JP5550946B2 - Coated paper for printing - Google Patents

Description

  The present invention relates to a coated paper for printing. In particular, the present invention relates to a method for producing a coated paper for printing having a high bulkiness, a high whiteness, and an excellent printing surface.

  In recent years, there has been an increasing demand for weight reduction of printing paper in order to reduce transportation and mail costs. However, simply reducing the weight, that is, reducing the basis weight of the printing paper is not preferable because the thickness of the paper is reduced and the volume of the booklet is impaired. The weight reduction demanded by paper users is to reduce the paper weight but not to reduce the paper thickness, and more preferably to increase the paper thickness. It is.

On the other hand, with the progress of visualization and colorization of printed materials, the demand for coated paper for printing having a smooth coated layer as an ink receiving layer is increasing year by year as compared with non-coated paper for printing. However, the pigment coating layer mainly composed of inorganic pigments such as calcium carbonate and kaolin has a higher specific gravity than the base paper coated with pulp as the main material, so it is low for weight reduction of the coated paper. The coating amount is effective.
From the viewpoint of increasing the bulk, it is conceivable to increase the bulk of the coated base paper, and one of the methods for reducing the density (increasing the volume) is to examine paper pulp. Generally, wood pulp is used for paper pulp. However, in order to reduce the density, a grinder is used rather than chemical pulp (KP) in which lignin, which is a reinforcing material in wood fibers, is extracted with chemicals. Fiber is more rigid and effective in ground pulp (GP) that grinds wood, refiner mechanical pulp (RMP) that refines wood with refiner, or mechanical pulp (MP) such as thermomechanical pulp (TMP) .
However, it is known that among mechanical pulps, thermomechanical pulp has a relatively long fiber length and high rigidity, so that the smoothness of the paper produced decreases. Further, when mechanical pulp is used, the whiteness of the pulp is lower than that of the chemical pulp, so that there is a problem that the whiteness of the paper is lowered as a whole.

Further, from the viewpoint of papermaking, a method using a bulking agent is known as a technique for increasing the bulk (lowering the density) of uncoated paper or coated base paper. As a known bulking agent, for example, a bulking agent for paper containing a specific alcohol and / or its polyoxyalkylene adduct (Patent Document 1), a nonionic surfactant (Patent Document 2), a polyhydric alcohol and a fatty acid. A paper bulking agent composed of an ester compound (Patent Document 3) is known, and a technology (Patent Document 4) in which these paper bulking agents are applied to paperboard, the coating amount is 10 to 25 g / m ^{2 on} one side. A glossy coated paper (Patent Document 5) is also proposed.
In addition, a fine coated paper obtained by coating a coating layer having 20 to 60 parts by weight of starch per 100 parts by weight of pigment so as to have an amount of ¹ to 5 g / m ² (Patent Document 6), Although a bulky coated paper (Patent Document 7) in which a coating layer comprising a pigment and a binder is provided on a coating base paper containing mechanical pulp is disclosed, it is limited that the base paper is derived from hardwood wood chips. In addition, the coating method is not limited, and does not suggest improving characteristics such as whiteness and printing surface feeling.

  However, with the above-described conventional technology, it has been difficult to produce a fine coated paper for printing that is bulky, has a high degree of whiteness, and has an excellent printing surface feeling while having a low coating amount.

International Publication No. 98/03730 Pamphlet JP-A-11-200263 Japanese Patent No. 2971447 Japanese Patent No. 3041294 JP-A-4-370298

  In view of such a situation, an object of the present invention is to provide a coated paper for printing that is bulky, has a high whiteness, and is excellent in printing surface feeling while having a low coating amount.

The present inventors include a pigment and an adhesive on a base paper containing a mechanical pulp produced by subjecting hardwood wood chips to normal pressure or pressure refining and having a density of 0.7 g / cm ³ or less. By applying a coating liquid containing 10 to 50 parts by weight of starch per 100 parts of pigment as an agent, by applying 0.5 to 5 g / m ² per side at an absolutely dry weight using a film transfer method, It was found that a coated paper for printing having a low coating amount and high whiteness and excellent printing surface can be obtained.
In the present invention, the mechanical pulp is impregnated with hardwood wood chips in an alkaline hydrogen peroxide solution and then subjected to normal pressure or pressure refining treatment, and then held at room temperature or under pressure for a certain time with a chemical solution. The machine pulp to be produced may be contained in the base paper, and the coating liquid may contain starch as an adhesive and may contain latex, and if it contains latex, the content of latex The starch may have a higher content than the starch, and the ratio of the starch and latex content of the coating solution may be starch: latex = 10: 1, and the starch may be hydroxyethyl etherified starch. good.
Moreover, after coating by a film transfer method, you may process with a linear pressure of 1-50 kN / m with a high temperature soft nip calender.

