Gravure printing paper

Abstract

To provide gravure printing paper which has good printability against offset printing, and has printability against gravure printing and oil resistant performance to some degree.SOLUTION: Gravure printing paper has kraft paper containing kraft pulp, and one or two or more coating layers on at least one surface of the kraft paper, wherein the outermost coating layer positioned at an outermost place based on the kraft paper in the coating layer contains kaolin, calcium carbonate, a hollow type white organic pigment, a polyvinyl alcohol-based resin and a styrene-butadiene-based resin, the outermost coating layer has a content relation such that the kaolin is 78 pts.mass or more and 93 pts.mass or less, the calcium carbonate is 6 pts.mass or more and 21 pts.mass or less, the hollow type white organic pigment is 1 pts.mass or more and 6 pts.mass or less, the polyvinyl alcohol-based resin is 0.8 pt.mass or more and 1.5 pts.mass or less, and the styrene-butadiene-based resin is 8 pts.mass or more and 15 pts.mass or less, and the gravure printing paper has oil resistant performance and is usable for wrapping.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a gravure printing paper having a coating layer on at least one side of kraft paper, and in particular to a gravure printing paper that has oil resistance and can be used for packaging such as secondary packaging. [Background technology]

[0002] Gravure printing papers or gravure coated papers already exist that can be used for packaging materials such as packaging sheets, packaging bags and containers, and carrier bags. For example, at least one side of the base paper has a pigment coating layer containing a pigment and an adhesive, the base paper contains softwood kraft pulp as raw pulp in an amount of 30% by weight or more of the total raw pulp, the pigment coating layer contains clay as a pigment having an aspect ratio of less than 10 and an average particle size (D50) of less than 1.0 μm in an amount of 60% by weight or more of the total pigment, and the coating weight of the pigment coating layer is 11 g / m2 in terms of solid content per side. 2 The above-mentioned coated paper for gravure printing to be used for packaging containers is known (see, for example, Patent Document 1). Patent Document 1 discloses that the coated paper for gravure printing described therein has sufficiently high burst strength and excellent suitability for gravure printing so as to be used for packaging containers and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-161595 Summary of the Invention [Problem to be solved by the invention]

[0004] There has been a growing call to move away from plastic in the field of packaging materials, such as packaging sheets, packaging bags and containers, and carrier bags. As a result, there are efforts to replace packaging materials that use resins such as polypropylene with packaging materials that use paper, i.e., packaging paper. Normally, printing on packaging materials is done by gravure printing, but offset printing machines are the mainstream among commercial printing machines on the market. Therefore, when printing on packaging paper, rather than on packaging materials using resin, gravure printing may not be used and offset printing may be used instead. Therefore, gravure printing paper that can be used for packaging needs to have printability for offset printing as well as printability for gravure printing.

[0005] Typical examples of packaged items are food ingredients, food, and cooked foods. Since the oil contained in the food ingredients reduces the strength of the paper, the paper used for these packages must have a certain degree of oil resistance, even if it is a secondary package that does not directly contact the packaged items and is not a primary package. Therefore, gravure printing paper that can be used for packaging must have a certain degree of oil resistance.

[0006] An object of the present invention is to provide a gravure printing paper which has good printability for offset printing and gravure printing, and has a certain degree of oil resistance and can be used for packaging. [Means for solving the problem]

[0007] The present inventors have invented a gravure printing paper according to the present invention as a result of intensive research.

[0008] [1] A gravure printing paper having a kraft paper containing kraft pulp and one or more coating layers on at least one side of the kraft paper, wherein the outermost coating layer located outermost with respect to the kraft paper contains at least kaolin, calcium carbonate, a hollow white organic pigment, a polyvinyl alcohol-based resin, and a styrene-butadiene-based resin, and the contents of the kaolin, calcium carbonate ...

