JP2021080625A - Water- and oil-resistant paper - Google Patents

Abstract

To provide a water- and oil-resistant paper capable of maintaining strength even when an oil and water are permeated in a paper layer, suppressing oozing of an oil and water to its opposite surface, and not needing a special adhesive when processing to form a container.SOLUTION: One embodiment of this invention is a water- and oil-resistant paper assembled with a surface layer, one or plural layers of intermediate layers, and a back layer, wherein the surface layer, the intermediate layer and the back layer include coniferous tree kraft pulp and hardwood kraft pulp as the main raw material, a compounding ratio of the coniferous tree kraft pulp in the kraft pulp is 70% or over in the surface layer and back layer and 70% or under in the intermediate layer; a compounding ratio of the coniferous tree kraft pulp in the surface layer and back layer is larger than the compounding ratio of the coniferous tree kraft pulp in the intermediate layer; a water absorbency with a contact time of 120 s is 10 g/m2 or over and 50 g/m2 or under; and the surface layer and the back layer include 30 kg/t or over and 70 kg/t or under of an oil resistant agent toward 1000 kg of the raw material pulp.SELECTED DRAWING: None

Description

The present invention relates to water and oil resistant paper.

Containers for storing foods such as bread, cakes, donuts, pizzas, and fried foods that contain a lot of oil and water include plastic trays and plastic trays inside a case made of plastic or white paperboard. A case or the like in which a resin such as polyethylene is laminated on the inside with white paperboard is used.

These containers have the advantage that the appearance of the container does not deteriorate due to the permeation of oil and water that have exuded from the food, but on the other hand, the oil and water that remain inside the container reattach to the food, resulting in the flavor of the food. And may impair the texture.

In order to prevent such oil and water from reattaching to food, there is also a method of forming the inner surface of the container (the side in contact with food) with a sheet having oil absorption and water absorption and using a container in which polyethylene or the like is laminated on the outer surface of the container. However, in that case, the sheet absorbs oil and water from the food, so that the sheet exudes to the outer surface of the container, which not only deteriorates the appearance but also reduces the strength of the container and may deform it. Further, such a sheet requires a laminating process, which may increase the manufacturing cost. Furthermore, since the container containing the laminated resin is discarded as plastic waste after use, it cannot be recycled as a raw material for recycled paper, and it may become a source of "microplastic", which is attracting attention as an environmental problem.

On the other hand, a paper container made of general white paperboard that is recyclable and absorbs oil and water from food has a low manufacturing cost and can be discarded as paper, but the permeated oil and water Problems such as deterioration of the appearance of the container, deterioration of strength, and deformation due to the above cannot be solved.

In response to such problems, the outer layer is made water resistant to ensure the strength of the container, while the inner layer in contact with the food is made to absorb moisture and water to adsorb and absorb water vapor and moisture emitted from the food, and this inner layer is used. A food board that is oil resistant and prevents stains due to permeation of oil is disclosed (see Patent Document 1).

However, in the paperboard of Patent Document 1, since the inner layer in contact with the food is oil resistant, the oil content adhering to the inner surface of the container adheres to the food again. In addition, 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.

Further, since the structure is such that the strength of the container is ensured in the outer layer using expensive pulp in order to satisfy the cosmeticity and printability required for the paper container, it is necessary to increase the amount of the outer layer, which is costly. There is a risk of high paperboard.

Japanese Unexamined Patent Publication No. 1-207498

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to prevent oil and water from food from reattaching to food, and the oil and water permeate into the paper layer. While maintaining the specified strength, it can prevent oil and water from seeping out on the opposite side, does not require a special adhesive when processing into a paper container, and is a source of microplastic after use. It is an object of the present invention to provide a water-resistant and oil-resistant paper that does not become, and a paper container formed from the water-resistant and oil-resistant paper.

One aspect of the present invention is a water- and oil-resistant paper having a surface layer, one or more intermediate layers, and a back layer, and the surface layer, the intermediate layer, and the back layer are mainly made of coniferous kraft pulp and broadleaf kraft pulp. The blending ratio of the coniferous kraft pulp to the broadleaf kraft pulp is 70% or more in the surface layer and the back layer, 70% or less in the intermediate layer, and the surface layer and the back layer. The blending ratio of the coniferous kraft pulp in the above intermediate layer is larger than the blending ratio of the coniferous kraft pulp in the intermediate layer, and the water absorption at a contact time of 120 seconds is 10 g / m ² or more and 50 g / m ² or less, and the surface layer and the back The layer contains 30 kg / t or more and 70 kg / t or less of an oil resistant agent with respect to 1000 kg of raw material pulp.

