US-12623438-B2 - Vapor deposition paper and method for producing same

US12623438B2US 12623438 B2US12623438 B2US 12623438B2US-12623438-B2

Abstract

A vapor deposition paper having barrier properties and excellent recyclability. The vapor deposition paper includes a clay coat layer; an undercoat layer; a vapor deposition layer; an overcoat layer; and a heat seal layer in this order on at least one surface of a paper substrate, in which the vapor deposition layer contains at least one of a metal and ceramic and has a thickness of 1 nm or more and 1000 nm or less, and the pulp recovery rate after re-disintegration of the vapor deposition paper is 80% or more.

Inventors

Yasutomo Noishiki
Yuta SHAMOTO
Misaki WAKABAYASHI
Miyoko TANAKA

Assignees

Oji Holdings Corporation

Dates

Publication Date: 20260512
Application Date: 20220113
Priority Date: 20210115

Claims (18)

1 . A vapor deposition paper comprising: a clay coat layer; an undercoat layer; a vapor deposition layer; an overcoat layer; and a heat seal layer in this order on at least one surface of a paper substrate, wherein the vapor deposition layer contains at least one selected from the group consisting of metal and ceramic and has a thickness of 1 nm or more and 1000 nm or less, the heat seal layer contains a lubricant, and a pulp recovery rate after re-disintegration of the vapor deposition paper is 80% or more.
2 . The vapor deposition paper according to claim 1 , wherein the heat seal layer contains a water-suspendable polymer.
3 . The vapor deposition paper according to claim 1 , wherein the heat seal layer contains at least one selected from the group consisting of a styrene-butadiene copolymer and an olefin-unsaturated carboxylic acid copolymer.
4 . The vapor deposition paper according to claim 1 , wherein the clay coat layer contains an inorganic pigment and a binder, and a content of the inorganic pigment in the clay coat layer is 68% by mass or more and 90% by mass or less.
5 . The vapor deposition paper according to claim 4 , wherein the inorganic pigment has an aspect ratio of 50 or less and a mean particle size of 5 μm or less.
6 . The vapor deposition paper according to claim 4 , wherein the inorganic pigment is kaolin.
7 . The vapor deposition paper according to claim 4 , wherein the binder contains one or more selected from the group consisting of a styrene-butadiene resin, a styrene-(meth) acrylic resin, an olefin-unsaturated carboxylic acid copolymer, and polylactic acid.
8 . The vapor deposition paper according to claim 1 , wherein the undercoat layer and/or the overcoat layer contain(s) a water-suspendable polymer.
9 . The vapor deposition paper according to claim 8 , wherein the water-suspendable polymer contains one or more selected from the group consisting of a polyester resin and a polyurethane resin.
10 . The vapor deposition paper according to claim 1 , wherein a content of hardwood pulp in raw material pulp constituting the paper substrate is 80% by mass or more.
11 . The vapor deposition paper according to claim 1 , wherein the vapor deposition layer contains inorganic oxide, and the inorganic oxide contains at least one selected from the group consisting of silicon oxide and aluminum oxide.
12 . The vapor deposition paper according to claim 1 , wherein the undercoat layer and/or the overcoat layer contain(s) one or more selected from the group consisting of a polyurethane resin and a polylactic acid, and the polyurethane resin contains at least one selected from the group consisting of a constituent unit derived from metaxylylene diisocyanate and a constituent unit derived from hydrogenated metaxylylene diisocyanate.
13 . A method for producing a vapor deposition paper having a clay coat layer, an undercoat layer, a vapor deposition layer, an overcoat layer, and a heat seal layer in this order on at least one surface of a paper substrate, the method comprising: applying a coating liquid in which a water-suspendable polymer is dispersed in an aqueous medium to form the undercoat layer and the overcoat layer, and applying a coating liquid in which a water-suspendable polymer and a lubricant are dispersed in an aqueous medium to form the heat seal layer.
14 . The method for producing a vapor deposition paper according to claim 13 , wherein the water-suspendable polymer in the step of forming the undercoat layer and/or the step of forming the overcoat layer contains one or more selected from the group consisting of a polyurethane resin and a polylactic acid, and the polyurethane resin contains at least one selected from the group consisting of a constituent unit derived from metaxylylene diisocyanate and a constituent unit derived from hydrogenated metaxylylene diisocyanate.
15 . A vapor deposition paper having a coating layer, a vapor deposition layer, an overcoat layer, and a heat seal layer in this order on one surface of a paper substrate, wherein the heat seal layer contains a lubricant, a Cobb water absorption degree of a surface on a side of the overcoat layer at a temperature of 23° C. for a contact time of 120 seconds measured according to JIS P 8140:1998 is 1.0 g/m 2 or less, a Cobb water absorption degree of a surface on a side opposite to the side of the overcoat layer at a temperature of 23° C. for a contact time of 120 seconds measured according to JIS P 8140:1998 is 10 g/m 2 or more, a surface specific electrical resistance of the surface on the side of the overcoat layer measured according to JIS C 2139:2008 is 1.0×10 12 Ω or more, and when a laminated sheet is formed by laminating a 20 μm thick unstretched polypropylene film on the overcoat layer of the vapor deposition paper, an oxygen permeability of the laminated sheet at a temperature of 23° C. and a relative humidity of 50% measured according to JIS K 7126-2:2006 is 2.0 mL/m 2 ·day·atm or less.
