JP5136864B2 - Surface coating liquid for papermaking and paper - Google Patents

Description

  The present invention relates to a papermaking surface coating solution used for paper manufacture and paper obtained using the same.

  The surface coating liquid for papermaking is applied to the paper surface using a coating machine such as a size press, gate roll, or calendar, thereby controlling the paper size effect (controlling the liquid absorptivity of the paper and the ink Used to improve writing performance, printability, and the like. The surface coating solution for papermaking usually has a surface sizing agent consisting of various polymer components that develop a size effect corresponding to the type of paper and the papermaking environment, and the strength of paper such as starch, polyvinyl alcohol, and polyacrylamide. It is prepared by mixing a paper-making paper strength agent made of a water-soluble polymer to be enhanced, and further appropriately mixing other additives.

For this reason, in order to improve the sizing performance of the paper coating surface coating solution (the performance of imparting a sizing effect to paper, the same applies hereinafter), the surface sizing agent added to the coating solution is mainly improved. Has been made. For example, in cationic surface sizing agents containing cationic monomers, the composition ratio of hydrophobic monomers such as styrenes and alkyl (meth) acrylates and cationic group-containing monomers such as dialkylaminoalkyl (meth) acrylates is in a specific range. By improving the hydrophobicity of the polymer by emulsifying and polymerizing a hydrophobic monomer in an aqueous medium having a cationic copolymer compound as an emulsifying dispersant, the emulsion improves the size performance (Patent Document 1). The technology of ensuring the size performance and stability of the coating liquid by making a mold (dispersion) (Patent Document 2), and the presence of a rosin resin in the polymerization reaction of a hydrophobic monomer and a cationic group-containing monomer A technique (Patent Document 3) that increases the size performance by performing the following is known. However, when these surface coating liquids for papermaking are used, for example, on a base paper having a low size effect such as a base paper not treated with an internal sizing agent, the coating liquid is relatively difficult to penetrate into the paper. When coating by a transfer method or the like, the paper size sizing agent contained in the coating solution may not exhibit the expected size performance, and the surface sizing agent polymer component contained in the paper surface coating solution It is considered that there is a limit to improving the paper size effect obtained only by improvement.

JP 2006-161259 A Japanese Patent Laid-Open No. 11-256696 JP 2001-073296 A

  An object of this invention is to provide the surface coating liquid for paper manufacture excellent in size performance.

  In the present invention, when the paper coating surface coating liquid using a specific cationic polymer as a constituent of the surface sizing agent further contains a water-soluble aluminum compound and starches, the size performance is unexpectedly improved. It was completed with the knowledge.

That is, the present invention relates to hydrophobic monomers (a1 and (meth) acrylic acid dialkylaminoalkyl esters composed of styrenes and / or nonionic (meth) acrylic acid esters having an ester substituent of 1 to 8 carbon atoms. It is obtained by copolymerizing (a2) and / or (meth) acrylic acid dialkylaminoalkylamide (a3) at a weight ratio of (a1): [(a2) + (a3)] = 15 to 90: 85-10. Copolymer having a structure in which all or part of amino groups derived from (meth) acrylic acid dialkylaminoalkyl ester (a2) and / or (meth) acrylic acid dialkylaminoalkylamide (a3) are quaternized water-soluble aluminum compound in a combined cationic water-soluble polymer (a) (B) and starches (C) a mixed Paper obtained by coating the surface coating solution and said papermaking surface coating liquid for papermaking obtained by relates.

  The surface-coating liquid for papermaking of the present invention can impart excellent sizing effect and ink jet aptitude to paper by being applied to the paper surface.

The surface coating solution for papermaking of the present invention comprises a cationic water-soluble polymer (A) (hereinafter referred to as component (A)), a water-soluble aluminum compound (B) (hereinafter referred to as component (B)) and starches ( C) (hereinafter referred to as component (C)).
As the component (A) , a hydrophobic monomer (a1) composed of styrenes and / or nonionic (meth) acrylic acid esters having an ester substituent having 1 to 8 carbon atoms (hereinafter referred to as component (a1)) ) And (meth) acrylic acid dialkylaminoalkyl ester (a2) (hereinafter referred to as component (a2)) and / or (meth) acrylic acid dialkylaminoalkylamide (a3) (hereinafter referred to as component (a3)) are essential monomers. Ingredients.

