JPH10168792A - Cast coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cast-coated paper excellent in white paper luster, surface smoothness and blister resistance suitability. SOLUTION: This cast-coated paper is obtained by providing at least one side of a base paper with an undercoating layer consisting essentially of a pigment and an adhesive, coating the undercoated layer with an aqueous coating composition for casting, bringing the coated paper into contact with a heating drum face having a mirror surface under pressure while the aqueous coating composition is in a wet state, drying and finishing the paper. Especially the maximum peak of pore diameter exists between pores of 0.15 and 0.40μm in a pore diameter distribution curve of the cast-coated paper (coated layer) by mercury intrusion method and the cast-coated paper has high luster of >=5cc/m<2> pore volume having <=0.5μm pore diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast coated paper, and more particularly to a cast coated paper having excellent white paper gloss, surface smoothness and blister resistance.

[0002]

2. Description of the Related Art In recent years, prints as media for publishing, public announcements, advertisements and the like have become more sophisticated such as visualization and colorization. Along with this, the demand for coated paper for printing is rapidly increasing, and the demand for coated paper quality such as high smoothness and high print gloss is also increasing.

[0003] Among the coated papers, cast coated papers are typical of coated papers having high gloss and high smoothness, and their applications are from the text paper of general books to covers, book covers, cosmetics. And the like, calendar paper, tack labels, and the like.

However, in recent years, with the upscaling of printed matter, paper containers, fashion bags, and the like, a transparent resin is added to ordinary coated paper or cast coated paper for the purpose of adding higher gloss, shine or smoothness. Varnished paper applied by printing etc., more resin is applied to the paper surface,
Gloss-finished press-coated paper and laminated paper having a plastic film such as polyethylene adhered to the surface are widely used.

By the way, varnished paper, press-coated paper,
Alternatively, laminated paper or the like cannot be printed thereon with a general printing ink. Therefore, it is usually disadvantageous in terms of process and cost, for example, it is necessary to print in advance and then apply varnishing or laminating to give a sense of quality, as well as being processed as described above. High gloss paper is difficult to recycle and disintegrate as used paper, and has difficulty in recycling.

In view of such a situation, cast coated paper having the same quality (high gloss and high smoothness) as those of varnishing and laminated paper, that is, more excellent than the current cast coated paper. There is a strong demand for the development of cast coated paper having both white gloss and printability.

[0007] It is possible to improve the glossiness of the blank and the print gloss of the cast coated paper to some extent by increasing the amount of the adhesive in the aqueous coating composition. The fact is that it has not been improved. On the other hand, as a method for improving white paper gloss or print gloss, there is a method in which a high-smooth undercoating base paper is cast-finished using a coating liquid containing a specific synthetic resin as a main component (Japanese Patent Application Laid-Open No. Hei 5
No. 33298) has been proposed.

According to this method, although a high gloss is obtained, the releasability is poor, and if the releasability of the resin is improved, there is a problem that the visual smoothness (bumpiness) of the cast paper surface deteriorates. In addition, especially for cast paper coated on the back side or double-sided cast paper that has been subjected to casting on both sides, increasing the gloss reduces the air permeability of the coating layer. There is a problem in that the moisture inside the paper hardly escapes to the outside as water vapor, and as a result, a blistering phenomenon known as a so-called blister is induced.

Therefore, in order to increase the force for suppressing the blister (herein, referred to as blister resistance), generally, the air permeability of the coating layer is increased, and the moisture in the base paper is quickly escaping to the outside as water vapor. The method is taken. However,
In order to increase the air permeability of the coating layer, it is necessary to finish the coating layer with many pores on the surface of the coating layer, and as a result, it is very difficult to achieve a high glossiness comparable to that of press-coated paper or laminated paper. It is actually difficult.

[0010]

From the above, the present inventors have intensively studied to obtain a high quality cast coated paper which is clearly improved over the conventional products. As a result, the present invention makes the undercoat coating layer porous and specifies the pore distribution state of the cast coating layer surface after providing the overcoat coating layer (cast coating layer). An object of the present invention is to provide a cast-coated paper that exhibits gloss and high smoothness and has excellent blister resistance and excellent printability. In particular, by incorporating a synthetic resin polymer composition into the overcoat layer, a high-quality cast coated paper having a high balance of high gloss and blister resistance is provided.

