WO2019039364A1

WO2019039364A1 - Coldset offset printing paper

Info

Publication number: WO2019039364A1
Application number: PCT/JP2018/030360
Authority: WO
Inventors: 川島　正典; 遼外岡
Original assignee: 日本製紙株式会社
Priority date: 2017-08-25
Filing date: 2018-08-15
Publication date: 2019-02-28
Also published as: JPWO2019039364A1

Abstract

Provided is printing paper with which it is possible to achieve excellent ink drying properties and ink coloring properties by coldset offset printing. This coldset offset printing paper is obtained by providing a pigment coating layer upon base paper, wherein the basis weight is 40–70 g/m2, the coating volume of the pigment coating layer is less than 5 g/m2 per side, and the base paper includes at least 30 parts by weight of chemical pulp per 100 parts by weight of pulp.

Description

Offset printing paper for cold setting

The present invention relates to a coldset offset printing sheet.

In offset printing using a penetration-drying type cold set ink, it is important that the paper have sufficient ink absorbency to dry the ink. If the ink absorbency is poor, problems such as the occurrence of stains on the printing press and the paper surface and the decrease in printing speed may occur. In such a printing method, generally, uncoated paper not provided with a pigment coated layer, particularly newsprint paper containing a large amount of waste paper pulp and not provided with a pigment coated layer is used. However, when uncoated paper or newsprint is used, although the ink drying property is good, there is a problem that the ink coloring property is not sufficient. In order to solve this problem, Patent Document 1 proposes a newspaper ink-compatible finely coated paper provided with a specific pigment coating layer. The fine coated paper can achieve excellent printability with excellent ink drying and sharpness. Further, Patent Document 2 proposes newsprint paper provided with a pigment coated layer of 0.3 to 3.0 g / cm ² per one side. The newsprint is said to have good ink drying properties. Further, Patent Document 3 proposes a microcoated paper provided with a pigment coated layer of 0.5 to 3.0 g / cm ² per one side. The said finely coated paper is excellent in ink drying property, and the clearness of a printing image is also favorable.

Japanese Patent Application Publication No. 2007-31927 JP, 2006-169706, A Japanese Patent Application Publication No. 2007-270377

Problems to be solved by the invention

There is still room for improvement in the ink color developability of the paper described in the above-mentioned patent documents. In view of the circumstances, it is an object of the present invention to provide a printing sheet which exhibits excellent ink drying property and ink coloring property in cold offset printing.

The inventors of the present invention describe that each of the papers described in Patent Documents 1 to 3 has a low density because it contains a large amount of mechanical pulp and deinking pulp and a bulking agent, and thus the paper has many voids between fibers. It was found that the ink drying property was good, but the ink penetrated the inside of the base paper excessively due to the low density, so that the ink coloring property was not sufficient. Then, the inventors have found that by using a large amount of chemical pulp to improve the density, it is possible to achieve both the ink drying property and the ink coloring property. Therefore, the above-mentioned subject is solved by the following present invention.
(1) A coldset offset printing paper comprising a pigment coated layer on a base paper,
The basis weight is 40 to 70 g / m ² ,
The coating amount of the pigment coating layer is less than 5 g / m ² per one side,
30 parts by weight or more of chemical pulp in 100 parts by weight of pulp in the base paper
Offset printing paper for cold setting.
(2) The coldset offset printing paper according to (1), wherein the density is 0.7 to 1.3 g / cm ³ .
(3) The offset printing paper for cold set of (1) or (2) which contains 50 parts by weight or less of used paper pulp in 100 parts by weight of pulp in the base paper.
(4) The cold set according to any one of (1) to (3), wherein 50 parts by weight or more of calcium carbonate having an average particle diameter of 0.5 to 1.0 μm is contained in 100 parts by weight of the pigment in the pigment coating layer Offset printing paper.
(5) The coldset offset printing paper according to any one of (1) to (4), wherein the coating amount of the pigment coating layer is 1.5 to 4.0 g / m ² per one side.
(6) The coldset offset printing paper according to any one of (1) to (5), having an Oken type smoothness of 10 to 200 seconds.
(7) The coldset offset printing paper according to any one of (1) to (6), having an ISO whiteness of 70% or more.
(8) A printing method comprising printing on the coldset offset printing paper according to any one of (1) to (7) using a rotary press.
(9) The method for producing a coldset offset printing paper according to any one of (1) to (8), comprising the step of providing a pigment coated layer by blade coating on one side or both sides of a base paper.

