Water-repellent paper and method for manufacturing the same

Abstract

The present invention aims to provide a water-repellent paper that exhibits excellent water repellency, water friction resistance, and blocking resistance even with a small mass per unit area of ​​the water-repellent layer. [Solution] The water-repellent paper has a paper base material and a water-repellent layer, the water-repellent layer contains an acrylic resin and a hydrocarbon wax, and the mass of the water-repellent layer per unit area is 5 g / m². 2 The following is a water-repellent paper: The water-repellent paper wherein the hydrocarbon wax is at least one selected from the group consisting of paraffin wax, microcrystalline wax, carnauba wax, and polyethylene wax.

Description

[Technical Field]

[0001] This invention relates to water-repellent paper and a method for producing the same. [Background technology]

[0002] Traditionally, synthetic resin films such as polyester film, nylon film, and polyolefin film have been widely used for packaging many products, including food, hygiene products, and daily necessities. These materials are highly valued because they possess the necessary functions for packaging, such as water resistance and strength. However, in recent years, marine plastic waste, including microplastics, has come into sharp focus as an environmental problem. This issue is being discussed worldwide, and reducing plastic waste is recognized as a global challenge.

[0003] However, even when replacing base materials with paper to reduce plastic use, a large amount of sealant film such as polyethylene or polypropylene is laminated onto the paper when it is processed into bags or containers to ensure various resistances. The amount of these plastics laminated varies depending on the intended use of the packaging material, but it is approximately 20-50 g / m². 2 Therefore, for sealant films with a high plastic content, the amount is 100g / m². 2 In some cases, the amount of plastic used may exceed this amount. Therefore, even in packaging materials where the base material has been replaced from plastic to paper, there is still a problem in that the amount of plastic used is not sufficiently reduced, and solutions to reduce the burden on the global environment are needed. Thus, the challenge is to develop water-repellent paper that reduces the amount of plastic used compared to laminated paper and also possesses water-repellent properties.

[0004] Patent Document 1 describes a water-repellent varnish for paper containing an acrylic resin and a hydrocarbon-based wax. However, it does not disclose examples of what happens when the mass per unit area of ​​the varnish is small. When the mass is small, the varnish penetrates into the paper substrate, which reduces the amount of coating on the surface of the paper substrate, potentially resulting in insufficient film-forming ability and a decrease in various resistances of the coating, such as water repellency. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-085741 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a water-repellent paper that exhibits excellent water repellency, water friction resistance, and blocking resistance even with a small mass per unit area of ​​the water-repellent layer. [Means for solving the problem]

[0007] As a result of diligent research into the aforementioned problems, the inventors have found that the above problems can be solved by using the water-repellent paper described below, and have thus come to present invention.

[0008] In other words, the present invention relates to the following [1] to [8].

[0009] [1] This is a water-repellent paper having a paper base material and a water-repellent layer. The water-repellent layer comprises an acrylic resin and a hydrocarbon wax. The mass per unit area of ​​the water-repellent layer is 5 g / m². 2 The following is water-repellent paper.

[0010] [2] The water-repellent paper according to [1], wherein the hydrocarbon wax is at least one selected from the group consisting of paraffin wax, microcrystalline wax, carnauba wax, and polyethylene wax.

[0011] [3] The water-repellent paper according to [1] or [2], wherein the content ratio of the acrylic resin to the hydrocarbon wax is 99:1 to 80:20.

[0012] [4] The water-repellent paper according to any one of [1] to [3], wherein the water-repellent layer further contains inorganic fine particles, and the inorganic fine particles are at least one selected from the group consisting of silica, calcium carbonate, and kaolin.

[0013] [5] The water-repellent paper according to [4], wherein the content ratio of the hydrocarbon wax to the inorganic fine particles is 90:10 to 10:90.

[0014] [6] Furthermore, between the paper base material and the water-repellent layer, there is an anchor layer, and the anchor layer contains at least one selected from the group consisting of acrylic resin, urethane resin, cellulose-based resin, and polylactic acid resin. The water-repellent paper according to any one of [1] to [5].

[0015] [7] The basis weight of the paper base material is 30 to 200 g / m 2 The water-repellent paper according to any one of [1] to [6].

[0016] [8] A method for manufacturing a water-repellent paper having a paper base material and a water-repellent layer, including a step of applying a water-repellent coating agent containing an acrylic resin and a hydrocarbon wax on the paper base material to form the water-repellent layer. The mass per unit area of the water-repellent layer is 5 g / m 2 or less. A method for manufacturing a water-repellent paper.

