JP2010248658A - Coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper having lightweight and excellent glossiness to solve the problem that when a relatively inexpensive material is used, it is extremely difficult to effectively suppress permeation of coating liquid through the surface of printing lightweight base paper and to efficiently form a coating film of a coated layer. <P>SOLUTION: The coated paper is obtained by treating at least one side of paper sheet consisting mainly of pulp with a surface treatment agent containing a cationic group-containing copolymer obtained by polymerizing a specific vinyl monomer with a specific cationic group-containing vinyl monomer, and then providing the treated surface of the paper with the surface treatment agent with a coated layer of a coating liquid containing pigment and a binder having a glass transition temperature in a specific range. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to coated paper.

  In recent years, there has been an increasing demand for weight reduction of printing paper in order to reduce transportation and mail costs. However, simply reducing the weight, that is, reducing the basis weight of the printing paper is not preferable because the thickness of the paper is reduced and the volume of the booklet is impaired. The reduction in weight required means that the paper thickness is reduced while the high glossiness of the coated paper is maintained while the paper thickness is not reduced. On the other hand, with the progress of visualization and colorization of printed materials, the demand for coated paper for printing with a smooth coating layer on the paper surface as an ink-receiving layer is increasing year by year as compared to uncoated printing paper. The coating layer mainly composed of inorganic pigments such as calcium carbonate and kaolin has a higher specific gravity than the base paper coated with pulp as the main material, and the coating amount can be reduced to reduce the weight of the coated paper. It needs to be reduced as little as possible. However, when the density of the base paper is reduced, the number of pores increases, so that the penetration of the coating liquid into the base paper increases during coating, making it difficult to uniformly coat the base paper surface with a low coating amount. . Therefore, if the base paper is calendered before coating in order to reduce the amount of pores in the base paper, the penetration of the coating liquid into the base paper is reduced, but the paper thickness is reduced, so low density paper cannot be obtained. In this way, to reduce the weight of the coated paper, even if a light and bulky base paper is used, simply applying a coating liquid mainly composed of a high specific gravity inorganic pigment will cause the coating liquid to penetrate. It is difficult to realize a light weight while maintaining a high glossiness of the coated paper because the amount of work increases.

  Further, as a method for suppressing the penetration of the coating liquid into the inside of the base paper, a method of sizing the base paper in order to reduce the wettability between the base paper and water that is a solvent of the coating liquid can be considered. For example, Patent Document 1 describes a treating agent containing cationic polyacrylamide and an anionic copolymer containing a monomer having a hydrophobic substituent. Reference 2 describes a coating agent for processed base paper comprising a branched copolymer polyacrylamide having a weight average molecular weight of 500,000 to 2,000,000 having a cationic group and / or an anionic group. In addition, a method of applying an aqueous solution containing a swellable mica and a binder in order to suppress the penetration of a release agent such as silicone into a release paper substrate is disclosed (see Patent Document 3). On the other hand, it has been proposed that a specific amount of swellable mica can be applied to the surface of a light bulky base paper for printing to effectively suppress the penetration of the hydrophilic paint (see Patent Document 4). Furthermore, it is disclosed that a coated paper having excellent optical properties and printability can be obtained by applying a coating composition containing a pigment, an aqueous binder, a water-soluble acetate, and a cationic resin to paper. (See Patent Document 5).

Japanese Patent Laid-Open No. 11-012981 JP 2006-283236 A JP-A-6-200500 JP 2005-89871 A Japanese Patent Laid-Open No. 2-84598

  However, as in Patent Document 1, even if such a treatment is performed on a low density base paper having a large amount of pores, the effect is small. Also, a coating agent is applied by applying a surface treatment agent mainly composed of a water-soluble polymer such as starch for coating and polyvinyl alcohol (PVA) to the paper surface to form a coating film on the paper surface. Although a method for suppressing the penetration of the liquid is also conceivable, it has been difficult to form an effective penetration inhibiting coating on the paper surface. Patent Document 2 is intended to improve the rigidity of a processing base paper used as a release paper, but is referred to as a coating base paper for obtaining a light and high gloss coated paper suitable for printing and the like. The point was not enough. The release paper coating solution used in Patent Document 3 is hydrophobic because it is mainly composed of toluene and silicone, and is hydrophilic for printing in which pigments and binders such as calcium carbonate and kaolin are dispersed in water at a high concentration. Since the physical properties of the coating liquid are remarkably different from those of the coating liquid, it does not solve the problem of general coated paper. Further, Patent Document 4 has a drawback that the swellable mica is very expensive and cannot be used for the production of general-purpose printing paper. Moreover, although patent document 5 confirmed the effect to some extent on the paper surface permeation suppression, it was difficult to form an effective permeation suppression coating film. Therefore, it has been very difficult to effectively form a coating film of the coating layer by effectively suppressing the penetration of the coating liquid on the surface of the lightweight base paper for printing by using a relatively inexpensive material.

  The subject of this invention is providing the coated paper which was lightweight and excellent in glossiness.

In the present invention, after treating a surface treatment agent containing a cationic group-containing copolymer on at least one surface of a paper mainly composed of pulp, a pigment and a binder are treated on the treated surface of the paper with the surface treatment agent. Is a coated paper provided with a coating layer of a coating liquid containing
The cationic group-containing copolymer is at least one selected from (A) a vinyl monomer represented by the general formula (I) and a vinyl monomer represented by the general formula (II) [hereinafter, ( A) and at least one selected from (B) a cationic group-containing vinyl monomer represented by the general formula (III) and a cationic group-containing vinyl monomer represented by the general formula (IV) A cationic group-containing copolymer obtained by polymerizing a seed [hereinafter referred to as component (B)],
The binder is at least selected from a styrene / butadiene-based polymer having a glass transition temperature of -40 ° C to 60 ° C and a (meth) acrylic acid ester-based polymer having a glass transition temperature (hereinafter referred to as Tg) of -40 ° C to 60 ° C. A polymer,
Related to coated paper.

[Wherein, R ¹ represents a hydrogen atom or a methyl group, and R ² and R ³ are the same or different and represent a hydrogen atom or a linear or branched alkyl group or alkenyl group having 1 to 4 carbon atoms. ]

[Wherein R ¹ represents the above-mentioned meaning, m represents a number of 0 or 1, A ¹ and A ² are the same or different, and the formula — (CH ₂ ) _n — (n is an integer of 2 to 6] And B represents a group selected from —O— and —CH ₂ —. ]

[R ¹ is as defined above, R ⁴ and R ⁵ are the same or different and each represents an alkyl group or alkenyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Y represents —O—, —NH— or —O—CH ₂ CH (OH) —, Z represents a linear or branched alkylene group having 1 to 4 carbon atoms, and X represents an acid. A conjugated base, a halogen atom or an alkyl sulfate group having 1 to 4 carbon atoms is shown. ]

[Wherein, R ⁷ and R ⁸ are the same or different and each represents a hydrogen atom or a methyl group; R ⁹ and R ¹⁰ are the same or different and each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Indicates meaning. ]

  The reason why the above-mentioned problem is solved by the coated paper of the present invention is not clear, but the presence of a specific cationic group-containing copolymer on the surface of the base paper makes the main component a binder having a pigment and a specific Tg. It is presumed that when the coating liquid is applied, a part of the coating liquid aggregates to suppress the penetration of the coating liquid mainly composed of an inorganic pigment into the paper.

