JP5357606B2 - Multi-layer paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide multi-layered paper having high glossiness and excellent beautifulness, also excellent in ruled line crack resistance and aptitude for corrugated board aptitude and paper container, and especially a highly glossy multi-layered cardboard. <P>SOLUTION: The multi-layered paper has a colored surface layer, and includes a coated layer consisting mainly of a pigment and an adhesive, and installed on the colored surface layer, wherein the coated layer is mirror-finished by a rewet casting method, glossiness measured at the coated layer surface is 60-90%, smoothness measured at the coated layer surface is 80-350 seconds, and air permeability measured at the multi-layered paper is not more than 5,000 seconds. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a multi-layer paper, particularly a high-gloss multi-layer paper board, which has excellent cosmetic properties and has ruled line crack resistance, corrugated board suitability, paper container suitability, print suitability and high smoothness.

  In recent years, in the paperboard / paper container field, a cardboard case or paper container for cosmetics or the like has been required to have a high-class feeling, and many high-glossy and good-looking papers or paperboards are used.

  Conventionally used as corrugated cardboard cases or paper containers with high gloss and good-looking paper or paperboard, with a printed layer, gloss coat layer or gloss coat layer on the surface of a paper substrate such as paperboard It has been. For example, a printing layer was formed on the surface of a paper substrate with an ultraviolet curable ink (hereinafter referred to as UV ink), and an overcoat layer made of an ultraviolet curable coating agent (hereinafter referred to as UV varnish) was formed on the printed layer. The configuration was common. As described above, high gloss prints using UV ink and UV varnish can provide high gloss. However, when the paper container or the like is used and recycled as recycled paper, it is dissolved as waste paper, and in the process of separating the printed layer including the pulp fiber and the overcoat layer, the separation property of the printed layer including the overcoat layer Therefore, it is difficult to reuse the printed matter having high glossiness for recycled paper in consideration of the environment.

  Further, as described above, as a method for increasing the surface gloss of a printed material without using UV varnish, for example, it is composed of an emulsion of an acrylic cast paint that is excellent in deinking property and does not use an organic solvent, that is, is environmentally friendly. There is a method in which a so-called aqueous coating agent is press-coated by applying a water-based coating agent to be applied, and then pressing the printed matter on which the aqueous coating agent is applied to form an overcoat layer. However, press coating the above water-based coating agent to form an overcoat layer makes it impossible to inline into a high-speed printing machine because the speed of the press coat itself is slow, resulting in poor production efficiency and high cost even when offline. There was a problem of becoming.

  Another method for increasing the surface glossiness is a casting method. In the casting method, an aqueous paint mainly composed of a pigment and a binder is applied onto a base paper, and then the wet coating layer surface is pressed against the mirror surface of the heating drum, dried, and released from the heating drum. Wet cast method, water-based paint on the base paper is once dried to form a coating layer, and after applying wet-plastic to the coating layer by applying a rewetting liquid, press contact with the surface of the heating drum, after drying, Rewet cast method (rewetting method) to remove and gloss finish, apply water-based paint in a gel state with the addition of a coagulant, press the wet coating layer surface against the mirror surface of the heating drum, There is a gelling cast method (coagulation method) obtained by drying and releasing from a heating drum. Cast coated paper produced by this casting method is widely used in various fields as packaging paper, book cover, notebook cover, catalog and printing paper because of its excellent high glossiness, high smoothness and printability.

  Cast coated paper is not only required to have high gloss and high smoothness, but it can also be released when the coated surface is released from the heated drum surface without resistance, and the coating film adheres to the pit (drum surface). And blisters (when the coated surface is dried, the moisture inside the coated paper expands momentarily, and water vapor cannot pass through the paint layer, causing swelling in the paper layer, that is, in the paper layer or delamination. The absence of defects) is an important requirement, and advanced technology is required.

  As a method for producing the cast coated paper, there are the following methods.

For example, in Patent Document 1, in a paint for cast-coated paper containing a pigment and an adhesive as main components, an average particle diameter of 0.1 to 0.3 μm as the adhesive with respect to 100 parts by weight of the pigment. 6 to 18 parts by weight of latex (A) and 3 to 12 parts by weight of latex (B) having an average particle size of 0.5 to 1.5 μm and latexes (A) and (B). A cast-coated paper coating composition containing a total of 9-13 parts by weight in solid content and a cast-coated paper obtained by coating the composition have been proposed. However, in the above technique, although the gloss of the cast coated paper is 88 to 91% in the examples, the coating composition is dry weight and the coating amount is 25 g / m ² and the coating film is thick, and the ruled line cracking occurs. As a result, there is a risk that poor quality occurs as corrugated cardboard paper or paperboard base paper.

In Patent Document 2, a smooth molding surface is pressure-bonded onto one surface of a sheet-like substrate and a coating liquid layer made of a coating composition for electron beam curable casting, and the coating liquid is irradiated by electron beam irradiation. The coating layer for the electron beam curable cast is formed by curing the layer to form an electron beam curable cast coating layer, and then peeled off from the molding surface. The coating amount of the electron beam curable cast coating layer is 1 to 20 g / m. ^2, and cast coated paper Oken type smoothness of the surface of the sheet substrate on the side provided with a paint coating layer the electron beam curing casting is characterized in that at least 500 seconds is proposed. However, since the technique is provided with a coating film layer for cured cast on the base paper, it is difficult to recycle it as recycled paper as described above.

