Oil-resistant paper

Abstract

This oil-resistant paper contains a paper base material containing pulp, and hydrophobized starch attached to the paper base material, wherein the amylose content of the hydrophobized starch is less than 18 mass%, the amount of amylose contained in the hydrophobized starch is 0.5‒5.0 mass% with respect to the total mass of the paper base material, and the Oken air permeability is less than 20,000 seconds.　The hydrophobized starch may be an esterified starch. The esterified starch may be octenyl succinate starch. 10 mass% or more of the pulp may be softwood pulp.

Description

Oil-resistant paper

[0001] This invention relates to oil-resistant paper. This application claims priority based on Japanese Patent Application No. 2024-180483, filed in Japan on October 16, 2024, the contents of which are incorporated herein by reference.

[0002] Oil-resistant paper, which is made by imparting oil resistance to a paper base material using an oil-resistant agent, is used for packaging food and other products. 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. Hydrophobized starch is known as a non-fluorine-based oil-resistant agent. Patent Document 1 discloses a paper product in which a coating composition containing hydrophobized starch, made from starch having a predetermined gel strength, is coated onto a paper base material.

[0003] Japanese Patent Publication No. 2002-69889

[0004] However, the paper product described in Patent Document 1 does not exhibit oil resistance throughout all layers in the thickness direction. When oil-containing foods such as fried foods come into contact with its cross-section, oil easily penetrates into the interior of the paper substrate from that area. To improve oil resistance, it is conceivable to increase the amount of coating composition applied. However, in this case, the breathability of the paper product decreases. Low breathability prevents steam from escaping, making it unsuitable for packaging high-temperature foods.

[0005] The present invention aims to provide oil-resistant paper that is excellent in breathability and oil resistance throughout all layers.

[0006] The present invention has the following embodiments: [1] Oil-resistant paper comprising a paper substrate containing pulp and hydrophobic starch attached to the paper substrate, wherein the amylose content of the hydrophobic starch is less than 18% by mass, the amount of amylose contained in the hydrophobic starch is 0.5 to 5.0% by mass relative to the total mass of the paper substrate, and the Wangken air permeability is less than 20,000 seconds. [1A] Oil-resistant paper comprising a paper substrate containing pulp and hydrophobic starch attached to the paper substrate, wherein the amylose content of the hydrophobic starch is 1 to 17% by mass, and the Wangken air permeability is less than 20,000 seconds. [2] Oil-resistant paper according to [1] or [1A], wherein the hydrophobic starch is esterified starch. [3] Oil-resistant paper according to [2], wherein the esterified starch is octenyl succinate starch. [4] Oil-resistant paper according to [1], [1A] or [2], wherein 10% by mass or more of the pulp is softwood pulp. [5] Basis weight of 10 to 100 g / m² ２ Oil-resistant paper according to any one of [1], [1A] to [4]. [6] Oil-resistant paper according to any one of [1], [1A] to [5], further comprising a crosslinking agent for crosslinking the hydrophobic starch. [7] Oil-resistant paper according to [6], wherein the content of the crosslinking agent is 1 to 10% by mass relative to the total of the hydrophobic starch and the crosslinking agent. [8] Oil-resistant paper according to any one of [1], [1A] to [7], for food packaging.

[0007] According to the present invention, it is possible to provide oil-resistant paper with excellent breathability and oil resistance throughout the entire layer.

[0008] In this specification, "Wang Ken method air permeability" refers to 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: Wang Ken method). Hereafter, Wang Ken method air permeability will also be simply referred to as "air permeability". The "amylose content" of starch is the mass ratio of amylose to the total mass of amylose and amylopectin that constitute the starch. Amylose and amylopectin may each be chemically modified. The amylose content is measured by enzyme chromatography or the like. The "~" indicating a numerical range means that the values ​​written 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.

[0009] <Oil-resistant paper> Oil-resistant paper according to one embodiment of the present invention comprises a paper substrate and hydrophobic starch attached to the paper substrate.

