1: Prepare the raw materials according to the mass ratio, and mix 680 parts of dichloromethane and 90 parts of methanol to form a mixed solvent; Step 2: Add 100 parts of cellulose triacetate, 15 parts of cellulose p-aldehyde benzoate, 20 parts of diethyl phthalate and 2 parts of UV absorber to the mixed solvent, stir to dissolve and form a homogeneous solution. Step 3: The solution is cast into a film with a thickness of 200 μm, dried at 20°C and normal pressure for 2 h, and then vacuum dried at 130°C for 0.5 h to obtain a UV-resistant TAC film.

[0046] Example 4

[0047] The only difference from Example 1 is that the mass fraction of cellulose p-aldehyde benzoate in the raw materials is adjusted to 10 parts, while the other steps and conditions are the same as in Example 1.

[0048] Example 5

[0049] The only difference from Example 1 is that the mass fraction of cellulose p-aldehyde benzoate in the raw materials is adjusted to 20 parts, while the other steps and conditions are the same as in Example 1.

[0050] Example 6

[0051] The only difference from Example 1 is that the mass fraction of the ultraviolet absorber in the raw materials is adjusted to 1 part.

[0052] Example 7

[0053] The only difference from Example 1 is that the mass fraction of the ultraviolet absorber in the raw materials is adjusted to 3 parts.

[0054] Examples 8-9

[0055] The only difference from Example 1 is the ratio of raw materials. All other conditions and steps are the same as in Example 1. The specific ratios are shown in Table 1.

[0056] Table 1

[0057] Comparative Example 1

[0058] The only difference from Example 1 is that cellulose triacetate is used instead of cellulose p-aldehyde benzoate by mass.

[0059] Preparation of ultraviolet absorbers: A1. Add 1,10-decanediamine to a flask and place it in an ice bath. Add phenylphosphine dichloride dropwise to 1,10-decanediamine at a molar ratio of 1:2. Under a nitrogen atmosphere, heat to 60°C and stir for 6 hours. After the reaction is complete, wash with water and dry to obtain the diamine derivative of phenylphosphine.

[0060] A2. Add DMF to a flask. Weigh 5% of 4-carboxybenzotriazole by mass of DMF and add it to the DMF. Then weigh the phenylphosphine diamine derivative according to a mass ratio of 3.0:1 to 4-carboxybenzotriazole and add it to the DMF. Stir to dissolve. Place the flask in an ice bath and add triethylamine dropwise while stirring. The molar ratio of triethylamine to 4-carboxybenzotriazole is 2.9:1. After stirring evenly, remove the ice bath and add EDC·HCl and DMAP. The molar ratio of 4-carboxybenzotriazole, EDC·HCl and DMAP is 1.0:1.1:0.2. Remove the ice bath and heat to 35℃. Stir and react for 12 hours. After the reaction is complete, remove the solvent by rotary evaporation and purify by chromatography to obtain the ultraviolet absorber.

[0061] Preparation of UV-resistant TAC thin films: Step 1: Prepare the raw materials according to the mass ratio, and mix 680 parts of dichloromethane and 90 parts of methanol to form a mixed solvent; Step 2: Add 115 parts of cellulose triacetate, 20 parts of diethyl phthalate and 2 parts of UV absorber to the mixed solvent, stir to dissolve and form a homogeneous solution; Step 3: The solution is cast into a film with a thickness of 200 μm. The film is first dried at 20°C and normal pressure for 2 h, and then dried under vacuum at 130°C for 0.5 h to obtain a UV-resistant TAC film.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that UV-328 is used instead of the UV absorber in the raw materials.

[0064] Preparation of cellulose p-aldehyde benzoate: S1. Using DMSO as solvent, weigh DMSO and add it to the reactor. Weigh cellulose at 5% of the mass of DMSO. Then weigh 1,8-diazabicycloundec-7-ene at a mass ratio of 3.0:1 to cellulose. Add the prepared 1,8-diazabicycloundec-7-ene and cellulose to the reactor. Under a carbon dioxide atmosphere, maintain a pressure of 0.35-0.4 MPa and stir for 20 min. Then raise the temperature to 50℃ and maintain a pressure of 0.2 MPa for 3 h for activation.

[0065] S2. Transfer the activated solution obtained in step S1 to a flask, heat to 115℃, add methyl p-formylbenzoate, the mass ratio of methyl p-formylbenzoate to cellulose is 0.4:1, stir and react for 24h under carbon dioxide atmosphere, remove the solvent by rotary evaporation under reduced pressure after the reaction is completed, wash with deionized water and dry under vacuum to obtain cellulose p-aldehyde benzoate.

