JP5462572B2 - 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. In particular, the present invention relates to a low density printing coated paper having excellent whiteness, opacity, and surface strength, and relates to a production method that can be efficiently produced with good operability. is there.

  In recent years, bulkiness is one of the important qualities required for paper products. Along with the recent increase in environmental protection, paper products that have been made lighter in weight while maintaining the thickness of paper, that is, paper products that have been reduced in density, are being used in order to effectively use paper pulp made from forest resources. Requested by users.

  Examples of a method for obtaining a low-density coated paper include a method in which the nip pressure of the calendar is lowered when the surface treatment is not performed or when the surface treatment is performed. In the coated paper for printing, after pigment coating with various coating apparatuses, surface treatment by a calendar is performed to give gloss and smoothness, and the product is commercialized. At this time, the density can be reduced to a certain degree by calendaring with a low nip pressure. However, if the nip pressure is too low, sufficient gloss and smoothness cannot be imparted to the surface of the coated paper, and the image reproducibility of the printed matter decreases.

  As another method for obtaining a low-density coated paper, use of mechanical pulp is considered from the raw material side. In general, refiner mechanical that refines timber with a refiner, such as Grandwood Pulp (GP), which refines wood with a grinder, compared with chemical pulp obtained by extracting lignin, a reinforcing material in wood fibers, with chemicals Mechanical pulp such as pulp (RMP) or thermomechanical pulp (TMP) has a high specific scattering coefficient and is effective in reducing the density because the fibers are rigid. However, in general, when using hardwood-derived mechanical pulp, compared to the case of using softwood-derived mechanical pulp, it is said that the strength is low and troubles such as paper breakage are likely to occur. Hardwood mechanical pulp is not commonly used in the field of coated paper for printing. Moreover, since the mechanical pulp derived from a conifer is manufactured from a conifer having a high lignin content, it is difficult to produce a pulp having a high whiteness, and there is a problem in producing a paper product that requires a high whiteness.

  As another method for obtaining low-density paper, from the chemical aspect, a bulking agent comprising a polyhydric alcohol and a fatty acid ester is added to hydrophobize the pulp fiber surface to produce a low-density paper. It has been proposed (see Patent Document 1). However, this method requires the use of expensive chemicals, resulting in increased costs and reduced paper strength.

  By the way, 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 mails. Although these commercial printed materials do not have a high commercial value of the printed materials themselves, it is important that the purpose is achieved as an advertising medium. Therefore, a coated paper having a low cost but a good printed finish is required.

  Under these circumstances, in order to produce coated paper efficiently at low cost, on-machine coaters in which a paper machine and a coating machine are integrated are widely used. There are mainly film transfer method and blade coating method. The film transfer method is a coating method in which the film of the coating solution is weighed on the applicator and transferred to the base paper to provide a coating layer. Compared with the blade coating method, the load applied to the base paper during coating Is small, so there is an advantage that there are few paper-cutting troubles during operation.

  However, the film transfer method has a problem that an operation problem called boiling occurs during high-speed operation. The transfer roll coater, which is a film transfer coating method, is a coater in which a coating solution is supplied onto the nip between an inner roll arranged outside the applicator roll and an outer roll outside the applicator roll. Since both the rolls are always rotating, the coating liquid may jump up when the coating liquid viscosity is high, resulting in a large operational problem. This is boiling.

  As a method for suppressing boiling, a method of lowering the viscosity by lowering the solid content concentration of the coating liquid is generally used. However, simply lowering the solid content concentration increases the permeability of the coating liquid to the base paper, reducing the amount of adhesive on the coated paper surface, thereby reducing the surface strength of the coated paper. There is a problem of doing. In particular, a base paper using a pulp such as the above mechanical pulp has a low density, and therefore has a high degree of penetration with respect to chemical pulp at the same drainage. When the surface strength is reduced due to the penetration of the coating liquid, paper slippage occurs on the blanket during offset printing, and the running performance is significantly reduced.

  As another method for suppressing boiling, there is a method of lowering the viscosity by lowering the binder content in the coating liquid. However, when the binder content is lowered, the surface strength of the coated paper is lowered. In particular, in a base paper using pulp such as the above mechanical pulp, since the degree of penetration is large, the binder component penetrates remarkably, and the surface strength is significantly reduced.

  As a method for compensating for the insufficient strength of the coated paper, there is a method of applying a clear coating solution mainly composed of starch or the like before providing a coating layer mainly composed of a pigment. Applying a clear coating solution to a base paper before pigment coating is called a size press. The coating equipment used at this time is a rod metering size press coater, blade metering size press coater, gate. A roll coater such as a roll coater or a 2-roll size press is mainly cited. However, the roll coater is a system in which the base paper is sandwiched between two applicator rolls for coating, and particularly when manufacturing at a high speed of 1000 m / min. It becomes a big problem in operation. In particular, in a low basis weight product, an on-machine coater that continuously performs from base paper to coating and calendering has a large adverse effect, resulting in a significant reduction in production efficiency. Also, in terms of quality, the base paper surface is cured by clear coating, so that minute irregularities are hardly crushed in the surface treatment step after pigment coating, and smoothness due to the surface treatment is deteriorated. Therefore, there is a method of applying a pigment to the base paper instead of the clear coating. However, like the size press, the operability and smoothness are deteriorated.

