JP5276910B2 - Highly opaque coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated paper produceable in good operability, having high printability, whiteness and opacity, and also having thick feeling. <P>SOLUTION: The coated paper has a coated layer consisting essentially of a base paper, and a pigment and a binder on the base paper. The coated layer includes two layers of an undercoat coated layer contacting the base paper, and a topcoat coated layer formed on the undercoat coated layer. The undercoat coated layer contains at least recycled particles and/or heavy calcium carbonate as the pigment, and the coated amount of the undercoat coated layer is 0.5-2.5 g/m<SP>2</SP>per one surface. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to coated paper. More specifically, the present invention relates to a coated paper for printing that has high printability and opacity, has a hand feeling, and can be suitably used for, for example, offset printing and gravure printing.

  Conventionally, coated paper having higher printability has been desired in the field of printing paper.

  As a method for improving printability, there is a method of adding kaolin clay, which can impart flatness to the surface of the coating layer, but kaolin clay is obtained with lower opacity and whiteness than heavy calcium carbonate. There is also a problem that the opacity and whiteness of paper are reduced.

  In addition, as a pigment having high opacity, a technique using heavy calcium carbonate, regenerated particles regenerated from paper sludge and deinking floss and regenerated particle aggregates is disclosed (see Patent Document 1). According to the technology, paper with high opacity can be obtained, but heavy calcium carbonate and recycled particles are not as effective in improving printability as clay. There was also a problem that sufficient printability could not be obtained as a craft paper.

  As a method for obtaining a coated paper having high printability, whiteness and opacity, a method of forming two coating layers mainly composed of a pigment and an adhesive is known (Patent Document 2). See). In other words, as an undercoating layer (undercoating layer) in contact with the base paper that is not directly printed, heavy calcium carbonate, which is poor in printability but has high opacity, is applied and printing is actually performed. As a surface coating layer (top coating layer), by applying clay with inferior opacity but good printability, it has high opacity derived from heavy calcium carbonate and high printability derived from clay. A craft paper can be obtained.

  However, the coated paper of the above-mentioned two-layer coating has a problem that the hand feeling derived from the pulp is lowered because the pulp component is reduced at the same basis weight as the two coating layers. If the total coating amount of the two coating layers is the same as when one layer coating is applied, it is necessary to halve the coating amount of each coating layer. In the current coating method, each layer is applied uniformly. There is a problem that it cannot be processed and has poor printability.

  The amount of coating that can be applied varies depending on the coating method. Common coating methods include size press, film transfer type roll coater (gate roll coater and rod metering size press), blade coater, air knife coater, curtain coater, spray coater, etc. Since it is difficult to reduce the coating amount, and the curtain coater and spray coater are not simple because the preparation of the coating solution is limited, a film transfer type roll coater or a blade coater is preferably used for reducing the coating amount.

A blade coater has a minimum coating amount of about 7 g / m ² per side, and a film transfer type roll coater has a minimum coating amount of about 6 g / m ² per side. When these coating amounts are halved, if a coating solution generally used for papermaking is applied as it is, coating unevenness and uncoated portions are generated, and there is a problem that printability is lowered. In addition, if the coating liquid concentration is reduced by reducing the coating liquid concentration, the water in the coating liquid increases, so the water absorbed by the paper during coating increases, and the tensile strength and tear strength decrease. There was a problem that the operability deteriorated, such as paper breakage.

As described above, there has not yet been obtained a method for providing a coated paper having high printability, whiteness and opacity, and having a hand feeling while being manufacturable with good operability.
JP 2007-197888 JP 2003-286687 A

  The present invention has been made to solve the problems of the prior art, and provides a coated paper that can be manufactured with good operability, has high printability, whiteness and opacity, and has a hand-feel. Objective.

  The present inventor comprises two coating layers of coated paper, uses regenerated particles and / or heavy calcium carbonate as the pigment of the undercoat coating layer, and sets the undercoat coating layer to a specific range of low It has been found that the above-mentioned problems can be solved by setting the coating amount.

That is, the coated paper of the present invention is a coated paper having a base paper and a coating layer mainly composed of a pigment and an adhesive on the base paper, and the coated layer is formed on the base paper. It consists of two layers composed of an undercoat coating layer in contact with and an overcoat coat layer formed on the undercoat coat layer, wherein the undercoat coat layer is at least regenerated particles and / or heavy calcium carbonate as a pigment. The coating amount of the undercoat coating layer is 0.5 to 2.5 g / m ² per side.

  The coated paper of the present invention can be produced with good operability, has high printability, whiteness and opacity, and has a hand feeling.

(Embodiment)
<Paper making>
First, the base paper which comprises the coated paper which concerns on this embodiment is demonstrated.
The base paper should just be obtained by papermaking a normal raw material pulp. The raw material pulp is not particularly limited. For example, chemical pulp such as unbleached softwood pulp (NUKP), unbleached hardwood pulp (LUKP), bleached softwood pulp (NBKP), bleached hardwood pulp (LBKP), etc .; Stone Grand Pulp (SGP) ), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Chemi Thermo Mechanical Pulp ( CTMP), refiner mechanical pulp (RMP) and other mechanical pulp; magazine waste paper, leaflet waste paper, waste paper pulp made from office waste paper, etc., waste paper pulp such as disaggregation, deinking, bleached waste paper pulp, etc. , Select one or more of these as appropriate, It can be used to adjust the focus.

  A filler conventionally used for papermaking can be added to the raw material pulp as an internal filler. Examples of the filler include inorganic fillers such as light calcium carbonate, talc, titanium dioxide, clay, calcined clay, synthetic zeolite, and silica, polystyrene latex, urea formalin resin, and the like. Although the compounding quantity of a filler is not specifically limited, It is preferable to add so that it may become 8 mass% or less by paper ash content, and 6 mass% or less is more preferable. If the ash content in the paper exceeds 8% by mass, hydrogen bonding between the pulps is likely to be hindered, so that the tensile strength is lowered, and in the undercoat coating described later, paper breakage due to water absorption tends to occur. When the internal ash content is reduced, there is a problem that the opacity of the coated paper generally decreases. However, in the present invention, a coating layer containing heavy calcium carbonate and / or regenerated particles is used as the undercoat coating layer. Therefore, even if the ash content is in the above range, sufficient opacity can be obtained. The ash content of the present invention is a value measured according to JISP8251 “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method”.

