JP5548361B2 - Manufacturing method of coated paper - Google Patents

Description

  The present invention relates to a coated paper and a method for producing the same.

  In recent years, the visualization and colorization of printed matter has progressed rapidly, and the demand for coated paper having a smooth coating layer on the paper surface as an ink-receiving layer is increasing year by year as compared to non-coated printing paper. In addition, with the recent trend toward cost reduction, there is an increasing demand for weight reduction while maintaining the conventional paper thickness and print quality. The smoothness of the coating layer is important for the printing quality of the coated paper, and surface smoothing is generally performed with a super calender or soft nip calender. However, this process pressurizes the paper to increase the smoothness of the surface, and at the same time the density increases and the paper thickness decreases. For this reason, if the paper thickness is maintained, the weight of the paper increases.

Therefore, attempts have been made to develop a low density and thick paper having high gloss and smoothness. For example, a technique (Patent Document 1) that applies a hydrophilic paint after forming a dry film layer of an organic polymer gel on paper having a density of 0.30 to 1.00 g / cm ³ is disclosed.

In addition, various polymer compounds such as starch have been conventionally used as paper surface treatments and adhesives, and various improvements have been proposed. For example, in order to obtain paper having high rigidity even if the amount of the surface coating agent applied is small, a technique using specific starch made from raw starch is disclosed (Patent Document 2). Moreover, in order to suppress the dispersion | variation in a viscosity, the method of adding a basic peroxide and gelatinizing the aqueous starch suspension is disclosed (patent document 3). In addition, after adding a specific water-soluble polymer such as a cationic water-soluble polymer or cationic starch to a papermaking raw material, an aqueous solution of an anionic water-soluble polymer with a reduced apparent viscosity is added. An improvement method is disclosed (Patent Document 4).
JP 2007-107171 A JP 2006-161216 A JP-A-5-163471 JP 2001-295196 A

  Obtaining coated paper with high glossiness is an issue in the industry, but the type of polymer compound used in the surface treatment agent and the coating amount are factors that affect glossiness. is there. Patent Document 1 discloses a technique for forming a dry film using a water-soluble polymer gelled with a polyvalent metal. However, since gelation occurs instantaneously on the surface layer of the base paper, it is uniform on the surface of the base paper. It is difficult to form the surface treatment layer and it is difficult to control the surface treatment layer. Furthermore, since the water-soluble polymer is gelled by polyvalent metal ions, handling is difficult, and implementation on an industrial scale is often accompanied by difficulty. Patent Document 2 also mentions that the coating amount of the surface treatment agent is small, but it is not sufficient as a means for increasing the glossiness.

  The subject of this invention is providing the manufacturing method of the coated paper from which the coated paper with high glossiness is obtained.

In the present invention, the B-type viscosity of a 5 wt% aqueous solution at 25 ° C. is 1800 mPa · s or more and 120,000 mPa · s or less, and the normal stress at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. 0-2400 Pa high molecular compound (a) [hereinafter referred to as component (a)] and electrolyte other than peroxide salt that releases metal ions in water (hereinafter referred to as component (b)) And a surface treatment step of obtaining a surface-treated base paper by applying a surface treatment agent containing water to a paper containing pulp as a main raw material, and a pigment and a binder on the surface-treated base paper obtained in the surface treatment step A coating process for obtaining a coated paper by coating a coating liquid containing an agent and water,
The present invention relates to a method for producing a coated paper.

  In the present invention, the B-type viscosity of a 5% by weight aqueous solution at 25 ° C. is 1800 mPa · s or more and 120,000 mPa · s or less, and the normal at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. The present invention relates to a surface treatment agent for coated paper containing a polymer compound (a) having a stress of 0 to 2400 Pa, an electrolyte (b) other than a salt of a peroxide that releases metal ions in water, and water.

The present invention also provides a coated paper surface treatment agent according to the present invention, wherein at least one side of a paper mainly composed of pulp is treated with a dry weight of 0.01 to 3.0 g / m ² per side. Concerning the base paper.

  When the surface treatment agent of the present invention is applied to the base paper surface and dried, the reason why the above problem is solved is not clear, but the coexistence of the component (a) and the component (b) allows the viscosity of the surface treatment agent. Decreases, handling becomes good, and surface treatment at a high concentration becomes possible. When the surface treatment is performed, the metal ions in the component (b) penetrate into the base paper, and the polymer compound of the component (a) remains on the base paper surface, so that the pigment and the binder are the main components. When the applied coating liquid is applied, the water in the coating liquid and the component (a) present on the surface of the base paper form a gel, so that the pigment in the coating liquid penetrates into the paper. This is presumed to be suppressed.

  According to the present invention, since the penetration of the paint into the base paper can be suppressed, a method for producing a highly glossy coated paper can be provided. Further, according to the present invention, a highly glossy coated paper can be obtained even with a small coating amount, and therefore a lighter coated paper can be provided. Such an effect of the present invention is exhibited even when the concentration of the component (a) in the surface treatment agent is lower than usual.

  The coated paper is required, for example, after a paper layer is formed on a wire mesh from a dilute liquid of pulp raw material, followed by a pressing process, a drying process, a sizing process, a drying process, a coating process, a drying process, and a calendar process. For example, it is manufactured through a humidity control process. In this invention, it has one of the characteristics in using a specific surface treating agent before a coating process in these processes. In the present invention, the coated paper includes both the coated paper after the calendar process and the coated paper after the humidity control process.

[Surface treatment process]
In the surface treatment process according to the present invention, a surface treatment agent containing a component (a) and a component (b) is applied to a paper mainly containing pulp (hereinafter, sometimes referred to as an uncoated base paper). This is a step of obtaining a base paper (hereinafter sometimes referred to as a coating base paper). The surface treatment agent may be applied on one side or both sides of the uncoated base paper.

  In the surface treatment step of the present invention, the B-type viscosity of a 5% by weight aqueous solution at 25 ° C. is 1800 mPa · s or more and 120,000 mPa · s or less, and the viscosity at a shear rate of 1000 (1 / second) at 25 ° C. is 300 mPa · s. A surface treatment agent prepared by mixing a polymer compound (a) having a normal stress of 0 to 2400 Pa, an electrolyte (b) other than a salt of a peroxide that releases metal ions in water, and water. It can be carried out as a process for obtaining a surface-treated base paper by applying it to paper made mainly of pulp.

