JP6117133B2 - White paperboard and its manufacturing method - Google Patents

Description

  The present invention relates to a white board having excellent printing durability, a sufficient ruled line cracking preventing effect, and good fading, and a method for producing the same.

White paperboard is generally printed and used for packaging. Therefore, white paperboard is an important issue not only for printability but also for box making or strength when used as a box. Here, the white paperboard is a thick paper having a basis weight of 150 g / m ² or more, and generally has a multilayer structure of 3 to 9 layers. White paperboard is manufactured by, for example, combining layers called a white layer, a white lower layer, and a middle layer. Specifically, the white paperboard is a layer using bleached pulp with high whiteness called the white layer on the outermost layer, and then a layer using old paper with relatively high whiteness called the white underlayer on the inner layer in contact with the white layer. Further, the inner layer is composed of a layer using waste paper pulp called a middle layer.

  White paperboard is processed into a box or the like through processes such as printing and punching. When assembling into a box, it is necessary to bend, and in order to bend as designed, a ruled line is put in advance at the folding position. When folded, the front side of the white paperboard receives an extension force, but if the strength of the front side part of the white paperboard is lost by this force, the whiteboard paper breaks and tears. This break is called “ruled line cracking” (sometimes called ruled cracking), and the surface layer of a mild one is cracked, but the case of a severe one is greatly cracked including the base paper. Those having the ruled line crack are not only unsightly in appearance but also the strength of the assembled box is lowered, which becomes a fatal defect as a packaging structure.

  This ruled line crack is likely to occur when the moisture content of the paperboard is 6% or less, and particularly occurs in the dry season in winter. Further, this ruled line breakage occurs when the ruled line portion is bent because the surface layer cannot withstand the force applied to the surface layer outside the bend, and is also affected by the surface layer strength of the paperboard.

  As a countermeasure against such ruled line cracking, a technique of incorporating a hygroscopic agent into the paperboard is disclosed (for example, see Patent Document 1). Moreover, the technique which contains a cationic surfactant in a surface layer is disclosed (for example, refer patent document 2).

JP 2007-197845 A JP-A-11-200209

  In Patent Document 1, as a moisturizing agent, specifically, sodium lactate is applied to the paper surface. However, since sodium lactate precipitates on the paper board surface as a salt after drying, the paper strength decreases as a result, and the paper peels off during printing. And so on. In the case of coated paper, even if it is applied to the base paper, the moisture absorption effect cannot be obtained and the desired effect cannot be obtained. Furthermore, it is not practical to use expensive sodium lactate for white paperboard made mainly from used paper raw materials, and it is difficult to use it on a commercial production basis. In Patent Document 2, a cationic surfactant is included on the front side, but what is illustrated is used as a bulking agent, and as a result, the paper strength is reduced and the paper is peeled off during printing. Connected. These focus only on ruled line breaks and cannot be printed.

  An object of the present invention is to solve the above-mentioned problems, to provide a white board having excellent printing durability, a sufficient ruled line cracking preventing effect, and good color fading, and a method for producing the same.

As a result of intensive studies on white paperboard, the present inventors have found that the problem can be achieved by the following configuration. That is, the white paperboard according to the present invention is a coating mainly composed of a pigment and an adhesive on at least one side of a base paper that is a multi-layered paper of three or more layers in which the mixing ratio of the used paper pulp is 60% by mass or more. In the white paperboard provided with the engineering layer, among the layers of the base paper, the layer disposed on one surface is the surface layer, the layer disposed on the other surface is the back layer, and the intermediate between the surface layer and the back layer When each of the arranged layers is represented as an intermediate layer, (1) the ratio of the used paper pulp in the front layer and the back layer is 20% by mass or less, and (2) the ratio of the used paper pulp in the intermediate layer is 90%. (3) The freeness of the pulp used for the surface layer is 200 to 400 ml of CSF, (4) the ash content of the surface layer is 7% by mass or less, and (5) the Z axis of the white paperboard The strength is 300 to 470 kN / m ² and (6 ) Density of the white paperboard is characterized by a 0.77~0.87g / cm ^3.

In the white paperboard according to the present invention, it is preferable that no water-soluble polymer is applied to the base paper, or the amount of the water-soluble polymer applied is 0.5 g / m ² or less per side of the base paper. By setting it within this range, the surface of the base paper is not hardened, and cracking of the ruled line can be prevented.

  In the white paperboard according to the present invention, it is preferable that the raw paper pulp used in the intermediate layer is newspaper waste paper, and the ratio of the used waste paper is 50 to 100% by mass of the waste paper pulp used in the intermediate layer. By setting it within this range, the density of the middle layer can be kept low, and the stress applied to the paperboard surface when folded can be released, and as a result, ruled cracks can be prevented.

  The method for producing white paperboard according to the present invention does not beat used paper pulp used for the intermediate layer, or beats the used paper pulp used for the intermediate layer, and freeness based on the freeness of unbeaten used paper pulp. The difference value is set within 100 ml. By not beating the waste paper pulp used for the intermediate layer or setting the freeness difference value within this range, the density of the intermediate layer can be kept low and the stress can be relieved when folded by crease processing. Cracking can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the white board paper which is excellent in printing durability, has a sufficient ruled line cracking prevention effect, and has a fading property, and its manufacturing method.

It is an observation image where the evaluation of the ruled crack test is ◎, (a) shows the MD direction, and (b) shows the CD direction. It is an observation image in which the ruled crack test is evaluated as ◯, (a) shows the MD direction, and (b) shows the CD direction. It is an observation image in which the evaluation of the ruled crack test is Δ, (a) shows the MD direction, and (b) shows the CD direction. An evaluation image of the ruled crack test is an observation image of ×, (a) shows the MD direction, and (b) shows the CD direction.

