JP2001140194A - Cast-coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bulky cast-coated paper which comprises a lightweight sheet having a high bulk, a low density, high rigidity, suitable for use as a paper container, or the like, can improve qualities as a cast-coated paper and productivity. SOLUTION: In this cast-coated paper obtained by coating a sheet with a coating composition consisting essentially of a pigment and an adhesive, bringing the sheet into contact with a heated drum surface under pressure and carrying out a glossy finish, the sheet has a multi-layer sheet formation structure, in which the number of sheet formation layers is three or more, and 90-600 g/m2 of the whole sheet weight, 0.50-0.75 g/cm3 of the whole sheet density, 15-100 g/cm3 of the outermost layer weight, 0.60-0.90 of the outermost layer density and 0.20-0.60 g/cm3 of the middle layer density are satisfied. The cast-coated paper comprises the sheet having <=1,500 second air permeability by a measurement based on Tappi paper pulp test method No.5. The cast-coated paper comprises the sheet having 0.6-1.5 g.cm interlaminar strength by a measurement based on Tappi paper pulp test method No.19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight cast-coated paper having a high level of smoothness, glossiness and printability. In more detail, the base paper is made bulky to reduce the density, voids are provided to increase the air permeability, the workability of the casting process is improved, and the adhesion with the mirror roll is increased,
The present invention relates to a cast-coated paper which has improved smoothness and specularity, and is thicker and more rigid than a sheet of the same rice tsubo by using a bulky base paper, thereby making it possible to reduce the weight as a result.

[0002]

2. Description of the Related Art Cast-coated paper is positioned as the finest coated printing paper with high smoothness and gloss.
It is used for multicolor art printing, magazine covers, record jackets, match boxes, etc. In addition to these printing applications,
It is also widely used for packaging such as high-end handbags, boxes for cosmetics, accessories, and confectionery, and is given quality suitable for each use. In particular, when used for magazines and packaging, there is a demand for not only sufficient paper strength but also a reduction in the weight of the sheet as with general paper. However, for cast-coated paper, a general paper or paperboard or a sheet with an undercoat layer on its surface is coated with a cast coat paint or wetting agent, and the wet coating layer is pressed against a heated mirror roll. It is manufactured by transferring the smoothness of the metal surface of the mirror roll and imparting high smoothness and gloss.
Coating amount is 15 to 15 per side to give high smoothness and surface properties
It was relatively large at 30 g / m ^2, and the amount of coating increased as the basis weight of the base paper increased as in the case of ordinary coated paper. Therefore, it was difficult to reduce the weight.

[0003] In addition, in the case of packaging paper box, the weight is 200 g.
/ M ² or more, the strength as a paper box is established, but when the weight of the base paper is increased, when the casting treatment is performed by pressing with a heating mirror surface, the moisture of the coating liquid penetrates the paper layer after steaming by heating. Not only reduces productivity, but also
There was a problem that the smoothness of the back surface was significantly reduced. Therefore, there have been proposals for improving the drying efficiency by improving the air permeability of the base paper so as to improve the drying efficiency (for example, Japanese Patent Application Laid-Open No. 56-26094).
However, in these methods, the coating amount is as large as 10 to 30 g / m ² , the amount of water to be evaporated is large, and the rice tsubo for the paper box is high, for example, 200 g. / M ² or more sheets have no means to increase rigidity, so resource saving and reduction of dust are considered important at present. Thus, the desired weight reduction cannot be achieved, and the rigidity is maintained, the weight is reduced, and the base paper cannot be efficiently cast.
Therefore, there has been a need for base paper that achieves both cast quality and productivity. Conventionally, base paper having a density of about 0.7 g / cm ³ and a basis weight of 60 g / m ² or more has been used. However, if a base paper having this density is used to reduce the weight, there are the following problems. For example, the base paper basis weight is changed from 100 g / m ² to 40 g / m ² ,
When the coating amount of the undercoat layer is 10 g / m ² and the coating amount of the cast coat layer is 25 g / m ² , the obtained cast coated paper becomes 75 g / m ² , which is about 40% lighter. However, when the basis weight is reduced using the current base paper, the stiffness is reduced and the thickness is reduced, so that there is a problem in that operability such as strikethrough or paper jam occurs when printing is performed. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lightweight sheet which is bulky and low in density, has high rigidity and is suitable for use in paper containers, etc., and further improves the quality and productivity as cast paper. An object of the present invention is to provide a bulky cast-coated paper capable of performing the following.

