High-heat-resistance bottle-grade polyester chip and preparation method thereof

Abstract

The invention discloses a high-heat-resistance bottle-grade polyester chip and a preparation method thereof, and belongs to the technical field of polyester materials. The invention aims to solve the problems of reduced processing adaptability, degraded transparency and insufficient dimensional stability caused by improvement of heat resistance in the prior art. The polyester chip is prepared by taking purified terephthalic acid and ethylene glycol as main monomers, introducing modified phosphate and citric acid, and carrying out multi-stage esterification-polycondensation and solid-phase tackifying, wherein the modified phosphate is chemically bonded with cyclodextrin through triphenyl phosphate and KH-550 to form a structure with thermal stability, interfacial compatibility and migration inhibition functions. According to the scheme, high transparency, good melt flowability and bottle blowing efficiency are kept, the vicat softening point and crystallization controllability are remarkably improved, and collaborative optimization of high heat resistance and comprehensive processing performance is achieved.

Description

Technical Field

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

[0002] Polyethylene terephthalate (PET), as the most widely used thermoplastic polyester material in the food packaging field, dominates the market for single-use or reusable packaging products such as beverage bottles and edible oil containers due to its excellent mechanical properties, gas barrier properties, and recyclability. However, with consumers' increasing demands for beverage quality and safety, especially with the widespread adoption of hot-fill technology in the production of juices, tea drinks, and functional beverages, conventional bottle-grade PET, due to its relatively low glass transition temperature (typically around 78°C), is prone to significant deformation during high-temperature filling processes above 90°C. This can lead to bottle collapse, seal failure, and even contamination of the contents, severely restricting its application expansion in the high-end hot-fill market.

[0003] Patent CN115260465A discloses a method for preparing rapidly crystallizing polyester chips. This method involves dispersing inorganic nucleating agents (such as talc and calcium carbonate) in ethylene glycol after surface modification with a coupling agent, followed by esterification and polycondensation reactions with terephthalic acid and ethylene glycol, thereby obtaining polyester chips with a relatively fast crystallization rate. While this method improves crystallization efficiency to some extent and helps shorten the molding cycle, the inorganic nucleating agents used, even after surface treatment, still tend to agglomerate during high-shear melt processing, easily leading to increased haze and decreased transparency in the final product. Furthermore, this technology does not effectively control the bottle shrinkage problem caused by "post-crystallization" after hot filling, which may affect the dimensional stability and sealing reliability of the bottle.

[0004] In summary, while existing technologies improve the heat resistance of bottle-grade polyester chips, they often fall short in terms of processing adaptability, optical properties, dimensional stability, or cost control. There is still a lack of a method for producing bottle-grade polyester chips that can synergistically achieve high heat resistance, good crystallization controllability, excellent transparency, and dimensional accuracy, as well as an efficient preparation method thereof. Summary of the Invention

[0005] The purpose of this invention is to provide a high heat-resistant bottle-grade polyester chip and its preparation method. The high heat-resistant bottle-grade polyester chip prepared by the provided method solves the problem of insufficient heat resistance of polyethylene terephthalate.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, a method for preparing high heat-resistant bottle-grade polyester chips includes the following steps: S1.0: Preparation of modified phosphate ester; S2.0: Purified terephthalic acid and ethylene glycol are subjected to esterification or transesterification in the presence of tetrabutyl titanate; then the modified phosphate ester and citric acid obtained in step S1.0 are added, and a pre-condensation reaction is carried out under pressure to obtain the first composite. S3.0: The first composite is subjected to a first-stage polycondensation reaction under reduced pressure and increased temperature until the intrinsic viscosity of the melt reaches 0.35~0.45 dL / g, to obtain the second composite. S4.0: The second composite is subjected to a second-stage polycondensation reaction under further reduced pressure and increased temperature until the intrinsic viscosity of the melt reaches 0.60~0.65 dL / g, to obtain the third composite. S5.0: After drying the third composite, a solid-state polycondensation reaction is carried out to increase the intrinsic viscosity of the melt to 0.82~0.85 dL / g. Then, it is cooled and sliced ​​to obtain the high heat-resistant bottle-grade polyester chips.