[0010] In oil-resistant paper, it is preferable that at least a portion of the hydrophobic starch is impregnated into the paper substrate. In other words, it is preferable that at least a portion of the hydrophobic starch is located inside the surface of the paper substrate. If all of the hydrophobic starch is located on the surface of the paper substrate, the surface of the paper substrate will be covered with a layer of hydrophobic starch, which may impair the breathability of the paper substrate. By impregnating at least a portion of the hydrophobic starch into the paper substrate, the breathability of the paper substrate is less likely to be impaired, and the presence of hydrophobic starch throughout the entire layer makes it easier for oil resistance to be exhibited not only on the surface of the paper substrate but throughout the entire layer. Oil-resistant paper in which at least a portion of the hydrophobic starch is impregnated into the paper substrate is typically obtained by applying a coating composition containing hydrophobic starch and water to the paper substrate and drying it. Details will be described later.

[0011] (Paper substrate) The paper substrate contains pulp. The paper substrate may further contain internal additives. The paper substrate may be general paper, such as bleached kraft paper, unbleached kraft paper, fine paper, cardboard, liner paper, coated paper, glossy paper, glassine paper, and graphane paper.

[0012] Examples of pulps include chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), bleached hardwood sulfite pulp (LBSP), 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.

[0013] To increase tear strength, the pulp preferably contains softwood pulp such as bleached softwood kraft pulp (NBKP) or bleached softwood sulfite pulp (NBSP). The softwood pulp content is preferably 10% by mass or more, more preferably 50% by mass or more, and may be 100% by mass, based on the total mass of the pulp.

[0014] To improve the form and printability, the pulp may contain hardwood pulp such as bleached hardwood kraft pulp (LBKP) or bleached hardwood sulfite pulp (LBSP). The hardwood pulp content may be, for example, 10% by mass or more, more than 50% by mass or more, or even 100% by mass, relative to the total mass of the pulp.

[0015] Coniferous pulp and hardwood pulp may be used in combination. Examples of coniferous trees used as raw materials for coniferous 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. Examples of hardwoods used as raw materials for hardwood pulp include eucalyptus, beech, oak, birch, and acacia. 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 viewpoint of production efficiency, it is preferable to use Eucalyptus species such as Eucalyptus camaldrensis. The broadleaf trees may be used individually or in combination of two or more species. In the paper substrate, it is preferable that the content of softwood pulp is 10 to 100% by mass and the content of broadleaf pulp is 0 to 90% by mass relative to the total mass of pulp, and it is more preferable that the content of softwood pulp is 50 to 100% by mass and the content of broadleaf pulp is 0 to 50% by mass. That is, the mass ratio of broadleaf pulp to softwood pulp (L / N ratio) is preferably 90 / 10 to 0 / 100, and more preferably 50 / 50 to 0 / 100.

[0016] 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.

[0017] 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.

[0018] 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 manufacture 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 0.7 parts by mass, and more preferably 0.2 to 0.6 parts by mass, per 100 parts by mass of pulp.

[0019] The paper substrate preferably contains a paper strength enhancer. By including a paper strength enhancer in the paper substrate, the hydrogen bonds between the pulps are reinforced, and the paper strength of the paper substrate can be increased. If the paper strength of the paper substrate is low, there is a risk that the oil-resistant paper may tear when tension is applied during processing. Known paper strength enhancers can be used, such as polyacrylamide-based paper strength enhancers, cationized starch, carboxymethylcellulose, and graft polymerized starch. Among these, polyacrylamide-based paper strength enhancers are preferred, and amphoteric polyacrylamide is more preferred. The content of the paper strength enhancer in the paper substrate is preferably 0.05 to 2.0 parts by mass, and more preferably 0.1 to 1.0 parts by mass, per 100 parts by mass of pulp.

[0020] The paper substrate may contain a sizing agent, but if the paper substrate contains a sizing agent, the coating liquid does not penetrate easily when applied, so a coating layer tends to form on the surface of the paper, increasing its air permeability. From the viewpoint of lowering the air permeability of oil-resistant paper, the less sizing agent it contains, the better. The sizing agent content in the paper substrate is preferably 0 to 0.1 parts by mass, more preferably 0 to 0.05 parts by mass, and particularly preferably 0 parts by mass, per 100 parts by mass of pulp. In other words, it is particularly preferable that the paper substrate is so-called no-sizing paper, which does not contain a sizing agent. Generally, paper sizing agents are one or more of rosin-based sizing agents, alkyl ketene dimer-based sizing agents, and alkenyl succinic anhydride-based sizing agents. Therefore, no-sizing paper may be paper that does not contain rosin-based sizing agents, alkyl ketene dimer-based sizing agents, and alkenyl succinic anhydride-based sizing agents.

