JP2010255165A - Matte coated paper for printing and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a matte coated paper for offset printing with low density, flexibility and opacity and whiteness suitable for practical use, in particular having specially high delta-gloss (=printing glossiness-white paper glossiness), excellent printing face feeling, and good surface strength and folding cracking strength. <P>SOLUTION: In the matte coated paper for printing constituted by arranging a coated layer containing pigments and an adhesive on base paper, the base paper contains 90 wt.% or more of craft pulp based on the whole pulp dry weight as a raw material, contains 65 wt.% or more of broadleaf tree pulp of freeness of 100 ml or more and 350 ml or less based on the whole craft pulp dry weight as the craft pulp, and further contains an organic compound having the action for inhibiting intrafiber bonding of the pulps. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a matte coated paper having excellent printability and a method for producing the same.

  In recent years, there has been a strong demand for coated paper for high-quality printing that can visually convey the contents of printed matter by using a lot of photographs and designs and further colorizing it. On the other hand, there is a strong demand for weight reduction of printed matter from the viewpoints of resource saving, transportation and mailing costs. These two demands are contradictory, and high-quality printing coated paper has a high density compared with the same basis weight due to a large amount of base paper and coating amount, and smoothing by surface treatment, etc. It does not meet the demand for weight reduction. It is possible to select a low basis weight paper for weight reduction of the printed matter, but if the density is equal, the paper thickness decreases with the weight reduction, which is not preferable because the volume of the booklet is impaired. For this reason, the paper thickness is high compared to the same basis weight, or the basis weight is low compared to the same paper thickness, that is, low density (bulk) and good printability such as print surface feeling and print gloss. Coated paper is required.

  In addition, coated paper used for magazines and the like has important properties such as texture, touch, and ease of turning. In particular, recently, there has been a demand for flexibility such as lightness, that is, bulkiness (low density) while being voluminous (paper thickness is high), and being easy to turn in a book. Conventionally, if the paper thickness is increased, the stiffness of the paper is increased and it is difficult to turn the paper. Therefore, it has been difficult to achieve both a sense of volume and ease of turning.

Coated paper is roughly classified into glossy coated paper and matte coated paper. Glossy coated paper includes art paper, super art paper used for high-grade printing, and coated paper used for catalogs, magazines, brochures, etc., and the glossy finish is high in both white paper gloss and printing gloss. It is. The matte coated paper has a dull tone and a matte tone, and has a lower gloss of white paper and printing gloss than a glossy tone. The matte tone has a lower white paper gloss than the dull tone. In particular, matte matte coated paper is easier to read after printing compared to conventional glossy paper, and demand has been increasing in recent years. Also, paper with a relatively high gloss after printing, that is, a high delta gloss (a value obtained by subtracting the white paper gloss from the print gloss), has a three-dimensional effect on the print area. As a higher quality coated paper, it tends to be particularly preferred.
Bulky coated paper used in offset printing applications is prone to blistering problems due to the heat of the dryer that dries the printed ink, and it is hoped that the strength against blisters will exceed a certain level. In particular, the strength required when the paper is folded in the folding process after printing is particularly necessary, and a certain level of crack strength is desired.

With regard to properties such as paper texture, touch, and ease of turning, thin-leaf book paper that uses specific spindle-shaped calcium carbonate as a filler and blends mechanical pulp with a water retention value of 100 to 150% for the purpose of improving the texture. It is disclosed (see Patent Document 1). Moreover, 90% by weight or more of hardwood kraft pulp having a freeness of CSF of 500 ml or more, the hardwood kraft pulp containing 50 to 100% by weight of dipterocarp pulp, calcium carbonate as a filler, and a density of 0.60 A low-density book paper of 0.40 g / cm ³ is disclosed (see Patent Document 2). However, since it is necessary to mix special pulp, these are disadvantageous in terms of cost, the paper itself is not sufficiently flexible, and the texture, touch, and ease of turning are not excellent.
Further, Patent Documents 3 to 5 are disclosed as bulky matte light weight coated paper.
Patent Document 3 describes a method in which a coating liquid composed of kaolin containing no calcium carbonate as a main component and a binder is applied to a base paper mainly composed of chemical pulp by a roll coater method. However, the base paper does not contain an organic compound that inhibits interfiber bonding, and a coated paper with low density and low stiffness cannot be obtained. In addition, when an organic compound that inhibits interfiber bonding is simply blended into the base paper, it is not preferable because the printing surface feeling and blister suitability are poor.
Patent Document 4 describes a technique using a stencil paper made using pulp obtained by mixing 40% by weight or less of pulp beaten to a freeness of 250 to 450 ml, which is a low freeness kraft pulp. Is not blended, and the blended amount of kraft pulp itself is less than that of the present invention, and therefore, the printed paper is inferior and coated paper with flexibility and blister suitability cannot be obtained.
Patent Document 5 also describes a method for producing matte coated paper, but the amount of low freeness pulp is small, and low density coated paper cannot be obtained. A coated paper higher than that of the present invention can be obtained.

