JP2008221668A - Moisture-proof decorative sheet and decorative laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture-proof decorative sheet which is a paper base material reusable as waste paper, excellent in moisture resistance, printing suitability and surface strengths, and little in discoloration by heat. <P>SOLUTION: The moisture-proof decorative sheet has, on at least one surface of a paper support, a moisture-proof layer containing a synthetic resin, a plate-like pigment and an antioxidant, wherein the antioxidant is at least either of a hindered phenol antioxidant or titanium dioxide. The decorative laminate is one in which the above moisture-proof decorative sheet is glued to a wood board. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a moisture-proof decorative sheet suitable for obtaining a decorative board by bonding to a wooden board or the like, and a decorative board obtained by bonding the moisture-proof decorative sheet.

Currently, there are plywood and parallel plywood, etc. for housing equipment such as doors provided in housing parts such as walls and ceilings of houses, doors and fences, or doors provided in storage parts of kitchens, etc. Alternatively, various wood materials such as a decorative board made of various wood boards such as particle boards and fiber boards are used.
Among these, fiberboard made by mixing wood fiber obtained by mechanical treatment or chemical treatment with an adhesive and hot pressing is homogeneous and has no anisotropy, and unused waste or low quality as a raw material. Wood is a recycled product mainly used, and it is excellent in cost. Therefore, it is often used as a base material for decorative boards.
Such fiber boards are mainly classified according to density, and are called an insulation board, a medium density fiber board (hereinafter referred to as MDF), and a hard board from the lower density. Of these, MDF is usually used as a decorative board substrate.
By the way, the wood material has a property that its moisture content changes with changes in temperature and humidity. Therefore, as a result of fluctuations in the amount of water due to temperature and humidity conditions, the shape may change due to material shrinkage or expansion, which may cause “warping” or “twisting”.
In particular, in the case of joinery, different spaces such as indoors and outdoors are partitioned, and the front and back surfaces are exposed to environments having different temperatures and humidity. Therefore, when used in such applications, the characteristics of being resistant to changes in temperature and humidity conditions and being less likely to change in shape are more important. For example, in the case of a door, when warping or twisting occurs, it becomes impossible to open and close, and a problem arises that a gap is generated between the door frame and the door.
In particular, in the case of fiber boards such as MDF among wooden boards, the moisture content, which is usually 8-9%, changes considerably due to changes in temperature and humidity conditions due to structural features, resulting in warping and twisting. There was a problem that it was easy.

Therefore, when a decorative board is manufactured using the above-mentioned wood board as a base material, it is generally used after being subjected to moisture proofing and waterproofing.
For example, there is a plastic decorative sheet on the front side of the wooden board, and a wooden decorative board in which a plastic film is bonded to the back side as moisture-proof and waterproof.
Alternatively, a plastic decorative sheet is bonded to the front side of the wooden board in the same manner as described above, and a laminate made of paper / plastic film / paper (plastic film with the front and back covered with paper) is bonded to the back side. There is a wood-based decorative board in which a laminate composed of metal foil / paper is laminated. In addition, it is easy to adhere the plastic film etc. to the wooden board by the porous nature of the paper because the paper is pasted to the front and back of the plastic film and the metal foil to be attached to the back side, and the wood quality obtained by this This has the effect of facilitating adhesion of the decorative decorative board to other objects.
Specifically, in Patent Document 1, as a moisture-proof interior material, a moisture-proof paper having a structure in which a moisture-proof sheet made of a plastic film, metal foil, or the like is used as a core layer on at least one side of a substrate and paper is laminated on the front and back sides. Discloses a configuration in which an adhesive is impregnated in an inner paper layer in contact with a substrate.
Patent Document 2 discloses that a moisture-proof waterproof coating layer containing a vinylidene chloride resin is formed on both front and back surfaces of a wooden board, and further a paper-based decorative sheet is provided on the front moisture-proof waterproof coating layer via an adhesive layer. A wood-based decorative board, which is attached, is disclosed.
However, such a conventional decorative sheet (moisture-proof decorative sheet) is difficult to reuse as waste paper because it is bonded to a film or a metal foil even if paper is used. Therefore, there has been a demand for a decorative sheet that can be regenerated using paper as a base material and that has excellent moisture resistance.
As the moisture-proof paper that can be recycled, there is a moisture-proof paper having a moisture-proof layer containing a wax (Patent Document 3, etc.). As the moisture-proof paper that can be used as a decorative sheet, in addition to moisture resistance, printability and Since the surface strength is required to be excellent, moisture-proof paper having a moisture-proof layer containing wax cannot be used as a decorative sheet in that respect.
Further, as a recyclable moisture-proof paper having printability and surface strength, Patent Document 4 having a moisture-proof layer made of a synthetic resin and a flat pigment is disclosed (Patent Document 4).

Japanese Patent Laid-Open No. 7-251407 JP 11-348180 A Japanese Patent Publication No.59-66598 JP-A-9-291499

However, it has been found that a new problem occurs when using such moisture-proof paper as a decorative sheet. That is, when a decorative sheet is bonded to a wooden board to produce a decorative sheet, the decorative sheet is bonded under heating conditions. At this time, the resin layer of the synthetic resin of the moisture-proof layer is discolored (mainly yellowed). Such discoloration impairs the aesthetics and durability of the product, and is very problematic as a decorative board and decorative sheet.
Accordingly, there has been a demand for a moisture-proof decorative sheet that is a paper base material that can be reused as waste paper, has excellent moisture resistance, printability, surface strength, and is less discolored by heat.

The present invention adopts the following method in order to solve the above problems.
That is, the first of the present invention has a moisture-proof layer containing a synthetic resin, a flat pigment, and an antioxidant on at least one side of a paper support, and the antioxidant is a hindered phenol-based antioxidant or titanium dioxide. A moisture-proof decorative sheet that is at least one of the following.

  A second aspect of the present invention is a decorative board in which the moisture-proof decorative sheet according to the first aspect of the present invention is bonded to a wooden board.

  According to the present invention, it is possible to obtain a moisture-proof decorative sheet that is a paper base material that can be reused as waste paper, is excellent in moisture resistance, printability, surface strength, and is less discolored by heat.

