JPH05195493A - Composition for coating paper - Google Patents

Abstract

PURPOSE:To obtain the subject composition capable of providing coated paper excellent in coating operation efficiency, water resistant strength and ink receptivity. CONSTITUTION:The objective composition for coating paper is characterized by including a carboxy-modified latex in an amount of 5-20 pts.wt. expressed in terms of solids and an alkali-soluble resin in an amount of 0.02-5 pts.wt. expressed in terms of the solids in 100 pts.wt. pigment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper coating composition used for pigment-coated paper, and more particularly, to a coated paper excellent in coating operability, water resistance and ink acceptability. It relates to a paper coating composition for giving.

[0002]

2. Description of the Related Art Pigment-coated paper is produced and consumed in large quantities because it improves the gloss, whiteness and smoothness of the paper itself, or the gloss of printed matter and the reproducibility of printed images. The pigment coated paper is a paper coated with a paper coating composition containing a pigment and a binder. As the pigment, for example,
White inorganic pigments such as clay, calcium carbonate, aluminum hydroxide, titanium dioxide, satin white, or organic pigments formed from organic compounds such as polystyrene are used. As the binder, for example, carboxy-modified latex is used as the main binder, and starch, casein, soybean protein, etc. are used as the auxiliary binder.

In the production of coated paper, a base paper is coated with a coating composition. As the coating device, a roll coater, an air knife coater, a bar coater, a blade coater, etc. are usually used. However, the coating composition may adhere to various rolls attached to these coaters, and when the adhered matter is difficult to clean, it requires a lot of manpower and time for cleaning, which reduces productivity. At the same time, if those deposits are transferred to the coated paper,
It causes defects in the coated paper and causes a great quality problem.

On the other hand, the manufactured coated paper is printed to be a final publication, a commercial print such as a poster, a leaflet, or a catalog. As a printing method, offset printing has become the mainstream in recent years. Since dampening water is used in offset printing, the coated paper, which is the printing medium, is required to have sufficient water resistance. In addition, excellent ink acceptability is required in order to obtain sufficient printing reproducibility.

The coating composition is apt to be washed off with water when applied to various rolls attached to a coater during coating,
Good detergency is required. In other words, the water resistance of the coating film formed from the coating composition is required to be low when the film is attached to a roll or the like and dried. On the other hand, the coated paper obtained by coating the base paper with the paper coating composition with a coater and subsequently drying it with a drier is:
It must have excellent water resistance and ink receptivity. That is, the paper coating composition is required to satisfy contradictory properties with respect to water resistance.

Conventionally, a method of adding a specific additive to a coating composition has been widely used in order to impart excellent water resistance and ink receptivity to the coated paper. Such additives are
Known as a printability improving agent, for example, polyamide-urea-formaldehyde resin (Japanese Patent Publication No. 44-116677).
No.), polyamide-urea-epihalohydrin-formaldehyde resin (Japanese Patent Publication No. 61-42393), N-alkyl-substituted polyalkylene polyamines (JP-A-59-59).
No. 996) has been proposed. Furthermore, JP-A-1-
132896, JP-A-2-216297, JP-A-2
-216298, JP-A-2-221498, etc.,
Improvements from these further modifications have been shown.

However, the paper coating composition using the above-mentioned known printability improver has poor detergency and adversely affects operability when the coating composition adheres to various rolls attached to the coater. Exert. Further, further improvements are required in water resistance and ink acceptability of the obtained coated paper.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a paper coating composition which gives a coated paper excellent in coating operability, water resistance and ink acceptability. The present inventors have overcome the above-mentioned problems of the prior art, further improve the water resistance and ink acceptability of the coated paper, and at the same time, when the coating composition is coated on the base paper by a coater, As a result of intensive research on a method for improving the cleaning property of a coating composition attached to various attached rolls, it was found that the above object can be achieved by combining a pigment, a carboxy-modified latex and an alkali-soluble resin. Has been completed.

[0009]

Thus, according to the present invention, 5 to 20 parts by weight of a carboxy-modified latex as a solid content and 100 parts by weight of a pigment as a solid content of an alkali-soluble resin dissolved in an aqueous alkaline solution are used as a solid content. And a paper coating composition containing 0.02 to 5 parts by weight.

