Coated white paperboard

Abstract

To provide a white coated paperboard with low density and excellent gravure printability.SOLUTION: In a white coated paperboard involving white coated paperboard base paper having at least three layers consisting of a surface layer, a surface lower layer, and a back layer, and a pigment coating layer coated on the surface layer, the surface layer does not include a size agent and the surface lower layer includes a size agent.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a coated white paperboard, and more particularly to a coated white paperboard having low density and excellent suitability for gravure printing. [Background technology]

[0002] Known types of white paperboard include high-grade white paperboard, which uses bleached chemical pulp on both sides and has a pigment coating layer on both sides, special white paperboard, which uses bleached chemical pulp or high-quality recycled paper pulp on both sides and is white on both sides, with a pigment coating layer on one side to improve printing effects, and coated white board. Coated white board, which is a type of coated white paperboard, is widely used as boxes for packaging goods, such as detergent boxes, tissue paper boxes, photographic film boxes, confectionery boxes, and over-the-counter medicine boxes. It is also used for purposes other than packaging, such as book covers and picture books.

[0003] Coated whiteboard generally consists of at least three layers, a top layer, a bottom layer, and a bottom layer, or at least four layers, a top layer, a bottom layer, a middle layer, and a bottom layer, and uses a large amount of recycled paper. The top layer, which requires high whiteness, is provided with a pigment coating, the bottom layer is made of paper that is mainly made of recycled paper pulp with a relatively high whiteness, and the middle and bottom layers are made mainly of recycled paper pulp with a relatively low whiteness. These whiteboards are mainly printed on the surface, and are often used after being processed for packaging. In recent years, even low-grade coated whiteboards are used for elaborate printing such as gravure printing, so gravure printability is also required.

[0004] As an example of balls having improved suitability for gravure printing, a coated white ball having improved smoothness by supercalendering is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-61690 Summary of the Invention [Problem to be solved by the invention]

[0006] However, it is difficult to obtain sufficient suitability for gravure printing with the configuration of Patent Document 1. In gravure printing, the amount of ink transferred is adjusted by the depth and shape of the intaglio part of the gravure roll that measures the ink, but this requires both smoothness and cushioning of the paper, and there is a problem that the density becomes too high and cushioning is lost in the case of the coated white ball described in Patent Document 1, in which only the smoothness is improved by super calendaring.

[0007] The present invention has been made to solve these problems, and an object of the present invention is to provide a coated white paperboard which has a low density and is excellent in suitability for gravure printing.

[0008] Other objects and advantages of the present invention will become readily apparent to those skilled in the art by reading the following description. [Means for solving the problem]

[0009] As a result of extensive research into coated white paperboard, the inventors of the present application have found that the object can be achieved by the following configuration. That is, the coated white paperboard of the present invention is a coated white paperboard having a base paper for coated white paperboard having at least three layers, a surface layer, a subsurface layer, and a back layer, and a pigment coating layer applied to the surface layer, characterized in that the surface layer does not contain a sizing agent, and the subsurface layer does contain a sizing agent. With this configuration, a coated white paperboard can be obtained in which the surface layer does not contain a sizing agent and therefore has excellent ink absorbency, and the subsurface layer has sizing properties and cushioning properties and therefore has excellent suitability for gravure printing.

[0010] In a preferred embodiment of the present invention, the sizing agent is preferably a fatty acid-based sizing agent. By using such a composition, it is possible to obtain a desired pigment paint absorption property even if the raw material is waste paper pulp.

[0011] In a preferred embodiment of the present invention, the amount of the sizing agent is preferably 0.1 to 0.8% by mass relative to 100% by mass of pulp. With this configuration, the sizing property is appropriate, and therefore a coated white paperboard having excellent suitability for gravure printing can be obtained.

[0012] In a preferred embodiment of the present invention, the pigment coating layer is two or more layers, and the thickness of the bottommost coating layer in contact with the surface layer is preferably 2 μm or more. When two or more pigment coating layers are provided, the topmost coating layer that forms the outer surface is called the topmost coating layer, and the bottommost coating layer in contact with the surface layer is called the bottommost coating layer. With this configuration, a suitable anchor effect is obtained by covering the coated white paperboard base paper with the bottom coating layer, and the gravure suitability of the topmost coating layer surface is favorable.

