JP4976878B2 - Coated paper for printing and method for producing the same - Google Patents

Description

The present invention relates to a coated paper for printing and a method for producing the same. More specifically, a coated paper for printing having a low basis weight of 32 to 45 g / m ² and having excellent glossiness, opacity and rigidity, and excellent printability and bookbinding workability, and such The present invention relates to a method capable of easily producing a coated paper for printing having excellent characteristics at low cost.

Conventionally, so-called non-coated paper such as high-quality paper and medium-quality paper having a basis weight exceeding 60 g / m ² has been used for magazines, direct mail, catalogs, manuals, and the like. In recent years, however, in these applications as well, with the trend toward visualization, colorization, and higher-grade prints, printing layers in which coating layers (coating layers) are formed on both sides of high-definition and excellent opacity The use of coated paper has progressed and is now occupying the mainstream.

  In recent years, in addition to environmental issues and resource savings, the flow of postage has been reduced due to the increase in postage due to the increase in the number of pages in magazines and direct mail. Weight reduction is progressing.

However, in general, lighter paper has a direct effect on the decrease in opacity and stiffness, and in order to ensure the quality that can meet the demand for visualization, colorization, and high-grade printing, which has been demanded in recent years. There is no choice but to sacrifice omission and deterioration of bookbinding workability. In particular, in a light-weight coated paper having a basis weight of less than 45 g / m ² , the tendency appears remarkably and an immediate improvement is required.

  Examples of conventional methods for improving the stiffness that decreases with the weight reduction of the paper and improving the printing and bookbinding workability include, for example, a method of reducing the coating amount of the coating agent, and reducing the ash content of the base paper. There are generally known methods, such as a method of reducing the calender nip pressure and improving the paper thickness to improve the rigidity.

  However, the reduction in coating amount, reduction in base paper ash content, and reduction in calender nip pressure are all lightweight coated paper for glossy, opacity, surface properties such as paper surface smoothness and flatness. As a result, the required quality is not satisfied.

  In particular, to improve the glossiness, it is most effective to increase the coating amount of the coating agent for forming the coating layer, and when using a coating agent mainly composed of clay as in the past, it is constant. The coating layer must be formed with a coating amount greater than the amount. Therefore, in order to keep the basis weight of the final coated paper constant, the basis weight of the base paper is inevitably lowered, and the pulp fibers in the coated paper are reduced, so that the stiffness of the coated paper is reduced. This results in a decrease in printing and bookbinding workability.

  Therefore, as a means for solving the above-described problem of stiffness reduction, for example, as a paper coating agent, a water-soluble resin mixture obtained by mixing an epoxy resin and a polyamine compound is used to improve the paper stiffness. A method has been proposed (see Patent Document 1). However, it is difficult to use an epoxy resin as a coating agent in this way as a general technique, and it is difficult to use it in actual production.

In addition, light-weight printing coated paper having a basis weight of less than 45 g / m ² is particularly problematic in that the opacity is greatly reduced, and the appearance looks worse due to print-through. In order to improve the opacity, for example, it has been tried to use titanium dioxide having excellent opacity in the base paper, but in addition to being expensive, the yield in paper is also high. However, it is not economical in terms of both cost and operation.

  Therefore, as a method of improving opacity without using titanium dioxide, for example, a method of adding bacterial cellulose to fibrous pulp (see Patent Document 2), or a method of internally adding a fibrous magnesium compound to pulp (patent) Document 3) has been proposed. However, since these bacterial cellulose and fibrous magnesium are special substances that are not generally marketed, they cannot be obtained at low cost and are not economical and difficult to use in actual production. It is.

  On the other hand, from the economical aspect, a measure for improving the opacity by using calcium carbonate, which can be obtained at low cost, as an internal filler has been studied. However, in order to ensure the desired opacity, it is necessary to considerably increase the ash content to the base paper, and the pulp fiber content decreases as the ash content increases. If it does so, the rigidity of the coated paper obtained will fall, and it will cause the deterioration of printing and bookbinding workability | operativity, and it does not come to solve the above problems.

As described above, the basis weight is below 45 g / m ^2, in particular basis weight in lightweight 32~45g / m ^2, glossiness, excellent opacity and stiffness, and fully satisfy the printability and binding workability The printing coated paper which can be performed is not yet obtained, and development of the printing coated paper which provided such a characteristic, and the method which can manufacture such a printing coated paper easily at low cost is awaited. ing.
JP 2004-300353 A JP 11-61678 A JP-A-9-209297

The present invention has been made in view of the background art described above, and has a basis weight of 32 to 45 g / m ² and is lightweight, while being excellent in glossiness, opacity and rigidity, and in printability and bookbinding workability. Another object of the present invention is to provide a method for easily producing a coated paper for printing and a coated paper for printing having such excellent characteristics at low cost.

