JP2010265572A - Surface-finishing agent for coated base paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-finishing agent for a coated base paper in a method for suppressing impregnation of a coating material into the base paper, wherein relatively inexpensive materials are used for effectively suppressing impregnation of the coating material to surface of the light-weight base paper for printing and a coating film of a coated layer is efficiently formed to obtain a light-weight highly gloss coated paper, so as to reduce the weight and to keep high glossiness of the coated paper, while having a problem of an increase in the coating amount caused by the impregnation of the coating material if the coating material composed mainly of an inorganic pigment having high specific gravity is just applied even when a light-weight bulky base paper is used for decreasing the weight of the coated paper. <P>SOLUTION: There are provided the surface-finishing agent for the coated base paper comprising a starch (a) exhibiting a specific viscosity behavior and having a specific normal stress, and the coating base paper treated with a specific coating amount of the surface-finishing agent. Further, the coated paper having a density of a specific level or less and having the coating layer of the coating material composed mainly of a pigment and a binder on the base paper for coating is provided. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a surface treatment agent for coated base paper, a coated base paper using the same, and 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 raw material. There is a need to reduce it. However, when the density of the base paper is reduced, the number of pores increases, so that the permeability of the paint into the base paper increases during coating, and it becomes 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 pore volume of the base paper, the penetrability of the paint 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 coated paper, even if a light and bulky base paper is used, simply applying a paint mainly composed of a high specific gravity inorganic pigment increases the coating amount due to the penetration of the paint. Thus, it is difficult to achieve light weight while maintaining the high gloss of the coated paper.

  Further, as a method of suppressing the penetration of the coating material into the base paper, a method of performing a sizing process on the base paper in order to reduce the wettability between the base paper and water as a solvent of the coating material 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. 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 base is disclosed (see Patent Document 2). In addition, 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 3). On the other hand, the penetration inhibitor composed of a sodium salt of carboxymethyl cellulose having specific physical properties suppresses the penetration of the hydrophilic paint into the inside of the support having a hydrophilic and porous surface layer like a bulky paper, and is small An effective coating layer with a coating amount has been proposed (see Patent Document 4).

  Patent Documents 5 and 6 disclose that a starch selected from a cationized starch, an amphoteric starch and a cationized cross-linked starch using raw starch as a raw material is used as a paper coating agent.

Japanese Patent Laid-Open No. 11-012981 JP-A-6-200500 JP 2005-89871 A Japanese Patent Application Laid-Open No. 2004-300624 JP 2006-161216 A JP 2006-283235 A

  As in Patent Document 1, even if such a treatment is applied to a low density base paper having a large amount of pores, the effect is small. Also, a coating agent that is applied to the surface of paper by applying a surface treatment agent mainly composed of water-soluble polymer such as starch for coating and polyvinyl alcohol (PVA) to form a coating film on the surface of paper. Although a method for suppressing the penetration of water is also conceivable, it has been difficult to form an effective penetration inhibiting coating on the paper surface. The release paper paint used in Patent Document 2 is hydrophobic because it is mainly composed of toluene and silicone, and is a hydrophilic printing paint in which pigments and binders such as calcium carbonate and kaolin are dispersed in water at a high concentration. Since the physical properties of paints differ significantly, they cannot solve the problem of general coated paper. Further, Patent Document 3 has a drawback that the swellable mica is very expensive and cannot be used for producing general-purpose printing paper. Therefore, it has been very difficult to effectively suppress the penetration of the coating material on the surface of the lightweight base paper for printing and to efficiently form the coating layer of the coating layer by using a relatively inexpensive material. Moreover, in patent document 4, although the penetration | permeation of a coating material is suppressed by the processing agent which consists of carboxymethylcellulose sodium salt which has a specific physical property, effectiveness is recognized by ventilation resistance, there are few effects, such as improvement of glossiness Met. Patent Documents 5 and 6 aim to improve the rigidity of the paper and reduce the adhesiveness, and do not mention improvement of gloss and weight reduction of the coated paper.

  An object of the present invention is to provide a surface treatment agent for coated base paper, which can provide a coated paper having high gloss and a light coated paper having high gloss.

  In the present invention, the viscosity of a 5 wt% aqueous solution at 25 ° C. is 2000 to 12000 mPa · s, the normal stress at a shear rate of 1000 (1 / second) at 25 ° C. is 300 mPa · s, and the normal stress is 0 to 2400 Pa. It is related with the surface treating agent for coating base paper containing a certain starch (a).

Further, in the present invention, the surface treatment agent for coated base paper of the present invention is treated at a dry weight of 0.01 to 3.0 g / m ² on one side on at least one side of a paper mainly composed of pulp. Related to coated base paper.

