JP4335951B2 - Multilayer glossy paperboard - Google Patents

Description

  The present invention relates to a multi-layer glossy paperboard having a colored layer having a high cosmetic appearance, wherein a resin is coated on the surface of a surface layer as a colored layer.

  Multi-layer paperboards having a colored layer are often used in gifts for gifts, and multilayer paperboards having a colored layer having a glossy surface are used particularly in the fields of ham, sausage, pastry and the like. Multi-layer paperboards having such a colored layer include printed products and papermaking products. The engraved product is a paperboard having a colored layer obtained by coloring a raw material such as pulp with a dye, and the printed product is, for example, a gravure printing machine, a flexographic printing machine, etc., and a white liner, K liner, jute Paperboard with oil-based or water-based ink printed on the liner.

  Here, the multilayer paperboard having a colored layer used in gifts for gifts is generally a printed product having a glossiness of 8 to 15%.

  In the conventional papermaking technology for papermaking products, when there is no coating equipment such as a coater, multilayer paperboard having a glossy colored layer on the surface could not be obtained. That is, for example, in the conventional papermaking technology for making paper products, as a method of increasing the glossiness, in the drying process of the paper machine, a drum roll that has been subjected to a mirror finish in which the wet paper is heated with steam, such as a dryer, is used. And a heat-resistant resin roll called a touch roll is passed while pressing, or paper is passed between multi-stage rolls pressurized in a calendar process after the drying process of the paper machine. However, in such a method of heating and drying the paper surface or smoothing the paper surface, the glossiness is limited to 6%, and it is impossible to produce glossiness like a printed product. there were. Therefore, in order to produce a glossiness of 8% or more, which is about the same as that of printed products, it is not possible to solve with conventional papermaking technology, and secondary processing such as coating glossy resin with a coater is required. There were problems such as becoming up.

  On the other hand, in printed products, for example, as shown in Patent Documents 1 and 2, by using a unit different from the ink unit used for printing ink and applying gloss resin such as OP varnish, the glossiness is reduced. A multilayer paperboard having a colored layer of 8-30% can be produced.

  In addition, as a method for producing a multilayer paperboard having a colored layer with high glossiness, varnishing that coats glossy resin with a coating equipment such as a coater, and press-coating with an aqueous coating agent are applied. Examples thereof include a press coating process to be performed and a laminating process in which a resin such as polyethylene, polypropylene, or polyester is bonded or pressure-bonded.

  However, in recent years, it has become important to be able to recycle due to environmental problems, and since it is difficult to remove a film from a laminated product, there is a problem that it is difficult to recycle as used paper. In addition, the above processing method involves an increase in the number of processes and an increase in processing equipment, and thus there is a problem that manufacturing time is lost and costs are increased.

  Furthermore, conventional glossy resins can be coated without problems if the drying equipment is a non-contact drying method such as IR or hot air dryer, and glossy paperboard can be produced. Occurs, the resin component agglomerates, the glossiness does not increase, the dry surface becomes dirty, the paper surface after coating is sticky, the releasability from the dry surface is poor, and the coating liquid is foamed There was a problem.

In addition, multilayer paperboard with colored layers is bonded with equipment such as a corrugator and then printed with a box or a gravure printing machine using equipment such as a flexo folder gluer. As the quality needs to be met.
JP 2007-99948 A JP-A-4-21493

  The present invention has been made in view of the above-described circumstances, and the object of the present invention is to provide a glossiness of 8% or more by coating a resin on the surface of a base paper having a colored layer on-machine, It is another object of the present invention to provide a multi-layered glossy paperboard having suitability for bonding, box making and printing as a corrugated cardboard.

The object of the present invention is that the base paper is composed of at least three layers of a surface layer, an intermediate layer, and a back layer, and at least the surface layer is mixed with a colorant to form a colored layer. The freeness value of the raw material pulp used for each of the surface layer, the middle layer, and the back layer is determined using any one of a direct dye, a cationic direct dye, and a basic dye, or a combination thereof. Freeness <Freeness of middle-layer raw material pulp <Freeness of raw material pulp of back layer, and coating of resin on the surface of the colored layer to provide a coating layer. This is achieved by providing a multi-layer glossy paperboard, wherein the glossy layer is formed by press-drying the layers and the glossiness of the glossy layer is 8% or more.

