JP2017119921A - Oil-resistant paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide oil-resistant paper which is oil-resistant paper containing no fluorine resin-based oil-resistant agent, and has excellent oil resistance as to prevent occurrence of falling-off of an oil content and bleed-out of the oil content even when the oil-resistant paper is thin leaf-like oil-resistant paper.SOLUTION: There is provided oil-resistant paper which has an undercoating layer and a top coating layer on at least one surface of a paper base material, where the undercoating layer contains at least one of oxidized starch, a fatty acid sizing agent and an alkyl ketene dimer, and the top coating layer contains at least one of oxidized starch and a styrene-butadiene copolymer.SELECTED DRAWING: None

Description

  The present invention relates to an oil-resistant paper used as a packaging container material.

  Oil-resistant paper is widely used as a material for packaging containers such as detergents, confectionery, and dried foods. There are various uses. As for the paperboard imparted with oil resistance, there are boxes for food such as confectionery, especially boxes for chocolate confectionery containing a large amount of oil and fat. As for the thin paper imparted with oil resistance, there are containers for packaging hamburgers and fried foods in fast food, packaging containers for take-out foods in convenience stores, and the like.

  As means for imparting oil resistance to paper, fluororesin-based oil resistance agents having excellent oil resistance have been widely used. For example, there are cooking sheets in which a fluororesin-based oilproofing agent is applied on the surface of paper and an oilproof layer is provided, or oil-resistant paperboard for confectionery boxes in which a fluororesin-based oilproofing layer is provided between paper layers. However, it is confirmed that papers using fluororesin-based oilproofing agents are likely to remain for a long time, such as fluorine-based alcohol compounds having 8 to 10 carbon atoms, when heated at a food cooking temperature of 100 to 180 ° C. Has been. In addition, when papers using these fluororesin-based oil-proofing agents are incinerated after use, there is a concern that fluorine compounds such as perfluorooctanoic acid and perfluorosulfonic acid are generated and affect the environment. . Therefore, there is a demand for oil-resistant paper that does not use a fluororesin-based oil resistant agent.

  As an oil-resistant paper that replaces the oil-resistant paper using the above-mentioned thermally decomposed fluororesin-based oil-resistant agent, polyethylene film-laminated paper, paper substrate coated with acrylic resin-based oil-resistant agent, polyethylene resin-coated paper, silicone Some use oil-based oil-proofing agents and wax-based oil-proofing agents. An oil-resistant paper using a fluorine-based resin whose manufacturing method has been improved so as not to generate an inert gas even when heat is applied is also disclosed. However, since both have problems, some of them have been put into practical use, but there are still strong requests for improvement from users.

  Patent Document 1 discloses an oil-resistant paper containing starch, polyvinyl alcohol, and a fatty acid in a coating layer as an oil-resistant paper that does not contain a fluororesin oil-resistant agent. Patent Document 2 discloses an oil-resistant paper containing a hydrophobic starch, a fatty acid, and a crosslinking agent in a coating layer.

Japanese Patent No. 4864331 International Publication No. 2005/014930

  However, the oil-resistant paper described in Patent Document 1 and Patent Document 2 is used when the oil content passes through the oil-resistant paper or the oil content becomes smudged when used as a wrapping paper for a fast food or the like containing a large amount of oil. Can be problematic. These problems are even more pronounced in the case of thin oil-resistant paper. Here, the passage of the oil component means that the oil component adhering to the front side surface of the oil resistant paper reaches the back side surface of the oil resistant paper and the oil component oozes out to the back side surface. In addition, oil stains are the oil that adheres to the front surface of the oil-resistant paper and spreads in part of the interior of the oil-resistant paper to form a reservoir of oil, and the oil is visible on spots when viewed through the paper. That is.

  The present invention has been made in view of such a situation. The present invention is an oil-resistant paper that does not contain a fluororesin-based oil-proofing agent, and can prevent oil leakage and oil stains from occurring even in thin oil-resistant paper, and has excellent oil resistance. The purpose is to provide paper.

  The present inventors use a specific starch and a specific sizing agent as a material constituting the oil-resistant coating layer, and when two coating layers are provided, penetration of oil into the oil-resistant paper surface. It has been found that the oil content can be prevented from spreading even when it penetrates into the interior. The present invention has the following configuration.

(1) An oil-resistant paper having an undercoat coating layer and an overcoat coating layer on at least one side of a paper substrate, wherein the undercoat coating layer is at least one of oxidized starch, fatty acid sizing agent and alkyl ketene dimer. And the top coat layer contains at least one of oxidized starch and a styrene-butadiene copolymer.

(2) The oil-resistant paper as described in (1) above, which has the undercoat coating layer and the topcoat coating layer on both the front and back surfaces of the paper substrate.

(3) The top coat layer on the surface of the paper substrate contains any one of oxidized starch and fatty acid sizing agent, oxidized starch and alkyl ketene dimer, and styrene butadiene copolymer. Oil-resistant paper as described in said (2).

(4) The oil-resistant paper as described in (2) or (3) above, wherein the top coat layer on the back surface of the paper substrate further contains inorganic fine particles.

(5) The oil-resistant paper according to any one of (1) to (4), wherein at least one of the undercoat coating layer and the topcoat coating layer is crosslinked with a crosslinking agent.

