A cellulose ester film and its preparation method and application

Abstract

The present invention belongs to the field of cellulose ester materials, and specifically relates to a cellulose ester film and a preparation method and application thereof. According to the physical and chemical properties of cellulose ester such as the degree of polymerization, the present invention selects a specific plasticizer compound to achieve good plasticizing efficiency, and specifically selects a hindered amine light stabilizer with excellent heat resistance and a number average molecular weight of not less than 1000g / mol, which has good compatibility with the system, ensures the mechanical properties of the cellulose ester film, and is not easy to precipitate from the cellulose ester film even in high temperature and high humidity application scenarios, has excellent anti-ultraviolet performance stability under high temperature and high humidity, and can meet the growing market demand for use in harsh environments.

Description

Technical Field

[0001] The present invention relates to the field of cellulose ester materials, in particular to the field of cellulose derivatives under IPC classification number C08L1 / 00, and more specifically to a cellulose ester film and a preparation method and application thereof. Background Art

[0002] Triacetyl cellulose film (TAC film) has excellent optical and physical properties. It is often used as a protective film for polarizers, the core component of liquid crystal displays (LCDs). It is compounded on both sides of the original PVA polarizing film and has the dual protective functions of increasing the strength of the PVA film and isolating external water vapor. It is the most basic key film material in the flat panel display industry chain.

[0003] With the rapid development of industrialization and intelligent industry, the use of liquid crystal display devices outdoors, such as mobile or in-car use, has increased, and the stability of TAC film under high temperature and high humidity conditions has become particularly important. Liquid crystal and polarizer are organic substances, which will undergo photochemical reactions and deteriorate under ultraviolet radiation. The anti-ultraviolet radiation performance of TAC film has a great influence on the service life of polarizer. Therefore, in order to extend the service life of liquid crystal molecules and polarizers, it is usually practiced to add a certain amount of ultraviolet absorber to TAC film to shield or absorb ultraviolet rays.

[0004] UV radiation during the application of TAC film mainly comes from solar radiation, which is a high-energy radiation with a wavelength between 100 and 400nm. In particular, UV-A (315-400nm) causes obvious damage to TAC film. With the widespread use of TAC film in the liquid crystal display industry, there are more stringent requirements for the application environment of TAC film. TAC film is required to have good anti-ultraviolet radiation stability under the conditions of temperature 85°C and humidity 85% (double 85). However, the existing TAC film has a serious attenuation of ultraviolet absorption performance under hot and humid conditions, which seriously affects the service life of the polarizer. Therefore, a TAC film with excellent anti-ultraviolet performance and excellent anti-ultraviolet performance stability under high temperature and high humidity conditions is currently a common market demand.

[0005] Prior art CN 104910424A discloses a cellulose triacetate film, which solves the problem of a large number of apparent crystal points in the cellulose triacetate film by selecting a cellulose triacetate raw material containing methanol, and achieves excellent optical properties. However, it does not improve the stability attenuation problem of its anti-ultraviolet performance under hot and humid conditions, and cannot meet the use requirements in harsh environments that have gradually increased in certain fields in recent years. Summary of the invention

[0006] In view of the defects of the prior art, the object of the present invention is to provide a cellulose ester film having excellent anti-ultraviolet performance and excellent anti-ultraviolet performance stability under high temperature and high humidity conditions.

[0007] On the other hand, the present invention also aims to provide a method for preparing the above-mentioned cellulose ester film with mild conditions, high production safety, simple process flow and stable product quality.

[0008] On the other hand, the present invention also aims to provide an application of the cellulose ester film or the cellulose ester film prepared by the above-mentioned cellulose ester film preparation process.

[0009] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0010] A cellulose ester film, wherein the raw materials for preparing the film include, by weight, 18 to 25 parts of C2 to C6 acid cellulose ester, 65 to 72 parts of mixed solvent, 5 to 15 parts of additives, and 0.001 to 12 parts of functional additives.

[0011] Preferably, the C2-C6 cellulose acid ester is selected from one or more of cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose dipropionate, cellulose butyrate, cellulose acetate propionate and cellulose acetate butyrate.

[0012] Preferably, the C2-C6 acid cellulose ester is a triacetate cellulose ester having a total degree of substitution DS2+DS3+DS6 of 2.68-2.96, a degree of polymerization of 280-300, and an acetification value of 30.6-61.4.

[0013] Preferably, the C2-C6 acid cellulose ester is selected from L20, L30, L40, L50, LT101, LT105, LT107 of Daicel Corporation, or Ca398-3, Ca398-6, Ca398-10, Ca398-30, Ca394-60S of Eastman Chemical Japan Co., Ltd.