[0007] The core of this preparation method lies in the synergistic effect of multi-stage polycondensation and functional modified phosphate esters to achieve enhanced rigidity and improved thermal stability of the polyester backbone. The key innovation in S1.0 is the preparation of modified phosphate esters, whose molecular design aims to introduce supramolecular structural units: the phosphate ester groups can undergo esterification with the polyester terminal hydroxyl groups, directly embedding into the backbone to form covalent bonds; while the modified silane-cyclodextrin composite structure inhibits chain segment thermal motion through physical entanglement and hydrogen bond networks. In S2.0, the esterification or transesterification reaction is completed under the catalysis of tetrabutyl titanate. This catalyst was chosen based on its high activity and low residue characteristics, avoiding the thermal degradation risk caused by traditional antimony-based catalysts. In the subsequent pre-polymerization stage, modified phosphate esters and citric acid (as side reaction inhibitors) are added. Pressure conditions are used to maintain the timely removal of small molecule byproducts, preventing reverse reactions, while ensuring the uniform dispersion of the modified phosphate esters and their participation in backbone construction. The stepped decompression polymerization design of S3.0 and S4.0 essentially utilizes vacuum gradients to control reaction kinetics: the first stage uses moderate decompression (5 kPa) to promote oligomer chain growth to moderate viscosity (0.35~0.45 dL / g), avoiding premature gelation; the second stage uses high vacuum (100 Pa) to accelerate the formation of high molecular weight polyester, and when the viscosity increases to 0.60~0.65 dL / g, the main chain rigidity is significantly enhanced, laying the foundation for solid-phase polycondensation. S5.0 solid-phase polycondensation eliminates moisture interference through drying pretreatment, and the nitrogen atmosphere and gradient temperature rise (170℃ to 190~200℃) of the fluidized bed reactor achieve chain-end diffusion control, precisely increasing the viscosity to 0.82~0.85 dL / g. This range corresponds to the balance point between crystallinity and heat resistance of bottle-grade polyester—too low a temperature results in insufficient heat deformation temperature, while too high a temperature deteriorates processing fluidity.

[0008] Furthermore, the preparation process of the modified phosphate ester in step S1.0 includes the following steps: S1.1: Triphenyl phosphate, ethylene glycol and deionized water are mixed and stirred, and then heated to 45~50℃ and stirred to continue the reaction to obtain the first modified solution; S1.2: Add silane coupling agent KH-550 to the first modified solution, stir and adjust the pH of the system to 4.5~5.5, then heat to 65~75℃ and continue stirring to obtain the second modified solution; S1.3: Add cyclodextrin to the second modified solution, cool to 35~40℃ and stir to react, then perform vacuum distillation to obtain the modified phosphate ester.

[0009] The modified phosphate ester is not a traditional flame retardant or heat stabilizer. Instead, it is produced by a partial transesterification reaction between triphenyl phosphate and ethylene glycol in a weakly acidic aqueous environment, generating a hydroxyl-containing phosphate ester intermediate. Subsequently, a silane coupling agent, KH-550, is introduced. Under weakly acidic conditions (pH 4.5-5.5), its amino groups condense with the hydroxyl groups in the phosphate ester, forming an organic hybrid structure containing silicon-oxygen-phosphorus bonds. Finally, cyclodextrin is introduced, utilizing its cavity structure to encapsulate the hydrophobic segments of the phosphate ester. Simultaneously, a large number of hydroxyl groups on its outer surface form a hydrogen bond network with the residual amino groups of the silane coupling agent or the hydroxyl groups of the phosphate ester, constructing a supramolecular modified phosphate ester with a "core-shell" structure. This modified phosphate ester can serve as a functional copolymer unit in subsequent polycondensation processes. It embeds itself into the main chain through esterification of its phosphate ester groups with the terminal hydroxyl groups of purified terephthalic acid. The silane structure provides steric hindrance, while the cyclodextrin regulates the local chain segment mobility through physical entanglement, thereby synergistically improving the glass transition temperature and thermal deformation stability of the material.

[0010] Furthermore, in step S1.1, the weight ratio of triphenyl phosphate, ethylene glycol and deionized water is (0.9-1.0):5:(0.1-0.2); the stirring speed is 200 r / min, the initial stirring is 10 min, and the stirring continues for 1-2 h after heating.

[0011] An excess of ethylene glycol promotes the forward transesterification process, while the water content is controlled at 0.1–0.2 parts to provide trace amounts for catalytic hydrolysis. However, excessive water will cause triphenyl phosphate to hydrolyze into phosphoric acid; a rotation speed of 200 r / min ensures that the renewal rate of the two-phase interface matches the reaction kinetics, 10 min of initial stirring eliminates the local concentration gradient, and 1-2 h of reaction time after heating covers the transesterification half-life to avoid incomplete reaction.

