High-ductility PVC calendering film and preparation method thereof

Abstract

The invention discloses a high-ductility PVC calendering film and a preparation method thereof. The preparation method comprises the following steps: step 1, weighing the components in parts by weight; 2, sequentially adding the raw materials in the step 1 into a high-speed hot mixing machine; 3, putting the materials subjected to hot mixing in the step 2 into a cold mixing machine; 4, feeding the material subjected to cold mixing in the step 3 into a twin-screw extrusion plasticator; 5, sequentially feeding the pre-plasticized material into a primary plastic mixing machine and a final plastic mixing machine; step 6, feeding the material sheet into a four-roller calender; seventhly, the rolled film is pulled to a cooling device through a traction device; and 8, coiling the cooled film, trimming, and inspecting to obtain the high-ductility PVC calendered film. PVC resin with a specific polymerization degree is selected and matched with a composite plasticizing system and a calcium-zinc stabilizer, so that the component compatibility, the processing stability and the environmental protection property and the ductility of the membrane material are improved.

Description

Technical Field

[0001] This invention relates to the field of PVC calendered film preparation, and more particularly to a high-ductility PVC calendered film and its preparation method. Background Technology

[0002] PVC calendered film is widely used in packaging, building materials, and light industry due to its low cost, good processability, and excellent overall performance. However, existing PVC calendered film manufacturing processes often suffer from problems such as insufficient elongation, easy cracking, and poor processing stability, which limit its application in high-end fields. In existing technologies, PVC resin has poor thermal stability during processing and is prone to degradation, which leads to a decrease in the mechanical properties of the membrane and affects its extensibility. In addition, traditional stabilizers are mostly lead salts, which have good thermal stability but pose environmental risks and do not meet the requirements of green production. On the other hand, when environmentally friendly stabilizers are used, improper formulation often leads to a narrow processing window and defects in the membrane. Therefore, it is necessary to consider how to solve the above problems. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-strength PVC calendered film and its preparation method. This method utilizes a PVC resin with a specific degree of polymerization, combined with a composite plasticizer system and a calcium-zinc stabilizer, to improve component compatibility, processing stability, and the environmental friendliness and stretchability of the film. High- and low-speed segmented mixing and twin-screw segmented temperature control processes ensure thorough plasticization of the material, guaranteeing uniform sheet size and improving calendered film performance. Precise temperature control in four-roll calendering, matching roll speed ratios, and three-stage cooling reduce shrinkage. Reasonable winding tension control ensures a flat film with stable dimensions and minimal defects.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a high-ductility PVC calendered film includes the following steps: Step 1: Weigh the following components by weight: 90-110 parts PVC resin, 30-50 parts DOP, 2-8 parts epoxidized soybean oil, 1-5 parts calcium-zinc composite stabilizer, 0.2-0.8 parts stearic acid, 0.1-0.5 parts PE wax, and 1-4 parts acrylic processing aids. Step 2: Add the raw materials from Step 1 to the high-speed hot mixer in sequence. First, stir at a low speed of 500-800 r / min for 3-5 minutes, then stir at a high speed of 1200-1500 r / min for 8-12 minutes. Control the material temperature to rise to 80-100℃ until the resin is fully swollen. Step 3: Place the material after hot mixing in Step 2 into a cold mixer and stir and cool it to about 50°C at 800-1000 r / min to obtain loose granular material; Step 4: Feed the material after cold mixing in Step 3 into a twin-screw extruder plasticizer. Use segmented temperature control: 140-145℃ for the feeding section, 145-155℃ for the compression section, and 155-160℃ for the metering section. Set the screw speed to 30-50 r / min for pre-plasticization. The plasticization degree should be ≥95%. Step 5: Feed the pre-plasticized material into the primary plasticizer and the final plasticizer in sequence. The roller temperature of the primary plasticizer is 150-155℃, the roller speed ratio is 1:1.2-1:1.5, and the plasticizing time is 3-5 minutes. The roller temperature of the final plasticizer is 155-160℃, the roller speed ratio is 1:1.5-1:2.0, and the plasticizing time is 2-4 minutes, to obtain a sheet with a thickness of 2-5mm. Step 6: Feed the sheet into a four-roll calender. The temperatures of the four rolls are as follows: upper roll 160-165℃, middle roll 165-170℃, lower roll 160-165℃, and bottom roll 155-160℃. The roll speed ratio is 1:1.2:1.5:1.8. Adjust the roll gap to the target film thickness and calender the sheet. Step 7: The calendered film is drawn to the cooling device by the traction device and cooled in three stages: slow cooling zone 80-100℃, rapid cooling zone 20-30℃, and constant temperature zone 25-30℃, until the film shrinkage rate is ≤1%; Step 8: Wind up the cooled film with a winding tension of 3-8 N / m. After winding, trim the edges and inspect to obtain a high-strength PVC calendered film.

