Insulating oligomer film material

Abstract

The invention discloses an insulating oligomer film material and relates to the field of electrical insulating materials, the film material is prepared from polyester resin through the steps of extrusion slicing, melt extrusion, sheet casting and two-way stretching film forming, and in the step of melt extrusion, an extruded material comprises the following raw materials in percentage by weight: 99.35-99.71% of polyethylene glycol terephthalate slices; 0.03 to 0.06 percent of antimony trioxide; 0.05 to 0.09 percent of triphenyl phosphate; 0.2 to 0.4 percent of silicon dioxide; 0.04 to 0.08 percent of titanium dioxide; 0.01 to 0.03 percent of magnesium acetate tetrahydrate; 0-0.01% of sodium acetate; wherein the oligomer content of the polyethylene glycol terephthalate slice is less than 0.65%, and the intrinsic viscosity of the polyethylene glycol terephthalate slice is 0.8-1.2 dL / g. The invention provides the insulating polyester film specially designed for the refrigeration compressor, and the insulating polyester film is relatively low in oligomer content and good in heat resistance.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation materials, and in particular to an insulating oligomer film material. Background Technology

[0002] Polyester PET film, a film material produced by biaxial stretching of polyethylene terephthalate, has been widely used in flexible packaging composites, electrical insulation materials, solar cell backsheet materials, and optical materials due to its excellent mechanical properties and electrical insulation, as well as its low water absorption, good transparency, and good dimensional stability.

[0003] In hermetic compressors, polyester (PET) film is used as an electrical insulation material. However, because ordinary polyester film contains a relatively high amount of oligomers, it is prone to duct blockage, affecting the normal operation of the compressor. Specifically, when refrigerant gas flows through the compressor's internal chambers along the normal path, it comes into contact with the polyester film. At this time, the oligomer components in the polyester film are absorbed by the gas. As the gas flows through the micro-ducts, the oligomers remain in the ducts, gradually causing blockage and even leading to functional breakdown of the compressor and electrical failure. Especially when the compressor operates in a high-temperature environment for extended periods, the oligomers inside the polyester film are more likely to precipitate, affecting the compressor's normal service life.

[0004] Therefore, this application provides an insulating polyester film specifically designed for refrigeration compressors, which has a low oligomer content and good heat resistance. Summary of the Invention

[0005] To address the aforementioned problems, this application provides an insulating oligomer film material.

[0006] The insulating oligomer film material provided in this application adopts the following technical solution: An insulating oligomer film material is obtained from polyester resin through extrusion slicing, melt extrusion, casting, and biaxial stretching. In the melt extrusion step, the extrudate comprises the following raw materials in weight percentages: Polyethylene terephthalate (PET) chips, 99.35-99.71% purity; Antimony trioxide 0.03-0.06%; Triphenyl phosphate 0.05-0.09%; 0.2-0.4% silicon dioxide; Titanium dioxide 0.04-0.08%; Magnesium acetate tetrahydrate 0.01-0.03%; Sodium acetate 0-0.01%; The polyethylene terephthalate chips have an oligomer content of less than 0.65% and an intrinsic viscosity of 0.8-1.2 dL / g.

[0007] By adopting the above technical solution, polyethylene terephthalate (PET) chips with low oligomer content and high intrinsic viscosity are selected as the main matrix in the polyester film material. Oligomers are the main cause of functional breakdown in hermetically sealed compressors. Therefore, using the PET chips of this application reduces the formation of oligomers, ensuring stable and long-lasting operation of the compressor. At the same time, PET chips have good insulation properties, mechanical properties, and extremely low water absorption, which meets the insulation requirements of compressor materials. Antimony trioxide and triphenyl phosphate are used synergistically to enhance flame retardant properties and improve the flame retardancy and flexibility of the polyester film material. Silica is used as an opening agent and anti-blocking agent to enhance the mechanical properties and thermal stability of the polyester film material and prevent the film material from curling and sticking. Titanium dioxide is used to improve the appearance of the polyester film, increase transparency, and prevent ultraviolet aging. Magnesium acetate tetrahydrate and sodium acetate are used as nucleating agents to increase the crystallinity of the PET molecular chain, improve processability and heat resistance, and enhance the electrostatic adsorption capacity in the film equipment process.

