JP2009242998A - Coated paper and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper with even coating layers formed by roll coating in the state that the generation of mist is sufficiently controlled regardless of a high speed at 1,500 m/min or over, with good printing quality with small coating unevenness or foreign objects and defectiveness, and with good touching feeling maintained, and a method for manufacturing such coated paper efficiently and with high productivity. <P>SOLUTION: The coated paper has at least two coating layers formed on at least one side of a base paper and is manufactured from the base paper mainly composed of pulp fibers, and the ratio of the pulp fibers with the fiber length of 1 mm or more and the fiber width of 25 μm or more is 10% or less by weight of the entire pulp fibers and at least two layers of the coating layers that are in contact with each other are formed by roll coating at a speed of 1,500 m/min or over. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coated paper and a method for producing the same. More specifically, a uniform coating layer was formed by roll coating in a state where occurrence of mist (spattering of paint) was sufficiently suppressed, there were few coating unevenness and foreign matter defects, and excellent print quality. The present invention relates to a coated paper in which hand feeling is maintained, for example, a coated paper suitable for printing paper, publishing paper, book paper, and the like, and a method capable of producing the coated paper with excellent productivity.

  In recent years, with the progress of visualization, the demand for printing paper capable of high-definition printing in full color has increased, and in order to obtain high-definition printed matter, a coating liquid is applied to the front and / or back of the base paper, There is a growing need for coated paper with a coating layer.

  The coated paper can be used for art paper (A1 grade), coated paper (A2 grade), lightweight coated paper (depending on the amount of coating liquid applied, the degree of flattening of the coating layer surface, and the required quality. A3 grade) and finely coated paper. A1 grade coated paper is used for high-quality art books, magazine covers, cutouts, calendars, posters, catalogs, brochures, labels, cigarette packaging, etc. that require particularly high-definition printing. A3 grade coated paper and fine coated paper are used for commercial printing such as flyers. Further, due to recent environmental conservation efforts, papers are also required to be lighter, and commercial printed materials preferably use A3 grade coated paper or fine coated paper with a smaller coating amount.

  Examples of the coating method of the coating liquid for producing coated paper include a method using a blade coater, an air knife coater, a transfer roll coater, a rod metering size press coater, a curtain coater, etc. For coated paper and fine coated paper, high printability is required even with a small coating amount, so roll coating (rod metal ring size press coater or blade metal ring) has good surface coverage of the base paper. Coating with a size press coater) is suitably performed.

  For example, when manufacturing blade coated paper for printing with low basis weight, if blade coating is performed, the coated surface becomes highly smooth and the printing quality is improved, but there is a structural weakness that the blade is strongly pressed. Therefore, the frequency of sheet cutting is high and productivity is poor.

On the other hand, in the roll coating, in order to improve the covering of base paper fibers, it is desirable that the coating amount per one surface 8~11g / m ^2, When the coating amount 8 g / m ² or more, the applicator When transferring the coating material from the roll to the base paper, the coating material scatters without being smoothly peeled off from the applicator roll, and the problem of generation of so-called “mist” occurs that stains the coated surface. Mist is generated when the coating layer is transferred from the roll to the paper and the transferred paint is difficult to peel off from the roll. More specifically, when the paint is not peeled off from the roll, the paint pulled by both the roll and the paper is dissociated inside, and the fine paint components generated at that time are scattered as droplets. In order to suppress the occurrence of such mist, the coating amount must be adjusted to a small amount of 7 g / m ² or less per side so that the coating can be easily transferred from the roll to the paper. There is a problem that sufficient printability is not imparted to the paper. In particular, when coating is performed at a high speed of 1500 m / min or more, the generation of mist becomes remarkable, and it is extremely difficult to increase the coating amount in order to obtain sufficient printability.

  In particular, with matte and dull-tone coated papers with a blank gloss of 40% or less, there is a problem that blank paper gloss increases beyond 40% when flattening is performed in order to improve print quality. In order to improve the quality, it is essential to increase the coating amount. However, for the reasons described above, it is difficult to achieve both print quality and low blank glossiness.

  For example, Patent Document 1 discloses a coated paper for printing that employs a film transfer method and forms a coating layer at a coating speed of 1000 m / min or more and has good blank paper quality and printing surface quality. . However, in the coating paper for printing, since polyvinyl alcohol is contained in the paint, the viscosity of the paint is high. For example, when applied at a high speed of 1500 m / min or more, mist is likely to occur. Blank paper quality and print quality will deteriorate.

  Patent Documents 2 to 5 disclose a coated paper in which a gate roll method is adopted and a coating layer is formed at a coating speed of 1400 m / min or more, and a method for manufacturing the coated paper. However, in the case of the gate roll method, since it is necessary to form a liquid pool between the fountain roll and the metering roll, a splash of liquid called boiling occurs, and coating unevenness and foreign matter defects occur in the resulting coated paper. There is a problem that is likely to occur. Further, in the methods disclosed in Patent Documents 2 to 5, since it is necessary to increase the viscosity of the paint, the gate roll method is inappropriate for high-speed coating. Moreover, even if a system other than the gate roll system is employed in the techniques disclosed in Patent Documents 2 to 5, the coating concentration is still high, so that the generation of mist is not sufficiently suppressed, and the obtained coated paper is also coated. It will include work irregularities and foreign object defects.

  Furthermore, Patent Document 6 discloses a coated paper in which a coating layer is formed at a coating speed of 1400 m / min or more by combining roll coating and curtain coating. However, in the case of curtain coating, the coating film is cut, so-called “curtain break” occurs, and an uncoated portion is likely to be generated, and a uniform coating layer is formed as if it was applied only by roll coating. It is difficult to obtain coated paper stably.

