Preparation method of high-transparency copolyester and application thereof in plates

Abstract

This invention discloses a method for preparing a high-transparency copolyester and its application in sheet materials, belonging to the field of polymer materials technology. The high-transparency copolyester of this invention comprises an aromatic diacid component, an aliphatic diol component, a polyfunctional acid component, and a polyfunctional alcohol component. The aromatic diacid component comprises 70-96 mol% terephthalic acid residues and 4-30 mol% isophthalic acid residues; the aliphatic diol component comprises 60-98 mol% ethylene glycol residues, 0.2-3 mol% diethylene glycol residues, 0-18 mol% neopentyl glycol residues, and 0-25 mol% cyclohexanediol residues; the polyfunctional acid component accounts for 0.001-0.1 mol% of the aromatic diacid component, and the polyfunctional alcohol component accounts for 0.001-1 mol% of the aliphatic diol component. This invention utilizes the introduction of polyfunctional acid and alcohol units into the copolyester chain segments to form a branched structure, disrupting the molecular chain regularity, reducing crystallinity, and forming an amorphous polyester that allows light to pass through smoothly, resulting in high transparency.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a method for preparing a highly transparent copolyester and its application in sheet materials. Background Technology

[0002] Polyethylene terephthalate (PET) is a resin composed of terephthalic acid and ethylene glycol. It is considered the world's most widely used resin, used to manufacture PET bottles, clothing, food trays, industrial films, and magnetic tapes. However, conventional PET suffers from problems such as rapid crystallization, high brittleness, and poor low-temperature resistance, limiting its application in many scenarios.

[0003] Modified PET copolyesters are synthesized using one or more diols as modifying monomers. In principle, the diols used as modifying monomers can be simple diols such as propylene glycol and butanediol, or special diols such as 1,4-cyclohexanediol and neopentyl glycol. This results in a copolyester with an amorphous structure that is not easily or slowly crystallizes, leading to good transparency and high gloss. However, the linear polyester molecular chains are regular and prone to crystallization, which causes light scattering. While high transparency can be obtained, the linear structure cannot achieve the same level of transparency as the branched structure. Furthermore, if catalyst residues, monomers, or oligomers remain during the polyester synthesis process, these impurities become light scattering points, leading to a decrease in transparency.

[0004] In summary, PET traditionally modified by copolymerization with diols or diacids still retains a linear molecular chain structure. This structure has inherent limitations: on the one hand, its high molecular chain regularity makes it prone to crystallization, leading to increased haze and decreased transparency in the finished product, making it impossible to achieve glass-like transparency; on the other hand, high transparency of linear polymer chains requires high molecular weight, but high molecular weight results in high melt viscosity, poor flowability, and requires higher temperatures and pressures during processing and molding, leading to high energy consumption and a higher risk of thermal degradation of the material.

[0005] Because some applications require transparent monitoring, such as in medical devices where it's necessary to observe whether the medication contains impurities and whether the infusion rate is normal, and in food packaging where it's crucial to confirm whether the contents have deteriorated or contain foreign objects, transparency is also essential for ensuring safe use. Furthermore, transparency can serve as an indirect indicator of material purity and processing quality. If PET copolyester appears cloudy or yellowish, it often indicates the presence of impurities, uneven crystallization, or degradation, indirectly reflecting that its physical properties (such as strength and aging resistance) may not meet standards. Therefore, modified PET copolyesters synthesized from one or more diols as modifying monomers can no longer meet the demands of high-precision applications; a new type of PET copolyester with high transparency, high impact resistance, and good melt flowability needs to be developed. Summary of the Invention

[0006] To address the problems existing in the prior art, and to solve the issues of linear structure, high molecular chain regularity, easy crystallization, and low transparency of existing PET or modified PET copolyesters; and the high molecular weight resulting in high melt viscosity, poor flowability, and difficult processing and molding, the present invention aims to design and provide a high-transparency copolyester, its preparation method, and its applications. The present invention mainly employs the introduction of multifunctional units into the copolyester chain segments to form a branched structure, thereby improving the amorphous state of the copolyester and simultaneously increasing the melt flowability, making it easier to process and mold. The high-transparency copolyester of the present invention, when melt-extruded, produces sheets with high transparency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The technical principle of this invention is as follows: This invention introduces multifunctional acid and alcohol units into the copolyester chain segment to form a branched structure. This branched structure will destroy the regularity of the molecular chain, reduce the crystallinity, and form an amorphous polyester that allows light to pass through smoothly and has high transparency.