[0012] Furthermore, in step S1.2, the amount of silane coupling agent KH-550 added is 0.4~0.6 parts by weight; the stirring speed after addition is 150 r / min, and the time is 5 min; the pH value of the system is adjusted using acetic acid or ammonia; and stirring is continued at 150 r / min at 65~75℃ for 2~4 h.

[0013] The dosage of KH-550 is 0.4~0.6 parts, corresponding to a hydroxyl molar ratio of 0.8:1 for the phosphate ester, ensuring sufficient grafting of silane without self-polymerization; a low rotation speed of 150 r / min maintains shear force in the laminar flow zone, and short stirring for 5 min only promotes dispersion; pH 4.5~5.5 precisely corresponds to the silane hydrolysis-condensation equilibrium point, and acetic acid / ammonia water adjustment avoids strong acid and strong base damage to the phosphate ester; the reaction temperature of 65~75℃ meets the silane condensation activation energy, and the time of 2~4 h covers the condensation reaction order.

[0014] Furthermore, in step S1.3, the amount of cyclodextrin added is 2.5~3.0 parts by weight; the mixture is stirred at 100 r / min at 35~40℃ for 8~12 h; and the vacuum distillation is carried out at 55℃ for 3 h.

[0015] Excessive cyclodextrin will lead to the precipitation of free cyclodextrin; stirring at low temperature of 35~40℃ to match the cyclodextrin envelope kinetics, and 8~12h time to ensure the establishment of envelope equilibrium; vacuum distillation at 55℃ to selectively remove volatile components under low pressure by utilizing the boiling point difference between ethylene glycol and water, thus avoiding thermal decomposition of cyclodextrin.

[0016] Furthermore, the esterification or transesterification reaction in step S2.0 specifically includes: drying purified terephthalic acid at 120~130℃ for 4~6h to obtain pretreated purified terephthalic acid; mixing the pretreated purified terephthalic acid with ethylene glycol, stirring at 80r / min for 20min under nitrogen protection, then raising the temperature to 220~230℃, adding tetrabutyl titanate, continuing to stir at 80r / min for 30min, then raising the temperature to 250~260℃, maintaining this temperature and stirring the reaction for 1~2h.

[0017] Excessive temperature will trigger decarboxylation of carboxyl groups; nitrogen atmosphere prevents glycol oxidation; rotation speed of 80 r / min maintains slurry uniformity; esterification temperature of 220~230℃ matches the reaction temperature of PTA and EG, reaction at 250~260℃ for 1~2h covers the complete esterification time, and the dosage of tetrabutyl titanate of 0.002~0.004 parts is at the catalytic threshold.

[0018] Furthermore, the pre-condensation reaction in step S2.0 specifically includes: after esterification or transesterification, adding the modified phosphate ester and citric acid obtained in step S1.0, adjusting the system pressure to 0.2 MPa, and continuing to stir the reaction at a speed of 80 r / min for 4 to 6 hours to obtain the first composite.

[0019] Pressurization of 0.2 MPa inhibits water vaporization and promotes the forward polycondensation; rotation speed of 80 r / min ensures uniform mass transfer of the melt; reaction time of 4~6 h corresponds to the formation window of prepolymer intrinsic viscosity of 0.2~0.3 dL / g. If the reaction time is too short, the end group conversion rate will be insufficient, and if it is too long, thermal degradation will occur.

[0020] Furthermore, the weight ratio of purified terephthalic acid, ethylene glycol, tetrabutyl titanate, modified phosphate ester and citric acid is 10:(3.4~3.6):(0.002~0.004):(0.035~0.04):(0.01~0.012).

[0021] EG excess compensates for volatilization loss; tetrabutyl titanate catalyst amount is accurate to ppm level to avoid coloring; 0.035~0.04 parts of modified phosphate ester ensures that 1~2 modified units are embedded for every 100 repeating units; 0.01~0.012 parts of citric acid are used as chain terminators to control molecular weight distribution.

[0022] Further, step S3.0 specifically involves: transferring the first composite to a twin-screw stirrer, reducing the absolute pressure of the system to 5 kPa, and stirring at 260-270°C at a speed of 12 r / min for 60-90 min until the intrinsic viscosity of the melt reaches 0.35-0.45 dL / g, thereby obtaining the second composite.

