JP2017179676A - Coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive in a coated later of a coated paper excellent in printing surface strength and glossiness and operability without increasing coating viscosity significantly.SOLUTION: An excellent coated paper can be manufactured at good efficiency by using a starch having average square rotation radius (<rg>) measured by a size exclusion chromatography multi-angle light scattering (SEC-MALS) method of 12 to 24 nm as an adhesive contained in a pigment coated layer.SELECTED DRAWING: None

Description

  The present invention relates to coated paper. In particular, the present invention relates to a coated paper containing a specific starch as an adhesive in a pigment coating layer.

  In recent years, the demand for coated paper for printing has increased in the commercial field for the purpose of advertising and advertising such as flyers, catalogs, pamphlets, and direct mail. In addition, offset printing is the mainstream commercial printing method. In offset printing, dampening water is applied to the paper surface during printing, so if you use paper with low surface strength or paper with low surface water resistance, paper dust accumulates on the blanket or mixes with ink, Troubles such as so-called blurring or white spots occur on the printing surface.

  In order to cope with such troubles during offset printing, it has been studied to increase the amount of latex that is part of the adhesive of the coating layer or to change the type (Patent Document 1). However, if the amount of latex is increased, the water absorption at the time of printing will decrease, resulting in poor ink deposition and high-quality printing, and it is more expensive than starch-based adhesives, so the manufacturing cost will be higher. .

  There is also a method of changing the type of starch-based binder that is part of the adhesive of the coating layer, but with oxidized starch, urea phosphate starch, acetylated starch, etc., the viscosity is high and the operability during printing and the printing surface It is difficult to achieve both strengths (Patent Documents 2, 3, 4). In addition, there is a method using cold water-soluble starch as a low-viscosity starch, but the operability deteriorates because the viscosity increases when the starch is dissolved (Patent Document 5).

JP 2001-73295 A JP 2006-322114 A JP-A-11-71403 Japanese Patent Laid-Open No. 7-189179 JP 58-169595 A

  The subject of this invention is providing the adhesive in the coating layer of the coated paper which is excellent in printing surface strength and glossiness, and is excellent in operativity without increasing a paint viscosity so much.

Although not limited to this, this invention includes the following aspect.
(1) A coated paper having a pigment coating layer containing a pigment and an adhesive on a base paper, the size exclusion chromatography-multi-angle light scattering (SEC-MALS) being used as an adhesive contained in the pigment coating layer. ) The above coated paper using starch having a mean square turning radius (<rg ² >) measured by the method of 12 to 24 nm.
(2) The coated paper according to (1), wherein the starch is roasted dextrin.
(3) The coated paper according to (1) or (2), wherein a styrene / butadiene latex and the starch are used in combination as the adhesive.
(4) The coated paper according to any one of (1) to (3), wherein 5 to 50 parts by mass of the starch is used with respect to 100 parts by mass of the pigment.
(5) The coated paper according to any one of (1) to (4), wherein the pigment contains calcium carbonate.

  The coated paper containing the starch specified in the present invention as an adhesive in the coating layer is excellent in printing surface strength and gloss. Moreover, since the starch used in the present invention does not increase the viscosity of the paint so much, it is excellent in operability.

The starch used in the present invention is characterized in that the mean square rotation radius (<rg ² >) measured by size exclusion chromatography-multi-angle light scattering (SEC-MALS) method is 12 to 24 nm. When the starch of the present invention is used as an adhesive (binder) for a pigment coating layer of coated paper, it is possible to improve printing surface soil and gloss.

  The coated paper of the present invention is not particularly limited as long as it is a coated paper in which a pigment coating layer containing a white pigment and an adhesive is provided on the base paper, and printing used for offset printing, gravure printing, letterpress printing, etc. Of course, white paperboard having a pigment coating layer on the paperboard base paper may be used.

  In the coated paper of the present invention, one or more pigment coated layers containing a pigment and an adhesive are provided on the base paper. On the base paper, a coating solution (size press solution) containing no pigment may be applied or not.