Advantages of the Invention

[0017] According to the present invention, it has become possible to provide a water-repellent paper excellent in water repellency, water friction resistance, and blocking resistance even when the mass per unit area of the water-repellent layer is small.

Embodiment for Carrying out the Invention

[0018] Hereinafter, the water-repellent paper of the present invention will be described.

[0019] <Water-repellent paper> The present invention is a water-repellent paper having a paper substrate and a water-repellent layer, the water-repellent layer contains an acrylic resin and a hydrocarbon wax, and the mass per unit area of the water-repellent layer is 5 g / m 2 as follows. Here, the mass per unit area of the water-repellent layer means the mass per unit area after drying. The mass per unit area of the water-repellent layer is preferably 0.5 to 5 g / m 2 more preferably 1 to 3 g / m 2 even more preferably 1.5 to 2.5 g / m 2 When the mass per unit area of the water-repellent paper is within the above range, the water repellency, water friction resistance, and blocking resistance are good.

[0020] The water-repellent paper of the present invention is used, for example, in packages such as bags, containers, boxes, wrapping papers that can directly contain fast food or takeout foods, cosmetic boxes, paper products, labels, catalogs, shopping bags, book covers, posters, etc. used for packaging food, pharmaceuticals, cosmetics, etc., and is useful as a paper for packages that require high gloss, oil resistance, alcohol resistance, scratch resistance, etc., and can be used as oil-resistant paper or paper containers.

[0021] Specifically, the water-repellent paper of the present invention can exemplify the following configurations, but is not limited thereto. In the following configuration representations, " / " means the boundary of each layer. · Paper substrate / Water-repellent layer · Paper substrate / Anchor layer / Water-repellent layer · Paper substrate / Printing layer / Water-repellent layer · Paper substrate / Printing layer / Anchor layer / Water-repellent layer · Paper substrate / Anchor layer / Printing layer / Water-repellent layer • Paper substrate / Water-repellent layer / Printing layer • Paper substrate / Anchor layer / Water-repellent layer / Printing layer

[0022] <Paper base material> The paper substrates that can be used include well-known paper substrates such as fine paper, coated paper, art paper, imitation paper, thin paper, and thick paper. The basis weight of the paper substrate should be between 30 and 200 g / m². 2 Preferably, it is 40-150 g / m² 2 It is more preferable that the amount be 50-100 g / m². 2 It is even more preferable that the basis weight of the paper substrate is within the above range. When the basis weight of the paper substrate is within the above range, water repellency, water abrasion resistance, and blocking resistance are good.

[0023] <Water-repellent layer> The water-repellent layer contains an acrylic resin and a hydrocarbon-based wax. From the viewpoint of water friction resistance and blocking resistance, it is preferable that the water-repellent layer further contains inorganic fine particles. The above water-repellent layer can be formed by applying the water-repellent coating agent described later to a paper substrate or the like and removing the volatile components.

[0024] <Water-based acrylic resin> As the acrylic resin, a water-based acrylic resin is preferred. As the aqueous acrylic resin, known aqueous acrylic resins can be used, but a styrene-acrylic copolymer is preferred. Furthermore, the aqueous acrylic resin may be a water-soluble acrylic resin or an emulsion-type acrylic resin, but from the viewpoint of water repellency, an emulsion-type acrylic resin is preferred. An emulsion-type acrylic resin refers to one that is insoluble or sparingly soluble in water but is dispersed and stabilized with a surfactant or the like. Among these, an emulsion-type styrene-acrylic copolymer is particularly preferred from the viewpoint of achieving both water repellency, water friction resistance, and blocking resistance. A styrene-acrylic copolymer is a copolymer obtained by emulsion polymerization of monomers containing a styrene monomer and a (meth)acrylic monomer. This type of copolymer can also be obtained by polymerizing other monomers copolymerizable with these, as needed. It may also be an emulsion that forms a core-shell structure.

[0025] Examples of styrene monomers include alkylstyrenes such as styrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, and α-hexylstyrene; halogenated styrenes such as 4-chlorostyrene, 3-chlorostyrene, and 3-bromostyrene; and styrene monomers such as 3-nitrostyrene, 4-methoxystyrene, and vinyltoluene.