Examples of the component (a1) include styrenes and nonionic (meth) acrylic acid esters, and these can be used alone or in combination of two or more. As styrenes, styrene and / or styrene derivatives can be used. Examples of the styrene derivative include α-methylstyrene, vinyl toluene, ethyl vinyl toluene, and chloromethyl styrene. Nonionic acrylic esters are esters of (meth) acrylic acid and various monovalent alcohols, and have one polymerizable double bond derived from (meth) acrylic acid in one molecule (meta ) Acrylic acid esters. In addition, nonionic means that it does not have the functional group which ionizes in an aqueous medium. The number of carbon atoms of the ester substituent in the nonionic acrylic ester is from the viewpoint of ensuring the high size performance of the obtained paper coating surface coating liquid and the miscibility with the component (B) and the component (C). It is preferable to set it as 1-8. Such an ester substituent may be a linear, branched or cyclic alkyl group. Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate (n-propyl, iso-propyl), butyl (meth) acrylate (n-butyl, iso-butyl, tert-butyl), neopentyl (meth) acrylate, hexyl (meth) acrylate (n-hexyl, cyclohexyl), 2-ethylhexyl (meth) acrylate, and the like.
Moreover, it is preferable in the point which can improve a size performance by making the ratio of styrenes in (a1) component 60-100 weight%.

As the component (a2), the general formula (1): CH ₂ ═C (R ¹ ) COOA ¹ NR ² R ² (where R ¹ represents hydrogen or a methyl group, R ² represents a methyl group or an ethyl group, A ¹ represents an alkylene group having 2 to 6 carbon atoms). Specific examples include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and diethylaminopropyl (meth) acrylate. As the component (a3), the general formula (2): CH ₂ = C (R ³ ) CONHA ² NR ⁴ R ⁴ (wherein R ³ represents hydrogen or a methyl group, R ⁴ represents a methyl group or an ethyl group, A ² represents a dialkylaminoalkyl (meth) acrylamide represented by 2 to 6 carbon atoms), specifically, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylamino Examples include ethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, and N, N-diethylaminopropyl (meth) acrylamide. In the present invention, monomers (a2) and (a3) may be acid addition salt monomers. Thereby, the process of acid addition (water-solubilization or dispersion) described later can be omitted.

The content ratio of the monomer in the component (A) needs to be (a1): [(a2) + (a3)] = 15 to 90:85 to 10 by weight ratio, and 50 to 85:50. It is preferable to set it to ~ 15. When the weight ratio of the component (a1) is less than 15 (similarly, when the weight ratio of [(a2) + (a3)] exceeds 85), the hydrophobic region in the polymer is insufficient and high A surface coating solution for papermaking having size performance cannot be obtained. When the weight ratio of the component (a1) exceeds 90 (similarly, when the weight ratio of [(a2) + (a3)] is less than 10), stability as an aqueous solution or other coating liquid Mixability with components becomes insufficient.

As the component (A), only the component (a1) that imparts hydrophobicity to the copolymer and the component (a2) or component (a3) that imparts cationicity derived from a tertiary amino group can be used. Even what is obtained by polymerizing may be obtained by copolymerizing the components (a2) and (a3) together.
In addition, other vinyl monomer components copolymerizable with the components (a1) to (a3) can be used in combination as long as the object of the present invention is not impaired. Other vinyl monomer components include, for example, further improving the stability of the produced polymer dispersion for the purpose of, for example, making the obtained component (A) water-soluble or further improving the dispersion stability. For the purpose, it has a hydroxyl group monomer such as hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxypropyl (meth) acrylate, and a carboxyl group such as (meth) acrylic acid. Monomers, hydrophilic monomers such as (meth) acrylamide, vinyl acetate, acrylonitrile and the like can be used. The content ratio of the other vinyl monomers is not particularly limited, but from the viewpoint of ensuring the size performance, it is usually preferably about 30% by weight or less with respect to the total polymerization components, and styrenes and carbon as the component (a1) When used in combination with nonionic acrylic esters having an ester substituent of 1 to 8, it is preferably about 20% by weight or less, and in any case, with respect to all polymerization components More preferably, the content is 10% by weight or less.