The present invention
(1) Coating for printing having a basis weight of 32 to 45 g / m ^{2 based} on JIS P 8124, wherein a coating layer is formed on at least one side of a base paper with a coating agent containing a pigment and an adhesive. Paper,
In the pulp constituting the base paper, 10 to 40% by mass of mechanical pulp is contained according to JIS P 8120,
As the pigment, an organic pigment, clay and calcium carbonate are contained in the coating agent,
In all pigments, the proportion of the organic pigment is 5 to 25 mass%, the proportion of the clay is 25 to 55 mass%, the proportion of the calcium carbonate is 30 to 55 mass%,
The present invention relates to a coated paper for printing, characterized in that the solid content of the coating agent forming the coating layer is 2.0 to 5.0 g / m ² per one side of the base paper.

The present invention also provides
(2) A printing coating having a basis weight of 32 to 45 g / m ² according to JIS P 8124, in which a coating layer is formed on at least one side of a base paper with a coating agent containing a pigment and an adhesive. A method for producing paper,
The base paper is composed of pulp containing 10 to 40% by mass of mechanical pulp in accordance with JIS P 8120,
As the pigment, a coating agent containing 5 to 25% by mass of organic pigment , 25 to 55% by mass of clay and 30 to 55% by mass of calcium carbonate in the total pigment , the solid content adhesion amount of the base paper as the per side 2.0~5.0g / m ^2, a coating layer was formed by coating on at least one surface of a base paper,
2. The printing coating according to claim 1, wherein the surface of the coating layer is flattened by a flattening treatment facility comprising a combination of an elastic roll and a metal roll having at least one nip. The present invention relates to a paper manufacturing method.

The coated paper for printing of the present invention is excellent in glossiness, opacity and rigidity, and in printability and bookbinding workability, while having a basis weight of 32 to 45 g / m ² and being lightweight. . Moreover, the coated paper for printing which has such an outstanding characteristic can be easily manufactured at low cost by the manufacturing method of this invention.

(Embodiment)
The coated paper for printing of the present invention has a coating layer formed of a coating agent containing a pigment and an adhesive on at least one side of the base paper. In the pulp constituting the base paper, mechanical pulp is According to JIS P 8120, 10 to 40% by mass is contained, and as a pigment, an organic pigment, clay and calcium carbonate are contained in the coating agent, and the solid content adhesion amount of the coating agent forming the coating layer is It is 2.0 to 5.0 g / m ² per one side of the base paper, and the basis weight based on JIS P 8124 is 32 to 45 g / m ² .

  First, the base paper used in the present invention will be described. As described above, a specific amount of mechanical pulp is used for the pulp constituting the base paper. Thus, the use of a specific amount of mechanical pulp is one of the major features of the present invention, and this can improve the opacity of the coated paper for printing.

  Examples of the mechanical pulp include Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP) and the like can be mentioned, and one or more of them can be appropriately selected and used.

  Among the mechanical pulps, thermomechanical pulp (TMP) and chemithermomechanical pulp (CTMP) are pulped after softening the chip fiber at high temperature, so that the fiber length is relatively long, high strength and bulky raw material This is preferable in that a pulp can be obtained.

  In the present invention, in terms of sufficiently improving the opacity of the coated paper for printing, in the pulp constituting the base paper, the mechanical pulp conforms to the “Fiber composition test method” described in JIS P 8120. When measured, it is contained in an amount of 10% by mass or more, preferably 15% by mass or more, and 40% by mass or less, preferably 35% by mass or less, from the viewpoint of ensuring the paper quality strength and the flatness of the paper surface.

  As the pulp constituting the base paper, in addition to the mechanical pulp, for example, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP) Chemical pulp such as softwood unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), softwood half-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp, etc .; tea waste paper, craft envelope waste paper, magazine waste paper, Waste newspaper, flyer waste, office waste paper, corrugated waste paper, Kami white waste paper, Kent waste paper, imitation waste paper, waste paper waste paper, disaggregation waste paper pulp, disaggregation / deinking waste paper pulp, disaggregation / deinking / bleaching waste paper pulp Waste paper pulp; such as pulp chemically or mechanically produced from non-wood fibers such as kenaf, hemp and straw Various known pulp and the like, one or more from among these suitably selected, can be used to adjust the mixing ratio.

  In consideration of the fact that the balance of the formation, printability and rigidity of the base paper is further improved, the kraft pulp is measured in accordance with JIS P 8120 in the pulp constituting the base paper. 90% by mass is preferably contained.

  The method for producing the base paper used in the present invention is not particularly limited. For example, nonionic surfactants, bulking agents such as ester compounds of polyhydric alcohols and fatty acids, organosiloxanes, glyceryl ethers, ammonium salts; kaolin, carbonic acid Fillers such as calcium, talc, titanium dioxide, urea formaldehyde resin; sizing agent such as rosin emulsion; paper strength enhancer such as starch, modified starch, vegetable gum, carboxymethyl cellulose, polyacrylamide; yield improver; freeness improver; After adding a normal paper making agent such as an ultraviolet ray inhibitor to the pulp as necessary, adjust the conditions such as pH as appropriate, and adopt a method of making paper in a normal paper making process using a paper machine or the like. Can do.

