JP2009293139A - Paperboard for printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost paperboard for printing, which has high ink adhesive strength, high printing gloss and high bond strength of coated layer to the paperboard. <P>SOLUTION: Base paper 1 comprises a plurality of layers. A surface layer 3 to be brought into contact with the coated layer 2 comprises needle-leaf tree pulp and an inorganic pigment in a specific ratio. A coating agent containing a styrene-based resin is applied to the base paper to form the coated layer. A paper density as the whole paperboard for printing is adjusted to a specific range. The coated layer has a coated amount of ≥0.1 g/m<SP>2</SP>and ≤0.8 g/m<SP>2</SP>in a dry state on at least one surface of the base paper. The coating agent of the coated layer contains a styrene-based resin, the surface layer of the base paper to be brought into contact with the coated layer comprises ≥5 wt.% and ≤50 wt.% of needle-leaf tree pulp in raw material pulp, the amount of the inorganic pigment is ≥3 wt.% and ≤20 wt.% and the paper density as the whole paperboard for printing is ≥0.8 g/cm<SP>3</SP>and ≤1.1 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printing board used for printing purposes, and more particularly to a printing board that achieves both ink adhesion and printing gloss.

  Conventionally, printing board used for printing is coated with acrylic resin or styrene resin, which is difficult to dissolve in ink solvent, on the surface to increase printing gloss, so that ink does not easily penetrate into the paper layer. It has been known. Also known is a coated paper in which a coating layer comprising an inorganic pigment such as clay and a binder is formed on the surface of the base paper.

  In addition, for use in both offset printing and gravure printing, printing with an overcoating layer comprising an inorganic pigment containing calcined kaolin, a binder pigment, and a binder resin on an undercoating layer comprising calcium carbonate and a binder resin White paperboard is also known (see, for example, Patent Document 1).

  In addition, in order to prevent halftone dot loss during gravure printing and to improve water resistance during offset printing, a predetermined amount of a sizing agent having a zeta potential in a predetermined range, such as an alkyl ketene dimer, is added to the coating layer, thereby increasing wet strength. A white board for printing with improved surface processing and printing characteristics is also known (see, for example, Patent Document 2).

  In addition, in the coating liner (paperboard), in order to prevent the loss of halftone dots during gravure printing and to ensure white paper and printing gloss, fired clay, structured kaolin or delaminated clay, and organic pigment on the surface of the base paper And a coating liner provided with a coating layer made of latex and a pigment containing 70% by weight or more of these components as a whole (for example, Patent Document 3, (See Patent Document 4).

In addition, a printing paper board provided with a coating layer made of an acrylic resin or a styrene resin, an organic pigment, and latex for improving printing gloss and ink adhesion is also known (for example, Patent Document 5).
JP-A-6-65898 JP-A-11-269798 Japanese Patent Application Laid-Open No. 11-279989 JP 2002-363877 A JP 2006-322081 A

  However, in the case of a paperboard in which the paper surface is coated with a styrene-based resin in order to ensure printing gloss, the ink does not penetrate into the paper layer, so that it is difficult to perform melt adhesion necessary for ink adhesion. Although bonding by hydrogen bonding can be considered instead of melt bonding, the coating agent has no hydroxyl group, so that hydrogen bonding hardly occurs, and there is a problem that printing is easily peeled off due to insufficient ink adhesion. In particular, in the ink using nitrified cotton resin, the adhesive force of the ink is steadily deteriorated.

  Further, the coated paper coated with a coating agent containing an inorganic pigment has a problem that the coating layer is easily peeled off from the base paper. In this regard, the white paperboard for printing (coated paper) disclosed in Patent Document 1 and Patent Document 2 is also a paperboard having a coating layer containing an inorganic pigment on the base paper, so that the coating layer is formed from the base paper. There is a problem that it is easy to peel off.