[0005] Preferably, the calcium-zinc composite stabilizer in step one has a calcium-zinc molar ratio of 3:1-5:1, and the calcium-zinc composite stabilizer also contains 0.5-1.0 parts of phosphite auxiliary stabilizer; the PVC resin is a suspension PVC resin with an average degree of polymerization of 1000-1200; and the epoxy value of the epoxidized soybean oil is ≥6.0%.

[0006] Preferably, in step six, the gap between the feed rollers of the four-roll calender is 2-3 mm, the gap at the discharge end is consistent with the target film thickness with an error of ±0.01 mm, and the film thickness is monitored in real time using an online thickness detector.

[0007] Preferably, during the winding process in step eight, 0.05-0.1% of an antistatic agent by weight of the film is sprayed onto the film surface, and the cut edge width is 5-10 mm.

[0008] Preferably, the components mentioned in step one are specifically in the following weight parts: 90 parts PVC resin, 30 parts DOP, 2 parts epoxidized soybean oil, 1 part calcium-zinc composite stabilizer, 0.2 parts stearic acid, 0.1 parts PE wax, and 1 part acrylate processing aid.

[0009] Preferably, the components mentioned in step one are specifically in the following weight parts: 100 parts PVC resin, 40 parts DOP, 4 parts epoxidized soybean oil, 3 parts calcium-zinc composite stabilizer, 0.4 parts stearic acid, 0.3 parts PE wax, and 2 parts acrylate processing aid.

[0010] Preferably, the components mentioned in step one are in the following weight parts: 110 parts PVC resin, 50 parts DOP, 6 parts epoxidized soybean oil, 5 parts calcium-zinc composite stabilizer, 0.6 parts stearic acid, 0.5 parts PE wax, and 3 parts acrylate processing aid.

[0011] Preferably, the components mentioned in step one are 95 parts by weight of PVC resin, 35 parts of DOP, 8 parts of epoxidized soybean oil, 2 parts of calcium-zinc composite stabilizer, 0.8 parts of stearic acid, 0.2 parts of PE wax, and 4 parts of acrylate processing aid.

[0012] The present invention also discloses a high-ductility PVC calendered film, which is prepared by the above-mentioned preparation method. The PVC calendered film has a thickness of 0.05-0.5 mm, an elongation at break of ≥300%, a tensile strength of ≥15 MPa, and a shrinkage rate of ≤1%.

[0013] Compared with the prior art, the beneficial effects of this invention are as follows: 1. By selecting PVC resin with a specific degree of polymerization, and combining it with DOP, epoxidized soybean oil composite plasticizer system and calcium-zinc composite stabilizer, the compatibility of each component is improved, the processing stability of PVC resin is enhanced, degradation during processing is avoided, the environmental friendliness of the membrane material is guaranteed, and the extensibility of the membrane material is significantly improved.

[0014] 2. The high- and low-speed segmented mixing process ensures that the material is fully swollen and mixed evenly, laying the foundation for subsequent plasticizing and calendering. The segmented temperature control of the twin-screw extrusion and the precise setting of plasticizing and calendering parameters can achieve full plasticization of the material, ensure uniform sheet texture, and improve the ductility and mechanical properties of the calendered film.

[0015] 3. The four-roll calender features precise temperature control and roll speed ratio matching, combined with a three-stage cooling process, which effectively reduces film shrinkage, improves dimensional stability, and prevents film deformation and cracking after cooling; reasonable winding tension control ensures flat film winding and reduces edge defects. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for preparing a high-ductility PVC calendered film according to the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0018] Example 1 Reference Figure 1 A method for preparing a high-ductility PVC calendered film includes the following steps: Step 1: Weigh the following components by weight: 90 parts PVC resin, using suspension PVC resin with an average degree of polymerization of 1000-1200. This degree of polymerization range balances processing fluidity and film mechanical strength. The resin obtained by the suspension process has high purity and uniform particle morphology, which can improve the subsequent plasticizing effect. 30 parts DOP, as the main plasticizer, has excellent compatibility with PVC resin and can effectively reduce intermolecular forces, improving the film's extensibility. 2 parts epoxidized soybean oil, as an auxiliary plasticizer and heat stabilizer, with an epoxy value ≥6.0%, which can enhance plasticizing compatibility and inhibit thermal degradation during PVC processing, improving environmental friendliness. 1 part calcium-zinc composite stabilizer, with a calcium-zinc molar ratio of 3:1-5:1, combined with 0.5-1.0 parts phosphite auxiliary stabilizer, which is lead-free and environmentally friendly. The synergistic effect of the two can extend the processing and molding cycle and prevent high-temperature degradation of materials. 0.2 parts stearic acid, as an internal lubricant, reduces internal friction of materials and improves plasticizing uniformity. 0.1 parts PE wax, used as an external lubricant, reduces friction between materials and equipment, preventing membrane adhesion after molding. 1 part acrylate processing aid improves the flowability of PVC processing and enhances the surface smoothness and mechanical strength of the membrane.