[0005]

SUMMARY OF THE INVENTION The present invention uses bulk laminated paperboard and optimizes the density of each layer of those sheets to create a bulky structure and maintain stiffness. In order to further improve the air permeability and reduce the weight of the cast-coated paper, and also enhance the mirror feeling and smoothness, and improve the productivity, the following configuration is specifically adopted. 1. In a cast coated paper in which a coating composition containing a pigment and an adhesive as a main component is coated on a sheet and pressed against a heating drum surface to give a glossy finish, the sheet has a multi-layered assembling structure. When the number is three or more, the basis weight of the entire sheet is 90 to 600 g / m ² , and the density is 0.50 to 0.5 g / m ² .
75 g / cm ³ and the basis weight of the outermost layer is 15 to 100 g
/ M ² , a density of 0.60 to 0.90 g / cm ³ , and a density of the middle layer of 0.20 to 0.60 g / cm ³ . 2. The air permeability of the sheet used for the cast coated paper is determined according to J Tappi Paper Pulp Test Method No. The air permeability measured in accordance with No. 5 is 1500 seconds or less. The cast coated paper as described. 3. The sheet used for cast-coated paper is J Tap
pi paper pulp test method no. Wherein the interlayer strength measured at 19 is 0.6 to 1.5 g · cm.
3. The cast-coated paper according to item 1.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cast coated paper which is coated on a sheet with a coating composition for coated paper containing a pigment and an adhesive as a main component and pressed against a heated drum surface to give a glossy finish. , To express the rigidity of the seat and reduce the weight,
The following methods are used to improve the productivity and quality during the casting process. That is, the sheet is obtained by drying a multi-layer sheet made from a plurality of wire parts of a paper machine, and the number of layers is three or more,
The basis weight is 90 to 600 g / m ² , and the density of the entire finished paperboard is 0.5 to 0.75 g / cm ³ . In order to obtain a sheet for cast coated paper having a high bulk and a high rigidity at such a density, the density of the middle layer is as low as 0.2 to 0.6 g / cm ³ , And the density of the paper layer formed as an outer layer in contact with the middle layer is set to 0.6 to 0.
A sheet having high rigidity by forming a sandwich structure while complementing the lowering of the Young's modulus of the low density layer formed in the middle layer by forming it as high as 9 g / cm ³ by adding an outer high density layer. Can be obtained.

The outer layer shown in these sandwich structures is a layer located outside the middle layer and is a layer which is substantially in contact with the middle layer or is located outside through another layer, and the outermost layer Refers to the layer present in the These sandwich structures need only be configured to complement the lower density middle layer with a higher density outer layer, ie, all layers except the lower density middle layer are outer layers.

[0008] When the stiffness S of the sheet considering the sheet and the cantilever, S = E · I / B · W = E · T 3/12 · W,
(E: Young's modulus MPa, I: Second moment of area N · c
m ² , B: sample width mm, W: sample mass kg, T: sample thickness mm), and stiffness S is 3 of Young's modulus and sheet thickness.
It can be considered proportional to the power.

Further, the stiffness of a sheet having a laminated structure such as a paperboard is described in Tappi Nov, 1963, Vol. 46,
No. 11A. T. According to Luey, similarly, the stiffness value of each layer is obtained from the Young's modulus of each layer and the moment of inertia of each layer using the above-described formula, and the stiffness value of all layers is obtained by the sum of the stiffness values of each layer. I have. Based on this concept, the stiffness increases as the distance from the center of the paper thickness increases, that is, as the paper thickness increases, so that the middle layer may be made bulky. Also, since the stiffness is represented by the product of the cube of the thickness and the Young's modulus, the higher the Young's modulus of the outer layer, the more effective the stiffness is.

[0010] From this, the density of the middle layer is 0.2-0.
It is necessary to be 6 g / cm ³ . 0.2 g / cm ³
If it is less than 0.6 g, the interlaminar strength described below will be drastically reduced. If it exceeds 0.6 g / cm ³ , the desired final bulky paperboard density cannot be obtained. More preferably, the density of the middle layer is 0.3 to 0.5 g / cm ³ . The density of the paper layer formed on the outer layer is 0.6 to 0.9 g / cm ³ . If it is less than 0.6 g / cm ³ , the Young's modulus is reduced, and improvement in rigidity cannot be expected. On the other hand, a higher density of the outer layer is better in terms of improving Young's modulus, but at present it is practically difficult to obtain a density exceeding 0.9 g / cm ³ at the papermaking stage.

