A polyester material and its preparation method

Abstract

The present invention provides a polyester material and a preparation method thereof. The polyester material is obtained by polymerizing an aromatic dicarboxylic acid or an aromatic diester and an aliphatic diol. Among them, the aliphatic diol is a mixture of 1,4 - cyclohexanediol, 2,3 - butanediol, and C2 - C6 linear straight-chain alkanediols. The polyester material provided by the present invention is an amorphous polyester material with high transparency, high glass transition temperature, high molecular weight.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material synthesis, and more particularly to a polyester material and a preparation method thereof. Background Art

[0002] In recent years, as the fossil energy crisis has become increasingly serious, countries around the world have paid more and more attention to the development and utilization of biomass monomers. As a result, the types of bio-based materials are also developing rapidly, and the application of various bio-based materials is becoming more and more extensive, gradually replacing petroleum-based materials.

[0003] Bio-based materials are green and environmentally friendly materials. Some of their raw materials are renewable biomass raw materials, which effectively reduces the use of non-renewable fossil energy and greatly alleviates environmental pressure. This is in line with the current trend of sustainable development and is conducive to environmental protection.

[0004] Nowadays, there are more and more types of bio-based polymers, and bio-based polyester materials are one of them. Due to its good mechanical properties, molding and processing properties, and easy degradation characteristics, polyester materials have been widely used in many fields such as films, fibers, and plates. It is one of the most important and largest synthetic materials in the world. With the continuous development of polyester materials, the types of polyester are also constantly expanding to adapt to various application environments. Among the many polyester products, there are few products with both high glass transition temperature and high light transmittance characteristics, which is one of the shortcomings of the polyester family.

[0005] 2,3-Butanediol is an isomer of 1,4-butanediol. It is a diol with two asymmetric methyl groups on its branches. The asymmetric methyl group can inhibit the rotation of the polyester molecular chain, destroy the regular structure of the molecular chain, and has a strong inhibitory ability on the movement of the molecular chain segments, which is beneficial to increase the glass transition temperature and inhibit crystallization. For example, Chinese invention patent CN102093543A discloses a method for preparing poly(2,3-butylene terephthalate) and its copolyester, and selects dicarboxylic acid monomer or dimethyl ester monomer and 2,3-butanediol and other reactive monomers to prepare copolyester. The reaction is divided into three steps: first, an aromatic dibasic acid or an aromatic dibasic ester is reacted with a linear diol by esterification or transesterification to prepare a prepolymer 1, then an aromatic dibasic acid or an aromatic dibasic ester is reacted with 2,3-butanediol to prepare a prepolymer 2, and finally the two prepolymers are subjected to an transesterification reaction to prepare a product. This method adds linear diols and adopts a prepolymer reaction method, which alleviates the difficulty of 2,3-butanediol polymerization to a certain extent. However, the polymerization method is cumbersome and requires the synthesis of two prepolymers separately, which has poor continuity. In addition, it is impossible to balance the molecular weight and glass transition temperature by using only linear diols, which is a loss of one thing while gaining another.

[0006] Chinese invention patent CN103159907A discloses a high molecular weight polyester plastic based on 2,3-butanediol and its preparation method. This patent uses aromatic dicarboxylic acids or aromatic diesters and 2,3-butanediol, supplemented by one or several of aliphatic dicarboxylic acids, aliphatic diols, and alicyclic diols to prepare 2,3-butanediol-based ester plastics. The polyester obtained by esterification and transesterification in this patent has a very low weight average molecular weight, only reaching below 5000. It is necessary to continue the reaction in a twin-screw extruder with an isocyanate as a chain extender to obtain a product with a certain molecular weight. The steps are also cumbersome. Moreover, the temperature in the transesterification stage is as high as 240-280°C. As is well known, long-term high temperature in the polyester reaction will inevitably be accompanied by intense side reactions, and the yellowing of the product is inevitable, affecting the aesthetics and light transmittance of the product.

