JP2017031544A - Paper board for paper carton - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent paper board for a paper carton.SOLUTION: Provided is a coating paper board for a paper carton provided with five or more paper layers and having a density of 0.70 to 0.90 g/cm. This coating paper board at least includes: a back layer; a back lower layer; a middle layer; a surface lower layer; and a surface layer from the side in contact with a content. All of the back lower layer, the middle layer and the surface lower layer are blended with TMP, and the surface of the surface layer is provided with one or pigment coating layers.SELECTED DRAWING: None

Description

  The present invention relates to a paperboard used for paper containers. More specifically, the present invention relates to a paperboard used mainly for a paper container such as a food tray, a food pack, a sheet for drawing, a cup noodle container, a paper cup, a food outer box, a sugar beet carton, or a carton.

  Generally, when using paperboard as a packaging material such as a paper container, it is required to reduce the burden on the environment, and the packaging material is being reduced in weight and bulk.

  In addition, demand for paper containers is increasing as containers for food take-out used in convenience stores and supermarkets. The food contained in the container often has oil or moisture, and the container is required to have water resistance and oil resistance. Conventionally, paperboards laminated with a resin such as polyethylene on the inside of the paper (the surface that comes into contact with food) were often used as containers. However, from the viewpoint of environmental protection and recycling, paper containers that do not use resins have been demanded. .

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-007888) discloses a multilayer paperboard for containing foods having oil and moisture. Specifically, 10% or more of mechanical pulp is used for the intermediate layer, the color tone of the intermediate layer is set to a specific range, the freeness of each layer constituting the paperboard is limited to 350 to 450 cc, and the paperboard It is described that a paperboard for food containers capable of maintaining a crispy texture of food can be obtained by setting the air permeability of 10 to 150 seconds.

  Furthermore, Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-189959) discloses a packaging board that is bulky and has a low density. Specifically, a paperboard is proposed in which mechanical pulp, curled fiber or mercerized pulp is used for the middle layer, and the density and basis weight of each paperboard layer are set within a specific range.

JP 2008-007888 A (Patent No. 4302124) JP 2001-189959 A (Patent No. 3714124)

  Conventional paperboard paperboard may not have sufficient oil resistance, water resistance, heat insulation, and the like, and there is a need for higher quality paperboardboard.

  Especially for oily foods such as croquettes, cutlets, tempura, french fries, and other foods with relatively high water content such as shumai, dumplings, takoyaki, taiyaki, etc. There has been a need for paper containers, and there has been a need for paperboard for use in such paper containers.

  In view of such a situation, the present invention is to provide a paperboard board having oil resistance and water resistance so that contents such as food can be accommodated, and being bulky and having cushioning properties and heat insulation properties.

  Moreover, in a preferred embodiment, the present invention has an object to provide a paperboard board that can exhibit sufficient oil resistance when an externally added oilproofing agent is applied. Conventionally, there has been a case where oil resistance is applied to the base paper by imparting oil resistance. In this case, depending on the type of the oil resistance, the paperboard may not be able to exhibit sufficient oil resistance.

  As a result of diligent examination of the above problems, the use of CTMP (chemothermomechanical pulp) as the middle layer after making the paper layer structure of paperboard paperboard into a multi-layered paper of 5 layers or more has excellent oil resistance and water resistance, The present inventors have found that a paperboard board which is bulky and excellent in heat insulation can be obtained, and has completed the present invention. A method to increase the oil resistance of the paper itself (internal oil resistance) by adding an internal oil resistance agent during paper making as an oil resistance agent for imparting oil resistance to the paper, and applying or impregnating an external oil additive to the surface layer of the paper. There is a method of imparting (externally added oil resistance). In the case of internally added oil resistance, the oil end face of the paper can also be given oil resistance, but the amount of the oil resistant agent used is large, and all the resulting paper becomes oil resistant paper and its use is limited. On the other hand, the oil added externally is a post-processing after the paper is manufactured, so that it is not limited to the use of the base paper, and the required amount of oil-resistant paper can be obtained. In addition, since an oilproofing agent is added to the surface of the paper, a small amount may be added compared to the internal addition.

  In a preferred embodiment, the paperboard board according to the present invention can sufficiently exhibit the effect of the oil resistant agent when the externally added oil resistant agent is coated on the paper surface.

