WO2020036223A1

WO2020036223A1 - Coated paper

Info

Publication number: WO2020036223A1
Application number: PCT/JP2019/032149
Authority: WO
Inventors: 謙史郎宮内; 川島　正典; 遼外岡
Original assignee: 日本製紙株式会社
Priority date: 2018-08-17
Filing date: 2019-08-16
Publication date: 2020-02-20
Also published as: JP2024020406A; JP7387610B2; JPWO2020036223A1

Abstract

Provided is a coated paper in which a pigment coating layer is provided on base paper, wherein: the amount coated is at least 5.0 g/m² per single surface; Oken smoothness is not more than 65 seconds; and ISO whiteness is at least 70%.

Description

Coated paper

The present invention relates to a coated paper having good ink drying properties.

In recent years, with the decrease in the number of newspaper sales on paper media, an effort to utilize a newspaper rotary press for applications other than newspapers has begun. In general, printing by a newspaper rotary press (offset printing) using an ink for cold setting of a penetration drying type has no drying step, and the ink is dried by penetrating the ink into the paper. Ink absorption is required. Poor ink absorptivity of paper causes problems such as generation of stains on the printing press and the paper surface, reduction in printing speed, and the like, resulting in deterioration of print quality and operability. In such a printing method, uncoated paper having no pigment coating layer, particularly newsprint containing a large amount of waste paper pulp, has been generally used. However, when uncoated paper or newsprint paper is used, the ink drying property is good, but there is a problem that the ink inking property and print gloss are not sufficient, so that cold set offset printing is used for printing information other than characters. Has been a major obstacle in using. To solve this problem, news inks corresponding fine coated paper having a single side per 0.5 g / m ² or more 4.0 g / m ² less pigment coating layer has been proposed in Patent Document 1. This finely coated paper makes it possible to achieve printability with excellent ink drying properties and sharpness comparable to newsprint. Patent Document 2 proposes an offset printing paper for cold setting in which a surface treatment agent containing a plastic pigment and a synthetic adhesive is applied at 4 g / m ² or more per side. This printing paper is said to have high print gloss, suitability for color printing, and little drag smear.

JP 2007-31927 A JP 2012-117174 A

An object of the present invention is to provide a coated paper having excellent ink drying properties, ink deposition, and printing gloss.

The above object is achieved by the present invention described below.
[1] Coated paper provided with a pigment coated layer on base paper,
The coating amount of the pigment coating layer is 5.0 g / m ² or more per side,
Oken type smoothness is 65 seconds or less,
Coated paper having ISO whiteness of 70% or more.
[2] The coated paper according to [1], wherein the total amount of calcium carbonate and clay is 80 parts by weight or more per 100 parts by weight of the pigment in the pigment coated layer.
[3] The coating according to [1] or [2], wherein the 75 ° glossiness when solid printing is performed using a newsprint ink for cold setting to have a print density of 1.6 is 30% or more. paper.
[4] The coated paper according to any one of [1] to [3], wherein the coating amount is 8.0 g / m ² or less per side.
[5] The coated paper according to any one of [1] to [4], wherein the coated paper has a basis weight of 45 to 75 g / m ² .
[6] The coated paper according to any one of [1] to [5], wherein the density of the coated paper is 0.5 to 1.0 g / cm ³ .
[7] The method according to any one of [1] to [6], further comprising a step of providing a pigment coating layer of 5.0 g / m ² or more per side on a base paper having an Oken type smoothness of 20 seconds or less. Manufacturing method of coated paper.

According to the present invention, it is possible to provide a coated paper having excellent ink drying properties, ink deposition properties, and printing gloss.

Hereinafter, the present invention will be described in detail. In the present invention, “X to Y” includes end values X and Y.

1. Coated paper In the present invention, coated paper is paper having a specific amount of a pigment coated layer on base paper. The coated paper of the present invention is particularly suitable for offset printing with cold setting ink such as news ink.

(1) Pigment coating layer The pigment coating layer is a layer containing a white pigment as a main component. The coated paper of the present invention has a pigment coated layer of 5.0 g / m ² or more per one side. The coating amount is preferably 5.5 to 8.0 g / m ² per one side, and the upper limit thereof is more preferably 7.0 g / m ² or less. As white pigments, commonly used pigments such as calcium carbonate, kaolin, clay, calcined kaolin, amorphous silica, zinc oxide, aluminum oxide, satin white, aluminum silicate, magnesium silicate, magnesium carbonate, titanium oxide, plastic pigment, etc. Is mentioned.