  The paper machine is preferably a gap former having a double-side dewatering mechanism, a hybrid former, an on-top former, etc., but is not limited to these, and any type of acidic papermaking and neutral papermaking Can also be used. Further, the press machine may be any of a straight-through type, an invar type, and a reverse type, and a combination thereof can also be used. Examples of the combined body include those used in general paper machines such as a twin bar + 3P type, a trinip + 4P type, a tiger event + 4P type, and a binip press. As the dehydration method, a conventional method such as a suction roll method or a grooved press method can be used. The material of the roll is preferably ceramic, but is not particularly limited, and a shoe press can be used.

In particular, in the present invention, the base paper is preferably made with a twin-wire paper machine made of an on-top former. Although the ontop former has a twin wire type wet paper web forming part similar to a gap former having a double-side dewatering mechanism, it has a long net part in part, so it has excellent formation forming ability and the present invention. Improvement of glossiness, opacity, stiffness, printability and bookbinding workability, which are the problems when forming a base paper for printing paper with a basis weight of 32 to 45 g / m ^{2 that} is extremely lightweight Can contribute the most.

The basis weight and ash content of the base paper thus obtained are not particularly limited, but the basis weight of the intended printing coated paper is 32 to 45 g / m ² , rigidity, printability and bookbinding workability. From the viewpoint that the paper is further improved, the basis weight of the base paper is preferably about 27 to 43 g / m ² and the ash content is preferably about 5% or less.

  Next, a coating agent for forming a coating layer on at least one side of the base paper will be described. The coating agent used in the present invention contains a pigment and an adhesive.

  The coating layer formed with the coating agent contains an organic pigment, clay and calcium carbonate as pigments, and is preferably adjusted in advance so that the SEM average particle diameter is 0.4 to 3.0 μm. And organic pigments, clays and pigments made of calcium carbonate.

  The SEM average particle size referred to in the present invention is the maximum of 12 pigments randomly selected from photographic images obtained by taking a photo of the coating layer surface at 25 locations and 7500 times with a scanning electron microscope. The longest diameter and the shortest diameter were individually measured, and the pigment particle diameter actual measurement values of a total of 500 points were calculated by averaging 20 points excluding the pigment having the maximum value and the pigment having the minimum value.

  In general, the average particle diameter of the pigment can be calculated from the average particle diameter of the individual pigments before preparing the coating agent. However, the lightweight coated paper for printing according to the present invention has a low base paper density due to the heavy use of mechanical pulp, and the amount of coating of the coating agent is smaller than that of conventional coated paper. Therefore, in the formation of the coating layer, for example, a relatively excessive pigment is positioned between the pulp fibers constituting the base paper so as to fill the gap, and the fine and easy-to-flow pigment has a gap between the excessive pigment and the fiber. Subsidence and behavior of the pigment in the coating layer change, such as filling. Therefore, in the coated paper for printing of the present invention, when the macro pigment on the surface of the coated layer is adjusted, that is, when the SEM average particle diameter is adjusted within the above range, for example, It is possible to determine the effect of the coated paper very effectively.

  Examples of organic pigments include styrene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins, melamine resins, and the like, and one or more of these can be appropriately selected and used. .

  In the present invention, the organic pigment can be a hollow organic pigment or a dense organic pigment, but has excellent dispersibility in the coating agent and has a dispersibility when forming a coating layer. Hollow organic pigments are particularly preferred because of their high cost.

  The organic pigment preferably has a SEM average particle size of 0.2 to 5.0 μm, more preferably 0.5 to 5.0 μm. When the SEM average particle diameter of the organic pigment deviates from this range, it is difficult to give desired blank paper glossiness and coverage to the coated paper for printing, and troubles such as printing unevenness may occur. Further, when the SEM average particle diameter of the organic pigment is less than 0.2 μm, the surface strength is lowered, and there is a possibility that the blending ratio of the adhesive in the coating agent must be increased. On the other hand, when the SEM average particle diameter of the organic pigment exceeds 5.0 μm, the glossiness of the white paper of the coated paper for printing may be lowered.

The proportion of the organic pigment in the total pigment is 5 to 25 wt%, Ru preferably 15 to 20% by mass. If the ratio of the organic pigment in the total pigment is less than 5% by mass, sufficient improvement in the glossiness of the white paper of the coated paper for printing cannot be expected. Conversely, if it exceeds 25% by mass, it is disadvantageous in terms of production cost. ing to.

  Examples of the clay include kaolin clay and delaminated clay. In the present invention, among clays, it is preferable to use engineered clay having a particle size of 2 μm or less and an aspect ratio of 8 to 14, and such engineered clay is preferably 90 to 100% by mass of the total amount of clay. .

