JP5809273B2 - Coated white paperboard and method for producing the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a coated white paperboard in which a pigment coating layer is provided on a base paper mixed with used paper, and relates to a white paper and a coated white paperboard having high printing gloss and a method for producing the same.

  The base paper of coated white paperboard is usually manufactured by multi-layer papermaking, and the surface layer uses a lot of expensive bleached chemical pulp with high whiteness, and the lower and middle layers are cheaper and cheaper than the exposed chemical pulp. Often used are deinked and undeinked waste paper pulp. The reason why the bleached chemical pulp is used for the surface layer is to keep the white unevenness on the surface of the coated white paperboard well and make it difficult to see foreign matters such as dust contained in the used paper pulp from the surface. In addition, the use of waste paper pulp for the lower and middle layers is from the viewpoint of environmental and cost reduction.

  In recent years, demands for environmental efforts and cost reductions are increasing, and the usage rate of waste paper pulp tends to increase. Along with this, the problem that white unevenness and foreign matters such as dust become conspicuous on the surface of the coated white paperboard is increasing. In order to remove foreign matters such as dust, it is necessary to enhance the deinking and dust removal treatment, but the yield becomes worse as the treatment is enhanced. In addition, as an improvement method using a coating solution, there is a method of increasing the coating amount. However, if the coating amount is too large, the operability is lowered, such as poor drying during coating, and printing unevenness due to binder migration. A new problem will occur.

  For example, Patent Documents 1 and 2 disclose a method for producing white paperboard by using a pigment having a high concealment property in the coating liquid. However, pigments with high hiding properties are expensive, and the advantage of reducing the cost by increasing the usage rate of waste paper pulp is lost.

  Patent Document 3 discloses a method for improving whiteness unevenness by making a difference in whiteness between a surface layer and a surface layer below a certain level from the viewpoint of a paper layer structure. However, in this method, the usage rate of waste paper pulp cannot be increased beyond a certain level due to the definition of whiteness difference.

  By the way, Patent Document 4 proposes to improve the apparent whiteness of printing paper using a blue or purple color material. However, the paperboard has not been studied, and there is no mention of white unevenness.

JP-A-6-166991 JP 2003-306882 A JP 2005-298998 A JP 2011-026754 A

  As already mentioned, the demand for environmental efforts and cost reductions is increasing, so the usage rate of waste paper pulp tends to increase even in the base paper of white paperboard. Occurrence and decrease in whiteness are problematic.

  In addition, when using multi-layer base paper as the base paper for coated white paperboard, use a relatively low whiteness pulp for the inner layer such as the front and lower layers and the back layer, and a relatively high whiteness pulp for the surface layer. However, it may be difficult to cover the occurrence of white unevenness and whiteness deterioration due to the inner layer only with the surface layer, and solve the problem of white unevenness and whiteness decrease of coated white paperboard. Is desired.

  In view of such a situation, an object of the present invention is to provide a technique for producing coated white paperboard having good white unevenness and whiteness with good operability.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have added a blue or purple color material to a pigment coating solution containing a white pigment and an adhesive, and this coating solution is applied to the base paperboard. By adjusting the b ^* value of the paper measured by the method of JIS P 8150 to −10 or more and less than −0.5 in the measurement including ultraviolet rays, the white unevenness of the coated white paperboard can be reduced. The inventors have found that a coated white board with high whiteness can be effectively produced by suppressing it, and the present invention has been completed.

That is, although not limited thereto, the present invention includes the following inventions.
(1) A pigment coating solution containing a blue or purple color material is applied to a base paper made of multilayer paper containing waste paper pulp, and the b ^* value of the paper measured by the method of JIS P 8150 is determined. A method for producing a coated white paperboard, which comprises adjusting the ultraviolet ray to -10 or more but less than -0.5.
(2) The method according to (1), wherein the whiteness of the inner layer is lower than the whiteness of the surface layer of the multilayer paper.
(3) The method according to (1) or (2), wherein the difference between the whiteness of the surface layer and the whiteness of the inner layer is 10 points or more with respect to the base paper of the multilayer papermaking.
(4) The method according to any one of (1) to (3), wherein the base paper for multilayer papermaking has a basis weight of 70 g / m ² or more.
(5) The method according to any one of (1) to (4), wherein the base paper for multi-layer papermaking has a basis weight of 100 g / m ² or more.
(6) The method according to any one of (1) to (5), wherein the whiteness of the multilayer paper is 75% or less.
(7) The method according to any one of (1) to (6), wherein the whiteness of the multilayer base paper is 70% or less.
(8) Any one of (1) to (7), including applying two or more types of pigment coating liquids, and a blue or purple color material being contained in one or more types of pigment coating liquids The method described in 1.
(9) The method according to (8), wherein a blue or purple pigment is blended in the outermost coating liquid.
(10) The method according to (8) or (9), wherein the pigment coating layer is applied by a blade coating method.
(11) Coated white paperboard produced by the method according to any one of (1) to (10).

