JP2018031092A - Water-resistant oil-resistant paper, and paper-made container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-resistant oil-resistant paper sustainable of strength even if oil and water are impregnated in a paper layer, capable of suppressing the exudation of oil and water onto an opposite side, and dispensing with a particular adhesive when processing into a container.SOLUTION: The water-resistant oil-resistant paper includes: a surface layer; one layer or a plurality of intermediate layers; and a back layer, where the surface layer, the intermediate layer, and the back layer are composed of a needle-leaved tree kraft pulp, and a broad-leaved tree kraft pulp as principal raw materials, in a blending ratio of the needle-leaved tree kraft pulp and the broad-leaved tree kraft pulp, the surface layer and the back layer have a blending ratio of the needle-leaved tree kraft pulp of 70% or more and 90% or less, and the intermediate layer has a blending ratio of the needle-leaved tree kraft pulp of 70% or less, the blending ratios of the needle-leaved tree kraft pulp of the surface layer and the back layer are greater than a blending ratio of the needle-leaved tree kraft pulp of the intermediate layer, the surface layer and the back layer contain a dry paper strengthening agent, a wet paper strengthening agent, an oil resistant agent, and a fixer, and the intermediate layer contains a dry paper strengthening agent, and a wet paper strengthening agent.SELECTED DRAWING: None

Description

  The present invention relates to a water and oil resistant paper and a paper container.

  Containers that contain foods such as bread, cakes, donuts, pizzas and fried foods that contain a lot of oil and moisture contain plastic trays inside plastic or white paperboard cases, in addition to plastic trays. Cases in which white paperboard is laminated with a resin such as polyethylene on the inside are used.

  Although these containers have the advantage that the appearance of the container due to oil oozing out from the food and moisture permeation does not occur, the oil and water staying inside the container will adhere to the food again, so that the flavor of the food Or the texture may be impaired.

  In order to prevent such oil and moisture from re-adhering to the food, there is a method of using a container in which the inner surface of the container (the side in contact with the food) is formed of an oil-absorbing / water-absorbing sheet and polyethylene is laminated on the outer surface of the container. However, in that case, the sheet absorbs and absorbs oil and moisture from the food, so that the sheet exudes to the outer surface of the container and deteriorates in appearance, and the strength of the container may be lowered and deformed. In addition, such a sheet requires a laminating process, which may increase manufacturing costs. Furthermore, since the container provided with the laminated resin is discarded as plastic waste after use, it cannot be recycled as a raw material for recycled paper, and may become a source of “microplastic” that is attracting attention as an environmental problem.

  On the other hand, paper containers that are recyclable and made of general white paperboard that absorbs oil and moisture from foods are low in production cost and can be disposed of as paper, but penetrated oil and moisture. Problems such as deterioration of the external appearance of the container, a decrease in strength, and deformation are not solved.

  For such problems, the outer layer is water-resistant and the strength as a container is secured, while the inner layer in contact with the food is hygroscopic and water-absorbing to adsorb and absorb water vapor and moisture from the food, and this inner layer is A paperboard for food that is oil resistant and prevents fouling due to oil penetration has been disclosed (see Patent Document 1).

  However, in the paperboard of the above-mentioned patent document 1, since the inner layer in contact with the food is oil resistant, the oil adhering to the inner surface of the container again adheres to the food. Moreover, when processing into a container, it is necessary to use a special adhesive for the oil resistant surface of the inner layer and the water resistant surface of the outer layer.

  Furthermore, since the container is configured to ensure the strength of the outer layer using expensive pulp in order to satisfy the cosmetics and printability required for the paper container, it is necessary to increase the amount of the outer layer and reduce the cost. There is a risk of high paperboard.

JP-A-1-207498

  The present invention has been made in view of the above-described circumstances, and its purpose is to prevent the oil and moisture from the food from reattaching to the food, and the oil and moisture penetrate into the paper layer. In addition, the specified strength can be maintained, oil and moisture can be prevented from oozing out on the opposite side, no special adhesive is required when processing into a paper container, It is an object of the present invention to provide a water- and oil-resistant paper that does not become, and a paper container formed from the water- and oil-resistant paper.

  The water and oil resistant paper according to the present invention is a water and oil resistant paper having a surface layer, one or more intermediate layers, and a back layer, wherein the surface layer, the intermediate layer and the back layer are made of softwood kraft pulp and hardwood kraft pulp. As a main raw material, the blending ratio of the softwood kraft pulp in the blending ratio of the softwood kraft pulp and the hardwood kraft pulp is 70% or more and 90% or less in the surface layer and the back layer, and 70% or less in the intermediate layer, The blending ratio of the softwood kraft pulp in the surface layer and the back layer is larger than the blending ratio of the softwood kraft pulp in the intermediate layer, and the surface layer and the back layer are a dry paper strength enhancer, a wet paper strength enhancer, and an oil resistance agent. And the intermediate layer contains a dry paper strength enhancer and a wet paper strength enhancer.

