JP2003306892A - Coated paperboard and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated paperboard having excellent whiteness and white- paper appearance and good printability and provide a method for the production of the paperboard. <P>SOLUTION: The coated paperboard has coating layers on one or both surfaces of a base paper. The coating layer of at least one surface of the base paper has two layers composed of a top-coating layer and an undercoating layer composed mainly of a pigment and an adhesive. The pigment of the undercoating layer contains 3-10 mass% plastic pigment based on the total solid pigment component of the undercoating layer. The amount of the coating layer of the coated paperboard is ≤30 g/m<SP>2</SP>for double-side coating and 8-17 g/m<SP>2</SP>for single-side coating. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paperboard having excellent whiteness and white paper appearance and good printability, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the importance of global environmental problems has been recognized worldwide, and resource saving and recycling measures are being actively promoted in Japan as well. In the field of coated paper, in order to protect forests and reduce paper waste, the content ratio of waste paper pulp in product raw materials is increased, and even in the coating layer, the coating composition along with fine fibers that are not recovered when the waste paper is made into pulp is used. After the wastewater treatment, a large amount of waste called papermaking sludge is generated, so it is desired to reduce the amount. In coated paperboard, waste paper pulp, which is a raw material for products, has already been added in a large amount, but it is desired to further reduce the coating amount of the coating layer.
In general, coated paperboard is caused by a decrease in the whiteness of the base paper due to the high content of waste paper, and the so-called residual carbon and fibers with ink still attached that could not be completely removed by deinking treatment. Since the unevenness of whiteness, that is, dullness, on the surface of the base paper becomes remarkable, a coating layer having higher whiteness and high hiding power is required on the base paper. In addition, in recent years, with the demand for high-concentration / high-speed coating and smoothing of the coating surface, the top layer is a flattening coating that tends to emphasize unevenness of whiteness on the coating surface, such as blade coating. Since many methods are adopted, in the field of coated paperboard, it is indispensable to coat with a coating layer of at least 20 g / m ^{2 on} one side, and it is difficult to reduce the coating amount.

[0003]

OBJECTS OF THE INVENTION It is therefore an object of the present invention, the coating weight of 30 g / m ² or less in terms of both coated compositions coated on the base paper surface, per side 8~17g / m ² It is an object of the present invention to provide a coated paperboard having excellent whiteness and white paper appearance and good printability, and a method for producing the same.

[0004]

SUMMARY OF THE INVENTION The present invention is a coated paperboard having a coating layer on one or both sides of a base paper, at least one side of which comprises an overcoat layer and an undercoat layer containing a pigment and an adhesive as main components. The present invention relates to a coated paperboard, which is formed of layers and contains 3 to 10% by mass of a plastic pigment as a pigment for the undercoat layer, based on the total pigment solid content of the undercoat layer. The coated amount of the coated paperboard is 30 g / both sides.
It is preferably m ² or less and 8 to 17 g / m ² per side. The plastic pigment of the undercoat layer preferably has an average particle size of 500 to 1500 nm and a hollow structure. 2 consisting of topcoat and undercoat
In the coating layer formed of layers, it is preferable that the undercoat layer is formed by a rod coater and the topcoat layer is formed by a blade coater.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Generally, in a coated paperboard having a pulp composition with a high content ratio of waste paper, a coating amount of 17 g / m ² or less on one side has a high whiteness on the coated surface and a dullness on the surface of the base paper It is difficult to obtain a good blank appearance that fully hides. In particular, when selecting a flattening coating such as blade coating for the uppermost layer coating, it achieves high whiteness and concealability of the coating surface compared to conventional contour coating methods such as air knife coating. Forming a coating layer becomes more difficult. Therefore, the inventors of the present invention have made extensive studies to solve the above-mentioned problems, and as a pigment for the undercoat coating layer of the coating layer, a plastic pigment is used for the total pigment solid content of the undercoat coating layer. By containing 3 to 10% by mass, it is possible to obtain a coated paperboard having a high whiteness of the coated surface, a concealing property of the surface of the base paper, that is, an excellent white paper appearance without unevenness in whiteness,
Moreover, a coated paperboard having good printability was obtained, and the desired object of the present invention could be achieved.