[0021] The air permeability of the paper substrate is set so that the air permeability of oil-resistant paper is less than 20,000 seconds. Since the air permeability increases when hydrophobic starch or the like is attached to the paper substrate, the air permeability of the paper substrate is set to a lower value than that of oil-resistant paper. The air permeability of the paper substrate is preferably 1,000 seconds or less, more preferably 500 seconds or less, even more preferably 200 seconds or less, and preferably 10 seconds or more, and more preferably 50 seconds or more. The air permeability of the paper substrate can be adjusted by the freeness of the pulp forming the paper substrate, the type and amount of internal additives, the basis weight of the paper substrate, the density, etc. For example, higher pulp freeness tends to result in lower air permeability. A lower sizing agent content in the paper substrate tends to result in lower air permeability.

[0022] The basis weight of the paper substrate is set considering the basis weight of the oil-resistant paper and the amount of hydrophobic starch attached. The basis weight of the paper substrate is set to 100 g / m², with the view that the basis weight of the oil-resistant paper will be less than or equal to the upper limit described later. ２ The following is preferable: 90 g / m ２ The following is more preferable: 70 g / m ２ The following is even more preferable, and from the viewpoint of increasing the tear strength of the oil-resistant paper, 13 g / m² ２ The above is preferable, and 18 g / m ２ The above is more preferable: 20 g / m ２ The above is even more preferable.

[0023] (Hydrophobic Starch) Hydrophobic starch is starch that has undergone hydrophobic treatment (hydrophobic processing). In hydrophobic treatment, at least some of the hydroxyl groups of the starch are replaced with functional groups containing hydrophobic groups. Examples of functional groups containing hydrophobic groups include hydrocarbon groups such as alkyl groups and alkenyl groups. The number of carbon atoms in the hydrocarbon group is, for example, 5 to 20. Hydrophobic treatments include, but are not limited to, treatments in which starch is contacted with an aqueous solution of organosilane in the presence of alkali aluminate or alkali hydroxide, treatments in which starch is derivatized with silicone or alkenyl, treatments in which starch is reacted with organic acid anhydrides (e.g., alkenyl succinic anhydrides such as octenyl succinic anhydride and dodecenyl succinic anhydride), treatments in which starch is copolymerized with hydrophobic monomers such as acrylonitrile or hydrophobic unsaturated monomers, treatments in which hydrophobic groups containing hydrocarbon groups are imparted to starch by etherification or esterification, and treatments in which alkyl succinic starch is produced. Hydrophobic starch may also be subjected to chemical treatments other than hydrophobic treatment. As hydrophobic starch, starch hydrophobized by esterification (hereinafter also referred to as "esterified-hydrophobic starch") is preferred from the viewpoint of oil resistance and economic efficiency.

[0024] (Esterified-Hydrophobic Starches) Esterified-hydrophobic starches are starches that have been made hydrophobic by esterifying their hydrophobic groups. Examples of starches esterified with fatty acids include acetylated starch, propionic acid esterified starch, laurate esterified starch, and stearate esterified starch. Examples of starches esterified with succinic acid include octenyl succinate starch and dodecenyl succinate starch. Other examples include maleate esterified starch and phthalate esterified starch, but these are not the only examples. Octenyl succinate starch is preferred as an esterified-hydrophobic starch in terms of oil resistance and cost-effectiveness.

[0025] The degree of esterification of esterified-hydrophobized starch is not particularly limited, but is generally in the range of 0.002 to 0.500. The degree of esterification of esterified-hydrophobized starch is an indicator of the extent to which the hydroxyl groups in the starch are replaced by ester groups. For example, the degree of esterification is... １The hydrogen content is determined by the integral ratio of the peaks derived from starch and hydrogen derived from the ester group using 1H-NMR.