For example the basis weight 157 g / ^{m 2} as a matte coated paper, double-sided coating amount 30 to 50 g / ^{m 2,} a density (bulk density) 0.88 g / cm ^3, typically quality matte coated paper of, 75 ° gloss 12 %, 60 ° printing glossiness of 27% (4-color overprinting section) (Non-patent Document 1). In order to reduce the weight of the matte matte coated paper, for example, when the basis weight and coating amount of the mat-coated paper are halved and the total basis weight is 80 g / m ² , the printing glossiness is remarkably lowered. In addition, there is an increased possibility that the opacity is lowered and the problem of show through occurs. If the coating weight of the coating layer is increased in order to improve the printing gloss while maintaining the total basis weight of 80 g / m ^2, the basis weight of the base paper must be reduced accordingly, and the opacity and rigidity are further increased. Insufficient and impractical. If the basis weight of the base paper is increased to improve the opacity and stiffness to a practical level, the coating coverage on the surface will be insufficient and the printing gloss will be extremely low. It will result in a low blurred image. Further, as a method for improving the opacity, a method of internally adding an inorganic filler such as titanium dioxide having a large opacity to the base paper is known. However, when the inorganic filler is internally added, the density of the base paper increases conversely. .

  Further, in order to improve the printing quality of the coated paper, particularly the printing surface feeling and the print glossiness of the image line portion, it is one of effective means to improve the smoothness of the coated paper. For this reason, with glossy coated paper or coated paper with a glossiness between the matte coated paper and glossy coated paper called dull tone, surface smoothing such as a super calendar is applied after coating. It is common. However, these treatments pressurize the paper to increase the smoothness of the surface, and at the same time, the white paper glossiness is high and the paper thickness is low. Was not enough.

  As a method of reducing the weight of the base paper while maintaining the paper thickness and opacity at a low density, a method of blending a capsule of a hollow synthetic organic substance, a synthetic organic foaming filler (for example, trade name EXPANCEL, which is foamed by the heat of a dryer during paper making) A method of blending Nippon Philite Co., Ltd.) is known. However, these methods are difficult to obtain stable operating conditions such as drying conditions during papermaking, and are not suitable for varieties that require mass production. Moreover, although it is not a filler, the method of adding fine fibrillated cellulose is proposed by Unexamined-Japanese-Patent No. 8-13380. However, in this method, it is necessary to separately adjust the fine fibrillated cellulose, which is complicated in operation and is not practical.

  In addition, a bulky and flexible printing paper is described in which the product of the density, breaking length, and Young's modulus is defined (see Patent Document 6). However, when this paper is used as a coating base paper and a coating layer containing a pigment and an adhesive is provided, there is a problem that the flexibility is inferior, the sheet is not easily turned, and the strength is inferior.

  In addition, a patent is disclosed in which an organic compound having an action of inhibiting interfiber bonding is blended to define the base paper ash content, the coating amount, and the interlayer strength (see Patent Document 7). In comparison at a density equivalent to that of the manufactured coated paper, it is difficult to obtain a coated paper having a particularly high delta gloss and a good printing surface feeling, and a good folding strength and surface strength. Thus, it is not possible to obtain a light-weight matte coated paper having desired characteristics by simply applying the conventional technology.

JP 08-246390 A JP-A-10-204790 JP 2001-234497 A JP 2006-274513 A JP 2004-277975 A JP 2001-234497 A JP 2003-213595 A

"Printing and Paper", 188 pages, Paper Industry Times, 1996

In view of such a situation, the problem of the present invention is that it has low density, flexibility, opacity and whiteness suitable for practical use, and in addition, delta gloss (= print glossiness−blank paper glossiness) is particularly excellent. It is an object of the present invention to provide a matte coated paper for offset printing having at least one of good printing surface feeling, blister suitability and surface strength, and a method for producing the same.
Furthermore, on the premise of having low density, flexibility and practically suitable opacity and whiteness, and particularly excellent and high delta gloss, printing surface feeling and printing glossiness are high, cracking, blister suitability, surface An object of the present invention is to provide a matte coated paper for offset printing having good strength and a method for producing the same.

As a result of intensive studies, the present inventors have completed the present invention. In order to achieve the above-mentioned problems, printing is performed by using mainly kraft pulp as a raw material, further containing hardwood kraft pulp with a specific drainage degree, and containing an organic compound having an action of inhibiting the interfiber bonding of the pulp. The present inventors have found that a matte coated paper having excellent quality such as surface texture can be obtained.
That is, the following invention is included.
In a matte coated paper for printing comprising a coating layer containing a pigment and an adhesive on a base paper, the base paper contains 90% by weight or more of kraft pulp as a raw material per total dry weight of the pulp, and The kraft pulp contains not less than 65% by weight of hardwood kraft pulp having a freeness of 100 ml or more and 350 ml or less per total dry weight of the kraft pulp, and contains an organic compound having an action of inhibiting the interfiber bonding of the pulp. A matte coated paper for printing. (Claim 1)
The matte coated paper for printing according to claim 1, wherein the ash content in the base paper is 5 to 20% per base paper weight. (Claim 2)
3. A coating layer of a film transfer method, wherein a coating layer obtained by coating 0.3 to 3.0 g / m ^{2 of} adhesive on one side is provided on a base paper before the coating layer is provided. Matte coated paper for printing as described in 1. (Claim 3)
The matte coated paper for printing according to claim 3, wherein a gate roll coater or a rod metering size press is adopted as a film transfer type coating method. (Claim 4)
The matte coated paper for printing according to any one of claims 1 to 4, wherein the coating amount of the coating layer is 4 to 10 g / m ² per side. (Claim 5)
The gloss for printing according to any one of claims 1 to 5, comprising 65 to 100 parts by weight of calcium carbonate having an average particle diameter of 0.2 to 1.5 µm as a pigment of the coating layer. Eraser coated paper. (Claim 6)
When the calcium carbonate is wet pulverized at a concentration of 50% or less using light calcium carbonate of spindle-shaped calcite crystal as a starting material, the average particle size (d ₅₀ ) measured by an X-ray transmission type particle size distribution analyzer is 0. 0.1 to 0.5 μm, the BET specific surface area is in the range of 10 to 30 m ² / g, and the following formula measured with an X-ray transmission type particle size distribution analyzer:
Sharpness = (d ₃₀ / d ₇₀ ) × 100
[Wherein d ₃₀ is a particle size of 30% by weight and d ₇₀ is a particle size of 70% by weight]
The matte coated paper for printing according to claim 6, wherein the sharpness of the particle size distribution represented by the formula is calcium carbonate. (Claim 7)
In a method for producing a matte coated paper for printing comprising a coating layer containing a pigment and an adhesive on a base paper, hardwood kraft pulp having a freeness of 100 ml or more and 350 ml or less is used as a raw material per total dry weight of pulp. After providing a coating layer coated with an adhesive on a base paper made of paper containing an organic compound containing 65% by weight or more and inhibiting the interfiber bonding of pulp, a pigment and an adhesive are further applied. A method for producing matte coated paper for printing, comprising forming a coating layer by processing. (Claim 8)