と When the pigment coating layer contains calcium carbonate or clay, the smoothness of the coated paper is improved, so that a printed image with high definition and good color development can be obtained. From this viewpoint, the total amount of calcium carbonate and clay is preferably at least 80 parts by weight, more preferably at least 90 parts by weight, per 100 parts by weight of the pigment in the pigment coating layer. The upper limit of the total amount is not limited and is 100 parts by weight or less.

カルシウム The average particle size of calcium carbonate is preferably 0.5 to 1.0 μm. The average particle diameter can be measured with a laser diffraction type particle size distribution analyzer such as a Mastersizer manufactured by Malvern, and D50 can be set as the average particle diameter. The content of the calcium carbonate particles having a particle diameter of 2.0 μm or less is preferably 90% by volume or more, more preferably 93% by volume or more, and further preferably 95% by volume or more. Examples of calcium carbonate include heavy calcium carbonate and light calcium carbonate. Further, as the light calcium carbonate, light calcium carbonate (caustic light calcium carbonate) described in Japanese Patent No. 5274077 or the like may be used.

The average particle diameter of the clay is preferably 6.0 µm or less. When the particle diameter of the clay is small, fine voids can be formed in the coating layer, and the ink drying property can be improved. The average particle size of the clay can also be measured with a laser diffraction type particle size distribution analyzer or the like, and D50 can be set as the average particle size. The lower limit of the average particle size is not limited, but is preferably 1.0 μm or more. From the viewpoint of whiteness, the clay content in the total amount of calcium carbonate and clay is preferably 50 parts by weight or less, more preferably 40 parts by weight or less.

The pigment coating layer contains an adhesive. Examples of the adhesive include oxidized starch, positive starch, urea phosphate esterified starch, etherified starch such as hydroxyethyl etherified starch, various starches such as dextrin, casein, soy protein, proteins such as synthetic protein, and polyvinyl. Alcohol, cellulose derivatives such as carboxymethylcellulose and methylcellulose, styrene-butadiene copolymer, conjugated diene-based polymer latex of methylmethacrylate-butadiene copolymer, acrylic-based polymer latex, and vinyl-based such as ethylene-vinyl acetate copolymer Polymer latex and the like can be mentioned. These can be used alone or in combination of two or more. It is preferable to use a mixture of a starch-based adhesive and a latex-based adhesive because the balance between the coating suitability of the pigment coating solution and the printability such as surface strength is excellent. The total amount of the adhesive in the pigment coating layer is preferably 1 to 15 parts by weight, more preferably 2 to 14 parts by weight, and still more preferably 3 to 13 parts by weight based on 100 parts by weight of the pigment. If the amount of the adhesive is less than 1 part by weight, the adhesive is insufficient and the strength of the coating layer is weakened, so that many defects such as white spots may occur during printing. On the other hand, if the amount is more than 15 parts by weight, the voids in the pigment coating layer become insufficient, so that the penetration type cold set type ink hardly penetrates the paper, and the drying property may be poor.

The pigment coating layer may contain various auxiliaries such as a dispersant, a thickener, an antifoaming agent, a coloring agent, an antistatic agent and a preservative used in the general paper manufacturing field.

The pigment coating layer can be provided by coating a coating liquid on one side or both sides of a base paper by a known method. The solid content concentration in the coating liquid is preferably about 30 to 70% by weight from the viewpoint of coating suitability. The pigment coating layer may be one or more layers, but is preferably one layer because it is a finely coated paper. The total coating amount of the pigment coating layer is 5.0 g / m ² or more per one surface, and preferably 5.5 g / m ² or more. The upper limit of the coating amount is preferably 8.0 g / m ² or less, and more preferably less than 7.0 g / m ² . If the coating amount is less than 5 g / m ² , the coating layer cannot sufficiently cover the base paper, so that the ink coloring property is reduced. On the other hand, if the coating amount is excessively high, the penetration of the ink becomes worse, and the ink drying property decreases.