Starch In the present invention, a pigment coating layer containing a pigment, an adhesive (binder), and water is mainly used to provide a pigment coating layer. As an adhesive (binder), size exclusion chromatography-multi-angle light scattering is used. Starch measured by the (SEC-MALS) method and having a mean square turning radius (<rg ² >) defined by the following formula 1 of 12 to 24 nm is used, but the mean square turning radius is 15 to 23 nm. May be. The mean square rotation radius indicates the spread of the polymer (conformation), and the present inventors have found that it correlates with the printing surface strength and gloss rather than other physical properties such as molecular weight. For the starch of the present invention, the detailed reason is unknown, but even if the concentration of the pigment coating solution is low, the penetration of the paint into the base paper is suppressed and the effective coating amount is increased. Various coated paper qualities such as improved strength are improved.
K * c / R (θ) = 1 / Mw [1+ <rg ² > sin ² (θ / 2) · 16π ² / 3λ ² ] + 2A ₂ (Formula 1)
K ^* (optical parameter) = 4π ² n ₀ ² (dn / dc) ² λ ₀ ^-4 N _A ^-1
n ₀ : refractive index of solvent dn / dc: concentration increment of refractive index N _A : Avogadro's number c: sample concentration (g / mL)
R (θ): Rayleigh ratio of excessive scattering Mw: weight average absolute molecular weight (g / mol)
<Rg ² >: Mean square turning radius (nm)
A ₂ : second virial coefficient λ ₀ : wavelength of incident light in vacuum From equation (1), the mean square turning radius from the initial slope of the plot of K * c / R (θ) and sin ² (θ / 2) <Rg ² > is calculated.

  In the present invention, starch having the above mean square turning radius is used as the adhesive. Starch refers to a mixture composed of amylose and amylopectin, and generally the mixing ratio varies depending on the plant that is the raw material of starch. As the starch, various processed starches and dextrins can be suitably used.

  The starch of the present invention is not particularly limited as long as it has the above-mentioned mean square turning radius, and the modification method, raw material varieties, and the like are also free. Examples of modified starch, modified starch, and the like include oxidized starch, hydroxyesterified starch (HES), phosphate starch, esterified starch, and dextrin. Of these, dextrin is preferred because the fluidity is further improved (low viscosity) when blended in a paint. Moreover, as a preferable raw material of the starch used by this invention, corn, a potato, tapioca etc. can be mentioned, Waxy type | mold corn (waxy corn) and tapioca are especially preferable.

  In a preferred embodiment of the present invention, the weight average absolute molecular weight (Mw) of starch is 80,000 to 450,000 g / mol, more preferably 90000 to 350,000 g / mol, still more preferably 100,000 to 230000 g / mol, and 100,000 to 200,000 g / mol. It may be mol. The higher the weight average absolute molecular weight, the higher the printed surface strength of the coated paper, but the operability during coating may deteriorate, so the printed surface strength and the operability during coating should be adjusted to be compatible. That's fine.

  In the present invention, since the viscosity is low and the viscosity stability is high, dextrin, particularly roasted dextrin is preferable as the adhesive. Dextrin is a general term for starch-based polymers obtained by hydrolyzing starch, and α-glucose is polymerized by glycosidic bonds, and is also called glue. Although ordinary starch has a large molecular weight, dextrin is an intermediate product produced in the hydrolysis process of starch, and has a molecular weight of about an oligomer (one having about 20 to 20 glucose bound). The roasted dextrin is a dextrin produced by adding an acid and baking with dry heat, and there are types such as white dextrin, yellow dextrin, and British gum. In the present invention, it is particularly preferable to use white dextrin. When the white dextrin is further hydrolyzed, it becomes a so-called yellow dextrin. However, since the yellow dextrin has low stability and the pigment coating layer may be colored, the use of white dextrin is preferred in the present invention.

  The roasted dextrin is obtained by subjecting starch to heat treatment in the presence or absence of an acid, hydrolysis and recombination. When an attempt is made to obtain a roasted dextrin in the absence of an acid catalyst, hydrolysis is unlikely to occur, and it is difficult to obtain the roasted dextrin used in the present invention, so it is preferable to use an acid catalyst. When an acid catalyst is used, any mineral acid can be used without any limitation. If the amount of the acid catalyst added is too small, the dextrinization reaction does not proceed easily, so it is desirable to add 0.008 mol / kg or more of hydrochloric acid. Moreover, since it is difficult for the dextrinization reaction to proceed if the heating temperature is too low, it is desirable to heat at 110 ° C. or higher. However, if the temperature is too high, it will be colored brown, so heating at a temperature that is not colored, particularly 150 ° C. or lower. Is preferred. The heating time depends on the amount of acid catalyst and the heating temperature, but if hydrochloric acid is 0.008 mol / kg and 110 ° C. or higher, it is preferable to stop the heating within 90 minutes.