  Here, the invention disclosed in Patent Document 1 relates to white paperboard for both offset printing and gravure printing, and does not sufficiently satisfy gravure printing suitability. In addition, it is used for decorative boxes and soap boxes as usage, and it is not used by laminating a plurality of papers with the core, outer layer, and inner layer like cardboard, but when folding the finished sheet, There is a problem that the coat layer cracks. The same applies to the invention of the coated paper disclosed in Patent Document 2.

On the other hand, the coating liner disclosed in Patent Document 3 has a coating amount of 3 to 12 g / m ² .
The coated white paperboard disclosed in Patent Document 4 has a coating amount of 8 to 12 g / m ² (total of two layers), and both have a problem that ruled line cracking is likely to occur because the coating amount is large. is there. In addition, the inventions disclosed in Patent Document 3 and Patent Document 4 are designed to improve the gravure printing suitability as a coating liner, to prevent omission of halftone dots and to improve blank paper and printing gloss. The paint formulation has been studied, and when used on the outer layer side for corrugated cardboard where a plurality of papers are bonded, it does not satisfy the ruled line cracking resistance.

  Further, the printing paperboard disclosed in the above document 5 is provided with a coating layer containing an acrylic resin or a styrene resin, latex, and an organic pigment on the front surface or the back surface of the base paper. Since the resin is easily dissolved in the ink solvent, the coating layer easily absorbs the ink, and the ink adhesion is improved, but the printing gloss may be lowered.

  The present invention solves the above-mentioned problems of the prior art, exerts ruled line cracking resistance even when used for corrugated cardboard, has no printing omission due to missing inorganic substances and fine fibers, and obtains high printing gloss. It is an object to provide a printing board suitable for gravure printing.

  For the base paper composed of a plurality of layers, the present inventors blended a specific ratio of softwood pulp and inorganic pigment in the surface layer in contact with the coating layer, and coated with a coating agent containing a styrenic resin thereon Thus, the present inventors have found that the above problem can be solved by providing a coating layer and adjusting the paper density of the printing board as a whole to a specific range, thereby completing the present invention.

Specifically, the present invention
A printing board having a base paper composed of a plurality of layers and a coating layer,
The coating layer is applied on at least one surface layer of the base paper in a dry state with a coating amount of 0.1 g / m ² or more and 0.8 g / m ² or less,
The coating agent for the coating layer contains a styrene resin,
The surface layer of the base paper in contact with the coating layer contains 5% to 50% by weight of softwood pulp in the raw material pulp, and 3% to 20% by weight of inorganic pigment. Has been
The present invention relates to a printing paperboard, wherein the paper density of the printing paperboard as a whole is adjusted to 0.8 g / cm ³ or more and 1.1 g / cm ³ or less.

  In the printing paperboard of the present invention, 5 to 50% by weight of softwood pulp is blended in the raw material pulp of the base paper surface layer in contact with the coating layer, and the inorganic pigment is in the range of 3 to 20% by weight. In addition, the bonding of the outermost pulp fibers is strong, and it is possible to prevent ruled cracks and to prevent the loss of fine fibers and inorganic substances. Also, by blending 3 wt% or more and 20 wt% of inorganic pigment in the outermost layer of the base paper, it is possible to seal between the pulp fibers of the base paper surface layer in contact with the coating layer, improving opacity and improving the printing surface. Smoothing can be achieved. Moreover, high printing gloss can be obtained by containing a styrene resin in the coating agent.

The coating amount of the coating layer is 0.1 g / m ² or more and 0.8 g / m ² or less in the dry state of the coating layer (that is, the state of the coating layer formed on the base paper). This is because if the amount is less than 0.1 g / m ² , the above-described effects cannot be exhibited sufficiently, while if it exceeds 0.8 g / m ² , the amount of the coating agent used increases and the production cost increases.

