JP-2026074632-A - Gas barrier laminate

Abstract

[Problem] To provide a laminate that does not crack even when molded into paper containers, etc., and exhibits excellent gas (especially oxygen) barrier properties by forming a sealing layer on a paper substrate that is less prone to defects during layer formation and molding, and further improving the interfacial peel strength between the sealing layer and the gas barrier layer with an anchor layer. [Solution] A laminate comprising a sealing layer, an anchor layer, and a gas barrier layer in this order on a paper substrate, wherein the sealing layer contains at least one of styrene-butadiene copolymer or acrylic resin, the viscosity of the dispersion obtained by dispersing it in water so that the glass transition temperature is 30°C or less and the solid content concentration is 40% by mass, at a shear rate of 150 s⁻¹ is 20 mPa·s or less at 25°C; the anchor layer contains at least a water-soluble amine resin; and the gas barrier layer contains at least cellulose nanocrystals. [Selection Diagram] Figure 1

Inventors

• 前田 慎一郎
• 長▲浜▼ 英昭
• 久富 祥人
• 浅野 誠

Assignees

• 東洋製罐グループホールディングス株式会社
• 東罐興業株式会社

Dates

Publication Date

20260507

Application Date

20241021

Claims (2)

1. A laminate comprising a paper substrate, a sealing layer, an anchoring layer, and a gas barrier layer in that order, The sealing layer contains at least one of a styrene-butadiene copolymer or an acrylic resin, wherein the dispersion, obtained by dispersing it in water so that the glass transition temperature is 30°C or lower and the solid content concentration is 40% by mass, has a viscosity at a shear rate of 150 s⁻¹ of 20 mPa·s or less at 25°C. The anchor layer contains at least a water-soluble amine resin, A laminate characterized in that the gas barrier layer contains at least cellulose nanocrystals.
2. A paper container having a laminated structure comprising a sealing layer, an anchoring layer, and a gas barrier layer in that order on a paper substrate, The sealing layer contains at least one of a styrene-butadiene copolymer or an acrylic resin, wherein the dispersion, obtained by dispersing the material in water so that its glass transition temperature is 30°C or lower and its solid content concentration is 40% by mass, has a viscosity of 20 mPa·s or less at a shear rate of 150 s⁻¹ at 25°C. The anchor layer contains at least a water-soluble amine resin, A paper container characterized in that the gas barrier layer contains at least cellulose nanocrystals.

Description

This invention relates to a laminate comprising a sealing layer, an anchoring layer, and a gas barrier layer formed on a paper substrate. More specifically, it relates to a laminate that does not crack even when molded into paper containers or the like, and that exhibits excellent gas barrier properties. Environmentally friendly paper substrates are widely used as materials for paper containers and other applications. Because paper substrates alone have poor liquid resistance and gas barrier properties, they are often used with a liquid-resistant resin layer or gas barrier layer laminated onto the substrate surface. However, since directly applying a gas barrier material to a liquid-resistant substrate does not result in a good gas barrier layer, a sealing layer made of liquid-resistant resin is sometimes used, with the gas barrier layer laminated on top. For example, Patent Document 1 below proposes a gas barrier paper material characterized in that a saturating layer made of styrene-butadiene copolymer is formed on at least one side of the base paper or processed paper by a coating method such that the resin solids content after drying is 0.1 to 30 g/ m² , the wetting tension of the surface of the saturating layer is 36 mN/m or more, and the Cobb water absorption is 10 g/ m² or less, and a gas barrier layer made of polyvinyl alcohol-based resin is formed on the saturating layer by a coating method such that the resin solids content after drying is 0.5 to 30 g/m². Patent No. 5869829 This is a cross-sectional view showing the basic structure of the laminate of the present invention. As shown in Figure 1, the laminate of the present invention is a laminate comprising a sealing layer 2, an anchor layer 3, and a gas barrier layer 4 on a paper substrate 1 in that order, wherein the sealing layer contains at least one of styrene-butadiene copolymers or acrylic resins such that the viscosity of the dispersion, obtained by dispersing it in water so that the glass transition temperature is 30°C or less and the solid content concentration is 40% by mass, at a shear rate of 150 s⁻¹ is 20 mPa·s or less at 25°C, the anchor layer contains at least a water-soluble amine resin, and the gas barrier layer contains at least cellulose nanocrystals. In the laminate of the present invention, the sealing layer contains a specific styrene-butadiene copolymer or acrylic resin, which prevents defects such as cracks and pinholes from occurring in the sealing layer during layer formation, and also prevents cracking during molding. In the anchor layer of the laminate of the present invention, the anchor layer contains a water-soluble amine resin, which improves the adhesion between the sealing layer and the gas barrier layer through an anchoring effect. Furthermore, as will be described later, the water-soluble amine resin in the anchor layer migrates to the gas barrier layer, forming the gas barrier layer as a layer composed of a mixture of cellulose nanocrystals and water-soluble amine resin. As a result, the self-assembled structure of cellulose nanocrystals is strengthened by the water-soluble amine resin, making it possible to exhibit gas barrier properties superior to those exhibited by cellulose nanocrystals alone. (Paper-based substrate) The paper substrate used as the base material for the laminate of the present invention is not limited to the above, but examples of known paper substrates include high-quality paper, imitation paper, art paper, coated paper, pure white roll paper, kraft paper, water-resistant label paper, cup base paper, cardboard, ivory paper, Manila cardboard, milk carton base paper, cup base paper, synthetic paper, clay-coated paper, water-resistant paper, and acid-resistant paper. The thickness of the paper substrate is preferably in the range of 50 to 450 μm, and when forming a cup-shaped container, it is preferably in the range of 150 to 400 μm. The basis weight of the paper substrate is preferably in the range of 100 to 400 g/ m² , and particularly preferably in the range of 150 to 350 g/ m² . (Sealing layer) In the laminate of the present invention, the sealing layer formed to impart water resistance to the paper substrate contains at least one of a styrene-butadiene copolymer or an acrylic resin such that the glass transition temperature and the viscosity of the dispersion are within a specific numerical range. This prevents defects such as cracks and pinholes from occurring during layer formation and also prevents cracks from occurring during molding. Furthermore, in combination with the presence of an anchor layer described later, the adhesion between the paper substrate and the gas barrier layer can be improved. The styrene-butadiene copolymer and acrylic resin used in the sealing layer of the present invention have a glass transition temperature of 30°C or lower, and the viscosity of the dispersion, obtained by dispersing them in water to a solid content concentration of 40% by mass, at a shear r