(6) The oil-resistant paper as described in (5) above, wherein the crosslinking agent is an epichlorohydrin crosslinking agent.

(7) Any one of the above (1) to (6), wherein the paper base material contains 0 to 0.3 parts by mass of the internally added sizing agent with respect to 100 parts by mass of the pulp of the paper base material. Oil-resistant paper according to item 1.

(8) The oil-resistant paper according to any one of (1) to (7), wherein a Canadian standard freeness of the paper base pulp is 80 to 350 ml.

(9) The oil-resistant paper according to any one of (1) to (8), wherein the basis weight is 20 to 150 g / m ² .

(10) In any one of (1) to (9), the total coating amount of the undercoat coating layer and the topcoat coating layer is 1 to 10 g / m ^{2 on} one side. Oil-resistant paper as described.

(11) Any one of (1) to (10), wherein the paper base material contains hardwood bleached kraft pulp in an amount of 60 to 100% by weight out of 100% by weight of the total pulp of the paper base material. Oil-resistant paper as described in 1.

  The oil-resistant paper of the present invention can prevent oil loss and oil stains from occurring even with thin leaf oil-resistant paper, and has excellent oil resistance.

  Embodiments of the present invention will be described below. However, embodiments of the present invention are not limited to the following embodiments.

(Oil resistant paper)
The oil-resistant paper of this embodiment has an undercoat coating layer and a topcoat coating layer having a specific component that does not contain a fluororesin-based oil resistant agent on at least one side of a paper base material. By having two oil-resistant layers, a base coat layer and a top coat layer with specific components, the synergistic effect of the two is created, preventing oil leakage and oil stains from occurring. Thus, even a thin oil-resistant paper can exhibit a high level of oil resistance.

  The undercoat coating layer and the topcoat coating layer may be formed only on one side of the paper substrate, or may be formed on both the front and back surfaces of the paper substrate. When the undercoat coating layer and the topcoat coating layer are formed only on one side of the paper substrate, it is effective when the oil resistant paper is used with a clear difference in oil resistance performance between the front surface and the back surface. If the undercoat layer and the topcoat layer are formed on both the front and back sides of the paper substrate, it can be used without distinguishing the front and back sides of the oil-resistant paper. This is preferable because the characteristics of the present invention can be further utilized.

  The undercoat coating layer in this embodiment contains oxidized starch and at least one of a fatty acid sizing agent and an alkyl ketene dimer. The top coat layer contains at least one of oxidized starch and styrene butadiene copolymer. Hereinafter, each component constituting the undercoat coating layer and the topcoat coating layer will be described.

  Oxidized starch has been conventionally used as a surface sizing agent. Oxidized starch can be obtained by oxidizing starch with sodium hypochlorite. When the non-crystalline portion of the starch particles is oxidized, molecules are depolymerized or carboxy groups are generated, whereby oxidized starch that is difficult to oxidize and has excellent viscosity stability and transparency can be obtained. Oxidized starch is chemically stable and excellent in oil resistance, so that it can impart excellent oil resistance to the paper base material when applied to the paper base material.

  Examples of the raw material for oxidized starch include corn starch (corn starch), waxy corn starch, potato starch, tapioca starch, wheat starch, sweet potato starch, and rice starch. These starches can be used in combination of two or more.

  Fatty acid sizing agents have been conventionally used as surface sizing agents. As the fatty acid sizing agent, it is sufficient that a fatty acid component is basically contained, and a modified fatty acid or a fatty acid salt may be used. For example, a fatty acid amide produced from a fatty acid and an amine, a fatty acid ester produced from a fatty acid and an alcohol, and the like can be suitably used. The fatty acid may be either a saturated fatty acid or an unsaturated fatty acid, and may be a vegetable fatty acid or an animal fatty acid.

  A typical fatty acid sizing agent for paper is a fatty acid modified with a cation. Specifically, a fatty acid, a fatty acid salt, or a fatty acid modified to impart functionality is provided with a polyamine cationic fixing agent, and is further epoxidized with an epichlorohydrin-based modifier. It is. The fatty acid sizing agent used in the present embodiment is not particularly limited as long as it is a sizing agent using these fatty acids, but among them, a polyamine is reacted with a higher fatty acid to produce a polyamide condensate, and further an epichlorohydrin compound is used as an epoxy. It is preferable that

  As the higher fatty acid, an aliphatic monocarboxylic acid or polyvalent carboxylic acid having 8 to 30 carbon atoms is preferable, and those having 12 to 25 carbon atoms are particularly preferable. Examples of the aliphatic carboxylic acid include stearic acid, oleic acid, lauric acid, palmitic acid, arachidic acid, behenic acid, tall oil fatty acid, alkyl succinic acid, alkenyl succinic acid and the like. Examples of the polyamine include polyalkylene polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, dipropylenetriamine and tripropylenetetramine; aminoethylethanolamine and the like. The thing obtained by the condensation reaction of a higher fatty acid and a polyamine is preferably an amide of a trivalent or higher valent amine and a higher fatty acid, such as a condensation product of polyethylene polyamine and a higher fatty acid, a reaction product of stearic acid and melamine, or the like. . As the condensate of fatty acid and polyvalent amine, a quaternary salt using epichlorohydrin can be used more suitably.

