JP4955291B2 - Neutral newsprint for offset printing - Google Patents

Description

  The present invention relates to a neutral newsprint for offset printing, and more particularly to a neutral newsprint for offset printing with a low basis weight and a high ash content that has an appropriate stiffness and does not impair the offset printing workability.

Between newsprint past 10 years, what was conventionally basis weight 50 g / m ² is the basis weight of 43 g / m ² to ultralight newspapers, even to lightweight one newspaper 40 g / m ² low basis Quantification (weight reduction) has advanced. In the background, there are demands for resource saving, low cost, and weight reduction by reducing raw materials, and in order to meet this demand, progress in offset printing technology and papermaking technology corresponding to weight reduction has promoted weight reduction.

  In addition, from the viewpoint of protecting forest resources and effectively utilizing pulp resources, the ratio of waste paper is increasing in recent years, and the ratio is currently over 50%. Since used paper undergoes disaggregation and deinking processes during the recycling process, the fibers themselves are damaged and the rigidity is lost by chemicals. Therefore, the high blending of used paper is a negative direction for bending stiffness.

  Further, in recent years, the number of neutral newspaper printing papers with a high blend of paper fillers has increased. Since this neutral newsprint paper has a high degree of whiteness and opacity, it has a characteristic that the finish of the color printing surface and the back-through are excellent in the printed finish. When neutral newspaper printing paper is reduced in weight and / or increased in filler, paper thickness and bending stiffness are reduced in terms of physical properties of paper compared to conventional acidic paper. The diameter of the newspaper roll is managed at each printing station, and it becomes difficult to maintain the diameter of the newspaper roll at the same level as acidic paper due to the decrease in the paper thickness of the printing paper. There are new problems that were not found in conventional acidic papers, such as the occurrence of wrinkles and lowering of paper due to dampening water adhering during printing. Assuming that the paper is made of a homogeneous material, the bending stiffness of the paper is proportional to the cube of the paper thickness in terms of material mechanics. As the paper becomes thinner, the paper thickness decreases, and the bending stiffness decreases sharply.

  In recent newspaper paper, full-color printing is increasing especially for advertisements and the like, and ink inking is an especially important factor in the printing quality of newspaper printing paper. In contrast to the decrease in paper thickness, a method is adopted in which the calender linear pressure is lowered on the papermaking surface to suppress the decrease in paper thickness and the bending stiffness is suppressed, but the smoothness of the paper decreases by reducing the calender linear pressure. Ink imperfections such as roughness and unevenness occur.

As a surface treatment agent for newspaper printing paper, a water-soluble surface paper strength agent such as starch is used for the purpose of suppressing paper dust piling on a blanket during offset printing. Usually, the coating amount of the surface paper strength agent is about 0.1 to 1.0 g / m ² per both sides of the paper. If the application amount of the surface paper strength agent such as starch is 1.0 g / m ² or more in order to improve the bending stiffness of the paper, the water-soluble surface strength agent on the paper surface is swollen by dampening water during offset printing. In such a state, the adhesiveness of the paper surface deteriorates, so that newspaper paper sticks to the blanket of the printing press at the time of offset printing, and so-called Nepari occurs, so there is a limit to increasing the amount of surface paper strength agent such as starch. And there was no sufficient bending stiffness. The increase in the coating amount of the surface paper strength agent is an effective means for paper dust piling and ink deposition. Therefore, the development of a technology that can increase the coating amount of the surface paper strength agent while suppressing spilling has been desired. .

  In order to improve the stiffness of newsprint for offset printing, it has been studied from various aspects. As an example of improvement from the paper layer structure of newsprint for offset printing, chemical pulp is applied to the surface layer, DIP and MP are added to the intermediate layer (see Patent Document 1), and heating steam is applied in front of the calendar. After that, there is a method of increasing the paper thickness by performing a soft calendar process (see Patent Document 2). However, these are limited in terms of pulp raw materials, production equipment, etc., and cannot be implemented with currently used equipment and pulp.

