Roughened polypropylene film production method based on SSA thermal grading technology and polypropylene film

Abstract

The invention discloses a coarsened polypropylene film production method based on an SSA thermal grading technology, which comprises the following steps: step S10, carrying out thermal grading treatment on a polypropylene material by adopting a DSC continuous self-nucleation annealing (SSA) thermal grading technology so as to rapidly characterize intra-chain and inter-chain stereodefect distribution, and calculating the weight-average methylene sequence length of the material; s11, according to the length of the weight-average methylene sequence, determining the longitudinal stretching preheating temperature, the longitudinal stretching temperature and the cooling casting piece temperature of the polypropylene film; and S12, under the determined processing conditions, carrying out longitudinal stretching treatment on the polypropylene material to form the polypropylene film with the roughened surface. The invention also discloses a corresponding coarsened propylene film. By implementing the method, the coarsening degree and the void ratio of the coarsened polypropylene film for the capacitor are improved by accurately controlling the thermal grading treatment process of the polypropylene material and optimizing the processing conditions, so that the impregnation effect and the electrical performance of the capacitor are improved.

Description

Technical Field

[0001] The invention relates to the technical field of oil-immersed capacitors, and in particular to a method for producing a roughened polypropylene film based on SSA thermal grading technology and a polypropylene film. Background Art

[0002] Capacitors are indispensable components in electronic circuits and are widely used in various electronic devices. In the manufacturing process of capacitors, the impregnation process is a key step, which determines the performance and stability of the capacitor. As an important material for capacitors, the surface characteristics and void structure of polypropylene film have a crucial influence on the impregnation effect.

[0003] The existing polypropylene film has a high crystallization temperature due to its high isotactic index and narrow molecular weight distribution. Although this makes the film have a high electrical strength, it also brings a problem: the film surface is not easy to coarsen and the porosity is low. This characteristic will make it difficult for the impregnation liquid to fully penetrate into the film during the capacitor impregnation process, thus affecting the electrical performance and long-term stability of the capacitor. Especially in oil-immersed capacitors, if the porosity of the polypropylene film is insufficient, the oil cannot be fully infiltrated, which in turn affects the heat dissipation effect and electrical insulation performance of the capacitor.

[0004] To solve this problem, the industry has been exploring how to improve the production process of polypropylene film to increase its surface roughness and porosity. However, traditional production processes often make it difficult to accurately control the microstructure of the film, resulting in unstable product performance and high production costs.

[0005] Therefore, there is an urgent need for a new polypropylene film production method that can accurately control the microstructure of the film, improve its surface roughness and porosity, so as to meet the needs of the capacitor impregnation process and improve the performance and stability of the capacitor. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for producing a roughened polypropylene film based on SSA thermal grading technology and a polypropylene film, aiming to improve the roughening degree and porosity of the roughened polypropylene film for capacitors by accurately controlling the thermal grading process of the polypropylene material and optimizing the processing conditions, thereby improving the impregnation effect and electrical performance of the capacitor.

[0007] In order to solve the above technical problems, as one aspect of the present invention, a method for producing a roughened polypropylene film based on SSA thermal grading technology is provided, which comprises the following steps:

[0008] Step S10, using DSC continuous self-nuclear annealing (SSA) thermal fractionation technology to perform thermal fractionation treatment on the polypropylene material to quickly characterize the distribution of intra-chain and inter-chain stereo defects and calculate the weight average methylene sequence length of the material;

[0009] Step S11, determining the longitudinal preheating temperature, longitudinal stretching temperature and cooling casting temperature of the polypropylene film according to the weight-average methylene sequence length;

[0010] Step S12, under certain processing conditions, longitudinally stretching the polypropylene material to form a polypropylene film with a roughened surface.

[0011] Preferably, in step S10, the specific parameters of the DSA continuous self-nuclear annealing (SSA) thermal grading technology are determined as follows: the initial temperature point Ts1 is 165-170°C, the cooling and melting rate is 5-30°C / min, the heat treatment temperature interval △T is 1-10°C, and the residence time tr is 5-30min.