  Next, the present invention will be described in detail with reference to embodiments, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.

The white paperboard according to this embodiment is a coating mainly composed of a pigment and an adhesive on at least one surface of a base paper which is a three-layer or more multi-layer paper having a ratio of waste paper pulp of 60% by mass or more. In the white paperboard provided with a layer, among the layers of the base paper, a layer disposed on one surface is a surface layer, a layer disposed on the other surface is a back surface layer, a layer disposed between the front surface layer and the back surface layer When expressed as an intermediate layer, (1) the proportion of waste paper pulp in the front layer and back layer is 20% by mass or less, (2) the proportion of waste paper pulp in the intermediate layer is 90% by mass or more, ( 3) The freeness of the pulp used for the surface layer is CSF 200 to 400 ml, (4) the ash content of the surface layer is 7% by mass or less, and (5) the Z-axis strength of the white paperboard is 300 to 470 kN / m ² . (6) The density of the white paperboard is 0.77 to 0.87 g / cm ³ . In the present specification, the front surface layer and the back surface layer are sometimes referred to as white layers. Of the intermediate layers, the intermediate layer in contact with the front surface layer or the back surface layer may be referred to as a white lower layer. Of the intermediate layers, an intermediate layer that is not in contact with the front surface layer or the back surface layer may be referred to as an intermediate layer. Further, as described above, the white paperboard of the present invention has a sufficient effect of preventing the ruled line cracking, but the ruled line cracking mainly occurs on the surface outside the bend when the white paperboard is bent. The white paperboard of the present invention has a sufficient ruled line cracking prevention effect by making the surface on the surface layer side a surface that is outside the bend.

  The freeness of the pulp used for the surface layer used for the base paper is CSF 200 to 400 ml. More preferably, it is CSF 250 ml-350 ml. If it is less than 200 ml, water breakage at the wire part deteriorates, and the wet sheet collapses during press squeezing at the press part in the next process, making production difficult. In addition, the surface layer becomes too hard and dense, and when bent, there is no degree of freedom of elongation, and ruled line cracks are likely to occur. If it exceeds 400 ml, the fiber-to-fiber bond of the pulp becomes weak, the paper strength is reduced, and it cannot withstand printing. Moreover, it becomes easy to generate | occur | produce a ruled line crack by weakness. In the present invention, the freeness of the pulp used for each layer of the base paper is obtained by measuring with a Canadian standard freeness tester (based on JIS P 8121: 1995 “Pulp Freeness Test Method”).

  In the white paperboard according to this embodiment, the waste paper pulp used for the intermediate layer is unbeaten waste paper pulp, or the waste paper pulp used for the intermediate layer is beaten, and the freeness of the unbeaten waste paper pulp is reduced. The reference freeness difference value is preferably within 100 ml of CSF. The freeness difference value based on the freeness of unbeaten waste paper pulp is a value obtained by subtracting the freeness of waste paper pulp after beating from the freeness of unbeaten wastepaper pulp (hereinafter abbreviated as “freeness difference value”). is there. The freeness difference value is more preferably 80 ml or less. More preferably, no beating is performed. Usually, freeness is reduced by unbeaten waste pulp. For this reason, the freeness difference value is usually 0 ml or more. Waste paper pulp has been shortened and keratinized more than fresh pulp because it has been disaggregated, beaten and dried at least once. For this reason, it is presumed that waste paper pulp subjected to excessive beating rapidly agglomerates the base paper. For this reason, when the freeness difference value of the used paper pulp exceeds CSF 100 ml, the base paper becomes dense, the density is increased and the bulk does not appear, and further, the desired Z-axis strength is not obtained, resulting in ruled line cracking.

  In the present embodiment, the freeness of the pulp used for the back surface layer is not particularly limited, but it is preferably CSF 200 to 400 ml, more preferably CFS 250 to 350 ml, similarly to the surface layer. Moreover, although the freeness of the pulp used for an intermediate | middle layer is not specifically limited, It is preferable to set it as CSF200ml -400ml, and it is more preferable to set it as CFS250-400ml.

  Waste paper pulp used for the base paper is largely classified into high-quality and medium-quality paper, but when using waste paper for the front surface layer and the back surface layer, it is preferable to use high-quality waste paper pulp to avoid fading. Examples of the high-quality waste paper pulp include pulps prepared from waste paper such as fine white, ruled white, curd, imitation, color, Kent, white art, and milk carton. As the used paper used in the white paperboard according to the present embodiment, not only the disaggregation or dust removal treatment, but preferably used paper pulp after each process such as deinking, bleaching, ink dispersion or washing is used. In particular, in the case of multilayer papermaking, fine ink may move to another layer when pressure dewatering is performed in the press part after papermaking. Therefore, it is more preferable to install a cleaning device capable of removing fine ink in the used paper processing step and go through the cleaning step by the device. As a result, fading can be improved.

  As the used paper pulp used for the intermediate layer, it is preferable to contain medium quality used paper pulp. Typical examples of medium-quality waste paper pulp include pulps prepared from waste paper such as newspapers, magazines, cutting, medium-size antiquarian, tea imitation, corrugated cardboard, mounts, paper certificates, cardboard, etc. The raw material of the used paper pulp is preferably newspaper waste paper, and the blending ratio is preferably 50 to 100% by mass of the used paper pulp used for the intermediate layer. More preferably, it is 70-100 mass%, More preferably, it is 90-100 mass%. By setting it in this range, the density of the intermediate layer can be kept low, and the stress applied to the paperboard surface when folded can be released, and as a result, ruled line cracking can be prevented. Used newspapers refer to used newspapers that are left unsold at stores, scraps from printing plants, and so-called collected newspapers that contain leaflets generated from households due to the collection of waste products. Newspaper paper is blended with mechanical pulp, and particularly contains a lot of softwood mechanical pulp, and the ash content is lower than that of magazine wastepaper, etc., so the density can be lowered by using wastepaper wastepaper. In addition, the more voids in the paper layer are not only flexible against bending, but in the case of mechanical pulp, since it is rigid, it is not entangled between layers, and the interlayer strength is kept moderate. As a result, when the paperboard is bent, the stress can be relieved by the separation of the layers even when there is no place for the inner layer.