  It is preferable to add an internal paper strength enhancer to the raw material pulp. In the present invention, since a low-concentration coating liquid is applied in the undercoat coating layer described later, the moisture of the undercoat coating liquid is easily absorbed into the base paper, the paper tensile strength is reduced, and paper breakage occurs. It becomes easy to do. Therefore, by adding an internal paper strength enhancer, particularly a wet paper strength enhancer, it is possible to prevent operational troubles such as paper breakage even if moisture absorption is high.

  Examples of the internal paper strength enhancer include amphoteric, anionic or cationic polyacrylamide resins (PAM), polyamine resins, urea-formaldehyde resins, melamine-formaldehyde resins, epoxy-polyamide resins, and the like. Of these, polyacrylamide resins, particularly amphoteric polyacrylamide resins, are particularly preferred because they are less likely to break during water absorption in the undercoat coating described below. Moreover, since the internal paper strength enhancer has an effect of improving the yield of fine fibers, it is preferable because it has a merit that the base paper has high flatness and good printability.

  When the added amount of the internal paper strength enhancer is 0.1 to 0.4% by mass in terms of solid content with respect to the pulp, the base paper can be effectively prevented from being cut in the undercoat coating described later. preferable. If the added amount of the internal paper strength enhancer is less than 0.1% by mass, the paper breakage cannot be prevented sufficiently, and if it exceeds 0.4% by mass, it aggregates and the texture is lost, and not only the printability is deteriorated. This is not preferable because the tensile strength is uneven and the paper is easily cut.

  Further, it is preferable to add a fixing agent of the internal paper strength enhancing agent in combination with the above internal paper strength enhancing agent. By adding the fixing agent, it is possible to improve the yield of the internally added paper strength enhancing agent, and it is more difficult to cause paper breakage. Examples of the fixing agent include inorganic or organic cationic chemicals. Among them, polyethyleneimine (PEI), polydiallyldimethylammonium chloride (PDADMAC), a sulfuric acid band, and the like are more preferable. It is more preferable because the yield effect of the internal paper strength enhancer is high and the effect of preventing paper breakage is high. In particular, when amphoteric PAM is used as an internal paper strength enhancer, it is preferable to use a sulfate band as a fixing agent because the yield of amphoteric PAM is particularly high and the effect of preventing paper breakage is particularly high.

  The addition amount of the sulfuric acid band is preferably 0.1 to 1.5% by mass in terms of solid content with respect to the pulp, and 0.3 to 1.0% by mass can effectively improve the yield of amphoteric PAM. Is more preferable. If the addition amount of the sulfuric acid band is less than 0.1% by mass, the yield of the paper strength enhancer is lowered, and not only paper breakage is likely to occur at the time of undercoating, but there is a problem that the hand feeling is lowered. Exceeding 1.5% by mass is not preferable because fine fibers aggregate and the texture deteriorates, and not only paper breakage is likely to occur, but also foreign matter is likely to occur and printability may be reduced.

  Furthermore, it is preferable to add an internal sizing agent to the raw pulp. In the present invention, since a low-concentration coating liquid is applied in the undercoat coating layer described later, the moisture of the undercoat coating liquid is easily absorbed into the base paper, the paper tensile strength is reduced, and paper breakage occurs. It becomes easy to do. Therefore, by adding an internal sizing agent, moisture absorption can be suppressed, and operational troubles such as paper breaks can be prevented.

  In the present embodiment, in addition to the internal paper strength enhancer, the raw pulp includes, for example, a paper thickness improver, a yield improver (water-soluble polymers such as various synthetic polymers and starches), Various additives that are usually blended into the base paper of the coated paper can be internally added by appropriately adjusting the type and blending amount.

  After making the papermaking raw material as described above in the wire part and then supplying it to the press part and the pre-dryer part to produce the base paper, and then coating the base paper with the coating liquid described later in the coater part It can be used for an after dryer part, a calendar part, a reel part, a winder part and the like to obtain a desired coated paper.

  In addition, when the coating liquid which has clay as a main component is top-coated in the top coat layer mentioned later, it is difficult to obtain coated paper with high whiteness. Therefore, in order to further improve the whiteness of the target coated paper, the whiteness of the base paper is measured by a color analyzer (model number: color i5, manufactured by Macbeth Gretag), 70% or more, and further 75. % Or more is preferable. When the coated paper for printing is manufactured from such a base paper, the whiteness can be set to 80% or more, for example, as will be described later. When such a coated paper for printing having a whiteness of 80% or more is used, for example, a high-quality printed material with higher definition and high contrast can be obtained compared to a coated paper for printing with a whiteness of less than 80%. It is done.

Although there is no particular limitation on the basis weight of the base paper, as will be described later, the basis weight of the target coated paper is preferably 40 to 100 g / m ² , and the basis weight of the base paper is Usually, it is preferable to adjust so as to be about 24 to 84 g / m ² .

<Undercoat>
Before providing an overcoating layer to be described later on the base paper, an undercoating layer containing heavy calcium carbonate and / or regenerated particles as a pigment is 0.5 to 2.5 g / m ² per side. Provide.
Conventionally, when coating with such a low coating amount by a film transfer method or a blade coating method, the coating liquid is likely to be absorbed into the base paper, and the tensile strength of the paper is reduced, so it is easy to break the paper. In the present invention, since the internal paper strength enhancer is contained in the base paper, even when a low-concentration coating solution is applied, the tensile strength of the paper is not easily lowered, thereby preventing the occurrence of paper breaks. As it is, paper can be manufactured.