  Alkyl ketene dimers have been conventionally used as neutral sizing agents. Preferred ketene dimers are alkyl ketene dimers prepared from linear saturated fatty acids having 14 to 22 carbon atoms. Alkyl ketene dimers are believed to impart size to paper substrates by esterifying hydroxyl groups in the surface fibers of the paper.

  Styrene-butadiene copolymers have been conventionally used as surface sizing agents. The styrene-butadiene copolymer is not particularly limited. The styrene-butadiene copolymer is usually used as a latex finely dispersed in water. The glass transition temperature of the styrene-butadiene copolymer is preferably in the range of −40 ° C. to 0 ° C. because the film formability is excellent and good oil resistance is obtained. Examples of the particle structure of the latex include a single structure, a core-shell structure, and a continuous different composition structure. About the average particle diameter of latex, the thing of 70-150 nm is preferable since the film formability is excellent.

In the oil-resistant paper of this embodiment, the component constituting the undercoat coating layer and the component constituting the topcoat coating layer may be the same or different.
The undercoat coating layer contains oxidized starch and at least one of a fatty acid sizing agent and an alkyl ketene dimer. As a component constituting the undercoat coating layer, it is preferable that oxidized starch is an essential component and a main component from the viewpoint of forming a film on the paper substrate and suppressing oil stains and spreading. Here, the main component means 50% by mass or more of the total solid content of the undercoat coating layer. 50-90 mass% is preferable and, as for the content rate of the oxidized starch in the total solid of an undercoat coating layer, 65-85 mass% is more preferable. In addition, the oxidized starch coating film is preferable because it generates less powder when the surface is rubbed with a machine or the like during bag making.

  Both the fatty acid sizing agent and the alkyl ketene dimer in the undercoat coating layer are components added to further improve the oil resistance of oxidized starch. Both are excellent in compatibility with oxidized starch. Further, from the viewpoint of forming an oxidized starch film, it is preferably less than 50% by mass of the total solid content of the undercoat coating layer containing any of them. The fatty acid sizing agent is a content ratio in the total solid content of the undercoat coating layer, preferably 5 to 49% by mass, and more preferably 10 to 25% by mass. The alkyl ketene dimer is a content ratio in the total solid content of the undercoat coating layer, preferably 5 to 49% by mass, and more preferably 10 to 25% by mass.

  The oil-resistant paper of the present embodiment has an undercoat coating layer having the above components, thereby preventing the oil from further penetrating into the inside even when the oil has passed through the topcoat coating layer. be able to. Further, since a part of the undercoat coating layer penetrates to a part of the paper base material, the oil content even when the oil adhering to the surface of the oil-resistant paper permeates the inside of the paper base material. Can be prevented from spreading.

  The top coat layer contains at least one of oxidized starch and a styrene butadiene copolymer. Oxidized starch and styrene-butadiene copolymer can form a coating film excellent in oil resistance, and therefore prevent oil adhering to the surface of the oil-resistant paper from penetrating into the inside.

  The oxidized starch constituting the undercoat coating layer or the topcoat coating layer is preferably crosslinked with a crosslinking agent. That is, it is preferable that at least one layer containing oxidized starch among the undercoat coating layer and the topcoat coating layer is crosslinked with a crosslinking agent. Oxidized starch can be further improved in oil resistance by being cross-linked with a cross-linking agent, and the oil resistance of the oil-resistant paper can be improved.

  The crosslinking agent for oxidized starch is not particularly limited, and specifically, isocyanate resin, aminoaldehyde resin, glyoxal resin, epoxy resin, carbodiimide resin, inorganic metal salt, phenol resin, melamine resin, urea resin And epichlorohydrin compounds. Among these, from the viewpoint of safety, economy, and reactivity, an epichlorohydrin-based crosslinking agent is preferable, and a polyamide epichlorohydrin resin is particularly preferable. The addition amount of the crosslinking agent may be added in an amount of 1 to 25% by mass with respect to the solid content of oxidized starch, although it depends on the type of crosslinking agent, the number of groups for reaction, and the reaction rate.

The coating amount of the undercoat coating layer is not particularly limited, on one side, is preferably 0.5 to 5 g / ^{m 2,} more preferably 1 to 3 g / ^{m 2.} Further, coating amount of the overcoat coating layer is not particularly limited, on one side, is preferably 0.5 to 5 g / ^{m 2,} more preferably 1 to 3 g / ^{m 2.} Further, the total coating amount of the undercoat coating layer and overcoat coating layer, on one side, is preferably 1 to 10 g / ^{m 2,} and more preferably 2 to 6 g / ^{m 2.} In addition, the total coating amount of the undercoat coating layer and the topcoat coating layer is preferably ² to ²⁰ g / m ² and more preferably 4 to 12 g / m ² on both sides.

  In the oil-resistant paper of this embodiment, when providing the undercoat coating layer and the topcoat coating layer on both the front and back surfaces of the paper substrate, the composition of the topcoat coating layer on the front side and the topcoat coating layer on the back side is set. Can be changed. For example, when forming the packaging container by distinguishing the front side and the back side of the oil resistant paper, when the front side is exclusively in contact with oil, the oil resistance of the top coat layer on the front side is the oil resistance of the top coat layer on the back side. It can be set as the structure improved rather than the property. When the oil resistance of the top coat layer on the front side is higher than the oil resistance of the top coat layer on the back side, the composition of the coating layer may be changed, the component concentration may be changed, and the coating amount May be changed.