  Furthermore, as an engineered clay, what has the said particle size distribution and whose SEM average particle diameter is 0.5-2.0 micrometers, Furthermore, 1.0-2.0 micrometers is used more preferably. When the SEM average particle diameter of the engineered clay deviates from this range, it tends to be difficult to give desired blank paper glossiness and covering property to the coated paper for printing.

The proportion of clay in the total pigment, 25 to 55 wt%, Ru preferably 35 to 40% by mass. When the ratio of the clay in the total pigment is less than 25 wt%, it is necessary to increase the amount of calcium carbonate to be described later, the fluidity of the coating agent is lowered, it is difficult to obtain the desired viscosity and conversely exceeds 55 wt%, too increase the viscosity of the coating agent, streaks during coating occurs, it decreases workability.

  Examples of the calcium carbonate include light calcium carbonate and heavy calcium carbonate. As such calcium carbonate, those having an SEM average particle size of 0.5 to 2.0 μm, more preferably 1.0 to 2.0 μm are preferable. When the SEM average particle diameter of calcium carbonate is less than 0.5 μm, it is difficult to obtain sufficient surface strength, and satisfactory workability may not be obtained during printing. On the contrary, when the SEM average particle diameter of calcium carbonate exceeds 2.0 μm, it is difficult to obtain satisfactory opacity during printing, and there may be a problem that the printed matter is broken through.

The proportion of calcium carbonate in the total pigment, 30 to 55 wt%, Ru preferably 40 to 50% by mass. If the proportion of calcium carbonate in the total pigment is less than 30 wt%, not obtained satisfactory opacity and conversely exceeds 55 wt%, satisfactory gloss not be obtained.

  In the present invention, the organic pigment, clay and calcium carbonate are contained in the pigment, and the total amount thereof is preferably adjusted so as to be, for example, 90% by mass or more in the total pigment.

  In the present invention, as the pigment, in addition to the organic pigment, clay and calcium carbonate, for example, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth. Soil, calcium silicate, magnesium silicate, synthetic amorphous silica (white carbon), colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, porous 1 or 2 types or more are appropriately selected from pigments generally blended in coating agents, such as porous synthetic amorphous silica, porous magnesium carbonate, and porous alumina. Can be used.

  The pigment contained in the coating layer contains organic pigment, clay and calcium carbonate, and other general pigments as required. The SEM average particle diameter is 0.4 to 3.0 μm, preferably 0.6 to 2.6 μm, and more preferably 0.7 to 2.4 μm. It is desirable to have been adjusted in advance. When the SEM average particle diameter of the pigment contained in the coating layer is less than 0.4 μm, it is difficult to obtain the covering property on the surface of the base paper. Conversely, when it exceeds 3.0 μm, the surface property may be deteriorated.

  Next, the adhesive compounded in the coating agent together with the pigment will be described.

  Examples of the adhesive include starches such as oxidized starch, positive starch, esterified starch, and dextrin; synthetic resin adhesives such as PVA; proteins such as casein, soy protein, and synthetic protein; styrene-butadiene copolymer Conjugated diene copolymer latex such as acrylate, acrylic copolymer latex such as acrylate polymer or copolymer, vinyl polymer latex such as ethylene-vinyl acetate polymer, carboxylate these various polymer latexes Used in ordinary coated paper fields, such as latexes such as polymer-soluble latexes that are alkali-soluble, alkali-swellable or alkali-insoluble, modified with functional group-containing monomers such as groups, such as water-soluble adhesives Various adhesives such as these are exemplified, and one or more of them can be appropriately selected and used. Among these, it is preferable to use starches and latexes in combination from the viewpoint that the effect as an adhesive is more fully expressed.

  The blending ratio of the pigment and the adhesive in the coating agent is set to 100 parts by mass of the pigment in terms of a solid content ratio so that the effect of improving the properties of the target coated paper for printing is fully expressed. On the other hand, it is preferable to adjust so that an adhesive agent may be 50 mass parts or less, Furthermore, 45 mass parts or less. Further, in order to prevent the amount of the adhesive from being too small and the adhesion of the coating agent to the base paper from becoming insufficient, the solid content ratio is 2 parts by mass or more of the adhesive with respect to 100 parts by mass of the pigment. Furthermore, it is preferable to adjust so that it may become 5 mass parts or more.

  In addition to the pigments and adhesives, the coating agent used in the present invention may be various types such as a water resistance agent, a curing agent, an antifoaming agent, a colorant, a flow modifier, a lubricant, etc., if necessary. An auxiliary agent can be appropriately blended within a range that does not impair the object of the present invention.

  There is no particular limitation on the method for preparing the coating agent, and the pigment, adhesive, and various auxiliary agents, if necessary, and the mixing ratio are appropriately adjusted so that the composition is uniform at an appropriate temperature. What is necessary is just to stir and mix.