[0019] Step 2: Add the raw materials from Step 1 to a high-speed hot mixer (reference model: SHR-500A) in sequence. First, stir at a low speed of 500-800 rpm for 3-5 minutes to initially disperse the raw material particles evenly and avoid local material agglomeration and overheating during high-speed stirring. Then, stir at a high speed of 1200-1500 rpm for 8-12 minutes.

[0020] Step 3: Place the hot-mixed material from Step 2 into a cold mixer (reference model: LCH-500), and stir and cool it to about 50°C at 800-1000 rpm. This rapidly lowers the material temperature, terminates the resin swelling reaction, prevents material agglomeration, and yields loose granular material, which is convenient for subsequent extrusion feeding. The equipment's water cooling system can be activated during the cooling process to improve cooling efficiency.

[0021] Step 4: Feed the cold-mixed material from Step 3 into a twin-screw extruder plasticizer (reference model: SHJ-65, screw L / D ratio 36:1), using segmented temperature control. Feeding section: 140-145℃ to maintain the material in a solid state and prevent premature plasticization and blockage. Compression section: 145-155℃, where the material gradually melts and internal air is expelled. Metering section: 155-160℃, maintaining a constant temperature to ensure full plasticization. Screw speed: 30-50 r / min for pre-plasticization, achieving a plasticization degree ≥95%. Plasticization degree is tested using a slice observation method to ensure no unplasticized particles are present.

[0022] Step 5: Feed the pre-plasticized material sequentially into the primary plasticizer and the final plasticizer. In the primary plasticizer, the roller temperature is 150-155℃, the roller speed ratio is 1:1.2-1:1.5, and the mixing time is 3-5 minutes to further homogenize the material and eliminate internal stress. In the final plasticizer, the roller temperature is 155-160℃, the roller speed ratio is 1:1.5-1:2.0, and the mixing time is 2-4 minutes to improve the fineness of the plasticized material, control the uniformity of the sheet thickness, and obtain a 2-5mm thick sheet with no bubbles or impurities on the surface.

[0023] Step Six: Feed the sheet into a four-roll calender (reference model: S4F-1600). The temperatures of the four rolls are sequentially set: upper roll 160-165℃, middle roll 165-170℃, lower roll 160-165℃, and bottom roll 155-160℃. This gradient temperature design ensures the sheet gradually stretches, preventing localized overheating or rapid cooling that could lead to film cracking. The roll speed ratio is 1:1.2:1.5:1.8, generating shear force through the speed difference to uniformly thin the sheet. Adjust the roll gap to the target film thickness. The feed end roll gap of the four-roll calender is 2-3mm, adapted to the sheet thickness, to avoid feed blockage. The discharge end gap is consistent with the target film thickness, with an error of ±0.01mm. An online thickness gauge (accuracy 0.001mm) is used to monitor the film thickness in real time, and the roll gap is adjusted promptly if any deviation is detected.

[0024] Step 7: The calendered film is drawn to the cooling device via a traction device (traction speed matched to calendering speed, deviation ≤5%), employing a three-stage cooling process. The slow cooling zone (80-100℃) gradually lowers the temperature, releasing internal stress in the film. The rapid cooling zone (20-30℃) quickly sets the film shape and controls its dimensions. The constant temperature zone (25-30℃) balances the film temperature and reduces shrinkage. Cooling continues until the film shrinkage rate is ≤1%. Shrinkage rate testing follows the GB / T13519-2008 standard.

[0025] Step 8: Wind up the cooled film with a tension of 3-8 N / m. Uniform tension prevents the film from stretching, deforming, or wrinkling. During winding, spray 0.05-0.1% (by weight) of antistatic agent onto the film surface. Use a non-ionic antistatic agent to prevent dust from adsorbing onto the film. After winding, trim and inspect the edges. The trimmed edge width should be 5-10 mm. Remove irregular parts to obtain a high-strength PVC calendered film.

[0026] The present invention also discloses a high-ductility PVC calendered film, which is prepared by the above-mentioned preparation method. The PVC calendered film has a thickness of 0.05-0.5 mm, an elongation at break of ≥300%, a tensile strength of ≥15 MPa, and a shrinkage rate of ≤1%.