  In order to ensure better oil resistance on the surface side, the top coat layer on the surface side of the paper substrate is either oxidized starch and fatty acid sizing agent, oxidized starch and alkyl ketene dimer, or styrene butadiene copolymer. It is preferable to contain one. Moreover, it is preferable that both the fatty acid sizing agent and the alkyl ketene dimer in the top coat layer are less than 50% by mass of the total solid content of the top coat layer contained from the viewpoint of forming an oxidized starch film. The fatty acid sizing agent is a content ratio in the total solid content of the topcoat coating layer, preferably 5 to 49% by mass, and more preferably 10 to 25% by mass. The alkyl ketene dimer is a content ratio in the total solid content of the topcoat coating layer, preferably 5 to 49% by mass, and more preferably 10 to 25% by mass. From the viewpoint of effectively suppressing oil stains, it is preferable that a fatty acid sizing agent is also contained in the top coat layer on the back side.

  Even when oxidized starch is used for the top coat layer, the oxidized starch is preferably the main component. That is, the content ratio of oxidized starch in the top coat layer is preferably 50% by mass or more based on the total solid content of the top coat layer. 50-90 mass% is preferable and, as for the content rate of the oxidized starch in the total solid of a top coat layer, 65-85 mass% is more preferable. Moreover, it is preferable to contain oxidized starch also in the top coat layer on the back side. Oxidized starch coating is preferred because it generates less powder when the surface is rubbed with a machine or the like during bag making.

  In the oil-resistant paper of the present embodiment, it is preferable that the top coat layer on the back surface of the paper base further contains inorganic fine particles in order to improve the processability during bag making or box making. By containing inorganic fine particles, the coefficient of friction between the papers can be increased, slippage and blocking during bag making and box making can be prevented, and workability can be improved.

  The inorganic fine particles are not particularly limited. Specific examples of the inorganic fine particles include heavy calcium carbonate, light calcium carbonate, kaolin, calcined kaolin, structural kaolin, delaminated kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide. , Silica, magnesium aluminosilicate, calcium silicate, white carbon, bentonite, zeolite, sericite, smectite and the like. Among these, heavy calcium carbonate, light calcium carbonate, silica, kaolin, calcined kaolin and the like are preferable.

  The coating liquid used for forming the coating layer may contain a binder, a pigment and the like in addition to the various components described above. Moreover, various auxiliary agents normally used, such as a dispersing agent, a thickener, a water retention agent, an antifoaming agent, and a coloring agent, can be used as needed.

  Binders include water-soluble polymers such as casein and polyvinyl alcohol, polyester resins, polyurethane resins, styrene-butadiene resins, vinyl acetate resins, ethylene-vinyl acetate resins, acrylonitrile-butadiene resins, polyethylene resins. Water dispersions such as polypropylene resins, carboxymethyl cellulose resins, polyamide resins, vinyl chloride resins, vinylidene chloride resins can be used.

  Examples of the pigment include, but are not limited to, clay, kaolin, talc, calcium carbonate, magnesium carbonate, magnesium oxide, aluminum hydroxide, alumina, silica, magnesium aluminosilicate, calcium silicate, white carbon, bentonite, zeolite, and sericite. , Smectite, calcium sulfate, barium sulfate, synthetic mica, titanium dioxide, zinc oxide and the like. These pigments can be used alone or in combination of two or more.

Oil paper of the present embodiment is not particularly limited, it is preferable that a basis weight of 20 to 150 g / ^{m 2,} and more preferably 25~80g / ^{m 2.} It can be used for molded containers such as packaging containers and boxes.

(Paper substrate)
The paper base material used for the oil-resistant paper of the present embodiment is not particularly limited, and various papers and paperboards can be used and can be appropriately selected according to the application. Specific examples include bleached or unbleached kraft paper, fine paper, medium quality paper, finely coated paper, coated paper, paperboard, white paperboard, liner, semi-glassine paper, glassine paper, glossy paper, parchment paper, etc. It is done.

  It does not specifically limit as a pulp which comprises a paper base material, All the things normally used for paper manufacture can be used. For example, chemical pulp such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood bleached sulfite pulp (LBSP), softwood bleached sulfite pulp (NBSP), stone grand pulp (GP), pressure stone Unbleached, semi-bleached or bleached pulp, sulfite pulp, waste paper such as ground pulp (PGW), refiner ground pulp (RGP), chemiground pulp (CGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP) Pulp etc. can be used. As the pulp of the paper base material, it is preferable to add a large amount of LBKP excellent in dimensional stability, and it is preferable to contain 60 to 100% by mass of 100% by mass of the total pulp of the paper base material. By containing LBKP within this range, when the coating liquid is infiltrated into the paper substrate and dried, the components of oxidized starch, fatty acid sizing agent or alkyl ketene dimer in the coating liquid are overcoated from the undercoat coating layer. By forming a coating layer having a concentration gradient such that it exists at a high concentration in the coating layer, oil leakage and oil stains can be effectively suppressed. The presence of oxidized starch with a concentration gradient in the thickness direction of the oil-resistant paper can be evaluated by visual observation from the intensity of the color of the cross section of the oil-resistant paper, for example, by coloring with iodine starch reaction.

