JPH06248598A - Cast-coated paper - Google Patents

Abstract

PURPOSE:To obtain cast-coated paper free from occurrence of harmful components such as smell during use of coated paper, having extremely excellent glossiness of cast-coated face, improved releasability from the surface of a planished drum during production of coated paper and reduced stain on the surface of the drum. CONSTITUTION:In cast-coated paper obtained by coating paper with a coating composition comprising pigment, an aqueous adhesive and a releasant as main components, containing no casein, a coating composition comprising 3-20 content of pigment having 1.0-2.6ml/g voids based on the weight of solid content of the coating composition and 1-30% content of aqueous urethane based on the weight of solid content of the coating composition is applied to paper to give cast-coated paper.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to cast coated paper. More specifically, the present invention is excellent in the glossiness of the cast coating surface even without containing casein which has been conventionally used as an essential component in the cast coating, and the separation from the cast drum during the production thereof. The present invention relates to a cast coated paper which has good moldability and does not have a casein odor and does not contain a phosphorus compound.

[0002]

2. Description of the Related Art As a method for producing high-gloss coated paper called cast coated paper, a coating solution containing a pigment, a water-based adhesive and an auxiliary agent as a main component is coated on the surface of the base paper and immediately heated. Direct method of drying while contacting the surface of a mirror-finished drum (see, for example, Japanese Examined Patent Publication No. 38-25160), coating the base paper surface with a coating solution whose main components are pigments, water-based adhesives and auxiliaries. After coating and drying, the coating layer is re-wetted with a wetting agent solution to be plasticized, and then dried while being in contact with the heated mirror-finished surface of the drum (for example, JP-B-32-7604). (Refer to the official gazette), after coating the base paper surface with a coating liquid consisting of a pigment, a water-based adhesive, and an auxiliary agent, the coating layer is brought into contact with the coagulating liquid solution to gel, and then heated mirror finish. Solidification method of drying while contacting with the surface of the drum being used (eg In Japanese Patent Publication 38-15751, JP-B-40-7207, JP-JP 47-7555 Publication reference) are known.

All of these casting finishing methods are common in that the coating layer in a plastic state is pressed against the surface of a heated mirror-finished drum, dried, and released from the mold. The rewetting method is particularly preferred and widely practiced because of its high speed and therefore high production efficiency.

Further, the adhesive in the coating liquid for cast coated paper is a natural adhesive such as various starches, casein and other proteins at almost the beginning of the development of the cast coating method. However, only casein was actually used in some form after that.

In recent years, when styrene-butadiene latex has been industrialized, casein and latex have come to be used in combination in any of the above three casting finishing methods.

[0006] Casein, which is commonly used in any of the casting finishing methods, belongs to phosphoprotein among proteins, and it easily becomes a variable gel due to salting or heat. This is to improve the releasability when the cast coated paper is released from the surface of the mirror-finished drum. For these reasons, it is considered that casein has been used as an essential component for cast coated papers to date.

The use of an aqueous urethane resin in cast coated paper is disclosed in Japanese Patent Application Laid-Open No. 3-167386. However, this publication discloses the combined use of casein with an aqueous urethane resin as shown in the examples.

Further, JP-A-3-252473 discloses a coating composition which uses an aqueous urethane resin and does not use a water-soluble polymer such as casein, and a strong glossy paper obtained by coating the same. However, the concept of void volume is not mentioned at all for the pigment used. Further, in this publication, tributyl phosphate is used as the defoaming agent as shown in the Examples, but when the phosphorus component is contained in the cast coated paper, as will be described later, it is unique in printing. There is a drawback that odor is generated and the catalyst used when treating the odor by combustion is damaged.

Since casein, which is currently used as a component of a coating liquid for cast coated paper, is a natural adhesive, it is unstable in terms of supply and price, and is also an animal protein. Unique odor is generated. Especially for drying the ink in the case of odor due to casein rot when producing coating liquid or high speed printing such as offset rotary printing.
The odor generated when passing through a dryer at 200 to 300 ° C for heat treatment causes pollution and poses a problem.

Therefore, when performing offset rotary printing using cast coated paper containing casein, the exhaust gas in the dryer for drying the ink is burned by an afterburner to perform deodorizing treatment. However, the platinum catalyst required for deodorization treatment by combustion is per 1 g
In addition to being expensive at around 1500 yen, it is easily deteriorated by the phosphorus component contained in casein, so the life of the catalyst is 1/5 or less compared to when it does not contain the phosphorus component, which is a great financial burden. Has become.