In the present invention, the coating base paper of the present invention is provided with a coating layer of a paint mainly composed of a pigment and a binder on the surface treated with the surface treatment agent for coating base paper. It is related with the coated paper which is 5 g / cm ³ or less.

Further, the present invention is a process for obtaining a coated base paper by treating the surface treating agent composition containing the surface treating agent for coated base paper of the present invention and water on at least one side of a paper mainly composed of pulp. (I) and a surface of the coated base paper obtained in the step (I) treated with the surface treating agent composition for a coating base paper mainly comprising a pigment and a binder, which are different from the surface treating agent composition. And a step (II) of providing a coating layer of a coating material as a component, and a method for producing a coated paper having a density of 1.5 g / cm ³ or less.

  When the surface treatment agent of the present invention is applied to the surface of the base paper and dried, the reason why the above problem is solved is not clear, but starch (a) having a specific viscosity behavior and having a specific normal stress is a base paper. Because it exists on the surface, the paint is agglomerated when the paint mainly composed of pigment and binder is applied, and the penetration of the paint mainly composed of inorganic pigment into the paper is suppressed. Presumed.

  Further, the starch (a) according to the present invention is a polymer having a three-dimensional stitch structure, and when this is present on the paper surface, when a paint mainly composed of a pigment and a binder is applied. By instantly absorbing moisture in the paint, a gel film is formed at the interface between the uncoated base paper and the coated pigment, and the paint becomes highly viscous and non-flowable so that the paint paper is mainly composed of inorganic pigment. Since the penetration into the inside is suppressed, it is estimated that the thickness of the coating layer increases, the surface of the coating layer is further flattened by calendering, and the gloss of the resulting coated paper is improved. .

  It is also estimated that the starch (a) suppresses the penetration of the paint into the base paper by filling the pores of the paper having a porous surface layer when applied to the paper surface. .

  According to the present invention, it is possible to suppress the penetration of the paint into the base paper, and an effective coating layer can be obtained with a small coating amount using a current paper machine or coating machine, which is lightweight, high in weight. A surface treating agent for coated base paper that can efficiently produce glossy coated paper is obtained. The coated paper produced from the coated base paper treated with the surface treating agent for coated base paper of the present invention is lightweight and has high gloss.

  In addition, when the same amount of coating layer is applied, a highly glossy coated paper can be obtained, so that the calender linear pressure can be lowered in the calendering step after applying the coating layer. In addition, the pulp and dye of coated paper can be reduced, leading to resource saving and energy saving as well as density reduction.

  The surface treatment agent for coated base paper of the present invention has a viscosity of 2000 to 12000 mPa · s at 5% by weight aqueous solution at 25 ° C. and a viscosity at 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. Contains starch (a) having a normal stress of 0 to 2400 Pa. The starch (a) of the present invention will be described below.

[Starch (a)]
The starch (a) used in the present invention has a viscosity of 2000 to 12000 mPa · s at 25 ° C., preferably from 2200 to 25 ° C., from the viewpoint of suppressing penetration into the base paper and improving the gloss of the coated paper. 10500 mPa · s, more preferably 240 to 10,000 mPa · s, still more preferably 2600 to 9500 mPa · s, and even more preferably 2700 to 9000 mPa · s. In addition, this viscosity is measured by the method as described in the below-mentioned Example. In the present invention, a surface treatment agent for coated base paper, which is a lightweight and highly glossy coated paper, is obtained by using a starch (a) having a viscosity of 2000 mPa · s or more at 25 ° C. at 25 ° C. Can be provided. Further, the upper limit of the viscosity is set to 12000 mPa · s or less because the effect is saturated and the coatability becomes difficult.

  When the starch (a) is an amphoteric starch, the viscosity of a 2% by weight aqueous solution at 25 ° C. is 200 to 5000 mPa · s, preferably 250, from the viewpoint of suppressing penetration into the base paper and improving the gloss of the coated paper. It is -4000mPa * s, More preferably, it is 250-3000mPa * s, More preferably, it is 250-2000mPa * s, More preferably, it is 280-1000mPa * s. From the same viewpoint, the viscosity of a 4 wt% aqueous solution at 25 ° C is preferably 800 to 8000 mPa · s, more preferably 1000 to 7000 mPa · s, still more preferably 1200 to 6000 mPa · s, and still more preferably 1200 to 5000 mPa · s, even more preferably 1200 to 3000 mPa · s. In addition, this viscosity is measured by the method as described in the below-mentioned Example. In the present invention, a surface treatment agent for coated base paper that provides a light, high-gloss coated paper by using an amphoteric starch having a 2% by weight aqueous solution at 25 ° C. having a viscosity of 200 mPa · s or more is provided. can do. The upper limit of the viscosity is set to 5000 mPa · s or less because the effect is saturated and the coatability becomes difficult.

