JP2009270211A - Multilayer-coated bulky coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bulky coated paper having excellent full-color printability such as offset printability and gravure printability while having ≤5 g/m<SP>2</SP>coated weight per one surface. <P>SOLUTION: The multilayer-coated bulky coated paper is a coated paper having at least two layers of coated layers at least on one surface of a base paper. The coated layer contacting with the base paper in the coated layers includes a water-soluble polymer and an inorganic filler regulated so that the proportion of the inorganic filler based on 100 pts.mass of the water-soluble polymer may be ≥1 and ≤100 pts.mass expressed in terms of dry mass, and the coated weight of the coated layer contacting with the base paper is ≤5 g/m<SP>2</SP>per one surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to coated paper. More specifically, the present invention relates to a multilayer coated bulky coated paper having a low coating amount and excellent printability.

  In recent years, with the development of visualization, demand for printing paper capable of high-definition printing in full color such as offset printing and gravure printing has increased, and in order to obtain a high-definition printed matter, the surface and / or the back surface of the base paper is coated. There is a growing need for coated papers that have been coated with a working solution to form 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 for commercial prints, bulky A3 grade lightweight coated paper and fine coated paper are preferably used.

  Patent Document 1 discloses a coated paper on which two coating layers are formed, and the coating layer (undercoat coating layer) on the side close to the base paper is a water-soluble polymer. A method for producing a coated paper is disclosed in which the outermost coating layer (top coating layer) is a coating layer mainly composed of a pigment. However, in the above case, since the flatness after the top coating is low, if the calendar process is performed at a high nip pressure in order to improve the flatness, there is a problem that the coated paper is crushed and the bulk becomes low. When finished in a low nip condition to produce a sufficient flatness, there was a problem that sufficient flatness could not be obtained.

  Patent Document 2 discloses a coated paper provided with two coating layers mainly composed of a pigment and an adhesive. When two coating layers of a pigment coating layer are applied, an undercoat coating layer is disclosed. However, although the total coating amount of the top coating layer is increased and the flatness is improved, there is a problem that a bulky coated paper cannot be obtained.

  For this reason, in the above-described production method, in both the top coat layer and the undercoat coat layer, the printability is reduced when the coating amount is reduced. Therefore, the bulky and high flatness coating is maintained while maintaining the printability. Paper was not obtained.

  Further, Patent Document 3 and Patent Document 4 disclose electrophotographic transfer paper using an organic pigment as a coating pigment, which is lighter than a coated paper using a general inorganic pigment and is suitable for printing. However, organic pigments are expensive and it is difficult to increase the concentration of the paint, and uniform coating properties cannot be obtained. Since the trouble of the calendar roll is likely to occur, the coated paper is not sufficiently high in printability.

As described above, in the above general coated paper manufacturing method, for example, the undercoat coating amount is 5 g / m ² or less per side and is light while being bulky and full color printing such as sufficient offset printing suitability and gravure printing. An appropriate coated paper was not obtained.

The bulkiness referred to in the present invention refers to a coated paper having a coated paper density of 1.2 g / cm ³ or less, preferably 1.1 g / cm ³ or less, more preferably 1.0 g / cm ³ or less. .
JP 2007-031925 A Japanese Patent No. 3257720 JP 2007-009361 A Japanese Patent Laid-Open No. 05-241366

The main problem to be solved by the present invention is to provide a bulky coated paper excellent in full color printability such as offset printability and gravure printability while the undercoat coating amount is 5 g / m ² or less per side. It is in.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
A coated paper having at least two coating layers formed on at least one side of a base paper,
Of the coating layers, the coating layer in contact with the base paper contains a water-soluble polymer and an inorganic pigment,
The ratio of the inorganic pigment to 100 parts by mass of the water-soluble polymer is 1 part by mass or more and 100 parts by mass or less by dry mass,
And the coating amount per side of the coating layer in contact with the base paper is 5 g / m ² or less,
A multilayer coated bulky coated paper characterized by the above.

[Invention of Claim 2]
The pigment contains 20 to 60% by mass of a pigment having a particle size of 10 to 30 μm (large particle pigment) and 40 to 80% by mass of a pigment having a particle size of 0.1 to 2.0 μm (small particle pigment).
The multilayer coated bulky coated paper according to claim 1.

[Invention of Claim 3]
The pigment is a recycled particle derived from papermaking sludge,
The multilayer coated bulky coated paper according to claim 1 or 2.

[Invention of Claim 4]
The water-soluble polymer is at least one of starch and starch derivatives;
The multilayer coated bulky coated paper according to any one of claims 1 to 3.

[Invention of Claim 5]
The multilayer coated bulky coated paper according to any one of claims 1 to 4, wherein the coating layer contains a polymer compound having water retention.

[Invention of Claim 6]
The polymer compound having water retention is a resin mainly composed of a methacrylic acid-acrylic acid copolymer,
The multilayer coated bulky coated paper according to claim 5.

[Invention of Claim 7]
The pigment is a regenerated particle aggregate derived from deinking floss,
The multilayer coated bulky coated paper according to any one of claims 1 to 6.

[Invention of Claim 8]
The blank paper glossiness measured in accordance with “Paper and paperboard—75-degree specular gloss measurement method” described in JIS P 8142: 2005 is 20 to 40%.
The multilayer coated bulky coated paper according to any one of claims 1 to 7.

According to the present invention, it becomes a bulky coated paper excellent in full color printing aptitude such as offset printing aptitude and gravure printing aptitude while the undercoat coating amount is 5 g / m ² or less per side.

