JP2008007888A - Multiply paperboard and paper container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiply paperboard without impairing appearance of a container in adhesion of oil component on a surface of anti-oilproof layer and causing oil spot on a multiply paperboard with oilproof property, and sustaining palate feeling of a food contained in the container in a preferable state with crispy palate feeling, and to provide a paper container manufactured by using the multiply paperboard. <P>SOLUTION: The multiply paperboard comprises at least a surface layer, a back layer and an interlayer installed between the surface layer and the back layer, and having oilproof property with 200-530 g/m<SP>2</SP>of basis weight, wherein the interlayer has 70-85 of lightnesses (L value) in shade of color, containing 10% of a mechanical pulp in the interlayer, and 10-150 sec of air permeance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-layer paperboard, and in particular, a multi-layer paperboard for use in a paper container for containing foods having oil and moisture such as croquette, cutlet, tempura, french fries, shumai, gyoza, takoyaki, and taiyaki. , And a paper container made by the multilayer paperboard.

  Conventionally, as a paper container for storing foods having oil and moisture such as croquettes and taiyaki, in addition to plastic trays, for example, a plastic tray is stored inside a case made of plastic or high-quality white paperboard. Cases made of white paperboard laminated with a resin such as polyethylene on the inside were used, but all were discarded in the same way as plastic trash after use.

  A paper container made of white paperboard laminated with a resin such as polyethylene on the inside does not transmit or absorb oil or moisture generated from food because the material constituting the inner surface of the paper container does not absorb oil or Although there is an advantage that moisture does not penetrate into the paperboard used on the outer surface, the oil and moisture adhering to the laminate surface will adhere to the food again, thereby impairing the flavor and texture of the food. This has the disadvantage that the greater the contact area between the inner surface of the container and the food contained in the container, the more redeposition of oil and moisture to the food, resulting in a significant reduction in the flavor and texture of the food. .

  Recently, from the viewpoint of environmental protection, food packaging materials having recyclable oil resistance, that is, oil-resistant paper for foods are required. Examples of such oil-resistant paper include single-side oil-resistant paper provided with an oil-resistant layer on the side in contact with food, or double-sided oil-resistant paper provided with an oil-resistant layer on both the front and back surfaces. Of these, double-sided oil-resistant paper is excellent in oil resistance, but it requires two oil-proof layers, so it is expensive and limited to use in some applications. Generally, single-sided oil-resistant paper is used. Has been. When these oil-resistant papers are processed into containers and used, in addition to oil resistance, strength and rigidity as a paper container are required, and therefore, high-basis weight multilayer paperboard is used. . In these multilayer paperboards, the side in contact with the food is configured as an oil-resistant layer so that the oil from the stored food does not penetrate into the container, and used paper pulp is frequently used for the intermediate layer from the viewpoint of environmental protection and cost.

  However, if food containing oil such as croquettes or fries adheres from the outside of the container during the operation of storing the food in a paper container, or if it comes into contact with the container, the outside of the container has no oil resistance function. The actual situation is that the oil content penetrates into the packaging material, the surface layer of the multi-layer paperboard becomes translucent, and the waste paper of the intermediate layer is raised to greatly deteriorate the appearance of the paper container. . In addition, the multi-layer paperboard with the oil resistance function has better air permeability than the resin-processed packaging material such as laminate, and it is difficult to impair the texture of the food to be stored. When food containing heat is contained, the moisture in the container becomes high, and there is a problem that the moisture is reattached to the food and the texture of the food is lowered.

  In view of such problems, for example, Patent Document 1 discloses that the outer layer of high-quality white paperboard is provided with water resistance to maintain the strength of the paper container, tray, or cup, and the inner layer is formed as a hygroscopic water-absorbing material. There is disclosed a food board which adsorbs and absorbs the generated water vapor and makes the inner layer oil-resistant and releasable so as to avoid fouling on oils and peel off cooked products.

However, even in the paperboard of Patent Document 1, since the inner layer in contact with food is moisture-absorbing and oil-resistant, the intermediate layer is water-absorbing, and the outer layer is water- and water-repellent, if oil adheres to the outer layer, oil stain As a result, the appearance of the container deteriorates. In addition, although the inner layer has hygroscopicity, the air permeability of the paperboard itself is the same as that of a conventionally known paperboard. Therefore, when food with heat or food containing a relatively large amount of water is contained, the moisture in the container However, there is a problem that it re-adheres to the food and impairs the flavor and texture of the food.
JP-A-1-207498

  The present invention has been made in view of the above-described circumstances, and the object of the present invention is to eliminate the disadvantages of the prior art as described above, and in the multilayer paperboard having oil resistance, the reaction of the multilayer paperboard is reduced. Even when oil adheres to the oil-resistant layer surface and oil stains occur, the appearance of the container does not deteriorate, and the air permeability of the multi-layer paperboard is improved, and the food that is stored in the container is crisp. To provide a multi-layer paperboard that can maintain a good texture (hereinafter referred to as “crispy texture”) and a paper container boxed using the multi-layer paperboard It is.

The object of the present invention is a multilayer paperboard comprising at least a surface layer, a back layer, and an intermediate layer disposed between the surface layer and the back layer, and having an oil resistance basis weight of 200 to 530 g / m ^2. The lightness (L value) in the color tone of the intermediate layer is 70 to 85, the intermediate layer contains at least 10% mechanical pulp, and the air permeability is 10 to 150 seconds. This is accomplished by providing multilayer paperboard.