[0008] Optionally, the polyethylene terephthalate chips are prepared by the following steps: The raw materials terephthalic acid, isophthalic acid, ethylene glycol and antioxidant are thoroughly mixed and esterified under a nitrogen atmosphere. After the reaction is completed, a catalyst and 1-fluoro-2,3-propanediol are added to the material to carry out a polycondensation reaction. After cooling, polyester resin is obtained. Polyester resin and pyromellitic anhydride are added together to a reactive extruder, melt-extruded, cooled and sliced ​​to obtain polyethylene terephthalate chips.

[0009] By adopting the above technical solution, isophthalic acid and antioxidants are added to the raw materials for preparing polyethylene terephthalate. The addition of a small amount of isophthalic acid can reduce the crystallization rate of PET, thereby lowering the melting point of the generated PET chips and reducing the subsequent melt extrusion processing temperature, thus reducing thermal degradation and oligomer formation during processing. The antioxidant can effectively alleviate the thermal degradation of PET during the reaction process and improve the intrinsic viscosity of the generated PET. The addition of 1-fluoro-2,3-propanediol as a third monomer during the polycondensation process improves the stability and high-temperature resistance of the generated PET chips, while reducing the water absorption rate of the PET chips. The generated polyester resin was coupled with pyromellitic anhydride for chain extension and viscosity enhancement, which increased the molecular weight and intrinsic viscosity of PET chips, reduced the end carboxyl group content of PET chips, and improved the high-temperature aging resistance of PET chips, enabling the polyester film to be used stably for a long time in high-temperature environments.

[0010] Optionally, in the preparation of the polyester resin, the raw materials are in the following weight proportions: 100 parts terephthalic acid; 1.5-3 parts isophthalic acid; 50-62 parts ethylene glycol; 0.1-0.3 parts antioxidant; 0.01-0.04 parts catalyst; 7-11 parts 1-fluoro-2,3-propanediol; and the weight ratio of the polyester resin to the pyromellitic anhydride is 1:0.8-1.1%.

[0011] By adopting the above technical solution and controlling the ratio of raw materials for producing PET chips, appropriate amounts of isophthalic acid, antioxidants, and pyromellitic anhydride can play a role in mitigating the thermal degradation of PET during the production and processing process, thereby enabling the produced PET chips to achieve lower oligomer content and long-term high-temperature resistance.

[0012] Optionally, the catalyst may be one or more of antimony trioxide, antimony glycol, titanium and bis(diphenylphosphineethyl)amine complex catalyst, or attapulgite-supported titanium glycol.

[0013] By adopting the above technical solution and using the above catalyst, the side reactions of polyester resin generation are reduced. The catalyst has good dispersibility in the reaction system and is not easily hydrolyzed, resulting in PET chips with good color and high transparency.

[0014] Optionally, the esterification reaction is carried out at a temperature of 200-240℃ and a pressure of 0.1-0.2MPa, and the reaction is stopped when the amount of water produced reaches 90%-95% of the theoretically complete reaction amount.

[0015] Optionally, the polycondensation reaction is carried out at a temperature of 240-270℃ and a pressure of 200-500Pa, and the reaction is stopped when the intrinsic viscosity of the system reaches 0.65-0.7dL / g.

[0016] Optionally, the conditions for extruding chips using the reaction extruder are: reaction section temperature of 230-260℃, vacuum degree of the impurity removal section of -0.08--0.1MPa, and screw speed of 45-55r / min.

[0017] By adopting the above technical solutions, the lower reaction zone temperature reduces the thermal degradation reaction during the extrusion process, reduces the formation of oligomers, and the higher screw speed and higher vacuum degree setting of the impurity removal zone effectively reduce the breakage of PET molecular chains, inhibit hydrolysis reaction, and obtain higher molecular weight and better extrudability.

