Rear face moisture-proof paper for decorative plate

Abstract

To provide rear face moisture-proof paper which has high moisture-proof performance, can prevent warpage of a decorative plate even when used in a place with a large difference in temperature and humidity environments between both sides, and reduces a used amount of plastic, thereby being environment-friendly.SOLUTION: Rear face moisture-proof paper 100 for a decorative plate includes a laminate having such a structure that a paper base material 11, a first resin layer 12, an aluminum vapor deposition layer 13 and a second resin layer 14 are laminated in this order, wherein thickness of the aluminum vapor deposition layer 13 is 60 nm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a moisture-proof paper for decorative panels used in interior door panels, etc., which is attached to the back surface of the decorative panel to prevent warping of the decorative panel caused by moisture absorption and release due to changes in indoor temperature and humidity. [Background technology]

[0002] Conventionally, decorative panels used for applications such as interior door panels have generally been formed by laminating a decorative sheet printed with a solid print layer to provide hiding properties or a patterned layer to improve design to the surface of a multi-layered wood-based substrate such as plywood, medium-density fiberboard (MDF), veneer, board material, or other material. If the moisture content of a wood-based substrate is lower than the equilibrium moisture content of the wood-based substrate under ambient conditions, the surface of the decorative board where the decorative sheet is not attached will absorb moisture, causing the surface to expand. If the moisture content is higher than the equilibrium moisture content of the wood-based substrate, the surface of the decorative board where the decorative sheet is not attached will release moisture, causing shrinkage. However, the surface where the decorative sheet is attached will hardly absorb or release moisture, causing deformation (warping, dimensional changes) of the decorative board.

[0003] Known methods for preventing this deformation include applying paint to the back of a decorative board with a decorative sheet attached to the surface, attaching a synthetic resin sheet such as polyvinyl chloride, polyethylene, or polypropylene, or attaching a moisture-proof sheet made of paper / polyethylene / paper (for example, Patent Document 1). Furthermore, when even higher moisture resistance is required, a method is known for preventing deformation of the decorative board, such as laminating a moisture-proof sheet having a vapor-deposited layer on a synthetic resin substrate. To achieve high moisture-proof performance, a vapor-deposited layer must be formed on a smooth surface, so synthetic resin substrates are generally chosen, and it is considered technically difficult to achieve high moisture-proof performance using a paper substrate.

[0004] On the other hand, however, in recent years, growing environmental awareness stemming from issues such as marine plastic waste has led to a growing trend toward a plastic-free society. From the perspective of reducing the amount of plastic material used, the use of paper instead of plastic materials has been considered in various fields. Furthermore, from the perspective of the Act on Promotion of Effective Utilization of Resources, there is a demand to increase the proportion of paper in the overall laminate having barrier properties. For example, Patent Document 2 listed below discloses a base paper for metallized paper, which has a specific clay coat layer and a resin layer, in that order, on at least one side of a specific paper substrate, for forming a metallized layer by vapor deposition. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3206408 [Patent Document 2] Patent No. 6958755 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional moisture-proof back sheets sometimes have insufficient moisture-proofing properties, and when used for long periods on doors, sliding doors, partitions, etc. where there is a large difference in temperature and humidity environments on both sides, the degree of expansion and contraction on both sides can differ, causing the decorative panel to warp. Furthermore, both of these products are primarily made of plastic materials, and there is a demand to reduce their use in order to reduce the environmental impact.

[0007] The present inventors have investigated various laminates comprising a paper base material, a first resin layer, an aluminum vapor-deposited layer, and a second resin layer as laminates with excellent environmental compatibility. They have found that such laminates have a high water vapor permeability and are unstable. In other words, the present inventors have newly discovered a problem in that some of the above-mentioned laminates according to conventional technology have low and unstable water vapor barrier properties (those with uneven water vapor barrier performance and low yields).

[0008] The present invention has been made to solve this problem, and aims to provide an environmentally friendly moisture-proof backside paper for decorative panels that has high moisture-proof performance, can prevent warping of the decorative panel even when used in a place where there is a large difference in temperature and humidity environment on both sides, and reduces the amount of plastic used. [Means for solving the problem]

[0009] In order to solve the above problems, the present disclosure provides the following moisture-proof backside paper for decorative boards. [1] A moisture-proof backside paper for decorative panels having a structure in which at least a paper base material, a first resin layer, an aluminum vapor-deposited layer, and a second resin layer are laminated in this order, wherein the thickness of the aluminum vapor-deposited layer is 60 nm or more. [2] The moisture-proof backside paper for decorative sheets according to [1], wherein the second resin layer contains a polyolefin having an acidic group. [3] The moisture-proof backside paper for decorative panels described in [1] or [2], wherein the first resin layer contains at least one selected from the group consisting of polyolefins having acidic groups, polyvinyl alcohol-based resins, and polyurethane-based resins. [4] Water vapor permeability at 40°C and 90% relative humidity is 5g / (m 2 The moisture-proof backside paper for decorative boards according to any one of [1] to [3], wherein the moisture-proof backside paper for decorative boards is 0.5-1 day or less. [5] The moisture-proof backside paper for decorative boards according to any one of [1] to [4], wherein the second resin layer contains an ethylene-unsaturated carboxylic acid copolymer. [6] The moisture-proof backside paper for decorative panels according to any one of [1] to [5], wherein the mass of the paper components contained in the paper base material is 50 mass% or more based on the mass of the entire moisture-proof backside paper for decorative panels. [7] The moisture-proof backside paper for decorative panels according to any one of [1] to [6], wherein an adhesive primer layer is provided on the exposed surface of the second resin layer.