  According to the present invention, coated white paperboard having good white unevenness and whiteness can be produced with good operability.

L ^* a ^* b ^* Hue change after colorant addition in hue system

The present invention relates to a coated white paperboard and a method for producing the same. In the present invention, the coated white paperboard is a base paper provided with a pigment coating layer on one side or both sides, and a blue or purple pigment and / or dye (hereinafter also referred to as a blue-violet material) is at least a pigment. The b ^* value of the paper blended in the coating layer and measured by the method of JIS P 8150 is adjusted to −10 or more and less than −0.5 in the measurement including ultraviolet rays.

Base Paper In the present invention, a white paperboard is produced using a base paper made of multilayer paper mixed with waste paper pulp. The whiteness of the base paper used in the present invention is not particularly limited. However, according to the present invention, even if the whiteness of the base paper is low, it is possible to obtain a white board with little whiteness unevenness. For example, when the whiteness of the base paper is 75% or less, preferably 70% or less, the effect of the present invention can be particularly greatly enjoyed. Here, the whiteness of the base paper refers to the whiteness of the base paper surface on the side where the coating layer is provided.

  The base paper used in the present invention is not particularly limited as long as waste paper pulp is blended, and for example, bleached chemical pulp, unbleached chemical pulp, and the like can be used. Waste paper pulp may or may not be deinked. As deinked pulp, selected waste paper such as high-quality paper, medium-quality paper, lower grade paper, newspapers, flyers, magazines, etc. and unselected waste paper mixed with these are used. Deinked pulp as a raw material can be used. In addition to waste paper pulp and chemical pulp, various pulps can be used depending on the application, for example, groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP). ), Chemiground pulp (CGP), semi-chemical pulp (SCP), and the like. The pulp blending may be a mixture of various pulps or may be the same pulp.

  In the base paper of the present invention, the content of waste paper pulp in the raw material pulp is preferably 50% by weight or more, more preferably 75% by weight or more, and more preferably 90% by weight or more in the total pulp. preferable.

  In the present invention, a base paper made of multilayer paper is used. About the pulp mixing | blending of each layer, it is good also as the same pulp mixing | blending, and you may laminate | stack one or more layers of a different pulp mixing | blending. For example, pulp with low whiteness can be used for the inner layer, the middle layer, and pulp with higher whiteness can be used for the front and back layers, or multiple layers of the same layer of pulp can be stacked. it can. In the case of multi-layer papermaking, there is a technical problem that white unevenness is likely to occur if the difference in whiteness between the surface layer and the layer immediately below it is large (the whiteness of the surface layer is high and the whiteness of the inner layer is low). According to the invention, white unevenness can be effectively suppressed even in such a case. In particular, when the difference in whiteness between the surface layer and the immediately lower layer is 10 points or more, it is easier to enjoy the effect of the present invention. The point mentioned here indicates a difference in whiteness. For example, when the whiteness of the surface layer is 80% and the whiteness of the immediately lower layer is 68%, it is 12 points lower.

  In the present invention, a filler may be added to the base paper. Known fillers can be arbitrarily used as the filler, such as heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, deramikaolin, white carbon, talc, magnesium carbonate. Inorganic fillers such as amorphous silica produced by neutralization of mineral products of barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate, Organic fillers such as urea-formalin resin, melamine resin, polystyrene resin, and phenol resin can be used alone or in combination. Among these, heavy calcium carbonate and light calcium carbonate, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used to improve opacity. The filler content in the paper is not particularly limited, but is preferably 1 to 40% by weight, and more preferably 10 to 35% by weight.

  In the present invention, known papermaking additives can be used. For example, sulfuric acid bands and various anionic, cationic, nonionic or amphoteric yield improvers, drainage improvers, various paper strength enhancers and internal additive sizing agents, etc. Can be used. Examples of the dry paper strength improver include polyacrylamide and cationized starch, and examples of the wet paper strength improver include polyamidoamine epichlorohydrin. These chemicals are added within a range that does not affect the formation and operability. Examples of neutral sizing agents include alkyl ketene dimers, alkenyl succinic anhydrides, and neutral rosin sizing agents. Furthermore, dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  In the present invention, the use of a base paper in which the whiteness of the inner layer is lower than the whiteness of the surface layer of the multi-layer base paper is particularly preferable because the effect of the present invention can be greatly enjoyed. That is, when such a base paper is used, white unevenness and low whiteness of the inner layer cannot be covered only by the outer layer (surface layer), and white unevenness is likely to occur. It is possible to effectively cope with problems related to the multi-layer paper.