Hereinafter, the present invention will be described in detail.
The moisture-proof layer of the moisture-proof decorative sheet of the present invention contains a synthetic resin, an inorganic layered compound, and an antioxidant.
A moisture-proof layer containing a synthetic resin and an inorganic stratiform compound is excellent as a moisture-proof layer of a moisture-proof decorative sheet because it is excellent in moisture-proof property, re-disintegration property, surface coating strength and printability.
The synthetic resin constituting the moisture-proof layer can be used without particular limitation as long as it has film-forming properties and exhibits water resistance. As an index of water resistance, a resin-only coating is prepared (a synthetic resin solution (aqueous solution or alkaline aqueous solution) or emulsion is applied in a glass plate shape so that the thickness after drying is 50 μm to 100 μm, After drying at 110 ° C. for 5 minutes, it is dried at 40 ° C. for 24 hours in a desiccator containing a desiccant). The film is immersed in water at 23 ° C. (water having a mass of 100 times or more of the sample mass) for 24 hours (slowly stirring with a stirrer), and the film is taken out and dried (drying condition: 110 ° C. After drying for 5 minutes, it is dried in a desiccator containing a desiccant for 24 hours at 40 ° C.), and its mass loss is 10% or less, more preferably 5% or less, and even more preferably 3% or less.

The moisture resistance of the single coating of the synthetic resin constituting the moisture-proof layer is such that the moisture permeability is 800 g / m ² · 24 hr or less, preferably 600 g / m ² · 24 hr or less, more preferably 400 g / m ² · 24 hr in terms of thickness 20 μm. It is as follows. A specific measurement method is to form a synthetic resin film in the same manner as the above water resistance index, measure moisture permeability by JIS-Z-0208 (cup method) B method (40 ° C. 90% RH), and the synthetic resin. The thickness of the coating is measured to determine the moisture permeability in terms of 20 μm. At this time, it is assumed that the moisture permeability is inversely proportional to the thickness.
The synthetic resin constituting the moisture-proof layer is preferably an aqueous emulsion (latex, emulsion, microemulsion, dispersion, etc. are also included in the emulsion) or one dissolved in alkaline water. A synthetic resin that is water-soluble or soluble in hot water (solubility in water or hot water of 5% or more) is not preferred because its moisture-proof property is much larger than the above-mentioned moisture permeability. For example, polyvinyl alcohol (PVA) has a solubility in water in the range of 5 to 30% (the solubility depends on the molecular weight or saponification degree), but the moisture permeability of the single coating (20 μm) is 1000 g / Since it exceeds m ² · 24 hr, it cannot be used in the present invention.

  Synthetic resins include aromatic vinyl monomers, aliphatic conjugated diene monomers, ethylenically unsaturated carboxylic acid ester monomers, unsaturated fatty acid monomers, α-olefin monomers. And those obtained by emulsion polymerization of one or more of the other copolymerizable monomers. Specifically, a styrene-butadiene copolymer (SBR) obtained by emulsion polymerization from an aromatic vinyl monomer and an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid ester monomer, Methyl methacrylate-butadiene copolymer (MBR) obtained by emulsion polymerization from aliphatic conjugated diene monomer, obtained by emulsion polymerization from aromatic vinyl monomer and ethylenically unsaturated carboxylic acid ester monomer Styrene-acrylic copolymer, ethylene-acrylic acid copolymer obtained from emulsion polymerization of α-olefin monomer and unsaturated fatty acid monomer, one type or two or more types of ethylenically unsaturated carboxylic acid Examples thereof include acrylic ester polymers obtained from emulsion polymerization of acid ester monomers. These copolymers may be used after being copolymerized with other monomers.

Next, the monomer will be described in detail. Aromatic vinyl monomers impart water resistance and moderate hardness to synthetic resins. Specific examples include styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene, and chlorostyrene. Yes, styrene is preferably used.
The aliphatic conjugated diene monomer imparts flexibility to the synthetic resin. Specifically, butadiene, 1,3-butadiene, isoprene, 2,3 dimethyl-1,3-butadiene, 1,3- Examples thereof include pentadiene, and 1,3-butadiene is preferably used.
The ethylenically unsaturated carboxylic acid ester monomer imparts water resistance to the synthetic resin and adjusts the hardness, glass transition temperature (Tg), and minimum film-forming temperature (MFT) of the synthetic resin. Are methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, (meth And (meth) acrylic acid ester monomers such as 2-ethylhexyl acrylate, n-octyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and hydroxypropyl (meth) acrylate.

The unsaturated fatty acid monomer improves the film-forming property of the synthetic resin and increases the stability of the copolymer as a colloid in water. Specifically, acrylic acid, methacrylic acid, crotonic acid, Unsaturated carboxylic acids such as cinnamic acid; unsaturated polycarboxylic acids such as fumaric acid, maleic acid, itaconic acid, butenetricarboxylic acid; itaconic acid monoethyl ester, fumaric acid monobutyl ester, maleic acid monobutyl ester, etc. And unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group; unsaturated sulfonic acids such as acrylamide propanesulfonic acid, sodium sulfoethyl acrylate, and sodium sulfopropyl methacrylate, and salts thereof. Acrylic acid, methacrylic acid, itaconic acid and fumaric acid are preferably used.
The α-olefin monomer imparts water resistance and flexibility to the synthetic resin, and specific examples include ethylene and propylene.

Other monomers that can be copolymerized with the above-mentioned monomers increase the water resistance of synthetic resins, increase the adhesiveness by introducing cationic groups, and increase the strength by introducing crosslinkable functional groups. Specifically, ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile; ethylenically unsaturated carboxylic acids such as β-hydroxyethyl acrylate, β-hydroxypropyl acrylate and β-hydroxyethyl methacrylate Acid hydroxyalkyl esters; ethylenically unsaturated carboxylic acid amides and derivatives thereof such as acrylamide, methacrylamide, N-methylolacrylamide and diacetone acrylamide; unsaturated carboxylic acid glycidyl esters such as glycidyl acrylate and glycidyl methacrylate; acrolein and allyl Vinylation of alcohol, etc. Things and the like.
An aqueous emulsion of a synthetic resin can be produced by a known emulsion polymerization method using the above monomers. That is, a desired monomer may be mixed, and an emulsifier, a polymerization initiator, etc. may be added thereto to carry out emulsion polymerization in an aqueous system, a method of batch charging and polymerization, a method of polymerization while continuously supplying each component, etc. Various methods can be applied.

  As an emulsifier for emulsion polymerization, anionic emulsifier such as alkyl or alkyl allyl sulfate, alkyl or alkyl allyl sulfonate, polyoxyethylene alkyl or alkyl allyl ether sulfate, dialkyl sulfosuccinate, alkyl trimethyl ammonium chloride, alkyl benzyl Examples include cationic emulsifiers such as ammonium chloride, and nonionic emulsifiers such as polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, and polyoxyethylene carboxylic acid ester. The amount of emulsifier used can vary depending on the properties required for the emulsion, but in general the amount of emulsifier used is for the purpose of improving the polymerization stability and improving the mechanical and chemical stability of the emulsion. In order to improve the water resistance of the dried film, it is desirable that the amount used is small, and usually in the range of about 0.1 to 5 parts by mass with respect to 100 parts by mass of the total amount of monomers. The amount to be used is determined according to the purpose.