[0010] The present inventors speculate as follows why conventional laminates have high and unstable water vapor permeability and why the laminate according to the present disclosure has high and stable water vapor barrier properties. Compared to plastic films, paper experiences greater dimensional changes due to moisture absorption and release. However, the moisture content of paper varies depending on the production lot. Furthermore, the moisture content of paper changes depending on the environmental conditions during the production, storage, and use of the gas barrier laminate. In paper made continuously on a paper machine, the fibers are oriented in the machine direction (MD) of the paper machine, resulting in greater expansion and contraction in the cross direction (CD). This prevents the vapor deposition layer from adapting to the dimensional changes in the paper caused by changes in moisture content, resulting in defects parallel to the MD. These defects impair the continuity of the aluminum vapor deposition layer, increasing the water vapor permeability of the laminate.

[0011] The second resin layer is formed, for example, by wet-coating a mixture of resin and solvent onto the aluminum vapor-deposited layer to form a coating film and then drying the coating film. Here, as the coating film dries, the solvent volatilizes and the second resin layer is formed. If the formation of the surface layer of the second resin layer proceeds without the solvent being completely volatilized, the solvent contained in the second resin layer may bump. This bumping of the solvent may cause micro-sized defects in the second resin layer. Furthermore, due to differences in the thermal shrinkage behavior between the paper substrate and the second resin layer, similar defects may occur in the second resin layer when the coating film for forming the second resin layer is dried. These defects in the second resin layer may reach the aluminum vapor-deposited layer. These defects in the aluminum vapor-deposited layer can cause unstable water vapor barrier properties. However, by making the thickness of the aluminum vapor-deposited layer 60 nm or more, defects caused by moisture absorption and desorption of the paper and defects caused by bumping of the solvent contained in the second resin layer can be suppressed, and as a result, the laminate has high and stable water vapor barrier properties. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a laminate having high and stable water vapor barrier properties and a moisture-proof backside paper for decorative panels, which has a high paper component ratio. Furthermore, according to one aspect of the present invention, a moisture-proof backside paper for decorative boards can be provided that contributes to reducing the amount of plastic materials used. In other words, according to one embodiment of the present invention, the moisture-proof backside paper for decorative panels has high moisture-proof performance, which makes it possible to prevent warping of the decorative panel even when used in a place where there is a large difference in temperature and humidity environment on both sides, and by reducing the amount of plastic used, it is possible to provide an environmentally friendly moisture-proof backside paper for decorative panels. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiment of the invention. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a moisture-proof backside paper for decorative panels according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view showing a configuration in which an adhesive primer layer is provided on the moisture-proof backside paper for decorative panels according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc., differ from the actual ones. Furthermore, the embodiments shown below are merely examples of configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not specify the materials, shapes, structures, etc. of the components to be described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0015] <Moisture-proof paper 100 for decorative panel backing> FIG. 1 is a schematic cross-sectional view showing the structure of moisture-proof backside paper 100 for decorative boards according to this embodiment. The moisture-proof backside paper 100 for decorative boards according to this embodiment is a moisture-proof paper that is pasted onto the backside of a decorative board used, for example, for an interior door panel, etc. In this embodiment, this moisture-proof backside paper 100 for decorative boards will hereinafter also be referred to simply as "moisture-proof paper 100." The moisture-proof paper 100 is used to prevent warping of the decorative board caused by moisture absorption and release due to changes in temperature and humidity in the room. The moisture-proof paper 100 of this embodiment has a structure in which at least a paper base material, a first resin layer, an aluminum vapor deposition layer, and a second resin layer are laminated in this order, and the thickness of the aluminum vapor deposition layer is 60 nm or more.

[0016] Figure 1 is a schematic cross-sectional view showing the structure of a moisture-proof paper 100 according to one embodiment. As shown in Figure 1, the moisture-proof paper 100 is broadly composed of two layers: a paper base material 11 and a moisture-proof layer 10 laminated on one side (e.g., the front surface) of the paper base material 11. The moisture-proof layer 10 includes a first resin layer 12, an aluminum vapor-deposited layer 13, and a second resin layer 14 in this order. By using the moisture-proof paper 100 on the back side of decorative panels, it is possible to provide a moisture-proof paper that addresses the movement to eliminate plastic and the problem of marine litter, has a high proportion of paper components, and has stable and excellent water vapor barrier properties.

[0017] [Moisture permeability of 100% moisture-proof paper on the back side of decorative panels] The moisture-proof paper 100 for decorative panels has a water vapor permeability of 5g / (m at a temperature of 40°C and a relative humidity of 90%. 2 ·day) or less, 4g / (m 2 ·day) or less, 3g / (m 2 ·day) or less, 2g / (m 2 ·day) or less, or 1g / (m 2 ·day) or less. Here, the water vapor transmission rate refers to a value measured by the method described in the Examples below.

[0018] <Paper base material> The paper substrate 11 is not particularly limited, and may be selected appropriately depending on the application of the moisture-proof backside paper 100 for decorative boards. Specific examples of the paper substrate 11 include tissue paper, fine paper, art paper, cast coated paper, kraft paper, titanium paper, linter paper, paperboard, gypsum board paper, coated paper, parchment paper, glassine paper, parchment paper, paraffin paper, and Japanese paper. Preferably, thin paper (so-called inter-sheet reinforced paper) in which synthetic resin is mixed into paper components (e.g., cellulose fiber) to enhance inter-sheet strength, or paper impregnated with latex or synthetic resin, is used.

[0019] The basis weight of the paper base material 11 is not particularly limited, but the basis weight of the paper base material 11 is preferably 20 g / m 2 If the paper substrate 11 has a basis weight of less than 200 g / m, it is too flexible and wrinkles tend to occur during processing. 2 If the basis weight is more than 20 g / m, peeling from the paper layer is likely to occur. 2 More than 200g / m 2 The following range is preferred: 20 g / m 2 More than 100g / m 2 The following range is more preferable: 20 g / m 2 More than 50g / m 2 The following ranges are more preferred: Furthermore, the surface of the paper substrate 11 may be subjected to a surface treatment such as corona treatment, plasma treatment, or flame treatment, if necessary.

