Preparation method of polypropylene coarsened film

Abstract

The invention discloses a preparation method of a polypropylene coarsened film, belongs to the technical field of preparation of electronic and electrical insulating materials, and particularly relates to preparation of the polypropylene coarsened film. The invention aims to solve the technical problem that the specific preparation process is difficult to regulate and control when the polypropylene coarsened film is prepared at present. By adjusting the heating temperature, the torque, the rotating speed of the motor, the gap between the die head and the machine lip, the temperature of the chilling roller, the casting rotating speed and the winding tension of each area of the extruder, the polypropylene coarsening film which is reasonable in surface appearance and thickness and excellent in dielectric property is obtained, the wettability of the obtained polypropylene coarsening film in insulating oil is good, the dielectric property is excellent, and the service life of the polypropylene coarsening film is prolonged. And the prepared oil-immersed capacitor has good energy storage performance. The polypropylene coarsened film prepared by the invention is mainly used for preparing metallized polypropylene films for oil-immersed capacitors and film capacitors.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic and electrical insulating material preparation, and specifically relates to the preparation of a polypropylene roughening film. The polypropylene roughening film is mainly used for preparing metallized polypropylene films for oil-immersed capacitors and film capacitors. Background Art

[0002] Polypropylene roughening film is an ideal material for solid insulating medium of oil-immersed power capacitors. It not only has a higher dielectric constant, higher breakdown strength, and lower dielectric loss, but also has good impregnation performance. It can completely replace capacitor paper and manufacture full-film high-voltage oil-immersed power capacitors, and can greatly reduce the volume of power capacitors. Therefore, polypropylene roughening film has been increasingly widely used in the power industry.

[0003] The surface roughening of the polypropylene roughened film is achieved by changing the crystal structure inside the polypropylene with the help of temperature and external force. High isotactic polypropylene resin is a crystalline polymer. By controlling the temperature of the extrusion melt and the casting, α and β crystals can be formed on the surface of the casting, and these two crystals can exist at the same time. α crystal is a stable crystal form, and β crystal is a thermodynamically unstable crystal form. Under the action of the force field and temperature field, β crystal can be transformed into a stable α crystal. Since the density of β crystal is greater than that of α crystal, after the β crystal is transformed into α crystal, a large number of fine and interconnected concave and convex rough surfaces are formed on the surface of the film, thereby forming a film with roughened surface. The roughened structure allows the impregnant to diffuse rapidly on both surfaces of the film at the same time, greatly improving and enhancing the impregnation performance of the film.

[0004] Therefore, how to control the roughness of the polypropylene roughened film and improve its dielectric properties by adjusting the process is of great significance to improving the application performance of oil-immersed capacitors. Summary of the invention

[0005] The present invention aims to solve the technical problem that the specific preparation process is difficult to control when preparing a polypropylene roughened film at present, and provides a preparation method of a polypropylene roughened film.

[0006] The preparation method of the polypropylene roughening film of the present invention is carried out according to the following steps:

[0007] Step 1: Add polypropylene granules into the feeding hopper of the twin-screw extruder, and then set the heating temperature, torque, motor speed and die lip gap of each zone of the extruder respectively;

[0008] Step 2: setting the chill roll temperature, casting speed and winding tension of the film continuous preparation system;

[0009] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0010] The polypropylene roughened film prepared by the above method is mainly used for preparing metallized polypropylene film for oil-immersed capacitors and film capacitors.

[0011] The present invention utilizes the transformation of crystal forms at different temperatures to change the tensile strain to increase the dielectric constant, reduce dielectric loss, increase the breakdown field strength, and thus improve the energy storage performance.