  According to the water- and oil-resistant paper according to the present invention, the surface layer that comes into contact with food stored when processed into a paper container and the back layer that touches other foods as the outer surface of the container have appropriate oil absorption and water absorption, Oil and moisture from the food are absorbed by the surface layer and the back layer. Thereby, it can suppress that the oil and water | moisture content which came out of foodstuff adhere to foodstuff again, and do not impair the flavor and food texture of foodstuff.

  In addition, the water- and oil-resistant paper according to the present invention has an appropriate oil absorption and water absorption of the surface layer and the back layer, so a special adhesive is required for pasting or box making when processing into a paper container. It can be processed in the same way as general paperboard.

  Furthermore, since the intermediate layer has water resistance, it is possible to prevent the oil and water that touched the surface layer or the back layer from oozing out to the opposite surface, and the appearance of the container is deteriorated and the commercial value may be reduced. In addition, the shape and strength of the container can be sufficiently maintained.

  Further, since a resin such as polyethylene is not used, it does not become a source of generation of microplastic, and can be recycled as a raw material for recycled paper.

  The water and oil resistant paper is JAPAN TAPPI paper pulp test method no. The oil resistance according to 41: 2000 is preferably 6 or more, and the residual ratio of wet tensile strength is 8% or more. By having the oil resistance, high oil repellency can be obtained and oil bleeding can be suppressed. Further, by having the residual ratio of the wet tensile strength, it is possible to prevent the water-resistant and oil-resistant paper from being easily broken even when the oil and water is infiltrated.

The Z-axis tensile strength of the water / oil resistant paper is preferably 250 kN / m ² or more, and the ratio of the average fiber orientation angle of the surface layer and the back layer to the longitudinal direction in the transverse direction is preferably 1.61 or more and 1.85 or less. By having the Z-axis tensile strength, generation of wrinkles and delamination can be prevented when cutting or box forming. Moreover, when the ratio of the average fiber orientation angle of the surface layer and the back layer to the longitudinal direction in the transverse direction is in the above range, the interlayer strength and the workability at the time of box forming can be ensured.

  A water-soluble resin is preferably applied to at least one of the surface layer, the intermediate layer, and the back layer. The oil resistance can be increased by applying the water-soluble resin.

  As described above, the water and oil resistant paper of the present invention has appropriate oil absorption and water absorption in the surface layer and the back layer, so that oil and moisture from the food can be prevented from reattaching to the food. It can be processed in the same way as general paperboard without the need for special adhesives for pasting or box making when processing into a paper container. In addition, since the intermediate layer has water resistance, it is possible to prevent oil and moisture from oozing out to the opposite surface, thereby preventing appearance deterioration and deformation of the container due to strength reduction. Furthermore, since a resin such as polyethylene is not used, it does not become a source of generation of microplastic.

  The water and oil resistant paper according to the present invention will be described by taking a water and oil resistant paper having a three-layer structure including a surface layer, one intermediate layer and a back layer as an example. In the following, the surface layer is a layer in contact with food, and when processed into a paper container, the surface of the surface layer becomes the inner surface of the paper container (the surface in contact with food), and the surface of the back layer becomes the outer surface of the paper container.

(Surface and back layers)
Since the surface layer and the back layer have appropriate oil absorption and water absorption, (a) the oil and moisture from the food are absorbed by the surface layer and the back layer that are in contact with the food. Can be prevented from re-adhering to the food, and the flavor and texture of the food will not be impaired. (B) Special adhesive is required in the process of processing into a paper container by bonding or box making. However, it can be processed in the same way as general paperboard.

  In order to fulfill the above roles (a) and (b), appropriate oil absorption and water absorption are imparted to the surface layer and the back layer. That is, the surface layer and the back layer have moderate oil absorption and water absorption, so that oil and moisture from foods such as bread, cakes, donuts, pizzas, and deep-fried foods that contain a lot of oil and moisture are absorbed. It is possible to prevent the oil and water from the oil from re-adhering to the food and to ensure good bonding and boxing suitability.

  As raw material pulp of such surface layer and back layer, mainly softwood kraft pulp (NKP) and hardwood kraft pulp (LKP), hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft Pulp (LUKP), softwood unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), softwood half-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp, etc. are suitably employed, and stone Grand pulp (SGP), Pressurized stone grand pulp (PGW), Refiner ground pulp (RGP), Thermo grand pulp (TGP), Chemi-ground pulp (CGP), Groundwood pulp (GP), Thermomechanical pulp (TMP), etc. Mechanical pulp or ke Off, hemp, and various known pulps such as chemically or mechanically produced pulp from non-wood fibers such as reed can be used.

