JP-2026075903-A - Paper containers and manufacturing methods

Abstract

[Problem] To provide a method for manufacturing a paper container that can ensure the desired barrier properties while press-molding barrier paper. [Solution] The method for manufacturing a paper container comprises: step A, preparing barrier paper in which a barrier layer mainly composed of polyvinylidene chloride is formed on a paper substrate; step B, heating the barrier layer to make the ratio I1/I2 of the absorption intensity I1 of the IR peak (1041 cm⁻¹ ) originating from the crystalline portion of polyvinylidene chloride, measured from FT-IR, to the absorption intensity I1/I2 of the IR peak (1067 cm⁻¹ ) originating from the amorphous portion of polyvinylidene chloride less than 1.4; and step C, press-molding the barrier paper while I1/I2 is less than 1.4. [Selection Diagram] None

Inventors

• 鈴木 麻友

Assignees

• ＴＯＰＰＡＮホールディングス株式会社

Dates

Publication Date

20260511

Application Date

20241023

Claims (4)

1. Step A involves preparing barrier paper in which a barrier layer mainly composed of polyvinylidene chloride is formed on a paper substrate, Step B involves heating the barrier layer to make the ratio I1/I2 between the absorption intensity I1 of the IR peak (1041 cm⁻¹ ) originating from the polyvinylidene chloride crystalline portion and the absorption intensity I1 of the IR peak (1067 cm⁻¹ ) originating from the polyvinylidene chloride amorphous portion, as measured by FT-IR, less than 1.4. Step C involves press-molding the barrier paper while the ratio I1/I2 is less than 1.4, Equipped with, A method for manufacturing paper containers.
2. Step B is performed by roll heating, which involves passing the barrier paper between heated rolls. A method for manufacturing a paper container according to claim 1.
3. In step B, a sealant layer mainly composed of polyethylene is formed on the barrier layer. A method for manufacturing a paper container according to claim 2.
4. A paper container formed by press-molding barrier paper, on which a barrier layer mainly composed of polyvinylidene chloride is formed on a paper base material, The gas barrier performance per unit internal area satisfies at least one of the following conditions: oxygen permeability of less than 20 cc/ m² ·day·atm and water vapor permeability of less than 20 g/ m² ·day·atm. Paper container.

Description

This invention relates to paper containers, and more particularly to paper containers manufactured by molding barrier paper. The invention also describes a method for manufacturing these paper containers. It is widely known that barrier containers can be manufactured using barrier paper, which has an oxygen barrier layer formed on a paper substrate. Patent Document 1 exemplifies polyvinylidene chloride as a material for the oxygen barrier layer in such barrier paper. Japanese Patent Publication No. 2014-5031 This is a schematic diagram showing the layer structure of barrier paper according to one embodiment of the present invention.This is a schematic diagram showing a paper container according to one embodiment of the present invention.This graph shows the crystallization index of the barrier layer in the manufacturing process of paper containers.This graph shows the change in the crystallization index of the barrier layer over time. One embodiment of the present invention will be described with reference to Figures 1 to 4. Figure 1 shows the layer structure of the barrier paper 1 according to this embodiment. As shown in Figure 1, the barrier paper 1 comprises a paper substrate 10, a barrier layer 20 formed on the first surface 10a of the paper substrate 10, and a sealant layer 30 formed on the second surface 10b of the paper substrate 10 and on the barrier layer 20. Various types of paper can be used as the material for the paper substrate 10, and a printing layer for various displays may be provided on one or both sides. Furthermore, a sealing layer to flatten surface irregularities may be provided on one or both sides. The barrier layer 20 is mainly composed of polyvinylidene chloride (PVDC), meaning it has the highest mass ratio of PVDC. PVDC is a crystalline polymer and exhibits excellent barrier properties against oxygen and water vapor. The sealant layer 30 is a layer used for heat sealing when attaching a lid to a container made of barrier paper. The material of the sealant layer 30 can be selected according to the configuration of the lid to be joined, and examples include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE). The sealant layer 30 may be provided on only one of the second surface 10b and the barrier layer 20. A paper container made from the barrier paper 1 can be manufactured by press molding the barrier paper 1. Figure 2 shows a schematic diagram of the paper container 50 according to this embodiment. The paper container 50 is formed by deforming a single sheet of barrier paper 1 by press molding, and as shown in Figure 2, it has a bottom surface 51, side surfaces 52 rising from the periphery of the bottom surface, and a flange 53 provided on the upper part of the side surfaces 52, and has an opening Op at the top. The paper container 50 is usually manufactured so that the barrier layer 20 is on the inner side, but this is not essential, and it may also be manufactured so that the barrier layer 20 is on the outer side. In the paper container 50, there are no particular restrictions on the planar shape viewed from the opening Op side (generally the same as the normal direction of the bottom surface 51), and various shapes such as rectangles, other polygons, circles, and ellipses can be appropriately selected. Within the range where tearing or other damage occurs to the barrier paper 1 during press molding, the number and height of the side surfaces 52, the angle of rise from the bottom surface 51, and the angle between the side surfaces 52 and the flange 53 can also be appropriately set. The upper limit of the amount of elongation of the barrier paper 1 that can be press-molded without tearing or other damage is approximately 10%. After filling a paper container with food or other contents, a barrier lid film (not shown) is heat-sealed to the sealant layer 30 of the flange 53 to seal the opening Op. This allows the contents to be preserved in an oxygen and water vapor barrier space until the lid film is removed and the container is opened. This extends the shelf life or best-before date of the contents, and, if the contents are food, contributes to reducing food waste. The inventor had been making numerous prototype paper containers using barrier paper 1, which uses PVDC as a barrier layer, when he encountered many cases in which the produced paper containers did not exhibit the expected barrier properties based on the barrier layer. When the inventors analyzed a prototype with insufficient barrier properties, they found numerous pinholes in the barrier layer, which they determined to be the main cause of the reduced barrier performance. Further investigation by the inventors revealed that pinholes are caused by two types of cracks: one resulting from cracks in the barrier layer when the barrier paper stretches during molding (hereinafter referred to as "mechanism 1"), and the other from the bursting of air bubbles gen