Modified polyesters, processes for their preparation and use

Abstract

The present application relates to the field of polyester, discloses a modified polyester and a preparation method and application thereof.The modified polyester contains modified ester units, the structure of the modified ester units is shown in at least one of formula (I), formula (II) and formula (III), and the content of the modified ester units in the modified polyester is 17-70wt%, wherein R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each independently is C1-C6 alkylene, R9, R 10 , R 11 and R 12 Each independently is hydrogen or C1-C4 alkyl, R 13 and R 14 Each independently is C0-C4 alkylene.The modified polyester has good antistatic property and heat resistance, and at the same time has high visible light transmittance, realizes the combination of the three performances, and also does not need to be used with polyester chips.

Description

Technical Field

[0001] This invention relates to the field of polyesters, and more specifically to a modified polyester, its preparation method, and its applications. Background Technology

[0002] In recent years, with the rise of smartphones, artificial intelligence, new energy vehicles, and solar power generation, PET polyester has seen rapid development in the electronics industry, with applications such as optical films, lithium battery separators, solar backsheets, and automotive decorative films. However, electrostatic discharge (ESD) hazards are a significant problem in these applications. This is mainly because PET products easily accumulate static charge, attract dust, and in severe cases, can damage precision electronic components, cause fires, and result in electric shocks. Furthermore, some digital and optical products require films with high transparency. Therefore, the development of PET polyester films that combine transparency and antistatic properties is of great practical importance.

[0003] Currently, there are three main methods to improve the antistatic properties of PET polyester: surface treatment, blending, and copolymerization. The first method involves coating the PET polyester surface with an antistatic agent, but this often results in a rough film surface, reduced transparency, and poor durability; the antistatic properties gradually diminish during processing and use as the antistatic agent is lost. The second method mainly involves blending with antistatic agents or other conductive fillers, but this also leads to opacity, poor antistatic durability, and reduced mechanical properties. The third method is the most feasible approach for preparing transparent antistatic polyester. Its principle is to introduce polar groups or reduce the crystallinity of the polyester molecule through copolymerization, thereby improving antistatic properties. However, aliphatic long-chain monomers are often used in copolymerization modification. The introduction of these flexible blocks reduces the regularity of the main chain, leading to a significant decrease in the glass transition temperature and thermal stability of the polyester.

[0004] CN107641295A discloses an antistatic masterbatch and a film using the same masterbatch. The antistatic masterbatch is prepared by adding graphene oxide as an antistatic component to polyester chips. While this imparts excellent conductivity to the polyester chips, the chips and film become opaque. CN104086957B discloses a highly transparent antistatic PET polyester film and its preparation method. A copolyester is obtained by copolymerizing modified monomers polyethylene glycol / polyethylene glycol monomethyl ether. The surface resistivity of the final polyester film is reduced to 10 Ω·cm. 8 -10 10 Ω, while maintaining high transparency. However, the heat resistance of the resulting copolyester is significantly reduced, thus requiring further compounding with polyester chips. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of existing technologies where polyesters with good antistatic properties have low heat resistance, low glass transition temperature, and low transparency. This invention provides a modified polyester, its preparation method, and its application. This modified polyester has good antistatic properties and heat resistance, while also having high visible light transmittance, achieving a balance of these three properties, and does not require mixing with polyester chips.

[0006] To achieve the above objectives, a first aspect of the present invention provides a modified polyester comprising modified ester units, the modified ester units having structures as shown in at least one of formulas (I), (II), and (III), wherein the modified ester units in the modified polyester comprise a content greater than or equal to 17-70 wt%.

[0007]

[0008]

[0009] Among them, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C6 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C4 alkyl, R 13 and R 14 Each is independently a C0-C4 alkylene group.

[0010] A second aspect of the present invention provides a method for preparing a modified polyester, the method comprising the following steps:

[0011] S1. Under esterification reaction conditions, an aromatic diacid monomer, an aliphatic diol monomer, a modified monomer, and a catalyst are subjected to a first-stage reaction to obtain a prepolymer; the modified monomer is selected from at least one of modified monomer a having the structure shown in formula (V), modified monomer b having the structure shown in formula (VI), and modified monomer c having the structure shown in formula (VII), wherein the structure of the aromatic diacid monomer is shown in formula (VIII), and the structure of the aliphatic diol monomer is shown in formula (IX).