  As pulp used for the base paper, in addition to waste paper pulp, virgin pulp as hardwood bleached sulfite pulp (LBSP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), softwood bleached kraft pulp (NBKP) Mechanical pulp (GP, TMP, BCTMP) or the like may be used. In addition to wood pulp, non-wood pulp, synthetic pulp, synthetic fiber, or the like may be used as necessary. In addition, it is preferable not to mix | blend mechanical pulp with a white lower layer or a middle layer from the surface of fading property. The deinked pulp (DIP) may be blended in the white layer if it is high-quality waste paper, but it is preferably blended in the white lower layer or the middle layer in the case of medium waste paper.

  In the white paperboard according to the present embodiment, the blending ratio of the used paper pulp of the front surface layer and the back surface layer is 20% by mass or less. More preferably, it is 10 mass% or less. More preferably, it is 0 mass%. If it exceeds 20% by mass, the fading property deteriorates.

Here, the blending ratio of the used paper pulp is calculated by Equation 1.
(Equation 1) Ratio of waste paper pulp (% by mass) = Amount of waste paper pulp / (Amount of virgin pulp + amount of waste paper pulp) × 100

  The mixing ratio of the used paper pulp in the layer excluding the intermediate layer, that is, the outermost layer (surface layer) on the front side of the base paper and the outermost layer (back side layer) on the back side is 90% by mass or more. More preferably, it is 95 mass% or more, More preferably, it is 100 mass%. If it is less than 90% by mass, the proportion of the used paper pulp in the entire base paper cannot be increased to 60% by mass or more unless the amount of the used paper mixed in the white layer is increased. In order to increase the waste paper content ratio of the entire white paperboard while maintaining the fading property, it is preferable to add a lot of waste paper to the intermediate layer and minimize the waste paper content to the front layer and the back layer. Moreover, it is preferable to mix | blend waste paper pulp with a whiteness higher than a middle layer in a white lower layer among intermediate | middle layers. In the present invention, the mixing ratio of the used paper pulp in the intermediate layer refers to the ratio of the used paper pulp to the total amount of the pulp in the intermediate layer. When the intermediate layer is formed as one layer, the ratio of the used paper pulp to the total amount of the pulp in the layer If the intermediate layer is formed of two or more layers, it means the ratio of waste paper pulp to the total amount of pulp in all intermediate layers.

  The mixing ratio of waste paper pulp in the entire base paper is 60% by mass or more. More preferably, it is 70 mass% or more.

  In the white paperboard according to this embodiment, a filler may be blended in the base paper. Examples of the filler used include light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, calcined clay, titanium dioxide, and aluminum hydroxide. Since the filler is excellent in whiteness and opacity, it is preferable to use it in the white layer when low whiteness DIP is used in the white lower layer or the middle layer.

  When the filler is blended in the white layer, it is blended so that at least the ash content of the surface layer is 7% by mass or less. The ash content of the surface layer is more preferably 5% by mass or less, and further preferably 3% by mass or less. If the ash content of the surface layer exceeds 7% by mass, the surface of the surface layer cannot withstand elongation when boxed with a ruled line, and the strength of the surface layer itself is insufficient, resulting in ruled line cracking. . Furthermore, it may cause paper peeling during printing. The surface layer may not be blended with filler, but by blending the filler so that the ash content of the surface layer is 1% by mass or more, effects such as improvement in whiteness and opacity can be obtained. Therefore, it is preferable to mix the filler in the surface layer so that the ash content of the surface layer is 1 to 7% by mass. The ash content of the surface layer is more preferably 2 to 5% by mass or more. The ash content of the back layer is not particularly limited, but is preferably 0 to 12% by mass in consideration of suitability for box making and the strength of the paper layer itself. More preferably, it is 1-9 mass%. Moreover, the ash content of the intermediate layer is not particularly limited, but is preferably 1 to 10% by mass, and more preferably 2 to 8% by mass. In the present specification, the ash content is measured according to JIS P 8251: 2003 “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method”.

  The ash content of the whole white paperboard becomes higher due to the influence of the remaining ash when DIP is blended in the base paper. The ash content of the whole white paperboard is preferably 3 to 25% by mass. More preferably, it is 5-21 mass%, More preferably, it is 9-17 mass%. To make it less than 3% by mass, it is necessary to eliminate the ash content in the DIP. If it exceeds 25% by mass, the pulp content may decrease and the weight may not be reduced. Also, the stiffness and ring crush may not be in the desired ranges. Here, the ash content of the entire white paperboard is the sum of the ash content of the base paper and the ash content of the coating layer.

  In the white paperboard according to this embodiment, in addition to pulp and filler, for example, sulfuric acid band, sizing agent, cationic starch, or polyacrylamide-based internal paper strength enhancer (hereinafter referred to as internal paper strength agent). Various auxiliary agents such as a yield improver, a freeness improver, a bulking agent, a coloring dye, a coloring pigment, a fluorescent brightening agent, a fluorescent decoloring agent or a pitch control agent, depending on each product. You may mix | blend.

