JP2012167384A - Coated paper for printing - Google Patents

Abstract

An object of the present invention is to provide a coated paper for printing which is excellent in base paper coverage, hardly causes uneven ink deposition, and does not cause a decrease in printing surface strength.
An object of the present invention is to provide a printing paper having at least one coating layer containing at least a pigment and an adhesive on a base paper, and at least kaolin as a pigment in the outermost coating layer. Contained in the range of 1 to 15 parts by mass of enzyme-modified dextrin and 3 to 6 parts by mass of latex as an adhesive with respect to 100 parts by mass of the total pigment in the outermost coating layer Achieved with coated paper.
[Selection figure] None

Description

  The present invention relates to a coated paper for printing. Specifically, the present invention relates to a coated paper for offset printing.

  In recent years, with higher definition, multicolor printing, and higher speed of printed matter, there has been a demand for improvements in white gloss and printing gloss, smoothness, ink setting, and base paper coverage, especially on the coated surface of coated paper for printing. ing. Known for coated paper for printing, which is formed by applying high-concentration coating solution containing kaolin for the purpose of improving white paper gloss, printing gloss, smoothness, and base paper coverage. (For example, refer to Patent Document 1). However, when the concentration of the coating liquid is increased, there are operational problems. That is, since the viscosity of the highly concentrated coating liquid increases, it may stay in the pipe during liquid feeding or streak may occur in the coating head part.

  As a method for suppressing an increase in the viscosity of a highly concentrated coating solution, it has been proposed to use fine kaolin for the pigment contained in the coating solution (see, for example, Patent Document 2). However, with a coated paper for printing formed by coating a highly concentrated coating solution containing fine kaolin, the gloss of the printed region, i.e., the printed gloss may be reduced even if the gloss of the white paper is excellent.

  In addition, using low-viscosity starch as an adhesive to increase the concentration of the coating liquid and improve the base paper coverage without increasing the viscosity of the high-concentration coating liquid. There is paper (for example, see Patent Documents 3, 4, and 5). However, in these methods, since the adhesive easily migrates in the drying process after coating, the ink coating unevenness is likely to occur when the obtained coated paper for printing is printed. There is a problem that the strength decreases.

  Accordingly, it has been desired to develop a coated paper for printing that has excellent base paper coverage and printing gloss, is less likely to cause uneven ink deposition, and does not cause a reduction in printing surface strength.

JP-A-7-229093 JP 59-30992 A Japanese Patent No. 1604822 JP-A-53-14818 JP 7-189179 A

  An object of the present invention is to provide a coated paper for printing which is excellent in base paper coverage, hardly causes uneven ink deposition, and does not cause a decrease in printing surface strength. In particular, it is suitable for printing coated paper formed by coating a highly concentrated coating solution.

  An object of the present invention is to provide a printing paper having at least one coating layer containing at least a pigment and an adhesive on a base paper, the outermost coating layer containing at least kaolin as a pigment, and the outermost coating layer. Coating for printing containing, as an adhesive, 1 to 15 parts by mass of enzyme-modified dextrin and 3 to 6 parts by mass of latex as an adhesive with respect to 100 parts by mass of the total pigment in the surface coating layer. Can be solved by paper.

  Moreover, it is preferable that the outermost coating layer contains kaolin in the range of 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the total pigment in the outermost coating layer.

  As another aspect of the present invention, in a method for producing a coated paper for printing comprising coating a coating liquid containing at least a pigment and an adhesive on a base paper, the coating liquid is applied on the base paper and applied. One or more layers are formed, and kaolin is contained as a pigment of the outermost coating layer in a range of 10 to 30 parts by mass with respect to 100 parts by mass of all pigments in the outermost coating layer. Enzyme-modified dextrin and latex are contained as an adhesive for the surface coating layer, and from 1 to 15 parts by weight of enzyme-modified dextrin and 3 parts by weight of latex with respect to 100 parts by weight of the total pigment in the outermost coating layer. It is the manufacturing method of the coated paper for printing which coats and forms the coating layer of the outermost layer which contains in the range of more than 6 parts by mass with the coating liquid whose solid content concentration is 65 mass% or more.

