Production method of BOPP (Biaxially-oriented Polypropylene) capacitor film

Abstract

The invention discloses a production method of a BOPP capacitor film. The capacitor film comprises an upper surface layer, a base layer and a lower surface layer, the upper surface layer is composed of PP, boron nitride, a cycloolefin polymer, calcium pimelate, paraffin and an antioxidant; the base layer is prepared from PP, low-molecular-weight polybutylene, chopped glass fibers, pimelic acid modified oyster shell powder and a coupling agent; the lower surface layer is composed of PP, magnesium salt whiskers, liquid ethylene propylene diene monomer and kaolin. The capacitor film prepared by the invention has relatively good mechanical properties and heat resistance.

Description

Technical Field

[0001] This invention relates to the field of BOPP film technology, specifically a method for producing BOPP capacitor film. Background Technology

[0002] Polypropylene (PP) film is the primary dielectric material for film capacitors due to its high breakdown field strength, low dielectric loss, excellent self-healing properties, ability to be made ultra-thin, and low cost. Currently, miniaturization, large capacitance, and high breakdown voltage resistance are the basic trends in the film capacitor market. However, when the operating temperature of PP film capacitors exceeds 85°C, most of the film's properties deteriorate, such as a sharp decrease in breakdown strength and a sharp increase in leakage loss, which can easily lead to capacitor failure. This necessitates higher requirements for the heat resistance of the dielectric material. Although polypropylene has many advantages, PP is still a plastic with relatively low tensile strength, and its products also have poor impact resistance and heat resistance. Summary of the Invention

[0003] In view of the above-mentioned deficiencies of the prior art, one object of the present invention is to provide a method for producing BOPP capacitor film.

[0004] To solve the above problems, the technical solution of the present invention is: a method for producing BOPP capacitor film, wherein the capacitor film includes an upper surface layer, a base layer and a lower surface layer; The upper surface layer is composed of PP, boron nitride, cyclic olefin polymer, calcium pimecronate, paraffin wax, and antioxidants; The base layer is composed of PP, low molecular weight polybutene, chopped glass fiber, pimelic acid modified oyster shell powder, and coupling agent; The lower surface layer is composed of PP, magnesium salt whiskers, liquid EPDM rubber, and kaolin. The production method includes the following steps: (1) Boron nitride was dried and then blended with PP, cyclic olefin polymer, calcium pimecronate, paraffin and antioxidant; low molecular weight polybutene-coated modified short glass fibers were prepared by surface coating modification, and the low molecular weight polybutene-coated modified short glass fibers were blended with PP, pimecronate-modified oyster shell powder and coupling agent; liquid EPDM rubber was coated on the surface of kaolin to obtain modified kaolin, and the modified kaolin was blended with PP and magnesium salt whiskers; (2) The raw materials for the upper surface layer, the base layer, and the lower surface layer are respectively fed into their respective extruders for melt mixing and plasticizing; (3) Use an air knife to attach the sheet to the cooling roller and cool it rapidly to form an unshaped sheet. Then, after cooling in a water bath, the sheet is shaped to form a cast sheet. (4) The cast sheet is stretched to form a thin film; (5) The thickness of the film is detected by infrared light and the corresponding thickness deviation is fed back to the die head. The thickness deviation of the film is corrected by micro-adjusting the heating power of the bolts at the corresponding positions. (6) The product is wound up.

[0005] Furthermore, the components of the upper surface layer are as follows by mass ratio: PP 75.8%, boron nitride 12%, cyclic olefin polymer 10%, calcium pimecronate 1%, paraffin wax 1%, and antioxidant 0.2%.

[0006] Furthermore, the components of the base layer are as follows by mass ratio: PP 71.4%, low molecular weight polybutene 1.5%, chopped glass fiber 15%, pimelic acid modified oyster shell powder 12%, and coupling agent 0.1%.