As described above, in order to improve the rigidity, it is preferable to form an outer layer on any side of the middle layer and further increase the Young's modulus of the outer layer. However, only one surface of the outer layer has a higher density and a higher Young's modulus. A method is also possible in which an outer layer is provided and the density of the outer layer alone is prevented from increasing by increasing the density of the outer layer. According to this method, the operability can be improved while the rigidity and the Young's modulus are balanced without increasing the density and the Young's modulus on the other surface and without reducing the overall thickness. However, the degree of improvement in rigidity of each outer layer is smaller than when the density and Young's modulus are increased.

Further, as a concept for improving the productivity and quality at the time of the casting treatment, it is necessary to set the air permeability, which is a characteristic value of air permeability, to a specific numerical range.
That is, in the cast coating method, since the wet coating layer is pressed against the mirror-finished metal surface and dried, the moisture in the coating layer needs to pass through the base paper layer and escape to the opposite side. In order to improve the drying efficiency, the air permeability of the base paper sheet may be improved. However, as described above, the air permeability that can be achieved at a low rice tsubo is, for example, 200 g /
m ² or more, the air permeability is remarkably deteriorated. Therefore, the air permeability of the sheet used for the cast coated paper is determined by J Tappi.
Paper pulp test method No. Air permeability measured according to 5 is 1
Set to 500 seconds or less. That is, in the cast coating method, since it is necessary to dry the wet coating layer while pressing the wet coating layer on the mirror-finished metal surface, the moisture in the coating layer must pass through the base paper layer to the opposite side and evaporate. Must. Therefore,
If the time exceeds 1500 seconds, the air permeability is poor and the drying efficiency is extremely poor, so that it is necessary to produce at a low speed, and the productivity is poor. However, it is not enough to simply improve the air permeability. That is, if good air permeability is maintained and the smoothness as the coated base paper and the interlayer strength of the base paper are not maintained, the mirror feeling, smoothness, and gloss as cast paper are inferior. Further, when the interlayer strength is low, a part of the coating layer is removed on the mirror-finished metal surface during production, or peeling occurs between layers of the paper layer, or a so-called drum pick occurs. In order to suppress these problems, the productivity of cast coated paper must be reduced. Therefore, as a result of intensive examination,
If the base sheet is made into a multilayer paper and the density of each layer is controlled by blending pulp and differentiated into functions, and if air permeability, smoothness and interlayer strength are compatible, high smoothness, glossiness and printability are provided. Thus, the workability of the casting process can be improved. In this method, as described above, the sheet is configured as a laminate having a multilayer structure.

There are no particular restrictions on the pulp used to increase the density used for the outer layer, and any type of pulp may be selected. However, N-wood (coniferous) pulp such as NUKP or NBKP has a high degree of beating. In order not to lose the rigidity and to improve the productivity of the cast paper described above, in order to reduce the air permeability, which is a characteristic value of air permeability, to 1500 seconds or less, the basis weight of the outermost layer is 15 to 100 g. / M ² . That is, if it is less than 15 g / m ² , papermaking cannot be performed, or even if it can be performed, the effect of expressing a high Young's modulus is small.
On the other hand, if it exceeds 100 g / m ² , the basis weight of the middle layer is relatively reduced, a bulky structure is hardly formed, and the ventilation performance is deteriorated due to the large number of dense layers.

As a method for producing paperboard, generally, several tens g / m 2 are provided on a plurality of wire parts of about 10 stations.
^The pulp slurry corresponding to the dried rice tsubo of No. ² is developed to form a wet sheet. For example, first, a pulp layer of about 40 g / m ² is formed on the wire part forming the outer layer located at the outermost layer, dehydrated, and then transferred to a blanket. Next, a paper layer is similarly formed with another wire part for the middle layer, and the outermost layer on a blanket is overlapped to form two layers. Repeat the method of superimposing these two layers on the paper layer formed by another wire part, and finally form the other outermost layer,
A multilayer paperboard of about 10 layers in total is obtained.