[0007] In summary, 2,3-butanediol is an excellent bio-based monomer for preparing polyester materials with high glass transition temperature and high transparency, which helps to alleviate the problem of energy depletion faced today and helps to make up for the deficiencies of polyester materials in the field of high-Tg transparent materials. However, since both hydroxyl groups of 2,3-butanediol are secondary hydroxyl groups, the reaction activity is low. At the same time, the asymmetric methyl groups increase the steric hindrance, making its polymerization difficult and it is very difficult to obtain a high molecular weight polyester, which limits its development. Summary of the Invention

[0008] To solve the above problems, the present invention provides a polyester material and its preparation method. The polyester material provided by the present invention is an amorphous polyester material with high transparency, high glass transition temperature, and high molecular weight, further enriching and optimizing the types of polyester products.

[0009] First, one of the purposes of the present invention is to provide a polyester material.

[0010] Specifically, the polyester material is obtained by polymerizing aromatic dicarboxylic acids or aromatic diesters and aliphatic diols, and its structural general formula is:

[0011]

[0012] Among them,

[0013] R1 is one or a combination of aromatic rings, preferably one or a combination of ; and / or,

[0014] R2 is one or a combination of C2-C6 linear straight-chain alkanediols, preferably one or a combination of C4-C6 linear straight-chain alkanediols;

[0015] x is 0.30 to 0.80 in mole fraction, preferably 0.35 to 0.65 in mole fraction; y is 0.08 to 0.40 in mole fraction, preferably 0.15 to 0.30 in mole fraction; z is 0 to 0.40 in mole fraction, preferably 0.10 to 0.35 in mole fraction.

[0016] The second object of the present invention is to provide a preparation method of the polyester material for the first object.

[0017] It includes the following steps:

[0018] After fully mixing an aromatic dicarboxylic acid or an aromatic diester, an aliphatic diol, a catalyst, and an antioxidant, first carry out a transesterification reaction to obtain a prepolymer, and then carry out a polycondensation reaction to prepare the polyester material.

[0019] Specifically, the preparation method includes the following steps:

[0020] S1. Transesterification reaction

[0021] Add an aromatic dicarboxylic acid or an aromatic diester, an aliphatic diol, a catalyst, and an antioxidant into a reaction kettle and mix them fully. Under the condition of a protective gas, the reaction system is slowly heated to 180 - 220°C within 2 - 4 h, preferably 200 - 220°C, and maintained at this temperature for 2 - 6 h. The slow heating process can also effectively prevent a large amount of evaporation and discharge of glycol monomers under high temperature conditions.

[0022] It is worth mentioning that, based on the traditional condensation device, a Vigreux column is additionally installed in this device. Its function is to control the temperature of the Vigreux column so that glycol monomers can flow back into the reaction kettle to continue participating in the reaction, while the small molecules generated by the reaction are discharged out of the reaction kettle, so that the reaction temperature can be raised above the boiling point of the monomers and the monomer loss can be effectively reduced.

[0023] Further, the molar ratio of the amount of the aromatic dicarboxylic acid or the aromatic diester to the amount of the aliphatic diol is 1:1.2 to 1:2, preferably 1:1.4 to 1:1.8.

[0024] Further, the amount of the catalyst is 0.05 - 1.0% of the total mass of the aromatic dicarboxylic acid or the aromatic diester and the aliphatic diol; preferably 0.2 - 0.6%.

[0025] Further, the amount of the antioxidant is 0.01 - 0.2% of the total mass of the aromatic dicarboxylic acid or the aromatic diester and the aliphatic diol; more preferably 0.01 - 0.1%.

[0026] Preferably, in a preferred embodiment of the present invention, the aromatic dicarboxylic acid or the aromatic diester is one or a combination of terephthalic acid, isophthalic acid, phthalic acid, and dimethyl terephthalate.

[0027] Preferably, in a preferred embodiment of the present invention, the aliphatic diol is a mixture of 1,4 - cyclohexanediol, 2,3 - butanediol, and C2 - C6 linear straight - chain alkanediols. Among them, in the aliphatic diol, 1,4 - cyclohexanediol accounts for 8 - 40% of the total molar ratio of the aliphatic diol, 2,3 - butanediol accounts for 30 - 80% of the total molar ratio of the aliphatic diol, and the straight - chain alkanediol accounts for 0 - 40% of the total molar ratio of the aliphatic diol.