Furthermore, in Patent Document 3, a high-performance sizing agent for neutral papermaking such as alkyl ketene dimer type and alkenyl succinic anhydride type is added to pulp together with cationized starch etc. to make paper in neutral range. Can provide a base paper suitable for cast coated paper, and in addition, an acrylic emulsion and / or latex gel as an adhesive contained in an undercoat layer provided between the base paper and the cast coated layer. It has been proposed that by optimizing the content rate, stabilization and speeding up of the cast coating operation can be achieved. However, in the above-mentioned technique, although the cast surface has a small number of pits and the cast surface has a gloss of 88 to 94%, the coating liquid for cast coating is 15 to 23 g / m ² by dry weight. However, there is a risk that quality defects may occur as corrugated cardboard paper or paperboard base paper due to the occurrence of ruled line cracks.

Furthermore, in Patent Document 4, as a means for ensuring the blocking resistance of double-sided cast-coated paper, an aqueous solution containing at least one metal salt containing zinc, magnesium, aluminum, and titanium is used as a rewetting liquid. It has been proposed that blocking does not occur even under high humidity and high pressure, or even if it is very slight, it can be reduced to such an extent that it can be easily released in the base paper setting operation in the printing process. However, although the above-mentioned technique has a glossiness of 80% or more, the coating amount of the coating material for cast coating is about 20 g / m ^2, and the coating film is thick. Poor quality may occur.

  Furthermore, Patent Document 5 proposes a cast coated paper in which a printed portion is formed on the back surface without impairing the aesthetic appearance of the glossy surface. However, in the above technique, there is no description of glossiness, and it is unclear whether the target glossiness is satisfied.

Japanese Patent No. 2664396 JP-A-8-311798 JP-A-6-123098 Japanese Patent No. 3013059 JP 2005-54308 A

  The present invention has been made in view of the above-mentioned circumstances, and its object is to have a high glossiness and excellent cosmetics, and excellent resistance to ruled line cracking, cardboard suitability, paper container suitability, and print suitability. It is another object of the present invention to provide a multilayer paper having high smoothness, particularly a high gloss multilayer paperboard.

The present invention is a multi-layer paper comprising a multi-layer paper having a colored surface layer, and a coating layer mainly comprising a pigment and an adhesive provided on the colored surface layer,
The coating layer is mirror-finished by a rewet cast method,
About the coating layer surface, the glossiness measured according to JIS-P8142 (2005) is 60 to 90%,
About the coating layer surface, the smoothness measured according to the smoothness test method by the Beck smoothness tester of JIS-8119 (1998) is 80 to 350 seconds,
The multilayer paper is characterized by having an air permeability measured in accordance with the Gurley tester method of JIS-8117 (1998) of 5000 seconds or less.

  Preferably, the coating layer contains a release agent in an amount of 1.4 to 3.0 parts by mass with respect to 100 parts by mass of the pigment, and the release agent has a melting point of 100 to 110 ° C. Contains a mold.

  According to the present invention, a multi-layer paper, particularly a high-gloss multi-layer paper board having a high gloss feeling and excellent cosmetics, and excellent in resistance to ruled line cracking, having cardboard suitability, paper container suitability, print suitability and high smoothness. Can be obtained.

The figure which shows the evaluation procedure of the ruled line crack in an Example

  Hereinafter, an embodiment of the multi-layer paper according to the present invention will be described in detail. It should be noted that the multilayer paper according to the present invention is not limited to the following embodiments, and can be appropriately changed without departing from the scope of the claims.

  The present embodiment relates to a high gloss multilayer paperboard. In the high gloss multilayer paperboard (hereinafter referred to as “the present high gloss paperboard”) according to the present embodiment, the base paper (multilayer paper) is constituted by three paper layers of the front layer, the middle layer, and the back layer. Has been.

(material)
The raw pulp used for the base paper of this high gloss paperboard is hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), waste paper Can be used for deinked and bleached waste paper pulp, unprinted waste paper such as Kent, upper white, extra white, medium white, etc., waste paper pulp obtained from old paper such as paper, corrugated paper, craft, imitation, magazine, etc. . In addition, there is an advantage that an environmental load is reduced when much waste paper pulp is used.

  The freeness of the raw material pulp used for the surface layer is preferably 150 to 400 ml, particularly 150 to 350 ml. If the freeness of the surface layer is less than 150 ml, the fibers are likely to become dense and the air permeability becomes too high. On the contrary, if it exceeds 400 ml, the fibers are likely to be sparse, the air permeability is lowered and the smoothness is lowered.

  The freeness of the raw material pulp used for the middle layer is preferably 250 to 450 ml, particularly 250 to 400 ml. If the amount is less than 250 ml, the fibers are likely to be dense and the air permeability becomes too high. Conversely, if it exceeds 450 ml, the fibers are likely to become sparse, resulting in low air permeability and low smoothness.

