Modified polyester composition, polyester sheet and manufacturing method thereof

Abstract

This invention discloses a modified polyester composition, a polyester sheet, and a method for manufacturing the same. The modified polyester composition comprises a polyester, at least one nucleating agent, at least one toughening agent, and at least one hydrolysis-resistant agent. The intrinsic viscosity of the polyester is 0.85 dL / g to 1.2 dL / g. Based on a total weight of 100 wt% of the modified polyester composition, the content of at least one nucleating agent is 0.5 wt% to 5 wt%, the content of at least one toughening agent is 1 wt% to 9 wt%, and the content of at least one hydrolysis-resistant agent is 0.1 wt% to 2 wt%. Therefore, the polyester sheet made from the modified polyester composition of this invention exhibits improved impact resistance, heat resistance, and hydrolysis resistance, while also being environmentally friendly.

Description

Technical Field

[0001] This invention relates to a polyester material and its applications, and in particular to a high-performance modified polyester composition, polyester sheet and its manufacturing method. Prior Technology

[0002] Heat sinks are a core component of cooling towers. Their purpose is to increase the contact area between water and air to promote heat exchange, thereby quickly dissipating heat from the water into the atmosphere. PVC is an ideal material for making cooling tower heat sinks due to its low cost, ease of processing, and corrosion resistance.

[0003] However, PVC heat sinks are not heat-resistant and are prone to deformation or deterioration due to high temperatures, resulting in reduced cooling efficiency. In addition, PVC heat sinks have low mechanical strength and are easily damaged by water flow, and may even bend or break, significantly shortening their service life.

[0004] PVC heat sinks are difficult to recycle and pose environmental pollution risks, and in practice they are often regarded as industrial waste with no recycling benefits. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a modified polyester composition that balances performance and environmental protection to replace PVC, and on this basis, to address the shortcomings of the prior art.

[0006] To address the aforementioned technical problems, one technical solution adopted by this invention is to provide a modified polyester composition comprising a polyester, at least one nucleating agent, at least one toughening agent, and at least one hydrolysis-resistant agent. In this invention, the intrinsic viscosity of the polyester is from 0.85 dL / g to 1.2 dL / g; based on a total weight of 100 wt% for the modified polyester composition, the content of the at least one nucleating agent is from 0.5 wt% to 5 wt%, the content of the at least one toughening agent is from 1 wt% to 9 wt%, and the content of the at least one hydrolysis-resistant agent is from 0.1 wt% to 2 wt%.

[0007] In a feasible or preferred embodiment of the present invention, the at least one nucleating agent includes at least one organic nucleating agent and at least one inorganic nucleating agent.

[0008] In a feasible or preferred embodiment of the present invention, the at least one organic nucleating agent is selected from the group consisting of polyethylene, sodium benzoate, sodium lignite and ethylene-methacrylic acid copolymer, and the at least one inorganic nucleating agent is selected from the group consisting of talc, titanium dioxide, silicon dioxide and calcium carbonate.

[0009] In a feasible or preferred embodiment of the present invention, the at least one nucleating agent is a combination of the polyethylene and the talc.

[0010] In a feasible or preferred embodiment of the present invention, the at least one toughening agent is selected from the group consisting of ethylene-methyl acrylate-glycidyl methacrylate copolymer (E-MA-GMA), polyolefin elastomer grafted with glycidyl methacrylate (POE-g-GMA), polyethylene grafted with glycidyl methacrylate (PE-g-GMA), polyethylene grafted with methyl acrylate (PE-g-MA), and methyl methacrylate-butadiene-styrene copolymer (MBS).

[0011] In a feasible or preferred embodiment of the present invention, the at least one toughening agent is a combination of the ethylene-methyl acrylate-glycidyl methacrylate copolymer and the polyethylene-grafted methyl acrylate.

[0012] In a feasible or preferred embodiment of the present invention, the at least one hydrolysis-resistant agent is carbodiimide.

[0013] In a feasible or preferred embodiment of the present invention, the modified polyester composition further includes at least 0.01 wt% to 1 wt% of an antioxidant and at least 0.01 wt% to 8 wt% of a lubricant.

