High viscosity polyester chip and method for producing the same

Abstract

This invention belongs to the field of polymer material preparation technology, specifically relating to a high-viscosity polyester chip and its preparation method. The preparation method includes the following steps: S1: Under nitrogen protection, terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, trimethylolpropane, nano-SiO2, pentaerythritol stearate, polyethylene glycol, and modified hydroxyapatite are mixed evenly to obtain a slurry; S2: The slurry is mixed with 50%~55% catalyst for esterification reaction; the remaining 45%~50% catalyst and stabilizer are added for polycondensation reaction, followed by post-treatment to obtain high-viscosity polyester chips. The preparation method of this invention is simple, and the obtained polyester chips have an intrinsic viscosity ≥0.78 dL / g, a low melting point, and high light transmittance, while also giving the polyester material excellent UV resistance.

Description

Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, specifically relating to a high-viscosity polyester chip and its preparation method. Background Technology

[0002] Polyethylene terephthalate-1,4-cyclohexanediethanol (PETG) is an amorphous copolyester prepared by copolymerization of terephthalic acid (PTA), ethylene glycol (EG), and 1,4-cyclohexanediethanol (CHDM). Its core principle lies in introducing the rigid cyclic structure of CHDM monomers into the traditional polyethylene terephthalate (PET) molecular chain, disrupting the molecular chain regularity, altering the crystallinity of PET, and thus endowing the material with a series of superior properties. Compared to PET, PETG not only retains the environmentally friendly, recyclable, and chemically resistant properties of polyester materials, but also possesses advantages such as high transparency, ease of processing, heat-sealing properties, and shrinkage resistance. It is currently used in various fields including packaging, fibers, films, 3D printing, and consumer electronics.

[0003] The current mainstream synthesis process for PETG is the direct esterification-polymerization process of PTA (Wang Kaili, Preparation and Performance Study of PETG, Rubber and Plastics Technology and Equipment, 2025). The specific process is as follows: First, PTA, EG, and CHDM undergo an esterification reaction under nitrogen protection to generate polyethylene terephthalate, cyclohexanediol terephthalate, and their oligomers. The esterification stage is completed when the esterification rate reaches over 95%. Subsequently, a catalyst is added, and a polymerization reaction is carried out under high vacuum conditions. The molecular chain grows by removing small molecule EG, ultimately yielding PETG. However, in this method, the performance control of PETG depends on adjusting the content of the single CHDM monomer: increasing the CHDM content reduces the crystallinity of the material, which optimizes processing fluidity to some extent, but weakens the intermolecular forces, making it difficult to improve the intrinsic viscosity. Furthermore, the PETG prepared by this method has low intrinsic viscosity and insufficient melt strength, which can easily lead to problems such as melt fracture and uneven wall thickness in extrusion and thick-walled product molding. If the viscosity is increased by extending the polycondensation time, the processing efficiency will decrease significantly and the processing requirements of low melting point (185~195℃) cannot be met. Summary of the Invention

[0004] The existing PETG has a relatively high melting point and high processing energy consumption, making it difficult to solve the problem of combining low melting point with high viscosity. In order to solve this problem, the present invention provides a high-viscosity polyester chip and its preparation method.

[0005] To achieve the objectives of this invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for preparing high-viscosity polyester chips, comprising the following steps: S1: Under nitrogen protection, terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, trimethylolpropane, nano-SiO2, pentaerythritol stearate, polyethylene glycol and modified hydroxyapatite are mixed evenly to obtain a slurry. S2: Mix the slurry with 50%~55% catalyst for esterification; add the remaining 45%~50% catalyst and stabilizer for polycondensation, and then perform post-treatment to obtain high-viscosity polyester chips.

[0006] By employing the above technical solutions, polyester is prepared by copolymerization of terephthalic acid, ethylene glycol, and 1,4-cyclohexanediethanol as basic monomers. Diethylene glycol is introduced as the core flexible monomer, utilizing its ether-bonded flexible segments to insert into the molecular chain, disrupting the molecular chain regularity and efficiently reducing the melting point. 2,2-Dimethyl-1,3-propanediol is introduced to form a flexible monomer synergistic system with diethylene glycol, regulating the molecular melting point and compensating for the mechanical property loss caused by the low melting point. Trimethylolpropane constructs a controllable semi-branched structure to achieve high viscosity. Nano-SiO2 and modified hydroxyapatite are uniformly dispersed in the matrix, jointly ensuring the high light transmittance of the polyester. Pentaerythritol stearate is combined with polyethylene glycol to further improve the flowability of high-viscosity melts, solving the problem of low-melting-point, high-viscosity melts adhering to equipment, while also improving the dispersion uniformity of nanofillers and preventing agglomeration.