[0013] In a preferred embodiment of the present invention, the PPS measurement value of the surface of the pigment coating layer is preferably 1.5 μm or less. With such a configuration, the surface of the pigment coating layer has high smoothness, and thus a coated white paperboard having better suitability for gravure printing can be obtained.

[0014] In a preferred embodiment of the present invention, the surface layer pulp, which is the raw material for the surface layer, preferably has a CSF of 200 to 500 ml. With this configuration, a coated white paperboard having excellent paper strength and runnability can be obtained.

[0015] In a preferred embodiment of the present invention, the density of the coated white paperboard is 0.77 to 0.87 g / cm 3 According to this configuration, a coated white paperboard having better suitability for gravure printing can be obtained.

[0016] The present invention can also be understood as an invention relating to a base paper for coated white paperboard.

[0017] The coated white paperboard base paper of the present invention has at least three layers, a surface layer, a subsurface layer, and a back layer, and is characterized in that the surface layer does not contain a sizing agent and the subsurface layer contains a sizing agent. With this configuration, a coated white paperboard base paper with excellent coating suitability for the pigment coating layer can be obtained. Effect of the Invention

[0018] According to the present invention, it is possible to provide a coated white paperboard which has a low density and is excellent in suitability for gravure printing. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of an example of the configuration of a coated white paperboard. [Diagram 2] 1 is a table showing the physical properties of coated white paperboard obtained in the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Next, the present invention will be described in detail with reference to the embodiments, but the present invention is not limited to these descriptions. Various modifications of the embodiments may be made as long as the effects of the present invention are achieved.

[0021] The coated white paperboard according to the present embodiment comprises a coated white paperboard base paper having at least three layers, a surface layer, a lower surface layer, and a back layer, and a pigment coating layer applied to the surface layer. An example of the structure of the coated white paperboard according to the present invention is shown in Figure 1. In the figure, 1 is a coated white paperboard, 10 is a coated white paperboard base paper (hereinafter sometimes referred to as a base paper), 11 is a surface layer, 12 is a lower surface layer, 13 is a back layer, 13a is an upper back layer, 13b is a lowermost back layer, 14 is a pigment coating layer, 14a is a topmost coating layer, and 14b is a bottommost coating layer. Also, the thickness of each layer in Figure 1 is not proportional to the actual thickness.

[0022] Fig. 1(a) shows an example of a structure in which one pigment coating layer 14 is provided on a four-layer coated white board base paper 10 having a one-layer surface layer 11, a one-layer undersurface layer 12, and a two-layer back layer 13. Fig. 1(b) shows an example of a structure in which two pigment coating layers 14 are provided on a five-layer coated white board base paper 10 having a one-layer surface layer 11, a one-layer undersurface layer 12, and a three-layer back layer 13. In the example of Fig. 1(a), the back layer 13 is composed of two layers of the same structure, while in the example of Fig. 1(b), the bottom layer 13b on the back side of the back layer 13 is structured separately from the top layer 13a on the inside.

[0023] In the present invention, the surface layer preferably has a coating suitability for a pigment coating layer, a certain degree of whiteness and opacity, and does not contain impurities. The pulp used for the surface layer is preferably a pulp with a relatively high whiteness, and examples of such pulp include high-quality waste paper such as white paper, ruled white paper, card, imitation paper, colored paper, Kent, white art, and milk carton, or fresh pulp. When high-quality waste paper is used, it is preferable to perform kneading to reduce ink and impurities, deinking with a floater, and bleaching and washing with hydrogen peroxide and FAS in order to remove impurities and ensure whiteness. In addition, when opacity is insufficient, it is preferable to appropriately supplement it with a filler.

[0024] The disintegration freeness of the surface layer pulp is preferably in the range of CSF 200 to 500 ml, and more preferably 250 to 400 ml. If the CSF is less than 200 ml, not only will the density increase, but the drainage in the wire part will deteriorate, and the wet sheet may collapse during pressurized water squeezing in the press part of the next process, making production impossible. On the other hand, if the CSF exceeds 500 ml, the interfiber bond will be weak, and the paper strength will decrease, so that it may not be able to withstand printing. In addition, when making a box, there is a risk that the crease cracks will easily occur due to the weak strength of the surface layer against bending. In the present invention, the disintegrated freeness of the pulp of each layer is determined by separating the base paper into each layer, adjusting the solid concentration to 1% by mass using a Tappi disintegrator (based on JIS P 8220:1998 "Pulp disintegration method"), disintegrating the slurry for 25 minutes, and measuring the slurry using a Canadian Standard Type Freeness Tester (based on JIS P 8121:1995 "Testing method for freeness of pulp").