  In the white paperboard according to the present embodiment, when an internal paper strength enhancer is used for the base paper, a polyacrylamide type (PAM type) paper strength agent is preferable, and an amphoteric or cationic polyacrylamide type paper strength agent is used. More preferred. By using a PAM-based paper strength agent, it is possible to further suppress ruled line cracking. The reason for this is not clear, but the PAM-based paper strength agent has higher charge density and higher hydrophobicity than the cationic starch conventionally used as an internal paper strength enhancer. It is presumed that it is difficult to move even during press pressurization and squeezing, and the strength within the layer is increased, but the interlayer strength is difficult to increase. The amphoteric or cationic polyacrylamide-based paper strength agent is preferably blended at 0.1 to 0.7% by weight, more preferably 0.2 to 0.6% by weight, based on the pulp of the layer to be blended. If it is less than 0.1% by mass with respect to the pulp of the layer containing the amphoteric or cationic polyacrylamide-based paper strength agent, printing trouble called bulge may occur when printing is actually performed. If it exceeds 0.7% by mass, the paper itself becomes hard and it is difficult to bend the paperboard, so it is necessary to make strong ruled lines, and as a result, cracking may easily occur.

  In the white paperboard according to this embodiment, a bulking agent may be used for the base paper. When using a bulking agent, it is preferable not to use for a surface layer and a back surface layer, but to make only an intermediate | middle layer. When used for the surface layer and the back layer, the strength of the layer is reduced, and there may be a problem that paper peeling or the like occurs during printing. When used in an intermediate layer, as a bulking agent, higher alcohol ethylene oxide adduct, higher alcohol propylene oxide adduct or higher alcohol ethylene oxide and propylene oxide adduct, polyhydric alcohol type nonionic surfactant, higher alcohol The ethylene oxide adduct of fatty acid, the ester compound of polyhydric alcohol and fatty acid, and the ethylene oxide adduct of ester compound of polyhydric alcohol and fatty acid are not used because they inhibit the size. In addition, as described above, in the case of multilayer papermaking, the bulking agent may move to another layer in the same manner as fine ink when pressure dewatering is performed by a press part after papermaking. The size property of the surface layer is also hindered, and as a result, water is easily absorbed, and there is a possibility that it may be hindered when used as a box that places importance on the protective function. When a bulking agent is used, the bulking agent is a component selected from fatty acid amides, hydroxyethyl derivatives of fatty acid amides or fatty acid polyamidoamines, polyalkyleneamine / fatty acid / epichlorohydrin resin polycondensates, and oxidized polyethylene wax. It is preferable.

  In the white paperboard according to the present embodiment, the method for producing the base paper is not particularly limited. For example, the white paperboard has three layers such as a long net multilayer paper machine, a circular net multilayer paper machine, and a long net circular net combination multilayer paper machine. It can be manufactured by various apparatuses which are paper machines capable of making the above-mentioned multilayer paper making.

  In the white paperboard according to the present embodiment, when the base paper is a multi-layered paper having five or more layers, a ratio obtained by dividing the sum of the basis weights of the surface layer and the white lower layer in contact with the surface layer by the sum of all layer basis weights, that is, The ratio of the total basis weight of the surface layer occupying the entire base paper and the white lower layer in contact with the surface layer is preferably 20 to 32%. More preferably, it is 22 to 30%. In the case of less than 20%, when a ruled line is put and then folded for box making, the stress cannot be withstood and cracking of the ruled line is likely to occur from the base paper. On the other hand, if it exceeds 32%, it becomes difficult to bend, and a large amount of energy is required for forcibly bending, and as a result, ruled line cracks may occur. In the case of multi-layer paper making of 5 or more base papers, it is preferable to appropriately manage not only the basis weight of the surface layer but also the basis weight of the white lower layer.

  In the white paperboard according to this embodiment, when the base paper is a multi-layered paper having five or more layers, the ash content of the white lower layer in contact with the surface layer is preferably 10% by mass or less, more preferably 8% by mass or less. When it exceeds 10% by mass, the paper layer strength becomes insufficient and the ruled line cracks are likely to occur. Generally, waste paper pulp or self-recovered waste paper is used for the white underlayer, and therefore it is preferable to have a process using a washing machine in the waste paper or waste paper processing step for ash removal. In the case of multi-layer paper making of five or more base papers, it is preferable to manage not only the surface layer but also the ash content of the white lower layer.

In the white paperboard according to this embodiment, starch for interlayer adhesion may be used in order to increase the interlayer strength of each layer of the base paper. However, when starch for interlayer adhesion is used, it is 0 for each interlayer of the middle layer. It is preferable to adhere starch in the range of 1 to 0.5 g / m ² . More preferably, it is 0.15-0.3 g / m < ² >. If it is less than 0.1 g / m ² , swelling may occur during printing, which may cause trouble. When it exceeds 0.5 g / m ² , when folded for box making, the middle layer is not easily peeled off, and it is difficult to swell to the folded valley side (inner side), and as a result, ruled line cracks are likely to occur. The starch for interlayer adhesion can be adhered by spraying, for example, on the surface of each intermediate layer. In addition, when performing size press treatment on the base paper, the water-soluble polymer added as a surface paper strength enhancer in the size press solution penetrates from the white layer to the white lower layer, thereby improving the interlayer strength, It is not necessary to use an interlayer adhesive between the white layer and the white lower layer. Rather, when a size press treatment is performed on the base paper, it is preferable not to use an interlayer adhesive in order to facilitate folding.