[0007] Further, in step S1, the molar ratio of terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol and trimethylolpropane is 1:(0.7~0.78):(0.2~0.3):(0.006~0.028):(0.003~0.015):(0.0014~0.0032).

[0008] By adopting the above technical solution and adjusting the molar ratio of polyols, a balance between the flexibility and rigidity of molecular chains can be achieved, effectively reducing the melting point while ensuring high viscosity and making it less prone to gel formation.

[0009] Further, in step S1, the mass ratio of terephthalic acid, nano-SiO2, pentaerythritol stearate, and polyethylene glycol is 1:(0.0014~0.0042):(0.0007~0.0023):(0.007~0.021); the catalyst is antimony glycolate, and the amount used is 0.02%~0.05% of the total mass of terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, and trimethylolpropane; the stabilizer is triphenyl phosphate, and the amount used is 0.08%~0.18% of the total mass of terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, and trimethylolpropane.

[0010] By adopting the above technical solution, antimony glycolate, as a catalyst, has high catalytic activity and few side reactions; triphenyl phosphate, as a stabilizer, can prevent the polymer from undergoing thermal oxidative degradation during high-temperature melting and prevent polyester yellowing; at this dosage, the material's color and molecular weight can be kept stable; at this dosage, substances such as nano-SiO2 have the best light transmittance and flowability, which can improve the overall performance of polyester.

[0011] Furthermore, in step S2, the esterification reaction temperature is 235~245℃ and the reaction time is 1.8~2.8h; in step S2, the polycondensation reaction temperature is 273~278℃.

[0012] By adopting the above technical solution, under the reaction temperature and time, the reaction is complete and there are few side reactions, thus obtaining high viscosity polyester.

[0013] Furthermore, the amount of modified hydroxyapatite used is 0.4% to 1.2% of the total mass of terephthalic acid, ethylene glycol, 1,4-cyclohexanediethanol, diethylene glycol, 2,2-dimethyl-1,3-propanediol and trimethylolpropane.

[0014] By adopting the above technical solution, at this dosage, the modified hydroxyapatite is evenly dispersed, which enables the polyester to have excellent UV resistance without affecting light transmittance and mechanical properties.

[0015] Furthermore, in step S1, the preparation method of modified hydroxyapatite includes the following steps: (1) Mix hydroxyapatite, KH550, ethanol and water evenly, adjust the pH value to 9~10, heat to 70~75℃ and react for 7~8h, centrifuge, wash and dry to obtain HAP-NH2; (2) HAP-NH2, 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether and xylene were mixed and reacted under nitrogen protection. The mixture was then centrifuged, precipitated, washed and dried to obtain modified hydroxyapatite.

[0016] By adopting the above technical solution, in step (1), under a weakly alkaline environment, the ethoxy group in KH550 undergoes hydrolysis and condenses with the hydroxyl group on the surface of hydroxyapatite, stably introducing an amino (-NH2) functional group, providing an active site for the subsequent reaction with benzotriazole, and ensuring the modification efficiency; in step (2), HAP-NH2 reacts with 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether to graft the anti-UV group onto the surface of hydroxyapatite, preventing it from agglomerating in the polyester melt and improving its dispersibility; the modified hydroxyapatite finally obtained can stably exert its anti-UV effect.

[0017] Furthermore, in step (1), the mass ratio of hydroxyapatite to KH550 is 1:(0.15~0.2).

[0018] By adopting the above technical solution, the grafting amount of KH550 is moderate, which can fully activate the surface without excessive self-aggregation.

[0019] Further, in step (2), the mass ratio of HAP-NH2 to 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether is 10:(2~5).

[0020] By adopting the above technical solution, the grafting is sufficient at this ratio, giving the polyester a long-lasting and efficient UV absorption capacity, and avoiding the problems of agglomeration or decreased light transmittance caused by excessive dosage.