  The starch of the present invention has good fluidity when blended in a coating solution. When fluidity is improved, it becomes possible to increase the concentration of the coating liquid, suppress the penetration of the coating liquid, and increase the effective coating layer, thereby improving the gloss development, whiteness, surface strength, etc. Improved coated paper quality.

  The compounding quantity of the starch of this invention is a preferable aspect. These adhesive agents are 1-50 mass parts per 100 mass parts of pigments, More preferably, it is used in the range of about 3-30 mass parts, and is 5-15 mass parts. May be used.

  In the present invention, only the above-mentioned starch can be used as the adhesive, but an adhesive conventionally used for coated paper can be used in combination with the above-mentioned starch. Examples of adhesives other than the above starch-derived polymer compounds include styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl acrylate. Synthetic adhesives such as polymers, polyvinyl alcohol, maleic anhydride copolymers, and acrylic acid / methyl methacrylate copolymers; proteins such as casein, soy protein, synthetic proteins; oxidized starches other than the above starches, positive Starch, etherified starch such as urea phosphate esterified starch and hydroxyethyl etherified starch, starches such as dextrin; and usual coated paper adhesives such as cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, etc. . One or more types of adhesives can be appropriately selected and used. In the present invention, it is preferable to use a latex having a different characteristic from that of the starch polymer compound as an adhesive, and in that case, it is preferable to use more starch polymer compound than the latex. Although both advantages of the starch compound and latex can be obtained by the combined use, it is preferable to increase the amount of the starch polymer compound used in order to exert the effect of the present invention.

  In the present invention, the blending amount of the adhesive in the coating liquid is not particularly limited, but is preferably 5 to 50 parts by mass and more preferably about 5 to 30 parts by mass per 100 parts by mass of the pigment. When using the said starch and other adhesives together as an adhesive agent, it is preferable that the total amount is the said range.

  In the present invention, the adhesive may contain a copolymer latex. When the copolymer latex is used, the content thereof can be 4 parts by mass or less with respect to 100 parts by mass of the pigment, preferably 1.5 parts by mass or more and 4 parts by mass or less, more preferably 1 .5 parts by mass or more and 3 parts by mass or less. Even when blending more than 4 parts by mass, the printing surface strength is excellent, but the cost is high and further effects cannot be expected.

  In the present invention, the method for preparing the coating liquid is not particularly limited and can be appropriately adjusted depending on the type of coater. When a blade type coater is used, the solid content concentration of the coating liquid is preferably 40 to 70 mass%, more preferably 50 to 60 mass%. The viscosity of the coating liquid is preferably 300 to 2000 mPa · s, more preferably 400 to 1000 mPa · s, according to a JIS K7117-1 B-type viscometer.

  In the present invention, various auxiliary agents blended in ordinary pigments for coated paper, such as dispersants, thickeners, water retention agents, antifoaming agents, water resistance agents, and colorants, can be used as necessary. .

Coating pigment The pigment (white pigment) used in the coating layer of the present invention is not particularly limited, and those conventionally used for coated paper can be used, for example, kaolin, clay, engineered kaolin. , Delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white and other solid pigments, solid type, hollow type Or, an organic pigment such as a core-shell type can be used alone or in admixture of two or more. In addition, as a kind of pigment, heavy calcium carbonate and light calcium carbonate are preferable from the viewpoint of a low binder requirement and improving surface strength with a small amount of adhesive, and high whiteness, and also improve opacity. From the viewpoint, light calcium carbonate having a uniform particle diameter and shape is particularly preferable. This is because the bulky coating layer structure scatters light efficiently.

  When blending calcium carbonate in the coating liquid, the light calcium carbonate or heavy calcium carbonate, or the combined content of both, is preferably 50 parts by mass or more, more preferably 70 parts by mass or more per 100 parts by mass of the pigment. 80 parts by mass or more is more preferable. Further, from the viewpoint of forming a uniform coating layer on the base paper, the average particle size is preferably 0.2 to 5 μm as measured by a laser diffraction type particle size distribution analyzer such as Mastersizer S manufactured by Malvern. 2 to 3 μm is more preferable.

In the present invention, any coater that is usually used may be used. An on-machine coater or an off-machine coater may be used, and if it is an on-machine coater, a roll coater such as a size press coater, a gate roll coater, a rod metering size press coater, a bill blade coater, a blade metering size press coater, a short dwell blade A coater such as a coater or a jet fountain blade coater can be used. The coating speed is not particularly limited, but it is preferably 500 to 1800 m / min for a blade coater and 500 to 2000 m / min for a size press coater in the current technology.

