Hydrolysis-resistant copolyester composition and preparation method thereof

Abstract

The invention discloses a hydrolysis-resistant copolyester composition and a preparation method thereof. The hydrolysis-resistant copolyester composition comprises 100 parts of hydrolysis-resistant copolyester chips, 0.3-1 part of a nucleating agent and 0.3-5 parts of a hydrolysis-resistant agent. Dihydric alcohol which contains hydrophobic long aliphatic branched chains and has the number of hydrogen atoms on beta-position carbon atoms smaller than or equal to 1 is introduced into the structure of the hydrolysis-resistant copolyester chip, and an epoxy compound containing a long hydrophobic chain segment is introduced to the tail end, so that the steric hindrance effect generated by the structure can prevent water vapor from attacking ester bonds; therefore, the hydrolysis resistance of the polyester is improved.

Description

Technical Field

[0001] This invention relates to the technical field of polymer materials, specifically to a hydrolysis-resistant copolyester composition and its preparation method. Background Technology

[0002] Polyesters are polymers containing ester functional groups (-COO-) in their main chain. These polymers possess excellent physical and chemical stability, superior mechanical and processing properties, good heat and chemical resistance, and high transparency, making them widely used in fibers, packaging materials, and engineering plastics. Copolyesters are polymers with even better properties obtained by introducing one or more modified monomers into the polyester molecular structure during copolymerization. However, in practical production applications, the ester bonds in the polyester molecular structure are prone to hydrolysis under humid and hot conditions, which can lead to a decrease in polymer molecular weight, reduced mechanical properties, and shortened product lifespan.

[0003] CN107973905A discloses a flexible hydrolysis-resistant polyester with a unique hexa-branched island structure. By introducing triglycidyl isocyanate and trimellitic anhydride into the polyester structure, it achieves excellent flexibility and hydrolysis resistance through unique structural regularity. However, this polyester is suitable for industrial coatings, but its application in fibers and films is limited. CN119264610A discloses a polyester composition containing polyester, a crystallization inhibitor, and a hydrolysis-resistant polyester. The introduction of a crystallization inhibitor addresses the problem of decreased hydrolysis resistance caused by crystallization during aging. However, from the perspective of polyester hydrolysis mechanism, water vapor attacks the amorphous region first, while the crystalline region can hinder the attack of water vapor. Introducing a crystallization inhibitor may lead to a decrease in hydrolysis resistance. CN112724609A discloses a hydrolysis-resistant polyester with added organic aluminum alkoxide and its preparation method. Organic aluminum alkoxide preferentially reacts with water during hydrolysis and acts as a capping agent. Many patents improve the hydrolysis resistance of polyester by adding auxiliaries with capping agent effects. However, the hydrolysis resistance achieved solely by hydrolysis-resistant additives is no longer sufficient to meet the stringent hydrolysis resistance requirements of high-demand fields.

[0004] In conclusion, how to utilize intrinsic hydrolysis resistance and the synergistic effect of additives to further improve the hydrolysis resistance of polyester and promote its application in high-requirement fields has become an urgent problem to be solved. Summary of the Invention

[0005] In order to solve one or more technical problems existing in the prior art, one of the objectives of this application is to provide a hydrolysis-resistant copolyester composition, which improves the hydrolysis resistance of polyester by copolymerization modification to change the polyester chain structure and by adding auxiliaries, based on the perspective of molecular structure and mechanism.

[0006] The second objective of this application is to provide a method for preparing a hydrolysis-resistant copolyester composition. The preparation process is simple and versatile. The prepared hydrolysis-resistant copolyester composition combines copolymerization modification and additive modification, which effectively improves the hydrolysis resistance of the polyester through a synergistic effect.

[0007] To address the aforementioned technical problems, one of the objectives of this application is achieved through the following technical solution: A hydrolysis-resistant copolyester composition, comprising 100 parts of hydrolysis-resistant copolyester chips, 0.3-1 parts of nucleating agent, and 0.3-5 parts of hydrolysis-resistant agent.