  Further, the above object of the present invention is characterized in that the lightness (L value) in the color tone of the intermediate layer is 70 to 80, the hue (a value) is -3 to 3, and the hue (b value) is 10 to 16. It is achieved more effectively by providing a multilayer paperboard.

The above-mentioned object of the present invention is achieved more effectively by providing a multilayer paperboard characterized in that the intermediate layer contains at least 0.7% of thermally foamable particles. .

  Furthermore, the above object of the present invention is achieved by providing a paper container that is boxed by the multilayer paperboard described above.

  According to the multilayer paperboard according to the present invention, the lightness (L value) in the color tone of the intermediate layer is set to 70 to 85, and further, mechanical pulp is contained at least 10%, so that the oil adheres to the multilayer paperboard. Even when oil stains occur, the appearance of the container does not deteriorate. Further, since a certain amount of mechanical pulp is blended in the intermediate layer, the air permeability of the multilayer paperboard can be improved, and the contents stored in the paper container can be kept good. Of course, since it is not bonded to a plastic film or the like or processed with resin, it can be recycled as a raw material for recycled paper.

  Moreover, the waste paper pulp was mix | blended with the intermediate | middle layer by setting the brightness (L value) in the color tone of an intermediate | middle layer to 70-80, hue (a value) to -3-3, and hue (b value) 10-16. Even when the oil component adheres to the multilayer paperboard and the oil penetrates, the appearance of the container appearance is not deteriorated, and the target multilayer paperboard can be efficiently obtained.

  In addition, by containing at least 0.7% of thermally foamable particles in the intermediate layer and setting the air permeability to 10 to 150 seconds, the air permeability of the multilayer paperboard can be improved, and the inside of the paper container A multilayer paperboard can be efficiently obtained that can satisfactorily maintain the crispy texture of the food contained in the container.

  Therefore, when a container is made using the above-mentioned multilayer paperboard, a paper container having the characteristics as described above can be realized.

  Hereinafter, the multilayer paperboard according to the present invention will be described in detail by taking, as an example, a case of three paper layers of a back layer, an intermediate layer and a surface layer. The multilayer paperboard according to the present invention is not limited to the following embodiments, and it is needless to say that the configuration can be changed as appropriate without departing from the scope of the claims.

  A multilayer paperboard (hereinafter referred to as “main paperboard”) 10 according to the present invention is composed of three paper layers, a back layer 11, an intermediate layer 12, and a surface layer 13, as shown in a sectional view in FIG. Yes. Below, the case where the paper-made container 20 which accommodates a foodstuff as shown in a perspective view in FIG. FIG. 2 shows only the container body, and the lid is removed.

  In the paper container 20, the surface of the surface layer 13 of the paperboard 10 is the outer surface 21 of the paper container 20, and the surface of the back layer 11 of the paperboard 10 is the inner surface 22 of the paper container 20, that is, the surface in contact with food. It is made in a box.

  The back layer 11 of the present paperboard 10 has oil resistance so that oils from foods such as croquette, cutlet, tempura, fried potato, shumai, gyoza, takoyaki, taiyaki, etc. are not oozed out through the present paperboard 10. It is a layer that plays a role. In addition, it is a layer that plays a role of having appropriate water resistance so that the paper container 20 made of the paperboard 10 does not swell or become bumpy due to moisture absorption due to moisture from the contained food.

  Here, as the oil resistance of the back layer 11 (TAPPI RC-33), Kit. No. 7-No. It is preferably 13. When the oil resistance of the back layer 11 is less than 7, the oil resistance function of the back layer 11 is lowered and the function as an oil resistant paper is insufficient. On the other hand, if the oil resistance of the back layer 11 exceeds 13, the adhesive at the time of pasting and boxing does not penetrate into the paper layer, resulting in poor adhesion and the addition of a large amount of chemicals. This leads to deterioration of sex and high cost.

It is preferable to water absorption of the (JIS8140) and ^5g / ^{m 2~} 40g / m ² as the water resistance of the backing layer ^11, 10~35g / m ^2, and more preferably set to 20 to 35 g / ^{m 2.} In order to make the water absorption of the back layer 11 less than 5 g / m ^2, it is necessary to add a large amount of chemicals, which leads to deterioration in operability and high cost. Moreover, the adhesiveness at the time of pasting and box making also deteriorates, and the solubility also deteriorates when recycled as used paper. On the other hand, when the water absorption of the back layer 11 exceeds 40 g / m ² , the water resistance function is deteriorated, the container swells or becomes loose due to moisture absorption, and the appearance of the container is greatly impaired.

  The back layer 11 of the present paperboard 10 can be obtained as follows.

  In order to impart oil resistance to the back layer 11, the back layer 11 is blended with a sizing agent and an oil resistant agent when paperboard is made. The blending amount of the sizing agent is suitably 0.5% by weight to 1.5% by weight in terms of solid content with respect to the pulp of the back layer 11. This is because even if the blending amount exceeds 1.5% by weight, the size effect is no longer changed and only the cost is increased. On the other hand, if the blending amount is less than 0.5% by weight, the water resistance imparting effect is small. . As this sizing agent, it is possible to use an acidic or neutral sizing agent that is usually used for papermaking. In particular, neutral rosin sizing agents, AKD sizing agents, ASA sizing agents, and other neutral regions. It is preferable to manufacture the back layer 11 with a hot water extraction PH of 5 to 8.5 using a sizing agent having a high size development effect. This is because the oil-resistant function of the oil-proofing agent described later tends to develop in the neutral region.