[0066] Preparation of UV-resistant TAC thin films: Step 1: Prepare the raw materials according to the mass ratio, and mix 680 parts of dichloromethane and 90 parts of methanol to form a mixed solvent; Step 2: Add 100 parts of cellulose triacetate, 15 parts of cellulose p-aldehyde benzoate, 20 parts of diethyl phthalate and 2 parts of UV-328 to the mixed solvent and stir to dissolve to form a homogeneous solution. Step 3: The solution is cast into a film with a thickness of 200 μm. The film is first dried at 20°C and normal pressure for 2 h, and then dried under vacuum at 130°C for 0.5 h to obtain a UV-resistant TAC film.

[0067] Comparative Example 3

[0068] The only difference from Example 1 is that methyl benzoate is used instead of methyl p-formylbenzoate when preparing cellulose p-aldehyde benzoate.

[0069] Preparation of cellulose p-aldehyde benzoate: S1. Using DMSO as solvent, weigh DMSO and add it to the reactor. Weigh cellulose at 5% of the mass of DMSO. Then weigh 1,8-diazabicycloundec-7-ene at a mass ratio of 3.0:1 to cellulose. Add the prepared 1,8-diazabicycloundec-7-ene and cellulose to the reactor. Under a carbon dioxide atmosphere, maintain a pressure of 0.35-0.4 MPa and stir for 20 min. Then raise the temperature to 50℃ and maintain a pressure of 0.2 MPa for 3 h for activation.

[0070] S2. Transfer the activated solution obtained in step S1 to a flask, heat to 115℃, add methyl benzoate, the mass ratio of methyl benzoate to cellulose is 0.4:1, stir and react for 24h under carbon dioxide atmosphere, remove the solvent by rotary evaporation under reduced pressure after the reaction is completed, wash with deionized water and dry under vacuum to obtain cellulose benzoate.

[0071] Preparation of ultraviolet absorbers: A1. Add 1,10-decanediamine to a flask and place it in an ice bath. Add phenylphosphine dichloride dropwise to 1,10-decanediamine at a molar ratio of 1:2. Under a nitrogen atmosphere, heat to 60°C and stir for 6 hours. After the reaction is complete, wash with water and dry to obtain the diamine derivative of phenylphosphine.

[0072] A2. Add DMF to a flask. Weigh 5% of 4-carboxybenzotriazole by mass of DMF and add it to the DMF. Then weigh the phenylphosphine diamine derivative according to a mass ratio of 3.0:1 to 4-carboxybenzotriazole and add it to the DMF. Stir to dissolve. Place the flask in an ice bath and add triethylamine dropwise while stirring. The molar ratio of triethylamine to 4-carboxybenzotriazole is 2.9:1. After stirring evenly, remove the ice bath and add EDC·HCl and DMAP. The molar ratio of 4-carboxybenzotriazole, EDC·HCl and DMAP is 1.0:1.1:0.2. Remove the ice bath and heat to 35℃. Stir and react for 12 hours. After the reaction is complete, remove the solvent by rotary evaporation and purify by chromatography to obtain the ultraviolet absorber.

[0073] Preparation of UV-resistant TAC thin films: Step 1: Prepare the raw materials according to the mass ratio, and mix 680 parts of dichloromethane and 90 parts of methanol to form a mixed solvent; Step 2: Add 100 parts of cellulose triacetate, 15 parts of cellulose benzoate, 20 parts of diethyl phthalate and 2 parts of UV absorber to the mixed solvent, stir to dissolve and form a homogeneous solution; Step 3: The solution is cast into a film with a thickness of 200 μm. The film is first dried at 20°C and normal pressure for 2 h, and then dried under vacuum at 130°C for 0.5 h to obtain a UV-resistant TAC film.

[0074] The performance of the TAC films prepared in Examples 1-9 and Comparative Examples 1-3 was tested, and the results are shown in Table 2.

[0075] The TAC films prepared in the examples and comparative examples were placed in a high temperature and high humidity (85°C, 85%RH) environment to test the UV transmittance at 380 nm.

[0076] The transmittance of the thin film was measured using an ultraviolet spectrophotometer, and the transmittance at 550 nm in the visible light band was selected as the test result.