[0011]

According to the present invention, there is provided an aqueous coating composition for casting, comprising, on at least one side of a base paper, an undercoating layer containing a pigment and an adhesive as a main component. , And while the aqueous coating composition is in a wet state, pressed against a heated drum surface having a mirror surface and dried to finish the cast coated paper (coated layer).
0.15 in the pore distribution curve of mercury intrusion method
The maximum peak of the pore diameter is present between pores of 0.40 μm, and the volume of pores having a pore diameter of 0.5 μm or less is 5 cc / pore.
It is a cast coated paper having a high gloss, characterized by having a m ² or more.

In particular, as the pigment for the undercoat layer, light calcium carbonate having an average particle size of 0.5 to 2 μm is contained in an amount of 30% by weight or more based on all the pigments in the undercoat layer, and the overcoat layer is formed. A cast coated paper, characterized in that the cast aqueous coating composition contains a synthetic resin polymer composition in an amount of 50% by weight or more based on the total solid content of the cast aqueous coating composition.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in order to improve blister resistance, a coated layer having good air permeability is finished so that water vapor in a paper layer generated by heating and drying during offset rotary printing can be quickly removed. A method of dissipating outside is known. By the way, in the present invention, the purpose is not only to improve the blister resistance, but also to further improve the surface gloss. In particular, the glossiness at 20 degrees in accordance with TAPPI T-653 pm-90 is as high as 60% or more. It is an object of the present invention to provide a high quality cast coated paper having both gloss and excellent blister resistance.

In particular, in order to impart high gloss, according to the conventional formulation, the surface of the cast coating layer is covered with a film-forming binder, and the air permeability is reduced, and the blister resistance is deteriorated. There is. To improve that point,
The present inventors have conducted intensive studies focusing on the pore structure inside the coating layer. As a result, it was found that by increasing the pore volume of the coating layer, excellent blister resistance was obtained despite high air permeability (poor air permeability) as coated paper. The invention has been completed.

That is, in a cast coated paper provided with two upper and lower coating layers (the upper layer is a cast coating layer), the undercoating layer is formed as an extremely porous coating layer, and the porous coating layer is formed. By forming a high-gloss, dense cast coating layer mainly composed of a synthetic resin binder with film-forming properties on the coating layer, a cast with extremely high gloss and high smoothness, and excellent blister resistance Coated paper was obtained.

In the present invention, the reason why the surface smoothness of the cast coated paper is improved by increasing the pore volume of the undercoat coating layer is not necessarily clear, but is estimated as follows. Is done. That is, the moisture in the cast coating composition is rapidly absorbed into the undercoat layer, thereby facilitating the immobilization of the wet cast layer, and the shrinkage of the base paper caused by heat drying on the cast drum. This is probably because the layer was not moved and coating unevenness was unlikely to occur.

It is considered that the effect of improving the blister resistance can be obtained by increasing the pore volume of the coating layer as follows. That is, in the offset rotary printing, the water in the base paper layer is instantaneously turned into steam by rapid hot-air drying after the ink is transferred to the coated paper for high-speed printing. It is thought that the rapid increase in internal pressure due to expansion is mitigated by the fine voids present in the coating layer, and blisters are effectively suppressed.

Thus, the cast coated paper of the present invention comprises a base paper having at least one surface provided with an undercoat coating layer containing a pigment and an adhesive as a main component, and then forming an aqueous coating for casting on the coating layer. In a cast coated paper which is coated with a composition and pressed against a heated drum surface having a mirror surface while the aqueous coating composition is in a wet state and dried and finished, the cast coated paper (coating layer) 0.15 in the pore distribution curve of mercury intrusion method
The maximum peak of the pore diameter exists between pores of about 0.40 μm to about 0.40 μm.
m ² or more, preferably 10 cc / m ² or more.