In the white paperboard according to this embodiment, the water-soluble polymer may not be applied to the base paper, or a water-soluble polymer may be applied. In the white paperboard according to this embodiment, the water-soluble polymer may be applied to the surface of the base paper with a coating machine such as a size press, but is preferably 0.5 g / m ² or less per side. The water-soluble polymer is applied as a surface paper strength enhancer. By applying a water-soluble polymer, the surface strength of the base paper can be improved, but at the same time, the surface of the base paper tends to be hard and the ruled line is liable to break. Therefore, it is preferable not to apply the water-soluble polymer to the surface of the base paper. Even if it is applied, cracking of the ruled line can be prevented by setting the amount to 0.01 to 0.5 g / m ² per side. . The amount of water-soluble polymer applied to the base paper is more preferably 0.05 to 0.3 g / m ² . Examples of the water-soluble polymer include starches, polyvinyl alcohol, and polyacrylamide. In the case of coating, a known coating machine such as a type provided with a pound such as a size press, a film metering type such as a gate roll size press or a shim sizer, a rod coater or an air knife coater can be used, but it is particularly limited. Is not to be done.

  In the white paperboard according to this embodiment, a coating layer mainly composed of a pigment and an adhesive is provided on the surface of the base paper or the surface of the base paper that has been subjected to surface sizing treatment as necessary. The coating layer may be provided only on the surface of the surface layer of the base paper, or may be provided on both the surface layer and the back surface layer. The pigment used in the coating layer is preferably a purified natural mineral pigment such as kaolin or heavy calcium carbonate (ground calcium carbonate), light calcium carbonate, or organic pigment. These may be used alone or in combination of two or more. Other materials are not particularly limited. For example, at least one of talc, satin white, lithopone, titanium dioxide, silica, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, and calcined kaolin is mixed. It doesn't matter. Further, when the coating layer is provided on both the surface layer and the back layer, the coating layer provided on the surface layer and the coating layer provided on the back layer have the same composition, or Different compositions may be used.

  Examples of the adhesive used for the coating layer include styrene-butadiene-based, acrylic-based, various copolymer latexes such as polyvinyl acetate or ethylene-vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide, urea, melamine / Examples thereof include water-soluble synthetic compounds such as formalin resin, polyethyleneimine or polyamide polyamine / epichlorohydrin. Furthermore, starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch or cold water soluble starch obtained by flash drying them, dextrin, mannan, chitosan, arabi It is a natural polysaccharide such as nogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose, hydroxyethylcellulose or the like, or an oligomer thereof or a modified product thereof. In addition, natural proteins such as casein, gelatin, soybean protein, and collagen, or modified products thereof, and synthetic polymers or oligomers such as polylactic acid and peptides. These may be used alone or in combination of two or more. In particular, a styrene-butadiene copolymer latex (SBR) that is excellent in improving the strength of the coating layer and is easy to extend from the viewpoint of composition is preferably used. The amount of the adhesive in the coating layer is preferably 11 to 25 parts by mass, more preferably 13 to 22 parts by mass, and still more preferably 15 to 20 parts by mass with respect to 100 parts by mass of the pigment. Further, when a starch-based adhesive is used, the coating layer tends to be easily broken. Therefore, it is preferable to minimize the use of the starch-based adhesive in the ink receiving layer that is the outermost layer. Specifically, the content of the starch-based adhesive in the ink receiving layer that is the outermost layer is preferably 1 part by mass or less and 100 parts by mass (not used) with respect to 100 parts by mass of the pigment. More preferred. When two or more ink receiving layers are provided, the content of the starch-based adhesive in the ink receiving layer other than the outermost layer is not particularly limited, but is preferably 5 parts by mass or less, and preferably 3 parts by mass or less. Is more preferable, and 0 part by mass (not used) is even more preferable. By setting it as this range, a ruled line crack can be suppressed more.

  In the white paperboard according to the present embodiment, the coating layer-forming coating material is usually used as necessary, such as a dispersant, an antifoaming agent, a water-resistant agent, a coloring dye, a coloring pigment, and a thickening agent. Various auxiliary agents, or those obtained by cationizing these various auxiliary agents may be used. The ratio of the pigment and the adhesive to the total mass of the coating layer is preferably 98% by mass or more, and more preferably 99% by mass or more.

  In the white paperboard according to the present embodiment, the method for coating the coating layer forming coating is not particularly limited, and various films such as a size press having a puddle, a metering size press, a gate roll, or a shim sizer. A transfer coater, an air knife coater, a rod coater, a blade coater, a direct fountain coater, a spray coater, a curtain coater, and the like are appropriately used.

In the white paperboard according to this embodiment, the coating amount of the coating layer is preferably 7 to 30 g / m ² in terms of solid content per one side of the base paper. More preferably 12~26g / ^{m 2.} Moreover, when the desired coating amount is not reached by one coating, the coating may be repeated twice or more. When the coating amount is less than 7 g / m ² , the printing finish is inferior and the desired print glossiness may not be achieved. If it exceeds 30 g / m ² , the strength of the coating layer is lowered and cracking of the ruled line is likely to occur, and paper dust or powder falling may occur during punching or box making, which may be a serious obstacle. The coating layer may be formed of one layer or two or more layers. In the case of forming two or more layers, an undercoat layer provided on the surface of the base paper or the surface of the base paper subjected to surface sizing treatment as necessary, and one or more overcoat layers provided on the surface of the undercoat layer are provided. The undercoat layer and the overcoat layer may have the same composition or different compositions. When the number of coating layers is two or more, it is preferably formed so that the total coating amount of all the coating layers is within the above-described range.