  According to the present invention, it is possible to obtain a coated paper for printing that is bulky, has a high whiteness, and has an excellent printing surface feeling while having a low coating amount.

With bulky paper, when the coated base paper is made bulky, the base paper becomes low density and voids increase, so the coating liquid penetrates into the base paper during coating, and uniformly coats the base paper surface with a low coating amount. It becomes difficult. In order to increase the weight and bulk of coated paper, even if a light and bulky base paper is used, simply applying a coating liquid mainly composed of a high specific gravity inorganic pigment will result in penetration of the coating liquid. In addition, when the coating amount is reduced, coating unevenness of the coating liquid occurs on the coating surface, and the printing surface feeling deteriorates due to uneven ink deposition during printing, In addition, since the whiteness of the paper is lower than when the coating amount is large, it is difficult to achieve a light and bulky high whiteness.
If the base paper is calendered before coating in order to reduce the amount of voids in the base paper, the paper thickness is reduced, and a bulky low density paper cannot be obtained.
In order to solve the above-mentioned new problem, the present inventors solved the problem by specifying the raw material of the pulp, increasing the amount of starch in the pigment coating liquid, and coating by the transfer roll method. The present inventors have found a coated paper for printing which is bulky and has a low coating amount.

Base Paper The base paper of the coated paper for printing in the present invention is mainly composed of pulp and filler. These components are described below.

Pulp The base paper of the coated paper for printing in the present invention is mainly composed of pulp and filler. As the pulp to be blended in the base paper of the present invention, chemical pulp, semi-chemical pulp, mechanical pulp, waste paper pulp and the like can be used. Since mechanical pulp is more rigid than chemical pulp and semi-chemical pulp, the base paper containing a large amount of mechanical pulp is less bulky due to various pressures applied in the paper making process, and becomes bulky as a whole. In the present invention, mechanical pulp is used to produce a bulky base paper. As the mechanical pulp, it is a mechanical pulp made from hardwood, for example, a pulp such as refiner grandwood pulp (RGP) subjected to only mechanical processing, a pulp such as thermomechanical pulp (TMP) Chemi-thermomechanical pulp (CTMP) obtained by chemical treatment, RGP or TMP treated with a chemical such as sodium sulfite, alkali hydrogen peroxide mechanical pulp (APMP) obtained by changing the chemical to alkaline hydrogen peroxide, And alkali hydrogen peroxide thermomechanical pulp (APTMP). Among them, it is preferable to use APMP and APTMP in terms of obtaining bulkiness, high opacity, and high whiteness.

In the present invention, in order to produce a bulky base paper, it is preferable that the total blending amount of one kind or two or more kinds of the mechanical pulp is 50% by weight or more per weight of the base paper, more preferably 70% by weight or more. Preferably it is 80 weight% or more. The hardwood pulp has the characteristics that the fiber length is longer than that of the softwood pulp and is thin, so that the smoothness tends to be high, while the density tends to be low.
In the present invention, when using thermomechanical pulp (TMP), the freeness of the disaggregated pulp is preferably 70 ml or more, more preferably 70 ml or more and 200 ml or less.

APMP is manufactured by impregnating wood chips with an aqueous alkali hydrogen peroxide solution containing, for example, sodium hydroxide, hydrogen peroxide, and sodium silicate, and performing refining treatment at atmospheric pressure. APTMP is refining treatment at high temperature and pressure. In order to obtain a higher whiteness, the refining treatment is performed, and the mixture is further maintained for 5 minutes or more at room temperature or under heating with an alkaline hydrogen peroxide solution.
For example, APMP and APTMP are manufactured through the following steps a) to i).
a) compressing hardwood wood chips at a compression ratio of at least 4: 1 and impregnating with a chelating agent upon pressure release:
b) Step of holding the impregnated chip at a temperature of 10 ° C. to 80 ° C. for 5 minutes or more:
c) a step of further compressing the impregnated chip at a compression ratio of at least 4: 1 and impregnating with an alkaline chemical when released:
d) A step of holding the impregnated chip at a temperature of 10 ° C. to 80 ° C. for about 10 minutes to 1 hour:
e) The step of impregnating the treated chip with an alkali peroxide and passing the chip through a pressurized or atmospheric refining device to defibrate the chip to produce wood pulp:
f) Step of holding the manufactured pulp at a temperature of 50 ° C. or higher for 5 minutes or longer:
g) Step of diluting the manufactured pulp to a concentration of 5% or less, washing it, and then concentrating it again to 15% or more:
h) Step of obtaining a pulp having a desired freeness by refining the produced pulp under pressure or atmospheric pressure:
i) A step in which the pulp thus obtained is bleached in one or more steps using an oxidizing agent or a reducing agent.