The basis weight of the base paper used in the present invention is not particularly limited, but is preferably 70 g / m ² or more, more preferably 100 g / m ² or more, and 150 g / m ² because it is used as a coated white paperboard. The above is more preferable, and 200 g / m ² or more is more preferable. The upper limit of the basis weight of the base paper is not particularly limited, but is preferably 500 g / m ² or less, and may be 400 g / m ² or less.

  The paper making method of the base paper in the present invention is not particularly limited, and a long paper machine including a top wire, an on-top former, a gap former, a round paper machine, a long paper machine and a round paper machine are used in combination. It can be performed using a paperboard machine, a Yankee dryer machine or the like. The pH during papermaking may be acidic, neutral or alkaline, but neutral or alkaline is preferred. The paper making speed is not particularly limited.

  In the present invention, as a means for improving the smoothness of the base paper, a clear paint mainly containing starch or a paint containing a pigment can be applied to the base paper before the pigment application. The pre-coated base paper may be subjected to pigment coating without undergoing a drying step, that is, in a state where the paint on the base paper is wet. Thus, the state of the base paper after pre-coating before being subjected to pigment coating is not limited.

In the present invention, clear coating means, for example, various starches such as starch and oxidized starch using a coater (coating machine) such as a size press, a gate roll coater, a pre-metering size press, a curtain coater, and a spray coater. It means that a coating liquid (surface treatment liquid) mainly composed of a water-soluble polymer such as polyacrylamide or polyvinyl alcohol is applied (size press) on a base paper. By applying clear coating on the base paper, the surface strength and smoothness of the base paper can be improved, and the coating property when applying pigment can be improved. In the present invention, a violet pigment and / or a blue pigment can be contained in the clear coating layer. In that case, a violet pigment and / or a blue pigment is blended in the clear coating liquid, and this is used as a base paper. Just coat it on top. The amount of clear coating is preferably 0.1 to 1.0 g / m ² , more preferably 0.2 to 0.8 g / m ² in terms of solid content per side.

  Further, the base paper may be smoothed in advance by an online soft calendar, online chilled calendar or the like before the coating process.

Pigment Coating In the present invention, a blue or purple color material is blended in at least one of the coating liquids containing a white pigment and an adhesive. More preferably, the outermost pigment coating layer contains a color material. By blending a blue / purple color material, it is possible to effectively improve the whiteness, opacity, white unevenness, and apparent whiteness of the coated paper. Known white pigments and adhesives can be appropriately used. Further, when a blue / purple color material is blended in a plurality of coating layers, the effect of improving white unevenness is higher than when blended in a single layer.

  In addition to the pigment coating layer, a color material may be contained in the size press solution or the base paper.

  In the present invention, one or more color materials selected from the group consisting of purple pigments, purple dyes, blue pigments, and blue dyes are used. The color material means a colored pigment or dye other than white. The pigment is a white or colored powder that is insoluble, hardly soluble or dispersed in water, oil, an organic solvent or the like, and includes an inorganic pigment and an organic pigment. In the present invention, any of an inorganic pigment and an organic pigment may be used as the color material. The dye means an organic dye that is dyed onto fibers, pigments, or the like by an appropriate dyeing method among organic dyes having a specific color by selectively absorbing or reflecting visible light. The dye is soluble in a solvent (such as water or an organic solvent). In the present invention, a dye may be used in combination, but it is preferable to use a violet and / or blue pigment from the viewpoint of excellent light resistance and preventing discoloration / coloring of paper over time. In the present invention, “use a blue / purple color material” includes a case where both a blue color material and a purple color material are used, and one of them is used. In the present invention, the “blue / purple color material” means “blue and / or purple color material”.

  Examples of commercially available blue pigments include EMT-Blue DS-18 manufactured by Toyo Ink Manufacturing Co., Ltd., and examples of commercially available purple pigments include SA Violet C12896 Gokoku Color Co., Ltd. Product made. A blue pigment alone or a purple pigment alone may be used, but both may be used in combination. In order to improve the opacity, it is preferable to use a purple pigment. Moreover, in this invention, you may add color materials other than blue and purple, such as black, red, and yellow, as needed.