  The solid content concentration of the coating agent is preferably in the range of 40 to 60 mass%, more preferably 45 to 50 mass%. When the solid content concentration is too high, the viscosity becomes too high, the occurrence of a peeling pattern or the like increases, and the operability may be lowered. On the other hand, if the solid content concentration is too low, the coating agent may soak into the base paper, and surface properties after coating, surface coverage, and uneven gloss may be reduced.

  The viscosity of the coating agent is preferably in the range of 0.20 to 0.40 Pa · s, more preferably 0.22 to 0.38 Pa · s. If the viscosity exceeds 0.40 Pa / s and is too high, coating unevenness may occur during coating, and surface properties may be deteriorated. On the other hand, if the viscosity is less than 0.20 Pa · s and too low, the desired coating amount may not be obtained.

  The coating agent is applied to at least one side of the base paper, preferably both sides, and dried to form a coating layer. For coating and drying of such a coating agent, a coating apparatus and a drying method used for producing a general coated paper can be appropriately used.

  Examples of the coating apparatus include double-sided coating such as blade coaters, air knife coaters, roll coaters, reverse roll coaters, bar coaters, curtain coaters, die slot coaters, gravure coaters, champlex coaters, size press coaters, and bill blade coaters. An on-machine or off-machine coater provided with a device can be mentioned.

In particular, in the present invention, a film transfer system such as a gate roll coater or a rod metering size press coater is suitably used as a coating apparatus for coating the coating agent. The reason why such a film transfer type coating apparatus is preferable is as follows. The coating agent containing clay has a tendency that the viscosity as a so-called dilatant fluid increases markedly with an increase in shearing force acting on the coating agent during coating, and the coating suitability tends to deteriorate. However, in a film transfer type coating apparatus, a high shear force unlike a blade coater generally used at the time of coating does not act. Further, in the case of a blade coater, since the shearing force increases as the coating amount decreases, the coating agent is applied at a coating amount as small as 2.0 to 5.0 g / m ² as in the present invention. The film transfer method is more suitable.

For coating of the coating agent on at least one side of the base paper, the solid content adhesion amount of the coating agent is 2.0 to 5.0 g / m ² , preferably 2.5 to 4.0 g per side of the base paper. / M ² is performed. When the solid content of the coating agent on one side of the base paper is less than 2.0 g / m ² , the solid content concentration of the coating agent must be greatly reduced in consideration of the limitations of a normal coating apparatus. As a result, the coverage with respect to the base paper is poor, and the blank glossiness of the target coated paper for printing is lowered. On the other hand, when the solid content adhesion amount of the coating agent per one side of the base paper exceeds 5.0 g / m ² , it is necessary to increase the solid content concentration of the coating agent, and a predetermined value such as 32 to 45 g / m ² is required. When a coated paper for printing having a basis weight of is obtained, its rigidity is low, and printing and bookbinding workability deteriorates.

  The coating speed of the coating agent is not particularly limited as long as a desired coating layer is formed, and may be about the paper making speed when manufacturing a normal coated paper.

  Further, the wet coating layer formed on the base paper as described above is conventionally known, for example, hot air heating, gas heater heating, high frequency heating, electric heater heating, infrared heater heating, laser heating, electron beam heating. Various heating drying methods such as the above may be adopted as appropriate.

After the coating layer is formed on at least one side of the base paper, the surface of the coating layer is subjected to a flattening treatment in order to give the target printing coated paper high glossiness, smoothness, and printability. The

Wherein when the flattening processing, Oh Mari pressurized without strongly pressure conditions large flattening effect, sheet gloss and smoothness of the coated paper for printing, a can be further improved printability, low even without having first nip, have use a flattening treatment facility comprising a combination of an elastic roll and a metal roll, it is suitably used soft calender or supercalender, a multi-stage soft calender or a multi-stage supercalender in particular consisting of two or more stages Can do.

  Furthermore, in the present invention, from the viewpoint of further improving the covering property to the base paper and also improving the ink setting property of the coating layer, before forming the coating layer, a water-soluble polymer compound as a main component. It is preferable to apply an undercoat agent to the surface of the base paper to form an undercoat layer.

  Examples of water-soluble polymer compounds that can be suitably used for the undercoat agent include starches, polyvinyl alcohol (hereinafter referred to as PVA), and the like, and these may be used alone or in combination. it can.

  In the present invention, it is more preferable to use esterified starch among the starches. Esterified starch is particularly excellent in the covering property on the surface of the base paper, and can greatly improve uneven penetration of the coating agent into the base paper.