As polymerization initiators, persulfates such as potassium persulfate and ammonium persulfate, water-soluble types such as hydrogen peroxide, t-butyl hydroperoxide, azobisamidinopropane hydrochloride, benzoyl peroxide, cumene hydroperoxide, Oil-soluble types such as dibutyl peroxide, diisopropyl peroxycarbonate, cumyl peroxyneodecanoate, cumyl peroxyoctoate, and azobisisobutyronitrile are used. Furthermore, if necessary, a redox system using a reducing agent such as acidic sodium sulfite, Rongalite, L-ascorbic acid, saccharides, amines and the like can also be used. The amount used thereof may be about 0.01 to 3 parts by mass with respect to 100 parts by mass of the total amount of monomers. The polymerization reaction is usually performed at about 35 to 90 ° C., and the reaction time is usually about 3 to 10 hours.
Incidentally, by adjusting the pH by adding a basic substance at the start or after the end of the emulsion polymerization, the polymerization stability, freezing stability, mechanical stability, chemical stability and the like of the emulsion can be improved. In particular, in order to obtain blending stability with the swellable inorganic layered compound, it is preferable to adjust the pH of the resulting emulsion to be 5 or more. Since the aqueous dispersion of the swellable inorganic layered compound usually exhibits alkalinity (pH 7 to 11), the synthetic resin emulsion is more preferably alkaline (pH 7 or more) from the viewpoint of miscibility. As the basic substance, ammonia, ethylamine, diethylamine, triethylamine, ethanolamine, triethanolamine, diethylethanolamine, caustic soda, caustic potash or the like can be used. In particular, ammonia is preferable in terms of moisture resistance.

The particle diameter of the synthetic resin aqueous dispersion is generally 100 nm to 300 nm, but if an aqueous dispersion having a particle diameter of 150 nm or less, particularly about 60 to 100 nm is used, the film formability is improved and a film with few defects can be formed. Therefore, it is preferable.
Synthetic resins include polyester resins, biodegradable resins (polylactic acid, polybutyric acid, polycaprolactam, etc., including natural biodegradable resins), polyurethane resins, and ethylene-vinyl acetate resins. Can be used.

There are no particular restrictions on the glass transition temperature (Tg), the minimum film increasing temperature (MFT), the gel fraction (insoluble content in toluene), etc. of the synthetic resin, but Tg is -30 ° C to 60 ° C, more preferably -20. It is -50 to 50 degreeC, More preferably, it is -10 to 40 degreeC. The MFT is preferably 70 ° C. or lower, more preferably 60 ° C. or lower, and still more preferably 50 ° C. or lower. The gel fraction is preferably 20% to 99%, more preferably 30% to 95%, and still more preferably 40% to 90%.
If Tg is less than −30 ° C., the moisture-proof surface has strong adhesiveness and is likely to cause blocking, and if Tg exceeds 60 ° C., the film formability deteriorates and the moisture-proof property deteriorates. When the MFT is higher than 70 ° C., the film formability is lowered and the moisture resistance is deteriorated. If the gel fraction is less than 20%, blocking tends to occur, and if it exceeds 99%, the film formability is lowered and the moisture resistance is deteriorated.

  The synthetic resin of the present invention is used in the form of an emulsion or latex. The synthetic resin emulsion or latex is preferably anionic. In order to make it anionic, it is preferable to use a synthetic resin obtained by copolymerizing a monomer having a carboxylic acid or sulfonic acid group. When the synthetic resin is anionic, the nitrogen-containing compound adsorbed on the inorganic layered compound has a strong overall effect, and the amino group or amide group in the nitrogen-containing compound and the carboxylic acid group or sulfonic acid group in the synthetic resin are strongly ionically bonded In the drying process, a dehydration reaction is caused to form a covalent bond, thereby improving the water resistance and consequently improving the moisture resistance.

Next, as a flat pigment that can be suitably used in the moisture-proof layer of the present invention, firstly, a phyllosilicate mineral is exemplified. Those belonging to the phyllosilicate mineral are plate-like or flaky and clearly cleaved, and are mica, pyrophyllite, talc, chlorite, septe chlorite, serpentine, stilpnolane, clay There are minerals. Among these, preferred are minerals such as mica and talc, which have large particles when produced and a large amount of production. The mica group includes muscovite (mascobite), sericite (sericite), phlogopite (flocopite), biotite (biotite), fluorophlogopite (artificial mica, synthetic mica), red mica, soda mica, vanadine mica Illite, cinnamonite, paragonite, brittle mica, potassium tetrasilicon mica, sodium tetrasilicon mica, sodium teniolite, lithium teniolite, and the like. Synthetic products such as synthetic mica that are similar in composition to talc are also included in the scope of the present invention.
Clay minerals such as kaolin are also generally called flat crystals. However, if one crystal is taken, there is a flat part, but it is granular as a whole. However, among kaolins, delaminated kaolin or the like which is intentionally exfoliated from a crystal layer to form a flat plate can be used as the flat pigment in the present invention. Further, it is preferable to use a flat pigment having a particle diameter corresponding to the film thickness of the moisture-proof layer. In that case, the flat pigment is pulverized and classified by a pulverizer such as a ball mill, sand grinder, cobol mill, jet mill or the like to obtain a desired particle size, and then used in the present invention.

As a second example of the flat pigment suitably used in the present invention, specific examples of the swellable inorganic layered compound include graphite, phosphate-based derivative compounds (such as zirconium phosphate compounds), chalcogenides, and hydrotalcite. Compound, lithium aluminum composite hydroxide, clay mineral, synthetic mica, synthetic smectite and the like.
Graphite, phosphate derivative compounds (zirconium phosphate compounds, etc.), chalcogenides, hydrotalcite compounds, and lithium aluminum composite hydroxides are compounds or substances in which unit crystal layers are stacked on each other and have a layered structure. Here, the layered structure refers to a structure in which surfaces in which atoms are strongly bonded by a covalent bond or the like and densely arranged are stacked substantially in parallel by a weak binding force such as van der Waals force.