  In step a), it is preferable to use about 0.05 to 0.4% of a chelating agent, and in step c), the alkaline agent used in step c) is about 0.2 ~ 2.0% sodium hydroxide, about 0.2-2.0% sodium silicate, about 0.01-0.2% magnesium sulfate, about 0.05-0.4% chelating agent and about An aqueous solution containing 0.2 to 5% hydrogen peroxide is preferable.

  In the step e), an alkali peroxide containing a chelating agent is added to the wood chip that has been bleached and softened immediately before the primary refining, and the wood fiber is dissolved in a pressure or atmospheric refining device. Be fine. For refining, a general defibrating apparatus is sufficient, and defibration is preferably performed with a single disc refiner, a conical disc refiner, a double disc refiner, a twin disc refiner, or the like.

  If the resulting bulky mechanical pulp requires high whiteness, the pulp can be further bleached by one or more known bleaching steps. In this case, an oxidizing agent such as hydrogen peroxide, ozone or peracetic acid or a reducing agent such as hydrosulfite (sodium dithionite), sodium hydrogen sulfate, sodium borohydride, formamidine sulfinic acid (FAS), etc. Can be used.

The mechanical pulp manufactured through the above manufacturing process has high whiteness, high opacity, and high strength. Especially mechanical pulp produced from volume with Runkeru ratio 4.0 or more heavy 450 kg / m ³ or more high volume weight material, because the fiber lumen (lumen) is rigid hardly collapse, sheet the pulp fibers are compounded The bulky structure can be maintained and the density can be lowered. As the tree species to be used, Eucalyptus is preferable, and Eucalyptus globules, Eucalyptus grandis and the like are more preferable. The sheet density of hardwood mechanical pulp is preferably 0.45 g / cm ³ or less to be used, more preferably 0.35 g / cm ³ or less.

  In addition to the above-mentioned bulky mechanical pulp, the raw paper of the coated paper for printing of the present invention includes chemical pulp (blown kraft pulp of softwood (NBKP) or unbleached kraft pulp (NUKP), bleached kraft pulp of hardwood (LBKP) ) Or unbleached kraft pulp (LUKP), mechanical pulp (groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), etc.), deinked pulp ( DIP) is used alone or mixed in any proportion.

Filler In the present invention, the type of filler contained in the base paper is not limited, for example, light calcium carbonate, heavy calcium carbonate, white carbon, talc, kaolin, clay, titanium oxide, zeolite, synthetic resin filler, etc. Of these, light calcium carbonate is preferred.
The light calcium carbonate may be either calcite or aragonite, and may be acicular, columnar, spindle-shaped, spherical, cubic, or rosetta-type. Rosetta-type light calcium carbonate refers to a shape in which spindle-shaped light calcium carbonate primary particles are aggregated in a chestnut shape, and has a characteristic of exhibiting a higher specific surface area and oil absorption than other light calcium carbonates. The content is preferably 5 to 25% by weight and more preferably 10 to 20% by weight when the total filler is 100% by weight. If it is less than 5% by weight, the stickiness reduction effect of the printed matter is not sufficient, and if it exceeds 25% by weight, the tensile strength of the coated paper is lowered.
As a result, in the present invention, when the base paper of the coated paper for printing is manufactured using Rosetta-type calcite light calcium carbonate under the condition of high blending of mechanical pulp, particularly excellent bulkiness and opacity Improvement effect, prevention of back-through, and good base paper surface properties are obtained.

  In the present invention, a light calcium carbonate-silica composite containing calcium carbonate can also be used. The light calcium carbonate-silica composite is obtained by coating the surface of the light calcium carbonate particles with silica, and is preferably used by replacing the entire amount or a part of the filler. By using the light calcium carbonate-silica composite particles, the density of the base paper can be lowered and the rigidity can be improved by increasing the paper thickness. As yet another effect, the light calcium carbonate-silica composite particles have an effect of reducing stickiness of printed matter. Further, even after the calendar process, the contradictory properties of high smoothness and low density can be achieved at the same time.

  In the present invention, when the light calcium carbonate-silica composite particles are used as a filler in paper, the content is preferably 5 to 25% by weight when the total filler is 100% by weight, More preferred is 20% by weight. If it is less than 5% by weight, the stickiness reduction effect of the printed matter is not sufficient, and if it exceeds 25% by weight, the tensile strength of the coated paper is lowered.

The light calcium carbonate-silica composite particles have a solid weight ratio of light calcium carbonate to silica of light calcium carbonate / silica = 30/70 to improve the balance between the stickiness of the printed matter and the ink inking property. 70/30 is preferred.
When the weight ratio of light calcium carbonate solids is smaller than light calcium carbonate / silica = 30/70, the surface strength during printing of the coated paper tends to be inferior. If the solid weight ratio of light calcium carbonate is more than light calcium carbonate / silica = 70/30, the effect of improving stickiness is not greater.
The light calcium carbonate of the light calcium carbonate-silica composite particles may be needle-shaped, columnar, spindle-shaped, spherical, cubic, or rosetta-type. Among them, rosette-type calcite-type light calcium carbonate is used. In particular, the effect of preventing see-through and improving opacity is improved.

