Environmentally friendly polyester film and preparation method thereof

Abstract

This application discloses an environmentally friendly polyester film and a method for preparing the same. The film comprises the following components, by weight: 40-51 parts terephthalic acid, 10-13 parts ethylene glycol, 0.002-0.004 parts titanium-based catalyst, and 1-2 parts stabilizer. The titanium-based catalyst is obtained by growing zinc-aluminum hydrotalcite on the surface of an organic titanium complex. The resulting environmentally friendly polyester film exhibits bright color and excellent tensile strength. The film also requires minimal processing, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] The present application relates to the field of polyester films, and in particular to an environmentally friendly polyester film and a preparation method thereof. Background Art

[0002] Polyester film generally refers to PET film, which is widely used in daily necessities due to its excellent chemical corrosion resistance, pollution resistance and processing performance.

[0003] PET synthesis methods can be broadly categorized into three types: direct esterification polycondensation, transesterification polycondensation, and the ethylene oxide process. Regardless of which method is used, a catalyst must be added during the polyester polymerization stage. Antimony-based catalysts are widely used in PET production due to their low cost and excellent catalytic performance. However, since antimony-based catalysts are heavy metal pollutants, they can leach from the polyester material and enter the environment during polyester film processing or use, polluting the environment and indirectly endangering human health. Consequently, environmentally friendly titanium has emerged as a PET catalyst in place of antimony. However, titanium-based catalysts suffer from poor selectivity and are prone to side reactions during the catalytic process, which can cause yellowing of PET chips and compromise product quality. Summary of the Invention

[0004] In order to solve the problem of preparing polyester film in an environmentally friendly manner while maintaining good product quality, the present application provides an environmentally friendly polyester film and a preparation method thereof.

[0005] In a first aspect, an environmentally friendly polyester film comprises the following components in parts by weight:

[0006] 40-51 parts of terephthalic acid, 10-13 parts of ethylene glycol, 0.002-0.004 parts of a titanium catalyst and 1-2 parts of a stabilizer, wherein the titanium catalyst is obtained by growing zinc-aluminum hydrotalcite on an organic titanium complex.

[0007] By adopting the above technical solution, titanium-based catalysts are selected to replace traditional antimony-based catalysts. Titanium metal resources are abundant and have no impact on the environment and human health. In addition, titanium-based catalysts also have good catalytic activity. The titanium-based catalyst of the present application is obtained by growing zinc-aluminum hydrotalcite on the surface of an organic titanium complex. The catalytic activity of titanium is regulated in the form of an organic titanium complex, reducing the side reactions caused by excessive catalyst activity and improving the hue and gloss of the polyester material. In addition, during the reaction of the organic titanium complex, the organic titanium complex is prone to moisture absorption and hydrolysis, and hydrotalcite is grown on the surface of the organic titanium complex. The hydrotalcite can protect the organic titanium complex, reduce the failure of the catalyst hydrolysis, thereby reducing the occurrence of side reactions and reducing the degree of yellowing of the polyester film. Zinc-aluminum hydrotalcite is selected. Zinc-aluminum hydrotalcite and an organic titanium complex can form a crystal rod structure, thereby increasing the specific surface area of ​​the catalyst. Moreover, due to the geometric effect of metallic zinc and metallic aluminum, the dispersion of titanium in the system can be improved, thereby enhancing the catalytic effect. Zinc and aluminum have good stability and can synergistically improve the catalytic stability of the titanium-based catalyst, further reduce the occurrence of side reactions, and further improve the hue and gloss of the polyester material. Zinc-aluminum hydrotalcite also has certain antioxidant and light resistance. When used in combination with a stabilizer, it can improve the light resistance and antioxidant properties of polyester film, reduce yellowing of the polyester film, and improve its tensile properties.

[0008] Preferably, the organic titanium complex comprises the following components in parts by weight: 4-6 parts of zirconium nitrate, 14-22 parts of ethyl titanate, and 30-32 parts of trimesic acid.