[0012]

[0013]

[0014] Among them, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C6 alkylene group, R9, R 10 R 11 and R 12Each is independently hydrogen or C1-C4 alkyl, R 13 and R 14 Each is independently a C0-C4 alkylene group;

[0015] S2. Under the conditions of polycondensation reaction, the prepolymer is subjected to a second-stage reaction;

[0016] The total molar amount of the modified monomer a and / or the modified monomer c and the molar ratio of the aliphatic diol monomer are 0.15-1.5:1, or the molar ratio of the modified monomer b and the aromatic dicarboxylic acid monomer is 0.2-1.2:1.

[0017] A third aspect of the present invention provides the application of the modified polyester described above or the modified polyester prepared by the above preparation method in electronic products, building materials, magnetic recording materials and photosensitive materials.

[0018] Through the above technical solution, the modified polyester provided by the present invention contains modified ester units, the structure of which is shown in at least one of formulas (I), (II), and (III). In the modified polyester, the content of the modified ester units is 17-70 wt%. The specific content and specific structure of the modified ester units enable the polyester to have good antistatic properties and heat resistance, while also possessing high transparency, achieving a balance of these three properties. It has good applications in electronic products, building materials, magnetic recording materials, and photosensitive materials. Attached Figure Description

[0019] Figure 1 This is the infrared spectrum of the modified copolyester prepared in Example 1;

[0020] Figure 2 This is a polymerization flow chart of modified copolyester. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] As previously stated, a first aspect of the present invention provides a modified polyester comprising modified ester units, the modified ester units having structures as shown in at least one of formulas (I), (II), and (III), wherein the modified ester units are present in a content of 17-70 wt% in the modified polyester.

[0023]

[0024] Among them, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C6 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C4 alkyl, R 13 and R 14 Each is independently a C0-C4 alkylene group.

[0025] During their research, the inventors discovered that the modified polyester contains modified ester units as shown in at least one of formulas (I), (II), and (III), and the content of the modified ester units in the modified polyester is 17-70 wt%. This gives the polyester good antistatic properties and heat resistance, while also possessing high transparency, achieving a balance of these three properties. It has promising applications in electronic products, building materials, magnetic recording materials, and photosensitive materials.

[0026] According to the present invention, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each can be independently methylene, ethylene, propylene, butylene, pentylene, or hexylene. R9, R 10 R 11 and R 12 Each can be independently hydrogen, methyl, ethyl, propyl, or butyl. R 13 and R 14 The modified ester units may be absent or can be methylene, ethylene, propylene, or butylene, each existing independently. The content of the modified ester units in the modified polyester can be 17wt%, 22wt%, 27wt%, 32wt%, 37wt%, 42wt%, 47wt%, 52wt%, 57wt%, 62wt%, 67wt%, 70wt%, or any value within a range formed by any two of these values.

[0027] Preferably, the modified ester unit has the structure shown in formula (I) and / or formula (III). Studies have found that having modified ester units as shown in formula (I) and / or formula (III) in the polyester, and controlling the content of the modified ester units in the modified polyester to 17-70 wt%, can effectively improve the heat resistance of the modified polyester. Further preferably, considering the ability to further improve the heat resistance of the modified polyester, the modified ester unit has the structure shown in formula (III).

[0028] Preferably, the modified ester unit content in the modified polyester is 34-55 wt%. Controlling the content of the modified ester unit within the above range can further improve the antistatic properties of the modified polyester.

[0029] Preferably, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C4 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C2 alkyl, R 13 and R 14 Each is independently a C0-C2 alkylene group. Studies have found that ester units with the above structure can further improve the antistatic properties, heat resistance, and transparency of the modified polyester. Further preferably, considering the ability to further improve the antistatic properties, heat resistance, and transparency of the modified polyester, R1, R2, R5, R6, R7, R8, and R... 15 Each is independently methylene or ethylene, R3 and R4 are independently C1-C3 alkylene, R9, R 10 R 11 and R 12 Each can be either hydrogen or methyl, R 13 and R 14 Each is independent of the other, either non-existent or methylene.