[0077] Table 2

[0078] As shown in Table 2, when the degree of substitution of cellulose with aldehyde benzoate is high, the compatibility between the UV absorber and the matrix is ​​better due to the cross-linking effect of the aldehyde and amino groups. Example 1 shows better UV blocking performance and higher transmittance compared to Example 2. The mass fraction of UV absorber in the raw materials of Examples 1, 6, and 7 is different. With the increase of UV absorber, the UV transmittance gradually decreases, but excessive UV absorber will reduce the transmittance of the film. Combining the results of Example 1 and Comparative Example 1, it can be seen that under the synergistic effect of cellulose with aldehyde benzoate, the amount of UV absorber migrating and precipitating is small, and the effect of the UV absorber on improving the UV resistance of the film is enhanced. Through the synergistic effect of cellulose with aldehyde benzoate and UV absorber, the TAC film prepared in the embodiments of this invention has excellent UV resistance and high transmittance.

[0079] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0080] 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 UV-resistant TAC film, characterized in that, By weight, it includes the following raw materials: 100 parts of cellulose triacetate, 10-20 parts of cellulose p-aldehyde benzoate, 650-700 parts of solvent, 70-120 parts of cosolvent, 15-25 parts of plasticizer, and 1-3 parts of ultraviolet absorber; The cellulose p-formaldehyde benzoate is prepared by transesterification of cellulose with methyl p-formylbenzoate. The ultraviolet absorber is prepared by condensation reaction of 4-carboxybenzotriazole with a diamine derivative of phenylphosphine and one of its terminal amino groups.

2. The UV-resistant TAC film according to claim 1, characterized in that, The preparation steps of the cellulose p-aldehyde benzoate are as follows: S1. Add DMSO as a solvent to the reactor, then add 1,8-diazabicycloundec-7-ene and cellulose. Under a carbon dioxide atmosphere, maintain a pressure of 0.3-0.4 MPa, stir for 10-30 min, then raise the temperature to 50℃ and maintain a pressure of 0.2 MPa for 3-4 h to activate. S2. Add the activated solution to a flask, heat to 110-120℃, add methyl p-formylbenzoate, and stir the reaction under a carbon dioxide atmosphere for 12-24 hours. After the reaction is completed, remove the solvent by rotary evaporation under reduced pressure, wash with deionized water and dry under vacuum to obtain cellulose p-aldehyde benzoate.

3. The UV-resistant TAC film according to claim 2, characterized in that, The cellulose is 3-7% of the mass of DMSO.

4. The UV-resistant TAC film according to claim 2, characterized in that, The mass ratio of 1,8-diazabicycloundec-7-ene to cellulose is (2.5-3.5):

1.

5. The UV-resistant TAC film according to claim 2, characterized in that, The mass ratio of methyl paraformylbenzoate to cellulose is (0.2-0.5):

1.

6. The UV-resistant TAC film according to claim 1, characterized in that, The preparation steps of the ultraviolet absorber are as follows: A1. Under ice bath conditions, phenylphosphoryl dichloride was added dropwise to 1,10-decanediamine at a molar ratio of 1:

2. Under nitrogen atmosphere, the temperature was raised to 58-60℃ and the mixture was stirred for 6-8 hours. After the reaction was completed, the mixture was washed with water and dried to obtain the diamine derivative of phenylphosphoryl. A2. Add the diamine derivative of phenylphosphine and 4-carboxybenzotriazole to DMF, stir to dissolve, add triethylamine dropwise while stirring under ice bath conditions, stir evenly and then remove the ice bath, add EDC·HCl and DMAP, remove the ice bath, heat to 30-40℃ and stir to react for 8-12 h, after the reaction is completed, remove the solvent by rotary evaporation, and purify by chromatography to obtain the ultraviolet absorber.

7. The UV-resistant TAC film according to claim 6, characterized in that, The mass ratio of the phenylphosphine diamine derivative to 4-carboxybenzotriazole is (2.8-3.2):

1.

8. The UV-resistant TAC film according to claim 6, characterized in that, The molar ratio of triethylamine to 4-carboxybenzotriazole is (2.8-3.1):1; The molar ratio of 4-carboxybenzotriazole, EDC·HCl and DMAP is 1.0:(1.1-1.2):(0.1-0.3).

9. The UV-resistant TAC film according to claim 1, characterized in that, The solvent is at least one of dichloromethane and trichloromethane; The co-solvent is at least one of methanol, ethanol, and isopropanol; The plasticizer is at least one of diethyl phthalate and triacetin.

10. A method for preparing a UV-resistant TAC film, characterized in that, The preparation of the UV-resistant TAC film as described in any one of claims 1-9 includes the following steps: Step 1: Prepare the raw materials according to the proportions, and mix the solvent and co-solvent to form a mixed solvent; Step 2: Add cellulose triacetate, cellulose p-aldehyde benzoate, plasticizer and UV absorber to the mixed solvent and stir to dissolve and form a homogeneous solution; Step 3: After the solution is cast into a film, it is dried to obtain a UV-resistant TAC film.

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