  Further, when a coating solution mainly containing a pigment and a binder having a specific Tg is applied due to the presence of a specific cationic group-containing copolymer having high hydrophilicity on the paper surface, the coating liquid is instantly applied. It is presumed that the absorption of water in the coating liquid is highly viscous and non-fluidized, thereby suppressing the penetration of the coating liquid mainly composed of inorganic pigment into the paper.

  In addition, when a specific cationic group-containing copolymer having high hydrophilicity is applied to the paper surface, the coating liquid penetrates into the base paper by filling the pores of the paper having a porous surface layer. It is estimated that it is suppressed.

  According to the present invention, a coated paper having light weight and excellent gloss is provided. The coated paper of the present invention can suppress the penetration of the coating liquid into the base paper, and an effective coating layer can be obtained with a small coating amount by using the current paper machine or coating machine. A lightweight, highly glossy coated paper can be produced efficiently.

The graph which shows the relationship between the coating amount of a coating liquid, and the glossiness of a coated paper about a part of Example and a comparative example

[Cationic group-containing copolymer]
The cationic group-containing copolymer according to the present invention includes (A): at least one selected from vinyl monomers represented by the above general formulas (I) and (II), and (B): the above general formula. It is obtained by polymerizing at least one selected from the cationic group-containing vinyl monomers represented by (III) and (IV).

[Component (A)]
The cationic group-containing copolymer according to the present invention contains at least one selected from vinyl monomers represented by general formulas (I) and (II) as a constituent component.

[Wherein, R ¹ represents a hydrogen atom or a methyl group, and R ² and R ³ are the same or different and represent a hydrogen atom or a linear or branched alkyl group or alkenyl group having 1 to 4 carbon atoms. The total number of carbon atoms of R ² and R ³ is preferably 6 or less, and more preferably 4 or less. ]

[Wherein R ¹ represents the above-mentioned meaning, m represents a number of 0 or 1, A ¹ and A ² are the same or different, and the formula — (CH ₂ ) _n — (n is an integer of 2 to 6] And B represents a group selected from —O— and —CH ₂ —. ]

  The monomer of the component (A) of the present invention is preferably hydrophilic. Here, hydrophilicity means the inorganic nature of the monomer from which the polymer units are obtained in the organic conceptual diagram-basics and applications-(written by Yoshio Koda, Sankyo Publishing Co., Ltd., issued on May 10, 1984). The ratio [I / O] between I) and organic (O) means 0.60 or more, preferably 1.00 or more, more preferably 1.30 or more.

  Examples of the vinyl monomer represented by the general formula (I) include (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, Examples include Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nt-butyl (meth) acrylamide, N-isobutyl (meth) acrylamide, and the like represented by the general formula (II). Examples of vinyl monomers include N- (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone and the like, but the present invention is not limited to such examples, and these vinyl monomers Can be used alone or in admixture of two or more. “(Meth) acryl” means acryl and / or methacryl (hereinafter the same).

  Among these monomers (A), (meth) acrylamide and N, N-disubstituted acrylamide are preferable, and (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-diethyl are further preferable. (Meth) acrylamide is preferred from the viewpoint of production of a cationic group-containing copolymer and from the viewpoint of handling as a surface treatment agent.

[(B) component]
The cationic group-containing copolymer according to the present invention comprises at least one selected from cationic group-containing vinyl monomers represented by general formulas (III) and (IV) as a constituent component.

[R ¹ is as defined above, R ⁴ and R ⁵ are the same or different and each represents an alkyl group or alkenyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Y represents —O—, —NH— or —O—CH ₂ CH (OH) —, Z represents a linear or branched alkylene group having 1 to 4 carbon atoms, and X represents an acid. A conjugated base, a halogen atom or an alkyl sulfate group having 1 to 4 carbon atoms is shown. ]

[Wherein, R ⁷ and R ⁸ are the same or different and each represents a hydrogen atom or a methyl group; R ⁹ and R ¹⁰ are the same or different and each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Indicates meaning. ]

  Specific examples of the compound represented by the general formula (III) include acid neutralized products obtained by neutralizing (meth) acrylic acid esters or (meth) acrylamides having a dialkylamino group exemplified above with an acid, or 4 A quaternary ammonium salt quaternized with a classifier may be mentioned, and specific examples of the compound represented by the general formula (IV) include the diallyl-type quaternary ammonium salts exemplified above.

  Preferred acids for obtaining the above acid neutralized product include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, tartaric acid, adipic acid, sulfamic acid, toluenesulfonic acid, lactic acid, pyrrolidone- Examples of preferred quaternizing agents for obtaining the quaternary ammonium salts include alkyl halides such as methyl chloride, ethyl chloride, methyl bromide and methyl iodide, and dimethyl sulfate. And general alkylating agents such as diethyl sulfate and di-n-propyl sulfate.

  Among the compounds represented by the general formulas (III) and (IV), dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl ( A quaternary ammonium salt obtained by quaternizing (meth) acrylamide with the above quaternizing agent, or dimethyldiallylammonium chloride may be mentioned.

  Specific examples of the cationic group-containing vinyl monomer include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, diisopropylaminoethyl (meth) acrylate, dibutylaminoethyl. (Meth) acrylate, diisobutylaminoethyl (meth) acrylate, di-t-butylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, dipropylaminopropyl (meth) acrylamide, diisopropylamino Propyl (meth) acrylamide, dibutylaminopropyl (meth) acrylamide, diisobutylaminopropyl (meth) acrylamide, di-t-butylamino Acid neutralized products or quaternary ammonium salts of monomers having amino groups such as (meth) acrylic acid esters or (meth) acrylamides having dialkylamino groups such as propyl (meth) acrylamide; dimethyldiallylammonium chloride, diethyl Diallyl-type quaternary ammonium salts such as diallylammonium chloride; vinylpyridines such as 4-vinylpyridine and 2-vinylpyridine; N-vinyl heterocyclic compounds such as N-vinylimidazole; aminoethyl vinyl ether, dimethylaminoethyl vinyl ether, etc. And acid neutralized products of quaternary ammonium salts such as vinyl ethers and the like. “(Meth) acrylate” means acrylate and / or methacrylate (the same applies hereinafter).