Although not limited to this, this invention includes the following aspect.
(1) A paperboard coated paperboard having a density of 0.70 to 0.90 g / cm ³ , comprising 5 or more paper layers, from the side in contact with the contents, the back layer, the back lower layer, and the middle layer The above-mentioned paperboard coated paperboard, which has at least a surface lower layer and a surface layer, has TMP blended in all of the back lower layer, the middle layer and the surface lower layer, and has one or more pigment coating layers on the surface layer.
(2) The coated paperboard for paper containers according to (1), wherein the paper container is a paper container for containing food.
(3) The paperboard coated paperboard according to (1) or (2), wherein the TMP is CTMP.
(4) The paperboard coated paperboard according to any one of (1) to (3), wherein no used paper pulp is used.
(5) The paperboard coated paperboard according to any one of (1) to (4), comprising 5 paper layers.
(6) The paperboard coated paperboard according to any one of (1) to (5), wherein the basis weight is 200 to 500 g / m ² .
(7) The paperboard coated paperboard according to any one of (1) to (6), wherein no pigment coating layer is present on the back layer.
(8) The paperboard coated paperboard according to any one of (1) to (6), which has one or more pigment coated layers on the back layer.
(9) The paperboard coated paperboard according to (8), wherein the backing pigment coating layer contains 50 parts by weight or more of kaolin.

  ADVANTAGE OF THE INVENTION According to this invention, the paperboard board which is excellent in oil resistance and water resistance, is bulky, and was excellent in heat insulation can be obtained. Moreover, the paperboard board of the present invention can be made bulky and the paper stiffness (rigidity) can be increased by making it into a multi-layer paper having 5 or more layers.

  Further, according to the present invention, by using CTMP in three or more layers including the middle layer, it is possible to obtain a paperboard board having a low density and maintaining a bulkiness even when a coating layer is provided. For example, by blending CTMP into the front lower layer, middle layer, and back lower layer, the color tone of the paperboard surface becomes a cream color, and oil stains can be made inconspicuous.

  Further, the paperboard board of the present invention can obtain sufficient oil resistance even when various oilproof agents are applied.

  Furthermore, since the paperboard board of the present invention is lightweight and excellent in rigidity, it is light and easy to hold even when the size of the paper container is large, and can be easily used by children, elderly people, and the like. Furthermore, the paperboard board of the present invention is soft to the touch, has high cushioning properties, and has good molding characteristics.

The paperboard coated paperboard according to the present invention has a density of 0.70 to 0.90 g / cm ³ , and from the side in contact with the contents such as food, the back layer, the back lower layer, the middle layer, the front lower layer, and the surface layer 5 Having at least a layer.

Paper containers for coated board for coated board present invention Shiki is the density of the entire board is 0.70~0.90g / cm ^3, preferably 0.74~0.87g / cm ^3, 0.78 ˜0.84 g / cm ³ is more preferred. If the density of the coated paperboard is less than 0.70 g / cm ³ , the rigidity becomes insufficient and the workability may be deteriorated. On the other hand, when the density of the coated paperboard exceeds 0.9 g / cm ³ , the density becomes high and the bulkiness is lowered, the cushioning property and the heat insulating property are deteriorated, and further, the paperboard itself is hardened, for example, bent. When processing is performed, paper breakage may occur, and processing suitability may deteriorate.

The basis weight of the coated board of the present invention, for example, be a 90~600g / ^{m 2,} preferably 150~500g / ^{m 2,} more preferably 200 to 400 g / ^{m 2,} more 250-350 g / It is good also as m2. Such a basis weight is suitable as a paperboard for paper containers to be carried.

  The paperboard coated paperboard according to the present invention has at least a back layer, a back bottom layer, a middle layer, a top bottom layer, and a top layer from the side in contact with the contents such as food. That is, the paperboard coated paperboard of the present invention has at least five paper layers, and can be produced by multi-layer papermaking by an ordinary method. In the present invention, a paper layer may be further provided in addition to the above five layers, and each layer such as a middle layer may further include a plurality of layers. By using multiple layers, TMP can be blended in more layers, and bulkiness can be maintained even when a coating layer is provided on the surface layer of the paperboard.

The density of each paper layer may be adjusted so that the density of the entire coated paperboard is 0.70 to 0.90 g / cm ³ , but the bulkiness is effectively imparted by reducing the density of the middle layer. be able to. The density of the middle layer is preferably 0.61~0.90g / cm ^3, more preferably 0.63~0.80g / cm ^3, more preferably 0.65~0.75g / cm ^3. In general, the back layer, the surface layer, and the pigment coating layer provided on the surface layer have a higher density than the middle layer using CTMP, so that the density of the entire paperboard is 0.70 to 0.90 g / cm ^3. It is necessary to lower the density of the middle layer. Although the density of the front lower layer and back lower layer which contact | connects a middle layer is not specifically limited, For example, it can be set as the density similar to a middle layer. In order to reduce the density (increase the bulk), there is a method of increasing the TMP content. In the coated paperboard of this invention, TMP can be mix | blended with a surface lower layer, a middle layer, and a back lower layer. However, when the TMP content is increased, the color tone becomes cream. Therefore, when using a paper container, the amount of TMP to be included in the middle layer and the back layer is lower than the surface layer close to the surface layer, which is preferred to have a higher white color for printing. It is better to have more.