[0020] The paper substrate 11 may have a coating layer (not shown) on at least the side of the paper substrate 11 that contacts the first resin layer 12. When the paper substrate 11 has a coating layer, the paper substrate 11 may have at least a paper layer and a coating layer. The coating layer may be provided on both surfaces (i.e., the front and back surfaces) of the paper substrate 11. The coating layer can prevent the first resin layer 12 from penetrating into the paper layer and also fulfill the role of filling in unevenness in the paper layer, allowing the first resin layer 12 to be formed uniformly without defects. The coating layer may contain, for example, various copolymers such as styrene-butadiene, styrene-acrylic, and ethylene-vinyl acetate copolymers, polyvinyl alcohol resins, cellulose resins, paraffin (wax), etc. as binder resins, and may contain, as fillers, clay, kaolin, calcium carbonate, talc, mica, etc. The coating layer may be a clay coating layer containing at least clay as a filler.

[0021] The change rate of the dimensions of the paper substrate 11 in the cross direction (CD) at 40°C and 90% RH (relative humidity) relative to the dimensions at 40°C and 20% RH may be 0.3% or more, 0.4% or more, or 0.6% or more, and may be 1.5%, 1.3%, or 1.0% or less. The change rate of the dimensions of the paper substrate 11 in the machine direction (MD) at 40°C and 90% RH relative to the dimensions at 40°C and 20% RH may be 0.05% or more, and 0.20% or less. If the rate of change of the paper substrate 11 is within the above range, the vapor-deposited layer can follow the dimensional changes of the paper that accompany changes in the moisture content, and defects parallel to the MD are less likely to occur.

[0022] If the paper substrate 11 has a coating layer, the thickness of the coating layer may be 1.5 μm or more and 15 μm or less. The thickness of the coating layer may also be 1.8 μm or more, 3 μm or more, 5 μm or more, or 6 μm or more. Furthermore, the thickness of the coating layer may be 12 μm or less, or 10 μm or less. When the coating layer thickness is within the above range, the moisture-proof paper 100 can more stably achieve higher water vapor barrier properties. The mass of the paper components contained in the paper base material 11 is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on the entire moisture-proof paper. If the mass of the paper components contained in the paper base material 11 is 50% by mass or more based on the entire moisture-proof paper, the amount of plastic material used can be sufficiently reduced, the entire moisture-proof paper can be said to be made of paper, and it has excellent recyclability.

[0023] <First resin layer> The first resin layer 12 is provided on the surface of the paper base material 11 to improve adhesion between the paper base material 11 and the aluminum vapor deposition layer 13 described later, and to improve the gas barrier properties (especially the water vapor barrier properties) of the moisture-proof paper 100. The first resin layer 12 may contain at least one selected from the group consisting of a polyolefin having an acidic group, a polyvinyl alcohol-based resin, and a polyurethane-based resin. From the viewpoint of more stably obtaining higher water vapor barrier properties, the first resin layer 12 preferably contains at least one of a polyolefin having an acidic group and a polyurethane-based resin, and more preferably contains a polyolefin having an acidic group.

[0024] When the first resin layer 12 contains a polyolefin having acidic groups, the first resin layer 12 has excellent flexibility, can suppress cracking of the aluminum vapor-deposited layer 13 described below after bending (folding), and can improve adhesion between the first resin layer 12 and the aluminum vapor-deposited layer 13. Furthermore, the inclusion of a polyolefin having acidic groups makes it possible to form a dense film due to the crystallinity of the polyolefin, and exhibits water vapor barrier properties. In other words, with the polyolefin having the above-mentioned acidic groups, water vapor barrier properties are exhibited due to the crystallinity of the polyolefin, and the presence of acidic groups exhibits adhesion to the aluminum vapor-deposited layer 13. The polyolefin having an acidic group may have at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester.

[0025] Examples of polyolefins having acidic groups include copolymers of ethylene or propylene with unsaturated carboxylic acids (unsaturated compounds having a carboxyl group, such as acrylic acid, methacrylic acid, and maleic anhydride), unsaturated carboxylic acid esters, and salts of carboxylic acids neutralized with basic compounds, as well as copolymers of vinyl acetate, epoxy compounds, chlorine compounds, urethane compounds, polyamide compounds, etc. The first resin layer 12 preferably contains an ethylene-unsaturated carboxylic acid copolymer, as this provides more stable water vapor barrier properties. Specific examples of polyolefins having an acidic group include copolymers of acrylic acid ester and maleic anhydride, ethylene-vinyl acetate copolymers, and ethylene-glycidyl methacrylate copolymers.

[0026] When the first resin layer 12 contains a polyvinyl alcohol-based resin, the polyvinyl alcohol-based resin has hydroxyl groups that easily bond with metals such as aluminum in the aluminum vapor-deposited layer 13, which can easily improve the adhesion between the aluminum vapor-deposited layer 13 and the first resin layer 12. Furthermore, such a first resin layer 12 has excellent flexibility and can suppress cracking of the aluminum vapor-deposited layer 13 after bending (folding). Polyvinyl alcohol-based resins are resins that contain vinyl alcohol as a constituent unit, and examples of polyvinyl alcohol-based resins include fully saponified polyvinyl alcohol resins, partially saponified polyvinyl alcohol resins, modified polyvinyl alcohol resins, and ethylene-vinyl alcohol copolymer resins.

