JP4086687B2 - Double-sided primer base paper for cast coated paper - Google Patents

Description

【００３６】
【表２】

【００３７】
評価；
実施例１〜４および比較例１〜２は、漂白パルプを主成分とする原紙の上にロットコーターおよびメタリングコーター方式で６〜１６ｇ/ｍ²の両面下塗り層を設けた。そのキャストコーテッド紙用原紙の両面塗工量、透気度および水分を確認後、前述のキャスト塗工液を２０ｇ/ｍ²塗工し、キャスト面ドラムピック、非キャスト面インキ着肉性およびＲＩドライピックを評価した。下塗り塗工量を変化させた結果、下塗り塗工液は６〜１２ｇ/ｍ²、好ましくは６〜１０ｇ/ｍ²が、キャスト面ドラムピックが良好であった。さらに、下塗り塗工量と透気度の相関が見い出され、透気度は３５００秒、好ましくは３０００秒以下であれば、キャスト面ドラムピックが良好であることが判明した。また、両面塗工量６ｇ/ｍ²以下であれば、非塗工面のＲＩインキ着肉性が劣る傾向も見受けられることが判明した。
【００３８】
実施例５〜９および比較例３において、前述実施例、比較例のごとく、両面下塗り塗工後の水分を変化させた結果、水分は７％以下、好ましくは６．５％以下であれば、キャスト面ドラムピックが良好であることが判明した。
【００３９】
実施例１０〜１４および比較例４〜５は、前述のごとく、下塗り塗工液の配合ラテックスのゲル含有量を変化させたものを配合した結果、ゲル含有量６０％以下好ましくは２０〜５０％のキャスト面ドラムピックが良好であり、６０％以上の場合は透気度３５００秒以上となった。
【００４０】
実施例１５〜１７および比較例６〜７では、前述のごとく、下塗り塗工液の配合ラテックスの粒径を変化させものを配合した結果、粒径が１００ｎｍ以上、好ましくは１１０ｍｎ以上のキャスト面ドラムピックが良好であり、１００ｎｍ以下であれば、透気度も３５００秒以上となった。
【００４１】
実施例１８〜２１および比較例８〜９は、前述のごとく、下塗り塗工液のラテックス配合を変化させたものは、１６部以下で、好ましくは８〜１４部配合が、キャスト面ドラムピックが良好であった。しかし、ラテックスの配合量が少なくなると、ＲＩドライピックの低下となる。
【００４２】
【発明の効果】
上記のとおり、本発明のキャストコーテッド紙用原紙は、特定のラテックスバインダーを用いた両面下塗り層を設けることで、高光沢度、高平滑度の高品質を保持しつつ、ピンホールやドラムピックの欠点がなく、非キャスト面への印刷適性を向上させることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a double-sided base paper for cast-coated paper. More specifically, while maintaining high quality with high glossiness and high smoothness, it has no defects of pinholes and drum picks and improves printability on non-cast surfaces. The present invention relates to a double-sided primer base paper for cast coated paper.
[0002]
[Prior art]
As a method for producing a coated paper called cast-coated paper, a wet cast method (direct method), a gelled cast method (solidification method), a rewet cast method (rewetting method) and the like are generally known.
[0003]
The wet casting method is a basic method of cast coating, and after applying a coating liquid for casting mainly composed of a pigment and an adhesive to a base paper, a mirror surface is applied while the coating layer is in a wet state. It is pressed against a heated cast drum. The coated surface is dried and released while being in close contact with the cast drum surface. The gelled casting method is a method in which an aqueous coating liquid is applied to a base paper, and then the coating layer is solidified into a deformable gel state that is not fluid but then pressed onto a cast drum and dried. (For example, refer to Patent Document 1.)
[0004]
In the rewet cast method, a coating solution is applied to a base paper and dried to obtain a dry coating layer. Thereafter, the coating layer is re-wet and plasticized with water or a suitable rewetting liquid, and finished by pressing against the cast drum surface. These cast finishing methods are common in that the surface of the coating layer in a plastic state is pressed against the heated cast drum and dried, and then released from the heated drum to copy the mirror surface.
[0005]
All moisture in the coating layer must pass through the paper layer and evaporate from the non-cast surface side, and dry from both sides and from the coating layer surface in order to press and dry the cast drum surface. The current situation is that it is forced to operate at a lower speed than general art paper and coated paper. In addition, if the evaporation rate exceeds a certain limit, part of the evaporated water in the paint will dissipate toward the cast drum surface, destroying the coating layer and coating the resulting cast coated paper. Innumerable pinholes on the surface of the work layer and so-called drum picking or drum fogging, in which part of the coating layer remains on the mirror drum as the operation speed increases, are likely to occur. For this reason, the current situation is that some of the white paper appearance and operability are sacrificed to some extent, and it is an important technical issue to further improve the productivity by increasing the coating speed.
[0006]
Reducing evaporated water is a fundamental issue. However, in the wet cast method and the gelled cast method, the suitability of coating such as the fluidity of the coating solution is also limited, and it is difficult to adjust or apply a coating solution having a higher concentration. In addition, even in the rewet cast method that can relatively reduce moisture, it is possible to deform against the press pressure, and in order to make the coating layer in a wet plastic state so as to be in close contact with the cast drum surface, too much moisture is used. In need of.
[0007]
In order to obtain high quality, a corresponding coating amount is still necessary. Increasing the coating speed by reducing the coating amount has already reached its limit when producing high-quality cast-coated paper. Various attempts have been made to promote steam drying by raising the heating temperature of the cast drum. However, in the cast coating as described above, when the temperature of the drum surface is the temperature of moisture evaporation, the moisture in the wet plastic coating layer starts to evaporate rapidly at the moment of contact with the drum surface, Since adhesion between the coating layer and the drum surface is hindered, it is generally necessary to limit the temperature of the drum surface to 100 ° C. or lower. Although there are reports that a high temperature of 120 to 130 ° C. is possible in the rewet cast method and the gelled cast method, in these examples, a sufficiently high-quality cast coated paper has not yet been obtained.