The basis weight of the respective paper layers is not particularly limited, for example, be a 15~150g / ^{m 2,} may be 20 to 100 g / ^{m 2} and 25~80g / ^{m 2} in a preferred embodiment.

  The paperboard board of the present invention has excellent oil resistance, and sufficient oil resistance is imparted when various oil resistance agents are applied. When the paperboard of the present invention is used as a paper container for food, the oil resistance of the back layer (the layer in contact with food) is determined based on TAPPI RC-33, Kit. No. It is preferable to adjust to 7-13. When the oil resistance value of the back layer is less than 7, when potatoes or fried chicken are stored for a long time, the oil resistance becomes insufficient, and the oil may ooze out to the surface of the paperboard. On the other hand, when the oil resistance exceeds 13, when the paper container is manufactured, the adhesive does not penetrate into the paper layer in bonding or box making, and it may be difficult to manufacture the paper container. The oil resistance of the back of the paperboard can be adjusted by applying an oil resistance agent.

The color tone of the paperboard board of the present invention is not particularly limited, and may be set according to the application. In a preferred embodiment, when the a ^* value of the hue on the front and back surfaces of the paperboard is set to -5 to 5 or the b ^* value is set to 1 to 9, the cream color has a natural color tone, so that the oil stain is not noticeable. The hue can be adjusted by blending pulp (TMP or the like) such as a surface layer, a surface lower layer, a back layer, or the like, or by various dyes or pigments. When adjusting with a blending amount of TMP or the like, a creamy texture is produced as the blending amount is increased.

  In addition, the paperboard board of the present invention preferably contains no fluorescent dye in order to improve safety in food use or infant use.

  In the present invention, known papermaking additives can be used. For example, sulfuric acid bands and various anionic, cationic, nonionic or amphoteric yield improvers, drainage improvers, paper strength enhancers and internal additive sizing agents, etc. Can be used. Furthermore, dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  Further, in the present invention, known fillers can be arbitrarily used, for example, white carbon, talc, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delami Amorphous silica produced by neutralization of kaolin, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate, etc. These inorganic fillers and organic fillers such as urea-formalin resin, melamine resin, polystyrene resin, and phenol resin can be used alone or in combination. Among these, calcium carbonate and light calcium carbonate-silica composite, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used.

  As a paper machine for paperboard of the present invention, any paper machine capable of multi-layer papermaking can be used without particular limitation. For example, a known paper machine such as a long paper machine, a gap former, or a hybrid former (on-top former) can be used. The papermaking conditions are not particularly specified, and the pH during papermaking may be acidic, neutral or alkaline. In order to improve the interlayer strength, a water-soluble polymer such as starch or a binder such as latex can be used between the paper layers.

  Further, in order to improve the surface strength, a clear coating liquid mainly composed of a water-soluble polymer such as starch can be applied to the paperboard (size press) to obtain a coated base paper.

  Since the paperboard paperboard of the present invention is used as a container, it is preferable to have an appropriate rigidity. For example, it may be 5 to 40 mN · m in the paper flow direction.

  Further, the paperboard board of the present invention can be particularly suitably used, for example, for containing food, but the contents (contained items) such as food are not particularly limited, and are used for containing tobacco. You can also The paperboard board of the present invention is excellent in oil resistance, water resistance, cushioning, etc., so it can be fried, croquette, cutlet, tempura, fried potato, shumai, gyoza, takoyaki, taiyaki, donut, etc. Even foods containing a lot of moisture can be used as food paper containers that suitably contain them. Since the paper container manufactured using the paperboard board of the present invention is lightweight, it can be suitably used as a takeout container. It can also be used when the content is other than food, for example, it can be used for toys for infants. It can also be used for publications and pops.

  As will be described later, since the paperboard board of the present invention is provided with a pigment coating layer on the surface layer, it can be printed beautifully there. Therefore, by using the paperboard board of the present invention, a paper container excellent in appeal to consumers can be produced.