[0014] Preferably, the C2-C6 acid cellulose ester can also be synthesized by a known method; more preferably, it is synthesized by the method disclosed in Japanese Patent JP Tokukaihei 10-45804.

[0015] Preferably, the mixed solvent is a mixed solution of a good solvent and a poor solvent for cellulose ester.

[0016] Preferably, the good solvent for cellulose ester includes one or more of acetone, dichloromethane and chloroform.

[0017] Preferably, the poor solvent for cellulose ester includes one or more of methanol, ethanol, propanol, n-butanol, and ethyl acetate.

[0018] Preferably, the mixed solvent is a mixture of dichloromethane, methanol and n-butanol;

[0019] Preferably, the volume ratio of dichloromethane to methanol in the mixed solution of dichloromethane, methanol and n-butanol is 80-90:10-15; more preferably, it is 87:13;

[0020] Preferably, the volume ratio of dichloromethane to n-butanol in the mixed solution of dichloromethane, methanol and n-butanol is 80-120:1; more preferably, it is 101:1.

[0021] Preferably, the additive comprises a plasticizer.

[0022] Preferably, the plasticizer is an ester plasticizer;

[0023] Preferably, the ester plasticizer includes one or more of ester, oligoester, and polyester plasticizer; further preferably, the molecular weight of the ester plasticizer is 100 to 10000;

[0024] Preferably, the plasticizer is a combination of TPP and BDP.

[0025] More preferably, the mass ratio of TPP to BDP is 1 to 3:1; more preferably, it is 2:1.

[0026] The ester plasticizer selected in the present invention is specifically selected according to the polymerization degree of the main material cellulose ester, and in particular, through the compounding of specific TPP and BDP plasticizers, it can achieve good plasticizing efficiency and good compatibility with the system, ensuring that the mechanical properties of the TAC film are good and stable. In order to increase the production rate, the present invention chooses to add a poor solvent for cellulose ester in the formula to assist in the peeling of the finished cellulose ester film, and in particular, adding a small amount of n-butanol with moderate volatility can slow down the volatilization of the solvent in the cellulose ester film, prevent the film from drying too fast to cause warping, crusting, shrinkage and other problems, improve the quality of the product, and ensure a proper drying speed of the film while increasing the moisture content of the cellulose ester film.

[0027] Preferably, the functional auxiliary agent includes an ultraviolet absorber and a light stabilizer.

[0028] Preferably, the weight percentage of the ultraviolet absorber in the raw material is 0.001-2%; more preferably, it is 0.1-2%;

[0029] Preferably, the weight percentage of the light stabilizer in the raw material is 0.001 to 10%; more preferably, it is 0.05 to 1%;

[0030] Preferably, the ultraviolet absorber is selected from benzotriazole, benzophenone, triazine, and alkylaminobutadiene ultraviolet absorbers;

[0031] Preferably, the ultraviolet absorber is a combination of two or more of UV326, UV928, and UV360;

[0032] Preferably, the ultraviolet absorber is UV326 and UV928.

[0033] Preferably, the light stabilizer is a hindered amine light stabilizer;

[0034] Preferably, the light stabilizer is selected from any one of the compounds represented by formula I to IV:

[0035]

[0036] wherein n is independently an integer from 1 to 200.

[0037] Preferably, the number average molecular weight of the light stabilizer is not less than 1000 g / mol.

[0038] Further preferably, the light stabilizer is selected from 2020, 944, 791, and 783 of BASF of Germany.

[0039] The present invention preferably selects hindered amine light stabilizers with excellent heat resistance of formula I to IV structures, which can withstand high temperature treatment of 280°C, have good compatibility with the cellulose ester system of the present invention, are not easy to precipitate under high temperature and high humidity conditions, and effectively reduce precipitation stripes, thereby maintaining stable anti-ultraviolet performance in high temperature and high humidity environments, expanding the application scenarios of cellulose ester film products. At the same time, the above-mentioned hindered amine light stabilizer selected by the present invention is a polymer with a number average molecular weight of not less than 1000g / mol, which is conducive to improving the stiffness and rigidity of the cellulose ester film of the present invention, further expanding the application field of cellulose ester film.

[0040] Preferably, the thickness of the cellulose ester film is 60-100 μm; more preferably, it is 80 μm.