Although a plastic pigment may be used as a pigment for the overcoat coating layer, the plastic pigment has high glossiness, and in a flattening coating method such as blade coating, a coating based on the thickness of the overcoat coating layer is used. The uneven gloss on the surface of the engineering paperboard is easily emphasized. Furthermore, since the difference in whiteness from the undercoat coating layer becomes large, unevenness in whiteness tends to be emphasized, which is not preferable. Further, when a contour coating method such as air knife coating is used, this tendency is reduced, but it is still insufficient, and it is difficult to obtain a coated surface having an excellent white paper appearance with high smoothness.

Although the coating amount of the coating layer and the composition of the coating layer as described above provide high whiteness of the coated surface, covering property of the base paper and good white paper appearance, it is not always clear. , Is considered as follows. That is, the specific gravity of the plastic pigment used for the undercoat coating layer is generally about 0.8, which is considerably smaller than that of the inorganic pigment having a specific gravity of about 2 to 5. Therefore, by using the plastic pigment as the pigment, In comparison with the coating layer using only the inorganic pigment, the coating layer is bulky at the same coating amount. As a result, a bulky coating layer can be obtained even with a small coating amount, and the surface of the base paper can be sufficiently covered. Also, the use of plastic pigments has the effect of increasing the whiteness of the coating layer, and the surface of the coating layer becomes highly white. Furthermore, by using plastic pigment for the undercoat layer, the whiteness of the undercoat layer is enhanced, and the difference in whiteness from the overcoat layer using a pigment of high whiteness such as titanium dioxide is small. It seems that the whiteness unevenness of the coating surface that is easily emphasized by a flattening coating method such as a small amount of topcoat coating or blade coating becomes relatively inconspicuous, and there is an effect of improving the appearance of blank paper. .

The plastic pigment used in the present invention is contained in an amount of 3 to 10% by mass based on the total pigment solid content of the undercoat layer. If used less than 3% by mass,
The high whiteness of the present invention cannot be obtained, and a bulky coating layer cannot be obtained, resulting in a poor appearance of white paper. Again 10
When the content is more than 100% by mass, the average particle size of the plastic pigment is very small, and the adhesion of the pigment is poor in the coating layer obtained by mixing with the adhesive, so the pigment falls off the surface of the coated paper during printing. It becomes easy to do so and causes printing problems such as blanket piling. Although it is conceivable to increase the amount of the adhesive as a measure against the above-mentioned printing strength, the optical properties such as whiteness and hiding property are deteriorated, or the drying property (ink set) of the ink at the time of printing is deteriorated. When another problem is caused and the whiteness and the hiding property are improved, and further the printability is effectively balanced, satisfactory results have not yet been obtained. In addition, if the compounding ratio of the plastic pigment is high, the coating workability of the coating composition, particularly the mechanical stability, may be deteriorated, which is not preferable.

The plastic pigment used in the present invention is, for example, a styrene-, acrylic-, or urea-resin-based pigment, or a binder pigment having a binder function by using a styrene-butadiene copolymer in the sheath of the pigment. And the like, and examples of the shape include pigments having various structures such as solid type, through-hole type, bowl type, flat type, and hollow particles, and the average particle size is 500 to 500 although not particularly specified. Those having a thickness of 1500 nm and having a hollow structure are preferably used because of the excellent white paper appearance obtained from the high hiding property based on the refractive index difference between the internal void and the shell portion. Incidentally, when it is less than 500 nm, the whiteness and Parker print surf roughness are lowered, and when it exceeds 1500 nm, the solid content concentration is lowered and backing rolls and the like are contaminated to cause a problem of operability.

The undercoat coating layer coating material is prepared by mixing and stirring other pigments and adhesives in addition to the above-mentioned plastic pigments. In addition, if necessary, a dispersant in the coating material; a pH adjusting agent such as caustic soda and ammonia water; an antifoaming agent; an antiseptic; a fluorescent dye; a release agent; a dye; a water-proofing agent; a flow modifier; a color pigment. It is also possible to appropriately add additives such as.

Pigments other than plastic pigments used in the present invention include conventional clays such as calcined clay, structured kaolin and delaminated clay, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, Within the scope of the present invention, one or more known and commonly used pigments used in the general coated paper manufacturing field such as silica, satin white, and talc are appropriately used. Among them, preferred pigments include calcined clay, ordinary clay such as structured kaolin and delaminated clay,
Examples include heavy calcium carbonate and light calcium carbonate.