Here, the mercury intrusion method is also called mercury polysimetry, and as described in Refractory Vol. 41, No. 6, pp. 297-303 / 1989, the pore structure of a porous material (fine). It is a widely used method for measuring pore size and pore volume). The measurement principle utilizes the fact that mercury has a large surface tension and cannot penetrate into the pores of a porous body unless pressure is applied.

That is, the surface tension of mercury is 0.480 (N /
m), and using a contact angle of 140 °, the relationship between the pressure applied to mercury and the pore diameter at which mercury can enter at that time is shown in the following general formula (1). P = -4σ cos θ / D (1) (Note) P: Pressure required for mercury to enter pores (psi) σ: Surface tension of mercury (480 dyn / cm) θ: Contact angle of mercury (140 °) D: pore diameter (μm) By substituting the values of σ and θ into the above equation (1), a general formula (2) for obtaining the pore diameter is obtained. D (μm) = 213 / P (psi) (2)

In order to obtain the pore distribution using the above principle, the pressure P applied to mercury is gradually changed, and the volume V of mercury that has entered the pores at that time is measured to determine the pressure P of mercury.
And the amount of mercury intrusion V is drawn, and the differential coefficient (dV / dP) of this relationship curve is determined and set as the vertical axis, and the value obtained by converting the pressure P to the pore diameter according to the above equation (2) is the horizontal axis. Is required. When the pore distribution of the coating layer is obtained by this method, a pore distribution curve showing two typical peaks is usually obtained. That is, two peaks appear in the pore range of 0.50 to 30 μm and in the pore range of 0.01 to 0.50 μm. The former peak appearing in the larger pore size distribution is derived from the base paper of the coated paper, while the latter peak appearing in the pore range of 0.01 to 0.50 μm is regarded as the peak derived from the coated layer. ing.

In the present invention, the pore volume is determined by the following method. That is, about 1 g of a sample of a single-sided cast coated paper (the back side is not coated) is precisely weighed, and the pressure of the mercury is changed from 1 to 30,000 psi using a mercury polysimeter and pressed into the paper layer. Of 466p corresponding to a pore diameter of 0.50 μm or less.
The pore volume per gram of the cast coated paper V (cc / cc /
g) is obtained. By multiplying the basis weight (g / m ² ) of the cast coated paper based on this value, the pore volume V (cc / m ² ) per 1 m ^{2 of the} cast coated paper is obtained.
Pores exceeding 0.5 μm were regarded as pores originating from the base paper layer, while pores having a diameter of 0.5 μm or less were regarded as pores generated in the coating layer. In addition, for cast paper coated on the back surface or double-sided cast paper provided with a cast layer on both sides, the paper layer is divided into two layers using a sheet splitter, and the side having the cast coating layer is divided into two layers. The measurement was performed on the divided paper.

The pore volume calculated according to the above formula is specified to be 5 cc / m ² or more, more preferably 10 cc / m ² or more, for the cast coated paper of the present invention.
By the way, if it is less than 5 cc / m ² , good blister resistance and good cast surface smoothness cannot be obtained. The upper limit is not particularly limited, but is usually 20 cc / m ² or less. 20c
If it exceeds c / m ² , the surface strength may be reduced.

Further, in order to obtain the desired smooth cast surface of the present invention, it is necessary that the pore diameter in the coated layer is larger than that of the ordinary coated paper. In the pore distribution curve, the pore diameter is 0.15 to 0.40
It is necessary to have the maximum peak of the pore diameter (the pore with the highest abundance ratio) in μm. By the way, when the maximum peak is less than 0.15 μm, the penetration of the water of the coating composition for casting into the undercoating layer becomes relatively slow, and the immobilization of the coating layer on the heating drum surface is correspondingly reduced. Delay and insufficient smoothness of the cast surface. On the other hand, if the maximum peak exceeds 0.40 μm, the gloss of the cast surface is undesirably reduced.

Next, specific formulas for obtaining a coating layer structure in the cast coated paper of the present invention will be described. In the present invention, as the pigment and the adhesive for the undercoat layer, those known and used in the field of production of general coated paper can be used. First, as the pigment, in order to obtain the desired pore volume of the present invention, so-called engineered kaolin or structured kaolin having a narrow particle size distribution width, or light calcium carbonate is preferably used.