[0041] The present invention also provides a method for preparing the above cellulose ester film, comprising the following steps:

[0042] S1: Weigh C2-C6 acid cellulose ester, mixed solvent, additives, and functional additives according to weight, and mix and stir them evenly in a container to obtain a preliminarily dissolved solution;

[0043] S2: heating and pressurizing the initially dissolved solution, and then cooling it to room temperature and pressure to continue dissolving, thereby obtaining a cellulose ester solution;

[0044] S3: The cellulose ester solution is transported at a controlled temperature, filtered 2 to 4 times in sequence, and then transported to a thermostat for standing and defoaming;

[0045] S4: conveying the defoamed cellulose ester solution to a casting nozzle, extruding and casting it onto a casting support to form a gel-like cellulose ester film; after the gel-like cellulose ester film is peeled off, it is sequentially stretched, dried, trimmed, and rolled up to obtain a cellulose ester film.

[0046] Preferably, the heating temperature in step S2 is 80-100° C., and the pressurizing pressure is 0.2-0.5 MPa.

[0047] Preferably, the mixing and stirring time in step S1 is 10 to 30 minutes;

[0048] Preferably, the heating and pressurizing time in step S2 is 20 to 30 minutes, and the time of cooling to room temperature and pressure and continuing to dissolve is 10 to 30 minutes.

[0049] Preferably, the temperature of the temperature-controlled transportation in step S3 is 31-37°C.

[0050] The present invention adopts a step-by-step dissolution method of pre-dissolution and heating and pressurizing dissolution, which promotes the uniform dispersion of cellulose ester and functional additives in the solvent, is conducive to the stability of product quality, further inhibits the precipitation of light stabilizer, and helps to improve the stability of the anti-ultraviolet performance of the product cellulose ester film. In addition, the present invention also controls the temperature of the cellulose ester solution during transportation, and a small temperature change can maintain the stability of the performance of the cellulose ester solution, so that the appearance performance of the prepared cellulose ester film product fluctuates little, the quality is stable, and it is more suitable for industrial production.

[0051] The present invention also provides an application of the cellulose ester film or the cellulose ester film prepared by the above-mentioned cellulose ester film preparation process; preferably, the application of the cellulose ester film to a polarizer.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The present invention specifically selects an ester plasticizer that is compatible with the polymerization degree of cellulose ester for compounding, which has high plasticizing efficiency and good system compatibility, ensuring that the mechanical properties of the TAC film are good and stable;

[0054] 2. The hindered amine light stabilizer selected in the present invention has good compatibility with the system, is resistant to high temperatures, is not easy to precipitate and lose its anti-ultraviolet performance in high temperature and high humidity scenes, has excellent anti-ultraviolet performance stability, and can adapt to harsh application scenes, especially high temperature and high humidity environments;

[0055] 3. The hindered amine light stabilizer selected in the present invention is an oligomer with a relatively high molecular weight, which is beneficial to improving the mechanical properties such as stiffness and rigidity of the cellulose ester film of the present invention;

[0056] 4. The present invention selects a compound of a good solvent and a poor solvent for cellulose ester, which is beneficial to the peeling of the finished cellulose ester film, and can also prevent the film from drying too quickly, resulting in warping, crusting, shrinkage and other problems, thereby improving the quality of the product, and while increasing the moisture content of the cellulose ester film, it can also ensure an appropriate drying speed of the film;

[0057] 5. The preparation method of the cellulose ester film adopted in the present invention has simple process, high safety, stable product quality, and is suitable for industrial production. DETAILED DESCRIPTION

[0058] Example 1

[0059] This embodiment provides a cellulose ester film, wherein the raw materials for preparing the film include, by weight, 18 parts of cellulose triacetate, 8.4 parts of a mixture of TPP and BDP plasticizers, 0.35 parts of UV326 ultraviolet absorber, 1.2 parts of UV928 ultraviolet absorber, 0.05 parts of hindered amine light stabilizer, and the mixed solvent makes up the balance to 100 parts;

[0060] The mixed solvent is a mixture of dichloromethane, methanol and n-butanol;

[0061] The volume ratio of dichloromethane to methanol is 87:13, and the volume ratio of dichloromethane to n-butanol is 101:1.

[0062] The mass ratio of TPP to BDP is 2:1;

[0063] The cellulose triacetate is Ca398-3 purchased from Eastman Chemical Japan Co., Ltd.;

[0064] The hindered amine light stabilizer has The structure of formula I is 2020 purchased from BASF, Germany.