For this reason, it is strongly desired to develop a cast coated paper which does not use casein and does not contain a phosphorus component. However, no matter how an adhesive other than casein is combined,
At present, it has not been possible to obtain an excellent cast coated surface having a gloss level comparable to the case of using casein.

[Problems to be Solved by the Invention]

In view of the above situation, the inventors of the present invention have earnestly studied a combination of a pigment and an adhesive for obtaining a cast coated paper, and as a result, by using a pigment having a specific porosity and an aqueous urethane resin in combination, Even without using any auxiliaries containing phosphorus component, the glossiness of the cast coated surface is remarkably excellent, and the release property of the cast coated paper from the drum surface, which is mirror-finished during production, is good, and the odor of The inventors have found that a cast coated paper that does not exist can be obtained and have completed the present invention.

Therefore, the object of the present invention is to solve the above-mentioned drawbacks of the prior art and to eliminate the use of auxiliaries such as odor when using coated paper because no auxiliary agent containing casein and phosphorus is used. Cast coating that does not occur, the glossiness of the cast coating surface is remarkably excellent, mold releasability from the mirror surface that is mirror-finished when manufacturing coated paper is good, and stains on the drum surface are also reduced. It is to provide craft paper.

[0014]

DISCLOSURE OF THE INVENTION The present invention relates to a cast coated paper obtained by applying a coating composition containing a pigment, an aqueous adhesive and a release agent as main components and containing no casein. The amount of the pigment is 1.0 ~ 2.6 ml / g is 3 to 20% based on the solid content weight of the coating composition, and the content of the aqueous urethane resin is 1 to the solid content weight of the coating composition. 30
% Of the coating composition is applied to the cast coated paper.

The cast coated paper of the present invention is a paper substrate (in the present specification, a base paper and a base paper provided with an undercoat layer containing a pigment or an adhesive as a main component on the base paper are collectively referred to as a paper. (Hereinafter referred to as a substrate), the coating composition is applied to form a cast coating layer, and then any of the known direct method, rewetting method, coagulation method,
It is preferably produced by the rewetting method.

The cast coated paper of the present invention has a void content of 1.0.
A pigment amount of up to 2.6 ml / g is used, and the void volume here is also referred to as porosity, and is measured by a Porosimeter 2000 Series (manufactured by CARLO ERBA) based on the so-called mercury intrusion method. By the way, the void diameter of the pigment to be measured is in the range of about 6 nm to 6 μm.

The pigment having a void volume in the range of 1.0 to 2.6 ml / g for the present invention is 3 to 20%, preferably 5 to 5% by weight of the coating solid content.
Contains ~ 15%.

When the content of the pigment is less than 3%, the glossiness of the cast coated surface cannot be sufficiently obtained, and the releasability of the cast coated surface from the drum surface and the stain on the drum surface are inferior.
On the other hand, when the content exceeds 20%, the cast coating surface is inferior in glossiness and the drum surface is also inferior in dirt, which is not suitable.

As mentioned above, the pigment used in the present invention has a void volume of 1.0 to 2.6 ml / g, preferably 1.2 to 2.3 ml / g.

If the amount of voids of the pigment is less than 1.0 ml / g, the effect of improving the glossiness of the coated surface of the cast coated paper, the releasability from the drum surface and the stain on the drum surface is not sufficient, and conversely If the amount exceeds 2.6 ml / g, there is a drawback that the fluidity of the coating liquid tends to be poor, coating becomes difficult, and the coating surface becomes uneven.

On the other hand, in the production of the cast coated paper of the present invention, a water-based urethane resin is used among the urethane resins as an adhesive. Urethane resin is a polymer having a urethane bond (-OOCHN-) in the molecule, and is generally a saturated polyol (HO-PE) having two or more OH groups.
-OH) and polycyanate (OCN-Ar-NCO).

Particularly, as the polyol used for the aqueous urethane resin, diol or triol is generally used. Examples of the diol include, in addition to usual glycols such as neopentyl glycol, 1,4-butanediol, and 1,6-hexadiol, polyethylene glycol, polypropylene glycol, polyether glycol represented by polytetramethylene glycol, and polyester. Examples thereof include polyols, acrylic polyols, epoxy polyols and polycarbonate polyols. or,
Examples also include diols having a tertiary amine such as N-methyldiethanolamine, and diols having a carboxyl group such as dimethylolpropionic acid.