[0009] By adopting the above technical solution, zirconium nitrate, ethyl titanate, and trimesic acid are used to form a zirconium and titanium bimetallic-organic framework. The metal-organic framework material has the advantages of high porosity, high specific surface area, and adjustable size. When titanium is selected as the main group element to form the metal-organic framework material, the aggregation of titanium metal ions can be reduced, thereby better exposing the catalytic sites on its surface and improving the catalytic effect. In addition, since the formed titanium metal-organic framework material has a molecular sieve effect, it can improve the contact between the substrate and the active sites of the catalyst, thereby improving the catalytic singleness of the catalyst. The titanium metal-organic framework material has a charge transfer effect and a matrix adsorption effect, which can improve the aggregation of the substrate on the active surface of the catalyst, improve the combination of the substrate and the catalytic center, and screen the corresponding substrate, thereby reducing the occurrence of side reactions, reducing the yellowing degree of the polyester film, and improving the tensile properties. Zirconium metal-organic framework materials, due to the strong affinity of zirconium atoms for oxygen, exhibit excellent hydrolysis resistance, thermal stability, and chemical stability. When zirconium metal is used as the ligand metal, the resulting titanium-zirconium bimetallic-organic framework not only has a large specific surface area and high catalytic activity, but also exhibits good hydrolysis resistance and thermal stability. Furthermore, the introduction of zirconium atoms can regulate the reversibility of the association / dissociation between titanium ions and ligands, thereby adjusting the catalytic activity of titanium ions, reducing side reactions and degradation reactions, reducing polyester yellowing, and improving tensile strength. Using trimesic acid as the organic framework, the resulting metal-organic framework has a porous structure that increases the number of active sites on the catalyst surface. Furthermore, the complexes formed by the carboxylic acid ligands with titanium and zirconium ions have good reversible association / dissociation, further reducing the degree of polyester yellowing.

[0010] Preferably, the organic titanium complex is prepared by the following steps:

[0011] Dissolve trimesic acid in ethanol, then add ethyl titanate and zirconium nitrate, stir for 3-4 hours, hydrothermally react at 130-150° C. for 24-30 hours, cool and dry to obtain an organic titanium complex.

[0012] By adopting the above technical solution, the preparation parameters of the organic titanium complex are optimized, so that the titanium-based catalyst has better catalytic selectivity and catalytic stability, and significantly improves the defects of the prepared polyester film such as yellowing and low tensile strength.

[0013] Preferably, the titanium-based catalyst comprises the following components in parts by weight: 0.4-1.2 parts of an organic titanium complex, 3-5 parts of zinc chloride, 0.5-1.5 parts of aluminum nitrate, 5-8 parts of sodium hydroxide, and 5-8 parts of sodium carbonate.

[0014] Typically, but not limiting, the sodium hydroxide and sodium carbonate are added in a 1:1 ratio.

[0015] By adopting the above technical solution and optimizing the component content of the titanium-based catalyst, the growth rate of zinc-aluminum hydrotalcite on the organic titanium complex can be significantly increased, and a three-dimensional structure that is beneficial to catalysis can be produced. The compatibility effect between the organic titanium complex and the zinc-aluminum hydrotalcite can also be improved, thereby improving the catalytic selectivity and catalytic stability of the titanium-based catalyst and improving the finished product quality of the polyester film.

[0016] Preferably, the raw material of the titanium-based catalyst further includes cerium nitrate, and the weight ratio of the cerium nitrate to zinc chloride is (0.5-0.8):1.

[0017] By adopting the above technical solution, the introduction of cerium atoms can change the structure of zinc-aluminum hydrotalcite, forming a ternary hydrotalcite composed of zinc, aluminum, and cerium. Due to the structural and performance differences between the three metal oxides, the ternary hydrotalcite can form a more complex hierarchical structure, further increasing the catalytic area after the hydrotalcite is grown on the organotitanium complex and improving catalytic stability. Furthermore, the cerium ions can also cooperate with the zinc and aluminum ions during the catalytic process, forming different coordination structures with the titanium ions, further regulating the catalytic activity and reducing the degree of yellowing of the polyester film. Furthermore, optimizing the incorporation level of cerium nitrate can improve the tensile strength of the polyester film while maintaining a high catalytic effect.