  The viscosity of the 5% by weight aqueous solution of starch (a) can be designed within a desired range by controlling the amount of cationizing agent or anionizing agent introduced later and the degree of crosslinking with a crosslinking agent. Generally, when the degree of crosslinking increases, the viscosity of starch tends to decrease, and when the degree of crosslinking decreases, the viscosity tends to increase.

  The normal stress at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. of the starch (a) of the present invention is from the viewpoint of reducing the spinnability of the surface treatment agent and improving the glossiness of the coated paper. 0 to 2400 Pa, preferably 10 to 2200 Pa, more preferably 50 to 2000 Pa, and still more preferably 100 to 2000 Pa.

  When a linear polymer or a solution thereof is subjected to shear stress, a 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 water-soluble polymer having cross-links or the like in the molecule such as the starch (a) of the present invention is considered to exhibit a low value as the normal stress because there is little entanglement between molecules. Here, the normal stress at a viscosity of 300 mPa · s at a shear rate of 1000 (1 / second) at 25 ° C. is measured by the method described in the examples. The normal stress is measured at a starch concentration at which the viscosity of the aqueous solution of starch (a) at a shear rate of 1000 (1 / second) is 300 mPa · s.

  The normal stress of starch (a) can be designed in a desired range by controlling the amount of cationizing agent or anionizing agent to be described later and the degree of crosslinking by the crosslinking agent. Generally, when the degree of crosslinking increases, the normal stress of starch (a) tends to decrease, and when the degree of crosslinking decreases, the normal stress tends to increase.

  The starch (a) used in the present invention is not particularly limited as long as it satisfies the above-mentioned viscosity and normal stress. Specific examples include, for example, acetyl starch, urea phosphate starch, phosphate starch, hydroxy Examples thereof include alkyl starch, carboxymethyl starch, cationized starch, amphoteric starch and cross-linked starch. Examples of the crosslinked starch include phosphoric acid crosslinked starch, adipic acid crosslinked starch, cationized crosslinked starch, epichlorohydrin crosslinked starch, formaldehyde crosslinked starch and the like.

Among these, from the viewpoint of suppressing penetration into the base paper and improving glossiness of the coated paper, starch selected from amphoteric starch, phosphate cross-linked starch, adipic acid cross-linked starch, cationized cross-linked starch is more preferable, amphoteric starch More preferably, starch selected from phosphoric acid crosslinked starch and adipic acid crosslinked starch. Therefore, as a suitable surface treatment agent for coated base paper of the present invention,
(1) The viscosity of a 5% by weight aqueous solution at 25 ° C is 2000 to 12000 mPa · s, and the normal stress at a shear rate of 1000 (1 / second) at 25 ° C is 300 mPa · s is 0 to 2400 Pa. Surface treatment agent for coated base paper containing amphoteric starch (a1),
(1 ′) The viscosity of a 5 wt% aqueous solution at 25 ° C. is 2000 to 12000 mPa · s, the viscosity of a 4 wt% aqueous solution at 25 ° C. is 800 to 8000 mPa · s, and a shear rate of 1000 (1 Surface treatment agent for coated base paper containing amphoteric starch (a1) having a normal stress at 0 to 2400 Pa at a viscosity of 300 mPa · s at 300 mPa · s,
(2) The viscosity of a 5 wt% aqueous solution at 25 ° C. is 2000 to 12000 mPa · s, and the normal stress at a shear rate of 1000 (1 / second) at 25 ° C. is 300 mPa · s is 0 to 2400 Pa. A surface treatment agent for coated base paper containing phosphoric acid crosslinked starch (a2),
(3) The viscosity of a 5% by weight aqueous solution at 25 ° C. is 2000 to 12000 mPa · s, and the normal stress at a shear rate of 1000 (1 / second) at 25 ° C. is 300 mPa · s is 0 to 2400 Pa. A surface treatment agent for coated base paper containing adipic acid starch (a3),
Is mentioned.

  The starch (a) used by this invention is manufactured by the well-known method. Examples of the raw material for the starch (a) include corn starch, tapioca starch, potato starch, sweet potato starch, wheat starch, rice starch, acetylated starch, hydroxyethylated starch, hydroxyl group introduced with a substituent by a known method. Examples include propylated starch. These starting material starches preferably have an amylopectin content of 40% by weight or more, more preferably 50% by weight or more, and 60% by weight or more from the viewpoint of reducing spinnability. Is more preferable, and it is still more preferable that it is 70 weight% or more.

  The starch (a) can be produced, for example, by reacting the above-mentioned raw material starch with a cationic group and / or an anionic group introduction agent or a crosslinking agent.