Pulp In the present invention, TMP (thermomechanical pulp) is used in at least three layers of the middle layer, the front lower layer, and the back lower layer. In a preferred embodiment, CTMP (chemothermomechanical pulp) is blended in the middle layer, the front lower layer, and the back lower layer. . Thereby, oil resistance and water resistance, as well as cushioning properties and heat insulation properties can be ensured while keeping the density of the entire paperboard low. CTMP is a kind of TMP, which is manufactured after immersing wood chips in chemicals. Moreover, although TMP used in this invention does not need to be bleached, in the case of a food use, bleached BCTMP can be used preferably. In addition, the Canadian standard freeness (CSF) of TMP may be adjusted as appropriate, but may be, for example, 50 to 500 ml, further 200 to 350 ml.

  The amount of TMP in each paper layer is not particularly limited, but for example, for the upper and lower layers located on the outside of the paper container and close to the surface layer where white is required, the amount of TMP is 80% by weight or less of the whole pulp. Is preferable, 70% by weight or less is more preferable, and may be 60% by weight or less. About a minimum, in order to enjoy the effect of this invention largely, it is preferable to set it as 10 weight% or more, It is more preferable to set it as 20 weight% or more, It is further more preferable to set it as 50% or more.

In addition, the amount of TMP in the middle layer is not particularly limited, but it can be blended more than the lower and lower layers. % By weight is more preferable, 50 to 90% by weight is more preferable, and 70 to 90% by weight may be set. Furthermore, although the compounding quantity of TMP in a back lower layer is not restrict | limited in particular, it can mix | blend more than a surface lower layer, and is good also as a middle layer. For example, the blending amount of TMP in the back lower layer is preferably 20 to 100% by weight of the whole pulp, more preferably 30 to 95% by weight, further preferably 45 to 90% by weight, still more preferably 50 to 90% by weight, It is good also as 70 to 90 weight%.
From the viewpoint of bulkiness, the blending ratio of TMP including the lower layer, middle layer, and back and lower layer, excluding the pigment coating layer of the paperboard board, is preferably 30 to 50% of the entire paperboard, and 35 to 45%. Is more desirable.

  As described above, TMP is used in the present invention, but the production method is not particularly limited, and can be produced by a conventional method. Moreover, the tree species of the pulp is not particularly limited, and NTMP (derived from coniferous tree) and LTMP (derived from broadleaf tree) can be used alone or in combination.

  In one preferred embodiment, CTMP can be used, but CTMP can be produced using chemicals such as sodium sulfite, for example. Specifically, CTMP can be manufactured by a manufacturing process including a chip pretreatment process using sodium sulfite or the like, a defibrating process by primary refining, and a beating process by secondary refining, for example. CTMP manufactured through such a manufacturing process is preferable because it makes the paper highly opaque and the strength of the paper is high. For example, as a pretreatment of the chip with sodium sulfite, an impregnation treatment with an aqueous sodium sulfite solution can be performed. In this case, the chip is compressed, and the chip is immersed in the sodium sulfite aqueous solution after being compressed or after being compressed. It can be impregnated with sodium sulfite while releasing and expanding the chip. In this step, the chip is preferably sufficiently impregnated with an aqueous sodium sulfite solution, and the compression ratio is preferably 4: 1 to 16: 1. When the compression ratio is lower than 4: 1, the restoring force of the chip is weak, and the penetration of the sodium sulfite aqueous solution into the chip becomes insufficient. On the other hand, it is impractical for the compression ratio to exceed 16: 1. It is. Here, the compression ratio is defined as the volume before compression: the volume after compression. In order to complete the impregnation with the aqueous sodium sulfite solution, a surge bin can be provided after the plex screw or the impressor.

  In a preferred embodiment, the addition rate of sodium sulfite is 0.5 to 2.0% by weight based on the absolutely dry chip. Depending on the pH of the aqueous sodium sulfite solution, the average fiber length after primary refining is slightly different. The initial pH of the sodium sulfite aqueous solution to be impregnated is 4.5 to 9.5, preferably 7.0 to 9.5. For this pH adjustment, sulfuric acid or sodium hydroxide is used. In this range, the higher the pH, the greater the long fiber content and the longer the average fiber length. If the pH exceeds 9.5, the level is turned off, resulting in poor chemical efficiency. A pH of less than 4.5 is not preferable because there is a risk of metal corrosion of the equipment.

  The chip impregnated with the sodium sulfite aqueous solution is preferably preheated (preheated) prior to the primary refining for the purpose of improving defibration. The temperature in this case is preferably 100 to 135 ° C.