[0021] Furthermore, in step (2), the reaction temperature is 90~110℃ and the reaction time is 9~12h.

[0022] By adopting the above technical solution, the grafting reaction is complete within the reaction temperature and time range, while not destroying the UV-resistant functional group structure of benzotriazole, and the modification effect is stable.

[0023] Secondly, the present invention provides a high-viscosity polyester chip prepared by the above-described preparation method.

[0024] By adopting the above technical solution, the obtained polyester chips have high viscosity, low melting point, high light transmittance, excellent UV resistance and good mechanical properties, wide range of applications and better processing performance.

[0025] In summary, the beneficial effects of this invention are: 1. This invention utilizes diethylene glycol and 2,2-dimethyl-1,3-propanediol to synergistically construct flexible segments, thereby disrupting the regularity of polyester molecular chains and lowering the melting point; it uses trimethylolpropane as a trace branched monomer to construct a sparse semi-branched structure, thereby increasing viscosity from the molecular chain entanglement level; and it combines pentaerythritol stearate, nano-SiO2, stabilizers, etc., to solve defects such as adhesion, haze increase, and thermal degradation in low-melting-point melt processing, thus improving polyester performance. 2. This invention performs two-step graft modification on hydroxyapatite, which significantly improves its compatibility and dispersibility in polyester and imparts stable UV protection. Attached Figure Description

[0026] Figure 1 This is a photograph of the high-viscosity polyester chips of this invention. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0029] Preparation Examples 1 to 4 Preparation Example 1 The preparation method of this example of modified hydroxyapatite includes the following specific steps: (1) 100g of hydroxyapatite (particle size 50~80nm), 400mL of ethanol and 45mL of water were ultrasonically dispersed for 10min to obtain mixture 1; 20g of KH550, 70mL of ethanol and 8mL of water were ultrasonically dispersed for 10min to obtain mixture 2; mixture 2 was added to mixture 1 and ultrasonically dispersed for 10min, and the pH was adjusted to 10. The mixture was heated to 70℃ and reacted for 8h, centrifuged, washed and vacuum dried at 80℃ for 10h to obtain HAP-NH2; (2) Disperse 50g HAP-NH2 with 350mL xylene by ultrasonication for 30min to obtain mixture 3; disperse 18g 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether with 120mL xylene by ultrasonication for 30min to obtain mixture 4; add mixture 4 to mixture 3 by ultrasonication for 10min, and react at 106℃ for 11h under nitrogen protection. Centrifuge, precipitate, wash, and vacuum dry at 60℃ for 24h to obtain modified hydroxyapatite.

[0030] Preparation Example 2 The preparation method of this example of modified hydroxyapatite includes the following specific steps: (1) 100g of hydroxyapatite (particle size 50~80nm), 400mL of ethanol and 45mL of water were ultrasonically dispersed for 10min to obtain mixture 1; 18g of KH550, 70mL of ethanol and 8mL of water were ultrasonically dispersed for 10min to obtain mixture 2; mixture 2 was added to mixture 1 and ultrasonically dispersed for 10min, and the pH was adjusted to 9. The mixture was heated to 75℃ and reacted for 8h, centrifuged, washed and vacuum dried at 80℃ for 10h to obtain HAP-NH2; (2) Disperse 50g HAP-NH2 with 350mL xylene by ultrasonication for 30min to obtain mixture 3; disperse 15g 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether with 120mL xylene by ultrasonication for 30min to obtain mixture 4; add mixture 4 to mixture 3 by ultrasonication for 10min, and react at 90℃ for 10h under nitrogen protection. Centrifuge, precipitate, wash, and vacuum dry at 60℃ for 24h to obtain modified hydroxyapatite.