[0065] This embodiment also provides a method for preparing the above-mentioned cellulose ester film, comprising the following steps:

[0066] S1: 18 parts of cellulose triacetate, 8.4 parts of a mixture of TPP and BDP plasticizers, 0.35 parts of UV326 ultraviolet absorber, 1.2 parts of UV928 ultraviolet absorber, and 0.05 parts of hindered amine light stabilizer of formula I are weighed, and the remaining amount is made up to 100 parts with a mixed solvent, and the above raw materials are mixed and stirred in a mixing kettle for 20 minutes to obtain a preliminarily dissolved solution;

[0067] S2: The preliminarily dissolved solution is heated to 80°C, pressurized to 0.5 MPa, stirred for 10 min, then cooled to room temperature (25°C) and continued to dissolve at normal pressure for 20 min to obtain a cellulose ester solution;

[0068] S3: The cellulose ester solution is transported at a temperature of 32±0.5°C, filtered three times in sequence, and then transported to a thermostat for static defoaming;

[0069] S4: The defoamed cellulose ester solution is transported to the casting nozzle, the casting thickness is set to a film thickness of 60 μm after drying, and the film is extruded and cast onto the casting support (stainless steel belt) to form a gel-like cellulose ester film; the gel-like cellulose ester film runs on the stainless steel belt for one circle and then is peeled off, enters the tentering machine for stretching and traction, and then enters the high-temperature drying zone for drying at 80°C, and is wound into a cellulose ester film after trimming and embossing through a winding device.

[0070] Example 2

[0071] This embodiment provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 20 parts, the amount of TPP and BDP plasticizer mixture added is 7.4 parts, the amount of UV326 added is 0.5 parts, UV928 is not added, and the amount of hindered amine light stabilizer added is 0.1 parts.

[0072] Example 3

[0073] This embodiment provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 22 parts, the amount of the TPP and BDP plasticizer mixture added is 8 parts, the amount of UV326 added is 0.3 parts, and the amount of the hindered amine light stabilizer added is 0.5 parts.

[0074] Example 4

[0075] This embodiment provides a cellulose ester film and a preparation method thereof, the implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 25 parts, the amount of TPP and BDP plasticizer mixture added is 8 parts, and the amount of hindered amine light stabilizer added is 0.45 parts. The cellulose triacetate was purchased from Sichuan Pushi Cellulose Acetate Co., Ltd.

[0076] Example 5

[0077] This embodiment provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 20 parts, the amount of TPP and BDP plasticizer mixture added is 7 parts, the amount of UV326 added is 0.5 parts, the amount of UV928 added is 1.5 parts, and the amount of hindered amine light stabilizer added is 1 part.

[0078] Example 6

[0079] This embodiment provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 20 parts, the amount of TPP and BDP plasticizer mixture added is 8 parts, the amount of UV326 added is 0.35 parts, the amount of UV928 added is 1.1 parts, and the amount of hindered amine light stabilizer added is 0.55 parts.

[0080] Example 7

[0081] This embodiment provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 20 parts, the amount of TPP and BDP plasticizer mixture added is 8 parts, the amount of UV326 added is 0.35 parts, the amount of UV928 added is 0.75 parts, and the amount of hindered amine light stabilizer added is 0.9 parts.

[0082] Comparative Example 1

[0083] This comparative example provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 20 parts, the amount of the TPP and BDP plasticizer mixture added is 7 parts, and no hindered amine light stabilizer is added.

[0084] Comparative Example 2

[0085] This comparative example provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 20 parts, the amount of the TPP and BDP plasticizer mixture added is 7 parts, the amount of UV326 added is 1 part, UV928 is not added, and the amount of hindered amine light stabilizer added is 1 part.

[0086] Comparative Example 3

[0087] This comparative example provides a cellulose ester film and a preparation method thereof. The implementation method is the same as that of Example 1, except that the amount of cellulose triacetate added is 20 parts, the amount of TPP and BDP plasticizer mixture added is 7 parts, the amount of UV360 added is 0.8 parts, UV326 and UV928 are not added, and the amount of hindered amine light stabilizer added is 1 part.

[0088] Performance Testing

[0089] (1) Mechanical strength evaluation: According to the method of GB / T 1040.2-2006, the cellulose ester films prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were tested for their mechanical strength (Young's modulus) using a universal material tensile testing machine (TA Company, USA, QJ212 series) at a tensile rate of 10 mm / s and a gauge length of 180 mm. The results are recorded in Table 1.

[0090] (2) Transparency and haze test: According to the method of GB / T2410-2008, the total light transmittance and haze of the cellulose ester films prepared in the above Examples 1 to 7 and Comparative Examples 1 to 3 were tested using a transmittance haze tester (WGT-S). The results are recorded in Table 1.