According to the water- and oil-resistant paper of the present invention, the surface layer in contact with the food contained when processed into a paper container and the back layer in contact with other foods as the outer surface of the container have appropriate oil absorption and water absorption. The oil and water from the above are absorbed by the surface layer and the back layer. As a result, it is possible to prevent the oil and water from the food from reattaching to the food, and the flavor and texture of the food are not impaired.

In addition, since the water- and oil-resistant paper has appropriate oil and water absorption in the surface layer and the back layer, it does not require a special adhesive for bonding 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 oil and water that have come into contact with the surface layer or the back layer from seeping out to the opposite surface, which may deteriorate the appearance of the container and reduce the commercial value. The shape and strength of the container can be sufficiently maintained.

Moreover, since it does not use a resin such as polyethylene, it does not become a source of microplastics and can be recycled as a raw material for recycled paper.

The water and oil resistant paper is the Japan TAPPI pulp and paper test method No. It is preferable that the oil resistance according to 41: 2000 is 6th grade or higher, and the residual ratio of wet tensile strength is 8% or higher. By having the above 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 torn even when the oil-water is infiltrated.

It is preferable that the Z-axis tensile strength of the water-resistant and oil-resistant paper is 250 kN / m ² or more, and the ratio of the average fiber orientation angles of the surface layer and the back layer to the horizontal direction is 1.61 or more and 1.85 or less. Having the Z-axis tensile strength can prevent the generation of wrinkles and delamination during cutting and box forming. Further, when the ratio of the average fiber orientation angles of the surface layer and the back layer to the vertical direction in the horizontal direction is in the above range, the interlayer strength and the processing suitability at the time of box molding can be ensured.

At least one layer of the surface layer, the intermediate layer and the back layer may be coated with a water-soluble resin. By applying the water-soluble resin, the oil resistance can be increased.

As described above, in the water-resistant and oil-resistant paper of the present invention, since the surface layer and the back layer have appropriate oil absorption and water absorption, it is possible to suppress the reattachment of oil and water from the food to the food. , No special adhesive is required for laminating or box making when processing into a paper container, and it can be processed in the same way as general paperboard. Further, since the intermediate layer has water resistance, it is possible to prevent oil and water from seeping out to the opposite surface, prevent deterioration of the appearance, and prevent deformation of the container due to a decrease in strength. Furthermore, since it does not use a resin such as polyethylene, it does not become a source of microplastics.

The water and oil resistant paper of the present invention will be described by taking as an example a water and oil resistant paper having a three-layer structure including a surface layer, a one-layer intermediate layer, and a back layer. In the following, the surface layer will be a layer in contact with food, and when processed into a paper container, the surface of the surface layer will be the inner surface of the paper container (the surface in contact with food), and the surface of the back layer will be 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 water from the food are absorbed by the surface and back layers in contact with the food, so that the oil and water from the food are absorbed. Can be prevented from reattaching to food and does not impair the flavor and texture of food. (B) A special adhesive is required in the process of processing into a paper container by laminating or box making. Instead, it plays a role such as being able to be processed in the same way as general paperboard.

In order to fulfill the roles of (a) and (b) above, appropriate oil absorption and water absorption are imparted to the surface layer and the back layer. That is, since the surface layer and the back layer have appropriate oil and water absorption, they absorb oil and water from foods such as breads, cakes, donuts, pizzas, and fried chicken that contain a lot of oil and water, and also foods. It is possible to prevent the oil and water from the pancake from re-adhering to the food, and to ensure good bonding and box-making suitability.