[0030] R1 and R2 can be the same or different, R5 and R6 can be the same or different, and R7 and R8 can be the same or different. Preferably, from the perspective of further improving the antistatic properties, heat resistance, and transparency of the modified polyester, R1 and R2 are the same, R5 and R6 are the same, and R7 and R8 are the same.

[0031] Preferably, the modified copolyester further contains ester unit B represented by formula (IV).

[0032]

[0033] The aforementioned ester unit B and the modified ester unit exhibit better interaction, thereby further improving the antistatic properties, heat resistance, and transparency of the modified copolyester. From the perspective of further enhancing the antistatic properties, heat resistance, and transparency of the modified copolyester, p is further preferably 0.

[0034] Preferably, the surface resistivity of the modified copolyester is 1×10⁻⁶. 8 -7.2×10 11 The modified copolyester has an Ω-cobalt temperature of 63-95℃, a thermal decomposition temperature of 392-412℃, and a visible light transmittance of 88%-91%. More preferably, the modified copolyester has a melting point of 220-248℃.

[0035] Surface resistivity was measured using a high-resistivity meter, and the test conditions were performed according to GB / T 33398-2016. DSC was used to test the T-slice. g T m The thermal decomposition temperature was tested using TGA. Transmittance was measured after extruding and stretching to prepare a 120 μm thick film, with test conditions performed according to GB / T2410-2008.

[0036] A second aspect of the present invention provides a method for preparing a modified polyester, the method comprising the following steps:

[0037] S1. Under esterification reaction conditions, an aromatic diacid monomer, an aliphatic diol monomer, a modified monomer, and a catalyst are subjected to a first-stage reaction to obtain a prepolymer; the modified monomer is selected from at least one of modified monomer a having the structure shown in formula (V), modified monomer b having the structure shown in formula (VI), and modified monomer c having the structure shown in formula (VII), wherein the structure of the aromatic diacid monomer is shown in formula (VIII), and the structure of the aliphatic diol monomer is shown in formula (IX).

[0038]

[0039] Among them, R1, R2, R3, R4, R5, R6, R7, and R8 are each independently C1-C6 alkylene groups, and R9, R... 10 R 11 and R 12 Each is independently hydrogen or C1-C4 alkyl, R 13 and R 14 Each is independently a C0-C4 alkylene group;

[0040] S2. Under the conditions of polycondensation reaction, the prepolymer is subjected to a second-stage reaction;

[0041] The total molar amount of the modified monomer a and / or the modified monomer c and the molar ratio of the aliphatic diol monomer are 0.15-1.5:1, or the molar ratio of the modified monomer b and the aromatic dicarboxylic acid monomer is 0.2-1.2:1.

[0042] During their research, the inventors discovered that the modified polyester prepared by the above method contains at least one modified ester unit as shown in formulas (I), (II), and (III), and the content of the modified ester unit in the modified polyester is 17-70 wt%. This gives the polyester good antistatic properties and heat resistance, while also possessing high transparency, achieving a balance of all four properties. It has promising applications in electronic products, building materials, magnetic recording materials, and photosensitive materials.

[0043] According to the present invention, when the modified monomer contains only modified monomer a and / or modified monomer c, the ratio of the total molar amount of modified monomer a and / or modified monomer c to the molar amount of the aliphatic diol monomer is 0.15-1.5:1, which can be 0.15:1, 0.3:1, 0.45:1, 0.6:1, 0.75:1, 0.9:1, 1.05:1, 1.2:1, 1.35:1, 1.5:1, or any value within the range formed by these ratios. When the modified monomer contains only modified monomer b, the molar ratio of the modified monomer c to the aromatic dicarboxylic acid monomer is 0.2-1.2:1, which can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, or any value within the range formed by these ratios. When the modified monomer contains modified monomer a, modified monomer c, and modified monomer b, the molar ratio of the ester unit formed by the modified monomer (the ester unit contains at least one of modified monomer a, modified monomer b, and modified monomer c) to the ester unit formed by the non-modified monomer (does not contain modified monomer a, modified monomer b, or modified monomer c) is 0.15-1.5:1, and can be 0.15:1, 0.3:1, 0.45:1, 0.6:1, 0.75:1, 0.9:1, 1.05:1, 1.2:1, 1.35:1, 1.5:1, or any value within the range formed by these ratios.

