Oil-resistant paper

Abstract

This oil-resistant paper is obtained by coating a pulp-containing paper substrate with a coating material. The pulp contains hardwood pulp; the coating material contains oil and / or fat; and the areal weight of the paper substrate is 10.0-50.0 g / m2. The coating amount for the coating material is 1-20 mass% of the paper substrate in terms of the solid fraction, and the content of the oil and / or fat is at least 60 mass% of the solid fraction of the coating material. The paper substrate may contain both a wet paper strength agent and a sizing agent. The coating material may contain one or both of a thickener and a water retention agent.

Description

Oil-resistant paper

[0001] This invention relates to oil-resistant paper. This application claims priority based on Japanese Patent Application No. 2024-180471, filed in Japan on October 16, 2024, the contents of which are incorporated herein by reference.

[0002] For packaging paper used in applications requiring oil resistance, water resistance, and water vapor permeability, such as hamburger and hot dog wrappers, laminated paper, which consists of a paper base laminated with polyethylene on one side, is a well-known option.

[0003] On the other hand, oil-resistant paper is known as packaging paper that has oil resistance, in which oil-based agents are used to impart oil resistance to the paper base material. Conventionally, fluorine-based oil-resistant agents were commonly used, but in recent years, non-fluorine-based oil-resistant agents have come into use, taking into consideration the environment and safety.

[0004] Hydrophobized starch is known as a non-fluorinated oil-resistant agent. Patent Document 1 discloses a paper product in which a coating composition containing hydrophobized starch is applied to a paper substrate.

[0005] Japanese Patent Publication No. 2002-69889

[0006] The paper product described in Patent Document 1 is preferable to laminated paper using polyethylene, a synthetic resin, from an environmental standpoint because it is given oil resistance by starch. However, Patent Document 1 does not satisfy all requirements of oil resistance, water resistance, and appropriate water vapor permeability. If the water resistance is insufficient, it will tear easily when wrapping or opening hamburgers, and sauces may seep through to the other side. If the water vapor permeability is too low, water vapor from hamburgers will not pass through, causing condensation inside and potentially impairing the taste of the hamburger. If the water vapor permeability is too high, the heat retention and moisture retention will be poor, causing cracks in the buns.

[0007] The present invention aims to provide an oil-resistant paper that is excellent in oil resistance and water resistance and has appropriate water vapor permeability.

[0008] The present invention has the following aspects: [1] Oil-resistant paper comprising a paper substrate containing pulp coated with a paint, wherein the pulp contains hardwood pulp, the paint contains oil and fat, and the basis weight of the paper substrate is 10.0 to 50.0 g / m² ２ Oil-resistant paper wherein the amount of coating of the coating is 1 to 20% by mass relative to the paper substrate in terms of solid content, and the oil content is 60% by mass or more relative to the solid content of the coating. [2] Oil-resistant paper according to [1], wherein the paper substrate contains both a wet strength enhancer and a sizing agent. [3] Oil-resistant paper according to [1] or [2], wherein the coating contains either or both a thickener and a water-retaining agent. [4] Oil-resistant paper according to [3], wherein the thickener is at least one selected from the group consisting of natural polysaccharides and their derivatives. [5] Oil-resistant paper according to any one of [1] to [4], wherein the oil is a fatty acid ester. [6] Oil-resistant paper according to any one of [1] to [4], wherein the oil is plant-derived. [7] Oil-resistant paper according to any one of [1] to [6], wherein the paper substrate contains a filler. [8] Water permeability is 10 to 5000 g / (m ２ - Oil-resistant paper according to any one of [1] to [7] (Japanese). [9] Oil-resistant paper according to claim 1 or 2, wherein the disintegration freeness is 500 mL or less.

[10] Oil-resistant paper according to any one of [1] to [8] for food packaging.

[0009] According to the present invention, it is possible to provide oil-resistant paper that has excellent oil resistance, water resistance, and appropriate water vapor permeability.

