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CN-122008665-A - Multilayer co-extrusion polypropylene composite film for capacitor and preparation method thereof

CN122008665ACN 122008665 ACN122008665 ACN 122008665ACN-122008665-A

Abstract

The scheme relates to the technical field of capacitance films, in particular to a multilayer coextrusion polypropylene composite film for a capacitor and a preparation method thereof, wherein the composite film is of an ABA three-layer coextrusion structure, the A layer contains a modified flame retardant, the B layer raw material contains BN@Si 2 -NH 2 and MAH-g-PP, the modified flame retardant is obtained by carrying out polymerization reaction on BN@SiO 2 -NH 2 , glycidyl methacrylate and an unsaturated phosphorus nitrogen flame retardant, and the BN@SiO 2 -NH 2 is obtained by hydrolyzing mechanically peeled BN and tetraethoxysilane to obtain BN@SiO 2 and finally carrying out reflux grafting on the BN@SiO 2 -NH 2 with a silane coupling agent. By modifying BN materials, BN@SiO 2 -NH 2 with high breakdown strength is prepared, the modified BN@SiO 2 -NH 2 is respectively placed in an AB layer, and an ABA three-layer composite film is prepared through a coextrusion die head, so that mutual interference of functional fillers is avoided, performances of all layers are independently optimized, and the synergistic promotion of flame retardance, dielectric property and breakdown strength is realized.

Inventors

  • WANG RUNXIAO
  • LIU YUANCHAO
  • TONG GUOQING
  • XIA JINGJING
  • KANG DONGDONG
  • XU DINGSHENG

Assignees

  • 扬州博恒新能源材料科技有限公司

Dates

Publication Date
20260512
Application Date
20260415

Claims (9)

