JP4668359B2 - Coated paper for printing and method for producing the same - Google Patents

Description

  The present invention relates to a low basis weight coated paper for glossy printing and a method for producing the same. In particular, the present invention relates to a low basis weight glossy coated coated paper having excellent opacity and good printability, particularly blister suitability.

  In recent years, the demand for coated paper for printing has increased in the commercial printing field for the purpose of advertising and promotion such as flyers, catalogs, pamphlets and direct mail. Although these commercial prints are not of high commercial value, it is important that the purpose of the advertising medium is achieved. Therefore, the printing paper used for such commercial prints has a low cost and good print finish. Is required.

  In addition, since entering the era of low growth in recent years, in order to reduce the cost of printing paper, the downgrading due to lower basis weight has been rapidly progressing in the coated paper for printing. This includes economic factors such as deterioration in corporate profits due to soaring raw material prices and reduction in transportation costs, as well as social factors based on social demands such as resource saving and environmental issues. Particularly in the mail order industry, where the market has been expanding over the past few years, there has been an increasing demand for lower basis weight in order to reduce postage costs such as catalogs and direct mail, reduce warehouse storage fees, and increase page measures.

  Even in the situation where such a low basis weight is required, a quality requirement for the coated paper for printing is also required. Among the quality of coated paper, there is a particularly high demand for opacity (especially, ink does not escape to the back side during printing), and it also has excellent whiteness, white paper gloss, quality after printing, and printing durability. is important.

  However, low basis weight and opacity are contradictory matters, and it is difficult to achieve both of these qualities. That is, when the basis weight is lowered, the opacity that is an important point in the coated paper for printing is lowered.

  As a means for improving the opacity of low-basis weight coated paper, there is a method of increasing the ash content of the coated paper by blending a large amount of an inorganic substance having a high specific scattering coefficient into the coated paper. Specifically, the ash content of the coated paper is increased by adding inorganic substances such as clay, talc, calcium carbonate or the like as a filler to the base paper or increasing the pigment coating layer (Patent Documents 1 and 2). ).

  However, both the increase in the ash content of the base paper and the decrease in the basis weight of the base paper due to the increase in the pigment coating layer both lead to a decrease in the strength of the base paper, and consequently the strength of the coated paper. For this reason, machine operability deteriorates, such as the occurrence of paper breaks in the coated paper manufacturing process, especially when paper coating, coating, and surface treatment are performed continuously on-machine, resulting in a significant reduction in production efficiency due to paper cutting. . Further, when the paper break occurs, there is a risk that the adverse effects on the manufacturing process such as breakage of the operation tool are remarkably increased. The adverse effects due to such insufficient paper strength are even greater in high speed operation.

  As described above, lower basis weight and opacity are contradictory matters, and as the gap in the paper layer decreases with the lower basis weight, both the frequency of light diffusion and the amount absorbed are reduced. Opacity decreases. Therefore, as another means for improving the opacity of the coated paper, there is a method of reducing the density of the paper in order to increase the volume of the voids in the paper layer.

  Furthermore, for glossy coated papers that require high white paper gloss, it is necessary to perform surface treatment at a high linear pressure, so conventionally glossy coated papers have been coated with various coating devices (hereinafter referred to as coaters). Once the coated paper coated with pigment is wound up, it is treated with a super calender at low temperatures (about 50 to 70 ° C) and in a multi-stage nip (usually 10 to 14 stages) to give gloss. It was granted and commercialized. In particular, in order to obtain a glossy coated paper having a blank paper glossiness of 40% or more using such a super calender, it is necessary to perform a calendar process at a high nip pressure, but the density increases due to the high nip pressure, Decrease in opacity and deterioration of penetration through printing are unavoidable.

  In addition, it has been proposed to produce glossy coated paper by blending an expensive pigment that is easily glossy and applying pigment so that high gloss is exhibited even with low nip pressure super calender treatment. An increase in cost is inevitable (Patent Document 3: Japanese Patent Laid-Open No. 54-125712).

  On the other hand, improving paper productivity is also an important technical issue. As described above, printing paper used for commercial printed materials is required to have low cost and good print finish, so it is important for paper manufacturers to increase productivity and reduce costs while maintaining high quality. is there.

  In general, one of the means to reduce costs from the viewpoint of manufacturing prescription is to reduce the coating amount, but if the coating amount is reduced, the surface properties such as white paper glossiness and smoothness and printability are inevitably lowered. In addition, opacity, which is a particularly important point for coated paper for printing, is also deteriorated.

JP 2008-248451 A JP 2000-170093 A JP 54-125712 A

  As described above, it has been extremely difficult to efficiently produce a low basis weight glossy coated paper having both high opacity and good printability. In view of the circumstances as described above, an object of the present invention is to provide a low basis weight glossy printing coated paper having high opacity and excellent printability, and to apply the low basis weight glossy printing coating. It is to provide a method for producing a working paper at an operation speed of 1300 m / min or more.