The raw material pulps for the surface and back layers are mainly coniferous kraft pulp (NKP) and broadleaf kraft pulp (LKP), broadleaf bleached kraft pulp (LBKP), coniferous bleached kraft pulp (NBKP), and broadleaf bleached kraft. Chemical pulps such as pulp (LUKP), unbleached coniferous kraft pulp (NUKP), semi-bleached broadleaf kraft pulp (LSBKP), semi-bleached coniferous kraft pulp (NSBKP), broadleaf sulfite pulp, and coniferous sulfite pulp are preferably used. Gland pulp (SGP), pressurized stone gland pulp (PGW), refiner gland pulp (RGP), thermogrand pulp (TGP), chemigrand pulp (CGP), crushed wood pulp (GP), thermomechanical pulp (TMP), etc. Various known pulps such as mechanical pulp or pulp chemically or mechanically produced from non-wood fibers such as kenaf, hemp and reed can also be used.

The water and oil resistance of the surface layer and the back layer are not unconditionally determined by the type, ratio, free water content, and basis weight of the raw material pulp, but the mixing ratio of NKP and LKP is mixed from 70:30 to 90:10. It is preferable to adjust the resulting raw material pulp by multi-layer fabrication or the like so that the water solubility 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 resistance and oil resistance of the surface layer and the back layer in a well-balanced and efficient manner, it is preferable to use the NKP in the surface layer and the back layer at a compounding ratio of NKP to LKP of 70:30 or more and 90:10 or less, preferably 80:20. It is more preferable to use it at 90:10 or less. If the compounding ratio of the NKP does not satisfy the above lower limit, the densities of the surface layer and the back layer become high, and it may be difficult to obtain the desired water and oil resistance. On the other hand, if the above upper limit is exceeded, the densities of the front layer and the back layer become low, which may reduce printability and processability.

In addition, by setting the freeness of the raw material pulp to 350 cc or more and not proceeding with beating, it is possible to suppress the fibrilization of the fibers constituting the raw material pulp, control the excessive increase in the critical surface area of the pulp fiber itself, and further increase the LKP. Since there is a problem that the interlayer strength and the surface strength are lowered in the blending, the above strength can be ensured and the oil resistance and oil repellency can be ensured by blending a large amount of NKP at a ratio of 70% to 90%.

The freshness of the raw material pulp of the surface layer and the back layer is preferably 350 cc or more and 500 cc or less, preferably 400 cc or more and 500 cc or less, from the viewpoint of obtaining the above-mentioned strength, water resistance and oil resistance, and ensuring the air permeability described later. It is more preferable to do so. If the free water content of the raw material pulp does not satisfy the above lower limit, the fiber length of the raw material pulp becomes short and the densities of the surface layer and the back layer become high, so that it becomes difficult to obtain the desired water and oil resistance, and water and oil resistance. It may be difficult to ensure the breathability of the paper. On the other hand, if the above upper limit is exceeded, the fiber length becomes long, the densities of the surface layer and the back layer become low, and the amount of oil and water that can be absorbed from food may decrease.

Here, the freeness is the Canadian standard freeness according to JIS-P8121-2: 2012 after the sample is dissociated with a standard dissociator according to JIS-P-8220-1: 2012. It is the value of the free water content measured by the testing machine.

Further, in order to obtain desired water resistance 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, and 80 g / m ² or more and 100 g / m ² or less. More preferred. If the basis weight does not meet the above lower limit, the amount of oil and water that can be absorbed from food may decrease. 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. 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 test method of basis weight described in JIS-P-8124 (1998).

It is preferable that the surface layer and the back layer contain a dry paper strength enhancer of 24 kg or more and 30 kg or less with respect to 1,000 kg of the raw material pulp of the surface layer and the back layer. When the dry paper strength enhancer is contained in the surface layer and the back layer in the above range, the strength of the surface layer and the back layer in a normal dry state can be ensured, so that the paper container is more likely to be damaged. Can be prevented.

The dry paper strength enhancer is not particularly limited, and one or more of known ones such as polyacrylamide, starch, and carboxymethyl cellulose can be appropriately selected and used. Among them, a dry paper force agent which is a primary and / or secondary amino group-containing vinyl polymer (cation-modified acrylamide polymer by Hofmann decomposition reaction of polyacrylamide) easily adheres to pulp, and other inhibitory factors such as anion trash. It is preferable because it is not easily affected by.

Further, it is preferable that the surface layer and the back layer contain 7 kg or more and 11 kg or less of the wet paper strength enhancer with respect to 1,000 kg of the raw material pulp of the surface layer and the back layer. When the wet paper strength enhancer is contained in the surface layer and the back layer in the above range, the strength of the surface layer and the back layer can be ensured even after absorbing moisture from the food, so that the inner surface of the paper container is fluffed or peeled. It is possible to further prevent the occurrence of damage such as.