  On the other hand, as a technology for improving the quality of newsprint for offset printing using a surface treatment agent, oxidized starch is often used, but when applying a surface treatment agent consisting only of this oxidized starch, in order to avoid the occurrence of nepari There is a limit to the amount of oxidized starch applied, and the stiffness cannot be increased sufficiently. As a technique for improving the stiffness of paper by using other external additive chemicals, for example, a composition for improving rigidity comprising a specific combination of water glass and a polymer emulsion or latex is disclosed (see Patent Document 3). A method of applying a coating agent containing a block copolymer composed of a polyvinyl alcohol polymer component and a polyacrylamide polymer component (see Patent Document 4), a specific weight of an acrylamide monomer in the presence of a polyvinyl alcohol polymer A method of applying a coating agent containing a polymer composition obtained by radical polymerization at a ratio (see Patent Document 5), a paper comprising an aqueous solution containing a polyvinyl alcohol resin containing an acetoacetate group and a zirconium salt Method for applying processing agent (see Patent Document 6), (meth) acrylamide, α, β-unsaturated carboxylic acid, N, N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylol (meta ) Contains a water-soluble copolymer containing 0.3 to 1 mole of ethylene urea as a polymerization component per mole of acrylamide. A method for applying a paper processing agent (see Patent Document 7), a method using an alkyl vinyl ether and a maleic anhydride copolymer (see Patent Document 8), a water-proofing agent comprising polyamide epichlorohydrin, glyoxal or melanin formalin resin And a method of applying a water-soluble resin such as polyvinyl alcohol, starch, polyacrylamide or carboxymethyl cellulose is disclosed (see Patent Document 9). However, these disclosed methods are problematic in terms of productivity and cost due to the use of special equipment and special compounds for implementation, and the high-speed offset of newspaper printing paper because Nepari issues are not considered. It is unsuitable for printing and has problems such as deterioration of disaggregation when used as waste paper. There is a demand for a surface treatment agent suitable for light weight and neutral high filler. Furthermore, in addition to bending stiffness, there has been no known method for improving printing quality and sizing such as ink deposition and back-through.

JP-A-3-227500 JP-A-4-361686 JP 59-130398 A JP-A-60-173197 JP 60-252800 A JP-A-1-156597 JP-A-6-65893 Japanese Patent Laid-Open No. 7-23890 JP-A-8-1000038

  To provide a neutral newsprint for offset printing having a low basis weight and a high ash content, having no problems with Nepari, having an appropriate stiffness, and not impairing offset printing workability.

A surface treatment agent containing a modified starch and a cationic surface sizing agent is applied to a base paper of neutral newspaper printing paper with an ash content of 10 to 20%, and 0.5 to 6.0 solids g / m ² on both sides in terms of the coating amount of the modified starch. After application, the coating is dried to obtain neutral newsprint for offset printing.

  A neutral newsprint for offset printing having a low basis weight and a high ash content can be provided without causing problems of Nepari and having an appropriate stiffness and without impairing offset printing workability.

  As a result of intensive investigations aimed at improving the stiffness of neutral newsprint for offset printing with a low basis weight and high ash content, the inventors of the present invention can improve the stiffness by increasing the coating amount of a modified starch having a specific range of viscosity. The present inventors have found that the problem of Nepari in newspaper printing paper with an increased coating amount of modified starch can be solved by adding a cationic surface sizing agent to the surface treatment agent, thereby completing the present invention.

  The raw material pulp of the neutral newsprint for offset printing according to the present invention is not particularly limited as long as it is a pulp normally used for newsprint. For example, Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGP), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Ground Pulp (GP), Thermomechanical Pulp (TMP) ), Chemi-thermomechanical pulp (CTMP), refiner mechanical pulp (RMP), etc., and used paper pulp, such as deinked pulp (DIP), can be used by appropriately selecting one or several kinds. If necessary, chemical pulp (CP) such as kraft pulp (KP) can also be used. From the viewpoint of effective utilization of pulp resources, the DIP content is preferably 50 to 100% by weight based on the total pulp.

  In addition, the neutral newsprint for offset printing of the present invention is reduced in the amount of sulfuric acid band added compared to conventional acidic papermaking, and the buffer effect of calcium carbonate used as a filler or calcium carbonate derived from used paper at the time of papermaking. Papermaking is carried out at a pH of 5-9.