[0018] Preferably, the titanium-based catalyst is prepared by the following steps:

[0019] An organic titanium complex, aluminum nitrate, zinc chloride and cerium nitrate are mixed with water to obtain a mixed solution, sodium hydroxide and sodium carbonate are added to the mixed solution, and the mixture is taken out after hydrothermal reaction to obtain a titanium catalyst.

[0020] Typically, but not limiting, the temperature of the hydrothermal reaction is set between 120-140° C. and the reaction time is 20-28 h.

[0021] By adopting the above technical solution, the organic titanium complex is mixed with the raw materials of hydrotalcite, and then a hydrothermal reaction is carried out, so that the hydrotalcite microsheets can grow on the basis of the organic titanium complex, and then form a more complex three-dimensional hierarchical structure. During the catalytic process, the organic titanium complex can cooperate with the metal ions in the hydrotalcite between the hierarchical structures to form a highly efficient and specific catalyst, further improving the catalytic effect and stability.

[0022] Preferably, the raw material of the environmentally friendly polyester film further includes isosorbide, and the weight ratio of the isosorbide to ethylene glycol is (2-3): (10-13).

[0023] By adopting the above technical solution, isosorbide has good rigidity. Introducing isosorbide during the polymerization process can reduce the flexibility of the molecular chain, increase the glass transition temperature of the polyester film, and improve the thermal stability of the polyester film, thereby reducing the degree of polyester yellowing. In addition, isosorbide has the ability to reduce the crystallization of the copolyester, and synergistically improves the catalytic effect and catalytic stability during the polyester synthesis process with the catalyst. In the case of the catalyst of the present application using zinc-aluminum hydrotalcite grown on the surface of an organic titanium complex, the reaction degree of isosorbide in the system can also be increased, thereby further reducing the degree of polyester yellowing and improving the catalytic effect of the polyester.

[0024] In a second aspect, a method for preparing an environmentally friendly polyester film comprises the following steps:

[0025] Esterification: Mix terephthalic acid, ethylene glycol and / or isosorbide, add titanium catalyst and stabilizer, and react to obtain polyester esterification product;

[0026] Polycondensation: nitrogen is passed into the esterification product and the temperature is adjusted to carry out polycondensation reaction to obtain environmentally friendly polyester resin;

[0027] Film drawing: The environmentally friendly polyester resin is melted, extruded and cast to obtain a cast sheet, which is then subjected to longitudinal stretching, transverse stretching and heat setting treatment to obtain an environmentally friendly polyester film.

[0028] Typically, but not limiting, the reaction temperature in the esterification step is 240-260°C and the reaction time is 1-2 hours; the reaction temperature in the polycondensation step is 260-280°C and the reaction time is 100-140 minutes; in the film drawing step, the melting temperature is 260-280°C, the longitudinal stretching temperature is 100-120°C, the stretching ratio is 4-5 times; the TD stretching temperature is 110-130°C, the stretching ratio is 4-5 times, and the heat setting temperature is 200°C.

[0029] By adopting the above-mentioned technical solution, the polyester film preparation method of the present application has no special restrictions and can be prepared using conventional processes, which is suitable for industrial production. Moreover, when the titanium-based catalyst and stabilizer of the present application are used, the prepared polyester film is green and environmentally friendly, has bright color, and has good tensile properties.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. The product obtained by growing zinc-aluminum hydrotalcite with an organic titanium complex is used as a catalyst, which improves the pollution problem of toxic antimony catalysts used in traditional industries. In addition, the polyester film synthesized under this catalyst has bright color and good tensile properties. When conventional titanium catalysts are not used, the polyester film is prone to severe yellowing and easy breakage.

[0032] 2. On the basis of growing zinc-aluminum hydrotalcite, cerium atoms are introduced to form ternary hydrotalcite, which further changes the three-dimensional structure of the growing catalyst, improves the catalytic effect of the catalyst while controlling the catalytic performance of titanium ions, thereby reducing the yellowing phenomenon of polyester film while achieving high catalytic efficiency. DETAILED DESCRIPTION

[0033] The raw materials used in the examples and preparation examples are all commercially available and are described in detail below. The present application is further described in detail with reference to the examples.