[0026] In this embodiment, the amylose content in the hydrophobic starch (i.e., the ratio of amylose to the total mass of hydrophobic starch (mass%), hereinafter also simply referred to as "amylose content") is less than 18% by mass. If it is below the above upper limit, the viscosity of the coating composition is low and the operability is improved. The amylose content is preferably 1 to 17% by mass, more preferably 4 to 16% by mass, and even more preferably 7 to 15% by mass. The amount of amylose in the oil-resistant paper (hereinafter also referred to as "paper substrate standard amylose amount") is 0.5 to 5.0% by mass relative to the total mass of the paper substrate, preferably 0.5 to 3.0% by mass, more preferably 0.7 to 2.5% by mass, and even more preferably 0.9 to 2.0% by mass. If the amylose content and / or the paper substrate standard amylose amount are above the above lower limit, the oil resistance of the entire layer and the oil resistance by the kit method are excellent. If the amylose content and / or the amount of amylose based on the paper substrate is below the above upper limit, the paper exhibits excellent oil resistance and breathability throughout. The amount of amylose based on the paper substrate can be measured by known methods. For example, it can be measured by analyzing the iodine colorimetric method, high-performance liquid chromatography, or gel permeation chromatography, after extracting starch from oil-resistant paper with hot water.

[0027] The amylose content and the amylose amount based on the paper substrate vary depending on the starch to be hydrophobized (hereinafter also referred to as the raw material starch). The amylose content and the amylose amount based on the paper substrate may be adjusted by mixing two or more kinds of raw material starches or by mixing two or more kinds of hydrophobized starches with different raw material starches. The raw material starches and their amylose contents are exemplified below. Tapioca starch (amylose content: 16 to 20% by mass), corn starch (amylose content: 0 to 23% by mass), potato starch (amylose content: 20 to 22% by mass), wheat starch (amylose content: 20 to 28% by mass), polished rice starch (amylose content: 15 to 25% by mass), glutinous rice starch (amylose content: 0% by mass), sago starch (amylose content: 25 to 30% by mass), sweet potato starch (amylose content: 18 to 22% by mass). Among corn starches, the amylose content of waxy corn starch is 0% by mass.

[0028] The adhesion amount of the hydrophobized starch per 1 m ２ of the paper substrate is preferably 1 to 20 g / m ２ , more preferably 1 to 10 g / m ２ , and even more preferably 2 to 6 g / m ２ . When the adhesion amount of the hydrophobized starch is not less than the above lower limit value, the oil resistance of the entire layer is more excellent, and when it is not more than the above upper limit value, the air permeability is more excellent.

[0029] When the adhesion amount of the hydrophobized starch is within the above range, the thickness of the hydrophobized starch adhering to the fiber surface of the paper substrate is considered to be about 5 μm or less, but it is not particularly limited. The thickness of the hydrophobized starch adhering to the fiber surface can be confirmed by microscopic observation of the fiber cross section.

[0030] (Crosslinking agent) The oil-resistant paper may further contain a crosslinking agent that crosslinks the hydrophobized starch. The crosslinking agent contributes to improving oil resistance and suppressing the elution of the hydrophobized starch into water by crosslinking the hydrophobized starches with each other or crosslinking the hydrophobized starch and the pulp in the paper base material. The crosslinking agent is not particularly limited as long as it can crosslink the hydrophobized starch. For example, polyamide epichlorohydrin resin, epichlorohydrin-based crosslinking agents such as epichlorohydrin, glyoxal, dialdehyde, polyacrolein, N-methylol urea, N-methylol melamine, activated vinyl compounds, various esters, diisocyanates, aluminum sulfate, etc. may be mentioned. Among these, epichlorohydrin-based crosslinking agents are preferred from the viewpoints of economy and more excellent influence on food. The crosslinking agent may be used alone or in combination of two or more kinds.

[0031] The content of the crosslinking agent is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, based on the total of the hydrophobized starch and the crosslinking agent. When the content of the crosslinking agent is at least the above lower limit value, the effect of the crosslinking agent is easily obtained. When the content of the crosslinking agent is at most the above upper limit value, the air permeability is more excellent.

[0032] (Other components) Other components other than the hydrophobized starch and the crosslinking agent may further adhere to the oil-resistant paper. Examples of other components include fatty acids, fatty acid salts, modified fatty acids, antifoaming agents, thickeners, water retention agents, pigments, antifoaming agents, preservatives, water repellents, antiblocking agents, lubricants, mold release agents, etc. The other components may be used alone or in combination of two or more kinds.