[0008] Nucleating agents and hydrolysis-resistant agents are introduced into hydrolysis-resistant copolyester chips. The introduction of nucleating agents can reduce the size of polyester spherulites, and the spherulites dispersed in the system can form multiple physical barriers to prevent water penetration. The introduction of hydrolysis-resistant agents can eliminate the terminal carboxyl groups generated during polyester hydrolysis, hinder the autocatalytic effect of polyester hydrolysis, or couple polymer chains, thereby increasing the molecular weight and suppressing the adverse effects of hydrolysis. In this study, insufficient nucleating agent had little impact on improving the crystallinity and hydrolysis resistance of the composition; excessive nucleating agent could damage the original crystal form of the polyester and reduce compatibility. Therefore, the nucleating agent content in 100 parts of hydrolysis-resistant copolyester chips was controlled at 0.3-1 part. Conversely, insufficient hydrolysis-resistant agent had little effect on improving the hydrolysis resistance of the polyester; excessive hydrolysis-resistant agent could lead to higher production costs and poorer actual hydrolysis resistance. Furthermore, excessive amounts of some hydrolysis-resistant agents could generate irritating odors during production, causing adverse environmental and social impacts. Therefore, the hydrolysis-resistant agent content in 100 parts of hydrolysis-resistant copolyester chips was controlled at 0.3-5 parts. By controlling the content of nucleating agent and hydrolysis-resistant agent, the hydrolysis resistance of the polyester could be improved from the perspective of molecular structure and mechanism through copolymerization modification and the synergistic effect of added additives.

[0009] Preferably, the hydrolysis-resistant copolyester chip has the structure shown in the following general formula (I): (I) Wherein, R1 represents phenyl, naphthyl, and biphenyl; R2 is derived from straight-chain aliphatic diols with 2 to 16 carbon atoms; R3 is derived from diols with less than or equal to 1 hydrogen atom on the β-position carbon atom; R4 is derived from epoxides with 8 to 17 carbon atoms; and m and n are independent integers from 1 to 100.

[0010] The hydrolysis-resistant copolyester chip structure incorporates a diol with one or fewer hydrogen atoms at the β-position carbon atom. This diol provides steric hindrance, blocking water molecules from attacking the ester bonds and hindering their hydrolysis, thus improving the hydrolysis resistance of the copolyester chips. Furthermore, in preparing the hydrolysis-resistant copolyester chip structure, in addition to introducing aliphatic long-chain diols, aliphatic long-chain epoxy compounds are also incorporated at the ends. These aliphatic long chains form a molecular-level water barrier and readily arrange themselves into crystalline regions, inhibiting water molecule diffusion into the material and preventing water vapor from attacking the ester bonds, thereby enhancing the hydrolysis resistance of the copolyester chips. Compared to existing technologies, this hydrolysis-resistant copolyester composition combines copolymerization modification and additive modification, achieving a synergistic effect to improve the hydrolysis resistance of the polyester.

[0011] Preferably, the number-average molecular weight of the hydrolysis-resistant copolyester chips is 18,000 to 30,000 g / mol.

[0012] Preferably, the intrinsic viscosity of the hydrolysis-resistant copolyester chips is 0.5~0.9 dL / g.

[0013] Preferably, in the structure of the hydrolysis-resistant copolyester chips of general formula (I), R1 is selected from any one of the following groups:

[0014] Preferably, in the structure of the hydrolysis-resistant copolyester chips of general formula (I), R2 is selected from any one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecanediol, and 1,16-hexadecanediol.

[0015] Preferably, in the structure of the hydrolysis-resistant copolyester chip of general formula (I), R3 is selected from any one of the following structures:

[0016] Where p, d, and w are independent integers from 8 to 20.

[0017] Preferably, in the structure of the hydrolysis-resistant copolyester chips of general formula (I), R4 is selected from any one of 1,2-epoxyoctane, 2-heptylepoxyethylene, 1,2-epoxydecane, 2-nonylepoxyethylene, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 2-tetrazylepoxyethylene, 1,2-epoxyhexadecane, glycidylheptyl ether, dodecyl glycidyl ether, tetradecyl glycidyl ether, and 2-ethylhexyl glycidyl ether.

[0018] Preferably, the method for preparing the hydrolysis-resistant copolyester chips includes: A1. Add compound A, compound B, compound C and catalyst D into the reactor, start stirring, monitor the temperature and pressure inside the reactor, maintain the esterification temperature at 230 ~ 270 °C, the esterification pressure at atmospheric pressure ~ 0.6 MPa, and the esterification time at 1.5 ~ 3.0 h; A2. After the esterification reaction is completed, add compound E and stir to mix evenly. Then, enter the polycondensation stage at a temperature of 280-300 °C for 1.0-3.5 h. During this stage, slowly draw a vacuum. When the vacuum level is 10-40 Pa, enter the high vacuum stage. Adjust the stirring speed to slow and continue the reaction until the stirring motor power no longer increases. The reaction is considered to have reached the endpoint. Then, pull the product into strips and cut them into pellets to obtain the target product, hydrolysis-resistant copolyester chips.