The basis weight of the white paperboard is preferably 150 g / m ² or more, and more preferably 200 g / m ² or more. If it is less than 150 g / m ² , the strength of the box may be insufficient. The upper limit of the basis weight of the white paperboard is preferably 900 g / m ² , and more preferably 600 g / m ² . If the basis weight of the white paper board exceeds 900 g / m ² , when it is processed into a box, it may be cracked when bent so that the ruled line is difficult to enter, and may not be used. Here, the basis weight of white paperboard is the sum of the mass per 1 m ² of the mass and the coating layer per 1 m ² of the base paper. Further, the basis weight of the base paper is preferably 130 g / m ² or more, and more preferably 180 g / m ² or more. If it is less than 130 g / m ² , the strength may be insufficient to exhibit the function as a box. Moreover, when it is set as a multilayer papermaking, the basic weight per layer is too low, and it becomes difficult to produce substantially. The basis weight of base paper is preferably at 870 g / ^{m 2} or less, more preferably 570 g / ^{m 2} or less. Further, when the base paper is made into a single layer paper at 130 g / m ² or more, the rigidity or strength is low, and the function as a substantial box is hardly achieved.

  The white paperboard according to this embodiment may be cast according to a desired quality requirement.

The white paperboard according to the present embodiment has a density of 0.77 to 0.87 g / cm ³ . More preferably, it is 0.80-0.85 g / cm < ³ >. If it is less than 0.77 g / cm ³ , the box-making process including the ease of putting a ruled line in the case of a box is easy to perform, but the strength of the paper layer becomes weak and peeling within the paper layer called swelling occurs during printing. When it exceeds 0.87 g / cm ³ , when a box is formed, ruled lines are difficult to enter, and cushioning properties are insufficient.

In the white paperboard according to the present embodiment, the Z-axis strength is 300 to 470 kN / m ² , preferably 300 to 390 kN / m ² . If it is less than 300 kN / m ² , the paper layer strength is insufficient, and paper peeling or blistering occurs during printing. If it exceeds 470 kN / m ² , it is difficult for ruled lines to enter, and ruled cracks are likely to occur during box making. The release layer at the time of measuring the Z-axis strength is preferably an intermediate layer, and the effect of the present invention is hardly exhibited when the release layer is not peeled off or when it is peeled between a white layer and an intermediate layer (including a white lower layer). It is important that when the sheet is folded for box making after the ruled line is formed, the middle layer peels off and easily swells to the folded valley side. The method for controlling the Z-axis strength is not particularly limited. For example, the above-described adjustment of the starch application amount for interlayer adhesion, the addition amount of the internal paper strength agent, or the adjustment of the total linear pressure of the press part. It can be controlled by.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified. The number of added parts is a value in terms of solid content.

  The following evaluation was performed about the white paperboard of the Example or the comparative example. The evaluation results are shown in Table 1. The evaluation method is as follows.

<Density>
Measured according to JIS P 8118: 1998 “Paper and paperboard—Test methods for thickness and density”.

<Ash content>
Measured according to JIS P 8251: 2003 “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method”.

<Z-axis strength>
JAPAN TAPPI Paper Pulp Test Method No 18-1: 2000 “Paper and paperboard—Internal bond strength test method—Part 1: Z-axis direction tensile test method”

<Rule cracking test>
1. The paper sample is cut to 5 cm × 10 cm, and then folded in half so that the surface layer is 5 cm × 5 cm, and the paper layer is sandwiched between round papermaking plates.
2. A crease was made with a round hand pressing press at a gauge pressure of 2 kgf / cm ² and a holding time of 30 seconds, and the folded outer portion was observed with a microscope and evaluated. The machine flow direction (MD direction) and the cross direction (CD direction) were both evaluated. The number of paper samples was three in each direction. Moreover, the image observed by the microscope in each evaluation criteria is shown in FIGS.
A: No cracks on the ruled line were observed on the ink receiving layer and the base paper.
◯: Some ruled line cracks are seen in the ink receiving layer, but it is good (practical level).
Δ: Cracking of ruled lines is observed in the entire ink receiving layer, but the usable level (practical lower limit).
X: The ruled line crack of the base paper is seen, and it cannot be used (practical).

<Press life>
Using Lilithon 40 (L-40) (manufactured by Komori Co., Ltd.) as an offset printing machine, printing four colors with black, indigo, red and yellow ink at a printing speed of 8500 sheets / hour, printing durability The power was evaluated.
(Double-circle): There is almost no dirt of a blanket and it is good (practical level).
○: There is some dirt on the blanket, but there is almost no omission in the image area, which is good (practical level).
(Triangle | delta): There are many stain | pollution | contaminations of a blanket, and there exists omission of an image line part (practical use lower limit level).
X: The blanket is severely soiled and the image area is often missing (impractical level).

<Color fading>
The white paperboard was processed with a hot air dryer at 105 ° C. for 1 hour, and the degree of fading was evaluated visually. The evaluation of the fading property was described according to the following procedure.
A: Almost no yellowing (practical level).
○: Slightly yellow (practical level).
Δ: Yellowish slightly (practical lower limit level).
X: Yellowing is remarkable (not suitable for practical use).