The present invention will be described in detail below. The paper coating composition of the present invention has excellent coating workability. That is,
When the coating composition is coated on the base paper with a coater, the coating composition adhered to various rolls attached to the coater can be easily washed off with water, which has excellent detergency. Further, the paper coating composition of the present invention gives a coated paper excellent in water resistance strength and ink acceptability. That is, the coated paper obtained by applying the paper coating composition of the present invention has excellent water resistance and ink acceptability required for offset printing.

The pigment used in the paper coating composition of the present invention is not particularly limited, and examples thereof include inorganic pigments such as clay, calcium carbonate, aluminum hydroxide, titanium dioxide and satin white, and organic pigments such as polystyrene. Examples include known pigments used for coated paper. These pigments can be used alone or in combination of two or more.

Examples of the carboxy-modified latex used in the present invention include a carboxy-modified synthetic copolymer latex which is generally used as a binder for a paper coating composition. Specific examples of the carboxy-modified latex include:
For example, carboxy-modified styrene-butadiene copolymer latex, carboxy-modified methyl methacrylate-butadiene copolymer latex, carboxy-modified styrene-methyl methacrylate-butadiene copolymer latex, carboxy-modified styrene-acrylonitrile-butadiene copolymer latex, carboxy-modified Styrene
Methyl methacrylate-acrylonitrile-butadiene copolymer latex and other carboxy-modified synthetic rubber latex, carboxy-modified acrylic acid ester-based, carboxy-modified styrene acrylic acid ester-based latex,
And mixtures of two or more of these.

Among these carboxy-modified latexes, a carboxy-modified aromatic vinyl-aliphatic conjugated diene-based copolymer latex containing an aromatic vinyl monomer and an aliphatic conjugated diene monomer as a copolymerization component, for example, carboxy A modified styrene-butadiene copolymer latex is preferable, and one having a glass transition temperature of less than 20 ° C. is particularly preferable.

The monomer used in the synthesis of the carboxyl-modified latex used in the present invention and the composition thereof are not particularly limited, but usually, the aliphatic conjugated diene monomer 20 to 60 is used.
% By weight, 10 to 75% by weight of aromatic vinyl monomer, 0.5 to 20% by weight of ethylenically unsaturated carboxylic acid monomer, and 0 to other monomer copolymerizable with these monomers. A monomer mixture consisting of 40% by weight is used.

The aliphatic conjugated diene monomer imparts flexibility to the copolymer, and when the amount is less than 20% by weight, the copolymer becomes too hard, and conversely 60% by weight. If it exceeds%, the water resistance decreases, which is not preferable.
Specific examples of the aliphatic conjugated diene-based monomer include 1,3 butadiene, 2-methyl-1,3 butadiene, 2-chloro-1,3 butadiene, and a mixture of two or more thereof. Yes, but among these,
3 butadiene is preferred.

The use of the aromatic vinyl monomer has the effect of imparting appropriate hardness and water resistance to the copolymer. If the amount is less than 10% by weight, a sufficient effect cannot be obtained, and conversely, if it exceeds 75% by weight, the film forming property is deteriorated and the adhesiveness is deteriorated, which is not preferable. As the aromatic vinyl monomer, styrene, α-methylstyrene,
Monochlorostyrene, vinyltoluene, and these two
Examples thereof include a mixture of two or more kinds, and among these, styrene is particularly preferable.

The ethylenically unsaturated carboxylic acid monomer is used for enhancing the adhesive force of the copolymer and improving the stability of the copolymer latex as a colloid. If the amount used is less than 0.5% by weight, the above effect cannot be sufficiently obtained, while if it exceeds 20% by weight, stability during polymerization may be problematic or the latex viscosity may become too high, making handling difficult. Such problems occur. Specific examples of the ethylenically unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid, and mixtures of two or more thereof. Is exemplified. Further, unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group such as itaconic acid monoethyl ester, fumaric acid monobutyl ester and maleic acid monobutyl ester can also be used.

