| 摘要 |
A poly-L-lactic acid (PLLA) solidified and extrusion-molded article which comprises a resin material containing a PLLA having a weight average molecular weight of 100,000 to 380,000, a melt viscosity (temperature: 240°C, shear rate: 120 sec-1) of 20 to 2,000 Pa*s and an L-form content of 80 to 100%, and has a thickness or diameter of 10 to 500 mm and tensile strength of 5 to 100 MPa at 66°C (wherein the article may additionally contain a filler; in this case, the tensile strength of the article may be 5 to 200 MPa); a downhole tool member or ball sealer for well drilling use, which is formed by machining the solidified and extrusion-molded article; a sealing plug equipped with the downhole tool member; a method for producing a PLLA solidified and extrusion-molded article, which comprises the steps of supplying a resin material containing a PLLA into an extruder, carrying out the solidification and extrusion molding of the resin material, pressurizing the resultant solidified and extruded product, and then drawing the pressurized product while applying a back pressure in the direction of a forming die to thereby prevent the expansion of the solidified and extruded product; and a well drilling method. |