The water resistance and oil resistance of the surface layer and the back layer are not generally determined by the type, ratio, freeness and basis weight of the raw pulp, but the mixing ratio of NKP and LKP is mixed from 70:30 to 90:10. It is preferable to adjust the raw material pulp by multilayer sheeting or the like so that the freeness is 350 cc or more and 500 cc or less and the basis weight is 50 g / m ² or more and 120 g / m ² or less.

  In order to obtain the above-mentioned water and oil resistance of the surface layer and the back layer efficiently in a balanced manner, it is preferable that the blending ratio of NKP to LKP in the surface layer and the back layer is 70:30 or more and 90:10 or less, and 80:20 More preferably, it is 90:10 or less. If the blending ratio of the NKP does not satisfy the above lower limit, the density of the surface layer and the back layer increases, and it may be difficult to obtain the desired water and oil resistance. On the other hand, when the above upper limit is exceeded, the density of the surface layer and the back layer is lowered, and the printability and workability may be lowered.

  In addition, by controlling the freeness of the raw pulp to 350 cc or more and not proceeding with beating, the fibrillation of the fibers constituting the raw pulp can be suppressed, the excessive increase in the critical surface area of the pulp fiber itself can be controlled, and the high LKP Since blending has a problem that the interlaminar strength and the surface strength are lowered, blending a large amount of NKP at a ratio of 70% to 90% can ensure the above-mentioned strength and ensure oil resistance and oil repellency.

  From the viewpoint of obtaining the above-mentioned strength and water / oil resistance, as well as ensuring air permeability described later, the freeness of the raw pulp of the surface layer and the back layer is preferably 350 cc or more and 500 cc or less, and 400 cc or more and 500 cc or less. More preferably. If the freeness of the raw material pulp does not satisfy the above lower limit, the fiber length of the raw material pulp will be shortened, and the density of the surface layer and the back layer will increase, making it difficult to obtain the desired water and oil resistance, and water and oil resistance. It may be difficult to ensure the air permeability of the paper. On the other hand, when the above upper limit is exceeded, the fiber length becomes long, the density of the surface layer and the back layer becomes low, and there is a possibility that the amount of oil and moisture that can be absorbed from food is reduced.

  Here, the freeness is a Canadian standard freeness in accordance with JIS-P8121-2: 2012 after the sample is disaggregated by a standard disintegrator in accordance with JIS-P-8220-1: 2012. It is a freeness value measured with a testing machine.

In order to obtain the desired water and oil resistance, the basis weight of the surface layer and the back layer is preferably 50 g / m ² or more and 120 g / m ² or less, more preferably 80 g / m ² or more and 100 g / m ² or less. More preferred. If the basis weight does not satisfy the lower limit, the amount of oil or moisture that can be absorbed from the food may be reduced. On the other hand, if the above upper limit is exceeded, the desired water and oil resistance can be obtained, but the basis weight of the intermediate layer must be reduced, so when processed into a paper container, the oil content and moisture from the food It may be difficult to maintain the strength of the container after absorbing the water.

  Here, the basis weight means a value measured according to the basis weight test method described in JIS-P-8124 (1998).

  The surface layer and the back layer preferably contain a dry paper strength enhancer in an amount of 24 kg to 30 kg with respect to 1,000 kg of the raw material pulp of the surface layer and the back layer. When the surface strength and the back layer contain a dry paper strength enhancer in the above range, the strength of the surface layer and the back layer in a normal dry state can be secured, so that the damage to the paper container is more likely to occur. Can be prevented.

  The dry paper strength enhancer is not particularly limited, and for example, one or two or more kinds can be appropriately selected from known ones such as polyacrylamide, starch, carboxymethylcellulose, and the like. Among them, the dry paper strength agent which is a primary and / or secondary amino group-containing vinyl polymer (cation-modified acrylamide polymer by Hofmann decomposition reaction of polyacrylamide) is easily fixed on pulp, and other inhibiting factors such as anion trash It is preferable because it is difficult to be influenced by the above.

  Further, it is preferable that the surface layer and the back layer contain a wet paper strength enhancer in an amount of 7 kg to 11 kg with respect to 1,000 kg of the raw material pulp of the surface layer and the back layer. When the surface layer and the back layer contain a wet paper strength enhancer in the above range, the strength of the surface layer and the back layer can be secured even after moisture is absorbed from the food. It is possible to further prevent the occurrence of damage.