  As a result of intensive studies on the above problems, the present inventors have found that the moisture content of the base paper before the pigment coating layer is 3 using a paper machine having a gap former in the forming part and one or more tandem shoe presses in the press part. By making less than% base paper, coating and surface treatment from paper making can be done efficiently at a high speed of 1300m / or more without any adverse effects such as paper breakage, increasing the density in the process where surface treatment is performed. As a result, the inventors have found that blistering during printing can be reduced and the present invention has been completed.

In one aspect, the present invention is a coated coated paper for printing and a method for producing the same. The present invention has a basis weight of 30g / m ² ~70g / m ² of coated paper, 35% to 50% is ash content, coated printing paper white paper glossiness of 40% to 60%, and its It is a manufacturing method. In particular, when the coated paper of the present invention has a specific scattering coefficient / density, which is a ratio of the specific scattering coefficient (cm ² / g) to the density (g / cm ³ ), of 400 or more, the opacity is low. Is preferable because it is difficult to cause print-through.

  The method for producing a coated paper for printing of the present invention uses a paper machine having a gap former as a forming part and one or more tandem shoe presses as a press part, and has a water content of 3% before providing a pigment coating layer. A process of making a base paper that is less than, a process of applying a coating liquid containing a pigment and an adhesive to provide a pigment coating layer, and a process of surface-treating the coating layer, This process is continuously performed on-machine at an operation speed of 1300 m / min or more.

  In a preferred embodiment of the present invention, in the step of making the base paper, an adhesive such as starch is not applied by size press before providing the pigment coating layer. By not applying clear coating, the air resistance of coated paper can be reduced, preventing blistering during offset printing, and increasing gloss development by surface treatment, so that it has good printability. A coated paper for tone printing can be obtained, which is preferable.

The present invention, by coating the 8g / m ² ~20g / m ² coating per side containing an adhesive and a pigment in the coating process, by increasing the ratio of high pigment component having a specific scattering coefficient, surface treatment The load in the process was reduced, and good opacity and, in turn, excellent through-through characteristics during printing were realized.

  Furthermore, in a preferred embodiment of the present invention, the surface treatment is performed using a thermal soft calender having at least 6 nips or more constituted by a metal roll and an elastic roll. As a result, it is possible to obtain a high smoothness while dispersing the calendar pressure in a plurality and suppressing the increase in density and maintaining the opacity.

Although not limited to the following, the present invention includes the following inventions.
(1) a basis weight of coated paper was at ^{30g / m 2 ~70g / m 2} , 35% ~50% is ash content, coated printing paper manufacturing process white paper glossiness of 40% to 60% Papermaking, pigment coating, and surface treatment are continuously performed on-machine, the operation speed is 1300 m / min or more, and the papermaking process has one or more tandem shoe presses in the press part. The method as described above, wherein the water content of the paper before the provision of the pigment coating layer is less than 3%, which is performed using a paper machine having a gap former.
(2) The method according to (1), wherein in the pigment coating step, a pigment coating layer of 8 to ²⁰ g / m ² is provided per side.
(3) The method according to (1) or (2), wherein in the surface treatment step, the pigment coating layer is subjected to a surface treatment under conditions of 6 nips or more using a soft calender composed of a metal roll and an elastic roll. .
(4) Any of (1) to (3), wherein the specific scattering coefficient / density, which is the ratio of the specific scattering coefficient (cm ² / g) to the density (g / cm ³ ), of the coated paper is 400 or more. The method described in 1.
(5) coated paper having a basis weight of ^{30g / m 2 ~70g / m 2} , 35% ~50% is ash content, a white paper glossiness of 40% to 60%, any of (1) to (4) Coated paper for printing obtained by this method.
(6) The coated paper according to (5), wherein the specific scattering coefficient / density, which is the ratio of the specific scattering coefficient (cm ² / g) to the density (g / cm ³ ), of the coated paper is 400 or more.

  According to the present invention, papermaking, coating and surface treatment can be continuously performed to produce low basis weight glossy coated paper having high opacity and good printability at an operation speed of 1300 m / min or more. It is.

The present invention relates to a coated paper for low basis weight gloss tone printing and a method for producing the same. The glossy printed coated paper of the present invention has a basis weight of the coated paper of 30 g / m ^{2 to} 70 g / m ² , an ash content of 35% to 50%, and a blank paper glossiness of 40% to 60%. That is, according to the present invention, it is possible to efficiently produce a low basis weight glossy coated paper having high opacity.

  In the present invention, the glossy coated coated paper means a coated coated paper having a glossy (glossy) coated paper surface, specifically, a blank paper glossiness of 40% to 60%. % Means coated paper for printing. In a preferred embodiment of the present invention, the blank paper glossiness is 45% or more, and in a more preferred embodiment, the blank paper glossiness is 48 to 55%. The coated paper for printing of the present invention having such white paper glossiness is excellent in printing finish and can reproduce a stretched image.