  When using a coated base paper with a surface treatment agent applied to the surface, penetration of the pigment into the base paper is suppressed when the coating liquid is applied, and the thickness of the coating layer increases, and the coating is applied by calendar treatment. Since the surface of the layer is further flattened, it is estimated that the gloss of the resulting coated paper is improved.

  From the viewpoint of improving the glossiness of the coated paper, the polymer compound (a) according to the present invention has a B-type viscosity at 25 ° C. of a 5% by weight aqueous solution of 1800 mPa · s to 120,000 mPa · s. This viscosity was measured for a 5% by weight aqueous solution of component (a) using a BM viscometer at a rotation speed of 60 rpm and 25 ° C., but this method cannot correctly measure the viscosity in the high viscosity region. There is a case. In that case, you may employ | adopt the viscosity measured at rotation speed 5rpm and 25 degreeC using the B8R type | mold viscosity meter about 5 weight% of aqueous solution of (a) component. Therefore, in the present invention, for a 5 wt% aqueous solution of the component (a), (I) the viscosity (hereinafter referred to as viscosity (I)) and (II) measured using a BM viscometer at a rotational speed of 60 rpm and 25 ° C. ) At least one of the viscosities (hereinafter referred to as “viscosity (II)”) measured at 5 rpm and 25 ° C. using a B8R viscometer may be 1800 mPa · s or more and 120,000 mPa · s or less. Generally, the viscosity (I) method is suitable for measuring a viscosity of 10,000 mPa · s or less, and the viscosity (II) method is suitable for measuring a viscosity of 10,000 mPa · s or more.

  These viscosities (I) and (II) are values measured in detail by the method described in the examples.

  In the component (a) of the present invention, the B-type viscosity at 25 ° C. of a 5% by weight aqueous solution is preferably 2400 mPa · s or more, more preferably 3000 mPa · s or more, preferably 110000 mPa · s or less, more preferably 100,000 mPa · s or less.

  The component (a) of the present invention is a normal line at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. from the viewpoint of improving the glossiness of the coated paper and reducing the spinnability of the component (a). The stress is 0 to 2400 Pa, more preferably 10 to 2200 Pa, more preferably 50 to 2000 Pa, and still more preferably 100 to 1800 Pa. In general, when a linear polymer is applied with shear stress, force acts in the shear direction and the normal direction. The force acting in the normal direction is called normal stress, and the normal stress increases when the entanglement between molecules such as a linear polymer is strong. On the other hand, a high molecular compound having a cross-linked structure in the molecule is less likely to be entangled between the molecules, and therefore it is estimated that the normal stress shows a low value. Here, the normal stress at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) is measured by the method described in the examples.

  The component (a) of the present invention is not particularly limited as long as it satisfies the aforementioned viscosity and normal stress. Specific examples include (i) polyacrylamide, (ii) modified polyacrylamide, and (iii) dialkyl. (Meth) acrylic acid ester or (meth) acrylamide having an amino group, styrene having a dialkylamino group, vinyl pyridine, N-vinyl heterocyclic compound, acid neutralized product or quaternary ammonium salt of a monomer having an amino group , Cationic group-containing vinyl monomers such as diallyl-type quaternary ammonium salts, and hydrophilic nonionic properties such as N-alkyl (meth) acrylamide, N, N-dialkyl (1 to 3 carbon atoms) substituted (meth) acrylamide Group-containing vinyl monomer or olefinically unsaturated carboxylic acid or salt thereof, olefinically unsaturated carboxylic acid ester, Olefinic unsaturated sulfonic acid or a salt thereof, olefinic unsaturated phosphoric acid or a salt thereof, and an anionic group-containing vinyl monomer having a polymerizable unsaturated group such as an olefinic unsaturated phosphate ester, respectively. A cationic group-containing vinyl copolymer such as a vinyl copolymer obtained by polymerizing at least one monomer, (iv) cellulose such as sodium carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyalkylcellulose, and cationized cellulose; Compounds, (v) starch, etherified starch (carboxymethyl starch, hydroxyalkyl starch, cationized starch, etc.), esterified starch (acetic acid starch, phosphate starch, etc.), amphoteric starch, and crosslinked starch (methylol) Cross-linking, phosphate cross-linking, urea phosphate cross-linking, di- (Vii) sugars such as sucrose and lactose, (vii) sugars such as sucrose and lactose, (vii) guar gum modified products such as guar gum, gum arabic, xanthan gum, hydroxyalkylated guar gum and cationized guar gum, (viii) ) And other natural polymers such as glue, gelatin and agar.

  The vinyl monomers can be used alone or in admixture of two or more. The vinyl copolymer in (iii) is obtained by polymerizing a monomer containing a cationic group-containing vinyl monomer and a hydrophilic nonionic group-containing vinyl monomer or an anionic group-containing vinyl monomer. More preferably, the resulting cationic group-containing vinyl copolymer is a monomer comprising a cationic group-containing vinyl monomer and a hydrophilic nonionic group-containing vinyl monomer or an anionic group-containing vinyl monomer as main components. A cationic group-containing vinyl copolymer obtained by polymerizing the polymer is more preferable. Moreover, the vinyl copolymer which contains the crosslinkable vinyl monomer which has at least 2 vinyl group etc. in a molecule | numerator as a structural component in the said vinyl copolymer is also mentioned. The cationic group-containing copolymer has a total of 80 hydrophilic nonionic group-containing vinyl monomers or the anionic group-containing vinyl monomer and the cationic group-containing vinyl monomer among the constituent monomers. It is preferable that it is -100 mol%, More preferably, it is 90-99.9 mol%.

  Among these, a cationic group-containing vinyl copolymer (in particular, a cation obtained by polymerizing a monomer mainly composed of a cationic group-containing vinyl monomer and a hydrophilic nonionic group-containing vinyl monomer) 1 type or more compound chosen from a cationic group containing vinyl copolymer), a cationized cellulose, a cationized starch, and an amphoteric starch.