[0009] The crystallinity of polyester is closely related to the regularity and symmetry of its molecular chains. When polyester molecular chains have a regular linear structure, they can be closely arranged, easily forming a crystalline structure. However, the introduction of branched structures disrupts the regularity and symmetry of the molecular chains. The presence of branched chains interferes with the arrangement of molecular chains into the crystal lattice, making it difficult for the molecular chains to arrange themselves in an orderly manner to form crystals, thus reducing the crystallinity of polyester. As the degree of branching increases, this destructive effect becomes more pronounced, and the crystallinity of polyester molecular chains decreases significantly, eventually leading to an amorphous state.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] On one hand, the present invention provides a highly transparent copolyester comprising an aromatic dicarboxylic acid component, an aliphatic diol component, a polyfunctional acid component, and a polyfunctional alcohol component; (the polyfunctional acid component and the polyfunctional alcohol component are both incorporated in the highly transparent copolyester product in the form of chain segments).

[0012] The aromatic dicarboxylic acid component, based on a total molar percentage of 100 mol%, contains 70-96 mol% of terephthalic acid residues and 4-30 mol% of isophthalic acid residues.

[0013] The aliphatic diol component, based on a total molar percentage of 100 mol%, comprises 60-98 mol% ethylene glycol residues, 0.2-3 mol% diethylene glycol residues, 0-18 mol% neopentyl glycol residues, and 0-25 mol% cyclohexanediethanol residues.

[0014] The total molar amount of the polyfunctional acid component is 0.001 to 0.1 mol of the total molar amount of the aromatic dicarboxylic acid component, and the polyfunctional acid component is selected from at least one polycarboxylic acid or its anhydride with a functionality of not less than 3.

[0015] Preferably, the polyfunctional acid component is selected from at least one of citric acid, pyromellitic acid, or trimellitic anhydride;

[0016] The total molar amount of the polyfunctional alcohol component is 0.001 to 1 mol of the total molar amount of the aliphatic diol component, and the polyfunctional alcohol component is selected from at least one polyol with a functionality of not less than 3.

[0017] Preferably, the polyfunctional alcohol component is selected from at least one of glycerol, trimethylolpropane, or trimethylolethane;

[0018] The molar ratio of total carboxyl functional groups in the aromatic dicarboxylic acid component and the polyfunctional acid component, and the molar ratio of total hydroxyl functional groups in the aliphatic diol component and the polyfunctional alcohol component is 1:1.05 to 1:1.30.

[0019] Secondly, the present invention provides a method for preparing a highly transparent copolyester, comprising the following steps:

[0020] Weigh out aromatic dicarboxylic acid, aliphatic diol, polyfunctional acid and polyfunctional alcohol, mix them, and beat them to obtain a mixed slurry;

[0021] The above slurry was subjected to an esterification reaction to obtain an esterified product;

[0022] The above esterified product is mixed with a catalyst and a heat stabilizer, and then subjected to a pre-condensation reaction and a final condensation reaction in sequence to obtain the product. The product is discharged, pelletized, and dried to obtain a highly transparent copolyester.

[0023] In the preparation method described above, the aromatic dicarboxylic acid is a terephthalic acid residue or an isophthalic acid residue;

[0024] The aliphatic diol is at least one of ethylene glycol residue, diethylene glycol residue, neopentyl glycol residue, or cyclohexanediethanol residue;

[0025] The polyfunctional acid is at least one of citric acid, pyromellitic acid, and trimellitic anhydride;

[0026] The polyfunctional alcohol is at least one of glycerol, trimethylolpropane, or trimethylolethane.

[0027] The preparation method described herein, wherein the esterification reaction conditions are: esterification temperature 235~268℃, pressure 40~120Kpa;

[0028] The esterification rate of the esterification reaction is above 95%.

[0029] In the preparation method described above, the catalyst is selected from at least one of antimony glycolate, antimony trioxide, tetrabutyl titanate, titanium oxalate, tetraisopropyl titanate, germanium oxide, or sodium germanate.

[0030] The catalyst is added in an amount of 0.01 to 0.1 wt.% of the total weight of the esterified product;

[0031] The heat stabilizer is a phosphorus-containing ester;

[0032] The amount of heat stabilizer added is 0.001~0.1 wt.% of the total weight of the esterified product.