[0044] Preferably, the modified monomer is modified monomer a and / or modified monomer c. Studies have found that polyesters modified with the above-mentioned modifying units have heat resistance properties. Further preferably, considering the potential to further improve the heat resistance of the modified polyester, the modified monomer is modified monomer c.

[0045] Preferably, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C4 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C2 alkyl, R 13 and R 14 Each monomer is independently a C0-C2 alkylene group. Studies have found that the above-mentioned modified monomers can further improve the antistatic properties, heat resistance, and transparency of the modified polyester. Further preferably, considering the ability to further improve the antistatic properties, heat resistance, and transparency of the modified polyester, R1, R2, R5, R6, R7, R8, and R... 15 Each is independently methylene or ethylene, R3 and R4 are independently C1-C3 alkylene, R9, R 10 R 11 and R 12Each can be either hydrogen or methyl, R 13 and R 14 Each is independent of the other, either non-existent or methylene.

[0046] R1 and R2 can be the same or different, R5 and R6 can be the same or different, and R7 and R8 can be the same or different. Preferably, from the perspective of further improving the antistatic properties, heat resistance, and transparency of the modified polyester, R1 and R2 are the same, R5 and R6 are the same, and R7 and R8 are the same.

[0047] Preferably, the modified monomer is selected from Thx-OH. IThx-OH Thx-COOMe IThx-COOMe and Manx-OH At least one of them.

[0048] Preferably, the ratio of the total molar amount of the modified monomer a and / or the modified monomer c to the molar amount of the aliphatic diol is 0.3-0.85:1; or the molar ratio of the modified monomer b to the aromatic dicarboxylic acid monomer is 0.6-1.2:1.

[0049] Preferably, the catalyst is an antimony-based catalyst, and the amount of the antimony-based catalyst, calculated based on antimony, is 145-180 ppm, based on the theoretical yield of the polyester. This can be 145 ppm, 150 ppm, 165 ppm, 170 ppm, 175 ppm, 180 ppm, or any value within a range formed by these values. Controlling the amount of antimony catalyst within the above range can further improve the antistatic properties, heat resistance, and transparency of the obtained modified copolyester.

[0050] Preferably, the antimony-based catalyst can be at least one selected from antimony oxide, antimony acetate, and antimony glycolate. Antimony glycolate is preferred.

[0051] Preferably, the conditions for the esterification reaction include at least the following: a temperature of 235-255°C, which can be 235°C, 240°C, 245°C, 250°C, 255°C, or any value within this range; and a time of 90-120 min, which can be 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 120 min, or any value within this range. The conditions for the polycondensation reaction include at least the following: a temperature of 270-280°C, which can be 270°C, 272°C, 274°C, 276°C, 278°C, 280°C, or any value within this range. The modified copolyester prepared under the above conditions exhibits higher antistatic properties, heat resistance, and transparency.

[0052] The third aspect of this invention provides the application of the modified copolyester described above or the modified copolyester prepared by the above preparation method in electronic products, building materials, magnetic recording materials and photosensitive materials.

[0053] The present invention will be described in detail below through embodiments. In the following embodiments, viscosity was obtained according to the national standard GB17931-2018; surface resistivity was measured using a high-resistivity meter, and the test conditions were performed according to GB / T 33398-2016. DSC test slice T was used. g T m The thermal decomposition temperature was tested using TGA. Transmittance was measured after extruding and stretching to prepare a 120 μm thick film, with test conditions performed according to GB / T2410-2008.

[0054] Example 1

[0055] 5000g of terephthalic acid, 2616g of ethylene glycol, 858g of Thx-OH, and 1.75g ​​of antimony glycolate catalyst were added to a 20L polymerization reactor. After the addition was complete, the reactor was purged with nitrogen three times, and the temperature was raised to 245℃. The esterification reaction was carried out at atmospheric pressure for 105 min. After the reaction, pre-polymerization was carried out under low vacuum for 45 min. The vacuum was further reduced to below 100 Pa, and the polycondensation reaction was carried out at 275℃. After the reaction was completed, the product was extruded and pelletized using a melt pump. The preparation process is described in [reference needed]. Figure 2 .