As another method for suppressing the boiling, a method of making a difference between the rotational speeds of the inner roll and the outer roll is known. For example, a method has been proposed in which the boiling phenomenon is improved by coating within a range where the peripheral speed ratio of the inner and outer rolls to the film transfer type transfer roll is 50 to 80% (see Patent Document 2). Further, there is a method for improving the boiling phenomenon by adjusting the peripheral speed of the outer roll within a range of 45% or less and 20% or more of the coating speed and the peripheral speed of the inner roll within a range of 85% or less and 60% or more of the coating speed. It has been proposed (see Patent Document 3). However, in these methods of changing the peripheral speed, since the thickness of the liquid film formed on the transfer roll is reduced, the fundamental problem that the amount of paint transferred to the base paper, that is, the coating amount is reduced. There is. If the coating amount is not more than a certain level, the optical suitability required for the coated paper for printing and the printing suitability including smoothness cannot be satisfied.
JP 11-350380 A JP 11-050392 A JP 2002-105893 A

  In view of the situation as described above, an object of the present invention is a method for producing a coated paper for printing having low whiteness, high whiteness, opacity, excellent surface strength, and good operability. Is to provide.

  As a result of intensive studies on the above problems, the present inventors used 10 to 80% by weight, preferably 40 to 80% by weight, of a specific chemithermomechanical pulp derived from hardwood as the pulp in the base paper. By applying a coating solution having an adhesive content of 10 to 40% by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the pigment by a film transfer method, low density and high whiteness, It has been found that a coated paper for printing that has transparency and excellent surface strength and does not cause paper smearing during printing can be produced without deteriorating operability, and has led to the completion of the present invention.

  In one aspect, the present invention is a coated coated paper for printing and a method for producing the same. In the present invention, 10 to 80% by weight, preferably 40 to 80% by weight of the pulp in the base paper is made from a base paper that is a hardwood-derived mechanical pulp, and the content of the adhesive in the coating liquid is 100 parts by weight of the pigment. It is a manufacturing method of the coating paper for printing which coats the coating liquid characterized by being 10-40 weight% with respect to 20 to 40 weight part with a film transfer system. In a preferred embodiment of the present invention, as the hardwood-derived mechanical pulp, Chemi-thermo-mechanical pulp (CTMP), when measured in accordance with JIS P8207, 95% by weight or more of the fiber passes through the 24 mesh of the screen. CTMP is used in which 10% by weight or more, preferably 20% by weight or more of the fibers do not pass through the 42 mesh of the screen. By using such hardwood mechanical pulp, deterioration of smoothness and roughening (swelling of fibers) can be suppressed, and a coated paper for printing having excellent printability can be efficiently produced.

  In a preferred embodiment of the present invention, mechanical pulp derived from the genus Eucalyptus having a bulk weight of 450 kg / cm 3 or more is used as the hardwood-derived mechanical pulp. By using such hardwood mechanical pulp, the bulky structure of the base paper can be maintained, and a coated paper for printing excellent in opacity can be produced.

  Furthermore, in a preferred embodiment, the production method of the present invention can be operated at a high speed of preferably 1100 m / min or more, more preferably 1200 m / min or more. According to the present invention, troubles such as paper breaks and boiling can be suppressed and stable operation becomes possible. Therefore, the present invention is suitable for high-speed operation where operability problems are important.

  In another preferred embodiment, the present invention is a coated paper for printing, wherein 10 to 80% by weight, preferably 40 to 80% by weight of the pulp in the base paper is hardwood-derived mechanical pulp, and adhesion in the coating layer It is a coated paper for printing in which the content of the agent is 10 to 40% by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the pigment. The coated paper for printing of the present invention can be produced by the production method of the present invention.

Moreover, although not limited to the following, this invention includes the following invention.
(1) When measured in accordance with JIS P8207, 95% by weight or more of a 24 mesh screen and 10% by weight or more of a hardwood chemisermomechanical pulp that does not pass a 42 mesh screen with respect to the total pulp. For printing, a coating liquid containing 10 to 40 parts by weight of an adhesive with respect to 100 parts by weight of a pigment is coated on a base paper obtained by making a paper material containing 10 to 80% by weight with a film transfer method Manufacturing method of coated paper.
(2) The method for producing a coated paper for printing according to (1), wherein the hardwood-derived mechanical pulp is derived from the genus Eucalyptus and has a bulk weight of 450 kg / m ³ or more.
(3) In a printing coated paper in which a coating layer containing a pigment and an adhesive is provided on a base paper, when measured in accordance with JIS P8207, 95% by weight or more passes through a 24 mesh screen, It is a base paper containing 10 to 80% by weight of hardwood chemisermomechanical pulp that does not pass 10% by weight or more through a 42 mesh screen, and the adhesive in the coating layer is 100 parts by weight of pigment. A coated paper for printing containing 10 to 40 parts by weight of an adhesive.