  In the present invention, the method for drying the wet coating layer is not limited, and various methods such as a steam superheated cylinder, a heated hot air air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer may be used alone or in combination. it can.

The coating amount of the coating liquid in the present invention can be appropriately selected according to the use, but in general, it is ² to 13 g / m ² in terms of solid content per side, and may be 4 to 12 g / m ² . 6-11 g / m < ² > may be sufficient.

Base Paper The coated paper of the present invention has a base paper layer. A base paper can be manufactured by a well-known method, for example, a paper-making raw material (paper material) can be made in a wire part, and then it can be used for a press part and a pre-dryer part to manufacture a base paper. The base paper used in the present invention may be single-layer paper or multi-layer paper, but when producing white paperboard, it is preferable to use multi-layer paper. The method for producing the base paper of the present invention is not particularly limited, and can be performed by a known method using known raw materials. The base paper used in the present invention is not particularly limited, except for commonly used high-quality paper, medium-quality paper, renewal paper, machine-coated paper, art paper, cast-coated paper, synthetic paper, resin-coated paper, plastic film, etc. Can be used without

  Chemical pulp can be used as a pulp raw material used for the base paper of the present invention. As the chemical pulp, hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) can be suitably used. In addition to chemical pulp, various pulps can be used depending on the application, for example, deinked pulp (DIP), groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermo. Examples include mechanical pulp (CTMP), chemi-ground pulp (CGP), and semi-chemical pulp (SCP). As the deinked pulp, it is possible to use deinked pulp made from selected waste paper such as high quality paper, medium quality paper, lower grade paper, newspaper, flyers, magazines, etc., or unselected waste paper mixed with these.

  In the present invention, known fillers can be arbitrarily used as fillers for base paper, such as heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, deramikaolin, white Amorphous produced by neutralization of carbon, talc, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate Inorganic fillers such as silica and organic fillers such as urea-formalin resin, melamine resin, polystyrene resin, and phenol resin can be used alone or in combination. Among these, heavy calcium carbonate and light calcium carbonate, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used to improve opacity. The filler content in the paper is not particularly limited, but is preferably 1 to 40 solids mass%, more preferably 10 to 35 solids mass%.

  In the present invention, known papermaking additives can be used. For example, sulfuric acid bands and various anionic, cationic, nonionic or amphoteric yield improvers, drainage improvers, various paper strength enhancers and internal additive sizing agents, etc. Can be used. 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 the formation and operability. Examples of neutral sizing agents include alkyl ketene dimers, alkenyl succinic anhydrides, and neutral rosin sizing agents. Furthermore, dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  The paper making method of the base paper in the present invention is not particularly limited, and a long paper machine including a top wire, an on-top former, a gap former, a round paper machine, a long paper machine and a round paper machine are used in combination. It can be performed using a paperboard machine, a Yankee dryer machine or the like. The pH during papermaking may be acidic, neutral or alkaline, but neutral or alkaline is preferred. The paper making speed is not particularly limited.

The basis weight of the base paper of the present invention is not particularly limited and can be appropriately selected depending on the application. For example, the basis weight of the base paper may be a ^{25~100g / m 2, 28~80g / m} 2, may be 31~60g / ^{m 2.}

Clear coating The coated paper of the present invention may have a clear (transparent) coating layer on one side or both sides of the base paper described above. By applying clear coating on the base paper, the surface strength and smoothness of the base paper can be improved, and the coating property when applying pigment can be improved. In this invention, you may contain the high molecular compound derived from the starch of this invention as a binder in a clear coating layer. The amount of clear coating is preferably 0.1 to 4.0 g / m ² , more preferably 0.5 to 2.5 g / m ² in terms of solid content on one side.

  In the present invention, clear coating means, for example, various starches such as starch and oxidized starch using a coater (coating machine) such as a size press, a gate roll coater, a pre-metering size press, a curtain coater, and a spray coater. It means that a coating liquid (surface treatment liquid) mainly composed of a water-soluble polymer such as polyacrylamide or polyvinyl alcohol is applied (size press) on a base paper.

Pre-calendar treatment In the present invention, pre-calendar processing is performed on the base paper before coating by an online soft calendar, online chilled calendar, etc., and smoothing the base paper in advance makes the coating layer after coating uniform. Preferred above. In this case, the treatment linear pressure is preferably 30 to 100 kN / m, more preferably 50 to 100 kN / m. Moreover, the moisture content of the base paper at the time of pre-calendering is also important, and the moisture content is preferably 3 to 5%.