[0026] Furthermore, examples of (meth)acrylic monomers include methyl acrylate, methyl methacrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, 2-ethylbutyl acrylate, 1,3-dimethylbutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, ethyl methacrylate, n-butyl methacrylate, 2-methylbutyl methacrylate, pentyl methacrylate, heptyl methacrylate, nonyl methacrylate, ethyl carbitol acrylate, 3-ethoxypropyl acrylate, 3-ethoxybutyl acrylate, Examples include aryl acrylates and aralkyl acrylates such as dimethylaminoethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate, ethyl-α-(hydroxymethyl) acrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, phenyl acrylate, benzyl acrylate, phenylethyl acrylate, and phenylethyl methacrylate; and monoacrylic acid esters or monomethacrylic acid esters of polyhydric alcohols such as diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, and bisphenol.

[0027] The acid value of the aqueous acrylic resin is preferably 10 to 300 mg KOH / g, more preferably 15 to 300 mg KOH / g, and even more preferably 15 to 250 mg KOH / g. When the acid value of the aqueous acrylic resin is within the above range, water repellency and water friction resistance tend to improve. The glass transition temperature of the aqueous acrylic resin is preferably -20 to 150°C, and more preferably -10 to 130°C. When the glass transition temperature of the aqueous acrylic resin is within the above range, adhesion to the substrate improves, and therefore water friction resistance and blocking resistance tend to improve. The weight-average molecular weight of the aqueous acrylic resin is preferably 5,000 to 700,000, more preferably 8,000 to 500,000, and even more preferably 8,000 to 200,000. When the weight-average molecular weight of the aqueous acrylic resin is within the above range, water friction resistance and blocking resistance tend to improve.

[0028] <Hydroxide-based waxes> Hydrocarbon waxes are organic substances mainly composed of long-chain alkyl groups, existing as solids at room temperature and changing to liquids when heated. These hydrocarbon waxes may contain functional groups such as acid groups, ester groups, and hydroxyl groups. Specific examples of hydrocarbon waxes include naturally derived waxes such as paraffin wax, microcrystalline wax, beeswax, montan wax, ozokerite, ceresin, carnauba wax, candelilla wax, beeswax, wood wax, and rice wax, as well as synthetic polyethylene wax, polypropylene wax, and Fischer-Tropsch wax. These can be used individually or in combination, with paraffin wax, microcrystalline wax, carnauba wax, and polyethylene wax being particularly preferred, and paraffin wax being more preferred.

[0029] The melting point of the hydrocarbon wax is preferably 30°C to 80°C, and more preferably 40°C to 70°C. When the melting point of the hydrocarbon wax is within the above range, it tends to have good water repellency, water friction resistance, and blocking resistance. From the viewpoint of friction resistance and blocking resistance, the melting point of the hydrocarbon wax is preferably 90 to 140°C, and more preferably 100 to 140°C. The content of the hydrocarbon wax in the water-repellent layer is preferably 0.1 to 20% by mass, and more preferably 1 to 10% by mass, of 100% by mass of the water-repellent layer.

[0030] The average particle size of the hydrocarbon wax obtained by laser diffraction / scattering particle size distribution measurement is not particularly limited, but is preferably 5 μm or less, and more preferably in the range of 0.01 to 5 μm. In addition, the molecular weight of the hydrocarbon wax measured by the viscosity method is preferably 2000 to 8000, and the number average molecular weight is preferably 500 to 6000. Since these waxes are fine particles and are water-dispersible, commercially available waxes can be used as appropriate. The content of hydrocarbon wax in the water-repellent layer is preferably 3.0 to 20.0% by mass, more preferably 5.0 to 15.0% by mass, and even more preferably 6.0 to 10.0% by mass, out of 100% by mass of the water-repellent layer. Furthermore, the melting point of the hydrocarbon wax in DSC measurement is preferably 90 to 150°C, and more preferably 100 to 120°C.

[0031] Specific examples of the paraffin waxes mentioned above include MP-28C, MP-22XF, and MP-28C (Micro Powders, Inc.). Natural waxes include paraffin waxes and microcrystalline waxes manufactured by Nippon Seiro Co., Ltd. and ENEOS Corporation. Furthermore, synthetic waxes such as FT115, FT0165, SX105, and FNP0090 from Nippon Seiro Co., Ltd., CERAMER polymer, POLYWAX polyethylene, UNICID carboxylic acid, UNILIN alcohol, UNITHOX ethoxylate, PETROLITE copolymer, and VYBAR polymer from Baker Hughes, Diacarna from Mitsubishi Chemical Corporation, and the Sunwax series and Viscol series from Sanyo Chemical Corporation are also mentioned.