[0009] In some embodiments, the gravure printing paper of the present invention is: [2] The gravure printing paper according to [1] above, wherein the kraft paper contains starches as a result of a size press treatment. Effect of the Invention

[0010] According to the present invention, it is possible to provide a gravure printing paper which has good printability for offset printing and gravure printing, and also has a certain degree of oil resistance and can be used for packaging. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below. The gravure printing paper of the present invention comprises a kraft paper containing kraft pulp and one or more coating layers on at least one side of the kraft paper. The layer located outermost relative to the kraft paper is called the outermost coating layer. When there is only one coating layer, this layer is the outermost coating layer. When the coating layer is two or more layers, the coating layer located between the kraft paper and the outermost coating layer is not particularly limited as long as it does not impair the effects of the present invention. Examples of the coating layer located between the kraft paper and the outermost coating layer include a coating layer containing a white pigment and a binder that is conventionally known in the field of coated paper.

[0012] In some embodiments, the gravure printing paper has one or more coating layers on both sides of the craft paper. This is because the gravure printing paper can be used as a printing surface regardless of whether it is the front or back side. In some embodiments, the gravure printing paper has one or more coating layers on only one side of the craft paper. This is because it is advantageous in terms of manufacturing costs of the gravure printing paper. In some embodiments, the gravure printing paper has one or more coating layers on the front side of the craft paper, and has a backcoat layer conventionally known in the field of coated paper on the back side of the craft paper. The backcoat layer has, for example, a function of improving dimensional stability and / or preventing curling. This improves the dimensional stability and / or curl prevention of the gravure printing paper. In some embodiments, the gravure printing paper has one or more coating layers on the front side of the craft paper, and has a water-coating and drying treatment conventionally known in the field of coated paper on the back side of the craft paper. The water-coating and drying treatment is, for example, effective in preventing curling of the gravure printing paper.

[0013] In some embodiments, the gravure printing paper has one or more coating layers on the surface of the kraft paper, and has a heat seal layer containing a heat sealable resin conventionally known in the packaging material field on the back side of the kraft paper, because the gravure printing paper can be used as a heat seal paper. Examples of heat-sealable resins include polyester-based resins, polyvinyl alcohol-based resins, vinyl-based resins, vinylidene chloride-based resins, (meth)acrylic-based resins, polyurethane-based resins, cellulose-based resins, melamine-based resins, polyamide-based resins, polyolefin-based resins, and polystyrene-based resins.

[0014] In some embodiments, the gravure printing paper has one or more coating layers on the surface of the kraft paper, and has a barrier layer on the back side of the kraft paper that contains a barrier material conventionally known in the field of packaging materials. This is because the gravure printing paper can have barrier properties. Examples of the barrier layer include a gas barrier layer such as an oxygen gas barrier layer, a water vapor barrier layer, a moisture permeable barrier layer, and an oil barrier layer. Barrier materials that exhibit these functions are known. Examples of gas barrier materials include polyvinyl alcohol resins such as fully saponified or partially saponified polyvinyl alcohol and modified polyvinyl alcohol, urethane resins, acrylic resins, vinylidene chloride resins, proteins such as casein, soy protein, and synthetic protein, starches such as oxidized starch, cationized starch, urea phosphate esterified starch, and hydroxyethyl etherified starch, celluloses such as carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose, polyvinylpyrrolidone, and sodium alginate. Examples of water vapor barrier materials and / or moisture permeable barrier materials include olefin-based resins such as polyethylene and polypropylene, acrylic-based resins, vinyl chloride-based resins, styrene-based resins, styrene-butadiene-based resins, olefin-unsaturated carboxylic acid-based resins, styrene-unsaturated carboxylic acid-based resins, vinyl acetate-based resins, styrene-vinyl acetate-based resins, acrylonitrile-styrene-based resins, acrylonitrile-olefin-based resins, maleic acid-based resins, ABS-based resins, AAS-based resins, AES-based resins, vinylidene chloride-based resins, urethane-based resins, vinylidene fluoride-based resins, vinyl fluoride-based resins, fluorine-based resins, polycarbonate-based resins, polyamide-based resins, polyacetal-based resins, polyphenylene oxide-based resins, polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate, polyphenylene sulfide-based resins, polyimide-based resins, polysulfone-based resins, polyethersulfone-based resins, and waxes. Examples of the oil barrier material include polyvinyl alcohol-based resins, styrene-acrylic resins, and fluorine-based resins.