[0031] Preparation Example 3 The preparation method of this example of modified hydroxyapatite includes the following specific steps: (1) 100g of hydroxyapatite (particle size 50~80nm), 400mL of ethanol and 45mL of water were ultrasonically dispersed for 10min to obtain mixture 1; 15g of KH550, 70mL of ethanol and 8mL of water were ultrasonically dispersed for 10min to obtain mixture 2; mixture 2 was added to mixture 1 and ultrasonically dispersed for 10min, and the pH was adjusted to 9. The mixture was heated to 73℃ and reacted for 8h, centrifuged, washed and vacuum dried at 80℃ for 10h to obtain HAP-NH2; (2) Disperse 50g HAP-NH2 with 350mL xylene by ultrasonication for 30min to obtain mixture 3; disperse 22g 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether with 120mL xylene by ultrasonication for 30min to obtain mixture 4; add mixture 4 to mixture 3 by ultrasonication for 10min, and react at 98℃ for 12h under nitrogen protection. Centrifuge, precipitate, wash, and vacuum dry at 60℃ for 24h to obtain modified hydroxyapatite.

[0032] Preparation Example 4 The preparation method of this example of modified hydroxyapatite includes the following specific steps: (1) 100g of hydroxyapatite (particle size 50~80nm), 400mL of ethanol and 45mL of water were ultrasonically dispersed for 10min to obtain mixture 1; 19g of KH550, 70mL of ethanol and 8mL of water were ultrasonically dispersed for 10min to obtain mixture 2; mixture 2 was added to mixture 1 and ultrasonically dispersed for 10min, and the pH was adjusted to 10. The mixture was heated to 75℃ and reacted for 7h, centrifuged, washed and vacuum dried at 80℃ for 10h to obtain HAP-NH2; (2) Disperse 50g HAP-NH2 with 350mL xylene by ultrasonication for 30min to obtain mixture 3; disperse 12g 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether with 120mL xylene by ultrasonication for 30min to obtain mixture 4; add mixture 4 to mixture 3 by ultrasonication for 10min, and react at 95℃ for 9h under nitrogen protection. Centrifuge, precipitate, wash, and vacuum dry at 60℃ for 24h to obtain modified hydroxyapatite.

[0033] Examples 1 to 5 Example 1 The specific steps of the method for preparing high-viscosity polyester chips in this embodiment are as follows: S1: Nitrogen gas is introduced into the polymerization reactor and purged for 30 minutes to ensure that no air remains in the reactor; 166.13g of terephthalic acid, 43.47g of ethylene glycol, 35.49g of 1,4-cyclohexanediol, 2.16g of diethylene glycol, 1.25g of 2,2-dimethyl-1,3-propanediol, and 0.25g of trimethylolpropane are added to the reactor in sequence; then 0.5618g of nano-SiO2, 0.167g of pentaerythritol stearate, 3.33g of polyethylene glycol, and 2g of the modified hydroxyapatite prepared in Preparation Example 2 are added respectively; the reactor is stirred at 400 r / min at room temperature for 30 minutes to obtain a slurry; S2: Weigh 0.087g of antimony glycolate, add 50% of it to the slurry prepared above, and stir for 10 min; turn on the heating device of the reactor, slowly raise the temperature to 235℃, maintain this temperature for 2 h, continuously introduce nitrogen gas during the esterification reaction, and promptly remove the water generated in the reaction; after the reaction, take a sample to test the esterification rate, ensuring that the esterification rate is ≥96%, and the esterification reaction is completed; add the remaining 50% of antimony glycolate to the reactor, then add 0.204g of triphenyl phosphate, and stir for 15 min; turn off the nitrogen gas supply, turn on the vacuum system, slowly evacuate to a vacuum degree ≤-0.095MPa, and slowly raise the temperature to 278℃; during the reaction, continuously stir and observe the change in melt viscosity; after the reaction, turn off the heating device and vacuum system, introduce nitrogen gas into the reactor to release the vacuum; cut into cylindrical particles with a size of 3mm×3mm; put the granulated polyester particles into a vacuum drying oven and vacuum dry at 80℃ for 4 h to obtain high-viscosity polyester chips.

[0034] Figure 1 This is a picture of a high-viscosity polyester chip product; for example... Figure 1 As shown, the polyester chips are cylindrical granules with no obvious clumping or yellowing, and have a uniform appearance.