Although the basic weight of a paper base material is not specifically limited, It is preferable that it is 16-150 g / m < ² >. By setting the basis weight of the paper substrate within the above range, the strength required when forming the coating layer can be maintained. In addition, when the basis weight of the paper base exceeds 150 g / m ² , the paper base tends to buckle at the crease, so that the paper base tends to crack and the oil resistance of the crease tends to decrease. It becomes. In addition, the paper base JAPAN TAPPI paper pulp test method No. The Oken air permeability measured according to 5-2: 2000 is not particularly limited, but is preferably 30 to 200 seconds.

  Furthermore, Canadian standard freeness (degree of beating) measured according to JIS P 8121-1995 of pulp of paper base material is not particularly limited. However, the permeability of the coating liquid, the strength of the paper base material at the time of coating, etc. From the viewpoint, it is preferably 80 to 350 ml. A more preferred range of Canadian standard freeness is 100-300 ml.

  The pulp used is, for example, a beater such as a beater, a Jordan, a single disk refiner, a conical refiner, a cylindrical refiner, a deluxe refiner, a double disk refiner (DDR), a medium agitating mill, a vibration mill, or the like. It is adjusted so that it becomes the beating degree. The beating conditions are not particularly limited, but the shape of the refiner blades, rotation speed, pulp concentration, pulp fiber length, pulp roughness, etc. will affect the physical properties of the pulp after beating, so the desired beating degree can be obtained. The beating conditions are selected as appropriate.

The density of the paper substrate is not particularly limited and is preferably 0.6 to 1.2 g / cm ^3, and more preferably to 0.7~1.1g / cm ^3. Thereby, the intensity | strength at the time of the coating of a paper base material can be raised. Specific methods for increasing the density of the paper base include pressing in wet paper when paper base is made, using a machine calendar, soft nip calender, gloss calendar after drying, or super-making after paper base making. Use a calendar. Among them, the pressure treatment used at the time of wet paper can apply pressure in a state where the water content of the paper base material is high even when compared with the calendar treatment after drying, and can increase the density efficiently. preferable.

  The sizing degree of the paper base material is not particularly limited, but it is preferable that the sizing degree according to JIS P 8122: 2004 is in the range of about 0 to 10 seconds. The sizing degree of the paper base material is the type and content of sizing agents such as rosin, alkyl ketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, petroleum resin, It can be controlled by a smoothing process or the like. Although content of an internal addition sizing agent is not specifically limited, The range of about 0-0.3 mass part is preferable with respect to 100 mass parts of pulp of a paper base material. The internal sizing agent is preferably added in a smaller amount than usual from the viewpoint of appropriately penetrating the coating liquid, and may not be added. More preferably, it is 0-0.25 mass part, More preferably, it is 0.05-0.25 mass part. By adding a small amount of the internal additive sizing agent to the paper substrate, even if the concentration of the coating liquid is low and the coating amount is large, there is no possibility that the paper substrate will be cut during coating. On the other hand, by setting the content of the internal sizing agent to 0.3 parts by mass or less, the oxidized starch, fatty acid sizing agent or alkyl ketene dimer component in the coating solution penetrates appropriately into the paper substrate, and It is possible to effectively form a coating layer having a concentration gradient such that the concentration is higher in the topcoat layer than in the undercoat layer.

  Moreover, the thickness of the paper substrate is not particularly limited, but is preferably 20 μm or more, and more preferably 30 μm or more. Further, the thickness of the paper substrate is preferably 500 μm or less, and more preferably 300 μm or less. By setting the thickness of the paper substrate within the above range, it is possible to have an appropriate strength and to improve the coating suitability of the coating layer.

  The paper base material may further contain an additive. Additives include sulfuric acid bands, fixing agents represented by cationic polymer electrolytes, clay, talc, calcium carbonate, calcined kaolin, aluminum oxide, aluminum hydroxide, titanium oxide, amorphous silica, urea-formalin resin particles Such as fillers, polyacrylamide polymers, paper strength enhancers represented by starch, melamine resins, urea resins, wet paper strength enhancers represented by polyamide-polyamine-epichlorohydrin resins, etc. Various auxiliary agents such as a liquid agent, a dye for color tone adjustment such as bluing, and a fluorescent dye can be mentioned.

(Oil-resistant paper manufacturing method)
<Paper substrate manufacturing method>
The paper base material can be obtained by making paper with various paper machines by a conventional method, forming wet paper, and then drying. Then, it is manufactured through a conventional process such as a smoothing process using a surface size press machine calendar.

  Examples of the paper machine include a long net paper machine having an air cushion head box or a hydraulic head box, a twin wire paper machine, an on-top type twin wire paper machine, and a Yankee paper machine.

<Preparation of coating solution>
The coating liquid is prepared by appropriately adding various auxiliary agents such as a binder, a pigment, and a dispersant, a thickener, a water retention agent, an antifoaming agent, and a colorant as required in addition to the above-described various components Is done. As a solvent for the coating solution, water is usually used. The concentration of the coating solution for the undercoat coating layer is preferably 2 to 10%, more preferably 4 to 8% in terms of solid content. The concentration of the coating solution for the topcoat coating layer is preferably 10 to 20%, more preferably 12 to 18% in terms of solid content. By setting the concentration of the coating liquid for the undercoat coating layer to 2 to 10%, the paper base material can be permeated as much as possible to effectively suppress the spread of oil stains. On the other hand, by setting the concentration of the coating liquid for the top coat layer to 10 to 20%, it is possible to block the penetration of oil as a coating layer without penetrating as much as possible to the paper substrate. That is, the coating solution for the topcoat layer has a higher concentration than the coating solution for the undercoat coating layer, and there may be a concentration gradient in the coating solution from the topcoat coating layer to the undercoat coating layer of the oil-resistant paper. preferable.