As the adhesive, a conjugated diene polymer latex such as a styrene / butadiene copolymer or a methyl methacrylate / butadiene copolymer; a polymer or copolymer of acrylic acid ester and / or methacrylic acid ester, etc. Acrylic polymer latexes; vinyl polymer latexes such as ethylene / vinyl acetate copolymers; or various polymer latexes modified with functional group-containing monomers such as carboxy groups for alkali solubility or alkali swelling Polymer latex; casein,
Proteins such as soybean protein and synthetic protein; synthetic resin adhesives such as polyvinyl alcohol, olefin / maleic anhydride resin, and melamine resin; starches such as positive starch, oxidized starch, thermochemically modified starch; carboxymethyl cellulose, hydroxyethyl cellulose And the like, and the like, and the like, which may be used alone or in admixture of two or more.

In the undercoat coating material, the ratio of the pigment to the adhesive is 100 parts by weight of the pigment, and the ratio of the adhesive is 5 parts.
It is preferably about 30 parts by mass.

The coating material for the top coating layer and the coating material in the case of a single coating layer are prepared by mixing and stirring the pigments, adhesives and additives described in the coating material for the undercoat coating layer. Among them, preferred pigments include calcined clay, ordinary clay such as structured kaolin and delaminated clay, heavy calcium carbonate, light calcium carbonate, and titanium dioxide.

[0015] Note that the coating amount of the coating layer for coating, 5 to 10 g / ^{m 2} in dry weight for the undercoating coating layer, the topcoat coating layer is at 3 to 10 g / ^{m 2} by dry weight In this range, the total coating amount of the undercoat and the topcoat may be selected so that the dry weight is in the range of 8 to 17 g / m ² . By the way, if the undercoat coating layer is less than 5 g / m ² , the surface of the base paper cannot be sufficiently covered and the hiding property desired in the present invention cannot be obtained. If it exceeds 10 g / m ² , the effect is saturated. Further, if the top coat layer is less than 3 g / m ² , the surface of the under coat layer cannot be sufficiently covered to cause defective ink transfer, and satisfactory printability cannot be obtained, and if it exceeds 10 g / m ^2. As with the undercoat layer, the effect is saturated. Further, the total coating amount of the undercoat and the top coat exceeds 17 g / m ² , and the coating amount of both sides is 30 g / m ^2.
If it exceeds, it is not possible to achieve the desired reduction of the coating layer. When one side has one coating layer, the dry coating amount is 8
Is in the range of -17 g / m ² .

The coating device is not particularly limited, and examples thereof include an air knife coater, a blade coater,
A rod coater, a bar coater and a gate roll coater, a roll coater such as a size press, a bill blade coater, a vervapa coater and the like are used in an appropriate combination as long as the effects of the present invention are not impaired. A rod coater is preferably used as a coating device, and a blade coater is preferably used as a coating device for forming an overcoat layer on a paper provided with an undercoat coating layer. When the coating layer is a single layer, a blade coater is preferably used.

A rod coater is preferably used as a coating device for the coating material for the undercoat layer, because it enables contour coating along irregularities on the surface of the base paper and can use high-concentration coating material at high speed. The reason is that coating is also possible. Further, the blade coater is preferably used as a coating apparatus for the coating material for the top coating layer, because it is easy to obtain a highly smooth coating surface, and like the rod coater used for the base coating, a high-concentration coating material is used. The reason is that high-speed coating is possible because it is possible.

It should be noted that an undercoat coating layer is formed by using a base paper whose smoothness is increased by using a machine calender or a Yankee dryer, or after the undercoat coating layer is formed, a smoothing treatment is performed by a soft calender or the like. You can also do Further, it is desirable to apply a coating composition for the overcoat coating layer, dry it, and then apply a smoothing treatment using a soft calender or a super calender. 1 coating layer
In the case of a layer as well, it is desirable to carry out a smoothing process similarly.

The base paper is composed of two or more layers of multi-layer paper, and the pulp used is not particularly limited, and examples include bleached or unbleached chemical pulp, mechanical pulp,
Further, one kind of deinked or undeinked waste paper pulp, or two or more kinds of them are appropriately mixed and used. In addition, a sizing agent, a paper strength agent, a drainage agent, a filler, a dye and the like can be appropriately added to the base paper, if necessary. The basis weight of the base paper is usually about 150 to 650 g / m ² .

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples. Of course, the invention is not limited to these examples. Unless otherwise specified, the parts and% in the examples
Indicate "parts by mass" and "% by mass", respectively.