[Mixing ratio of monomer components]
In the cationic group-containing copolymer according to the present invention, the composition ratio (molar ratio) of the component (A) to the component (B) is the component (A) / component (B), preferably 97/3 to 30/70. More preferably, it is 97/3 to 40/60. If it is within these composition ratios, when a coating liquid mainly composed of a pigment and a binder is applied, a part of the coating liquid aggregates, and the copolymer is instantaneously contained in the coating liquid. Since the moisture is absorbed, an effect that the penetration of the coating liquid into the paper can be suppressed is exhibited. Furthermore, when it exists in the said composition ratio, the adhesive force to the paper surface of a surface treating agent improves, and it can fully suppress the peeling strength fall of a base paper and a coating layer.

  In the cationic monomer-containing copolymer according to the present invention, the total of the component (A) and the component (B) is preferably 80 to 100 mol%, more preferably 90 to 99.9, in the constituent monomers. Mol%.

[Component (C)]
The cationic group-containing copolymer according to the present invention may be a crosslinkable vinyl monomer (excluding the monomer represented by the general formula (IV)) as the component (C) as necessary. It can be a component. The crosslinkable vinyl monomer preferably has at least two groups selected from a vinyl group, an acryloyl group, a methacryloyl group and an allyl group in the molecule. Examples of the crosslinkable vinyl monomer having at least two vinyl groups in the molecule include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and propylene glycol di (meth) acrylate. , Dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,2-butylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate , Polyglycerol such as glycerol di (meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate (Meth) acrylic acid esters; acrylamides such as N-methylallylacrylamide, N-vinylacrylamide, N, N′-methylenebis (meth) acrylamide, and bisacrylamideacetic acid; divinyl such as divinylbenzene, divinyl ether, and divinylethyleneurea Compounds: polyallyl compounds such as diallyl phthalate, diallyl malate, diallylamine, triallylamine, triallyl ammonium salt, allyl etherified pentaerythritol, and allyl etherified sucrose having at least two allyl ether units in the molecule; (Meth) acrylic esters of unsaturated alcohols such as vinyl (meth) acrylate, allyl (meth) acrylate, 2-hydroxy-3-acryloyloxypropyl (meth) acrylate Etc., and the like.

  Among these crosslinkable vinyl monomers, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, divinylbenzene, pentaerythritol triallyl ether, and pentaerythritol tetraallyl ether are preferable.

  In the cationic group-containing copolymer according to the present invention, the proportion of the crosslinkable vinyl monomer of the component (C) is 0 in the total of the component (A), the component (B), and the component (C). 0.005 to 5 mol% is preferable, and 0.001 to 1 mol% is particularly preferable. That is, (C) component / [(A) component + (B) component + (C) component] × 100 (mol%) is preferably 0.0005 to 5 mol%, more preferably 0.001 to 1 mol%. . When the ratio of the crosslinkable vinyl monomer is 0.0005 mol% or more, the degree of crosslinking of the obtained cationic group-containing copolymer is appropriate, and the cationic group-containing copolymer was applied to paper. At this time, the ratio of staying on the paper surface is improved, and it is difficult to penetrate into the paper. For this reason, when a coating liquid is applied, a part of the coating liquid aggregates, or a cationic group-containing copolymer is present on the paper surface, so that the coating liquid mainly contains a pigment and a binder. When the coating liquid is instantly absorbed, the coating liquid becomes highly viscous and non-fluidized, or when the cationic group-containing copolymer is applied to the paper surface, it becomes porous. The effect of suppressing the penetration of the coating liquid into the base paper is sufficiently exhibited by filling the pores of the paper having the surface layer portion. When the amount is 5 mol% or less, when the cationic group-containing copolymer is applied to paper, the water in the coating liquid is absorbed even when the cationic group-containing copolymer is applied to the coating liquid. From the result that the coating liquid becomes highly viscous and the non-fluidizing effect can be maintained without lowering the ability to perform coating, it is preferable that the coating liquid hardly penetrates into the paper. In addition, when (C) component is used, the total of (A) component, (B) component, and (C) component is 90-100 mol in the structural monomer in the cationic group containing copolymer which concerns on this invention. %, More preferably 95 to 100 mol%.

[Other monomer components]
The cationic group-containing copolymer according to the present invention is a copolymer having the at least two kinds of vinyl monomers as essential constituents, and preferably further having the crosslinkable vinyl monomer as a constituent. Other vinyl monomers copolymerizable with these vinyl monomers can also be used as constituents.

  Examples of other vinyl monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, neopentyl (meth) acrylate, cyclopentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, Ryl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, phenyl (meth) acrylate, toluyl (meth) acrylate, xylyl (meth) acrylate, benzyl (meth) acrylate, 2-ethoxyethyl (meth) Acrylate, 2-butoxyethyl (meth) acrylate, 2-phenoxy (meth) acrylate, 2-methoxypropyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-ethoxypropyl (meth) acrylate, 3-ethoxypropyl (Meth) acrylate, ethylene glycol mono (meth) acrylate, diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, tetraethylene glycol mono ( ) Acrylate, polyethylene glycol # 210 mono (meth) acrylate, polyethylene glycol # 400 mono (meth) acrylate, polyethylene glycol # 600 mono (meth) acrylate, polyethylene glycol # 1000 mono (meth) acrylate, methoxyethylene glycol (meth) Acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate, methoxypolyethylene glycol # 210 (meth) acrylate, methoxypolyethylene glycol # 400 (meth) acrylate, methoxypolyethylene glycol # 600 (meth) acrylate, methoxypolyethylene glycol # 100 (Meth) acrylic acid derivatives such as 0 (meth) acrylate (numbers after # indicate weight average molecular weight); 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, acrylic acid, methacrylic acid, Anionic group-containing monomers such as 2-sulfoethyl methacrylate; N- (3-sulfopropyl) -N-acryloyloxyethyl-N, N-dimethylammonium betaine, N- (3-sulfopropyl) -N-methacryloyl Amidopropyl-N, N-dimethylammonium betaine, N- (3-carboxymethyl) -N-methacryloylamidopropyl-N, N-dimethylammonium betaine, N- (3-sulfopropyl) -N-methacryloyloxyethyl-N , N-dimethylammonium betaine, N-carbo Shimechiru -N- methacryloyloxyethyl -N, betaines such as N- dimethylammonium betaine.

[Polymerization method]
The method for producing the cationic group-containing copolymer according to the present invention is not necessarily limited, but it is usually preferable to use a method such as an aqueous solution polymerization method, a reverse phase suspension polymerization method or a precipitation polymerization method. For example, as an aqueous solution polymerization method, a monomer component and a crosslinking agent are uniformly dissolved in water or a hydrophilic organic solvent that can be uniformly mixed with water, or a solvent such as a mixed solvent thereof. A method may be mentioned in which dissolved oxygen in the system is removed by substitution with an inert gas or the like, and then a polymerization initiator is added and reacted. The polymerization initiation temperature is usually about 20 to 90 ° C., and the reaction time is about 1 to 10 hours. When using a component that is hardly soluble in water as a monomer, it is desirable to use a hydrophilic organic solvent in combination.