  Examples of cationic group introduction agents include tertiary amine introduction agents such as diethylaminoethyl chloride, quaternary ammonium salt introduction agents such as 3-chloro-2-hydroxypropyltrimethylammonium chloride and 2,3-epoxypropyltrimethylammonium chloride. Is mentioned. These cationizing agents can be used alone or in combination of two or more.

  Examples of the anionic group-introducing agent include propane sultone, butane sultone, monochloroacetic acid, chlorosulfonic acid, maleic anhydride, succinic anhydride, orthophosphoric acid, orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid and hexametaphosphoric acid. Examples thereof include alkali metal salts or alkaline earth metal salts of phosphoric acids, a combination of urea and monosodium phosphate, and disodium phosphate. These anionizing agents can be used alone or in combination of two or more.

  Examples of the alkali metal constituting the alkali metal salt or alkaline earth metal salt of phosphoric acid include sodium and potassium, and examples of the alkaline earth metal include calcium and magnesium. The anionizing agent comprising the alkali metal salt or alkaline earth metal salt of phosphoric acid is preferably sodium tripolyphosphate, urea and monosodium phosphate, or a combination of dibasic sodium phosphate. It is done.

  Examples of the crosslinking agent include phosphorus-based crosslinking agents such as phosphorus oxychloride, phosphoric anhydride, trimetaphosphate, and hexametaphosphate, dicarboxylic acid crosslinking agents such as adipic anhydride, epichlorohydrin, and formaldehyde. Examples of the salt of the phosphorus-based crosslinking agent include alkali metal salts and alkaline earth metal salts similar to the phosphoric acids of the anionizing agent. The addition amount of the cross-linking agent is appropriately selected according to the type of raw material starch, the type of cross-linking agent, etc., but is 0.001 to 5% by weight, and further 0.001 to 1% by weight based on 100% by weight of the raw material starch. % Is preferably used.

  In the case where the starch (a) is an amphoteric starch, from the viewpoint of easy control of viscosity and normal stress, after the raw material starch is cationized with a cationizing agent, urea and monobasic sodium phosphate, It is preferable to add amphoteric starch by adding disodium acid and heating it.

  When the starch (a) is an amphoteric starch, the nitrogen content (N%) is preferably from 0.01 to 0.8, more preferably from 0.05 to 0.6, from the viewpoint of suppressing penetration into the base paper and improving the gloss of the coated paper. More preferably, it is 0.1-0.5. Here, the nitrogen content (N%) of the amphoteric starch is measured by the Kjeldahl method, specifically by the method described in the examples.

<Surface treatment agent for coated paper>
The suitable aspect of the surface treating agent for coated base paper of this invention is the liquid composition containing the starch (a) which concerns on this invention, and water, Content of starch (a) in this liquid composition Is from 0.1 to 30% by weight, preferably from 0.3 to 20% by weight, more preferably from 0.5 to 10% by weight, still more preferably from 1 to 8% by weight, from the viewpoint of improving the glossiness of the coated paper. The liquid composition is preferably an aqueous solution or an aqueous dispersion.

  The method for treating the surface of the coated base paper with the surface treatment agent of the present invention is not particularly limited, and is applied to the surface of the base paper or the coated base paper prepared in advance.

The paper that is the target of the surface treatment agent of the present invention is one that uses pulp as a main raw material, and preferably has a density of 0.30 to 1.00 g / cm ³ , more preferably 0.35 to 0.85 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. Also, for paper with a density of 1.00 g / cm ³ or less, since the surface treatment agent of the present invention is properly processed on the surface of the base paper, it has an appropriate air resistance and has good blister resistance during offset printing. There are no restrictions on the use as coated paper.

  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), high yield pulp (SCP, CGP, etc. and bleached pulp) and In addition, recovered pulp such as waste paper pulp and 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.

  Further, from the viewpoint of workability, it is preferable to reduce the viscosity of the surface treatment agent by a known method. Examples of the viscosity reducing method include adjustment of pH, addition of inorganic metal salt, and the like, but addition of inorganic metal salt is preferable.

The coating amount of the surface treatment agent in the present invention is preferably 0.01~3.0g / m ² as dry weight per sheet one side, more preferably, 0.03~2.0g / m ^2, more preferably 0.05 to 1.0 g / m ² It is. If it is 0.01 g / m ² or more, a paint permeation suppression effect is exhibited, and if it is 3.0 g / m ² or less, the total coating amount on both sides is 6 g / m ² or less, so that the weight of the paper can be reduced.

  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.