[0027] Polyurethane resins are obtained by bonding the acid groups of an acid group-containing polyurethane with the amino groups of a polyamine used as a crosslinking agent. That is, polyurethane resins can be said to be a reaction product of an acid group-containing polyurethane and a polyamine, or to be formed by crosslinking an acid group-containing polyurethane with a polyamine. The bond between the acid groups of the acid group-containing polyurethane and the amino groups of the polyamine may be an ionic bond (e.g., an ionic bond between a carboxyl group and a tertiary amino group) or a covalent bond (e.g., an amide bond).

[0028] The acid group-containing polyurethane constituting the polyurethane-based resin has anionic properties and self-emulsifying properties due to the presence of acid groups, and is also referred to as anionic self-emulsifying polyurethane. The acid groups of the acid group-containing polyurethane can bond with amino groups (primary amino groups, secondary amino groups, tertiary amino groups, etc.) of the polyamine constituting the polyurethane-based resin. Examples of the acid groups include carboxyl groups and sulfonic acid groups. The acid groups can usually be neutralized with a neutralizing agent (base) and may form a salt with the base. The acid groups may be located at the terminal or side chain of the acid group-containing polyurethane, but are preferably located at least on the side chain.

[0029] The acid value of the acid group-containing polyurethane can be selected within a range that ensures water dispersibility, and can be 5 to 100 mgKOH / g, or alternatively 10 to 70 mgKOH / g, or even 15 to 60 mgKOH / g. When the acid value of the acid group-containing polyurethane is equal to or greater than the lower limit of the above range, the water dispersibility of the acid group-containing polyurethane is easily achieved, and uniform dispersion of the polyurethane resin with other materials and dispersion stability of the coating agent are easily ensured. When the acid value of the acid group-containing polyurethane is equal to or less than the upper limit of the above range, the water resistance and gas barrier properties of the first resin layer 12 are easily ensured. The acid value of the acid group-containing polyurethane is measured by a method in accordance with JIS K 0070.

[0030] From the viewpoint of gas barrier properties, the total concentration of urethane groups and urea groups in the acid group-containing polyurethane can be 15% by mass or more, or may be 20 to 60% by mass, of the entire acid group-containing polyurethane. When the total concentration of urethane groups and urea groups is equal to or greater than the lower limit of the above range, the gas barrier properties of the first resin layer 12 tend to be good. When the total concentration of urethane groups and urea groups is equal to or less than the upper limit of the above range, the first resin layer 12 tends to be prevented from becoming rigid and brittle. The urethane group concentration refers to the ratio of the molecular weight of the urethane group (59 g / equivalent) to the molecular weight of the constituent units of the polyurethane resin. The urea group concentration refers to the ratio of the molecular weight of the urea group (primary amino group (amino group): 58 g / equivalent, secondary amino group (imino group): 57 g / equivalent) to the molecular weight of the constituent units of the polyurethane resin. When a mixture of two or more types of acid group-containing polyurethane is used, the urethane group concentration and urea group concentration can be calculated based on the charged reactants, i.e., the proportion of each component used.

[0031] The acid group-containing polyurethane may have at least rigid units (units composed of hydrocarbon rings) and short-chain units (e.g., units composed of hydrocarbon chains). The constituent units of the acid group-containing polyurethane may contain a hydrocarbon ring (at least one of an aromatic and a non-aromatic hydrocarbon ring) derived from a polyisocyanate component, a polyhydroxy acid component, a polyol component, or a chain extender component (particularly, at least a polyisocyanate component). The proportion of units formed from hydrocarbon rings in the structural units of the acid group-containing polyurethane can be 10 to 70 mass %, alternatively 15 to 65 mass %, or even 20 to 60 mass %, relative to the total of all structural units. When the proportion of units formed from hydrocarbon rings is equal to or greater than the lower limit of the above range, the gas barrier properties of the first resin layer 12 are likely to be improved. When the proportion of units formed from hydrocarbon rings is equal to or less than the upper limit of the above range, the first resin layer 12 is likely to be prevented from becoming rigid and brittle.

[0032] The number average molecular weight of the acid group-containing polyurethane can be appropriately selected, but can be 800 to 1,000,000, or alternatively 800 to 200,000, or 800 to 100,000. When the number average molecular weight of the acid group-containing polyurethane is equal to or less than the upper limit of the above range, the coating agent is likely to have an appropriate viscosity. When the number average molecular weight of the acid group-containing polyurethane is equal to or greater than the lower limit of the above range, the first resin layer 12 is likely to have good gas barrier properties. The number average molecular weight of the acid group-containing polyurethane is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0033] The acid group-containing polyurethane may be crystalline to improve gas barrier properties. The glass transition temperature of the acid group-containing polyurethane may be 100°C or higher, or may be 110°C or higher, or may be 120°C or higher. When the glass transition temperature of the acid group-containing polyurethane is 100°C or higher, the gas barrier properties of the first resin layer 12 tend to be good. The glass transition temperature of the acid group-containing polyurethane may be 200°C or lower, or may be 180°C or lower, or may be 150°C or lower. Therefore, the glass transition temperature of the acid group-containing polyurethane may be 100 to 200°C, or may be 110 to 180°C, or may be 120 to 150°C. The glass transition temperature of the acid group-containing polyurethane is measured by differential scanning calorimetry (DSC).

[0034] The polyamine constituting the polyurethane resin is a compound having two or more basic nitrogen atoms. The basic nitrogen atom is a nitrogen atom that can bond with the acid group of the acid group-containing polyurethane, and examples thereof include nitrogen atoms in amino groups such as primary amino groups, secondary amino groups, and tertiary amino groups. The polyamine is not particularly limited as long as it can bond with the acid group of the acid group-containing polyurethane and improve the gas barrier property, and various compounds having two or more basic nitrogen atoms can be used. The polyamine can be a polyamine having two or more amino groups of at least one type selected from the group consisting of primary amino groups, secondary amino groups, and tertiary amino groups.