Surface Treatment In the present invention, the paper produced as described above is subjected to a surface treatment as necessary. For smoothing processing, a smoothing processing device such as a normal super calendar, gloss calendar, soft calendar, thermal calendar, shoe calendar, or the like can be used. The smoothing apparatus is appropriately used on-machine or off-machine, and the form of the pressure device, the number of pressure nips, heating, and the like are also adjusted as appropriate. In a preferred embodiment, the coated paper of the present invention can be surface-treated with a calendar such as a super calender or a high temperature soft nip calender. By the surface treatment, the smoothness and glossiness of the coated paper can be improved. In the present invention, soft nip calendering is preferred. Both softness and opacity are improved by soft nip calendering. In the soft nip calendering process, the linear pressure at the surface temperature of the metal roll of 20 ° C. to 60 ° C. is 30 to 60 kN / m, more preferably 40 to 60 kN / m. Further, if the surface temperature of the metal roll is a high temperature soft nip calendering treatment at 40 ° C. to 250 ° C., the linear pressure is 60 to 400 kN / m, preferably 100 to 350 kN / m, more preferably 150 to 300 kN / m. It is. Increasing the temperature improves the gloss and smoothness of the coated paper surface.

  The coated paper of the present invention can correspond to various printing methods, and can be used for offset printing coated paper, relief printing coated paper, gravure printing coated paper, and the like. In particular, since the coated paper of the present invention has excellent surface strength and glossiness, it can be suitably used for offset printing applications, and is particularly suitable for offset rotary printing applications.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this. In addition, unless otherwise specified, in this specification, a numerical range is described as including its end points, and “part” and “%” indicate “part by weight” and “% by weight”, respectively.

Evaluation Method (1) Measurement of Average Square Rotation Radius <R ² >, Weight Average Absolute Molecular Weight (Mw) The average square rotation radius and weight average absolute molecular weight of roasted dextrin were determined by size exclusion chromatography according to the following equipment and conditions: It was measured by a multi-angle light scattering (SEC-MALS) method.
-Separation column: 2 Shodex GPC KB-806M, 1 Shodex GPC KB-802-Column temperature: 40 ° C
Mobile phase solvent: 0.1 mol / L NaNa ₃ aqueous solution Mobile phase flow rate: 0.5 mL / min
・ Injection volume: 300 μL
Detector 1: Multi-angle light scattering detector (manufactured by Wyatt, DAWN HELEOSII)
Detector 2: Refractive index (RI) detector (Waters, Model 2414)
Sample: [steamed] stirred at 100 ° C. for 20 minutes [concentration] 0.12 w / v%
[Filtration] Chromatodisc pore size 0.45μm (Kurabo)
・ Data processing: ASTRA (manufactured by Wyatt)
(2) Average lithographic printing 10-pick evaluation Using a Roland sheet-fed printing press R302, using Toyo Ink's Leo Echo SOYL Indigo (low tack ink for off-wheel), printing indigo solid at a speed of 800 sph, 10 sheets The number of F-side and W-side picking that occurred during printing was measured.
(3) Glossiness: The glossiness of the F surface was measured according to JIS P8142.

Production of coated paper [Example 1]
Heavy calcium carbonate (trade name: FMT-97, manufactured by FMT) is used as a pigment, and styrene / butadiene copolymer latex and a roasted dextrin having an average square rotation radius of 12.5 nm as an adhesive (raw corn starch and hydrochloric acid). 5.4 mmol / kg was added, and a weight average absolute molecular weight of 10.0 × 10 ⁴ obtained by heating at 130 ° C. for 90 minutes was blended to prepare a paint having a solid content concentration of 55% (B type viscosity: About 275 mPas). To 100 parts of heavy calcium carbonate, 1.5 parts of styrene / butadiene copolymer latex and 10 parts of roasted white dextrin having an average square rotation radius of 12.5 nm were blended.

Sided coating at a coating speed of a blade coater of the thus prepared paint basis weight 34g / m ² of wood containing base paper coated amount per one surface is 8 g / m ² by solid content in 1000 m / min Worked. Further, a coated paper was obtained by surface treatment with a hot soft nip calender at a processing temperature of 130 ° C., a processing speed of 357 m / min, and a 4-nip condition (basis weight: about 50 g / m ² ).

[Example 2]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square rotation radius of 14.5 nm (5.0 mmol / kg of hydrochloric acid was added to raw corn starch and heated at 130 ° C. for 90 minutes. A coated paper was obtained in the same manner as in Example 1, except that the weight average absolute molecular weight of about 24.3 × 10 ⁴ ) was used.