Specific examples of other monomers copolymerizable with each of the above monomers include alkyl esters of unsaturated carboxylic acids such as methyl acrylate, methyl methacrylate, ethyl acrylate and butyl acrylate; Acrylonitrile,
Ethylene-based nitrile compounds such as methacrylonitrile;
Hydroxyalkyl esters of unsaturated carboxylic acids such as β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, β-hydroxyethyl methacrylate;
Amides of unsaturated carboxylic acids such as acrylamide, methacrylamide, N-methylol acrylamide, and diacetone acrylamide and derivatives thereof; glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate and glycidyl methacrylate; methylaminoethyl (meth) acrylate, Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as t-butylaminoethyl (meth) acrylate and N, N-dimethylaminoethyl (meth) acrylate; acrolein, allyl alcohol,
Other vinyl compounds such as vinyl acetate may be mentioned. These can be used alone or in combination of two or more.

The alkyl ester of unsaturated carboxylic acid is
It is effective for imparting an appropriate hardness and an appropriate hydrophilicity to the copolymer, and is preferably used in a proportion of 5 to 30% by weight. If the amount used is too large, the water resistance is adversely affected.

The ethylenically unsaturated nitrile is effective in imparting oil resistance to the copolymer and enhancing the printing gloss of coated paper, and is preferably 5 to 30% by weight. If the amount used is too large, the copolymer becomes too hard and the ink receptivity of the coated paper decreases, which is not preferable.

The hydroxyalkyl ester of unsaturated carboxylic acid is effective for improving the stability of the copolymer latex. Unsaturated carboxylic acid amides and their derivatives are also effective in improving the stability of the copolymer latex. When necessary, these monomers are preferably used in the range of 40% by weight or less.

The alkali-soluble resin used in the present invention is a copolymer resin obtained by copolymerizing an ethylenically unsaturated carboxylic acid with an aromatic vinyl monomer and / or another copolymerizable monomer. And is a resin that dissolves in an alkaline aqueous solution. It is essential that this copolymer resin is alkali-soluble.

Such an alkali-soluble resin can be produced by the method disclosed in JP-B-43-2460. It is disclosed in Japanese Examined Patent Publication No. 43-2460 that the alkali-soluble resin is used as a pigment dispersant, an emulsifier, a film forming agent and the like. Then, Japanese Patent Laid-Open No.
-97298 discloses that an alkali-soluble resin is used as an emulsifier in emulsion polymerization and the resulting copolymer aqueous resin dispersion (that is, latex) is used in a coating composition for pressing.

The alkali-soluble resin used in the present invention is not particularly limited in its monomer composition, but in order to impart alkali-solubility, it contains an ethylenically unsaturated carboxylic acid as a monomer component. Is mandatory. Examples of the ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid, and a mixture of two or more thereof. .. Acrylic acid or methacrylic acid is preferred.

Examples of the monomer copolymerized with the ethylenically unsaturated carboxylic acid forming the alkali-soluble resin include aromatic vinyl monomers, alkyl esters of unsaturated carboxylic acids, and ethylenically unsaturated nitriles. Can be mentioned. Aromatic vinyl monomers and alkyl esters of unsaturated carboxylic acids are preferably used. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, monochlorostyrene, vinyltoluene, and a mixture of two or more kinds thereof, with styrene being preferred. Examples of the alkyl ester of unsaturated carboxylic acid include methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and a mixture of two or more thereof. Other copolymerizable monomers are used as long as they do not inhibit alkali solubility.

The alkali-soluble resin containing styrene and (meth) acrylic acid as main components is particularly preferably used in the present invention. An alkali-soluble resin containing styrene and (meth) acrylic acid as main components is called an alkali-soluble styrene acrylic resin.

In the present invention, the alkali-soluble resin is
It is used in the form of being dissolved in an alkaline aqueous solution. Examples of the alkali used in the alkaline aqueous solution include sodium hydroxide, potassium hydroxide, aqueous ammonia, organic amine,
Examples thereof include triethanolamine and monoethanolamine, and among these, ammonia water is particularly preferable.

The concentration of the alkaline aqueous solution of the alkali-soluble resin used in the present invention is not particularly limited, but is preferably 5 to 40% by weight. If the concentration of the alkali-soluble resin is less than 5% by weight, the concentration of the coating composition is lowered, which is not preferable. On the other hand, if it exceeds 40% by weight, the viscosity of the aqueous alkali solution becomes too high, which makes addition difficult. It causes problems and is not preferable. The amount of the alkali added to the aqueous alkali solution is not limited as long as it is an amount sufficient to dissolve the alkali-soluble resin, but an alkali solution having a pH range of 6 to 9 is obtained. The addition amount is preferable. It is preferable to add an alkali-soluble resin to ammonia water having a concentration of 1 to 10% by weight to prepare a solution having a resin content concentration of 5 to 40% by weight.