[0025] In the present invention, the surface layer preferably has sizing properties and a certain degree of whiteness, and does not contain impurities. The whiteness of the surface layer is preferably intermediate between the surface layer and the back layer, and if the whiteness of the surface layer is too low, color unevenness may be visually observed through the coating layer and the surface layer. As an example, the whiteness of each layer is preferably about 70 to 80% for the surface layer, 50 to 60% for the surface layer, and about 45% for the back layer.

[0026] The underside layer is a layer mainly made of recycled paper pulp, but considering the influence of the whiteness on the surface of the coated white paperboard, it is preferable to use recycled paper pulp with a relatively high whiteness. By adopting such a configuration, uneven whiteness on the surface of the coated white paperboard due to show-through can be prevented. In the coated white paperboard according to this embodiment, the raw material of the recycled paper pulp used for the underside layer is not particularly limited, but examples thereof include high-quality recycled paper such as white paper, ruled white paper, card, imitation, colored paper, Kent, white art, and milk carton, and medium-quality recycled paper such as newspapers, magazines, cut paper, medium-quality waste paper, brown imitation, cardboard, mount paper, ground paper, and cardboard. If necessary, it is preferable to perform bleaching with hydrogen peroxide or the like, deinking with a floatator, and fine reduction of ink and impurities by kneading.

[0027] In the coated white paperboard according to the present embodiment, a sizing agent is not blended in the surface layer, but is blended in the undersurface layer. In order to improve suitability for gravure printing, cushioning and surface smoothness are necessary, and the sizing agent contributes to cushioning. When providing a pigment coating layer on the surface of the base paper, it is necessary to blend a sizing agent in the base paper to prevent excessive penetration of the coating liquid into the base paper. The layer containing the sizing agent has an inhibitory effect on interfiber bonding, and becomes a bulkier layer than a layer without the sizing agent. The layer containing the sizing agent becomes a bulkier layer, which improves the cushioning of the entire coated white paperboard, and is expected to improve suitability for gravure printing. However, blending a sizing agent in the surface layer to increase the bulk impairs the smoothness of the surface layer, and as a result, the suitability for gravure printing is impaired. Another problem is that if a sizing agent is included in the surface layer, the coating liquid becomes less likely to penetrate into the surface layer when the pigment coating layer is provided, and the adhesive components in the pigment coating layer are distributed in large amounts on the surface of the pigment coating layer. This reduces the ink setting property, and as a result, the suitability for gravure printing is impaired.

[0028] Therefore, in the present invention, a sizing agent is not blended in the surface layer, but in the undersurface layer. By adopting such a configuration, it is possible to increase the cushioning of the entire coated white ball without impairing the smoothness and ink setting of the surface layer, and improve the suitability for gravure printing. Examples of the sizing agent used here include fatty acid-based sizing agents, alkyl ketene dimers (AKD), alkenyl succinic anhydrides (ASA), reinforced rosin sizing agents, rosin emulsion sizing agents, etc., and among these, fatty acid-based sizing agents that exhibit a sizing effect on a papermaking machine and are not easily affected by the papermaking pH are particularly preferred.

[0029] The content of the sizing agent in the undersurface layer is preferably in the range of 0.1 to 0.8% by mass relative to the pulp, and more preferably in the range of 0.2 to 0.6% by mass. If the content is less than 0.1% by mass, the water-soluble components of the coating liquid for the pigment coating layer will penetrate too much into the base paper, resulting in the pigment coating layer being more likely to fall off from the surface. Conversely, if the content exceeds 0.8% by mass, the high sizing ability of the undersurface layer may cause too much of the water-soluble components of the coating liquid for the pigment coating layer to remain on the surface of the base paper, resulting in reduced ink absorption and reduced suitability for gravure printing.