[0033] To enhance oil resistance, at least one fatty acid selected from the group consisting of fatty acids, fatty acid salts, and denatured fatty acids can be attached to the paper substrate. Examples of fatty acids include saturated fatty acids, unsaturated fatty acids, distilled fatty acids, and hydrogenated fatty acids. Fatty acids may be plant-derived or animal-derived. The number of carbon atoms in fatty acids is, for example, 8 to 30. Examples of salts in fatty acid salts include sodium salts and potassium salts. As denatured fatty acids, various fatty acids that have been denatured to impart functionality can be used, such as fatty acids denatured with epichlorohydrin-based drugs (epichlorohydrin-based drug-denatured fatty acids), fatty acid amides, and fatty acid esters. An example of an epichlorohydrin-based drug is epichlorohydrin. Here, "denatured with an epichlorohydrin-based drug" includes not only cases where a structure derived from an epichlorohydrin-based drug has been introduced into the fatty acid, but also cases where an epichlorohydrin-based drug has been imparted to the fatty acid in some form, such as by using an epichlorohydrin-based drug as a dispersant for fatty acids. Fatty acids may also be fatty acid sizing agents. Fatty acid sizing agents include fatty acids, fatty acid salts, or modified fatty acids that have been treated with cationic fixing agents such as polyamine-based drugs, and some are epoxidized with epichlorohydrin-based drugs. All of these can be preferably used as fatty acids.

[0034] The content of other components is preferably 0 to 5% by mass, and more preferably 0 to 3% by mass, relative to the hydrophobic starch.

[0035] (Properties of Oil-Resistant Paper) The air permeability of the oil-resistant paper is less than 20,000 seconds, preferably 16,000 seconds or less, more preferably 13,000 seconds or less, even more preferably 10,000 seconds or less, particularly preferably 5,000 seconds or less, and also preferably 100 seconds or more, more preferably 300 seconds or more. The air permeability of the paper base material is lower than that of the oil-resistant paper. When the air permeability of the oil-resistant paper is below the above upper limit value, due to the low air permeability of the paper base material, the coating composition containing hydrophobized starch and water is likely to penetrate into the paper base material. Therefore, oil resistance can be imparted to the entire layer of the paper base material. In addition, it is difficult to form a coating layer that significantly impairs the air permeability on the surface of the paper base material, and sufficient air permeability can be ensured, so steam can easily escape, and it can also be applied to the packaging of high-temperature fried foods, etc. When the air permeability of the oil-resistant paper is above the above lower limit value, a sufficient amount of hydrophobized starch can be adhered to the paper base material, and the oil resistance of the entire layer and the oil resistance by the kit method are improved. The air permeability of the oil-resistant paper can be adjusted by the air permeability of the paper base material, the adhesion amount of hydrophobized starch, the type of hydrophobized starch, etc. For example, when the adhesion amount of hydrophobized starch is small, the air permeability of the oil-resistant paper tends to be low.

[0036] The basis weight of the oil-resistant paper is preferably 20 to 400 g / m ２ and more preferably 25 to 100 g / m ２ and even more preferably 30 to 70 g / m ２ When the basis weight of the oil-resistant paper is above the above lower limit value, the tear strength of the oil-resistant paper increases, and it is less likely to be torn during processing, improving the processing suitability. When the basis weight of the oil-resistant paper is below the above upper limit value, the hydrophobized starch is likely to impregnate the entire layer in the thickness direction of the paper base material. In addition, it becomes easier to perform processing such as bending, improving the processing suitability. The basis weight of the oil-resistant paper is measured in accordance with JIS P 8124:2011.

[0037] The Canadian standard water content (hereinafter also referred to as "disintegration freeness") of the pulp obtained by disintegrating oil-resistant paper is preferably 150 to 500 mL, more preferably 200 to 450 mL, and even more preferably 250 to 400 mL. When the disintegration freeness is within the above range, the oil-resistant paper has high tear strength and excellent processability. Furthermore, when the disintegration freeness is above the lower limit, the coating composition containing hydrophobic starch and water penetrates the paper substrate more easily, and the breathability tends to be better. Disintegration of oil-resistant paper is carried out in accordance with JIS P 8220-1:2012. The Canadian standard water content is measured in accordance with JIS P 8121-2:2012. Disintegration freeness can be adjusted by the degree of pulp beating.