[0015] In this specification, the terms "front side" and "back side" of the kraft paper are expressions for convenience of distinguishing the sides of the kraft paper, and do not mean the front side and back side of the support based on a specific difference. The printability relates to the side having the outermost coating layer of the gravure printing paper.

[0016] The outermost coating layer contains at least kaolin, calcium carbonate, a hollow white organic pigment, a polyvinyl alcohol-based resin, and a styrene-butadiene-based resin. Kaolin is a white inorganic pigment that has been conventionally known in the field of coated paper. Kaolin is usually produced by industrially refining and processing naturally occurring kaolin ore, and is produced through processes such as crushing, washing, iron removal, and classification. Kaolin also includes highly processable kaolin, such as delaminated kaolin, which is made into a thin plate shape by applying shear force to improve the aspect ratio, engineered kaolin, which has a narrow particle size distribution range, and calcined kaolin, which has improved cohesiveness.

[0017] In some embodiments, the kaolin contained in the outermost coating layer has at least two peaks in the particle size range of 0.20 μm or more and 7.00 μm or less in a particle size distribution curve relating to the volume-based particle size determined by laser diffraction / scattering particle size distribution measurement. This is because printability for gravure printing is improved and / or folding cracks of the outermost coating layer that occur when the outermost coating layer surface is folded outward are reduced. The peaks also include shoulder peaks.

[0018] The calcium carbonate is a white inorganic pigment conventionally known in the field of coated paper. Calcium carbonate available on the market is mainly classified into light calcium carbonate, which is chemically produced using limestone (main component: calcium carbonate) as a raw material, and heavy calcium carbonate, which is produced by physically crushing and classifying limestone. Light calcium carbonate is also called precipitated calcium carbonate or synthetic calcium carbonate. Light calcium carbonate has various shapes derived from the crystal structure. On the other hand, heavy calcium carbonate is amorphous. Therefore, they can be distinguished by their shapes. In some embodiments, the calcium carbonate contains a greater proportion of light calcium carbonate than heavy calcium carbonate. In at least one embodiment, the calcium carbonate is light calcium carbonate. This is because light calcium carbonate has good printability for gravure printing while retaining printability for offset printing.

[0019] The hollow white organic pigment is a type of white organic pigment. The hollow white organic pigment is conventionally known in the field of coated paper. Examples of hollow white organic pigments include white organic pigments produced by a method of controlling particle morphology during emulsion polymerization or an alkali / acid two-stage treatment method. Examples of monomers to be emulsion polymerized include styrene, (meth)acrylic acid and its salts, (meth)acrylic acid esters, (meth)acrylonitrile, vinyl chloride, vinyl acetate, ethylene, and butadiene. For emulsion polymerization, for example, one or more monomers selected from the group consisting of the above monomers are selected. Hollow white organic pigments are commercially available from, for example, Asahi Kasei Corporation, JSR Corporation, and The Dow Chemical Company. The hollow white organic pigment is not particularly limited as long as it has a particle-like apparent overall shape and has a hollow portion inside. In some embodiments, the hollow white organic pigment has one or more hollow portions per particle having a particle-like apparent overall shape. In some embodiments, the hollow white organic pigment has one or more openings connecting the outside of the shell of the particle to the hollow portion in a particle having a particle-like apparent overall shape. In some embodiments, the hollow white organic pigment has a particle-like apparent overall shape having a hollow portion inside, and the shape of the shell is not limited.