[0028] Preferably, in a preferred embodiment of the present invention, the C2 - C6 linear straight - chain alkanediol is one or a combination of ethylene glycol, 1,3 - propanediol, 1,4 - butanediol, 1,5 - pentanediol, and 1,6 - hexanediol.

[0029] Preferably, in a preferred embodiment of the present invention, the catalyst is one or a combination of selenium dioxide, antimony trioxide, antimony glycolate, p - toluenesulfonic acid, acetate, alkylaluminum with 1 - 12 carbon atoms, organotin compounds, and titanates; preferably stannous octoate.

[0030] Preferably, in a preferred embodiment of the present invention, the antioxidant is one or a combination of phosphoric acid, phosphorous acid, phosphate esters, phosphite esters, and phenyl phosphate.

[0031] S2. Polycondensation reaction

[0032] First, raise the temperature of the reaction system to 200 - 240 °C, preferably 210 - 230 °C, and pre - polycondense for 1 - 4 h under 3 - 10 kPa; then evacuate the reaction system to below 500 Pa and carry out final polycondensation for 2 - 12 h to complete the reaction. Among them, the polycondensation reaction temperature can not only ensure a considerable reaction rate of the reaction system but also prevent a large number of thermal degradation reactions in the system.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The present invention uses bio - based 2,3 - butanediol and bio - based straight - chain diol as raw materials to prepare polyester materials, alleviating the problem of the impending depletion of petrochemical energy.

[0035] 2. The present invention optimizes the reaction process, adds a Vigreux column and improves the reaction temperature, effectively improving the reaction efficiency, suppressing the yellowing phenomenon, and significantly enhancing the molecular weight and aesthetics of the material.

[0036] 3. By simultaneously introducing 1,4 - cyclohexanediol and straight - chain diol into the polyester material, the present invention successfully prepares a polyester material with 2,3 - butanediol, solves the problem of difficult polymerization of 2,3 - butanediol, balances the relationship between the molecular weight and the glass transition temperature, and obtains a polyester material with both a relatively high molecular weight and a high Tg, enriching and optimizing the types of polyester materials.

[0037] 4. The present invention prepares polyester materials by replacing part of 2,3-butanediol with 1,4-cyclohexanediol, utilizing the higher reactivity of 1,4-cyclohexanediol than 2,3-butanediol, and further improving the glass transition temperature and appearance.

[0038] 5. The polyester material prepared by the present invention through aromatic dibasic acid or dibasic ester, 2,3-butanediol, 1,4-cyclohexanediol and linear diol has a high glass transition temperature and a high upper limit of use temperature, which is sufficient to meet most of the medium and high temperature use requirements in daily life and has broad application prospects.

[0039] 6. The polyester material obtained by the present invention is an amorphous material with good light transmittance and low haze, no obvious yellowing, and good aesthetics. This polyester material can be used in transparent packaging and other fields with high requirements on transparency and operating temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the NMR spectrum of the polyester material prepared in the preferred embodiment 1 of the present invention; DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention still fall within the scope of protection of the present invention.

[0042] The raw materials and reagents used in the following examples are all commercially available products.

[0043] Example 1

[0044] Dimethyl terephthalate, 2,3-butanediol, 1,4-cyclohexanediol and ethylene glycol were added to a reactor, wherein the molar ratio of dimethyl terephthalate to glycol was 1:1.2, and the molar ratio of the three glycols was 0.35:0.3:0.35. Stannous octoate (0.3% of the total mass) and triphenyl phosphite (0.03% of the total mass) were added to a reactor with a reflux condenser and fully mixed under a nitrogen atmosphere.

[0045] The system was slowly heated to 200°C within 2 hours, maintained at normal pressure, reacted at 200°C for 4 hours, and methanol was discharged; then the system was heated to 220°C, the air pressure was reduced to 5 kPa, and prepolymerization was continued for 2 hours. Finally, the system was continuously evacuated to vacuum, and condensation was continued until the reaction was completed. The structure of the obtained polyester material is as follows, wherein x=0.35, y=0.30, and z=0.35.