  The component (b) according to the present invention is an electrolyte other than a peroxide salt that releases metal ions in water. The component (b) is an electrolyte that is ionized into a metal ion and its counter ion in water, and thus is preferably a compound containing a metal. Examples of the metal ion include ions of monovalent metals such as sodium and potassium, and ions of polyvalent metals such as calcium, magnesium and aluminum.

  The electrolyte that releases metal ions is preferably at least one selected from inorganic salts and organic salts. Examples thereof include organic acids such as citric acid, malic acid, succinic acid, and lactic acid, or salts of inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, and phosphoric acid, and cations that form such salts include sodium, Examples thereof include alkali metals such as potassium, aluminum and the like.

  Examples of the electrolyte that releases metal ions include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

  The component (b) according to the present invention includes (b1) a water-soluble salt of an acid selected from organic acids and inorganic acids and a metal selected from alkali metals and alkaline earth metals, and (b2) alkali metals and alkalis. One or more water-soluble compounds selected from metal hydroxides selected from earth metals are preferred. (B1) Preferred specific examples of the water-soluble salt include alkali metal salts of inorganic acids such as sodium chloride, sodium sulfate, sodium phosphate, sodium borate, sodium carbonate, sodium hydrogencarbonate; alkalis of inorganic acids such as calcium chloride Earth metal salts: Alkali metal salts of organic acids such as alkyl sulfates such as trisodium citrate and sodium alkyl sulfate. (B2) Preferred specific examples of the hydroxide include sodium hydroxide and potassium hydroxide.

  In the present invention, the alkaline earth metal refers to calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), beryllium (Be), and magnesium (Mg). Further, the water solubility of the component (b) means that 90% by weight or more dissolves when 1 part by weight is added to 99 parts by weight of water at 25 ° C. The solubility is calculated from the solid content in the filtrate by filtering the aqueous solution with a filter paper (No. 2).

  The surface treatment agent used in the surface treatment step is preferably a liquid mixture containing the component (a), the component (b) and water, particularly an aqueous solution. The concentration of the component (a) in the surface treatment agent, particularly the aqueous solution containing the component (a), the component (b) and water, is preferably 0.5 to 4% by weight, more preferably 1 to 3% by weight. Further, the metal ion concentration in the surface treatment agent is preferably 0.005 to 2% by weight, more preferably 0.01 to 1% by weight, and the component (b) is preferably used in such an amount that this can be achieved. Furthermore, it is preferable that 0.01% by weight or more, further 0.05% by weight or more of the metal ions in the surface treatment agent is derived from the component (b). The (a) component and the (b) component are preferably used at a weight ratio of (a) / (b) of 100/1 to 1/1, and more preferably 50/1 to 4/1.

  The surface treatment agent according to the present invention is preferably an aqueous solution containing the component (a), the component (b) and water, and the viscosity (40 ° C.) of the aqueous solution is from the viewpoint of ease of application. At the coating temperature or 25 ° C., 1 to 5000 mPa · s is preferable, and 1 to 4000 mPa · s is more preferable. Although the preparation method of a surface treating agent is not specifically limited, For example, the method which melt | dissolves in water after mixing (a) component and (b) component with a solid, (a) The component or (b) component was melt | dissolved in water The method of adding (b) component or (a) later is mentioned. Preparation of the aqueous solution of the component (a) is usually performed while heating, but the addition time of the component (b) may be any before heating, during heating, or after cooling.

  In the present invention, it is preferable to apply a surface treatment agent at 10 to 90 ° C. to uncoated base paper. This temperature is the temperature (liquid temperature) of the surface treatment agent during coating, and is preferably 20 to 80 ° C, more preferably 30 to 75 ° C, and even more preferably 50 to 70 ° C.

  The coating of the surface treatment agent can be performed using a normal paper coating apparatus, and is not particularly limited, but as the coating apparatus, a two-roll size press coater, a gate roll coater, a blade metering size, or the like. Film transfer type roll coater such as press coater, rod metering size press coater, shim sizer, curtain coater, die coater, gravure coater, kiss coater, rod (bar) coater, air knife coater, blade coater, roll coater, spray, etc. Although a coating method using a coating apparatus such as a 2-roll size press coater, a gate roll coater, or a rod metering size press coater can keep a large amount of the surface treatment agent on the paper surface, it is more preferably used. In addition, since these papermaking coating apparatuses are usually provided with means capable of adjusting the temperature of the coating liquid (surface treatment agent), they are also suitable for using the surface treatment agent at the above temperature.

In the present invention, a surface treatment agent, on at least one side of the paper that the pulp as the main raw material, per side, 0.01~3.0g / m ² by dry weight, further 0.05~0.8g / m ² treatment (Applying) is preferable. Thereby, the surface treatment agent for coated paper according to the present invention has a dry weight of 0.01 to 3.0 g / m ² per side on at least one side of a paper mainly composed of pulp, and further 0.05 to A coated base paper treated with 0.8 g / m ² is obtained.

The coating amount of the surface treatment agent is not particularly limited, but from the viewpoint of reducing the weight of the paper, the dry weight of the component (a) is preferably 1 g / m ² or less, and 0.8 g / m ² per side of the uncoated base paper. The following is more preferable. Further, from the viewpoint of gloss improvement, 0.05 g / m ² or more preferably, 0.1 g / m ² or more is rather more preferable, 0.2 g / m ² or more is more preferred, 0.25 g / m ² or more Is even more preferable. Therefore, 0.05-1 g / m < ² > is preferable per one side of uncoated base paper.

  As the uncoated base paper to which the surface treatment agent is applied, a normal base paper for coated paper can be used. As a paper making method for obtaining an uncoated base paper, a general paper machine such as a long net type, a circular net type, a short net type, a twin wire type, and an inclined wire type paper machine can be used. In particular, the twin wire type is preferable from the viewpoint of reducing the difference between the front and back of the paper.

  As the pulp used for the base paper, any pulp made from wood or grass fibers, which are vegetable fibers, can be used. That is, bleached chemical pulp (NBKP, LBKP, etc.), mechanical pulp (TMP, BCTMP, GP, RGP, etc. and bleached pulp thereof), high yield pulp (SCP, CGP, etc. and bleached pulp thereof) and In addition, recovered pulp such as waste paper pulp and deinked waste paper pulp (DIP) and bleached pulp (BDIP) can be used. From the point of gloss of the coated paper, the pulp to be used preferably contains 50% by weight or more of chemical pulp, more preferably 90% by weight or more.