In addition, the object of the present invention is that the resin is an acrylic resin having a glass transition temperature (Tg) of 40 to 60 ° C. and a viscosity of 13 to 105 mPa · s, and the resin is applied to the surface of the colored layer. 1.8 to 6.0 g / m ² (dry), and the base paper after the resin is applied has a slip angle of 19 degrees or more and a cob size of 15 to 50 g / m ² (120 sec cobb). This is achieved effectively by providing a multi-layer glossy paperboard characterized by

  Furthermore, the object of the present invention is characterized in that the surface strength of the base paper after coating the resin is 14 A or more, the smoothness is 35 seconds or more, and the air permeability is 500 seconds or less, and has gravure printing suitability. This is achieved more effectively by providing a multi-layer glossy paperboard.

  According to the multi-layered glossy paperboard of the present invention, the base paper is composed of at least three layers of the surface layer, the middle layer, and the back layer, and at least the surface layer is a colored layer, and the resin is applied on the surface of the colored layer on-machine. Thus, a glossy layer can be formed and the glossiness can be 8% or more, so that it is possible to produce a multi-layer glossy paperboard excellent in cosmetics at low cost.

  Hereinafter, the multi-layer glossy paperboard according to the present invention will be described in detail. Note that the multi-layer glossy paperboard having the colored layer according to the present invention is not limited to the following embodiments, and it is needless to say that the multilayer paper glossy paperboard can be appropriately changed without departing from the scope of the claims.

  The multi-layered glossy paperboard (hereinafter referred to as “real glossy paperboard”) according to the present invention comprises a base paper composed of three paper layers, a surface layer, a middle layer, and a back layer, and at least the surface ( In the present glossy paperboard, the surface layer) is colored to form a colored layer.

  The raw pulp used for the base paper of this glossy paperboard is hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), conifer hardwood Pulp and chips chemically treated with wood fibers such as sulfite pulp and coniferous sulfite pulp, or non-wood fibers such as kenaf, hemp, and straw, which are fiber materials other than wood, and chemically treated as the main material Ground pulp obtained by mechanical pulping of the pulp and chips, chemi ground pulp mechanically pulped with chemicals added to wood or chips, and digestion until chips become soft, then pulped with a refiner etc. Virgin pulp such as semi-chemical pulp, kraft pulp, semi-chemical pulp, enzyme drift Office waste paper including pulp is deinked, bleached pulp, milk pack waste paper, high quality cut-off waste paper, coat cut-off waste paper, upper white, extra white, medium white, etc., unprinted, lottery, new stage, newspaper, craft envelope, For example, recovered pulp obtained from imitation or magazine waste paper can be used. 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 become dense and the air permeability becomes too high, and moisture in the paper is difficult to escape to the back surface during drying after coating the resin. 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 glossy 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.

  Moreover, 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.

  In the base paper, fillers, yield improvers, freeness improvers, paper strength enhancers, fixing agents, fluorescent whitening agents, pH adjusters, antifoaming agents, pitch control agents, slime control are included as necessary. An internal additive for papermaking such as an agent can be appropriately blended.

  In addition, the glossy paperboard has a coloring layer formed by mixing a coloring agent in the raw material pulp, and the surface of the paperboard is colored. The glossy paperboard can achieve the desired purpose by blending a colorant into at least the raw material pulp of the surface layer, but the middle layer and / or the middle layer and / or the back layer of the raw material pulp can be blended with the colorant. Alternatively, the back layer may be a colored 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 two or more of these dyes are added, the order of addition of the dyes is that an anionic direct dye is added at an early stage, a pH is adjusted by adding a sulfuric acid band, and 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.

The basis weight of the base paper of the present glossy paperboard is not particularly limited, but is usually 120 to 320 g / m ² , preferably 150 to 280 g / 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).