  According to the present invention, it is possible to efficiently produce a coated paper for printing having low whiteness, high whiteness and opacity, and excellent surface strength. In particular, according to the present invention, papermaking, coating, and surface treatment can be continuously performed on-machine, and stable operation is possible even at a high speed of 1000 m / min or more, preferably 1100 m / min or more. It is.

The present invention relates to a coated paper for printing and a method for producing the same. In the coated paper of the present invention, the basis weight is not particularly limited, but it has a feature of high opacity, and therefore has a particularly high advantage in a relatively low basis weight region. Specifically, coated printing paper of the present invention preferably has a basis weight of 30~55g / ^{m 2,} more preferably 30 to 50 g / ^{m 2,} more preferably say 35~47g / ^{m 2} Has a basis weight. The density of the coated paper for printing of the present invention is preferably 0.60 to 0.75 g / m ³ , more preferably 0.60 to 0.70 g / m ³ .

  In addition, the printing coated paper of the present invention can correspond to various printing methods, and is preferably used for offset printing coated paper, relief printing coated paper, gravure printing coated paper, and the like. Can do. Since the coated paper for printing of the present invention has improved surface strength and blister resistance, it can be particularly suitably used for offset printing applications.

  In the method for producing a coated paper for printing according to the present invention, a base paper is made by making a paper stock containing 10 to 80% by weight, preferably 40 to 80% by weight, of a pulp in the base paper containing a hardwood-derived mechanical pulp. And coating the coating liquid containing the pigment and adhesive with a film transfer type on-machine coater to provide a coating layer, and these can be performed continuously on-machine. It is. In particular, since the production method of the present invention has high operability, when the present invention is applied when paper processing, coating, and if necessary, surface treatment is continuously performed on-machine, production efficiency is high and extremely advantageous. . In the on-machine high-speed operation, the operability is remarkably lowered due to a paper-cutting trouble. However, the manufacturing method of the present invention is less likely to cause a paper-cutting trouble, which is advantageous for the on-machine high-speed operation.

  In the production method of the present invention, the operation speed is not particularly limited, but the present invention has high superiority and is suitable for operations at 1000 m / min or more. In particular, it is preferable to operate at a high speed of 1100 m / min or more, and 1200 m / min or more is more preferable. .

Papermaking The method for producing a coated paper for printing according to the present invention is to obtain a base paper by papermaking a stock containing 10 to 80% by weight, preferably 40 to 80% by weight, of a pulp derived from hardwood. Moreover, the coated paper for printing of this invention is 10-80 weight% of the pulp which comprises a base paper, Preferably 40-80 weight% is a hardwood-derived mechanical pulp.

  The hardwood mechanical pulp used for the coated base paper of the present invention is not particularly limited as long as it is a mechanical pulp made from hardwood, and it is not limited to Grandwood Pulp (GP), Refiner Grandwood Pulp (RGP), Thermomechanical Pulp (TMP). ), Chemi-thermomechanical pulp (CTMP), alkali hydrogen peroxide mechanical pulp (APMP), alkali hydrogen peroxide thermomechanical pulp (APTMP), and the like. In particular, TMP is preferably used in the present invention in terms of obtaining bulkiness, high opacity, and high whiteness, and among these, CTMP, APMP, APTMP, particularly CTMP is preferably used.

  In the present invention, the tree species of the broad-leaved mechanical pulp is not particularly limited as long as it is a broad-leaved tree. For example, the genus Eucalyptus can be suitably used. Fastigata or the like can be cited as a preferred example. In particular, in the present invention, a mechanical pulp derived from the genus Eucalyptus is preferable because the bulkiness of the fiber is easily maintained and the opacity of the paper can be improved. However, considering availability and quality, Eucalyptus Eurograndis and Eucalyptus Globulus are particularly preferable. Is particularly preferred.

Moreover, it is preferable that the hardwood mechanical pulp used in the present invention is derived from a hardwood material having a bulk weight of 450 kg / m ³ or more. Such a pulp can maintain a bulky structure because the fiber lumen (lumen) is hard to collapse and is rigid. Mechanical pulp produced from hardwood used in the present invention include those which density of Handsheets made from this pulp is 0.45 g / cm ³ or less, and more preferable to be 0.35 g / cm ³ or less .