  As the blue-violet pigment, both inorganic pigments and organic pigments can be used as described above. Specific examples of blue pigments include, for example, ultramarine, azurite, prussian blue, ultramarine, smalto, cobalt blue (cobalt aluminate), cerulean blue (cobalt stannate), cobalt chrome blue, cobalt, aluminum, and silicon. Examples thereof include oxide, cobalt / zinc / silicon oxide, manganese blue, and phthalocyanine. Specific examples of purple pigments include, for example, cobalt violet (cobalt arsenate, cobalt phosphate, cobalt lithium phosphate, hydrous ammonium phosphate, cobalt borate, etc.), purple ultramarine blue, iron oxide purple, manganese violet, mineral Examples thereof include inorganic pigments such as violet, indigoid, quinacridone, oxazine, anthraquinone, carbonium, and xanthene organic pigments.

  In the present invention, by adding a certain amount of the color material to the white paperboard to make the hue a certain range, the surface color of the white paperboard is bluish, enhancing the whiteness of appearance and preventing white unevenness. be able to.

When a color material is added in the present invention, the hue of the paper can be changed in the direction shown in FIG. FIG. 1 shows the change in hue of paper that does not contain the color material of the present invention and paper that has been incorporated, based on the L ^* a ^* b ^* color system. When the hue is expressed as 0 ° in the (+) direction of the a ^* value, 180 ° in the (−) direction, b ^* (90) in the (+) direction, and 270 ° in the (−) direction, Assuming that the position of the origin is zero, when a blue color material is added, the hue of the paper after the addition changes to the portion of 210 ° or more and less than 280 ° shown in FIG. When it is added, it indicates that the hue of the paper after the addition changes to a portion of 280 ° to less than 335 ° shown in FIG. 1 as “purple”.

The color material used in the present invention is preferably 0.4 to 3.5 mg, more preferably 0.9 to 3.0 mg per 1 m ^{2 of} white paperboard. Other preferred embodiments, embodiments employing colorant white paperboard 1 m ² per 0.7～3.0Mg, embodiments employing colorant white paperboard 1 m ² per 0.7mg~2.0mg also included. In general, when the amount is less than 0.4 mg, light absorption by the coloring material is small, and thus the concealability contributing to opacity is insufficient, which is not preferable. In general, when the amount is more than 3.5 mg, the amount of light absorbed by the coloring material is large, which greatly contributes to the improvement in opacity, but the hue is greatly deviated from 0 point, and it is not preferable to feel white. Absent. The total content of the color material can be appropriately adjusted depending on the whiteness of the raw material or the base paper.

  In the present invention, the coating method of the coating layer is not particularly limited, and any coating machine that is usually used may be used. An on-machine coater or an off-machine coater may be used, and if it is an on-machine coater, a coater such as a roll coater such as a size press coater or a gate roll coater, a bill blade coater, or a blade metering size press coater can be used. In the present invention, it is particularly preferable to use a blade coater, and even when a base paper in which white unevenness is likely to occur is used, white unevenness can be effectively suppressed and whiteness can be increased. In addition, a coating layer can be provided by curtain coating, and since the base paper can be effectively coated with a bulky and uniform coating layer in curtain coating, the whiteness and opacity of the coated paper are further improved. Can be improved.

  In a preferred embodiment of the present invention, two or more coating layers containing a pigment can be provided. When coating using a blade coater, the coating layer is preferably three or more layers.

  In the present specification, the outermost coating layer may be referred to as a top coating layer, and the coating liquid for forming the top coating layer may be referred to as a top coating liquid. A layer adjacent to the outermost layer and closer to the base paper is referred to as an undercoat coating layer, and a coating solution for forming the undercoat coating layer is referred to as an undercoat coating solution. The undercoat layer may be a plurality of layers. When there are a plurality of coating layers, the blue-violet material may be included in any coating layer. In this case, the color material amount of the blue-violet material is a value obtained by adding the color material contents of the respective layers.

  In this invention, water and a required component are mixed and a coating liquid is adjusted. In the preparation of the coating liquid, ordinary mixing means such as a mixer may be used. Each component will be described below.

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

  The pigment of the undercoat coating solution is not particularly limited, but examples thereof include kaolin, clay, engineered kaolin, delaminated clay, calcined clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate. Use inorganic pigments such as zinc oxide, silicic acid, silicate, colloidal silica, and satin white, and organic pigments such as solid type, hollow type, or core-shell type, as required, alone or in combination of two or more. Can do. As the types of pigments, heavy calcium carbonate and light calcium carbonate are preferable because the required amount of binder is small and the surface strength can be improved with a small amount of adhesive. Moreover, it is preferable to use the pigment with a comparatively large average particle diameter from a viewpoint of the whiteness of a white paperboard, or a white nonuniformity. For example, the average particle size (D50) is 1.0 to 3.0 μm, preferably 1.5 to 2.5 μm. The amount used is not particularly limited, but it is preferably 40% by weight or more, more preferably 50% by weight or more, still more preferably 60% by weight or more, and even more preferably 80% by weight or more. Become.

