JP3047611B2 - Coating composition for cast paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for cast paper, and more particularly to a coating composition for cast paper for printing on a multi-color offset rotary press, which does not cause printing trouble due to ink piling. is there.

[0002]

2. Description of the Related Art As a method for producing a glossy paper for printing called a cast paper, an aqueous coating liquid containing a mineral pigment is applied to the base paper surface, and immediately dried while being brought into contact with a heated mirror-finished surface. Method (Japanese Patent Publication No. 38-25160, U.S. Pat. No. 1,719,166), an aqueous coating liquid containing a mineral pigment is applied to the base paper surface, dried, and if necessary, calendered. A rewet method (Japanese Patent Publication No. 32-7604, U.S. Pat. No. 2,759,847) is known in which rewet plasticization is carried out with a wetting agent solution and drying is carried out while being brought into contact with a heated mirror-finished surface.

An aqueous coating solution containing a mineral pigment is applied to the surface of a base paper, and then is brought into contact with a coagulant solution to gel the coating layer and then dried while being brought into contact with the heated mirror-finished surface. Japanese Patent Publication No. 38-15575, Japanese Patent Publication No. 40-7207, Japanese Patent Publication No. 47-7555, and US Pat. No. 3,377,192 are also known.

On the other hand, in the printing industry, so-called sheet-fed printing, which conventionally prints paper cut one sheet at a time in a predetermined size, has been common. Offset rotary printing has become widespread, labor savings and high speeds have been achieved, and large numbers of tens to hundreds of thousands of sheets have been printed.

However, in the case of cast paper, the glossiness and smoothness of the surface are far superior to those of other uncoated papers, art papers, etc. In this case, the problem of ink piling is likely to occur.

[0006] To explain the ink piling, in a multi-color offset rotary printing press, the ink applied to the paper surface by the first cylinder is reversely transferred to the blanket of the second cylinder and thereafter. When the amount of the reverse transfer is large, the density of the printed matter is reduced, and when the amount is severe, the ink is deposited, and the reversely transferred ink is transferred again to the printed matter to generate stain.

Therefore, the printing operation must be interrupted and the blanket must be cleaned. Further, in a severe case, the blanket may be damaged by the ink deposited by the reverse transfer. When ink piling occurs in this manner, the printing efficiency is significantly reduced.

[0008]

In the various methods for producing cast paper as described above, there is no particular problem in the case of cast paper used for printing a small number of sheets on a sheet-by-sheet basis. In the production of paper, there are methods to increase the affinity with the ink at the expense of the surface gloss to some extent by giving micropores to the coating film surface or reducing the finish slightly to prevent ink piling. Necessary cast paper which is characteristic of glossiness can be obtained only with low commercial value.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high gloss cast paper for offset rotary printing which solves the above-mentioned drawbacks of the prior art and does not cause a reduction in work efficiency due to the occurrence of ink piling.

[0010]

According to the present invention, there is provided an aqueous coating liquid containing a pigment and an adhesive as a main component, wherein at least one of the pigments has an oil absorption according to JIS K-5101 of 70 to 280 ml / 100 g. A certain pigment is contained in an amount of 3 to 20% by weight based on the solid content of the coating solution, and at least one styrene-butadiene copolymer latex is contained in the adhesive in an amount of 3 to 30% by weight based on the solid content of the coating solution. % By weight , and the styrene-butadiene copolymer
10 to 40% by weight of methyl methacrylate per weight of
It is a coating liquid composition for cast paper contained.

Now, the oil absorption according to JIS K-5101
Specific examples of pigments whose is 70 to 280 ml / 100 g
For example, white carbon, diatomaceous earth, firing
Diatomaceous earth, calcined clay, flux calcined diatomaceous earth, fine particles
Anhydrous aluminum oxide, fine titanium oxide, fine particles
Anhydrous silica, magnesium carbonate and the like.

In the present invention, the pigment has an oil absorption of 70 to 70%.
280 ml / 100 g, preferably 90-260 ml /
100 g are used. Oil absorption 70ml / 10
If the pigment is less than 0 g, the effect of improving ink piling is not sufficient. Conversely, if the oil absorption is more than 280 ml / 100 g, the dispersibility when blended into a paint tends to be poor, and the fluidity of the paint tends to be impaired. There is.

Further, the oil absorption amount is 70 to 280 ml / 10
0 g of the pigment is blended in an amount of 3 to 20% by weight, preferably 5 to 15% by weight, based on the solid weight of the coating solution. When the content is less than 3% by weight, the effect of preventing ink piling cannot be obtained. On the other hand, when the content is more than 20% by weight, sufficient gloss cannot easily be obtained, and the strength of the coating film tends to decrease. I can't say.