[0019] Preferably, compound A is selected from any one of terephthalic acid, isophthalic acid, phthalic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenylenedicarboxylic acid, 3,3'-biphenylenedicarboxylic acid, and 3,4'-biphenylenedicarboxylic acid.

[0020] Preferably, compound B is selected from any one of R2.

[0021] Preferably, compound C is selected from any one of R3.

[0022] Preferably, the compound E is selected from any one of R4. Preferably, the catalyst D is selected from any one of titanium-based catalysts.

[0023] Preferably, the molar ratio of compound A, compound B, compound C and compound E is 1:1.1~1.3:0.1~0.15:0.003~0.007.

[0024] In step A1, if the molar ratio of the feed is too low, the substitution reaction will be insufficient, there will be more unsubstituted products, or the yield will be significantly reduced; if the molar ratio of the feed is too high, the total yield will be reduced, the by-products will be increased, and the production cost will be increased. Therefore, by controlling the molar ratio, the above problems can be solved.

[0025] Preferably, the amount of catalyst D is 0.0025% to 0.004% of the mass of compound A monomer.

[0026] In step A1, if the amount of catalyst is too low, the reaction efficiency will be low, the reaction will be incomplete, and the yield will be reduced; if the amount of catalyst is too high, the amount of by-products will increase and the production cost will increase. Therefore, controlling the amount of catalyst and using it at 0.0025% to 0.004% of the mass of compound A monomer can avoid the above problems.

[0027] Preferably, the nucleating agent includes any one or more of talc, carbonate, boron nitride, mica, zinc oxide, silicon dioxide, titanium dioxide, nano-silver, carbon nanotubes, graphene, sodium benzoate, potassium benzoate, sodium formate, sodium acetate, barium sulfate, ethylene-propylene sodium copolymer, ethylene-methacrylate sodium copolymer, and polyhedral oligomeric silsesquioxane.

[0028] Preferably, the hydrolysis-resistant agent includes any one or more of carbodiimide, epoxy, and isocyanate compounds.

[0029] The second objective of this application is achieved through the following technical solution: A method for preparing a hydrolysis-resistant copolyester composition, the method comprising: drying hydrolysis-resistant copolyester chips at 120 °C for 8-12 hours, sealing and storing them in a sealed container, cooling them, mixing them with a nucleating agent and a hydrolysis-resistant agent in proportion using a high-speed mixer, feeding the mixture evenly into a twin-screw extruder for granulation, and obtaining the target hydrolysis-resistant copolyester composition.

[0030] Hydrolysis-resistant copolyester compositions are prepared by copolymerization modification to produce hydrolysis-resistant copolyester chips. Starting from molecular structure design, the diffusion of water molecules within the material is hindered. Nucleating agents are added to form dispersed crystalline regions within the material, further impeding water molecule penetration. Hydrolysis-resistant agents are added to eliminate terminal carboxyl groups generated after hydrolysis, inhibiting the autocatalytic effect of the hydrolysis reaction, or to couple polymer segments, thereby improving the material's hydrolysis resistance. The synergistic effect of copolymerization modification and added auxiliaries further enhances the hydrolysis resistance of the polyester.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention introduces a diol with one or fewer hydrogen atoms at the β-position of the carbon atom and containing a hydrophobic long aliphatic branch into the structure of a hydrolysis-resistant copolyester chip, and an epoxy compound containing a long hydrophobic segment at the end. The introduction of the diol causes the polyester backbone to extend long side chains, providing steric protection for the ester bonds in the backbone and improving the hydrolysis resistance of the polyester. The introduction of the epoxy compound provides a molecular-level water barrier, making it easier for the copolyester backbone to arrange itself in a more regular manner to form crystalline regions, increasing the crystallinity of the polyester, thereby hindering moisture erosion and improving hydrolysis resistance. Furthermore, this hydrolysis-resistant copolyester composition combines copolymerization modification and additive modification, improving the hydrolysis resistance of the polyester through a synergistic effect. Attached Figure Description

[0032] Figure 1 This is a comparison chart of intrinsic viscosity retention rates under different hydrolysis times in the embodiments and comparative examples of this invention. Detailed Implementation

[0033] The present application will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0034] In the following embodiments, unless otherwise specified, the raw materials or processing techniques used are conventional commercially available raw materials or conventional processing techniques in the art.