  As a raw material starch for esterification when obtaining the esterified starch, for example, various starch-containing materials are used in addition to untreated starch and treated starch. Examples of the raw material starch include wheat starch, potato starch, corn starch, sweet potato starch, tapioca starch, sago starch, rice starch, waxy corn starch, high amylose content corn starch and the like; wheat flour, tapioca starch, corn flour And starch-containing materials such as rice flour; those obtained by oxidizing and acid-treating these starches and starch-containing materials. Among these, esterified starch made from tapioca starch is preferable because it is superior to those made from other cereal starches in terms of viscosity, coatability, elasticity, and extensibility.

  In the esterified starch, the degree of esterification is not particularly limited, but the average number of ester bonds introduced is preferably 1 to 3, and more preferably 1 to 2 per glucose unit. Of the esterified starches, hydroxyesterified starch is preferred. Such hydroxyesterified starch can be obtained easily and inexpensively by subjecting the raw material starch to an oxidation treatment and reducing the carboxymethyl group to a hydroxyethyl group.

  In particular, a hydrophobic group-containing ester-modified tapioca starch in which a hydrophobic group is introduced into the terminal group of the ester-modified starch can be suitably used.

  Furthermore, in the present invention, the terminal group has a carboxylic acid (—COOH) structure, and in a neutral region, ionization like —COO— cannot secure a bond due to a hydrogen bond and exhibits resilience. The esterified starch exhibiting thixotropic properties is preferable from the viewpoint that it exhibits fluidity during coating, hardly penetrates into the base paper after coating on the base paper surface, and exhibits high coating properties on the base paper surface. Moreover, the esterified starch which exhibits such thixotropic properties can further enhance the affinity between the base paper and the coating layer by using it together with a binder resin having a high coating property such as PVA.

  As the esterified starch exhibiting thixotropic properties as described above, 1-octenyl succinic esterified starch obtained by using tapioca starch as a main raw material and ester-modifying it is particularly preferable. 1-Octenyl succinate esterified starch is particularly excellent in terms of viscosity, film elasticity, and coating properties. For example, in combination with PVA, in addition to improving printing operability and imparting more remarkable coating properties, Thus, it is possible to improve ink density and ink setting when printing is performed on the coated paper for printing.

  The undercoat agent used in the present invention is mainly composed of the water-soluble polymer compound, for example. In addition to the water-soluble polymer compound, if necessary, for example, a water-resistant agent, a curing agent. Various auxiliary agents such as an antifoaming agent, a colorant, a flow modifier, and a lubricant can be appropriately blended within a range not impairing the object of the present invention.

  There is no particular limitation on the method for preparing the undercoat agent. For example, the water-soluble polymer compound and various kinds of auxiliary agents, if necessary, and the mixing ratio are appropriately adjusted so that a uniform composition can be obtained at an appropriate temperature. And stirring and mixing.

  The undercoat agent is applied to the surface of the base paper and dried to form an undercoat layer. For coating and drying of such an undercoat agent, a coating apparatus and a drying method used for producing a general coated paper can be appropriately used.

  In the present invention, a coating layer is formed on at least one side of the base paper, and an undercoat layer is formed between the base paper and the coating layer as necessary. When provided simultaneously, it may be two layers or three or more layers, and may be appropriately determined according to the purpose of use of the resulting coated paper for printing. In the case where three or more layers are formed on the surface of the base paper, in consideration of the white paper glossiness and printability of the resulting coated paper for printing, there are 2 layers between the outermost coating layer and the base paper. It is preferable that an undercoat layer equal to or more than one layer is formed.

The coated paper for printing thus obtained has a basis weight measured in accordance with the “basis weight measurement method” described in JIS P 8124 of 32 g / m ² or more, preferably 33 g / m ² or more, and 45 g / m ² or less, preferably 44 g / m ² or less. If the basis weight is less than 32 g / m ² , the paper strength and opacity are insufficient, and it is inappropriate as a coated paper for printing. On the other hand, if the basis weight exceeds 45 g / m ² , it is not the intended lightweight coated paper for printing, and the required weight reduction of the printed matter cannot be achieved.

The longitudinal stiffness of the coated paper for printing is obtained from “Paper Clark stiffness tester” described in JIS P 8143 from the viewpoint of obtaining sufficient rigidity as the coated paper and improving printing and bookbinding workability. and measured according to stiffness test method ", 10.0 cm ^3/100 or more, preferably further is 10.1 cm ^3/100 or more and reduces the suppleness, to ensure stiffness does not occur the Clark stiffness of such vertical direction, 13cm ^3/100 or less, and further preferably not 12.5 cm ^3/100 or less.

  In order to prevent the appearance of printed matter using such coated paper from being deteriorated too much, the 75 ° white paper gloss of the coated paper for printing is described in “75 ° specular gloss of paper and paperboard” described in JIS P 8142. It is preferably 20% or more, more preferably 21% or more as measured in accordance with the “test method”, and it is difficult to form a disparity with respect to the printed part and to eliminate the possibility that the printed image becomes inconspicuous. The white paper glossiness is preferably 40% or less, more preferably 39% or less. In addition, in order to make the 75 degree blank paper glossiness of the coated paper for printing 20% or more, for example, a method of treating the surface of the coating layer with a multi-stage super calender, or the surface temperature of the roll is 100 to 250 ° C., A method of processing with a soft calendar with heating may be adopted.