[0030] In the present invention, the back layer does not need to have whiteness, but the purpose is to reduce the amount of impurities in the layer that contacts the surface of the coated white paperboard, and to cover the basis weight when a certain basis weight is required for the entire coated white paperboard. In the coated white paperboard according to this embodiment, for example, when it is made into a coated white board, it is preferable to use recycled paper pulp for the back layer. There is no limit to the recycled paper pulp used, but in order to prevent the inclusion of sticky foreign matter, it is preferable to perform a dust removal process, and further a kneading process. The most preferable order is to perform the kneading process after the dust removal process. This is because when the coated white paperboard is made into a rolled product or a flat product, the surface and back of the coated white paperboard are in contact with each other, so if sticky foreign matter is mixed into the back layer, the surface may be contaminated by the transfer of the sticky foreign matter, which may cause problems. In addition, when a pigment coating layer is not provided on the back side, it is preferable not to increase the whiteness too much in order to make the impurities less noticeable, and it is also preferable not to perform a process to increase the whiteness, such as deinking or bleaching.

[0031] In the present invention, the back layer may be two or more layers depending on the required basis weight. When the back layer is two or more layers, it may be configured to have two or more layers of the same composition, or to have two or more layers of different raw material compositions. When multiple back layers with different raw material compositions are provided, it is preferable to mainly use medium-quality waste paper for the upper back layer (see FIG. 1(b) 13a) that is not exposed to the back side even though it is a back layer, and not to perform kneading treatment, deinking treatment, bleaching treatment, etc. for finely pulping impurities. By eliminating unnecessary treatment, it is possible to avoid using unnecessary energy and to suppress the release of alkali elution and ash from waste paper pulp into the environment, which is preferable from the environmental and cost perspectives. The bottom layer of the back layer (see FIG. 1(b) 13b) exposed to the back side among the back layers may be configured in the same way as when the back layer is provided as a single layer.

[0032] In addition to the above, the pulp used for each layer may be fresh pulp such as bleached hardwood sulfite pulp (LBSP), bleached hardwood kraft pulp (LBKP), bleached softwood sulfite pulp (NBSP), bleached softwood kraft pulp (NBKP), mechanical pulp (GP, TMP, BCTMP), etc., which may be used appropriately depending on the purpose. Note that "fresh pulp" here does not mean recycled waste paper, but is pulp produced directly from wood or non-wood, and is also called virgin pulp.

[0033] In the coated white paperboard according to this embodiment, a filler may be blended in each layer. Examples of fillers that can be used include light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, calcined clay, titanium dioxide, and aluminum hydroxide. Among the fillers, light calcium carbonate and heavy calcium carbonate are excellent in improving whiteness and opacity, so when a low-whiteness DIP (De-Inked Pulp) is used in the back layer, it is preferable to blend these fillers in the surface layer to improve the whiteness and opacity of the surface layer.

[0034] In the coated white paperboard according to this embodiment, in addition to the pulp, filler and sizing agent, various auxiliary agents such as aluminum sulfate, cationic starch or polyacrylamide-based internal paper strength enhancers, retention aids, drainage aids, bulking agents, colored dyes, colored pigments, fluorescent brightening agents, fluorescent decolorizing agents or pitch control agents may be blended in each layer to the extent that the intended effect of the present invention is not impaired.

[0035] In the coated white paperboard according to this embodiment, various papermaking auxiliaries can be applied to the surface of the front layer and / or back layer to the extent that the intended effect of the present invention is not impaired. For example, starches, paper strength agents such as polyvinyl alcohol and polyacrylamide, various dyes, and fluorescent dyes can be used. There are no particular limitations on the application method, and known application machines such as a type equipped with a pond 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.

[0036] The basis weight of each layer is not particularly limited, but the surface layer is 15 to 80 g / m 2 , more preferably 30 to 60 g / m 2 , the surface layer is 15~80g / m 2 , more preferably 20 to 60 g / m 2 If the basis weight of the surface layer is too large or the basis weight of the undersurface layer is too small, the effect of the present invention, which is achieved by not including a sizing agent in the surface layer but including a sizing agent in the undersurface layer, may be diminished. The basis weight of the back layer is not particularly limited, and may be, for example, 10 to 500 g / m 2 The backing layer may be made up of multiple layers.