[0014] To address the aforementioned technical problems, another technical solution adopted by this invention is to provide a method for manufacturing a polyester sheet, comprising: preparing polyester granules from the modified polyester composition as described above; melt-blending the polyester granules to form a melt; and extruding and molding the melt into a polyester sheet. In this invention, the polyester sheet has an impact strength greater than 4 KJ / m² according to ASTM D3420 and a heat distortion temperature greater than 130°C according to ASTM D648; the polyester sheet undergoes a 100°C pressure cooker test (PCT) for 5 days, and the mechanical strength retention rate is greater than or equal to 65%.

[0015] In a feasible or preferred embodiment of the present invention, the melt extrusion temperature of the polyester granules is 240°C to 275°C.

[0016] In a feasible or preferred embodiment of the present invention, the melt is solidified and formed into the polyester sheet under the action of a forming wheel assembly, wherein the surface temperature of the forming wheel assembly is 110°C to 130°C.

[0017] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide a polyester sheet, which is formed of the modified polyester composition as described in claim 1; wherein the polyester sheet has an impact strength greater than 4 KJ / m2 as tested according to ASTM D3420 standard and a heat distortion temperature greater than 130°C as tested according to ASTM D648 standard; wherein the polyester sheet, after undergoing a pressure cooker test (PCT) at 100°C for 5 days, has a mechanical strength retention rate greater than or equal to 65%.

[0018] In general, the modified polyester composition provided by the present invention, wherein at least one nucleating agent, at least one toughening agent and at least one hydrolysis resistant agent are used in combination with polyester with an IV value of 0.8-1.2 in a specific amount, can achieve the expected impact resistance (impact strength > 4 KJ / m2), heat resistance (HDT > 130°C) and hydrolysis resistance (mechanical strength retention rate after PCT ≥ 65%).

[0019] Furthermore, the polyester sheets made from the modified polyester composition of the present invention can withstand the harsh environment inside cooling towers and are very suitable for replacing polyvinyl chloride heat dissipation materials used inside cooling towers.

[0020] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Simple Explanation of the Diagram

[0021] Figure 1 is a flowchart of the method for manufacturing the polyester sheet of the present invention.

[0022] Figures 2 and 3 are schematic diagrams illustrating the operation of the method for manufacturing the polyester sheet of the present invention. Implementation

[0023] The following specific embodiments illustrate the implementation of the "modified polyester composition, polyester sheet and its manufacturing method" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention. Furthermore, the accompanying drawings of this invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention.

[0024] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term "or" as used herein should, as appropriate, include any combination of one or more of the associated listed items.

[0025] Unless otherwise defined, the terms used herein have the same meaning as commonly understood by those skilled in the art. Materials involved in the embodiments are commercially available or made according to prior art, unless otherwise specified. Methods or operations involved in the embodiments are conventional methods or operations in the art, unless otherwise specified.

[0026] Most cooling towers use PVC fins, which have poor heat resistance and are prone to deformation or deterioration at high temperatures, leading to reduced cooling efficiency. Furthermore, PVC fins have low mechanical strength and are easily damaged by water flow, potentially bending or breaking, significantly shortening their lifespan. Moreover, PVC fins are difficult to recycle and pose environmental pollution risks, often being considered industrial waste with no recycling benefits. Therefore, this invention provides a modified polyester composition that balances performance and environmental friendliness as a substitute for PVC.

[0027] The modified polyester composition of the present invention comprises a polyester, at least one nucleating agent, at least one toughening agent, and at least one hydrolysis-resistant agent. Therefore, polyester sheets made from the modified polyester composition of the present invention exhibit improved impact resistance, heat resistance, and hydrolysis resistance, and can withstand the harsh environment inside cooling towers, making them ideal for use as heat sinks inside cooling towers.

[0028] The polyesters applicable to this invention can be homopolymers polymerized from only a fixed set of diols and diacids, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycyclohexanediol terephthalate (PCT), and polypropylene terephthalate (PTT). Alternatively, copolyesters incorporating a third or more monomers can be used, and the copolymerization method can be random copolymerization or block copolymerization.