According to the present invention, it is possible to provide a printing sheet which exhibits excellent ink drying property and ink color developability in cold set type offset printing.

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

1. Coldset Offset Printing Paper The coldset offset printing paper of the present invention (hereinafter, also simply referred to as the "printing paper of the present invention") comprises a specific amount of a pigment-coated layer on one side or both sides of a base paper.

(1) Pigment Coating Layer The pigment coating layer is a layer containing a white pigment as a main component. The printing paper of the present invention has a pigment coating layer of less than 5 g / m ² per side. The coating amount is preferably 1.5 to 4.0 g / m ² per one side. 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 pigments and the like as white pigments Can be mentioned. Above all, it is preferable to contain calcium carbonate having an average particle diameter of 0.5 to 1.0 μm from the viewpoint of improving the ink penetration property and improving the smoothness of the printing paper. The average particle size can be measured by a laser diffraction type particle size distribution measuring instrument such as Mastersizer manufactured by Malvern. The content of 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 still more preferably 95% by volume or more. Examples of calcium carbonate include ground calcium carbonate and light calcium carbonate. Alternatively, light calcium carbonate (causticized light calcium carbonate) described in Japanese Patent No. 5274077 and the like may be used as light calcium carbonate. The calcium carbonate content is preferably 50 parts by weight or more, and more preferably 70 parts by weight or more in 100 parts by weight of the white pigment. Although the upper limit of calcium carbonate content is not limited, 100 parts by weight or less is preferable, and 90 parts by weight or less is more preferable. The 50% volume average particle diameter (D50) measured by the above-mentioned laser diffraction type particle size distribution measuring device or the like can be used as the average particle diameter of the pigment. By containing 50 parts by weight or more of calcium carbonate, highly white printing paper can be obtained.

Further, it is preferable to use kaolin or clay in the pigment coating layer in order to improve the ink drying property and the smoothness. The kaolin or clay is preferably 10 parts by weight or more in 100 parts by weight of the white pigment. The upper limit is preferably 30 parts by weight or less in 100 parts by weight of the white pigment. When using kaolin and clay together, it is preferable that the total amount of both is between the said upper limit and lower limit. By containing the above-mentioned calcium carbonate, kaolin or clay in the pigment coating layer of the present invention, the smoothness of the printing paper is improved, so that it is possible to obtain a printed image with fine color and good color.

The pigment coating layer contains an adhesive. Examples of the adhesive include etherified starches such as oxidized starch, positive starch, urea phosphate-esterified starch, hydroxyethyl etherified starch, various starches such as dextrin, proteins such as casein, soybean protein, synthetic protein, and polyvinyl alcohol Alcohol, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, vinyl polymer such as acrylic polymer latex, ethylene-vinyl acetate copolymer Polymer latex etc. are 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 with respect to 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 coated 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 will be insufficient, making it difficult for the penetration type cold set ink to penetrate the paper, and the drying property may be poor.

The pigment coating layer may contain various assistants such as dispersants, thickeners, antifoaming agents, colorants, antistatic agents, preservatives and the like used in the general paper manufacturing field.

The pigment coating layer can be provided by coating the coating liquid on one side or both sides of the 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 the amount of coating is small. The coating amount of the pigment coating layer is less than 5 g / m ^{2 in} total per one side, and preferably 4 g / m ² or less. The lower limit is preferably 1.5 g / m ² or more. When the coating amount is higher than 5 g / m ^{2, the} penetration of the ink is aggravated and the ink drying property is reduced. On the other hand, if the coating amount is excessively low, the base paper can not be sufficiently coated, and the ink coloring property is lowered.