In addition, after coating the coating layer on at least one surface layer of the base paper, the coating agent is adjusted by adjusting the paper density of the entire printing board to 0.8 g / cm ³ or more and 1.1 g / cm ³ or less. It becomes difficult to be absorbed into the base paper. For this reason, it is possible to reduce the coating amount of the coating agent, and the coating layer can be made thin and smooth. The same applies to the case where the coating layer is applied to both surface layers of the base paper.

  Since softwood pulp is soft and easily crushed when calendered, calendering the base paper consisting of multiple layers before applying the coating layer further flattens the surface of the base paper. It becomes possible to apply the work layer more uniformly.

  The coating agent preferably further contains latex and an organic pigment. Latex has an appropriate film-forming property, is flexible and has good ink deposition properties, and, when combined with an organic pigment, exhibits an effect of preventing the printing board from being raised from the middle layer. Moreover, the ruled line cracking prevention effect increases by including latex and an organic pigment in a coating agent. Organic pigments are more preferable than inorganic pigments in terms of printability because particles have elasticity and gloss compared to inorganic pigments.

  As the inorganic pigment, mineral pigments such as clay, kaolin, calcium, silica and the like can be used in general. However, the deinking floss discharged in the deinking process of the used paper processing process for producing the used paper pulp is calcined as a main raw material. The aggregate is preferably a composite aggregate containing calcium, silicon and aluminum.

  The blending ratio in the coating agent is preferably 4% to 30% by weight of styrene resin, 10% to 48% by weight of latex, and 10% to 70% by weight of organic pigment.

  The printing paperboard of the present invention has no cracks, has high print gloss, and has printability without ink loss or blurring. Further, since the thickness of the coating layer is thin, the ink easily penetrates into the base paper, and the ink adhesion is high. Furthermore, even in the case of bonding with a hot melt adhesive, neither the printing nor the coating layer is peeled off, which is suitable for gravure printing.

  Hereinafter, the printing paperboard of the present invention will be described in detail. The present invention is not limited to the following description.

  The printing paperboard of the present invention has a base paper composed of a plurality of layers, and a coating layer coated on at least one surface of the base paper. The base paper is composed of, for example, a plurality of layers manufactured by a method such as combining two to seven layers of wet paper. The coating layer may be applied only to one side of the base paper or may be applied to both sides depending on the use of the printing board.

  FIG. 1 shows a cross-sectional view of a printing paper board having a base paper 1 composed of five layers and a coating layer 2 coated on one surface of the base paper. The base paper 1 includes a surface layer 3, a surface lower layer 4, a center layer 5, a back surface lower layer 6, and a back surface layer 7. In this figure, the surface layer 3 is in contact with the coating layer 2.

  In the surface layer 3, softwood pulp is blended in the raw material pulp in an amount of 5 wt% to 50 wt%, and the inorganic pigment is blended in a range of 3 wt% to 20 wt%. The raw materials of the four layers other than the surface layer are not limited, but in general, the wet paper of the lower surface lower layer 4 and the lower back surface layer 6 is appropriately made of medium white old paper or the like consisting of white waste of upper white used paper and coated paper. The main layer 5 and the back layer 7 are mainly used waste paper, such as white balls made from paper, newspapers, magazines, etc. Paper is made using raw material pulp. Such a five-layered base paper can be made by sequentially combining wet paper of each layer with a long net multilayer paper machine or the like.

  Each layer of wet paper is formed by feeding a raw slurry from an inlet onto a respective net or wire. The surface layer 3 in contact with the coating layer 2 is preferably 5% by weight or more and 50% by weight or less, more preferably 10% by weight or more and 30% by weight or less, as a percentage by weight with respect to the whole raw pulp. . If it is less than 5% by weight, ruled cracks are likely to occur due to a decrease in long fiber pulp. If it exceeds 50% by weight, there is too much long fiber pulp, and the surface layer 3 cannot be uniformly ground, resulting in poor printing. It is because it causes.