[0010] In this specification, the "solids content" of a paint is the residue when the paint is heated under the conditions of the drying loss method described in JIS K 0068. "Basis weight" is measured in accordance with JIS P 8124:2011. "Water permeability" is measured in accordance with JIS Z 0208. "Oken method air permeability" is the air permeability (air permeability resistance) measured in accordance with J. TAPPI Paper and Pulp Test Method No. 5-2:2000 (Paper and cardboard - Smoothness and air permeability test methods - Part 2: Oken method). Hereinafter, the Oken method air permeability will also be simply referred to as "air permeability". The "~" indicating a numerical range means that the values ​​described before and after it are included as the lower and upper limits. The lower and upper limits of the numerical ranges disclosed in this specification can be arbitrarily combined to create new numerical ranges.

[0011] <Oil-resistant paper> Oil-resistant paper according to one embodiment of the present invention is obtained by coating a paper substrate with a paint. The paper substrate contains pulp. The paint contains oils and fats.

[0012] A paper substrate coated with paint has solid components of the paint, such as oils and greases, adhering to it. From the viewpoint of oil resistance and water resistance, it is preferable that at least a portion of the solid components of the paint are located on the surface of the paper substrate. In this case, oil-resistant paper has a coating layer consisting of solid components of the paint on the surface of the paper substrate. A portion of the solid components of the paint may be located inside the surface of the paper substrate.

[0013] (Paper substrate) The paper substrate contains pulp. The paper substrate may further contain internal additives.

[0014] Pulp includes hardwood pulp. The inclusion of hardwood pulp provides excellent design possibilities through printing. Hardwood pulp can be any pulp made from hardwoods, and its manufacturing method is not particularly limited. Examples include chemical pulps such as bleached hardwood kraft pulp (LBKP) and bleached hardwood sulfite pulp (LBSP). Other examples include unbleached, semi-bleached, and bleached pulps such as stone ground pulp (GP), pressure stone ground pulp (PGW), refiner ground pulp (RGP), chemiground pulp (CGP), thermomechanical pulp (TMP), and chemothermetic pulp (CTMP). Sulfite pulp and recycled paper pulp are also examples. Examples of hardwoods used as raw materials for hardwood pulp include Eucalyptus, Fagus, Oak, Betula, and Acacia genera. Specific examples include Eucalyptus globulus, Eucalyptus grandis, Eucalyptus eurograndis, Eucalyptus maculata, Eucalyptus punctata, Eucalyptus saligna, Eucalyptus telenicornis, Eucalyptus pelita, Eucalyptus camaldrensis, Eucalyptus deglupta, Eucalyptus brassiana, Eucalyptus naitens, Eucalyptus europhylla, Acacia mangium, Acacia auricarformis, Acacia catechu, Acacia decalens, Acacia holoselicia, Acacia leptocarpa, Acacia maideniai, Acacia melancii, Acacia melanoxylon, Acacia neriphora, Acacia silivestris, Acacia peregrinalis, Acacia auracocarpa, and Acacia classicalcarpa. Hybrids of these species are also acceptable. From the standpoint of production efficiency, it is preferable to use Eucalyptus species such as Eucalyptus camaldrensis. Broadleaf trees may be used individually or in combination of two or more species.

[0015] The pulp may contain other types of pulp besides hardwood pulp. Examples of other types of pulp include softwood pulp, non-wood pulp (such as hemp pulp), and synthetic pulp. Two or more of these may be used in combination.

[0016] Other types of pulp include softwood pulp, which is preferred for its increased tear strength. Softwood pulp can be made from softwood as its raw material, and its manufacturing method is not particularly limited. Examples include chemical pulps such as bleached softwood kraft pulp (NBKP) and bleached softwood sulfite pulp (NBSP). Other examples include unbleached, semi-bleached, and bleached pulps such as stone ground pulp (GP), pressure stone ground pulp (PGW), refiner ground pulp (RGP), chemiground pulp (CGP), thermomechanical pulp (TMP), and chemothermetic pulp (CTMP). Sulfite pulp and recycled paper pulp are also examples. Examples of softwoods used as raw materials for softwood pulp include spruce, hemlock, fir, pine, and cedar. Specific examples include white spruce, black spruce, hemlock, white fir, Douglas fir, balsam fir, southern pine, radiata pine, lodgepole pine, Elliott pine, Caribbean pine, slash pine, redwood, aspen, larch, and red cedar. Coniferous trees may be used individually or in combination of two or more species.