[0091] (3) Evaluation of ultraviolet absorption performance: The ultraviolet absorption performance of the cellulose ester films prepared in Examples 1 to 7 and Comparative Examples 1 to 3 was tested using an ultraviolet spectrophotometer (high energy blue light 1700) according to the method of HG / T3862-2006. The transmittance at 380 nm was taken as the transmittance after aging for 0 h (see Table 1).

[0092] (4) Evaluation of wet heat aging stability: The cellulose ester films prepared in the above Examples 1 to 7 and Comparative Examples 1 to 3 were placed in a double 85 (temperature 85°C, humidity 85%) aging test box (Zhuozhou Lantian Special Lighting Development Co., Ltd.) for aging for 1000 hours. After aging, the number of precipitation stripes on the surface of the cellulose ester film was observed and counted, and recorded in Table 1; the ultraviolet absorption performance of the cellulose ester film after aging for 1000 hours was tested, and the light transmittance at 380nm was recorded (see Table 1).

[0093] Table 1

[0094]

Claims

1. A cellulose ester film, characterized in that The raw materials for its preparation include 22 parts of cellulose triacetate, 8 parts of a mixture of TPP and BDP plasticizers, 0.3 parts of UV326 ultraviolet absorber, 1.2 parts of UV928 ultraviolet absorber, 0.5 parts of hindered amine light stabilizer, and the mixed solvent makes up the balance to 100 parts; The mixed solvent is a mixture of dichloromethane, methanol and n-butanol; The volume ratio of dichloromethane to methanol is 87:13, and the volume ratio of dichloromethane to n-butanol is 101:1; The mass ratio of TPP to BDP is 2:1; The cellulose triacetate is Ca398-3 purchased from Eastman Chemical Japan Co., Ltd.; The hindered amine light stabilizer has The structure of formula I is 2020 purchased from BASF, Germany.

2. A cellulose ester film, characterized in that The raw materials for its preparation include 25 parts of cellulose triacetate, 8 parts of a mixture of TPP and BDP plasticizers, 0.35 parts of UV326 ultraviolet absorber, 1.2 parts of UV928 ultraviolet absorber, 0.45 parts of hindered amine light stabilizer, and the mixed solvent makes up the balance to 100 parts; The mixed solvent is a mixture of dichloromethane, methanol and n-butanol; The volume ratio of dichloromethane to methanol is 87:13, and the volume ratio of dichloromethane to n-butanol is 101:1; The mass ratio of TPP to BDP is 2:1; The cellulose triacetate was purchased from Sichuan Pushi Cellulose Acetate Co., Ltd. The hindered amine light stabilizer has The structure of formula I is 2020 purchased from BASF, Germany.

3. A cellulose ester film, characterized in that The raw materials for its preparation include 20 parts of cellulose triacetate, 8 parts of a mixture of TPP and BDP plasticizers, 0.35 parts of UV326 ultraviolet absorber, 1.1 parts of UV928 ultraviolet absorber, 0.55 parts of hindered amine light stabilizer, and the mixed solvent makes up the balance to 100 parts; The mixed solvent is a mixture of dichloromethane, methanol and n-butanol; The volume ratio of dichloromethane to methanol is 87:13, and the volume ratio of dichloromethane to n-butanol is 101:1; The mass ratio of TPP to BDP is 2:1; The cellulose triacetate is Ca398-3 purchased from Eastman Chemical Japan Co., Ltd.; The hindered amine light stabilizer has The structure of formula I is 2020 purchased from BASF, Germany.

4. A method for preparing a cellulose ester film according to any one of claims 1 to 3, characterized in that: The steps include: S1: weighing cellulose triacetate, a mixed solvent, a mixture of TPP and BDP plasticizers, a UV326 ultraviolet absorber, a UV928 ultraviolet absorber and a hindered amine light stabilizer according to weight, mixing and stirring them in a container to obtain a preliminarily dissolved solution; S2: heating and pressurizing the initially dissolved solution, and then cooling it to room temperature and pressure to continue dissolving, thereby obtaining a cellulose ester solution; S3: The cellulose ester solution is transported at a controlled temperature, filtered 2 to 4 times in sequence, and then transported to a thermostat for static defoaming; S4: conveying the defoamed cellulose ester solution to a casting nozzle, extruding and casting it onto a casting support to form a gel-like cellulose ester film; after the gel-like cellulose ester film is peeled off, it is sequentially stretched, dried, trimmed, and rolled up to obtain a cellulose ester film.

5. Use of the cellulose ester film according to any one of claims 1 to 3 or the cellulose ester film prepared by the method for preparing a cellulose ester film according to claim 4, characterized in that: Used in polarizers.

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