Water-soluble film and package
[Problem to be solved] To provide a water-soluble film capable of suppressing formation of holes when used as a package while maintaining water solubility, and a package using such a water-soluble film. [Solution] A water-soluble film containing a polyvinyl alcohol resin, wherein within a square A 1 with a side of 1 cm or more and 5 cm or less positioned at an arbitrary location on at least one surface of the water-soluble film, each side of an area of square A 2 with a side of 5 μm is divided into 64 to divide the entire area into 4096 pixels, and when elastic moduli of the pixels are measured by an atomic force microscope, a number average value of the elastic moduli of the pixels is 1 to 200 MPa, and a coefficient of variation of the elastic moduli of the pixels is 0.1 to 0.7.
1 . A water-soluble film containing a polyvinyl alcohol resin,
wherein within a square A 1 with a side of 1 cm or more and 5 cm or less positioned at an arbitrary location on at least one surface of the water-soluble film, each side of an area of square A 2 with a side of 5 μm is divided into 64 to divide the entire area into 4096 pixels, and when elastic moduli of the pixels are measured by an atomic force microscope, a number average value of the elastic moduli of the pixels is 1 to 200 MPa, and a coefficient of variation of the elastic moduli of the pixels is 0.1 to 0.7, wherein the water-soluble film is prepared by a method comprising filtering a film forming stock solution containing the polyvinyl alcohol resin through a filter medium, wherein the filter medium has from 300 to 475 mesh.
2 . The water-soluble film as claimed in claim 1 , wherein the square A 1 is positioned in a central portion of a width direction of the water-soluble film.
3 . The water-soluble film as claimed in claim 1 , wherein the square A 2 is positioned in at least one central portion or vertex of the square A 1 .
4 . The water-soluble film as claimed in claim 3 , wherein the square A 2 is positioned at the central portion and four vertices of the square A 1 .
5 . The water-soluble film as claimed in claim 1 , wherein the side of the square A 1 is 1 cm.
6 . The water-soluble film as claimed in- claim 1 , wherein the number average value of the elastic moduli is from 1 to 200 MPa and the coefficient of variation of the elastic moduli is from 0.1 to 0.7 on both surfaces of the water-soluble film.
7 . A package in which the water-soluble film as claimed in claim 1 stores a chemical.
8 . The package as claimed in claim 7 , wherein the chemical is a pesticide, a detergent or a disinfectant.
9 . The package as claimed in claim 7 , wherein the chemical is in a liquid form.
10 . The water-soluble film as claimed in claim 1 , wherein the water-soluble film is prepared by a method comprising:
contacting a support with a film forming stock solution containing the polyvinyl alcohol resin, wherein a surface temperature of the support is from 60 to 100° C.; and
blowing hot air on the film forming stock solution, wherein a temperature of the hot air is from 75 to 105° C.
11 . The water-soluble film as claimed in claim 10 , wherein a wind speed of the hot air is from 1 to 10 m/sec.
12 . The water-soluble film as claimed in claim 1 , wherein a complete dissolution time of the water-soluble film in water at 10° C. is 90 seconds or less.
13 . The water-soluble film as claimed in claim 1 , further comprising a plasticizer, wherein the plasticizer comprises at least one polyhydric alcohol selected from the group consisting of ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, and sorbitol.
14 . The water-soluble film as claimed in claim 1 , further comprising a plasticizer, wherein the plasticizer comprises glycerin.
15 . The water-soluble film as claimed in claim 1 , further comprising a plasticizer in an amount from 1 to 70 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol resin.
16 . The water-soluble film as claimed in claim 1 , further comprising a surfactant, wherein the surfactant comprises at least one nonionic surfactant selected from the group consisting of polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene laurate, polyoxyethylene lauryl amino ether, polyoxyethylene lauric acid amide, polyoxyethylene polyoxypropylene ether, lauric acid diethanolamide, oleic acid diethanolamide, and polyoxyalkylene allyl phenyl ether.
17 . The water-soluble film as claimed in claim 1 , further comprising a surfactant, wherein the surfactant comprises lauric acid diethanolamide.
18 . The water-soluble film as claimed in claim 1 , further comprising a surfactant in an amount from 0.01 to 1 part by mass with respect to 100 parts by mass of the polyvinyl alcohol resin.
19 . The water-soluble film as claimed in claim 1 , wherein the polyvinyl alcohol resin comprises a methyl maleate-modified polyvinyl alcohol resin.