A “chalcogenide” is a dichalcogenide of a group IV (Ti, Zr, Hf), group V (V, Nb, Ta) and / or group VI (Mo, W) element, which has the formula MX ₂ (M is The above element, X represents a chalcogen (S, Se, Te).
Clay-based minerals generally have a two-layer structure having an octahedral layer with aluminum, magnesium, etc. as the central metal at the top of the silica tetrahedral layer, and a silica tetrahedral layer, with aluminum, magnesium, etc. It is classified into a type having a three-layer structure in which an octahedral layer made of a central metal is sandwiched from both sides. Examples of the former two-layer structure type include kaolinite group and antigolite group. Examples of the latter three-layer structure type include smectite group, vermiculite group, mica group, etc. depending on the number of interlayer cations. Can do.
Examples of these clay minerals include clay minerals such as smectite group and vermiculite group. More specifically, kaolinite, dickite, nacrite, halloysite, antigolite, chrysotile, pyrophyllite, montmorillonite, hectorite, tetrasilic mica, sodium teniolite, margarite, talc, vermiculite, xanthophyllite, Chlorite and the like can be mentioned. References can also be made to articles such as Haruo Shiramizu, “Clay Mineralogy”, 1988, Asakura Shoten. Smectite is particularly preferred, and examples of the smectite include montmorillonite, hydelite, nontronite, saponite, iron saponite, hectorite, soconite, and stevensite.

Besides clay minerals (natural products) also, the composition may be any of processing products (for example, a silane coupling agent surface treated product of) the synthetic smectite, the formula Na _{0.1 to 1.0} Mg _{2.4 to 2.9 li} 0.0~0.6 Si 3.5~4.0 O 9.0~10.6 those represented by (OH and / or F) _{1.5 to 2.5} and the like. There are three methods for producing synthetic smectite and synthetic mica, namely, a hydrothermal reaction method (JP-A-6-345419), a solid-phase reaction method, and a melting method (see JP-A-5-270815).
In the hydrothermal reaction method, an aqueous solution or aqueous slurry containing various raw materials such as silicate, magnesium salt, alkali metal ion, alkali metal salt, and fluorine ion is heated at a high temperature and high pressure of 100 to 400 ° C. in an autoclave or a pipe reactor. This is a method of reacting and synthesizing the original. In the hydrothermal reaction method, since the crystal growth is slow, generally large particles cannot be obtained, and generally the particle size is generally 10 to 100 nm. Of course, the hydrothermal reaction can produce large particles having a particle diameter of 1 μm or more if they are synthesized under conditions of low concentration, low temperature and long time, but there is a problem that the production cost becomes extremely high.

The solid phase reaction method is a method for producing synthetic mica by reacting with talc, alkali silicofluoride and other raw materials for several hours in the range of 400 ° C. to 1000 ° C. In solid phase reaction, element migration occurs while leaving the talc structure of the raw material, and mica is produced (topotaxy), so the quality of the resulting synthetic mica depends on the talc physical properties of the raw material and its impurities, or the element transfer is completely Since it cannot be controlled, there is a problem that the purity and crystallinity of synthetic mica are low.
In the melting method, anhydrous silicic acid, magnesium oxide, aluminum oxide, potassium silicofluoride, potassium carbonate, and other raw materials are melted at a melting point (for example, 1500 ° C.) or higher of mica and then slowly cooled to crystallize synthetic mica and synthetic smectite. It is a manufacturing method. Also, depending on the heating method, there are an external heating type melting method and an internal heating type melting method. The external heating type melting method is a method in which the crucible containing the raw material is put into a chamber having a temperature higher than the melting point and the temperature is raised, and then moved to a chamber having a temperature lower than the melting point. There is a point. The internal heating type melting method is a method in which a raw material is heated and melted by energization in a vessel equipped with a graphite (carbon) electrode or a metal electrode, and then cooled. In the fusion method, the internal heating type melting method is generally used. is there. The melt fusion method can produce a synthetic product having a controlled particle size by pulverizing and classifying the cooled and crystallized mass. The fusion method can use raw materials with high purity as raw materials, and since the raw materials can be mixed uniformly, it produces high-crystallinity, large particle size, high-purity synthetic mica and synthetic smectite. There is an advantage that can be done.

Synthetic flat pigments include fluorine phlogopite (KMg ₃ AlSi ₃ O ₁₀ F, melting method or solid phase reaction method), potassium tetrasilicon mica (KMg _2.5 Si ₄ O ₁₀ F ₂ , melting method), sodium tetra Silicon mica (NaMg _2.5 Si ₄ O ₁₀ F ₂ , melting method), sodium teniolite (NaMg ₂ LiSi ₄ O ₁₀ F ₂ , melting method), lithium teniolite (LiMg ₂ LiSi ₄ O ₁₀ F ₂ , melting method) ), Etc., sodium hectorite (Na _0.33 Mg _2.67 Li _0.33 Si _4.0 O ₁₀ (OH or F) ₂ , hydrothermal reaction method or melting method), lithium hectorite (Na _0.33) Mg _2.67 Li _0.33 Si _4.0 O ₁₀ (OH or F) ₂ , hydrothermal reaction method or melting method), saponite (Na _0.33 Mg _2.67 AlSi _4.0 Synthetic smectite such as O ₁₀ (OH) ₂ , hydrothermal reaction method).
As commercial products of clay minerals, natural bentonite generally called sodium bennite, Kunipia (natural montmorillonite, manufactured by Kunimine Industry), Smecton (hydrothermal reaction method synthetic smectite, manufactured by Kunimine Industry Co., Ltd.), Veegum (Trademark: Vanderbilt) Laponite (Trademark: Laporte), DM Clean A, DMA-350, Na-Ts, NTO-5 (Melting Method, Sodium Tetrasilicon Mica, Trademark: Topy Industries), Bengel (Trademark: Toyoshun) Yoko Co., Ltd.), Somasif ME-100 (solid phase reaction method synthetic mica, trademark: Co-op Chemical) and the like can be used, and these can be used alone or in admixture of two or more.

Preferred according to the invention are swellable inorganic layered compounds that readily swell, open and disperse in water. The degree of the “swelling / cleavage” property of the swellable inorganic layered compound to the solvent can be evaluated by the following “swelling / cleavage” test. The swellability of the swellable inorganic layered compound is preferably about 5 mL or more (more preferably about 20 mL or more) in the following swellability test. Specific examples of swellability include Kunipia (swelling force: 65 mL / 2 g or more), Smecton (swelling force: 60 mL / 2 g or more), DM Clean A, DMA-350, Na-Ts (swelling force: 30 mL / 2 g or more), ME-100 (trademark: manufactured by Coop Chemical Co., swelling power: 20 mL / 2 g or more), Bengel (swelling power: 38 mL / 2 g or more), and the like.
On the other hand, the cleavage property of the swellable inorganic layered compound is preferably about 5 mL or more (more preferably about 20 mL or more) in the following cleavage test. In these cases, a solvent having a density smaller than that of the swellable inorganic layered compound is used as the solvent. As the solvent, water is preferably used.

