HK1192594A - A coated whiteboard paper - Google Patents

Description

Coated white board paper

Technical Field

The present invention relates to a coated white board, particularly a coated white board using waste paper pulp in a core layer, and more particularly, to a coated white board having a white paper appearance without noticeable white spots on the appearance.

Background

The white board can be printed and used as packaging paper. Therefore, the white board needs to be suitable for printingThe performance should be maintained. Further, white cardboard is white and free from white spots, which is an important problem. The weight of the white board as referred to herein is 150g/m per square meter²The thick paper is generally composed of a multilayer structure of 3 to 9 layers. For example, a multi-layer white board called a face layer, a liner layer, a core layer, a base layer is produced by papermaking. FIG. 1 shows the structure of 1 example of such a white board. Fig. 1 is a cross-sectional view of a white board. In fig. 1, 101 denotes a white board, 110 denotes a surface layer, 120 denotes a backing layer, 130 denotes a core layer, and 140 denotes a bottom layer. Further, the proportions of the layers in FIG. 1 are not necessarily proportional to actual thickness. Specifically, in fig. 1, bleached pulp having a high whiteness is generally used as the surface layer (110) constituting the outermost layer. Waste pulp having a high whiteness is generally used for the liner layer (120) adjacent to the inner side of the surface layer (110) and the bottom layer (140) constituting the inner layer. And the core layer (130) constituting the inner layer is usually made of waste pulp. Typically the waste pulp used in the core layer (130) is dark grey. In order to hide the dark grey color of the core layer, the face and backing layers are typically embossed to produce a high whiteness layer. With this configuration, while reuse of used paper is sought, white cardboard can be obtained. However, even if the surface layer or the under layer is used, the dark gray color of the core layer cannot be sufficiently hidden, and there is a problem that white spots appear in appearance.

Accordingly, a method of reducing white spots of a white board by specifying a weight range per square meter of a surface layer and a liner layer and a difference between a whiteness of the surface layer and a whiteness of the liner layer is disclosed (for example, patent document 1).

Coated white cardboard paper having a pigment coating layer on at least one side of the white cardboard paper is produced for the purpose of imparting printing suitability, improving the whiteness of the surface of the white paper, and improving white spots on the surface of the white paper. As such a coated white board, a method of using an inorganic pigment such as titanium dioxide having a high hiding property in a pigment coating layer has been disclosed (for example, patent document 2). However, a large amount of expensive titanium dioxide must be used, which leads to a problem of high production cost. Further, since the weight per square meter of the white board is large, the difference in weight per square meter of a part is also likely to be large, and when coating is performed using a so-called smoothing coater such as a blade coater or a bar coater, the amount of coating of a part is likely to be varied. Therefore, even if a pigment coating layer containing titanium dioxide and having high hiding properties is provided, white spots on the appearance of the coated white board cannot be eliminated.

[ patent document 1] Japanese patent laid-open No. 2005-298998

[ patent document 2] Japanese patent application laid-open No. 2006-328574

Disclosure of Invention

The invention aims to provide a coated white board which reduces white spots on the surface of the coated white board.

In order to solve the above problem, the present invention adopts the following configuration. That is, the coated white board of the present invention is a coated white board having a multilayer structure including at least a surface layer, a core layer and a back layer, and a pigment coating layer containing an inorganic pigment provided on at least one surface of the white board, wherein the surface layer contains calcium carbonate as the inorganic pigment, the calcium carbonate content of the surface layer is 3 to 20 mass% with respect to the pulp amount of the surface layer, the pigment coating layer is provided on the surface of the surface layer, and heavy calcium carbonate is contained as the inorganic pigment contained in the pigment coating layer. With this configuration, a coated white sheet can be obtained which has a low possibility of paper dust falling off from the paper surface during printing and which has no white spots in appearance.

Further, with respect to the coated white board of the present invention, the content of calcium carbonate of the face layer may be 3% by mass or more and less than 10% by mass with respect to the amount of pulp of the face layer. According to this configuration, it is possible to obtain coated white board paper in which the possibility of paper dust falling off from the paper surface at the time of printing is further reduced.

Further, regarding the coated white board of the present invention, calcium carbonate contained in the face layer may be a BET specific surface area of 6.0m²More than g and less than 10.0m²Light calcium carbonate per gram. With this configuration, a coated white board having little paper dust falling off from the paper surface during printing and having no white spots in appearance can be obtained.

In the coated white paper of the present invention, the calcium carbonate contained in the top layer may be heavy calcium carbonate containing particles having a particle diameter of 2 μm or less in an amount of 70 to less than 95 mass%. With this configuration, coated white paper having high whiteness and no white spots in appearance can be obtained.