Further, the blending amount of the oil proofing agent is preferably 0.3% by weight to 1.5% by weight in terms of solid content with respect to the pulp of the back layer 11, and more preferably 0.7% by weight to 1.5% by weight. preferable. This is because even if the blending amount exceeds 1.5% by weight, the oil resistance effect is no longer changed and only the cost is increased. On the other hand, if the blending amount is less than 0.3% by weight, the oil resistance imparting effect is small. .

As the oil proofing agent, an acrylic resin, a styrene butadiene resin, or a fluororesin is used. The oil proofing agent has an oil resistance of the back layer 11 of JAPAN TAPPI No. It is contained in the back layer 11 so as to be grade 7 or higher according to the kit method defined in No.41. In the back layer 11, when the oil resistance is less than 7th grade, the oil component exuded from the food penetrates into the intermediate layer 12 and the surface layer 13 and appears as an oil stain on the appearance of the paper container 20. Detract from the shine. Further, since the oil component penetrates into the intermediate layer 12 and the surface layer 13, the strength and rigidity of the paper container 20 itself are impaired.
For this reason, a function is insufficient as an oil-resistant layer of paperboard used for a container for containing food containing oil.

  As the oil resistant agent, an oil resistant agent using a fluororesin is particularly preferable. For example, Asahi Guard series (AG950, etc.) manufactured by Asahi Glass Co., Ltd., Sumirez Resin FP-110 manufactured by Sumitomo Chemical Co., Ltd., Zonyl RP manufactured by DuPont Co., Ltd. And Rhodain 2000 manufactured by Ciba Specialty Chemicals.

For the oil-resistant fixing agent, generally used, for example, polyamide resin, polyamine resin, shrimp chlorohydrin resin, cationic urea, cationic polyacrylamide resin, polyethyleneimine resin and the like are used.

  Further, it is preferable that the back layer 11 contains a wet paper strength enhancer in an amount of 0.05 to 0.5% by mass in terms of solid content with respect to the raw material pulp of the back layer 11. This is because the back layer 11 has a function of absorbing oil and moisture from the food to be stored and absorbs a certain amount of oil and moisture. However, even when the oil and moisture are absorbed, the back layer 11 is rubbed with food. The strength of the layer 11 is ensured so that the surface of the layer 11 is not damaged such as fuzz or paper peeling.

  Examples of the raw material pulp for the back layer 11 of the paperboard 10 include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), and hardwood half Bleached kraft pulp (LSBKP), softwood semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp and other chemical pulp, stone grand pulp (SGP), pressurized stone grand pulp (PGW), refiner grand pulp (RGP) , Thermo-Grand Pulp (TGP), Chemi-Grand Pulp (CGP), Crushed Wood Pulp (GP), Thermo-mechanical Pulp (TMP), etc. Mechanical Pulp, Tea Waste Paper, Craft Envelope Waste Paper, Magazine Waste Paper, Newspaper Paper, Flyer Waste Paper, Office Waste Paper , Cardboard waste paper, top white waste paper, Chemicals from disintegrated waste paper pulp, disaggregated / deinked waste paper pulp, disaggregated / deinked / bleached waste paper pulp, or non-wood fibers such as kenaf, hemp, and straw Various known pulps can be used, such as pulps that have been produced mechanically or mechanically.

  However, since the back layer 11 is a part that comes into contact with food, the pulp to be used is preferably chemical pulp, and more preferably ECF (Elemental Chlorine Free) pulp or TCF (Total Chlorine Free) pulp.

  The main paperboard 10 can be recycled as used paper, but depending on the food to be stored, a large amount of oil adheres to the paper container 20 and may be incinerated when the paper container 20 is disposed. When 20 is incinerated, the combustion temperature may become high due to oil leached from the food.

Since ECF pulp and TCF pulp are chlorine-free bleaching, generation of chlorides such as dioxin can be prevented even when the combustion temperature becomes high during incineration. Further, when ECF or TCF pulp is used, the amount of chloride contained in the exhaust gas can be reduced when incinerated with other incinerated substances containing chlorine at the time of incineration.
Further, in order to achieve various quality characteristics and the like of the back layer 11 of the paperboard 10 which is the inner surface of the paper container 20 in a balanced and efficient manner, the ratio of NKP and LKP is 10 to 50:90 to 50:50. It is preferable to use it at 15:85 to 40:60. When NKP is less than 10%, the density of the back layer 11 tends to be high, and it becomes difficult to obtain appropriate water absorption and oil absorption. On the other hand, if NKP exceeds 50%, it becomes difficult to retain a certain amount of water absorption and oil absorption in the back layer 11.

  In addition, the freeness of the back layer 11 is that the raw pulp of the back layer 11 has a certain level of water absorption and oil absorption, and the air permeability of the paperboard according to the present invention described later is secured. It is preferable to set it as 350-450cc, and it is more preferable to set it as 380-420cc. That is, when the freeness of the raw material pulp of the back layer 11 is less than 350 cc, the fiber length of the raw material pulp becomes short, so that the density of the back layer 11 becomes high and the water absorption / oil absorption function becomes insufficient. Moreover, it becomes difficult to ensure the air permeability of the paperboard according to the present invention described later. Further, if the drainage of the raw material pulp of the back layer 11 exceeds 450 cc, the fiber length becomes long, so that the density of the back layer 11 decreases, and the amount of oil and moisture that can be absorbed from the food is small. The function is insufficient.

  In addition, the freeness in this invention is the drainage measured by the Canadian standard freeness tester according to JIS-P8121 after disaggregating the sample with the standard breaker according to JIS-P8220. It is a value of degree (hereinafter the same).