The swelling test will be described in detail. Slowly add 2 g of swellable inorganic layered compound to 100 mL of solvent (100 mL graduated cylinder as container). The volume of the former (swellable inorganic layered compound dispersion layer) is read from the scale of the interface between the swellable inorganic layered compound dispersion layer and the supernatant after 24 hours at 23 ° C. The larger this value, the higher the swelling property.
The cleavage test will be described in detail. Slowly add 30 g of the swellable inorganic layered compound to 1500 mL of the solvent, and using a disperser (manufactured by Asada Tekko Co., Ltd., Desper MH-L, blade diameter 52 mm, rotation speed 3100 rpm, container capacity 3 L, bottom-blade distance 28 mm) After dispersing for 90 minutes at a peripheral speed of 8.5 m / sec (23 ° C.), take 100 mL of the dispersion, place it in a graduated cylinder and let stand for 60 minutes, then read the volume of the swellable inorganic layered compound dispersion layer from the interface with the supernatant .

The swellable inorganic layered compound preferred for use in the present invention has a cation exchange capacity of 30 to 300 meq, more preferably 50 to 250 meq, particularly preferably 60 to 200 meq per 100 g. When the cation exchange capacity is less than 30 meq / 100 g, the effect of the nitrogen-containing compound is reduced and the moisture resistance is not excellent. On the other hand, if it exceeds 300 meq / 100 g, the coating tends to aggregate, which is not preferable. In general, natural and synthetic squametites having a cation exchange capacity of 85 to 130 meq / 100 g are particularly preferred in the present invention.
The cation exchange capacity is generally measured by an alcohol washing method (Schollenberger method or its improved method, see Mitsufumi Wada (1981) Clay Science 21, 160-163). About 0.2 to 1.0 g of the swellable inorganic layered compound powder or about 10 to 30 ml of about 1 to 3% aqueous dispersion is collected in a centrifuge tube having a capacity of 100 ml. Add 1N ammonium acetate (CH ₃ COONH ₄ ) solution (pH 7) to make about 80 ml, shake well, then centrifuge and discard the supernatant (centrifuge washing). After centrifuge washing is repeated 4 times, centrifuge washing is performed 3 times with 80% ethanol aqueous solution (pH 7) in order to remove excess salt remaining in the centrifuge tube. Next, the centrifuge washing is repeated 4 times using a 10% NaCl aqueous solution, and all the supernatant of the centrifuge tube is collected to obtain an extract. NH4 in the extract is quantified by distillation, and the number of milligram equivalents (meq) per dry mass (100 g) of the sample is taken as the value of cation exchange capacity (CEC). The measurement is performed in an environment of 23 ° C. The measurement was performed at 7 points, and the average of 5 points excluding the maximum value and the minimum value was used as the measurement value.

  The swellable inorganic layered compound preferably has an aspect ratio of 50 to 5000. The aspect ratio (Z) is indicated by the relationship Z = L / a, where L is the average particle diameter of the swellable inorganic layered compound in water (measured by laser diffraction method. HORIBA, Ltd. LA-910, refractive index). 1.3, median diameter of 50% volume distribution), and a is the thickness of the swellable inorganic layered compound. Thickness is the value which calculated | required the cross section of the moisture-proof layer by the photograph observation by SEM or TEM. The average particle size is preferably from 0.1 to 100 μm, particularly preferably from 0.5 to 50 μm. When the particle diameter is less than 0.1 μm, the aspect ratio becomes small and it becomes difficult to arrange the moisture-proof layer in parallel to the moisture-proof surface, resulting in insufficient moisture-proof effect. When the particle diameter exceeds 100 μm, the swellable inorganic layered compound protrudes from the moisture-proof layer, which is not preferable.

Among these swellable inorganic layered compounds, sodium tetrasilicon mica, sodium teniolite, lithium teniolite, sodium hectorite, lithium hectorite, saponite, and natural smectite (montmorillonite) are preferable. Among these, sodium tetrasilicon mica (manufactured by Topy Kogyo Co., DMA350) and talc produced by the fusion method from the viewpoint of particle size, aspect ratio, and crystallinity, and silicon fluoride are intercalated and fired at about 800 ° C. Swellable fluorine mica obtained in this way is particularly preferred.
Further, the flat pigment used in the present invention preferably has an average particle diameter of 20 nm to 100 μm, preferably 0.1 μm to 50 μm, more preferably dispersed in water or a solvent. Is 1 μm to 30 μm. When the average particle size is less than 20 nm, the aspect ratio becomes small, and the effect of improving moisture resistance is small. On the other hand, when the thickness exceeds 100 μm, the pigment protrudes from the surface of the coating layer, which leads to poor appearance and reduced moisture resistance.

The average particle diameter of the flat pigment used in the present invention dispersed in water or solvent is a value measured by a particle size distribution measuring apparatus by laser diffraction applying light scattering theory when the average particle diameter is 0.1 μm or more. . In addition, the value measured by the dynamic light scattering method is used when the average particle size dispersed in water or solvent is 0.1 μm.
Further, the preferred aspect ratio of the tabular pigment used in the present invention is 5 or more, and particularly preferably the aspect ratio is 10 or more. When the aspect ratio is less than 5, the curve effect is small, so that the moisture resistance is lowered. The higher the aspect ratio, the higher the number of layers in the coating layer of the flat pigment, and the higher the moisture resistance. The thickness of the flat pigment is measured from a cross-sectional photograph of the moisture-proof film. The thickness of 0.1 μm or more is obtained by image analysis from an electron micrograph. Those having a thickness of less than 0.1 μm are obtained by image analysis from a transmission electron micrograph. The aspect ratio referred to in the present invention is obtained by dividing the average particle size dispersed in the water or solvent by the thickness obtained from the cross-sectional photograph of the moisture-proof film.
The blending amount of the synthetic resin and the flat pigment in the moisture-proof layer is preferably 99/1 to 30/70 in terms of mass, more preferably 93/7 to 35/65, and particularly preferably 95/5 to 40/60. . When the compounding amount of the flat pigment is less than 1%, the moisture resistance improving effect and the disaggregation improving effect become small. If the tabular pigment is larger than 70%, the resin filling the space between the tabular pigments is insufficient, resulting in an increase in voids and pinholes, resulting in deterioration of moisture resistance.