The average particle size of the composite particles is preferably 1.0 to 10.0 μm as measured by a laser diffraction particle size distribution analyzer (Mastersizer 2000 manufactured by Malvern).
The coated paper for printing of the present invention can exhibit contradictory properties such as maintaining a low density and high smoothness even after performing a calendar process during coating.

Bulking agent In the present invention, a bulking agent (a density-reducing agent) such as a surfactant, which is an organic compound having an action of inhibiting the interfiber bonding of pulp, is used in order to reduce the density of the base paper (increase the bulk). can do. By adding a bulking agent, the base paper has a low density and air permeability is improved.
An organic compound having an action of inhibiting the interfiber bonding of pulp (hereinafter abbreviated as a binding inhibitor) is a compound having a hydrophobic group and a hydrophilic group, and has recently been put on the market for paper making to increase the bulk of paper. Further, the density reducing agent (or bulking agent) is suitable as the binding inhibitor of the present invention. For example, WO98 / 03730, JP-A-11-200284, JP-A-11-350380, JP-A-2003-2003 No. 96694, Japanese Patent Application Laid-Open No. 2003-96695, and the like.
Specifically, higher alcohol ethylene and / or propylene oxide adduct, polyhydric alcohol type nonionic surfactant, higher fatty acid ethylene oxide adduct, polyhydric alcohol and fatty acid ester compound, polyhydric alcohol and fatty acid Ethylene oxide adducts of these ester compounds, fatty acid polyamidoamines, fatty acid diamidoamines, fatty acid monoamides, or polyalkylenepolyamine / fatty acid / epichlorohydrin condensates can be used alone or in combination of two or more. can do.
Preferred are polyhydric alcohol and fatty acid ester compounds, fatty acid polyamidoamines, fatty acid diamidoamines, fatty acid monoamides, polyalkylene polyamine / fatty acid / epichlorohydrin condensates and the like. Bulky chemicals on the market include BASF's Sulsol VL, Bayer's Bi-Volume P Liquid, Kao's KB-08T, 08W, KB110, 115, Sanki's React Pake, Seiko PMC ), PT-205, Nippon Oil & Fats Co., Ltd. DZ2220, DU3605, Arakawa Chemical Co., Ltd. R21001, and these may be used alone or in combination of two or more.

  In this invention, when adding a bulking agent, it is preferable to add 0.1-10 weight part of bulking agents with respect to 100 weight part of pulps, and it is preferable to add 0.2-1.0 weight part especially.

  Furthermore, in the base paper of the present invention, in addition to pulp and filler, sulfuric acid bands and various anionic, cationic, nonionic or amphoteric yield improvers, freeness improvers, paper strength enhancers and internal sizing agents An internal additive for papermaking such as can be used as necessary. Furthermore, papermaking additives such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents and slime control agents can be added as necessary.

Papermaking method The papermaking method of the base paper in the present invention is not particularly limited, and a machine having a former section such as a long web former, an on-top hybrid former, and a gap former (paper machine) conventionally used for papermaking. Can be used to make paper.
In particular, in the present invention, it is preferable to use an on-top hybrid former or a gap former in order to make it easier to keep the internal filler on the surface layer. Papermaking can be carried out by any of acid papermaking, neutral papermaking, and alkali papermaking.
The basis weight of the coating base paper of the present invention are those generally about 25~400g / ^{m 2} to be used, preferably it is possible to use those of 40 and 80 g / ^{m 2,} a density 0.4~0.63g / Cm ³ is also acceptable. The whiteness of the base paper is 50 to 90%, preferably 75 to 85%.

Ash content in paper The amount of ash content in the base paper of the present invention is preferably 10% by weight or more. A more preferable amount of base paper ash is 12% by weight or more in the base paper, and more preferably 15% by weight or more. In consideration of an increase in density of the base paper and a decrease in strength, the base paper ash content is preferably 40% by weight or less.
In the case of the low-density base paper of the present invention, when the base paper ash content is less than 10% by weight, the base paper has a large penetration when the coating liquid is applied, resulting in uneven coating of the coating liquid after coating. , The printing surface may be deteriorated.
By making the base paper ash content 10% by weight or more, the filler fills the gaps on the surface of the base paper, and the coating suitability is improved even under conditions where it is difficult to maintain the base paper coverage of 0.5-5 g / m ^2. To do.
In addition to pulp and filler, the base paper of the present invention includes a sulfuric acid band and various anionic, cationic, nonionic or amphoteric yield improvers, drainage improvers, paper strength enhancers and internal sizing agents. An internal additive for papermaking can be used as necessary. Furthermore, papermaking additives such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents and slime control agents can be added as necessary.