In the coated white paper of the present invention, 60 mass% or more of the total inorganic pigment contained in the surface layer and the pigment coating layer provided on the surface of the surface layer may be calcium carbonate. According to the structure, the coated white board paper with high whiteness and no white spots on the appearance can be obtained while the cost is reduced.

According to the present invention, a coated white board can be obtained which has a low possibility of paper dust falling off from the paper surface during printing and which has no white spots on the appearance. This can improve the appearance of the coated white board, and can improve white spots in appearance even when the coated white board provided with the coating layer mainly composed of the pigment is manufactured. In addition, in the production of the coated white board of the present invention, since the pH at the time of papermaking is in the neutral or weakly alkaline range, a large amount of waste paper can be used. That is, in the neutral papermaking of paper and newspaper, calcium carbonate used therein is dissolved in acid papermaking, and therefore, the use of a large amount of waste paper is limited. However, if the paper is made in a neutral or weakly alkaline range like the present invention, such a limitation is not imposed, and a large amount of waste paper can be used.

Detailed Description

The embodiments of the present invention are described in detail below.

The coated white board paper is a multilayer structure formed by papermaking of the following layers in the order of a surface layer/a lining layer/a core layer/a bottom layer, wherein the surface layer contains virgin pulp and high-whiteness bleached waste paper pulp; the liner layer and the bottom layer contain waste pulp having a lower whiteness than pulp contained in the top layer, and the core layer contains waste pulp having a lower whiteness than pulp contained in the liner layer and the bottom layer. Therein, althoughHowever, when the weight per square meter of the surface layer is increased by processing such as increasing the weight per square meter of the surface layer, the structure without the lining layer can be made by simply using the surface layer. 1 example of a coated white board according to the invention is shown in FIG. 2. Fig. 2 is a cross-sectional view of a coated white board according to the present invention. In fig. 2, 10 is a white board, 1 is a face layer, 2 is a liner layer, 3 is a core layer, 4 is a base layer, and 5 is a pigment coating layer. Further, the proportions of the layers in FIG. 2 are not necessarily proportional to actual thickness. As a specific structural example, the coated white board is constituted such that the weight per square meter of the core layer is 50g/m²～500g/m²The whiteness is 35 to 60 percent; the weight per square meter of the backing layer was 20g/m²～80g/m²The whiteness is 55 to 75 percent; the weight of the surface layer per square meter is 15g/m²～60g/m²The whiteness is 70-85%. The structure of the base layer may be changed depending on the application of the coated white board, but may be the same as the structure of the liner layer or the top layer. The pigment coating layer is at least arranged on the surface of the surface layer. Since the coated white board is widely used for covers of books and paper containers, its weight per square meter covers 150g/m²～600g/m²Is large. When the weight per square meter of the coated white board is changed, the number of core layers and the weight per square meter can be mainly selected and changed from the viewpoint of effective use of waste paper and reduction of production cost. Further, depending on the application, coated white board paper having no difference in whiteness between the top and bottom layers is desired, and in this case, the type of pulp used for the raw material of each layer and the weight per square meter of each layer are adjusted so that the top and bottom layers have the same degree of whiteness. For example, when white board having no difference in whiteness of the top sheet and the bottom sheet is obtained by using the same raw material pulp for the top sheet and the bottom sheet, the weight per square meter of the bottom sheet is larger than that of the top sheet because the concealing property of the core layer having lower whiteness must be improved. Alternatively, a base layer having the same structure as the under layer may be provided between the core layer and the under layer, and a structure of face layer/under layer/core layer/base layer/under layer may be formed by papermaking. In addition, in the application that does not require whiteness of one side of the white board, the bottom layer is alsoThe same raw material composition as the backing layer may be used. Further, a pigment coating layer may be provided on the surface of the top layer, the bottom layer, or both of the top layer and the bottom layer. In the case where the pigment coating layers are provided on both surfaces of the top layer and the bottom layer, the difference in whiteness can be provided by changing the coating amounts on one surface and the other surface. These configurations can be appropriately changed according to the application of the coated white board.

The whiteness and white spots in appearance of coated white board paper become more necessary for improvement depending on the use thereof. When used for a hardbound paper container, it is necessary to use a coated white board having high whiteness and little visual white spots. In adjusting the whiteness and the white spots in appearance, this can be achieved mainly by adjusting the weight per square meter of the face layer. The increase in the weight per square meter of the surface layer increases the whiteness, thereby improving white spots, but on the other hand, there is a problem that waste paper cannot be effectively used and the cost cannot be reduced. As the proportion of the surface layer, it is desired to achieve a low weight per square meter, a high whiteness, and a high concealing property so as not to cause a noticeable white spot.