In addition to the above-mentioned synthetic resin and flat pigment, the moisture-proof layer preferably contains a nitrogen-containing compound for improving moisture resistance.
The nitrogen-containing compound that can be used in the present invention is not particularly limited as long as it is a compound that exhibits a cationic property in an aqueous solution, but a cationization degree of 0.1 to 10 meq / g is preferable, and 0.2 to 7 meq / g. Is more preferable, and 0.5 to 5 meq / g is particularly preferable. When the degree of cationization is less than 0.1 meq / g, the cationic property is weak and the adsorption power to the inorganic layered compound is weakened, so the moisture-proof property is deteriorated, and when it exceeds 9 meq / g, the paint tends to aggregate. Not only is it difficult to handle, but the moisture resistance also deteriorates.
Specific examples of the nitrogen-containing compound include polyalkylene polyamine, polyamide compound, polyamidoamine-epihalohydrin or formaldehyde condensation reaction product, polyamine-epihalohydrin or formaldehyde condensation reaction product, polyamide polyurea-epihalohydrin or formaldehyde condensation reaction product, Polyamine polyurea-epihalohydrin or formaldehyde condensation reaction product, and polyamidoamine polyurea-epihalohydrin or formaldehyde condensation reaction product, polyamide polyurea compound, polyamine polyurea compound, polyamidoamine polyurea compound and polyamidoamine compound, polyethyleneimine, polyvinyl Examples include pyridine, amino-modified acrylamide compounds, polyvinylamine, and polyvinylamine. Moreover, the nitrogen-containing compound described in JP-A-9-291499 can also be used.

Further, as nitrogen-containing compounds, those referred to as imine compounds and amine compounds are representative. Among these, as the imine compound, polyalkyleneimine is representative, polyethyleneimine, alkyl or cyclopentyl-modified polyethyleneimine, imine adduct of ethylene urea, poly (ethyleneimine-urea) and ethyleneimine adduct of polyamine polyamide, or There is a polyimine compound selected from the group consisting of these alkyl-modified products, alkenyl-modified products, benzyl-modified products, or aliphatic cyclic hydrocarbon-modified products, polyamideimides, and polyimide varnishes.
Examples of amine compounds include polyalkylene polyamines. For example, there are compounds such as polyethylene polyamine, ethylenediamine, diethylenetriamine, triethylenetetramine. In addition, examples of the same effect include polyamides such as polyamidoimide adducts of polyamides, hydrazine compounds, and epichlorohydrin adducts of polyamine polyamides (saturated dibasic carboxylic acids having 3 to 10 carbon atoms and polyamines). Polyamineamide compounds such as water-soluble and cationic thermosetting resins obtained by reacting polyamides with epichlorohydrin from alkylene polyamines, quaternary nitrogen-containing acrylic polymers, quaternary nitrogen-containing benzyl polymers, urethanes, carboxylate amines There are nitrogen-containing quaternary salt compounds such as compounds having a base, compounds such as methylolated melamine, and cationic polyurethane. Further, cationic resins such as cation-modified polyurethane resins, polyvinyl pyrrolidone, vinyl pyrrolidone-vinyl acetate copolymers, tertiary nitrogen-containing acrylic resins and the like can be mentioned (for cation resins, JP-A-8-90898, JP (See JP-A-63-162275 and JP-A-62-148292). Furthermore, urea compounds such as urea, thiourea, guanylurea, methylurea, dimethylurea, and dicyandiamide derivatives are also within the scope of the present invention.

  Further, since the nitrogen-containing compound is cationic, it may cause a shock (coagulation of paint) when mixed with an anionic portion of a flat pigment or an anionic synthetic resin emulsion. In order to prevent such a shock, it is preferable to add a basic substance to a nitrogen-containing compound, an aqueous solution of a flat pigment, or a synthetic resin emulsion to adjust the alkali side (preferably pH 7 to 10). In particular, a method of adding a basic compound to a nitrogen-containing compound has a great effect of preventing shock. As the basic substance, ammonia, ethylamine, diethylamine, triethylamine, ethanolamine, triethanolamine, diethylethanolamine, caustic soda, caustic potash or the like can be used. In particular, ammonia is preferable in terms of moisture resistance.

  In addition, the present inventors investigated the cause of discoloration of the moisture-proof layer. As a result, the synthetic resin (styrene-butadiene copolymer or acrylic-styrene copolymer) contained in the moisture-proof layer is oxidized by oxygen and heating. It was found to occur. That is, it is considered that a radical is generated by oxygen as a trigger, and the synthetic resin is altered by the radical, thereby causing discoloration. The present inventors have further studied and found that discoloration is suppressed by adding oxygen and a radical substance by adding an antioxidant to the moisture-proof layer.

Examples of the antioxidant that can be used in the present invention include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, and titanium dioxide. Among these, it discovered that the hindered phenolic antioxidant which is 1 type of a phenolic antioxidant, and the discoloration suppression effect of titanium dioxide were excellent.
Other antioxidants such as phosphorus antioxidants and sulfur antioxidants can be used in combination with the hindered phenol antioxidants and titanium dioxide of the present invention.

A hindered phenol-based antioxidant is an organic compound having a phenol-derived hydroxyl group having a structure having an alkyl group at a position adjacent to the hydroxyl group of phenol.
Specific examples of the hindered phenol antioxidant include 2,6-tert-butyl-4-methylphenol, 2-tert-butyl-4-methoxy-phenol, n-octadecyl-3- (3,5-di- -Tert-butyl-4-hydroxyphenyl) propionate, 2,2'-ethylidene-bis (2,4-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 1, 3,5-trimethyl, 2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, Tris (4-tert-butyl-2,6-dimethyl-3-hydroxybenzyl) isocyanurate, tetrakis- [methylene-3- (3 ', 5'-di-tert-butyl) -4'- Droxy-phenyl) propionate] methane, 3,9-bis [1,1-di-methyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl]- 2,4,8,10-tetraoxaspiro [5,5] undecane, 4,4'-thio-bis (3-methyl-6-tert-butylphenol) and the like.
These antioxidants are used by adding 0.1 to 10 parts by mass with respect to the synthetic resin. A more preferable addition range is 0.5 to 7 parts by mass, and a more preferable addition range is 1 to 5 parts by mass. When the addition amount is less than 0.1 parts by mass, the discoloration prevention effect is insufficient, and when the addition amount exceeds 10 parts by mass, the discoloration prevention effect reaches its peak, which is uneconomical.
Titanium dioxide includes anatase type and rutile type, both of which can be used as the antioxidant of the present invention. The particle diameter of titanium dioxide is preferably 5 to 300 nm.

In the present invention, weather resistance can be improved by adding a light stabilizer such as an ultraviolet absorber or a hindered amine compound to the moisture-proof layer.
Specific examples of the ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 5,5'-methylenebis (2-hydroxy-4-methoxybenzophenone). 2-hydroxybenzophenones such as 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole, 2- (2- Hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 , 2'-methylenebis (4-tert-octyl-6-benzotriazole) phenol, etc. Triazoles, resorcinol monobenzoate, 2,4-di-tert-butylphenyl-3'-5'-di-tert-butyl-4'-hydroxybenzoate, hexadecyl-3-5-di-tert-butyl-4-hydroxybenzoate And other benzoates.

