JP4306362B2 - Surface sizing agent for newsprint and newsprint - Google Patents

Description

  The present invention relates to a newsprint paper surface sizing agent and newsprint paper coated with the same.

In order to meet the recent demands for high-speed, large-scale printing and multicolor printing, the newspaper printing system is shifting from the conventional relief printing system to the offset (lithographic) printing system.

However, in the offset printing method, as is well known, since dampening water is also supplied to the printing paper during printing, the paper absorbs water and the paper surface becomes sticky and sticks to the printing cylinder (blanket cylinder). (Wet tackiness) phenomenon occurs, and the equipment may become dirty due to pulp peeling, the printing surface may be disturbed, and in severe cases, the paper may be cut off.

Therefore, the size is usually given to control the water absorption of the printing paper, but the method of adding chemicals at the time of the pulp slurry like the internally added size has a poor yield of chemicals on the pulp sheet. In order to obtain the size effect, a large amount of sizing agent is required, which is disadvantageous in cost. In particular, when DIP (deinked pulp), whose demand has been increasing in recent years, is used, there is a problem that the size effect is difficult to be exhibited due to poor paper quality. If the size effect is low, printability such as ink fillability deteriorates, and disadvantages such as image quality deterioration occur.

Therefore, in this field, there is a movement to replace the internal sizing agent with the surface sizing agent. Since the surface sizing agent yields almost 100% on the surface of the printing paper, it can effectively exert a size effect and is advantageous in terms of cost. Further, operational problems such as paper-making stains and fluctuations in the size effect due to the paper-making temperature. Have various advantages.

Various surface sizing agents for newspaper are already known, and for example, a surface sizing agent containing an olefin / maleic acid-based water-soluble copolymer as a component (for example, see Patent Document 1) is proposed. Has been. However, although this can reduce Nepari alone, there is a disadvantage that it is inferior in size effect.

  In addition, a copolymer composed of an ethylenically unsaturated carboxylic acid and an ethylenically unsaturated carboxylic acid ester (see, for example, Patent Document 2) has been proposed. Also, there is a problem that foaming occurs when the sizing agent is applied with a gate roll or the like.

Japanese Patent Publication No.57-4760 JP-A-11-315493

  The problem to be solved by the present invention is to provide a surface sizing agent for newsprint paper that has a good balance between the good size and the suppression of nipparity during offset printing, and has less foaming during sizing coating.

  As a result of intensive studies to solve the above problems, the present applicant has obtained a copolymer composed of an olefin and maleic acid from an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated carboxylic acid ester monomer. It was found that a surface sizing agent for newsprint that can solve the above-mentioned problems can be obtained by mixing the water-soluble copolymer.

That is, the present invention is a water-soluble composition comprising 45 to 60% by weight of an ethylenically unsaturated carboxylic acid monomer and 55 to 40% by weight of an ethylenically unsaturated carboxylic acid ester monomer containing butyl (meth) acrylate . Copolymer (A) (hereinafter referred to as copolymer (A)) , and a water solution comprising a linear α-olefin having 9 to 20 carbon atoms, 2,4,4-trimethyl-1-pentene, and maleic acid A surface sizing agent for newsprints comprising a water-soluble copolymer (hereinafter referred to as copolymer (B)) in a solid content weight ratio of 7/3 to 3/7 ; Related to newspaper.

  According to the surface sizing agent for newsprint according to the present invention, it is possible to suppress the newsprint of newsprint during offset printing and to impart high sizing properties to newsprint. And since there is little foaming at the time of sizing agent coating, operativity can be made favorable.

  First, the copolymer (A) will be described. The copolymer (A) acts as a factor for improving the size effect of the surface sizing agent for newsprint according to the present invention. The ethylenically unsaturated carboxylic acid monomer constituting the copolymer (A) can be used without particular limitation as long as it has a carboxyl group or a salt thereof in the molecule. For example, (meth) acrylic acid (acrylic) Monocarboxylic acid, maleic acid, itaconic acid, citraconic acid, fumaric acid, muconic acid and other dicarboxylic acids or their anhydrides, and their sodium and potassium salts And alkali metal salts such as alkaline earth metal salts, ammonium salts, and salts of organic bases.