Moreover, in order to obtain the above water / oil resistance, the basis weight of the back layer 11 is preferably 40 g / m ^{2 to} 80 g / m ^2, and more preferably 45 g / m ^{2 to} 65 g / m ² . When the basis weight is less than 40 g / m ² , the water and oil resistance function of shielding oil and moisture from the food with the back layer 11 becomes insufficient. When the basis weight exceeds 80 g / m ² , although the water and oil resistance function is excellent, the basis weight of the intermediate layer 12 described later becomes small, and it becomes difficult to ensure the strength as the main paperboard 10. In addition, the cost increases.

  The intermediate layer 12 in the paperboard 10 is a layer that plays a role of having water resistance that does not impair the strength and rigidity of the paper container 20 even if moisture from the food permeates through the back layer 11, and in particular the paperboard. 10 is a layer that plays a role of not deteriorating the appearance of the container appearance even when the oil component adheres to the surface layer 13, that is, the anti-oil resistant layer surface, and the oil component penetrates the main paperboard 10. It is also a layer that plays a role of improving the air permeability of the food and maintaining it well without impairing the crispy texture of the food contained in the paper container 20.

It is preferable to water absorption of the (JISP8140) and ^5g / ^{m 2~} 40g / m ² as the water resistance of the intermediate layer ^12, 10~35g / m ^2, and more preferably set to 20 to 35 g / ^{m 2.}

  The back layer 11 is in contact with the food, and the oil from the food is shielded by the back layer 11, but the intermediate layer 12 does not liquefy the water vapor generated from the stored food, and even when the intermediate layer 12 reaches the intermediate layer 12. In order to prevent the strength from being lowered, it is preferable to use a material which is given a strong size and is given water resistance.

  The blending amount of the sizing agent of the intermediate layer 12 is suitably 0.3% by weight to 1.5% by weight in terms of solid content with respect to the pulp, similarly to the blending amount of the sizing agent with respect to the back layer 11, and 0.6 A weight percent to 1.5 weight percent is more preferred.

  When selecting the raw material pulp of the intermediate layer 12, chemical pulp may be used. However, from the viewpoint of reducing the load on the energy intensity and the environment, the waste paper pulp is within the range that does not impair the functionality that bears strength. It is advantageous in terms of cost to add as much as possible.

  Waste paper pulp used for the intermediate layer 12 is manufactured from tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, corrugated waste paper, upper white waste paper, Kent waste paper, imitation waste paper, waste paper waste paper, etc. Disintegrated waste paper pulp, disaggregated / deinked waste paper pulp, or disaggregated / deinked / bleached waste paper pulp can be used. Among these waste paper pulps, it is preferable to use deinked waste paper pulp, particularly in the present paperboard 10. That is, even if the surface layer 13 absorbs oil and becomes translucent and the used paper pulp of the intermediate layer 12 is transparent, it is difficult to impair the appearance.

  Specifically, in the present paperboard 10, the lightness (L value) in the color tone of the intermediate layer 12 is set to 70-80. By doing this, even when oil adheres to the surface layer 13 that is the anti-oil resistant layer surface and the oil penetrates, the appearance of the paper container 20 does not deteriorate. Furthermore, even when used paper pulp is blended, the lightness (L value) in the color tone of the intermediate layer 12 is 70 to 80, the hue (a value) is -3 to 3, and the hue (b value) is 10 to 10. By setting the number to 16, the oil content adheres to the anti-oil resistant layer surface of the multi-layer paperboard, and even when the oil penetrates, the appearance of the container is not deteriorated, and the multi-layer paperboard that is the subject is efficiently processed. Can be obtained.

  In order to make the intermediate layer 12 have such a color tone, various waste paper pulps can be selected and blended. Moreover, you may color by dye and a pigment as needed.

  In the present paperboard 10, the air permeability is preferably adjusted to 10 seconds to 150 seconds, and preferably adjusted to 20 seconds to 100 seconds, in order to obtain a good crispy texture of the food contained in the paper container 20. It is more preferable. If the air permeability exceeds 150 seconds, the air permeability of the main paperboard 10 is deteriorated, and moisture such as water vapor from the stored food is trapped in the paper container 20 and the crispy texture of the food is impaired. End up. Also, when the air permeability is less than 10 seconds, a preferable crispy texture of food cannot be obtained. This can be achieved by:

  In the present paperboard 10, the intermediate layer 12 preferably contains at least 10% mechanical pulp, and more preferably 15-40%. That is, since mechanical pulp contains a large amount of resin and the pulp fibers are rigid, voids are easily formed between the fibers, and the air permeability of the present paperboard 10 is improved. When the content of mechanical pulp exceeds 40%, the interfiber bond becomes weak, and delamination that is a problem peculiar to multilayer paperboard tends to occur.

  As the mechanical pulp, known materials such as PGW (Pressurized Grand Wood Pulp), TMP (Thermo Mechanical Pulp), RGP (Refan A Grand Pulp), GP (Grand Wood Pulp) can be used. Among them, it is particularly preferable to use PGW and TMP for the present paperboard 10 in terms of color tone and air permeability.

  Further, the intermediate layer 12 of the present paperboard 10 preferably contains thermally foamable particles, preferably contains at least 0.7%, and preferably contains 0.7% to 3.5%. Is more preferable. Furthermore, it is particularly preferable to contain 1.5% to 3.0%.