According to the present invention, it has low density, flexibility, and opacity and whiteness suitable for practical use, high delta gloss (= print glossiness−blank paper glossiness), and at least printing surface feeling, blister suitability and surface A matte coated paper for offset printing with good strength and a method for producing the same can be obtained.
Furthermore, it is possible to obtain a matte coated paper for offset printing, which has a high printing surface feeling and printing glossiness, and has good creases, blister suitability, and surface strength, and a method for producing the same.

  In the bulky coated paper, the present inventors use hardwood kraft pulp having a specific drainage degree in order to achieve both flexibility and rigidity, have good delta gloss, and at least printing surface feeling, blister suitability and In order to improve the surface strength, the density and the coating amount are optimally combined. In addition, the base paper is balanced by the transfer method, and an adhesive-containing layer is applied to the lower layer of the pigment coating layer. In addition, by making the coating amount of ash and starch contained in the base paper into a specific range and adopting a specific starch coating method, the printing surface feeling and printing glossiness are high, and it is suitable for cracking and blistering And surface strength both improved.

As a method for reducing the density (bulking) of the pulp base paper to be blended with the base paper, it is known to use mechanical pulp, particularly groundwood pulp, which has a rigid fiber and is effective in reducing the density. However, groundwood pulp is mechanical pulp, and blending with fine paper has problems in terms of specifications, and blending tends to cause problems in terms of paper quality, for example, quality such as a decrease in whiteness. In, kraft pulp is mainly used.

  The pulp to be blended with the base paper of the present invention is mainly preferably kraft pulp. It can be contained in an amount of 90% by weight or more, preferably 95% by weight or more based on the absolute dry weight of all raw pulps. In order to reduce fading over time, it is preferable to use kraft pulp alone. As long as it is a kraft pulp, either a coniferous raw material (hereinafter referred to as a coniferous kraft pulp) or a broadleaf tree raw material (hereinafter referred to as a hardwood kraft pulp) may be used. From the viewpoint of flexibility, it is preferable to contain more hardwood kraft pulp than softwood kraft pulp. However, when softwood kraft pulp is contained, the rigidity increases and bar wrinkles can be further suppressed. Therefore, it is preferable to contain a certain amount. The blending amount of softwood kraft pulp is preferably 35% by weight or less, more preferably 20% by weight or less, based on the total kraft pulp.

The hardwood kraft pulp to be blended with the base paper of the present invention can be blended with a freeness of 100 ml to 350 ml of 65% by weight or more based on the total kraft pulp. In order to increase the bulk, it is better to increase the freeness of the pulp. However, by making the freeness 100 to 350 ml, which is lower than the usual, the smoothness and rigidity are appropriately given to the base paper. can do. More preferably, the freeness is 240 ml or more and 310 ml or less.
If the freeness is 100 ml or less, there is a tendency for the productivity to be reduced due to a load on the beating machine in the manufacturing process. If the freeness is 350 ml or more, there is a concern that the printing surface is inferior and blistering occurs or the surface strength is insufficient. Therefore, it is not preferable. In addition, if the hardwood chemical pulp having a freeness of 100 to 350 ml is less than 65% by weight, it is not preferable because printing surface feeling and delta gloss decrease.
The total freeness of the kraft pulp is 200 to 450 ml, preferably 300 to 400 ml. If it is smaller than 200 ml, it tends to reduce the productivity due to a load on the beating machine in the manufacturing process, and if it has a freeness greater than 450 ml, it is not preferable because there is a concern about the occurrence of blistering or insufficient surface strength. .
Other pulps include chemical pulp (conifer bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, chemithermomechanical pulp, etc.), deinked pulp (waste paper pulp) ) May be used alone or in admixture at any ratio.