[0029] In practical applications, the total weight of the modified polyester composition based on the present invention is 100 wt%, and the polyester content is preferably 90 wt% or more. The polyester in the modified polyester composition of the present invention may include virgin polyester, recycled polyester, or a combination thereof. Sources of recycled polyester include, but are not limited to, recycled polyester films and recycled polyester pellets.

[0030] In embodiments of the present invention, the polyester is preferably PET and has an intrinsic viscosity (IV) of 0.85 dL / g to 1.2 dL / g. When the IV is in the range of 0.85 dL / g to 1.2 dL / g, the polyester has a longer molecular chain, which is beneficial to improving mechanical properties; and the polyester has a lower content of terminal carboxyl groups, which is beneficial to improving hydrolysis resistance. It should be noted that if the IV of the polyester is lower than 0.85 dL / g, the product (polyester sheet) will not meet the required mechanical strength, such as an impact strength greater than 4 KJ / m2; if the IV of the polyester is higher than 1.2 dL / g, it will lead to processing difficulties, and the product (polyester sheet) cannot be successfully molded.

[0031] At least one nucleating agent can optimize the crystallization behavior of polyester; the total weight of the modified polyester composition based on the present invention is 100 wt%, and the content of at least one nucleating agent is preferably 0.5 wt% to 5 wt%, more preferably 1.5 wt% to 3.5 wt%. In the modified polyester composition of the present invention, in order to match the high IV polyester, the at least one nucleating agent preferably includes at least one organic nucleating agent and at least one inorganic nucleating agent; the weight ratio of at least one organic nucleating agent to at least one inorganic nucleating agent can be in the range of 1:1 to 2:1.

[0032] Furthermore, at least one organic nucleating agent and at least one inorganic nucleating agent can produce a synergistic effect to comprehensively improve the crystallization rate, crystallinity, and crystallization uniformity of high-IV polyester, which is beneficial to improving the heat resistance and mechanical strength of the product (polyester sheet). For example, at least one inorganic nucleating agent can provide nucleation sites and reduce the energy barrier for the ordered arrangement of polyester molecular chains; at least one organic nucleating agent can induce the local ordered arrangement of polyester molecular chains.

[0033] As the nucleating agent for the modified polyester composition of the present invention, the organic nucleating agent can be selected from the group consisting of polyethylene, sodium benzoate, sodium lignite, and ethylene-methacrylic acid copolymer (DuPont's Surlyn resin) neutralized by metal ions (such as Na+, Zn2+, etc.); the inorganic nucleating agent can be selected from the group consisting of talc, titanium dioxide, silicon dioxide, and calcium carbonate. Considering performance, processability, and cost, the combination of at least one organic nucleating agent and at least one inorganic nucleating agent is preferably a combination of polyethylene and talc.

[0034] In practical applications, the content of at least one nucleating agent in the modified polyester composition of the present invention can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0035] At least one toughening agent can effectively improve the brittleness of polyester through mechanisms such as energy absorption, interface modification, and induced plastic deformation. Based on the total weight of the modified polyester composition of the present invention being 100 wt%, the content of at least one toughening agent is preferably 1 wt% to 9 wt%, more preferably 3 wt% to 6 wt%. In the modified polyester composition of the present invention, at least one toughening agent can be selected from the group consisting of ethylene-methyl acrylate-glycidyl methacrylate copolymer (E-MA-GMA), polyolefin elastomer grafted with glycidyl methacrylate (POE-g-GMA), polyethylene grafted with glycidyl methacrylate (PE-g-GMA), polyethylene grafted with methyl acrylate (PE-g-MA), and methyl methacrylate-butadiene-styrene copolymer (MBS).