  The fiber length of the hardwood mechanical pulp used in the present invention is not particularly limited, but from the viewpoint of the smoothness, strength, roughening, etc. of the product, the proportion of fibers passing through a 24 mesh screen measured according to JIS P8207 is It is preferably 95% by weight or more, and more preferably 97% by weight or more. In general, when mechanical pulp is used, deterioration of smoothness due to rigid and large fibers and roughening (fiber swell) that occurs at the time of pigment coating and printing tend to occur, but pass through a 24 mesh screen as described above. By using hardwood mechanical pulp with a high fiber ratio, it is possible to obtain coated paper for printing that has excellent smoothness and opacity, printability such as roughening, especially excellent image reproducibility and showthrough. it can.

  In general, thermomechanical pulp (TMP) of mechanical pulp is characterized by a relatively long fiber length, and a typical thermomechanical pulp has fibers passing through 24 mesh when measured according to JIS P8207. 80% by weight or less. Therefore, even if a typical thermomechanical pulp is used for printing coated paper, the manufactured sheet tends to have low smoothness and image reproducibility during printing tends to be low. Further, when pigment is applied, or when printing is performed with a heat-set type offset rotary press, roughening in which fibers float on the coated paper surface is likely to occur.

  In addition, since the deterioration of operability due to the use of mechanical pulp can be suppressed to the minimum without impairing good smoothness expression, the hardwood mechanical pulp of the present invention passes through a 42 mesh screen measured in accordance with JIS P8207. The ratio of the fibers not to be used is 10% by weight or more, preferably 15% by weight or more, more preferably 20% by weight or more, and further preferably 25% by weight or more. By using such hardwood mechanical pulp, strength reduction can be minimized and paper breakage trouble can be suppressed, and operability at on-machine coater and high speed is excellent.

  Here, when measured according to JIS P8207, typical groundwood pulp (GP) has 90% or more of fibers passing through 24 mesh, and can obtain good smoothness. There are few fibers that do not pass. That is, since a typical GP has a relatively large amount of short fibers, the manufactured sheet has low strength and tends to cause a decrease in operability due to paper breakage or the like.

  The use amount of the hardwood mechanical pulp of the present invention is 10 to 80% by weight, preferably 40 to 80% by weight, more preferably 50 to 70% by weight in the total pulp. When the amount used is less than 10% by weight, the effect of the invention is reduced, and when the amount used exceeds 80% by weight, the operability is deteriorated due to strength reduction, and roughening or the like easily occurs and the surface property is also lowered. .

Hardwood CTMP
As described above, in the present invention, CTMP is used as the hardwood mechanical pulp, but the production method is not particularly limited, and the hardwood CTMP obtained by a conventional method can be used. Here, chemithermomechanical pulp (CTMP) is a kind of TMP, and is a pulp produced after dipping a wood chip in a chemical.

  For example, in a preferred embodiment of the present invention, as CTMP, pulp obtained by a manufacturing process including a chip pretreatment process using sodium sulfite or the like, a defibrating process by primary refining, and a beating process by secondary refining may be used. it can. The mechanical pulp manufactured through such a manufacturing process is preferable because it makes the paper highly opaque and the strength of the paper is high. For example, as a pretreatment of the chip with sodium sulfite, an impregnation treatment with an aqueous sodium sulfite solution can be performed. In this case, the chip is compressed, and the chip is immersed in the sodium sulfite aqueous solution after being compressed or after being compressed. It can be impregnated with sodium sulfite while releasing and expanding the chip. In this step, the chip is preferably sufficiently impregnated with an aqueous sodium sulfite solution, and the compression ratio is preferably 4: 1 to 16: 1. When the compression ratio is lower than 4: 1, the restoring force of the chip is weak, and the penetration of the sodium sulfite aqueous solution into the chip becomes insufficient. On the other hand, it is impractical for the compression ratio to exceed 16: 1. It is. Here, the compression ratio is defined as the volume before compression: the volume after compression. In order to complete the impregnation with the aqueous sodium sulfite solution, a surge bin can be provided after the plex screw or the impressor.

  In a preferred embodiment, the addition rate of sodium sulfite is 0.5 to 2.0% by weight based on the absolutely dry chip. Depending on the pH of the aqueous sodium sulfite solution, the average fiber length after primary refining is slightly different. The initial pH of the sodium sulfite aqueous solution to be impregnated is 4.5 to 9.5, preferably 7.0 to 9.5. For this pH adjustment, sulfuric acid or sodium hydroxide is used. In this range, the higher the pH, the greater the long fiber content and the longer the average fiber length. If the pH exceeds 9.5, the level is turned off, resulting in poor chemical efficiency. A pH of less than 4.5 is not preferable because there is a risk of metal corrosion of the equipment.

  The chip impregnated with the sodium sulfite aqueous solution is preferably preheated (preheated) prior to the primary refining for the purpose of improving defibration. The temperature in this case is preferably 100 to 135 ° C.