  The thermally foamable particles are foamed by a dryer in the drying step. The thermally foamable particles are heated above the softening point of the thermoplastic synthetic resin that constitutes the outer shell, and at the same time, the low boiling solvent encapsulated is vaporized, the vapor pressure rises, the outer shell expands, and the particles expand. . At the time of expansion, the internal pressure and the tension / external pressure of the shell are balanced to maintain the expanded state. In general, the expanded state is expanded to this state and used as a lightening agent, bulking agent, cushioning agent, heat insulating agent and the like.

  In the present invention, when heat is further applied to the expanded thermally expandable particles, that is, excessive heat is applied, gas permeates and diffuses from the expanded and thin shell, and the shell tension and external force are superior to the internal pressure. Utilizes the occurrence of shrinkage. That is, the heat-expandable particles are superheated and expanded, and further, the heat-expandable particles expanded and contracted are shrunk, thereby creating voids in the paper layer and significantly improving the air permeability.

  The thermally foamable particles that can be used in the present invention are those in which a low-boiling solvent is encapsulated in a fine particle outer shell of a thermoplastic synthetic resin. An average particle diameter is 5-30 micrometers, and a diameter expands 4-5 times and a volume 50-130 times by heating at 80-200 degreeC.

  Examples of the thermoplastic synthetic resin constituting the outer shell include copolymers such as vinylidene chloride, acrylonitrile, acrylic acid ester, and methacrylic acid ester.

  Examples of the low boiling point solvent enclosed in the outer shell include isobutane, pentane, petroleum ether, hexane, low boiling point halogenated hydrocarbon, and methylsilane.

  Examples of these thermally expandable particles include “Matsumoto Microsphere F-20 Series”, “F-30 Series”, “F-36 Series”, and “F-46 Series” manufactured by Matsumoto Yushi Seiyaku Co., Ltd. In addition, “Expancel WU” and “Same DU” sold by Nippon Philite Co., Ltd. can be used, but the foamable microcapsules used in the present invention are not limited to these. However, in the present invention, since the temperature of the paper drying step is generally about 130 ° C., the expansion start temperature of the thermally foamable particles is preferably a low temperature expansion type having a temperature of 130 ° C. or less.

  Further, in order to set the air permeability of the main paperboard 10 to 10 seconds to 150 seconds, the adjustment based on the freeness is effective from the viewpoint of adjusting the balance with other qualities. That is, it is easy to achieve by adjusting the freeness of the intermediate layer 12 to 350 to 450 cc, preferably 380 to 420 cc.

  Although waste paper pulp can be used for the intermediate layer 12 as described above, when a large amount of low-grade waste paper containing many fine fibers and having low freeness is mixed, the air permeability becomes high. That is, the air permeability is deteriorated, moisture from the food is trapped in the container, and the crispy texture of the food is impaired. Therefore, even when the used paper is used for the intermediate layer 12, the air permeability is 10 to 10. It is preferable to adjust to 150 seconds. Thereby, this paperboard 10 whose air permeability is 10 to 150 seconds can be obtained.

Incidentally, the basis weight of the intermediate layer 12 will vary depending layer structure and the basis weight of the paperboard according to the present invention ^is suitably ^{40g / m 2~ 250g / m 2} . In terms of cost, it is advantageous to increase the number of intermediate layers 12 as much as possible within a range not impairing the effects of the present invention.

  The surface layer 13 laminated subsequent to the intermediate layer 12 is (b) a layer that becomes the outer surface 21 of the paper container 20 for food, and thus ensures aesthetics, printability, etc. (b) a paper container It is a layer that plays a role such as having good bonding at the time of processing to 20 and having boxing suitability.

  In addition, in order to achieve a good balance between various quality characteristics of the surface layer 13 of the main paperboard 10 serving as the outer surface 21 of the paper container 20 and the quality characteristics of the main paperboard 10, NKP and LKP are set to 10:90 to The ratio is preferably 50:50, more preferably 15:85 to 40:60. When NKP is less than 10%, the density of the surface layer tends to be high, and it is difficult to obtain an appropriate air permeability. Moreover, since the content rate of NKP with a long fiber length decreases, ruled line cracks are likely to occur during box making. On the other hand, if NKP exceeds 50%, the texture of the surface layer 13 is deteriorated and the flatness is also lowered, so that the printability of the present paperboard 10 is likely to be lowered. Such appearance unevenness and printing unevenness deteriorate the appearance of the container appearance.

  Moreover, the freeness of the surface layer 13 is preferably 350 to 450 cc from the viewpoint of ensuring the beauty, printability, and the air permeability of the paperboard according to the present invention. More preferably, it is 380 to 420 cc.

The basis weight of the paperboard 10 will vary also depending on the size and intended use of the paper container 20, but is preferably in the range of from ^200g / ^{m 2~} 530g / m ² such is manufactured, More preferably, it is in the range of 250 g / m ^{2 to} 470 g / m ² .

  That is, the present paperboard 10 is a paperboard used for a paper container 20 containing a food having oil and moisture, such as croquette, cutlet, tempura, french fries, shumai, dumplings, takoyaki, taiyaki, etc. 20 requires strength and rigidity.

Further, in order to obtain a water / oil resistance function, the back layer 11 preferably has a basis weight of 40 g / m ² or more, and the remaining intermediate layer 12 needs to ensure strength and rigidity as the paper container 20. The basis weight of the present paperboard 10 needs to be 200 g / m ² or more. Further, even if the basis weight of the present paperboard 10 exceeds 530 g / m ² , only the excessive quality and cost increase are caused.

  The multilayer paperboard according to the present invention is produced by papermaking the raw materials of each layer satisfying the above-described configuration in a state of being laminated by a paper machine.