[0023] 5 kPa absolute pressure effectively removes polycondensation byproducts; 260-270℃ temperature balances reaction rate and thermal stability; 12 r / min low rotation speed adapts to high viscosity melts and avoids shear heat generation; 60-90 min time covers the intrinsic viscosity range of 0.35-0.45 dL / g, which ensures controllable melt flowability and chain growth.

[0024] Further, step S4.0 specifically involves: transferring the second composite into a cage stirrer, further reducing the absolute pressure of the system to 100 Pa, and stirring at 278~282℃ at a speed of 5 r / min for 120~180 min until the intrinsic viscosity of the melt reaches 0.60~0.65 dL / g, thereby obtaining the third composite.

[0025] A 100Pa high vacuum keeps the boiling point of water below -10℃, completely eliminating small molecules; the temperature selection of 278~282℃ is based on the melting point and thermal decomposition critical point of polyester, in which the molecular chain diffusion ability is strongest; an ultra-low rotation speed of 5r / min prevents the high-viscosity melt from breaking; and the time is precisely controlled from 120 to 180min to achieve an intrinsic viscosity of 0.60~0.65dL / g.

[0026] Further, step S5.0 specifically includes: drying the third composite at 140~150℃ and 5KPa absolute pressure for 8~10h, then placing it in a fluidized bed reactor, and holding it at 170℃ for 2h under nitrogen protection with a gas flow rate of 1.0m / s, and then raising the temperature to 190~200℃ for solid-phase polycondensation for 10~14h.

[0027] Drying at 140~150℃ / 5KPa eliminates residual moisture and avoids high-temperature hydrolysis; a fluidized bed with a gas velocity of 1.0m / s ensures uniform particle suspension; holding at 170℃ for 2h improves crystallinity and provides a thermally stable framework for subsequent high-temperature polycondensation; polycondensation at 190~200℃ for 10~14h covers the chain-end diffusion control stage, and when the viscosity increases to 0.82~0.85dL / g, the crystallinity and molecular weight reach the bottle-grade standard.

[0028] In a second aspect, the present invention provides a high heat-resistant bottle-grade polyester chip, obtained by the preparation method described in any embodiment of the first aspect.

[0029] The beneficial effects of this invention are: (1) The key innovation of this invention lies in the molecular design of the modified phosphate ester and its multifunctional synergistic mechanism in the polymerization system. The triphenyl phosphate structure in the modified phosphate ester provides thermal degradation inhibition. Its phosphorus element can capture free radicals and promote the formation of carbon layers at high temperatures, thereby delaying the main chain breakage. The silane coupling agent KH-550 introduces an aminosiloxane group on the phosphate ester molecule through hydrolysis condensation reaction. This group forms hydrogen bonds with the polyester carbonyl group, which significantly improves the interfacial bonding force between the modifier and the polyester matrix and effectively prevents migration and precipitation during high-temperature processing. The cyclodextrin encapsulates the small phosphate ester molecules through its hydrophobic cavity, forming a steric barrier, which further inhibits its thermal volatilization and catalytic side reaction activity. At the same time, the hydroxyl groups on the outer wall of the cyclodextrin can participate in the transesterification reaction to achieve covalent anchoring, fundamentally solving the problem of poor compatibility of traditional phosphorus-containing additives.

[0030] (2) In the preparation method provided by this invention, the efficient catalysis of tetrabutyl titanate in the esterification or transesterification reaction stage ensures the full conversion of raw materials and avoids the risk of thermal degradation caused by traditional catalysts. The subsequent pressurized pre-condensation conditions not only remove small molecule byproducts in time to prevent reverse reaction, but also ensure the uniform dispersion of modified phosphate ester and its deep integration with polyester end groups. At the same time, the introduction of citric acid effectively inhibits the side reaction activity. The step-by-step decompression polycondensation process, through the precise design of the vacuum gradient, promotes the controllable growth of oligomer chains in the first stage with medium decompression, avoiding premature gelation to maintain melt fluidity. The second stage with high vacuum accelerates the formation of high molecular weight polyester, significantly enhancing the rigidity of the main chain and laying the structural foundation for subsequent processes. Finally, the drying treatment before solid-phase polycondensation completely eliminates moisture interference. Combined with the chain end diffusion control mechanism of gradient heating, the molecular weight is precisely controlled to the ideal range, which not only optimizes the crystallization kinetics, enabling the material to achieve rapid and uniform crystal growth in blow molding and effectively suppressing the increase of haze, but also ensures the best balance between processing fluidity and thermal stability.