The isocyanate used for the aqueous urethane resin is toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, 4,4'-cyclohexyl isocyanate, methylcyclohexane-2,4. (2,6) -diisocyanate, 1,3
-Cyclohexane, isophorone diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate and the like can be mentioned.

Further, as disclosed in Japanese Patent Application Laid-Open No. 3-167386, a polymer is polymerized with amines such as triethylamine and dimethylethanolamine, or a water-soluble amino such as methylated melamine resin is used. resin,
It is also possible to use an aqueous polyurethane resin obtained by crosslinking with aziridine, an epoxy resin, a zinc complex or the like.

The aqueous urethane resin thus obtained is used in a water-soluble state or in an emulsion or colloidal dispersion state.

The content of the aqueous urethane resin in the cast coated paper of the present invention is 1 to 30% based on the solid content of the coating liquid,
It is preferably 3 to 20%. When the content of the water-based urethane resin is less than 1%, sufficient glossiness of the mirror-finished coated surface of the obtained cast coated paper cannot be obtained, and conversely, when it exceeds 30%, the glossiness of the coated surface Is not preferable because the cost does not improve to a certain level or more and the cost increases.

The mechanism of action in which the effect of the cast coated paper of the present invention is exhibited is not particularly clear, but it is considered as follows. Casein easily becomes a variable gel due to chlorination and heat, so after the coating film is dried, it improves the releasability when the coated paper is released from the mirror-finished drum surface, and It has the effect of improving the glossiness.

Further, since casein itself is hydrophilic and water-retaining, it has the effect of making the distribution of the components such as pigments and adhesives uniform when the coated surface is dried, which strengthens the adhesive strength of the coating film. Therefore, a fine coating film is taken and gradually deposited on the surface of the cast drum, and as a result, it is possible to prevent a problem that the glossiness of the obtained cast paper is lowered.

On the other hand, when the water-based urethane resin is used without using casein, the above-mentioned effects due to casein are lacking, so that problems such as mold release failure and gloss reduction are likely to become apparent.

However, in the cast coated paper of the present invention, the void volume of at least one pigment in the coating liquid is in the range of 1.0 to 2.6 ml / g during production, and the pigment itself has appropriate voids. It is considered that this increases the affinity between water in the coating liquid, the adhesive agent and the like and the pigment, and contributes to the improvement of water retention and adhesive strength. Further, before the mirror finish of the coating film, the affinity with the coagulating liquid or rewetting liquid applied to the coating film is increased to improve the absorption and retention of the coagulating liquid and rewetting liquid in the coating film, This is probably because the plasticizing effect of the film can be fully exerted.

On the other hand, the water, the adhesive, the coagulating liquid, the rewetting liquid, etc. infiltrate into the gaps between the adjacent pigments in the coating film itself when the cast coated paper is manufactured, as is conventionally seen. However, since it is held, a holding effect due to the gap between the pigments is naturally expected, but such a holding effect only in the gap between the pigments is not sufficient, and as in the cast coated paper of the present invention, the pigment itself has It is considered that the effect of the voids having a void diameter in the range of 6 nm to 6 μm that can be measured with a Porosimeter acts synergistically to further enhance the retention effect.

The coating liquid composition for producing the cast coated paper of the present invention contains pigments, adhesives and auxiliaries as main components as in the conventional cast coating liquid composition. Examples of the pigment include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium dioxide, barium sulfate,
Of ordinary pigments for coated paper such as zinc oxide, satin white, plastic pigments, etc., the void volume is 1.0 ml / g
Those of less than 1.0 ml and those of 1.0 ml / g or more can be appropriately selected and used in combination.

In the coating liquid composition for cast coated paper of the present invention, it is an essential condition to include an aqueous urethane resin as an adhesive. As the adhesive other than the aqueous urethane resin, for example, a conjugated diene polymer latex such as a styrene-butadiene copolymer, a methylmethacrylate-butadiene copolymer, a polymer or copolymer of an acrylic ester and / or a methacrylic ester. Acrylic polymer latex such as, vinyl polymer latex such as ethylene-vinyl acetate copolymer, or these various polymer latex modified with a monomer containing a functional group such as carboxyl group Adhesives for ordinary coated paper such as soluble polymer latex, olefin maleic anhydride resin, melamine resin and other synthetic resin adhesives; starches such as oxidized starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose Can be mentioned, these adhesives One or more the aqueous urethane resin as appropriate in combination may be used.

