Abstract: A method for preparing a hollow fiber-type separation membrane from high density polyethylene is provided, which includes the steps of: melt-spinning a mixture of a high density polyethylene and a diluting agent to produce a phase-separated undrawn hollow fiber; detecting a tensile strength of the undrawn fiber during an alternative and repetitive winding and unwinding procedure between two bobbins, said undrawn fiber being drawn during the alternative and repetitive winding and unwinding procedure; reducing a rotation speed of one of the two bobbins when the detected tensile strength is larger than a predetermined value; and increasing a rotation speed of one of the two bobbins when the detected tensile strength is smaller than the predetermined value to yield the hollow fiber-type separation membrane.

Abstract: A heated high pressure air and/or a high pressure water are spouted through nozzles. Therefore, the coated layer is removed without crushing the bumper unlike in the conventional method, and therefore, a plurality of process steps can be skipped. Thus the bulk of the apparatus can be reduced, the operating cost can be lowered, and the environment can be protected. The method for removing a coated layer includes the step of installing a bumper to be subjected to a removal of the coated layer. Then the coated layer is removed from the bumper by spouting water and/or a pre-heated air to the bumper. Then the bumper is carried to a predetermined psition after removing the coated layer, and then the bumper is detached. The apparatus includes an installing/detaching means for installing/detaching the bumper to be subjected to a removal of the coated layer.

Abstract: A heated high pressure air and/or a high pressure water are spouted through nozzles. Therefore, the coated layer is removed without crushing the bumper unlike in the conventional method, and therefore, a plurality of process steps can be skipped. Thus the bulk of the apparatus can be reduced, the operating cost can be lowered, and the environment can be protected. The method for removing a coated layer includes the step of installing a bumper to be subjected to a removal of the coated layer. Then the coated layer is removed from the bumper by spouting water and/or a pre-heated air to the bumper. Then the bumper is carried to a predetermined psition after removing the coated layer, and then the bumper is detached. The apparatus includes an installing/detaching means for installing/detaching the bumper to be subjected to a removal of the coated layer.