  The inorganic pigment added to the raw material pulp of the surface layer 3 is preferably 3% by weight or more and 20% by weight or less, and more preferably 5% by weight or more and 15% by weight or less. If the amount is less than 3% by weight, the gap between the pulp fibers is not sufficient, which leads to a decrease in printing gloss and the like. This is because the fiber bond is lowered, resulting in a decrease in paper strength and a cause of ruled cracks.

The basis weight of the base paper is preferably 100 g / m ² or more and 500 g / m ² or less. If it is less than 100 g / m ^2, when used in a cardboard applications, there is a problem compressive strength of the case is lower, when it exceeds 500 g / m ^2, the sheet thickness becomes large, when the bending stress of the surface This is because it becomes too strong, and the problem arises that the surface coating layer and the surface layer are cracked.

  The wet paper formed on the wire is dried by a press part and a dryer part. Thereafter, the coating layer 2 is applied on the surface layer 3. At this time, after the surface treatment of the base paper with the calendar part before coating, the coating agent is coated on the surface layer 3, in order to coat the coating layer uniformly and smoothly, More preferred.

  As the styrenic resin used for the coating agent, for example, trade name “Polymalon 351S” manufactured by Arakawa Chemical Industries, Ltd. is preferably used, and those having a molecular weight of 20,000 to 100,000 are preferable. When the molecular weight is less than 20,000, the viscosity of the resin is lowered, so that when coated, the resin is easily absorbed by the base paper, and it becomes difficult to apply the coating layer to the base paper. On the other hand, when the molecular weight exceeds 100,000, the viscosity becomes too high, leading to troubles such as coating unevenness.

  As the latex, SBR (styrene butadiene rubber) having a Tg (glass transition temperature) of −20 ° C. or more and 50 ° C. or less can be suitably used. If the Tg is less than -20 ° C, the latex will easily melt at low temperatures, which may cause stains on the dryer, calendar, etc. On the other hand, if it exceeds 50 ° C, the cushioning properties of the coating layer will be lost and printing will occur. This is because the aptitude decreases. Examples of the SBR latex include trade name “PA5036”: manufactured by Japan A & L Co., Ltd. (Tg = 1 ° C.), and trade name “JSR 0589”: manufactured by Japan JSR Corporation (Tg = 0 ° C.). .

  The organic pigment is preferably a spherical or hollow PP (Plastic Pigment). This is because the hardness is lower than that of inorganic particles, the deformation of the pigment itself is easy, and the resistance to ruled cracking of the coating layer is improved. In addition, when the particle size of the organic pigment is less than 2 μm, the thickness of the coating layer becomes too thin when the printing board is calendered after coating the coating agent, and the cushioning property of the coating layer is reduced. This causes printing blurring during gravure printing. On the other hand, when the particle diameter of the organic pigment exceeds 12 μm, the coating layer is difficult to be crushed when the coating agent is applied and then calendered, so that the surface becomes uneven, causing printing blurring during gravure printing.

The coating agent containing styrene resin, latex and organic pigment is applied on the base paper surface layer at a coating amount (dry state) of 0.1 g / m ² or more and 0.8 g / m ² or less. This coating agent is applied by a coating machine such as a bar coater, a rod coater, or an air knife installed in a paper machine.

When the coating amount is less than 0.1 g / m ² , the thickness of the coating layer becomes too thin, and ink is easily absorbed into the base paper, resulting in a decrease in printing gloss. On the other hand, when the coating amount exceeds 0.8 g / m ² , the ink is not absorbed into the base paper at all, and the adhesive force of the ink is reduced. In view of cost and quality, it is more preferable to use a coating amount (in a dry state) of 0.2 g / m ² or more and 0.5 g / m ² .

  After making the base paper, it is also possible to apply the coating agent by a secondary processing using a coating machine such as a printing machine, a bar coater, a rod coater, or an air knife.