On the other hand, styrene-butadiene copolymer latex is one of those usually called synthetic rubber latex.
It is a seed, for example, produced by a method as disclosed in JP-A-61-698. The ratio of styrene / butadiene is appropriately selected depending on the application,
Generally, the higher the content of styrene in the copolymer, the higher the hardness tends to be, and it seems that styrene having around 50% is generally used for clay coating of paper.

The styrene-butadiene copolymer latex preferably used in the present invention contains 10 to 40% by weight of methyl methacrylate in the composition (per 100% by weight of the latex). Although the content of methyl methacrylate in the latex can be determined as appropriate, the inventors of the present invention have variously studied that, surprisingly, those having a methyl methacrylate content of 10 to 40 wt% are It turned out to show a remarkable effect.

Here, the methyl methacrylate content is 40
Even if it exceeds 10% by weight, the effect on the prevention of ink piling does not change any more. Conversely, when the styrene-butadiene component is reduced by that amount, the adhesive strength, hardness, etc., which are characteristic of the styrene-butadiene copolymer latex, are reduced. May be done.

The styrene-butadiene copolymer latex is used in an amount of 3 to 30% by weight, preferably 8 to 25% by weight, based on the weight of the solid content of the coating solution. 3% by weight
If the amount is less than 30% by weight, on the other hand, the effect on the strength of the coating film is saturated and the cost is increased.

[0018]

The present invention can be achieved for the first time by combining a pigment having a large oil absorption as described above and a styrene-butadiene copolymer latex, and its mechanism of action is considered as follows. Can be.

First, a pigment having a large oil absorption partly absorbs oily ink at the time of printing, and the adhesion between the ink and the cast paper surface is improved by a so-called anchor effect, thereby preventing ink piling.

[0020] Pigments having high oil absorbency include starch and PV.
A, casein and other water-soluble adhesives have little affinity, but easily adsorb synthetic resin-based adhesives such as emulsions and latexes, hindering uniform film formation of these and creating porous coatings. Easy to form. The very small voids in the coating film formed by this also promote the anchoring effect on the ink, and the ink piling is improved.

The cast paper has a flat and extremely dense coating film surface as compared with ordinary uncoated paper, coated paper, and art paper, and the anchoring effect of the ink is unlikely to appear. The fact that the anchoring effect of the ink is reliably obtained as in the present invention is a very excellent feature not found in the prior art.

On the other hand, when a pigment having a large oil-absorbing property is used as in the present invention, uniform film formation of a synthetic resin-based adhesive tends to be hindered. . In order to maintain the strength of the coating film, it is conceivable to increase the ratio of the adhesive, but this is not a desirable method because the cost increases. Here, the present inventors have found that the film strength can be sufficiently maintained by using a styrene-butadiene copolymer as at least one of the adhesives.

In particular, if the styrene-butadiene copolymer latex contains 10 to 40% by weight of methyl methacrylate in the composition, the ink piling is further improved as described above.

The reason why the styrene-butadiene copolymer latex having the above specific composition is effective in preventing ink piling must be linked to further studies, but generally, colorants (organic pigments, organic pigments, etc.) are contained in printing inks. An extremely large number of components such as inorganic pigments and dyes, vehicles (resins, oils, solvents, plasticizers), additives (waxes, metal soaps, etc.) are mixed, and these are mixed with the methyl methacrylate component in the latex. It is presumed to show strong affinity and to increase the adhesion.

The method for producing cast paper using the coating composition for cast paper according to the present invention will be illustrated below. The pigment having an oil absorption of 70 to 280 ml / 100 g used in the present invention is clay, kaolin, aluminum hydroxide, calcium carbonate, titanium dioxide, barium sulfate, zinc oxide, satin white plastic used in the production of ordinary coated paper. And at least one pigment selected from pigments and the like.

Examples of adhesives other than the styrene-butadiene copolymer latex include proteins such as casein, soybean protein, and synthetic protein; conjugated diene-based polymer latex such as methyl methacrylate butadiene copolymer; Or an acrylic polymer latex such as a polymer or copolymer of methacrylate, ethylene-
Vinyl-based polymer latex such as vinyl acetate copolymer, or an alkali-soluble or alkali-insoluble polymer latex obtained by modifying these various polymers with a functional group-containing monomer such as a carboxyl group; polyvinyl alcohol Olefin-maleic anhydride copolymer resin, synthetic resin adhesives such as melamine resin, positive starch, starches such as oxidized starch,
It is used in combination with at least one kind of adhesive selected from cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose.