  As the pigment, it is preferable to use heavy calcium carbonate and / or regenerated particles having high opacity, because it is easy to impart high opacity to the coated paper even at a low coating amount. On the contrary, the printability tends to decrease, but since printing is performed on the surface of the topcoat coating layer described later, by using a pigment (for example, clay) having high printability in the topcoat layer, the undercoat is used. It is possible to cover the disadvantages of reduced printability when heavy calcium carbonate and / or regenerated particles are used for coating. In addition, heavy calcium carbonate and regenerated particles have an advantage that the particles are indeterminate and the viscosity of the undercoat coating solution is lower than that of plate-like clay, so that it is difficult to break the paper during the undercoat coating.

  By using heavy calcium carbonate and / or regenerated particles, sufficient opacity can be obtained even at a low coating amount. However, the above-mentioned paper strength enhancer and fixing agent, particularly polyacrylamide and sulfate bands are added. The combined use is preferable because a coated paper can be obtained while sufficiently preventing paper break even at a low concentration and a low coating amount.

(Regenerated particles)
In the present invention, in order to improve opacity, at least one selected from the group consisting of the following regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates, which is a filler particularly excellent in opacity, is used. It is preferable to do. In particular, the regenerated particle aggregate and the silica-coated regenerated particle aggregate are particles formed by agglomeration of the regenerated particles, and are particularly highly opaque, and the particles are less likely to sink into the base paper. Since it can form, it is especially preferable.

a) Recycled particles derived from paper sludge As the regenerated particles derived from paper sludge, for example, those described in Japanese Patent No. 3819706 can be used. Specifically, paper sludge is extruded into a string with a diameter of 3 to 10 mm, cut to a length of 8 to 10 cm, then incinerated with a rotary kiln at 500 to 1000 ° C., and the incinerated ash obtained by this incineration is dry-pulverized A white pigment having an average particle diameter of 0.1 to 10 μm obtained by pulverization in the order of wet pulverization can be used.

  As the quality of the regenerated particles derived from papermaking sludge, for example, the whiteness (powder whiteness meter (manufactured by Kett Scientific Laboratory, type C-100)) is 60% or more, and the hardness (plastic wire wear degree) (Nippon Filcon, 3 hours)) of less than 100 mg can be used.

b) Regenerated particle aggregate derived from deinking floss As the regenerated particle aggregate derived from deinking floss, for example, those described in Japanese Patent No. 3869455 and Japanese Patent No. 3872091 can be used. Specifically, a flocculant is added to deinking floss having a moisture content of about 95 to 98% by mass, dehydrated to about 50 to 60% by mass, the dehydrated product is dried with hot air and classified, and then in a range of 450 to 650 ° C. Then, it is baked and agglomerated so that the unburned rate becomes 10 mass% or more and less than 15 mass%. White particles obtained by pulverizing the calcined inorganic particle aggregate so that the primary particles have an average particle diameter of 0.01 to 0.1 μm and the secondary particles in which the primary particles have aggregated have an average particle diameter of 0.1 to 10 μm. Pigments can be used.

As the quality of the regenerated particle aggregate derived from deinking floss, for example, the oil absorption is 30 to 100 ml / 100 g. Moreover, the peak height of the average particle diameter in the differential curve of the particle size distribution by the Coulter counter method is adjusted to 30% or more, and furthermore, calcium, silica and aluminum in the raw material sludge are converted into oxides in an amount of 30 to 82: 9 to By adjusting the mass ratio to 35: 9 to 35, the pore volume of the inorganic particle aggregate is 0.15 to 0.60 cc / g, the pore surface area is 10 to 25 m ² / g, and the pore radius is 300 to White pigments adjusted to 1000 angstroms can also be used.

  In terms of filler quality, regenerated particle aggregates derived from deinked floss are preferred over regenerated particles derived from papermaking sludge. In addition to deinking floss, papermaking sludge contains sludge and heavy foreign matter that have been processed from papermaking wastewater, so firing unevenness is likely to occur, and it cannot be uniformly fired. Increase in objects and decrease in whiteness and opacity are likely to occur.

  In the coated paper of this embodiment, the above regenerated particles or regenerated particle aggregates can be used as a pigment for the undercoat coating layer. Since this recycled particle or recycled particle aggregate can be recycled by baking papermaking sludge or deinked floss, it does not require disposal such as landfill as waste, reducing the environmental burden. This greatly contributes to resource saving. Further, since the raw material is papermaking sludge or deinking floss generated in the used paper processing step, there is an advantage that it is inexpensive, the amount of new natural inorganic mineral used can be suppressed, and the manufacturing cost is sufficiently reduced.

c) Silica-coated regenerated particle aggregate In the present embodiment, as a regenerated particle suitable as a pigment for the undercoat coating layer, a silica-coated regenerated particle aggregate in which the surface of the regenerated particle aggregate is coated with silica is used. Since whiteness is high, it is more preferable.

  As the silica-coated regenerated particle aggregate, for example, those described in Japanese Patent No. 3907688 and Japanese Patent No. 393596 can be used. Specifically, deinked floss dehydrated to 95 to 98% moisture is further dehydrated to 40% to 70%, and then dried with hot air at 100 to 200 ° C. to a moisture content of 2 to 20% by mass. To do. The dried product is adjusted so that the particle size of 355 to 2000 μm is 70% by mass or more. The dried product is baked and agglomerated in the range of 510 to 750 ° C., and after adjusting the unburned matter, it is finely pulverized, the primary particles have an average particle diameter of 0.01 to 0.1 μm, and the primary particles are agglomerated secondary. The particles are adjusted so as to have an average particle diameter of 0.1 to 10 μm to obtain regenerated particle aggregates.

In the regenerated particle aggregate, the peak height of the average particle diameter in the differential curve of the particle size distribution by the Coulter counter method is adjusted to 30% or more, and further, calcium, silicon and aluminum in the deinking floss are converted to 30 in terms of oxide. By adjusting the mass ratio to ˜82: 9 to 35: 9 to 35, the pore volume of the inorganic particle aggregate is 0.15 to 0.60 cc / g, the pore surface area is 10 to 25 m ² / g, fine. It is preferable that the white pigment has a pore radius adjusted to 300 to 1000 angstroms.