[0046]

[0047] Figure 1 The NMR spectrum of the polyester material prepared in this example is shown in the figure. It can be seen from the figure that the absorption peak at 5.39 ppm (d, d`) corresponds to the -O-CH(CH3)- in different chiral 2,3-BDO in the molecular chain. The absorption peak at 1.44 ppm (c, i, i`) corresponds to the -CH3 characteristic absorption peak of different chiral 2,3-BDO structural units in the molecular chain and at the molecular chain end. The absorption peaks at 3.92 ppm and 4.03 ppm (h, h`) correspond to the HO-CH(CH3)- in 2,3-BDO at the chain end. The characteristic absorption peaks at 4.52 ppm and 4.57 ppm (g, g`) correspond to the HO-CH(CH3)-CH(CH3)- in 2,3-BDO at the chain end. The absorption peak at 8.05 ppm (a) corresponds to the characteristic absorption peak on the benzene ring (CH). The absorption peak at 4.69 ppm (b) corresponds to the characteristic absorption peak of -O-CH2-CH2-O- in EG. The absorption peak at 5.18 ppm (e) corresponds to the -O-CH- in 1,4-CHD monomer. The absorption peak at 2.17 ppm to 1.80 ppm (f) corresponds to the -CH2- on the six-membered ring.

[0048] Example 2

[0049] Dimethyl terephthalate, 2,3-butanediol, 1,4-cyclohexanediol, and ethylene glycol were added to a reaction kettle. The molar ratio of dimethyl terephthalate to diols was 1:1.5, and the molar ratio of the three diols was 0.65:0.08:0.27. Stannous octoate (0.05% of the total mass) and phosphorous acid (0.1% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0050] The system was slowly heated to 180°C within 2 h, maintained at normal pressure, and reacted at 180°C for 3 h to discharge methanol. Then the system was heated to 200°C, the pressure was reduced to 5 kPa, and pre-polymerization was continued for 2 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The structure of the obtained polyester material is as follows, where x = 0.65, y = 0.08, and z = 0.27.

[0051]

[0052] Example 3

[0053] Add terephthalic acid, 2,3-butanediol, 1,4-cyclohexanediol, and 1,4-butanediol into the reaction kettle. The molar ratio of dimethyl terephthalate to diol is 1:1.5, and the molar ratio of the three diols is 0.5:0.2:0.3. Add tetrabutyl titanate (1.0% of the total mass) and triethyl phosphate (0.2% of the total mass) into the reaction kettle equipped with a reflux condenser, and mix well under a nitrogen atmosphere.

[0054] Slowly heat the system to 200 °C within 2 h, keep the normal pressure, react at 200 °C for 4 h, and discharge methanol; then heat the system to 220 °C, reduce the pressure to 5 kPa, and continue pre-polymerization for 3 h. Finally, continuously evacuate the system to vacuum and continue polycondensation until the reaction ends. The structure of the obtained polyester material is as follows, where x = 0.5, y = 0.2, and z = 0.3.

[0055]

[0056] Example 4

[0057] Add phthalic acid, dimethyl terephthalate, 2,3-butanediol, 1,4-cyclohexanediol, and 1,6-hexanediol into the reaction kettle. The molar ratio of phthalic acid, dimethyl terephthalate to diol is 1:1.5 (where the molar ratio of phthalic acid to dimethyl terephthalate is 1:2), and the molar ratio of the three diols is 0.65:0.3:0.05. Add antimony trioxide (1.0% of the total mass) and trimethyl phosphite (0.1% of the total mass) into the reaction kettle equipped with a reflux condenser, and mix well under a nitrogen atmosphere.

[0058] Slowly heat the system to 220 °C within 2 h, keep the normal pressure, react at 220 °C for 3 h, and discharge methanol; then heat the system to 240 °C, reduce the pressure to 5 kPa, and continue pre-polymerization for 4 h. Finally, continuously evacuate the system to vacuum and continue polycondensation until the reaction ends. The structure of the obtained polyester material is as follows, where x = 0.65, y = 0.3, z = 0.05, and R is = 1:2.

[0059]

[0060] Example 5

[0061] Add isophthalic acid, 2,3-butanediol, 1,4-cyclohexanediol, and 1,5-pentanediol into the reaction kettle. The molar ratio of isophthalic acid to diol is 1:1.7, and the molar ratio of the three diols is 0.55:0.3:0.15. Add antimony glycolate (0.6% of the total mass) and triphenyl phosphite (0.2% of the total mass) into the reaction kettle equipped with a reflux condenser, and mix well under a nitrogen atmosphere.