The wet paper strength enhancer is not particularly limited, and is one or two of known ones such as polyamide polyamine epichlorohydrin, melamine resin, melamine formaldehyde resin, urea formaldehyde resin, polyamide, polyamide epoxy, and polyvinylamine. More than a 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 improving effect and safety for food use. Currently, polyamide polyamine epichlorohydrin is sometimes referred to as polyamide epichlorohydrin resin for simplification.

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

The oil-resistant agent is not particularly limited, and one or more of known ones such as acrylic resin, styrene-butadiene resin, and fluororesin can be appropriately selected and used. Of these, fluorine-based resins are preferable because they utilize the oil repellency derived from fluorine, but reduce the surface tension of the paper and prevent oil from penetrating from the phenomenon of wetting. Of these, a hydrocarbon-based perfluorinated oil-resistant agent is particularly preferable. Typical examples of the perfluorinated hydrocarbon-based oil resistant agent include an acrylate polymer type and a phosphoric acid ester type. The functional group for fixing to paper is hydrophilic, and is generally anionic or nonionic. The oil resistance of fluorine-based oil-resistant agents is that phosphoric acid ester groups and the like are fixed to paper due to their hydrophilicity, perfluoroalkyl groups are oriented outward on the paper surface, and the surface tension of the processed surface is that of oil-based substances. It develops when it becomes lower than the surface tension.

It is preferable that the surface layer and the back layer contain 8 kg or more and 12 kg or less of the fixing agent 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 surface layer and the back layer in the above range, the effect of the oil resistant agent can be obtained. If the content of the fixing agent is less than the above lower limit, the sufficient effect of the oil resistant agent cannot be obtained, and if it is larger than the above upper limit, the ionicity of the pulp fiber and the oil resistant agent is blocked by the free fixing agent, and the fixing of the oil resistant agent is carried out. It may be hindered and the oil resistance may decrease.

The fixing agent is not particularly limited, and for example, a sulfuric acid band, a polyamide resin typified by a cationic polymer electrolyte, a polyamine resin, a shrimp chlorohydrin resin, a cationic urea, a cationic polyacrylamide resin, a polyethylene imine resin, and the like. One type or two or more types can be appropriately selected and used from the known ones. By using the fixing agent, it is possible to improve the so-called yield of various chemicals, maintain the strength of the paper, and 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 setting the fiber orientation angle within the above range, it is possible to secure the interlayer strength and ensure the processing suitability for a paper container while maintaining the oil resistance and the water resistance within a desired range.

Here, the fiber orientation angle refers to the 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" of Nomura Shoji Co., Ltd.).

It is preferable to apply a water-soluble resin to the surface layer and the back layer. By applying the water-soluble resin, oil resistance is improved. The water-soluble resin is not particularly limited, and polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC), which are widely used for food applications and have excellent coatability at the time of production, can be used. Above all, it is preferable to apply PVA to the surface of the back layer at 0.5 g / m ² or more and 3.5 g / m ^{2 or less, and more preferably 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 above lower limit is not satisfied, the oil resistance may not be improved. Further, if the above upper limit is exceeded, the oil resistance does not change and the manufacturing cost and productivity may deteriorate.

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

That is, even if the oil and water from the contained food are absorbed by the surface layer and the back layer, the water and oil resistance of the intermediate layer allows the oil and water absorbed by the surface layer and the back layer to be absorbed by the thickness of the water and oil resistant paper. Can be blocked in the direction. Therefore, it is possible to prevent oil and water from seeping out to the opposite layer.

As the raw material pulp of the intermediate layer, various known raw material pulps can be used in the same manner as the raw material pulps of the surface layer and the back layer described above. Further, for the same reason as the surface layer and the back layer, it is preferable to use 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, still more preferably 60% or more and 70 or less. Further, 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 may become white and the unbleached color with a natural texture may not be obtained. On the other hand, if 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 surface layer and the back layer, and there is a possibility that the interlayer strength cannot be secured.