Thus, in high-speed coating of 1500 m / min or more, coated paper, particularly mat, in which a uniform coating layer is formed, particularly by roll coating, without the generation of mist. The actual situation is that a coated paper having a good print quality and an excellent hand feeling has not yet been obtained in coated and dull coated paper.
JP 2006-249607 A JP 2002-105893 A JP-A-2005-240243 JP 2000-129593 A Japanese Patent Laid-Open No. 11-12981 JP 2007-177378 A

  The present invention has been made in view of the background art described above. For example, a uniform coating layer is formed by roll coating in a state in which generation of mist is sufficiently suppressed despite high speed of, for example, 1500 m / min or more. Provided with coated paper with good coating quality and excellent hand feeling in coated paper with less coating unevenness and foreign matter defects, especially matte and dull coated paper Another object of the present invention is to provide a method for efficiently producing the coated paper with excellent productivity.

That is, the present invention
A coated paper having at least two coating layers formed on at least one side of a base paper,
The base paper has pulp fibers as a main component, the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is 10% by mass or less of the total pulp fibers, and the coating layers are in contact with each other. And at least two coating layers formed on at least one side of the base paper, each of which is formed by roll coating at a speed of 1500 m / min or more. Production of coated paper in which a construction layer is formed, the base paper is composed mainly of pulp fibers, and the proportion of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is 10% by mass or less of the total pulp fibers. A method,
Of the coating layers, at least two coating layers in contact with each other are all formed by roll coating at a speed of 1500 m / min or more, and the present invention relates to a method for producing coated paper.

  Although the coated paper of the present invention has a high speed of 1500 m / min or more, a uniform coating layer is stably formed by roll coating in a state where generation of mist is sufficiently suppressed. In addition, the coating unevenness and the foreign matter defect are very small, the printing quality is excellent, and the excellent hand feeling is maintained. For example, it can be suitably used as printing paper, publishing paper, book paper and the like. Moreover, such a coated paper can be efficiently produced with excellent productivity by the production method of the present invention.

(Embodiment)
As described above, the coated paper of the present invention has at least two coated layers formed on at least one side of the base paper.

  First, the pulp fiber which is the main component of the base paper constituting the coated paper of the present invention will be described. As a raw material pulp which is a raw material of this pulp fiber, what is generally used for the papermaking use can be illustrated. The type of the raw material pulp is not particularly limited, but it is preferable to use a pulp made of hardwood with few long fibers from the viewpoint that mist generation can be more efficiently prevented. As a kind of raw material pulp, a chemical pulp, a mechanical pulp, a used paper pulp etc. are illustrated suitably, for example.

  Examples of the chemical pulp include unbleached softwood pulp (NUKP), unbleached hardwood pulp (LUKP), bleached softwood pulp (NBKP), bleached hardwood pulp (LBKP), and the like, one or two of these The above can be appropriately selected and used, but it is preferable to use LBKP or LUKP made of a broad-leaved tree having a shorter fiber length.

  In addition to the chemical pulp, for example, waste paper pulp made of waste paper that is friendly to the environment in recent years and can effectively use resources can be used. The waste paper pulp includes, for example, tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, corrugated waste paper, upper white waste paper, Kent waste paper, imitation waste paper, and ground ticket waste paper, etc. Examples include pulp, disaggregation / deinked waste paper pulp, disaggregation / deinking / bleached waste paper pulp, and the like, and one or more of these can be appropriately selected and used.

  Mechanical pulp can also be used, for example, stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), chemi-ground pulp (CGP), thermo-ground pulp (TGP), Grand pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP), etc. are exemplified, and one or more of these are appropriately selected and used. Can do.

  Here, even when any of the above raw material pulps is used, the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is 10% by mass or less, preferably 5% by mass or less of the total pulp fibers, It is one of the major features of the present invention that the adjustment is more preferably 3% by mass or less.

  A base paper made of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more in excess of 10% by mass has many protruding pulp fibers on the surface thereof. When roll coating is applied to the base paper in such a state, after the coating layer is transferred to the base paper, when peeling from the roll, the coating layer is cracked starting from the fibers protruding from the base paper surface, The coating liquid becomes mist and scatters.

  However, in the present invention, as described above, the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is adjusted to 10% by mass or less of the total pulp fibers. Thus, the coating layer is cracked, and the coating liquid is sufficiently suppressed from being scattered as mist. In the present invention, since it is preferable to reduce the presence of protruding pulp fibers as much as possible on the surface of the base paper, the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more in all pulp fibers is 0. The closer to mass%, the better.

  That is, in the present invention, for example, as described later, after providing a clear coating layer mainly composed of a water-soluble polymer compound as an undercoat coating layer, so as to be in contact with the undercoat coating layer, When a pigment coating layer mainly composed of a pigment and an adhesive is provided as the outermost layer, the pulp fiber protruding from the base paper surface is coated, and when the top coating agent for the pigment coating layer is applied Although the generation of mist is sufficiently suppressed, as described above, the ratio of long fiber components (components having a fiber length of 1 mm or more and a fiber width of 25 μm or more) contained in the pulp fibers constituting the base paper is constant such as 10% by mass or less Adjusting to a lower value not only increases the effect of suppressing mist generation when applying a top coat, but also applies a base coat for an undercoat layer. Can also prevent the occurrence of mist That.

  In order to set the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more to 10 mass% or less of the total pulp fibers, the kind and blending ratio of the raw material pulp and the freeness of the disaggregated pulp may be appropriately adjusted. .

  For example, when NBKP and LBKP are used in combination as raw material pulp, it is preferable to adjust the blending ratio of both and the freeness of each disaggregated pulp, for example, as follows. That is, it is preferable to adjust the ratio of NBKP and LBKP to less than 20:80, further 10:90 or less, particularly 5:95 or less (NBKP: LBKP (mass ratio)), and most preferably, NBKP is adjusted without blending. Regarding NBKP, Canadian Standard Freeness (in accordance with “Pulp Freeness Test Method” described in JIS P 8121 of a disaggregated pulp disaggregated in accordance with “Pulp-Disaggregation Method” described in JIS P 8220. Hereinafter, it is preferable to adjust the “CSF”) to 500 to 580 ml, more preferably 500 to 540 ml.