  After this regenerated particle aggregate is added and dispersed in an aqueous alkali silicate solution to prepare a slurry, a dilute solution of a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid is added at a liquid temperature of 70 to 100 ° C. while stirring with heating, and a silica sol is prepared. The white pigment obtained by generating silica sol particles having a particle diameter of 10 to 20 nm on the regenerated particle aggregate surface by adjusting the pH of the final reaction solution to a range of 8.0 to 11.0. . This silica-coated regenerated particle aggregate improves the oil absorption and opacity due to the silica precipitation effect by making calcium, silicon and aluminum into mass ratios of 30 to 62:29 to 55: 9 to 35 in terms of oxides. Can be made.

  The quality of the silica-coated regenerated particle aggregate is, for example, an oil absorption of 30 to 100 ml / 100 g, and when used as an internal additive in the paper making process, a white pigment having an average particle size adjusted to 0.1 to 10 μm is used. It can also be used.

  Regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates have higher opacity than heavy calcium carbonate, but have lower whiteness than heavy calcium carbonate. Therefore, regenerated particles and heavy calcium carbonate are used in combination. This is preferable because both opacity and whiteness can be improved.

  Examples of the heavy calcium carbonate include those having an average particle diameter of about 5 μm or less obtained by dry pulverization or wet pulverization of white crystalline limestone.

  The blending ratio of the regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates is preferably 50 to 95 parts by mass with respect to 100 parts by mass of the pigment in the undercoat coating layer. When the amount is less than 50 parts by mass or exceeds 95 parts by mass, the coated paper is inferior in balance between whiteness and opacity. Moreover, the blending ratio of heavy calcium carbonate is 5 to 100 parts by weight of the pigment in the undercoat coating layer so as to complement the blending amount of the regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates. 50 parts by mass is preferred.

  In the case of the above pigment range, a coated paper having excellent whiteness and opacity can be obtained, but all of the regenerated particles, regenerated particle aggregates, silica-coated regenerated particle aggregates, and heavy calcium carbonate have low water retention. Because of the pigment, the base paper can easily absorb the water in the undercoat coating liquid, and in order to apply these in combination within the above range, an internal paper strength enhancer and preferably a fixing agent are used as described above. It is preferable to use together. It is preferable to use polyacrylamide as a paper strength enhancer and a sulfuric acid band as a fixing agent, since coated paper can be produced stably with little paper breakage.

(Recycled particles, fillers other than heavy calcium carbonate)
Kaolin clay may be used in combination as a pigment other than heavy calcium carbonate or regenerated particles. By using clay together, the flatness after the undercoating can be improved, so that the flatness and the printability after the overcoating can also be improved.

  The blending ratio of clay is preferably 0 to 20 parts by mass with respect to 100 parts by mass of the pigment in the undercoat coating layer. Exceeding 20 parts by mass is not preferable because the whiteness decreases.

  In addition to heavy calcium carbonate, regenerated particles, regenerated particle aggregates, silica-coated regenerated particle aggregates, and clay, pigments commonly used for papermaking can be used for the undercoat coating layer. Examples of such pigments include calcined kaolin, deramikaolin, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide. , Magnesium hydroxide, zinc hydroxide and the like, and one or more kinds can be used in combination as required.

(adhesive)
As an adhesive for the undercoat coating layer, an adhesive that can generally be used for papermaking can be used in combination. For example, proteins such as casein and soy protein; conjugated diene latex such as methyl methacrylate-butadiene copolymer latex, styrene-methyl methacrylate-butadiene copolymer latex, polymer latex of acrylate ester and / or methacrylate ester, or Acrylic latex such as copolymer latex, vinyl latex such as ethylene-vinyl acetate polymer latex, or alkali partial solubility obtained by modifying these various copolymer latexes with a functional group-containing monomer such as a carboxyl group or Latexes such as insoluble latex; synthetic resin adhesives such as polyvinyl alcohol, olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin; oxidized starch, positive starch, esterified starch, dextrin, etc. Flour; carboxymethyl cellulose, and cellulose derivatives such as hydroxyethyl cellulose, are adhesives exemplified usually used for coated paper can be used in combination one or more from among the appropriately selected and. Among these, starches are particularly preferable because they have high water retention and are difficult to cut paper, and the uniform coating performance in low concentration coating is good. In particular, it is preferable to use a paper strength enhancer and a fixing agent in the base paper. Furthermore, when polyacrylamide is used as the paper strength enhancer and a sulfuric acid band is used as the fixing agent, there is little paper breakage. Since paper can be manufactured, it is preferable.

  The blending ratio of the pigment and the adhesive in the undercoat coating solution is preferably 20 to 45 parts by mass, more preferably 30 to 40 parts by mass with respect to 100 parts by mass of the pigment in the undercoat coating layer. preferable. If the blending amount of the adhesive is less than 20 parts by mass, it is not preferable because the subsidence of the pigment into the base paper cannot be sufficiently prevented, the flatness after the undercoating is deteriorated, and the printability after the overcoating is reduced. Absent. In addition, it is difficult to adhere the pigment to the coating liquid, and the dropped pigment tends to contaminate the paper machine or the coating machine system, which is not preferable because the operability is lowered. If the amount of the adhesive exceeds 45 parts by mass, it is not preferable when applying a coating liquid containing pigment and starch at a low coating amount because uniform coating is difficult and printability tends to decrease. .

  In addition, as for the compounding quantity of the adhesive agent with respect to a pigment, a general undercoat coating liquid is 5-10 mass parts, while the undercoat coating liquid of this invention is 20-45 mass parts compared with the past. Increased by about 10 to 40 parts. This is because, when a lower concentration coating liquid is applied, the fluidity of the coating liquid is high and it becomes difficult to fix the pigment to the surface of the base paper, so the amount of the adhesive required is increased. is there. For this reason, as a coating method used for undercoating, it is preferable to use a film transfer method in which the coating layer is easily retained on the surface of the base paper as described below.