  Representative examples of the hydrophilic organic solvent include, for example, lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol, cyclic ethers such as tetrahydrofuran and dioxane, acetone, acetonitrile, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and the like. Can be mentioned. Of these, tetrahydrofuran, acetonitrile, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like are particularly preferable.

  In addition, as the polymerization initiator, a peroxide that is uniformly dissolved in a solvent, an organic or inorganic peracid or a salt thereof, an azobis-based compound alone or a redox-based compound in combination with a reducing agent is used. Typical examples include t-butyl peroxide, t-amyl peroxide, cumyl peroxide, acetyl peroxide, propionyl peroxide, benzoyl peroxide, benzoylisobutyryl peroxide, lauroyl peroxide, t-butyl. Hydroperoxide, cyclohexyl hydroperoxide, tetralin hydroperoxide, t-butyl peracetate, t-butyl perbenzoate, bis (2-ethylhexyl peroxydicarbonate), 2,2′-azobisisobutyronite , Phenylazotriphenylmethane, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride Salt, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, persulfate and triethylamine, triethanolamine And combinations with tertiary amines such as dimethylaniline.

  Of these, t-butyl peroxide, benzoyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [ 2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, sodium persulfate, Preference is given to potassium sulfate or ammonium persulfate alone, or a combination of these persulfates with tertiary amines such as triethylamine, triethanolamine or dimethylaniline.

  There is no restriction | limiting in particular as a polymerization apparatus used when manufacturing the cationic group containing copolymer which concerns on this invention, For example, a general kneader and a cylindrical reaction container are used.

  In the aqueous solution polymerization method, an example of a procedure for producing the cationic group-containing copolymer according to the present invention is shown. An aqueous solution of 10 to 50% by weight of the monomer mixture is fed into a kneader having a lid, and is necessary. Depending on the system, the system is replaced with an inert gas such as nitrogen, a water-soluble radical polymerization initiator is added, the polymerization is started at 20 to 90 ° C., and the hydrogel polymer produced as the polymerization proceeds Examples thereof include a method of completing the polymerization while being subdivided by a shearing force generated by rotation of a kneader blade. Of course, the scope of the present invention is not limited by this example. The initial concentration of the aqueous monomer mixture used here is preferably 10 to 50% by weight.

  The amount of the polymerization initiator used is in the range of 0.01 to 5 mol%, preferably 0.01 to 3 mol%, particularly preferably 0.01 to 1 mol%, based on the monomer component. Incidentally, when the amount of the polymerization initiator used is 5 mol% or less based on the monomer component, the degree of polymerization of the polymer chain of the main chain is increased, and the proportion of polymer chains that are not crosslinked is reduced. Performances such as expected water absorption capacity and thickening action are fully exhibited. On the other hand, when it is 0.01 mol% or more, the reaction rate of the polymerization reaction is increased and the amount of residual monomer is reduced, which is preferable.

  The reaction product is in the form of a gel containing the solvent used in the reaction, and is usually pulverized with a rotary cutter or the like, further dried by removing the solvent by a method such as heating or decompression, and pulverized to obtain a powder.

  Further, an aqueous solution polymerization method using a general cylindrical closed reaction vessel is also used. In this case, the system is replaced with an inert gas such as nitrogen as necessary while adding or dripping an aqueous solution of 10 to 50% by weight of the monomer mixture, and a water-soluble radical polymerization initiator is added. In addition, there is a method in which polymerization is started by heating at room temperature or 30 to 80 ° C. to obtain a liquid copolymer.

  In the reversed-phase suspension polymerization method, the monomer component and the crosslinking agent are uniformly dissolved in water and the polymerization reaction is performed by suspending or emulsifying in an organic solvent that is not uniformly mixed with water using a dispersant or the like. . As a polymerization initiator, not only a water-soluble thing but a thing soluble in an organic solvent is necessarily used. As the organic solvent used here, in addition to the above, for example, hydrocarbon organic solvents such as hexane, cyclohexane, heptane, octane, benzene, toluene, xylene, ethylbenzene, and halogenated carbonization such as carbon tetrachloride and dichloroethane. Hydrogen-based organic solvents, mineral oil such as Isobar, etc. are also used.

  Further, as the dispersant, for example, sorbitan monostearate, sorbitan monopalmitate, polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, sugar ester, etc., and more generally used as an emulsifying dispersant. Surfactant etc. are mentioned.

  Removal of dissolved oxygen in the system, treatment of reaction products, etc. are the same as described above, and the reaction conditions are not necessarily limited, but are generally as follows. Solvent usage: equimolar to 20 times the monomer aqueous solution, preferably equivalent to 10 times, polymerization initiator usage: 0.01 to 5 mol%, preferably 0.01 based on the monomer component ˜3 mol%, polymerization initiation temperature: about 10 to 90 ° C., reaction time: about 1 to 10 hours.

  In the cationic group-containing copolymer according to the present invention, the viscosity of a 1% by weight aqueous solution is preferably 5 mPa · s or more, more preferably 10 mPa · s or more, and further preferably 15 mPa · s or more. Further, the cationic group-containing copolymer according to the present invention preferably has a 10 wt% aqueous solution viscosity of 500 mPa · s or more, more preferably 1000 mPa · s or more, and still more preferably 3000 mPa · s or more. These viscosities are measured by a B-type viscometer at a rotor rotational speed of 60 rpm after allowing a 1 wt% aqueous solution or a 10 wt% aqueous solution to stand in a thermostatic bath at 25 ° C. for 30 minutes or more.

  The cationic group-containing copolymer according to the present invention preferably has no spinnability in a 1% by weight aqueous solution, and further in a 10% by weight aqueous solution.

  The cationic group-containing copolymer in the present invention can be obtained as a solution, powder, block, or dispersion. The preferred embodiment of the paper surface treatment agent of the present invention is preferably 0.1 to 30% by weight, more preferably 0.5 to 20% by weight, and still more preferably the cationic group-containing copolymer according to the present invention. An aqueous solution or water dispersion containing 0.8 to 10% by weight.

  In the present invention, the method for treating the surface of the paper with the surface treatment agent containing the cationic group-containing copolymer is not particularly limited, and is applied to the surface of a base paper or a coating base paper prepared in advance. Coating is suitable as the treatment.