[0034] Preparation of organic titanium complexes

[0035] Preparation Example 1-1, an organic titanium complex, is prepared by the following steps:

[0036] 31 g of trimesic acid was dissolved in 500 ml of anhydrous ethanol, and then 18 g of ethyl titanate and 5 g of zirconium nitrate were added. The mixture was stirred for 3.5 h, and hydrothermally reacted at 140° C. for 27 h. After natural cooling, the mixture was dried in an oven at 65° C. to obtain an organic titanium complex.

[0037] Preparation Example 1-2, an organic titanium complex, is prepared by the following steps:

[0038] 32 g of trimesic acid was dissolved in 500 ml of anhydrous ethanol, and then 22 g of ethyl titanate and 6 g of zirconium nitrate were added. The mixture was stirred for 4 h, and hydrothermally reacted at 150° C. for 24 h. After natural cooling, the mixture was dried in an oven at 65° C. to obtain an organic titanium complex.

[0039] Preparation Example 1-3, an organic titanium complex, is prepared by the following steps:

[0040] 30 g of trimesic acid was dissolved in 500 ml of anhydrous ethanol, and then 14 g of ethyl titanate and 4 g of zirconium nitrate were added. The mixture was stirred for 3 h, and hydrothermally reacted at 130° C. for 30 h. After natural cooling, the mixture was dried in an oven at 65° C. to obtain an organic titanium complex.

[0041] Preparation Example 1-4, an organic titanium complex, differs from Preparation Example 1-1 in that zirconium nitrate is replaced by an equal amount of ethyl titanate.

[0042] Preparation of titanium catalysts

[0043] Preparation Example 2-1, a titanium catalyst, is prepared by the following steps:

[0044] Take 0.8 g of organic titanium complex, 1 g of aluminum nitrate, 4 g of zinc chloride and 0.65 g of cerium nitrate, add 100 mL of ethanol solution (the volume ratio of ethanol to water is 1:1), mix, and stir evenly to obtain a mixed solution. Add 6.5 g of sodium hydroxide and 6.5 g of sodium carbonate to the mixed solution, mix, and hydrothermally react at 130°C for 24 hours. Then take out, wash and dry to obtain a titanium-based catalyst.

[0045] The organic titanium complex is derived from Preparation Example 1-1.

[0046] Preparation Example 2-2, a titanium catalyst, is prepared by the following steps:

[0047] 1 g of organic titanium complex, 1.5 g of aluminum nitrate, 5 g of zinc chloride and 0.8 g of cerium nitrate were added to 100 mL of ethanol solution (the volume ratio of ethanol to water was 1:1), stirred evenly to obtain a mixed solution, 8 g of sodium hydroxide and 5 g of sodium carbonate were added to the mixed solution, and the mixture was hydrothermally reacted at 120° C. for 28 h, then taken out, washed and dried to obtain a titanium-based catalyst.

[0048] The organic titanium complex is derived from Preparation Example 1-2.

[0049] Preparation Example 2-3, a titanium catalyst, is prepared by the following steps:

[0050] 0.6 g of organic titanium complex, 0.5 g of aluminum nitrate, 3 g of zinc chloride and 0.5 g of cerium nitrate were added to 100 mL of ethanol solution (the volume ratio of ethanol to water was 1:1), stirred evenly to obtain a mixed solution, 5 g of sodium hydroxide and 8 g of sodium carbonate were added to the mixed solution, and the mixture was hydrothermally reacted at 140° C. for 20 h, then taken out, washed and dried to obtain a titanium-based catalyst.

[0051] The organic titanium complex is derived from Preparation Example 1-3.

[0052] Preparation Example 2-4 is a titanium-based catalyst, which is different from Preparation Example 2-1 in that the organic titanium complex is derived from Preparation Example 1-4.

[0053] Preparation Example 2-5, a titanium-based catalyst, is different from Preparation Example 2-1 in that the amount of the organic titanium complex added is 1.2 g, that is, the weight portion of the organic titanium complex in the components is 1.2 parts.

[0054] Preparation Example 2-6, a titanium-based catalyst, is different from Preparation Example 2-1 in that the amount of the organic titanium complex added is 0.4 g, that is, the weight portion of the organic titanium complex in the components is 0.4 parts.