Specific examples of the ethylenically unsaturated carboxylic acid monomer constituting the copolymer (A) include various alcohol esters and half esters of the ethylenically unsaturated carboxylic acid monomer. Examples of the group include linear, branched or cyclic alkyl groups having about 1 to 18 carbon atoms, such as 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, etc.), decyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate It is below. In the present invention, the ethylenically unsaturated carboxylic acid ester monomer is butyl (meth) acrylate, particularly ( It contains essential n-butyl acrylate . Moreover, it is preferable to use together n-butyl acrylate and n-butyl methacrylate as this butyl (meth) acrylate . In this case, the preferred range of use amount is about 0.3 to 0.6 by weight ratio of n-butyl acrylate / n-butyl methacrylate.

The copolymer (A) needs to contain 45 to 60% by weight of the ethylenically unsaturated carboxylic acid monomer in the molecule, and also contains ethylenically unsaturated butyl (meth) acrylate. It is necessary to contain 55 to 40% by weight of a carboxylic acid ester monomer. Here, when the amount of the ethylenically unsaturated carboxylic acid monomer is less than 45 % by weight, Nepari tends to be suppressed, but at the same time, the size tends to decrease, and foaming tends to easily occur during the sizing agent coating. . On the other hand, when the amount of the monomer exceeds 60 % by weight, the size increases, but Nepari tends to be strong.

Further, other polymerizable monomers may be used as necessary as a constituent of the copolymer (A) as long as the object of the present invention is not deviated and the effect can be maintained. The Other polymerizable monomers, vinyl acetate, vinyl esters such as vinyl propionate, alkyl vinyl ethers having 1 to 22 carbon atoms, mention may be made of nonionic unsaturated monomers such as vinyl pyrrolidone. The amount of the polymerizable monomer used is usually about 10% by weight or less in the copolymer (A) molecule.

  The copolymer (A) can be produced by various known polymerization methods. Specific examples include emulsion polymerization. First, the ethylenically unsaturated carboxylic acid monomer, the ethylenically unsaturated carboxylic acid ester monomer and, if necessary, a reaction vessel equipped with a suitable heating device and stirrer. The other polymerizable monomer is charged in a predetermined amount, and then water and various known emulsifiers are charged in the container to emulsify and dissolve these monomers. Furthermore, what is necessary is just to add a well-known polymerization initiator and a chain transfer agent, to heat at about 20-120 degreeC, and to carry out emulsion polymerization over about 2 to 12 hours under stirring.

  Moreover, solution polymerization is mentioned as manufacturing methods other than an emulsion polymerization method. Specifically, an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated carboxylic acid ester monomer, and other polymerizable monomers as required, in a reaction vessel equipped with a suitable heating device and a stirrer In a predetermined amount, and then water and an organic solvent are added to the container, and a known polymerization initiator and chain transfer agent are added, heated to about 20 to 120 ° C., and stirred for 2 to 12 hours. What is necessary is just to superpose | polymerize. In addition, it is preferable that a copolymer (A) is manufactured by the said emulsion polymerization from a viewpoint that a size effect and Nepari suppression are excellent.

  Examples of the organic solvent include alcohols such as ethyl alcohol and propyl alcohol; aromatic hydrocarbons such as benzene and toluene; lower ketones such as acetone and methyl ethyl ketone; ethyl acetate, chloroform and dimethylformamide. However, in view of environmental load and work hygiene, it is desirable to distill off these organic solvents by distillation under reduced pressure or the like.