Clear coating In the present invention, if necessary, an adhesive such as starch may be applied to the base paper before pigment coating by a size press or the like. Although it does not specifically limit as an adhesive agent used for clear coating, For example, starches, such as an oxidation starch, hydroxyethyl etherified starch, oxygen-modified starch, polyacrylamide (PAM), polyvinyl alcohol (PVA), etc. Can be used alone or in combination. Moreover, you may perform clear coating (application | coating), adding auxiliary agents, such as a surface sizing agent, a water-resistant agent, a water retention agent, a thickener, and a lubricant, as needed.

  The coating method and the coating apparatus used in the size press treatment of the present invention are not particularly limited, and a known coating apparatus can be used, such as a rod metalling type size press, a pound type size press, a gate roll coater, and a spray coater. It is preferable to use a blade coater or a curtain coater.

Coating liquid
As the pigment used in the coating layer containing the pigment and the adhesive on the pigment base paper, those conventionally used for coated paper can be used, for example, kaolin, clay, engineered kaolin, delaminator. Ted 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 inorganic pigments and solid, hollow or core shell Organic pigments such as molds can be used alone or in admixture of two or more as required.
In addition, as the type of pigment, heavy calcium carbonate can suppress the increase in coating solution viscosity compared to kaolin, clay, engineered kaolin, and delaminated clay, and as a result, the coating solution concentration is increased. Therefore, it is preferable because the penetration of the coating liquid can be suppressed and a bulky effect is easily exhibited.
A preferable heavy calcium carbonate content in the pigment is 50 parts by weight or more per 100 parts by weight of the pigment, more preferably 70 parts by weight or more, and further preferably 80 parts by weight or more. Further, from the viewpoint of forming a good printing surface feeling, the average particle size is preferably 0.5 to 3 μm, more preferably 0.8, as measured with a laser diffraction particle size distribution analyzer (Mastersizer 2000 manufactured by Malvern). ~ 2.5 μm.

Adhesive In the present invention, as an adhesive used for a coating layer containing a pigment and an adhesive on a base paper, those conventionally used for coated paper can be used, for example, styrene-butadiene. Styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, etc., polyvinyl alcohol, maleic anhydride copolymer, acrylic acid / methyl methacrylate Synthetic adhesives such as polymers, proteins such as casein, soy protein, synthetic protein, oxidized starch, cationized starch, urea phosphate esterified starch, starch such as hydroxyethyl etherified starch, carboxymethylcellulose, hydroxymethylcellulose, Cellulose such as hydroxyethyl cellulose Derivatives etc., may be used to select one or more appropriate.
In this invention, 1 or more types of starch is contained as an adhesive agent. More preferably, hydroxyethyl etherified starch is preferable from the viewpoint of the coating solution viscosity and stable operability.

10 to 50 parts by weight of starch is added to 100 parts by weight of the pigment. More preferably, it is 12-40 weight part, More preferably, it is 25-45 weight%. When the amount exceeds 50 parts by weight, the viscosity of the coating solution increases, and the coating suitability in various coating methods deteriorates. On the other hand, when the amount is less than 10 parts by weight, sufficient base paper coverage and surface strength cannot be obtained, which is not preferable.

The adhesive of the present invention may not contain latex, but in order to increase the stability and the rigidity of the coated paper for printing, together with starches, styrene / butadiene, styrene / acrylic, ethylene It is preferably used in combination with latex such as various copolymers such as vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl acrylate.
The latex is preferably a styrene / butadiene copolymer latex.
When used latex, the compounding ratio of starch and latex, preferably starches / latex = 1 / 1-10 / 1. More preferably, it is 6/1 to 1/1. If the ratio is lower than 1/1, the rigidity tends to decrease. If the ratio is higher than this ratio, the viscosity of the paint increases and the coating suitability deteriorates.
In the coating liquid containing the pigment and adhesive of the present invention, various commonly used auxiliaries such as a dispersant, a thickener, a water retention agent, an antifoaming agent, a water resistance agent, a dye, and a fluorescent dye are used as auxiliaries. Can be used.

Method for Coating Pigment Coating Layer In the present invention, the method for coating the pigment coating layer is preferably a film transfer system. Examples of the film transfer method include a metal ring size press coater or a gate roll coater.
The film transfer method is preferred because the coating amount control is easier and the base paper coverage is better in the low coating amount region than in the blade coating method.
The coating amount per side in the present invention is preferably 0.5 to 5 g / m ² in terms of solid content. When the coating amount is less than 0.5 g / m ² , coating unevenness of the coating liquid occurs and the printing surface feeling is deteriorated, which is not preferable. On the other hand, when the coating amount is 5.0 g / m ² or more, the density of the coated paper increases, and it is difficult to produce a bulky coated paper, which is not preferable. The more preferable single-side coating amount in the present invention is 0.5 to 4.0 g / m ² , and more preferably 0.5 to 3.0 g / m ² .