The paper coating composition of the present invention contains the carboxy-modified latex in a solid content of 5 to 100 parts by weight of the pigment.
It is characterized by containing 20 parts by weight and an alkali aqueous solution of an alkali-soluble resin in a proportion of 0.02 to 5 parts by weight in terms of solid content.

When the compounding ratio (solid content) of the carboxy-modified latex is less than 5 parts by weight, sufficient water resistance cannot be obtained,
On the other hand, when it exceeds 20 parts by weight, the washability of the coating film is deteriorated and the operability is lowered, and the ink acceptability of the obtained coated paper is also lowered. A preferred blending ratio (solid content) of the carboxy-modified latex is 5 to 17 parts by weight.

Mixing ratio of alkali-soluble resin (solid content)
If the amount is less than 0.02 parts by weight, the desired effect cannot be obtained, while if it exceeds 5 parts by weight, the effect is not enhanced. The alkali-soluble resin is added in the form of being dissolved by an alkaline aqueous solution.

In the present invention, the mixing method of each component is
It is not particularly limited. For example, an alkali-soluble resin may be mixed with a carboxy-modified latex in advance, and the mixed latex may be added to a pigment to prepare a paper coating composition, or each may be separately added to the pigment and then mixed. it can. All components may be mixed together. Even when the carboxy-modified latex is mixed with the alkali-soluble resin in advance, the alkali-soluble resin is mixed in the form of being dissolved by the aqueous alkali solution.

The effect on the washability of the coating film, the water resistance of the coated paper and the ink acceptability is as follows. A carboxy-modified latex and an alkali-soluble resin are mixed in advance and then added to the pigment mixture to prepare a coating composition. In the case of doing, it appears more remarkably than in the case of adding them separately to prepare a coating composition.

The paper coating composition of the present invention contains water, a pigment, a carboxy-modified latex, an alkali-soluble resin, and, if desired, a water-soluble binder such as starch, casein, soybean protein, a dispersant, and a pH adjusting agent. Various additives such as a lubricant, a water retention agent, a defoaming agent, a dye, a coloring pigment, a fluorescent dye, and a preservative can be added. Further, a known printability improving agent may be used in combination within a range not impairing the object of the present invention.

The type of paper to which the paper coating composition is applied is not limited, and of course, paperboard is included.
The coating method may be a known coating facility such as an air knife coater, roll coater, bar coater or blade coater.

[0036]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In these examples, parts and% are based on weight unless otherwise specified.

The methods for measuring the physical properties are as follows. (1) Detergency The coating composition is applied to a polyester film with an applicator bar and dried at room temperature for 30 minutes. This film is immersed in water and the state after 10 minutes is observed, and the degree of dissolution is judged according to the following four stages. ◎: Completely dissolved, ○: Almost dissolved, △: Partially dissolved,
X: Not dissolved.

(2) Water resistance A RI printing tester (manufactured by Akira Seisakusho Co., Ltd.) was used to apply water to the coated paper with a molton roll, and then a picking test ink (tuck 18) was printed to print. The occurrence of surface picking was observed and judged. Evaluation is made by a 5-point method, and the larger the number, the better the water resistance. The 5-point method (water resistance point) was evaluated by visually determining the ratio of picked areas (pick area ratio) according to the following criteria. 5: 0%, 4: 0% excess, 25% or less, 3: 25% excess, 50% or less, 2: 50% excess, 75% or less, 1: 75% excess, 100% or less.

(3) Ink Receptivity The RI printing tester (manufactured by Akira Seisakusho Co., Ltd.) was used to apply water to the coated paper with a rubber roll coated with water, and then the black ink for offset printing was printed. Density meter for ink density on printed surface [DS DM-4 manufactured by Dainippon Screen Mfg. Co., Ltd.]
00] to determine the ink acceptability. The larger the ink density value, the better the ink acceptability.

Example 1 28 parts of styrene, 15 parts of methyl methacrylate, 10 parts of acrylonitrile, 44 parts of butadiene, 1 part of itaconic acid, and 2 parts of acrylic acid, for a total of 1 part.
A carboxy-modified latex having a monomer composition of 00 parts was prepared by emulsion polymerization.