[0018] Optionally, in the melt extrusion step, the extrudate is mixed at 150-170℃ for 3-7 minutes, the melt temperature is 270-290℃, and the extrusion speed is controlled at 20-35 r / min.

[0019] By adopting the above technical solution, stability is achieved in the melt extrusion process through the synergistic effect of PET chips and other auxiliary materials.

[0020] Optionally, in the casting step, the polyester melt is cooled by a cold drum with a surface temperature of 15-30°C and then passed through a high-voltage electrostatic film-attachment system to form a casting with a crystallinity of less than 5%.

[0021] Optionally, the biaxial stretching film-forming step includes longitudinal stretching and transverse stretching. The temperature of the preheating roller for longitudinal stretching is controlled at 75-85℃, the stretching temperature is controlled at 100-125℃, the cooling temperature is controlled at 10-20℃, and the stretching ratio is controlled at 3.0-3.5 times. The temperature of the preheating roller for transverse stretching is controlled at 105-115℃, the stretching temperature is controlled at 120-135℃, and the stretching ratio is controlled at 3.0-3.3 times. After stretching, the film is set at 230-245℃ and then gradually cooled to room temperature to control the crystallinity of the polyester film to reach more than 30%.

[0022] In summary, this application has at least one of the following beneficial effects: 1. In the polyester film material, polyethylene terephthalate (PET) chips with low oligomer content and high intrinsic viscosity are selected as the main matrix. Oligomers are the main cause of functional breakdown in hermetically sealed compressors. Therefore, using the PET chips of this application reduces the formation of oligomers, ensuring stable and long-lasting operation of the compressor. At the same time, PET chips have good insulation properties, mechanical properties, and extremely low water absorption, which meets the insulation requirements of compressor materials. Antimony trioxide and triphenyl phosphate are used synergistically to enhance flame retardant properties and improve the flame retardancy and flexibility of the polyester film material. Silica is used as an opening agent and anti-blocking agent to enhance the mechanical properties and thermal stability of the polyester film material and prevent the film material from curling and sticking. Titanium dioxide is used to improve the appearance of the polyester film, increase transparency, and prevent UV aging. Magnesium acetate tetrahydrate and sodium acetate are used as nucleating agents to increase the crystallinity of the PET molecular chain, improve processability and heat resistance, and enhance the electrostatic adsorption capacity in the film equipment process.

[0023] 2. In the preparation of polyethylene terephthalate (PET), isophthalic acid and antioxidants are added. The addition of a small amount of isophthalic acid can reduce the crystallization rate of PET, thereby lowering the melting point of the generated PET chips and reducing the subsequent melt extrusion processing temperature, thus reducing thermal degradation and oligomer formation during processing. The antioxidant can effectively alleviate the thermal degradation of PET during the reaction process and improve the intrinsic viscosity of the generated PET. The addition of 1-fluoro-2,3-propanediol as a third monomer during the polycondensation process improves the stability and high-temperature resistance of the generated PET chips, while reducing the water absorption rate of the PET chips. The generated polyester resin was coupled with pyromellitic anhydride for chain extension and viscosity enhancement, which increased the molecular weight and intrinsic viscosity of PET chips, reduced the end carboxyl group content of PET chips, and improved the high-temperature aging resistance of PET chips, enabling the polyester film to be used stably for a long time in high-temperature environments. Detailed Implementation

[0024] The present application will be further described in detail below with reference to Examples 1-6.