As a dryer for drying the wet coating layer after coating, a general dryer can be used, for example, a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, a cylinder dryer. A normal device such as can be used.
The coated and dried coated paper can be subjected to a smoothing process without performing a calendar process, or with a super calendar, a high-temperature soft nip calender, or the like.
Further, as a method for increasing the bulk of paper from the viewpoint of calendar processing, a method using soft calendar processing at a high temperature is known. The surface treatment by the high temperature soft nip calender is based on a mechanism in which the inner layer portion of the paper is kept in a relatively low temperature state and only the surface layer portion is plasticized by the high temperature and the surface of the metal roll is transferred to the surface layer portion of the paper. . Therefore, compared with the conventional super calender process, only the surface layer of the paper is densified to improve the glossiness of the blank paper, and the inner layer of the paper is not crushed without applying temperature. The bulkiness of can be maintained.

As a preferable method in the present invention, when calendering is not performed or when calendering is performed, in order to obtain a coated paper for printing having excellent printing quality and workability, good surface strength and low density, A soft nip calendering treatment is preferred.
As the calendering conditions, 1 to 2 nips are preferable, and 1 nip is more preferable. When the number of calendar nips exceeds 2 nips, the density of the coated paper increases, and it becomes difficult to produce a bulky coated paper, which is not preferable.
Although it does not restrict | limit especially as temperature conditions of the metal roll of a calender, 30-250 degreeC is preferable from the point of the density of the produced bulky coated paper. Further, the linear pressure of the calendar is preferably 1 to 50 kN / m, more preferably 2 to 30 kN / m. When the linear pressure is 50 kN / m or more, the density of the coated paper increases, and it becomes difficult to produce a bulky coated paper.

The basis weight of the coated paper for printing of the present invention is not particularly limited and is set according to various uses, but is preferably 25 to 200 g / m ² , more preferably 30 to 150 g / m ² . Yes, more preferably 30 to 70 g / m ² .
The density of the coated paper for printing of the present invention is preferably low density, and is preferably 0.70 g / cm ³ or less, more preferably 0.40 or less as a condition that the present invention is most effective. 0.60 g / cm ³ or less, still more preferably 0.40~0.55g / cm ³ or less.
The whiteness of the coated paper for printing of the present invention is preferably 70% or more, more preferably 75% or more.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, parts and% indicate parts by weight and% by weight.

(Evaluation method)
The coating liquid and the obtained coated paper for offset printing were tested based on the following evaluation method.
(1) Density: Measured based on JIS P 8118.
(2) Whiteness: Measured based on JIS P 8148.
(3) Printed surface texture: printed on a Roland flat-screen printing machine (4 colors) using a flat-printing ink (High Unity M manufactured by Toyo Ink) at a printing speed of 8000 sheets / min. The surface feeling (ink unevenness of ink) was visually evaluated according to the following criteria.
A: No unevenness is observed at all O: Almost unevenness is not observed Δ: Some unevenness is observed ×: Unevenness is observed (4) Smoothness: JAPAN Tappi No5 Measured with a Oken type smoothness tester.
(5) Surface strength: After printing using offset sheet-fed ink (Toyo Ink High Unity M) on a Roland offset sheet-fed press (two colors), visually check the surface of the indigo single-color solid part. evaluated. A: Very good, B: Good, B: Slightly inferior, X: Inferior

[Example 1]
<Manufacture of bulky hardwood TMP>
Manufacture of pulp by APMP (alkali hydrogen peroxide mechanical pulp) method.
2. After impregnating wood chips with DTPA (diethylenetriaminepentaacetic acid) to 0.2% per wood chip dry weight, sodium hydroxide 1.5%, hydrogen peroxide 2.0%, sodium silicate The chemical solution was added so that it would be 0%, magnesium sulfate 0.1%, and DTPA 0.2%, and the wood chips were divided and infiltrated during the chemical solution impregnation and immediately before the primary refining. After holding the chip at a temperature of 60 ° C. for 30 minutes, primary refining was performed using a laboratory normal pressure refiner (BR-300CB, manufactured by Kumagai Riki Kogyo Co., Ltd.). The obtained pulp was kept at about 60 ° C. for 30 minutes to allow the reaction of the remaining chemicals to proceed, and then the pulp concentration was diluted to 4%, the pH was adjusted to 4-8, and washing was performed. The washed pulp was again concentrated to a concentration of 20%, and subjected to secondary refining using a laboratory pressure refiner (BR-300CB, manufactured by Kumagaya Riki Kogyo Co., Ltd.). Moreover, the freeness after secondary refining was adjusted to 100 ml by Canadian Standard Freeness (CSF).