In the cast coated paper of the present invention, the ratio of the pigment to the adhesive used is such that the weight ratio of pigment to adhesive is 95: 5 to solid.
It is adjusted within the range of 40:60, preferably 90:10 to 60:40.

In addition to the above-mentioned adhesive and pigment components, in the coating liquid composition used for the cast coated paper of the present invention, if necessary, a defoaming agent, a coloring agent, a water-proofing agent and a releasing agent are added. Mold agent,
Various auxiliary agents such as a flow modifier and a coagulant can be appropriately mixed and used, but none containing a phosphorus component is used.

For example, as the coagulant, any coagulant that coagulates the adhesive component of the coating film, such as organic acids such as formic acid, crotonic acid, itaconic acid, and electrolytes such as calcium formate and calcium chloride can be used.

In coating the above-mentioned coating liquid composition on a paper substrate, a coater which is commonly used in the production of general coated paper, such as a blade coater or an air knife coater,
A coater provided with a coating device such as a roll coater, a reverse roll coater, a bar coater, a curtain coater, a die slot coater, a gravure coater, and a chanplex coater can be used to coat one layer or multiple layers. At that time, the solid content concentration of the coating liquid is 40 to 70% by weight.
However, this concentration is appropriately adjusted depending on the type and speed of the coater.

As the paper substrate, a paper base or board base base paper having a basis weight of 30 to 400 g / m ² used for general printing coated paper or cast coated paper is used. Is not particularly limited, and may be acidic papermaking, alkaline papermaking, single-layer papermaking, or multi-layer papermaking, and of course, medium-quality base paper containing about 10% by weight or more of high-yield pulp can be used. In addition, the undercoating of the above paper base material, the coated paper with the back side of the cast coating layer having a general pigment coating, or the cast side surface (back side) with improved glossiness by the mirror finishing method Coated paper and the like can also be used as the paper substrate.

The coating amount of the coating liquid composition on the paper substrate is in the range of 10 to 50 g / m ^{2 on} a dry weight basis. In terms of 15-35g /
It is desirable to adjust within the range of m ² .

The degree of drying of the coated paper depends on the type of paper base material and the type of coating liquid composition, but the water content is 2
To 10%, preferably 4-8%.

The coated paper after drying is subjected to a smoothing treatment such as a machine calender or a super calender, if necessary, but an excessive amount such as to significantly impair the bulkiness and the rigidity characteristic of the cast coated paper. Of course processing should be avoided.

In the case of the re-wetting method, the coating layer is re-wet and pressed to the heated mirror-finished drum surface to give gloss, but re-wetting at the time of re-wetting. The liquid is not particularly limited, and for example, clear water, warm water, hot water, an aqueous solution containing a release agent, sodium citrate, zinc sulfate, or an aqueous solution containing amines such as dicyandiamide urea is known. A rewetting liquid is used.

Since the cast coated paper of the present invention is produced by using the above coating composition containing neither casein nor phosphorus component, no bad odor is generated during production and printing, and the cast coated surface is The glossiness is remarkably excellent, the cast coating surface is easily released from the drum surface even during production, and the stain on the surface of the cast drum is small.

[0044]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in Examples and Comparative Examples represent parts by weight and% by weight, respectively. In addition, all coating amounts are indicated by absolute dry weight%.

Example 1 First, a pigment was dispersed with water in a deleter (manufactured by Serie) in the following blending ratio to prepare a pigment slurry (S1) having a solid content concentration of 65%. Pigment Slurry (S1) Kaolin (U.S. Engelhard, UW-90, void volume 0.41ml / g) 80% Heavy calcium carbonate (Made in-house, average particle size 1μm, void volume 0.40ml / g) 12% Light calcium carbonate (Shiraishi Kogyo, Callite KT, void volume 1.89 ml / g) 8% Sodium polyacrylate (Toagosei, T-40) 0.4 parts per 100 parts pigment

Then, using this pigment slurry, a coating liquid for cast coating was prepared with the following composition. Pigment slurry (S1) (absolutely dry) 45% Aqueous urethane resin (Mitsui Toatsu, Olestar UD100N) 20% Latex (Asahi Kasei, L-1537) 34% Release agent (San Nopco, wax emulsion) 1% 0.5 parts of calcium formate, 0.2 parts of fluorescent dye, 0.1 part of non-phosphoric acid type defoaming agent, and water were sequentially added to 100 parts of coating solution solid content, and after stirring well, the pH was made alkaline with 25% ammonia water. To obtain an aqueous coating solution having a solid content concentration of 40%. At this time, the content of the pigment having a void volume of 1.89 ml / g in the solid content of the coating liquid was 3.6%, and the content of the aqueous urethane resin was 20%.