It is known that kaolin, talc, calcium carbonate, titanium, and the like are used as fillers contained in the top layer in order to improve the hiding property of the paper while maintaining the whiteness. Kaolin has a high hiding power but a lower whiteness than calcium carbonate and is also expensive. Talc has a lower whiteness than calcium carbonate and is inferior in hiding property. Titanium is excellent in whiteness and hiding, but its application is difficult because of low yield and high price in the paper-making line. From the viewpoint of whiteness and hiding properties, calcium carbonate is an inexpensive and easy-to-use internal filler.

However, in the coated white board in the past, calcium carbonate is rarely used as a filler contained in the top layer. In particular, in the production of coated white board paper having a pigment coating layer mainly composed of kaolin, calcium carbonate has never been used as an internal filler in the surface layer of the coated white board paper. The reason is that since the pigment coating layer mainly composed of kaolin has high hiding properties, calcium carbonate is not necessarily contained in the surface layer. In addition, when calcium carbonate is contained in the surface layer, the sizing degree of an acidic rosin sizing agent conventionally used as a sizing agent is easily lowered, and a neutral rosin sizing agent is required. In addition, calcium carbonate itself is also likely to cause a decrease in yield as compared with kaolin and talc. Further, it is considered that white water utilizing a waste paper liner is easily affected by blackening, and whiteness and white spots cannot be improved even when calcium carbonate, particularly heavy calcium carbonate having a hiding property similar to that of talc, is used for the surface layer. In spite of these findings, it is surprising that the whiteness and white spots can be improved by adding calcium carbonate having excellent properties of whiteness and hiding property to the top layer in the present invention.

The coated white board of the present invention is characterized in that the surface layer contains calcium carbonate as an inorganic pigment, and the content of the calcium carbonate is 3 to 20 mass% based on the amount of pulp in the surface layer. When the content of calcium carbonate is less than 3% by mass based on the amount of pulp in the surface layer, the improvement of whiteness and covering power due to calcium carbonate are poor, and white spots in appearance cannot be improved. On the other hand, when the content of calcium carbonate is more than 20 mass% based on the amount of the paper pulp in the surface layer, the covering power is improved with the increase of the whiteness, and the white spots in the appearance are remarkably improved, but there is a possibility that the paper dust is peeled off from the paper surface at the time of printing. In the present invention, the calcium carbonate content in the top layer can be set to 3 mass% or more and less than 10 mass%, and a coated white board can be obtained in which no paper dust falls off from the paper surface during printing.

As the calcium carbonate used in the present invention, heavy calcium carbonate and/or light calcium carbonate is preferable. The heavy calcium carbonate is obtained by crushing limestone by a dry method or a wet method. The light calcium carbonate is synthesized by calcining limestone in kiln to obtain lime, adding water for digestion, introducing carbon dioxide, and carbonizing. Although ground calcium carbonate is inferior to light calcium carbonate in whiteness and hiding property, it has higher whiteness than kaolin and talc, and also has improved white spots in appearance. In addition, although ground calcium carbonate is a filler having high line abrasion, it is possible to improve abrasion by wet grinding and reducing the particle size, and it is possible to sufficiently utilize the ground calcium carbonate as an internal filler in a papermaking process at a relatively low papermaking speed. Light calcium carbonate has higher whiteness and hiding properties than heavy calcium carbonate, and is low in line abrasion, so that light calcium carbonate can be suitably used as an internal filler.

In the coated white paper of the present invention, the calcium carbonate contained in the surface layer has a specific surface area of 6.0m as measured by the BET method²More than g and less than 10.0m²Light calcium carbonate per gram. The BET specific surface area of the light calcium carbonate is less than 6.0m²At/g, the effect of improving white spots in appearance tends to be small. BET specific surface area of 10.0m²Although the white spot improving effect of the light calcium carbonate of the concentration of the calcium carbonate is remarkable, the strength of the paper layer is also reduced due to the reduction of the particle size of the light calcium carbonate, and therefore, paper dust may be peeled off from the paper surface during printing.

In the coated white paper of the present invention, the calcium carbonate contained in the top layer may be a heavy calcium carbonate containing 70 mass% or more and less than 95 mass% of particles having a particle diameter of 2 μm or less. When the proportion of the heavy calcium carbonate having a particle size of 2 μm or less is less than 70% by mass, the whiteness may be improved or reduced, and white spots may not be sufficiently improved. On the other hand, if the ratio exceeds 95 mass%, the improvement of white spots is good, but the strength of the paper layer is also reduced due to the reduction of the particle size, and therefore paper dust may be detached from the paper surface during printing. As described above, heavy calcium carbonate contained in the surface layer is preferably ground by a wet grinding process in view of the abrasion resistance of the production line. Since the ground calcium carbonate treated by wet grinding tends to have a sharper particle size distribution than that of the ground calcium carbonate treated by dry grinding, handling is easy and the abrasion resistance of the production line can be improved.