On the wire part, the concentration of the pulp slurry is initially about 0.5% by mass, but is dehydrated on the wire to rise to a concentration of about 10% by mass to form a wet sheet. The wet sheet is taken with a blanket and the wet sheet formed by the next wire part is overlaid.
Such a process is repeated a plurality of times, and the integrated wet sheet is introduced into the press part and roughly dewatered by a plurality of press rolls. In the case of a multi-layer laminated paper, the paper is laminated in a wet paper state in order to efficiently increase the interlayer strength.

The coating layer is re-wetted during the casting process, but the air permeability as the airflow resistance when the moisture of the coating layer passes through the base paper layer is coated. It should be grasped as the numerical value as the previous base paper layer. Report by the Printing Bureau, 1970, by Eiichi Masaki, No. 2, 37
As described above, the coating layer has a capillary radius one order of magnitude smaller than that of the base paper layer, and the probability density value of the voids is about 1/3 that of the paper-only sheet. Therefore, in the presence of the coating layer, the characteristic value of each paper sheet cannot be grasped. Therefore, in advance, such as wet cast method, gel cast method,
If the coating process is performed while coating the coated base paper with the paint after drying it on the cast drum surface, the air permeability properties of the base paper before coating can be grasped, but after the coating, the paint is once dried. When the base paper before paper coating cannot be obtained as in the rewet casting method in which the coating layer is re-wet plasticized after the coating, the coating layer on the coated paper before the casting treatment is peeled off, Need to measure temper.

The multilayer laminated sheet sample was prepared according to JIS-P-8.
139. The interlayer between the front layer including the coating layer and the middle layer is measured by a delamination method based on the peel strength test method of the laminated layer of the paperboard described in 139. When peeling of each layer is difficult, the multilayer laminated sheet sample is immersed in warm water of 60 ° C. for 1 hour and then peeled off. The remaining base paper layer from which the coating layer was peeled off was sandwiched by a drying frame used for hand-made sheet drying, dried in a dryer at 100 ° C., and conditioned at 65% RH and 20 ° C., and then J Tappi paper pulp test Method No. Measure with an Oken type air permeability meter according to 5. The air permeability at this time is 15
If it is within 00 seconds, the air permeability of the sheet before coating is 1500
It can be estimated that it was less than seconds. If the air permeability exceeds 1500 seconds according to these measurement methods, characteristics with poor air permeability can be grasped before casting. The occurrence of the swelling state and the phenomenon of increased density during the casting process can be grasped by the management after the paper making before the casting process. On the other hand, besides these measures, to control density increase and delamination, if the pulp freeness is controlled within a certain range, high smoothness, glossiness and printability are maintained while maintaining air permeability. It is also possible to improve the workability of the casting process.

The cast-coated paper of the present invention may be basically composed of a low-density middle layer and a high-density outer layer. However, depending on the intended use, a coating layer is formed on one or both of the outer layers. Good printability can be obtained. Pigments used in the coating layer include calcium carbonate, kaolin clay, talc, titanium oxide, plastic pigment and the like, and known binders such as SBR latex, starch, casein and poval can be used. The coating amount is about ²⁰ to 30 g / m ^{2 as a} whole, and these can be formed as a single layer or two layers. This coating layer can be formed directly on the pulp layer that constitutes the middle layer.However, the obtained smoothness is often low and the printability is poor. It forms a layer. Further, it is preferable that the outer layer with respect to the middle layer immediately below these coating layers be a smoothed paper layer by increasing the degree of refining, but in this case, the other outer layer has a reduced basis weight to improve air permeability. It is necessary to design to further reduce the air permeability value.

The pulp freeness of the outer layer is determined as follows: the freeness of the pulp slurry which has been exfoliated without applying a load after removing the outer layer after the production as a paperboard is 350 to 750 mlcs.
It is preferably f. 350ml as freeness
If it is less than csf, the density as the outer layer can be easily obtained, but the air permeability of the base paper as a whole exceeds 1500 seconds, and the air permeability is inferior. In order to avoid this, it is necessary to take measures such as extremely lowering the manufacturing speed, which is not practical.
On the other hand, if it exceeds 750 mlcsf, the air permeability can be reduced, but the obtained rigidity and surface smoothness are reduced.