[0038] (Method for manufacturing oil-resistant paper) The oil-resistant paper according to this embodiment can be manufactured, for example, by coating a paper substrate with a coating composition containing hydrophobic starch and water, and then drying it. The coating composition may contain a crosslinking agent. The coating composition may contain other components.

[0039] 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.

[0040] For the preparation of a pulp slurry for papermaking, it is preferable to disintegrate the 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 such as additive A as needed, dispersed in water, and a pulp slurry of a concentration suitable for papermaking may be prepared. If the paper substrate is unsized paper, no sizing agent is mixed in.

[0041] The wet paper obtained from the paper machine is preferably dried using a multi-stage cylinder dryer, an air dryer, or a Yankee dryer.

[0042] A paint composition can be prepared by mixing the materials that make up the paint composition. The method of coating the paint composition 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 paint composition may be coated on one side or both sides of a paper substrate. From the viewpoint of full-layer oil resistance, coating on both sides is preferred. The coating amount of the paint composition is set considering the amount of hydrophobic starch that adheres. ２ Converted to the mass of hydrophobic starch per square meter, this is 1 to 20 g / m². ２ Preferably, 1 to 10 g / m ２ More preferably, 2 to 6 g / m ２ That is even more preferable.

[0043] 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 applying the coating composition, as long as it does not impair the effects of the invention.

[0044] 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.

[0045] 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 oil-containing foods are more preferred, and oil-containing foods that are packaged at high temperatures (e.g., 90 to 180°C) or oil-containing foods that are heated to high temperatures after packaging are particularly preferred due to the high usefulness of excellent breathability. Specific examples of oil-containing foods include french fries, hamburgers, donuts, croquettes, fried chicken, fried mochi, pasta, and fried rice. 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. As a method for packaging articles with packaging materials, known packaging methods can be applied.

[0046] 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.

[0047] (Examples 1-3) <Manufacturing of paper substrate> Pulp consisting of 40% by mass of LBKP and 60% by mass of NBKP (L / N ratio: 40 / 60) was mixed with 0.5% of the oven-dry mass of a wet paper strength enhancer (polyamide epichlorohydrin resin, trade name: WS4024, manufactured by Seikoh PMC) and 0.4% of the oven-dry mass of a paper strength enhancer (polyacrylamide, trade name: Polystron TS-1, manufactured by Arakawa Chemical Industries) as internal additives, and paper was manufactured on a paper machine with a basis weight of 40 g / m². ２ The 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 300 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).

[0048] <Preparation of Paint Composition> Hydrophobized starch with an amylose content of 18% (hydrophobized tapioca starch) and hydrophobized starch with an amylose content of 0% (hydrophobized waxy corn starch) were dispersed in water so that the total amylose content of the hydrophobized starch was as shown in Table 1 to prepare a paint composition (solid content concentration of 15%).

[0049] <Coating> Using a gate roll coater, the coating composition is applied to both sides of the paper substrate, with a total coating amount (total for both sides) of 4 g / m² after drying. ２ The paper was coated and dried to obtain oil-resistant paper.

[0050] (Example 4) Oil-resistant paper was obtained in the same manner as in Example 1, except that in the preparation of the coating composition, the amount of crosslinking agent (polyamide epichlorohydrin resin, trade name: WS4024, manufactured by Seikoh PMC) shown in Table 1 was dispersed in water along with two types of hydrophobic starch.

[0051] (Example 5) In preparing the coating composition, the coating composition was adjusted with two types of hydrophobic starch to the values ​​shown in Table 1, and the coating composition (solid content concentration 20%) was applied to both sides of the paper substrate using a gate roll coater, with a coating amount (total for both sides) of 9 g / m² after drying. ２ Oil-resistant paper was obtained in the same manner as in Example 1, except that it was coated in such a manner.

[0052] (Example 6) In preparing the coating composition, the coating composition was adjusted with two types of hydrophobic starch to the values ​​shown in Table 1, and the coating composition (solid content concentration 10%) was applied to both sides of the paper substrate using a gate roll coater, with a coating amount (total for both sides) of 2.5 g / m² after drying. ２ Oil-resistant paper was obtained in the same manner as in Example 1, except that it was coated in such a manner.

