Package of porous film
A method for producing a porous film having a water content percentage of less than 1000 ppm, the method including the steps of: (1) obtaining a porous film (A) having a water content percentage of not less than 1000 ppm; (2) obtaining a package by causing the obtained porous film (A) and a drying agent to be contained in a water vapor barrier packaging container and sealing the water vapor barrier packaging container; and (3) storing the obtained package.
1. A sealed package comprising:
a sealed water vapor barrier packaging container;
a porous film (A) contained in the water vapor barrier packaging container and having a water content percentage of not less than 1000 ppm; and
a drying agent contained in the water vapor barrier packaging container in an amount of not less than X mass % with respect to a mass of the porous film (A), the X being calculated based on the following equation (I):
X=Y /( a× 100) (I)
where a represents an amount of moisture absorption (g) per 100 g of the drying agent at a temperature of 24° C. and a humidity of 10%, and Y represents a water content percentage (ppm) of the porous film (A).
2. The sealed package as set forth in claim 1 , wherein the sealed package is stored for a period of not less than 1 hour after the package is sealed.
3. The sealed package as set forth in claim 2 , wherein the water vapor barrier packaging container contains therein (i) the porous film which has a water content percentage of less than 1000 ppm and (ii) the drying agent.
4. The sealed package as set forth in claim 3 , wherein the drying agent has a water content percentage of not less than 10000 ppm.
5. The sealed package as set forth in claim 1 , wherein the water vapor barrier packaging container has a water vapor transmittance of 0.1 g/m2/24 hr to 5 g/m2/24 hr at a temperature of 40° C. and a humidity of 90% RH.
6. The sealed package as set forth in claim 1 , wherein the porous film is a roll porous film.
7. The sealed package as set forth in claim 1 , wherein the porous film is a nonaqueous secondary battery separator.
8. A sealed package comprising:
a sealed water vapor barrier packaging container;
a porous film contained in the water vapor barrier packaging container and having a water content percentage of less than 1000 ppm; and
a drying agent contained in the water vapor barrier packaging container and having a water content percentage of not less than 1000 ppm,
in a case where part of moisture contained in the drying agent is moved to the porous film so that the porous film has a water content percentage of 1000 ppm, the drying agent having, during drying, a mass that is not less than X′ mass % with respect to a mass of a porous film (A′), which is the porous film to which the moisture has been moved, the X′ being calculated based on the following equation:
X′=Y ′/( a× 100)
where a represents an amount of moisture absorption (g) per 100 g of the drying agent at a temperature of 24° C. and a humidity of 10%, and Y′ represents a water content percentage of 1000 ppm of the porous film (A′), which is the porous film to which the moisture has been moved.