(2) Base Paper The raw material of the base paper used in the present invention is not particularly limited, and mechanical pulp such as grand pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), waste paper pulp (deinked pulp Chemical pulps such as DIP), softwood kraft pulp (NKP), softwood kraft pulp (LKP) and the like can be used. As waste paper pulp, classified waste paper such as high-grade paper, medium-grade paper, lower grade paper, newspaper, flyers, magazines and non-sorted waste paper derived from mixed waste paper can be used, but medium-grade paper containing mechanical pulp It is preferable that the waste paper pulp contains lower grade paper or newsprint as a raw material. The printing paper of the present invention contains 30 parts by weight or more of chemical pulp in 100 parts by weight of pulp. By containing a large amount of chemical pulp, the density of printing paper can be improved, and excessive penetration of the ink into the deep part of the base paper can be suppressed, whereby the ink coloring property can be improved. From this viewpoint, the lower limit of the chemical pulp content is preferably 40 parts by weight or more, and more preferably 50 parts by weight or more. On the other hand, it is preferable to contain waste paper pulp that contains a certain amount of mechanical pulp or mechanical pulp as a raw material, since a suitable degree of paper stiffness is required in printing or processing steps, or when it is made into a book. Therefore, the upper limit of the chemical pulp content is preferably 90 parts by weight or less, and more preferably 80 parts by weight or less.

The printing paper of the present invention preferably contains mechanical pulp or waste paper pulp containing mechanical pulp in an amount of 10 parts by weight or more in total, and more preferably 20 parts by weight or more in 100 parts by weight of pulp. . The upper limit of the total amount is preferably 50 parts by weight or less. If the total amount exceeds this value, the density may be lowered to lower the ink color developability, and furthermore, the whiteness may be lowered and the image brightness may be lowered.

Known fillers can be added to the base paper. As fillers, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delami kaolin, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, Inorganic fillers such as magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, amorphous silica produced by neutralization of sodium silicate with mineral acid, urea-formalin resin, melamine resin, polystyrene resin, phenol Organic fillers such as resins may be mentioned. These may be used alone or in combination. Among these, calcium carbonate and light calcium carbonate-silica composites, which are typical fillers in neutral paper making and alkaline paper making, and which can obtain high opacity, are preferable.

As internal additives, bulking agents, dry strength improvers, wet strength improvers, freeness improvers, dyes, neutral sizing agents and the like may be used as necessary. Examples of the dry strength improver include polyacrylamide and cationic starch, and examples of the wet strength improver include polyamidoamine epichlorohydrin. These chemicals are added in the range which does not have influence, such as formation and operativity. The neutral sizing agent includes alkyl ketene dimer, alkenyl succinic anhydride, neutral rosin sizing agent and the like. Although bulking agents may be used, they are preferably used in small amounts, and more preferably not used because they may become too bulky. When a bulking agent is used, it is preferable to adjust the thickness of the paper by calendering or the like so that the density of the paper falls within the range of the present invention. These internally added chemicals can be used as pulp together with fillers as needed and used as a stock.

The base paper is manufactured by a known papermaking method. For example, although it can be carried out 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, etc., it is not limited thereto. The offset printing paper for cold setting of the present invention may be manufactured by an on-machine method in which a paper making process and a pigment coating process are continuous, and manufactured by an off-machine system in which coating is performed in a pigment coating process after the paper making process. You may The paper making and coating speed is preferably 400 to 2000 m / min.

(3) Other Treatments The printing paper of the present invention may further have a clear coating layer mainly composed of an adhesive on one side 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 to improve the base paper coverage of the pigment coating layer, which is preferable as an adhesive to be used. 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 is preferably 0.5 g / m ² or more and 5.0 g / m ² or less on both sides, more preferably 1.0 g / m ² or more and 4.5 g / m ² or less. More preferably, it is 2.0 g / m ² or more and 4.0 g / m ² or less.