  When making paper, a sizing agent, a filler, a yield improver, a drainage improver, a paper strength improver and the like that are generally used may be added as necessary. 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. Some of these papermaking chemicals contain compounds that release metal ions in water, but even if metal ions are added internally during papermaking, there is no effect, and the component (a) of the present invention is used as a surface treatment agent. The effect of the present invention cannot be obtained unless the surface of the paper is treated together.

  Furthermore, from the viewpoint of low density, the uncoated base paper may be obtained by making a paper after adding a fiber binding inhibitor to the pulp slurry.

  The fiber binding inhibitor is a compound having an action of inhibiting binding between pulp fibers. Examples of the fiber binding inhibitor include compounds used as a surfactant having a hydrophobic group and a hydrophilic group. For example, a bulking agent for paper can be used. In the bulking agent for paper, it is presumed that hydrophilic groups are adsorbed on the pulp surface, and binding between pulp fibers is inhibited by hydrophobic groups. And since the space | gap in uncoated base paper is kept large rather than the case where the bulking agent for paper is not added, it is thought that it becomes a low density. The fiber binding inhibitor can be regarded as a so-called internal additive for papermaking, and the addition to the pulp slurry can be emulsified or dispersed in water. Examples of the compound include fatty acid polyhydric alcohol ester which is an ester of polyhydric alcohol and fatty acid, polyoxyalkylene adduct of fatty acid polyhydric alcohol ester, polyoxyalkylene adduct of higher fatty acid ester, ester of polyhydric fatty acid and alcohol. Polyhydric fatty acid alcohol ester, polyoxyalkylene adduct of polyhydric fatty acid alcohol ester, polyoxyalkylene adduct of polyamine and fatty acid ester compound, anion to the hydroxyl group of ester compound of polyhydric alcohol and fatty acid or hydroxyl carboxylic acid Ester compounds such as compounds having a group introduced therein, ester compounds of fatty acid amine polyoxyalkylene adducts and fatty acids, higher alcohol polyoxyalkylene adducts and fatty acid ester compounds, and the like Conductor: Fatty acid monoamide, polyoxyalkylene adduct of fatty acid amide amine, fatty acid polyamide amine, fatty acid diamide amine, polyalkylene polyamine / fatty acid / epichlorohydrin condensate, polyalkylene polyamine / fatty acid / urea condensate, polyvalent fatty acid and polyamine Amide compounds such as amide compounds, polyamides of polyhydric fatty acids and linear amines, and derivatives thereof; polyoxyalkylene adducts of fatty acid amide amines and ester compounds of fatty acids, etc. Compounds having higher alcohols; polyoxyalkylene adducts of higher alcohols or higher fatty acids, polyhydric alcohol-type nonionic surfactants, sugar alcohol-based nonionic surfactants, sugar-based nonionic surfactants, oil-based nonionic surfactants , Etc. other than the above Alkylene adducts and derivatives thereof; as other compounds, higher alcohols, sulfosuccinic acid derivatives, heavy units having structural units containing a surface active moiety and structural units derived from one or more of anionic monomers and cationic monomers. Coalescence, etc. can be used. Among these, from the viewpoint of reducing the density of the coated paper, it is preferable to use ester compounds and derivatives thereof, amide compounds and derivatives thereof, polyoxyalkylene adducts other than those described above, and derivatives thereof. More preferably, alcohol esters, fatty acid monoamides, polyalkylene polyamine / fatty acid / epichlorohydrin condensates, polyalkylene polyamine / fatty acid / urea condensates, polyoxyalkylene adducts of higher alcohols, and the like are used.

  The fiber binding inhibitor is preferably used in a proportion of 0.01 to 10 parts by weight, and further 0.1 to 5 parts by weight with respect to 100 parts by weight of the pulp. In addition, when using a fiber bond inhibitor, it is preferable to use together the fixing accelerator which accelerates | stimulates the fixing to the pulp of fiber bond inhibitors, such as a polyacrylamide polymer, a cationized starch, and a sulfuric acid band.

  In the present invention, from the viewpoint of improving the gloss of the coated paper, it is preferable to perform a calendar process on the uncoated base paper before the surface treatment agent is applied. As the calendar process, a calendar device such as a machine calendar, a super calendar, a soft calendar, or a gloss calendar can be used, and a machine calendar is preferable among these devices.

  Further, the Beck smoothness according to JIS-P8119 of the uncoated base paper before the surface treatment agent is applied is preferably 5 to 100 seconds, and more preferably 20 to 100 seconds, from the viewpoint of improving the gloss of the coated paper.

[Coating process]
The coating process according to the present invention is a process for obtaining a pre-calendar coated paper by applying a coating liquid containing a pigment, a binder and water to a surface-treated base paper coated with a surface-treating agent. . The coating liquid is an aqueous pigment slurry, and is applied to the surface of the coating base paper on which the surface treatment agent is applied.

  Examples of the coating liquid include pigment paint (coating color). Examples of the pigment include kaolin, precipitated calcium carbonate, finely ground heavy calcium carbonate, waxy clay, titanium dioxide, satin white, barium sulfate, water. Inorganic pigments such as aluminum oxide and organic pigments such as plastic pigments can be used. Among these, inorganic pigments are preferable from the viewpoint of economy.

Moreover, the coating liquid contains a binder (binder). Examples of the binder include aqueous solutions of polymers such as casein, starch derivatives, and fiber derivatives, and synthetic latex emulsions such as SBR (styrene butadiene rubber) and MBR (methyl methacrylate butadiene rubber). The ratio of the pigment to the binder can be adjusted depending on the type and use of the pigment, but it is preferable to add 10 to 50 parts by weight of the binder to 100 parts by weight of the pigment. In addition to pigments and binders, paint additives such as dyes, antifoaming agents, lubricants, dispersants, viscosity modifiers, and pH control agents can be used in combination with the coating liquid. The solid concentration of the coating liquid is preferably 50 to 75% by weight, and water is the remainder of the coating liquid. 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 glossy paper, the coating amount of the coating liquid (in terms of solid content) per one side of the base paper is preferably from 1 to 30 g / m ^2, more preferably 8~25g / m ^2, even more preferably from 12~20g / m ^2. In general, in order to obtain a high gloss, it is necessary to increase the coating amount of the coating solution. However, in the present invention, the gloss after the calendar process can be improved, so the coating amount of the coating solution is reduced. And lightweight paper can be obtained.