[0035] Examples of polyamines include alkylenediamines, polyalkylenepolyamines, and silicon compounds having multiple basic nitrogen atoms. Examples of alkylenediamines include alkylenediamines having 2 to 10 carbon atoms, such as ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butanediamine, and 1,6-hexamethylenediamine. Examples of polyalkylenepolyamines include tetraalkylenepolyamine. Examples of silicon compounds having multiple basic nitrogen atoms (including nitrogen atoms such as amino groups) include silane coupling agents having multiple basic nitrogen atoms, such as 2-[N-(2-aminoethyl)amino]ethyltrimethoxysilane and 3-[N-(2-aminoethyl)amino]propyltriethoxysilane.

[0036] The amine value of the polyamine can be 100 to 1900 mgKOH / g, or alternatively 150 to 1900 mgKOH / g, 200 to 1900 mgKOH / g, 200 to 1700 mgKOH / g, or 300 to 1500 mgKOH / g. When the amine value of the polyamine is equal to or greater than the lower limit of the above range, the gas barrier properties of the first resin layer 12 tend to be good. When the amine value of the polyamine is equal to or less than the upper limit of the above range, the aqueous dispersion stability of the polyurethane resin tends to be good.

[0037] [Method for measuring amine value] The amine value of the polyamine is measured by the following method. Accurately weigh out 0.5 to 2 g of sample (sample weight S g). Add 30 g of ethanol to the weighed sample and dissolve. Add bromophenol blue as an indicator to the resulting solution and titrate with 0.2 mol / L ethanolic hydrochloric acid solution (titer f). The point at which the color of the solution changes from green to yellow is set as the endpoint, and the titer (A mL) at this point is used to calculate the amine value using the following formula 1. Calculation formula 1: Amine value = A x f x 0.2 x 56.108 / S [mgKOH / g]

[0038] When forming the polyurethane resin, the molar ratio of the acid groups of the acid group-containing polyurethane to the basic nitrogen atoms of the polyamine (acid groups / basic nitrogen atoms) can be 10 / 1 to 0.1 / 1, or may be 5 / 1 to 0.2 / 1. As the polyurethane-based resin, a commercially available polyurethane-based resin may be used, or a polyurethane-based resin produced by a known production method may be used.

[0039] Methods for producing polyurethane resins are not particularly limited, and examples include typical aqueous polyurethane resin technologies such as the acetone method and the prepolymer method. In the urethanization reaction, urethanization catalysts such as amine catalysts, tin catalysts, and lead catalysts may be used as needed. For example, acid group-containing polyurethanes can be prepared by reacting a polyisocyanate compound with a polyhydroxy acid and, optionally, at least one of a polyol component and a chain extender component in an inert organic solvent such as a ketone such as acetone, an ether such as tetrahydrofuran, or a nitrile such as acetonitrile. More specifically, an aqueous dispersion of acid group-containing polyurethane can be prepared by reacting a polyisocyanate compound with a polyhydroxy acid and a polyol component in an inert organic solvent (particularly a hydrophilic or water-soluble organic solvent) to produce a prepolymer having isocyanate groups at its terminals. This prepolymer is then neutralized with a neutralizing agent and dissolved or dispersed in an aqueous medium. The chain extender component is then added and reacted, and the organic solvent is removed. A polyurethane resin in the form of an aqueous dispersion can be prepared by adding a polyamine to the aqueous dispersion of the acid group-containing polyurethane obtained in this manner and heating it as needed. When heating, the heating temperature can be 30 to 60°C.

[0040] The first resin layer 12 may contain other components in addition to the polyolefin having an acidic group, the polyvinyl alcohol-based resin, and the polyurethane-based resin, such as polyolefins other than the above-mentioned polyolefins having an acidic group, silane coupling agents, organic titanates, polyacrylics, polyesters, polyurethanes, polycarbonates, polyureas, polyamides, polyimides, melamine, and phenols. The content of at least one resin selected from the group consisting of polyolefins having acidic groups, polyvinyl alcohol-based resins, and polyurethane-based resins in the first resin layer 12 may be, for example, 50% by mass or more of the entire first resin layer 12, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0041] The thickness of the first resin layer 12 may be, for example, 0.5 μm or more, 1 μm or more, 2 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the first resin layer 12 is 0.5 μm or more, the unevenness of the paper base material 11 described above can be efficiently filled, and the aluminum vapor deposition layer 13 described below can be laminated uniformly. Furthermore, if the thickness of the first resin layer 12 is 20 μm or less, the aluminum vapor deposition layer 13 can be laminated uniformly while keeping costs down.

[0042] Examples of solvents contained in the coating liquid for forming the first resin layer 12 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination. Among these, from the viewpoint of properties, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred. Methods for providing the first resin layer 12 include applying a coating liquid containing the above-mentioned polyolefin, polyvinyl alcohol-based resin, or polyurethane-based resin having an acidic group and a solvent, etc., onto the paper substrate 11 to form a coating film, and then drying the coating film.

[0043] <Aluminum vapor deposition layer> The aluminum vapor-deposited layer 13 is a layer formed by vapor-depositing aluminum or an aluminum compound. The aluminum vapor-deposited layer 13 may be obtained by vapor-depositing aluminum, or may contain aluminum oxide (AlOx), silicon oxide (SiOx), or the like. The thickness of the aluminum vapor-deposited layer 13 is 60 nm or more, and may be greater than 60 nm, greater than 70 nm, 80 nm or more, or 90 nm or more. The thickness of the aluminum vapor-deposited layer 13 may be 300 nm or less, 200 nm or less, or 100 nm or less. The thickness of the aluminum vapor-deposited layer 13 is measured by the method in the examples described below.