[0025] Example 1 This embodiment discloses an insulating oligomer film, which is prepared by polyester resin through extrusion slicing, melt extrusion, casting, and biaxial stretching to form a film. The specific steps are as follows: S1. Preparation and extrusion of polyester resin (all parts mentioned below are by weight): 100 parts terephthalic acid, 1.5 parts isophthalic acid, 50 parts ethylene glycol and 0.1 parts antioxidant were thoroughly mixed. Antioxidant 1076 was selected. The esterification reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 200℃ and the reaction pressure was 0.1MPa. The reaction was stopped when the amount of water produced reached 90%-95% of the theoretically complete reaction amount. After completion, 0.01 parts of catalyst and 7 parts of 1-fluoro-2,3-propanediol were added to the material. Antimony trioxide was selected as the catalyst to carry out polycondensation reaction. The reaction temperature was 240℃ and the pressure was 200Pa. The reaction was stopped when the intrinsic viscosity of the system reached 0.65-0.7dL / g. After cooling, polyester resin was obtained. Polyester resin and 0.8% (by weight) of pyromellitic anhydride were added together into a reactive extruder. The temperature of the reaction section was set at 230-260℃, specifically 230℃ for zone 1, 255℃ for zone 2, 240℃ for zone 3, and 260℃ for zone 4 (die head). The vacuum degree of the impurity removal section was -0.08MPa, and the screw speed was set at 45r / min. After melt extrusion and cooling, polyethylene terephthalate chips were obtained.

[0026] S2. Melt extrusion (all percentages mentioned below are by weight): The polyethylene terephthalate obtained above was mixed with other auxiliary materials in a certain proportion to obtain the extrudate, specifically: 99.35% polyethylene terephthalate chips, 0.06% antimony trioxide, 0.09% triphenyl phosphate, 0.38% silicon dioxide, 0.08% titanium dioxide, 0.03% magnesium acetate tetrahydrate, and 0.01% sodium acetate. The extrudate was mixed at 150°C for 3 minutes and then fed into a twin-screw extruder. The melt temperature was controlled at 270°C. The extrudate was extruded through a metering pump, a filter, and a melt line from the die, with the extrusion speed controlled at 20 r / min.

[0027] S3. Casting The polyester melt is cooled by a cold drum with a surface temperature of 15°C, and then passed through a high-voltage electrostatic film deposition system to form a cast sheet with a crystallinity of less than 5%.

[0028] S4, biaxial stretching film formation After preheating, the cast film is fed into a preheated longitudinal stretching roller assembly for longitudinal stretching along its length. During preheating, the preheating roller temperature is controlled at 75°C, the stretching temperature at 100°C, the cooling temperature at 10°C, and the stretching ratio at 3.0 times. The longitudinally stretched film is then fed into a preheated transverse stretching roller assembly, with the preheating roller temperature controlled at 105°C, the stretching temperature at 120°C, and the stretching ratio at 3.0 times. After stretching, the film is set at 230°C and then gradually cooled to room temperature, ensuring that the crystallinity of the polyester film reaches more than 30%. After stretching, a polyester film is obtained, which is then drawn and wound to obtain the insulating oligomer film material of this application, with a film thickness of 75 μm.

[0029] Example 2 This embodiment discloses an insulating oligomer film, which is prepared by polyester resin through extrusion slicing, melt extrusion, casting, and biaxial stretching to form a film. The specific steps are as follows: S1. Preparation and extrusion of polyester resin (all parts mentioned below are by weight): 100 parts terephthalic acid, 3 parts isophthalic acid, 62 parts ethylene glycol and 0.3 parts antioxidant were thoroughly mixed. Antioxidant 1010 was selected. The esterification reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 240℃ and the reaction pressure was 0.2MPa. The reaction was stopped when the water output reached 90%-95% of the theoretically complete reaction output. After completion, 0.04 parts of catalyst and 11 parts of 1-fluoro-2,3-propanediol were added to the material. The catalyst used was antimony glycolide. Polycondensation reaction was carried out at a temperature of 270℃ and a pressure of 500Pa. The reaction was stopped when the intrinsic viscosity of the system reached 0.65-0.7dL / g. After cooling, polyester resin was obtained. Polyester resin and pyromellitic anhydride (1.1% by weight of polyester resin) are added together into a reactive extruder. The temperature of the reaction section is set at 230-260℃, specifically 230℃ for zone 1, 255℃ for zone 2, 240℃ for zone 3, and 260℃ for zone 4 (die head). The vacuum degree of the impurity removal section is -0.1MPa, and the screw speed is set at 55r / min. After melt extrusion and cooling, polyethylene terephthalate chips are obtained.