Next, an embodiment of the present invention will be described.
The coated paper of this embodiment is a coated paper having at least two coated layers, and among the coated layers, a water-soluble polymer and an inorganic pigment are applied to a coated layer (undercoat coated layer) in contact with the base paper. And a coating layer in which the coating amount per side of the undercoat coating layer is 5 g / m ² or less is formed, so that the coated paper is excellent in printability and bulkiness.

〔Base paper〕
The base paper of this form has pulp fiber as a main component. The kind of raw material pulp which is the raw material of this pulp fiber is not specifically limited, What can generally be used for papermaking use can be illustrated. Specifically, for example, chemical pulp, mechanical pulp, waste paper pulp and the like are preferably exemplified.

  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.

  Examples of the mechanical pulp include stone grand pulp (SGP), pressurized stone grand pulp (PGW), refiner ground pulp (RGP), chemi-ground pulp (CGP), thermo grand pulp (TGP), ground pulp (GP), Thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP) and the like are exemplified, and one or more of them can be appropriately selected and used.

  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, Kamihiro waste paper, Kent waste paper, imitation waste paper, and old paper waste paper, etc. Examples include 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.

  In addition, rag pulp, straw pulp, esparto pulp, bagasse pulp, bamboo pulp, kenaf pulp, and other auxiliary pulps such as bast pulp, etc. made from cotton, flax, hemp, jute, manila hemp, ramie, etc. are used. You may do it.

  In this embodiment, the raw material pulp is mixed to prepare a papermaking raw material (stock slurry). For the raw material pulp, for example, an internal additive, an internal additive 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 are no particular limitations on the papermaking equipment that can be used when making the papermaking raw material (raw pulp) to produce the base paper, but in order to obtain a lighter and lighter coated paper, the following equipment is combined: Is preferably used.

  First, the wire part is not particularly limited, such as a long net former, a combination of a long net former and an on-top former, or a twin wire former, but the paper jet jetted from the head box is composed of two wires. Since the gap type gap former that is immediately sandwiched dehydrates without breaking the formation, wet paper density unevenness hardly occurs, and coated paper with uniform bulkiness can be obtained, so paper breakage is less likely to occur preferable.

  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, but the shoe press is more than necessary because it can improve not only the dehydration property but also the smoothness. Furthermore, it is more preferable because it can be dehydrated without increasing the linear pressure, is bulky, can prevent the decrease in the tensile strength and tear strength of the paper, and the occurrence of paper breakage.

  The wet paper that has passed through the press part is transferred to a single-deck type pre-dryer part and dried. As the pre-dryer part, a single deck dryer of a no-open draw type that can be dried with high efficiency without lowering the tensile strength and tear strength of the paper is preferable because a bulky coated paper can be obtained. Although it is possible to dry with the double deck method, the single deck method is adopted because it is inferior to the single deck method in terms of operability such as canvas marks, paper breaks, wrinkles, bulk, and paper splicing. It is preferable.

  As mentioned above, combining a wire part consisting of a gap former, a straight-through press part that eliminates an open draw, and a pre-dryer part consisting of a single-deck dryer results in bulkiness even in lighter and lighter coated paper. This is particularly preferable in that the decrease in the tensile strength and tear strength of the paper is small and the paper breakage hardly occurs.

  As described above, when the system is adopted in the wire part and the press part, the paper may be cut even if the kind and blending ratio of the raw material pulp and the decrease in the tensile strength and tear strength of the paper due to the bulkiness occur. There is an advantage that a coated paper can be obtained in which the decrease in productivity is minimized.

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 30 to In consideration of the fact that it is preferably 80 g / m ² , the basis weight of the base paper is preferably adjusted to be 15 to 79 g / m ² . If the basis weight of the target coated paper is less than 30 g / m ² , the tensile strength and tear strength of the paper are low, and for example, it may be difficult to use in commercial printing applications. If the basis weight of the paper is greater than 80 g / m ² , it cannot be said to be a lightweight coated paper.

[Undercoat layer]
In this embodiment, at least two coating layers are formed on at least one side (one side or both sides) of the base paper thus obtained, and the coating layer (undercoat coating layer) in contact with the base paper is an inorganic pigment for the water-soluble polymer. The ratio is suppressed to 1% by mass or more and 100% by mass or less by dry mass (that is, the compounding amount of the pigment is the same as or small amount with the compounding amount of the water-soluble polymer).

  In this respect, in the conventional pigment coated paper, since the pigment is not blended in the undercoat coating layer, the printability is inferior (see the above-mentioned Patent Document 1), or 100 parts by mass of the pigment as the undercoat coating layer. On the other hand, the adhesive was approximately 70 parts by mass or less (see Patent Document 2), and was not a bulky coated paper. In addition, electrophotographic transfer paper has failed to obtain full color printability such as offset printability and gravure printability.

  In this embodiment, the pigment is mixed in an amount of 1 to 100% by mass (1 to 100 parts by mass of the pigment with respect to 100 parts by mass of the water-soluble polymer), preferably 10 to 80% by mass with respect to the water-soluble polymer. As a result, the increase in density of the pigment-derived coating layer can be suppressed, so that the weight of the coated paper can be reduced, and not only the water-soluble polymer but also the pigment is partially contained in the coating layer, so that the printability is good. Can also be improved. When the proportion of the pigment is less than 1% by mass, the flatness of the coating layer is inferior and the printability is lowered. When the ratio of the pigment exceeds 100% by mass, the hand feeling derived from the water-soluble polymer is lowered.