(2) Base Paper The pulp raw material of the base paper used in the present invention is not particularly limited, and mechanical pulp such as ground pulp (GP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP), waste paper pulp (deinking pulp ( DIP)), chemical pulp such as softwood kraft pulp (NKP) and softwood kraft pulp (LKP). As the waste paper pulp, selected waste paper such as high quality paper, medium quality paper, lower grade paper, newsprint, flyer, magazine and the like and unsorted waste paper mixed with these can be used, but medium quality paper containing mechanical pulp can be used. It is preferably used paper pulp containing raw paper, lower grade paper and newsprint as raw materials. The printing paper of the present invention contains at least 30 parts by weight of chemical pulp based on 100 parts by weight of pulp. By containing a large amount of chemical pulp, the density of the printing paper can be improved and the ink can be prevented from excessively penetrating deep into the base paper, so that the ink coloring property can be improved. In this respect, the lower limit of the chemical pulp content is preferably equal to or greater than 40 parts by weight, and more preferably equal to or greater than 50 parts by weight. On the other hand, paper is required to have an appropriate degree of rigidity in a printing step, a processing step, or when a book is formed. Therefore, it is preferable to contain a certain amount of mechanical pulp or waste paper pulp containing mechanical pulp as a raw material. Therefore, the upper limit of the chemical pulp content is preferably 90 parts by weight or less, more preferably 80 parts by weight or less.

The coated paper of the present invention preferably contains mechanical pulp or waste paper pulp containing mechanical pulp in 100 parts by weight of pulp, and more preferably 10 parts by weight or more in total, and more preferably 20 parts by weight or more. . The upper limit of the total amount is preferably 50 parts by weight or less. When the total amount exceeds this value, the density may decrease and the ink colorability may decrease, and further, the whiteness may decrease and the appearance of an image may decrease.

A known filler can be added to the base paper. As the filler, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delamikaolin, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, Inorganic fillers such as amorphous silica produced by neutralization of magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide and sodium silicate with mineral acids, urea-formalin resin, melamine resin, polystyrene resin, phenol Organic fillers such as resins are included. These may be used alone or in combination. Among these, calcium carbonate and light calcium carbonate-silica composite, which are representative fillers in neutral paper and alkali paper, and provide high opacity, are preferred.

嵩 As internal additives, bulking agents, dry paper strength improvers, wet paper strength improvers, drainage improvers, dyes, neutral sizing agents and the like may be used as necessary. Examples of the dry paper strength improver include polyacrylamide and cationized starch, and examples of the wet paper strength improver include polyamidoamine epichlorohydrin. These chemicals are added within a range that does not affect formation or operability. Examples of the neutral sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, and neutral rosin sizing agent. Although a bulking agent may be used, it is preferable to use a small amount thereof, and it is more preferable not to use the bulking agent because it may be too bulky. When a bulking agent is used, the paper thickness is preferably adjusted by calendering or the like so that the density of the paper falls within the range of the present invention. These internal additives can be used together with pulp and filler as needed to make paper stock.

The base paper is preferably a single-layer paper, and is manufactured by a known papermaking method. For example, it can be performed using a fourdrinier paper machine, a gap former type paper machine, a hybrid former type paper machine, an on-top former type paper machine, a round net paper machine, or the like, but is not limited thereto. The offset printing paper for cold setting of the present invention may be manufactured by an on-machine system in which a papermaking process and a pigment coating process are continuous, or an off-machine system in which coating is performed in a pigment coating process after the papermaking process. May be. The papermaking and coating speed is preferably from 400 to 2000 m / min.

The Oken type smoothness of the base paper is preferably 20 seconds or less. When the smoothness is 20 seconds or less, the smoothness of the surface of the base paper is at a relatively low level. However, when the smoothness of the base paper is at this level, even if the coating amount of the pigment coating layer is large, ink Drying property can be improved. Although the reason for this is not clear, when the smoothness of the base paper is within the above range, the specific surface area of the coated paper after providing the pigment coating layer is increased, and the smoothness is low, so that It is presumed that the ink absorbability is improved due to the low base paper covering property and the easy absorption of the ink into the exposed base paper. The lower limit of the Oken type smoothness is not limited, but is preferably 5 seconds or more, and more preferably 10 seconds or more. Furthermore, since the coated paper of the present invention has a pigment coating layer of 5 g / m ² or more, the ink inking property and the printing gloss are good, and the ink has both ink drying property, ink inking property and high printing gloss. .

(3) Other treatments The coated paper of the present invention may further have a clear coating layer containing an adhesive as a main component on one or both sides of the base paper. The clear coating layer is preferably adjacent to the base paper layer, but may be provided on the outermost layer farthest from the base paper. The adhesive used for the clear coating layer is as described above. When a clear coating layer is provided adjacent to the base paper, it is possible to suppress the penetration of the pigment coating liquid into the base paper, and it is preferable because the base paper coatability of the pigment coating layer is improved. Starch is preferred. In addition, the strength of the base paper is improved by the penetration of the clear coating liquid into the base paper. From the above, the coating amount of the clear coating layer on both sides, preferably 0.5 ~ 5.0g / ^{m 2,} more preferably ^{1.0 ~ 4.5g / m 2, 2.0} ~ 4.0g / m ² is more preferred.