[0035] Example 1: The preparation process of hydrolysis-resistant copolyester chips P1 is as follows: (1) Add 16.67 g (0.1 mol) of phthalic acid, 7.13 g (0.115 mol) of ethylene glycol, 1.90 g (0.013 mol) of 1,2-octanediol and 0.00058 g of tetrabutyl titanate to the reaction vessel, start stirring, monitor the temperature and pressure inside the vessel, maintain the esterification temperature at 265 °C, the esterification pressure at atmospheric pressure to 0.6 MPa, and the esterification time at 1.5 to 3.0 h; (2) After the esterification reaction is completed, add 0.11 g (0.0005 mol) of 1,2-epoxytetradecane, stir and mix evenly, and enter the polycondensation stage. The temperature is 285 °C and the polycondensation time is 1.0 ~ 3.5 h. During this stage, the vacuum is slowly drawn. When the vacuum degree is 10 ~ 40 Pa, the high vacuum stage is entered. The stirring speed is adjusted to slow speed and the reaction continues until the stirring motor power no longer increases. The reaction is considered to have reached the endpoint. Then, the product is stretched and granulated to obtain the target product, hydrolysis resistant copolyester chips P1.

[0036] The preparation process of the hydrolysis-resistant copolyester composition is as follows: After drying the hydrolysis-resistant copolyester chips P1 at 120 °C for 8-12 hours, they were sealed and stored in a sealed container. After cooling, the raw materials were prepared according to the components and weight parts in Table 1. They were mixed using a high-speed mixer and fed into a twin-screw extruder for granulation to obtain the target hydrolysis-resistant copolyester composition.

[0037] Example 2: The preparation process of hydrolysis-resistant copolyester chips P2 is as follows: (1) Add 16.67 g (0.1 mol) of phthalic acid, 7.13 g (0.115 mol) of ethylene glycol, 4.08 g (0.013 mol) of 1,2-eicosanediol and 0.00058 g of tetrabutyl titanate to the reaction vessel, start stirring, monitor the temperature and pressure inside the vessel, maintain the esterification temperature at 265 °C, the esterification pressure at atmospheric pressure to 0.6 MPa, and the esterification time at 1.5 to 3.0 h; (2) After the esterification reaction is completed, add 0.11 g (0.0005 mol) of 1,2-epoxytetradecane, stir and mix evenly, and enter the polycondensation stage. The temperature is 285 °C and the polycondensation time is 1.0 ~ 3.5 h. During this stage, the vacuum is slowly drawn. When the vacuum degree is 10 ~ 40 Pa, the high vacuum stage is entered. The stirring speed is adjusted to slow speed and the reaction continues until the stirring motor power no longer increases. The reaction is considered to have reached the endpoint. Then, the product is stretched and granulated to obtain the target product, hydrolysis resistant copolyester chips P2.

[0038] The preparation process of the hydrolysis-resistant copolyester composition is as follows: After drying the hydrolysis-resistant copolyester chips P2 at 120 °C for 8-12 hours, they were sealed and stored in a sealed container. After cooling, the raw materials were prepared according to the components and weight parts in Table 1. They were mixed using a high-speed mixer and fed into a twin-screw extruder for granulation to obtain the target hydrolysis-resistant copolyester composition.

[0039] Example 3: The preparation process of hydrolysis-resistant copolyester chips P3 is as follows: (1) Add 16.67 g (0.1 mol) of phthalic acid, 7.13 g (0.115 mol) of ethylene glycol, 1.90 g (0.013 mol) of 1,2-octanediol and 0.00058 g of tetrabutyl titanate to the reaction vessel, start stirring, monitor the temperature and pressure inside the vessel, maintain the esterification temperature at 265 °C, the esterification pressure at atmospheric pressure to 0.6 MPa, and the esterification time at 1.5 to 3.0 h; (2) After the esterification reaction is completed, add 0.064 g (0.0005 mol) of 1,2-epoxyoctane, stir and mix evenly, and enter the polycondensation stage. The temperature is 285 °C and the polycondensation time is 1.0 ~ 3.5 h. During this stage, the vacuum is slowly drawn. When the vacuum degree is 10 ~ 40 Pa, the high vacuum stage is entered. The stirring speed is adjusted to slow speed and the reaction continues until the stirring motor power no longer increases. The reaction is considered to have reached the endpoint. Then, the product is drawn into strips and granulated to obtain the target product, hydrolysis resistant copolyester chips P3.