Example 1
<Preparation of base paper>
As a pulp used for the surface layer and the back layer, a pulp prepared in a CSF of 300 ml consisting of 90% of all hardwood pulp (L-BKP) and 10% of softwood pulp (N-BKP) is used. CSF 300ml newspaper deinked old waste paper is used as unbattered as the intermediate layer (contacting the back layer and the back layer), and the middle layer (intermediate layer not touching the surface layer or the back layer) is provided with two layers. The waste paper pulp treated with the deinked newspaper raw material was used as it was unbeaten, and a base paper having a total basis weight of 380 g / m ^{2 was made at} a paper making speed of 200 m / min with a short net combination type paper machine. The basis weight of the surface layer is 40 g / m ² , the basis weight of the white lower layer (intermediate layer) in contact with the surface layer is 60 g / m ² , and the basis weight of the middle layer (intermediate layer) is 95 g / m ² , respectively. The basis weight of the white lower layer (intermediate layer) in contact with was 60 g / m ² , and the basis weight of the back layer was 30 g / m ² . Light calcium carbonate (manufactured by Okutama Kogyo Co., Ltd., TP121S) is added to the surface layer and the back layer so that the ash content is 3 parts, and polyacrylamide (Arakawa Chemical Industries, Ltd.) is used as an internal paper strength enhancer in all six layers. Company Polystron 619) 0.4% of the pulp amount in each layer, and sulfuric acid band as a coagulant aid 0.5% to the pulp amount of the front layer and back layer, each white lower layer and middle layer pulp Rosin emulsion sizing agent (neutral size 738 manufactured by Harima Kasei Co., Ltd.) for neutrality as a sizing agent is 0.3% with respect to the pulp amount of the surface layer and the back layer (for the white lower layer and the middle layer) Is not used), and a yield improver (HH220 manufactured by Kurita Kogyo Co., Ltd.) was added to all 6 layers at 300 ppm based on the amount of pulp in each layer. The ratio of the used paper pulp in the front layer and the back layer was 0%, and the ratio of the used paper pulp processed from the newspaper in the middle layer was 100%. The four layers from the white lower layer on the surface layer side to the white lower layer on the back layer side have 0.1 g / m ² of esterified tapioca starch (MS # 5300, manufactured by Nippon Shokuhin Kako Co., Ltd.) as an interlayer adhesive between the respective layers. Sprayed and laminated.

<Press part / Dryer part>
The rolls and smoother presses of Nos. 1 to 3 were pressed and squeezed with a total linear pressure of 400 kg / cm and dried with a dryer.

<Size press processing>
A 2% concentration solution of oxidized starch (MS3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was applied to both sides of the base paper with a pound size press at a solid content of 0.3 g / m ² on one side and dried.

<Formation of coating layer on surface layer>
On the surface layer of the base paper, as an undercoat paint, 20 parts of kaolin (Hydra Sparse made by Keimin Co., Ltd.) and 80 parts of wet heavy calcium carbonate (Carbital 60 produced by Imeris Mineramez Japan Co., Ltd.), as an adhesive Using a paint consisting of 12 parts of SBR (styrene-butadiene rubber) latex (B-1541 manufactured by Asahi Kasei Chemical Co., Ltd.) and 3 parts of urea phosphate esterified starch, this paint for the undercoat layer is solidified with a rod coater. An undercoat layer was provided by coating and drying so as to be 10 g / m ² . Next, 30 parts of kaolin (Amazon SB manufactured by Kadam), 60 parts of wet heavy calcium carbonate (Carbital 90 manufactured by Imeris Mineramez Japan Co., Ltd.) and titanium oxide (RPS-Vantage manufactured by DuPont) are used as the paint for the topcoat layer. Using a coating composition consisting of 10 parts and 13 parts of SBR latex (B-1541 manufactured by Asahi Kasei Chemical Co., Ltd.) as an adhesive, this top coat coating was applied to a solid content of 10 g / m ² with a rod coater. And dried to form an overcoat layer.

<Formation of coating layer on back layer>
On the back layer of the base paper, the coating material for the top coat layer was applied with a rod coater so as to have a solid content of 10 g / m ² and dried to form a coating layer.

<Smoothing processing>
A calendar treatment was performed at a linear pressure of 50 kg / cm, and then the surface was treated with a raster press at 80 kg / cm and 140 ° C. to obtain a white paperboard.

(Example 2)
The same as Example 1 except that the freeness of the pulp of the surface layer was changed from 300 ml of CSF to 200 ml.

(Example 3)
The same as Example 1 except that the freeness of the pulp of the surface layer was changed from 300 ml of CSF to 400 ml.

Example 4
The same procedure as in Example 1 was conducted except that the addition rate of light calcium carbonate was adjusted so that the ash content of the surface layer was 3% to 7%.

(Example 5)
The procedure of Example 1 was repeated except that the internal paper strength enhancer added to the intermediate layer was changed from 0.4% to 0.2%.

(Example 6)
The same procedure as in Example 1 was conducted except that the internal paper strength enhancer added to the intermediate layer was changed from 0.4% to 0.6%.

(Example 7)
The same as Example 1 except that the total linear pressure of the press part was changed from 400 kg / cm to 250 kg / cm.

(Example 8)
The same as Example 1 except that the total linear pressure of the press part was changed from 400 kg / cm to 500 kg / cm.

Example 9
The same procedure as in Example 1 was performed except that the size press treatment was not performed.

(Example 10)
Example except that the layer adhesive was sprayed to 0.1 g / m ² between the surface layer and the white lower layer in contact with the surface layer and between the back layer and the white lower layer in contact with the back layer without performing size press treatment. Same as 1.

(Example 11)
The same procedure as in Example 1 was conducted except that the waste paper pulp used for the middle layer was changed from a newspaper raw material to a magazine raw material.

(Example 12)
The same procedure as in Example 1 was conducted except that the waste paper pulp used for the middle layer was changed from 100% by mass of newspaper raw material to 50% by mass of newspaper raw material and 50% by mass of magazine raw material.

(Example 13)
The same procedure as in Example 1 was repeated except that the waste paper pulp used for the middle layer was beaten to make the CSF 300 ml to 200 ml.

(Example 14)
The pulp used for the front layer and the back layer was the same as Example 1 except that the hardwood pulp was changed to 70%, softwood pulp 10%, and unbeaten newspaper-deinked bleached old paper 20%.

(Example 15)
The same procedure as in Example 1 was conducted, except that the amount of urea phosphate esterified starch added to the paint for the undercoat layer was changed from 3 parts to 0 parts and the SBR latex was changed from 12 parts to 15 parts.

(Comparative Example 1)
The same as Example 1 except that the freeness of the pulp of the surface layer was changed from 300 ml of CSF to 190 ml.