[0027] Beneficial effects: This embodiment features a balanced raw material ratio, low production energy consumption, suitability for large-scale industrial production, and controllable production costs. The prepared PVC calendered film balances extensibility and mechanical strength, exhibits excellent dimensional stability, is lead-free and environmentally friendly, and can meet the needs of general packaging, building material coating, and other fields. Through segmented mixing, gradient calendering, and three-stage cooling processes, the film surface is smooth and flawless, with good thickness uniformity.

[0028] Example 2 Reference Figure 1 A method for preparing a high-ductility PVC calendered film includes the following steps: Step 1: Weigh the following components by weight: 100 parts PVC resin, using suspension PVC resin with an average degree of polymerization of 1000-1200. This degree of polymerization range ensures that the film material has both extensibility and stiffness. Suspension resin particles are uniform and have high plasticizing efficiency. 40 parts DOP, as the main plasticizer, the dosage is suitable for medium to high extensibility requirements, and can significantly reduce the glass transition temperature of PVC resin and improve the flexibility of the film material. 4 parts epoxidized soybean oil, as an auxiliary plasticizer and heat stabilizer, with an epoxy value ≥6.0%, which is more environmentally friendly than traditional plasticizers, while also improving the aging resistance of the film material. 3 parts calcium-zinc composite stabilizer, with a calcium-zinc molar ratio of 3:1-5:1, combined with 0.5-1.0 parts phosphite auxiliary stabilizer, to synergistically improve thermal stability performance, adapt to the processing requirements of higher plasticizing systems, and prevent material degradation. 0.4 parts stearic acid, as an internal lubricant, the dosage is suitable for the material viscosity to ensure uniform plasticization. 0.3 parts PE wax, used as an external lubricant to prevent the membrane from sticking to the equipment and improve the surface smoothness of the membrane. 2 parts acrylate processing aid to improve the processing fluidity of the high plasticizing system and prevent pitting and bubbles from appearing on the membrane.

[0029] Step 2: Add the raw materials from Step 1 to a high-speed hot mixer (reference model: SHR-800A) in sequence. First, stir at a low speed of 500-800 rpm for 3-5 minutes to achieve initial dispersion of the raw materials, avoid local aggregation of plasticizer during high-speed stirring, and ensure uniform mixing. Then, stir at a high speed of 1200-1500 rpm for 8-12 minutes.

[0030] Step 3: Place the material after hot mixing in Step 2 into a cold mixer (reference model: LCH-800), stir and cool it to about 50°C at 800-1000r / min. Rapid cooling stops the swelling. Stirring loosens the material particles, making it easier to feed for subsequent extrusion. Cooling to 50°C can prevent the material temperature from being too high and causing over-plasticization during extrusion, resulting in loose granular material.

[0031] Step 4: Feed the cold-mixed material from Step 3 into a twin-screw extruder plasticizer (reference model: SHJ-80, screw L / D ratio 36:1), using segmented temperature control. The feeding section is 140-145℃ to maintain the material in a solid state and ensure smooth feeding. The compression section is 145-155℃, where the material melts and discharges internal voids, increasing plasticized density. The metering section is 155-160℃, maintaining a constant temperature to control the degree of plasticization and avoid uneven plasticization due to temperature fluctuations. The screw speed is 30-50 r / min for pre-plasticization, achieving a plasticization degree ≥95%. A torque rheometer is used to detect the plasticization degree to ensure it meets requirements.

[0032] Step 5: Feed the pre-plasticized material sequentially into the primary plasticizer and the final plasticizer. In the primary plasticizer, the roller temperature is 150-155℃, the roller speed ratio is 1:1.2-1:1.5, and the plasticizing time is 3-5 minutes to eliminate internal stress in the material and ensure uniform dispersion of the plasticizer. In the final plasticizer, the roller temperature is 155-160℃, the roller speed ratio is 1:1.5-1:2.0, and the plasticizing time is 2-4 minutes to refine the microstructure of the material and control the sheet thickness deviation to ≤0.2mm, resulting in sheets with a thickness of 2-5mm.

[0033] Step Six: Feed the sheet into a four-roll calender (reference model: S4F-1800). The temperatures of the four rolls are sequentially set: upper roll 160-165℃, middle roll 165-170℃, lower roll 160-165℃, and bottom roll 155-160℃. This temperature gradient allows the sheet to gradually stretch during calendering, preventing the film from breaking due to excessive heat. The roll speed ratio is 1:1.2:1.5:1.8. The shearing force generated by the speed difference makes the sheet thinner uniformly, improving the film's extensibility. Adjust the roll gap to the target film thickness and calender. The feed end roll gap of the four-roll calender is 2-3mm, and the discharge end gap is consistent with the target film thickness, with an error of ±0.01mm. An online thickness gauge monitors the film thickness in real time, and the monitoring data is fed back to the control system in real time to achieve automatic gap adjustment.