The present invention relates to a coated paper for printing having a low basis weight and a method for producing the same. Low basis weight coated printing paper of the present invention specifically has a basis weight of ^{30g / m 2 ~70g / m 2} , a. According to the present invention, it is also possible to efficiently produce glossy-printed coated paper having a basis weight of the coated paper of around 50 g / m ² . The basis weight of the coated printing paper of the present invention in a preferred embodiment, 40 g / m ² was ~65g / m ^2, more preferably 45g / m ² ~65g / m ² In embodiment, further preferred embodiment 50 g / m ² ˜65 g / m ² .

  In the glossy printing paper of the present invention, the ash content of the coated paper is 35 wt% to 50 wt%, preferably 35 wt% to 45 wt%, more preferably 35 wt% to 40 wt%. By setting the ash content of the coated paper to 35% by weight to 50% by weight, excellent penetration and opacity can be obtained while maintaining the strength and blister resistance of the paper. In the present invention, the ash content of the coated paper is a value obtained by adding the ash content of the base paper and the ash content of the coating layer.

  There are two types of coating paper ash increase: base paper ash increase and pigment coating layer ash increase (increase in pigment coating layer). Increase in the air resistance increases, so that the blister suitability at the time of printing is remarkably deteriorated. Here, a blister is a drying part after inking in a rotary offset printing press, and when the coated paper is heated suddenly together with the ink and the water in the coated paper evaporates, the vapor forms a coating layer. This phenomenon is caused by blistering caused by the ink layer. The interlaminar strength, air resistance, and moisture content of the coated paper are major factors. The quality of the coated paper including blister suitability is adjusted by adjusting to -6%. However, since the coating liquid stays on the surface of the base paper and covers the base paper during coating, the coating liquid is intensively dried in the drying part after coating. Therefore, it is difficult to suppress the generation of blisters simply by adjusting the moisture content of the coated paper.

  Further, in the case of high-speed coating with an on-machine coater as in the present invention, if the ash content of the base paper is high, the interlaminar strength of the paper becomes weak, paper breakage occurs, and the operability is significantly reduced. Further, if the ash content is increased by increasing the coating amount, the high-speed machine increases the drying load due to the high speed, and the operability is significantly reduced. Thus, in order to improve the opacity, it is very difficult to increase the ash content of the coated paper in the on-machine high-speed coating.

  In the present invention, as a paper machine, by using a paper machine having one or more tandem shoe presses and having a gap former, the paper is made without causing paper break even if the ash content of the base paper is increased. Can be made paper.

  The factor that determines the opacity of the paper is light scattering and absorption in the paper layer. As a method for increasing the opacity, there is an increase in the absorption coefficient and an increase in the scattering coefficient. However, increasing the absorption coefficient decreases the whiteness of the paper, leading to a decrease in the quality of the coated paper. Therefore, in order to increase the opacity of the coated paper, it is important to make the paper opaque by increasing the paper scattering coefficient.

Although the coated paper for printing of the present invention has a low basis weight and high opacity, it is particularly difficult to cause print-through. Specifically, in the coated paper for printing of the present invention, the specific scattering coefficient / density, which is the ratio of the specific scattering coefficient (cm ² / g) to the density (g / cm ³ ), is preferably 400 or more, and 420 or more. More preferred is 450 or more. The coated paper for printing according to the present invention having such a ratio of specific scattering coefficient and density is suitable because it has low opacity and high opacity, and is particularly difficult to cause print-through. Here, the parameter of specific scattering coefficient / density is an index of opacity of the coated paper for printing, and the larger the value, the higher the opacity of the coated paper. That is, when the specific scattering coefficient is high (that is, when light is often scattered in the coated paper) or when the density is low (that is, when there are many voids inside the coated paper and light is easily scattered), The parameter is a large value of specific scattering coefficient / density.

In the present invention, the specific scattering coefficient (cm ² / g) is preferably 400 or more, more preferably 450 or more, and further preferably 500 or more. If the specific scattering coefficient (cm ² / g) is smaller than 400, the print quality such as back-through tends to be lowered. The specific scattering coefficient can be increased, for example, by increasing the amount of ash, but can also be increased if light is well scattered in the coated paper, such as by reducing the density.

In the present invention, the density (g / cm ³ ) is preferably 1.4 or less. In order to set the glossiness of blank paper to 40% to 60%, the lower limit is preferably about 0.8.

  The printing coated paper of the present invention can correspond to various printing methods and can be suitably used for offset printing coated paper, relief printing coated paper, gravure printing coated paper, and the like. . Especially, since the coated paper for printing of this invention is excellent in the blister property, it can be used especially suitably for offset printing use.

  In the production method of the present invention, the paper making process, the coating process, and the surface treatment process are continuously performed using an on-machine coater, and the operation speed is 1300 m / min or more. Therefore, the present invention has a high production efficiency and is extremely advantageous. In high-speed operation with an on-machine coater, the operability is significantly reduced due to a paper-cutting trouble. However, since the present invention uses a paper machine having a gap former, a paper-cutting trouble hardly occurs. This is particularly advantageous during high-speed operation. Since the superiority of the present invention is particularly high in high-speed operation, it is preferable to operate under conditions of 1500 m / min or more, and it is more preferable to operate under conditions of 1600 m / min or more.