[0053] (Comparative Example 1) Oil-resistant paper was obtained in the same manner as in Example 1, except that in the preparation of the paint composition, the paint composition was prepared using only hydrophobized starch with an amylose content of 18%.

[0054] (Comparative Example 2) In the preparation of the coating composition, the coating composition was prepared using only hydrophobic starch with an amylose content of 18%, and the coating composition (solid content concentration of 20%) was applied to both sides of the paper substrate using a gate roll coater, with a coating amount (total for both sides) of 9 g / m² after drying. ２ Oil-resistant paper was obtained in the same manner as in Example 1, except that it was coated in such a manner.

[0055] (Comparative Example 3) Oil-resistant paper was obtained in the same manner as in Example 1, except that the paint composition was prepared with two types of hydrophobic starch to the values ​​shown in Table 1.

[0056] (Evaluation) The following measurements and evaluations were performed on the obtained oil-resistant paper. The results are shown in Table 1.

[0057] <Measurement of air permeability> The air permeability of oil-resistant paper was measured in accordance with J. TAPPI Test Methods for Paper and Pulp No. 5-2:2000 (Paper and cardboard - Test methods for smoothness and air permeability - Part 2: Wang Gan method).

[0058] <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.

[0059] <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.

[0060] <Evaluation of Oil Resistance of All Layers> Kit test solutions No. 6 and No. 3, conforming to the "Paper and Paperboard - Oil Repellency Test Method - Kit Method" specified in J. TAPPI No. 41:2000, were dropped onto the cross-section of the oil-resistant paper. After 15 seconds, the drops were wiped off, and the penetration state was visually confirmed. The oil resistance of all layers was evaluated according to the following criteria: ○: No penetration was observed in either case. △: No penetration was observed with solution No. 3, but penetration (transparency of the paper) was observed with solution No. 6. ×: Penetration was observed even with solution No. 3.

[0061] <Evaluation of Operability> After the paint composition was left to stand at room temperature for 3 hours, it was stirred again and the viscosity was measured in accordance with JIS Z8803, and the operability (stability of the paint composition) was evaluated according to the following criteria. ○: No increase in viscosity of the paint after standing, and the viscosity is less than twice that of the paint before standing. △: Increase in viscosity was observed in the paint after standing, and the viscosity is more than twice that of the paint before standing. ×: The paint has gelled and is not fluid.

[0062]

[0063] The oil-resistant papers of Examples 1 to 6 had low air permeability and excellent breathability. They also exhibited excellent oil resistance throughout the entire layer, and had good oil resistance (kit) and operability. On the other hand, Comparative Examples 1 and 2, which had an amylose content of 18% in the hydrophobic starch, were inferior in breathability, oil resistance throughout the entire layer, and operability. Comparative Example 3, which had a paper substrate standard amylose content of 0.2%, was inferior in oil resistance throughout the entire layer and in oil resistance.

[0064] According to the present invention, it is possible to provide oil-resistant paper with excellent breathability and oil resistance throughout the entire layer.

Claims

1. Oil-resistant paper comprising a paper substrate containing pulp and hydrophobic starch attached to the paper substrate, wherein the amylose content of the hydrophobic starch is less than 18% by mass, the amount of amylose contained in the hydrophobic starch is 0.5 to 5.0% by mass relative to the total mass of the paper substrate, and the Wangyan air permeability is less than 20,000 seconds.

2. The oil-resistant paper according to claim 1, wherein the hydrophobic starch is esterified starch.

3. The oil-resistant paper according to claim 2, wherein the esterified starch is octenyl succinate starch.

4. The oil-resistant paper according to claim 1 or 2, wherein 10% by mass or more of the pulp is softwood pulp.

5. Basis weight: 10-100 g / m² ２ The oil-resistant paper according to claim 1 or 2.

6. The oil-resistant paper according to claim 1 or 2, further comprising a crosslinking agent for crosslinking the hydrophobic starch.

7. The oil-resistant paper according to claim 6, wherein the content of the crosslinking agent is 1 to 10% by mass relative to the total of the hydrophobic starch and the crosslinking agent.

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

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