[0032] The ratio of acrylic resin to hydrocarbon wax in the water-repellent layer (acrylic resin content: hydrocarbon wax content) is preferably 99:1 to 80:20 from the viewpoint of water repellency, water friction resistance, and blocking resistance.

[0033] <Additives other than hydrocarbon waxes> The water-repellent layer may also contain additives such as chelating crosslinking agents, extender pigments, leveling agents, defoaming agents, plasticizers, infrared absorbers, and ultraviolet absorbers, for the purpose of imparting basic physical properties. In particular, it is preferable to include inorganic fine particles from the viewpoint of water friction resistance and blocking resistance.

[0034] <Inorganic fine particles> The inorganic fine particles used in the present invention include, for example, inorganic pigments such as titanium dioxide, calcium carbonate, barium sulfate, talc, zinc oxide, silica, mica, montmorillonite, smectite, zeolite, and kaolinite, among which silica, calcium carbonate, and kaolin (clay) are preferred, with silica being more preferred. These inorganic fine particles may be subjected to known surface treatments such as rosinic acid, or they can be used in an untreated state. The inorganic fine particles described above preferably have an average particle diameter of 1 to 10 μm, and more preferably 2 to 8 μm, in order to improve adhesion. When the average particle diameter of the inorganic fine particles is within the above range, water friction resistance and blocking resistance tend to improve. In particular, when the average particle diameter of the inorganic fine particles is 2 μm or more, the inorganic fine particles are more likely to be exposed from the surface of the water-repellent coating, thus improving the protective capacity of the coating surface, and thus tending to further improve water friction resistance and blocking resistance. The average particle diameter of the inorganic fine particles refers to the particle size at 50% of the cumulative value (D50) in the particle size distribution, and can be determined by the Coulter counter method. The specific surface area of ​​the inorganic fine particles is 50 to 600 m² by the BET method. 2 It is preferable that the amount be / g, and 100-450m 2 It is more preferable that it be / g.

[0035] From the viewpoint of water repellency and blocking resistance, the ratio of hydrocarbon wax to inorganic fine particles in the water-repellent layer (hydrocarbon wax content: inorganic fine particle content) is preferably 90:10 to 10:90.

[0036] <Water-repellent coating agent> A water-repellent coating agent can be applied to a paper substrate, and a water-repellent layer can be formed by removing volatile components. The water-repellent coating agent can be obtained by stirring and mixing the above-mentioned acrylic resin and hydrocarbon wax, as well as the medium described later. The water-repellent coating agent may further contain additives other than the above-mentioned hydrocarbon wax. If inorganic fine particles are included, dispersion treatments such as ball milling, bead milling, roller milling, pebble milling, attritoring, and sand milling may be applied to uniformly disperse the inorganic fine particles.

[0037] <Aqueous medium> As a medium, an aqueous medium is preferred. Considering safety and environmental impact, it is particularly preferable to use only water as the aqueous medium, but a mixture of water and an organic solvent that is miscible may also be used. Specifically, examples of aqueous mediums include water, an organic solvent that is miscible with water, and mixtures thereof. The aqueous medium used in the water-repellent coating agent used in the present invention preferably has water as its main component, and may also contain an organic solvent as needed. There are no restrictions on the organic solvents that can be used, but considering environmental considerations and the durability of the printing plate (flexographic printing), an alcohol-based solvent is particularly recommended. The content of the above alcohol-based solvent is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and particularly preferably 1 to 8% by mass, based on the mass of the water-repellent coating agent.

[0038] Examples of the above-mentioned alcohol-based solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, t-butyl alcohol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-n-hexyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol mono-n-hexyl ether, and 2,2,4-trimethylpentanediol, 1,3-monoisobutyrate (Texanol, manufactured by Eastman Chemical Corporation), with isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, ethanol, and methanol being particularly preferred.