Example 1 45 parts of structured kaolin (trade name: Exilon, manufactured by Engelhard), heavy calcium carbonate (trade name: Hydrocurb 60, Bihoku Kogaku Kogyo) 50 parts by weight) was used as a dispersant, and 0.2 parts of sodium polyacrylate was added as a dispersant, and a pigment slurry having a solid content concentration of 70% was prepared using a Choles disperser. Add to this slurry a hollow-structured plastic pigment (particle size 1
000 nm, trade name: HP1055, manufactured by Rohm & Haas Co., Ltd. 5 parts, phosphate esterified starch (trade name: PN50)
0, manufactured by Sanwa Starch Co., Ltd.) 5 parts (solid content), and solid concentration 5
0% styrene-butadiene copolymer latex (trade name: X-400A, glass transition temperature: -23 ° C, JSR
15 parts (solid content) (manufactured by the same company) were added, and water was further added to prepare a coating material having a solid content concentration of 62%.

As a pigment for preparing the coating material for the top coating layer, 60 parts of kaolin (trade name: UW-90, manufactured by Engelhard), light calcium carbonate (trade name: T
P-221-GS, Okutama Kogyo Co., Ltd.) 35 parts, titanium dioxide (trade name: Kronos KA-15, Titanium Kogyo Co., Ltd.)
Using 5 parts, 0.2 part of sodium polyacrylate was added as a dispersant to all the pigments described above, and a pigment slurry having a solid content concentration of 68% was prepared using a Choles disperser.
Phosphoric esterified starch (trade name: PN5) was added to this slurry.
00, manufactured by Sanwa Starch Co., Ltd.) 3 parts (solid content), solid concentration 50%
Styrene-butadiene copolymer latex (trade name:
L-1825, glass transition temperature: 8 ° C, manufactured by Asahi Kasei Corp.) 2
0 part (solid content) was added, and water was further added to prepare a coating material having a solid content concentration of 60%.

Preparation of Undercoat Layer Coated Paper On both sides of a coated paperboard base paper of 290 g / m ^{2 having} a basis weight of 290 g / m ² , which is made up of deinked waste paper pulp for each layer, the undercoat coating obtained above is applied. The coating material for layers was coated using a rod coater so that the dry weight per side was 8 g / m ^2, and dried to obtain an undercoat layer-coated paper.

Preparation of coated paperboard The above-mentioned coating material for topcoat layer is applied to both sides of the above-mentioned undercoat layer coated paper using a blade coater so that the dry weight per side is 7 g / m ^2. Covered, dried and 2 on both sides
A layer type coated paperboard was obtained. Next, the paper was passed through a 2-stack soft calender having a metal roll surface temperature of 150 ° C. and a nip of 2 to obtain a coated paperboard having two coated layers on both sides, which was smoothed on both sides.

Example 2 The same as Example 1 except that a plastic pigment having a hollow structure (particle size: 500 nm, trade name: MH5055, manufactured by Zeon Corporation) was used in the preparation of the coating material for the undercoat layer of Example 1. A coated paperboard was obtained.

Example 3 Example 1 was repeated, except that a plastic pigment having a bowl-shaped particle structure (particle size 800 nm, trade name: V1005, manufactured by Zeon Corporation) was used in the preparation of the coating material for the undercoat layer of Example 1. A coated paperboard was obtained in the same manner as in.

Example 4 In the preparation of the coating material for the undercoat layer of Example 1, a plastic pigment having a solid particle structure (having a particle size of 320 nm,
A coated paperboard was obtained in the same manner as in Example 1 except that the trade name: V1004, manufactured by Zeon Corporation) was used.

Example 5 In the preparation of the coating material for the undercoat layer of Example 1, 40 parts of structured kaolin and 50 parts of heavy calcium carbonate were used as pigments.
Parts and plastic pigments were changed to 10 parts to obtain coated paperboard in the same manner as in Example 1.

Example 6 In the coating of the top coating layer of the coated paperboard of Example 1, water was added to the top coating layer coating material to dilute it to obtain a solid content concentration of 40%.
A coated paperboard was obtained in the same manner as in Example 1, except that the coating was performed using an air knife coater.

Comparative Example 1 A coated paperboard was prepared in the same manner as in Example 1 except that 50 parts of structured kaolin and 50 parts of ground calcium carbonate were used as pigments in the preparation of the coating material for the undercoat layer of Example 1. Obtained.