[0008]
[Patent Document 1]
JP-A-4-246000
[Problems to be solved by the invention]
An object of the present invention is to provide a double-coated base paper for cast-coated paper that maintains high quality with high glossiness and high smoothness, has no drawbacks of pinholes and drum picks, and has improved printability on non-cast surfaces. It is to provide.
[0010]
[Means for Solving the Problems]
The present inventors pay attention to the fact that moisture in the coating layer and the base paper evaporates from the non-cast surface side when applying a coating layer mainly composed of pigment and adhesive on the base paper in the cast coater. Emphasis was placed on facilitating the smooth evaporation of moisture to the cast surface and improving the printability of the non-cast surface, and as a result of earnest research, the inventors have invented the double-coated base paper for cast-coated paper of the present invention. It was.
[0011]
That is, the base coated base paper for cast coated paper of the present invention is
A coating amount of 6 to 12 g / m, comprising a pigment and an adhesive as main components on a base paper, and containing a latex binder having a gel content of 60% by mass or less and an average particle diameter of 100 nm or more based on the pigment. ² undercoat layers are provided, the water content is 3 to 7% by mass, and the Gurley air permeability is 3500 seconds or less.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In order to reduce the water content of the cast coating liquid in the cast coater, it is possible to reduce the amount of cast coating by applying a primer, and to improve the printability of non-cast surfaces, pigments and adhesives are used. A double-sided coated base paper provided with a coating layer as a main component was obtained. However, if the coating amount of the base paper increases, that is, the air permeability increases, moisture evaporation to the non-cast surface is inhibited, and a part of the evaporated water in the cast coating layer is diverted toward the cast drum surface. The coating layer is scattered and the coating layer is destroyed, and numerous pinholes and part of the coating layer remain on the mirror drum, and so-called drum pick and drum fogging are easily generated.
[0013]
In the cast coater, it is generally known that the air permeability of the base paper for cast coated paper has a large effect in order to allow water vapor to scatter from the non-coated surface. Therefore, it is most important to make a base paper with a high air permeability, that is, a base paper for cast coated paper. As a result of earnest research, in order to increase the air permeability of the base paper for cast coated paper, the coating amount of the base paper for cast coated paper, the blending amount of the adhesive in the coating layer, that is, the latex binder, and the gel content It was found that the average particle size and the final moisture content of the base paper for cast coated paper were greatly affected.
[0014]
Here, the gel content indicates a portion insoluble in an organic solvent such as toluene or benzene, and therefore indicates the degree of crosslinking of the polymer constituting the latex binder. If the gel content is lowered, the air permeability of the coating layer is improved, but the pick strength characteristics are lowered.
[0015]
The average particle diameter of the latex binder referred to here is a value obtained by observing the Brownian motion of the latex binder in water by a dynamic laser light scattering method and analyzing the value by a photon correlation method such as a time interval method.
[0016]
In the present invention, known coating machines such as an air knife, a rod bar, a blade coater, a size press coater, a gate roll coater, a shim sizer, and a metering bar can be used as the coating method for coating the base paper for cast coated paper.
[0017]
In the present invention, the pigment used in the undercoat coating liquid is not particularly limited. For example, various natural mineral pigments such as kaolin, talc, and ground calcium carbonate, composite synthetic pigments such as satin white, and titanium oxide. And semi-synthetic pigments such as precipitated calcium carbonate and alumina hydroxide, and synthetic pigments such as plastic pigments.
[0018]
Examples of the starch used in the undercoat coating liquid include ordinary starch, oxidized starch, etherified starch, esterified starch, enzyme-modified starch, and cold water-soluble starch obtained by flash drying them.
[0019]
The thickeners used in the undercoat coating solution include water-soluble polymers such as carboxymethylcellulose, sodium alginate, methylcellulose, hydroxyethylcellulose, casein, and sodium polyacrylate, polyacrylate, and styrene-maleic anhydride. Examples thereof include synthetic polymers such as coalescence, inorganic polymers such as silicate, and the like.