  As a water-soluble polymer compound, for example, as an undercoat coating agent such as oxidized starch, hydroxyethyl etherified starch (HES), acetylated oxidized starch (AOS), starch such as enzyme-modified starch, polyacrylamide (PAM), etc. What is normally used can be used individually or in mixture of 2 or more types, respectively. The undercoat coating agent refers to a coating solution mainly composed of the water-soluble polymer and the pigment.

  The conventional pigment paint mainly composed of a pigment and an adhesive has a concentration of about 60% by mass, whereas the paint of this embodiment has a low concentration of 10 to 30% by mass, and the paint sinks into the base paper. There was a problem that the coating layer surface was difficult to be flattened, and printability was liable to deteriorate.

  For this reason, in the water-soluble polymer, it is preferable to use at least one of starch and starch derivatives that do not sink into the base paper and easily stay on the surface. In particular, in this embodiment, since the pigment is less than the water-soluble polymer, the pigment is likely to sink in proportion to the sink of the water-soluble polymer, and there is a problem that printability is further deteriorated. The use of PAM as a water-soluble polymer has the advantage that the resulting coated paper has a high hand feeling and improves the stiffness of the paper. However, PAM is more likely to sink into the base paper than starch, so the paper can be flattened. Is low.

  The pigment used for the undercoat layer in this form 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, sulfuric acid Inorganic pigments such as barium, white carbon, calcined kaolin, structured kaolin, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite These can be used, and one or more of them can be appropriately selected and used.

  In this embodiment, organic pigments such as polystyrene resin fine particles, urea formalin resin fine particles, fine hollow particles, and porous fine particles can be used in combination, but they are expensive, the concentration of the undercoat coating agent is reduced, and uniform. Since there is a problem that the coating cannot be obtained, it is preferably not contained, and even if contained, the content is preferably 5% by mass or less with respect to the water-soluble polymer.

  When a pigment having a large particle size is used as the pigment, there is an advantage that the water-soluble polymer has a large resistance to sinking into the base paper and is likely to stay on the base paper surface. From this point, the pigment of this embodiment has a particle size of 10 to 30 μm, preferably 10 to 20 μm, and the pigment (large particle size pigment) is 20 to 60% by mass, preferably 40 to 60% by mass of the whole pigment. , Which is preferable. A pigment having a particle diameter of less than 10 μm is likely to sink into the base paper. On the other hand, a pigment having a particle diameter exceeding 30 μm decreases the flatness of the surface of the coating layer, so that the printability may be reduced. Moreover, if the blending amount of the large particle size pigment is less than 20% by mass, sinking is likely to occur. On the other hand, if the blending amount of the large particle size pigment exceeds 60% by mass, the effect of flattening the coating layer surface becomes low. , Both of which are not preferable because printability is lowered.

  Further, as the above-mentioned large particle size pigment, a high flat pigment having an aspect ratio of 3 to 10 has a particularly high sinking effect on the base paper, and also has a good effect of improving the printability due to the good coverage of the base paper. Therefore, it is preferable.

  On the other hand, when the blending amount of the large particle size pigment is 20 to 60% by mass as described above, the effect of flattening the surface of the coating layer is high and the printability is improved. There was unevenness and there was room for improvement. Accordingly, as a result of intensive studies, the inventors set the blending amount of the large particle size pigment within the above range, and a pigment (small particle size of 0.1 to 2.0 μm, preferably 0.5 to 1.5 μm). It has been found that when the (pigment diameter) is blended so as to be 40 to 80% by mass, preferably 40 to 60% by mass, based on the whole pigment, some printing unevenness can be eliminated. In this regard, if the blending amount of the large particle size pigment is in the above range, the coating layer surface has only a large particle size pigment, although there is little sinking into the base paper and the coverage is good, so the effect of flattening the base paper is high. If it is covered with, the roughness derived from the large particle size pigment cannot be improved. Therefore, in order to improve the roughness derived from the large particle size pigment, the coating property derived from the large particle size pigment and the small particle can be obtained by using the small particle size pigment having a smaller particle size in combination within the above range. A further flatness improvement effect derived from the diameter pigment can be obtained.

  Here, pigments having a particle size of less than 0.1 μm are likely to sink into the base paper, while pigments having a particle size of more than 2.0 μm have a low flattening effect on the surface of the coating layer, and are therefore suitable for printing. May not be sufficiently improved. Further, when the blending amount of the small particle size pigment is less than 40% by mass, the smoothness cannot be improved, and the printability is deteriorated. On the other hand, when the blending amount of the small particle size pigment exceeds 80% by mass, Sinking is likely to occur and printability is reduced.

  In addition, the blending ratio of the large particle size pigment and the small particle size pigment is preferably 2: 8 to 6: 4, particularly preferably 4: 6 to 6: 4, in terms of dry mass ratio. Even if the ratio of the small particle size pigment exceeds 2: 8, only a small amount of small particle size pigment sinks into the base paper, which may not lead to improvement in printability. On the other hand, when the ratio of the small particle size pigment is less than 6: 4, it becomes difficult to obtain the effect of improving the printability derived from the small particle size pigment.