  Examples of the emulsifier include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, sorbitan alkyl ester, polyoxyethylene sorbitan alkyl ester and oxyethyleneoxypropylene block copolymer. Two or more of these may be used in combination. Examples of the anionic surfactant include alkyl sulfonates, alkyl sulfo fatty acid ester salts, dialkyl sulfosuccinic acid esters, polyoxyalkylene alkyl ether sulfosuccinic acid monoester salts, polyoxyalkylene alkenyl ether sulfosuccinic acid monoester salts, and polyoxyalkylenes. Aryl ether sulfosuccinic acid monoester salt, alkyl diphenyl ether disulfonate, sulfated oil, sulfated fatty acid ester salt, alkyl sulfate ester salt, alkenyl sulfate ester salt, polyoxyalkylene alkenyl ether sulfate ester, polyoxyalkylene aryl ether sulfate ester Salt, alkyl phosphate ester salt, polyoxyalkylene alkyl ether phosphate ester salt, polyoxyalkylene alkenyl Terurin acid ester salts, polyoxyalkylene aryl ether phosphoric acid ester salts and the like can be exemplified. Two or more of these may be used in combination. In addition, as the cationic surfactant, a hydrophilic group is a primary to quaternary ammonium group, a pyridinium group, or the like. Specifically, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, chloride Octadecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, dioctyldimethylammonium chloride, distearyldimethylammonium chloride, lauryldimethylbenzylammonium chloride, myristyldimethylbenzylammonium chloride, stearyldimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride Examples include octadecyldimethylbenzylammonium chloride and oxyethyldodecylamine. Kill. Two or more of these may be used in combination. In addition, if it is a nonionic emulsifier, since it is possible to complete emulsion polymerization with a relatively small usage-amount, there exists an advantage that the foaming at the time of sizing agent coating can be suppressed.

Various known initiators can be used without particular limitation as the polymerization initiator. Specific examples include inorganic peroxides such as hydrogen peroxide, ammonium persulfate, and potassium persulfate; organic peroxides such as benzoyl peroxide, dicumyl peroxide, and lauryl peroxide; 2,2′-azobisisobutyl Examples include azo compounds such as nitrile and dimethyl-2,2′azobisisobutyrate. When the polymerization initiator is a radical polymerization initiator, a reducing agent such as sodium sulfite or sodium thiosulfate may be used in combination to make the reaction system a redox system. In addition, various known chain transfer agents such as n-dodecyl mercaptan, n-octyl mercaptan, terlead decyl mercaptan, n-octadecyl are used for the purpose of adjusting the degree of polymerization (molecular weight) during polymerization to make the water-soluble polymer have a desired molecular weight. Alkyl mercaptan chain transfer agents such as mercaptan and n-hexadecyl mercaptan, 2-mercaptobenzothiazole, bromotrichloromethane, alpha-methylstyrene dimer and the like can also be used. In addition, about 0.01 to 5 weight% is suitable for the usage-amount of a polymerization initiator or a chain transfer agent normally with respect to each monomer whole quantity which comprises the said water-soluble polymer.

The copolymer (A) thus obtained usually has a solid content of about 10 to 30% by weight, a viscosity in the solid content concentration range of about 10 to 10,000 mPa · s (25 ° C.), and a pH of 8.0 to 9. About 5. The molecular weight is not particularly limited, but if it is too large, the viscosity tends to increase and the Nepari tends to be strong at the time of printing, and if it is too low, the size tends to be insufficient. Therefore, the weight average molecular weight is usually 10,000 to 100,000. The degree, preferably in the range of 20000 to 50000.

Next, the copolymer (B) will be described. A copolymer (B) acts as a factor which suppresses the Nepari of the surface sizing agent for newsprint according to the present invention. As the olefin monomer constituting the copolymer (B) , 2,4,4-trimethyl-1-pentene and It is necessary to use a combination of α-olefins having 9 to 20 carbon atoms (1-decene, 1-dodecene) . Moreover, in the range which does not impair the objective of this invention, the alpha olefin which may be linear, branched, and cyclic other than these can be used. Specifically, ethylene, propylene, 2-methyl-1-propene (isobutylene), 1-butene, 1-pentene, 1-hexene, 1-octene , 3-methyl-1-butene, 3-methyl-1- pentene, vinylcyclohexane, 4-vinylcyclohexene is Ru can be exemplified. Other olefinic monomer components such as cycloolefin and diolefin may be copolymerized.

The maleic acid constituting the copolymer (B) includes maleic acid, maleic anhydride, half esters of maleic acid and alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts and ammonium salts. And salts of organic bases.

Further, other polymerizable monomers may be used as necessary as a constituent of the copolymer (B) as long as the object of the present invention is not deviated and the effect can be maintained. Examples of the other polymerizable monomers include ethylenically unsaturated carboxylic acid ester, styrene, α-methylstyrene, vinyltoluene, divinylbenzene, (meth) acrylamide, vinyl acetate, propion used in the copolymer (A). Examples thereof include vinyl esters such as vinyl acid, nonionic unsaturated monomers such as alkyl vinyl ethers having 1 to 22 carbon atoms, and vinyl pyrrolidone. The amount of the polymerizable monomer used is usually about 0 to 10% by weight in the copolymer (B) molecule.