[0020]
As binders other than starch used in the undercoat coating solution, various copolymer latexes such as styrene-butadiene, acrylic and vinyl acetate, polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, polyacrylamide, urea or melamine are used. / Formalin resin, polyethyleneimine, polyamide polyamine / water-soluble synthetic compounds such as epichlorohydrin, natural products such as wax, casein, soybean protein, and cationized products thereof.
[0021]
Moreover, various auxiliary agents normally used, such as a dispersing agent, an antifoamer, a water-resistant agent, and a coloring agent, and these various auxiliary agents are used suitably as needed.
[0022]
The base paper used in the present invention includes chemical pulps such as LBKP and NBKP such as chlorine dioxide and ozone, and mechanical pulps such as GP, TMP, CTMP, and CGP, and various pulps such as waste paper pulp. Various fillers such as calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, sizing agent, fixing agent, retention agent, paper strength enhancer, etc. are suitably blended, and any of acidic, neutral or alkaline However, it can be made and is not limited.
[0023]
In the base paper of the present invention, no-size press base paper, base paper size-pressed with starch, polyvinyl alcohol, or the like can be used.
[0024]
The base paper for cast coated paper that has been coated and dried in a series of operations may be subjected to various calendar processes as necessary.
[0025]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In addition, unless otherwise indicated, all the parts and% in an Example show a mass part and mass%.
[0026]
Example 1
<Base paper formulation>
Pulp mainly composed of chlorine dioxide bleach, 90 parts of LBKP (freezing degree 450 mlcsf), 10 parts of NBKP (freezing degree 500 mlcsf), and if necessary, the following internal additives are blended. A commercially available 7-layer paperboard having a basis weight of 190 g / m ² was made by adjusting 0.03 part of a commercially available cationic polyacrylamide yield improver with pulp and the internal chemicals with the above composition.
[0027]
<Composition of undercoat coating liquid>
Commercial first grade kaolin clay 50 parts, commercial heavy calcium carbonate 50 parts, commercial polyacrylic acid dispersant 0.1 part, latex binder 12 parts, commercial phosphorylated ester starch 8 parts, calcium stearate 0.5 part, printing suitability agent 0.5 part was adjusted to pH 9.8 with aqueous ammonia and used as an undercoat coating solution. The base paper was coated with an undercoat coating liquid of 12.2 g / m ² using a rod bar and metering bar type coating machine at a coating speed of 130 m / min. The latex binder used was a gel content of 50% and an average particle size of 120 nm.
[0028]
Examples 2 to 21 and Comparative Examples 1 to 9
An undercoat base paper for cast coated paper was produced in the same manner as in Example 1 except that the double-sided coating amount, the gel content of the latex binder, the average particle diameter, and the blending ratio in Example 1 were changed to the values shown in Table 1.
[0029]
The base paper for cast coated paper of Examples and Comparative Examples was evaluated by the following evaluation methods, and the results are shown in Tables 1 and 2.
[0030]
(1) Air Permeability The air permeability of the base paper for cast coated paper was measured with a JIS P8117 Gurley Densometer and used as evaluation data.
[0031]
(2) Moisture after double-sided undercoating The moisture after double-sided undercoating was measured as moisture data by measuring absolutely dry moisture with a 105 ° C. dryer.
[0032]
(3) As a cast surface drum pick cast coating solution, 20 parts of light calcium carbonate, 80 parts of kaolin, 0.5 part of sodium polyacrylate are dispersed in water using a core dispersion, and the solid content is 65%. A pigment slurry was obtained. In this slurry, 0.5 part of antifoaming agent tributyl phosphate, 1.0 part of release agent ammonium stearate, 10 parts of 15% casein aqueous solution dissolved as ammonia as an adhesive (as a solid content), ZnSO 2 parts of ₄ and water were added to prepare a cast coating solution having a solid content concentration of 45%. The cast coating solution is applied on one side to a base paper for cast coated paper, which has been coated with 190 g / m ^{2 of} base paper on a weight basis, and the cast finish is brought into pressure contact with a heated mirror drum. The drum pick on the cast surface was observed, and a judgment was made as (◎ good → × bad).
[0033]
(4) Non-cast coating surface ink inking property Ink printing is visually observed by printing with tack ink (DIC soybean oil ink, tack value of 15) using an RI printing aptitude tester (◎ good → × Bad).
[0034]
(5) Non-cast coated surface Dry pick RI printing aptitude tester is used to visually print the ink in the tack ink (soybean oil ink manufactured by DIC, tack value 20) (◎ good → × bad) [0035] judged by
[Table 1]