For the copolymerization of the components (a1) to (a3), various known methods such as bulk polymerization and solution polymerization can be appropriately employed in the presence of an appropriate polymerization initiator. When solution polymerization is employed, aromatic solvents such as benzene and toluene, lower ketones such as acetone and methyl ethyl ketone, alcohols such as n-propyl alcohol and iso-propyl alcohol, and the like can be used as a solvent. The object of the present invention can be achieved even when the copolymerization reaction is carried out in the presence of a rosin resin. The kind of the polymerization initiator is not particularly limited, and a known one can be used. For example, 2,2′-azobisisobutyronitrile, azo compounds such as 2,2′-azobis-2,4-methylvaleronitrile, benzoyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, Any organic peroxide such as milperoxide and lauryl peroxide, and other redox catalyst polymerization initiators can be used. In the polymerization, chain transfer agents such as α-methylstyrene dimer, mercaptans and secondary alcohols can be used. As conditions for the polymerization reaction, the reaction temperature is usually about 70 to 140 ° C. and the reaction time is about 1 to 10 hours.

The copolymer thus obtained usually has a weight average molecular weight (polystyrene conversion value by gel permeation chromatography) of about 5,000 to 40,000. In the present invention, water and an inorganic acid such as hydrochloric acid and sulfuric acid or an organic acid such as formic acid, acetic acid and propionic acid are added to the copolymer to form an acid addition salt, which is obtained as a water-soluble polymer and used as component (A). .

The component (A), further, present in the copolymer (a2) quaternizing all or part of the tertiary amino groups derived from the component and / or (a3) component. Quaternization improves the water solubility or dispersion stability (storage stability) of the cationic polymer by increasing the cationic property of the component (A), and further improves the size performance of the coating solution. Can do. As the degree of quaternization, it is preferable that at least about 50 mol% of the amino group of the component (a2) and / or the component (a3) present in the copolymer of the component (A) is quaternized. Various commonly used quaternizing agents can be used. Typical examples include benzyl chloride, methyl chloride, dimethyl sulfate, ethylene chlorohydrin, allyl chloride, styrene oxide, propylene oxide, and epichlorohydrin. Of these, at least one selected from the group consisting of benzyl chloride, methyl chloride, dimethyl sulfate and epichlorohydrin is preferable from the viewpoint of improving the stability of the resulting cationic polymer. As the reaction conditions with the quaternizing agent, it is usually sufficient to keep the temperature at 50 to 90 ° C. for 1 to 4 hours.

In addition, as a manufacturing method of (A) component, you may manufacture by making it copolymerize using the monomer component which quaternized the (a2) component and / or (a3) component which are monomer components previously. In this case, the conditions for the quaternization of the monomer component and the conditions for the copolymerization reaction may be the same as described above.

As the component (B), various known materials can be used, and at least one selected from aluminum sulfate, aluminum chloride, basic aluminum sulfate, basic aluminum chloride, aluminum sulfate silicate, and polymers thereof is used. Is preferred. Among these, aluminum sulfate is particularly preferable from the viewpoint of cost.

As the component (C), various starches and / or modified starches used in paper coating liquids can be used. Examples of the starch include raw material starches such as corn starch, potato starch, tapioca starch, and wheat starch. The modified starch is derived from the raw material starch, for example, oxidized starch, pregelatinized starch, esterified starch, etherified starch, cross-linked starch, grafted starch, ammonium persulfate-modified starch, enzyme-modified starch, cationized starch, etc. Can be mentioned. Among these, processed starch, especially oxidized starch, ether starch, ammonium persulfate-modified starch, enzyme-modified starch in terms of low viscosity even when used at a high concentration, high aging resistance, and excellent film-forming ability. Is preferably used.

The content ratio of the component (A), the component (B), and the component (C) in the paper coating surface coating liquid of the present invention is not particularly limited and may be appropriately adjusted. From the viewpoint of size performance, it is preferable that (A) :( B) is 8:92 to 80:20 in terms of weight ratio (non-volatile content conversion), and (A) :( B) is It is more preferable to set it as 20: 80-67: 33. From the same viewpoint, the content of (A) and (B) with respect to 100 parts by weight of component (C) is preferably 0.5 to 50 parts by weight in terms of nonvolatile content, and more preferably 1.5 to More preferably, it is 15 parts by weight.