[0055] Preparation Example 2-7, a titanium-based catalyst, differs from Preparation Example 2-1 in that cerium nitrate is replaced by an equal amount of aluminum nitrate.

[0056] Preparation Example 2-8, a titanium-based catalyst, differs from Preparation Example 2-1 in that zinc chloride is replaced by an equal amount of ferric chloride.

[0057] Preparation Example 2-9, a titanium-based catalyst, differs from Preparation Example 2-1 in that aluminum nitrate is replaced by an equal amount of ferric chloride.

[0058] Preparation Example 2-10, a titanium-based catalyst, differs from Preparation Example 2-1 in that zinc chloride and aluminum nitrate are both replaced by equal amounts of ferric chloride. Example

[0059] Example 1, an environmentally friendly polyester film, is prepared by the following steps:

[0060] Esterification: 46 g of terephthalic acid, 11.5 g of ethylene glycol, and 2.5 g of isosorbide were mixed, 0.003 g of a titanium catalyst and 1.5 g of trimethyl phosphate were added, and the mixture was reacted at 250°C for 1.5 h to obtain the esterified product.

[0061] Polycondensation: nitrogen is passed through the esterification product, and the polycondensation reaction is carried out at 270°C for 120 minutes. After longitudinal stretching, transverse stretching, and heat setting treatment, an environmentally friendly polyester resin is obtained;

[0062] Film drawing: The environmentally friendly polyester resin is melted, extruded and cast to obtain a cast sheet, which is then subjected to longitudinal stretching, transverse stretching and heat setting treatment to obtain an environmentally friendly polyester film.

[0063] The titanium catalyst was derived from Preparation Example 2-1. In the film drawing step, the melt temperature was 270°C, the longitudinal stretching temperature was 110°C, the stretch ratio was 4.5 times, the TD stretching temperature was 120°C, the stretch ratio was 4.5 times, and the heat setting temperature was 200°C.

[0064] Example 2: An environmentally friendly polyester film is prepared by the following steps:

[0065] Esterification: Mix 51g of terephthalic acid, 13g of ethylene glycol and 3g of isosorbide, add 0.004g of titanium catalyst and 2g of trimethyl phosphate, and react at 240°C for 2h to obtain the esterified product;

[0066] Polycondensation: nitrogen is passed through the esterification product, and the polycondensation reaction is carried out at 280°C for 100 minutes. After longitudinal stretching, transverse stretching, and heat setting treatment, an environmentally friendly polyester resin is obtained;

[0067] Film drawing: The environmentally friendly polyester resin is melt-extruded and cast at 280°C to obtain a cast sheet, which is then subjected to longitudinal stretching, transverse stretching, and heat setting treatment to obtain an environmentally friendly polyester film.

[0068] The titanium catalyst was obtained from Preparation Example 2-2. The melting temperature was 280°C, the longitudinal stretching temperature was 120°C, the stretching ratio was 5 times, the TD stretching temperature was 130°C, the stretching ratio was 4 times, and the heat setting temperature was 200°C.

[0069] Example 3, an environmentally friendly polyester film, prepared by the following steps

[0070] Esterification: Mix 40g of terephthalic acid, 10g of ethylene glycol and 2g of isosorbide, add 0.002g of titanium catalyst and 1g of trimethyl phosphate, and react at 260℃ for 1h to obtain the esterified product;

[0071] Polycondensation: nitrogen is passed into the esterification product, and the polycondensation reaction is carried out at 260°C for 140 minutes. After longitudinal stretching, transverse stretching, and heat setting treatment, an environmentally friendly polyester film is obtained.

[0072] The titanium catalyst was obtained from Preparation Example 2-3. In the film drawing step, the melting temperature was 260°C, the longitudinal stretching temperature was 100°C, the stretching ratio was 4 times, the TD stretching temperature was 110°C, the stretching ratio was 5 times, and the heat setting temperature was 200°C.

[0073] Example 4 is an environmentally friendly polyester film, which is different from Example 1 in that the titanium-based catalyst is derived from Preparation Example 2-4.

[0074] Example 5, an environmentally friendly polyester film, is different from Example 1 in that the titanium-based catalyst is derived from Preparation Example 2-5.