Papermaking The method for producing a coated paper for printing of the present invention has a papermaking process, and uses a papermaking machine having one or more tandem shoe presses and a gap former as a papermaking machine, before providing a pigment coating layer. A base paper having a water content of less than 3% is made.

  In the present invention, paper making is performed using a paper machine having a gap former. According to this gap former, the paper material jetted from the head box runs between two wires and travels on both sides of the wet paper. Dehydrated almost evenly. In particular, in the present invention, it is preferable to use a paper machine having a roll-and-blade type gap former having a dewatering mechanism with a dewatering blade immediately after the initial dewatering with a forming roll. By using such a gap former type paper machine, it is possible to stably make a base paper having a high ash content and no difference in front and back at a high paper making speed of 1300 m / min or more while maintaining good operability. When a roll-and-blade type former is used, the initial dewatering is performed in the lap area of the forming roll having the vacuum, and immediately after that, the blade dewatering is performed by the pressure blade module. This mechanism enables slower dehydration than conventional formers, so that paper with a uniform paper layer structure and texture can be obtained, and the blister resistance of coated paper can be improved even under relatively high ash conditions. Can be maintained. If the diameter of the forming roll used at this time is small, a sufficient holding angle cannot be obtained, and adjustment of dehydration becomes insufficient, so that it is preferably 1500 mm or more. In addition to a dewatering mechanism using a forming roll or a blade, dryness can be adjusted by appropriately using a dewatering device such as a suction unit or a high vacuum suction box in the subsequent stage.

  The paper machine used in the present invention has at least one tandem type shoe press in the press part in consideration of moisture after pressing. More preferably, the interlayer strength and the blister resistance are improved by performing the treatment in two or more stages using a tandem type shoe press. In a preferred embodiment, the shoe press has a nip width in the range of about 150 to 250 mm, and the processing conditions are preferably 100 kN / m to 1100 kN / m, more preferably 500 kN / m to 1100 kN / m. Further, when two or more shoe presses are used, it is preferable to pass the paper so that the transfer belt comes into contact with the shoe press on the dryer part side, because paper breakage hardly occurs and high-speed operability is excellent.

  As the dryer of the paper machine, a public apparatus can be used, and the drying conditions are not particularly limited, and can be appropriately set within a normal operating range.

  In the present invention, the blister suitability during offset printing can be greatly improved by setting the moisture content of the base paper before providing the pigment coating layer to less than 3%, more preferably less than 2.5%. Blisters are thought to be largely due to the interlaminar strength, low air permeability, and moisture content of coated paper. Conventionally, the moisture content of the coated paper has been adjusted to 4-6%. In the drying part after the coating of the paper, the coating liquid is mainly dried. Therefore, even if the moisture content of the coated paper is adjusted by the drying part, it is difficult to suppress the generation of blisters. On the other hand, in this invention, blister suitability is improved by adjusting the moisture content of the base paper before providing a pigment coating layer. Although the details of the reason why the blister resistance is improved by setting the moisture content of the base paper to less than 3% are not clear, the water content of the base paper portion is small, so that the water vapor generated by the heat during printing decreases, and the base paper has It is conceivable that the effect of the paper strength agent added internally is maximized.

  In the present invention, in an on-machine high-speed coater, a paper machine having a gap former is used, and the ash content of the coated paper is increased, so that the operability is good and the high opacity and low basis weight printing coating is performed. Paper can be obtained.

  In the present invention, as the raw paper pulp, chemical pulp (conifer bleached kraft pulp (NBKP) or unbleached kraft pulp (NUKP), hardwood bleached kraft pulp (LBKP) or unbleached kraft pulp (LUKP), etc.) Mechanical pulp (groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), etc.), deinked pulp (DIP), etc. are mixed alone or in any proportion. To use. The deinked pulp may be any deinked pulp made from high-quality paper, medium-quality paper, low-grade paper, newspaper, flyers, magazines, etc., or unselected waste paper mixed with these. Absent. In the present invention, even when the deinked pulp is 30% by weight or more with respect to the pulp, effects such as no difference in front and back and good interlayer strength can be exhibited.

  In the present invention, known fillers can be arbitrarily used, such as white carbon, talc, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, deramikaolin, Inorganic such as amorphous silica produced by neutralization by mineral production of magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate Fillers and organic fillers such as urea-formalin resins, melamine resins, polystyrene resins and phenol resins can be used alone or in combination. Among these, calcium carbonate and light calcium carbonate-silica composite, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used. The filler content in the paper is not particularly limited, but is preferably 10 to 40% by solid weight. Since the opacity of the coated paper increases as the ash content increases, the effect of the present invention is greater when the present invention is applied to the production of a low-basis weight printing base paper for which it is difficult to achieve opacity. From this viewpoint, the filler content in the paper is preferably 10 to 40% by weight, more preferably 12 to 35% by weight.