[0030] S2. Melt extrusion (all percentages mentioned below are by weight): The polyethylene terephthalate obtained above was mixed with other auxiliary materials in a certain proportion to obtain the extrudate, specifically: 99.67% polyethylene terephthalate chips, 0.03% antimony trioxide, 0.05% triphenyl phosphate, 0.2% silicon dioxide, 0.04% titanium dioxide, and 0.01% magnesium acetate tetrahydrate. The extrudate was mixed at 170°C for 7 minutes and then placed in a twin-screw extruder. The melt temperature was controlled at 290°C. The extrudate was extruded through a metering pump, a filter, and a melt line from the die, with the extrusion speed controlled at 35 r / min.

[0031] S3. Casting The polyester melt is cooled by a cold drum with a surface temperature of 30°C, and then passed through a high-voltage electrostatic film-attachment system to form a cast sheet with a crystallinity of less than 5%.

[0032] S4, biaxial stretching film formation After preheating, the cast film is fed into a preheated longitudinal stretching roller assembly for longitudinal stretching along its length. During preheating, the preheating roller temperature is controlled at 85°C, the stretching temperature at 125°C, the cooling temperature at 20°C, and the stretching ratio at 3.5 times. The longitudinally stretched film is then fed into a preheated transverse stretching roller assembly, with the preheating roller temperature controlled at 115°C, the stretching temperature at 135°C, and the stretching ratio at 3.3 times. After stretching, the film is set at 245°C and then gradually cooled to room temperature, ensuring that the crystallinity of the polyester film reaches more than 30%. After stretching, a polyester film is obtained, which is then drawn and wound to obtain the insulating oligomer film material of this application, with a film thickness of 65 μm.

[0033] Example 3 This embodiment discloses an insulating oligomer film, which is prepared by polyester resin through extrusion slicing, melt extrusion, casting, and biaxial stretching to form a film. The specific steps are as follows: S1. Preparation and extrusion of polyester resin (all parts mentioned below are by weight): 100 parts terephthalic acid, 2.3 parts isophthalic acid, 58 parts ethylene glycol and 0.2 parts antioxidant were thoroughly mixed. The antioxidants used were 0.1 parts antioxidant 1076 and 0.1 parts antioxidant 1010. The esterification reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 220℃ and the reaction pressure was 0.15MPa. The reaction was stopped when the amount of water produced reached 90%-95% of the theoretically complete reaction amount. After completion, 0.03 parts of catalyst and 9 parts of 1-fluoro-2,3-propanediol were added to the material. The catalyst used was attapulgite-supported titanium glycol. Polycondensation reaction was carried out at a temperature of 250℃ and a pressure of 350Pa. The reaction was stopped when the intrinsic viscosity of the system reached 0.65-0.7dL / g. After cooling, polyester resin was obtained. Polyester resin and pyromellitic anhydride at a weight ratio of 1% of the polyester resin are added together into a reactive extruder. The temperature of the reaction section is set at 230-260℃, specifically 230℃ for zone 1, 255℃ for zone 2, 240℃ for zone 3, and 260℃ for zone 4 (die head). The vacuum degree of the impurity removal section is -0.09MPa, and the screw speed is set at 50r / min. After melt extrusion and cooling, polyethylene terephthalate chips are obtained.

[0034] S2. Melt extrusion (all percentages mentioned below are by weight): The polyethylene terephthalate obtained above was mixed with other auxiliary materials in a certain proportion to obtain the extrudate, specifically: 99.39% polyethylene terephthalate chips, 0.05% antimony trioxide, 0.07% triphenyl phosphate, 0.4% silicon dioxide, 0.06% titanium dioxide, 0.02% magnesium acetate tetrahydrate, and 0.01% sodium acetate. The extrudate was mixed at 160°C for 5 minutes and then placed in a twin-screw extruder. The melt temperature was controlled at 280°C. The extrudate was extruded through a metering pump, filter, and melt line from the die, and the extrusion speed was controlled at 28 r / min.

[0035] S3. Casting The polyester melt is cooled by a cold drum with a surface temperature of 24°C, and then passed through a high-voltage electrostatic film-attachment system to form a cast sheet with a crystallinity of less than 5%.