<Preparation of coated base paper>
The base paper for coating is 45 parts of the above bulky hardwood TMP, NBKP: 10 parts of softwood bleached chemical pulp (CSF 450 ml), 45 parts of bleached GP (CSF 70 ml), and a pulp slurry containing 1.6% sulfate band based on the pulp weight, Paper strength agent (EX-230, manufactured by Harima Chemicals Co., Ltd.) 0.2% is added, and Rosetta-type light calcium carbonate (average particle size: 4.0 μm) 10% is contained per weight of the base paper as an internal filler. The paper stock thus added was made at a speed of 800 m / min with a duoformer FD type paper machine, and a coated base paper having a density of 0.45 g / cm ³ and a basis weight of 62 g / m ² was used.

<Preparation of coating solution>
As a pigment slurry, 100 parts of fine heavy calcium carbonate slurry (FMT-90, manufactured by PMMA Tech) (solid content), 10 parts of styrene butadiene copolymer latex (glass transition temperature 20 ° C., gel content 85%), hydroxy After adding 30 parts of ethyl etherified starch (PG295 manufactured by Penford), water was further added to a solid content concentration of 30% to prepare a coating solution. After coating the above coating liquid on the base paper with a gate roll coater at a coating speed of 800 m / min so that the coating amount per side is 1.0 g / m ² , Dried to 5%. Then, using a two-roll one-stack high-temperature soft calender having an elastic roll with a shore hardness of 91 °, calendering one nip under the conditions of a metal roll surface temperature of 150 ° C. and a linear pressure of 4 kN / m, and coated paper for printing Got.

[Example 2]
Coating for printing in the same manner as in Example 1 except that the bulky hardwood TMP used in Example 1 was changed to 25 parts, 30 parts NBKP (CSF 450 ml), and 45 parts bleached GP (CSF 70 ml). Obtained paper.

[Example 3]
In the preparation of the coating liquid, a coated paper for printing was obtained in the same manner as in Example 1 except that the blending number of hydroxyethyl etherified starch (PG295 manufactured by Penford) was changed from 30 parts to 50 parts.

[Example 4]
In the preparation of the coating liquid, a coated paper for printing was obtained in the same manner as in Example 1 except that the blending number of hydroxyethyl etherified starch (PG295 manufactured by Penford) was changed from 30 parts to 60 parts.

[Example 5]
In the preparation of the coating liquid, the coated paper for printing was prepared in the same manner as in Example 1 except that the number of latex blended parts was changed from 10 parts to 15 parts, and the number of starch blended parts was changed from 30 parts to 20 parts. Obtained.

[Example 6]
In the preparation of the coating liquid, the coated paper for printing was prepared in the same manner as in Example 1 except that the blending part of latex was changed from 10 parts to no blending and the blending part of starch was changed from 30 parts to 50 parts. Obtained.

[Example 7]
In the preparation of the coating solution, printing was performed in the same manner as in Example 1 except that the type of starch used was changed from hydroxyethyl etherified starch (PG295 manufactured by Penford) to oxidized starch (Mermaid M210 manufactured by Shikishima Starch). Coated paper was obtained.

[Example 8]
A finely coated paper for printing was obtained in the same manner as in Example 1 except that the coating amount per side was adjusted to 1.0 to 2.0 g / m ² .

[Example 9]
A finely coated paper for printing was obtained in the same manner as in Example 3 except that the coating amount per side was adjusted to 1.0 to 2.0 g / m ² .

[Example 10]
A coated paper for printing was obtained in the same manner as in Example 1 except that the coating amount per side was adjusted to 1.0 to 4.0 g / m ² .

[Example 11]
In the preparation of the coating solution, 100 parts (solid content) of fine heavy calcium carbonate slurry (FMT-90 manufactured by PMMA TECH) was used as the pigment slurry, and fine clay (Hydra Gloss, manufactured by KaMin) was used as the pigment slurry. ) Was added as a dispersant (0.2 parts of inorganic pigment) and dispersed with a serie mixer to prepare a fine clay slurry with a solid content of 73%, and 50 parts of the resulting fine clay slurry ( In the same manner as in Example 1, except that 50 parts (solid content) of fine heavy calcium carbonate slurry (Fimatec FMT-90) was added to the solid content, and a pigment slurry was used. Obtained paper.

[Example 12]
In the preparation of the coating liquid, a pigment slurry was prepared by adding 30 parts (solid content) of fine heavy calcium carbonate slurry (FMT-90, manufactured by PMMA Tech) to 70 parts (solid content) of fine clay slurry. A coated paper for printing was obtained in the same manner as in Example 11 except for the above.

[Example 13]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1, except that the calendering linear pressure was changed from 4 kN / m to 12 kN / m.