[Example 3]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square rotation radius of 18.2 nm (4.7 mmol / kg of hydrochloric acid added to raw corn starch and heated at 130 ° C. for 90 minutes) A coated paper was obtained in the same manner as in Example 1 except that the weight average absolute molecular weight 27.8 × 10 ⁴ ) was used.

[Example 4]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square rotation radius of 22.1 nm (4.6 mmol / kg of hydrochloric acid was added to raw corn starch and heated at 130 ° C. for 90 minutes. A coated paper was obtained in the same manner as in Example 1 except that the weight average absolute molecular weight obtained was about 29.2 × 10 ⁴ ).

[Example 5]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square rotation radius of 23.4 nm (4.5 mmol / kg of hydrochloric acid added to raw corn starch and heated at 130 ° C. for 90 minutes) A coated paper was obtained in the same manner as in Example 1 except that the weight average absolute molecular weight obtained was about 31.9 × 10 ⁴ ).

[Example 6]
In Example 1, a coated paper was obtained in the same manner as in Example 1 except that the solid content concentration of the paint was 60%.

[Example 7]
In Example 1, coated paper was obtained in the same manner as in Example 1 except that the solid content concentration of the coating material was 63%.

[Example 8]
In Example 2, a coated paper was obtained in the same manner as in Example 1 except that the solid content concentration of the paint was 60%.

[Example 9]
In Example 2, a coated paper was obtained in the same manner as in Example 1 except that the solid content concentration of the coating material was 63%.

[Comparative Example 1]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square rotation radius of 10.1 nm (5.8 mmol / kg of hydrochloric acid was added to raw corn starch and heated at 130 ° C. for 90 minutes. A coated paper was obtained in the same manner as in Example 1 except that the weight average absolute molecular weight of about 3.1 × 10 ⁴ ) was used.

[Comparative Example 2]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square rotation radius of 11.4 nm (5.5 mmol / kg of hydrochloric acid was added to raw corn starch and heated at 130 ° C. for 90 minutes. A coated paper was obtained in the same manner as in Example 1 except that the weight average absolute molecular weight of about 6.4 × 10 ⁴ ) was used.

[Comparative Example 3]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square turning radius of 24.1 nm (4.4 mmol / kg of hydrochloric acid was added to raw corn starch and heated at 130 ° C. for 90 minutes. A coated paper was obtained in the same manner as in Example 1 except that the weight average absolute molecular weight of about 34.6 × 10 ⁴ ) was used.

[Comparative Example 4]
In Example 1, styrene-butadiene copolymer latex as an adhesive and roasted white dextrin having an average square rotation radius of 25.2 nm (adding 4.2 mmol / kg of hydrochloric acid to raw corn starch and heating at 130 ° C. for 90 minutes) A coated paper was obtained in the same manner as in Example 1 except that the weight average absolute molecular weight obtained was about 42.9 × 10 ⁴ ).

  Table 1 shows the evaluation results. As is apparent from Table 1, by adding roasted dextrin having an average square rotation radius of 12 to 24 nm, a coated paper having high average lithographic printing 10 picks (high surface strength) and excellent glossiness is obtained. I was able to.

  On the other hand, in Comparative Examples 1 and 2 using roasted dextrin having an average square rotation radius of less than 12 nm, the average lithographic printing 10 sheet pick was low (surface strength was low), and the average square rotation radius was higher than 24 nm. In Comparative Examples 3 and 4 using baked dextrin, the glossiness was inferior.

Further, when Examples 1, 6, 7 and Examples 2, 8, and 9 were compared, according to the present invention, there was no problem in operability even when the paint concentration of the pigment coating liquid was increased, and printing was performed efficiently. Coated paper could be manufactured.

Claims (5)

A coated paper having a pigment coating layer containing a pigment and an adhesive on a base paper,
As an adhesive contained in the pigment coating layer, starch having an average square rotation radius (<rg ² >) measured by a size exclusion chromatography-multi-angle light scattering (SEC-MALS) method of 12 to 24 nm was used. The above coated paper.   The coated paper according to claim 1, wherein the starch is roasted dextrin.   The coated paper according to claim 1 or 2, wherein a styrene-butadiene latex and the starch are used in combination as the adhesive.   The coated paper according to any one of claims 1 to 3, wherein 5 to 50 parts by mass of the starch is used with respect to 100 parts by mass of the pigment. The coated paper according to any one of claims 1 to 4, wherein the pigment contains calcium carbonate.