(Comparative Example 2)
The same as Example 1 except that the freeness of the pulp of the surface layer was changed from CSF 300 ml to 410 ml.

(Comparative Example 3)
The same procedure as in Example 1 was conducted, except that the addition rate of light calcium carbonate was adjusted so that the ash content of the surface layer was 3% to 8%.

(Comparative Example 4)
The same procedure as in Example 1 was conducted except that the internal paper strength enhancer added to the intermediate layer was changed from 0.4% to 0.1%.

(Comparative Example 5)
The same procedure as in Example 1 was conducted, except that the internal paper strength enhancer added to the intermediate layer was changed from 0.4% to 0.8%.

(Comparative Example 6)
The same as Example 1 except that the total linear pressure of the press part was changed from 500 kg / cm to 300 kg / cm.

(Comparative Example 7)
The same as Example 1 except that the total linear pressure of the press part was changed from 500 kg / cm to 650 kg / cm.

(Comparative Example 8)
The same procedure as in Example 1 was repeated except that the waste paper pulp used for the middle layer was beaten to make the CSF 300 ml to 180 ml.

(Comparative Example 9)
The finished raw materials of the surface layer raw material, white lower layer raw material, and middle layer raw material in Example 1 were mixed in a ratio of surface layer raw material: white lower layer raw material: middle layer raw material = 30: 60: 100, and long. The procedure was the same as Example 1 except that a base paper having a mesh size of 380 g / m ² was used.

  As is clear from Table 1, all of the white paperboards of Examples 1 to 14 were excellent in printing durability, had a sufficient ruled line cracking prevention effect, and were excellent in fading. In Comparative Example 1, since the freeness of the pulp used for the surface layer was low, the printing strength was increased due to the entanglement of the pulp, but the surface was hard, so that it did not stretch when bent, and a ruled line crack occurred from the base paper layer. In Comparative Example 2, since the freeness of the pulp used for the surface layer was high, the desired printing durability could not be maintained. In Comparative Example 3, since the ash content of the surface layer was large, the strength of the layer was low and could not withstand printing durability and ruled line cracking. In Comparative Example 4, the Z-axis strength was low and the desired range was not achieved, so that the printing durability was lowered and could not be used. In Comparative Example 5, the Z-axis strength was not high and was not in the desired range, and when the ruled line was inserted and bent, the intermediate layer was strong and did not peel off, resulting in a ruled crack and a problem. In Comparative Example 6, the Z-axis strength was not high and did not fall within the desired range, and when the ruled line was inserted and bent, the intermediate layer was strong and did not peel off, resulting in a problem of ruled line cracking. Further, since the desired density was not achieved, the cushioning property was insufficient and the ruled line was poorly formed, resulting in crease cracks. In Comparative Example 7, the Z-axis strength was low and the desired range was not achieved, so that the printing durability was lowered and could not be used. In Comparative Example 8, the Z-axis strength was not high and did not fall within the desired range, and when the ruled line was inserted and bent, the intermediate layer was strong and thus did not peel off, resulting in a problem of ruled line cracking. Further, since the desired density was not achieved, the cushioning property was insufficient and the ruled line was poorly formed, resulting in crease cracks. In Comparative Example 9, since single layer papermaking was used, waste paper pulp was highly blended on the surface, and as a result, fading was greatly deteriorated. Further, unbeaten waste paper pulp was highly blended on the surface, and the printing durability deteriorated.

  In Example 3, Examples 5, 7, 9, 10 and Comparative Examples 4 and 7, no ruled crack was observed as shown in FIG. As shown in FIG. 2, Examples 1 and 11 and 14 had a good appearance although some ruled cracks were observed in the ink receiving layer. In Example 2, Examples 4, 6, 8, 12, and 13 and Comparative Examples 2 and 9, as shown in FIG. 3, cracks were observed over the entire ink receiving layer, but they had a good appearance. . In Comparative Example 1, Comparative Examples 3, 5, 6, and 8, as shown in FIG. 4, ruled cracks were observed in the base paper, and the appearance was poor.

Claims (4)

In the white paperboard in which a coating layer mainly composed of a pigment and an adhesive is provided on at least one surface of a base paper which is a multilayer papermaking of three or more layers, in which the proportion of waste paper pulp is 60% by mass or more,
Of the layers of the base paper, a layer disposed on one surface is represented as a surface layer, a layer disposed on the other surface is represented as a back surface layer, and a layer disposed between the surface layer and the back surface layer is represented as an intermediate layer. When
(1) The ratio of the waste paper pulp of the surface layer and the back layer is 20% by mass or less,
(2) The mixing ratio of the waste paper pulp of the intermediate layer is 90% by mass or more,
(3) The freeness of the pulp used for the surface layer is CSF 200 to 400 ml,
(4) The ash content of the surface layer is 7% by mass or less,
(5) Z-axis intensity of the white paperboard is 300~470kN / ^{m 2,}
(6) The white paperboard, wherein the density of the white paperboard is 0.77 to 0.87 g / cm ³ . ^2. The white paperboard according to claim 1, wherein a water-soluble polymer is not applied to the base paper, or a coating amount of the water-soluble polymer is 0.5 g / m ² or less per one side of the base paper. .   The raw material of the used paper pulp used for the intermediate layer is newspaper used paper, and the blending ratio of the used paper pulp is 50 to 100% by mass of the used paper pulp used for the intermediate layer. White paperboard. It is a manufacturing method of the white paperboard of Claims 1-3,
The waste paper pulp used for the intermediate layer is not beaten, or the waste paper pulp used for the intermediate layer is beaten, and the freeness difference value based on the freeness of the unbeaten waste paper pulp is within 100 ml, To manufacture white paperboard.