16 . The vapor deposition paper according to claim 15 , wherein a water vapor permeability at a temperature of 40° C. and a relative humidity of 90% measured according to JIS Z 0208:1976 (cup method), B method is 1.0 g/(m 2 ·day) or less.
17 . The vapor deposition paper according to claim 15 , wherein the coating layer has a clay coat layer and an undercoat layer in this order from a side of the paper substrate.
18 . The vapor deposition paper according to claim 15 , wherein the coating layer has a clay coat layer and an undercoat layer in this order from a side of the paper substrate, the undercoat layer and/or the overcoat layer contain(s) one or more selected from the group consisting of a polyurethane resin and a polylactic acid, and the polyurethane resin contains at least one selected from the group consisting of a constituent unit derived from metaxylylene diisocyanate and a constituent unit derived from hydrogenated metaxylylene diisocyanate.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application PCT/JP2022/000825, filed Jan. 13, 2022, which claims priority to Japanese Patent Application No. 2021-005202, filed Jan. 15, 2021; Japanese Patent Application No. 2021-067015, filed Apr. 12, 2021; and Japanese Patent Application No. 2021-074836, filed Apr. 27, 2021, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a vapor deposition paper and a method for producing the same. BACKGROUND ART Conventionally, packaging materials obtained by imparting water vapor barrier properties of blocking water vapor or gas barrier properties of blocking gases other than water vapor to paper substrates, particularly packaging materials obtained by imparting oxygen barrier properties of blocking oxygen to paper substrates, have been used for preventing, in packaging food, medical products, electronic parts, and the like, deterioration of quality of the contents. As methods for imparting the water vapor barrier properties and the gas barrier properties to paper substrates, a method which includes laminating a synthetic resin film having excellent water vapor barrier properties and gas barrier properties on the paper substrate is common. However, materials in which the synthetic resin film or the like is laminated on the paper substrate have posed environmental problems due to a difficulty in recycling the paper, the synthetic resin, and the like after use. Thus, the development of barrier materials having the water vapor barrier properties and the gas barrier properties without using the synthetic resin films or the like has been advanced. For example, Patent Literature 1 discloses a paper packaging material having barrier properties against moisture and oxygen provided with an organic material coating layer, a metal or metal oxide layer, and an organic material coating layer inside a paper layer. On the other hand, a metallized paper has been widely used for a label paper having excellent design properties for alcoholic beverages, beer, soft drinks, and the like, a packaging paper for confectionery, and the like utilizing its glossy feeling. However, the metallized paper requires the formation of a metal thin film on a paper substrate, and therefore an improvement of the adhesiveness and production methods thereof have been examined. For example, Patent Literature 2 discloses an aluminum metallized paper obtained by providing an aluminum vapor deposition layer on a base paper, the base paper having a rear surface treated such that the natural polarization potential value of the surface of the vapor deposition layer falls within a specific range. Patent Literature 3 discloses a sealing sheet for PTP packaging having a filling coating layer by a polyolefin aqueous dispersion liquid, a vapor deposition thin film layer containing inorganic oxide, and a heat seal resin layer sequentially formed on one surface of a thin paper having a basis weight equal to or less than a specific value. PRIOR ART Patent Literature Patent Literature 1: JP 2002-321307 APatent Literature 2: JP 1992-65599 APatent Literature 3: JP 1995-223686 A SUMMARY OF INVENTION Technical Problem The vapor deposition paper described in each of Patent Literature 1 and 2 has a problem of difficulty in recovering pulp in re-disintegration, resulting in poor recyclability. Hereinafter, this problem is referred to as the first problem. Further, it has been found that the sealing sheet for PTP packaging described in Patent Literature 3 has a problem of poor barrier properties (oxygen barrier properties). Hereinafter, this problem is referred to as the second problem. Thus, it is an object of the present invention to provide a vapor deposition paper having barrier properties and excellent recyclability. The first problem of the present invention can be solved by the following structures <A1> to <A22>. <A1> A paper laminate comprising: a clay coat layer; an undercoat layer; a vapor deposition layer; an overcoat layer; and a heat seal layer in this order on at least one surface of a paper substrate, wherein the vapor deposition layer is at least one of a layer comprising metal and a layer comprising ceramic and has a thickness of 1 nm or more and 1000 nm or less, and the pulp recovery rate after re-disintegration of the paper laminate is 80% or more. <A2> The paper laminate according to <A1>, wherein the undercoat layer, the overcoat layer, and the heat seal layer contain a water-suspendable polymer. <A3> The paper laminate according to <A1> or <A2>, wherein the undercoat layer, the overcoat layer, and the heat seal layer are formed using an aqueous medium. <A4> The paper laminate according to any one of <A1> to <A3>, wherein the clay coat layer contains clay and a water-suspendable polymer, and the clay content in the clay coat layer is 68% by mass or more and 90% by mass