Subsequently, a paper base material having a basis weight of 90 g / m ² was made into paper by a known paper machine using a mixed pulp composed of 90% hardwood bleached kraft pulp and 10% softwood bleached kraft pulp. One side of this paper substrate was coated with the cast coater shown in FIG. 1 to produce cast coated paper.

That is, a paper substrate 1 was coated with an air knife coater 2 to a dry weight of 23 g / m 2, and dried with a drier 3 to a paper moisture content of 6%. Spray 0.3% concentration zinc sulfate aqueous solution on the coating layer with the sprayer 4,
Immediately, the drum 6 having a mirror-finished surface with a surface temperature of 110 ° C is pressed with a press roll 5 and after drying, a take-off roll.
Peel from the drum having a mirror-finished surface in 7,
Cast coated paper 8 was obtained. The winding speed at this time is 100m /
It was a minute. This method is generally called "rewetting method", and the quality of the obtained cast coated paper was evaluated as follows.

(1) Glossiness of cast coated surface It was measured according to JIS P 8142 (75 degree method).

(2) Odor of cast coated paper Five cast coated papers of 10 cm × 10 cm size were left for 5 minutes in a laboratory circulation oven at 150 ° C., and smelled of the paper immediately after being taken out. The presence or absence of odor was evaluated.

(3) Releasability The state when the cast coating surface is separated from the drum having the mirror-finished surface was visually evaluated and shown as follows. ◯: The cast coated surface separates from the drum without any resistance. Δ: The cast coated surface is slightly attached to the drum,
It's a little hard to separate. □: The cast coated surface adheres to the drum and is difficult to remove. ○ to △ and △ to □ indicate intermediate levels between them.

(4) Dirt on the surface of the mirror-finished drum The surface of the drum after continuous coating of 5000 m was visually observed and evaluated as follows. ◯: Clean and can be continuously processed. Δ: Some white and light dirt is attached, but a little more continuous treatment is possible. □: There is a lot of dirt, so it is necessary to stop the coater and wipe the drum surface again. ○ to △ and △ to □ indicate intermediate levels between them.

Example 2 A pigment slurry (S2) was prepared by changing the compounding ratio of the pigment for preparing the pigment slurry as follows. Pigment Slurry (S2) Kaolin (US Engelhard, UW-90) 74% Light Calcium Carbonate (Shiraishi Industry, Callite KT) 26% Sodium Polyacrylate (Toa Gosei, T-40) 0.4 parts per 100 parts pigment Then, using this pigment slurry, a coating liquid for cast coating was prepared with the following formulation. Pigment slurry (S2) 74% Water-based urethane resin (Mitsui Toatsu, Orestar UD100N) 20% Latex (Asahi Kasei, L-1537) 5% Release agent (San Nopco, wax emulsion) 1% At this time, void volume The content of the pigment of 1.89 ml / g in the solid content of the coating liquid was 19.2%, and the content of the aqueous urethane resin was 20%. Using this coating liquid, cast coated paper was manufactured in the same manner as in Example 1, and its quality was evaluated.

Example 3 A cast coated paper was produced in the same manner as in Example 2 except that the pigment slurry (S3) was prepared by changing the compounding ratio of the pigment for preparing the pigment slurry as follows. evaluated. Pigment Slurry (S3) Kaolin (US Engelhard, UW-90) 80% Heavy Calcium Carbonate (Made in-house, average particle size 1μ) 7% Light Calcium Carbonate (Shiraishi Kogyo, Brilliant 15, Void volume 1.27ml / g) ) 13% Sodium polyacrylate (T-40, manufactured by Toagosei) 0.4 parts per 100 parts pigment At this time, the content of the pigment having a void volume of 1.27 ml / g in the coating liquid solid content is 9.6%, and the aqueous urethane 20% resin content
Met.

Example 4 A pigment slurry (S4) was prepared except that 13% of light calcium carbonate (Brilliant 15) was replaced with 13% of talc (Takara HE-5, talc HE-5, void volume 1.41 ml / g). Cast coated paper was manufactured in exactly the same manner as in Example 3 and its quality was evaluated. At this time, the content of the pigment having a void volume of 1.41 ml / g in the solid content of the coating liquid was 9.6%, and the content of the aqueous urethane resin was 20%.