Moreover, as a kind of filler mix | blended with a base paper, well-known fillers, such as a hydrated silicic acid, white carbon, a talc, a kaolin, a clay, a calcium carbonate, a titanium oxide, a synthetic resin filler, can be used. In addition, if necessary, a sulfuric acid band, a sizing agent, a paper strength enhancer, a yield improver, a colorant, a dye, an antifoaming agent, and the like may be contained.
The ash content in the base paper is 1% to 30% by weight, preferably 5% to 30% by weight, and more preferably about 5% to 15% by weight. If the ash content is less than 5% by weight, the rigidity may increase. If the ash content is 30% by weight or more, the interlayer strength of the base paper becomes weak, and this tendency is observed even if it exceeds 25% by weight.

In the present invention, in order to prevent generation of blisters during offset printing, it is preferable to set the interlayer strength to 500 kPa or more and the air resistance to 5000 seconds or less using a tensile tester manufactured by Lorentzen and Wettre. When the interlayer strength is 500 kPa or less, or when the air permeation resistance is 5000 seconds or more, there are many concerns about the occurrence of blisters in practical use.
If the interlayer strength is less than 500 kPa, delamination tends to occur, and printability tends to be reduced. The interlayer strength is more preferably 550 kPa or more.

In the present invention, the density of the base paper can be reduced and the bulk can be increased by containing an organic compound having an action of inhibiting the fiber-to-fiber bond of the pulp.
The organic compound which has the effect | action which inhibits the fiber bond of the pulp of this invention can be selected by the following tests. Using a pulp slurry in which 0.3 parts by weight of an organic compound to be tested is blended with 100 parts by weight of an absolutely dry pulp in a pulp composition constituting the target paper, an experimental orientation paper machine (manufactured by Kumagaya Riken Co., Ltd.) The paper was made at a rotational speed of 900 rpm, and pressed and dried according to the method of JIS 8209.

In addition, about drying conditions, it processed at 50 degreeC and 1 hour with the ventilation drying machine. The test paper is left in an environment of 23 ° C. and 50% relative humidity for 24 hours, and then the tensile strength is measured according to JIS P8113. The compound having a reduced tensile strength is an organic compound having an action of inhibiting the interfiber bonding of the present invention.
In this case, if the rate of decrease is too small, the bulkiness effect is small, so it is necessary to add a large amount. Those with a large reduction rate have a bulky effect when added in a small amount.
Accordingly, any organic chemicals with reduced tensile strength can be used, but those with a reduction rate of 0.3% are preferably 5 to 30%, particularly those with 8 to 20%. preferable.

The organic compound (hereinafter referred to as “binding inhibitor”) having an action of inhibiting the fiber-to-fiber bond of the pulp of the present invention was a compound having a hydrophobic group and a hydrophilic group. It is what you have.
Recently, a density-reducing agent (or bulking agent) marketed for paper production to increase the bulk of paper is suitable as a binding inhibitor of the present invention, and is a higher alcohol ethylene and / or propylene oxide adduct, Of monohydric alcohol type nonionic surfactant, ethylene oxide adduct of higher fatty acid, ester compound of polyhydric alcohol and fatty acid, ethylene oxide adduct of polyhydric alcohol and fatty acid ester compound, fatty acid monoamide, fatty acid diamide, fatty acid amide Examples include hydroxyethyl derivatives and fatty acid polyamidoamines, preferably polyhydric alcohol and fatty acid ester compounds, higher alcohol propylene oxide adducts, fatty acid polyamidoamines, fatty acid monoamides, fatty acid diamides, hydroxyethyl derivatives of fatty acid amides. Etc. For example, WO98 / 03,730 discloses, see Japanese Unexamined 11-200284 and JP Hei 11-350380, etc.).

The bulky chemicals sold include BASF's Sulsol VL, Bayer's Bi-Volume P Liquid, Kao's KB-08T, 08W, KB110, 115, Sanki's React Pake, You may use individually or in combination of 2 or more types.
The matte coated paper of the present invention preferably contains 0.1 to 10 parts by weight of a pulp binding inhibitor per 100 parts by weight of pulp in order to make the paper bulky and flexible. It is preferable to contain 1.0 part by weight.

Adhesive application
In the present invention, it is preferable to apply an adhesive such as starch or polyvinyl alcohol on the coated base paper.
Coating amount is per side, it is possible to ^{0.3g / m 2 ~3g / m 2} , preferably from 1.0 to 2.0 g / ^{m 2.} If it is less than 0.3 g / m ² , it is not preferable because the surface strength may be lowered, and if it is more than 3 g / m ² , it is necessary to increase the coating concentration of the adhesive solution during operation, so that This is not preferable because problems such as generation of adhesive agglomerates occur, and it is not preferable because folding after printing tends to occur.
Any method may be used as the coating method, but a pound transfer method or a film transfer coating method such as a gate roll coater or a rod metering size press is preferable.
In addition, if a pound size press is used to apply the adhesive, the blister suitability will be improved, but the amount of starch solution absorbed on the machine will increase the speed of printing, and the cracking strength will decrease significantly after printing. There are things to do.