  After the pretreatment process, the chip is subjected to a defibrating process by primary refining. In this step, a pressure refining device can be used, and other conditions are defibrated to pulp fibers by a known method except for a refiner plate (refiner segment). As the refining device, a single disc refiner, a conical disc refiner, a double disc refiner, a twin disc refiner, or the like can be used. However, the higher the concentration during defibration, the more fibrillation of the pulp fibers proceeds and a high quality pulp can be obtained. Therefore, a single disc refiner is preferably used. The concentration of chips during the refining process is preferably about 20 to 60% by solid weight, and the processing temperature is preferably 100 to 180 ° C. More preferably, it is 120-135 degreeC.

  The defibrated pulp is then sent to the secondary refiner under normal pressure and beaten to the target freeness. In the beating step by secondary refining, a known refining apparatus can be used and refined under known conditions, and the pulp freeness is reduced to a desired level. This step is performed under normal pressure, and it is preferable to use a general normal pressure type apparatus as the refining apparatus, and the concentration can be carried out at about 4 to 60%. The secondary refiner may be a single stage or a plurality of stages.

  After the secondary refining, a bleaching treatment may be performed as necessary. As a bleaching agent, a known bleaching agent used in the production of BCTMP can be used, and there is no particular limitation. Preferably, a peroxide such as hydrogen peroxide is used. In this case, a chelating agent such as ethylenediaminetetraacetate (EDTA) can be used in combination for the purpose of preventing the decomposition of the peroxide by metal ions. These treatments can be performed under known conditions. The hardwood mechanical pulp of the present invention preferably has a Canadian standard freeness of 50 to 350 ml.

  In the present invention, as pulp of base paper, in addition to the above-mentioned hardwood mechanical pulp, chemical pulp (softwood bleached kraft pulp (NBKP) or unbleached kraft pulp (NUKP), hardwood bleached kraft pulp (LBKP) or unbleached kraft Pulp (LUKP), etc., softwood mechanical pulp (groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), etc.), deinked pulp (DIP), etc. They can be used alone or mixed at any ratio.

  In the present invention, a known filler can be arbitrarily used as a filler for the base paper. For example, white carbon, talc, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin , Amorphous produced by neutralization of dermikaolin, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate Inorganic fillers such as silica and organic fillers such as urea-formalin resin, melamine resin, polystyrene resin, and phenol resin can be used alone or in combination. Among these, 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 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, dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  In the present invention, the base paper can be produced by a known paper machine such as a long net paper machine, a gap former, or a hybrid former (on-top former). The papermaking conditions are not particularly specified, and the pH during papermaking may be acidic, neutral or alkaline. In order to improve the surface strength, the base paper can be coated with a clear coating liquid mainly composed of a water-soluble polymer such as starch (size press) to obtain a coated base paper.

In the present invention, the basis weight of the coated base paper can be set while balancing the coating amount of the coating layer containing the following pigment and adhesive. For example, the basis weight of the base paper is 20 to 50 g / m. It can be about ² . In the present invention, it is preferable to smooth the base paper in advance with an on-line soft calender, an on-line chilled calender or the like in order to make the coating layer after coating uniform.

Coating The method for producing a coated paper for printing of the present invention is a method for coating a coating liquid containing a pigment and an adhesive on the coated base paper obtained as described above. Therefore, the printing coated paper of the present invention has a pigment coating layer on the base paper.

The coating liquid used in the present invention includes a pigment and an adhesive. 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, 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 and other inorganic pigments Organic pigments such as plastic pigments, organic / inorganic composite pigments, and the like can be used. These pigments can be used alone or in admixture of two or more.
As a pigment for pigment coating of the present invention, calcium carbonate obtained by wet pulverization of light calcium carbonate of spindle-shaped calcite crystal, which has an average particle size (measured with an X-ray transmission particle size distribution analyzer) d ₅₀ ) is 0.1 to 0.5 μm, the BET specific surface area is in the range of 10 to 30 m ² / g, and is measured by an X-ray transmission type particle size distribution analyzer:
Sharpness = (d ₃₀ / d ₇₀ ) × 100
[Wherein d ₃₀ is a particle size of 30% by weight and d ₇₀ is a particle size of 70% by weight]
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.

Further, when using the above calcium carbonate in the present invention, 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. The average particle diameter (d ₅₀ ) measured with the previous light calcium carbonate X-ray transmission particle size distribution analyzer is 1.4 to 3.0 μm, and the BET specific surface area is 4 to 12 m ² / g. More preferred. Furthermore, when using said calcium carbonate in this invention, it is preferable to perform a wet grinding using a multipass-type grinder. The blending amount of the pulverized calcium carbonate is preferably 20 to 60 parts by weight and more preferably 30 to 50 parts by weight per 100 parts by weight of the pigment.