  The neutral newsprint paper for offset printing of the present invention can be used without any limitation as long as it is a filler normally used in neutral papermaking. For example, heavy calcium carbonate, light calcium carbonate, light calcium carbonate generated in the pulp causticizing process, light calcium carbonate-silica composite, magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, 1 selected from inorganic fillers such as zinc hydroxide, clay, calcined kaolin, delaminated kaolin, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, urea-formalin resin, polystyrene resin, phenol resin, fine hollow particles, etc. More than one type can be used in combination.

The ash content in the neutral newsprint paper for offset printing according to the present invention is 10 to 20% by weight in total of the ash content from the waste paper and the ash content by adding a fresh filler. While ash content in ordinary newsprint is less than 10% by weight, high blending of ash in this way provides high whiteness and high opacity, and ink breakthrough is greatly improved. Since the surface strength is reduced, there is a problem that paper powder is easily dropped during offset printing. Within the range of ash content in the paper, by applying a high amount of starch-based surface paper strength agent on both sides as in the present invention, not only the bending stiffness but also the effect of suppressing paper dust can be obtained. The coating amount of the modified starch is preferably 0.5 to 6.0 solids g / m ² on both sides, more preferably 1.0 to 6.0 solids g / m ^{2, and} still more preferably 2.0 to 6.0 solids g / m ² . However, if the ash content in the paper exceeds 20%, not only the bending stiffness but also the strength properties such as tear strength and tensile strength are excessively reduced, and the starch-based surface paper strength agent is applied to both sides as in the present invention. There is a problem in that printing runnability is hindered even at high application amounts.

  Neutral sizing agent, paper strength improver, yield improver, wet paper strength enhancer, dye, fluorescent whitening agent, antifoaming agent, pitch control agent, slime control agent, etc. Auxiliary chemicals may be added internally.

  The surface treatment agent applied to the base paper of the neutral newsprint for offset printing contains a modified starch and a cationic surface sizing agent as main components. Examples of the modified starch include oxidized starch, hydroxyethylated starch, cationized starch, cationized oxidized starch, acetylated starch, esterified starch, heat-modified starch, enzyme-modified starch, and aldehyde-modified starch. Among these, it is preferable to use oxidized starch and hydroxyethylated starch which are excellent in mechanical stability and anti-aging stability.

  In the present invention, as a device for applying a surface treatment agent, a roll type coater such as a gate roll coater, a size press coater, a rod metaling size press coater, an air knife coater, a blade coater, a rod coater, a metering bar coater, Any device such as a gravure coater or a spray coater may be used.

  High-speed gate roll coaters of 1,000 m / min or more are mainly used as newspaper printing paper coating apparatuses, and it is preferable to use a gate roll coater also in the production of neutral newsprint paper for offset printing according to the present invention. .

When using a gate roll coater to apply a surface treatment agent composed mainly of the modified starch and the cationic sizing agent, the high viscosity of the surface treatment agent in high-speed coating may hinder operations such as boiling. Therefore, it is necessary to reduce the viscosity of the surface treatment agent. On the other hand, when the coating amount is particularly large at 0.5 solids g / m ² or more on both sides, it is necessary to increase the concentration of the surface treatment agent or increase the viscosity due to the characteristics of the gate roll coater. As described above, problems such as boiling occur. Therefore, it can be understood that the surface treatment agent may be made to have a high concentration and a low viscosity in order to stably operate and increase the coating amount using the gate roll coater. Since the cationic sizing agent has a lower viscosity than the modified starch, it is necessary to reduce the viscosity of the modified starch to be blended in order to reduce the viscosity of the surface treatment agent. That is, it is necessary to use a modified starch having a low molecular weight and a low viscosity as much as possible. As a result of examining the viscosity of the modified starch, the present inventors have found that if the modified starch paste solution has a concentration of 10% and the liquid temperature is 30 ° C. and the B-type viscosity at 60 rpm is 100 mPa · s or less, the coating can be applied without any problem of boiling. It was found that amounts of 0.5 g / m ² or more and 3.0 g / m ² or less can be obtained. It was also found that even in apparatuses other than gate rolls, operation up to a coating amount of 6 g / m ² can be stably performed by using a surface treatment agent containing modified starch having such viscosity properties. That is, if the 0.5 to 3.0 g / m ² is necessary coating amount of both surfaces of the modified starch, at a gate roll coater is also possible coating in 2-roll size press, necessary coating amount of the 3.0~6.0g / m ^{2 2} -Apply using a roll size press.