Machine Calendar The base paper of the present invention can be smoothed in a calendar device called a machine calendar (pre-calendar) or hot soft nip calender after production of the base paper, if necessary.
In the present invention, since sufficient print quality can be obtained without performing calendar processing, it is preferable not to perform calendar processing when it is desired to reduce the density.
By processing with a calendar, the glossiness of white paper is the same and the glossiness of printing is high, that is, the delta gloss tends to be high. When the coating amount is small, a bulky coated paper having a good printing surface can be obtained by calendering.
When performing the calendar process, the linear pressure, the number of nips, and the surface temperature of the metal roll can be appropriately adjusted according to the target delta gloss (= print glossiness−blank paper glossiness) and product density. In order to obtain a coated paper having a high delta gloss and a good printing surface, and low-density coated paper, the machine calender conditions are 1-2 nip treatment, linear pressure 5-100 kN / m, metal roll surface temperature 20- Weak treatment conditions of 200 ° C. are preferred. Furthermore, a 1-2 nip treatment, a linear pressure of 5-30 kN / m, and a metal roll surface temperature of 20-100 ° C. are preferable. If the number of nips is too large or the linear pressure is too high, the density increases, which is not preferable. Also, the delta gloss is lowered, and the three-dimensional effect on the printing surface is lost.

The present invention contains an organic compound that inhibits fiber-to-fiber bonding of the pulp, lowers the density of the base paper and imparts flexibility, while slightly increasing the freeness of hardwood kraft pulp to 350 ml or less. However, the surface of the base paper is smoothed and the rigidity is also given, and as a total, a base paper having a low density and a high smoothness can be obtained as compared with the case where the above method is not performed.
In the present invention, it has been found that a bulky matte coated paper having a high bulkiness, a high delta gloss and a good printing surface can be provided by coating a coating on the base paper.

Pigment of coating layer The pigment used in the coating layer of the present invention is conventionally used for coated paper, kaolin, clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate. Inorganic pigments such as calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, and satin white, and organic pigments such as plastic pigments. These pigments can be used alone or in combination of two or more. In the present invention, it is preferable to mainly use calcium carbonate.
In the present invention, from the viewpoint of printing quality such as delta gloss and ink setting properties, calcium carbonate having an average particle diameter of 0.2 to 1.5 μm is used in an amount of 65 to 100 parts by weight, preferably 75 to 100 parts by weight. be able to. When the thickness is smaller than 0.2 μm, the ink setting property is increased, and the delta gloss (print glossiness−blank paper glossiness) tends to decrease. If it is larger than 1.5 μm, the glossiness of white paper is lowered and the printing glossiness tends to be lowered.

Calcium carbonate as a pigment used in the present invention is an average particle measured by an X-ray transmission type particle size distribution analyzer by wet grinding at a concentration of 50% or less using light calcium carbonate of spindle-shaped calcite crystals as a starting material. The diameter (d ₅₀ ) is 0.1 to 0.5 μm, the BET specific surface area is in the range of 10 to 30 m ² / g, and the following formula measured with an X-ray transmission particle size distribution analyzer:
Sharpness = (d ₃₀ / d ₇₀ ) × 100
[Wherein d ₃₀ is a particle size of 30% by weight and d ₇₀ is a particle size of 70% by weight]
It is preferable to use engineered calcium carbonate having a particle size distribution sharpness of 50 or more. Further, in the present invention, as the light calcium carbonate before pulverization, it is preferable to use a calcite crystal in which spindle-shaped primary particles are aggregated to form Rosetta-shaped secondary particles, and X of light calcium carbonate before pulverization is used. It is more preferable that the average particle diameter (d ₅₀ ) measured with a line transmission particle size distribution analyzer is 1.4 to 3.0 μm and the BET specific surface area is 4 to 12 m ² / g. Furthermore, in the present invention, wet pulverization is preferably performed using a multi-pass pulverizer.
By using such engineered calcium carbonate as a pigment, a coated paper having features such as bulkiness, high opacity, (high white paper glossiness), and high whiteness can be obtained.

Adhesive for coating layer The adhesive used in the present invention is conventionally used for coated paper, styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, acetic acid. Synthetic adhesives such as vinyl / butyl acrylate copolymers, polyvinyl alcohol, maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer, etc .: Proteins such as casein, soy protein, and synthetic protein: Oxidized starch, positive starch, urea phosphated starch, etherified starch such as hydroxyethyl etherified starch, and starches such as dextrin: normal coated paper adhesive such as cellulose derivatives such as carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose Select one or more agents for your convenience It is.
These adhesives are used in an amount of about 5 to 50 parts by weight, more preferably about 10 to 30 parts by weight per 100 parts by weight of the pigment. In the present invention, it is preferable to add 4 parts by weight or more of starch as an adhesive per 100 parts by weight of pigment.
The present invention relates to a low-density coated paper, and for that purpose, it is necessary to apply to a low-density base paper. Since the base paper of low density base paper is porous, the paint generally penetrates into the base paper, and the base paper coverage tends to decrease. Therefore, the coating property of a coating layer becomes favorable by mix | blending 4 weight part or more of starch whose water retention is favorable compared with binders, such as latex. In addition, as a technique for improving water retention, it is also effective to mix various natural and synthetic water retention agents.

  In the coating liquid of the present invention, various commonly used auxiliaries such as a dispersant, a thickener, a water retention agent, an antifoaming agent, and a water resistance-imparting agent may be used.

As a base paper for general coating, a paper base or paperboard base paper having a basis weight of about 30 to 400 g / m ² is appropriately used. However, the effect of the present invention is remarkable because the base paper is opaque. in question come 157 g / ^{m 2} or less, particularly 25~120g / ^{m 2,} a further 45~100g / ^{m 2.}
Further, in the present invention, it is preferable to supply matte coated paper having a density of 0.90 g / cm ³ or less, more preferably 0.85 g / cm ³ or less. Is preferred.
There is no particular limitation on the paper making method of the base paper, and long paper machine including top wire, round net machine, paperboard machine using both of them, Yankee dryer machine, etc., acid paper making, neutral paper making, Any of the base papers made by the alkaline paper making method may be used.