The freeness of the raw material pulp in 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 in the surface layer and the back layer. If the freeness of the raw material pulp does not satisfy the above lower limit, the fiber length of the raw material pulp becomes short and the density of the intermediate layer becomes high, which makes it difficult to obtain the desired water and oil resistance, and also makes it difficult to obtain the desired water and oil resistance of the water and oil resistant paper. It may be difficult to ensure breathability. On the other hand, if the above upper limit is exceeded, the fiber length becomes long, the density of the intermediate layer becomes low, and the amount of oil and water that can be absorbed from food may decrease.

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 above lower limit, it may be difficult to prevent the oil and water absorbed in the surface layer and the back layer from permeating into the intermediate layer and exhibiting bleeding on the opposite surface. On the other hand, if the above upper limit is exceeded, the manufacturing cost increases and the water and oil resistance may be impaired due to bending during processing.

Although one intermediate layer can be effective, two layers are preferable, and a four-layer structure is more preferable. By forming the intermediate layer into four layers, the oil and water absorbed in the surface layer and the back layer can be effectively permeated through the intermediate layer, and the bleeding prevention effect is improved on the opposite surface. On the other hand, if the number of intermediate layers is 5 or more, the effect of preventing bleeding on the opposite surface does not change, and the manufacturing cost may increase.

It is preferable that the intermediate layer 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 pulps of the surface layer and the back layer. When 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 ensured, so that damage to the paper container can be further prevented. it can.

Further, it is preferable that the intermediate layer 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 wet paper strength enhancer is contained in the intermediate layer in the above range, the strength of the intermediate layer can be ensured even after absorbing moisture from food, so that the inner surface of the paper container is damaged such as fluffing and peeling. It can be more prevented from occurring.

Although it is possible to include an oil resistant agent in the intermediate layer, the inclusion of the oil resistant agent may lead to excessive quality, and also reduce the interlayer strength and increase the flexibility, resulting in wrinkles during processing and impairing water and oil resistance. There is.

(Water resistant and oil resistant paper)
Next, the water and oil resistant paper will be described. The water-resistant and oil-resistant paper is produced by laminating the raw material pulps of the surface layer, the intermediate layer and the back layer in order by a paper machine. That is, the water-resistant and 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, they may be laminated in the reverse order.

Regarding the oil resistance of the water-resistant and oil-resistant paper, the Japan TAPPI pulp and paper test method No. It is preferable that the oil resistance, which is the number of kits when tested in accordance with 41: 2000, is 6th grade or higher. If the oil resistance is less than 6th grade, the oil adhering to one surface of the water-resistant and oil-resistant paper may seep out to the other surface, which may reduce the strength of the paper container or spoil the appearance of the container. is there.

As for the water absorption of the water-resistant and oil-resistant paper, the water absorption of the contact time of 120 seconds measured in accordance with JIS-P8140: 1998 ^{is preferably 10 g / m 2} or more and 50 g / m ² or less, preferably 20 g / m ^2. More preferably, it is 30 g / m ^{2 or less.} If the water absorption does not satisfy the lower limit, the reattachment of water 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 layers of the front and back layers during bonding and box making, and the adhesiveness deteriorates. When recycling water- and oil-resistant paper as recycled paper, Solubility may deteriorate. Further, it is necessary to add a large amount of chemicals, and as a result, the operability may be deteriorated and the manufacturing cost may be increased. On the other hand, if the above upper limit is exceeded, although the water absorption is excellent, the adhesive permeates too much into the paper layers of the surface layer and the back layer at the time of bonding and box making, and the adhesiveness deteriorates, or a large amount of adhesive is applied. May have to be done.

Further, it is preferable that the residual ratio of the wet tensile strength of the water-resistant and oil-resistant paper is 8% or more. If the residual ratio of wet tensile strength is 8% or less, it may be easily torn when water or oil permeates.

The residual ratio of wet tensile strength is a value calculated by the following (Equation 1).
(Equation 1)
Residual percentage of wet tensile strength (%) = (wet tensile strength / dry tensile strength) x 100

The Z-axis strength of the water- and oil-resistant paper is determined by the Japan TAPPI pulp and paper test method No. The Z-axis intensity measured according to 18-1: 2000 ^{is preferably 250 kN / m 2} or more. By having the Z-axis strength, for example, it is possible to prevent the occurrence of wrinkles when adjusting the curl curl at the time of flat judgment cutting with a decaler, and the occurrence of delamination and wrinkles at the time of container molding.