  In the present invention, known papermaking additives can be used. For example, sulfuric acid bands and various anionic, cationic, nonionic or amphoteric yield improvers, drainage improvers, paper strength enhancers and internal additive sizing agents, etc. Can be used. Furthermore, by adding a cationic paper strength enhancer to the base paper and adding 50 kg to 150 kg / t of pulp, it is possible to obtain good printability, particularly blister characteristics. In addition, dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  In general, for the purpose of improving the surface strength and the like, a clear coating layer is provided by applying a coating liquid mainly composed of an adhesive such as starch to a coated base paper. In particular, when the ash content of the coated paper is increased, the strength of the base paper decreases, so as a method to compensate for the lack of strength of the base paper, a clear coating solution mainly composed of an adhesive such as starch is coated on the base paper. Thus, in addition to improving the surface properties of the base paper, the interlayer strength due to the penetration of the adhesive is improved. Applying such a clear coating solution to the base paper before pigment coating in advance is generally called a size press, but the coating equipment used at this time is a rod metalling size press coater, blade metalling. A roll coater such as a size press coater, a gate roll size press coater, or a two roll size press is often used.

  However, in the present invention, such a clear coating is not performed, and it is preferable to provide a pigment coating layer as it is on the base paper. That is, when producing at a high speed of 1300 m / min or more with an on-machine coater as in the present invention, it is preferable not to perform clear coating with a size press because clear coating may be a significant adverse effect on operability. . That is, by not performing the clear coating, it is possible to avoid the wetting of the base paper due to the size press, the paper break due to the nip, and the increase in defects due to the mist. In addition, by applying a surface treatment agent mainly composed of a water-soluble polymer such as starch to the coated base paper (size press), the base paper surface becomes hard, so that minute irregularities are not easily crushed in the surface treatment process. , Glossiness deteriorates. Furthermore, the size press deteriorates the air permeability of the base paper, which in turn affects the blister suitability during printing.

  In the present invention, it is particularly preferable to smooth the base paper in advance using an on-line soft calendar or an on-line chilled calendar in order to make the coating layer after coating uniform.

Pigment coating The method for producing a coated paper for printing of the present invention includes a step of coating a coating liquid containing a pigment and an adhesive on the coating base paper obtained as described above with an on-machine coater. It becomes. Therefore, the printing coated paper of the present invention has a pigment coating layer on the base paper.

  There is no restriction | limiting in particular in the pigment used by this invention, The pigment conventionally used for coated paper can be used. For example, inorganic pigments such as kaolin, clay, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white Organic pigments such as plastic pigments, organic / inorganic composite pigments, and the like can be used. These pigments can be used alone or in combination of two or more as required.

Further, as a pigment for pigment coating of the present invention, calcium carbonate obtained by wet milling light calcium carbonate of spindle-shaped calcite crystal, which is an average particle measured by an X-ray transmission type particle size distribution analyzer The diameter (d50: particle diameter of 50% by weight) is 0.1 to 0.5 μm, the BET specific surface area is in the range of 10 to 30 m ² / g, and is measured with an X-ray transmission type particle size distribution analyzer. The following formula:
Sharpness = (d30 / d70) × 100
[Wherein d30 is a particle size of 30% by weight and d70 is a particle size of 70% by weight]
It is preferable to use calcium carbonate having a sharpness of the particle size distribution represented by It is preferable to apply such calcium carbonate with a pigment because a coated paper for printing excellent in see-through can be obtained.

In the present invention, when the above calcium carbonate is used, it is preferable to use a calcite crystal in which spindle-shaped primary particles aggregate to form rosette-shaped secondary particles as light calcium carbonate before pulverization. More preferably, the average particle size (d50) measured by the previous light calcium carbonate X-ray transmission type particle size distribution analyzer is 1.4 to 3.0 μm, and the BET specific surface area is 4 to 12 m ² / g. preferable. Furthermore, when using said calcium carbonate in this invention, it is preferable to perform a wet grinding using a multipass-type grinder. The compounding amount of the pulverized calcium carbonate is preferably 40 to 100 parts by weight, more preferably 60 to 90 parts by weight per 100 parts by weight of the pigment.

  There is no restriction | limiting in particular in the adhesive agent used by this invention, The adhesive agent (binder) conventionally used for coated paper can be used. For example, various copolymers such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, polyvinyl alcohol, maleic anhydride copolymer, acrylic acid / methyl Synthetic adhesives such as methacrylate copolymers; proteins such as casein, soy protein, synthetic proteins; etherified starches such as oxidized starch, positive starch, urea phosphate esterified starch, hydroxyethyl etherified starch, dextrin, etc. Starch: One or more kinds of ordinary adhesives for coated paper such as cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and hydroxymethylcellulose can be appropriately selected and used. In a preferred embodiment, these adhesives are used in the range of about 5 to 50 parts by weight, more preferably about 8 to 30 parts by weight per 100 parts by weight of the pigment. Moreover, various auxiliary | assistant mix | blended with the pigment for normal coated papers, such as a dispersing agent, a thickener, a water retention agent, an antifoamer, a water-resistant agent, and a coloring agent, are used suitably as needed.