[0035] Example 2 The specific steps of the method for preparing high-viscosity polyester chips in this embodiment are as follows: S1: Nitrogen gas is introduced into the polymerization reactor and purged for 30 minutes to ensure that no air remains in the reactor; 166.13g of terephthalic acid, 44.89g of ethylene glycol, 29.42g of 1,4-cyclohexanediol, 0.75g of diethylene glycol, 0.36g of 2,2-dimethyl-1,3-propanediol, and 0.43g of trimethylolpropane are added to the reactor in sequence; then 0.6645g of nano-SiO2, 0.3323g of pentaerythritol stearate, 1.329g of polyethylene glycol, and 1.2g of the modified hydroxyapatite prepared in Preparation Example 2 are added respectively; the reactor is stirred at 400 r / min at room temperature for 30 minutes to obtain a slurry; S2: Weigh 0.051g of antimony glycolate, add 55% of it to the slurry prepared above, and stir for 10 min; turn on the heating device of the reactor, slowly raise the temperature to 245℃, maintain this temperature for 1.8 h, continuously introduce nitrogen gas during the esterification reaction, and promptly remove the water generated in the reaction; after the reaction, take a sample to test the esterification rate, ensuring that the esterification rate is ≥96%, and the esterification reaction is completed; add the remaining 45% of antimony glycolate to the reactor, and then add 0.266g of triphenyl phosphate, and stir for 15 min; turn off the nitrogen gas supply, turn on the vacuum system, slowly evacuate to a vacuum degree ≤-0.095MPa, and slowly raise the temperature to 275℃; during the reaction, continuously stir and observe the change in melt viscosity; after the reaction, turn off the heating device and vacuum system, introduce nitrogen gas into the reactor to release the vacuum; cut into cylindrical particles with a size of 3mm×3mm; put the granulated polyester particles into a vacuum drying oven and vacuum dry at 80℃ for 4 h to obtain high-viscosity polyester chips.

[0036] Example 3 The specific steps of the method for preparing high-viscosity polyester chips in this embodiment are as follows: S1: Nitrogen gas is introduced into the polymerization reactor and purged for 30 minutes to ensure that no air remains in the reactor; 166.13g of terephthalic acid, 47.68g of ethylene glycol, 42.15g of 1,4-cyclohexanediol, 2.85g of diethylene glycol, 1.48g of 2,2-dimethyl-1,3-propanediol, and 0.2g of trimethylolpropane are added to the reactor in sequence; then 0.4153g of nano-SiO2, 0.2658g of pentaerythritol stearate, 2.1597g of polyethylene glycol, and 2.865g of the modified hydroxyapatite prepared in Preparation Example 1 are added respectively; the reactor is stirred at 400 r / min at room temperature for 30 minutes to obtain a slurry; S2: Weigh 0.122g of antimony glycolate, add 55% of it to the slurry prepared above, and stir for 10 min; turn on the heating device of the reactor, slowly raise the temperature to 243℃, maintain this temperature for 2.5 h, continuously introduce nitrogen gas during the esterification reaction, and promptly remove the water generated in the reaction; after the reaction, take a sample to test the esterification rate, ensuring that the esterification rate is ≥96%, and the esterification reaction is completed; add the remaining 45% of antimony glycolate to the reactor, and then add 0.338g of triphenyl phosphate, and stir for 15 min; turn off the nitrogen gas supply, turn on the vacuum system, slowly evacuate to a vacuum degree ≤-0.095MPa, and slowly raise the temperature to 273℃; during the reaction, continuously stir and observe the change in melt viscosity; after the reaction, turn off the heating device and vacuum system, introduce nitrogen gas into the reactor to release the vacuum; cut into cylindrical particles with a size of 3mm×3mm; put the granulated polyester particles into a vacuum drying oven and vacuum dry at 80℃ for 4 h to obtain high-viscosity polyester chips.