The undercoat coating solution can be applied by various known methods in the size press process during the paper making process, but is preferably applied by a film transfer method. In the film transfer method, a coating layer with a certain film thickness can be applied to the surface of the base paper. For example, compared to a method of forming a coating liquid pound like a two-roll size press and applying it to the inside of the base paper. This is characterized in that the penetration of the coating liquid is suppressed and thin film coating is possible on the surface of the base paper. Therefore, when undercoating is applied by the film transfer method, even if the coating amount is as low as 0.5 to 2.5 g / m ² as in the present invention, the coating layer is uniformly applied to the base paper. It can be formed, the flatness of the coated paper after the top coating is increased, and the printability is improved. In particular, as in the present invention, when heavy calcium carbonate or recycled particles having low printability are used for the undercoat coating layer, it is important to perform the undercoat coating by a film transfer method. When applied by the blade coating method, the flatness of the resulting undercoat layer is high, but since the surface of the base paper cannot be sufficiently covered with the above coating amount, an uncoated portion is generated and printability is reduced. Because there is a fear, it is not preferable. The two-roll size press is not preferable because the coating liquid is easily impregnated into the base paper and paper breakage is likely to occur.

  For this reason, coating with a film transfer method is preferable because it has high printability and can produce coated paper with good operability by suppressing the occurrence of paper breakage, but it prevents the coating liquid from sinking into the base paper. Because it is not a thing, it is difficult to completely suppress the occurrence of paper breaks. Therefore, in the film transfer system, it is preferable to use polyacrylamide as a paper strength enhancer and a base paper containing a sulfuric acid band as a fixing agent, because coated paper can be produced with sufficient operability.

The concentration of the undercoat coating solution is not particularly limited, and may be appropriately adjusted so that the coating amount is in the range of 0.5 to 2.5 g / m ² . For example, the concentration may be 3 to 20% by mass, and 5 to 15% by mass is preferable because more uniform coating can be performed within the above coating amount range. When the concentration is less than 3% by mass, water absorption to the base paper is likely to increase, so that it is easy to break the paper during undercoating. If the concentration exceeds 20% by mass, uniform coating is difficult to obtain, and not only the hand feeling is lowered, but also the flatness after undercoating and thus the printability after overcoating are unfavorable.

Subbing coating layer, the coating amount per one surface at a solids coating weight, 0.5 to 2.5 g / m ^2, is applied to preferably be 1.0 to 2.0 g / m ² . If the undercoat is not applied or the solid content is less than 0.5 g / m ² , not only sufficient opacity will not be obtained, but also the base paper will be difficult to flatten and the printability after topcoat will be reduced. To do. If the amount of the top coat is increased at less than 0.5 g / m ² to improve the printability and opacity, it is necessary to increase the amount of coating excessively and reduce pulp. It is necessary and there is a problem that the hand feeling is lowered. On the other hand, if it exceeds 2.5 g / m ² , the opacity is excellent, but the rice paper of the base paper has to be reduced correspondingly, and there is a problem that the hand feeling is inferior. In addition, when the amount of the undercoat coating is increased, the amount of water absorbed by the base paper is increased, so that paper breakage is likely to occur. In the range of the above coating amount, it is possible to obtain a coated paper while suppressing paper breakage by applying the primer coating by the film transfer method. When 4% by mass, 0.1 to 1.5% by mass of a sulfuric acid band is used as a fixing agent and the coating amount is applied in the range of 0.5 to 2.5 g / m ² , the printability is good, A coated paper having a high transparency and a hand feeling is preferable because it can be produced with good operability while suppressing paper breaks.

<Pre-calendar>
The base paper after the undercoating is preferably subjected to a pre-calendering before the top coating (pigment coating) because the flatness after the top coating can be improved. As the pre-calender, a soft calender in which a metal roll and an elastic roll are combined is preferable because the surface is highly improved. The pre-calendar can be performed in one stage or a combination of two or more stages as required. The surface of the base paper after undercoating is flattened by the pre-calender treatment, and the base paper surface is flattened without reducing the hand feeling of the paper by not requiring excessive flattening treatment in the later calendar. It is possible to improve the printability, and sufficient printability and hand feeling as a coated paper can be obtained. Further, the surface of the undercoat coating layer is planarized to improve the coatability of the topcoat coating and to suppress coating unevenness of the coating liquid. The linear pressure of the pre-calender is preferably 10 to 80 kN / m, more preferably 10 to 50 kN / m. If it is less than 10 kN / m, flattening of the base paper after undercoating will not proceed, and if it exceeds 80 kN / m, the base paper will be compressed more than necessary, so that the paper strength and rigidity will be reduced.

<Topcoat coating>
An undercoating layer is formed, and an overcoating layer mainly composed of a pigment and an adhesive is provided on a base paper that has been preferably flattened with a pre-calender.

  There are no particular limitations on the type of pigment used for top coating, and those generally used as papermaking pigments can be used. Examples of the pigment include heavy calcium carbonate, light calcium carbonate, kaolin clay, delaminated kaolin, talc, white carbon, titanium dioxide, calcium sulfate, satin white, calcium sulfite, gypsum, barium sulfate, diatomaceous earth, magnesium carbonate, Inorganic pigments such as aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, polystyrene resin fine particles, urea formalin resin fine particles, fine hollow particles, porous fine particles, etc. Special pigments such as organic pigments are exemplified, and one or more of them can be appropriately selected and blended.

  Among the above pigments, when kaolin clay is used, the glossiness and smoothness of the coated paper are easily improved, and the printability becomes better, which is preferable. In particular, when heavy calcium carbonate and / or regenerated particles having low printability are used in the undercoat layer as in the present invention, it is preferable to add clay to the topcoat coating liquid in order to improve printability. By blending clay, the coated paper surface is easy to flatten, and it is possible to reduce the linear pressure in the calendering process described later, so there is no need to apply excessive linear pressure and the pulp in the coated paper is less likely to be crushed. Therefore, a coated paper having a good hand feeling can be obtained.