[0044] <Second resin layer> The second resin layer 14 is provided on the surface of the aluminum vapor-deposited layer 13 so as to be in contact with the aluminum vapor-deposited layer 13. The second resin layer 14 may contain a polyolefin having an acidic group. The polyolefin having an acidic group may have at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester. Examples of polyolefins having an acidic group include copolymers of ethylene or propylene with unsaturated carboxylic acids (unsaturated compounds having a carboxyl group, such as acrylic acid and methacrylic acid) or unsaturated carboxylic acid esters, and salts of carboxylic acids neutralized with basic compounds. Other examples of polyolefins that can be used include copolymers of ethylene or propylene with vinyl acetate, epoxy compounds, chlorine compounds, urethane compounds, polyamide compounds, and the like.

[0045] Specific examples of polyolefins having an acidic group include copolymers of acrylic acid esters and maleic anhydride, ethylene-unsaturated carboxylic acid copolymers, ethylene-vinyl acetate copolymers, and ethylene-glycidyl methacrylate copolymers. By including a polyolefin having an acidic group, the second resin layer 14 has excellent flexibility, can suppress cracking of the aluminum vapor deposition layer after bending (folding), and has excellent adhesion to the aluminum vapor deposition layer. Furthermore, by including the above-mentioned polyolefin having an acidic group, it is possible to form a dense film due to the crystallinity of the polyolefin, and water vapor barrier properties are exhibited. Furthermore, the presence of an acidic group exhibits adhesion to the aluminum vapor deposition layer 13.

[0046] The second resin layer 14 preferably contains an ethylene-unsaturated carboxylic acid copolymer, as this provides more stable water vapor barrier properties. The second resin layer 14 may contain other components in addition to the polyolefin having an acidic group, such as a silane coupling agent, organic titanate, polyacrylic, polyester, polyurethane, polycarbonate, polyurea, polyamide, polyolefin emulsion, polyimide, melamine, and phenol. The content of the polyolefin having an acidic group in the second resin layer 14 may be, for example, 50% by mass or more of the entire second resin layer 14, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0047] The thickness of the second resin layer 14 may be, for example, 0.05 μm or more, 0.5 μm or more, 1 μm or more, 2 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the second resin layer 14 is 0.05 μm or more, it can fully fulfill its role as a protective layer for the aluminum vapor-deposited layer 13 described above. If the thickness of the second resin layer 14 is 20 μm or less, it can fully fulfill its adhesion to the aluminum vapor-deposited layer 13 and its barrier properties while keeping costs down. Furthermore, by setting the thickness of the second resin layer 14 to 2 μm or more and 10 μm or less, the aluminum vapor-deposited layer 13 becomes less likely to crack, and sufficient water vapor barrier properties and oil resistance can be obtained even after bending.

[0048] Examples of solvents contained in the coating liquid for forming the second resin layer 14 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination. Among these, from the viewpoint of properties, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

[0049] The second resin layer 14 can be provided by applying a coating liquid containing the above-described polyolefin having acidic groups and a solvent onto the aluminum vapor-deposited layer 13 to form a coating film, followed by drying the coating film. The melting point of the polyolefin having acidic groups in the coating liquid is preferably 70 to 160°C, more preferably 80 to 120°C. If the melting point of the polyolefin having acidic groups is 70°C or higher, blocking tends to be less likely to occur in high-temperature environments. To prevent blocking, the particle size of the polyolefin having acidic groups should be large so as to reduce the contact area. Although not particularly limited, the particle size (D50) of the polyolefin having acidic groups may be 1 nm or more, 0.1 μm or more, or 1 μm or less, 0.7 μm or less, or 0.5 μm or less.

[0050] <Adhesive primer layer> In this embodiment, as shown in FIG. 2, an adhesive primer layer 15 may be provided on the exposed surface of the second resin layer 14. The adhesive primer layer 15 is used when laminating and adhering to the surface of various substrates, and is provided for the purpose of ensuring sufficient adhesion with various laminating adhesives, such as isocyanate-curing urethane resins and modified vinyl acetate resin emulsions. Known materials for this primer include various types of primers such as ester resins, urethane resins, acrylic resins, polycarbonate resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral resins, and nitrocellulose resins, and one of these is selected to match the type of laminating adhesive. For example, when a modified vinyl acetate resin emulsion adhesive is used as the laminating adhesive, good adhesion can be obtained with a urethane adhesive primer.

[0051] Furthermore, if an inorganic fine powder such as silica is added to the adhesive primer layer 15, the surface of the adhesive primer layer 15 will be roughened, which will prevent blocking when the moisture-proof paper 100 is rolled up and stored, and will also improve adhesion to the laminating adhesive due to its anchoring effect. The adhesive primer layer 15 can be formed by using an adhesive composition, either alone or in combination, and applying it by a suitable coating method such as roll coating or gravure printing.

[0052] [Effects of this embodiment] The moisture-proof backside paper 100 for decorative boards according to this embodiment has the following effects. (1) The moisture-proof backside paper 100 for decorative panels in this embodiment is a laminate having a structure in which a paper base material 11, a first resin layer 12, an aluminum vapor-deposited layer 13, and a second resin layer 14 are laminated in this order, and the thickness of the aluminum vapor-deposited layer is 60 nm or more. With this configuration, moisture-proofing performance is improved, warping of the decorative board can be prevented even when used in a place where there is a large difference in temperature and humidity environment on both sides, and the amount of plastic used can be reduced.

[0053] (2) The second resin layer 14 constituting the moisture-proof backside paper 100 for decorative boards according to this embodiment may contain a polyolefin having an acidic group. With this configuration, the second resin layer 14 has excellent flexibility, can suppress cracking of the aluminum vapor deposition layer 13 after bending (folding), and has excellent adhesion to the aluminum vapor deposition layer 13. As a result, excellent water vapor barrier properties can be imparted to the moisture-proof backside paper 100 for decorative boards.