Further, in the production of the glossy paperboard, in order to adjust the water absorption of the resin into the base paper, a known sizing agent such as an acidic rosin sizing agent, a neutral rosin sizing agent, or an alkyl ketene dimer is internally added to JIS. -P8140 100~200g / ^{m 2} Cobb sizing degree before the base paper for coating the measured resin according the contact time 120 seconds, it is preferably is adjusted such that the 150~190g / ^{m 2} preferable. When the cobb sizing degree of the base paper before coating is less than 100 g / m ² , the resin described later cannot be sufficiently applied in the subsequent resin coating process, and the target glossiness cannot be obtained. On the other hand, when the cobb sizing degree of the base paper before coating exceeds 200 g / m ² , the amount of resin to be applied penetrates into the base paper and the air permeability increases.

  The paper making method of the base paper of the glossy paperboard is not particularly limited, and any of acid paper making method, neutral paper making method, and 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.

  The resin is applied on-machine to at least one surface (surface of the colored layer) of the base paper of the glossy paperboard that has been colored and made as described above. That is, at least the surface of the base paper is coated or coated with a resin in the coating process after the dryer of the paper machine to provide a coating layer, and then pressed and dried while pressing the coating layer on the dryer. Thus, the coating layer is made a glossy layer. Thereby, the glossiness of this glossy paperboard can be 8% or more.

  The glossy paperboard constructed as described above has a glossiness of 8% or more, but as the glossiness increases, the slip angle tends to decrease, and the cardboard case made of the glossy paperboard has a problem of collapse. Since there exists a possibility that it may generate | occur | produce, the range whose glossiness is 8 to 16% is preferable practically.

  In this way, the resin is applied on-machine. As an application method, if it is on-machine, generally known coating apparatuses such as a calendar, a blade coater, an air knife coater, a roll coater, a reverse roll coater, and a bar coater are used. Curtain coaters, slot die coaters, gravure coaters, Champlex coaters, brush coaters, slide bead coaters, two-roll or metering blade type size press coaters, bill blade coaters, short dwell coaters, gate roll coaters and the like can be used.

The coating amount of the resin is 1.8 to 6.0 g / m ² (dry), preferably 2.0 to 6.0 g / m ² (dry). When the coating amount is less than 1.8 g / m ² (dry), the gloss cannot be increased to the desired value of the present application, that is, the gloss cannot be increased to 8% or more. On the other hand, when the coating amount exceeds 6.0 g / m ² (dry), there arises a problem that the paper is not sufficiently dried in the drying step after coating the resin.

  Examples of the resin coated on the glossy paperboard include various polyol resins such as acrylic, silicon, medium, OP varnish, UV varnish, vinylidene chloride, polyester polyol, acrylic polyol, polyether polyol, melamine, amino Alkyd, epoxy resin, cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, proteins such as casein, soybean protein, polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyacrylic acid amide, olefin-maleic anhydride Resin, conjugated diene copolymer latex such as styrene-butadiene latex, acrylonitrile-butadiene latex, methyl methacrylate-butadiene latex, ( A) Acrylic emulsions such as polymers or copolymers of acrylic esters, vinyl acetate emulsions such as ethylene-vinyl acetate emulsions, styrene-acrylic emulsions, vinylidene chloride emulsions, polyester emulsions, polyurethane emulsions, polyamides Resins such as emulsions can be used, but acrylic resins are preferred.

  In the case of acrylic resins, those having a glass transition temperature (Tg) of 40 to 60 ° C., preferably 45 to 55 ° C., and a resin viscosity of 13 to 105 mPa · s are used. When the resin has a Tg of less than 40 ° C., stickiness occurs on the paper surface after the resin is applied, and in a contact drying method such as a dryer, the paper adheres to the drying surface of the dryer roll, Problems such as adhesion and contamination occur. On the other hand, if the resin has a Tg of more than 60 ° C., the coated surface of the resin and the dried surface of the dryer are difficult to adhere, so the glossiness of the glossy paperboard cannot be 8% or more.