  Moreover, it is preferable that the freeness of the raw material pulp used for a back layer is 300-450 ml, especially 300-400 ml. If it is less than 300 ml, the fibers are likely to be dense, the air permeability becomes too high, and moisture in the paper is difficult to escape to the back surface during drying after coating. On the other hand, if it exceeds 450 ml, the difference between the surface layer raw material freeness and the back layer raw material freeness of the high gloss paperboard becomes large, and curling occurs after drying.

  In addition, the freeness of the raw pulp of each layer satisfies the condition of “freeness of the raw material pulp of the surface layer <freeness of the raw material pulp of the middle layer <freeness of the raw material pulp of the back layer” so that moisture on the dry surface can easily escape to the back side of the paper. It is more preferable.

  As a method for adjusting the freeness, a known beating machine such as a single disc refiner (SDR), a double disc refiner (DDR), or a conical refiner can be used.

  In addition, in this specification, freeness is based on the freeness test method of a JIS-P8121 (1995) pulp after disintegrating a sample with a standard disintegrator based on the JIS-P8220 (1998) disaggregation method. This is a value measured by a Canadian standard freeness tester.

(Various additive chemicals)
In the base paper, fillers, yield improvers, freeness improvers, paper strength enhancers, fixing agents, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime are added as necessary. An internal additive for papermaking such as a control agent can be appropriately blended.

In the production of the high gloss paperboard, a known sizing agent such as an acidic rosin sizing agent, a neutral rosin sizing agent, or an alkyl ketene dimer is internally added in order to adjust the water absorption into the base paper of the paint for casting. it by, 25~90g / ^{m 2} Cobb sizing degree with a contact time of 120 seconds to JIS-P8140 measured coating Maehara paper according to (substrate paper), preferably adjusted so that 25~80g / ^{m 2} It is preferred that When the cobb sizing degree of the base paper before coating is less than 25 g / m ² , the casting paint described later cannot be sufficiently applied in the subsequent casting paint application process, and the target glossiness is obtained. I can't. On the other hand, if the cobb sizing degree of the base paper before coating exceeds 90 g / m ² , the amount of penetration of the cast paint to be applied into the inside of the base paper increases, resulting in high cost and high air permeability. Due to this, there is a risk of causing poor drying.

  Moreover, this high gloss paperboard mix | blends a coloring agent in the raw material pulp of a surface layer, and makes it a colored layer. In the high gloss paperboard, the middle layer and / or the back layer may be used as a colored layer by blending a colorant into the raw pulp of the middle layer or the back layer.

  As the colorant, a basic dye having a beautiful color and a high color density can be used together with an anionic direct dye or a cationic direct dye. In addition, when adding two or more of these dyes, the order of addition of the dyes is that an anionic direct dye is added at an early stage, pH is adjusted by adding a sulfuric acid band, then a basic dye and necessary for it. It is preferable to add a cationic direct dye having a high speed dyeing property near the inlet, high exhaustibility, good water fastness and good fastness to sunlight. Furthermore, by adding a pigment, it is possible to realize coloring with a deeper color and higher weather resistance. Various known pigments can be used as the pigment.

(Basis weight)
The basis weight of the base paper of the present high gloss paperboard, but are not particularly limited, usually 120~320g / ^{m 2,} preferably 150~280g / ^{m 2.} If the basis weight is less than 120 g / m ² , it is difficult to ensure strength as a corrugated base paper. Conversely, if the basis weight exceeds 320 g / m ² , not only will the quality be excessive, but also the manufacturing cost will be high. In addition, the basic weight in this specification is the value measured based on the basic weight measuring method of JIS-P8124 (1998).

(Paper making method)
The paper making method of the base paper of the high gloss paperboard is not particularly limited, and any of an acid paper making method, a neutral paper making method, and an alkaline paper making method may be used. Also, the paper machine is not particularly limited, and is well known in the art, such as a long net paper machine, a twin wire paper machine, a circular net paper machine, a short net combination machine, a Yankee paper machine, and an inclined wire paper machine. Various paper machines can be used as appropriate.

  By the way, in the present invention, it is preferable to provide a surface treatment layer on the surface of the base paper in order to improve the smoothness and improve the yield of the coating material for casting applied in the subsequent process. Any surface treating agent can be used without particular limitation as long as it does not impair the effects of the present invention. For example, starch such as corn, potato, tapioca, wheat, rice, etc., starch derivatives such as oxidized starch, etherified starch, phosphated starch, cationized starch, synthetic water-soluble such as polyacrylamide resin and polyvinyl alcohol A water-soluble polymer such as a binder and a copolymer latex such as a styrene-butadiene copolymer may be used, and these may be used alone or in combination. Among these, oxidized starch is easy to use as a surface treatment agent because it is inexpensive.

  As a method for coating the surface treatment agent, generally known coating apparatuses such as a calendar, blade coater, air knife coater, roll coater, reverse roll coater, bar coater, curtain coater, slot die coater, gravure coater, Champlex coater, A brush coater, a slide bead coater, a two-roll or metering blade type size press coater, a bill blade coater, a short dwell coater, a gate roll coater, or the like can be used.