[0036] In embodiments of the present invention, to overcome the limitations of a single toughening agent, at least one toughening agent may be a composite design, i.e., at least one toughening agent may be a composite toughening agent composed of two or more of E-MA-GMA, POE-g-GMA, PE-g-GMA, PE-g-MA, and MBS. Therefore, the synergistic effect of different toughening mechanisms can improve the overall impact resistance, balance the contradictions between different performance indicators (such as impact strength, tensile strength, and heat resistance), and improve processing compatibility and dispersibility. Preferably, the at least one toughening agent is a combination of E-MA-GMA and PE-g-GMA, wherein E-MA-GMA can enhance interfacial bonding and prevent phase separation, while the molecular backbone of PE-g-GMA has high flexibility and can effectively absorb energy upon impact.

[0037] In practical applications, the content of at least one toughening agent in the modified polyester composition of the present invention can be 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, or 9 wt%.

[0038] At least one hydrolysis-resistant agent can inhibit or delay the hydrolysis reaction, thereby maintaining the mechanical properties and long-term stability of the material. Based on the total weight of the modified polyester composition of the present invention being 100 wt%, the content of the at least one hydrolysis-resistant agent is preferably from 0.1 wt% to 2 wt%, more preferably from 0.4 wt% to 1.1 wt%. In the modified polyester composition of the present invention, the at least one hydrolysis-resistant agent can be selected from the group consisting of carbodiimide, glycol-modified polyethylene terephthalate (PETG), organosiloxanes, and polyethylene grafted glycidyl methacrylate (PE-g-GMA). Considering efficiency, cost-effectiveness, and compatibility, the at least one hydrolysis-resistant agent is preferably carbodiimide.

[0039] In practical applications, the content of at least one hydrolysis-resistant agent in the modified polyester composition of the present invention can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, or 2 wt%.

[0040] As needed, the modified polyester composition of the present invention may contain other functional additives. In embodiments of the present invention, to improve processing performance and prevent oxidative decomposition of polyester, the modified polyester composition of the present invention may further contain at least one lubricant and at least one antioxidant; based on a total weight of 100 wt% for the modified polyester composition of the present invention, the content of at least one lubricant is preferably from 0.01 wt% to 8 wt%, and the content of at least one antioxidant is preferably from 0.01 wt% to 1 wt%. However, the examples given above are merely one possible embodiment and are not intended to limit the present invention.

[0041] The lubricant suitable for use in this invention can be a stearate, polyethylene wax, silicate-modified material, or fluoropolymer. Examples of stearates include, but are not limited to, zinc stearate, sodium stearate, and calcium stearate. Examples of silicate-modified materials include, but are not limited to, polydimethylsiloxane, silicate graft copolymers, and amino- or epoxy-modified silicates. Examples of fluoropolymers include, but are not limited to, polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA), polyvinylidene fluoride (PVDF), and ethylene-tetrafluoroethylene copolymer (ETFE).

[0042] The antioxidants suitable for use in this invention can be hindered phenols, phosphites, or thioesters; depending on the need, compound antioxidants can also be used, such as a combination of hindered phenolic antioxidants and phosphite or thioester antioxidants. Examples of hindered phenols include, but are not limited to, products with trade names / trademarks such as Irganox 1010 and Irganox 1076. Examples of phosphites include, but are not limited to, products with trade names / trademarks such as Irgafos 168 and Ultranox 626. Examples of thioesters include, but are not limited to, dilauryl thiodipropionate (DLTDP) and distearate thiodipropionate (DSTDP).

[0043] Referring to Figure 1, the modified polyester composition of the present invention can be used to manufacture polyester sheets, the steps of which include: step S100, making polyester granules from the modified polyester composition; step S102, melting and mixing the polyester granules to form a melt; and step S104, extruding the melt and forming it into a polyester sheet.

[0044] It is worth noting that the modified polyester composition of this invention can withstand the harsh environment inside cooling towers, making it ideal for replacing PVC heat dissipation materials used inside cooling towers. Specifically, the resulting polyester sheet has an impact strength greater than 4 KJ / m² according to ASTM D3420 and a heat distortion temperature greater than 130°C according to ASTM D648. Furthermore, the resulting polyester sheet exhibits a mechanical strength retention rate of greater than or equal to 65% after undergoing a 5-day pressure cooker test at 100°C.