An alkali-soluble styrene acrylic resin having a monomer composition of 76 parts of styrene and 24 parts of acrylic acid in total of 100 parts was polymerized by solution polymerization, and the solvent was removed. The obtained alkali-soluble styrene acrylic resin was dissolved in 5% ammonia water to obtain an alkali-soluble styrene acrylic resin solution having a resin content concentration of 35%.

A coating composition was obtained by blending the following coating composition. The alkali-soluble resin was added in the form of a solution dissolved in the above ammonia water. Clay (UW90, manufactured by Engelhard) 70 parts Calcium carbonate 30 parts (Carbital 90, manufactured by EC Japan Co., Ltd.) Dispersant (Aron T40, manufactured by Toagosei Kagaku Co., Ltd.) 0.5 part Carboxy modified latex 11 parts (solid content) Alkali-soluble styrene acrylic resin 0.1 part (solid content) Oxidized starch 4 parts (Oji Ace, manufactured by Oji Cornstarch) The paper coating composition was prepared so that the total solid content was 62%.

The washability of the obtained paper coating composition was measured. A paper coating composition was applied to a high-quality paper of 60 g / m ^{2 at} a coating amount of 15 g / m ² on one side, dried, and further supercalendered to obtain a coated paper. The water resistance and ink acceptability of the obtained coated paper were measured. Table 1 shows the measurement results of the cleaning property, water resistance and ink acceptability.

[Example 2] B as an alkali-soluble resin
A paper coating composition was prepared in the same manner as in Example 1 except that -36 (John Krill, manufactured by Johnson Polymer Co., Ltd .; alkali-soluble styrene acrylic resin) was used, and the detergency was measured. A coated paper is prepared in the same manner as in Example 1,
Water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

Example 3 Example 2 was repeated except that the amount of the alkali-soluble resin compounded was 2.0 parts.
A paper coating composition was prepared in the same manner as in (1) and the detergency was measured. A coated paper was prepared in the same manner as in Example 1 and its water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

Example 4 To 100 parts (solid content) of the carboxy-modified latex described in Example 1 was added B-36 (John Polymer Co., Ltd., Johncryl; alkali-soluble styrene acrylic resin) in 5% aqueous ammonia. 1.0 part (solid content) of the dissolved solution (resin concentration 35%) was added and thoroughly mixed to prepare an alkali-soluble resin-containing carboxy-modified latex.

A paper coating composition having a total solid content of 62 was prepared with the following composition.
% Was prepared. Clay (UW90, manufactured by Engelhard) 70 parts Calcium carbonate 20 parts (Carbital 90, manufactured by EC Sea Japan) Sachin White (SW, manufactured by Shiraishi Industry Co., Ltd.) 10 parts Dispersant (Aron T40, manufactured by Toagosei Kagaku) 0 .5 parts Alkali-soluble resin-containing carboxy-modified latex 13 parts (solid content) Oxidized starch 4 parts (Oji Ace, Oji Corn Starch)

The washability of the obtained coating composition was measured.
A coated paper was prepared in the same manner as in Example 1 using the coating composition, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1. In this example, the alkali-soluble resin was added at a ratio of 0.129 parts in terms of solid content to 100 parts of the pigment.

Example 5 23 parts of styrene, 15 parts of methyl methacrylate, 10 parts of acrylonitrile, 48 parts of butadiene, 2 parts of methacrylic acid, and 2 parts of acrylic amide.
A carboxy-modified latex having a total monomer composition of 100 parts was prepared by emulsion polymerization.

Obtained carboxy modified latex 100
0.5 parts (solid content) of a solution (Jonkryl 678, manufactured by Johnson Polymer Co .; John Kryl; alkali-soluble styrene acrylic resin) dissolved in 5% ammonia water to 30 parts (solid content). Was added and mixed well to prepare an alkali-soluble resin-containing carboxy-modified latex.