  There is no restriction | limiting in particular about the adhesive agent (binder) used by this invention, The adhesive agent conventionally used for coated paper can be used. For example, as preferred adhesives, various copolymers such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, and polyvinyl alcohol and maleic anhydride copolymers. Synthetic adhesives such as acrylic acid / methyl methacrylate copolymer; Proteins such as casein, soybean protein, synthetic protein; Etherification of oxidized starch, positive starch, urea phosphated starch, hydroxyethyl etherified starch, etc. One or more ordinary adhesives for coated paper such as starches and starches such as dextrin; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and hydroxymethylcellulose can be appropriately selected and used.

  The amount of the adhesive used in the present invention is preferably 10 to 40 parts by weight, preferably 20 to 40 parts by weight, preferably 25 to 35 parts by weight with respect to 100 parts by weight of the pigment, from the viewpoints of printability and coating suitability. More preferred are parts by weight. This range is preferable when the total amount of the adhesive exceeds 40 parts by weight, and the viscosity of the coating becomes high, and operation trouble such as boiling is likely to occur when coating by the film transfer method. This is because it is difficult to obtain sufficient surface strength when coated on a base paper by a film transfer method.

  In the coating liquid of the present invention, in addition to the pigment and the adhesive, if necessary, a dispersant, a thickener, a water retention agent, an antifoaming agent, a water resistant agent, a colorant, etc. Various auxiliaries blended in the pigment can be used as appropriate.

  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 40 to 55 weight%, More preferably, it is 45 to 55 weight%. The viscosity of the coating solution is preferably in the range of 500 to 1000 mPa · s as measured by the B-type viscosity measured at 60 rpm.

  In the present invention, using a film transfer type coating apparatus such as a gate roll coater, a rod metering size press coater, a blade metering size press coater or the like, a single layer or two or more layers of a paint containing a pigment and an adhesive is used. Is coated on one or both sides to provide a pigment coating layer. Film transfer type coating devices such as gate roll coaters, rod metering size press coaters, blade metering size press coaters, etc. are used to transfer the measured coating solution on the applicator roll to the base paper to provide a coating layer. Compared to the blade coating method, the load applied to the base paper at the time of coating is small, so that there is an advantage that there are few paper breakage troubles at the time of operation. Further, in the present invention, by adjusting the viscosity of the paint to an appropriate range, it is possible to suppress the boiling that becomes a problem in coating by a film transfer type coating apparatus such as a gate roll coater, and to improve operability. be able to. In the present invention, the coating can be performed by an on-machine or an off-machine coater. However, since the production method of the present invention is excellent in operability, particularly at high speed, the operation speed is 1000 m / min or more. It is particularly suitable and has great advantages when used with an on-machine coater.

The coating amount of the coating liquid to be applied by the coating method is preferably 3 to 10 g / m ^{2 and} more preferably ⁴ to 8 g / m ² per side. When the coating amount is within this range, the coating layer can sufficiently cover the base paper, and the printability of the coated paper becomes excellent.

  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 In the present invention, the paper provided with the coating layer as described above is subjected to a surface treatment as necessary. In a preferred embodiment, the coated paper for printing of the present invention can be subjected to surface treatment without calendaring or with a calendar such as a super calender or a hot soft nip calender. By the surface treatment, the smoothness and glossiness of the coated paper can be improved.

  Thus, according to the present invention, hardwood-derived mechanical pulp is blended, and the content of the adhesive in the coating liquid is 10 to 40 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the pigment. By coating the coating liquid onto the base paper using the film transfer method, it is possible to efficiently produce a coated paper for printing having low whiteness, high whiteness and opacity, and excellent surface strength. it can. In particular, according to the present invention, stable operation can be performed at a high speed of 1100 m / min or more with an on-machine coater for papermaking and coating of base paper.

EXAMPLES Hereinafter, although an Example of this invention is given and this invention is demonstrated further in detail, this invention is not limited 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.
<Evaluation method>
(1) Density: Measured according to JIS P8118.
(2) Whiteness: Measured according to JIS P 8123.
(3) Opacity: Measured according to JIS P 8138.
(4) Surface strength: Using a RI-I type printing machine (Ming Seisakusho), using ink for offset printing (manufactured by Toyo Ink Manufacturing Co., Ltd .: TK mark V617), printing on one side with a constant ink amount of 0.4 cc. The degree of smearing on the coated paper surface was evaluated. The case where no smear occurred was marked with ◎, the case where scarcely occurred was marked with ◯, the matter where it occurred was marked with △, and the mark with marked occurrence was marked with ×.
(5) Blister resistance: Using a RI-I type printer (Ming Seisakusho), using offset printing ink (manufactured by Toyo Ink Manufacturing Co., Ltd .: TK Mark V617), printing on both sides with a constant ink amount of 0.8 cc Then, after conditioning all day and night (23 ° C., 50% RH), the test piece was immersed in a constant temperature oil bath set at a temperature of 140 ° C., and the occurrence of blisters was visually determined. The case where no blisters occurred was marked with ◎, the case where almost no blisters occurred, the case where the blisters occurred, Δ, and the case where the blisters occurred markedly.
(6) Back-through: 20,000 copies were printed in the order of black, indigo, red, yellow, using an offset web offset press (4 colors) in the order of black, indigo, red, yellow. After that, the condition of the back-through was visually evaluated. The evaluation criteria are as follows.
◎ = Very good, ○ = Good, Δ = Slightly inferior, X = Inferior (7) High-speed operability: The operability was evaluated in terms of the frequency of sheet breakage and the degree of boiling during coating. The case where almost no paper breakage or boiling occurred was rated as ◯, the case where slight paper breakage occurred as Δ, and the case where remarkable paper breakage occurred as x.