  By beating as described above, the tear strength of the pulp decreases, and in some cases, paper breakage is likely to occur at the paper making stage described later.In the present invention, for example, by specifying the paper making equipment, the tear strength is increased. Even if it falls, it is possible to suppress the occurrence of paper break as much as possible.

  In the present invention, the raw material pulp is mixed to prepare a papermaking raw material (stock slurry). The raw material pulp includes, for example, an internal filler, an internal sizing agent, a paper strength enhancer, and a paper thickness improver. Various additives usually added to coated paper, such as a yield improver, can be internally added by appropriately adjusting the type and amount of the additive.

  There is no particular limitation on the papermaking equipment that can be used in the present invention when producing the papermaking by making the papermaking raw material, but the intended coating using raw pulp with low basis weight and low tear strength In order to obtain paper, it is preferable to use equipment combining the following configurations.

  For example, the wire part is not particularly limited, such as a long web former, a combination of a long web former and an on-top former, or a twin wire former, but the paper jet ejected from the head box is immediately used with two wires. A gap-type gap former that is sandwiched is dehydrated without destroying the formation, which is preferable from the point that the density unevenness of the wet paper does not easily occur and the paper break does not easily occur.

  The paper layer in the wire part is transferred to the press part and further dewatered. The press machine can be either a straight-through type, an invar type, or a reverse type, and a combination of these can also be used. This is preferable in that there are few operational troubles such as paper breaks. As the dehydration method, a conventional suction roll method or a grooved press method can be adopted. However, the shoe press can improve not only the dehydration property but also the smoothness. It is more preferable because the effect of preventing the occurrence is high.

  The wet paper that has passed through the press part is transferred to a single-deck type pre-dryer part and dried. The pre-dryer part is preferably a no-open draw type single-deck dryer that can be dried efficiently with little paper breakage and no reduction in bulk. Although it is possible to dry with the double deck method, it is inferior to the single deck method in terms of operability such as canvas marks, paper breaks, wrinkles, and paper splicing. preferable.

  As described above, when a wire part consisting of a gap former, a straight-through press part that eliminates an open draw, and a dryer part consisting of a single deck dryer, the pulp fibers are beaten, the fiber length is 1 mm or more, and the fiber width is 25 μm. Even if the ratio of the above pulp fibers is adjusted to 10% by mass or less based on the total pulp fibers, it is particularly preferable from the viewpoint that paper breakage due to a decrease in tear strength hardly occurs.

  As described above, when a specific system is adopted in the wire part and the press part, the kind and blending ratio of the raw material pulp and the freeness of the disaggregated pulp are adjusted, and when coating is performed at a high speed of 1500 m / min or more. Even if the tear strength of the base paper is lowered, there is an advantage that the coated paper can be obtained with no fear of breaking the paper and suppressing the reduction in productivity as much as possible.

Although there is no particular limitation on the basis weight of the base paper, the basis weight measured in accordance with “paper and paperboard—basis weight measurement method” described in JIS P 8124: 1998 is 46 to In consideration of the fact that it is preferably 100 g / m ² , the basis weight of the base paper is preferably adjusted to be 30 to 84 g / m ² , more preferably 30 to 50 g / m ² . If the basis weight of the target coated paper is less than 46 g / m ² , the strength of the paper is low, and for example, it may be difficult to satisfy the strength required for commercial printing applications. If the basis weight of the paper is larger than 100 g / m ² , it becomes heavy and may not be practical.

  In the present invention, at least two coating layers are formed on at least one side of the base paper thus obtained. The outermost layer of the coating layer is a pigment coating layer mainly composed of a pigment and an adhesive. The coating layer with less coating unevenness and foreign matter defects due to the occurrence of mist is that the undercoat coating layer in contact with the outermost layer is a clear coating layer mainly composed of a water-soluble polymer compound. This is preferable in that paper is obtained.

  First, for the purpose of improving the smoothness of the surface of the base paper, an undercoat coating agent mainly composed of a water-soluble polymer compound is undercoated to form an undercoat coating layer (clear coating layer). .

  Examples of the water-soluble polymer compound include starch such as oxidized starch, hydroxyethyl etherified starch (hereinafter referred to as “HES”), acetylated oxidized starch (hereinafter referred to as “AOS”), enzyme-modified starch, and polyacrylamide. Those usually used as an undercoat coating agent (hereinafter referred to as “PAM”) can be used alone or in admixture of two or more.

  In the present invention, since the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is adjusted to be 10% by mass or less of all pulp fibers, generation of mist is sufficiently suppressed. Among the water-soluble polymer compounds, oxidized starch and PAM are preferable, and particularly when oxidized starch is used, since the effect of the undercoat coating agent staying on the surface of the base paper is high, the fibers protruding from the surface of the base paper are further coated, There exists an advantage that the mist in top coat coating mentioned later can be reduced more.

  In addition, when starch, especially oxidized starch and / or PAM is used, the effect of imparting a hand feeling to the paper is high, and even if the coated paper has a low basis weight and low tear strength, the paper is improved and the paper is cut off. There is an advantage that it can be reduced.

  In addition to the water-soluble polymer compound, the undercoat coating agent includes, for example, a paper strength enhancer for the purpose of improving water resistance and surface strength, and an externally added sizing agent for the purpose of imparting size. It can mix | blend suitably. Moreover, the pigment generally used for the papermaking use mentioned later can be used together within the range which does not prevent the coating property of the water-soluble polymer compound used for this invention. The range that does not hinder the coating property of the water-soluble polymer compound is generally in the range of 0 to 100% by mass with respect to 100% by mass of the water-soluble polymer compound, although it varies depending on the pigment used together. When the amount used exceeds 100% by mass, the pigment becomes the main component of the undercoat coating layer, the coating property derived from the water-soluble polymer compound is lowered, and it is difficult to prevent the generation of mist, which is not preferable.