In addition to the above pigments, for example, general kaolin and calcined kaolin, amorphous silica, zinc oxide, aluminum oxide, aluminum hydroxide, heavy calcium carbonate, satin white, aluminum silicate, magnesium silicate, magnesium carbonate, One or more inorganic or organic pigments such as plastic pigments are appropriately used in combination. The mixing ratio of the pigment is not particularly limited, but light calcium carbonate having an average particle size of 0.5 to 2.0 μm is preferably 30% by weight or more, more preferably 30% by weight or more, based on the total solid content. It is particularly preferable to contain 50% by weight or more in order to increase the pore volume and obtain the maximum peak of the pore diameter of 0.15 μm or more.

Generally, when the particle size of the pigment is reduced, the pore size tends to be reduced. Therefore, when the particle size of the light calcium carbonate is less than 0.5 μm, the pore size of 0.15 μm or more desired by the present invention is desired. In the case where the thickness exceeds 2.0 μm, the surface smoothness of the undercoating layer is reduced, and as a result, the glossiness of the cast coated paper may be reduced. .

Examples of the adhesive used in combination with the pigment include various starches such as starch and oxidized starch, proteins such as casein, soybean protein and synthetic protein, polyvinyl alcohol, and the like.
Cellulose derivatives such as carboxymethylcellulose and methylcellulose, styrene-butadiene copolymer, conjugated diene-based polymer latex of methylmethacrylate-butadiene copolymer, acrylic polymer latex, vinyl-based polymer such as ethylene-vinyl acetate copolymer Conventionally known adhesives generally used for coated paper, such as latex, may be used alone or in combination of two or more. The amount of the adhesive is adjusted in the range of 5 to 30% by weight, more preferably 8 to 20% by weight, based on the pigment. In general, the use of a large amount of these adhesives reduces the pore volume of the coating layer, and therefore it is desirable to use an amount as small as possible within a range where the printing strength is maintained. Therefore, a styrene-butadiene copolymer latex having relatively high strength is particularly preferably used. In addition, various auxiliaries such as a dispersant, a thickener, an antifoaming agent, a coloring agent, an antistatic agent, and a preservative used in the production of general coated paper can be appropriately added.

The undercoating coating composition comprising the above-mentioned materials is generally adjusted so that the solid content concentration is about 20 to 70% by weight, and is prepared on a base paper having a rice basis of about 20 to 400 g / m ^2. A blade coater so that the dry weight is about 5 to 50 g / m ² , preferably about 10 to 30 g / m ² ;
It is dried after coating by various known coating apparatuses such as an air knife coater, a roll coater, a brush coater, a rod blade coater, a bar coater, a gravure coater, a lip coater, and a curtain coater.

The base paper is not particularly limited, and acid paper or neutral paper used for general coated paper is appropriately used.

The characteristics of the cast coated paper in the present invention are as follows.
In particular, even when finished to a product having an extremely high glossiness of 60% or more at 20 ° glossiness conforming to TAPPI T-653 pm-90 with a surface gloss thereof, excellent offset rotary printing suitability without deteriorating blister resistance. It can be a product having. In order to obtain such high gloss, it is necessary to incorporate a large amount of a film-forming component in the coating composition for casting, and in particular, a cast containing a synthetic resin polymer composition as a main component. It is preferable to use a coating composition for use (hereinafter, referred to as a paint).

The above synthetic resin polymer composition includes, for example, methyl acrylate, ethyl acrylate,
Acrylates such as butyl acrylate and lauryl acrylate; methacrylates such as methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate and glycidyl methacrylate; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; acrylamide; methacrylamide; N −
Polymers or copolymers of ethylenically unsaturated carboxylic amides such as methylol acrylamide, or various ethylenic monomers such as vinyl chloride, vinyl acetate, vinyl propionate, ethylene and butadiene, and monoolefin aromatic monomers such as styrene. No. Among them, a copolymer composition of styrene, an acrylate and a methacrylate is particularly preferably used in terms of adhesive strength, gloss, and ink gloss. Further, it is particularly desirable that the above synthetic resin polymer composition has a glass transition temperature of 40 to 80 ° C. By the way, when the temperature is lower than 40 ° C., the releasability is deteriorated and the operability may be lowered. On the other hand, if the temperature exceeds 80 ° C., there is a concern that the glossiness of blank paper may be reduced.