  The wet paper strength enhancer is not particularly limited, and for example, one or two known materials such as polyamide polyamine epichlorohydrin, melamine resin, melamine formaldehyde resin, urea formaldehyde resin, polyamide, polyamide epoxy, polyvinylamine, and the like. More than one species can be appropriately selected and used. Polyamide polyamine epichlorohydrin resin which is an aqueous solution obtained by reacting aliphatic dibasic acid, polyalkylene polyamine and epichlorohydrin is preferable from the viewpoint of strength improvement effect and safety for food use. Currently, polyamide polyamine epichlorohydrin is sometimes simply referred to as polyamide epichlorohydrin resin.

  Moreover, it is preferable to contain 30 kg or more and 70 kg or less of an oil proofing agent in the surface layer and the back layer with respect to 1,000 kg of the raw material pulp of the surface layer and the back layer. By making the surface layer and the back layer contain the oil resistance in the above range, the desired oil resistance can be ensured.

  The oil-proofing agent is not particularly limited, and for example, one or two or more types can be appropriately selected from known ones such as acrylic resins, styrene butadiene resins, and fluorine resins. Of these, fluorine-based oil repellency is used, but a fluorine-based resin is preferable from the viewpoint of lowering the surface tension of paper and preventing oil penetration from the phenomenon of wetting. Of these, a fluorocarbon-based oil resistant agent is particularly preferable. Typical examples of the fluorocarbon-based oilproofing agent include an acrylate polymer type and a phosphate ester type. The functional group for fixing to paper is hydrophilic and generally has anionic or nonionic properties. The oil resistance of fluorinated oil-resistant agents is that phosphoric acid ester groups are fixed on the paper due to their hydrophilicity, the perfluoroalkyl groups are oriented outward on the paper surface, and the surface tension of the processed surface is It is expressed by being lower than the surface tension.

  It is preferable that the surface layer and the back layer contain a fixing agent in an amount of 8 kg to 12 kg with respect to 1,000 kg of the raw material pulp of the surface layer and the back layer. By including the fixing agent in the above-mentioned range in the surface layer and the back layer, the effect of the oil resistance agent can be obtained. If the content of the fixing agent is less than the above lower limit, the sufficient effect of the oil resistance agent cannot be obtained. If the content is larger than the upper limit, the ionicity of the pulp fiber and the oil resistance agent is blocked by the free fixing agent, and the oil resistance agent is fixed. The oil resistance may be impaired.

  The fixing agent is not particularly limited. For example, sulfate band, polyamide resin represented by cationic polymer electrolyte, polyamine resin, shrimp chlorohydrin resin, cationic urea, cationic polyacrylamide resin, polyethyleneimine resin, etc. 1 type or 2 types or more can be suitably selected and used from these well-known things. By using the fixing agent, it is possible to improve the so-called yield of various chemicals, to maintain the strength of the paper, and to ensure uniform oil resistance.

  The fiber orientation angles of the surface layer and the back layer are preferably 1.61 or more and 1.85 or less. By keeping the fiber orientation angle within the above range, it is possible to ensure the interlaminar strength and suitability for processing into a paper container while maintaining the oil resistance and water resistance within the desired ranges.

  Here, the fiber orientation angle refers to an angle formed by the reference direction and the fiber, and is measured by, for example, an ultrasonic conduction type orientation angle meter (for example, “SST-3000” manufactured by Nomura Corporation).

It is preferable to apply a water-soluble resin to the surface layer and the back layer. The oil resistance is improved by applying the water-soluble resin. The water-soluble resin is not particularly limited, and polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC), which are frequently used for food applications and excellent in coatability during production, can be used. Especially, it is preferable to apply 0.5 g / m ² or more and 3.5 g / m ² or less of PVA on the surface of the back layer, and more preferable to apply 0.7 g / m ² or more and 2 g / m ² or less. By applying PVA to the back layer in the above range, oil resistance can be improved and good printability can be obtained. On the other hand, if the lower limit is not satisfied, the oil resistance may not be improved. Moreover, when the said upper limit is exceeded, oil resistance does not change and there exists a possibility that manufacturing cost and productivity may worsen.

(Middle layer)
Next, the intermediate layer will be described. The intermediate layer is a layer that plays a role of preventing the oil and moisture absorbed in the surface layer and the back layer from penetrating into the intermediate layer, and in order to fulfill this role, water and oil resistance is imparted.

  That is, even if oil or moisture from the stored food is absorbed by the surface layer and the back layer, the water and oil resistance of the intermediate layer causes the oil and water absorbed in the surface layer and back layer to be absorbed by the thickness of the water and oil resistant paper. Can be blocked by direction. Therefore, it is possible to prevent oil and moisture from spreading to the opposite layer.