  There is no particular limitation on the method for preparing the undercoat coating agent, and the mixing ratio of various auxiliary agents such as a water-soluble polymer compound, a paper strength enhancer, and an external sizing agent as necessary is appropriately adjusted. What is necessary is just to stir and mix so that it may become a uniform composition at temperature. Further, the solid content concentration of the undercoat coating agent is not particularly limited, and it is preferable to appropriately adjust it according to the coating conditions in roll coating such as coating amount and coating speed.

  Examples of the undercoating agent mainly composed of the water-soluble polymer compound include a 2-roll size press coater, a gate roll coater (GR), a blade metalling size press coater, a rod metalling size press coater (RMSP), and a shim sizer. It can be applied to at least one side of the base paper by a coating machine such as a film transfer type roll coater such as JF sizer. In particular, if a film transfer type roll coater (rod metering size press coater, shim sizer, JF sizer) with better coverage is used, the fiber can be effectively prevented from protruding from the surface of the base paper, and the top coat is applied. There is an advantage that generation of mist at the time can be more easily suppressed.

The undercoat coating layer, a primer coating agent, per side 0.1 g / m ² or more, and it is more preferably formed by coating at 0.5 g / m ² or more coating amount, also one side It is preferably formed by coating with a coating amount of not more than 3.0 g / m ² and more preferably not more than 1.0 g / m ² . If the coating amount is less than 0.1 g / m ² , the covering property of the base paper surface is poor, and the effect of suppressing the generation of mist during the top coating may not be sufficiently exhibited. Conversely, if the coating amount exceeds 3.0 g / m ² , it is necessary to increase the concentration of the undercoat coating agent, and there is a risk that uniform coating may become difficult due to an increase in viscosity, and print quality may also deteriorate. This is not preferable.

  Although the thickness of the undercoat coating layer to be formed is not particularly limited, it is preferably about 0.1 to 3.0 μm in order to sufficiently prevent the fiber from protruding from the surface of the base paper.

  The base paper that has been subjected to the undercoating as described above is preferably subjected to a flattening treatment with a pre-calender before the overcoating that will be described later. Even if there are fibers protruding from the surface of the base paper that could not be coated even by the undercoat coating, such protruding fibers can be further reduced by performing the flattening treatment. There exists an advantage that generation | occurrence | production of the mist at the time of coating becomes easy to be suppressed.

  In the pre-calendar, the nip pressure is preferably 10 to 50 kN / m, more preferably 20 to 30 kN / m, in consideration of preventing a decrease in hand feeling of the coated paper obtained. If the nip pressure in the pre-calender is less than 10 kN / m, the flattening effect may be reduced. Conversely, if it exceeds 50 kN / m, the flattening process proceeds too much and the transferability of the top coating agent is lowered and uniform. Transferability may not be obtained, and the flatness of the pigment coating layer may be deteriorated. In any case, the effect of suppressing the generation of mist may not be sufficiently exhibited.

  Moreover, it is preferable that the processing temperature (roll temperature) of a planarization process is 50-90 degreeC, Furthermore, it is preferable that it is 60-90 degreeC. If the treatment temperature is less than 50 ° C, the effect of suppressing the occurrence of mist may be reduced. Conversely, if the treatment temperature is more than 90 ° C, fiber scorch occurs, not only the whiteness decreases, but the fibers are easily damaged, This is not preferable because hand feeling may be reduced.

  In general, the calendar equipment sandwiches the paper with a roll and flattens it by applying a nip pressure. Therefore, the paper tends to sag and the hand feeling tends to decrease. However, when an undercoat coating layer mainly composed of a water-soluble polymer compound such as starch or PAM is provided, it is possible to sufficiently prevent a decrease in hand feeling. Therefore, when performing a planarization process using a pre-calendar, it is preferable to form the said clear coating layer on a base paper surface as an undercoat coating layer.

  In the present invention, when obtaining the effect of reducing the occurrence of mist by appropriately adjusting the kind and blending ratio of the raw pulp and the freeness of the disaggregated pulp, the pulp fibers are rarely damaged by beating and become a paper that tends to sag. However, in this way, a clear coating layer mainly composed of a water-soluble polymer compound is provided as an undercoat coating layer, and further a flattening treatment by a pre-calendar makes it possible to produce a coated paper that is not lumpy. Can be easily obtained.

Moreover, in this invention, although it is preferable to increase the coating amount of the top coat coating agent mentioned later with 8.0-11.0g / m < ² > per single side, if it does so, there will be little pulp content and it will become easy to reduce hand feeling. In some cases, the provision of an undercoat coating layer as described above is preferred because it can improve the hand feeling.

  Next, the undercoat coating layer (clear coating layer) is formed, and preferably an overcoat mainly composed of a pigment and an adhesive is applied to one side or both sides of a base paper that has been flattened by a pre-calender. Apply the coating agent to form a pigment coating layer.

  The pigment used in the present invention is not particularly limited as long as it is generally used in papermaking applications. For example, kaolin clay, heavy calcium carbonate, talc, satin white, calcium sulfite, gypsum, barium sulfate, white carbon, Inorganic pigments such as calcined kaolin, structured kaolin, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, and polystyrene resin fine particles Organic pigments such as urea formalin fine particles, fine hollow particles, and porous fine particles are exemplified, and one or more of these can be appropriately selected and used.

  In the present invention, as the pigment, kaolin clay and heavy calcium carbonate are preferably contained in a ratio of 10:90 or more, more preferably 20:80 or more (kaolin clay: heavy calcium carbonate (mass ratio)), Further, it is preferably contained at a ratio of 60:40 or less, more preferably 50:50 or less (kaolin clay: heavy calcium carbonate (mass ratio)). If the ratio between kaolin clay and heavy calcium carbonate is below the lower limit, the flatness of the pigment coating layer may be difficult to obtain, and conversely, the ratio between kaolin clay and heavy calcium carbonate exceeds the upper limit. If it exceeds the upper limit, the viscosity of the overcoating agent increases, and the solid content needs to be lowered, so that the print quality may be lowered.