  In addition, it is preferable that the composition of the monomer which comprises a copolymer (B) is adjusted so that an olefin monomer may be 10 to 55 weight% and maleic acid 5 to 50 weight%. By setting it as such a numerical range, the surface sizing agent for newsprint according to the present invention can exhibit the desired effect.

  The copolymer (B) may be produced by various known solution polymerization methods. For example, the olefinic monomer and maleic acid are charged in predetermined amounts in a reaction vessel equipped with a suitable heating device and stirrer. Then, the organic solvent listed above is charged into the container, and these monomers are dissolved. Furthermore, the known polymerization initiator and chain transfer agent described above are added, heated to about 20 to 120 ° C., and solution polymerization may be performed over 2 to 12 hours with stirring.

  The obtained copolymer (B) has a solid content of usually about 10 to 30% by weight, a viscosity in the solid content concentration range of about 10 to 5000 mPa · s (40 ° C.), and a pH of about 8.0 to 9.5. It is a water-soluble polymer. In addition, although it does not restrict | limit especially about molecular weight, Usually, it is about 1000-1 million, Preferably it is set as the range of 2000-100000. When the molecular weight is less than 1000, a sufficient size effect tends not to be obtained. When the molecular weight exceeds 1000000, not only the viscosity tends to be excessively increased and the Nepari tends to be strong, but also the transfer and coating of the surface sizing agent is difficult. Handling during construction tends to be difficult.

  The surface sizing agent for newsprint according to the present invention is obtained by mixing the copolymer (B) with the copolymer (A). The timing and means of mixing are not particularly limited. For example, the copolymer (A) and the copolymer (B) may be mixed immediately before actual use, or may be mixed in advance. Moreover, you may use not only a mixture but the mixture formed by manufacturing a copolymer (A) continuously in the same reaction system, after manufacturing a copolymer (B). The weight ratio (solid content) of the copolymer (A) and the copolymer (B) is not particularly limited, but is preferably about 7/3 to 3/7, particularly preferably 6/4 to 4/6. is there. By setting it as such a range, it is possible to achieve both a high size effect and Nepari suppression. That is, when the used weight of the copolymer (A) exceeds the upper limit, the size becomes good but the Nepari tends to become strong. On the contrary, if the lower limit is not reached, the Nepari tends to be suppressed but the size is insufficient. There is a tendency.

The solid content concentration of the surface sizing agent for newsprint according to the present invention is usually about 10 to 30% by weight, and the viscosity at a solid content concentration of 20% by weight (Brookfield rotational viscometer: 40 ° C.) is 10 to 5000 mPa · s. The pH is adjusted to about 8.0 to 9.5 and is put to practical use.

Examples of the surface sizing agent for newsprint according to the present invention include oxidized starch, phosphate esterified starch, enzyme-modified starch, starch derivatives (hydroxyethyl starch, dialdehyde starch, etc.), starch such as cationized starch; carboxymethylcellulose, etc. Cellulose strength enhancers such as polyvinyl alcohols, polyacrylamides, and sodium alginate can be used in combination. In this way, the paper strength of the newsprint paper coated with the sizing agent can be increased.

The surface sizing agent for newsprint according to the present invention is applied to a newsprint base paper by a conventionally known method such as an impregnation method, a size press method, a gate roll method, a bar coater method, a calendar method, or a spray method. Its coating amount is usually 0.001 to 1 g / ^{m 2} in terms of solid content, preferably from 0.01 to 0.5 g / ^{m 2.} When the coating amount is less than 0.001 g / m ² , the effect of the surface sizing agent is not sufficiently exhibited at the size imparting point. On the other hand, even if the coating amount is more than 1 g / m ^{2, the} desired size effect cannot be obtained, and the cost is disadvantageous.

  In addition, if necessary, various other known sizing agents, emulsion type sizing agents, anti-slip agents, antiseptics, rust inhibitors, pH adjusters, antifoaming agents, thickeners, fillers, antioxidants, water resistance Agents, film-forming aids, pigments, dyes and the like can be added.