  The base paper of the high gloss paperboard is usually subjected to a smoothing process. The smoothing process is performed on-machine or off-machine using a known apparatus such as a Yankee dryer, a super calendar, a gloss calendar, or a soft calendar. The processing conditions such as the pressure of the pressure device, the heating temperature, and the number of nips are appropriately adjusted.

  In addition, it is preferable that the base paper manufactured with the said papermaking method is 24 to 90 seconds by the smoothness by the Beck smoothness tester of JIS-P8119 (1998). When the smoothness is less than 24 seconds, the surface of the paper is rough, so that coating unevenness occurs when the coating agent is applied in a subsequent process, and the glossiness and smoothness that are the object of the present application are satisfied. Glossy paperboard cannot be obtained. On the other hand, if the smoothness exceeds 90 seconds, it becomes an excessive quality for uniformly applying the coating agent without coating unevenness in the subsequent step.

  The base paper produced by the paper making method preferably has an air permeability measured in accordance with the Gurley tester method of JIS-P8117 (1998) of 80 to 350 seconds. If the air permeability is less than 80 seconds, overdrying may occur in the drying step after the coating agent is applied in the subsequent step, and blistering may occur. On the other hand, if the air permeability exceeds 350 seconds, drying may be insufficient in the drying process after the coating agent is applied in the subsequent process, and pits may be generated.

Furthermore, it is preferable that the base paper manufactured by the paper making method has a Cobb sizing degree (2-minute cobb) measured according to the Cobb method of JIS-P8140 (1998) of 25 to 90 g / m ² . When the Cobb sizing degree is less than 25 g / m ² , when the coating agent is applied in the subsequent step, the coating agent does not penetrate into the base paper, but the quality becomes excessive and the cost is increased. If the cobb sizing degree exceeds 90 g / m ² , the coating agent penetrates into the base paper when the coating agent is applied in the post-process, and the glossiness and smoothness that are the object of the present application during the casting process. High gloss paperboard satisfying the degree cannot be obtained.

(Coating layer)
A coating layer mainly composed of a pigment and an adhesive is provided on the surface of the colored surface layer of the base paper produced as described above. The coating layer preferably further contains a release agent.

(Pigment)
The pigment used in the coating layer is not particularly limited. For example, kaolin, delaminated kaolin, talc, clay, light calcium carbonate, heavy calcium carbonate, satin white, calcium sulfite, gypsum, barium sulfate, white carbon, baking Kaolin, structured kaolin, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, silica, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, and other inorganic pigments and polystyrene resin fine particles One or more kinds of organic pigments such as urea formalin resin fine particles, fine hollow particles, and porous fine particles can be appropriately selected and used.

  Among the above pigments, clay is low in water absorption, and high gloss and smoothness can be obtained. Therefore, it is preferable to add 20 to 80 parts by mass of 100 parts by mass of the pigment. If the blending amount is less than 20 parts by mass, the water absorption, glossiness and smoothness are inferior because it is inferior. On the other hand, if it exceeds 80 parts by mass, the fluidity of the coating liquid deteriorates and the profile during coating deteriorates. Since uneven glossiness and smoothness are likely to occur, the appearance is degraded.

  As a pigment to be used in combination with clay, heavy calcium carbonate with improved whiteness and good appearance and good paintability due to low water retention of the paint, less uneven coating, and good economic efficiency Is preferred. The blending amount is preferably 20 to 80 parts by mass so as to complement the blending amount of clay.

  Among the above pigments, silica is also a pigment that gives glossiness. However, silica is not preferable because it is a pigment having high liquid absorbency and is poor in water resistance. When silica is blended in an amount of 5% by mass or more, further 10% by mass or more of the whole pigment, it is not preferable because it is particularly poor in water resistance.

  As described above, when clay and calcium carbonate are used as pigments, preferably a total of 95% by mass or more of the total pigments, the resulting high-gloss paperboard has low water absorption and good coatability, resulting in high glossiness and Since smoothness can be obtained, this high gloss paperboard suitable for corrugated cardboard and paper container applications can be obtained, which is preferable.

  In addition to pigments and adhesives, the coating agent of the present embodiment includes, for example, fluorescent whitening agents, fluorescent whitening agent dyed substances, antifoaming agents, mold release agents, coloring agents, water retention agents, etc. Various auxiliary agents that are usually used can be appropriately blended.

(adhesive)
In this embodiment, an adhesive generally used in coated paper production can be used. Specifically, for example, proteins such as casein and soybean protein; conjugated diene latexes such as styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, styrene-methyl methacrylate-butadiene copolymer latex; Acrylic latex such as acrylic acid ester and / or methacrylic acid ester polymer latex or copolymer latex; vinyl latex such as ethylene-vinyl acetate polymer latex; Latexes such as alkali partially soluble or insoluble latex modified with group-containing monomers; synthetic resin adhesives such as olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin; oxidized starch, positive Starch, ester Starches, starches such as dextrin; carboxymethyl cellulose, may be mentioned cellulose derivatives such as hydroxyethyl cellulose, it can be used by selecting one or more from among these as appropriate. Among the adhesives, it is preferable to use a styrene-butadiene copolymer latex that has a high ability to fix a pigment and has a small decrease in ink deposition property.