  As the raw material pulp for the intermediate layer, various known pulps can be used as in the case of the raw material pulp for the surface layer and the back layer. In addition, for the same reason as the surface layer and the back layer, it is preferable to use a chemical pulp mainly composed of NKP and LKP. The blending ratio of NKP in the blending ratio of NKP and LKP in the intermediate layer is preferably 70% or less, more preferably 40% or more and 70% or less, and further preferably 60% or more and 70 or less. Moreover, it is preferable that the blending ratio of NKP in the intermediate layer is smaller than the blending ratio of NKP in the surface layer and the back layer. If the blending ratio of the NKP in the intermediate layer does not satisfy the above lower limit, the color becomes white and there is a possibility that the unbleached color with a natural texture does not occur. On the other hand, when the above upper limit is exceeded, the blending ratio of NKP in the intermediate layer becomes larger than the blending ratio of NKP in the front layer and the back layer, and there is a possibility that the interlayer strength cannot be secured.

  The freeness of the raw material pulp of the intermediate layer is preferably 350 cc or more and 450 cc or less, and more preferably 380 cc or more and 420 cc or less, for the same reason as the surface layer and the back layer. If the freeness of the raw pulp does not satisfy the above lower limit, the fiber length of the raw pulp is shortened, the density of the intermediate layer is increased, and it becomes difficult to obtain the desired water and oil resistance. It may be difficult to ensure air permeability. On the other hand, when the above upper limit is exceeded, the fiber length becomes long, the density of the intermediate layer becomes low, and there is a possibility that the amount of oil or moisture that can be absorbed from food is reduced.

The basis weight of the intermediate layer is preferably 130 g / m ² or more and 300 g / m ² or less, and more preferably 190 g / m ² or more and 260 g / m ² or less. If the basis weight does not satisfy the lower limit, it may be difficult to prevent oil and water absorbed in the surface layer and the back layer from penetrating the intermediate layer and bleeding on the opposite surface. On the other hand, when the above upper limit is exceeded, the production cost increases, and the water and oil resistance may be impaired by bending during processing.

  Even if the intermediate layer is one layer, the effect can be exhibited, but two layers are preferable, and a four-layer structure is more preferable. By making the intermediate layer into four layers, the oil and moisture absorbed in the surface layer and the back layer can be effectively infiltrated into the intermediate layer, and the effect of preventing bleeding is increased on the opposite surface. On the other hand, if the intermediate layer is 5 layers or more, the effect of preventing bleeding on the opposite surface does not change, and the production cost may increase.

  The intermediate layer preferably contains a dry paper strength enhancer of 27 kg or more and 30 kg or less with respect to 1,000 kg of the raw material pulp of the front layer and the back layer. If the intermediate layer contains a dry paper strength enhancer in the above range, the strength of the intermediate layer in a normal dry state can be secured, so that the occurrence of damage to the paper container can be further prevented. it can.

  The intermediate layer preferably contains a wet paper strength enhancer of 7 kg or more and 11 kg or less with respect to 1,000 kg of the raw material pulp of the intermediate layer. When the intermediate layer contains a wet paper strength enhancer in the above range, the strength of the intermediate layer can be ensured even after moisture is absorbed from food, so there is damage such as fluffing and paper peeling on the inner surface of the paper container. Occurrence can be further prevented.

  Although it is possible to contain an oil proofing agent in the intermediate layer, the inclusion of the oil proofing agent leads to excessive quality, and the interlaminar strength is lowered and the flexibility is increased, so that wrinkles may occur during processing and the water and oil resistance may be impaired. There is.

(Water and oil resistant paper)
Next, the water and oil resistant paper will be described. The water- and oil-resistant paper is produced by sequentially laminating raw material pulps of the surface layer, the intermediate layer, and the back layer by a paper machine. That is, the water / oil resistant paper is formed by laminating an intermediate layer on the surface of the surface layer and laminating a back layer on the surface of the intermediate layer by a paper machine. Of course, the layers may be stacked in the reverse order.

  Regarding the oil resistance of the water and oil resistant paper, the JAPAN TAPPI paper pulp test method No. It is preferable that the oil resistance, which is the number of kits when tested according to 41: 2000, is grade 6 or higher. If the oil resistance is less than grade 6, the oil adhering to one surface of the water-resistant and oil-resistant paper may ooze out to the other surface, reducing the strength of the paper container or impairing the appearance of the container. is there.