The pulp used for the middle layer is made of mercerized pulp or pulp obtained by subjecting finished pulp such as curled fiber to a chemical treatment so as to exhibit its low density, and pulp such as TMP and CTMP. Mechanical pulp, partially mechanically treated mechanical pulp, or pulp having a number average pulp fiber length of 1.0 mm or less and a fraction of 9.0 mass% or less, but mercerized pulp and curled fiber are expensive. It is not preferable to use a large amount because of the presence or limited supply amount, and mechanical pulp is most preferable. Further, mechanical pulp is generally obtained by simply crushing N material by mechanical force and then disintegrating it.
There are MP, RGP and the like, but TMP is preferable. Among them, those obtained from wood such as radiata pine, southern pine, Douglas fir, when the fiber is rigid and hard to deform and forms a paper layer, the tendency to become low density is remarkable, and the density decrease during pressing is small, Particularly preferred. The present invention also includes a method of adding a chemical during mechanical crushing and a pulp that undergoes a step of bleaching after pulping.

Further, as another object of the present invention, there is a problem of interlayer strength. In general, when the above mechanical pulp is used, the required interlayer strength measured by an internal bond tester is 0.6 to 1.5 kg-cm, more preferably about 0.7 to 0.9 kg-cm. If it is less than 0.6, when it is used as a paper container, it causes delamination in the middle layer during printing, especially when printing solid with printing ink with strong tack, causing partial swelling or passing through a box making machine at high speed When the sheets are stacked, they may be peeled from the edge of the paper container as a starting point, which is not preferable. 1.5kg-c
If it exceeds m, the strength is sufficient, but the Young's modulus becomes extremely high, which may make it difficult to break the creases and wind it into a roll.

In order to increase the interlaminar strength of the paperboard to be made into a multilayer paper, a method of spraying a dispersed aqueous solution of starch particles between the respective layers to form particles, and heating the mixture with the moisture contained in the drying zone to gelatinize the paperboard. is there. In the present invention, since the interlayer strength of the middle low-density layer in particular tends to decrease, it is preferable to use starch having a gelatinization temperature of 45 to 70 ° C. If the gelatinization temperature is lower than 45 ° C., the temperature of the dispersion rises in summer, and the starch dispersion itself is gelatinized, which is not preferable. If the temperature exceeds 70 ° C., the starch particles remaining in the paper are not gelatinized completely and remain as the particles, so that it is not possible to contribute to the improvement of the interlayer strength.

Further, for the middle layer, the above-mentioned material mainly composed of mechanical pulp should be used. However, the density can be arbitrarily adjusted by blending general-purpose magazine waste paper or newspaper waste paper to use the mechanical pulp. The balance between cost and density obtained by reducing the amount can be set arbitrarily. When blending waste paper, the lower the density, the better the use of rigid pulp. The Runkel ratio of the pulp species used is particularly preferably 1.2 or more. The Runkel ratio is a value obtained by dividing the diameter of the fiber by the thickness of the seed coat, and the larger the Runkel ratio, the harder and thicker the lower-density middle layer can be formed.

If necessary, a filler for general papermaking, a sizing agent, a retention improver, a paper strength enhancer, and the like can be added to the stock as long as the quality of the bulky paperboard of the present invention is not impaired. . The pH of the paper machine can be in the range from about 4.5 for acidic paper to about 6 to 8 for neutral paper. In addition, coating can be performed by installing various coaters. What is sprayed on the surface or in the middle of paper or what is added by filling is polyvinyl alcohol, latex, alkyl ketene dimer system, maleic anhydride system, styrene acrylic acid system, styrene acrylic system, etc. various sizing agents, pigments, dyes Can be applied or impregnated. Generally, the paper machine may be any machine that can make a multi-layer, and a paper machine such as a circular net multi-layer or a long net multi-layer can be used as appropriate.

The cast coat paper of the present invention has a rice tsubo of from 90 to
600 g / m ² , 150 to 450 g for general use
/ M is ² about the cast coated paper, a cast-coated paper that can reduce even basis weight 100 g / m ² or more by increasing the rigidity.

Since this sheet is reduced in density and made bulky, it can be made thicker with the same weight as the conventional sheet, the rigidity is improved, and a strong paper box can be manufactured. Further, in the case of a sheet having the same thickness as a conventional sheet, the weight can be reduced due to the lower density, so that a lighter cast coated paper can be manufactured.