  1-35 mass parts is preferable with respect to 100 mass parts of pigments, and, as for the compounding quantity of an adhesive component, 3-15 mass parts is more preferable. If the amount is less than 1 part by mass, the pigment cannot be fixed and the gloss derived from the pigment is not only inferior, but also a part of the coating layer is easily peeled off by bending stress, which is not preferable. On the other hand, if it exceeds 35 parts by mass, an adhesive film is formed to form a film-like surface, and the gloss derived from the pigment is lowered, and the ink-inking property is lowered and printing sharpness is inferior. It is not preferable.

(Release agent)
In this invention, you may contain a mold release agent suitably in the cast coating layer.

  Examples of mold release agents include mold release agents conventionally used for corrugated cardboard and paper containers, mold release agents used in cast coating, and the like, for example, fatty acid or higher fatty acid chlorides, fatty acid amides. , Higher alcohols, polyhydric alcohols, tributyl phosphoric acid, nonionic surfactants, etc., but when these are used, sufficient gloss and ruled line crack resistance cannot be imparted for corrugated cardboard and paper containers It was.

  As other mold release agents, polyolefin resins are generally used, and are copolymers with unsaturated carboxylic acids such as acrylic acid and methacrylic acid, copolymers with vinyl compounds such as acrylic acid esters, methacrylic acid esters and vinyl acetate, Examples thereof include polymers obtained by graft-reacting unsaturated carboxylic acid monomers with peroxides to these homopolymers and copolymers. However, even when these are used, sufficient gloss and ruled line crack resistance for corrugated cardboard and paper containers cannot be imparted.

  In the present invention, it has been found that, when a polyethylene resin is used among synthetic resins such as a polyolefin resin, sufficient resistance to ruled line cracking can be obtained in cardboard and paper container applications.

  Specific examples of the polyethylene resin include high pressure method low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultrahigh molecular weight polyethylene, ethylene-methacrylic acid copolymer, maleic acid and acrylic acid. Examples thereof include copolymerized modified polyethylene and polyethylene oxide. These polyolefins may be produced by any production method. Among these, when polyethylene oxide is used, the glossiness and ruled line crack resistance required particularly for corrugated cardboard and paper container applications can be obtained.

  The polyethylene resin generally has a melting point of 100 to 120 ° C, but in the present invention, it is preferable to use a polyethylene resin having a melting point of 100 to 110 ° C. If the melting point exceeds 110 ° C, the reason for the coating layer being coated on the base paper is unknown, but it is easy to move into the base paper as well as the moisture in the coating layer, and sufficient gloss is obtained. Further, it is not preferable because it is inferior in resistance to ruled line cracking. If the melting point is below 100 ° C., the reason is unknown, but the glossiness of the white paper is also lowered, which is not preferable.

  It is preferable that the compounding quantity of a polyethylene resin is 1.4-3.0 mass parts in conversion of solid content with respect to 100 mass parts of pigments, More preferably, it is 1.5-2.5 mass parts. When the amount is less than 1.4 parts by mass, sufficient gloss cannot be obtained. When the amount exceeds 3.0 parts by mass, not only the gloss effect reaches a peak, but also the printing ink is easily repelled, and the print sharpness decreases. It is not preferable because it is easy.

  The coating layer containing the release agent is preferably provided on the surface of the base paper. When a coating layer is provided on the surface of the base paper, the contact area between the base paper and the coating layer is small, so the release agent remaining in the coating layer tends to remain in the coating layer, resulting in a low coating amount. Is preferable because sufficient glossiness can be imparted.

  As described above, when a polyethylene release agent, preferably a polyethylene release agent having a melting point of 100 to 110 ° C., is contained in an amount of 1.4 to 3.0 parts by mass in terms of solid content with respect to 100 parts by mass of the pigment, It is preferable because the water resistance effect tends to remain in the coating layer while the printing sharpness is good. In particular, it is preferable to use an oxidized polyethylene resin as a release agent because it is particularly excellent in print sharpness and high gloss.

  In the present invention, two or more release agents may be added.

(Coating method for coating agent)
It is sufficient to apply the coating agent to the surface of the base paper using general application paper application equipment, for example, calendar, blade coater, air knife coater, roll coater, reverse roll coater, bar coater, curtain coater, slot die coater. , Gravure coater, champlex coater, brush coater, slide bead coater, two-roll or metering blade size press coater, bill blade coater, short dwell coater, on-machine coater with gate roll coater etc. It can be coated on the base paper with a machine coater. Among these, it is preferable to use a blade coater from the viewpoint that high flatness of the coating layer surface is ensured. Moreover, as a drying method in the dryer part, for example, various heating drying methods such as hot air heating, gas heater heating, infrared heater heating and the like can be appropriately employed.

The coating amount of the coating layer is preferably 3 to 10 g / m ² , more preferably 6 to 8 g / m ² per side. If it is less than 3 g / m ² , the covering property of the base paper is lowered, and good glossiness and print sharpness cannot be obtained. Exceeding 10 g / m ² is not preferable because the resistance to ruled line cracking of the coating layer tends to decrease.