The printing paper of the present invention may be subjected to surface treatment. The surface treatment includes treatment with a soft calendar, a super calendar, a gloss calendar, a heat calendar, and a shoe calendar.

(4) Properties of Printing Paper of the Present Invention 1) Basis Weight The basis weight of the printing paper of the present invention is 40 to 70 g / m ² . If the basis weight exceeds the upper limit, the weight per one book will be large when the printed matter is made into a book or the like, which may reduce the transport efficiency. In addition, if it is less than the lower limit, there is a possibility that problems occur in the printing and processing steps due to lack of rigidity of the paper, and furthermore, the ink is transmitted to the back side of the paper due to lack of opacity and the print quality of the back side There is a possibility of damage.

2) Density The density of the printing paper of the present invention is preferably 0.7 to 1.3 g / cm ³ . If the density exceeds the upper limit, paper stiffness may be reduced. If the amount is less than the lower limit, ink penetration may be excessive. Furthermore, when the density of the paper is low, the smoothness of the paper tends to be reduced, and the ink color developability may be reduced. From this viewpoint, the lower limit value of the density is preferably 0.75 g / cm ³ or more, and more preferably 0.8 g / cm ³ or more. The upper limit value of the density is preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, and still more preferably 1.0 g / cm ³ or less.

4) Oken Type Smoothness The printing paper of the present invention preferably has Oken type smoothness (JIS P8155) of 10 to 200 seconds. If this value exceeds the upper limit, the penetration speed of the ink may be slowed and the drying property may be reduced. If the value is less than the lower limit, the ink coloring property may be reduced.

5) ISO Whiteness The printing paper of the present invention preferably has an ISO whiteness (JIS P8148) of 70% or more, more preferably 75% or more. When the degree of whiteness is less than 70%, the degree of whiteness of the white paper portion may be reduced, and the brightness of the image after printing may also be reduced.

2. Method of Producing Printing Paper of the Present Invention It is preferable that the printing paper of the present invention is produced through the step of providing a pigment coating layer of the coating amount by blade coating on one side or both sides of the base paper. The pigment coating layer can also be provided by roll coating in addition to this, but blade coating is a coating method in which the coating liquid is scraped off with a blade after coating, so a coated surface with high smoothness should be obtained. It is possible to obtain a printing sheet with good ink colorability.

3. Applications The printing paper of the present invention exhibits excellent ink drying properties and ink colorability in coldset offset printing, and is therefore suitable for coldset offset printing. In particular, by using for offset printing for cold set using a rotary press, a large amount of high-quality printed matter can be efficiently produced at high speed. Therefore, the printing paper of the present invention is most suitable as a textbook for which such characteristics are required.

Example 1
A stock containing 30% by weight of NBKP, 23% by weight of LBKP, 27% by weight of deinked pulp, and 12% by weight of light calcium carbonate as a filler is prepared as a base paper, and papermaking is carried out. Density 0.75 g / cm ³ , basis weight A printing paper of 61 g / m ² was prepared.

Heavy calcium carbonate (Fimatech Co., Ltd., trade name: FMT 97, proportion of particles with a particle diameter of 2 μm or less according to the sedimentation method: 97%, D 50 = 0.64 μm) 82 parts by weight (solid content) and secondary 18 parts by weight (solid content) of clay (manufactured by IMERYS, trade name: KCS, D50 = 4.9 μm) was used, to which 4.8 parts by weight of styrene-butadiene copolymer latex and 7 of starch oxide were used as adhesives. 4 parts by weight and 0.5 parts by weight of a fluorescent dye were mixed, and water was further added to obtain a pigment coating liquid having a solid content concentration of 50% by weight.

The pigment coating liquid was coated by a blade coater on one side of the base paper so that the dry coating amount would be 1.0 g / m ^2, and then dried to obtain printing paper. The said printing paper was evaluated by the method mentioned later.

[Examples 2 and 3]
Printing paper was obtained and evaluated in the same manner as in Example 1 except that the coating amount was changed to 2.9 g / m ² and 4.5 g / m ² , respectively.