[0037] In the coated white paperboard according to this embodiment, a pigment coating layer containing a pigment and an adhesive is provided on the surface of the surface layer. Two or more pigment coating layers may be provided as necessary. When two or more pigment coating layers are provided, the uppermost coating layer that becomes the outer surface is referred to as the uppermost coating layer, and the lowermost coating layer that contacts the surface layer is referred to as the lowermost coating layer. The pigments used in the pigment coating layer are preferably kaolin, refined natural mineral pigments such as heavy calcium carbonate (ground calcium carbonate), light calcium carbonate, and organic pigments. These may be used alone or in combination of two or more. The other pigments are not particularly limited, and for example, at least one of talc, satin white, lithopone, titanium dioxide, silica, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, and calcined kaolin can be used.

[0038] In the coated white paperboard according to the present embodiment, examples of adhesives used in the pigment coating layer include various copolymer latexes such as styrene-butadiene, acrylic, polyvinyl acetate, or ethylene-vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide, urea or melamine / formalin resin, polyethyleneimine, or polyamidepolyamine / epichlorohydrin, etc. Furthermore, examples include 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 thereof, natural polysaccharides such as dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose, and hydroxyethylcellulose, or oligomers or modified forms thereof. Other examples include natural proteins such as casein, gelatin, soybean protein, and collagen, or modified forms thereof, and synthetic polymers or oligomers such as polylactic acid and peptides. These may be used alone or in combination of two or more kinds.

[0039] When two or more pigment coating layers are provided, the topmost coating layer, which is the outer surface, needs to be strong, and it is preferable to use styrene-butadiene copolymer latex (SBR). Specifically, when two or more pigment coating layers are provided, the topmost coating layer preferably contains 10 parts by mass or more of SBR per 100 parts by mass of pigment, and more preferably 12 parts by mass or more. There are no particular restrictions on the amount of SBR contained in coating layers other than the topmost coating layer, but even if SBR is contained, it is preferable to use a smaller amount than that of the topmost coating layer.

[0040] Another point to be noted when two or more pigment coating layers are provided is that the top coating layer preferably has a strength suitable for box-making. If the strength of the top coating layer is insufficient during box-making, it may crack when folded or the like, and the box may not function as a box. In order to make the top coating layer less likely to crack when folded or the like, it is preferable to minimize the amount of starch-based adhesive blended. Specifically, the content of the starch-based adhesive in the top coating layer of the pigment coating layer is preferably 1 part by mass or less, and more preferably 0.5 parts by mass or less, per 100 parts by mass of pigment. The amount of starch-based adhesive blended is not particularly limited for coating layers other than the top coating layer, but it is preferable that the amount of starch-based adhesive blended is not too large for other coating layers, although it is not as strict as for the top coating layer.

[0041] In the coated white paperboard according to this embodiment, the paint for the pigment coating layer may contain, as necessary, various commonly used auxiliary agents such as dispersants, defoamers, water-resistant agents, coloring dyes, coloring pigments, thickeners, or cationized versions of these various auxiliary agents.

[0042] In the coated white paperboard according to this embodiment, the method for applying the coating liquid for the pigment coating layer is not particularly limited, and various methods such as various film transfer coaters such as a metering size press and a sim sizer, an air knife coater, a rod coater, a blade coater, a direct fountain coater, a spray coater, and a curtain coater are appropriately used. Here, it is preferable to use a scraping method, such as a rod coater or a blade coater, for coating the pigment coating layer that is the bottom layer. By increasing the smoothness of the base, the smoothness of the final top layer can be improved, and as a result, suitability for gravure printing with fewer missed dots can be easily obtained.

[0043] In the coated white paperboard according to this embodiment, the thickness of the pigment coating layer is preferably 3 to 20 μm, and more preferably 8 to 17 μm. If the desired coating amount is not achieved by one coating, coating may be repeated two or more times. If the thickness of the pigment coating layer is less than 3 μm, the rate of missed dots during gravure printing may deteriorate, and the desired print gloss may not be achieved. On the other hand, if the thickness of the pigment coating layer exceeds 20 μm, the strength of the coating layer may decrease, causing paper dust or powder falling during punching or box making, which may cause serious problems.