[0034] Step 7: The calendered film is drawn to the cooling device via a traction device (traction speed 3-5 m / min, synchronized with the calendering speed), employing a three-stage cooling process. The slow cooling zone (80-100℃) releases internal stress in the film material, reducing subsequent shrinkage. The rapid cooling zone (20-30℃) quickly sets the film shape, ensuring dimensional accuracy. The constant temperature zone (25-30℃) balances the film temperature, improving dimensional stability. Cooling continues until the film shrinkage rate is ≤1%.

[0035] Step 8: Wind up the cooled film with a tension of 3-8 N / m. Adjust the tension according to the film thickness: 3-5 N / m for thinner films and 5-8 N / m for thicker films to prevent deformation. During winding, spray 0.05-0.1% (by weight) of antistatic agent onto the film surface. Use a long-lasting antistatic agent to improve the film's antistatic durability. After winding, trim and inspect the edges. The trimmed edge width should be 5-10 mm to obtain a high-strength PVC calendered film.

[0036] The present invention also discloses a high-ductility PVC calendered film, which is prepared by the above-mentioned preparation method. The PVC calendered film has a thickness of 0.05-0.5 mm, an elongation at break of ≥300%, a tensile strength of ≥15 MPa, and a shrinkage rate of ≤1%.

[0037] Beneficial effects: In this embodiment, the plasticizer dosage is optimized, significantly improving the film's extensibility and increasing the elongation at break compared to Example 1. The calcium-zinc composite stabilizer dosage is suitable for the high-plasticization system, resulting in strong processing stability and no degradation. The prepared film exhibits excellent flexibility and good aging resistance, making it suitable for applications requiring high extensibility, such as elastic packaging and food packaging. The high degree of automation allows for online closed-loop thickness control, ensuring good product consistency.

[0038] Example 3 Reference Figure 1 A method for preparing a high-ductility PVC calendered film includes the following steps: Step 1: Weigh the following components by weight: 110 parts PVC resin (select suspension PVC resin with an average degree of polymerization of 1000-1200). Increasing the resin content improves the mechanical strength of the film, meeting the strength requirements under high extensibility. 50 parts DOP (Dry Oxide), as the main plasticizer; high dosage maximizes the extensibility of the film, meeting the stretching requirements of special scenarios. 6 parts epoxidized soybean oil, as an auxiliary plasticizer and heat stabilizer, with an epoxy value ≥6.0%. High dosage enhances the environmental friendliness and weather resistance of the film, while inhibiting the thermal degradation of the high-plasticization system. 5 parts calcium-zinc composite stabilizer (calcium-zinc molar ratio of 3:1-5:1), combined with 0.5-1.0 parts phosphite auxiliary stabilizer. High dosage ensures the thermal stability of the high-resin, high-plasticization system, extending the processing window. 0.6 parts stearic acid, as an internal lubricant, suitable for high-viscosity materials, improving plasticizing fluidity. 0.5 parts PE wax, used as an external lubricant, prevents high-viscosity materials from sticking to equipment and improves processing smoothness. 3 parts acrylate processing aid; high dosage can significantly improve the processing performance of high-viscosity materials and prevent defects such as flow marks and material shortages in the film.

[0039] Step Two: Add the raw materials from Step One to a high-speed hot mixer (reference model: SHR-1000A) in sequence. First, stir at a low speed of 500-800 rpm for 3-5 minutes to mix the resin, stabilizer, and lubricant evenly. Then add the plasticizer to avoid uneven adsorption. Next, stir at a high speed of 1200-1500 rpm for 8-12 minutes, extending the high-speed stirring time to 10-12 minutes to ensure that the high dosage of plasticizer is fully integrated with the resin. Raise the temperature to 90-100℃ to promote full swelling of the resin. Control the material temperature to 80-100℃ until the resin is fully swollen.

[0040] Step 3: Place the material after hot mixing in Step 2 into a cold mixer (reference model: LCH-1000), and stir and cool it to about 50°C at 800-1000r / min. For materials with high resin content, heat dissipation is slower. You can turn on the strong cooling mode of the cooling device to ensure that it cools to 50°C within 30 minutes to obtain loose granular material and avoid clumping.