[0039] <Anchor Coat Layer> The water-repellent paper of the present invention preferably further includes an anchor coat layer, which is preferably located between the paper substrate and the water-repellent layer. The anchor coat layer preferably contains a resin, and the resin contained in the anchor coat layer may be either an oil-based resin or an aqueous resin, but from the viewpoint of adhesion to the water-repellent layer, an aqueous resin is preferred. Examples of resins that can be used include polyester resin, urethane resin, acrylic resin, vinyl alcohol resin, ethylene vinyl alcohol resin, vinyl-modified resin, epoxy resin, oxazoline group-containing resin, modified styrene resin, modified silicone resin, and polylactic acid resin. These resins may be used individually or in mixtures of two or more. In particular, it is preferable to include urethane resin, acrylic resin, cellulose-based resin, and polylactic acid resin, and more preferably urethane resin. The anchor coat layer is very effective in improving the adhesion between the paper substrate layer and the water-repellent layer. The amount of the anchor coat layer applied after drying is not particularly limited, but is preferably 0.5 to 10.0 g / m². 2 Preferably, 1.0 to 5.0 g / m 2 This is preferable.

[0040] <urethane resin> The urethane resin may be either an oil-based or water-based urethane resin, but a water-based urethane resin is preferable from the viewpoint of adhesion with the water-repellent layer. Water-based urethane resins are generally obtained by reacting polyisocyanates with hydroxyl group-containing compounds such as polyols, and among these, those containing 3 to 30% by weight of PEG units in the solid content are particularly preferred. The reaction molar ratio of isocyanate groups to hydroxyl groups in the water-based urethane resin is preferably in the range of 0.9 to 0.99, and more preferably 0.94 to 0.98. This appropriately controls the molecular weight and number of urethane bonds of the resin, resulting in excellent blocking resistance and water friction resistance. Furthermore, the acid value of the water-based urethane resin is preferably 25 mg KOH / g or higher. Water-based urethane resins have excellent dispersibility and solubility in water due to the neutralization of acidic functional groups with a base, and also exhibit excellent storage stability of inks, dispersibility and resolubility of pigments.

[0041] Examples of polyols include polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, polyolefin polyols, castor oil polyols, hydrogenated castor oil polyols, dimer diols, and hydrogenated dimer diols. From the viewpoint of water friction resistance and blocking resistance, polyester polyols are preferred.

[0042] Examples of polyisocyanates include aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate, as well as aliphatic or aliphatic cyclic structure-containing diisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. These can be used individually or in combination of two or more.

[0043] When reacting a polyol with a polyisocyanate, it is desirable to adjust the amounts of polyol and polyisocyanate so that the ratio of the number of moles of isocyanate groups in the polyisocyanate to the total number of hydroxyl groups in the polymer polyol (NCO / OH ratio) is in the range of 1.1 to 3.0. From the viewpoint of balancing the softness and hardness of the resin by adjusting the urethane bond concentration, and improving the blocking resistance of the coating film, as well as the adhesion and conformability to the substrate in flexible packaging applications, the NCO / OH ratio is more preferably in the range of 1.2 to 2.5, and even more preferably in the range of 1.5 to 1.8.

[0044] In the present invention, basic compounds that can be used to neutralize aqueous urethane resins include ammonia, organic amines such as triethylamine, morpholine, monoethanolamine, and diethylethanolamine. In particular, the use of ammonia and triethylamine contributes to improving the hot water resistance, corrosion resistance, and chemical resistance of the coating film. Furthermore, for neutralizing polymers containing anionic groups such as carboxyl groups and sulfonic acid groups, pyridine, various organic amines, alkanolamines, and metal base compounds containing sodium (Na), potassium (K), lithium (Li), calcium (Ca), etc., can also be used. These neutralizing agents are also important for improving the storage stability of the water-repellent coating agent, and it is recommended to use the neutralizing agent in an appropriate ratio to the anionic groups of the polymer. Ideally, the degree of neutralization should be 30 mol% to 300 mol%, and particularly preferably 150 mol% or less, relative to the molar equivalent number of anionic groups of the polymer. If necessary, additional neutralization may be performed using bases such as sodium hydroxide or potassium hydroxide.

[0045] <Anchor coating agent> The anchor coating agent used in the present invention can be obtained by mixing and stirring the resin and solvent described in <Anchor Coat Layer>. The form of the solvent is not particularly limited, but if the resin is aqueous, the preferred form of the solvent can be found by referring to the contents of <Aqueous Medium> described above.

[0046] <Print layer> The water-repellent paper of the present invention may further have a printed layer. The printed layer used in the present invention is not particularly limited, but for example, the printing method can be traditional printing techniques such as offset, gravure, flexographic, letterpress, and screen printing, or inkjet printing, to print known inks such as gravure inks and flexographic inks, and then remove volatile components to form the printed layer. The film thickness of the printed layer is preferably in the range of 0.1 to 5 μm, and more preferably in the range of 0.3 to 3 μm.