[0031] (3) The polyester chips described in this invention exhibit rapid and uniform crystallization behavior during blow molding. Since the modified phosphate ester has both nucleation induction and crystallization regulation functions, it can provide a large number of heterogeneous nucleation sites in the early stage of melt cooling, which promotes the orderly growth of crystals in a short time and avoids stress concentration and haze increase caused by local overcooling; at the same time, the presence of cyclodextrin inclusion structure limits excessive grain growth, thereby ensuring that the haze of the product is less than 1.5%. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0033] Example 1

[0034] This embodiment provides a high heat-resistant bottle-grade polyester chip, which is prepared through the following steps: S1.0: Preparation of modified phosphate esters: S1.1: Mix 0.9 parts by weight of triphenyl phosphate, 5 parts by weight of ethylene glycol and 0.1 parts by weight of deionized water, stir at 200 r / min for 10 min, then heat to 45℃ and continue stirring at the same speed for 1 h to obtain the first modified solution; S1.2: Add 0.4 parts by weight of silane coupling agent KH-550 to the first modified solution, stir at 150 r / min for 5 min, then adjust the pH of the system to 4.5 with acetic acid or ammonia, then heat to 65℃ and continue stirring at 150 r / min for 2 h to obtain the second modified solution. S1.3: Add 2.5 parts by weight of β-cyclodextrin to the second modified solution, cool to 35°C, stir at 100 r / min for 8 h, and then perform vacuum distillation at 55°C for 3 h to remove residual water and low-boiling point byproducts in the system to obtain modified phosphate ester. S2.0: 10 parts by weight of purified terephthalic acid were dried at 120°C for 4 hours to obtain pretreated purified terephthalic acid; the pretreated purified terephthalic acid was mixed with 3.4 parts by weight of ethylene glycol and stirred at 80 r / min for 20 minutes under a nitrogen atmosphere. Then the temperature was raised to 220°C, 0.002 parts by weight of tetrabutyl titanate was added, and the mixture was stirred at 80 r / min for 30 minutes. The temperature was then raised to 250°C, maintained, and stirred for 1 hour. Then 0.035 parts by weight of the modified phosphate ester obtained in step S1.0 and 0.01 parts by weight of citric acid were added, the system pressure was adjusted to 0.2 MPa, and the mixture was stirred at 80 r / min for 4 hours to obtain the first composite. S3.0: Transfer the first composite to a twin-screw stirrer, reduce the absolute pressure of the system to 5 kPa, and stir at 260°C and 12 r / min for 60 min until the intrinsic viscosity of the melt reaches 0.35 dL / g to obtain the second composite. S4.0: Transfer the second composite to a cage stirrer, further reduce the absolute pressure of the system to 100 Pa, and stir at 278 °C and 5 r / min for 120 min until the intrinsic viscosity of the melt reaches 0.60 dL / g to obtain the third composite. S5.0: After drying the third composite at 140℃ and 5KPa absolute pressure for 8h, it is placed in a fluidized bed reactor and held at 170℃ for 2h under a nitrogen protective atmosphere with a gas flow rate of 1.0m / s. Then, it is heated to 195℃ and held for solid-phase polycondensation for 10h to increase the intrinsic viscosity of the melt to 0.82dL / g. Subsequently, it is cooled to 80℃ and slicing is performed to obtain high heat-resistant bottle-grade polyester chips.

[0035] Example 2

[0036] The difference between this embodiment and Embodiment 1 is that: In the preparation of modified phosphate ester, step S1.3 uses 2.7 parts by weight of α-cyclodextrin, and the rest is the same as in Example 1; in the preparation of polyester chips, 0.036 parts by weight of modified phosphate ester is added in step S2.0, and the solid-state polycondensation temperature in step S5.0 is 190℃ and held for 14 hours; the remaining raw materials and preparation process are the same as in Example 1.