  Coating (coating) of the coating liquid onto the surface-treated base paper, which is a base paper for coating, can be performed using a normal papermaking coating device, and is not particularly limited. Film transfer type roll coaters such as roll size press coaters, gate roll coaters, blade metering size press coaters, rod metering size press coaters, shim sizers, curtain coaters, die coaters, gravure coaters, kiss coaters, rod (bar) coaters , Air knife coater, blade coater, roll coater, spray and the like, and the coating liquid is preferably applied using a blade coater.

  In the coating process according to the present invention, the water content of the surface-treated base paper is not particularly limited, but from the viewpoint of improving the glossiness of the coated paper, the water content of the surface-treated base paper is set to 0 to 10% by weight. It is preferably 1 to 8% by weight, more preferably 2 to 7% by weight, and still more preferably 3 to 6% by weight.

In the present invention, from the viewpoint of suppressing pigment penetration by gel formation between the water in the coating liquid and the component (a) treated on the surface of the base paper, the ratio (% by weight) of water in the coating liquid and (a) The ratio of the component to the coating amount (g / m ² ) [ratio of water in the coating liquid / (a) component coating amount] is 25 to 1000, preferably 30 to 900, more preferably 35 to 800. Range. Therefore, it is necessary to adjust the amount of water in the coating liquid according to the coating amount of the polymer compound when the surface treatment agent is used.

Further, in the present invention, from the viewpoint of obtaining glossy paper, the ratio between the glossiness of the blank paper (%) of the coated paper and the coating amount (g / m ² ) of the coating liquid (whitepaper glossiness of the coated paper / coating The coating amount of the working liquid is preferably in the range of 3.5 to 11.0, more preferably 3.5 to 10.0, and still more preferably 3.5 to 9.0. In order to control to the said range, it is preferable to adjust the coating amount of a coating liquid, a calendar linear pressure, and a calendar temperature.

[Calendar process]
In the production method of the present invention, it is preferable to further perform a calendar process in which the coated paper obtained in the coating process (hereinafter referred to as pre-calendar coated paper) is calendered to obtain a post-calendar coated paper. The moisture content of the pre-calendar coated paper in the calendar process for the coated paper is not particularly limited. However, from the viewpoint of reducing the weight of the coated paper, it is preferable to perform the calendar treatment with the moisture content of the pre-calendar coated paper being 0 to 5.5% by weight, more preferably 1 to 4.5% by weight. More preferred is ˜4% by weight. In addition, when performing a calendar process in multiple times, it is preferable to perform the moisture content before each calendar | calender as 0 to 5.5 weight% at least once. More preferably, all calendaring is performed at 0 to 5.5% by weight.

  Examples of the method for adjusting the moisture content of the pre-calendar coated paper include a method of adjusting the conditions (temperature, humidity, air volume, time, etc.) of the drying step before the calendar step. Examples of the drying method include steam drying, gas heater drying, electric heater drying, and infrared heater drying. In a general papermaking process, the moisture content of the pre-calendar coated paper is about 6 to 7% by weight.

  Also, know the moisture content of pre-calendar coated paper by measuring with a BM meter [Basis weight / Moisture (basis weight / moisture) meter] or by measuring the weight loss by completely drying uncoated paper. Can do.

  In the calendar process, a calendar device such as a super calendar, a soft calendar, a machine calendar, or a gloss calendar can be used, and these may be used in combination. The surface temperature of the calendar is not particularly limited, but is preferably 25 ° C. or higher, more preferably 50 ° C. or higher, and still more preferably 70 ° C. or higher. From the viewpoint of obtaining coated paper with high gloss, it is preferable to use a super calender device.

  The pre-calendar coated paper according to the present invention is difficult to be compressed by the calendar when the moisture content before the calendar is 0 to 5.5% by weight. Therefore, the calendar pressure (pressure applied to the paper measured by the method described in Examples) is set. The pressure can be 9 to 80 MPa, and further 9 to 50 MPa. From the viewpoint of gloss and low density of the coated paper, the calendar pressure is preferably 25 to 80 MPa, more preferably 25 to 50 MPa. In addition, the number of calendar processes is preferably 2 or more from the viewpoint of increasing gloss.

[Humidity control process]
In the manufacturing method of the present invention, when the moisture content of the pre-calendar coated paper is set to 0 to 5.5% by weight, the moisture content of the post-calendar coated paper (coated paper) is further after the calendar process. It is preferable to have a humidity control step that increases the rate. By passing through the humidity adjustment process, the density increased by the calendar process is reduced, and a coated paper with a lower density can be obtained. This is presumably because the coated paper compressed by the calendar process swells again due to hydrogen bonding between the pulps through water. The moisture content is preferably increased by 0.1 to 9 points, more preferably by 1 to 7 points, and further preferably by 1 to 6 points in terms of% by weight relative to the moisture content of the pre-calendar coated paper. That is, (moisture content value of pre-calendar coated paper + 0.1) to (moisture content value of pre-calendar coated paper + 9) (wt%) is preferable, and (water content value of pre-calendar coated paper + 1) ) To (moisture content value of pre-calendar coated paper + 7) (weight%), more preferably (moisture content value of pre-calendar coated paper + 1) to (moisture content value of pre-calendar coated paper + 6) More preferably (wt%).

  As the humidity control device, a water coating device, an electrostatic humidification device, a steam humidification device, or the like can be arranged together with the calendar, and can be used in appropriate combination.

[Coated paper]
The blank paper glossiness of the coated paper produced according to the present invention is preferably 40% or more, more preferably 50% or more, and still more preferably 60% or more. In the present invention, the blank paper glossiness of the coated paper is a value measured according to JIS-P8142.

The coated paper produced according to the present invention preferably has a density of 1.15 g / cm ³ or less, more preferably 1.1 g / cm ³ or less, and still more preferably 1.05 g / cm ^3. cm ³ or less.