The viscosity of the resin is 13 to 105 mPa · s, preferably 13 to 65 mPa · s, or the viscosity measured with a Zahn cup viscometer # 4 (hereinafter abbreviated as “Zahn cup viscosity”) is 6.5 to 12 seconds, preferably Is in the range of 6.5 to 10 seconds. In addition, the viscosity (mPa · s) in the present specification is a value measured with a digital viscometer (manufacturer: Brookfield, model: LVDV-E). If the viscosity is less than 13 mPa · s or the resin having a Zahn cup viscosity of less than 6.5 seconds, the coating amount of the resin decreases, and the coating amount becomes 1.8 to 6.0 g / m ² (dry). The glossiness cannot be 8% or more, which is the desired value of the present invention. On the contrary, if the viscosity exceeds 105 mPa · s, or the resin has a Zahn cup viscosity exceeding 12 seconds, the amount of the resin applied increases, and the amount of application is set as desired in the present invention 1.8 to 6. It cannot be set to 0 g / m ² (dry). Accordingly, the paper is not sufficiently dried in the drying process after the resin coating, and the resin is scattered during the resin coating, resulting in a deterioration in operability.

Thus, when an acrylic resin having a Tg of 40 to 60 ° C. and a viscosity of 13 to 105 mPa · s is used as the resin applied to the glossy paperboard, the slip angle of the glossy paperboard is 19 degrees or more. The cob sizing degree can be 15 to 50 g / m ² (120 second cobb). In addition, the slip angle in this specification is a value measured according to “Inclination method of friction coefficient test method for paper and paperboard” of JIS-P8147 (1994). Moreover, the Cobb sizing degree in this specification is a value measured according to the Cobb sizing degree test method / Cobb method (120-second Cobb) of JIS-P8140 (1998).

  If the slip angle of the glossy paperboard is less than 19 degrees, the glossy paperboard may collapse when the glossy paperboard is processed into a cardboard case or the like. However, if the sliding angle becomes too high, it may cause sheet clogging in a pasting machine such as a corrugator or a box making machine such as a flexo folder gluer, and from the viewpoint of preventing the cardboard case from collapsing. In view of excessive quality, the slip angle is preferably in the range of 19 to 30 degrees for practical use.

Also, when the cobb sizing degree is less than 15 g / m ² , the adhesive of the gluer joint part deteriorates when a cardboard case is manufactured using this glossy paperboard, and a special adhesive is required. In addition, the solubility becomes worse when the glossy paperboard is recycled as used paper. Conversely, when the cob size exceeds 50 g / m ² , when manufacturing cardboard cases using this glossy paperboard, the adhesive that glues the gluer joints penetrates into the middle layer, causing joint peeling. In addition, there is a problem that the amount of adhesive used increases and the manufacturing cost increases. Moreover, since the usage-amount of a sizing agent will increase when a Cobb sizing degree is made too low, and it will become a cost increase, it is preferable to make a Cobb sizing degree into the range of 20-50 g / m < ² > practically.

  The above acrylic resins can be applied without problems in the non-contact drying method, but in the contact drying method, uneven coating occurs, resin components aggregate, the gloss does not increase, and the dry surface becomes dirty. Various problems occur, such as stickiness on the surface of the paper after coating, poor releasability from the dry surface, and foaming of the coating liquid. This problem can be improved by appropriately adding a release agent, a leveling agent and an antifoaming agent to the glossy resin.

  The glossy 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.

  The glossy paperboard formed as described above preferably has gravure printing suitability with a surface strength of 14 A or more, a smoothness of 35 seconds or more, and an air permeability of 500 seconds or less.

  That is, this glossy paperboard is JAPAN TAPPI No. The surface strength measured in accordance with the surface strength test method with 1 wax is 14 A or more. When the surface strength is less than 14A, the surface layer may peel off at the gluer joint when manufacturing a cardboard case using this glossy paperboard, and there is a problem of picking in printing using high viscosity ink such as offset printing. Will occur. However, even if the surface strength exceeds 23A, it is excessive quality in normal printability, so 14 to 23A is practically preferable.