Comparative Example 2 In the preparation of the undercoat coating composition of Example 1, 48 parts of structured kaolin and 50 parts of ground calcium carbonate were used as pigments.
Part and a plastic pigment 2 parts were obtained in the same manner as in Example 1 to obtain a coated paperboard.

Comparative Example 3 In the preparation of the coating material for the undercoat layer of Comparative Example 1, 35 parts of structured kaolin and 50 parts of ground calcium carbonate were used as pigments.
Part and plastic pigment 15 parts were changed to obtain a coated paperboard in the same manner as in Example 1.

Comparative Example 4 In the preparation of the coating material for the overcoat layer of Comparative Example 1, 55 parts of kaolin, 35 parts of light calcium carbonate, 5 parts of titanium dioxide, plastic pigment (trade name: HP
A coated paperboard was obtained in the same manner as in Comparative Example 1 except that the amount of the component was changed to 5 parts (1055, manufactured by Rohm & Haas Company).

Comparative Example 5 In the coating of the top coating layer of the coated paperboard of Comparative Example 4, water was added to the top coating material to dilute it, and the solid content concentration was 40% except that the coating was performed using an air knife coater. Comparative Example 4
A coated paperboard was obtained in the same manner as in.

The 11 kinds of coated paperboards obtained as described above were conditioned under JIS P8111 for 6 hours, and then evaluated for whiteness, surface hiding property, uneven glossiness, and offset printability. The evaluation results are shown in Table 1. Each evaluation test was carried out according to the following.

[Whiteness] The whiteness was measured using a spectral whiteness colorimeter (manufactured by Suga Test Instruments Co., Ltd.) according to JIS 8212.

[Surface Hiding Property] The degree of color unevenness (whiteness unevenness) on the surface of the obtained coated paperboard was visually evaluated. ◎: Uniform and no color unevenness ○: Some color unevenness is observed, but there is no problem in practical use △: Color unevenness is noticeable and there is a problem in practical use ×: Color unevenness is very noticeable

[Glossiness Unevenness] The degree of uneven glossiness of the surface of the obtained coated paperboard was evaluated visually from an oblique direction. ◎: Uniform and no uneven glossiness ○: Some uneven glossiness is recognized, but there is no problem in practical use Δ: Uneven glossiness is noticeable and there is a problem in practical use ×: Uneven glossiness is very noticeable

[Blanket piling] An offset sheet-fed printing machine (trade name: Mitsubishi Diamond 4E-4 type, manufactured by Mitsubishi Heavy Industries) was used to perform continuous 5000 parts color four-color printing on the coated paper surface. The degree of accumulation of paper powder in the blanket non-image area was visually determined. ⊚: No paper dust is generated ○: Paper dust is slightly generated, but there is no problem in operation △: Paper dust is recognized and there is a problem in operation ×: A large amount of paper dust is accumulated on the blanket There is.

[Ink Transferability in Offset Printing]
The printed matter obtained above was visually evaluated. ⊚: Transfer of ink to the coated surface is uniform and there is no uneven absorption. ○: Some absorption unevenness is observed depending on the gradation part, but there is no problem in practical use △: Transferability is uneven throughout, uneven absorption is observed, there is a problem in practical use ×: Transfer failure, uneven absorption Very bad.

[0041]

[Table 1]

As is clear from Table 1, the coated paperboard according to the present invention was found to have excellent whiteness and white paper appearance and good printability.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4L055 AG11 AG12 AG19 AG27 AG48                       AG63 AG76 AG89 AH02 AH37                       AJ01 AJ04 BE09 BE20 CH12                       CH14 EA14 EA16 EA32 FA11                       FA12 FA15 GA05 GA19

Claims (4)

[Claims] 1. A coated paperboard having a coating layer on one side or both sides of a base paper, at least one side of which is formed of two layers of an overcoat layer and an undercoat layer containing a pigment and an adhesive as a main component. As a pigment, a plastic pigment is contained in an amount of 3 to 10% by mass based on the total pigment solid content of the undercoat layer. 2. The coating amount of the coated paperboard is 30 g on both sides.
/ M ² or less, 8 to 17 g / m ² per side, The coated paperboard according to claim 1. 3. The coated paperboard according to claim 1, wherein the plastic pigment of the undercoat layer has an average particle diameter of 500 to 1500 nm and a hollow structure. 4. The coating layer formed of two layers including an overcoat layer and an undercoat layer, wherein the undercoat layer is a rod coater and the overcoat layer is a blade coater.
4. The method for producing a coated paperboard according to any one of 3 to 3.