[0040] The preparation process of the hydrolysis-resistant copolyester composition is as follows: After drying hydrolysis-resistant copolyester chips P3 at 120 °C for 8-12 hours, they were sealed and stored in a sealed container. After cooling, the raw materials were prepared according to the components and weight parts in Table 1. They were mixed using a high-speed mixer and fed into a twin-screw extruder for granulation to obtain the target hydrolysis-resistant copolyester composition.

[0041] Example 4: The preparation process of hydrolysis-resistant copolyester chips P4 is as follows: (1) Add 16.67 g (0.1 mol) of phthalic acid, 7.13 g (0.115 mol) of ethylene glycol, 4.08 g (0.013 mol) of 1,2-eicosanediol and 0.00058 g of tetrabutyl titanate to the reaction vessel, start stirring, monitor the temperature and pressure inside the vessel, maintain the esterification temperature at 265 °C, the esterification pressure at atmospheric pressure to 0.6 MPa, and the esterification time at 1.5 to 3.0 h; (2) After the esterification reaction is completed, add 0.064 g (0.0005 mol) of 1,2-epoxyoctane, stir and mix evenly, and enter the polycondensation stage. The temperature is 285 °C and the polycondensation time is 1.0 ~ 3.5 h. During this stage, the vacuum is slowly drawn. When the vacuum degree is 10 ~ 40 Pa, the high vacuum stage is entered. The stirring speed is adjusted to slow speed and the reaction continues until the stirring motor power no longer increases. The reaction is considered to have reached the endpoint. Then, the product is drawn into strips and granulated to obtain the target product, hydrolysis resistant copolyester chips P4.

[0042] The preparation process of the hydrolysis-resistant copolyester composition is as follows: After drying the hydrolysis-resistant copolyester chips P4 at 120 °C for 8-12 hours, they were sealed and stored in a sealed container. After cooling, the raw materials were prepared according to the components and weight parts in Table 1. They were mixed using a high-speed mixer and fed into a twin-screw extruder for granulation to obtain the target hydrolysis-resistant copolyester composition.

[0043] Table 1 Formulation table of hydrolysis-resistant copolyester compositions of Examples 1-4 and Comparative Examples 1-5

[0044] In Table 1, P1-P4 in component (P) are hydrolysis-resistant copolyester chips prepared in Examples 1-4; P5 in component (P) is pure polyethylene terephthalate (PET) chips; component (N) is silicon dioxide; and component H is polycarbodiimide.

[0045] Determination of intrinsic viscosity: The hydrolysis-resistant copolyester composition was thoroughly dried in a vacuum drying oven. 0.125 ± 0.005 g of the sample was weighed using an analytical balance and placed in a 50 ml Erlenmeyer flask. 25 ml of a phenol / 1,1,2,2-tetrachloroethane (mass ratio 50:50) mixed solvent was added to the flask, and the flask was placed on a heating stage equipped with a magnetic stirrer to completely dissolve the sample. After cooling, an appropriate amount of solution was added dropwise to an Ubbelohde viscometer until the page was between the filling marks. The flask was placed vertically in a constant temperature water bath at 25.0 ± 0.05 °C for 15 min, and the flow time t1 was measured. The measurement was repeated three times; the range should not exceed 0.2 s. The average flow time t0 of the solvent was measured using the same Ubbelohde viscometer and the same method. The measurement was repeated five times; the range should not exceed 0.1 s. The intrinsic viscosity was calculated using the following formula: c = m * 100 / 25 η r =t1 / t0 η sp =η r -1 [η]=((1+1.4*η sp ) 1 / 2 -1) / (0.7*c) c — solution concentration, in grams per 100 milliliters (g / 100 ml). m — Mass of the sample, in grams (g); t0 — the time it takes for the mixed solvent to flow through, in seconds (s); t1 — the time it takes for the solution to flow through, in seconds (s); η r —Relative viscosity; η sp —Increase specific viscosity; [η]——Intrinsic viscosity.

[0046] The test results are shown in Table 2.