  In addition, for example, when kaolin clay and heavy calcium carbonate are blended as pigments at a ratio as described above, it is possible to obtain any glossy, dull, or matte coated paper depending on the conditions of the flattening treatment described later. However, in the present invention, matte and dull-coated paper, particularly dull-coated paper, which requires a high coating amount in order to obtain print quality and hand feeling, Compared to matte and dull-coated paper, it is particularly preferable because the printing quality is remarkably improved.

  In general, in order to obtain glossy coated paper having a high glossiness of white paper, it is necessary to flatten with a high nip pressure, and the reduction in hand feeling tends to be large. In addition, since matte coated paper is flattened with a low nip pressure, the smoothness of the paper surface is low, printability is low, and it is difficult to make a good-looking paper. On the other hand, in the case of dull tone coated paper, since it is flattened with an appropriate nip pressure, the hand feeling does not decrease, and the printability can be improved. There is an advantage of becoming.

  In addition, in this specification, the dull tone coated paper means a white paper glossiness of 20 to 40% measured according to “Paper and paperboard—Measurement method of 75-degree specular gloss” described in JIS P 8142: 2005. This means coated paper. The dull-tone coated paper has a lower white paper gloss than the gloss-tone coated paper, has excellent visibility of printing information, and has a higher smoothness on the surface of the coating layer than the mat-tone coated paper. Excellent print quality and less uneven printing. Therefore, the dull-tone coated paper is a high-quality coated paper that complements the weak points of the gloss-tone coated paper and the matte-coated paper.

  There are no particular limitations on the type of adhesive blended into the topcoat coating agent together with the pigment, for example, proteins such as casein and soybean protein; styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, Conjugated diene latex such as styrene-methyl methacrylate-butadiene copolymer latex, acrylic latex such as acrylic acid ester and / or methacrylic acid ester polymer latex or copolymer latex, ethylene-vinyl acetate polymer latex, etc. Vinyl-based latex, or latexes such as alkali partially soluble or insoluble latex obtained by modifying these various copolymer latexes with a functional group-containing monomer such as a carboxyl group; polyvinyl alcohol, olefin-maleic anhydride resin , Me Synthetic resin adhesives such as min resin, urea resin and urethane resin; starches such as oxidized starch, positive starch, esterified starch and dextrin; ordinary coated paper such as cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose Adhesives used in the above are exemplified, and one or more of them can be appropriately selected and used.

  Among the adhesives, it is preferable to use latexes and starches in combination because the viscosity of the coating agent is improved and the transferability of the top coating agent is increased. Addition of starch is preferable in that the effect of improving the waist of the paper is exhibited, and the reduction in hand feeling can be minimized. In particular, when a styrene-butadiene copolymer latex and oxidized starch are used in combination, a synergistic effect between the improvement effect of printability derived from the film-forming property of the latex and the improvement effect of hand feeling derived from the oxidized starch is obtained. In particular, there is an advantage that a coated paper excellent in hand feeling and printing quality can be obtained.

  When latexes and starches are used in combination, it is preferable to adjust the ratio of the two (latexes: starches (mass ratio)) to 1: 4 or more, further 1: 3 or more. : It is preferable to adjust so that it may become 2 or less. If the ratio of latexes and starches is below the lower limit, the transferability of the top coating agent may be reduced. Conversely, if the ratio of latexes and starches exceeds the upper limit, There is a possibility that the flatness of the work layer is lowered and the printing quality is lowered.

  When latexes and starches are used in combination, these latexes and starches are preferably contained in a total of 5 parts by mass or more, more preferably 8 parts by mass or more based on 100 parts by mass of the total pigments. It is preferably contained in an amount of 15 parts by mass or less, and more preferably 12 parts by mass or less. If the total amount of latexes and starches is below the lower limit, the surface strength and wet paper strength will be low, and paper scumming may occur during printing, which may reduce the print quality. Conversely, if the total amount of latexes and starches exceeds the upper limit, the viscosity of the top coating agent increases, mist is likely to be generated, and the print quality may also deteriorate.

  As latexes, those having an average particle diameter of 90 to 130 μm, more preferably 90 to 110 μm are particularly preferable. When the average particle size of the latex is less than 90 μm, the binder component sinks into the base paper layer, which may reduce the printing quality. Conversely, when the average particle size of the latex exceeds 130 μm, the strength of the pigment coating layer is lowered, and the print quality may be lowered, which is not preferable.

  In addition to the pigments and adhesives, the top coating agent includes, for example, a fluorescent whitening agent and a fluorescent whitening agent fixing agent, an antifoaming agent, a release agent, a coloring agent, a water retention agent, and the like. Various auxiliary agents usually used can be appropriately blended.

  There is no particular limitation on the method for preparing the top coating agent, and the mixing ratio of pigments and adhesives and various auxiliary agents as necessary is adjusted as appropriate, and the mixture is stirred and mixed at an appropriate temperature so as to obtain a uniform composition. do it. Further, the solid content concentration of the top coating agent is not particularly limited, and it is preferable to appropriately adjust it according to the coating conditions in roll coating such as coating amount and coating speed.

  It is preferable that the top coat coating agent is applied to at least one side of the base paper, for example, in a coater part between dryer parts which is performed in a plurality of stages, usually two stages of a pre-dryer part and an after dryer part. In this coater part, a film transfer roll coating, particularly an on-machine coater or an off-machine coater provided with a rod metering size press, is preferably provided on the undercoat coating layer, in one layer or multiple layers. Coated.

  Further, in the present invention, when the on-machine coater is used, after applying the undercoat coating agent for the undercoat coating layer, the topcoat coating agent can be applied immediately in a state where the paper surface temperature is high. Therefore, there is an advantage that the base paper has high liquid absorbency, the transferability of the top coating agent is improved, and the generation of mist can be prevented more efficiently. However, if the liquid absorbency of the base paper is too high, the flatness of the pigment coating layer may decrease due to the sinking of the top coating agent, and the print quality may deteriorate. When the formation and the planarization treatment by pre-calendering on the undercoat coating layer are combined, the flatness of the undercoat coating layer is further improved, so that there is an advantage that the deterioration of the printing quality is extremely slight.