[0037] Example 3

[0038] The difference between this embodiment and Embodiment 1 is that: In the preparation of modified phosphate ester, S1.1 used 0.92 parts by weight of triphenyl phosphate and 0.12 parts by weight of deionized water, S1.2 used 0.55 parts by weight of silane coupling agent KH-550, and the pH was adjusted to 4.8. The rest was the same as in Example 1. In the preparation of polyester chips, the reaction time of S3.0 was 80 min, the temperature of S4.0 was 279℃, and the rest of the raw materials and preparation process were the same as in Example 1.

[0039] Example 4

[0040] The difference between this embodiment and Embodiment 1 is that: In the preparation of modified phosphate ester, S1.3 used 3.0 parts by weight of γ-cyclodextrin, and the rest was the same as in Example 1; in the preparation of polyester chips, S2.0 used 0.012 parts by weight of citric acid, and the solid-state polycondensation temperature of S5.0 was 200℃ for 10h, and the rest of the raw materials and preparation process were the same as in Example 1.

[0041] Example 5

[0042] This embodiment provides a high heat-resistant bottle-grade polyester chip, which is prepared through the following steps: S1.0: Preparation of modified phosphate esters: S1.1: Mix 1.0 parts by weight of triphenyl phosphate, 5 parts by weight of ethylene glycol and 0.2 parts by weight of deionized water, stir at 200 r / min for 10 min, then heat to 50℃ and continue stirring at the same speed for 2 h to obtain the first modified solution; S1.2: Add 0.6 parts by weight of silane coupling agent KH-550 to the first modified solution, stir at 150 r / min for 5 min, then adjust the pH of the system to 5.5 with acetic acid or ammonia, then heat to 75℃ and continue stirring at 150 r / min for 4 h to obtain the second modified solution. S1.3: Add 3.0 parts by weight of cyclodextrin to the second modified solution, cool to 40°C, stir at 100 r / min for 12 h, and then perform vacuum distillation at 55°C for 3 h to remove residual water and low-boiling point byproducts in the system to obtain modified phosphate ester. S2.0: 10 parts by weight of purified terephthalic acid were dried at 130℃ for 6 hours to obtain pretreated purified terephthalic acid; the pretreated purified terephthalic acid was mixed with 3.6 parts by weight of ethylene glycol and stirred at 80 r / min for 20 minutes under a nitrogen atmosphere. Then the temperature was raised to 230℃, 0.004 parts by weight of tetrabutyl titanate was added, and the mixture was stirred at 80 r / min for 30 minutes. The temperature was then raised to 260℃, maintained, and stirred for 2 hours. Then 0.04 parts by weight of the modified phosphate ester obtained in step S1.0 and 0.012 parts by weight of citric acid were added, the system pressure was adjusted to 0.2 MPa, and the mixture was stirred at 80 r / min for 6 hours to obtain the first composite. S3.0: Transfer the first composite to a twin-screw stirrer, reduce the absolute pressure of the system to 5 kPa, and stir at 270°C and 12 r / min for 90 min until the intrinsic viscosity of the melt reaches 0.35~0.45 dL / g to obtain the second composite. S4.0: Transfer the second composite to a cage stirrer, further reduce the absolute pressure of the system to 100 Pa, and stir at 282 °C at a speed of 5 r / min for 180 min until the intrinsic viscosity of the melt reaches 0.60~0.65 dL / g to obtain the third composite. S5.0: After drying the third composite at 140~150℃ and 5KPa absolute pressure for 8~10h, it is placed in a fluidized bed reactor and heated at 170℃ for 2h in a nitrogen protective atmosphere with a gas flow rate of 1.0m / s. Then, it is heated to 200℃ and held for solid-phase polycondensation for 14h to increase the intrinsic viscosity of the melt to 0.85dL / g. Finally, it is cooled to 80℃ and slicing is performed to obtain high heat-resistant bottle-grade polyester chips.

[0043] Comparative Example 1

[0044] The difference between this comparative example and Example 5 is as follows: The modified phosphate ester in Example 5 was removed, while the remaining raw materials and preparation process remained the same as in Example 1.

[0045] Comparative Example 2

[0046] The difference between this comparative example and Example 1 is that: The modified phosphate ester in Example 5 was replaced with triphenyl phosphate, while the remaining raw materials and preparation process remained the same as in Example 1.

[0047] Comparative Example 3

[0048] The difference between this comparative example and Example 1 is that: The modified phosphate ester in Example 5 was removed, and 0.6 parts by weight of silane coupling agent KH-550 was added. The remaining raw materials and preparation process were the same as in Example 1.