[0062] The system was slowly heated to 220 °C within 2 h, kept at normal pressure, reacted at 220 °C for 4 h, and methanol was discharged; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre-polymerization was continued for 4 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The structure of the obtained polyester material is as follows, where x = 0.55, y = 0.3, and z = 0.15.

[0063]

[0064] Example 6

[0065] Terephthalic acid, dimethyl terephthalate, 2,3-butanediol, 1,4-cyclohexanediol, and 1,4-butanediol were added to a reaction kettle. The molar ratio of terephthalic acid, dimethyl terephthalate to diol was 1:1.5 (where the molar ratio of terephthalic acid to dimethyl terephthalate was 1:1), and the molar ratio of the three diols was 0.35:0.3:0.35. Stannous octoate (0.3% of the total mass) and triphenyl phosphite (0.1% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0066] The system was slowly heated to 200 °C within 2 h, kept at normal pressure, reacted at 200 °C for 3 h, and methanol was discharged; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre-polymerization was continued for 2 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The structure of the obtained polyester material is as follows, where x = 0.35, y = 0.3, and z = 0.35.

[0067]

[0068] Example 7

[0069] Terephthalic acid, 2,3-butanediol, 1,4-cyclohexanediol, and 1,4-butanediol were added to a reaction kettle. The molar ratio of terephthalic acid to diol was 1:1.7, and the molar ratio of the three diols was 0.42:0.28:0.3. Tetraethyl titanate (0.5% of the total mass) and trimethyl phosphite (0.1% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0070] The system was slowly heated to 210 °C within 2 h, kept at normal pressure, reacted at 210 °C for 3 h, and methanol was discharged; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre-polymerization was continued for 2 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The structure of the obtained polyester material is as follows, where x = 0.42, y = 0.28, and z = 0.3.

[0071]

[0072] Example 8

[0073] Dimethyl terephthalate, 2,3 - butanediol, 1,4 - cyclohexanediol, and ethylene glycol were added to a reaction kettle. The molar ratio of dimethyl terephthalate to diols was 1:2, and the molar ratio of the three diols was 0.42:0.28:0.3. Selenium dioxide (0.05% of the total mass) and trimethyl phosphite (0.1% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0074] The system was slowly heated to 200 °C within 2 h, kept at atmospheric pressure, and reacted at 200 °C for 2 h to discharge methanol; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre - polymerization was continued for 2 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The obtained polyester material had the following structure, where x = 0.42, y = 0.28, and z = 0.3.

[0075]

[0076] Example 9

[0077] Dimethyl terephthalate, 2,3 - butanediol, and 1,4 - cyclohexanediol were added to a reaction kettle. The molar ratio of dimethyl terephthalate to diols was 1:1.5, and the molar ratio of the two diols was 0.7:0.3. Stannous octoate (0.3% of the total mass) and triphenyl phosphite (0.03% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0078] The system was slowly heated to 200 °C within 2 h, kept at atmospheric pressure, and reacted at 200 °C for 3 h to discharge methanol; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre - polymerization was continued for 4 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The obtained polyester material had the following structure, where x = 0.7 and y = 0.3.

[0079]

[0080] Comparative Example 1

[0081] Dimethyl terephthalate, 2,3 - butanediol, and ethylene glycol were added to a reaction kettle. The molar ratio of dimethyl terephthalate to diols was 1:1.5, and the molar ratio of the two diols was 0.5:0.5. Stannous octoate (0.3% of the total mass) and triphenyl phosphite (0.03% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0082] The system was slowly heated to 200 °C within 2 h, kept at atmospheric pressure, reacted at 200 °C for 2 h, and methanol was discharged; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre-polymerization was continued for 2 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The structure of the obtained polyester material is as follows, where x = 0.5 and z = 0.5.