Coating method of pigment coating layer The method of applying the adjusted coating solution to the base paper is as follows: blade coater, bar coater, roll coater, air knife coater, reverse roll coater, curtain coater, size press coater, gate roll coater Etc., one side or two or more layers are coated on one side or both sides simultaneously on the base paper.
Preferably, the coating amount is 4 g / m ² or more and 10 g / m ² or less on one side, more preferably 6 g / m ² or more and 9 g / m ² or less on one side, so that the blister suitability is relatively high. A matte coated paper with good printing surface and printing glossiness and flexibility can be obtained. In addition, when the coating amount is higher than 10 g / m ² , good printing surface feeling and high printing gloss can be obtained, but blister suitability during offset printing is reduced, and when compared with the same basis weight, In particular, the density tends to increase. On the other hand, when the coating amount is less than 4 g / m ² , when compared with the same basis weight, the density is lowered, but the printing surface feeling and the printing glossiness are lowered.

  As a method for drying the wet coating layer, various methods such as a steam heating cylinder, a heated hot air air dryer, a gas heater dryer, an electric heater dryer, an infrared heater dryer, and a high frequency heater dryer are used alone or in combination.

The coated paper coated and dried as described above can be smoothed with a super calender, a high temperature soft nip calender, or the like. The effect of the present invention is particularly excellent in matte matte coated paper having a basis weight of 25 to 120 g / m ² and a blank paper glossiness of 20% to 40%. In the present invention, in order to provide a sheet having a low density and a high delta gloss, it is preferable that the calendering after coating be as weak or untreated as possible.

EXAMPLES The present invention will be specifically described below with reference to examples, but it is needless to say that the present invention is not limited to these examples. In addition, unless otherwise indicated, the part and% in an example show weight%, respectively. Further, the coating liquid and the matte coated paper obtained were tested based on the evaluation method as shown below.
<Evaluation methods>
(1) Blank paper glossiness: measured based on JIS P8142.
(2) Opacity: Measured based on JIS P8138.
(3) Interlaminar strength: evaluated using a delamination strength tester manufactured by Lorentzen and Wettre.
(4) Glossiness of printing, delta gloss: Ink offset density of solid part at a printing speed of 500 rpm using offset printing ink (Toyo Ink's Leo Echo SOY-M) on a Toshiba web offset press (4 colors). The ink is printed in the order of ink indigo red and yellow so that it becomes black 1.85, indigo 1.65, red 1.55, yellow 1.40 (according to Japan color standard printing, measured with X-Rite520 made by X-Rite). After that, the printing glossiness of the red and black solid two-color overlapping portion was measured. Delta gloss is the value obtained by subtracting the glossiness of blank paper from the obtained printing glossiness.
(5) ISO bending stiffness: The MD direction (machine direction) of the coated paper was measured using a stiffness measuring tester manufactured by Lorentzen and Wettre. For unit conversion, the Xa value (average value, angle 15 °) was multiplied by 3.352 and described as μNm ² / m.

(6) Print surface feeling: About the printed matter by the offset rotary press obtained by printing of said (4), the print surface feeling of the location where a red halftone dot is 50% was evaluated visually.
◎: Extremely good, ○: Good, △: Slightly inferior, X: Inferior (7) Fracture strength (Folded part strength measurement): Paper surface temperature after dryer using offset rotary press (Toshiba B2T-600) About the printed matter which performed the fold processing immediately after making it dry at 130 degreeC, the state of the folding part was evaluated visually.
○: Good, Δ: Slightly inferior, ×: Inferior (8) Blister suitability: Using an offset rotary press (Toshiba B2T-600), printing was performed at a printing speed of 500 rpm, the paper surface temperature was raised, and blistering occurred. The blister suitability was evaluated from the temperature at that time.

(9) Surface strength: Using a RI-II type printing tester, printing was performed using 0.40 cc of sheet-fed process ink (trade name: SMX tack grade 20) manufactured by Toyo Ink Manufacturing Co., Ltd. I copied it on the mount. The surface strength was evaluated from the copied mount as follows.
A: No peeling of the surface is observed. ○: The peeling of the surface is hardly seen. Δ: Some peeling of the surface is observed, but there is no problem in use. X: The surface is severely peeled off and cannot be used.
(10) Average particle diameter, sharpness: The particle size distribution of calcium carbonate was measured using a Sedigraph 5100 (particle size distribution measuring instrument of X-ray transmission method) manufactured by Micromeritex Co., Ltd., and d ₃₀ (total 30% by weight) Particle diameter), d ₅₀ (particle diameter of 50% by weight), and d ₇₀ (particle diameter of 70% by weight) were obtained. The average particle size was evaluated by d _50. (D ₃₀ / d ₇₀ × 100) was used as an index (sharpness) of the sharpness of the particle size distribution. The closer the value is to 100, the narrower the particle size distribution.
(11) BET specific surface area: Measured by a nitrogen adsorption method (Micromeritics Gemini 2360, manufactured by Shimadzu Corporation).