<Manufacture of coated paper for printing>
[Example 1]
As hardwood mechanical pulp, using eucalyptus globulus chips with a bulk weight of 580 kg / m ³ as a raw material, using sodium sulfite according to the method described in the specification, 100% of the fiber is 24 mesh of screen as measured according to JIS P8207. A hardwood chemisermomechanical pulp (CTMP: handsheet density 0.37 g / cm ³ , Canadian standard freeness 128 ml) prepared so that 20% of the fiber did not pass through 42 mesh of the screen was used. The CTMP handsheet was prepared at a basis weight of 60 g / m ² based on JIS P 8222: 1998, and the thickness and basis weight of the prepared handsheet were actually measured. Density was calculated. For other pulps as well, a handsheet having a basis weight of 60 g / m ² was prepared based on JIS P 8222: 1998, and the sheet density was measured.

A pulp slurry containing 50 parts of this hardwood CTMP, 35 parts of hardwood kraft pulp (LBKP) and 15 parts of softwood kraft pulp (NBKP) was prepared, 12 parts of light calcium carbonate as a filler, and an internal paper strength agent. A paper stock was prepared by adding 0.5% of a cationic paper strength enhancer to the pulp. Using this stock, paper was made with an on-top former at a paper making speed of 1200 m / min to obtain a base paper having a basis weight of 37 g / m ² .

Next, 20 parts of oxidized starch and carboxy modified as an adhesive with respect to 100 parts of pigment containing 90 parts of heavy calcium carbonate (FMT-90, manufactured by Phimatech) and 10 parts of kaolin (Hydragloss, manufactured by Imerys) 15 parts of styrene / butadiene copolymer latex is blended, and 0.05 part of polyacrylic soda is added as a dispersant to prepare a coating solution with a solid content of 50%. Using a gate roll coater, base paper A pigment was coated on both sides so as to be 5.0 g / m ² per side and dried to obtain a coated paper having a basis weight of 47 g / m ² .
Subsequently, surface treatment was performed using a soft calender to obtain a coated paper for printing. Since papermaking, coating and surface treatment were performed continuously, not only the papermaking speed but also the coating speed and surface treatment speed were 1200 m / min.

[Example 2]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1 except that the pulp composition of the base paper was changed to 70 parts of hardwood chemisermomechanical pulp, 15 parts of hardwood kraft pulp, and 15 parts of softwood kraft pulp. .

[Example 3]
In Example 1, the content of the adhesive in the coating solution was changed to 25 parts in total (14 parts of oxidized starch and 11 parts of carboxy-modified styrene / butadiene copolymer latex) with respect to 100 parts of pigment. A coated paper for printing was obtained in the same manner.

[Example 4]
Instead of the hardwood chemisermomechanical pulp of Example 1, 98% of the fibers passed through the 24 mesh of the screen and 33% of the fibers did not pass through the 42 mesh of the screen as measured according to JIS P8207. A coated paper for printing was obtained in the same manner as in Example 1 except that hardwood chemithermomechanical pulp (CTMP: handmade sheet density 0.33 g / cm ³ , Canadian standard freeness 249 ml) was used.

[Example 5]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1 except that the following pulverized light calcium carbonate was used instead of heavy 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) was made a solid content concentration 20%, By adding 1.5 parts by weight of a polyacrylate dispersant to form a slurry, and then performing wet grinding using SC Mill Long (manufactured by Mitsui Mining Co., Ltd .: SC Mill 100), which is a multi-pass mill. The resulting calcium carbonate was used as a pigment.

The light calcium carbonate after wet pulverization has an average particle diameter (d ₅₀ ) measured by an X-ray transmission type particle size distribution analyzer of 0.38 μm, a BET specific surface area of 22.5 m ² / g, The following formula measured with a transmission type particle size distribution analyzer (Cedigraph 5100, manufactured by Micromeritics):
Sharpness = (d ₃₀ / d ₇₀ ) × 100
[Wherein d ₃₀ is a particle size of 30% by weight and d ₇₀ is a particle size of 70% by weight]
The sharpness of the particle size distribution represented by 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 average particle diameter (d ₅₀ ) measured was 2.2 μm, and the BET specific surface area was 5.9 m ² / g.

