| 摘要 |
<p>A flat permeable polyolefin membrane 10 to 500 um in thickness, which has in one surface thereof a compact layer formed of intimately bound fine polyolefin particles and possessed of fine pores and in the interior and the other surface thereof a layer formed of an aggregate of fine discrete polyolefin particles of an average diameter in the range of 0.01 to 5um so adjoined as to form fine labyrinthically continuing through pores andwhich, therefore, establish communication between the opposite surfaces of said membrane. The method for the manufacture of the flat permeable membranes is characterized by the steps of mixing a polyolefin, an organic filler uniformly dispersable in the molten polyolefin, and a crystal seed forming agent, discharging the molten resultant mixture through a die, bringing one surface of the discharqed molten membrane into contact with a cooling roll thereby cooling and solidifying the membrane, and placing the cooled and solidified flat membrane into contact with an extractant incapable of dissolving the polyolefin thereby extracting and removing the organic filler from the web of the membrane, wherein the temperature of the cooling roll is 10-100.degree.C.</p> |
