Method for manufacturing paper barrier base material
A method for manufacturing a paper barrier base material includes a step of applying a water vapor barrier layer coating liquid that contains at least a water vapor barrier resin and a pigment onto a paper base material by a curtain coating method to form a water vapor barrier layer, and a step of applying a gas barrier layer coating liquid that contains at least one polymer selected from water-soluble polymers and water-dispersible polymers onto the water vapor barrier layer by a curtain coating method without a drying step interposed between the two steps to form a gas barrier layer. The gas barrier layer coating liquid has a B-type viscosity equal to or higher than a B-type viscosity of the water vapor barrier layer coating liquid. The method is intended to suppress the occurrence of coating unevenness in wet-on-wet coating by a curtain coating method.
1. A method for manufacturing a paper barrier base material, comprising:
a step of applying a water vapor barrier layer coating liquid that contains at least a water vapor barrier resin and a pigment onto a paper base material by a curtain coating method to form a water vapor barrier layer, wherein the pigment has an aspect ratio of 10 or more and a 50% volume-average particle size, D50, of 5 μm or more; and
a step of applying a gas barrier layer coating liquid that contains at least one polymer selected from water-soluble polymers and water-dispersible polymers onto the water vapor barrier layer by a curtain coating method without a drying step interposed between the two steps to form a gas barrier layer,
wherein a B-type viscosity of the gas barrier layer coating liquid is 10 to 220 mPa·s higher than a B-type viscosity of the water vapor barrier layer coating liquid, wherein the B-type viscosity is a viscosity in mPa·s measured with a B-type viscometer at a temperature of 25° C. at a rotation speed of 60 rpm.
2. The method for manufacturing a paper barrier base material according to claim 1 , wherein the gas barrier layer coating liquid has a static surface tension equal to or lower than a static surface tension of the water vapor barrier layer coating liquid.
3. The method for manufacturing a paper barrier base material according to claim 2 ,
wherein the water vapor barrier layer coating liquid has a B-type viscosity of 100 mPa·s or more and 400 mPa·s or less at a temperature of 25° C., and
the gas barrier layer coating liquid has a B-type viscosity of 150 mPa·s or more and 500 mPa·s or less at a temperature of 25° C.
4. The method for manufacturing a paper barrier base material according to claim 3 ,
wherein the water vapor barrier layer coating liquid has a static surface tension of 30 mN/m or more and 40 mN/m or less at a temperature of 25° C., and
the gas barrier layer coating liquid has a static surface tension of 25 mN/m or more and 35 mN/m or less at a temperature of 25° C.
5. The method for manufacturing a paper barrier base material according to claim 4 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.
6. The method for manufacturing a paper barrier base material according to claim 3 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.
7. The method for manufacturing a paper barrier base material according to claim 2 ,
wherein the water vapor barrier layer coating liquid has a static surface tension of 30 mN/m or more and 40 mN/m or less at a temperature of 25° C., and
the gas barrier layer coating liquid has a static surface tension of 25 mN/m or more and 35 mN/m or less at a temperature of 25° C.
8. The method for manufacturing a paper barrier base material according to claim 7 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.
9. The method for manufacturing a paper barrier base material according to claim 2 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.
10. The method for manufacturing a paper barrier base material according to claim 1 ,
wherein the water vapor barrier layer coating liquid has a B-type viscosity of 100 mPa·s or more and 400 mPa·s or less at a temperature of 25° C., and
the gas barrier layer coating liquid has a B-type viscosity of 150 mPa·s or more and 500 mPa·s or less at a temperature of 25° C.
11. The method for manufacturing a paper barrier base material according to claim 10 ,
wherein the water vapor barrier layer coating liquid has a static surface tension of 30 mN/m or more and 40 mN/m or less at a temperature of 25° C., and
the gas barrier layer coating liquid has a static surface tension of 25 mN/m or more and 35 mN/m or less at a temperature of 25° C.
12. The method for manufacturing a paper barrier base material according to claim 11 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.
13. The method for manufacturing a paper barrier base material according to claim 10 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.
14. The method for manufacturing a paper barrier base material according to claim 1 ,
wherein the water vapor barrier layer coating liquid has a static surface tension of 30 mN/m or more and 40 mN/m or less at a temperature of 25° C., and
the gas barrier layer coating liquid has a static surface tension of 25 mN/m or more and 35 mN/m or less at a temperature of 25° C.
15. The method for manufacturing a paper barrier base material according to claim 14 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.
16. The method for manufacturing a paper barrier base material according to claim 1 ,
wherein the water vapor barrier layer coating liquid has a solid content concentration of 25% by weight or more and 45% by weight or less, and
the gas barrier layer coating liquid has a solid content concentration of 15% by weight or more and 35% by weight or less.