In the coated white paper of the present invention, calcium carbonate is contained in both the surface layer and the pigment coating layer provided on the surface layer. The surface layer and the pigment coating layer may each contain an inorganic pigment other than calcium carbonate, but the weight of calcium carbonate is preferably 60 mass% or more based on the total inorganic pigment contained in the surface layer and the pigment coating layer. With this configuration, coated white board having high whiteness and no white spots can be produced at low cost.

The raw material pulp used for the top sheet of the present invention is not particularly limited. For example, bleached hardwood kraft pulp (L-BKP) mainly derived from natural pulp such as wood fiber, bast fiber, and bast fiber can be used as the main component. Specific examples of the wood pulp include bleached softwood kraft pulp (N-BKP), bleached softwood sulfite pulp (N-BSP), and bleached hardwood sulfite pulp (L-BSP). Further, mechanical pulp (GP), chemithermomechanical pulp (CTMP), deinked pulp (DIP) can be mixed in any ratio depending on the application. Although waste pulp can be used, it is necessary to use high-whiteness quality waste pulp or the like or to use a small amount thereof in order to avoid lowering the whiteness. In the present invention, for example, the bleached hardwood kraft pulp (L-BKP) can be contained in an amount of 70 mass% or more, for example, 75 to 98 mass% in the whole pulp. Further, the drainability (Canadian Standard freeness, CSF) of the pulp is preferably adjusted to a range of 250 to 600 cc.

In the liner layer, waste pulp having a lower whiteness than the top layer pulp is used, and in the core layer, waste pulp having a lower whiteness is used, but the drainability of the pulp is not particularly limited. The filler is not particularly limited as long as it is added within a range in which the strength of the paper layer is not reduced. The composition of the base layer may be appropriately changed depending on the application of the coated white board, and may have the same composition as the liner layer or the top layer.

Coagulant aids, paper strength enhancers, coloring and odor-imparting dyes, coloring and odor-imparting pigments, sizing agents may be used in the top layer, under layer, core layer and under layer within the range not to impair the effects of the present invention. In addition, a yield improving agent, a drainage improving agent, and a defoaming agent may be appropriately used in order to improve the workability in papermaking. For example, in the present invention, the additive may be added in an amount of 0.001 to 5 mass% based on the amount of the pulp in the top sheet. Specifically, aluminum sulfate is used as the coagulant aid, and in the present invention, for example, 0.01 to 2 mass% of the amount of the pulp in the top layer may be added. The paper strength enhancer may be polyacrylamide, and in the present invention, for example, 0.01 to 2 mass% of the amount of the paper pulp in the top layer may be added. The sizing agent is a neutral rosin, and may be added in an amount of 0.01 to 2 mass% based on the amount of the paper pulp in the top layer.

The surface layer, the lining layer, the core layer and the bottom layer are respectively made by papermaking, and then the white board paper which forms the coated white board paper base paper is produced by papermaking. In this case, the paper is preferably made under neutral or weakly alkaline conditions, for example, at pH6.8 to 8.5. The paper-making method may be a known paper-making method such as a long-wire method or a cylinder-wire method. A pigment coating layer is provided for the purpose of imparting printing suitability to such a white board. The pigment coating layer is formed by coating and drying a coating material composed of a pigment and a binder.

The inorganic pigment in the pigment coating layer contains ground calcium carbonate. In addition, although known and commonly used pigments such as clay, light calcium carbonate, titanium dioxide, plastic pigment, and the like can be used in combination as appropriate, heavy calcium carbonate is mainly preferably used. Even if the solid content of the coating material in the pigment coating layer is 64 mass% or more, the ground calcium carbonate in the pigment may be used in an amount of at least 60 mass%, preferably 65 to 95 mass%, in order to improve the fluidity and suppress the occurrence of streaks. The ground calcium carbonate used herein is preferably ground calcium carbonate obtained by wet grinding because it has a sharper particle size distribution than ground calcium carbonate obtained by dry grinding and is easy to handle.

Examples of the binder in the pigment coating layer include conjugated diene polymer rubbers such as styrene-butadiene copolymer rubber (SBR) and methyl methacrylate-butadiene copolymer rubber, and cellulose derivatives such as polyvinyl alcohol, oxidized starch, carboxymethyl cellulose and hydroxyethyl cellulose, and may be used singly or in combination of 2 or more. The binder may be used in an amount of, for example, 5 to 30 parts by weight based on 100 parts by weight of the pigment.

Further, as necessary, a dispersant, a pH adjuster such as caustic soda or aqueous ammonia, an antifoaming agent, a coloring dye/pigment, a water repellent, a flow modifier, and the like can be suitably used for the coating material used for the pigment coating layer.