[0037] Example 4 The specific steps of the method for preparing high-viscosity polyester chips in this embodiment are as follows: S1: Nitrogen gas is introduced into the polymerization reactor and purged for 30 minutes to ensure that no air remains in the reactor; 166.13g of terephthalic acid, 45.12g of ethylene glycol, 40.45g of 1,4-cyclohexanediol, 1.64g of diethylene glycol, 0.92g of 2,2-dimethyl-1,3-propanediol, and 0.38g of trimethylolpropane are added to the reactor in sequence; then 0.3322g of nano-SiO2, 0.1993g of pentaerythritol stearate, 2.8242g of polyethylene glycol, and 1.91g of the modified hydroxyapatite prepared in Preparation Example 1 are added respectively; the reactor is stirred at 400 r / min at room temperature for 30 minutes to obtain a slurry; S2: Weigh 0.073g of antimony glycolate, add 50% of it to the slurry prepared above, and stir for 10 min; turn on the heating device of the reactor, slowly raise the temperature to 240℃, maintain this temperature for 2.5 h, continuously introduce nitrogen gas during the esterification reaction, and promptly remove the water generated in the reaction; after the reaction, take a sample to test the esterification rate, ensuring that the esterification rate is ≥96%, and the esterification reaction is completed; add the remaining 50% of antimony glycolate to the reactor, and then add 0.439g of triphenyl phosphate, and stir for 15 min; turn off the nitrogen gas supply, turn on the vacuum system, slowly evacuate to a vacuum degree ≤-0.095MPa, and slowly raise the temperature to 275℃; during the reaction, continuously stir and observe the change in melt viscosity; after the reaction, turn off the heating device and vacuum system, introduce nitrogen gas into the reactor to release the vacuum; cut into cylindrical particles with a size of 3mm×3mm; put the granulated polyester particles into a vacuum drying oven and vacuum dry at 80℃ for 4 h to obtain high-viscosity polyester chips.

[0038] Example 5 The specific steps of the method for preparing high-viscosity polyester chips in this embodiment are as follows: S1: Nitrogen gas is introduced into the polymerization reactor and purged for 30 minutes to ensure that no air remains in the reactor; 166.13g of terephthalic acid, 48.3g of ethylene glycol, 32.48g of 1,4-cyclohexanediol, 1.33g of diethylene glycol, 0.67g of 2,2-dimethyl-1,3-propanediol, and 0.31g of trimethylolpropane are added to the reactor in sequence; then 0.6312g of nano-SiO2, 0.3655g of pentaerythritol stearate, 3.1565g of polyethylene glycol, and 1.67g of the modified hydroxyapatite prepared in Preparation Example 2 are added respectively; the reactor is stirred at 400 r / min at room temperature for 30 minutes to obtain a slurry; S2: Weigh 0.105g of antimony glycolate, add 50% of it to the slurry prepared above, and stir for 10 min; turn on the heating device of the reactor, slowly raise the temperature to 245℃, maintain this temperature for 2.2 h, continuously introduce nitrogen gas during the esterification reaction, and promptly remove the water generated in the reaction; after the reaction, take a sample to test the esterification rate, ensuring that the esterification rate is ≥96%, and the esterification reaction is completed; add the remaining 50% of antimony glycolate to the reactor, then add 0.25g of triphenyl phosphate, and stir for 15 min; turn off the nitrogen gas supply, turn on the vacuum system, slowly evacuate to a vacuum degree ≤-0.095MPa, and slowly raise the temperature to 276℃; during the reaction, continuously stir and observe the change in melt viscosity; after the reaction, turn off the heating device and vacuum system, introduce nitrogen gas into the reactor to release the vacuum; cut into cylindrical particles with a size of 3mm×3mm; place the granulated polyester particles in a vacuum drying oven and vacuum dry at 80℃ for 4 h to obtain high-viscosity polyester chips.

[0039] Comparative Example 1 The difference from Example 1 is that: This comparative example is a polyester chip without modified hydroxyapatite, and all other aspects are the same as in Example 1.

[0040] Comparative Example 2 The difference from Example 1 is that: In this comparative example, a polyester chip was prepared by replacing the modified hydroxyapatite with an equal amount of unmodified hydroxyapatite, and all other aspects were the same as in Example 1.

[0041] Comparative Example 3 This comparative example is a polyester chip without added polyethylene glycol, and all other aspects are the same as in Example 1.

[0042] Comparative Example 4 This comparative example is a polyester chip without the addition of trimethylolpropane, and all other aspects are the same as in Example 1.

[0043] Comparative Example 5 This comparative example uses a polyester chip made from a conventional terephthalic acid-ethylene glycol-1,4-cyclohexanediethanol polyester system, without the addition of diethylene glycol, 2,2-dimethyl-1,3-propanediol, or trimethylolpropane, and otherwise identical to that in Example 1.

[0044] Related performance tests The polyester chips prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were subjected to relevant performance tests in accordance with GB / T 14190-2017 and GB / T 2410-2008.