[Example 1]
To a pigment composed of 77 parts of light calcium carbonate (average particle size 0.95 μm) and 23 parts of fine kaolin (manufactured by JMHuber, Japan Gloss), add 0.2 part of a dispersant as a counter pigment and disperse with a serie mixer. A pigment slurry having a solid content concentration of 70% was prepared. To the pigment slurry thus obtained, 8.5 parts of styrene / butadiene latex and 4.8 parts of hydroxyethyl etherified starch were added, and water was further added to obtain a coating solution having a solid content concentration of 64%.
Using 80% bleached hardwood kraft pulp with a freeness of 250 ml and 20% bleached softwood kraft pulp as pulp, containing 20% light calcium carbonate as the internal filler per base paper weight, and inhibiting the binding between pulp fibers bulky chemicals (manufactured by Kao Corporation, KB110) as the organic compound with the quality base paper having a basis weight of 81.5 g / ^{m 2} containing 0.5% per base paper weight, duplex coating amount of the 1.5 g / ^{m 2} on a solids After applying the oxidized starch with a gate roll coater, calendering was performed at 1 nip, 15 kN / m, and a metal roll surface temperature of 50 ° C. Thereafter, the coating liquid was applied with a blade coater having a coating speed of 700 m / min so that the coating amount on one side was 9 g / m ² in terms of solid content, and dried to obtain matte coated paper. .

[Example 2]
In Example 1, as a pigment, calcium carbonate of calcite crystal (produced by Okutama Kogyo Co., Ltd .: TP221BM, average particle size 2.2 μm) in which spindle-shaped primary particles aggregate to form rosette-shaped secondary particles is used as a solid content. The concentration was adjusted to 20%, and 1.5 parts by weight of a polyacrylate dispersant (manufactured by Kao Corporation: Poise 535M) was added to form a slurry.
The obtained slurry was pulverized using a multi-pass pulverizer (manufactured by Mitsui Mining Co., Ltd .: SC mill 100 type). The pulverized calcium carbonate had an average particle size of 0.38 μm, a BET specific surface area of 22.5 m ² / g, and a sharpness of 62, as measured with a particle size distribution analyzer of the X-ray transmission method.
Matte in the same manner as in Example 1 except that 77 parts of calcium carbonate obtained by pulverization and 23 parts of fine kaolin (manufactured by JMHuber: Japan Gross) were prepared to 100 parts of pigment containing BR> L. Coated paper was obtained.

[Example 3]
In Example 1, a matte coated paper was obtained in the same manner as in Example 1 except that 0.3% of the monoamide compound of fatty acid was contained per weight of the base paper as the organic compound inhibiting the fiber-fiber bond of the pulp.

[Example 4]
A matte coated paper was obtained in the same manner as in Example 1 except that the internal filler was changed to 10% per base paper weight in Example 1.

[Example 5]
In Example 1, a matte coated paper was obtained in the same manner as in Example 1 except that the internal filler was changed to 30% by weight per base paper weight.

[Example 6]
Example except that 70% bleached hardwood kraft pulp with a freeness of 250 ml as pulp, 30% bleached softwood kraft pulp, 11% light calcium carbonate as internal filler per weight of base paper, and no calendering In the same manner as in No. 1, a matte coated paper was obtained.

[Example 7]
A matte coated paper was obtained in the same manner as in Example 6 except that the internal filler was changed to 6% by weight per base paper weight.

[Example 8]
In Example 1, one surface coating weight 3 g / m ^2, except that base paper having a basis weight 93.5 g / m ^2, to obtain a matte coated paper in the same manner as in Example 1.

[Example 9]
A matte coated paper was obtained in the same manner as in Example 4 except that the calendar process was not performed.

[Example 10]
A matte coated paper was obtained in the same manner as in Example 4 except that starch was applied with a pound size press.

[Example 11]
A matte coated paper was obtained in the same manner as in Example 4 except that starch was applied with a lot metering size press.

[Example 12]
A matte coated paper was obtained in the same manner as in Example 4 except that starch was applied with a pound size press and no calendar treatment was performed.

[Comparative Example 1]
In Example 1, matte coated paper was obtained in the same manner as in Example 1 except that hardwood kraft pulp having a freeness of 400 ml was used.

[Comparative Example 2]
In Example 1, matte coated paper was obtained in the same manner as in Example 1 except that 50% hardwood kraft pulp and 50% softwood kraft pulp were used.

[Comparative Example 3]
In Example 1, matte coated paper was obtained in the same manner as in Example 1 except that no organic compound having an effect of inhibiting the interfiber bonding of the pulp was used.

[Comparative Example 4]
In Example 1, matte coated paper was obtained in the same manner as in Example 1 except that 80% hardwood kraft pulp and 20% thermomechanical pulp were used.

[Comparative Example 5]
In Example 1, a matte coated paper was obtained in the same manner as in Example 1 except that the coating amount on one side was 12 g / m ² and the basis weight of the base paper was 75.5 g / m ² .

The above results are shown in Table 1-3.