<Formation method of coating layer>
The coating liquid for undercoat coating layer is applied to at least one surface of the paper substrate, and then the coating liquid is dried through a dryer. Next, each coating layer can be formed by applying the coating liquid for the top coating layer and subsequently drying the coating liquid through a dryer.

  Moreover, the coating layer on the front surface side and the back surface side of the undercoat coating layer and the top coating layer may be applied simultaneously or sequentially. From the viewpoint of productivity, it is preferable to apply at the same time. On the other hand, from the viewpoint of reliably forming each coating layer, it is preferable to perform sequential coating.

  As a coating method of the coating liquid, generally known coating apparatuses can be used, for example, blade coater, air knife coater, roll coater, reverse roll coater, bar coater, curtain coater, slot die coater, gravure coater, Champlex coater, brush coater, slide bead coater, size press coater of two-roll or rod metering method, pound size press coater, bill rod metering size press coater, short dwell coater, gate roll coater, nip coater with calender, etc. Used as appropriate. Among them, it is preferable to use a bar coater or a blade coater in order to increase production efficiency. Examples of the film transfer coater include a gate roll coater, a rod metering size press coater, and a blade metering size press coater. As for coating, on-machine coating is preferable in terms of production efficiency. In this embodiment, when the component which comprises an undercoat coating layer is the same, it is preferable to apply with a two roll type pound size press coater. As a result, a coating liquid reservoir is formed between the two rolls, the paper base passes through the liquid reservoir, and is further squeezed by the two rolls, so that the undercoat coating liquid is applied to the inside of the paper base. Can penetrate. On the other hand, when the components constituting the top coat layer are different, the film transfer coater is used from the viewpoint of increasing the production efficiency by simultaneously applying different coating liquids on the front and back sides and forming a more uniform film. It is preferable to use it. Although these coating methods are not particularly limited, for example, by combining a pound size press coater and a film transfer coater, components such as oxidized starch or fatty acid sizing agent in the coating solution appropriately penetrate into the paper substrate. Moreover, it is possible to effectively form a coating layer having a concentration gradient in which the concentration is higher in the topcoat layer than in the undercoat layer. In the present invention, it is preferable to use uncoated paper as the paper base material because this effect can be exhibited without regret.

  Moreover, in this embodiment, after forming a coating layer, a smoothing process can be performed as needed. The smoothing process is performed on-machine or off-machine using a smoothing processing apparatus such as a normal super calendar, gloss calendar, or soft calendar. In addition, as long as the effects of the present invention are not impaired, it is also possible to smooth the paper base material before coating layer coating or the base coating base paper on which the base coating layer is formed.

  The oil-resistant paper of the present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these. In the examples and comparative examples, “parts” and “%” indicate “parts by mass” and “% by mass”, respectively, unless otherwise specified.

Example 1
[Preparation of liquid A (coating liquid for undercoat coating layer)]
Hereinafter, 75 parts of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), 15 parts of fatty acid sizing agent (trade name: Size Pine DL-FA20, manufactured by Arakawa Chemical Co., Ltd.), polyamide / polyamide A composition comprising 10 parts of an epichlorohydrin-based cross-linking agent (polyamide epichlorohydrin resin, trade name: WS4024, manufactured by Seiko PMC) is mixed, water is added, and a coating solution for an undercoat coating layer having a solid content concentration of 8% is added. (Liquid A) was obtained.

[Preparation of liquid B (coating liquid for top coat layer)]
Hereinafter, 75 parts of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), 15 parts of fatty acid sizing agent (trade name: Size Pine DL-FA20, manufactured by Arakawa Chemical Co., Ltd.), polyamide / polyamide A composition comprising 10 parts of an epichlorohydrin-based cross-linking agent (polyamide epichlorohydrin resin, trade name: WS4024, manufactured by Seiko PMC Co., Ltd.) is mixed, water is added, and a coating solution for a top coat layer having a solid content concentration of 15% is added. (Liquid B) was obtained.

[Preparation of liquid C (coating liquid for top coat layer)]
Hereinafter, 30 parts of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), 15 parts of fatty acid sizing agent (trade name: Size Pine DL-FA20, manufactured by Arakawa Chemical Co., Ltd.), heavy in terms of solid content. A composition comprising 55 parts of calcium carbonate (trade name: FMT-97, manufactured by Phimatech) was mixed, and water was added to obtain a coating solution (C solution) for a top coating layer having a solid content concentration of 15%. .