[0033] In the preparation method described above, the heat stabilizer is selected from at least one of polyphosphoric acid, trimethyl phosphate, triethyl phosphate, or triphenyl phosphate.

[0034] The product prepared by the method described herein has an intrinsic viscosity of 0.72~0.84 dL / g.

[0035] The preparation method described above, wherein the conditions for the pre-condensation reaction are: time 60-90 min, melt temperature 265-285℃, and vacuum pressure 0.8-3 kPa;

[0036] The conditions for the final polycondensation reaction are: time 120-240 min, melt temperature 270-285℃, and vacuum pressure 50-300 Pa.

[0037] Thirdly, the present invention provides a highly transparent part, which is prepared by the aforementioned highly transparent polyester;

[0038] The high-transparency component has a transparency of ≥92% and a haze of ≤0.3%.

[0039] Fourthly, the present invention provides a method for preparing a highly transparent part, comprising the following steps:

[0040] The highly transparent copolyester is dried and melt-extruded to obtain highly transparent parts;

[0041] The temperature of the melt extrusion is 230~250℃.

[0042] The high-transparency copolyester provided by this invention is expected to be applied to sheet products with higher requirements for transparency.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The high-transparency copolyester material designed in this invention has a branched structure. This branched structure can effectively break the stacking of crystalline molecules, disrupt the regular arrangement of molecular chains, inhibit crystallization, reduce crystallinity, avoid light scattering caused by high crystallinity, and improve the transparency of the material, which is the key to achieving high transparency. Experiments show a decrease in haze and an increase in light transmittance.

[0045] 2. The branching point of the branched copolyester structure of the present invention increases the molecular chain entanglement, which helps to improve the impact resistance of the material.

[0046] 3. The branched structure of the copolyester material of the present invention reduces the melt viscosity and crystallization tendency, so that the copolyester can maintain good melt flowability in a wide processing temperature window and at lower temperatures, exhibiting excellent processing and molding performance. Attached Figure Description

[0047] Figure 1 A photograph of the copolyester prepared in Example 1;

[0048] Figure 2 The image shows the actual product of the copolyester prepared in Example 2. Detailed Implementation

[0049] The technical solution of the present invention will be further described below through embodiments.

[0050] Example 1:

[0051] 2000g of terephthalic acid, 100g of isophthalic acid, 823g of ethylene glycol, 10g of diethylene glycol, 200g of neopentyl glycol, 0.2g of citric acid, 0.1g of pyromellitic acid, 0.6g of glycerol, 0.6g of tetrabutyl titanate catalyst, and 1g of triphenyl phosphate stabilizer were added to a 10L reactor. The air inside the polymerization reactor was replaced with an inert gas, and then the materials were stirred to mix them evenly. The pressure inside the polymerization reactor was controlled at 70KPa, and the temperature inside the polymerization reactor was controlled at 245℃. The esterification efficiency was calculated by the liquid yield. When the conversion rate reached 96%, the esterification reaction ended, and the pressure was released.

[0052] The reactor was evacuated, and the pressure inside the reactor was controlled at 3 kPa. The temperature inside the polymerization reactor was controlled at 268°C, and the pre-condensation reaction was carried out for 75 min. Then, the pressure inside the reactor was controlled at 100 Pa, and the temperature inside the polymerization reactor was controlled at 273°C, and the final condensation reaction was carried out for 200 min. After the intrinsic viscosity reached 0.78 dL / g, the product was discharged, cooled, and pelletized to obtain a highly transparent copolyester.

[0053] The copolyester was dried at 65℃ for 10 hours. The dried, highly transparent copolyester was then melt-extruded at a processing temperature of 230–250℃ to obtain 2.5 mm thick sheets and 80 × 10 mm notched strips. Performance tests showed that the sheets had a transparency of 94%, a haze of 0.1%, and an impact strength of 6.5 KJ / m². 2 Melt index 5.5 g / 10 min (230℃ / 2.16 kg).