The surface coating liquid for papermaking according to the present invention may be produced by appropriately mixing the component (A) with the component (B) and the component (C). If necessary, the component (A) may be previously mixed with an inorganic acid. After adding an organic acid or an alkali such as sodium hydroxide, potassium hydroxide, ammonia, etc., mixing and dissolving the component (B), and finally adjusting the pH to the range of 2 to 6, the component (C) It is preferable to prepare by mixing. Moreover, you may mix various additives, such as a chelating agent, a slipper, a lubricant, an antifoamer, antioxidant, a film increasing aid, a pigment, and dye, as needed.

The surface coating liquid for papermaking thus obtained is usually cloudy and has a pH of 2 to 8, preferably 5 to 7, and each component in the coating liquid is dissolved or dispersed in an aqueous medium. Exists.

Examples of paper and paperboard to which the surface coating liquid for papermaking of the present invention can be applied include newspaper roll paper, writing paper, wallpaper, PPC paper, inkjet paper, printing paper, and paperboard such as a liner and a core. It is done. Various methods can be adopted as a coating method on the paper surface. Examples thereof include impregnation methods, bar coater methods, calendar methods, spray methods, two-roll size press methods, gate roll size presses, and shim size press film transfer methods. Further, the coating amount of the papermaking surface coating agent is usually 0.01-5 g / ^{m 2} about (nonvolatile content), preferably 0.04~2g / ^{m 2.}

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In each example, all parts and% are based on weight unless otherwise specified.

[Synthesis of Cationic Polymer (A)]
(Synthesis Example 1)
In a flask equipped with a stirrer, condenser, dropping funnel, nitrogen inlet tube and thermometer, 70 parts of styrene, 30 parts of dimethylaminoethyl methacrylate, 42.9 parts of isopropyl alcohol, and 2,2′-azobisisobutyronitrile 2.5 parts was charged, and a polymerization reaction was performed at 80 to 85 ° C. for 5 hours while stirring under a nitrogen stream. Subsequently, 11.5 parts of acetic acid and 300 parts of water were added. 17.7 parts of epichlorohydrin was added to the obtained copolymer, and the mixture was kept at 80 ° C. for 2 hours to quaternize the copolymer to form a cationic copolymer compound. Was adjusted to 20% to obtain a cationic water-soluble polymer (A1). Table 1 shows the viscosity and pH of the obtained cationic water-soluble polymer (A1) at 25 ° C.

(Synthesis Examples 2 to 13)
In Synthesis Example 1, the reaction was carried out in the same manner as in Synthesis Example 1 except that the type and amount of monomers used in the synthesis and the amount of epichlorohydrin used in quaternization were changed as shown in Table 1. Various cationic water-soluble polymers (A2 to A13) having a partial concentration of 20% were obtained. Table 1 shows the viscosity and pH of the obtained cationic water-soluble polymer (A2 to A13) at 25 ° C.

表中の記号は以下のとおりである。
ＤＭＡ：ジメチルアミノエチルメタクリレート、ＤＭＡＡ：ジメチルアミノプロピルアクリルアミド、ＭＭＡ：メチルメタクリレート、２ＥＨＡ：２−エチルヘキシルアクリレート、ＢＡ：ブチルアクリレート、ＬＡ：ラウリルアクリレート、ＥＣＨ：エピクロルヒドリン

The symbols in the table are as follows.
DMA: dimethylaminoethyl methacrylate, DMAA: dimethylaminopropyl acrylamide, MMA: methyl methacrylate, 2EHA: 2-ethylhexyl acrylate, BA: butyl acrylate, LA: lauryl acrylate, ECH: epichlorohydrin

[Preparation and performance evaluation test of surface coating solution for papermaking]
A coating solution is prepared using each of the cationic water-soluble polymers obtained as described above, and applied to (1) neutral high-quality base paper, (2) acidic high-quality base paper, and (3) paperboard, and the following test method Thus, their performance was evaluated.

(Sticking sizing degree; Testing Method for Stoechizing Sizing Degree of Paper)
In accordance with JIS P-8122, the Steecht sizing degree (second) was measured. The larger the value, the better the sizing degree.