[0056] The polyester prepared in Example 1 was subjected to infrared detection to obtain... Figure 1 .Depend on Figure 1 It can be seen that polyester is at 1100.45cm -1 The presence of a characteristic diffraction peak indicates that the peak represents the stretching vibration of the COC ether bond in Thx-OH, suggesting that Thx-OH is embedded in the polyester molecular chain.

[0057] Example 2

[0058] Polyesters were prepared according to the method of Example 1, except that the amount of ethylene glycol used was 2176 g and the amount of Thx-OH used was 1748 g.

[0059] Example 3

[0060] Polyesters were prepared according to the method of Example 1, except that the amount of ethylene glycol used was 1698g and the amount of Thx-OH used was 2974g.

[0061] Example 4

[0062] Polyesters were prepared according to the method of Example 1, except that the amount of ethylene glycol used was 1254g and the amount of Thx-OH used was 4000g.

[0063] Example 5

[0064] Polyesters were prepared according to the method of Example 1, except that Thx-OH was replaced with THx-COOMe, and the amount of terephthalic acid was 3790g, the amount of ethylene glycol was 3000g, and the amount of THx-COOMe was 1156g.

[0065] Example 6

[0066] Polyesters were prepared according to the method of Example 5, except that the amount of terephthalic acid used was 2860g and the amount of THx-COOMe used was 2070g.

[0067] Example 7

[0068] Polyesters were prepared according to the method of Example 5, except that the amount of terephthalic acid used was 1900g and the amount of THx-COOMe used was 2564g.

[0069] Example 8

[0070] Polyesters were prepared according to the method of Example 1, except that Thx-OH was replaced with IThx-OH, and the amount of ethylene glycol was 2595g and the amount of IThx-OH was 1026g.

[0071] Example 9

[0072] Polyesters were prepared according to the method of Example 8, except that the amount of ethylene glycol used was 2176 g and the amount of IThx-OH used was 1955 g.

[0073] Example 10

[0074] Polyesters were prepared according to the method of Example 8, except that the amount of ethylene glycol used was 1698 g and the amount of IThx-OH used was 3327 g.

[0075] Example 11

[0076] Polyesters were prepared according to the method of Example 1, except that Thx-OH was replaced with Manx-OH, and the amount of ethylene glycol was 2585g and the amount of Manx-OH was 1346g.

[0077] Example 12

[0078] Polyesters were prepared according to the method of Example 11, except that the amount of ethylene glycol used was 2295g and the amount of Manx-OH used was 2320g.

[0079] Example 13

[0080] Polyesters were prepared according to the method of Example 11, except that the amount of ethylene glycol used was 1870 g and the amount of Manx-OH used was 3715 g.

[0081] Comparative Example 1

[0082] Polyesters were prepared according to the method of Example 1, except that Thx-OH was not added.

[0083] Comparative Example 2

[0084] Polyesters were prepared according to the method of Example 1, except that the amount of ethylene glycol used was 2858g and the amount of Thx-OH used was 300g.

[0085] Comparative Example 3

[0086] Polyesters were prepared according to the method of Example 1, except that the amount of ethylene glycol used was 964 g and the amount of Thx-OH used was 4500 g.

[0087] Comparative Example 4

[0088] Polyester was prepared according to the method of Example 1, except that Thx-OH was replaced with polyethylene glycol, and the amount of ethylene glycol was 3000g and the amount of polyethylene glycol was 1980g.

[0089] Comparative Example 5

[0090] The copolyester was prepared according to the method of Example 1, except that Thx-OH was replaced with spirocyclic diol, and the amount of spirocyclic diol was 3035g.

[0091] Test case

[0092] The parameters of the polyesters obtained in the examples and comparative examples are shown in Table 1.

[0093] Table 1

[0094]

[0095]

[0096] As can be seen from the results in Table 1, the surface resistivity of the embodiment is worse than that of Comparative Example 1 and Comparative Example 2, the thermal decomposition temperature of the embodiment is higher than that of Comparative Example 3 and Comparative Example 4, and the light transmittance of the embodiment is higher than that of Comparative Example 5. This indicates that the modified polyester provided by the embodiment can take into account antistatic properties, heat resistance properties and light transmittance properties.

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified polyester, characterized in that, The modified polyester contains modified ester units, the structures of which are shown in at least one of formulas (I), (II), and (III), and the content of the modified ester units in the modified polyester is 17-70 wt%. Among them, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C6 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C4 alkyl, R 13 and R 14 Each is independently a C0-C4 alkylene group.