A coating composition having the following composition was prepared so that the total solid content was 62%. Clay (UW90, manufactured by Engelhardt) 70 parts Calcium carbonate 20 parts (Carbital 90, manufactured by ECC Japan) Titanium white (Taipek W10, manufactured by Ishihara Sangyo Co., Ltd.) 10 parts Dispersant (Aron T40, manufactured by Toagosei Co., Ltd.) 0.5 parts Alkali-soluble resin-containing carboxy-modified latex 13 parts (solid content) Oxidized starch 4 parts (Oji Ace, Oji Corn Starch)

The washability of the obtained coating composition was measured.
A coated paper was prepared in the same manner as in Example 1 using the coating composition, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1. In this example, the alkali-soluble resin was added in an amount of 0.065 parts as a solid content with respect to 100 parts of the pigment.

Example 6 Using the alkali-soluble resin-containing carboxy-modified latex of Example 5, a coating composition having the following composition was prepared so that the total solid content would be 62%.
In this example, Sumirez resin 636 (manufactured by Sumitomo Chemical Co., Ltd .; polyamide polyurea resin) was blended as a printability improving agent. Clay (UW90, manufactured by Engelhardt) 70 parts Calcium carbonate 20 parts (Carbital 90, manufactured by ECC Japan) Titanium white (Taipek W10, manufactured by Ishihara Sangyo Co., Ltd.) 10 parts Dispersant (Aron T40, manufactured by Toagosei Co., Ltd.) 0.5 parts Alkali-soluble resin-containing carboxy-modified latex 13 parts (solid content) Sumirez Resin 636 0.5 parts Oxidized starch 4 parts (Oji Ace, Oji Corn Starch)

The washability of the obtained coating composition was measured.
A coated paper was prepared in the same manner as in Example 1 using the coating composition, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

Example 7 A carboxy-modified latex having a monomer composition of 33 parts of styrene, 10 parts of methyl methacrylate, 10 parts of acrylonitrile, 44 parts of butadiene, 1 part of itaconic acid, and 2 parts of acrylic acid was prepared by emulsion polymerization. Prepared.

51 parts styrene, 21 methyl methacrylate
Parts, and 28 parts of acrylic acid, a total of 100 parts of an alkali-soluble resin having a monomer composition was polymerized by solution polymerization and the solvent was removed. 5% of the obtained alkali-soluble resin
It was dissolved in ammonia water to obtain an alkali-soluble styrene acrylic resin solution having a resin content of 35%.

Alkali-soluble resin-containing carboxy-modified latex was prepared by adding 1.0 part (solid content) of the alkali-soluble resin solution to 100 parts (solid content) of the carboxy-modified latex and mixing them well.

A paper coating composition having a total solid content of 62 was prepared in the following composition.
% Was prepared. Clay (UW90, manufactured by Engelhardt) 70 parts Calcium carbonate 20 parts (Carbital 90, manufactured by ECC Japan Co., Ltd.) Sachin White (SW, manufactured by Shiraishi Industry Co., Ltd.) 10 parts Dispersant (Aron T40, manufactured by Toagosei Co., Ltd.) 0 .5 parts Alkali-soluble resin-containing carboxy-modified latex 13 parts (solid content) Oxidized starch 4 parts (Oji Ace, Oji Corn Starch)

The washability of the obtained coating composition was measured.
A coated paper was prepared in the same manner as in Example 1 using the coating composition, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

Example 8 Styrene 38 parts, methyl methacrylate 5 parts, acrylonitrile 5 parts, butadiene 48
Part, 1 part of itaconic acid, 1 part of acrylic acid, and 2 parts of acrylamide were used to prepare a carboxy-modified latex by emulsion polymerization.

34 parts of styrene, 23 of methyl methacrylate
Parts, and 43 parts of acrylic acid, a total of 100 parts of an alkali-soluble resin having a monomer composition was polymerized by solution polymerization and the solvent was removed. 5% of the obtained alkali-soluble resin
It was dissolved in aqueous ammonia to obtain an alkali-soluble styrene acrylic resin solution having a resin content of 35%.

Alkali-soluble resin-containing carboxy-modified latex was prepared by adding 1.0 part (solid content) of the alkali-soluble resin solution to 100 parts (solid content) of the carboxy-modified latex and mixing them well.