The paper density of the coated paper for printing is reduced in flexibility. For example, in order to eliminate the possibility that cracking is likely to occur due to folding in the bookbinding process, the “paper and paperboard—thickness and density as measured in accordance with the test method ", 0.95 g / cm ³ or less, preferably further is 0.94 g / cm ³ or less, also the inter-fiber strength is lowered, the printing process and bookbinding process, printing In order to eliminate the possibility that the coated paper is peeled off, the paper density is preferably 0.90 g / cm ³ or more, more preferably 0.92 g / cm ³ or more.

  The opacity of the coated paper for printing is described in JIS P 8149 as “Paper and paperboard—Opacity test method (paper backing) -Diffusion”. It is preferably 74% or more as measured according to the “illumination method”.

  The paper thickness of the printing coated paper is not particularly limited as long as it is about the same as that of a normal lightweight printing coated paper. However, in consideration of bookbinding workability, hand feeling, and the like, it is described in “JIS P 8118”. It is preferably about 30 to 42 μm as measured according to “Paper and paperboard—Test method for thickness and density”.

The coated paper for printing of the present invention specifies a coating agent containing three types of pigments, such as organic pigment, clay and calcium carbonate, and an adhesive on a base paper made from pulp containing a specific proportion of mechanical pulp. Coating is performed so that the amount of adhesion is within a range, and a coating layer is formed. Accordingly, the coated paper for printing of the present invention is lightweight with a basis weight of 32 to 45 g / m ² , and is excellent in glossiness, opacity and rigidity, and in printability and bookbinding workability. And the coated paper for printing provided with such the outstanding characteristic can be easily manufactured at low cost by the manufacturing method of this invention.

  Next, although the coated paper for printing of this invention and its manufacturing method are demonstrated further in detail based on an Example, this invention is not limited only to these Examples.

Production Examples 1 to 16 and Comparative Examples 1 to 5 (Preparation of base paper)
Mechanical pulp (TMP) and kraft pulp (NBKP, LBKP) were blended at a ratio shown in Table 1 to prepare a pulp slurry. To this pulp slurry, 10 parts by mass of rosin emulsion (product number: SPN-773, manufactured by Arakawa Chemical Industries, Ltd.) is added to 100 parts by mass of pulp solids, and a twin wire paper machine consisting of an on-top former is used. Papermaking was performed to obtain base papers 1 to 16 and comparative base papers 1 to 5 having a base paper basis weight of 27 to 43 g / m ² and an ash content of about 5%.

  In addition, the ratio of the pulp was determined based on the method described in JIS P 8120.

Preparation Examples 1-16 and Comparative Preparation Examples 1-5 (Preparation of coating agent)
The pigments and adhesives shown in Table 2 are stirred and mixed at room temperature until a uniform composition is obtained, diluted with purified water, and coating agents 1 to 16 having a solid content concentration and viscosity shown in Table 3 and a comparative coating are prepared. Preparation agents 1 to 5 were prepared. In Table 2, the SEM average particle diameter of the pigment is also shown. The amount of adhesive in Table 2 is a solid content ratio (parts by mass) with respect to 100 parts by mass of the pigment.

The pigments and adhesives in Table 2 are as follows.
(1) Pigment organic pigment Hollow organic pigment (SEM average particle size: see Table 2)
Clay Engineered clay (SEM average particle size: see Table 2,
Aspect ratio: 12)
Calcium carbonate Heavy calcium carbonate (SEM average particle size: see Table 2)
(2) Adhesive starch Oxidized starch latex Styrene-butadiene copolymer latex

Examples 1 to 16 and Comparative Examples 1 to 5 (Preparation of coated paper for printing)
As shown in Table 3, coated paper for printing was prepared by appropriately combining base papers 1 to 16 and comparative base papers 1 to 5, coating agents 1 to 16 and comparative coating agents 1 to 5.

  Using a gate roll coater as the coating device, adjust the coating speed as appropriate, and apply the coating on both sides of the base paper so that the solid content of the coating agent on one side of the base paper is the amount shown in Table 3. The agent was applied and dried. This was subjected to a flattening process under the conditions of at least 1 nip, 90 ° C. and 170 kg / cm with a super calender (11 stages) in which an elastic roll and a metal roll were combined, and a thickness of about 1.0 to 5.0 μm. The coated layer was formed to obtain a coated paper for printing.

  With respect to the obtained coated paper for printing, the basis weight, the stiffness of the Clark in the vertical direction, the 75 ° white paper gloss, the paper density, the opacity and the paper thickness were measured by the following methods. These results are shown in Table 4.

(A) Basis weight It measured based on the method of JISP8124.