[0007] Furthermore, the components of the lower surface layer are as follows by mass ratio: PP 73%, magnesium salt whiskers 16%, liquid EPDM rubber 1%, and kaolin 10%.

[0008] Furthermore, the method of preparing low molecular weight polybutene-coated modified short-cut glass fibers by surface coating modification is as follows: short-cut glass fibers and low molecular weight polybutene are mixed in a high-speed mixer for 3 minutes, the viscous low molecular weight polybutene is crushed and dispersed, and uniformly coated on the surface of the short-cut glass fibers.

[0009] Furthermore, the preparation method of pimelic acid modified oyster shell powder is as follows: clean and dry the oyster shells, crush the oyster shells with a pulverizer, screen out the oyster shell powder, add the oyster shell powder to the pimelic acid solution, stir at 60°C for 2.5 h, and obtain oyster shell powder with pimelic acid coating on the surface.

[0010] Furthermore, the specific preparation method of modified kaolin is as follows: Kaolin and liquid EPDM rubber are added to a high-speed mixer at a speed of 25000 r / min and mixed for 3 min. The viscous liquid EPDM rubber is crushed and dispersed by high-speed shearing action and uniformly coated on the surface of kaolin to obtain modified kaolin.

[0011] The beneficial effects of this invention are as follows: the addition of boron nitride to the upper surface layer improves the impact performance, flexural performance, and melt flowability of the composite material, has a toughening effect, and can also maintain the good insulation properties of the composite material. Cyclic olefin polymers have the characteristics of high heat resistance, low water absorption, chemical resistance, low shrinkage, and dimensional stability. The use of cyclic olefin polymers with high glass transition temperatures can enhance the heat resistance of PP. Calcium pimecrolate can improve the impact strength, tensile strength, and flexural strength of the material. The low molecular weight polybutene-coated modified short-cut glass fiber in the base layer improves the dispersion performance of short-cut glass fiber in the PP matrix and enhances the interfacial adhesion between the two phases, which can achieve reinforcement and toughening modification of the PP matrix; pimelic acid-modified oyster shell powder filler in PP can improve the thermal stability and impact toughness of PP. The magnesium salt whiskers in the lower surface layer can improve the mechanical properties and heat distortion temperature of PP. The lower surface layer consists of PP, magnesium salt whiskers, liquid EPDM rubber, and kaolin. Liquid EPDM rubber modified kaolin can improve the mechanical properties, processing properties, and flame retardant properties of PP. Liquid EPDM rubber improves the compatibility between kaolin and the PP matrix and increases its dispersibility in the PP matrix. Modified kaolin can increase the elastic modulus of the material. As a toughening agent, liquid EPDM rubber can moderately improve the impact toughness of PP. Detailed Implementation

[0012] To provide a more intuitive and complete understanding of the technical solution of this invention, the following non-limiting features are described: A method for producing BOPP capacitor film, wherein the capacitor film comprises an upper surface layer, a base layer and a lower surface layer; The upper surface layer is composed of PP, boron nitride, cyclic olefin polymer, calcium pimecronate, paraffin wax, and antioxidants; The base layer is composed of PP, low molecular weight polybutene, chopped glass fiber, pimelic acid modified oyster shell powder, and coupling agent; The lower surface layer is composed of PP, magnesium salt whiskers, liquid EPDM rubber, and kaolin. The antioxidant is antioxidant 1010, and the coupling agent is a silane coupling agent.

[0013] The production method of BOPP capacitor film includes the following steps: (1) Boron nitride was dried and then blended with PP, cyclic olefin polymer, calcium pimecronate, paraffin and antioxidant; low molecular weight polybutene-coated modified short glass fibers were prepared by surface coating modification, and the low molecular weight polybutene-coated modified short glass fibers were blended with PP, pimecronate-modified oyster shell powder and coupling agent; liquid EPDM rubber was coated on the surface of kaolin to obtain modified kaolin, and the modified kaolin was blended with PP and magnesium salt whiskers; (2) The raw materials for the upper surface layer, the base layer, and the lower surface layer are respectively fed into their respective extruders for melt mixing and plasticizing; (3) Use an air knife to attach the sheet to the cooling roller and cool it rapidly to form an unshaped sheet. Then, after cooling in a water bath, the sheet is shaped to form a cast sheet. (4) The cast sheet is stretched to form a thin film; (5) The thickness of the film is detected by infrared light and the corresponding thickness deviation is fed back to the die head. The thickness deviation of the film is corrected by micro-adjusting the heating power of the bolts at the corresponding positions. (6) The product is wound up.

