Biaxially oriented polypropylene film for capacitor

Abstract

The film comprises an upper surface layer, a middle layer and a lower surface layer, and is prepared by the following steps: respectively feeding polypropylene resin A serving as a middle layer raw material and polypropylene resin B serving as a surface layer raw material into a main extruder and an auxiliary extruder for melting and plasticizing; extruding through a three-runner composite die head to obtain flaky fluid; the obtained sheet fluid is subjected to casting forming through a chilling roller and a high-pressure air knife, longitudinal stretching and transverse stretching are sequentially conducted through a longitudinal stretching machine and a transverse stretching machine, and the biaxially stretched polypropylene film for the capacitor is obtained. The polypropylene film provided by the invention is used in a capacitor, can meet the oil immersion requirement, and can also meet the electrical performance index requirements such as breakdown voltage and the like.

Description

technical field [0001] The invention belongs to the field of capacitor films, in particular to a biaxially stretched polypropylene film for capacitors. Background technique [0002] Biaxially oriented polypropylene (BOPP) films are widely used due to their excellent properties, such as high tensile strength, low gas permeability, good transparency and gloss, excellent chemical stability, and heat and cold resistance. Used in food, medicine, daily necessities and other packaging fields. In addition, it can also be used as a capacitive film in electronic fields such as AC motors, household appliances, and power capacitors by taking advantage of its excellent pressure resistance, temperature resistance, and electrical properties. [0003] In polypropylene film for capacitors, low dielectric loss is an important criterion to measure the quality of polypropylene. This is because the film made of polypropylene with low dielectric loss can allow the capacitor to work in a harsher...

AI Technical Summary

Problems solved by technology

The roughness is mainly related to the crystallinity and the film-drawing process. If the crystallinity is too low, no matter how the film-drawing process is controlled, the roughness is difficult to meet the requirements.

In order to improve the processing suitability of polypropylene film for capacitors, surface roughening is necessary, but in general, surface roughening also has the negative effect of reducing the withstand voltage characteristics

Although the improvement of withstand voltage characteristics can be achieved by high stereoregularity and high crystallinity of polypropylene resin, however, high stereoregularity and high crystallinity lead to a decrease in stretchability, and film breakage tends to occur during stretching. Increased manufacturing difficulty

[0005] It can be seen from the above that there are defects in the prior art that the oil impregnation performance, voltage resistance and processability of the biaxially oriented polypropylene film are difficult to improve simultaneously.

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