The pigment coating layer on the white board constituting the base paper is generally formed of a lower coating layer and an upper coating layer 2, but may be a single layer or 3 or more layers. The pigment coating layer is usually applied in an amount of 5g/m per average dry mass²～15g/m²The range of (1). For example, in the case of a pigment coating layer provided as 2 layers, the coating weight of the under-coating layer is 5g/m in terms of dry mass²～15g/m²The coating is carried out in the range of 5g/m²～13g/m²Coating is performed within the range of (1). In addition, in order to prevent curling from occurring on the surface of the white board base layer, a dry mass in the range of 1g/m may be set²～15g/m²The single-layer coating layer of (3) may be a pigment coating layer or a coating layer mainly composed of a binder containing no pigment. In particular, when the bottom layer is formed into a layer containing waste paper, a coating layer may be provided on the surface of the bottom layer in order to hide impurities derived from waste paper contained in the layer and prevent the impurities from falling off.

The coating machine for forming the coating layer is not limited, and roll coating machines such as an air knife coater, a rod coater (rod coater), a curtain coater, a gate roll coater, and a screen coater may be used in combination as appropriate. When two or more coating layers are provided, a bar coater is preferably used as the lower coating forming device, and a bar coater or a blade coater is preferably used as the upper coating forming device. The coating may be performed separately, for example, by using a bar coater as the coating layer constituting the lowermost layer, a bar coater as the second coating layer constituting the intermediate layer, and a knife coater as the third coating layer constituting the outermost layer.

Examples

The present invention will be described in more detail with reference to examples below, but it is needless to say that the present invention is not limited to these examples. In the following examples and comparative examples, parts and% represent parts by mass of solid content and% by mass of solid content, respectively.

Each evaluation method was carried out in the following manner.

1) Measurement of whiteness

In compliance with ISO 2470: 1999 Paper, board and boards-Measurement of pigment blue reflection factor (ISO brightness) measured the pigment coating layer provided on the surface of the face layer.

2) Determination of BET specific surface area of light calcium carbonate

The measurement was carried out by the nitrogen adsorption method (TriStar II 3020, manufactured by Micromeritics).

3) Determination of particle size of wet ground calcium carbonate

The cumulative mass% of the particle diameter of 2 μm or less was measured by a laser beam diffraction/scattering particle size distribution measuring apparatus (LA-920/horiba, Ltd.).

4) White spot

The white spots on the pigment coated face layer provided on the face layer surface were evaluated by visual inspection using 5 grades. Of the 5 grades, the good case in which white spots were not observed at all was evaluated as 5, and the most severe case was evaluated as 1. Among 5 grades, the evaluation is 3-5, the grade is judged to be qualified, and the grade has no problem in actual application; the evaluation was 1 or 2, and the white spot was serious, and thus the film was judged as a defective film.

5) Evaluation of paper dust falling during printing

The degree of separation of the paper powder was visually evaluated by printing on the surface of the pigment-coated layer provided on the surface of the top layer at 60rpm using an RI printing tester manufactured by Mingkudu, SMX-25 black ink manufactured by Toyo ink K.K.K., 0.4 cc. Evaluation was performed in 4 grades. Among the 4 grades, the good condition that no paper dust fall off was observed at all was evaluated as 4; the occurrence of a large amount of paper dust falling was evaluated as 1. Among the 4 levels, the evaluation value is 2-4, the evaluation value is judged to be qualified, and the evaluation value is a level without problems in actual application; the evaluation value was 1, and a large amount of paper dust was dropped, and thus the paper was judged as defective.

Examples

< preparation of coating Material for undercoating layer >

20 parts of kaolin (hydraspese manufactured by KEIMIN corporation), 80 parts of wet ground calcium carbonate (carbobital 60 manufactured by impays Minerals Japan k.k., ltd.), 15 parts of styrene-butadiene polymer rubber, and 3 parts of phosphated starch were dispersed in water to obtain a coating material for an under-coating layer having a solid content of 64 mass%.

< preparation of coating Material for Upper coating layer >

30 parts of kaolin (manufactured by CADAM corporation, Amazon SB), 60 parts of wet ground calcium carbonate (ejection Minerals Japan K.K. manufactured carbital 90), 10 parts of titanium dioxide (DuPont Co., Ltd. manufactured RPS-Vantage) and 15 parts of styrene-butadiene polymer rubber were dispersed in water to obtain a coating material for an upper coating layer having a solid content of 64 mass%.