These adhesives are used in an amount of 5 to 50% by weight, generally 10 to 30% by weight, per 100% by weight of the pigment. In addition, various auxiliaries such as an antifoaming agent, a colorant, and a flow modifier can be used as needed.

The coating liquid composition of the present invention can be used for blade coaters, air knife coaters, roll coaters, brush coaters, curtain coaters, champlex coaters, bar coaters, gravure coaters, size press coaters used in the production of general coated paper. Is coated on the base paper in one layer or multiple layers by an on-machine or off-machine coater provided with a coating device such as The solid content concentration of the coating composition at that time is generally 35 to 70% by weight, but preferably 45 to 65% by weight in consideration of operability.

As the base paper, rice tsubo 30-400 g / m ² used for general printing coated paper or cast coated paper is used.
Paper-based or board-based base paper is used. These are base papers made by an acidic or alkaline papermaking method. Of course, medium base papers containing about 10% by weight or more of high yield pulp can also be used. Further, coated paper in which a general pigment coating is provided on the back surface of the preliminary coating or cast coating layer can also be used as the base paper.

The amount of the coating composition applied to the base paper is about 10 to 50 g / m ² in terms of dry weight. Most preferably, it is adjusted in the range of 15 to 35 g / m ² . The cast finishing method may be performed by a method similar to a normal casting method such as a direct method, a coagulation method, and a rewetting method.

[0031]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is of course not limited to these examples. In the examples, parts and% represent% by weight, respectively, unless otherwise specified. In addition, all coating amounts are indicated by absolute dry weight.

Example 1 To a pigment having the following composition, sodium polyacrylate was added.
Add 4 parts and disperse with water with a Serie delicator,
A pigment having a solid content of 55% was prepared. Pigment slurry A: 80 parts kaolin (manufactured by EMC, USA, trade name UW-90, oil absorption 46 ml / 100 g) 80 parts activated clay (manufactured by Mizusawa Chemical Co., trade name Shilton, oil absorption 80)
ml / 100g) 20 parts

On the other hand, casein was dissolved by heating with ammonia water to prepare a casein aqueous solution having a solid content of 15%, and a coating solution was prepared with the following composition. Coating liquid: 80 parts of pigment slurry A (the slurry) 9 parts of aqueous casein solution (the aqueous solution) 9 parts of styrene-butadiene latex (trade name, manufactured by Asahi Kasei Corporation, L-1225-09; St / B)
u / MMA = 43/28/20) 10 parts Release agent (manufactured by San Nopco, wax emulsion) 1 part

To the above coating solution, 0.2 part of a fluorescent dye, 0.1 part of an antifoaming agent and water were sequentially added, and the mixture was stirred well. The mixture was adjusted to pH 9.5 with 25% aqueous ammonia and solidified. Minor concentration 4
A 0% aqueous coating solution was obtained. A pulp mixture of 90 parts of bleached hardwood kraft pulp and 10 parts of softwood bleached kraft pulp was formed on a known paper machine to obtain a basis weight of 90 g /
It was coated with a cast coater of Figure 1 on one side of the m ² base paper. The coating method is as follows.

The base paper 1 has a dry weight of 1 with a roll coater 2.
Coating was performed so as to be 5 g / m ² . In this case, dryer 3
The press roll 4 was immediately pressed against a cast drum 5 having a surface temperature of 90 ° C. without using the nozzle 7, dried, and peeled off from the cast drum 5 with a take-off roll 8 to obtain a cast coated paper 9. The speed at this time is 40m / m
in. I went in. This method is generally called "direct method". The quality of the obtained cast paper was evaluated by the following method.

1) Gloss of cast surface Measured according to JIS P 8142 (75 ° method).
The higher the value, the better the gloss. 2) Ink Piling Test In the ink piling test, a test piece 18 is first mounted on an impression cylinder 19 using an RI printing machine shown in FIG. Next, the ink is applied to the rubber roller 20, the metal roller 22 is brought into contact with the ink, and the ink is kneaded for 1 minute. The ink density of the test piece 18 after the ink of the piece 18 was re-transferred was measured using a Macbeth reflection densitometer manufactured by Sakata Inx. The higher the concentration, the better. It has been found by previous tests that the occurrence of ink piling in an actual printing press occurs at the test concentration of less than 0.50. The ink used here was MOROHOS
HI PRINTING INK Co. Ltd. Made,
WEB SHINE) Indigo.