  According to the present invention, it is possible to obtain a coated paper for printing which is excellent in base paper coverage, hardly causes uneven ink deposition, and does not cause a decrease in printing surface strength.

The present invention will be described below.
In the present invention, the printing coated paper has at least one coating layer containing at least a pigment and an adhesive on the base paper, and the outermost coating layer contains at least kaolin as a pigment. The outermost coating layer is the outermost coating layer as viewed from the base paper. When the coating layer is one layer, the one layer becomes the outermost coating layer.

  In the present invention, kaolin contained in the outermost coating layer is a clay mineral mainly composed of a hydrous aluminum silicate mineral. Examples of such kaolins include conventionally known kaolins such as commercially available grade kaolins, structural kaolins, and delaminated kaolins.

  In the present invention, the outermost coating layer contains an enzyme-modified dextrin and latex as an adhesive. Kaolin has a flat plate shape, and it is considered that a sandwich structure is easily formed by sandwiching an adhesive between particles, and the viscosity of a coating solution using kaolin and an adhesive is relatively increased. When only enzyme-modified dextrin is used as an adhesive, the increase in viscosity of the concentrated coating liquid can be suppressed even when used in combination with kaolin, but the quality is insufficient in terms of uneven ink deposition and printed surface strength. is there. When the content of the enzyme-modified dextrin is increased in order to supplement the printing surface strength, the increase in the viscosity of the coating liquid when the concentration is increased cannot be suppressed. In addition, when only latex is used as the adhesive, the viscosity may increase when the concentration of the coating solution using kaolin and latex is increased, and the resulting coated coated paper may be obtained without increasing the viscosity. The quality is insufficient in terms of uneven ink deposition and printed surface strength.

  In the present invention, the enzyme-modified dextrin contained in the outermost coating layer is not particularly limited in the production method. For example, after the starch slurry is adjusted to a predetermined concentration and pH, α-amylase or other substances as required The enzyme can be liquefied using the enzyme, and then the enzyme is inactivated by heat treatment (for example, 110 ° C. to 150 ° C.) or acid treatment, and dried. Such enzyme-modified dextrin is commercially available from Sanwa Starch Co., Ltd. and can also be obtained.

  In the present invention, examples of the latex contained in the outermost coating layer include conjugated diene copolymer latex such as styrene / butadiene copolymer latex and methyl methacrylate / butadiene copolymer latex, and methyl acrylate / styrene copolymer latex. , Obtained by copolymerizing a vinyl group copolymer latex of acrylic acid ester or methacrylate ester such as methyl methacrylate / vinyl acetate copolymer latex, or a monomer containing functional groups such as carboxyl groups of these various copolymer latexes. Conventionally known latexes such as modified latexes can be used. From the viewpoint of printing surface strength, styrene / butadiene copolymer latex is preferable.

  In the present invention, the content of the enzyme-modified dextrin and latex in the outermost coating layer is 1 to 15 parts by mass and 3 parts by mass with respect to 100 parts by mass of the total pigment in the outermost coating layer. The range is 6 parts by mass or less.

  Since kaolin is flat, it has excellent base paper coverage and smoothness and white paper gloss, but it tends to thicken in a coating solution containing kaolin and an adhesive. Enzyme-modified dextrins are rich in water solubility, and thus migration of enzyme-modified dextrins tends to cause uneven ink deposits on the coated paper for printing and a decrease in printing surface strength. On the other hand, latex adsorbs to kaolin and forms a film through a drying process. However, since the latex film has low water retention, a water film is formed in offset printing, and uneven ink deposition tends to occur. Further, although depending on the drying temperature in the drying process and the particle diameter of the latex, the film may not be uniformly formed, and the printing surface strength is lowered.

  In the present invention, by containing kaolin as a pigment and enzyme-modified dextrin and latex as an adhesive in the outermost coating layer within the above content range, an increase in the viscosity of the highly concentrated coating liquid can be suppressed. By using a highly concentrated coating liquid, it is possible to obtain a coated paper for printing which is excellent in base paper coverage, hardly causes uneven ink deposition, and has excellent printing surface strength.