  In addition, as a drying method in the said dryer part, various heat drying systems, such as hot air heating, gas heater heating, infrared heater heating, can be employ | adopted suitably, for example.

The pigment coating layer is preferably formed by applying a top coating agent at a coating amount of 8.0 g / m ² or more, more preferably 9.0 g / m ² or more per side. It is preferably formed by coating at a coating amount of not more than 11.0 g / m ² and more preferably not more than 10.0 g / m ² . If the coating amount is less than 8.0 g / m ² , the target print quality may not be obtained. On the other hand, if the coating amount exceeds 11.0 g / m ² , the pulp content of the coated paper is reduced, and the hand feeling may be reduced.

In particular, when the undercoat coating layer is provided in advance, the occurrence of mist can be sufficiently prevented even when the coating amount of the topcoat coating agent is 8.0 g / m ² per side. Is preferable. Moreover, as described above, kaolin clay and heavy calcium carbonate are included at a ratio of 10:90 to 60:40 (kaolin clay: heavy calcium carbonate (mass ratio)) as a pigment of the pigment coating layer, When the latex and starch are contained in an amount of 5 to 15 parts by mass in total with respect to 100 parts by mass of the total pigment, the pigment coating layer is 9.0 to 11. Being formed on both sides of the base paper at a coating amount of 0 g / m ² , the pigment coating layer is uniform, and the occurrence of mist is further reduced when the top coating agent is applied. It is preferable in that an excellent coated paper can be obtained.

  The thickness of the formed pigment coating layer is not particularly limited, but is preferably about 8 to 11 μm per side in order to further improve the printability of the resulting coated paper.

In particular, in the present invention, the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is adjusted so as to be 10% by mass or less of the total pulp fibers, so that mist is sufficiently generated during coating. However, by forming a clear coating layer mainly composed of a water-soluble polymer compound as an undercoat coating layer on at least one side of the base paper and flattening it with a pre-calender, the flatness of the base paper A synergistic effect is improved, and the occurrence of mist can be further reduced when the top coat agent is applied. Furthermore, the further effect which prevents generation | occurrence | production of mist is acquired by coating topcoat coating agent with an on-machine coater. Thereby, in particular, even when the coating amount of the top coating agent is 8.0 to 11.0 g / m ² per side, it is possible to sufficiently prevent the occurrence of mist, especially in dull-coated paper. Can obtain a significantly higher print quality than before.

  In the coated paper of the present invention, at least two coating layers are formed on at least one side of the base paper. Among these coating layers, any of at least two coating layers in contact with each other is used. It is formed by roll coating at a speed of 1500 m / min or more. The coated paper of the present invention is adjusted such that the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is 10% by mass or less of the total pulp fibers. In spite of its high speed, it has a uniform coating layer formed in a state in which the generation of mist is sufficiently suppressed, and has few coating unevenness and foreign matter defects.

  Of the at least two coating layers, the outermost layer is a pigment coating layer mainly composed of the pigment and an adhesive, and the undercoat coating layer in contact with the outermost layer is a water-soluble high layer. Although it is preferably a clear coating layer containing a molecular compound as a main component, the configuration of the coating layer in the coated paper of the present invention is not limited to this, depending on the use of the resulting coated paper, etc. Can be changed as appropriate.

  Thus, among the at least two coating layers in contact with each other, a step of forming an undercoat coating layer close to the base paper, a step of applying a flattening treatment to the undercoat coating layer using a pre-calender, and the 2 Of the coating layers of the layer, the process of forming the other coating layer close to the surface layer is performed sequentially in sequence, coating unevenness and foreign matter defects are extremely small, and the print quality is extremely excellent, and more It is particularly preferable in that a coated paper in which excellent hand feeling is maintained can be efficiently obtained with excellent productivity.

  Furthermore, in the present invention, for the purpose of imparting gloss, smoothness and printability to the coating layer, it is preferable to perform a flattening treatment using, for example, a hot roll.

  In general, in the flattening process, a coated paper is passed between an elastic roll and a metal roll, a high nip pressure is applied to the coated paper, the surface of the coated paper is polished by frictional force, and gloss is given. Since the paper is crushed by pressure, excessive flattening impairs the hand-feel of the paper, and the nip pressure and friction force concentrate on the fine convex parts of the coated paper, causing fiber scorching, and heat and pressure. There is a problem of fading that the coated paper itself turns yellow. Further, in the conventional dull-tone coated paper, the flattening process is performed at a medium nip pressure (50 to 200 kN / m) in order to perform the flattening while suppressing the glossiness of the blank paper to 20 to 40%. Then, not only high print quality cannot be obtained, but the coated paper is crushed and the hand feeling is lowered.

  Therefore, in the present invention, when the coating layer is subjected to a flattening process, it is preferable to use a soft calender that can be flattened with a lower nip pressure as a calendar facility. Among them, the multi-nip calender, more desirably 6-, 8-, and 10-stage multi-nip calenders, is easy to adjust the nip pressure, and has a high effect of improving the glossiness of the blank paper without reducing the whiteness of the coated paper. This is preferable.

  Moreover, as an installation place of a calendar, an on-machine type integrated with a paper machine and a coating machine is preferable. With the on-machine type, flattening can be performed immediately after coating with the paper surface at a high temperature, so the glossiness of blank paper is easily improved, and the linear pressure necessary to obtain the desired coated paper is increased. It is preferable in that it is low, has little decrease in whiteness and hand feeling, and is less likely to break.

  In such a calendar, the nip pressure is preferably 15 to 150 kN / m, more preferably 110 to 150 kN / m. If the nip pressure on the calender is less than 15 kN / m, the flatness of the coating layer may not be sufficiently improved. Conversely, if the nip pressure exceeds 150 kN / m, the hand feeling may be reduced.