[0017] The hardwood pulp content is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass, based on the total mass of the pulp. If the pulp contains other pulps, the hardwood pulp content is preferably 50% by mass or less, and more preferably 70% by mass or less, based on the total mass of the pulp.

[0018] In paper substrates, it is preferable that the content of hardwood pulp is 50 to 100% by mass and the content of softwood pulp is 0 to 50% by mass relative to the total mass of pulp; more preferably, the content of hardwood pulp is 70 to 100% by mass and the content of softwood pulp is 0 to 30% by mass; and even more preferably, the content of hardwood pulp is 90 to 100% by mass and the content of softwood pulp is 0 to 10% by mass. That is, the mass ratio of hardwood pulp to softwood pulp (L / N ratio) is preferably 50 / 50 to 100 / 0, more preferably 70 / 30 to 100 / 0, and even more preferably 90 / 10 to 100 / 0.

[0019] The pulp content in the paper substrate is preferably 70% by mass or more, and more preferably 90% by mass or more, relative to the total mass of the paper substrate. The masses of the paper substrate and pulp are oven-dry masses. Oven-dry masses are measured in accordance with JIS P 8203. The total content of pulp and internal additives shall not exceed 100% by mass relative to the total mass of the paper substrate.

[0020] Examples of internal additives include fillers, wet strength enhancers, paper strength enhancers, sizing agents, yield enhancers, pH adjusters, water drainage enhancers, water resistance enhancers, softeners, antistatic agents, defoamers, slime control agents, dyes, and pigments. Two or more internal additives may be used in combination.

[0021] The paper substrate preferably contains a filler. When the coating described later is applied to the paper substrate, oils and greases fill the voids in the paper substrate, increasing its transparency. In some cases, it is undesirable for articles wrapped in oil-resistant paper to be visible from the outside. By including a filler in the paper substrate, the opacity, which makes articles wrapped in oil-resistant paper difficult to see from the outside, can be improved. Examples of fillers include titanium dioxide, kaolin, calcium carbonate, talc, and silica. Among these, titanium dioxide is preferred in terms of opacity. Two or more types of fillers may be used in combination. The amount of filler in the paper substrate varies depending on the desired opacity, but it is preferably 1 to 15 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of pulp.

[0022] The paper substrate preferably contains a wet strength enhancer. By including a wet strength enhancer in the paper substrate, the pulp fibers can be crosslinked, thereby increasing the wet strength of the paper substrate. If the wet strength of the paper substrate is low, the paper substrate may tear when the coating composition is applied to it during the production of oil-resistant paper. Known wet strength enhancers can be used, such as polyamide epichlorohydrin resin, epichlorohydrin-based wet strength enhancers, polyvinylamine resin, polyethyleneimine resin, melamine resin, and citric acid. Among these, epichlorohydrin-based wet strength enhancers are preferred, and polyamide epichlorohydrin resin is more preferred. The content of the wet strength enhancer in the paper substrate is preferably 0.1 to 1.5 parts by mass, and more preferably 0.3 to 0.8 parts by mass, per 100 parts by mass of pulp.

[0023] The paper substrate preferably contains a sizing agent. By including a sizing agent in the paper substrate, when a coating is applied to the paper substrate, the coating does not penetrate easily, a sufficient coating layer is formed on the surface of the paper substrate, and superior oil resistance and water resistance are achieved. Examples of sizing agents include rosin-based sizing agents, alkyl ketene dimer-based sizing agents, alkenyl succinic anhydride-based sizing agents, and fatty acid sizing agents. Among these, rosin-based sizing agents are preferred in terms of sizing properties against high-temperature foods and sauces. The content of the sizing agent in the paper substrate is preferably 0.1 to 1.0 parts by mass, and more preferably 0.2 to 0.5 parts by mass, per 100 parts by mass of pulp.