  The coated paper produced according to the present invention can be applied to various types of paper. For example, mention may be made of paper made of acid, neutral or alkaline paper, such as coated paper used for book paper or magazines, printing paper such as coated paper used for catalogs and posters, or ink jet paper or packaging paper. it can.

  More specifically, it is suitable for A0 art paper, A1 art paper, A2 coated paper, A3 coated paper, medium coated paper, fine coated paper, and the like.

<Examples 1-13 and Comparative Examples 1-6>
(1) Manufacture of uncoated base paper Chemical pulp LBKP (hardwood bleached pulp) was used as a pulp raw material, and it was disaggregated and beaten with a beater at 25 ° C. to obtain an LBKP slurry having a pulp concentration of 2.2% by weight. The Canadian standard freeness (JIS P 8121) of this product was 450 ml. This LBKP slurry is weighed so that the basis weight of the sheet after paper making is about 80 g / m ² , and then diluted with water so that the pulp concentration becomes 0.5% by weight. The paper was made with 80 mesh wire to obtain a wet sheet. The wet 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 drum dryer to obtain a pulp sheet. The obtained pulp sheet was conditioned for 12 hours under the conditions of 23 ° C. and 50% relative humidity, and then calendered under the following conditions for the purpose of uniforming the surface roughness of the base paper to obtain an uncoated base paper. The moisture content of the uncoated base paper after humidity control was 7% by weight, and the Beck smoothness according to JIS-P8119 was 30 seconds.

<Calendar processing conditions for pulp sheet>
Calendering (linear pressure: 10 kg / cm, processing speed: 10 m / min, roll temperature: 80 ° C.) under the conditions of 23 ° C. and relative humidity of 50% using a lab calendar device (30FC-200E super calender manufactured by Kumagaya Riki Kogyo Co., Ltd.) 2 times of treatment).

(2) Production of coated base paper (surface treatment process)
Using a bar coater, the surface treatment agent containing the components (a), (b) and water shown in Table 1 was spread and a casting film was formed on the glass plate. The temperature of the surface treatment agent at this time was 40 to 50 ° C. Next, the uncoated base paper (12 cm wide × 12 cm long) obtained above was placed on a casting film, covered with a piece of 100 g / m ² filter paper, and a roll (diameter 200 mm, width 200 mm, linear pressure 230 g / cm). ) And the liquid film of the surface treatment agent was transferred from the glass plate to the surface of the base paper. Subsequently, it dried for 2 minutes at 105 degreeC using the mirror surface dryer. These series of operations were performed promptly without intermission. The dried pulp sheet was conditioned for 1 day at 23 ° C. and 50% humidity. This operation was performed on both the front and back surfaces to obtain double-sided treated paper. In addition, the groove width of the bar coater was adjusted such that the coating amount of the casting film (in terms of solid content) was the numerical value shown in the table. The polymer compounds used are as follows.

-Polymer compound a-1: Polymer compound obtained by the following production example * Production example of polymer compound a-1 In a 1 L beaker, 267.4 g of ion-exchanged water, MOEDES (a solution of dimethylaminoethyl methacrylate and dimethyl sulfate) Mole adducts, all 188.53 g of reagent, manufactured by Wako Pure Chemical Industries, Ltd., DMAAm (N, N-dimethylacrylamide, reagent, manufactured by Wako Pure Chemical Industries, Ltd.) 110.46 g, NK-14G (crosslinking agent, Polyethylene glycol dimethacrylate, manufactured by Okanakamura Chemical Co., Ltd.) 0.415 g, V-50 (polymerization initiator, 2,2′-azobis (2-amidinopropane) dihydrochloride, manufactured by Wako Pure Chemical Industries, Ltd. 0.952 g was mixed to obtain an aqueous monomer solution a.

  Into a 5 L glass container, 1648 g of cyclohexane and 1.94 g of sugar ester S-770 (manufactured by Mitsubishi Kasei Co., Ltd.) as a dispersant were charged and dissolved uniformly at 60 ° C. over 1 hour. After dissolution, the mixture was cooled to 30 ° C. to obtain a dispersant solution b.

  The monomer aqueous solution a is added to the dispersant solution b, and the mixture is set in a homomixer (ROBOMICS, manufactured by Tokushu 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 whole amount was charged into a 5 L SUS tank equipped with a stirrer, a thermometer and a cooling tube, purged with nitrogen, heated, and polymerized at 55 ° C. for 1 hour. Further, after aging at 70 ° C. for 1 hour, a dehydrating tube with a cooling tube was attached, and 269 g of water was removed from the system. As dehydration progressed, the temperature in the tank increased from 70 ° C to 90 ° C. Subsequently, it cooled to 40 degrees C or less, the content was moved to the stainless steel tray, and it dried at 80 degreeC with hot air. Then, it lightly grind | pulverized for about 1 second with the household coffee mill, and the high molecular compound a-1 with an average particle diameter of 4.0 micrometers was obtained.

-Polymer compound a-2: Polymer compound obtained by the following production example * Production example of polymer compound a-2 In a 1 L beaker, 123.9 g of ion-exchanged water, MOEDES (a solution of dimethylaminoethyl methacrylate and dimethyl sulfate) Mole adduct (effective content 90%), both reagents, Wako Pure Chemical Industries, Ltd. 76.3 g (effective content 68.7 g), acrylic acid (Toagosei Co., Ltd.) (effective content 80.6%) )) 19.8 g (effective amount 15.9 g), NK-14G (crosslinking agent, polyethylene glycol dimethacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) 0.129 g, V-50 (polymerization initiator, 2,2′- Monomer aqueous solution A was prepared by mixing 0.131 g of azobis (2-amidinopropane) dihydrochloride, manufactured by Wako Pure Chemical Industries, Ltd. A 3 L glass container was charged with 777 g of cyclohexane and 0.840 g of S-770 (dispersant, sugar ester, manufactured by Mitsubishi Kasei Co., Ltd.) and dissolved uniformly at 50 ° C. over 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 whole amount was charged into a 2 L stirrer, a thermometer, and a glass tank equipped with a cooling tube. Further, after aging at 70 ° C. for 1 hour, a dehydrating tube with a cooling tube was attached, and 115 g of water was removed from the system over about 3 hours. The contents were transferred to a stainless steel tray and the solvent was removed by vacuum drying to obtain polymer compound a-2.