[0012] The method of the present invention melts polypropylene at a certain temperature, and then adjusts the molecular orientation, surface morphology and thickness of the film by regulating the quenching temperature and stress. When the cast film is extruded from the extruder head and stretched on the quenching roller, the cast film becomes thinner, and then the film thickness is reduced for the second time by the stretching effect of the tension reel. During the two stretching processes, the action of the tension causes the thickness of the film and the orientation of the molecular chain to change. At the same time, due to the cooling effect of the quenching roller, the cast film crystallizes on the quenching roller. When stretched by the tension shaft, the thickness of the amorphous region decreases while the thickness of the crystalline region remains unchanged, which changes the surface morphology of the film and makes the film roughened. This method can optimize the surface wettability and dielectric properties of the roughened film, thereby improving the energy storage performance of the oil-immersed capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 FT-IR spectrum of the roughened polypropylene film prepared in Comparative Example 1;

[0014] Figure 2 The XRD pattern of the roughened polypropylene film prepared in Comparative Example 1;

[0015] Figure 3 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Comparative Example 1;

[0016] Figure 4 FT-IR spectrum of the roughened polypropylene film prepared in Example 1;

[0017] Figure 5 The XRD pattern of the roughened polypropylene film prepared in Example 1;

[0018] Figure 6 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 1;

[0019] Figure 7 FT-IR spectrum of the roughened polypropylene film prepared in Example 2;

[0020] Figure 8 The XRD pattern of the roughened polypropylene film prepared in Example 2;

[0021] Fig. 9 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 2;

[0022] Fig.10 FT-IR spectrum of the roughened polypropylene film prepared in Example 3;

[0023] Fig.11 The XRD pattern of the roughened polypropylene film prepared in Example 3;

[0024] Fig.12 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 3;

[0025] Fig.13 FT-IR spectrum of the roughened polypropylene film prepared in Example 4;

[0026] Fig.14 The XRD pattern of the roughened polypropylene film prepared in Example 4;

[0027] Fig.15 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 4;

[0028] Fig.16 FT-IR spectrum of the roughened polypropylene film prepared in Example 5;

[0029] Fig.17 The XRD pattern of the roughened polypropylene film prepared in Example 5;

[0030] Fig.18 The breakdown field intensity spectra at 25°C and 85°C of the roughened polypropylene film prepared in Example 5 were fitted using the Weibull distribution analysis method. DETAILED DESCRIPTION

[0031] Specific implementation method 1: This implementation method is a method for preparing a polypropylene roughening film, which is specifically carried out according to the following steps:

[0032] Step 1: Add polypropylene granules into the feeding hopper of the twin-screw extruder, and then set the heating temperature, torque, motor speed and die lip gap of each zone of the extruder respectively;

[0033] Step 2: setting the chill roll temperature, casting speed and winding tension of the film continuous preparation system;

[0034] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0035] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the heating temperature of each zone of the extruder in step 1 is 190° C. to 240° C. The rest is the same as specific embodiment 1.

[0036] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the torque described in step 1 is 10N·m to 40N·m. Other aspects are the same as specific implementation method 1 or 2.

[0037] Specific implementation method 4: This implementation method is different from the specific implementation methods 1 to 3 in that the motor speed in step 1 is 40 rpm to 100 rpm. The rest is the same as the specific implementation methods 1 to 3.

[0038] Specific implementation method 5: This implementation method is different from specific implementation method 4 in that the die head lip gap described in step 1 is 0.1 mm to 1.5 mm. Other aspects are the same as specific implementation method 4.

[0039] Specific implementation example 6: This implementation example is different from the specific implementation example 5 in that the temperature of the chilled roller in step 2 is maintained at 100° C. to 140° C. The rest is the same as the specific implementation example 5.

[0040] Specific implementation method 7: This implementation method is different from specific implementation method 6 in that the casting speed in step 2 is 5 Hz to 50 Hz. The rest is the same as specific implementation method 6.

[0041] Specific implementation example eight: This implementation example is different from specific implementation example seven in that the winding tension in step two is 0.2N to 10N. The rest is the same as specific implementation example seven.

[0042] The present invention is verified by the following tests:

[0043] The extruder used in the following is the RM-200C insulation film continuous preparation system produced by Harbin Harp Electrical Technology Co., Ltd.