[0036] S4, biaxial stretching film formation After preheating, the cast film is fed into a preheated longitudinal stretching roller assembly for longitudinal stretching along its length. During preheating, the preheating roller temperature is controlled at 80°C, the stretching temperature at 115°C, the cooling temperature at 15°C, and the stretching ratio at 3.3 times. The longitudinally stretched film is then fed into a preheated transverse stretching roller assembly. The preheating roller temperature is controlled at 110°C, the stretching temperature at 125°C, and the stretching ratio at 3.3 times. After stretching, the film is set at 240°C and then gradually cooled to room temperature, controlling the crystallinity of the polyester film to reach more than 30%. After stretching, a polyester film is obtained, which is then drawn and wound to obtain the insulating oligomer film material of this application, with a film thickness of 90 μm.

[0037] Example 4 The difference between this embodiment and Embodiment 1 is that the raw materials used in the preparation of polyethylene terephthalate (PET) chips are different.

[0038] In this embodiment, polyethylene terephthalate chips are prepared through the following steps: 100 parts terephthalic acid, 1.5 parts isophthalic acid, 50 parts ethylene glycol and 0.1 parts antioxidant were thoroughly mixed. Antioxidant 1076 was selected. The esterification reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 200℃ and the reaction pressure was 0.1MPa. The reaction was stopped when the amount of water produced reached 90%-95% of the theoretically complete reaction amount. After completion, 0.01 parts of catalyst and 7 parts of 1-fluoro-2,3-propanediol were added to the material. Antimony trioxide was selected as the catalyst. Polycondensation reaction was carried out at a temperature of 240℃ and a pressure of 200Pa. The reaction was stopped when the intrinsic viscosity of the system reached 0.65-0.7dL / g. After cooling, polyester resin was obtained. The polyester resin was directly melt-extruded and cooled to obtain polyethylene terephthalate chips.

[0039] In this embodiment, the process of coupling and chain extension by reacting polyester resin and pyromellitic anhydride is omitted, and the polyester resin is directly extruded and sliced ​​before proceeding with the subsequent processes.

[0040] Example 5 The difference between this embodiment and Embodiment 1 is that the raw materials used in the preparation of polyethylene terephthalate (PET) chips are different.

[0041] In this embodiment, polyethylene terephthalate chips are prepared through the following steps: 100 parts terephthalic acid, 1.5 parts isophthalic acid, 50 parts ethylene glycol and 0.1 parts antioxidant were thoroughly mixed. Antioxidant 1076 was selected. The esterification reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 200℃ and the reaction pressure was 0.1MPa. The reaction was stopped when the amount of water produced reached 90%-95% of the theoretically complete reaction amount. After the reaction was completed, 0.01 parts of catalyst were added to the material. Antimony trioxide was selected as the catalyst to carry out the polycondensation reaction. The reaction temperature was 240℃ and the pressure was 200Pa. The reaction was stopped when the intrinsic viscosity of the system reached 0.65-0.7dL / g. After cooling, polyester resin was obtained. Polyester resin and 0.8% (by weight) of pyromellitic anhydride were added together into a reactive extruder. The temperature of the reaction section was set at 230-260℃, specifically 230℃ for zone 1, 255℃ for zone 2, 240℃ for zone 3, and 260℃ for zone 4 (die head). The vacuum degree of the impurity removal section was -0.08MPa, and the screw speed was set at 45r / min. After melt extrusion and cooling, polyethylene terephthalate chips were obtained.

[0042] In this embodiment, 1-fluoro-2,3-propanediol was not added as a third monomer during the polycondensation process of the polyester resin.

[0043] Example 6 The difference between this embodiment and Embodiment 1 is that the raw materials used in the preparation of polyethylene terephthalate (PET) chips are different.