-Polymer compound a-3: Polymer compound obtained by the following production example * Production example of polymer compound a-3 1,000 g of hydroxypropyl corn starch was dissolved in 1,500 ml of water, and the pH was adjusted to water. It adjusted to 11.2-11.5 using the aqueous solution (4 weight%) of sodium oxide. After adding 4.8% by weight of starch to a starch slurry maintained at 43 ° C., a 60% by weight solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride, which is a quaternary ammonium salt introducing agent, as a cationizing agent, The cationization reaction was carried out with stirring for 20 hours. After the reaction, the starch slurry was adjusted to pH 7.0 with a 10 wt% aqueous HCl solution, purified and dehydrated by a conventional method, and dried at room temperature. A solution obtained by dissolving 9.0% by weight of urea with respect to starch and 2.4% by weight of orthophosphoric acid with respect to starch in a small amount of water and adjusting the pH to 8.0 with a 10% by weight NaOH aqueous solution is used as the above cationic starch. The mixture was added with stirring and mixed well. Subsequently, it dried at 50 degreeC in the hot air circulation dryer, and adjusted the water | moisture content to 4.0 weight%. Next, 380 g of the cationic starch having a solid content weight is taken into an eggplant type flask, heated in an oil bath heated to 140 ° C. for 5 minutes to give a urea phosphorylation reaction, and then cooled to room temperature to be polymer compound a-3 Got.

* Preparation method of the surface treatment agent Among the surface treatment agents containing the component (b), the component (a) is a-1, a-2, the ion-exchanged water is heated up to 80 ° C., and then the component (a) And the component (b) was added so that it might become predetermined | prescribed density | concentration (Table 1), and it stirred at 80 degreeC for 1 hour, Then, it cooled and prepared at the speed | rate of 5 degree-C / min. Further, among the surface treatment agents containing the component (b), those having the component (a) a-3 are such that the components (a) and (b) have a predetermined concentration (Table 1) in the ion-exchanged water. In addition, the temperature was raised to 90 ° C. with stirring, maintained for 1 hour, and then cooled and prepared at a rate of 5 ° C./min. (B) The surface treating agent which does not contain a component was prepared by the same method as the above except that the component (b) was not added.

(3) Manufacture of coated paper (coating process, calendar process and humidity control process)
On the first surface of the coated base paper (pulp sheet) coated with the surface treatment agent, 50 parts by weight of heavy calcium carbonate, 50 parts by weight of fine kaolin, 0.075 parts by weight of a dispersing agent (poise 535M: manufactured by Kao) A coating solution obtained by adding water to 0.02 parts by weight of sodium hydroxide, 11 parts by weight of latex, and 3 parts by weight of starch was used as a lab blade coater (manufactured by Kumagai Riki Kogyo, speed 25 m / min). The coating was carried out so as to be 15 g / m ² (solid content conversion) per side. The coating liquid used here had a solid content concentration of 65% by weight and a water content of 35% by weight.

After coating, it was dried at 105 ° C. for 2 minutes using a drum dryer. Next, the coating liquid is applied to the second side of the single-side coated paper that has not yet been coated (opposite side of the first side, uncoated side) with the lab blade coater at 15 g / m ² (solid content). Coating). After coating, it was dried at 105 ° C. for 2 minutes using a drum dryer to obtain double-sided coated paper (pre-calendar coated paper).

  Next, the obtained double-sided coated paper was dried and adjusted to a moisture content of 6.0% by weight, and calendered under the following conditions so that the first surface was in contact with the metal roll. Next, the double-sided coated paper was dried and adjusted to a moisture content of 6.0% by weight, and the double-sided coated paper was calendered under the following conditions so that the second side was in contact with the metal roll, Humidity was adjusted for 12 hours at a relative humidity of 50% to obtain a coated paper having a water content of 6.0% by weight.

<Calendar processing conditions for double-sided coated paper>
Calendering (linear pressure 200 kg / cm, processing speed 10 m / min, roll temperature 80 ° C.) under the conditions of 23 ° C. and relative humidity 50% using a lab calender device (30FC-200E super calendar manufactured by Kumagaya Riki Kogyo Co., Ltd.) , The number of treatments was once). The temperature setting of the apparatus was used for the metal roll surface temperature of the calendar apparatus. As a precaution, we measured with a thermometer (DIGIITAL THERMOMETER MODEL 2455 (iuchi)) and confirmed that the temperature was correct.

  The moisture content of the pre-calendar coated paper was measured as follows. Cut the pre-calendar coated paper to a size of 12 cm x 12 cm, put it in a 200 ml media vial, dry at 105 ° C for 30 minutes, seal with a lid and cool to room temperature to obtain a pre-calendar coated paper. The moisture content of the pre-calendar coated paper was 0% by weight. Next, when the moisture content of the pre-calendar coated paper of 0% by weight is adjusted at 23 ° C. and a relative humidity of 65%, and when the desired moisture content is obtained while checking the weight increase, (3) The moisture content at this time is taken as the moisture content of the pre-calendar coated paper. The moisture content represents the weight percent of water relative to the weight of the paper.

  Further, the relationship between the linear pressure of the lab calendar apparatus and the pressure applied to the paper was determined by the following method. The pressure-sensitive paper “Prescale” (manufactured by FUJIFILM Corporation) was passed through a lab calendar apparatus while changing the linear pressure under the above conditions, and the pressure was determined from the degree of color development of the thermal paper at that time. When the linear pressure is less than 100 kg / cm, medium pressure is used, and when the linear pressure is 100 kg / cm or more, high pressure is used. As a result, the pressure was 9 MPa at a linear pressure of 21 kg / cm, the pressure was 25 MPa at a linear pressure of 42 kg / cm, the pressure was 49 MPa at a linear pressure of 200 kg / cm, the pressure was 56 MPa at a linear pressure of 250 kg / cm, and the pressure was 80 MPa at a linear pressure of 500 kg / cm. .

<Evaluation>
About the coated paper obtained by the Example and comparative example of Table 1, surface blank paper glossiness was measured according to JIS-P8142. Moreover, the measuring method of the viscosity and normal stress of (a) component is as follows. Moreover, the measuring method of the viscosity of a surface treating agent is as follows. The results are shown in Table 1. The coated papers of the examples all had a density in the range of 1.25 ± 2 g / cm ³ .