  Moreover, it is preferable that the processing temperature (roll temperature) of a planarization process is 100-180 degreeC, Furthermore, it is preferable that it is 130-150 degreeC. If the treatment temperature is lower than 100 ° C, the flatness of the coating layer may not be sufficiently improved. Conversely, if the processing temperature is higher than 180 ° C, the whiteness of the coated paper may be lowered, which is not preferable.

  The coated paper of the present invention obtained as described above is adjusted so that the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is 10% by mass or less of the total pulp fibers. Little or no mist is generated when roll coating is performed at a high speed of 1500 m / min or more.

  Furthermore, when the undercoat coating layer is formed with an undercoat coating agent mainly composed of a water-soluble polymer compound, and when the pre-calender is subjected to a flattening treatment, the smoothness of the base paper is improved. Generation of mist is further reduced.

  In addition, by providing a pigment coating layer in which the type, amount, blending ratio, etc. of the pigment and adhesive are appropriately adjusted on the surface of the undercoat coating layer, the generation of mist is further reduced. Thus, a coated paper having excellent printability without being mixed in can be obtained.

  In addition, for example, in papermaking equipment (wire part, press part, dryer part), coating equipment (on-machine coater, on-machine calendar), etc., by combining specific configurations, the reduction of hand feeling due to pulp beating is minimized. In addition, the paper is less likely to break, the operability and productivity are good, and the target coated paper under the above-mentioned raw pulp conditions and coating conditions, particularly excellent printability, has high quality. A dull-coated paper suitable for printed matter can be obtained.

  In addition, although the blank paper glossiness of the coated paper of the present invention varies depending on the application, as described above, for example, when a dull-tone coated paper is used, the “paper and paper” described in JIS P 8142: 2005 is used. It is 20 to 40%, preferably 30 to 40% as measured in accordance with “Paperboard—Measuring method of 75 ° specular gloss”.

  Next, although the coated paper of this invention and its manufacturing method are demonstrated still in detail based on the following Examples, this invention is not limited only to these Examples.

Examples 1-57 and Comparative Examples 1-3
First, as a raw material pulp, LBKP (CSF of disaggregated pulp: 400 ml) and NBKP beaten so that the CSF of disaggregated pulp had the values shown in Tables 1 and 2 were mixed in the ratios shown in Tables 1 and 2. With respect to 100 parts by mass (absolute dry amount) of this pulp, 0.02 parts by mass of an internal sizing agent (product number: AK-720H, manufactured by Harima Kasei Co., Ltd.), cationized starch (product number: Amylofax T), each in solid content -2600, manufactured by Abebe Japan Co., Ltd.) 1.0 part by mass and a yield improver (product number: NP442, manufactured by Nissan Eka Chemicals Co., Ltd.) 0.02 part by mass were added to obtain a pulp slurry.

Next, the pulp slurry is sequentially supplied to a wire part, a press part, and a pre-dryer part to produce a base paper having a basis weight of about 39 to 41 g / m ² , and then the undercoat shown in Tables 3 to 4 is formed on both sides of the base paper. The coating agent is applied at a rate of 1500 m / min with the coating amount (per one side) and the coating method shown in Tables 3 to 4, and the undercoat coating layer has a thickness of about 0.5 to 0.9 μm. (Clear coating layer) was formed.

Next, the base paper on which the undercoat coating layer is formed on both sides is subjected to an after dryer part, and after drying this undercoat coating layer, a flattening treatment is performed under the nip pressure and roll temperature conditions shown in Tables 3 to 4. gave. Next, on the surface of the undercoat coating layer that has been flattened by the coater part, the topcoat coating agent having the composition shown in Tables 5 to 7 is applied at a coating amount (per one side) shown in Tables 5 to 1500 m / Roll coating was performed at a speed of minutes to form a pigment coating layer having a thickness of about 6 to 11 μm. Thereafter, a flattening process is performed under the conditions of a nip pressure of 120 kN / m and a roll temperature of 140 ° C., and the measurement is performed according to “Paper and paperboard—75-degree specular gloss measurement method” described in JIS P 8142: 2005. The glossiness of the blank paper was adjusted to 35-40%, and then subjected to the reel part and winder part in order to obtain a coated paper having a basis weight of about 59-61 g / m ² .

In addition, the water-soluble polymer compound, the pigment, the adhesive, and the coating method shown in Tables 3 to 7 are as follows.
<Undercoat coating agent>
(Water-soluble polymer compound)
・ Oxidized starch (manufactured by Eliere Shoko)
・ PAM (Part No .: Haricoat G-51, manufactured by Harima Kasei Co., Ltd.)
・ HES (Part No .: Coat Master K49F, manufactured by Sanki Co., Ltd.)
・ AOS
(Acetylated oxidized tapioca starch, product number: Mermaid MC-3000, manufactured by Sanki Co., Ltd.)
(Coating method)
・ RMSP: Rod metering size press coater ・ GR: Gate roll coater ・ Curtain: Curtain coater

<Topcoat coating agent>
(Pigment)
・ Kaolin Clay (Part No .: Kao Fine, manufactured by Imeris)
・ Wet heavy calcium carbonate (Product number: Hydro curve 90K, manufactured by Omiya Korea)
(adhesive)
SBR: styrene-butadiene copolymer latex (average particle size: 100 μm, product number: PA-1071, manufactured by Nippon A & L Co., Ltd.)
NBR: acrylonitrile-butadiene latex (average particle size: 100 μm, product number: Nipol 1571CL, manufactured by Nippon Zeon Co., Ltd.)
・ Oxidized starch (Product No .: Coat Master K96F, manufactured by Sanki Co., Ltd.)
・ HES (Part No .: Coat Master K49F, manufactured by Sanki Co., Ltd.)
・ AOS
(Acetylated oxidized tapioca starch, product number: Mermaid MC-3000, manufactured by Sanki Co., Ltd.)