Topcoat coating liquid The topcoat coating liquid used in the present invention comprises a pigment and an adhesive as in the case of the undercoat coating liquid. A pigment is not restrict | limited, The pigment conventionally used for coated paper can be used. For example, inorganic pigments such as kaolin, clay, heavy calcium carbonate, light calcium carbonate, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white, and organic pigments such as plastic pigments Organic / inorganic composite pigments can be used. Of these, heavy calcium carbonate or light calcium carbonate is preferred. These pigments can be used alone, but if necessary, two or more kinds may be mixed and used.

  In the present invention, it is preferable to use a pigment having a relatively small average particle diameter as the pigment of the topcoat coating solution. For example, the average particle diameter (D50) is 0.2 to 1.0 μm (may be 0.5 to 1.0 μm), and the particle diameter (D75) and 25 cumulative at 75 cumulative mass% of the particle size distribution curve by the sedimentation method. Calcium carbonate (preferably heavy calcium carbonate) having a particle size (D25) ratio (D75 / D25) in mass% of 3.0 or more and 5.0 or less (may be 3.5 or more and 5.0 or less) is used. By doing so, a dense coating layer is formed, and it is suppressed that the ink setting property of white paperboard becomes too fast, and the printing gloss tends to be improved. The usage fee for the calcium carbonate is not particularly limited, but is preferably 60% by weight or more, and more preferably 80% by weight or more. When used in such a range, the effect becomes remarkable.

  It is preferable to mix | blend an adhesive agent (binder) with the topcoat coating liquid of this invention. The adhesive is not particularly limited, and an adhesive conventionally used for coated paper can be used. Examples of adhesives include styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, and other copolymers, polyvinyl alcohol, maleic anhydride copolymer And synthetic adhesives such as acrylic acid / methyl methacrylate copolymers; proteins such as casein, soy protein, synthetic protein; oxidized starch, positive starch, urea phosphated starch, hydroxyethyl etherified starch, etc. Conventional adhesives for coated paper such as starches such as etherified starch and dextrin; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and hydroxymethylcellulose are included. One or more types of adhesives can be appropriately selected and used. In a preferred embodiment, these adhesives are used in the range of 5 to 50 parts by weight, more preferably 8 to 30 parts by weight, and more preferably 8 to 15 parts by weight per 100 parts by weight of the pigment. A synthetic adhesive having a low viscosity increase of the paint is preferred. In addition, polyvinyl alcohol having a low polymerization degree (polymerization degree of 1000 or less or may be about 500) is preferable because the adhesion effect can be enhanced without greatly increasing the viscosity.

  In the coating liquid of the present invention, if necessary, it is blended with ordinary pigments for coated paper, such as a dispersant, a thickener, a water retention agent, an antifoaming agent, a water resistance agent, a colorant, and a surfactant. Various auxiliary agents can be used as appropriate.

The solid content concentration of the top coating liquid is preferably 40 to 75% by weight, more preferably 50 to 70% by weight, and still more preferably 60 to 70% by weight. When the solid content concentration of the topcoat coating liquid is less than 40% by weight, the volume change of the coating layer during coating drying increases, resulting in poor surface smoothness after coating. For example, in the case of a blade coater, if it is more than 75% by weight, the fluidity of the coating solution is deteriorated, and the blade edge of the blade coater becomes noticeable, resulting in poor coating surface feeling. In the case of a curtain coater, if it is more than 75% by weight, the fluidity of the coating liquid is deteriorated and it becomes difficult to form a uniform curtain film. In the present invention, it is preferable to 2 to 30 g / ^{m 2} of coating amount of overcoat layer is the outermost layer, more preferably, to 4~20g / ^{m 2,} be 6~20g / ^{m 2} Is more preferable, and it is more preferable to set it as 6-15 g / m < ² >. Also, the coating amount of the inner coating layer, preferably in a 5 to 30 g / ^{m 2,} and more preferably set to 10 to 25 g / ^{m 2.} In the present invention, the coating amount of the outermost coating layer may be larger or smaller than the coating amount of the inner coating layer. By adjusting the coating amount of each coating layer, only the surface layer part of white paperboard that has a great influence on the ink setting property is made a void structure suitable for printing, and the ink setting property is adjusted, and the whiteness is greatly affected. Can maintain the majority of the inner primer layer.

In this invention, the coating amount of a pigment coating layer is the sum total of each layer, and 5-50 g / m < ² > is preferable by dry weight per single side | surface. When the coating amount is less than 5 g / m ² , the coating layer becomes thin, and the whiteness and white unevenness of white paperboard cannot be sufficiently improved. On the other hand, if the coating amount of one layer exceeds 50 g / m ² , it is not preferable because the operability is deteriorated, for example, the drying property at the time of coating is deteriorated, or printing unevenness due to binder migration is caused.