[Production of oil-resistant paper]
With a basis weight of 43.6 g / m ² containing 3% of titanium oxide (trade name: R780, manufactured by Ishihara Sangyo Co., Ltd.) as an internal filler, using pulp made of LBKP adjusted with a refiner so that the Canadian standard freeness is 220 ml. Paper-made uncoated paper was used as a paper substrate. On the both sides of this paper base material, with a pound size press coater, the A coating is applied so that the coating amount after drying is 3 g / m ^{2 on} both sides and dried to form an undercoat coating layer. Thus, an undercoat base paper was obtained. Using this undercoat base paper, the coating amount after drying the B liquid on one side is 1.7 g / m ^{2 in a} rod metering size press coater (also referred to as a rod metalizing sizer) as a film transfer coater. The liquid C was applied to the other surface so that the coating amount after drying was 1.7 g / m ² and dried. By going through the above steps, an undercoat coating layer using A liquid and an overcoat coating layer using B liquid are formed on the surface side, and an undercoat coating layer and C liquid using A liquid are formed on the back surface side. An oil-resistant paper having an undercoat coating layer and a topcoat coating layer on both the front and back surfaces was obtained. The basis weight of this oil resistant paper was 50 g / m ² . Further, the sizing degree of the paper substrate was 1 second or less.

(Example 2)
In the production of the oil resistant paper of Example 1, an oil resistant paper was obtained in the same manner as in Example 1 except that the liquid B was used in place of the liquid C as the coating liquid for the top coat layer.

(Example 3)
[Preparation of liquid D (coating liquid for undercoat coating layer)]
Hereinafter, a composition composed of 90 parts of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 10 parts of alkyl ketene dimer (trade name: AD1606, manufactured by Seiko PMC) in terms of solid content is mixed. Water was added to obtain an undercoat coating layer coating solution (D solution) having a solid content concentration of 8%.

[Preparation of liquid E (coating liquid for top coat layer)]
Hereinafter, a composition composed of 90 parts of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 10 parts of alkyl ketene dimer (trade name: AD1606, manufactured by Seiko PMC) in terms of solid content is mixed. Water was added to obtain a coating solution (E solution) for a top coating layer having a solid content concentration of 15%.

[Preparation of liquid F (coating liquid for top coat layer)]
Hereinafter, a composition comprising 30 parts of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 70 parts of heavy calcium carbonate (trade name: FMT-97, manufactured by Phimatec Co., Ltd.) in terms of solid content. Were added, and water was added to obtain a coating solution (F solution) for a top coating layer having a solid content concentration of 15%.

[Production of oil-resistant paper]
In the production of the oil-resistant paper of Example 1, the same as Example 1 except that the D liquid was used instead of the A liquid, the E liquid was used instead of the B liquid, and the F liquid was used instead of the C liquid. An oil-resistant paper was obtained.

Example 4
[Preparation of liquid G (coating liquid for top coat layer)]
Hereinafter, 6 parts of aqueous solution of carboxy-modified polyvinyl alcohol (trade name: T330H, manufactured by Nippon Synthetic Chemical Co., Ltd.), 60 parts of kaolin (trade name: HT Clay, manufactured by BASF Japan Co.) aqueous dispersion in terms of solid content, styrene -A composition comprising 34 parts of a butadiene copolymer latex (trade name: A6160, Tg: 20 ° C, average particle size 135 nm, manufactured by Asahi Kasei Co., Ltd.) is mixed, and water is added to form an overcoat with a solid content concentration of 30%. A layer coating solution (G solution) was obtained.

[Preparation of liquid H (coating liquid for top coat layer)]
Hereinafter, 2.5 parts of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 67.5 parts of kaolin (trade name: HT clay, manufactured by BASF Japan Co.) aqueous dispersion in terms of solid content. , A composition comprising 30 parts of a styrene-butadiene copolymer latex (trade name: A6160, Tg: 20 ° C., average particle size 135 nm, manufactured by Asahi Kasei Co., Ltd.) is mixed, and water is added to form an overcoat with a solid content concentration of 35%. A coating layer coating liquid (H liquid) was obtained.

[Production of oil-resistant paper]
An oil-resistant paper was obtained in the same manner as in Example 1 except that the G liquid was used instead of the B liquid and the H liquid was used instead of the C liquid in the production of the oil resistant paper of Example 1.

(Example 5)
An oil-resistant paper was obtained in the same manner as in Example 1 except that no crosslinking agent was used in the preparation of Liquid A and Liquid B in Example 1.

(Example 6)
An oil-resistant paper was obtained in the same manner as in Example 2 except that no crosslinking agent was used in the preparation of Liquid A and Liquid B in Example 2.

(Example 7)
In preparing the liquid A of Example 4, an oil-resistant paper was obtained in the same manner as in Example 4 except that no crosslinking agent was used.

(Example 8)
In the preparation of the liquid B of Example 1, the amount of oxidized starch was changed to 40 parts instead of 75 parts, and the amount of fatty acid sizing agent was changed to 50 parts instead of 15 parts. I got paper.

(Comparative Example 1)
In the preparation of the oil resistant paper of Example 1, without forming the undercoat coating layer, the topcoat coating layer using the B liquid was formed on the surface side of the paper substrate, and the topcoat coating using the C liquid on the back side An oil-resistant paper was obtained in the same manner as in Example 1 except that the construction layer was formed to have a single-layer structure having only the topcoat coating layer.

(Comparative Example 2)
In the production of the oil-resistant paper of Example 4, without forming the undercoat coating layer, the topcoat coating layer using the G solution was formed on the front side of the paper substrate, and the topcoat coating using the H solution on the back side An oil-resistant paper was obtained in the same manner as in Example 4 except that the work layer was formed to have a single-layer structure consisting of only the top coat layer.