[Example 14]
In the treatment after coating, printing was performed in the same manner as in Example 1 except that the calendar to be used was changed from a high temperature soft calendar to a super calender (2 rolls 1 stack, metal roll surface temperature 70 ° C., linear pressure 4 kN / m). A coating was obtained.

[Comparative Example 1]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1 except that the gate roll coater was changed to a blade coater as a method for applying the coating liquid.

[Comparative Example 2]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1 except that the bulky hardwood TMP blended with the base paper was not blended and 55 parts of NBKP was blended instead.

[Comparative Example 3]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1 except that the bulky hardwood TMP blended in the base paper was not blended and 55 parts of softwood TMP was blended instead.

[Comparative Example 4]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1 except that the prepared coating liquid was not applied on the base paper.

[Comparative Example 5]
In the preparation of the coating liquid, a coated paper for printing was obtained in the same manner as in Example 1 except that the blending number of hydroxyethyl etherified starch (PG295 manufactured by Penford) was changed from 30 parts to 5 parts.

[Comparative Example 6]
In Example 1, instead of coating the coating solution prepared on the base paper, oxidized starch (manufactured by Nippon Corn Starch, SK-20) was cooked to a solid content concentration of 20% and diluted with water. A coated paper for printing was obtained in the same manner as in Example 1 except that a size press solution having a solid content concentration of 10% was applied on both sides so that the coating amount on one side was 0.5 g / m ² .

[Comparative Example 7]
A coated paper for printing was obtained in the same manner as in Example 1 except that the coating amount per side was adjusted to 1.0 to 0.4 g / m ² .

[Comparative Example 8]
A coated paper for printing was obtained in the same manner as in Example 1 except that the coating amount per side was adjusted to 1.0 to 6.0 g / m ² .

As shown in Table 1, in Examples 1-10, the coated paper for printing which was bulky and high in whiteness, and excellent in printing surface feeling and surface strength was able to be obtained. Comparative Examples 2-3 and 8 are high in density and not bulky. Comparative Examples 1, 4, 6 and 7 are inferior in printing surface feeling. Further, Comparative Examples 1, 4, 5 and 7 were inferior in surface strength.
From the results of Example 1 and Comparative Example 1, it was found that when the coating liquid was applied by a blade coater that was not a roll coater, even if the coating amount was the same, the coating was applied to the base paper by the blade coater. The density of the coated paper increases.
According to the results of Example 1, Example 9, and Comparative Examples 2, 3 and 8, when the content of hardwood TMP is too low or the coating amount is too high, the density of the coated paper increases. From the viewpoint of increasing the whiteness, it is better for the pigment to increase the blending amount of calcium carbonate.
When the coating is not performed as in Comparative Example 4, the printing surface feeling and the surface strength are particularly deteriorated.
According to the result of Comparative Example 5, when the starch content is reduced, the surface strength tends to decrease. According to the result of Comparative Example 6, when the size press liquid containing only starch is applied instead of the coating liquid containing pigment, the printing surface feeling tends to be lowered. According to the result of Comparative Example 7, when the coating amount is too small, the printing surface feeling and the surface strength are deteriorated. Conversely, when the coating amount is too large as in Comparative Example 8, the density becomes too high.
As described above, the present invention employs a base paper having a specific density containing mechanical pulp obtained from a hardwood wood chip by a specific process, and applies a specific coating solution by a specific method. By making the coated paper for printing, the remarkable effect of being bulky and high in whiteness, excellent in printing surface feeling and surface strength is exhibited.

Claims (5)

A hardwood wood chip is blended with mechanical pulp produced by subjecting it to atmospheric pressure or pressure refining treatment at 80% by weight or more per weight of the base paper, and a base paper having a density of 0.7 g / cm ³ or less, a pigment, and Coating containing 30-60 parts by weight of starch as an adhesive per 100 parts by weight of pigment , further containing latex, and the content of starch is the same or higher than the content of latex A coated paper for printing, which is obtained by coating a liquid at a dry weight of 0.5 to 5 g / m ² using a film transfer method.   As the mechanical pulp, after impregnating hardwood wood chips with alkaline hydrogen peroxide solution, after performing normal pressure or pressure refining treatment, mechanical pulp manufactured by holding for a certain time at room temperature or under pressure with chemical solution The coated paper for printing according to claim 1, which is contained in a base paper. The ratio of content of starch and latex in the coating liquid is starch: latex = 1: 1 = 10: 1, and the printing coating according to claim 1 or 2, Craft paper. The coated paper for printing according to any one of claims 1 to 3, wherein the starch is hydroxyethyl etherified starch. The coating for printing according to any one of claims 1 to 4, wherein the coating is performed at a linear pressure of 1 to 50 kN / m in a high temperature soft nip calender after coating by a film transfer method. paper.