Polyolefin micropore barrier diaphragm and method for producing the same

Abstract

The invention relates to a polyolefin microporous diaphragm, which belongs to the field of thin-film manufacture. The polyolefin microporous diaphragm consists of a polyolefin microporous basal membraneand oxide layer(s) on or / and under the polyolefin microporous basal membrane, wherein the polyolefin microporous basal membrane consists of 96.5 to 99.995 percent of homo-polypropylene resin and 0.005 to 3.5 percent of beta crystal form nucleating agent according to weight percentage; the polyolefin microporous basal membrane has the average pore size between 80and 200 nanometers, the porosity between 30 and 50 percent and the air permeability between 1.5 and 15 ml / cm<2>.sec.atm; and the thickness of the oxide layer is between 0.05 and 2 microns. The polyolefin microporous diaphragm has the characteristics of uniform micropores, good air permeability, good thermal shrinkage properties and high ionic electrical conductivity, and can be widely applied to medical dialysis membranes, industrial water treatment membranes and lithium-ion secondary battery diaphragms.

Description

technical field [0001] The invention relates to a polyolefin microporous diaphragm and a manufacturing method thereof, belonging to the field of film manufacturing. Background technique [0002] Due to the wide application and considerable economic benefits of polyolefin microporous films, domestic research on polyolefin microporous films has gradually heated up in recent years. The polyolefin microporous film can be used for the bottom membrane of gas separation membrane and reverse osmosis membrane; it can also be used for medical purposes such as dialysis and aseptic packaging; industrial water treatment membrane and lithium ion battery diaphragm. CN1272374C discloses "a kind of polypropylene microporous film and its preparation method" is to adopt polypropylene, one-component nucleating agent and oils as raw materials, through extruding flat film, annealing, two-stage uniaxial stretching, heat setting and Rolled to make polypropylene microporous membrane. However, in t...

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Problems solved by technology

However, in the production process of the microporous membrane, due to the two-time uniaxial stretching method, the total elongation is 30% to 300%, so the pore shape of the prepared microporous membrane is narrow and long, resulting in difficult pore diameter. control

In addition, its lack of strength in the transverse direction causes the film to be easily torn, making it difficult to be industrially utilized

And CN1233051C discloses " a kind of production method of lithium battery separator ", although can solve the problem that pore diameter is difficult to control by longitudinal and transverse bidirectional stretching respectively, but because longitudinal stretching and transverse stretching adopt the same stretching ratio , it is easy to cause micropores through the film, and because this method does not perform pre-shrinkage relaxation treatment at high temperature, the thermal shrinkage rate of the separator made by this method is relatively large. These shortcomings make it easy to use as a lithium-ion battery separator. short-circuit a lithium-ion battery

In addition, due to the non-hydrophilicity of polypropylene, this kind of film has poor ability to absorb electrolyte as a lithium-ion battery separator. At the same time, due to the low ionic conductivity, the internal resistance of lithium-ion batteries is too high, which affects the performance of lithium-ion batteries.

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