Although the internal additives used in the present invention are not particularly limited, various commonly used anionic, nonionic, cationic or amphoteric retention improvers, paper strength enhancers, size enhancers, etc. An agent or the like is appropriately selected and used.

Specifically, examples of paper strength enhancers and retention aids include polyacrylamide-based cationic, nonionic, anionic and amphoteric resins, polyethyleneimine and its derivatives, polyethylene oxide, polyamine, polyamide and polyamide. Polyamine and its derivatives, cationic and amphoteric starch, oxidized starch, carboxymethylated starch, vegetable gum, polyvinyl alcohol, urea-formaldehyde resin, melamine formalin resin, organic compounds such as hydrophilic polymer particles, and sulfate band, alumina sol, Aluminum compounds such as basic aluminum sulfate, basic aluminum chloride and basic polyaluminum hydroxide, as well as inorganic compounds such as ferrous sulfate, ferric chloride or colloidal silica, bentonite and the like are used in appropriate combinations. To.

As the sizing agent, various sizes such as a rosin sizing agent, a petroleum resin sizing agent as an acid paper sizing agent, an alkyl ketene dimer sizing agent, and an alkenyl succinic anhydride sizing agent as a neutral paper sizing agent. Agents can be mentioned. And, in the pulp slurry mixed with the expandable particles, generally known fillers, such as talc, kaolin, calcined kaolin, clay, diatomaceous earth, heavy calcium carbonate, magnesium carbonate, aluminum hydroxide, titanium dioxide, magnesium sulfate, Mineral fillers such as silica, aluminosilicate and bentonite, and organic synthetic fillers such as polystyrene particles and urea formalin resin particles can be appropriately selected and used in combination. In addition, papermaking additive aids such as dyes, pH adjusters, slime control agents, defoamers, and tackifiers can be used as appropriate depending on the application. It is also possible to apply starch, polyvinyl alcohol, various surface sizing agents, pigments and the like to the surface of the sheet by a coating method such as a size press or a gate roll.

The above constituent raw materials are used as main raw materials, and are formed into sheets by a normal paper making machine. First, after forming into a sheet through the wire part of the paper making process, dewatering is performed by the press part, and drying treatment is performed by the dryer part. It is also possible to raise.

Undercoat paints consist of mineral pigments, adhesives and auxiliaries. Pigments include kaolin, heavy calcium carbonate, and limestone clay in natural products, and light calcium carbonate, titanium oxide, aluminum hydroxide,
There are plastic pigments and the like. The adhesives are mainly water-soluble polymers such as various modified starch, casein, carboxymethylcellulose (CMC), various proteins, polyvinyl alcohol, styrene-butadiene copolymer latex (SBR), metal methacrylate-butadiene copolymer latex And the like. Other examples include a dispersant, a waterproofing agent, a water retention agent dye, and the like, and these are mixed and dispersed to form a paint.

The coating amount of the undercoat paint is preferably about 5 to 20 g / m ^{2 in a} dry state. In order to further improve the smoothness, a calender treatment may be performed after the undercoat agent is applied.
The treatment is preferably performed in a range of 0 kg / cm. Cast coat paint mainly consists of mineral pigments and adhesives,
In addition, a coagulant, a release agent, a dye, etc. are added, dispersed and mixed. The same pigments and adhesives as those used for the undercoat paint described above can be used. Examples of the release agent include insoluble or soluble soaps such as magnesium oleate and ammonium stearate, animal and vegetable oils and fats, synthetic resin emulsions, alkyl ketene dimers, and alkyl phosphates.

In addition, as the coagulant, any coagulant that solidifies the adhesive component in the coating film, such as organic acids such as formic acid, crotonic acid, itaconic acid and acrylic acid, and electrolytes such as calcium formate and calcium chloride, may be used. Can be. The coating amount (dry state) of this cast coat paint is 15 to 30 g / m.
It is appropriately selected in the range of ² and applied to base paper by various coating methods. That is, a direct method or a semi-direct method in which the paint is directly or slightly dried while the paint is still in a wet state, and then dried by pressing against the mirror surface of a heated cast drum, or an aqueous solution having a coagulating action after coating. (Coating method by contacting the coating film with an aqueous solution of an acid or an electrolyte, gelling, pressing and drying on a cast drum, drying once after coating, finishing if necessary, and applying water or a wetting agent, etc.) A rewet method or the like in which an aqueous solution is applied to swell the surface of the coating film and then pressed against a cast drum.