Example 5 A pigment slurry (S5) was prepared by replacing 13% of light calcium carbonate (Brilliant 15) with 13% of calcined clay (Engelhard, USA, Ansilex 93, void volume 2.10 ml / g). Manufactured a cast coated paper in exactly the same manner as in Example 3 and evaluated its quality. At this time, the void volume is 2.10 ml
The content of the pigment / g of the pigment in the coating liquid solid content was 9.6%, and the content of the aqueous urethane resin was 20%.

Example 6 13% of light calcium carbonate (Brilliant 15) was mixed with urea-based plastic pigment (Mitsui Toatsu, Eupearl C-12).
0, void volume 2.49 ml / g) Pigment slurry (S6) instead of 13%
Cast coated paper was manufactured in the same manner as in Example 3 except that the above was prepared, and the quality thereof was evaluated. At this time, the void volume
The content of the pigment of 2.49 ml / g in the solid content of the coating liquid is 9.6.
%, And the content rate of the aqueous urethane resin was 20%.

Example 7 A cast coated paper was produced in the same manner as in Example 5 except that the composition of the coating liquid for the cast coated paper was changed as follows, and its quality was evaluated. Pigment slurry (S5) 74% Water-based urethane resin (Mitsui Toatsu, Orestar UD100N) 2% Latex (Asahi Kasei, L-1537) 20% Oxidized starch (Oji corn starch, Oji ace A) 2% Release agent ( Wax emulsion made by San Nopco) 2% At this time, the content of the pigment having a void volume of 2.10 ml / g in the solid content of the coating liquid was 9.6%, and the content of the aqueous urethane resin was 2%.

Example 8 Casting was carried out in the same manner as in Example 5 except that the water-based urethane resin was Barrier Star XUD2193 (manufactured by Mitsui Toatsu) and the composition of the coating liquid for the cast coated paper was changed as follows. Coated paper was manufactured and its quality was evaluated. Pigment slurry (S5) 66% Water-based urethane resin (Mitsui Toatsu, Barrier Star XUD2193) 28% Latex (Asahi Kasei, L-1537) 5% Release agent (San Nopco, wax emulsion) 1% At this time, void volume Content of 2.10 ml / g of pigment in coating liquid solid content is 8.6%, water urethane resin content is 28%
Met.

Example 9 A cast coated paper was produced in the same manner as in Example 5 except that the aqueous urethane resin was Barrier Star XUD2193 and the composition of the coating liquid for the cast coated paper was changed as follows. , Evaluated its quality. Pigment slurry (S5) 74% Water-based urethane resin (Mitsui Toatsu, Barrier Star XUD2193) 10% Latex (Asahi Kasei, L-1537) 15% Release agent (San Nopco, wax emulsion) 1% At this time, void volume Content of 2.10 ml / g of pigment in coating liquid solid content is 9.6%, content of aqueous urethane resin is 10%
Met.

Example 10 The following aqueous coating solution was applied to both sides of the paper substrate of Example 1 on one side.
8g / m ² each is coated with a blade coater and dried to a water content of 6%.
After drying, a super calender treatment was performed at a nip pressure of 200 kg / cm to produce a paper base material for cast coating. Composition of aqueous coating liquid for paper base material Kaolin (UW-90 manufactured by Engelhard, USA) 26% Calcium carbonate (made in-house, average particle size 2μ) 60% Oxidized starch (Oji Cornstarch, Oji Ace) ) 2% Latex (L-1537 manufactured by Asahi Kasei) 12% Sodium polyacrylate as a dispersant per 100 parts of the pigment
0.3 parts, 0.5 parts of calcium stearate as a lubricant, 0.2 parts of fluorescent dye are added in order and thoroughly mixed and dispersed, then 25%
Adjust the pH to alkaline with aqueous ammonia,
An aqueous coating solution having a solid content concentration of 60% was prepared. The same coating solution for cast coating as in Example 9 was applied to one surface of the above-mentioned undercoated paper substrate to produce cast coated paper, and its quality was evaluated. At this time, the content of the pigment having a void volume of 2.10 ml / g in the solid content of the coating liquid was 9.6%, and the content of the aqueous urethane resin was 10%.