3) Dry Pick In the ink piling test method using the RI printing machine shown in FIG. 3, the ink on the test piece 18 is transferred by the rubber roller 21. At this time, the cast paper with a weak coating film strength is picked, that is, the surface of the cast paper is peeled off and taken to the ink side, and spots where ink does not adhere to the coating film surface (this is called white spots) are generated. I do. This is referred to as a dry pick, and those without white spots are evaluated as having better dry picks. The ink used here is LK NT-3 (trade name, manufactured by Toyo Ink Co., Ltd.) and black ink.

Example 2 Using the same base paper and coating liquid as in Example 1, the base paper 1 was coated with a roll coater 2 to a dry weight of 18 g / m ² in FIG. The solid concentration in the membrane is 55-60
%, And pressed against a cast drum 5 having a surface temperature of 110 ° C. with a press roll 4. At this time, a coagulating liquid of 0.5% calcium formate was applied to a press nip 6 from a nozzle 7. After drying, the film was peeled off from the cast drum 5 with a take-off roll 8 to obtain a cast coated paper 9.
The coating speed at this time was 60 m / min. I went in. This is a method generally called “coagulation method”. The quality of the obtained cast paper was evaluated in the same manner as in Example 1.

Example 3 A base paper having a basis weight of 104 g / m ² was produced using the coating solution shown in Example 1 by the method shown in FIG. In FIG. 2, the base paper 10 was dried with an air knife coater 11 to a dry weight of 23 g / m ² . Then 0.3%
Spray an aqueous zinc sulfate solution with a sprayer 13 and immediately
Was pressed against a cast drum 15 having a surface temperature of 5 mm with a press roll 14, dried, and peeled off from the cast drum 15 with a take-off roll 16 to obtain a cast coated paper. The coating speed at this time was 100 m / min. I went in. This is a method generally called a “rewetting method”. The quality of the obtained cast paper was evaluated in the same manner as in Example 1.

Example 4 Example 3 was repeated except that the composition of the aqueous coating solution was changed as follows.
A cast paper was obtained in the same manner as described above. Pigment slurry (same as Example 1) 75 parts Casein (same as Example 1) 9 parts Styrene-butadiene latex (same as Example 1)
10 parts vinyl acetate emulsion (trade name, manufactured by Hoechst Gosei Co., Ltd.)
Movinyl 507) 5 parts Release agent (same as in Example 1) 1 part

Example 5 Example 3 was repeated except that the composition of the aqueous coating solution was changed as follows.
A cast paper was obtained in the same manner as described above. Pigment slurry (same as in Example 1) 75 parts Casein (same as in Example 1) 7 parts Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name, PVA-
105) 2 parts styrene-butadiene latex (identical to Example 1)
15 parts Release agent (same as in Example 1) 1 part

Example 6 Example 3 was repeated except that the composition of the aqueous coating solution was changed as follows.
A cast paper was obtained in the same manner as described above. Pigment slurry (same as Example 1) 70 parts Casein (same as Example 1) 9 parts Styrene-butadiene latex (same as Example 1)
20 parts Release agent (same as Example 1) 1 part

Example 7 A pigment slurry B was prepared by changing 90 parts of kaolin and 10 parts of activated clay in the pigment slurry A of Example 1.
Using this slurry B, a cast paper was obtained in the same manner as in Example 6.

Example 8 Styrene-butadiene latex was added to Polyrac 518E
-003 (Mitsui Toatsu, st / Bu / MMA = 44 /
36/13), except that cast paper was obtained in the same manner as in Example 3.

Example 9 A styrene-butadiene latex was prepared according to JSR-0619.
(St / Bu / MMA = 44/36, manufactured by Nippon Synthetic Rubber Co., Ltd.)
A cast paper was obtained in the same manner as in Example 3, except that / 13) was used. Example 10 Styrene-butadiene latex was converted to JSR-0613
(St / Bu / MMA = 52/37, manufactured by Nippon Synthetic Rubber Co., Ltd.)
/ 5), except that the cast paper was obtained in the same manner as in Example 3.

Example 11 Cast paper was obtained in the same manner as in Example 3, except that magnesium carbonate (manufactured by Tokuyama Soda Co., oil absorption: 90 ml / 100 g) was used instead of activated clay. Example 12 Instead of the activated clay of Example 12, calcined clay (EMC
Company name, Ansilex 93, oil absorption 104ml /
A cast paper was obtained in the same manner as in Example 3 except that 100 g) was used.