(example 1)

A flow slurry was prepared by dispersing 90 parts of hardwood pulp (L-BKP) and 10 parts of softwood pulp (N-BKP) in water to CSF350cc, and a light calcium carbonate (trade name: TP 121-6S/Audo Mol, Ltd., BET specific surface area of 7.0 m) was mixed with the flow slurry in an amount of 4% based on the amount of the pulp²Per g) the starting material for the top layer is obtained. Then dispersing unbleached deinked and bleached waste paper pulp in water to obtain the raw materials of the lining layer and the bottom layer. Then dispersing the deinking waste journal pulp in water to obtain the raw material of the core layer. Adopting a fourdrinier paper machine to make paper by using various raw materials under the condition of pH7.7, wherein the paper is composed of 4 layers of surface layer/lining layer/core layer/bottom layer, and the weight per square meter is 310g/m²The white board of (1). Of the resulting white boardThe weight per square meter of the surface layer is 25g/m²The whiteness is 78%; the weight per square meter of the backing layer was 40g/m²The whiteness is 66%; the weight per square meter of the core layer was 190g/m²The whiteness is 55%; the weight per square meter of the bottom layer was 55g/m²The whiteness was 66%. Polyacrylamide as a paper strength enhancer and aluminum sulfate as a coagulant aid, and neutral rosin as a sizing agent are added to the top layer, wherein the amount of polyacrylamide added is 0.2% of the amount of pulp in the top layer, the amount of aluminum sulfate added is 0.2% of the amount of pulp in the top layer, and the amount of neutral rosin added is 0.3% of the amount of pulp in the top layer. Starch was added as a paper strength enhancer to the liner layer, core layer and bottom layer in an amount of 0.2% based on the amount of each layer of pulp. The surface of the top layer of the white board paper obtained as described above was provided with a pigment coating layer constituting a lower layer, the pigment coating layer being obtained by applying a coating material for the lower coating layer to a solid content of 10g/m by means of a bar coater²And drying the mixture. Then, a pigment coating layer constituting an upper layer was provided on the surface of the pigment coating layer constituting the lower layer, and the coating layer for coating the upper layer was coated with a coating material for coating layer using a blade coater so that the solid content was 10g/m, thereby obtaining a coated white sheet²And drying the mixture.

(example 2)

Light calcium carbonate (trade name: TP 121-6S/Audo Moore Kabushiki Kaisha BET specific surface area of 7.0 m) mixed in a white board surface layer raw material²Coated white board paper was obtained in the same manner as in example 1 except that the amount of the aqueous solution was changed to 9% based on the amount of the pulp.

(example 3)

The calcium carbonate mixed in the white board paper surface layer raw material is changed into light calcium carbonate (the ABET specific surface area of a test product is 9.5 m)²(g) except for this, a coated white paper was obtained in the same manner as in example 1.

(example 4)

The calcium carbonate mixed in the white board paper surface layer raw material is changed into light calcium carbonate (BBET specific surface area of a test product is 6.0 m)²(g) was prepared into coated white board by the same method as in example 1 except that the amount of the additive was 9% based on the amount of the pulp.

(example 5)

Light calcium carbonate (trade name: TP 121-6S/Audo Moore Kabushiki Kaisha BET specific surface area of 7.0 m) mixed in a white board surface layer raw material²Coated white cardboard was obtained in the same manner as in example 1 except that the amount of the additive was 10.5% based on the amount of the pulp.

(example 6)

The calcium carbonate mixed in the white board paper surface layer raw material is changed into light calcium carbonate (the CBET specific surface area of a test product is 5.0 m)²(g) was prepared into coated white board by the same method as in example 1 except that the amount of the additive was 9% based on the amount of the pulp.

(example 7)

The calcium carbonate mixed in the white board paper surface layer raw material is changed into light calcium carbonate (the DBET specific surface area of a test product is 11.0 m)²(g) was prepared into coated white board by the same method as in example 1 except that the amount of the additive was 9% based on the amount of the pulp.

(example 8)

The calcium carbonate mixed in the white board paper surface layer raw material is changed into light calcium carbonate (the CBET specific surface area of a test product is 5.0 m)²(g) was prepared into coated white board by the same method as in example 1 except that the amount of the additive was 3% based on the amount of the pulp.

(example 9)

The calcium carbonate mixed in the white board paper surface layer raw material is changed into light calcium carbonate (the DBET specific surface area of a test product is 11.0 m)²(g) was prepared into coated white board by the same method as in example 1 except that the amount of the additive was 20% based on the amount of the pulp.

(example 10)

On the surface of the base layer of the coated white board obtained in example 1, a coating material for an under-coating layer was applied using a blade coater so that the solid content was 10g/m²And drying to set the pigment coating layer to obtain the coated white paperboard with the pigment coating layers on the two layers of the surface layer and the bottom layer.

(example 11)

Using the respective raw materials in example 1, the weight per square meter consisting of the surface layer/core layer/bottom layer 3 layers was 350g/m by papermaking using a fourdrinier machine²The weight per square meter of the face layer of the white board paper is 55g/m²The weight per square meter of the core layer is 220g/m²The weight per square meter of the bottom layer was 75g/m²Otherwise, a coated white board was obtained by papermaking in the same manner as in example 1.