  After the pretreatment process, the chip is subjected to a defibrating process by primary refining. In this step, a pressure refining device can be used, and other conditions are defibrated to pulp fibers by a known method except for a refiner plate (refiner segment). As the refining device, a single disc refiner, a conical disc refiner, a double disc refiner, a twin disc refiner, or the like can be used. However, the higher the concentration during defibration, the more fibrillation of the pulp fibers proceeds and a high quality pulp can be obtained. Therefore, a single disc refiner is preferably used. The concentration of chips during the refining process is preferably about 20 to 60% by solid weight, and the processing temperature is preferably 100 to 180 ° C. More preferably, it is 120-135 degreeC.

  The defibrated pulp is then sent to the secondary refiner under normal pressure and beaten to the target freeness. In the beating step by secondary refining, a known refining apparatus can be used and refined under known conditions, and the pulp freeness is reduced to a desired level. This step is performed under normal pressure, and it is preferable to use a general normal pressure type apparatus as the refining apparatus, and the concentration can be carried out at about 4 to 60%. The secondary refiner may be a single stage or a plurality of stages.

  After the secondary refining, a bleaching treatment may be performed as necessary. As a bleaching agent, a known bleaching agent used in the production of BCTMP can be used, and there is no particular limitation. Preferably, a peroxide such as hydrogen peroxide is used. In this case, a chelating agent such as ethylenediaminetetraacetate (EDTA) can be used in combination for the purpose of preventing the decomposition of the peroxide by metal ions. These treatments can be performed under known conditions. The CTMP of the present invention preferably has a Canadian standard freeness (CSF) of 50 to 350 ml.

  In the paperboard board of the present invention, as described above, TMP is blended in the middle layer, the back lower layer, and the front lower layer, but other pulps can be freely selected and used.

  As the raw material pulp used in the present invention, in addition to the above TMP, for example, chemical pulp (KP), mechanical pulp (MP), groundwood pulp (GP), refiner ground pulp (RGP), waste paper pulp, etc. It can be used by mixing at an arbitrary ratio. The raw material of the pulp is not particularly limited, and may be wood such as coniferous or hardwood, or non-wood such as kenaf, straw, bamboo, or sugarcane.

  However, it is preferable not to use waste paper pulp in the paperboard board of the present invention. When used paper pulp is used, fluorescent dyes brought in from used paper may be mixed into the paperboard board, which is not preferable as a paper container requiring safety, such as a food paper container.

  In the paperboard board of the present invention, it is preferable that the pulp beating freeness of each paper layer is adjusted to 200 to 500 ml.

Pigment coating layer (surface layer)
The paperboard board of the present invention has one or more pigment coating layers on the surface layer. By providing the pigment coating layer on the surface layer, the pigment coating layer is provided on the surface on which the container is printed (the outer surface of the paper container), so that printing and other processing can be performed cleanly. The pigment coating layer provided on the surface layer may be one layer or more, but in a preferred embodiment, when it is a two-layer coating, printability is particularly improved. In addition, the surface pigment coating layer can have water gravure printing suitability.

  The pigment coating layer on the surface layer can be provided by a general method. Specifically, a coating liquid in which a pigment, a binder and other components are mixed with water is prepared and applied to paper. Just work. In the coating liquid, various assistants that are blended in ordinary coating paper pigments such as dispersants, thickeners, water retention agents, antifoaming agents, water resistance agents, colorants, surfactants, etc., as necessary. Agents can be used as appropriate. In the preparation of the coating liquid, ordinary mixing means such as a mixer may be used.

The coating amount of the pigment coating layer on the surface layer is preferably 5 to 50 g / m ² in terms of dry weight per side in total for each layer. When the coating amount is less than 5 g / m ² , the coating layer becomes thin, and when the whiteness and color unevenness of the paperboard cannot be sufficiently improved, the printability may not be sufficiently improved. If the coating amount exceeds 50 g / m ² , it is not preferable because operability is lowered such as poor drying properties during coating, printing unevenness due to binder migration, and further, it is difficult to reduce the weight of the paperboard.

  The coating speed at the time of providing the pigment coating layer is not particularly limited, but can be generally about 50 m / min to 1000 m / min, about 100 m / min to 800 m / min, and further 200 m / min. It is good also as min-600m / min.

  The paperboard board of the present invention is produced through a normal drying process after a coating layer is coated on the base paper, but may be smoothed by a surface treatment process or the like as necessary. For smoothing processing, a smoothing processing device such as a normal super calendar, gloss calendar, soft calendar, thermal calendar, shoe calendar, or the like can be used. The smoothing apparatus is appropriately used on-machine or off-machine, and the form of the pressure device, the number of pressure nips, heating, and the like may be appropriately selected.