Since the papermaking method is not particularly limited, either the acid papermaking method, the neutral papermaking method, or the alkaline papermaking method may be used, but in order to fix the oilproofing agent and efficiently exhibit the oilproofing function, It is preferable to produce by neutral papermaking so that the hot water extraction PH is 5 to 8.5.
Also, the paper machine is not particularly limited, and various known paper machines such as a long net paper machine, a twin wire paper machine, a circular net paper machine, and a short net combination machine can be used. .

  In addition, since the surface layer 13 of the paperboard 10 is printed, a water-soluble substance is added to the surface of the paperboard 10 as necessary in order to improve printing gloss and surface strength or adjust slipperiness. It is preferable to apply various means for improving the printability, for example, by applying a coating liquid containing as a main component.

Examples of such water-soluble substances include polyacrylamide and derivatives thereof, polyvinyl alcohol, cellulose derivatives, starch, modified starch, polystyrene-butadiene-based, acrylic-based, polyvinyl acetate-based latex, wax emulsion, and the like in this field. Various known materials that are usually used can be used alone or in admixture of two or more.
For example, polyvinyl alcohol can be obtained a good printability at 0.5g ^{/ m 2} ~3.5g ^/ m 2 to the coating on the surface layer surface. It is more preferable to apply 0.7-2 g / m ² .
Furthermore, if the coating liquid which has a pigment and a binder as a main component is applied to a surface layer using a coating apparatus, a more beautiful printing can be achieved.

  Further, the surface of the main paperboard 10 may be smoothed. This smoothing process is preferably performed by, for example, pressing the paperboard 10 between pressurizable rolls. When the smoothing treatment is performed, the roll in contact with the surface of the surface layer 13 of the present paperboard 10 is preferably a metal roll that has a smooth surface and can be heated.

  In addition, the smoothing process in the main paperboard 10 is a process of making the main paperboard 10 in addition to the above-described smoothing process, for example, a calendar process using a calendar roll provided with one or more pairs of metal rolls (according to a machine calendar). Calendar processing), calendar processing with a calendar roll provided with one or a plurality of metal rolls and resin rolls (calendar processing with a soft calendar), drying processing with a Yankee dryer, and the like.

  Further, the present paperboard 10 may contain starch, filler, antifoaming agent, paper strength enhancer, anti-slip agent, pH adjuster and the like in addition to the above-mentioned oilproofing agent, fixing agent and sizing agent.

  As described above, the case where the paper layer is composed of the three paper layers of the back layer 11, the intermediate layer 12, and the surface layer 13 has been described in the present paperboard 10. However, the present invention is not limited to such paperboard. As shown in the sectional view, the intermediate layer 12 is composed of two layers of 12A and 12B, and the whole is composed of four layers. Alternatively, as shown in the sectional view of FIG. 4, the intermediate layer 12 is composed of 12A, 12B and 12C. It is good also as the paperboard 10 '' comprised as a whole by 3 layers as 3 layers.

  In order to confirm the effects of the multilayer paperboard according to the present invention (the above-described three-layer paperboard 10) and a food container made using this multilayer paperboard (the above-mentioned paper container 20). The following various samples were prepared, and a test for evaluating the quality of each sample was performed. In addition, in a present Example, the numerical value which shows a mixing | blending, a density | concentration, etc. is a numerical value based on the weight of a solid content or an active ingredient. In addition, the pulp, chemicals, and the like shown in this example are merely examples, and it goes without saying that the present invention is not limited by these examples and can be appropriately selected.

21 types of paperboards according to the present invention (referred to as “Example 1” to “Example 21”) and four types of paperboards (referred to as “Example 1” to “Example 21”) “Comparative Example 1” to “Comparative Example 4” were prepared under the manufacturing conditions (layer configuration and raw material blending) shown in Table 1 and below.

［実施例１」
＜裏層＞（前記裏層１１）
針葉樹晒クラフトパルプ（ＮＢＫＰ）２０質量％と広葉樹晒クラフトパルプ（ＬＢＫＰ
）８０質量％とを配合した後に、離解フリーネスを４００ｃｃに調整した裏層用の原料パルプに、硫酸バンド０．５％、サイズ剤（星光ＰＭＣ株式会社製ＡＫＤサイズ剤）を固形分換算で０．７％、乾燥紙力増強剤（星光ＰＭＣ株式会社製 両性ポリアクリルアマイド）を固形分換算で０．３％、湿潤紙力増強剤（星光ＰＭＣ株式会社製 エピクロロヒドリン）を固形分換算で０．１％、耐油剤０．８％（チバスペシャリティケミカルズ社製のローダイン２０００）、耐油剤の定着剤０．０６％（クラリアントジャパン社製 Ａｒｋｏｆｉｘ）を添加して裏層用の原料スラリーを調整した。

Example 1
<Back layer> (Back layer 11)
Softwood bleached kraft pulp (NBKP) 20% by mass and hardwood bleached kraft pulp (LBKP)
) After blending 80% by mass, 0% of sulfuric acid band and sizing agent (AKD sizing agent by Seiko PMC Co., Ltd.) were converted to solid content in the raw material pulp for the back layer whose disintegration freeness was adjusted to 400cc. .7%, Dry paper strength enhancer (Amotropic polyacrylamide made by Seiko PMC Co., Ltd.) 0.3% in terms of solid content, Wet paper strength enhancer (Epichlorohydrin made by Seiko PMC Co., Ltd.) in solid content In addition, 0.1% of oil resistance, 0.8% of oil resistance agent (Rhodain 2000 manufactured by Ciba Specialty Chemicals Co., Ltd.), 0.06% of oil resistance agent fixer (Arkofix manufactured by Clariant Japan Co., Ltd.), and the raw material slurry for the back layer are added. It was adjusted.