After forming a coating layer on the surface layer of the base paper to obtain a printing board, a paper calender, a calendar with several layers of metal rolls such as hard chilled ore, etc. are used, and the paper density of the printing board as a whole is 0.8. Adjust to g / cm ³ or more and 1.1 g / cm ³ or less. If it is less than 0.8 g / cm ³ , irregularities on the surface of the coating layer become large, which causes blurring of printing. On the other hand, if it exceeds 1.1 g / cm ³ , the cushioning property as a printing paper board is lowered, and gravure printing causes printing blur. The paper density of the printing board as a whole is more preferably adjusted to 0.9 g / cm ³ or more and 1.0 g / cm ³ or less.

  The paperboard for printing of the present invention is not only the improvement of the coating liquid, but also by adjusting the raw material composition of the surface layer in contact with the coating layer, the amount of inorganic pigment added, and the density of the entire paper to the above specific range, For the first time, it satisfies gravure printing suitability and can exhibit the crease resistance required for cardboard applications.

  Next, examples of the present invention will be described in comparison with comparative examples.

  A printing paperboard having a five-layer base paper as shown in FIG. 1 and a coating layer was produced. Freeness was adjusted to 400 cc with a double desk refiner for pulp mixed with various weight ratios of softwood virgin pulp and hardwood virgin pulp. Paper was made by adding Clay Amazo Plus JPG (add a trade name and a specific substance name) as an inorganic pigment in this pulp in an amount of 2 to 22% by weight based on the weight of the raw pulp. This was used as the wet paper of the base paper surface layer in contact with the coating layer.

The wet paper of the lower surface layer and the lower back layer was made using a raw material slurry mainly composed of upper white waste paper and middle white waste paper mixed at a weight ratio of 1: 1. In addition, the center layer and the back layer were paper-made using a raw slurry mainly composed of old paper. These five layers of wet paper were made into a base paper (board) having a basis weight of 210 g / m ² and a five-layer structure.

On the surface layer of this five-layer base paper, 20% by weight of styrene resin (trade name “Polymaron 351S”, manufactured by Arakawa Chemical Industries, Ltd.), SBR latex (trade name “PA5036 (Tg = 1 ° C.)”, Nippon A & L Co., Ltd.) 45% by weight, organic pigment (Plastic Pigment, trade name “V1005”, manufactured by Nippon Zeon Co., Ltd.) 35% by weight, 0.05g / m ² -0.9g by bar coater Coating was carried out at a coating amount of / m ² to obtain a printing board. In addition, the weight% of the three components is a numerical value in a dry state.

Furthermore, changing the pressure conditions of the gloss calender was adjusted paper density of the entire printing paperboard ^{0.78g / m 2 ~1.15 g / m} 2. Table 1 shows the raw material pulp of the base paper surface layer, the addition rate of the inorganic pigment, the paper density of the entire printing board, and the coating amount of the coating agent.

  The printing paperboards of Examples and Comparative Examples were evaluated for printing gloss, ink loss, ruled line cracking, and ink adhesion by the following methods. The evaluation results are as shown in Table 1.

  The printing gloss on the surface of the coating layer is the paperboard for printing using the standard duck grade ink used in the IGT printability tester specified in JIS-P8129, using the KRK Universal Printability Tester manufactured by Kumagaya Riki Kogyo Co., Ltd. After printing on the coated layer, it was evaluated by measuring the 75 degree white paper gloss (%) defined in JIS-P8142. A print gloss of 3% or more was judged as “appropriate”.

To remove ink, use gravure ink NT-2000 made by Sakata Inks Co., Ltd. in a gravure printing machine, print solid on printing board using a 100-line, 50μ depth gravure roll, and print board (A4 size) The number of pinholes having a diameter of 0.3 mm or more generated on the coating layer was confirmed with the naked eye.
◎: The number of pinholes is 5 or less ○: The number of pinholes is 6 to 10 △: The number of pinholes is 11 to 20 ×: The number of pinholes is more than 20 Is