[0044] In this embodiment, polyethylene terephthalate chips are prepared through the following steps: Mix 100 parts terephthalic acid, 50 parts ethylene glycol and 0.1 parts antioxidant thoroughly. Antioxidant 1076 is selected. The esterification reaction is carried out under a nitrogen atmosphere. The reaction temperature is controlled at 200℃ and the reaction pressure is 0.1MPa. The reaction is stopped when the water output reaches 90%-95% of the theoretically complete reaction output. After completion, 0.01 parts of catalyst and 7 parts of 1-fluoro-2,3-propanediol were added to the material. Antimony trioxide was selected as the catalyst to carry out polycondensation reaction. The reaction temperature was 240℃ and the pressure was 200Pa. The reaction was stopped when the intrinsic viscosity of the system reached 0.65-0.7dL / g. After cooling, polyester resin was obtained. Polyester resin and 0.8% (by weight) of pyromellitic anhydride were added together into a reactive extruder. The temperature of the reaction section was set at 230-260℃, specifically 230℃ for zone 1, 255℃ for zone 2, 240℃ for zone 3, and 260℃ for zone 4 (die head). The vacuum degree of the impurity removal section was -0.08MPa, and the screw speed was set at 45r / min. After melt extrusion and cooling, polyethylene terephthalate chips were obtained.

[0045] In this embodiment, isophthalic acid was not added as a raw material during the esterification reaction of the polyester resin.

[0046] Performance testing Xylene Extraction Value: Accurately weigh a certain amount of polyester film sample, cut it into small pieces, wrap it in filter paper, and place it in a Soxhlet extractor. Use xylene as the solvent and heat with a heating mantle for extraction. The extraction time is 24 hours. After extraction, the solvent is recovered by distillation, and the extract is dried in an oven until constant weight is achieved. Weigh the extract and calculate the xylene extraction value (%). The lower the xylene extraction value, the lower the oligomer content in the polyester film.

[0047] Heat aging resistance: PET film was cut into rectangular strips of 200mm × 15mm, and some strips were placed in a 210℃ forced-air oven for heat aging. After 72 hours, the strips were removed. The tensile strength (MPa) of the strips before and after heat aging was tested using an electronic universal testing machine at a tensile speed of 10mm / min, and the percentage decrease in tensile strength was calculated.

[0048] Water absorption rate: The water absorption rate (%) of polyester film materials was tested according to ASTM-D-570, "Standard Test Method for Water Absorption of Plastics".

[0049] Insulation performance: The surface of the prepared polyester film was cleaned using a dust extraction device, and its surface resistivity was then tested, reaching 10. 14 A value of Ω or higher indicates good insulation.

[0050] Table 1 shows the performance test results for each embodiment.

[0051] Table 1 Sample Xylene extract value Water absorption rate Insulation performance Tensile strength before aging Tensile strength after aging percentage decrease Example 1 0.54 0.6 good 136.8 61.8 54.8 Example 2 0.55 0.5 good 142.4 62.2 56.3 Example 3 0.57 0.6 good 138.5 63.6 54.1 Example 4 0.85 0.7 good 132.9 32.7 75.4 Example 5 0.60 0.9 good 135.3 50.5 62.7 Example 6 0.73 0.6 good 134.1 46.7 65.2 As shown in Table 1, the polyester film prepared in this application, through the selection of polyethylene terephthalate chips, exhibits low extraction performance and excellent high-temperature and heat aging resistance, while also possessing low water absorption and good insulation properties. When applied as electrical insulation material in refrigeration compressors, the film material of this application can operate stably for a long period, is not prone to functional breakdown, and has a long service life.

[0052] Meanwhile, after testing other properties, the polyester film prepared in this application has a haze of 92%, a heat shrinkage rate of only 1% at 150°C for 30 minutes, high transparency, compatibility with terephthalic acid or isophthalic acid ester-based impregnating varnishes, and can withstand a high temperature environment of 150°C.

[0053] The performance comparison of the polyester film materials in Examples 4-6 demonstrates that the added raw materials isophthalic acid, 1-fluoro-2,3-propanediol, and pyromellitic anhydride in the preparation of polyethylene terephthalate chips can synergistically reduce the thermal degradation of PET chips, reduce the growth of oligomers during the reaction process, and affect the heat aging resistance and water absorption of the polyester film.