(Undercoating)
In the present invention, two pigment coating layers can be applied to the surface layer, but the undercoat coating solution comprises a pigment and an adhesive (binder). Adhesives are not particularly limited. For example, various copolymers such as styrene / butadiene, styrene / acryl, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, polyvinyl alcohol, and maleic anhydride. Synthetic adhesives such as acid copolymers and acrylic acid / methyl methacrylate copolymers; proteins such as casein, soy protein, synthetic proteins; oxidized starch, positive starch, urea phosphated starch, hydroxyethyl etherified Examples include etherified starch such as starch, starches such as dextrin; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxymethyl cellulose. In the present invention, polyvinyl alcohol and starch are preferred. In the present invention, it is preferable to use a synthetic adhesive and starches in combination. In a preferred embodiment, these adhesives are used in a total amount of 5 to 50 parts by weight, more preferably 8 to 30 parts by weight, and more preferably about 8 to 15 parts by weight per 100 parts by weight of the pigment.

  The pigment of the undercoat coating solution is not particularly limited, but examples thereof include kaolin, clay, engineered kaolin, delaminated clay, calcined clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate. Use inorganic pigments such as zinc oxide, silicic acid, silicate, colloidal silica, and satin white, and organic pigments such as solid type, hollow type, or core-shell type, as required, alone or in combination of two or more. Can do. As the types of pigments, heavy calcium carbonate and light calcium carbonate are preferable because the required amount of binder is small and the surface strength can be improved with a small amount of adhesive. The content of heavy calcium carbonate and light calcium carbonate is preferably 50 parts by weight or more.

(Top coat coating)
The topcoat coating solution used in the present invention comprises a pigment and an adhesive as in the case of the undercoat coating solution. A pigment is not restrict | limited, The pigment conventionally used for coated paper can be used. Examples include inorganic pigments such as kaolin, clay, heavy calcium carbonate, light calcium carbonate, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, and satin white, and organic pigments such as plastic pigments. Organic / inorganic composite pigments can be used. Of these, kaolin, clay, heavy calcium carbonate or light calcium carbonate is preferred. These pigments can be used alone, but if necessary, two or more kinds may be mixed and used. A flat pigment such as kaolin or clay is preferably contained in an amount of 50 parts by weight or more. Furthermore, when imparting water gravure printability, it is preferable to change 20 parts by weight or more of the flat pigment to deramikaolin having an aspect ratio of 20 or more, preferably 40 or more engineered kaolin. Examples of the engineered kaolin having an aspect ratio of 40 or more include Contour 1500 (manufactured by Imeris Corporation).

  It is preferable to mix | blend an adhesive agent (binder) with the topcoat coating liquid of this invention. The adhesive is not particularly limited, and an adhesive conventionally used for coated paper can be used. Examples of adhesives include styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, and other copolymers, polyvinyl alcohol, maleic anhydride copolymer And synthetic adhesives such as acrylic acid / methyl methacrylate copolymers; proteins such as casein, soy protein, synthetic protein; oxidized starch, positive starch, urea phosphated starch, hydroxyethyl etherified starch, etc. Conventional adhesives for coated paper such as starches such as etherified starch and dextrin; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and hydroxymethylcellulose are included. One or more types of adhesives can be appropriately selected and used. In a preferred embodiment, these adhesives are used in the range of 5 to 50 parts by weight, more preferably 8 to 30 parts by weight, and more preferably about 8 to 20 parts by weight per 100 parts by weight of the pigment. Moreover, when providing aqueous | water-based gravure aptitude, it is preferable that starch is 1-5 weight part per 100 weight part of pigments.

  The solid content concentration of the top coating liquid is preferably 40 to 75% by weight, more preferably 50 to 70% by weight, and still more preferably 60 to 70% by weight. When the solid content concentration of the topcoat coating liquid is less than 40% by weight, the volume change of the coating layer during coating drying increases, resulting in poor surface smoothness after coating. For example, in the case of a blade coater, if it is more than 75% by weight, the fluidity of the coating solution is deteriorated, and the blade edge of the blade coater becomes noticeable, resulting in poor coating surface feeling. In the case of a curtain coater, if it is more than 75% by weight, the fluidity of the coating liquid is deteriorated and it becomes difficult to form a uniform curtain film.