[0041] Step 4: Feed the cold-mixed material from Step 3 into a twin-screw extruder (reference model: SHJ-95, screw L / D ratio 40:1), using segmented temperature control. Feeding section: 140-145℃. Appropriately lower the feeding section temperature to prevent premature plasticization and blockage of high-resin materials. Compression section: 145-155℃. Increase the compression section temperature to promote melting of high-viscosity materials. Metering section: 155-160℃. Maintain constant temperature control to ensure uniform plasticization. Screw speed: 30-50 r / min. Select 30-40 r / min to extend the plasticization time for pre-plasticization, achieving a plasticization degree ≥95%.

[0042] Step 5: Feed the pre-plasticized material sequentially into the primary plasticizer and the final plasticizer. The primary plasticizer roller temperature is 150-155℃, roller speed ratio is 1:1.2-1:1.5, and plasticizing time is 4-5 minutes. Extending the primary mixing time ensures uniform mixing of the high-viscosity material. The final plasticizer roller temperature is 155-160℃, roller speed ratio is 1:1.5-1:2.0, and plasticizing time is 3-4 minutes. This refines the material structure, controls the uniformity of the sheet thickness, and yields sheets 2-5 mm thick.

[0043] Step Six: Feed the sheet into a four-roll calender (reference model: S4F-2000). The temperatures of the four rolls are as follows: upper roll 160-165℃, middle roll 165-170℃, lower roll 160-165℃, and bottom roll 155-160℃, maintaining a temperature gradient. High-viscosity sheets require temperature adjustment to improve fluidity. The roll speed ratio is 1:1.2:1.5:1.8, but a ratio of 1:1.3:1.5:1.8 is selected to increase shear force. Adjust the roll gap to the target film thickness and calender. The feed end roll gap of the four-roll calender is 2.5-3mm, suitable for feeding high-viscosity sheets. The discharge end gap is consistent with the target film thickness, with an error of ±0.01mm, and the film thickness is monitored in real time using an online thickness gauge.

[0044] Step 7: The calendered film is drawn to the cooling device via a traction device (traction speed 2-4 m / min; reduce the traction speed to avoid stretching and deformation of the highly ductile film material), employing a three-stage cooling process. The slow cooling zone is 80-100℃, with the slow cooling time extended to 5-8 minutes to fully release internal stress. The rapid cooling zone is 20-30℃, and the constant temperature zone is 25-30℃, cooling until the film shrinkage rate is ≤1%.

[0045] Step 8: Wind the cooled film with a tension of 3-8 N / m, preferably 3-6 N / m, to reduce tension and avoid stretching. During winding, spray 0.08-0.1% (by weight of film weight) of antistatic agent onto the film surface to increase the amount of antistatic agent and meet the antistatic requirements of high resin content film materials. After winding, trim and inspect the edges, with a trim width of 5-10 mm, to obtain a high-strength PVC calendered film.

[0046] The present invention also discloses a high-ductility PVC calendered film, which is prepared by the above-mentioned preparation method. The PVC calendered film has a thickness of 0.05-0.5 mm, an elongation at break of ≥300%, a tensile strength of ≥15 MPa, and a shrinkage rate of ≤1%.

[0047] Beneficial Effects: In this embodiment, the amounts of PVC resin and plasticizer are relatively high, resulting in optimal film extensibility and further increased elongation at break, making it suitable for applications with extremely high tensile performance requirements. By optimizing processing parameters, extending mixing and plasticizing times, and reducing traction speed, the problem of processing high-viscosity materials is solved. The prepared film material balances mechanical strength and extensibility, exhibits good weather resistance, and meets environmental standards, satisfying the needs of high-end packaging applications.

[0048] Example 4 Reference Figure 1 A method for preparing a high-ductility PVC calendered film includes the following steps: Step 1: Weigh the following components by weight: 95 parts PVC resin (select suspension PVC resin with an average degree of polymerization of 1000-1200, balancing processability and strength); 35 parts DOP (as the main plasticizer, moderate dosage, balancing extensibility and stiffness); 8 parts epoxidized soybean oil (as an auxiliary plasticizer and heat stabilizer, epoxy value ≥6.0%, high dosage can significantly improve the heat resistance, weather resistance and environmental performance of the film material, suitable for outdoor or high-temperature applications); 2 parts calcium-zinc composite stabilizer (calcium-zinc molar ratio 3:1-5:1), combined with 0.5-1.0 parts phosphite auxiliary stabilizer, synergistically improving thermal stability, suitable for high-dosage systems of epoxidized soybean oil); 0.8 parts stearic acid (as an internal lubricant, high dosage can reduce material viscosity and improve processing fluidity); 0.2 parts PE wax (as an external lubricant, ensuring a smooth film surface). Four parts of acrylate processing aid; a high dosage can improve the impact resistance and processing stability of the membrane material and prevent it from becoming brittle.