[0047] <Method for manufacturing water-repellent paper> The present invention relates to a method for manufacturing water-repellent paper having a paper substrate and a water-repellent layer, and includes the step of applying a water-repellent coating agent containing an acrylic resin and a hydrocarbon wax emulsion to the paper substrate to form the water-repellent layer, wherein the mass per unit area of ​​the water-repellent layer is 5 g / m². 2 The following is a method for manufacturing water-repellent paper. Here, the mass per unit area of ​​the water-repellent layer refers to the mass per unit area after drying.

[0048] Known coating techniques can be used to apply coating compositions to paper substrates or other layers. Examples include coating methods using comma coaters, roll coaters, reverse roll coaters, gravure coaters, flexo coaters, roll kiss coaters, reverse kiss coaters, air doctor coaters, knife coaters, bar coaters, wire bar coaters, die coaters, lip coaters, dip coaters, blade coaters, brush coaters, curtain coaters, die slot coaters, etc. Spray coating and dip coating methods can also be selected, with gravure coating being the preferred method.

[0049] <Gravure Coater> (Gravure version) A gravure printing plate is a cylindrical metal plate, and recesses are created in each color by engraving, etching, or laser. There are no restrictions on the use of engraving or laser, and the settings can be arbitrarily adjusted according to the design. Line screens of 100 to 300 lines are used as appropriate, with higher line screens allowing for finer printing. The thickness of the printed layer is preferably 0.1 μm to 100 μm.

[0050] (printing machine) In a gravure printing press, each printing unit is equipped with the aforementioned gravure plate and doctor blade. Multiple printing units are available, and units corresponding to organic solvent-based printing inks and image inks can be configured. Each unit has an oven drying unit. Printing is performed by rotary press using a roll printing method. The type of plate and doctor blade are selected as appropriate, according to the specifications. [Examples]

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In these examples, unless otherwise specified, "%" means "mass percent" and "parts" means "parts by mass". Also, the numbers for the quantities of each material in the table mean "parts by mass". The unit of acid value is mgKOH / g.

[0052] <Acid value> The acid value is the number of milligrams of potassium hydroxide required to neutralize the free fatty acids, resin acids, etc., contained in 1 g of the sample, and was measured by the method described in JIS K 0070.

[0053] <Ingredients used> <Acrylic resin> A-1: BASF Corporation Product Name: Joncryl HPB1631 (Modified styrene acrylic emulsion, solids content: 50%) ·A-2: Seiko PMC Co., Ltd. Product name: SEIKOAT PE-2273 (Acrylic emulsion, solids content: 50%)

[0054] <Hydroxide-based waxes> B-1: EMUSTAR-0135 manufactured by Nippon Seiro Co., Ltd. (paraffin wax emulsion, 40% solids) B-2: EMUSTAR-042X (microcrystalline wax emulsion, 40% solids) manufactured by Nippon Seiro Co., Ltd. B-3: EMUSTAR-0413 (carnauba wax emulsion, 40% solids) manufactured by Nippon Seiro Co., Ltd. B-4: CERAFLOUR991 (polyethylene wax, 100% solids) manufactured by Big Chemie Japan Co., Ltd. <Other waxes> B-5: CERAFLOUR994 (Amide wax, 100% solids) manufactured by Big Chemie Japan Co., Ltd.

[0055] <Inorganic fine particles> C-1: Mizusawa Chemical Industry Co., Ltd. Mizukasil P-707 (silica, 100% solids, average particle size 2.2 μm) C-2: Shiraishi Kogyo Co., Ltd. Tsunex-E (calcium carbonate, 100% solids, average particle size 4.4 μm) C-3: BASF Kaolin Clay ASP-200 (Kaolin, 100% solids, average particle size 0.4 μm)

[0056] <Urethane resin (D)> • D-1: Water-based urethane resin from manufacturing example 1