The paper that is the target of the surface treatment agent of the present invention is mainly made of pulp, and preferably has a density of 0.30 to 1.00 g / cm ³ , more preferably 0.35 to 0.00. 85 g / cm ³ . When the density is 0.30 g / cm ³ or more, a decrease in paper strength can be suppressed, so that the frequency of sheet cutting during coating is reduced and stable operation is possible. In addition, since the surface treatment agent of the present invention is appropriately processed on the surface of the base paper, the paper having a density of 1.00 g / cm ³ or less has an appropriate air resistance, and the blister resistance during offset printing is good. There are no restrictions on the use as coated paper for printing.

  As the pulp used for the base paper, any pulp made of wood or herbaceous fibers, which are vegetable fibers, can be used. That is, bleached chemical pulp (NBKP, LBKP, etc.), mechanical pulp (TMP, CTMP, GP, RGP, etc. and bleached pulp thereof), high yield pulp (SCP, CGP, etc. and bleached pulp thereof) and Recovered pulp such as waste paper pulp, deinked waste paper pulp (DIP), and bleached pulp (BDIP) can be used.

  Moreover, you may add auxiliary chemicals for paper manufacture, such as a filler, a paper strength enhancer, a sizing agent, a yield improver, a drainage improver, and a bulkiness agent, as needed. Examples of sizing agents include alkyl ketene dimer sizing agents, alkenyl succinic anhydride sizing agents, and neutral rosin sizing agents. Examples of the filler include calcium carbonate.

The treatment amount of the surface treatment agent in the present invention (e.g., coating weight), preferably 0.01~3.0g / m ² as dry weight per sheet one side, more preferably, 0.02~2.0g / m ² , more preferably 0.03 to 1.0 g / m ^2, and even more preferably from 0.05 to 1.0 g / m ^2. When it is 0.01 g / m ² or more, a coating liquid permeation suppressing effect is exhibited, and when it is 3.0 g / m ² or less, the total treatment amount (for example, coating amount) is 6 g / m ² or less. Paper weight reduction is achieved.

  The treatment method for the surface treatment agent can be appropriately selected from known methods. In particular, a two-roll size press, a blade metalling size press, a rod metalling size press, a curtain coater, a die coater, a gravure coater, and a kiss coater. A bar coater, a roll coater, a pound type size press, a gate roll coater, a spray coater and the like are preferable.

  The method for applying the surface treatment agent to the paper surface is not limited, but as a general method, a solution or dispersion containing the cationic group-containing copolymer according to the present invention is used. As the solvent or dispersion medium in this case, water or an organic solvent is used, and water is particularly desirable.

  When the solution or dispersion is used, the cationic group-containing copolymer according to the present invention, which is a powder or block obtained by copolymerization, has an average particle size of 1 mm or less, preferably 300 μm or less, by a method such as pulverization. More preferably, the average particle size is 50 μm or less, and the mixture is mixed with a solvent or a dispersion medium to be used as a solution or a dispersion. When the average particle size of the copolymer is 1 mm or more, it is not desirable because it takes time for dissolution and dispersion. When the cationic group-containing copolymer is obtained as a solution or dispersion, it is used as it is or diluted.

  The present invention relates to a coated paper in which a coating layer of a specific coating liquid mainly composed of a pigment and a binder is provided on a coating base paper obtained by treating the surface of the paper with the specific surface treatment agent. That is, the present invention relates to a coated paper in which a coating layer of a coating liquid containing a pigment and a specific binder is provided on the surface treated with the surface treatment agent according to the present invention.

  The coating liquid according to the present invention is selected from a styrene / butadiene polymer having a glass transition temperature of −40 ° C. to 60 ° C. and a (meth) acrylic acid ester polymer having a glass transition temperature of −40 ° C. to 60 ° C. as the binder. At least one polymer [hereinafter referred to as component (D)]. (D) Tg of a component is -30 degreeC or more, Furthermore, -25 degreeC or more is preferable. When Tg is −40 ° C. or higher, the coated layer formed by drying and calendering does not lose the smoothness of the coated paper surface due to internal stress generated during calendering, and high gloss performance is obtained. Further, when Tg is 60 ° C. or lower, Tg is not higher than the normal calendering temperature, so that sufficient smoothness is obtained even after calendering and high gloss performance is obtained.

  Here, the Tg of the binder is measured by a differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments Inc., heating rate 4 ° C./min).

  As the component (D), a styrene / butadiene polymer having a Tg in the above range and / or a (meth) acrylic acid ester polymer having a Tg in the above range is used. Since these polymers have moderate elasticity, they can exhibit the ability as a binder and form a good coating layer. In addition, (meth) acrylic acid means methacrylic acid and / or acrylic acid (hereinafter the same).

  The component (D) styrene / butadiene-based polymer contains styrene and butadiene as constituent monomers, and monomers other than styrene and butadiene include acrylonitrile and vinylpyridine, acrylic acid, methacrylic acid, itaconic acid, Vinyl monomers having a carboxyl group such as fumaric acid and maleic acid are used.

  The component (D) component (meth) acrylic acid ester-based polymer contains (meth) acrylic acid ester as a constituent monomer, and monomers other than (meth) acrylic acid ester include styrene, acrylonitrile, and acrylic acid. Vinyl monomers having a carboxyl group such as methacrylic acid, itaconic acid, fumaric acid and maleic acid are used.

  The Tg of the component (D) is a formula described in page 23 of the mechanical properties of the polymer (L. NIELSEN, translated by Shigeharu Onoki, Chemical Dojin, 1st edition, 7th edition, issued on May 1, 1969). (8) Copolymer composition and glass transition temperature) and the like can be designed in a desired range. For example, in the case of a styrene / butadiene-based polymer, a high Tg polymer can be obtained by increasing the styrene ratio, while a low Tg polymer can be obtained by increasing the butadiene ratio. In the case of a styrene / (meth) acrylate polymer, a high Tg polymer can be obtained by increasing the styrene ratio, while a low Tg polymer can be obtained by increasing the (meth) acrylate ratio. Can be obtained.

  The weight average molecular weight of the component (D) polymer is preferably 10,000 or more, and more preferably 20,000 or more. When the molecular weight of the component (D) polymer is 10,000 or more, sufficient strength and adhesiveness can be obtained in the coating layer. The weight average molecular weight can be measured by a GPC method using chloroform as a solvent and polystyrene as a standard substance.

  Examples of the method for synthesizing the component (D) polymer include a method of producing using a general radical polymerization method.

  Specific examples of the component (D) include styrene / butadiene-based polymers, (D1) styrene / butadiene copolymers, styrene / butadiene / acrylonitrile copolymers, styrene / butadiene / vinylpyridine copolymers, and these copolymers. (D) a copolymer of (meth) acrylic acid ester and styrene as a (meth) acrylic acid ester polymer, (meth) A copolymer of acrylic acid ester, styrene, and (meth) acrylic acid can be mentioned.