[0024] The paper substrate is particularly preferably composed of both a wet strength enhancer and a sizing agent. The total content of the wet strength enhancer and sizing agent is preferably 0.2 to 2.5 parts by mass, and more preferably 0.5 to 1.3 parts by mass, per 100 parts by mass of pulp.

[0025] A primer layer may be applied to the paper substrate before applying the oil-resistant coating. The primer layer preferably contains a filler. The inclusion of a filler prevents excessive penetration of the oil-resistant coating into the substrate, allowing for high performance with a smaller coating amount. Examples of fillers include kaolin, artificial mica, calcium carbonate, talc, silica, and titanium dioxide. Two or more fillers may be used in combination.

[0026] The basis weight of the paper substrate is 10.0 to 50.0 g / m². ２ The range is 15.0 to 45.0 g / m². ２ Preferably, 19.0 to 41.0 g / m² ２ This is more preferable. If the basis weight of the paper substrate is above the lower limit, the oil-resistant paper has sufficient strength as packaging paper. If the basis weight of the paper substrate is below the upper limit, it is easier to wrap food and other items in the oil-resistant paper.

[0027] (Paint) Paint (hereinafter also referred to as "paint composition") contains oils and fats. Paint typically further contains water. The water is removed by drying after application. Paint may further contain solid components other than oils and fats.

[0028] Oils and fats function as oil-resistant agents. Examples of oils and fats include fatty acid esters and waxes (excluding fatty acid esters). Examples of fatty acid esters include esters of fatty acids having 10 to 30 carbon atoms and alcohols. An example of an alcohol is glycerin. Specific examples of fatty acid esters include hydrogenated castor oil, rice wax, carnauba wax, hydrogenated palm oil, hydrogenated soybean oil, and beeswax. Examples of waxes (excluding fatty acid esters) include polyolefin waxes such as paraffin wax, carboxyl group-containing paraffin wax, microcrystalline wax, polyethylene wax, carboxyl group-containing polyethylene wax, polypropylene wax, and ethylene-propylene copolymer wax, as well as candelilla wax, rice wax, montan wax, fatty acids such as stearic acid, fatty acid amides such as stearic acid amide, stearate bisamide, oleic acid amide, and palmitic acid amide, and fatty acid metal salts such as zinc stearate and calcium stearate.

[0029] As for the oils and fats, fatty acid esters are preferred from the viewpoint of oil resistance. Fatty acid esters may be used in combination with other oils and fats. The ratio of fatty acid esters to the total mass of oils and fats is preferably 50% by mass or more, preferably 70% by mass or more, and may be 100% by mass.

[0030] For oils and fats, plant-derived oils and fats are preferred from an environmental and safety standpoint. Among these, plant-derived fatty acid esters such as hydrogenated castor oil, carnauba wax, and rice wax are preferred. Two or more types of oils and fats may be used in combination.

[0031] The melting point of the oil is preferably between 40°C and 120°C. If the melting point is below the upper limit, the oil resistance is more likely to improve as it melts and forms a film due to the heat generated during coating and drying. If the melting point of the oil is above the lower limit, it is less likely to block during the actual use of the oil-resistant paper.

[0032] The oil content is 60% by mass or more, preferably 90% by mass or more, and may be 100% by mass, based on the solid content of the coating composition. When the coating composition contains solid components other than oil, the content of components other than oil is 40% by mass or less, preferably 10% by mass or less, based on the solid content of the coating.

[0033] Examples of the solid components other than oil include thickeners, water retention agents, defoamers, fillers, pigments, film-forming aids, binders, dyes, and lubricants. Two or more of these may be used in combination.

[0034] The coating preferably contains either or both of a thickener and a water retention agent. By containing either or both of a thickener and a water retention agent, when the coating is applied to a paper substrate, the coating is less likely to penetrate, a coating layer is sufficiently formed on the surface of the paper substrate, and more excellent oil resistance is exhibited. Examples of the thickener or water retention agent include natural polysaccharides such as sodium alginate, carboxymethyl cellulose, guar gum, starch, and their derivatives, polyvinyl alcohol, polyacrylic acid and its salts, gelatin, gum arabic, casein, and the like. Among them, at least one selected from the group consisting of natural polysaccharides and their derivatives is preferable from the viewpoints of environment and film-forming properties.