  1. 1. A multilayer coextrusion polypropylene composite film for a capacitor is characterized by being of an ABA three-layer coextrusion structure, wherein the A layer raw material comprises, by weight, 100 parts of polypropylene resin, 2-8 parts of modified flame retardant, 0.1-0.5 part of nucleating agent and 0.1-0.5 part of antioxidant, the B layer raw material comprises, by weight, 100 parts of polypropylene resin, 0.5-2 parts of aluminum oxide, 2-5 parts of BN@SiO 2 -NH 2 and 8-10 parts of MAH-g-PP, The modified flame retardant is obtained by carrying out polymerization reaction on BN@SiO 2 -NH 2 and glycidyl methacrylate and unsaturated phosphorus nitrogen flame retardant; The preparation process of BN@SiO 2 -NH 2 is as follows: Mixing boron nitride and urea, placing the mixture into a ball mill, performing ball milling for 10-20 hours, performing mechanical stripping, then dispersing the mixture into an ethanol water solution by ultrasonic, adding tetraethoxysilane and ammonia water, stirring and hydrolyzing to obtain BN@Si 2 , and finally performing reflux grafting with gamma-aminopropyl triethoxysilane to obtain BN@SiO 2 -NH 2 ; the structural formula of the unsaturated phosphorus-nitrogen flame retardant is 。
  2. 2. The multilayer co-extruded polypropylene composite film for a capacitor according to claim 1, wherein the raw material of the layer B is prepared by mixing MAH-g-PP with bn@sio 2 -NH 2 , feeding the mixture into a twin-screw extruder, and melt-extruding and granulating the mixture at 180-220 ℃ to obtain premixed granules, and then blending the premixed granules with the rest raw materials.
  3. 3. The multilayer coextruded polypropylene composite film for capacitors according to claim 1, characterized in that the grafting ratio of MAH-g-PP is 1.2% -1.5%.
  4. 4. The multilayer coextruded polypropylene composite film for capacitors according to claim 1, characterized in that the bn@sio 2 -NH 2 is prepared as follows: 1) Mixing boron nitride and urea according to a mass ratio of 1:20-40, placing the mixture in a ball mill, wherein a ball material ratio is 80:1-120:1, a rotating speed is 400-600 r/min, and performing mechanical stripping after ball milling for 15-20 hours to obtain stripped boron nitride which is recorded as BN; 2) Ultrasonically dispersing BN in an ethanol water solution, regulating the pH to 8-9 by using dilute ammonia water, slowly dripping tetraethoxysilane into the BN dispersion, stirring for 6 hours at 40 ℃, and centrifugally washing to obtain BN@SiO 2 ; 3) And dispersing BN@SiO 2 in ethanol, and adding 30-50% of gamma-aminopropyl triethoxysilane by mass of BN@SiO 2 to perform reflux grafting to obtain BN@SiO 2 -NH 2 .
  5. 5. The multilayer coextruded polypropylene composite film for capacitors according to claim 1, characterized in that the preparation process of the modified flame retardant is as follows: Adding BN@SiO 2 -NH 2 and initiator AIBN into a reaction bottle, carrying out ultrasonic dispersion to uniformly disperse the components, introducing nitrogen to blow for 30min, dissolving glycidyl methacrylate and an unsaturated phosphorus nitrogen flame retardant into tetrahydrofuran to form mixed monomer liquid, adding the mixed monomer liquid into the reaction bottle under the protection of nitrogen, heating to 70 ℃ for reaction for 4-8 h, cooling to room temperature after the reaction is finished, adding tetrahydrofuran to dilute a reaction system, precipitating in anhydrous methanol, filtering, washing and drying to obtain the modified acrylic acid.
  6. 6. The multilayer co-extruded polypropylene composite film for a capacitor according to claim 1, wherein the molar ratio of the glycidyl methacrylate to the unsaturated phosphorus nitrogen flame retardant is 3-6:4-7, and the mass ratio of the total mass of monomers to BN@SiO 2 -NH 2 is 0.5-2:1.
  7. 7. The multilayer coextruded polypropylene composite film for capacitors according to claim 1, wherein the nucleating agent is talc powder with a particle size of 100-200nm, and the antioxidant is antioxidant 1010 or antioxidant 168.
  8. 8. The multilayer coextruded polypropylene composite film for capacitors according to claim 1, wherein the ABA three-layer structure film thickness ratio of the composite film is 1:1 to 3:1.
  9. 9. The method for producing a multilayer coextruded polypropylene composite film for capacitors according to any one of claims 1 to 8, characterized by comprising the steps of: S1, mixing polypropylene resin, a modified flame retardant, a nucleating agent and an antioxidant in a high-speed mixer to obtain a layer A raw material, mixing MAH-g-PP and BN@Si 2 -NH 2 , putting the mixture into a double-screw extruder, carrying out melt extrusion granulation at 180-220 ℃ to obtain premixed granules, and then mixing the premixed granules with polypropylene resin and aluminum oxide in the high-speed mixer to obtain a layer B raw material; s2, respectively melting the raw materials of the layer A and the raw materials of the layer B through independent screw extruders at 200-240 ℃, and then forming an A-B-A three-layer composite cast sheet through A co-extrusion die head; S3, performing biaxial stretching on the cast sheet, preheating the cast sheet at 50-70 ℃, then performing longitudinal stretching at 110-130 ℃ with a stretching multiplying power of 3-3.6, preheating the cast sheet at 80-120 ℃ and performing transverse stretching at 110-130 ℃ with a stretching multiplying power of 2.6-3.2; And S4, performing heat setting on the biaxially stretched film, cooling at 50 ℃, performing corona treatment, traction and winding to obtain the film.