[0054] (3) The first resin layer 12 constituting the moisture-proof paper 100 for decorative panels with a back surface in this embodiment may contain at least one selected from the group consisting of polyolefins having acidic groups, polyvinyl alcohol-based resins, and polyurethane-based resins. With this configuration, the first resin layer 12 improves the adhesion between the paper substrate 11 and the aluminum vapor deposition layer 13. As a result, the moisture-proof backside paper for decorative boards 100 can be provided with excellent water vapor barrier properties.

[0055] (4) The moisture-proof backside paper 100 for decorative sheets according to this embodiment has a water vapor permeability of 5 g / (m 2·day) or less. With this configuration, moisture-proofing performance is improved, warping of the decorative board can be prevented even when used in a place where there is a large difference in temperature and humidity environment on both sides, and the amount of plastic used can be reduced.

[0056] (5) The second resin layer 14 constituting the moisture-proof backside paper 100 for decorative boards according to this embodiment may contain an ethylene-unsaturated carboxylic acid copolymer. With this configuration, the water vapor barrier property can be made more stable, and as a result, the moisture-proof backside paper 100 for decorative boards can be provided with excellent water vapor barrier property.

[0057] (6) The mass of the paper components contained in the paper substrate 11 constituting the moisture-proof back paper 100 for decorative panels in this embodiment may be 50% by mass or more based on the total mass of the moisture-proof back paper 100 for decorative panels. With this configuration, the amount of plastic material used can be significantly reduced.

[0058] (7) The moisture-proof backside paper 100 for decorative boards according to this embodiment may have an adhesive primer layer 15 provided on the exposed surface of the second resin layer 14 . With this configuration, it is possible to ensure sufficient adhesion between the moisture-proof backside paper 100 for decorative boards and the laminating adhesive. [Example]

[0059] The present disclosure will be described in more detail with reference to the following examples, but the present disclosure is not limited to these examples. The following clay-coated papers 1 and 2 were prepared as paper substrates. Clay coated paper 1: When the temperature was changed from 40°C and 20% relative humidity to 40°C and 90% relative humidity, the dimensional change was CD = 0.75%, MD = 0.13%, and the basis weight was 60 g / m. 2 Clay-coated paper 2: When the temperature was changed from 40°C and 20% relative humidity to 40°C and 90% relative humidity, the dimensional change was CD = 0.55%, MD = 0.07%, and the basis weight was 60 g / m.2

[0060] <Preparing moisture-proof paper> Example 1 Clay-coated paper 1 was used as the paper substrate. ZAIKXEN AC (Sumitomo Seika Chemicals, aqueous dispersion of ammonium salt of ethylene-acrylic acid copolymer) was applied to the surface of the paper substrate (on the clay coating layer) using a gravure coater to form a coating. The coating was dried to obtain a first laminate in which a first resin layer (thickness: 3 μm) was formed on the clay coating layer. Next, while the first laminate was being conveyed using a roll-to-roll vacuum deposition device, aluminum was deposited on the surface of the first resin layer to form an aluminum deposition layer (thickness: 66 nm). The method for measuring the thickness of the deposition layer will be described later. Next, Chemipearl S100 (Mitsui Chemicals, an aqueous dispersion of a metal salt of an ethylene-unsaturated carboxylic acid copolymer) was applied onto the aluminum vapor deposition layer using a gravure coater to form a coating, and the coating was dried to form a second resin layer (thickness: 3 μm), thereby obtaining the moisture-proof paper of Example 1.

[0061] Examples 2 and 3 The moisture-proof papers of Examples 2 and 3 were obtained in the same manner as Example 1, except that the conveying speed of the first laminate was slowed down when vapor-depositing aluminum to form an aluminum vapor-deposited layer of the thickness shown in Table 1.

[0062] (Comparative Examples 1 and 2) The moisture-proof papers of Comparative Examples 1 and 2 were obtained in the same manner as Example 1, except that the conveying speed of the first laminate was increased when vapor-depositing aluminum to form an aluminum vapor-deposited layer of the thickness shown in Table 2.

[0063] Example 4 Clay-coated paper 2 was used as the paper substrate. An aqueous solution of Poval 5-98 (Kuraray, fully saponified PVA) was applied to the surface of the paper substrate (on the clay coating layer) using a gravure coater to form a coating film. The coating film was dried to obtain a first laminate in which a first resin layer (thickness: 4 μm) was formed on the clay coating layer. Next, while the first laminate was being conveyed using a roll-to-roll type vacuum deposition device, aluminum was deposited on the surface of the first resin layer to form an aluminum deposition layer (thickness: 61 nm). Next, Chemipearl S500 (Mitsui Chemicals, an emulsion of acid-modified polyolefin) was applied onto the aluminum vapor deposition layer using a gravure coater to form a coating film, and the coating film was dried to form a second resin layer (thickness: 3 μm), thereby obtaining the moisture-proof paper of Example 4.

[0064] Examples 5 and 6 The moisture-proof papers of Examples 5 and 6 were obtained in the same manner as Example 4, except that the conveying speed of the first laminate was slowed down when vapor-depositing aluminum to form an aluminum vapor-deposited layer of the thickness shown in Table 1.

[0065] (Comparative Examples 3 and 4) The moisture-proof papers of Comparative Examples 3 and 4 were obtained in the same manner as Example 4, except that the conveying speed of the first laminate was increased when vapor-depositing aluminum to form an aluminum vapor-deposited layer of the thickness shown in Table 2.