[0035] The total content of the thickener and the water retention agent is preferably 0.1 to 5.0% by mass, more preferably 0.3 to 2.0% by mass, based on the solid content of the coating. When the total content is at least the above lower limit value, the oil resistance tends to be more excellent. When the total content is at most the above upper limit value, the water resistance tends to be more excellent. The total content of the oil, thickener, and water retention agent is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass, based on the solid content of the coating.

[0036] Examples of the filler include kaolin, synthetic mica, calcium carbonate, talc, silica, titanium oxide, and the like. Kaolin or titanium oxide is preferable from the viewpoints of improving the barrier property and opacity of the oil-resistant paper.

[0037] Examples of the film-forming aid or binder include starches and their derivatives, water-soluble polymers such as polyvinyl alcohol, etc. The content of the water-soluble polymer is preferably 80 parts by mass or less with respect to 100 parts by mass of the oil and fat. By being below the above upper limit value, the water resistance of the oil-resistant paper can be enhanced.

[0038] The coating amount of the paint is 1 to 20% by mass in terms of solid content with respect to the paper substrate, preferably 2 to 18% by mass, and more preferably 5 to 15% by mass. When the coating amount of the paint is within the above range, the water vapor permeability tends to be within an appropriate range. Also, when the coating amount of the paint is at least the above lower limit value, it tends to be excellent in oil resistance and water resistance. Further, the content of the oil and fat in the oil-resistant paper after drying is preferably 4 to 25% by mass in terms of solid content with respect to the paper substrate, more preferably 6 to 20% by mass, and even more preferably 8 to 15% by mass. When the content of the oil and fat in the oil-resistant paper after drying is within the above range, the water vapor permeability tends to be within an appropriate range. Also, when the content of the oil and fat in the oil-resistant paper after drying is at least the above lower limit value, it tends to be excellent in oil resistance and water resistance.

[0039] (Properties of the oil-resistant paper) The moisture permeability of the oil-resistant paper is preferably less than 5000 g / (m ２ ·day), more preferably 4000 g / (m ２ ·day) or less, more preferably 3500 g / (m ２ ·day) or less, more preferably 3000 g / (m ２ ·day) or less, more preferably 2000 g / (m ２ ·day) or less, even more preferably 10 g / (m ２ ·day) or more, preferably 30 g / (m ２ ·day) or more, more preferably 100 g / (m ２ ·day) or more. When the moisture permeability of the oil-resistant paper is at most the above upper limit value, by suppressing the permeation of water vapor, it is excellent in heat retention and moisture retention of food. When the moisture permeability of the oil-resistant paper is at least the above lower limit value, by allowing water vapor to permeate moderately, it is possible to prevent dew condensation from occurring inside the oil-resistant paper after packaging and water droplets from adhering to the food. The moisture permeability of the oil-resistant paper can be adjusted by the air permeability of the paper substrate, the coating amount of the paint, the components contained in the paint, etc.

[0040] The air permeability of the oil-resistant paper is preferably less than 100,000 seconds, more preferably 60,000 seconds or less, and even more preferably 30,000 seconds or less. The lower limit of the air permeability is not particularly limited, but for example, it is 25 seconds or more. The air permeability of the oil-resistant paper can be adjusted by the air permeability of the paper substrate, the amount of coating applied, the components contained in the coating, etc.

[0041] The Canadian standard filtration freeness (hereinafter also referred to as "disintegration freeness") of the pulp obtained by disintegrating oil-resistant paper is preferably 500 mL or less, more preferably 450 mL or less, and preferably 150 mL or more, and more preferably 250 mL or more. When the disintegration freeness is below the above upper limit, the paint does not easily penetrate the paper substrate, and the oil resistance and water resistance tend to be better. Also, when the disintegration freeness is within the above range, the tear strength of the oil-resistant paper tends to be high and the processability tends to be excellent. Disintegration of oil-resistant paper is carried out in accordance with JIS P 8220-1:2012. The Canadian standard filtration freeness is measured in accordance with JIS P 8121-2:2012. Disintegration freeness can be adjusted by the degree of pulp beating.