[0054] Example 2:

[0055] 2000g of terephthalic acid, 100g of isophthalic acid, 823g of ethylene glycol, 5g of diethylene glycol, 300g of neopentyl glycol, 0.5g of trimellitic anhydride, 2g of trimethylolethane, 2.8g of germanium oxide catalyst, and 0.2g of polyphosphoric acid stabilizer were added to a 10L reactor. The air inside the reactor was replaced with an inert gas, and the materials were stirred and mixed evenly. The pressure inside the reactor was controlled at 105 kPa, and the temperature inside the reactor was controlled at 265℃. The esterification efficiency was calculated based on the liquid yield. The esterification reaction ended when the conversion rate reached 95%, and the pressure was released.

[0056] The reactor was evacuated, the pressure was controlled at 1 kPa, the temperature inside the polymerization reactor was controlled at 270℃, and the reaction was carried out for 80 min. Then the pressure was controlled at 150 Pa, the temperature inside the polymerization reactor was controlled at 275℃, and the reaction was carried out for 160 min. After the intrinsic viscosity reached 0.84 dL / g, the product was discharged, cooled, and pelletized to obtain a highly transparent copolyester.

[0057] The copolyester was dried at 65℃ for 10 hours. The dried high-transparency copolyester was then melt-extruded at 230–250℃, producing 2.5mm thick sheets and 80×10mm notched strips. Performance tests were conducted, and the sheets showed a transparency of 92%, a haze of 0.3%, and an impact strength of 7.8 KJ / m². 2 Melt index 3.2 g / 10 min (230℃ / 2.16 kg).

[0058] Example 3:

[0059] 2000g of terephthalic acid, 105.26g of isophthalic acid, 834.66g of ethylene glycol, 30.86g of diethylene glycol, 0.19g of citric acid, 0.16g of glycerol, 2g of tetrabutyl titanate catalyst, and 1g of triphenyl phosphate stabilizer were added to a 10L reactor. The air inside the reactor was replaced with an inert gas, and then the materials were stirred to mix them evenly. The pressure inside the reactor was controlled at 40KPa, and the temperature inside the reactor was controlled at 235℃. The esterification efficiency was calculated by the liquid yield. When the conversion rate reached 96%, the esterification reaction ended, and the pressure was released.

[0060] The reactor was evacuated, and the pressure was controlled at 0.8 kPa. The temperature inside the polymerization reactor was controlled at 265°C, and the pre-condensation reaction was carried out for 60 min. Then, the pressure was controlled at 300 Pa, and the temperature inside the polymerization reactor was controlled at 285°C, and the final condensation reaction was carried out for 120 min. After the intrinsic viscosity reached 0.72 dL / g, the product was discharged, cooled, and pelletized to obtain a highly transparent copolyester.

[0061] The copolyester was dried at 65℃ for 10 hours. The dried, highly transparent copolyester was then melt-extruded at a processing temperature of 230–250℃ to obtain 2.5 mm thick sheets and 80 × 10 mm notched strips. Performance tests showed that the sheets had a transparency of 93%, a haze of 0.5%, and an impact strength of 5.0 KJ / m². 2 Melt index 4.9 g / 10 min (230℃ / 2.16 kg).

[0062] Example 4:

[0063] 2000g of terephthalic acid, 189.47g of isophthalic acid, 722.14g of ethylene glycol, 11.44g of diethylene glycol, 81.35g of neopentyl glycol, 189.0g of cyclohexanediol, 0.85g of trimellitic anhydride, 0.26g of trimethylolethane, 2.8g of germanium oxide catalyst, and 0.2g of polyphosphoric acid stabilizer were added to a 10L reactor. The air inside the reactor was replaced with an inert gas, and then the materials were stirred to mix them evenly. The pressure inside the reactor was controlled at 120KPa, and the temperature inside the reactor was controlled at 268℃. The esterification efficiency was calculated based on the liquid yield. When the conversion rate reached 96%, the esterification reaction ended, and the pressure was released.

[0064] The reactor was evacuated, and the pressure inside the reactor was controlled at 2 kPa. The temperature inside the polymerization reactor was controlled at 285°C, and the pre-condensation reaction was carried out for 90 min. Then, the pressure inside the reactor was controlled at 500 Pa, and the temperature inside the polymerization reactor was controlled at 270°C, and the final condensation reaction was carried out for 240 min. After the intrinsic viscosity reached 0.80 dL / g, the product was discharged, cooled, and pelletized to obtain a highly transparent copolyester.