  Paper was made using a gap former for the wire part, a straight-through type without an open draw for the press part, and a single deck dryer for the dryer part. In the coater part, after applying an undercoat coating agent with a rod metalling size press, a flattening treatment was performed with a pre-calender, and an overcoat coating agent was applied with a rod metalling size press. In the calendar part, a flattening process was performed using a multi-nip calendar. For the coater part and the calendar part, an on-machine coater and an on-machine calendar incorporated in the paper machine were used.

  About the obtained coated paper, each characteristic was investigated with the following method. These results are shown in Tables 8-9.

(A) Long fiber ratio The coated paper is disaggregated according to “pulp-disaggregation method” described in JIS P 8220, and the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is determined from the measured values. The long fiber ratio was obtained. The measurement was performed using a fiber length measurement tester (model number: FiberLab P43030371 V2.0, manufactured by Metso), and the cut-off was set at 0.02 mm.

(B) Printing quality Printing on a coated paper was performed under the following conditions to produce a printing specimen.
・ Printing machine: RI-3 type, manufactured by Akira Seisakusho Co., Ltd. ・ Ink: WebRexNouverHIMARK process (indigo), manufactured by Dainichi Seika Co., Ltd.
Test method: The ink was kneaded for 3 minutes each with the upper and lower rolls (kneaded for 2 minutes, then the roll was inverted and further kneaded for 1 minute), and two-color simultaneous printing was performed at a rotation speed of 30 rpm.
About the said printing test body, the generation | occurrence | production degree of white spot was observed visually and with a magnifier (10 times), and it evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: There is no white spot and the print quality is particularly excellent.
○: Occurrence of white spots is slight and print quality is excellent.
(Triangle | delta): There are few generation | occurrence | production of white spots and print quality is favorable.
X: White spots occur and print quality is poor.
Of the evaluation criteria, ◎, ○, and Δ are judged to be actually usable.

(C) Hand feeling 20 sheets of A4 size (210 mm x 297 mm) coated paper are stacked, and one side of the long side is stapled at 3 locations (top, center, bottom) and placed horizontally, 10 sheets in total On the other hand, hand feeling was evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: The paper after turning does not sag and is particularly excellent in hand feeling.
○: Sag of paper after turning is slight and excellent hand feeling.
Δ: Little paper sagging after turning and good hand feeling.
X: The paper after turning is sagging, and the hand feeling is inferior.
Of the evaluation criteria, ◎, ○, and Δ are judged to be actually usable.

(D) Generation | occurrence | production of mist During manufacture of the said coated paper, coating of the topcoat coating agent was performed continuously for 24 hours, and the generation amount of mist was evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: There is no generation of mist, and the operability is particularly excellent.
○: Occurrence of mist is slight and the operability is excellent.
Δ: Little occurrence of mist and good operability.
X: Mist is generated and the operability is inferior.
Of the evaluation criteria, ◎, ○, and Δ are judged to be actually usable.

  From the results shown in Tables 8 to 9, the coated papers of Examples 1 to 57 are all coated with two pulp layers formed by a roll coater method, and all pulp fibers contained in the base paper The ratio of pulp fibers with a fiber length of 1 mm or more and a fiber width of 25 μm or more is as low as 10% by mass or less, so that no mist is generated even though papermaking / coating is performed at a speed of 1500 m / min. It can be seen that the print quality and hand feeling are excellent.

  On the other hand, in the coated papers of Comparative Examples 1 to 3, the percentage of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more in all pulp fibers contained in the base paper exceeds 10% by mass ( Comparative Example 1), only one coating layer is formed (Comparative Example 2), one of the two coating layers is not formed by the roll coater method (Comparative Example 3) Therefore, it can be seen that when paper is made and coated at a speed of 1500 m / min, mist is generated so much that the printing quality and hand feeling are inferior.

  The coated paper of the present invention can be suitably used as, for example, printing paper, publishing paper, book paper and the like.

Claims (6)

A coated paper having at least two coating layers formed on at least one side of a base paper,
The base paper has pulp fibers as a main component, the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is 10% by mass or less of the total pulp fibers, and the coating layers are in contact with each other. The coated paper is characterized in that at least two coated layers are formed by roll coating at a speed of 1500 m / min or more. The outermost layer of the coating layer is a pigment coating layer mainly composed of a pigment and an adhesive, and the pigment coating layer is formed at a coating amount of 8.0 to 11.0 g / m ² per side. The undercoat coating layer in contact with the outermost layer is a clear coating layer mainly composed of a water-soluble polymer compound, and the clear coating layer is 0.1 to 3.0 g / m per side. The coated paper according to claim 1, which is formed with a coating amount of ² . As a pigment of the pigment coating layer, kaolin clay and heavy calcium carbonate are contained in a ratio of 10:90 to 60:40 (kaolin clay: heavy calcium carbonate (mass ratio)), and latex is used as the adhesive. Coated paper according to claim 2, wherein 5 to 15 parts by mass in total of starch and starch is contained with respect to 100 parts by mass of the total pigment.   The water-soluble polymer compound is oxidized starch and / or polyacrylamide, the clear coating layer is formed by a rod metalling size press coater, and the clear coating layer is planarized by a pre-calender. The coated paper of Claim 2 or 3 formed by these. At least two coating layers are formed on at least one side of the base paper, the base paper is mainly composed of pulp fibers, and the ratio of pulp fibers having a fiber length of 1 mm or more and a fiber width of 25 μm or more is the total pulp fibers A method for producing a coated paper of 10% by mass or less,
Among the coating layers, at least two coating layers that are in contact with each other are formed by roll coating at a speed of 1500 m / min or more.   Of the two coating layers, a step of forming an undercoat coating layer close to the base paper, a step of applying a planarization treatment to the undercoat coating layer using a pre-calender, and the two coating layers The manufacturing method according to claim 5, wherein the steps of forming the other coating layer close to the surface layer are sequentially performed.