  That is, the concentration is selected from the types of modified starches such as oxidized starch, hydroxyethylated starch, cationized starch, cationized oxidized starch, acetylated starch, esterified starch, heat-modified starch, enzyme-modified starch, and aldehyde-modified starch. It is preferable to select and use a starch having a B-type viscosity of 60 rpm of 100 mPa · s or less at 10% and a liquid temperature of 30 ° C. Alternatively, these generally available modified starches are further subjected to low molecular weight treatment by known methods such as enzyme denaturation and oxidative denaturation, and when the concentration is 10% and the liquid temperature is 30 ° C., the B-type viscosity at 60 rpm is 100 mPa · s or less. It is preferable to use the above.

  Known cationic surface sizing agents can be used. Specifically, the cationic surface size described in WO2005 / 003457 pamphlet, JP-A-2005-105488, JP-A-2005-248338, JP-A-2006-16713, JP-A-2006-16712, etc. And cationic surface sizing agents described in Japanese Patent Application Nos. 2004-283987, 2005-144636, 2005-223106, 2005-312381, and 2006-17607, which are filed by the present applicant. It is done. Among these, the following cationic surface sizing agent A or cationic surface sizing agent B is preferably used.

[Cationic surface sizing agent A]
(A) 20 to 40% by weight of a tertiary amino group-containing monomer, (b) 10 to 80% by weight of C4-C18 alkyl ester of (meth) acrylic acid, and (c) 0 to 70% by weight of styrenes The
This is a copolymer obtained by quaternizing a copolymer having a weight average molecular weight of 30,000 to 60,000 obtained by polymerization in the presence of a chain transfer agent using an azo polymerization initiator.

[Cationic surface sizing agent B]
A copolymer obtained by copolymerizing the following component (a) and component (b), or a copolymer obtained by copolymerizing component (a), component (b) and component (c), Alternatively, among these copolymers, a copolymer obtained by using a tertiary amine group-containing vinyl monomer as the component (b) and quaternized with the component (d). : Styrenic monomer At least one styrenic monomer selected from styrene, α-methylstyrene, chlorostyrene, and cyanostyrene.
Component (b): a cationic monomer A vinyl monomer containing any one of a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium group.
Component (c): other hydrophobic monomer copolymerizable monomer, at least one hydrophobic monomer selected from methacrylic acid esters and acrylic acid esters.
Component (d): Quaternizing agent At least one quaternizing agent selected from epichlorohydrin, methyl chloride, ethyl chloride, benzyl chloride, dimethyl sulfate, diethyl sulfate, oxides, epoxy compounds, and organic halides.

The mixing ratio of the modified starch and the cationic surface sizing agent is 100/5 to 100/30 in terms of solid content weight. By using a cationic sizing agent within the range of this mixing ratio, the Nepari strength is low even when the coating amount of the modified starch is as large as 0.5 to 6.0 g / m ^2, and the bending stiffness is improved without causing Nepari trouble. Can be made. Although this mechanism is not clear, newspaper printing paper obtained by applying a surface treatment agent containing modified starch and a cationic surface sizing agent to the base paper and drying it was treated with a dampening solution during offset printing. Since starch is hydrophobized to some extent by the cationic surface sizing agent, swelling of the modified starch by the fountain solution is suppressed, so that the Nepari strength is low, and Nepari is considered to have no problem. When the mixing ratio of the cationic sizing agent is lower than this range, the Nepari strength is high and becomes a problem. On the other hand, even if the mixing ratio of the cationic sizing agent is higher than this range, the effect of lowering the Neppari strength is small and uneconomical. In addition, the neutral newsprint paper for offset printing obtained by applying a cationic sizing agent to the base paper of neutral newsprint paper for offset printing is more sizing than conventional acidic newsprint paper with anionic sizing agent applied. Is obtained. Furthermore, since the coating amount of the modified starch is large, the covering property is improved by the sealing effect on the paper surface, and a good sizing property can be obtained even when the cationic surface sizing agent is small.