[0044] In order to reduce the rate of mis-dots, which is important in gravure printing, it is preferable to form the pigment coating layer in two or more layers rather than in one layer. By forming two or more pigment coating layers, the bottommost coating layer exerts an anchor effect, improving the smoothness of the surface of the topmost pigment coating layer and reducing the rate of mis-dots. When forming two or more pigment coating layers, the thickness of the bottommost pigment coating layer is preferably 2 μm or more, and more preferably 3 μm or more. If it is less than 2 μm, it is not possible to sufficiently fill the recesses present on the surface of the base paper, and the effect of reducing the rate of mis-dots is poor. On the other hand, if it exceeds 15 μm, the strength of the coating layer decreases, and paper dust or powder falling is likely to occur during punching or box making.

[0045] In the coated white paperboard according to this embodiment, a coating liquid called a backing liquid or anti-curling liquid (hereinafter referred to as backing liquid or anti-curling liquid) may be applied to the surface of the back layer for the purpose of preventing curling. The backing liquid may be an aqueous solution of a known water-soluble polymer such as starch, polyvinyl alcohol, or polyacrylamide. In addition to the water-soluble polymer, the backing liquid may also contain a sizing agent, a colorant, or a fluorescent dye as an auxiliary. There are no particular limitations on the method for applying the backing liquid, but known coaters such as a film metering type such as a Simsizer, a rod coater, a blade coater, or an air knife coater may be used.

[0046] The coated white paperboard according to this embodiment may be subjected to a calendaring treatment to improve smoothness, a luster press treatment to increase glossiness, or the like, depending on the application.

[0047] The coated white paperboard according to this embodiment has a density of 0.77 to 0.87 g / cm 3 It is preferable that the density is 0.81 to 0.86 g / cm 3 It is more preferable if the density is 0.77 g / cm 3 If the density is less than 0.87g / cm, not only will the paper peel off due to a decrease in printing strength, but the stiffness of the coated white board itself will decrease, which may reduce workability such as transportation. Also, if the paper is too bulky, it will tend to have a low smoothness, which may worsen the rate of missed dots during gravure printing. On the other hand, if the density is less than 0.87g / cm, 3 If the thickness exceeds 100 mm, the paper tends to have poor cushioning and may cause a deterioration in the rate of dot misses during gravure printing. In addition, the paper is relatively heavy, which is unfavorable for the environment as it requires a large amount of energy for transportation.

[0048] In the coated white paperboard according to the present embodiment, the PPS measurement value of the pigment coating layer surface is preferably 1.5 μm or less, more preferably 1.3 μm or less, and even more preferably 1.1 μm or less. There is no particular restriction on the lower limit of the PPS measurement value, but if calendaring is performed to reduce the PPS measurement value, the density increases and cushioning properties are impaired, which may impair the suitability for gravure printing. Therefore, the PPS measurement value is preferably 0.5 μm or more. The PPS measurement value is an index of smoothness, and if this value is within the above range, it is easy to reduce the rate of missed dots during gravure printing. Note that the clamping pressure and packing material can be selected for PPS, and in the present invention, the conditions of a clamping pressure of 1000 kPa and the use of hard packing are selected as conditions that are likely to correlate with the suitability for gravure printing. In addition to calendaring, the PPS measurement value of the pigment coating layer surface can also be adjusted by changing the composition of the pigment coating layer. Generally, it is easy to increase the PSS measurement value by increasing the coating weight or by increasing the amount of flat pigment used as a pigment. EXAMPLES

[0049] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" refer to "parts by mass" and "% by mass", respectively, unless otherwise specified. The number of parts added is a value calculated as a solid content.

[0050] The coated white paperboards of the Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Figure 2. The evaluation methods are as follows.

[0051] <Gravure printing suitability evaluation: PPS smoothness measurement> Measurements were made according to JIS P8151:04 Paper and cardboard - Surface roughness and smoothness test method (air leak method) - Print surf tester method. Note that the conditions were a clamp pressure of 1000kPa and hard packing.

[0052] <density> Measurements were performed in accordance with JIS P8118:14 Paper and paperboard - Test methods for thickness, density and specific volume.