Example 11 Using a bleached kraft mixed pulp having a ratio of hardwood bleached kraft pulp and softwood bleached kraft pulp of 8: 2, the middle layer was woven with a known three-layer papermaking machine and the basis weight was 40 g / m ² . An outer layer having a basis weight of 90 g / m ² was laminated on both sides of each of the papers to produce a paper base material having a total basis weight of 220 g / m ² . Using this paper base material, cast coated paper was manufactured in the same manner as in Example 9, and the quality thereof was evaluated. At this time, the content rate of the pigment having a void volume of 2.10 ml / g in the coating liquid solid content is 9.6%, and the content rate of the aqueous urethane resin is 1%.
It was 0%.

Example 12 Using the same paper base material and coating liquid for cast coating as in Example 1, a cast coater shown in FIG. / m ² and then pre-dried in a dryer 11 so that the solid content concentration in the coating film becomes 55 to 60%, and a drum 13 having a mirror-finished surface with a surface temperature of 110 ° C. Pressed with the press roll 12,
At this time, the coagulating liquid of 0.5% calcium formate was supplied to the press nip 14 from the nozzle 15. After drying, it was peeled off from the drum with a take-off roll 16 to obtain cast coated paper 17. The winding speed at this time was 60 m / min. This cast coating method is generally called a "solidification method". The quality of the obtained cast coated paper was evaluated. At this time, the void volume is 1.
The content rate of 89 ml / g pigment in the coating solution solids is 3.6.
%, And the content rate of the aqueous urethane resin was 20%.

Comparative Example 1 A cast coated paper was produced in exactly the same manner as in Example 1 except that the pigment slurry (S6) was prepared by the following formulation.
Evaluated the quality. Pigment Slurry (S6) Kaolin (UW-90 manufactured by Engelhard, USA) 84% Heavy calcium carbonate (Made in-house, average particle size 1μ) 12% Light calcium carbonate (Shiraishi Kogyo, Callite KT) 4% Sodium polyacrylate (Toa Gosei Co., Ltd., T-40) 0.4 parts per 100 parts of pigment At this time, the content rate of the pigment with a void volume of 1.89 ml / g in the coating liquid is
The content of the aqueous urethane resin was 1.8% and 20%.

Comparative Example 2 A cast coated paper was produced in exactly the same manner as in Example 1 except that a pigment slurry (S7) was prepared according to the following formulation.
The quality was evaluated. Pigment Slurry (S7) Kaolin (US Engelhard, UW-90) 50% Light Calcium Carbonate (Shiraishi Industry, Callite KT) 50% Sodium Polyacrylate (Toa Gosei, T-40) 0.4 parts per 100 parts pigment At this time, the content of the pigment having a void volume of 1.89 ml / g in the solid content of the coating liquid was 22.5%, and the content of the aqueous urethane resin was 20%.

Comparative Example 3 A cast coated paper was produced in exactly the same manner as in Example 2 except that the pigment slurry (S8) was prepared by the following formulation.
The quality was evaluated. Pigment Slurry (S8) Kaolin (Made by Engelhard, USA, UW-90) 76% Heavy calcium carbonate (Made in-house, average particle size 1μ) 12% Talc (Misstron vapor from Japan, Mistron vapor, Void volume 0.84 ml / g) 12% Sodium polyacrylate (T-40 manufactured by Toagosei) 0.4 parts per 100 parts of pigment At this time, the content of the pigment having a void volume of 0.84 ml / g in the solid content of the coating liquid is 8.9%, the aqueous urethane The resin content was 20%.

Comparative Example 4 A cast coated paper was produced in exactly the same manner as in Example 2 except that the pigment slurry (S9) was prepared by the following formulation.
The quality was evaluated. Pigment Slurry (S9) Kaolin (Made in Engelhard, UW-90) 80% Heavy calcium carbonate (Made in-house, average particle size 1μ) 12% Silica (Made in Bayer, Bisical AD, 2.88ml / g) 8% Sodium polyacrylate (T-40, manufactured by Toagosei) 0.4 parts per 100 parts of pigment At this time, the content of the pigment having a void volume of 2.88 ml / g in the solid content of the coating liquid is 5.9%, and the content of the aqueous urethane resin is included. The rate was 20%.

Comparative Example 5 Pigment slurry (S3) 74%, latex (L-1537) 23%, oxidized starch (Oji cornstarch, Oji Ace A) 2%, not containing aqueous urethane resin as an adhesive, separated A cast coated paper was produced in the same manner as in Example 3 except that the mold agent (wax emulsion) was 1%, and the quality thereof was evaluated. At this time, the content of the pigment having a void volume of 1.27 ml / g in the solid content of the coating liquid was 9.6%, and the content of the aqueous urethane resin was 0%. However, when a cast coated paper was produced using this coating liquid, the mold release property of the cast coated paper from the drum was poor, and a cast coated paper having normal gloss could not be obtained.