[0042] (Method for manufacturing oil-resistant paper) The oil-resistant paper according to this embodiment can be manufactured, for example, by coating the paper substrate with the coating in the amount specified above and drying it.

[0043] Paper substrates can be manufactured, for example, by papermaking using various paper machines, forming wet paper, and drying it. The paper machines are not particularly limited. Examples include long-wire paper machines, gap former type paper machines, cylinder paper machines, and short-wire paper machines. From an economic standpoint, paper machines equipped with an on-machine coating machine are preferred.

[0044] For the preparation of pulp slurry for papermaking, it is preferable to disintegrate pulp containing hardwood pulp and beat it using a refiner and beater to give the pulp appropriate flexibility and fluffiness. However, the pulp beating method is not particularly limited. The preferred range for disintegration-freeness, which is an indicator of the degree of pulp beating, is as described above. The beaten pulp may be mixed with an internal additive as needed, dispersed in water, and a pulp slurry of a concentration suitable for papermaking may be prepared.

[0045] The wet paper obtained from the paper machine is preferably dried using a multi-stage cylinder dryer, an air dryer, or a Yankee dryer.

[0046] Paper substrates typically have higher moisture permeability and lower air permeability than the final oil-resistant paper. The moisture permeability and air permeability of paper substrates can be adjusted by the freeness of the pulp forming the substrate, the type and amount of additives used, the basis weight, and density of the paper substrate. For example, higher pulp freeness tends to result in higher moisture permeability and lower air permeability. Similarly, a lower sizing agent content in the paper substrate tends to result in higher moisture permeability and lower air permeability.

[0047] The coating can be prepared by mixing the various materials that make up the coating. The method of coating the coating is not particularly limited, and various coating machines that are generally available can be used. Examples of coating machines include blade coaters, air knife coaters, roll coaters, reverse roll coaters, bar coaters, curtain coaters, slot die coaters, gravure coaters, champlex coaters, brush coaters, slide bead coaters, two-roll size press coaters, pound size press coaters, rod metering size press coaters, blade metering size press coaters, short dwell coaters, gate roll coaters, and nip coaters with a calender. Among these, on-machine coating machines are preferred in terms of productivity. Examples of on-machine coating machines include blade coaters, bar coaters, gate roll coaters, rod metering size press coaters, blade metering size press coaters, and pound size press coaters. The coating may be applied to one side or both sides of the paper substrate. From the viewpoint of printability, it is preferable to coat one side.

[0048] If necessary, the oil-resistant paper may be smoothed. The smoothing treatment can be performed on-machine or off-machine using a standard smoothing device such as a supercalender, gloss calender, or soft calender. The paper substrate may be smoothed before coating with paint, as long as it does not impair the effects of the invention.

[0049] The resulting oil-resistant paper is wound into a roll. Subsequently, the ends of the roll may be removed using a slitter to adjust the width of the oil-resistant paper to match the width of the processing machine in the next process.

[0050] The uses of the oil-resistant paper of this embodiment are not particularly limited, but examples include packaging materials and liners. The oil-resistant paper of this embodiment is suitable as a packaging material, and in particular for food packaging. Examples of items to be packaged with the packaging material include fried foods, bread, confectionery and other foods, and desiccants. Among these, food is preferred, and food containing oil and moisture is more preferred, as the excellent water vapor permeability is highly useful. Food that is packaged while containing oil and moisture, or food that contains oil and moisture and is packaged at a high temperature, generating water vapor even after packaging, is particularly preferred. Specific examples of food include hamburgers, hot dogs, croquettes, steamed buns and shumai. The oil-resistant paper may be used as a packaging material as is, or it may be processed in some way before being used as a packaging material. Known processing methods can be applied. Examples of packaging materials made by processing oil-resistant paper include gusseted bags, single-opening bags, flat bags, square-bottom bags and other various containers. Known packaging methods can be applied to package items with the packaging material.

[0051] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description. "Parts" and "%" refer to "parts by mass" and "% by mass," respectively.