The water absorption of the water and oil resistant paper is preferably 10 g / m ² or more and 50 g / m ² or less at a contact time of 120 seconds as measured in accordance with JIS-P8140: 1998, and 20 g / m ^2. More preferably, it is 30 g / m ² or less. If the water absorption does not satisfy the above lower limit, the reattachment of moisture to the food cannot be prevented, and the flavor and texture of the food may be impaired. In addition, a special adhesive is required because the adhesive does not penetrate into the paper layer of the front layer and the back layer at the time of pasting and box making, and a special adhesive is required, and when recycling water-resistant and oil-resistant paper as recycled paper There is a risk of poor solubility. Furthermore, it is necessary to add a large amount of chemicals. As a result, the operability is deteriorated and the manufacturing cost may be increased. On the other hand, if the above upper limit is exceeded, although it is excellent in water absorption, the adhesive penetrates too much into the paper layer of the front layer and the back layer at the time of bonding and box making, or the adhesiveness deteriorates, or a large amount of adhesive is applied. There is a risk of having to.

  Moreover, it is preferable that the residual ratio of the wet tensile strength of the water- and oil-resistant paper is 8% or more. If the residual ratio of the wet tensile strength is 8% or less, there is a possibility that it will be easily broken when moisture and oil penetrate.

In addition, the residual ratio of wet tensile strength is a value calculated by the following (Formula 1).
(Formula 1)
Residual ratio of wet tensile strength (%) = (wet tensile strength / dry tensile strength) × 100

As the Z-axis strength of the water and oil resistant paper, the JAPAN TAPPI paper pulp test method No. The k-axis strength measured in accordance with 18-1: 2000 is preferably 250 kN / m ² or more. By having the Z-axis strength, for example, generation of wrinkles when adjusting curl curl at the time of flat judgment with a decurler and generation of delamination and wrinkles during container molding can be prevented.

  The smoothness of the water- and oil-resistant paper is preferably 6.0 seconds or more and 14.0 seconds or less in terms of Beck smoothness measured in accordance with JIS-P-8119: 1998. When the Beck smoothness is in the above-described range, it is possible to prevent occurrence of double feeding and overshooting defects when forming into a sheet-fed printing machine or container mold.

  The calendar device for the surface smoothing treatment is not particularly limited, and for example, a machine calendar, a soft calendar, or the like is used as appropriate.

  The air permeability of the water and oil resistant paper is preferably 100 seconds or more and 200 seconds or less, more preferably 130 seconds or more and 170 seconds or less in terms of air permeability measured according to JIS-P-8117: 1998. When the air permeability is within the above range, when the water-resistant and oil-resistant paper is processed into a heating container in particular, it is externally used without causing the steam generated from the food to be stored in the container. Can prevent the food from being deteriorated by steam and can maintain a good texture.

  The water and oil resistant paper may be provided with other layers such as a sealing layer between the surface layer and the intermediate layer and / or between the intermediate layer and the back layer as long as the object of the present invention is not adversely affected.

  In addition, the water- and oil-resistant paper may use interlayer starch as the interlayer adhesive. The presence of interlayer starch can improve strength and printability.

  Since the back layer, which is the outermost layer of paper containers, is often printed, the back layer is used as necessary to improve the gloss and surface strength of the back layer and to adjust the slipperiness. It is preferable to apply various means for improving the printability by, for example, applying a coating solution containing a water-soluble substance as a main component to the surface.

  The water-soluble substance is not particularly limited. For example, polyacrylamide and derivatives thereof, cellulose derivatives such as PVA and CMC, starch, modified starch, polystyrene-butadiene-based, acrylic-based, polyvinyl acetate-based latex, and wax emulsion. 1 type or 2 types or more can be suitably selected from the well-known thing which can be used for foodstuffs, such as.

  In addition to the above-mentioned dry paper strength enhancer, wet paper strength enhancer, fixing agent, oil resistant agent, and water-soluble substance, the water-resistant and oil-resistant paper may be an agent that can be used for food applications. Fillers, antifoaming agents, anti-slip agents, pH adjusting agents and the like may be contained.

<Method for producing water and oil resistant paper>
The method for producing the water- and oil-resistant paper is not particularly limited, and may be either a neutral papermaking method or an alkaline papermaking method, but the oilproof agent is fixed on the surface layer and the back layer to efficiently exhibit oil resistance. Therefore, it is preferable to produce by a neutral papermaking method so that the hot water extraction PH is 5 to 8.5. Also, the paper machine is not particularly limited, but for multilayer papermaking, it is desirable to use, for example, a round net paper machine, a long net paper machine, etc., and a round net paper machine is more preferable.