From the results of Table 1-3, Examples 1 to 4 have good delta gloss, low density, flexibility, and opacity suitable for practical use, good printing surface feeling, surface strength, and blister suitability. Further, a matte coated paper having excellent crack strength and the like can be obtained.
From the results of Example 5, when the ash content of the base paper is increased, the delta gloss is good, but the printing surface feeling is good, the opacity is high, the bending stiffness is low, and the blister suitability tends to be slightly inferior. I understand.
From the results of Examples 6 and 7, if the calendar treatment is not performed, the interlayer strength is high, and the low density can be achieved while the blister suitability, the cracking property and the surface strength are kept good.
According to the results of Example 8, it can be seen that, when the starch coating amount is reduced, the delta gloss, blister suitability, and crackability are good, but the printing surface feeling and surface strength are lowered.
From the results of Examples 9 and 11, when the ash content of the base paper is 10% by weight, the presence / absence of calendering and if the starch coating method is a gate roll and rod metering size press, the delta gloss is good. It can be seen that the surface strength, crackability and blister suitability are good.
On the other hand, as in Examples 10 and 12, when the starch coating method is the pound type, the resulting coated paper has good delta gloss but deteriorates cracking properties.

From the result of Comparative Example 1, since the freeness of hardwood kraft pulp (LBKP) is high, even when the ash content of the base paper is 20%, the printing glossiness, blank paper glossiness, printing surface feeling, blister suitability, and surface strength are high. It is inferior and the interlayer strength is weak, which is not preferable.
Comparative Example 2 is not preferable because the blending amount of softwood kraft pulp (NBKP) is large, so that the printing surface feeling and surface strength are weak, the stiffness is high, and the blister suitability is poor.
Since Comparative Example 3 does not contain a bulking agent, even if the printing surface feeling, crease, blister suitability, and surface strength are good, even if it is a low density originally intended to be obtained by the present invention, printing This is not preferable because it does not provide a coated paper having properties that some of the surface feeling, cracking, blister suitability and surface strength are good, and the density is high.
Since Comparative Example 4 contains mechanical pulp, the density is low, but the printing surface feeling is inferior, the blister suitability and the surface strength are inferior.
Since Comparative Example 5 has a large coating amount, blister suitability is inferior even if the white paper glossiness and the like are good.

As described above, the present invention has a high content of low freeness hardwood kraft pulp as a raw material, so that the delta gloss is good, and at least one of printing surface feeling, blister suitability and surface strength is good. A craft paper can be obtained.
In addition, when the ash content of the base paper is reduced, the starch coating amount is increased, and the starch is applied by the gate roll method or the rod metering size press method, the delta gloss is good and the printing surface feel is good. In addition, it is possible to obtain a matte coated paper for offset printing that has high printing glossiness, good folding, blister suitability, and surface strength.
In addition, the bulky coated paper is liable to cause a printing trouble called white spot where the surface of the coating layer is peeled off during printing. Therefore, a surface strength of a certain level or more is desired.
Furthermore, by applying 0.3 to 3.0 g / m ^{2 of} an adhesive containing starch on the base paper, the printing surface feeling can be improved, and the average particle size is 0.2 as a pigment. By including 65 to 100 parts by weight of calcium carbonate of ˜1.5 μm, delta gloss can be improved.

Claims (8)

In matte coated paper for printing in which a coating layer containing a pigment and an adhesive is provided on a base paper,
The base paper contains, as a raw material, 90% by weight or more of kraft pulp per total dry weight of pulp,
And,
As said kraft pulp, hardwood kraft pulp having a freeness of 100 ml or more and 350 ml or less is contained in an amount of 65% by weight or more per total dry weight of kraft pulp,
And,
A matte coated paper for printing, comprising an organic compound having an action of inhibiting the interfiber bonding of pulp.   The matte coated paper for printing according to claim 1, wherein the ash content in the base paper is 5 to 20% per base paper weight. 3. The coating layer according to claim 1 or 2, wherein a coating layer obtained by coating 0.3 to 3.0 g / m < ² > of adhesive on one side of the base paper before providing the coating layer is provided by a film transfer method. Matte coated paper for printing as described.   The matte coated paper for printing according to claim 3, wherein a gate roll coater or a rod metering size press is adopted as a film transfer type coating method. The matte coated paper for printing according to any one of claims 1 to 4, wherein the coating amount of the coating layer is 4 to 10 g / m ² per side.   The gloss for printing according to any one of claims 1 to 5, comprising 65 to 100 parts by weight of calcium carbonate having an average particle diameter of 0.2 to 1.5 µm as a pigment of the coating layer. Eraser coated paper. When the calcium carbonate is wet pulverized at a concentration of 50% or less using light calcium carbonate of spindle-shaped calcite crystal as a starting material, the average particle size (d ₅₀ ) measured by an X-ray transmission type particle size distribution analyzer is 0. 0.1 to 0.5 μm, the BET specific surface area is in the range of 10 to 30 m ² / g, and the following formula measured with an X-ray transmission type particle size distribution analyzer:
Sharpness = (d ₃₀ / d ₇₀ ) × 100
[Wherein d ₃₀ is a particle size of 30% by weight and d ₇₀ is a particle size of 70% by weight]
The matte coated paper for printing according to claim 6, wherein the sharpness of the particle size distribution represented by the formula is calcium carbonate. In a method for producing a matte coated paper for printing comprising a coating layer containing a pigment and an adhesive on a base paper, hardwood kraft pulp having a freeness of 100 ml or more and 350 ml or less is used as a raw material per total dry weight of pulp. After providing a coating layer coated with an adhesive on a base paper made of paper containing an organic compound containing 65% by weight or more and inhibiting the interfiber bonding of pulp, a pigment and an adhesive are further applied. A method for producing matte coated paper for printing, comprising forming a coating layer by processing.