  In the present invention, when applying a paint mainly composed of a pigment and an adhesive, a blade coater, a bar coater, a roll coater, an air knife coater, a reverse roll coater, a curtain coater, a size press coater, and a gate roll coater are used. One layer or two or more layers can be coated on one side or both sides of the base paper by a coating machine or the like in which a paint such as OptiSpray is applied or directly sprayed onto the base paper by a spray nozzle. Among these, in consideration of image reproducibility after printing, a blade system using a flooded nip type blade coater, a jet fountain type blade coater, a short dwell time application type blade coater or the like is preferable. Further, in the present invention, an appropriate coating amount is required to obtain excellent penetration properties, and therefore it is preferable to employ a jet fountain blade coater with a wide adjustment range of the coating amount.

The coating amount of the paint applied by the above coating method is preferably 8 to 20 g / m ² , more preferably 9 to 15 g / m ² per side. Thereby, since a coating layer can fully coat | cover a base paper, favorable glossiness expression is obtained. In addition, the pigment coating layer may be one or plural.

  Although the preparation method of a pigment coating liquid is not specifically limited, In a preferable aspect, solid content concentration of a coating liquid is about 30 to 68 weight%.

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

Surface Treatment The method for producing a coated paper for printing of the present invention comprises a step of surface-treating the coating layer. In particular, as the surface treatment in the present invention, it is preferable to perform the surface treatment with an online thermal soft calender composed of a metal roll and an elastic roll.

  Generally, when surface treatment is performed using an online thermal soft calender composed of a metal roll and an elastic roll after the coating layer is provided, the surface temperature of the metal roll and the nip pressure of the calender have a large effect on the density. Density is an important factor because it greatly contributes to gloss and opacity.

  In the surface treatment of the present invention, the surface treatment is preferably performed under conditions of 6 nips or more. In general, in a low basis weight coated paper, increasing the calendar load to improve smoothness leads to a decrease in opacity, and paper breakage or the like is likely to occur. By performing the surface treatment under conditions of 6 nips or more, the calendar load can be dispersed, and the density increase that affects the opacity can be suppressed while obtaining the target smoothness. In particular, by applying a surface treatment with a thermal soft calender of at least 6 nips or more, a coated paper for printing can be applied to a papermaking process, a coating with a low basis weight, without losing quality under high-speed operating conditions. It has become possible to continuously manufacture the process and surface treatment process online.

  The surface temperature of the metal roll is preferably 100 ° C. or higher and 300 ° C. or lower. If the moisture content of the coated paper is appropriate, the coating layer can be smoothed with a low nip pressure or a short nip residence time by using a metal roll heated to 100 ° C. or higher. Low density, high opacity, coated paper with good smoothness, and faster processing than conventional super calenders, eliminating the need for rewinding frames, etc., enabling efficient production Excellent operability.

  Moreover, as a preferable condition when using a high temperature soft nip calender, for example, the Shore D hardness of the elastic roll is preferably 80 to 100, and more preferably 85 to 97. The sheet passing speed is preferably about 1000 to 3000 m / min, and the linear pressure is preferably about 30 to 500 kg / cm. The pre-calendar coating moisture is preferably 3 to 12%, but more preferably 4 to 8% in order to achieve both smoothness and operability.

  The material of the elastic roll used in pair with the metal roll of the soft calender is not particularly limited, but generally at high temperature and high pressure such as modified urethane resin, epoxy resin, polyamide resin, phenol resin, polyether resin, polyacrylate resin, etc. A resin roll exhibiting durability is preferably used.

  The type of soft calender used in the present invention is preferably 6 stacks or more with two tandem type rolls in consideration of easy paper passing and space saving. The tandem type is a soft calendar of a type in which two rolls obtained by overlapping a pair of metal rolls and elastic rolls are arranged in parallel.

As described above, the present invention provides a gap former in which the process of making a base paper is one or more tandem shoe presses in a low basis weight printing coated paper manufactured by an on-machine coater having an operation speed of 1300 m / min or more. The moisture content of the base paper before providing the pigment coating layer is less than 3%, the basis weight of the coated paper is 30 g / m ^{2 to} 70 g / m ² , the ash content is 35% to 50%, and the blank paper glossiness is By setting it to 40% to 60%, it has an excellent penetration through property at the time of printing while having a low basis weight, and it can have printing suitability, particularly good blister suitability. In particular, when the coated paper of the present invention has a specific scattering coefficient / density, which is a ratio of the specific scattering coefficient (cm ² / g) to the density (g / cm ³ ), of 400 or more, the opacity is low. Therefore, it is possible to efficiently suppress print-through.

  EXAMPLES Hereinafter, although an Example of this invention is given and this invention is demonstrated further in detail, this invention is not limited at all by these. Unless otherwise specified, in the present specification, “part” and “%” respectively represent “part by weight” and “% by weight”, and the numerical range is described as including the end points.