[0057] <Manufacturing Example 1: Manufacturing of Water-Based Urethane Resin> (Synthesis of water-based urethane resin) In a reactor equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas inlet, 96.89 parts of poly(3-methyl-1,5-pentaneadipate)diol with a number average molecular weight of 400, 24.18 parts of polyethylene glycol with a number average molecular weight of 2000, 21.56 parts of 2,2-dimethylolpropionic acid, and 138.24 parts of isophorone diisocyanate were reacted at a boiling point for 6 hours in 200 parts of methyl ethyl ketone to obtain a terminal isocyanate prepolymer. After cooling to 40°C, 100 parts of acetone were added to obtain a solvent solution of the terminal isocyanate prepolymer. Next, 580.87 parts of the obtained terminal isocyanate prepolymer solution were gradually added at room temperature to a mixture of 14.35 parts of 2-hydroxyethylethylenediamine, 4.78 parts of isophoronediamine, and 400 parts of acetone, and reacted at 50°C for 3 hours to obtain a solvent-type polyurethane resin solution. Next, 9.76 parts of 28% aqueous ammonia and 700 parts of deionized water were gradually added to the solvent-type polyurethane resin solution to neutralize it and make it water-soluble. After further removing all of the methyl ethyl ketone and acetone under azeotropic distillation, water was added to adjust the viscosity, yielding aqueous urethane resin D-1 with an acid value of 30 mg KOH / g, a solid content of 30%, a viscosity of 780 mPa·s, and a weight-average molecular weight of 22000.

[0058] <Manufacturing Example 2: Manufacturing of Anchor Coating Agent> 30 parts of water-based urethane resin (D-1), 0.10 parts of polysiloxane-based defoaming agent (100% solids), 10 parts of isopropyl alcohol, and 29.90 parts of water were stirred and mixed, then kneaded in a sand mill. After that, 20 parts of water-based urethane resin (D-1), 5 parts of isopropyl alcohol, and 10 parts of water were stirred and mixed to obtain an anchor coating agent.

[0059] <Manufacturing Example 3: Manufacturing of Water-Repellent Coating Agent X1> While stirring 70.5 parts of acrylic resin (A-1), 5 parts of hydrocarbon wax (B-2), 1 part of inorganic fine particles (C-1), 0.1 parts of polysiloxane-based defoaming agent (100% solids), and 23.4 parts of water were added and mixed and stirred to obtain a water-repellent coating agent X1.

[0060] <Manufacturing Examples 4-14: Manufacturing of Water-Repellent Coating Agents X2-12> Water-repellent coating agents X2 to X12 were obtained in the same manner as in Production Example 3, except that the types and amounts of acrylic resin, hydrocarbon wax, and inorganic fine particles were changed according to Table 1.

[0061] [Table 1]

[0062] (Manufacturing of barrier laminates) <Example 1> Water-repellent paper P1 Dilution was performed by adding 10 parts water to 100 parts of water-repellent coating agent X1, and dilution was also performed by adding 20 parts of a mixed solvent (water / isopropyl alcohol = 50 / 50) to 100 parts of anchor coating agent. Subsequently, a paper substrate (Daio Paper Corporation Nagoya Saraki Ryuo, basis weight 70 g / m²) was used. 2 Using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm, a diluted anchor coat agent was printed onto the glossy surface of a single-sided glossy paper (or similar) at a printing speed of 30 m / min and an in-line oven at 80°C to form an anchor coat layer. On the anchor coat layer, using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm, a diluted water-repellent coating agent X1 was printed at a printing speed of 30 m / min and an in-line oven at 80°C to form a water-repellent layer, thereby obtaining water-repellent paper P1 with the configuration of paper substrate / anchor coat layer / water-repellent layer. The mass per unit area of ​​the anchor coat layer of water-repellent paper P1 is 2.0 g / m². 2 The mass per unit area of ​​the water-repellent layer is 3.0 g / m². 2 That was the case.

[0063] <Examples 2-15, Comparative Examples 1 and 2> Water-repellent paper P2-17 Laminates P2-1 were obtained in the same manner as in Example 1, except that the type of water-repellent coating agent, the mass of the water-repellent coating agent per unit area, the basis weight of the paper substrate, and the lamination configuration were changed to achieve the configurations shown in Table 2. In Examples 2-15 and Comparative Examples 1 and 2, the water-repellent layer was formed directly on the glossy surface of the paper substrate, rather than on the anchor coat layer. In Example 3, the mass per unit area was increased to 5 g / m² by printing the water-repellent coating agent twice. 2 In Comparative Example 1, the water-repellent coating agent was printed in four layers, resulting in a mass of 10 g / m² per unit area. 2 That's what I decided. In Table 2, the paper substrate used in Example 14 was Nippon Paper Industries' standard form paper (basis weight 20 g / m²). 2 ) and the paper substrate used in Example 15 was K-liner manufactured by Kashiwara Paper Processing Co., Ltd. (basis weight 210 g / m²). 2 )

[0064] The water-repellent paper obtained was evaluated as follows.