[0045] Referring to Figures 2 and 3, in step S100, the modified polyester composition of the present invention is fed into a twin-screw extruder 1, where it is melt-blended, extruded, cooled, and solidified before being cut into polyester granules. In step S102, the polyester granules are melt-extruded through the twin-screw extruder, and the melt extrusion temperature can be controlled within the range of 240°C to 275°C. In step S104, the melt extruded from the die of the extruder is solidified and formed into a polyester sheet 3 under the action of a forming wheel assembly 2. The surface temperature of the forming wheel assembly 2 can be controlled within the range of 110°C to 130°C to ensure that the PET quickly forms a uniform microcrystalline structure during the cooling process, thereby reducing product defects and improving product dimensional stability.

[0046] [Example 1]

[0047] Polyester, at least one nucleating agent, at least one toughening agent, at least one hydrolysis-resistant agent, at least one lubricant, and at least one antioxidant are added to a twin-screw extruder according to the formulation ratio in Table 1. After melt mixing, extrusion molding, cooling and solidification, the product is cut into polyester granules. The temperatures of each section of the extruder are set as follows: Section 1: 270°C; Section 2: 245°C; Sections 3 to 11: 265°C; Die head: 270°C. In Example 1, the polyester is virgin PET with an IV value of 1.1; at least one nucleating agent is a combination of polyethylene and talc; at least one toughening agent is a combination of E-MA-GMA and PE-g-GMA; at least one hydrolysis-resistant agent is carbodiimide; at least one lubricant is polyethylene wax; and at least one antioxidant is the hindered phenolic antioxidant Irganox 1010. Polyester granules are melt-extruded through a twin-screw extruder; the temperature settings for each section of the extruder are: 240°C for the first section; 270°C for the second to tenth sections; and 275°C for the die. The melt extruded from the die of the extruder is shaped by a 120°C forming wheel to produce sheet samples.

[0048] Example 2 uses the same manufacturing method as Example 1, except that the polyester in Example 2 is recycled PET with an IV value of 1.1.

[0049] Comparative Example 1 and Example 1 were prepared using the same method, except that the polyester in Comparative Example 1 was virgin PET with an IV value of 0.8.

[0050] Comparative Example 2 was prepared using the same method as Example 1, except that the polyester used in Comparative Example 1 was virgin PET with an IV value of 1.3.

[0051] Comparative Example 3 and Example 1 were prepared using the same method, except that the content of at least one nucleating agent in the polyester composition was less than 0.5 wt%.

[0052] Comparative Example 4 and Example 1 were prepared using the same method, except that the content of at least one nucleating agent in the polyester composition was higher than 5 wt%.

[0053] Comparative Example 5 was prepared using the same method as Example 1, except that the content of at least one toughening agent in the polyester composition was less than 1 wt.

[0054] Comparative Example 6 was prepared using the same method as Example 1, except that the content of at least one toughening agent in the polyester composition was higher than 9 wt%.

[0055] Comparative Example 7 was prepared using the same method as Example 1, except that no hydrolysis resistant agent was added to the polyester composition of Comparative Example 7.

[0056] Mechanical strength, heat resistance, hydrolysis resistance and formability tests were conducted on the sheet metal samples of Examples 1 and 2 and Comparative Examples 1-7. The test methods are described below, and the test results are summarized in Tables 1 to 3 below.

[0057] Impact Strength: Tested according to ASTM D3420 standard method.

[0058] Tensile Strength: Tested according to ASTM D638 standard method.

[0059] Heat Deflection Temperature (HDT): Tested according to ASTM D648 standard method, with an applied stress of 0.45 MPa; the higher the HDT, the better the heat resistance of the board.

[0060] Hydrolysis resistance: The impact strength and tensile strength retention rate of the test board sample before and after the pressure cooker test (PCT) is measured. The test conditions include a temperature of 100°C and a duration of 5 days. The higher the retention rate, the better the hydrolysis resistance of the board.

[0061] Formability: When the melt exits from the extrusion die at a uniform speed and thickness and maintains its shape on the surface of the forming wheel, the formability of the sheet sample is judged to be OK.