  The paper machine used for making the neutral newsprint for offset printing of the present invention may be any known apparatus, and a long net paper machine, an on-top twin wire paper machine, a gap former, or the like is used.

The basis weight of the neutral newsprint for offset printing of the present invention is 35 to 43 g / m ² . When performing a calendar process, it is preferable to use a hot soft nip calender. The hot soft nip calender has higher smoothness at the same linear pressure than the hard nip calender, and the paper thickness is less reduced to obtain the same smoothness. The neutral newsprint paper for offset printing of the present invention with low basis weight and high ash content tends to decrease in thickness as the amount of ash in the paper increases and the number of fibers decreases. A technique for increasing the height is preferably used. The paper thickness after the calendar process is preferably 55 to 75 μm.

  Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. Table 1 shows the values of type B viscosity measured at a solid content concentration of 10%, a liquid temperature of 30 ° C., and 60 rpm of the modified starch used in the following Examples and Comparative Examples.

[Example 1]
A mixed pulp slurry consisting of 20 parts of TMP, 75 parts of DIP and 5 parts of NBKP was prepared, and 1.3 parts of sulfuric acid band and 9 parts of calcium carbonate (trade name: Optical HF, manufactured by Imeris Co., Ltd.) for 100 parts (solid weight) of this mixed pulp And a neutral newspaper printing paper having a basis weight of 43 g / m ² , a thickness of 85 μm and an ash content of 12% was obtained using a twin wire type paper machine. Hydroxyethylated starch A (trade name: ETHYLEX-2025, manufactured by STAYLEY) was prepared to a concentration of 12%, and cationic surface sizing agent A (trade name: LC-123L, manufactured by Harima Chemical Co., Ltd.) The surface treating agent was prepared by adding. Next, with a gate roll coater, the surface treatment agent is applied to the above base paper at a coating speed of 1200 m / min, the starch coating amount is 2.0 g / m ^{2 on} both sides, and the cationic sizing agent A coating amount is 0.08 g / m ^{2 on} both sides. After coating and drying, neutral nip paper for offset printing was obtained by 1-nip treatment with a hot soft nip calender at 130 ° C. The linear pressure of the hot soft nip calender was adjusted so that the paper thickness was 72 μm.

[Example 2]
Neutral newsprint paper for offset printing was obtained in the same manner as in Example 1 except that the adjusted concentration after cooking of hydroxyethylated starch A was 10% and the starch coating amount was 1.5 g / m ² per both sides.

[Example 3]
Neutral newspaper for offset printing was obtained in the same manner as in Example 1 except that the adjusted concentration after cooking of hydroxyethylated starch A was 6% and the starch coating amount was 0.5 g / m ² per both sides.

[Example 4]
Use hydroxyethylated starch B (trade name: ETHYLEX-2035, manufactured by STAYLEY) instead of hydroxyethylated starch A, adjust the concentration after cooking to 10%, and apply starch to 2.0 g / m2 per side A neutral newsprint for offset printing was obtained in the same manner as in Example 1 except that.

[Example 5]
Instead of hydroxyethylated starch A, hydroxyethylated starch C (trade name: PG295, manufactured by PENFORD) was used, and the adjusted concentration after cooking was 14%, so that the starch coating amount was 2.0 g / m ² per side. A neutral newsprint for offset printing was obtained in the same manner as Example 1 except for the above.

[Example 6]
Except for using hydroxyethylated starch D (trade name: PG280, manufactured by PENFORD) instead of hydroxyethylated starch A, adjusting the concentration after cooking to 12% and applying the starch to 2.0 g / m2 per side Produced neutral newsprint for offset printing in the same manner as in Example 1.

[Example 7]
Use oxidized starch (trade name: SK-20, manufactured by Nippon Corn Starch Co., Ltd.) instead of hydroxyethylated starch A, and adjust the concentration after cooking to 12% to make the starch coating amount 2.0g / m ² per side A neutral newsprint for offset printing was obtained in the same manner as in Example 1 except that.