[0075] Example 6, an environmentally friendly polyester film, is different from Example 1 in that the titanium-based catalyst is derived from Preparation Example 2-6.

[0076] Example 7, an environmentally friendly polyester film, is different from Example 1 in that the titanium-based catalyst is derived from Preparation Example 2-7.

[0077] Example 8 is an environmentally friendly polyester film, which differs from Example 1 in that isosorbide is replaced by an equal amount of ethylene glycol.

[0078] Comparative Example

[0079] Comparative Example 1 is an environmentally friendly polyester film, which differs from Example 1 in that the titanium-based catalyst is derived from Preparation Example 2-8.

[0080] Comparative Example 2 is an environmentally friendly polyester film, which differs from Example 1 in that the titanium-based catalyst is derived from Preparation Example 2-9.

[0081] Comparative Example 3 is an environmentally friendly polyester film, which differs from Example 1 in that the titanium-based catalyst is derived from Preparation Example 2-10.

[0082] Comparative Example 4 is an environmentally friendly polyester film. The difference from Example 1 is that the titanium-based catalyst directly uses the organic titanium complex prepared in Preparation Example 1-1 as the catalyst.

[0083] Comparative Example 5 is an environmentally friendly polyester film, which differs from Example 8 in that the titanium-based catalyst directly uses the organic titanium complex prepared in Preparation Example 1-1.

[0084] Comparative Example 6, a method for preparing a titanium composite catalyst for polyester synthesis, the specific preparation steps are as follows:

[0085] S1. Esterification reaction is carried out at 235° C. using a dicarboxylic acid or its derivative (diethyl terephthalate) and a diol (ethylene glycol). 6.5 ppm (calculated based on the equivalent amount of titanium in the catalyst) of a titanium composite catalyst is added before the esterification reaction. The esterification reaction pressure is 0.30 MPa and the esterification reaction time is 1.5 hours to obtain a prepolymer.

[0086] S2. The prepolymer is subjected to a polycondensation reaction under vacuum conditions at a temperature of 280° C., a pressure of 100 Pa, and a time of 2.5 h to obtain a polyester;

[0087] S3, film drawing: take the polyester melt and extrude the cast film to obtain the cast sheet, and then obtain the environmentally friendly polyester film through longitudinal stretching, transverse stretching and heat setting treatment.

[0088] Among them, in the film drawing step, the melting temperature is 270°C, the longitudinal stretching temperature is 110°C, the stretching ratio is 4.5 times; the TD stretching temperature is 120°C, the stretching ratio is 4.5 times, and the heat setting temperature is 200°C.

[0089] The titanium composite catalyst is prepared by the following steps:

[0090] (1) Preparation of titanium silicon catalyst precursor: first, silicon compound (tetrapropyl silicate), ethanol, distilled water and nitric acid are added to the reactor in a molar ratio of 1:1.5:0.5:0.05 and mixed; then, the mixed material is stirred at a speed of 600 r / min while being heated and refluxed at 60°C for 3 h; after the silicon compound is completely hydrolyzed, titanium compound (tetraisopropyl titanate) is added thereto, and the ratio of the added mass of the titanium compound to the mass of the silicon compound is 4.5:5.5, and mixed evenly; then, using a constant pressure burette, 30% of the molar amount of distilled water of the titanium compound is added dropwise at a dropping rate of 20 mL / min. After the addition is complete, the mixture is refluxed at 60°C for 5 h to prepare a titanium silicon catalyst precursor;

[0091] (2) Preparation of titanium-silicon composite catalyst: first, the titanium-silicon catalyst precursor obtained in step (1) is mixed evenly with a biomass carbon material with a lignin content of 22% in a mass ratio of 0.04:1; then, the mixed mixture is aged at room temperature, and after aging, it is dried in a forced air drying oven at 110°C for 18 hours to remove water and ethanol solvent in the reaction system; then, the dried mixture is placed in a muffle furnace, the firing temperature is set to 500°C, the heating rate is set to 10°C / min, and the mixture is fired in the muffle furnace for 4 hours; after the firing is completed, the fired material is taken out and allowed to cool naturally, and after wet grinding, the small-sized titanium-silicon catalyst powder is squeezed into the porous structure of the biomass carbon material under mechanical force, and finally a titanium-silicon composite catalyst with an average particle size of 280 nm is obtained;