[0052] (Example 1) <Manufacturing of paper substrate> Pulp consisting of 70% by mass of LBKP and 30% by mass of NBKP (L / N ratio: 70 / 30) was mixed with the following internal additives: filler (titanium dioxide, trade name: R780, manufactured by Ishihara Chemical Co., Ltd.) at 5% relative to the oven-dry mass of pulp, aluminum sulfate at 4.0% relative to the oven-dry mass of pulp, paper strength enhancer (polyacrylamide, trade name: FT-12, manufactured by Arakawa Chemical Industries, Ltd.) at 0.6% relative to the oven-dry mass of pulp, wet paper strength enhancer (polyamide epichlorohydrin resin, trade name: WS4024, manufactured by Seikoh PMC Co., Ltd.) at 0.3% relative to the oven-dry mass of pulp, and sizing agent (rosin, trade name: AL1220, manufactured by Seikoh PMC Co., Ltd.) at 0.3% relative to the oven-dry mass of pulp. Paper was then manufactured on a paper machine with a basis weight of 23 g / m². ２The paper was manufactured to obtain a paper base material. The degree of pulp beating was adjusted so that the disintegration-freeness of the resulting oil-resistant paper was 200 mL. The L / N ratio is the mass ratio expressed as hardwood pulp / softwood pulp. The basis weight was measured in accordance with JIS P 8124:2011 (the same applies below).

[0053] <Preparation of Paint> A paint (solid content concentration 28%) was prepared by mixing 99 parts of the following oil 1, 1 part of the following thickener, and water. Oil 1: Fatty acid ester (product name: SEIKOAT-G T-EF201, manufactured by Seikoh PMC, melting point 86°C). Thickener: Sodium alginate (product name: Snow Algin, manufactured by Fuji Chemical Industry Co., Ltd.).

[0054] <Coating> Using a gravure coater, the coating is applied to one side of the paper substrate, with a coating amount of 3 g / m² after drying. ２ The paper was coated and dried to obtain oil-resistant paper.

[0055] (Example 2) The coating amount of paint (after drying) was 2.1 g / m ２ Except for the above, oil-resistant paper was obtained in the same manner as in Example 1.

[0056] (Example 3) Oil-resistant paper was obtained in the same manner as in Example 1, except that oil 2 was used instead of oil 1 in the preparation of the coating. Oil 2: Carnauba wax (product name: EMUSTAR-0413, manufactured by Nippon Seiro Co., Ltd., melting point 85°C).

[0057] (Example 4) Oil-resistant paper was obtained in the same manner as in Example 1, except that the amount of oil 1 was 100 parts and no thickener was added in the preparation of the paint.

[0058] (Example 5) Oil-resistant paper was obtained in the same manner as in Example 1, except that 100% by mass of LBKP was used as the pulp.

[0059] (Example 6) Oil-resistant paper was obtained in the same manner as in Example 1, except that the pulp consisted of 30% by mass of LBKP and 70% by mass of NBKP.

[0060] (Example 7) Oil-resistant paper was obtained in the same manner as in Example 1, except that no wet paper strength enhancer was added as an internal additive.

[0061] (Example 8) Oil-resistant paper was obtained in the same manner as in Example 1, except that no sizing agent was added as an internal additive.

[0062] (Example 9) Oil-resistant paper was obtained in the same manner as in Example 1, except that the disintegration-freeness of the resulting oil-resistant paper was adjusted to 400 ml.

[0063] (Example 10) Oil-resistant paper was obtained in the same manner as in Example 1, except that in the preparation of the paint, 70 parts of oil 1, 30 parts of hydrophobically modified starch (product name: Filmkote 370, manufactured by Ingredion Co., Ltd.), and water were mixed to make the paint.

[0064] (Comparative Example 1) Oil-resistant paper was obtained in the same manner as in Example 1, except that 100 parts of hydrophobized starch (trade name: Filmkote 370, manufactured by Ingredion) were used instead of oil 1 and thickener in the preparation of the paint composition.

[0065] (Comparative Example 2) The coating amount of paint (after drying) was 0.2 g / m ２ Except for the above, oil-resistant paper was obtained in the same manner as in Example 1.