The reason for this is not clear, but it is presumed that it is as follows.
While kaolin and latex form a sandwich structure, the enzyme-modified dextrin suppresses the thickening of the coating solution due to its hydrophilicity and ease of migration, and complements the water retention of the outermost coating layer. On the other hand, it is considered that latex complements the printing surface strength by adsorption with kaolin, and suppresses excessive migration of enzyme-modified dextrin in the outermost coating layer due to its hydrophobicity and film formation between kaolin particles.

  The composite action as described above of the present invention is such that the content of the enzyme-modified dextrin and latex is 1 to 15 parts by mass and 3 parts by mass with respect to 100 parts by mass of the total pigment in the outermost coating layer, respectively. It can be obtained when it is in the range of not less than 6 parts by mass. If any one of the ranges is out of this range, at least one of the effects of the present invention cannot be satisfied.

  In the present invention, the content of kaolin in the outermost coating layer is not particularly limited, but preferably 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the total pigment in the outermost coating layer. It is a range. By setting the kaolin content of the outermost coating layer within the above range, excellent printing gloss can be obtained. In particular, when fine kaolin having a particle diameter of less than 2 μm and having a particle diameter of less than 2 μm is used in order to obtain a glossy white paper, the kaolin content of the outermost coating layer is more remarkable in the above range. Become. In the present invention, the ratio of particles having a particle diameter of less than 2 μm is a particle size distribution measured by a laser diffraction / scattering particle size distribution meter (trade name: Microtrac MT-3000II series, manufactured by Nikkiso Co., Ltd.). The volume integration of the particles is obtained.

  In the present invention, the outermost coating layer preferably contains other pigments in combination with kaolin. For example, heavy calcium carbonate, light calcium carbonate, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, alumina hydrate, amorphous silica, colloidal silica, magnesium carbonate, magnesium oxide, magnesium aluminosilicate, Organic pigments such as calcium silicate, white carbon, satin white, bentonite, zeolite, sericite, smectite, polystyrene resin, styrene / acrylic copolymer resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin, benzoguanamine resin The conventionally well-known pigment used for a pigment and other coated paper can be mentioned. In addition, pigments of various shapes such as these fine hollow particle types and through-hole types can also be used. You may select combining these from these.

  In the present invention, the pigment used in combination with the kaolin of the outermost coating layer may contain a pigment having a smaller specific surface area than the kaolin of the outermost coating layer in terms of suppressing a decrease in printing surface strength. preferable.

  In a preferred embodiment of the present invention, the concentration of the coating solution for forming the outermost coating layer is preferably high. Printing paper that does not prevent the coating solution of the outermost coating layer from having a low concentration or medium concentration, but forms a coating layer of the outermost layer by coating a coating solution with a high concentration In this case, the effect of the present invention becomes remarkable. In the present invention, the high concentration means that the solid content concentration of the coating liquid is 65% by mass or more, and the effect of the present invention becomes remarkable when the solid content concentration of the coating liquid is 65% by mass or more. The concentration of the outermost layer coating liquid is preferably as high as possible, but it is more preferably 70% by mass or less because it causes the preparation of the coating liquid and crystal precipitation in the equipment.

  In the present invention, as another aspect, there is provided a method for producing a coated paper for printing obtained by coating a coating liquid containing at least a pigment and an adhesive on a base paper. The outermost layer coating layer contains kaolin as a pigment for the outermost coating layer in an amount of 10 to 30 parts by weight with respect to 100 parts by weight of the total pigment in the outermost coating layer. Enzyme-modified dextrin and latex are contained as a layer adhesive, and enzyme-modified dextrin is 1 to 15 parts by mass and latex is 3 to 6 parts by mass with respect to 100 parts by mass of the total pigment in the outermost coating layer. It is the manufacturing method of the coating paper for printing which forms the coating layer of the outermost layer contained in the range below a part by applying the coating liquid whose solid content concentration is 65 mass% or more.