  The method for applying the surface treating agent to the paper surface is not limited, but as a general method, a solution or dispersion containing the starch (a) 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 starch (a) has a mean particle size of 1 mm or less, preferably 300 μm or less, more preferably 300 μm or less by a method such as pulverization from the viewpoint of dissolving and dispersing in a short time. It is 50 μm or less, and is used as a solution or dispersion by mixing with a solvent or dispersion medium. When the starch (a) according to the present invention is obtained as a solution or dispersion, it is used as it is or after dilution.

The present invention relates to a paper surface treatment agent containing starch (a), and further comprises a pigment and an adhesive as main components on a coated base paper coated with the surface treatment agent of the present invention on the paper surface. The present invention relates to a coated paper provided with a coating layer of paint. That is, the coating surface of the coated base paper according to the present invention is provided with a coating layer of a paint mainly composed of a pigment and a binder on the treated surface of the present invention, and the density is 1.5 g / cm ³ or less. It relates to coated paper. Such a coated paper is, for example, a coated base paper obtained by treating the surface treating agent composition containing the surface treating agent for coated base paper of the present invention and water on at least one side of a paper mainly composed of pulp. The surface of the coated base paper obtained in step (I) is treated with the surface treatment agent composition, and the pigment and the binder are different from the surface treatment agent composition. And a step (II) of providing a coating layer of the paint.

  The gloss of the coated paper can be improved by passing through the above production process, and as a result, a lighter coated paper can be produced. Therefore, the present invention is a process for obtaining a coated base paper by treating the surface treating agent composition containing the surface treating agent for coated base paper of the present invention and water on at least one side of the paper mainly made of pulp ( I) and a surface of the coated base paper obtained in step (I) treated with the surface treatment agent composition, which is different from the surface treatment agent composition, and a paint mainly composed of a pigment and a binder. And a step (II) of providing a coating layer.

  The treatment of the surface treating agent composition in the step (I) can be performed as described above. It is preferable to apply a surface treating agent composition of 40 ° C. or higher to a paper whose main raw material is pulp, that is, an uncoated base paper. This temperature is the temperature (liquid temperature) of the surface treatment agent composition used for coating, and is preferably 50 ° C. or higher, and more preferably 60 ° C. or higher from the viewpoint of improving workability.

  As a pigment and an adhesive used as a paint for forming a coating layer, those used for ordinary coated paper can be used. Examples of the pigment include inorganics such as kaolin, clay, calcium carbonate, and titanium dioxide. Organic pigments such as pigments and plastic pigments can be used. Various adhesives such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl acrylate, which are conventionally used for coated paper, are also available. Polymer latex, oxidized starch, positive starch, phosphate esterified starch, urea phosphate esterified starch, etherified starch such as hydroxyethyl etherified starch, starch such as dextrin, and the like can be used. These adhesives are used in the range of 5 to 50% by weight, more preferably about 10 to 30% by weight per 100% by weight of the pigment. If necessary, various commonly used auxiliaries such as a dispersant, a thickener, a water retention agent, an antifoaming agent, and a water resistant agent are used.

  The coating can be applied using a normal papermaking coating device, and is not particularly limited. Examples of the coating device include a 2-roll size press coater, a gate roll coater, and a blade metering size press coater. , Film transfer type roll coater such as rod metering size press coater and shim sizer, curtain coater, die coater, gravure coater, kiss coater, rod (bar) coater, air knife coater, blade coater, roll coater, spray etc. The pigment slurry is preferably applied using a blade coater.

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 coating liquid (paint) (solid content conversion) is preferably 6 g / m ² or more per one surface, more preferably 6 to 25 g / m ^2, more preferably from 7~20g / 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 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.