Further, the smoothness of the water-resistant 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 within the above range, it is possible to prevent the occurrence of double feeding and poor feeding when molding into a sheet-fed printing press or a 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 appropriately used.

The air permeability of the water-resistant and oil-resistant paper is preferably 100 seconds or more and 200 seconds or less, and more preferably 130 seconds or more and 170 seconds or less, as measured in accordance with JIS-P-8117: 1998. When the air permeability is within the above range, the steam emitted from the contained food is not trapped in the container when the water-resistant and oil-resistant paper is processed and used, especially in a heating container. It can be discharged to the food, prevent deterioration of food due to steam, and maintain a good texture.

The water-resistant and oil-resistant paper may be provided with another layer 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 does not contradict the object of the present invention.

Further, the water-resistant and oil-resistant paper may use an interlayer starch as an adhesive between the above layers. The presence of interlayer starch can improve strength and printability.

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

The water-soluble substance is not particularly limited, and is, for example, polyacrylamide and its derivatives, cellulose derivatives such as PVA and CMC, starch, modified starch, latex-butadiene-based, acrylic-based, polyvinyl acetate-based latex, and wax emulsion. One or more of the known ones that can be used for food applications such as, etc. can be appropriately selected and used.

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 used as necessary as long as it is a chemical that can be used for food. It may contain a filler, an antifoaming agent, an antislip agent, a PH adjuster and the like.

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

When making with a round net paper machine, the pulp fibers of the paper support are oriented in the thickness direction of the paper compared to the long net paper machine, so the interlayer strength required for water and oil resistant paper can be improved. The oil resistant agent adhering to the surface of the raw material pulp fiber is evenly distributed in the Z-axis direction (paper thickness direction), and the paper machine made by the Nagami paper machine has the oil resistant agent removed by dehydration at the wire part. It is distributed more on the wire surface side than on the felt surface side, but in a round net paper machine, the wire part (circular net cylinder) does not forcibly dehydrate, so the oil resistant agent does not easily flow out to the white water side, so high oil resistance can be obtained. it can. In addition, the round net paper machine has a slow papermaking speed, does not require excessive pressurization in the press / calendar process, and the amount of each layer can be changed, so the amount of oil resistant layer (front layer and back layer) is applied. By adjusting the above, it is easy to obtain oil resistance because it is possible to manufacture paper that does not allow oil to strike through even if the middle layer does not contain an oil resistant agent. Furthermore, the circular net forward flow bat of the round net paper machine can easily obtain oil resistance because it can form a sheet with a beautiful texture. Further, in the round net multi-layered paper, the directions of the fibers in the raw material pulp are difficult to be aligned at the time of papering and the fibers are easily entangled with each other in the round net multi-layered paper, so that the interlayer strength can be ensured.

The case where the paper layer is composed of three layers, a surface layer, an intermediate layer, and a back layer, has been described above with respect to the water- and oil-resistant paper according to the present invention. The desired effect of the present invention can be obtained even if another layer such as a sealing layer is provided between the surface layer and the intermediate layer and / or between the intermediate layer and the back layer within a range that does not contradict. Can be done.

Hereinafter, the present invention will be described in more detail with reference to Examples, but 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 1-28, Comparative Examples 1-5]
The surface layer, the back layer, and the intermediate layer were obtained under the conditions shown in Table 1. In addition, the column where no drug is used is marked with "-".

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

As for the intermediate layer, softwood kraft pulp (NKP) was 65%, 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 four. A papermaking raw material containing 28 kg / t of a dry paper strength enhancer and 9 kg / t of a wet paper strength enhancer was obtained.

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

[Examples 2-28, Comparative Examples 1-5]
In Examples 2 to 28 and Comparative Examples 1 to 5, as shown in Table 1, various conditions were changed to obtain the water and oil resistant paper of Table 2. 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.

[Bleeding on the other side of salad oil]
Water-resistant and oil-resistant paper is molded into a box container, and salad oil (commercially available canola oil extracted from erucic acid (erucic acid) and glucosinolate-free canola varieties among rapeseed oils by breeding) is heated to 80 degrees. After 30 minutes, the salad oil was visually observed for bleeding on the opposite surface, and the evaluation was made based on the following evaluation criteria.
(Evaluation criteria)
⊚: No bleeding of cooking oil on the opposite side is observed.
◯: Slightly bleeding of salad oil on the opposite side is observed.
Δ: Salad oil bleeding on the opposite side is observed.
X: Salad oil bleeding on the opposite side is remarkable.