  In the present embodiment, the outermost layer needs to be mirror-finished, and this mirror-finishing is performed by a so-called cast coating method. In general, the cast coating method includes (1) a wet casting method (direct method) in which a coating layer is in a wet state and is dried by pressure bonding (pressure contact) to a mirror-finished heating drum, and (2) a wet coating method. Re-wet casting method (re-wetting method) in which the work layer is once (semi-) dried and then swelled and plasticized (wet) with a re-wetting liquid, and then pressed onto a mirror-finished heating drum (drying method). (3) Wet coating The layer is made into a gel state by a coagulation treatment with a coagulation liquid, etc., and can be divided into three types, a gelation cast method (coagulation method) in which it is pressed against a mirror-finished heating drum and dried. However, since the present embodiment can achieve excellent crease resistance, the rewet cast method is applied. The wet cast method and the gelled cast method are not preferable because fine cracks enter the surface of the coating layer, which tends to be inferior in water resistance and ruled line crack resistance.

  In the high gloss paperboard of this embodiment, only one cast coating layer is sufficient, but another layer may be provided between the base paper and the cast coating layer. However, if the coating amount is increased, the resistance to ruled line cracking tends to decrease, which is not preferable.

  A coating layer may not be provided on the non-surface of the base paper, the above-described cast coating layer may be provided, or a coating layer other than the cast coating layer may be provided. There is no particular limitation on whether a cast coating layer is provided only on one side and what kind of processing is performed on the other side or no processing is performed. Of course, a coating layer mainly composed of pigments and adhesives that do not satisfy the above various conditions may be provided, and various external additive coating agents for paper such as starch or starch derivatives, sizing agents and synthetic paper strength agents. May be applied. In addition, water coating can be performed from the viewpoint of curling prevention.

The high-gloss paperboard of this embodiment thus obtained has 20 to 80 parts by mass of clay as a pigment, 20 to 80 parts by mass of heavy calcium carbonate, and 100 parts by mass of a styrene-butadiene copolymer latex as an adhesive. On the other hand, a coating layer in which 1.4 to 3.0 parts by mass of a polyethylene resin having a melting point of 100 to 110 ° C. as a release agent with respect to 100 parts by mass of the pigment is mixed with the base paper. By applying 3 to 10 g / m ^{2 on} the surface of the sheet, this high-gloss paperboard excellent in ruled line cracking resistance can be obtained, and in particular, this high-gloss paperboard suitable for corrugated cardboard and paper container applications can be obtained. In addition, it is preferable to provide a cast coating layer by the rewet cast method because the above high-gloss paperboard excellent for corrugated cardboard and paper containers can be efficiently produced.

  Moreover, the glossiness of the coating layer surface measured according to JIS-8142 (2005) is 60-90% of this high gloss paperboard formed as mentioned above. When the glossiness is less than 60%, there is no sense of quality when processed into corrugated cardboard and paper containers, and the glossiness intended by the present application cannot be satisfied. On the other hand, when the glossiness exceeds 90%, the quality is excessive and the cost is increased. Preferably it is 70 to 90%.

  The high gloss paperboard has a coating layer surface smoothness of 80 to 350 seconds measured in accordance with a smoothness test method using a Beck smoothness tester of JIS-8119 (1998). When the smoothness is less than 80 seconds, the paper surface is rough, so there is no sense of quality when processed into corrugated cardboard and paper containers, and the high smoothness intended by the present application cannot be satisfied. In particular, there is a risk of ink bleeding and reproducibility in the halftone dot portion, and the printability is deteriorated. On the other hand, if the smoothness exceeds 350 seconds, the paper becomes excessively high in terms of high-quality paper and printability, resulting in high costs. Preferably, it is 150 to 300 seconds.

  Furthermore, this high gloss paperboard has an air permeability measured in accordance with the Gurley tester method of JIS-8117 (1998) of 5000 seconds or less. This glossy paperboard with air permeability exceeding 5000 seconds is used as corrugated base paper, and when processing into corrugated sheets with corrugators and other pasting equipment, moisture loss during drying is poor, so corrugated board sheets When the warpage occurs, a production loss at the time of production occurs, and the productivity may be deteriorated. Preferably, it is 2000 to 3000 seconds.

  Furthermore, according to the inclination method of the friction coefficient test method for paper and paperboard of JIS-P8147 (1994), the coating layer surface and the coating layer surface are in the flow direction (vertically). The sliding angle measured so as to be in contact with each other is preferably 18 degrees or more, and more preferably 20 degrees or more. When the sliding angle is less than 18 degrees, for example, when the corrugated cardboard cases are stacked, load collapse is likely to occur, and problems such as deterioration of processing suitability due to slipping during the corrugated cardboard processing are likely to occur.

As described above, the sliding angle of the present high-gloss paperboard can be achieved by providing a coating layer containing 1.4 to 3.0 parts by mass of polyethylene resin with respect to 100 parts by mass of pigment. Furthermore, 20 to 80 parts by mass of clay as a pigment, 20 to 80 parts by mass of heavy calcium carbonate, and 1 to 35 parts by mass of a styrene-butadiene copolymer latex as an adhesive with respect to 100 parts by mass of the pigment. By coating the applied coating layer on the surface of the base paper by 3 to 10 g / m ² rewet cast method, the achievement becomes easier.