[0036]
[Table 2]

[0037]
Evaluation;
In Examples 1 to 4 and Comparative Examples 1 and ^2, a double-sided undercoat layer of 6 to 16 g / m ² was provided on a base paper mainly composed of bleached pulp by a lot coater and a metalling coater method. After confirming the double-sided coating amount, air permeability and moisture of the base paper for cast coated paper, the above-mentioned cast coating solution was applied at 20 g / m ^2, and the cast surface drum pick, non-cast surface ink inking property and RI Dry pick was evaluated. As a result of changing the undercoat coating amount, the undercoat coating liquid was 6 to 12 g / m ² , preferably 6 to 10 g / m ² , and the cast surface drum pick was good. Furthermore, a correlation between the amount of undercoat coating and air permeability was found, and it was found that the cast surface drum pick was good when the air permeability was 3500 seconds, preferably 3000 seconds or less. It was also found that when the double-sided coating amount was 6 g / m ² or less, there was a tendency that the RI ink inking property of the non-coated surface was inferior.
[0038]
In Examples 5 to 9 and Comparative Example 3, as in the above Examples and Comparative Examples, the moisture after the double-sided undercoating was changed. As a result, the moisture was 7% or less, preferably 6.5% or less. It was found that the cast surface drum pick was good.
[0039]
In Examples 10 to 14 and Comparative Examples 4 to 5, as described above, the gel content of the mixed latex of the undercoat coating solution was changed. As a result, the gel content was 60% or less, preferably 20 to 50%. The cast surface drum pick was good, and when it was 60% or more, the air permeability was 3500 seconds or more.
[0040]
In Examples 15 to 17 and Comparative Examples 6 to 7, as described above, a cast surface drum having a particle size of 100 nm or more, preferably 110 nm or more was obtained as a result of blending the mixed latex with the undercoat coating liquid by changing the particle size. When the pick was good and the thickness was 100 nm or less, the air permeability was 3500 seconds or more.
[0041]
In Examples 18 to 21 and Comparative Examples 8 to 9, as described above, the latex coating composition of the undercoat coating solution was changed to 16 parts or less, preferably 8 to 14 parts, but the cast surface drum pick was used. It was good. However, when the amount of latex is decreased, the RI dry pick is lowered.
[0042]
【The invention's effect】
As described above, the base paper for cast coated paper of the present invention is provided with a double-sided undercoat layer using a specific latex binder, while maintaining high quality with high glossiness and high smoothness, while maintaining pinhole and drum pick quality. There is no defect, and the printability on the non-cast surface can be improved.

Claims (1)

A coating amount of 6 to 12 g / m, comprising a pigment and an adhesive as main components on a base paper, and containing a latex binder having a gel content of 60% by mass or less and an average particle diameter of 100 nm or more based on the pigment. A double-sided base paper for cast-coated paper, comprising ^two double-sided undercoat layers, having a moisture content of 3 to 7% by mass and a Gurley air permeability of 3500 seconds or less.