[0054] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An insulating oligomeric film material, characterized by: The film material is prepared from polyester resin by the steps of extruding slice, melting extrusion, casting slice and biaxial stretching into film, in the step of melting extrusion, the extrusion material comprises the following raw materials in percentage by weight: Polyethylene terephthalate slice 99.35-99.71%; Antimony trioxide 0.03-0.06%; Triphenyl phosphate 0.05-0.09%; Silicon dioxide 0.2-0.4%; Titanium dioxide 0.04-0.08%; Magnesium acetate tetrahydrate 0.01-0.03%; Sodium acetate 0-0.01%; The oligomer content of the polyethylene terephthalate slice is less than 0.65%, and the intrinsic viscosity is 0.8-1.2 dL / g.

2. An insulating oligomeric film material according to claim 1, characterized in that: The polyethylene terephthalate slice is prepared by the following steps: The raw materials terephthalic acid, isophthalic acid, ethylene glycol and antioxidant are mixed thoroughly, and esterification reaction is carried out under nitrogen atmosphere; after the reaction is completed, catalyst and 1-fluoro-2,3-propanediol are added to the material, and polycondensation reaction is carried out, and polyester resin is obtained after cooling; The polyester resin and pyromellitic anhydride are added into a reaction extruder, and then melting extrusion, cooling and slicing are carried out to obtain polyethylene terephthalate slice.

3. An insulating oligomeric film material according to claim 2, wherein In the preparation of the polyester resin, the weight parts of the raw materials are as follows: terephthalic acid 100 parts; isophthalic acid 1.5-3 parts; ethylene glycol 50-62 parts; antioxidant 0.1-0.3 parts; catalyst 0.01-0.04 parts; 1-fluoro-2,3-propanediol 7-11 parts; and the weight ratio of the polyester resin to the pyromellitic anhydride is 1:0.8-1.1%.

4. An insulating oligomeric film material according to claim 3, characterized in that: The catalyst is selected from one or more of antimony trioxide, ethylene glycol antimony, complex catalyst formed by titanium and bis(diphenylphosphinoethyl) amine, and titanium glycol supported on attapulgite.

5. The insulating oligomeric film material of claim 2, wherein: The reaction temperature of the esterification reaction is 200-240℃, the reaction pressure is 0.1-0.2 MPa, and the reaction is stopped when the water output reaches 90%-95% of the theoretical complete reaction water output.

6. An insulating oligomeric film material according to claim 2, wherein: The reaction temperature of the polycondensation reaction is 240-270℃, the pressure is 200-500 Pa, and the reaction is stopped when the system intrinsic viscosity reaches 0.65-0.7 dL / g.

7. An insulating oligomeric film material according to claim 2, wherein: The conditions for extruding slice by the reaction extruder are as follows: the reaction section temperature is 230-260℃, the vacuum degree of the impurity removal section is -0.08--0.1 MPa, and the screw rotation speed is 45-55 r / min.

8. The insulating oligomeric film material of claim 1, wherein: In the step of melting extrusion, the extrusion material is mixed at 150-170℃ for 3-7 min, the melting temperature is 270-290℃, and the extrusion speed is controlled at 20-35 r / min.

9. The insulating oligomeric film material of claim 1, wherein: In the step of casting slice, the polyester melt is cooled by a cold drum with a surface temperature of 15-30℃, and then passes through a high-voltage electrostatic film forming system to form a casting slice with a crystallinity of less than 5%.

10. The insulating oligomeric film material of claim 1, wherein: In the step of biaxial stretching film formation, the longitudinal stretching is controlled at a preheating roller temperature of 75-85°C, a stretching temperature of 100-125°C, a cooling temperature of 10-20°C, and a stretching ratio of 3.0-3.5 times; the transverse stretching is controlled at a preheating roller temperature of 105-115°C, a stretching temperature of 120-135°C, and a stretching ratio of 3.0-3.3 times, and after stretching, the film is set at a temperature of 230-245°C, and then gradually cooled to room temperature, so that the crystallinity of the polyester film is controlled to be more than 30%.