  As described above, the high glossy paperboard has been described with respect to the case where the base paper is composed of three paper layers of the surface layer, the middle layer, and the back layer. You may comprise from the middle layer more than a layer, and a back layer and four or more paper layers.

  In order to confirm the effect of the high gloss paperboard according to the present invention, the following various samples were prepared, and a test for evaluating the quality of each sample was performed. In addition, in a present Example, the numerical value which shows a mixing | blending, a density | concentration, etc. is a numerical value of the solid content or the mass reference | standard of an active ingredient. Moreover, since the pulp, chemical | medical agent, etc. which are shown in a present Example are only examples, it cannot be overemphasized that this invention is not restrict | limited by these Examples, and can be selected suitably.

  In order to compare with 26 types of high gloss paperboards according to the present invention (referred to as “Example 1” to “Example 26”) and these Examples 1 to 26, three types of paperboard ( This was referred to as “Comparative Example 1” to “Comparative Example 3”), and was prepared with the configuration shown in Table 1.

[Example 1]
<Surface>
Using 100% by mass of hardwood bleached kraft pulp (LBKP), the raw pulp was adjusted with a double disc refiner so that the freeness (CSF) was 154 ml, and a raw pulp slurry for the surface layer was prepared. A coloring agent, a fixing agent, and a sizing agent were added to the raw material raw material slurry. As the colorant, anionic direct dyes of “Blue 5B200” (manufactured by Nikka Co., Ltd.) and “Turkis MP” (manufactured by Toa Kasei Co., Ltd.) were used. Further, a sulfuric acid band was used as a fixing agent, and 3.0% by mass was added. Further, an acidic rosin sizing agent was used as a sizing agent, and 0.4% by mass was added as an active ingredient to the raw material pulp.

<Middle layer>
Using 100% by mass of Kent waste paper pulp, the raw pulp was adjusted with a double disc refiner so that the freeness (CSF) was 300 ml, and a raw pulp slurry for the middle layer was obtained.

<Back layer>
The raw pulp was adjusted so that the freeness (CSF) was 341 ml with a double disc refiner using 100% by mass of old paper pulp, and a raw pulp slurry for the back layer was obtained. A fixing agent and a sizing agent were added to the raw material pulp slurry for the back layer. A sulfuric acid band was used as a fixing agent, and 0.4% by mass was added. Moreover, the acidic rosin sizing agent was used as a sizing agent, and 0.25 mass% was added as an active ingredient with respect to raw material pulp.

Using the raw material pulp slurry of each of the surface layer, middle layer, and back layer, the surface layer (colored layer), 3 layers of the middle layer, and back layer of the raw material pulp slurry were combined by a circular mesh 5-layer paper machine. A multilayer paperboard (base paper) made of a five-layer base paper having an amount of 170 g / m ² was made.

  An evaluation test was conducted on the glossiness, air permeability, and cobb size of the multilayer paperboard. The results were as shown in Table 1.

<Coating fluid>
The coating liquid prepared as follows was used.

First grade clay UD60 (manufactured by Engelhard): 60.0 parts Light calcium carbonate TP-123CS (manufactured by Shiroishi Calcium): 40.0 parts Styrene-butadiene copolymer latex L-1388 (manufactured by Asahi Kasei): 19. 0 parts Casein PO gazein (manufactured by Racpol): 12.0 parts polyethylene release agent (A) SN286 (manufactured by San Nopco) Melting point 105 ° C .: 1.5 parts polyethylene mold release agent (B) BERCHEM 4095 (manufactured by Basen) ) No melting point: 0.6 parts The coating solution was applied to the colored layer surface of the multilayer paperboard with an air knife so that the coating amount in Table 1 was converted to solid content. After coating, mirror finishing was performed by a rewet cast method (rewetting method) to produce a highly glossy multilayer paperboard.

  In Examples 2 to 5, the high gloss multilayer papermaking was performed in the same manner as in Example 1 except that the freeness of the raw material pulp of the surface layer, middle layer and back layer was adjusted and the smoothness of the base paper was changed as described in Table 1. Board paper was produced.

  In Examples 6 to 9, the high gloss multi-layer was formed in the same manner as in Example 1 except that the freeness of the raw pulp of the surface layer, middle layer and back layer was adjusted and the air permeability of the base paper was changed as described in Table 1. Paperboard was produced.

  In Examples 10 to 13, a high-gloss multilayer paperboard was prepared in the same manner as in Example 1 except that the amount of sizing agent in the surface layer was adjusted and the cobb sizing degree of the base paper was changed as shown in Table 1. Manufactured.

  In Examples 14 to 16, high gloss multilayer paperboards were produced in the same manner as in Example 1 except that the coating amount was changed as shown in Table 1.

  In Example 17, a high gloss multilayer paperboard was produced in the same manner as in Example 1 except that the type of the release agent A was changed. Nopco 1097-AH (manufactured by San Nopco, calcium stearate, melting point 150 ° C.) was used as a release agent.

  In Examples 18 to 25, high gloss multilayer paperboards were produced in the same manner as in Example 1 except that the addition amounts of the release agents (A) and (B) were changed as shown in Table 1.