In the present invention, it is preferable to 2 to 30 g / ^{m 2} of coating amount of overcoat layer is the outermost layer, more preferably, to 4~20g / ^{m 2,} be 6~20g / ^{m 2} Is more preferable, and it is still more preferable to set it as 6-15 g / m < ² >. Also, the coating amount of the inner coating layer, preferably in a 5 to 30 g / ^{m 2,} and more preferably set to 10 to 25 g / ^{m 2.} In the present invention, the coating amount of the outermost coating layer may be larger or smaller than the coating amount of the inner coating layer. By adjusting the coating amount of each coating layer, only the surface layer part of the coated paperboard that has a great influence on the ink setting property is made a void structure suitable for printing, and the ink setting property is adjusted, and the whiteness is large. It is possible to maintain most of the inner primer layer that affects it.

Pigment coating layer (back layer)
The paperboard board of the present invention can be provided with one or more pigment coating layers on the back layer, that is, on the side in contact with the contents such as food. According to the study by the present inventors, by providing a pigment coating layer on the back layer and then coating an externally added acrylic oil resistance agent, the effect of the oil resistance agent can be greatly expressed. That is, when an acrylic oil-proofing agent is applied to the back layer side as an oil-proofing agent, it is better to provide oil resistance to the paperboard board by providing a pigment coating layer so that the oil-proofing agent does not penetrate inside the paper layer. Can do.

  On the other hand, the paperboard board of the present invention may not have one or more pigment coating layers on the back layer. According to the study by the present inventors, for example, when an externally added impregnated type oil resistant agent (fluorine type oil resistant agent) or the like is used as the oil resistant agent, the effect of the oil resistant agent is not provided on the back surface. Can be expressed greatly.

  When providing a pigment coating layer on a back layer, the pigment coating layer should just be one or more layers, but it is good also as two-layer coating. The pigment coating layer can be provided by a general method in the same manner as the above-described top coating pigment coating layer on the surface layer. Specifically, a pigment, a binder and other components are mixed with water. What is necessary is just to prepare a working liquid and apply it to paper. As the pigment, it is preferable to contain a flat pigment such as kaolin so that an acrylic oil-proofing agent that forms a film on the surface layer does not penetrate into the paper layer. The content of kaolin is preferably 50 parts by weight or more. In the coating liquid, various assistants that are blended in ordinary coating paper pigments such as dispersants, thickeners, water retention agents, antifoaming agents, water resistance agents, colorants, surfactants, etc., as necessary. Agents can be used as appropriate. In the preparation of the coating liquid, ordinary mixing means such as a mixer may be used.

Oilproofing The paperboard board of the present invention can be treated with an externally added oilproofing agent on the back side, particularly in applications where oil resistance is required. In general, fluorine-based and acrylic-based external additives are often used. Typical products of fluorine-based oil-proofing agents include Solvera (manufactured by Solvay) and Asahi Guard (manufactured by Asahi Glass), which uses low surface tension to repel oil and water (chemical water-resistant oil-resistant) Is. Typical products of acrylic oil-proofing agents include Herville (first paint) and Jonkrill (manufactured by BASF), which form a film on the surface and do not allow oil to penetrate (physical oil resistance). . In general, the inner surface of the paper container that comes into contact with food, that is, the back layer of the paperboard of the present invention is oil-resistant.

  The paperboard board of the present invention can obtain sufficient oil resistance even when any of the above oil resistance agents is applied. As described above, in the case of performing oil resistance processing using an acrylic oil resistance agent, it is preferable to provide one or more pigment coating layers on the paper layer on the side where the oil resistance agent is applied. In the case of performing oil resistance processing using a fluorine-based oil resistance agent, it is preferable not to provide a pigment coating layer on the paper layer on the application side from the viewpoint of forming good film properties.

  Hereinafter, the present invention will be described in more detail based on specific experimental examples, but the present invention is not limited to the following experimental examples. Further, in this specification, unless otherwise specified, concentrations and the like are based on weight, and numerical ranges are described as including the end points.

Manufacture of paperboard board Based on the following prescription, a 5-layer paperboard was manufactured using a multi-layer paperboard machine (basis weight: 210-315 g / m ² ). As the raw material pulp, hardwood bleached kraft pulp (LBKP, freeness CSF: 400 ml) and chemi thermomechanical pulp (CTMP, conifer, CSF: 250 ml, pulp whiteness: 60) were used, and starch was used as an interlayer adhesive.

A two-layer pigment coating layer was coated on the surface layer of a five-layer base paper to produce a paperboard coated paperboard. The under layer and the top layer are both coated with 8.5 g / m ² , and the pigment composition of the under layer is 100% heavy calcium carbonate (coating solution concentration 64%, using starch and latex as a binder), and the pigment composition of the top layer Was blade coated with 60% kaolin, 30% heavy calcium carbonate, 10% light calcium carbonate (coating solution concentration 62%, using starch and latex as binder).