  When making paper with a round net paper machine, the pulp fiber of the paper support is oriented in the thickness direction of the paper, which is relatively different from that of the long net paper machine, so that the interlayer strength required for water and oil resistant paper can be improved. The oil proofing agent adhering to the surface of the raw pulp fiber is uniformly distributed in the Z-axis direction (paper thickness direction), and the paper base made by the long net paper machine has the oil proofing agent by dehydration in the wire part. Although distributed more on the wire surface side than on the felt surface side, the round net paper machine does not forcibly dewater the wire part (circular cylinder), so it is difficult for the oil-resistant agent to flow out to the white water side, so high oil resistance can be obtained. it can. Also, the round net paper machine has a slow paper making speed, and it is not necessary to apply excessive pressure in the press and calendar process, and the amount of each layer can be changed, so the amount of oil-resistant layer (surface layer and back layer) can be changed. It is easy to obtain the oil resistance from the fact that it is possible to produce a paper that does not allow oil to penetrate even if the middle layer does not contain an oil resistant agent. In addition, the forward flow bat of the circular net of a round net paper machine can easily form a sheet with a beautiful texture, so that it is easy to obtain oil resistance. In addition, in the round net multilayer paper making, compared to the long net multilayer paper making, the directions of the fibers in the raw pulp are difficult to align at the time of paper making, and the fibers are easily entangled with each other, so that the interlayer strength can be ensured.

  As described above, the water-resistant and oil-resistant paper according to the present invention has been described with respect to the case where the paper layer is composed of the three layers of the surface layer, the intermediate layer, and the back layer. Even if other layers such as a sealing layer are provided between the surface layer and the intermediate layer and / or between the intermediate layer and the back layer, the desired effect of the present invention can be obtained without departing from the scope. Can do.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. Unless otherwise specified, the content of each drug is described as a solid content.

[Examples 1 to 28, Comparative Examples 1 to 5]
A surface layer, a back layer, and an intermediate layer were obtained under the conditions shown in Table 1. In addition, the column which does not use the medicine is “−”.

[Example 1]
About the surface layer and the back layer, the ratio of the softwood kraft pulp (NKP) was 70%, the hardwood kraft pulp (LKP) was 30%, the basis weight was 85 g / m ² , and the freeness was 500 cc. A papermaking raw material having a dry paper strength enhancer of 28 kg / t, a wet paper strength enhancer of 9 kg / t, a fixing agent of 10 kg / t, and an oil resistance of 40 kg / t was obtained.

About the intermediate | middle layer, the ratio of the softwood kraft pulp (NKP) was 65%, the hardwood kraft pulp (LKP) was 35%, the basis weight was 225 g / m ² , the freeness was 400 cc, and the number of layers was 4 layers. A papermaking raw material having a dry paper strength enhancer of 28 kg / t and a wet paper strength enhancer of 9 kg / t was obtained.

  The surface layer, the back layer and the intermediate layer were made with a round net paper machine and pressed with a press calender at 50 N / mm to obtain a water and oil resistant paper of Example 1 in Table 2.

[Examples 2-28, Comparative Examples 1-5]
In Examples 2-28 and Comparative Examples 1-5, as shown in Table 1, various conditions were changed, and the water-resistant and oil-resistant paper shown in Table 2 was obtained. The conditions other than those shown in Table 1 were not changed.

  The obtained water and oil resistant paper was evaluated by the following evaluation method.

[Blood on the opposite side of salad oil]
Water-resistant oil-resistant paper is molded into a box container, and salad oil (commercial canola oil extracted from canola varieties that do not contain erucic acid (erucic acid) and glucosinolate by cultivar improvement) is heated to 80 degrees. Then, it was poured into the box container, and after 30 minutes, it was visually observed whether or not the salad oil oozed on the opposite surface, and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: No bleeding of salad oil on the opposite side is observed.
○: Slightly oozing salad oil on the opposite side.
Δ: Salad oil bleeding on the opposite side is observed.
X: Salad oil bleeding on the opposite side is remarkable.

[Bleeding on the outer surface of the cupcake when baking]
Water- and oil-resistant paper is molded into a box container, 100 g of commercially available hot cake mix, 80 g of butter, 80 g of granulated sugar and 2 eggs (medium balls) are poured into the box container and baked in an oven preheated to 180 ° C. for about 15 minutes. Then, the outer surface (outer side surface and bottom surface) of the container was visually observed for bleeding of oil and moisture, and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: No bleeding of oil or moisture on the outer surface is observed.
○: Some bleeding of oil and moisture on the outer surface is observed.
Δ: Oil and moisture bleeding on the outer surface is observed.
X: The oil and moisture ooze out on the outer surface.

  The evaluation results are shown in Table 2 together with the quality of the water and oil resistant paper.

  Considering Comparative Examples 1 to 5 in which suitable evaluation could not be obtained, Comparative Example 1 has a desired oil resistance and wet tension because the blending ratio of NKP in the surface layer and the back layer does not satisfy the lower limit. It is considered that the remaining ratio of strength and the Z-axis strength were not obtained. On the other hand, in Comparative Example 2, it is considered that the desired oil resistance and Z-axis strength were not obtained because the blending ratio of NKP in the surface layer and the back layer exceeded the upper limit.