  In addition, when a regenerated particle obtained by regenerating from papermaking sludge, a regenerated particle aggregate regenerated from deinking floss, or a silica-coated regenerated particle agglomerate is used as the pigment, the bulk effect derived from the pigment is high and the resulting coating is obtained. This is preferable because not only the bulk of the paper is improved (the density is reduced), but also the effect of preventing sinking into the base paper is obtained. Unlike general pigments, regenerated particles have irregular shapes and bulky pigments, and because of their irregular shape, they have a high resistance to sinking water-soluble polymers into the base paper and remain on the base paper surface. Cheap. The regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates may be used as either large particle size pigments or small particle size pigments, but are preferably used for both.

  Here, a method for producing regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates will be described.

a) Recycled particles derived from paper sludge Recycled particles derived from paper sludge (white pigment obtained by pulverizing incinerated ash obtained by incineration of paper sludge), for example, those described in JP-A-2002-167523 can do. Specifically, for example, paper sludge is extruded into a string shape having a diameter of 3 to 10 mm, cut to a length of 8 to 10 cm, and then incinerated at 500 to 1000 ° C. with a rotary kiln. A white pigment having an average particle size of 0.1 to 40 μm obtained by pulverization in the order of dry pulverization and 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 agglomerates derived from deinked floss Regenerated particles derived from deinked floss (obtained by dehydrating, drying, firing and crushing papermaking sludge made mainly from deinked floss discharged from the waste paper processing step) Examples of regenerated particles that are agglomerated in the firing step and contain three components of calcium, silicon, and aluminum in the particles) are, for example, those described in JP-A 2007-99613 and JP-A 2007-1000026 Can be used. Specifically, for example, a flocculant is added to deinked floss having a moisture content of about 95 to 98% by mass, dehydrated to about 50 to 60% by mass, and the dehydrated product is dried with hot air and classified, and then 450 to 650 ° C. In such a range, it is fired and agglomerated so that the unburned ratio 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 40 μm. Pigments can be used. As the quality of the regenerated particles derived from the 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 particles 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 processed from papermaking wastewater, so firing unevenness is likely to occur, it cannot be uniformly fired, and foreign matter due to unfired or overfired occurs, Increase in the amount of impurities in the coated paper and reduction in opacity are likely to occur.

  Recycled particles can be recycled by baking paper sludge or deinked floss, so there is no need to dispose of landfills as waste, greatly reducing environmental impact and saving resources. It contributes. 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 particles As silica-coated regenerated particles, for example, those described in Japanese Patent Application Laid-Open No. 2007-146354 and Japanese Patent Application Laid-Open No. 2007-186800 can be used. Specifically, for example, after deinking floss dehydrated to a moisture content of 95 to 98% is further dehydrated to 40% to 70%, the moisture content becomes 2 to 20 mass% with hot air at 100 to 200 ° C. To dry. 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 40 μm to obtain a regenerated particle aggregate. In this 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 furthermore, calcium, silicon and aluminum in the deinking floss are converted into oxides. By adjusting to a mass ratio of 30 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, A white pigment having a pore radius adjusted to 300 to 1000 angstroms is preferred. This regenerated particle aggregate is added to and dispersed in an aqueous alkali silicate solution, and a slurry is prepared. Then, while heating and stirring, a diluted solution of mineral acid such as sulfuric acid, hydrochloric acid, nitric acid is added at a liquid temperature of 70 to 100 ° C. to produce a silica sol. By adjusting the pH of the final reaction solution to a range of 8.0 to 11.0, a white pigment obtained by generating silica sol particles having a particle diameter of 10 to 20 nm on the surface of the regenerated particle aggregate can be used. This silica-coated regenerated particles improve the oil absorption and opacity due to the silica precipitation effect by making calcium, silicon and aluminum into a mass ratio of 30 to 62:29 to 55: 9 to 35 in terms of oxides. Can do. As the quality of the silica-coated regenerated particles, for example, the oil absorption is 30 to 100 ml / 100 g.

  The silica-coated regenerated particles are preferably adjusted with a known pulverizer such as a wet pulverizer to an average particle size of 0.1 to 40 μm, and the ratio of the particle size of 0.1 to 40 μm is at least 80% or more. Is more preferable. When the average particle diameter is less than 0.1 μm, the pigment is liable to sink into the base paper and the printability is lowered, which is not preferable.

  Silica-coated regenerated particles can be made to react with sodium hydroxide in the used paper processing step for recycle use and contribute to recycle use of the raw material for papermaking and recycle particles as a buffering agent and bleaching aid. Further, when such silica-coated regenerated particles are used as a pigment, effects such as printability, hand feeling, ink drying property, ink absorption unevenness, and bulkiness are further increased than when regenerated particles not coated with silica are used. Can be further improved.

  As described above, a coating with a pigment content equal to or less than that of the water-soluble polymer is used for the undercoat coating layer, so that a coating having excellent printability even with a small coating amount. Work paper is obtained. In particular, it is preferable to use at least one of starch and starch derivatives as the water-soluble polymer, and the blending amount of the large particle pigment is preferably in the above range, and the blending amount of the small particle pigment is more preferably in the above range. It is particularly preferable to use regenerated particles regenerated from paper sludge, regenerated particle aggregates regenerated from deinking floss, and silica-coated regenerated particle aggregates as pigments.

  In the present embodiment, in addition to the above configuration, it is preferable to use a water retention agent (polymer compound having water retention property) that can impart a thickening effect to the paint in order to further prevent the paint from sinking.