  Further, the glossy paperboard has a smoothness of 35 seconds or more measured according to a smoothness test method using a Beck smoothness tester of JIS-8119 (1998). When the smoothness is less than 35 seconds, the surface of the paper is rough, and in gravure printing, there is a risk of ink bleeding, particularly in the halftone dot portion, causing problems in reproducibility, and the gravure printing suitability is reduced. . However, in gravure printing usually applied to paperboard, if the smoothness exceeds 80 seconds, excessive quality is obtained, and therefore, practically, the smoothness is preferably 40 to 80 seconds.

  Furthermore, this glossy paperboard has an air permeability measured in accordance with the Gurley tester method of JIS-8117 (1998) of 500 seconds or less. When the air permeability is 500 seconds or more, there is a problem that moisture in the paper is difficult to escape to the back surface during drying after coating the resin. Therefore, for practical reasons, the air permeability is preferably 450 seconds or less for the above reasons.

  Further, the glossy paperboard has gravure printing suitability and can suppress the occurrence of ruled cracks during bonding and box making.

  As described above, the present glossy paperboard has been described with respect to the case where the base paper is composed of the three layers of the surface layer, the middle layer, and the back layer. , And a back layer and four or more paper layers.

  In order to confirm the effect of the glossy paperboard according to the present invention, the following various samples were prepared, and a test for evaluating the quality of these samples 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 make a comparison with 20 types of multi-layer glossy paperboards (referred to as “Example 1” to “Example 20”) according to the present invention and these Examples 1 to 20, there are three types of glossy paperboards. Multi-layer paperboards and glossy paperboards having colored layers (referred to as “Comparative Example 1” to “Comparative Example 3”) were prepared as 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.
<Middle layer>
The raw pulp was adjusted using a double disc refiner so that the freeness (CSF) was 300 ml using 100% by weight of the waste paper pulp that had been cut from the coat, 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 the waste 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. Further, an acidic rosin sizing agent was used as a sizing agent, and 0.25% by mass was added.
Using the raw material pulp slurries of each of the surface layer, the middle layer, and the back layer, the surface pulp, the 3 layers of the middle layer, and the back layer of the raw material pulp slurry were combined with a circular mesh 5-layer paper machine, and the basis weight (rice basis weight) ) Was made from a colored paper board consisting of a base paper having a five-layer structure of 170 g / m ² .
<Resin adjustment>
First, Brighton (sample) manufactured by Sakata Inx Co., Ltd., which is an acrylic resin, was used as a glossy resin. This resin is applied to the surface of the base layer of the base paper, which is a colored layer, so that the coating amount is 3.6 g / m ² (dry) in solids at the coating part after the pre-dryer to form a coating layer Then, it was pressure-dried with a mirror-finished drier, and a glossy layer was formed on the surface of the base paper to obtain a glossy paperboard (Example 1).

  Further, Examples 2 to 20 and Comparative Examples 1 to 3 were produced in the same manner as in Example 1 except for the conditions shown in Table 1, and the evaluation of the present invention was performed. In addition, calcium stearate was used for the lubricant in this example. In Comparative Example 2, a multilayer paperboard having a colored layer commercially available from another company was used for evaluation.

  Evaluation of quality for all Examples and Comparative Examples, namely, glossiness of glossy paperboard (all layers), slip angle, cobb sizing degree, surface strength, smoothness, air permeability, printability, ruled cracks, and overall evaluation A test was conducted. The results are shown in Table 2. 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 is a 75-degree gloss meter (manufacturer: HORIBA, Ltd., model: the glossiness of the surface of the glossy paperboard of each sample according to JIS-P8142 (2005). It is the value measured by IG-320).

  “Slip angle (degree)” is a value obtained by measuring the slipperiness of glossy paperboard according to each sample in accordance with the slope method of the paper and paperboard friction coefficient test method of JIS-P8147 (1994).