[0012] Preferably, the step S10 further comprises:

[0013] The sample was heated from room temperature to 200 °C at a rate of 10 °C / min and maintained for 5 min to eliminate the thermal history;

[0014] The cooling rate was 10 °C / min, and the sample was cooled to 0 °C and kept for 5 min;

[0015] The sample was heated to the selected initial temperature point (Ts1) at a heating rate of τ °C / min and maintained for tr min;

[0016] Cooling from Ts to 0℃ at a cooling rate of τ℃ / min, the corresponding heat treatment effect will be reflected in the crystallization of the sample;

[0017] The sample is heated at a heating rate of τ℃ / min to the next temperature point, which is △T℃ lower than Ts, and isothermally maintained for tr min;

[0018] Repeat the above heating and cooling steps; finally, heat the sample from 0°C to 200°C at a heating rate of 10K / min, and record the DSC curve;

[0019] The DSC curve with multiple melting peaks is fitted and separated, the corresponding methylene sequence length value is calculated according to the melting point of each peak, and the weight average methylene sequence length of the material is calculated.

[0020] Preferably, in step S11, when the weight average methylene sequence length is 80-100 nm, the longitudinal drawing preheating temperature is 116-128°C, the longitudinal drawing temperature is 140-142°C, and the cooling casting temperature is 85-86°C.

[0021] Preferably, in step S11, when the weight average methylene sequence length is greater than 100 nm, the longitudinal drawing preheating temperature is 116-131°C, the longitudinal drawing temperature is 140-145°C, and the cooling casting temperature is 86-89°C.

[0022] Preferably, the method further comprises the step of preheating the polypropylene material before the longitudinal stretching process.

[0023] Preferably, in step S12, the longitudinal stretching process is performed using a longitudinal stretching machine, and the stretching speed is a preset value.

[0024] Preferably, the method further comprises a step of post-treating the prepared roughened polypropylene film, including heat setting and surface treatment.

[0025] Correspondingly, as another aspect of the present invention, a roughened polypropylene film based on the SSA thermal grading technology is also provided, which is produced by the production method as described above.

[0026] The implementation of the embodiments of the present invention has the following beneficial effects:

[0027] The present invention provides a method for producing a roughened polypropylene film based on SSA thermal grading technology and a roughened polypropylene film. By adopting DSC continuous self-nuclear annealing (SSA) thermal grading technology, the present invention can accurately control the heat treatment process of the polypropylene material, thereby optimizing the distribution of intra-chain and inter-chain stereo defects. This precise heat treatment enables the polypropylene film to form a more roughened surface in the subsequent longitudinal drawing process, significantly improving the void ratio of the film. This is not only beneficial to the impregnation effect of the capacitor, but also enhances the electrical properties of the film.

[0028] In the present invention, based on the weight-average methylene sequence length obtained by the SSA thermal fractionation technology, the present invention provides a specific optimization range of longitudinal preheating temperature, longitudinal stretching temperature and cooling casting temperature. These optimization conditions ensure that the polypropylene material can form an ideal crystal structure during the processing, thereby obtaining the best coarsening effect.

[0029] In the present invention, since the roughness and porosity of the film are significantly improved, when the polypropylene film produced by the present invention is used as the dielectric material of the capacitor, the impregnation effect and electrical strength of the capacitor can be significantly improved. This helps to improve the overall performance of the capacitor, including its capacity, stability and service life.

[0030] The method of the present invention is applicable to polypropylene materials with different weight-average methylene sequence lengths, and an ideal roughening effect can be obtained by adjusting the processing conditions, which makes the present invention widely applicable and can meet the needs of different capacitor products.

[0031] Although the present invention involves multiple steps, the entire production process is continuous and automated without the need for complex operations or additional equipment, which helps to simplify the production process, reduce production costs, and improve production efficiency.