A moisture-proof coating containing the synthetic resin, flat pigment, and antioxidant described above is prepared, and this is applied to a paper support to form the moisture-proof layer of the present invention. The coating equipment is not particularly limited, and can be appropriately selected from known methods such as a blade coater, a bar coater, an air knife coater, a slit die coater, and a curtain coater. In particular, coating equipment of a type that scrapes the coating surface, such as a blade coater, a bar coater, an air knife coater, and a slit die coater, is preferable in terms of promoting the orientation of the flat pigment and improving the moisture resistance.
The coating amount of the moisture-proof layer in the present invention, 0.1 to 20 g / ^{m 2} is a suitable range. If the moisture-proof layer coating amount is less than 0.1 g / m ² , it is not preferable because sufficient moisture-proof property cannot be obtained. On the other hand, if the coating amount exceeds 20 g / m ² , the moisture resistance reaches a peak, which is uneconomical, and the value of the waste paper decreases due to an increase in the proportion of the moisture-proof layer.
In addition, the moisture-proof coating for forming the moisture-proof layer of the present invention includes a dispersant such as polycarboxylic acid, a defoaming agent such as silicone, a surfactant, a water retention agent, a color adjusting agent, and a flat pigment as necessary. It is possible to add other pigments (calcium carbonate, clay, kaolin, mica) and the like.

In addition, the paper base material used in the present invention is not particularly limited as long as it has pulp as a main component, but generally used bleached kraft paper or unbleached kraft paper, or for corrugated cardboard, for building materials, A paperboard used for white balls, chip balls, and the like is preferable. More preferably, it is a piece of glossy paper that has been forcibly dried with a Yankee dryer or the like, or a kraft paper that has been subjected to a calendar process. When using a paper substrate having high smoothness as described above, the orientation of the flat pigment in the thickness direction of the moisture-proof layer is easy to arrange uniformly in parallel to the coated surface, so that moisture-proof performance is achieved. Greatly improved. Furthermore, the decorative sheet is usually provided with various printing layers such as a wood grain pattern for imparting cosmetic properties, but the printability is improved by arranging the flat pigments uniformly.
Further, in the present invention, in order to further improve the printability, after the moisture-proof layer is formed, a calender treatment can be further performed to improve the surface smoothness.
Moreover, you may provide an anchor layer between a base material and a moisture-proof layer for the applicability | paintability of a moisture-proof coating material, or the coating amount reduction.

  The moisture-proof decorative sheet of the present invention is more preferably provided with a protective resin layer as the outermost layer. The protective resin layer can be appropriately selected according to the purpose from any synthetic resin usually used for coating, but acrylic urethane, polyester urethane, polyurethane, vinyl chloride-vinyl acetate copolymer, etc. are preferably used. It is done.

A veneer is obtained by bonding the moisture-proof decorative sheet of the present invention to at least one surface of a wooden board.
The wood board is not particularly limited as long as it is a face material made of a wood material, and a single board, a plywood, a parallel plywood, a particle board, and a fiber board such as an insulation board, an MDF, and a hard board can be used. .
Among these, even in MDF in which warpage easily occurs due to the influence of humidity, an excellent warpage prevention effect is exhibited by bonding the moisture-proof decorative sheet of the present invention.
In the case where the moisture-proof decorative sheet is bonded to the wooden board, it is preferable to use an adhesive. There is no restriction | limiting in particular in the adhesive agent to be used, According to a required physical property etc., it can select and use suitably from a conventionally well-known adhesive agent. For example, specifically, acrylic resin, ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, vinyl acetate resin, polyamide resin, thermoplastic resin such as thermoplastic urethane resin, or curability of urethane resin, etc. Resin or the like can be used.
These adhesives can be applied to the wooden board in any form such as a solution, dispersion, or melt. The coating can be performed by a conventionally known method such as roll coating or spray coating.

  Hereinafter, the present invention will be described in detail by way of examples.

<Example 1>
After adding 5.5 parts of 25% aqueous ammonia (made by Wako Pure Chemicals, special grade) to 83 parts by mass of water with stirring, a cationic resin (trademark: SPI203, manufactured by Sumitomo Chemical Co., Ltd., solid content 50%, polyamine polyamide resin) 41 parts by mass was added and stirred for 10 minutes. After adding 1000 parts by mass of SBR latex (trade name LX407S12, solid content 46%) to this aqueous dispersion, an aqueous dispersion of inorganic layered compound (trade name NTO-5, solid content 6.0%, manufactured by Topy Industries, Ltd.). 460 parts by mass of synthetic mica, sodium tetrasilicon mica), and stirred for 10 minutes. In this aqueous dispersion, 4,4′-butylidenebis (6-tertiarybutyl-3-methylphenol) (molecular weight 383, melting point 205 ° C. or higher, manufactured by Kawaguchi Chemical Industries, Ltd.) as a hindered phenol antioxidant as an antioxidant. Trademark: Antage W-300) aqueous dispersion (solid content 30%, 1% by weight of polycarboxylic acid-based dispersant added to antioxidant, and dispersed by 30% with Cowles disperser) 46% Part was added and stirred for 10 minutes to obtain a moisture-proof paint.
The obtained moisture-proof paint is bar coated on a glossy surface of glazed bleached kraft paper (trade name: Flex S-45, basis weight 45 g / m ² , made by Oji Specialty Paper) and dried (drying temperature 140 ° C.). A moisture-proof decorative sheet was produced.

<Example 2>
2,2′-methylenebis- (4-methyl-6-tert-butylphenol) (molecular weight: 341, melting point of 120 ° C. or higher, manufactured by Kawaguchi Chemical Industry, trademark: Antage W-400) is used as a hindered phenol antioxidant. A moisture-proof decorative sheet was produced in the same manner as in Example 1 except that.

<Example 3>
2,2′-methylenebis- (4-ethyl-6-tert-butylphenol) (molecular weight: 369, melting point of 120 ° C. or higher, manufactured by Kawaguchi Chemical Industry, trademark: Antage W-500) is used as a hindered phenol antioxidant. A moisture-proof decorative sheet was produced in the same manner as in Example 1 except that.