[0049] Comparative Example 4

[0050] The difference between this comparative example and Example 1 is that: Modified phosphate ester was obtained by stirring 1 part by weight of triphenyl phosphate, 0.6 parts by weight of silane coupling agent KH-550 and 3 parts by weight of γ-cyclodextrin at a speed of 100 r / min for 2 h. The remaining raw materials and preparation process were the same as in Example 1.

[0051] Performance testing

[0052] Performance tests were conducted on the embodiments and comparative examples, with the specific items as follows: 1. Intrinsic viscosity (Ⅳ): Measured at 25±0.05℃ using phenol / tetrachloroethane (1:1 mass ratio) as solvent; 2. Vicat softening point (VST): determined using the A50 method (10 N load, heating rate 50℃ / h); 3. Haze: The slices were injection molded into transparent plates with a thickness of 1.0 mm and measured in accordance with GB / T 2410-2008; 4. Hot filling simulated deformation rate: The slices were blown into 500 mL standard beverage bottles, filled in 95℃ hot water and left to stand for 30 min. The change in bottle shoulder height and the depth of bottle bottom concavity were measured, and the axial shrinkage rate (%) was calculated. 5. Melt Flow Rate (MFR): Determined according to GB / T 3682.1-2018 at 275℃ and 2.16 kg load; 6. Yellowness Index (YI): Measured according to ASTM E313, using a D65 light source and a 10° viewing angle for injection molded boards; 7. Terminal carboxyl group content (ECG): determined by titration according to GB / T 14190-2017; 8. Crystallization half-life (T) 1 / 2 Differential scanning calorimetry (DSC) was used to cool the sample to 180℃ for isothermal crystallization at a rate of 20℃ / min, and the time required for the exothermic peak of crystallization to reach half of its maximum value was recorded. The results are shown in Table 1: Table 1

[0053] As shown in Table 1, Examples 1 to 5 all meet the technical requirements of Vicat softening point ≥88℃, haze <1.5%, and axial shrinkage <1.0%. Furthermore, with the optimization of the proportions of each component in the modified phosphate ester and the upgrading of the cyclodextrin type, the overall performance shows a gradient improvement trend. In contrast, Comparative Example 1, lacking modified phosphate ester, exhibits significantly insufficient heat resistance; Comparative Example 2, while improving heat resistance, suffers from excessive haze, indicating that the unmodified phosphate ester induces phase separation; Comparative Example 3, using the additive alone, fails to achieve a synergistic effect; and the physical mixture system of Comparative Example 4, lacking chemical bonding, still suffers from interfacial defects, resulting in higher haze and shrinkage.

[0054] In summary, this invention successfully achieves a balance between high heat resistance, high transparency, low shrinkage, and good processability by constructing a modified phosphate ester with a dual inclusion-bonding stabilization mechanism and coupling it with a titanium-citric acid catalytic stabilization system and a three-stage viscosity control process. This solves the fundamental contradictions mentioned in the background art and has outstanding substantive features and significant progress.

[0055] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A process for the production of a high heat resistant bottle grade polyester chip, characterized by, The method comprises the following steps: S1.0: preparing modified phosphate ester; S2.0: performing esterification or transesterification reaction on purified terephthalic acid and ethylene glycol in the presence of tetrabutyl titanate; then adding the modified phosphate ester obtained in step S1.0 and citric acid, and performing pre-polycondensation reaction under pressurized conditions to obtain a first compound; S3.0: performing first-stage polycondensation reaction on the first compound under reduced pressure and temperature rising conditions until the melt intrinsic viscosity reaches 0.35-0.45 dL / g, to obtain a second compound; S4.0: performing second-stage polycondensation reaction on the second compound under further reduced pressure and temperature rising conditions until the melt intrinsic viscosity reaches 0.60-0.65 dL / g, to obtain a third compound; S5.0: after drying the third compound, performing solid-phase polycondensation reaction to increase the melt intrinsic viscosity to 0.82-0.85 dL / g, and then cooling and slicing to obtain the high-heat-resistance bottle-grade polyester chip.