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

Examples A1, A2 and Comparative Examples A1-A5
[Method for measuring viscosity of aqueous starch solution]
Viscosity measurement was performed by the method shown below using a B-type viscometer (model: BM, manufacturer: Toki Sangyo Co., Ltd.). An aqueous starch solution having a concentration of 2% by weight, 4% by weight or 5% by weight (the preparation method is as described later) was added to a viscosity beaker and immersed in a 25 ° C. water bath for 1 hour or longer. After confirming that the temperature of the aqueous starch solution reached 25 ° C. with a thermometer, a rotor corresponding to the viscosity of the aqueous starch solution was selected and attached to the viscometer. The viscosity beaker containing the starch 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 nitrogen content]
The measurement of the nitrogen content was performed by the method shown below with an apparatus (KJEL-AUTO DTP-3S, manufacturer: Mitamura Riken Kogyo Co., Ltd.) that can perform the Kjeldahl method.
(1) Preparation of titration solution 30 g of boric acid was dissolved in ion-exchanged water and diluted to 1000 ml with ion-exchanged water (hereinafter referred to as “solution A”). 200 mg of methyl red was dissolved in 100 ml of absolute alcohol and completely dissolved with a hot water bath, followed by filtration to obtain a filtrate (hereinafter referred to as “B solution”). 100 mg of methylene blue was dissolved in 100 ml of absolute alcohol and completely dissolved with a hot water bath, followed by filtration to obtain a filtrate (hereinafter referred to as “C solution”). The said B liquid and C liquid were mixed by 1: 1, and D liquid was obtained. The A liquid and D liquid were mixed at a ratio of 100: 1 to obtain a titration reagent E liquid. 25 ml of E solution was added to the titration bottle, and the titration bottle was set at a predetermined position of the apparatus.
(2) Measurement of nitrogen content 1 g of sample, 10 mL of sulfuric acid, and 1 tablet of Keltab C tablet (degradation accelerator) were put into a Kjeldahl tube to obtain a measurement sample. Separately, 10 mL of sulfuric acid and 1 tablet of Keltab C tablet (degradation accelerator) were put into a Kjeldahl tube to make a blank. The following operations were performed with the measurement sample and blank. The Kjeldahl tube was installed in a decomposition apparatus installed and heated at 420 ° C. and left to heat for 3 hours. The Kjeldahl tube was taken out from the decomposition apparatus, allowed to cool to room temperature, and diluted by adding 10 mL of ion exchange water. A 30% by weight sodium hydroxide solution was added to the diluted solution to make it alkaline. Next, steam was blown into the alkaline solution, and the resulting distillate was distilled into the titration bottle (containing 25 ml of E solution). The distillate was titrated with 100 / N sulfuric acid. The consumed sulfuric acid was converted into the nitrogen content of the sample using the following mathematical formula.
Nitrogen content (% by weight) = [14.007 × normality of titrant × (V−V _o )] / sample weight (mg) × 100
V: Sample titration (ml)
V ₀ : Blank titration (ml)

[Method of measuring normal stress]
The normal stress of the starch aqueous solution was measured by the following method. The starch aqueous solution was prepared according to the following starch aqueous solution preparation method by adding a predetermined amount of the target compound and ion-exchanged water so as to be 2% by weight to 18% by weight. Using a viscoelasticity measuring device (Anton Paar, Physica MCR300) for the prepared aqueous solution at a temperature of 25 ° C., using a cone plate with a diameter of 50 mm, a gap of 0.052 mm, and a cone angle of 0.02 rad, the change in shear rate is 0.01 to The normal stress and viscosity were measured at 1000 (1 / second). Read the values of normal stress and viscosity at a shear rate of 1000 (1 / sec) at each aqueous solution concentration, create an approximate expression of the viscosity and normal stress, and calculate the viscosity at 300 mPa · s from the obtained approximate expression. The linear stress was calculated and taken as the normal stress value at a shear rate of 1000 (1 / second).

The starches used in Examples and Comparative Examples are shown below.
• Amphoteric starch (1): NT110M (raw material is corn starch), manufactured by Nippon Food & Chemical Co., Ltd. • Amphoteric starch (2): KH-1000 (raw material is corn starch), manufactured by Oji Cornstarch Co., Ltd./ Cationized Starch (1): cato308 (starting starch is tapioca starch), manufactured by Nippon SC Co., Ltd., comparative amphoteric starch (1): cato 315 (starting starch is tapioca starch), manufactured by Nippon NS Co., Ltd., comparative amphoteric Starch (2): cato 3210 (starting starch is tapioca starch), manufactured by Nippon SC Co., Ltd./Oxidized starch (1): manufactured by Ace A, Oji Cornstarch Co., Ltd.

* Preparation method of aqueous starch solution (surface treatment agent) Add 343 g of ion-exchanged water and 7 g of starch to a 500 ml beaker, raise the temperature to 90 ° C. while stirring, and further stir at the temperature for 1 hour. An aqueous solution was obtained. Next, the aqueous solution was cooled at a rate of 5 ° C./min to obtain a 2% by weight starch aqueous solution (aqueous solution used for surface treatment and viscosity measurement). In addition, except that the amount of starch was adjusted so that the aqueous solution concentration of starch was 4% by weight and 5% by weight, operations similar to the above were performed, and 4% by weight and 5% by weight starch aqueous solution (measurement of viscosity) To obtain an aqueous solution).

[Production method of base paper]
(1) 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 .

[Treatment method with surface treatment agent]
A 2% by weight aqueous starch solution (surface treatment agent) shown in Table 1 was spread on a glass plate with a bar coater to form a casting film on the glass plate. The surface treatment agent and glass plate used at this time were preheated to 40 ° 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). 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 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 base paper for coating.

[Production method of coated paper]
On one side (surface treated with a surface treatment agent) of the base paper for coating (surface-treated paper) obtained above, paint is applied to a blade-type coating machine (flexible trailing blade coater, coating speed 25 m / min, coating speed). The coating was applied at a working pressure of 0.7 kg / cm ² (manufactured by Kumagai Riki Kogyo Co., Ltd.) and dried at 105 ° C. for 2 minutes using a mirror dryer.