[0049] Step Two: Add the raw materials from Step One to a high-speed hot mixer (reference model: SHR-600A) in sequence. First, stir at a low speed of 500-800 rpm for 3-5 minutes to mix the resin, stabilizer, and additives. Then, slowly add DOP and epoxidized soybean oil to prevent plasticizer volatilization. Next, stir at a high speed of 1200-1500 rpm for 8-12 minutes, raising the temperature to 85-95℃ to promote the full integration of epoxidized soybean oil and resin. Control the material temperature to rise to 80-100℃ until the resin is fully swollen.

[0050] Step 3: Place the hot-mixed material from Step 2 into a cold mixer (reference model: LCH-600), and stir at 800-1000 r / min to cool it to about 50°C. The epoxidized soybean oil system cools down relatively quickly, so normal stirring is sufficient to obtain loose granular material.

[0051] Step 4: Feed the material after cold mixing in Step 3 into a twin-screw extruder plasticizer (reference model: SHJ-75, screw length-to-diameter ratio 38:1), using segmented temperature control. Feeding section: 140-145℃; Compression section: 145-155℃; Metering section: 155-160℃; Screw speed: 30-50 r / min. Pre-plasticize to a plasticization degree ≥95%. Epoxidized soybean oil can improve plasticization efficiency and ensure uniform plasticization.

[0052] Step 5: Feed the pre-plasticized material sequentially into the primary plasticizer and the final plasticizer. The primary plasticizer roller temperature is 150-155℃, roller speed ratio is 1:1.2-1:1.5, and plasticizing time is 3-5 minutes. The final plasticizer roller temperature is 155-160℃, roller speed ratio is 1:1.5-1:2.0, and plasticizing time is 2-4 minutes. Acrylic ester processing aids can improve material flowability, ensuring a smooth plasticizing process and yielding 2-5mm thick sheets.

[0053] Step Six: Feed the sheet into a four-roll calender (reference model: S4F-1700). The temperatures of the four rolls are as follows: upper roll 160-165℃, middle roll 165-170℃, lower roll 160-165℃, and bottom roll 155-160℃. Epoxidized soybean oil system sheet has good heat resistance and can be calendered stably. The roll speed ratio is 1:1.2:1.5:1.8. Adjust the roll gap to the target film thickness and calender. The infeed roll gap of the four-roll calender is 2-3mm, and the outlet roll gap is consistent with the target film thickness, with an error of ±0.01mm. An online thickness gauge is used to monitor the film thickness in real time.

[0054] Step 7: The calendered film is drawn to the cooling device via a traction device and cooled in three stages: slow cooling zone 80-100℃, rapid cooling zone 20-30℃, and constant temperature zone 25-30℃. Epoxidized soybean oil enhances the heat resistance of the film material, making it less prone to cracking during the cooling process. Cooling is continued until the film shrinkage rate is ≤1%.

[0055] Step 8: Wind the cooled film at a tension of 3-8 N / m. During winding, spray 0.05-0.1% (by weight) of antistatic agent onto the film surface. After winding, trim and inspect the edges, ensuring a trim width of 5-10 mm, to obtain a high-strength PVC calendered film.

[0056] The present invention also discloses a high-ductility PVC calendered film, which is prepared by the above-mentioned preparation method. The PVC calendered film has a thickness of 0.05-0.5 mm, an elongation at break of ≥300%, a tensile strength of ≥15 MPa, and a shrinkage rate of ≤1%.

[0057] Beneficial Effects: This embodiment emphasizes a high dosage of epoxidized soybean oil, resulting in optimal heat resistance, weather resistance, and environmental performance of the membrane material. It can be used for extended periods outdoors in high-temperature environments, such as for outdoor building material coatings. The high dosage of acrylate processing aids enhances the membrane material's impact resistance, preventing brittleness. The raw material ratio balances ductility, strength, and weather resistance, ensuring strong processing stability, making it suitable for fields with specific environmental and weather resistance requirements.