<Manufacture of coated paper for printing>
[Example 1]
A pulp slurry containing 30 parts of waste paper pulp (DIP) and 70 parts of hardwood kraft pulp (LBKP) was prepared as a raw material for the base paper, 12 parts of light calcium carbonate as a filler, and cationic paper as an internal paper strength agent. A paper stock was prepared by adding 0.5% of a strength enhancer to the pulp.

Using this paper stock, a paper machine having a roll-and-blade-former gap former and having two tandem shoe presses in the press part was used, and the moisture content was 2.8% and the basis weight was 45.6 g / m. ² base papers were obtained. The papermaking speed was 1500 m / min, and clear coating by a size press or the like was not performed on the base paper.

Next, 100 parts of pigment containing 73 parts of heavy calcium carbonate and 27 parts of kaolin are combined with 11.5 parts of oxidized starch and carboxy-modified styrene / butadiene copolymer latex as an adhesive to obtain a solid content concentration. A 64% coating solution was prepared. Using this coating solution, a pigment coating layer was provided on both sides with a jet fountain-applied blade coater so that the coating amount was 9.0 g / m ² per side.

Subsequently, in the surface treatment process, the surface of the pigment coating layer is continuously treated using a 2-roll / 6-stack thermal soft calender at a surface temperature of the metal roll of 200 ° C. and a linear pressure of 250 kN / m. Thus, a coated paper for printing was obtained. The basis weight of the resulting coated paper for printing was 64.0 g / m ² , the blank paper glossiness was 50.0%, and the ratio of specific scattering coefficient to density was 455.

  In this example, since the paper making process, the coating process, and the surface treatment process were continuously performed on-line, not only the paper making speed but also the coating speed and the calendar speed were 1500 m / min.

[Example 2]
The machine speed 1300 m / min, 2.5% the base paper moisture after drying, 46.6 g / m ² base paper basis weight, except that the coating amount of the pigment coating layer per one surface 8.5 g / m ² is A coated paper was produced in exactly the same manner as in Example 1 above.

[Example 3]
The machine speed 1300 m / min, 2.2% the base paper moisture after drying, 35.2 g / m ² base paper basis weight, except that the coating amount of the pigment coating layer per one surface 8.0 g / m ² is A coated paper was produced in exactly the same manner as in Example 1 above.

[Example 4]
Except for the papermaking speed of 1300 m / min, the moisture of the base paper after drying was 2.2%, the base weight of the base paper was 36.2 g / m ² , and the coating amount of the pigment coating layer was 7.5 g / m ² per side. A coated paper was produced in exactly the same manner as in Example 1 above.

[Example 5]
The machine speed 1300 m / min, 2.5% of base paper moisture after drying, 46.6 g / m ² base paper basis weight, the coating amount of the pigment coating layer per one surface 8.5 g / m ^2, the pigment coating A coated paper was produced in exactly the same manner as in Example 1 except that instead of the heavy calcium carbonate in the working layer, the following pulverized light calcium carbonate was used.

(Crushed light calcium carbonate)
In this example, as calcium carbonate, spindle-shaped primary particles agglomerated to form Rosetta-shaped secondary particles, calcium carbonate of calcite crystal (Okutama Kogyo Co., Ltd .: TP221BM) is made a solid content concentration 20%, After 1.5 parts by weight of a polyacrylate dispersant is added to form a slurry, wet milling is performed using SC Mill Long (manufactured by Mitsui Mining Co., Ltd .: SC Mill 100), which is a multi-pass mill. Was used as a pigment. The pulverized calcium carbonate had an average particle size of 0.38 μm, a BET specific surface area of 22.5 m 2 / g, and a sharpness of 62, as measured with a particle size distribution analyzer of the X-ray transmission method.

The light calcium carbonate after wet pulverization has an average particle size (d50: particle size of 50% by weight) measured by an X-ray transmission particle size distribution analyzer of 0.38 μm and a BET specific surface area of 22.5 m ^2. / G and measured by an X-ray transmission particle size distribution analyzer (Cedigraph 5100, manufactured by Micromeritics):
Sharpness = (d30 / d70) × 100
[Wherein d30 is a particle size of 30% by weight and d70 is a particle size of 70% by weight]
The sharpness of the particle size distribution represented by is 62.

In addition, as light calcium carbonate before grinding, a calcite crystal in which spindle-shaped primary particles agglomerate to form rosette-shaped secondary particles is used. The measured average particle size (d50) was 2.2 μm, and the BET specific surface area was 5.9 m ² / g.

[Example 6]
The machine speed 1300 m / min, 2.5% of base paper moisture after drying, 46.6 g / m ² base paper basis weight, the coating amount of the pigment coating layer per one surface 8.5 g / m ^2, the pigment coating A coated paper was produced in exactly the same manner as in Example 1 above, except that a clear coating was applied to the base paper with a size press using a coating solution having a starch concentration of 6% before the work.

[Example 7]
Base paper basis weight of 35 g / m ^2, except that the coating amount of the pigment coating layer was per side 9.5 g / m ² was prepared a coated paper in the same manner as in Example 1.