2. The modified polyester according to claim 1, characterized in that, The surface resistivity of the modified copolyester is 1×10⁻⁶. 8 -7.2×10 11 Ω, glass transition temperature is 63-95℃, thermal decomposition temperature is 392-412℃, and visible light transmittance is 88%-91%; Preferably, the modified copolyester has a melting point of 220-248°C.

3. The modified polyester according to claim 1, characterized in that, The structure of the modified ester unit is shown in formula (I) and / or formula (III); Preferably, the structure of the modified ester unit is as shown in formula (III); Preferably, the modified ester unit content in the modified polyester is 34-55 wt%.

4. The modified polyester according to any one of claims 1 to 3, characterized in that, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C4 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C2 alkyl, R 13 and R 14 Each is independently a C0-C2 alkylene group; Preferably, R1, R2, R5, R6, R7, R8 and R 15 Each is independently methylene or ethylene, R3 and R4 are independently C1-C3 alkylene, R9, R 10 R 11 and R 12 Each can be either hydrogen or methyl, R 13 and R 14 Each is independently either absent or methylene; Preferably, R1 and R2 are the same, R5 and R6 are the same, and R7 and R8 are the same.

5. The modified polyester according to any one of claims 1 to 3, characterized in that, The modified copolyester also contains ester unit B as shown in formula (IV).

6. A method for preparing a modified polyester, characterized in that, The method includes the following steps: S1. Under esterification reaction conditions, an aromatic diacid monomer, an aliphatic diol monomer, a modified monomer, and a catalyst are subjected to a first-stage reaction to obtain a prepolymer; the modified monomer is selected from at least one of modified monomer a having the structure shown in formula (V), modified monomer b having the structure shown in formula (VI), and modified monomer c having the structure shown in formula (VII), wherein the structure of the aromatic diacid monomer is shown in formula (VIII), and the structure of the aliphatic diol monomer is shown in formula (IX). Among them, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C6 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C4 alkyl, R 13 and R 14 Each is independently a C0-C4 alkylene group; S2. Under the conditions of polycondensation reaction, the prepolymer is subjected to a second-stage reaction; The ratio of the total molar amount of the modified monomer a and / or the modified monomer c to the molar amount of the aliphatic diol monomer is 0.15-1.5:1, or the molar ratio of the modified monomer b to the aromatic dicarboxylic acid monomer is 0.2-1.2:

1.

7. The preparation method according to claim 6, characterized in that, The ratio of the total molar amount of the modified monomer a and / or the modified monomer c to the molar amount of the aliphatic diol monomer is 0.3-0.85:1, or the molar ratio of the modified monomer b to the aromatic dicarboxylic acid monomer is 0.6-1.2:1; Preferably, the modified monomer is modified monomer a and / or modified monomer c; Preferably, the modified monomer is modified monomer c.

8. The preparation method according to claim 6 or 7, characterized in that, R1, R2, R3, R4, R5, R6, R7, R8 and R 15 Each is independently a C1-C4 alkylene group, R9, R 10 R 11 and R 12 Each is independently hydrogen or C1-C2 alkyl, R 13 and R 14 Each is independently a C0-C2 alkylene group; Preferably, R1, R2, R5, R6, R7, R8 and R 15 Each is independently methylene or ethylene, R3 and R4 are independently C1-C3 alkylene, R9, R 10 R 11 and R 12 Each can be either hydrogen or methyl, R 13 and R 14 Each is independently either absent or methylene; Preferably, R1 and R2 are the same, R5 and R6 are the same, and R7 and R8 are the same.

9. The preparation method according to claim 6 or 7, characterized in that, The catalyst is an antimony-based catalyst, and the amount of the antimony-based catalyst, calculated as antimony, is 145-180 ppm based on the theoretical yield of the polyester. Preferably, the conditions for the esterification reaction include at least: a temperature of 235-255°C and a time of 90-120 min, and the conditions for the polycondensation reaction include at least: a temperature of 270-280°C.

10. The application of the modified polyester according to any one of claims 1 to 5 or the modified polyester prepared by the preparation method according to any one of claims 6 to 9 in electronic products, building materials, magnetic recording materials and photosensitive materials.

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