[0032] In summary, the present invention successfully improves the coarsening degree and porosity of the polypropylene film by adopting the SSA thermal grading technology and optimizing the processing conditions, thereby improving the performance of the capacitor. At the same time, the present invention also has the advantages of wide applicability and simplified production process, providing strong technical support for the development of the capacitor industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technical personnel in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0034] Figure 1 It is a main process diagram of a method for producing a roughened polypropylene film based on the SSA thermal grading technology provided by the present invention;

[0035] Figure 2 A schematic diagram of the surface microstructure of a polypropylene film obtained by the prior art;

[0036] Figure 3 The schematic diagram of the surface microstructure of the polypropylene film obtained by the method of the present invention is shown in FIG. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, a schematic diagram of the main process of a method for producing a roughened polypropylene film based on SSA thermal grading technology provided by the present invention is shown; Figure 2 and Figure 3 As shown, in this embodiment, the production method includes the following steps:

[0039] Step S10, using DSC continuous self-nuclear annealing (SSA) thermal fractionation technology to perform thermal fractionation treatment on the polypropylene material to quickly characterize the distribution of intra-chain and inter-chain stereo defects and calculate the weight average methylene sequence length of the material;

[0040] It is understandable that in step S10, the specific parameters of the DSA continuous self-nucleation annealing (SSA) thermal grading technology need to be determined as follows: the initial temperature point (i.e., the first self-nucleation temperature) Ts1 is 165-170°C, the cooling and melting speed is 5-30°C / min, the heat treatment temperature interval △T is 1-10°C, and the residence time tr is 5-30min. Among them, Ts1 has the most important influence on the SSA accuracy.

[0041] In a specific example, the step S10 further includes:

[0042] The sample was heated from room temperature to 200 °C at a rate of 10 °C / min and maintained for 5 min to eliminate the thermal history;

[0043] The cooling rate was 10 °C / min, and the sample was cooled to 0 °C and kept for 5 min;

[0044] The sample was heated to the selected initial temperature point (Ts1) at a heating rate of τ °C / min and maintained for tr min;

[0045] Cooling from Ts to 0℃ at a cooling rate of τ℃ / min, the corresponding heat treatment effect will be reflected in the crystallization of the sample;

[0046] The sample is heated at a heating rate of τ℃ / min to the next temperature point, which is △T℃ lower than Ts, and isothermally maintained for tr min;

[0047] Repeat the above heating and cooling steps; finally, heat the sample from 0°C to 200°C at a heating rate of 10K / min, and record the DSC curve;

[0048] The DSC curve with multiple melting peaks is fitted and separated, the corresponding methylene sequence length value is calculated according to the melting point of each peak, and the weight average methylene sequence length of the material is calculated.

[0049] It can be understood that in this embodiment, the self-nucleation temperature Ts1 should be at the tail of the polypropylene melting peak, preferably 165-170°C. If the temperature is too low, it cannot be completely melted, and the crystallization is incomplete during annealing, and the effect of complete separation cannot be achieved; if the temperature is too high, self-nucleation crystallization cannot be achieved in the high region, and the melting peak appears to have a shoulder peak or is relatively small at high temperature, which is difficult to separate;

[0050] The cooling and melting rate τ is 5-30℃ / min. If the heating rate is too high or too low, the melting peaks cannot be completely separated, and the purpose of SSA thermal classification cannot be achieved.

[0051] The heat treatment temperature interval △T is 1-10℃. A shorter temperature interval can obtain more multiple melting peaks, but if the interval is too short, some melting peaks will overlap and cannot be effectively separated; the longer the temperature interval, the smaller the multiple melting peaks obtained and the lower the resolution, which affects the thermal fractionation effect.

[0052] The residence time tr is 5-30min. The extension of isothermal time will improve the separation effect of SSA thermal fractionation. However, too long isothermal time will greatly increase the test time and occupy too much experimental machine time.

[0053] Step S11, determining the longitudinal preheating temperature, longitudinal stretching temperature and cooling casting temperature of the polypropylene film according to the weight-average methylene sequence length;

[0054] In a specific example, in step S11, when the weight average methylene sequence length is 80-100 nm, the longitudinal drawing preheating temperature is 116-128°C, the longitudinal drawing temperature is 140-142°C, and the cooling casting temperature is 85-86°C.