  The coating speed of the present invention is not particularly limited, but is generally about 100 m / min to 800 m / min.

  The coated white paperboard of the present invention is produced through a normal drying step after providing a coating layer on the base paper, but may be smoothed in a surface treatment step or the like as necessary. In a preferred embodiment, it is finished by adjusting so that the water content of the coated paper after production is about 3 to 10% by weight, more preferably about 4 to 8% by weight. For smoothing processing, a smoothing processing device such as a normal super calendar, gloss calendar, soft calendar, thermal calendar, shoe calendar, or the like can be used.

  The smoothing apparatus is appropriately used on-machine or off-machine, and the form of the pressure device, the number of pressure nips, heating, and the like are also adjusted as appropriate.

Coated white paperboard The hue of the coated whiteboard produced in the present invention is preferably adjusted to a b ^* value of −6 or more and less than −0.5 in the measurement including ultraviolet rays specified in JIS P 8150. The b ^* value is more preferably −4 or more and less than −1, and the b ^* value is more preferably −3.5 or more and less than −1. Thus, by making b ^* value comparatively low, while the whiteness of the appearance of the coated white paperboard can be enhanced, white unevenness can be improved. Further, the a ^* value in the same measurement is not particularly limited because it does not greatly contribute to the whiteness and opacity of the coated white paperboard, but is usually preferably −1 or more and less than 7, more preferably −1 or more and less than 5. Preferably, it is more preferably −1 or more and less than 3. If it is out of the range, the color of the coated white paperboard may not appear white, which is not preferable.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, in this specification, “part” and “%” respectively represent “part by weight” and “% by weight”, and the numerical range is described as including the end points.

<Evaluation method>
Whiteness: Measured according to JIS P8148 “Paper, paperboard and pulp—Method for measuring ISO whiteness (diffuse blue light reflectance)”.
Hue (a *, b *): Measured with a light source including ultraviolet light using a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. according to JIS P8150.
-White unevenness: Evaluated visually by 4 steps according to the following criteria.
A: Unevenness is not noticeable. ○: Mild unevenness is observed. Δ Unevenness is recognized, which may cause a problem in practical use. X: Remarkable unevenness was recognized and not suitable for practical use. Basis weight: Measured according to JIS P8124 “Paper and paperboard—basis weight measurement method”.
Density: Measured according to JIS P8118 “Paper and paperboard—Test method for thickness and density”.
-Appearance whiteness: The whiteness of the coated paper for printing was visually evaluated under indoor fluorescent lighting. This is because the whiteness of the color does not necessarily correlate with the whiteness when viewed with the human eye. Visual evaluation was made into 4 steps. A: Very white, B: White, B: Slightly dull, or slightly yellowish, B: Dullish, or yellowish.

<Experiment A (Manufacture of coated white paperboard)>
Example A1
Base paper Using pulp material containing 100% deinked waste paper pulp, whiteness 68%, basis weight 40g / m ² surface layer, undeinked waste paper pulp made from magazine waste paper at 100% rate Using the blended pulp raw material, a back layer having a whiteness of 45% and a basis weight of 40 g / m ² is made by using the same pulp as the intermediate layer and a white layer of 55% and a basis weight of 220 g / m ^2. Bonding, pressing, and drying were performed to obtain a coated white paperboard base paper having a basis weight of 300 g / m ² . The whiteness of the base paper was 65%. The paper making speed was 300 m / min.

Undercoat coating Dephosphorylated starch (MS4600, 100 parts of pigment consisting of 45 parts of delaminated kaolin (Contour 1500, Imeris) and 55 parts of light calcium carbonate (TP-121-7C, Okutama Kogyo Co., Ltd.) 5 parts by Nippon Food Processing Co., Ltd., 12 parts of styrene / butadiene copolymer latex (ALB1735, manufactured by Asahi Kasei Chemical Co., Ltd.), 0.003 parts of blue pigment (EMT-Blue DS-18, manufactured by Toyo Ink Co., Ltd.), purple pigment ( 0.002 part of SA Violet C12896 (manufactured by Mikuni Dye Co., Ltd.) was added, and water was further added to prepare an undercoat coating solution having a solid concentration of 60%. The B-type viscosity of the undercoat coating solution at 20 ° C. and 60 rpm was about 1000 mPa · s.

This undercoat coating solution was applied to the surface layer of the base paper with a bar coater at 12 g / m ² and dried. The coating speed was 300 m / min, the same as the papermaking speed, since it was performed consistently with the papermaking by on-machine.