[0053] Printing was performed using a halftone gravure plate with a Ministry of Finance Printing Bureau type gravure printability tester (Kumagaya Riki Kogyo Co., Ltd.), and the missing dots in the 10-70% halftone dot area were visually evaluated, and the setting was evaluated by rubbing the solid area with a finger immediately after printing. The ink used was OGH91 Sumi manufactured by Toyo Ink Mfg. Co., Ltd. <Missing Dot Evaluation> ◎: No missing dots, good. ◯: Very few missing dots, good. △: A few missing dots are observed. (Lower limit of use) ×: Missing dots are clearly visible. (Not available) <Setting evaluation> ◎: Does not come off even when rubbed with fingers. Good. ○: Does not come off even when rubbed with fingers. Good. △: When rubbed with a finger, a small amount of ink stains the finger. (Lower limit of use) ×: When you rub the ink with your finger, it stains on your finger. (Not for use)

[0054] Example 1 <Preparation of base paper> The surface layer was formed using 90 parts of high-quality recycled paper pulp adjusted to 300 ml of CSF, 10 parts of softwood bleached kraft pulp (N-BKP) adjusted to 500 ml of CSF, heavy calcium carbonate (manufactured by Imerys Minerals Japan, product name: Carbital 90) with an ash content of 3 mass% relative to the mass of pulp, and 0.5 parts of aluminum sulfate per 100 mass parts of pulp as a coagulation aid. The lower surface layer was formed using 100 parts of unbeaten waste paper pulp that had been deinked and bleached from 300 ml of CSF recycled newspaper, 2.0 parts by mass of aluminum sulfate per 100 parts by mass of pulp as a coagulation aid, and 0.4 parts by mass of a fatty acid-based sizing agent (manufactured by Arakawa Chemical Industries, Ltd., product name: Size Pine CA956) per 100 parts by mass of pulp as a sizing agent. The upper back layer was formed of three layers using 100 parts of unbeaten waste paper pulp obtained by removing dust from 300 ml of CSF waste magazine paper and 2.0 parts by mass of aluminum sulfate per 100 parts by mass of pulp as a flocculating aid. The bottom back layer was made of 100 parts of unbeaten waste paper pulp obtained by removing dust from 300 ml of CSF waste newspaper. The paper was made at a speed of 200 m / min using a short wire combination papermaking machine, and the total basis weight was 310 g / m for six layers, consisting of one surface layer, one undersurface layer, and four back layers. 2 The coated white board base paper was obtained. The surface layer had a basis weight of 40 g / m 2 The surface layer has a basis weight of 30g / m 2 The basis weight of the back layer and the top layer is 70g / m 2 The basis weight of the bottom layer of the backing is 30 g / m 2 In addition to the above-mentioned raw materials, 0.4 parts of polyacrylamide (manufactured by Arakawa Chemical Industries, Ltd., product name: Polystron 619) was added as a paper strength agent to each of the six layers per 100 parts by mass of pulp, and 0.03 parts of a retention aid (manufactured by Kurita Water Industries, Ltd., product name: HH220) was added as a paper strength agent to each of the six layers per 100 parts by mass of pulp.

[0055] <Formation of coating layer on the surface> A paint for the bottom coating layer was prepared by dispersing in water 20 parts of kaolin (manufactured by Keimin, product name: Hydrasperse) and 80 parts of wet heavy calcium carbonate (manufactured by Imerys Minerals Japan, product name: Carbital 60) as pigments, 12 parts of SBR (styrene-butadiene rubber) latex (manufactured by Asahi Kasei Chemical, product name: B-1541) as adhesives, and 3 parts of urea phosphate esterified starch. A paint for the top coating layer was prepared by dispersing in water 30 parts of kaolin (manufactured by Kadam, product name: Amazon SB) and 60 parts of wet heavy calcium carbonate (manufactured by Imerys Minerals Japan, product name: Carbital 90) as pigments, and 10 parts of titanium oxide (manufactured by DuPont, product name: RPS-Vantage) as adhesives, and 13 parts of SBR latex (manufactured by Asahi Kasei Chemical, product name: B-1541) as adhesives. Next, the surface of the obtained coated white board base paper was coated with a rod coater in a coating amount of 8 g / m2 in solid content. 2The coating material for the bottom coating layer was applied and dried to provide an undercoat layer. Next, a coating amount of 7 g / m2 solid content was applied to the bottom coating layer using a rod coater. 2 The paint for the uppermost coating layer was applied so as to obtain the above-mentioned coating composition, and then dried to form the uppermost coating layer.