In the present invention, a paint containing the above-mentioned synthetic resin polymer composition as a main component is preferably used for the coating layer for casting, and the above-mentioned synthetic resin polymer composition is contained in the paint. In addition to the above, an inorganic pigment, a release agent, and the like can be appropriately added for the purpose of imparting stable coating suitability and release properties. As the pigment in that case, for example, clay, kaolin, calcined clay, amorphous silica, colloidal silica, aluminum hydroxide, titanium oxide, barium sulfate,
Zinc oxide, satin white, calcium sulfate, talc,
Pigments used in the field of general coated paper such as plastic pigment, light calcium carbonate and heavy calcium carbonate are exemplified. The amount of the pigment is appropriately adjusted to 150 parts by weight or less based on 100 parts by weight of the synthetic resin polymer composition. By the way, if it exceeds 150 parts by weight, it is difficult to obtain the high gloss desired by the present invention.

Examples of the releasing agent include fatty acids such as stearic acid and oleic acid and / or salts thereof such as calcium, zinc, sodium and ammonium; amides such as stearic acid amide and methylenebisstearic acid amide; Examples include hydrocarbons such as microcrystalline wax, paraffin wax, and polyethylene emulsion, fats and oils such as funnel oil and lecithin, various surfactants such as fluorine-containing surfactants, and fluorine-based polymers such as tetrafluoroethylene polymer. You. In addition, various assistants such as dispersants, water-proofing agents, thickeners, defoamers, coloring agents, fluorescent dyes, antistatic agents and preservatives used in the production of general coated and cast coated papers. Agents are also used as appropriate.

The coating material for casting composed of the above-mentioned materials is generally adjusted to have a solid content of about 20 to 70% by weight, and is dried on a base paper provided with the above-mentioned undercoating layer in a dry weight of 1 to 70% by weight. Cast coating is applied so as to be about 10 g / m ² . That is, a coating material for casting is coated on a base paper provided with an undercoating layer, immediately pressed against a heated mirror drum, dried and peeled to obtain a cast coated paper. In this case, the surface temperature of the mirror drum is usually 60
-100 ° C.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples, but it is needless to say that the present invention is not limited thereto. Parts and% in the examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 [Back Coating Cast] (Production of base coat base paper) Kaolin (trade name: UW-90 /
A pigment comprising 40 parts of Engelhard Co., 60 parts of light calcium carbonate (trade name: Tamapearl 121-7K / Okutama Industry Co., Ltd.), and 0.5 part of a dispersant (trade name: Alon A-9 / Toa Gosei Co., Ltd.) The pigment was dispersed in water using a Cores disperser to obtain a pigment slurry having a solid content of 60%. To this slurry, 2 parts of an aqueous starch solution (trade name: Ace A / Oji Cornstarch Co., Ltd.) and 11 parts of styrene-butadiene copolymer latex (trade name: SN-307 / Sumitomo A & L Co.) (all as solids) are added. Then, an undercoat paint having a solid concentration of 55% was prepared. ^On a high quality base paper of 100 g / m ² of rice tsubo, both sides are coated with a blade coater so that the coating amount after drying of the under coating is 25 g / m ² per side,
It was dried to obtain a base paper for casting.

(Production of cast coated paper) Separately, as a coating for casting, 50 parts of a styrene-2-methylhexyl acrylate copolymer having a glass transition temperature of 50 ° C. and 50 parts of kaolin (UW-90 / Engelhard Co.) were separated. A cast paint having a solids concentration of 45% and comprising 2 parts of zinc stearate as a mold agent was prepared. The coating was applied onto the base paper using a roll coater, immediately pressed against a mirror drum having a surface temperature of 80 ° C., dried, and then released to obtain a cast coated paper. The dry coating amount at this time is 2 g / m
^{Was 2} .