[Comparative Example 1]
Using a paper machine with a hybrid former at a paper making speed of 1300 m / min and two tandem shoe presses in the press part, a base paper with a moisture content of 4.0% and a basis weight of 36.2 g / m ² Obtained. Next, the pigment coating layer was provided on both sides so that the coating amount of the pigment coating layer was 7.5 g / m ² per side. Subsequently, the pigment coating layer was surface-treated using a 2-roll, 4-stack thermal soft calender. A coated paper was produced in the same manner as in Example 1 except for this.

[Comparative Example 2]
The machine speed 1300 m / min, 2.5% the base paper moisture after drying, 35.2 g / m ² base paper basis weight, except that the coating amount of the pigment coating layer per one surface 8.0 g / m ² is A coated paper was produced in exactly the same manner as in Example 1 above.

[Comparative Example 3]
The machine speed 1300 m / min, the sheet moisture after drying 4.0%, 46.6g / m ² base paper basis weight, except that the coating amount of the pigment coating layer per one surface 8.5 g / m ² is A coated paper was produced in exactly the same manner as in Example 1 above.

[Comparative Example 4]
A coated paper was produced in the same manner as in Comparative Example 1 except that the base paper basis weight was 29 g / m ² and the coating amount of the pigment coating layer was 10.5 g / m ² per side. However, a paper break occurred during the operation, and the coated paper could not be produced stably.

<Quality evaluation method>
(1) Coated paper ash content Measured according to JIS P-8251.
(2) Gloss of white paper Measured at an angle of 75 degrees according to JIS P-8142.
(3) Specific scattering coefficient / density (opacity)
The specific scattering coefficient was calculated according to ISO-9416, and the density was measured according to P-8118.
(4) Printability (blister suitability)
Using a RI-I type printing machine (Ming Seisakusho), using Toyo Ink (TK Mark V617), printing on both sides with a constant ink amount of 0.8 cc and adjusting the humidity all day and night, the test piece was heated to 140 ° C. It was immersed in a set temperature oil bath, and the occurrence of blisters was visually judged according to the following criteria: ◎ = Not generated at all, ○ = Not generated at all, △ = Generated, X = Significantly generated (5) Print quality Meat unevenness)
Using an offset rotary printing press (4 colors), print 20,000 copies at a printing speed of 500 rpm in the order of black, indigo, red, and yellow using off-ring printing ink (Toyo Ink Leo-X M), then in halftone. The unevenness of the flesh was visually evaluated according to the following criteria: ◎ = very good, ○ = good, △ = slightly inferior, x = poor (6) print quality (through-through)
Using an offset rotary printing press (4 colors), 20,000 copies were printed in the order of black, indigo, red and yellow at a printing speed of 500 rpm using off-ring printing ink (Toyo Ink LeoX M). Was visually evaluated according to the following criteria: ◎ = very good, ○ = good, △ = slightly inferior, x = poor (7) high speed operability In view of the absence of occurrence of shrinkage, the occurrence of shrinkage wrinkles during calendering, the durability of the elastic roll, etc., the suitability of high-speed operability was evaluated according to the following criteria: ◎ = very good, ◯ = good, △ = slightly bad, x = bad

表１に結果を示す。表１から明らかなように、本発明によると、高速操業性を損なうことなく、オフセット印刷時の耐ブリスター性と裏抜け性に優れた塗工紙を得ることができた。

Table 1 shows the results. As is apparent from Table 1, according to the present invention, a coated paper having excellent blister resistance and reverse penetration properties during offset printing could be obtained without impairing high-speed operability.

  When the water content of the base paper is low, the blister resistance is improved, and when the coated paper has a high ash content or the use of pulverized light calcium carbonate, there is a tendency that the back-through is improved. Moreover, the high-speed operability was particularly suitable when a gap former was used and the ash content was about 35 to 50%. Furthermore, when the ash content was increased, paper breakage occurred in paper machines other than the gap former, and the operability deteriorated remarkably.

Further, the uneven printing thickness tends to improve when the coating amount is 8 g / m ² or more.

Claims (4)

Basis weight ^30g / ^{m 2 ~70g} / m 2 of coated paper, 35% to 50% is ash content, sheet gloss is a method for producing a coated printing paper is 40% to 60%,
Papermaking, pigment coating, and surface treatment are continuously performed using an on-machine coater, the operation speed is 1300 m / min or more, the papermaking process has one or more tandem shoe presses in the press part, and the forming part The method as described above, wherein the water content of the paper before the provision of the pigment coating layer is less than 3%, using a paper machine having a gap former. The method according to claim 1, wherein in the pigment coating step, a pigment coating layer of 8 to ²⁰ g / m ² is provided per side.   The method according to claim 1 or 2, wherein in the surface treatment step, the pigment coating layer is subjected to a surface treatment under a condition of 6 nips or more using a soft calender composed of a metal roll and an elastic roll. The method according to any one of claims 1 to 3, wherein a specific scattering coefficient / density which is a ratio of a specific scattering coefficient (cm ² / g) and a density (g / cm ³ ) of the coated paper is 400 or more.