Comparative Example 6 74% of pigment slurry (S3), 18% of latex (L-1537), 2% of oxidized starch (Oji Ace A), 5% of casein, containing no aqueous urethane resin as an adhesive, Cast coated paper was produced in the same manner as in Example 3 except that the release agent (wax emulsion) was 1%, and the quality thereof was evaluated.

The results obtained in Examples 1 to 12 are shown in Table 1.
The results obtained in Comparative Examples 1 to 6 are shown in Table 2.

[0070]

[Table 1]

[0071]

[Table 2]

As can be seen from Table 1, the void volume is 1.0 to 2.6.
The content of pigment in the range of ml / g is within the range of 3 to 20%, and the content of the aqueous urethane resin as an adhesive is 1
The cast coated paper of the present invention obtained by cast coating the coating composition in the range of -30%, the gloss of the cast coated surface is remarkably excellent, not only odor, but also in the production thereof. Good releasability from the cast drum and little stain (Examples 1 to 12), but the content of the pigment in the range of 1.0 to 2.6 ml / g is less than 3%, Is 1.0
When only a pigment as small as less than ml / g is used, the gloss of the cast coated paper is deteriorated, and the releasability from the drum and the stain are also deteriorated (Comparative Example 1 and Comparative Example 3). Even if the content of urethane resin is appropriate, if the content of such pigment is high, the glossiness of the cast coating surface is conspicuously lowered, and the release property from the drum during manufacturing is excellent, but the stain deteriorates. (Comparative Example 2) If the amount of voids in the pigment is too high, the fluidity of the coating liquid deteriorates even if the content of the aqueous urethane resin is appropriate, and the coating surface becomes non-uniform and unusable ( Comparative Example 4) Without the use of the aqueous urethane resin, the glossiness of the cast coating surface was remarkably deteriorated, and the releasability from the drum and the stain were remarkable, even if the void content and content of the pigment were appropriate. It becomes worse (Comparative Example 5).
Also, in the case of the conventional method of containing casein in the cast coating liquid, although the gloss of the cast coating surface, the releasability from the drum, and the dirt on the drum surface are good, the odor of the cast coating paper is strong and the commercial value Is inferior (Comparative Example 6).

[0073]

Since the cast coated paper of the present invention does not use a compound containing casein and a phosphorus component, there is no odor peculiar to casein, and the exhaust gas generated during drying is harmless. The glossiness of the cast coated surface of the paper is remarkably excellent, the mold release property of the cast coated paper from the drum surface is good at the time of production, and the dirt on the drum surface is significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic manufacturing process drawing of cast coated paper by a rewetting method.

FIG. 2 is a schematic manufacturing process diagram of cast coated paper by a coagulation method.

[Explanation of symbols]

 1 ・ ・ Paper substrate 2 ・ ・ Air knife coater 3 ・ ・ Dryer 4 ・ ・ Sprayer 5 ・ ・ Press roll 6 ・ ・ Drum with mirror-finished surface 7 ・ ・ Take off roll 8 ・ ・ Cast coated paper 9・ ・ Paper substrate 10 ・ ・ Roll coater 11 ・ ・ Dryer 12 ・ ・ Press roll 13 ・ ・ Drum 14 with mirror-finished surface ・ ・ Press nip 15 ・ ・ Nozzle 16 ・ ・ Take off roll 17 ・ ・ Cast coating Craft paper

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Hidetoshi Hatta 373 Yoshioka, Yonago, Tottori Prefecture Yonago Mill, Oji Paper Co., Ltd. 72) Inventor Kosumi Kusumi 373 Yoshioka, Yonago, Tottori Prefecture Yonago Mill, Oji Paper Co., Ltd.

Claims (1)

[Claims] 1. A cast coated paper comprising a coating composition comprising a pigment, an aqueous adhesive and a release agent as main components and containing no casein and having a void volume of 1.0 to 2.6 ml.
The content of the pigment which is / g is 3 based on the solid content weight of the coating composition.
A cast coated paper characterized by being coated with a coating composition having a water-based urethane resin content of 1 to 30% based on the weight of the solid content of the coating composition.