[0014] The components of the upper surface layer are as follows by mass ratio: PP 75.8%, boron nitride 12%, cyclic olefin polymer 10%, calcium pimecronate 1%, paraffin wax 1%, and antioxidant 0.2%.

[0015] The components of the base layer are as follows by mass ratio: PP 71.4%, low molecular weight polybutene 1.5%, chopped glass fiber 15%, pimecrolic acid modified oyster shell powder 12%, and coupling agent 0.1%.

[0016] The components of the lower surface layer are as follows by mass ratio: PP 73%, magnesium salt whiskers 16%, liquid EPDM rubber 1%, and kaolin 10%.

[0017] The method of preparing low molecular weight polybutene-coated modified short-cut glass fibers by surface coating modification is as follows: short-cut glass fibers and low molecular weight polybutene are mixed in a high-speed mixer for 3 minutes, the viscous low molecular weight polybutene is crushed and dispersed, and uniformly coated on the surface of the short-cut glass fibers.

[0018] The preparation method of pimelic acid modified oyster shell powder is as follows: clean and dry the oyster shells, crush the oyster shells with a pulverizer, screen out the oyster shell powder, add the oyster shell powder to the pimelic acid solution, stir at 60℃ for 2.5h to obtain oyster shell powder with pimelic acid coating on the surface.

[0019] The specific preparation method of modified kaolin is as follows: Kaolin and liquid EPDM rubber are added to a high-speed mixer at a speed of 25000 r / min and mixed for 3 min. The viscous liquid EPDM rubber is crushed and dispersed by high-speed shearing action and uniformly coated on the surface of kaolin to obtain modified kaolin.

[0020] The addition of boron nitride to the upper surface improves the impact performance, flexural performance, and melt flow of the composite material, providing a toughening effect and maintaining its good insulation properties. Cyclic olefin polymers possess characteristics such as high heat resistance, low water absorption, chemical resistance, low shrinkage, and dimensional stability. Utilizing cyclic olefin polymers with high glass transition temperatures can enhance the heat resistance of PP. Calcium pimecrolate is a β-crystal nucleating agent with good thermal stability. Modifying PP with calcium pimecrolate does not result in regular delamination fracture on the brittle fracture surface, and the nucleating agent particles are evenly distributed. During the fracture process under stress, the irregular fracture surface indicates that each region bears a relatively equal amount of stress, absorbing more energy during impact and thus improving its mechanical properties, including impact strength, tensile strength, and flexural strength. The low molecular weight polybutene-coated modified short-cut glass fibers in the base layer improve the dispersion performance of short-cut glass fibers in the PP matrix and enhance the interfacial adhesion between the two phases, thereby achieving reinforcement and toughening modification of the PP matrix; pimelic acid-modified oyster shell powder filler in PP can improve the thermal stability and impact toughness of PP. Pimelic acid-modified oyster shell powder can promote the formation of β crystal form in PP, and β-PP has a higher heat distortion temperature than α-PP. The magnesium salt whiskers in the lower surface layer can improve the mechanical properties and heat distortion temperature of PP. The lower surface layer consists of PP, magnesium salt whiskers, liquid EPDM rubber, and kaolin. Liquid EPDM rubber modified kaolin can improve the mechanical properties, processing properties, and flame retardant properties of PP. Liquid EPDM rubber improves the compatibility of kaolin with the PP matrix and increases its dispersibility in the PP matrix. Modified kaolin can increase the elastic modulus of the material because kaolin is an inorganic rigid particle with a high modulus and can restrict the movement of PP molecular chains. Liquid EPDM rubber, as a toughening agent, can moderately improve the impact toughness of PP.