<Example 4>
After adding 5.5 parts of 25% aqueous ammonia (made by Wako Pure Chemicals, special grade) to 153 parts by mass of water with stirring, a cationic resin (trademark: SPI203, manufactured by Sumitomo Chemical Co., Ltd., solid content 50%, polyamine polyamide resin) 41 parts by mass was added and stirred for 10 minutes. After adding 1000 parts by mass of SBR latex (trade name LX407S12, solid content 46%) to this aqueous dispersion, an aqueous dispersion of inorganic layered compound (trade name NTO-5, solid content 6.0%, manufactured by Topy Industries, Ltd.). 460 parts by mass of synthetic mica, sodium tetrasilicon mica), and stirred for 10 minutes. An aqueous dispersion of titanium dioxide (sulfuric acid method titanium oxide, anatase type, manufactured by Ishihara Sangyo, trademark: W-10, average particle size 0.15 μm) as an antioxidant in this aqueous dispersion (solid content 60%, polycarboxylic acid) 1% by mass of a system dispersant was added to titanium dioxide and dispersed for 30% with a Cowles disperser) and 77 parts by mass was added and stirred for 10 minutes to obtain a moisture-proof paint.
The obtained moisture-proof paint is bar coated on a glossy surface of glazed bleached kraft paper (trade name: Flex S-45, basis weight 45 g / m ² , made by Oji Specialty Paper) and dried (drying temperature 140 ° C.). A moisture-proof decorative sheet was produced.

<Example 5>
A moisture-proof decorative sheet was produced in the same manner as in Example 4 except that titanium dioxide (chlorine titanium oxide, rutile type, manufactured by Ishihara Sangyo, trademark: CR-50, average particle diameter of 0.25 μm) was used as the antioxidant. .

<Comparative Example 1>
After adding 5.5 parts of 25% aqueous ammonia (made by Wako Pure Chemicals, special grade) to 88 parts by weight of water with stirring, a cationic resin (trade name: SPI203, manufactured by Sumitomo Chemical Co., Ltd., solid content 50%, polyamine polyamide resin) 41 parts by mass was added and stirred for 10 minutes. After adding 1000 parts by mass of SBR latex (trade name LX407S12, solid content 46%) to this aqueous dispersion, an aqueous dispersion of inorganic layered compound (trade name NTO-5, solid content 6.0%, manufactured by Topy Industries, Ltd.). 460 parts by mass of synthetic mica, sodium tetrasilicon mica) and stirred for 10 minutes to obtain a moisture-proof paint.
The obtained moisture-proof paint is bar coated on a glossy surface of glazed bleached kraft paper (trade name: Flex S-45, basis weight 45 g / m ² , made by Oji Specialty Paper) and dried (drying temperature 140 ° C.). A moisture-proof decorative sheet was produced.

<Comparative example 2>
A moisture-proof decorative sheet was produced in the same manner as in Example 1 except that a phosphorus-based antioxidant (trademark: Sumilizer P-16, manufactured by Sumitomo Chemical Co., Ltd.) was used as the antioxidant.

<Comparative Example 3>
A moisture-proof decorative sheet was produced in the same manner as in Example 1 except that a sulfur-based antioxidant (trademark: Sumilizer TPS) was used as the antioxidant.

<Comparative Example 4>
A moisture-proof decorative sheet was produced in the same manner as in Example 4 except that silicon dioxide (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.) was used as the antioxidant.
<Comparative Example 5>
Low-density using a T-die type melt extrusion laminating machine (Toyo Seiki, Labo Plast Mill) on glossy surface of single gloss bleached kraft paper (Oji Specialty Paper, trademark: Flex S-45, basis weight 45 g / m ² ) A moisture-proof decorative sheet was manufactured by laminating a polyethylene resin (trade name: LC522, manufactured by Nippon Polychem Co., Ltd.) to a thickness of 15 μm.

The moisture-proof decorative sheets obtained in Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 1.
[Evaluation methods]
1. Test of heat-resistant yellowing After 10 sheets of moisture-proof decorative sheets were stacked and kept at a constant temperature machine adjusted to 70 ° C. for 3 days, L ^* a ^* b ^* values were measured. The measurement was carried out by taking three moistureproof decorative sheets stacked one by one from the middle. The measurement surface was a moisture-proof surface and a dark box was installed on the opposite side. As a measuring device, a spectral white clock “SC-10WP” manufactured by Suga Test Instruments Co., Ltd. was used.
ΔE = (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ) When ΔE defined by ^1/2 is less than 1, the result is 1 or more.
ΔL ^* = (after heat treatment ΔL ^*) - (before the heat treatment ΔL ^*)
Δa ^* = (after heat treatment Δa ^*) - (before the heat treatment Δa ^*)
Δb ^* = (after heat treatment Δb ^*) - (before the heat treatment Δb ^*)

2. Measurement of moisture permeability The moisture permeability was measured by JIS-Z-0208 (cup method) B method (40 ° C 90% RH) with the coated surface of the moisture-proof wrapping paper facing outward. (Unit: g / ^{m 2} · 24hr)

3. Gravure printing suitability and surface strength After printing with a gravure printing machine using solvent-based ink (trademark: Univia NT, manufactured by Dainippon Ink) on the moisture-proof layer surface of the moisture-proof decorative sheet of Examples and Comparative Examples, once at 80 ° C It was made to dry and it left still for 24 hours on 40 degreeC conditions.
The printability of the printed surface of the obtained moisture-proof decorative sheet was visually evaluated to evaluate printability.
If there was no faint printing or cosmetics, it was rated as ○.
Further, the printed surface was strongly rubbed 10 times with tissue paper.

4). Warpage evaluation of decorative board MDF (manufactured by Ichiyu Science and Technology, thickness 2.7 mm) is prepared as a wooden board, and vinyl acetate resin adhesive is applied to one side of the MDF by a roll coating method to give 50 g / m ² (solid content Criteria) After application, the moisture-proof decorative sheets obtained in Examples and Comparative Examples were bonded together, and then dried by heating at 80 ° C. After drying, a moisture-proof decorative sheet was similarly bonded to the other side of the MDF, and then heat-dried at 80 ° C. to obtain a wooden decorative board.
The obtained wood-based decorative board was used for each face material of the front and back, and a door was produced. The door was subjected to a resistance test against changes in temperature and humidity.
The resistance test condition was that a door was installed between room A maintained at 5 ° C. and humidity 70% and room B maintained at 30 ° C. and humidity 30%. When the presence or absence of twisting was visually evaluated, no warping or twisting occurred in any of the examples and comparative examples.
In addition, as a control experiment, a decorative board obtained by laminating single-sided bleached kraft paper (made by Oji Specialty Paper, trademark: Flex S-45, basis weight 45 g / m ² ) on both sides of the MDF was manufactured. When a door was made using a face material and a resistance test was performed in the same manner, warping occurred.

Claims (2)

  It has a moisture-proof layer containing a synthetic resin, a flat pigment, and an antioxidant on at least one side of a paper support, and the antioxidant is at least one of a hindered phenol antioxidant or titanium dioxide. Moisture-proof cosmetic sheet.   A moisture-proof decorative sheet according to claim 1 is bonded to a wooden board.