(Comparative Example 3)
In preparing the liquid B of Comparative Example 1, an oil-resistant paper was obtained in the same manner as in Comparative Example 1 except that no crosslinking agent was used.

  The oil-resistant paper thus obtained was evaluated as follows. The results were as shown in Table 1.

(Oil resistance)
The oil resistance of the coated surface on the surface side of the oil-resistant paper was measured by the TAPPI UM-557 method (kit method). In the present invention, the oil resistance is preferably 5 or more.

(Oil stain)
Place a 3 × 3 cm square filter paper impregnated with salad oil on the coated surface of the oil-resistant paper. After 30 minutes, remove the filter paper, wipe off the oil, and spread the oil spread on the oil-resistant paper. Visual observation was made and the following criteria were evaluated. It was determined that grade 3 or higher was preferable.
5th grade: No stains are visible.
Fourth grade: Almost no small spots are seen.
Third grade: Slight spots are seen but there is almost no spread.
2nd grade: Blots appear to spread, but the spread is incomplete in the shape of filter paper (square).
First grade: The stain is remarkable and spreads to the shape of a perfect filter paper (square).

(Oil loss)
Place the oil-resistant paper on the white copy paper with the back side overlapped, put a drop of salad oil on the coated surface of the oil-resistant paper, and place a 4 x 4 cm plastic plate on top of the plastic plate. A weight of 100 g was placed on the test piece, and after 30 minutes, oil leakage to the copy paper laid under the oil-resistant paper was visually observed and evaluated according to the following criteria. ○ It was determined that the above is preferable.
A: The oil does not come off at all, and no oil stain is seen on the copy paper.
○: There is almost no oil leakage, and there is almost no oil stain on the copy paper.
Δ: Oil has been removed, and several small spots can be seen on the copy paper.
X: The oil has fallen out remarkably, and a large spot is seen on the copy paper.

(Coefficient of friction)
Place the oil-resistant paper cut into A4 face-to-face on a friction coefficient measuring machine (manufactured by Sagawa Seisakusho Co., Ltd.) and place a 1000 g weight of 6 × 10 cm on top to fix the lower oil-resistant paper. The weight placed on the upper oil-resistant paper was pulled 45 mm at a speed of 150 mm / min, and the coefficient of static friction between the back surfaces of the oil-resistant paper was measured. In the present invention, there is a risk of causing landslides or winding slips during the process of manufacturing oil-resistant paper or processing using oil-resistant paper. It is preferable that the coefficient of static friction between each other is high. When the friction coefficient was 0.3 or more, it was determined to be preferable.

  In Examples 1-8, it was excellent in any oil resistance of a kit method, an oil stain, and oil omission. Example 2 and Example 6 had a small coefficient of friction and could cause mountain collapse, and there was concern about processability during bag making. However, the top coat coating layer on the back side of the paper base material contained inorganic fine particles. Example 1, Example 3-5, and Example 7 to be contained had a high coefficient of friction and were excellent in workability during bag making.

  On the other hand, since Comparative Example 1 did not have an undercoat coating layer, the oil resistance by the kit method was low, and the oil resistance of oil stains and oil removal was also inferior. Since Comparative Example 2 did not have an undercoat coating layer as in Comparative Example 1, the oil resistance by the kit method was low and the oil resistance of the oil stain was poor. Comparative Example 3 was inferior in oil stain as compared with Comparative Example 1 due to the configuration in which no crosslinking agent was added to Comparative Example 1.

Claims (11)

An oil-resistant paper having an undercoat coating layer and a topcoat coating layer on at least one side of a paper substrate,
The undercoat coating layer contains oxidized starch and at least one of a fatty acid sizing agent and an alkyl ketene dimer,
The topcoat coating layer contains at least one of oxidized starch and a styrene-butadiene copolymer.   2. The oil-resistant paper according to claim 1, wherein the undercoat coating layer and the topcoat coating layer are provided on both the front surface and the back surface of the paper base material.   3. The top coat layer on the surface of the paper substrate contains any one of oxidized starch and fatty acid sizing agent, oxidized starch and alkyl ketene dimer, and styrene butadiene copolymer. Oil-resistant paper as described in 1.   The oil-resistant paper according to claim 2 or 3, wherein the top coat layer on the back surface of the paper base further contains inorganic fine particles.   5. The oil-resistant paper according to claim 1, wherein at least one of the undercoat coating layer and the topcoat coating layer is crosslinked with a crosslinking agent.   6. The oil-resistant paper according to claim 5, wherein the crosslinking agent is an epichlorohydrin crosslinking agent.   The oil resistance according to any one of claims 1 to 6, wherein the paper base material contains 0 to 0.3 parts by mass of an internal sizing agent with respect to 100 parts by mass of the pulp of the paper base material. paper.   The oil-resistant paper according to any one of claims 1 to 7, wherein a Canadian standard freeness of the paper base pulp is 80 to 350 ml. Oil paper according to any one of claims 1 to 8, wherein the basis weight of 20 to 150 g / ^{m 2.} 10. The oil-resistant paper according to claim 1, wherein the total coating amount of the undercoat coating layer and the topcoat coating layer is 1 to 10 g / m ^{2 on} one side.   The oil-proof paper according to any one of claims 1 to 10, wherein the paper base material contains hardwood bleached kraft pulp in an amount of 60 to 100% by weight out of 100% by weight of the total pulp of the paper base material.