  In the present invention, as the binder, compounds other than the component (D) such as vinyl acetate polymer, ethylene vinyl acetate polymer, oxidized starch, phosphate esterified starch (phosphate modified starch), carboxymethyl cellulose, casein, and polyvinyl alcohol are used. Can be used.

  In the present invention, the binder and the component (D) are preferably used in the range of 5 to 50% by weight, more preferably 5 to 30% by weight, based on 100% by weight of the pigment. Moreover, it is preferable that (D) component is 50 to 100 weight% in the whole quantity of a binder, and also 60 to 99.8 weight%.

  The coating liquid of the present invention is preferably an anionic coating liquid. The “anionic” coating liquid refers to a coating liquid containing a component selected from a polymer having an anionic group such as carboxylic acid and sulfonic acid, an anionic emulsifier, and an anionic dispersant. The anionic emulsifier may be an anionic emulsifier used in emulsion polymerization of a polymer. The anionic dispersant may be an anionic dispersant used in producing the coating liquid.

  In the present invention, when a specific cationic group-containing copolymer is present on the base paper surface, when a coating liquid mainly composed of a pigment and a binder having a specific Tg is applied, a part of the coating liquid is It is presumed that high gloss performance can be obtained by suppressing the penetration of the coating liquid containing an inorganic pigment as a main component into the paper by agglomeration and existing more on the paper surface. Also from such a viewpoint, it is preferable to use an anionic coating solution.

  Moreover, as a pigment of a coating liquid, organic pigments, such as inorganic pigments, such as a kaolin, clay, a calcium carbonate, and titanium dioxide, and a plastic pigment, can be used. The coating liquid preferably contains 40 to 70% by weight, more preferably 50 to 65% by weight of pigment.

  The coating solution contains water. The water content is preferably 20 to 55% by weight, more preferably 25 to 50% by weight. The effective component concentration (concentration of components other than water) is preferably 80 to 45% by weight, more preferably 75 to 55% by weight.

  Moreover, the coating liquid can also contain various adjuvants normally used, such as a dispersing agent, a thickener, a thickener, a water retention agent, an antifoamer, and a water resistance agent, as needed. These auxiliaries can be used in an amount usually used in the art. For example, they are used in an amount of 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, based on 100% by weight of the pigment. The

  As coating methods of coating liquid, blade coater, air knife coater, gate roll coater, blade metering size press, rod metering size press, curtain coater, die coater, blade coater, roll coater, pound type size press, A known method such as a gate roll coater can be used.

The thickness of the coating layer is not particularly limited and is set according to the application and quality of the coated paper. From the viewpoint of obtaining high gloss paper, the coating amount of the coating liquid (in terms of solid content) is one side. per, by dry weight, 3 g / m ² or more, more preferably 3 to 30 g / m ^2, more preferably from 4~25g / m ^2.

  As a drying method, a normal method such as a steam heater, a hot air heater, an infrared heater, a gas heater, or a cylinder dryer is used. Further, smoothing processing such as super calendar and soft calendar is performed as necessary.

In order to further exhibit the effect of the present invention, the density of the coated paper is preferably from 1.5 g / cm ³ or less, more preferably 0.40~1.40g / cm ^3.

  The coated paper of the present invention is, for example, used for catalogs, posters, book paper, magazines, newsprint paper, etc., for coated printing paper for offset printing, gravure printing, etc., or PPC paper, foam paper, inkjet It can be used for information paper such as paper. In addition, the coated paper of the present invention is effective for various printing coated papers that require improved surface gloss such as art paper, medium-coated paper, high-quality coated paper, fine-coated paper, and cast-coated paper. Can be used.

  According to the present invention, after treating a surface treatment agent containing a cationic group-containing copolymer on at least one surface of a paper mainly composed of pulp, a pigment and a binder are treated on the treated surface of the paper with the surface treatment agent. In which a coating layer of a coating solution containing a coating liquid is provided, wherein the cationic group-containing copolymer is a cationic group-containing copolymer of the component (A) according to the present invention. There is provided a method for producing a coated paper, wherein the binder is the polymer compound of the component (B) according to the present invention.

  Hereinafter, “parts” and “%” indicating the blending amounts all indicate “parts by weight of solids” and “% by weight of solids”.

[Method for producing cationic group-containing copolymer]
A cationic group-containing copolymer was produced by the following method using the monomers shown in Table 1.

<Production Example 1 of cationic group-containing copolymer>
In a 2 L beaker, 560.0 g of ion-exchanged water, MOEDES (Equimolar adduct of dimethylaminoethyl methacrylate and dimethyl sulfate (effective content 90% by weight), both reagents, Wako Pure Chemical Industries, Ltd.) 413.67 g (effective) 372.30 g), AAm (N, N-dimethylacrylamide, reagent, manufactured by Wako Pure Chemical Industries, Ltd.) 84.98 g, NK-14G (crosslinking agent, polyethylene glycol dimethacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) 1.056 g and V-50 (polymerization initiator, 2,2≡-azobis (2-amidinopropane) dihydrochloride, manufactured by Wako Pure Chemical Industries, Ltd.) 0.707 g were mixed to prepare monomer aqueous solution A. . A 5 L glass container was charged with 1977 g of cyclohexane and 4.58 g of sugar ester S-770 (manufactured by Mitsubishi Kasei Co., Ltd.) as a dispersing agent, and uniformly dissolved at 60 ° C. for 1 hour. After dissolution, the mixture was cooled to 30 ° C. to obtain Dispersant Solution B.

  The monomer aqueous solution A is added to the dispersant solution B, set in a homomixer (ROBOMICS, manufactured by Tokki Kika Kogyo Co., Ltd.), and stirred at 9000 rpm for 4 minutes to obtain a monomer dispersion having an average particle size of 5 μm. . The entire amount was charged into a 5 L SUS tank equipped with a stirrer, a thermometer, and a cooling tube, and after replacing with nitrogen, the temperature was raised and polymerization was carried out at 70 ° C. for 1 hour. Further, after aging at 70 ° C. for 1 hour, a dehydrating tube with a cooling tube was attached, and 532 g of water was removed from the system over about 2 hours. As dehydration progressed, the temperature in the tank rose from 70 ° C to 81 ° C.

  Subsequently, the mixture was cooled to 40 ° C. or lower, and the contents were transferred to a stainless steel tray and dried with hot air at 80 ° C. to remove the solvent. Thus, white and granular cationic group-containing copolymer 1 was obtained. The cationic group-containing copolymer 1 used in the examples was lightly pulverized in a household coffee mill for about 1 second to obtain a cationic group-containing copolymer 1 having an average particle size of 3.8 μm.

<Production example 2 of cationic group-containing copolymer>
In accordance with Production Example 1 of a cationic group-containing copolymer, a cationic group-containing copolymer 2 having an average particle size of 4.0 μm was obtained with the monomer composition shown in Table 1.