(Pen writing size)
The evaluation of pen writing sizing degree is described in J. Tappi
No. 12 was used to measure the pen writing size. A sample having no ink bleeding was designated as 6, and a material in which ink was blurred and the line was thickened as a whole was designated as 1. The larger the value, the better the sizing degree.

(Water absorption test [Cobb method])
Cobb value (g / m ² ) was measured according to JIS P-8140. The contact time with water is 2 minutes, and the smaller the value, the better the sizing degree.

(1) Evaluation with neutral fine paper (Example 1) Preparation of surface coating liquid for papermaking (C) Oxidized starch was gelatinized at a non-volatile content of 15% as a component, and this was used as a non-volatile content. (C) A 5% concentration starch solution was prepared. Using this starch solution, the cationic water-soluble polymer A1 4 obtained in Synthesis Example 1 as the component (B) and 3 parts of the aluminum sulfate as the component (A) and 100 parts of the component (C) in terms of nonvolatile content, respectively. Parts were mixed to obtain a surface coating solution.

(Examples 2 to 26 and Comparative Examples 1 to 4) Preparation of surface coating liquid for papermaking Example 1 except that components (A) to (C) used in Example 1 were changed to those in Table 2. In the same manner, a paper coating surface coating solution was prepared. In addition, since Example (A) component (A12) to be used is not quaternized, Example 26 is treated as a reference example.

表中の記号は、以下のとおりである。
ＡＬＵＭ；硫酸アルミニウム、ＰＡＣ；ポリ塩化アルミニウム、塩基ＡＬＵＭ；塩基性硫酸アルミニウム、ＡＰＳ澱粉；過硫酸アンモニウム変性澱粉

The symbols in the table are as follows.
ALUM; aluminum sulfate, PAC; polyaluminum chloride, base ALUM; basic aluminum sulfate, APS starch; ammonium persulfate modified starch

(Performance test of paper coating surface coating solution)
A neutral paper having a basis weight of 70 g / m ² was made at pH 7.2 using a slurry having the following composition.
Blending of slurry: 65 parts of L-BKP (360 ml CSF), 35 parts of N-BKP (420 ml CSF), 10 parts of calcium carbonate (Tama Pearl 121 manufactured by Okutama Kogyo Co., Ltd.), neutral rosin sizing agent (Size Pine NT-78 Arakawa Chemical Industries) Co., Ltd.) 0.2 part, aluminum sulfate 0.5 part, amphoteric starch (Cata 3210 made by Nippon NSC Co., Ltd.) 1 part, yield improver (Polytension 1000 Arakawa Chemical Industries, Ltd.) 0.03 part was obtained. After coating each of the coating liquids of Examples 1 to 26 and Comparative Examples 1 to 4 (Table 2) on a base paper using a lab size press coating machine, it was passed through a rotary drum dryer at 105 ° C. for 1 minute. Coated paper was obtained by drying, and the sizing degree and pen writing sizing degree were measured by the following methods. The results are shown in Table 3.
In this performance test and the following performance tests, the abbreviations of the pulp types used for blending the slurry are as follows.
L-BKP: Hardwood bleached kraft pulp N-BKP: Softwood bleached kraft pulp L-UKP: Hardwood unbleached kraft pulp

(2) Evaluation on acidic fine paper (Examples 27 to 45 and Comparative Examples 5 to 8) Preparation of surface coating solution for papermaking The components (A) to (C) used in Example 1 above are those in Table 4. A surface coating solution for papermaking was prepared in the same manner as in Example 1 except that it was changed to. In addition, since Example (A) component (A12) to be used is not quaternized, Example 45 is treated as a reference example.

(Performance test of paper coating surface coating solution)
An acidic paper having a basis weight of 80 g / m ^{2 was made} at pH 4.7 using a slurry having the following composition.
Blending of slurry: 60 parts of L-BKP (350 ml CSF), 40 parts of N-BKP (400 ml CSF), 20 parts of talc (manufactured by Talc ND Japan Talc Co., Ltd.), rosin emulsion sizing agent (Size Pine N-773 Arakawa Chemical Industries, Ltd.) 0.2 parts, aluminum sulfate 1.25 parts, yield improver (Polytension 1000 Arakawa Chemical Industries, Ltd.) 0.03 parts
After applying each coating liquid (Table 4) of Examples 27-45 and Comparative Examples 5-8 to the obtained base paper using a laboratory size press coating machine, it was applied to a rotary drum dryer at 105 ° C. The coated paper was obtained by drying for 1 minute to obtain coated papers. The results are shown in Table 5.