塗 The coated paper of the present invention may be subjected to a surface treatment. Examples of the surface treatment include treatment with a soft calender, a super calender, a gloss calender, a heat calender, and a shoe calender.

(4) Properties of Coated Paper of the Present Invention 1) Oken Type Smoothness The coated paper of the present invention has an Oken type smoothness (JIS P8155) of 65 seconds or less, preferably 60 seconds or less. If this value exceeds the upper limit, the permeation speed of the ink becomes slow, and the drying property decreases. The lower limit is not limited, but is preferably 30 seconds or more from the viewpoint of surface properties such as print gloss.

2) ISO Whiteness The coated paper of the present invention has an ISO whiteness (JIS P8148) of 70% or more, preferably 75% or more, more preferably 80% or more. If the whiteness is less than 75%, the whiteness of the white paper portion decreases, and the appearance of an image after printing also decreases.

3) Printing Gloss The coated paper of the present invention preferably has a 75 ° gloss of 30% or more when solid printed using newspaper ink for cold setting so that the printing density is 1.6. , 35% or more. When the glossiness is less than 30%, the glossiness of the printed matter is insufficient, and the appearance of an image after printing may be reduced.

4) Basis Weight and Density The basis weight of the coated paper of the present invention is preferably 45 g / m ² or more, more preferably 50 g / m ² or more, and further preferably 55 g / m ² or more. In addition, the upper limit of the grammage is preferably 75 g / m ² or less, more preferably 70 g / m ² or less, and even more preferably 65 g / m ² or less. From the viewpoint of ease of turning when making a book, Most preferably, it is 63 g / m ₂ or less. If the basis weight is less than 45 g / m ^2, such as insufficient stiffness of the paper upon the book, there is a possibility that the hand Nikkan poor, if it is 75 g / m ^2, greater than a monolayer from the viewpoint of drainage May make it difficult to make paper. The density of the paper is preferably 0.5 to 1.0 g / cm ³ , more preferably 0.6 to 0.9 g / cm ³ .

2. Method for Producing Coated Paper of the Present Invention The coated paper of the present invention is preferably produced through a step of providing a pigment-coated layer having the above-mentioned coating amount by blade coating on one or both sides of the base paper. The pigment coating layer can also be provided by roll coating in addition to this, but since blade coating is a coating method in which the coating liquid is applied and then scraped with a blade, a coating surface with high smoothness is obtained. And a printing paper having good ink coloring properties can be obtained.

3. Applications The coated paper of the present invention exhibits excellent ink drying properties, ink deposition, and print gloss in offset printing for cold setting, and thus is suitable for offset printing for cold setting. In particular, when used for cold-set offset printing using a rotary press, a large amount of high-quality printed matter can be efficiently produced at high speed. Therefore, the coated paper of the present invention is suitable for applications in which printing with cold setting ink is used, and is useful, for example, as newsprint paper, book paper, comic paper, textbook paper, and the like. Further, since the coated paper of the present invention has good ink drying properties, it can also be used in an on-demand printing method such as ink jet, which requires ink drying properties and color developing properties.

[Example 1]
As base paper, NBKP30 wt%, LBKP23 wt%, 27 wt% deinked pulp, and paper making to prepare a paper stock containing 12 wt% precipitated calcium carbonate as GP20 wt% filler, density of 0.56 g / cm ^3, a basis A base paper 2 having an amount of 54 g / m ² was prepared. 82 parts by weight (solid content) of heavy calcium carbonate (manufactured by Fimatec Co., Ltd., trade name: FMT97, particle size of 2 μm or less by sedimentation method: 97%, D50 = 0.64 μm) as a pigment 18 parts by weight (solid content) of clay (trade name: KCS, D50 = 4.9 μm, manufactured by IMERYS), 5 parts by weight of a styrene-butadiene copolymer latex as an adhesive, and 7.5 parts by weight of oxidized starch Were added, and water was further added to obtain a coating liquid 1 having a solid content concentration of 55% by weight. On one side of the base paper, the pigment coating liquid was coated with a blade coater so that the dry coating amount was 5.5 g / m ² (target coating amount), and then dried to obtain a coated paper. . The coated paper was evaluated by the method described below.