“Cobb sizing degree (g / m ² )” is a value obtained by measuring the degree of water absorption of the glossy paperboard relating to each sample in accordance with the Cobb method of JIS-P8140 (1998).

  “Surface strength (A)” refers to the strength of the surface of the glossy paperboard of each sample according to JAPAN TAPPI No. This is a value measured in accordance with the surface strength test method using No. 1 wax.

  “Smoothness (seconds)” is a value obtained by measuring the smoothness of the glossy paperboard surface of each sample according to a smoothness test method using a Beck smoothness tester of JIS-8119 (1998).

  “Air permeability (seconds)” is a value obtained by measuring the ease of air flow of the glossy paperboard of each sample in accordance with the Gurley tester method of JIS-8117 (1998).

“Printability” means that each sample is subjected to gravure printing with a hand-coated coater having a gravure roll having 175 lines, and this printing state is evaluated visually visually. The evaluation criteria were as follows.
○: There is printability.
Δ: Printability is slightly inferior, but there is no practical problem.
X: Printability is not good.

Furthermore, the “rule crack” is a sensory measurement of the strength against breakage of glossy paperboard relating to each sample. As a measuring method, a bent portion is formed as shown in FIG. 1, and the bent portion is evaluated. That is, first, as shown in FIG. 1 (a), each sample was cut into a size of 200 mm in the width direction of the paper and 250 mm in the flow direction, and placed in a hot air dryer set at a drying temperature of 100 ° C. for 30 seconds. Take out after putting. Thereafter, as shown in FIG. 1 (b), the paper (the cut sample) is not folded, and the edges of the 200 mm wide are overlapped and pressed so that the surface of the paper becomes the front, while FIG. As shown in Fig. 1, an iron pipe having a diameter of 32 mm is placed at the end of the curved portion, and then the pipe is rolled and bent at a stroke as shown in Fig. 1 (d). The evaluation method is performed by evaluating the degree of peeling of the surface layer or the surface layer and the middle layer of the paper when the bent portion is viewed from the front.
○: Ruled lines do not break.
Δ: Some cracks occur, but there is no practical problem.
X: Ruled cracks occur.

Lastly, the glossiness of the base paper after coating, the quality as a corrugated board base paper and the processing suitability were comprehensively judged 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.

From Table 2, the multi-layered glossy paperboard having the colored layer according to the present invention, that is, the multi-layered glossy paperboard having the colored layer according to Examples 1 to 20, is obtained by applying a resin on the surface of the base paper on-machine. In addition, it can be seen that a high glossiness of 8% or more can be obtained, and that it is suitable for processing as a corrugated cardboard.

It is a figure which shows the evaluation procedure at the time of evaluating the rule crack of the multilayer papermaking glossy paperboard which has a colored layer which concerns on this invention.

Claims (3)

The base paper is composed of at least three layers of a surface layer, an intermediate layer, and a back layer, and at least a multilayer paper glossy paperboard having a coloring layer mixed with a colorant in the surface layer ,
While using any one or a combination of an anionic direct dye, a cationic direct dye, a basic dye for the colorant,
The value of the freeness of the raw material pulp used in each of the surface layer, the middle layer, and the back layer is set so 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, and ,
A resin layer is applied on the surface of the colored layer to provide a coating layer, and the coating layer is pressure-dried to form a gloss layer,
A multi-layer glossy paperboard, wherein the glossiness of the glossy layer is 8% or more. The resin is an acrylic resin having a glass transition temperature (Tg) of 40 to 60 ° C. and a viscosity of 13 to 105 mPa · s,
The resin is coated on the surface of the colored layer by 1.8 to 6.0 g / m ² (dry),
The multi-layer glossy sheet according to claim 1, wherein the base paper after the resin coating has a slip angle of 19 degrees or more and a cobb size of 15 to 50 g / m ² (120 sec cobb). Paperboard. The base paper after coating the resin has a surface strength of 14 A or more, a smoothness of 35 seconds or more, and an air permeability of 500 seconds or less, and has gravure printing suitability. Multilayer glossy paperboard as described.

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