  In Example 26, a highly glossy multilayer paperboard was produced in the same manner as in Example 1 except that only the release agent (A) was added.

  In Comparative Examples 1 and 2, high-gloss multilayer paperboard was produced in the same manner as in Example 1 except that the coating amount was changed as shown in Table 1.

  In Comparative Example 3, the multilayer paperboard of Example 1 was evaluated before the coating layer was provided.

  Evaluation tests were conducted on the quality evaluation of all of these Examples and Comparative Examples, that is, the glossiness, slip angle, smoothness, air permeability, and ruled line cracking of the high gloss multilayer paperboard (all layers). The results were as shown in Table 1. This quality evaluation was performed under environmental conditions of a temperature of 23 ± 2 ° C. and a humidity of 50 ± 2% in accordance with JIS-P8111.

  “Glossiness (%)” in Table 1 refers to the degree of gloss on the surface of the coating layer in the high gloss multilayer paperboard relating to each sample, 75 degree gloss meter (in accordance with JIS-P8142 (2005)) (Manufacturer: Horiba, Model: IG-320).

  “Slip angle (degree)” is a value obtained by measuring the slipperiness of the high gloss multilayer paperboard according to each sample in accordance with the inclination method of the friction coefficient test method for paper and paperboard of JIS-P8147 (1994). It is. In addition, it is the value measured so that the coating layer surface and the coating layer surface may contact each other in the flow direction (vertical).

“Cobb sizing degree (g / m ² )” is a value obtained by measuring the degree of water absorption of the base paper according to each sample in accordance with the Cobb method of JIS-P8140 (1998). The contact time with water was 120 seconds.

  “Smoothness (seconds)” is a measurement of the flatness of the surface of a base paper or glossy paperboard according to each sample, using a Beck smoothness tester of JIS-8119 (1998) in accordance with a high flatness multi-layer test method. It is the value.

  “Air permeability (seconds)” is a value obtained by measuring the ease of air flow of the base paper or glossy paperboard of each sample according to the Gurley test method of JIS-8117 (1998).

  Furthermore, “ruled line cracking” is an evaluation of the strength against breakage of a high gloss multilayer paperboard. As an evaluation procedure, as shown in FIG. 1, (a) each sample has a paper width of 200 mm. Cut into a flow of 250 mm, put it in a hot air dryer set at a temperature of 100 ° C. for 30 seconds, and then remove it. (B) Width so that the paper surface 1 faces outward and the back surface 2 faces inward without folding the paper. (C) Place the φ32 mm iron pipe 3 at the end of the curved portion while keeping the 200 mm end sides overlapped and bend at once. (D) Evaluation is made by examining the degree to which the paper coating layer is cracked or peeled when the bent portion 4 is viewed from the front (in the direction of the arrow 5).

A: There are 1 to 2 cracks less than 3 mm.
A: There are 1 to 2 cracks of 3 mm or more and less than 5 mm.
Δ: There are 3 to 4 cracks less than 5 mm.
X: There are many cracks of 5 mm or more.

  Finally, the glossiness of the high gloss multilayer paperboard, the quality as a paperboard and the processing suitability were comprehensively evaluated and evaluated as a comprehensive evaluation.

(Double-circle): There exists a glossiness and it is excellent in quality and processability.
○: Glossy, quality and processability.
Δ: Glossy, but quality and processability are slightly inferior.
X: There is no glossiness.

1 surface (colored layer)
2 Back side (non-colored layer)
3 Pipe (bending rod)
4 Folded part 5 Observation direction for visual evaluation

Claims (1)

A multilayer paper having a colored surface layer, and a multilayer paper comprising a coating layer mainly composed of a pigment and an adhesive provided on the colored surface layer,
The multi-layer paper is composed of three paper layers, a surface layer, a middle layer, and a back layer. The freeness of the raw material pulp used for the front layer is 150 to 400 ml, and the freeness of the raw material pulp used for the middle layer is 250 to 450 ml. , The freeness of the raw material pulp used for the back layer is 300 to 450 ml, and the freeness of the raw material pulp of each layer satisfies the condition that the freeness of the raw material pulp of the surface layer <the freeness of the raw material pulp of the middle layer <the freeness of the raw material pulp of the back layer Meet,
The coating amount is 3 to 10 g / m ² .
The coating layer is mirror-finished by a rewet cast method,
In the coating layer, containing a release agent composed of a polyethylene resin having a melting point of 100 to 110 ° C. with respect to 100 parts by mass of the pigment,
About the coating layer surface, the glossiness measured according to JIS-P8142 (2005) is 60 to 90%,
About the coating layer surface, the smoothness measured according to the smoothness test method by the Beck smoothness tester of JIS-8119 (1998) is 80 to 350 seconds,
Regarding the coating layer surface, the coating layer surface and the coating layer surface are in contact with each other in the flow direction (vertically) according to the inclination method of the friction coefficient test method for paper and paperboard of JIS-P8147 (1994). The measured sliding angle is 18 degrees or more,
Air permeability measured according to the Gurley tester method of JIS-8117 (1998) for a multilayer paper made of a coating layer mainly composed of a pigment and an adhesive provided on the colored surface layer. Multi-layered paper characterized in that is less than 5000 seconds.

Images