[Example 2]
A coated paper was obtained and evaluated in the same manner as in Example 1, except that the coating amount was changed as shown in Table 3.

[Example 3]
Coating liquid 2 was obtained in the same manner as coating liquid 1, except that 100 parts by weight (solid content) of a secondary clay (manufactured by IMERYS, trade name: KCS, D50 = 4.9 μm) was used as the pigment. A coated paper was obtained and evaluated in the same manner as in Example 1, except that the coating liquid 1 was changed to the coating liquid 2.

[Comparative Examples 1 and 2]
Coated paper was obtained and evaluated in the same manner as in Example 1, except that the target coating amount was changed to 4.0 g / m ² and 3.0 g / m ² , respectively.

[Comparative Examples 3 and 4]
Base paper 2 was calendered at a linear pressure of 20 kg to obtain base paper 1. Coated paper was obtained and evaluated in the same manner as in Example 2 and Comparative Example 1 except that this was used.

[Comparative Example 5]
The coated paper obtained in Comparative Example 3 was calendered at a linear pressure of 60 kg, and a coated paper was obtained and evaluated in the same manner as in Comparative Example 3.

示す As shown in Table 3, it is clear that the coated paper of the present invention has excellent ink drying properties, ink deposition and printing gloss in offset printing for cold setting.

The details of the evaluation method will be described below.
(1) White paper glossiness Measured according to JIS P8142.
(2) Basis Weight The basis weight was measured in accordance with “Method for measuring basis weight” described in JIS P8124.
(3) Paper Thickness and Density Measured in accordance with JIS 8118 “Paper and paperboard-Test method for thickness and density”.
(4) Oken-type smoothness Measured based on JIS P8155.
(5) Whiteness ISO whiteness measurement method: Measured with a light source containing ultraviolet light using a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. in accordance with JIS P8148.
(6) Ink drying properties Offset printing for cold setting (Media Shine black manufactured by DIC Graphics Co., Ltd.) is performed with a manual RI printing machine (manufactured by Akira Seisakusho Co., Ltd.), and the printed matter after 1 minute of printing is coated. It was transferred to paper, and the degree of soiling of the coated paper was evaluated visually and numerically. In the numerical evaluation, the Y value difference (white paper-ink transfer portion) was evaluated using X-Rite (manufactured by X-Rite).
A: Transfer of ink is small and drying property is excellent.
B: Transfer of ink was slight, but no problem in use.
C: The ink is not dried and cannot be used.
(7) Ink Ink Concentration The print density of the sample printed in (6) was measured one hour after printing using X-Rite (manufactured by X-Rite).
A: Above 1.50, good ink deposition.
B: 1.40 to 1.50, and ink deposition was slightly good.
C: Less than 1.40, poor ink deposition.
(8) Printing Gloss The printing gloss of the sample printed in the above (6) was measured according to JIS P-8142 after being left for 1 day in an environment of 23 ° C. and 50% relative humidity after printing. The print glossiness is equivalent to 75 ° glossiness when solid printing is performed using a cold setting news ink so that the print density is 1.6.
A: Exceeds 35% and print gloss is quite good.
B: 30 to 35%, slightly good printing gloss.
C: Less than 30%, poor print gloss.

Claims

Coated paper having a pigment coated layer on base paper,
The coating amount of the pigment coating layer is 5.0 g / m 2 or more per side,
Oken type smoothness is 65 seconds or less,
Coated paper having ISO whiteness of 70% or more.
The coated paper according to claim 1, wherein the total amount of calcium carbonate and clay is 80 parts by weight or more per 100 parts by weight of the pigment in the pigment coated layer.
The coated paper according to claim 1 or 2, wherein the coated paper has a 75 ° glossiness of 30% or more when solid-printed using a newspaper ink for cold setting to a print density of 1.6.
The coated paper according to any one of claims 1 to 3, wherein the coating amount is 8.0 g / m 2 or less per one side.
The coated paper according to any one of claims 1 to 4, wherein the coated paper has a basis weight of 45 to 75 g / m 2 .
The coated paper according to any one of claims 1 to 5, wherein the density of the coated paper is 0.5 to 1.0 g / cm 3 .
The production of a coated paper according to any one of claims 1 to 6, further comprising a step of providing a pigment coating layer of 5.0 g / m 2 or more per side on base paper having an Oken type smoothness of 20 seconds or less. Method.