[0045] Table 1 Test Results

[0046] The polyester chips prepared in Examples 1 to 5 of this invention have an intrinsic viscosity of ≥0.78 dL / g, a melting point of 187~192℃, and a light transmittance of ≥90%, achieving high viscosity, low melting point, and high light transmittance.

[0047] Comparing Comparative Example 1 with Example 1, it can be seen that Comparative Example 1 has similar viscosity, melting point, and light transmittance to Example 1, but it has virtually no UV resistance and poor weather resistance.

[0048] Comparing Comparative Example 2 with Example 1, it can be seen that the unmodified hydroxyapatite has poor dispersion, increased haze, and decreased light transmittance.

[0049] Comparing Comparative Example 3 with Example 1, it can be seen that the optical properties do not change much, but the melt flowability is worse, and melt fracture is more likely to occur during processing.

[0050] Comparing Comparative Example 4 with Example 1, it can be seen that the polyester molecular chain has an unbranched structure, the viscosity is significantly lower, the melting point is higher, and the high viscosity and low melting point effect cannot be achieved.

[0051] Comparing Comparative Example 5 with Example 1, it can be seen that without the synergistic effect of monomers such as diethylene glycol, the polyester has a higher melting point and lower viscosity, which cannot meet the requirements of high viscosity and low melting point.

[0052] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing high-viscosity polyester chips, characterized in that, Includes the following steps: S1: Under nitrogen protection, terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, trimethylolpropane, nano-SiO2, pentaerythritol stearate, polyethylene glycol and modified hydroxyapatite are mixed evenly to obtain a slurry. S2: Mix the slurry with 50%~55% catalyst for esterification reaction; add the remaining 45%~50% catalyst and stabilizer for polycondensation reaction, and then perform post-treatment to obtain high-viscosity polyester chips. In step S1, the preparation method of the modified hydroxyapatite includes the following steps: (1) Mix hydroxyapatite, KH550, ethanol and water evenly, adjust the pH value to 9~10, heat to 70~75℃ and react for 7~8h, centrifuge, wash and dry to obtain HAP-NH2; (2) HAP-NH2, 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether and xylene were mixed and reacted under nitrogen protection. The mixture was then centrifuged, precipitated, washed and dried to obtain modified hydroxyapatite.

2. The method for preparing high-viscosity polyester chips according to claim 1, characterized in that, In step S1, the molar ratio of terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol and trimethylolpropane is 1:(0.7~0.78):(0.2~0.3):(0.006~0.028):(0.003~0.015):(0.0014~0.0032).

3. The method for preparing high-viscosity polyester chips according to claim 1, characterized in that, In step S1, the mass ratio of terephthalic acid, nano-SiO2, pentaerythritol stearate, and polyethylene glycol is 1:(0.0014~0.0042):(0.0007~0.0023):(0.007~0.021); the catalyst is antimony glycolate, and the amount used is 0.02%~0.05% of the total mass of terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, and trimethylolpropane; the stabilizer is triphenyl phosphate, and the amount used is 0.08%~0.18% of the total mass of terephthalic acid, ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, and trimethylolpropane.

4. The method for preparing high-viscosity polyester chips according to claim 1, characterized in that, In step S2, the esterification reaction temperature is 235~245℃ and the reaction time is 1.8~2.8h; in step S2, the polycondensation reaction temperature is 273~278℃.

5. The method for preparing high-viscosity polyester chips according to claim 1, characterized in that, The modified hydroxyapatite is used in an amount of 0.4% to 1.2% of the total mass of terephthalic acid, ethylene glycol, 1,4-cyclohexanediethanol, diethylene glycol, 2,2-dimethyl-1,3-propanediol and trimethylolpropane.

6. The method for preparing high-viscosity polyester chips according to claim 1, characterized in that, In step (1), the mass ratio of hydroxyapatite to KH550 is 1:(0.15~0.2).

7. The method for preparing high-viscosity polyester chips according to claim 1, characterized in that, In step (2), the mass ratio of HAP-NH2 to 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole-5-yl-epoxypropyl ether is 10:(2~5).

8. The method for preparing high-viscosity polyester chips according to claim 1, characterized in that, In step (2), the reaction temperature is 90~110℃ and the reaction time is 9~12h.

9. A high-viscosity polyester chip, characterized in that, It is prepared by any one of claims 1 to 8.

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