Topcoat coating Pigment slurry consisting of 43 parts of delaminated kaolin (Contour 1500, manufactured by Imeris), 50 parts of light calcium carbonate (TP-221GS, manufactured by Okutama Kogyo Co., Ltd.) and 7 parts of titanium oxide (RPS-V, manufactured by DuPont) After preparing 100 parts of pigment, 2 parts of phosphate esterified starch (MS4600, manufactured by Nippon Food Processing Co., Ltd.), 14 parts of styrene / butadiene copolymer latex (manufactured by Asahi Kasei Chemical Co., ALB1443), lubricant (DEF-783TF) , Nissin Chemical Co., Ltd.) 0.5 parts, Blue pigment (EMT-Blue DS-18, Toyo Ink Manufacturing Co., Ltd.) 0.003 parts, Purple pigment (SA Violet C12896, Gokoku Color Co., Ltd.) 0.002 parts Then, water was further added to prepare a topcoat coating solution having a B-type viscosity at 60 rpm of 1000 mPa · s and a solid content concentration of 63%.

This topcoat coating solution was applied to the surface layer of the base paper after the undercoat coating with a blade coater at 8 g / m ² and dried. The coating speed was 300 m / min, the same as the papermaking speed, since it was performed consistently with the papermaking by on-machine.

Finishing treatment The coated white paperboard obtained was supercalendered to obtain a coated white paperboard having a basis weight of 320 g / m ² and a density of 0.85 g / cm ³ . The processing speed was 300 m / min, which was the same as the papermaking speed and the coating speed, because it was performed consistently with the papermaking and coating by on-machine.

Comparative Example A1
In the examples, coated white paperboard was obtained in the same manner as in the examples except that neither the blue pigment nor the violet pigment was added to any of the undercoat coating solution and the topcoat coating solution.

  As can be seen from Table 1, in Example A1, blue and purple pigments were added to the undercoat coating solution and the topcoat coating solution even in the case of a low whiteness base paper using deinked pulp as the surface layer. By adjusting the hue within an appropriate range, the scattering property of the coating layer can be increased and the white unevenness of the base paper can be made inconspicuous. On the other hand, in the comparative example A1 in which the blue pigment and the violet pigment are not added to the undercoat coating liquid and the topcoat coating liquid, white unevenness occurs remarkably.

<Experiment B (Manufacture of coated white paperboard)>
Example B1
White paper using 100% kraft pulp raw material, 80% whiteness, 25g / m ² surface layer, 100% pulp material containing 100% deinked waste paper pulp degree 68%, the table lower basis weight 35 g / ^{m 2,} whiteness of 45% using a pulp material containing a combination of non-deinking waste paper pulp in a ratio of 100% for a magazine wastepaper as a raw material, basis weight 65 g / ^{m 2} Using the same pulp as the middle layer and the middle layer, each of the back layers having a whiteness of 45% and a basis weight of 65 g / m ² is made, combined, pressed and dried, and coated with a basis weight of 190 g / m ² . White paperboard was obtained. The whiteness of the base paper was 69.5%. The paper making speed was 750 m / min.

Undercoat coating Modified starch (PS-266-3, Akira Guangxi) for 100 parts of pigment consisting of 85 parts of heavy calcium carbonate (Hydrocarb60, manufactured by omya) and 15 parts of calcined clay (Britex98, manufactured by Shanxi Jinyang Calcinated Kaolin) 4 parts of Yoyo), 8 parts of styrene / butadiene copolymer latex (DTO6128, Stylon) and water were further added to prepare an undercoat coating solution having a solid concentration of 66%. The B-type viscosity of the undercoat coating solution at 20 ° C. and 60 rpm was about 2500 mPa · s.

This undercoat coating solution was applied to the surface layer of the base paper with a blade coater at 14 g / m ² and dried. The coating speed was 750 m / min, the same as the papermaking speed, since it was performed consistently with on-machine papermaking.

Furthermore, 12 g / m ^{2 of the} undercoat coating solution was applied thereon with a blade coater and dried. The coating speed was 750 m / min, the same as the papermaking speed, since it was performed consistently with on-machine papermaking.

Topcoat Coating After preparing a pigment slurry consisting of 100 parts of heavy calcium carbonate (Setacarb, manufactured by omya), 13 parts of styrene / butadiene copolymer latex (SPB72, manufactured by Styron) and lubricant (DEF) -791TF, manufactured by Nissin Chemical Co., Ltd.) 0.5 parts, blue pigment (EMT-Blue DS-18, manufactured by Toyo Ink Manufacturing Co., Ltd.) 0.0005 parts, purple pigment (SA Violet C12896, manufactured by Gokoku Color Co., Ltd.) 0.007 parts Then, water was further added to prepare a topcoat coating solution having a B-type viscosity of 1140 mPa · s at 60 rpm and a solid content concentration of 67%.