[Example 8]
Other than using acetylated starch (trade name: XMJP, manufactured by Changchun Taiseisha) instead of hydroxyethylated starch A, adjusting the concentration after cooking to 4.5%, and applying starch to 1.5 g / m ² per side Produced neutral newsprint for offset printing in the same manner as in Example 1.

[Example 9]
For offset printing as in Example 1, except that acetylated starch was used instead of hydroxyethylated starch A, the adjusted concentration after cooking was 3.5%, and the starch coating amount was 0.5 g / m ² per side. I got a neutral newspaper.

[Example 10]
Neutral newspaper for offset printing is obtained in the same manner as in Example 1 except that the cationic surface sizing agent B (trade name: LC-5, manufactured by Harima Chemicals Co., Ltd.) is used instead of the cationic surface sizing agent A. It was.

[Example 11]
Example 1 except that the adjusted concentration of hydroxyethylated starch A was 10%, the coating system was changed from a gate roll coater to a 2-roll size press, and the starch coating amount was 5.5 g / m ² per side. Similarly, neutral newsprint for offset printing was obtained.

[Example 12]
Add 12 parts of calcium carbonate, change to base paper of neutral newspaper printing paper with ash content of 15%, and further adjust the concentration of hydroxyethylated starch A after cooking to 10%. ^A neutral newsprint for offset printing was obtained in the same manner as in Example 1 except that ² .

[Example 13]
Example 1 except that hard nip calendering is performed instead of hot soft nip calendering, the calender linear pressure is adjusted to achieve the same smoothness as in Example 1, and the paper thickness after calendering is 68 μm. In the same manner, neutral newsprint for offset printing was obtained.

[Comparative Example 1]
Neutral newspaper for offset printing was obtained in the same manner as in Example 3 except that an anionic surface sizing agent (trade name: KN-520, manufactured by Harima Chemicals Co., Ltd.) was used instead of the cationic surface sizing agent A. It was.

[Comparative Example 2]
Neutral newsprint paper for offset printing was obtained in the same manner as in Comparative Example 1 except that the adjusted concentration after cooking of hydroxyethylated starch A was 10% and the starch coating amount was 1.5 g / m ² per both sides.

[Comparative Example 3]
Neutral newsprint paper for offset printing was obtained in the same manner as in Comparative Example 1 except that the adjusted concentration of the hydroxyethylated starch A after cooking was 3% and the starch coating amount was 0.2 g / m ² per both sides.

[Comparative Example 4]
Add 6 parts of calcium carbonate, change to base paper of neutral newspaper printing paper with 8% ash, and further adjust the concentration of hydroxyethylated starch A after cooking to 6%. ^A neutral newsprint for offset printing was obtained in the same manner as in Comparative Example 1 except that ² .

[Comparative Example 5]
Offset printing as in Comparative Example 1, except that acetylated starch was used instead of hydroxyethylated starch A, the adjusted concentration after cooking was 3.5%, and the starch coating amount was 0.5 g / m ² per side. A neutral newspaper was obtained.

[Comparative Example 6]
Neutral newsprint paper for offset printing was obtained in the same manner as Comparative Example 1 except that no surface treating agent was applied.

The following measurements were performed on the neutral newsprint paper for offset printing obtained in the above Examples and Comparative Examples.
(1) Starch coating amount: Measured using Biosensor BF2 (Oji Scientific Instruments).
(2) Bending stiffness: Bending resistance was measured using L & W Bending Tester Code 160 (manufactured by Lorentzen & Wettre), and bending stiffness was calculated by the following formula.
S _b = (F ・ L ²・ 60) / (θ ・ π ・ b)
(Where S _b is the bending stiffness (mN), F is the bending resistance (mNm), L is the paper piece length (10 mm), θ is the bending angle (15 °), and b is the paper piece width (38 mm))
(3) Ink density: A single-sided printing was performed on a paper sample using newspaper ink (trade name: New King VANTEAN Eco Black ST, manufactured by Toyo Ink Co., Ltd.) using an RI printer. The ink density on the solid surface of the black ink was measured using a Macbeth reflection densitometer RD-918 (manufactured by Colmogen Corporation, USA).
(4) Nepari strength: Two newspaper papers were cut into 4 x 6 cm pieces, the wire side of one piece of paper was immersed in water at a temperature of 20 ° C for 5 seconds, and then this side was attached to the felt side of the other piece of paper. . Further, the two pieces of laminated paper were sandwiched between large size filter papers, passed through a roll at a pressure of 50 kg / m ² , and conditioned at 23 ° C. and 50 RH% for 24 hours. The pasted paper pieces were cut to a size of 3 × 6 cm, and the tensile strength was measured with a tensile tester at a tensile speed of 30 mm / min. The larger the measured value, the worse the peelability, that is, the newspaper paper has a strong adhesiveness in a wet state, and it means that Nepari trouble is likely to occur.
(5) Drip water absorption: The felt side of the printing paper was measured according to JAPAN TAPPI No.33. The higher the value, the higher the water absorption resistance. Higher drip water absorbency is better from the viewpoint of running properties such as water-cut paper due to dampening water adhesion in offset printing and wet inking after the second color in multicolor printing.