Example 2 [Cast on back side coating] (Preparation of paint for casting) Kaolin (UW-90) 70
And 30 parts of light calcium carbonate (TP121-7K), and 0.5 part of a dispersant (Aron A-9) were dispersed using a Cores disperser to obtain a pigment slurry having a solid content of 60%. To this slurry, 10 parts of a casein solution dissolved with ammonia and 13 parts of a styrene-butadiene copolymer latex (SN-307) (both as solids) were added to prepare a cast paint having a solids concentration of 45%.

(Production of Cast Coated Paper) The above coating material was applied on one side of a base paper for casting used in Example 1 with a roll coater, and the coating was performed while the coated surface was wet.
The coated surface is immersed and gelled in a 0% calcium formate solution, immediately pressed, dried and peeled at a linear pressure of 50 kg / cm onto a chrome-plated metal roll having a mirror surface heated to 100 ° C. and cast coated. A paper was obtained. At this time, the coating amount after drying of the casting paint was 15 g / m ² .

Example 3 [Cast on back side coating] (Preparation of paint for casting) Kaolin (UW-90) 70
Part, light calcium carbonate (trade name: PX / Shiraishi Industry Co., Ltd.)
30 parts of pigment and dispersant (Aron A-9)
0.5 parts was dispersed using a Cores disperser to obtain a pigment slurry having a solid content of 60%. 10 parts of an aqueous solution of casein dissolved in ammonia in this slurry, and styrene-
13 parts of butadiene copolymer latex (SN-307) (all as solids) were added, and the solids concentration was 45%.
Was prepared.

(Production of Cast Coated Paper) The above coating material was coated on one side of a base paper for casting used in Example 1 with a roll coater, and immediately heated to 80 ° C., and had a chrome-plated metal having a mirror surface. Roll pressure of 30kg / cm
To obtain a cast coated paper. The dry coating amount of the casting paint in this case was 13 g / m ² .

Example 4 [Back Coating Cast] In the production of the base paper for casting in Example 1, the coating amount of the undercoat paint applied to the high quality base paper of 100 g / m ² of rice was 15 g / m ² on one side. Was obtained in the same manner as in Example 1 except for changing to. At this time, the dry coating amount of the casting paint was 2 g / m ² .

Example 5 [Back Cast Coating] A pigment composed of 60 parts of kaolin (UW-90), 40 parts of light calcium carbonate (Tamapearl 121-7K), and 0.5 part of a dispersant (Aron A-9) were added. The pigment was dispersed in water using a Cores disperser to obtain a pigment slurry having a solid content of 60%. To this slurry, 3 parts of an aqueous starch solution (Ace A) and a styrene-butadiene copolymer latex (SN-
307) 10 parts (all as solid contents) were added to prepare undercoating materials having a solid concentration of 55%.

The undercoating composition was coated on the base paper used in Example 1 by using a blade coater and dried so that the coating amount after drying was 20 g / m ^{2 on} one side. Using the casting paint used in Example 1, casting was performed in the same manner as in Example 1 to obtain a cast coated paper.

Example 6 [Back Cast Coating] A pigment consisting of 20 parts of kaolin (UW-90), 80 parts of light calcium carbonate (Tamapearl 121-7K), and 0.3 part of a dispersant (Aron A-9) were added. The pigment was dispersed in water using a Cores disperser to obtain a pigment slurry having a solid content of 60%. 2 parts of an aqueous starch solution (Ace A) and a styrene-butadiene copolymer latex (SN-
307) 11 parts (all as solids) were added, respectively, to prepare an undercoat paint having a solids concentration of 55%.

The undercoating composition was coated on the base paper used in Example 1 using a blade coater and dried so that the coating amount after drying was 20 g / m ² per one side, and then dried. A cast coated paper was obtained in the same manner as in Example 1 using the coating composition for casting used in Example 1.

Example 7 [Uncoated backside cast] In the production of the base paper for casting in Example 1, the coating amount for the undercoating paint on only one side of the required base paper after drying is 25 g / m ^2. The coating was dried in the same manner as described above to obtain a base paper for casting having the other side uncoated. Then, the coating composition for casting used in Example 1 was coated on the undercoating layer, and a cast coated paper was obtained in the same manner as in Example 1.