[0083]

[0084] Comparative Example 2

[0085] Dimethyl terephthalate, 1,4-cyclohexanediol, and ethylene glycol were added to a reaction kettle, where the molar ratio of dimethyl terephthalate to diol was 1:1.5, and the molar ratio of the two diols was 0.5:0.5. Stannous octoate (0.3% of the total mass) and triphenyl phosphite (0.03% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0086] The system was slowly heated to 200 °C within 2 h, kept at atmospheric pressure, reacted at 200 °C for 2 h, and methanol was discharged; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre-polymerization was continued for 2 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The structure of the obtained polyester material is as follows, where y = 0.5 and z = 0.5

[0087]

[0088] Comparative Example 3

[0089] Dimethyl terephthalate, 2,3-butanediol, 1,4-cyclohexanediol, and ethylene glycol were added to a reaction kettle, where the molar ratio of dimethyl terephthalate to diol was 1:1.5, and the molar ratio of the three diols was 0.2:0.2:0.6. Stannous octoate (0.3% of the total mass) and triphenyl phosphite (0.02% of the total mass) were added to the reaction kettle equipped with a reflux condenser and mixed thoroughly under a nitrogen atmosphere.

[0090] The system was slowly heated to 200 °C within 2 h, kept at atmospheric pressure, reacted at 200 °C for 4 h, and methanol was discharged; then the system was heated to 220 °C, the pressure was reduced to 5 kPa, and pre-polymerization was continued for 2 h. Finally, the system was continuously evacuated to vacuum and polycondensation was continued until the reaction ended. The structure of the obtained polyester material is as follows, where x = 0.2, y = 0.2, and z = 0.6.

[0091]

[0092] Comparative Example 4

[0093] This comparative example follows the preparation method and formulation provided in Chinese Patent CN 103159907A. 46.6 g of dimethyl terephthalate, 32.4 g of 2,3-butanediol, 41.8 g of 1,4-cyclohexanediol, and 0.12 g of tetrabutyl titanate were added to a three-necked flask, and the reaction was carried out under a nitrogen atmosphere. The mixture was heated to 220 °C, and after the reactants formed a homogeneous system, the reaction temperature was controlled at 220 °C for 3 h. During this process, water was distilled out as a by-product from the reaction mixture until the amount of distillate reached 92% of the theoretically calculated amount. 0.12 g of antimony trioxide and 0.10 g of trimethyl phosphate were added to the reaction mixture as a polycondensation catalyst (i.e., the second catalyst) and a heat stabilizer, respectively. The polymerization reaction was carried out at a temperature of 250 °C, the vacuum was pumped to less than 500 Pa, and stirring was continued for 3 h before stopping the reaction. The resulting polyester material had the following structure, where x = 0.5 and y = 0.5.

[0094]

[0095] Table 1 is used to illustrate the properties of the polyester materials prepared in Examples 1-9 and Comparative Examples 1-4, which are as follows:

[0096]

[0097] It can be seen from the data in Table 1 that the glass transition temperatures of a series of polyester materials prepared by the present invention are all above 95 °C, which is at a relatively high level, and the light transmittances are all maintained above 89%, which is also very excellent. Among them, the glass transition temperature of the polyester material prepared in Example 9 can reach 121 °C, and the light transmittance can reach 91%, which is higher than that of most polyester materials. From Comparative Example 1, it can be seen that in the case of not adding 1,4-cyclohexanediol, the light transmittance of the polyester material decreased to a large extent, which is attributed to the more stable six-membered ring structure, and side reactions are not likely to occur during the reaction, making the system more homogeneous, and its strong rigid structure further destroys the crystallization ability of the polyester; from Comparative Example 2, it can be seen that in the case of not adding 2,3-butanediol, the polyester material showed a crystallization phenomenon, becoming opaque, and the glass transition temperature also decreased significantly, which indicates that the 2,3-butanediol unit has a strong ability to destroy crystallization and inhibit chain segment movement, which is crucial for the preparation of high-Tg transparent materials; from Comparative Example 3, it can be seen that when the amount of linear diol is too much, the polyester material will show a crystallization phenomenon. Therefore, it is necessary to strictly control the amount of linear diol when preparing polyester materials; from Comparative Example 4, it can be seen that the present application provides a preparation method for polyester materials with relatively excellent molecular weight, Tg, and light transmittance.