Newsprint base paper to which the surface sizing agent for newsprint according to the present invention is applied is mechanical pulp (MP) such as ground pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and semi-chemical pulp. ), Chemical pulp (CP) typified by kraft pulp (KP), deinked pulp (DIP) obtained by deinking waste paper containing these pulps, and recovery obtained by removing damaged paper from the papermaking process Pulp and the like are mixed alone or in an arbitrary ratio, and are generally made by a publicly known paper machine. The blending ratio of DIP is preferably in the range of 50 to 100% in view of the recent trend toward high blending of DIP. Moreover, the basis weight of the base paper is not particularly limited, but is about 34 to 45 g / m ² .

Note that this newsprint base paper may be a base paper with an internal size. However, in the present invention, there is also a meaning to solve the problems associated with the internal addition as described above. Therefore, the effect of the present invention is more exhibited by using a base paper that has not been subjected to the internal addition size. be able to. That is, by adding the surface treatment agent of the present invention, it is possible to impart a size property equal to or greater than the size of the internal additive without performing the internal size.

The newsprint base paper to which the surface sizing agent according to the present invention is applied may be acid newsprint base paper, or neutral or alkaline paper newsprint base paper.

The newsprint according to the present invention is obtained by applying the surface sizing agent for newsprint according to the present invention to the newsprint base paper with the coating amount and drying it by a known means.

  Hereinafter, the present invention will be specifically described with reference to reference examples, 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.

Production Example 1 <Production of Copolymer (A): A-1>
While introducing nitrogen into a reactor equipped with a stirrer, a reflux condenser, and a nitrogen introduction tube, 200 parts of soft water and 1.2 parts of a nonionic surfactant (trade name “Neugen ET190” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) An anionic surfactant (trade name “Neohaitenol S-70” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was charged, and the system was heated to 80 ° C. while stirring. Next, a monomer mixture obtained by mixing 45 parts of methacrylic acid, 35 parts of butyl methacrylate, 20 parts of butyl acrylate and 0.5 part of n-dodecyl mercaptan as a chain transfer agent from the dropping funnel is dropped over about 2 hours. At the same time, an aqueous solution prepared by dissolving 4 parts of ammonium persulfate as an initiator in 100 parts of water was dropped from another dropping funnel over about 2 hours. The system was then kept warm for 2 hours to complete the reaction. Thereafter, 43.6 parts of a 48% aqueous sodium hydroxide solution (100 mol% with respect to acrylic acid) was added, diluted with water and adjusted so that the concentration of the copolymer was 15%, and the viscosity at 25 ° C. was 1000 mPa · s. A copolymer aqueous solution A-1 was obtained.

Production Examples 2 and 3
Copolymer aqueous solutions A-2 and A-3 were obtained in the same manner as in Example 1 except that the monomers shown in Table 1 were used.

Production Example 4 <Production of Copolymer (B): B-1>
A flask equipped with a stirrer, condenser, dropping funnel, nitrogen inlet tube and thermometer was charged with 68.8 parts of isobutyl alcohol half ester of maleic acid, 58.8 parts of maleic acid and 75.2 parts of toluene, and stirred nitrogen stream The temperature was raised to 110 ° C. 73.7 parts of diisobutylene (76% content of 2,2,4-trimethyl-1-pentene) and 56 parts of 1-octene in the dropping funnel, and 12.0 parts of t-butyl peroxybenzoate in another dropping funnel And 35 parts of toluene were charged. These were added dropwise to the flask in about 1.5 hours from the dropping funnel, and kept warm for about 2 hours under reflux. Thereafter, 4.8 parts of t-butyl peroxybenzoate and 15 parts of toluene were dropped over about 30 minutes, and the mixture was further kept at the same temperature for 1 hour. Toluene was distilled off under reduced pressure, and the polymer was neutralized with 13.3 parts of sodium hydroxide, a predetermined amount of water and 87.4 parts of 28% aqueous ammonia to obtain an aqueous copolymer solution B-1. The solid content was 20.5%, the pH was 9.0, and the viscosity at 25 ° C. was 80 mPa · s.

In Table 1, MAA: methacrylic acid, BA: butyl acrylate, BMA: butyl methacrylate, C8: 1-octene, DIB: diisobutylene (2,4,4-trimethyl-1-pentene), MAn-IBA: malein An ester consisting of an acid and isobutyl alcohol, MAn: means maleic acid.