A paper coating composition having a total solid content of 62 was prepared in the following composition.
% Was prepared. Clay (UW90, manufactured by Engelhard) 70 parts Calcium carbonate 20 parts (Carbital 90, manufactured by EC Sea Japan) Sachin White (SW, manufactured by Shiraishi Industry Co., Ltd.) 10 parts Dispersant (Aron T40, manufactured by Toagosei Kagaku) 0 .5 parts Alkali-soluble resin-containing carboxy-modified latex 13 parts (solid content) Oxidized starch 4 parts (Oji Ace, Oji Corn Starch)

The washability of the obtained coating composition was measured.
A coated paper was prepared in the same manner as in Example 1 using the coating composition, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

Comparative Example 1 (without alkali-soluble resin) Using the carboxy-modified latex of Example 1, a coating composition was prepared with the following composition. Clay (UW90, manufactured by Engelhardt) 70 parts Calcium carbonate 30 parts (Carbital 90, manufactured by ECC Japan) Dispersant (Aron T40, manufactured by Toagosei Co., Ltd.) 0.5 part Carboxy modified latex 11 parts (solid content) Oxidized starch 4 parts (Oji Ace, Oji Corn Starch)

The paper coating composition was prepared so that the total solid content was 62%. The washability of the obtained coating composition was measured. A coated paper was prepared in the same manner as in Example 1, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

[Comparative Example 2] (without alkali-soluble resin) Using the carboxy-modified latex of Example 1, a paper coating composition having a total solid content of 62% was prepared according to the following formulation.
In this comparative example, Sumireze resin 636 (manufactured by Sumitomo Chemical Co., Ltd., polyamide polyurea resin) was blended as a printability improver. Clay (UW90, manufactured by Engelhard) 70 parts Calcium carbonate 30 parts (Carbital 90, manufactured by EC Japan Co., Ltd.) Dispersant (Aron T40, manufactured by Toagosei Kagaku Co., Ltd.) 0.5 part Carboxy modified latex 11 parts (solid content) Sumireze Resin 636 0.1 part Oxidized starch 4 parts (Oji Ace, Oji Corn Starch)

The washability of the obtained paper coating composition was measured. A coated paper was prepared in the same manner as in Example 1, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

Comparative Example 3 Using the latex used in Example 5 as the carboxy-modified latex, a paper coating composition having the following composition was prepared. Clay (UW90, manufactured by Engelhardt) 70 parts Calcium carbonate 20 parts (Carbital 90, manufactured by ECC Japan) Titanium white (Taipek W10, manufactured by Ishihara Sangyo Co., Ltd.) 10 parts Dispersant (Aron T40, manufactured by Toagosei Co., Ltd.) 0.5 part Carboxy modified latex 13 parts (solid content) Sumireze resin 636 0.5 part Oxidized starch 4 parts (Oji Ace, Oji Cornstarch)

The washability of the obtained paper coating composition was measured. A coated paper was prepared in the same manner as in Example 1, and water resistance and ink acceptability were measured. The measurement results are shown in Table 1.

[0071]

[Table 1]

As is clear from Table 1, the paper coating compositions of the present invention examples (Examples 1 to 8) all had good detergency,
It showed water resistance and ink acceptability. In particular, the paper coating compositions of Examples 4 to 8 in which the carboxy-modified latex was mixed with the alkali-soluble copolymer latex in advance and showed excellent effects. On the other hand, the paper coating compositions of Comparative Examples 1 to 3 in which the alkali-soluble resin was not blended were all inferior in washability, water resistance and ink acceptability. Also in the paper coating compositions of Comparative Examples 2 to 3 using the known printability improving agent, the effect of improving the cleaning property, water resistance and ink acceptability obtained in each Example of the present invention was obtained. I couldn't do it.

[0073]

EFFECTS OF THE INVENTION According to the present invention, there is provided a paper coating composition which gives a coated paper which is excellent in detergency, water resistance and ink receptivity. When the paper coating composition of the present invention is used, it can be easily washed even if it adheres to various rolls attached to a coater during coating, and excellent workability can be obtained. The coated paper coated with the paper coating composition of the present invention exhibits excellent water resistance and ink acceptability, and is particularly suitable for offset printing.

Claims (1)

[Claims] 1. A carboxy-modified latex in a solid content of 5 to 20 parts by weight, and an alkali-soluble resin dissolved in an alkaline aqueous solution in a solid content of 0.
A paper coating composition, characterized in that it is contained in a proportion of 02 to 5 parts by weight.