Description

Multilayer co-extrusion polypropylene composite film for capacitor and preparation method thereof Technical Field The invention relates to the technical field of capacitance films, in particular to a multilayer co-extrusion polypropylene composite film for a capacitor and a preparation method thereof. Background The polypropylene (PP) film has the advantages of low density, good chemical corrosion resistance, low cost and the like, and is widely applied to the fields of food packaging, medical packaging, production and conveying pipelines, textiles, electronic components and the like. The capacitor is one of three passive components, and has a figure in various electronic products. The thin film capacitor is widely applied to new energy fields such as new energy automobiles, photovoltaic and wind power generation due to the characteristics of high pressure resistance, temperature resistance, stability and the like. With the continuous progress and rapid development of technology, the performance requirement of the thin film capacitor is also higher and higher, and the performance of the capacitor device is optimized and improved by improving the performance of the capacitor film material as the core material of the thin film capacitor, which is one of the main attack directions in the field at present. Biaxially oriented polypropylene film (BOPP) is the most successful commercial polymer dielectric material at present, which has high breakdown strength, excellent temperature stability, relatively low cost and processability suitable for large-scale automated production. While BOPP films offer significant advantages, their physical properties also limit their application in some high-end scenarios, in which BOPP performs well at low temperatures, its breakdown field strength is rapidly reduced and dielectric loss is significantly increased in high temperature (> 70 ℃) environments. The difficulty of raising the dielectric constant is great, and raising the dielectric constant tends to sacrifice the insulation strength and the temperature resistance. In addition, polypropylene has poor flame retardant property, the limiting oxygen index is generally only about 17-18, and potential safety hazards exist. In order to improve the flame retardance, a flame retardant is usually selected to be added into PP, and the inorganic flame retardant can cause local stress concentration due to agglomeration in a polymer system, so that the brittleness of a film is increased and the mechanical strength is reduced. Aiming at the problems, the prior art adopts a single modification strategy, such as adding a single functional filler or simply blending, and is difficult to simultaneously meet multiple requirements of flame retardance, high dielectric property, high breakdown and the like. Therefore, developing a polypropylene capacitor film with excellent comprehensive performance becomes a technical problem to be solved in the field. Disclosure of Invention Aiming at the defects in the prior art, the invention provides a heat-resistant flame-retardant electric breakdown-resistant multilayer co-extrusion polypropylene base film which meets the performance requirements of an electric container. In order to achieve the above purpose, the present invention provides the following technical solutions: The multilayer coextrusion polypropylene composite film for the capacitor is of an ABA three-layer coextrusion structure, wherein the A layer raw material comprises, by weight, 100 parts of polypropylene resin, 2-8 parts of modified flame retardant, 0.1-0.5 part of nucleating agent and 0.1-0.5 part of antioxidant, the B layer raw material comprises, by weight, 100 parts of polypropylene resin, 0.5-2 parts of aluminum oxide, 2-5 parts of BN@SiO 2-NH2 and 8-10 parts of MAH-g-PP, The modified flame retardant is obtained by carrying out polymerization reaction on BN@SiO 2-NH2 and glycidyl methacrylate and unsaturated phosphorus nitrogen flame retardant; The preparation process of BN@SiO 2-NH2 is as follows: Mixing boron nitride and urea, placing the mixture into a ball mill, performing ball milling for 10-20 hours, performing mechanical stripping, then dispersing the mixture into an ethanol water solution by ultrasonic, adding tetraethoxysilane and ammonia water, stirring and hydrolyzing to obtain BN@Si 2, and finally performing reflux grafting with gamma-aminopropyl triethoxysilane to obtain BN@SiO 2-NH2; the structural formula of the unsaturated phosphorus-nitrogen flame retardant is 。 Further, in the raw material of the layer B, MAH-g-PP and BN@Si 2-NH2 are firstly mixed and put into a double-screw extruder, and melt extrusion granulation is carried out at 180-220 ℃ to obtain premixed granules, and then the premixed granules are blended with the rest raw materials. Further, the grafting rate of the MAH-g-PP is 1.2% -1.5%. Further, the preparation process of the BN@SiO 2-NH2 is as follows: 1) Mixing boron nitride and urea according to a m