Here, “disaggregation freeness (CC)” means that each sample is cut into a size of about 3 cm ² to give a test piece having a weight of about 25 g, and this test piece is immersed in 1 liter of water for 24 hours. In accordance with JIS-P8220, 15 separation and disassembly treatment was performed with a standard disaggregator, and after confirming that the test piece was completely disaggregated, a Canadian standard freeness tester according to JIS-P8121 It is a freeness value measured at.
<Intermediate layer> (intermediate layer 12)
Softwood bleached kraft pulp (NBKP) 20% by mass and hardwood bleached kraft pulp (LBKP)
) After blending 70% by mass and 10% by mass of mechanical pulp (TMP), the raw material pulp for the intermediate layer whose disintegration freeness was adjusted to 400 cc was added to 0.7% sulfuric acid band, sizing agent (AKD size manufactured by Seiko PMC Co., Ltd.) Agent) 0.5% in terms of solid content, dry paper strength enhancer (amphoteric polyacrylamide made by Seiko PMC Co., Ltd.) 0.7% in terms of solid content, wet paper strength enhancer (produced by Seiko PMC Co., Ltd.) The raw material slurry for the intermediate layer was prepared by adding 0.3% of chlorohydrin) in terms of solid content.
<Surface> (Surface 13)
Softwood bleached kraft pulp (NBKP) 20% by mass and hardwood bleached kraft pulp (LBKP)
) After blending 80% by mass, a surface layer raw pulp whose disintegration freeness is adjusted to 400 cc is mixed with a sulfuric acid band 0.7% and a sizing agent (AKD sizing agent manufactured by Seiko PMC Co., Ltd.) 0.5 in terms of solid content. %, 0.7% of dry paper strength enhancer (amphoteric polyacrylamide made by Seiko PMC Co., Ltd.) in terms of solid content, and 0% wet paper strength enhancer (Epichlorohydrin made by Seiko PMC Co., Ltd.) in terms of solid content The raw material slurry for the surface layer was prepared by adding 3%.

Using these raw material slurries, the back layer, the intermediate layer, and the surface paper layer were made together with a circular three-layer paper machine, the amount of the back layer applied was 55 g / m ² , the intermediate layer was 200 g / m ² , A multilayer paperboard “Example 1” with a three-layer paper having a surface layer of 55 g / m ² and a basis weight of the whole multilayer paperboard of 310 g / m ² was obtained.
"Examples 2 to 5"
The multilayer paperboard obtained in the same manner as “Example 1” except that the mechanical pulp content and the L material content of the intermediate layer were adjusted to the values shown in Table 1.
"Example 6" The mechanical pulp content and L material content of the intermediate layer were adjusted to the values shown in Table 1, and 0.3% of thermally foamable particles (Matsumoto Yushi Seiyaku Co., Ltd., Matsumoto Microsphere F-36) ) Other than the addition, the multilayer paperboard obtained in the same manner as in Example 1.
"Examples 7 to 11"
Other than the adjustment of the heat-expandable particles of the intermediate layer to the values shown in Table 1, the multilayer paperboard obtained in the same manner as in “Example 6”.
"Example 12"
The multilayer paperboard obtained in the same manner as “Example 1” except that the heat-expandable particles of the intermediate layer and the L value of the intermediate layer were adjusted to the values shown in Table 1.
“Examples 13 to 14” Multilayer paperboard obtained in the same manner as “Example 9” except that the L value of the intermediate layer was adjusted to the values shown in Table 1.
“Examples 15 to 20” Multilayer paperboard obtained in the same manner as “Example 9” except that the a value of the intermediate layer was adjusted to the values shown in Table 1.
"Examples 21 to 25"
The other points except that the b value of the intermediate layer was adjusted to the values shown in Table 1 were multilayer paperboards obtained in the same manner as in “Example 9”.
"Comparative Examples 1-2"
The multilayer paperboard obtained in the same manner as “Example 1” except that the mechanical pulp content and the L material content of the intermediate layer were adjusted to the values shown in Table 1.
"Comparative Example 3" A multilayer paperboard obtained in the same manner as in "Example 9" except that the heat-expandable particles in the intermediate layer were adjusted to the values shown in Table 1.
"Comparative Example 4" Multilayer paperboard obtained in the same manner as "Example 9" except that the heat-expandable particles of the intermediate layer and the L value of the intermediate layer were adjusted to the values shown in Table 1 is there.

For all these Examples and Comparative Examples, the basis weight of all layers (US basis), density, air permeability, color tone of intermediate layer (lightness L, hue a, hue b), oil resistance of the back layer surface, food container Table 2 shows the results of actual measurement and evaluation of each evaluation item of the aesthetic feeling (look at the time of oil stain) and the crispy texture of the food contained in the paper container.