[0020] The outermost coating layer of gravure printing paper may contain a white pigment conventionally known in the field of coated paper in addition to kaolin, calcium carbonate, and hollow white organic pigments. Examples of the white pigment include white inorganic pigments such as talc, satin white, lithopone, titanium oxide, zinc oxide, amorphous silica, colloidal silica, alumina, aluminum hydroxide, zinc oxide, activated clay, and diatomaceous earth. Examples of the white pigment include white organic pigments other than hollow white organic pigments, such as solid pigments made of urea resin. In some embodiments, the total content of kaolin, calcium carbonate and hollow white organic pigment in the outermost coating layer is 90% by mass or more based on the total white pigment contained in the outermost coating layer, including kaolin, calcium carbonate and hollow white organic pigment, because this improves printability for gravure printing and / or offset printing.

[0021] The polyvinyl alcohol resin is a conventionally known binder in the field of coated paper. The concept of polyvinyl alcohol resin includes polyvinyl alcohols of various saponification degrees and polyvinyl alcohols of various polymerization degrees, as well as various modified polyvinyl alcohols thereof. Modifications include, for example, acetoacetyl group modification, ethanediol group modification, carboxy group modification, cationic group modification, silanol group modification, ethylene modification, 1,2-diol modification, and alkyl group modification.

[0022] The styrene-butadiene resin is a binder that has been conventionally known in the field of coated paper. The styrene butadiene resin is, for example, a copolymer of a styrene monomer and a butadiene monomer, in which the total monomers of the styrene monomer and the butadiene monomer account for more than 50 mol% in the copolymer. Examples of the styrene monomer include styrene derivatives having a substituent on the vinyl group, such as styrene and α-methylstyrene, and styrene derivatives having a substituent on the benzene ring, such as vinyltoluene and p-chlorostyrene. Examples of the butadiene monomer include 1,3-butadiene, and derivatives having a substituent, such as 2-methyl-1,3-butadiene and 2-chloro-1,3-dibutadiene. Furthermore, the styrene butadiene resin may have, in addition to the styrene monomer and the butadiene monomer, other monomers that are copolymerizable with the styrene monomer and the butadiene monomer. Examples of other monomers include (meth)acrylonitrile, (meth)acrylic acid, (meth)acrylates, (meth)acrylates, maleic acid, vinyl acetate, vinyl chloride, vinylidene chloride, and ethylene. The styrene-butadiene resin can be obtained by emulsion polymerization while adding each monomer constituting the copolymer and adjusting the concentration of each monomer. The styrene-butadiene resin can be obtained by radical polymerization of a copolymer oligomer of styrene butadiene with a styrene monomer, a butadiene monomer, another monomer, a copolymer oligomer of styrene butadiene, and a copolymer oligomer of a styrene monomer or a butadiene monomer with another monomer.

[0023] The outermost coating layer of gravure printing paper may contain a binder conventionally known in the field of coated paper in addition to the polyvinyl alcohol resin and styrene-butadiene resin. Examples of the binder include starches, celluloses, casein, gelatin, soybean protein, pullulan, gum arabic, karaya gum, albumin, and other naturally derived resins and modified products thereof, polypropylene glycol, polyethylene glycol, maleic acid resins, acrylic resins, olefin unsaturated carboxylic acid resins, ethylene vinyl acetate resins other than styrene-butadiene resins, and various synthetic resins, as well as thermosetting resins such as melamine resins and urea resins, urethane resins, polyester resins, polyvinyl butyral, and alkyd resins. In some embodiments, the total content of the polyvinyl alcohol-based resin and the styrene-butadiene-based resin in the outermost coating layer is 90% by mass or more based on the total binder contained in the outermost coating layer, including the polyvinyl alcohol-based resin and the styrene-butadiene-based resin, because this improves printability in gravure printing, printability in offset printing, and / or oil resistance.