  As the water retention agent, those conventionally used for papermaking can be used. For example, any of starch, cellulose, hyaluronic acid, polyvinyl alcohol, acrylic, and acrylamide can be used. Among these, it is preferable to use a cellulose type or an acrylic type which has a high effect of improving the viscosity and preventing the paint from sinking into the base paper. Furthermore, it is more preferable to use carboxymethylcellulose or an acrylic acid copolymer, and in particular, a copolymer of acrylic acid and methacrylic acid has a high effect of preventing the coating from sinking in a film transfer type roll coater described later, Even at a low coating amount, the effect of improving the printability is high, which is preferable.

  The content of the water retention agent is preferably 0.1 to 1.0% by mass, and more preferably 0.3 to 0.7% by mass with respect to the water-soluble polymer. If the amount is less than 0.1% by mass, the sinking of the coating increases. On the other hand, if the amount exceeds 1.0% by mass, the coating layer is not uniform because of excessive thickening. There is a fear.

  As described above, the use of a pigment having the above particle size characteristics in combination with a coating layer mainly composed of a water-soluble polymer increases the effect of improving printability. By using in combination, it is possible to further prevent the paint from sinking into the base paper, and the effect of improving the printability is particularly high.

  In addition to the water-soluble polymer compound, the pigment, and the water retention agent, for example, a paper strength enhancer for the purpose of improving water resistance and improving the surface strength, an externally added sizing agent for the purpose of imparting sizing properties, etc. can do.

  There is no particular limitation on the method of preparing the paint, water-soluble polymer compounds, pigments, water retention agents, and optionally adjusting the blending ratio of various auxiliary agents such as paper strength enhancer and external sizing agent, What is necessary is just to stir and mix so that it may become a uniform composition at appropriate temperature. Further, the solid content concentration of the coating is not particularly limited, and it is preferable to appropriately adjust it according to coating conditions such as a coating amount and a coating speed.

  Examples of the paint mainly composed of the water-soluble polymer compound include a two-roll size press coater, a gate roll coater (GR), a blade metering size press coater, a rod metering size press coater (RMSP), a shim sizer, and a JF sizer. Undercoating can be performed on at least one side of the base paper by a coating machine such as a film transfer type roll coater. In particular, when a film transfer type roll coater (rod metal ring size press coater, shim sizer, JF sizer) with better coverage is used, the coatability is higher and the coatability is higher because the coatability is lower and the coatability is higher. This is preferable because it provides a processed paper.

The undercoat coating layer is formed by coating a coating material with a coating amount of 0.1 g / m ² or more per side, further 0.3 g / m ² or more, particularly 0.5 g / m ² or more. it is preferable, also less per side 5.0 g / m ^2, more 3.0 g / m ² or less, is preferably formed in particular coated at a coat weight of 1.0 g / m ² or less. When the coating amount is less than 0.1 g / m ² , the covering property of the base paper surface is poor, and the glossiness of the white paper and the printability may be reduced. Conversely, when the coating amount exceeds 5.0 g / m ² , A high concentration of the coating liquid is required, and uniform coating may be difficult due to an increase in viscosity, which is not preferable because print quality is deteriorated. On the other hand, when the coating amount exceeds 5.0 g / m ² , the tightness is lowered and the hand feeling is impaired.

  The undercoat coated paper thus obtained can be subjected to flattening such as calendaring as necessary. The linear pressure of the calendar 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 linear pressure in the pre-calendar is less than 10 kN / m, the flattening effect is low, and printability may be reduced. On the other hand, if the linear pressure exceeds 50 kN / m, not only the flattening effect reaches a peak, but also the tensile strength. In addition, tear strength and bulkiness may be reduced.

  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. When the treatment temperature is lower than 50 ° C, the flattening effect is reduced. Conversely, when the treatment temperature is higher than 90 ° C, the fiber is burnt and not only the whiteness is lowered but also the fiber is easily damaged, and the tensile strength and tear strength are reduced. Therefore, it is not preferable.

  As described above, in addition to the composition of the coating solution, a film transfer type roll coater is used, and an appropriate coating amount is applied and flattened under an appropriate calendar condition, so that the coating amount of an overcoat layer described later can be reduced. At least, a coated paper with high printability can be obtained.

  The undercoating paper obtained as described above is further provided with a coating layer comprising a pigment and an adhesive as an overcoating layer.

  It is preferable that the calendar process (pre-calendar process) is performed before the top coat is applied. The pre-calendar treatment has the advantage of not only flattening the surface of the undercoat coating layer, but also improving the flatness of the surface of the topcoat coating layer. The printability is improved even with a lower coating amount. Since the nip pressure can be reduced, a bulky coated paper can be obtained.

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

  In this embodiment, kaolin clay and heavy calcium carbonate are used as a pigment for the top coat layer in a ratio of 10:90 or more, further 20:80 or more (kaolin clay: heavy calcium carbonate (mass ratio)). Preferably, it is contained in a ratio of 60:40 or less, more preferably 50:50 or less (kaolin clay: heavy calcium carbonate (mass ratio)). When the proportion of kaolin clay is below the lower limit, it is difficult to achieve flatness of the coating layer, and conversely, when the proportion of kaolin clay exceeds the upper limit, it is necessary to increase the viscosity of the paint and lower the solid content. Impair print quality.

  In addition, for example, when kaolin clay and heavy calcium carbonate are blended as pigments at the ratio as described above, it is possible to obtain any of glossy, dull and matte coated paper depending on the conditions of the flattening treatment described later. Can do. However, with glossy coated paper, the target glossiness and printability can be obtained by sufficiently flattening, but with matte and dull coated paper, the gloss becomes too flat There is a problem that it is too far out of the gloss range of matte and dull-coated paper. For this reason, matte and dull tones, especially dull-tone coated paper, have a high coating amount in order to improve printing quality without performing flattening more than necessary, and tend to be difficult to obtain bulky coated paper. is there. The present invention is particularly preferable because high printing quality can be obtained even with a low coating amount, as compared with these conventional matte and dull tone coated papers.