Table 1 shows the evaluation results of the neutral newsprint paper for offset printing in Examples and Comparative Examples.

The paper quality results of the obtained neutral newsprint for offset printing were as follows. In both the examples and comparative examples, the bending stiffness increased as the starch coating amount was increased. However, from the comparison between Example 3 and Comparative Example 1, the comparison between Example 2 and Comparative Example 2, and the comparison between Example 9 and Comparative Example 5, a surface treatment agent using a modified starch and an anionic sizing agent was used. In the applied comparative example, the Nepari strength increases remarkably as the coating amount increases, whereas in the examples where a surface treatment agent using a combination of modified starch and a cationic surface sizing agent is applied, the increase in Nepari strength is slight and denatured. There was no problem even with high starch application. Furthermore, it was found that the greater the starch coating amount, the higher the smoothness and the ink concentration, and the drip water absorption rate becomes higher even with the same sizing agent coating amount.

Claims (4)

10% to 20% solid weight by weight of neutral newsprint paper with a solid content concentration of 10%, a liquid temperature of 30 ° C., and a B-type viscosity measured at 60 rpm is 100 mPa · s or less. The surface treatment agent containing a modified starch and a cationic surface sizing agent is applied, the coating amount of the modified starch is 2.0 to 6.0 g / m ² on both sides, and the basis weight is 35 to 43 g / m ^2. Neutral newsprint for offset printing in the range. The cationic sizing agent is
(A) 20-40% by weight of a tertiary amino group-containing monomer,
(B) 10 to 80% by weight of C4-C18 alkyl ester of (meth) acrylic acid,
(C) 0 to 70% by weight of styrenes,
The copolymer obtained by polymerizing in the presence of a chain transfer agent using an azo polymerization initiator, which is a copolymer obtained by quaternizing a copolymer having a weight average molecular weight of 30,000 to 60,000. 1. Neutral newsprint for offset printing according to 1. The cationic surface sizing agent is (1) a copolymer obtained by copolymerizing the following components (a) and (b), (2) component (a), component (b) and component (c) ), Or (3) a copolymer obtained by using a tertiary amine group-containing vinyl monomer as component (b) among these copolymers. The neutral newsprint for offset printing according to claim 1, which is one of the copolymers quaternized in d).
Component (a): Styrenic monomer At least one styrenic monomer selected from styrene, α-methylstyrene, chlorostyrene, and cyanostyrene.
Component (b): a cationic monomer A vinyl monomer containing any one of a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium group.
Component (c): other hydrophobic monomer copolymerizable monomer, at least one hydrophobic monomer selected from methacrylic acid esters and acrylic acid esters.
Component (d): Quaternizing agent At least one quaternizing agent selected from epichlorohydrin, methyl chloride, ethyl chloride, benzyl chloride, dimethyl sulfate, diethyl sulfate, oxides, epoxy compounds, and organic halides.   The neutral newspaper printing paper is characterized in that the ratio of waste paper pulp in the total pulp of the base paper is 50% by weight or more, and smoothing treatment is performed with a hot soft nip calender so that the paper thickness is 55 to 75 μm. The neutral newsprint for offset printing according to any one of claims 1 to 3.