<Production Example 3 of Cationic Group-Containing Copolymer>
DADMAC (diallyldimethylammonium chloride, 65% aqueous solution, manufactured by Daiso Corporation) in a stainless steel kneader having two sigma-type stirring arms with an internal volume of 1 liter and externally circulating 70 ° C. oil in a jacket. 92 g (solid content 29.85 g), acrylamide (AAm, reagent, manufactured by Wako Pure Chemical Industries, Ltd.) 48.28 g, NK-14G (crosslinking agent, polyethylene glycol dimethacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) A monomer aqueous solution previously substituted with nitrogen consisting of 0214 g and ion exchanged water 350 g was added, and the temperature of the monomer aqueous solution was increased while nitrogen gas was blown into the reaction system for 30 minutes and nitrogen was substituted in the reaction system. Next, 0.22 g of V-50 was added as a polymerization initiator. The viscosity increased 15 minutes after the addition of the polymerization initiator, and the entire system became a soft gel after 1 hour. The polymerization was continued for 4 hours. The soot-like polymer was taken out and dried at 95 ° C. Then, it grind | pulverized with the coffee mill and the jet mill. The pulverized crosslinked particles were classified with a high volter to obtain a cationic group-containing copolymer 3. (Average particle size 45μm)

<Cationic group-containing copolymer 4>
As the cationic group-containing copolymer 4, commercially available GAFQUAT HS-100 [vinylpyrrolidone / methacrylamideamidopropyltrimethylammonium chloride copolymer, manufactured by GAF Japan] was used.

[Binder production method]
<Binder Production Example 1>
In a glass reactor equipped with a 2 L stirrer, thermometer, and cooling tube, 475.25 g of ion-exchanged water and 28.00 g of anionic surfactant Emar 20C (solid content 25%, manufactured by Kao Corporation) were added to acrylic acid. (Hereinafter referred to as AA) (manufactured by Toagosei Chemical Co., Ltd.) 0.06 g, 2-ethylhexyl acrylate (hereinafter referred to as 2EHA) (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) 4.29 g, styrene A monomer solution mixed with 13.15 g (hereinafter referred to as “St”) (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was charged and purged with nitrogen for 30 minutes. Ammonium persulfate (hereinafter referred to as APS) (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) (0.45 g) was dissolved in 5 g of ion-exchanged water, added to the reaction system, and heated to 80 ° C. while purging with nitrogen. . After confirming the cloudiness, a monomer solution in which 1.20 g of AA, 81.46 g of 2EHA, and 249.84 g of St were mixed was added dropwise over 2 hours. An aqueous solution in which 1.35 g of APS was dissolved in 15 g of ion-exchanged water was divided into three during dropping, and charged into the system. Subsequently, after aging at 80 ° C. for 2 hours, the mixture was cooled to 35 ° C. or lower to obtain a binder 11.

<Binder Production Example 2>
Binder 12 was obtained with the monomer composition shown in Table 3 in accordance with Binder Production Example 1.

[Production method of base paper]
<Pulp raw material>
As a pulp raw material, virgin pulp was used in which LBKP (hardwood bleached pulp) was disaggregated and beaten with a beater at 25 ° C. to obtain a 2.2 wt% LBKP slurry. The Canadian standard freeness (JIS P 8121) of this product was 450 ml.

<Paper making method>
The virgin pulp slurry was weighed so that the pulp basis weight of the pulp sheet after papermaking would be 80 g / m ² ± 1 g / m ^2, and paper was made with 80 mesh wire (area 625 cm ² ) using a square tappi paper machine. A sheet was obtained. The sheet after paper making was pressed with a press at 3.5 kg / cm ² for 5 minutes and dried at 105 ° C. for 2 minutes using a mirror dryer. The dried pulp sheet was conditioned at 23 ° C. and a humidity of 50% for 1 day to obtain a base paper for surface treatment. The bulk density of the base paper was 0.574 g / cm ³ .

[Method of treating surface treatment agent]
A 50 g / m ² casting film was formed on a glass plate using an aqueous solution containing the cation group-containing copolymer of Table 1 at a predetermined concentration as a surface treating agent using a wire coater. Next, the base paper (width 12.5 cm × length 25 cm) is placed on the casting film, covered with one piece of 100 g / m ² filter paper, and the roll (diameter 200 mm, width 200 mm, linear pressure 230 g / cm) is rolled, The treatment agent was transferred from the glass plate to the base paper surface. Subsequently, it dried for 2 minutes at 105 degreeC using the mirror surface dryer. These series of operations were operated promptly without any intermission. The dried pulp sheet was conditioned at 23 ° C. and a humidity of 50% for 1 day to obtain a coated base paper. In addition, aqueous solution density | concentration etc. were adjusted so that application quantity (solid content conversion) might become the numerical value in Table 4.

[Production method of coated paper]
On one side of the coating base paper (surface-treated paper) obtained above, a coating liquid is applied to a blade-type coating machine (flexible trailing blade coater, coating speed 140 m / min, coating pressure 0.5 to 1). The coating amount after drying was 14.5 g / m ² at 0.5 kg / cm ² (manufactured by Kumagaya Riki Kogyo Co., Ltd.). Subsequently, it dried using the mirror surface dryer for 20 second at 105 degreeC.

  Here, the coating liquid contains 50 g of calcium carbonate (FMT97, manufactured by Phimatech Co., Ltd.) as a pigment and 50 g of fine kaolin (Amazon Plus, manufactured by Kadem Co., Ltd.), and polyacrylic acid soda (poise 535M) as a dispersant. , 31% effective content, manufactured by Kao Corporation), 0.075 g as an effective component, and 0.020 g of 2N caustic soda were added and dispersed, and 11 g of the binder of Table 2 as an effective component per 100 g of the pigment, It is a coating solution prepared by mixing 3.0 g of modified starch (phosphate-modified starch, manufactured by Oji Corn Starch Co., Ltd.) with an effective content of 65% (the balance is water).

  Further, a coated paper is obtained by performing a 2-nip treatment with a linear pressure of 200 kg / cm (pressure 49 MPa), a processing speed of 10 m / min, a roll temperature of 50 ° C., using a test super calendar (manufactured by Kumagaya Riki Kogyo Co., Ltd.). It was.

[Method for evaluating coated paper]
<Application amount of surface treatment agent>
The coated base paper (surface-treated paper) obtained by the treatment with the surface treatment agent and the base paper before the surface treatment are each conditioned at 23 ° C. and a humidity of 50% for 1 day, and the difference between them is the area of the sample (width) The coating amount (g / m ² ) was calculated from the value divided by 12.5 cm × length 25 cm (average value of 3 sheets to be measured). In the case where coating with a surface treatment agent was not performed, the coating amount was 0 g / m ² .