(B) Longitudinal Clark stiffness Measured according to the method described in JIS P 8143.

(C) 75 degree white paper glossiness It measured based on the method of JISP8142.

(D) Paper density It measured based on the method of JISP8118.

(E) Opacity Measured according to the method described in JIS P 8149.

(F) Paper thickness It measured based on the method of JISP8118.

  Next, each characteristic was investigated about the coated paper for printing of Examples 1-16 and Comparative Examples 1-5 based on the following test examples 1-2. The results are shown in Table 5.

Test example 1 (printability)
Using an RI printing aptitude evaluation machine (manufactured by Meisei Seisakusho Co., Ltd.), 0.5 mL of indigo ink (product number: TRANS-G, manufactured by Dainippon Ink & Chemicals, Inc.) is developed and printed on printing paper. did. The printed matter was visually observed for unevenness of ink and ink transfer failure, and evaluated based on the following evaluation criteria.
(Evaluation criteria)
(Double-circle): Neither uneven-thickness nor poor ink transfer was confirmed.
◯: Only a slight unevenness of ink deposition and poor ink transfer were confirmed.
Δ: Ink unevenness and poor ink transfer were confirmed.
X: There were many unevenness of unevenness and poor ink transfer.

Test example 2 (bookbinding workability)
With an automatic bookbinding machine (model number: AF220C, manufactured by Duplo), the edges were bound and separated. The occurrence of fluff and paper dust on the cut surface was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: Generation of fluff and paper dust was not recognized, and automatic bookbinding workability such as adhesion was excellent.
○: Some fluff was slightly seen, but the automatic bookbinding operation could be carried out without any problems.
(Triangle | delta): Fluff and paper dust generate | occur | produced and the automatic bookbinding work environment fell.
X: Not only fluff and paper dust were generated, but also throat lines (wrinkles generated in the vicinity of the signature) occurred in the back glue part.

As shown in Table 4 and Table 5, the coated papers for printing in Examples 1 to 16 were blank paper glossiness, opacity and clerk even though the basis weight was as light as 32 to 45 g / m ^2. The stiffness is a value in an appropriate range, and is excellent in all of glossiness, opacity and stiffness. And the coated paper for printing of Examples 1-16 is excellent also in printability and bookbinding workability | operativity simultaneously.

  On the other hand, in the coated paper for printing of Comparative Examples 1 to 5, the amount of mechanical pulp constituting the base paper is inappropriate (Comparative Example 1), or the amount of the coating agent attached to the base paper is inadequate. Since it is appropriate (Comparative Examples 2 to 5), it is not compatible with light weight and excellent glossiness, opacity and rigidity, and inferior in printability and bookbinding workability. It is.

  The coated paper for printing of the present invention can be suitably used for, for example, offset printing, gravure printing and the like. Moreover, such a coated paper for printing can be easily manufactured at low cost by the manufacturing method of the present invention.

Claims (4)

A coated paper for printing having a basis weight of 32 to 45 g / m ² according to JIS P 8124, in which a coating layer is formed with a coating agent containing a pigment and an adhesive on at least one side of a base paper. And
In the pulp constituting the base paper, 10 to 40% by mass of mechanical pulp is contained according to JIS P 8120,
As the pigment, an organic pigment, clay and calcium carbonate are contained in the coating agent,
In all pigments, the proportion of the organic pigment is 5 to 25 mass%, the proportion of the clay is 25 to 55 mass%, the proportion of the calcium carbonate is 30 to 55 mass%,
The coated paper for printing, wherein the solid content of the coating agent forming the coating layer is 2.0 to 5.0 g / m ² per one side of the base paper. Longitudinal Clark stiffness conforming to JIS P 8143 in the 10 cm ^3/100 or more,
75 ° sheet gloss conforming to JIS P 8142 is Ru der 20% or more, coated printing paper according to claim 1. As an adhesive, starches and latexes can be contained in the coating agent, the viscosity of the coating factory agent Ru 0.20~0.40Pa · s der, for coated printing according to claim 1 or 2 paper. Production of coated paper for printing having a basis weight of 32 to 45 g / m ² according to JIS P 8124, in which a coating layer is formed with a coating agent containing a pigment and an adhesive on at least one side of a base paper A method,
The base paper is composed of pulp containing 10 to 40% by mass of mechanical pulp in accordance with JIS P 8120,
As the pigment, a coating agent containing 5 to 25% by mass of organic pigment , 25 to 55% by mass of clay and 30 to 55% by mass of calcium carbonate in the total pigment , the solid content adhesion amount of the base paper as the per side 2.0~5.0g / m ^2, a coating layer was formed by coating on at least one surface of a base paper,
2. The printing coating according to claim 1, wherein the surface of the coating layer is flattened by a flattening treatment facility comprising a combination of an elastic roll and a metal roll having at least one nip. Paper manufacturing method.