Also, cast-coated paper is often dried excessively, and may be significantly curled by absorbing moisture in the atmosphere after the coating treatment. Therefore, usually, the back surface is coated with water or subjected to a humidifying treatment. Action is taken. Further, depending on the application, there is also a back surface having the same coating as a general coated paper.

[0035]

The present invention will be described in detail with reference to the following Examples, but it should be understood that the present invention is not limited by these Examples. In the following, the amount, concentration,
The numerical values indicating the application amount and the like are solid contents or numerical values based on the mass of the active ingredient. Example 1 The following three types of pulp were beaten using a pulp beater manufactured by Kumagaya Riki Kogyo at a wire speed of 300 m / min using an oriented paper machine manufactured by Kumagaya Riki Kogyo Co., Ltd. And then combine them. At the time of mixing, the starch ONL510 of Oji cornstarch was sprayed onto the front side (felt side) of each layer with a starch concentration of 2.0% by spray spraying so that the solid component adhesion amount was 1.0 g / m ² . Combine. Commercially available NBKP, 45
0mlcsf, 40g / m ^2, Radiata pine TM
P350mlcsf, 170g / m ² , commercially available NBKP
450mlcsf, 40g / m ^2. Furthermore, the nip pressure is controlled to 10 kg by controlling the air pressure of the calender of the Yuri roll machine.
/ Cm, and a wet paper-like sheet made at a speed of 30 m / min is sandwiched between monoplastic canvas sheets made by Shikishima Canvas and subjected to pressure treatment. Thereafter, drying is performed using a ferro-type cylindrical heating dryer type dryer.
Further, after that, the humidity is controlled at 20 ° C. and 65% RH, and the nip pressure is set to 20 kg / cm by a calender of a Yuri roll machine and calendered at a speed of 20 m / min to obtain a base paper sheet before coating. After that, at 20 ° C and 65% RH
And measure the basis weight, thickness, density and Z strength.

The coated base paper sheet was undercoated with an undercoat paint. That is, 80 parts of calcium carbonate, 11 parts of modified starch, and 0.5 part of dispersant (Aron T6330)
Toa Gosei Chemical Co., Ltd.) and 0.2 parts of an antifoaming agent (manufactured by Formaster AP San Nopco) were mixed and stirred by a Cowles disperser, and 8 parts of styrene-butadiene copolymer latex was added thereto.
0.08 parts of a wetting agent was added thereto, and the mixture was sufficiently stirred, and an undercoat paint adjusted to a solid content of 40% was applied at a rate of 15 g / m ² by a metaling bar method. afterwards,
Super calendering was performed at a linear pressure of 50 kgf / cm. Further, 75 parts of a coating clay (manufactured by Ansilex 93EMC), 20 parts of calcium carbonate (Softon 2200, manufactured by Shiraishi Calcium Co.), 5 parts of titanium dioxide (W-10, manufactured by Ishihara Sangyo Co., Ltd.), and 0.1 part of sodium pyrophosphate. 5 parts are mixed and stirred in a kneader with 35 parts of water to form a slurry. Separately dissolved 15% casein solution (60 ± 1 ° C. in the presence of 1.5% caustic soda based on pure casein)
13 parts (as solid content) were added to the above slurry, and 17 parts (as solid content) of styrene / butadiene copolymer latex were mixed and sufficiently stirred. .25 parts were added to adjust the final solid content of the paint to 40%. The viscosity of this paint is 900 mPa · s (Brookfield viscometer 60 rpm, 20 ° C.)
Was 7.2. This coating material is applied to a base paper coated with the above-mentioned undercoat agent by a metaling bar method so as to have a dry weight of 25 g / m ² , and then the solid content concentration of the coating film is reduced to 52% by an infrared preheater. Then, it was brought into contact with a 0.5% formic acid aqueous solution, pressure-bonded to the surface of a cast drum whose surface temperature was kept at 110 ° C. by an internal heating method, and dried in a state of close contact. The water content of the obtained coated paper was 4%.

Example 2 The composition of the base paper was commercially available NBKP, 450 mlcsf, 40
g / m ² , 650 mlc of curled fiber (CF)
sf, 130 g / m ² , commercially available NBKP 450 mlcs
f, and a cast coat process was performed under the same conditions as in Example 1 except that the amount was 30 g / m ² .