[0055] In step S11, when the weight average methylene sequence length is greater than 100 nm, the material has thicker lamellae, and the melting point and crystallinity are relatively high. In order to obtain sufficient β crystals to improve the roughness of the material surface, the processing temperature should be improved and optimized at this time. The longitudinal drawing preheating temperature can be set to 116-131°C, the longitudinal drawing temperature can be set to 140-145°C, and the cooling casting temperature can be set to 86-89°C.

[0056] Step S12, under certain processing conditions, longitudinally stretching the polypropylene material to form a polypropylene film with a roughened surface.

[0057] It can be understood that, in step S12, it also includes a step of preheating the polypropylene material before the longitudinal stretching process.

[0058] In step S12, the longitudinal stretching process is performed using a longitudinal stretching machine, and the stretching speed is a preset value.

[0059] It can be understood that, in some examples, the method further includes post-processing the roughened polypropylene film, including heat setting and surface treatment.

[0060] Accordingly, as another aspect of the present invention, a roughened polypropylene film based on SSA thermal grading technology is also provided, which adopts the above Figure 1 For more details, please refer to the above-mentioned Figure 1 The description is not repeated here.

[0061] In order to more conveniently understand the method of the present invention and the roughened polypropylene film prepared, an example is used as an example to illustrate the method.

[0062] Embodiment 1:

[0063] Step 1: The sample was heated from room temperature to 200 °C at a rate of 10 °C / min and maintained for 5 min to eliminate the thermal history using DSC continuous self-nuclear annealing (SSA) thermal grading technique;

[0064] Step 2, cooling the sample to 0°C at a cooling rate of 10°C / min and holding for 5 min;

[0065] Step 3, the sample was heated to the selected initial temperature point of 169°C at a heating rate of 10°C / min and maintained for 15 min;

[0066] Step 4, cooling from 169°C to 0°C at a cooling rate of 10°C / min, the corresponding heat treatment effect will be reflected in the crystallization of the sample;

[0067] Step 5, heating the sample at a heating rate of 10°C / min to the next temperature point, which is 4°C lower than the initial temperature point, and maintaining the temperature isothermally for 15 min;

[0068] Repeat steps 3 to 5; finally, heat the sample from 0°C to 200°C at a heating rate of 10°C / min, and record the DSC curve;

[0069] The curve with multiple melting peaks was fitted and separated, and the corresponding methylene sequence length value was calculated according to the melting point of each peak. The statistically obtained weight average methylene sequence length of the material was 104 nm.

[0070] The following improved processing conditions were used: longitudinal preheating temperature was 116-131°C, longitudinal stretching temperature was 140-145°C, and cooling casting temperature was 86-89°C. The surface morphology of the roughened film sample prepared is shown in Figure 2 As shown, the porosity is 8.3%. Compared with the polypropylene film produced in the prior art (such as Figure 2 As shown, its void ratio is 3.9%), which is a significant improvement.

[0071] The implementation of the embodiments of the present invention has the following beneficial effects:

[0072] The present invention provides a method for producing a roughened polypropylene film based on SSA thermal grading technology and a roughened polypropylene film. By adopting DSC continuous self-nuclear annealing (SSA) thermal grading technology, the present invention can accurately control the heat treatment process of the polypropylene material, thereby optimizing the distribution of intra-chain and inter-chain stereo defects. This precise heat treatment enables the polypropylene film to form a more roughened surface in the subsequent longitudinal drawing process, significantly improving the void ratio of the film. This is not only beneficial to the impregnation effect of the capacitor, but also enhances the electrical properties of the film.

[0073] In the present invention, based on the weight-average methylene sequence length obtained by the SSA thermal fractionation technology, the present invention provides a specific optimization range of longitudinal preheating temperature, longitudinal stretching temperature and cooling casting temperature. These optimization conditions ensure that the polypropylene material can form an ideal crystal structure during the processing, thereby obtaining the best coarsening effect.