  As the clay, those conventionally used for papermaking can be used. For example, large particle size clay, fine particle clay, calcined clay, high white clay and the like can be mentioned. Among these, the use of fine clay is more preferable because the effect of improving the roughness of the surface of the undercoat coating layer is high, so that the printability can be improved.

The blending amount of the clay is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the total amount of the pigment to be blended in the top coat layer.

When the heavy calcium carbonate is used as the above-mentioned pigment, it is preferable because the whiteness is easily improved. However, the surface property after coating is deteriorated and the printability is inferior, so that the effect of the present invention is not impaired. It is preferable. In particular, kaolin clay and heavy calcium carbonate are preferably used in combination as the pigment of the top coat layer. In this case, the amount of heavy calcium carbonate is 100 parts by weight of the total amount of the pigment blended in the top coat layer. It is preferable to set it as 70-95 mass parts with respect to it.

  As an adhesive used for the top coat layer, an adhesive that can be generally used for papermaking can be used in combination. For example, proteins such as casein and soy protein; conjugated diene latex such as methyl methacrylate-butadiene copolymer latex, styrene-methyl methacrylate-butadiene copolymer latex, polymer latex of acrylate ester and / or methacrylate ester, or Acrylic latex such as copolymer latex, vinyl latex such as ethylene-vinyl acetate polymer latex, or alkali partial solubility obtained by modifying these various copolymer latexes with a functional group-containing monomer such as a carboxyl group or Latexes such as insoluble latex; synthetic resin adhesives such as polyvinyl alcohol, olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin; oxidized starch, positive starch, esterified starch, dextrin, etc. Flour; carboxymethyl cellulose, and cellulose derivatives such as hydroxyethyl cellulose, are adhesives exemplified usually used for coated paper can be used in combination one or more from among the appropriately selected and. Of these, styrene-butadiene copolymer latex is particularly preferable because of its good thermal stability and good adhesion to the pigment.

  The blending ratio of the pigment and the adhesive in the topcoat coating liquid is preferably 3 to 10 parts by mass, and more preferably 4 to 8 parts by mass with respect to 100 parts by mass of the pigment in the topcoat coating layer. It is more preferable to adjust so. If the blending amount of the adhesive is less than 3 parts by mass, it is not preferable because the coating layer is easily smeared with a metal roll when performing a flattening process with a super calender or the like. On the contrary, when the compounding amount of the adhesive exceeds 10 parts by mass, the adhesive is formed in the coating layer, the smoothness of the coating layer surface is lowered, the ink is difficult to transfer, and the printability is lowered. Therefore, it is not preferable.

  In addition to pigments and adhesives, the top coating liquid used in the present embodiment includes, for example, dust preventing agents, fluorescent dyes, fluorescent dye brighteners, antifoaming agents, mold release agents, colorants, water retention agents, and the like. Various auxiliary agents generally used in papermaking applications can be appropriately blended within a range not impairing the object of the present invention.

  There is no particular limitation on the method for preparing the topcoat coating solution, and the mixing ratio of pigments, adhesives, dust inhibitors, and various auxiliary agents as necessary is adjusted appropriately, and a uniform composition at an appropriate temperature. What is necessary is just to stir and mix so that it may become. In addition, the solid content concentration of the topcoat coating liquid is not particularly limited, and is preferably adjusted to, for example, about 60 to 75% by mass according to the coating apparatus and the coating amount.

The top coat layer is preferably applied to both sides of the base paper at a solid content of 3 to 10 g / m ² per side of the base paper, and more preferably 5 to 9 g / m ^2. preferable. When the coating amount is less than 3 g / m ² per side, the coating layer is not sufficiently flattened, and the flatness and printability of the coating layer surface are poor. When the amount exceeds 10 g / m ² , the amount of pulp that can be used for the base paper is reduced, and thus the coated paper has a low hand feeling.

  The top coat layer formed as described above is flattened with a flattening facility that combines an elastic roll and a metal roll, such as a super calender and a soft calender, for the purpose of further improving gloss, smoothness, and printability. Processing can be performed. Unlike conventional machine calenders, such flattening equipment treats the surface of the paper with a wide surface at a high temperature so that it can be flattened without excessively increasing the density of the base paper or the coating layer. For example, a suitable printing surface can be formed in offset printing, electrophotographic printing, and the like. Among them, a multi-nip calender, more preferably a 6-stage, 8-stage, or 10-stage multi-nip calender is preferable because the nip pressure can be easily adjusted. Especially when clay is highly blended in the top coat layer, the printability is likely to improve, so the use of a multi-nip calender that can adjust the linear pressure appropriately minimizes the reduction of hand feeling compared to other calender equipment. Since it can suppress, it is especially preferable.

  Moreover, as an installation place of a calendar, an on-machine type integrated with a paper machine and a coating machine is preferable. In the on-machine type, flattening can be performed immediately after coating with a high paper surface temperature, so the glossiness of blank paper is easy to improve, the linear pressure required to obtain the desired coated paper is low, and the coated paper is Since it is difficult to be crushed, a coated paper with a high hand feeling is preferable.

  The linear pressure, temperature, and speed of the flattening treatment using various calendar facilities are not particularly limited. To improve the smoothness of the coated layer after the treatment and improve the hand feeling, for example, the linear pressure is 100. It is preferable to adjust so that it may become -300 kN / m, a metal roll temperature may be 100-200 degreeC, and a speed | rate may be 1,000-2,000 m / min.

The basis weight of the coated paper thus obtained is 30 to 100 g / m ^{2 as} measured in accordance with the method described in JISP 8124 “Basis weight measurement method” from the viewpoint of ensuring printability and hand feeling. preferably, it is preferred that even at ^{50g / m 2 ~80g / m 2} . If the basis weight is less than 30 g / m ^2, for example while securing the printability, it may become difficult to secure the paper quality strength simultaneously, if the basis weight exceeds 100 g / m ² is required in recent years There is a risk that it will be difficult to achieve the weight saving and resource saving.