[Example 6]
Instead of the hardwood mechanical pulp of Example 1, 100% of the fibers passed through the 24 mesh of the screen as measured according to JIS P8207 using aspen with a bulk weight of 380 kg / m ³ , and 26% of the fibers of the screen Coating for printing was carried out in the same manner as in Example 1 except that hardwood chemisermomechanical pulp (CTMP: handmade sheet density 0.41 g / cm ³ , Canadian standard freeness 130 ml) prepared so as not to pass 42 mesh was used. Obtained paper.

[Comparative Example 1]
In Example 1, a coated paper for printing was obtained in the same manner as in Example 1 except that the pulp composition of the base paper was changed to 100 parts of hardwood chemisermomechanical pulp.

[Comparative Example 2]
In Example 1, the content of the adhesive in the coating solution was changed to 8 parts in total with respect to 100 parts of pigment (5 parts of oxidized starch, 3 parts of carboxy-modified styrene / butadiene copolymer latex). A coated paper for printing was obtained in the same manner.

[Comparative Example 3]
Example 1 is the same as Example 1 except that the content of the adhesive in the coating solution is changed to 51 parts in total (30 parts of oxidized starch and 21 parts of carboxy-modified styrene / butadiene copolymer latex) with respect to 100 parts of pigment. A coated paper for printing was obtained in the same manner.

[Comparative Example 4]
In Example 1, 50 parts of thermomechanical pulp (TMP: handmade sheet density 0.48 g / cm ³ , Canadian standard freeness 90 ml) produced by using a softwood (radiata pine) chip as a base paper pulp blend, hardwood craft A coated paper for printing was obtained in the same manner as in Example 1 except for changing to 35 parts of pulp and 15 parts of softwood kraft pulp.

[Comparative Example 5]
In Example 1, 50 parts of groundwood pulp (GP: handmade sheet density 0.48 g / cm ³ , Canadian standard freeness 64 ml) manufactured from Akamatsu, 35 parts of hardwood kraft pulp, 15 parts of conifer craft pulp A coated paper for printing was obtained in the same manner as in Example 1 except for the change.

[Comparative Example 6]
In Example 1, 100% of the fibers passed through the 24 mesh of the screen as measured in accordance with JIS P8207 using aspen with a Runckel ratio of 4.1 and a bulk weight of 380 kg / m ³ as the hardwood mechanical pulp. Example 1 except that hardwood chemisermo mechanical pulp (CTMP: handsheet density 0.47 g / cm ³ , Canadian standard freeness 104 ml) prepared so that 8% does not pass through 42 mesh of the screen. The coated paper for printing was obtained by the method.

  Table 1 shows the evaluation results. As is clear from Table 1, 10 to 80% by weight of mechanical pulp derived from hardwood is blended in the raw material, and a pigment coating layer is provided by a film transfer method, thereby providing low density, high whiteness, and high opacity. Furthermore, it was possible to produce a coated paper for printing having printing quality such as excellent surface strength and blister resistance with good operability.

Claims (9)

Wide Haci chemithermomechanical pulp base paper papermaking using a paper stock comprising at 10 to 80 wt% of the total pulp, coating containing from 20 to 40 parts by weight of the adhesive per 100 parts by weight of the pigment A method for producing a coated paper for printing having a basis weight of 30 to 55 g / m ² , comprising coating a liquid by a film transfer method ,
The hardwood chemithermomechanical pulp is derived from the genus Eucalyptus having a bulk weight of 450 kg / m ³ or more, and when measured according to JIS P8207, 95% by weight or more passes through a 24 mesh screen, and 42 mesh The above method, wherein 10% by weight or more does not pass through the screen . The method according to claim 1, wherein the coating speed is 1000 m / min or more. The coating amount is 3 to 10 g / m per side ² The method according to claim 1 or 2, wherein The method in any one of Claims 1-3 whose solid content concentration of a coating liquid is 40 to 55 weight%. The density of the coated paper is 0.60 to 0.75 g / m ³ The method according to claim 1, wherein Wide Haci chemithermomechanical pulp base paper that contains at 10 to 80 wt% of the total pulp, provided with a film transfer method a coated layer containing 20 to 40 parts by weight of the adhesive per 100 parts by weight of the pigment Further, a coated paper for printing having a basis weight of 30 to 55 g / m ² ,
The hardwood chemithermomechanical pulp is derived from the genus Eucalyptus having a bulk weight of 450 kg / m ³ or more, and when measured according to JIS P8207, 95% by weight or more passes through a 24 mesh screen, and 42 mesh The coated paper for printing, wherein 10% by weight or more does not pass through the screen . The coated paper for printing according to claim 6, wherein the coating speed is 1000 m / min or more. The coating amount is 3 to 10 g / m per side ² The coated paper for printing according to claim 6 or 7. The density of the coated paper is 0.60 to 0.75 g / m ³ The coated paper for printing according to any one of claims 6 to 8.