  The coated paper for printing obtained by the above production method has excellent base paper coverage and printing gloss, suppresses an increase in the viscosity of the highly concentrated coating liquid, and is difficult to cause uneven ink deposition. Excellent surface strength.

  In the present invention, in addition to kaolin, enzyme-modified dextrin, latex, the pigment, and the adhesive, a conventionally known auxiliary agent used for producing coated paper is appropriately used for the outermost coating layer. Can be contained. For example, a dispersant, a water retention agent, an antifoaming agent, a water resistant agent, a colorant, a pH adjuster and the like can be mentioned.

  In the present invention, the method for coating the outermost coating layer is not particularly limited. For example, blade coater, air knife coater, roll coater, bar coater, curtain coater, short dwell coater, shim sizer, gate roll coater, etc. Various conventionally known coating methods can be used.

In the present invention, the coating amount of the outermost coating layer is not particularly limited, but is preferably 6 to 25 g / m ² , more preferably 8 to ²⁰ g / m ^{2 in} terms of solid content. When the coating amount is 6 to 25 g / m ² per side, the base paper or the intermediate coating layer to be described later can be coated relatively evenly, resulting in excellent white paper gloss and uneven ink deposition. It is preferable because it is difficult. When it is 8 to ²⁰ g / m ² per one side, it can be coated more uniformly, which is preferable.

  In the present invention, a coating layer (hereinafter referred to as “intermediate coating layer”) can be provided between the outermost coating layer and the base paper. In the intermediate coating layer, conventionally known pigments, adhesives and various auxiliaries used for coated paper for printing can be appropriately selected and contained.

  In the present invention, examples of the pigment contained in the intermediate coating layer include heavy calcium carbonate, light calcium carbonate, clay, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, amorphous silica, and colloidal. Silica, alumina, alumina hydrate, magnesium carbonate, magnesium oxide, magnesium aluminosilicate, calcium silicate, white carbon, satin white, bentonite, zeolite, sericite, smectite, etc., polystyrene resin, styrene / acrylic copolymer Examples thereof include organic pigments such as resins, urea resins, melamine resins, acrylic resins, vinylidene chloride resins, and benzoguanamine resins, and other conventionally known pigments used for coated paper. In addition, pigments of various shapes such as these fine hollow particle types and through-hole types can also be used. At least one of these can be appropriately selected and used.

  In the present invention, as the adhesive contained in the intermediate coating layer, enzyme-modified dextrin or latex contained in the outermost coating layer, and conventionally known, for example, cationized starch, oxidized starch, ethylated starch, acetylated Examples thereof include starches such as starch and phosphate esterified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, and gums such as polyvinyl alcohol, guar gum and locust bean gum. Also, at least one of these can be appropriately selected and used.

  In the present invention, the intermediate coating layer is a conventionally known layer used for producing coated paper such as a dispersant, a water retention agent, an antifoaming agent, a water resistant agent, a colorant, and a pH adjuster as necessary. These various auxiliary agents can be appropriately contained.

  In the present invention, the method of coating the intermediate coating layer is not particularly limited, for example, blade coater, air knife coater, roll coater, bar coater, curtain coater, short dwell coater, shim sizer, gate roll coater, etc. Various known coating methods can be used.

In the present invention, the coating amount of the intermediate coating layer is not particularly limited, but is preferably 6 to 25 g / m ² per side in terms of solid content. In particular, the coating layer in contact with the base paper can coat the base paper relatively uniformly when the coating amount is 6 to 25 g / m ² per side, and as a result, the outermost layer provided on the intermediate coating layer This is preferable because the coated paper layer has better white paper gloss and is less likely to cause uneven ink deposition.

  In the present invention, the base paper is not particularly limited. For example, chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, PGW, RMP, TMP, CTMP, and CGP, and various conventionally known pulps such as waste paper pulp Contains at least one, and if necessary, conventionally known various fillers and sizing agents such as light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, fixing agent, retention agent, paper strength enhancer, etc. A paper stock containing these various additives can be made by paper, and any of paper making methods of acid, neutral and alkaline may be used.