(example 12)

On the surface of the base layer of the coated white board obtained in example 11, a coating material for an under-coating layer was applied by a blade coater so that the solid content was 10g/m²And drying to set the pigment coating layer to obtain the coated white paperboard with the pigment coating layers on the two layers of the surface layer and the bottom layer.

(example 13)

60 parts of high-quality waste pulp, 30 parts of hardwood pulp (L-BKP) and 10 parts of softwood pulp (N-BKP) were dispersed in water, adjusted to CSF350cc to obtain a slurry, and wet-milled ground calcium carbonate (trade name: calcium 90/Imerys Minerals Japan K.K. manufactured with a particle size of 2 μm or less at a particle content ratio of 90 mass%) in an amount of 7% relative to the amount of the pulp was mixed with the slurry to obtain a raw material for the top layer. And dispersing unbleached deinked and bleached waste newspaper pulp in water to obtain the raw material of the lining. Then dispersing the deinking waste journal pulp in water to obtain the raw material of the core layer. And dispersing unbleached deinked and bleached waste newspaper pulp in water to obtain a raw material of a bottom layer. Adopting a fourdrinier paper machine to make 4 layers of surface layer/lining layer/core layer/bottom layer by using various raw materials under the condition of pH7.5The weight per square meter of the composition is 260g/m²The white board of (1). The weight per square meter of the surface layer of the obtained white board paper is 30g/m²The whiteness is 78%; the weight per square meter of the backing layer was 45g/m²The whiteness is 60%; the weight per square meter of the core layer was 140g/m²The whiteness is 50%; the weight per square meter of the bottom layer was 45g/m²The whiteness is 60%. Polyacrylamide as a paper strength enhancer and aluminum sulfate as a coagulant aid, and neutral rosin as a sizing agent are added to the top layer, wherein the amount of polyacrylamide added is 0.2% of the amount of pulp in the top layer, the amount of aluminum sulfate added is 0.3% of the amount of pulp in the top layer, and the amount of neutral rosin added is 0.3% of the amount of pulp in the top layer. Starch was added as a paper strength enhancer to the liner layer, core layer and bottom layer in an amount of 0.2% based on the amount of each layer of pulp. On the surface of the top layer of the white board obtained as described above, a pigment coating layer constituting a lower layer was provided, the pigment coating layer being formed by applying a coating material for the lower coating layer by a bar coater so that the solid content was 10g/m²And drying the mixture. Then, a pigment coating layer constituting an upper layer was provided on the surface of the pigment coating layer constituting the lower layer, and the coating layer for coating the upper layer was coated with a coating material for coating layer using a blade coater so that the solid content was 10g/m, thereby obtaining a coated white sheet²And drying the mixture.

(example 14)

Coated white board paper was obtained in the same manner as in example 13 except that wet ground calcium carbonate (trade name: calcium 90/Imperys Minerals Japan K.K. 90% by mass of the content of particles having a particle size of 2 μm or less) mixed with the surface material of the white board was added to 9% based on the amount of pulp.

(example 15)

Coated white board paper was produced in the same manner as in example 13 except that wet ground calcium carbonate (trade name: calcium 90/Imperys Minerals Japan K.K. 90% by mass of particles having a particle size of 2 μm or less) mixed with the surface layer material of the white board was added to the resulting mixture in an amount of 4% by mass based on the amount of pulp.

(example 16)

Coated white paper was obtained in the same manner as in example 13 except that the calcium carbonate mixed in the surface layer material of white paper was changed to wet ground heavy calcium carbonate (the content of particles having a particle size of 2 μm or less in the sample X was 75% by mass).

(example 17)

Coated white paper was obtained in the same manner as in example 13 except that the calcium carbonate mixed in the surface layer material of white paper was changed to wet ground heavy calcium carbonate (the content of particles having a particle diameter of 2 μm or less in the sample product Y was 93% by mass).

(example 18)

Coated white board paper was prepared in the same manner as in example 13 except that wet ground calcium carbonate (trade name: calcium 90/Imprys Minerals Japan K.K. 90% by mass of particles having a particle size of 2 μm or less) mixed with the surface layer material of the white board was added to 11% of the amount of pulp, and the resulting mixture was subjected to papermaking in the same manner as in example 13 to obtain coated white board paper

(example 19)

Coated white paper was obtained in the same manner as in example 13 except that the amount of calcium carbonate mixed in the surface layer material of white paper was changed to wet-ground heavy calcium carbonate (the content of particles having a particle size of 2 μm or less in the sample Z was 65% by mass), and the amount added was 3% based on the amount of pulp.

(example 20)

Coated white board paper was produced in the same manner as in example 13 except that wet ground calcium carbonate (trade name: calcium 90/Imperys Minerals Japan K.K. 90% by mass of particles having a particle size of 2 μm or less) mixed with the surface layer material of the white board was added to the pulp in an amount of 20% by mass.