[0065] The copolyester was dried at 65℃ for 10 hours. The dried, highly transparent copolyester was then melt-extruded at a processing temperature of 230–250℃ to obtain 2.5 mm thick sheets and 80 × 10 mm notched samples. Performance tests showed that the sheets had a transparency of 91%, a haze of 0.2%, and an impact strength of 5.5 KJ / m². 2 Melt index 4.8 g / 10 min (230℃ / 2.16 kg).

[0066] Example 5:

[0067] 2000g of terephthalic acid, 285.87g of isophthalic acid, 745.5g of ethylene glycol, 4.58g of diethylene glycol, 105.7g of neopentyl glycol, 177.0g of cyclohexanediol, 3.937g of pyromellitic acid, 15.722g of trimethylolpropane, 3g of antimony glycolate catalyst, and 1.5g of triphenyl phosphate stabilizer were added to a 10L reactor. The air inside the polymerization reactor was replaced with an inert gas, and then the materials were stirred to mix them evenly. The pressure inside the polymerization reactor was controlled at 80KPa, and the temperature inside the polymerization reactor was controlled at 275℃. The esterification efficiency was calculated by the liquid yield. When the conversion rate reached 96%, the esterification reaction ended, and the pressure was released.

[0068] The reactor was evacuated, and the pressure inside the reactor was controlled at 3 kPa. The temperature inside the polymerization reactor was controlled at 268°C, and the pre-condensation reaction was carried out for 75 min. Then, the pressure inside the reactor was controlled at 200 Pa, and the temperature inside the polymerization reactor was controlled at 273°C, and the final condensation reaction was carried out for 180 min. After the intrinsic viscosity reached 0.84 dL / g, the product was discharged, cooled, and pelletized to obtain a highly transparent copolyester.

[0069] The copolyester was dried at 65℃ for 10 hours. The dried, highly transparent copolyester was then melt-extruded at 230–250℃ to obtain 2.5 mm thick sheets and 80 × 10 mm notched strips. Performance tests showed that the sheets had a transparency of 90%, a haze of 1.2%, and an impact strength of 7.4 KJ / m². 2 Melt index 3.5 g / 10 min (230℃ / 2.16 kg).

[0070] Comparative Example 1:

[0071] The preparation method of the copolyester is the same as that in Example 1, except that citric acid, pyromellitic acid and glycerol are not added, that is, polyfunctional acid components and polyfunctional alcohol components are not added.

[0072] Experimental test results: The product sheet achieved a transmittance of 88%, a haze of 4.3%, and an impact strength of 3.2 KJ / m². 2 Melt index 6.8 g / 10 min (230℃ / 2.16 kg).

[0073] The above data shows that if polyfunctional acid and polyfunctional alcohol components are not added, the product will form a linear copolyester with high molecular chain regularity, which makes it easy to crystallize during processing and cooling. This results in increased haze and decreased light transmittance of the product, making it unable to meet the requirements of high transparency applications. At the same time, the linear structure leads to poor impact toughness and poor melt flow, making processing difficult.

[0074] Comparative Example 2:

[0075] The preparation method of the copolyester is the same as that in Example 1, except that citric acid and pyromellitic acid are not added, that is, no polyfunctional acid components are added.

[0076] Experimental test results: The product sheet achieved a transmittance of 91%, a haze of 1.9%, and an impact strength of 4.5 KJ / m². 2 Melt index 6.5 g / 10 min (230℃ / 2.16 kg).

[0077] Comparative Example 3:

[0078] The preparation method of the copolyester is the same as that in Example 1, except that glycerol is not added, that is, no polyfunctional alcohol component is added.

[0079] Experimental test results: The product sheet achieved a transmittance of 92%, a haze of 1.5%, and an impact strength of 5.8 KJ / m². 2 Melt index 6.3 g / 10 min (230℃ / 2.16 kg).

[0080] The data above shows that "low haze" provides a greater sense of visual clarity than "high light transmittance." For example... Figure 1 and 2 As shown, this invention maintains high transparency while keeping the substrate low in haze, resulting in better clarity and transparency. The products in Comparative Examples 1-3, due to insufficient optical stability, are more prone to oriented crystallization under heat and force, leading to whitening and increased haze. The branched structure of the products in Examples 1-5 of this invention reduces the tendency and rate of crystallization, making the optical properties of the products more stable and resistant to environmental stress whitening.