[0062] Table 1 Unit: wt% Example 1 Example 2 Comparative Example 1 Native PET IV = 0.8 91 IV = 1.1 91 IV = 1.3 Recycled PET IV = 1.1 91 nucleating agent polyethylene 1.5 1.5 1.5 talcum powder 1.1 1.1 1.1 toughening agent E-MA-GMA 2.5 2.5 2.5 PE-g-GMA 2.5 2.5 2.5 Hydrolysis resistant agent carbodiimide 1 1 1 lubricant Polyethylene wax 0.3 0.3 0.3 antioxidants Irganox 1010 0.1 0.1 0.1 Mechanical strength Impact strength (KJ / m2) 4 4 3.3 Tensile strength (MPa) 57.7 57.6 56.3 Heat resistance HDT(°C) 131.7 131.5 126.4 Hydrolysis resistance (PCT) Impact strength retention rate (%) 85 84.8 51.3 Tensile strength retention rate (%) 99.6 99.5 95.3 Sheet formability OK OK OK Table 2 Unit: wt% Comparative Example 2 Comparative Example 3 Comparative Example 4 Native PET IV = 0.8 IV = 1.1 93.2 88.4 IV = 1.3 91 Recycled PET IV = 1.1 nucleating agent polyethylene 1.5 0.2 2.6 talcum powder 1.1 0.2 2.6 toughening agent E-MA-GMA 2.5 2.5 2.5 PE-g-GMA 2.5 2.5 2.5 Hydrolysis resistant agent carbodiimide 1 1 1 lubricant Polyethylene wax 0.3 0.3 0.3 antioxidants Irganox 1010 0.1 0.1 0.1 Mechanical strength Impact strength (KJ / m2) 4.2 4.3 3.7 Tensile strength (MPa) 57.8 58.2 53.1 Heat resistance HDT(°C) 133.5 100.6 138.5 Hydrolysis resistance (PCT) Impact strength retention rate (%) 69.4 83.2 85.3 Tensile strength retention rate (%) 97.3 98.3 98.8 Sheet formability NG OK OK Table 3 Unit: wt% Comparative Example 5 Comparative Example 6 Comparative Example 7 Native PET IV = 0.8 IV = 1.1 95.1 86 92 IV = 1.3 Recycled PET IV = 1.1 91 nucleating agent polyethylene 1.5 1.5 1.5 talcum powder 1.1 1.1 1.1 toughening agent E-MA-GMA 0.45 5 2.5 PE-g-GMA 0.45 5 2.5 Hydrolysis resistant agent carbodiimide 1 1 lubricant Polyethylene wax 0.3 0.3 0.3 antioxidants Irganox 1010 0.1 0.1 0.1 Mechanical strength Impact strength (KJ / m2) 2.8 5.5 4 Tensile strength (MPa) 58.3 50.3 58.1 Heat resistance HDT(°C) 141.1 121.3 130.9 Hydrolysis resistance (PCT) Impact strength retention rate (%) 84.5 76.5 47.5 Tensile strength retention rate (%) 98.9 97.3 96.4 Sheet formability OK OK OK

[0063] Comparing Examples 1 and 2, it can be seen that when the IV value and content of polyester, as well as the contents of various additives, all fall within the numerical range disclosed in this invention, the expected impact resistance (impact strength > 4 KJ / m2), heat resistance (HDT > 130°C), and hydrolysis resistance (mechanical strength retention rate after PCT ≥ 65%) can be achieved regardless of whether virgin or recycled polyester is used. This proves that recycled polyester can replace virgin polyester, which meets environmental protection requirements.

[0064] Comparing Examples 1 and 2 with Comparative Examples 1 and 2, it can be seen that when using polyester with a lower IV value, the impact strength, heat resistance, and hydrolysis resistance of the resulting sheets do not meet the standards; when using polyester with a higher IV value, the formability of the resulting sheets is poor (extrusion is not smooth). This proves that the IV value of the polyester needs to be in the range of 0.85 to 1.2.