[0024] The outermost coating layer has a content relationship of 78 to 93 parts by mass of kaolin, 6 to 21 parts by mass of calcium carbonate, 1 to 6 parts by mass of hollow white organic pigment, 0.8 to 1.5 parts by mass of polyvinyl alcohol resin, and 8 to 15 parts by mass of styrene butadiene resin. The synergistic effect of the materials and the content relationship of the materials allows the gravure printing paper to have good printability for offset printing and gravure printing, and to have a certain degree of oil resistance. If the materials and the content relationship of the materials are not satisfied, the printability for offset printing, the printability for gravure printing, and / or the oil resistance will deteriorate. The inventors conducted extensive research into gravure printing paper, which has good printability for offset printing and gravure printing and has a certain degree of oil resistance so that it can be used for packaging, and as a result, they discovered the above combination of materials and the relationship between the amounts of the above materials.

[0025] In addition to the white pigment and the binder, the outermost coating layer may contain additives conventionally known in the field of coated paper, if necessary and to the extent that does not impair the effects of the present invention, such as printability improvers, fixing agents, dispersants, thickeners, water retention agents, defoamers, lubricants, water resistance agents, colorants, ultraviolet absorbers, fluorescent agents, surfactants, and waxes.

[0026] The coating layers, including the outermost coating layer, can be obtained by applying and drying a coating solution containing a predetermined material. For example, the coating and drying can be performed using a coating device and a drying device that are conventionally known in the field of coated paper. Examples of the coating device include a Comma Coater (registered trademark), a film press coater, an air knife coater, a rod blade coater, a bar coater, a blade coater, a gravure coater, a curtain coater, an E-bar coater, and a film transfer coater, etc. Examples of coating include coating using a wire bar for manual coating, which is an experimental method. Examples of the drying device include various drying devices such as hot air dryers such as a linear tunnel dryer, an arch dryer, an air loop dryer, and a sine curve air float dryer, an infrared heating dryer, and a dryer that utilizes microwaves.

[0027] After the gravure paper has been coated with the coating layers, including the outermost coating layer, it can be subjected to a calendering process, which is conventionally known in the papermaking industry, because this improves the final smoothness of the kraft paper. Calendering can be achieved using a calendering device conventionally known in the papermaking industry, such as the same calendering device as the example given for the calendering of kraft paper below.

[0028] Kraft paper, which is the base material for gravure printing paper, is made by papermaking a stock in which pulp produced by the Kraft process is dispersed in water. Papermaking can be achieved, for example, by a method using a papermaking machine conventionally known in the papermaking field. Examples of papermaking machines include a Fourdrinier papermaking machine, a cylinder papermaking machine, and a twin-wire papermaking machine. The raw material of the pulp produced by the kraft process is wood or non-wood conventionally known in the papermaking field. The raw material of the pulp can be, for example, wood of coniferous and broadleaf trees, and non-wood such as hemp, linter, straw, bamboo, sugarcane, reed, fruit, paper mulberry, Mitsumata and gampi. In some embodiments, the raw material of the pulp is one or more selected from coniferous and broadleaf trees. In at least one embodiment, the kraft pulp is one or two selected from bleached coniferous kraft pulp (NBKP) and bleached broadleaf kraft pulp (LBKP). This is because the strength of the gravure printing paper is improved.

[0029] The above-mentioned paper stock may contain, in addition to kraft pulp, conventionally known pulps such as mechanical pulp, deinked waste paper pulp, and pulp obtained by disintegrating broke generated in paper mills. In some embodiments, the content of kraft pulp in the kraft paper is 900 parts by mass or more per 1000 parts by mass of the total pulp contained in the kraft paper. In at least one embodiment, the content of kraft pulp in the kraft paper is 1000 parts by mass per 1000 parts by mass of the total pulp contained in the kraft paper. The reason for this is that the strength of the gravure printing paper is improved.