  In glossy coated paper, since it is necessary to increase the glossiness of the blank paper, it is necessary to flatten it with a high nip pressure, and the reduction in hand feeling tends to be large. Dull-tone coated paper, on the other hand, has a hand feeling because it is flattened at a low nip pressure compared to glossy-coated paper, and has a low blank paper gloss level, so it has excellent print information visibility. Yes.

  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-coated paper, it is possible to increase the smoothness of the coating layer surface while maintaining bulkiness by flattening with an appropriate nip pressure. There is an advantage that the coated paper is suitable for high-quality printed matter without causing printing unevenness. 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.

  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.

  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 these adhesives, when latexes and starches are used in combination, the viscosity of the color is improved. Therefore, when a film transfer type roll coater described later is used, the transferability of the top coating is increased, which is preferable. Moreover, the addition of starch has the effect of improving the waist of the paper, 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 of improving the printability derived from the film-forming property of the latex and improving the hand feeling derived from the oxidized starch is obtained. And coated paper with excellent print quality.

  When latexes and starches are used in combination, it is preferable to adjust the ratio of the two (latexes: starches (mass ratio)) to 4: 1 or more, further 3: 1 or more. It is preferable to adjust so that it may become 1 or less. When the ratio of starch is below the lower limit, the transferability of the top coating with a film transfer type roll coater described later deteriorates. Conversely, when the ratio of starch exceeds the upper limit, the flatness of the coating layer Is unfavorable because the printing quality deteriorates and the print quality deteriorates.

  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. When the total amount of latexes and starches is less than the lower limit, the surface strength and wet paper strength are low, and paper scumming occurs at the time of printing, resulting in a reduction in printing quality. On the other hand, when the total amount of latexes and starches exceeds the upper limit, the viscosity of the coating increases and the printing quality decreases.

  In addition, as latex, it is preferable to use a thing with an average particle diameter of 90-130 micrometers, and also 90-110 micrometers. When the average particle size of the latex is less than 90 μm, the binder component sinks into the base paper layer, and the print quality is deteriorated. On the other hand, when the average particle size of the latex exceeds 130 μm, the coating layer strength is lowered and the printing quality is lowered.

  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 topcoat coating agent is not particularly limited, and it is preferable to adjust appropriately according to coating conditions such as a coating amount and a 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, the topcoat coating agent is preferably applied onto the undercoat coating layer by film transfer roll coating, particularly by an on-machine coater or an off-machine coater provided with a rod metering size press. The coating method is not particularly limited, but a film transfer type roll coater capable of obtaining uniform coverage with a lower coating amount is preferable.

  Further, in this embodiment, when an on-machine coater is used, after applying the undercoat coating agent for the undercoat coating layer, the topcoat coating agent can be applied immediately, and the paper surface temperature is high. Since the top coat can be applied in a state, the liquid absorbency of the base paper is high, and the transferability of the paint is improved. Therefore, there is an advantage that it is possible to prevent a decrease in printing quality due to scattering (mist) of the paint. If the base paper has a high liquid absorbency, the flatness of the coating layer tends to decrease due to the sinking of the paint, and the print quality tends to deteriorate. However, a pre-calender is combined with the undercoat coating layer as in this embodiment. In this case, even if the undercoating is a low coating amount, the flatness after the undercoating is improved, so that the deterioration of the printing quality after the overcoating is slight.

  In addition, as a drying method in the dryer part, for example, various heating drying methods such as hot air heating, gas heater heating, and infrared heater heating can be appropriately employed.

The overcoat coating layer, since the provided the undercoat coating layer, it is possible to reduce the top coat coating weight, for example per side 6 g / m ² or more, further at 7 g / m ² or more coating amount It can be formed by coating, and is preferably formed by coating at a coating amount of 10 g / m ² or less, more preferably 9 g / m ² or less per side. If the coating amount is less than 6 g / m ² , not only the target print quality cannot be obtained, but also the glossiness of the white paper is lowered, and there is a possibility that it becomes a matte coated paper. On the other hand, if it exceeds 10 g / m ² , the pigment component of the top coating will increase compared to the water-soluble polymer of pulp and undercoating, which will not only reduce hand feeling, but also corresponds to lightweight coated paper No longer. By using the present invention, it is possible to obtain a coated paper having high strength and high printing quality, particularly in a lightweight coated paper.

As a pigment for the top coat 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 an average particle is used as an adhesive. When a total of 5 to 15 parts by mass of latexes and starches having a diameter of 60 to 120 μm are contained with respect to 100 parts by mass of the total pigment, the top coat layer is 7 to 9 g / m per side. Even if it is formed on both sides of the base paper with a low coating amount of ² , the top coat layer can be applied uniformly, and therefore it is preferable because it can be a lightweight coated paper with excellent printing quality.

In particular, in the above embodiment, since the topcoat layer is combined with the undercoat layer, offset printing is performed while both the undercoat layer and the topcoat layer have a lower coating amount. It can be set as the coated paper which has full color printing aptitude, such as aptitude and gravure printing aptitude. Furthermore, a pre-calendar treatment is performed after the undercoating, whereby a synergistic effect for improving the flatness of the coated base paper is expressed, and the amount of top coating can be further reduced. Furthermore, the effect of further improving printability can be obtained by overcoating with a film transfer type roll coater on-machine. As a result, even if the coating amount of the top coat is as small as 7 to 9 g / m ² per side, sufficient print quality can be obtained. Especially in dull-coated paper, the print quality is significantly higher than before. Is obtained.