[0065] Comparing Examples 1 and 2 with Comparative Examples 3 and 4, it can be seen that when the content of the nucleating agent is too low, the heat resistance of the resulting board is insufficient; while when the content of the nucleating agent is too high, the impact resistance of the resulting board decreases. This proves that the content of the nucleating agent needs to be in the range of 0.5 wt% to 5 wt%.

[0066] Comparing Examples 1 and 2 with Comparative Examples 5 and 6, it can be seen that when the toughening agent content is too low, the impact strength of the resulting sheet is insufficient; while when the toughening agent content is too high, the heat resistance of the resulting sheet decreases. This proves that the toughening agent content needs to be in the range of 1 wt% to 9 wt%.

[0067] Comparing Examples 1 and 2 with Comparative Example 7, it can be seen that without the addition of a hydrolysis-resistant agent, the mechanical strength retention rate after PCT is less than 50%. This demonstrates the necessity of a hydrolysis-resistant agent.

[0068] [Beneficial Effects of the Examples]

[0069] In general, the modified polyester composition provided by the present invention, wherein at least one nucleating agent, at least one toughening agent and at least one hydrolysis resistant agent are used in combination with polyester with an IV value of 0.8-1.2 in a specific amount, can achieve the expected impact resistance (impact strength > 4 KJ / m2), heat resistance (HDT > 130°C) and hydrolysis resistance (mechanical strength retention rate after PCT ≥ 65%).

[0070] Furthermore, the polyester sheets made from the modified polyester composition of the present invention can withstand the harsh environment inside cooling towers and are very suitable for replacing polyvinyl chloride heat dissipation materials used inside cooling towers.

[0071] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification and drawings are included in the scope of the patent application of the present invention.

[0072] 1: Twin-screw extruder 2: Molded wheel set 3: Polyester sheet S100, S102, S104: Steps

Claims

1. A modified polyester composition comprising a polyester, at least one nucleating agent, at least one toughening agent, and at least one hydrolysis-resistant agent; wherein, based on a total weight of 100 wt% of the modified polyester composition, the content of the at least one nucleating agent is 0.5 wt% to 5 wt%, the content of the at least one toughening agent is 1 wt% to 9 wt%, and the content of the at least one hydrolysis-resistant agent is 0.1 wt% to 2 wt%; wherein the intrinsic viscosity of the polyester is 0.85 dL / g to 1.2 dL / g; wherein the polyester is polyethylene terephthalate, the at least one nucleating agent is a combination of polyethylene and talc, the at least one toughening agent is a combination of ethylene-methyl acrylate-glycidyl methacrylate copolymer and polyethylene grafted with glycidyl methacrylate, and the at least one hydrolysis-resistant agent is carbodiimide.

2. The modified polyester composition as claimed in claim 1, further comprising 0.01 wt% to 1 wt% of at least one antioxidant and 0.01 wt% to 8 wt% of at least one lubricant.

3. A method for manufacturing a polyester sheet, comprising: The modified polyester composition as described in claim 1 is prepared into polyester pellets; the polyester pellets are melt-blended to form a melt; The melt is extruded and formed into a polyester sheet; wherein the polyester sheet has an impact strength greater than 4 KJ / m2 as tested according to ASTM D3420 and a heat distortion temperature greater than 130°C as tested according to ASTM D648; wherein the polyester sheet undergoes a pressure cooker test (PCT) at 100°C for 5 days and retains a mechanical strength of greater than or equal to 65%.

4. The method for manufacturing the polyester sheet as described in claim 3, wherein, The melt extrusion temperature of the polyester granules is 240°C to 275°C.

5. A method for manufacturing a polyester sheet as described in claim 3, wherein, The melt is solidified and formed into the polyester sheet under the action of a forming wheel assembly, wherein the surface temperature of the forming wheel assembly is 110°C to 130°C.

6. A polyester sheet formed from a modified polyester composition as described in claim 1; wherein the polyester sheet has an impact strength greater than 4 KJ / m² as tested according to ASTM D3420 and a heat distortion temperature greater than 130°C as tested according to ASTM D648; wherein the polyester sheet retains a mechanical strength of greater than or equal to 65% after undergoing a pressure cooker test (PCT) at 100°C for 5 days.

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