[0044] Comparative Example 1: A method for preparing a polypropylene roughened film, specifically carried out according to the following steps:

[0045] Step 1, adding polypropylene particles into the feeding hopper of the twin-screw extruder, setting the heating temperature of each zone of the extruder to: 190°C for zone 1, 200°C for zone 2, 210°C for zone 3, 210°C for zone 4, 210°C for zone 5, 210°C for zone 6 (the six zones correspond to the feeding zone, preheating zone, melting zone, mixing zone, exhaust zone and cooling zone in sequence), and the die head to 210°C; setting the torque of the extruder to 20N·m, the motor speed to 60rpm, and the die head lip clearance to 0.5mm;

[0046] Step 2: Set the working conditions of the film continuous preparation system: the chilled roller temperature is 90°C, the casting speed is 10Hz, and the winding tension is 5N;

[0047] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0048] Example 1: This example is a method for preparing a polypropylene roughened film, which is specifically carried out according to the following steps:

[0049] Step 1, adding polypropylene granules into the feeding hopper of the twin-screw extruder, setting the heating temperature of each zone of the extruder to: 200°C for zone 1, 210°C for zone 2, 220°C for zone 3, 220°C for zone 4, 220°C for zone 5, 220°C for zone 6 (the six zones correspond to the feeding zone, preheating zone, melting zone, mixing zone, exhaust zone and cooling zone in sequence), and the die head to 220°C; setting the torque of the extruder to 30N·m, the motor speed to 80rpm, and the die head lip clearance to 1mm;

[0050] Step 2: Set the working conditions of the film continuous preparation system: the chill roll temperature is 100°C, the casting speed is 10Hz, and the winding tension is 10N;

[0051] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0052] Example 2: This example is a method for preparing a polypropylene roughened film, which is specifically carried out according to the following steps:

[0053] Step 1, add polypropylene granules into the feeding hopper of the twin-screw extruder, set the heating temperature of each zone of the extruder to: zone 1 to 190°C, zone 2 to 200°C, zone 3 to 210°C, zone 4 to 210°C, zone 5 to 210°C, zone 6 to 210°C, and die head to 210°C; set the torque of the extruder to 40N·m, the motor speed to 80rpm, and the die head lip clearance to 0.6mm;

[0054] Step 2: Set the working conditions of the film continuous preparation system: the chill roll temperature is 110°C, the casting speed is 5Hz, and the winding tension is 15N;

[0055] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0056] Embodiment 3: This embodiment is a method for preparing a polypropylene roughened film, which is specifically carried out according to the following steps:

[0057] Step 1, add polypropylene granules into the feeding hopper of the twin-screw extruder, set the heating temperature of each zone of the extruder to: zone 1 to 190°C, zone 2 to 200°C, zone 3 to 210°C, zone 4 to 210°C, zone 5 to 210°C, zone 6 to 210°C, and die head to 210°C; set the torque of the extruder to 30N·m, the motor speed to 50rpm, and the die head lip gap to 0.8mm;

[0058] Step 2: Set the working conditions of the film continuous preparation system: the chill roll temperature is 120°C, the casting speed is 5Hz, and the winding tension is 10N;

[0059] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0060] Embodiment 4: This embodiment is a method for preparing a polypropylene roughened film, which is specifically carried out according to the following steps:

[0061] Step 1, add polypropylene granules into the feeding hopper of the twin-screw extruder, set the heating temperature of each zone of the extruder to: zone 1 to 190°C, zone 2 to 200°C, zone 3 to 210°C, zone 4 to 210°C, zone 5 to 210°C, zone 6 to 210°C, and die head to 210°C; set the torque of the extruder to 40N·m, the motor speed to 60rpm, and the die head lip gap to 1mm;

[0062] Step 2: Set the working conditions of the film continuous preparation system: the chill roll temperature is 130°C, the casting speed is 5Hz, and the winding tension is 20N;

[0063] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0064] Example 5: This example is a method for preparing a polypropylene roughened film, which is specifically carried out according to the following steps:

[0065] Step 1, add polypropylene granules into the feeding hopper of the twin-screw extruder, set the heating temperature of each zone of the extruder to: zone 1 to 190°C, zone 2 to 200°C, zone 3 to 210°C, zone 4 to 210°C, zone 5 to 210°C, zone 6 to 210°C, and die head to 210°C; set the torque of the extruder to 35N·m, the motor speed to 80rpm, and the die head lip gap to 1.5mm;

[0066] Step 2: Set the working conditions of the film continuous preparation system: the chill roll temperature is 140°C, the casting speed is 5Hz, and the winding tension is 25N;

[0067] Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

[0068] Figure 1 FT-IR spectrum of the roughened polypropylene film prepared in Comparative Example 1; Figure 2 The XRD pattern of the roughened polypropylene film prepared in Comparative Example 1; Figure 3 The breakdown field strength spectra at 25°C and 85°C of the roughened polypropylene film prepared in Comparative Example 1 were fitted using the Weibull distribution analysis method.