[0058] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-ductility PVC calendered film, characterized in that, Includes the following steps: Step 1: Weigh the following components by weight: 90-110 parts PVC resin, 30-50 parts DOP, 2-8 parts epoxidized soybean oil, 1-5 parts calcium-zinc composite stabilizer, 0.2-0.8 parts stearic acid, 0.1-0.5 parts PE wax, and 1-4 parts acrylic processing aids. Step 2: Add the raw materials from Step 1 to the high-speed hot mixer in sequence. First, stir at a speed of 500-800 r / min for 3-5 minutes, then stir at a speed of 1200-1500 r / min for 8-12 minutes. Control the material temperature to rise to 80-100℃ until the resin is fully swollen. Step 3: Place the material after hot mixing in Step 2 into a cold mixer and stir and cool it to about 50°C at a speed of 800-1000 r / min to obtain loose granular material; Step 4: Feed the material after cold mixing in Step 3 into a twin-screw extruder plasticizer. Use segmented temperature control: 140-145℃ for the feeding section, 145-155℃ for the compression section, and 155-160℃ for the metering section. Set the screw speed to 30-50 r / min for pre-plasticization. The plasticization degree should be ≥95%. Step 5: Feed the pre-plasticized material into the primary plasticizer and the final plasticizer in sequence. The roller temperature of the primary plasticizer is 150-155℃, the roller speed ratio is 1:1.2-1:1.5, and the plasticizing time is 3-5 minutes. The roller temperature of the final plasticizer is 155-160℃, the roller speed ratio is 1:1.5-1:2.0, and the plasticizing time is 2-4 minutes, to obtain a sheet with a thickness of 2-5mm. Step 6: Feed the sheet into a four-roll calender. The temperatures of the four rolls are as follows: upper roll 160-165℃, middle roll 165-170℃, lower roll 160-165℃, and bottom roll 155-160℃. The roll speed ratio is 1:1.2:1.5:1.

8. Adjust the roll gap to the target film thickness and calender the sheet. Step 7: The calendered film is drawn to the cooling device by the traction device and cooled in three stages: slow cooling zone 80-100℃, rapid cooling zone 20-30℃, and constant temperature zone 25-30℃, until the film shrinkage rate is ≤1%; Step 8: Wind up the cooled film with a winding tension of 3-8 N / m. After winding, trim the edges and inspect to obtain a high-strength PVC calendered film.

2. The method for preparing a high-ductility PVC calendered film according to claim 1, characterized in that, The calcium-zinc composite stabilizer mentioned in step one has a calcium-zinc molar ratio of 3:1-5:1, and the calcium-zinc composite stabilizer also contains 0.5-1.0 parts of phosphite auxiliary stabilizer. The PVC resin is a suspension PVC resin with an average degree of polymerization of 1000-1200. The epoxy value of the epoxidized soybean oil is ≥6.0%.

3. The method for preparing a high-ductility PVC calendered film according to claim 1, characterized in that, In step six, the gap between the feed rollers of the four-roll calender is 2-3 mm, and the gap at the discharge end is consistent with the target film thickness with an error of ±0.01 mm. The film thickness is monitored in real time using an online thickness detector.

4. The method for preparing a high-ductility PVC calendered film according to claim 1, characterized in that, In step eight, during the winding process, spray 0.05-0.1% of the film weight of antistatic agent onto the film surface, and cut the edge width to 5-10 mm.

5. The method for preparing a high-ductility PVC calendered film according to claim 1, characterized in that, The specific weight parts of the components mentioned in step one are 90 parts of PVC resin, 30 parts of DOP, 2 parts of epoxidized soybean oil, 1 part of calcium-zinc composite stabilizer, 0.2 parts of stearic acid, 0.1 parts of PE wax, and 1 part of acrylate processing aid.

6. The method for preparing a high-ductility PVC calendered film according to claim 1, characterized in that, The specific weight parts of the components mentioned in step one are 100 parts of PVC resin, 40 parts of DOP, 4 parts of epoxidized soybean oil, 3 parts of calcium-zinc composite stabilizer, 0.4 parts of stearic acid, 0.3 parts of PE wax, and 2 parts of acrylate processing aid.

7. The method for preparing a high-ductility PVC calendered film according to claim 1, characterized in that, The specific weight parts of the components mentioned in step one are 110 parts of PVC resin, 50 parts of DOP, 6 parts of epoxidized soybean oil, 5 parts of calcium-zinc composite stabilizer, 0.6 parts of stearic acid, 0.5 parts of PE wax, and 3 parts of acrylate processing aid.

8. The method for preparing a high-ductility PVC calendered film according to claim 1, characterized in that, The specific weight parts of the components mentioned in step one are 95 parts of PVC resin, 35 parts of DOP, 8 parts of epoxidized soybean oil, 2 parts of calcium-zinc composite stabilizer, 0.8 parts of stearic acid, 0.2 parts of PE wax, and 4 parts of acrylate processing aid.

9. A high-strength PVC calendered film, characterized in that, The PVC calendered film is prepared by the preparation method according to any one of claims 1-8, and has a thickness of 0.05-0.5 mm, an elongation at break of ≥300%, a tensile strength of ≥15 MPa, and a shrinkage rate of ≤1%.

Images