In Table 1, “molecular weight” means the weight average molecular weight of the obtained copolymer, and the value is a styrene equivalent value measured by gel permeation chromatography (trade name “High Speed GPC System HLC8120” manufactured by Tosoh Corporation). Means.

<Adjustment of test coating solution>
The aqueous copolymer solution (solution) obtained in Production Examples 1 to 4 was mixed at the ratio (solid content) shown in Table 2, and then commercial starch (trade name “Oji Ace A”, Oji Corn Starch Co., Ltd.) )) Was mixed so as to have the ratio shown in Table 2 (solid weight ratio), and further diluted with distilled water to prepare a coating solution. In Table 2, “Viscosity (mPa · s / 40 ° C.)” indicates a value measured with a Brookfield viscometer.

<Creation of test paper>
Using acid newspaper base paper (weighing 43 g / m ² ) as base paper, each surface sizing agent obtained by the above method was applied using a gate roll coater so that the coating amount of the sizing agent was as shown in Table 2. Next, each coated paper was dried at 80 ° C. for 30 seconds using a rotary drum dryer to obtain a target test paper. The acid newspaper base paper coated only with starch is shown in Table 2 as a reference example.

Examples 1-6 , Comparative Examples 1-5 , Reference Example (Measurement of sizing degree: Drop sizing degree)
Using each test paper obtained by the above method, 5 μl of water was dropped on the paper surface based on the method based on Japan TAPPI No. 33, the time until the water droplet was absorbed by the paper surface was measured, and the surface size ( Drop size) degree (second) was measured. Note that the measurement of the drop size is considered to indicate the paper behavior in the time from when the paper is dampened with the offset rotary press until it is discharged as printed matter. The higher the number (longer seconds), the better the size. The results are shown in Table 2.

(Measurement of sizing: measurement of contact angle)
Using each test paper obtained by the above method, using a Dynamic Adsorption Tester 1100 DAT (manufactured by Fibro), 1 μl of water droplet is dropped on the paper surface, and the contact angle is measured 0.1 seconds and 1 second after dropping. did. This contact angle is considered to indicate the paper behavior in a short time between the cylinders in an actual newspaper offset printing press. The larger the contact angle (degree), the better the size. The results are shown in Table 2.

(Measurement of Neppari)
Using each test paper obtained by the above method, two test papers were dipped in water for 1 second, then pulled up, and passed through a roll with a linear pressure of 980 N / cm in a state where the surfaces were bonded together. After the test paper was air-dried, the T-shaped peel strength (N / m) was measured using a tensile tester (trade name “LRX” manufactured by Yasuda Seiki Shokai Co., Ltd.). The obtained measured value is defined as Nepari intensity. The higher the value, the stronger Nepari. The results are shown in Table 2.

(Foaming test)
In the copolymers (mixtures) described in Examples 1 to 9 and Comparative Examples 1 to 3, commercially available starch (trade name “Oji Ace A”, manufactured by Oji Corn Starch Co., Ltd.) was used. Prepared to be 0.0 wt% / 1.3 wt%, then heated the resulting mixture to 50 ° C and treated with a home mixer for 2 minutes, then measured the liquid level immediately after treatment did. The liquid level before the treatment is 60 mm. The results are shown in Table 2.

The surface sizing agent according to the present invention is particularly suitably used for newsprint applications.

Claims (3)

Water-soluble copolymer (A) comprising 45 to 60% by weight of an ethylenically unsaturated carboxylic acid monomer and 55 to 40% by weight of an ethylenically unsaturated carboxylic acid ester monomer containing butyl (meth) acrylate And
A water-soluble copolymer (B) comprising 2,4,4-trimethyl-1-pentene, a linear α-olefin having 9 to 20 carbon atoms, and maleic acid,
A surface sizing agent for newsprint, comprising a solid content by weight ratio of 7/3 to 3/7 . The surface for newsprint according to claim 1, wherein the butyl (meth) acrylate is composed of n-butyl acrylate and n-butyl methacrylate, and the weight ratio thereof is 0.3 to 0.6. Sizing agent. Newsprint paper which coats the surface sizing agent for newsprint paper according to claim 1 or 2 on the surface.