[0066] (Comparative Example 3) Oil-resistant paper was obtained in the same manner as in Example 1, except that in the preparation of the paint, 50 parts of oil 1, 50 parts of hydrophobically modified starch (product name: Filmkote 370, manufactured by Ingredion Co., Ltd.), and water were mixed to make the paint.

[0067] (Evaluation) The following measurements and evaluations were performed on the obtained oil-resistant paper. The results are shown in Table 1.

[0068] <Measurement of Air Permeability> The air permeability of oil-resistant paper was measured in accordance with J. TAPPI Paper and Pulp Test Methods No. 5-2:2000 (Paper and cardboard - Test methods for smoothness and air permeability - Part 2: Oken method). The higher the air permeability, the less air can pass through.

[0069] <Measurement of Disintegration Freeness> Oil-resistant paper was disintegrated in accordance with JIS P 8220-1, and the freeness (Canadian standard filtration rate) of the obtained pulp was measured in accordance with JIS P 8121-2:2012, and this value was defined as the disintegration freeness.

[0070] <Evaluation of Oil Resistance (Kit)> The oil resistance (kit) of oil-resistant paper was evaluated in accordance with "Paper and cardboard - Oil repellency test method - Kit method" as specified in J. TAPPI No. 41:2000. A higher numerical value indicates better oil resistance.

[0071] <Measurement of moisture permeability> The moisture permeability of oil-resistant paper was measured in accordance with JIS Z 0208. The lower the moisture permeability, the less water vapor is transmitted.

[0072] <Evaluation of water resistance> 200 μl of ion-exchanged water at 25°C was dropped onto the oil-resistant paper using a dropper, and wiped off with a cloth after 10 seconds. The condition of the oil-resistant paper after wiping was visually evaluated according to the following criteria. ○: No obvious water penetration occurred. △: Slight water stains were present. ×: Significant and clearly visible water penetration.

[0073]

[0074] The oil-resistant papers of Examples 1 to 10 had appropriate water vapor permeability (moisture permeability) and obtained good results in the evaluation of oil resistance (kit) and water resistance. On the other hand, Comparative Example 1, which used starch instead of oil, had high water vapor permeability and poor results in the evaluation of water resistance. Comparative Example 2, in which the amount of coating was less than 1% of the paper substrate, also had high water vapor permeability and poor results in the evaluation of water resistance. Furthermore, its oil resistance (kit) was also inferior. In addition, even in the mixture of oil and starch, Comparative Example 3, which had a high proportion of starch, showed inferior water resistance.

[0075] According to the present invention, it is possible to provide oil-resistant paper that has excellent oil resistance, water resistance, and appropriate water vapor permeability.

Claims

1. Oil-resistant paper comprising a paper substrate containing pulp coated with a paint, wherein the pulp contains hardwood pulp, the paint contains oil and fat, and the basis weight of the paper substrate is 10.0 to 50.0 g / m². ２ Oil-resistant paper wherein the amount of coating of the paint is 1 to 20% by mass relative to the paper substrate in terms of solid content, and the oil content is 60% by mass or more relative to the solid content of the paint.

2. The oil-resistant paper according to claim 1, wherein the paper substrate comprises both a wet strength enhancer and a sizing agent.

3. The oil-resistant paper according to claim 1 or 2, wherein the coating comprises either a thickener or a water-retaining agent or both.

4. The oil-resistant paper according to claim 3, wherein the thickening agent is at least one selected from the group consisting of natural polysaccharides and their derivatives.

5. The oil-resistant paper according to claim 1 or 2, wherein the oil is a fatty acid ester.

6. The oil-resistant paper according to claim 1 or 2, wherein the oil is of plant origin.

7. The oil-resistant paper according to claim 1 or 2, wherein the paper substrate contains a filler.

8. Moisture permeability of 10-5000 g / m ２ Oil-resistant paper according to claim 1 or 2, wherein the paper is a Japanese product.

9. The oil-resistant paper according to claim 1 or 2, wherein the disintegration freeness is 500 mL or less.

10. Oil-resistant paper according to claim 1 or 2, for use in food packaging.

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