(3) Evaluation with paperboard (Examples 46 to 63 and Comparative Examples 9 to 12) Preparation of surface coating solution for papermaking The components (A) to (C) used in Example 1 above were changed to those in Table 6 A paper coating surface coating solution was prepared in the same manner as in Example 1 except that. In addition, since Example 63 (A) component (A12) to be used is not quaternized, it is treated as a reference example.

(Performance test of paper coating surface coating solution)
Slurry prepared by making a base paper having a basis weight of 160 g / m ² at pH 6.8 using a slurry having the following composition: 100 parts of L-UKP (400 ml CSF), 0.125 part of aluminum sulfate After coating each of the coating liquids of Examples 46 to 63 and Comparative Examples 9 to 12 (Table 6) using a coating machine, the coating liquid was dried by passing through a rotary drum dryer at 105 ° C. for 1 minute. Papers were obtained and their water absorption test (Cobb method) was carried out. The results are shown in Table 7.

Claims (10)

Hydrophobic monomers consisting of styrenes and / or nonionic (meth) acrylic acid esters having an ester substituent of 1 to 8 carbon atoms (a1 and (meth) acrylic acid dialkylaminoalkyl esters (a2) and / or (Meth) acrylic acid obtained by copolymerizing dialkylaminoalkylamide (meth) acrylic acid (a3) at a weight ratio of (a1): [(a2) + (a3)] = 15 to 90: 85-10 Cationic water solution which is a copolymer having a structure in which all or part of amino groups derived from dialkylaminoalkyl ester (a2) and / or (meth) acrylic acid dialkylaminoalkylamide (a3) are quaternized water-soluble aluminum compound in sex polymer (a) (B) and the resulting et by mixing starch (C) Papermaking surface coating liquid that. The surface coating liquid for papermaking of Claim 1 containing the nonionic (meth) acrylic acid ester which has styrenes and / or a C1-C8 ester substituent as a hydrophobic monomer (a1). The surface coating solution for papermaking according to claim 2, wherein the ratio of styrenes in the hydrophobic monomer (a1) is 60 to 100% by weight. The paper coating surface coating solution according to claim 2 or 3, wherein the ester substituent in the nonionic (meth) acrylic acid ester has 4 to 8 carbon atoms. (Meth) acrylic acid dialkylaminoalkyl ester (a2) and / or (meth) amino group derived from acrylic acid dialkylaminoalkyl amide (a3) at least 50 mole percent of claims 1-4 which is quaternized The surface coating liquid for paper manufacture in any one. The amino group derived from (meth) acrylic acid dialkylaminoalkyl ester (a2) and / or (meth) acrylic acid dialkylaminoalkylamide (a3) is selected from the group consisting of benzyl chloride, methyl chloride, dimethyl sulfate and epichlorohydrin. The surface coating solution for papermaking according to any one of claims 1 to 5 , which is quaternized using at least one selected. The water-soluble aluminum compound (B) is at least one selected from the group consisting of aluminum sulfate, aluminum chloride, basic aluminum sulfate, basic aluminum chloride, aluminum sulfate oxalate and polymers thereof. The surface coating liquid for papermaking as described in any one of 6 . The surface coating solution for papermaking according to any one of claims 1 to 7 , wherein the starch (C) is at least one selected from the group consisting of oxidized starch, ether starch, ammonium persulfate-modified starch and enzyme-modified starch. The content ratio (nonvolatile content conversion) of the cationic water-soluble polymer (A) and the water-soluble aluminum-based compound (B) is (A) :( B) = 8: 92 to 80:20 by weight ratio, and starches (C) The total amount of (A) and (B) with respect to 100 parts by weight is 0.5 to 50 parts by weight. The surface coating solution for papermaking according to any one of claims 1 to 8 . A paper obtained by applying the surface coating liquid for papermaking according to any one of claims 1 to 9 .