  As described above, at least two coating layers are formed on at least one side of the base paper. Among these coating layers, at least two coating layers that are in contact with each other are all formed by roll coating. Preferably it is formed. Since the coated paper of this embodiment has the undercoat coating layer and the topcoat coating layer, the flatness and printability after coating are inferior to blade coating and air knife coating. Even with a coater, sufficient print quality can be obtained.

  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 highly water-soluble coating 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 this embodiment is not limited to this, depending on the use of the resulting coated paper, etc. Can be changed as appropriate.

  Furthermore, in this embodiment, for the purpose of imparting gloss, smoothness and printability to the coating layer, for example, it is preferable to perform a flattening treatment using 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. Because the paper is crushed by pressure, excessive flattening impairs the hand feeling of the paper, and the nip pressure and friction force concentrate on the fine convex parts of the coated paper, causing problems such as fiber scorching and heat. There is a problem of fading that the coated paper itself changes yellow due to pressure. Moreover, 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 to 20 to 40%. In addition to not being able to obtain high print quality, the coated paper is crushed and the hand feeling is reduced.

  Therefore, in the present embodiment, when a flattening process is performed on the coating layer, it is preferable to use a soft calendar that can be flattened with a lower nip pressure as the calendering equipment. 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. Therefore, sufficient printability can be obtained even at a lower coating amount.

  In such a calendar, the nip pressure is preferably 15 to 150 kN / m, more preferably 110 to 150 kN / m. When the nip pressure on the calender is less than 15 kN / m, the flatness of the coating layer is low. On the other hand, when the nip pressure exceeds 150 kN / m, the hand feeling is impaired.

  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. When the processing temperature is lower than 100 ° C, the flatness is inferior, and when the processing temperature is higher than 180 ° C, the whiteness may be lowered.

  The coated paper of the present embodiment obtained as described above is mainly composed of a water-soluble polymer as an undercoat coating layer, and is used in combination with a pigment in the same or a small amount as the water-soluble polymer. Since the pigment having the proportion and shape as described above is used, a coated paper having good flatness and printability can be obtained even with a lower coating amount.

  In addition, the undercoat coating layer is pre-calendered and then overcoated to improve the printability by providing a pigment coating layer in which the type, amount, blending ratio, etc. of the pigment and adhesive are appropriately adjusted. In addition, since the flatness of the undercoat coating layer is high, it is possible to reduce the amount of the topcoat coating more than usual while maintaining the printability, and lighter weight coated paper, especially dull than conventional ones. Toned lightweight coated paper is obtained.

  Also, for example, in the paper making equipment (wire part, press part, dryer part, pre-calendar part), coating equipment (on-machine coater, on-machine calendar), etc. Improves flatness, prevents paper breakage, has good operability and productivity, and combines with the top coat layer and undercoat layer to achieve the desired lightweight coated paper, especially excellent A dull-weight lightweight coated paper suitable for high-quality printed matter can be obtained.

  The white paper glossiness of the coated paper of the present embodiment varies depending on the application, but as described above, for example, when a dull-tone coated paper is used, “paper and paperboard” described in JIS P 8142: 2005 is used. It is 20 to 40%, preferably 30 to 40% as measured according to "Measurement method of 75 degree specular gloss".

  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.

  First, LBKP and NBKP as raw pulp were mixed at a ratio of 80:20. 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% by mass were added to obtain a pulp slurry.

Next, after subjecting the pulp slurry to a wire part, a press part and a pre-dryer part in order to produce a base paper having a basis weight of about 39 to 41 g / m ² , it is shown in Tables 1 and 2 on both sides of the base paper. The undercoat coating composition is applied with a gate roll coater (GR) or a rod metering size press coater (RMSP) at the coating amount (per side) shown in Tables 1 and 2 to form an undercoat coating layer. did.

Next, the base paper having an undercoat coating layer formed on both sides is provided to an after dryer part, and after drying the undercoat coating layer, a flattening treatment (pre-treatment is performed under conditions of a nip pressure of 25 KN / m and a roll temperature of 70 ° C. Calendar). Next, in the coater part, on the surface of the undercoat coating layer that has been subjected to the flattening treatment, an overcoat coating comprising 40 parts by mass of kaolin clay and 60 parts by mass of calcium carbonate and 10 parts by mass of the adhesive shown in Tables 1 and 2 The coating amount (per one side) shown in Tables 1 and 2 was applied to the agent with a film transfer type roll coater to form a topcoat coating layer. Thereafter, except for Example 58, a flattening process of 2 nips was performed under the conditions of a nip pressure of 120 KN / m and a roll temperature of 140 ° C., and in Example 58, a nip pressure of 7 KN / m and a roll temperature of 140 ° C. After performing the flattening treatment, the white paper glossiness measured in accordance with “Paper and paperboard—Method of measuring 75 ° specular gloss” described in JIS P 8142: 2005 is adjusted as shown in Tables 1 and 2, and then A coated paper having a basis weight of about 52 to 64 g / m ² was obtained by sequentially applying to a reel part and a winder part.