[0030] The above-mentioned paper stock may contain, as necessary, additives for papermaking conventionally known in the papermaking field, such as sizing agents, paper strength agents, paper strength enhancers, fixing agents, retention agents, retention improvers, colorants, fillers, waterproofing agents, dispersants, thickeners, flow improvers, defoamers, foam suppressors, release agents, foaming agents, penetrating agents, fluorescent brightening agents, ultraviolet absorbing agents, antioxidants, preservatives, and mold inhibitors.

[0031] In some embodiments, the kraft paper contains a surface sizing agent, starch, by a size press process conventionally known in the papermaking art, because this improves printability and oil resistance for offset printing. The size press treatment can be achieved by applying a size press liquid containing a surface sizing agent and the like conventionally known in the papermaking field using a size press device conventionally known in the papermaking field. That is, the kraft paper contains starches by applying the size press liquid to the kraft paper using a size press device. The starches contained in the kraft paper due to the size press treatment are consequently present in large amounts near the surface layer of the kraft paper, and therefore the above-mentioned effects are easily achieved.

[0032] Examples of the size press device include an inclined size press, a horizontal size press, a rod metering size press, a roll metering size press, and a blade metering size press as film transfer systems, a shim sizer, an opti sizer, a speed sizer, and a film press as rod metering size presses, and a gate roll coater as a roll metering size press. Other examples of the size press device include a bill blade coater, a twin blade coater, a velbapa coater, a tab size press, and a calendar size press.

[0033] The above-mentioned starches are conventionally known in the papermaking field. The concept of starches includes unmodified starch, unprocessed starch, various modified and various processed starches. Examples of starches include starch, oxidized starch, enzyme-modified starch, etherified starch, cationic starch, amphoteric starch, dialdehyde starch, esterified starch such as phosphate esterified starch and urea phosphate esterified starch, hydroxyethylated starch, and hydroxybutylated starch.

[0034] The size press liquid may contain a conventionally known surface sizing agent in addition to starches, such as alkyl ketene dimer-based sizing agents, cellulose-based sizing agents, polyvinyl alcohol-based sizing agents, styrene acrylic-based sizing agents, olefin-based sizing agents, styrene maleic acid-based sizing agents, and acrylamide-based sizing agents. In some embodiments, the size press liquid contains 90% by mass or more of starches based on the total surface sizing agent contained in the size press liquid, including starches, because this improves printability and oil resistance in offset printing.

[0035] The kraft paper can be subjected to a calendering process. Calendering can be achieved using a calendering device conventionally known in the papermaking field. Examples of the calendering device include a machine calender, a soft nip calender, a super calender, a multi-stage calender, and a multi-nip calender.

[0036] The order of the size press treatment and the calendar treatment is not particularly limited. In some embodiments, the kraft paper is subjected to a size press treatment with a size press liquid and then a calendar treatment. The reason for this is that the final smoothness of the kraft paper is improved.

[0037] In some embodiments, the density of the gravure paper is 0.85 g / cm 3 More than 1.10g / cm 3 The reason for this is that, for example, it reduces the occurrence of cracks in the outermost coating layer when the outermost coating layer surface is folded outward without impairing the strength required for packaging. The density of gravure printing paper is a value determined in accordance with ISO534:2011 "Paper and board-Determination of thickness, density and specific volume".

[0038] The density of gravure printing paper is a physical quantity that is conventionally known in the papermaking field, and can be adjusted by a method conventionally known in the papermaking field. The density of gravure printing paper can be adjusted, for example, by the type and beating degree of pulp for kraft paper, the supply amount of paper material, the conditions of the press part of the papermaking process, the conditions of the dryer part of the papermaking process, and the presence or absence and conditions of calendaring, and further, the coating amount and the presence or absence and conditions of calendaring for the coating layer. The density of gravure printing paper can be reduced, for example, by low beating of pulp, reducing the press pressure of the press part, reducing the drying strength of the dryer part, not performing calendaring, performing calendaring with a small number of nips, performing calendaring with a lighter line pressure, and reducing the coating amount of the coating layer.