Claims

1. A polyester material, characterized in that, The polyester material is obtained by polymerization of aromatic dibasic acid or aromatic dibasic ester and aliphatic diol, and has the general structural formula: in, R1 is one or a combination thereof; and / or, R2 is one or a combination of C2~C6 linear straight-chain alkanediols; x is 0.30~0.80 mole fraction; y is 0.08~0.40 mole fraction; z is 0~0.40 mole fraction.

2. The polyester material according to claim 1, characterized in that, In the general structural formula, R2 is one or a combination of C4~C6 linear straight-chain alkanediols; x is 0.35~0.65 mole fraction; y is 0.15~0.30 mole fraction; z is 0.10~0.35 mole fraction.

3. A method for preparing a polyester material as described in claim 1 or 2, characterized in that, The following steps are involved: After the aromatic dibasic acid or aromatic dibasic ester, aliphatic diol, catalyst and antioxidant are fully mixed, an ester exchange reaction is first carried out to obtain a prepolymer, and then a polycondensation reaction is carried out to obtain the polyester material.

4. The method for preparing a polyester material according to claim 3, characterized in that: The aromatic dibasic acid or aromatic dibasic ester is one or a combination of terephthalic acid, isophthalic acid, and dimethyl terephthalate; and / or, The aliphatic diol is a mixture of 1,4-cyclohexanediol, 2,3-butanediol, and C2-C6 linear straight-chain alkanediol; The C2-C6 linear straight-chain alkanediol is one or a combination of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol.

5. The method for preparing a polyester material according to claim 4, characterized in that: In the aliphatic diols, the 1,4-cyclohexanediol accounts for 8-40% of the total molar ratio of the aliphatic diols, the 2,3-butanediol accounts for 30-80% of the total molar ratio of the aliphatic diols, and the C2-C6 linear straight-chain alkanediol accounts for 0-40% of the total molar ratio of the aliphatic diols.

6. The method for preparing a polyester material according to claim 3, characterized in that: The molar ratio of the aromatic dibasic acid or aromatic dibasic ester to the aliphatic diol is 1:1.4 to 1:1.

8.

7. The method for preparing a polyester material according to claim 3, characterized in that: The catalyst is one or a combination of selenium dioxide, antimony trioxide, antimony glycol, p-toluenesulfonic acid, acetate, alkyl aluminum with 1 to 12 carbon atoms, organic tin compounds, and titanate; The amount of the catalyst used is 0.05-1.0% of the total mass of the aromatic dibasic acid or aromatic dibasic ester and the aliphatic diol.

8. The method for preparing a polyester material according to claim 3, characterized in that: The antioxidant is one or a combination of phosphoric acid, phosphorous acid, phosphate ester, and phosphite ester; The amount of the antioxidant used is 0.01-0.2% of the total mass of the aromatic dibasic acid or aromatic dibasic ester and the aliphatic diol.

9. The method for preparing a polyester material according to claim 7 or 8, characterized in that: The catalyst is stannous octoate; The antioxidant is phenyl phosphate.

10. The method for preparing a polyester material according to claim 3, characterized in that: The transesterification reaction is carried out under a protective gas condition, and the transesterification reaction system needs to be heated to 180 - 220 °C within 2 - 4 h and maintained at this temperature for 2 - 6 h; When the polycondensation reaction is carried out, the reaction system is first heated to 200 - 240 °C and pre-polycondensed at 3 - 10 kPa for 1 - 4 h; then the reaction system is evacuated to below 500 Pa and polycondensed for 2 - 12 h.

11. The method for preparing a polyester material according to claim 7, 8 or 10, characterized in that the dosage of the catalyst is 0.2 - 0.6% of the total mass of the aromatic dicarboxylic acid or aromatic diester and the aliphatic diol; and / or the dosage of the antioxidant is 0.01 - 0.1% of the total mass of the aromatic dicarboxylic acid or aromatic diester and the aliphatic diol; and / or The transesterification reaction is carried out under a protective gas condition, and the transesterification reaction system needs to be heated to 200 - 220 °C within 2 - 4 h and maintained at this temperature for 2 - 6 h; When the polycondensation reaction is carried out, the reaction system is first heated to 210 - 230 °C and pre-polycondensed at 3 - 10 kPa for 1 - 4 h; then the reaction system is evacuated to below 500 Pa and polycondensed for 2 - 12 h.

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