| 摘要 |
PROBLEM TO BE SOLVED: To easily produce a permeable sheet for a drainage material satisfying a required value by adding and mixing a master batch comprising a synthetic resin material and a foaming agent to a synthetic resin base material and performing extrusion and foaming. SOLUTION: A master batch comprising a synthetic resin material and a foaming agent is added to and mixed with a base material comprising a thermosetting resin, a synthetic resin feedstock uniformly dispersing the foaming agent is compounded, a number of communicating holes are formed in the thickness direction by extrusion foaming, required values as a permeable sheet for a drainage material 2, i.e., a permeable coefficient of 2.0×10<-2> cm/s or more and tensile strength of 3 kgf/30 mm or more are satisfied. The permeable sheets 2, 3 are adhered to the surface and the rear face of a synthetic resin-made core material 1 forming a number of projections to form a drainage material 10 forming a water communicating gap 4. In addition, the permeable sheet 2 is wound around the peripheral face of a cylindrical core material forming a number of holes to form a cylindrical drainage material. Thus, the permeable sheet for the drainage material 2 satisfying the required values can be easily produced.
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