[Bleeding to the outer surface of the container when baking cupcakes]
Mold water- and oil-resistant paper into a box container, pour 100 g of commercially available hot cake mix, 80 g of butter, 80 g of granulated sugar, and two eggs (medium balls) into the box container, and bake 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 water, and evaluated based on the following evaluation criteria.
(Evaluation criteria)
⊚: No oil or water bleeding on the outer surface is observed.
◯: Slight bleeding of oil and water on the outer surface is observed.
Δ: Oil and water bleeding on the outer surface is observed.
X: Significant bleeding of oil and water on the outer surface.

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

When Comparative Examples 1 to 5 for which a suitable evaluation could not be obtained were examined, in Comparative Example 1, since the blending ratio of NKP in the surface layer and the back layer did not satisfy the lower limit, the desired oil resistance and wet tension were obtained. It is probable that the residual ratio of strength and Z-axis strength could not be obtained. On the other hand, in Comparative Example 2, it is considered that the desired oil resistance and Z-axis strength could not be 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 paper strength enhancer were not added to the intermediate layer, it is considered that the desired residual ratios 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 exceeded the upper limit, it is considered that the desired oil resistance, residual ratio of wet tensile strength and Z-axis strength could not be 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, the residual ratio of the wet tensile strength, and the Z-axis strength could not be 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.

Based on the above, it is a water- and oil-resistant paper having a surface layer, one layer or a plurality of intermediate layers, and a back layer, and the blending ratio of softwood kraft pulp and hardwood kraft pulp, as well as a dry paper strength enhancer, a wet paper strength enhancer, and fixing. It can be seen that a water- and oil-resistant paper having excellent water and oil resistance can be obtained by setting the contents of the agent and the oil-resistant agent within a predetermined range.

As described above, in the water-resistant and oil-resistant paper of the present invention, since the surface layer and the back layer have appropriate oil absorption and water absorption, it is possible to suppress the reattachment of oil and water from the food to the food. , No special adhesive is required for laminating or box making when processing into a paper container, and it can be processed in the same way as general paperboard. Further, since the intermediate layer has water resistance, it is possible to prevent oil and water from seeping out to the opposite surface, prevent deterioration of the appearance, and prevent deformation of the container due to a decrease in strength. Furthermore, since it does not use a resin such as polyethylene, it does not become a source of microplastics.

Claims (7)

A water and oil resistant paper having a surface layer, one or more intermediate layers, and a back layer.
The 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 to the hardwood kraft pulp is 70% or more 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 water absorption rate for a contact time of 120 seconds is 10 g / m ² or more and 50 g / m ² or less.
A water- and oil-resistant paper in which the surface layer and the back layer contain an oil-resistant agent of 30 kg / t or more and 70 kg / t or less with respect to 1000 kg of raw material pulp. JAPAN TAPPI Pulp and Paper Test Method No. The oil resistance according to 41: 2000 is 6th grade or higher,
The water- and 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- and oil-resistant paper according to claim 1 or 2, wherein the ratio of the average fiber orientation angle of the surface layer and the back layer to the vertical direction in the horizontal direction is 1.61 or more and 1.85 or less. The water-resistant and oil-resistant paper according to any one of claims 1, 2 or 3, wherein the surface layer and the back layer contain 8 kg / t or more and 12 kg / t or less of a fixing agent with respect to 1000 kg of the raw material pulp. .. The water and oil resistant paper according to claim 4, wherein the fixing agent is a polyamine resin. From claim 1, the surface layer and the back layer contain a dry paper strength enhancer of 24 kg / t or more and 30 kg / t or less and a wet paper strength enhancer of 7 kg / t or more and 11 kg / t or less with respect to 1000 kg of the raw material pulp. The water and oil resistant paper according to any one of claims 5. Claim that the intermediate layer contains a dry paper strength enhancer of 27 kg / t or more and 30 kg / t or less and a wet paper strength enhancer of 7 kg / t or more and 11 kg / t or less with respect to 1000 kg of raw material pulp of the surface layer and the back layer. The water and oil resistant paper according to any one of claims 1 to 6.