[0065] <Water repellency> From the obtained water-repellent paper, rectangular test pieces measuring 300 mm x 200 mm were cut out. The water-repellent side of the test piece was placed facing upwards on a stand inclined at a 45° angle, and the water repellency was measured in accordance with JAPAN TAPPI No. 68 and evaluated according to the following criteria. A, B, and C represent ranges that are acceptable for practical use. [Evaluation Criteria] A (Excellent): Water repellency R9~R10 B (Good): Water repellency R6~R8 C (acceptable): Water repellency R3~R5 D (not allowed): Water repellency R0~R2

[0066] <Blocking resistance test> Two 40mm square pieces were cut from the obtained water-repellent paper. The water-repellent layer of one piece of water-repellent paper and the paper base material of the other piece of water-repellent paper were completely overlapped, and the pieces were left standing for 24 hours at 40°C and 80% RH under a 10kg load. After that, the two overlapping pieces of water-repellent paper were separated, and the state of peeling of the water-repellent layer was visually observed and evaluated according to the following criteria. Grades A, B, and C represent a range that is acceptable for practical use. [Evaluation Criteria] A (Excellent): No resistance during peeling, and no damage to the water-repellent layer. B (Good): There is some resistance when peeling, but the water-repellent layer is not damaged. C (Acceptable): There is some rubbing in the water-repellent layer, and the area affected by rubbing is 20% or less. D (Unacceptable): There is tangles in the water-repellent layer, and the area affected by tangles exceeds 20% of the total area.

[0067] <Water friction resistance> A rectangular test piece measuring 25 mm x 170 mm was cut from the obtained water-repellent paper. Using a JSPS-type friction fastness tester, Kanakin No. 3 paper containing 0.1 parts of water was used as the test paper, and a load of 200 g was applied. The number of cycles required for the paper substrate to tear was evaluated according to the following criteria. A, B, and C represent ranges that are acceptable for practical use. [Evaluation Criteria] A (Excellent): Number of round trips: 20 or more. B (Good): Number of round trips: 10 or more, but less than 20. C (Acceptable): Number of round trips is 5 or more but less than 10. D (Not allowed): Fewer than 5 round trips.

[0068] [Table 2]

[0069] Based on the above, in Comparative Example 1, the mass per unit area of ​​the water-repellent layer is 5 g / m². 2 Because it was too thin, it had poor blocking resistance. In Comparative Example 2, the water-repellent layer did not contain hydrocarbon wax, resulting in poor water repellency and water friction resistance. In contrast, one example shows a water-repellent layer comprising an acrylic resin and a hydrocarbon wax, with a mass of 5 g / m² per unit area of ​​the water-repellent layer. 2 Therefore, it had excellent water repellency, water abrasion resistance, and blocking resistance.

Claims

1. This is a water-repellent paper having a paper base material and a water-repellent layer. The water-repellent layer comprises an acrylic resin and a hydrocarbon wax. The mass per unit area of ​​the water-repellent layer is 5 g / m². ２ The following is water-repellent paper.

2. The water-repellent paper according to claim 1, wherein the hydrocarbon wax is at least one selected from the group consisting of paraffin wax, microcrystalline wax, carnauba wax, and polyethylene wax.

3. The water-repellent paper according to claim 1 or 2, wherein the content ratio of acrylic resin to hydrocarbon wax is 99:1 to 80:

20.

4. The water-repellent paper according to claim 1 or 2, wherein the water-repellent layer further comprises inorganic fine particles, and the inorganic fine particles are at least one selected from the group consisting of silica, calcium carbonate, and kaolin.

5. The water-repellent paper according to claim 4, wherein the content ratio of hydrocarbon wax to inorganic fine particles is 90:10 to 10:

90.

6. Furthermore, the water-repellent paper according to claim 1 or 2, wherein the anchor layer is located between the paper substrate and the water-repellent layer, and the anchor layer comprises at least one selected from the group consisting of acrylic resin, urethane resin, cellulose resin, and polylactic acid resin.

7. The basis weight of the paper substrate is 30 to 200 g / m². ２ The water-repellent paper according to claim 1 or 2.

8. A method for manufacturing water-repellent paper having a paper substrate and a water-repellent layer, The process includes a step of applying a water-repellent coating agent containing an acrylic resin and a hydrocarbon wax onto a paper substrate to form the water-repellent layer, The mass per unit area of ​​the water-repellent layer is 5 g / m². ２ The following is a method for manufacturing water-repellent paper.

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