Samples other than sample 2 were also provided with a 8.5 g / m ² pigment coating layer on the back layer. The pigment composition is the same as that of the top layer of the surface layer: kaolin 60%, heavy calcium carbonate 30%, and light calcium carbonate 10%.

  Next, the surface of the coating layer was smoothed with a calendar to produce a paperboard coated paperboard.

Evaluation / Test Method Paperboard paperboard was evaluated and tested based on the following method.

Basis weight: JIS P 8124: 2011
Thickness and density: JIS P 8118: 1998
Thickness / density of each layer:
Each layer is peeled between the layers by the method described in JIS P 8139 (Peeling strength test method for paperboard making layer), and the thickness (mm) and basis weight (g / m ² ) are determined. However, since the thickness of each peeled layer is fluffed by peeling and becomes thicker than the actual thickness, the correction factor value (correction factor value = total thickness before peeling / total value of each layer after peeling) ) Is calculated, the thickness of each layer after peeling is corrected, and the density of each layer is calculated.

In addition, when it is difficult to divide each layer by the delamination method of JIS P 8139, a multilayer laminated sheet sample is immersed in warm water at 60 ° C. for 1 hour and then separated into each layer. Each peeled layer was air-dried to determine the thickness (mm) and the basis weight (g / m ² ).

  In addition, when the coating layer is provided on the back layer and / or the surface layer, since the process of peeling off the coating layer from the back layer and / or the surface layer is not performed, the density of the back layer and the surface layer in the following table is: If there is a coating layer, the value includes it.

Stiffness: JIS P8125
Hue:
Based on JIS P8150, a ^* value and b ^* value were measured with a light source including ultraviolet light using a color difference meter (manufactured by Murakami Color Co., Ltd., CMS-35SPX).

Oil resistance (degree of oil stain):
The cooking oil was put on the back side of the paperboard, and the degree of oil stain was visually evaluated when viewed from the surface after 2 hours. The oil resistance was evaluated in three stages according to the following evaluation criteria.
○: No oozing, △: Slight oozing, x: Oil bleed spread Molding suitability:
A comprehensive evaluation was made from the ruled line cracks and tears when the paperboard was formed into a tray.
○ Good, △ = Slightly inferior, × Defective Printability (table): Printed on the surface of bulky white paperboard with a Roland flat-format printing machine (4 colors), printing surface feeling (fineness of printed matter, wearing Meat unevenness, uneven glossiness, etc.) were visually evaluated relative to each other.
The evaluation criteria are as follows.
○ = Good, △ = Slightly inferior, X = Inferior

  When the paperboard board of the present invention produced as described above was evaluated, the printability of the surface was good (◯). In addition, all the samples had good moldability as a paper container (moldability: ◯). Furthermore, the oil resistance was good (◯) in any sample.

Manufacture and evaluation of food container A box capable of containing six donuts was manufactured using the above coated paperboard, but the processability was good. Furthermore, the doughnut was accommodated in this food container (box), and oil resistance and water resistance were confirmed. After 2 hours, 4 hours, 6 hours, and 24 hours, oil stain was confirmed, but there was no oil stain until 6 hours, and some oil stain was confirmed after 24 hours. That is, the coated paperboard of the present invention had sufficient quality as a food paper container.

Claims (9)

5 or more layers with paper layers, the density is a paper container for coated board is 0.70~0.90g / cm ^3,
From the side in contact with the contents, it has at least a back layer, a back layer, a middle layer, a surface layer, a surface layer, and TMP is blended in all of the back layer, middle layer, and surface layer,
The paperboard coated paperboard having one or more pigment coated layers on the surface layer.   The coated paperboard for paper containers of Claim 1 whose said paper container is a paper container for accommodating a foodstuff.   The paperboard coated paperboard according to claim 1 or 2, wherein the TMP is CTMP.   The coated paperboard for paper containers in any one of Claims 1-3 in which used paper pulp is not used.   The paperboard coated paperboard according to any one of claims 1 to 4, comprising five paper layers. The coated paperboard for paper containers in any one of Claims 1-5 whose basic weight is 200-500 g / m < ² >.   The paperboard coated paperboard according to any one of claims 1 to 6, wherein no pigment coating layer is present on the back layer.   The paperboard coated paperboard according to any one of claims 1 to 6, further comprising one or more pigment coated layers on the back layer. The coated paperboard for paper containers of Claim 8 which contains 50 weight part or more of kaolin in the pigment coating layer of a back layer.