Example 3 The base paper was blended with commercially available NBKP, 450 mlcsf, 40
g / m ² , 550 mlcs of mercerized pulp (MP)
f, 130 g / m ² , 450 mLcs of commercial NBKP
f, and a cast coat process was performed under the same conditions as in Example 1 except that the amount was 30 g / m ² .

Comparative Example 1 The composition of the base paper was as follows: commercial NBKP, 450 mlcsf / commercial LBKP, 400 mlcsf = 50/50.
The basis weight is 200 g / m ² as a single-layer paper without mixing.
The cast coating was performed under the same conditions as in Example 1 except for the above.

Comparative Example 2 The base paper was blended with commercially available NBKP, 450 ml csf / commercial LBKP, 400 ml csf = 20/80. The single-layer paper was not blended. The basis weight was 200 g / m ^2. Obtain coated base paper without performing. Other conditions were the same as in Example 1, and the cast coating was performed.

Comparative Example 3 The composition of the base paper was as follows: commercial NBKP, 450 mlcsf / commercial LBKP, 400 mlcsf = 50/50.
The basis weight is 400 g / m ² as a single-layer paper without mixing.
The cast coating was performed under the same conditions as in Example 1 except for the above.

Table 1 shows the paper quality of Examples 1 to 3 and Comparative Examples 1 to 3. The measurement method for each paper quality evaluation was as follows. 1. Base paper air permeability (before application): J Tappi paper pulp test method No. According to No. 5, the measurement was carried out using an Oken-type smooth air permeability measuring device manufactured by Asahi Seiko Co., Ltd. 2. Base paper air permeability (after coating layer peeling): Coating paper before coating and after coating with a paint is applied by the delamination method according to the peel strength test method of the lamination layer of paperboard described in JIS-P-8139. The peeling between the front layer including the layer and the middle layer is measured.
The multilayer assembling sheet sample is immersed in warm water at 60 ° C. for 1 hour and then peeled off. The remaining base paper layer from which the coating layer has been peeled off is sandwiched between the drying frames used for drying the handmade sheet, and
Dry in a dryer at 0 ° C., and further dry at 65% RH at 20 ° C.
And the humidity was adjusted with J Tappi paper pulp test method No. 5
Measure with an Oken-type air permeability meter according to. 3. Stiffness (Taber stiffness): Using a Taber stiffness tester manufactured by Kumagai Riki Kogyo Co., Ltd., the stiffness in the CD and fiber directions was JIS-
Measured by P-8125. 4. Oken Smoothness: A sample conditioned after casting was measured for smoothness using an Oken-type smooth air permeability measurement device manufactured by Asahi Seiko. As the measured value, a value after a measurement time of 20 seconds was adopted. 5. Gloss: Measured using a gloss meter from Murakami Color Research Laboratory at an angle of 75 degrees according to JIS-P-8142.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

The cast-coated paper manufactured by the above-described method uses a bulky and low-density base paper,
Lighter weight and increased stiffness increase the range of use for general paper boxes, as well as improved air-permeability to improve wetness and dryness of the coated surface during casting, resulting in mirror-like, smooth, and workable surfaces. And a cast-coated paper having good sheet productivity and an increased sheet-like productivity can be obtained.

Claims (3)

[Claims] 1. A cast-coated paper which is coated with a coating composition containing a pigment and an adhesive as a main component on a sheet, and is pressed against a heating drum surface to give a glossy finish. The number of layers is 3 or more, the basis weight of the entire sheet is 90 to 600 g / m ² , and the density is 0.
50 to 0.75 g / cm ³ , and the basis weight of the outermost layer is 15
１００100 g / m ² , the density of which is 0.60 to 0.90 g / m ²
cm ^3, and the density of the middle layer is 0.20~0.60g / c
cast-coated paper, which is a m ^3. 2. The air permeability of the sheet used for the cast coated paper is determined according to J Tappi paper pulp test method No. 2. 5
The cast-coated paper according to claim 1, wherein the air permeability measured according to (1) is 1500 seconds or less. 3. The sheet used for the cast coated paper is J Tappi paper pulp test method No. 2. The cast coated paper according to claim 1, wherein the interlayer strength measured in step 19 is 0.6 to 1.5 g · cm.