[0039] In some embodiments, the total coating weight, including the outermost coating layer, of the gravure printing paper is 6 g / m2 in terms of dry solids. 2 More than 12g / m 2 In at least one embodiment, the total coating weight, including the outermost coating layer, of the gravure printing paper is 6 g / m2 or less in terms of dry solids. 2 More than 12g / m 2 and the outermost coating layer accounts for 70 mass % or more of the total coating amount, because printability for gravure printing is improved. EXAMPLES

[0040] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. Here, "parts by mass" and "% by mass" represent the amount of dry solids or the amount of substantial components, respectively. The coating amount of the coating layer represents the amount of dry solids.

[0041] <Kraft paper> A pulp slurry consisting of 800 parts by mass of LBKP with a CSF freeness of 470 ml and 200 parts by mass of NBKP with a CSF freeness of 580 ml was mixed with 4 parts by mass of a rosin-based sizing agent, 12 parts by mass of a starch-based strength agent, 10 parts by mass of an aluminum sulfate fixing agent, and 0.1 parts by mass of an acrylamide-based retention agent to prepare a paper stock. The paper stock was made into a paper sheet using a Fourdrinier paper machine. Both sides of the paper sheet were subjected to a size press treatment using a size press liquid containing a surface sizing agent, and then a calendar treatment was performed using a machine calendar to obtain a kraft paper substrate. The amount of the surface sizing agent attached was 1 g / m per side. 2 The surface sizing agents used are listed in Table 1. The final density of the gravure printing paper was 0.97 to 0.99 g / cm 3 The supply amount of paper stock, the conditions of the press part and the dryer part of the papermaking process, and the calendering conditions were set so that the density of the gravure printing paper was within the range of . The density of the gravure printing paper was measured in accordance with ISO534:2011.

[0042] <Coating liquid for the outermost coating layer> The coating solution for the outermost coating layer was prepared according to the following: White inorganic pigment. Type and mass part are shown in Table 1. White organic pigments: Type and mass parts are listed in Table 1 Binder: Type and mass are listed in Table 1. Defoamer (2,4,7,9-tetramethyl-5-decyne-4,7-diol) 0.1 part by mass Lubricant (calcium stearate) 0.3 parts by weight The above ingredients were mixed and dispersed in water to adjust the concentration to 60% by mass.

[0043] The materials listed in Table 1 are as follows: Starch A: Oxidized starch Starch B: Phosphate starch AKD: Alkyl ketene dimer sizing agent Kaolin: Kaolin with an average particle size of 1.22 μm A 1:1 mixture of kaolin with an average particle size of 0.25 μm Light calcium carbonate: Light calcium carbonate Heavy calcium carbonate: Heavy calcium carbonate Hollow: Styrene acrylic hollow white organic pigment Solid: styrene acrylic solid type white organic pigment PVA: Fully saponified polyvinyl alcohol with an average degree of polymerization of 400 SBR: Styrene butadiene resin

[0044] <Gravure printing paper> A gravure printing paper was prepared according to the following procedure. The coating solution for the outermost coating layer was applied to one side of the above kraft paper using a blade coater, and then dried. After drying, the paper was subjected to a calendaring treatment using a super calendar. The coating amount was 9 g / m per side. 2 It was decided.

[0045] <Printability for offset printing> The printability for offset printing was evaluated by printing on the outermost coated side of gravure printing paper using four colors, black, indigo, red and yellow inks, using a Komori Lithrone 40 (L-40) offset printing machine, and visually observing the resulting prints. The evaluation was performed according to the following criteria from the viewpoint of blanket piling. In the present invention, gravure printing paper is considered to have good printability for offset printing if it is rated A or B. A: The blanket is in good condition with almost no stains. B: Although there is some soiling of the blanket, there is almost no loss of image area and the result is generally good. C: The blanket was dirty and slight voids in the image area were observed, which is at the lower limit of practical use. D: The blanket was dirty and some printing lines were missing, making it difficult to use.