Example 8 [Double-sided casting] In Example 1, the coating material for casting used in Example 1 was coated on the back surface (coated surface) of the obtained cast coated paper with a roll coater, and immediately heated to 80 ° C. It was pressed against the heated mirror-surface drum, dried, and released to obtain a double-sided cast coated paper. The dry coating amount at this time was 2 g / m ² .

Comparative Example 1 [Back Coated Cast] (Production of Undercoated Paper) Kaolin (UW-90) 50
Parts, a pigment consisting of 50 parts of heavy calcium carbonate (trade name: FMT90 / Fimatec Co.) and 0.5 part of a dispersant (Aron A-9) were dispersed using a Coreless disperser,
A pigment slurry having a solid content of 60% was obtained.

An aqueous starch solution (ace A) 6 was added to the slurry.
Of styrene-butadiene copolymer latex (trade name: JSR0696 / Nippon Synthetic Rubber Co., Ltd.) (each as a solid content), and a solid content concentration of 55%
Was prepared. Next, the above coating material was coated on the base paper for cast coated paper used in Example 1 with a blade coater so that the coating amount after drying on one side was 25 g / m ^2, and the coating was performed. An undercoat base paper was obtained.

The undercoating base paper was coated with the coating material for casting used in Example 1 and cast-finished in the same manner as in Example 1. The dry coating amount of the paint for casting at this time was 1.5 g / m ² .

Comparative Example 2 [Cast Coated on the Back Side] 80 parts of heavy calcium carbonate (trade name: Softon 1400 / Bikita Koka Co., Ltd.), light calcium carbonate (Tamapearl 12)
1-7K) 20 parts of a pigment and 0.6 part of a dispersant (Aron A-9) were dispersed using a Cores disperser to obtain a pigment slurry having a solid content of 65%. To this slurry, 1 part of a starch aqueous solution (Ace A) and 8 parts of styrene-butadiene copolymer latex (trade name: JSR0696 / Nippon Synthetic Rubber Co., Ltd.) (all as solid contents) were added, and the solid content concentration was 55%. Was prepared.

Next, the above undercoating paint was coated on the base paper for cast coated paper used in Example 1 with a blade coater so that the coating amount after drying on one side was 35 g / m ^2. , And dried to obtain a base paper for casting.
The coating material for casting used in Example 1 was coated on the base paper, and a cast coated paper was obtained in the same manner as in Example 1. At this time, the dry coating amount of the paint for casting was 2 g / m.
^{Was 2} .

Comparative Example 3 [Cast on Back Coating] A pigment consisting of 80 parts of kaolin (UW-90), 20 parts of light calcium carbonate (Tamapearl 121-7K), and 0.5 part of a dispersant (Aron A-9) was used. The pigment was dispersed using a Cores disperser to obtain a pigment slurry having a solid content of 60%. To this slurry was added 3 parts of an aqueous starch solution (Ace A) and a styrene-butadiene copolymer latex (JSR0).
696) and 12 parts (all as solids) were added to prepare an undercoat paint having a solids concentration of 55%.

Next, the above-mentioned undercoating paint was coated on the base paper for cast coated paper used in Example 1 with a blade coater so that the coating amount after drying on one side was 25 g / m ^2. , And dried to obtain a base paper for casting.
The coating material for casting used in Example 1 was coated on the base paper, and a cast coated paper was obtained in the same manner as in Example 1. At this time, the dry coating amount of the paint for casting was 2 g / m.
^{Was 2} .

Comparative Example 4 [Back Coated Cast] The undercoating base paper used in Comparative Example 1 was coated with the coating liquid for casting used in Example 3 and cast coated paper in the same manner as in Example 3. I got At this time, the dry coating amount of the coating liquid for casting was 12 g / m ² .

Comparative Example 5 [Uncoated Coating on Back Side] In Comparative Example 1, the undercoating coating liquid was applied to only one side of the base paper so that the dry coating amount was 25 g / m ^2, and dried.
The coating liquid for casting used in Example 1 was applied on the undercoating layer, and a cast coated paper was obtained in the same manner as in Comparative Example 1. At this time, the dry coating amount of the cast coating liquid is 2 g.
/ M ² .