  Here, 50 g of calcium carbonate (FMT97, manufactured by Phimatech Co., Ltd.) and 50 g of fine kaolin (Amazon Plus, manufactured by Kadem Co., Ltd.) are blended, and polyacrylic acid soda (Poise 535M, Kao Corporation) is used as a dispersant. )) 0.2g and 2N caustic soda 0.2g were added and dispersed, and SBR latex (LX-430, acrylic acid-modified SBR latex for papermaking, manufactured by Nippon Zeon Co., Ltd.) with respect to 100g of pigment as an adhesive. ) 11 g and modified starch (phosphate-modified starch, manufactured by Oji Constarch Co., Ltd.) 3.5 g.

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

[Method for evaluating coated paper]
<Amount of surface treatment agent>
After calculating the respective basis weights from the weight of the base paper before the surface treatment and the weight of the surface treatment agent immediately after the surface treatment (before drying the dryer), the basis weight of the base paper immediately after the surface treatment-before the surface treatment From the value of the basis weight of the base paper) × (starch concentration in the surface treatment agent), the coating amount (g / m ² ) of the surface treatment agent was calculated (average value of 3 sheets measured). In the case where the treatment with the surface treatment agent was not performed, the treatment amount was set to 0 g / m ² .

<Amount of paint applied>
A sample obtained by cutting the coated paper obtained by the production of the coated paper into a width of 12.0 cm and a length of 10.0 cm, and a coated base paper (surface treated paper) obtained by the treatment with the surface treatment agent (width 12. 0 cm × length 12.0 cm) for 1 day under conditions of 23 ° C. and humidity 50%, respectively, and calculating the basis weight, respectively, (basis weight of coated paper−basis weight of surface-treated paper) The coating amount (g / m ² ) was calculated from the value (average value of the number of measured sheets 3).

<Glossiness of blank paper>
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 higher the blank paper glossiness, the higher the glossiness, and the difference of 4% in the blank paper glossiness value is sufficiently recognized as a significant difference. In Comparative Example 1, the glossiness of blank paper was measured for coated paper (treatment amount 0 g / m ² ) obtained without performing the treatment with the surface treatment agent.

<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 smaller the bulk density, the lighter the weight, and the difference of 0.02 g / cm ^{3 in} the bulk density is sufficiently recognized as a significant difference.

  From Table 1, Examples A1 and A2 in which the surface treatment of the present invention was applied to hand-made paper were much more difficult than Comparative Examples A1 to A5 which were not subjected to the surface treatment or were subjected to a surface treatment different from the present invention. Shows a high glossiness. This is because, in the case where the coating amount of the pigment-containing paint and the calender conditions are the same, the penetration of the paint in the example was suppressed, and as a result, more effective coating layers contributed to improving the glossiness than in the comparative example. It seems to be because.

Examples B1-B5 and Comparative Examples B1-B5, and Examples C1-C4 and Comparative Examples C1-C5

[Method for measuring viscosity of aqueous starch solution]
Viscosity measurement was performed by the method shown below using a B-type viscometer (model: BM, manufacturer: Toki Sangyo Co., Ltd.). A starch aqueous solution having a concentration of 5% by weight (the preparation method is as described later) was added to a viscosity beaker and immersed in a 25 ° C. water bath for 1 hour or longer. After confirming that the temperature of the aqueous starch solution reached 25 ° C. with a thermometer, a rotor corresponding to the viscosity of the aqueous starch solution was selected and attached to the viscometer. The viscosity beaker containing the starch 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.

  The normal stress was measured in the same manner as in Example A1 above.

The starches used in Examples and Comparative Examples are shown below.
・ Phosphoric acid cross-linked starch (1): MATSUTANI HANA, manufactured by Matsutani Chemical Co., Ltd. ・ Phosphoric acid cross-linked starch (2): C ☆ CREAMTEX 75728 (raw material is tapioca starch), manufactured by Tokai Starch Co., Ltd. ・ Phosphoric acid cross-linked starch (3): C ☆ CREAMTEX 75720 (starting from tapioca starch), manufactured by Tokai Starch Co., Ltd., comparative phosphate cross-linked starch (1): C ☆ CREAMTEX 75705 (starting from tapioca starch), manufactured by Tokai Starch Co., Ltd./oxidized Starch (1): Ace A, manufactured by Oji Cornstarch Co., Ltd .; Cationized starch (1): cato304 (starting starch is tapioca starch), Nippon NS Co., Ltd., phosphorylated starch (1): Spread # 250 Japan Made by Food Chemical Co., Ltd.