Comparative example 1

Light calcium carbonate (trade name: TP 121-6S/Audo Moore Kabushiki Kaisha BET specific surface area of 7.0 m) mixed in a white board surface layer raw material²Coated white board paper was obtained in the same manner as in example 1 except that talc was used instead of talc in an amount of 10% based on the amount of the pulp.

Comparative example 2

Light calcium carbonate (trade name: TP 121-6S/Audo Moore Kabushiki Kaisha BET specific surface area of 7.0 m) mixed in a white board surface layer raw material²Coated white cardboard was obtained in the same manner as in example 1 except that the amount of the additive was 2% based on the amount of the pulp.

Comparative example 3

Coated white board paper was obtained in the same manner as in example 13 except that wet ground calcium carbonate (trade name: calcium 90/Imperys Minerals Japan K.K. 90% by mass of the content of particles having a particle size of 2 μm or less) mixed with the surface material of the white board was added to the pulp in an amount of 2% by mass.

Comparative example 4

Light calcium carbonate (trade name: TP 121-6S/Audo Moore Kabushiki Kaisha BET specific surface area of 7.0 m) mixed in a white board surface layer raw material²Coated white board paper was obtained in the same manner as in example 1 except that the amount of the additive/g) was 25% based on the amount of the pulp.

Comparative example 5

Coated white board paper was produced in the same manner as in example 13 except that wet ground calcium carbonate (trade name: calcium 90/Imperys Minerals Japan K.K. 90% by mass of the content of particles having a particle size of 2 μm or less) mixed with the surface material of the white board was added to 25% of the amount of the pulp.

The evaluation results of the white board or coated white board obtained in each of examples and comparative examples are shown in table 1. As is clear from table 1, the coated white sheets obtained in examples 1 to 20 were difficult to observe white spots, had good visual observation results, and could satisfy the requirement of paper dust falling during printing.

The coated white board obtained in example 8 had a low whiteness and a large white spot in appearance, compared with other examples, because the coated white board had a relatively small amount of light calcium carbonate added to the surface layer and a small BET specific surface area of the light calcium carbonate used, but it was still of a level that had no problem in practical use.

The coated white board obtained in example 9 had a large amount of precipitated calcium carbonate added to the surface layer and a large BET specific surface area of precipitated calcium carbonate used, and therefore, the paper dust falling phenomenon during printing was serious as compared with other examples, but it was still of a level that had no problem in practical use.

The coated white board obtained in example 19 had a low degree of whiteness and a high degree of white spots in appearance, compared with other examples, because the amount of ground calcium carbonate added to the surface layer was relatively small and the content of particles having a particle size of 2 μm or less was low.

The coated white sheet obtained in example 20 had a large amount of ground calcium carbonate added to the surface layer and a high content of particles having a particle size of 2 μm or less, and therefore, the paper dust falling phenomenon during printing was serious as compared with other examples, but it was still of a level that had no problem in practical use.

The coated white board obtained in comparative example 1 had a low whiteness and a large white spot at a ratio of the amount of addition, because talc was used as an inorganic pigment contained in the surface layer, and thus it was not practical.

The coated white sheets obtained in comparative examples 2 and 3 had insufficient hiding property of the surface layer due to an excessively small amount of calcium carbonate added to the surface layer, and thus had low whiteness and severe white spots, which were not satisfactory for practical use.

The coated white sheets obtained in comparative examples 4 and 5 had an excessive amount of calcium carbonate added to the surface layer, and therefore, the sheets had a significant paper dust falling off during printing, and thus, they could not be used practically.

Claims (5)

1. A coated white board comprising a white board having a multilayer structure comprising at least a top sheet, a back sheet, a core sheet and a back sheet, and a pigment-coated layer containing an inorganic pigment provided on at least one side of the white board,

the facing layer contains calcium carbonate as an inorganic pigment;

the content of the calcium carbonate in the surface layer is 3-20% by mass relative to the amount of the pulp in the surface layer;

the pigment coating layer is arranged on the surface of the surface layer;

the inorganic pigment contained in the pigment coating layer contains ground calcium carbonate.

2. The coated white board according to claim 1, wherein the calcium carbonate content of the face layer is 3% by mass or more and less than 10% by mass relative to the amount of pulp of the face layer.

3. The coated white board according to claim 1 or 2, wherein the calcium carbonate contained in the top layer has a BET specific surface area of 6.0m²More than g and less than 10.0m²Light calcium carbonate per gram.

4. The coated white paper according to claim 1 or 2, wherein the calcium carbonate contained in the top layer is a ground calcium carbonate containing 70 mass% or more and less than 95 mass% of particles having a particle diameter of 2 μm or less.

5. The coated white board according to any one of claims 1 to 4, wherein at least 60 mass% of the total inorganic pigment contained in the surface layer and the pigment coating layer provided on the surface of the surface layer is calcium carbonate.