[0066] Example 7 Clay-coated paper 2 was used as the paper substrate. Takelac WPB-341 (Mitsui Chemicals, polyurethane resin emulsion) was applied to the surface of the paper substrate (clay coating layer) using a gravure coater to form a coating film. The coating film was dried to obtain a first laminate in which a first resin layer (thickness: 1 μm) was formed on the clay coating layer. Next, aluminum was vapor-deposited onto the surface of the first resin layer while the first laminate was being transported using a roll-to-roll vacuum deposition device, forming an aluminum vapor-deposited layer (thickness: 68 nm). ZAIKXEN AC (Sumitomo Seika Chemicals, an aqueous dispersion of ammonium salt of ethylene-acrylic acid copolymer) was applied onto the aluminum vapor-deposited layer using a gravure coater to form a coating, and the coating was dried to form a second resin layer (thickness: 4 μm), thereby obtaining the moisture-proof paper of Example 7.

[0067] Examples 8 and 9 The moisture-proof papers of Examples 8 and 9 were obtained in the same manner as Example 7, except that the conveying speed of the first laminate was slowed down when vapor-depositing aluminum to form an aluminum vapor-deposited layer of the thickness shown in Table 1.

[0068] (Comparative Examples 5 and 6) The moisture-proof papers of Comparative Examples 5 and 6 were obtained in the same manner as in Example 7, except that the conveying speed of the first laminate was increased when vapor-depositing aluminum to form an aluminum vapor-deposited layer of the thickness shown in Table 2.

[0069] <Evaluation> (Examples 1 to 9 and Comparative Examples 1 to 6) The moisture-proof paper (gas barrier laminate) of each of the examples and comparative examples was cut into nine regions, three rows along the TD and three rows along the MD, to obtain nine measurement samples. The film thickness and water vapor permeability of the aluminum vapor deposition layer were measured using the measurement samples.

[0070] [Thickness of aluminum vapor deposition layer] The measurement sample was embedded in UV-curable resin. The measurement sample was cut using a cryomicrotome to expose a cross section, and a specimen for cross-sectional observation was obtained. The obtained sample was observed using a scanning electron microscope (observation magnification: 50,000x), and an image of the cross section was taken. The thickness of the aluminum vapor deposition layer was measured from the obtained image. The average value of the thickness of the aluminum vapor deposition layer measured for each of the nine measurement samples was taken as the film thickness of the aluminum vapor deposition layer. The results are shown in Tables 1 and 2.

[0071] [Water vapor permeability] According to JIS K7129-2, the water vapor permeability was measured by the Mocon method under conditions of a temperature of 40°C and a relative humidity of 90%RH. Measurements were performed twice for each of the nine measurement samples, yielding a total of 18 measurement data. The average value of the 18 data was used as the water vapor permeability. The standard deviation of the 18 data was also calculated. Results (unit of water vapor permeability: g / (m 2 ·day)) are shown in Tables 1 and 2.

[0072] [Table 1]

[0073] [Table 2]

[0074] As is clear from the results in Tables 1 and 2, in Comparative Examples 1 to 6, in which the thickness of the aluminum vapor-deposited layer was less than 60 nm, the average water vapor permeability and standard deviation were large and the water vapor barrier property was unstable, whereas the moisture-proof papers of Examples 1 to 9, which have an aluminum vapor-deposited layer with a thickness of 60 nm or more, consistently achieved excellent water vapor barrier property. In other words, the moisture-proof papers of Examples 1 to 9, which have an aluminum vapor-deposited layer with a thickness of 60 nm or more, achieved excellent water vapor barrier property evenly (with good yield). The moisture-proof paper in each example has a moisture-proof layer with an aluminum vapor deposition layer of 60 nm or more, which has been shown to have improved water vapor barrier performance, and is expected to have the effect of reducing warping of the decorative panel caused by moisture absorption and release due to changes in indoor temperature and humidity compared to conventional products, and to reduce the amount of plastic material used.

[0075] This has enabled us to verify that it is possible to provide a moisture-proof paper for the back side of decorative panels that can prevent warping even when used in places where there is a large difference in temperature and humidity environments on both sides, and that is also environmentally friendly, which is the objective of this invention. [Explanation of symbols]

[0076] 10: Moisture-proof layer 11:Paper base material 12: 1st resin layer 13: Aluminum vapor deposition layer 14:Second resin layer 15: Primer layer (adhesive primer layer) 100: Moisture-proof paper on the back of decorative panels (moisture-proof paper)

Claims

1. The laminate has a structure in which a paper base material, a first resin layer, an aluminum vapor-deposited layer, and a second resin layer are laminated in this order, The thickness of the aluminum vapor-deposited layer is 60 nm or more.

2. The moisture-proof backside paper for decorative sheets according to claim 1 , wherein the second resin layer contains a polyolefin having an acidic group.

3. The moisture-proof backside paper for decorative panels according to claim 1 or claim 2, wherein the first resin layer comprises at least one selected from the group consisting of polyolefins having acidic groups, polyvinyl alcohol-based resins, and polyurethane-based resins.

4. The water vapor permeability at a temperature of 40°C and a relative humidity of 90% is 5 g / (m ２ The moisture-proof backside paper for decorative panels according to claim 1 or 2, wherein the moisture-proof backside paper for decorative panels has a moisture-proofing effect of 100% or less.

5. The moisture-proof backside paper for decorative panels according to claim 1 or 2, wherein the second resin layer contains an ethylene-unsaturated carboxylic acid copolymer.

6. The moisture-proof backside paper for decorative panels according to claim 1 or claim 2, characterized in that the mass of the paper components contained in the paper base material is 50 mass% or more based on the mass of the entire moisture-proof backside paper for decorative panels.

7. 3. The moisture-proof backing paper for decorative sheets according to claim 1, wherein an adhesive primer layer is provided on the exposed surface of the second resin layer.

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