[0092] The prepared titanium-silicon composite catalyst consists of a porous biochar and a titanium-silicon catalyst loaded in the porous structure; the average pore diameter of the porous biochar is 120 nm; the average particle size of the titanium-silicon catalyst in the titanium-silicon composite catalyst is 60 nm;

[0093] (3) Preparation of titanium composite catalyst for polyester synthesis: A titanium composite catalyst for polyester synthesis was prepared by mixing a titanium-silicon composite catalyst with a mass ratio of 1:0.1 and a phosphate ester (triphosphate ester).

[0094] Performance testing

[0095] The polyester films prepared in Examples 1-8 and Comparative Examples 1-6 were subjected to performance tests, and the tests were conducted 6 times in parallel to obtain the average value.

[0096] Test 1: Haze test: The test was conducted according to the method of GB / T2410 “Determination of light transmittance and haze of transparent plastics”. The results are shown in Table 1.

[0097] Test 2: Hue test: The sample was measured using a colorimeter and the corresponding b value was calculated. The results are shown in Table 1.

[0098] Test 3: Tensile strength test, refer to ASTM D-882 for measuring the tensile properties of plastic films and thin sheets.

[0099] Table 1: Test results of Examples 1-8 and Comparative Examples 1-6

[0100] Group Haze / % b-value Tensile strength / Mpa Example 1 0.5 -2.1 237 Example 2 0.6 -1.6 234 Example 3 0.6 -1.7 233 Example 4 1.2 -0.3 215 Example 5 1.7 0.2 217 Example 6 2 -1 231 Example 7 1.4 -0.8 229 Example 8 1.1 0 230 Comparative Example 1 2.1 2.9 226 Comparative Example 2 1.9 2.1 230 Comparative Example 3 3.9 3.1 220 Comparative Example 4 4.1 3.4 206 Comparative Example 5 4.4 3.6 192 Comparative Example 6 2 3 189

[0101] From Examples 1-4 and Table 1, it can be seen that when the titanium-based catalyst contains zirconium, the resulting polyester film has lower haze, better hue, and better tensile strength. The possible reason is that when preparing the organic titanium complex, zirconium is selected as a coordinating element, which can improve the catalytic stability of the organic titanium complex and also regulate the reversibility of the association / dissociation of titanium ions and ligands, thereby regulating the catalytic activity of titanium ions, reducing the occurrence of side reactions and degradation reactions, reducing yellowing of polyester, and improving tensile strength.

[0102] According to Example 1, Examples 5-7, Comparative Examples 1-4 and Combination 1, it can be seen that the hydrotalcites with different metal ions grown on the organic titanium complex have an impact on the hue and tensile strength of the polyester. The reason is that the ternary hydrotalcite formed by zinc ions, aluminum ions and cerium ions forms a certain hierarchical structure on the organic complex, which protects the organic titanium complex from hydrolysis failure while improving its catalytic stability; and the zinc ions, aluminum ions, cerium ions and titanium ions can also form different coordination structures with other atoms, regulating the catalytic activity of the titanium ions, reducing the yellowing degree of the polyester film, and reducing the degradation reaction during the polyester synthesis process, thereby reducing the b value of the polyester film and improving the tensile strength.

[0103] According to Example 1, Example 8, Comparative Example 5, and Table 1, it can be seen that the addition of isosorbide to the raw materials of the polyester film can increase the tensile strength of the polyester film and improve the hue of the polyester film to a certain extent. At the same time, the growth of zinc-aluminum hydrotalcite on the organic titanium complex can enhance the modification effect of isosorbide on the polyester film. This is because isosorbide can reduce the flexibility of the molecular chain, increase the glass transition temperature of the polyester film, and improve the thermal stability of the polyester film, thereby reducing the degree of yellowing of the polyester. In addition, isosorbide has the ability to reduce the crystallization of the copolyester and synergistically improves the catalytic effect and catalytic stability during the polyester synthesis process with the catalyst. Furthermore, the ligand structure containing zinc ions, aluminum ions, cerium ions, and titanium ions has higher catalytic activity for isosorbide, which can further enhance the modification effect of isosorbide on the polyester film.