This topcoat coating liquid was applied to the surface layer of the base paper after the undercoat coating by a blade coater at 14 g / m ² and dried. The coating speed was 750 m / min, the same as the papermaking speed, since it was performed consistently with on-machine papermaking.

Finishing treatment The obtained coated white board was subjected to hot soft nip calendering (40 kN / m, 120 ° C.) to obtain a coated white board having a basis weight of 230 g / m ² and a density of 0.87 g / cm ³ . The processing speed was 750 m / min, the same as the papermaking speed and the coating speed, because the papermaking and coating were performed on-machine.

Example B2
In Example B1, a coated white paperboard was produced in the same manner as in Example B1, except that the pigment of the topcoat coating solution was changed to 100 parts of heavy calcium carbonate (Hydrocarb90, manufactured by omya).

Example B3
A coated white paperboard was produced in the same manner as in Example B1, except that in Example B1, the blue pigment was changed to 0.0001 part and the purple pigment was changed to 0.007 part.
Comparative Example B1
In the examples, coated white paperboard was obtained in the same manner as in Example B1 except that neither the blue pigment nor the purple pigment was added in any of the undercoat coating solution and the topcoat coating solution.

  As can be seen from Table 2, in Example B1, blue and purple pigments were added to the undercoating liquid and the topcoating liquid even in the case of a low whiteness base paper using deinked pulp as the surface layer. By adjusting the hue within an appropriate range, the scattering property of the coating layer can be increased and the white unevenness of the base paper can be made inconspicuous. On the other hand, in the comparative example B1 in which the blue pigment and the violet pigment are not added to the undercoat coating solution and the topcoat coating solution, white unevenness occurs remarkably.

Claims (18)

A pigment coating solution containing a blue or purple color material is applied on a multilayer paper base paper containing waste paper pulp, and the b ^* value of the paper measured by the method of JIS P 8150 includes ultraviolet rays. A method for producing a coated white paperboard, comprising making it −10 or more and less than −0.5 in measurement,
The method as described above, wherein the multilayer paper is 10 points or more lower in whiteness of the inner layer than in the surface layer. The method of Claim 1 that a ^* value of the said coated white paperboard is -1 or more and less than 7.   The method according to claim 1, further comprising a smoothing treatment using a super calender after the pigment coating liquid is applied.   The method according to any one of claims 1 to 3, wherein 50% by weight or more of waste paper pulp in the total pulp is blended with the multi-layer base paper. The method according to any one of claims 1 to 4, wherein the multi-layer base paper has a basis weight of 150 g / m ² or more.   The method according to any one of claims 1 to 5, wherein the whiteness of the multilayer paper is 75% or less.   The method according to any one of claims 1 to 6, wherein the whiteness of the multilayer paper is 70% or less.   The method according to any one of claims 1 to 7, comprising applying two or more types of pigment coating liquids, wherein a blue or purple color material is contained in the one or more types of pigment coating liquids.   The method of Claim 8 which mix | blends a blue or purple pigment with the coating liquid of outermost layer.   The method according to claim 8 or 9, wherein the pigment coating layer is applied by a blade coating method. A coated white paperboard with a pigment coating layer containing a blue or purple color material on a multilayer paper base paper containing waste paper pulp,
The b ^* value of the coated white paperboard measured by the method of JIS P 8150 is −10 or more and less than −0.5 in the measurement including ultraviolet rays, and the multilayer paper base paper has an inner side of the whiteness of the surface layer. The above coated white paperboard, wherein the whiteness of the layer is lower by 10 points or more. A of the coated white paperboard ^* The coated white paperboard of Claim 11 whose value is -1 or more and less than 7. The coated white paperboard according to claim 11 or 12, wherein the multilayer base paper contains 50% by weight or more of waste paper pulp in the total pulp. The multilayer base paper is 150 g / m ² The coated white paperboard according to any one of claims 11 to 13, having the above basis weight. The coated white paperboard according to any one of claims 11 to 14, wherein the whiteness of the multilayer base paper is 75% or less. The coated white paperboard according to any one of claims 11 to 15, wherein the whiteness of the multilayer base paper is 70% or less. The coated white paperboard according to any one of claims 11 to 16, further comprising two or more types of pigment coating layers, wherein a blue or purple color material is contained in one or more types of pigment coating layers. The coated white paperboard according to claim 17, wherein a blue or purple pigment is blended in the outermost coating layer.

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