  The whiteness of the coated paper varies slightly depending on the application, but from the viewpoint of obtaining a sufficiently satisfactory aesthetic appearance as a printed matter or recorded matter, it is measured with a color analyzer (model number: i5, manufactured by Macbeth Gretag). It is preferably 83% or more, more preferably 85% or more.

  Similarly, the opacity is slightly different depending on the application, but it is a color analyzer from the viewpoint of obtaining sufficient aesthetics by preventing back-through of printed images as printed matter and recorded matter, and obtaining sufficient visibility for characters. It is preferably 85% or more, more preferably 88% or more as measured by (model number: i5, manufactured by Macbeth Gretag).

Like this invention, it consists of two layers comprised from the undercoat coating layer which touches a base paper, and the topcoat coating layer formed on the said undercoat coating layer, The said undercoat coating layer reproduces | regenerates at least as a pigment In the coated paper, which contains particles and / or heavy calcium carbonate, and the coating amount of the undercoat coating layer is 0.5 to 2.5 g / m ² per side, undercoat coating Since the amount is low, the proportion of pulp in the coated paper is large, and a coated paper with excellent hand feeling can be obtained.

As described above, the coating composition comprises at least regenerated particles and / or heavy calcium carbonate as a pigment for the undercoat coating layer, and the undercoat coating amount is 0.5 to 2.5 g / m ² per side. In industrial paper, the percentage of pulp in the coated paper is large, and a coated paper with excellent hand feeling can be obtained.However, in order to achieve a low coating amount, the concentration of the coating solution during undercoating is reduced. Since it is necessary to make it low as 3-20 mass% and also 5-15 mass%, it is easy to generate | occur | produce a paper break. Therefore, by containing an internal paper strength enhancer and a fixing agent in the base paper, in particular, by containing a polyacrylamide resin as an internal paper strength enhancer, and more preferably by adding a sulfuric acid band as a fixing agent. Even if the undercoat coating liquid penetrates into the base paper, it is difficult to cause paper breakage and the coated paper can be produced with good operability. Furthermore, the ash content in the base paper is 8% by mass or less, and the amount of the adhesive contained in the undercoat coating layer is 20 to 45 parts by mass with respect to 100 parts by mass of the pigment in the undercoat coating layer. Even when the base paper absorbs the undercoat coating liquid, it is particularly difficult for paper breaks to occur, and the coated paper can be produced with good operability.

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

Examples and Comparative Examples Papermaking, undercoating, pre-calendering, topcoating and calendering were carried out in the types and proportions shown in Tables 1 and 2 to obtain coated paper for printing. In addition, light calcium carbonate was suitably added so that ash might become the ash of Table 1 and 2. The pigments, raw materials and chemicals used are as follows.

(1) Papermaking Paper strength enhancer amphoteric polyacrylamide (amphoteric PAM)
(Product number: Hermide DN710, manufactured by Harima Chemicals)
Cationic polyacrylamide (cationic PAM)
(Product number: Harifix UF-570, manufactured by Harima Kasei Co., Ltd.)
Anionic polyacrylamide (anionic PAM)
(Product number: Hermide C-10, manufactured by Harima Kasei Co., Ltd.)
Epoxy-modified polyamide (polyamide)
(Product number: Hermide PY-525A, manufactured by Harima Chemicals)
Cationic modified polyamine (polyamine)
(Product number: WS-4052, manufactured by Seiko PMC)
・ Fixing agent sulfuric acid band (Product number: sulfuric acid band, manufactured by Asahi Chemical Industry Co., Ltd.)
PEI (polyethyleneimine) (Part No .: Cassiofast SF, manufactured by BASF)
PDADMAC (polydiallyldimethylammonium chloride) (Part No .: Nalco 2020, manufactured by Katayama Nalco)
・ Light calcium carbonate (Product No .: TP-121-6S, manufactured by Okutama Kogyo Co., Ltd.)

(2) Undercoat coating (pigment)
Recycled particles a) Recycled particles derived from paper sludge (recycled particles)
The particle size was adjusted by the production method of Japanese Patent No. 3819706. Specifically, paper sludge obtained by dehydrating to 55-65% with a DIP floater floss or dewatering equipment is cut into a string of 4.5 mm in diameter and 8-10 cm in length, and then incinerated. Regenerated particles having a secondary particle diameter of 3 μm were produced by incineration at 1000 ° C. in a furnace.
b) Regenerated particles derived from deinked floss (aggregates)
It was produced by adjusting the particle diameter by the production method of Japanese Patent No. 3869455. Specifically, the deinking floss discharged from the waste paper treatment process is dehydrated to a moisture content of 60% (dehydration process), dried at 120 ° C. (drying process), and the moisture content at the firing process inlet becomes 3%. In the first firing step, the unburned portion is 7% so that the unburned portion is 12% by weight (baking step), and the particle size is 500 μm. Grinding (grinding step) produced regenerated particle aggregates.
c) Recycled silica-coated particles (silica composite)
It was produced by adjusting the particle size by the production method of Japanese Patent No. 3907688. Specifically, deinked floss discharged from the waste paper processing process is dehydrated to a moisture content of 50% (dehydration process), dried at 130 ° C. (drying process), and the moisture content at the firing process inlet becomes 3%. In the first firing step, the unburned portion is 7% so that the unburned portion is 12% by weight (baking step), and the particle size is 500 μm. By pulverizing (pulverizing step), a silica-coated regenerated particle aggregate in which silica was deposited on the surface of the regenerated particle aggregate was produced.
・ Calcium carbonate: Heavy calcium carbonate (Product number: Hydro curve 90K, manufactured by Omiya Korea)
・ Kaolin clay: Fine clay (Product number: Kao Fine, manufactured by Imeris)

(3) Top coating (pigment)
・ Kaolin clay: Fine clay (Product number: Kao Fine, manufactured by Imeris)
・ Calcium carbonate: Heavy calcium carbonate (Product number: Hydro curve 90K, manufactured by Omiya Korea)
(adhesive)
・ Styrene-butadiene copolymer latex (Product No .: XY4, manufactured by Nippon A & L)
(Manufacturing procedure)
LBKP and NBKP are blended at a mass ratio of 80:20 as raw pulp, and the paper strength enhancer and fixing agent shown in Tables 1 and 2 are respectively added to the pulp (absolutely dry amount) in solid content. Sizing agent (product number: AK-720H, manufactured by Harima Chemicals Co., Ltd.) 0.02% by mass, cationized starch (product number: Amilofax T-2600, manufactured by Abebe Japan Co., Ltd.) 1.0% by mass, and yield A pulp slurry was obtained by adding 0.02% by mass of an improver (product number: NP442, manufactured by Nissan Eka Chemicals Co., Ltd.).

