A kind of high porosity polypropylene microporous film and preparation method thereof
A technology of microporous membrane and nucleating agent, which is applied in the direction of coating, structural parts, electrical components, etc., can solve the problem of uneven micropore distribution of βPP microporous membrane, and achieve the effect of increasing porosity and uniformity
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[0023] The invention provides a method for preparing a high-porosity biaxially stretched βPP microporous film. A β-nucleating agent is used as a filler to prepare an oriented βPP pre-set film through an extrusion casting process, and then through biaxial stretching. Microporous membranes were prepared from pre-stretched βPP membranes. This preparation method mainly comprises the following steps:
[0024] 1) Preparation of PP / nucleating agent masterbatch: blending 1% nucleating agent and PP matrix in a twin-screw extruder for granulation, and then adding pure PP resin to the blended granules to form The weight content of the nucleating agent is diluted to 0.1%-0.3%. Wherein the temperature of the twin-screw extruder is set at 160°C to 200°C. Nucleating agents may include TMB-5, WBG-II, or combinations thereof. In the following, TMB-5 is used as an example of the nucleating agent for illustration, but it should be understood that the nucleating agent may be one or both of TMB...
specific Embodiment approach
[0041] The porosity described in the embodiment is measured by the following method:
[0042] The porosity of the microporous membrane was determined by the imbibition method. The specific method is to weigh the microporous membrane, soak it in n-hexadecane for 2 hours, take it out, gently wipe the remaining n-hexadecane on the surface of the microporous membrane with filter paper, and weigh it again. The experiment was repeated at least three times, and the average value was calculated by the following formula.
[0043]
[0044] The density of n-hexadecane in the formula is 0.774g / cm 3 ,The density of PP is related to the degree of crystallinity, and there are certain differences between different film thicknesses, but the difference is not large.
Embodiment 1
[0046] A preparation method of a high-porosity βPP microporous membrane, comprising the steps of:
[0047] 1) Preparation of oriented βPP preset film: TMB-5 with a weight content of 0.2% is prepared into PP / TMB-5 masterbatch through a twin-screw extruder; For plasticization, the temperature of the single-screw extruder is set to 165°C, 215°C, 230°C, and the die temperature is 230°C; the speed of the extruder is 20rpm / min; the temperature of the upper and middle rolls of the three-roll calender is Set it to 120°C, adjust the speed of the three-roll calender, and control the thickness of the prepared preset film at 120 μm, and its density is 0.9057g / cm 3 .
[0048] 2) Preparation of microporous membrane: stretch the prepared preset membrane along the TD direction at 90°C to a strain of 300% at a speed of 10mm / min, heat-set at 125°C for 5min, and Then along the MD direction, at 125° C., stretch 300% of the strain amount at a speed of 10 mm / min, and heat set at 130° C. for 5 min...
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Abstract
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