Comparative Example 6 [double-sided cast] In Comparative Example 1, the casting paint used in Comparative Example 1 was coated on the back surface of the obtained cast coated paper with a roll coater, and immediately heated to 80 ° C. Pressing, drying,
The mold was released to obtain a double-sided cast coated paper. The dry coating amount at this time was 2 g / m ² .

Tables 1, 2 and 3 show the quality results of the cast coated papers in the examples and comparative examples obtained as described above.
It was shown to. In addition, each evaluation method was shown below.

[Pore of pore volume and pore diameter] As for the back-coated cast paper, the obtained cast paper was divided into two layers, front and back, by a sheet splitter (manufactured by Beloit Co., Ltd.). The divided paper on the side with the mercury porosimeter (PMI porosimeter / Porous Ma)
terials Inc. ) Was measured by the method described above. For the double-sided cast paper, the paper layer was divided in the same manner, and the measurement was performed on the divided paper having the side on which the cast treatment was performed later. For the uncoated cast paper on the back side, the measurement was performed as it was.

[Gloss] TAPPI T-653 pm-
The 20 degree glossiness according to 90 was measured on the cast surface. For double-sided cast paper, the measurement was performed on the divided paper having the side on which the cast treatment was performed later.

[Smoothness] Evaluation was made visually. A: Very good smoothness B: Good smoothness B: Slightly poor smoothness. X: The surface is uneven and gloss unevenness is poor. (Note): For double-sided cast paper, the measurement was made on the divided paper on the side that was finished later.

[Blister resistance] Using an RI printing machine (manufactured by Meisho Seisakusho), the coated paper surface was double-sided printed with 1 cc of offset ink (Graf-G black / Dainippon Ink and Chemicals). The sample after printing was immersed in heated silicone oil, and the presence or absence of blister generation was observed. The temperature of the silicone oil was increased in increments of 5 degrees, and the temperature at which blisters first started to be formed was used as an index of blister resistance (the higher the temperature, the better the blister resistance).

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

[0068]

As is clear from the results of Tables 1 to 3,
The cast coated paper according to the present invention was a cast coated paper having excellent gloss and visual smoothness and excellent blister resistance (offset rotary printing suitability).

Claims (6)

[Claims] An undercoating layer comprising a pigment and an adhesive as a main component is provided on at least one side of a base paper, and an aqueous coating composition for casting is coated on the undercoating layer. In a cast coated paper which is finished by pressing and drying the surface of a heated drum having a mirror surface while the composition is in a wet state, the cast coated paper (coated layer) has a pore distribution curve of 0 in a mercury intrusion method. A cast having a strong gloss characterized by having a maximum peak of pore diameter between pores of 15 to 0.40 µm, and having a pore volume of 0.5 cc or less and 5 cc / m ² or more. Coated paper. 2. The pore volume of a pore having a pore diameter of 0.5 μm or less is 10c.
The cast coated paper according to claim 1, which has a c / m ² or more. 3. The cast coated paper has a surface glossiness of TAPPI.
60% at 20 degree glossiness based on T-653 pm-90
The cast coated paper according to claim 1, which is as described above. 4. An aqueous coating composition for casting, wherein light calcium carbonate having an average particle diameter of 0.5 to 2 μm is contained in the undercoating layer in an amount of at least 30% by weight based on all pigments in the undercoating layer. The cast coated paper according to claim 1, wherein the synthetic resin polymer composition is contained in an amount of 50% by weight or more based on the total solid content of the cast aqueous coating composition. 5. The cast coating according to claim 4, wherein light calcium carbonate having an average particle diameter of 0.5 to 2 μm is contained in the undercoating layer in an amount of 50% by weight or more based on all the pigments in the undercoating layer. Covered paper. 6. The cast coated paper according to claim 4, wherein a synthetic resin polymer composition having a glass transition temperature of 40 to 80 ° C. is used as the synthetic resin polymer composition.