Claims

1. A method for producing BOPP capacitor film, characterized in that: The capacitor film consists of an upper surface layer, a base layer, and a lower surface layer; The upper surface layer is composed of PP, boron nitride, cyclic olefin polymer, calcium pimecronate, paraffin wax, and antioxidants; The base layer is composed of PP, low molecular weight polybutene, chopped glass fiber, pimelic acid modified oyster shell powder, and coupling agent; The lower surface layer is composed of PP, magnesium salt whiskers, liquid EPDM rubber, and kaolin. The production method includes the following steps: (1) Boron nitride was dried and then blended with PP, cyclic olefin polymer, calcium pimecronate, paraffin and antioxidant; low molecular weight polybutene-coated modified short glass fibers were prepared by surface coating modification, and the low molecular weight polybutene-coated modified short glass fibers were blended with PP, pimecronate-modified oyster shell powder and coupling agent; liquid EPDM rubber was coated on the surface of kaolin to obtain modified kaolin, and the modified kaolin was blended with PP and magnesium salt whiskers; (2) The raw materials for the upper surface layer, the base layer, and the lower surface layer are respectively fed into their respective extruders for melt mixing and plasticizing; (3) Use an air knife to attach the sheet to the cooling roller and cool it rapidly to form an unshaped sheet. Then, after cooling in a water bath, the sheet is shaped to form a cast sheet. (4) The cast sheet is stretched to form a thin film; (5) The thickness of the film is detected by infrared light and the corresponding thickness deviation is fed back to the die head. The thickness deviation of the film is corrected by micro-adjusting the heating power of the bolts at the corresponding positions. (6) The product is wound up.

2. The method for producing a BOPP capacitor film according to claim 1, characterized in that: The components of the upper surface layer are as follows by mass ratio: PP 75.8%, boron nitride 12%, cyclic olefin polymer 10%, calcium pimecronate 1%, paraffin wax 1%, and antioxidant 0.2%.

3. A method for producing a BOPP capacitor film according to claim 1, characterized in that: The components of the base layer are as follows by mass ratio: PP 71.4%, low molecular weight polybutene 1.5%, chopped glass fiber 15%, pimecrolic acid modified oyster shell powder 12%, and coupling agent 0.1%.

4. A method for producing a BOPP capacitor film according to claim 1, characterized in that: The components of the lower surface layer are as follows by mass ratio: PP 73%, magnesium salt whiskers 16%, liquid EPDM rubber 1%, and kaolin 10%.

5. The method for producing a BOPP capacitor film according to claim 1, characterized in that: The method of preparing low molecular weight polybutene-coated modified short-cut glass fibers by surface coating modification is as follows: short-cut glass fibers and low molecular weight polybutene are mixed in a high-speed mixer for 3 minutes, the viscous low molecular weight polybutene is crushed and dispersed, and uniformly coated on the surface of the short-cut glass fibers.

6. The method for producing a BOPP capacitor film according to claim 1, characterized in that: The preparation method of pimelic acid modified oyster shell powder is as follows: clean and dry the oyster shells, crush the oyster shells with a pulverizer, screen out the oyster shell powder, add the oyster shell powder to the pimelic acid solution, stir at 60℃ for 2.5h to obtain oyster shell powder with pimelic acid coating on the surface.

7. The method for producing a BOPP capacitor film according to claim 1, characterized in that: The specific preparation method of modified kaolin is as follows: Kaolin and liquid EPDM rubber are added to a high-speed mixer at a speed of 25,000 r / min and mixed for 3 min. The viscous liquid EPDM rubber is crushed and dispersed by high-speed shearing action and uniformly coated on the surface of kaolin to obtain modified kaolin.