[0056] <Application of anti-curl solution to the back layer> Next, a 1% starch paste solution (manufactured by Nippon Shokuhin Kako Co., Ltd., product name: MS#3800) was applied to the surface of the bottom layer of the back layer of the coated white board base paper on which the bottom and top coating layers had been formed, at a solid content of 0.1 g / m2, using a rod coater. 2 The mixture was applied and dried so that the result was as shown in FIG.

[0057] <Smoothing processing> Next, a calendaring treatment was carried out at a linear pressure of 50 kg / cm, and then the surface was treated with a luster press at 80 kg / cm and 140° C. to obtain a coated white paperboard according to Example 1.

[0058] Example 2 A coated white paperboard according to Example 2 was obtained in the same manner as in Example 1, except that the addition ratio of the fatty acid-based sizing agent used in the undersurface layer was changed from 0.4 parts to 0.2 parts.

[0059] Example 3 A coated white paperboard according to Example 3 was obtained in the same manner as in Example 1, except that the addition ratio of the fatty acid-based sizing agent used in the undersurface layer was changed from 0.4 parts to 0.6 parts.

[0060] Example 4 A coated white paperboard according to Example 4 was obtained in the same manner as in Example 1, except that the fatty acid-based sizing agent used in the lower surface layer was changed to a rosin emulsion sizing agent (Size Pine NT78, manufactured by Arakawa Chemical Industries Co., Ltd.).

[0061] Example 5 The smoothing process is performed with a line pressure of 50kg / cm to 100kg / cm, and the basis weight of the upper and lower layers is 70g / m 2 75g / m 2 A coated white paperboard according to Example 5 was obtained in the same manner as in Example 1, except that the above-mentioned conditions were satisfied.

[0062] Example 6 The smoothing treatment was performed with a line pressure of 50kg / cm to 20kg / cm, and the basis weight of the upper and lower layers was 70g / m 2 From 65 g / m 2 A coated white paperboard according to Example 6 was obtained in the same manner as in Example 1, except that the above-mentioned conditions were satisfied.

[0063] Comparative Example 1 A coated white paperboard according to Comparative Example 1 was obtained in the same manner as in Example 1, except that 0.4 parts of the fatty acid-based sizing agent used in the subsurface layer was added to the surface layer.

[0064] As is clear from Figure 2, the coated white paperboards of Examples 1 to 6 all had small PPS values ​​and were excellent in suitability for gravure printing. In contrast, the coated white paperboard of Comparative Example 1 used a sizing agent in the surface layer as well, which caused resins such as latex to be localized on the surface, resulting in poor ink absorption and making the paper unsuitable for practical use in terms of both missing dot evaluation and setting ability. [Explanation of symbols]

[0065] 1. Coated white paperboard 10. Base paper for coated white board 11 Surface layer 12 Lower surface layer 13 Lining 13a Upper lining layer 13b Bottom layer 14 Pigment coating layer 14a Top coating layer 14b Bottom coating layer

Claims

1. A coated white paperboard having a base paper for coated white paperboard having at least three layers, i.e., a surface layer, a subsurface layer, and a back layer, and a pigment coating layer applied to the surface layer, The coated white paperboard has two or more pigment coating layers, the uppermost coating layer of the pigment coating layers contains 10 parts by mass or more of styrene-butadiene copolymer latex (SBR) per 100 parts by mass of pigment, the surface layer does not contain a sizing agent, and the undersurface layer contains a sizing agent.

2. 2. The coated white paperboard according to claim 1, wherein the sizing agent is a fatty acid-based sizing agent.

3. The coated white paperboard according to claim 2, characterized in that the amount of the sizing agent is 0.1 to 0.8% by mass based on 100% by mass of pulp.

4. A coated whiteboard paperboard as described in any one of claims 1 to 3, characterized in that the thickness of the lowermost coating layer among the pigment coating layers that is in contact with the surface layer is 2 μm or more.

5. 2. The coated white paperboard according to claim 1, wherein the PPS measurement value of the surface of the uppermost coating layer is 1.5 μm or less.

6. 2. The coated white paperboard according to claim 1, characterized in that the surface layer pulp, which is the raw material for the surface layer, has a disintegrated freeness of 200 to 500 ml of CSF.

7. Density: 0.77 to 0.87 g / cm 3 2. The coated white paperboard according to claim 1,

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