ここに、「坪量（ｇ／ｍ^２）」とは、ＪＩＳ−Ｐ８１２４に記載の「紙及び板紙―坪量測定方法」に準拠して測定した値であり、「密度（ｇ／ｃｍ³）」とは、ＪＩＳ−Ｐ８１１８に記載の「紙及び板紙―厚さ及び密度の試験方法」に準拠して測定、算出した値であり、「透気度（秒）」とは、ＪＩＳ−Ｐ８１１７に記載の「紙及び板紙―透気度試験方法」に準拠して測定した値であり、「中間層の色調」とは、ＪＩＳ Ｚ ８７２２に準拠して測定した明度（Ｌ）、色相（ａ）、色相（ｂ）の値であり、そして「耐油度」とは、ＴＡＰＰＩ実用試験法ＵＭ５５７（１９８８）に準拠したキット試験に準拠して測定した耐油度（Ｋｉｔ値）である。

Here, “basis weight (g / m ² )” is a value measured based on “paper and paperboard—basis weight measuring method” described in JIS-P8124, and “density (g / cm ³ )”. "Is a value measured and calculated in accordance with" Paper and paperboard-thickness and density test method "described in JIS-P8118." Air permeability (seconds) "is JIS-P8117. It is a value measured in accordance with “Paper and paperboard—air permeability test method” described in the description, and “color tone of intermediate layer” means lightness (L) and hue (a) measured in accordance with JIS Z 8722 , Hue (b), and “oil resistance” is the oil resistance (Kit value) measured according to the kit test based on TAPPI practical test method UM557 (1988).

  Note that layer peeling in the measurement of “color tone of intermediate layer” was performed according to the following procedure. First, each sample obtained from each sample is immersed in water at room temperature for about 1 hour. Each sample immersed in water is wound around a round bar of about 10 mmΦ starting from a corner, and then the round bar is rolled to squeeze each sample. This operation is repeated starting from all four corners of each sample, and the ironing force is applied to the sample from each direction. As a result, a part of the layers between the samples peels off, and this is used to separate the back layer, the intermediate layer, and the surface layer to perform layer peeling. After delamination, the intermediate layer sample was dried with a sheet dryer or a hot air dryer and used for the test. The sample was dried at 120 ° C. or lower so that the color tone did not change.

“Beauty” (appearance at the time of oil stain) is a work table on which bread crumbs containing oil generated when fried croquettes are scattered, and put freshly fried croquettes in paper containers made with each sample. The portion where the oil stain on the appearance of the paper container was generated after 60 minutes was observed and evaluated as follows.
(Double-circle): There is no deterioration in appearance, such as darkening and discoloration, due to the raised raw material of the intermediate layer.
○: Discoloration due to the rising of the raw material of the intermediate layer is recognized, but the appearance does not matter.
×: Darkening or discoloration due to the raised raw material of the intermediate layer is conspicuous, looks bad, and feels inappropriate as a food container.

“Food texture” means that freshly fried croquettes are put in a paper container boxed with each sample and covered. After 60 minutes, 10 adult men and 10 adult women eat this croquette. It is a graded evaluation.
◎: Very good with a crispy texture (crisp texture).
○ mark: The decrease in texture due to re-adsorption of moisture is good to the extent that it does not matter.
X mark: The croquette has a sticky texture due to re-adsorption of water adhering to the inner surface of the paper container, and is poor (no crispy texture).

  When the production conditions (layer structure and raw material composition) shown in Table 1 and the quality evaluation results shown in Table 2 were examined in comparison with Examples and Comparative Examples, the following facts were found.

That is, it consists of at least three layers of a surface layer, an intermediate layer, and a back layer, has oil resistance, and has a basis weight of 3
10 g / m ² (The preferable range of the basis weight is 200 to 530 g / m ² , and the more preferable range is 25.
The lightness (L value) in the color tone of the intermediate layer of 70 to 85 is 0 to 470 g / m ² as described above, and the intermediate layer contains at least 10% of mechanical pulp. A paper container formed with a multilayer paperboard having an air permeability of 10 to 150 seconds (more preferably 20 to 100 seconds) has an aesthetics (appearance of the appearance of the container at the time of oil stain) and a texture ( The crispy texture of the food contained in the paper container is far superior to the comparative example.

In particular, the lightness (L value) in the color tone of the intermediate layer is 70 to 80, the hue (a value) is -3 to 3,
In the case of a multilayer paperboard having a hue (b value) of 10 to 16, and further in the case of a multilayer paperboard containing at least 0.7% of thermally foamable particles in the intermediate layer, the aesthetics are further improved. In addition, a paper container having an excellent texture can be provided.

It is a schematic sectional drawing which shows the layer structure of the multilayer paperboard based on the Example of this invention. It is a perspective view of the paper-made container boxed with the multilayer paperboard based on the Example of this invention. It is a schematic sectional drawing which shows the other layer structure of the multilayer paperboard based on this invention. It is a schematic sectional drawing which shows the further another layer structure of the multilayer paperboard based on this invention.

Explanation of symbols

10, 10 ', 10 "multilayer paperboard 11 (according to the present invention) Back layer 12 (12A, 12B, 12C) intermediate layer 13 surface layer 20 (made with multilayer paperboard according to the present invention) paper container 21 outer surface (of paper container) 22 inner surface (of paper container)

Claims (4)

A multilayer paperboard having at least a surface layer, a back layer, and an intermediate layer disposed between the surface layer and the back layer, and having an oil resistance basis weight of 200 to 530 g / m ² , The lightness (L value) in the color tone is 70 to 85, and at least 10% mechanical pulp is present in the intermediate layer.
A multilayer paperboard which is contained and has an air permeability of 10 to 150 seconds.   2. The multilayer according to claim 1, wherein the lightness (L value) in the color tone of the intermediate layer is 70 to 80, the hue (a value) is −3 to 3, and the hue (b value) is 10 to 16. Paperboard.   The multilayer paperboard according to claim 1 or 2, wherein the intermediate layer contains at least 0.7% of thermally foamable particles.   A paper container formed by the multilayer paperboard according to any one of claims 1 to 3.

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