Example 4
Printing paper was obtained in the same manner as in Example 1 except that the base paper pulp was changed to 25% by weight of NBKP, 5% by weight of LBKP, 55% by weight of deinked pulp, and 15% by weight of GP.

Comparative Examples 1 and 2
Printing paper was obtained and evaluated in the same manner as in Example 1 except that the coating amount was changed to 5.5 g / m ² and 7.5 g / m ² , respectively.

Comparative Example 3
The base paper was evaluated in the same manner as in Example 1.

The results are shown in Table 1. It is clear that the printing paper of the present invention has excellent ink dryness and ink colorability in coldset offset printing.

Details of the evaluation method are described below.
(1) White paper glossiness It measured based on JISP8142.
(2) Basis Weight Measured in accordance with “Method for measuring basis weight” described in JIS P8124.
(3) Paper thickness and density Measured in accordance with "Paper and board-test method for thickness and density" described in JIS P8118.
(4) Oken type smoothness It measured based on JIS P8155.
(5) Whiteness Measured according to JIS P8148 and measured with a light source containing ultraviolet light using a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. according to JIS P8148.
(6) Oken type air permeability resistance It measured based on JISP8117.

(7) Ink drying property Offset printing (4 colors) for cold set is performed with an offset rotary press (B2T-600, manufactured by Toshiba Corporation), and the surface of the printing part is rubbed with a finger for 2 to 3 minutes after printing. The dryness was evaluated. The ink drying property was evaluated for the character part, the halftone dot part, and the solid part, and they were integrated to determine the ink drying property of the printing surface.
A: The drying property is excellent without rubbing the ink.
B: The ink slightly rubs but there is no problem in use.
C: The ink is not dry and can not be used.

(8) Ink color developability Offset printing (4 colors) was performed, and the color developability of the printed matter was visually evaluated.
A: Color development is good.
B: Slightly dull, but relatively clean.
C: The coloration is bad and dull.

(9) Paper peeling Measured in accordance with JIS P8129. Using an ink with an ink tack value of 20, print using an IGT printability tester with printing pressure 400N, printing speed 7 m / s as initial value and increasing printing speed, and measure the position where paper peeling was started did. The farther the position is, the less the paper peeling and the higher the paper peeling strength, and therefore the evaluation was made according to the following criteria.
A: It is hard to peel off paper and printing strength is strong.
B: Can be used to print something that peels off a little.
C: It is easy to peel off the paper and the printing strength is weak.

Claims

An offset printing paper for cold setting comprising a pigment coated layer on a base paper,
The basis weight is 40 to 70 g / m 2 ,
The coating amount of the pigment coating layer is less than 5 g / m 2 per one side,
30 parts by weight or more of chemical pulp in 100 parts by weight of pulp in the base paper
Offset printing paper for cold setting.
Density of 0.7 ~ 1.3g / cm 3, coldset offset printing paper as claimed in claim 1.
The coldset offset printing paper according to claim 1 or 2, wherein the used paper pulp contains 50 parts by weight or less of used paper pulp in 100 parts by weight of pulp in the base paper.
The coldset offset printing paper according to any one of claims 1 to 3, wherein 50 parts by weight or more of calcium carbonate having an average particle diameter of 0.5 to 1.0 μm is contained in 100 parts by weight of the pigment in the pigment coating layer.
The coldset offset printing paper according to any one of claims 1 to 4, wherein the coating amount of the pigment coating layer is 1.5 to 4.0 g / m 2 per one side.
The coldset offset printing paper according to any one of claims 1 to 5, wherein the Oken smoothness is 10 to 200 seconds.
The coldset offset printing paper according to any one of claims 1 to 6, wherein the ISO whiteness is 70% or more.
A printing method comprising printing on the coldset offset printing paper according to any one of claims 1 to 7 using a rotary press.
The method for producing a coldset offset printing paper according to any one of claims 1 to 8, comprising the step of providing a pigment coated layer by blade coating on one side or both sides of the base paper.