[0046] <Printability for gravure printing> The printability of gravure printing paper was evaluated in two ways: "print finish" and "missed dots." The evaluations were performed as follows. The worse of the evaluation results A to D was designated as the final evaluation. In the present invention, gravure printing paper is considered to have good printability for gravure printing if it is rated A or B.

[0047] <Print finish> The finish was evaluated by printing on the outermost coated side of gravure printing paper using Gravoproof CM (Nissho Gravure Co., Ltd.) with water-based gravure ink, and visually observing the resulting printout with reference to the print finish of gravure printing on polypropylene packaging material. A gravure plate for image evaluation was used for the gravure printing. The evaluation was based on the impression of the print finish in terms of color density, color saturation, and color vividness, and was performed according to the following criteria. A: It doesn't leave a bad impression. B: Although it is inferior to A above, the impression is not bad overall. C: Inferior to B above, the impression is slightly worse, but still within the acceptable level for practical use. D: Less impressive than C above.

[0048] <Miss Dot> Miss dots were printed on the outermost coated side of the packaging paper using Gravoproof CM (Nissho Gravure Co., Ltd.) with water-based gravure ink, and the print obtained was visually observed and evaluated. A halftone dot gravure plate was used for the gravure printing. The evaluation was based on the observation of the occurrence of miss dots (missing halftone dots) in the printed halftone, using the following criteria. A: Good level with no missing dots. B: Inferior to A above, Although there are very slight missing dots in the low-tone areas, the overall result is good. C: Inferior to B above, Although there are very slight to minor areas of missing dots, the image is still usable. D: Inferior to C above, with missing dots observed.

[0049] <Oil resistance> The oil resistance of the outermost coating layer of gravure printing paper was evaluated in accordance with J.TAPPI Pulp Test Method No. 41:2000 "Oil repellency test method for paper and paperboard (kit method)". Measurements were performed five times, and the final value was calculated as the average of the five values, and the value was rounded down to one decimal place. Evaluation was performed based on the results of the oil repellency measurement using the kit method, according to the following criteria. In the present invention, gravure printing paper is deemed to have a certain level of oil resistance and can be used for packaging if it is rated A, B, or C, i.e., if the oil resistance value is 3.0 or more. A: Value is 6.0 or higher. B: Value is 5.0 or greater but less than 6.0. C: Value is 3.0 or greater but less than 5.0. D: Value is 2.0 or more and less than 3.0. E: Value is less than 2.0.

[0050] The evaluation results are shown in Table 1.

[0051] [Table 1]

[0052] From Table 1, it can be seen that Examples 1 to 12 corresponding to the present invention are gravure printing papers that have good printability for offset printing and gravure printing, and have a certain degree of oil resistance and can be used for packaging. On the other hand, Comparative Examples 1 to 13, which do not satisfy the configuration of the present invention, fail to satisfy at least one of these effects.

[0053] Mainly from a comparison between Example 3 and Example 12, it can be seen that when the base kraft paper of gravure printing paper contains starches due to size press treatment, the printability and oil resistance for offset printing are improved.

Claims

1. A gravure printing paper having oil resistance and usable for packaging, comprising: craft paper containing craft pulp; and one or more coating layers on at least one side of the craft paper, wherein an outermost coating layer located outermost with respect to the craft paper among the coating layers contains at least kaolin, calcium carbonate, a hollow white organic pigment, a polyvinyl alcohol-based resin, and a styrene-butadiene-based resin, and wherein the contents of the kaolin in the outermost coating layer are from 78 to 93 parts by mass, calcium carbonate from 6 to 21 parts by mass, the hollow white organic pigment from 1 to 6 parts by mass, the polyvinyl alcohol-based resin from 0.8 to 1.5 parts by mass, and the styrene-butadiene-based resin from 8 to 15 parts by mass.

2. 2. The gravure printing paper according to claim 1, wherein the kraft paper contains starches due to size press treatment.

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