Other starches used in Examples and Comparative Examples are shown below.
・ Adipic acid cross-linked starch (1): C ☆ POLARTEX 06719 (raw material is waxy corn starch), manufactured by Tokai Starch Co., Ltd. ・ Adipic acid cross-linked starch (2): Crealam CH2020 (raw material is waxy corn starch), Tokai starch (stock) ) And comparative adipic acid cross-linked starch (1): C ☆ POLARTEX 06716 (raw material is waxy corn starch), Tokai Starch Co., Ltd. and comparative adipic acid cross-linked starch (2): C ☆ POLARTEX 06748 (raw material is waxy corn starch) ), Tokai Starch Co., Ltd./Oxidized Starch (1): Ace A (raw starch is corn starch), Oji Corn Starch Co., Ltd./cationized starch (1): cato 304 (starting starch is tapioca starch), Nippon NS Made by Sea Co., Ltd.

* Preparation method of aqueous starch solution (surface treatment agent) Add ion-exchanged water and starch to a 500 ml beaker so that the concentration of the starch suspension is 2% by weight. Furthermore, stirring was performed at the temperature for 1 hour to obtain an aqueous starch solution. Next, the aqueous solution was cooled at a rate of 5 ° C./min to obtain a 2% by weight starch aqueous solution (aqueous solution used for the surface treatment). Moreover, except having adjusted the quantity of starch so that the aqueous solution density | concentration of starch might be 5 weight%, operation similar to the above was performed and 5 weight% starch aqueous solution (aqueous solution used for a viscosity measurement) was obtained.

  The base paper was manufactured in the same manner as in Example A1 above.

  Using the starch shown in Tables 2 and 3, it was treated with a surface treatment agent in the same manner as in Example A1 above to obtain a base paper for coating.

  A coated paper was produced in the same manner as Example A1 from the coating base paper (surface-treated paper) obtained above. However, the paint is composed of 50 g of calcium carbonate (FMT97, manufactured by Phimatech Co., Ltd.) and 50 g of fine kaolin (Amazon Plus, manufactured by Kadem Co., Ltd.), and polyacrylic acid soda (Poise 535M, Kao Corporation) as a dispersant. 0.2 g of sodium hydroxide and 0.2 g of 2N caustic soda were added and dispersed, and 100 g of pigment as an adhesive, 11 g of latex (NP200B, manufactured by JSR), modified starch (phosphate-modified starch, Oji corn starch) A paint having an effective concentration of 65% prepared by mixing 3.5 g.

  Furthermore, a coated paper is obtained by performing a 2-nip treatment with a test super calender (manufactured by Kumagaya Riki Kogyo Co., Ltd.) with a linear pressure of 200 kg / cm, (pressure 49 MPa), a processing speed of 10 m / min, a roll temperature of 70 ° C. It was.

  The coated paper was evaluated in the same manner as in Example A1 above with respect to the treatment amount of the surface treatment agent, the coating amount of the paint, and the white paper glossiness.

  From Tables 2 and 3, Examples B1 to B5 and Examples C1 to C4, in which the surface treatment of the present invention was applied to handmade paper, were not subjected to surface treatment, or were comparative examples in which a surface treatment different from the present invention was applied. It turns out that very high glossiness is shown compared with B1-B5 and Comparative Examples C1-C4. This is because, in the case where the coating amount of the pigment-containing paint and the calender conditions are the same, the penetration of the paint in the example was suppressed, and as a result, more effective coating layers contributed to improving the glossiness than in the comparative example. It seems to be because.

Claims (5)

A starch having a viscosity of 5 to 12000 mPa · s at 25 ° C. of 2000 to 12000 mPa · s, a normal stress at a shear rate of 1000 (1 / sec) at 25 ° C. of 300 mPa · s and 0 to 2400 Pa (a ) Containing a surface treatment agent for coated base paper. The surface treating agent for coated base paper according to claim 1, wherein the content of starch (a) is 0.1 to 30% by weight. A coated base paper obtained by treating the surface treatment agent for coated base paper according to claim 1 or 2 at 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. . A density of 1.5 g / cm ³ formed by providing a coating layer of a coating material mainly composed of a pigment and a binder on the surface of the coated base paper according to claim 3 treated with the surface treating agent for a coated base paper. The coated paper that is below. A process (I) for obtaining a coated base paper by treating the surface treating agent composition containing the surface treating agent for coated base paper according to claim 1 or 2 and water on at least one side of a paper mainly made of pulp. And a surface of the coated base paper obtained in the step (I) treated with the surface treating agent composition for coated base paper, which is different from the surface treating agent composition, and contains a pigment and a binder as main components. A method of producing a coated paper having a density of 1.5 g / cm ³ or less.