[Measurement method of viscosity (I)]
Viscosity measurement was performed by a method shown below using a B-type viscometer (model: BM, manufactured by Toki Sangyo Co., Ltd.). The 5% by weight aqueous polymer compound solution prepared by the above preparation method was added to a beaker and immersed in a 25 ° C. water bath for 1 hour or longer. After confirming that the temperature of the polymer compound aqueous solution reached 25 ° C. with a thermometer, a rotor corresponding to the viscosity of the polymer compound aqueous solution was selected and attached to the viscometer. The beaker containing the polymer compound aqueous solution was moved to a predetermined position, the rotor was immersed in the sample for 15 minutes, and the temperature of the rotor was adjusted to 25 ° C. The viscosity was obtained by a conversion formula by reading the indicated value when the rotor was rotated for 1 minute at a rotational speed of 60 rpm and stopped.

[Measurement method of viscosity (II)]
Viscosity measurement was performed by the method shown below using a B-type viscometer (model: B8R, manufactured by TOKIMEC). The 5% by weight aqueous polymer compound solution prepared by the above preparation method was added to a beaker and immersed in a 25 ° C. water bath for 1 hour or longer. After confirming that the temperature of the polymer compound aqueous solution reached 25 ° C. with a thermometer, a rotor corresponding to the viscosity of the polymer compound aqueous solution was selected and attached to the viscometer. The beaker containing the polymer compound aqueous solution was moved to a predetermined position, and the viscosity was measured. The viscosity was obtained by a conversion formula by reading the indicated value when the rotor was rotated for 1 minute at a rotation speed of 5 rpm and stopped.

[Method of measuring normal stress]
The normal stress was measured by the following method. The target compound was diluted with ion-exchanged water, and an aqueous solution (0.2 wt% to 18 wt%) of the polymer compound was prepared according to the above preparation method. Using a viscoelasticity measuring device (Anton Paar, Physica MCR300) at 25 ° C, using a cone plate (Diameter: 50mm, Angle: 1 °, Truncation: 52μm, Anton Paar, CP50-1) The change in shear rate was set to 0.01 to 1000 (1 / second), and normal stress and viscosity were measured. Read the values of normal stress and viscosity at a shear rate of 1000 (1 / sec) at each aqueous solution concentration (0.2 wt% to 18 wt%), create an approximate expression of viscosity and normal stress, and obtain the approximation The normal stress at a viscosity of 300 mPa · s was calculated from the equation, and the normal stress value at a shear rate of 1000 (1 / second) was obtained.

[Method for measuring viscosity of surface treatment agent]
The viscosity of the surface treatment agent was measured according to the method for measuring the viscosity (I) described above. That is, the viscosity of the surface treating agent at 25 ° C. is determined by using a B-type viscometer (model: BM, manufactured by Toki Sangyo Co., Ltd.), rotating the rotor at a rotation speed of 60 rpm for 1 minute, and indicating the indicated value when stopped. It was obtained by reading and conversion formula.

  The coating amount of component (a) is the coating amount in terms of solid content per side. The metal ion concentration is a concentration (% by weight) in the surface treatment agent. Moreover, the surface treating agent was used so that it might become the coating amount of (a) component in Table 1.

  “Gloss improvement ability” in the table is the improvement in gloss expected from actual blank equipment from the value of glossiness of blank paper. ○ means high improvement ability and × means low improvement ability. . “Coating property” is an evaluation of the coating workability expected when the surface treatment agent is applied with a gate roll coater (actual equipment), and ○ is a viscosity of 3000 mPa · s or less. Good coatability and x means that the boiling phenomenon may occur at a viscosity exceeding 3000 mPa · s, and the coatability is poor.

  Comparing the example and the comparative example, when used as a surface treating agent using the component (b) together with the component (a) having a specific viscosity behavior and normal stress, the example has a better coating property. It can be seen that coated paper with good and high glossiness can be produced.

Claims (7)

The B-type viscosity of a 5% by weight aqueous solution at 25 ° C. is 3000 mPa · s to 120,000 mPa · s, and the normal stress at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. is 0 to 2400 Pa. A polymer compound (a) [hereinafter referred to as component (a)], an electrolyte other than a salt of a peroxide that releases metal ions in water (b) [hereinafter referred to as component (b)], water A surface treatment step of obtaining a surface-treated base paper by applying a surface-treating agent containing a pulp mainly as a raw material to the surface-treated base paper obtained in the surface treatment step, a pigment, a binder and water A coating process to obtain a coated paper by coating a coating liquid containing
I have a,
(A) The component is one or more compounds selected from cationic group-containing vinyl copolymers,
Manufacturing method of coated paper. The component (b) is selected from (b1) a water-soluble salt of an acid selected from organic acids and inorganic acids and a metal selected from alkali metals and alkaline earth metals, and (b2) selected from alkali metals and alkaline earth metals. metal hydroxides is one or more water-soluble compound selected from the method for producing a coated paper according to claim 1, wherein. The manufacturing method of the coated paper of Claim 1 or 2 whose weight ratio of (a) component and (b) component is 100/1-1/1 by (a) / (b). The manufacturing method of the coated paper of any one of Claims 1-3 whose application quantity (solid content conversion) of a coating liquid is 1-30 g / m < ² > per single side | surface of a surface-treated base paper. The B-type viscosity of a 5% by weight aqueous solution at 25 ° C. is 3000 mPa · s to 120,000 mPa · s, and the normal stress at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. is 0 to 2400 Pa. A polymer compound (a) [hereinafter referred to as component (a)] , an electrolyte other than a salt of peroxide that releases metal ions in water (b) [hereinafter referred to as component (b)] , water containing the door,
(A) The component is one or more compounds selected from cationic group-containing vinyl copolymers,
Surface treatment agent for coated paper. The surface treatment agent for coated paper according to claim 5, wherein the weight ratio of the component (a) to the component (b) is 100/1 to 1/1 in terms of (a) / (b). A surface-treated base paper, wherein the surface-treating agent for coated paper according to claim 5 or 6 is treated with 0.01 to 3.0 g / m ^{2 in} dry weight per side on at least one side of a paper mainly composed of pulp.