Ruled line cracking is done by cutting the printed paper board in the same way as ink loss to A4 size (longitudinal), folding it into two with respect to the long side, pressing for 5 minutes at a press pressure of 2.0 kg / m ² , and then visually It evaluated by confirming the presence or absence of the crack of a crease part.
◎: No cracks occurred ○: Cracks with a total length of less than 15% with respect to the crease length △: Cracks with a total length of 15% to less than 30% with respect to the crease length X: Cracks with a total length of 30% or more with respect to the crease length

For the ink adhesion, the standard tack grade ink used in the IGT printability tester specified in JIS-P8129 is applied to the printing paper board coating layer using the KRK Universal Printability Tester manufactured by Kumagaya Riki Kogyo Co., Ltd. After printing, it was evaluated by the RI printability test.
◎: No fuzz or paper peeling on the surface ○: No more than 2 mm fuzz or paper peeling △: 3-5 fuzz or paper peeling 0.5 mm or more ×: 0.5 mm or more Has more than 6 fluffs

  The printing gloss of Examples 1 to 12 was all 3% or more, and had practicality as a printing board. In addition, there was no “x” in the evaluation of ink loss, ruled line cracking, and ink adhesion.

  On the other hand, in Comparative Examples 1 to 11, any one of ink loss, ruled line cracking, and ink adhesive force is evaluated as “x”, or the printing gloss is less than 3%, which is practical as a printing board. Lacked sex.

  From the results shown in Table 1, the styrene-based resin is blended at a ratio of 4 wt% to 30 wt%, the latex is blended at a ratio of 10 wt% to 48 wt%, and the organic pigment is blended at a ratio of 10 wt% to 70 wt%. It was confirmed that a coating agent was preferable.

  Thus, softwood pulp and inorganic pigment are blended at a specific ratio in the base paper surface layer, and a coating agent containing a styrenic resin is applied on the surface layer at a specific coating amount to provide a coating layer, By adjusting the paper density of the entire printing paperboard to a specific range, a printing paperboard having quality without any problems was obtained for all items of printing gloss, ink loss, ruled line cracking, and ink adhesion.

  In the above embodiment, the printing board having the coating layer provided only on one side of the base paper has been described. For example, in the structure of the printing board shown in FIG. If it makes it, it can be set as the board for printing which provided the same coating layer on both surfaces. In that case, it is preferable that the back lower layer 6 is also made of the same material as the front lower layer 4, and the coating agent, the coating amount, and the paper density as a whole of the printing board are also the printing board provided with the coating layer only on one side of the base paper. Must be the same.

  The printing board of the present invention is useful in the fields of papermaking and printing as a printing board having excellent printing characteristics and low cost.

It is sectional drawing showing an example of the paperboard for printing (base paper is 5 layer structure) of this invention.

Explanation of symbols

1: base paper 2: coating layer 3: surface layer (layer in contact with coating layer)
4: Lower surface layer 5: Center layer 6: Lower layer on the back surface 7: Back surface layer

Claims (4)

A printing board having a base paper composed of a plurality of layers and a coating layer,
The coating layer is applied on at least one surface of the base paper at a coating amount of 0.1 g / m ² or more and 0.8 g / m ² or less in a dry state,
The coating agent for the coating layer contains a styrene resin,
The surface layer of the base paper in contact with the coating layer contains 5% to 50% by weight of softwood pulp in the raw material pulp, and 3% to 20% by weight of inorganic pigment. Has been
A paperboard for printing, wherein the paper density of the whole paperboard for printing is adjusted to 0.8 g / cm ³ or more and 1.1 g / cm ³ or less.   The paperboard for printing according to claim 1, wherein the coating agent further contains a latex and an organic pigment.   The paperboard for printing according to claim 1 or 2, wherein the inorganic pigment is an aggregate particle containing silica, calcium, and aluminum. The blending ratio in the coating agent is 4% to 30% by weight of a styrene resin, 10% to 48% by weight of latex, and 10% to 70% by weight of an organic pigment. Paperboard for printing.

Images