| 摘要 |
PROBLEM TO BE SOLVED: To inexpensively obtain an agricultural heat insulating material, especially, a water absorbable heat insulating material for cultivativing a strawberry by laminating a porous film and a nonwoven fabric and setting the absorbing speed of waterdrops dripped on the rear surface of the film to specific sec or less. SOLUTION: A heat insulating material is constituted by laminating a porous film and a nonwoven fabric. The absorbing speed of waterdrops of this heat insulating material is set to 60sec or less. When the absorbing speed of waterdrops exceeds 60sec, the absorbing speed becomes markedly slow because of partial irregularity or possibility not perfectly absorbing waterdrops is partially generated. The average pore size of the porous film is set to about 10-1,500μm. If the average pore size is small, the absorbing speed of generated dew becomes low and, if the average pore size becomes too large, the heat insulating effect of the film becomes low. Therefore, waterdrops dripped on a strawberry is rapidly removed and the damage ratio of a strawberry is lowered and yield is enhanced. Further, the absorption of the radiant heat of the heat of the earth is good and heat insulating effect and heat transfer are well-balanced and, therefore, the total heat insulating effect is enhanced.
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