[0069] Figure 4 FT-IR spectrum of the roughened polypropylene film prepared in Example 1; Figure 5 The XRD pattern of the roughened polypropylene film prepared in Example 1; Figure 6 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 1;

[0070] Figure 7 FT-IR spectrum of the roughened polypropylene film prepared in Example 2; Figure 8 The XRD pattern of the roughened polypropylene film prepared in Example 2; Fig. 9 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 2;

[0071] Fig.10 FT-IR spectrum of the roughened polypropylene film prepared in Example 3; Fig.11 The XRD pattern of the roughened polypropylene film prepared in Example 3; Fig.12 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 3;

[0072] Fig.13 FT-IR spectrum of the roughened polypropylene film prepared in Example 4; Fig.14The XRD pattern of the roughened polypropylene film prepared in Example 4; Fig.15 The breakdown field intensity spectra at 25°C and 85°C fitted by Weibull distribution analysis method for the roughened polypropylene film prepared in Example 4;

[0073] Fig.16 FT-IR spectrum of the roughened polypropylene film prepared in Example 5; Fig.17 The XRD pattern of the roughened polypropylene film prepared in Example 5; Fig.18 The breakdown field intensity spectra at 25°C and 85°C of the roughened polypropylene film prepared in Example 5 were fitted using the Weibull distribution analysis method.

[0074] It can be seen from the test data in the above figures that compared with the characterization and test of the polypropylene roughening film prepared in Comparative Example 1, the molecular structure and crystalline structure of the polypropylene roughening film prepared in Examples 1-5 of the present invention have changed to varying degrees, and the electrical properties have also been greatly improved. The breakdown field strength of Example 1 is 236.8 kV / mm at 25°C and 209.4 kV / mm at 85°C; the breakdown field strength of Example 2 is 269. 7kV / mm at 85°C, 238.3kV / mm at 85°C; the breakdown field strength of Example 3 is 188.1kV / mm at 25°C, 167.6kV / mm at 85°C; the breakdown field strength of Example 4 is 456.0kV / mm at 25°C, 407.1kV / mm at 85°C; the breakdown field strength of Example 5 is 460.4kV / mm at 25°C, 431.5kV / mm at 85°C. Compared with Comparative Example 1, the breakdown field strength at 25°C is increased by 15% to 200%; the breakdown field strength at 85°C is increased by 20% to 230%. It can be seen that the dielectric energy storage performance of the polypropylene roughened film has been greatly improved.

Claims

1. A method for preparing a polypropylene roughened film, characterized in that The preparation method of the polypropylene roughened film is carried out according to the following steps: Step 1: Add polypropylene granules into the feeding hopper of the twin-screw extruder, and then set the heating temperature, torque, motor speed and die lip gap of each zone of the extruder respectively; Step 2: setting the chill roll temperature, casting speed and winding tension of the film continuous preparation system; Step 3: Start each part of the equipment, wait for the die head to extrude the melt, pass the melt around each shaft of the film continuous preparation system, and wind it on the tension-controlled shaft to complete the preparation of the polypropylene roughened film.

2. The method for preparing a polypropylene roughened film according to claim 1, characterized in that In step 1, the heating temperature of each zone of the extruder is 190°C to 240°C.

3. The method for preparing a polypropylene roughened film according to claim 1, characterized in that The torque described in step 1 is 10 N·m to 40 N·m.

4. The method for preparing a polypropylene roughened film according to claim 1, characterized in that The motor speed described in step 1 is 40 rpm to 100 rpm.

5. The method for preparing a polypropylene roughened film according to claim 1, characterized in that The die head lip gap described in step 1 is 0.1 mm to 1.5 mm.

6. The method for preparing a polypropylene roughened film according to claim 1, characterized in that The temperature of the chilled roller in step 2 is maintained at 100°C to 140°C.

7. The method for preparing a polypropylene roughened film according to claim 1, characterized in that The casting speed described in step 2 is 5 Hz to 50 Hz.

8. The method for preparing a polypropylene roughened film according to claim 1, characterized in that The winding tension described in step 2 is 0.2N to 10N.

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