  In Comparative Example 3, since the dry paper strength enhancer and the wet strength enhancer were not added to the intermediate layer, it is considered that the desired residual ratio of oil resistance and wet tensile strength could not be obtained. On the other hand, in Comparative Example 4, since the blending ratio of NKP in the intermediate layer exceeds the upper limit, it is considered that the desired oil resistance, residual ratio of wet tensile strength and Z-axis strength were not obtained.

  In Comparative Example 5, since the dry paper strength enhancer and the wet paper strength enhancer were not added to the intermediate layer, it is considered that the desired oil resistance, residual ratio of wet tensile strength and Z-axis strength were not obtained.

  As shown in the results of Table 2, it can be seen that the water and oil resistant papers of Examples 1 to 20 have good water and oil resistance.

  From the above, a water- and oil-resistant paper having a surface layer, one or a plurality of intermediate layers, and a back layer, the mixing ratio of softwood kraft pulp and hardwood kraft pulp, dry paper strength enhancer, wet paper strength enhancer, fixing It turns out that the water-resistant oil-resistant paper excellent in water-and-oil resistance is obtained by making content of an agent and an oil-proof agent into a predetermined range.

As described above, the water and oil resistant paper of the present invention has appropriate oil absorption and water absorption in the surface layer and the back layer, so that oil and moisture from the food can be prevented from reattaching to the food. It can be processed in the same way as general paperboard without the need for special adhesives for pasting or box making when processing into a paper container. In addition, since the intermediate layer has water resistance, it is possible to prevent oil and moisture from oozing out to the opposite surface, thereby preventing appearance deterioration and deformation of the container due to strength reduction. Furthermore, since a resin such as polyethylene is not used, it does not become a source of generation of microplastic.

Claims (7)

A water and oil resistant paper comprising a surface layer, one or more intermediate layers, and a back layer,
The above surface layer, intermediate layer and back layer are mainly made of softwood kraft pulp and hardwood kraft pulp,
The blending ratio of the softwood kraft pulp in the blending ratio of the softwood kraft pulp and the hardwood kraft pulp is 70% or more and 90% or less in the surface layer and the back layer, and 70% or less in the intermediate layer,
The blending ratio of the softwood kraft pulp in the surface layer and the back layer is larger than the blending ratio of the softwood kraft pulp in the intermediate layer,
The surface layer and the back layer contain a dry paper strength enhancer, a wet paper strength enhancer, an oil resistance agent and a fixing agent,
The water and oil resistant paper, wherein the intermediate layer contains a dry paper strength enhancer and a wet paper strength enhancer. JAPAN TAPPI Paper Pulp Test Method No. The oil resistance according to 41: 2000 is grade 6 or higher,
The water / oil resistant paper according to claim 1, wherein the residual ratio of wet tensile strength is 8% or more. Z-axis strength is 250 kN / m ² or more,
The water / oil resistant paper according to claim 1 or 2, wherein a ratio of an average fiber orientation angle of the surface layer and the back layer to a longitudinal direction in a transverse direction is 1.61 or more and 1.85 or less.   The water and oil resistant paper according to claim 1, 2 or 3, wherein a water-soluble resin is applied to the surface layer, the intermediate layer, and / or the back layer. A method for producing a water and oil resistant paper having a surface layer, one or more intermediate layers, and a back layer,
Comprising a step of paper-making the surface layer, intermediate layer, and back layer,
The above surface layer, intermediate layer, and back layer are mainly made of softwood kraft pulp and hardwood kraft pulp,
The blending ratio of the softwood kraft pulp in the blending ratio of the softwood kraft pulp and the hardwood kraft pulp is 70% or more and 90% or less in the surface layer and the back layer, and 70% or less in the intermediate layer,
The blending ratio of the softwood kraft pulp in the surface layer and the back layer is larger than the blending ratio of the softwood kraft pulp in the intermediate layer,
The above surface layer and back layer contain a dry paper strength enhancer, a wet paper strength enhancer, an oil resistance agent and a fixing agent,
A method for producing a water- and oil-resistant paper, wherein the intermediate layer contains a dry paper strength enhancer and a wet paper strength enhancer.   Orient the pulp fibers of the softwood kraft pulp and hardwood kraft pulp in the thickness direction of the paper by a round net paper machine, and the oil resistant agent adhering to the surface of the pulp fibers is uniformly distributed in the thickness direction of the paper A method for producing a water- and oil-resistant paper according to claim 5. A paper container formed from the water and oil resistant paper according to any one of claims 1 to 4.