2. A process for the preparation of a high heat resistant bottle grade polyester chip as claimed in claim 1, wherein, The preparation process of the modified phosphate ester in step S1.0 comprises the following steps: S1.1: mixing triphenyl phosphate, ethylene glycol and deionized water and stirring, then heating to 45-50 DEG C and continuing to stir to obtain a first modified liquid; S1.2: adding silane coupling agent KH-550 to the first modified liquid, stirring, adjusting the pH value of the system to 4.5-5.5, and then heating to 65-75 DEG C and continuing to stir to obtain a second modified liquid; S1.3: adding cyclodextrin to the second modified liquid, stirring at 35-40 DEG C, and then performing reduced pressure distillation to obtain the modified phosphate ester.

3. A process for the preparation of a high heat resistant bottle grade polyester chip as claimed in claim 2, wherein, In step S1.1, the weight ratio of triphenyl phosphate, ethylene glycol and deionized water is (0.9-1.0):5:(0.1-0.2); the stirring speed is 200 r / min, and the initial stirring time is 10 min, and the stirring is continued for 1-2 h after heating; In step S1.2, the addition amount of the silane coupling agent KH-550 is 0.4-0.6 parts by weight; the stirring speed after addition is 150 r / min, and the stirring time is 5 min; acetic acid or ammonia is used to adjust the pH value of the system; the stirring is continued at 150 r / min for 2-4 h at 65-75 DEG C; In step S1.3, the addition amount of the cyclodextrin is 2.5-3.0 parts by weight; the stirring speed is 100 r / min at 35-40 DEG C, and the stirring time is 8-12 h; the reduced pressure distillation temperature is 55 DEG C, and the time is 3 h.

4. A process for the preparation of high heat resistant bottle grade polyester chips as claimed in claim 1, wherein, In step S2.0, the esterification or transesterification reaction specifically comprises the following steps: drying purified terephthalic acid at 120-130 DEG C for 4-6 h to obtain pretreated purified terephthalic acid; mixing the pretreated purified terephthalic acid with ethylene glycol, stirring at 80 r / min under nitrogen protection for 20 min, then heating to 220-230 DEG C, adding tetrabutyl titanate, continuing to stir at 80 r / min for 30 min, then heating to 250-260 DEG C, maintaining the temperature and stirring for 1-2 h.

5. The process for the preparation of high heat resistant bottle grade polyester chip as claimed in claim 1, wherein, The prepolymerization reaction in step S2.0 specifically comprises: after esterification or transesterification, the modified phosphate ester and citric acid obtained in step S1.0 are added, the system pressure is adjusted to 0.2 MPa, and the stirring is continued at a rotation speed of 80 r / min for 4-6 h to obtain the first composite.

6. A process for the preparation of high heat resistant bottle grade polyester chips as claimed in claim 1, wherein, The weight ratio of the purified terephthalic acid, ethylene glycol, tetrabutyl titanate, modified phosphate ester and citric acid is 10:(3.4-3.6):(0.002-0.004):(0.035-0.04):(0.01-0.012).

7. A process for the preparation of high heat resistant bottle grade polyester chips as claimed in claim 1, wherein, Step S3.0 specifically comprises: the first composite is transferred to a double screw stirrer, the absolute pressure of the system is reduced to 5 KPa, and stirring is carried out at 260-270 DEG C at a rotation speed of 12 r / min for 60-90 min until the melt characteristic viscosity reaches 0.35-0.45 dL / g to obtain the second composite.

8. A process for the preparation of a high heat resistant bottle grade polyester chip as claimed in claim 1, wherein, Step S4.0 specifically comprises: the second composite is transferred to a squirrel-cage stirrer, the absolute pressure of the system is further reduced to 100 Pa, and stirring is carried out at 278-282 DEG C at a rotation speed of 5 r / min for 120-180 min until the melt characteristic viscosity reaches 0.60-0.65 dL / g to obtain the third composite.

9. A process for the preparation of a high heat resistant bottle grade polyester chip as claimed in claim 1, wherein, Step S5.0 specifically comprises: after the third composite is dried at 140-150 DEG C under an absolute pressure of 5 KPa for 8-10 h, it is placed in a fluidized bed reactor, and under the protection of nitrogen, the gas flow rate is 1.0 m / s, first heat preservation is carried out at 170 DEG C for 2 h, then the temperature is raised to 190-200 DEG C for heat preservation, and solid-phase polycondensation is carried out for 10-14 h.

10. A highly heat resistant bottle grade polyester chip, characterized by, A high-heat-resistance bottle-grade polyester chip is prepared by the preparation method of any one of claims 1-9. A high-heat-resistance bottle-grade polyester chip is prepared by the preparation method of any one of claims 1-9.

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