<Glossiness>
Using a gloss meter (GMX-203 type, 75 ° type, manufactured by Murakami Color Research Laboratory Co., Ltd.) according to JIS P8142, the white paper glossiness of the coated surface was measured, and the average value was obtained (number of measurement points: 6 / 1 sheet, 3 sheets measured, average value of 18 points). The results are shown in Table 4. The greater the glossiness, the better the glossiness, and the difference of 1% (1 point) in glossiness is fully recognized as a significant difference, and the difference becomes more prominent when the difference becomes 3% (3 points). It becomes.

<Bulk density>
The tightness was measured according to JIS P8118 to obtain the bulk density (average value of the number of measured sheets 3). The results are shown in Table 4. The smaller the bulk density, the lighter the weight, and the difference of 0.02 in the bulk density is sufficiently recognized as a significant difference.

  In addition, about the component used by the Example and the comparative example, the monomer composition etc. of a cation group containing copolymer are shown in Table 1, the kind and Tg of a binder are shown in Table 2, and the single quantity of the binders 11 and 12 in Table 3. Body composition etc. were shown.

  In Table 4, the surface treatment agent according to the present invention was applied to handmade paper, and the coating paper of Examples 1 to 12 was coated with a coating solution using a binder having a specific Tg, and the treatment with the surface treatment agent. When compared with the coated paper of Comparative Example 1 that is not treated, that is, untreated, it is clear that Examples 1 to 12 show much higher gloss. Similarly, when Examples 1 to 12 and Comparative Examples 2 to 5 using a binder having a low Tg as a binder of the coating liquid are compared, Examples 1 to 12 clearly show higher glossiness. I understand.

  In some examples and comparative examples in Table 4, the same evaluation as above was performed on the coated paper obtained in the same manner as described above except that the coating amount of the coating liquid was changed as shown in Table 5. . The results are shown in Table 5. Moreover, the graph which shows the relationship between the coating amount of a coating liquid and the glossiness of a coated paper among the results of Table 5 was shown in FIG. In FIG. 1, curve A is the result of Examples 2a, 2, 2b, curve B is the result of Examples 8a, 8, 8b, curve C is the result of Comparative Examples 4a, 4, 4b, and curve D is the comparison. The results of Examples 1a, 1, 1b are connected.

  From Table 5 and FIG. 1, it can be seen that, at the same coating amount, the combination of the specific surface treatment agent and the specific coating liquid selected in the present invention significantly improves the glossiness. Therefore, when the glossiness is the same, the coated paper of the present invention can significantly reduce the coating amount of a coating liquid containing an inorganic pigment having a high specific gravity as a main component, thereby reducing the bulk density of the coated paper. The weight of the coated paper can be reduced.

  Thus, in this invention, glossiness is improving compared with the existing technique (for example, comparative example 1) by giving a specific surface treating agent to base paper, and also apply | coating a specific coating liquid. It is clear. These are effective coatings that contribute to improved gloss compared to the comparative examples because the penetration of the coating solution is suppressed when the coating amount and calendar conditions of the coating solution are the same. This seems to be because there are many layers.

Claims (9)

After treating a surface treatment agent containing a cationic group-containing copolymer on at least one side of a paper mainly composed of pulp, a coating containing a pigment and a binder is treated on the surface treated with the surface treatment agent of the paper. A coated paper provided with a coating layer of a working fluid,
The cationic group-containing copolymer is at least one selected from (A) a vinyl monomer represented by the general formula (I) and a vinyl monomer represented by the general formula (II) [hereinafter, ( A) and at least one selected from (B) a cationic group-containing vinyl monomer represented by the general formula (III) and a cationic group-containing vinyl monomer represented by the general formula (IV) A cationic group-containing copolymer obtained by polymerizing a seed [hereinafter referred to as component (B)],
The binder is at least one polymer selected from a styrene / butadiene-based polymer having a glass transition temperature of −40 ° C. to 60 ° C. and a (meth) acrylate polymer having a glass transition temperature of −40 ° C. to 60 ° C. ,
Coated paper.

[Wherein, R ¹ represents a hydrogen atom or a methyl group, and R ² and R ³ are the same or different and represent a hydrogen atom or a linear or branched alkyl group or alkenyl group having 1 to 4 carbon atoms. ]

[Wherein R ¹ represents the above-mentioned meaning, m represents a number of 0 or 1, A ¹ and A ² are the same or different, and the formula — (CH ₂ ) _n — (n is an integer of 2 to 6] And B represents a group selected from —O— and —CH ₂ —. ]

[R ¹ is as defined above, R ⁴ and R ⁵ are the same or different and each represents an alkyl group or alkenyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Y represents —O—, —NH— or —O—CH ₂ CH (OH) —, Z represents a linear or branched alkylene group having 1 to 4 carbon atoms, and X represents an acid. A conjugated base, a halogen atom or an alkyl sulfate group having 1 to 4 carbon atoms is shown. ]

[Wherein, R ⁷ and R ⁸ are the same or different and each represents a hydrogen atom or a methyl group; R ⁹ and R ¹⁰ are the same or different and each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Indicates meaning. ]   The styrene / butadiene-based polymer having a glass transition temperature of −40 ° C. to 60 ° C. and / or the (meth) acrylic acid ester-based polymer having a glass transition temperature of −40 ° C. to 60 ° C. are a carboxyl group, a hydroxyl group, and a sulfone. The coated paper of Claim 1 which is an anionic polymer formed by copolymerizing the monomer containing the vinyl monomer which has at least 1 type of group chosen from group.   The styrene / butadiene-based polymer having a glass transition temperature of −40 ° C. to 60 ° C. and / or the (meth) acrylic acid ester-based polymer having a glass transition temperature of −40 ° C. to 60 ° C. are acrylic acid, methacrylic acid, and itacon. The coated paper according to claim 1 or 2, which is an anionic polymer obtained by copolymerizing a monomer containing at least one monomer selected from acid, fumaric acid and maleic acid.   The cationic group-containing copolymer comprises (A) component, (B) component, and (C) a crosslinkable vinyl monomer [provided that the monomer represented by the general formula (IV) is excluded. The coated paper according to any one of claims 1 to 3, obtained by polymerizing [hereinafter referred to as component (C)].   The component (A) is at least one selected from (meth) acrylamide, N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide. Coated paper.   The amount of the component (C) in the cationic group-containing copolymer is 0.0005 to 5 mol% in the total of the component (A), the component (B) and the component (C). Coated paper. The processing amount of the surface treating agent, per side, a 0.01~3.0g / m ² by dry weight, coated paper according to any one of claims 1-6. The coating amount of the coating liquid, per side, is 3 to 30 g / m ² by dry weight, coated paper according to any one of claims 1-7. The coated paper of any one of Claims 1-8 whose density is 1.5 g / cm < ³ > or less.

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