  In the present invention, the base paper can be subjected to size press treatment with a size press liquid containing starch, polyvinyl alcohol and the like. Further, calendering can be performed to obtain the required density, smoothness and thickness of the base paper.

  In the present invention, the coated paper for printing can be subjected to a calendar process such as a super calendar, a gloss calendar, or a soft calendar at each stage where the outermost coating layer or the intermediate coating layer is provided.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. When there is no notice in particular, "part" is a mass part and "%" is the mass%. Further, “part” or “%” of the solid content is shown.

<Preparation of base paper>
A paper stock was prepared with the following composition, and a base paper having a basis weight of 70 g / m ² was made.
(Combination)
LBKP (freeness 440 mlcsf) 70 parts NBKP (freeness 490 mlcsf) 30 parts light calcium carbonate 6 parts cationized starch 1 part sulfate band 1 part alkyl ketene dimer internal sizing agent (AKD) 0.2 parts cationic poly Acrylamide yield improver 0.03 parts

To this base paper, 0.30 g / m ² of oxidized starch was adhered by a size press per both sides to obtain a base paper for coating.

The production of the coated paper for printing was performed as follows.
Using a blade coater, a coating liquid having a composition corresponding to each example or each comparative example was applied to both sides at a coating speed of 14 g / m ^{2 on} one side of the base paper for coating. Worked and dried. The obtained coated paper was calendered using a super calender finishing device (rigid roll: chilled roll, elastic roll: cotton roll, linear pressure: 2.2 kN / cm) to produce a coated paper for printing.

  The applicability of the coating liquid having a formulation corresponding to each Example or each Comparative Example and the evaluation of the coated paper for printing obtained in each Example or each Comparative Example were performed by the following methods.

<Coating suitability of coating liquid>
The B-type viscosity and capillary viscosity of each coating solution prepared with a solid content concentration of 65% or more were measured. The B type viscosity was measured using a commercially available B type viscometer under the conditions of a temperature of 25 ° C. and a rotation speed of 60 rpm. The capillary viscosity was measured using “ACAV” manufactured by ACA Systems Oy under the conditions of a temperature of 25 ° C., a pressure of 20 MPa, and a capillary inner diameter of 0.5 mm. From the measured value, the suitability of the coating solution was judged according to the following criteria. In this invention, if evaluation is (circle), it can be said that there exists applicability | paintability of a coating liquid.
○: B-type viscosity value of 3000 mPa · s or less and capillary viscosity value of 150 mPa · s or less Δ: Either B-type viscosity value or capillary viscosity value does not satisfy the above x: B-type viscosity value of more than 3000 mPa · s and capillary viscosity Value over 150 mPa · s

<Base paper coverage>
The obtained coated paper for printing was cut into A4 size and immersed in a solution of deionized water / ethanol / ammonium chloride = 50/45/5 by mass ratio for 1 hour. Thereafter, the coated paper for printing was taken out of the solution and sandwiched with filter paper to wipe off the excess solution. Further, it was put in a dryer at 150 ° C. for 3 hours and then taken out. As a result, the base paper portion made of organic matter is burnt brown, and the portion covered with the coating layer remains white. The more white parts there are, the better the base paper is coated with the coating layer. The degree of the white part was judged visually and evaluated in four stages. If it is 3 or more, there is no practical problem.
4: There are almost no brown parts and almost all are white parts.
3: The brown part is present but slightly visible, and the white part is overwhelming.
2: Although the brown part is visible, it is almost the same as the white part or slightly white part.
1: There are more brown parts.