Claims

1. A highly transparent copolyester, characterized in that, It contains aromatic dicarboxylic acid components, aliphatic diol components, polyfunctional acid components, and polyfunctional alcohol components; The aromatic dicarboxylic acid component, based on a total molar percentage of 100 mol%, contains 70-96 mol% of terephthalic acid residues and 4-30 mol% of isophthalic acid residues. The aliphatic diol component, based on a total molar percentage of 100 mol%, comprises 60-98 mol% ethylene glycol residues, 0.2-3 mol% diethylene glycol residues, 0-18 mol% neopentyl glycol residues, and 0-25 mol% cyclohexanediethanol residues. The total molar amount of the polyfunctional acid component is 0.001 to 0.1 mol of the total molar amount of the aromatic dicarboxylic acid component, and the polyfunctional acid component is selected from at least one polycarboxylic acid or its anhydride with a functionality of not less than 3. The total molar amount of the polyfunctional alcohol component is 0.001 to 1 mol of the total molar amount of the aliphatic diol component, and the polyfunctional alcohol component is selected from at least one polyol with a functionality of not less than 3. The molar ratio of the total carboxyl functional groups in the aromatic dicarboxylic acid component and the polyfunctional acid component to the total hydroxyl functional groups in the aliphatic diol component and the polyfunctional alcohol component is 1:1.05 to 1:1.

30.

2. The high-transparency copolyester as described in claim 1, characterized in that, The polyfunctional acid component is selected from at least one of citric acid, pyromellitic acid, or trimellitic anhydride. The polyfunctional alcohol component is selected from at least one of glycerol, trimethylolpropane, or trimethylolethane.

3. The method for preparing a highly transparent copolyester as described in claim 1, characterized in that, Includes the following steps: Weigh out aromatic dicarboxylic acid, aliphatic diol, polyfunctional acid and polyfunctional alcohol, mix them evenly under an inert gas atmosphere, and beat them to obtain a mixed slurry; The above slurry was subjected to an esterification reaction to obtain an esterified product; The above esterified product is mixed with a catalyst and a heat stabilizer, and then subjected to a pre-condensation reaction and a final condensation reaction in sequence to obtain the product. The product is discharged, pelletized, and dried to obtain a highly transparent copolyester.

4. The preparation method according to claim 3, characterized in that, The aromatic dicarboxylic acid is a terephthalic acid residue or an isophthalic acid residue; The aliphatic diol is at least one of ethylene glycol residue, diethylene glycol residue, neopentyl glycol residue, or cyclohexanediethanol residue; The polyfunctional acid is at least one of citric acid, pyromellitic acid, and trimellitic anhydride; The polyfunctional alcohol is at least one of glycerol, trimethylolpropane, or trimethylolethane.

5. The preparation method according to claim 3, characterized in that, The conditions for the esterification reaction are: esterification temperature 235~268℃, pressure 40~120Kpa; The esterification rate of the esterification reaction is above 95%; The conditions for the pre-polymerization reaction are: time 60-90 min, melt temperature 265-285℃, and vacuum pressure 0.8-3 kPa; The conditions for the final polycondensation reaction are: time 120-240 min, melt temperature 270-285℃, and vacuum pressure 50-300 Pa.

6. The preparation method according to claim 3, characterized in that, The catalyst is selected from at least one of antimony glycol, antimony trioxide, tetrabutyl titanate, titanium oxalate, tetraisopropyl titanate, germanium oxide, or sodium germanate. The catalyst is added in an amount of 0.01 to 0.1 wt.% of the total weight of the esterified product; The heat stabilizer is a phosphorus-containing ester; The amount of heat stabilizer added is 0.001~0.1 wt.% of the total weight of the esterified product.

7. The preparation method according to claim 3, characterized in that, The heat stabilizer is selected from at least one of polyphosphoric acid, trimethyl phosphate, triethyl phosphate, or triphenyl phosphate.

8. The preparation method according to claim 3, characterized in that, The intrinsic viscosity of the product is 0.72~0.84 dL / g.

9. A highly transparent component, characterized in that, It is prepared by the high transparency copolyester as described in claim 1 or 2; The high-transparency component has a transparency of ≥92% and a haze of ≤0.3%.

10. The method for preparing a highly transparent part as described in claim 9, characterized in that, Includes the following steps: The high-transparency copolyester described in claim 1 is dried and melt-extruded to obtain a high-transparency part; The temperature of the melt extrusion is 230~250℃.

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