[0074] In the present invention, since the roughness and porosity of the film are significantly improved, when the polypropylene film produced by the present invention is used as the dielectric material of the capacitor, the impregnation effect and electrical strength of the capacitor can be significantly improved. This helps to improve the overall performance of the capacitor, including its capacity, stability and service life.

[0075] The method of the present invention is applicable to polypropylene materials with different weight-average methylene sequence lengths, and an ideal roughening effect can be obtained by adjusting the processing conditions, which makes the present invention widely applicable and can meet the needs of different capacitor products.

[0076] Although the present invention involves multiple steps, the entire production process is continuous and automated without the need for complex operations or additional equipment, which helps to simplify the production process, reduce production costs, and improve production efficiency.

[0077] In summary, the present invention successfully improves the coarsening degree and porosity of the polypropylene film by adopting the SSA thermal grading technology and optimizing the processing conditions, thereby improving the performance of the capacitor. At the same time, the present invention also has the advantages of wide applicability and simplified production process, providing strong technical support for the development of the capacitor industry.

[0078] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for producing a roughened polypropylene film based on SSA thermal grading technology, characterized in that: The following steps are involved: Step S10, using DSC continuous self-nuclear annealing (SSA) thermal fractionation technology to perform thermal fractionation treatment on the polypropylene material, and calculate the weight average methylene sequence length of the material; Step S11, determining the longitudinal preheating temperature, longitudinal stretching temperature and cooling casting temperature of the polypropylene film according to the weight-average methylene sequence length; Step S12, under certain processing conditions, longitudinally stretching the polypropylene material to form a polypropylene film with a roughened surface.

2. The production method according to claim 1, characterized in that In step S10, the specific parameters of the DSA continuous self-nucleation annealing (SSA) thermal grading technology are determined as follows: the initial temperature point Ts1 is 165-170°C, the cooling and melting rates are 5-30°C / min, the heat treatment temperature interval △T is 1-10°C, and the residence time tr is 5-30min.

3. The production method according to claim 2, characterized in that: The step S10 further comprises: The sample was heated from room temperature to 200 °C at a rate of 10 °C / min and maintained for 5 min to eliminate the thermal history; The cooling rate was 10 °C / min, and the sample was cooled to 0 °C and kept for 5 min; The sample was heated to the selected initial temperature point (Ts1) at a heating rate of τ °C / min and maintained for tr min; Cooling from Ts to 0℃ at a cooling rate of τ℃ / min, the corresponding heat treatment effect will be reflected in the crystallization of the sample; The sample is heated at a heating rate of τ℃ / min to the next temperature point, which is △T℃ lower than Ts, and isothermally maintained for tr min; Repeat the above heating and cooling steps; finally, heat the sample from 0°C to 200°C at a heating rate of 10K / min, and record the DSC curve; The DSC curve with multiple melting peaks is fitted and separated, the corresponding methylene sequence length value is calculated according to the melting point of each peak, and the weight average methylene sequence length of the material is calculated.

4. The production method according to claim 3, characterized in that: In step S11, when the weight average methylene sequence length is 80-100 nm, the longitudinal drawing preheating temperature is 116-128°C, the longitudinal drawing temperature is 140-142°C, and the cooling casting temperature is 85-86°C.

5. The production method according to claim 3, characterized in that: In step S11, when the weight average methylene sequence length is greater than 100 nm, the longitudinal drawing preheating temperature is 116-131°C, the longitudinal drawing temperature is 140-145°C, and the cooling casting temperature is 86-89°C.

6. The production method according to claim 4 or 5, characterized in that: The method also includes the step of preheating the polypropylene material before the longitudinal stretching process.

7. The production method according to claim 6, characterized in that: In step S12, the longitudinal stretching process is performed using a longitudinal stretching machine, and the stretching speed is a preset value.

8. The production method according to claim 7, characterized in that: The method also includes a step of post-treating the prepared roughened polypropylene film, including heat setting and surface treatment.

9. A roughened polypropylene film based on SSA thermal grading technology, characterized in that: The method is produced according to any one of claims 1 to 8.

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