Example 13 In place of the activated clay of Example 12, light calcium carbonate (trade name, Callite KT, manufactured by Shiraishi Industry Co., Ltd., oil absorption 12
0 ml / 100 g), except that cast paper was obtained in the same manner as in Example 3. Example 14 Instead of the activated clay of Example 12, silica (trade name, Tokusil GU-N, manufactured by Tokuyama Soda Co., Ltd., oil absorption 255 ml /
A cast paper was obtained in the same manner as in Example 3 except that 100 g) was used. Example 15 The same as Example 3 except that the activated clay of Example 12 was replaced with an organic pigment of urea resin type (trade name, manufactured by Mitsui Toatsu Co., trade name, Eupearl C-120, oil absorption 100 ml / 100 g). To obtain cast paper.

Example 16 The following aqueous coating solution was applied to both sides of the base paper of Example 1 by a blade coater at a rate of 8 g / m ² per side, and then subjected to a super calender treatment (nip pressure: 200 kg / cm). Base paper was manufactured. Aqueous coating liquid for base paper: Kaolin (trade name UW-90, manufactured by EMC, USA) 30
Part heavy calcium carbonate (manufactured, particle size 1-4 μm) 70
Part Oxidized starch (Oji Ace A 10% liquid) 2 parts Latex (L-1537) 50% liquid 14 parts

To the above components, 0.3% of sodium polyacrylate as a dispersion per pigment, 0.5% of calcium stearate as a lubricant, and 0.2% of a fluorescent dye were sequentially added and mixed well and dispersed. Using an aqueous ammonia solution,
The pH was adjusted to alkaline. The solid concentration was 60%. A cast paper was manufactured using this base paper in the same manner as in Example 3.

Comparative Examples 1 to 3 Cast paper was produced in the same manner as in Examples 1 to 3, except that 100 parts of kaolin was used in the pigment slurry A of Example 1 without using activated clay. Comparative Examples 4 to 6 In the same manner as in Examples 1 to 3, except that in place of the styrene-butadiene latex, an acrylic ester copolymer emulsion (trade name, Movinyl 987, manufactured by Hoechst Gosei Co., Ltd.) was used. To produce cast paper. Comparative Example 7 In the pigment slurry A of Example 1, magnesium aluminosilicate (manufactured by Fuji Chemical Co., Ltd.,
A cast paper was produced in the same manner as in Example 3 except that the oil absorption amount was 320 ml / 100 g).

Table 1 shows the quality evaluation results of the cast papers obtained in Examples 1 to 17 and Comparative Examples 1 to 7.

[0052]

[Table 1]

As is clear from Table 1, Comparative Examples 1 to 3 all have inferior ink piling evaluations, and Comparative Example 7 has a disadvantage that the fluidity is slightly inferior at the time of pigment slurry preparation and coating liquid preparation. was there.

[0054]

As described above, the present invention, as is apparent from the examples, can be applied to the cast paper coating liquid composition by the direct method, the coagulation method,
It can be applied to any coating method such as a rewetting method, and the cast paper obtained by this method has a high glossiness, and has an excellent effect of not causing ink piling in multi-color offset rotary printing.

[Brief description of the drawings]

FIG. 1 is a flow sheet of an example of a method for producing cast paper.

FIG. 2 is a flow sheet of another method for producing cast paper.

FIG. 3 is a schematic explanatory view of an RI-1 type printability tester.

[Explanation of symbols]

 1, 10: base paper 2: roll coater 3, 12: dryer 4, 14: press roll 5, 15: cast drum 6: press nip 7: nozzle 8, 16: take-off roll 9, 17: cast coated paper 11: Air knife coater 13: Zinc sulfate aqueous solution sprayer 18: Test piece 19: Impression cylinder 20, 21: Rubber roller 22: Metal roller

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shun Sunaga 373 Yoshioka, Yonago City, Tottori Prefecture Oji Paper Co., Ltd.Yonago Mill Co., Ltd. In-plant (58) Field surveyed (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (1)

(57) [Claims] 1. An aqueous coating liquid containing a pigment and an adhesive as main components, wherein at least one of the pigments is JIS.
Oil absorption by K-5101 is 70 to 280 ml / 100
g is contained in the adhesive in an amount of 3 to 20% by weight based on the solid content of the coating solution.
The styrene-butadiene copolymer latex is contained in an amount of 3 to 30% by weight based on the solid content of the coating solution, and the styrene-butadiene copolymer is contained in an amount of 10 to 40% by weight based on the weight of the styrene-butadiene copolymer. A coating liquid composition for cast paper.