The water-soluble polymer compounds, pigments and adhesives shown in Tables 1 and 2 are as follows.
<Undercoat coating agent>
(Water-soluble polymer compound)
・ Oxidized starch (Product No .: Oxidized starch manufactured by Eliere Shoko)
・ Polyacrylamide (PAM, product number: Haricoat G-51, manufactured by Harima Chemicals)
・ Hydroxyethyl etherified starch (HES, product number: Coatmaster K49F, manufactured by Sankisha)
(Pigment)
a) Regenerated particles derived from paper sludge (regenerated particles)
It manufactured by adjusting the particle size by the manufacturing method of Unexamined-Japanese-Patent No. 2002-167523, Test Example 8. 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 were produced by incineration at 1000 ° C. in a furnace.

b) Regenerated particle aggregate derived from deinking floss (regenerated particle aggregate)
It manufactured by adjusting the particle size by the manufacturing method of Unexamined-Japanese-Patent No. 2007-146354 and Example 3. FIG. 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 pulverized (pulverizing step). Regenerated particle aggregates were produced.

c) Silica-coated regenerated particle aggregate (silica coating)
It manufactured by adjusting the particle size by the manufacturing method of Unexamined-Japanese-Patent No. 2007-146354 and Example 15. 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 pulverized (pulverizing step). Then, a silica-coated regenerated particle aggregate in which silica was precipitated was formed on the surface of the regenerated particle aggregate.

d) Kaolin clay / Kaolin clay (Product number: Kao Fine, manufactured by Imeris)

e) Calcium carbonate / wet heavy calcium carbonate (Product number: Hydro curve 90K, manufactured by Omiya Korea)

(Water retention agent)
・ Starch (Product No .: Coat Master K49F, manufactured by GPC)
Acrylic resin (Product number: SN thickener 929-S, manufactured by San Nopco)
・ Methacrylic acid-acrylic acid ester copolymer (Part No .: Somalex 270K, manufactured by Somaru)
<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)
・ Oxidized starch (Product No .: Coat Master K96F, manufactured by Sankisha)
・ Hydroxyethyl etherified starch (HES, product number: Coatmaster K49F, manufactured by Sankisha)
Acetylated oxidized tapioca starch (AOS, product number: Mermaid MC-3000, manufactured by Sankisha)
Styrene-butadiene copolymer latex (SBR, average particle size: 100 μm, product number: PA-1071, manufactured by Nippon A & L)
Acrylonitrile-butadiene latex (NBR, average particle size: 100 μm, product number: Nipol 1571CL, manufactured by Nippon Zeon)
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 the undercoat coating agent with a gate roll coater (GR) or rod metering size press coater (RMSP), flattening with a pre-calender, and top coating agent with a rod metaling size press. Coated. 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 physical property was investigated with the following method. These results are shown in Tables 1 and 2.
(A) White Paper Glossiness The coated paper was measured according to “Paper and paperboard—Measurement method of 75 ° specular gloss” described in JIS P 8142: 2005.

(B) Density (bulk)
The coated paper was measured according to “Paper and paperboard—Test method for thickness and density” described in JIS P 8118: 1998.

(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) 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 and printing nonuniformity was observed visually and with a magnifier (10 times), and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: There are no white spots or uneven printing, and the print quality is particularly excellent.
○: Occurrence of white spots and print unevenness is slight, and the print quality is excellent.
(Triangle | delta): There are few generation | occurrence | production of a white spot and printing nonuniformity, and print quality is favorable.
X: White spots and uneven printing occur, resulting in poor print quality.
Of the evaluation criteria, ◎, ○, and Δ are judged to be actually usable.

  From the results shown in Tables 1 and 2, since the coated paper of the example contains 1 to 100% by mass of the pigment with respect to the water-soluble polymer, the print quality is low even if the coating amount is small. It turns out that it is excellent in. On the other hand, since the coated paper of the comparative example does not contain 1 to 100% by mass of pigment with respect to the water-soluble polymer, it can be seen that the coated paper is poor in print quality.

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

Claims (8)

A coated paper having at least two coating layers formed on at least one side of a base paper,
Of the coating layers, the coating layer in contact with the base paper contains a water-soluble polymer and an inorganic pigment,
The ratio of the inorganic pigment to 100 parts by mass of the water-soluble polymer is 1 part by mass or more and 100 parts by mass or less by dry mass,
And the coating amount per side of the coating layer in contact with the base paper is 5 g / m ² or less,
A multilayer coated bulky coated paper characterized by the above. The pigment contains 20 to 60% by mass of a pigment having a particle size of 10 to 30 μm (large particle pigment) and 40 to 80% by mass of a pigment having a particle size of 0.1 to 2.0 μm (small particle pigment).
The multilayer coated bulky coated paper according to claim 1. The pigment is a recycled particle derived from papermaking sludge,
The multilayer coated bulky coated paper according to claim 1 or 2. The water-soluble polymer is at least one of starch and starch derivatives;
The multilayer coated bulky coated paper according to any one of claims 1 to 3.   The multilayer coated bulky coated paper according to any one of claims 1 to 4, wherein the coating layer contains a polymer compound having water retention. The polymer compound having water retention is a resin mainly composed of a methacrylic acid-acrylic acid copolymer,
The multilayer coated bulky coated paper according to claim 5. The pigment is a regenerated particle aggregate derived from deinking floss,
The multilayer coated bulky coated paper according to any one of claims 1 to 6. The blank paper glossiness measured in accordance with “Paper and paperboard—75-degree specular gloss measurement method” described in JIS P 8142: 2005 is 20 to 40%.
The multilayer coated bulky coated paper according to any one of claims 1 to 7.