[0047] Accelerated damp heat aging test: The hydrolysis-resistant copolyester composition was placed in a PCT aging test chamber (model YH-PCT) for accelerated damp heat aging. The temperature was set at 121 °C, the pressure at 2 atm, and the humidity at 100%. Samples were taken out every 24 hours for intrinsic viscosity testing. The test results are shown in Table 2.

[0048] Table 2 Performance Test Table of Hydrolysis-Resistant Copolyester Compositions of Examples 1-4 and Comparative Examples 1-5

[0049] Combination Figure 1Examples 1-4 and Comparative Examples 1-5 were analyzed and compared. First, Examples 1-4 were analyzed, such as... Figure 1 As shown, the intrinsic viscosity retention rate of each sample after the damp heat aging test exceeded 95%, indicating that the copolyester composition of the present invention has excellent hydrolysis resistance. This is attributed to the steric hindrance effect of the long hydrophobic side chains and the increased crystallinity of the terminal aliphatic long chains in the molecular structure of the hydrolysis-resistant copolyester chips of the present invention, as well as the synergistic effect brought about by the addition of hydrolysis-resistant agents and nucleating agents. In the molecular structure of the hydrolysis-resistant copolyester chips, the longer the side chains and terminal epoxy compound segments, the better the hydrolysis resistance of the polyester. The longer the side chains, the greater the steric hindrance effect on the ester bonds in the molecular backbone; while the longer the terminal epoxy compound segments, the more beneficial it is to the regular arrangement of the molecular chains, thereby improving the crystallinity and the hydrolysis resistance of the polyester. The intrinsic viscosity retention rate results after 24-hour and 48-hour damp heat aging tests show that the length of the terminal epoxy compound segments has a significant impact on the intrinsic viscosity retention rate, but it can still be maintained above 95%.

[0050] By comparing and analyzing Example 1 and Comparative Example 1, it can be found that replacing the hydrolysis-resistant copolyester chips prepared in this invention with conventional polyethylene terephthalate chips, as... Figure 1 As shown, the intrinsic viscosity retention rate decreased to 91% after 24 h of damp heat aging test and to 86% after 48 h of damp heat aging test, indicating a significant reduction in intrinsic viscosity. This is because, compared with the self-made hydrolysis-resistant copolyester chips, the pure PET chips lack long hydrophobic side chains protecting the ester bonds and terminal aliphatic long chains to enhance crystallinity, resulting in a decrease in the composition's damp heat resistance.

[0051] Comparative analysis of Example 1 and Comparative Examples 2 and 3 reveals that when the amount of nucleating agent added exceeds the range of 0.3-1 part, insufficient addition reduces the retention rate of intrinsic viscosity after damp heat aging, while excessive addition has no significant effect on improving the composition's damp heat resistance; in fact, it tends to decrease with increasing damp heat aging time. This indicates that whether the amount of nucleating agent added is within a reasonable range has a significant impact on the composition's damp heat aging resistance. However, the retention rate of intrinsic viscosity did not decrease significantly, which is attributed to the self-made hydrolysis-resistant copolyester chip structure of this invention, resulting in good hydrolysis resistance of the composition.

[0052] Comparative analysis of Example 1 and Comparative Examples 4 and 5 reveals that when the content of the hydrolysis-resistant agent exceeds the range of 0.3-5 parts, it significantly affects the composition's resistance to damp heat aging. Both excessive and insufficient hydrolysis-resistant agent content reduce the composition's resistance to damp heat, indicating that whether the hydrolysis-resistant agent content is within a reasonable range has a significant impact on the composition's hydrolysis resistance. However, the lowest intrinsic viscosity retention rate after the 48-hour damp heat aging test is still above 90%, which is attributed to the improved hydrolysis resistance of the composition due to the self-made hydrolysis-resistant copolyester chips of this invention.

[0053] In summary, the combination of hydrolysis-resistant copolyester chips, nucleating agent, and hydrolysis-resistant agent provided by this invention has a significant impact on the hydrolysis resistance of the composition. The hydrolysis-resistant copolyester chips provided by this invention contain long hydrophobic segments in their molecular structure, which can provide steric hindrance protection for ester bonds and prevent water vapor from eroding the molecular backbone. The hydrolysis-resistant copolyester chips provided by this invention contain aliphatic long chains at their ends, which can improve the crystallinity of the chips and enhance the hydrolysis resistance of the composition. The hydrolysis-resistant copolyester composition provided by this invention improves the hydrolysis resistance of the polyester through the synergistic effect of copolymerization modification and the addition of auxiliaries.