  Next, in the winder part using the paper making system including wire part, press part, pre-dryer part, undercoater part, pre-calender part, after-dryer part, top coater part, scuff dryer part, calendar part, reel part Finished product.

First, the pulp slurry is made with a wire part, then used for a press part and a pre-dryer part to produce a base paper with a basis weight of 33 to 37 g / m ² , and then with an undercoater part, in Tables 1 and 2 Undercoat coating liquids prepared by mixing pigments and adhesives (product number: modified starch starch, manufactured by Eliere Shoko Co., Ltd.) in the amounts shown in Tables 1 and 2 in terms of solid content are shown in Tables 1 and 2 per side. The both sides were undercoated so that the coating amount (g / m ² ) described in ( ¹ ) was applied, and dried with an after dryer part. Then, it planarized with the pre-calender (linear pressure 50kN / m).

Next, on the top coater part, both sides of the coating liquid consisting of 8 parts by mass of pigments and latex (product number: XY4, manufactured by Nippon A & L Co., Ltd.) listed in Tables 1 and 2 are overcoated so that the amount is 8 g / m ² per side. The coated paper for printing having a basis weight of 54 g / m ² was manufactured. In addition, the compounding quantity of latex was made into the weight part with respect to 100 mass parts of pigments.

  Next, the calender part was subjected to a flattening treatment at a linear pressure of 200 kN / m and a speed of 1,000 m / min, and was applied to a winder part to obtain a coated paper for printing.

  In addition to the above, the manufacturing system may use an off-machine coater in which the paper machine and the coater part are separated, or a system including an off-machine calendar in which the paper machine and the soft calendar are separated.

  In addition, paper was made using a gap former in the wire part, a rod metering size press coater was used in the undercoater part, and a blade coater was used in the top coater part. In the calendar part, a super calendar was used.

  About the obtained coated paper, each physical property and characteristic were investigated with the following method. The results are shown in Tables 1 and 2.

(A) Whiteness Measured with a color analyzer (model number: color i5, manufactured by Macbeth Gretag). Measurement conditions are UVIN (including ultraviolet rays), SCI (including reflected light), C light source, viewing angle 2 °.

(B) Opacity Measured by a method based on JISP8149 using a color analyzer (model number: color i5, manufactured by Macbeth Gretag).

(C) Hand feeling 20 samples of A4 size (210 mm x 297 mm) are stacked, one side of the long side is stapled at 3 locations (top, center, bottom) and placed horizontally, turning 10 sheets in total, The hand feeling of paper was evaluated based on the following evaluation criteria.
A: The paper after turning does not sag and is excellent in hand feeling.
○: The paper after turning is slightly sagged and slightly inferior to the hand feeling.
Δ: The paper after turning is slightly sagging and slightly inferior to the hand feeling.
X: The paper after turning is sagging, and the hand feeling is inferior.

(D) Printability Using an offset printing machine (model number: Lithopia L-BT3-1100, manufactured by Mitsubishi Heavy Industries, Ltd.), color 4 (color: product number: ADVAN, manufactured by Dainippon Ink & Chemicals, Inc.) 5000 copies of color printing were performed. About this printing surface, the printing nonuniformity of the printed matter was observed visually and with a magnifying glass (10 times), and the degree thereof was evaluated based on the following evaluation criteria.
A: There is no printing unevenness, excellent printability, and practical use.
○: Printing unevenness occurs slightly and printability is slightly inferior, but it can be used in practice.
Δ: Some printing unevenness occurs and printability is slightly inferior, but it can be used in practice.
X: Printing unevenness occurs, printability is poor, and actual use is impossible.

(E) Operability The number of occurrences of sheet breakage during continuous operation for 3 days was evaluated based on the following evaluation criteria.
◎: Paper break does not occur ○: Paper break has occurred once but can be used actually △: Paper break has occurred twice, but can be used actually ×: Paper break has occurred more than 3 times and cannot be used

  The coated paper of the present invention can be suitably used as a coated paper for printing used in offset printing, gravure printing and the like.

Claims (4)

A coated paper having a base paper and a coating layer mainly composed of a pigment and an adhesive on the base paper,
The coating layer consists of two layers composed of an undercoat coating layer in contact with the base paper, and an overcoat coating layer formed on the undercoat coating layer,
The undercoat coating layer contains at least play particles及BiShigeru calcium carbonate as a pigment,
The regenerated particles are regenerated particle aggregates or silica-coated regenerated particle aggregates,
The regenerated particle aggregate or silica-coated regenerated particle aggregate is 50 to 95 parts by mass, and the heavy calcium carbonate is 5 to 50 parts by mass with respect to 100 parts by mass of the pigment in the undercoat coating layer,
The undercoat coating coating weight per side of the layer 0.5 to 2.5 g / ^m are ^two der,
In the top coat layer, the blending amount of clay is 30 parts by weight or less and the blending amount of heavy calcium carbonate is 70 parts by weight or more with respect to 100 parts by weight of the total amount of the pigment blended in the top coat layer. coated paper, wherein there <br/> that.   The coated paper according to claim 1, wherein the base paper contains a polyacrylamide resin as an internal paper strength enhancer.   The coated paper according to claim 1 or 2, wherein the ash content in the base paper is 8% by mass or less.   The compounding quantity of the adhesive agent contained in the said undercoat coating layer is 20-45 mass parts with respect to 100 mass parts of pigments in an undercoat coating layer, The any one of Claims 1-3 characterized by the above-mentioned. Coated paper as described in 1.