<Print gloss>
After using the RI printing aptitude tester, indigo, red and yellow heavy solid printing, leave it at room temperature all day and night, and use a Murakami gloss meter to measure the glossiness at 60 ° -60 ° reflectivity. It was measured. The gloss value was evaluated according to the following criteria. In the present invention, excellent print gloss is an evaluation of 3 or more.
4: Print gloss is 70% or more 3: Print gloss is 65% or more and less than 70% 2: Print gloss is 60% or more and less than 65% 1: Print gloss is less than 60%

<Ink unevenness>
A four-color overprint halftone of Dainippon Ink Co., Ltd. space color fusion-G was printed using a Mitsubishi Heavy Industries diamond four-color printing machine, and ink inking unevenness was evaluated in the following five stages by visual judgment. If it is 3 or more, there is no practical problem.
5: Best 4: Good 3: Acceptable level 2: Poor 1: Extremely bad

<Print surface strength>
Using an RI printing aptitude tester, a single color solid printing of a strong tack ink for IGT testing was performed, and the paper peeling state was evaluated as the printing surface strength according to the following four stages by visual judgment. If it is 3 or more, there is no practical problem.
4: Good with no paper peeling 3: Slight paper peeling is observed, but there is no problem Level 2: Paper peeling is recognized 1: Many paper peeling

<Preparation of coated paper for printing>
Example 1
75 parts of heavy calcium carbonate (trade name: FMT-90 / Pimatec) and 25 parts of primary kaolin (trade name: KAOFINE90 / Shiraishi Calcium Co., Ltd., the ratio of particle diameter of less than 2 μm is 95 to 100% by volume) An enzyme-modified dextrin (trade name: High Coaster PC-11 / 3) was added to a dispersion obtained by adding 0.1 part of an acrylic acid dispersant (trade name: Aron T-40 / Toa Gosei Co., Ltd.) and dispersing with a disperser. 7 parts of Japanese starch industry) was added. To this, 5 parts of styrene / butadiene copolymer latex and 0.3 part of calcium stearate were added, the pH was adjusted to 9.8 with sodium hydroxide, and a coating solution having a solid content concentration of 68% was obtained with adjusted water. Coating was performed on the base paper for coating by the above-described method, and the coated paper for printing of Example 1 was obtained.

(Examples 2 to 10, Comparative Examples 1 to 7)
In Example 1, it carried out similarly to Example 1 except having changed into the mixing | blending of the coating liquid described in Table 1, and it was set as each Example or each comparative example. The concentration was adjusted by adjusting water or concentration, respectively. The concentration of each coating solution is shown in Table 1. In addition, since the coating liquid corresponding to the comparative example 5 and the comparative example 6 increased in viscosity and could not be applied at a high concentration, it was applied at a concentration of less than 65%. A coated paper for printing was obtained.

The materials indicated by the alphabets listed in Table 1 are as follows.
A: Heavy calcium carbonate (trade name: FMT-90 / Pimatech)
B: Light calcium carbonate (trade name: Tama Pearl TP-123 / Okutama Kogyo Co., Ltd.)
C: Urea phosphate esterified starch (trade name: MS4600 / Nippon Shokuhin Kako)
D: Low-viscosity phosphate esterified starch (trade name: HSS Coat 300 / Oji Cornstarch)

  Table 1 shows the composition and evaluation results of each Example and each Comparative Example.

  As is clear from Table 1, it can be seen that Examples 1 to 10 according to the present invention have a coating suitability by suppressing an increase in viscosity even when the concentration of the coating solution is increased. It can be seen that the obtained coated paper for printing has excellent base paper coverage, little occurrence of uneven ink deposition, and no reduction in printing surface strength. In particular, when the kaolin content is 10 parts or more and 30 parts or less with respect to 100 parts of the total pigment in the outermost coating layer as in Examples 1 to 5, Example 7, Example 9 and Example 10, the printed gloss It turns out that it is superior. On the other hand, such an effect is not obtained in the comparative example. The coated paper for printing obtained with the formulation not according to the present invention did not satisfy any of the effects.

Claims (2)

  A printing paper having at least one coating layer containing at least a pigment and an adhesive on a base paper, wherein the outermost coating layer contains at least kaolin as a pigment, and the outermost coating layer A coating for printing, comprising 100 parts by mass of all pigments as an adhesive and containing 1 to 15 parts by mass of enzyme-modified dextrin and 3 to 6 parts by mass of latex. paper.   The coated paper for printing according to claim 1, wherein the outermost coating layer contains kaolin in a range of 10 parts by mass to 30 parts by mass with respect to 100 parts by mass of all pigments in the outermost coating layer. .