[0104] According to Example 1, Comparative Example 6, and Table 1, the polyester film obtained by the technical solution of the present application exhibits improved hue and tensile strength. This is because the titanium-based catalyst of the present application is obtained by growing zinc-aluminum hydrotalcite on the surface of an organic titanium complex. The use of an organic titanium complex regulates the catalytic activity of titanium, reduces side reactions caused by excessive catalyst activity, and improves the hue and gloss of the polyester material. Furthermore, during the reaction of the organic titanium complex, the organic titanium complex readily absorbs moisture and hydrolyzes, which causes hydrotalcite to grow on the surface of the organic titanium complex. The hydrotalcite protects the organic titanium complex, reducing catalyst hydrolysis failure, thereby reducing side reactions and reducing the degree of yellowing of the polyester film. Zinc-aluminum hydrotalcite is selected. Zinc-aluminum hydrotalcite and organic titanium complex can form a crystal rod structure, which increases the specific surface area of ​​the catalyst. Due to the geometric effect of metallic zinc and metallic aluminum, the dispersion of titanium in the system can be improved, thereby improving the catalytic effect. Zinc and aluminum have good stability and can synergistically improve the catalytic stability of titanium-based catalysts, further reduce the occurrence of side reactions, and further improve the hue and gloss of polyester materials. Zinc-aluminum hydrotalcite also has certain antioxidant and light resistance. When used in combination with a stabilizer, it can improve the light resistance and antioxidant properties of polyester films and reduce yellowing and tensile properties of polyester films.

[0105] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A polyester film, characterized in that According to parts by weight, it includes the following components: 40-51 parts of terephthalic acid, 10-13 parts of ethylene glycol, 0.002-0.004 parts of a titanium catalyst, 1-2 parts of a stabilizer, and isosorbide; wherein the titanium catalyst is obtained by growing zinc-aluminum hydrotalcite on an organic titanium complex, and the weight ratio of isosorbide to ethylene glycol is (2-3):(10-13); The organic titanium complex comprises the following components, in parts by weight: 4-6 parts of zirconium nitrate, 14-22 parts of ethyl titanate, and 30-32 parts of trimesic acid, and is prepared by the following steps: dissolving the trimesic acid in ethanol, then adding the ethyl titanate and zirconium nitrate, stirring for 3-4 hours, hydrothermally reacting at 130-150° C. for 24-30 hours, cooling, and then drying to obtain the organic titanium complex; The components of the titanium-based catalyst include: 0.6-1 parts of an organic titanium complex, 3-5 parts of zinc chloride, 0.5-1.5 parts of aluminum nitrate, 5-8 parts of sodium hydroxide, 5-8 parts of sodium carbonate, and cerium nitrate, wherein the weight ratio of cerium nitrate to zinc chloride is (0.5-0.8):(3-5).

2. A polyester film according to claim 1, characterized in that: It is characterized by: The stabilizer is one of citric acid, hypophosphorous acid and trimethyl phosphate.

3. A polyester film according to claim 1, characterized in that: The titanium-based catalyst is prepared by the following steps: An organic titanium complex, aluminum nitrate, zinc chloride and cerium nitrate are mixed with ethanol to obtain a mixed solution, sodium hydroxide and sodium carbonate are added to the mixed solution, and the mixture is taken out after hydrothermal reaction to obtain a titanium catalyst.

4. The method for preparing a polyester film according to any one of claims 1 to 3, comprising the steps of: Esterification: Mix terephthalic acid, ethylene glycol and isosorbide, add titanium catalyst and stabilizer, and react to obtain polyester esterification product; Polycondensation: nitrogen is passed into the esterification product and the temperature is adjusted to carry out polycondensation reaction to obtain environmentally friendly polyester resin; Film drawing: The environmentally friendly polyester resin is melted, extruded and cast to obtain a cast sheet, which is then subjected to longitudinal stretching, transverse stretching and heat setting treatment to obtain an environmentally friendly polyester film.