[0054] The above embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of protection of this application. Any non-substantial changes and substitutions made by those skilled in the art based on this application shall fall within the scope of protection claimed by this application.

Claims

1. A hydrolysis-resistant copolyester composition, characterized in that: The raw materials include 100 parts of hydrolysis-resistant copolyester chips, 0.3-1 parts of nucleating agent, and 0.3-5 parts of hydrolysis-resistant agent.

2. The hydrolysis-resistant copolyester composition according to claim 1, characterized in that: The nucleating agent includes any one or more of the following: talc, carbonate, boron nitride, mica, zinc oxide, silicon dioxide, titanium dioxide, nano-silver, carbon nanotubes, graphene, sodium benzoate, potassium benzoate, sodium formate, sodium acetate, barium sulfate, ethylene-propylene sodium copolymer, ethylene-methacrylate sodium copolymer, and polyhedral oligomeric silsesquioxane.

3. The hydrolysis-resistant copolyester composition according to claim 1, characterized in that: The hydrolysis-resistant agent includes any one or more of carbodiimide, epoxy, and isocyanate compounds.

4. The hydrolysis-resistant copolyester composition according to claim 1, characterized in that: The hydrolysis-resistant copolyester chips have the structure shown in the following general formula (Ⅰ): （Ⅰ） Wherein, R1 represents phenyl, naphthyl, and biphenyl; R2 is derived from straight-chain aliphatic diols with 2 to 16 carbon atoms; R3 is derived from diols with less than or equal to 1 hydrogen atom on the β-position carbon atom; R4 is derived from epoxides with 8 to 17 carbon atoms; and m and n are independent integers from 1 to 100.

5. The hydrolysis-resistant copolyester composition according to claim 4, characterized in that: In the structure of the hydrolysis-resistant copolyester chips of general formula (Ⅰ), R1 is selected from any one of the following groups: 。 6. The hydrolysis-resistant copolyester composition according to claim 4, characterized in that: In the structure of the hydrolysis-resistant copolyester chips of general formula (Ⅰ), R2 is selected from any one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecanediol, and 1,16-hexadecanediol.

7. The hydrolysis-resistant copolyester composition according to claim 4, characterized in that: In the structure of the hydrolysis-resistant copolyester chip of general formula (Ⅰ), R3 is selected from any one of the following structures: Where p, d, and w are independent integers from 8 to 20.

8. The hydrolysis-resistant copolyester composition according to claim 4, characterized in that: In the structure of the hydrolysis-resistant copolyester chips of general formula (Ⅰ), R4 is selected from any one of 1,2-epoxyoctane, 2-heptylepoxyethylene, 1,2-epoxydecane, 2-nonylepoxyethylene, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 2-tetrazylepoxyethylene, 1,2-epoxyhexadecane, glycidylheptyl ether, dodecyl glycidyl ether, tetradecyl glycidyl ether, and 2-ethylhexyl glycidyl ether.

9. The hydrolysis-resistant copolyester composition according to claim 4, characterized in that: The method for preparing the hydrolysis-resistant copolyester chips includes: A1. Add compound A, compound B, compound C and catalyst D into the reactor, start stirring, monitor the temperature and pressure inside the reactor, maintain the esterification temperature at 230 ~ 270 °C, the esterification pressure at atmospheric pressure ~ 0.6 MPa, and the esterification time at 1.5 ~ 3.0 h; A2. After the esterification reaction is completed, add compound E and stir to mix evenly. Then, enter the polycondensation stage at a temperature of 280 ~ 300 °C for 1.0 ~ 3.5 h. During this stage, slowly draw a vacuum. When the vacuum level is 10 ~ 40 Pa, enter the high vacuum stage. Adjust the stirring speed to slow and continue the reaction until the stirring motor power no longer increases. The reaction is considered to have reached the endpoint. Then, pull the product into strips and cut them into pellets to obtain the target product, hydrolysis-resistant copolyester chips.

10. A method for preparing a hydrolysis-resistant copolyester composition, characterized in that: The preparation method includes: drying the hydrolysis-resistant copolyester chips as described in any one of claims 1 to 12 at 120 °C for 8-12 hours, sealing and storing them in a sealed container, cooling them, mixing them with a nucleating agent and a hydrolysis-resistant agent in proportion using a high-speed mixer, feeding the mixture evenly into a twin-screw extruder for granulation, and obtaining the target hydrolysis-resistant copolyester composition.

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